Rename mscorlib to System.Private.Corelib (#17926)

* diff from just renaming folder mscorlib to System.Private.CoreLib

* Updating build.proj to reflect name change

Fixes: #17905

1185 files changed, 319909 insertions, 0 deletions

diff --git a/src/System.Private.CoreLib/Common/NotImplemented.cs b/src/System.Private.CoreLib/Common/NotImplemented.cs
new file mode 100644
index 0000000000..82f4e18ddc
--- /dev/null
+++ b/src/System.Private.CoreLib/Common/NotImplemented.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    //
+    // This simple class enables one to throw a NotImplementedException using the following
+    // idiom:
+    //
+    //     throw NotImplemented.ByDesign;
+    //
+    // Used by methods whose intended implementation is to throw a NotImplementedException (typically
+    // virtual methods in public abstract classes that intended to be subclassed by third parties.)
+    //
+    // This makes it distinguishable both from human eyes and CCI from NYI's that truly represent undone work.
+    //
+    internal static class NotImplemented
+    {
+        internal static Exception ByDesign
+        {
+            get
+            {
+                return new NotImplementedException();
+            }
+        }
+
+        internal static Exception ByDesignWithMessage(string message)
+        {
+            return new NotImplementedException(message);
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/Common/System/SR.cs b/src/System.Private.CoreLib/Common/System/SR.cs
new file mode 100644
index 0000000000..0b6db1298e
--- /dev/null
+++ b/src/System.Private.CoreLib/Common/System/SR.cs
@@ -0,0 +1,196 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Resources;
+using System.Runtime.CompilerServices;
+using System.Threading;
+
+namespace System
+{
+    internal static partial class SR
+    {
+        private static ResourceManager ResourceManager
+        {
+            get;
+            set;
+        }
+
+        // This method is used to decide if we need to append the exception message parameters to the message when calling SR.Format. 
+        // by default it returns false.
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static bool UsingResourceKeys()
+        {
+            return false;
+        }
+
+        // Needed for debugger integration
+        internal static string GetResourceString(string resourceKey)
+        {
+            return GetResourceString(resourceKey, String.Empty);
+        }
+
+        internal static string GetResourceString(string resourceKey, string defaultString)
+        {
+            string resourceString = null;
+            try { resourceString = InternalGetResourceString(resourceKey); }
+            catch (MissingManifestResourceException) { }
+
+            if (defaultString != null && resourceKey.Equals(resourceString, StringComparison.Ordinal))
+            {
+                return defaultString;
+            }
+
+            return resourceString;
+        }
+
+        private static object _lock = new object();
+        private static List<string> _currentlyLoading;
+        private static int _infinitelyRecursingCount;
+        private static bool _resourceManagerInited = false;
+
+        private static string InternalGetResourceString(string key)
+        {
+            if (key == null || key.Length == 0)
+            {
+                Debug.Fail("SR::GetResourceString with null or empty key.  Bug in caller, or weird recursive loading problem?");
+                return key;
+            }
+
+            // We have a somewhat common potential for infinite 
+            // loops with mscorlib's ResourceManager.  If "potentially dangerous"
+            // code throws an exception, we will get into an infinite loop
+            // inside the ResourceManager and this "potentially dangerous" code.
+            // Potentially dangerous code includes the IO package, CultureInfo,
+            // parts of the loader, some parts of Reflection, Security (including 
+            // custom user-written permissions that may parse an XML file at
+            // class load time), assembly load event handlers, etc.  Essentially,
+            // this is not a bounded set of code, and we need to fix the problem.
+            // Fortunately, this is limited to mscorlib's error lookups and is NOT
+            // a general problem for all user code using the ResourceManager.
+
+            // The solution is to make sure only one thread at a time can call 
+            // GetResourceString.  Also, since resource lookups can be 
+            // reentrant, if the same thread comes into GetResourceString
+            // twice looking for the exact same resource name before 
+            // returning, we're going into an infinite loop and we should 
+            // return a bogus string.  
+
+            bool lockTaken = false;
+            try
+            {
+                Monitor.Enter(_lock, ref lockTaken);
+
+                // Are we recursively looking up the same resource?  Note - our backout code will set
+                // the ResourceHelper's currentlyLoading stack to null if an exception occurs.
+                if (_currentlyLoading != null && _currentlyLoading.Count > 0 && _currentlyLoading.LastIndexOf(key) != -1)
+                {
+                    // We can start infinitely recursing for one resource lookup,
+                    // then during our failure reporting, start infinitely recursing again.
+                    // avoid that.
+                    if (_infinitelyRecursingCount > 0)
+                    {
+                        return key;
+                    }
+                    _infinitelyRecursingCount++;
+
+                    // Note: our infrastructure for reporting this exception will again cause resource lookup.
+                    // This is the most direct way of dealing with that problem.
+                    string message = $"Infinite recursion during resource lookup within {System.CoreLib.Name}.  This may be a bug in {System.CoreLib.Name}, or potentially in certain extensibility points such as assembly resolve events or CultureInfo names.  Resource name: {key}";
+                    Environment.FailFast(message);
+                }
+                if (_currentlyLoading == null)
+                    _currentlyLoading = new List<string>();
+
+                // Call class constructors preemptively, so that we cannot get into an infinite
+                // loop constructing a TypeInitializationException.  If this were omitted,
+                // we could get the Infinite recursion assert above by failing type initialization
+                // between the Push and Pop calls below.
+                if (!_resourceManagerInited)
+                {
+                    RuntimeHelpers.RunClassConstructor(typeof(ResourceManager).TypeHandle);
+                    RuntimeHelpers.RunClassConstructor(typeof(ResourceReader).TypeHandle);
+                    RuntimeHelpers.RunClassConstructor(typeof(RuntimeResourceSet).TypeHandle);
+                    RuntimeHelpers.RunClassConstructor(typeof(BinaryReader).TypeHandle);
+                    _resourceManagerInited = true;
+                }
+
+                _currentlyLoading.Add(key); // Push
+
+                if (ResourceManager == null)
+                {
+                    ResourceManager = new ResourceManager(SR.ResourceType);
+                }
+                string s = ResourceManager.GetString(key, null);
+                _currentlyLoading.RemoveAt(_currentlyLoading.Count - 1); // Pop
+
+                Debug.Assert(s != null, "Managed resource string lookup failed.  Was your resource name misspelled?  Did you rebuild mscorlib after adding a resource to resources.txt?  Debug this w/ cordbg and bug whoever owns the code that called SR.GetResourceString.  Resource name was: \"" + key + "\"");
+                return s ?? key;
+            }
+            catch
+            {
+                if (lockTaken)
+                {
+                    // Backout code - throw away potentially corrupt state
+                    ResourceManager = null;
+                    _currentlyLoading = null;
+                }
+                throw;
+            }
+            finally
+            {
+                if (lockTaken)
+                {
+                    Monitor.Exit(_lock);
+                }
+            }
+        }
+
+        internal static string Format(string resourceFormat, params object[] args)
+        {
+            if (args != null)
+            {
+                if (UsingResourceKeys())
+                {
+                    return resourceFormat + String.Join(", ", args);
+                }
+
+                return String.Format(resourceFormat, args);
+            }
+
+            return resourceFormat;
+        }
+
+        internal static string Format(string resourceFormat, object p1)
+        {
+            if (UsingResourceKeys())
+            {
+                return String.Join(", ", resourceFormat, p1);
+            }
+
+            return String.Format(resourceFormat, p1);
+        }
+
+        internal static string Format(string resourceFormat, object p1, object p2)
+        {
+            if (UsingResourceKeys())
+            {
+                return String.Join(", ", resourceFormat, p1, p2);
+            }
+
+            return String.Format(resourceFormat, p1, p2);
+        }
+
+        internal static string Format(string resourceFormat, object p1, object p2, object p3)
+        {
+            if (UsingResourceKeys())
+            {
+                return String.Join(", ", resourceFormat, p1, p2, p3);
+            }
+            return String.Format(resourceFormat, p1, p2, p3);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/CreateRuntimeRootILLinkDescriptorFile.targets b/src/System.Private.CoreLib/CreateRuntimeRootILLinkDescriptorFile.targets
new file mode 100644
index 0000000000..967d71cb8d
--- /dev/null
+++ b/src/System.Private.CoreLib/CreateRuntimeRootILLinkDescriptorFile.targets
@@ -0,0 +1,33 @@
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+
+  <PropertyGroup>
+    <CompileDependsOn>_CreateILLinkRuntimeRootDescriptorFile;$(CompileDependsOn)</CompileDependsOn>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <_ILLinkRuntimeRootDescriptorFileName Condition=" '$(_ILLinkRuntimeRootDescriptorFileName)' == '' ">System.Private.CoreLib.xml</_ILLinkRuntimeRootDescriptorFileName>
+    <_ILLinkRuntimeRootDescriptorFilePath Condition=" '$(_ILLinkRuntimeRootDescriptorFilePath)' == '' ">$(IntermediateOutputPath)$(_ILLinkRuntimeRootDescriptorFileName)</_ILLinkRuntimeRootDescriptorFilePath>
+    <_NamespaceFilePath Condition=" '$(_NamespaceFilePath)' == '' ">$(MSBuildThisFileDirectory)..\vm\namespace.h</_NamespaceFilePath>
+    <_MscorlibFilePath Condition=" '$(_MscorlibFilePath)' == '' ">$(MSBuildThisFileDirectory)..\vm\mscorlib.h</_MscorlibFilePath>
+    <_CortypeFilePath Condition=" '$(_CortypeFilePath)' == '' ">$(MSBuildThisFileDirectory)..\inc\cortypeinfo.h</_CortypeFilePath>
+    <_RexcepFilePath Condition=" '$(_RexcepFilePath)' == '' ">$(MSBuildThisFileDirectory)..\vm\rexcep.h</_RexcepFilePath>
+    <_ILLinkTrimXmlFilePath Condition=" '$(_ILLinkTrimXmlFilePath)' == '' ">$(MSBuildThisFileDirectory)ILLinkTrim.xml</_ILLinkTrimXmlFilePath>
+    <_ILLinkTasksToolsDir>$(PackagesDir)/illink.tasks/$(ILLinkTasksPackageVersion)/tools</_ILLinkTasksToolsDir>
+    <_ILLinkTasksDir>$(_ILLinkTasksToolsDir)/net46/</_ILLinkTasksDir>
+    <_ILLinkTasksDir Condition="'$(MSBuildRuntimeType)' == 'Core'">$(_ILLinkTasksToolsDir)/netcoreapp2.0/</_ILLinkTasksDir>
+  </PropertyGroup>
+
+  <!-- Generates the xml root descriptor file for ILLink. The file contains roots required by the runtime. -->
+  <UsingTask TaskName="CreateRuntimeRootILLinkDescriptorFile" AssemblyFile="$(_ILLinkTasksDir)ILLink.Tasks.dll" />
+  <Target Name="_CreateILLinkRuntimeRootDescriptorFile"
+          Inputs="$(_NamespaceFilePath);$(_MscorlibFilePath);$(_CortypeFilePath);$(_RexcepFilePath);$(_ILLinkTrimXmlFilePath)"
+          Outputs="$(_ILLinkRuntimeRootDescriptorFilePath)">
+    <Message Text="Generating ILLink roots file: $(_ILLinkRuntimeRootDescriptorFilePath)" />
+    <CreateRuntimeRootILLinkDescriptorFile NamespaceFilePath="$(_NamespaceFilePath)"
+                                           MscorlibFilePath="$(_MscorlibFilePath)"
+                                           CortypeFilePath="$(_CortypeFilePath)"
+                                           RexcepFilePath="$(_RexcepFilePath)"
+                                           ILLinkTrimXmlFilePath="$(_ILLinkTrimXmlFilePath)"
+                                           RuntimeRootDescriptorFilePath="$(_ILLinkRuntimeRootDescriptorFilePath)" />
+  </Target>
+</Project>
diff --git a/src/System.Private.CoreLib/GenerateCompilerResponseFile.targets b/src/System.Private.CoreLib/GenerateCompilerResponseFile.targets
new file mode 100644
index 0000000000..ed9136ffc6
--- /dev/null
+++ b/src/System.Private.CoreLib/GenerateCompilerResponseFile.targets
@@ -0,0 +1,22 @@
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  
+  <PropertyGroup>
+    <CompileDependsOn>GenerateCompilerResponseFile;$(CompileDependsOn)</CompileDependsOn>
+  </PropertyGroup>
+
+  <Target Name="GenerateCompilerResponseFile">
+    <Message Text="Generating module name response file: $(IntermediateOutputPath)\moduleName.$(AssemblyName).rsp" />
+
+    <!-- We need to set the runtimemetadataversion -->
+    <WriteLinesToFile File="$(IntermediateOutputPath)\moduleName.$(AssemblyName).rsp"
+                      Lines="/runtimemetadataversion:v4.0.30319"
+                      Overwrite="true" />
+
+    <ItemGroup>
+      <Clean Include="$(IntermediateOutputPath)\moduleName.$(AssemblyName).rsp" />
+    </ItemGroup>
+    <PropertyGroup>
+      <CompilerResponseFile>$(IntermediateOutputPath)\moduleName.$(AssemblyName).rsp;$(CompilerResponseFile)</CompilerResponseFile>
+    </PropertyGroup>
+  </Target>
+</Project>
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/GenerateSplitStringResources.targets b/src/System.Private.CoreLib/GenerateSplitStringResources.targets
new file mode 100644
index 0000000000..6041cbe0e3
--- /dev/null
+++ b/src/System.Private.CoreLib/GenerateSplitStringResources.targets
@@ -0,0 +1,42 @@
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <PrepareResourcesDependsOn>GenerateSplitStringResources;$(PrepareResourcesDependsOn)</PrepareResourcesDependsOn>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <PreprocessFileTaskAsssemblyPath Condition="'$(PreprocessFileTaskAsssemblyPath)' == ''">$(BuildToolsTaskDir)Microsoft.DotNet.Build.Tasks.dll</PreprocessFileTaskAsssemblyPath>
+  </PropertyGroup>
+
+  <UsingTask TaskName="PreprocessFile" AssemblyFile="$(PreprocessFileTaskAsssemblyPath)" />
+
+  <Target Name="GenerateSplitStringResources"
+          Inputs="@(SplitTextStringResource)"
+          Outputs="@(SplitTextStringResource->'$(IntermediateOutputPath)%(Filename).txt')">
+         
+    <ItemGroup>
+      <Internal_ResGenDefines Remove="@(Internal_ResGenDefines)" />
+      <Internal_ResGenDefines Include="INCLUDE_DEBUG" />
+      <Internal_ResGenDefines Include="INCLUDE_RUNTIME" />
+      <Internal_ResGenDefines Include="%(SplitTextStringResource.ResGenDefines)" />
+    </ItemGroup>    
+
+    <PreprocessFile SourceFile="%(SplitTextStringResource.Identity)" OutputFile="$(IntermediateOutputPath)%(SplitTextStringResource.Filename).txt" Defines="@(Internal_ResGenDefines)" />
+
+    <GenerateResource Sources="$(IntermediateOutputPath)%(SplitTextStringResource.Filename).txt"
+                      OutputResources="$(IntermediateOutputPath)%(SplitTextStringResource.Filename).resources"
+                      ExecuteAsTool="false" />
+
+    <ItemGroup>
+      <EmbeddedResource Include="@(SplitTextStringResource->'$(IntermediateOutputPath)%(Filename).resources')">
+        <WithCulture>false</WithCulture>
+        <ManifestResourceName>%(Filename)</ManifestResourceName>
+      </EmbeddedResource>
+      <Clean Include="$(IntermediateOutputPath)%(SplitTextStringResource.Filename).txt" />
+      <Clean Include="$(IntermediateOutputPath)%(SplitTextStringResource.Filename).resources" />
+    </ItemGroup>
+
+    <ItemGroup>
+      <Internal_ResGenDefines Remove="@(Internal_ResGenDefines)" />
+    </ItemGroup>    
+  </Target>
+</Project>
diff --git a/src/System.Private.CoreLib/ILLink.targets b/src/System.Private.CoreLib/ILLink.targets
new file mode 100644
index 0000000000..f33e2203ea
--- /dev/null
+++ b/src/System.Private.CoreLib/ILLink.targets
@@ -0,0 +1,136 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="12.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <TargetsTriggeredByCompilation>
+      $(TargetsTriggeredByCompilation);
+      ILLinkTrimAssembly
+    </TargetsTriggeredByCompilation>
+  </PropertyGroup>
+
+  <!-- Inputs and outputs of ILLinkTrimAssembly -->
+  <PropertyGroup>
+    <ILLinkTasksToolsDir>$(PackagesDir)/illink.tasks/$(ILLinkTasksPackageVersion)/tools</ILLinkTasksToolsDir>
+    <ILLinkTasksDir>$(ILLinkTasksToolsDir)/net46/</ILLinkTasksDir>
+    <ILLinkTasksDir Condition="'$(MSBuildRuntimeType)' == 'Core'">$(ILLinkTasksToolsDir)/netcoreapp2.0/</ILLinkTasksDir>
+    <ILLinkTasksPath>$(ILLinkTasksDir)ILLink.Tasks.dll</ILLinkTasksPath>
+    <ILLinkTrimAssembly Condition="'$(ILLinkTrimAssembly)' == ''">true</ILLinkTrimAssembly>
+    <ILLinkTrimAssemblyPath>$(IntermediateOutputPath)$(TargetName)$(TargetExt)</ILLinkTrimAssemblyPath>
+    <ILLinkTrimAssemblySymbols>$(IntermediateOutputPath)$(TargetName).pdb</ILLinkTrimAssemblySymbols>
+    <ILLinkTrimInputPath>$(IntermediateOutputPath)PreTrim/</ILLinkTrimInputPath>
+    <ILLinkTrimInputAssembly>$(ILLinkTrimInputPath)$(TargetName)$(TargetExt)</ILLinkTrimInputAssembly>
+    <ILLinkTrimInputSymbols>$(ILLinkTrimInputPath)$(TargetName).pdb</ILLinkTrimInputSymbols>
+    <ILLinkTrimOutputPath>$(IntermediateOutputPath)</ILLinkTrimOutputPath>
+
+    <!-- if building a PDB, tell illink to rewrite the symbols file -->
+    <ILLinkRewritePDBs Condition="'$(ILLinkRewritePDBs)' == '' AND '$(DebugSymbols)' != 'false'">true</ILLinkRewritePDBs>
+  </PropertyGroup>
+
+  <!-- Custom binplacing for pre/post-trimming and reports that is useful for analysis 
+       Must be enabled by setting BinPlaceILLinkTrimAssembly=true
+  --> 
+  <ItemGroup Condition="'$(BinPlaceILLinkTrimAssembly)' == 'true'">
+    <BinPlaceConfiguration Include="$(BuildConfiguration)">
+      <RuntimePath>$(BinDir)ILLinkTrimAssembly/$(BuildConfiguration)/trimmed</RuntimePath>
+      <ItemName>TrimmedItem</ItemName>
+    </BinPlaceConfiguration>
+    <BinPlaceConfiguration Include="$(BuildConfiguration)">
+      <RuntimePath>$(BinDir)ILLinkTrimAssembly/$(BuildConfiguration)/reports</RuntimePath>
+      <ItemName>TrimmingReport</ItemName>
+    </BinPlaceConfiguration>
+    <BinPlaceConfiguration Include="$(BuildConfiguration)">
+      <RuntimePath>$(BinDir)ILLinkTrimAssembly/$(BuildConfiguration)/pretrimmed</RuntimePath>
+      <ItemName>PreTrimmedItem</ItemName>
+    </BinPlaceConfiguration>
+  </ItemGroup>
+
+  <!-- ILLinkTrimAssembly
+       Examines the "input assembly" for IL that is unreachable from public API and trims that,
+       rewriting the assembly to an "output assembly"
+  -->
+  <UsingTask TaskName="ILLink" AssemblyFile="$(ILLinkTasksPath)" />
+  <Target Name="ILLinkTrimAssembly" Condition="'$(ILLinkTrimAssembly)' == 'true'" DependsOnTargets="EnsureBuildToolsRuntime">
+    <PropertyGroup>
+      <ILLinkArgs>$(ILLinkArgs)-r $(TargetName)</ILLinkArgs>
+      <!-- default action for core assemblies -->
+      <ILLinkArgs>$(ILLinkArgs) -c skip</ILLinkArgs>
+      <!-- default action for non-core assemblies -->
+      <ILLinkArgs>$(ILLinkArgs) -u skip</ILLinkArgs>
+      <!-- trim the target assembly -->
+      <ILLinkArgs>$(ILLinkArgs) -p link $(TargetName)</ILLinkArgs>
+      <ILLinkArgs Condition="'$(ILLinkRewritePDBs)' == 'true' AND Exists('$(ILLinkTrimAssemblySymbols)')">$(ILLinkArgs) -b true</ILLinkArgs>
+      <!-- keep types and members required by Debugger-related attributes -->
+      <ILLinkArgs>$(ILLinkArgs) -v true</ILLinkArgs>
+      <!-- don't remove the embedded root xml resource since ILLink may run again on the assembly -->
+      <ILLinkArgs>$(ILLinkArgs) --strip-resources false</ILLinkArgs>
+      <!-- reflection heuristics to apply -->
+      <ILLinkArgs>$(ILLinkArgs) -h LdtokenTypeMethods,InstanceConstructors</ILLinkArgs>
+    </PropertyGroup>
+
+    <MakeDir Directories="$(ILLinkTrimInputPath)" />
+
+    <!-- Move the assembly into a subdirectory for ILLink -->
+    <Move SourceFiles="$(ILLinkTrimAssemblyPath)"
+          DestinationFolder="$(ILLinkTrimInputPath)"
+    />
+
+    <!-- Move the PDB into a subdirectory for ILLink if we are rewriting PDBs -->
+    <Move SourceFiles="$(ILLinkTrimAssemblySymbols)"
+          DestinationFolder="$(ILLinkTrimInputPath)"
+          Condition="'$(ILLinkRewritePDBs)' == 'true' AND Exists('$(ILLinkTrimAssemblySymbols)')"
+    />
+
+    <ILLink AssemblyPaths="$(ILLinkTrimInputAssembly)"
+            RootAssemblyNames=""
+            OutputDirectory="$(ILLinkTrimOutputPath)"
+            ClearInitLocals="true"
+            ClearInitLocalsAssemblies="$(TargetName)"
+            ExtraArgs="$(ILLinkArgs)" />
+
+  </Target>
+
+  <!-- ILLink reporting.
+       Only enabled when developer specifies a path to the AsmDiff tool with property AsmDiffCmd.
+       EG: AsmDiffCmd=d:\tools\asmdiff\asmdiff.exe
+       This is necessary until the AsmDiff tool is ported to .NET Core. -->
+  <Target Name="_CreateILLinkTrimAssemblyReports"
+          AfterTargets="ILLinkTrimAssembly"
+          Condition="'$(AsmDiffCmd)' != ''">
+    <PropertyGroup>
+      <AsmDiffArgs>$(AsmDiffArgs) $(ILLinkTrimInputAssembly)</AsmDiffArgs>
+      <AsmDiffArgs>$(AsmDiffArgs) $(ILLinkTrimAssemblyPath)</AsmDiffArgs>
+      <AsmDiffArgs>$(AsmDiffArgs) -includePrivateApis -includeInternalApis -alwaysDiffMembers -diffAttributes</AsmDiffArgs>
+
+      <AsmDiffReport>$(IntermediateOutputPath)$(TargetName).diff.html</AsmDiffReport>
+      <AsmDiffReportArgs>$(AsmDiffArgs) -out:$(AsmDiffReport)</AsmDiffReportArgs>
+      <AsmDiffReportArgs>$(AsmDiffReportArgs) -unchanged -changed -added -removed</AsmDiffReportArgs>
+
+      <AsmDiffList>$(IntermediateOutputPath)$(TargetName).diff.csv</AsmDiffList>
+      <AsmDiffListArgs>$(AsmDiffArgs) -out:$(AsmDiffList)</AsmDiffListArgs>
+      <AsmDiffListArgs>$(AsmDiffListArgs) -unchanged -changed -added -removed </AsmDiffListArgs>
+      <AsmDiffListArgs>$(AsmDiffListArgs) -diffWriter:CSV</AsmDiffListArgs>
+    </PropertyGroup>
+
+    <Exec Command="$(AsmDiffCmd) $(AsmDiffReportArgs)" />
+    <Message Text="Assembly trimming diff: $(AsmDiffReport)" />
+    <Exec Command="$(AsmDiffCmd) $(AsmDiffListArgs)" />
+    <Message Text="Assembly trimming report: $(AsmDiffList)" />
+  </Target>
+  
+  <!-- Similar to _CheckForCompileOutputs and runs in the same places, 
+       always set these even if compile didn't run. -->
+  <Target Name="_CheckForILLinkTrimAssemblyOutputs" 
+          BeforeTargets="CopyFilesToOutputDirectory;_CleanGetCurrentAndPriorFileWrites"
+          Condition="'$(ILLinkTrimAssembly)' == 'true'">
+    <ItemGroup>
+      <PreTrimmedItem Condition="Exists('$(ILLinkTrimInputAssembly)')" Include="$(ILLinkTrimInputAssembly)" />
+      <PreTrimmedItem Condition="'$(ILLinkRewritePDBs)' == 'true' AND Exists('$(ILLinkTrimInputSymbols)')" Include="$(ILLinkTrimInputSymbols)" />
+      <FileWrites Include="@(PreTrimmedItem)" />
+
+      <TrimmedItem Condition="Exists('$(ILLinkTrimAssemblyPath)')" Include="$(ILLinkTrimAssemblyPath)" />
+      <TrimmedItem Condition="'$(ILLinkRewritePDBs)' == 'true' AND Exists('$(ILLinkTrimAssemblySymbols)')" Include="$(ILLinkTrimAssemblySymbols)" />
+
+      <TrimmingReport Condition="Exists('$(AsmDiffReport)')" Include="$(AsmDiffReport)" />
+      <TrimmingReport Condition="Exists('$(AsmDiffList)')" Include="$(AsmDiffList)" />
+    </ItemGroup>
+  </Target>
+</Project>
diff --git a/src/System.Private.CoreLib/ILLinkTrim.xml b/src/System.Private.CoreLib/ILLinkTrim.xml
new file mode 100644
index 0000000000..8c1071d546
--- /dev/null
+++ b/src/System.Private.CoreLib/ILLinkTrim.xml
@@ -0,0 +1,39 @@
+<linker>
+  <assembly fullname="System.Private.CoreLib">
+    <type fullname="System.CommonlyUsedGenericInstantiations">
+      <!-- Method is purely an aid for NGen to statically deduce which
+           instantiations to save in the ngen image. -->
+      <method name="CommonlyUsedWinRTRedirectedInterfaceStubs" />
+    </type>
+    <!-- Properties and methods used by a debugger. -->
+    <type fullname="System.Threading.Tasks.Task">
+      <property name="ParentForDebugger" />
+      <property name="StateFlagsForDebugger" />
+      <method name="GetDelegateContinuationsForDebugger" />
+    </type>
+    <type fullname="System.Threading.ThreadPool">
+      <method name="GetQueuedWorkItemsForDebugger" />
+      <method name="GetGloballyQueuedWorkItemsForDebugger" />
+      <method name="GetLocallyQueuedWorkItemsForDebugger" />
+    </type> 
+    <type fullname="System.Threading.Tasks.TaskScheduler">
+      <method name="GetScheduledTasksForDebugger" />
+      <method name="GetTaskSchedulersForDebugger" /> 
+    </type>
+    <type fullname="System.Runtime.CompilerServices.AsyncMethodBuilderCore">
+      <method name="TryGetStateMachineForDebugger" />
+    </type>
+    <type fullname="System.Runtime.CompilerServices.AsyncVoidMethodBuilder">
+      <property name="ObjectIdForDebugger" />
+    </type>
+    <type fullname="System.Runtime.CompilerServices.AsyncTaskMethodBuilder*">
+      <property name="ObjectIdForDebugger" />
+    </type>
+    <type fullname="System.Threading.Tasks.Task">
+      <!-- Methods is used by VS Tasks Window. -->
+      <method name="GetActiveTaskFromId" />
+    </type>
+    <!-- Accessed via private reflection by tracing controller. -->
+    <type fullname="System.Diagnostics.Tracing.EventPipe*" />
+  </assembly>
+</linker>
diff --git a/src/System.Private.CoreLib/MembersMustExist.AnalyzerData b/src/System.Private.CoreLib/MembersMustExist.AnalyzerData
new file mode 100644
index 0000000000..b5e7a6d742
--- /dev/null
+++ b/src/System.Private.CoreLib/MembersMustExist.AnalyzerData
@@ -0,0 +1,3 @@
+# Visual Studio
+private int System.Threading.Thread._managedThreadId
+
diff --git a/src/System.Private.CoreLib/PinvokeAnalyzerExceptionList.analyzerdata b/src/System.Private.CoreLib/PinvokeAnalyzerExceptionList.analyzerdata
new file mode 100644
index 0000000000..4bbdccae19
--- /dev/null
+++ b/src/System.Private.CoreLib/PinvokeAnalyzerExceptionList.analyzerdata
@@ -0,0 +1,3 @@
+<!-- Not a bug, these APIs are in the allowed list but under kernel32 and we need it under normaliz.dll -->
+normaliz.dll!IsNormalizedString
+normaliz.dll!NormalizeString
diff --git a/src/System.Private.CoreLib/Resources/Strings.resx b/src/System.Private.CoreLib/Resources/Strings.resx
new file mode 100644
index 0000000000..cb7243ae09
--- /dev/null
+++ b/src/System.Private.CoreLib/Resources/Strings.resx
@@ -0,0 +1,3736 @@
+<?xml version="1.0" encoding="utf-8"?>
+<root>
+  <!-- 
+    Microsoft ResX Schema 
+    
+    Version 2.0
+    
+    The primary goals of this format is to allow a simple XML format 
+    that is mostly human readable. The generation and parsing of the 
+    various data types are done through the TypeConverter classes 
+    associated with the data types.
+    
+    Example:
+    
+    ... ado.net/XML headers & schema ...
+    <resheader name="resmimetype">text/microsoft-resx</resheader>
+    <resheader name="version">2.0</resheader>
+    <resheader name="reader">System.Resources.ResXResourceReader, System.Windows.Forms, ...</resheader>
+    <resheader name="writer">System.Resources.ResXResourceWriter, System.Windows.Forms, ...</resheader>
+    <data name="Name1"><value>this is my long string</value><comment>this is a comment</comment></data>
+    <data name="Color1" type="System.Drawing.Color, System.Drawing">Blue</data>
+    <data name="Bitmap1" mimetype="application/x-microsoft.net.object.binary.base64">
+        <value>[base64 mime encoded serialized .NET Framework object]</value>
+    </data>
+    <data name="Icon1" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
+        <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
+        <comment>This is a comment</comment>
+    </data>
+                
+    There are any number of "resheader" rows that contain simple 
+    name/value pairs.
+    
+    Each data row contains a name, and value. The row also contains a 
+    type or mimetype. Type corresponds to a .NET class that support 
+    text/value conversion through the TypeConverter architecture. 
+    Classes that don't support this are serialized and stored with the 
+    mimetype set.
+    
+    The mimetype is used for serialized objects, and tells the 
+    ResXResourceReader how to depersist the object. This is currently not 
+    extensible. For a given mimetype the value must be set accordingly:
+    
+    Note - application/x-microsoft.net.object.binary.base64 is the format 
+    that the ResXResourceWriter will generate, however the reader can 
+    read any of the formats listed below.
+    
+    mimetype: application/x-microsoft.net.object.binary.base64
+    value   : The object must be serialized with 
+            : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
+            : and then encoded with base64 encoding.
+    
+    mimetype: application/x-microsoft.net.object.soap.base64
+    value   : The object must be serialized with 
+            : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.bytearray.base64
+    value   : The object must be serialized into a byte array 
+            : using a System.ComponentModel.TypeConverter
+            : and then encoded with base64 encoding.
+    -->
+  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
+    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
+    <xsd:element name="root" msdata:IsDataSet="true">
+      <xsd:complexType>
+        <xsd:choice maxOccurs="unbounded">
+          <xsd:element name="metadata">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" />
+              </xsd:sequence>
+              <xsd:attribute name="name" use="required" type="xsd:string" />
+              <xsd:attribute name="type" type="xsd:string" />
+              <xsd:attribute name="mimetype" type="xsd:string" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="assembly">
+            <xsd:complexType>
+              <xsd:attribute name="alias" type="xsd:string" />
+              <xsd:attribute name="name" type="xsd:string" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="data">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
+              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
+              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="resheader">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" />
+            </xsd:complexType>
+          </xsd:element>
+        </xsd:choice>
+      </xsd:complexType>
+    </xsd:element>
+  </xsd:schema>
+  <resheader name="resmimetype">
+    <value>text/microsoft-resx</value>
+  </resheader>
+  <resheader name="version">
+    <value>2.0</value>
+  </resheader>
+  <resheader name="reader">
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <resheader name="writer">
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <data name="Acc_CreateAbst" xml:space="preserve">
+    <value>Cannot create an abstract class.</value>
+  </data>
+  <data name="Acc_CreateAbstEx" xml:space="preserve">
+    <value>Cannot create an instance of {0} because it is an abstract class.</value>
+  </data>
+  <data name="Acc_CreateArgIterator" xml:space="preserve">
+    <value>Cannot dynamically create an instance of ArgIterator.</value>
+  </data>
+  <data name="Acc_CreateGeneric" xml:space="preserve">
+    <value>Cannot create a type for which Type.ContainsGenericParameters is true.</value>
+  </data>
+  <data name="Acc_CreateGenericEx" xml:space="preserve">
+    <value>Cannot create an instance of {0} because Type.ContainsGenericParameters is true.</value>
+  </data>
+  <data name="Acc_CreateInterface" xml:space="preserve">
+    <value>Cannot create an instance of an interface.</value>
+  </data>
+  <data name="Acc_CreateInterfaceEx" xml:space="preserve">
+    <value>Cannot create an instance of {0} because it is an interface.</value>
+  </data>
+  <data name="Acc_CreateVoid" xml:space="preserve">
+    <value>Cannot dynamically create an instance of System.Void.</value>
+  </data>
+  <data name="Acc_NotClassInit" xml:space="preserve">
+    <value>Type initializer was not callable.</value>
+  </data>
+  <data name="Acc_ReadOnly" xml:space="preserve">
+    <value>Cannot set a constant field.</value>
+  </data>
+  <data name="Access_Void" xml:space="preserve">
+    <value>Cannot create an instance of void.</value>
+  </data>
+  <data name="AggregateException_ctor_DefaultMessage" xml:space="preserve">
+    <value>One or more errors occurred.</value>
+  </data>
+  <data name="AggregateException_ctor_InnerExceptionNull" xml:space="preserve">
+    <value>An element of innerExceptions was null.</value>
+  </data>
+  <data name="AggregateException_DeserializationFailure" xml:space="preserve">
+    <value>The serialization stream contains no inner exceptions.</value>
+  </data>
+  <data name="AggregateException_InnerException" xml:space="preserve">
+    <value>(Inner Exception #{0}) </value>
+    <comment>This text is prepended to each inner exception description during aggregate exception formatting</comment>
+  </data>
+  <data name="AppDomain_AppBaseNotSet" xml:space="preserve">
+    <value>The ApplicationBase must be set before retrieving this property.</value>
+  </data>
+  <data name="Arg_AccessException" xml:space="preserve">
+    <value>Cannot access member.</value>
+  </data>
+  <data name="Arg_AccessViolationException" xml:space="preserve">
+    <value>Attempted to read or write protected memory. This is often an indication that other memory is corrupt.</value>
+  </data>
+  <data name="Arg_AmbiguousMatchException" xml:space="preserve">
+    <value>Ambiguous match found.</value>
+  </data>
+  <data name="Arg_AppDomainUnloadedException" xml:space="preserve">
+    <value>Attempted to access an unloaded AppDomain.</value>
+  </data>
+  <data name="Arg_ApplicationException" xml:space="preserve">
+    <value>Error in the application.</value>
+  </data>
+  <data name="Arg_ArgumentException" xml:space="preserve">
+    <value>Value does not fall within the expected range.</value>
+  </data>
+  <data name="Arg_ArgumentOutOfRangeException" xml:space="preserve">
+    <value>Specified argument was out of the range of valid values.</value>
+  </data>
+  <data name="Arg_ArithmeticException" xml:space="preserve">
+    <value>Overflow or underflow in the arithmetic operation.</value>
+  </data>
+  <data name="Arg_ArrayLengthsDiffer" xml:space="preserve">
+    <value>Array lengths must be the same.</value>
+  </data>
+  <data name="Arg_ArrayPlusOffTooSmall" xml:space="preserve">
+    <value>Destination array is not long enough to copy all the items in the collection. Check array index and length.</value>
+  </data>
+  <data name="Arg_ArrayTypeMismatchException" xml:space="preserve">
+    <value>Attempted to access an element as a type incompatible with the array.</value>
+  </data>
+  <data name="Arg_ArrayZeroError" xml:space="preserve">
+    <value>Array must not be of length zero.</value>
+  </data>
+  <data name="Arg_BadDecimal" xml:space="preserve">
+    <value>Read an invalid decimal value from the buffer.</value>
+  </data>
+  <data name="Arg_BadImageFormatException" xml:space="preserve">
+    <value>Format of the executable (.exe) or library (.dll) is invalid.</value>
+  </data>
+  <data name="Arg_BadLiteralFormat" xml:space="preserve">
+    <value>Encountered an invalid type for a default value.</value>
+  </data>
+  <data name="Arg_BogusIComparer" xml:space="preserve">
+    <value>Unable to sort because the IComparer.Compare() method returns inconsistent results. Either a value does not compare equal to itself, or one value repeatedly compared to another value yields different results. IComparer: '{0}'.</value>
+  </data>
+  <data name="Arg_BufferTooSmall" xml:space="preserve">
+    <value>Not enough space available in the buffer.</value>
+  </data>
+  <data name="Arg_CannotBeNaN" xml:space="preserve">
+    <value>TimeSpan does not accept floating point Not-a-Number values.</value>
+  </data>
+  <data name="Arg_CannotHaveNegativeValue" xml:space="preserve">
+    <value>String cannot contain a minus sign if the base is not 10.</value>
+  </data>
+  <data name="Arg_CannotMixComparisonInfrastructure" xml:space="preserve">
+    <value>The usage of IKeyComparer and IHashCodeProvider/IComparer interfaces cannot be mixed; use one or the other.</value>
+  </data>
+  <data name="Arg_CATypeResolutionFailed" xml:space="preserve">
+    <value>Failed to resolve type from string "{0}" which was embedded in custom attribute blob.</value>
+  </data>
+  <data name="Arg_COMAccess" xml:space="preserve">
+    <value>Must specify property Set or Get or method call for a COM Object.</value>
+  </data>
+  <data name="Arg_COMException" xml:space="preserve">
+    <value>Error HRESULT E_FAIL has been returned from a call to a COM component.</value>
+  </data>
+  <data name="Arg_COMPropSetPut" xml:space="preserve">
+    <value>Only one of the following binding flags can be set: BindingFlags.SetProperty, BindingFlags.PutDispProperty,  BindingFlags.PutRefDispProperty.</value>
+  </data>
+  <data name="Arg_CreatInstAccess" xml:space="preserve">
+    <value>Cannot specify both CreateInstance and another access type.</value>
+  </data>
+  <data name="Arg_CryptographyException" xml:space="preserve">
+    <value>Error occurred during a cryptographic operation.</value>
+  </data>
+  <data name="Arg_CustomAttributeFormatException" xml:space="preserve">
+    <value>Binary format of the specified custom attribute was invalid.</value>
+  </data>
+  <data name="Arg_DataMisalignedException" xml:space="preserve">
+    <value>A datatype misalignment was detected in a load or store instruction.</value>
+  </data>
+  <data name="Arg_DateTimeRange" xml:space="preserve">
+    <value>Combination of arguments to the DateTime constructor is out of the legal range.</value>
+  </data>
+  <data name="Arg_DecBitCtor" xml:space="preserve">
+    <value>Decimal byte array constructor requires an array of length four containing valid decimal bytes.</value>
+  </data>
+  <data name="Arg_DirectoryNotFoundException" xml:space="preserve">
+    <value>Attempted to access a path that is not on the disk.</value>
+  </data>
+  <data name="Arg_DivideByZero" xml:space="preserve">
+    <value>Attempted to divide by zero.</value>
+  </data>
+  <data name="Arg_DlgtNullInst" xml:space="preserve">
+    <value>Delegate to an instance method cannot have null 'this'.</value>
+  </data>
+  <data name="Arg_DlgtTargMeth" xml:space="preserve">
+    <value>Cannot bind to the target method because its signature or security transparency is not compatible with that of the delegate type.</value>
+  </data>
+  <data name="Arg_DlgtTypeMis" xml:space="preserve">
+    <value>Delegates must be of the same type.</value>
+  </data>
+  <data name="Arg_DllNotFoundException" xml:space="preserve">
+    <value>Dll was not found.</value>
+  </data>
+  <data name="Arg_DriveNotFoundException" xml:space="preserve">
+    <value>Attempted to access a drive that is not available.</value>
+  </data>
+  <data name="Arg_DuplicateWaitObjectException" xml:space="preserve">
+    <value>Duplicate objects in argument.</value>
+  </data>
+  <data name="Arg_EHClauseNotClause" xml:space="preserve">
+    <value>This ExceptionHandlingClause is not a clause.</value>
+  </data>
+  <data name="Arg_EHClauseNotFilter" xml:space="preserve">
+    <value>This ExceptionHandlingClause is not a filter.</value>
+  </data>
+  <data name="Arg_EmptyArray" xml:space="preserve">
+    <value>Array may not be empty.</value>
+  </data>
+  <data name="Arg_EmptyOrNullString" xml:space="preserve">
+    <value>String may not be empty or null.</value>
+  </data>
+  <data name="Arg_EndOfStreamException" xml:space="preserve">
+    <value>Attempted to read past the end of the stream.</value>
+  </data>
+  <data name="Arg_EntryPointNotFoundException" xml:space="preserve">
+    <value>Entry point was not found.</value>
+  </data>
+  <data name="Arg_EnumAndObjectMustBeSameType" xml:space="preserve">
+    <value>Object must be the same type as the enum. The type passed in was '{0}'; the enum type was '{1}'.</value>
+  </data>
+  <data name="Arg_EnumFormatUnderlyingTypeAndObjectMustBeSameType" xml:space="preserve">
+    <value>Enum underlying type and the object must be same type or object. Type passed in was '{0}'; the enum underlying type was '{1}'.</value>
+  </data>
+  <data name="Arg_EnumIllegalVal" xml:space="preserve">
+    <value>Illegal enum value: {0}.</value>
+  </data>
+  <data name="Arg_EnumLitValueNotFound" xml:space="preserve">
+    <value>Literal value was not found.</value>
+  </data>
+  <data name="Arg_EnumUnderlyingTypeAndObjectMustBeSameType" xml:space="preserve">
+    <value>Enum underlying type and the object must be same type or object must be a String. Type passed in was '{0}'; the enum underlying type was '{1}'.</value>
+  </data>
+  <data name="Arg_EnumValueNotFound" xml:space="preserve">
+    <value>Requested value '{0}' was not found.</value>
+  </data>
+  <data name="Arg_ExecutionEngineException" xml:space="preserve">
+    <value>Internal error in the runtime.</value>
+  </data>
+  <data name="Arg_ExternalException" xml:space="preserve">
+    <value>External component has thrown an exception.</value>
+  </data>
+  <data name="Arg_FieldAccessException" xml:space="preserve">
+    <value>Attempted to access a field that is not accessible by the caller.</value>
+  </data>
+  <data name="Arg_FieldDeclTarget" xml:space="preserve">
+    <value>Field '{0}' defined on type '{1}' is not a field on the target object which is of type '{2}'.</value>
+  </data>
+  <data name="Arg_FldGetArgErr" xml:space="preserve">
+    <value>No arguments can be provided to Get a field value.</value>
+  </data>
+  <data name="Arg_FldGetPropSet" xml:space="preserve">
+    <value>Cannot specify both GetField and SetProperty.</value>
+  </data>
+  <data name="Arg_FldSetArgErr" xml:space="preserve">
+    <value>Only the field value can be specified to set a field value.</value>
+  </data>
+  <data name="Arg_FldSetGet" xml:space="preserve">
+    <value>Cannot specify both Get and Set on a field.</value>
+  </data>
+  <data name="Arg_FldSetInvoke" xml:space="preserve">
+    <value>Cannot specify Set on a Field and Invoke on a method.</value>
+  </data>
+  <data name="Arg_FldSetPropGet" xml:space="preserve">
+    <value>Cannot specify both SetField and GetProperty.</value>
+  </data>
+  <data name="Arg_FormatException" xml:space="preserve">
+    <value>One of the identified items was in an invalid format.</value>
+  </data>
+  <data name="Arg_GenericParameter" xml:space="preserve">
+    <value>Method must be called on a Type for which Type.IsGenericParameter is false.</value>
+  </data>
+  <data name="Arg_GetMethNotFnd" xml:space="preserve">
+    <value>Property Get method was not found.</value>
+  </data>
+  <data name="Arg_GuidArrayCtor" xml:space="preserve">
+    <value>Byte array for GUID must be exactly {0} bytes long.</value>
+  </data>
+  <data name="Arg_HandleNotAsync" xml:space="preserve">
+    <value>Handle does not support asynchronous operations. The parameters to the FileStream constructor may need to be changed to indicate that the handle was opened synchronously (that is, it was not opened for overlapped I/O).</value>
+  </data>
+  <data name="Arg_HandleNotSync" xml:space="preserve">
+    <value>Handle does not support synchronous operations. The parameters to the FileStream constructor may need to be changed to indicate that the handle was opened asynchronously (that is, it was opened explicitly for overlapped I/O).</value>
+  </data>
+  <data name="Arg_HexStyleNotSupported" xml:space="preserve">
+    <value>The number style AllowHexSpecifier is not supported on floating point data types.</value>
+  </data>
+  <data name="Arg_HTCapacityOverflow" xml:space="preserve">
+    <value>Hashtable's capacity overflowed and went negative. Check load factor, capacity and the current size of the table.</value>
+  </data>
+  <data name="Arg_IndexMustBeInt" xml:space="preserve">
+    <value>All indexes must be of type Int32.</value>
+  </data>
+  <data name="Arg_IndexOutOfRangeException" xml:space="preserve">
+    <value>Index was outside the bounds of the array.</value>
+  </data>
+  <data name="Arg_InsufficientExecutionStackException" xml:space="preserve">
+    <value>Insufficient stack to continue executing the program safely. This can happen from having too many functions on the call stack or function on the stack using too much stack space.</value>
+  </data>
+  <data name="Arg_InvalidANSIString" xml:space="preserve">
+    <value>The ANSI string passed in could not be converted from the default ANSI code page to Unicode.</value>
+  </data>
+  <data name="Arg_InvalidBase" xml:space="preserve">
+    <value>Invalid Base.</value>
+  </data>
+  <data name="Arg_InvalidCastException" xml:space="preserve">
+    <value>Specified cast is not valid.</value>
+  </data>
+  <data name="Arg_InvalidComObjectException" xml:space="preserve">
+    <value>Attempt has been made to use a COM object that does not have a backing class factory.</value>
+  </data>
+  <data name="Arg_InvalidFilterCriteriaException" xml:space="preserve">
+    <value>Specified filter criteria was invalid.</value>
+  </data>
+  <data name="Arg_InvalidHandle" xml:space="preserve">
+    <value>Invalid handle.</value>
+  </data>
+  <data name="Arg_InvalidHexStyle" xml:space="preserve">
+    <value>With the AllowHexSpecifier bit set in the enum bit field, the only other valid bits that can be combined into the enum value must be a subset of those in HexNumber.</value>
+  </data>
+  <data name="Arg_InvalidNeutralResourcesLanguage_Asm_Culture" xml:space="preserve">
+    <value>The NeutralResourcesLanguageAttribute on the assembly "{0}" specifies an invalid culture name: "{1}".</value>
+  </data>
+  <data name="Arg_InvalidNeutralResourcesLanguage_FallbackLoc" xml:space="preserve">
+    <value>The NeutralResourcesLanguageAttribute specifies an invalid or unrecognized ultimate resource fallback location: "{0}".</value>
+  </data>
+  <data name="Arg_InvalidOleVariantTypeException" xml:space="preserve">
+    <value>Specified OLE variant was invalid.</value>
+  </data>
+  <data name="Arg_InvalidOperationException" xml:space="preserve">
+    <value>Operation is not valid due to the current state of the object.</value>
+  </data>
+  <data name="Arg_InvalidSearchPattern" xml:space="preserve">
+    <value>Search pattern '{0}' cannot contain ".." to move up directories and can be contained only internally in file/directory names, as in "a..b".</value>
+  </data>
+  <data name="Arg_InvalidTypeInRetType" xml:space="preserve">
+    <value>The return Type must be a type provided by the runtime.</value>
+  </data>
+  <data name="Arg_InvalidTypeInSignature" xml:space="preserve">
+    <value>The signature Type array contains some invalid type (i.e. null, void)</value>
+  </data>
+  <data name="Arg_InvalidUTF8String" xml:space="preserve">
+    <value>The UTF8 string passed in could not be converted to Unicode.</value>
+  </data>
+  <data name="Arg_IOException" xml:space="preserve">
+    <value>I/O error occurred.</value>
+  </data>
+  <data name="Arg_KeyNotFound" xml:space="preserve">
+    <value>The given key was not present in the dictionary.</value>
+  </data>
+  <data name="Arg_KeyNotFoundWithKey" xml:space="preserve">
+    <value>The given key '{0}' was not present in the dictionary.</value>
+  </data>
+  <data name="Arg_LongerThanDestArray" xml:space="preserve">
+    <value>Destination array was not long enough. Check the destination index, length, and the array's lower bounds.</value>
+  </data>
+  <data name="Arg_LongerThanSrcArray" xml:space="preserve">
+    <value>Source array was not long enough. Check the source index, length, and the array's lower bounds.</value>
+  </data>
+  <data name="Arg_LongerThanSrcString" xml:space="preserve">
+    <value>Source string was not long enough. Check sourceIndex and count.</value>
+  </data>
+  <data name="Arg_LowerBoundsMustMatch" xml:space="preserve">
+    <value>The arrays' lower bounds must be identical.</value>
+  </data>
+  <data name="Arg_MarshalAsAnyRestriction" xml:space="preserve">
+    <value>AsAny cannot be used on return types, ByRef parameters, ArrayWithOffset, or parameters passed from unmanaged to managed.</value>
+  </data>
+  <data name="Arg_MarshalDirectiveException" xml:space="preserve">
+    <value>Marshaling directives are invalid.</value>
+  </data>
+  <data name="Arg_MethodAccessException" xml:space="preserve">
+    <value>Attempt to access the method failed.</value>
+  </data>
+  <data name="Arg_MethodAccessException_WithMethodName" xml:space="preserve">
+    <value>Attempt to access the method "{0}" on type "{1}" failed.</value>
+  </data>
+  <data name="Arg_MissingFieldException" xml:space="preserve">
+    <value>Attempted to access a non-existing field.</value>
+  </data>
+  <data name="Arg_MissingManifestResourceException" xml:space="preserve">
+    <value>Unable to find manifest resource.</value>
+  </data>
+  <data name="Arg_MissingMemberException" xml:space="preserve">
+    <value>Attempted to access a missing member.</value>
+  </data>
+  <data name="Arg_MissingMethodException" xml:space="preserve">
+    <value>Attempted to access a missing method.</value>
+  </data>
+  <data name="Arg_MulticastNotSupportedException" xml:space="preserve">
+    <value>Attempted to add multiple callbacks to a delegate that does not support multicast.</value>
+  </data>
+  <data name="Arg_MustBeBoolean" xml:space="preserve">
+    <value>Object must be of type Boolean.</value>
+  </data>
+  <data name="Arg_MustBeByte" xml:space="preserve">
+    <value>Object must be of type Byte.</value>
+  </data>
+  <data name="Arg_MustBeChar" xml:space="preserve">
+    <value>Object must be of type Char.</value>
+  </data>
+  <data name="Arg_MustBeDateTime" xml:space="preserve">
+    <value>Object must be of type DateTime.</value>
+  </data>
+  <data name="Arg_MustBeDateTimeOffset" xml:space="preserve">
+    <value>Object must be of type DateTimeOffset.</value>
+  </data>
+  <data name="Arg_MustBeDecimal" xml:space="preserve">
+    <value>Object must be of type Decimal.</value>
+  </data>
+  <data name="Arg_MustBeDelegate" xml:space="preserve">
+    <value>Type must derive from Delegate.</value>
+  </data>
+  <data name="Arg_MustBeDouble" xml:space="preserve">
+    <value>Object must be of type Double.</value>
+  </data>
+  <data name="Arg_MustBeEnum" xml:space="preserve">
+    <value>Type provided must be an Enum.</value>
+  </data>
+  <data name="Arg_MustBeEnumBaseTypeOrEnum" xml:space="preserve">
+    <value>The value passed in must be an enum base or an underlying type for an enum, such as an Int32.</value>
+  </data>
+  <data name="Arg_MustBeGuid" xml:space="preserve">
+    <value>Object must be of type GUID.</value>
+  </data>
+  <data name="Arg_MustBeInt16" xml:space="preserve">
+    <value>Object must be of type Int16.</value>
+  </data>
+  <data name="Arg_MustBeInt32" xml:space="preserve">
+    <value>Object must be of type Int32.</value>
+  </data>
+  <data name="Arg_MustBeInt64" xml:space="preserve">
+    <value>Object must be of type Int64.</value>
+  </data>
+  <data name="Arg_MustBeInterface" xml:space="preserve">
+    <value>Type passed must be an interface.</value>
+  </data>
+  <data name="Arg_MustBePointer" xml:space="preserve">
+    <value>Type must be a Pointer.</value>
+  </data>
+  <data name="Arg_MustBePrimArray" xml:space="preserve">
+    <value>Object must be an array of primitives.</value>
+  </data>
+  <data name="Arg_MustBeSByte" xml:space="preserve">
+    <value>Object must be of type SByte.</value>
+  </data>
+  <data name="Arg_MustBeSingle" xml:space="preserve">
+    <value>Object must be of type Single.</value>
+  </data>
+  <data name="Arg_MustBeStatic" xml:space="preserve">
+    <value>Method must be a static method.</value>
+  </data>
+  <data name="Arg_MustBeString" xml:space="preserve">
+    <value>Object must be of type String.</value>
+  </data>
+  <data name="Arg_MustBeTimeSpan" xml:space="preserve">
+    <value>Object must be of type TimeSpan.</value>
+  </data>
+  <data name="Arg_MustBeType" xml:space="preserve">
+    <value>Type must be a type provided by the runtime.</value>
+  </data>
+  <data name="Arg_MustBeUInt16" xml:space="preserve">
+    <value>Object must be of type UInt16.</value>
+  </data>
+  <data name="Arg_MustBeUInt32" xml:space="preserve">
+    <value>Object must be of type UInt32.</value>
+  </data>
+  <data name="Arg_MustBeUInt64" xml:space="preserve">
+    <value>Object must be of type UInt64.</value>
+  </data>
+  <data name="Arg_MustBeVersion" xml:space="preserve">
+    <value>Object must be of type Version.</value>
+  </data>
+  <data name="Arg_MustContainEnumInfo" xml:space="preserve">
+    <value>Must specify valid information for parsing in the string.</value>
+  </data>
+  <data name="Arg_NamedParamNull" xml:space="preserve">
+    <value>Named parameter value must not be null.</value>
+  </data>
+  <data name="Arg_NamedParamTooBig" xml:space="preserve">
+    <value>Named parameter array cannot be bigger than argument array.</value>
+  </data>
+  <data name="Arg_NDirectBadObject" xml:space="preserve">
+    <value>No PInvoke conversion exists for value passed to Object-typed parameter.</value>
+  </data>
+  <data name="Arg_Need1DArray" xml:space="preserve">
+    <value>Array was not a one-dimensional array.</value>
+  </data>
+  <data name="Arg_Need2DArray" xml:space="preserve">
+    <value>Array was not a two-dimensional array.</value>
+  </data>
+  <data name="Arg_Need3DArray" xml:space="preserve">
+    <value>Array was not a three-dimensional array.</value>
+  </data>
+  <data name="Arg_NeedAtLeast1Rank" xml:space="preserve">
+    <value>Must provide at least one rank.</value>
+  </data>
+  <data name="Arg_NegativeArgCount" xml:space="preserve">
+    <value>Argument count must not be negative.</value>
+  </data>
+  <data name="Arg_NoAccessSpec" xml:space="preserve">
+    <value>Must specify binding flags describing the invoke operation required (BindingFlags.InvokeMethod CreateInstance GetField SetField GetProperty SetProperty).</value>
+  </data>
+  <data name="Arg_NoDefCTor" xml:space="preserve">
+    <value>No parameterless constructor defined for this object.</value>
+  </data>
+  <data name="Arg_NoITypeInfo" xml:space="preserve">
+    <value>Specified TypeInfo was invalid because it did not support the ITypeInfo interface.</value>
+  </data>
+  <data name="Arg_NoITypeLib" xml:space="preserve">
+    <value>Specified TypeLib was invalid because it did not support the ITypeLib interface.</value>
+  </data>
+  <data name="Arg_NonZeroLowerBound" xml:space="preserve">
+    <value>The lower bound of target array must be zero.</value>
+  </data>
+  <data name="Arg_NoStaticVirtual" xml:space="preserve">
+    <value>Method cannot be both static and virtual.</value>
+  </data>
+  <data name="Arg_NotFiniteNumberException" xml:space="preserve">
+    <value>Number encountered was not a finite quantity.</value>
+  </data>
+  <data name="Arg_NotFoundIFace" xml:space="preserve">
+    <value>Interface not found.</value>
+  </data>
+  <data name="Arg_NotGenericMethodDefinition" xml:space="preserve">
+    <value>{0} is not a GenericMethodDefinition. MakeGenericMethod may only be called on a method for which MethodBase.IsGenericMethodDefinition is true.</value>
+  </data>
+  <data name="Arg_NotGenericParameter" xml:space="preserve">
+    <value>Method may only be called on a Type for which Type.IsGenericParameter is true.</value>
+  </data>
+  <data name="Arg_NotGenericTypeDefinition" xml:space="preserve">
+    <value>{0} is not a GenericTypeDefinition. MakeGenericType may only be called on a type for which Type.IsGenericTypeDefinition is true.</value>
+  </data>
+  <data name="Arg_NotImplementedException" xml:space="preserve">
+    <value>The method or operation is not implemented.</value>
+  </data>
+  <data name="Arg_NotSupportedException" xml:space="preserve">
+    <value>Specified method is not supported.</value>
+  </data>
+  <data name="Arg_NullIndex" xml:space="preserve">
+    <value>Arrays indexes must be set to an object instance.</value>
+  </data>
+  <data name="Arg_NullReferenceException" xml:space="preserve">
+    <value>Object reference not set to an instance of an object.</value>
+  </data>
+  <data name="Arg_ObjObj" xml:space="preserve">
+    <value>Object type cannot be converted to target type.</value>
+  </data>
+  <data name="Arg_ObjObjEx" xml:space="preserve">
+    <value>Object of type '{0}' cannot be converted to type '{1}'.</value>
+  </data>
+  <data name="Arg_OleAutDateInvalid" xml:space="preserve">
+    <value>Not a legal OleAut date.</value>
+  </data>
+  <data name="Arg_OleAutDateScale" xml:space="preserve">
+    <value>OleAut date did not convert to a DateTime correctly.</value>
+  </data>
+  <data name="Arg_OverflowException" xml:space="preserve">
+    <value>Arithmetic operation resulted in an overflow.</value>
+  </data>
+  <data name="Arg_ParamName_Name" xml:space="preserve">
+    <value>Parameter name: {0}</value>
+  </data>
+  <data name="Arg_ParmArraySize" xml:space="preserve">
+    <value>Must specify one or more parameters.</value>
+  </data>
+  <data name="Arg_ParmCnt" xml:space="preserve">
+    <value>Parameter count mismatch.</value>
+  </data>
+  <data name="Arg_PathEmpty" xml:space="preserve">
+    <value>The path is empty.</value>
+  </data>
+  <data name="Arg_PathIllegalUNC_Path" xml:space="preserve">
+    <value>The UNC path '{0}' should be of the form \\\\server\\share.</value>
+  </data>
+  <data name="Arg_PlatformNotSupported" xml:space="preserve">
+    <value>Operation is not supported on this platform.</value>
+  </data>
+  <data name="Arg_PrimWiden" xml:space="preserve">
+    <value>Cannot widen from source type to target type either because the source type is a not a primitive type or the conversion cannot be accomplished.</value>
+  </data>
+  <data name="Arg_PropSetGet" xml:space="preserve">
+    <value>Cannot specify both Get and Set on a property.</value>
+  </data>
+  <data name="Arg_PropSetInvoke" xml:space="preserve">
+    <value>Cannot specify Set on a property and Invoke on a method.</value>
+  </data>
+  <data name="Arg_RankException" xml:space="preserve">
+    <value>Attempted to operate on an array with the incorrect number of dimensions.</value>
+  </data>
+  <data name="Arg_RankIndices" xml:space="preserve">
+    <value>Indices length does not match the array rank.</value>
+  </data>
+  <data name="Arg_RankMultiDimNotSupported" xml:space="preserve">
+    <value>Only single dimensional arrays are supported for the requested action.</value>
+  </data>
+  <data name="Arg_RanksAndBounds" xml:space="preserve">
+    <value>Number of lengths and lowerBounds must match.</value>
+  </data>
+  <data name="Arg_ReflectionOnlyCA" xml:space="preserve">
+    <value>It is illegal to reflect on the custom attributes of a Type loaded via ReflectionOnlyGetType (see Assembly.ReflectionOnly) -- use CustomAttributeData instead.</value>
+  </data>
+  <data name="Arg_ReflectionOnlyField" xml:space="preserve">
+    <value>It is illegal to get or set the value on a field on a Type loaded via ReflectionOnlyGetType.</value>
+  </data>
+  <data name="Arg_ReflectionOnlyInvoke" xml:space="preserve">
+    <value>It is illegal to invoke a method on a Type loaded via ReflectionOnlyGetType.</value>
+  </data>
+  <data name="Arg_RegBadKeyKind" xml:space="preserve">
+    <value>The specified RegistryValueKind is an invalid value.</value>
+  </data>
+  <data name="Arg_RegGetOverflowBug" xml:space="preserve">
+    <value>RegistryKey.GetValue does not allow a String that has a length greater than Int32.MaxValue.</value>
+  </data>
+  <data name="Arg_RegInvalidKeyName" xml:space="preserve">
+    <value>Registry key name must start with a valid base key name.</value>
+  </data>
+  <data name="Arg_RegKeyNotFound" xml:space="preserve">
+    <value>The specified registry key does not exist.</value>
+  </data>
+  <data name="Arg_RegKeyStrLenBug" xml:space="preserve">
+    <value>Registry key names should not be greater than 255 characters.</value>
+  </data>
+  <data name="Arg_RegSetBadArrType" xml:space="preserve">
+    <value>RegistryKey.SetValue does not support arrays of type '{0}'. Only Byte[] and String[] are supported.</value>
+  </data>
+  <data name="Arg_RegSetMismatchedKind" xml:space="preserve">
+    <value>The type of the value object did not match the specified RegistryValueKind or the object could not be properly converted.</value>
+  </data>
+  <data name="Arg_RegSetStrArrNull" xml:space="preserve">
+    <value>RegistryKey.SetValue does not allow a String[] that contains a null String reference.</value>
+  </data>
+  <data name="Arg_RegSubKeyValueAbsent" xml:space="preserve">
+    <value>No value exists with that name.</value>
+  </data>
+  <data name="Arg_RegValStrLenBug" xml:space="preserve">
+    <value>Registry value names should not be greater than 16,383 characters.</value>
+  </data>
+  <data name="Arg_RemoveArgNotFound" xml:space="preserve">
+    <value>Cannot remove the specified item because it was not found in the specified Collection.</value>
+  </data>
+  <data name="Arg_ResMgrNotResSet" xml:space="preserve">
+    <value>Type parameter must refer to a subclass of ResourceSet.</value>
+  </data>
+  <data name="Arg_ResourceFileUnsupportedVersion" xml:space="preserve">
+    <value>The ResourceReader class does not know how to read this version of .resources files. Expected version: {0}  This file: {1}</value>
+  </data>
+  <data name="Arg_ResourceNameNotExist" xml:space="preserve">
+    <value>The specified resource name "{0}" does not exist in the resource file.</value>
+  </data>
+  <data name="Arg_SafeArrayRankMismatchException" xml:space="preserve">
+    <value>Specified array was not of the expected rank.</value>
+  </data>
+  <data name="Arg_SafeArrayTypeMismatchException" xml:space="preserve">
+    <value>Specified array was not of the expected type.</value>
+  </data>
+  <data name="Arg_SecurityException" xml:space="preserve">
+    <value>Security error.</value>
+  </data>
+  <data name="SerializationException" xml:space="preserve">
+    <value>Serialization error.</value>
+  </data>
+  <data name="Arg_SetMethNotFnd" xml:space="preserve">
+    <value>Property set method not found.</value>
+  </data>
+  <data name="Arg_StackOverflowException" xml:space="preserve">
+    <value>Operation caused a stack overflow.</value>
+  </data>
+  <data name="Arg_SurrogatesNotAllowedAsSingleChar" xml:space="preserve">
+    <value>Unicode surrogate characters must be written out as pairs together in the same call, not individually. Consider passing in a character array instead.</value>
+  </data>
+  <data name="Arg_SynchronizationLockException" xml:space="preserve">
+    <value>Object synchronization method was called from an unsynchronized block of code.</value>
+  </data>
+  <data name="Arg_SystemException" xml:space="preserve">
+    <value>System error.</value>
+  </data>
+  <data name="Arg_TargetInvocationException" xml:space="preserve">
+    <value>Exception has been thrown by the target of an invocation.</value>
+  </data>
+  <data name="Arg_TargetParameterCountException" xml:space="preserve">
+    <value>Number of parameters specified does not match the expected number.</value>
+  </data>
+  <data name="Arg_ThreadStartException" xml:space="preserve">
+    <value>Thread failed to start.</value>
+  </data>
+  <data name="Arg_ThreadStateException" xml:space="preserve">
+    <value>Thread was in an invalid state for the operation being executed.</value>
+  </data>
+  <data name="Arg_TimeoutException" xml:space="preserve">
+    <value>The operation has timed out.</value>
+  </data>
+  <data name="Arg_TypeAccessException" xml:space="preserve">
+    <value>Attempt to access the type failed.</value>
+  </data>
+  <data name="Arg_TypedReference_Null" xml:space="preserve">
+    <value>The TypedReference must be initialized.</value>
+  </data>
+  <data name="Arg_TypeLoadException" xml:space="preserve">
+    <value>Failure has occurred while loading a type.</value>
+  </data>
+  <data name="Arg_TypeLoadNullStr" xml:space="preserve">
+    <value>A null or zero length string does not represent a valid Type.</value>
+  </data>
+  <data name="Arg_TypeRefPrimitve" xml:space="preserve">
+    <value>TypedReferences cannot be redefined as primitives. Field name '{0}'.</value>
+  </data>
+  <data name="Arg_TypeUnloadedException" xml:space="preserve">
+    <value>Type had been unloaded.</value>
+  </data>
+  <data name="Arg_UnauthorizedAccessException" xml:space="preserve">
+    <value>Attempted to perform an unauthorized operation.</value>
+  </data>
+  <data name="Arg_UnboundGenField" xml:space="preserve">
+    <value>Late bound operations cannot be performed on fields with types for which Type.ContainsGenericParameters is true.</value>
+  </data>
+  <data name="Arg_UnboundGenParam" xml:space="preserve">
+    <value>Late bound operations cannot be performed on types or methods for which ContainsGenericParameters is true.</value>
+  </data>
+  <data name="Arg_UnknownTypeCode" xml:space="preserve">
+    <value>Unknown TypeCode value.</value>
+  </data>
+  <data name="Arg_VarMissNull" xml:space="preserve">
+    <value>Missing parameter does not have a default value.</value>
+  </data>
+  <data name="Arg_VersionString" xml:space="preserve">
+    <value>Version string portion was too short or too long.</value>
+  </data>
+  <data name="Arg_WrongAsyncResult" xml:space="preserve">
+    <value>IAsyncResult object did not come from the corresponding async method on this type.</value>
+  </data>
+  <data name="Arg_WrongType" xml:space="preserve">
+    <value>The value "{0}" is not of type "{1}" and cannot be used in this generic collection.</value>
+  </data>
+  <data name="Argument_AbsolutePathRequired" xml:space="preserve">
+    <value>Absolute path information is required.</value>
+  </data>
+  <data name="Argument_AddingDuplicate" xml:space="preserve">
+    <value>An item with the same key has already been added.</value>
+  </data>
+  <data name="Argument_AddingDuplicate__" xml:space="preserve">
+    <value>Item has already been added. Key in dictionary: '{0}'  Key being added: '{1}'</value>
+  </data>
+  <data name="Argument_AddingDuplicateWithKey" xml:space="preserve">
+    <value>An item with the same key has already been added. Key: {0}</value>
+  </data>
+  <data name="Argument_AdjustmentRulesNoNulls" xml:space="preserve">
+    <value>The AdjustmentRule array cannot contain null elements.</value>
+  </data>
+  <data name="Argument_AdjustmentRulesOutOfOrder" xml:space="preserve">
+    <value>The elements of the AdjustmentRule array must be in chronological order and must not overlap.</value>
+  </data>
+  <data name="Argument_AlreadyACCW" xml:space="preserve">
+    <value>The object already has a CCW associated with it.</value>
+  </data>
+  <data name="Argument_AlreadyBoundOrSyncHandle" xml:space="preserve">
+    <value>'handle' has already been bound to the thread pool, or was not opened for asynchronous I/O.</value>
+  </data>
+  <data name="Argument_ArgumentZero" xml:space="preserve">
+    <value>Argument cannot be zero.</value>
+  </data>
+  <data name="Argument_ArrayGetInterfaceMap" xml:space="preserve">
+    <value>Interface maps for generic interfaces on arrays cannot be retrieved.</value>
+  </data>
+  <data name="Argument_ArraysInvalid" xml:space="preserve">
+    <value>Array or pointer types are not valid.</value>
+  </data>
+  <data name="Argument_BadAttributeOnInterfaceMethod" xml:space="preserve">
+    <value>Interface method must be abstract and virtual.</value>
+  </data>
+  <data name="Argument_BadConstantValue" xml:space="preserve">
+    <value>Bad default value.</value>
+  </data>
+  <data name="Argument_BadConstructor" xml:space="preserve">
+    <value>Cannot have private or static constructor.</value>
+  </data>
+  <data name="Argument_BadConstructorCallConv" xml:space="preserve">
+    <value>Constructor must have standard calling convention.</value>
+  </data>
+  <data name="Argument_BadExceptionCodeGen" xml:space="preserve">
+    <value>Incorrect code generation for exception block.</value>
+  </data>
+  <data name="Argument_BadFieldForConstructorBuilder" xml:space="preserve">
+    <value>Field must be on the same type of the given ConstructorInfo.</value>
+  </data>
+  <data name="Argument_BadFieldSig" xml:space="preserve">
+    <value>Field signatures do not have return types.</value>
+  </data>
+  <data name="Argument_BadFieldType" xml:space="preserve">
+    <value>Bad field type in defining field.</value>
+  </data>
+  <data name="Argument_BadFormatSpecifier" xml:space="preserve">
+    <value>Format specifier was invalid.</value>
+  </data>
+  <data name="Argument_BadImageFormatExceptionResolve" xml:space="preserve">
+    <value>A BadImageFormatException has been thrown while parsing the signature. This is likely due to lack of a generic context. Ensure genericTypeArguments and genericMethodArguments are provided and contain enough context.</value>
+  </data>
+  <data name="Argument_BadLabel" xml:space="preserve">
+    <value>Bad label in ILGenerator.</value>
+  </data>
+  <data name="Argument_BadLabelContent" xml:space="preserve">
+    <value>Bad label content in ILGenerator.</value>
+  </data>
+  <data name="Argument_BadNestedTypeFlags" xml:space="preserve">
+    <value>Visibility of interfaces must be one of the following: NestedAssembly, NestedFamANDAssem, NestedFamily, NestedFamORAssem, NestedPrivate or NestedPublic.</value>
+  </data>
+  <data name="Argument_BadObjRef" xml:space="preserve">
+    <value>Invalid ObjRef provided to '{0}'.</value>
+  </data>
+  <data name="Argument_BadParameterCountsForConstructor" xml:space="preserve">
+    <value>Parameter count does not match passed in argument value count.</value>
+  </data>
+  <data name="Argument_BadParameterTypeForCAB" xml:space="preserve">
+    <value>Cannot emit a CustomAttribute with argument of type {0}.</value>
+  </data>
+  <data name="Argument_BadPropertyForConstructorBuilder" xml:space="preserve">
+    <value>Property must be on the same type of the given ConstructorInfo.</value>
+  </data>
+  <data name="Argument_BadSigFormat" xml:space="preserve">
+    <value>Incorrect signature format.</value>
+  </data>
+  <data name="Argument_BadSizeForData" xml:space="preserve">
+    <value>Data size must be &gt; 1 and &lt; 0x3f0000</value>
+  </data>
+  <data name="Argument_BadTypeAttrInvalidLayout" xml:space="preserve">
+    <value>Bad type attributes. Invalid layout attribute specified.</value>
+  </data>
+  <data name="Argument_BadTypeAttrNestedVisibilityOnNonNestedType" xml:space="preserve">
+    <value>Bad type attributes. Nested visibility flag set on a non-nested type.</value>
+  </data>
+  <data name="Argument_BadTypeAttrNonNestedVisibilityNestedType" xml:space="preserve">
+    <value>Bad type attributes. Non-nested visibility flag set on a nested type.</value>
+  </data>
+  <data name="Argument_BadTypeAttrReservedBitsSet" xml:space="preserve">
+    <value>Bad type attributes. Reserved bits set on the type.</value>
+  </data>
+  <data name="Argument_BadTypeInCustomAttribute" xml:space="preserve">
+    <value>An invalid type was used as a custom attribute constructor argument, field or property.</value>
+  </data>
+  <data name="Argument_CannotCreateTypedReference" xml:space="preserve">
+    <value>Cannot use function evaluation to create a TypedReference object.</value>
+  </data>
+  <data name="Argument_CannotGetTypeTokenForByRef" xml:space="preserve">
+    <value>Cannot get TypeToken for a ByRef type.</value>
+  </data>
+  <data name="Argument_CannotSetParentToInterface" xml:space="preserve">
+    <value>Cannot set parent to an interface.</value>
+  </data>
+  <data name="Argument_CodepageNotSupported" xml:space="preserve">
+    <value>{0} is not a supported code page.</value>
+  </data>
+  <data name="Argument_CompareOptionOrdinal" xml:space="preserve">
+    <value>CompareOption.Ordinal cannot be used with other options.</value>
+  </data>
+  <data name="Argument_ConflictingDateTimeRoundtripStyles" xml:space="preserve">
+    <value>The DateTimeStyles value RoundtripKind cannot be used with the values AssumeLocal, AssumeUniversal or AdjustToUniversal.</value>
+  </data>
+  <data name="Argument_ConflictingDateTimeStyles" xml:space="preserve">
+    <value>The DateTimeStyles values AssumeLocal and AssumeUniversal cannot be used together.</value>
+  </data>
+  <data name="Argument_ConstantDoesntMatch" xml:space="preserve">
+    <value>Constant does not match the defined type.</value>
+  </data>
+  <data name="Argument_ConstantNotSupported" xml:space="preserve">
+    <value>{0} is not a supported constant type.</value>
+  </data>
+  <data name="Argument_ConstantNull" xml:space="preserve">
+    <value>Null is not a valid constant value for this type.</value>
+  </data>
+  <data name="Argument_ConstructorNeedGenericDeclaringType" xml:space="preserve">
+    <value>The specified constructor must be declared on a generic type definition.</value>
+  </data>
+  <data name="Argument_ConversionOverflow" xml:space="preserve">
+    <value>Conversion buffer overflow.</value>
+  </data>
+  <data name="Argument_ConvertMismatch" xml:space="preserve">
+    <value>The conversion could not be completed because the supplied DateTime did not have the Kind property set correctly.  For example, when the Kind property is DateTimeKind.Local, the source time zone must be TimeZoneInfo.Local.</value>
+  </data>
+  <data name="Argument_CORDBBadMethod" xml:space="preserve">
+    <value>Cannot find the method on the object instance.</value>
+  </data>
+  <data name="Argument_CORDBBadVarArgCallConv" xml:space="preserve">
+    <value>Cannot evaluate a VarArgs function.</value>
+  </data>
+  <data name="Argument_CultureIetfNotSupported" xml:space="preserve">
+    <value>Culture IETF Name {0} is not a recognized IETF name.</value>
+  </data>
+  <data name="Argument_CultureInvalidIdentifier" xml:space="preserve">
+    <value>{0} is an invalid culture identifier.</value>
+  </data>
+  <data name="Argument_CultureIsNeutral" xml:space="preserve">
+    <value>Culture ID {0} (0x{0:X4}) is a neutral culture; a region cannot be created from it.</value>
+  </data>
+  <data name="Argument_CultureNotSupported" xml:space="preserve">
+    <value>Culture is not supported.</value>
+  </data>
+  <data name="Argument_CustomAssemblyLoadContextRequestedNameMismatch" xml:space="preserve">
+    <value>Resolved assembly's simple name should be the same as of the requested assembly.</value>
+  </data>
+  <data name="Argument_CustomCultureCannotBePassedByNumber" xml:space="preserve">
+    <value>Customized cultures cannot be passed by LCID, only by name.</value>
+  </data>
+  <data name="Argument_DateTimeBadBinaryData" xml:space="preserve">
+    <value>The binary data must result in a DateTime with ticks between DateTime.MinValue.Ticks and DateTime.MaxValue.Ticks.</value>
+  </data>
+  <data name="Argument_DateTimeHasTicks" xml:space="preserve">
+    <value>The supplied DateTime must have the Year, Month, and Day properties set to 1.  The time cannot be specified more precisely than whole milliseconds.</value>
+  </data>
+  <data name="Argument_DateTimeHasTimeOfDay" xml:space="preserve">
+    <value>The supplied DateTime includes a TimeOfDay setting.   This is not supported.</value>
+  </data>
+  <data name="Argument_DateTimeIsInvalid" xml:space="preserve">
+    <value>The supplied DateTime represents an invalid time.  For example, when the clock is adjusted forward, any time in the period that is skipped is invalid.</value>
+  </data>
+  <data name="Argument_DateTimeIsNotAmbiguous" xml:space="preserve">
+    <value>The supplied DateTime is not in an ambiguous time range.</value>
+  </data>
+  <data name="Argument_DateTimeKindMustBeUnspecified" xml:space="preserve">
+    <value>The supplied DateTime must have the Kind property set to DateTimeKind.Unspecified.</value>
+  </data>
+  <data name="Argument_DateTimeKindMustBeUnspecifiedOrUtc" xml:space="preserve">
+    <value>The supplied DateTime must have the Kind property set to DateTimeKind.Unspecified or DateTimeKind.Utc.</value>
+  </data>
+  <data name="Argument_DateTimeOffsetInvalidDateTimeStyles" xml:space="preserve">
+    <value>The DateTimeStyles value 'NoCurrentDateDefault' is not allowed when parsing DateTimeOffset.</value>
+  </data>
+  <data name="Argument_DateTimeOffsetIsNotAmbiguous" xml:space="preserve">
+    <value>The supplied DateTimeOffset is not in an ambiguous time range.</value>
+  </data>
+  <data name="Argument_DestinationTooShort" xml:space="preserve">
+    <value>Destination is too short.</value>
+  </data>
+  <data name="Argument_DuplicateTypeName" xml:space="preserve">
+    <value>Duplicate type name within an assembly.</value>
+  </data>
+  <data name="Argument_EmitWriteLineType" xml:space="preserve">
+    <value>EmitWriteLine does not support this field or local type.</value>
+  </data>
+  <data name="Argument_EmptyDecString" xml:space="preserve">
+    <value>Decimal separator cannot be the empty string.</value>
+  </data>
+  <data name="Argument_EmptyFileName" xml:space="preserve">
+    <value>Empty file name is not legal.</value>
+  </data>
+  <data name="Argument_EmptyName" xml:space="preserve">
+    <value>Empty name is not legal.</value>
+  </data>
+  <data name="Argument_EmptyPath" xml:space="preserve">
+    <value>Empty path name is not legal.</value>
+  </data>
+  <data name="Argument_EmptyWaithandleArray" xml:space="preserve">
+    <value>Waithandle array may not be empty.</value>
+  </data>
+  <data name="Argument_EncoderFallbackNotEmpty" xml:space="preserve">
+    <value>Must complete Convert() operation or call Encoder.Reset() before calling GetBytes() or GetByteCount(). Encoder '{0}' fallback '{1}'.</value>
+  </data>
+  <data name="Argument_EncodingConversionOverflowBytes" xml:space="preserve">
+    <value>The output byte buffer is too small to contain the encoded data, encoding '{0}' fallback '{1}'.</value>
+  </data>
+  <data name="Argument_EncodingConversionOverflowChars" xml:space="preserve">
+    <value>The output char buffer is too small to contain the decoded characters, encoding '{0}' fallback '{1}'.</value>
+  </data>
+  <data name="Argument_EncodingNotSupported" xml:space="preserve">
+    <value>'{0}' is not a supported encoding name. For information on defining a custom encoding, see the documentation for the Encoding.RegisterProvider method.</value>
+  </data>
+  <data name="Argument_EnumTypeDoesNotMatch" xml:space="preserve">
+    <value>The argument type, '{0}', is not the same as the enum type '{1}'.</value>
+  </data>
+  <data name="Argument_FallbackBufferNotEmpty" xml:space="preserve">
+    <value>Cannot change fallback when buffer is not empty. Previous Convert() call left data in the fallback buffer.</value>
+  </data>
+  <data name="Argument_FieldDeclaringTypeGeneric" xml:space="preserve">
+    <value>Cannot resolve field {0} because the declaring type of the field handle {1} is generic. Explicitly provide the declaring type to GetFieldFromHandle.</value>
+  </data>
+  <data name="Argument_FieldNeedGenericDeclaringType" xml:space="preserve">
+    <value>The specified field must be declared on a generic type definition.</value>
+  </data>
+  <data name="Argument_GenConstraintViolation" xml:space="preserve">
+    <value>GenericArguments[{0}], '{1}', on '{2}' violates the constraint of type '{3}'.</value>
+  </data>
+  <data name="Argument_GenericArgsCount" xml:space="preserve">
+    <value>The number of generic arguments provided doesn't equal the arity of the generic type definition.</value>
+  </data>
+  <data name="Argument_GenericsInvalid" xml:space="preserve">
+    <value>Generic types are not valid.</value>
+  </data>
+  <data name="Argument_GlobalFunctionHasToBeStatic" xml:space="preserve">
+    <value>Global members must be static.</value>
+  </data>
+  <data name="Argument_HandleLeak" xml:space="preserve">
+    <value>Cannot pass a GCHandle across AppDomains.</value>
+  </data>
+  <data name="Argument_HasToBeArrayClass" xml:space="preserve">
+    <value>Must be an array type.</value>
+  </data>
+  <data name="Argument_IdnBadBidi" xml:space="preserve">
+    <value>Left to right characters may not be mixed with right to left characters in IDN labels.</value>
+  </data>
+  <data name="Argument_IdnBadLabelSize" xml:space="preserve">
+    <value>IDN labels must be between 1 and 63 characters long.</value>
+  </data>
+  <data name="Argument_IdnBadNameSize" xml:space="preserve">
+    <value>IDN names must be between 1 and {0} characters long.</value>
+  </data>
+  <data name="Argument_IdnBadPunycode" xml:space="preserve">
+    <value>Invalid IDN encoded string.</value>
+  </data>
+  <data name="Argument_IdnBadStd3" xml:space="preserve">
+    <value>Label contains character '{0}' not allowed with UseStd3AsciiRules</value>
+  </data>
+  <data name="Argument_IdnIllegalName" xml:space="preserve">
+    <value>Decoded string is not a valid IDN name.</value>
+  </data>
+  <data name="Argument_IllegalEnvVarName" xml:space="preserve">
+    <value>Environment variable name cannot contain equal character.</value>
+  </data>
+  <data name="Argument_IllegalName" xml:space="preserve">
+    <value>Illegal name.</value>
+  </data>
+  <data name="Argument_ImplementIComparable" xml:space="preserve">
+    <value>At least one object must implement IComparable.</value>
+  </data>
+  <data name="Argument_IndexOutOfArrayBounds" xml:space="preserve">
+    <value>The specified index is out of bounds of the specified array.</value>
+  </data>
+  <data name="Argument_InsufficientSpaceToCopyCollection" xml:space="preserve">
+    <value>The specified space is not sufficient to copy the elements from this Collection.</value>
+  </data>
+  <data name="Argument_InterfaceMap" xml:space="preserve">
+    <value>'this' type cannot be an interface itself.</value>
+  </data>
+  <data name="Argument_InvalidAppendMode" xml:space="preserve">
+    <value>Append access can be requested only in write-only mode.</value>
+  </data>
+  <data name="Argument_InvalidArgumentForComparison" xml:space="preserve">
+    <value>Type of argument is not compatible with the generic comparer.</value>
+  </data>
+  <data name="Argument_InvalidArrayLength" xml:space="preserve">
+    <value>Length of the array must be {0}.</value>
+  </data>
+  <data name="Argument_InvalidArrayType" xml:space="preserve">
+    <value>Target array type is not compatible with the type of items in the collection.</value>
+  </data>
+  <data name="Argument_InvalidAssemblyName" xml:space="preserve">
+    <value>Assembly names may not begin with whitespace or contain the characters '/', or '\\' or ':'.</value>
+  </data>
+  <data name="Argument_InvalidCalendar" xml:space="preserve">
+    <value>Not a valid calendar for the given culture.</value>
+  </data>
+  <data name="Argument_InvalidCharSequence" xml:space="preserve">
+    <value>Invalid Unicode code point found at index {0}.</value>
+  </data>
+  <data name="Argument_InvalidCharSequenceNoIndex" xml:space="preserve">
+    <value>String contains invalid Unicode code points.</value>
+  </data>
+  <data name="Argument_InvalidCodePageBytesIndex" xml:space="preserve">
+    <value>Unable to translate bytes {0} at index {1} from specified code page to Unicode.</value>
+  </data>
+  <data name="Argument_InvalidCodePageConversionIndex" xml:space="preserve">
+    <value>Unable to translate Unicode character \\u{0:X4} at index {1} to specified code page.</value>
+  </data>
+  <data name="Argument_InvalidConstructorDeclaringType" xml:space="preserve">
+    <value>The specified constructor must be declared on the generic type definition of the specified type.</value>
+  </data>
+  <data name="Argument_InvalidConstructorInfo" xml:space="preserve">
+    <value>The ConstructorInfo object is not valid.</value>
+  </data>
+  <data name="Argument_InvalidCultureName" xml:space="preserve">
+    <value>Culture name '{0}' is not supported.</value>
+  </data>
+  <data name="Argument_InvalidDateTimeKind" xml:space="preserve">
+    <value>Invalid DateTimeKind value.</value>
+  </data>
+  <data name="Argument_InvalidDateTimeStyles" xml:space="preserve">
+    <value>An undefined DateTimeStyles value is being used.</value>
+  </data>
+  <data name="Argument_InvalidDigitSubstitution" xml:space="preserve">
+    <value>The DigitSubstitution property must be of a valid member of the DigitShapes enumeration. Valid entries include Context, NativeNational or None.</value>
+  </data>
+  <data name="Argument_InvalidEnum" xml:space="preserve">
+    <value>The Enum type should contain one and only one instance field.</value>
+  </data>
+  <data name="Argument_InvalidEnumValue" xml:space="preserve">
+    <value>The value '{0}' is not valid for this usage of the type {1}.</value>
+  </data>
+  <data name="Argument_InvalidFieldDeclaringType" xml:space="preserve">
+    <value>The specified field must be declared on the generic type definition of the specified type.</value>
+  </data>
+  <data name="Argument_InvalidFileModeAndAccessCombo" xml:space="preserve">
+    <value>Combining FileMode: {0} with FileAccess: {1} is invalid.</value>
+  </data>
+  <data name="Argument_InvalidFlag" xml:space="preserve">
+    <value>Value of flags is invalid.</value>
+  </data>
+  <data name="Argument_InvalidGenericArg" xml:space="preserve">
+    <value>The generic type parameter was not valid</value>
+  </data>
+  <data name="Argument_InvalidGenericInstArray" xml:space="preserve">
+    <value>Generic arguments must be provided for each generic parameter and each generic argument must be a RuntimeType.</value>
+  </data>
+  <data name="Argument_InvalidGroupSize" xml:space="preserve">
+    <value>Every element in the value array should be between one and nine, except for the last element, which can be zero.</value>
+  </data>
+  <data name="Argument_InvalidHandle" xml:space="preserve">
+    <value>The handle is invalid.</value>
+  </data>
+  <data name="Argument_InvalidHighSurrogate" xml:space="preserve">
+    <value>Found a high surrogate char without a following low surrogate at index: {0}. The input may not be in this encoding, or may not contain valid Unicode (UTF-16) characters.</value>
+  </data>
+  <data name="Argument_InvalidId" xml:space="preserve">
+    <value>The specified ID parameter '{0}' is not supported.</value>
+  </data>
+  <data name="Argument_InvalidKindOfTypeForCA" xml:space="preserve">
+    <value>This type cannot be represented as a custom attribute.</value>
+  </data>
+  <data name="Argument_InvalidLabel" xml:space="preserve">
+    <value>Invalid Label.</value>
+  </data>
+  <data name="Argument_InvalidLowSurrogate" xml:space="preserve">
+    <value>Found a low surrogate char without a preceding high surrogate at index: {0}. The input may not be in this encoding, or may not contain valid Unicode (UTF-16) characters.</value>
+  </data>
+  <data name="Argument_InvalidMemberForNamedArgument" xml:space="preserve">
+    <value>The member must be either a field or a property.</value>
+  </data>
+  <data name="Argument_InvalidMethodDeclaringType" xml:space="preserve">
+    <value>The specified method must be declared on the generic type definition of the specified type.</value>
+  </data>
+  <data name="Argument_InvalidName" xml:space="preserve">
+    <value>Invalid name.</value>
+  </data>
+  <data name="Argument_InvalidNativeDigitCount" xml:space="preserve">
+    <value>The NativeDigits array must contain exactly ten members.</value>
+  </data>
+  <data name="Argument_InvalidNativeDigitValue" xml:space="preserve">
+    <value>Each member of the NativeDigits array must be a single text element (one or more UTF16 code points) with a Unicode Nd (Number, Decimal Digit) property indicating it is a digit.</value>
+  </data>
+  <data name="Argument_InvalidNeutralRegionName" xml:space="preserve">
+    <value>The region name {0} should not correspond to neutral culture; a specific culture name is required.</value>
+  </data>
+  <data name="Argument_InvalidNormalizationForm" xml:space="preserve">
+    <value>Invalid or unsupported normalization form.</value>
+  </data>
+  <data name="Argument_InvalidNumberStyles" xml:space="preserve">
+    <value>An undefined NumberStyles value is being used.</value>
+  </data>
+  <data name="Argument_InvalidOffLen" xml:space="preserve">
+    <value>Offset and length were out of bounds for the array or count is greater than the number of elements from index to the end of the source collection.</value>
+  </data>
+  <data name="Argument_InvalidOpCodeOnDynamicMethod" xml:space="preserve">
+    <value>Ldtoken, Ldftn and Ldvirtftn OpCodes cannot target DynamicMethods.</value>
+  </data>
+  <data name="Argument_InvalidParameterInfo" xml:space="preserve">
+    <value>The ParameterInfo object is not valid.</value>
+  </data>
+  <data name="Argument_InvalidParamInfo" xml:space="preserve">
+    <value>Invalid type for ParameterInfo member in Attribute class.</value>
+  </data>
+  <data name="Argument_InvalidPathChars" xml:space="preserve">
+    <value>Illegal characters in path.</value>
+  </data>
+  <data name="Argument_InvalidRegistryViewCheck" xml:space="preserve">
+    <value>The specified RegistryView value is invalid.</value>
+  </data>
+  <data name="Argument_InvalidResourceCultureName" xml:space="preserve">
+    <value>The given culture name '{0}' cannot be used to locate a resource file. Resource filenames must consist of only letters, numbers, hyphens or underscores.</value>
+  </data>
+  <data name="Argument_InvalidSafeBufferOffLen" xml:space="preserve">
+    <value>Offset and length were greater than the size of the SafeBuffer.</value>
+  </data>
+  <data name="Argument_InvalidSeekOrigin" xml:space="preserve">
+    <value>Invalid seek origin.</value>
+  </data>
+  <data name="Argument_InvalidSerializedString" xml:space="preserve">
+    <value>The specified serialized string '{0}' is not supported.</value>
+  </data>
+  <data name="Argument_InvalidTimeSpanStyles" xml:space="preserve">
+    <value>An undefined TimeSpanStyles value is being used.</value>
+  </data>
+  <data name="Argument_InvalidToken" xml:space="preserve">
+    <value>Token {0:x} is not valid in the scope of module {1}.</value>
+  </data>
+  <data name="Argument_InvalidTypeForCA" xml:space="preserve">
+    <value>Cannot build type parameter for custom attribute with a type that does not support the AssemblyQualifiedName property. The type instance supplied was of type '{0}'.</value>
+  </data>
+  <data name="Argument_InvalidTypeForDynamicMethod" xml:space="preserve">
+    <value>Invalid type owner for DynamicMethod.</value>
+  </data>
+  <data name="Argument_InvalidTypeName" xml:space="preserve">
+    <value>The name of the type is invalid.</value>
+  </data>
+  <data name="Argument_InvalidTypeWithPointersNotSupported" xml:space="preserve">
+    <value>Cannot use type '{0}'. Only value types without pointers or references are supported.</value>
+  </data>
+  <data name="Argument_InvalidUnity" xml:space="preserve">
+    <value>Type '{0}' is not deserializable.</value>
+  </data>
+  <data name="Argument_InvalidValue" xml:space="preserve">
+    <value>Value was invalid.</value>
+  </data>
+  <data name="Argument_LargeInteger" xml:space="preserve">
+    <value>Integer or token was too large to be encoded.</value>
+  </data>
+  <data name="Argument_LongEnvVarValue" xml:space="preserve">
+    <value>Environment variable name or value is too long.</value>
+  </data>
+  <data name="Argument_MethodDeclaringTypeGeneric" xml:space="preserve">
+    <value>Cannot resolve method {0} because the declaring type of the method handle {1} is generic. Explicitly provide the declaring type to GetMethodFromHandle.</value>
+  </data>
+  <data name="Argument_MethodDeclaringTypeGenericLcg" xml:space="preserve">
+    <value>Method '{0}' has a generic declaring type '{1}'. Explicitly provide the declaring type to GetTokenFor.</value>
+  </data>
+  <data name="Argument_MethodNeedGenericDeclaringType" xml:space="preserve">
+    <value>The specified method cannot be dynamic or global and must be declared on a generic type definition.</value>
+  </data>
+  <data name="Argument_MinMaxValue" xml:space="preserve">
+    <value>'{0}' cannot be greater than {1}.</value>
+  </data>
+  <data name="Argument_MismatchedArrays" xml:space="preserve">
+    <value>Two arrays, {0} and {1}, must be of  the same size.</value>
+  </data>
+  <data name="Argument_MissingDefaultConstructor" xml:space="preserve">
+    <value>was missing default constructor.</value>
+  </data>
+  <data name="Argument_MustBeFalse" xml:space="preserve">
+    <value>Argument must be initialized to false</value>
+  </data>
+  <data name="Argument_MustBeRuntimeAssembly" xml:space="preserve">
+    <value>Assembly must be a runtime Assembly object.</value>
+  </data>
+  <data name="Argument_MustBeRuntimeFieldInfo" xml:space="preserve">
+    <value>FieldInfo must be a runtime FieldInfo object.</value>
+  </data>
+  <data name="Argument_MustBeRuntimeMethodInfo" xml:space="preserve">
+    <value>MethodInfo must be a runtime MethodInfo object.</value>
+  </data>
+  <data name="Argument_MustBeRuntimeModule" xml:space="preserve">
+    <value>Module must be a runtime Module object.</value>
+  </data>
+  <data name="Argument_MustBeRuntimeReflectionObject" xml:space="preserve">
+    <value>The object must be a runtime Reflection object.</value>
+  </data>
+  <data name="Argument_MustBeRuntimeType" xml:space="preserve">
+    <value>Type must be a runtime Type object.</value>
+  </data>
+  <data name="Argument_MustBeTypeBuilder" xml:space="preserve">
+    <value>'type' must contain a TypeBuilder as a generic argument.</value>
+  </data>
+  <data name="Argument_MustHaveAttributeBaseClass" xml:space="preserve">
+    <value>Type passed in must be derived from System.Attribute or System.Attribute itself.</value>
+  </data>
+  <data name="Argument_MustHaveLayoutOrBeBlittable" xml:space="preserve">
+    <value>The specified structure must be blittable or have layout information.</value>
+  </data>
+  <data name="Argument_NativeOverlappedAlreadyFree" xml:space="preserve">
+    <value>'overlapped' has already been freed.</value>
+  </data>
+  <data name="Argument_NativeOverlappedWrongBoundHandle" xml:space="preserve">
+    <value>'overlapped' was not allocated by this ThreadPoolBoundHandle instance.</value>
+  </data>
+  <data name="Argument_NeedGenericMethodDefinition" xml:space="preserve">
+    <value>Method must represent a generic method definition on a generic type definition.</value>
+  </data>
+  <data name="Argument_NeedNonGenericObject" xml:space="preserve">
+    <value>The specified object must not be an instance of a generic type.</value>
+  </data>
+  <data name="Argument_NeedNonGenericType" xml:space="preserve">
+    <value>The specified Type must not be a generic type definition.</value>
+  </data>
+  <data name="Argument_NeedStructWithNoRefs" xml:space="preserve">
+    <value>The specified Type must be a struct containing no references.</value>
+  </data>
+  <data name="Argument_NeverValidGenericArgument" xml:space="preserve">
+    <value>The type '{0}' may not be used as a type argument.</value>
+  </data>
+  <data name="Argument_NoDomainManager" xml:space="preserve">
+    <value>The domain manager specified by the host could not be instantiated.</value>
+  </data>
+  <data name="Argument_NoEra" xml:space="preserve">
+    <value>No Era was supplied.</value>
+  </data>
+  <data name="Argument_NoModuleFileExtension" xml:space="preserve">
+    <value>Module file name '{0}' must have file extension.</value>
+  </data>
+  <data name="Argument_NoRegionInvariantCulture" xml:space="preserve">
+    <value>There is no region associated with the Invariant Culture (Culture ID: 0x7F).</value>
+  </data>
+  <data name="Argument_NotATP" xml:space="preserve">
+    <value>Type must be a TransparentProxy</value>
+  </data>
+  <data name="Argument_NotAWritableProperty" xml:space="preserve">
+    <value>Not a writable property.</value>
+  </data>
+  <data name="Argument_NotEnoughBytesToRead" xml:space="preserve">
+    <value>There are not enough bytes remaining in the accessor to read at this position.</value>
+  </data>
+  <data name="Argument_NotEnoughBytesToWrite" xml:space="preserve">
+    <value>There are not enough bytes remaining in the accessor to write at this position.</value>
+  </data>
+  <data name="Argument_NotEnoughGenArguments" xml:space="preserve">
+    <value>The type or method has {1} generic parameter(s), but {0} generic argument(s) were provided. A generic argument must be provided for each generic parameter.</value>
+  </data>
+  <data name="Argument_NotExceptionType" xml:space="preserve">
+    <value>Does not extend Exception.</value>
+  </data>
+  <data name="Argument_NotInExceptionBlock" xml:space="preserve">
+    <value>Not currently in an exception block.</value>
+  </data>
+  <data name="Argument_NotMethodCallOpcode" xml:space="preserve">
+    <value>The specified opcode cannot be passed to EmitCall.</value>
+  </data>
+  <data name="Argument_NotSerializable" xml:space="preserve">
+    <value>Argument passed in is not serializable.</value>
+  </data>
+  <data name="Argument_NoUnderlyingCCW" xml:space="preserve">
+    <value>The object has no underlying COM data associated with it.</value>
+  </data>
+  <data name="Argument_NoUninitializedStrings" xml:space="preserve">
+    <value>Uninitialized Strings cannot be created.</value>
+  </data>
+  <data name="Argument_ObjIsWinRTObject" xml:space="preserve">
+    <value>The object's type must not be a Windows Runtime type.</value>
+  </data>
+  <data name="Argument_ObjNotComObject" xml:space="preserve">
+    <value>The object's type must be __ComObject or derived from __ComObject.</value>
+  </data>
+  <data name="Argument_OffsetAndCapacityOutOfBounds" xml:space="preserve">
+    <value>Offset and capacity were greater than the size of the view.</value>
+  </data>
+  <data name="Argument_OffsetLocalMismatch" xml:space="preserve">
+    <value>The UTC Offset of the local dateTime parameter does not match the offset argument.</value>
+  </data>
+  <data name="Argument_OffsetOfFieldNotFound" xml:space="preserve">
+    <value>Field passed in is not a marshaled member of the type '{0}'.</value>
+  </data>
+  <data name="Argument_OffsetOutOfRange" xml:space="preserve">
+    <value>Offset must be within plus or minus 14 hours.</value>
+  </data>
+  <data name="Argument_OffsetPrecision" xml:space="preserve">
+    <value>Offset must be specified in whole minutes.</value>
+  </data>
+  <data name="Argument_OffsetUtcMismatch" xml:space="preserve">
+    <value>The UTC Offset for Utc DateTime instances must be 0.</value>
+  </data>
+  <data name="Argument_OneOfCulturesNotSupported" xml:space="preserve">
+    <value>Culture name {0} or {1} is not supported.</value>
+  </data>
+  <data name="Argument_OnlyMscorlib" xml:space="preserve">
+    <value>Only mscorlib's assembly is valid.</value>
+  </data>
+  <data name="Argument_OutOfOrderDateTimes" xml:space="preserve">
+    <value>The DateStart property must come before the DateEnd property.</value>
+  </data>
+  <data name="Argument_PathEmpty" xml:space="preserve">
+    <value>Path cannot be the empty string or all whitespace.</value>
+  </data>
+  <data name="Argument_PathFormatNotSupported_Path" xml:space="preserve">
+    <value>The format of the path '{0}' is not supported.</value>
+  </data>
+  <data name="Argument_PreAllocatedAlreadyAllocated" xml:space="preserve">
+    <value>'preAllocated' is already in use.</value>
+  </data>
+  <data name="Argument_RecursiveFallback" xml:space="preserve">
+    <value>Recursive fallback not allowed for character \\u{0:X4}.</value>
+  </data>
+  <data name="Argument_RecursiveFallbackBytes" xml:space="preserve">
+    <value>Recursive fallback not allowed for bytes {0}.</value>
+  </data>
+  <data name="Argument_RedefinedLabel" xml:space="preserve">
+    <value>Label multiply defined.</value>
+  </data>
+  <data name="Argument_ResolveField" xml:space="preserve">
+    <value>Token {0:x} is not a valid FieldInfo token in the scope of module {1}.</value>
+  </data>
+  <data name="Argument_ResolveFieldHandle" xml:space="preserve">
+    <value>Type handle '{0}' and field handle with declaring type '{1}' are incompatible. Get RuntimeFieldHandle and declaring RuntimeTypeHandle off the same FieldInfo.</value>
+  </data>
+  <data name="Argument_ResolveMember" xml:space="preserve">
+    <value>Token {0:x} is not a valid MemberInfo token in the scope of module {1}.</value>
+  </data>
+  <data name="Argument_ResolveMethod" xml:space="preserve">
+    <value>Token {0:x} is not a valid MethodBase token in the scope of module {1}.</value>
+  </data>
+  <data name="Argument_ResolveMethodHandle" xml:space="preserve">
+    <value>Type handle '{0}' and method handle with declaring type '{1}' are incompatible. Get RuntimeMethodHandle and declaring RuntimeTypeHandle off the same MethodBase.</value>
+  </data>
+  <data name="Argument_ResolveModuleType" xml:space="preserve">
+    <value>Token {0} resolves to the special module type representing this module.</value>
+  </data>
+  <data name="Argument_ResolveString" xml:space="preserve">
+    <value>Token {0:x} is not a valid string token in the scope of module {1}.</value>
+  </data>
+  <data name="Argument_ResolveType" xml:space="preserve">
+    <value>Token {0:x} is not a valid Type token in the scope of module {1}.</value>
+  </data>
+  <data name="Argument_ResultCalendarRange" xml:space="preserve">
+    <value>The result is out of the supported range for this calendar. The result should be between {0} (Gregorian date) and {1} (Gregorian date), inclusive.</value>
+  </data>
+  <data name="Argument_SemaphoreInitialMaximum" xml:space="preserve">
+    <value>The initial count for the semaphore must be greater than or equal to zero and less than the maximum count.</value>
+  </data>
+  <data name="Argument_ShouldNotSpecifyExceptionType" xml:space="preserve">
+    <value>Should not specify exception type for catch clause for filter block.</value>
+  </data>
+  <data name="Argument_ShouldOnlySetVisibilityFlags" xml:space="preserve">
+    <value>Should only set visibility flags when creating EnumBuilder.</value>
+  </data>
+  <data name="Argument_SigIsFinalized" xml:space="preserve">
+    <value>Completed signature cannot be modified.</value>
+  </data>
+  <data name="Argument_StreamNotReadable" xml:space="preserve">
+    <value>Stream was not readable.</value>
+  </data>
+  <data name="Argument_StreamNotWritable" xml:space="preserve">
+    <value>Stream was not writable.</value>
+  </data>
+  <data name="Argument_StringFirstCharIsZero" xml:space="preserve">
+    <value>The first char in the string is the null character.</value>
+  </data>
+  <data name="Argument_StringZeroLength" xml:space="preserve">
+    <value>String cannot be of zero length.</value>
+  </data>
+  <data name="Argument_StructMustNotBeValueClass" xml:space="preserve">
+    <value>The structure must not be a value class.</value>
+  </data>
+  <data name="Argument_TimeSpanHasSeconds" xml:space="preserve">
+    <value>The TimeSpan parameter cannot be specified more precisely than whole minutes.</value>
+  </data>
+  <data name="Argument_TimeZoneInfoBadTZif" xml:space="preserve">
+    <value>The tzfile does not begin with the magic characters 'TZif'.  Please verify that the file is not corrupt.</value>
+  </data>
+  <data name="Argument_TimeZoneInfoInvalidTZif" xml:space="preserve">
+    <value>The TZif data structure is corrupt.</value>
+  </data>
+  <data name="Argument_ToExclusiveLessThanFromExclusive" xml:space="preserve">
+    <value>fromInclusive must be less than or equal to toExclusive.</value>
+  </data>
+  <data name="Argument_TooManyFinallyClause" xml:space="preserve">
+    <value>Exception blocks may have at most one finally clause.</value>
+  </data>
+  <data name="Argument_TransitionTimesAreIdentical" xml:space="preserve">
+    <value>The DaylightTransitionStart property must not equal the DaylightTransitionEnd property.</value>
+  </data>
+  <data name="Argument_TypedReferenceInvalidField" xml:space="preserve">
+    <value>Field '{0}' in TypedReferences cannot be static or init only.</value>
+  </data>
+  <data name="Argument_TypeIsWinRTType" xml:space="preserve">
+    <value>The type must not be a Windows Runtime type.</value>
+  </data>
+  <data name="Argument_TypeMustBeVisibleFromCom" xml:space="preserve">
+    <value>The specified type must be visible from COM.</value>
+  </data>
+  <data name="Argument_TypeMustNotBeComImport" xml:space="preserve">
+    <value>The type must not be imported from COM.</value>
+  </data>
+  <data name="Argument_TypeNameTooLong" xml:space="preserve">
+    <value>Type name was too long. The fully qualified type name must be less than 1,024 characters.</value>
+  </data>
+  <data name="Argument_TypeNotActivatableViaWindowsRuntime" xml:space="preserve">
+    <value>Type '{0}' does not have an activation factory because it is not activatable by Windows Runtime.</value>
+  </data>
+  <data name="Argument_TypeNotComObject" xml:space="preserve">
+    <value>The type must be __ComObject or be derived from __ComObject.</value>
+  </data>
+  <data name="Argument_TypeNotValid" xml:space="preserve">
+    <value>The Type object is not valid.</value>
+  </data>
+  <data name="Argument_UnclosedExceptionBlock" xml:space="preserve">
+    <value>The IL Generator cannot be used while there are unclosed exceptions.</value>
+  </data>
+  <data name="Argument_Unexpected_TypeSource" xml:space="preserve">
+    <value>Unexpected TypeKind when marshaling Windows.Foundation.TypeName.</value>
+  </data>
+  <data name="Argument_UnknownUnmanagedCallConv" xml:space="preserve">
+    <value>Unknown unmanaged calling convention for function signature.</value>
+  </data>
+  <data name="Argument_UnmanagedMemAccessorWrapAround" xml:space="preserve">
+    <value>The UnmanagedMemoryAccessor capacity and offset would wrap around the high end of the address space.</value>
+  </data>
+  <data name="Argument_UnmatchedMethodForLocal" xml:space="preserve">
+    <value>Local passed in does not belong to this ILGenerator.</value>
+  </data>
+  <data name="Argument_UnmatchingSymScope" xml:space="preserve">
+    <value>Non-matching symbol scope.</value>
+  </data>
+  <data name="Argument_UnrecognizedLoaderOptimization" xml:space="preserve">
+    <value>Unrecognized LOADER_OPTIMIZATION property value.  Supported values may include "SingleDomain", "MultiDomain", "MultiDomainHost", and "NotSpecified".</value>
+  </data>
+  <data name="Argument_UTCOutOfRange" xml:space="preserve">
+    <value>The UTC time represented when the offset is applied must be between year 0 and 10,000.</value>
+  </data>
+  <data name="Argument_VerStringTooLong" xml:space="preserve">
+    <value>The unmanaged Version information is too large to persist.</value>
+  </data>
+  <data name="Argument_WaitHandleNameTooLong" xml:space="preserve">
+    <value>The name '{0}' can be no more than {1} characters in length.</value>
+  </data>
+  <data name="Argument_WinRTSystemRuntimeType" xml:space="preserve">
+    <value>Cannot marshal type '{0}' to Windows Runtime. Only 'System.RuntimeType' is supported.</value>
+  </data>
+  <data name="ArgumentException_BadMethodImplBody" xml:space="preserve">
+    <value>MethodOverride's body must be from this type.</value>
+  </data>
+  <data name="ArgumentException_BufferNotFromPool" xml:space="preserve">
+    <value>The buffer is not associated with this pool and may not be returned to it.</value>
+  </data>
+  <data name="ArgumentException_OtherNotArrayOfCorrectLength" xml:space="preserve">
+    <value>Object is not a array with the same number of elements as the array to compare it to.</value>
+  </data>
+  <data name="ArgumentException_TupleIncorrectType" xml:space="preserve">
+    <value>Argument must be of type {0}.</value>
+  </data>
+  <data name="ArgumentException_TupleLastArgumentNotATuple" xml:space="preserve">
+    <value>The last element of an eight element tuple must be a Tuple.</value>
+  </data>
+  <data name="ArgumentException_ValueTupleIncorrectType" xml:space="preserve">
+    <value>Argument must be of type {0}.</value>
+  </data>
+  <data name="ArgumentException_ValueTupleLastArgumentNotAValueTuple" xml:space="preserve">
+    <value>The last element of an eight element ValueTuple must be a ValueTuple.</value>
+  </data>
+  <data name="ArgumentNull_Array" xml:space="preserve">
+    <value>Array cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_ArrayElement" xml:space="preserve">
+    <value>At least one element in the specified array was null.</value>
+  </data>
+  <data name="ArgumentNull_ArrayValue" xml:space="preserve">
+    <value>Found a null value within an array.</value>
+  </data>
+  <data name="ArgumentNull_Assembly" xml:space="preserve">
+    <value>Assembly cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_AssemblyName" xml:space="preserve">
+    <value>AssemblyName cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_AssemblyNameName" xml:space="preserve">
+    <value>AssemblyName.Name cannot be null or an empty string.</value>
+  </data>
+  <data name="ArgumentNull_Buffer" xml:space="preserve">
+    <value>Buffer cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_Collection" xml:space="preserve">
+    <value>Collection cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_Dictionary" xml:space="preserve">
+    <value>Dictionary cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_FileName" xml:space="preserve">
+    <value>File name cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_Generic" xml:space="preserve">
+    <value>Value cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_GUID" xml:space="preserve">
+    <value>GUID cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_Key" xml:space="preserve">
+    <value>Key cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_Obj" xml:space="preserve">
+    <value>Object cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_Path" xml:space="preserve">
+    <value>Path cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_SafeHandle" xml:space="preserve">
+    <value>SafeHandle cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_Stream" xml:space="preserve">
+    <value>Stream cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_String" xml:space="preserve">
+    <value>String reference not set to an instance of a String.</value>
+  </data>
+  <data name="ArgumentNull_Type" xml:space="preserve">
+    <value>Type cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_TypedRefType" xml:space="preserve">
+    <value>Type in TypedReference cannot be null.</value>
+  </data>
+  <data name="ArgumentNull_Waithandles" xml:space="preserve">
+    <value>The waitHandles parameter cannot be null.</value>
+  </data>
+  <data name="ArgumentOutOfRange_ActualValue" xml:space="preserve">
+    <value>Actual value was {0}.</value>
+  </data>
+  <data name="ArgumentOutOfRange_AddressSpace" xml:space="preserve">
+    <value>The number of bytes cannot exceed the virtual address space on a 32 bit machine.</value>
+  </data>
+  <data name="ArgumentOutOfRange_AddValue" xml:space="preserve">
+    <value>Value to add was out of range.</value>
+  </data>
+  <data name="ArgumentOutOfRange_ArrayLB" xml:space="preserve">
+    <value>Number was less than the array's lower bound in the first dimension.</value>
+  </data>
+  <data name="ArgumentOutOfRange_ArrayLBAndLength" xml:space="preserve">
+    <value>Higher indices will exceed Int32.MaxValue because of large lower bound and/or length.</value>
+  </data>
+  <data name="ArgumentOutOfRange_BadHourMinuteSecond" xml:space="preserve">
+    <value>Hour, Minute, and Second parameters describe an un-representable DateTime.</value>
+  </data>
+  <data name="ArgumentOutOfRange_BadYearMonthDay" xml:space="preserve">
+    <value>Year, Month, and Day parameters describe an un-representable DateTime.</value>
+  </data>
+  <data name="ArgumentOutOfRange_BiggerThanCollection" xml:space="preserve">
+    <value>Larger than collection size.</value>
+  </data>
+  <data name="ArgumentOutOfRange_BinaryReaderFillBuffer" xml:space="preserve">
+    <value>The number of bytes requested does not fit into BinaryReader's internal buffer.</value>
+  </data>
+  <data name="ArgumentOutOfRange_Bounds_Lower_Upper" xml:space="preserve">
+    <value>Argument must be between {0} and {1}.</value>
+  </data>
+  <data name="ArgumentOutOfRange_CalendarRange" xml:space="preserve">
+    <value>Specified time is not supported in this calendar. It should be between {0} (Gregorian date) and {1} (Gregorian date), inclusive.</value>
+  </data>
+  <data name="ArgumentOutOfRange_Capacity" xml:space="preserve">
+    <value>Capacity exceeds maximum capacity.</value>
+  </data>
+  <data name="ArgumentOutOfRange_Count" xml:space="preserve">
+    <value>Count must be positive and count must refer to a location within the string/array/collection.</value>
+  </data>
+  <data name="ArgumentOutOfRange_DateArithmetic" xml:space="preserve">
+    <value>The added or subtracted value results in an un-representable DateTime.</value>
+  </data>
+  <data name="ArgumentOutOfRange_DateTimeBadMonths" xml:space="preserve">
+    <value>Months value must be between +/-120000.</value>
+  </data>
+  <data name="ArgumentOutOfRange_DateTimeBadTicks" xml:space="preserve">
+    <value>Ticks must be between DateTime.MinValue.Ticks and DateTime.MaxValue.Ticks.</value>
+  </data>
+  <data name="ArgumentOutOfRange_DateTimeBadYears" xml:space="preserve">
+    <value>Years value must be between +/-10000.</value>
+  </data>
+  <data name="ArgumentOutOfRange_Day" xml:space="preserve">
+    <value>Day must be between 1 and {0} for month {1}.</value>
+  </data>
+  <data name="ArgumentOutOfRange_DayOfWeek" xml:space="preserve">
+    <value>The DayOfWeek enumeration must be in the range 0 through 6.</value>
+  </data>
+  <data name="ArgumentOutOfRange_DayParam" xml:space="preserve">
+    <value>The Day parameter must be in the range 1 through 31.</value>
+  </data>
+  <data name="ArgumentOutOfRange_DecimalRound" xml:space="preserve">
+    <value>Decimal can only round to between 0 and 28 digits of precision.</value>
+  </data>
+  <data name="ArgumentOutOfRange_DecimalScale" xml:space="preserve">
+    <value>Decimal's scale value must be between 0 and 28, inclusive.</value>
+  </data>
+  <data name="ArgumentOutOfRange_EndIndexStartIndex" xml:space="preserve">
+    <value>endIndex cannot be greater than startIndex.</value>
+  </data>
+  <data name="ArgumentOutOfRange_Enum" xml:space="preserve">
+    <value>Enum value was out of legal range.</value>
+  </data>
+  <data name="ArgumentOutOfRange_Era" xml:space="preserve">
+    <value>Time value was out of era range.</value>
+  </data>
+  <data name="ArgumentOutOfRange_FileLengthTooBig" xml:space="preserve">
+    <value>Specified file length was too large for the file system.</value>
+  </data>
+  <data name="ArgumentOutOfRange_FileTimeInvalid" xml:space="preserve">
+    <value>Not a valid Win32 FileTime.</value>
+  </data>
+  <data name="ArgumentOutOfRange_GenericPositive" xml:space="preserve">
+    <value>Value must be positive.</value>
+  </data>
+  <data name="ArgumentOutOfRange_GetByteCountOverflow" xml:space="preserve">
+    <value>Too many characters. The resulting number of bytes is larger than what can be returned as an int.</value>
+  </data>
+  <data name="ArgumentOutOfRange_GetCharCountOverflow" xml:space="preserve">
+    <value>Too many bytes. The resulting number of chars is larger than what can be returned as an int.</value>
+  </data>
+  <data name="ArgumentOutOfRange_HashtableLoadFactor" xml:space="preserve">
+    <value>Load factor needs to be between 0.1 and 1.0.</value>
+  </data>
+  <data name="ArgumentOutOfRange_HugeArrayNotSupported" xml:space="preserve">
+    <value>Arrays larger than 2GB are not supported.</value>
+  </data>
+  <data name="ArgumentOutOfRange_Index" xml:space="preserve">
+    <value>Index was out of range. Must be non-negative and less than the size of the collection.</value>
+  </data>
+  <data name="ArgumentOutOfRange_IndexCount" xml:space="preserve">
+    <value>Index and count must refer to a location within the string.</value>
+  </data>
+  <data name="ArgumentOutOfRange_IndexCountBuffer" xml:space="preserve">
+    <value>Index and count must refer to a location within the buffer.</value>
+  </data>
+  <data name="ArgumentOutOfRange_IndexLargerThanMaxValue" xml:space="preserve">
+    <value>This collection cannot work with indices larger than Int32.MaxValue - 1 (0x7FFFFFFF - 1).</value>
+  </data>
+  <data name="ArgumentOutOfRange_IndexLength" xml:space="preserve">
+    <value>Index and length must refer to a location within the string.</value>
+  </data>
+  <data name="ArgumentOutOfRange_IndexString" xml:space="preserve">
+    <value>Index was out of range. Must be non-negative and less than the length of the string.</value>
+  </data>
+  <data name="ArgumentOutOfRange_InvalidEraValue" xml:space="preserve">
+    <value>Era value was not valid.</value>
+  </data>
+  <data name="ArgumentOutOfRange_InvalidHighSurrogate" xml:space="preserve">
+    <value>A valid high surrogate character is between 0xd800 and 0xdbff, inclusive.</value>
+  </data>
+  <data name="ArgumentOutOfRange_InvalidLowSurrogate" xml:space="preserve">
+    <value>A valid low surrogate character is between 0xdc00 and 0xdfff, inclusive.</value>
+  </data>
+  <data name="ArgumentOutOfRange_InvalidUTF32" xml:space="preserve">
+    <value>A valid UTF32 value is between 0x000000 and 0x10ffff, inclusive, and should not include surrogate codepoint values (0x00d800 ~ 0x00dfff).</value>
+  </data>
+  <data name="ArgumentOutOfRange_Length" xml:space="preserve">
+    <value>The specified length exceeds maximum capacity of SecureString.</value>
+  </data>
+  <data name="ArgumentOutOfRange_LengthGreaterThanCapacity" xml:space="preserve">
+    <value>The length cannot be greater than the capacity.</value>
+  </data>
+  <data name="ArgumentOutOfRange_LengthTooLarge" xml:space="preserve">
+    <value>The specified length exceeds the maximum value of {0}.</value>
+  </data>
+  <data name="ArgumentOutOfRange_LessEqualToIntegerMaxVal" xml:space="preserve">
+    <value>Argument must be less than or equal to 2^31 - 1 milliseconds.</value>
+  </data>
+  <data name="ArgumentOutOfRange_ListInsert" xml:space="preserve">
+    <value>Index must be within the bounds of the List.</value>
+  </data>
+  <data name="ArgumentOutOfRange_Month" xml:space="preserve">
+    <value>Month must be between one and twelve.</value>
+  </data>
+  <data name="ArgumentOutOfRange_MonthParam" xml:space="preserve">
+    <value>The Month parameter must be in the range 1 through 12.</value>
+  </data>
+  <data name="ArgumentOutOfRange_MustBeNonNegInt32" xml:space="preserve">
+    <value>Value must be non-negative and less than or equal to Int32.MaxValue.</value>
+  </data>
+  <data name="ArgumentOutOfRange_MustBeNonNegNum" xml:space="preserve">
+    <value>'{0}' must be non-negative.</value>
+  </data>
+  <data name="ArgumentOutOfRange_MustBePositive" xml:space="preserve">
+    <value>'{0}' must be greater than zero.</value>
+  </data>
+  <data name="ArgumentOutOfRange_NeedNonNegNum" xml:space="preserve">
+    <value>Non-negative number required.</value>
+  </data>
+  <data name="ArgumentOutOfRange_NeedNonNegOrNegative1" xml:space="preserve">
+    <value>Number must be either non-negative and less than or equal to Int32.MaxValue or -1.</value>
+  </data>
+  <data name="ArgumentOutOfRange_NeedPosNum" xml:space="preserve">
+    <value>Positive number required.</value>
+  </data>
+  <data name="ArgumentOutOfRange_NeedValidId" xml:space="preserve">
+    <value>The ID parameter must be in the range {0} through {1}.</value>
+  </data>
+  <data name="ArgumentOutOfRange_NegativeCapacity" xml:space="preserve">
+    <value>Capacity must be positive.</value>
+  </data>
+  <data name="ArgumentOutOfRange_NegativeCount" xml:space="preserve">
+    <value>Count cannot be less than zero.</value>
+  </data>
+  <data name="ArgumentOutOfRange_NegativeLength" xml:space="preserve">
+    <value>Length cannot be less than zero.</value>
+  </data>
+  <data name="ArgumentOutOfRange_OffsetLength" xml:space="preserve">
+    <value>Offset and length must refer to a position in the string.</value>
+  </data>
+  <data name="ArgumentOutOfRange_OffsetOut" xml:space="preserve">
+    <value>Either offset did not refer to a position in the string, or there is an insufficient length of destination character array.</value>
+  </data>
+  <data name="ArgumentOutOfRange_ParamSequence" xml:space="preserve">
+    <value>The specified parameter index is not in range.</value>
+  </data>
+  <data name="ArgumentOutOfRange_PartialWCHAR" xml:space="preserve">
+    <value>Pointer startIndex and length do not refer to a valid string.</value>
+  </data>
+  <data name="ArgumentOutOfRange_PeriodTooLarge" xml:space="preserve">
+    <value>Period must be less than 2^32-2.</value>
+  </data>
+  <data name="ArgumentOutOfRange_PositionLessThanCapacityRequired" xml:space="preserve">
+    <value>The position may not be greater or equal to the capacity of the accessor.</value>
+  </data>
+  <data name="ArgumentOutOfRange_Range" xml:space="preserve">
+    <value>Valid values are between {0} and {1}, inclusive.</value>
+  </data>
+  <data name="ArgumentOutOfRange_RoundingDigits" xml:space="preserve">
+    <value>Rounding digits must be between 0 and 15, inclusive.</value>
+  </data>
+  <data name="ArgumentOutOfRange_SmallCapacity" xml:space="preserve">
+    <value>capacity was less than the current size.</value>
+  </data>
+  <data name="ArgumentOutOfRange_SmallMaxCapacity" xml:space="preserve">
+    <value>MaxCapacity must be one or greater.</value>
+  </data>
+  <data name="ArgumentOutOfRange_StartIndex" xml:space="preserve">
+    <value>StartIndex cannot be less than zero.</value>
+  </data>
+  <data name="ArgumentOutOfRange_StartIndexLargerThanLength" xml:space="preserve">
+    <value>startIndex cannot be larger than length of string.</value>
+  </data>
+  <data name="ArgumentOutOfRange_StartIndexLessThanLength" xml:space="preserve">
+    <value>startIndex must be less than length of string.</value>
+  </data>
+  <data name="ArgumentOutOfRange_StreamLength" xml:space="preserve">
+    <value>Stream length must be non-negative and less than 2^31 - 1 - origin.</value>
+  </data>
+  <data name="ArgumentOutOfRange_TimeoutTooLarge" xml:space="preserve">
+    <value>Time-out interval must be less than 2^32-2.</value>
+  </data>
+  <data name="ArgumentOutOfRange_UIntPtrMax" xml:space="preserve">
+    <value>The length of the buffer must be less than the maximum UIntPtr value for your platform.</value>
+  </data>
+  <data name="ArgumentOutOfRange_UnmanagedMemStreamLength" xml:space="preserve">
+    <value>UnmanagedMemoryStream length must be non-negative and less than 2^63 - 1 - baseAddress.</value>
+  </data>
+  <data name="ArgumentOutOfRange_UnmanagedMemStreamWrapAround" xml:space="preserve">
+    <value>The UnmanagedMemoryStream capacity would wrap around the high end of the address space.</value>
+  </data>
+  <data name="ArgumentOutOfRange_UtcOffset" xml:space="preserve">
+    <value>The TimeSpan parameter must be within plus or minus 14.0 hours.</value>
+  </data>
+  <data name="ArgumentOutOfRange_UtcOffsetAndDaylightDelta" xml:space="preserve">
+    <value>The sum of the BaseUtcOffset and DaylightDelta properties must within plus or minus 14.0 hours.</value>
+  </data>
+  <data name="ArgumentOutOfRange_Version" xml:space="preserve">
+    <value>Version's parameters must be greater than or equal to zero.</value>
+  </data>
+  <data name="ArgumentOutOfRange_Week" xml:space="preserve">
+    <value>The Week parameter must be in the range 1 through 5.</value>
+  </data>
+  <data name="ArgumentOutOfRange_Year" xml:space="preserve">
+    <value>Year must be between 1 and 9999.</value>
+  </data>
+  <data name="Arithmetic_NaN" xml:space="preserve">
+    <value>Function does not accept floating point Not-a-Number values.</value>
+  </data>
+  <data name="ArrayTypeMismatch_CantAssignType" xml:space="preserve">
+    <value>Source array type cannot be assigned to destination array type.</value>
+  </data>
+  <data name="ArrayTypeMismatch_ConstrainedCopy" xml:space="preserve">
+    <value>Array.ConstrainedCopy will only work on array types that are provably compatible, without any form of boxing, unboxing, widening, or casting of each array element.  Change the array types (i.e., copy a Derived[] to a Base[]), or use a mitigation strategy in the CER for Array.Copy's less powerful reliability contract, such as cloning the array or throwing away the potentially corrupt destination array.</value>
+  </data>
+  <data name="Arugment_EmitMixedContext1" xml:space="preserve">
+    <value>Type '{0}' was loaded in the ReflectionOnly context but the AssemblyBuilder was not created as AssemblyBuilderAccess.ReflectionOnly.</value>
+  </data>
+  <data name="Arugment_EmitMixedContext2" xml:space="preserve">
+    <value>Type '{0}' was not loaded in the ReflectionOnly context but the AssemblyBuilder was created as AssemblyBuilderAccess.ReflectionOnly.</value>
+  </data>
+  <data name="AssertionFailed" xml:space="preserve">
+    <value>Assertion failed.</value>
+  </data>
+  <data name="AssertionFailed_Cnd" xml:space="preserve">
+    <value>Assertion failed: {0}</value>
+  </data>
+  <data name="AssumptionFailed" xml:space="preserve">
+    <value>Assumption failed.</value>
+  </data>
+  <data name="AssumptionFailed_Cnd" xml:space="preserve">
+    <value>Assumption failed: {0}</value>
+  </data>
+  <data name="AsyncMethodBuilder_InstanceNotInitialized" xml:space="preserve">
+    <value>The builder was not properly initialized.</value>
+  </data>
+  <data name="BadImageFormat_BadILFormat" xml:space="preserve">
+    <value>Bad IL format.</value>
+  </data>
+  <data name="BadImageFormat_InvalidType" xml:space="preserve">
+    <value>Corrupt .resources file.  The specified type doesn't exist.</value>
+  </data>
+  <data name="BadImageFormat_NegativeStringLength" xml:space="preserve">
+    <value>Corrupt .resources file. String length must be non-negative.</value>
+  </data>
+  <data name="BadImageFormat_ParameterSignatureMismatch" xml:space="preserve">
+    <value>The parameters and the signature of the method don't match.</value>
+  </data>
+  <data name="BadImageFormat_ResourceDataLengthInvalid" xml:space="preserve">
+    <value>Corrupt .resources file.  The specified data length '{0}' is not a valid position in the stream.</value>
+  </data>
+  <data name="BadImageFormat_ResourceNameCorrupted" xml:space="preserve">
+    <value>Corrupt .resources file. A resource name extends past the end of the stream.</value>
+  </data>
+  <data name="BadImageFormat_ResourceNameCorrupted_NameIndex" xml:space="preserve">
+    <value>Corrupt .resources file. The resource name for name index {0} extends past the end of the stream.</value>
+  </data>
+  <data name="BadImageFormat_ResourcesDataInvalidOffset" xml:space="preserve">
+    <value>Corrupt .resources file. Invalid offset '{0}' into data section.</value>
+  </data>
+  <data name="BadImageFormat_ResourcesHeaderCorrupted" xml:space="preserve">
+    <value>Corrupt .resources file. Unable to read resources from this file because of invalid header information. Try regenerating the .resources file.</value>
+  </data>
+  <data name="BadImageFormat_ResourcesIndexTooLong" xml:space="preserve">
+    <value>Corrupt .resources file. String for name index '{0}' extends past the end of the file.</value>
+  </data>
+  <data name="BadImageFormat_ResourcesNameInvalidOffset" xml:space="preserve">
+    <value>Corrupt .resources file. Invalid offset '{0}' into name section.</value>
+  </data>
+  <data name="BadImageFormat_ResourcesNameTooLong" xml:space="preserve">
+    <value>Corrupt .resources file. Resource name extends past the end of the file.</value>
+  </data>
+  <data name="BadImageFormat_TypeMismatch" xml:space="preserve">
+    <value>Corrupt .resources file.  The specified type doesn't match the available data in the stream.</value>
+  </data>
+  <data name="CancellationToken_CreateLinkedToken_TokensIsEmpty" xml:space="preserve">
+    <value>No tokens were supplied.</value>
+  </data>
+  <data name="CancellationToken_SourceDisposed" xml:space="preserve">
+    <value>The CancellationTokenSource associated with this CancellationToken has been disposed.</value>
+  </data>
+  <data name="CancellationTokenSource_Disposed" xml:space="preserve">
+    <value>The CancellationTokenSource has been disposed.</value>
+  </data>
+  <data name="ConcurrentCollection_SyncRoot_NotSupported" xml:space="preserve">
+    <value>The SyncRoot property may not be used for the synchronization of concurrent collections.</value>
+  </data>
+  <data name="ConcurrentDictionary_ArrayIncorrectType" xml:space="preserve">
+    <value>The array is multidimensional, or the type parameter for the set cannot be cast automatically to the type of the destination array.</value>
+  </data>
+  <data name="ConcurrentDictionary_ArrayNotLargeEnough" xml:space="preserve">
+    <value>The index is equal to or greater than the length of the array, or the number of elements in the dictionary is greater than the available space from index to the end of the destination array.</value>
+  </data>
+  <data name="ConcurrentDictionary_CapacityMustNotBeNegative" xml:space="preserve">
+    <value>The capacity argument must be greater than or equal to zero.</value>
+  </data>
+  <data name="ConcurrentDictionary_ConcurrencyLevelMustBePositive" xml:space="preserve">
+    <value>The concurrencyLevel argument must be positive.</value>
+  </data>
+  <data name="ConcurrentDictionary_IndexIsNegative" xml:space="preserve">
+    <value>The index argument is less than zero.</value>
+  </data>
+  <data name="ConcurrentDictionary_ItemKeyIsNull" xml:space="preserve">
+    <value>TKey is a reference type and item.Key is null.</value>
+  </data>
+  <data name="ConcurrentDictionary_KeyAlreadyExisted" xml:space="preserve">
+    <value>The key already existed in the dictionary.</value>
+  </data>
+  <data name="ConcurrentDictionary_TypeOfKeyIncorrect" xml:space="preserve">
+    <value>The key was of an incorrect type for this dictionary.</value>
+  </data>
+  <data name="ConcurrentDictionary_TypeOfValueIncorrect" xml:space="preserve">
+    <value>The value was of an incorrect type for this dictionary.</value>
+  </data>
+  <data name="event_Barrier_PhaseFinished" xml:space="preserve">
+    <value>Barrier finishing phase {1}.</value>
+  </data>
+  <data name="event_ConcurrentBag_TryPeekSteals" xml:space="preserve">
+    <value>ConcurrentBag stealing in TryPeek.</value>
+  </data>
+  <data name="event_ConcurrentBag_TryTakeSteals" xml:space="preserve">
+    <value>ConcurrentBag stealing in TryTake.</value>
+  </data>
+  <data name="event_ConcurrentDictionary_AcquiringAllLocks" xml:space="preserve">
+    <value>ConcurrentDictionary acquiring all locks on {0} bucket(s).</value>
+  </data>
+  <data name="event_ConcurrentStack_FastPopFailed" xml:space="preserve">
+    <value>Pop from ConcurrentStack spun {0} time(s).</value>
+  </data>
+  <data name="event_ConcurrentStack_FastPushFailed" xml:space="preserve">
+    <value>Push to ConcurrentStack spun {0} time(s).</value>
+  </data>
+  <data name="event_ParallelFork" xml:space="preserve">
+    <value>Task {1} entering fork/join {2}.</value>
+  </data>
+  <data name="event_ParallelInvokeBegin" xml:space="preserve">
+    <value>Beginning ParallelInvoke {2} from Task {1} for {4} actions.</value>
+  </data>
+  <data name="event_ParallelInvokeEnd" xml:space="preserve">
+    <value>Ending ParallelInvoke {2}.</value>
+  </data>
+  <data name="event_ParallelJoin" xml:space="preserve">
+    <value>Task {1} leaving fork/join {2}.</value>
+  </data>
+  <data name="event_ParallelLoopBegin" xml:space="preserve">
+    <value>Beginning {3} loop {2} from Task {1}.</value>
+  </data>
+  <data name="event_ParallelLoopEnd" xml:space="preserve">
+    <value>Ending loop {2} after {3} iterations.</value>
+  </data>
+  <data name="event_SpinLock_FastPathFailed" xml:space="preserve">
+    <value>SpinLock beginning to spin.</value>
+  </data>
+  <data name="event_SpinWait_NextSpinWillYield" xml:space="preserve">
+    <value>Next spin will yield.</value>
+  </data>
+  <data name="event_TaskCompleted" xml:space="preserve">
+    <value>Task {2} completed.</value>
+  </data>
+  <data name="event_TaskScheduled" xml:space="preserve">
+    <value>Task {2} scheduled to TaskScheduler {0}.</value>
+  </data>
+  <data name="event_TaskStarted" xml:space="preserve">
+    <value>Task {2} executing.</value>
+  </data>
+  <data name="event_TaskWaitBegin" xml:space="preserve">
+    <value>Beginning wait ({3}) on Task {2}.</value>
+  </data>
+  <data name="event_TaskWaitEnd" xml:space="preserve">
+    <value>Ending wait on Task {2}.</value>
+  </data>
+  <data name="EventSource_AbstractMustNotDeclareEventMethods" xml:space="preserve">
+    <value>Abstract event source must not declare event methods ({0} with ID {1}).</value>
+  </data>
+  <data name="EventSource_AbstractMustNotDeclareKTOC" xml:space="preserve">
+    <value>Abstract event source must not declare {0} nested type.</value>
+  </data>
+  <data name="EventSource_AddScalarOutOfRange" xml:space="preserve">
+    <value>Getting out of bounds during scalar addition.</value>
+  </data>
+  <data name="EventSource_BadHexDigit" xml:space="preserve">
+    <value>Bad Hexidecimal digit "{0}".</value>
+  </data>
+  <data name="EventSource_ChannelTypeDoesNotMatchEventChannelValue" xml:space="preserve">
+    <value>Channel {0} does not match event channel value {1}.</value>
+  </data>
+  <data name="EventSource_DataDescriptorsOutOfRange" xml:space="preserve">
+    <value>Data descriptors are out of range.</value>
+  </data>
+  <data name="EventSource_DuplicateStringKey" xml:space="preserve">
+    <value>Multiple definitions for string "{0}".</value>
+  </data>
+  <data name="EventSource_EnumKindMismatch" xml:space="preserve">
+    <value>The type of {0} is not expected in {1}.</value>
+  </data>
+  <data name="EventSource_EvenHexDigits" xml:space="preserve">
+    <value>Must have an even number of Hexidecimal digits.</value>
+  </data>
+  <data name="EventSource_EventChannelOutOfRange" xml:space="preserve">
+    <value>Channel {0} has a value of {1} which is outside the legal range (16-254).</value>
+  </data>
+  <data name="EventSource_EventIdReused" xml:space="preserve">
+    <value>Event {0} has ID {1} which is already in use.</value>
+  </data>
+  <data name="EventSource_EventMustHaveTaskIfNonDefaultOpcode" xml:space="preserve">
+    <value>Event {0} (with ID {1}) has a non-default opcode but not a task.</value>
+  </data>
+  <data name="EventSource_EventMustNotBeExplicitImplementation" xml:space="preserve">
+    <value>Event method {0} (with ID {1}) is an explicit interface method implementation. Re-write method as implicit implementation.</value>
+  </data>
+  <data name="EventSource_EventNameDoesNotEqualTaskPlusOpcode" xml:space="preserve">
+    <value>Event {0} (with ID {1}) has a name that is not the concatenation of its task name and opcode.</value>
+  </data>
+  <data name="EventSource_EventNameReused" xml:space="preserve">
+    <value>Event name {0} used more than once.  If you wish to overload a method, the overloaded method should have a NonEvent attribute.</value>
+  </data>
+  <data name="EventSource_EventParametersMismatch" xml:space="preserve">
+    <value>Event {0} was called with {1} argument(s), but it is defined with {2} parameter(s).</value>
+  </data>
+  <data name="EventSource_EventSourceGuidInUse" xml:space="preserve">
+    <value>An instance of EventSource with Guid {0} already exists.</value>
+  </data>
+  <data name="EventSource_EventTooBig" xml:space="preserve">
+    <value>The payload for a single event is too large.</value>
+  </data>
+  <data name="EventSource_EventWithAdminChannelMustHaveMessage" xml:space="preserve">
+    <value>Event {0} specifies an Admin channel {1}. It must specify a Message property.</value>
+  </data>
+  <data name="EventSource_IllegalKeywordsValue" xml:space="preserve">
+    <value>Keyword {0} has a value of {1} which is outside the legal range (0-0x0000080000000000).</value>
+  </data>
+  <data name="EventSource_IllegalOpcodeValue" xml:space="preserve">
+    <value>Opcode {0} has a value of {1} which is outside the legal range (11-238).</value>
+  </data>
+  <data name="EventSource_IllegalTaskValue" xml:space="preserve">
+    <value>Task {0} has a value of {1} which is outside the legal range (1-65535).</value>
+  </data>
+  <data name="EventSource_IllegalValue" xml:space="preserve">
+    <value>Illegal value "{0}" (prefix strings with @ to indicate a literal string).</value>
+  </data>
+  <data name="EventSource_IncorrentlyAuthoredTypeInfo" xml:space="preserve">
+    <value>Incorrectly-authored TypeInfo - a type should be serialized as one field or as one group</value>
+  </data>
+  <data name="EventSource_InvalidCommand" xml:space="preserve">
+    <value>Invalid command value.</value>
+  </data>
+  <data name="EventSource_InvalidEventFormat" xml:space="preserve">
+    <value>Can't specify both etw event format flags.</value>
+  </data>
+  <data name="EventSource_KeywordCollision" xml:space="preserve">
+    <value>Keywords {0} and {1} are defined with the same value ({2}).</value>
+  </data>
+  <data name="EventSource_KeywordNeedPowerOfTwo" xml:space="preserve">
+    <value>Value {0} for keyword {1} needs to be a power of 2.</value>
+  </data>
+  <data name="EventSource_ListenerCreatedInsideCallback" xml:space="preserve">
+    <value>Creating an EventListener inside a EventListener callback.</value>
+  </data>
+  <data name="EventSource_ListenerNotFound" xml:space="preserve">
+    <value>Listener not found.</value>
+  </data>
+  <data name="EventSource_ListenerWriteFailure" xml:space="preserve">
+    <value>An error occurred when writing to a listener.</value>
+  </data>
+  <data name="EventSource_MaxChannelExceeded" xml:space="preserve">
+    <value>Attempt to define more than the maximum limit of 8 channels for a provider.</value>
+  </data>
+  <data name="EventSource_MismatchIdToWriteEvent" xml:space="preserve">
+    <value>Event {0} was assigned event ID {1} but {2} was passed to WriteEvent.</value>
+  </data>
+  <data name="EventSource_NeedGuid" xml:space="preserve">
+    <value>The Guid of an EventSource must be non zero.</value>
+  </data>
+  <data name="EventSource_NeedName" xml:space="preserve">
+    <value>The name of an EventSource must not be null.</value>
+  </data>
+  <data name="EventSource_NeedPositiveId" xml:space="preserve">
+    <value>Event IDs must be positive integers.</value>
+  </data>
+  <data name="EventSource_NoFreeBuffers" xml:space="preserve">
+    <value>No Free Buffers available from the operating system (e.g. event rate too fast).</value>
+  </data>
+  <data name="EventSource_NonCompliantTypeError" xml:space="preserve">
+    <value>The API supports only anonymous types or types decorated with the EventDataAttribute. Non-compliant type: {0} dataType.</value>
+  </data>
+  <data name="EventSource_NoRelatedActivityId" xml:space="preserve">
+    <value>EventSource expects the first parameter of the Event method to be of type Guid and to be named "relatedActivityId" when calling WriteEventWithRelatedActivityId.</value>
+  </data>
+  <data name="EventSource_NotSupportedArrayOfBinary" xml:space="preserve">
+    <value>Arrays of Binary are not supported.</value>
+  </data>
+  <data name="EventSource_NotSupportedArrayOfNil" xml:space="preserve">
+    <value>Arrays of Nil are not supported.</value>
+  </data>
+  <data name="EventSource_NotSupportedArrayOfNullTerminatedString" xml:space="preserve">
+    <value>Arrays of null-terminated string are not supported.</value>
+  </data>
+  <data name="EventSource_NotSupportedCustomSerializedData" xml:space="preserve">
+    <value>Enumerables of custom-serialized data are not supported</value>
+  </data>
+  <data name="EventSource_NotSupportedNestedArraysEnums" xml:space="preserve">
+    <value>Nested arrays/enumerables are not supported.</value>
+  </data>
+  <data name="EventSource_NullInput" xml:space="preserve">
+    <value>Null passed as a event argument.</value>
+  </data>
+  <data name="EventSource_OpcodeCollision" xml:space="preserve">
+    <value>Opcodes {0} and {1} are defined with the same value ({2}).</value>
+  </data>
+  <data name="EventSource_PinArrayOutOfRange" xml:space="preserve">
+    <value>Pins are out of range.</value>
+  </data>
+  <data name="EventSource_RecursiveTypeDefinition" xml:space="preserve">
+    <value>Recursive type definition is not supported.</value>
+  </data>
+  <data name="EventSource_SessionIdError" xml:space="preserve">
+    <value>Bit position in AllKeywords ({0}) must equal the command argument named "EtwSessionKeyword" ({1}).</value>
+  </data>
+  <data name="EventSource_StopsFollowStarts" xml:space="preserve">
+    <value>An event with stop suffix must follow a corresponding event with a start suffix.</value>
+  </data>
+  <data name="EventSource_TaskCollision" xml:space="preserve">
+    <value>Tasks {0} and {1} are defined with the same value ({2}).</value>
+  </data>
+  <data name="EventSource_TaskOpcodePairReused" xml:space="preserve">
+    <value>Event {0} (with ID {1}) has the same task/opcode pair as event {2} (with ID {3}).</value>
+  </data>
+  <data name="EventSource_TooManyArgs" xml:space="preserve">
+    <value>Too many arguments.</value>
+  </data>
+  <data name="EventSource_TooManyFields" xml:space="preserve">
+    <value>Too many fields in structure.</value>
+  </data>
+  <data name="EventSource_ToString" xml:space="preserve">
+    <value>EventSource({0}, {1})</value>
+  </data>
+  <data name="EventSource_TraitEven" xml:space="preserve">
+    <value>There must be an even number of trait strings (they are key-value pairs).</value>
+  </data>
+  <data name="EventSource_TypeMustBeSealedOrAbstract" xml:space="preserve">
+    <value>Event source types must be sealed or abstract.</value>
+  </data>
+  <data name="EventSource_TypeMustDeriveFromEventSource" xml:space="preserve">
+    <value>Event source types must derive from EventSource.</value>
+  </data>
+  <data name="EventSource_UndefinedChannel" xml:space="preserve">
+    <value>Use of undefined channel value {0} for event {1}.</value>
+  </data>
+  <data name="EventSource_UndefinedKeyword" xml:space="preserve">
+    <value>Use of undefined keyword value {0} for event {1}.</value>
+  </data>
+  <data name="EventSource_UndefinedOpcode" xml:space="preserve">
+    <value>Use of undefined opcode value {0} for event {1}.</value>
+  </data>
+  <data name="EventSource_UnknownEtwTrait" xml:space="preserve">
+    <value>Unknown ETW trait "{0}".</value>
+  </data>
+  <data name="EventSource_UnsupportedEventTypeInManifest" xml:space="preserve">
+    <value>Unsupported type {0} in event source.</value>
+  </data>
+  <data name="EventSource_UnsupportedMessageProperty" xml:space="preserve">
+    <value>Event {0} specifies an illegal or unsupported formatting message ("{1}").</value>
+  </data>
+  <data name="EventSource_VarArgsParameterMismatch" xml:space="preserve">
+    <value>The parameters to the Event method do not match the parameters to the WriteEvent method. This may cause the event to be displayed incorrectly.</value>
+  </data>
+  <data name="Exception_EndOfInnerExceptionStack" xml:space="preserve">
+    <value>--- End of inner exception stack trace ---</value>
+  </data>
+  <data name="Exception_EndStackTraceFromPreviousThrow" xml:space="preserve">
+    <value>--- End of stack trace from previous location where exception was thrown ---</value>
+  </data>
+  <data name="Exception_WasThrown" xml:space="preserve">
+    <value>Exception of type '{0}' was thrown.</value>
+  </data>
+  <data name="ExecutionContext_ExceptionInAsyncLocalNotification" xml:space="preserve">
+    <value>An exception was not handled in an AsyncLocal&lt;T&gt; notification callback.</value>
+  </data>
+  <data name="FieldAccess_InitOnly" xml:space="preserve">
+    <value>InitOnly (aka ReadOnly) fields can only be initialized in the type/instance constructor.</value>
+  </data>
+  <data name="FileNotFound_ResolveAssembly" xml:space="preserve">
+    <value>Could not resolve assembly '{0}'.</value>
+  </data>
+  <data name="Format_AttributeUsage" xml:space="preserve">
+    <value>Duplicate AttributeUsageAttribute found on attribute type {0}.</value>
+  </data>
+  <data name="Format_Bad7BitInt32" xml:space="preserve">
+    <value>Too many bytes in what should have been a 7 bit encoded Int32.</value>
+  </data>
+  <data name="Format_BadBase" xml:space="preserve">
+    <value>Invalid digits for the specified base.</value>
+  </data>
+  <data name="Format_BadBase64Char" xml:space="preserve">
+    <value>The input is not a valid Base-64 string as it contains a non-base 64 character, more than two padding characters, or an illegal character among the padding characters.</value>
+  </data>
+  <data name="Format_BadBase64CharArrayLength" xml:space="preserve">
+    <value>Invalid length for a Base-64 char array or string.</value>
+  </data>
+  <data name="Format_BadBoolean" xml:space="preserve">
+    <value>String '{0}' was not recognized as a valid Boolean.</value>
+  </data>
+  <data name="Format_BadDatePattern" xml:space="preserve">
+    <value>Could not determine the order of year, month, and date from '{0}'.</value>
+  </data>
+  <data name="Format_BadDateTime" xml:space="preserve">
+    <value>String '{0}' was not recognized as a valid DateTime.</value>
+  </data>
+  <data name="Format_BadDateTimeCalendar" xml:space="preserve">
+    <value>The DateTime represented by the string '{0}' is not supported in calendar '{1}'.</value>
+  </data>
+  <data name="Format_BadDayOfWeek" xml:space="preserve">
+    <value>String '{0}' was not recognized as a valid DateTime because the day of week was incorrect.</value>
+  </data>
+  <data name="Format_BadFormatSpecifier" xml:space="preserve">
+    <value>Format specifier '{0}' was invalid.</value>
+  </data>
+  <data name="Format_NoFormatSpecifier" xml:space="preserve">
+    <value>No format specifiers were provided.</value>
+  </data>
+  <data name="Format_BadQuote" xml:space="preserve">
+    <value>Cannot find a matching quote character for the character '{0}'.</value>
+  </data>
+  <data name="Format_BadTimeSpan" xml:space="preserve">
+    <value>String '{0}' was not recognized as a valid TimeSpan.</value>
+  </data>
+  <data name="Format_DateOutOfRange" xml:space="preserve">
+    <value>The DateTime represented by the string '{0}' is out of range.</value>
+  </data>
+  <data name="Format_EmptyInputString" xml:space="preserve">
+    <value>Input string was either empty or contained only whitespace.</value>
+  </data>
+  <data name="Format_ExtraJunkAtEnd" xml:space="preserve">
+    <value>Additional non-parsable characters are at the end of the string.</value>
+  </data>
+  <data name="Format_GuidBrace" xml:space="preserve">
+    <value>Expected {0xdddddddd, etc}.</value>
+  </data>
+  <data name="Format_GuidBraceAfterLastNumber" xml:space="preserve">
+    <value>Could not find a brace, or the length between the previous token and the brace was zero (i.e., '0x,'etc.).</value>
+  </data>
+  <data name="Format_GuidComma" xml:space="preserve">
+    <value>Could not find a comma, or the length between the previous token and the comma was zero (i.e., '0x,'etc.).</value>
+  </data>
+  <data name="Format_GuidDashes" xml:space="preserve">
+    <value>Dashes are in the wrong position for GUID parsing.</value>
+  </data>
+  <data name="Format_GuidEndBrace" xml:space="preserve">
+    <value>Could not find the ending brace.</value>
+  </data>
+  <data name="Format_GuidHexPrefix" xml:space="preserve">
+    <value>Expected hex 0x in '{0}'.</value>
+  </data>
+  <data name="Format_GuidInvalidChar" xml:space="preserve">
+    <value>Guid string should only contain hexadecimal characters.</value>
+  </data>
+  <data name="Format_GuidInvLen" xml:space="preserve">
+    <value>Guid should contain 32 digits with 4 dashes (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx).</value>
+  </data>
+  <data name="Format_GuidUnrecognized" xml:space="preserve">
+    <value>Unrecognized Guid format.</value>
+  </data>
+  <data name="Format_IndexOutOfRange" xml:space="preserve">
+    <value>Index (zero based) must be greater than or equal to zero and less than the size of the argument list.</value>
+  </data>
+  <data name="Format_InvalidEnumFormatSpecification" xml:space="preserve">
+    <value>Format string can be only "G", "g", "X", "x", "F", "f", "D" or "d".</value>
+  </data>
+  <data name="Format_InvalidGuidFormatSpecification" xml:space="preserve">
+    <value>Format string can be only "D", "d", "N", "n", "P", "p", "B", "b", "X" or "x".</value>
+  </data>
+  <data name="Format_InvalidString" xml:space="preserve">
+    <value>Input string was not in a correct format.</value>
+  </data>
+  <data name="Format_MissingIncompleteDate" xml:space="preserve">
+    <value>There must be at least a partial date with a year present in the input string '{0}'.</value>
+  </data>
+  <data name="Format_NeedSingleChar" xml:space="preserve">
+    <value>String must be exactly one character long.</value>
+  </data>
+  <data name="Format_NoParsibleDigits" xml:space="preserve">
+    <value>Could not find any recognizable digits.</value>
+  </data>
+  <data name="Format_OffsetOutOfRange" xml:space="preserve">
+    <value>The time zone offset of string '{0}' must be within plus or minus 14 hours.</value>
+  </data>
+  <data name="Format_RepeatDateTimePattern" xml:space="preserve">
+    <value>DateTime pattern '{0}' appears more than once with different values.</value>
+  </data>
+  <data name="Format_StringZeroLength" xml:space="preserve">
+    <value>String cannot have zero length.</value>
+  </data>
+  <data name="Format_UnknownDateTimeWord" xml:space="preserve">
+    <value>The string '{0}' was not recognized as a valid DateTime. There is an unknown word starting at index '{1}'.</value>
+  </data>
+  <data name="Format_UTCOutOfRange" xml:space="preserve">
+    <value>The UTC representation of the date '{0}' falls outside the year range 1-9999.</value>
+  </data>
+  <data name="Globalization_cp_1200" xml:space="preserve">
+    <value>Unicode</value>
+  </data>
+  <data name="Globalization_cp_12000" xml:space="preserve">
+    <value>Unicode (UTF-32)</value>
+  </data>
+  <data name="Globalization_cp_12001" xml:space="preserve">
+    <value>Unicode (UTF-32 Big-Endian)</value>
+  </data>
+  <data name="Globalization_cp_1201" xml:space="preserve">
+    <value>Unicode (Big-Endian)</value>
+  </data>
+  <data name="Globalization_cp_20127" xml:space="preserve">
+    <value>US-ASCII</value>
+  </data>
+  <data name="Globalization_cp_28591" xml:space="preserve">
+    <value>Western European (ISO)</value>
+  </data>
+  <data name="Globalization_cp_65000" xml:space="preserve">
+    <value>Unicode (UTF-7)</value>
+  </data>
+  <data name="Globalization_cp_65001" xml:space="preserve">
+    <value>Unicode (UTF-8)</value>
+  </data>
+  <data name="IndexOutOfRange_ArrayRankIndex" xml:space="preserve">
+    <value>Array does not have that many dimensions.</value>
+  </data>
+  <data name="IndexOutOfRange_UMSPosition" xml:space="preserve">
+    <value>Unmanaged memory stream position was beyond the capacity of the stream.</value>
+  </data>
+  <data name="InsufficientMemory_MemFailPoint" xml:space="preserve">
+    <value>Insufficient available memory to meet the expected demands of an operation at this time.  Please try again later.</value>
+  </data>
+  <data name="InsufficientMemory_MemFailPoint_TooBig" xml:space="preserve">
+    <value>Insufficient memory to meet the expected demands of an operation, and this system is likely to never satisfy this request.  If this is a 32 bit system, consider booting in 3 GB mode.</value>
+  </data>
+  <data name="InsufficientMemory_MemFailPoint_VAFrag" xml:space="preserve">
+    <value>Insufficient available memory to meet the expected demands of an operation at this time, possibly due to virtual address space fragmentation.  Please try again later.</value>
+  </data>
+  <data name="Interop_COM_TypeMismatch" xml:space="preserve">
+    <value>Type mismatch between source and destination types.</value>
+  </data>
+  <data name="Interop_Marshal_Unmappable_Char" xml:space="preserve">
+    <value>Cannot marshal: Encountered unmappable character.</value>
+  </data>
+  <data name="InvalidCast_CannotCastNullToValueType" xml:space="preserve">
+    <value>Null object cannot be converted to a value type.</value>
+  </data>
+  <data name="InvalidCast_CannotCoerceByRefVariant" xml:space="preserve">
+    <value>Object cannot be coerced to the original type of the ByRef VARIANT it was obtained from.</value>
+  </data>
+  <data name="InvalidCast_DBNull" xml:space="preserve">
+    <value>Object cannot be cast to DBNull.</value>
+  </data>
+  <data name="InvalidCast_DownCastArrayElement" xml:space="preserve">
+    <value>At least one element in the source array could not be cast down to the destination array type.</value>
+  </data>
+  <data name="InvalidCast_Empty" xml:space="preserve">
+    <value>Object cannot be cast to Empty.</value>
+  </data>
+  <data name="InvalidCast_FromDBNull" xml:space="preserve">
+    <value>Object cannot be cast from DBNull to other types.</value>
+  </data>
+  <data name="InvalidCast_FromTo" xml:space="preserve">
+    <value>Invalid cast from '{0}' to '{1}'.</value>
+  </data>
+  <data name="InvalidCast_IConvertible" xml:space="preserve">
+    <value>Object must implement IConvertible.</value>
+  </data>
+  <data name="InvalidCast_OATypeMismatch" xml:space="preserve">
+    <value>OleAut reported a type mismatch.</value>
+  </data>
+  <data name="InvalidCast_StoreArrayElement" xml:space="preserve">
+    <value>Object cannot be stored in an array of this type.</value>
+  </data>
+  <data name="InvalidCast_WinRTIPropertyValueArrayCoersion" xml:space="preserve">
+    <value>Object in an IPropertyValue is of type '{0}' which cannot be convereted to a '{1}' due to array element '{2}': {3}.</value>
+  </data>
+  <data name="InvalidCast_WinRTIPropertyValueCoersion" xml:space="preserve">
+    <value>Object in an IPropertyValue is of type '{0}' with value '{1}', which cannot be converted to a '{2}'.</value>
+  </data>
+  <data name="InvalidCast_WinRTIPropertyValueElement" xml:space="preserve">
+    <value>Object in an IPropertyValue is of type '{0}', which cannot be converted to a '{1}'.</value>
+  </data>
+  <data name="InvalidOperation_AsyncFlowCtrlCtxMismatch" xml:space="preserve">
+    <value>AsyncFlowControl objects can be used to restore flow only on a Context that had its flow suppressed.</value>
+  </data>
+  <data name="InvalidOperation_AsyncIOInProgress" xml:space="preserve">
+    <value>The stream is currently in use by a previous operation on the stream.</value>
+  </data>
+  <data name="InvalidOperation_BadEmptyMethodBody" xml:space="preserve">
+    <value>Method '{0}' does not have a method body.</value>
+  </data>
+  <data name="InvalidOperation_BadILGeneratorUsage" xml:space="preserve">
+    <value>ILGenerator usage is invalid.</value>
+  </data>
+  <data name="InvalidOperation_BadInstructionOrIndexOutOfBound" xml:space="preserve">
+    <value>MSIL instruction is invalid or index is out of bounds.</value>
+  </data>
+  <data name="InvalidOperation_BadInterfaceNotAbstract" xml:space="preserve">
+    <value>Interface must be declared abstract.</value>
+  </data>
+  <data name="InvalidOperation_BadMethodBody" xml:space="preserve">
+    <value>Method '{0}' cannot have a method body.</value>
+  </data>
+  <data name="InvalidOperation_BadTypeAttributesNotAbstract" xml:space="preserve">
+    <value>Type must be declared abstract if any of its methods are abstract.</value>
+  </data>
+  <data name="InvalidOperation_CalledTwice" xml:space="preserve">
+    <value>The method cannot be called twice on the same instance.</value>
+  </data>
+  <data name="InvalidOperation_CannotImportGlobalFromDifferentModule" xml:space="preserve">
+    <value>Unable to import a global method or field from a different module.</value>
+  </data>
+  <data name="InvalidOperation_CannotRemoveLastFromEmptyCollection" xml:space="preserve">
+    <value>Cannot remove the last element from an empty collection.</value>
+  </data>
+  <data name="InvalidOperation_CannotRestoreUnsupressedFlow" xml:space="preserve">
+    <value>Cannot restore context flow when it is not suppressed.</value>
+  </data>
+  <data name="InvalidOperation_CannotSupressFlowMultipleTimes" xml:space="preserve">
+    <value>Context flow is already suppressed.</value>
+  </data>
+  <data name="InvalidOperation_CannotUseAFCMultiple" xml:space="preserve">
+    <value>AsyncFlowControl object can be used only once to call Undo().</value>
+  </data>
+  <data name="InvalidOperation_CannotUseAFCOtherThread" xml:space="preserve">
+    <value>AsyncFlowControl object must be used on the thread where it was created.</value>
+  </data>
+  <data name="InvalidOperation_CantInstantiateAbstractClass" xml:space="preserve">
+    <value>Instances of abstract classes cannot be created.</value>
+  </data>
+  <data name="InvalidOperation_CantInstantiateFunctionPointer" xml:space="preserve">
+    <value>Instances of function pointers cannot be created.</value>
+  </data>
+  <data name="InvalidOperation_CollectionBackingDictionaryTooLarge" xml:space="preserve">
+    <value>The collection backing this Dictionary contains too many elements.</value>
+  </data>
+  <data name="InvalidOperation_CollectionBackingListTooLarge" xml:space="preserve">
+    <value>The collection backing this List contains too many elements.</value>
+  </data>
+  <data name="InvalidOperation_CollectionCorrupted" xml:space="preserve">
+    <value>A prior operation on this collection was interrupted by an exception. Collection's state is no longer trusted.</value>
+  </data>
+  <data name="InvalidOperation_ConcurrentOperationsNotSupported" xml:space="preserve">
+    <value>Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct.</value>
+  </data>
+  <data name="InvalidOperation_ConstructorNotAllowedOnInterface" xml:space="preserve">
+    <value>Interface cannot have constructors.</value>
+  </data>
+  <data name="InvalidOperation_CriticalTransparentAreMutuallyExclusive" xml:space="preserve">
+    <value>SecurityTransparent and SecurityCritical attributes cannot be applied to the assembly scope at the same time.</value>
+  </data>
+  <data name="InvalidOperation_DateTimeParsing" xml:space="preserve">
+    <value>Internal Error in DateTime and Calendar operations.</value>
+  </data>
+  <data name="InvalidOperation_DebuggerLaunchFailed" xml:space="preserve">
+    <value>Debugger unable to launch.</value>
+  </data>
+  <data name="InvalidOperation_DefaultConstructorILGen" xml:space="preserve">
+    <value>Unable to access ILGenerator on a constructor created with DefineDefaultConstructor.</value>
+  </data>
+  <data name="InvalidOperation_EndReadCalledMultiple" xml:space="preserve">
+    <value>EndRead can only be called once for each asynchronous operation.</value>
+  </data>
+  <data name="InvalidOperation_EndWriteCalledMultiple" xml:space="preserve">
+    <value>EndWrite can only be called once for each asynchronous operation.</value>
+  </data>
+  <data name="InvalidOperation_EnumEnded" xml:space="preserve">
+    <value>Enumeration already finished.</value>
+  </data>
+  <data name="InvalidOperation_EnumFailedVersion" xml:space="preserve">
+    <value>Collection was modified; enumeration operation may not execute.</value>
+  </data>
+  <data name="InvalidOperation_EnumNotStarted" xml:space="preserve">
+    <value>Enumeration has not started. Call MoveNext.</value>
+  </data>
+  <data name="InvalidOperation_EnumOpCantHappen" xml:space="preserve">
+    <value>Enumeration has either not started or has already finished.</value>
+  </data>
+  <data name="InvalidOperation_EventInfoNotAvailable" xml:space="preserve">
+    <value>This API does not support EventInfo tokens.</value>
+  </data>
+  <data name="InvalidOperation_EventTokenTableRequiresDelegate" xml:space="preserve">
+    <value>Type '{0}' is not a delegate type.  EventTokenTable may only be used with delegate types.</value>
+  </data>
+  <data name="InvalidOperation_GenericParametersAlreadySet" xml:space="preserve">
+    <value>The generic parameters are already defined on this MethodBuilder.</value>
+  </data>
+  <data name="InvalidOperation_GetVersion" xml:space="preserve">
+    <value>OSVersion's call to GetVersionEx failed.</value>
+  </data>
+  <data name="InvalidOperation_GlobalsHaveBeenCreated" xml:space="preserve">
+    <value>Type definition of the global function has been completed.</value>
+  </data>
+  <data name="InvalidOperation_HandleIsNotInitialized" xml:space="preserve">
+    <value>Handle is not initialized.</value>
+  </data>
+  <data name="InvalidOperation_HandleIsNotPinned" xml:space="preserve">
+    <value>Handle is not pinned.</value>
+  </data>
+  <data name="InvalidOperation_HashInsertFailed" xml:space="preserve">
+    <value>Hashtable insert failed. Load factor too high. The most common cause is multiple threads writing to the Hashtable simultaneously.</value>
+  </data>
+  <data name="InvalidOperation_IComparerFailed" xml:space="preserve">
+    <value>Failed to compare two elements in the array.</value>
+  </data>
+  <data name="InvalidOperation_MethodBaked" xml:space="preserve">
+    <value>Type definition of the method is complete.</value>
+  </data>
+  <data name="InvalidOperation_MethodBuilderBaked" xml:space="preserve">
+    <value>The signature of the MethodBuilder can no longer be modified because an operation on the MethodBuilder caused the methodDef token to be created. For example, a call to SetCustomAttribute requires the methodDef token to emit the CustomAttribute token.</value>
+  </data>
+  <data name="InvalidOperation_MethodHasBody" xml:space="preserve">
+    <value>Method already has a body.</value>
+  </data>
+  <data name="InvalidOperation_MustCallInitialize" xml:space="preserve">
+    <value>You must call Initialize on this object instance before using it.</value>
+  </data>
+  <data name="InvalidOperation_NativeOverlappedReused" xml:space="preserve">
+    <value>NativeOverlapped cannot be reused for multiple operations.</value>
+  </data>
+  <data name="InvalidOperation_NoMultiModuleAssembly" xml:space="preserve">
+    <value>You cannot have more than one dynamic module in each dynamic assembly in this version of the runtime.</value>
+  </data>
+  <data name="InvalidOperation_NoPublicAddMethod" xml:space="preserve">
+    <value>Cannot add the event handler since no public add method exists for the event.</value>
+  </data>
+  <data name="InvalidOperation_NoPublicRemoveMethod" xml:space="preserve">
+    <value>Cannot remove the event handler since no public remove method exists for the event.</value>
+  </data>
+  <data name="InvalidOperation_NotADebugModule" xml:space="preserve">
+    <value>Not a debug ModuleBuilder.</value>
+  </data>
+  <data name="InvalidOperation_NotAllowedInDynamicMethod" xml:space="preserve">
+    <value>The requested operation is invalid for DynamicMethod.</value>
+  </data>
+  <data name="InvalidOperation_NotAllowedInReflectionOnly" xml:space="preserve">
+    <value>The requested operation is invalid in the ReflectionOnly context.</value>
+  </data>
+  <data name="InvalidOperation_NotAVarArgCallingConvention" xml:space="preserve">
+    <value>Calling convention must be VarArgs.</value>
+  </data>
+  <data name="InvalidOperation_NotGenericType" xml:space="preserve">
+    <value>This operation is only valid on generic types.</value>
+  </data>
+  <data name="InvalidOperation_NotSupportedOnWinRTEvent" xml:space="preserve">
+    <value>Adding or removing event handlers dynamically is not supported on WinRT events.</value>
+  </data>
+  <data name="InvalidOperation_NotWithConcurrentGC" xml:space="preserve">
+    <value>This API is not available when the concurrent GC is enabled.</value>
+  </data>
+  <data name="InvalidOperation_NoUnderlyingTypeOnEnum" xml:space="preserve">
+    <value>Underlying type information on enumeration is not specified.</value>
+  </data>
+  <data name="InvalidOperation_NoValue" xml:space="preserve">
+    <value>Nullable object must have a value.</value>
+  </data>
+  <data name="InvalidOperation_NullArray" xml:space="preserve">
+    <value>The underlying array is null.</value>
+  </data>
+  <data name="InvalidOperation_NullContext" xml:space="preserve">
+    <value>Cannot call Set on a null context</value>
+  </data>
+  <data name="InvalidOperation_NullModuleHandle" xml:space="preserve">
+    <value>The requested operation is invalid when called on a null ModuleHandle.</value>
+  </data>
+  <data name="InvalidOperation_OpenLocalVariableScope" xml:space="preserve">
+    <value>Local variable scope was not properly closed.</value>
+  </data>
+  <data name="InvalidOperation_Overlapped_Pack" xml:space="preserve">
+    <value>Cannot pack a packed Overlapped again.</value>
+  </data>
+  <data name="InvalidOperation_PropertyInfoNotAvailable" xml:space="preserve">
+    <value>This API does not support PropertyInfo tokens.</value>
+  </data>
+  <data name="InvalidOperation_ReadOnly" xml:space="preserve">
+    <value>Instance is read-only.</value>
+  </data>
+  <data name="InvalidOperation_ResMgrBadResSet_Type" xml:space="preserve">
+    <value>'{0}': ResourceSet derived classes must provide a constructor that takes a String file name and a constructor that takes a Stream.</value>
+  </data>
+  <data name="InvalidOperation_ResourceNotStream_Name" xml:space="preserve">
+    <value>Resource '{0}' was not a Stream - call GetObject instead.</value>
+  </data>
+  <data name="InvalidOperation_ResourceNotString_Name" xml:space="preserve">
+    <value>Resource '{0}' was not a String - call GetObject instead.</value>
+  </data>
+  <data name="InvalidOperation_ResourceNotString_Type" xml:space="preserve">
+    <value>Resource was of type '{0}' instead of String - call GetObject instead.</value>
+  </data>
+  <data name="InvalidOperation_SetData_OnlyOnce" xml:space="preserve">
+    <value>SetData can only be used to set the value of a given name once.</value>
+  </data>
+  <data name="InvalidOperation_ShouldNotHaveMethodBody" xml:space="preserve">
+    <value>Method body should not exist.</value>
+  </data>
+  <data name="InvalidOperation_StrongNameKeyPairRequired" xml:space="preserve">
+    <value>A strong name key pair is required to emit a strong-named dynamic assembly.</value>
+  </data>
+  <data name="InvalidOperation_ThreadWrongThreadStart" xml:space="preserve">
+    <value>The thread was created with a ThreadStart delegate that does not accept a parameter.</value>
+  </data>
+  <data name="InvalidOperation_TimeoutsNotSupported" xml:space="preserve">
+    <value>Timeouts are not supported on this stream.</value>
+  </data>
+  <data name="InvalidOperation_TypeCannotBeBoxed" xml:space="preserve">
+    <value>The given type cannot be boxed.</value>
+  </data>
+  <data name="InvalidOperation_TypeHasBeenCreated" xml:space="preserve">
+    <value>Unable to change after type has been created.</value>
+  </data>
+  <data name="InvalidOperation_TypeNotCreated" xml:space="preserve">
+    <value>Type has not been created.</value>
+  </data>
+  <data name="InvalidOperation_UnknownEnumType" xml:space="preserve">
+    <value>Unknown enum type.</value>
+  </data>
+  <data name="InvalidOperation_WriteOnce" xml:space="preserve">
+    <value>This property has already been set and cannot be modified.</value>
+  </data>
+  <data name="InvalidOperation_WrongAsyncResultOrEndCalledMultiple" xml:space="preserve">
+    <value>Either the IAsyncResult object did not come from the corresponding async method on this type, or the End method was called multiple times with the same IAsyncResult.</value>
+  </data>
+  <data name="InvalidOperation_WrongAsyncResultOrEndReadCalledMultiple" xml:space="preserve">
+    <value>Either the IAsyncResult object did not come from the corresponding async method on this type, or EndRead was called multiple times with the same IAsyncResult.</value>
+  </data>
+  <data name="InvalidOperation_WrongAsyncResultOrEndWriteCalledMultiple" xml:space="preserve">
+    <value>Either the IAsyncResult object did not come from the corresponding async method on this type, or EndWrite was called multiple times with the same IAsyncResult.</value>
+  </data>
+  <data name="InvalidProgram_Default" xml:space="preserve">
+    <value>Common Language Runtime detected an invalid program.</value>
+  </data>
+  <data name="InvalidTimeZone_InvalidFileData" xml:space="preserve">
+    <value>The time zone ID '{0}' was found on the local computer, but the file at '{1}' was corrupt.</value>
+  </data>
+  <data name="InvalidTimeZone_InvalidRegistryData" xml:space="preserve">
+    <value>The time zone ID '{0}' was found on the local computer, but the registry information was corrupt.</value>
+  </data>
+  <data name="InvalidTimeZone_InvalidJulianDay" xml:space="preserve">
+    <value>Invalid Julian day in POSIX strings.</value>
+  </data>
+  <data name="InvalidTimeZone_NJulianDayNotSupported" xml:space="preserve">
+    <value>Julian n day in POSIX strings is not supported.</value>
+  </data>
+  <data name="InvalidTimeZone_NoTTInfoStructures" xml:space="preserve">
+    <value>There are no ttinfo structures in the tzfile.  At least one ttinfo structure is required in order to construct a TimeZoneInfo object.</value>
+  </data>
+  <data name="InvalidTimeZone_UnparseablePosixMDateString" xml:space="preserve">
+    <value>'{0}' is not a valid POSIX-TZ-environment-variable MDate rule.  A valid rule has the format 'Mm.w.d'.</value>
+  </data>
+  <data name="InvariantFailed" xml:space="preserve">
+    <value>Invariant failed.</value>
+  </data>
+  <data name="InvariantFailed_Cnd" xml:space="preserve">
+    <value>Invariant failed: {0}</value>
+  </data>
+  <data name="IO_DriveNotFound_Drive" xml:space="preserve">
+    <value>Could not find the drive '{0}'. The drive might not be ready or might not be mapped.</value>
+  </data>
+  <data name="IO_EOF_ReadBeyondEOF" xml:space="preserve">
+    <value>Unable to read beyond the end of the stream.</value>
+  </data>
+  <data name="IO_FileLoad" xml:space="preserve">
+    <value>Could not load the specified file.</value>
+  </data>
+  <data name="IO_FileName_Name" xml:space="preserve">
+    <value>File name: '{0}'</value>
+  </data>
+  <data name="IO_FileNotFound" xml:space="preserve">
+    <value>Unable to find the specified file.</value>
+  </data>
+  <data name="IO_FileNotFound_FileName" xml:space="preserve">
+    <value>Could not find file '{0}'.</value>
+  </data>
+  <data name="IO_AlreadyExists_Name" xml:space="preserve">
+    <value>Cannot create '{0}' because a file or directory with the same name already exists.</value>
+  </data>
+  <data name="IO_BindHandleFailed" xml:space="preserve">
+    <value>BindHandle for ThreadPool failed on this handle.</value>
+  </data>
+  <data name="IO_FileExists_Name" xml:space="preserve">
+    <value>The file '{0}' already exists.</value>
+  </data>
+  <data name="IO_FileStreamHandlePosition" xml:space="preserve">
+    <value>The OS handle's position is not what FileStream expected. Do not use a handle simultaneously in one FileStream and in Win32 code or another FileStream. This may cause data loss.</value>
+  </data>
+  <data name="IO_FileTooLong2GB" xml:space="preserve">
+    <value>The file is too long. This operation is currently limited to supporting files less than 2 gigabytes in size.</value>
+  </data>
+  <data name="IO_FileTooLongOrHandleNotSync" xml:space="preserve">
+    <value>IO operation will not work. Most likely the file will become too long or the handle was not opened to support synchronous IO operations.</value>
+  </data>
+  <data name="IO_FixedCapacity" xml:space="preserve">
+    <value>Unable to expand length of this stream beyond its capacity.</value>
+  </data>
+  <data name="IO_InvalidStringLen_Len" xml:space="preserve">
+    <value>BinaryReader encountered an invalid string length of {0} characters.</value>
+  </data>
+  <data name="IO_SeekAppendOverwrite" xml:space="preserve">
+    <value>Unable seek backward to overwrite data that previously existed in a file opened in Append mode.</value>
+  </data>
+  <data name="IO_SeekBeforeBegin" xml:space="preserve">
+    <value>An attempt was made to move the position before the beginning of the stream.</value>
+  </data>
+  <data name="IO_SetLengthAppendTruncate" xml:space="preserve">
+    <value>Unable to truncate data that previously existed in a file opened in Append mode.</value>
+  </data>
+  <data name="IO_SharingViolation_File" xml:space="preserve">
+    <value>The process cannot access the file '{0}' because it is being used by another process.</value>
+  </data>
+  <data name="IO_SharingViolation_NoFileName" xml:space="preserve">
+    <value>The process cannot access the file because it is being used by another process.</value>
+  </data>
+  <data name="IO_StreamTooLong" xml:space="preserve">
+    <value>Stream was too long.</value>
+  </data>
+  <data name="IO_PathNotFound_NoPathName" xml:space="preserve">
+    <value>Could not find a part of the path.</value>
+  </data>
+  <data name="IO_PathNotFound_Path" xml:space="preserve">
+    <value>Could not find a part of the path '{0}'.</value>
+  </data>
+  <data name="IO_PathTooLong" xml:space="preserve">
+    <value>The specified file name or path is too long, or a component of the specified path is too long.</value>
+  </data>
+  <data name="IO_PathTooLong_Path" xml:space="preserve">
+    <value>The path '{0}' is too long, or a component of the specified path is too long.</value>
+  </data>
+  <data name="IO_UnknownFileName" xml:space="preserve">
+    <value>[Unknown]</value>
+  </data>
+  <data name="Lazy_CreateValue_NoParameterlessCtorForT" xml:space="preserve">
+    <value>The lazily-initialized type does not have a public, parameterless constructor.</value>
+  </data>
+  <data name="Lazy_ctor_ModeInvalid" xml:space="preserve">
+    <value>The mode argument specifies an invalid value.</value>
+  </data>
+  <data name="Lazy_StaticInit_InvalidOperation" xml:space="preserve">
+    <value>ValueFactory returned null.</value>
+  </data>
+  <data name="Lazy_ToString_ValueNotCreated" xml:space="preserve">
+    <value>Value is not created.</value>
+  </data>
+  <data name="Lazy_Value_RecursiveCallsToValue" xml:space="preserve">
+    <value>ValueFactory attempted to access the Value property of this instance.</value>
+  </data>
+  <data name="Loader_ContextPolicies" xml:space="preserve">
+    <value>Context Policies:</value>
+  </data>
+  <data name="Loader_Name" xml:space="preserve">
+    <value>Name:</value>
+  </data>
+  <data name="Loader_NoContextPolicies" xml:space="preserve">
+    <value>There are no context policies.</value>
+  </data>
+  <data name="ManualResetEventSlim_ctor_SpinCountOutOfRange" xml:space="preserve">
+    <value>The spinCount argument must be in the range 0 to {0}, inclusive.</value>
+  </data>
+  <data name="ManualResetEventSlim_ctor_TooManyWaiters" xml:space="preserve">
+    <value>There are too many threads currently waiting on the event. A maximum of {0} waiting threads are supported.</value>
+  </data>
+  <data name="ManualResetEventSlim_Disposed" xml:space="preserve">
+    <value>The event has been disposed.</value>
+  </data>
+  <data name="Marshaler_StringTooLong" xml:space="preserve">
+    <value>Marshaler restriction: Excessively long string.</value>
+  </data>
+  <data name="MissingConstructor_Name" xml:space="preserve">
+    <value>Constructor on type '{0}' not found.</value>
+  </data>
+  <data name="MissingField" xml:space="preserve">
+    <value>Field not found.</value>
+  </data>
+  <data name="MissingField_Name" xml:space="preserve">
+    <value>Field '{0}' not found.</value>
+  </data>
+  <data name="MissingManifestResource_LooselyLinked" xml:space="preserve">
+    <value>Could not find a manifest resource entry called "{0}" in assembly "{1}". Please check spelling, capitalization, and build rules to ensure "{0}" is being linked into the assembly.</value>
+  </data>
+  <data name="MissingManifestResource_MultipleBlobs" xml:space="preserve">
+    <value>A case-insensitive lookup for resource file "{0}" in assembly "{1}" found multiple entries. Remove the duplicates or specify the exact case.</value>
+  </data>
+  <data name="MissingManifestResource_NoNeutralAsm" xml:space="preserve">
+    <value>Could not find any resources appropriate for the specified culture or the neutral culture.  Make sure "{0}" was correctly embedded or linked into assembly "{1}" at compile time, or that all the satellite assemblies required are loadable and fully signed.</value>
+  </data>
+  <data name="MissingManifestResource_NoNeutralDisk" xml:space="preserve">
+    <value>Could not find any resources appropriate for the specified culture (or the neutral culture) on disk.</value>
+  </data>
+  <data name="MissingManifestResource_NoPRIresources" xml:space="preserve">
+    <value>Unable to open Package Resource Index.</value>
+  </data>
+  <data name="MissingManifestResource_ResWFileNotLoaded" xml:space="preserve">
+    <value>Unable to load resources for resource file "{0}" in package "{1}".</value>
+  </data>
+  <data name="MissingMember" xml:space="preserve">
+    <value>Member not found.</value>
+  </data>
+  <data name="MissingMember_Name" xml:space="preserve">
+    <value>Member '{0}' not found.</value>
+  </data>
+  <data name="MissingMemberNestErr" xml:space="preserve">
+    <value>TypedReference can only be made on nested value Types.</value>
+  </data>
+  <data name="MissingMemberTypeRef" xml:space="preserve">
+    <value>FieldInfo does not match the target Type.</value>
+  </data>
+  <data name="MissingMethod_Name" xml:space="preserve">
+    <value>Method '{0}' not found.</value>
+  </data>
+  <data name="MissingSatelliteAssembly_Culture_Name" xml:space="preserve">
+    <value>The satellite assembly named "{1}" for fallback culture "{0}" either could not be found or could not be loaded. This is generally a setup problem. Please consider reinstalling or repairing the application.</value>
+  </data>
+  <data name="MissingSatelliteAssembly_Default" xml:space="preserve">
+    <value>Resource lookup fell back to the ultimate fallback resources in a satellite assembly, but that satellite either was not found or could not be loaded. Please consider reinstalling or repairing the application.</value>
+  </data>
+  <data name="Multicast_Combine" xml:space="preserve">
+    <value>Delegates that are not of type MulticastDelegate may not be combined.</value>
+  </data>
+  <data name="MustUseCCRewrite" xml:space="preserve">
+    <value>An assembly (probably "{1}") must be rewritten using the code contracts binary rewriter (CCRewrite) because it is calling Contract.{0} and the CONTRACTS_FULL symbol is defined.  Remove any explicit definitions of the CONTRACTS_FULL symbol from your project and rebuild.  CCRewrite can be downloaded from http://go.microsoft.com/fwlink/?LinkID=169180. \r\nAfter the rewriter is installed, it can be enabled in Visual Studio from the project's Properties page on the Code Contracts pane.  Ensure that "Perform Runtime Contract Checking" is enabled, which will define CONTRACTS_FULL.</value>
+  </data>
+  <data name="NotImplemented_ResourcesLongerThanInt64Max" xml:space="preserve">
+    <value>Resource files longer than 2^63 bytes are not currently implemented.</value>
+  </data>
+  <data name="NotSupported_AbstractNonCLS" xml:space="preserve">
+    <value>This non-CLS method is not implemented.</value>
+  </data>
+  <data name="NotSupported_ActivAttr" xml:space="preserve">
+    <value>Activation Attributes are not supported.</value>
+  </data>
+  <data name="NotSupported_AppX" xml:space="preserve">
+    <value>{0} is not supported in AppX.</value>
+  </data>
+  <data name="NotSupported_AssemblyLoadFromHash" xml:space="preserve">
+    <value>Assembly.LoadFrom with hashValue is not supported.</value>
+  </data>
+  <data name="NotSupported_ByRefLike" xml:space="preserve">
+    <value>Cannot create boxed ByRef-like values.</value>
+  </data>
+  <data name="NotSupported_ByRefLikeArray" xml:space="preserve">
+    <value>Cannot create arrays of ByRef-like values.</value>
+  </data>
+  <data name="NotSupported_ByRefToByRefLikeReturn" xml:space="preserve">
+    <value>ByRef to ByRefLike return values not supported in reflection invocation.</value>
+  </data>
+  <data name="NotSupported_ByRefToVoidReturn" xml:space="preserve">
+    <value>ByRef to void return values not supported in reflection invocation.</value>
+  </data>
+  <data name="NotSupported_CallToVarArg" xml:space="preserve">
+    <value>Vararg calling convention not supported.</value>
+  </data>
+  <data name="NotSupported_CannotCallEqualsOnSpan" xml:space="preserve">
+    <value>Equals() on Span and ReadOnlySpan is not supported. Use operator== instead.</value>
+  </data>
+  <data name="NotSupported_CannotCallGetHashCodeOnSpan" xml:space="preserve">
+    <value>GetHashCode() on Span and ReadOnlySpan is not supported.</value>
+  </data>
+  <data name="NotSupported_ChangeType" xml:space="preserve">
+    <value>ChangeType operation is not supported.</value>
+  </data>
+  <data name="NotSupported_CollectibleAssemblyResolve" xml:space="preserve">
+    <value>Resolving to a collectible assembly is not supported.</value>
+  </data>
+  <data name="NotSupported_CollectibleBoundNonCollectible" xml:space="preserve">
+    <value>A non-collectible assembly may not reference a collectible assembly.</value>
+  </data>
+  <data name="NotSupported_CollectibleCOM" xml:space="preserve">
+    <value>COM Interop is not supported for collectible types.</value>
+  </data>
+  <data name="NotSupported_CollectibleDelegateMarshal" xml:space="preserve">
+    <value>Delegate marshaling for types within collectible assemblies is not supported.</value>
+  </data>
+  <data name="NotSupported_CreateInstanceWithTypeBuilder" xml:space="preserve">
+    <value>CreateInstance cannot be used with an object of type TypeBuilder.</value>
+  </data>
+  <data name="NotSupported_DBNullSerial" xml:space="preserve">
+    <value>Only one DBNull instance may exist, and calls to DBNull deserialization methods are not allowed.</value>
+  </data>
+  <data name="NotSupported_DelegateMarshalToWrongDomain" xml:space="preserve">
+    <value>Delegates cannot be marshaled from native code into a domain other than their home domain.</value>
+  </data>
+  <data name="NotSupported_DelegateSerHolderSerial" xml:space="preserve">
+    <value>DelegateSerializationHolder objects are designed to represent a delegate during serialization and are not serializable themselves.</value>
+  </data>
+  <data name="NotSupported_DynamicAssembly" xml:space="preserve">
+    <value>The invoked member is not supported in a dynamic assembly.</value>
+  </data>
+  <data name="NotSupported_DynamicAssemblyNoRunAccess" xml:space="preserve">
+    <value>Cannot execute code on a dynamic assembly without run access.</value>
+  </data>
+  <data name="NotSupported_DynamicMethodFlags" xml:space="preserve">
+    <value>Wrong MethodAttributes or CallingConventions for DynamicMethod. Only public, static, standard supported</value>
+  </data>
+  <data name="NotSupported_DynamicModule" xml:space="preserve">
+    <value>The invoked member is not supported in a dynamic module.</value>
+  </data>
+  <data name="NotSupported_FileStreamOnNonFiles" xml:space="preserve">
+    <value>FileStream was asked to open a device that was not a file. For support for devices like 'com1:' or 'lpt1:', call CreateFile, then use the FileStream constructors that take an OS handle as an IntPtr.</value>
+  </data>
+  <data name="NotSupported_FixedSizeCollection" xml:space="preserve">
+    <value>Collection was of a fixed size.</value>
+  </data>
+  <data name="NotSupported_GenericMethod" xml:space="preserve">
+    <value>Generic methods with NativeCallableAttribute are not supported.</value>
+  </data>
+  <data name="NotSupported_GlobalMethodSerialization" xml:space="preserve">
+    <value>Serialization of global methods (including implicit serialization via the use of asynchronous delegates) is not supported.</value>
+  </data>
+  <data name="NotSupported_IDispInvokeDefaultMemberWithNamedArgs" xml:space="preserve">
+    <value>Invoking default method with named arguments is not supported.</value>
+  </data>
+  <data name="NotSupported_IllegalOneByteBranch" xml:space="preserve">
+    <value>Illegal one-byte branch at position: {0}. Requested branch was: {1}.</value>
+  </data>
+  <data name="NotSupported_KeyCollectionSet" xml:space="preserve">
+    <value>Mutating a key collection derived from a dictionary is not allowed.</value>
+  </data>
+  <data name="NotSupported_ManagedActivation" xml:space="preserve">
+    <value>Cannot create uninitialized instances of types requiring managed activation.</value>
+  </data>
+  <data name="NotSupported_MaxWaitHandles" xml:space="preserve">
+    <value>The number of WaitHandles must be less than or equal to 64.</value>
+  </data>
+  <data name="NotSupported_MemStreamNotExpandable" xml:space="preserve">
+    <value>Memory stream is not expandable.</value>
+  </data>
+  <data name="NotSupported_MustBeModuleBuilder" xml:space="preserve">
+    <value>Module argument must be a ModuleBuilder.</value>
+  </data>
+  <data name="NotSupported_NativeCallableTarget" xml:space="preserve">
+    <value>Methods with NativeCallableAttribute cannot be used as delegate target.</value>
+  </data>
+  <data name="NotSupported_NoCodepageData" xml:space="preserve">
+    <value>No data is available for encoding {0}. For information on defining a custom encoding, see the documentation for the Encoding.RegisterProvider method.</value>
+  </data>
+  <data name="NotSupported_NonBlittableTypes" xml:space="preserve">
+    <value>Non-blittable parameter types are not supported for NativeCallable methods.</value>
+  </data>
+  <data name="NotSupported_NonReflectedType" xml:space="preserve">
+    <value>Not supported in a non-reflected type.</value>
+  </data>
+  <data name="NotSupported_NonStaticMethod" xml:space="preserve">
+    <value>Non-static methods with NativeCallableAttribute are not supported.</value>
+  </data>
+  <data name="NotSupported_NoParentDefaultConstructor" xml:space="preserve">
+    <value>Parent does not have a default constructor. The default constructor must be explicitly defined.</value>
+  </data>
+  <data name="NotSupported_NoTypeInfo" xml:space="preserve">
+    <value>Cannot resolve {0} to a TypeInfo object.</value>
+  </data>
+  <data name="NotSupported_NYI" xml:space="preserve">
+    <value>This feature is not currently implemented.</value>
+  </data>
+  <data name="NotSupported_ObsoleteResourcesFile" xml:space="preserve">
+    <value>Found an obsolete .resources file in assembly '{0}'. Rebuild that .resources file then rebuild that assembly.</value>
+  </data>
+  <data name="NotSupported_OleAutBadVarType" xml:space="preserve">
+    <value>The given Variant type is not supported by this OleAut function.</value>
+  </data>
+  <data name="NotSupported_OpenType" xml:space="preserve">
+    <value>Cannot create arrays of open type.</value>
+  </data>
+  <data name="NotSupported_OutputStreamUsingTypeBuilder" xml:space="preserve">
+    <value>Output streams do not support TypeBuilders.</value>
+  </data>
+  <data name="NotSupported_PIAInAppxProcess" xml:space="preserve">
+    <value>A Primary Interop Assembly is not supported in AppX.</value>
+  </data>
+  <data name="NotSupported_Reading" xml:space="preserve">
+    <value>Accessor does not support reading.</value>
+  </data>
+  <data name="NotSupported_ReadOnlyCollection" xml:space="preserve">
+    <value>Collection is read-only.</value>
+  </data>
+  <data name="NotSupported_ResourceObjectSerialization" xml:space="preserve">
+    <value>Cannot read resources that depend on serialization.</value>
+  </data>
+  <data name="NotSupported_SignalAndWaitSTAThread" xml:space="preserve">
+    <value>SignalAndWait on a STA thread is not supported.</value>
+  </data>
+  <data name="NotSupported_StringComparison" xml:space="preserve">
+    <value>The string comparison type passed in is currently not supported.</value>
+  </data>
+  <data name="NotSupported_SubclassOverride" xml:space="preserve">
+    <value>Derived classes must provide an implementation.</value>
+  </data>
+  <data name="NotSupported_SymbolMethod" xml:space="preserve">
+    <value>Not supported in an array method of a type definition that is not complete.</value>
+  </data>
+  <data name="NotSupported_TooManyArgs" xml:space="preserve">
+    <value>Stack size too deep. Possibly too many arguments.</value>
+  </data>
+  <data name="NotSupported_Type" xml:space="preserve">
+    <value>Type is not supported.</value>
+  </data>
+  <data name="NotSupported_TypeCannotDeserialized" xml:space="preserve">
+    <value>Direct deserialization of type '{0}' is not supported.</value>
+  </data>
+  <data name="NotSupported_TypeNotYetCreated" xml:space="preserve">
+    <value>The invoked member is not supported before the type is created.</value>
+  </data>
+  <data name="NotSupported_UmsSafeBuffer" xml:space="preserve">
+    <value>This operation is not supported for an UnmanagedMemoryStream created from a SafeBuffer.</value>
+  </data>
+  <data name="NotSupported_UnitySerHolder" xml:space="preserve">
+    <value>The UnitySerializationHolder object is designed to transmit information about other types and is not serializable itself.</value>
+  </data>
+  <data name="NotSupported_UnknownTypeCode" xml:space="preserve">
+    <value>TypeCode '{0}' was not valid.</value>
+  </data>
+  <data name="NotSupported_UnreadableStream" xml:space="preserve">
+    <value>Stream does not support reading.</value>
+  </data>
+  <data name="NotSupported_UnseekableStream" xml:space="preserve">
+    <value>Stream does not support seeking.</value>
+  </data>
+  <data name="NotSupported_UnwritableStream" xml:space="preserve">
+    <value>Stream does not support writing.</value>
+  </data>
+  <data name="NotSupported_ValueClassCM" xml:space="preserve">
+    <value>Custom marshalers for value types are not currently supported.</value>
+  </data>
+  <data name="NotSupported_ValueCollectionSet" xml:space="preserve">
+    <value>Mutating a value collection derived from a dictionary is not allowed.</value>
+  </data>
+  <data name="NotSupported_VoidArray" xml:space="preserve">
+    <value>Arrays of System.Void are not supported.</value>
+  </data>
+  <data name="NotSupported_WinRT_PartialTrust" xml:space="preserve">
+    <value>Windows Runtime is not supported in partial trust.</value>
+  </data>
+  <data name="NotSupported_Writing" xml:space="preserve">
+    <value>Accessor does not support writing.</value>
+  </data>
+  <data name="NotSupported_WrongResourceReader_Type" xml:space="preserve">
+    <value>This .resources file should not be read with this reader. The resource reader type is "{0}".</value>
+  </data>
+  <data name="NullReference_This" xml:space="preserve">
+    <value>The pointer for this method was null.</value>
+  </data>
+  <data name="ObjectDisposed_FileClosed" xml:space="preserve">
+    <value>Cannot access a closed file.</value>
+  </data>
+  <data name="ObjectDisposed_Generic" xml:space="preserve">
+    <value>Cannot access a disposed object.</value>
+  </data>
+  <data name="ObjectDisposed_ObjectName_Name" xml:space="preserve">
+    <value>Object name: '{0}'.</value>
+  </data>
+  <data name="ObjectDisposed_WriterClosed" xml:space="preserve">
+    <value>Cannot write to a closed TextWriter.</value>
+  </data>
+  <data name="ObjectDisposed_ReaderClosed" xml:space="preserve">
+    <value>Cannot read from a closed TextReader.</value>
+  </data>
+  <data name="ObjectDisposed_RegKeyClosed" xml:space="preserve">
+    <value>Cannot access a closed registry key.</value>
+  </data>
+  <data name="ObjectDisposed_ResourceSet" xml:space="preserve">
+    <value>Cannot access a closed resource set.</value>
+  </data>
+  <data name="ObjectDisposed_StreamClosed" xml:space="preserve">
+    <value>Cannot access a closed Stream.</value>
+  </data>
+  <data name="ObjectDisposed_ViewAccessorClosed" xml:space="preserve">
+    <value>Cannot access a closed accessor.</value>
+  </data>
+  <data name="OperationCanceled" xml:space="preserve">
+    <value>The operation was canceled.</value>
+  </data>
+  <data name="OutOfMemory_GCHandleMDA" xml:space="preserve">
+    <value>The GCHandle MDA has run out of available cookies.</value>
+  </data>
+  <data name="Overflow_Byte" xml:space="preserve">
+    <value>Value was either too large or too small for an unsigned byte.</value>
+  </data>
+  <data name="Overflow_Char" xml:space="preserve">
+    <value>Value was either too large or too small for a character.</value>
+  </data>
+  <data name="Overflow_Currency" xml:space="preserve">
+    <value>Value was either too large or too small for a Currency.</value>
+  </data>
+  <data name="Overflow_Decimal" xml:space="preserve">
+    <value>Value was either too large or too small for a Decimal.</value>
+  </data>
+  <data name="Overflow_Double" xml:space="preserve">
+    <value>Value was either too large or too small for a Double.</value>
+  </data>
+  <data name="Overflow_Duration" xml:space="preserve">
+    <value>The duration cannot be returned for TimeSpan.MinValue because the absolute value of TimeSpan.MinValue exceeds the value of TimeSpan.MaxValue.</value>
+  </data>
+  <data name="Overflow_Int16" xml:space="preserve">
+    <value>Value was either too large or too small for an Int16.</value>
+  </data>
+  <data name="Overflow_Int32" xml:space="preserve">
+    <value>Value was either too large or too small for an Int32.</value>
+  </data>
+  <data name="Overflow_Int64" xml:space="preserve">
+    <value>Value was either too large or too small for an Int64.</value>
+  </data>
+  <data name="Overflow_NegateTwosCompNum" xml:space="preserve">
+    <value>Negating the minimum value of a twos complement number is invalid.</value>
+  </data>
+  <data name="Overflow_NegativeUnsigned" xml:space="preserve">
+    <value>The string was being parsed as an unsigned number and could not have a negative sign.</value>
+  </data>
+  <data name="Overflow_SByte" xml:space="preserve">
+    <value>Value was either too large or too small for a signed byte.</value>
+  </data>
+  <data name="Overflow_Single" xml:space="preserve">
+    <value>Value was either too large or too small for a Single.</value>
+  </data>
+  <data name="Overflow_TimeSpanElementTooLarge" xml:space="preserve">
+    <value>The TimeSpan string '{0}' could not be parsed because at least one of the numeric components is out of range or contains too many digits.</value>
+  </data>
+  <data name="Overflow_TimeSpanTooLong" xml:space="preserve">
+    <value>TimeSpan overflowed because the duration is too long.</value>
+  </data>
+  <data name="Overflow_UInt16" xml:space="preserve">
+    <value>Value was either too large or too small for a UInt16.</value>
+  </data>
+  <data name="Overflow_UInt32" xml:space="preserve">
+    <value>Value was either too large or too small for a UInt32.</value>
+  </data>
+  <data name="Overflow_UInt64" xml:space="preserve">
+    <value>Value was either too large or too small for a UInt64.</value>
+  </data>
+  <data name="PlatformNotSupported_ArgIterator" xml:space="preserve">
+    <value>ArgIterator is not supported on this platform.</value>
+  </data>
+  <data name="PlatformNotSupported_ComInterop" xml:space="preserve">
+    <value>COM Interop is not supported on this platform.</value>
+  </data>
+  <data name="PlatformNotSupported_NamedSynchronizationPrimitives" xml:space="preserve">
+    <value>The named version of this synchronization primitive is not supported on this platform.</value>
+  </data>
+  <data name="PlatformNotSupported_NamedSyncObjectWaitAnyWaitAll" xml:space="preserve">
+    <value>Wait operations on multiple wait handles including a named synchronization primitive are not supported on this platform.</value>
+  </data>
+  <data name="PlatformNotSupported_OSXFileLocking" xml:space="preserve">
+    <value>Locking/unlocking file regions is not supported on this platform. Use FileShare on the entire file instead.</value>
+  </data>
+  <data name="PlatformNotSupported_ReflectionOnly" xml:space="preserve">
+    <value>ReflectionOnly loading is not supported on this platform.</value>
+  </data>
+  <data name="PlatformNotSupported_Remoting" xml:space="preserve">
+    <value>Remoting is not supported on this platform.</value>
+  </data>
+  <data name="PlatformNotSupported_SecureBinarySerialization" xml:space="preserve">
+    <value>Secure binary serialization is not supported on this platform.</value>
+  </data>
+  <data name="PlatformNotSupported_StrongNameSigning" xml:space="preserve">
+    <value>Strong-name signing is not supported on this platform.</value>
+  </data>
+  <data name="PlatformNotSupported_WinRT" xml:space="preserve">
+    <value>Windows Runtime is not supported on this operating system.</value>
+  </data>
+  <data name="PlatformNotSupported_OverlappedIO" xml:space="preserve">
+    <value>This API is specific to the way in which Windows handles asynchronous I/O, and is not supported on this platform.</value>
+  </data>
+  <data name="Policy_CannotLoadSemiTrustAssembliesDuringInit" xml:space="preserve">
+    <value>All assemblies loaded as part of AppDomain initialization must be fully trusted.</value>
+  </data>
+  <data name="PostconditionFailed" xml:space="preserve">
+    <value>Postcondition failed.</value>
+  </data>
+  <data name="PostconditionFailed_Cnd" xml:space="preserve">
+    <value>Postcondition failed: {0}</value>
+  </data>
+  <data name="PostconditionOnExceptionFailed" xml:space="preserve">
+    <value>Postcondition failed after throwing an exception.</value>
+  </data>
+  <data name="PostconditionOnExceptionFailed_Cnd" xml:space="preserve">
+    <value>Postcondition failed after throwing an exception: {0}</value>
+  </data>
+  <data name="PreconditionFailed" xml:space="preserve">
+    <value>Precondition failed.</value>
+  </data>
+  <data name="PreconditionFailed_Cnd" xml:space="preserve">
+    <value>Precondition failed: {0}</value>
+  </data>
+  <data name="Rank_MultiDimNotSupported" xml:space="preserve">
+    <value>Only single dimension arrays are supported here.</value>
+  </data>
+  <data name="Rank_MustMatch" xml:space="preserve">
+    <value>The specified arrays must have the same number of dimensions.</value>
+  </data>
+  <data name="ReflectionTypeLoad_LoadFailed" xml:space="preserve">
+    <value>Unable to load one or more of the requested types.</value>
+  </data>
+  <data name="Remoting_AppDomainUnloaded_ThreadUnwound" xml:space="preserve">
+    <value>The application domain in which the thread was running has been unloaded.</value>
+  </data>
+  <data name="ResourceReaderIsClosed" xml:space="preserve">
+    <value>ResourceReader is closed.</value>
+  </data>
+  <data name="Resources_StreamNotValid" xml:space="preserve">
+    <value>Stream is not a valid resource file.</value>
+  </data>
+  <data name="RFLCT_AmbigCust" xml:space="preserve">
+    <value>Multiple custom attributes of the same type found.</value>
+  </data>
+  <data name="RFLCT_Ambiguous" xml:space="preserve">
+    <value>Ambiguous match found.</value>
+  </data>
+  <data name="InvalidFilterCriteriaException_CritInt" xml:space="preserve">
+    <value>An Int32 must be provided for the filter criteria.</value>
+  </data>
+  <data name="InvalidFilterCriteriaException_CritString" xml:space="preserve">
+    <value>A String must be provided for the filter criteria.</value>
+  </data>
+  <data name="RFLCT_InvalidFieldFail" xml:space="preserve">
+    <value>'{0}' field specified was not found.</value>
+  </data>
+  <data name="RFLCT_InvalidPropFail" xml:space="preserve">
+    <value>'{0}' property specified was not found.</value>
+  </data>
+  <data name="RFLCT_Targ_ITargMismatch" xml:space="preserve">
+    <value>Object does not match target type.</value>
+  </data>
+  <data name="RFLCT_Targ_StatFldReqTarg" xml:space="preserve">
+    <value>Non-static field requires a target.</value>
+  </data>
+  <data name="RFLCT_Targ_StatMethReqTarg" xml:space="preserve">
+    <value>Non-static method requires a target.</value>
+  </data>
+  <data name="RuntimeWrappedException" xml:space="preserve">
+    <value>An object that does not derive from System.Exception has been wrapped in a RuntimeWrappedException.</value>
+  </data>
+  <data name="Security_CannotReadFileData" xml:space="preserve">
+    <value>The time zone ID '{0}' was found on the local computer, but the application does not have permission to read the file.</value>
+  </data>
+  <data name="Security_CannotReadRegistryData" xml:space="preserve">
+    <value>The time zone ID '{0}' was found on the local computer, but the application does not have permission to read the registry information.</value>
+  </data>
+  <data name="Security_RegistryPermission" xml:space="preserve">
+    <value>Requested registry access is not allowed.</value>
+  </data>
+  <data name="SemaphoreSlim_ctor_InitialCountWrong" xml:space="preserve">
+    <value>The initialCount argument must be non-negative and less than or equal to the maximumCount.</value>
+  </data>
+  <data name="SemaphoreSlim_ctor_MaxCountWrong" xml:space="preserve">
+    <value>The maximumCount argument must be a positive number. If a maximum is not required, use the constructor without a maxCount parameter.</value>
+  </data>
+  <data name="SemaphoreSlim_Disposed" xml:space="preserve">
+    <value>The semaphore has been disposed.</value>
+  </data>
+  <data name="SemaphoreSlim_Release_CountWrong" xml:space="preserve">
+    <value>The releaseCount argument must be greater than zero.</value>
+  </data>
+  <data name="SemaphoreSlim_Wait_TimeoutWrong" xml:space="preserve">
+    <value>The timeout must represent a value between -1 and Int32.MaxValue, inclusive.</value>
+  </data>
+  <data name="Serialization_BadParameterInfo" xml:space="preserve">
+    <value>Non existent ParameterInfo. Position bigger than member's parameters length.</value>
+  </data>
+  <data name="Serialization_CorruptField" xml:space="preserve">
+    <value>The value of the field '{0}' is invalid.  The serialized data is corrupt.</value>
+  </data>
+  <data name="Serialization_DateTimeTicksOutOfRange" xml:space="preserve">
+    <value>Invalid serialized DateTime data. Ticks must be between DateTime.MinValue.Ticks and DateTime.MaxValue.Ticks.</value>
+  </data>
+  <data name="Serialization_DelegatesNotSupported" xml:space="preserve">
+    <value>Serializing delegates is not supported on this platform.</value>
+  </data>
+  <data name="Serialization_InsufficientDeserializationState" xml:space="preserve">
+    <value>Insufficient state to deserialize the object. Missing field '{0}'. More information is needed.</value>
+  </data>
+  <data name="Serialization_InsufficientState" xml:space="preserve">
+    <value>Insufficient state to return the real object.</value>
+  </data>
+  <data name="Serialization_InvalidData" xml:space="preserve">
+    <value>An error occurred while deserializing the object.  The serialized data is corrupt.</value>
+  </data>
+  <data name="Serialization_InvalidDelegateType" xml:space="preserve">
+    <value>Cannot serialize delegates over unmanaged function pointers, dynamic methods or methods outside the delegate creator's assembly.</value>
+  </data>
+  <data name="Serialization_InvalidEscapeSequence" xml:space="preserve">
+    <value>The serialized data contained an invalid escape sequence '\\{0}'.</value>
+  </data>
+  <data name="Serialization_InvalidFieldState" xml:space="preserve">
+    <value>Object fields may not be properly initialized.</value>
+  </data>
+  <data name="Serialization_InvalidOnDeser" xml:space="preserve">
+    <value>OnDeserialization method was called while the object was not being deserialized.</value>
+  </data>
+  <data name="Serialization_InvalidPtrValue" xml:space="preserve">
+    <value>An IntPtr or UIntPtr with an eight byte value cannot be deserialized on a machine with a four byte word size.</value>
+  </data>
+  <data name="Serialization_InvalidType" xml:space="preserve">
+    <value>Only system-provided types can be passed to the GetUninitializedObject method. '{0}' is not a valid instance of a type.</value>
+  </data>
+  <data name="Serialization_KeyValueDifferentSizes" xml:space="preserve">
+    <value>The keys and values arrays have different sizes.</value>
+  </data>
+  <data name="Serialization_MemberOutOfRange" xml:space="preserve">
+    <value>The deserialized value of the member "{0}" in the class "{1}" is out of range.</value>
+  </data>
+  <data name="Serialization_MemberTypeNotRecognized" xml:space="preserve">
+    <value>Unknown member type.</value>
+  </data>
+  <data name="Serialization_MissField" xml:space="preserve">
+    <value>Field {0} is missing.</value>
+  </data>
+  <data name="Serialization_MissingDateTimeData" xml:space="preserve">
+    <value>Invalid serialized DateTime data. Unable to find 'ticks' or 'dateData'.</value>
+  </data>
+  <data name="Serialization_MissingKeys" xml:space="preserve">
+    <value>The Keys for this Hashtable are missing.</value>
+  </data>
+  <data name="Serialization_MissingValues" xml:space="preserve">
+    <value>The values for this dictionary are missing.</value>
+  </data>
+  <data name="Serialization_NonSerType" xml:space="preserve">
+    <value>Type '{0}' in Assembly '{1}' is not marked as serializable.</value>
+  </data>
+  <data name="Serialization_NoParameterInfo" xml:space="preserve">
+    <value>Serialized member does not have a ParameterInfo.</value>
+  </data>
+  <data name="Serialization_NotFound" xml:space="preserve">
+    <value>Member '{0}' was not found.</value>
+  </data>
+  <data name="Serialization_NullKey" xml:space="preserve">
+    <value>One of the serialized keys is null.</value>
+  </data>
+  <data name="Serialization_NullSignature" xml:space="preserve">
+    <value>The method signature cannot be null.</value>
+  </data>
+  <data name="Serialization_OptionalFieldVersionValue" xml:space="preserve">
+    <value>Version value must be positive.</value>
+  </data>
+  <data name="Serialization_SameNameTwice" xml:space="preserve">
+    <value>Cannot add the same member twice to a SerializationInfo object.</value>
+  </data>
+  <data name="Serialization_StringBuilderCapacity" xml:space="preserve">
+    <value>The serialized Capacity property of StringBuilder must be positive, less than or equal to MaxCapacity and greater than or equal to the String length.</value>
+  </data>
+  <data name="Serialization_StringBuilderMaxCapacity" xml:space="preserve">
+    <value>The serialized MaxCapacity property of StringBuilder must be positive and greater than or equal to the String length.</value>
+  </data>
+  <data name="Serialization_UnableToFindModule" xml:space="preserve">
+    <value>The given module {0} cannot be found within the assembly {1}.</value>
+  </data>
+  <data name="Serialization_UnknownMember" xml:space="preserve">
+    <value>Cannot get the member '{0}'.</value>
+  </data>
+  <data name="SpinLock_Exit_SynchronizationLockException" xml:space="preserve">
+    <value>The calling thread does not hold the lock.</value>
+  </data>
+  <data name="SpinLock_IsHeldByCurrentThread" xml:space="preserve">
+    <value>Thread tracking is disabled.</value>
+  </data>
+  <data name="SpinLock_TryEnter_ArgumentOutOfRange" xml:space="preserve">
+    <value>The timeout must be a value between -1 and Int32.MaxValue, inclusive.</value>
+  </data>
+  <data name="SpinLock_TryEnter_LockRecursionException" xml:space="preserve">
+    <value>The calling thread already holds the lock.</value>
+  </data>
+  <data name="SpinLock_TryReliableEnter_ArgumentException" xml:space="preserve">
+    <value>The tookLock argument must be set to false before calling this method.</value>
+  </data>
+  <data name="SpinWait_SpinUntil_ArgumentNull" xml:space="preserve">
+    <value>The condition argument is null.</value>
+  </data>
+  <data name="SpinWait_SpinUntil_TimeoutWrong" xml:space="preserve">
+    <value>The timeout must represent a value between -1 and Int32.MaxValue, inclusive.</value>
+  </data>
+  <data name="StackTrace_InFileLineNumber" xml:space="preserve">
+    <value>in {0}:line {1}</value>
+  </data>
+  <data name="Task_ContinueWith_ESandLR" xml:space="preserve">
+    <value>The specified TaskContinuationOptions combined LongRunning and ExecuteSynchronously.  Synchronous continuations should not be long running.</value>
+  </data>
+  <data name="Task_ContinueWith_NotOnAnything" xml:space="preserve">
+    <value>The specified TaskContinuationOptions excluded all continuation kinds.</value>
+  </data>
+  <data name="Task_Delay_InvalidDelay" xml:space="preserve">
+    <value>The value needs to translate in milliseconds to -1 (signifying an infinite timeout), 0 or a positive integer less than or equal to Int32.MaxValue.</value>
+  </data>
+  <data name="Task_Delay_InvalidMillisecondsDelay" xml:space="preserve">
+    <value>The value needs to be either -1 (signifying an infinite timeout), 0 or a positive integer.</value>
+  </data>
+  <data name="Task_Dispose_NotCompleted" xml:space="preserve">
+    <value>A task may only be disposed if it is in a completion state (RanToCompletion, Faulted or Canceled).</value>
+  </data>
+  <data name="Task_FromAsync_LongRunning" xml:space="preserve">
+    <value>It is invalid to specify TaskCreationOptions.LongRunning in calls to FromAsync.</value>
+  </data>
+  <data name="Task_FromAsync_PreferFairness" xml:space="preserve">
+    <value>It is invalid to specify TaskCreationOptions.PreferFairness in calls to FromAsync.</value>
+  </data>
+  <data name="Task_MultiTaskContinuation_EmptyTaskList" xml:space="preserve">
+    <value>The tasks argument contains no tasks.</value>
+  </data>
+  <data name="Task_MultiTaskContinuation_FireOptions" xml:space="preserve">
+    <value>It is invalid to exclude specific continuation kinds for continuations off of multiple tasks.</value>
+  </data>
+  <data name="Task_MultiTaskContinuation_NullTask" xml:space="preserve">
+    <value>The tasks argument included a null value.</value>
+  </data>
+  <data name="Task_RunSynchronously_AlreadyStarted" xml:space="preserve">
+    <value>RunSynchronously may not be called on a task that was already started.</value>
+  </data>
+  <data name="Task_RunSynchronously_Continuation" xml:space="preserve">
+    <value>RunSynchronously may not be called on a continuation task.</value>
+  </data>
+  <data name="Task_RunSynchronously_Promise" xml:space="preserve">
+    <value>RunSynchronously may not be called on a task not bound to a delegate, such as the task returned from an asynchronous method.</value>
+  </data>
+  <data name="Task_RunSynchronously_TaskCompleted" xml:space="preserve">
+    <value>RunSynchronously may not be called on a task that has already completed.</value>
+  </data>
+  <data name="Task_Start_AlreadyStarted" xml:space="preserve">
+    <value>Start may not be called on a task that was already started.</value>
+  </data>
+  <data name="Task_Start_ContinuationTask" xml:space="preserve">
+    <value>Start may not be called on a continuation task.</value>
+  </data>
+  <data name="Task_Start_Promise" xml:space="preserve">
+    <value>Start may not be called on a promise-style task.</value>
+  </data>
+  <data name="Task_Start_TaskCompleted" xml:space="preserve">
+    <value>Start may not be called on a task that has completed.</value>
+  </data>
+  <data name="Task_ThrowIfDisposed" xml:space="preserve">
+    <value>The task has been disposed.</value>
+  </data>
+  <data name="Task_WaitMulti_NullTask" xml:space="preserve">
+    <value>The tasks array included at least one null element.</value>
+  </data>
+  <data name="TaskCanceledException_ctor_DefaultMessage" xml:space="preserve">
+    <value>A task was canceled.</value>
+  </data>
+  <data name="TaskCompletionSourceT_TrySetException_NoExceptions" xml:space="preserve">
+    <value>The exceptions collection was empty.</value>
+  </data>
+  <data name="TaskCompletionSourceT_TrySetException_NullException" xml:space="preserve">
+    <value>The exceptions collection included at least one null element.</value>
+  </data>
+  <data name="TaskExceptionHolder_UnhandledException" xml:space="preserve">
+    <value>A Task's exception(s) were not observed either by Waiting on the Task or accessing its Exception property. As a result, the unobserved exception was rethrown by the finalizer thread.</value>
+  </data>
+  <data name="TaskExceptionHolder_UnknownExceptionType" xml:space="preserve">
+    <value>(Internal)Expected an Exception or an IEnumerable&lt;Exception&gt;</value>
+  </data>
+  <data name="TaskScheduler_ExecuteTask_WrongTaskScheduler" xml:space="preserve">
+    <value>ExecuteTask may not be called for a task which was previously queued to a different TaskScheduler.</value>
+  </data>
+  <data name="TaskScheduler_FromCurrentSynchronizationContext_NoCurrent" xml:space="preserve">
+    <value>The current SynchronizationContext may not be used as a TaskScheduler.</value>
+  </data>
+  <data name="TaskScheduler_InconsistentStateAfterTryExecuteTaskInline" xml:space="preserve">
+    <value>The TryExecuteTaskInline call to the underlying scheduler succeeded, but the task body was not invoked.</value>
+  </data>
+  <data name="TaskSchedulerException_ctor_DefaultMessage" xml:space="preserve">
+    <value>An exception was thrown by a TaskScheduler.</value>
+  </data>
+  <data name="TaskT_DebuggerNoResult" xml:space="preserve">
+    <value>{Not yet computed}</value>
+  </data>
+  <data name="TaskT_TransitionToFinal_AlreadyCompleted" xml:space="preserve">
+    <value>An attempt was made to transition a task to a final state when it had already completed.</value>
+  </data>
+  <data name="Threading_AbandonedMutexException" xml:space="preserve">
+    <value>The wait completed due to an abandoned mutex.</value>
+  </data>
+  <data name="Threading_WaitHandleCannotBeOpenedException" xml:space="preserve">
+    <value>No handle of the given name exists.</value>
+  </data>
+  <data name="Threading_WaitHandleCannotBeOpenedException_InvalidHandle" xml:space="preserve">
+    <value>A WaitHandle with system-wide name '{0}' cannot be created. A WaitHandle of a different type might have the same name.</value>
+  </data>
+  <data name="Threading_WaitHandleTooManyPosts" xml:space="preserve">
+    <value>The WaitHandle cannot be signaled because it would exceed its maximum count.</value>
+  </data>
+  <data name="Threading_SemaphoreFullException" xml:space="preserve">
+    <value>Adding the specified count to the semaphore would cause it to exceed its maximum count.</value>
+  </data>
+  <data name="ThreadLocal_Disposed" xml:space="preserve">
+    <value>The ThreadLocal object has been disposed.</value>
+  </data>
+  <data name="ThreadLocal_Value_RecursiveCallsToValue" xml:space="preserve">
+    <value>ValueFactory attempted to access the Value property of this instance.</value>
+  </data>
+  <data name="ThreadLocal_ValuesNotAvailable" xml:space="preserve">
+    <value>The ThreadLocal object is not tracking values. To use the Values property, use a ThreadLocal constructor that accepts the trackAllValues parameter and set the parameter to true.</value>
+  </data>
+  <data name="TimeZoneNotFound_MissingData" xml:space="preserve">
+    <value>The time zone ID '{0}' was not found on the local computer.</value>
+  </data>
+  <data name="TypeInitialization_Default" xml:space="preserve">
+    <value>Type constructor threw an exception.</value>
+  </data>
+  <data name="TypeInitialization_Type" xml:space="preserve">
+    <value>The type initializer for '{0}' threw an exception.</value>
+  </data>
+  <data name="TypeLoad_ResolveNestedType" xml:space="preserve">
+    <value>Could not resolve nested type '{0}' in type "{1}'.</value>
+  </data>
+  <data name="TypeLoad_ResolveType" xml:space="preserve">
+    <value>Could not resolve type '{0}'.</value>
+  </data>
+  <data name="TypeLoad_ResolveTypeFromAssembly" xml:space="preserve">
+    <value>Could not resolve type '{0}' in assembly '{1}'.</value>
+  </data>
+  <data name="UnauthorizedAccess_IODenied_NoPathName" xml:space="preserve">
+    <value>Access to the path is denied.</value>
+  </data>
+  <data name="UnauthorizedAccess_IODenied_Path" xml:space="preserve">
+    <value>Access to the path '{0}' is denied.</value>
+  </data>
+  <data name="UnauthorizedAccess_MemStreamBuffer" xml:space="preserve">
+    <value>MemoryStream's internal buffer cannot be accessed.</value>
+  </data>
+  <data name="UnauthorizedAccess_RegistryKeyGeneric_Key" xml:space="preserve">
+    <value>Access to the registry key '{0}' is denied.</value>
+  </data>
+  <data name="UnauthorizedAccess_RegistryNoWrite" xml:space="preserve">
+    <value>Cannot write to the registry key.</value>
+  </data>
+  <data name="UnauthorizedAccess_SystemDomain" xml:space="preserve">
+    <value>Cannot execute an assembly in the system domain.</value>
+  </data>
+  <data name="UnknownError_Num" xml:space="preserve">
+    <value>Unknown error "{0}".</value>
+  </data>
+  <data name="Verification_Exception" xml:space="preserve">
+    <value>Operation could destabilize the runtime.</value>
+  </data>
+  <data name="Word_At" xml:space="preserve">
+    <value>at</value>
+  </data>
+  <data name="DebugAssertBanner" xml:space="preserve">
+    <value>---- DEBUG ASSERTION FAILED ----</value>
+  </data>
+  <data name="DebugAssertLongMessage" xml:space="preserve">
+    <value>---- Assert Long Message ----</value>
+  </data>
+  <data name="DebugAssertShortMessage" xml:space="preserve">
+    <value>---- Assert Short Message ----</value>
+  </data>
+  <data name="LockRecursionException_ReadAfterWriteNotAllowed" xml:space="preserve">
+    <value>A read lock may not be acquired with the write lock held in this mode.</value>
+  </data>
+  <data name="LockRecursionException_RecursiveReadNotAllowed" xml:space="preserve">
+    <value>Recursive read lock acquisitions not allowed in this mode.</value>
+  </data>
+  <data name="LockRecursionException_RecursiveWriteNotAllowed" xml:space="preserve">
+    <value>Recursive write lock acquisitions not allowed in this mode.</value>
+  </data>
+  <data name="LockRecursionException_RecursiveUpgradeNotAllowed" xml:space="preserve">
+    <value>Recursive upgradeable lock acquisitions not allowed in this mode.</value>
+  </data>
+  <data name="LockRecursionException_WriteAfterReadNotAllowed" xml:space="preserve">
+    <value>Write lock may not be acquired with read lock held. This pattern is prone to deadlocks. Please ensure that read locks are released before taking a write lock. If an upgrade is necessary, use an upgrade lock in place of the read lock.</value>
+  </data>
+  <data name="SynchronizationLockException_MisMatchedUpgrade" xml:space="preserve">
+    <value>The upgradeable lock is being released without being held.</value>
+  </data>
+  <data name="SynchronizationLockException_MisMatchedRead" xml:space="preserve">
+    <value>The read lock is being released without being held.</value>
+  </data>
+  <data name="SynchronizationLockException_IncorrectDispose" xml:space="preserve">
+    <value>The lock is being disposed while still being used. It either is being held by a thread and/or has active waiters waiting to acquire the lock.</value>
+  </data>
+  <data name="LockRecursionException_UpgradeAfterReadNotAllowed" xml:space="preserve">
+    <value>Upgradeable lock may not be acquired with read lock held.</value>
+  </data>
+  <data name="LockRecursionException_UpgradeAfterWriteNotAllowed" xml:space="preserve">
+    <value>Upgradeable lock may not be acquired with write lock held in this mode. Acquiring Upgradeable lock gives the ability to read along with an option to upgrade to a writer.</value>
+  </data>
+  <data name="SynchronizationLockException_MisMatchedWrite" xml:space="preserve">
+    <value>The write lock is being released without being held.</value>
+  </data>
+  <data name="ConcurrentStack_PushPopRange_CountOutOfRange" xml:space="preserve">
+    <value>The count argument must be greater than or equal to zero.</value>
+  </data>
+  <data name="ConcurrentStack_PushPopRange_InvalidCount" xml:space="preserve">
+    <value>The sum of the startIndex and count arguments must be less than or equal to the collection's Count.</value>
+  </data>
+  <data name="ConcurrentStack_PushPopRange_StartOutOfRange" xml:space="preserve">
+    <value>The startIndex argument must be greater than or equal to zero.</value>
+  </data>
+  <data name="ConcurrentDictionary_SourceContainsDuplicateKeys" xml:space="preserve">
+    <value>The source argument contains duplicate keys.</value>
+  </data>
+  <data name="NotSupported_SignatureType" xml:space="preserve">
+    <value>This method is not supported on signature types.</value>
+  </data>
+  <data name="MemoryDisposed" xml:space="preserve">
+    <value>Memory&lt;T&gt; has been disposed.</value>
+  </data>
+  <data name="Memory_OutstandingReferences" xml:space="preserve">
+    <value>Release all references before disposing this instance.</value>
+  </data>
+  <data name="HashCode_HashCodeNotSupported" xml:space="preserve">
+    <value>HashCode is a mutable struct and should not be compared with other HashCodes. Use ToHashCode to retrieve the computed hash code.</value>
+  </data>
+  <data name="HashCode_EqualityNotSupported" xml:space="preserve">
+    <value>HashCode is a mutable struct and should not be compared with other HashCodes.</value>
+  </data>
+  <data name="Arg_TypeNotSupported" xml:space="preserve">
+    <value>Specified type is not supported</value>
+  </data>
+  <data name="IO_InvalidReadLength" xml:space="preserve">
+    <value>The read operation returned an invalid length.</value>
+  </data>
+  <data name="Arg_BasePathNotFullyQualified" xml:space="preserve">
+    <value>Basepath argument is not fully qualified.</value>
+  </data>
+  <data name="Arg_ElementsInSourceIsGreaterThanDestination" xml:space="preserve">
+    <value>Number of elements in source vector is greater than the destination array</value>
+  </data>
+  <data name="Arg_NullArgumentNullRef" xml:space="preserve">
+    <value>The method was called with a null array argument.</value>
+  </data>
+  <data name="Argument_CannotPrepareAbstract" xml:space="preserve">
+    <value>Abstract methods cannot be prepared.</value>
+  </data>
+  <data name="Argument_InvalidGenericInstantiation" xml:space="preserve">
+    <value>The given generic instantiation was invalid.</value>
+  </data>
+  <data name="Argument_OverlapAlignmentMismatch" xml:space="preserve">
+    <value>Overlapping spans have mismatching alignment.</value>
+  </data>
+  <data name="Arg_InsufficientNumberOfElements" xml:space="preserve">
+    <value>At least {0} element(s) are expected in the parameter "{1}".</value>
+  </data>
+  <data name="Arg_MustBeNullTerminatedString" xml:space="preserve">
+    <value>The string must be null-terminated.</value>
+  </data>
+</root>
diff --git a/src/System.Private.CoreLib/System.Private.CoreLib.csproj b/src/System.Private.CoreLib/System.Private.CoreLib.csproj
new file mode 100644
index 0000000000..244b9f82d0
--- /dev/null
+++ b/src/System.Private.CoreLib/System.Private.CoreLib.csproj
@@ -0,0 +1,669 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <!-- Include common build properties -->
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.props))\dir.props" />
+  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
+  <!-- Compilation options -->
+  <PropertyGroup>
+    <AvailablePlatforms>amd64,x86,arm,armel,arm64</AvailablePlatforms>
+    <Configuration Condition=" '$(Configuration)' == '' ">$(BuildType)</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">$(BuildArch)</Platform>
+    <!-- The CLR properties use amd64 as their platform string, we want to keep in sync with those, so set Platform appropriately,
+         though still use the 'x64' output path (see use of BuildArch below) -->
+    <Platform Condition=" '$(Platform)' == 'x64' ">amd64</Platform>
+    <Platform Condition=" '$(Platform)' == 'armel' ">arm</Platform>
+    <ProjectGuid>{3DA06C3A-2E7B-4CB7-80ED-9B12916013F9}</ProjectGuid>
+    <OutputType>Library</OutputType>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <!-- This prevents the default MsBuild targets from referencing System.Core.dll -->
+    <AddAdditionalExplicitAssemblyReferences>false</AddAdditionalExplicitAssemblyReferences>
+    <!-- These prevent the default MsBuild targets from referencing System.dll and mscorlib.dll -->
+    <ExcludeMscorlibFacade>true</ExcludeMscorlibFacade>
+    <NoStdLib>true</NoStdLib>
+    <NoCompilerStandardLib>true</NoCompilerStandardLib>
+    <SubsystemVersion>6.00</SubsystemVersion>
+    <UTF8OutPut>true</UTF8OutPut>
+    <HighEntropyVA>true</HighEntropyVA>
+    <ErrorReport>prompt</ErrorReport>
+    <CLSCompliant>true</CLSCompliant>
+    <WarningLevel>4</WarningLevel>
+    <TreatWarningsAsErrors>false</TreatWarningsAsErrors>
+    <WarningsNotAsErrors>$(WarningsNotAsErrors);618</WarningsNotAsErrors>
+    <NoWarn>649,3019,414,169,3015</NoWarn>
+    <GenerateTargetFrameworkAttribute>false</GenerateTargetFrameworkAttribute>
+    <SignAssembly>true</SignAssembly>
+    <DelaySign>true</DelaySign>
+    <DefineConstants>$(DefineConstants);CORECLR;_USE_NLS_PLUS_TABLE;RESOURCE_SATELLITE_CONFIG;CODE_ANALYSIS_BASELINE;netcoreapp</DefineConstants>
+    <!-- We don't use any of MSBuild's resolution logic for resolving the framework, so just set these two properties to any folder that exists to skip
+         the GenerateReferenceAssemblyPaths task (not target) and to prevent it from outputting a warning (MSB3644). -->
+    <_TargetFrameworkDirectories>$(MSBuildThisFileDirectory)/Documentation</_TargetFrameworkDirectories>
+    <_FullFrameworkReferenceAssemblyPaths>$(MSBuildThisFileDirectory)/Documentation</_FullFrameworkReferenceAssemblyPaths>
+    <SkipCommonResourcesIncludes>true</SkipCommonResourcesIncludes>
+    <LangVersion>latest</LangVersion>
+  </PropertyGroup>
+  <!-- Add Serviceable attribute to the project's metadata -->
+  <ItemGroup>
+    <AssemblyMetadata Include="Serviceable">
+      <Value>True</Value>
+      <Visible>false</Visible>
+    </AssemblyMetadata>
+  </ItemGroup>
+  <!-- Platform specific properties -->
+  <PropertyGroup Condition="'$(Platform)' == 'amd64'">
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+    <CheckCDefines Condition="'$(CheckCDefines)'==''">true</CheckCDefines>
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+  <!--
+    Import common targets: codeAnalysis, Microsoft.CSharp, sign, versioning, codeOptimizations, etc.
+    In doing so, override versioning targets.
+  -->
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
+  <PropertyGroup>
+    <!-- Overwrite the key that we are going to use for signing -->
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+    <!-- Don't need a strong name signature because we only ship the native image -->
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+    <!-- Use a different nativeresource file to avoid conflicts with mscorlib-->
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+  <Import Project="CreateRuntimeRootILLinkDescriptorFile.targets" />
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diff --git a/src/System.Private.CoreLib/System.Private.CoreLib.sln b/src/System.Private.CoreLib/System.Private.CoreLib.sln
new file mode 100644
index 0000000000..d4052f8058
--- /dev/null
+++ b/src/System.Private.CoreLib/System.Private.CoreLib.sln
@@ -0,0 +1,55 @@
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diff --git a/src/System.Private.CoreLib/Tools/Versioning/GenerateVersionInfo.targets b/src/System.Private.CoreLib/Tools/Versioning/GenerateVersionInfo.targets
new file mode 100644
index 0000000000..0e9a2263cc
--- /dev/null
+++ b/src/System.Private.CoreLib/Tools/Versioning/GenerateVersionInfo.targets
@@ -0,0 +1,90 @@
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+  <PropertyGroup Condition="'$(GenerateAssemblyInfo)'=='true'">
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+      <AssemblyInfoLines Include="[assembly:System.Runtime.InteropServices.ComVisible(false)]" />
+      <AssemblyInfoLines Include="[assembly:System.Resources.NeutralResourcesLanguage(&quot;en-US&quot;)]" />
+      <AssemblyInfoLines Include="[assembly:System.Runtime.InteropServices.DefaultDllImportSearchPathsAttribute(System.Runtime.InteropServices.DllImportSearchPath.AssemblyDirectory | System.Runtime.InteropServices.DllImportSearchPath.System32)]" />
+  </ItemGroup>
+
+  <!-- #################################### -->
+  <!-- Generate Native Version Info -->
+  <!-- #################################### -->
+  <PropertyGroup Condition="'$(GenerateNativeVersionInfo)'=='true'">
+    <NativeVersionHeaderFile>$(IntermediateOutputPath)GeneratedVersion.h</NativeVersionHeaderFile>
+    <BeforeResourceCompileTargets>$(BeforeResourceCompileTargets);GenerateVersionHeader</BeforeResourceCompileTargets>
+    <Win32Resource>$(IntermediateOutputPath)\NativeVersion.res</Win32Resource>
+    <CoreCompileDependsOn>$(CoreCompileDependsOn);NativeResourceCompile</CoreCompileDependsOn>
+  </PropertyGroup>
+
+  <Target Name="GenerateVersionHeader"
+          Condition="'$(GenerateNativeVersionInfo)'=='true'"
+          Inputs="$(MSBuildProjectFile)"
+          Outputs="$(NativeVersionHeaderFile)">
+
+    <ItemGroup>
+      <NativeVersionLines Include="#define VER_COMPANYNAME_STR         &quot;Microsoft Corporation&quot;" />
+      <NativeVersionLines Include="#define VER_FILEDESCRIPTION_STR     &quot;$(AssemblyName)&quot;" />
+      <NativeVersionLines Include="#define VER_INTERNALNAME_STR        VER_FILEDESCRIPTION_STR" />
+      <NativeVersionLines Include="#define VER_ORIGINALFILENAME_STR    VER_FILEDESCRIPTION_STR" />
+      <NativeVersionLines Include="#define VER_PRODUCTNAME_STR         &quot;Microsoft\xae .NET Framework&quot;" />
+      <NativeVersionLines Include="#define VER_PRODUCTVERSION          $(MajorVersion),$(MinorVersion),$(BuildNumberMajor),$(BuildNumberMinor)" />
+      <NativeVersionLines Include="#define VER_PRODUCTVERSION_STR      &quot;$(MajorVersion).$(MinorVersion).$(BuildNumberMajor).$(BuildNumberMinor)&quot;" />
+      <NativeVersionLines Include="#define VER_FILEVERSION             $(MajorVersion),$(MinorVersion),$(BuildNumberMajor),$(BuildNumberMinor)" />
+      <NativeVersionLines Include="#define VER_FILEVERSION_STR         &quot;$(MajorVersion).$(MinorVersion).$(BuildNumberMajor).$(BuildNumberMinor)&quot;" />
+      <NativeVersionLines Include="#define VER_LEGALCOPYRIGHT_STR      &quot;\xa9 Microsoft Corporation.  All rights reserved.&quot;" />
+      <NativeVersionLines Condition="'$(Configuration)'=='Debug'" Include="#define VER_DEBUG                   VS_FF_DEBUG" />
+      <NativeVersionLines Condition="'$(Configuration)'!='Debug'" Include="#define VER_DEBUG                   0" />
+    </ItemGroup>
+
+    <WriteLinesToFile File="$(NativeVersionHeaderFile)"
+                      Lines="@(NativeVersionLines)"
+                      Overwrite="true" />
+
+    <ItemGroup>
+      <FileWrites Include="$(NativeVersionHeaderFile)" />
+    </ItemGroup>
+  </Target>
+
+  
+  <PropertyGroup Condition="'$(GenerateNativeVersionInfo)'=='true'">
+    <WindowsSdkDir Condition="'$(WindowsSdkDir)'==''">$(registry:HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Microsoft SDKs\Windows\v8.1@InstallationFolder)</WindowsSdkDir>
+    <RCPath Condition="'$(RCPath)' == ''">$(WindowsSdkDir)bin\x86\rc.exe</RCPath>
+  </PropertyGroup>
+  
+  <Target Name="NativeResourceCompile"
+          Condition="'$(GenerateNativeVersionInfo)'=='true'"
+          DependsOnTargets="GenerateVersionHeader"
+          Inputs="$(MsBuildThisFileDirectory)NativeVersion.rc"
+          Outputs="$(Win32Resource)">
+
+    <Exec Command="&quot;$(RCPath)&quot; /nologo /x /i &quot;$(IntermediateOutputPath.TrimEnd('\'))&quot; /i &quot;$(WindowsSdkDir)Include\$(WindowsSDKVersion)um&quot; /i &quot;$(WindowsSdkDir)Include\$(WindowsSDKVersion)\shared&quot; /D _UNICODE /D UNICODE /l&quot;0x0409&quot; /r /fo &quot;$(Win32Resource)&quot; &quot;$(MsBuildThisFileDirectory)NativeVersion.rc&quot;" />
+
+  </Target>
+</Project>
diff --git a/src/System.Private.CoreLib/Tools/Versioning/NativeVersion.rc b/src/System.Private.CoreLib/Tools/Versioning/NativeVersion.rc
new file mode 100644
index 0000000000..6a26d16c27
--- /dev/null
+++ b/src/System.Private.CoreLib/Tools/Versioning/NativeVersion.rc
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#include "GeneratedVersion.h"
+
+#include <windows.h>
+
+VS_VERSION_INFO VERSIONINFO
+FILEVERSION     VER_FILEVERSION
+PRODUCTVERSION  VER_PRODUCTVERSION
+FILEFLAGSMASK   VS_FFI_FILEFLAGSMASK
+FILEFLAGS       VER_DEBUG
+FILEOS          VOS__WINDOWS32
+FILETYPE        VFT_DLL
+FILESUBTYPE     VFT2_UNKNOWN
+BEGIN
+    BLOCK "StringFileInfo"
+    BEGIN
+        BLOCK "040904E4"
+        BEGIN
+            VALUE "CompanyName",      VER_COMPANYNAME_STR
+            VALUE "FileDescription",  VER_FILEDESCRIPTION_STR
+            VALUE "FileVersion",      VER_FILEVERSION_STR
+            VALUE "InternalName",     VER_INTERNALNAME_STR
+            VALUE "LegalCopyright",   VER_LEGALCOPYRIGHT_STR
+            VALUE "OriginalFilename", VER_ORIGINALFILENAME_STR
+            VALUE "ProductName",      VER_PRODUCTNAME_STR
+            VALUE "ProductVersion",   VER_PRODUCTVERSION_STR
+        END
+    END
+
+    BLOCK "VarFileInfo"
+    BEGIN
+        /* The following line should only be modified for localized versions.     */
+        /* It consists of any number of WORD,WORD pairs, with each pair           */
+        /* describing a language,codepage combination supported by the file.      */
+        /*                                                                        */
+        /* For example, a file might have values "0x409,1252" indicating that it  */
+        /* supports English language (0x409) in the Windows ANSI codepage (1252). */
+
+        VALUE "Translation", 0x409, 1252
+
+    END
+END
diff --git a/src/System.Private.CoreLib/shared/Internal/IO/File.Unix.cs b/src/System.Private.CoreLib/shared/Internal/IO/File.Unix.cs
new file mode 100644
index 0000000000..50fa0f0d0c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Internal/IO/File.Unix.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Internal.IO
+{
+    internal static partial class File
+    {
+        internal static bool InternalExists(string fullPath)
+        {
+            Interop.Sys.FileStatus fileinfo;
+
+            // First use stat, as we want to follow symlinks.  If that fails, it could be because the symlink
+            // is broken, we don't have permissions, etc., in which case fall back to using LStat to evaluate
+            // based on the symlink itself.
+            if (Interop.Sys.Stat(fullPath, out fileinfo) < 0 &&
+                Interop.Sys.LStat(fullPath, out fileinfo) < 0)
+            {
+                return false;
+            }
+
+            return ((fileinfo.Mode & Interop.Sys.FileTypes.S_IFMT) != Interop.Sys.FileTypes.S_IFDIR);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Internal/IO/File.Windows.cs b/src/System.Private.CoreLib/shared/Internal/IO/File.Windows.cs
new file mode 100644
index 0000000000..0acae3b457
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Internal/IO/File.Windows.cs
@@ -0,0 +1,77 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32;
+using Microsoft.Win32.SafeHandles;
+using System.IO;
+using System.Runtime.InteropServices;
+
+namespace Internal.IO
+{
+    internal static partial class File
+    {
+        internal static bool InternalExists(string fullPath)
+        {
+            Interop.Kernel32.WIN32_FILE_ATTRIBUTE_DATA data = new Interop.Kernel32.WIN32_FILE_ATTRIBUTE_DATA();
+            int errorCode = FillAttributeInfo(fullPath, ref data, returnErrorOnNotFound: true);
+
+            return (errorCode == 0) && (data.dwFileAttributes != -1)
+                    && ((data.dwFileAttributes & Interop.Kernel32.FileAttributes.FILE_ATTRIBUTE_DIRECTORY) == 0);
+        }
+
+        /// <summary>
+        /// Returns 0 on success, otherwise a Win32 error code.  Note that
+        /// classes should use -1 as the uninitialized state for dataInitialized.
+        /// </summary>
+        /// <param name="returnErrorOnNotFound">Return the error code for not found errors?</param>
+        internal static int FillAttributeInfo(string path, ref Interop.Kernel32.WIN32_FILE_ATTRIBUTE_DATA data, bool returnErrorOnNotFound)
+        {
+            int errorCode = Interop.Errors.ERROR_SUCCESS;
+
+            using (DisableMediaInsertionPrompt.Create())
+            {
+                if (!Interop.Kernel32.GetFileAttributesEx(path, Interop.Kernel32.GET_FILEEX_INFO_LEVELS.GetFileExInfoStandard, ref data))
+                {
+                    errorCode = Marshal.GetLastWin32Error();
+                    if (errorCode == Interop.Errors.ERROR_ACCESS_DENIED)
+                    {
+                        // Files that are marked for deletion will not let you GetFileAttributes,
+                        // ERROR_ACCESS_DENIED is given back without filling out the data struct.
+                        // FindFirstFile, however, will. Historically we always gave back attributes
+                        // for marked-for-deletion files.
+
+                        var findData = new Interop.Kernel32.WIN32_FIND_DATA();
+                        using (SafeFindHandle handle = Interop.Kernel32.FindFirstFile(path, ref findData))
+                        {
+                            if (handle.IsInvalid)
+                            {
+                                errorCode = Marshal.GetLastWin32Error();
+                            }
+                            else
+                            {
+                                errorCode = Interop.Errors.ERROR_SUCCESS;
+                                data.PopulateFrom(ref findData);
+                            }
+                        }
+                    }
+                }
+            }
+
+            if (errorCode != Interop.Errors.ERROR_SUCCESS && !returnErrorOnNotFound)
+            {
+                switch (errorCode)
+                {
+                    case Interop.Errors.ERROR_FILE_NOT_FOUND:
+                    case Interop.Errors.ERROR_PATH_NOT_FOUND:
+                    case Interop.Errors.ERROR_NOT_READY: // Removable media not ready
+                        // Return default value for backward compatibility
+                        data.dwFileAttributes = -1;
+                        return Interop.Errors.ERROR_SUCCESS;
+                }
+            }
+
+            return errorCode;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Internal/IO/File.cs b/src/System.Private.CoreLib/shared/Internal/IO/File.cs
new file mode 100644
index 0000000000..2fcc0f391f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Internal/IO/File.cs
@@ -0,0 +1,77 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+using System.Security;
+using System.IO;
+
+namespace Internal.IO
+{
+    //
+    // Subsetted clone of System.IO.File for internal runtime use.
+    // Keep in sync with https://github.com/dotnet/corefx/tree/master/src/System.IO.FileSystem.
+    //
+    internal static partial class File
+    {
+        // Tests if a file exists. The result is true if the file
+        // given by the specified path exists; otherwise, the result is
+        // false.  Note that if path describes a directory,
+        // Exists will return true.
+        public static bool Exists(string path)
+        {
+            try
+            {
+                if (path == null)
+                    return false;
+                if (path.Length == 0)
+                    return false;
+
+                path = Path.GetFullPath(path);
+
+                // After normalizing, check whether path ends in directory separator.
+                // Otherwise, FillAttributeInfo removes it and we may return a false positive.
+                // GetFullPath should never return null
+                Debug.Assert(path != null, "File.Exists: GetFullPath returned null");
+                if (path.Length > 0 && PathInternal.IsDirectorySeparator(path[path.Length - 1]))
+                {
+                    return false;
+                }
+
+                return InternalExists(path);
+            }
+            catch (ArgumentException) { }
+            catch (NotSupportedException) { } // Security can throw this on ":"
+            catch (SecurityException) { }
+            catch (IOException) { }
+            catch (UnauthorizedAccessException) { }
+
+            return false;
+        }
+
+        public static byte[] ReadAllBytes(string path)
+        {
+            // bufferSize == 1 used to avoid unnecessary buffer in FileStream
+            using (FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize: 1))
+            {
+                long fileLength = fs.Length;
+                if (fileLength > int.MaxValue)
+                    throw new IOException(SR.IO_FileTooLong2GB);
+
+                int index = 0;
+                int count = (int)fileLength;
+                byte[] bytes = new byte[count];
+                while (count > 0)
+                {
+                    int n = fs.Read(bytes, index, count);
+                    if (n == 0)
+                        throw Error.GetEndOfFile();
+                    index += n;
+                    count -= n;
+                }
+                return bytes;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Internal/Runtime/CompilerServices/Unsafe.cs b/src/System.Private.CoreLib/shared/Internal/Runtime/CompilerServices/Unsafe.cs
new file mode 100644
index 0000000000..aeff3ce2ca
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Internal/Runtime/CompilerServices/Unsafe.cs
@@ -0,0 +1,371 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+
+#if BIT64
+using nuint = System.UInt64;
+using nint = System.Int64;
+#else
+using nuint = System.UInt32;
+using nint = System.Int32;
+#endif
+
+//
+// The implementations of most the methods in this file are provided as intrinsics.
+// In CoreCLR, the body of the functions are replaced by the EE with unsafe code. See see getILIntrinsicImplementationForUnsafe for details.
+// In CoreRT, see Internal.IL.Stubs.UnsafeIntrinsics for details.
+//
+
+namespace Internal.Runtime.CompilerServices
+{
+    //
+    // Subsetted clone of System.Runtime.CompilerServices.Unsafe for internal runtime use.
+    // Keep in sync with https://github.com/dotnet/corefx/tree/master/src/System.Runtime.CompilerServices.Unsafe.
+    //
+
+    /// <summary>
+    /// For internal use only. Contains generic, low-level functionality for manipulating pointers.
+    /// </summary>
+    [CLSCompliant(false)]
+    public static unsafe class Unsafe
+    {
+        /// <summary>
+        /// Returns a pointer to the given by-ref parameter.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void* AsPointer<T>(ref T value)
+        {
+            throw new PlatformNotSupportedException();
+
+            // ldarg.0
+            // conv.u
+            // ret
+        }
+
+        /// <summary>
+        /// Returns the size of an object of the given type parameter.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int SizeOf<T>()
+        {
+#if CORECLR
+            typeof(T).ToString(); // Type token used by the actual method body
+#endif
+            throw new PlatformNotSupportedException();
+
+            // sizeof !!0
+            // ret
+        }
+
+        /// <summary>
+        /// Casts the given object to the specified type, performs no dynamic type checking.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static T As<T>(object value) where T : class
+        {
+            throw new PlatformNotSupportedException();
+
+            // ldarg.0
+            // ret
+        }
+
+        /// <summary>
+        /// Reinterprets the given reference as a reference to a value of type <typeparamref name="TTo"/>.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ref TTo As<TFrom, TTo>(ref TFrom source)
+        {
+            throw new PlatformNotSupportedException();
+
+            // ldarg.0
+            // ret
+        }
+
+        /// <summary>
+        /// Adds an element offset to the given reference.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ref T Add<T>(ref T source, int elementOffset)
+        {
+#if CORECLR
+            typeof(T).ToString(); // Type token used by the actual method body
+            throw new PlatformNotSupportedException();
+#else
+            return ref AddByteOffset(ref source, (IntPtr)(elementOffset * (nint)SizeOf<T>()));
+#endif
+        }
+
+        /// <summary>
+        /// Adds an element offset to the given reference.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ref T Add<T>(ref T source, IntPtr elementOffset)
+        {
+#if CORECLR
+            typeof(T).ToString(); // Type token used by the actual method body
+            throw new PlatformNotSupportedException();
+#else
+            return ref AddByteOffset(ref source, (IntPtr)((nint)elementOffset * (nint)SizeOf<T>()));
+#endif
+        }
+
+        /// <summary>
+        /// Adds an element offset to the given pointer.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void* Add<T>(void* source, int elementOffset)
+        {
+#if CORECLR
+            typeof(T).ToString(); // Type token used by the actual method body
+            throw new PlatformNotSupportedException();
+#else
+            return (byte*)source + (elementOffset * (nint)SizeOf<T>());
+#endif
+        }
+
+        /// <summary>
+        /// Adds an element offset to the given reference.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static ref T AddByteOffset<T>(ref T source, nuint byteOffset)
+        {
+            return ref AddByteOffset(ref source, (IntPtr)(void*)byteOffset);
+        }
+
+        /// <summary>
+        /// Determines whether the specified references point to the same location.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool AreSame<T>(ref T left, ref T right)
+        {
+            throw new PlatformNotSupportedException();
+
+            // ldarg.0
+            // ldarg.1
+            // ceq
+            // ret
+        }
+
+        /// <summary>
+        /// Determines whether the memory address referenced by <paramref name="left"/> is greater than
+        /// the memory address referenced by <paramref name="right"/>.
+        /// </summary>
+        /// <remarks>
+        /// This check is conceptually similar to "(void*)(&amp;left) &gt; (void*)(&amp;right)".
+        /// </remarks>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool IsAddressGreaterThan<T>(ref T left, ref T right)
+        {
+            throw new PlatformNotSupportedException();
+
+            // ldarg.0
+            // ldarg.1
+            // cgt.un
+            // ret
+        }
+
+        /// <summary>
+        /// Determines whether the memory address referenced by <paramref name="left"/> is less than
+        /// the memory address referenced by <paramref name="right"/>.
+        /// </summary>
+        /// <remarks>
+        /// This check is conceptually similar to "(void*)(&amp;left) &lt; (void*)(&amp;right)".
+        /// </remarks>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool IsAddressLessThan<T>(ref T left, ref T right)
+        {
+            throw new PlatformNotSupportedException();
+
+            // ldarg.0
+            // ldarg.1
+            // clt.un
+            // ret
+        }
+
+        /// <summary>
+        /// Initializes a block of memory at the given location with a given initial value 
+        /// without assuming architecture dependent alignment of the address.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void InitBlockUnaligned(ref byte startAddress, byte value, uint byteCount)
+        {
+            for (uint i = 0; i < byteCount; i++)
+                AddByteOffset(ref startAddress, i) = value;
+        }
+
+        /// <summary>
+        /// Reads a value of type <typeparamref name="T"/> from the given location.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static T ReadUnaligned<T>(void* source)
+        {
+#if CORECLR
+            typeof(T).ToString(); // Type token used by the actual method body
+            throw new PlatformNotSupportedException();
+#else
+            return Unsafe.As<byte, T>(ref *(byte*)source);
+#endif
+        }
+
+        /// <summary>
+        /// Reads a value of type <typeparamref name="T"/> from the given location.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static T ReadUnaligned<T>(ref byte source)
+        {
+#if CORECLR
+            typeof(T).ToString(); // Type token used by the actual method body
+            throw new PlatformNotSupportedException();
+#else
+            return Unsafe.As<byte, T>(ref source);
+#endif
+        }
+
+        /// <summary>
+        /// Writes a value of type <typeparamref name="T"/> to the given location.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void WriteUnaligned<T>(void* destination, T value)
+        {
+#if CORECLR
+            typeof(T).ToString(); // Type token used by the actual method body
+            throw new PlatformNotSupportedException();
+#else
+            Unsafe.As<byte, T>(ref *(byte*)destination) = value;
+#endif
+        }
+
+        /// <summary>
+        /// Writes a value of type <typeparamref name="T"/> to the given location.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void WriteUnaligned<T>(ref byte destination, T value)
+        {
+#if CORECLR
+            typeof(T).ToString(); // Type token used by the actual method body
+            throw new PlatformNotSupportedException();
+#else
+            Unsafe.As<byte, T>(ref destination) = value;
+#endif
+        }
+
+        /// <summary>
+        /// Adds an element offset to the given reference.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ref T AddByteOffset<T>(ref T source, IntPtr byteOffset)
+        {
+            // This method is implemented by the toolchain
+            throw new PlatformNotSupportedException();
+
+            // ldarg.0
+            // ldarg.1
+            // add
+            // ret
+        }
+
+        /// <summary>
+        /// Reads a value of type <typeparamref name="T"/> from the given location.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static T Read<T>(void* source)
+        {
+            return Unsafe.As<byte, T>(ref *(byte*)source);
+        }
+
+        /// <summary>
+        /// Reads a value of type <typeparamref name="T"/> from the given location.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static T Read<T>(ref byte source)
+        {
+            return Unsafe.As<byte, T>(ref source);
+        }
+
+        /// <summary>
+        /// Writes a value of type <typeparamref name="T"/> to the given location.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void Write<T>(void* destination, T value)
+        {
+            Unsafe.As<byte, T>(ref *(byte*)destination) = value;
+        }
+
+        /// <summary>
+        /// Writes a value of type <typeparamref name="T"/> to the given location.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void Write<T>(ref byte destination, T value)
+        {
+            Unsafe.As<byte, T>(ref destination) = value;
+        }
+
+        /// <summary>
+        /// Reinterprets the given location as a reference to a value of type <typeparamref name="T"/>.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ref T AsRef<T>(void* source)
+        {
+            return ref Unsafe.As<byte, T>(ref *(byte*)source);
+        }
+
+        /// <summary>
+        /// Determines the byte offset from origin to target from the given references.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static IntPtr ByteOffset<T>(ref T origin, ref T target)
+        {
+            throw new PlatformNotSupportedException();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/Interop.Errors.cs b/src/System.Private.CoreLib/shared/Interop/Unix/Interop.Errors.cs
new file mode 100644
index 0000000000..9cb05809db
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/Interop.Errors.cs
@@ -0,0 +1,209 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    /// <summary>Common Unix errno error codes.</summary>
+    internal enum Error
+    {
+        // These values were defined in src/Native/System.Native/fxerrno.h
+        //
+        // They compare against values obtained via Interop.Sys.GetLastError() not Marshal.GetLastWin32Error()
+        // which obtains the raw errno that varies between unixes. The strong typing as an enum is meant to
+        // prevent confusing the two. Casting to or from int is suspect. Use GetLastErrorInfo() if you need to
+        // correlate these to the underlying platform values or obtain the corresponding error message.
+        // 
+
+        SUCCESS          = 0,
+
+        E2BIG            = 0x10001,           // Argument list too long.
+        EACCES           = 0x10002,           // Permission denied.
+        EADDRINUSE       = 0x10003,           // Address in use.
+        EADDRNOTAVAIL    = 0x10004,           // Address not available.
+        EAFNOSUPPORT     = 0x10005,           // Address family not supported.
+        EAGAIN           = 0x10006,           // Resource unavailable, try again (same value as EWOULDBLOCK),
+        EALREADY         = 0x10007,           // Connection already in progress.
+        EBADF            = 0x10008,           // Bad file descriptor.
+        EBADMSG          = 0x10009,           // Bad message.
+        EBUSY            = 0x1000A,           // Device or resource busy.
+        ECANCELED        = 0x1000B,           // Operation canceled.
+        ECHILD           = 0x1000C,           // No child processes.
+        ECONNABORTED     = 0x1000D,           // Connection aborted.
+        ECONNREFUSED     = 0x1000E,           // Connection refused.
+        ECONNRESET       = 0x1000F,           // Connection reset.
+        EDEADLK          = 0x10010,           // Resource deadlock would occur.
+        EDESTADDRREQ     = 0x10011,           // Destination address required.
+        EDOM             = 0x10012,           // Mathematics argument out of domain of function.
+        EDQUOT           = 0x10013,           // Reserved.
+        EEXIST           = 0x10014,           // File exists.
+        EFAULT           = 0x10015,           // Bad address.
+        EFBIG            = 0x10016,           // File too large.
+        EHOSTUNREACH     = 0x10017,           // Host is unreachable.
+        EIDRM            = 0x10018,           // Identifier removed.
+        EILSEQ           = 0x10019,           // Illegal byte sequence.
+        EINPROGRESS      = 0x1001A,           // Operation in progress.
+        EINTR            = 0x1001B,           // Interrupted function.
+        EINVAL           = 0x1001C,           // Invalid argument.
+        EIO              = 0x1001D,           // I/O error.
+        EISCONN          = 0x1001E,           // Socket is connected.
+        EISDIR           = 0x1001F,           // Is a directory.
+        ELOOP            = 0x10020,           // Too many levels of symbolic links.
+        EMFILE           = 0x10021,           // File descriptor value too large.
+        EMLINK           = 0x10022,           // Too many links.
+        EMSGSIZE         = 0x10023,           // Message too large.
+        EMULTIHOP        = 0x10024,           // Reserved.
+        ENAMETOOLONG     = 0x10025,           // Filename too long.
+        ENETDOWN         = 0x10026,           // Network is down.
+        ENETRESET        = 0x10027,           // Connection aborted by network.
+        ENETUNREACH      = 0x10028,           // Network unreachable.
+        ENFILE           = 0x10029,           // Too many files open in system.
+        ENOBUFS          = 0x1002A,           // No buffer space available.
+        ENODEV           = 0x1002C,           // No such device.
+        ENOENT           = 0x1002D,           // No such file or directory.
+        ENOEXEC          = 0x1002E,           // Executable file format error.
+        ENOLCK           = 0x1002F,           // No locks available.
+        ENOLINK          = 0x10030,           // Reserved.
+        ENOMEM           = 0x10031,           // Not enough space.
+        ENOMSG           = 0x10032,           // No message of the desired type.
+        ENOPROTOOPT      = 0x10033,           // Protocol not available.
+        ENOSPC           = 0x10034,           // No space left on device.
+        ENOSYS           = 0x10037,           // Function not supported.
+        ENOTCONN         = 0x10038,           // The socket is not connected.
+        ENOTDIR          = 0x10039,           // Not a directory or a symbolic link to a directory.
+        ENOTEMPTY        = 0x1003A,           // Directory not empty.
+        ENOTRECOVERABLE  = 0x1003B,           // State not recoverable.
+        ENOTSOCK         = 0x1003C,           // Not a socket.
+        ENOTSUP          = 0x1003D,           // Not supported (same value as EOPNOTSUP).
+        ENOTTY           = 0x1003E,           // Inappropriate I/O control operation.
+        ENXIO            = 0x1003F,           // No such device or address.
+        EOVERFLOW        = 0x10040,           // Value too large to be stored in data type.
+        EOWNERDEAD       = 0x10041,           // Previous owner died.
+        EPERM            = 0x10042,           // Operation not permitted.
+        EPIPE            = 0x10043,           // Broken pipe.
+        EPROTO           = 0x10044,           // Protocol error.
+        EPROTONOSUPPORT  = 0x10045,           // Protocol not supported.
+        EPROTOTYPE       = 0x10046,           // Protocol wrong type for socket.
+        ERANGE           = 0x10047,           // Result too large.
+        EROFS            = 0x10048,           // Read-only file system.
+        ESPIPE           = 0x10049,           // Invalid seek.
+        ESRCH            = 0x1004A,           // No such process.
+        ESTALE           = 0x1004B,           // Reserved.
+        ETIMEDOUT        = 0x1004D,           // Connection timed out.
+        ETXTBSY          = 0x1004E,           // Text file busy.
+        EXDEV            = 0x1004F,           // Cross-device link.
+        ESOCKTNOSUPPORT  = 0x1005E,           // Socket type not supported.
+        EPFNOSUPPORT     = 0x10060,           // Protocol family not supported.
+        ESHUTDOWN        = 0x1006C,           // Socket shutdown.
+        EHOSTDOWN        = 0x10070,           // Host is down.
+        ENODATA          = 0x10071,           // No data available.
+
+        // POSIX permits these to have the same value and we make them always equal so
+        // that CoreFX cannot introduce a dependency on distinguishing between them that
+        // would not work on all platforms.
+        EOPNOTSUPP      = ENOTSUP,            // Operation not supported on socket.
+        EWOULDBLOCK     = EAGAIN,             // Operation would block.
+    }
+
+
+    // Represents a platform-agnostic Error and underlying platform-specific errno
+    internal struct ErrorInfo
+    {
+        private Error _error;
+        private int _rawErrno;
+
+        internal ErrorInfo(int errno)
+        {
+            _error = Interop.Sys.ConvertErrorPlatformToPal(errno);
+            _rawErrno = errno;
+        }
+
+        internal ErrorInfo(Error error)
+        {
+            _error = error;
+            _rawErrno = -1;
+        }
+
+        internal Error Error
+        {
+            get { return _error; }
+        }
+
+        internal int RawErrno
+        {
+            get { return _rawErrno == -1 ? (_rawErrno = Interop.Sys.ConvertErrorPalToPlatform(_error)) : _rawErrno; }
+        }
+
+        internal string GetErrorMessage()
+        {
+            return Interop.Sys.StrError(RawErrno);
+        }
+
+        public override string ToString()
+        {
+            return string.Format(
+                "RawErrno: {0} Error: {1} GetErrorMessage: {2}", // No localization required; text is member names used for debugging purposes
+                RawErrno, Error, GetErrorMessage());
+        }
+    }
+
+    internal partial class Sys
+    {
+        internal static Error GetLastError()
+        {
+            return ConvertErrorPlatformToPal(Marshal.GetLastWin32Error());
+        }
+
+        internal static ErrorInfo GetLastErrorInfo()
+        {
+            return new ErrorInfo(Marshal.GetLastWin32Error());
+        }
+
+        internal static unsafe string StrError(int platformErrno)
+        {
+            int maxBufferLength = 1024; // should be long enough for most any UNIX error
+            byte* buffer = stackalloc byte[maxBufferLength];
+            byte* message = StrErrorR(platformErrno, buffer, maxBufferLength);
+
+            if (message == null)
+            {
+                // This means the buffer was not large enough, but still contains
+                // as much of the error message as possible and is guaranteed to
+                // be null-terminated. We're not currently resizing/retrying because
+                // maxBufferLength is large enough in practice, but we could do
+                // so here in the future if necessary.
+                message = buffer;
+            }
+
+            return Marshal.PtrToStringAnsi((IntPtr)message);
+        }
+
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_ConvertErrorPlatformToPal")]
+        internal static extern Error ConvertErrorPlatformToPal(int platformErrno);
+
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_ConvertErrorPalToPlatform")]
+        internal static extern int ConvertErrorPalToPlatform(Error error);
+
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_StrErrorR")]
+        private static extern unsafe byte* StrErrorR(int platformErrno, byte* buffer, int bufferSize);
+    }
+}
+
+// NOTE: extension method can't be nested inside Interop class.
+internal static class InteropErrorExtensions
+{
+    // Intended usage is e.g. Interop.Error.EFAIL.Info() for brevity
+    // vs. new Interop.ErrorInfo(Interop.Error.EFAIL) for synthesizing
+    // errors. Errors originated from the system should be obtained
+    // via GetLastErrorInfo(), not GetLastError().Info() as that will
+    // convert twice, which is not only inefficient but also lossy if
+    // we ever encounter a raw errno that no equivalent in the Error
+    // enum.
+    public static Interop.ErrorInfo Info(this Interop.Error error)
+    {
+        return new Interop.ErrorInfo(error);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/Interop.IOErrors.cs b/src/System.Private.CoreLib/shared/Interop/Unix/Interop.IOErrors.cs
new file mode 100644
index 0000000000..5babcd1d05
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/Interop.IOErrors.cs
@@ -0,0 +1,172 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+using System.IO;
+using System.Runtime.InteropServices;
+using Microsoft.Win32.SafeHandles;
+
+internal static partial class Interop
+{
+    private static void ThrowExceptionForIoErrno(ErrorInfo errorInfo, string path, bool isDirectory, Func<ErrorInfo, ErrorInfo> errorRewriter)
+    {
+        Debug.Assert(errorInfo.Error != Error.SUCCESS);
+        Debug.Assert(errorInfo.Error != Error.EINTR, "EINTR errors should be handled by the native shim and never bubble up to managed code");
+
+        if (errorRewriter != null)
+        {
+            errorInfo = errorRewriter(errorInfo);
+        }
+
+        throw Interop.GetExceptionForIoErrno(errorInfo, path, isDirectory);
+    }
+
+    internal static void CheckIo(Error error, string path = null, bool isDirectory = false, Func<ErrorInfo, ErrorInfo> errorRewriter = null)
+    {
+        if (error != Interop.Error.SUCCESS)
+        {
+            ThrowExceptionForIoErrno(error.Info(), path, isDirectory, errorRewriter);
+        }
+    }
+
+    /// <summary>
+    /// Validates the result of system call that returns greater than or equal to 0 on success
+    /// and less than 0 on failure, with errno set to the error code.
+    /// If the system call failed for any reason, an exception is thrown. Otherwise, the system call succeeded.
+    /// </summary>
+    /// <param name="result">The result of the system call.</param>
+    /// <param name="path">The path with which this error is associated.  This may be null.</param>
+    /// <param name="isDirectory">true if the <paramref name="path"/> is known to be a directory; otherwise, false.</param>
+    /// <param name="errorRewriter">Optional function to change an error code prior to processing it.</param>
+    /// <returns>
+    /// On success, returns the non-negative result long that was validated.
+    /// </returns>
+    internal static long CheckIo(long result, string path = null, bool isDirectory = false, Func<ErrorInfo, ErrorInfo> errorRewriter = null)
+    {
+        if (result < 0)
+        {
+            ThrowExceptionForIoErrno(Sys.GetLastErrorInfo(), path, isDirectory, errorRewriter);
+        }
+
+        return result;
+    }
+
+    /// <summary>
+    /// Validates the result of system call that returns greater than or equal to 0 on success
+    /// and less than 0 on failure, with errno set to the error code.
+    /// If the system call failed for any reason, an exception is thrown. Otherwise, the system call succeeded.
+    /// </summary>
+    /// <returns>
+    /// On success, returns the non-negative result int that was validated.
+    /// </returns>
+    internal static int CheckIo(int result, string path = null, bool isDirectory = false, Func<ErrorInfo, ErrorInfo> errorRewriter = null)
+    {
+        CheckIo((long)result, path, isDirectory, errorRewriter);
+
+        return result;
+    }
+
+    /// <summary>
+    /// Validates the result of system call that returns greater than or equal to 0 on success
+    /// and less than 0 on failure, with errno set to the error code.
+    /// If the system call failed for any reason, an exception is thrown. Otherwise, the system call succeeded.
+    /// </summary>
+    /// <returns>
+    /// On success, returns the non-negative result IntPtr that was validated.
+    /// </returns>
+    internal static IntPtr CheckIo(IntPtr result, string path = null, bool isDirectory = false, Func<ErrorInfo, ErrorInfo> errorRewriter = null)
+    {
+        CheckIo((long)result, path, isDirectory, errorRewriter);
+
+        return result;
+    }
+
+    /// <summary>
+    /// Validates the result of system call that returns greater than or equal to 0 on success
+    /// and less than 0 on failure, with errno set to the error code.
+    /// If the system call failed for any reason, an exception is thrown. Otherwise, the system call succeeded.
+    /// </summary>
+    /// <returns>
+    /// On success, returns the valid SafeFileHandle that was validated.
+    /// </returns>
+    internal static TSafeHandle CheckIo<TSafeHandle>(TSafeHandle handle, string path = null, bool isDirectory = false, Func<ErrorInfo, ErrorInfo> errorRewriter = null)
+        where TSafeHandle : SafeHandle
+    {
+        if (handle.IsInvalid)
+        {
+            ThrowExceptionForIoErrno(Sys.GetLastErrorInfo(), path, isDirectory, errorRewriter);
+        }
+
+        return handle;
+    }
+
+    /// <summary>
+    /// Gets an Exception to represent the supplied error info.
+    /// </summary>
+    /// <param name="error">The error info</param>
+    /// <param name="path">The path with which this error is associated.  This may be null.</param>
+    /// <param name="isDirectory">true if the <paramref name="path"/> is known to be a directory; otherwise, false.</param>
+    /// <returns></returns>
+    internal static Exception GetExceptionForIoErrno(ErrorInfo errorInfo, string path = null, bool isDirectory = false)
+    {
+        // Translate the errno into a known set of exception types.  For cases where multiple errnos map
+        // to the same exception type, include an inner exception with the details.
+        switch (errorInfo.Error)
+        {
+            case Error.ENOENT:
+                if (isDirectory)
+                {
+                    return !string.IsNullOrEmpty(path) ?
+                        new DirectoryNotFoundException(SR.Format(SR.IO_PathNotFound_Path, path)) :
+                        new DirectoryNotFoundException(SR.IO_PathNotFound_NoPathName);
+                }
+                else
+                {
+                    return !string.IsNullOrEmpty(path) ?
+                        new FileNotFoundException(SR.Format(SR.IO_FileNotFound_FileName, path), path) :
+                        new FileNotFoundException(SR.IO_FileNotFound);
+                }
+
+            case Error.EACCES:
+            case Error.EBADF:
+            case Error.EPERM:
+                Exception inner = GetIOException(errorInfo);
+                return !string.IsNullOrEmpty(path) ?
+                    new UnauthorizedAccessException(SR.Format(SR.UnauthorizedAccess_IODenied_Path, path), inner) :
+                    new UnauthorizedAccessException(SR.UnauthorizedAccess_IODenied_NoPathName, inner);
+
+            case Error.ENAMETOOLONG:
+                return !string.IsNullOrEmpty(path) ?
+                    new PathTooLongException(SR.Format(SR.IO_PathTooLong_Path, path)) :
+                    new PathTooLongException(SR.IO_PathTooLong);
+
+            case Error.EWOULDBLOCK:
+                return !string.IsNullOrEmpty(path) ?
+                    new IOException(SR.Format(SR.IO_SharingViolation_File, path), errorInfo.RawErrno) :
+                    new IOException(SR.IO_SharingViolation_NoFileName, errorInfo.RawErrno);
+
+            case Error.ECANCELED:
+                return new OperationCanceledException();
+
+            case Error.EFBIG:
+                return new ArgumentOutOfRangeException("value", SR.ArgumentOutOfRange_FileLengthTooBig);
+
+            case Error.EEXIST:
+                if (!string.IsNullOrEmpty(path))
+                {
+                    return new IOException(SR.Format(SR.IO_FileExists_Name, path), errorInfo.RawErrno);
+                }
+                goto default;
+
+            default:
+                return GetIOException(errorInfo);
+        }
+    }
+
+    internal static Exception GetIOException(Interop.ErrorInfo errorInfo)
+    {
+        return new IOException(errorInfo.GetErrorMessage(), errorInfo.RawErrno);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/Interop.Libraries.cs b/src/System.Private.CoreLib/shared/Interop/Unix/Interop.Libraries.cs
new file mode 100644
index 0000000000..02d0092445
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/Interop.Libraries.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+internal static partial class Interop
+{
+    internal static partial class Libraries
+    {
+        internal const string GlobalizationNative = "System.Globalization.Native";
+        internal const string SystemNative = "System.Native";
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Calendar.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Calendar.cs
new file mode 100644
index 0000000000..55553cc7ea
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Calendar.cs
@@ -0,0 +1,33 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Globalization;
+using System.Runtime.InteropServices;
+using System.Text;
+
+internal static partial class Interop
+{
+    internal static partial class Globalization
+    {
+        internal delegate void EnumCalendarInfoCallback(
+           [MarshalAs(UnmanagedType.LPWStr)] string calendarString,
+           IntPtr context);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_GetCalendars")]
+        internal static extern int GetCalendars(string localeName, CalendarId[] calendars, int calendarsCapacity);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_GetCalendarInfo")]
+        internal static extern ResultCode GetCalendarInfo(string localeName, CalendarId calendarId, CalendarDataType calendarDataType, [Out] StringBuilder result, int resultCapacity);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_EnumCalendarInfo")]
+        internal static extern bool EnumCalendarInfo(EnumCalendarInfoCallback callback, string localeName, CalendarId calendarId, CalendarDataType calendarDataType, IntPtr context);
+
+        [DllImport(Libraries.GlobalizationNative, EntryPoint = "GlobalizationNative_GetLatestJapaneseEra")]
+        internal static extern int GetLatestJapaneseEra();
+
+        [DllImport(Libraries.GlobalizationNative, EntryPoint = "GlobalizationNative_GetJapaneseEraStartDate")]
+        internal static extern bool GetJapaneseEraStartDate(int era, out int startYear, out int startMonth, out int startDay);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Casing.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Casing.cs
new file mode 100644
index 0000000000..503a864d69
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Casing.cs
@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+using System.Security;
+using System.Text;
+
+internal static partial class Interop
+{
+    internal static partial class Globalization
+    {
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_ChangeCase")]
+        internal static extern unsafe void ChangeCase(char* src, int srcLen, char* dstBuffer, int dstBufferCapacity, bool bToUpper);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_ChangeCaseInvariant")]
+        internal static extern unsafe void ChangeCaseInvariant(char* src, int srcLen, char* dstBuffer, int dstBufferCapacity, bool bToUpper);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_ChangeCaseTurkish")]
+        internal static extern unsafe void ChangeCaseTurkish(char* src, int srcLen, char* dstBuffer, int dstBufferCapacity, bool bToUpper);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Collation.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Collation.cs
new file mode 100644
index 0000000000..9942882f1a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Collation.cs
@@ -0,0 +1,81 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Globalization;
+using System.Runtime.InteropServices;
+using System.Security;
+
+internal static partial class Interop
+{
+    internal static partial class Globalization
+    {
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_GetSortHandle")]
+        internal static extern unsafe ResultCode GetSortHandle(byte[] localeName, out SafeSortHandle sortHandle);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_CloseSortHandle")]
+        internal static extern unsafe void CloseSortHandle(IntPtr handle);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_CompareString")]
+        internal static extern unsafe int CompareString(SafeSortHandle sortHandle, char* lpStr1, int cwStr1Len, char* lpStr2, int cwStr2Len, CompareOptions options);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_IndexOf")]
+        internal static extern unsafe int IndexOf(SafeSortHandle sortHandle, string target, int cwTargetLength, char* pSource, int cwSourceLength, CompareOptions options, int* matchLengthPtr);
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_IndexOf")]
+        internal static extern unsafe int IndexOf(SafeSortHandle sortHandle, char* target, int cwTargetLength, char* pSource, int cwSourceLength, CompareOptions options, int* matchLengthPtr);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_LastIndexOf")]
+        internal static extern unsafe int LastIndexOf(SafeSortHandle sortHandle, string target, int cwTargetLength, char* pSource, int cwSourceLength, CompareOptions options);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_IndexOfOrdinalIgnoreCase")]
+        internal static extern unsafe int IndexOfOrdinalIgnoreCase(string target, int cwTargetLength, char* pSource, int cwSourceLength, bool findLast);
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_IndexOfOrdinalIgnoreCase")]
+        internal static extern unsafe int IndexOfOrdinalIgnoreCase(char* target, int cwTargetLength, char* pSource, int cwSourceLength, bool findLast);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_StartsWith")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern unsafe bool StartsWith(SafeSortHandle sortHandle, char* target, int cwTargetLength, char* source, int cwSourceLength, CompareOptions options);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_EndsWith")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern unsafe bool EndsWith(SafeSortHandle sortHandle, char* target, int cwTargetLength, char* source, int cwSourceLength, CompareOptions options);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_StartsWith")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern unsafe bool StartsWith(SafeSortHandle sortHandle, string target, int cwTargetLength, string source, int cwSourceLength, CompareOptions options);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_EndsWith")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern unsafe bool EndsWith(SafeSortHandle sortHandle, string target, int cwTargetLength, string source, int cwSourceLength, CompareOptions options);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_GetSortKey")]
+        internal static extern unsafe int GetSortKey(SafeSortHandle sortHandle, string str, int strLength, byte* sortKey, int sortKeyLength, CompareOptions options);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_CompareStringOrdinalIgnoreCase")]
+        internal static extern unsafe int CompareStringOrdinalIgnoreCase(char* lpStr1, int cwStr1Len, char* lpStr2, int cwStr2Len);
+
+        [DllImport(Libraries.GlobalizationNative, EntryPoint = "GlobalizationNative_GetSortVersion")]
+        internal static extern int GetSortVersion(SafeSortHandle sortHandle);
+
+        internal class SafeSortHandle : SafeHandle
+        {
+            private SafeSortHandle() :
+                base(IntPtr.Zero, true)
+            {
+            }
+
+            public override bool IsInvalid
+            {
+                get { return handle == IntPtr.Zero; }
+            }
+
+            protected override bool ReleaseHandle()
+            {
+                CloseSortHandle(handle);
+                SetHandle(IntPtr.Zero);
+                return true;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.ICU.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.ICU.cs
new file mode 100644
index 0000000000..a16c813b2f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.ICU.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+
+internal static partial class Interop
+{
+    internal static partial class Globalization
+    {
+        [DllImport(Libraries.GlobalizationNative, EntryPoint = "GlobalizationNative_LoadICU")]
+        internal static extern int LoadICU();
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Idna.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Idna.cs
new file mode 100644
index 0000000000..89b6c3cebe
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Idna.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Globalization
+    {
+        internal const int AllowUnassigned = 0x1;
+        internal const int UseStd3AsciiRules = 0x2;
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_ToAscii")]
+        internal static extern unsafe int ToAscii(uint flags, char* src, int srcLen, char* dstBuffer, int dstBufferCapacity);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_ToUnicode")]
+        internal static extern unsafe int ToUnicode(uint flags, char* src, int srcLen, char* dstBuffer, int dstBufferCapacity);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Locale.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Locale.cs
new file mode 100644
index 0000000000..9ef41dedf2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Locale.cs
@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+using System.Text;
+
+internal static partial class Interop
+{
+    internal static partial class Globalization
+    {
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_GetLocaleName")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern unsafe bool GetLocaleName(string localeName, [Out] StringBuilder value, int valueLength);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_GetLocaleInfoString")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern unsafe bool GetLocaleInfoString(string localeName, uint localeStringData, [Out] StringBuilder value, int valueLength);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_GetDefaultLocaleName")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern unsafe bool GetDefaultLocaleName([Out] StringBuilder value, int valueLength);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_GetLocaleTimeFormat")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern unsafe bool GetLocaleTimeFormat(string localeName, bool shortFormat, [Out] StringBuilder value, int valueLength);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_GetLocaleInfoInt")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern unsafe bool GetLocaleInfoInt(string localeName, uint localeNumberData, ref int value);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_GetLocaleInfoGroupingSizes")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern unsafe bool GetLocaleInfoGroupingSizes(string localeName, uint localeGroupingData, ref int primaryGroupSize, ref int secondaryGroupSize);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_GetLocales")]
+        internal static extern unsafe int GetLocales([Out] Char[] value, int valueLength);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Normalization.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Normalization.cs
new file mode 100644
index 0000000000..d442da0ea1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Normalization.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+using System.Text;
+
+internal static partial class Interop
+{
+    internal static partial class Globalization
+    {
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_IsNormalized")]
+        internal static extern int IsNormalized(NormalizationForm normalizationForm, string src, int srcLen);
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_NormalizeString")]
+        internal static extern int NormalizeString(NormalizationForm normalizationForm, string src, int srcLen, [Out] char[] dstBuffer, int dstBufferCapacity);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.ResultCode.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.ResultCode.cs
new file mode 100644
index 0000000000..4a9933f929
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.ResultCode.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+internal static partial class Interop
+{
+    internal static partial class Globalization
+    {
+        // needs to be kept in sync with ResultCode in System.Globalization.Native
+        internal enum ResultCode
+        {
+            Success = 0,
+            UnknownError = 1,
+            InsufficentBuffer = 2,
+            OutOfMemory = 3
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.TimeZoneInfo.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.TimeZoneInfo.cs
new file mode 100644
index 0000000000..47cf26662b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.TimeZoneInfo.cs
@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using System.Text;
+
+internal static partial class Interop
+{
+    internal static partial class Globalization
+    {
+        // needs to be kept in sync with TimeZoneDisplayNameType in System.Globalization.Native
+        internal enum TimeZoneDisplayNameType
+        {
+            Generic = 0,
+            Standard = 1,
+            DaylightSavings = 2,
+        }
+
+        [DllImport(Libraries.GlobalizationNative, CharSet = CharSet.Unicode, EntryPoint = "GlobalizationNative_GetTimeZoneDisplayName")]
+        internal static extern ResultCode GetTimeZoneDisplayName(
+            string localeName, 
+            string timeZoneId, 
+            TimeZoneDisplayNameType type, 
+            [Out] StringBuilder result, 
+            int resultLength);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Utils.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Utils.cs
new file mode 100644
index 0000000000..9887bd4f0b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Globalization.Native/Interop.Utils.cs
@@ -0,0 +1,52 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Text;
+
+internal static partial class Interop
+{
+    /// <summary>
+    /// Helper for making interop calls that return a string, but we don't know
+    /// the correct size of buffer to make. So invoke the interop call with an
+    /// increasing buffer until the size is big enough.
+    /// </summary>
+    internal static bool CallStringMethod<TArg1, TArg2, TArg3>(
+        Func<TArg1, TArg2, TArg3, StringBuilder, Interop.Globalization.ResultCode> interopCall,
+        TArg1 arg1,
+        TArg2 arg2,
+        TArg3 arg3,
+        out string result)
+    {
+        const int initialStringSize = 80;
+        const int maxDoubleAttempts = 5;
+
+        StringBuilder stringBuilder = StringBuilderCache.Acquire(initialStringSize);
+
+        for (int i = 0; i < maxDoubleAttempts; i++)
+        {
+            Interop.Globalization.ResultCode resultCode = interopCall(arg1, arg2, arg3, stringBuilder);
+
+            if (resultCode == Interop.Globalization.ResultCode.Success)
+            {
+                result = StringBuilderCache.GetStringAndRelease(stringBuilder);
+                return true;
+            }
+            else if (resultCode == Interop.Globalization.ResultCode.InsufficentBuffer)
+            {
+                // increase the string size and loop
+                stringBuilder.EnsureCapacity(stringBuilder.Capacity * 2);
+            }
+            else
+            {
+                // if there is an unknown error, don't proceed
+                break;
+            }
+        }
+
+        StringBuilderCache.Release(stringBuilder);
+        result = null;
+        return false;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Close.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Close.cs
new file mode 100644
index 0000000000..8d192398a0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Close.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_Close", SetLastError = true)]
+        internal static extern int Close(IntPtr fd);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.FLock.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.FLock.cs
new file mode 100644
index 0000000000..22934a3e77
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.FLock.cs
@@ -0,0 +1,31 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+using Microsoft.Win32.SafeHandles;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        internal enum LockOperations : int
+        {
+            LOCK_SH = 1,    /* shared lock */
+            LOCK_EX = 2,    /* exclusive lock */
+            LOCK_NB = 4,    /* don't block when locking*/
+            LOCK_UN = 8,    /* unlock */
+        }
+
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_FLock", SetLastError = true)]
+        internal static extern int FLock(SafeFileHandle fd, LockOperations operation);
+
+        /// <summary>
+        /// Exposing this for SafeFileHandle.ReleaseHandle() to call.
+        /// Normal callers should use FLock(SafeFileHandle fd).
+        /// </summary>
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_FLock", SetLastError = true)]
+        internal static extern int FLock(IntPtr fd, LockOperations operation);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.FSync.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.FSync.cs
new file mode 100644
index 0000000000..e3ab970931
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.FSync.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using Microsoft.Win32.SafeHandles;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_FSync", SetLastError = true)]
+        internal static extern int FSync(SafeFileHandle fd);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.FTruncate.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.FTruncate.cs
new file mode 100644
index 0000000000..5dad650362
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.FTruncate.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using Microsoft.Win32.SafeHandles;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_FTruncate", SetLastError = true)]
+        internal static extern int FTruncate(SafeFileHandle fd, long length);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.GetCwd.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.GetCwd.cs
new file mode 100644
index 0000000000..a8bef6bde8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.GetCwd.cs
@@ -0,0 +1,74 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Buffers;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_GetCwd", SetLastError = true)]
+        private static extern unsafe byte* GetCwd(byte* buffer, int bufferLength);
+
+        internal static unsafe string GetCwd()
+        {      
+            const int StackLimit = 256;
+       
+            // First try to get the path into a buffer on the stack
+            byte* stackBuf = stackalloc byte[StackLimit];
+            string result = GetCwdHelper(stackBuf, StackLimit);
+            if (result != null)
+            {
+                return result;
+            }
+
+            // If that was too small, try increasing large buffer sizes
+            int bufferSize = StackLimit;
+            do
+            {
+                checked { bufferSize *= 2; }
+                byte[] buf = ArrayPool<byte>.Shared.Rent(bufferSize);
+                try
+                {
+                    fixed (byte* ptr = &buf[0])
+                    {
+                        result = GetCwdHelper(ptr, buf.Length);
+                        if (result != null)
+                        {
+                            return result;
+                        }
+                    }
+                }
+                finally
+                {
+                    ArrayPool<byte>.Shared.Return(buf);
+                }
+            }
+            while (true);
+        }
+
+        private static unsafe string GetCwdHelper(byte* ptr, int bufferSize)
+        {
+            // Call the real getcwd
+            byte* result = GetCwd(ptr, bufferSize);
+
+            // If it returned non-null, the null-terminated path is in the buffer
+            if (result != null)
+            {
+                return Marshal.PtrToStringAnsi((IntPtr)ptr);
+            }
+
+            // Otherwise, if it failed due to the buffer being too small, return null;
+            // for anything else, throw.
+            ErrorInfo errorInfo = Interop.Sys.GetLastErrorInfo();
+            if (errorInfo.Error == Interop.Error.ERANGE)
+            {
+               return null;
+            }
+            throw Interop.GetExceptionForIoErrno(errorInfo);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.GetRandomBytes.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.GetRandomBytes.cs
new file mode 100644
index 0000000000..e911b13583
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.GetRandomBytes.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal unsafe partial class Sys
+    {
+        [DllImport(Interop.Libraries.SystemNative, EntryPoint = "SystemNative_GetNonCryptographicallySecureRandomBytes")]
+        internal static extern unsafe void GetNonCryptographicallySecureRandomBytes(byte* buffer, int length);
+    }
+
+    internal static unsafe void GetRandomBytes(byte* buffer, int length)
+    {
+        Sys.GetNonCryptographicallySecureRandomBytes(buffer, length);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.LSeek.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.LSeek.cs
new file mode 100644
index 0000000000..7f8df7c6bf
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.LSeek.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using Microsoft.Win32.SafeHandles;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        internal enum SeekWhence
+        {
+            SEEK_SET = 0,
+            SEEK_CUR = 1,
+            SEEK_END = 2
+        }
+
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_LSeek", SetLastError = true)]
+        internal static extern long LSeek(SafeFileHandle fd, long offset, SeekWhence whence);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.LockFileRegion.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.LockFileRegion.cs
new file mode 100644
index 0000000000..23b48a4f5d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.LockFileRegion.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        internal enum LockType : short
+        {
+            F_WRLCK = 1,    // exclusive or write lock
+            F_UNLCK = 2     // unlock
+        }
+        
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_LockFileRegion", SetLastError=true)]
+        internal static extern int LockFileRegion(SafeHandle fd, long offset, long length, LockType lockType);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.MksTemps.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.MksTemps.cs
new file mode 100644
index 0000000000..b8694d9007
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.MksTemps.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_MksTemps", SetLastError = true)]
+        internal static extern IntPtr MksTemps(
+            byte[] template, 
+            int suffixlen);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Open.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Open.cs
new file mode 100644
index 0000000000..a9a994c78c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Open.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using Microsoft.Win32.SafeHandles;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_Open", SetLastError = true)]
+        internal static extern SafeFileHandle Open(string filename, OpenFlags flags, int mode);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.OpenFlags.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.OpenFlags.cs
new file mode 100644
index 0000000000..f9e54c3cbc
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.OpenFlags.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        [Flags]
+        internal enum OpenFlags
+        {
+            // Access modes (mutually exclusive)
+            O_RDONLY = 0x0000,
+            O_WRONLY = 0x0001,
+            O_RDWR   = 0x0002,
+
+            // Flags (combinable)
+            O_CLOEXEC = 0x0010,
+            O_CREAT   = 0x0020,
+            O_EXCL    = 0x0040,
+            O_TRUNC   = 0x0080,
+            O_SYNC    = 0x0100,
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.PathConf.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.PathConf.cs
new file mode 100644
index 0000000000..7213cb0264
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.PathConf.cs
@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        internal enum PathConfName : int
+        {
+            PC_LINK_MAX         = 1,
+            PC_MAX_CANON        = 2,
+            PC_MAX_INPUT        = 3,
+            PC_NAME_MAX         = 4,
+            PC_PATH_MAX         = 5,
+            PC_PIPE_BUF         = 6,
+            PC_CHOWN_RESTRICTED = 7,
+            PC_NO_TRUNC         = 8,
+            PC_VDISABLE         = 9,
+        }
+
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_PathConf", SetLastError = true)]
+        private static extern int PathConf(string path, PathConfName name);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Permissions.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Permissions.cs
new file mode 100644
index 0000000000..f1d13787d2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Permissions.cs
@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        [Flags]
+        internal enum Permissions
+        {
+            Mask = S_IRWXU | S_IRWXG | S_IRWXO,
+
+            S_IRWXU = S_IRUSR | S_IWUSR | S_IXUSR,
+            S_IRUSR = 0x100,
+            S_IWUSR = 0x80,
+            S_IXUSR = 0x40,
+
+            S_IRWXG = S_IRGRP | S_IWGRP | S_IXGRP,
+            S_IRGRP = 0x20,
+            S_IWGRP = 0x10,
+            S_IXGRP = 0x8,
+
+            S_IRWXO = S_IROTH | S_IWOTH | S_IXOTH,
+            S_IROTH = 0x4,
+            S_IWOTH = 0x2,
+            S_IXOTH = 0x1,
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.PosixFAdvise.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.PosixFAdvise.cs
new file mode 100644
index 0000000000..ad8b73aed2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.PosixFAdvise.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using Microsoft.Win32.SafeHandles;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        internal enum FileAdvice : int
+        {
+            POSIX_FADV_NORMAL       = 0,    /* no special advice, the default value */
+            POSIX_FADV_RANDOM       = 1,    /* random I/O access */
+            POSIX_FADV_SEQUENTIAL   = 2,    /* sequential I/O access */
+            POSIX_FADV_WILLNEED     = 3,    /* will need specified pages */
+            POSIX_FADV_DONTNEED     = 4,    /* don't need the specified pages */
+            POSIX_FADV_NOREUSE      = 5,    /* data will only be accessed once */
+        }
+
+        /// <summary>
+        /// Notifies the OS kernel that the specified file will be accessed in a particular way soon; this allows the kernel to
+        /// potentially optimize the access pattern of the file.
+        /// </summary>
+        /// <param name="fd">The file descriptor of the file</param>
+        /// <param name="offset">The start of the region to advise about</param>
+        /// <param name="length">The number of bytes of the region (until the end of the file if 0)</param>
+        /// <param name="advice">The type of advice to give the kernel about the specified region</param>
+        /// <returns>
+        /// Returns 0 on success; otherwise, the error code is returned
+        /// </returns>
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_PosixFAdvise", SetLastError = false /* this is explicitly called out in the man page */)]
+        internal static extern int PosixFAdvise(SafeFileHandle fd, long offset, long length, FileAdvice advice);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Read.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Read.cs
new file mode 100644
index 0000000000..1be5e789c2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Read.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using Microsoft.Win32.SafeHandles;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        /// <summary>
+        /// Reads a number of bytes from an open file descriptor into a specified buffer.
+        /// </summary>
+        /// <param name="fd">The open file descriptor to try to read from</param>
+        /// <param name="buffer">The buffer to read info into</param>
+        /// <param name="count">The size of the buffer</param>
+        /// <returns>
+        /// Returns the number of bytes read on success; otherwise, -1 is returned
+        /// Note - on fail. the position of the stream may change depending on the platform; consult man 2 read for more info
+        /// </returns>
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_Read", SetLastError = true)]
+        internal static extern unsafe int Read(SafeFileHandle fd, byte* buffer, int count);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.ReadDir.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.ReadDir.cs
new file mode 100644
index 0000000000..d98c4285c0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.ReadDir.cs
@@ -0,0 +1,102 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+using System.Threading;
+using Microsoft.Win32.SafeHandles;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        private static readonly int s_readBufferSize = GetReadDirRBufferSize();
+
+        internal enum NodeType : int
+        {
+            DT_UNKNOWN  =  0,
+            DT_FIFO     =  1,
+            DT_CHR      =  2,
+            DT_DIR      =  4,
+            DT_BLK      =  6,
+            DT_REG      =  8,
+            DT_LNK      = 10,
+            DT_SOCK     = 12,
+            DT_WHT      = 14
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        private unsafe struct InternalDirectoryEntry
+        {
+            internal IntPtr     Name;
+            internal int        NameLength;
+            internal NodeType   InodeType;
+        }
+
+        internal struct DirectoryEntry
+        {
+            internal NodeType   InodeType;
+            internal string     InodeName;
+        }
+
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_OpenDir", SetLastError = true)]
+        internal static extern Microsoft.Win32.SafeHandles.SafeDirectoryHandle OpenDir(string path);
+
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_GetReadDirRBufferSize", SetLastError = false)]
+        internal static extern int GetReadDirRBufferSize();
+
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_ReadDirR", SetLastError = false)]
+        private static extern unsafe int ReadDirR(IntPtr dir, byte* buffer, int bufferSize, out InternalDirectoryEntry outputEntry);
+
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_CloseDir", SetLastError = true)]
+        internal static extern int CloseDir(IntPtr dir);
+
+        // The calling pattern for ReadDir is described in src/Native/System.Native/pal_readdir.cpp
+        internal static int ReadDir(SafeDirectoryHandle dir, out DirectoryEntry outputEntry)
+        {
+            bool addedRef = false;
+            try
+            {
+                // We avoid a native string copy into InternalDirectoryEntry.
+                // - If the platform suppors reading into a buffer, the data is read directly into the buffer. The
+                //   data can be read as long as the buffer is valid.
+                // - If the platform does not support reading into a buffer, the information returned in
+                //   InternalDirectoryEntry points to native memory owned by the SafeDirectoryHandle. The data is only
+                //   valid until the next call to CloseDir/ReadDir. We extend the reference until we have copied all data
+                //   to ensure it does not become invalid by a CloseDir; and we copy the data so our caller does not
+                //   use the native memory held by the SafeDirectoryHandle.
+                dir.DangerousAddRef(ref addedRef);
+
+                unsafe
+                {
+                    // s_readBufferSize is zero when the native implementation does not support reading into a buffer.
+                    byte* buffer = stackalloc byte[s_readBufferSize];
+                    InternalDirectoryEntry temp;
+                    int ret = ReadDirR(dir.DangerousGetHandle(), buffer, s_readBufferSize, out temp);
+                    // We copy data into DirectoryEntry to ensure there are no dangling references.
+                    outputEntry = ret == 0 ?
+                                new DirectoryEntry() { InodeName = GetDirectoryEntryName(temp), InodeType = temp.InodeType } : 
+                                default(DirectoryEntry);
+
+                    return ret;
+                }
+            }
+            finally
+            {
+                if (addedRef)
+                {
+                    dir.DangerousRelease();
+                }
+            }
+        }
+
+        private static unsafe string GetDirectoryEntryName(InternalDirectoryEntry dirEnt)
+        {
+            if (dirEnt.NameLength == -1)
+                return Marshal.PtrToStringAnsi(dirEnt.Name);
+            else
+                return Marshal.PtrToStringAnsi(dirEnt.Name, dirEnt.NameLength);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.ReadLink.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.ReadLink.cs
new file mode 100644
index 0000000000..50f1ae545e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.ReadLink.cs
@@ -0,0 +1,63 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using System.Buffers;
+using System.Text;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        /// <summary>
+        /// Takes a path to a symbolic link and attempts to place the link target path into the buffer. If the buffer is too
+        /// small, the path will be truncated. No matter what, the buffer will not be null terminated. 
+        /// </summary>
+        /// <param name="path">The path to the symlink</param>
+        /// <param name="buffer">The buffer to hold the output path</param>
+        /// <param name="bufferSize">The size of the buffer</param>
+        /// <returns>
+        /// Returns the number of bytes placed into the buffer on success; bufferSize if the buffer is too small; and -1 on error.
+        /// </returns>
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_ReadLink", SetLastError = true)]
+        private static extern unsafe int ReadLink(string path, byte[] buffer, int bufferSize);
+
+        /// <summary>
+        /// Takes a path to a symbolic link and returns the link target path.
+        /// </summary>
+        /// <param name="path">The path to the symlink</param>
+        /// <returns>
+        /// Returns the link to the target path on success; and null otherwise.
+        /// </returns>
+        public static string ReadLink(string path)
+        {
+            int bufferSize = 256;
+            do
+            {
+                byte[] buffer = ArrayPool<byte>.Shared.Rent(bufferSize);
+                try
+                {
+                    int resultLength = Interop.Sys.ReadLink(path, buffer, buffer.Length);
+                    if (resultLength < 0)
+                    {
+                        // error
+                        return null;
+                    }
+                    else if (resultLength < buffer.Length)
+                    {
+                        // success
+                        return Encoding.UTF8.GetString(buffer, 0, resultLength);
+                    }
+                }
+                finally
+                {
+                    ArrayPool<byte>.Shared.Return(buffer);
+                }
+
+                // buffer was too small, loop around again and try with a larger buffer.
+                bufferSize *= 2;
+            } while (true);
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Stat.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Stat.cs
new file mode 100644
index 0000000000..0ca199b70d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Stat.cs
@@ -0,0 +1,65 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+using Microsoft.Win32.SafeHandles;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        // Even though csc will by default use a sequential layout, a CS0649 warning as error
+        // is produced for un-assigned fields when no StructLayout is specified.
+        //
+        // Explicitly saying Sequential disables that warning/error for consumers which only
+        // use Stat in debug builds.
+        [StructLayout(LayoutKind.Sequential)]
+        internal struct FileStatus
+        {
+            internal FileStatusFlags Flags;
+            internal int Mode;
+            internal uint Uid;
+            internal uint Gid;
+            internal long Size;
+            internal long ATime;
+            internal long ATimeNsec;
+            internal long MTime;
+            internal long MTimeNsec;
+            internal long CTime;
+            internal long CTimeNsec;
+            internal long BirthTime;
+            internal long BirthTimeNsec;
+            internal long Dev;
+            internal long Ino;
+        }
+
+        internal static class FileTypes
+        {
+            internal const int S_IFMT = 0xF000;
+            internal const int S_IFIFO = 0x1000;
+            internal const int S_IFCHR = 0x2000;
+            internal const int S_IFDIR = 0x4000;
+            internal const int S_IFREG = 0x8000;
+            internal const int S_IFLNK = 0xA000;
+            internal const int S_IFSOCK = 0xC000;
+        }
+
+        [Flags]
+        internal enum FileStatusFlags
+        {
+            None = 0,
+            HasBirthTime = 1,
+        }
+
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_FStat2", SetLastError = true)]
+        internal static extern int FStat(SafeFileHandle fd, out FileStatus output);
+
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_Stat2", SetLastError = true)]
+        internal static extern int Stat(string path, out FileStatus output);
+
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_LStat2", SetLastError = true)]
+        internal static extern int LStat(string path, out FileStatus output);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.SysLog.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.SysLog.cs
new file mode 100644
index 0000000000..6b6a74b743
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.SysLog.cs
@@ -0,0 +1,58 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        internal enum SysLogPriority : int
+        {
+            // Priorities
+            LOG_EMERG       = 0,        /* system is unusable */
+            LOG_ALERT       = 1,        /* action must be taken immediately */
+            LOG_CRIT        = 2,        /* critical conditions */
+            LOG_ERR         = 3,        /* error conditions */
+            LOG_WARNING     = 4,        /* warning conditions */
+            LOG_NOTICE      = 5,        /* normal but significant condition */
+            LOG_INFO        = 6,        /* informational */
+            LOG_DEBUG       = 7,        /* debug-level messages */
+            // Facilities
+            LOG_KERN        = (0<<3),   /* kernel messages */
+            LOG_USER        = (1<<3),   /* random user-level messages */
+            LOG_MAIL        = (2<<3),   /* mail system */
+            LOG_DAEMON      = (3<<3),   /* system daemons */
+            LOG_AUTH        = (4<<3),   /* authorization messages */
+            LOG_SYSLOG      = (5<<3),   /* messages generated internally by syslogd */
+            LOG_LPR         = (6<<3),   /* line printer subsystem */
+            LOG_NEWS        = (7<<3),   /* network news subsystem */
+            LOG_UUCP        = (8<<3),   /* UUCP subsystem */
+            LOG_CRON        = (9<<3),   /* clock daemon */
+            LOG_AUTHPRIV    = (10<<3),  /* authorization messages (private) */
+            LOG_FTP         = (11<<3),  /* ftp daemon */
+            // Between FTP and Local is reserved for system use
+            LOG_LOCAL0      = (16<<3),  /* reserved for local use */
+            LOG_LOCAL1      = (17<<3),  /* reserved for local use */
+            LOG_LOCAL2      = (18<<3),  /* reserved for local use */
+            LOG_LOCAL3      = (19<<3),  /* reserved for local use */
+            LOG_LOCAL4      = (20<<3),  /* reserved for local use */
+            LOG_LOCAL5      = (21<<3),  /* reserved for local use */
+            LOG_LOCAL6      = (22<<3),  /* reserved for local use */
+            LOG_LOCAL7      = (23<<3),  /* reserved for local use */
+        }
+
+        /// <summary>
+        /// Write a message to the system logger, which in turn writes the message to the system console, log files, etc. 
+        /// See man 3 syslog for more info
+        /// </summary>
+        /// <param name="priority">
+        /// The OR of a priority and facility in the SysLogPriority enum to declare the priority and facility of the log entry
+        /// </param>
+        /// <param name="message">The message to put in the log entry</param>
+        /// <param name="arg1">Like printf, the argument is passed to the variadic part of the C++ function to wildcards in the message</param>
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_SysLog")]
+        internal static extern void SysLog(SysLogPriority priority, string message, string arg1);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Unlink.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Unlink.cs
new file mode 100644
index 0000000000..829210fa7e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Unlink.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_Unlink", SetLastError = true)]
+        internal static extern int Unlink(string pathname);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Write.cs b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Write.cs
new file mode 100644
index 0000000000..0636615a8b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Unix/System.Native/Interop.Write.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using Microsoft.Win32.SafeHandles;
+
+internal static partial class Interop
+{
+    internal static partial class Sys
+    {
+        /// <summary>
+        /// Writes the specified buffer to the provided open file descriptor
+        /// </summary>
+        /// <param name="fd">The file descriptor to try and write to</param>
+        /// <param name="buffer">The data to attempt to write</param>
+        /// <param name="bufferSize">The amount of data to write, in bytes</param>
+        /// <returns>
+        /// Returns the number of bytes written on success; otherwise, returns -1 and sets errno
+        /// </returns>
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_Write", SetLastError = true)]
+        internal static extern unsafe int Write(SafeFileHandle fd, byte* buffer, int bufferSize);
+
+        [DllImport(Libraries.SystemNative, EntryPoint = "SystemNative_Write", SetLastError = true)]
+        internal static extern unsafe int Write(int fd, byte* buffer, int bufferSize);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/BCrypt/Interop.BCryptGenRandom.cs b/src/System.Private.CoreLib/shared/Interop/Windows/BCrypt/Interop.BCryptGenRandom.cs
new file mode 100644
index 0000000000..75288accd9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/BCrypt/Interop.BCryptGenRandom.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class BCrypt
+    {
+        internal static unsafe int BCryptGenRandom(byte* pbBuffer, int count)
+        {
+            Debug.Assert(pbBuffer != null);
+            Debug.Assert(count >= 0);
+
+            return BCryptGenRandom(IntPtr.Zero, pbBuffer, count, BCRYPT_USE_SYSTEM_PREFERRED_RNG);
+        }
+
+        private const int BCRYPT_USE_SYSTEM_PREFERRED_RNG = 0x00000002;
+        internal const int STATUS_SUCCESS = 0x0;
+        internal const int STATUS_NO_MEMORY = unchecked((int)0xC0000017);
+
+        [DllImport(Libraries.BCrypt, CharSet = CharSet.Unicode)]
+        private static extern unsafe int BCryptGenRandom(IntPtr hAlgorithm, byte* pbBuffer, int cbBuffer, int dwFlags);
+    }
+
+    internal static unsafe void GetRandomBytes(byte* buffer, int length)
+    {
+        int status = BCrypt.BCryptGenRandom(buffer, length);
+        if (status != BCrypt.STATUS_SUCCESS)
+        {
+            if (status == BCrypt.STATUS_NO_MEMORY)
+            {
+                throw new OutOfMemoryException();
+            }
+            else
+            {
+                throw new InvalidOperationException();
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Crypt32/Interop.CryptProtectMemory.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Crypt32/Interop.CryptProtectMemory.cs
new file mode 100644
index 0000000000..b10cb6a041
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Crypt32/Interop.CryptProtectMemory.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+using System.Security;
+
+internal partial class Interop
+{
+    internal partial class Crypt32
+    {
+        internal const uint CRYPTPROTECTMEMORY_BLOCK_SIZE = 16;
+        internal const uint CRYPTPROTECTMEMORY_SAME_PROCESS = 0;
+
+        [DllImport(Libraries.Crypt32, CharSet = CharSet.Unicode, SetLastError = true)]
+        internal static extern bool CryptProtectMemory(SafeBSTRHandle pData, uint cbData, uint dwFlags);
+
+        [DllImport(Libraries.Crypt32, CharSet = CharSet.Unicode, SetLastError = true)]
+        internal static extern bool CryptUnprotectMemory(SafeBSTRHandle pData, uint cbData, uint dwFlags);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Interop.BOOL.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Interop.BOOL.cs
new file mode 100644
index 0000000000..9f4dab8935
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Interop.BOOL.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+internal partial class Interop
+{
+    /// <summary>
+    /// Blittable version of Windows BOOL type. It is convenient in situations where
+    /// manual marshalling is required, or to avoid overhead of regular bool marshalling.
+    /// </summary>
+    /// <remarks>
+    /// Some Windows APIs return arbitrary integer values although the return type is defined
+    /// as BOOL. It is best to never compare BOOL to TRUE. Always use bResult != BOOL.FALSE
+    /// or bResult == BOOL.FALSE .
+    /// </remarks>
+    internal enum BOOL : int
+    {
+        FALSE = 0,
+        TRUE = 1,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Interop.Errors.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Interop.Errors.cs
new file mode 100644
index 0000000000..7f907fb6ca
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Interop.Errors.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+internal partial class Interop
+{
+    // As defined in winerror.h and https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382.aspx
+    internal partial class Errors
+    {
+        internal const int ERROR_SUCCESS = 0x0;
+        internal const int ERROR_FILE_NOT_FOUND = 0x2;
+        internal const int ERROR_PATH_NOT_FOUND = 0x3;
+        internal const int ERROR_ACCESS_DENIED = 0x5;
+        internal const int ERROR_INVALID_HANDLE = 0x6;
+        internal const int ERROR_NOT_ENOUGH_MEMORY = 0x8;
+        internal const int ERROR_INVALID_DRIVE = 0xF;
+        internal const int ERROR_NO_MORE_FILES = 0x12;
+        internal const int ERROR_NOT_READY = 0x15;
+        internal const int ERROR_SHARING_VIOLATION = 0x20;
+        internal const int ERROR_HANDLE_EOF = 0x26;
+        internal const int ERROR_FILE_EXISTS = 0x50;
+        internal const int ERROR_INVALID_PARAMETER = 0x57;
+        internal const int ERROR_BROKEN_PIPE = 0x6D;
+        internal const int ERROR_INSUFFICIENT_BUFFER = 0x7A;
+        internal const int ERROR_INVALID_NAME = 0x7B;
+        internal const int ERROR_BAD_PATHNAME = 0xA1;
+        internal const int ERROR_ALREADY_EXISTS = 0xB7;
+        internal const int ERROR_ENVVAR_NOT_FOUND = 0xCB;
+        internal const int ERROR_FILENAME_EXCED_RANGE = 0xCE;
+        internal const int ERROR_NO_DATA = 0xE8;
+        internal const int ERROR_MORE_DATA = 0xEA;
+        internal const int ERROR_NO_MORE_ITEMS = 0x103;
+        internal const int ERROR_NOT_OWNER = 0x120;
+        internal const int ERROR_TOO_MANY_POSTS = 0x12A;
+        internal const int ERROR_ARITHMETIC_OVERFLOW = 0x216;
+        internal const int ERROR_MUTANT_LIMIT_EXCEEDED = 0x24B;
+        internal const int ERROR_OPERATION_ABORTED = 0x3E3;
+        internal const int ERROR_IO_PENDING = 0x3E5;
+        internal const int ERROR_NO_UNICODE_TRANSLATION = 0x459;
+        internal const int ERROR_NOT_FOUND = 0x490;
+        internal const int ERROR_BAD_IMPERSONATION_LEVEL = 0x542;
+        internal const int ERROR_NO_SYSTEM_RESOURCES = 0x5AA;        
+        internal const int E_FILENOTFOUND = unchecked((int)0x80070002);
+        internal const int ERROR_TIMEOUT = 0x000005B4;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Interop.Libraries.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Interop.Libraries.cs
new file mode 100644
index 0000000000..45d910bfcc
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Interop.Libraries.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+internal static partial class Interop
+{
+    internal static partial class Libraries
+    {
+        internal const string BCrypt = "BCrypt.dll";
+        internal const string Crypt32 = "crypt32.dll";
+        internal const string Kernel32 = "kernel32.dll";
+        internal const string Ole32 = "ole32.dll";
+        internal const string OleAut32 = "oleaut32.dll";
+        internal const string User32 = "user32.dll";
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CREATEFILE2_EXTENDED_PARAMETERS.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CREATEFILE2_EXTENDED_PARAMETERS.cs
new file mode 100644
index 0000000000..16365ee651
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CREATEFILE2_EXTENDED_PARAMETERS.cs
@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.IO;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        internal unsafe struct CREATEFILE2_EXTENDED_PARAMETERS
+        {
+            internal uint dwSize;
+            internal uint dwFileAttributes;
+            internal uint dwFileFlags;
+            internal uint dwSecurityQosFlags;
+            internal SECURITY_ATTRIBUTES* lpSecurityAttributes;
+            internal IntPtr hTemplateFile;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CancelIoEx.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CancelIoEx.cs
new file mode 100644
index 0000000000..fc99e3052f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CancelIoEx.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System.Runtime.InteropServices;
+using System.Threading;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, SetLastError = true)]
+        internal static extern unsafe bool CancelIoEx(SafeHandle handle, NativeOverlapped* lpOverlapped);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CloseHandle.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CloseHandle.cs
new file mode 100644
index 0000000000..96ed922a84
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CloseHandle.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern bool CloseHandle(IntPtr handle);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CreateFile.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CreateFile.cs
new file mode 100644
index 0000000000..9ee1e16fa6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CreateFile.cs
@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.IO;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        /// <summary>
+        /// WARNING: This method does not implicitly handle long paths. Use CreateFile.
+        /// </summary>
+        [DllImport(Libraries.Kernel32, EntryPoint = "CreateFileW", SetLastError = true, CharSet = CharSet.Unicode, BestFitMapping = false)]
+        private static extern SafeFileHandle CreateFilePrivate(
+            string lpFileName,
+            int dwDesiredAccess,
+            System.IO.FileShare dwShareMode,
+            ref SECURITY_ATTRIBUTES securityAttrs,
+            System.IO.FileMode dwCreationDisposition,
+            int dwFlagsAndAttributes,
+            IntPtr hTemplateFile);
+
+        internal static SafeFileHandle CreateFile(
+            string lpFileName,
+            int dwDesiredAccess,
+            System.IO.FileShare dwShareMode,
+            ref SECURITY_ATTRIBUTES securityAttrs,
+            System.IO.FileMode dwCreationDisposition,
+            int dwFlagsAndAttributes,
+            IntPtr hTemplateFile)
+        {
+            lpFileName = PathInternal.EnsureExtendedPrefixOverMaxPath(lpFileName);
+            return CreateFilePrivate(lpFileName, dwDesiredAccess, dwShareMode, ref securityAttrs, dwCreationDisposition, dwFlagsAndAttributes, hTemplateFile);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CreateFile2.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CreateFile2.cs
new file mode 100644
index 0000000000..ddc18f6c42
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.CreateFile2.cs
@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System.IO;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, EntryPoint = "CreateFile2", SetLastError = true, CharSet = CharSet.Unicode)]
+        private static extern SafeFileHandle CreateFile2Private(
+            string lpFileName,
+            int dwDesiredAccess,
+            FileShare dwShareMode,
+            FileMode dwCreationDisposition,
+            ref Kernel32.CREATEFILE2_EXTENDED_PARAMETERS pCreateExParams);
+
+        internal static SafeFileHandle CreateFile2(
+            string lpFileName,
+            int dwDesiredAccess,
+            FileShare dwShareMode,
+            FileMode dwCreationDisposition,
+            ref Kernel32.CREATEFILE2_EXTENDED_PARAMETERS pCreateExParams)
+        {
+            lpFileName = PathInternal.EnsureExtendedPrefixOverMaxPath(lpFileName);
+            return CreateFile2Private(lpFileName, dwDesiredAccess, dwShareMode, dwCreationDisposition, ref pCreateExParams);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FILE_INFO_BY_HANDLE_CLASS.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FILE_INFO_BY_HANDLE_CLASS.cs
new file mode 100644
index 0000000000..e31a453ba9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FILE_INFO_BY_HANDLE_CLASS.cs
@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        internal enum FILE_INFO_BY_HANDLE_CLASS : uint
+        {
+            FileBasicInfo = 0x0u,
+            FileStandardInfo = 0x1u,
+            FileNameInfo = 0x2u,
+            FileRenameInfo = 0x3u,
+            FileDispositionInfo = 0x4u,
+            FileAllocationInfo = 0x5u,
+            FileEndOfFileInfo = 0x6u,
+            FileStreamInfo = 0x7u,
+            FileCompressionInfo = 0x8u,
+            FileAttributeTagInfo = 0x9u,
+            FileIdBothDirectoryInfo = 0xAu,
+            FileIdBothDirectoryRestartInfo = 0xBu,
+            FileIoPriorityHintInfo = 0xCu,
+            FileRemoteProtocolInfo = 0xDu,
+            FileFullDirectoryInfo = 0xEu,
+            FileFullDirectoryRestartInfo = 0xFu,
+            FileStorageInfo = 0x10u,
+            FileAlignmentInfo = 0x11u,
+            FileIdInfo = 0x12u,
+            FileIdExtdDirectoryInfo = 0x13u,
+            FileIdExtdDirectoryRestartInfo = 0x14u,
+            MaximumFileInfoByHandleClass = 0x15u,
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FileAttributes.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FileAttributes.cs
new file mode 100644
index 0000000000..725a25a719
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FileAttributes.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        internal partial class FileAttributes
+        {
+            internal const int FILE_ATTRIBUTE_NORMAL = 0x00000080;
+            internal const int FILE_ATTRIBUTE_READONLY = 0x00000001;
+            internal const int FILE_ATTRIBUTE_DIRECTORY = 0x00000010;
+            internal const int FILE_ATTRIBUTE_REPARSE_POINT = 0x00000400;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FileTypes.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FileTypes.cs
new file mode 100644
index 0000000000..9d52f1f4f4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FileTypes.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        internal partial class FileTypes
+        {
+            internal const int FILE_TYPE_UNKNOWN = 0x0000;
+            internal const int FILE_TYPE_DISK = 0x0001;
+            internal const int FILE_TYPE_CHAR = 0x0002;
+            internal const int FILE_TYPE_PIPE = 0x0003;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FindClose.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FindClose.cs
new file mode 100644
index 0000000000..fcf9254aca
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FindClose.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, SetLastError = true)]
+        internal static extern bool FindClose(IntPtr hFindFile);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FindFirstFileEx.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FindFirstFileEx.cs
new file mode 100644
index 0000000000..80b1ddd28d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FindFirstFileEx.cs
@@ -0,0 +1,43 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.IO;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        /// <summary>
+        /// WARNING: This method does not implicitly handle long paths. Use FindFirstFile.
+        /// </summary>
+        [DllImport(Libraries.Kernel32, EntryPoint = "FindFirstFileExW", SetLastError = true, CharSet = CharSet.Unicode)]
+        private static extern SafeFindHandle FindFirstFileExPrivate(string lpFileName, FINDEX_INFO_LEVELS fInfoLevelId, ref WIN32_FIND_DATA lpFindFileData, FINDEX_SEARCH_OPS fSearchOp, IntPtr lpSearchFilter, int dwAdditionalFlags);
+
+        internal static SafeFindHandle FindFirstFile(string fileName, ref WIN32_FIND_DATA data)
+        {
+            fileName = PathInternal.EnsureExtendedPrefixOverMaxPath(fileName);
+
+            // use FindExInfoBasic since we don't care about short name and it has better perf
+            return FindFirstFileExPrivate(fileName, FINDEX_INFO_LEVELS.FindExInfoBasic, ref data, FINDEX_SEARCH_OPS.FindExSearchNameMatch, IntPtr.Zero, 0);
+        }
+
+        internal enum FINDEX_INFO_LEVELS : uint
+        {
+            FindExInfoStandard = 0x0u,
+            FindExInfoBasic = 0x1u,
+            FindExInfoMaxInfoLevel = 0x2u,
+        }
+
+        internal enum FINDEX_SEARCH_OPS : uint
+        {
+            FindExSearchNameMatch = 0x0u,
+            FindExSearchLimitToDirectories = 0x1u,
+            FindExSearchLimitToDevices = 0x2u,
+            FindExSearchMaxSearchOp = 0x3u,
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FlushFileBuffers.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FlushFileBuffers.cs
new file mode 100644
index 0000000000..e10a2279cf
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FlushFileBuffers.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern bool FlushFileBuffers(SafeHandle hHandle);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FormatMessage.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FormatMessage.cs
new file mode 100644
index 0000000000..94722b6c8b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FormatMessage.cs
@@ -0,0 +1,112 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Text;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        private const int FORMAT_MESSAGE_IGNORE_INSERTS = 0x00000200;
+        private const int FORMAT_MESSAGE_FROM_HMODULE = 0x00000800;
+        private const int FORMAT_MESSAGE_FROM_SYSTEM = 0x00001000;
+        private const int FORMAT_MESSAGE_ARGUMENT_ARRAY = 0x00002000;
+
+
+        private const int ERROR_INSUFFICIENT_BUFFER = 0x7A;
+
+        [DllImport(Libraries.Kernel32, CharSet = CharSet.Unicode, EntryPoint = "FormatMessageW", SetLastError = true, BestFitMapping = true)]
+        private static extern int FormatMessage(
+            int dwFlags,
+            IntPtr lpSource,
+            uint dwMessageId,
+            int dwLanguageId,
+            [Out] StringBuilder lpBuffer,
+            int nSize,
+            IntPtr[] arguments);
+
+        /// <summary>
+        ///     Returns a string message for the specified Win32 error code.
+        /// </summary>
+        internal static string GetMessage(int errorCode)
+        {
+            return GetMessage(IntPtr.Zero, errorCode);
+        }
+
+        internal static string GetMessage(IntPtr moduleHandle, int errorCode)
+        {
+            var sb = new StringBuilder(InitialBufferSize);
+            do
+            {
+                string errorMsg;
+                if (TryGetErrorMessage(moduleHandle, errorCode, sb, out errorMsg))
+                {
+                    return errorMsg;
+                }
+                else
+                {
+                    // increase the capacity of the StringBuilder.
+                    sb.Capacity *= BufferSizeIncreaseFactor;
+                }
+            }
+            while (sb.Capacity < MaxAllowedBufferSize);
+
+            // If you come here then a size as large as 65K is also not sufficient and so we give the generic errorMsg.
+            return string.Format("Unknown error (0x{0:x})", errorCode);
+        }
+
+        private static bool TryGetErrorMessage(IntPtr moduleHandle, int errorCode, StringBuilder sb, out string errorMsg)
+        {
+            errorMsg = "";
+
+            int flags = FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ARGUMENT_ARRAY;
+            if (moduleHandle != IntPtr.Zero)
+            {
+                flags |= FORMAT_MESSAGE_FROM_HMODULE;
+            }
+
+            int result = FormatMessage(flags, moduleHandle, (uint)errorCode, 0, sb, sb.Capacity, null);
+            if (result != 0)
+            {
+                int i = sb.Length;
+                while (i > 0)
+                {
+                    char ch = sb[i - 1];
+                    if (ch > 32 && ch != '.') break;
+                    i--;
+                }
+                errorMsg = sb.ToString(0, i);
+            }
+            else if (Marshal.GetLastWin32Error() == ERROR_INSUFFICIENT_BUFFER)
+            {
+                return false;
+            }
+            else
+            {
+                errorMsg = string.Format("Unknown error (0x{0:x})", errorCode);
+            }
+
+            return true;
+        }
+
+        // Windows API FormatMessage lets you format a message string given an errorcode.
+        // Unlike other APIs this API does not support a way to query it for the total message size.
+        //
+        // So the API can only be used in one of these two ways.
+        // a. You pass a buffer of appropriate size and get the resource.
+        // b. Windows creates a buffer and passes the address back and the onus of releasing the buffer lies on the caller.
+        //
+        // Since the error code is coming from the user, it is not possible to know the size in advance.
+        // Unfortunately we can't use option b. since the buffer can only be freed using LocalFree and it is a private API on onecore.
+        // Also, using option b is ugly for the managed code and could cause memory leak in situations where freeing is unsuccessful.
+        // 
+        // As a result we use the following approach.
+        // We initially call the API with a buffer size of 256 and then gradually increase the size in case of failure until we reach the maximum allowed limit of 65K.
+        private const int InitialBufferSize = 256;
+        private const int BufferSizeIncreaseFactor = 4;
+        private const int MaxAllowedBufferSize = 65 * 1024;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FreeEnvironmentStrings.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FreeEnvironmentStrings.cs
new file mode 100644
index 0000000000..c372a8553e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FreeEnvironmentStrings.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, EntryPoint = "FreeEnvironmentStringsW", SetLastError = true, CharSet = CharSet.Unicode, BestFitMapping = false)]
+        internal static extern unsafe bool FreeEnvironmentStrings(char* lpszEnvironmentBlock);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FreeLibrary.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FreeLibrary.cs
new file mode 100644
index 0000000000..c70865350a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.FreeLibrary.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, CharSet = CharSet.Unicode, SetLastError = true, ExactSpelling = true)]
+        internal static extern bool FreeLibrary(IntPtr hModule);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetCPInfo.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetCPInfo.cs
new file mode 100644
index 0000000000..1665119420
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetCPInfo.cs
@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.IO;
+using System.Text;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        internal unsafe struct CPINFO
+        {
+            internal int MaxCharSize;
+
+            internal fixed byte DefaultChar[2 /* MAX_DEFAULTCHAR */];
+            internal fixed byte LeadByte[12 /* MAX_LEADBYTES */];
+        }
+
+        [DllImport(Libraries.Kernel32)]
+        internal static extern unsafe int GetCPInfo(uint codePage, CPINFO* lpCpInfo);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetEnvironmentStrings.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetEnvironmentStrings.cs
new file mode 100644
index 0000000000..29a686026a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetEnvironmentStrings.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, EntryPoint = "GetEnvironmentStringsW", SetLastError = true, CharSet = CharSet.Unicode, BestFitMapping = false)]
+        internal static extern unsafe char* GetEnvironmentStrings();
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFileAttributesEx.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFileAttributesEx.cs
new file mode 100644
index 0000000000..181fb10105
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFileAttributesEx.cs
@@ -0,0 +1,94 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.IO;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        /// <summary>
+        /// WARNING: This method does not implicitly handle long paths. Use GetFileAttributesEx.
+        /// </summary>
+        [DllImport(Libraries.Kernel32, EntryPoint = "GetFileAttributesExW", SetLastError = true, CharSet = CharSet.Unicode)]
+        private static extern bool GetFileAttributesExPrivate(string name, GET_FILEEX_INFO_LEVELS fileInfoLevel, ref WIN32_FILE_ATTRIBUTE_DATA lpFileInformation);
+
+        internal static bool GetFileAttributesEx(string name, GET_FILEEX_INFO_LEVELS fileInfoLevel, ref WIN32_FILE_ATTRIBUTE_DATA lpFileInformation)
+        {
+            name = PathInternal.EnsureExtendedPrefixOverMaxPath(name);
+            return GetFileAttributesExPrivate(name, fileInfoLevel, ref lpFileInformation);
+        }
+
+        internal enum GET_FILEEX_INFO_LEVELS : uint
+        {
+            GetFileExInfoStandard = 0x0u,
+            GetFileExMaxInfoLevel = 0x1u,
+        }
+
+        internal struct WIN32_FILE_ATTRIBUTE_DATA
+        {
+            internal int dwFileAttributes;
+            internal uint ftCreationTimeLow;
+            internal uint ftCreationTimeHigh;
+            internal uint ftLastAccessTimeLow;
+            internal uint ftLastAccessTimeHigh;
+            internal uint ftLastWriteTimeLow;
+            internal uint ftLastWriteTimeHigh;
+            internal uint fileSizeHigh;
+            internal uint fileSizeLow;
+
+            internal void PopulateFrom(ref WIN32_FIND_DATA findData)
+            {
+                // Copy the information to data
+                dwFileAttributes = (int)findData.dwFileAttributes;
+                ftCreationTimeLow = findData.ftCreationTime.dwLowDateTime;
+                ftCreationTimeHigh = findData.ftCreationTime.dwHighDateTime;
+                ftLastAccessTimeLow = findData.ftLastAccessTime.dwLowDateTime;
+                ftLastAccessTimeHigh = findData.ftLastAccessTime.dwHighDateTime;
+                ftLastWriteTimeLow = findData.ftLastWriteTime.dwLowDateTime;
+                ftLastWriteTimeHigh = findData.ftLastWriteTime.dwHighDateTime;
+                fileSizeHigh = findData.nFileSizeHigh;
+                fileSizeLow = findData.nFileSizeLow;
+            }
+        }
+
+        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+        [BestFitMapping(false)]
+        internal unsafe struct WIN32_FIND_DATA
+        {
+            internal uint dwFileAttributes;
+            internal FILE_TIME ftCreationTime;
+            internal FILE_TIME ftLastAccessTime;
+            internal FILE_TIME ftLastWriteTime;
+            internal uint nFileSizeHigh;
+            internal uint nFileSizeLow;
+            internal uint dwReserved0;
+            internal uint dwReserved1;
+            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
+            internal string cFileName;
+            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 14)]
+            internal string cAlternateFileName;
+        }
+
+        internal struct FILE_TIME
+        {
+            internal uint dwLowDateTime;
+            internal uint dwHighDateTime;
+
+            internal FILE_TIME(long fileTime)
+            {
+                dwLowDateTime = (uint)fileTime;
+                dwHighDateTime = (uint)(fileTime >> 32);
+            }
+
+            internal long ToTicks()
+            {
+                return ((long)dwHighDateTime << 32) + dwLowDateTime;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFileInformationByHandleEx.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFileInformationByHandleEx.cs
new file mode 100644
index 0000000000..1106cff1c5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFileInformationByHandleEx.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, SetLastError = true)]
+        internal static extern bool GetFileInformationByHandleEx(SafeFileHandle hFile, FILE_INFO_BY_HANDLE_CLASS FileInformationClass, out FILE_STANDARD_INFO lpFileInformation, uint dwBufferSize);
+
+        internal struct FILE_STANDARD_INFO
+        {
+            internal long AllocationSize;
+            internal long EndOfFile;
+            internal uint NumberOfLinks;
+            internal BOOL DeletePending;
+            internal BOOL Directory;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFileType_SafeHandle.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFileType_SafeHandle.cs
new file mode 100644
index 0000000000..faa57cc2f1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFileType_SafeHandle.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, SetLastError = true)]
+        internal static extern int GetFileType(SafeHandle hFile);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFullPathNameW.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFullPathNameW.cs
new file mode 100644
index 0000000000..197b0a9be5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetFullPathNameW.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        /// <summary>
+        /// WARNING: This method does not implicitly handle long paths. Use GetFullPathName or PathHelper.
+        /// </summary>
+        [DllImport(Libraries.Kernel32, SetLastError = true, CharSet = CharSet.Unicode, BestFitMapping = false, ExactSpelling = true)]
+        internal static extern uint GetFullPathNameW(ref char lpFileName, uint nBufferLength, ref char lpBuffer, IntPtr lpFilePart);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetLongPathNameW.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetLongPathNameW.cs
new file mode 100644
index 0000000000..81b4d096f5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetLongPathNameW.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        /// <summary>
+        /// WARNING: This method does not implicitly handle long paths. Use GetFullPath/PathHelper.
+        /// </summary>
+        [DllImport(Libraries.Kernel32, SetLastError = true, CharSet = CharSet.Unicode, BestFitMapping = false, ExactSpelling = true)]
+        internal static extern uint GetLongPathNameW(ref char lpszShortPath, ref char lpszLongPath, uint cchBuffer);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetTempFileNameW.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetTempFileNameW.cs
new file mode 100644
index 0000000000..97e1d82847
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetTempFileNameW.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, CharSet = CharSet.Unicode, SetLastError = true, BestFitMapping = false)]
+        internal static extern uint GetTempFileNameW(ref char lpPathName, string lpPrefixString, uint uUnique, ref char lpTempFileName);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetTempPathW.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetTempPathW.cs
new file mode 100644
index 0000000000..7f7bb775c8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.GetTempPathW.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, CharSet = CharSet.Unicode, BestFitMapping = false)]
+        internal static extern uint GetTempPathW(int bufferLen, ref char buffer);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.Globalization.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.Globalization.cs
new file mode 100644
index 0000000000..2227d59b0e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.Globalization.cs
@@ -0,0 +1,133 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static unsafe partial class Kernel32
+    {
+        internal const int  LOCALE_NAME_MAX_LENGTH      = 85;
+        internal const uint LOCALE_ALLOW_NEUTRAL_NAMES  = 0x08000000; // Flag to allow returning neutral names/lcids for name conversion
+        internal const uint LOCALE_SUPPLEMENTAL         = 0x00000002;
+        internal const uint LOCALE_REPLACEMENT          = 0x00000008;
+        internal const uint LOCALE_NEUTRALDATA          = 0x00000010;
+        internal const uint LOCALE_SPECIFICDATA         = 0x00000020;
+        internal const int  COMPARE_STRING              = 0x0001;
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+        internal static extern unsafe int LCIDToLocaleName(int locale, char *pLocaleName, int cchName, uint dwFlags);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+        internal static extern int LocaleNameToLCID(string lpName, uint dwFlags);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+        internal static extern unsafe int LCMapStringEx(
+                    string lpLocaleName,
+                    uint dwMapFlags,
+                    char* lpSrcStr,
+                    int cchSrc,
+                    void* lpDestStr,
+                    int cchDest,
+                    void* lpVersionInformation,
+                    void* lpReserved,
+                    IntPtr sortHandle);
+
+        [DllImport("kernel32.dll", EntryPoint = "FindNLSStringEx")]
+        internal static extern unsafe int FindNLSStringEx(
+                    char* lpLocaleName,
+                    uint dwFindNLSStringFlags,
+                    char* lpStringSource,
+                    int cchSource,
+                    char* lpStringValue,
+                    int cchValue,
+                    int* pcchFound,
+                    void* lpVersionInformation,
+                    void* lpReserved,
+                    IntPtr sortHandle);
+
+        [DllImport("kernel32.dll", EntryPoint = "CompareStringEx")]
+        internal static extern unsafe int CompareStringEx(
+                    char* lpLocaleName,
+                    uint dwCmpFlags,
+                    char* lpString1,
+                    int cchCount1,
+                    char* lpString2,
+                    int cchCount2,
+                    void* lpVersionInformation,
+                    void* lpReserved,
+                    IntPtr lParam);
+
+        [DllImport("kernel32.dll", EntryPoint = "CompareStringOrdinal")]
+        internal static extern unsafe int CompareStringOrdinal(
+                    char* lpString1,
+                    int cchCount1,
+                    char* lpString2,
+                    int cchCount2,
+                    bool bIgnoreCase);
+
+        [DllImport("kernel32.dll", EntryPoint = "FindStringOrdinal")]
+        internal static extern unsafe int FindStringOrdinal(
+                    uint dwFindStringOrdinalFlags,
+                    char* lpStringSource,
+                    int cchSource,
+                    char* lpStringValue,
+                    int cchValue,
+                    int bIgnoreCase);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+        internal static extern unsafe bool IsNLSDefinedString(
+                    int  Function,
+                    uint dwFlags,
+                    IntPtr lpVersionInformation,
+                    char* lpString,
+                    int cchStr);
+
+#if !ENABLE_WINRT
+        [DllImport("Kernel32.dll", CharSet = CharSet.Auto)]
+        internal static extern bool GetUserPreferredUILanguages(uint dwFlags, out uint pulNumLanguages, char [] pwszLanguagesBuffer, ref uint pcchLanguagesBuffer);
+#endif //!ENABLE_WINRT
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+        internal static extern int GetLocaleInfoEx(string lpLocaleName, uint LCType, void* lpLCData, int cchData);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+        internal static extern bool EnumSystemLocalesEx(EnumLocalesProcEx lpLocaleEnumProcEx, uint dwFlags, void* lParam, IntPtr reserved);
+
+        internal delegate BOOL EnumLocalesProcEx(char* lpLocaleString, uint dwFlags, void* lParam);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+        internal static extern int ResolveLocaleName(string lpNameToResolve, char* lpLocaleName, int cchLocaleName);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+        internal static extern bool EnumTimeFormatsEx(EnumTimeFormatsProcEx lpTimeFmtEnumProcEx, string lpLocaleName, uint dwFlags, void* lParam);
+  
+        internal delegate BOOL EnumTimeFormatsProcEx(char* lpTimeFormatString, void* lParam);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+        internal static extern int GetCalendarInfoEx(string lpLocaleName, uint Calendar, IntPtr lpReserved, uint CalType, IntPtr lpCalData, int cchData, out int lpValue);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+        internal static extern int GetCalendarInfoEx(string lpLocaleName, uint Calendar, IntPtr lpReserved, uint CalType, IntPtr lpCalData, int cchData, IntPtr lpValue);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+        internal static extern bool EnumCalendarInfoExEx(EnumCalendarInfoProcExEx pCalInfoEnumProcExEx, string lpLocaleName, uint Calendar, string lpReserved, uint CalType, void* lParam);
+        
+        internal delegate BOOL EnumCalendarInfoProcExEx(char* lpCalendarInfoString, uint Calendar, IntPtr lpReserved, void* lParam);
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal struct NlsVersionInfoEx
+        {
+            internal int dwNLSVersionInfoSize;
+            internal int dwNLSVersion;
+            internal int dwDefinedVersion;
+            internal int dwEffectiveId;
+            internal Guid guidCustomVersion;
+        }
+        
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+        internal static extern unsafe bool GetNLSVersionEx(int function, string localeName, NlsVersionInfoEx* lpVersionInformation);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.LoadLibraryEx.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.LoadLibraryEx.cs
new file mode 100644
index 0000000000..4eef5852fe
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.LoadLibraryEx.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        internal const int LOAD_LIBRARY_AS_DATAFILE = 0x00000002;
+
+        [DllImport(Libraries.Kernel32, EntryPoint = "LoadLibraryExW", CharSet = CharSet.Unicode, SetLastError = true)]
+        internal static extern SafeLibraryHandle LoadLibraryEx(string libFilename, IntPtr reserved, int flags);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.LockFile.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.LockFile.cs
new file mode 100644
index 0000000000..a21d00f4f6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.LockFile.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.IO;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, SetLastError = true)]
+        internal static extern bool LockFile(SafeFileHandle handle, int offsetLow, int offsetHigh, int countLow, int countHigh);
+
+        [DllImport(Libraries.Kernel32, SetLastError = true)]
+        internal static extern bool UnlockFile(SafeFileHandle handle, int offsetLow, int offsetHigh, int countLow, int countHigh);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.MAX_PATH.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.MAX_PATH.cs
new file mode 100644
index 0000000000..f7fa32669b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.MAX_PATH.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        internal const int MAX_PATH = 260;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.MUI.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.MUI.cs
new file mode 100644
index 0000000000..6ed7aa2dc4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.MUI.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+using System.Text;
+
+internal static partial class Interop
+{
+    internal static partial class Kernel32
+    {
+        internal const uint MUI_PREFERRED_UI_LANGUAGES = 0x10;
+
+        [DllImport(Libraries.Kernel32, CharSet = CharSet.Unicode, SetLastError = true, ExactSpelling = true)]
+        internal static extern bool GetFileMUIPath(uint flags, String filePath, [Out] StringBuilder language, ref int languageLength, [Out] StringBuilder fileMuiPath, ref int fileMuiPathLength, ref Int64 enumerator);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.MultiByteToWideChar.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.MultiByteToWideChar.cs
new file mode 100644
index 0000000000..158e4db3fd
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.MultiByteToWideChar.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32)]
+        internal static extern unsafe int MultiByteToWideChar(
+            uint CodePage, uint dwFlags,
+            byte* lpMultiByteStr, int cbMultiByte,
+            char* lpWideCharStr, int cchWideChar);
+
+        internal const uint MB_PRECOMPOSED = 0x00000001;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.OutputDebugString.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.OutputDebugString.cs
new file mode 100644
index 0000000000..8da50ff8ab
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.OutputDebugString.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Interop.Libraries.Kernel32, CharSet = CharSet.Unicode, EntryPoint = "OutputDebugStringW", ExactSpelling = true)]
+        internal static extern void OutputDebugString(string message);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.ReadFile_SafeHandle_IntPtr.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.ReadFile_SafeHandle_IntPtr.cs
new file mode 100644
index 0000000000..076f7f136f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.ReadFile_SafeHandle_IntPtr.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, SetLastError = true)]
+        internal static extern unsafe int ReadFile(
+            SafeHandle handle,
+            byte* bytes,
+            int numBytesToRead,
+            out int numBytesRead,
+            IntPtr mustBeZero);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.ReadFile_SafeHandle_NativeOverlapped.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.ReadFile_SafeHandle_NativeOverlapped.cs
new file mode 100644
index 0000000000..3ae65a8806
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.ReadFile_SafeHandle_NativeOverlapped.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.Runtime.InteropServices;
+using System.Threading;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, SetLastError = true)]
+        internal static extern unsafe int ReadFile(
+            SafeHandle handle,
+            byte* bytes,
+            int numBytesToRead,
+            IntPtr numBytesRead_mustBeZero,
+            NativeOverlapped* overlapped);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SECURITY_ATTRIBUTES.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SECURITY_ATTRIBUTES.cs
new file mode 100644
index 0000000000..8d31f8622f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SECURITY_ATTRIBUTES.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [StructLayout(LayoutKind.Sequential)]
+        internal struct SECURITY_ATTRIBUTES
+        {
+            internal uint nLength;
+            internal IntPtr lpSecurityDescriptor;
+            internal BOOL bInheritHandle;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SecurityOptions.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SecurityOptions.cs
new file mode 100644
index 0000000000..4a4402484f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SecurityOptions.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        internal partial class SecurityOptions
+        {
+            internal const int SECURITY_SQOS_PRESENT = 0x00100000;
+            internal const int SECURITY_ANONYMOUS = 0 << 16;
+            internal const int SECURITY_IDENTIFICATION = 1 << 16;
+            internal const int SECURITY_IMPERSONATION = 2 << 16;
+            internal const int SECURITY_DELEGATION = 3 << 16;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SetEndOfFile.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SetEndOfFile.cs
new file mode 100644
index 0000000000..e5d60041a8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SetEndOfFile.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, SetLastError = true)]
+        internal static extern bool SetEndOfFile(SafeFileHandle hFile);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SetEnvironmentVariable.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SetEnvironmentVariable.cs
new file mode 100644
index 0000000000..cff406fca5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SetEnvironmentVariable.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, EntryPoint = "SetEnvironmentVariableW", SetLastError = true, CharSet = CharSet.Unicode, BestFitMapping = false)]
+        internal static extern bool SetEnvironmentVariable(string lpName, string lpValue);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SetFilePointerEx.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SetFilePointerEx.cs
new file mode 100644
index 0000000000..c0e5247a52
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SetFilePointerEx.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, SetLastError = true)]
+        internal static extern bool SetFilePointerEx(SafeFileHandle hFile, long liDistanceToMove, out long lpNewFilePointer, uint dwMoveMethod);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SetThreadErrorMode.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SetThreadErrorMode.cs
new file mode 100644
index 0000000000..123eb75d7b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.SetThreadErrorMode.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, SetLastError = true, ExactSpelling = true)]
+        internal static extern bool SetThreadErrorMode(uint dwNewMode, out uint lpOldMode);
+
+        internal const uint SEM_FAILCRITICALERRORS = 1;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.TimeZone.Registry.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.TimeZone.Registry.cs
new file mode 100644
index 0000000000..062d1caeba
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.TimeZone.Registry.cs
@@ -0,0 +1,31 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Kernel32
+    {
+        [StructLayout(LayoutKind.Sequential)]
+        internal struct REG_TZI_FORMAT
+        {
+            internal int Bias;
+            internal int StandardBias;
+            internal int DaylightBias;
+            internal SYSTEMTIME StandardDate;
+            internal SYSTEMTIME DaylightDate;
+
+            internal REG_TZI_FORMAT(in TIME_ZONE_INFORMATION tzi)
+            {
+                Bias = tzi.Bias;
+                StandardDate = tzi.StandardDate;
+                StandardBias = tzi.StandardBias;
+                DaylightDate = tzi.DaylightDate;
+                DaylightBias = tzi.DaylightBias;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.TimeZone.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.TimeZone.cs
new file mode 100644
index 0000000000..68d4583b54
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.TimeZone.cs
@@ -0,0 +1,94 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Kernel32
+    {
+        internal struct SYSTEMTIME
+        {
+            internal ushort Year;
+            internal ushort Month;
+            internal ushort DayOfWeek;
+            internal ushort Day;
+            internal ushort Hour;
+            internal ushort Minute;
+            internal ushort Second;
+            internal ushort Milliseconds;
+
+            internal bool Equals(in SYSTEMTIME other) =>
+                    Year == other.Year &&
+                    Month == other.Month &&
+                    DayOfWeek == other.DayOfWeek &&
+                    Day == other.Day &&
+                    Hour == other.Hour &&
+                    Minute == other.Minute &&
+                    Second == other.Second &&
+                    Milliseconds == other.Milliseconds;
+        }
+
+        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+        internal unsafe struct TIME_DYNAMIC_ZONE_INFORMATION
+        {
+            internal int Bias;
+            internal fixed char StandardName[32];
+            internal SYSTEMTIME StandardDate;
+            internal int StandardBias;
+            internal fixed char DaylightName[32];
+            internal SYSTEMTIME DaylightDate;
+            internal int DaylightBias;
+            internal fixed char TimeZoneKeyName[128];
+            internal byte DynamicDaylightTimeDisabled;
+
+            internal string GetTimeZoneKeyName()
+            {
+                fixed (char* p = TimeZoneKeyName)
+                    return new string(p);
+            }
+        }
+
+        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+        internal unsafe struct TIME_ZONE_INFORMATION
+        {
+            internal int Bias;
+            internal fixed char StandardName[32];
+            internal SYSTEMTIME StandardDate;
+            internal int StandardBias;
+            internal fixed char DaylightName[32];
+            internal SYSTEMTIME DaylightDate;
+            internal int DaylightBias;
+
+            internal TIME_ZONE_INFORMATION(in TIME_DYNAMIC_ZONE_INFORMATION dtzi)
+            {
+                // The start of TIME_DYNAMIC_ZONE_INFORMATION has identical layout as TIME_ZONE_INFORMATION
+                fixed (TIME_ZONE_INFORMATION* pTo = &this)
+                fixed (TIME_DYNAMIC_ZONE_INFORMATION* pFrom = &dtzi)
+                    *pTo = *(TIME_ZONE_INFORMATION*)pFrom;
+            }
+
+            internal string GetStandardName()
+            {
+                fixed (char* p = StandardName)
+                    return new string(p);
+            }
+
+            internal string GetDaylightName()
+            {
+                fixed (char* p = DaylightName)
+                    return new string(p);
+            }
+        }
+
+        internal const uint TIME_ZONE_ID_INVALID = unchecked((uint)-1);
+
+        [DllImport(Libraries.Kernel32, CharSet = CharSet.Unicode, SetLastError = true, ExactSpelling = true)]
+        internal static extern uint GetDynamicTimeZoneInformation(out TIME_DYNAMIC_ZONE_INFORMATION pTimeZoneInformation);
+
+        [DllImport(Libraries.Kernel32, CharSet = CharSet.Unicode, SetLastError = true, ExactSpelling = true)]
+        internal static extern uint GetTimeZoneInformation(out TIME_ZONE_INFORMATION lpTimeZoneInformation);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.WideCharToMultiByte.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.WideCharToMultiByte.cs
new file mode 100644
index 0000000000..a06c9153f4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.WideCharToMultiByte.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32)]
+        internal static extern unsafe int WideCharToMultiByte(
+            uint CodePage, uint dwFlags,
+            char* lpWideCharStr, int cchWideChar,
+            byte* lpMultiByteStr, int cbMultiByte,
+            IntPtr lpDefaultChar, IntPtr lpUsedDefaultChar);
+
+        internal const uint CP_ACP = 0;
+        internal const uint WC_NO_BEST_FIT_CHARS = 0x00000400;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.WriteFile_SafeHandle_IntPtr.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.WriteFile_SafeHandle_IntPtr.cs
new file mode 100644
index 0000000000..69651ca1ca
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.WriteFile_SafeHandle_IntPtr.cs
@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        // Note there are two different WriteFile prototypes - this is to use 
+        // the type system to force you to not trip across a "feature" in 
+        // Win32's async IO support.  You can't do the following three things
+        // simultaneously: overlapped IO, free the memory for the overlapped 
+        // struct in a callback (or an EndWrite method called by that callback),
+        // and pass in an address for the numBytesRead parameter.
+
+        [DllImport(Libraries.Kernel32, SetLastError = true)]
+        internal static extern unsafe int WriteFile(SafeHandle handle, byte* bytes, int numBytesToWrite, out int numBytesWritten, IntPtr mustBeZero);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.WriteFile_SafeHandle_NativeOverlapped.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.WriteFile_SafeHandle_NativeOverlapped.cs
new file mode 100644
index 0000000000..dc1e97555b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Kernel32/Interop.WriteFile_SafeHandle_NativeOverlapped.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.Runtime.InteropServices;
+using System.Threading;
+internal partial class Interop
+{
+    internal partial class Kernel32
+    {
+        // Note there are two different WriteFile prototypes - this is to use 
+        // the type system to force you to not trip across a "feature" in 
+        // Win32's async IO support.  You can't do the following three things
+        // simultaneously: overlapped IO, free the memory for the overlapped 
+        // struct in a callback (or an EndWrite method called by that callback),
+        // and pass in an address for the numBytesRead parameter.
+        [DllImport(Libraries.Kernel32, SetLastError = true)]
+        internal static extern unsafe int WriteFile(SafeHandle handle, byte* bytes, int numBytesToWrite, IntPtr numBytesWritten_mustBeZero, NativeOverlapped* lpOverlapped);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Normaliz/Interop.Idna.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Normaliz/Interop.Idna.cs
new file mode 100644
index 0000000000..f49ce8dd61
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Normaliz/Interop.Idna.cs
@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Normaliz
+    {
+        //
+        //  Idn APIs
+        //
+
+        [DllImport("Normaliz.dll", CharSet = CharSet.Unicode, SetLastError = true)]
+        internal static extern unsafe int IdnToAscii(
+                                        uint dwFlags,
+                                        char* lpUnicodeCharStr,
+                                        int cchUnicodeChar,
+                                        char* lpASCIICharStr,
+                                        int cchASCIIChar);
+
+        [DllImport("Normaliz.dll", CharSet = CharSet.Unicode, SetLastError = true)]
+        internal static extern unsafe int IdnToUnicode(
+                                        uint dwFlags,
+                                        char* lpASCIICharStr,
+                                        int cchASCIIChar,
+                                        char* lpUnicodeCharStr,
+                                        int cchUnicodeChar);
+
+        internal const int IDN_ALLOW_UNASSIGNED = 0x1;
+        internal const int IDN_USE_STD3_ASCII_RULES = 0x2;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Normaliz/Interop.Normalization.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Normaliz/Interop.Normalization.cs
new file mode 100644
index 0000000000..3e49f1f64c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Normaliz/Interop.Normalization.cs
@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class Normaliz
+    {
+        [DllImport("Normaliz.dll", CharSet = CharSet.Unicode, SetLastError = true)]
+        internal static extern bool IsNormalizedString(int normForm, string source, int length);
+
+        [DllImport("Normaliz.dll", CharSet = CharSet.Unicode, SetLastError = true)]
+        internal static extern int NormalizeString(
+                                        int normForm,
+                                        string source,
+                                        int sourceLength,
+                                        [System.Runtime.InteropServices.OutAttribute()]
+                                        char[] destination,
+                                        int destinationLength);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/Ole32/Interop.CoCreateGuid.cs b/src/System.Private.CoreLib/shared/Interop/Windows/Ole32/Interop.CoCreateGuid.cs
new file mode 100644
index 0000000000..57accbe7c0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/Ole32/Interop.CoCreateGuid.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Ole32
+    {
+        [DllImport(Interop.Libraries.Ole32)]
+        internal static extern int CoCreateGuid(out Guid guid);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/OleAut32/Interop.SysAllocStringLen.cs b/src/System.Private.CoreLib/shared/Interop/Windows/OleAut32/Interop.SysAllocStringLen.cs
new file mode 100644
index 0000000000..1af2b3fce9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/OleAut32/Interop.SysAllocStringLen.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+using System.Security;
+
+internal partial class Interop
+{
+    internal partial class OleAut32
+    {
+        [DllImport(Libraries.OleAut32, CharSet = CharSet.Unicode)]
+        internal static extern SafeBSTRHandle SysAllocStringLen(IntPtr src, uint len);
+
+        [DllImport(Libraries.OleAut32, CharSet = CharSet.Unicode)]
+        internal static extern IntPtr SysAllocStringLen(String src, int len);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/OleAut32/Interop.SysFreeString.cs b/src/System.Private.CoreLib/shared/Interop/Windows/OleAut32/Interop.SysFreeString.cs
new file mode 100644
index 0000000000..8673cc6724
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/OleAut32/Interop.SysFreeString.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class OleAut32
+    {
+        [DllImport(Libraries.OleAut32)]
+        internal static extern void SysFreeString(IntPtr bstr);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/OleAut32/Interop.SysStringLen.cs b/src/System.Private.CoreLib/shared/Interop/Windows/OleAut32/Interop.SysStringLen.cs
new file mode 100644
index 0000000000..cf65d6b086
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/OleAut32/Interop.SysStringLen.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+using System.Security;
+
+internal partial class Interop
+{
+    internal partial class OleAut32
+    {
+        [DllImport(Libraries.OleAut32)]
+        internal static extern uint SysStringLen(SafeBSTRHandle bstr);
+
+        [DllImport(Libraries.OleAut32)]
+        internal static extern uint SysStringLen(IntPtr bstr);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/User32/Interop.Constants.cs b/src/System.Private.CoreLib/shared/Interop/Windows/User32/Interop.Constants.cs
new file mode 100644
index 0000000000..f1f09740e9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/User32/Interop.Constants.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+internal partial class Interop
+{
+    internal partial class User32
+    {
+        internal const int HWND_BROADCAST = 0xffff;
+        internal const int WM_SETTINGCHANGE = 0x001A;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/User32/Interop.LoadString.cs b/src/System.Private.CoreLib/shared/Interop/Windows/User32/Interop.LoadString.cs
new file mode 100644
index 0000000000..d3d575e221
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/User32/Interop.LoadString.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using System.Text;
+using Microsoft.Win32.SafeHandles;
+
+internal partial class Interop
+{
+    internal partial class User32
+    {
+        [DllImport(Libraries.User32, SetLastError = true, EntryPoint = "LoadStringW", CharSet = CharSet.Unicode)]
+        internal static extern int LoadString(SafeLibraryHandle handle, int id, [Out] StringBuilder buffer, int bufferLength);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Interop/Windows/User32/Interop.SendMessageTimeout.cs b/src/System.Private.CoreLib/shared/Interop/Windows/User32/Interop.SendMessageTimeout.cs
new file mode 100644
index 0000000000..c8a97e6b9d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Interop/Windows/User32/Interop.SendMessageTimeout.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    internal partial class User32
+    {
+        [DllImport(Libraries.User32, EntryPoint = "SendMessageTimeoutW", CharSet = CharSet.Unicode)]
+        public static extern IntPtr SendMessageTimeout(IntPtr hWnd, int msg, IntPtr wParam, string lParam, int flags, int timeout, IntPtr pdwResult);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/CriticalHandleMinusOneIsInvalid.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/CriticalHandleMinusOneIsInvalid.cs
new file mode 100644
index 0000000000..a76c51d966
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/CriticalHandleMinusOneIsInvalid.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace Microsoft.Win32.SafeHandles
+{
+    // Class of critical handle which uses only -1 as an invalid handle.
+    public abstract class CriticalHandleMinusOneIsInvalid : CriticalHandle
+    {
+        protected CriticalHandleMinusOneIsInvalid()
+            : base(new IntPtr(-1))
+        {
+        }
+
+        public override bool IsInvalid => handle == new IntPtr(-1);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/CriticalHandleZeroOrMinusOneIsInvalid.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/CriticalHandleZeroOrMinusOneIsInvalid.cs
new file mode 100644
index 0000000000..28d0219489
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/CriticalHandleZeroOrMinusOneIsInvalid.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace Microsoft.Win32.SafeHandles
+{
+    // Class of critical handle which uses 0 or -1 as an invalid handle.
+    public abstract class CriticalHandleZeroOrMinusOneIsInvalid : CriticalHandle
+    {
+        protected CriticalHandleZeroOrMinusOneIsInvalid()
+            : base(IntPtr.Zero)
+        {
+        }
+
+        public override bool IsInvalid => handle == IntPtr.Zero || handle == new IntPtr(-1);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeDirectoryHandle.Unix.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeDirectoryHandle.Unix.cs
new file mode 100644
index 0000000000..f7435eaae1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeDirectoryHandle.Unix.cs
@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace Microsoft.Win32.SafeHandles
+{
+    internal sealed class SafeDirectoryHandle : SafeHandle
+    {
+        private SafeDirectoryHandle() : base(IntPtr.Zero, true)
+        {
+        }
+
+        protected override bool ReleaseHandle()
+        {
+            return Interop.Sys.CloseDir(handle) == 0;
+        }
+
+        public override bool IsInvalid
+        {
+            get { return handle == IntPtr.Zero; }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFileHandle.Unix.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFileHandle.Unix.cs
new file mode 100644
index 0000000000..52973f2abb
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFileHandle.Unix.cs
@@ -0,0 +1,145 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+using System.IO;
+using System.Runtime.InteropServices;
+
+namespace Microsoft.Win32.SafeHandles
+{
+    public sealed class SafeFileHandle : SafeHandleZeroOrMinusOneIsInvalid
+    {
+        private SafeFileHandle() : this(ownsHandle: true)
+        {
+        }
+
+        private SafeFileHandle(bool ownsHandle)
+            : base(ownsHandle)
+        {
+            SetHandle(new IntPtr(-1));
+        }
+
+        public SafeFileHandle(IntPtr preexistingHandle, bool ownsHandle) : this(ownsHandle)
+        {
+            SetHandle(preexistingHandle);
+        }
+
+        internal bool? IsAsync { get; set; }
+
+        /// <summary>Opens the specified file with the requested flags and mode.</summary>
+        /// <param name="path">The path to the file.</param>
+        /// <param name="flags">The flags with which to open the file.</param>
+        /// <param name="mode">The mode for opening the file.</param>
+        /// <returns>A SafeFileHandle for the opened file.</returns>
+        internal static SafeFileHandle Open(string path, Interop.Sys.OpenFlags flags, int mode)
+        {
+            Debug.Assert(path != null);
+            SafeFileHandle handle = Interop.Sys.Open(path, flags, mode);
+
+            if (handle.IsInvalid)
+            {
+                handle.Dispose();
+                Interop.ErrorInfo error = Interop.Sys.GetLastErrorInfo();
+
+                // If we fail to open the file due to a path not existing, we need to know whether to blame
+                // the file itself or its directory.  If we're creating the file, then we blame the directory,
+                // otherwise we blame the file.
+                //
+                // When opening, we need to align with Windows, which considers a missing path to be
+                // FileNotFound only if the containing directory exists.
+
+                bool isDirectory = (error.Error == Interop.Error.ENOENT) &&
+                    ((flags & Interop.Sys.OpenFlags.O_CREAT) != 0
+                    || !DirectoryExists(Path.GetDirectoryName(PathInternal.TrimEndingDirectorySeparator(path))));
+
+                Interop.CheckIo(
+                    error.Error,
+                    path,
+                    isDirectory,
+                    errorRewriter: e => (e.Error == Interop.Error.EISDIR) ? Interop.Error.EACCES.Info() : e);
+            }
+
+            // Make sure it's not a directory; we do this after opening it once we have a file descriptor 
+            // to avoid race conditions.
+            Interop.Sys.FileStatus status;
+            if (Interop.Sys.FStat(handle, out status) != 0)
+            {
+                handle.Dispose();
+                throw Interop.GetExceptionForIoErrno(Interop.Sys.GetLastErrorInfo(), path);
+            }
+            if ((status.Mode & Interop.Sys.FileTypes.S_IFMT) == Interop.Sys.FileTypes.S_IFDIR)
+            {
+                handle.Dispose();
+                throw Interop.GetExceptionForIoErrno(Interop.Error.EACCES.Info(), path, isDirectory: true);
+            }
+
+            return handle;
+        }
+
+        private static bool DirectoryExists(string fullPath)
+        {
+            Interop.Sys.FileStatus fileinfo;
+
+            // First use stat, as we want to follow symlinks.  If that fails, it could be because the symlink
+            // is broken, we don't have permissions, etc., in which case fall back to using LStat to evaluate
+            // based on the symlink itself.
+            if (Interop.Sys.Stat(fullPath, out fileinfo) < 0 &&
+                Interop.Sys.LStat(fullPath, out fileinfo) < 0)
+            {
+                return false;
+            }
+
+            return ((fileinfo.Mode & Interop.Sys.FileTypes.S_IFMT) == Interop.Sys.FileTypes.S_IFDIR);
+        }
+
+        /// <summary>Opens a SafeFileHandle for a file descriptor created by a provided delegate.</summary>
+        /// <param name="fdFunc">
+        /// The function that creates the file descriptor. Returns the file descriptor on success, or an invalid
+        /// file descriptor on error with Marshal.GetLastWin32Error() set to the error code.
+        /// </param>
+        /// <returns>The created SafeFileHandle.</returns>
+        internal static SafeFileHandle Open(Func<SafeFileHandle> fdFunc)
+        {
+            SafeFileHandle handle = Interop.CheckIo(fdFunc());
+
+            Debug.Assert(!handle.IsInvalid, "File descriptor is invalid");
+            return handle;
+        }
+
+        protected override bool ReleaseHandle()
+        {
+            // When the SafeFileHandle was opened, we likely issued an flock on the created descriptor in order to add 
+            // an advisory lock.  This lock should be removed via closing the file descriptor, but close can be
+            // interrupted, and we don't retry closes.  As such, we could end up leaving the file locked,
+            // which could prevent subsequent usage of the file until this process dies.  To avoid that, we proactively
+            // try to release the lock before we close the handle. (If it's not locked, there's no behavioral
+            // problem trying to unlock it.)
+            Interop.Sys.FLock(handle, Interop.Sys.LockOperations.LOCK_UN); // ignore any errors
+
+            // Close the descriptor. Although close is documented to potentially fail with EINTR, we never want
+            // to retry, as the descriptor could actually have been closed, been subsequently reassigned, and
+            // be in use elsewhere in the process.  Instead, we simply check whether the call was successful.
+            int result = Interop.Sys.Close(handle);
+#if DEBUG
+            if (result != 0)
+            {
+                Debug.Fail(string.Format(
+                    "Close failed with result {0} and error {1}", 
+                    result, Interop.Sys.GetLastErrorInfo()));
+            }
+#endif
+            return result == 0;
+        }
+
+        public override bool IsInvalid
+        {
+            get
+            {
+                long h = (long)handle;
+                return h < 0 || h > int.MaxValue;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs
new file mode 100644
index 0000000000..4eabe8f08c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs
@@ -0,0 +1,50 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Security;
+using System.Runtime.InteropServices;
+using System.Threading;
+using Microsoft.Win32;
+
+namespace Microsoft.Win32.SafeHandles
+{
+    public sealed class SafeFileHandle : SafeHandleZeroOrMinusOneIsInvalid
+    {
+        private bool? _isAsync;
+
+        private SafeFileHandle() : base(true)
+        {
+            _isAsync = null;
+        }
+
+        public SafeFileHandle(IntPtr preexistingHandle, bool ownsHandle) : base(ownsHandle)
+        {
+            SetHandle(preexistingHandle);
+
+            _isAsync = null;
+        }
+
+        internal bool? IsAsync
+        {
+            get
+            {
+                return _isAsync;
+            }
+
+            set
+            {
+                _isAsync = value;
+            }
+        }
+
+        internal ThreadPoolBoundHandle ThreadPoolBinding { get; set; }
+
+        override protected bool ReleaseHandle()
+        {
+            return Interop.Kernel32.CloseHandle(handle);
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFindHandle.Windows.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFindHandle.Windows.cs
new file mode 100644
index 0000000000..4ba05409fd
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeFindHandle.Windows.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Security;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Microsoft.Win32;
+
+namespace Microsoft.Win32.SafeHandles
+{
+    internal sealed class SafeFindHandle : SafeHandleZeroOrMinusOneIsInvalid
+    {
+        internal SafeFindHandle() : base(true) { }
+
+        override protected bool ReleaseHandle()
+        {
+            return Interop.Kernel32.FindClose(handle);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeHandleMinusOneIsInvalid.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeHandleMinusOneIsInvalid.cs
new file mode 100644
index 0000000000..5415f2c35d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeHandleMinusOneIsInvalid.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace Microsoft.Win32.SafeHandles
+{
+    // Class of safe handle which uses only -1 as an invalid handle.
+    public abstract class SafeHandleMinusOneIsInvalid : SafeHandle
+    {
+        protected SafeHandleMinusOneIsInvalid(bool ownsHandle) : base(new IntPtr(-1), ownsHandle)
+        {
+        }
+
+        public override bool IsInvalid => handle == new IntPtr(-1);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeHandleZeroOrMinusOneIsInvalid.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeHandleZeroOrMinusOneIsInvalid.cs
new file mode 100644
index 0000000000..8d0220bf90
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeHandleZeroOrMinusOneIsInvalid.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace Microsoft.Win32.SafeHandles
+{
+    // Class of safe handle which uses 0 or -1 as an invalid handle.
+    public abstract class SafeHandleZeroOrMinusOneIsInvalid : SafeHandle
+    {
+        protected SafeHandleZeroOrMinusOneIsInvalid(bool ownsHandle) : base(IntPtr.Zero, ownsHandle)
+        {
+        }
+
+        public override bool IsInvalid => handle == IntPtr.Zero || handle == new IntPtr(-1);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeLibraryHandle.cs b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeLibraryHandle.cs
new file mode 100644
index 0000000000..3be2e354ab
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/Microsoft/Win32/SafeHandles/SafeLibraryHandle.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.Win32.SafeHandles
+{
+    sealed internal class SafeLibraryHandle : SafeHandleZeroOrMinusOneIsInvalid
+    {
+        internal SafeLibraryHandle() : base(true) { }
+
+        override protected bool ReleaseHandle()
+        {
+            return Interop.Kernel32.FreeLibrary(handle);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/README.md b/src/System.Private.CoreLib/shared/README.md
new file mode 100644
index 0000000000..beda969ff7
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/README.md
@@ -0,0 +1,19 @@
+# System.Private.CoreLib Shared Sources
+
+This directory contains the shared sources for System.Private.CoreLib. These are shared between [dotnet/corert](https://github.com/dotnet/corert/tree/master/src/System.Private.CoreLib/shared), [dotnet/coreclr](https://github.com/dotnet/coreclr/tree/master/src/mscorlib/shared) and [dotnet/corefx](https://github.com/dotnet/corefx/tree/master/src/Common/src/CoreLib).
+
+The sources are synchronized with a mirroring tool that watches for new commits on either side and creates new pull requests (as @dotnet-bot) in the other repository.
+
+## Conventions
+
+Code in the shared directory should have no code specific to CoreCLR, CoreRT or CoreFX. Parts of classes that need to have different implementations on different runtimes should use partial classes and &#42;.CoreRT.cs/&#42;.CoreCLR.cs/&#42;.CoreFX.cs files in the non shared portion. Code that is different based on platform (Windows/Unix) is fine to leave in the shared portion. Remember to follow the [style guidelines](https://github.com/dotnet/corefx/blob/master/Documentation/coding-guidelines/coding-style.md).
+
+## Getting clean CI and merging the mirror PRs
+
+Once the mirror PR is created there is a chance that the new code will require changes to get a clean CI. Any changes can be added to the PR by checking out the PR branch and adding new commits. Please follow the following guidelines for modifying these PRs.
+
+ - **DO NOT** modify the commits made by @dotnet-bot in any way.
+ - **TRY** to only make changes outside of shared.
+   - Changes made in the shared folder in additional commits will get mirrored properly if the mirror PR is merged with a **REBASE**
+ - **ALWAYS** Merge the mirror PR with the **REBASE** option.
+   - Using one of the other options will cause the mirror to miss commits
diff --git a/src/System.Private.CoreLib/shared/System.Private.CoreLib.Shared.projitems b/src/System.Private.CoreLib/shared/System.Private.CoreLib.Shared.projitems
new file mode 100644
index 0000000000..ca804e3b7a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System.Private.CoreLib.Shared.projitems
@@ -0,0 +1,827 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <MSBuildAllProjects>$(MSBuildAllProjects);$(MSBuildThisFileFullPath)</MSBuildAllProjects>
+    <HasSharedItems>true</HasSharedItems>
+    <SharedGUID>c5ed3c1d-b572-46f1-8f96-522a85ce1179</SharedGUID>
+  </PropertyGroup>
+  <PropertyGroup Label="Configuration">
+    <Import_RootNamespace />
+  </PropertyGroup>
+  <PropertyGroup>
+    <TargetsWindows Condition="'$(TargetsWindows)' != 'true'">false</TargetsWindows>
+    <TargetsUnix Condition="'$(TargetsUnix)' != 'true'">false</TargetsUnix>
+    <TargetsOSX Condition="'$(TargetsOSX)' != 'true'">false</TargetsOSX>
+  </PropertyGroup>
+  <ItemDefinitionGroup>
+    <Compile>
+      <Visible>true</Visible>
+    </Compile>
+  </ItemDefinitionGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildThisFileDirectory)Internal\IO\File.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Internal\Runtime\CompilerServices\Unsafe.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Microsoft\Win32\SafeHandles\CriticalHandleMinusOneIsInvalid.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Microsoft\Win32\SafeHandles\CriticalHandleZeroOrMinusOneIsInvalid.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Microsoft\Win32\SafeHandles\SafeHandleMinusOneIsInvalid.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Microsoft\Win32\SafeHandles\SafeHandleZeroOrMinusOneIsInvalid.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Action.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\AccessViolationException.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\ApplicationException.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\AggregateException.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\ArgumentException.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\ArgumentNullException.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\ArgumentOutOfRangeException.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\ArithmeticException.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\ArraySegment.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\ArrayTypeMismatchException.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\AssemblyLoadEventArgs.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\AssemblyLoadEventHandler.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\AsyncCallback.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\AttributeTargets.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\AttributeUsageAttribute.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\BadImageFormatException.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\BitConverter.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Boolean.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Buffers\ArrayPool.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Buffers\ArrayPoolEventSource.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Buffers\ConfigurableArrayPool.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Buffers\IMemoryOwner.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Buffers\IPinnable.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Buffers\MemoryHandle.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Buffers\MemoryManager.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Buffers\TlsOverPerCoreLockedStacksArrayPool.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Buffers\Utilities.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Buffers\Text\FormattingHelpers.CountDigits.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Byte.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Char.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\CharEnumerator.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\CLSCompliantAttribute.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Comparer.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\DictionaryEntry.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\Dictionary.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\ICollection.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\ICollectionDebugView.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\IComparer.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\IDictionary.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\IDictionaryDebugView.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\IEnumerable.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\IEnumerator.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\IEqualityComparer.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\IList.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\IReadOnlyCollection.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\IReadOnlyDictionary.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\IReadOnlyList.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\KeyNotFoundException.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\KeyValuePair.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Collections\Generic\NonRandomizedStringEqualityComparer.cs" />
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+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.SECURITY_ATTRIBUTES.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.SecurityOptions.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.SetEndOfFile.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.SetEnvironmentVariable.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.SetThreadErrorMode.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.SetFilePointerEx.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.WideCharToMultiByte.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.WriteFile_SafeHandle_IntPtr.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.WriteFile_SafeHandle_NativeOverlapped.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Normaliz\Interop.Idna.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Normaliz\Interop.Normalization.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.TimeZone.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Ole32\Interop.CoCreateGuid.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\OleAut32\Interop.SysAllocStringLen.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\OleAut32\Interop.SysFreeString.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\OleAut32\Interop.SysStringLen.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Internal\IO\File.Windows.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Microsoft\Win32\SafeHandles\SafeFileHandle.Windows.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Microsoft\Win32\SafeHandles\SafeFindHandle.Windows.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\CalendarData.Windows.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\CompareInfo.Windows.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\CultureData.Windows.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\HijriCalendar.Win32.cs" Condition="'$(EnableWinRT)' != 'true' and '$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\HijriCalendar.WinRT.cs" Condition="'$(EnableWinRT)' == 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\IdnMapping.Windows.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\JapaneseCalendar.Win32.cs" Condition="'$(EnableWinRT)' != 'true' and '$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\JapaneseCalendar.WinRT.cs" Condition="'$(EnableWinRT)' == 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\Normalization.Windows.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\TextInfo.Windows.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Guid.Windows.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\FileStream.Windows.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\FileStreamCompletionSource.Win32.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\Path.Windows.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\PathHelper.Windows.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\PathInternal.Windows.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\DisableMediaInsertionPrompt.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Security\SafeBSTRHandle.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Security\SecureString.Windows.cs" />
+  </ItemGroup>
+  <ItemGroup Condition="$(TargetsWindows) and '$(EnableWinRT)' != 'true'">
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\FileStream.Win32.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\TimeZoneInfo.Win32.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Microsoft\Win32\SafeHandles\SafeLibraryHandle.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.LoadLibraryEx.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.FreeLibrary.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.CreateFile.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.MUI.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.TimeZone.Registry.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\User32\Interop.Constants.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\User32\Interop.SendMessageTimeout.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\User32\Interop.LoadString.cs" />
+  </ItemGroup>
+  <ItemGroup Condition="$(TargetsWindows) and '$(EnableWinRT)' == 'true'">
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\FileStream.WinRT.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.CreateFile2.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.CREATEFILE2_EXTENDED_PARAMETERS.cs" />
+  </ItemGroup>
+  <ItemGroup Condition="$(TargetsWindows) or '$(FeaturePal)'=='true'">
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Interop.Errors.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Windows\Kernel32\Interop.FormatMessage.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\Win32Marshal.cs" />
+  </ItemGroup>
+  <ItemGroup Condition="$(TargetsUnix)">
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\Interop.Errors.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\Interop.IOErrors.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\Interop.Libraries.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Globalization.Native\Interop.Calendar.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Globalization.Native\Interop.Casing.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Globalization.Native\Interop.Collation.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Globalization.Native\Interop.ICU.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Globalization.Native\Interop.Idna.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Globalization.Native\Interop.Locale.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Globalization.Native\Interop.Normalization.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Globalization.Native\Interop.ResultCode.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Globalization.Native\Interop.TimeZoneInfo.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Globalization.Native\Interop.Utils.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.Close.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.FLock.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.FSync.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.FTruncate.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.GetCwd.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.GetRandomBytes.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.LockFileRegion.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.LSeek.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.MksTemps.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.Open.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.OpenFlags.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.PathConf.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.Permissions.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.PosixFAdvise.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.Read.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.ReadDir.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.ReadLink.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.Stat.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.SysLog.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.Unlink.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Interop\Unix\System.Native\Interop.Write.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Internal\IO\File.Unix.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Microsoft\Win32\SafeHandles\SafeDirectoryHandle.Unix.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Microsoft\Win32\SafeHandles\SafeFileHandle.Unix.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\Debug.Unix.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\CalendarData.Unix.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\CompareInfo.Unix.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\CultureData.Unix.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\HijriCalendar.Unix.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\IdnMapping.Unix.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\JapaneseCalendar.Unix.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\LocaleData.Unix.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\Normalization.Unix.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Globalization\TextInfo.Unix.cs" Condition="'$(EnableDummyGlobalizationImplementation)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Guid.Unix.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\FileStream.OSX.cs" Condition="'$(TargetsOSX)' == 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\FileStream.Linux.cs" Condition="'$(TargetsOSX)' != 'true'" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\FileStream.Unix.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\Path.Unix.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\PathInternal.Unix.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Security\SecureString.Unix.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\TimeZoneInfo.Unix.cs" />
+  </ItemGroup>
+</Project>
diff --git a/src/System.Private.CoreLib/shared/System/AccessViolationException.cs b/src/System.Private.CoreLib/shared/System/AccessViolationException.cs
new file mode 100644
index 0000000000..280d9b8a97
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/AccessViolationException.cs
@@ -0,0 +1,51 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception class representing an AV that was deemed unsafe and may have corrupted the application.
+**
+**
+=============================================================================*/
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class AccessViolationException : SystemException
+    {
+        public AccessViolationException()
+            : base(SR.Arg_AccessViolationException)
+        {
+            HResult = HResults.E_POINTER;
+        }
+
+        public AccessViolationException(String message)
+            : base(message)
+        {
+            HResult = HResults.E_POINTER;
+        }
+
+        public AccessViolationException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.E_POINTER;
+        }
+
+        protected AccessViolationException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+
+#pragma warning disable 169  // Field is not used from managed.
+        private IntPtr _ip;             // Address of faulting instruction.
+        private IntPtr _target;         // Address that could not be accessed.
+        private int _accessType;        // 0:read, 1:write
+#pragma warning restore 169
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Action.cs b/src/System.Private.CoreLib/shared/System/Action.cs
new file mode 100644
index 0000000000..6e3ccff48c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Action.cs
@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    public delegate void Action();
+    public delegate void Action<in T>(T obj);
+    public delegate void Action<in T1, in T2>(T1 arg1, T2 arg2);
+    public delegate void Action<in T1, in T2, in T3>(T1 arg1, T2 arg2, T3 arg3);
+    public delegate void Action<in T1, in T2, in T3, in T4>(T1 arg1, T2 arg2, T3 arg3, T4 arg4);
+    public delegate void Action<in T1, in T2, in T3, in T4, in T5>(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5);
+    public delegate void Action<in T1, in T2, in T3, in T4, in T5, in T6>(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6);
+    public delegate void Action<in T1, in T2, in T3, in T4, in T5, in T6, in T7>(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6, T7 arg7);
+    public delegate void Action<in T1, in T2, in T3, in T4, in T5, in T6, in T7, in T8>(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6, T7 arg7, T8 arg8);
+
+    public delegate TResult Func<out TResult>();
+    public delegate TResult Func<in T, out TResult>(T arg);
+    public delegate TResult Func<in T1, in T2, out TResult>(T1 arg1, T2 arg2);
+    public delegate TResult Func<in T1, in T2, in T3, out TResult>(T1 arg1, T2 arg2, T3 arg3);
+    public delegate TResult Func<in T1, in T2, in T3, in T4, out TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4);
+    public delegate TResult Func<in T1, in T2, in T3, in T4, in T5, out TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5);
+    public delegate TResult Func<in T1, in T2, in T3, in T4, in T5, in T6, out TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6);
+    public delegate TResult Func<in T1, in T2, in T3, in T4, in T5, in T6, in T7, out TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6, T7 arg7);
+    public delegate TResult Func<in T1, in T2, in T3, in T4, in T5, in T6, in T7, in T8, out TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6, T7 arg7, T8 arg8);
+
+    public delegate int Comparison<in T>(T x, T y);
+
+    public delegate TOutput Converter<in TInput, out TOutput>(TInput input);
+
+    public delegate bool Predicate<in T>(T obj);
+}
+
+namespace System.Buffers
+{
+    public delegate void SpanAction<T, in TArg>(Span<T> span, TArg arg);
+    public delegate void ReadOnlySpanAction<T, in TArg>(ReadOnlySpan<T> span, TArg arg);
+}
diff --git a/src/System.Private.CoreLib/shared/System/AggregateException.cs b/src/System.Private.CoreLib/shared/System/AggregateException.cs
new file mode 100644
index 0000000000..99ba703a52
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/AggregateException.cs
@@ -0,0 +1,484 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.ExceptionServices;
+using System.Runtime.Serialization;
+using System.Security;
+using System.Text;
+using System.Threading;
+
+namespace System
+{
+    /// <summary>Represents one or more errors that occur during application execution.</summary>
+    /// <remarks>
+    /// <see cref="AggregateException"/> is used to consolidate multiple failures into a single, throwable
+    /// exception object.
+    /// </remarks>
+    [Serializable]
+    [DebuggerDisplay("Count = {InnerExceptionCount}")]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class AggregateException : Exception
+    {
+        private ReadOnlyCollection<Exception> m_innerExceptions; // Complete set of exceptions. Do not rename (binary serialization)
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AggregateException"/> class.
+        /// </summary>
+        public AggregateException()
+            : base(SR.AggregateException_ctor_DefaultMessage)
+        {
+            m_innerExceptions = new ReadOnlyCollection<Exception>(Array.Empty<Exception>());
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AggregateException"/> class with
+        /// a specified error message.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        public AggregateException(string message)
+            : base(message)
+        {
+            m_innerExceptions = new ReadOnlyCollection<Exception>(Array.Empty<Exception>());
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AggregateException"/> class with a specified error
+        /// message and a reference to the inner exception that is the cause of this exception.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        /// <param name="innerException">The exception that is the cause of the current exception.</param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="innerException"/> argument
+        /// is null.</exception>
+        public AggregateException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+            if (innerException == null)
+            {
+                throw new ArgumentNullException(nameof(innerException));
+            }
+
+            m_innerExceptions = new ReadOnlyCollection<Exception>(new Exception[] { innerException });
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AggregateException"/> class with
+        /// references to the inner exceptions that are the cause of this exception.
+        /// </summary>
+        /// <param name="innerExceptions">The exceptions that are the cause of the current exception.</param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="innerExceptions"/> argument
+        /// is null.</exception>
+        /// <exception cref="T:System.ArgumentException">An element of <paramref name="innerExceptions"/> is
+        /// null.</exception>
+        public AggregateException(IEnumerable<Exception> innerExceptions) :
+            this(SR.AggregateException_ctor_DefaultMessage, innerExceptions)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AggregateException"/> class with
+        /// references to the inner exceptions that are the cause of this exception.
+        /// </summary>
+        /// <param name="innerExceptions">The exceptions that are the cause of the current exception.</param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="innerExceptions"/> argument
+        /// is null.</exception>
+        /// <exception cref="T:System.ArgumentException">An element of <paramref name="innerExceptions"/> is
+        /// null.</exception>
+        public AggregateException(params Exception[] innerExceptions) :
+            this(SR.AggregateException_ctor_DefaultMessage, innerExceptions)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AggregateException"/> class with a specified error
+        /// message and references to the inner exceptions that are the cause of this exception.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        /// <param name="innerExceptions">The exceptions that are the cause of the current exception.</param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="innerExceptions"/> argument
+        /// is null.</exception>
+        /// <exception cref="T:System.ArgumentException">An element of <paramref name="innerExceptions"/> is
+        /// null.</exception>
+        public AggregateException(string message, IEnumerable<Exception> innerExceptions)
+            // If it's already an IList, pass that along (a defensive copy will be made in the delegated ctor).  If it's null, just pass along
+            // null typed correctly.  Otherwise, create an IList from the enumerable and pass that along. 
+            : this(message, innerExceptions as IList<Exception> ?? (innerExceptions == null ? (List<Exception>)null : new List<Exception>(innerExceptions)))
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AggregateException"/> class with a specified error
+        /// message and references to the inner exceptions that are the cause of this exception.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        /// <param name="innerExceptions">The exceptions that are the cause of the current exception.</param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="innerExceptions"/> argument
+        /// is null.</exception>
+        /// <exception cref="T:System.ArgumentException">An element of <paramref name="innerExceptions"/> is
+        /// null.</exception>
+        public AggregateException(string message, params Exception[] innerExceptions) :
+            this(message, (IList<Exception>)innerExceptions)
+        {
+        }
+
+        /// <summary>
+        /// Allocates a new aggregate exception with the specified message and list of inner exceptions.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        /// <param name="innerExceptions">The exceptions that are the cause of the current exception.</param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="innerExceptions"/> argument
+        /// is null.</exception>
+        /// <exception cref="T:System.ArgumentException">An element of <paramref name="innerExceptions"/> is
+        /// null.</exception>
+        private AggregateException(string message, IList<Exception> innerExceptions)
+            : base(message, innerExceptions != null && innerExceptions.Count > 0 ? innerExceptions[0] : null)
+        {
+            if (innerExceptions == null)
+            {
+                throw new ArgumentNullException(nameof(innerExceptions));
+            }
+
+            // Copy exceptions to our internal array and validate them. We must copy them,
+            // because we're going to put them into a ReadOnlyCollection which simply reuses
+            // the list passed in to it. We don't want callers subsequently mutating.
+            Exception[] exceptionsCopy = new Exception[innerExceptions.Count];
+
+            for (int i = 0; i < exceptionsCopy.Length; i++)
+            {
+                exceptionsCopy[i] = innerExceptions[i];
+
+                if (exceptionsCopy[i] == null)
+                {
+                    throw new ArgumentException(SR.AggregateException_ctor_InnerExceptionNull);
+                }
+            }
+
+            m_innerExceptions = new ReadOnlyCollection<Exception>(exceptionsCopy);
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AggregateException"/> class with
+        /// references to the inner exception dispatch info objects that represent the cause of this exception.
+        /// </summary>
+        /// <param name="innerExceptionInfos">
+        /// Information about the exceptions that are the cause of the current exception.
+        /// </param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="innerExceptionInfos"/> argument
+        /// is null.</exception>
+        /// <exception cref="T:System.ArgumentException">An element of <paramref name="innerExceptionInfos"/> is
+        /// null.</exception>
+        internal AggregateException(IEnumerable<ExceptionDispatchInfo> innerExceptionInfos) :
+            this(SR.AggregateException_ctor_DefaultMessage, innerExceptionInfos)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AggregateException"/> class with a specified error
+        /// message and references to the inner exception dispatch info objects that represent the cause of 
+        /// this exception.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        /// <param name="innerExceptionInfos">
+        /// Information about the exceptions that are the cause of the current exception.
+        /// </param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="innerExceptionInfos"/> argument
+        /// is null.</exception>
+        /// <exception cref="T:System.ArgumentException">An element of <paramref name="innerExceptionInfos"/> is
+        /// null.</exception>
+        internal AggregateException(string message, IEnumerable<ExceptionDispatchInfo> innerExceptionInfos)
+            // If it's already an IList, pass that along (a defensive copy will be made in the delegated ctor).  If it's null, just pass along
+            // null typed correctly.  Otherwise, create an IList from the enumerable and pass that along. 
+            : this(message, innerExceptionInfos as IList<ExceptionDispatchInfo> ??
+                                (innerExceptionInfos == null ?
+                                    (List<ExceptionDispatchInfo>)null :
+                                    new List<ExceptionDispatchInfo>(innerExceptionInfos)))
+        {
+        }
+
+        /// <summary>
+        /// Allocates a new aggregate exception with the specified message and list of inner 
+        /// exception dispatch info objects.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        /// <param name="innerExceptionInfos">
+        /// Information about the exceptions that are the cause of the current exception.
+        /// </param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="innerExceptionInfos"/> argument
+        /// is null.</exception>
+        /// <exception cref="T:System.ArgumentException">An element of <paramref name="innerExceptionInfos"/> is
+        /// null.</exception>
+        private AggregateException(string message, IList<ExceptionDispatchInfo> innerExceptionInfos)
+            : base(message, innerExceptionInfos != null && innerExceptionInfos.Count > 0 && innerExceptionInfos[0] != null ?
+                                innerExceptionInfos[0].SourceException : null)
+        {
+            if (innerExceptionInfos == null)
+            {
+                throw new ArgumentNullException(nameof(innerExceptionInfos));
+            }
+
+            // Copy exceptions to our internal array and validate them. We must copy them,
+            // because we're going to put them into a ReadOnlyCollection which simply reuses
+            // the list passed in to it. We don't want callers subsequently mutating.
+            Exception[] exceptionsCopy = new Exception[innerExceptionInfos.Count];
+
+            for (int i = 0; i < exceptionsCopy.Length; i++)
+            {
+                var edi = innerExceptionInfos[i];
+                if (edi != null) exceptionsCopy[i] = edi.SourceException;
+
+                if (exceptionsCopy[i] == null)
+                {
+                    throw new ArgumentException(SR.AggregateException_ctor_InnerExceptionNull);
+                }
+            }
+
+            m_innerExceptions = new ReadOnlyCollection<Exception>(exceptionsCopy);
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AggregateException"/> class with serialized data.
+        /// </summary>
+        /// <param name="info">The <see cref="T:System.Runtime.Serialization.SerializationInfo"/> that holds
+        /// the serialized object data about the exception being thrown.</param>
+        /// <param name="context">The <see cref="T:System.Runtime.Serialization.StreamingContext"/> that
+        /// contains contextual information about the source or destination. </param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="info"/> argument is null.</exception>
+        /// <exception cref="T:System.Runtime.Serialization.SerializationException">The exception could not be deserialized correctly.</exception>
+        protected AggregateException(SerializationInfo info, StreamingContext context) :
+            base(info, context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+
+            Exception[] innerExceptions = info.GetValue("InnerExceptions", typeof(Exception[])) as Exception[];
+            if (innerExceptions == null)
+            {
+                throw new SerializationException(SR.AggregateException_DeserializationFailure);
+            }
+
+            m_innerExceptions = new ReadOnlyCollection<Exception>(innerExceptions);
+        }
+
+        /// <summary>
+        /// Sets the <see cref="T:System.Runtime.Serialization.SerializationInfo"/> with information about
+        /// the exception.
+        /// </summary>
+        /// <param name="info">The <see cref="T:System.Runtime.Serialization.SerializationInfo"/> that holds
+        /// the serialized object data about the exception being thrown.</param>
+        /// <param name="context">The <see cref="T:System.Runtime.Serialization.StreamingContext"/> that
+        /// contains contextual information about the source or destination. </param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="info"/> argument is null.</exception>
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+
+            Exception[] innerExceptions = new Exception[m_innerExceptions.Count];
+            m_innerExceptions.CopyTo(innerExceptions, 0);
+            info.AddValue("InnerExceptions", innerExceptions, typeof(Exception[]));
+        }
+
+        /// <summary>
+        /// Returns the <see cref="System.AggregateException"/> that is the root cause of this exception.
+        /// </summary>
+        public override Exception GetBaseException()
+        {
+            // Returns the first inner AggregateException that contains more or less than one inner exception
+
+            // Recursively traverse the inner exceptions as long as the inner exception of type AggregateException and has only one inner exception
+            Exception back = this;
+            AggregateException backAsAggregate = this;
+            while (backAsAggregate != null && backAsAggregate.InnerExceptions.Count == 1)
+            {
+                back = back.InnerException;
+                backAsAggregate = back as AggregateException;
+            }
+            return back;
+        }
+
+        /// <summary>
+        /// Gets a read-only collection of the <see cref="T:System.Exception"/> instances that caused the
+        /// current exception.
+        /// </summary>
+        public ReadOnlyCollection<Exception> InnerExceptions
+        {
+            get { return m_innerExceptions; }
+        }
+
+
+        /// <summary>
+        /// Invokes a handler on each <see cref="T:System.Exception"/> contained by this <see
+        /// cref="AggregateException"/>.
+        /// </summary>
+        /// <param name="predicate">The predicate to execute for each exception. The predicate accepts as an
+        /// argument the <see cref="T:System.Exception"/> to be processed and returns a Boolean to indicate
+        /// whether the exception was handled.</param>
+        /// <remarks>
+        /// Each invocation of the <paramref name="predicate"/> returns true or false to indicate whether the
+        /// <see cref="T:System.Exception"/> was handled. After all invocations, if any exceptions went
+        /// unhandled, all unhandled exceptions will be put into a new <see cref="AggregateException"/>
+        /// which will be thrown. Otherwise, the <see cref="Handle"/> method simply returns. If any
+        /// invocations of the <paramref name="predicate"/> throws an exception, it will halt the processing
+        /// of any more exceptions and immediately propagate the thrown exception as-is.
+        /// </remarks>
+        /// <exception cref="AggregateException">An exception contained by this <see
+        /// cref="AggregateException"/> was not handled.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="predicate"/> argument is
+        /// null.</exception>
+        public void Handle(Func<Exception, bool> predicate)
+        {
+            if (predicate == null)
+            {
+                throw new ArgumentNullException(nameof(predicate));
+            }
+
+            List<Exception> unhandledExceptions = null;
+            for (int i = 0; i < m_innerExceptions.Count; i++)
+            {
+                // If the exception was not handled, lazily allocate a list of unhandled
+                // exceptions (to be rethrown later) and add it.
+                if (!predicate(m_innerExceptions[i]))
+                {
+                    if (unhandledExceptions == null)
+                    {
+                        unhandledExceptions = new List<Exception>();
+                    }
+
+                    unhandledExceptions.Add(m_innerExceptions[i]);
+                }
+            }
+
+            // If there are unhandled exceptions remaining, throw them.
+            if (unhandledExceptions != null)
+            {
+                throw new AggregateException(Message, unhandledExceptions);
+            }
+        }
+
+
+        /// <summary>
+        /// Flattens the inner instances of <see cref="AggregateException"/> by expanding its contained <see cref="Exception"/> instances
+        /// into a new <see cref="AggregateException"/>
+        /// </summary>
+        /// <returns>A new, flattened <see cref="AggregateException"/>.</returns>
+        /// <remarks>
+        /// If any inner exceptions are themselves instances of
+        /// <see cref="AggregateException"/>, this method will recursively flatten all of them. The
+        /// inner exceptions returned in the new <see cref="AggregateException"/>
+        /// will be the union of all of the inner exceptions from exception tree rooted at the provided
+        /// <see cref="AggregateException"/> instance.
+        /// </remarks>
+        public AggregateException Flatten()
+        {
+            // Initialize a collection to contain the flattened exceptions.
+            List<Exception> flattenedExceptions = new List<Exception>();
+
+            // Create a list to remember all aggregates to be flattened, this will be accessed like a FIFO queue
+            List<AggregateException> exceptionsToFlatten = new List<AggregateException>();
+            exceptionsToFlatten.Add(this);
+            int nDequeueIndex = 0;
+
+            // Continue removing and recursively flattening exceptions, until there are no more.
+            while (exceptionsToFlatten.Count > nDequeueIndex)
+            {
+                // dequeue one from exceptionsToFlatten
+                IList<Exception> currentInnerExceptions = exceptionsToFlatten[nDequeueIndex++].InnerExceptions;
+
+                for (int i = 0; i < currentInnerExceptions.Count; i++)
+                {
+                    Exception currentInnerException = currentInnerExceptions[i];
+
+                    if (currentInnerException == null)
+                    {
+                        continue;
+                    }
+
+                    AggregateException currentInnerAsAggregate = currentInnerException as AggregateException;
+
+                    // If this exception is an aggregate, keep it around for later.  Otherwise,
+                    // simply add it to the list of flattened exceptions to be returned.
+                    if (currentInnerAsAggregate != null)
+                    {
+                        exceptionsToFlatten.Add(currentInnerAsAggregate);
+                    }
+                    else
+                    {
+                        flattenedExceptions.Add(currentInnerException);
+                    }
+                }
+            }
+
+
+            return new AggregateException(Message, flattenedExceptions);
+        }
+
+        /// <summary>Gets a message that describes the exception.</summary>
+        public override string Message
+        {
+            get
+            {
+                if (m_innerExceptions.Count == 0)
+                {
+                    return base.Message;
+                }
+
+                StringBuilder sb = StringBuilderCache.Acquire();
+                sb.Append(base.Message);
+                sb.Append(' ');
+                for (int i = 0; i < m_innerExceptions.Count; i++)
+                {
+                    sb.Append('(');
+                    sb.Append(m_innerExceptions[i].Message);
+                    sb.Append(") ");
+                }
+                sb.Length -= 1;
+                return StringBuilderCache.GetStringAndRelease(sb);
+            }
+        }
+
+        /// <summary>
+        /// Creates and returns a string representation of the current <see cref="AggregateException"/>.
+        /// </summary>
+        /// <returns>A string representation of the current exception.</returns>
+        public override string ToString()
+        {
+            StringBuilder text = new StringBuilder();
+            text.Append(base.ToString());
+
+            for (int i = 0; i < m_innerExceptions.Count; i++)
+            {
+                text.AppendLine();
+                text.Append("---> ");
+                text.AppendFormat(CultureInfo.InvariantCulture, SR.AggregateException_InnerException, i);
+                text.Append(m_innerExceptions[i].ToString());
+                text.Append("<---");
+                text.AppendLine();
+            }
+
+            return text.ToString();
+        }
+
+        /// <summary>
+        /// This helper property is used by the DebuggerDisplay.
+        /// 
+        /// Note that we don't want to remove this property and change the debugger display to {InnerExceptions.Count} 
+        /// because DebuggerDisplay should be a single property access or parameterless method call, so that the debugger 
+        /// can use a fast path without using the expression evaluator.
+        /// 
+        /// See http://msdn.microsoft.com/en-us/library/x810d419.aspx
+        /// </summary>
+        private int InnerExceptionCount
+        {
+            get
+            {
+                return InnerExceptions.Count;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ApplicationException.cs b/src/System.Private.CoreLib/shared/System/ApplicationException.cs
new file mode 100644
index 0000000000..f36e2c1274
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ApplicationException.cs
@@ -0,0 +1,58 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: The base class for all "less serious" exceptions that must be
+**          declared or caught.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    // The ApplicationException is the base class for nonfatal, 
+    // application errors that occur.  These exceptions are generated 
+    // (i.e., thrown) by an application, not the Runtime. Applications that need 
+    // to create their own exceptions do so by extending this class. 
+    // ApplicationException extends but adds no new functionality to 
+    // RecoverableException.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class ApplicationException : Exception
+    {
+        // Creates a new ApplicationException with its message string set to
+        // the empty string, its HRESULT set to COR_E_APPLICATION, 
+        // and its ExceptionInfo reference set to null. 
+        public ApplicationException()
+            : base(SR.Arg_ApplicationException)
+        {
+            HResult = HResults.COR_E_APPLICATION;
+        }
+
+        // Creates a new ApplicationException with its message string set to
+        // message, its HRESULT set to COR_E_APPLICATION, 
+        // and its ExceptionInfo reference set to null. 
+        // 
+        public ApplicationException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_APPLICATION;
+        }
+
+        public ApplicationException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_APPLICATION;
+        }
+
+        protected ApplicationException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ArgumentException.cs b/src/System.Private.CoreLib/shared/System/ArgumentException.cs
new file mode 100644
index 0000000000..8a8fe3e5e4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ArgumentException.cs
@@ -0,0 +1,97 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception class for invalid arguments to a method.
+**
+**
+=============================================================================*/
+
+using System.Globalization;
+using System.Runtime.Serialization;
+
+namespace System
+{
+    // The ArgumentException is thrown when an argument does not meet 
+    // the contract of the method.  Ideally it should give a meaningful error
+    // message describing what was wrong and which parameter is incorrect.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class ArgumentException : SystemException
+    {
+        private String _paramName;
+
+        // Creates a new ArgumentException with its message 
+        // string set to the empty string. 
+        public ArgumentException()
+            : base(SR.Arg_ArgumentException)
+        {
+            HResult = HResults.COR_E_ARGUMENT;
+        }
+
+        // Creates a new ArgumentException with its message 
+        // string set to message. 
+        // 
+        public ArgumentException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_ARGUMENT;
+        }
+
+        public ArgumentException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_ARGUMENT;
+        }
+
+        public ArgumentException(String message, String paramName, Exception innerException)
+            : base(message, innerException)
+        {
+            _paramName = paramName;
+            HResult = HResults.COR_E_ARGUMENT;
+        }
+
+        public ArgumentException(String message, String paramName)
+            : base(message)
+        {
+            _paramName = paramName;
+            HResult = HResults.COR_E_ARGUMENT;
+        }
+
+        protected ArgumentException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            _paramName = info.GetString("ParamName");
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("ParamName", _paramName, typeof(string));
+        }
+
+        public override String Message
+        {
+            get
+            {
+                String s = base.Message;
+                if (!String.IsNullOrEmpty(_paramName))
+                {
+                    String resourceString = SR.Format(SR.Arg_ParamName_Name, _paramName);
+                    return s + Environment.NewLine + resourceString;
+                }
+                else
+                    return s;
+            }
+        }
+
+        public virtual String ParamName
+        {
+            get { return _paramName; }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ArgumentNullException.cs b/src/System.Private.CoreLib/shared/System/ArgumentNullException.cs
new file mode 100644
index 0000000000..80e43cc265
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ArgumentNullException.cs
@@ -0,0 +1,55 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception class for null arguments to a method.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    // The ArgumentException is thrown when an argument 
+    // is null when it shouldn't be.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class ArgumentNullException : ArgumentException
+    {
+        // Creates a new ArgumentNullException with its message 
+        // string set to a default message explaining an argument was null.
+        public ArgumentNullException()
+             : base(SR.ArgumentNull_Generic)
+        {
+            // Use E_POINTER - COM used that for null pointers.  Description is "invalid pointer"
+            HResult = HResults.E_POINTER;
+        }
+
+        public ArgumentNullException(String paramName)
+            : base(SR.ArgumentNull_Generic, paramName)
+        {
+            HResult = HResults.E_POINTER;
+        }
+
+        public ArgumentNullException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.E_POINTER;
+        }
+
+        public ArgumentNullException(String paramName, String message)
+            : base(message, paramName)
+        {
+            HResult = HResults.E_POINTER;
+        }
+
+        protected ArgumentNullException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ArgumentOutOfRangeException.cs b/src/System.Private.CoreLib/shared/System/ArgumentOutOfRangeException.cs
new file mode 100644
index 0000000000..604caa8ee8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ArgumentOutOfRangeException.cs
@@ -0,0 +1,100 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception class for method arguments outside of the legal range.
+**
+**
+=============================================================================*/
+
+using System.Globalization;
+using System.Runtime.Serialization;
+
+namespace System
+{
+    // The ArgumentOutOfRangeException is thrown when an argument 
+    // is outside the legal range for that argument.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class ArgumentOutOfRangeException : ArgumentException
+    {
+        private Object _actualValue;
+
+        // Creates a new ArgumentOutOfRangeException with its message 
+        // string set to a default message explaining an argument was out of range.
+        public ArgumentOutOfRangeException()
+            : base(SR.Arg_ArgumentOutOfRangeException)
+        {
+            HResult = HResults.COR_E_ARGUMENTOUTOFRANGE;
+        }
+
+        public ArgumentOutOfRangeException(String paramName)
+            : base(SR.Arg_ArgumentOutOfRangeException, paramName)
+        {
+            HResult = HResults.COR_E_ARGUMENTOUTOFRANGE;
+        }
+
+        public ArgumentOutOfRangeException(String paramName, String message)
+            : base(message, paramName)
+        {
+            HResult = HResults.COR_E_ARGUMENTOUTOFRANGE;
+        }
+
+        public ArgumentOutOfRangeException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_ARGUMENTOUTOFRANGE;
+        }
+
+        // We will not use this in the classlibs, but we'll provide it for
+        // anyone that's really interested so they don't have to stick a bunch
+        // of printf's in their code.
+        public ArgumentOutOfRangeException(String paramName, Object actualValue, String message)
+            : base(message, paramName)
+        {
+            _actualValue = actualValue;
+            HResult = HResults.COR_E_ARGUMENTOUTOFRANGE;
+        }
+
+        protected ArgumentOutOfRangeException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            _actualValue = info.GetValue("ActualValue", typeof(object));
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("ActualValue", _actualValue, typeof(object));
+        }
+
+        public override String Message
+        {
+            get
+            {
+                String s = base.Message;
+                if (_actualValue != null)
+                {
+                    String valueMessage = SR.Format(SR.ArgumentOutOfRange_ActualValue, _actualValue.ToString());
+                    if (s == null)
+                        return valueMessage;
+                    return s + Environment.NewLine + valueMessage;
+                }
+                return s;
+            }
+        }
+
+        // Gets the value of the argument that caused the exception.
+        // Note - we don't set this anywhere in the class libraries in 
+        // version 1, but it might come in handy for other developers who
+        // want to avoid sticking printf's in their code.
+        public virtual Object ActualValue
+        {
+            get { return _actualValue; }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ArithmeticException.cs b/src/System.Private.CoreLib/shared/System/ArithmeticException.cs
new file mode 100644
index 0000000000..606f1debfd
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ArithmeticException.cs
@@ -0,0 +1,53 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception class for bad arithmetic conditions!
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    // The ArithmeticException is thrown when overflow or underflow
+    // occurs.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class ArithmeticException : SystemException
+    {
+        // Creates a new ArithmeticException with its message string set to
+        // the empty string, its HRESULT set to COR_E_ARITHMETIC, 
+        // and its ExceptionInfo reference set to null. 
+        public ArithmeticException()
+            : base(SR.Arg_ArithmeticException)
+        {
+            HResult = HResults.COR_E_ARITHMETIC;
+        }
+
+        // Creates a new ArithmeticException with its message string set to
+        // message, its HRESULT set to COR_E_ARITHMETIC, 
+        // and its ExceptionInfo reference set to null. 
+        // 
+        public ArithmeticException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_ARITHMETIC;
+        }
+
+        public ArithmeticException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_ARITHMETIC;
+        }
+
+        protected ArithmeticException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ArraySegment.cs b/src/System.Private.CoreLib/shared/System/ArraySegment.cs
new file mode 100644
index 0000000000..3a13595e83
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ArraySegment.cs
@@ -0,0 +1,368 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Convenient wrapper for an array, an offset, and
+**          a count.  Ideally used in streams & collections.
+**          Net Classes will consume an array of these.
+**
+**
+===========================================================*/
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System
+{
+    // Note: users should make sure they copy the fields out of an ArraySegment onto their stack
+    // then validate that the fields describe valid bounds within the array.  This must be done
+    // because assignments to value types are not atomic, and also because one thread reading 
+    // three fields from an ArraySegment may not see the same ArraySegment from one call to another
+    // (ie, users could assign a new value to the old location).  
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public readonly struct ArraySegment<T> : IList<T>, IReadOnlyList<T>
+    {
+        // Do not replace the array allocation with Array.Empty. We don't want to have the overhead of
+        // instantiating another generic type in addition to ArraySegment<T> for new type parameters.
+        public static ArraySegment<T> Empty { get; } = new ArraySegment<T>(new T[0]);
+
+        private readonly T[] _array; // Do not rename (binary serialization)
+        private readonly int _offset; // Do not rename (binary serialization)
+        private readonly int _count; // Do not rename (binary serialization)
+
+        public ArraySegment(T[] array)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+
+            _array = array;
+            _offset = 0;
+            _count = array.Length;
+        }
+
+        public ArraySegment(T[] array, int offset, int count)
+        {
+            // Validate arguments, check is minimal instructions with reduced branching for inlinable fast-path
+            // Negative values discovered though conversion to high values when converted to unsigned
+            // Failure should be rare and location determination and message is delegated to failure functions
+            if (array == null || (uint)offset > (uint)array.Length || (uint)count > (uint)(array.Length - offset))
+                ThrowHelper.ThrowArraySegmentCtorValidationFailedExceptions(array, offset, count);
+
+            _array = array;
+            _offset = offset;
+            _count = count;
+        }
+
+        public T[] Array => _array;
+
+        public int Offset => _offset;
+
+        public int Count => _count;
+
+        public T this[int index]
+        {
+            get
+            {
+                if ((uint)index >= (uint)_count)
+                {
+                    ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+                }
+
+                return _array[_offset + index];
+            }
+            set
+            {
+                if ((uint)index >= (uint)_count)
+                {
+                    ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+                }
+
+                _array[_offset + index] = value;
+            }
+        }
+
+        public Enumerator GetEnumerator()
+        {
+            ThrowInvalidOperationIfDefault();
+            return new Enumerator(this);
+        }
+
+        public override int GetHashCode()
+        {
+            if (_array == null)
+            {
+                return 0;
+            }
+
+            int hash = 5381;
+            hash = System.Numerics.Hashing.HashHelpers.Combine(hash, _offset);
+            hash = System.Numerics.Hashing.HashHelpers.Combine(hash, _count);
+
+            // The array hash is expected to be an evenly-distributed mixture of bits,
+            // so rather than adding the cost of another rotation we just xor it.
+            hash ^= _array.GetHashCode();
+            return hash;
+        }
+
+        public void CopyTo(T[] destination) => CopyTo(destination, 0);
+
+        public void CopyTo(T[] destination, int destinationIndex)
+        {
+            ThrowInvalidOperationIfDefault();
+            System.Array.Copy(_array, _offset, destination, destinationIndex, _count);
+        }
+
+        public void CopyTo(ArraySegment<T> destination)
+        {
+            ThrowInvalidOperationIfDefault();
+            destination.ThrowInvalidOperationIfDefault();
+
+            if (_count > destination._count)
+            {
+                ThrowHelper.ThrowArgumentException_DestinationTooShort();
+            }
+
+            System.Array.Copy(_array, _offset, destination._array, destination._offset, _count);
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (obj is ArraySegment<T>)
+                return Equals((ArraySegment<T>)obj);
+            else
+                return false;
+        }
+
+        public bool Equals(ArraySegment<T> obj)
+        {
+            return obj._array == _array && obj._offset == _offset && obj._count == _count;
+        }
+
+        public ArraySegment<T> Slice(int index)
+        {
+            ThrowInvalidOperationIfDefault();
+            
+            if ((uint)index > (uint)_count)
+            {
+                ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+            }
+
+            return new ArraySegment<T>(_array, _offset + index, _count - index);
+        }
+
+        public ArraySegment<T> Slice(int index, int count)
+        {
+            ThrowInvalidOperationIfDefault();
+
+            if ((uint)index > (uint)_count || (uint)count > (uint)(_count - index))
+            {
+                ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+            }
+
+            return new ArraySegment<T>(_array, _offset + index, count);
+        }
+
+        public T[] ToArray()
+        {
+            ThrowInvalidOperationIfDefault();
+
+            if (_count == 0)
+            {
+                return Empty._array;
+            }
+
+            var array = new T[_count];
+            System.Array.Copy(_array, _offset, array, 0, _count);
+            return array;
+        }
+
+        public static bool operator ==(ArraySegment<T> a, ArraySegment<T> b)
+        {
+            return a.Equals(b);
+        }
+
+        public static bool operator !=(ArraySegment<T> a, ArraySegment<T> b)
+        {
+            return !(a == b);
+        }
+
+        public static implicit operator ArraySegment<T>(T[] array) => array != null ? new ArraySegment<T>(array) : default;
+
+        #region IList<T>
+        T IList<T>.this[int index]
+        {
+            get
+            {
+                ThrowInvalidOperationIfDefault();
+                if (index < 0 || index >= _count)
+                    ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+
+                return _array[_offset + index];
+            }
+
+            set
+            {
+                ThrowInvalidOperationIfDefault();
+                if (index < 0 || index >= _count)
+                    ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+
+                _array[_offset + index] = value;
+            }
+        }
+
+        int IList<T>.IndexOf(T item)
+        {
+            ThrowInvalidOperationIfDefault();
+
+            int index = System.Array.IndexOf<T>(_array, item, _offset, _count);
+
+            Debug.Assert(index == -1 ||
+                            (index >= _offset && index < _offset + _count));
+
+            return index >= 0 ? index - _offset : -1;
+        }
+
+        void IList<T>.Insert(int index, T item)
+        {
+            ThrowHelper.ThrowNotSupportedException();
+        }
+
+        void IList<T>.RemoveAt(int index)
+        {
+            ThrowHelper.ThrowNotSupportedException();
+        }
+        #endregion
+
+        #region IReadOnlyList<T>
+        T IReadOnlyList<T>.this[int index]
+        {
+            get
+            {
+                ThrowInvalidOperationIfDefault();
+                if (index < 0 || index >= _count)
+                    ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+
+                return _array[_offset + index];
+            }
+        }
+        #endregion IReadOnlyList<T>
+
+        #region ICollection<T>
+        bool ICollection<T>.IsReadOnly
+        {
+            get
+            {
+                // the indexer setter does not throw an exception although IsReadOnly is true.
+                // This is to match the behavior of arrays.
+                return true;
+            }
+        }
+
+        void ICollection<T>.Add(T item)
+        {
+            ThrowHelper.ThrowNotSupportedException();
+        }
+
+        void ICollection<T>.Clear()
+        {
+            ThrowHelper.ThrowNotSupportedException();
+        }
+
+        bool ICollection<T>.Contains(T item)
+        {
+            ThrowInvalidOperationIfDefault();
+
+            int index = System.Array.IndexOf<T>(_array, item, _offset, _count);
+
+            Debug.Assert(index == -1 ||
+                            (index >= _offset && index < _offset + _count));
+
+            return index >= 0;
+        }
+
+        bool ICollection<T>.Remove(T item)
+        {
+            ThrowHelper.ThrowNotSupportedException();
+            return default(bool);
+        }
+        #endregion
+
+        #region IEnumerable<T>
+
+        IEnumerator<T> IEnumerable<T>.GetEnumerator() => GetEnumerator();
+        #endregion
+
+        #region IEnumerable
+
+        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+        #endregion
+
+        private void ThrowInvalidOperationIfDefault()
+        {
+            if (_array == null)
+            {
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_NullArray);
+            }
+        }
+
+        public struct Enumerator : IEnumerator<T>
+        {
+            private readonly T[] _array;
+            private readonly int _start;
+            private readonly int _end; // cache Offset + Count, since it's a little slow
+            private int _current;
+
+            internal Enumerator(ArraySegment<T> arraySegment)
+            {
+                Debug.Assert(arraySegment.Array != null);
+                Debug.Assert(arraySegment.Offset >= 0);
+                Debug.Assert(arraySegment.Count >= 0);
+                Debug.Assert(arraySegment.Offset + arraySegment.Count <= arraySegment.Array.Length);
+
+                _array = arraySegment.Array;
+                _start = arraySegment.Offset;
+                _end = arraySegment.Offset + arraySegment.Count;
+                _current = arraySegment.Offset - 1;
+            }
+
+            public bool MoveNext()
+            {
+                if (_current < _end)
+                {
+                    _current++;
+                    return (_current < _end);
+                }
+                return false;
+            }
+
+            public T Current
+            {
+                get
+                {
+                    if (_current < _start)
+                        ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumNotStarted();
+                    if (_current >= _end)
+                        ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumEnded();
+                    return _array[_current];
+                }
+            }
+
+            object IEnumerator.Current => Current;
+
+            void IEnumerator.Reset()
+            {
+                _current = _start - 1;
+            }
+
+            public void Dispose()
+            {
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ArrayTypeMismatchException.cs b/src/System.Private.CoreLib/shared/System/ArrayTypeMismatchException.cs
new file mode 100644
index 0000000000..49820f58f5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ArrayTypeMismatchException.cs
@@ -0,0 +1,53 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: The arrays are of different primitive types.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    // The ArrayMismatchException is thrown when an attempt to store
+    // an object of the wrong type within an array occurs.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class ArrayTypeMismatchException : SystemException
+    {
+        // Creates a new ArrayMismatchException with its message string set to
+        // the empty string, its HRESULT set to COR_E_ARRAYTYPEMISMATCH, 
+        // and its ExceptionInfo reference set to null. 
+        public ArrayTypeMismatchException()
+            : base(SR.Arg_ArrayTypeMismatchException)
+        {
+            HResult = HResults.COR_E_ARRAYTYPEMISMATCH;
+        }
+
+        // Creates a new ArrayMismatchException with its message string set to
+        // message, its HRESULT set to COR_E_ARRAYTYPEMISMATCH, 
+        // and its ExceptionInfo reference set to null. 
+        // 
+        public ArrayTypeMismatchException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_ARRAYTYPEMISMATCH;
+        }
+
+        public ArrayTypeMismatchException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_ARRAYTYPEMISMATCH;
+        }
+
+        protected ArrayTypeMismatchException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/AssemblyLoadEventArgs.cs b/src/System.Private.CoreLib/shared/System/AssemblyLoadEventArgs.cs
new file mode 100644
index 0000000000..d7e5249693
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/AssemblyLoadEventArgs.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+
+namespace System
+{
+    public class AssemblyLoadEventArgs : EventArgs
+    {
+        public AssemblyLoadEventArgs(Assembly loadedAssembly)
+        {
+            LoadedAssembly = loadedAssembly;
+        }
+
+        public Assembly LoadedAssembly { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/AssemblyLoadEventHandler.cs b/src/System.Private.CoreLib/shared/System/AssemblyLoadEventHandler.cs
new file mode 100644
index 0000000000..752379fdc7
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/AssemblyLoadEventHandler.cs
@@ -0,0 +1,8 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    public delegate void AssemblyLoadEventHandler(object sender, AssemblyLoadEventArgs args);
+}
diff --git a/src/System.Private.CoreLib/shared/System/AsyncCallback.cs b/src/System.Private.CoreLib/shared/System/AsyncCallback.cs
new file mode 100644
index 0000000000..036d44a4b9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/AsyncCallback.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Interface: AsyncCallbackDelegate
+**
+** Purpose: Type of callback for async operations
+**
+===========================================================*/
+
+namespace System
+{
+    public delegate void AsyncCallback(IAsyncResult ar);
+}
diff --git a/src/System.Private.CoreLib/shared/System/AttributeTargets.cs b/src/System.Private.CoreLib/shared/System/AttributeTargets.cs
new file mode 100644
index 0000000000..c33d19e85e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/AttributeTargets.cs
@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+
+namespace System
+{
+    // Enum used to indicate all the elements of the
+    // VOS it is valid to attach this element to.
+    [Flags]
+    public enum AttributeTargets
+    {
+        Assembly = 0x0001,
+        Module = 0x0002,
+        Class = 0x0004,
+        Struct = 0x0008,
+        Enum = 0x0010,
+        Constructor = 0x0020,
+        Method = 0x0040,
+        Property = 0x0080,
+        Field = 0x0100,
+        Event = 0x0200,
+        Interface = 0x0400,
+        Parameter = 0x0800,
+        Delegate = 0x1000,
+        ReturnValue = 0x2000,
+        GenericParameter = 0x4000,
+
+        All = Assembly | Module | Class | Struct | Enum | Constructor |
+                        Method | Property | Field | Event | Interface | Parameter |
+                        Delegate | ReturnValue | GenericParameter
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/AttributeUsageAttribute.cs b/src/System.Private.CoreLib/shared/System/AttributeUsageAttribute.cs
new file mode 100644
index 0000000000..219dc43e15
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/AttributeUsageAttribute.cs
@@ -0,0 +1,57 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: The class denotes how to specify the usage of an attribute
+**          
+**
+===========================================================*/
+
+using System.Reflection;
+
+namespace System
+{
+    /* By default, attributes are inherited and multiple attributes are not allowed */
+    [AttributeUsage(AttributeTargets.Class, Inherited = true)]
+    public sealed class AttributeUsageAttribute : Attribute
+    {
+        private AttributeTargets _attributeTarget = AttributeTargets.All; // Defaults to all
+        private bool _allowMultiple = false; // Defaults to false
+        private bool _inherited = true; // Defaults to true
+
+        internal static AttributeUsageAttribute Default = new AttributeUsageAttribute(AttributeTargets.All);
+
+        //Constructors 
+        public AttributeUsageAttribute(AttributeTargets validOn)
+        {
+            _attributeTarget = validOn;
+        }
+        internal AttributeUsageAttribute(AttributeTargets validOn, bool allowMultiple, bool inherited)
+        {
+            _attributeTarget = validOn;
+            _allowMultiple = allowMultiple;
+            _inherited = inherited;
+        }
+
+        public AttributeTargets ValidOn
+        {
+            get { return _attributeTarget; }
+        }
+
+        public bool AllowMultiple
+        {
+            get { return _allowMultiple; }
+            set { _allowMultiple = value; }
+        }
+
+        public bool Inherited
+        {
+            get { return _inherited; }
+            set { _inherited = value; }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/BadImageFormatException.cs b/src/System.Private.CoreLib/shared/System/BadImageFormatException.cs
new file mode 100644
index 0000000000..1743075a6f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/BadImageFormatException.cs
@@ -0,0 +1,129 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Exception to an invalid dll or executable format.
+**
+** 
+===========================================================*/
+
+using System.Globalization;
+using System.IO;
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public partial class BadImageFormatException : SystemException
+    {
+        private String _fileName;  // The name of the corrupt PE file.
+        private String _fusionLog = null;  // fusion log (when applicable)
+
+        public BadImageFormatException()
+            : base(SR.Arg_BadImageFormatException)
+        {
+            HResult = HResults.COR_E_BADIMAGEFORMAT;
+        }
+
+        public BadImageFormatException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_BADIMAGEFORMAT;
+        }
+
+        public BadImageFormatException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_BADIMAGEFORMAT;
+        }
+
+        public BadImageFormatException(String message, String fileName) : base(message)
+        {
+            HResult = HResults.COR_E_BADIMAGEFORMAT;
+            _fileName = fileName;
+        }
+
+        public BadImageFormatException(String message, String fileName, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_BADIMAGEFORMAT;
+            _fileName = fileName;
+        }
+
+        protected BadImageFormatException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            _fileName = info.GetString("BadImageFormat_FileName");
+            _fusionLog = info.GetString("BadImageFormat_FusionLog");
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("BadImageFormat_FileName", _fileName, typeof(string));
+            info.AddValue("BadImageFormat_FusionLog", _fusionLog, typeof(string));
+        }
+
+        public override String Message
+        {
+            get
+            {
+                SetMessageField();
+                return _message;
+            }
+        }
+
+        private void SetMessageField()
+        {
+            if (_message == null)
+            {
+                if ((_fileName == null) &&
+                    (HResult == HResults.COR_E_EXCEPTION))
+                    _message = SR.Arg_BadImageFormatException;
+
+                else
+                    _message = FileLoadException.FormatFileLoadExceptionMessage(_fileName, HResult);
+            }
+        }
+
+        public String FileName
+        {
+            get { return _fileName; }
+        }
+
+        public override String ToString()
+        {
+            String s = GetType().ToString() + ": " + Message;
+
+            if (_fileName != null && _fileName.Length != 0)
+                s += Environment.NewLine + SR.Format(SR.IO_FileName_Name, _fileName);
+
+            if (InnerException != null)
+                s = s + " ---> " + InnerException.ToString();
+
+            if (StackTrace != null)
+                s += Environment.NewLine + StackTrace;
+
+            if (_fusionLog != null)
+            {
+                if (s == null)
+                    s = " ";
+                s += Environment.NewLine;
+                s += Environment.NewLine;
+                s += _fusionLog;
+            }
+
+            return s;
+        }
+
+        public String FusionLog
+        {
+            get { return _fusionLog; }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/BitConverter.cs b/src/System.Private.CoreLib/shared/System/BitConverter.cs
new file mode 100644
index 0000000000..e3cf20eb6a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/BitConverter.cs
@@ -0,0 +1,474 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+using Internal.Runtime.CompilerServices;
+
+namespace System
+{
+    // The BitConverter class contains methods for
+    // converting an array of bytes to one of the base data 
+    // types, as well as for converting a base data type to an
+    // array of bytes.
+    public static class BitConverter
+    {
+        // This field indicates the "endianess" of the architecture.
+        // The value is set to true if the architecture is
+        // little endian; false if it is big endian.
+#if BIGENDIAN
+        public static readonly bool IsLittleEndian /* = false */;
+#else
+        public static readonly bool IsLittleEndian = true;
+#endif
+
+        // Converts a Boolean into an array of bytes with length one.
+        public static byte[] GetBytes(bool value)
+        {
+            byte[] r = new byte[1];
+            r[0] = (value ? (byte)1 : (byte)0);
+            return r;
+        }
+
+        // Converts a Boolean into a Span of bytes with length one.
+        public static bool TryWriteBytes(Span<byte> destination, bool value)
+        {
+            if (destination.Length < sizeof(byte))
+                return false;
+
+            Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), value ? (byte)1 : (byte)0);
+            return true;
+        }
+
+        // Converts a char into an array of bytes with length two.
+        public static byte[] GetBytes(char value)
+        {
+            byte[] bytes = new byte[sizeof(char)];
+            Unsafe.As<byte, char>(ref bytes[0]) = value;
+            return bytes;
+        }
+
+        // Converts a char into a Span
+        public static bool TryWriteBytes(Span<byte> destination, char value)
+        {
+            if (destination.Length < sizeof(char))
+                return false;
+
+            Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), value);
+            return true;
+        }
+
+        // Converts a short into an array of bytes with length
+        // two.
+        public static byte[] GetBytes(short value)
+        {
+            byte[] bytes = new byte[sizeof(short)];
+            Unsafe.As<byte, short>(ref bytes[0]) = value;
+            return bytes;
+        }
+
+        // Converts a short into a Span
+        public static bool TryWriteBytes(Span<byte> destination, short value)
+        {
+            if (destination.Length < sizeof(short))
+                return false;
+
+            Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), value);
+            return true;
+        }
+
+        // Converts an int into an array of bytes with length 
+        // four.
+        public static byte[] GetBytes(int value)
+        {
+            byte[] bytes = new byte[sizeof(int)];
+            Unsafe.As<byte, int>(ref bytes[0]) = value;
+            return bytes;
+        }
+
+        // Converts an int into a Span
+        public static bool TryWriteBytes(Span<byte> destination, int value)
+        {
+            if (destination.Length < sizeof(int))
+                return false;
+
+            Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), value);
+            return true;
+        }
+
+        // Converts a long into an array of bytes with length 
+        // eight.
+        public static byte[] GetBytes(long value)
+        {
+            byte[] bytes = new byte[sizeof(long)];
+            Unsafe.As<byte, long>(ref bytes[0]) = value;
+            return bytes;
+        }
+
+        // Converts a long into a Span
+        public static bool TryWriteBytes(Span<byte> destination, long value)
+        {
+            if (destination.Length < sizeof(long))
+                return false;
+
+            Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), value);
+            return true;
+        }
+
+        // Converts an ushort into an array of bytes with
+        // length two.
+        [CLSCompliant(false)]
+        public static byte[] GetBytes(ushort value)
+        {
+            byte[] bytes = new byte[sizeof(ushort)];
+            Unsafe.As<byte, ushort>(ref bytes[0]) = value;
+            return bytes;
+        }
+
+        // Converts a ushort into a Span
+        [CLSCompliant(false)]
+        public static bool TryWriteBytes(Span<byte> destination, ushort value)
+        {
+            if (destination.Length < sizeof(ushort))
+                return false;
+
+            Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), value);
+            return true;
+        }
+
+        // Converts an uint into an array of bytes with
+        // length four.
+        [CLSCompliant(false)]
+        public static byte[] GetBytes(uint value)
+        {
+            byte[] bytes = new byte[sizeof(uint)];
+            Unsafe.As<byte, uint>(ref bytes[0]) = value;
+            return bytes;
+        }
+
+        // Converts a uint into a Span
+        [CLSCompliant(false)]
+        public static bool TryWriteBytes(Span<byte> destination, uint value)
+        {
+            if (destination.Length < sizeof(uint))
+                return false;
+
+            Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), value);
+            return true;
+        }
+
+        // Converts an unsigned long into an array of bytes with
+        // length eight.
+        [CLSCompliant(false)]
+        public static byte[] GetBytes(ulong value)
+        {
+            byte[] bytes = new byte[sizeof(ulong)];
+            Unsafe.As<byte, ulong>(ref bytes[0]) = value;
+            return bytes;
+        }
+
+        // Converts a ulong into a Span
+        [CLSCompliant(false)]
+        public static bool TryWriteBytes(Span<byte> destination, ulong value)
+        {
+            if (destination.Length < sizeof(ulong))
+                return false;
+
+            Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), value);
+            return true;
+        }
+
+        // Converts a float into an array of bytes with length 
+        // four.
+        public static byte[] GetBytes(float value)
+        {
+            byte[] bytes = new byte[sizeof(float)];
+            Unsafe.As<byte, float>(ref bytes[0]) = value;
+            return bytes;
+        }
+
+        // Converts a float into a Span
+        public static bool TryWriteBytes(Span<byte> destination, float value)
+        {
+            if (destination.Length < sizeof(float))
+                return false;
+
+            Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), value);
+            return true;
+        }
+
+        // Converts a double into an array of bytes with length 
+        // eight.
+        public static byte[] GetBytes(double value)
+        {
+            byte[] bytes = new byte[sizeof(double)];
+            Unsafe.As<byte, double>(ref bytes[0]) = value;
+            return bytes;
+        }
+
+        // Converts a double into a Span
+        public static bool TryWriteBytes(Span<byte> destination, double value)
+        {
+            if (destination.Length < sizeof(double))
+                return false;
+
+            Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), value);
+            return true;
+        }
+
+        // Converts an array of bytes into a char.  
+        public static char ToChar(byte[] value, int startIndex) => unchecked((char)ToInt16(value, startIndex));
+
+        // Converts a Span into a char
+        public static char ToChar(ReadOnlySpan<byte> value)
+        {
+            if (value.Length < sizeof(char))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.value);
+            return Unsafe.ReadUnaligned<char>(ref MemoryMarshal.GetReference(value));
+        }
+
+        // Converts an array of bytes into a short.  
+        public static short ToInt16(byte[] value, int startIndex)
+        {
+            if (value == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
+            if (unchecked((uint)startIndex) >= unchecked((uint)value.Length))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index);
+            if (startIndex > value.Length - sizeof(short))
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall, ExceptionArgument.value);
+
+            return Unsafe.ReadUnaligned<short>(ref value[startIndex]);
+        }
+
+        // Converts a Span into a short
+        public static short ToInt16(ReadOnlySpan<byte> value)
+        {
+            if (value.Length < sizeof(short))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.value);
+            return Unsafe.ReadUnaligned<short>(ref MemoryMarshal.GetReference(value));
+        }
+
+        // Converts an array of bytes into an int.  
+        public static int ToInt32(byte[] value, int startIndex)
+        {
+            if (value == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
+            if (unchecked((uint)startIndex) >= unchecked((uint)value.Length))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index);
+            if (startIndex > value.Length - sizeof(int))
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall, ExceptionArgument.value);
+
+            return Unsafe.ReadUnaligned<int>(ref value[startIndex]);
+        }
+
+        // Converts a Span into an int
+        public static int ToInt32(ReadOnlySpan<byte> value)
+        {
+            if (value.Length < sizeof(int))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.value);
+            return Unsafe.ReadUnaligned<int>(ref MemoryMarshal.GetReference(value));
+        }
+
+        // Converts an array of bytes into a long.  
+        public static long ToInt64(byte[] value, int startIndex)
+        {
+            if (value == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
+            if (unchecked((uint)startIndex) >= unchecked((uint)value.Length))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index);
+            if (startIndex > value.Length - sizeof(long))
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall, ExceptionArgument.value);
+
+            return Unsafe.ReadUnaligned<long>(ref value[startIndex]);
+        }
+
+        // Converts a Span into a long
+        public static long ToInt64(ReadOnlySpan<byte> value)
+        {
+            if (value.Length < sizeof(long))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.value);
+            return Unsafe.ReadUnaligned<long>(ref MemoryMarshal.GetReference(value));
+        }
+
+        // Converts an array of bytes into an ushort.
+        // 
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(byte[] value, int startIndex) => unchecked((ushort)ToInt16(value, startIndex));
+
+        // Converts a Span into a ushort
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(ReadOnlySpan<byte> value)
+        {
+            if (value.Length < sizeof(ushort))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.value);
+            return Unsafe.ReadUnaligned<ushort>(ref MemoryMarshal.GetReference(value));
+        }
+
+        // Converts an array of bytes into an uint.
+        // 
+        [CLSCompliant(false)]
+        public static uint ToUInt32(byte[] value, int startIndex) => unchecked((uint)ToInt32(value, startIndex));
+
+        // Convert a Span into a uint
+        [CLSCompliant(false)]
+        public static uint ToUInt32(ReadOnlySpan<byte> value)
+        {
+            if (value.Length < sizeof(uint))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.value);
+            return Unsafe.ReadUnaligned<uint>(ref MemoryMarshal.GetReference(value));
+        }
+
+        // Converts an array of bytes into an unsigned long.
+        // 
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(byte[] value, int startIndex) => unchecked((ulong)ToInt64(value, startIndex));
+
+        // Converts a Span into an unsigned long
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(ReadOnlySpan<byte> value)
+        {
+            if (value.Length < sizeof(ulong))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.value);
+            return Unsafe.ReadUnaligned<ulong>(ref MemoryMarshal.GetReference(value));
+        }
+
+        // Converts an array of bytes into a float.  
+        public static float ToSingle(byte[] value, int startIndex) => Int32BitsToSingle(ToInt32(value, startIndex));
+
+        // Converts a Span into a float
+        public static float ToSingle(ReadOnlySpan<byte> value)
+        {
+            if (value.Length < sizeof(float))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.value);
+            return Unsafe.ReadUnaligned<float>(ref MemoryMarshal.GetReference(value));
+        }
+
+        // Converts an array of bytes into a double.  
+        public static double ToDouble(byte[] value, int startIndex) => Int64BitsToDouble(ToInt64(value, startIndex));
+
+        // Converts a Span into a double
+        public static double ToDouble(ReadOnlySpan<byte> value)
+        {
+            if (value.Length < sizeof(double))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.value);
+            return Unsafe.ReadUnaligned<double>(ref MemoryMarshal.GetReference(value));
+        }
+
+        // Converts an array of bytes into a String.  
+        public static string ToString(byte[] value, int startIndex, int length)
+        {
+            if (value == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
+            if (startIndex < 0 || startIndex >= value.Length && startIndex > 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index);
+            if (length < 0)
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_GenericPositive);
+            if (startIndex > value.Length - length)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall, ExceptionArgument.value);
+
+            if (length == 0)
+            {
+                return string.Empty;
+            }
+
+            if (length > (int.MaxValue / 3))
+            {
+                // (Int32.MaxValue / 3) == 715,827,882 Bytes == 699 MB
+                throw new ArgumentOutOfRangeException(nameof(length), SR.Format(SR.ArgumentOutOfRange_LengthTooLarge, (int.MaxValue / 3)));
+            }
+
+            return string.Create(length * 3 - 1, (value, startIndex, length), (dst, state) =>
+            {
+                const string HexValues = "0123456789ABCDEF";
+
+                var src = new ReadOnlySpan<byte>(state.value, state.startIndex, state.length);
+
+                int i = 0;
+                int j = 0;
+
+                byte b = src[i++];
+                dst[j++] = HexValues[b >> 4];
+                dst[j++] = HexValues[b & 0xF];
+
+                while (i < src.Length)
+                {
+                    b = src[i++];
+                    dst[j++] = '-';
+                    dst[j++] = HexValues[b >> 4];
+                    dst[j++] = HexValues[b & 0xF];
+                }
+            });
+        }
+
+        // Converts an array of bytes into a String.  
+        public static string ToString(byte[] value)
+        {
+            if (value == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
+            return ToString(value, 0, value.Length);
+        }
+
+        // Converts an array of bytes into a String.  
+        public static string ToString(byte[] value, int startIndex)
+        {
+            if (value == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
+            return ToString(value, startIndex, value.Length - startIndex);
+        }
+
+        /*==================================ToBoolean===================================
+        **Action:  Convert an array of bytes to a boolean value.  We treat this array 
+        **         as if the first 4 bytes were an Int4 an operate on this value.
+        **Returns: True if the Int4 value of the first 4 bytes is non-zero.
+        **Arguments: value -- The byte array
+        **           startIndex -- The position within the array.
+        **Exceptions: See ToInt4.
+        ==============================================================================*/
+        // Converts an array of bytes into a boolean.  
+        public static bool ToBoolean(byte[] value, int startIndex)
+        {
+            if (value == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
+            if (startIndex < 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index);
+            if (startIndex > value.Length - 1)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index); // differs from other overloads, which throw base ArgumentException
+
+            return value[startIndex] != 0;
+        }
+
+        public static bool ToBoolean(ReadOnlySpan<byte> value)
+        {
+            if (value.Length < sizeof(byte))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.value);
+            return Unsafe.ReadUnaligned<byte>(ref MemoryMarshal.GetReference(value)) != 0;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe long DoubleToInt64Bits(double value)
+        {
+            return *((long*)&value);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe double Int64BitsToDouble(long value)
+        {
+            return *((double*)&value);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe int SingleToInt32Bits(float value)
+        {
+            return *((int*)&value);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe float Int32BitsToSingle(int value)
+        {
+            return *((float*)&value);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Boolean.cs b/src/System.Private.CoreLib/shared/System/Boolean.cs
new file mode 100644
index 0000000000..fdbc905332
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Boolean.cs
@@ -0,0 +1,349 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: The boolean class serves as a wrapper for the primitive
+** type boolean.
+**
+** 
+===========================================================*/
+
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    [Serializable]
+    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct Boolean : IComparable, IConvertible, IComparable<Boolean>, IEquatable<Boolean>
+    {
+        //
+        // Member Variables
+        //
+        private bool m_value; // Do not rename (binary serialization)
+
+        // The true value.
+        //
+        internal const int True = 1;
+
+        // The false value.
+        //
+        internal const int False = 0;
+
+
+        //
+        // Internal Constants are real consts for performance.
+        //
+
+        // The internal string representation of true.
+        // 
+        internal const String TrueLiteral = "True";
+
+        // The internal string representation of false.
+        // 
+        internal const String FalseLiteral = "False";
+
+
+        //
+        // Public Constants
+        //
+
+        // The public string representation of true.
+        // 
+        public static readonly String TrueString = TrueLiteral;
+
+        // The public string representation of false.
+        // 
+        public static readonly String FalseString = FalseLiteral;
+
+        //
+        // Overriden Instance Methods
+        //
+        /*=================================GetHashCode==================================
+        **Args:  None
+        **Returns: 1 or 0 depending on whether this instance represents true or false.
+        **Exceptions: None
+        **Overriden From: Value
+        ==============================================================================*/
+        // Provides a hash code for this instance.
+        public override int GetHashCode()
+        {
+            return (m_value) ? True : False;
+        }
+
+        /*===================================ToString===================================
+        **Args: None
+        **Returns:  "True" or "False" depending on the state of the boolean.
+        **Exceptions: None.
+        ==============================================================================*/
+        // Converts the boolean value of this instance to a String.
+        public override String ToString()
+        {
+            if (false == m_value)
+            {
+                return FalseLiteral;
+            }
+            return TrueLiteral;
+        }
+
+        public String ToString(IFormatProvider provider)
+        {
+            return ToString();
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten)
+        {
+            string s = m_value ? TrueLiteral : FalseLiteral;
+
+            if (s.AsSpan().TryCopyTo(destination))
+            {
+                charsWritten = s.Length;
+                return true;
+            }
+            else
+            {
+                charsWritten = 0;
+                return false;
+            }
+        }
+
+        // Determines whether two Boolean objects are equal.
+        public override bool Equals(Object obj)
+        {
+            //If it's not a boolean, we're definitely not equal
+            if (!(obj is Boolean))
+            {
+                return false;
+            }
+
+            return (m_value == ((Boolean)obj).m_value);
+        }
+
+        [NonVersionable]
+        public bool Equals(Boolean obj)
+        {
+            return m_value == obj;
+        }
+
+        // Compares this object to another object, returning an integer that
+        // indicates the relationship. For booleans, false sorts before true.
+        // null is considered to be less than any instance.
+        // If object is not of type boolean, this method throws an ArgumentException.
+        // 
+        // Returns a value less than zero if this  object
+        // 
+        public int CompareTo(Object obj)
+        {
+            if (obj == null)
+            {
+                return 1;
+            }
+            if (!(obj is Boolean))
+            {
+                throw new ArgumentException(SR.Arg_MustBeBoolean);
+            }
+
+            if (m_value == ((Boolean)obj).m_value)
+            {
+                return 0;
+            }
+            else if (m_value == false)
+            {
+                return -1;
+            }
+            return 1;
+        }
+
+        public int CompareTo(Boolean value)
+        {
+            if (m_value == value)
+            {
+                return 0;
+            }
+            else if (m_value == false)
+            {
+                return -1;
+            }
+            return 1;
+        }
+
+        //
+        // Static Methods
+        // 
+
+        // Determines whether a String represents true or false.
+        // 
+        public static Boolean Parse(String value)
+        {
+            if (value == null) throw new ArgumentNullException(nameof(value));
+            return Parse(value.AsSpan());
+        }
+
+        public static bool Parse(ReadOnlySpan<char> value) =>
+            TryParse(value, out bool result) ? result : throw new FormatException(SR.Format(SR.Format_BadBoolean, new string(value)));
+
+        // Determines whether a String represents true or false.
+        // 
+        public static Boolean TryParse(String value, out Boolean result)
+        {
+            if (value == null)
+            {
+                result = false;
+                return false;
+            }
+
+            return TryParse(value.AsSpan(), out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> value, out bool result)
+        {
+            ReadOnlySpan<char> trueSpan = TrueLiteral.AsSpan();
+            if (trueSpan.EqualsOrdinalIgnoreCase(value))
+            {
+                result = true;
+                return true;
+            }
+
+            ReadOnlySpan<char> falseSpan = FalseLiteral.AsSpan();
+            if (falseSpan.EqualsOrdinalIgnoreCase(value))
+            {
+                result = false;
+                return true;
+            }
+
+            // Special case: Trim whitespace as well as null characters.
+            value = TrimWhiteSpaceAndNull(value);
+
+            if (trueSpan.EqualsOrdinalIgnoreCase(value))
+            {
+                result = true;
+                return true;
+            }
+
+            if (falseSpan.EqualsOrdinalIgnoreCase(value))
+            {
+                result = false;
+                return true;
+            }
+
+            result = false;
+            return false;
+        }
+
+        private static ReadOnlySpan<char> TrimWhiteSpaceAndNull(ReadOnlySpan<char> value)
+        {
+            const char nullChar = (char)0x0000;
+
+            int start = 0;
+            while (start < value.Length)
+            {
+                if (!Char.IsWhiteSpace(value[start]) && value[start] != nullChar)
+                {
+                    break;
+                }
+                start++;
+            }
+
+            int end = value.Length - 1;
+            while (end >= start)
+            {
+                if (!Char.IsWhiteSpace(value[end]) && value[end] != nullChar)
+                {
+                    break;
+                }
+                end--;
+            }
+
+            return value.Slice(start, end - start + 1);
+        }
+
+        //
+        // IConvertible implementation
+        // 
+
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.Boolean;
+        }
+
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            return m_value;
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Boolean", "Char"));
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return Convert.ToSByte(m_value);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return Convert.ToByte(m_value);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return Convert.ToInt16(m_value);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return Convert.ToUInt16(m_value);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return Convert.ToInt32(m_value);
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return Convert.ToUInt32(m_value);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return Convert.ToInt64(m_value);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return Convert.ToUInt64(m_value);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            return Convert.ToSingle(m_value);
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            return Convert.ToDouble(m_value);
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            return Convert.ToDecimal(m_value);
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Boolean", "DateTime"));
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/ArrayPool.cs b/src/System.Private.CoreLib/shared/System/Buffers/ArrayPool.cs
new file mode 100644
index 0000000000..22ad7821f0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Buffers/ArrayPool.cs
@@ -0,0 +1,98 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Buffers
+{
+    /// <summary>
+    /// Provides a resource pool that enables reusing instances of type <see cref="T:T[]"/>. 
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// Renting and returning buffers with an <see cref="ArrayPool{T}"/> can increase performance
+    /// in situations where arrays are created and destroyed frequently, resulting in significant
+    /// memory pressure on the garbage collector.
+    /// </para>
+    /// <para>
+    /// This class is thread-safe.  All members may be used by multiple threads concurrently.
+    /// </para>
+    /// </remarks>
+    public abstract class ArrayPool<T>
+    {
+        /// <summary>
+        /// Retrieves a shared <see cref="ArrayPool{T}"/> instance.
+        /// </summary>
+        /// <remarks>
+        /// The shared pool provides a default implementation of <see cref="ArrayPool{T}"/>
+        /// that's intended for general applicability.  It maintains arrays of multiple sizes, and 
+        /// may hand back a larger array than was actually requested, but will never hand back a smaller 
+        /// array than was requested. Renting a buffer from it with <see cref="Rent"/> will result in an 
+        /// existing buffer being taken from the pool if an appropriate buffer is available or in a new 
+        /// buffer being allocated if one is not available.
+        /// byte[] and char[] are the most commonly pooled array types. For these we use a special pool type
+        /// optimized for very fast access speeds, at the expense of more memory consumption.
+        /// The shared pool instance is created lazily on first access.
+        /// </remarks>
+        public static ArrayPool<T> Shared { get; } = new TlsOverPerCoreLockedStacksArrayPool<T>();
+
+        /// <summary>
+        /// Creates a new <see cref="ArrayPool{T}"/> instance using default configuration options.
+        /// </summary>
+        /// <returns>A new <see cref="ArrayPool{T}"/> instance.</returns>
+        public static ArrayPool<T> Create() => new ConfigurableArrayPool<T>();
+
+        /// <summary>
+        /// Creates a new <see cref="ArrayPool{T}"/> instance using custom configuration options.
+        /// </summary>
+        /// <param name="maxArrayLength">The maximum length of array instances that may be stored in the pool.</param>
+        /// <param name="maxArraysPerBucket">
+        /// The maximum number of array instances that may be stored in each bucket in the pool.  The pool
+        /// groups arrays of similar lengths into buckets for faster access.
+        /// </param>
+        /// <returns>A new <see cref="ArrayPool{T}"/> instance with the specified configuration options.</returns>
+        /// <remarks>
+        /// The created pool will group arrays into buckets, with no more than <paramref name="maxArraysPerBucket"/>
+        /// in each bucket and with those arrays not exceeding <paramref name="maxArrayLength"/> in length.
+        /// </remarks>
+        public static ArrayPool<T> Create(int maxArrayLength, int maxArraysPerBucket) =>
+            new ConfigurableArrayPool<T>(maxArrayLength, maxArraysPerBucket);
+
+        /// <summary>
+        /// Retrieves a buffer that is at least the requested length.
+        /// </summary>
+        /// <param name="minimumLength">The minimum length of the array needed.</param>
+        /// <returns>
+        /// An <see cref="T:T[]"/> that is at least <paramref name="minimumLength"/> in length.
+        /// </returns>
+        /// <remarks>
+        /// This buffer is loaned to the caller and should be returned to the same pool via 
+        /// <see cref="Return"/> so that it may be reused in subsequent usage of <see cref="Rent"/>.  
+        /// It is not a fatal error to not return a rented buffer, but failure to do so may lead to 
+        /// decreased application performance, as the pool may need to create a new buffer to replace
+        /// the one lost.
+        /// </remarks>
+        public abstract T[] Rent(int minimumLength);
+
+        /// <summary>
+        /// Returns to the pool an array that was previously obtained via <see cref="Rent"/> on the same 
+        /// <see cref="ArrayPool{T}"/> instance.
+        /// </summary>
+        /// <param name="array">
+        /// The buffer previously obtained from <see cref="Rent"/> to return to the pool.
+        /// </param>
+        /// <param name="clearArray">
+        /// If <c>true</c> and if the pool will store the buffer to enable subsequent reuse, <see cref="Return"/>
+        /// will clear <paramref name="array"/> of its contents so that a subsequent consumer via <see cref="Rent"/> 
+        /// will not see the previous consumer's content.  If <c>false</c> or if the pool will release the buffer,
+        /// the array's contents are left unchanged.
+        /// </param>
+        /// <remarks>
+        /// Once a buffer has been returned to the pool, the caller gives up all ownership of the buffer 
+        /// and must not use it. The reference returned from a given call to <see cref="Rent"/> must only be
+        /// returned via <see cref="Return"/> once.  The default <see cref="ArrayPool{T}"/>
+        /// may hold onto the returned buffer in order to rent it again, or it may release the returned buffer
+        /// if it's determined that the pool already has enough buffers stored.
+        /// </remarks>
+        public abstract void Return(T[] array, bool clearArray = false);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/ArrayPoolEventSource.cs b/src/System.Private.CoreLib/shared/System/Buffers/ArrayPoolEventSource.cs
new file mode 100644
index 0000000000..d0563c4977
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Buffers/ArrayPoolEventSource.cs
@@ -0,0 +1,104 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics.Tracing;
+
+namespace System.Buffers
+{
+    [EventSource(Guid = "0866B2B8-5CEF-5DB9-2612-0C0FFD814A44", Name = "System.Buffers.ArrayPoolEventSource")]
+    internal sealed class ArrayPoolEventSource : EventSource
+    {
+        internal readonly static ArrayPoolEventSource Log = new ArrayPoolEventSource();
+
+        /// <summary>The reason for a BufferAllocated event.</summary>
+        internal enum BufferAllocatedReason : int
+        {
+            /// <summary>The pool is allocating a buffer to be pooled in a bucket.</summary>
+            Pooled,
+            /// <summary>The requested buffer size was too large to be pooled.</summary>
+            OverMaximumSize,
+            /// <summary>The pool has already allocated for pooling as many buffers of a particular size as it's allowed.</summary>
+            PoolExhausted
+        }
+
+        // The ArrayPoolEventSource GUID is {0866b2b8-5cef-5db9-2612-0c0ffd814a44}
+        private ArrayPoolEventSource() : base(new Guid(0x0866b2b8, 0x5cef, 0x5db9, 0x26, 0x12, 0x0c, 0x0f, 0xfd, 0x81, 0x4a, 0x44), "System.Buffers.ArrayPoolEventSource") { }
+
+        /// <summary>
+        /// Event for when a buffer is rented.  This is invoked once for every successful call to Rent,
+        /// regardless of whether a buffer is allocated or a buffer is taken from the pool.  In a
+        /// perfect situation where all rented buffers are returned, we expect to see the number
+        /// of BufferRented events exactly match the number of BuferReturned events, with the number
+        /// of BufferAllocated events being less than or equal to those numbers (ideally significantly
+        /// less than).
+        /// </summary>
+        [Event(1, Level = EventLevel.Verbose)]
+        internal unsafe void BufferRented(int bufferId, int bufferSize, int poolId, int bucketId)
+        {
+            EventData* payload = stackalloc EventData[4];
+            payload[0].Size = sizeof(int);
+            payload[0].DataPointer = ((IntPtr)(&bufferId));
+            payload[0].Reserved = 0;
+            payload[1].Size = sizeof(int);
+            payload[1].DataPointer = ((IntPtr)(&bufferSize));
+            payload[1].Reserved = 0;
+            payload[2].Size = sizeof(int);
+            payload[2].DataPointer = ((IntPtr)(&poolId));
+            payload[2].Reserved = 0;
+            payload[3].Size = sizeof(int);
+            payload[3].DataPointer = ((IntPtr)(&bucketId));
+            payload[3].Reserved = 0;
+            WriteEventCore(1, 4, payload);
+        }
+
+        /// <summary>
+        /// Event for when a buffer is allocated by the pool.  In an ideal situation, the number
+        /// of BufferAllocated events is significantly smaller than the number of BufferRented and
+        /// BufferReturned events.
+        /// </summary>
+        [Event(2, Level = EventLevel.Informational)]
+        internal unsafe void BufferAllocated(int bufferId, int bufferSize, int poolId, int bucketId, BufferAllocatedReason reason)
+        {
+            EventData* payload = stackalloc EventData[5];
+            payload[0].Size = sizeof(int);
+            payload[0].DataPointer = ((IntPtr)(&bufferId));
+            payload[0].Reserved = 0;
+            payload[1].Size = sizeof(int);
+            payload[1].DataPointer = ((IntPtr)(&bufferSize));
+            payload[1].Reserved = 0;
+            payload[2].Size = sizeof(int);
+            payload[2].DataPointer = ((IntPtr)(&poolId));
+            payload[2].Reserved = 0;
+            payload[3].Size = sizeof(int);
+            payload[3].DataPointer = ((IntPtr)(&bucketId));
+            payload[3].Reserved = 0;
+            payload[4].Size = sizeof(BufferAllocatedReason);
+            payload[4].DataPointer = ((IntPtr)(&reason));
+            payload[4].Reserved = 0;
+            WriteEventCore(2, 5, payload);
+        }
+
+        /// <summary>
+        /// Event raised when a buffer is returned to the pool.  This event is raised regardless of whether
+        /// the returned buffer is stored or dropped.  In an ideal situation, the number of BufferReturned
+        /// events exactly matches the number of BufferRented events.
+        /// </summary>
+        [Event(3, Level = EventLevel.Verbose)]
+        internal void BufferReturned(int bufferId, int bufferSize, int poolId) => WriteEvent(3, bufferId, bufferSize, poolId);
+
+        /// <summary>
+        /// Event raised when we attempt to free a buffer due to inactivity or memory pressure (by no longer
+        /// referencing it). It is possible (although not commmon) this buffer could be rented as we attempt
+        /// to free it. A rent event before or after this event for the same ID, is a rare, but expected case.
+        /// </summary>
+        [Event(4, Level = EventLevel.Informational)]
+        internal void BufferTrimmed(int bufferId, int bufferSize, int poolId) => WriteEvent(4, bufferId, bufferSize, poolId);
+
+        /// <summary>
+        /// Event raised when we check to trim buffers.
+        /// </summary>
+        [Event(5, Level = EventLevel.Informational)]
+        internal void BufferTrimPoll(int milliseconds, int pressure) => WriteEvent(5, milliseconds, pressure);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/ConfigurableArrayPool.cs b/src/System.Private.CoreLib/shared/System/Buffers/ConfigurableArrayPool.cs
new file mode 100644
index 0000000000..f7b6034d20
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Buffers/ConfigurableArrayPool.cs
@@ -0,0 +1,265 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Threading;
+
+namespace System.Buffers
+{
+    internal sealed partial class ConfigurableArrayPool<T> : ArrayPool<T>
+    {
+        /// <summary>The default maximum length of each array in the pool (2^20).</summary>
+        private const int DefaultMaxArrayLength = 1024 * 1024;
+        /// <summary>The default maximum number of arrays per bucket that are available for rent.</summary>
+        private const int DefaultMaxNumberOfArraysPerBucket = 50;
+
+        private readonly Bucket[] _buckets;
+
+        internal ConfigurableArrayPool() : this(DefaultMaxArrayLength, DefaultMaxNumberOfArraysPerBucket)
+        {
+        }
+
+        internal ConfigurableArrayPool(int maxArrayLength, int maxArraysPerBucket)
+        {
+            if (maxArrayLength <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(maxArrayLength));
+            }
+            if (maxArraysPerBucket <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(maxArraysPerBucket));
+            }
+
+            // Our bucketing algorithm has a min length of 2^4 and a max length of 2^30.
+            // Constrain the actual max used to those values.
+            const int MinimumArrayLength = 0x10, MaximumArrayLength = 0x40000000;
+            if (maxArrayLength > MaximumArrayLength)
+            {
+                maxArrayLength = MaximumArrayLength;
+            }
+            else if (maxArrayLength < MinimumArrayLength)
+            {
+                maxArrayLength = MinimumArrayLength;
+            }
+
+            // Create the buckets.
+            int poolId = Id;
+            int maxBuckets = Utilities.SelectBucketIndex(maxArrayLength);
+            var buckets = new Bucket[maxBuckets + 1];
+            for (int i = 0; i < buckets.Length; i++)
+            {
+                buckets[i] = new Bucket(Utilities.GetMaxSizeForBucket(i), maxArraysPerBucket, poolId);
+            }
+            _buckets = buckets;
+        }
+
+        /// <summary>Gets an ID for the pool to use with events.</summary>
+        private int Id => GetHashCode();
+
+        public override T[] Rent(int minimumLength)
+        {
+            // Arrays can't be smaller than zero.  We allow requesting zero-length arrays (even though
+            // pooling such an array isn't valuable) as it's a valid length array, and we want the pool
+            // to be usable in general instead of using `new`, even for computed lengths.
+            if (minimumLength < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(minimumLength));
+            }
+            else if (minimumLength == 0)
+            {
+                // No need for events with the empty array.  Our pool is effectively infinite
+                // and we'll never allocate for rents and never store for returns.
+                return Array.Empty<T>();
+            }
+
+            var log = ArrayPoolEventSource.Log;
+            T[] buffer = null;
+
+            int index = Utilities.SelectBucketIndex(minimumLength);
+            if (index < _buckets.Length)
+            {
+                // Search for an array starting at the 'index' bucket. If the bucket is empty, bump up to the
+                // next higher bucket and try that one, but only try at most a few buckets.
+                const int MaxBucketsToTry = 2;
+                int i = index;
+                do
+                {
+                    // Attempt to rent from the bucket.  If we get a buffer from it, return it.
+                    buffer = _buckets[i].Rent();
+                    if (buffer != null)
+                    {
+                        if (log.IsEnabled())
+                        {
+                            log.BufferRented(buffer.GetHashCode(), buffer.Length, Id, _buckets[i].Id);
+                        }
+                        return buffer;
+                    }
+                }
+                while (++i < _buckets.Length && i != index + MaxBucketsToTry);
+
+                // The pool was exhausted for this buffer size.  Allocate a new buffer with a size corresponding
+                // to the appropriate bucket.
+                buffer = new T[_buckets[index]._bufferLength];
+            }
+            else
+            {
+                // The request was for a size too large for the pool.  Allocate an array of exactly the requested length.
+                // When it's returned to the pool, we'll simply throw it away.
+                buffer = new T[minimumLength];
+            }
+
+            if (log.IsEnabled())
+            {
+                int bufferId = buffer.GetHashCode(), bucketId = -1; // no bucket for an on-demand allocated buffer
+                log.BufferRented(bufferId, buffer.Length, Id, bucketId);
+                log.BufferAllocated(bufferId, buffer.Length, Id, bucketId, index >= _buckets.Length ?
+                    ArrayPoolEventSource.BufferAllocatedReason.OverMaximumSize : ArrayPoolEventSource.BufferAllocatedReason.PoolExhausted);
+            }
+
+            return buffer;
+        }
+
+        public override void Return(T[] array, bool clearArray = false)
+        {
+            if (array == null)
+            {
+                throw new ArgumentNullException(nameof(array));
+            }
+            else if (array.Length == 0)
+            {
+                // Ignore empty arrays.  When a zero-length array is rented, we return a singleton
+                // rather than actually taking a buffer out of the lowest bucket.
+                return;
+            }
+
+            // Determine with what bucket this array length is associated
+            int bucket = Utilities.SelectBucketIndex(array.Length);
+
+            // If we can tell that the buffer was allocated, drop it. Otherwise, check if we have space in the pool
+            if (bucket < _buckets.Length)
+            {
+                // Clear the array if the user requests
+                if (clearArray)
+                {
+                    Array.Clear(array, 0, array.Length);
+                }
+
+                // Return the buffer to its bucket.  In the future, we might consider having Return return false
+                // instead of dropping a bucket, in which case we could try to return to a lower-sized bucket,
+                // just as how in Rent we allow renting from a higher-sized bucket.
+                _buckets[bucket].Return(array);
+            }
+
+            // Log that the buffer was returned
+            var log = ArrayPoolEventSource.Log;
+            if (log.IsEnabled())
+            {
+                log.BufferReturned(array.GetHashCode(), array.Length, Id);
+            }
+        }
+
+        /// <summary>Provides a thread-safe bucket containing buffers that can be Rent'd and Return'd.</summary>
+        private sealed class Bucket
+        {
+            internal readonly int _bufferLength;
+            private readonly T[][] _buffers;
+            private readonly int _poolId;
+
+            private SpinLock _lock; // do not make this readonly; it's a mutable struct
+            private int _index;
+
+            /// <summary>
+            /// Creates the pool with numberOfBuffers arrays where each buffer is of bufferLength length.
+            /// </summary>
+            internal Bucket(int bufferLength, int numberOfBuffers, int poolId)
+            {
+                _lock = new SpinLock(Debugger.IsAttached); // only enable thread tracking if debugger is attached; it adds non-trivial overheads to Enter/Exit
+                _buffers = new T[numberOfBuffers][];
+                _bufferLength = bufferLength;
+                _poolId = poolId;
+            }
+
+            /// <summary>Gets an ID for the bucket to use with events.</summary>
+            internal int Id => GetHashCode();
+
+            /// <summary>Takes an array from the bucket.  If the bucket is empty, returns null.</summary>
+            internal T[] Rent()
+            {
+                T[][] buffers = _buffers;
+                T[] buffer = null;
+
+                // While holding the lock, grab whatever is at the next available index and
+                // update the index.  We do as little work as possible while holding the spin
+                // lock to minimize contention with other threads.  The try/finally is
+                // necessary to properly handle thread aborts on platforms which have them.
+                bool lockTaken = false, allocateBuffer = false;
+                try
+                {
+                    _lock.Enter(ref lockTaken);
+
+                    if (_index < buffers.Length)
+                    {
+                        buffer = buffers[_index];
+                        buffers[_index++] = null;
+                        allocateBuffer = buffer == null;
+                    }
+                }
+                finally
+                {
+                    if (lockTaken) _lock.Exit(false);
+                }
+
+                // While we were holding the lock, we grabbed whatever was at the next available index, if
+                // there was one.  If we tried and if we got back null, that means we hadn't yet allocated
+                // for that slot, in which case we should do so now.
+                if (allocateBuffer)
+                {
+                    buffer = new T[_bufferLength];
+
+                    var log = ArrayPoolEventSource.Log;
+                    if (log.IsEnabled())
+                    {
+                        log.BufferAllocated(buffer.GetHashCode(), _bufferLength, _poolId, Id,
+                            ArrayPoolEventSource.BufferAllocatedReason.Pooled);
+                    }
+                }
+
+                return buffer;
+            }
+
+            /// <summary>
+            /// Attempts to return the buffer to the bucket.  If successful, the buffer will be stored
+            /// in the bucket and true will be returned; otherwise, the buffer won't be stored, and false
+            /// will be returned.
+            /// </summary>
+            internal void Return(T[] array)
+            {
+                // Check to see if the buffer is the correct size for this bucket
+                if (array.Length != _bufferLength)
+                {
+                    throw new ArgumentException(SR.ArgumentException_BufferNotFromPool, nameof(array));
+                }
+
+                // While holding the spin lock, if there's room available in the bucket,
+                // put the buffer into the next available slot.  Otherwise, we just drop it.
+                // The try/finally is necessary to properly handle thread aborts on platforms
+                // which have them.
+                bool lockTaken = false;
+                try
+                {
+                    _lock.Enter(ref lockTaken);
+
+                    if (_index != 0)
+                    {
+                        _buffers[--_index] = array;
+                    }
+                }
+                finally
+                {
+                    if (lockTaken) _lock.Exit(false);
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/IMemoryOwner.cs b/src/System.Private.CoreLib/shared/System/Buffers/IMemoryOwner.cs
new file mode 100644
index 0000000000..44f16c5827
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Buffers/IMemoryOwner.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Buffers
+{
+    /// <summary>
+    /// Owner of Memory<typeparamref name="T"/> that is responsible for disposing the underlying memory appropriately.
+    /// </summary>
+    public interface IMemoryOwner<T> : IDisposable
+    {
+        /// <summary>
+        /// Returns a Memory<typeparamref name="T"/>.
+        /// </summary>
+        Memory<T> Memory { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/IPinnable.cs b/src/System.Private.CoreLib/shared/System/Buffers/IPinnable.cs
new file mode 100644
index 0000000000..623e716a05
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Buffers/IPinnable.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Buffers
+{
+    /// <summary>
+    /// Provides a mechanism for pinning and unpinning objects to prevent the GC from moving them.
+    /// </summary>
+    public interface IPinnable
+    {
+        /// <summary>
+        /// Call this method to indicate that the IPinnable object can not be moved by the garbage collector.
+        /// The address of the pinned object can be taken.
+        /// <param name="elementIndex">The offset to the element within the memory at which the returned <see cref="MemoryHandle"/> points to.</param>
+        /// </summary>
+        MemoryHandle Pin(int elementIndex);
+
+        /// <summary>
+        /// Call this method to indicate that the IPinnable object no longer needs to be pinned.
+        /// The garbage collector is free to move the object now.
+        /// </summary>
+        void Unpin();
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/MemoryHandle.cs b/src/System.Private.CoreLib/shared/System/Buffers/MemoryHandle.cs
new file mode 100644
index 0000000000..231add1c01
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Buffers/MemoryHandle.cs
@@ -0,0 +1,59 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime;
+using System.Runtime.InteropServices;
+
+namespace System.Buffers
+{
+    /// <summary>
+    /// A handle for the memory.
+    /// </summary>
+    public unsafe struct MemoryHandle : IDisposable
+    {
+        private void* _pointer;
+        private GCHandle _handle;
+        private IPinnable _pinnable;
+
+        /// <summary>
+        /// Creates a new memory handle for the memory.
+        /// </summary>
+        /// <param name="pointer">pointer to memory</param>
+        /// <param name="pinnable">reference to manually managed object, or default if there is no memory manager</param>
+        /// <param name="handle">handle used to pin array buffers</param>
+        [CLSCompliant(false)]
+        public MemoryHandle(void* pointer, GCHandle handle = default, IPinnable pinnable = default)
+        {
+            _pointer = pointer;
+            _handle = handle;
+            _pinnable = pinnable;
+        }
+
+        /// <summary>
+        /// Returns the pointer to memory, where the memory is assumed to be pinned and hence the address won't change.
+        /// </summary>
+        [CLSCompliant(false)]
+        public void* Pointer => _pointer;
+
+        /// <summary>
+        /// Frees the pinned handle and releases IPinnable.
+        /// </summary>
+        public void Dispose()
+        {
+            if (_handle.IsAllocated)
+            {
+                _handle.Free();
+            }
+
+            if (_pinnable != null)
+            {
+                _pinnable.Unpin();
+                _pinnable = null;
+            }
+
+            _pointer = null;
+        }
+
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/MemoryManager.cs b/src/System.Private.CoreLib/shared/System/Buffers/MemoryManager.cs
new file mode 100644
index 0000000000..acba3d2a94
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Buffers/MemoryManager.cs
@@ -0,0 +1,76 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime;
+using System.Runtime.CompilerServices;
+
+namespace System.Buffers
+{
+    /// <summary>
+    /// Manager of <see cref="System.Memory{T}"/> that provides the implementation.
+    /// </summary>
+    public abstract class MemoryManager<T> : IMemoryOwner<T>, IPinnable
+    {
+        /// <summary>
+        /// Returns a <see cref="System.Memory{T}"/>.
+        /// </summary>
+        public virtual Memory<T> Memory => new Memory<T>(this, GetSpan().Length);
+
+        /// <summary>
+        /// Returns a span wrapping the underlying memory.
+        /// </summary>
+        public abstract Span<T> GetSpan();
+
+        /// <summary>
+        /// Returns a handle to the memory that has been pinned and hence its address can be taken.
+        /// </summary>
+        /// <param name="elementIndex">The offset to the element within the memory at which the returned <see cref="MemoryHandle"/> points to. (default = 0)</param>
+        public abstract MemoryHandle Pin(int elementIndex = 0);
+
+        /// <summary>
+        /// Lets the garbage collector know that the object is free to be moved now.
+        /// </summary>
+        public abstract void Unpin();
+
+        /// <summary>
+        /// Returns a <see cref="System.Memory{T}"/> for the current <see cref="MemoryManager{T}"/>.
+        /// </summary>
+        /// <param name="length">The element count in the memory, starting at offset 0.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        protected Memory<T> CreateMemory(int length) => new Memory<T>(this, length);
+
+        /// <summary>
+        /// Returns a <see cref="System.Memory{T}"/> for the current <see cref="MemoryManager{T}"/>.
+        /// </summary>
+        /// <param name="start">The offset to the element which the returned memory starts at.</param>
+        /// <param name="length">The element count in the memory, starting at element offset <paramref name="start"/>.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        protected Memory<T> CreateMemory(int start, int length) => new Memory<T>(this, start, length);
+
+        /// <summary>
+        /// Returns an array segment.
+        /// <remarks>Returns the default array segment if not overriden.</remarks>
+        /// </summary>
+        protected internal virtual bool TryGetArray(out ArraySegment<T> segment)
+        {
+            segment = default;
+            return false;
+        }
+
+        /// <summary>
+        /// Implements IDisposable.
+        /// </summary>
+        void IDisposable.Dispose()
+        {
+            Dispose(disposing: true);
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// Clean up of any leftover managed and unmanaged resources.
+        /// </summary>
+        protected abstract void Dispose(bool disposing);
+
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Text/FormattingHelpers.CountDigits.cs b/src/System.Private.CoreLib/shared/System/Buffers/Text/FormattingHelpers.CountDigits.cs
new file mode 100644
index 0000000000..709ac4fba6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Text/FormattingHelpers.CountDigits.cs
@@ -0,0 +1,132 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+
+namespace System.Buffers.Text
+{
+    internal static partial class FormattingHelpers
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int CountDigits(ulong value)
+        {
+            int digits = 1;
+            uint part;
+            if (value >= 10000000)
+            {
+                if (value >= 100000000000000)
+                {
+                    part = (uint)(value / 100000000000000);
+                    digits += 14;
+                }
+                else
+                {
+                    part = (uint)(value / 10000000);
+                    digits += 7;
+                }
+            }
+            else
+            {
+                part = (uint)value;
+            }
+
+            if (part < 10)
+            {
+                // no-op
+            }
+            else if (part < 100)
+            {
+                digits += 1;
+            }
+            else if (part < 1000)
+            {
+                digits += 2;
+            }
+            else if (part < 10000)
+            {
+                digits += 3;
+            }
+            else if (part < 100000)
+            {
+                digits += 4;
+            }
+            else if (part < 1000000)
+            {
+                digits += 5;
+            }
+            else
+            {
+                Debug.Assert(part < 10000000);
+                digits += 6;
+            }
+
+            return digits;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int CountDigits(uint value)
+        {
+            int digits = 1;
+            if (value >= 100000)
+            {
+                value = value / 100000;
+                digits += 5;
+            }
+
+            if (value < 10)
+            {
+                // no-op
+            }
+            else if (value < 100)
+            {
+                digits += 1;
+            }
+            else if (value < 1000)
+            {
+                digits += 2;
+            }
+            else if (value < 10000)
+            {
+                digits += 3;
+            }
+            else
+            {
+                Debug.Assert(value < 100000);
+                digits += 4;
+            }
+
+            return digits;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int CountHexDigits(ulong value)
+        {
+            // TODO: When x86 intrinsic support comes online, experiment with implementing this using lzcnt.
+            // return 16 - (int)((uint)Lzcnt.LeadingZeroCount(value | 1) >> 3);
+
+            int digits = 1;
+
+            if (value > 0xFFFFFFFF)
+            {
+                digits += 8;
+                value >>= 0x20;
+            }
+            if (value > 0xFFFF)
+            {
+                digits += 4;
+                value >>= 0x10;
+            }
+            if (value > 0xFF)
+            {
+                digits += 2;
+                value >>= 0x8;
+            }
+            if (value > 0xF)
+                digits++;
+
+            return digits;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/TlsOverPerCoreLockedStacksArrayPool.cs b/src/System.Private.CoreLib/shared/System/Buffers/TlsOverPerCoreLockedStacksArrayPool.cs
new file mode 100644
index 0000000000..96efb0d521
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Buffers/TlsOverPerCoreLockedStacksArrayPool.cs
@@ -0,0 +1,496 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using Internal.Runtime.Augments;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Buffers
+{
+    /// <summary>
+    /// Provides an ArrayPool implementation meant to be used as the singleton returned from ArrayPool.Shared.
+    /// </summary>
+    /// <remarks>
+    /// The implementation uses a tiered caching scheme, with a small per-thread cache for each array size, followed
+    /// by a cache per array size shared by all threads, split into per-core stacks meant to be used by threads
+    /// running on that core.  Locks are used to protect each per-core stack, because a thread can migrate after
+    /// checking its processor number, because multiple threads could interleave on the same core, and because
+    /// a thread is allowed to check other core's buckets if its core's bucket is empty/full.
+    /// </remarks>
+    internal sealed partial class TlsOverPerCoreLockedStacksArrayPool<T> : ArrayPool<T>
+    {
+        // TODO: #7747: "Investigate optimizing ArrayPool heuristics"
+        // - Explore caching in TLS more than one array per size per thread, and moving stale buffers to the global queue.
+        // - Explore changing the size of each per-core bucket, potentially dynamically or based on other factors like array size.
+        // - Explore changing number of buckets and what sizes of arrays are cached.
+        // - Investigate whether false sharing is causing any issues, in particular on LockedStack's count and the contents of its array.
+        // ...
+
+        /// <summary>The number of buckets (array sizes) in the pool, one for each array length, starting from length 16.</summary>
+        private const int NumBuckets = 17; // Utilities.SelectBucketIndex(2*1024*1024)
+        /// <summary>Maximum number of per-core stacks to use per array size.</summary>
+        private const int MaxPerCorePerArraySizeStacks = 64; // selected to avoid needing to worry about processor groups
+        /// <summary>The maximum number of buffers to store in a bucket's global queue.</summary>
+        private const int MaxBuffersPerArraySizePerCore = 8;
+
+        /// <summary>The length of arrays stored in the corresponding indices in <see cref="_buckets"/> and <see cref="t_tlsBuckets"/>.</summary>
+        private readonly int[] _bucketArraySizes;
+        /// <summary>
+        /// An array of per-core array stacks. The slots are lazily initialized to avoid creating
+        /// lots of overhead for unused array sizes.
+        /// </summary>
+        private readonly PerCoreLockedStacks[] _buckets = new PerCoreLockedStacks[NumBuckets];
+        /// <summary>A per-thread array of arrays, to cache one array per array size per thread.</summary>
+        [ThreadStatic]
+        private static T[][] t_tlsBuckets;
+
+        private int _callbackCreated;
+
+        private readonly static bool s_trimBuffers = GetTrimBuffers();
+
+        /// <summary>
+        /// Used to keep track of all thread local buckets for trimming if needed
+        /// </summary>
+        private static readonly ConditionalWeakTable<T[][], object> s_allTlsBuckets = s_trimBuffers ? new ConditionalWeakTable<T[][], object>() : null;
+
+        /// <summary>Initialize the pool.</summary>
+        public TlsOverPerCoreLockedStacksArrayPool()
+        {
+            var sizes = new int[NumBuckets];
+            for (int i = 0; i < sizes.Length; i++)
+            {
+                sizes[i] = Utilities.GetMaxSizeForBucket(i);
+            }
+            _bucketArraySizes = sizes;
+        }
+
+        /// <summary>Allocate a new PerCoreLockedStacks and try to store it into the <see cref="_buckets"/> array.</summary>
+        private PerCoreLockedStacks CreatePerCoreLockedStacks(int bucketIndex)
+        {
+            var inst = new PerCoreLockedStacks();
+            return Interlocked.CompareExchange(ref _buckets[bucketIndex], inst, null) ?? inst;
+        }
+
+        /// <summary>Gets an ID for the pool to use with events.</summary>
+        private int Id => GetHashCode();
+
+        public override T[] Rent(int minimumLength)
+        {
+            // Arrays can't be smaller than zero.  We allow requesting zero-length arrays (even though
+            // pooling such an array isn't valuable) as it's a valid length array, and we want the pool
+            // to be usable in general instead of using `new`, even for computed lengths.
+            if (minimumLength < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(minimumLength));
+            }
+            else if (minimumLength == 0)
+            {
+                // No need to log the empty array.  Our pool is effectively infinite
+                // and we'll never allocate for rents and never store for returns.
+                return Array.Empty<T>();
+            }
+
+            ArrayPoolEventSource log = ArrayPoolEventSource.Log;
+            T[] buffer;
+
+            // Get the bucket number for the array length
+            int bucketIndex = Utilities.SelectBucketIndex(minimumLength);
+
+            // If the array could come from a bucket...
+            if (bucketIndex < _buckets.Length)
+            {
+                // First try to get it from TLS if possible.
+                T[][] tlsBuckets = t_tlsBuckets;
+                if (tlsBuckets != null)
+                {
+                    buffer = tlsBuckets[bucketIndex];
+                    if (buffer != null)
+                    {
+                        tlsBuckets[bucketIndex] = null;
+                        if (log.IsEnabled())
+                        {
+                            log.BufferRented(buffer.GetHashCode(), buffer.Length, Id, bucketIndex);
+                        }
+                        return buffer;
+                    }
+                }
+
+                // We couldn't get a buffer from TLS, so try the global stack.
+                PerCoreLockedStacks b = _buckets[bucketIndex];
+                if (b != null)
+                {
+                    buffer = b.TryPop();
+                    if (buffer != null)
+                    {
+                        if (log.IsEnabled())
+                        {
+                            log.BufferRented(buffer.GetHashCode(), buffer.Length, Id, bucketIndex);
+                        }
+                        return buffer;
+                    }
+                }
+
+                // No buffer available.  Allocate a new buffer with a size corresponding to the appropriate bucket.
+                buffer = new T[_bucketArraySizes[bucketIndex]];
+            }
+            else
+            {
+                // The request was for a size too large for the pool.  Allocate an array of exactly the requested length.
+                // When it's returned to the pool, we'll simply throw it away.
+                buffer = new T[minimumLength];
+            }
+
+            if (log.IsEnabled())
+            {
+                int bufferId = buffer.GetHashCode(), bucketId = -1; // no bucket for an on-demand allocated buffer
+                log.BufferRented(bufferId, buffer.Length, Id, bucketId);
+                log.BufferAllocated(bufferId, buffer.Length, Id, bucketId, bucketIndex >= _buckets.Length ?
+                    ArrayPoolEventSource.BufferAllocatedReason.OverMaximumSize :
+                    ArrayPoolEventSource.BufferAllocatedReason.PoolExhausted);
+            }
+
+            return buffer;
+        }
+
+        public override void Return(T[] array, bool clearArray = false)
+        {
+            if (array == null)
+            {
+                throw new ArgumentNullException(nameof(array));
+            }
+
+            // Determine with what bucket this array length is associated
+            int bucketIndex = Utilities.SelectBucketIndex(array.Length);
+
+            // If we can tell that the buffer was allocated (or empty), drop it. Otherwise, check if we have space in the pool.
+            if (bucketIndex < _buckets.Length)
+            {
+                // Clear the array if the user requests.
+                if (clearArray)
+                {
+                    Array.Clear(array, 0, array.Length);
+                }
+
+                // Check to see if the buffer is the correct size for this bucket
+                if (array.Length != _bucketArraySizes[bucketIndex])
+                {
+                    throw new ArgumentException(SR.ArgumentException_BufferNotFromPool, nameof(array));
+                }
+
+                // Write through the TLS bucket.  If there weren't any buckets, create them
+                // and store this array into it.  If there were, store this into it, and
+                // if there was a previous one there, push that to the global stack.  This
+                // helps to keep LIFO access such that the most recently pushed stack will
+                // be in TLS and the first to be popped next.
+                T[][] tlsBuckets = t_tlsBuckets;
+                if (tlsBuckets == null)
+                {
+                    t_tlsBuckets = tlsBuckets = new T[NumBuckets][];
+                    tlsBuckets[bucketIndex] = array;
+                    if (s_trimBuffers)
+                    {
+                        s_allTlsBuckets.Add(tlsBuckets, null);
+                        if (Interlocked.Exchange(ref _callbackCreated, 1) != 1)
+                        {
+                            Gen2GcCallback.Register(Gen2GcCallbackFunc, this);
+                        }
+                    }
+                }
+                else
+                {
+                    T[] prev = tlsBuckets[bucketIndex];
+                    tlsBuckets[bucketIndex] = array;
+
+                    if (prev != null)
+                    {
+                        PerCoreLockedStacks stackBucket = _buckets[bucketIndex] ?? CreatePerCoreLockedStacks(bucketIndex);
+                        stackBucket.TryPush(prev);
+                    }
+                }
+            }
+
+            // Log that the buffer was returned
+            ArrayPoolEventSource log = ArrayPoolEventSource.Log;
+            if (log.IsEnabled())
+            {
+                log.BufferReturned(array.GetHashCode(), array.Length, Id);
+            }
+        }
+
+        public bool Trim()
+        {
+            int milliseconds = Environment.TickCount;
+            MemoryPressure pressure = GetMemoryPressure();
+
+            ArrayPoolEventSource log = ArrayPoolEventSource.Log;
+            if (log.IsEnabled())
+                log.BufferTrimPoll(milliseconds, (int)pressure);
+
+            foreach (PerCoreLockedStacks bucket in _buckets)
+            {
+                bucket?.Trim((uint)milliseconds, Id, pressure, _bucketArraySizes);
+            }
+
+            if (pressure == MemoryPressure.High)
+            {
+                // Under high pressure, release all thread locals
+                if (log.IsEnabled())
+                {
+                    foreach (KeyValuePair<T[][], object> tlsBuckets in s_allTlsBuckets)
+                    {
+                        T[][] buckets = tlsBuckets.Key;
+                        for (int i = 0; i < buckets.Length; i++)
+                        {
+                            T[] buffer = Interlocked.Exchange(ref buckets[i], null);
+                            if (buffer != null)
+                            {
+                                // As we don't want to take a perf hit in the rent path it
+                                // is possible that a buffer could be rented as we "free" it.
+                                log.BufferTrimmed(buffer.GetHashCode(), buffer.Length, Id);
+                            }
+                        }
+                    }
+                }
+                else
+                {
+                    foreach (KeyValuePair<T[][], object> tlsBuckets in s_allTlsBuckets)
+                    {
+                        T[][] buckets = tlsBuckets.Key;
+                        Array.Clear(buckets, 0, buckets.Length);
+                    }
+                }
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// This is the static function that is called from the gen2 GC callback.
+        /// The input object is the instance we want the callback on.
+        /// </summary>
+        /// <remarks>
+        /// The reason that we make this function static and take the instance as a parameter is that
+        /// we would otherwise root the instance to the Gen2GcCallback object, leaking the instance even when
+        /// the application no longer needs it.
+        /// </remarks>
+        private static bool Gen2GcCallbackFunc(object target)
+        {
+            return ((TlsOverPerCoreLockedStacksArrayPool<T>)(target)).Trim();
+        }
+
+        private enum MemoryPressure
+        {
+            Low,
+            Medium,
+            High
+        }
+
+        private static MemoryPressure GetMemoryPressure()
+        {
+            const double HighPressureThreshold = .90;       // Percent of GC memory pressure threshold we consider "high"
+            const double MediumPressureThreshold = .70;     // Percent of GC memory pressure threshold we consider "medium"
+
+            GC.GetMemoryInfo(out uint threshold, out _, out uint lastLoad, out _, out _);
+            if (lastLoad >= threshold * HighPressureThreshold)
+            {
+                return MemoryPressure.High;
+            }
+            else if (lastLoad >= threshold * MediumPressureThreshold)
+            {
+                return MemoryPressure.Medium;
+            }
+            return MemoryPressure.Low;
+        }
+
+        private static bool GetTrimBuffers()
+        {
+            // Environment uses ArrayPool, so we have to hit the API directly.
+#if !CORECLR
+            // P/Invokes are different for CoreCLR/RT- for RT we'll not allow
+            // enabling/disabling for now.
+            return true;
+#else
+            return CLRConfig.GetBoolValueWithFallbacks("System.Buffers.ArrayPool.TrimShared", "DOTNET_SYSTEM_BUFFERS_ARRAYPOOL_TRIMSHARED", defaultValue: true);
+#endif
+        }
+
+        /// <summary>
+        /// Stores a set of stacks of arrays, with one stack per core.
+        /// </summary>
+        private sealed class PerCoreLockedStacks
+        {
+            /// <summary>The stacks.</summary>
+            private readonly LockedStack[] _perCoreStacks;
+
+            /// <summary>Initializes the stacks.</summary>
+            public PerCoreLockedStacks()
+            {
+                // Create the stacks.  We create as many as there are processors, limited by our max.
+                var stacks = new LockedStack[Math.Min(Environment.ProcessorCount, MaxPerCorePerArraySizeStacks)];
+                for (int i = 0; i < stacks.Length; i++)
+                {
+                    stacks[i] = new LockedStack();
+                }
+                _perCoreStacks = stacks;
+            }
+
+            /// <summary>Try to push the array into the stacks. If each is full when it's tested, the array will be dropped.</summary>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            public void TryPush(T[] array)
+            {
+                // Try to push on to the associated stack first.  If that fails,
+                // round-robin through the other stacks.
+                LockedStack[] stacks = _perCoreStacks;
+                int index = RuntimeThread.GetCurrentProcessorId() % stacks.Length;
+                for (int i = 0; i < stacks.Length; i++)
+                {
+                    if (stacks[index].TryPush(array)) return;
+                    if (++index == stacks.Length) index = 0;
+                }
+            }
+
+            /// <summary>Try to get an array from the stacks.  If each is empty when it's tested, null will be returned.</summary>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            public T[] TryPop()
+            {
+                // Try to pop from the associated stack first.  If that fails,
+                // round-robin through the other stacks.
+                T[] arr;
+                LockedStack[] stacks = _perCoreStacks;
+                int index = RuntimeThread.GetCurrentProcessorId() % stacks.Length;
+                for (int i = 0; i < stacks.Length; i++)
+                {
+                    if ((arr = stacks[index].TryPop()) != null) return arr;
+                    if (++index == stacks.Length) index = 0;
+                }
+                return null;
+            }
+
+            public bool Trim(uint tickCount, int id, MemoryPressure pressure, int[] bucketSizes)
+            {
+                LockedStack[] stacks = _perCoreStacks;
+                for (int i = 0; i < stacks.Length; i++)
+                {
+                    stacks[i].Trim(tickCount, id, pressure, bucketSizes[i]);
+                }
+                return true;
+            }
+        }
+
+        /// <summary>Provides a simple stack of arrays, protected by a lock.</summary>
+        private sealed class LockedStack
+        {
+            private readonly T[][] _arrays = new T[MaxBuffersPerArraySizePerCore][];
+            private int _count;
+            private uint _firstStackItemMS;
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            public bool TryPush(T[] array)
+            {
+                bool enqueued = false;
+                Monitor.Enter(this);
+                if (_count < MaxBuffersPerArraySizePerCore)
+                {
+                    if (s_trimBuffers && _count == 0)
+                    {
+                        // Stash the time the bottom of the stack was filled
+                        _firstStackItemMS = (uint)Environment.TickCount;
+                    }
+
+                    _arrays[_count++] = array;
+                    enqueued = true;
+                }
+                Monitor.Exit(this);
+                return enqueued;
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            public T[] TryPop()
+            {
+                T[] arr = null;
+                Monitor.Enter(this);
+                if (_count > 0)
+                {
+                    arr = _arrays[--_count];
+                    _arrays[_count] = null;
+                }
+                Monitor.Exit(this);
+                return arr;
+            }
+
+            public void Trim(uint tickCount, int id, MemoryPressure pressure, int bucketSize)
+            {
+                const uint StackTrimAfterMS = 60 * 1000;                        // Trim after 60 seconds for low/moderate pressure
+                const uint StackHighTrimAfterMS = 10 * 1000;                    // Trim after 10 seconds for high pressure
+                const uint StackRefreshMS = StackTrimAfterMS / 4;               // Time bump after trimming (1/4 trim time)
+                const int StackLowTrimCount = 1;                                // Trim one item when pressure is low
+                const int StackMediumTrimCount = 2;                             // Trim two items when pressure is moderate
+                const int StackHighTrimCount = MaxBuffersPerArraySizePerCore;   // Trim all items when pressure is high
+                const int StackLargeBucket = 16384;                             // If the bucket is larger than this we'll trim an extra when under high pressure
+                const int StackModerateTypeSize = 16;                           // If T is larger than this we'll trim an extra when under high pressure
+                const int StackLargeTypeSize = 32;                              // If T is larger than this we'll trim an extra (additional) when under high pressure
+
+                if (_count == 0)
+                    return;
+                uint trimTicks = pressure == MemoryPressure.High ? StackHighTrimAfterMS : StackTrimAfterMS;
+
+                lock (this)
+                {
+                    if (_count > 0 && _firstStackItemMS > tickCount || (tickCount - _firstStackItemMS) > trimTicks)
+                    {
+                        // We've wrapped the tick count or elapsed enough time since the
+                        // first item went into the stack. Drop the top item so it can
+                        // be collected and make the stack look a little newer.
+
+                        ArrayPoolEventSource log = ArrayPoolEventSource.Log;
+                        int trimCount = StackLowTrimCount;
+                        switch (pressure)
+                        {
+                            case MemoryPressure.High:
+                                trimCount = StackHighTrimCount;
+
+                                // When pressure is high, aggressively trim larger arrays.
+                                if (bucketSize > StackLargeBucket)
+                                {
+                                    trimCount++;
+                                }
+                                if (Unsafe.SizeOf<T>() > StackModerateTypeSize)
+                                {
+                                    trimCount++;
+                                }
+                                if (Unsafe.SizeOf<T>() > StackLargeTypeSize)
+                                {
+                                    trimCount++;
+                                }
+                                break;
+                            case MemoryPressure.Medium:
+                                trimCount = StackMediumTrimCount;
+                                break;
+                        }
+
+                        while (_count > 0 && trimCount-- > 0)
+                        {
+                            T[] array = _arrays[--_count];
+                            _arrays[_count] = null;
+
+                            if (log.IsEnabled())
+                            {
+                                log.BufferTrimmed(array.GetHashCode(), array.Length, id);
+                            }
+                        }
+
+                        if (_count > 0 && _firstStackItemMS < uint.MaxValue - StackRefreshMS)
+                        {
+                            // Give the remaining items a bit more time
+                            _firstStackItemMS += StackRefreshMS;
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Buffers/Utilities.cs b/src/System.Private.CoreLib/shared/System/Buffers/Utilities.cs
new file mode 100644
index 0000000000..b675100b03
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Buffers/Utilities.cs
@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+
+namespace System.Buffers
+{
+    internal static class Utilities
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static int SelectBucketIndex(int bufferSize)
+        {
+            Debug.Assert(bufferSize >= 0);
+
+            // bufferSize of 0 will underflow here, causing a huge
+            // index which the caller will discard because it is not
+            // within the bounds of the bucket array.
+            uint bitsRemaining = ((uint)bufferSize - 1) >> 4;
+
+            int poolIndex = 0;
+            if (bitsRemaining > 0xFFFF) { bitsRemaining >>= 16; poolIndex = 16; }
+            if (bitsRemaining > 0xFF)   { bitsRemaining >>= 8;  poolIndex += 8; }
+            if (bitsRemaining > 0xF)    { bitsRemaining >>= 4;  poolIndex += 4; }
+            if (bitsRemaining > 0x3)    { bitsRemaining >>= 2;  poolIndex += 2; }
+            if (bitsRemaining > 0x1)    { bitsRemaining >>= 1;  poolIndex += 1; }
+
+            return poolIndex + (int)bitsRemaining;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static int GetMaxSizeForBucket(int binIndex)
+        {
+            int maxSize = 16 << binIndex;
+            Debug.Assert(maxSize >= 0);
+            return maxSize;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Byte.cs b/src/System.Private.CoreLib/shared/System/Byte.cs
new file mode 100644
index 0000000000..31185f0ed0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Byte.cs
@@ -0,0 +1,284 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    [Serializable]
+    [StructLayout(LayoutKind.Sequential)]
+    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct Byte : IComparable, IConvertible, IFormattable, IComparable<Byte>, IEquatable<Byte>, ISpanFormattable
+    {
+        private byte m_value; // Do not rename (binary serialization)
+
+        // The maximum value that a Byte may represent: 255.
+        public const byte MaxValue = (byte)0xFF;
+
+        // The minimum value that a Byte may represent: 0.
+        public const byte MinValue = 0;
+
+
+        // Compares this object to another object, returning an integer that
+        // indicates the relationship. 
+        // Returns a value less than zero if this  object
+        // null is considered to be less than any instance.
+        // If object is not of type byte, this method throws an ArgumentException.
+        // 
+        public int CompareTo(Object value)
+        {
+            if (value == null)
+            {
+                return 1;
+            }
+            if (!(value is Byte))
+            {
+                throw new ArgumentException(SR.Arg_MustBeByte);
+            }
+
+            return m_value - (((Byte)value).m_value);
+        }
+
+        public int CompareTo(Byte value)
+        {
+            return m_value - value;
+        }
+
+        // Determines whether two Byte objects are equal.
+        public override bool Equals(Object obj)
+        {
+            if (!(obj is Byte))
+            {
+                return false;
+            }
+            return m_value == ((Byte)obj).m_value;
+        }
+
+        [NonVersionable]
+        public bool Equals(Byte obj)
+        {
+            return m_value == obj;
+        }
+
+        // Gets a hash code for this instance.
+        public override int GetHashCode()
+        {
+            return m_value;
+        }
+
+        public static byte Parse(String s)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo);
+        }
+
+        public static byte Parse(String s, NumberStyles style)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, style, NumberFormatInfo.CurrentInfo);
+        }
+
+        public static byte Parse(String s, IFormatProvider provider)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.GetInstance(provider));
+        }
+
+        // Parses an unsigned byte from a String in the given style.  If
+        // a NumberFormatInfo isn't specified, the current culture's 
+        // NumberFormatInfo is assumed.
+        public static byte Parse(String s, NumberStyles style, IFormatProvider provider)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public static byte Parse(ReadOnlySpan<char> s, NumberStyles style = NumberStyles.Integer, IFormatProvider provider = null)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return Parse(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        private static byte Parse(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info)
+        {
+            int i = 0;
+            try
+            {
+                i = Number.ParseInt32(s, style, info);
+            }
+            catch (OverflowException e)
+            {
+                throw new OverflowException(SR.Overflow_Byte, e);
+            }
+
+            if (i < MinValue || i > MaxValue) throw new OverflowException(SR.Overflow_Byte);
+            return (byte)i;
+        }
+
+        public static bool TryParse(String s, out Byte result)
+        {
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return TryParse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, out byte result)
+        {
+            return TryParse(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        public static bool TryParse(String s, NumberStyles style, IFormatProvider provider, out Byte result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return TryParse((ReadOnlySpan<char>)s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider provider, out byte result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return TryParse(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        private static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info, out Byte result)
+        {
+            result = 0;
+            int i;
+            if (!Number.TryParseInt32(s, style, info, out i))
+            {
+                return false;
+            }
+            if (i < MinValue || i > MaxValue)
+            {
+                return false;
+            }
+            result = (byte)i;
+            return true;
+        }
+
+        public override String ToString()
+        {
+            return Number.FormatInt32(m_value, null, null);
+        }
+
+        public String ToString(String format)
+        {
+            return Number.FormatInt32(m_value, format, null);
+        }
+
+        public String ToString(IFormatProvider provider)
+        {
+            return Number.FormatInt32(m_value, null, provider);
+        }
+
+        public String ToString(String format, IFormatProvider provider)
+        {
+            return Number.FormatInt32(m_value, format, provider);
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider provider = null)
+        {
+            return Number.TryFormatInt32(m_value, format, provider, destination, out charsWritten);
+        }
+
+        //
+        // IConvertible implementation
+        // 
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.Byte;
+        }
+
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            return Convert.ToBoolean(m_value);
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            return Convert.ToChar(m_value);
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return Convert.ToSByte(m_value);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return m_value;
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return Convert.ToInt16(m_value);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return Convert.ToUInt16(m_value);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return Convert.ToInt32(m_value);
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return Convert.ToUInt32(m_value);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return Convert.ToInt64(m_value);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return Convert.ToUInt64(m_value);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            return Convert.ToSingle(m_value);
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            return Convert.ToDouble(m_value);
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            return Convert.ToDecimal(m_value);
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Byte", "DateTime"));
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/CLSCompliantAttribute.cs b/src/System.Private.CoreLib/shared/System/CLSCompliantAttribute.cs
new file mode 100644
index 0000000000..d895b5ac71
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/CLSCompliantAttribute.cs
@@ -0,0 +1,33 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Container for assemblies.
+**
+**
+=============================================================================*/
+
+namespace System
+{
+    [AttributeUsage(AttributeTargets.All, Inherited = true, AllowMultiple = false)]
+    public sealed class CLSCompliantAttribute : Attribute
+    {
+        private bool _compliant;
+
+        public CLSCompliantAttribute(bool isCompliant)
+        {
+            _compliant = isCompliant;
+        }
+        public bool IsCompliant
+        {
+            get
+            {
+                return _compliant;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Char.cs b/src/System.Private.CoreLib/shared/System/Char.cs
new file mode 100644
index 0000000000..d3ed1f5b68
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Char.cs
@@ -0,0 +1,1076 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: This is the value class representing a Unicode character
+** Char methods until we create this functionality.
+**
+**
+===========================================================*/
+
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.InteropServices;
+
+namespace System
+{
+    [Serializable]
+    [StructLayout(LayoutKind.Sequential)]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")] 
+    public struct Char : IComparable, IComparable<Char>, IEquatable<Char>, IConvertible
+    {
+        //
+        // Member Variables
+        //
+        private char m_value; // Do not rename (binary serialization)
+
+        //
+        // Public Constants
+        //
+        // The maximum character value.
+        public const char MaxValue = (char)0xFFFF;
+        // The minimum character value.
+        public const char MinValue = (char)0x00;
+
+        // Unicode category values from Unicode U+0000 ~ U+00FF. Store them in byte[] array to save space.
+        private static readonly byte[] s_categoryForLatin1 = {
+            (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control,    // 0000 - 0007
+            (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control,    // 0008 - 000F
+            (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control,    // 0010 - 0017
+            (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control,    // 0018 - 001F
+            (byte)UnicodeCategory.SpaceSeparator, (byte)UnicodeCategory.OtherPunctuation, (byte)UnicodeCategory.OtherPunctuation, (byte)UnicodeCategory.OtherPunctuation, (byte)UnicodeCategory.CurrencySymbol, (byte)UnicodeCategory.OtherPunctuation, (byte)UnicodeCategory.OtherPunctuation, (byte)UnicodeCategory.OtherPunctuation,    // 0020 - 0027
+            (byte)UnicodeCategory.OpenPunctuation, (byte)UnicodeCategory.ClosePunctuation, (byte)UnicodeCategory.OtherPunctuation, (byte)UnicodeCategory.MathSymbol, (byte)UnicodeCategory.OtherPunctuation, (byte)UnicodeCategory.DashPunctuation, (byte)UnicodeCategory.OtherPunctuation, (byte)UnicodeCategory.OtherPunctuation,    // 0028 - 002F
+            (byte)UnicodeCategory.DecimalDigitNumber, (byte)UnicodeCategory.DecimalDigitNumber, (byte)UnicodeCategory.DecimalDigitNumber, (byte)UnicodeCategory.DecimalDigitNumber, (byte)UnicodeCategory.DecimalDigitNumber, (byte)UnicodeCategory.DecimalDigitNumber, (byte)UnicodeCategory.DecimalDigitNumber, (byte)UnicodeCategory.DecimalDigitNumber,    // 0030 - 0037
+            (byte)UnicodeCategory.DecimalDigitNumber, (byte)UnicodeCategory.DecimalDigitNumber, (byte)UnicodeCategory.OtherPunctuation, (byte)UnicodeCategory.OtherPunctuation, (byte)UnicodeCategory.MathSymbol, (byte)UnicodeCategory.MathSymbol, (byte)UnicodeCategory.MathSymbol, (byte)UnicodeCategory.OtherPunctuation,    // 0038 - 003F
+            (byte)UnicodeCategory.OtherPunctuation, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter,    // 0040 - 0047
+            (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter,    // 0048 - 004F
+            (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter,    // 0050 - 0057
+            (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.OpenPunctuation, (byte)UnicodeCategory.OtherPunctuation, (byte)UnicodeCategory.ClosePunctuation, (byte)UnicodeCategory.ModifierSymbol, (byte)UnicodeCategory.ConnectorPunctuation,    // 0058 - 005F
+            (byte)UnicodeCategory.ModifierSymbol, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter,    // 0060 - 0067
+            (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter,    // 0068 - 006F
+            (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter,    // 0070 - 0077
+            (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.OpenPunctuation, (byte)UnicodeCategory.MathSymbol, (byte)UnicodeCategory.ClosePunctuation, (byte)UnicodeCategory.MathSymbol, (byte)UnicodeCategory.Control,    // 0078 - 007F
+            (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control,    // 0080 - 0087
+            (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control,    // 0088 - 008F
+            (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control,    // 0090 - 0097
+            (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control, (byte)UnicodeCategory.Control,    // 0098 - 009F
+            (byte)UnicodeCategory.SpaceSeparator, (byte)UnicodeCategory.OtherPunctuation, (byte)UnicodeCategory.CurrencySymbol, (byte)UnicodeCategory.CurrencySymbol, (byte)UnicodeCategory.CurrencySymbol, (byte)UnicodeCategory.CurrencySymbol, (byte)UnicodeCategory.OtherSymbol, (byte)UnicodeCategory.OtherSymbol,    // 00A0 - 00A7
+            (byte)UnicodeCategory.ModifierSymbol, (byte)UnicodeCategory.OtherSymbol, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.InitialQuotePunctuation, (byte)UnicodeCategory.MathSymbol, (byte)UnicodeCategory.DashPunctuation, (byte)UnicodeCategory.OtherSymbol, (byte)UnicodeCategory.ModifierSymbol,    // 00A8 - 00AF
+            (byte)UnicodeCategory.OtherSymbol, (byte)UnicodeCategory.MathSymbol, (byte)UnicodeCategory.OtherNumber, (byte)UnicodeCategory.OtherNumber, (byte)UnicodeCategory.ModifierSymbol, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.OtherSymbol, (byte)UnicodeCategory.OtherPunctuation,    // 00B0 - 00B7
+            (byte)UnicodeCategory.ModifierSymbol, (byte)UnicodeCategory.OtherNumber, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.FinalQuotePunctuation, (byte)UnicodeCategory.OtherNumber, (byte)UnicodeCategory.OtherNumber, (byte)UnicodeCategory.OtherNumber, (byte)UnicodeCategory.OtherPunctuation,    // 00B8 - 00BF
+            (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter,    // 00C0 - 00C7
+            (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter,    // 00C8 - 00CF
+            (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.MathSymbol,    // 00D0 - 00D7
+            (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.UppercaseLetter, (byte)UnicodeCategory.LowercaseLetter,    // 00D8 - 00DF
+            (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter,    // 00E0 - 00E7
+            (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter,    // 00E8 - 00EF
+            (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.MathSymbol,    // 00F0 - 00F7
+            (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter, (byte)UnicodeCategory.LowercaseLetter,    // 00F8 - 00FF
+        };
+
+        // Return true for all characters below or equal U+00ff, which is ASCII + Latin-1 Supplement.
+        private static bool IsLatin1(char ch)
+        {
+            return (ch <= '\x00ff');
+        }
+
+        // Return true for all characters below or equal U+007f, which is ASCII.
+        private static bool IsAscii(char ch)
+        {
+            return (ch <= '\x007f');
+        }
+
+        // Return the Unicode category for Unicode character <= 0x00ff.      
+        private static UnicodeCategory GetLatin1UnicodeCategory(char ch)
+        {
+            Debug.Assert(IsLatin1(ch), "Char.GetLatin1UnicodeCategory(): ch should be <= 007f");
+            return (UnicodeCategory)(s_categoryForLatin1[(int)ch]);
+        }
+
+        //
+        // Private Constants
+        //
+
+        //
+        // Overriden Instance Methods
+        //
+
+        // Calculate a hashcode for a 2 byte Unicode character.
+        public override int GetHashCode()
+        {
+            return (int)m_value | ((int)m_value << 16);
+        }
+
+        // Used for comparing two boxed Char objects.
+        //
+        public override bool Equals(Object obj)
+        {
+            if (!(obj is Char))
+            {
+                return false;
+            }
+            return (m_value == ((Char)obj).m_value);
+        }
+
+        [System.Runtime.Versioning.NonVersionable]
+        public bool Equals(Char obj)
+        {
+            return m_value == obj;
+        }
+
+        // Compares this object to another object, returning an integer that
+        // indicates the relationship. 
+        // Returns a value less than zero if this  object
+        // null is considered to be less than any instance.
+        // If object is not of type Char, this method throws an ArgumentException.
+        //
+        public int CompareTo(Object value)
+        {
+            if (value == null)
+            {
+                return 1;
+            }
+            if (!(value is Char))
+            {
+                throw new ArgumentException(SR.Arg_MustBeChar);
+            }
+
+            return (m_value - ((Char)value).m_value);
+        }
+
+        public int CompareTo(Char value)
+        {
+            return (m_value - value);
+        }
+
+        // Overrides System.Object.ToString.
+        public override String ToString()
+        {
+            return Char.ToString(m_value);
+        }
+
+        public String ToString(IFormatProvider provider)
+        {
+            return Char.ToString(m_value);
+        }
+
+        //
+        // Formatting Methods
+        //
+
+        /*===================================ToString===================================
+        **This static methods takes a character and returns the String representation of it.
+        ==============================================================================*/
+        // Provides a string representation of a character.
+        public static string ToString(char c) => string.CreateFromChar(c);
+
+        public static char Parse(String s)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+
+            if (s.Length != 1)
+            {
+                throw new FormatException(SR.Format_NeedSingleChar);
+            }
+            return s[0];
+        }
+
+        public static bool TryParse(String s, out Char result)
+        {
+            result = '\0';
+            if (s == null)
+            {
+                return false;
+            }
+            if (s.Length != 1)
+            {
+                return false;
+            }
+            result = s[0];
+            return true;
+        }
+
+        //
+        // Static Methods
+        //
+        /*=================================ISDIGIT======================================
+        **A wrapper for Char.  Returns a boolean indicating whether    **
+        **character c is considered to be a digit.                                    **
+        ==============================================================================*/
+        // Determines whether a character is a digit.
+        public static bool IsDigit(char c)
+        {
+            if (IsLatin1(c))
+            {
+                return (c >= '0' && c <= '9');
+            }
+            return (CharUnicodeInfo.GetUnicodeCategory(c) == UnicodeCategory.DecimalDigitNumber);
+        }
+
+
+        /*=================================CheckLetter=====================================
+        ** Check if the specified UnicodeCategory belongs to the letter categories.
+        ==============================================================================*/
+        internal static bool CheckLetter(UnicodeCategory uc)
+        {
+            switch (uc)
+            {
+                case (UnicodeCategory.UppercaseLetter):
+                case (UnicodeCategory.LowercaseLetter):
+                case (UnicodeCategory.TitlecaseLetter):
+                case (UnicodeCategory.ModifierLetter):
+                case (UnicodeCategory.OtherLetter):
+                    return (true);
+            }
+            return (false);
+        }
+
+        /*=================================ISLETTER=====================================
+        **A wrapper for Char.  Returns a boolean indicating whether    **
+        **character c is considered to be a letter.                                   **
+        ==============================================================================*/
+        // Determines whether a character is a letter.
+        public static bool IsLetter(char c)
+        {
+            if (IsLatin1(c))
+            {
+                if (IsAscii(c))
+                {
+                    c |= (char)0x20;
+                    return ((c >= 'a' && c <= 'z'));
+                }
+                return (CheckLetter(GetLatin1UnicodeCategory(c)));
+            }
+            return (CheckLetter(CharUnicodeInfo.GetUnicodeCategory(c)));
+        }
+
+        private static bool IsWhiteSpaceLatin1(char c)
+        {
+            // There are characters which belong to UnicodeCategory.Control but are considered as white spaces.
+            // We use code point comparisons for these characters here as a temporary fix.
+
+            // U+0009 = <control> HORIZONTAL TAB
+            // U+000a = <control> LINE FEED
+            // U+000b = <control> VERTICAL TAB
+            // U+000c = <contorl> FORM FEED
+            // U+000d = <control> CARRIAGE RETURN
+            // U+0085 = <control> NEXT LINE
+            // U+00a0 = NO-BREAK SPACE
+            return
+                c == ' ' ||
+                (uint)(c - '\x0009') <= ('\x000d' - '\x0009') || // (c >= '\x0009' && c <= '\x000d')
+                c == '\x00a0' ||
+                c == '\x0085';
+        }
+
+        /*===============================ISWHITESPACE===================================
+        **A wrapper for Char.  Returns a boolean indicating whether    **
+        **character c is considered to be a whitespace character.                     **
+        ==============================================================================*/
+        // Determines whether a character is whitespace.
+        public static bool IsWhiteSpace(char c)
+        {
+            if (IsLatin1(c))
+            {
+                return (IsWhiteSpaceLatin1(c));
+            }
+            return CharUnicodeInfo.IsWhiteSpace(c);
+        }
+
+
+        /*===================================IsUpper====================================
+        **Arguments: c -- the characater to be checked.
+        **Returns:  True if c is an uppercase character.
+        ==============================================================================*/
+        // Determines whether a character is upper-case.
+        public static bool IsUpper(char c)
+        {
+            if (IsLatin1(c))
+            {
+                if (IsAscii(c))
+                {
+                    return (c >= 'A' && c <= 'Z');
+                }
+                return (GetLatin1UnicodeCategory(c) == UnicodeCategory.UppercaseLetter);
+            }
+            return (CharUnicodeInfo.GetUnicodeCategory(c) == UnicodeCategory.UppercaseLetter);
+        }
+
+        /*===================================IsLower====================================
+        **Arguments: c -- the characater to be checked.
+        **Returns:  True if c is an lowercase character.
+        ==============================================================================*/
+        // Determines whether a character is lower-case.
+        public static bool IsLower(char c)
+        {
+            if (IsLatin1(c))
+            {
+                if (IsAscii(c))
+                {
+                    return (c >= 'a' && c <= 'z');
+                }
+                return (GetLatin1UnicodeCategory(c) == UnicodeCategory.LowercaseLetter);
+            }
+            return (CharUnicodeInfo.GetUnicodeCategory(c) == UnicodeCategory.LowercaseLetter);
+        }
+
+        internal static bool CheckPunctuation(UnicodeCategory uc)
+        {
+            switch (uc)
+            {
+                case UnicodeCategory.ConnectorPunctuation:
+                case UnicodeCategory.DashPunctuation:
+                case UnicodeCategory.OpenPunctuation:
+                case UnicodeCategory.ClosePunctuation:
+                case UnicodeCategory.InitialQuotePunctuation:
+                case UnicodeCategory.FinalQuotePunctuation:
+                case UnicodeCategory.OtherPunctuation:
+                    return (true);
+            }
+            return (false);
+        }
+
+
+        /*================================IsPunctuation=================================
+        **Arguments: c -- the characater to be checked.
+        **Returns:  True if c is an punctuation mark
+        ==============================================================================*/
+        // Determines whether a character is a punctuation mark.
+        public static bool IsPunctuation(char c)
+        {
+            if (IsLatin1(c))
+            {
+                return (CheckPunctuation(GetLatin1UnicodeCategory(c)));
+            }
+            return (CheckPunctuation(CharUnicodeInfo.GetUnicodeCategory(c)));
+        }
+
+        /*=================================CheckLetterOrDigit=====================================
+        ** Check if the specified UnicodeCategory belongs to the letter or digit categories.
+        ==============================================================================*/
+        internal static bool CheckLetterOrDigit(UnicodeCategory uc)
+        {
+            switch (uc)
+            {
+                case UnicodeCategory.UppercaseLetter:
+                case UnicodeCategory.LowercaseLetter:
+                case UnicodeCategory.TitlecaseLetter:
+                case UnicodeCategory.ModifierLetter:
+                case UnicodeCategory.OtherLetter:
+                case UnicodeCategory.DecimalDigitNumber:
+                    return (true);
+            }
+            return (false);
+        }
+
+        // Determines whether a character is a letter or a digit.
+        public static bool IsLetterOrDigit(char c)
+        {
+            if (IsLatin1(c))
+            {
+                return (CheckLetterOrDigit(GetLatin1UnicodeCategory(c)));
+            }
+            return (CheckLetterOrDigit(CharUnicodeInfo.GetUnicodeCategory(c)));
+        }
+
+        /*===================================ToUpper====================================
+        **
+        ==============================================================================*/
+        // Converts a character to upper-case for the specified culture.
+        // <;<;Not fully implemented>;>;
+        public static char ToUpper(char c, CultureInfo culture)
+        {
+            if (culture == null)
+                throw new ArgumentNullException(nameof(culture));
+            return culture.TextInfo.ToUpper(c);
+        }
+
+        /*=================================TOUPPER======================================
+        **A wrapper for Char.toUpperCase.  Converts character c to its **
+        **uppercase equivalent.  If c is already an uppercase character or is not an  **
+        **alphabetic, nothing happens.                                                **
+        ==============================================================================*/
+        // Converts a character to upper-case for the default culture.
+        //
+        public static char ToUpper(char c)
+        {
+            return CultureInfo.CurrentCulture.TextInfo.ToUpper(c);
+        }
+
+
+        // Converts a character to upper-case for invariant culture.
+        public static char ToUpperInvariant(char c)
+        {
+            return CultureInfo.InvariantCulture.TextInfo.ToUpper(c);
+        }
+
+
+        /*===================================ToLower====================================
+        **
+        ==============================================================================*/
+        // Converts a character to lower-case for the specified culture.
+        // <;<;Not fully implemented>;>;
+        public static char ToLower(char c, CultureInfo culture)
+        {
+            if (culture == null)
+                throw new ArgumentNullException(nameof(culture));
+            return culture.TextInfo.ToLower(c);
+        }
+
+        /*=================================TOLOWER======================================
+        **A wrapper for Char.toLowerCase.  Converts character c to its **
+        **lowercase equivalent.  If c is already a lowercase character or is not an   **
+        **alphabetic, nothing happens.                                                **
+        ==============================================================================*/
+        // Converts a character to lower-case for the default culture.
+        public static char ToLower(char c)
+        {
+            return CultureInfo.CurrentCulture.TextInfo.ToLower(c);
+        }
+
+
+        // Converts a character to lower-case for invariant culture.
+        public static char ToLowerInvariant(char c)
+        {
+            return CultureInfo.InvariantCulture.TextInfo.ToLower(c);
+        }
+
+
+        //
+        // IConvertible implementation
+        //    
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.Char;
+        }
+
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Char", "Boolean"));
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            return m_value;
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return Convert.ToSByte(m_value);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return Convert.ToByte(m_value);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return Convert.ToInt16(m_value);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return Convert.ToUInt16(m_value);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return Convert.ToInt32(m_value);
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return Convert.ToUInt32(m_value);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return Convert.ToInt64(m_value);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return Convert.ToUInt64(m_value);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Char", "Single"));
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Char", "Double"));
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Char", "Decimal"));
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Char", "DateTime"));
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+        public static bool IsControl(char c)
+        {
+            if (IsLatin1(c))
+            {
+                return (GetLatin1UnicodeCategory(c) == UnicodeCategory.Control);
+            }
+            return (CharUnicodeInfo.GetUnicodeCategory(c) == UnicodeCategory.Control);
+        }
+
+        public static bool IsControl(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            char c = s[index];
+            if (IsLatin1(c))
+            {
+                return (GetLatin1UnicodeCategory(c) == UnicodeCategory.Control);
+            }
+            return (CharUnicodeInfo.GetUnicodeCategory(s, index) == UnicodeCategory.Control);
+        }
+
+
+        public static bool IsDigit(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            char c = s[index];
+            if (IsLatin1(c))
+            {
+                return (c >= '0' && c <= '9');
+            }
+            return (CharUnicodeInfo.GetUnicodeCategory(s, index) == UnicodeCategory.DecimalDigitNumber);
+        }
+
+        public static bool IsLetter(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            char c = s[index];
+            if (IsLatin1(c))
+            {
+                if (IsAscii(c))
+                {
+                    c |= (char)0x20;
+                    return ((c >= 'a' && c <= 'z'));
+                }
+                return (CheckLetter(GetLatin1UnicodeCategory(c)));
+            }
+            return (CheckLetter(CharUnicodeInfo.GetUnicodeCategory(s, index)));
+        }
+
+        public static bool IsLetterOrDigit(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            char c = s[index];
+            if (IsLatin1(c))
+            {
+                return CheckLetterOrDigit(GetLatin1UnicodeCategory(c));
+            }
+            return CheckLetterOrDigit(CharUnicodeInfo.GetUnicodeCategory(s, index));
+        }
+
+        public static bool IsLower(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            char c = s[index];
+            if (IsLatin1(c))
+            {
+                if (IsAscii(c))
+                {
+                    return (c >= 'a' && c <= 'z');
+                }
+                return (GetLatin1UnicodeCategory(c) == UnicodeCategory.LowercaseLetter);
+            }
+
+            return (CharUnicodeInfo.GetUnicodeCategory(s, index) == UnicodeCategory.LowercaseLetter);
+        }
+
+        /*=================================CheckNumber=====================================
+        ** Check if the specified UnicodeCategory belongs to the number categories.
+        ==============================================================================*/
+
+        internal static bool CheckNumber(UnicodeCategory uc)
+        {
+            switch (uc)
+            {
+                case (UnicodeCategory.DecimalDigitNumber):
+                case (UnicodeCategory.LetterNumber):
+                case (UnicodeCategory.OtherNumber):
+                    return (true);
+            }
+            return (false);
+        }
+
+        public static bool IsNumber(char c)
+        {
+            if (IsLatin1(c))
+            {
+                if (IsAscii(c))
+                {
+                    return (c >= '0' && c <= '9');
+                }
+                return (CheckNumber(GetLatin1UnicodeCategory(c)));
+            }
+            return (CheckNumber(CharUnicodeInfo.GetUnicodeCategory(c)));
+        }
+
+        public static bool IsNumber(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            char c = s[index];
+            if (IsLatin1(c))
+            {
+                if (IsAscii(c))
+                {
+                    return (c >= '0' && c <= '9');
+                }
+                return (CheckNumber(GetLatin1UnicodeCategory(c)));
+            }
+            return (CheckNumber(CharUnicodeInfo.GetUnicodeCategory(s, index)));
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  IsPunctuation
+        //
+        //  Determines if the given character is a punctuation character.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        public static bool IsPunctuation(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            char c = s[index];
+            if (IsLatin1(c))
+            {
+                return (CheckPunctuation(GetLatin1UnicodeCategory(c)));
+            }
+            return (CheckPunctuation(CharUnicodeInfo.GetUnicodeCategory(s, index)));
+        }
+
+
+        /*================================= CheckSeparator ============================
+        ** Check if the specified UnicodeCategory belongs to the seprator categories.
+        ==============================================================================*/
+
+        internal static bool CheckSeparator(UnicodeCategory uc)
+        {
+            switch (uc)
+            {
+                case UnicodeCategory.SpaceSeparator:
+                case UnicodeCategory.LineSeparator:
+                case UnicodeCategory.ParagraphSeparator:
+                    return (true);
+            }
+            return (false);
+        }
+
+        private static bool IsSeparatorLatin1(char c)
+        {
+            // U+00a0 = NO-BREAK SPACE
+            // There is no LineSeparator or ParagraphSeparator in Latin 1 range.
+            return (c == '\x0020' || c == '\x00a0');
+        }
+
+        public static bool IsSeparator(char c)
+        {
+            if (IsLatin1(c))
+            {
+                return (IsSeparatorLatin1(c));
+            }
+            return (CheckSeparator(CharUnicodeInfo.GetUnicodeCategory(c)));
+        }
+
+        public static bool IsSeparator(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            char c = s[index];
+            if (IsLatin1(c))
+            {
+                return (IsSeparatorLatin1(c));
+            }
+            return (CheckSeparator(CharUnicodeInfo.GetUnicodeCategory(s, index)));
+        }
+
+        public static bool IsSurrogate(char c)
+        {
+            return (c >= HIGH_SURROGATE_START && c <= LOW_SURROGATE_END);
+        }
+
+        public static bool IsSurrogate(String s, int index)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            return (IsSurrogate(s[index]));
+        }
+
+        /*================================= CheckSymbol ============================
+         ** Check if the specified UnicodeCategory belongs to the symbol categories.
+         ==============================================================================*/
+
+        internal static bool CheckSymbol(UnicodeCategory uc)
+        {
+            switch (uc)
+            {
+                case (UnicodeCategory.MathSymbol):
+                case (UnicodeCategory.CurrencySymbol):
+                case (UnicodeCategory.ModifierSymbol):
+                case (UnicodeCategory.OtherSymbol):
+                    return (true);
+            }
+            return (false);
+        }
+
+        public static bool IsSymbol(char c)
+        {
+            if (IsLatin1(c))
+            {
+                return (CheckSymbol(GetLatin1UnicodeCategory(c)));
+            }
+            return (CheckSymbol(CharUnicodeInfo.GetUnicodeCategory(c)));
+        }
+
+        public static bool IsSymbol(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            char c = s[index];
+            if (IsLatin1(c))
+            {
+                return (CheckSymbol(GetLatin1UnicodeCategory(c)));
+            }
+            return (CheckSymbol(CharUnicodeInfo.GetUnicodeCategory(s, index)));
+        }
+
+
+        public static bool IsUpper(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            char c = s[index];
+            if (IsLatin1(c))
+            {
+                if (IsAscii(c))
+                {
+                    return (c >= 'A' && c <= 'Z');
+                }
+                return (GetLatin1UnicodeCategory(c) == UnicodeCategory.UppercaseLetter);
+            }
+
+            return (CharUnicodeInfo.GetUnicodeCategory(s, index) == UnicodeCategory.UppercaseLetter);
+        }
+
+        public static bool IsWhiteSpace(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+
+            if (IsLatin1(s[index]))
+            {
+                return IsWhiteSpaceLatin1(s[index]);
+            }
+
+            return CharUnicodeInfo.IsWhiteSpace(s, index);
+        }
+
+        public static UnicodeCategory GetUnicodeCategory(char c)
+        {
+            if (IsLatin1(c))
+            {
+                return (GetLatin1UnicodeCategory(c));
+            }
+            return CharUnicodeInfo.GetUnicodeCategory((int)c);
+        }
+
+        public static UnicodeCategory GetUnicodeCategory(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            if (IsLatin1(s[index]))
+            {
+                return (GetLatin1UnicodeCategory(s[index]));
+            }
+            return CharUnicodeInfo.InternalGetUnicodeCategory(s, index);
+        }
+
+        public static double GetNumericValue(char c)
+        {
+            return CharUnicodeInfo.GetNumericValue(c);
+        }
+
+        public static double GetNumericValue(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            return CharUnicodeInfo.GetNumericValue(s, index);
+        }
+
+
+        /*================================= IsHighSurrogate ============================
+         ** Check if a char is a high surrogate.
+         ==============================================================================*/
+        public static bool IsHighSurrogate(char c)
+        {
+            return ((c >= CharUnicodeInfo.HIGH_SURROGATE_START) && (c <= CharUnicodeInfo.HIGH_SURROGATE_END));
+        }
+
+        public static bool IsHighSurrogate(String s, int index)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+            if (index < 0 || index >= s.Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            return (IsHighSurrogate(s[index]));
+        }
+
+        /*================================= IsLowSurrogate ============================
+         ** Check if a char is a low surrogate.
+         ==============================================================================*/
+        public static bool IsLowSurrogate(char c)
+        {
+            return ((c >= CharUnicodeInfo.LOW_SURROGATE_START) && (c <= CharUnicodeInfo.LOW_SURROGATE_END));
+        }
+
+        public static bool IsLowSurrogate(String s, int index)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+            if (index < 0 || index >= s.Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            return (IsLowSurrogate(s[index]));
+        }
+
+        /*================================= IsSurrogatePair ============================
+         ** Check if the string specified by the index starts with a surrogate pair.
+         ==============================================================================*/
+        public static bool IsSurrogatePair(String s, int index)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+            if (index < 0 || index >= s.Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            if (index + 1 < s.Length)
+            {
+                return (IsSurrogatePair(s[index], s[index + 1]));
+            }
+            return (false);
+        }
+
+        public static bool IsSurrogatePair(char highSurrogate, char lowSurrogate)
+        {
+            return ((highSurrogate >= CharUnicodeInfo.HIGH_SURROGATE_START && highSurrogate <= CharUnicodeInfo.HIGH_SURROGATE_END) &&
+                    (lowSurrogate >= CharUnicodeInfo.LOW_SURROGATE_START && lowSurrogate <= CharUnicodeInfo.LOW_SURROGATE_END));
+        }
+
+        internal const int UNICODE_PLANE00_END = 0x00ffff;
+        // The starting codepoint for Unicode plane 1.  Plane 1 contains 0x010000 ~ 0x01ffff.
+        internal const int UNICODE_PLANE01_START = 0x10000;
+        // The end codepoint for Unicode plane 16.  This is the maximum code point value allowed for Unicode.
+        // Plane 16 contains 0x100000 ~ 0x10ffff.
+        internal const int UNICODE_PLANE16_END = 0x10ffff;
+
+        internal const int HIGH_SURROGATE_START = 0x00d800;
+        internal const int LOW_SURROGATE_END = 0x00dfff;
+
+
+
+        /*================================= ConvertFromUtf32 ============================
+         ** Convert an UTF32 value into a surrogate pair.
+         ==============================================================================*/
+
+        public static String ConvertFromUtf32(int utf32)
+        {
+            // For UTF32 values from U+00D800 ~ U+00DFFF, we should throw.  They
+            // are considered as irregular code unit sequence, but they are not illegal.
+            if ((utf32 < 0 || utf32 > UNICODE_PLANE16_END) || (utf32 >= HIGH_SURROGATE_START && utf32 <= LOW_SURROGATE_END))
+            {
+                throw new ArgumentOutOfRangeException(nameof(utf32), SR.ArgumentOutOfRange_InvalidUTF32);
+            }
+
+            if (utf32 < UNICODE_PLANE01_START)
+            {
+                // This is a BMP character.
+                return (Char.ToString((char)utf32));
+            }
+
+            unsafe
+            {
+                // This is a supplementary character.  Convert it to a surrogate pair in UTF-16.
+                utf32 -= UNICODE_PLANE01_START;
+                uint surrogate = 0; // allocate 2 chars worth of stack space
+                char* address = (char*)&surrogate;
+                address[0] = (char)((utf32 / 0x400) + (int)CharUnicodeInfo.HIGH_SURROGATE_START);
+                address[1] = (char)((utf32 % 0x400) + (int)CharUnicodeInfo.LOW_SURROGATE_START);
+                return new string(address, 0, 2);
+            }
+        }
+
+
+        /*=============================ConvertToUtf32===================================
+        ** Convert a surrogate pair to UTF32 value                                    
+        ==============================================================================*/
+
+        public static int ConvertToUtf32(char highSurrogate, char lowSurrogate)
+        {
+            if (!IsHighSurrogate(highSurrogate))
+            {
+                throw new ArgumentOutOfRangeException(nameof(highSurrogate), SR.ArgumentOutOfRange_InvalidHighSurrogate);
+            }
+            if (!IsLowSurrogate(lowSurrogate))
+            {
+                throw new ArgumentOutOfRangeException(nameof(lowSurrogate), SR.ArgumentOutOfRange_InvalidLowSurrogate);
+            }
+            return (((highSurrogate - CharUnicodeInfo.HIGH_SURROGATE_START) * 0x400) + (lowSurrogate - CharUnicodeInfo.LOW_SURROGATE_START) + UNICODE_PLANE01_START);
+        }
+
+        /*=============================ConvertToUtf32===================================
+        ** Convert a character or a surrogate pair starting at index of the specified string 
+        ** to UTF32 value.
+        ** The char pointed by index should be a surrogate pair or a BMP character.
+        ** This method throws if a high-surrogate is not followed by a low surrogate.
+        ** This method throws if a low surrogate is seen without preceding a high-surrogate.
+        ==============================================================================*/
+
+        public static int ConvertToUtf32(String s, int index)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+
+            if (index < 0 || index >= s.Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+            }
+            // Check if the character at index is a high surrogate.
+            int temp1 = (int)s[index] - CharUnicodeInfo.HIGH_SURROGATE_START;
+            if (temp1 >= 0 && temp1 <= 0x7ff)
+            {
+                // Found a surrogate char.
+                if (temp1 <= 0x3ff)
+                {
+                    // Found a high surrogate.
+                    if (index < s.Length - 1)
+                    {
+                        int temp2 = (int)s[index + 1] - CharUnicodeInfo.LOW_SURROGATE_START;
+                        if (temp2 >= 0 && temp2 <= 0x3ff)
+                        {
+                            // Found a low surrogate.
+                            return ((temp1 * 0x400) + temp2 + UNICODE_PLANE01_START);
+                        }
+                        else
+                        {
+                            throw new ArgumentException(SR.Format(SR.Argument_InvalidHighSurrogate, index), nameof(s));
+                        }
+                    }
+                    else
+                    {
+                        // Found a high surrogate at the end of the string.
+                        throw new ArgumentException(SR.Format(SR.Argument_InvalidHighSurrogate, index), nameof(s));
+                    }
+                }
+                else
+                {
+                    // Find a low surrogate at the character pointed by index.
+                    throw new ArgumentException(SR.Format(SR.Argument_InvalidLowSurrogate, index), nameof(s));
+                }
+            }
+            // Not a high-surrogate or low-surrogate. Genereate the UTF32 value for the BMP characters.
+            return ((int)s[index]);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/CharEnumerator.cs b/src/System.Private.CoreLib/shared/System/CharEnumerator.cs
new file mode 100644
index 0000000000..ea9915a7c4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/CharEnumerator.cs
@@ -0,0 +1,80 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Enumerates the characters on a string.  skips range
+**          checks.
+**
+**
+============================================================*/
+
+using System.Collections;
+using System.Collections.Generic;
+
+namespace System
+{
+    public sealed class CharEnumerator : IEnumerator, IEnumerator<char>, IDisposable, ICloneable
+    {
+        private String _str;
+        private int _index;
+        private char _currentElement;
+
+        internal CharEnumerator(String str)
+        {
+            _str = str;
+            _index = -1;
+        }
+
+        public object Clone()
+        {
+            return MemberwiseClone();
+        }
+
+        public bool MoveNext()
+        {
+            if (_index < (_str.Length - 1))
+            {
+                _index++;
+                _currentElement = _str[_index];
+                return true;
+            }
+            else
+                _index = _str.Length;
+            return false;
+        }
+
+        public void Dispose()
+        {
+            if (_str != null)
+                _index = _str.Length;
+            _str = null;
+        }
+
+        Object IEnumerator.Current
+        {
+            get { return Current; }
+        }
+
+        public char Current
+        {
+            get
+            {
+                if (_index == -1)
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumNotStarted);
+                if (_index >= _str.Length)
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumEnded);
+                return _currentElement;
+            }
+        }
+
+        public void Reset()
+        {
+            _currentElement = (char)0;
+            _index = -1;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Comparer.cs b/src/System.Private.CoreLib/shared/System/Collections/Comparer.cs
new file mode 100644
index 0000000000..6fcedc09ab
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Comparer.cs
@@ -0,0 +1,77 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Purpose: Default IComparer implementation.
+**
+===========================================================*/
+
+using System.Globalization;
+using System.Runtime.Serialization;
+
+namespace System.Collections
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class Comparer : IComparer, ISerializable
+    {
+        private CompareInfo _compareInfo;
+
+        public static readonly Comparer Default = new Comparer(CultureInfo.CurrentCulture);
+        public static readonly Comparer DefaultInvariant = new Comparer(CultureInfo.InvariantCulture);
+
+        public Comparer(CultureInfo culture)
+        {
+            if (culture == null)
+                throw new ArgumentNullException(nameof(culture));
+
+            _compareInfo = culture.CompareInfo;
+        }
+
+        private Comparer(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+                throw new ArgumentNullException(nameof(info));
+
+            _compareInfo = (CompareInfo)info.GetValue("CompareInfo", typeof(CompareInfo));
+        }
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+                throw new ArgumentNullException(nameof(info));
+
+            info.AddValue("CompareInfo", _compareInfo);
+        }
+
+        // Compares two Objects by calling CompareTo.
+        // If a == b, 0 is returned.
+        // If a implements IComparable, a.CompareTo(b) is returned.
+        // If a doesn't implement IComparable and b does, -(b.CompareTo(a)) is returned.
+        // Otherwise an exception is thrown.
+        // 
+        public int Compare(Object a, Object b)
+        {
+            if (a == b) return 0;
+            if (a == null) return -1;
+            if (b == null) return 1;
+
+            string sa = a as string;
+            string sb = b as string;
+            if (sa != null && sb != null)
+                return _compareInfo.Compare(sa, sb);
+
+            IComparable ia = a as IComparable;
+            if (ia != null)
+                return ia.CompareTo(b);
+
+            IComparable ib = b as IComparable;
+            if (ib != null)
+                return -ib.CompareTo(a);
+
+            throw new ArgumentException(SR.Argument_ImplementIComparable);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/CompatibleComparer.cs b/src/System.Private.CoreLib/shared/System/Collections/CompatibleComparer.cs
new file mode 100644
index 0000000000..587fd68391
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/CompatibleComparer.cs
@@ -0,0 +1,61 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#pragma warning disable 618 // obsolete types
+
+namespace System.Collections
+{
+    internal sealed class CompatibleComparer : IEqualityComparer
+    {
+        private readonly IHashCodeProvider _hcp;
+        private readonly IComparer _comparer;
+
+        internal CompatibleComparer(IHashCodeProvider hashCodeProvider, IComparer comparer)
+        {
+            _hcp = hashCodeProvider;
+            _comparer = comparer;
+        }
+
+        internal IHashCodeProvider HashCodeProvider => _hcp;
+
+        internal IComparer Comparer => _comparer;
+
+        public new bool Equals(object a, object b) => Compare(a, b) == 0;
+
+        public int Compare(object a, object b)
+        {
+            if (a == b)
+                return 0;
+            if (a == null)
+                return -1;
+            if (b == null)
+                return 1;
+
+            if (_comparer != null)
+            {
+                return _comparer.Compare(a, b);
+            }
+
+            IComparable ia = a as IComparable;
+            if (ia != null)
+            {
+                return ia.CompareTo(b);
+            }
+
+            throw new ArgumentException(SR.Argument_ImplementIComparable);
+        }
+
+        public int GetHashCode(object obj)
+        {
+            if (obj == null)
+            {
+                throw new ArgumentNullException(nameof(obj));
+            }
+
+            return _hcp != null ?
+                _hcp.GetHashCode(obj) :
+                obj.GetHashCode();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/DictionaryEntry.cs b/src/System.Private.CoreLib/shared/System/Collections/DictionaryEntry.cs
new file mode 100644
index 0000000000..3c1c0befa3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/DictionaryEntry.cs
@@ -0,0 +1,59 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+
+namespace System.Collections
+{
+    // A DictionaryEntry holds a key and a value from a dictionary.
+    // It is returned by IDictionaryEnumerator::GetEntry().
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct DictionaryEntry
+    {
+        private Object _key; // Do not rename (binary serialization)
+        private Object _value; // Do not rename (binary serialization)
+
+        // Constructs a new DictionaryEnumerator by setting the Key
+        // and Value fields appropriately.
+        public DictionaryEntry(Object key, Object value)
+        {
+            _key = key;
+            _value = value;
+        }
+
+        public Object Key
+        {
+            get
+            {
+                return _key;
+            }
+
+            set
+            {
+                _key = value;
+            }
+        }
+
+        public Object Value
+        {
+            get
+            {
+                return _value;
+            }
+
+            set
+            {
+                _value = value;
+            }
+        }
+
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public void Deconstruct(out object key, out object value)
+        {
+            key = Key;
+            value = Value;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/Dictionary.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/Dictionary.cs
new file mode 100644
index 0000000000..da5d8bb86b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/Dictionary.cs
@@ -0,0 +1,1624 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.Serialization;
+using System.Threading;
+
+namespace System.Collections.Generic
+{
+    /// <summary>
+    /// Used internally to control behavior of insertion into a <see cref="Dictionary{TKey, TValue}"/>.
+    /// </summary>
+    internal enum InsertionBehavior : byte
+    {
+        /// <summary>
+        /// The default insertion behavior.
+        /// </summary>
+        None = 0,
+
+        /// <summary>
+        /// Specifies that an existing entry with the same key should be overwritten if encountered.
+        /// </summary>
+        OverwriteExisting = 1,
+
+        /// <summary>
+        /// Specifies that if an existing entry with the same key is encountered, an exception should be thrown.
+        /// </summary>
+        ThrowOnExisting = 2
+    }
+
+    [DebuggerTypeProxy(typeof(IDictionaryDebugView<,>))]
+    [DebuggerDisplay("Count = {Count}")]
+    [Serializable]
+    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class Dictionary<TKey, TValue> : IDictionary<TKey, TValue>, IDictionary, IReadOnlyDictionary<TKey, TValue>, ISerializable, IDeserializationCallback
+    {
+        private struct Entry
+        {
+            public int hashCode;    // Lower 31 bits of hash code, -1 if unused
+            public int next;        // Index of next entry, -1 if last
+            public TKey key;           // Key of entry
+            public TValue value;         // Value of entry
+        }
+
+        private int[] _buckets;
+        private Entry[] _entries;
+        private int _count;
+        private int _freeList;
+        private int _freeCount;
+        private int _version;
+        private IEqualityComparer<TKey> _comparer;
+        private KeyCollection _keys;
+        private ValueCollection _values;
+        private object _syncRoot;
+
+        // constants for serialization
+        private const string VersionName = "Version"; // Do not rename (binary serialization)
+        private const string HashSizeName = "HashSize"; // Do not rename (binary serialization). Must save buckets.Length
+        private const string KeyValuePairsName = "KeyValuePairs"; // Do not rename (binary serialization)
+        private const string ComparerName = "Comparer"; // Do not rename (binary serialization)
+
+        public Dictionary() : this(0, null) { }
+
+        public Dictionary(int capacity) : this(capacity, null) { }
+
+        public Dictionary(IEqualityComparer<TKey> comparer) : this(0, comparer) { }
+
+        public Dictionary(int capacity, IEqualityComparer<TKey> comparer)
+        {
+            if (capacity < 0) ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.capacity);
+            if (capacity > 0) Initialize(capacity);
+            if (comparer != EqualityComparer<TKey>.Default)
+            {
+                _comparer = comparer;
+            }
+
+            if (typeof(TKey) == typeof(string) && _comparer == null)
+            {
+                // To start, move off default comparer for string which is randomised
+                _comparer = (IEqualityComparer<TKey>)NonRandomizedStringEqualityComparer.Default;
+            }
+        }
+
+        public Dictionary(IDictionary<TKey, TValue> dictionary) : this(dictionary, null) { }
+
+        public Dictionary(IDictionary<TKey, TValue> dictionary, IEqualityComparer<TKey> comparer) :
+            this(dictionary != null ? dictionary.Count : 0, comparer)
+        {
+            if (dictionary == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.dictionary);
+            }
+
+            // It is likely that the passed-in dictionary is Dictionary<TKey,TValue>. When this is the case,
+            // avoid the enumerator allocation and overhead by looping through the entries array directly.
+            // We only do this when dictionary is Dictionary<TKey,TValue> and not a subclass, to maintain
+            // back-compat with subclasses that may have overridden the enumerator behavior.
+            if (dictionary.GetType() == typeof(Dictionary<TKey, TValue>))
+            {
+                Dictionary<TKey, TValue> d = (Dictionary<TKey, TValue>)dictionary;
+                int count = d._count;
+                Entry[] entries = d._entries;
+                for (int i = 0; i < count; i++)
+                {
+                    if (entries[i].hashCode >= 0)
+                    {
+                        Add(entries[i].key, entries[i].value);
+                    }
+                }
+                return;
+            }
+
+            foreach (KeyValuePair<TKey, TValue> pair in dictionary)
+            {
+                Add(pair.Key, pair.Value);
+            }
+        }
+
+        public Dictionary(IEnumerable<KeyValuePair<TKey, TValue>> collection) : this(collection, null) { }
+
+        public Dictionary(IEnumerable<KeyValuePair<TKey, TValue>> collection, IEqualityComparer<TKey> comparer) :
+            this((collection as ICollection<KeyValuePair<TKey, TValue>>)?.Count ?? 0, comparer)
+        {
+            if (collection == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.collection);
+            }
+
+            foreach (KeyValuePair<TKey, TValue> pair in collection)
+            {
+                Add(pair.Key, pair.Value);
+            }
+        }
+
+        protected Dictionary(SerializationInfo info, StreamingContext context)
+        {
+            // We can't do anything with the keys and values until the entire graph has been deserialized
+            // and we have a resonable estimate that GetHashCode is not going to fail.  For the time being,
+            // we'll just cache this.  The graph is not valid until OnDeserialization has been called.
+            HashHelpers.SerializationInfoTable.Add(this, info);
+        }
+
+        public IEqualityComparer<TKey> Comparer
+        {
+            get
+            {
+                return (_comparer == null || _comparer is NonRandomizedStringEqualityComparer) ? EqualityComparer<TKey>.Default : _comparer;
+            }
+        }
+
+        public int Count
+        {
+            get { return _count - _freeCount; }
+        }
+
+        public KeyCollection Keys
+        {
+            get
+            {
+                if (_keys == null) _keys = new KeyCollection(this);
+                return _keys;
+            }
+        }
+
+        ICollection<TKey> IDictionary<TKey, TValue>.Keys
+        {
+            get
+            {
+                if (_keys == null) _keys = new KeyCollection(this);
+                return _keys;
+            }
+        }
+
+        IEnumerable<TKey> IReadOnlyDictionary<TKey, TValue>.Keys
+        {
+            get
+            {
+                if (_keys == null) _keys = new KeyCollection(this);
+                return _keys;
+            }
+        }
+
+        public ValueCollection Values
+        {
+            get
+            {
+                if (_values == null) _values = new ValueCollection(this);
+                return _values;
+            }
+        }
+
+        ICollection<TValue> IDictionary<TKey, TValue>.Values
+        {
+            get
+            {
+                if (_values == null) _values = new ValueCollection(this);
+                return _values;
+            }
+        }
+
+        IEnumerable<TValue> IReadOnlyDictionary<TKey, TValue>.Values
+        {
+            get
+            {
+                if (_values == null) _values = new ValueCollection(this);
+                return _values;
+            }
+        }
+
+        public TValue this[TKey key]
+        {
+            get
+            {
+                int i = FindEntry(key);
+                if (i >= 0) return _entries[i].value;
+                ThrowHelper.ThrowKeyNotFoundException(key);
+                return default;
+            }
+            set
+            {
+                bool modified = TryInsert(key, value, InsertionBehavior.OverwriteExisting);
+                Debug.Assert(modified);
+            }
+        }
+
+        public void Add(TKey key, TValue value)
+        {
+            bool modified = TryInsert(key, value, InsertionBehavior.ThrowOnExisting);
+            Debug.Assert(modified); // If there was an existing key and the Add failed, an exception will already have been thrown.
+        }
+
+        void ICollection<KeyValuePair<TKey, TValue>>.Add(KeyValuePair<TKey, TValue> keyValuePair)
+            => Add(keyValuePair.Key, keyValuePair.Value);
+
+        bool ICollection<KeyValuePair<TKey, TValue>>.Contains(KeyValuePair<TKey, TValue> keyValuePair)
+        {
+            int i = FindEntry(keyValuePair.Key);
+            if (i >= 0 && EqualityComparer<TValue>.Default.Equals(_entries[i].value, keyValuePair.Value))
+            {
+                return true;
+            }
+            return false;
+        }
+
+        bool ICollection<KeyValuePair<TKey, TValue>>.Remove(KeyValuePair<TKey, TValue> keyValuePair)
+        {
+            int i = FindEntry(keyValuePair.Key);
+            if (i >= 0 && EqualityComparer<TValue>.Default.Equals(_entries[i].value, keyValuePair.Value))
+            {
+                Remove(keyValuePair.Key);
+                return true;
+            }
+            return false;
+        }
+
+        public void Clear()
+        {
+            int count = _count;
+            if (count > 0)
+            {
+                Array.Clear(_buckets, 0, _buckets.Length);
+
+                _count = 0;
+                _freeList = -1;
+                _freeCount = 0;
+                Array.Clear(_entries, 0, count);
+            }
+            _version++;
+        }
+
+        public bool ContainsKey(TKey key)
+            => FindEntry(key) >= 0;
+
+        public bool ContainsValue(TValue value)
+        {
+            Entry[] entries = _entries;
+            if (value == null)
+            {
+                for (int i = 0; i < _count; i++)
+                {
+                    if (entries[i].hashCode >= 0 && entries[i].value == null) return true;
+                }
+            }
+            else
+            {
+                if (default(TValue) != null)
+                {
+                    // ValueType: Devirtualize with EqualityComparer<TValue>.Default intrinsic
+                    for (int i = 0; i < _count; i++)
+                    {
+                        if (entries[i].hashCode >= 0 && EqualityComparer<TValue>.Default.Equals(entries[i].value, value)) return true;
+                    }
+                }
+                else
+                {
+                    // Object type: Shared Generic, EqualityComparer<TValue>.Default won't devirtualize
+                    // https://github.com/dotnet/coreclr/issues/17273
+                    // So cache in a local rather than get EqualityComparer per loop iteration
+                    EqualityComparer<TValue> defaultComparer = EqualityComparer<TValue>.Default;
+                    for (int i = 0; i < _count; i++)
+                    {
+                        if (entries[i].hashCode >= 0 && defaultComparer.Equals(entries[i].value, value)) return true;
+                    }
+                }
+            }
+            return false;
+        }
+
+        private void CopyTo(KeyValuePair<TKey, TValue>[] array, int index)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if ((uint)index > (uint)array.Length)
+            {
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            }
+
+            if (array.Length - index < Count)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall);
+            }
+
+            int count = _count;
+            Entry[] entries = _entries;
+            for (int i = 0; i < count; i++)
+            {
+                if (entries[i].hashCode >= 0)
+                {
+                    array[index++] = new KeyValuePair<TKey, TValue>(entries[i].key, entries[i].value);
+                }
+            }
+        }
+
+        public Enumerator GetEnumerator()
+            => new Enumerator(this, Enumerator.KeyValuePair);
+
+        IEnumerator<KeyValuePair<TKey, TValue>> IEnumerable<KeyValuePair<TKey, TValue>>.GetEnumerator()
+            => new Enumerator(this, Enumerator.KeyValuePair);
+
+        public virtual void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.info);
+            }
+
+            info.AddValue(VersionName, _version);
+            info.AddValue(ComparerName, _comparer ?? EqualityComparer<TKey>.Default, typeof(IEqualityComparer<TKey>));
+            info.AddValue(HashSizeName, _buckets == null ? 0 : _buckets.Length); // This is the length of the bucket array
+
+            if (_buckets != null)
+            {
+                var array = new KeyValuePair<TKey, TValue>[Count];
+                CopyTo(array, 0);
+                info.AddValue(KeyValuePairsName, array, typeof(KeyValuePair<TKey, TValue>[]));
+            }
+        }
+
+        private int FindEntry(TKey key)
+        {
+            if (key == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
+            }
+
+            int i = -1;
+            int[] buckets = _buckets;
+            Entry[] entries = _entries;
+            int collisionCount = 0;
+            if (buckets != null)
+            {
+                IEqualityComparer<TKey> comparer = _comparer;
+                if (comparer == null)
+                {
+                    int hashCode = key.GetHashCode() & 0x7FFFFFFF;
+                    // Value in _buckets is 1-based
+                    i = buckets[hashCode % buckets.Length] - 1;
+                    if (default(TKey) != null)
+                    {
+                        // ValueType: Devirtualize with EqualityComparer<TValue>.Default intrinsic
+                        do
+                        {
+                            // Should be a while loop https://github.com/dotnet/coreclr/issues/15476
+                            // Test in if to drop range check for following array access
+                            if ((uint)i >= (uint)entries.Length || (entries[i].hashCode == hashCode && EqualityComparer<TKey>.Default.Equals(entries[i].key, key)))
+                            {
+                                break;
+                            }
+
+                            i = entries[i].next;
+                            if (collisionCount >= entries.Length)
+                            {
+                                // The chain of entries forms a loop; which means a concurrent update has happened.
+                                // Break out of the loop and throw, rather than looping forever.
+                                ThrowHelper.ThrowInvalidOperationException_ConcurrentOperationsNotSupported();
+                            }
+                            collisionCount++;
+                        } while (true);
+                    }
+                    else
+                    {
+                        // Object type: Shared Generic, EqualityComparer<TValue>.Default won't devirtualize
+                        // https://github.com/dotnet/coreclr/issues/17273
+                        // So cache in a local rather than get EqualityComparer per loop iteration
+                        EqualityComparer<TKey> defaultComparer = EqualityComparer<TKey>.Default;
+                        do
+                        {
+                            // Should be a while loop https://github.com/dotnet/coreclr/issues/15476
+                            // Test in if to drop range check for following array access
+                            if ((uint)i >= (uint)entries.Length || (entries[i].hashCode == hashCode && defaultComparer.Equals(entries[i].key, key)))
+                            {
+                                break;
+                            }
+
+                            i = entries[i].next;
+                            if (collisionCount >= entries.Length)
+                            {
+                                // The chain of entries forms a loop; which means a concurrent update has happened.
+                                // Break out of the loop and throw, rather than looping forever.
+                                ThrowHelper.ThrowInvalidOperationException_ConcurrentOperationsNotSupported();
+                            }
+                            collisionCount++;
+                        } while (true);
+                    }
+                }
+                else
+                {
+                    int hashCode = comparer.GetHashCode(key) & 0x7FFFFFFF;
+                    // Value in _buckets is 1-based
+                    i = buckets[hashCode % buckets.Length] - 1;
+                    do
+                    {
+                        // Should be a while loop https://github.com/dotnet/coreclr/issues/15476
+                        // Test in if to drop range check for following array access
+                        if ((uint)i >= (uint)entries.Length ||
+                            (entries[i].hashCode == hashCode && comparer.Equals(entries[i].key, key)))
+                        {
+                            break;
+                        }
+
+                        i = entries[i].next;
+                        if (collisionCount >= entries.Length)
+                        {
+                            // The chain of entries forms a loop; which means a concurrent update has happened.
+                            // Break out of the loop and throw, rather than looping forever.
+                            ThrowHelper.ThrowInvalidOperationException_ConcurrentOperationsNotSupported();
+                        }
+                        collisionCount++;
+                    } while (true);
+                }
+            }
+
+            return i;
+        }
+
+        private int Initialize(int capacity)
+        {
+            int size = HashHelpers.GetPrime(capacity);
+
+            _freeList = -1;
+            _buckets = new int[size];
+            _entries = new Entry[size];
+
+            return size;
+        }
+
+        private bool TryInsert(TKey key, TValue value, InsertionBehavior behavior)
+        {
+            if (key == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
+            }
+
+            _version++;
+            if (_buckets == null)
+            {
+                Initialize(0);
+            }
+
+            Entry[] entries = _entries;
+            IEqualityComparer<TKey> comparer = _comparer;
+
+            int hashCode = ((comparer == null) ? key.GetHashCode() : comparer.GetHashCode(key)) & 0x7FFFFFFF;
+
+            int collisionCount = 0;
+            ref int bucket = ref _buckets[hashCode % _buckets.Length];
+            // Value in _buckets is 1-based
+            int i = bucket - 1;
+
+            if (comparer == null)
+            {
+                if (default(TKey) != null)
+                {
+                    // ValueType: Devirtualize with EqualityComparer<TValue>.Default intrinsic
+                    do
+                    {
+                        // Should be a while loop https://github.com/dotnet/coreclr/issues/15476
+                        // Test uint in if rather than loop condition to drop range check for following array access
+                        if ((uint)i >= (uint)entries.Length)
+                        {
+                            break;
+                        }
+
+                        if (entries[i].hashCode == hashCode && EqualityComparer<TKey>.Default.Equals(entries[i].key, key))
+                        {
+                            if (behavior == InsertionBehavior.OverwriteExisting)
+                            {
+                                entries[i].value = value;
+                                return true;
+                            }
+
+                            if (behavior == InsertionBehavior.ThrowOnExisting)
+                            {
+                                ThrowHelper.ThrowAddingDuplicateWithKeyArgumentException(key);
+                            }
+
+                            return false;
+                        }
+
+                        i = entries[i].next;
+                        if (collisionCount >= entries.Length)
+                        {
+                            // The chain of entries forms a loop; which means a concurrent update has happened.
+                            // Break out of the loop and throw, rather than looping forever.
+                            ThrowHelper.ThrowInvalidOperationException_ConcurrentOperationsNotSupported();
+                        }
+                        collisionCount++;
+                    } while (true);
+                }
+                else
+                {
+                    // Object type: Shared Generic, EqualityComparer<TValue>.Default won't devirtualize
+                    // https://github.com/dotnet/coreclr/issues/17273
+                    // So cache in a local rather than get EqualityComparer per loop iteration
+                    EqualityComparer<TKey> defaultComparer = EqualityComparer<TKey>.Default;
+                    do
+                    {
+                        // Should be a while loop https://github.com/dotnet/coreclr/issues/15476
+                        // Test uint in if rather than loop condition to drop range check for following array access
+                        if ((uint)i >= (uint)entries.Length)
+                        {
+                            break;
+                        }
+
+                        if (entries[i].hashCode == hashCode && defaultComparer.Equals(entries[i].key, key))
+                        {
+                            if (behavior == InsertionBehavior.OverwriteExisting)
+                            {
+                                entries[i].value = value;
+                                return true;
+                            }
+
+                            if (behavior == InsertionBehavior.ThrowOnExisting)
+                            {
+                                ThrowHelper.ThrowAddingDuplicateWithKeyArgumentException(key);
+                            }
+
+                            return false;
+                        }
+
+                        i = entries[i].next;
+                        if (collisionCount >= entries.Length)
+                        {
+                            // The chain of entries forms a loop; which means a concurrent update has happened.
+                            // Break out of the loop and throw, rather than looping forever.
+                            ThrowHelper.ThrowInvalidOperationException_ConcurrentOperationsNotSupported();
+                        }
+                        collisionCount++;
+                    } while (true);
+                }
+            }
+            else
+            {
+                do
+                {
+                    // Should be a while loop https://github.com/dotnet/coreclr/issues/15476
+                    // Test uint in if rather than loop condition to drop range check for following array access
+                    if ((uint)i >= (uint)entries.Length)
+                    {
+                        break;
+                    }
+
+                    if (entries[i].hashCode == hashCode && comparer.Equals(entries[i].key, key))
+                    {
+                        if (behavior == InsertionBehavior.OverwriteExisting)
+                        {
+                            entries[i].value = value;
+                            return true;
+                        }
+
+                        if (behavior == InsertionBehavior.ThrowOnExisting)
+                        {
+                            ThrowHelper.ThrowAddingDuplicateWithKeyArgumentException(key);
+                        }
+
+                        return false;
+                    }
+
+                    i = entries[i].next;
+                    if (collisionCount >= entries.Length)
+                    {
+                        // The chain of entries forms a loop; which means a concurrent update has happened.
+                        // Break out of the loop and throw, rather than looping forever.
+                        ThrowHelper.ThrowInvalidOperationException_ConcurrentOperationsNotSupported();
+                    }
+                    collisionCount++;
+                } while (true);
+
+            }
+
+            bool updateFreeList = false;
+            int index;
+            if (_freeCount > 0)
+            {
+                index = _freeList;
+                updateFreeList = true;
+                _freeCount--;
+            }
+            else
+            {
+                int count = _count;
+                if (count == entries.Length)
+                {
+                    Resize();
+                    bucket = ref _buckets[hashCode % _buckets.Length];
+                }
+                index = count;
+                _count = count + 1;
+                entries = _entries;
+            }
+
+            ref Entry entry = ref entries[index];
+
+            if (updateFreeList)
+            {
+                _freeList = entry.next;
+            }
+            entry.hashCode = hashCode;
+            // Value in _buckets is 1-based
+            entry.next = bucket - 1;
+            entry.key = key;
+            entry.value = value;
+            // Value in _buckets is 1-based
+            bucket = index + 1;
+
+            // Value types never rehash
+            if (default(TKey) == null && collisionCount > HashHelpers.HashCollisionThreshold && comparer is NonRandomizedStringEqualityComparer)
+            {
+                // If we hit the collision threshold we'll need to switch to the comparer which is using randomized string hashing
+                // i.e. EqualityComparer<string>.Default.
+                _comparer = null;
+                Resize(entries.Length, true);
+            }
+
+            return true;
+        }
+
+        public virtual void OnDeserialization(object sender)
+        {
+            HashHelpers.SerializationInfoTable.TryGetValue(this, out SerializationInfo siInfo);
+
+            if (siInfo == null)
+            {
+                // We can return immediately if this function is called twice. 
+                // Note we remove the serialization info from the table at the end of this method.
+                return;
+            }
+
+            int realVersion = siInfo.GetInt32(VersionName);
+            int hashsize = siInfo.GetInt32(HashSizeName);
+            _comparer = (IEqualityComparer<TKey>)siInfo.GetValue(ComparerName, typeof(IEqualityComparer<TKey>));
+
+            if (hashsize != 0)
+            {
+                Initialize(hashsize);
+
+                KeyValuePair<TKey, TValue>[] array = (KeyValuePair<TKey, TValue>[])
+                    siInfo.GetValue(KeyValuePairsName, typeof(KeyValuePair<TKey, TValue>[]));
+
+                if (array == null)
+                {
+                    ThrowHelper.ThrowSerializationException(ExceptionResource.Serialization_MissingKeys);
+                }
+
+                for (int i = 0; i < array.Length; i++)
+                {
+                    if (array[i].Key == null)
+                    {
+                        ThrowHelper.ThrowSerializationException(ExceptionResource.Serialization_NullKey);
+                    }
+                    Add(array[i].Key, array[i].Value);
+                }
+            }
+            else
+            {
+                _buckets = null;
+            }
+
+            _version = realVersion;
+            HashHelpers.SerializationInfoTable.Remove(this);
+        }
+
+        private void Resize()
+            => Resize(HashHelpers.ExpandPrime(_count), false);
+
+        private void Resize(int newSize, bool forceNewHashCodes)
+        {
+            // Value types never rehash
+            Debug.Assert(!forceNewHashCodes || default(TKey) == null);
+            Debug.Assert(newSize >= _entries.Length);
+
+            int[] buckets = new int[newSize];
+            Entry[] entries = new Entry[newSize];
+
+            int count = _count;
+            Array.Copy(_entries, 0, entries, 0, count);
+
+            if (default(TKey) == null && forceNewHashCodes)
+            {
+                for (int i = 0; i < count; i++)
+                {
+                    if (entries[i].hashCode >= 0)
+                    {
+                        Debug.Assert(_comparer == null);
+                        entries[i].hashCode = (entries[i].key.GetHashCode() & 0x7FFFFFFF);
+                    }
+                }
+            }
+
+            for (int i = 0; i < count; i++)
+            {
+                if (entries[i].hashCode >= 0)
+                {
+                    int bucket = entries[i].hashCode % newSize;
+                    // Value in _buckets is 1-based
+                    entries[i].next = buckets[bucket] - 1;
+                    // Value in _buckets is 1-based
+                    buckets[bucket] = i + 1;
+                }
+            }
+
+            _buckets = buckets;
+            _entries = entries;
+        }
+
+        // The overload Remove(TKey key, out TValue value) is a copy of this method with one additional
+        // statement to copy the value for entry being removed into the output parameter.
+        // Code has been intentionally duplicated for performance reasons.
+        public bool Remove(TKey key)
+        {
+            if (key == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
+            }
+
+            if (_buckets != null)
+            {
+                int hashCode = (_comparer?.GetHashCode(key) ?? key.GetHashCode()) & 0x7FFFFFFF;
+                int bucket = hashCode % _buckets.Length;
+                int last = -1;
+                // Value in _buckets is 1-based
+                int i = _buckets[bucket] - 1;
+                while (i >= 0)
+                {
+                    ref Entry entry = ref _entries[i];
+
+                    if (entry.hashCode == hashCode && (_comparer?.Equals(entry.key, key) ?? EqualityComparer<TKey>.Default.Equals(entry.key, key)))
+                    {
+                        if (last < 0)
+                        {
+                            // Value in _buckets is 1-based
+                            _buckets[bucket] = entry.next + 1;
+                        }
+                        else
+                        {
+                            _entries[last].next = entry.next;
+                        }
+                        entry.hashCode = -1;
+                        entry.next = _freeList;
+
+                        if (RuntimeHelpers.IsReferenceOrContainsReferences<TKey>())
+                        {
+                            entry.key = default;
+                        }
+                        if (RuntimeHelpers.IsReferenceOrContainsReferences<TValue>())
+                        {
+                            entry.value = default;
+                        }
+                        _freeList = i;
+                        _freeCount++;
+                        _version++;
+                        return true;
+                    }
+
+                    last = i;
+                    i = entry.next;
+                }
+            }
+            return false;
+        }
+
+        // This overload is a copy of the overload Remove(TKey key) with one additional
+        // statement to copy the value for entry being removed into the output parameter.
+        // Code has been intentionally duplicated for performance reasons.
+        public bool Remove(TKey key, out TValue value)
+        {
+            if (key == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
+            }
+
+            if (_buckets != null)
+            {
+                int hashCode = (_comparer?.GetHashCode(key) ?? key.GetHashCode()) & 0x7FFFFFFF;
+                int bucket = hashCode % _buckets.Length;
+                int last = -1;
+                // Value in _buckets is 1-based
+                int i = _buckets[bucket] - 1;
+                while (i >= 0)
+                {
+                    ref Entry entry = ref _entries[i];
+
+                    if (entry.hashCode == hashCode && (_comparer?.Equals(entry.key, key) ?? EqualityComparer<TKey>.Default.Equals(entry.key, key)))
+                    {
+                        if (last < 0)
+                        {
+                            // Value in _buckets is 1-based
+                            _buckets[bucket] = entry.next + 1;
+                        }
+                        else
+                        {
+                            _entries[last].next = entry.next;
+                        }
+
+                        value = entry.value;
+
+                        entry.hashCode = -1;
+                        entry.next = _freeList;
+
+                        if (RuntimeHelpers.IsReferenceOrContainsReferences<TKey>())
+                        {
+                            entry.key = default;
+                        }
+                        if (RuntimeHelpers.IsReferenceOrContainsReferences<TValue>())
+                        {
+                            entry.value = default;
+                        }
+                        _freeList = i;
+                        _freeCount++;
+                        _version++;
+                        return true;
+                    }
+
+                    last = i;
+                    i = entry.next;
+                }
+            }
+            value = default;
+            return false;
+        }
+
+        public bool TryGetValue(TKey key, out TValue value)
+        {
+            int i = FindEntry(key);
+            if (i >= 0)
+            {
+                value = _entries[i].value;
+                return true;
+            }
+            value = default;
+            return false;
+        }
+
+        public bool TryAdd(TKey key, TValue value)
+            => TryInsert(key, value, InsertionBehavior.None);
+
+        bool ICollection<KeyValuePair<TKey, TValue>>.IsReadOnly => false;
+
+        void ICollection<KeyValuePair<TKey, TValue>>.CopyTo(KeyValuePair<TKey, TValue>[] array, int index)
+            => CopyTo(array, index);
+
+        void ICollection.CopyTo(Array array, int index)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            if (array.Rank != 1)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
+            if (array.GetLowerBound(0) != 0)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NonZeroLowerBound);
+            if ((uint)index > (uint)array.Length)
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            if (array.Length - index < Count)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall);
+
+            if (array is KeyValuePair<TKey, TValue>[] pairs)
+            {
+                CopyTo(pairs, index);
+            }
+            else if (array is DictionaryEntry[] dictEntryArray)
+            {
+                Entry[] entries = _entries;
+                for (int i = 0; i < _count; i++)
+                {
+                    if (entries[i].hashCode >= 0)
+                    {
+                        dictEntryArray[index++] = new DictionaryEntry(entries[i].key, entries[i].value);
+                    }
+                }
+            }
+            else
+            {
+                object[] objects = array as object[];
+                if (objects == null)
+                {
+                    ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                }
+
+                try
+                {
+                    int count = _count;
+                    Entry[] entries = _entries;
+                    for (int i = 0; i < count; i++)
+                    {
+                        if (entries[i].hashCode >= 0)
+                        {
+                            objects[index++] = new KeyValuePair<TKey, TValue>(entries[i].key, entries[i].value);
+                        }
+                    }
+                }
+                catch (ArrayTypeMismatchException)
+                {
+                    ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                }
+            }
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+            => new Enumerator(this, Enumerator.KeyValuePair);
+
+        /// <summary>
+        /// Ensures that the dictionary can hold up to 'capacity' entries without any further expansion of its backing storage
+        /// </summary>
+        public int EnsureCapacity(int capacity)
+        {
+            if (capacity < 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.capacity);
+            int currentCapacity = _entries == null ? 0 : _entries.Length;
+            if (currentCapacity >= capacity)
+                return currentCapacity;
+            if (_buckets == null)
+                return Initialize(capacity);
+            int newSize = HashHelpers.GetPrime(capacity);
+            Resize(newSize, forceNewHashCodes: false);
+            return newSize;
+        }
+
+        /// <summary>
+        /// Sets the capacity of this dictionary to what it would be if it had been originally initialized with all its entries
+        /// 
+        /// This method can be used to minimize the memory overhead 
+        /// once it is known that no new elements will be added. 
+        /// 
+        /// To allocate minimum size storage array, execute the following statements:
+        /// 
+        /// dictionary.Clear();
+        /// dictionary.TrimExcess();
+        /// </summary>
+        public void TrimExcess()
+            => TrimExcess(Count);
+
+        /// <summary>
+        /// Sets the capacity of this dictionary to hold up 'capacity' entries without any further expansion of its backing storage
+        /// 
+        /// This method can be used to minimize the memory overhead 
+        /// once it is known that no new elements will be added. 
+        /// </summary>
+        public void TrimExcess(int capacity)
+        {
+            if (capacity < Count)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.capacity);
+            int newSize = HashHelpers.GetPrime(capacity);
+
+            Entry[] oldEntries = _entries;
+            int currentCapacity = oldEntries == null ? 0 : oldEntries.Length;
+            if (newSize >= currentCapacity)
+                return;
+
+            int oldCount = _count;
+            Initialize(newSize);
+            Entry[] entries = _entries;
+            int[] buckets = _buckets;
+            int count = 0;
+            for (int i = 0; i < oldCount; i++)
+            {
+                int hashCode = oldEntries[i].hashCode;
+                if (hashCode >= 0)
+                {
+                    ref Entry entry = ref entries[count];
+                    entry = oldEntries[i];
+                    int bucket = hashCode % newSize;
+                    // Value in _buckets is 1-based
+                    entry.next = buckets[bucket] - 1;
+                    // Value in _buckets is 1-based
+                    buckets[bucket] = count + 1;
+                    count++;
+                }
+            }
+            _count = count;
+            _freeCount = 0;
+        }
+
+        bool ICollection.IsSynchronized => false;
+
+        object ICollection.SyncRoot
+        {
+            get
+            {
+                if (_syncRoot == null)
+                {
+                    Interlocked.CompareExchange<object>(ref _syncRoot, new object(), null);
+                }
+                return _syncRoot;
+            }
+        }
+
+        bool IDictionary.IsFixedSize => false;
+
+        bool IDictionary.IsReadOnly => false;
+
+        ICollection IDictionary.Keys => (ICollection)Keys;
+
+        ICollection IDictionary.Values => (ICollection)Values;
+
+        object IDictionary.this[object key]
+        {
+            get
+            {
+                if (IsCompatibleKey(key))
+                {
+                    int i = FindEntry((TKey)key);
+                    if (i >= 0)
+                    {
+                        return _entries[i].value;
+                    }
+                }
+                return null;
+            }
+            set
+            {
+                if (key == null)
+                {
+                    ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
+                }
+                ThrowHelper.IfNullAndNullsAreIllegalThenThrow<TValue>(value, ExceptionArgument.value);
+
+                try
+                {
+                    TKey tempKey = (TKey)key;
+                    try
+                    {
+                        this[tempKey] = (TValue)value;
+                    }
+                    catch (InvalidCastException)
+                    {
+                        ThrowHelper.ThrowWrongValueTypeArgumentException(value, typeof(TValue));
+                    }
+                }
+                catch (InvalidCastException)
+                {
+                    ThrowHelper.ThrowWrongKeyTypeArgumentException(key, typeof(TKey));
+                }
+            }
+        }
+
+        private static bool IsCompatibleKey(object key)
+        {
+            if (key == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
+            }
+            return (key is TKey);
+        }
+
+        void IDictionary.Add(object key, object value)
+        {
+            if (key == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
+            }
+            ThrowHelper.IfNullAndNullsAreIllegalThenThrow<TValue>(value, ExceptionArgument.value);
+
+            try
+            {
+                TKey tempKey = (TKey)key;
+
+                try
+                {
+                    Add(tempKey, (TValue)value);
+                }
+                catch (InvalidCastException)
+                {
+                    ThrowHelper.ThrowWrongValueTypeArgumentException(value, typeof(TValue));
+                }
+            }
+            catch (InvalidCastException)
+            {
+                ThrowHelper.ThrowWrongKeyTypeArgumentException(key, typeof(TKey));
+            }
+        }
+
+        bool IDictionary.Contains(object key)
+        {
+            if (IsCompatibleKey(key))
+            {
+                return ContainsKey((TKey)key);
+            }
+
+            return false;
+        }
+
+        IDictionaryEnumerator IDictionary.GetEnumerator()
+            => new Enumerator(this, Enumerator.DictEntry);
+
+        void IDictionary.Remove(object key)
+        {
+            if (IsCompatibleKey(key))
+            {
+                Remove((TKey)key);
+            }
+        }
+
+        public struct Enumerator : IEnumerator<KeyValuePair<TKey, TValue>>,
+            IDictionaryEnumerator
+        {
+            private Dictionary<TKey, TValue> _dictionary;
+            private int _version;
+            private int _index;
+            private KeyValuePair<TKey, TValue> _current;
+            private int _getEnumeratorRetType;  // What should Enumerator.Current return?
+
+            internal const int DictEntry = 1;
+            internal const int KeyValuePair = 2;
+
+            internal Enumerator(Dictionary<TKey, TValue> dictionary, int getEnumeratorRetType)
+            {
+                _dictionary = dictionary;
+                _version = dictionary._version;
+                _index = 0;
+                _getEnumeratorRetType = getEnumeratorRetType;
+                _current = new KeyValuePair<TKey, TValue>();
+            }
+
+            public bool MoveNext()
+            {
+                if (_version != _dictionary._version)
+                {
+                    ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion();
+                }
+
+                // Use unsigned comparison since we set index to dictionary.count+1 when the enumeration ends.
+                // dictionary.count+1 could be negative if dictionary.count is Int32.MaxValue
+                while ((uint)_index < (uint)_dictionary._count)
+                {
+                    ref Entry entry = ref _dictionary._entries[_index++];
+
+                    if (entry.hashCode >= 0)
+                    {
+                        _current = new KeyValuePair<TKey, TValue>(entry.key, entry.value);
+                        return true;
+                    }
+                }
+
+                _index = _dictionary._count + 1;
+                _current = new KeyValuePair<TKey, TValue>();
+                return false;
+            }
+
+            public KeyValuePair<TKey, TValue> Current => _current;
+
+            public void Dispose()
+            {
+            }
+
+            object IEnumerator.Current
+            {
+                get
+                {
+                    if (_index == 0 || (_index == _dictionary._count + 1))
+                    {
+                        ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumOpCantHappen();
+                    }
+
+                    if (_getEnumeratorRetType == DictEntry)
+                    {
+                        return new DictionaryEntry(_current.Key, _current.Value);
+                    }
+                    else
+                    {
+                        return new KeyValuePair<TKey, TValue>(_current.Key, _current.Value);
+                    }
+                }
+            }
+
+            void IEnumerator.Reset()
+            {
+                if (_version != _dictionary._version)
+                {
+                    ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion();
+                }
+
+                _index = 0;
+                _current = new KeyValuePair<TKey, TValue>();
+            }
+
+            DictionaryEntry IDictionaryEnumerator.Entry
+            {
+                get
+                {
+                    if (_index == 0 || (_index == _dictionary._count + 1))
+                    {
+                        ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumOpCantHappen();
+                    }
+
+                    return new DictionaryEntry(_current.Key, _current.Value);
+                }
+            }
+
+            object IDictionaryEnumerator.Key
+            {
+                get
+                {
+                    if (_index == 0 || (_index == _dictionary._count + 1))
+                    {
+                        ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumOpCantHappen();
+                    }
+
+                    return _current.Key;
+                }
+            }
+
+            object IDictionaryEnumerator.Value
+            {
+                get
+                {
+                    if (_index == 0 || (_index == _dictionary._count + 1))
+                    {
+                        ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumOpCantHappen();
+                    }
+
+                    return _current.Value;
+                }
+            }
+        }
+
+        [DebuggerTypeProxy(typeof(DictionaryKeyCollectionDebugView<,>))]
+        [DebuggerDisplay("Count = {Count}")]
+        public sealed class KeyCollection : ICollection<TKey>, ICollection, IReadOnlyCollection<TKey>
+        {
+            private Dictionary<TKey, TValue> _dictionary;
+
+            public KeyCollection(Dictionary<TKey, TValue> dictionary)
+            {
+                if (dictionary == null)
+                {
+                    ThrowHelper.ThrowArgumentNullException(ExceptionArgument.dictionary);
+                }
+                _dictionary = dictionary;
+            }
+
+            public Enumerator GetEnumerator()
+                => new Enumerator(_dictionary);
+
+            public void CopyTo(TKey[] array, int index)
+            {
+                if (array == null)
+                {
+                    ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+                }
+
+                if (index < 0 || index > array.Length)
+                {
+                    ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+                }
+
+                if (array.Length - index < _dictionary.Count)
+                {
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall);
+                }
+
+                int count = _dictionary._count;
+                Entry[] entries = _dictionary._entries;
+                for (int i = 0; i < count; i++)
+                {
+                    if (entries[i].hashCode >= 0) array[index++] = entries[i].key;
+                }
+            }
+
+            public int Count => _dictionary.Count;
+
+            bool ICollection<TKey>.IsReadOnly => true;
+
+            void ICollection<TKey>.Add(TKey item)
+                => ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_KeyCollectionSet);
+
+            void ICollection<TKey>.Clear()
+                => ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_KeyCollectionSet);
+
+            bool ICollection<TKey>.Contains(TKey item)
+                => _dictionary.ContainsKey(item);
+
+            bool ICollection<TKey>.Remove(TKey item)
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_KeyCollectionSet);
+                return false;
+            }
+
+            IEnumerator<TKey> IEnumerable<TKey>.GetEnumerator()
+                => new Enumerator(_dictionary);
+
+            IEnumerator IEnumerable.GetEnumerator()
+                => new Enumerator(_dictionary);
+
+            void ICollection.CopyTo(Array array, int index)
+            {
+                if (array == null)
+                    ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+                if (array.Rank != 1)
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
+                if (array.GetLowerBound(0) != 0)
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NonZeroLowerBound);
+                if ((uint)index > (uint)array.Length)
+                    ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+                if (array.Length - index < _dictionary.Count)
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall);
+
+                if (array is TKey[] keys)
+                {
+                    CopyTo(keys, index);
+                }
+                else
+                {
+                    object[] objects = array as object[];
+                    if (objects == null)
+                    {
+                        ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                    }
+
+                    int count = _dictionary._count;
+                    Entry[] entries = _dictionary._entries;
+                    try
+                    {
+                        for (int i = 0; i < count; i++)
+                        {
+                            if (entries[i].hashCode >= 0) objects[index++] = entries[i].key;
+                        }
+                    }
+                    catch (ArrayTypeMismatchException)
+                    {
+                        ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                    }
+                }
+            }
+
+            bool ICollection.IsSynchronized => false;
+
+            object ICollection.SyncRoot => ((ICollection)_dictionary).SyncRoot;
+
+            public struct Enumerator : IEnumerator<TKey>, IEnumerator
+            {
+                private Dictionary<TKey, TValue> _dictionary;
+                private int _index;
+                private int _version;
+                private TKey _currentKey;
+
+                internal Enumerator(Dictionary<TKey, TValue> dictionary)
+                {
+                    _dictionary = dictionary;
+                    _version = dictionary._version;
+                    _index = 0;
+                    _currentKey = default;
+                }
+
+                public void Dispose()
+                {
+                }
+
+                public bool MoveNext()
+                {
+                    if (_version != _dictionary._version)
+                    {
+                        ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion();
+                    }
+
+                    while ((uint)_index < (uint)_dictionary._count)
+                    {
+                        ref Entry entry = ref _dictionary._entries[_index++];
+
+                        if (entry.hashCode >= 0)
+                        {
+                            _currentKey = entry.key;
+                            return true;
+                        }
+                    }
+
+                    _index = _dictionary._count + 1;
+                    _currentKey = default;
+                    return false;
+                }
+
+                public TKey Current => _currentKey;
+
+                object IEnumerator.Current
+                {
+                    get
+                    {
+                        if (_index == 0 || (_index == _dictionary._count + 1))
+                        {
+                            ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumOpCantHappen();
+                        }
+
+                        return _currentKey;
+                    }
+                }
+
+                void IEnumerator.Reset()
+                {
+                    if (_version != _dictionary._version)
+                    {
+                        ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion();
+                    }
+
+                    _index = 0;
+                    _currentKey = default;
+                }
+            }
+        }
+
+        [DebuggerTypeProxy(typeof(DictionaryValueCollectionDebugView<,>))]
+        [DebuggerDisplay("Count = {Count}")]
+        public sealed class ValueCollection : ICollection<TValue>, ICollection, IReadOnlyCollection<TValue>
+        {
+            private Dictionary<TKey, TValue> _dictionary;
+
+            public ValueCollection(Dictionary<TKey, TValue> dictionary)
+            {
+                if (dictionary == null)
+                {
+                    ThrowHelper.ThrowArgumentNullException(ExceptionArgument.dictionary);
+                }
+                _dictionary = dictionary;
+            }
+
+            public Enumerator GetEnumerator()
+                => new Enumerator(_dictionary);
+
+            public void CopyTo(TValue[] array, int index)
+            {
+                if (array == null)
+                {
+                    ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+                }
+
+                if (index < 0 || index > array.Length)
+                {
+                    ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+                }
+
+                if (array.Length - index < _dictionary.Count)
+                {
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall);
+                }
+
+                int count = _dictionary._count;
+                Entry[] entries = _dictionary._entries;
+                for (int i = 0; i < count; i++)
+                {
+                    if (entries[i].hashCode >= 0) array[index++] = entries[i].value;
+                }
+            }
+
+            public int Count => _dictionary.Count;
+
+            bool ICollection<TValue>.IsReadOnly => true;
+
+            void ICollection<TValue>.Add(TValue item)
+                => ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ValueCollectionSet);
+
+            bool ICollection<TValue>.Remove(TValue item)
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ValueCollectionSet);
+                return false;
+            }
+
+            void ICollection<TValue>.Clear()
+                => ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ValueCollectionSet);
+
+            bool ICollection<TValue>.Contains(TValue item)
+                => _dictionary.ContainsValue(item);
+
+            IEnumerator<TValue> IEnumerable<TValue>.GetEnumerator()
+                => new Enumerator(_dictionary);
+
+            IEnumerator IEnumerable.GetEnumerator()
+                => new Enumerator(_dictionary);
+
+            void ICollection.CopyTo(Array array, int index)
+            {
+                if (array == null)
+                    ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+                if (array.Rank != 1)
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
+                if (array.GetLowerBound(0) != 0)
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NonZeroLowerBound);
+                if ((uint)index > (uint)array.Length)
+                    ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+                if (array.Length - index < _dictionary.Count)
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall);
+
+                if (array is TValue[] values)
+                {
+                    CopyTo(values, index);
+                }
+                else
+                {
+                    object[] objects = array as object[];
+                    if (objects == null)
+                    {
+                        ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                    }
+
+                    int count = _dictionary._count;
+                    Entry[] entries = _dictionary._entries;
+                    try
+                    {
+                        for (int i = 0; i < count; i++)
+                        {
+                            if (entries[i].hashCode >= 0) objects[index++] = entries[i].value;
+                        }
+                    }
+                    catch (ArrayTypeMismatchException)
+                    {
+                        ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                    }
+                }
+            }
+
+            bool ICollection.IsSynchronized => false;
+
+            object ICollection.SyncRoot => ((ICollection)_dictionary).SyncRoot;
+
+            public struct Enumerator : IEnumerator<TValue>, IEnumerator
+            {
+                private Dictionary<TKey, TValue> _dictionary;
+                private int _index;
+                private int _version;
+                private TValue _currentValue;
+
+                internal Enumerator(Dictionary<TKey, TValue> dictionary)
+                {
+                    _dictionary = dictionary;
+                    _version = dictionary._version;
+                    _index = 0;
+                    _currentValue = default;
+                }
+
+                public void Dispose()
+                {
+                }
+
+                public bool MoveNext()
+                {
+                    if (_version != _dictionary._version)
+                    {
+                        ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion();
+                    }
+
+                    while ((uint)_index < (uint)_dictionary._count)
+                    {
+                        ref Entry entry = ref _dictionary._entries[_index++];
+
+                        if (entry.hashCode >= 0)
+                        {
+                            _currentValue = entry.value;
+                            return true;
+                        }
+                    }
+                    _index = _dictionary._count + 1;
+                    _currentValue = default;
+                    return false;
+                }
+
+                public TValue Current => _currentValue;
+
+                object IEnumerator.Current
+                {
+                    get
+                    {
+                        if (_index == 0 || (_index == _dictionary._count + 1))
+                        {
+                            ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumOpCantHappen();
+                        }
+
+                        return _currentValue;
+                    }
+                }
+
+                void IEnumerator.Reset()
+                {
+                    if (_version != _dictionary._version)
+                    {
+                        ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion();
+                    }
+                    _index = 0;
+                    _currentValue = default;
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/ICollection.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/ICollection.cs
new file mode 100644
index 0000000000..78ee5cb1f5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/ICollection.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.CompilerServices;
+
+namespace System.Collections.Generic
+{
+    // Base interface for all collections, defining enumerators, size, and 
+    // synchronization methods.
+    public interface ICollection<T> : IEnumerable<T>
+    {
+        // Number of items in the collections.        
+        int Count { get; }
+
+        bool IsReadOnly { get; }
+
+        void Add(T item);
+
+        void Clear();
+
+        bool Contains(T item);
+
+        // CopyTo copies a collection into an Array, starting at a particular
+        // index into the array.
+        // 
+        void CopyTo(T[] array, int arrayIndex);
+
+        //void CopyTo(int sourceIndex, T[] destinationArray, int destinationIndex, int count);
+
+        bool Remove(T item);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/ICollectionDebugView.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/ICollectionDebugView.cs
new file mode 100644
index 0000000000..9916e857e2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/ICollectionDebugView.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Collections.Generic
+{
+    internal sealed class ICollectionDebugView<T>
+    {
+        private readonly ICollection<T> _collection;
+
+        public ICollectionDebugView(ICollection<T> collection)
+        {
+            if (collection == null)
+            {
+                throw new ArgumentNullException(nameof(collection));
+            }
+
+            _collection = collection;
+        }
+
+        [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+        public T[] Items
+        {
+            get
+            {
+                T[] items = new T[_collection.Count];
+                _collection.CopyTo(items, 0);
+                return items;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/IComparer.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/IComparer.cs
new file mode 100644
index 0000000000..713d499cc8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/IComparer.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Collections.Generic
+{
+    // The generic IComparer interface implements a method that compares 
+    // two objects. It is used in conjunction with the Sort and 
+    // BinarySearch methods on the Array, List, and SortedList classes.
+    public interface IComparer<in T>
+    {
+        // Compares two objects. An implementation of this method must return a
+        // value less than zero if x is less than y, zero if x is equal to y, or a
+        // value greater than zero if x is greater than y.
+        // 
+        int Compare(T x, T y);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/IDictionary.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/IDictionary.cs
new file mode 100644
index 0000000000..05677da3b2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/IDictionary.cs
@@ -0,0 +1,50 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Collections.Generic
+{
+    // An IDictionary is a possibly unordered set of key-value pairs.
+    // Keys can be any non-null object.  Values can be any object.
+    // You can look up a value in an IDictionary via the default indexed
+    // property, Items.
+    public interface IDictionary<TKey, TValue> : ICollection<KeyValuePair<TKey, TValue>>
+    {
+        // Interfaces are not serializable
+        // The Item property provides methods to read and edit entries 
+        // in the Dictionary.
+        TValue this[TKey key]
+        {
+            get;
+            set;
+        }
+
+        // Returns a collections of the keys in this dictionary.
+        ICollection<TKey> Keys
+        {
+            get;
+        }
+
+        // Returns a collections of the values in this dictionary.
+        ICollection<TValue> Values
+        {
+            get;
+        }
+
+        // Returns whether this dictionary contains a particular key.
+        //
+        bool ContainsKey(TKey key);
+
+        // Adds a key-value pair to the dictionary.
+        // 
+        void Add(TKey key, TValue value);
+
+        // Removes a particular key from the dictionary.
+        //
+        bool Remove(TKey key);
+
+        bool TryGetValue(TKey key, out TValue value);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/IDictionaryDebugView.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/IDictionaryDebugView.cs
new file mode 100644
index 0000000000..4721642fee
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/IDictionaryDebugView.cs
@@ -0,0 +1,80 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Collections.Generic
+{
+    internal sealed class IDictionaryDebugView<K, V>
+    {
+        private readonly IDictionary<K, V> _dict;
+
+        public IDictionaryDebugView(IDictionary<K, V> dictionary)
+        {
+            if (dictionary == null)
+                throw new ArgumentNullException(nameof(dictionary));
+
+            _dict = dictionary;
+        }
+
+        [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+        public KeyValuePair<K, V>[] Items
+        {
+            get
+            {
+                KeyValuePair<K, V>[] items = new KeyValuePair<K, V>[_dict.Count];
+                _dict.CopyTo(items, 0);
+                return items;
+            }
+        }
+    }
+
+    internal sealed class DictionaryKeyCollectionDebugView<TKey, TValue>
+    {
+        private readonly ICollection<TKey> _collection;
+
+        public DictionaryKeyCollectionDebugView(ICollection<TKey> collection)
+        {
+            if (collection == null)
+                throw new ArgumentNullException(nameof(collection));
+
+            _collection = collection;
+        }
+
+        [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+        public TKey[] Items
+        {
+            get
+            {
+                TKey[] items = new TKey[_collection.Count];
+                _collection.CopyTo(items, 0);
+                return items;
+            }
+        }
+    }
+
+    internal sealed class DictionaryValueCollectionDebugView<TKey, TValue>
+    {
+        private readonly ICollection<TValue> _collection;
+
+        public DictionaryValueCollectionDebugView(ICollection<TValue> collection)
+        {
+            if (collection == null)
+                throw new ArgumentNullException(nameof(collection));
+
+            _collection = collection;
+        }
+
+        [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+        public TValue[] Items
+        {
+            get
+            {
+                TValue[] items = new TValue[_collection.Count];
+                _collection.CopyTo(items, 0);
+                return items;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/IEnumerable.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/IEnumerable.cs
new file mode 100644
index 0000000000..ddb798e8a6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/IEnumerable.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+
+namespace System.Collections.Generic
+{
+    // Implement this interface if you need to support foreach semantics.
+    public interface IEnumerable<out T> : IEnumerable
+    {
+        // Returns an IEnumerator for this enumerable Object.  The enumerator provides
+        // a simple way to access all the contents of a collection.
+        /// <include file='doc\IEnumerable.uex' path='docs/doc[@for="IEnumerable.GetEnumerator"]/*' />
+        new IEnumerator<T> GetEnumerator();
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/IEnumerator.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/IEnumerator.cs
new file mode 100644
index 0000000000..6360576974
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/IEnumerator.cs
@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace System.Collections.Generic
+{
+    // Base interface for all generic enumerators, providing a simple approach
+    // to iterating over a collection.
+    public interface IEnumerator<out T> : IDisposable, IEnumerator
+    {
+        // Returns the current element of the enumeration. The returned value is
+        // undefined before the first call to MoveNext and following a
+        // call to MoveNext that returned false. Multiple calls to
+        // GetCurrent with no intervening calls to MoveNext 
+        // will return the same object.
+        // 
+        /// <include file='doc\IEnumerator.uex' path='docs/doc[@for="IEnumerator.Current"]/*' />
+        new T Current
+        {
+            get;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/IEqualityComparer.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/IEqualityComparer.cs
new file mode 100644
index 0000000000..543bdb5fce
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/IEqualityComparer.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Collections.Generic
+{
+    // The generic IEqualityComparer interface implements methods to if check two objects are equal
+    // and generate Hashcode for an object.
+    // It is use in Dictionary class.  
+    public interface IEqualityComparer<in T>
+    {
+        bool Equals(T x, T y);
+        int GetHashCode(T obj);
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/IList.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/IList.cs
new file mode 100644
index 0000000000..2abc7b9142
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/IList.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections;
+using System.Runtime.CompilerServices;
+
+namespace System.Collections.Generic
+{
+    // An IList is an ordered collection of objects.  The exact ordering
+    // is up to the implementation of the list, ranging from a sorted
+    // order to insertion order.  
+    public interface IList<T> : ICollection<T>
+    {
+        // The Item property provides methods to read and edit entries in the List.
+        T this[int index]
+        {
+            get;
+            set;
+        }
+
+        // Returns the index of a particular item, if it is in the list.
+        // Returns -1 if the item isn't in the list.
+        int IndexOf(T item);
+
+        // Inserts value into the list at position index.
+        // index must be non-negative and less than or equal to the 
+        // number of elements in the list.  If index equals the number
+        // of items in the list, then value is appended to the end.
+        void Insert(int index, T item);
+
+        // Removes the item at position index.
+        void RemoveAt(int index);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/IReadOnlyCollection.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/IReadOnlyCollection.cs
new file mode 100644
index 0000000000..9eea39de22
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/IReadOnlyCollection.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.CompilerServices;
+
+namespace System.Collections.Generic
+{
+    // Provides a read-only, covariant view of a generic list.
+    public interface IReadOnlyCollection<out T> : IEnumerable<T>
+    {
+        int Count { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/IReadOnlyDictionary.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/IReadOnlyDictionary.cs
new file mode 100644
index 0000000000..300b996611
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/IReadOnlyDictionary.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Collections.Generic
+{
+    // Provides a read-only view of a generic dictionary.
+    public interface IReadOnlyDictionary<TKey, TValue> : IReadOnlyCollection<KeyValuePair<TKey, TValue>>
+    {
+        bool ContainsKey(TKey key);
+        bool TryGetValue(TKey key, out TValue value);
+
+        TValue this[TKey key] { get; }
+        IEnumerable<TKey> Keys { get; }
+        IEnumerable<TValue> Values { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/IReadOnlyList.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/IReadOnlyList.cs
new file mode 100644
index 0000000000..7193805b06
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/IReadOnlyList.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.CompilerServices;
+
+namespace System.Collections.Generic
+{
+    // Provides a read-only, covariant view of a generic list.
+    public interface IReadOnlyList<out T> : IReadOnlyCollection<T>
+    {
+        T this[int index] { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/KeyNotFoundException.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/KeyNotFoundException.cs
new file mode 100644
index 0000000000..48eddb8745
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/KeyNotFoundException.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System.Collections.Generic
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class KeyNotFoundException : SystemException
+    {
+        public KeyNotFoundException()
+            : base(SR.Arg_KeyNotFound)
+        {
+            HResult = HResults.COR_E_KEYNOTFOUND;
+        }
+
+        public KeyNotFoundException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_KEYNOTFOUND;
+        }
+
+        public KeyNotFoundException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_KEYNOTFOUND;
+        }
+
+        protected KeyNotFoundException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/KeyValuePair.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/KeyValuePair.cs
new file mode 100644
index 0000000000..82c786d407
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/KeyValuePair.cs
@@ -0,0 +1,83 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Text;
+
+namespace System.Collections.Generic
+{
+    // Provides the Create factory method for KeyValuePair<TKey, TValue>.
+    public static class KeyValuePair
+    {
+        // Creates a new KeyValuePair<TKey, TValue> from the given values.
+        public static KeyValuePair<TKey, TValue> Create<TKey, TValue>(TKey key, TValue value)
+        {
+            return new KeyValuePair<TKey, TValue>(key, value);
+        }
+
+        /// <summary>
+        /// Used by KeyValuePair.ToString to reduce generic code
+        /// </summary>
+        internal static string PairToString(object key, object value)
+        {
+            StringBuilder s = StringBuilderCache.Acquire();
+            s.Append('[');
+
+            if (key != null)
+            {
+                s.Append(key);
+            }
+
+            s.Append(", ");
+
+            if (value != null)
+            {
+                s.Append(value);
+            }
+
+            s.Append(']');
+
+            return StringBuilderCache.GetStringAndRelease(s);
+        }
+    }
+
+    // A KeyValuePair holds a key and a value from a dictionary.
+    // It is used by the IEnumerable<T> implementation for both IDictionary<TKey, TValue>
+    // and IReadOnlyDictionary<TKey, TValue>.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public readonly struct KeyValuePair<TKey, TValue>
+    {
+        private readonly TKey key; // Do not rename (binary serialization)
+        private readonly TValue value; // Do not rename (binary serialization)
+
+        public KeyValuePair(TKey key, TValue value)
+        {
+            this.key = key;
+            this.value = value;
+        }
+
+        public TKey Key
+        {
+            get { return key; }
+        }
+
+        public TValue Value
+        {
+            get { return value; }
+        }
+
+        public override string ToString()
+        {
+            return KeyValuePair.PairToString(Key, Value);
+        }
+
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public void Deconstruct(out TKey key, out TValue value)
+        {
+            key = Key;
+            value = Value;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/List.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/List.cs
new file mode 100644
index 0000000000..6b9f9b45b3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/List.cs
@@ -0,0 +1,1188 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Threading;
+
+namespace System.Collections.Generic
+{
+    // Implements a variable-size List that uses an array of objects to store the
+    // elements. A List has a capacity, which is the allocated length
+    // of the internal array. As elements are added to a List, the capacity
+    // of the List is automatically increased as required by reallocating the
+    // internal array.
+    // 
+    [DebuggerTypeProxy(typeof(ICollectionDebugView<>))]
+    [DebuggerDisplay("Count = {Count}")]
+    [Serializable]
+    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class List<T> : IList<T>, IList, IReadOnlyList<T>
+    {
+        private const int DefaultCapacity = 4;
+
+        private T[] _items; // Do not rename (binary serialization)
+        private int _size; // Do not rename (binary serialization)
+        private int _version; // Do not rename (binary serialization)
+        [NonSerialized]
+        private object _syncRoot;
+
+        private static readonly T[] s_emptyArray = new T[0];
+
+        // Constructs a List. The list is initially empty and has a capacity
+        // of zero. Upon adding the first element to the list the capacity is
+        // increased to DefaultCapacity, and then increased in multiples of two
+        // as required.
+        public List()
+        {
+            _items = s_emptyArray;
+        }
+
+        // Constructs a List with a given initial capacity. The list is
+        // initially empty, but will have room for the given number of elements
+        // before any reallocations are required.
+        // 
+        public List(int capacity)
+        {
+            if (capacity < 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.capacity, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (capacity == 0)
+                _items = s_emptyArray;
+            else
+                _items = new T[capacity];
+        }
+
+        // Constructs a List, copying the contents of the given collection. The
+        // size and capacity of the new list will both be equal to the size of the
+        // given collection.
+        // 
+        public List(IEnumerable<T> collection)
+        {
+            if (collection == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.collection);
+
+            if (collection is ICollection<T> c)
+            {
+                int count = c.Count;
+                if (count == 0)
+                {
+                    _items = s_emptyArray;
+                }
+                else
+                {
+                    _items = new T[count];
+                    c.CopyTo(_items, 0);
+                    _size = count;
+                }
+            }
+            else
+            {
+                _size = 0;
+                _items = s_emptyArray;
+                AddEnumerable(collection);
+            }
+        }
+
+        // Gets and sets the capacity of this list.  The capacity is the size of
+        // the internal array used to hold items.  When set, the internal 
+        // array of the list is reallocated to the given capacity.
+        // 
+        public int Capacity
+        {
+            get
+            {
+                return _items.Length;
+            }
+            set
+            {
+                if (value < _size)
+                {
+                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.value, ExceptionResource.ArgumentOutOfRange_SmallCapacity);
+                }
+
+                if (value != _items.Length)
+                {
+                    if (value > 0)
+                    {
+                        T[] newItems = new T[value];
+                        if (_size > 0)
+                        {
+                            Array.Copy(_items, 0, newItems, 0, _size);
+                        }
+                        _items = newItems;
+                    }
+                    else
+                    {
+                        _items = s_emptyArray;
+                    }
+                }
+            }
+        }
+
+        // Read-only property describing how many elements are in the List.
+        public int Count => _size;
+
+        bool IList.IsFixedSize => false;
+
+        // Is this List read-only?
+        bool ICollection<T>.IsReadOnly => false;
+
+        bool IList.IsReadOnly => false;
+
+        // Is this List synchronized (thread-safe)?
+        bool ICollection.IsSynchronized => false;
+
+        // Synchronization root for this object.
+        object ICollection.SyncRoot
+        {
+            get
+            {
+                if (_syncRoot == null)
+                {
+                    Interlocked.CompareExchange<object>(ref _syncRoot, new object(), null);
+                }
+                return _syncRoot;
+            }
+        }
+
+        // Sets or Gets the element at the given index.
+        public T this[int index]
+        {
+            get
+            {
+                // Following trick can reduce the range check by one
+                if ((uint)index >= (uint)_size)
+                {
+                    ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+                }
+                return _items[index];
+            }
+
+            set
+            {
+                if ((uint)index >= (uint)_size)
+                {
+                    ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+                }
+                _items[index] = value;
+                _version++;
+            }
+        }
+
+        private static bool IsCompatibleObject(object value)
+        {
+            // Non-null values are fine.  Only accept nulls if T is a class or Nullable<U>.
+            // Note that default(T) is not equal to null for value types except when T is Nullable<U>. 
+            return ((value is T) || (value == null && default(T) == null));
+        }
+
+        object IList.this[int index]
+        {
+            get
+            {
+                return this[index];
+            }
+            set
+            {
+                ThrowHelper.IfNullAndNullsAreIllegalThenThrow<T>(value, ExceptionArgument.value);
+
+                try
+                {
+                    this[index] = (T)value;
+                }
+                catch (InvalidCastException)
+                {
+                    ThrowHelper.ThrowWrongValueTypeArgumentException(value, typeof(T));
+                }
+            }
+        }
+
+        // Adds the given object to the end of this list. The size of the list is
+        // increased by one. If required, the capacity of the list is doubled
+        // before adding the new element.
+        //
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Add(T item)
+        {
+            _version++;
+            T[] array = _items;
+            int size = _size;
+            if ((uint)size < (uint)array.Length)
+            {
+                _size = size + 1;
+                array[size] = item;
+            }
+            else
+            {
+                AddWithResize(item);
+            }
+        }
+
+        // Non-inline from List.Add to improve its code quality as uncommon path
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private void AddWithResize(T item)
+        {
+            int size = _size;
+            EnsureCapacity(size + 1);
+            _size = size + 1;
+            _items[size] = item;
+        }
+
+        int IList.Add(object item)
+        {
+            ThrowHelper.IfNullAndNullsAreIllegalThenThrow<T>(item, ExceptionArgument.item);
+
+            try
+            {
+                Add((T)item);
+            }
+            catch (InvalidCastException)
+            {
+                ThrowHelper.ThrowWrongValueTypeArgumentException(item, typeof(T));
+            }
+
+            return Count - 1;
+        }
+
+        // Adds the elements of the given collection to the end of this list. If
+        // required, the capacity of the list is increased to twice the previous
+        // capacity or the new size, whichever is larger.
+        //
+        public void AddRange(IEnumerable<T> collection)
+            => InsertRange(_size, collection);
+
+        public ReadOnlyCollection<T> AsReadOnly()
+            => new ReadOnlyCollection<T>(this);
+
+        // Searches a section of the list for a given element using a binary search
+        // algorithm. Elements of the list are compared to the search value using
+        // the given IComparer interface. If comparer is null, elements of
+        // the list are compared to the search value using the IComparable
+        // interface, which in that case must be implemented by all elements of the
+        // list and the given search value. This method assumes that the given
+        // section of the list is already sorted; if this is not the case, the
+        // result will be incorrect.
+        //
+        // The method returns the index of the given value in the list. If the
+        // list does not contain the given value, the method returns a negative
+        // integer. The bitwise complement operator (~) can be applied to a
+        // negative result to produce the index of the first element (if any) that
+        // is larger than the given search value. This is also the index at which
+        // the search value should be inserted into the list in order for the list
+        // to remain sorted.
+        // 
+        // The method uses the Array.BinarySearch method to perform the
+        // search.
+        // 
+        public int BinarySearch(int index, int count, T item, IComparer<T> comparer)
+        {
+            if (index < 0)
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            if (count < 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+            if (_size - index < count)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
+
+            return Array.BinarySearch<T>(_items, index, count, item, comparer);
+        }
+
+        public int BinarySearch(T item)
+            => BinarySearch(0, Count, item, null);
+
+        public int BinarySearch(T item, IComparer<T> comparer)
+            => BinarySearch(0, Count, item, comparer);
+
+        // Clears the contents of List.
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Clear()
+        {
+            _version++;
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+            {
+                int size = _size;
+                _size = 0;
+                if (size > 0)
+                {
+                    Array.Clear(_items, 0, size); // Clear the elements so that the gc can reclaim the references.
+                }
+            }
+            else
+            {
+                _size = 0;
+            }
+        }
+
+        // Contains returns true if the specified element is in the List.
+        // It does a linear, O(n) search.  Equality is determined by calling
+        // EqualityComparer<T>.Default.Equals().
+        //
+        public bool Contains(T item)
+        {
+            // PERF: IndexOf calls Array.IndexOf, which internally
+            // calls EqualityComparer<T>.Default.IndexOf, which
+            // is specialized for different types. This
+            // boosts performance since instead of making a
+            // virtual method call each iteration of the loop,
+            // via EqualityComparer<T>.Default.Equals, we
+            // only make one virtual call to EqualityComparer.IndexOf.
+
+            return _size != 0 && IndexOf(item) != -1;
+        }
+
+        bool IList.Contains(object item)
+        {
+            if (IsCompatibleObject(item))
+            {
+                return Contains((T)item);
+            }
+            return false;
+        }
+
+        public List<TOutput> ConvertAll<TOutput>(Converter<T, TOutput> converter)
+        {
+            if (converter == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.converter);
+            }
+
+            List<TOutput> list = new List<TOutput>(_size);
+            for (int i = 0; i < _size; i++)
+            {
+                list._items[i] = converter(_items[i]);
+            }
+            list._size = _size;
+            return list;
+        }
+
+        // Copies this List into array, which must be of a 
+        // compatible array type.  
+        public void CopyTo(T[] array)
+            => CopyTo(array, 0);
+
+        // Copies this List into array, which must be of a 
+        // compatible array type.  
+        void ICollection.CopyTo(Array array, int arrayIndex)
+        {
+            if ((array != null) && (array.Rank != 1))
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
+            }
+
+            try
+            {
+                // Array.Copy will check for NULL.
+                Array.Copy(_items, 0, array, arrayIndex, _size);
+            }
+            catch (ArrayTypeMismatchException)
+            {
+                ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+            }
+        }
+
+        // Copies a section of this list to the given array at the given index.
+        // 
+        // The method uses the Array.Copy method to copy the elements.
+        // 
+        public void CopyTo(int index, T[] array, int arrayIndex, int count)
+        {
+            if (_size - index < count)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
+            }
+
+            // Delegate rest of error checking to Array.Copy.
+            Array.Copy(_items, index, array, arrayIndex, count);
+        }
+
+        public void CopyTo(T[] array, int arrayIndex)
+        {
+            // Delegate rest of error checking to Array.Copy.
+            Array.Copy(_items, 0, array, arrayIndex, _size);
+        }
+
+        // Ensures that the capacity of this list is at least the given minimum
+        // value. If the current capacity of the list is less than min, the
+        // capacity is increased to twice the current capacity or to min,
+        // whichever is larger.
+        //
+        private void EnsureCapacity(int min)
+        {
+            if (_items.Length < min)
+            {
+                int newCapacity = _items.Length == 0 ? DefaultCapacity : _items.Length * 2;
+                // Allow the list to grow to maximum possible capacity (~2G elements) before encountering overflow.
+                // Note that this check works even when _items.Length overflowed thanks to the (uint) cast
+                if ((uint)newCapacity > Array.MaxArrayLength) newCapacity = Array.MaxArrayLength;
+                if (newCapacity < min) newCapacity = min;
+                Capacity = newCapacity;
+            }
+        }
+
+        public bool Exists(Predicate<T> match)
+            => FindIndex(match) != -1;
+
+        public T Find(Predicate<T> match)
+        {
+            if (match == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
+            }
+
+            for (int i = 0; i < _size; i++)
+            {
+                if (match(_items[i]))
+                {
+                    return _items[i];
+                }
+            }
+            return default;
+        }
+
+        public List<T> FindAll(Predicate<T> match)
+        {
+            if (match == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
+            }
+
+            List<T> list = new List<T>();
+            for (int i = 0; i < _size; i++)
+            {
+                if (match(_items[i]))
+                {
+                    list.Add(_items[i]);
+                }
+            }
+            return list;
+        }
+
+        public int FindIndex(Predicate<T> match)
+            => FindIndex(0, _size, match);
+
+        public int FindIndex(int startIndex, Predicate<T> match)
+            => FindIndex(startIndex, _size - startIndex, match);
+
+        public int FindIndex(int startIndex, int count, Predicate<T> match)
+        {
+            if ((uint)startIndex > (uint)_size)
+            {
+                ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
+            }
+
+            if (count < 0 || startIndex > _size - count)
+            {
+                ThrowHelper.ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count();
+            }
+
+            if (match == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
+            }
+
+            int endIndex = startIndex + count;
+            for (int i = startIndex; i < endIndex; i++)
+            {
+                if (match(_items[i])) return i;
+            }
+            return -1;
+        }
+
+        public T FindLast(Predicate<T> match)
+        {
+            if (match == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
+            }
+
+            for (int i = _size - 1; i >= 0; i--)
+            {
+                if (match(_items[i]))
+                {
+                    return _items[i];
+                }
+            }
+            return default;
+        }
+
+        public int FindLastIndex(Predicate<T> match)
+            => FindLastIndex(_size - 1, _size, match);
+
+        public int FindLastIndex(int startIndex, Predicate<T> match)
+            => FindLastIndex(startIndex, startIndex + 1, match);
+
+        public int FindLastIndex(int startIndex, int count, Predicate<T> match)
+        {
+            if (match == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
+            }
+
+            if (_size == 0)
+            {
+                // Special case for 0 length List
+                if (startIndex != -1)
+                {
+                    ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
+                }
+            }
+            else
+            {
+                // Make sure we're not out of range
+                if ((uint)startIndex >= (uint)_size)
+                {
+                    ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
+                }
+            }
+
+            // 2nd have of this also catches when startIndex == MAXINT, so MAXINT - 0 + 1 == -1, which is < 0.
+            if (count < 0 || startIndex - count + 1 < 0)
+            {
+                ThrowHelper.ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count();
+            }
+
+            int endIndex = startIndex - count;
+            for (int i = startIndex; i > endIndex; i--)
+            {
+                if (match(_items[i]))
+                {
+                    return i;
+                }
+            }
+            return -1;
+        }
+
+        public void ForEach(Action<T> action)
+        {
+            if (action == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.action);
+            }
+
+            int version = _version;
+
+            for (int i = 0; i < _size; i++)
+            {
+                if (version != _version)
+                {
+                    break;
+                }
+                action(_items[i]);
+            }
+
+            if (version != _version)
+                ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion();
+        }
+
+        // Returns an enumerator for this list with the given
+        // permission for removal of elements. If modifications made to the list 
+        // while an enumeration is in progress, the MoveNext and 
+        // GetObject methods of the enumerator will throw an exception.
+        //
+        public Enumerator GetEnumerator()
+            => new Enumerator(this);
+
+        IEnumerator<T> IEnumerable<T>.GetEnumerator()
+            => new Enumerator(this);
+
+        IEnumerator IEnumerable.GetEnumerator()
+            => new Enumerator(this);
+
+        public List<T> GetRange(int index, int count)
+        {
+            if (index < 0)
+            {
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            }
+
+            if (count < 0)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (_size - index < count)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
+            }
+
+            List<T> list = new List<T>(count);
+            Array.Copy(_items, index, list._items, 0, count);
+            list._size = count;
+            return list;
+        }
+
+
+        // Returns the index of the first occurrence of a given value in a range of
+        // this list. The list is searched forwards from beginning to end.
+        // The elements of the list are compared to the given value using the
+        // Object.Equals method.
+        // 
+        // This method uses the Array.IndexOf method to perform the
+        // search.
+        // 
+        public int IndexOf(T item)
+            => Array.IndexOf(_items, item, 0, _size);
+
+        int IList.IndexOf(object item)
+        {
+            if (IsCompatibleObject(item))
+            {
+                return IndexOf((T)item);
+            }
+            return -1;
+        }
+
+        // Returns the index of the first occurrence of a given value in a range of
+        // this list. The list is searched forwards, starting at index
+        // index and ending at count number of elements. The
+        // elements of the list are compared to the given value using the
+        // Object.Equals method.
+        // 
+        // This method uses the Array.IndexOf method to perform the
+        // search.
+        // 
+        public int IndexOf(T item, int index)
+        {
+            if (index > _size)
+                ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+            return Array.IndexOf(_items, item, index, _size - index);
+        }
+
+        // Returns the index of the first occurrence of a given value in a range of
+        // this list. The list is searched forwards, starting at index
+        // index and upto count number of elements. The
+        // elements of the list are compared to the given value using the
+        // Object.Equals method.
+        // 
+        // This method uses the Array.IndexOf method to perform the
+        // search.
+        // 
+        public int IndexOf(T item, int index, int count)
+        {
+            if (index > _size)
+                ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+
+            if (count < 0 || index > _size - count)
+                ThrowHelper.ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count();
+
+            return Array.IndexOf(_items, item, index, count);
+        }
+
+        // Inserts an element into this list at a given index. The size of the list
+        // is increased by one. If required, the capacity of the list is doubled
+        // before inserting the new element.
+        // 
+        public void Insert(int index, T item)
+        {
+            // Note that insertions at the end are legal.
+            if ((uint)index > (uint)_size)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_ListInsert);
+            }
+            if (_size == _items.Length) EnsureCapacity(_size + 1);
+            if (index < _size)
+            {
+                Array.Copy(_items, index, _items, index + 1, _size - index);
+            }
+            _items[index] = item;
+            _size++;
+            _version++;
+        }
+
+        void IList.Insert(int index, object item)
+        {
+            ThrowHelper.IfNullAndNullsAreIllegalThenThrow<T>(item, ExceptionArgument.item);
+
+            try
+            {
+                Insert(index, (T)item);
+            }
+            catch (InvalidCastException)
+            {
+                ThrowHelper.ThrowWrongValueTypeArgumentException(item, typeof(T));
+            }
+        }
+
+        // Inserts the elements of the given collection at a given index. If
+        // required, the capacity of the list is increased to twice the previous
+        // capacity or the new size, whichever is larger.  Ranges may be added
+        // to the end of the list by setting index to the List's size.
+        //
+        public void InsertRange(int index, IEnumerable<T> collection)
+        {
+            if (collection == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.collection);
+            }
+
+            if ((uint)index > (uint)_size)
+            {
+                ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+            }
+
+            if (collection is ICollection<T> c)
+            {
+                int count = c.Count;
+                if (count > 0)
+                {
+                    EnsureCapacity(_size + count);
+                    if (index < _size)
+                    {
+                        Array.Copy(_items, index, _items, index + count, _size - index);
+                    }
+
+                    // If we're inserting a List into itself, we want to be able to deal with that.
+                    if (this == c)
+                    {
+                        // Copy first part of _items to insert location
+                        Array.Copy(_items, 0, _items, index, index);
+                        // Copy last part of _items back to inserted location
+                        Array.Copy(_items, index + count, _items, index * 2, _size - index);
+                    }
+                    else
+                    {
+                        c.CopyTo(_items, index);
+                    }
+                    _size += count;
+                }
+            }
+            else if (index < _size)
+            {
+                // We're inserting a lazy enumerable. Call Insert on each of the constituent items.
+                using (IEnumerator<T> en = collection.GetEnumerator())
+                {
+                    while (en.MoveNext())
+                    {
+                        Insert(index++, en.Current);
+                    }
+                }
+            }
+            else
+            {
+                // We're adding a lazy enumerable because the index is at the end of this list.
+                AddEnumerable(collection);
+            }
+            _version++;
+        }
+
+        // Returns the index of the last occurrence of a given value in a range of
+        // this list. The list is searched backwards, starting at the end 
+        // and ending at the first element in the list. The elements of the list 
+        // are compared to the given value using the Object.Equals method.
+        // 
+        // This method uses the Array.LastIndexOf method to perform the
+        // search.
+        // 
+        public int LastIndexOf(T item)
+        {
+            if (_size == 0)
+            {  // Special case for empty list
+                return -1;
+            }
+            else
+            {
+                return LastIndexOf(item, _size - 1, _size);
+            }
+        }
+
+        // Returns the index of the last occurrence of a given value in a range of
+        // this list. The list is searched backwards, starting at index
+        // index and ending at the first element in the list. The 
+        // elements of the list are compared to the given value using the 
+        // Object.Equals method.
+        // 
+        // This method uses the Array.LastIndexOf method to perform the
+        // search.
+        // 
+        public int LastIndexOf(T item, int index)
+        {
+            if (index >= _size)
+                ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+            return LastIndexOf(item, index, index + 1);
+        }
+
+        // Returns the index of the last occurrence of a given value in a range of
+        // this list. The list is searched backwards, starting at index
+        // index and upto count elements. The elements of
+        // the list are compared to the given value using the Object.Equals
+        // method.
+        // 
+        // This method uses the Array.LastIndexOf method to perform the
+        // search.
+        // 
+        public int LastIndexOf(T item, int index, int count)
+        {
+            if ((Count != 0) && (index < 0))
+            {
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            }
+
+            if ((Count != 0) && (count < 0))
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (_size == 0)
+            {  // Special case for empty list
+                return -1;
+            }
+
+            if (index >= _size)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_BiggerThanCollection);
+            }
+
+            if (count > index + 1)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_BiggerThanCollection);
+            }
+
+            return Array.LastIndexOf(_items, item, index, count);
+        }
+
+        // Removes the element at the given index. The size of the list is
+        // decreased by one.
+        public bool Remove(T item)
+        {
+            int index = IndexOf(item);
+            if (index >= 0)
+            {
+                RemoveAt(index);
+                return true;
+            }
+
+            return false;
+        }
+
+        void IList.Remove(object item)
+        {
+            if (IsCompatibleObject(item))
+            {
+                Remove((T)item);
+            }
+        }
+
+        // This method removes all items which matches the predicate.
+        // The complexity is O(n).
+        public int RemoveAll(Predicate<T> match)
+        {
+            if (match == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
+            }
+
+            int freeIndex = 0;   // the first free slot in items array
+
+            // Find the first item which needs to be removed.
+            while (freeIndex < _size && !match(_items[freeIndex])) freeIndex++;
+            if (freeIndex >= _size) return 0;
+
+            int current = freeIndex + 1;
+            while (current < _size)
+            {
+                // Find the first item which needs to be kept.
+                while (current < _size && match(_items[current])) current++;
+
+                if (current < _size)
+                {
+                    // copy item to the free slot.
+                    _items[freeIndex++] = _items[current++];
+                }
+            }
+
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+            {
+                Array.Clear(_items, freeIndex, _size - freeIndex); // Clear the elements so that the gc can reclaim the references.
+            }
+
+            int result = _size - freeIndex;
+            _size = freeIndex;
+            _version++;
+            return result;
+        }
+
+        // Removes the element at the given index. The size of the list is
+        // decreased by one.
+        public void RemoveAt(int index)
+        {
+            if ((uint)index >= (uint)_size)
+            {
+                ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+            }
+            _size--;
+            if (index < _size)
+            {
+                Array.Copy(_items, index + 1, _items, index, _size - index);
+            }
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+            {
+                _items[_size] = default;
+            }
+            _version++;
+        }
+
+        // Removes a range of elements from this list.
+        public void RemoveRange(int index, int count)
+        {
+            if (index < 0)
+            {
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            }
+
+            if (count < 0)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (_size - index < count)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
+
+            if (count > 0)
+            {
+                int i = _size;
+                _size -= count;
+                if (index < _size)
+                {
+                    Array.Copy(_items, index + count, _items, index, _size - index);
+                }
+
+                _version++;
+                if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+                {
+                    Array.Clear(_items, _size, count);
+                }
+            }
+        }
+
+        // Reverses the elements in this list.
+        public void Reverse()
+            => Reverse(0, Count);
+
+        // Reverses the elements in a range of this list. Following a call to this
+        // method, an element in the range given by index and count
+        // which was previously located at index i will now be located at
+        // index index + (index + count - i - 1).
+        //
+        public void Reverse(int index, int count)
+        {
+            if (index < 0)
+            {
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            }
+
+            if (count < 0)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (_size - index < count)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
+
+            if (count > 1)
+            {
+                Array.Reverse(_items, index, count);
+            }
+            _version++;
+        }
+
+        // Sorts the elements in this list.  Uses the default comparer and 
+        // Array.Sort.
+        public void Sort()
+            => Sort(0, Count, null);
+
+        // Sorts the elements in this list.  Uses Array.Sort with the
+        // provided comparer.
+        public void Sort(IComparer<T> comparer)
+            => Sort(0, Count, comparer);
+
+        // Sorts the elements in a section of this list. The sort compares the
+        // elements to each other using the given IComparer interface. If
+        // comparer is null, the elements are compared to each other using
+        // the IComparable interface, which in that case must be implemented by all
+        // elements of the list.
+        // 
+        // This method uses the Array.Sort method to sort the elements.
+        // 
+        public void Sort(int index, int count, IComparer<T> comparer)
+        {
+            if (index < 0)
+            {
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            }
+
+            if (count < 0)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (_size - index < count)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
+
+            if (count > 1)
+            {
+                Array.Sort<T>(_items, index, count, comparer);
+            }
+            _version++;
+        }
+
+        public void Sort(Comparison<T> comparison)
+        {
+            if (comparison == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.comparison);
+            }
+
+            if (_size > 1)
+            {
+                ArraySortHelper<T>.Sort(_items, 0, _size, comparison);
+            }
+            _version++;
+        }
+
+        // ToArray returns an array containing the contents of the List.
+        // This requires copying the List, which is an O(n) operation.
+        public T[] ToArray()
+        {
+            if (_size == 0)
+            {
+                return s_emptyArray;
+            }
+
+            T[] array = new T[_size];
+            Array.Copy(_items, 0, array, 0, _size);
+            return array;
+        }
+
+        // Sets the capacity of this list to the size of the list. This method can
+        // be used to minimize a list's memory overhead once it is known that no
+        // new elements will be added to the list. To completely clear a list and
+        // release all memory referenced by the list, execute the following
+        // statements:
+        // 
+        // list.Clear();
+        // list.TrimExcess();
+        // 
+        public void TrimExcess()
+        {
+            int threshold = (int)(((double)_items.Length) * 0.9);
+            if (_size < threshold)
+            {
+                Capacity = _size;
+            }
+        }
+
+        public bool TrueForAll(Predicate<T> match)
+        {
+            if (match == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
+            }
+
+            for (int i = 0; i < _size; i++)
+            {
+                if (!match(_items[i]))
+                {
+                    return false;
+                }
+            }
+            return true;
+        }
+
+        private void AddEnumerable(IEnumerable<T> enumerable)
+        {
+            Debug.Assert(enumerable != null);
+            Debug.Assert(!(enumerable is ICollection<T>), "We should have optimized for this beforehand.");
+
+            _version++; // Even if the enumerable has no items, we can update _version.
+            using (IEnumerator<T> en = enumerable.GetEnumerator())
+            {
+
+                while (en.MoveNext())
+                {
+                    // Capture Current before doing anything else. If this throws
+                    // an exception, we want to make a clean break.
+                    T current = en.Current;
+
+                    if (_size == _items.Length)
+                    {
+                        EnsureCapacity(_size + 1);
+                    }
+
+                    _items[_size++] = current;
+                }
+            }
+        }
+
+        public struct Enumerator : IEnumerator<T>, IEnumerator
+        {
+            private List<T> _list;
+            private int _index;
+            private int _version;
+            private T _current;
+
+            internal Enumerator(List<T> list)
+            {
+                _list = list;
+                _index = 0;
+                _version = list._version;
+                _current = default;
+            }
+
+            public void Dispose()
+            {
+            }
+
+            public bool MoveNext()
+            {
+                List<T> localList = _list;
+
+                if (_version == localList._version && ((uint)_index < (uint)localList._size))
+                {
+                    _current = localList._items[_index];
+                    _index++;
+                    return true;
+                }
+                return MoveNextRare();
+            }
+
+            private bool MoveNextRare()
+            {
+                if (_version != _list._version)
+                {
+                    ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion();
+                }
+
+                _index = _list._size + 1;
+                _current = default;
+                return false;
+            }
+
+            public T Current => _current;
+
+            object IEnumerator.Current
+            {
+                get
+                {
+                    if (_index == 0 || _index == _list._size + 1)
+                    {
+                        ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumOpCantHappen();
+                    }
+                    return Current;
+                }
+            }
+
+            void IEnumerator.Reset()
+            {
+                if (_version != _list._version)
+                {
+                    ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion();
+                }
+
+                _index = 0;
+                _current = default;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/NonRandomizedStringEqualityComparer.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/NonRandomizedStringEqualityComparer.cs
new file mode 100644
index 0000000000..e7efa22b24
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/NonRandomizedStringEqualityComparer.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Collections.Generic
+{
+    // NonRandomizedStringEqualityComparer is the comparer used by default with the Dictionary<string,...> 
+    // We use NonRandomizedStringEqualityComparer as default comparer as it doesnt use the randomized string hashing which 
+    // keeps the performance not affected till we hit collision threshold and then we switch to the comparer which is using 
+    // randomized string hashing.
+    [Serializable] // Required for compatibility with .NET Core 2.0 as we exposed the NonRandomizedStringEqualityComparer inside the serialization blob
+    // Needs to be public to support binary serialization compatibility
+    public sealed class NonRandomizedStringEqualityComparer : EqualityComparer<string>, ISerializable
+    {
+        internal static new IEqualityComparer<string> Default { get; } = new NonRandomizedStringEqualityComparer();
+
+        private NonRandomizedStringEqualityComparer() { }
+
+        // This is used by the serialization engine.
+        private NonRandomizedStringEqualityComparer(SerializationInfo information, StreamingContext context) { }
+
+        public sealed override bool Equals(string x, string y) => string.Equals(x, y);
+
+        public sealed override int GetHashCode(string obj) => obj?.GetLegacyNonRandomizedHashCode() ?? 0;
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            // We are doing this to stay compatible with .NET Framework.
+            info.SetType(typeof(GenericEqualityComparer<string>));
+        }
+    }
+} 
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/ValueListBuilder.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/ValueListBuilder.cs
new file mode 100644
index 0000000000..72da4a9e19
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/ValueListBuilder.cs
@@ -0,0 +1,76 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Buffers;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+
+namespace System.Collections.Generic
+{
+    internal ref partial struct ValueListBuilder<T>
+    {
+        private Span<T> _span;
+        private T[] _arrayFromPool;
+        private int _pos;
+
+        public ValueListBuilder(Span<T> initialSpan)
+        {
+            _span = initialSpan;
+            _arrayFromPool = null;
+            _pos = 0;
+        }
+
+        public int Length => _pos;
+
+        public ref T this[int index]
+        {
+            get
+            {
+                Debug.Assert(index < _pos);
+                return ref _span[index];
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Append(T item)
+        {
+            int pos = _pos;
+            if (pos >= _span.Length)
+                Grow();
+
+            _span[pos] = item;
+            _pos = pos + 1;
+        }
+
+        public ReadOnlySpan<T> AsSpan()
+        {
+            return _span.Slice(0, _pos);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Dispose()
+        {
+            if (_arrayFromPool != null)
+            {
+                ArrayPool<T>.Shared.Return(_arrayFromPool);
+                _arrayFromPool = null;
+            }
+        }
+
+        private void Grow()
+        {
+            T[] array = ArrayPool<T>.Shared.Rent(_span.Length * 2);
+
+            bool success = _span.TryCopyTo(array);
+            Debug.Assert(success);
+
+            T[] toReturn = _arrayFromPool;
+            _span = _arrayFromPool = array;
+            if (toReturn != null)
+            {
+                ArrayPool<T>.Shared.Return(toReturn);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/HashHelpers.SerializationInfoTable.cs b/src/System.Private.CoreLib/shared/System/Collections/HashHelpers.SerializationInfoTable.cs
new file mode 100644
index 0000000000..d91dfd878e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/HashHelpers.SerializationInfoTable.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// Used by Hashtable and Dictionary's SeralizationInfo .ctor's to store the SeralizationInfo
+// object until OnDeserialization is called.
+
+using System.Threading;
+using System.Runtime.CompilerServices;
+using System.Runtime.Serialization;
+
+namespace System.Collections
+{
+    internal static partial class HashHelpers
+    {        
+        private static ConditionalWeakTable<object, SerializationInfo> s_serializationInfoTable;
+
+        public static ConditionalWeakTable<object, SerializationInfo> SerializationInfoTable
+        {
+            get
+            {
+                if (s_serializationInfoTable == null)
+                    Interlocked.CompareExchange(ref s_serializationInfoTable, new ConditionalWeakTable<object, SerializationInfo>(), null);
+
+                return s_serializationInfoTable;
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/shared/System/Collections/HashHelpers.cs b/src/System.Private.CoreLib/shared/System/Collections/HashHelpers.cs
new file mode 100644
index 0000000000..ba2c75c89c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/HashHelpers.cs
@@ -0,0 +1,92 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System.Diagnostics;
+
+namespace System.Collections
+{
+    internal static partial class HashHelpers
+    {
+        public const int HashCollisionThreshold = 100;
+
+        // This is the maximum prime smaller than Array.MaxArrayLength
+        public const int MaxPrimeArrayLength = 0x7FEFFFFD;
+
+        public const int HashPrime = 101;
+
+        // Table of prime numbers to use as hash table sizes. 
+        // A typical resize algorithm would pick the smallest prime number in this array
+        // that is larger than twice the previous capacity. 
+        // Suppose our Hashtable currently has capacity x and enough elements are added 
+        // such that a resize needs to occur. Resizing first computes 2x then finds the 
+        // first prime in the table greater than 2x, i.e. if primes are ordered 
+        // p_1, p_2, ..., p_i, ..., it finds p_n such that p_n-1 < 2x < p_n. 
+        // Doubling is important for preserving the asymptotic complexity of the 
+        // hashtable operations such as add.  Having a prime guarantees that double 
+        // hashing does not lead to infinite loops.  IE, your hash function will be 
+        // h1(key) + i*h2(key), 0 <= i < size.  h2 and the size must be relatively prime.
+        // We prefer the low computation costs of higher prime numbers over the increased
+        // memory allocation of a fixed prime number i.e. when right sizing a HashSet.
+        public static readonly int[] primes = {
+            3, 7, 11, 17, 23, 29, 37, 47, 59, 71, 89, 107, 131, 163, 197, 239, 293, 353, 431, 521, 631, 761, 919,
+            1103, 1327, 1597, 1931, 2333, 2801, 3371, 4049, 4861, 5839, 7013, 8419, 10103, 12143, 14591,
+            17519, 21023, 25229, 30293, 36353, 43627, 52361, 62851, 75431, 90523, 108631, 130363, 156437,
+            187751, 225307, 270371, 324449, 389357, 467237, 560689, 672827, 807403, 968897, 1162687, 1395263,
+            1674319, 2009191, 2411033, 2893249, 3471899, 4166287, 4999559, 5999471, 7199369 };
+
+        public static bool IsPrime(int candidate)
+        {
+            if ((candidate & 1) != 0)
+            {
+                int limit = (int)Math.Sqrt(candidate);
+                for (int divisor = 3; divisor <= limit; divisor += 2)
+                {
+                    if ((candidate % divisor) == 0)
+                        return false;
+                }
+                return true;
+            }
+            return (candidate == 2);
+        }
+
+        public static int GetPrime(int min)
+        {
+            if (min < 0)
+                throw new ArgumentException(SR.Arg_HTCapacityOverflow);
+
+            for (int i = 0; i < primes.Length; i++)
+            {
+                int prime = primes[i];
+                if (prime >= min)
+                    return prime;
+            }
+
+            //outside of our predefined table. 
+            //compute the hard way. 
+            for (int i = (min | 1); i < int.MaxValue; i += 2)
+            {
+                if (IsPrime(i) && ((i - 1) % HashPrime != 0))
+                    return i;
+            }
+            return min;
+        }
+
+        // Returns size of hashtable to grow to.
+        public static int ExpandPrime(int oldSize)
+        {
+            int newSize = 2 * oldSize;
+
+            // Allow the hashtables to grow to maximum possible size (~2G elements) before encountering capacity overflow.
+            // Note that this check works even when _items.Length overflowed thanks to the (uint) cast
+            if ((uint)newSize > MaxPrimeArrayLength && MaxPrimeArrayLength > oldSize)
+            {
+                Debug.Assert(MaxPrimeArrayLength == GetPrime(MaxPrimeArrayLength), "Invalid MaxPrimeArrayLength");
+                return MaxPrimeArrayLength;
+            }
+
+            return GetPrime(newSize);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Hashtable.cs b/src/System.Private.CoreLib/shared/System/Collections/Hashtable.cs
new file mode 100644
index 0000000000..1ee12138f8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/Hashtable.cs
@@ -0,0 +1,1650 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Class:  Hashtable
+**
+** Purpose: Represents a collection of key/value pairs
+**          that are organized based on the hash code
+**          of the key.
+**
+===========================================================*/
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.Serialization;
+using System.Threading;
+
+namespace System.Collections
+{
+    // The Hashtable class represents a dictionary of associated keys and values
+    // with constant lookup time.
+    // 
+    // Objects used as keys in a hashtable must implement the GetHashCode
+    // and Equals methods (or they can rely on the default implementations
+    // inherited from Object if key equality is simply reference
+    // equality). Furthermore, the GetHashCode and Equals methods of
+    // a key object must produce the same results given the same parameters for the
+    // entire time the key is present in the hashtable. In practical terms, this
+    // means that key objects should be immutable, at least for the time they are
+    // used as keys in a hashtable.
+    // 
+    // When entries are added to a hashtable, they are placed into
+    // buckets based on the hashcode of their keys. Subsequent lookups of
+    // keys will use the hashcode of the keys to only search a particular bucket,
+    // thus substantially reducing the number of key comparisons required to find
+    // an entry. A hashtable's maximum load factor, which can be specified
+    // when the hashtable is instantiated, determines the maximum ratio of
+    // hashtable entries to hashtable buckets. Smaller load factors cause faster
+    // average lookup times at the cost of increased memory consumption. The
+    // default maximum load factor of 1.0 generally provides the best balance
+    // between speed and size. As entries are added to a hashtable, the hashtable's
+    // actual load factor increases, and when the actual load factor reaches the
+    // maximum load factor value, the number of buckets in the hashtable is
+    // automatically increased by approximately a factor of two (to be precise, the
+    // number of hashtable buckets is increased to the smallest prime number that
+    // is larger than twice the current number of hashtable buckets).
+    // 
+    // Each object provides their own hash function, accessed by calling
+    // GetHashCode().  However, one can write their own object 
+    // implementing IEqualityComparer and pass it to a constructor on
+    // the Hashtable.  That hash function (and the equals method on the 
+    // IEqualityComparer) would be used for all objects in the table.
+    //
+    [DebuggerTypeProxy(typeof(System.Collections.Hashtable.HashtableDebugView))]
+    [DebuggerDisplay("Count = {Count}")]
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class Hashtable : IDictionary, ISerializable, IDeserializationCallback, ICloneable
+    {
+        /*
+          This Hashtable uses double hashing.  There are hashsize buckets in the 
+          table, and each bucket can contain 0 or 1 element.  We use a bit to mark
+          whether there's been a collision when we inserted multiple elements
+          (ie, an inserted item was hashed at least a second time and we probed 
+          this bucket, but it was already in use).  Using the collision bit, we
+          can terminate lookups & removes for elements that aren't in the hash
+          table more quickly.  We steal the most significant bit from the hash code
+          to store the collision bit.
+
+          Our hash function is of the following form:
+    
+          h(key, n) = h1(key) + n*h2(key)
+    
+          where n is the number of times we've hit a collided bucket and rehashed
+          (on this particular lookup).  Here are our hash functions:
+    
+          h1(key) = GetHash(key);  // default implementation calls key.GetHashCode();
+          h2(key) = 1 + (((h1(key) >> 5) + 1) % (hashsize - 1));
+    
+          The h1 can return any number.  h2 must return a number between 1 and
+          hashsize - 1 that is relatively prime to hashsize (not a problem if 
+          hashsize is prime).  (Knuth's Art of Computer Programming, Vol. 3, p. 528-9)
+          If this is true, then we are guaranteed to visit every bucket in exactly
+          hashsize probes, since the least common multiple of hashsize and h2(key)
+          will be hashsize * h2(key).  (This is the first number where adding h2 to
+          h1 mod hashsize will be 0 and we will search the same bucket twice).
+          
+          We previously used a different h2(key, n) that was not constant.  That is a 
+          horrifically bad idea, unless you can prove that series will never produce
+          any identical numbers that overlap when you mod them by hashsize, for all
+          subranges from i to i+hashsize, for all i.  It's not worth investigating,
+          since there was no clear benefit from using that hash function, and it was
+          broken.
+    
+          For efficiency reasons, we've implemented this by storing h1 and h2 in a 
+          temporary, and setting a variable called seed equal to h1.  We do a probe,
+          and if we collided, we simply add h2 to seed each time through the loop.
+    
+          A good test for h2() is to subclass Hashtable, provide your own implementation
+          of GetHash() that returns a constant, then add many items to the hash table.
+          Make sure Count equals the number of items you inserted.
+
+          Note that when we remove an item from the hash table, we set the key
+          equal to buckets, if there was a collision in this bucket.  Otherwise
+          we'd either wipe out the collision bit, or we'd still have an item in
+          the hash table.
+
+           -- 
+        */
+
+        private const Int32 InitialSize = 3;
+
+        private const String LoadFactorName = "LoadFactor"; // Do not rename (binary serialization)
+        private const String VersionName = "Version"; // Do not rename (binary serialization)
+        private const String ComparerName = "Comparer"; // Do not rename (binary serialization)
+        private const String HashCodeProviderName = "HashCodeProvider"; // Do not rename (binary serialization)
+        private const String HashSizeName = "HashSize";  // Must save buckets.Length. Do not rename (binary serialization)
+        private const String KeysName = "Keys"; // Do not rename (binary serialization)
+        private const String ValuesName = "Values"; // Do not rename (binary serialization)
+        private const String KeyComparerName = "KeyComparer"; // Do not rename (binary serialization)
+
+        // Deleted entries have their key set to buckets
+
+        // The hash table data.
+        // This cannot be serialized
+        private struct bucket
+        {
+            public Object key;
+            public Object val;
+            public int hash_coll;   // Store hash code; sign bit means there was a collision.
+        }
+
+        private bucket[] _buckets;
+
+        // The total number of entries in the hash table.
+        private int _count;
+
+        // The total number of collision bits set in the hashtable
+        private int _occupancy;
+
+        private int _loadsize;
+        private float _loadFactor;
+
+        private volatile int _version;
+        private volatile bool _isWriterInProgress;
+
+        private ICollection _keys;
+        private ICollection _values;
+
+        private IEqualityComparer _keycomparer;
+        private Object _syncRoot;
+
+        [Obsolete("Please use EqualityComparer property.")]
+        protected IHashCodeProvider hcp
+        {
+            get
+            {
+                if (_keycomparer is CompatibleComparer)
+                {
+                    return ((CompatibleComparer)_keycomparer).HashCodeProvider;
+                }
+                else if (_keycomparer == null)
+                {
+                    return null;
+                }
+                else
+                {
+                    throw new ArgumentException(SR.Arg_CannotMixComparisonInfrastructure);
+                }
+            }
+            set
+            {
+                if (_keycomparer is CompatibleComparer)
+                {
+                    CompatibleComparer keyComparer = (CompatibleComparer)_keycomparer;
+                    _keycomparer = new CompatibleComparer(value, keyComparer.Comparer);
+                }
+                else if (_keycomparer == null)
+                {
+                    _keycomparer = new CompatibleComparer(value, (IComparer)null);
+                }
+                else
+                {
+                    throw new ArgumentException(SR.Arg_CannotMixComparisonInfrastructure);
+                }
+            }
+        }
+
+        [Obsolete("Please use KeyComparer properties.")]
+        protected IComparer comparer
+        {
+            get
+            {
+                if (_keycomparer is CompatibleComparer)
+                {
+                    return ((CompatibleComparer)_keycomparer).Comparer;
+                }
+                else if (_keycomparer == null)
+                {
+                    return null;
+                }
+                else
+                {
+                    throw new ArgumentException(SR.Arg_CannotMixComparisonInfrastructure);
+                }
+            }
+            set
+            {
+                if (_keycomparer is CompatibleComparer)
+                {
+                    CompatibleComparer keyComparer = (CompatibleComparer)_keycomparer;
+                    _keycomparer = new CompatibleComparer(keyComparer.HashCodeProvider, value);
+                }
+                else if (_keycomparer == null)
+                {
+                    _keycomparer = new CompatibleComparer((IHashCodeProvider)null, value);
+                }
+                else
+                {
+                    throw new ArgumentException(SR.Arg_CannotMixComparisonInfrastructure);
+                }
+            }
+        }
+
+
+        protected IEqualityComparer EqualityComparer
+        {
+            get
+            {
+                return _keycomparer;
+            }
+        }
+
+        // Note: this constructor is a bogus constructor that does nothing
+        // and is for use only with SyncHashtable.
+        internal Hashtable(bool trash)
+        {
+        }
+
+        // Constructs a new hashtable. The hashtable is created with an initial
+        // capacity of zero and a load factor of 1.0.
+        public Hashtable() : this(0, 1.0f)
+        {
+        }
+
+        // Constructs a new hashtable with the given initial capacity and a load
+        // factor of 1.0. The capacity argument serves as an indication of
+        // the number of entries the hashtable will contain. When this number (or
+        // an approximation) is known, specifying it in the constructor can
+        // eliminate a number of resizing operations that would otherwise be
+        // performed when elements are added to the hashtable.
+        // 
+        public Hashtable(int capacity) : this(capacity, 1.0f)
+        {
+        }
+
+        // Constructs a new hashtable with the given initial capacity and load
+        // factor. The capacity argument serves as an indication of the
+        // number of entries the hashtable will contain. When this number (or an
+        // approximation) is known, specifying it in the constructor can eliminate
+        // a number of resizing operations that would otherwise be performed when
+        // elements are added to the hashtable. The loadFactor argument
+        // indicates the maximum ratio of hashtable entries to hashtable buckets.
+        // Smaller load factors cause faster average lookup times at the cost of
+        // increased memory consumption. A load factor of 1.0 generally provides
+        // the best balance between speed and size.
+        // 
+        public Hashtable(int capacity, float loadFactor)
+        {
+            if (capacity < 0)
+                throw new ArgumentOutOfRangeException(nameof(capacity), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (!(loadFactor >= 0.1f && loadFactor <= 1.0f))
+                throw new ArgumentOutOfRangeException(nameof(loadFactor), SR.Format(SR.ArgumentOutOfRange_HashtableLoadFactor, .1, 1.0));
+
+            // Based on perf work, .72 is the optimal load factor for this table.  
+            _loadFactor = 0.72f * loadFactor;
+
+            double rawsize = capacity / _loadFactor;
+            if (rawsize > Int32.MaxValue)
+                throw new ArgumentException(SR.Arg_HTCapacityOverflow, nameof(capacity));
+
+            // Avoid awfully small sizes
+            int hashsize = (rawsize > InitialSize) ? HashHelpers.GetPrime((int)rawsize) : InitialSize;
+            _buckets = new bucket[hashsize];
+
+            _loadsize = (int)(_loadFactor * hashsize);
+            _isWriterInProgress = false;
+            // Based on the current algorithm, loadsize must be less than hashsize.
+            Debug.Assert(_loadsize < hashsize, "Invalid hashtable loadsize!");
+        }
+
+        public Hashtable(int capacity, float loadFactor, IEqualityComparer equalityComparer) : this(capacity, loadFactor)
+        {
+            _keycomparer = equalityComparer;
+        }
+
+        [Obsolete("Please use Hashtable(IEqualityComparer) instead.")]
+        public Hashtable(IHashCodeProvider hcp, IComparer comparer)
+            : this(0, 1.0f, hcp, comparer)
+        {
+        }
+
+        public Hashtable(IEqualityComparer equalityComparer) : this(0, 1.0f, equalityComparer)
+        {
+        }
+
+        [Obsolete("Please use Hashtable(int, IEqualityComparer) instead.")]
+        public Hashtable(int capacity, IHashCodeProvider hcp, IComparer comparer)
+            : this(capacity, 1.0f, hcp, comparer)
+        {
+        }
+
+        public Hashtable(int capacity, IEqualityComparer equalityComparer)
+            : this(capacity, 1.0f, equalityComparer)
+        {
+        }
+
+        // Constructs a new hashtable containing a copy of the entries in the given
+        // dictionary. The hashtable is created with a load factor of 1.0.
+        // 
+        public Hashtable(IDictionary d) : this(d, 1.0f)
+        {
+        }
+
+        // Constructs a new hashtable containing a copy of the entries in the given
+        // dictionary. The hashtable is created with the given load factor.
+        // 
+        public Hashtable(IDictionary d, float loadFactor)
+            : this(d, loadFactor, (IEqualityComparer)null)
+        {
+        }
+
+        [Obsolete("Please use Hashtable(IDictionary, IEqualityComparer) instead.")]
+        public Hashtable(IDictionary d, IHashCodeProvider hcp, IComparer comparer)
+            : this(d, 1.0f, hcp, comparer)
+        {
+        }
+
+        public Hashtable(IDictionary d, IEqualityComparer equalityComparer)
+            : this(d, 1.0f, equalityComparer)
+        {
+        }
+
+        [Obsolete("Please use Hashtable(int, float, IEqualityComparer) instead.")]
+        public Hashtable(int capacity, float loadFactor, IHashCodeProvider hcp, IComparer comparer)
+            : this(capacity, loadFactor)
+        {
+            if (hcp != null || comparer != null)
+            {
+                _keycomparer = new CompatibleComparer(hcp, comparer);
+            }
+        }
+
+        [Obsolete("Please use Hashtable(IDictionary, float, IEqualityComparer) instead.")]
+        public Hashtable(IDictionary d, float loadFactor, IHashCodeProvider hcp, IComparer comparer)
+            : this((d != null ? d.Count : 0), loadFactor, hcp, comparer)
+        {
+            if (d == null)
+                throw new ArgumentNullException(nameof(d), SR.ArgumentNull_Dictionary);
+
+            IDictionaryEnumerator e = d.GetEnumerator();
+            while (e.MoveNext())
+                Add(e.Key, e.Value);
+        }
+
+        public Hashtable(IDictionary d, float loadFactor, IEqualityComparer equalityComparer)
+            : this((d != null ? d.Count : 0), loadFactor, equalityComparer)
+        {
+            if (d == null)
+                throw new ArgumentNullException(nameof(d), SR.ArgumentNull_Dictionary);
+
+            IDictionaryEnumerator e = d.GetEnumerator();
+            while (e.MoveNext())
+                Add(e.Key, e.Value);
+        }
+
+        protected Hashtable(SerializationInfo info, StreamingContext context)
+        {
+            //We can't do anything with the keys and values until the entire graph has been deserialized
+            //and we have a reasonable estimate that GetHashCode is not going to fail.  For the time being,
+            //we'll just cache this.  The graph is not valid until OnDeserialization has been called.
+            HashHelpers.SerializationInfoTable.Add(this, info);
+        }
+
+        // ?InitHash? is basically an implementation of classic DoubleHashing (see http://en.wikipedia.org/wiki/Double_hashing)  
+        //
+        // 1) The only ?correctness? requirement is that the ?increment? used to probe 
+        //    a. Be non-zero
+        //    b. Be relatively prime to the table size ?hashSize?. (This is needed to insure you probe all entries in the table before you ?wrap? and visit entries already probed)
+        // 2) Because we choose table sizes to be primes, we just need to insure that the increment is 0 < incr < hashSize
+        //
+        // Thus this function would work: Incr = 1 + (seed % (hashSize-1))
+        // 
+        // While this works well for ?uniformly distributed? keys, in practice, non-uniformity is common. 
+        // In particular in practice we can see ?mostly sequential? where you get long clusters of keys that ?pack?. 
+        // To avoid bad behavior you want it to be the case that the increment is ?large? even for ?small? values (because small 
+        // values tend to happen more in practice). Thus we multiply ?seed? by a number that will make these small values
+        // bigger (and not hurt large values). We picked HashPrime (101) because it was prime, and if ?hashSize-1? is not a multiple of HashPrime
+        // (enforced in GetPrime), then incr has the potential of being every value from 1 to hashSize-1. The choice was largely arbitrary.
+        // 
+        // Computes the hash function:  H(key, i) = h1(key) + i*h2(key, hashSize).
+        // The out parameter seed is h1(key), while the out parameter 
+        // incr is h2(key, hashSize).  Callers of this function should 
+        // add incr each time through a loop.
+        private uint InitHash(Object key, int hashsize, out uint seed, out uint incr)
+        {
+            // Hashcode must be positive.  Also, we must not use the sign bit, since
+            // that is used for the collision bit.
+            uint hashcode = (uint)GetHash(key) & 0x7FFFFFFF;
+            seed = (uint)hashcode;
+            // Restriction: incr MUST be between 1 and hashsize - 1, inclusive for
+            // the modular arithmetic to work correctly.  This guarantees you'll
+            // visit every bucket in the table exactly once within hashsize
+            // iterations.  Violate this and it'll cause obscure bugs forever.
+            // If you change this calculation for h2(key), update putEntry too!
+            incr = (uint)(1 + ((seed * HashHelpers.HashPrime) % ((uint)hashsize - 1)));
+            return hashcode;
+        }
+
+        // Adds an entry with the given key and value to this hashtable. An
+        // ArgumentException is thrown if the key is null or if the key is already
+        // present in the hashtable.
+        // 
+        public virtual void Add(Object key, Object value)
+        {
+            Insert(key, value, true);
+        }
+
+        // Removes all entries from this hashtable.
+        public virtual void Clear()
+        {
+            Debug.Assert(!_isWriterInProgress, "Race condition detected in usages of Hashtable - multiple threads appear to be writing to a Hashtable instance simultaneously!  Don't do that - use Hashtable.Synchronized.");
+
+            if (_count == 0 && _occupancy == 0)
+                return;
+
+            _isWriterInProgress = true;
+            for (int i = 0; i < _buckets.Length; i++)
+            {
+                _buckets[i].hash_coll = 0;
+                _buckets[i].key = null;
+                _buckets[i].val = null;
+            }
+
+            _count = 0;
+            _occupancy = 0;
+            UpdateVersion();
+            _isWriterInProgress = false;
+        }
+
+        // Clone returns a virtually identical copy of this hash table.  This does
+        // a shallow copy - the Objects in the table aren't cloned, only the references
+        // to those Objects.
+        public virtual Object Clone()
+        {
+            bucket[] lbuckets = _buckets;
+            Hashtable ht = new Hashtable(_count, _keycomparer);
+            ht._version = _version;
+            ht._loadFactor = _loadFactor;
+            ht._count = 0;
+
+            int bucket = lbuckets.Length;
+            while (bucket > 0)
+            {
+                bucket--;
+                Object keyv = lbuckets[bucket].key;
+                if ((keyv != null) && (keyv != lbuckets))
+                {
+                    ht[keyv] = lbuckets[bucket].val;
+                }
+            }
+
+            return ht;
+        }
+
+        // Checks if this hashtable contains the given key.
+        public virtual bool Contains(Object key)
+        {
+            return ContainsKey(key);
+        }
+
+        // Checks if this hashtable contains an entry with the given key.  This is
+        // an O(1) operation.
+        // 
+        public virtual bool ContainsKey(Object key)
+        {
+            if (key == null)
+            {
+                throw new ArgumentNullException(nameof(key), SR.ArgumentNull_Key);
+            }
+
+            uint seed;
+            uint incr;
+            // Take a snapshot of buckets, in case another thread resizes table
+            bucket[] lbuckets = _buckets;
+            uint hashcode = InitHash(key, lbuckets.Length, out seed, out incr);
+            int ntry = 0;
+
+            bucket b;
+            int bucketNumber = (int)(seed % (uint)lbuckets.Length);
+            do
+            {
+                b = lbuckets[bucketNumber];
+                if (b.key == null)
+                {
+                    return false;
+                }
+                if (((b.hash_coll & 0x7FFFFFFF) == hashcode) &&
+                    KeyEquals(b.key, key))
+                    return true;
+                bucketNumber = (int)(((long)bucketNumber + incr) % (uint)lbuckets.Length);
+            } while (b.hash_coll < 0 && ++ntry < lbuckets.Length);
+            return false;
+        }
+
+
+
+        // Checks if this hashtable contains an entry with the given value. The
+        // values of the entries of the hashtable are compared to the given value
+        // using the Object.Equals method. This method performs a linear
+        // search and is thus be substantially slower than the ContainsKey
+        // method.
+        // 
+        public virtual bool ContainsValue(Object value)
+        {
+            if (value == null)
+            {
+                for (int i = _buckets.Length; --i >= 0;)
+                {
+                    if (_buckets[i].key != null && _buckets[i].key != _buckets && _buckets[i].val == null)
+                        return true;
+                }
+            }
+            else
+            {
+                for (int i = _buckets.Length; --i >= 0;)
+                {
+                    Object val = _buckets[i].val;
+                    if (val != null && val.Equals(value))
+                        return true;
+                }
+            }
+            return false;
+        }
+
+        // Copies the keys of this hashtable to a given array starting at a given
+        // index. This method is used by the implementation of the CopyTo method in
+        // the KeyCollection class.
+        private void CopyKeys(Array array, int arrayIndex)
+        {
+            Debug.Assert(array != null);
+            Debug.Assert(array.Rank == 1);
+
+            bucket[] lbuckets = _buckets;
+            for (int i = lbuckets.Length; --i >= 0;)
+            {
+                Object keyv = lbuckets[i].key;
+                if ((keyv != null) && (keyv != _buckets))
+                {
+                    array.SetValue(keyv, arrayIndex++);
+                }
+            }
+        }
+
+        // Copies the keys of this hashtable to a given array starting at a given
+        // index. This method is used by the implementation of the CopyTo method in
+        // the KeyCollection class.
+        private void CopyEntries(Array array, int arrayIndex)
+        {
+            Debug.Assert(array != null);
+            Debug.Assert(array.Rank == 1);
+
+            bucket[] lbuckets = _buckets;
+            for (int i = lbuckets.Length; --i >= 0;)
+            {
+                Object keyv = lbuckets[i].key;
+                if ((keyv != null) && (keyv != _buckets))
+                {
+                    DictionaryEntry entry = new DictionaryEntry(keyv, lbuckets[i].val);
+                    array.SetValue(entry, arrayIndex++);
+                }
+            }
+        }
+
+        // Copies the values in this hash table to an array at
+        // a given index.  Note that this only copies values, and not keys.
+        public virtual void CopyTo(Array array, int arrayIndex)
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array), SR.ArgumentNull_Array);
+            if (array.Rank != 1)
+                throw new ArgumentException(SR.Arg_RankMultiDimNotSupported, nameof(array));
+            if (arrayIndex < 0)
+                throw new ArgumentOutOfRangeException(nameof(arrayIndex), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (array.Length - arrayIndex < Count)
+                throw new ArgumentException(SR.Arg_ArrayPlusOffTooSmall);
+
+            CopyEntries(array, arrayIndex);
+        }
+
+        // Copies the values in this Hashtable to an KeyValuePairs array.
+        // KeyValuePairs is different from Dictionary Entry in that it has special
+        // debugger attributes on its fields.
+
+        internal virtual KeyValuePairs[] ToKeyValuePairsArray()
+        {
+            KeyValuePairs[] array = new KeyValuePairs[_count];
+            int index = 0;
+            bucket[] lbuckets = _buckets;
+            for (int i = lbuckets.Length; --i >= 0;)
+            {
+                Object keyv = lbuckets[i].key;
+                if ((keyv != null) && (keyv != _buckets))
+                {
+                    array[index++] = new KeyValuePairs(keyv, lbuckets[i].val);
+                }
+            }
+
+            return array;
+        }
+
+
+        // Copies the values of this hashtable to a given array starting at a given
+        // index. This method is used by the implementation of the CopyTo method in
+        // the ValueCollection class.
+        private void CopyValues(Array array, int arrayIndex)
+        {
+            Debug.Assert(array != null);
+            Debug.Assert(array.Rank == 1);
+
+            bucket[] lbuckets = _buckets;
+            for (int i = lbuckets.Length; --i >= 0;)
+            {
+                Object keyv = lbuckets[i].key;
+                if ((keyv != null) && (keyv != _buckets))
+                {
+                    array.SetValue(lbuckets[i].val, arrayIndex++);
+                }
+            }
+        }
+
+        // Returns the value associated with the given key. If an entry with the
+        // given key is not found, the returned value is null.
+        // 
+        public virtual Object this[Object key]
+        {
+            get
+            {
+                if (key == null)
+                {
+                    throw new ArgumentNullException(nameof(key), SR.ArgumentNull_Key);
+                }
+
+                uint seed;
+                uint incr;
+
+
+                // Take a snapshot of buckets, in case another thread does a resize
+                bucket[] lbuckets = _buckets;
+                uint hashcode = InitHash(key, lbuckets.Length, out seed, out incr);
+                int ntry = 0;
+
+                bucket b;
+                int bucketNumber = (int)(seed % (uint)lbuckets.Length);
+                do
+                {
+                    int currentversion;
+
+                    //     A read operation on hashtable has three steps:
+                    //        (1) calculate the hash and find the slot number.
+                    //        (2) compare the hashcode, if equal, go to step 3. Otherwise end.
+                    //        (3) compare the key, if equal, go to step 4. Otherwise end.
+                    //        (4) return the value contained in the bucket.
+                    //     After step 3 and before step 4. A writer can kick in a remove the old item and add a new one 
+                    //     in the same bucket. So in the reader we need to check if the hash table is modified during above steps.
+                    //
+                    // Writers (Insert, Remove, Clear) will set 'isWriterInProgress' flag before it starts modifying 
+                    // the hashtable and will ckear the flag when it is done.  When the flag is cleared, the 'version'
+                    // will be increased.  We will repeat the reading if a writer is in progress or done with the modification 
+                    // during the read.
+                    //
+                    // Our memory model guarantee if we pick up the change in bucket from another processor, 
+                    // we will see the 'isWriterProgress' flag to be true or 'version' is changed in the reader.
+                    //                    
+                    SpinWait spin = new SpinWait();
+                    while (true)
+                    {
+                        // this is volatile read, following memory accesses can not be moved ahead of it.
+                        currentversion = _version;
+                        b = lbuckets[bucketNumber];
+
+                        if (!_isWriterInProgress && (currentversion == _version))
+                            break;
+
+                        spin.SpinOnce();
+                    }
+
+                    if (b.key == null)
+                    {
+                        return null;
+                    }
+                    if (((b.hash_coll & 0x7FFFFFFF) == hashcode) &&
+                        KeyEquals(b.key, key))
+                        return b.val;
+                    bucketNumber = (int)(((long)bucketNumber + incr) % (uint)lbuckets.Length);
+                } while (b.hash_coll < 0 && ++ntry < lbuckets.Length);
+                return null;
+            }
+
+            set
+            {
+                Insert(key, value, false);
+            }
+        }
+
+        // Increases the bucket count of this hashtable. This method is called from
+        // the Insert method when the actual load factor of the hashtable reaches
+        // the upper limit specified when the hashtable was constructed. The number
+        // of buckets in the hashtable is increased to the smallest prime number
+        // that is larger than twice the current number of buckets, and the entries
+        // in the hashtable are redistributed into the new buckets using the cached
+        // hashcodes.
+        private void expand()
+        {
+            int rawsize = HashHelpers.ExpandPrime(_buckets.Length);
+            rehash(rawsize);
+        }
+
+        // We occasionally need to rehash the table to clean up the collision bits.
+        private void rehash()
+        {
+            rehash(_buckets.Length);
+        }
+
+        private void UpdateVersion()
+        {
+            // Version might become negative when version is Int32.MaxValue, but the oddity will be still be correct. 
+            // So we don't need to special case this. 
+            _version++;
+        }
+
+        private void rehash(int newsize)
+        {
+            // reset occupancy
+            _occupancy = 0;
+
+            // Don't replace any internal state until we've finished adding to the 
+            // new bucket[].  This serves two purposes: 
+            //   1) Allow concurrent readers to see valid hashtable contents 
+            //      at all times
+            //   2) Protect against an OutOfMemoryException while allocating this 
+            //      new bucket[].
+            bucket[] newBuckets = new bucket[newsize];
+
+            // rehash table into new buckets
+            int nb;
+            for (nb = 0; nb < _buckets.Length; nb++)
+            {
+                bucket oldb = _buckets[nb];
+                if ((oldb.key != null) && (oldb.key != _buckets))
+                {
+                    int hashcode = oldb.hash_coll & 0x7FFFFFFF;
+                    putEntry(newBuckets, oldb.key, oldb.val, hashcode);
+                }
+            }
+
+            // New bucket[] is good to go - replace buckets and other internal state.
+            _isWriterInProgress = true;
+            _buckets = newBuckets;
+            _loadsize = (int)(_loadFactor * newsize);
+            UpdateVersion();
+            _isWriterInProgress = false;
+            // minimum size of hashtable is 3 now and maximum loadFactor is 0.72 now.
+            Debug.Assert(_loadsize < newsize, "Our current implementation means this is not possible.");
+        }
+
+        // Returns an enumerator for this hashtable.
+        // If modifications made to the hashtable while an enumeration is
+        // in progress, the MoveNext and Current methods of the
+        // enumerator will throw an exception.
+        //
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return new HashtableEnumerator(this, HashtableEnumerator.DictEntry);
+        }
+
+        // Returns a dictionary enumerator for this hashtable.
+        // If modifications made to the hashtable while an enumeration is
+        // in progress, the MoveNext and Current methods of the
+        // enumerator will throw an exception.
+        //
+        public virtual IDictionaryEnumerator GetEnumerator()
+        {
+            return new HashtableEnumerator(this, HashtableEnumerator.DictEntry);
+        }
+
+        // Internal method to get the hash code for an Object.  This will call
+        // GetHashCode() on each object if you haven't provided an IHashCodeProvider
+        // instance.  Otherwise, it calls hcp.GetHashCode(obj).
+        protected virtual int GetHash(Object key)
+        {
+            if (_keycomparer != null)
+                return _keycomparer.GetHashCode(key);
+            return key.GetHashCode();
+        }
+
+        // Is this Hashtable read-only?
+        public virtual bool IsReadOnly
+        {
+            get { return false; }
+        }
+
+        public virtual bool IsFixedSize
+        {
+            get { return false; }
+        }
+
+        // Is this Hashtable synchronized?  See SyncRoot property
+        public virtual bool IsSynchronized
+        {
+            get { return false; }
+        }
+
+        // Internal method to compare two keys.  If you have provided an IComparer
+        // instance in the constructor, this method will call comparer.Compare(item, key).
+        // Otherwise, it will call item.Equals(key).
+        // 
+        protected virtual bool KeyEquals(Object item, Object key)
+        {
+            Debug.Assert(key != null, "key can't be null here!");
+            if (Object.ReferenceEquals(_buckets, item))
+            {
+                return false;
+            }
+
+            if (Object.ReferenceEquals(item, key))
+                return true;
+
+            if (_keycomparer != null)
+                return _keycomparer.Equals(item, key);
+            return item == null ? false : item.Equals(key);
+        }
+
+        // Returns a collection representing the keys of this hashtable. The order
+        // in which the returned collection represents the keys is unspecified, but
+        // it is guaranteed to be          buckets = newBuckets; the same order in which a collection returned by
+        // GetValues represents the values of the hashtable.
+        // 
+        // The returned collection is live in the sense that any changes
+        // to the hash table are reflected in this collection.  It is not
+        // a static copy of all the keys in the hash table.
+        // 
+        public virtual ICollection Keys
+        {
+            get
+            {
+                if (_keys == null)
+                    _keys = new KeyCollection(this);
+                return _keys;
+            }
+        }
+
+        // Returns a collection representing the values of this hashtable. The
+        // order in which the returned collection represents the values is
+        // unspecified, but it is guaranteed to be the same order in which a
+        // collection returned by GetKeys represents the keys of the
+        // hashtable.
+        // 
+        // The returned collection is live in the sense that any changes
+        // to the hash table are reflected in this collection.  It is not
+        // a static copy of all the keys in the hash table.
+        // 
+        public virtual ICollection Values
+        {
+            get
+            {
+                if (_values == null)
+                    _values = new ValueCollection(this);
+                return _values;
+            }
+        }
+
+        // Inserts an entry into this hashtable. This method is called from the Set
+        // and Add methods. If the add parameter is true and the given key already
+        // exists in the hashtable, an exception is thrown.
+        private void Insert(Object key, Object nvalue, bool add)
+        {
+            if (key == null)
+            {
+                throw new ArgumentNullException(nameof(key), SR.ArgumentNull_Key);
+            }
+
+            if (_count >= _loadsize)
+            {
+                expand();
+            }
+            else if (_occupancy > _loadsize && _count > 100)
+            {
+                rehash();
+            }
+
+            uint seed;
+            uint incr;
+            // Assume we only have one thread writing concurrently.  Modify
+            // buckets to contain new data, as long as we insert in the right order.
+            uint hashcode = InitHash(key, _buckets.Length, out seed, out incr);
+            int ntry = 0;
+            int emptySlotNumber = -1; // We use the empty slot number to cache the first empty slot. We chose to reuse slots
+            // create by remove that have the collision bit set over using up new slots.
+            int bucketNumber = (int)(seed % (uint)_buckets.Length);
+            do
+            {
+                // Set emptySlot number to current bucket if it is the first available bucket that we have seen
+                // that once contained an entry and also has had a collision.
+                // We need to search this entire collision chain because we have to ensure that there are no 
+                // duplicate entries in the table.
+                if (emptySlotNumber == -1 && (_buckets[bucketNumber].key == _buckets) && (_buckets[bucketNumber].hash_coll < 0))//(((buckets[bucketNumber].hash_coll & unchecked(0x80000000))!=0)))
+                    emptySlotNumber = bucketNumber;
+
+                // Insert the key/value pair into this bucket if this bucket is empty and has never contained an entry
+                // OR
+                // This bucket once contained an entry but there has never been a collision
+                if ((_buckets[bucketNumber].key == null) ||
+                    (_buckets[bucketNumber].key == _buckets && ((_buckets[bucketNumber].hash_coll & unchecked(0x80000000)) == 0)))
+                {
+                    // If we have found an available bucket that has never had a collision, but we've seen an available
+                    // bucket in the past that has the collision bit set, use the previous bucket instead
+                    if (emptySlotNumber != -1) // Reuse slot
+                        bucketNumber = emptySlotNumber;
+
+                    // We pretty much have to insert in this order.  Don't set hash
+                    // code until the value & key are set appropriately.
+                    _isWriterInProgress = true;
+                    _buckets[bucketNumber].val = nvalue;
+                    _buckets[bucketNumber].key = key;
+                    _buckets[bucketNumber].hash_coll |= (int)hashcode;
+                    _count++;
+                    UpdateVersion();
+                    _isWriterInProgress = false;
+
+                    return;
+                }
+
+                // The current bucket is in use
+                // OR
+                // it is available, but has had the collision bit set and we have already found an available bucket
+                if (((_buckets[bucketNumber].hash_coll & 0x7FFFFFFF) == hashcode) &&
+                    KeyEquals(_buckets[bucketNumber].key, key))
+                {
+                    if (add)
+                    {
+                        throw new ArgumentException(SR.Format(SR.Argument_AddingDuplicate__, _buckets[bucketNumber].key, key));
+                    }
+                    _isWriterInProgress = true;
+                    _buckets[bucketNumber].val = nvalue;
+                    UpdateVersion();
+                    _isWriterInProgress = false;
+
+                    return;
+                }
+
+                // The current bucket is full, and we have therefore collided.  We need to set the collision bit
+                // unless we have remembered an available slot previously.
+                if (emptySlotNumber == -1)
+                {// We don't need to set the collision bit here since we already have an empty slot
+                    if (_buckets[bucketNumber].hash_coll >= 0)
+                    {
+                        _buckets[bucketNumber].hash_coll |= unchecked((int)0x80000000);
+                        _occupancy++;
+                    }
+                }
+
+                bucketNumber = (int)(((long)bucketNumber + incr) % (uint)_buckets.Length);
+            } while (++ntry < _buckets.Length);
+
+            // This code is here if and only if there were no buckets without a collision bit set in the entire table
+            if (emptySlotNumber != -1)
+            {
+                // We pretty much have to insert in this order.  Don't set hash
+                // code until the value & key are set appropriately.
+                _isWriterInProgress = true;
+                _buckets[emptySlotNumber].val = nvalue;
+                _buckets[emptySlotNumber].key = key;
+                _buckets[emptySlotNumber].hash_coll |= (int)hashcode;
+                _count++;
+                UpdateVersion();
+                _isWriterInProgress = false;
+
+                return;
+            }
+
+            // If you see this assert, make sure load factor & count are reasonable.
+            // Then verify that our double hash function (h2, described at top of file)
+            // meets the requirements described above. You should never see this assert.
+            Debug.Fail("hash table insert failed!  Load factor too high, or our double hashing function is incorrect.");
+            throw new InvalidOperationException(SR.InvalidOperation_HashInsertFailed);
+        }
+
+        private void putEntry(bucket[] newBuckets, Object key, Object nvalue, int hashcode)
+        {
+            Debug.Assert(hashcode >= 0, "hashcode >= 0");  // make sure collision bit (sign bit) wasn't set.
+
+            uint seed = (uint)hashcode;
+            uint incr = unchecked((uint)(1 + ((seed * HashHelpers.HashPrime) % ((uint)newBuckets.Length - 1))));
+            int bucketNumber = (int)(seed % (uint)newBuckets.Length);
+            do
+            {
+                if ((newBuckets[bucketNumber].key == null) || (newBuckets[bucketNumber].key == _buckets))
+                {
+                    newBuckets[bucketNumber].val = nvalue;
+                    newBuckets[bucketNumber].key = key;
+                    newBuckets[bucketNumber].hash_coll |= hashcode;
+                    return;
+                }
+
+                if (newBuckets[bucketNumber].hash_coll >= 0)
+                {
+                    newBuckets[bucketNumber].hash_coll |= unchecked((int)0x80000000);
+                    _occupancy++;
+                }
+                bucketNumber = (int)(((long)bucketNumber + incr) % (uint)newBuckets.Length);
+            } while (true);
+        }
+
+        // Removes an entry from this hashtable. If an entry with the specified
+        // key exists in the hashtable, it is removed. An ArgumentException is
+        // thrown if the key is null.
+        // 
+        public virtual void Remove(Object key)
+        {
+            if (key == null)
+            {
+                throw new ArgumentNullException(nameof(key), SR.ArgumentNull_Key);
+            }
+
+            Debug.Assert(!_isWriterInProgress, "Race condition detected in usages of Hashtable - multiple threads appear to be writing to a Hashtable instance simultaneously!  Don't do that - use Hashtable.Synchronized.");
+
+            uint seed;
+            uint incr;
+            // Assuming only one concurrent writer, write directly into buckets.
+            uint hashcode = InitHash(key, _buckets.Length, out seed, out incr);
+            int ntry = 0;
+
+            bucket b;
+            int bn = (int)(seed % (uint)_buckets.Length);  // bucketNumber
+            do
+            {
+                b = _buckets[bn];
+                if (((b.hash_coll & 0x7FFFFFFF) == hashcode) &&
+                    KeyEquals(b.key, key))
+                {
+                    _isWriterInProgress = true;
+                    // Clear hash_coll field, then key, then value
+                    _buckets[bn].hash_coll &= unchecked((int)0x80000000);
+                    if (_buckets[bn].hash_coll != 0)
+                    {
+                        _buckets[bn].key = _buckets;
+                    }
+                    else
+                    {
+                        _buckets[bn].key = null;
+                    }
+                    _buckets[bn].val = null;  // Free object references sooner & simplify ContainsValue.
+                    _count--;
+                    UpdateVersion();
+                    _isWriterInProgress = false;
+                    return;
+                }
+                bn = (int)(((long)bn + incr) % (uint)_buckets.Length);
+            } while (b.hash_coll < 0 && ++ntry < _buckets.Length);
+        }
+
+        // Returns the object to synchronize on for this hash table.
+        public virtual Object SyncRoot
+        {
+            get
+            {
+                if (_syncRoot == null)
+                {
+                    System.Threading.Interlocked.CompareExchange<Object>(ref _syncRoot, new Object(), null);
+                }
+                return _syncRoot;
+            }
+        }
+
+        // Returns the number of associations in this hashtable.
+        // 
+        public virtual int Count
+        {
+            get { return _count; }
+        }
+
+        // Returns a thread-safe wrapper for a Hashtable.
+        //
+        public static Hashtable Synchronized(Hashtable table)
+        {
+            if (table == null)
+                throw new ArgumentNullException(nameof(table));
+            return new SyncHashtable(table);
+        }
+
+        public virtual void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+
+            // This is imperfect - it only works well if all other writes are
+            // also using our synchronized wrapper.  But it's still a good idea.
+            lock (SyncRoot)
+            {
+                // This method hasn't been fully tweaked to be safe for a concurrent writer.
+                int oldVersion = _version;
+                info.AddValue(LoadFactorName, _loadFactor);
+                info.AddValue(VersionName, _version);
+
+                //
+                // We need to maintain serialization compatibility with Everett and RTM.
+                // If the comparer is null or a compatible comparer, serialize Hashtable
+                // in a format that can be deserialized on Everett and RTM.            
+                //
+                // Also, if the Hashtable is using randomized hashing, serialize the old
+                // view of the _keycomparer so perevious frameworks don't see the new types
+#pragma warning disable 618
+                IEqualityComparer keyComparerForSerilization = _keycomparer;
+
+                if (keyComparerForSerilization == null)
+                {
+                    info.AddValue(ComparerName, null, typeof(IComparer));
+                    info.AddValue(HashCodeProviderName, null, typeof(IHashCodeProvider));
+                }
+                else if (keyComparerForSerilization is CompatibleComparer)
+                {
+                    CompatibleComparer c = keyComparerForSerilization as CompatibleComparer;
+                    info.AddValue(ComparerName, c.Comparer, typeof(IComparer));
+                    info.AddValue(HashCodeProviderName, c.HashCodeProvider, typeof(IHashCodeProvider));
+                }
+                else
+                {
+                    info.AddValue(KeyComparerName, keyComparerForSerilization, typeof(IEqualityComparer));
+                }
+#pragma warning restore 618
+
+                info.AddValue(HashSizeName, _buckets.Length); //This is the length of the bucket array.
+                Object[] serKeys = new Object[_count];
+                Object[] serValues = new Object[_count];
+                CopyKeys(serKeys, 0);
+                CopyValues(serValues, 0);
+                info.AddValue(KeysName, serKeys, typeof(Object[]));
+                info.AddValue(ValuesName, serValues, typeof(Object[]));
+
+                // Explicitly check to see if anyone changed the Hashtable while we 
+                // were serializing it.  That's a race in their code.
+                if (_version != oldVersion)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumFailedVersion);
+                }
+            }
+        }
+
+        //
+        // DeserializationEvent Listener 
+        //
+        public virtual void OnDeserialization(Object sender)
+        {
+            if (_buckets != null)
+            {
+                // Somebody had a dependency on this hashtable and fixed us up before the ObjectManager got to it.
+                return;
+            }
+
+            SerializationInfo siInfo;
+            HashHelpers.SerializationInfoTable.TryGetValue(this, out siInfo);
+
+            if (siInfo == null)
+            {
+                throw new SerializationException(SR.Serialization_InvalidOnDeser);
+            }
+
+            int hashsize = 0;
+            IComparer c = null;
+
+#pragma warning disable 618
+            IHashCodeProvider hcp = null;
+#pragma warning restore 618
+
+            Object[] serKeys = null;
+            Object[] serValues = null;
+
+            SerializationInfoEnumerator enumerator = siInfo.GetEnumerator();
+
+            while (enumerator.MoveNext())
+            {
+                switch (enumerator.Name)
+                {
+                    case LoadFactorName:
+                        _loadFactor = siInfo.GetSingle(LoadFactorName);
+                        break;
+                    case HashSizeName:
+                        hashsize = siInfo.GetInt32(HashSizeName);
+                        break;
+                    case KeyComparerName:
+                        _keycomparer = (IEqualityComparer)siInfo.GetValue(KeyComparerName, typeof(IEqualityComparer));
+                        break;
+                    case ComparerName:
+                        c = (IComparer)siInfo.GetValue(ComparerName, typeof(IComparer));
+                        break;
+                    case HashCodeProviderName:
+#pragma warning disable 618
+                        hcp = (IHashCodeProvider)siInfo.GetValue(HashCodeProviderName, typeof(IHashCodeProvider));
+#pragma warning restore 618
+                        break;
+                    case KeysName:
+                        serKeys = (Object[])siInfo.GetValue(KeysName, typeof(Object[]));
+                        break;
+                    case ValuesName:
+                        serValues = (Object[])siInfo.GetValue(ValuesName, typeof(Object[]));
+                        break;
+                }
+            }
+
+            _loadsize = (int)(_loadFactor * hashsize);
+
+            // V1 object doesn't has _keycomparer field.
+            if ((_keycomparer == null) && ((c != null) || (hcp != null)))
+            {
+                _keycomparer = new CompatibleComparer(hcp, c);
+            }
+
+            _buckets = new bucket[hashsize];
+
+            if (serKeys == null)
+            {
+                throw new SerializationException(SR.Serialization_MissingKeys);
+            }
+            if (serValues == null)
+            {
+                throw new SerializationException(SR.Serialization_MissingValues);
+            }
+            if (serKeys.Length != serValues.Length)
+            {
+                throw new SerializationException(SR.Serialization_KeyValueDifferentSizes);
+            }
+            for (int i = 0; i < serKeys.Length; i++)
+            {
+                if (serKeys[i] == null)
+                {
+                    throw new SerializationException(SR.Serialization_NullKey);
+                }
+                Insert(serKeys[i], serValues[i], true);
+            }
+
+            _version = siInfo.GetInt32(VersionName);
+
+            HashHelpers.SerializationInfoTable.Remove(this);
+        }
+
+        // Implements a Collection for the keys of a hashtable. An instance of this
+        // class is created by the GetKeys method of a hashtable.
+        private class KeyCollection : ICollection
+        {
+            private Hashtable _hashtable;
+
+            internal KeyCollection(Hashtable hashtable)
+            {
+                _hashtable = hashtable;
+            }
+
+            public virtual void CopyTo(Array array, int arrayIndex)
+            {
+                if (array == null)
+                    throw new ArgumentNullException(nameof(array));
+                if (array.Rank != 1)
+                    throw new ArgumentException(SR.Arg_RankMultiDimNotSupported, nameof(array));
+                if (arrayIndex < 0)
+                    throw new ArgumentOutOfRangeException(nameof(arrayIndex), SR.ArgumentOutOfRange_NeedNonNegNum);
+                if (array.Length - arrayIndex < _hashtable._count)
+                    throw new ArgumentException(SR.Arg_ArrayPlusOffTooSmall);
+                _hashtable.CopyKeys(array, arrayIndex);
+            }
+
+            public virtual IEnumerator GetEnumerator()
+            {
+                return new HashtableEnumerator(_hashtable, HashtableEnumerator.Keys);
+            }
+
+            public virtual bool IsSynchronized
+            {
+                get { return _hashtable.IsSynchronized; }
+            }
+
+            public virtual Object SyncRoot
+            {
+                get { return _hashtable.SyncRoot; }
+            }
+
+            public virtual int Count
+            {
+                get { return _hashtable._count; }
+            }
+        }
+
+        // Implements a Collection for the values of a hashtable. An instance of
+        // this class is created by the GetValues method of a hashtable.
+        private class ValueCollection : ICollection
+        {
+            private Hashtable _hashtable;
+
+            internal ValueCollection(Hashtable hashtable)
+            {
+                _hashtable = hashtable;
+            }
+
+            public virtual void CopyTo(Array array, int arrayIndex)
+            {
+                if (array == null)
+                    throw new ArgumentNullException(nameof(array));
+                if (array.Rank != 1)
+                    throw new ArgumentException(SR.Arg_RankMultiDimNotSupported, nameof(array));
+                if (arrayIndex < 0)
+                    throw new ArgumentOutOfRangeException(nameof(arrayIndex), SR.ArgumentOutOfRange_NeedNonNegNum);
+                if (array.Length - arrayIndex < _hashtable._count)
+                    throw new ArgumentException(SR.Arg_ArrayPlusOffTooSmall);
+                _hashtable.CopyValues(array, arrayIndex);
+            }
+
+            public virtual IEnumerator GetEnumerator()
+            {
+                return new HashtableEnumerator(_hashtable, HashtableEnumerator.Values);
+            }
+
+            public virtual bool IsSynchronized
+            {
+                get { return _hashtable.IsSynchronized; }
+            }
+
+            public virtual Object SyncRoot
+            {
+                get { return _hashtable.SyncRoot; }
+            }
+
+            public virtual int Count
+            {
+                get { return _hashtable._count; }
+            }
+        }
+
+        // Synchronized wrapper for hashtable
+        private class SyncHashtable : Hashtable, IEnumerable
+        {
+            protected Hashtable _table;
+
+            internal SyncHashtable(Hashtable table) : base(false)
+            {
+                _table = table;
+            }
+
+            internal SyncHashtable(SerializationInfo info, StreamingContext context) : base(info, context)
+            {
+                throw new PlatformNotSupportedException();
+            }
+
+            public override void GetObjectData(SerializationInfo info, StreamingContext context)
+            {
+                throw new PlatformNotSupportedException();
+            }
+
+            public override int Count
+            {
+                get { return _table.Count; }
+            }
+
+            public override bool IsReadOnly
+            {
+                get { return _table.IsReadOnly; }
+            }
+
+            public override bool IsFixedSize
+            {
+                get { return _table.IsFixedSize; }
+            }
+
+            public override bool IsSynchronized
+            {
+                get { return true; }
+            }
+
+            public override Object this[Object key]
+            {
+                get
+                {
+                    return _table[key];
+                }
+                set
+                {
+                    lock (_table.SyncRoot)
+                    {
+                        _table[key] = value;
+                    }
+                }
+            }
+
+            public override Object SyncRoot
+            {
+                get { return _table.SyncRoot; }
+            }
+
+            public override void Add(Object key, Object value)
+            {
+                lock (_table.SyncRoot)
+                {
+                    _table.Add(key, value);
+                }
+            }
+
+            public override void Clear()
+            {
+                lock (_table.SyncRoot)
+                {
+                    _table.Clear();
+                }
+            }
+
+            public override bool Contains(Object key)
+            {
+                return _table.Contains(key);
+            }
+
+            public override bool ContainsKey(Object key)
+            {
+                if (key == null)
+                {
+                    throw new ArgumentNullException(nameof(key), SR.ArgumentNull_Key);
+                }
+                return _table.ContainsKey(key);
+            }
+
+            public override bool ContainsValue(Object key)
+            {
+                lock (_table.SyncRoot)
+                {
+                    return _table.ContainsValue(key);
+                }
+            }
+
+            public override void CopyTo(Array array, int arrayIndex)
+            {
+                lock (_table.SyncRoot)
+                {
+                    _table.CopyTo(array, arrayIndex);
+                }
+            }
+
+            public override Object Clone()
+            {
+                lock (_table.SyncRoot)
+                {
+                    return Hashtable.Synchronized((Hashtable)_table.Clone());
+                }
+            }
+
+            IEnumerator IEnumerable.GetEnumerator()
+            {
+                return _table.GetEnumerator();
+            }
+
+            public override IDictionaryEnumerator GetEnumerator()
+            {
+                return _table.GetEnumerator();
+            }
+
+            public override ICollection Keys
+            {
+                get
+                {
+                    lock (_table.SyncRoot)
+                    {
+                        return _table.Keys;
+                    }
+                }
+            }
+
+            public override ICollection Values
+            {
+                get
+                {
+                    lock (_table.SyncRoot)
+                    {
+                        return _table.Values;
+                    }
+                }
+            }
+
+            public override void Remove(Object key)
+            {
+                lock (_table.SyncRoot)
+                {
+                    _table.Remove(key);
+                }
+            }
+
+            public override void OnDeserialization(Object sender)
+            {
+                // Does nothing.  We have to implement this because our parent HT implements it,
+                // but it doesn't do anything meaningful.  The real work will be done when we
+                // call OnDeserialization on our parent table.
+            }
+
+            internal override KeyValuePairs[] ToKeyValuePairsArray()
+            {
+                return _table.ToKeyValuePairsArray();
+            }
+        }
+
+
+        // Implements an enumerator for a hashtable. The enumerator uses the
+        // internal version number of the hashtable to ensure that no modifications
+        // are made to the hashtable while an enumeration is in progress.
+        private class HashtableEnumerator : IDictionaryEnumerator, ICloneable
+        {
+            private Hashtable _hashtable;
+            private int _bucket;
+            private int _version;
+            private bool _current;
+            private int _getObjectRetType;   // What should GetObject return?
+            private Object _currentKey;
+            private Object _currentValue;
+
+            internal const int Keys = 1;
+            internal const int Values = 2;
+            internal const int DictEntry = 3;
+
+            internal HashtableEnumerator(Hashtable hashtable, int getObjRetType)
+            {
+                _hashtable = hashtable;
+                _bucket = hashtable._buckets.Length;
+                _version = hashtable._version;
+                _current = false;
+                _getObjectRetType = getObjRetType;
+            }
+
+            public object Clone() => MemberwiseClone();
+
+            public virtual Object Key
+            {
+                get
+                {
+                    if (_current == false)
+                        throw new InvalidOperationException(SR.InvalidOperation_EnumNotStarted);
+                    return _currentKey;
+                }
+            }
+
+            public virtual bool MoveNext()
+            {
+                if (_version != _hashtable._version)
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumFailedVersion);
+                while (_bucket > 0)
+                {
+                    _bucket--;
+                    Object keyv = _hashtable._buckets[_bucket].key;
+                    if ((keyv != null) && (keyv != _hashtable._buckets))
+                    {
+                        _currentKey = keyv;
+                        _currentValue = _hashtable._buckets[_bucket].val;
+                        _current = true;
+                        return true;
+                    }
+                }
+                _current = false;
+                return false;
+            }
+
+            public virtual DictionaryEntry Entry
+            {
+                get
+                {
+                    if (_current == false)
+                        throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+                    return new DictionaryEntry(_currentKey, _currentValue);
+                }
+            }
+
+
+            public virtual Object Current
+            {
+                get
+                {
+                    if (_current == false)
+                        throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+
+                    if (_getObjectRetType == Keys)
+                        return _currentKey;
+                    else if (_getObjectRetType == Values)
+                        return _currentValue;
+                    else
+                        return new DictionaryEntry(_currentKey, _currentValue);
+                }
+            }
+
+            public virtual Object Value
+            {
+                get
+                {
+                    if (_current == false)
+                        throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+                    return _currentValue;
+                }
+            }
+
+            public virtual void Reset()
+            {
+                if (_version != _hashtable._version)
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumFailedVersion);
+                _current = false;
+                _bucket = _hashtable._buckets.Length;
+                _currentKey = null;
+                _currentValue = null;
+            }
+        }
+
+        // internal debug view class for hashtable
+        internal class HashtableDebugView
+        {
+            private Hashtable _hashtable;
+
+            public HashtableDebugView(Hashtable hashtable)
+            {
+                if (hashtable == null)
+                {
+                    throw new ArgumentNullException(nameof(hashtable));
+                }
+
+                _hashtable = hashtable;
+            }
+
+            [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+            public KeyValuePairs[] Items
+            {
+                get
+                {
+                    return _hashtable.ToKeyValuePairsArray();
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/ICollection.cs b/src/System.Private.CoreLib/shared/System/Collections/ICollection.cs
new file mode 100644
index 0000000000..b8eba71c24
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/ICollection.cs
@@ -0,0 +1,69 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Collections
+{
+    // Base interface for all collections, defining enumerators, size, and 
+    // synchronization methods.
+    public interface ICollection : IEnumerable
+    {
+        // Interfaces are not serializable
+        // CopyTo copies a collection into an Array, starting at a particular
+        // index into the array.
+        // 
+        void CopyTo(Array array, int index);
+
+        // Number of items in the collections.
+        int Count
+        { get; }
+
+
+        // SyncRoot will return an Object to use for synchronization 
+        // (thread safety).  You can use this object in your code to take a
+        // lock on the collection, even if this collection is a wrapper around
+        // another collection.  The intent is to tunnel through to a real 
+        // implementation of a collection, and use one of the internal objects
+        // found in that code.
+        //
+        // In the absence of a static Synchronized method on a collection, 
+        // the expected usage for SyncRoot would look like this:
+        // 
+        // ICollection col = ...
+        // lock (col.SyncRoot) {
+        //     // Some operation on the collection, which is now thread safe.
+        //     // This may include multiple operations.
+        // }
+        // 
+        // 
+        // The system-provided collections have a static method called 
+        // Synchronized which will create a thread-safe wrapper around the 
+        // collection.  All access to the collection that you want to be 
+        // thread-safe should go through that wrapper collection.  However, if
+        // you need to do multiple calls on that collection (such as retrieving
+        // two items, or checking the count then doing something), you should
+        // NOT use our thread-safe wrapper since it only takes a lock for the
+        // duration of a single method call.  Instead, use Monitor.Enter/Exit
+        // or your language's equivalent to the C# lock keyword as mentioned 
+        // above.
+        // 
+        // For collections with no publicly available underlying store, the 
+        // expected implementation is to simply return the this pointer.  Note 
+        // that the this pointer may not be sufficient for collections that 
+        // wrap other collections;  those should return the underlying 
+        // collection's SyncRoot property.
+        Object SyncRoot
+        { get; }
+
+        // Is this collection synchronized (i.e., thread-safe)?  If you want a 
+        // thread-safe collection, you can use SyncRoot as an object to 
+        // synchronize your collection with.  If you're using one of the 
+        // collections in System.Collections, you could call the static 
+        // Synchronized method to get a thread-safe wrapper around the 
+        // underlying collection.
+        bool IsSynchronized
+        { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/IComparer.cs b/src/System.Private.CoreLib/shared/System/Collections/IComparer.cs
new file mode 100644
index 0000000000..cef91c3ffa
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/IComparer.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Collections
+{
+    // The IComparer interface implements a method that compares two objects. It is
+    // used in conjunction with the Sort and BinarySearch methods on
+    // the Array and List classes.
+    // 
+    // Interfaces are not serializable
+    public interface IComparer
+    {
+        // Compares two objects. An implementation of this method must return a
+        // value less than zero if x is less than y, zero if x is equal to y, or a
+        // value greater than zero if x is greater than y.
+        // 
+        int Compare(Object x, Object y);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/IDictionary.cs b/src/System.Private.CoreLib/shared/System/Collections/IDictionary.cs
new file mode 100644
index 0000000000..b934c2399c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/IDictionary.cs
@@ -0,0 +1,60 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Collections
+{
+    // An IDictionary is a possibly unordered set of key-value pairs.
+    // Keys can be any non-null object.  Values can be any object.
+    // You can look up a value in an IDictionary via the default indexed
+    // property, Items.
+    public interface IDictionary : ICollection
+    {
+        // Interfaces are not serializable
+        // The Item property provides methods to read and edit entries 
+        // in the Dictionary.
+        Object this[Object key]
+        {
+            get;
+            set;
+        }
+
+        // Returns a collections of the keys in this dictionary.
+        ICollection Keys
+        {
+            get;
+        }
+
+        // Returns a collections of the values in this dictionary.
+        ICollection Values
+        {
+            get;
+        }
+
+        // Returns whether this dictionary contains a particular key.
+        //
+        bool Contains(Object key);
+
+        // Adds a key-value pair to the dictionary.
+        // 
+        void Add(Object key, Object value);
+
+        // Removes all pairs from the dictionary.
+        void Clear();
+
+        bool IsReadOnly
+        { get; }
+
+        bool IsFixedSize
+        { get; }
+
+        // Returns an IDictionaryEnumerator for this dictionary.
+        new IDictionaryEnumerator GetEnumerator();
+
+        // Removes a particular key from the dictionary.
+        //
+        void Remove(Object key);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/IDictionaryEnumerator.cs b/src/System.Private.CoreLib/shared/System/Collections/IDictionaryEnumerator.cs
new file mode 100644
index 0000000000..451cf68976
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/IDictionaryEnumerator.cs
@@ -0,0 +1,68 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Collections
+{
+    // This interface represents an enumerator that allows sequential access to the
+    // elements of a dictionary. Upon creation, an enumerator is conceptually
+    // positioned before the first element of the enumeration. The first call to the
+    // MoveNext method brings the first element of the enumeration into view,
+    // and each successive call to MoveNext brings the next element into
+    // view until MoveNext returns false, indicating that there are no more
+    // elements to enumerate. Following each call to MoveNext, the
+    // Key and Value methods are used to obtain the key and
+    // value of the element currently in view. The values returned by calls to
+    // Key and Value are undefined before the first call to
+    // MoveNext and following a call to MoveNext that returned false.
+    // Enumerators are typically used in while loops of the form
+    // 
+    // IDictionaryEnumerator e = ...;
+    // while (e.MoveNext()) {
+    //     Object key = e.Key;
+    //     Object value = e.Value;
+    //     ...
+    // }
+    // 
+    // The IDictionaryEnumerator interface extends the IEnumerator
+    // inerface and can thus be used as a regular enumerator. The Current 
+    // method of an IDictionaryEnumerator returns a DictionaryEntry containing
+    // the current key and value pair.  However, the GetEntry method will
+    // return the same DictionaryEntry and avoids boxing the DictionaryEntry (boxing
+    // is somewhat expensive).
+    // 
+    public interface IDictionaryEnumerator : IEnumerator
+    {
+        // Returns the key of the current element of the enumeration. The returned
+        // value is undefined before the first call to GetNext and following
+        // a call to GetNext that returned false. Multiple calls to
+        // GetKey with no intervening calls to GetNext will return
+        // the same object.
+        // 
+        Object Key
+        {
+            get;
+        }
+
+        // Returns the value of the current element of the enumeration. The
+        // returned value is undefined before the first call to GetNext and
+        // following a call to GetNext that returned false. Multiple calls
+        // to GetValue with no intervening calls to GetNext will
+        // return the same object.
+        // 
+        Object Value
+        {
+            get;
+        }
+
+        // GetBlock will copy dictionary values into the given Array.  It will either
+        // fill up the array, or if there aren't enough elements, it will
+        // copy as much as possible into the Array.  The number of elements
+        // copied is returned.
+        // 
+        DictionaryEntry Entry
+        {
+            get;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/IEnumerable.cs b/src/System.Private.CoreLib/shared/System/Collections/IEnumerable.cs
new file mode 100644
index 0000000000..e5edeff266
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/IEnumerable.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace System.Collections
+{
+    public interface IEnumerable
+    {
+        // Returns an IEnumerator for this enumerable Object.  The enumerator provides
+        // a simple way to access all the contents of a collection.
+        IEnumerator GetEnumerator();
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/IEnumerator.cs b/src/System.Private.CoreLib/shared/System/Collections/IEnumerator.cs
new file mode 100644
index 0000000000..2c2c2e4a97
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/IEnumerator.cs
@@ -0,0 +1,41 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace System.Collections
+{
+    // Base interface for all enumerators, providing a simple approach
+    // to iterating over a collection.
+    public interface IEnumerator
+    {
+        // Advances the enumerator to the next element of the enumeration and
+        // returns a boolean indicating whether an element is available. Upon
+        // creation, an enumerator is conceptually positioned before the first
+        // element of the enumeration, and the first call to MoveNext 
+        // brings the first element of the enumeration into view.
+        // 
+        bool MoveNext();
+
+        // Returns the current element of the enumeration. The returned value is
+        // undefined before the first call to MoveNext and following a
+        // call to MoveNext that returned false. Multiple calls to
+        // GetCurrent with no intervening calls to MoveNext 
+        // will return the same object.
+        // 
+        Object Current
+        {
+            get;
+        }
+
+        // Resets the enumerator to the beginning of the enumeration, starting over.
+        // The preferred behavior for Reset is to return the exact same enumeration.
+        // This means if you modify the underlying collection then call Reset, your
+        // IEnumerator will be invalid, just as it would have been if you had called
+        // MoveNext or Current.
+        //
+        void Reset();
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/IEqualityComparer.cs b/src/System.Private.CoreLib/shared/System/Collections/IEqualityComparer.cs
new file mode 100644
index 0000000000..35513f577d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/IEqualityComparer.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Collections
+{
+    // An IEqualityComparer is a mechanism to consume custom performant comparison infrastructure
+    // that can be consumed by some of the common collections.
+    public interface IEqualityComparer
+    {
+        bool Equals(Object x, Object y);
+        int GetHashCode(Object obj);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/IHashCodeProvider.cs b/src/System.Private.CoreLib/shared/System/Collections/IHashCodeProvider.cs
new file mode 100644
index 0000000000..7d6c63f9f1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/IHashCodeProvider.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Collections
+{
+    /// <summary>
+    /// Provides a mechanism for a <see cref="Hashtable"/> user to override the default
+    /// GetHashCode() function on Objects, providing their own hash function.
+    /// </summary>
+    [Obsolete("Please use IEqualityComparer instead.")]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public interface IHashCodeProvider
+    {
+        /// <summary>Returns a hash code for the given object.</summary>
+        int GetHashCode(object obj);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/IList.cs b/src/System.Private.CoreLib/shared/System/Collections/IList.cs
new file mode 100644
index 0000000000..0110eca1f5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/IList.cs
@@ -0,0 +1,59 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Collections
+{
+    // An IList is an ordered collection of objects.  The exact ordering
+    // is up to the implementation of the list, ranging from a sorted
+    // order to insertion order.
+    public interface IList : ICollection
+    {
+        // The Item property provides methods to read and edit entries in the List.
+        Object this[int index]
+        {
+            get;
+            set;
+        }
+
+        // Adds an item to the list.  The exact position in the list is 
+        // implementation-dependent, so while ArrayList may always insert
+        // in the last available location, a SortedList most likely would not.
+        // The return value is the position the new element was inserted in.
+        int Add(Object value);
+
+        // Returns whether the list contains a particular item.
+        bool Contains(Object value);
+
+        // Removes all items from the list.
+        void Clear();
+
+        bool IsReadOnly
+        { get; }
+
+
+        bool IsFixedSize
+        {
+            get;
+        }
+
+
+        // Returns the index of a particular item, if it is in the list.
+        // Returns -1 if the item isn't in the list.
+        int IndexOf(Object value);
+
+        // Inserts value into the list at position index.
+        // index must be non-negative and less than or equal to the 
+        // number of elements in the list.  If index equals the number
+        // of items in the list, then value is appended to the end.
+        void Insert(int index, Object value);
+
+        // Removes an item from the list.
+        void Remove(Object value);
+
+        // Removes the item at position index.
+        void RemoveAt(int index);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/IStructuralComparable.cs b/src/System.Private.CoreLib/shared/System/Collections/IStructuralComparable.cs
new file mode 100644
index 0000000000..a5e4834b9b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/IStructuralComparable.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Collections
+{
+    public interface IStructuralComparable
+    {
+        Int32 CompareTo(Object other, IComparer comparer);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/IStructuralEquatable.cs b/src/System.Private.CoreLib/shared/System/Collections/IStructuralEquatable.cs
new file mode 100644
index 0000000000..4e61d5e75f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/IStructuralEquatable.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Collections
+{
+    public interface IStructuralEquatable
+    {
+        Boolean Equals(Object other, IEqualityComparer comparer);
+        int GetHashCode(IEqualityComparer comparer);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/KeyValuePairs.cs b/src/System.Private.CoreLib/shared/System/Collections/KeyValuePairs.cs
new file mode 100644
index 0000000000..9ec6365b92
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/KeyValuePairs.cs
@@ -0,0 +1,33 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Class:  KeyValuePairs
+**
+** Purpose: Defines key/value pairs for displaying items
+**          in a collection class under the debugger.
+**
+===========================================================*/
+
+using System.Diagnostics;
+
+namespace System.Collections
+{
+    [DebuggerDisplay("{_value}", Name = "[{_key}]")]
+    internal class KeyValuePairs
+    {
+        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
+        private readonly object _key;
+
+        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
+        private readonly object _value;
+
+        public KeyValuePairs(object key, object value)
+        {
+            _value = value;
+            _key = key;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/ListDictionaryInternal.cs b/src/System.Private.CoreLib/shared/System/Collections/ListDictionaryInternal.cs
new file mode 100644
index 0000000000..eccb9f0347
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/ListDictionaryInternal.cs
@@ -0,0 +1,509 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: List for exceptions.
+**
+** 
+===========================================================*/
+
+
+namespace System.Collections
+{
+    ///    This is a simple implementation of IDictionary using a singly linked list. This
+    ///    will be smaller and faster than a Hashtable if the number of elements is 10 or less.
+    ///    This should not be used if performance is important for large numbers of elements.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    // Needs to be public to support binary serialization compatibility
+    public class ListDictionaryInternal : IDictionary
+    {
+        private DictionaryNode head; // Do not rename (binary serialization)
+        private int version; // Do not rename (binary serialization)
+        private int count; // Do not rename (binary serialization)
+        [NonSerialized]
+        private Object _syncRoot;
+
+        public ListDictionaryInternal()
+        {
+        }
+
+        public Object this[Object key]
+        {
+            get
+            {
+                if (key == null)
+                {
+                    throw new ArgumentNullException(nameof(key), SR.ArgumentNull_Key);
+                }
+                DictionaryNode node = head;
+
+                while (node != null)
+                {
+                    if (node.key.Equals(key))
+                    {
+                        return node.value;
+                    }
+                    node = node.next;
+                }
+                return null;
+            }
+            set
+            {
+                if (key == null)
+                {
+                    throw new ArgumentNullException(nameof(key), SR.ArgumentNull_Key);
+                }
+
+
+                version++;
+                DictionaryNode last = null;
+                DictionaryNode node;
+                for (node = head; node != null; node = node.next)
+                {
+                    if (node.key.Equals(key))
+                    {
+                        break;
+                    }
+                    last = node;
+                }
+                if (node != null)
+                {
+                    // Found it
+                    node.value = value;
+                    return;
+                }
+                // Not found, so add a new one
+                DictionaryNode newNode = new DictionaryNode();
+                newNode.key = key;
+                newNode.value = value;
+                if (last != null)
+                {
+                    last.next = newNode;
+                }
+                else
+                {
+                    head = newNode;
+                }
+                count++;
+            }
+        }
+
+        public int Count
+        {
+            get
+            {
+                return count;
+            }
+        }
+
+        public ICollection Keys
+        {
+            get
+            {
+                return new NodeKeyValueCollection(this, true);
+            }
+        }
+
+        public bool IsReadOnly
+        {
+            get
+            {
+                return false;
+            }
+        }
+
+        public bool IsFixedSize
+        {
+            get
+            {
+                return false;
+            }
+        }
+
+        public bool IsSynchronized
+        {
+            get
+            {
+                return false;
+            }
+        }
+
+        public Object SyncRoot
+        {
+            get
+            {
+                if (_syncRoot == null)
+                {
+                    System.Threading.Interlocked.CompareExchange<Object>(ref _syncRoot, new Object(), null);
+                }
+                return _syncRoot;
+            }
+        }
+
+        public ICollection Values
+        {
+            get
+            {
+                return new NodeKeyValueCollection(this, false);
+            }
+        }
+
+        public void Add(Object key, Object value)
+        {
+            if (key == null)
+            {
+                throw new ArgumentNullException(nameof(key), SR.ArgumentNull_Key);
+            }
+
+
+            version++;
+            DictionaryNode last = null;
+            DictionaryNode node;
+            for (node = head; node != null; node = node.next)
+            {
+                if (node.key.Equals(key))
+                {
+                    throw new ArgumentException(SR.Format(SR.Argument_AddingDuplicate__, node.key, key));
+                }
+                last = node;
+            }
+            if (node != null)
+            {
+                // Found it
+                node.value = value;
+                return;
+            }
+            // Not found, so add a new one
+            DictionaryNode newNode = new DictionaryNode();
+            newNode.key = key;
+            newNode.value = value;
+            if (last != null)
+            {
+                last.next = newNode;
+            }
+            else
+            {
+                head = newNode;
+            }
+            count++;
+        }
+
+        public void Clear()
+        {
+            count = 0;
+            head = null;
+            version++;
+        }
+
+        public bool Contains(Object key)
+        {
+            if (key == null)
+            {
+                throw new ArgumentNullException(nameof(key), SR.ArgumentNull_Key);
+            }
+            for (DictionaryNode node = head; node != null; node = node.next)
+            {
+                if (node.key.Equals(key))
+                {
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        public void CopyTo(Array array, int index)
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array));
+
+            if (array.Rank != 1)
+                throw new ArgumentException(SR.Arg_RankMultiDimNotSupported);
+
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (array.Length - index < this.Count)
+                throw new ArgumentException(SR.ArgumentOutOfRange_Index, nameof(index));
+
+            for (DictionaryNode node = head; node != null; node = node.next)
+            {
+                array.SetValue(new DictionaryEntry(node.key, node.value), index);
+                index++;
+            }
+        }
+
+        public IDictionaryEnumerator GetEnumerator()
+        {
+            return new NodeEnumerator(this);
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return new NodeEnumerator(this);
+        }
+
+        public void Remove(Object key)
+        {
+            if (key == null)
+            {
+                throw new ArgumentNullException(nameof(key), SR.ArgumentNull_Key);
+            }
+            version++;
+            DictionaryNode last = null;
+            DictionaryNode node;
+            for (node = head; node != null; node = node.next)
+            {
+                if (node.key.Equals(key))
+                {
+                    break;
+                }
+                last = node;
+            }
+            if (node == null)
+            {
+                return;
+            }
+            if (node == head)
+            {
+                head = node.next;
+            }
+            else
+            {
+                last.next = node.next;
+            }
+            count--;
+        }
+
+        private class NodeEnumerator : IDictionaryEnumerator
+        {
+            private ListDictionaryInternal list;
+            private DictionaryNode current;
+            private int version;
+            private bool start;
+
+
+            public NodeEnumerator(ListDictionaryInternal list)
+            {
+                this.list = list;
+                version = list.version;
+                start = true;
+                current = null;
+            }
+
+            public Object Current
+            {
+                get
+                {
+                    return Entry;
+                }
+            }
+
+            public DictionaryEntry Entry
+            {
+                get
+                {
+                    if (current == null)
+                    {
+                        throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+                    }
+                    return new DictionaryEntry(current.key, current.value);
+                }
+            }
+
+            public Object Key
+            {
+                get
+                {
+                    if (current == null)
+                    {
+                        throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+                    }
+                    return current.key;
+                }
+            }
+
+            public Object Value
+            {
+                get
+                {
+                    if (current == null)
+                    {
+                        throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+                    }
+                    return current.value;
+                }
+            }
+
+            public bool MoveNext()
+            {
+                if (version != list.version)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumFailedVersion);
+                }
+                if (start)
+                {
+                    current = list.head;
+                    start = false;
+                }
+                else
+                {
+                    if (current != null)
+                    {
+                        current = current.next;
+                    }
+                }
+                return (current != null);
+            }
+
+            public void Reset()
+            {
+                if (version != list.version)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumFailedVersion);
+                }
+                start = true;
+                current = null;
+            }
+        }
+
+
+        private class NodeKeyValueCollection : ICollection
+        {
+            private ListDictionaryInternal list;
+            private bool isKeys;
+
+            public NodeKeyValueCollection(ListDictionaryInternal list, bool isKeys)
+            {
+                this.list = list;
+                this.isKeys = isKeys;
+            }
+
+            void ICollection.CopyTo(Array array, int index)
+            {
+                if (array == null)
+                    throw new ArgumentNullException(nameof(array));
+                if (array.Rank != 1)
+                    throw new ArgumentException(SR.Arg_RankMultiDimNotSupported);
+                if (index < 0)
+                    throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_NeedNonNegNum);
+                if (array.Length - index < list.Count)
+                    throw new ArgumentException(SR.ArgumentOutOfRange_Index, nameof(index));
+                for (DictionaryNode node = list.head; node != null; node = node.next)
+                {
+                    array.SetValue(isKeys ? node.key : node.value, index);
+                    index++;
+                }
+            }
+
+            int ICollection.Count
+            {
+                get
+                {
+                    int count = 0;
+                    for (DictionaryNode node = list.head; node != null; node = node.next)
+                    {
+                        count++;
+                    }
+                    return count;
+                }
+            }
+
+            bool ICollection.IsSynchronized
+            {
+                get
+                {
+                    return false;
+                }
+            }
+
+            Object ICollection.SyncRoot
+            {
+                get
+                {
+                    return list.SyncRoot;
+                }
+            }
+
+            IEnumerator IEnumerable.GetEnumerator()
+            {
+                return new NodeKeyValueEnumerator(list, isKeys);
+            }
+
+
+            private class NodeKeyValueEnumerator : IEnumerator
+            {
+                private ListDictionaryInternal list;
+                private DictionaryNode current;
+                private int version;
+                private bool isKeys;
+                private bool start;
+
+                public NodeKeyValueEnumerator(ListDictionaryInternal list, bool isKeys)
+                {
+                    this.list = list;
+                    this.isKeys = isKeys;
+                    version = list.version;
+                    start = true;
+                    current = null;
+                }
+
+                public Object Current
+                {
+                    get
+                    {
+                        if (current == null)
+                        {
+                            throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+                        }
+                        return isKeys ? current.key : current.value;
+                    }
+                }
+
+                public bool MoveNext()
+                {
+                    if (version != list.version)
+                    {
+                        throw new InvalidOperationException(SR.InvalidOperation_EnumFailedVersion);
+                    }
+                    if (start)
+                    {
+                        current = list.head;
+                        start = false;
+                    }
+                    else
+                    {
+                        if (current != null)
+                        {
+                            current = current.next;
+                        }
+                    }
+                    return (current != null);
+                }
+
+                public void Reset()
+                {
+                    if (version != list.version)
+                    {
+                        throw new InvalidOperationException(SR.InvalidOperation_EnumFailedVersion);
+                    }
+                    start = true;
+                    current = null;
+                }
+            }
+        }
+
+        [Serializable]
+        private class DictionaryNode
+        {
+            public Object key;
+            public Object value;
+            public DictionaryNode next;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/ObjectModel/Collection.cs b/src/System.Private.CoreLib/shared/System/Collections/ObjectModel/Collection.cs
new file mode 100644
index 0000000000..1e1b2c7959
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/ObjectModel/Collection.cs
@@ -0,0 +1,396 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System.Collections.ObjectModel
+{
+    [Serializable]
+    [DebuggerTypeProxy(typeof(ICollectionDebugView<>))]
+    [DebuggerDisplay("Count = {Count}")]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class Collection<T> : IList<T>, IList, IReadOnlyList<T>
+    {
+        private IList<T> items; // Do not rename (binary serialization)
+        [NonSerialized]
+        private Object _syncRoot;
+
+        public Collection()
+        {
+            items = new List<T>();
+        }
+
+        public Collection(IList<T> list)
+        {
+            if (list == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.list);
+            }
+            items = list;
+        }
+
+        public int Count
+        {
+            get { return items.Count; }
+        }
+
+        protected IList<T> Items
+        {
+            get { return items; }
+        }
+
+        public T this[int index]
+        {
+            get { return items[index]; }
+            set
+            {
+                if (items.IsReadOnly)
+                {
+                    ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+                }
+
+                if (index < 0 || index >= items.Count)
+                {
+                    ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+                }
+
+                SetItem(index, value);
+            }
+        }
+
+        public void Add(T item)
+        {
+            if (items.IsReadOnly)
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+
+            int index = items.Count;
+            InsertItem(index, item);
+        }
+
+        public void Clear()
+        {
+            if (items.IsReadOnly)
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+
+            ClearItems();
+        }
+
+        public void CopyTo(T[] array, int index)
+        {
+            items.CopyTo(array, index);
+        }
+
+        public bool Contains(T item)
+        {
+            return items.Contains(item);
+        }
+
+        public IEnumerator<T> GetEnumerator()
+        {
+            return items.GetEnumerator();
+        }
+
+        public int IndexOf(T item)
+        {
+            return items.IndexOf(item);
+        }
+
+        public void Insert(int index, T item)
+        {
+            if (items.IsReadOnly)
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+
+            if (index < 0 || index > items.Count)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_ListInsert);
+            }
+
+            InsertItem(index, item);
+        }
+
+        public bool Remove(T item)
+        {
+            if (items.IsReadOnly)
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+
+            int index = items.IndexOf(item);
+            if (index < 0) return false;
+            RemoveItem(index);
+            return true;
+        }
+
+        public void RemoveAt(int index)
+        {
+            if (items.IsReadOnly)
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+
+            if (index < 0 || index >= items.Count)
+            {
+                ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+            }
+
+            RemoveItem(index);
+        }
+
+        protected virtual void ClearItems()
+        {
+            items.Clear();
+        }
+
+        protected virtual void InsertItem(int index, T item)
+        {
+            items.Insert(index, item);
+        }
+
+        protected virtual void RemoveItem(int index)
+        {
+            items.RemoveAt(index);
+        }
+
+        protected virtual void SetItem(int index, T item)
+        {
+            items[index] = item;
+        }
+
+        bool ICollection<T>.IsReadOnly
+        {
+            get
+            {
+                return items.IsReadOnly;
+            }
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return ((IEnumerable)items).GetEnumerator();
+        }
+
+        bool ICollection.IsSynchronized
+        {
+            get { return false; }
+        }
+
+        object ICollection.SyncRoot
+        {
+            get
+            {
+                if (_syncRoot == null)
+                {
+                    ICollection c = items as ICollection;
+                    if (c != null)
+                    {
+                        _syncRoot = c.SyncRoot;
+                    }
+                    else
+                    {
+                        System.Threading.Interlocked.CompareExchange<Object>(ref _syncRoot, new Object(), null);
+                    }
+                }
+                return _syncRoot;
+            }
+        }
+
+        void ICollection.CopyTo(Array array, int index)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (array.Rank != 1)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
+            }
+
+            if (array.GetLowerBound(0) != 0)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NonZeroLowerBound);
+            }
+
+            if (index < 0)
+            {
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            }
+
+            if (array.Length - index < Count)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall);
+            }
+
+            T[] tArray = array as T[];
+            if (tArray != null)
+            {
+                items.CopyTo(tArray, index);
+            }
+            else
+            {
+                //
+                // Catch the obvious case assignment will fail.
+                // We can't find all possible problems by doing the check though.
+                // For example, if the element type of the Array is derived from T,
+                // we can't figure out if we can successfully copy the element beforehand.
+                //
+                Type targetType = array.GetType().GetElementType();
+                Type sourceType = typeof(T);
+                if (!(targetType.IsAssignableFrom(sourceType) || sourceType.IsAssignableFrom(targetType)))
+                {
+                    ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                }
+
+                //
+                // We can't cast array of value type to object[], so we don't support 
+                // widening of primitive types here.
+                //
+                object[] objects = array as object[];
+                if (objects == null)
+                {
+                    ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                }
+
+                int count = items.Count;
+                try
+                {
+                    for (int i = 0; i < count; i++)
+                    {
+                        objects[index++] = items[i];
+                    }
+                }
+                catch (ArrayTypeMismatchException)
+                {
+                    ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                }
+            }
+        }
+
+        object IList.this[int index]
+        {
+            get { return items[index]; }
+            set
+            {
+                ThrowHelper.IfNullAndNullsAreIllegalThenThrow<T>(value, ExceptionArgument.value);
+
+                try
+                {
+                    this[index] = (T)value;
+                }
+                catch (InvalidCastException)
+                {
+                    ThrowHelper.ThrowWrongValueTypeArgumentException(value, typeof(T));
+                }
+            }
+        }
+
+        bool IList.IsReadOnly
+        {
+            get
+            {
+                return items.IsReadOnly;
+            }
+        }
+
+        bool IList.IsFixedSize
+        {
+            get
+            {
+                // There is no IList<T>.IsFixedSize, so we must assume that only
+                // readonly collections are fixed size, if our internal item 
+                // collection does not implement IList.  Note that Array implements
+                // IList, and therefore T[] and U[] will be fixed-size.
+                IList list = items as IList;
+                if (list != null)
+                {
+                    return list.IsFixedSize;
+                }
+                return items.IsReadOnly;
+            }
+        }
+
+        int IList.Add(object value)
+        {
+            if (items.IsReadOnly)
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+            ThrowHelper.IfNullAndNullsAreIllegalThenThrow<T>(value, ExceptionArgument.value);
+
+            try
+            {
+                Add((T)value);
+            }
+            catch (InvalidCastException)
+            {
+                ThrowHelper.ThrowWrongValueTypeArgumentException(value, typeof(T));
+            }
+
+            return this.Count - 1;
+        }
+
+        bool IList.Contains(object value)
+        {
+            if (IsCompatibleObject(value))
+            {
+                return Contains((T)value);
+            }
+            return false;
+        }
+
+        int IList.IndexOf(object value)
+        {
+            if (IsCompatibleObject(value))
+            {
+                return IndexOf((T)value);
+            }
+            return -1;
+        }
+
+        void IList.Insert(int index, object value)
+        {
+            if (items.IsReadOnly)
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+            ThrowHelper.IfNullAndNullsAreIllegalThenThrow<T>(value, ExceptionArgument.value);
+
+            try
+            {
+                Insert(index, (T)value);
+            }
+            catch (InvalidCastException)
+            {
+                ThrowHelper.ThrowWrongValueTypeArgumentException(value, typeof(T));
+            }
+        }
+
+        void IList.Remove(object value)
+        {
+            if (items.IsReadOnly)
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+
+            if (IsCompatibleObject(value))
+            {
+                Remove((T)value);
+            }
+        }
+
+        private static bool IsCompatibleObject(object value)
+        {
+            // Non-null values are fine.  Only accept nulls if T is a class or Nullable<U>.
+            // Note that default(T) is not equal to null for value types except when T is Nullable<U>. 
+            return ((value is T) || (value == null && default(T) == null));
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Collections/ObjectModel/ReadOnlyCollection.cs b/src/System.Private.CoreLib/shared/System/Collections/ObjectModel/ReadOnlyCollection.cs
new file mode 100644
index 0000000000..dbf88d8b8d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Collections/ObjectModel/ReadOnlyCollection.cs
@@ -0,0 +1,279 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System.Collections.ObjectModel
+{
+    [Serializable]
+    [DebuggerTypeProxy(typeof(ICollectionDebugView<>))]
+    [DebuggerDisplay("Count = {Count}")]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class ReadOnlyCollection<T> : IList<T>, IList, IReadOnlyList<T>
+    {
+        private IList<T> list; // Do not rename (binary serialization)
+        [NonSerialized]
+        private Object _syncRoot;
+
+        public ReadOnlyCollection(IList<T> list)
+        {
+            if (list == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.list);
+            }
+            this.list = list;
+        }
+
+        public int Count
+        {
+            get { return list.Count; }
+        }
+
+        public T this[int index]
+        {
+            get { return list[index]; }
+        }
+
+        public bool Contains(T value)
+        {
+            return list.Contains(value);
+        }
+
+        public void CopyTo(T[] array, int index)
+        {
+            list.CopyTo(array, index);
+        }
+
+        public IEnumerator<T> GetEnumerator()
+        {
+            return list.GetEnumerator();
+        }
+
+        public int IndexOf(T value)
+        {
+            return list.IndexOf(value);
+        }
+
+        protected IList<T> Items
+        {
+            get
+            {
+                return list;
+            }
+        }
+
+        bool ICollection<T>.IsReadOnly
+        {
+            get { return true; }
+        }
+
+        T IList<T>.this[int index]
+        {
+            get { return list[index]; }
+            set
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+        }
+
+        void ICollection<T>.Add(T value)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+
+        void ICollection<T>.Clear()
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+
+        void IList<T>.Insert(int index, T value)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+
+        bool ICollection<T>.Remove(T value)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            return false;
+        }
+
+        void IList<T>.RemoveAt(int index)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return ((IEnumerable)list).GetEnumerator();
+        }
+
+        bool ICollection.IsSynchronized
+        {
+            get { return false; }
+        }
+
+        object ICollection.SyncRoot
+        {
+            get
+            {
+                if (_syncRoot == null)
+                {
+                    ICollection c = list as ICollection;
+                    if (c != null)
+                    {
+                        _syncRoot = c.SyncRoot;
+                    }
+                    else
+                    {
+                        System.Threading.Interlocked.CompareExchange<Object>(ref _syncRoot, new Object(), null);
+                    }
+                }
+                return _syncRoot;
+            }
+        }
+
+        void ICollection.CopyTo(Array array, int index)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (array.Rank != 1)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
+            }
+
+            if (array.GetLowerBound(0) != 0)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NonZeroLowerBound);
+            }
+
+            if (index < 0)
+            {
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            }
+
+            if (array.Length - index < Count)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall);
+            }
+
+            T[] items = array as T[];
+            if (items != null)
+            {
+                list.CopyTo(items, index);
+            }
+            else
+            {
+                //
+                // Catch the obvious case assignment will fail.
+                // We can't find all possible problems by doing the check though.
+                // For example, if the element type of the Array is derived from T,
+                // we can't figure out if we can successfully copy the element beforehand.
+                //
+                Type targetType = array.GetType().GetElementType();
+                Type sourceType = typeof(T);
+                if (!(targetType.IsAssignableFrom(sourceType) || sourceType.IsAssignableFrom(targetType)))
+                {
+                    ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                }
+
+                //
+                // We can't cast array of value type to object[], so we don't support 
+                // widening of primitive types here.
+                //
+                object[] objects = array as object[];
+                if (objects == null)
+                {
+                    ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                }
+
+                int count = list.Count;
+                try
+                {
+                    for (int i = 0; i < count; i++)
+                    {
+                        objects[index++] = list[i];
+                    }
+                }
+                catch (ArrayTypeMismatchException)
+                {
+                    ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                }
+            }
+        }
+
+        bool IList.IsFixedSize
+        {
+            get { return true; }
+        }
+
+        bool IList.IsReadOnly
+        {
+            get { return true; }
+        }
+
+        object IList.this[int index]
+        {
+            get { return list[index]; }
+            set
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+        }
+
+        int IList.Add(object value)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            return -1;
+        }
+
+        void IList.Clear()
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+
+        private static bool IsCompatibleObject(object value)
+        {
+            // Non-null values are fine.  Only accept nulls if T is a class or Nullable<U>.
+            // Note that default(T) is not equal to null for value types except when T is Nullable<U>. 
+            return ((value is T) || (value == null && default(T) == null));
+        }
+
+        bool IList.Contains(object value)
+        {
+            if (IsCompatibleObject(value))
+            {
+                return Contains((T)value);
+            }
+            return false;
+        }
+
+        int IList.IndexOf(object value)
+        {
+            if (IsCompatibleObject(value))
+            {
+                return IndexOf((T)value);
+            }
+            return -1;
+        }
+
+        void IList.Insert(int index, object value)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+
+        void IList.Remove(object value)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+
+        void IList.RemoveAt(int index)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ComponentModel/DefaultValueAttribute.cs b/src/System.Private.CoreLib/shared/System/ComponentModel/DefaultValueAttribute.cs
new file mode 100644
index 0000000000..3cdc907297
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ComponentModel/DefaultValueAttribute.cs
@@ -0,0 +1,228 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.ComponentModel;
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.InteropServices;
+
+namespace System.ComponentModel
+{
+    /// <devdoc>
+    ///    <para>Specifies the default value for a property.</para>
+    /// </devdoc>
+    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1019:DefineAccessorsForAttributeArguments")]
+    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1813:AvoidUnsealedAttributes")]
+    [AttributeUsage(AttributeTargets.All)]
+    public class DefaultValueAttribute : Attribute
+    {
+        /// <devdoc>
+        ///     This is the default value.
+        /// </devdoc>
+        private object _value;
+
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/> class, converting the
+        ///    specified value to the
+        ///    specified type, and using the U.S. English culture as the
+        ///    translation
+        ///    context.</para>
+        /// </devdoc>
+        public DefaultValueAttribute(Type type, string value)
+        {
+            // The try/catch here is because attributes should never throw exceptions.  We would fail to
+            // load an otherwise normal class.
+            try
+            {
+                if (type.IsSubclassOf(typeof(Enum)))
+                {
+                    _value = Enum.Parse(type, value, true);
+                }
+                else if (type == typeof(TimeSpan))
+                {
+                    _value = TimeSpan.Parse(value);
+                }
+                else
+                {
+                    _value = Convert.ChangeType(value, type, CultureInfo.InvariantCulture);
+                }
+            }
+            catch
+            {
+            }
+        }
+
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/> class using a Unicode
+        ///    character.</para>
+        /// </devdoc>
+        public DefaultValueAttribute(char value)
+        {
+            _value = value;
+        }
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/> class using an 8-bit unsigned
+        ///    integer.</para>
+        /// </devdoc>
+        public DefaultValueAttribute(byte value)
+        {
+            _value = value;
+        }
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/> class using a 16-bit signed
+        ///    integer.</para>
+        /// </devdoc>
+        public DefaultValueAttribute(short value)
+        {
+            _value = value;
+        }
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/> class using a 32-bit signed
+        ///    integer.</para>
+        /// </devdoc>
+        public DefaultValueAttribute(int value)
+        {
+            _value = value;
+        }
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/> class using a 64-bit signed
+        ///    integer.</para>
+        /// </devdoc>
+        public DefaultValueAttribute(long value)
+        {
+            _value = value;
+        }
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/> class using a
+        ///    single-precision floating point
+        ///    number.</para>
+        /// </devdoc>
+        public DefaultValueAttribute(float value)
+        {
+            _value = value;
+        }
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/> class using a
+        ///    double-precision floating point
+        ///    number.</para>
+        /// </devdoc>
+        public DefaultValueAttribute(double value)
+        {
+            _value = value;
+        }
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/> class using a <see cref='System.Boolean'/>
+        /// value.</para>
+        /// </devdoc>
+        public DefaultValueAttribute(bool value)
+        {
+            _value = value;
+        }
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/> class using a <see cref='System.String'/>.</para>
+        /// </devdoc>
+        public DefaultValueAttribute(string value)
+        {
+            _value = value;
+        }
+
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/>
+        /// class.</para>
+        /// </devdoc>
+        public DefaultValueAttribute(object value)
+        {
+            _value = value;
+        }
+
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/> class using a <see cref='System.SByte'/>
+        /// value.</para>
+        /// </devdoc>
+        [CLSCompliant(false)]
+        public DefaultValueAttribute(sbyte value)
+        {
+            _value = value;
+        }
+
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/> class using a <see cref='System.UInt16'/>
+        /// value.</para>
+        /// </devdoc>
+        [CLSCompliant(false)]
+        public DefaultValueAttribute(ushort value)
+        {
+            _value = value;
+        }
+
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/> class using a <see cref='System.UInt32'/>
+        /// value.</para>
+        /// </devdoc>
+        [CLSCompliant(false)]
+        public DefaultValueAttribute(uint value)
+        {
+            _value = value;
+        }
+
+        /// <devdoc>
+        /// <para>Initializes a new instance of the <see cref='System.ComponentModel.DefaultValueAttribute'/> class using a <see cref='System.UInt64'/>
+        /// value.</para>
+        /// </devdoc>
+        [CLSCompliant(false)]
+        public DefaultValueAttribute(ulong value)
+        {
+            _value = value;
+        }
+
+        /// <devdoc>
+        ///    <para>
+        ///       Gets the default value of the property this
+        ///       attribute is
+        ///       bound to.
+        ///    </para>
+        /// </devdoc>
+        public virtual object Value
+        {
+            get
+            {
+                return _value;
+            }
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (obj == this)
+            {
+                return true;
+            }
+
+            DefaultValueAttribute other = obj as DefaultValueAttribute;
+
+            if (other != null)
+            {
+                if (Value != null)
+                {
+                    return Value.Equals(other.Value);
+                }
+                else
+                {
+                    return (other.Value == null);
+                }
+            }
+            return false;
+        }
+
+        public override int GetHashCode()
+        {
+            return base.GetHashCode();
+        }
+
+        protected void SetValue(object value)
+        {
+            _value = value;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ComponentModel/EditorBrowsableAttribute.cs b/src/System.Private.CoreLib/shared/System/ComponentModel/EditorBrowsableAttribute.cs
new file mode 100644
index 0000000000..9b4d6e626e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ComponentModel/EditorBrowsableAttribute.cs
@@ -0,0 +1,48 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.ComponentModel
+{
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Enum | AttributeTargets.Constructor | AttributeTargets.Method | AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Event | AttributeTargets.Delegate | AttributeTargets.Interface)]
+    public sealed class EditorBrowsableAttribute : Attribute
+    {
+        private EditorBrowsableState browsableState;
+
+        public EditorBrowsableAttribute(EditorBrowsableState state)
+        {
+            browsableState = state;
+        }
+
+        public EditorBrowsableAttribute() : this(EditorBrowsableState.Always) { }
+
+        public EditorBrowsableState State
+        {
+            get { return browsableState; }
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (obj == this)
+            {
+                return true;
+            }
+
+            EditorBrowsableAttribute other = obj as EditorBrowsableAttribute;
+
+            return (other != null) && other.browsableState == browsableState;
+        }
+
+        public override int GetHashCode()
+        {
+            return base.GetHashCode();
+        }
+    }
+
+    public enum EditorBrowsableState
+    {
+        Always,
+        Never,
+        Advanced
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Configuration/Assemblies/AssemblyHashAlgorithm.cs b/src/System.Private.CoreLib/shared/System/Configuration/Assemblies/AssemblyHashAlgorithm.cs
new file mode 100644
index 0000000000..aca8da5932
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Configuration/Assemblies/AssemblyHashAlgorithm.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Configuration.Assemblies
+{
+    public enum AssemblyHashAlgorithm
+    {
+        None = 0,
+        MD5 = 0x8003,
+        SHA1 = 0x8004,
+        SHA256 = 0x800c,
+        SHA384 = 0x800d,
+        SHA512 = 0x800e,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Configuration/Assemblies/AssemblyVersionCompatibility.cs b/src/System.Private.CoreLib/shared/System/Configuration/Assemblies/AssemblyVersionCompatibility.cs
new file mode 100644
index 0000000000..ef7b3eb45f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Configuration/Assemblies/AssemblyVersionCompatibility.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Configuration.Assemblies
+{
+    public enum AssemblyVersionCompatibility
+    {
+        SameMachine = 1,
+        SameProcess = 2,
+        SameDomain = 3,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Convert.Base64.cs b/src/System.Private.CoreLib/shared/System/Convert.Base64.cs
new file mode 100644
index 0000000000..7e2aee31b2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Convert.Base64.cs
@@ -0,0 +1,217 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System
+{
+    public static partial class Convert
+    {
+        /// <summary>
+        /// Decode the span of UTF-16 encoded text represented as base 64 into binary data.
+        /// If the input is not a multiple of 4, or contains illegal characters, it will decode as much as it can, to the largest possible multiple of 4.
+        /// This invariant allows continuation of the parse with a slower, whitespace-tolerant algorithm.
+        ///
+        /// <param name="utf16">The input span which contains UTF-16 encoded text in base 64 that needs to be decoded.</param>
+        /// <param name="bytes">The output span which contains the result of the operation, i.e. the decoded binary data.</param>
+        /// <param name="consumed">The number of input bytes consumed during the operation. This can be used to slice the input for subsequent calls, if necessary.</param>
+        /// <param name="written">The number of bytes written into the output span. This can be used to slice the output for subsequent calls, if necessary.</param>
+        /// <returns>Returns:
+        /// - true  - The entire input span was successfully parsed.
+        /// - false - Only a part of the input span was successfully parsed. Failure causes may include embedded or trailing whitespace, 
+        ///           other illegal Base64 characters, trailing characters after an encoding pad ('='), an input span whose length is not divisible by 4
+        ///           or a destination span that's too small. <paramref name="consumed"/> and <paramref name="written"/> are set so that 
+        ///           parsing can continue with a slower whitespace-tolerant algorithm.
+        ///           
+        /// Note: This is a cut down version of the implementation of Base64.DecodeFromUtf8(), modified the accept UTF16 chars and act as a fast-path
+        /// helper for the Convert routines when the input string contains no whitespace.
+        ///           
+        /// </summary> 
+        private static bool TryDecodeFromUtf16(ReadOnlySpan<char> utf16, Span<byte> bytes, out int consumed, out int written)
+        {
+            ref char srcChars = ref MemoryMarshal.GetReference(utf16);
+            ref byte destBytes = ref MemoryMarshal.GetReference(bytes);
+
+            int srcLength = utf16.Length & ~0x3;  // only decode input up to the closest multiple of 4.
+            int destLength = bytes.Length;
+
+            int sourceIndex = 0;
+            int destIndex = 0;
+
+            if (utf16.Length == 0)
+                goto DoneExit;
+
+            ref sbyte decodingMap = ref s_decodingMap[0];
+
+            // Last bytes could have padding characters, so process them separately and treat them as valid.
+            const int skipLastChunk = 4;
+
+            int maxSrcLength;
+            if (destLength >= (srcLength >> 2) * 3)
+            {
+                maxSrcLength = srcLength - skipLastChunk;
+            }
+            else
+            {
+                // This should never overflow since destLength here is less than int.MaxValue / 4 * 3 (i.e. 1610612733)
+                // Therefore, (destLength / 3) * 4 will always be less than 2147483641
+                maxSrcLength = (destLength / 3) * 4;
+            }
+
+            while (sourceIndex < maxSrcLength)
+            {
+                int result = Decode(ref Unsafe.Add(ref srcChars, sourceIndex), ref decodingMap);
+                if (result < 0)
+                    goto InvalidExit;
+                WriteThreeLowOrderBytes(ref Unsafe.Add(ref destBytes, destIndex), result);
+                destIndex += 3;
+                sourceIndex += 4;
+            }
+
+            if (maxSrcLength != srcLength - skipLastChunk)
+                goto InvalidExit;
+
+            // If input is less than 4 bytes, srcLength == sourceIndex == 0
+            // If input is not a multiple of 4, sourceIndex == srcLength != 0
+            if (sourceIndex == srcLength)
+            {
+                goto InvalidExit;
+            }
+
+            int i0 = Unsafe.Add(ref srcChars, srcLength - 4);
+            int i1 = Unsafe.Add(ref srcChars, srcLength - 3);
+            int i2 = Unsafe.Add(ref srcChars, srcLength - 2);
+            int i3 = Unsafe.Add(ref srcChars, srcLength - 1);
+            if (((i0 | i1 | i2 | i3) & 0xffffff00) != 0)
+                goto InvalidExit;
+
+            i0 = Unsafe.Add(ref decodingMap, i0);
+            i1 = Unsafe.Add(ref decodingMap, i1);
+
+            i0 <<= 18;
+            i1 <<= 12;
+
+            i0 |= i1;
+
+            if (i3 != EncodingPad)
+            {
+                i2 = Unsafe.Add(ref decodingMap, i2);
+                i3 = Unsafe.Add(ref decodingMap, i3);
+
+                i2 <<= 6;
+
+                i0 |= i3;
+                i0 |= i2;
+
+                if (i0 < 0)
+                    goto InvalidExit;
+                if (destIndex > destLength - 3)
+                    goto InvalidExit;
+                WriteThreeLowOrderBytes(ref Unsafe.Add(ref destBytes, destIndex), i0);
+                destIndex += 3;
+            }
+            else if (i2 != EncodingPad)
+            {
+                i2 = Unsafe.Add(ref decodingMap, i2);
+
+                i2 <<= 6;
+
+                i0 |= i2;
+
+                if (i0 < 0)
+                    goto InvalidExit;
+                if (destIndex > destLength - 2)
+                    goto InvalidExit;
+                Unsafe.Add(ref destBytes, destIndex) = (byte)(i0 >> 16);
+                Unsafe.Add(ref destBytes, destIndex + 1) = (byte)(i0 >> 8);
+                destIndex += 2;
+            }
+            else
+            {
+                if (i0 < 0)
+                    goto InvalidExit;
+                if (destIndex > destLength - 1)
+                    goto InvalidExit;
+                Unsafe.Add(ref destBytes, destIndex) = (byte)(i0 >> 16);
+                destIndex += 1;
+            }
+
+            sourceIndex += 4;
+
+            if (srcLength != utf16.Length)
+                goto InvalidExit;
+
+        DoneExit:
+            consumed = sourceIndex;
+            written = destIndex;
+            return true;
+
+        InvalidExit:
+            consumed = sourceIndex;
+            written = destIndex;
+            Debug.Assert((consumed % 4) == 0);
+            return false;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int Decode(ref char encodedChars, ref sbyte decodingMap)
+        {
+            int i0 = encodedChars;
+            int i1 = Unsafe.Add(ref encodedChars, 1);
+            int i2 = Unsafe.Add(ref encodedChars, 2);
+            int i3 = Unsafe.Add(ref encodedChars, 3);
+
+            if (((i0 | i1 | i2 | i3) & 0xffffff00) != 0)
+                return -1; // One or more chars falls outside the 00..ff range. This cannot be a valid Base64 character.
+
+            i0 = Unsafe.Add(ref decodingMap, i0);
+            i1 = Unsafe.Add(ref decodingMap, i1);
+            i2 = Unsafe.Add(ref decodingMap, i2);
+            i3 = Unsafe.Add(ref decodingMap, i3);
+
+            i0 <<= 18;
+            i1 <<= 12;
+            i2 <<= 6;
+
+            i0 |= i3;
+            i1 |= i2;
+
+            i0 |= i1;
+            return i0;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void WriteThreeLowOrderBytes(ref byte destination, int value)
+        {
+            destination = (byte)(value >> 16);
+            Unsafe.Add(ref destination, 1) = (byte)(value >> 8);
+            Unsafe.Add(ref destination, 2) = (byte)value;
+        }
+
+        // Pre-computing this table using a custom string(s_characters) and GenerateDecodingMapAndVerify (found in tests)
+        private static readonly sbyte[] s_decodingMap = {
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,         //62 is placed at index 43 (for +), 63 at index 47 (for /)
+            52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,         //52-61 are placed at index 48-57 (for 0-9), 64 at index 61 (for =)
+            -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
+            15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,         //0-25 are placed at index 65-90 (for A-Z)
+            -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
+            41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,         //26-51 are placed at index 97-122 (for a-z)
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,         // Bytes over 122 ('z') are invalid and cannot be decoded
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,         // Hence, padding the map with 255, which indicates invalid input
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        };
+
+        private const byte EncodingPad = (byte)'='; // '=', for padding
+    }
+} 
diff --git a/src/System.Private.CoreLib/shared/System/Convert.cs b/src/System.Private.CoreLib/shared/System/Convert.cs
new file mode 100644
index 0000000000..63342ad000
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Convert.cs
@@ -0,0 +1,2918 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Globalization;
+using System.Threading;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+using System.Security;
+using System.Diagnostics;
+
+namespace System
+{
+    [Flags]
+    public enum Base64FormattingOptions
+    {
+        None = 0,
+        InsertLineBreaks = 1
+    }
+
+    // Returns the type code of this object. An implementation of this method
+    // must not return TypeCode.Empty (which represents a null reference) or
+    // TypeCode.Object (which represents an object that doesn't implement the
+    // IConvertible interface). An implementation of this method should return
+    // TypeCode.DBNull if the value of this object is a database null. For
+    // example, a nullable integer type should return TypeCode.DBNull if the
+    // value of the object is the database null. Otherwise, an implementation
+    // of this method should return the TypeCode that best describes the
+    // internal representation of the object.
+    // The Value class provides conversion and querying methods for values. The
+    // Value class contains static members only, and it is not possible to create
+    // instances of the class.
+    //
+    // The statically typed conversion methods provided by the Value class are all
+    // of the form:
+    //
+    //    public static XXX ToXXX(YYY value)
+    //
+    // where XXX is the target type and YYY is the source type. The matrix below
+    // shows the set of supported conversions. The set of conversions is symmetric
+    // such that for every ToXXX(YYY) there is also a ToYYY(XXX).
+    //
+    // From:  To: Bol Chr SBy Byt I16 U16 I32 U32 I64 U64 Sgl Dbl Dec Dat Str
+    // ----------------------------------------------------------------------
+    // Boolean     x       x   x   x   x   x   x   x   x   x   x   x       x
+    // Char            x   x   x   x   x   x   x   x   x                   x
+    // SByte       x   x   x   x   x   x   x   x   x   x   x   x   x       x
+    // Byte        x   x   x   x   x   x   x   x   x   x   x   x   x       x
+    // Int16       x   x   x   x   x   x   x   x   x   x   x   x   x       x
+    // UInt16      x   x   x   x   x   x   x   x   x   x   x   x   x       x
+    // Int32       x   x   x   x   x   x   x   x   x   x   x   x   x       x
+    // UInt32      x   x   x   x   x   x   x   x   x   x   x   x   x       x
+    // Int64       x   x   x   x   x   x   x   x   x   x   x   x   x       x
+    // UInt64      x   x   x   x   x   x   x   x   x   x   x   x   x       x
+    // Single      x       x   x   x   x   x   x   x   x   x   x   x       x
+    // Double      x       x   x   x   x   x   x   x   x   x   x   x       x
+    // Decimal     x       x   x   x   x   x   x   x   x   x   x   x       x
+    // DateTime                                                        x   x
+    // String      x   x   x   x   x   x   x   x   x   x   x   x   x   x   x
+    // ----------------------------------------------------------------------
+    //
+    // For dynamic conversions, the Value class provides a set of methods of the
+    // form:
+    //
+    //    public static XXX ToXXX(object value)
+    //
+    // where XXX is the target type (Boolean, Char, SByte, Byte, Int16, UInt16,
+    // Int32, UInt32, Int64, UInt64, Single, Double, Decimal, DateTime,
+    // or String). The implementations of these methods all take the form:
+    //
+    //    public static XXX toXXX(object value) {
+    //        return value == null? XXX.Default: ((IConvertible)value).ToXXX();
+    //    }
+    //
+    // The code first checks if the given value is a null reference (which is the
+    // same as Value.Empty), in which case it returns the default value for type
+    // XXX. Otherwise, a cast to IConvertible is performed, and the appropriate ToXXX()
+    // method is invoked on the object. An InvalidCastException is thrown if the
+    // cast to IConvertible fails, and that exception is simply allowed to propagate out
+    // of the conversion method.
+
+    // Constant representing the database null value. This value is used in
+    // database applications to indicate the absence of a known value. Note
+    // that Value.DBNull is NOT the same as a null object reference, which is
+    // represented by Value.Empty.
+    //
+    // The Equals() method of DBNull always returns false, even when the
+    // argument is itself DBNull.
+    //
+    // When passed Value.DBNull, the Value.GetTypeCode() method returns
+    // TypeCode.DBNull.
+    //
+    // When passed Value.DBNull, the Value.ToXXX() methods all throw an
+    // InvalidCastException.
+
+    public static partial class Convert
+    {
+        //A typeof operation is fairly expensive (does a system call), so we'll cache these here
+        //statically.  These are exactly lined up with the TypeCode, eg. ConvertType[TypeCode.Int16]
+        //will give you the type of an Int16.
+        internal static readonly Type[] ConvertTypes = {
+            typeof(System.Empty),
+            typeof(Object),
+            typeof(System.DBNull),
+            typeof(Boolean),
+            typeof(Char),
+            typeof(SByte),
+            typeof(Byte),
+            typeof(Int16),
+            typeof(UInt16),
+            typeof(Int32),
+            typeof(UInt32),
+            typeof(Int64),
+            typeof(UInt64),
+            typeof(Single),
+            typeof(Double),
+            typeof(Decimal),
+            typeof(DateTime),
+            typeof(Object), //TypeCode is discontinuous so we need a placeholder.
+            typeof(String)
+        };
+
+        // Need to special case Enum because typecode will be underlying type, e.g. Int32
+        private static readonly Type EnumType = typeof(Enum);
+
+        internal static readonly char[] base64Table = {'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O',
+                                                       'P','Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d',
+                                                       'e','f','g','h','i','j','k','l','m','n','o','p','q','r','s',
+                                                       't','u','v','w','x','y','z','0','1','2','3','4','5','6','7',
+                                                       '8','9','+','/','=' };
+
+        private const Int32 base64LineBreakPosition = 76;
+
+#if DEBUG
+        private static bool TriggerAsserts = DoAsserts();
+        private static bool DoAsserts()
+        {
+            Debug.Assert(ConvertTypes != null, "[Convert.cctor]ConvertTypes!=null");
+            Debug.Assert(ConvertTypes.Length == ((int)TypeCode.String + 1), "[Convert.cctor]ConvertTypes.Length == ((int)TypeCode.String + 1)");
+            Debug.Assert(ConvertTypes[(int)TypeCode.Empty] == typeof(System.Empty),
+                            "[Convert.cctor]ConvertTypes[(int)TypeCode.Empty]==typeof(System.Empty)");
+            Debug.Assert(ConvertTypes[(int)TypeCode.String] == typeof(String),
+                            "[Convert.cctor]ConvertTypes[(int)TypeCode.String]==typeof(System.String)");
+            Debug.Assert(ConvertTypes[(int)TypeCode.Int32] == typeof(int),
+                            "[Convert.cctor]ConvertTypes[(int)TypeCode.Int32]==typeof(int)");
+            return true;
+        }
+#endif
+
+        public static readonly Object DBNull = System.DBNull.Value;
+
+        // Returns the type code for the given object. If the argument is null,
+        // the result is TypeCode.Empty. If the argument is not a value (i.e. if
+        // the object does not implement IConvertible), the result is TypeCode.Object.
+        // Otherwise, the result is the type code of the object, as determined by
+        // the object's implementation of IConvertible.
+        public static TypeCode GetTypeCode(object value)
+        {
+            if (value == null) return TypeCode.Empty;
+            IConvertible temp = value as IConvertible;
+            if (temp != null)
+            {
+                return temp.GetTypeCode();
+            }
+            return TypeCode.Object;
+        }
+
+        // Returns true if the given object is a database null. This operation
+        // corresponds to "value.GetTypeCode() == TypeCode.DBNull".
+        public static bool IsDBNull(object value)
+        {
+            if (value == System.DBNull.Value) return true;
+            IConvertible convertible = value as IConvertible;
+            return convertible != null ? convertible.GetTypeCode() == TypeCode.DBNull : false;
+        }
+
+        // Converts the given object to the given type. In general, this method is
+        // equivalent to calling the Value.ToXXX(value) method for the given
+        // typeCode and boxing the result.
+        //
+        // The method first checks if the given object implements IConvertible. If not,
+        // the only permitted conversion is from a null to TypeCode.Empty, the
+        // result of which is null.
+        //
+        // If the object does implement IConvertible, a check is made to see if the
+        // object already has the given type code, in which case the object is
+        // simply returned. Otherwise, the appropriate ToXXX() is invoked on the
+        // object's implementation of IConvertible.
+        public static Object ChangeType(Object value, TypeCode typeCode)
+        {
+            return ChangeType(value, typeCode, CultureInfo.CurrentCulture);
+        }
+
+        public static Object ChangeType(Object value, TypeCode typeCode, IFormatProvider provider)
+        {
+            if (value == null && (typeCode == TypeCode.Empty || typeCode == TypeCode.String || typeCode == TypeCode.Object))
+            {
+                return null;
+            }
+
+            IConvertible v = value as IConvertible;
+            if (v == null)
+            {
+                throw new InvalidCastException(SR.InvalidCast_IConvertible);
+            }
+
+            // This line is invalid for things like Enums that return a TypeCode
+            // of Int32, but the object can't actually be cast to an Int32.
+            //            if (v.GetTypeCode() == typeCode) return value;
+            switch (typeCode)
+            {
+                case TypeCode.Boolean:
+                    return v.ToBoolean(provider);
+                case TypeCode.Char:
+                    return v.ToChar(provider);
+                case TypeCode.SByte:
+                    return v.ToSByte(provider);
+                case TypeCode.Byte:
+                    return v.ToByte(provider);
+                case TypeCode.Int16:
+                    return v.ToInt16(provider);
+                case TypeCode.UInt16:
+                    return v.ToUInt16(provider);
+                case TypeCode.Int32:
+                    return v.ToInt32(provider);
+                case TypeCode.UInt32:
+                    return v.ToUInt32(provider);
+                case TypeCode.Int64:
+                    return v.ToInt64(provider);
+                case TypeCode.UInt64:
+                    return v.ToUInt64(provider);
+                case TypeCode.Single:
+                    return v.ToSingle(provider);
+                case TypeCode.Double:
+                    return v.ToDouble(provider);
+                case TypeCode.Decimal:
+                    return v.ToDecimal(provider);
+                case TypeCode.DateTime:
+                    return v.ToDateTime(provider);
+                case TypeCode.String:
+                    return v.ToString(provider);
+                case TypeCode.Object:
+                    return value;
+                case TypeCode.DBNull:
+                    throw new InvalidCastException(SR.InvalidCast_DBNull);
+                case TypeCode.Empty:
+                    throw new InvalidCastException(SR.InvalidCast_Empty);
+                default:
+                    throw new ArgumentException(SR.Arg_UnknownTypeCode);
+            }
+        }
+
+        internal static Object DefaultToType(IConvertible value, Type targetType, IFormatProvider provider)
+        {
+            Debug.Assert(value != null, "[Convert.DefaultToType]value!=null");
+            if (targetType == null)
+            {
+                throw new ArgumentNullException(nameof(targetType));
+            }
+
+            if (ReferenceEquals(value.GetType(), targetType))
+            {
+                return value;
+            }
+
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.Boolean]))
+                return value.ToBoolean(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.Char]))
+                return value.ToChar(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.SByte]))
+                return value.ToSByte(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.Byte]))
+                return value.ToByte(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.Int16]))
+                return value.ToInt16(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.UInt16]))
+                return value.ToUInt16(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.Int32]))
+                return value.ToInt32(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.UInt32]))
+                return value.ToUInt32(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.Int64]))
+                return value.ToInt64(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.UInt64]))
+                return value.ToUInt64(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.Single]))
+                return value.ToSingle(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.Double]))
+                return value.ToDouble(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.Decimal]))
+                return value.ToDecimal(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.DateTime]))
+                return value.ToDateTime(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.String]))
+                return value.ToString(provider);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.Object]))
+                return (Object)value;
+            //  Need to special case Enum because typecode will be underlying type, e.g. Int32
+            if (ReferenceEquals(targetType, EnumType))
+                return (Enum)value;
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.DBNull]))
+                throw new InvalidCastException(SR.InvalidCast_DBNull);
+            if (ReferenceEquals(targetType, ConvertTypes[(int)TypeCode.Empty]))
+                throw new InvalidCastException(SR.InvalidCast_Empty);
+
+            throw new InvalidCastException(string.Format(SR.InvalidCast_FromTo, value.GetType().FullName, targetType.FullName));
+        }
+
+        public static Object ChangeType(Object value, Type conversionType)
+        {
+            return ChangeType(value, conversionType, CultureInfo.CurrentCulture);
+        }
+
+        public static Object ChangeType(Object value, Type conversionType, IFormatProvider provider)
+        {
+            if (ReferenceEquals(conversionType, null))
+            {
+                throw new ArgumentNullException(nameof(conversionType));
+            }
+
+            if (value == null)
+            {
+                if (conversionType.IsValueType)
+                {
+                    throw new InvalidCastException(SR.InvalidCast_CannotCastNullToValueType);
+                }
+                return null;
+            }
+
+            IConvertible ic = value as IConvertible;
+            if (ic == null)
+            {
+                if (value.GetType() == conversionType)
+                {
+                    return value;
+                }
+                throw new InvalidCastException(SR.InvalidCast_IConvertible);
+            }
+
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.Boolean]))
+                return ic.ToBoolean(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.Char]))
+                return ic.ToChar(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.SByte]))
+                return ic.ToSByte(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.Byte]))
+                return ic.ToByte(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.Int16]))
+                return ic.ToInt16(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.UInt16]))
+                return ic.ToUInt16(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.Int32]))
+                return ic.ToInt32(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.UInt32]))
+                return ic.ToUInt32(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.Int64]))
+                return ic.ToInt64(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.UInt64]))
+                return ic.ToUInt64(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.Single]))
+                return ic.ToSingle(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.Double]))
+                return ic.ToDouble(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.Decimal]))
+                return ic.ToDecimal(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.DateTime]))
+                return ic.ToDateTime(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.String]))
+                return ic.ToString(provider);
+            if (ReferenceEquals(conversionType, ConvertTypes[(int)TypeCode.Object]))
+                return (Object)value;
+
+            return ic.ToType(conversionType, provider);
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void ThrowCharOverflowException() { throw new OverflowException(SR.Overflow_Char); }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void ThrowByteOverflowException() { throw new OverflowException(SR.Overflow_Byte); }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void ThrowSByteOverflowException() { throw new OverflowException(SR.Overflow_SByte); }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void ThrowInt16OverflowException() { throw new OverflowException(SR.Overflow_Int16); }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void ThrowUInt16OverflowException() { throw new OverflowException(SR.Overflow_UInt16); }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void ThrowInt32OverflowException() { throw new OverflowException(SR.Overflow_Int32); }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void ThrowUInt32OverflowException() { throw new OverflowException(SR.Overflow_UInt32); }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void ThrowInt64OverflowException() { throw new OverflowException(SR.Overflow_Int64); }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void ThrowUInt64OverflowException() { throw new OverflowException(SR.Overflow_UInt64); }
+
+        // Conversions to Boolean
+        public static bool ToBoolean(Object value)
+        {
+            return value == null ? false : ((IConvertible)value).ToBoolean(null);
+        }
+
+        public static bool ToBoolean(Object value, IFormatProvider provider)
+        {
+            return value == null ? false : ((IConvertible)value).ToBoolean(provider);
+        }
+
+
+        public static bool ToBoolean(bool value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static bool ToBoolean(sbyte value)
+        {
+            return value != 0;
+        }
+
+        // To be consistent with IConvertible in the base data types else we get different semantics
+        // with widening operations. Without this operator this widen succeeds,with this API the widening throws.
+        public static bool ToBoolean(char value)
+        {
+            return ((IConvertible)value).ToBoolean(null);
+        }
+
+        public static bool ToBoolean(byte value)
+        {
+            return value != 0;
+        }
+
+
+        public static bool ToBoolean(short value)
+        {
+            return value != 0;
+        }
+
+        [CLSCompliant(false)]
+        public static bool ToBoolean(ushort value)
+        {
+            return value != 0;
+        }
+
+        public static bool ToBoolean(int value)
+        {
+            return value != 0;
+        }
+
+        [CLSCompliant(false)]
+        public static bool ToBoolean(uint value)
+        {
+            return value != 0;
+        }
+
+        public static bool ToBoolean(long value)
+        {
+            return value != 0;
+        }
+
+        [CLSCompliant(false)]
+        public static bool ToBoolean(ulong value)
+        {
+            return value != 0;
+        }
+
+        public static bool ToBoolean(String value)
+        {
+            if (value == null)
+                return false;
+            return Boolean.Parse(value);
+        }
+
+        public static bool ToBoolean(String value, IFormatProvider provider)
+        {
+            if (value == null)
+                return false;
+            return Boolean.Parse(value);
+        }
+
+        public static bool ToBoolean(float value)
+        {
+            return value != 0;
+        }
+
+        public static bool ToBoolean(double value)
+        {
+            return value != 0;
+        }
+
+        public static bool ToBoolean(decimal value)
+        {
+            return value != 0;
+        }
+
+        public static bool ToBoolean(DateTime value)
+        {
+            return ((IConvertible)value).ToBoolean(null);
+        }
+
+        // Disallowed conversions to Boolean
+        // public static bool ToBoolean(TimeSpan value)
+
+        // Conversions to Char
+
+
+        public static char ToChar(object value)
+        {
+            return value == null ? (char)0 : ((IConvertible)value).ToChar(null);
+        }
+
+        public static char ToChar(object value, IFormatProvider provider)
+        {
+            return value == null ? (char)0 : ((IConvertible)value).ToChar(provider);
+        }
+
+        public static char ToChar(bool value)
+        {
+            return ((IConvertible)value).ToChar(null);
+        }
+
+        public static char ToChar(char value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static char ToChar(sbyte value)
+        {
+            if (value < 0) ThrowCharOverflowException();
+            return (char)value;
+        }
+
+        public static char ToChar(byte value)
+        {
+            return (char)value;
+        }
+
+        public static char ToChar(short value)
+        {
+            if (value < 0) ThrowCharOverflowException();
+            return (char)value;
+        }
+
+        [CLSCompliant(false)]
+        public static char ToChar(ushort value)
+        {
+            return (char)value;
+        }
+
+        public static char ToChar(int value)
+        {
+            if (value < 0 || value > Char.MaxValue) ThrowCharOverflowException();
+            return (char)value;
+        }
+
+        [CLSCompliant(false)]
+        public static char ToChar(uint value)
+        {
+            if (value > Char.MaxValue) ThrowCharOverflowException();
+            return (char)value;
+        }
+
+        public static char ToChar(long value)
+        {
+            if (value < 0 || value > Char.MaxValue) ThrowCharOverflowException();
+            return (char)value;
+        }
+
+        [CLSCompliant(false)]
+        public static char ToChar(ulong value)
+        {
+            if (value > Char.MaxValue) ThrowCharOverflowException();
+            return (char)value;
+        }
+
+        //
+        // @VariantSwitch
+        // Remove FormatExceptions;
+        //
+        public static char ToChar(String value)
+        {
+            return ToChar(value, null);
+        }
+
+        public static char ToChar(String value, IFormatProvider provider)
+        {
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            if (value.Length != 1)
+                throw new FormatException(SR.Format_NeedSingleChar);
+
+            return value[0];
+        }
+
+        // To be consistent with IConvertible in the base data types else we get different semantics
+        // with widening operations. Without this operator this widen succeeds,with this API the widening throws.
+        public static char ToChar(float value)
+        {
+            return ((IConvertible)value).ToChar(null);
+        }
+
+        // To be consistent with IConvertible in the base data types else we get different semantics
+        // with widening operations. Without this operator this widen succeeds,with this API the widening throws.
+        public static char ToChar(double value)
+        {
+            return ((IConvertible)value).ToChar(null);
+        }
+
+        // To be consistent with IConvertible in the base data types else we get different semantics
+        // with widening operations. Without this operator this widen succeeds,with this API the widening throws.
+        public static char ToChar(decimal value)
+        {
+            return ((IConvertible)value).ToChar(null);
+        }
+
+        public static char ToChar(DateTime value)
+        {
+            return ((IConvertible)value).ToChar(null);
+        }
+
+
+        // Disallowed conversions to Char
+        // public static char ToChar(TimeSpan value)
+
+        // Conversions to SByte
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(object value)
+        {
+            return value == null ? (sbyte)0 : ((IConvertible)value).ToSByte(null);
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(object value, IFormatProvider provider)
+        {
+            return value == null ? (sbyte)0 : ((IConvertible)value).ToSByte(provider);
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(bool value)
+        {
+            return value ? (sbyte)Boolean.True : (sbyte)Boolean.False;
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(sbyte value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(char value)
+        {
+            if (value > SByte.MaxValue) ThrowSByteOverflowException();
+            return (sbyte)value;
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(byte value)
+        {
+            if (value > SByte.MaxValue) ThrowSByteOverflowException();
+            return (sbyte)value;
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(short value)
+        {
+            if (value < SByte.MinValue || value > SByte.MaxValue) ThrowSByteOverflowException();
+            return (sbyte)value;
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(ushort value)
+        {
+            if (value > SByte.MaxValue) ThrowSByteOverflowException();
+            return (sbyte)value;
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(int value)
+        {
+            if (value < SByte.MinValue || value > SByte.MaxValue) ThrowSByteOverflowException();
+            return (sbyte)value;
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(uint value)
+        {
+            if (value > SByte.MaxValue) ThrowSByteOverflowException();
+            return (sbyte)value;
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(long value)
+        {
+            if (value < SByte.MinValue || value > SByte.MaxValue) ThrowSByteOverflowException();
+            return (sbyte)value;
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(ulong value)
+        {
+            if (value > (ulong)SByte.MaxValue) ThrowSByteOverflowException();
+            return (sbyte)value;
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(float value)
+        {
+            return ToSByte((double)value);
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(double value)
+        {
+            return ToSByte(ToInt32(value));
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(decimal value)
+        {
+            return Decimal.ToSByte(Decimal.Round(value, 0));
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(String value)
+        {
+            if (value == null)
+                return 0;
+            return SByte.Parse(value, CultureInfo.CurrentCulture);
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(String value, IFormatProvider provider)
+        {
+            return SByte.Parse(value, NumberStyles.Integer, provider);
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(DateTime value)
+        {
+            return ((IConvertible)value).ToSByte(null);
+        }
+
+        // Disallowed conversions to SByte
+        // public static sbyte ToSByte(TimeSpan value)
+
+        // Conversions to Byte
+
+        public static byte ToByte(object value)
+        {
+            return value == null ? (byte)0 : ((IConvertible)value).ToByte(null);
+        }
+
+        public static byte ToByte(object value, IFormatProvider provider)
+        {
+            return value == null ? (byte)0 : ((IConvertible)value).ToByte(provider);
+        }
+
+        public static byte ToByte(bool value)
+        {
+            return value ? (byte)Boolean.True : (byte)Boolean.False;
+        }
+
+        public static byte ToByte(byte value)
+        {
+            return value;
+        }
+
+        public static byte ToByte(char value)
+        {
+            if (value > Byte.MaxValue) ThrowByteOverflowException();
+            return (byte)value;
+        }
+
+        [CLSCompliant(false)]
+        public static byte ToByte(sbyte value)
+        {
+            if (value < Byte.MinValue) ThrowByteOverflowException();
+            return (byte)value;
+        }
+
+        public static byte ToByte(short value)
+        {
+            if (value < Byte.MinValue || value > Byte.MaxValue) ThrowByteOverflowException();
+            return (byte)value;
+        }
+
+        [CLSCompliant(false)]
+        public static byte ToByte(ushort value)
+        {
+            if (value > Byte.MaxValue) ThrowByteOverflowException();
+            return (byte)value;
+        }
+
+        public static byte ToByte(int value)
+        {
+            if (value < Byte.MinValue || value > Byte.MaxValue) ThrowByteOverflowException();
+            return (byte)value;
+        }
+
+        [CLSCompliant(false)]
+        public static byte ToByte(uint value)
+        {
+            if (value > Byte.MaxValue) ThrowByteOverflowException();
+            return (byte)value;
+        }
+
+        public static byte ToByte(long value)
+        {
+            if (value < Byte.MinValue || value > Byte.MaxValue) ThrowByteOverflowException();
+            return (byte)value;
+        }
+
+        [CLSCompliant(false)]
+        public static byte ToByte(ulong value)
+        {
+            if (value > Byte.MaxValue) ThrowByteOverflowException();
+            return (byte)value;
+        }
+
+        public static byte ToByte(float value)
+        {
+            return ToByte((double)value);
+        }
+
+        public static byte ToByte(double value)
+        {
+            return ToByte(ToInt32(value));
+        }
+
+        public static byte ToByte(decimal value)
+        {
+            return Decimal.ToByte(Decimal.Round(value, 0));
+        }
+
+        public static byte ToByte(String value)
+        {
+            if (value == null)
+                return 0;
+            return Byte.Parse(value, CultureInfo.CurrentCulture);
+        }
+
+        public static byte ToByte(String value, IFormatProvider provider)
+        {
+            if (value == null)
+                return 0;
+            return Byte.Parse(value, NumberStyles.Integer, provider);
+        }
+
+        public static byte ToByte(DateTime value)
+        {
+            return ((IConvertible)value).ToByte(null);
+        }
+
+
+        // Disallowed conversions to Byte
+        // public static byte ToByte(TimeSpan value)
+
+        // Conversions to Int16
+
+        public static short ToInt16(object value)
+        {
+            return value == null ? (short)0 : ((IConvertible)value).ToInt16(null);
+        }
+
+        public static short ToInt16(object value, IFormatProvider provider)
+        {
+            return value == null ? (short)0 : ((IConvertible)value).ToInt16(provider);
+        }
+
+        public static short ToInt16(bool value)
+        {
+            return value ? (short)Boolean.True : (short)Boolean.False;
+        }
+
+        public static short ToInt16(char value)
+        {
+            if (value > Int16.MaxValue) ThrowInt16OverflowException();
+            return (short)value;
+        }
+
+        [CLSCompliant(false)]
+        public static short ToInt16(sbyte value)
+        {
+            return value;
+        }
+
+        public static short ToInt16(byte value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static short ToInt16(ushort value)
+        {
+            if (value > Int16.MaxValue) ThrowInt16OverflowException();
+            return (short)value;
+        }
+
+        public static short ToInt16(int value)
+        {
+            if (value < Int16.MinValue || value > Int16.MaxValue) ThrowInt16OverflowException();
+            return (short)value;
+        }
+
+        [CLSCompliant(false)]
+        public static short ToInt16(uint value)
+        {
+            if (value > Int16.MaxValue) ThrowInt16OverflowException();
+            return (short)value;
+        }
+
+        public static short ToInt16(short value)
+        {
+            return value;
+        }
+
+        public static short ToInt16(long value)
+        {
+            if (value < Int16.MinValue || value > Int16.MaxValue) ThrowInt16OverflowException();
+            return (short)value;
+        }
+
+        [CLSCompliant(false)]
+        public static short ToInt16(ulong value)
+        {
+            if (value > (ulong)Int16.MaxValue) ThrowInt16OverflowException();
+            return (short)value;
+        }
+
+        public static short ToInt16(float value)
+        {
+            return ToInt16((double)value);
+        }
+
+        public static short ToInt16(double value)
+        {
+            return ToInt16(ToInt32(value));
+        }
+
+        public static short ToInt16(decimal value)
+        {
+            return Decimal.ToInt16(Decimal.Round(value, 0));
+        }
+
+        public static short ToInt16(String value)
+        {
+            if (value == null)
+                return 0;
+            return Int16.Parse(value, CultureInfo.CurrentCulture);
+        }
+
+        public static short ToInt16(String value, IFormatProvider provider)
+        {
+            if (value == null)
+                return 0;
+            return Int16.Parse(value, NumberStyles.Integer, provider);
+        }
+
+        public static short ToInt16(DateTime value)
+        {
+            return ((IConvertible)value).ToInt16(null);
+        }
+
+
+        // Disallowed conversions to Int16
+        // public static short ToInt16(TimeSpan value)
+
+        // Conversions to UInt16
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(object value)
+        {
+            return value == null ? (ushort)0 : ((IConvertible)value).ToUInt16(null);
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(object value, IFormatProvider provider)
+        {
+            return value == null ? (ushort)0 : ((IConvertible)value).ToUInt16(provider);
+        }
+
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(bool value)
+        {
+            return value ? (ushort)Boolean.True : (ushort)Boolean.False;
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(char value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(sbyte value)
+        {
+            if (value < 0) ThrowUInt16OverflowException();
+            return (ushort)value;
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(byte value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(short value)
+        {
+            if (value < 0) ThrowUInt16OverflowException();
+            return (ushort)value;
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(int value)
+        {
+            if (value < 0 || value > UInt16.MaxValue) ThrowUInt16OverflowException();
+            return (ushort)value;
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(ushort value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(uint value)
+        {
+            if (value > UInt16.MaxValue) ThrowUInt16OverflowException();
+            return (ushort)value;
+        }
+
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(long value)
+        {
+            if (value < 0 || value > UInt16.MaxValue) ThrowUInt16OverflowException();
+            return (ushort)value;
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(ulong value)
+        {
+            if (value > UInt16.MaxValue) ThrowUInt16OverflowException();
+            return (ushort)value;
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(float value)
+        {
+            return ToUInt16((double)value);
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(double value)
+        {
+            return ToUInt16(ToInt32(value));
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(decimal value)
+        {
+            return Decimal.ToUInt16(Decimal.Round(value, 0));
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(String value)
+        {
+            if (value == null)
+                return 0;
+            return UInt16.Parse(value, CultureInfo.CurrentCulture);
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(String value, IFormatProvider provider)
+        {
+            if (value == null)
+                return 0;
+            return UInt16.Parse(value, NumberStyles.Integer, provider);
+        }
+
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(DateTime value)
+        {
+            return ((IConvertible)value).ToUInt16(null);
+        }
+
+        // Disallowed conversions to UInt16
+        // public static ushort ToUInt16(TimeSpan value)
+
+        // Conversions to Int32
+
+        public static int ToInt32(object value)
+        {
+            return value == null ? 0 : ((IConvertible)value).ToInt32(null);
+        }
+
+        public static int ToInt32(object value, IFormatProvider provider)
+        {
+            return value == null ? 0 : ((IConvertible)value).ToInt32(provider);
+        }
+
+
+        public static int ToInt32(bool value)
+        {
+            return value ? Boolean.True : Boolean.False;
+        }
+
+        public static int ToInt32(char value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static int ToInt32(sbyte value)
+        {
+            return value;
+        }
+
+        public static int ToInt32(byte value)
+        {
+            return value;
+        }
+
+        public static int ToInt32(short value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static int ToInt32(ushort value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static int ToInt32(uint value)
+        {
+            if (value > Int32.MaxValue) ThrowInt32OverflowException();
+            return (int)value;
+        }
+
+        public static int ToInt32(int value)
+        {
+            return value;
+        }
+
+        public static int ToInt32(long value)
+        {
+            if (value < Int32.MinValue || value > Int32.MaxValue) ThrowInt32OverflowException();
+            return (int)value;
+        }
+
+        [CLSCompliant(false)]
+        public static int ToInt32(ulong value)
+        {
+            if (value > Int32.MaxValue) ThrowInt32OverflowException();
+            return (int)value;
+        }
+
+        public static int ToInt32(float value)
+        {
+            return ToInt32((double)value);
+        }
+
+        public static int ToInt32(double value)
+        {
+            if (value >= 0)
+            {
+                if (value < 2147483647.5)
+                {
+                    int result = (int)value;
+                    double dif = value - result;
+                    if (dif > 0.5 || dif == 0.5 && (result & 1) != 0) result++;
+                    return result;
+                }
+            }
+            else
+            {
+                if (value >= -2147483648.5)
+                {
+                    int result = (int)value;
+                    double dif = value - result;
+                    if (dif < -0.5 || dif == -0.5 && (result & 1) != 0) result--;
+                    return result;
+                }
+            }
+            throw new OverflowException(SR.Overflow_Int32);
+        }
+
+        public static int ToInt32(decimal value)
+        {
+            return Decimal.ToInt32(Decimal.Round(value, 0));
+        }
+
+        public static int ToInt32(String value)
+        {
+            if (value == null)
+                return 0;
+            return Int32.Parse(value, CultureInfo.CurrentCulture);
+        }
+
+        public static int ToInt32(String value, IFormatProvider provider)
+        {
+            if (value == null)
+                return 0;
+            return Int32.Parse(value, NumberStyles.Integer, provider);
+        }
+
+        public static int ToInt32(DateTime value)
+        {
+            return ((IConvertible)value).ToInt32(null);
+        }
+
+
+        // Disallowed conversions to Int32
+        // public static int ToInt32(TimeSpan value)
+
+        // Conversions to UInt32
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(object value)
+        {
+            return value == null ? 0 : ((IConvertible)value).ToUInt32(null);
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(object value, IFormatProvider provider)
+        {
+            return value == null ? 0 : ((IConvertible)value).ToUInt32(provider);
+        }
+
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(bool value)
+        {
+            return value ? (uint)Boolean.True : (uint)Boolean.False;
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(char value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(sbyte value)
+        {
+            if (value < 0) ThrowUInt32OverflowException();
+            return (uint)value;
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(byte value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(short value)
+        {
+            if (value < 0) ThrowUInt32OverflowException();
+            return (uint)value;
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(ushort value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(int value)
+        {
+            if (value < 0) ThrowUInt32OverflowException();
+            return (uint)value;
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(uint value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(long value)
+        {
+            if (value < 0 || value > UInt32.MaxValue) ThrowUInt32OverflowException();
+            return (uint)value;
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(ulong value)
+        {
+            if (value > UInt32.MaxValue) ThrowUInt32OverflowException();
+            return (uint)value;
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(float value)
+        {
+            return ToUInt32((double)value);
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(double value)
+        {
+            if (value >= -0.5 && value < 4294967295.5)
+            {
+                uint result = (uint)value;
+                double dif = value - result;
+                if (dif > 0.5 || dif == 0.5 && (result & 1) != 0) result++;
+                return result;
+            }
+            throw new OverflowException(SR.Overflow_UInt32);
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(decimal value)
+        {
+            return Decimal.ToUInt32(Decimal.Round(value, 0));
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(String value)
+        {
+            if (value == null)
+                return 0;
+            return UInt32.Parse(value, CultureInfo.CurrentCulture);
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(String value, IFormatProvider provider)
+        {
+            if (value == null)
+                return 0;
+            return UInt32.Parse(value, NumberStyles.Integer, provider);
+        }
+
+        [CLSCompliant(false)]
+        public static uint ToUInt32(DateTime value)
+        {
+            return ((IConvertible)value).ToUInt32(null);
+        }
+
+        // Disallowed conversions to UInt32
+        // public static uint ToUInt32(TimeSpan value)
+
+        // Conversions to Int64
+
+        public static long ToInt64(object value)
+        {
+            return value == null ? 0 : ((IConvertible)value).ToInt64(null);
+        }
+
+        public static long ToInt64(object value, IFormatProvider provider)
+        {
+            return value == null ? 0 : ((IConvertible)value).ToInt64(provider);
+        }
+
+
+        public static long ToInt64(bool value)
+        {
+            return value ? Boolean.True : Boolean.False;
+        }
+
+        public static long ToInt64(char value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static long ToInt64(sbyte value)
+        {
+            return value;
+        }
+
+        public static long ToInt64(byte value)
+        {
+            return value;
+        }
+
+        public static long ToInt64(short value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static long ToInt64(ushort value)
+        {
+            return value;
+        }
+
+        public static long ToInt64(int value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static long ToInt64(uint value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static long ToInt64(ulong value)
+        {
+            if (value > Int64.MaxValue) ThrowInt64OverflowException();
+            return (long)value;
+        }
+
+        public static long ToInt64(long value)
+        {
+            return value;
+        }
+
+
+        public static long ToInt64(float value)
+        {
+            return ToInt64((double)value);
+        }
+
+        public static long ToInt64(double value)
+        {
+            return checked((long)Math.Round(value));
+        }
+
+        public static long ToInt64(decimal value)
+        {
+            return Decimal.ToInt64(Decimal.Round(value, 0));
+        }
+
+        public static long ToInt64(string value)
+        {
+            if (value == null)
+                return 0;
+            return Int64.Parse(value, CultureInfo.CurrentCulture);
+        }
+
+        public static long ToInt64(String value, IFormatProvider provider)
+        {
+            if (value == null)
+                return 0;
+            return Int64.Parse(value, NumberStyles.Integer, provider);
+        }
+
+        public static long ToInt64(DateTime value)
+        {
+            return ((IConvertible)value).ToInt64(null);
+        }
+
+        // Disallowed conversions to Int64
+        // public static long ToInt64(TimeSpan value)
+
+        // Conversions to UInt64
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(object value)
+        {
+            return value == null ? 0 : ((IConvertible)value).ToUInt64(null);
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(object value, IFormatProvider provider)
+        {
+            return value == null ? 0 : ((IConvertible)value).ToUInt64(provider);
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(bool value)
+        {
+            return value ? (ulong)Boolean.True : (ulong)Boolean.False;
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(char value)
+        {
+            return value;
+        }
+
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(sbyte value)
+        {
+            if (value < 0) ThrowUInt64OverflowException();
+            return (ulong)value;
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(byte value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(short value)
+        {
+            if (value < 0) ThrowUInt64OverflowException();
+            return (ulong)value;
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(ushort value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(int value)
+        {
+            if (value < 0) ThrowUInt64OverflowException();
+            return (ulong)value;
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(uint value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(long value)
+        {
+            if (value < 0) ThrowUInt64OverflowException();
+            return (ulong)value;
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(UInt64 value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(float value)
+        {
+            return ToUInt64((double)value);
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(double value)
+        {
+            return checked((ulong)Math.Round(value));
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(decimal value)
+        {
+            return Decimal.ToUInt64(Decimal.Round(value, 0));
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(String value)
+        {
+            if (value == null)
+                return 0;
+            return UInt64.Parse(value, CultureInfo.CurrentCulture);
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(String value, IFormatProvider provider)
+        {
+            if (value == null)
+                return 0;
+            return UInt64.Parse(value, NumberStyles.Integer, provider);
+        }
+
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(DateTime value)
+        {
+            return ((IConvertible)value).ToUInt64(null);
+        }
+
+        // Disallowed conversions to UInt64
+        // public static ulong ToUInt64(TimeSpan value)
+
+        // Conversions to Single
+
+        public static float ToSingle(object value)
+        {
+            return value == null ? 0 : ((IConvertible)value).ToSingle(null);
+        }
+
+        public static float ToSingle(object value, IFormatProvider provider)
+        {
+            return value == null ? 0 : ((IConvertible)value).ToSingle(provider);
+        }
+
+        [CLSCompliant(false)]
+        public static float ToSingle(sbyte value)
+        {
+            return value;
+        }
+
+        public static float ToSingle(byte value)
+        {
+            return value;
+        }
+
+        public static float ToSingle(char value)
+        {
+            return ((IConvertible)value).ToSingle(null);
+        }
+
+        public static float ToSingle(short value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static float ToSingle(ushort value)
+        {
+            return value;
+        }
+
+        public static float ToSingle(int value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static float ToSingle(uint value)
+        {
+            return value;
+        }
+
+        public static float ToSingle(long value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static float ToSingle(ulong value)
+        {
+            return value;
+        }
+
+        public static float ToSingle(float value)
+        {
+            return value;
+        }
+
+        public static float ToSingle(double value)
+        {
+            return (float)value;
+        }
+
+        public static float ToSingle(decimal value)
+        {
+            return (float)value;
+        }
+
+        public static float ToSingle(String value)
+        {
+            if (value == null)
+                return 0;
+            return Single.Parse(value, CultureInfo.CurrentCulture);
+        }
+
+        public static float ToSingle(String value, IFormatProvider provider)
+        {
+            if (value == null)
+                return 0;
+            return Single.Parse(value, NumberStyles.Float | NumberStyles.AllowThousands, provider);
+        }
+
+
+        public static float ToSingle(bool value)
+        {
+            return value ? Boolean.True : Boolean.False;
+        }
+
+        public static float ToSingle(DateTime value)
+        {
+            return ((IConvertible)value).ToSingle(null);
+        }
+
+        // Disallowed conversions to Single
+        // public static float ToSingle(TimeSpan value)
+
+        // Conversions to Double
+
+        public static double ToDouble(object value)
+        {
+            return value == null ? 0 : ((IConvertible)value).ToDouble(null);
+        }
+
+        public static double ToDouble(object value, IFormatProvider provider)
+        {
+            return value == null ? 0 : ((IConvertible)value).ToDouble(provider);
+        }
+
+
+        [CLSCompliant(false)]
+        public static double ToDouble(sbyte value)
+        {
+            return value;
+        }
+
+        public static double ToDouble(byte value)
+        {
+            return value;
+        }
+
+        public static double ToDouble(short value)
+        {
+            return value;
+        }
+
+        public static double ToDouble(char value)
+        {
+            return ((IConvertible)value).ToDouble(null);
+        }
+
+        [CLSCompliant(false)]
+        public static double ToDouble(ushort value)
+        {
+            return value;
+        }
+
+        public static double ToDouble(int value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static double ToDouble(uint value)
+        {
+            return value;
+        }
+
+        public static double ToDouble(long value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static double ToDouble(ulong value)
+        {
+            return value;
+        }
+
+        public static double ToDouble(float value)
+        {
+            return value;
+        }
+
+        public static double ToDouble(double value)
+        {
+            return value;
+        }
+
+        public static double ToDouble(decimal value)
+        {
+            return (double)value;
+        }
+
+        public static double ToDouble(String value)
+        {
+            if (value == null)
+                return 0;
+            return Double.Parse(value, CultureInfo.CurrentCulture);
+        }
+
+        public static double ToDouble(String value, IFormatProvider provider)
+        {
+            if (value == null)
+                return 0;
+            return Double.Parse(value, NumberStyles.Float | NumberStyles.AllowThousands, provider);
+        }
+
+        public static double ToDouble(bool value)
+        {
+            return value ? Boolean.True : Boolean.False;
+        }
+
+        public static double ToDouble(DateTime value)
+        {
+            return ((IConvertible)value).ToDouble(null);
+        }
+
+        // Disallowed conversions to Double
+        // public static double ToDouble(TimeSpan value)
+
+        // Conversions to Decimal
+
+        public static decimal ToDecimal(object value)
+        {
+            return value == null ? 0 : ((IConvertible)value).ToDecimal(null);
+        }
+
+        public static decimal ToDecimal(object value, IFormatProvider provider)
+        {
+            return value == null ? 0 : ((IConvertible)value).ToDecimal(provider);
+        }
+
+        [CLSCompliant(false)]
+        public static decimal ToDecimal(sbyte value)
+        {
+            return value;
+        }
+
+        public static decimal ToDecimal(byte value)
+        {
+            return value;
+        }
+
+        public static decimal ToDecimal(char value)
+        {
+            return ((IConvertible)value).ToDecimal(null);
+        }
+
+        public static decimal ToDecimal(short value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static decimal ToDecimal(ushort value)
+        {
+            return value;
+        }
+
+        public static decimal ToDecimal(int value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static decimal ToDecimal(uint value)
+        {
+            return value;
+        }
+
+        public static decimal ToDecimal(long value)
+        {
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public static decimal ToDecimal(ulong value)
+        {
+            return value;
+        }
+
+        public static decimal ToDecimal(float value)
+        {
+            return (decimal)value;
+        }
+
+        public static decimal ToDecimal(double value)
+        {
+            return (decimal)value;
+        }
+
+        public static decimal ToDecimal(String value)
+        {
+            if (value == null)
+                return 0m;
+            return Decimal.Parse(value, CultureInfo.CurrentCulture);
+        }
+
+        public static Decimal ToDecimal(String value, IFormatProvider provider)
+        {
+            if (value == null)
+                return 0m;
+            return Decimal.Parse(value, NumberStyles.Number, provider);
+        }
+
+        public static decimal ToDecimal(decimal value)
+        {
+            return value;
+        }
+
+        public static decimal ToDecimal(bool value)
+        {
+            return value ? Boolean.True : Boolean.False;
+        }
+
+        public static decimal ToDecimal(DateTime value)
+        {
+            return ((IConvertible)value).ToDecimal(null);
+        }
+
+        // Disallowed conversions to Decimal
+        // public static decimal ToDecimal(TimeSpan value)
+
+        // Conversions to DateTime
+
+        public static DateTime ToDateTime(DateTime value)
+        {
+            return value;
+        }
+
+        public static DateTime ToDateTime(object value)
+        {
+            return value == null ? DateTime.MinValue : ((IConvertible)value).ToDateTime(null);
+        }
+
+        public static DateTime ToDateTime(object value, IFormatProvider provider)
+        {
+            return value == null ? DateTime.MinValue : ((IConvertible)value).ToDateTime(provider);
+        }
+
+        public static DateTime ToDateTime(String value)
+        {
+            if (value == null)
+                return new DateTime(0);
+            return DateTime.Parse(value, CultureInfo.CurrentCulture);
+        }
+
+        public static DateTime ToDateTime(String value, IFormatProvider provider)
+        {
+            if (value == null)
+                return new DateTime(0);
+            return DateTime.Parse(value, provider);
+        }
+
+        [CLSCompliant(false)]
+        public static DateTime ToDateTime(sbyte value)
+        {
+            return ((IConvertible)value).ToDateTime(null);
+        }
+
+        public static DateTime ToDateTime(byte value)
+        {
+            return ((IConvertible)value).ToDateTime(null);
+        }
+
+        public static DateTime ToDateTime(short value)
+        {
+            return ((IConvertible)value).ToDateTime(null);
+        }
+
+        [CLSCompliant(false)]
+        public static DateTime ToDateTime(ushort value)
+        {
+            return ((IConvertible)value).ToDateTime(null);
+        }
+
+        public static DateTime ToDateTime(int value)
+        {
+            return ((IConvertible)value).ToDateTime(null);
+        }
+
+        [CLSCompliant(false)]
+        public static DateTime ToDateTime(uint value)
+        {
+            return ((IConvertible)value).ToDateTime(null);
+        }
+
+        public static DateTime ToDateTime(long value)
+        {
+            return ((IConvertible)value).ToDateTime(null);
+        }
+
+        [CLSCompliant(false)]
+        public static DateTime ToDateTime(ulong value)
+        {
+            return ((IConvertible)value).ToDateTime(null);
+        }
+
+        public static DateTime ToDateTime(bool value)
+        {
+            return ((IConvertible)value).ToDateTime(null);
+        }
+
+        public static DateTime ToDateTime(char value)
+        {
+            return ((IConvertible)value).ToDateTime(null);
+        }
+
+        public static DateTime ToDateTime(float value)
+        {
+            return ((IConvertible)value).ToDateTime(null);
+        }
+
+        public static DateTime ToDateTime(double value)
+        {
+            return ((IConvertible)value).ToDateTime(null);
+        }
+
+        public static DateTime ToDateTime(decimal value)
+        {
+            return ((IConvertible)value).ToDateTime(null);
+        }
+
+        // Disallowed conversions to DateTime
+        // public static DateTime ToDateTime(TimeSpan value)
+
+        // Conversions to String
+
+        public static string ToString(Object value)
+        {
+            return ToString(value, null);
+        }
+
+        public static string ToString(Object value, IFormatProvider provider)
+        {
+            IConvertible ic = value as IConvertible;
+            if (ic != null)
+                return ic.ToString(provider);
+            IFormattable formattable = value as IFormattable;
+            if (formattable != null)
+                return formattable.ToString(null, provider);
+            return value == null ? String.Empty : value.ToString();
+        }
+
+        public static string ToString(bool value)
+        {
+            return value.ToString();
+        }
+
+        public static string ToString(bool value, IFormatProvider provider)
+        {
+            return value.ToString();
+        }
+
+        public static string ToString(char value)
+        {
+            return Char.ToString(value);
+        }
+
+        public static string ToString(char value, IFormatProvider provider)
+        {
+            return value.ToString();
+        }
+
+        [CLSCompliant(false)]
+        public static string ToString(sbyte value)
+        {
+            return value.ToString(CultureInfo.CurrentCulture);
+        }
+
+        [CLSCompliant(false)]
+        public static string ToString(sbyte value, IFormatProvider provider)
+        {
+            return value.ToString(provider);
+        }
+
+        public static string ToString(byte value)
+        {
+            return value.ToString(CultureInfo.CurrentCulture);
+        }
+
+        public static string ToString(byte value, IFormatProvider provider)
+        {
+            return value.ToString(provider);
+        }
+
+        public static string ToString(short value)
+        {
+            return value.ToString(CultureInfo.CurrentCulture);
+        }
+
+        public static string ToString(short value, IFormatProvider provider)
+        {
+            return value.ToString(provider);
+        }
+
+        [CLSCompliant(false)]
+        public static string ToString(ushort value)
+        {
+            return value.ToString(CultureInfo.CurrentCulture);
+        }
+
+        [CLSCompliant(false)]
+        public static string ToString(ushort value, IFormatProvider provider)
+        {
+            return value.ToString(provider);
+        }
+
+        public static string ToString(int value)
+        {
+            return value.ToString(CultureInfo.CurrentCulture);
+        }
+
+        public static string ToString(int value, IFormatProvider provider)
+        {
+            return value.ToString(provider);
+        }
+
+        [CLSCompliant(false)]
+        public static string ToString(uint value)
+        {
+            return value.ToString(CultureInfo.CurrentCulture);
+        }
+
+        [CLSCompliant(false)]
+        public static string ToString(uint value, IFormatProvider provider)
+        {
+            return value.ToString(provider);
+        }
+
+        public static string ToString(long value)
+        {
+            return value.ToString(CultureInfo.CurrentCulture);
+        }
+
+        public static string ToString(long value, IFormatProvider provider)
+        {
+            return value.ToString(provider);
+        }
+
+        [CLSCompliant(false)]
+        public static string ToString(ulong value)
+        {
+            return value.ToString(CultureInfo.CurrentCulture);
+        }
+
+        [CLSCompliant(false)]
+        public static string ToString(ulong value, IFormatProvider provider)
+        {
+            return value.ToString(provider);
+        }
+
+        public static string ToString(float value)
+        {
+            return value.ToString(CultureInfo.CurrentCulture);
+        }
+
+        public static string ToString(float value, IFormatProvider provider)
+        {
+            return value.ToString(provider);
+        }
+
+        public static string ToString(double value)
+        {
+            return value.ToString(CultureInfo.CurrentCulture);
+        }
+
+        public static string ToString(double value, IFormatProvider provider)
+        {
+            return value.ToString(provider);
+        }
+
+        public static string ToString(decimal value)
+        {
+            return value.ToString(CultureInfo.CurrentCulture);
+        }
+
+        public static string ToString(Decimal value, IFormatProvider provider)
+        {
+            return value.ToString(provider);
+        }
+
+        public static string ToString(DateTime value)
+        {
+            return value.ToString();
+        }
+
+        public static string ToString(DateTime value, IFormatProvider provider)
+        {
+            return value.ToString(provider);
+        }
+
+        public static String ToString(String value)
+        {
+            return value;
+        }
+
+        public static String ToString(String value, IFormatProvider provider)
+        {
+            return value; // avoid the null check
+        }
+
+
+        //
+        // Conversions which understand Base XXX numbers.
+        //
+        // Parses value in base base.  base can only
+        // be 2, 8, 10, or 16.  If base is 16, the number may be preceded
+        // by 0x; any other leading or trailing characters cause an error.
+        //
+        public static byte ToByte(String value, int fromBase)
+        {
+            if (fromBase != 2 && fromBase != 8 && fromBase != 10 && fromBase != 16)
+            {
+                throw new ArgumentException(SR.Arg_InvalidBase);
+            }
+
+            if (value == null)
+            {
+                return 0;
+            }
+
+            int r = ParseNumbers.StringToInt(value.AsSpan(), fromBase, ParseNumbers.IsTight | ParseNumbers.TreatAsUnsigned);
+            if (r < Byte.MinValue || r > Byte.MaxValue)
+                ThrowByteOverflowException();
+            return (byte)r;
+        }
+
+        // Parses value in base fromBase.  fromBase can only
+        // be 2, 8, 10, or 16.  If fromBase is 16, the number may be preceded
+        // by 0x; any other leading or trailing characters cause an error.
+        //
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(String value, int fromBase)
+        {
+            if (fromBase != 2 && fromBase != 8 && fromBase != 10 && fromBase != 16)
+            {
+                throw new ArgumentException(SR.Arg_InvalidBase);
+            }
+
+            if (value == null)
+            {
+                return 0;
+            }
+
+            int r = ParseNumbers.StringToInt(value.AsSpan(), fromBase, ParseNumbers.IsTight | ParseNumbers.TreatAsI1);
+            if (fromBase != 10 && r <= Byte.MaxValue)
+                return (sbyte)r;
+
+            if (r < SByte.MinValue || r > SByte.MaxValue)
+                ThrowSByteOverflowException();
+            return (sbyte)r;
+        }
+
+        // Parses value in base fromBase.  fromBase can only
+        // be 2, 8, 10, or 16.  If fromBase is 16, the number may be preceded
+        // by 0x; any other leading or trailing characters cause an error.
+        //
+        public static short ToInt16(String value, int fromBase)
+        {
+            if (fromBase != 2 && fromBase != 8 && fromBase != 10 && fromBase != 16)
+            {
+                throw new ArgumentException(SR.Arg_InvalidBase);
+            }
+
+            if (value == null)
+            {
+                return 0;
+            }
+
+            int r = ParseNumbers.StringToInt(value.AsSpan(), fromBase, ParseNumbers.IsTight | ParseNumbers.TreatAsI2);
+            if (fromBase != 10 && r <= UInt16.MaxValue)
+                return (short)r;
+
+            if (r < Int16.MinValue || r > Int16.MaxValue)
+                ThrowInt16OverflowException();
+            return (short)r;
+        }
+
+        // Parses value in base fromBase.  fromBase can only
+        // be 2, 8, 10, or 16.  If fromBase is 16, the number may be preceded
+        // by 0x; any other leading or trailing characters cause an error.
+        //
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(String value, int fromBase)
+        {
+            if (fromBase != 2 && fromBase != 8 && fromBase != 10 && fromBase != 16)
+            {
+                throw new ArgumentException(SR.Arg_InvalidBase);
+            }
+
+            if (value == null)
+            {
+                return 0;
+            }
+
+            int r = ParseNumbers.StringToInt(value.AsSpan(), fromBase, ParseNumbers.IsTight | ParseNumbers.TreatAsUnsigned);
+            if (r < UInt16.MinValue || r > UInt16.MaxValue)
+                ThrowUInt16OverflowException();
+            return (ushort)r;
+        }
+
+        // Parses value in base fromBase.  fromBase can only
+        // be 2, 8, 10, or 16.  If fromBase is 16, the number may be preceded
+        // by 0x; any other leading or trailing characters cause an error.
+        //
+        public static int ToInt32(String value, int fromBase)
+        {
+            if (fromBase != 2 && fromBase != 8 && fromBase != 10 && fromBase != 16)
+            {
+                throw new ArgumentException(SR.Arg_InvalidBase);
+            }
+            return value != null ?
+                ParseNumbers.StringToInt(value.AsSpan(), fromBase, ParseNumbers.IsTight) :
+                0;
+        }
+
+        // Parses value in base fromBase.  fromBase can only
+        // be 2, 8, 10, or 16.  If fromBase is 16, the number may be preceded
+        // by 0x; any other leading or trailing characters cause an error.
+        //
+        [CLSCompliant(false)]
+        public static uint ToUInt32(String value, int fromBase)
+        {
+            if (fromBase != 2 && fromBase != 8 && fromBase != 10 && fromBase != 16)
+            {
+                throw new ArgumentException(SR.Arg_InvalidBase);
+            }
+            return value != null ?
+                (uint)ParseNumbers.StringToInt(value.AsSpan(), fromBase, ParseNumbers.TreatAsUnsigned | ParseNumbers.IsTight) :
+                0;
+        }
+
+        // Parses value in base fromBase.  fromBase can only
+        // be 2, 8, 10, or 16.  If fromBase is 16, the number may be preceded
+        // by 0x; any other leading or trailing characters cause an error.
+        //
+        public static long ToInt64(String value, int fromBase)
+        {
+            if (fromBase != 2 && fromBase != 8 && fromBase != 10 && fromBase != 16)
+            {
+                throw new ArgumentException(SR.Arg_InvalidBase);
+            }
+            return value != null ?
+                ParseNumbers.StringToLong(value.AsSpan(), fromBase, ParseNumbers.IsTight) :
+                0;
+        }
+
+        // Parses value in base fromBase.  fromBase can only
+        // be 2, 8, 10, or 16.  If fromBase is 16, the number may be preceded
+        // by 0x; any other leading or trailing characters cause an error.
+        //
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(String value, int fromBase)
+        {
+            if (fromBase != 2 && fromBase != 8 && fromBase != 10 && fromBase != 16)
+            {
+                throw new ArgumentException(SR.Arg_InvalidBase);
+            }
+            return value != null ?
+                (ulong)ParseNumbers.StringToLong(value.AsSpan(), fromBase, ParseNumbers.TreatAsUnsigned | ParseNumbers.IsTight) :
+                0;
+        }
+
+        // Convert the byte value to a string in base fromBase
+        public static String ToString(byte value, int toBase)
+        {
+            if (toBase != 2 && toBase != 8 && toBase != 10 && toBase != 16)
+            {
+                throw new ArgumentException(SR.Arg_InvalidBase);
+            }
+            return ParseNumbers.IntToString((int)value, toBase, -1, ' ', ParseNumbers.PrintAsI1);
+        }
+
+        // Convert the Int16 value to a string in base fromBase
+        public static String ToString(short value, int toBase)
+        {
+            if (toBase != 2 && toBase != 8 && toBase != 10 && toBase != 16)
+            {
+                throw new ArgumentException(SR.Arg_InvalidBase);
+            }
+            return ParseNumbers.IntToString((int)value, toBase, -1, ' ', ParseNumbers.PrintAsI2);
+        }
+
+        // Convert the Int32 value to a string in base toBase
+        public static String ToString(int value, int toBase)
+        {
+            if (toBase != 2 && toBase != 8 && toBase != 10 && toBase != 16)
+            {
+                throw new ArgumentException(SR.Arg_InvalidBase);
+            }
+            return ParseNumbers.IntToString(value, toBase, -1, ' ', 0);
+        }
+
+        // Convert the Int64 value to a string in base toBase
+        public static String ToString(long value, int toBase)
+        {
+            if (toBase != 2 && toBase != 8 && toBase != 10 && toBase != 16)
+            {
+                throw new ArgumentException(SR.Arg_InvalidBase);
+            }
+            return ParseNumbers.LongToString(value, toBase, -1, ' ', 0);
+        }
+
+        public static String ToBase64String(byte[] inArray)
+        {
+            if (inArray == null)
+            {
+                throw new ArgumentNullException(nameof(inArray));
+            }
+            return ToBase64String(new ReadOnlySpan<byte>(inArray), Base64FormattingOptions.None);
+        }
+
+        public static String ToBase64String(byte[] inArray, Base64FormattingOptions options)
+        {
+            if (inArray == null)
+            {
+                throw new ArgumentNullException(nameof(inArray));
+            }
+            return ToBase64String(new ReadOnlySpan<byte>(inArray), options);
+        }
+
+        public static String ToBase64String(byte[] inArray, int offset, int length)
+        {
+            return ToBase64String(inArray, offset, length, Base64FormattingOptions.None);
+        }
+
+        public static String ToBase64String(byte[] inArray, int offset, int length, Base64FormattingOptions options)
+        {
+            if (inArray == null)
+                throw new ArgumentNullException(nameof(inArray));
+            if (length < 0)
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_Index);
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_GenericPositive);
+            if (offset > (inArray.Length - length))
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_OffsetLength);
+
+            return ToBase64String(new ReadOnlySpan<byte>(inArray, offset, length), options);
+        }
+
+        public static string ToBase64String(ReadOnlySpan<byte> bytes, Base64FormattingOptions options = Base64FormattingOptions.None)
+        {
+            if (options < Base64FormattingOptions.None || options > Base64FormattingOptions.InsertLineBreaks)
+            {
+                throw new ArgumentException(string.Format(SR.Arg_EnumIllegalVal, (int)options), nameof(options));
+            }
+
+            if (bytes.Length == 0)
+            {
+                return string.Empty;
+            }
+
+            bool insertLineBreaks = (options == Base64FormattingOptions.InsertLineBreaks);
+            string result = string.FastAllocateString(ToBase64_CalculateAndValidateOutputLength(bytes.Length, insertLineBreaks));
+
+            unsafe
+            {
+                fixed (byte* bytesPtr = &MemoryMarshal.GetReference(bytes))
+                fixed (char* charsPtr = result)
+                {
+                    int charsWritten = ConvertToBase64Array(charsPtr, bytesPtr, 0, bytes.Length, insertLineBreaks);
+                    Debug.Assert(result.Length == charsWritten, $"Expected {result.Length} == {charsWritten}");
+                }
+            }
+
+            return result;
+        }
+
+        public static int ToBase64CharArray(byte[] inArray, int offsetIn, int length, char[] outArray, int offsetOut)
+        {
+            return ToBase64CharArray(inArray, offsetIn, length, outArray, offsetOut, Base64FormattingOptions.None);
+        }
+
+        public static unsafe int ToBase64CharArray(byte[] inArray, int offsetIn, int length, char[] outArray, int offsetOut, Base64FormattingOptions options)
+        {
+            //Do data verfication
+            if (inArray == null)
+                throw new ArgumentNullException(nameof(inArray));
+            if (outArray == null)
+                throw new ArgumentNullException(nameof(outArray));
+            if (length < 0)
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_Index);
+            if (offsetIn < 0)
+                throw new ArgumentOutOfRangeException(nameof(offsetIn), SR.ArgumentOutOfRange_GenericPositive);
+            if (offsetOut < 0)
+                throw new ArgumentOutOfRangeException(nameof(offsetOut), SR.ArgumentOutOfRange_GenericPositive);
+
+            if (options < Base64FormattingOptions.None || options > Base64FormattingOptions.InsertLineBreaks)
+            {
+                throw new ArgumentException(string.Format(SR.Arg_EnumIllegalVal, (int)options), nameof(options));
+            }
+
+
+            int retVal;
+
+            int inArrayLength;
+            int outArrayLength;
+            int numElementsToCopy;
+
+            inArrayLength = inArray.Length;
+
+            if (offsetIn > (int)(inArrayLength - length))
+                throw new ArgumentOutOfRangeException(nameof(offsetIn), SR.ArgumentOutOfRange_OffsetLength);
+
+            if (inArrayLength == 0)
+                return 0;
+
+            bool insertLineBreaks = (options == Base64FormattingOptions.InsertLineBreaks);
+            //This is the maximally required length that must be available in the char array
+            outArrayLength = outArray.Length;
+
+            // Length of the char buffer required
+            numElementsToCopy = ToBase64_CalculateAndValidateOutputLength(length, insertLineBreaks);
+
+            if (offsetOut > (int)(outArrayLength - numElementsToCopy))
+                throw new ArgumentOutOfRangeException(nameof(offsetOut), SR.ArgumentOutOfRange_OffsetOut);
+
+            fixed (char* outChars = &outArray[offsetOut])
+            {
+                fixed (byte* inData = &inArray[0])
+                {
+                    retVal = ConvertToBase64Array(outChars, inData, offsetIn, length, insertLineBreaks);
+                }
+            }
+
+            return retVal;
+        }
+
+        public static unsafe bool TryToBase64Chars(ReadOnlySpan<byte> bytes, Span<char> chars, out int charsWritten, Base64FormattingOptions options = Base64FormattingOptions.None)
+        {
+            if (options < Base64FormattingOptions.None || options > Base64FormattingOptions.InsertLineBreaks)
+            {
+                throw new ArgumentException(string.Format(SR.Arg_EnumIllegalVal, (int)options), nameof(options));
+            }
+
+            if (bytes.Length == 0)
+            {
+                charsWritten = 0;
+                return true;
+            }
+
+            bool insertLineBreaks = (options == Base64FormattingOptions.InsertLineBreaks);
+
+            int charLengthRequired = ToBase64_CalculateAndValidateOutputLength(bytes.Length, insertLineBreaks);
+            if (charLengthRequired > chars.Length)
+            {
+                charsWritten = 0;
+                return false;
+            }
+
+            fixed (char* outChars = &MemoryMarshal.GetReference(chars))
+            fixed (byte* inData = &MemoryMarshal.GetReference(bytes))
+            {
+                charsWritten = ConvertToBase64Array(outChars, inData, 0, bytes.Length, insertLineBreaks);
+                return true;
+            }
+        }
+
+        private static unsafe int ConvertToBase64Array(char* outChars, byte* inData, int offset, int length, bool insertLineBreaks)
+        {
+            int lengthmod3 = length % 3;
+            int calcLength = offset + (length - lengthmod3);
+            int j = 0;
+            int charcount = 0;
+            //Convert three bytes at a time to base64 notation.  This will consume 4 chars.
+            int i;
+
+            // get a pointer to the base64Table to avoid unnecessary range checking
+            fixed (char* base64 = &base64Table[0])
+            {
+                for (i = offset; i < calcLength; i += 3)
+                {
+                    if (insertLineBreaks)
+                    {
+                        if (charcount == base64LineBreakPosition)
+                        {
+                            outChars[j++] = '\r';
+                            outChars[j++] = '\n';
+                            charcount = 0;
+                        }
+                        charcount += 4;
+                    }
+                    outChars[j] = base64[(inData[i] & 0xfc) >> 2];
+                    outChars[j + 1] = base64[((inData[i] & 0x03) << 4) | ((inData[i + 1] & 0xf0) >> 4)];
+                    outChars[j + 2] = base64[((inData[i + 1] & 0x0f) << 2) | ((inData[i + 2] & 0xc0) >> 6)];
+                    outChars[j + 3] = base64[(inData[i + 2] & 0x3f)];
+                    j += 4;
+                }
+
+                //Where we left off before
+                i = calcLength;
+
+                if (insertLineBreaks && (lengthmod3 != 0) && (charcount == base64LineBreakPosition))
+                {
+                    outChars[j++] = '\r';
+                    outChars[j++] = '\n';
+                }
+
+                switch (lengthmod3)
+                {
+                    case 2: //One character padding needed
+                        outChars[j] = base64[(inData[i] & 0xfc) >> 2];
+                        outChars[j + 1] = base64[((inData[i] & 0x03) << 4) | ((inData[i + 1] & 0xf0) >> 4)];
+                        outChars[j + 2] = base64[(inData[i + 1] & 0x0f) << 2];
+                        outChars[j + 3] = base64[64]; //Pad
+                        j += 4;
+                        break;
+                    case 1: // Two character padding needed
+                        outChars[j] = base64[(inData[i] & 0xfc) >> 2];
+                        outChars[j + 1] = base64[(inData[i] & 0x03) << 4];
+                        outChars[j + 2] = base64[64]; //Pad
+                        outChars[j + 3] = base64[64]; //Pad
+                        j += 4;
+                        break;
+                }
+            }
+
+            return j;
+        }
+
+        private static int ToBase64_CalculateAndValidateOutputLength(int inputLength, bool insertLineBreaks)
+        {
+            long outlen = ((long)inputLength) / 3 * 4;          // the base length - we want integer division here. 
+            outlen += ((inputLength % 3) != 0) ? 4 : 0;         // at most 4 more chars for the remainder
+
+            if (outlen == 0)
+                return 0;
+
+            if (insertLineBreaks)
+            {
+                long newLines = outlen / base64LineBreakPosition;
+                if ((outlen % base64LineBreakPosition) == 0)
+                {
+                    --newLines;
+                }
+                outlen += newLines * 2;              // the number of line break chars we'll add, "\r\n"
+            }
+
+            // If we overflow an int then we cannot allocate enough
+            // memory to output the value so throw
+            if (outlen > int.MaxValue)
+                throw new OutOfMemoryException();
+
+            return (int)outlen;
+        }
+
+
+        /// <summary>
+        /// Converts the specified string, which encodes binary data as Base64 digits, to the equivalent byte array.
+        /// </summary>
+        /// <param name="s">The string to convert</param>
+        /// <returns>The array of bytes represented by the specified Base64 string.</returns>
+        public static Byte[] FromBase64String(String s)
+        {
+            // "s" is an unfortunate parameter name, but we need to keep it for backward compat.
+
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+
+
+            unsafe
+            {
+                fixed (Char* sPtr = s)
+                {
+                    return FromBase64CharPtr(sPtr, s.Length);
+                }
+            }
+        }
+
+        public static bool TryFromBase64String(string s, Span<byte> bytes, out int bytesWritten)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+
+            return TryFromBase64Chars(s.AsSpan(), bytes, out bytesWritten);
+        }
+
+        public static bool TryFromBase64Chars(ReadOnlySpan<char> chars, Span<byte> bytes, out int bytesWritten)
+        {
+            // This is actually local to one of the nested blocks but is being declared at the top as we don't want multiple stackallocs
+            // for each iteraton of the loop. 
+            Span<char> tempBuffer = stackalloc char[4];  // Note: The tempBuffer size could be made larger than 4 but the size must be a multiple of 4.
+
+            bytesWritten = 0;
+
+            while (chars.Length != 0)
+            {
+                // Attempt to decode a segment that doesn't contain whitespace.
+                bool complete = TryDecodeFromUtf16(chars, bytes, out int consumedInThisIteration, out int bytesWrittenInThisIteration);
+                bytesWritten += bytesWrittenInThisIteration;
+                if (complete)
+                    return true;
+
+                chars = chars.Slice(consumedInThisIteration);
+                bytes = bytes.Slice(bytesWrittenInThisIteration);
+
+                Debug.Assert(chars.Length != 0); // If TryDecodeFromUtf16() consumed the entire buffer, it could not have returned false.
+                if (chars[0].IsSpace())
+                {
+                    // If we got here, the very first character not consumed was a whitespace. We can skip past any consecutive whitespace, then continue decoding.
+
+                    int indexOfFirstNonSpace = 1;
+                    for (; ; )
+                    {
+                        if (indexOfFirstNonSpace == chars.Length)
+                            break;
+                        if (!chars[indexOfFirstNonSpace].IsSpace())
+                            break;
+                        indexOfFirstNonSpace++;
+                    }
+
+                    chars = chars.Slice(indexOfFirstNonSpace);
+
+                    if ((bytesWrittenInThisIteration % 3) != 0 && chars.Length != 0)
+                    {
+                        // If we got here, the last successfully decoded block encountered an end-marker, yet we have trailing non-whitespace characters.
+                        // That is not allowed.
+                        bytesWritten = default;
+                        return false;
+                    }
+
+                    // We now loop again to decode the next run of non-space characters. 
+                }
+                else
+                {
+                    Debug.Assert(chars.Length != 0 && !chars[0].IsSpace());
+
+                    // If we got here, it is possible that there is whitespace that occurred in the middle of a 4-byte chunk. That is, we still have
+                    // up to three Base64 characters that were left undecoded by the fast-path helper because they didn't form a complete 4-byte chunk.
+                    // This is hopefully the rare case (multiline-formatted base64 message with a non-space character width that's not a multiple of 4.)
+                    // We'll filter out whitespace and copy the remaining characters into a temporary buffer.
+                    CopyToTempBufferWithoutWhiteSpace(chars, tempBuffer, out int consumedFromChars, out int charsWritten);
+                    if ((charsWritten & 0x3) != 0)
+                    {
+                        // Even after stripping out whitespace, the number of characters is not divisible by 4. This cannot be a legal Base64 string.
+                        bytesWritten = default;
+                        return false;
+                    }
+
+                    tempBuffer = tempBuffer.Slice(0, charsWritten);
+                    if (!TryDecodeFromUtf16(tempBuffer, bytes, out int consumedFromTempBuffer, out int bytesWrittenFromTempBuffer))
+                    {
+                        bytesWritten = default;
+                        return false;
+                    }
+                    bytesWritten += bytesWrittenFromTempBuffer;
+                    chars = chars.Slice(consumedFromChars);
+                    bytes = bytes.Slice(bytesWrittenFromTempBuffer);
+
+                    if ((bytesWrittenFromTempBuffer % 3) != 0)
+                    {
+                        // If we got here, this decode contained one or more padding characters ('='). We can accept trailing whitespace after this
+                        // but nothing else.
+                        for (int i = 0; i < chars.Length; i++)
+                        {
+                            if (!chars[i].IsSpace())
+                            {
+                                bytesWritten = default;
+                                return false;
+                            }
+                        }
+                        return true;
+                    }
+
+                    // We now loop again to decode the next run of non-space characters. 
+                }
+            }
+
+            return true;
+        }
+
+        private static void CopyToTempBufferWithoutWhiteSpace(ReadOnlySpan<char> chars, Span<char> tempBuffer, out int consumed, out int charsWritten)
+        {
+            Debug.Assert(tempBuffer.Length != 0); // We only bound-check after writing a character to the tempBuffer.
+
+            charsWritten = 0;
+            for (int i = 0; i < chars.Length; i++)
+            {
+                char c = chars[i];
+                if (!c.IsSpace())
+                {
+                    tempBuffer[charsWritten++] = c;
+                    if (charsWritten == tempBuffer.Length)
+                    {
+                        consumed = i + 1;
+                        return;
+                    }
+                }
+            }
+            consumed = chars.Length;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static bool IsSpace(this char c) => c == ' ' || c == '\t' || c == '\r' || c == '\n';
+
+        /// <summary>
+        /// Converts the specified range of a Char array, which encodes binary data as Base64 digits, to the equivalent byte array.     
+        /// </summary>
+        /// <param name="inArray">Chars representing Base64 encoding characters</param>
+        /// <param name="offset">A position within the input array.</param>
+        /// <param name="length">Number of element to convert.</param>
+        /// <returns>The array of bytes represented by the specified Base64 encoding characters.</returns>
+        public static Byte[] FromBase64CharArray(Char[] inArray, Int32 offset, Int32 length)
+        {
+            if (inArray == null)
+                throw new ArgumentNullException(nameof(inArray));
+
+            if (length < 0)
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_Index);
+
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_GenericPositive);
+
+            if (offset > inArray.Length - length)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_OffsetLength);
+
+
+            if (inArray.Length == 0)
+            {
+                return Array.Empty<byte>();
+            }
+
+            unsafe
+            {
+                fixed (Char* inArrayPtr = &inArray[0])
+                {
+                    return FromBase64CharPtr(inArrayPtr + offset, length);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Convert Base64 encoding characters to bytes:
+        ///  - Compute result length exactly by actually walking the input;
+        ///  - Allocate new result array based on computation;
+        ///  - Decode input into the new array;
+        /// </summary>
+        /// <param name="inputPtr">Pointer to the first input char</param>
+        /// <param name="inputLength">Number of input chars</param>
+        /// <returns></returns>
+        private static unsafe Byte[] FromBase64CharPtr(Char* inputPtr, Int32 inputLength)
+        {
+            // The validity of parameters much be checked by callers, thus we are Critical here.
+
+            Debug.Assert(0 <= inputLength);
+
+            // We need to get rid of any trailing white spaces.
+            // Otherwise we would be rejecting input such as "abc= ":
+            while (inputLength > 0)
+            {
+                Int32 lastChar = inputPtr[inputLength - 1];
+                if (lastChar != (Int32)' ' && lastChar != (Int32)'\n' && lastChar != (Int32)'\r' && lastChar != (Int32)'\t')
+                    break;
+                inputLength--;
+            }
+
+            // Compute the output length:
+            Int32 resultLength = FromBase64_ComputeResultLength(inputPtr, inputLength);
+
+            Debug.Assert(0 <= resultLength);
+
+            // resultLength can be zero. We will still enter FromBase64_Decode and process the input.
+            // It may either simply write no bytes (e.g. input = " ") or throw (e.g. input = "ab").
+
+            // Create result byte blob:
+            Byte[] decodedBytes = new Byte[resultLength];
+
+            // Convert Base64 chars into bytes:
+            if (!TryFromBase64Chars(new ReadOnlySpan<char>(inputPtr, inputLength), decodedBytes, out int _))
+                throw new FormatException(SR.Format_BadBase64Char);
+
+            // Note that the number of bytes written can differ from resultLength if the caller is modifying the array
+            // as it is being converted. Silently ignore the failure.
+            // Consider throwing exception in an non in-place release.
+
+            // We are done:
+            return decodedBytes;
+        }
+
+        /// <summary>
+        /// Compute the number of bytes encoded in the specified Base 64 char array:
+        /// Walk the entire input counting white spaces and padding chars, then compute result length
+        /// based on 3 bytes per 4 chars.
+        /// </summary>
+        private static unsafe Int32 FromBase64_ComputeResultLength(Char* inputPtr, Int32 inputLength)
+        {
+            const UInt32 intEq = (UInt32)'=';
+            const UInt32 intSpace = (UInt32)' ';
+
+            Debug.Assert(0 <= inputLength);
+
+            Char* inputEndPtr = inputPtr + inputLength;
+            Int32 usefulInputLength = inputLength;
+            Int32 padding = 0;
+
+            while (inputPtr < inputEndPtr)
+            {
+                UInt32 c = (UInt32)(*inputPtr);
+                inputPtr++;
+
+                // We want to be as fast as possible and filter out spaces with as few comparisons as possible.
+                // We end up accepting a number of illegal chars as legal white-space chars.
+                // This is ok: as soon as we hit them during actual decode we will recognise them as illegal and throw.
+                if (c <= intSpace)
+                    usefulInputLength--;
+
+                else if (c == intEq)
+                {
+                    usefulInputLength--;
+                    padding++;
+                }
+            }
+
+            Debug.Assert(0 <= usefulInputLength);
+
+            // For legal input, we can assume that 0 <= padding < 3. But it may be more for illegal input.
+            // We will notice it at decode when we see a '=' at the wrong place.
+            Debug.Assert(0 <= padding);
+
+            // Perf: reuse the variable that stored the number of '=' to store the number of bytes encoded by the
+            // last group that contains the '=':
+            if (padding != 0)
+            {
+                if (padding == 1)
+                    padding = 2;
+                else if (padding == 2)
+                    padding = 1;
+                else
+                    throw new FormatException(SR.Format_BadBase64Char);
+            }
+
+            // Done:
+            return (usefulInputLength / 4) * 3 + padding;
+        }
+    }  // class Convert
+}  // namespace
+
diff --git a/src/System.Private.CoreLib/shared/System/CurrentSystemTimeZone.cs b/src/System.Private.CoreLib/shared/System/CurrentSystemTimeZone.cs
new file mode 100644
index 0000000000..bab6a92bf5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/CurrentSystemTimeZone.cs
@@ -0,0 +1,197 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: 
+** This class represents the current system timezone.  It is
+** the only meaningful implementation of the TimeZone class 
+** available in this version.
+**
+** The only TimeZone that we support in version 1 is the 
+** CurrentTimeZone as determined by the system timezone.
+**
+**
+============================================================*/
+
+using System;
+using System.Text;
+using System.Collections;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    [Obsolete("System.CurrentSystemTimeZone has been deprecated.  Please investigate the use of System.TimeZoneInfo.Local instead.")]
+    internal partial class CurrentSystemTimeZone : TimeZone
+    {
+        // Standard offset in ticks to the Universal time if
+        // no daylight saving is in used.
+        // E.g. the offset for PST (Pacific Standard time) should be -8 * 60 * 60 * 1000 * 10000.
+        // (1 millisecond = 10000 ticks)
+        private long m_ticksOffset;
+        private String m_standardName;
+        private String m_daylightName;
+
+        internal CurrentSystemTimeZone()
+        {
+            TimeZoneInfo local = TimeZoneInfo.Local;
+
+            m_ticksOffset = local.BaseUtcOffset.Ticks;
+            m_standardName = local.StandardName;
+            m_daylightName = local.DaylightName;
+        }
+
+        public override String StandardName
+        {
+            get
+            {
+                return m_standardName;
+            }
+        }
+
+        public override String DaylightName
+        {
+            get
+            {
+                return m_daylightName;
+            }
+        }
+
+        internal long GetUtcOffsetFromUniversalTime(DateTime time, ref Boolean isAmbiguousLocalDst)
+        {
+            // Get the daylight changes for the year of the specified time.
+            TimeSpan offset = new TimeSpan(m_ticksOffset);
+            DaylightTime daylightTime = GetDaylightChanges(time.Year);
+            isAmbiguousLocalDst = false;
+
+            if (daylightTime == null || daylightTime.Delta.Ticks == 0)
+            {
+                return offset.Ticks;
+            }
+
+            // The start and end times represent the range of universal times that are in DST for that year.                
+            // Within that there is an ambiguous hour, usually right at the end, but at the beginning in
+            // the unusual case of a negative daylight savings delta.
+            DateTime startTime = daylightTime.Start - offset;
+            DateTime endTime = daylightTime.End - offset - daylightTime.Delta;
+            DateTime ambiguousStart;
+            DateTime ambiguousEnd;
+
+            if (daylightTime.Delta.Ticks > 0)
+            {
+                ambiguousStart = endTime - daylightTime.Delta;
+                ambiguousEnd = endTime;
+            }
+            else
+            {
+                ambiguousStart = startTime;
+                ambiguousEnd = startTime - daylightTime.Delta;
+            }
+
+            Boolean isDst = false;
+            if (startTime > endTime)
+            {
+                // In southern hemisphere, the daylight saving time starts later in the year, and ends in the beginning of next year.
+                // Note, the summer in the southern hemisphere begins late in the year.
+                isDst = (time < endTime || time >= startTime);
+            }
+            else
+            {
+                // In northern hemisphere, the daylight saving time starts in the middle of the year.
+                isDst = (time >= startTime && time < endTime);
+            }
+
+            if (isDst)
+            {
+                offset += daylightTime.Delta;
+
+                // See if the resulting local time becomes ambiguous. This must be captured here or the
+                // DateTime will not be able to round-trip back to UTC accurately.
+                if (time >= ambiguousStart && time < ambiguousEnd)
+                {
+                    isAmbiguousLocalDst = true;
+                }
+            }
+            return offset.Ticks;
+        }
+
+        public override DateTime ToLocalTime(DateTime time)
+        {
+            if (time.Kind == DateTimeKind.Local)
+            {
+                return time;
+            }
+            Boolean isAmbiguousLocalDst = false;
+            Int64 offset = GetUtcOffsetFromUniversalTime(time, ref isAmbiguousLocalDst);
+            long tick = time.Ticks + offset;
+            if (tick > DateTime.MaxTicks)
+            {
+                return new DateTime(DateTime.MaxTicks, DateTimeKind.Local);
+            }
+            if (tick < DateTime.MinTicks)
+            {
+                return new DateTime(DateTime.MinTicks, DateTimeKind.Local);
+            }
+            return new DateTime(tick, DateTimeKind.Local, isAmbiguousLocalDst);
+        }
+
+        public override DaylightTime GetDaylightChanges(int year)
+        {
+            if (year < 1 || year > 9999)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year), SR.Format(SR.ArgumentOutOfRange_Range, 1, 9999));
+            }
+
+            return GetCachedDaylightChanges(year);
+        }
+
+        private static DaylightTime CreateDaylightChanges(int year)
+        {
+            DaylightTime currentDaylightChanges = null;
+
+            if (TimeZoneInfo.Local.SupportsDaylightSavingTime)
+            {
+                DateTime start;
+                DateTime end;
+                TimeSpan delta;
+
+                foreach (var rule in TimeZoneInfo.Local.GetAdjustmentRules())
+                {
+                    if (rule.DateStart.Year <= year && rule.DateEnd.Year >= year && rule.DaylightDelta != TimeSpan.Zero)
+                    {
+                        start = TimeZoneInfo.TransitionTimeToDateTime(year, rule.DaylightTransitionStart);
+                        end = TimeZoneInfo.TransitionTimeToDateTime(year, rule.DaylightTransitionEnd);
+                        delta = rule.DaylightDelta;
+
+                        currentDaylightChanges = new DaylightTime(start, end, delta);
+                        break;
+                    }
+                }
+            }
+
+            if (currentDaylightChanges == null)
+            {
+                currentDaylightChanges = new DaylightTime(DateTime.MinValue, DateTime.MinValue, TimeSpan.Zero);
+            }
+
+            return currentDaylightChanges;
+        }
+
+        public override TimeSpan GetUtcOffset(DateTime time)
+        {
+            if (time.Kind == DateTimeKind.Utc)
+            {
+                return TimeSpan.Zero;
+            }
+            else
+            {
+                return new TimeSpan(TimeZone.CalculateUtcOffset(time, GetDaylightChanges(time.Year)).Ticks + m_ticksOffset);
+            }
+        }
+    } // class CurrentSystemTimeZone
+}
diff --git a/src/System.Private.CoreLib/shared/System/DBNull.cs b/src/System.Private.CoreLib/shared/System/DBNull.cs
new file mode 100644
index 0000000000..3cee2b15c8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/DBNull.cs
@@ -0,0 +1,119 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    public sealed class DBNull : ISerializable, IConvertible
+    {
+        private DBNull()
+        {
+        }
+
+        private DBNull(SerializationInfo info, StreamingContext context)
+        {
+            throw new NotSupportedException(SR.NotSupported_DBNullSerial);
+        }
+
+        public static readonly DBNull Value = new DBNull();
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            UnitySerializationHolder.GetUnitySerializationInfo(info, UnitySerializationHolder.NullUnity);
+        }
+
+        public override string ToString()
+        {
+            return string.Empty;
+        }
+
+        public string ToString(IFormatProvider provider)
+        {
+            return string.Empty;
+        }
+
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.DBNull;
+        }
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.InvalidCast_FromDBNull);
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.InvalidCast_FromDBNull);
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.InvalidCast_FromDBNull);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.InvalidCast_FromDBNull);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.InvalidCast_FromDBNull);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.InvalidCast_FromDBNull);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.InvalidCast_FromDBNull);
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.InvalidCast_FromDBNull);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.InvalidCast_FromDBNull);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.InvalidCast_FromDBNull);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.InvalidCast_FromDBNull);
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.InvalidCast_FromDBNull);
+        }
+
+        decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.InvalidCast_FromDBNull);
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.InvalidCast_FromDBNull);
+        }
+
+        object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/DataMisalignedException.cs b/src/System.Private.CoreLib/shared/System/DataMisalignedException.cs
new file mode 100644
index 0000000000..2a245b6ef7
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/DataMisalignedException.cs
@@ -0,0 +1,42 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+** Purpose: The exception class for a misaligned access exception
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class DataMisalignedException : SystemException
+    {
+        public DataMisalignedException()
+            : base(SR.Arg_DataMisalignedException)
+        {
+            HResult = HResults.COR_E_DATAMISALIGNED;
+        }
+
+        public DataMisalignedException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_DATAMISALIGNED;
+        }
+
+        public DataMisalignedException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_DATAMISALIGNED;
+        }
+
+        internal DataMisalignedException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/DateTime.cs b/src/System.Private.CoreLib/shared/System/DateTime.cs
new file mode 100644
index 0000000000..9c3b3989e4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/DateTime.cs
@@ -0,0 +1,1586 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+using System.Threading;
+using System.Globalization;
+using System.Runtime;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Runtime.Serialization;
+using System.Runtime.Versioning;
+using System.Security;
+using CultureInfo = System.Globalization.CultureInfo;
+using Calendar = System.Globalization.Calendar;
+
+namespace System
+{
+    // This value type represents a date and time.  Every DateTime 
+    // object has a private field (Ticks) of type Int64 that stores the 
+    // date and time as the number of 100 nanosecond intervals since 
+    // 12:00 AM January 1, year 1 A.D. in the proleptic Gregorian Calendar.
+    //
+    // Starting from V2.0, DateTime also stored some context about its time
+    // zone in the form of a 3-state value representing Unspecified, Utc or
+    // Local. This is stored in the two top bits of the 64-bit numeric value
+    // with the remainder of the bits storing the tick count. This information 
+    // is only used during time zone conversions and is not part of the 
+    // identity of the DateTime. Thus, operations like Compare and Equals
+    // ignore this state. This is to stay compatible with earlier behavior
+    // and performance characteristics and to avoid forcing  people into dealing 
+    // with the effects of daylight savings. Note, that this has little effect
+    // on how the DateTime works except in a context where its specific time
+    // zone is needed, such as during conversions and some parsing and formatting
+    // cases.
+    //
+    // There is also 4th state stored that is a special type of Local value that
+    // is used to avoid data loss when round-tripping between local and UTC time.
+    // See below for more information on this 4th state, although it is 
+    // effectively hidden from most users, who just see the 3-state DateTimeKind
+    // enumeration.
+    //
+    // For compatibility, DateTime does not serialize the Kind data when used in
+    // binary serialization.
+    // 
+    // For a description of various calendar issues, look at
+    // 
+    // Calendar Studies web site, at 
+    // http://serendipity.nofadz.com/hermetic/cal_stud.htm.
+    // 
+    // 
+    [StructLayout(LayoutKind.Auto)]
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")] 
+    public readonly partial struct DateTime : IComparable, IFormattable, IConvertible, IComparable<DateTime>, IEquatable<DateTime>, ISerializable, ISpanFormattable
+    {
+        // Number of 100ns ticks per time unit
+        private const long TicksPerMillisecond = 10000;
+        private const long TicksPerSecond = TicksPerMillisecond * 1000;
+        private const long TicksPerMinute = TicksPerSecond * 60;
+        private const long TicksPerHour = TicksPerMinute * 60;
+        private const long TicksPerDay = TicksPerHour * 24;
+
+        // Number of milliseconds per time unit
+        private const int MillisPerSecond = 1000;
+        private const int MillisPerMinute = MillisPerSecond * 60;
+        private const int MillisPerHour = MillisPerMinute * 60;
+        private const int MillisPerDay = MillisPerHour * 24;
+
+        // Number of days in a non-leap year
+        private const int DaysPerYear = 365;
+        // Number of days in 4 years
+        private const int DaysPer4Years = DaysPerYear * 4 + 1;       // 1461
+        // Number of days in 100 years
+        private const int DaysPer100Years = DaysPer4Years * 25 - 1;  // 36524
+        // Number of days in 400 years
+        private const int DaysPer400Years = DaysPer100Years * 4 + 1; // 146097
+
+        // Number of days from 1/1/0001 to 12/31/1600
+        private const int DaysTo1601 = DaysPer400Years * 4;          // 584388
+        // Number of days from 1/1/0001 to 12/30/1899
+        private const int DaysTo1899 = DaysPer400Years * 4 + DaysPer100Years * 3 - 367;
+        // Number of days from 1/1/0001 to 12/31/1969
+        internal const int DaysTo1970 = DaysPer400Years * 4 + DaysPer100Years * 3 + DaysPer4Years * 17 + DaysPerYear; // 719,162
+        // Number of days from 1/1/0001 to 12/31/9999
+        private const int DaysTo10000 = DaysPer400Years * 25 - 366;  // 3652059
+
+        internal const long MinTicks = 0;
+        internal const long MaxTicks = DaysTo10000 * TicksPerDay - 1;
+        private const long MaxMillis = (long)DaysTo10000 * MillisPerDay;
+
+        internal const long UnixEpochTicks = DaysTo1970 * TicksPerDay;
+        private const long FileTimeOffset = DaysTo1601 * TicksPerDay;
+        private const long DoubleDateOffset = DaysTo1899 * TicksPerDay;
+        // The minimum OA date is 0100/01/01 (Note it's year 100).
+        // The maximum OA date is 9999/12/31
+        private const long OADateMinAsTicks = (DaysPer100Years - DaysPerYear) * TicksPerDay;
+        // All OA dates must be greater than (not >=) OADateMinAsDouble
+        private const double OADateMinAsDouble = -657435.0;
+        // All OA dates must be less than (not <=) OADateMaxAsDouble
+        private const double OADateMaxAsDouble = 2958466.0;
+
+        private const int DatePartYear = 0;
+        private const int DatePartDayOfYear = 1;
+        private const int DatePartMonth = 2;
+        private const int DatePartDay = 3;
+
+        private static readonly int[] s_daysToMonth365 = {
+            0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365};
+        private static readonly int[] s_daysToMonth366 = {
+            0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366};
+
+        public static readonly DateTime MinValue = new DateTime(MinTicks, DateTimeKind.Unspecified);
+        public static readonly DateTime MaxValue = new DateTime(MaxTicks, DateTimeKind.Unspecified);
+        public static readonly DateTime UnixEpoch = new DateTime(UnixEpochTicks, DateTimeKind.Utc);
+
+        private const UInt64 TicksMask = 0x3FFFFFFFFFFFFFFF;
+        private const UInt64 FlagsMask = 0xC000000000000000;
+        private const UInt64 LocalMask = 0x8000000000000000;
+        private const Int64 TicksCeiling = 0x4000000000000000;
+        private const UInt64 KindUnspecified = 0x0000000000000000;
+        private const UInt64 KindUtc = 0x4000000000000000;
+        private const UInt64 KindLocal = 0x8000000000000000;
+        private const UInt64 KindLocalAmbiguousDst = 0xC000000000000000;
+        private const Int32 KindShift = 62;
+
+        private const String TicksField = "ticks"; // Do not rename (binary serialization)
+        private const String DateDataField = "dateData"; // Do not rename (binary serialization)
+
+        // The data is stored as an unsigned 64-bit integer
+        //   Bits 01-62: The value of 100-nanosecond ticks where 0 represents 1/1/0001 12:00am, up until the value
+        //               12/31/9999 23:59:59.9999999
+        //   Bits 63-64: A four-state value that describes the DateTimeKind value of the date time, with a 2nd
+        //               value for the rare case where the date time is local, but is in an overlapped daylight
+        //               savings time hour and it is in daylight savings time. This allows distinction of these
+        //               otherwise ambiguous local times and prevents data loss when round tripping from Local to
+        //               UTC time.
+        private readonly UInt64 _dateData;
+
+        // Constructs a DateTime from a tick count. The ticks
+        // argument specifies the date as the number of 100-nanosecond intervals
+        // that have elapsed since 1/1/0001 12:00am.
+        //
+        public DateTime(long ticks)
+        {
+            if (ticks < MinTicks || ticks > MaxTicks)
+                throw new ArgumentOutOfRangeException(nameof(ticks), SR.ArgumentOutOfRange_DateTimeBadTicks);
+            _dateData = (UInt64)ticks;
+        }
+
+        private DateTime(UInt64 dateData)
+        {
+            this._dateData = dateData;
+        }
+
+        public DateTime(long ticks, DateTimeKind kind)
+        {
+            if (ticks < MinTicks || ticks > MaxTicks)
+            {
+                throw new ArgumentOutOfRangeException(nameof(ticks), SR.ArgumentOutOfRange_DateTimeBadTicks);
+            }
+            if (kind < DateTimeKind.Unspecified || kind > DateTimeKind.Local)
+            {
+                throw new ArgumentException(SR.Argument_InvalidDateTimeKind, nameof(kind));
+            }
+            _dateData = ((UInt64)ticks | ((UInt64)kind << KindShift));
+        }
+
+        internal DateTime(long ticks, DateTimeKind kind, Boolean isAmbiguousDst)
+        {
+            if (ticks < MinTicks || ticks > MaxTicks)
+            {
+                throw new ArgumentOutOfRangeException(nameof(ticks), SR.ArgumentOutOfRange_DateTimeBadTicks);
+            }
+            Debug.Assert(kind == DateTimeKind.Local, "Internal Constructor is for local times only");
+            _dateData = ((UInt64)ticks | (isAmbiguousDst ? KindLocalAmbiguousDst : KindLocal));
+        }
+
+        // Constructs a DateTime from a given year, month, and day. The
+        // time-of-day of the resulting DateTime is always midnight.
+        //
+        public DateTime(int year, int month, int day)
+        {
+            _dateData = (UInt64)DateToTicks(year, month, day);
+        }
+
+        // Constructs a DateTime from a given year, month, and day for
+        // the specified calendar. The
+        // time-of-day of the resulting DateTime is always midnight.
+        //
+        public DateTime(int year, int month, int day, Calendar calendar)
+            : this(year, month, day, 0, 0, 0, calendar)
+        {
+        }
+
+        // Constructs a DateTime from a given year, month, day, hour,
+        // minute, and second.
+        //
+        public DateTime(int year, int month, int day, int hour, int minute, int second)
+        {
+            _dateData = (UInt64)(DateToTicks(year, month, day) + TimeToTicks(hour, minute, second));
+        }
+
+        public DateTime(int year, int month, int day, int hour, int minute, int second, DateTimeKind kind)
+        {
+            if (kind < DateTimeKind.Unspecified || kind > DateTimeKind.Local)
+            {
+                throw new ArgumentException(SR.Argument_InvalidDateTimeKind, nameof(kind));
+            }
+            Int64 ticks = DateToTicks(year, month, day) + TimeToTicks(hour, minute, second);
+            _dateData = ((UInt64)ticks | ((UInt64)kind << KindShift));
+        }
+
+        // Constructs a DateTime from a given year, month, day, hour,
+        // minute, and second for the specified calendar.
+        //
+        public DateTime(int year, int month, int day, int hour, int minute, int second, Calendar calendar)
+        {
+            if (calendar == null)
+                throw new ArgumentNullException(nameof(calendar));
+            _dateData = (UInt64)calendar.ToDateTime(year, month, day, hour, minute, second, 0).Ticks;
+        }
+
+        // Constructs a DateTime from a given year, month, day, hour,
+        // minute, and second.
+        //
+        public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond)
+        {
+            if (millisecond < 0 || millisecond >= MillisPerSecond)
+            {
+                throw new ArgumentOutOfRangeException(nameof(millisecond), SR.Format(SR.ArgumentOutOfRange_Range, 0, MillisPerSecond - 1));
+            }
+            Int64 ticks = DateToTicks(year, month, day) + TimeToTicks(hour, minute, second);
+            ticks += millisecond * TicksPerMillisecond;
+            if (ticks < MinTicks || ticks > MaxTicks)
+                throw new ArgumentException(SR.Arg_DateTimeRange);
+            _dateData = (UInt64)ticks;
+        }
+
+        public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, DateTimeKind kind)
+        {
+            if (millisecond < 0 || millisecond >= MillisPerSecond)
+            {
+                throw new ArgumentOutOfRangeException(nameof(millisecond), SR.Format(SR.ArgumentOutOfRange_Range, 0, MillisPerSecond - 1));
+            }
+            if (kind < DateTimeKind.Unspecified || kind > DateTimeKind.Local)
+            {
+                throw new ArgumentException(SR.Argument_InvalidDateTimeKind, nameof(kind));
+            }
+            Int64 ticks = DateToTicks(year, month, day) + TimeToTicks(hour, minute, second);
+            ticks += millisecond * TicksPerMillisecond;
+            if (ticks < MinTicks || ticks > MaxTicks)
+                throw new ArgumentException(SR.Arg_DateTimeRange);
+            _dateData = ((UInt64)ticks | ((UInt64)kind << KindShift));
+        }
+
+        // Constructs a DateTime from a given year, month, day, hour,
+        // minute, and second for the specified calendar.
+        //
+        public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, Calendar calendar)
+        {
+            if (calendar == null)
+                throw new ArgumentNullException(nameof(calendar));
+            if (millisecond < 0 || millisecond >= MillisPerSecond)
+            {
+                throw new ArgumentOutOfRangeException(nameof(millisecond), SR.Format(SR.ArgumentOutOfRange_Range, 0, MillisPerSecond - 1));
+            }
+            Int64 ticks = calendar.ToDateTime(year, month, day, hour, minute, second, 0).Ticks;
+            ticks += millisecond * TicksPerMillisecond;
+            if (ticks < MinTicks || ticks > MaxTicks)
+                throw new ArgumentException(SR.Arg_DateTimeRange);
+            _dateData = (UInt64)ticks;
+        }
+
+        public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, Calendar calendar, DateTimeKind kind)
+        {
+            if (calendar == null)
+                throw new ArgumentNullException(nameof(calendar));
+            if (millisecond < 0 || millisecond >= MillisPerSecond)
+            {
+                throw new ArgumentOutOfRangeException(nameof(millisecond), SR.Format(SR.ArgumentOutOfRange_Range, 0, MillisPerSecond - 1));
+            }
+            if (kind < DateTimeKind.Unspecified || kind > DateTimeKind.Local)
+            {
+                throw new ArgumentException(SR.Argument_InvalidDateTimeKind, nameof(kind));
+            }
+            Int64 ticks = calendar.ToDateTime(year, month, day, hour, minute, second, 0).Ticks;
+            ticks += millisecond * TicksPerMillisecond;
+            if (ticks < MinTicks || ticks > MaxTicks)
+                throw new ArgumentException(SR.Arg_DateTimeRange);
+            _dateData = ((UInt64)ticks | ((UInt64)kind << KindShift));
+        }
+
+        private DateTime(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+                throw new ArgumentNullException(nameof(info));
+
+            Boolean foundTicks = false;
+            Boolean foundDateData = false;
+            Int64 serializedTicks = 0;
+            UInt64 serializedDateData = 0;
+
+
+            // Get the data
+            SerializationInfoEnumerator enumerator = info.GetEnumerator();
+            while (enumerator.MoveNext())
+            {
+                switch (enumerator.Name)
+                {
+                    case TicksField:
+                        serializedTicks = Convert.ToInt64(enumerator.Value, CultureInfo.InvariantCulture);
+                        foundTicks = true;
+                        break;
+                    case DateDataField:
+                        serializedDateData = Convert.ToUInt64(enumerator.Value, CultureInfo.InvariantCulture);
+                        foundDateData = true;
+                        break;
+                    default:
+                        // Ignore other fields for forward compatibility.
+                        break;
+                }
+            }
+            if (foundDateData)
+            {
+                _dateData = serializedDateData;
+            }
+            else if (foundTicks)
+            {
+                _dateData = (UInt64)serializedTicks;
+            }
+            else
+            {
+                throw new SerializationException(SR.Serialization_MissingDateTimeData);
+            }
+            Int64 ticks = InternalTicks;
+            if (ticks < MinTicks || ticks > MaxTicks)
+            {
+                throw new SerializationException(SR.Serialization_DateTimeTicksOutOfRange);
+            }
+        }
+
+
+
+        internal Int64 InternalTicks
+        {
+            get
+            {
+                return (Int64)(_dateData & TicksMask);
+            }
+        }
+
+        private UInt64 InternalKind
+        {
+            get
+            {
+                return (_dateData & FlagsMask);
+            }
+        }
+
+        // Returns the DateTime resulting from adding the given
+        // TimeSpan to this DateTime.
+        //
+        public DateTime Add(TimeSpan value)
+        {
+            return AddTicks(value._ticks);
+        }
+
+        // Returns the DateTime resulting from adding a fractional number of
+        // time units to this DateTime.
+        private DateTime Add(double value, int scale)
+        {
+            long millis = (long)(value * scale + (value >= 0 ? 0.5 : -0.5));
+            if (millis <= -MaxMillis || millis >= MaxMillis)
+                throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_AddValue);
+            return AddTicks(millis * TicksPerMillisecond);
+        }
+
+        // Returns the DateTime resulting from adding a fractional number of
+        // days to this DateTime. The result is computed by rounding the
+        // fractional number of days given by value to the nearest
+        // millisecond, and adding that interval to this DateTime. The
+        // value argument is permitted to be negative.
+        //
+        public DateTime AddDays(double value)
+        {
+            return Add(value, MillisPerDay);
+        }
+
+        // Returns the DateTime resulting from adding a fractional number of
+        // hours to this DateTime. The result is computed by rounding the
+        // fractional number of hours given by value to the nearest
+        // millisecond, and adding that interval to this DateTime. The
+        // value argument is permitted to be negative.
+        //
+        public DateTime AddHours(double value)
+        {
+            return Add(value, MillisPerHour);
+        }
+
+        // Returns the DateTime resulting from the given number of
+        // milliseconds to this DateTime. The result is computed by rounding
+        // the number of milliseconds given by value to the nearest integer,
+        // and adding that interval to this DateTime. The value
+        // argument is permitted to be negative.
+        //
+        public DateTime AddMilliseconds(double value)
+        {
+            return Add(value, 1);
+        }
+
+        // Returns the DateTime resulting from adding a fractional number of
+        // minutes to this DateTime. The result is computed by rounding the
+        // fractional number of minutes given by value to the nearest
+        // millisecond, and adding that interval to this DateTime. The
+        // value argument is permitted to be negative.
+        //
+        public DateTime AddMinutes(double value)
+        {
+            return Add(value, MillisPerMinute);
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // months to this DateTime. The result is computed by incrementing
+        // (or decrementing) the year and month parts of this DateTime by
+        // months months, and, if required, adjusting the day part of the
+        // resulting date downwards to the last day of the resulting month in the
+        // resulting year. The time-of-day part of the result is the same as the
+        // time-of-day part of this DateTime.
+        //
+        // In more precise terms, considering this DateTime to be of the
+        // form y / m / d + t, where y is the
+        // year, m is the month, d is the day, and t is the
+        // time-of-day, the result is y1 / m1 / d1 + t,
+        // where y1 and m1 are computed by adding months months
+        // to y and m, and d1 is the largest value less than
+        // or equal to d that denotes a valid day in month m1 of year
+        // y1.
+        //
+        public DateTime AddMonths(int months)
+        {
+            if (months < -120000 || months > 120000) throw new ArgumentOutOfRangeException(nameof(months), SR.ArgumentOutOfRange_DateTimeBadMonths);
+            GetDatePart(out int y, out int m, out int d);
+            int i = m - 1 + months;
+            if (i >= 0)
+            {
+                m = i % 12 + 1;
+                y = y + i / 12;
+            }
+            else
+            {
+                m = 12 + (i + 1) % 12;
+                y = y + (i - 11) / 12;
+            }
+            if (y < 1 || y > 9999)
+            {
+                throw new ArgumentOutOfRangeException(nameof(months), SR.ArgumentOutOfRange_DateArithmetic);
+            }
+            int days = DaysInMonth(y, m);
+            if (d > days) d = days;
+            return new DateTime((UInt64)(DateToTicks(y, m, d) + InternalTicks % TicksPerDay) | InternalKind);
+        }
+
+        // Returns the DateTime resulting from adding a fractional number of
+        // seconds to this DateTime. The result is computed by rounding the
+        // fractional number of seconds given by value to the nearest
+        // millisecond, and adding that interval to this DateTime. The
+        // value argument is permitted to be negative.
+        //
+        public DateTime AddSeconds(double value)
+        {
+            return Add(value, MillisPerSecond);
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // 100-nanosecond ticks to this DateTime. The value argument
+        // is permitted to be negative.
+        //
+        public DateTime AddTicks(long value)
+        {
+            long ticks = InternalTicks;
+            if (value > MaxTicks - ticks || value < MinTicks - ticks)
+            {
+                throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_DateArithmetic);
+            }
+            return new DateTime((UInt64)(ticks + value) | InternalKind);
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // years to this DateTime. The result is computed by incrementing
+        // (or decrementing) the year part of this DateTime by value
+        // years. If the month and day of this DateTime is 2/29, and if the
+        // resulting year is not a leap year, the month and day of the resulting
+        // DateTime becomes 2/28. Otherwise, the month, day, and time-of-day
+        // parts of the result are the same as those of this DateTime.
+        //
+        public DateTime AddYears(int value)
+        {
+            if (value < -10000 || value > 10000)
+            {
+                // DateTimeOffset.AddYears(int years) is implemented on top of DateTime.AddYears(int value). Use the more appropriate
+                // parameter name out of the two for the exception.
+                throw new ArgumentOutOfRangeException("years", SR.ArgumentOutOfRange_DateTimeBadYears);
+            }
+            return AddMonths(value * 12);
+        }
+
+        // Compares two DateTime values, returning an integer that indicates
+        // their relationship.
+        //
+        public static int Compare(DateTime t1, DateTime t2)
+        {
+            Int64 ticks1 = t1.InternalTicks;
+            Int64 ticks2 = t2.InternalTicks;
+            if (ticks1 > ticks2) return 1;
+            if (ticks1 < ticks2) return -1;
+            return 0;
+        }
+
+        // Compares this DateTime to a given object. This method provides an
+        // implementation of the IComparable interface. The object
+        // argument must be another DateTime, or otherwise an exception
+        // occurs.  Null is considered less than any instance.
+        //
+        // Returns a value less than zero if this  object
+        public int CompareTo(Object value)
+        {
+            if (value == null) return 1;
+            if (!(value is DateTime))
+            {
+                throw new ArgumentException(SR.Arg_MustBeDateTime);
+            }
+
+            return Compare(this, (DateTime)value);
+        }
+
+        public int CompareTo(DateTime value)
+        {
+            return Compare(this, value);
+        }
+
+        // Returns the tick count corresponding to the given year, month, and day.
+        // Will check the if the parameters are valid.
+        private static long DateToTicks(int year, int month, int day)
+        {
+            if (year >= 1 && year <= 9999 && month >= 1 && month <= 12)
+            {
+                int[] days = IsLeapYear(year) ? s_daysToMonth366 : s_daysToMonth365;
+                if (day >= 1 && day <= days[month] - days[month - 1])
+                {
+                    int y = year - 1;
+                    int n = y * 365 + y / 4 - y / 100 + y / 400 + days[month - 1] + day - 1;
+                    return n * TicksPerDay;
+                }
+            }
+            throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadYearMonthDay);
+        }
+
+        // Return the tick count corresponding to the given hour, minute, second.
+        // Will check the if the parameters are valid.
+        private static long TimeToTicks(int hour, int minute, int second)
+        {
+            //TimeSpan.TimeToTicks is a family access function which does no error checking, so
+            //we need to put some error checking out here.
+            if (hour >= 0 && hour < 24 && minute >= 0 && minute < 60 && second >= 0 && second < 60)
+            {
+                return (TimeSpan.TimeToTicks(hour, minute, second));
+            }
+            throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadHourMinuteSecond);
+        }
+
+        // Returns the number of days in the month given by the year and
+        // month arguments.
+        //
+        public static int DaysInMonth(int year, int month)
+        {
+            if (month < 1 || month > 12) throw new ArgumentOutOfRangeException(nameof(month), SR.ArgumentOutOfRange_Month);
+            // IsLeapYear checks the year argument
+            int[] days = IsLeapYear(year) ? s_daysToMonth366 : s_daysToMonth365;
+            return days[month] - days[month - 1];
+        }
+
+        // Converts an OLE Date to a tick count.
+        // This function is duplicated in COMDateTime.cpp
+        internal static long DoubleDateToTicks(double value)
+        {
+            // The check done this way will take care of NaN
+            if (!(value < OADateMaxAsDouble) || !(value > OADateMinAsDouble))
+                throw new ArgumentException(SR.Arg_OleAutDateInvalid);
+
+            // Conversion to long will not cause an overflow here, as at this point the "value" is in between OADateMinAsDouble and OADateMaxAsDouble
+            long millis = (long)(value * MillisPerDay + (value >= 0 ? 0.5 : -0.5));
+            // The interesting thing here is when you have a value like 12.5 it all positive 12 days and 12 hours from 01/01/1899
+            // However if you a value of -12.25 it is minus 12 days but still positive 6 hours, almost as though you meant -11.75 all negative
+            // This line below fixes up the millis in the negative case
+            if (millis < 0)
+            {
+                millis -= (millis % MillisPerDay) * 2;
+            }
+
+            millis += DoubleDateOffset / TicksPerMillisecond;
+
+            if (millis < 0 || millis >= MaxMillis) throw new ArgumentException(SR.Arg_OleAutDateScale);
+            return millis * TicksPerMillisecond;
+        }
+
+        // Checks if this DateTime is equal to a given object. Returns
+        // true if the given object is a boxed DateTime and its value
+        // is equal to the value of this DateTime. Returns false
+        // otherwise.
+        //
+        public override bool Equals(Object value)
+        {
+            if (value is DateTime)
+            {
+                return InternalTicks == ((DateTime)value).InternalTicks;
+            }
+            return false;
+        }
+
+        public bool Equals(DateTime value)
+        {
+            return InternalTicks == value.InternalTicks;
+        }
+
+        // Compares two DateTime values for equality. Returns true if
+        // the two DateTime values are equal, or false if they are
+        // not equal.
+        //
+        public static bool Equals(DateTime t1, DateTime t2)
+        {
+            return t1.InternalTicks == t2.InternalTicks;
+        }
+
+        public static DateTime FromBinary(Int64 dateData)
+        {
+            if ((dateData & (unchecked((Int64)LocalMask))) != 0)
+            {
+                // Local times need to be adjusted as you move from one time zone to another, 
+                // just as they are when serializing in text. As such the format for local times
+                // changes to store the ticks of the UTC time, but with flags that look like a 
+                // local date.
+                Int64 ticks = dateData & (unchecked((Int64)TicksMask));
+                // Negative ticks are stored in the top part of the range and should be converted back into a negative number
+                if (ticks > TicksCeiling - TicksPerDay)
+                {
+                    ticks = ticks - TicksCeiling;
+                }
+                // Convert the ticks back to local. If the UTC ticks are out of range, we need to default to
+                // the UTC offset from MinValue and MaxValue to be consistent with Parse. 
+                Boolean isAmbiguousLocalDst = false;
+                Int64 offsetTicks;
+                if (ticks < MinTicks)
+                {
+                    offsetTicks = TimeZoneInfo.GetLocalUtcOffset(DateTime.MinValue, TimeZoneInfoOptions.NoThrowOnInvalidTime).Ticks;
+                }
+                else if (ticks > MaxTicks)
+                {
+                    offsetTicks = TimeZoneInfo.GetLocalUtcOffset(DateTime.MaxValue, TimeZoneInfoOptions.NoThrowOnInvalidTime).Ticks;
+                }
+                else
+                {
+                    // Because the ticks conversion between UTC and local is lossy, we need to capture whether the 
+                    // time is in a repeated hour so that it can be passed to the DateTime constructor.
+                    DateTime utcDt = new DateTime(ticks, DateTimeKind.Utc);
+                    Boolean isDaylightSavings = false;
+                    offsetTicks = TimeZoneInfo.GetUtcOffsetFromUtc(utcDt, TimeZoneInfo.Local, out isDaylightSavings, out isAmbiguousLocalDst).Ticks;
+                }
+                ticks += offsetTicks;
+                // Another behaviour of parsing is to cause small times to wrap around, so that they can be used
+                // to compare times of day
+                if (ticks < 0)
+                {
+                    ticks += TicksPerDay;
+                }
+                if (ticks < MinTicks || ticks > MaxTicks)
+                {
+                    throw new ArgumentException(SR.Argument_DateTimeBadBinaryData, nameof(dateData));
+                }
+                return new DateTime(ticks, DateTimeKind.Local, isAmbiguousLocalDst);
+            }
+            else
+            {
+                return DateTime.FromBinaryRaw(dateData);
+            }
+        }
+
+        // A version of ToBinary that uses the real representation and does not adjust local times. This is needed for
+        // scenarios where the serialized data must maintain compatibility
+        internal static DateTime FromBinaryRaw(Int64 dateData)
+        {
+            Int64 ticks = dateData & (Int64)TicksMask;
+            if (ticks < MinTicks || ticks > MaxTicks)
+                throw new ArgumentException(SR.Argument_DateTimeBadBinaryData, nameof(dateData));
+            return new DateTime((UInt64)dateData);
+        }
+
+        // Creates a DateTime from a Windows filetime. A Windows filetime is
+        // a long representing the date and time as the number of
+        // 100-nanosecond intervals that have elapsed since 1/1/1601 12:00am.
+        //
+        public static DateTime FromFileTime(long fileTime)
+        {
+            return FromFileTimeUtc(fileTime).ToLocalTime();
+        }
+
+        public static DateTime FromFileTimeUtc(long fileTime)
+        {
+            if (fileTime < 0 || fileTime > MaxTicks - FileTimeOffset)
+            {
+                throw new ArgumentOutOfRangeException(nameof(fileTime), SR.ArgumentOutOfRange_FileTimeInvalid);
+            }
+
+            // This is the ticks in Universal time for this fileTime.
+            long universalTicks = fileTime + FileTimeOffset;
+            return new DateTime(universalTicks, DateTimeKind.Utc);
+        }
+
+        // Creates a DateTime from an OLE Automation Date.
+        //
+        public static DateTime FromOADate(double d)
+        {
+            return new DateTime(DoubleDateToTicks(d), DateTimeKind.Unspecified);
+        }
+
+        void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+
+            // Serialize both the old and the new format
+            info.AddValue(TicksField, InternalTicks);
+            info.AddValue(DateDataField, _dateData);
+        }
+
+        public Boolean IsDaylightSavingTime()
+        {
+            if (Kind == DateTimeKind.Utc)
+            {
+                return false;
+            }
+            return TimeZoneInfo.Local.IsDaylightSavingTime(this, TimeZoneInfoOptions.NoThrowOnInvalidTime);
+        }
+
+        public static DateTime SpecifyKind(DateTime value, DateTimeKind kind)
+        {
+            return new DateTime(value.InternalTicks, kind);
+        }
+
+        public Int64 ToBinary()
+        {
+            if (Kind == DateTimeKind.Local)
+            {
+                // Local times need to be adjusted as you move from one time zone to another, 
+                // just as they are when serializing in text. As such the format for local times
+                // changes to store the ticks of the UTC time, but with flags that look like a 
+                // local date.
+
+                // To match serialization in text we need to be able to handle cases where
+                // the UTC value would be out of range. Unused parts of the ticks range are
+                // used for this, so that values just past max value are stored just past the
+                // end of the maximum range, and values just below minimum value are stored
+                // at the end of the ticks area, just below 2^62.
+                TimeSpan offset = TimeZoneInfo.GetLocalUtcOffset(this, TimeZoneInfoOptions.NoThrowOnInvalidTime);
+                Int64 ticks = Ticks;
+                Int64 storedTicks = ticks - offset.Ticks;
+                if (storedTicks < 0)
+                {
+                    storedTicks = TicksCeiling + storedTicks;
+                }
+                return storedTicks | (unchecked((Int64)LocalMask));
+            }
+            else
+            {
+                return (Int64)_dateData;
+            }
+        }
+
+        // Returns the date part of this DateTime. The resulting value
+        // corresponds to this DateTime with the time-of-day part set to
+        // zero (midnight).
+        //
+        public DateTime Date
+        {
+            get
+            {
+                Int64 ticks = InternalTicks;
+                return new DateTime((UInt64)(ticks - ticks % TicksPerDay) | InternalKind);
+            }
+        }
+
+        // Returns a given date part of this DateTime. This method is used
+        // to compute the year, day-of-year, month, or day part.
+        private int GetDatePart(int part)
+        {
+            Int64 ticks = InternalTicks;
+            // n = number of days since 1/1/0001
+            int n = (int)(ticks / TicksPerDay);
+            // y400 = number of whole 400-year periods since 1/1/0001
+            int y400 = n / DaysPer400Years;
+            // n = day number within 400-year period
+            n -= y400 * DaysPer400Years;
+            // y100 = number of whole 100-year periods within 400-year period
+            int y100 = n / DaysPer100Years;
+            // Last 100-year period has an extra day, so decrement result if 4
+            if (y100 == 4) y100 = 3;
+            // n = day number within 100-year period
+            n -= y100 * DaysPer100Years;
+            // y4 = number of whole 4-year periods within 100-year period
+            int y4 = n / DaysPer4Years;
+            // n = day number within 4-year period
+            n -= y4 * DaysPer4Years;
+            // y1 = number of whole years within 4-year period
+            int y1 = n / DaysPerYear;
+            // Last year has an extra day, so decrement result if 4
+            if (y1 == 4) y1 = 3;
+            // If year was requested, compute and return it
+            if (part == DatePartYear)
+            {
+                return y400 * 400 + y100 * 100 + y4 * 4 + y1 + 1;
+            }
+            // n = day number within year
+            n -= y1 * DaysPerYear;
+            // If day-of-year was requested, return it
+            if (part == DatePartDayOfYear) return n + 1;
+            // Leap year calculation looks different from IsLeapYear since y1, y4,
+            // and y100 are relative to year 1, not year 0
+            bool leapYear = y1 == 3 && (y4 != 24 || y100 == 3);
+            int[] days = leapYear ? s_daysToMonth366 : s_daysToMonth365;
+            // All months have less than 32 days, so n >> 5 is a good conservative
+            // estimate for the month
+            int m = (n >> 5) + 1;
+            // m = 1-based month number
+            while (n >= days[m]) m++;
+            // If month was requested, return it
+            if (part == DatePartMonth) return m;
+            // Return 1-based day-of-month
+            return n - days[m - 1] + 1;
+        }
+
+        // Exactly the same as GetDatePart(int part), except computing all of
+        // year/month/day rather than just one of them.  Used when all three
+        // are needed rather than redoing the computations for each.
+        internal void GetDatePart(out int year, out int month, out int day)
+        {
+            Int64 ticks = InternalTicks;
+            // n = number of days since 1/1/0001
+            int n = (int)(ticks / TicksPerDay);
+            // y400 = number of whole 400-year periods since 1/1/0001
+            int y400 = n / DaysPer400Years;
+            // n = day number within 400-year period
+            n -= y400 * DaysPer400Years;
+            // y100 = number of whole 100-year periods within 400-year period
+            int y100 = n / DaysPer100Years;
+            // Last 100-year period has an extra day, so decrement result if 4
+            if (y100 == 4) y100 = 3;
+            // n = day number within 100-year period
+            n -= y100 * DaysPer100Years;
+            // y4 = number of whole 4-year periods within 100-year period
+            int y4 = n / DaysPer4Years;
+            // n = day number within 4-year period
+            n -= y4 * DaysPer4Years;
+            // y1 = number of whole years within 4-year period
+            int y1 = n / DaysPerYear;
+            // Last year has an extra day, so decrement result if 4
+            if (y1 == 4) y1 = 3;
+            // compute year
+            year = y400 * 400 + y100 * 100 + y4 * 4 + y1 + 1;
+            // n = day number within year
+            n -= y1 * DaysPerYear;
+            // dayOfYear = n + 1;
+            // Leap year calculation looks different from IsLeapYear since y1, y4,
+            // and y100 are relative to year 1, not year 0
+            bool leapYear = y1 == 3 && (y4 != 24 || y100 == 3);
+            int[] days = leapYear ? s_daysToMonth366 : s_daysToMonth365;
+            // All months have less than 32 days, so n >> 5 is a good conservative
+            // estimate for the month
+            int m = (n >> 5) + 1;
+            // m = 1-based month number
+            while (n >= days[m]) m++;
+            // compute month and day
+            month = m;
+            day = n - days[m - 1] + 1;
+        }
+
+        // Returns the day-of-month part of this DateTime. The returned
+        // value is an integer between 1 and 31.
+        //
+        public int Day
+        {
+            get
+            {
+                return GetDatePart(DatePartDay);
+            }
+        }
+
+        // Returns the day-of-week part of this DateTime. The returned value
+        // is an integer between 0 and 6, where 0 indicates Sunday, 1 indicates
+        // Monday, 2 indicates Tuesday, 3 indicates Wednesday, 4 indicates
+        // Thursday, 5 indicates Friday, and 6 indicates Saturday.
+        //
+        public DayOfWeek DayOfWeek
+        {
+            get
+            {
+                return (DayOfWeek)((InternalTicks / TicksPerDay + 1) % 7);
+            }
+        }
+
+        // Returns the day-of-year part of this DateTime. The returned value
+        // is an integer between 1 and 366.
+        //
+        public int DayOfYear
+        {
+            get
+            {
+                return GetDatePart(DatePartDayOfYear);
+            }
+        }
+
+        // Returns the hash code for this DateTime.
+        //
+        public override int GetHashCode()
+        {
+            Int64 ticks = InternalTicks;
+            return unchecked((int)ticks) ^ (int)(ticks >> 32);
+        }
+
+        // Returns the hour part of this DateTime. The returned value is an
+        // integer between 0 and 23.
+        //
+        public int Hour
+        {
+            get
+            {
+                return (int)((InternalTicks / TicksPerHour) % 24);
+            }
+        }
+
+        internal Boolean IsAmbiguousDaylightSavingTime()
+        {
+            return (InternalKind == KindLocalAmbiguousDst);
+        }
+
+        public DateTimeKind Kind
+        {
+            get
+            {
+                switch (InternalKind)
+                {
+                    case KindUnspecified:
+                        return DateTimeKind.Unspecified;
+                    case KindUtc:
+                        return DateTimeKind.Utc;
+                    default:
+                        return DateTimeKind.Local;
+                }
+            }
+        }
+
+        // Returns the millisecond part of this DateTime. The returned value
+        // is an integer between 0 and 999.
+        //
+        public int Millisecond
+        {
+            get
+            {
+                return (int)((InternalTicks / TicksPerMillisecond) % 1000);
+            }
+        }
+
+        // Returns the minute part of this DateTime. The returned value is
+        // an integer between 0 and 59.
+        //
+        public int Minute
+        {
+            get
+            {
+                return (int)((InternalTicks / TicksPerMinute) % 60);
+            }
+        }
+
+        // Returns the month part of this DateTime. The returned value is an
+        // integer between 1 and 12.
+        //
+        public int Month
+        {
+            get
+            {
+                return GetDatePart(DatePartMonth);
+            }
+        }
+
+        // Returns a DateTime representing the current date and time. The
+        // resolution of the returned value depends on the system timer.
+        public static DateTime Now
+        {
+            get
+            {
+                DateTime utc = UtcNow;
+                Boolean isAmbiguousLocalDst = false;
+                Int64 offset = TimeZoneInfo.GetDateTimeNowUtcOffsetFromUtc(utc, out isAmbiguousLocalDst).Ticks;
+                long tick = utc.Ticks + offset;
+                if (tick > DateTime.MaxTicks)
+                {
+                    return new DateTime(DateTime.MaxTicks, DateTimeKind.Local);
+                }
+                if (tick < DateTime.MinTicks)
+                {
+                    return new DateTime(DateTime.MinTicks, DateTimeKind.Local);
+                }
+                return new DateTime(tick, DateTimeKind.Local, isAmbiguousLocalDst);
+            }
+        }
+
+        // Returns the second part of this DateTime. The returned value is
+        // an integer between 0 and 59.
+        //
+        public int Second
+        {
+            get
+            {
+                return (int)((InternalTicks / TicksPerSecond) % 60);
+            }
+        }
+
+        // Returns the tick count for this DateTime. The returned value is
+        // the number of 100-nanosecond intervals that have elapsed since 1/1/0001
+        // 12:00am.
+        //
+        public long Ticks
+        {
+            get
+            {
+                return InternalTicks;
+            }
+        }
+
+        // Returns the time-of-day part of this DateTime. The returned value
+        // is a TimeSpan that indicates the time elapsed since midnight.
+        //
+        public TimeSpan TimeOfDay
+        {
+            get
+            {
+                return new TimeSpan(InternalTicks % TicksPerDay);
+            }
+        }
+
+        // Returns a DateTime representing the current date. The date part
+        // of the returned value is the current date, and the time-of-day part of
+        // the returned value is zero (midnight).
+        //
+        public static DateTime Today
+        {
+            get
+            {
+                return DateTime.Now.Date;
+            }
+        }
+
+        // Returns the year part of this DateTime. The returned value is an
+        // integer between 1 and 9999.
+        //
+        public int Year
+        {
+            get
+            {
+                return GetDatePart(DatePartYear);
+            }
+        }
+
+        // Checks whether a given year is a leap year. This method returns true if
+        // year is a leap year, or false if not.
+        //
+        public static bool IsLeapYear(int year)
+        {
+            if (year < 1 || year > 9999)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year), SR.ArgumentOutOfRange_Year);
+            }
+            return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
+        }
+
+        // Constructs a DateTime from a string. The string must specify a
+        // date and optionally a time in a culture-specific or universal format.
+        // Leading and trailing whitespace characters are allowed.
+        // 
+        public static DateTime Parse(String s)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return (DateTimeParse.Parse(s, DateTimeFormatInfo.CurrentInfo, DateTimeStyles.None));
+        }
+
+        // Constructs a DateTime from a string. The string must specify a
+        // date and optionally a time in a culture-specific or universal format.
+        // Leading and trailing whitespace characters are allowed.
+        // 
+        public static DateTime Parse(String s, IFormatProvider provider)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return (DateTimeParse.Parse(s, DateTimeFormatInfo.GetInstance(provider), DateTimeStyles.None));
+        }
+
+        public static DateTime Parse(String s, IFormatProvider provider, DateTimeStyles styles)
+        {
+            DateTimeFormatInfo.ValidateStyles(styles, nameof(styles));
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return (DateTimeParse.Parse(s, DateTimeFormatInfo.GetInstance(provider), styles));
+        }
+
+        public static DateTime Parse(ReadOnlySpan<char> s, IFormatProvider provider = null, DateTimeStyles styles = DateTimeStyles.None)
+        {
+            DateTimeFormatInfo.ValidateStyles(styles, nameof(styles));
+            return DateTimeParse.Parse(s, DateTimeFormatInfo.GetInstance(provider), styles);
+        }
+
+        // Constructs a DateTime from a string. The string must specify a
+        // date and optionally a time in a culture-specific or universal format.
+        // Leading and trailing whitespace characters are allowed.
+        // 
+        public static DateTime ParseExact(String s, String format, IFormatProvider provider)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            if (format == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.format);
+            return (DateTimeParse.ParseExact(s, format, DateTimeFormatInfo.GetInstance(provider), DateTimeStyles.None));
+        }
+
+        // Constructs a DateTime from a string. The string must specify a
+        // date and optionally a time in a culture-specific or universal format.
+        // Leading and trailing whitespace characters are allowed.
+        // 
+        public static DateTime ParseExact(String s, String format, IFormatProvider provider, DateTimeStyles style)
+        {
+            DateTimeFormatInfo.ValidateStyles(style, nameof(style));
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            if (format == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.format);
+            return (DateTimeParse.ParseExact(s, format, DateTimeFormatInfo.GetInstance(provider), style));
+        }
+
+        public static DateTime ParseExact(ReadOnlySpan<char> s, ReadOnlySpan<char> format, IFormatProvider provider, DateTimeStyles style = DateTimeStyles.None)
+        {
+            DateTimeFormatInfo.ValidateStyles(style, nameof(style));
+            return DateTimeParse.ParseExact(s, format, DateTimeFormatInfo.GetInstance(provider), style);
+        }
+
+        public static DateTime ParseExact(String s, String[] formats, IFormatProvider provider, DateTimeStyles style)
+        {
+            DateTimeFormatInfo.ValidateStyles(style, nameof(style));
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return DateTimeParse.ParseExactMultiple(s, formats, DateTimeFormatInfo.GetInstance(provider), style);
+        }
+
+        public static DateTime ParseExact(ReadOnlySpan<char> s, string[] formats, IFormatProvider provider, DateTimeStyles style = DateTimeStyles.None)
+        {
+            DateTimeFormatInfo.ValidateStyles(style, nameof(style));
+            return DateTimeParse.ParseExactMultiple(s, formats, DateTimeFormatInfo.GetInstance(provider), style);
+        }
+
+        public TimeSpan Subtract(DateTime value)
+        {
+            return new TimeSpan(InternalTicks - value.InternalTicks);
+        }
+
+        public DateTime Subtract(TimeSpan value)
+        {
+            long ticks = InternalTicks;
+            long valueTicks = value._ticks;
+            if (ticks - MinTicks < valueTicks || ticks - MaxTicks > valueTicks)
+            {
+                throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_DateArithmetic);
+            }
+            return new DateTime((UInt64)(ticks - valueTicks) | InternalKind);
+        }
+
+        // This function is duplicated in COMDateTime.cpp
+        private static double TicksToOADate(long value)
+        {
+            if (value == 0)
+                return 0.0;  // Returns OleAut's zero'ed date value.
+            if (value < TicksPerDay) // This is a fix for VB. They want the default day to be 1/1/0001 rathar then 12/30/1899.
+                value += DoubleDateOffset; // We could have moved this fix down but we would like to keep the bounds check.
+            if (value < OADateMinAsTicks)
+                throw new OverflowException(SR.Arg_OleAutDateInvalid);
+            // Currently, our max date == OA's max date (12/31/9999), so we don't 
+            // need an overflow check in that direction.
+            long millis = (value - DoubleDateOffset) / TicksPerMillisecond;
+            if (millis < 0)
+            {
+                long frac = millis % MillisPerDay;
+                if (frac != 0) millis -= (MillisPerDay + frac) * 2;
+            }
+            return (double)millis / MillisPerDay;
+        }
+
+        // Converts the DateTime instance into an OLE Automation compatible
+        // double date.
+        public double ToOADate()
+        {
+            return TicksToOADate(InternalTicks);
+        }
+
+        public long ToFileTime()
+        {
+            // Treats the input as local if it is not specified
+            return ToUniversalTime().ToFileTimeUtc();
+        }
+
+        public long ToFileTimeUtc()
+        {
+            // Treats the input as universal if it is not specified
+            long ticks = ((InternalKind & LocalMask) != 0) ? ToUniversalTime().InternalTicks : this.InternalTicks;
+            ticks -= FileTimeOffset;
+            if (ticks < 0)
+            {
+                throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_FileTimeInvalid);
+            }
+            return ticks;
+        }
+
+        public DateTime ToLocalTime()
+        {
+            return ToLocalTime(false);
+        }
+
+        internal DateTime ToLocalTime(bool throwOnOverflow)
+        {
+            if (Kind == DateTimeKind.Local)
+            {
+                return this;
+            }
+            Boolean isDaylightSavings = false;
+            Boolean isAmbiguousLocalDst = false;
+            Int64 offset = TimeZoneInfo.GetUtcOffsetFromUtc(this, TimeZoneInfo.Local, out isDaylightSavings, out isAmbiguousLocalDst).Ticks;
+            long tick = Ticks + offset;
+            if (tick > DateTime.MaxTicks)
+            {
+                if (throwOnOverflow)
+                    throw new ArgumentException(SR.Arg_ArgumentOutOfRangeException);
+                else
+                    return new DateTime(DateTime.MaxTicks, DateTimeKind.Local);
+            }
+            if (tick < DateTime.MinTicks)
+            {
+                if (throwOnOverflow)
+                    throw new ArgumentException(SR.Arg_ArgumentOutOfRangeException);
+                else
+                    return new DateTime(DateTime.MinTicks, DateTimeKind.Local);
+            }
+            return new DateTime(tick, DateTimeKind.Local, isAmbiguousLocalDst);
+        }
+
+        public String ToLongDateString()
+        {
+            return DateTimeFormat.Format(this, "D", null);
+        }
+
+        public String ToLongTimeString()
+        {
+            return DateTimeFormat.Format(this, "T", null);
+        }
+
+        public String ToShortDateString()
+        {
+            return DateTimeFormat.Format(this, "d", null);
+        }
+
+        public String ToShortTimeString()
+        {
+            return DateTimeFormat.Format(this, "t", null);
+        }
+
+        public override String ToString()
+        {
+            return DateTimeFormat.Format(this, null, null);
+        }
+
+        public String ToString(String format)
+        {
+            return DateTimeFormat.Format(this, format, null);
+        }
+
+        public String ToString(IFormatProvider provider)
+        {
+            return DateTimeFormat.Format(this, null, provider);
+        }
+
+        public String ToString(String format, IFormatProvider provider)
+        {
+            return DateTimeFormat.Format(this, format, provider);
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider provider = null) =>
+            DateTimeFormat.TryFormat(this, destination, out charsWritten, format, provider);
+
+        public DateTime ToUniversalTime()
+        {
+            return TimeZoneInfo.ConvertTimeToUtc(this, TimeZoneInfoOptions.NoThrowOnInvalidTime);
+        }
+
+        public static Boolean TryParse(String s, out DateTime result)
+        {
+            if (s == null)
+            {
+                result = default;
+                return false;
+            }
+            return DateTimeParse.TryParse(s, DateTimeFormatInfo.CurrentInfo, DateTimeStyles.None, out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, out DateTime result)
+        {
+            return DateTimeParse.TryParse(s, DateTimeFormatInfo.CurrentInfo, DateTimeStyles.None, out result);
+        }
+
+        public static Boolean TryParse(String s, IFormatProvider provider, DateTimeStyles styles, out DateTime result)
+        {
+            DateTimeFormatInfo.ValidateStyles(styles, nameof(styles));
+
+            if (s == null)
+            {
+                result = default;
+                return false;
+            }
+
+            return DateTimeParse.TryParse(s, DateTimeFormatInfo.GetInstance(provider), styles, out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, IFormatProvider provider, DateTimeStyles styles, out DateTime result)
+        {
+            DateTimeFormatInfo.ValidateStyles(styles, nameof(styles));
+            return DateTimeParse.TryParse(s, DateTimeFormatInfo.GetInstance(provider), styles, out result);
+        }
+
+        public static Boolean TryParseExact(String s, String format, IFormatProvider provider, DateTimeStyles style, out DateTime result)
+        {
+            DateTimeFormatInfo.ValidateStyles(style, nameof(style));
+
+            if (s == null || format == null)
+            {
+                result = default;
+                return false;
+            }
+
+            return DateTimeParse.TryParseExact(s, format, DateTimeFormatInfo.GetInstance(provider), style, out result);
+        }
+
+        public static bool TryParseExact(ReadOnlySpan<char> s, ReadOnlySpan<char> format, IFormatProvider provider, DateTimeStyles style, out DateTime result)
+        {
+            DateTimeFormatInfo.ValidateStyles(style, nameof(style));
+            return DateTimeParse.TryParseExact(s, format, DateTimeFormatInfo.GetInstance(provider), style, out result);
+        }
+
+        public static Boolean TryParseExact(String s, String[] formats, IFormatProvider provider, DateTimeStyles style, out DateTime result)
+        {
+            DateTimeFormatInfo.ValidateStyles(style, nameof(style));
+
+            if (s == null)
+            {
+                result = default;
+                return false;
+            }
+
+            return DateTimeParse.TryParseExactMultiple(s, formats, DateTimeFormatInfo.GetInstance(provider), style, out result);
+        }
+
+        public static bool TryParseExact(ReadOnlySpan<char> s, string[] formats, IFormatProvider provider, DateTimeStyles style, out DateTime result)
+        {
+            DateTimeFormatInfo.ValidateStyles(style, nameof(style));
+            return DateTimeParse.TryParseExactMultiple(s, formats, DateTimeFormatInfo.GetInstance(provider), style, out result);
+        }
+
+        public static DateTime operator +(DateTime d, TimeSpan t)
+        {
+            long ticks = d.InternalTicks;
+            long valueTicks = t._ticks;
+            if (valueTicks > MaxTicks - ticks || valueTicks < MinTicks - ticks)
+            {
+                throw new ArgumentOutOfRangeException(nameof(t), SR.ArgumentOutOfRange_DateArithmetic);
+            }
+            return new DateTime((UInt64)(ticks + valueTicks) | d.InternalKind);
+        }
+
+        public static DateTime operator -(DateTime d, TimeSpan t)
+        {
+            long ticks = d.InternalTicks;
+            long valueTicks = t._ticks;
+            if (ticks - MinTicks < valueTicks || ticks - MaxTicks > valueTicks)
+            {
+                throw new ArgumentOutOfRangeException(nameof(t), SR.ArgumentOutOfRange_DateArithmetic);
+            }
+            return new DateTime((UInt64)(ticks - valueTicks) | d.InternalKind);
+        }
+
+        public static TimeSpan operator -(DateTime d1, DateTime d2)
+        {
+            return new TimeSpan(d1.InternalTicks - d2.InternalTicks);
+        }
+
+        public static bool operator ==(DateTime d1, DateTime d2)
+        {
+            return d1.InternalTicks == d2.InternalTicks;
+        }
+
+        public static bool operator !=(DateTime d1, DateTime d2)
+        {
+            return d1.InternalTicks != d2.InternalTicks;
+        }
+
+        public static bool operator <(DateTime t1, DateTime t2)
+        {
+            return t1.InternalTicks < t2.InternalTicks;
+        }
+
+        public static bool operator <=(DateTime t1, DateTime t2)
+        {
+            return t1.InternalTicks <= t2.InternalTicks;
+        }
+
+        public static bool operator >(DateTime t1, DateTime t2)
+        {
+            return t1.InternalTicks > t2.InternalTicks;
+        }
+
+        public static bool operator >=(DateTime t1, DateTime t2)
+        {
+            return t1.InternalTicks >= t2.InternalTicks;
+        }
+
+
+        // Returns a string array containing all of the known date and time options for the 
+        // current culture.  The strings returned are properly formatted date and 
+        // time strings for the current instance of DateTime.
+        public String[] GetDateTimeFormats()
+        {
+            return (GetDateTimeFormats(CultureInfo.CurrentCulture));
+        }
+
+        // Returns a string array containing all of the known date and time options for the 
+        // using the information provided by IFormatProvider.  The strings returned are properly formatted date and 
+        // time strings for the current instance of DateTime.
+        public String[] GetDateTimeFormats(IFormatProvider provider)
+        {
+            return (DateTimeFormat.GetAllDateTimes(this, DateTimeFormatInfo.GetInstance(provider)));
+        }
+
+
+        // Returns a string array containing all of the date and time options for the 
+        // given format format and current culture.  The strings returned are properly formatted date and 
+        // time strings for the current instance of DateTime.
+        public String[] GetDateTimeFormats(char format)
+        {
+            return (GetDateTimeFormats(format, CultureInfo.CurrentCulture));
+        }
+
+        // Returns a string array containing all of the date and time options for the 
+        // given format format and given culture.  The strings returned are properly formatted date and 
+        // time strings for the current instance of DateTime.
+        public String[] GetDateTimeFormats(char format, IFormatProvider provider)
+        {
+            return (DateTimeFormat.GetAllDateTimes(this, format, DateTimeFormatInfo.GetInstance(provider)));
+        }
+
+        //
+        // IConvertible implementation
+        // 
+
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.DateTime;
+        }
+
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "DateTime", "Boolean"));
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "DateTime", "Char"));
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "DateTime", "SByte"));
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "DateTime", "Byte"));
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "DateTime", "Int16"));
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "DateTime", "UInt16"));
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "DateTime", "Int32"));
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "DateTime", "UInt32"));
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "DateTime", "Int64"));
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "DateTime", "UInt64"));
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "DateTime", "Single"));
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "DateTime", "Double"));
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "DateTime", "Decimal"));
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            return this;
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+
+        // Tries to construct a DateTime from a given year, month, day, hour,
+        // minute, second and millisecond.
+        //
+        internal static Boolean TryCreate(int year, int month, int day, int hour, int minute, int second, int millisecond, out DateTime result)
+        {
+            result = DateTime.MinValue;
+            if (year < 1 || year > 9999 || month < 1 || month > 12)
+            {
+                return false;
+            }
+            int[] days = IsLeapYear(year) ? s_daysToMonth366 : s_daysToMonth365;
+            if (day < 1 || day > days[month] - days[month - 1])
+            {
+                return false;
+            }
+            if (hour < 0 || hour >= 24 || minute < 0 || minute >= 60 || second < 0 || second >= 60)
+            {
+                return false;
+            }
+            if (millisecond < 0 || millisecond >= MillisPerSecond)
+            {
+                return false;
+            }
+            long ticks = DateToTicks(year, month, day) + TimeToTicks(hour, minute, second);
+
+            ticks += millisecond * TicksPerMillisecond;
+            if (ticks < MinTicks || ticks > MaxTicks)
+            {
+                return false;
+            }
+            result = new DateTime(ticks, DateTimeKind.Unspecified);
+            return true;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/DateTimeKind.cs b/src/System.Private.CoreLib/shared/System/DateTimeKind.cs
new file mode 100644
index 0000000000..33c9bd925f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/DateTimeKind.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    // This enum is used to indentify DateTime instances in cases when they are known to be in local time, 
+    // UTC time or if this information has not been specified or is not applicable.
+
+    public enum DateTimeKind
+    {
+        Unspecified = 0,
+        Utc = 1,
+        Local = 2,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/DateTimeOffset.cs b/src/System.Private.CoreLib/shared/System/DateTimeOffset.cs
new file mode 100644
index 0000000000..3c3f3f42a2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/DateTimeOffset.cs
@@ -0,0 +1,1005 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.InteropServices;
+using System.Runtime.Serialization;
+
+namespace System
+{
+    // DateTimeOffset is a value type that consists of a DateTime and a time zone offset, 
+    // ie. how far away the time is from GMT. The DateTime is stored whole, and the offset
+    // is stored as an Int16 internally to save space, but presented as a TimeSpan. 
+    //
+    // The range is constrained so that both the represented clock time and the represented
+    // UTC time fit within the boundaries of MaxValue. This gives it the same range as DateTime
+    // for actual UTC times, and a slightly constrained range on one end when an offset is
+    // present. 
+    //
+    // This class should be substitutable for date time in most cases; so most operations
+    // effectively work on the clock time. However, the underlying UTC time is what counts
+    // for the purposes of identity, sorting and subtracting two instances.
+    //
+    //
+    // There are theoretically two date times stored, the UTC and the relative local representation
+    // or the 'clock' time. It actually does not matter which is stored in m_dateTime, so it is desirable
+    // for most methods to go through the helpers UtcDateTime and ClockDateTime both to abstract this
+    // out and for internal readability.
+
+    [StructLayout(LayoutKind.Auto)]
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")] 
+    public struct DateTimeOffset : IComparable, IFormattable, IComparable<DateTimeOffset>, IEquatable<DateTimeOffset>, ISerializable, IDeserializationCallback, ISpanFormattable
+    {
+        // Constants
+        internal const Int64 MaxOffset = TimeSpan.TicksPerHour * 14;
+        internal const Int64 MinOffset = -MaxOffset;
+
+        private const long UnixEpochSeconds = DateTime.UnixEpochTicks / TimeSpan.TicksPerSecond; // 62,135,596,800
+        private const long UnixEpochMilliseconds = DateTime.UnixEpochTicks / TimeSpan.TicksPerMillisecond; // 62,135,596,800,000
+
+        internal const long UnixMinSeconds = DateTime.MinTicks / TimeSpan.TicksPerSecond - UnixEpochSeconds;
+        internal const long UnixMaxSeconds = DateTime.MaxTicks / TimeSpan.TicksPerSecond - UnixEpochSeconds;
+
+        // Static Fields
+        public static readonly DateTimeOffset MinValue = new DateTimeOffset(DateTime.MinTicks, TimeSpan.Zero);
+        public static readonly DateTimeOffset MaxValue = new DateTimeOffset(DateTime.MaxTicks, TimeSpan.Zero);
+        public static readonly DateTimeOffset UnixEpoch = new DateTimeOffset(DateTime.UnixEpochTicks, TimeSpan.Zero);
+
+        // Instance Fields
+        private DateTime _dateTime;
+        private Int16 _offsetMinutes;
+
+        // Constructors
+
+        // Constructs a DateTimeOffset from a tick count and offset
+        public DateTimeOffset(long ticks, TimeSpan offset)
+        {
+            _offsetMinutes = ValidateOffset(offset);
+            // Let the DateTime constructor do the range checks
+            DateTime dateTime = new DateTime(ticks);
+            _dateTime = ValidateDate(dateTime, offset);
+        }
+
+        // Constructs a DateTimeOffset from a DateTime. For Local and Unspecified kinds,
+        // extracts the local offset. For UTC, creates a UTC instance with a zero offset.
+        public DateTimeOffset(DateTime dateTime)
+        {
+            TimeSpan offset;
+            if (dateTime.Kind != DateTimeKind.Utc)
+            {
+                // Local and Unspecified are both treated as Local
+                offset = TimeZoneInfo.GetLocalUtcOffset(dateTime, TimeZoneInfoOptions.NoThrowOnInvalidTime);
+            }
+            else
+            {
+                offset = new TimeSpan(0);
+            }
+            _offsetMinutes = ValidateOffset(offset);
+            _dateTime = ValidateDate(dateTime, offset);
+        }
+
+        // Constructs a DateTimeOffset from a DateTime. And an offset. Always makes the clock time
+        // consistent with the DateTime. For Utc ensures the offset is zero. For local, ensures that
+        // the offset corresponds to the local.
+        public DateTimeOffset(DateTime dateTime, TimeSpan offset)
+        {
+            if (dateTime.Kind == DateTimeKind.Local)
+            {
+                if (offset != TimeZoneInfo.GetLocalUtcOffset(dateTime, TimeZoneInfoOptions.NoThrowOnInvalidTime))
+                {
+                    throw new ArgumentException(SR.Argument_OffsetLocalMismatch, nameof(offset));
+                }
+            }
+            else if (dateTime.Kind == DateTimeKind.Utc)
+            {
+                if (offset != TimeSpan.Zero)
+                {
+                    throw new ArgumentException(SR.Argument_OffsetUtcMismatch, nameof(offset));
+                }
+            }
+            _offsetMinutes = ValidateOffset(offset);
+            _dateTime = ValidateDate(dateTime, offset);
+        }
+
+        // Constructs a DateTimeOffset from a given year, month, day, hour,
+        // minute, second and offset.
+        public DateTimeOffset(int year, int month, int day, int hour, int minute, int second, TimeSpan offset)
+        {
+            _offsetMinutes = ValidateOffset(offset);
+            _dateTime = ValidateDate(new DateTime(year, month, day, hour, minute, second), offset);
+        }
+
+        // Constructs a DateTimeOffset from a given year, month, day, hour,
+        // minute, second, millsecond and offset
+        public DateTimeOffset(int year, int month, int day, int hour, int minute, int second, int millisecond, TimeSpan offset)
+        {
+            _offsetMinutes = ValidateOffset(offset);
+            _dateTime = ValidateDate(new DateTime(year, month, day, hour, minute, second, millisecond), offset);
+        }
+
+        // Constructs a DateTimeOffset from a given year, month, day, hour,
+        // minute, second, millsecond, Calendar and offset.
+        public DateTimeOffset(int year, int month, int day, int hour, int minute, int second, int millisecond, Calendar calendar, TimeSpan offset)
+        {
+            _offsetMinutes = ValidateOffset(offset);
+            _dateTime = ValidateDate(new DateTime(year, month, day, hour, minute, second, millisecond, calendar), offset);
+        }
+
+        // Returns a DateTimeOffset representing the current date and time. The
+        // resolution of the returned value depends on the system timer.
+        public static DateTimeOffset Now
+        {
+            get
+            {
+                return new DateTimeOffset(DateTime.Now);
+            }
+        }
+
+        public static DateTimeOffset UtcNow
+        {
+            get
+            {
+                return new DateTimeOffset(DateTime.UtcNow);
+            }
+        }
+
+        public DateTime DateTime
+        {
+            get
+            {
+                return ClockDateTime;
+            }
+        }
+
+        public DateTime UtcDateTime
+        {
+            get
+            {
+                return DateTime.SpecifyKind(_dateTime, DateTimeKind.Utc);
+            }
+        }
+
+        public DateTime LocalDateTime
+        {
+            get
+            {
+                return UtcDateTime.ToLocalTime();
+            }
+        }
+
+        // Adjust to a given offset with the same UTC time.  Can throw ArgumentException
+        //
+        public DateTimeOffset ToOffset(TimeSpan offset)
+        {
+            return new DateTimeOffset((_dateTime + offset).Ticks, offset);
+        }
+
+
+        // Instance Properties
+
+        // The clock or visible time represented. This is just a wrapper around the internal date because this is
+        // the chosen storage mechanism. Going through this helper is good for readability and maintainability.
+        // This should be used for display but not identity.
+        private DateTime ClockDateTime
+        {
+            get
+            {
+                return new DateTime((_dateTime + Offset).Ticks, DateTimeKind.Unspecified);
+            }
+        }
+
+        // Returns the date part of this DateTimeOffset. The resulting value
+        // corresponds to this DateTimeOffset with the time-of-day part set to
+        // zero (midnight).
+        //
+        public DateTime Date
+        {
+            get
+            {
+                return ClockDateTime.Date;
+            }
+        }
+
+        // Returns the day-of-month part of this DateTimeOffset. The returned
+        // value is an integer between 1 and 31.
+        //
+        public int Day
+        {
+            get
+            {
+                return ClockDateTime.Day;
+            }
+        }
+
+        // Returns the day-of-week part of this DateTimeOffset. The returned value
+        // is an integer between 0 and 6, where 0 indicates Sunday, 1 indicates
+        // Monday, 2 indicates Tuesday, 3 indicates Wednesday, 4 indicates
+        // Thursday, 5 indicates Friday, and 6 indicates Saturday.
+        //
+        public DayOfWeek DayOfWeek
+        {
+            get
+            {
+                return ClockDateTime.DayOfWeek;
+            }
+        }
+
+        // Returns the day-of-year part of this DateTimeOffset. The returned value
+        // is an integer between 1 and 366.
+        //
+        public int DayOfYear
+        {
+            get
+            {
+                return ClockDateTime.DayOfYear;
+            }
+        }
+
+        // Returns the hour part of this DateTimeOffset. The returned value is an
+        // integer between 0 and 23.
+        //
+        public int Hour
+        {
+            get
+            {
+                return ClockDateTime.Hour;
+            }
+        }
+
+
+        // Returns the millisecond part of this DateTimeOffset. The returned value
+        // is an integer between 0 and 999.
+        //
+        public int Millisecond
+        {
+            get
+            {
+                return ClockDateTime.Millisecond;
+            }
+        }
+
+        // Returns the minute part of this DateTimeOffset. The returned value is
+        // an integer between 0 and 59.
+        //
+        public int Minute
+        {
+            get
+            {
+                return ClockDateTime.Minute;
+            }
+        }
+
+        // Returns the month part of this DateTimeOffset. The returned value is an
+        // integer between 1 and 12.
+        //
+        public int Month
+        {
+            get
+            {
+                return ClockDateTime.Month;
+            }
+        }
+
+        public TimeSpan Offset
+        {
+            get
+            {
+                return new TimeSpan(0, _offsetMinutes, 0);
+            }
+        }
+
+        // Returns the second part of this DateTimeOffset. The returned value is
+        // an integer between 0 and 59.
+        //
+        public int Second
+        {
+            get
+            {
+                return ClockDateTime.Second;
+            }
+        }
+
+        // Returns the tick count for this DateTimeOffset. The returned value is
+        // the number of 100-nanosecond intervals that have elapsed since 1/1/0001
+        // 12:00am.
+        //
+        public long Ticks
+        {
+            get
+            {
+                return ClockDateTime.Ticks;
+            }
+        }
+
+        public long UtcTicks
+        {
+            get
+            {
+                return UtcDateTime.Ticks;
+            }
+        }
+
+        // Returns the time-of-day part of this DateTimeOffset. The returned value
+        // is a TimeSpan that indicates the time elapsed since midnight.
+        //
+        public TimeSpan TimeOfDay
+        {
+            get
+            {
+                return ClockDateTime.TimeOfDay;
+            }
+        }
+
+        // Returns the year part of this DateTimeOffset. The returned value is an
+        // integer between 1 and 9999.
+        //
+        public int Year
+        {
+            get
+            {
+                return ClockDateTime.Year;
+            }
+        }
+
+        // Returns the DateTimeOffset resulting from adding the given
+        // TimeSpan to this DateTimeOffset.
+        //
+        public DateTimeOffset Add(TimeSpan timeSpan)
+        {
+            return new DateTimeOffset(ClockDateTime.Add(timeSpan), Offset);
+        }
+
+        // Returns the DateTimeOffset resulting from adding a fractional number of
+        // days to this DateTimeOffset. The result is computed by rounding the
+        // fractional number of days given by value to the nearest
+        // millisecond, and adding that interval to this DateTimeOffset. The
+        // value argument is permitted to be negative.
+        //
+        public DateTimeOffset AddDays(double days)
+        {
+            return new DateTimeOffset(ClockDateTime.AddDays(days), Offset);
+        }
+
+        // Returns the DateTimeOffset resulting from adding a fractional number of
+        // hours to this DateTimeOffset. The result is computed by rounding the
+        // fractional number of hours given by value to the nearest
+        // millisecond, and adding that interval to this DateTimeOffset. The
+        // value argument is permitted to be negative.
+        //
+        public DateTimeOffset AddHours(double hours)
+        {
+            return new DateTimeOffset(ClockDateTime.AddHours(hours), Offset);
+        }
+
+        // Returns the DateTimeOffset resulting from the given number of
+        // milliseconds to this DateTimeOffset. The result is computed by rounding
+        // the number of milliseconds given by value to the nearest integer,
+        // and adding that interval to this DateTimeOffset. The value
+        // argument is permitted to be negative.
+        //
+        public DateTimeOffset AddMilliseconds(double milliseconds)
+        {
+            return new DateTimeOffset(ClockDateTime.AddMilliseconds(milliseconds), Offset);
+        }
+
+        // Returns the DateTimeOffset resulting from adding a fractional number of
+        // minutes to this DateTimeOffset. The result is computed by rounding the
+        // fractional number of minutes given by value to the nearest
+        // millisecond, and adding that interval to this DateTimeOffset. The
+        // value argument is permitted to be negative.
+        //
+        public DateTimeOffset AddMinutes(double minutes)
+        {
+            return new DateTimeOffset(ClockDateTime.AddMinutes(minutes), Offset);
+        }
+
+        public DateTimeOffset AddMonths(int months)
+        {
+            return new DateTimeOffset(ClockDateTime.AddMonths(months), Offset);
+        }
+
+        // Returns the DateTimeOffset resulting from adding a fractional number of
+        // seconds to this DateTimeOffset. The result is computed by rounding the
+        // fractional number of seconds given by value to the nearest
+        // millisecond, and adding that interval to this DateTimeOffset. The
+        // value argument is permitted to be negative.
+        //
+        public DateTimeOffset AddSeconds(double seconds)
+        {
+            return new DateTimeOffset(ClockDateTime.AddSeconds(seconds), Offset);
+        }
+
+        // Returns the DateTimeOffset resulting from adding the given number of
+        // 100-nanosecond ticks to this DateTimeOffset. The value argument
+        // is permitted to be negative.
+        //
+        public DateTimeOffset AddTicks(long ticks)
+        {
+            return new DateTimeOffset(ClockDateTime.AddTicks(ticks), Offset);
+        }
+
+        // Returns the DateTimeOffset resulting from adding the given number of
+        // years to this DateTimeOffset. The result is computed by incrementing
+        // (or decrementing) the year part of this DateTimeOffset by value
+        // years. If the month and day of this DateTimeOffset is 2/29, and if the
+        // resulting year is not a leap year, the month and day of the resulting
+        // DateTimeOffset becomes 2/28. Otherwise, the month, day, and time-of-day
+        // parts of the result are the same as those of this DateTimeOffset.
+        //
+        public DateTimeOffset AddYears(int years)
+        {
+            return new DateTimeOffset(ClockDateTime.AddYears(years), Offset);
+        }
+
+        // Compares two DateTimeOffset values, returning an integer that indicates
+        // their relationship.
+        //
+        public static int Compare(DateTimeOffset first, DateTimeOffset second)
+        {
+            return DateTime.Compare(first.UtcDateTime, second.UtcDateTime);
+        }
+
+        // Compares this DateTimeOffset to a given object. This method provides an
+        // implementation of the IComparable interface. The object
+        // argument must be another DateTimeOffset, or otherwise an exception
+        // occurs.  Null is considered less than any instance.
+        //
+        int IComparable.CompareTo(Object obj)
+        {
+            if (obj == null) return 1;
+            if (!(obj is DateTimeOffset))
+            {
+                throw new ArgumentException(SR.Arg_MustBeDateTimeOffset);
+            }
+
+            DateTime objUtc = ((DateTimeOffset)obj).UtcDateTime;
+            DateTime utc = UtcDateTime;
+            if (utc > objUtc) return 1;
+            if (utc < objUtc) return -1;
+            return 0;
+        }
+
+        public int CompareTo(DateTimeOffset other)
+        {
+            DateTime otherUtc = other.UtcDateTime;
+            DateTime utc = UtcDateTime;
+            if (utc > otherUtc) return 1;
+            if (utc < otherUtc) return -1;
+            return 0;
+        }
+
+
+        // Checks if this DateTimeOffset is equal to a given object. Returns
+        // true if the given object is a boxed DateTimeOffset and its value
+        // is equal to the value of this DateTimeOffset. Returns false
+        // otherwise.
+        //
+        public override bool Equals(Object obj)
+        {
+            if (obj is DateTimeOffset)
+            {
+                return UtcDateTime.Equals(((DateTimeOffset)obj).UtcDateTime);
+            }
+            return false;
+        }
+
+        public bool Equals(DateTimeOffset other)
+        {
+            return UtcDateTime.Equals(other.UtcDateTime);
+        }
+
+        public bool EqualsExact(DateTimeOffset other)
+        {
+            //
+            // returns true when the ClockDateTime, Kind, and Offset match
+            //
+            // currently the Kind should always be Unspecified, but there is always the possibility that a future version
+            // of DateTimeOffset overloads the Kind field
+            //
+            return (ClockDateTime == other.ClockDateTime && Offset == other.Offset && ClockDateTime.Kind == other.ClockDateTime.Kind);
+        }
+
+        // Compares two DateTimeOffset values for equality. Returns true if
+        // the two DateTimeOffset values are equal, or false if they are
+        // not equal.
+        //
+        public static bool Equals(DateTimeOffset first, DateTimeOffset second)
+        {
+            return DateTime.Equals(first.UtcDateTime, second.UtcDateTime);
+        }
+
+        // Creates a DateTimeOffset from a Windows filetime. A Windows filetime is
+        // a long representing the date and time as the number of
+        // 100-nanosecond intervals that have elapsed since 1/1/1601 12:00am.
+        //
+        public static DateTimeOffset FromFileTime(long fileTime)
+        {
+            return new DateTimeOffset(DateTime.FromFileTime(fileTime));
+        }
+
+        public static DateTimeOffset FromUnixTimeSeconds(long seconds)
+        {
+            if (seconds < UnixMinSeconds || seconds > UnixMaxSeconds)
+            {
+                throw new ArgumentOutOfRangeException(nameof(seconds),
+                    SR.Format(SR.ArgumentOutOfRange_Range, UnixMinSeconds, UnixMaxSeconds));
+            }
+
+            long ticks = seconds * TimeSpan.TicksPerSecond + DateTime.UnixEpochTicks;
+            return new DateTimeOffset(ticks, TimeSpan.Zero);
+        }
+
+        public static DateTimeOffset FromUnixTimeMilliseconds(long milliseconds)
+        {
+            const long MinMilliseconds = DateTime.MinTicks / TimeSpan.TicksPerMillisecond - UnixEpochMilliseconds;
+            const long MaxMilliseconds = DateTime.MaxTicks / TimeSpan.TicksPerMillisecond - UnixEpochMilliseconds;
+
+            if (milliseconds < MinMilliseconds || milliseconds > MaxMilliseconds)
+            {
+                throw new ArgumentOutOfRangeException(nameof(milliseconds),
+                    SR.Format(SR.ArgumentOutOfRange_Range, MinMilliseconds, MaxMilliseconds));
+            }
+
+            long ticks = milliseconds * TimeSpan.TicksPerMillisecond + DateTime.UnixEpochTicks;
+            return new DateTimeOffset(ticks, TimeSpan.Zero);
+        }
+
+        // ----- SECTION: private serialization instance methods  ----------------*
+
+        void IDeserializationCallback.OnDeserialization(Object sender)
+        {
+            try
+            {
+                _offsetMinutes = ValidateOffset(Offset);
+                _dateTime = ValidateDate(ClockDateTime, Offset);
+            }
+            catch (ArgumentException e)
+            {
+                throw new SerializationException(SR.Serialization_InvalidData, e);
+            }
+        }
+
+
+        void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+
+            info.AddValue("DateTime", _dateTime); // Do not rename (binary serialization)
+            info.AddValue("OffsetMinutes", _offsetMinutes); // Do not rename (binary serialization)
+        }
+
+
+        private DateTimeOffset(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+
+            _dateTime = (DateTime)info.GetValue("DateTime", typeof(DateTime)); // Do not rename (binary serialization)
+            _offsetMinutes = (Int16)info.GetValue("OffsetMinutes", typeof(Int16)); // Do not rename (binary serialization)
+        }
+
+        // Returns the hash code for this DateTimeOffset.
+        //
+        public override int GetHashCode()
+        {
+            return UtcDateTime.GetHashCode();
+        }
+
+        // Constructs a DateTimeOffset from a string. The string must specify a
+        // date and optionally a time in a culture-specific or universal format.
+        // Leading and trailing whitespace characters are allowed.
+        // 
+        public static DateTimeOffset Parse(String input)
+        {
+            if (input == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.input);
+
+            TimeSpan offset;
+            DateTime dateResult = DateTimeParse.Parse(input,
+                                                      DateTimeFormatInfo.CurrentInfo,
+                                                      DateTimeStyles.None,
+                                                      out offset);
+            return new DateTimeOffset(dateResult.Ticks, offset);
+        }
+
+        // Constructs a DateTimeOffset from a string. The string must specify a
+        // date and optionally a time in a culture-specific or universal format.
+        // Leading and trailing whitespace characters are allowed.
+        // 
+        public static DateTimeOffset Parse(String input, IFormatProvider formatProvider)
+        {
+            if (input == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.input);
+            return Parse(input, formatProvider, DateTimeStyles.None);
+        }
+
+        public static DateTimeOffset Parse(String input, IFormatProvider formatProvider, DateTimeStyles styles)
+        {
+            styles = ValidateStyles(styles, nameof(styles));
+            if (input == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.input);
+
+            TimeSpan offset;
+            DateTime dateResult = DateTimeParse.Parse(input,
+                                                      DateTimeFormatInfo.GetInstance(formatProvider),
+                                                      styles,
+                                                      out offset);
+            return new DateTimeOffset(dateResult.Ticks, offset);
+        }
+
+        public static DateTimeOffset Parse(ReadOnlySpan<char> input, IFormatProvider formatProvider = null, DateTimeStyles styles = DateTimeStyles.None)
+        {
+            styles = ValidateStyles(styles, nameof(styles));
+            DateTime dateResult = DateTimeParse.Parse(input, DateTimeFormatInfo.GetInstance(formatProvider), styles, out TimeSpan offset);
+            return new DateTimeOffset(dateResult.Ticks, offset);
+        }
+
+        // Constructs a DateTimeOffset from a string. The string must specify a
+        // date and optionally a time in a culture-specific or universal format.
+        // Leading and trailing whitespace characters are allowed.
+        // 
+        public static DateTimeOffset ParseExact(String input, String format, IFormatProvider formatProvider)
+        {
+            if (input == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.input);
+            if (format == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.format);
+            return ParseExact(input, format, formatProvider, DateTimeStyles.None);
+        }
+
+        // Constructs a DateTimeOffset from a string. The string must specify a
+        // date and optionally a time in a culture-specific or universal format.
+        // Leading and trailing whitespace characters are allowed.
+        // 
+        public static DateTimeOffset ParseExact(String input, String format, IFormatProvider formatProvider, DateTimeStyles styles)
+        {
+            styles = ValidateStyles(styles, nameof(styles));
+            if (input == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.input);
+            if (format == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.format);
+
+            TimeSpan offset;
+            DateTime dateResult = DateTimeParse.ParseExact(input,
+                                                           format,
+                                                           DateTimeFormatInfo.GetInstance(formatProvider),
+                                                           styles,
+                                                           out offset);
+            return new DateTimeOffset(dateResult.Ticks, offset);
+        }
+
+        public static DateTimeOffset ParseExact(ReadOnlySpan<char> input, ReadOnlySpan<char> format, IFormatProvider formatProvider, DateTimeStyles styles = DateTimeStyles.None)
+        {
+            styles = ValidateStyles(styles, nameof(styles));
+            DateTime dateResult = DateTimeParse.ParseExact(input, format, DateTimeFormatInfo.GetInstance(formatProvider), styles, out TimeSpan offset);
+            return new DateTimeOffset(dateResult.Ticks, offset);
+        }
+
+        public static DateTimeOffset ParseExact(String input, String[] formats, IFormatProvider formatProvider, DateTimeStyles styles)
+        {
+            styles = ValidateStyles(styles, nameof(styles));
+            if (input == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.input);
+
+            TimeSpan offset;
+            DateTime dateResult = DateTimeParse.ParseExactMultiple(input,
+                                                                   formats,
+                                                                   DateTimeFormatInfo.GetInstance(formatProvider),
+                                                                   styles,
+                                                                   out offset);
+            return new DateTimeOffset(dateResult.Ticks, offset);
+        }
+
+        public static DateTimeOffset ParseExact(ReadOnlySpan<char> input, string[] formats, IFormatProvider formatProvider, DateTimeStyles styles = DateTimeStyles.None)
+        {
+            styles = ValidateStyles(styles, nameof(styles));
+            DateTime dateResult = DateTimeParse.ParseExactMultiple(input, formats, DateTimeFormatInfo.GetInstance(formatProvider), styles, out TimeSpan offset);
+            return new DateTimeOffset(dateResult.Ticks, offset);
+        }
+
+        public TimeSpan Subtract(DateTimeOffset value)
+        {
+            return UtcDateTime.Subtract(value.UtcDateTime);
+        }
+
+        public DateTimeOffset Subtract(TimeSpan value)
+        {
+            return new DateTimeOffset(ClockDateTime.Subtract(value), Offset);
+        }
+
+
+        public long ToFileTime()
+        {
+            return UtcDateTime.ToFileTime();
+        }
+
+        public long ToUnixTimeSeconds()
+        {
+            // Truncate sub-second precision before offsetting by the Unix Epoch to avoid
+            // the last digit being off by one for dates that result in negative Unix times.
+            //
+            // For example, consider the DateTimeOffset 12/31/1969 12:59:59.001 +0
+            //   ticks            = 621355967990010000
+            //   ticksFromEpoch   = ticks - DateTime.UnixEpochTicks          = -9990000
+            //   secondsFromEpoch = ticksFromEpoch / TimeSpan.TicksPerSecond = 0
+            //
+            // Notice that secondsFromEpoch is rounded *up* by the truncation induced by integer division,
+            // whereas we actually always want to round *down* when converting to Unix time. This happens
+            // automatically for positive Unix time values. Now the example becomes:
+            //   seconds          = ticks / TimeSpan.TicksPerSecond = 62135596799
+            //   secondsFromEpoch = seconds - UnixEpochSeconds      = -1
+            //
+            // In other words, we want to consistently round toward the time 1/1/0001 00:00:00,
+            // rather than toward the Unix Epoch (1/1/1970 00:00:00).
+            long seconds = UtcDateTime.Ticks / TimeSpan.TicksPerSecond;
+            return seconds - UnixEpochSeconds;
+        }
+
+        public long ToUnixTimeMilliseconds()
+        {
+            // Truncate sub-millisecond precision before offsetting by the Unix Epoch to avoid
+            // the last digit being off by one for dates that result in negative Unix times
+            long milliseconds = UtcDateTime.Ticks / TimeSpan.TicksPerMillisecond;
+            return milliseconds - UnixEpochMilliseconds;
+        }
+
+        public DateTimeOffset ToLocalTime()
+        {
+            return ToLocalTime(false);
+        }
+
+        internal DateTimeOffset ToLocalTime(bool throwOnOverflow)
+        {
+            return new DateTimeOffset(UtcDateTime.ToLocalTime(throwOnOverflow));
+        }
+
+        public override String ToString()
+        {
+            return DateTimeFormat.Format(ClockDateTime, null, null, Offset);
+        }
+
+        public String ToString(String format)
+        {
+            return DateTimeFormat.Format(ClockDateTime, format, null, Offset);
+        }
+
+        public String ToString(IFormatProvider formatProvider)
+        {
+            return DateTimeFormat.Format(ClockDateTime, null, formatProvider, Offset);
+        }
+
+        public String ToString(String format, IFormatProvider formatProvider)
+        {
+            return DateTimeFormat.Format(ClockDateTime, format, formatProvider, Offset);
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider formatProvider = null) =>
+            DateTimeFormat.TryFormat(ClockDateTime, destination, out charsWritten, format, formatProvider, Offset);
+
+        public DateTimeOffset ToUniversalTime()
+        {
+            return new DateTimeOffset(UtcDateTime);
+        }
+
+        public static Boolean TryParse(String input, out DateTimeOffset result)
+        {
+            TimeSpan offset;
+            DateTime dateResult;
+            Boolean parsed = DateTimeParse.TryParse(input,
+                                                    DateTimeFormatInfo.CurrentInfo,
+                                                    DateTimeStyles.None,
+                                                    out dateResult,
+                                                    out offset);
+            result = new DateTimeOffset(dateResult.Ticks, offset);
+            return parsed;
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> input, out DateTimeOffset result)
+        {
+            bool parsed = DateTimeParse.TryParse(input, DateTimeFormatInfo.CurrentInfo, DateTimeStyles.None, out DateTime dateResult, out TimeSpan offset);
+            result = new DateTimeOffset(dateResult.Ticks, offset);
+            return parsed;
+        }
+
+        public static Boolean TryParse(String input, IFormatProvider formatProvider, DateTimeStyles styles, out DateTimeOffset result)
+        {
+            styles = ValidateStyles(styles, nameof(styles));
+            if (input == null)
+            {
+                result = default(DateTimeOffset);
+                return false;
+            }
+
+            TimeSpan offset;
+            DateTime dateResult;
+            Boolean parsed = DateTimeParse.TryParse(input,
+                                                    DateTimeFormatInfo.GetInstance(formatProvider),
+                                                    styles,
+                                                    out dateResult,
+                                                    out offset);
+            result = new DateTimeOffset(dateResult.Ticks, offset);
+            return parsed;
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> input, IFormatProvider formatProvider, DateTimeStyles styles, out DateTimeOffset result)
+        {
+            styles = ValidateStyles(styles, nameof(styles));
+            bool parsed = DateTimeParse.TryParse(input, DateTimeFormatInfo.GetInstance(formatProvider), styles, out DateTime dateResult, out TimeSpan offset);
+            result = new DateTimeOffset(dateResult.Ticks, offset);
+            return parsed;
+        }
+
+        public static Boolean TryParseExact(String input, String format, IFormatProvider formatProvider, DateTimeStyles styles,
+                                            out DateTimeOffset result)
+        {
+            styles = ValidateStyles(styles, nameof(styles));
+            if (input == null || format == null)
+            {
+                result = default(DateTimeOffset);
+                return false;
+            }
+
+            TimeSpan offset;
+            DateTime dateResult;
+            Boolean parsed = DateTimeParse.TryParseExact(input,
+                                                         format,
+                                                         DateTimeFormatInfo.GetInstance(formatProvider),
+                                                         styles,
+                                                         out dateResult,
+                                                         out offset);
+            result = new DateTimeOffset(dateResult.Ticks, offset);
+            return parsed;
+        }
+
+        public static bool TryParseExact(
+            ReadOnlySpan<char> input, ReadOnlySpan<char> format, IFormatProvider formatProvider, DateTimeStyles styles, out DateTimeOffset result)
+        {
+            styles = ValidateStyles(styles, nameof(styles));
+            bool parsed = DateTimeParse.TryParseExact(input, format, DateTimeFormatInfo.GetInstance(formatProvider), styles, out DateTime dateResult, out TimeSpan offset);
+            result = new DateTimeOffset(dateResult.Ticks, offset);
+            return parsed;
+        }
+
+        public static Boolean TryParseExact(String input, String[] formats, IFormatProvider formatProvider, DateTimeStyles styles,
+                                            out DateTimeOffset result)
+        {
+            styles = ValidateStyles(styles, nameof(styles));
+            if (input == null)
+            {
+                result = default(DateTimeOffset);
+                return false;
+            }
+
+            TimeSpan offset;
+            DateTime dateResult;
+            Boolean parsed = DateTimeParse.TryParseExactMultiple(input,
+                                                                 formats,
+                                                                 DateTimeFormatInfo.GetInstance(formatProvider),
+                                                                 styles,
+                                                                 out dateResult,
+                                                                 out offset);
+            result = new DateTimeOffset(dateResult.Ticks, offset);
+            return parsed;
+        }
+
+        public static bool TryParseExact(
+            ReadOnlySpan<char> input, string[] formats, IFormatProvider formatProvider, DateTimeStyles styles, out DateTimeOffset result)
+        {
+            styles = ValidateStyles(styles, nameof(styles));
+            bool parsed = DateTimeParse.TryParseExactMultiple(input, formats, DateTimeFormatInfo.GetInstance(formatProvider), styles, out DateTime dateResult, out TimeSpan offset);
+            result = new DateTimeOffset(dateResult.Ticks, offset);
+            return parsed;
+        }
+
+        // Ensures the TimeSpan is valid to go in a DateTimeOffset.
+        private static Int16 ValidateOffset(TimeSpan offset)
+        {
+            Int64 ticks = offset.Ticks;
+            if (ticks % TimeSpan.TicksPerMinute != 0)
+            {
+                throw new ArgumentException(SR.Argument_OffsetPrecision, nameof(offset));
+            }
+            if (ticks < MinOffset || ticks > MaxOffset)
+            {
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.Argument_OffsetOutOfRange);
+            }
+            return (Int16)(offset.Ticks / TimeSpan.TicksPerMinute);
+        }
+
+        // Ensures that the time and offset are in range.
+        private static DateTime ValidateDate(DateTime dateTime, TimeSpan offset)
+        {
+            // The key validation is that both the UTC and clock times fit. The clock time is validated
+            // by the DateTime constructor.
+            Debug.Assert(offset.Ticks >= MinOffset && offset.Ticks <= MaxOffset, "Offset not validated.");
+
+            // This operation cannot overflow because offset should have already been validated to be within
+            // 14 hours and the DateTime instance is more than that distance from the boundaries of Int64.
+            Int64 utcTicks = dateTime.Ticks - offset.Ticks;
+            if (utcTicks < DateTime.MinTicks || utcTicks > DateTime.MaxTicks)
+            {
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.Argument_UTCOutOfRange);
+            }
+            // make sure the Kind is set to Unspecified
+            //
+            return new DateTime(utcTicks, DateTimeKind.Unspecified);
+        }
+
+        private static DateTimeStyles ValidateStyles(DateTimeStyles style, String parameterName)
+        {
+            if ((style & DateTimeFormatInfo.InvalidDateTimeStyles) != 0)
+            {
+                throw new ArgumentException(SR.Argument_InvalidDateTimeStyles, parameterName);
+            }
+            if (((style & (DateTimeStyles.AssumeLocal)) != 0) && ((style & (DateTimeStyles.AssumeUniversal)) != 0))
+            {
+                throw new ArgumentException(SR.Argument_ConflictingDateTimeStyles, parameterName);
+            }
+            if ((style & DateTimeStyles.NoCurrentDateDefault) != 0)
+            {
+                throw new ArgumentException(SR.Argument_DateTimeOffsetInvalidDateTimeStyles, parameterName);
+            }
+
+            // RoundtripKind does not make sense for DateTimeOffset; ignore this flag for backward compatibility with DateTime
+            style &= ~DateTimeStyles.RoundtripKind;
+
+            // AssumeLocal is also ignored as that is what we do by default with DateTimeOffset.Parse             
+            style &= ~DateTimeStyles.AssumeLocal;
+
+            return style;
+        }
+
+        // Operators
+
+        public static implicit operator DateTimeOffset(DateTime dateTime)
+        {
+            return new DateTimeOffset(dateTime);
+        }
+
+        public static DateTimeOffset operator +(DateTimeOffset dateTimeOffset, TimeSpan timeSpan)
+        {
+            return new DateTimeOffset(dateTimeOffset.ClockDateTime + timeSpan, dateTimeOffset.Offset);
+        }
+
+
+        public static DateTimeOffset operator -(DateTimeOffset dateTimeOffset, TimeSpan timeSpan)
+        {
+            return new DateTimeOffset(dateTimeOffset.ClockDateTime - timeSpan, dateTimeOffset.Offset);
+        }
+
+        public static TimeSpan operator -(DateTimeOffset left, DateTimeOffset right)
+        {
+            return left.UtcDateTime - right.UtcDateTime;
+        }
+
+        public static bool operator ==(DateTimeOffset left, DateTimeOffset right)
+        {
+            return left.UtcDateTime == right.UtcDateTime;
+        }
+
+        public static bool operator !=(DateTimeOffset left, DateTimeOffset right)
+        {
+            return left.UtcDateTime != right.UtcDateTime;
+        }
+
+        public static bool operator <(DateTimeOffset left, DateTimeOffset right)
+        {
+            return left.UtcDateTime < right.UtcDateTime;
+        }
+
+        public static bool operator <=(DateTimeOffset left, DateTimeOffset right)
+        {
+            return left.UtcDateTime <= right.UtcDateTime;
+        }
+
+        public static bool operator >(DateTimeOffset left, DateTimeOffset right)
+        {
+            return left.UtcDateTime > right.UtcDateTime;
+        }
+
+        public static bool operator >=(DateTimeOffset left, DateTimeOffset right)
+        {
+            return left.UtcDateTime >= right.UtcDateTime;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/DayOfWeek.cs b/src/System.Private.CoreLib/shared/System/DayOfWeek.cs
new file mode 100644
index 0000000000..f67d10e181
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/DayOfWeek.cs
@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Enum for the day of the week.
+**
+**
+============================================================*/
+
+namespace System
+{
+    public enum DayOfWeek
+    {
+        Sunday = 0,
+        Monday = 1,
+        Tuesday = 2,
+        Wednesday = 3,
+        Thursday = 4,
+        Friday = 5,
+        Saturday = 6,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/DefaultBinder.cs b/src/System.Private.CoreLib/shared/System/DefaultBinder.cs
new file mode 100644
index 0000000000..f8d8c0c168
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/DefaultBinder.cs
@@ -0,0 +1,1221 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+using System.Diagnostics;
+using CultureInfo = System.Globalization.CultureInfo;
+
+namespace System
+{
+#if CORERT
+    public sealed
+#else
+    internal
+#endif
+    partial class DefaultBinder : Binder
+    {
+        // This method is passed a set of methods and must choose the best
+        // fit.  The methods all have the same number of arguments and the object
+        // array args.  On exit, this method will choice the best fit method
+        // and coerce the args to match that method.  By match, we mean all primitive
+        // arguments are exact matchs and all object arguments are exact or subclasses
+        // of the target.  If the target OR is an interface, the object must implement
+        // that interface.  There are a couple of exceptions
+        // thrown when a method cannot be returned.  If no method matchs the args and
+        // ArgumentException is thrown.  If multiple methods match the args then 
+        // an AmbiguousMatchException is thrown.
+        // 
+        // The most specific match will be selected.  
+        // 
+        public sealed override MethodBase BindToMethod(
+            BindingFlags bindingAttr, MethodBase[] match, ref object[] args,
+            ParameterModifier[] modifiers, CultureInfo cultureInfo, string[] names, out object state)
+        {
+            if (match == null || match.Length == 0)
+                throw new ArgumentException(SR.Arg_EmptyArray, nameof(match));
+
+            MethodBase[] candidates = (MethodBase[])match.Clone();
+
+            int i;
+            int j;
+
+            state = null;
+
+#region Map named parameters to candidate parameter positions
+            // We are creating an paramOrder array to act as a mapping
+            //  between the order of the args and the actual order of the
+            //  parameters in the method.  This order may differ because
+            //  named parameters (names) may change the order.  If names
+            //  is not provided, then we assume the default mapping (0,1,...)
+            int[][] paramOrder = new int[candidates.Length][];
+
+            for (i = 0; i < candidates.Length; i++)
+            {
+                ParameterInfo[] par = candidates[i].GetParametersNoCopy();
+
+                // args.Length + 1 takes into account the possibility of a last paramArray that can be omitted
+                paramOrder[i] = new int[(par.Length > args.Length) ? par.Length : args.Length];
+
+                if (names == null)
+                {
+                    // Default mapping
+                    for (j = 0; j < args.Length; j++)
+                        paramOrder[i][j] = j;
+                }
+                else
+                {
+                    // Named parameters, reorder the mapping.  If CreateParamOrder fails, it means that the method
+                    // doesn't have a name that matchs one of the named parameters so we don't consider it any further.
+                    if (!CreateParamOrder(paramOrder[i], par, names))
+                        candidates[i] = null;
+                }
+            }
+#endregion
+
+            Type[] paramArrayTypes = new Type[candidates.Length];
+
+            Type[] argTypes = new Type[args.Length];
+
+#region Cache the type of the provided arguments
+            // object that contain a null are treated as if they were typeless (but match either object 
+            // references or value classes).  We mark this condition by placing a null in the argTypes array.
+            for (i = 0; i < args.Length; i++)
+            {
+                if (args[i] != null)
+                {
+                    argTypes[i] = args[i].GetType();
+                }
+            }
+#endregion
+
+
+            // Find the method that matches...
+            int CurIdx = 0;
+            bool defaultValueBinding = ((bindingAttr & BindingFlags.OptionalParamBinding) != 0);
+
+            Type paramArrayType = null;
+
+#region Filter methods by parameter count and type
+            for (i = 0; i < candidates.Length; i++)
+            {
+                paramArrayType = null;
+
+                // If we have named parameters then we may have a hole in the candidates array.
+                if (candidates[i] == null)
+                    continue;
+
+                // Validate the parameters.
+                ParameterInfo[] par = candidates[i].GetParametersNoCopy();
+
+#region Match method by parameter count
+                if (par.Length == 0)
+                {
+#region No formal parameters
+                    if (args.Length != 0)
+                    {
+                        if ((candidates[i].CallingConvention & CallingConventions.VarArgs) == 0)
+                            continue;
+                    }
+
+                    // This is a valid routine so we move it up the candidates list.
+                    paramOrder[CurIdx] = paramOrder[i];
+                    candidates[CurIdx++] = candidates[i];
+
+                    continue;
+#endregion
+                }
+                else if (par.Length > args.Length)
+                {
+#region Shortage of provided parameters
+                    // If the number of parameters is greater than the number of args then 
+                    // we are in the situation were we may be using default values.
+                    for (j = args.Length; j < par.Length - 1; j++)
+                    {
+                        if (par[j].DefaultValue == System.DBNull.Value)
+                            break;
+                    }
+
+                    if (j != par.Length - 1)
+                        continue;
+
+                    if (par[j].DefaultValue == System.DBNull.Value)
+                    {
+                        if (!par[j].ParameterType.IsArray)
+                            continue;
+
+                        if (!par[j].IsDefined(typeof(ParamArrayAttribute), true))
+                            continue;
+
+                        paramArrayType = par[j].ParameterType.GetElementType();
+                    }
+#endregion
+                }
+                else if (par.Length < args.Length)
+                {
+#region Excess provided parameters
+                    // test for the ParamArray case
+                    int lastArgPos = par.Length - 1;
+
+                    if (!par[lastArgPos].ParameterType.IsArray)
+                        continue;
+
+                    if (!par[lastArgPos].IsDefined(typeof(ParamArrayAttribute), true))
+                        continue;
+
+                    if (paramOrder[i][lastArgPos] != lastArgPos)
+                        continue;
+
+                    paramArrayType = par[lastArgPos].ParameterType.GetElementType();
+#endregion
+                }
+                else
+                {
+#region Test for paramArray, save paramArray type
+                    int lastArgPos = par.Length - 1;
+
+                    if (par[lastArgPos].ParameterType.IsArray
+                        && par[lastArgPos].IsDefined(typeof(ParamArrayAttribute), true)
+                        && paramOrder[i][lastArgPos] == lastArgPos)
+                    {
+                        if (!par[lastArgPos].ParameterType.IsAssignableFrom(argTypes[lastArgPos]))
+                            paramArrayType = par[lastArgPos].ParameterType.GetElementType();
+                    }
+#endregion
+                }
+#endregion
+
+                Type pCls = null;
+                int argsToCheck = (paramArrayType != null) ? par.Length - 1 : args.Length;
+
+#region Match method by parameter type
+                for (j = 0; j < argsToCheck; j++)
+                {
+#region Classic argument coersion checks
+                    // get the formal type
+                    pCls = par[j].ParameterType;
+
+                    if (pCls.IsByRef)
+                        pCls = pCls.GetElementType();
+
+                    // the type is the same
+                    if (pCls == argTypes[paramOrder[i][j]])
+                        continue;
+
+                    // a default value is available
+                    if (defaultValueBinding && args[paramOrder[i][j]] == Type.Missing)
+                        continue;
+
+                    // the argument was null, so it matches with everything
+                    if (args[paramOrder[i][j]] == null)
+                        continue;
+
+                    // the type is Object, so it will match everything
+                    if (pCls == typeof(object))
+                        continue;
+
+                    // now do a "classic" type check
+                    if (pCls.IsPrimitive)
+                    {
+                        if (argTypes[paramOrder[i][j]] == null || !CanChangePrimitiveObjectToType(args[paramOrder[i][j]], pCls))
+                        {
+                            break;
+                        }
+                    }
+                    else
+                    {
+                        if (argTypes[paramOrder[i][j]] == null)
+                            continue;
+
+                        if (!pCls.IsAssignableFrom(argTypes[paramOrder[i][j]]))
+                        {
+                            if (argTypes[paramOrder[i][j]].IsCOMObject)
+                            {
+                                if (pCls.IsInstanceOfType(args[paramOrder[i][j]]))
+                                    continue;
+                            }
+                            break;
+                        }
+                    }
+#endregion
+                }
+
+                if (paramArrayType != null && j == par.Length - 1)
+                {
+#region Check that excess arguments can be placed in the param array
+                    for (; j < args.Length; j++)
+                    {
+                        if (paramArrayType.IsPrimitive)
+                        {
+                            if (argTypes[j] == null || !CanChangePrimitiveObjectToType(args[j], paramArrayType))
+                                break;
+                        }
+                        else
+                        {
+                            if (argTypes[j] == null)
+                                continue;
+
+                            if (!paramArrayType.IsAssignableFrom(argTypes[j]))
+                            {
+                                if (argTypes[j].IsCOMObject)
+                                {
+                                    if (paramArrayType.IsInstanceOfType(args[j]))
+                                        continue;
+                                }
+
+                                break;
+                            }
+                        }
+                    }
+#endregion
+                }
+#endregion
+
+                if (j == args.Length)
+                {
+#region This is a valid routine so we move it up the candidates list
+                    paramOrder[CurIdx] = paramOrder[i];
+                    paramArrayTypes[CurIdx] = paramArrayType;
+                    candidates[CurIdx++] = candidates[i];
+#endregion
+                }
+            }
+#endregion
+
+            // If we didn't find a method 
+            if (CurIdx == 0)
+                throw new MissingMethodException(SR.MissingMember);
+
+            if (CurIdx == 1)
+            {
+#region Found only one method
+                if (names != null)
+                {
+                    state = new BinderState((int[])paramOrder[0].Clone(), args.Length, paramArrayTypes[0] != null);
+                    ReorderParams(paramOrder[0], args);
+                }
+
+                // If the parameters and the args are not the same length or there is a paramArray
+                //  then we need to create a argument array.
+                ParameterInfo[] parms = candidates[0].GetParametersNoCopy();
+
+                if (parms.Length == args.Length)
+                {
+                    if (paramArrayTypes[0] != null)
+                    {
+                        object[] objs = new object[parms.Length];
+                        int lastPos = parms.Length - 1;
+                        Array.Copy(args, 0, objs, 0, lastPos);
+                        objs[lastPos] = Array.CreateInstance(paramArrayTypes[0], 1);
+                        ((Array)objs[lastPos]).SetValue(args[lastPos], 0);
+                        args = objs;
+                    }
+                }
+                else if (parms.Length > args.Length)
+                {
+                    object[] objs = new object[parms.Length];
+
+                    for (i = 0; i < args.Length; i++)
+                        objs[i] = args[i];
+
+                    for (; i < parms.Length - 1; i++)
+                        objs[i] = parms[i].DefaultValue;
+
+                    if (paramArrayTypes[0] != null)
+                        objs[i] = Array.CreateInstance(paramArrayTypes[0], 0); // create an empty array for the 
+
+                    else
+                        objs[i] = parms[i].DefaultValue;
+
+                    args = objs;
+                }
+                else
+                {
+                    if ((candidates[0].CallingConvention & CallingConventions.VarArgs) == 0)
+                    {
+                        object[] objs = new object[parms.Length];
+                        int paramArrayPos = parms.Length - 1;
+                        Array.Copy(args, 0, objs, 0, paramArrayPos);
+                        objs[paramArrayPos] = Array.CreateInstance(paramArrayTypes[0], args.Length - paramArrayPos);
+                        Array.Copy(args, paramArrayPos, (System.Array)objs[paramArrayPos], 0, args.Length - paramArrayPos);
+                        args = objs;
+                    }
+                }
+#endregion
+
+                return candidates[0];
+            }
+
+            int currentMin = 0;
+            bool ambig = false;
+            for (i = 1; i < CurIdx; i++)
+            {
+#region Walk all of the methods looking the most specific method to invoke
+                int newMin = FindMostSpecificMethod(candidates[currentMin], paramOrder[currentMin], paramArrayTypes[currentMin],
+                                                    candidates[i], paramOrder[i], paramArrayTypes[i], argTypes, args);
+
+                if (newMin == 0)
+                {
+                    ambig = true;
+                }
+                else if (newMin == 2)
+                {
+                    currentMin = i;
+                    ambig = false;
+                }
+#endregion
+            }
+
+            if (ambig)
+                throw new AmbiguousMatchException(SR.Arg_AmbiguousMatchException);
+
+            // Reorder (if needed)
+            if (names != null)
+            {
+                state = new BinderState((int[])paramOrder[currentMin].Clone(), args.Length, paramArrayTypes[currentMin] != null);
+                ReorderParams(paramOrder[currentMin], args);
+            }
+
+            // If the parameters and the args are not the same length or there is a paramArray
+            //  then we need to create a argument array.
+            ParameterInfo[] parameters = candidates[currentMin].GetParametersNoCopy();
+            if (parameters.Length == args.Length)
+            {
+                if (paramArrayTypes[currentMin] != null)
+                {
+                    object[] objs = new object[parameters.Length];
+                    int lastPos = parameters.Length - 1;
+                    Array.Copy(args, 0, objs, 0, lastPos);
+                    objs[lastPos] = Array.CreateInstance(paramArrayTypes[currentMin], 1);
+                    ((Array)objs[lastPos]).SetValue(args[lastPos], 0);
+                    args = objs;
+                }
+            }
+            else if (parameters.Length > args.Length)
+            {
+                object[] objs = new object[parameters.Length];
+
+                for (i = 0; i < args.Length; i++)
+                    objs[i] = args[i];
+
+                for (; i < parameters.Length - 1; i++)
+                    objs[i] = parameters[i].DefaultValue;
+
+                if (paramArrayTypes[currentMin] != null)
+                {
+                    objs[i] = Array.CreateInstance(paramArrayTypes[currentMin], 0);
+                }
+                else
+                {
+                    objs[i] = parameters[i].DefaultValue;
+                }
+
+                args = objs;
+            }
+            else
+            {
+                if ((candidates[currentMin].CallingConvention & CallingConventions.VarArgs) == 0)
+                {
+                    object[] objs = new object[parameters.Length];
+                    int paramArrayPos = parameters.Length - 1;
+                    Array.Copy(args, 0, objs, 0, paramArrayPos);
+                    objs[paramArrayPos] = Array.CreateInstance(paramArrayTypes[currentMin], args.Length - paramArrayPos);
+                    Array.Copy(args, paramArrayPos, (System.Array)objs[paramArrayPos], 0, args.Length - paramArrayPos);
+                    args = objs;
+                }
+            }
+
+            return candidates[currentMin];
+        }
+
+
+        // Given a set of fields that match the base criteria, select a field.
+        // if value is null then we have no way to select a field
+        public sealed override FieldInfo BindToField(BindingFlags bindingAttr, FieldInfo[] match, object value, CultureInfo cultureInfo)
+        {
+            if (match == null)
+            {
+                throw new ArgumentNullException(nameof(match));
+            }
+
+            int i;
+            // Find the method that match...
+            int CurIdx = 0;
+
+            Type valueType = null;
+
+            FieldInfo[] candidates = (FieldInfo[])match.Clone();
+
+            // If we are a FieldSet, then use the value's type to disambiguate
+            if ((bindingAttr & BindingFlags.SetField) != 0)
+            {
+                valueType = value.GetType();
+
+                for (i = 0; i < candidates.Length; i++)
+                {
+                    Type pCls = candidates[i].FieldType;
+                    if (pCls == valueType)
+                    {
+                        candidates[CurIdx++] = candidates[i];
+                        continue;
+                    }
+                    if (value == Empty.Value)
+                    {
+                        // the object passed in was null which would match any non primitive non value type
+                        if (pCls.IsClass)
+                        {
+                            candidates[CurIdx++] = candidates[i];
+                            continue;
+                        }
+                    }
+                    if (pCls == typeof(object))
+                    {
+                        candidates[CurIdx++] = candidates[i];
+                        continue;
+                    }
+                    if (pCls.IsPrimitive)
+                    {
+                        if (CanChangePrimitiveObjectToType(value, pCls))
+                        {
+                            candidates[CurIdx++] = candidates[i];
+                            continue;
+                        }
+                    }
+                    else
+                    {
+                        if (pCls.IsAssignableFrom(valueType))
+                        {
+                            candidates[CurIdx++] = candidates[i];
+                            continue;
+                        }
+                    }
+                }
+                if (CurIdx == 0)
+                    throw new MissingFieldException(SR.MissingField);
+                if (CurIdx == 1)
+                    return candidates[0];
+            }
+
+            // Walk all of the methods looking the most specific method to invoke
+            int currentMin = 0;
+            bool ambig = false;
+            for (i = 1; i < CurIdx; i++)
+            {
+                int newMin = FindMostSpecificField(candidates[currentMin], candidates[i]);
+                if (newMin == 0)
+                    ambig = true;
+                else
+                {
+                    if (newMin == 2)
+                    {
+                        currentMin = i;
+                        ambig = false;
+                    }
+                }
+            }
+            if (ambig)
+                throw new AmbiguousMatchException(SR.Arg_AmbiguousMatchException);
+            return candidates[currentMin];
+        }
+
+        // Given a set of methods that match the base criteria, select a method based
+        // upon an array of types.  This method should return null if no method matchs
+        // the criteria.
+        public sealed override MethodBase SelectMethod(BindingFlags bindingAttr, MethodBase[] match, Type[] types, ParameterModifier[] modifiers)
+        {
+            int i;
+            int j;
+
+            Type[] realTypes = new Type[types.Length];
+            for (i = 0; i < types.Length; i++)
+            {
+                realTypes[i] = types[i].UnderlyingSystemType;
+                if (!(realTypes[i].IsRuntimeImplemented() || realTypes[i] is SignatureType))
+                    throw new ArgumentException(SR.Arg_MustBeType, nameof(types));
+            }
+            types = realTypes;
+
+            // We don't automatically jump out on exact match.
+            if (match == null || match.Length == 0)
+                throw new ArgumentException(SR.Arg_EmptyArray, nameof(match));
+
+            MethodBase[] candidates = (MethodBase[])match.Clone();
+
+            // Find all the methods that can be described by the types parameter. 
+            //  Remove all of them that cannot.
+            int CurIdx = 0;
+            for (i = 0; i < candidates.Length; i++)
+            {
+                ParameterInfo[] par = candidates[i].GetParametersNoCopy();
+                if (par.Length != types.Length)
+                    continue;
+                for (j = 0; j < types.Length; j++)
+                {
+                    Type pCls = par[j].ParameterType;
+                    if (types[j].MatchesParameterTypeExactly(par[j]))
+                        continue;
+                    if (pCls == typeof(object))
+                        continue;
+
+                    Type type = types[j];
+                    if (type is SignatureType signatureType)
+                    {
+                        if (!(candidates[i] is MethodInfo methodInfo))
+                            break;
+                        type = signatureType.TryResolveAgainstGenericMethod(methodInfo);
+                        if (type == null)
+                            break;
+                    }
+
+                    if (pCls.IsPrimitive)
+                    {
+                        if (!(type.UnderlyingSystemType.IsRuntimeImplemented()) ||
+                            !CanChangePrimitive(type.UnderlyingSystemType, pCls.UnderlyingSystemType))
+                            break;
+                    }
+                    else
+                    {
+                        if (!pCls.IsAssignableFrom(type))
+                            break;
+                    }
+                }
+                if (j == types.Length)
+                    candidates[CurIdx++] = candidates[i];
+            }
+            if (CurIdx == 0)
+                return null;
+            if (CurIdx == 1)
+                return candidates[0];
+
+            // Walk all of the methods looking the most specific method to invoke
+            int currentMin = 0;
+            bool ambig = false;
+            int[] paramOrder = new int[types.Length];
+            for (i = 0; i < types.Length; i++)
+                paramOrder[i] = i;
+            for (i = 1; i < CurIdx; i++)
+            {
+                int newMin = FindMostSpecificMethod(candidates[currentMin], paramOrder, null, candidates[i], paramOrder, null, types, null);
+                if (newMin == 0)
+                    ambig = true;
+                else
+                {
+                    if (newMin == 2)
+                    {
+                        currentMin = i;
+                        ambig = false;
+                        currentMin = i;
+                    }
+                }
+            }
+            if (ambig)
+                throw new AmbiguousMatchException(SR.Arg_AmbiguousMatchException);
+            return candidates[currentMin];
+        }
+
+        // Given a set of properties that match the base criteria, select one.
+        public sealed override PropertyInfo SelectProperty(BindingFlags bindingAttr, PropertyInfo[] match, Type returnType,
+                    Type[] indexes, ParameterModifier[] modifiers)
+        {
+            // Allow a null indexes array. But if it is not null, every element must be non-null as well.
+            if (indexes != null)
+            {
+                foreach (Type index in indexes)
+                {
+                    if (index == null)
+                        throw new ArgumentNullException(nameof(indexes));
+                }
+            }
+
+            if (match == null || match.Length == 0)
+                throw new ArgumentException(SR.Arg_EmptyArray, nameof(match));
+
+            PropertyInfo[] candidates = (PropertyInfo[])match.Clone();
+
+            int i, j = 0;
+
+            // Find all the properties that can be described by type indexes parameter
+            int CurIdx = 0;
+            int indexesLength = (indexes != null) ? indexes.Length : 0;
+            for (i = 0; i < candidates.Length; i++)
+            {
+                if (indexes != null)
+                {
+                    ParameterInfo[] par = candidates[i].GetIndexParameters();
+                    if (par.Length != indexesLength)
+                        continue;
+
+                    for (j = 0; j < indexesLength; j++)
+                    {
+                        Type pCls = par[j].ParameterType;
+
+                        // If the classes  exactly match continue
+                        if (pCls == indexes[j])
+                            continue;
+                        if (pCls == typeof(object))
+                            continue;
+
+                        if (pCls.IsPrimitive)
+                        {
+                            if (!(indexes[j].UnderlyingSystemType.IsRuntimeImplemented()) ||
+                                !CanChangePrimitive(indexes[j].UnderlyingSystemType, pCls.UnderlyingSystemType))
+                                break;
+                        }
+                        else
+                        {
+                            if (!pCls.IsAssignableFrom(indexes[j]))
+                                break;
+                        }
+                    }
+                }
+
+                if (j == indexesLength)
+                {
+                    if (returnType != null)
+                    {
+                        if (candidates[i].PropertyType.IsPrimitive)
+                        {
+                            if (!(returnType.UnderlyingSystemType.IsRuntimeImplemented()) ||
+                                !CanChangePrimitive(returnType.UnderlyingSystemType, candidates[i].PropertyType.UnderlyingSystemType))
+                                continue;
+                        }
+                        else
+                        {
+                            if (!candidates[i].PropertyType.IsAssignableFrom(returnType))
+                                continue;
+                        }
+                    }
+                    candidates[CurIdx++] = candidates[i];
+                }
+            }
+            if (CurIdx == 0)
+                return null;
+            if (CurIdx == 1)
+                return candidates[0];
+
+            // Walk all of the properties looking the most specific method to invoke
+            int currentMin = 0;
+            bool ambig = false;
+            int[] paramOrder = new int[indexesLength];
+            for (i = 0; i < indexesLength; i++)
+                paramOrder[i] = i;
+            for (i = 1; i < CurIdx; i++)
+            {
+                int newMin = FindMostSpecificType(candidates[currentMin].PropertyType, candidates[i].PropertyType, returnType);
+                if (newMin == 0 && indexes != null)
+                    newMin = FindMostSpecific(candidates[currentMin].GetIndexParameters(),
+                                              paramOrder,
+                                              null,
+                                              candidates[i].GetIndexParameters(),
+                                              paramOrder,
+                                              null,
+                                              indexes,
+                                              null);
+                if (newMin == 0)
+                {
+                    newMin = FindMostSpecificProperty(candidates[currentMin], candidates[i]);
+                    if (newMin == 0)
+                        ambig = true;
+                }
+                if (newMin == 2)
+                {
+                    ambig = false;
+                    currentMin = i;
+                }
+            }
+
+            if (ambig)
+                throw new AmbiguousMatchException(SR.Arg_AmbiguousMatchException);
+            return candidates[currentMin];
+        }
+
+        // ChangeType
+        // The default binder doesn't support any change type functionality.
+        // This is because the default is built into the low level invoke code.
+        public override object ChangeType(object value, Type type, CultureInfo cultureInfo)
+        {
+            throw new NotSupportedException(SR.NotSupported_ChangeType);
+        }
+
+        public sealed override void ReorderArgumentArray(ref object[] args, object state)
+        {
+            BinderState binderState = (BinderState)state;
+            ReorderParams(binderState._argsMap, args);
+            if (binderState._isParamArray)
+            {
+                int paramArrayPos = args.Length - 1;
+                if (args.Length == binderState._originalSize)
+                    args[paramArrayPos] = ((object[])args[paramArrayPos])[0];
+                else
+                {
+                    // must be args.Length < state.originalSize
+                    object[] newArgs = new object[args.Length];
+                    Array.Copy(args, 0, newArgs, 0, paramArrayPos);
+                    for (int i = paramArrayPos, j = 0; i < newArgs.Length; i++, j++)
+                    {
+                        newArgs[i] = ((object[])args[paramArrayPos])[j];
+                    }
+                    args = newArgs;
+                }
+            }
+            else
+            {
+                if (args.Length > binderState._originalSize)
+                {
+                    object[] newArgs = new object[binderState._originalSize];
+                    Array.Copy(args, 0, newArgs, 0, binderState._originalSize);
+                    args = newArgs;
+                }
+            }
+        }
+
+        // Return any exact bindings that may exist. (This method is not defined on the
+        //  Binder and is used by RuntimeType.)
+        public static MethodBase ExactBinding(MethodBase[] match, Type[] types, ParameterModifier[] modifiers)
+        {
+            if (match == null)
+                throw new ArgumentNullException(nameof(match));
+
+            MethodBase[] aExactMatches = new MethodBase[match.Length];
+            int cExactMatches = 0;
+
+            for (int i = 0; i < match.Length; i++)
+            {
+                ParameterInfo[] par = match[i].GetParametersNoCopy();
+                if (par.Length == 0)
+                {
+                    continue;
+                }
+                int j;
+                for (j = 0; j < types.Length; j++)
+                {
+                    Type pCls = par[j].ParameterType;
+
+                    // If the classes  exactly match continue
+                    if (!pCls.Equals(types[j]))
+                        break;
+                }
+                if (j < types.Length)
+                    continue;
+
+                // Add the exact match to the array of exact matches.
+                aExactMatches[cExactMatches] = match[i];
+                cExactMatches++;
+            }
+
+            if (cExactMatches == 0)
+                return null;
+
+            if (cExactMatches == 1)
+                return aExactMatches[0];
+
+            return FindMostDerivedNewSlotMeth(aExactMatches, cExactMatches);
+        }
+
+        // Return any exact bindings that may exist. (This method is not defined on the
+        //  Binder and is used by RuntimeType.)
+        public static PropertyInfo ExactPropertyBinding(PropertyInfo[] match, Type returnType, Type[] types, ParameterModifier[] modifiers)
+        {
+            if (match == null)
+                throw new ArgumentNullException(nameof(match));
+
+            PropertyInfo bestMatch = null;
+            int typesLength = (types != null) ? types.Length : 0;
+            for (int i = 0; i < match.Length; i++)
+            {
+                ParameterInfo[] par = match[i].GetIndexParameters();
+                int j;
+                for (j = 0; j < typesLength; j++)
+                {
+                    Type pCls = par[j].ParameterType;
+
+                    // If the classes  exactly match continue
+                    if (pCls != types[j])
+                        break;
+                }
+                if (j < typesLength)
+                    continue;
+                if (returnType != null && returnType != match[i].PropertyType)
+                    continue;
+
+                if (bestMatch != null)
+                    throw new AmbiguousMatchException(SR.Arg_AmbiguousMatchException);
+
+                bestMatch = match[i];
+            }
+            return bestMatch;
+        }
+
+        private static int FindMostSpecific(ParameterInfo[] p1, int[] paramOrder1, Type paramArrayType1,
+                                            ParameterInfo[] p2, int[] paramOrder2, Type paramArrayType2,
+                                            Type[] types, object[] args)
+        {
+            // A method using params is always less specific than one not using params
+            if (paramArrayType1 != null && paramArrayType2 == null) return 2;
+            if (paramArrayType2 != null && paramArrayType1 == null) return 1;
+
+            // now either p1 and p2 both use params or neither does.
+
+            bool p1Less = false;
+            bool p2Less = false;
+
+            for (int i = 0; i < types.Length; i++)
+            {
+                if (args != null && args[i] == Type.Missing)
+                    continue;
+
+                Type c1, c2;
+
+                //  If a param array is present, then either
+                //      the user re-ordered the parameters in which case
+                //          the argument to the param array is either an array
+                //              in which case the params is conceptually ignored and so paramArrayType1 == null
+                //          or the argument to the param array is a single element
+                //              in which case paramOrder[i] == p1.Length - 1 for that element
+                //      or the user did not re-order the parameters in which case
+                //          the paramOrder array could contain indexes larger than p.Length - 1 (see VSW 577286)
+                //          so any index >= p.Length - 1 is being put in the param array
+
+                if (paramArrayType1 != null && paramOrder1[i] >= p1.Length - 1)
+                    c1 = paramArrayType1;
+                else
+                    c1 = p1[paramOrder1[i]].ParameterType;
+
+                if (paramArrayType2 != null && paramOrder2[i] >= p2.Length - 1)
+                    c2 = paramArrayType2;
+                else
+                    c2 = p2[paramOrder2[i]].ParameterType;
+
+                if (c1 == c2) continue;
+
+                switch (FindMostSpecificType(c1, c2, types[i]))
+                {
+                    case 0: return 0;
+                    case 1: p1Less = true; break;
+                    case 2: p2Less = true; break;
+                }
+            }
+
+            // Two way p1Less and p2Less can be equal.  All the arguments are the
+            //  same they both equal false, otherwise there were things that both
+            //  were the most specific type on....
+            if (p1Less == p2Less)
+            {
+                // if we cannot tell which is a better match based on parameter types (p1Less == p2Less),
+                // let's see which one has the most matches without using the params array (the longer one wins).
+                if (!p1Less && args != null)
+                {
+                    if (p1.Length > p2.Length)
+                    {
+                        return 1;
+                    }
+                    else if (p2.Length > p1.Length)
+                    {
+                        return 2;
+                    }
+                }
+
+                return 0;
+            }
+            else
+            {
+                return (p1Less == true) ? 1 : 2;
+            }
+        }
+
+        private static int FindMostSpecificType(Type c1, Type c2, Type t)
+        {
+            // If the two types are exact move on...
+            if (c1 == c2)
+                return 0;
+
+            if (t is SignatureType signatureType)
+            {
+                if (signatureType.MatchesExactly(c1))
+                    return 1;
+
+                if (signatureType.MatchesExactly(c2))
+                    return 2;
+            }
+            else
+            {
+                if (c1 == t)
+                    return 1;
+
+                if (c2 == t)
+                    return 2;
+            }
+
+            bool c1FromC2;
+            bool c2FromC1;
+
+            if (c1.IsByRef || c2.IsByRef)
+            {
+                if (c1.IsByRef && c2.IsByRef)
+                {
+                    c1 = c1.GetElementType();
+                    c2 = c2.GetElementType();
+                }
+                else if (c1.IsByRef)
+                {
+                    if (c1.GetElementType() == c2)
+                        return 2;
+
+                    c1 = c1.GetElementType();
+                }
+                else
+                {
+                    if (c2.GetElementType() == c1)
+                        return 1;
+
+                    c2 = c2.GetElementType();
+                }
+            }
+
+
+            if (c1.IsPrimitive && c2.IsPrimitive)
+            {
+                c1FromC2 = CanChangePrimitive(c2, c1);
+                c2FromC1 = CanChangePrimitive(c1, c2);
+            }
+            else
+            {
+                c1FromC2 = c1.IsAssignableFrom(c2);
+                c2FromC1 = c2.IsAssignableFrom(c1);
+            }
+
+            if (c1FromC2 == c2FromC1)
+                return 0;
+
+            if (c1FromC2)
+            {
+                return 2;
+            }
+            else
+            {
+                return 1;
+            }
+        }
+
+        private static int FindMostSpecificMethod(MethodBase m1, int[] paramOrder1, Type paramArrayType1,
+                                                  MethodBase m2, int[] paramOrder2, Type paramArrayType2,
+                                                  Type[] types, object[] args)
+        {
+            // Find the most specific method based on the parameters.
+            int res = FindMostSpecific(m1.GetParametersNoCopy(), paramOrder1, paramArrayType1,
+                                       m2.GetParametersNoCopy(), paramOrder2, paramArrayType2, types, args);
+
+            // If the match was not ambigous then return the result.
+            if (res != 0)
+                return res;
+
+            // Check to see if the methods have the exact same name and signature.
+            if (CompareMethodSig(m1, m2))
+            {
+                // Determine the depth of the declaring types for both methods.
+                int hierarchyDepth1 = GetHierarchyDepth(m1.DeclaringType);
+                int hierarchyDepth2 = GetHierarchyDepth(m2.DeclaringType);
+
+                // The most derived method is the most specific one.
+                if (hierarchyDepth1 == hierarchyDepth2)
+                {
+                    return 0;
+                }
+                else if (hierarchyDepth1 < hierarchyDepth2)
+                {
+                    return 2;
+                }
+                else
+                {
+                    return 1;
+                }
+            }
+
+            // The match is ambigous.
+            return 0;
+        }
+
+        private static int FindMostSpecificField(FieldInfo cur1, FieldInfo cur2)
+        {
+            // Check to see if the fields have the same name.
+            if (cur1.Name == cur2.Name)
+            {
+                int hierarchyDepth1 = GetHierarchyDepth(cur1.DeclaringType);
+                int hierarchyDepth2 = GetHierarchyDepth(cur2.DeclaringType);
+
+                if (hierarchyDepth1 == hierarchyDepth2)
+                {
+                    Debug.Assert(cur1.IsStatic != cur2.IsStatic, "hierarchyDepth1 == hierarchyDepth2");
+                    return 0;
+                }
+                else if (hierarchyDepth1 < hierarchyDepth2)
+                    return 2;
+                else
+                    return 1;
+            }
+
+            // The match is ambigous.
+            return 0;
+        }
+
+        private static int FindMostSpecificProperty(PropertyInfo cur1, PropertyInfo cur2)
+        {
+            // Check to see if the fields have the same name.
+            if (cur1.Name == cur2.Name)
+            {
+                int hierarchyDepth1 = GetHierarchyDepth(cur1.DeclaringType);
+                int hierarchyDepth2 = GetHierarchyDepth(cur2.DeclaringType);
+
+                if (hierarchyDepth1 == hierarchyDepth2)
+                {
+                    return 0;
+                }
+                else if (hierarchyDepth1 < hierarchyDepth2)
+                    return 2;
+                else
+                    return 1;
+            }
+
+            // The match is ambigous.
+            return 0;
+        }
+
+        public static bool CompareMethodSig(MethodBase m1, MethodBase m2)
+        {
+            ParameterInfo[] params1 = m1.GetParametersNoCopy();
+            ParameterInfo[] params2 = m2.GetParametersNoCopy();
+
+            if (params1.Length != params2.Length)
+                return false;
+
+            int numParams = params1.Length;
+            for (int i = 0; i < numParams; i++)
+            {
+                if (params1[i].ParameterType != params2[i].ParameterType)
+                    return false;
+            }
+
+            return true;
+        }
+
+        private static int GetHierarchyDepth(Type t)
+        {
+            int depth = 0;
+
+            Type currentType = t;
+            do
+            {
+                depth++;
+                currentType = currentType.BaseType;
+            } while (currentType != null);
+
+            return depth;
+        }
+
+        internal static MethodBase FindMostDerivedNewSlotMeth(MethodBase[] match, int cMatches)
+        {
+            int deepestHierarchy = 0;
+            MethodBase methWithDeepestHierarchy = null;
+
+            for (int i = 0; i < cMatches; i++)
+            {
+                // Calculate the depth of the hierarchy of the declaring type of the
+                // current method.
+                int currentHierarchyDepth = GetHierarchyDepth(match[i].DeclaringType);
+
+                // The two methods have the same name, signature, and hierarchy depth.
+                // This can only happen if at least one is vararg or generic.
+                if (currentHierarchyDepth == deepestHierarchy)
+                {
+                    throw new AmbiguousMatchException(SR.Arg_AmbiguousMatchException);
+                }
+
+                // Check to see if this method is on the most derived class.
+                if (currentHierarchyDepth > deepestHierarchy)
+                {
+                    deepestHierarchy = currentHierarchyDepth;
+                    methWithDeepestHierarchy = match[i];
+                }
+            }
+
+            return methWithDeepestHierarchy;
+        }
+
+        // This method will sort the vars array into the mapping order stored
+        //  in the paramOrder array.
+        private static void ReorderParams(int[] paramOrder, object[] vars)
+        {
+            object[] varsCopy = new object[vars.Length];
+            for (int i = 0; i < vars.Length; i++)
+                varsCopy[i] = vars[i];
+
+            for (int i = 0; i < vars.Length; i++)
+                vars[i] = varsCopy[paramOrder[i]];
+        }
+
+        // This method will create the mapping between the Parameters and the underlying
+        //  data based upon the names array.  The names array is stored in the same order
+        //  as the values and maps to the parameters of the method.  We store the mapping
+        //  from the parameters to the names in the paramOrder array.  All parameters that
+        //  don't have matching names are then stored in the array in order.
+        private static bool CreateParamOrder(int[] paramOrder, ParameterInfo[] pars, string[] names)
+        {
+            bool[] used = new bool[pars.Length];
+
+            // Mark which parameters have not been found in the names list
+            for (int i = 0; i < pars.Length; i++)
+                paramOrder[i] = -1;
+            // Find the parameters with names. 
+            for (int i = 0; i < names.Length; i++)
+            {
+                int j;
+                for (j = 0; j < pars.Length; j++)
+                {
+                    if (names[i].Equals(pars[j].Name))
+                    {
+                        paramOrder[j] = i;
+                        used[i] = true;
+                        break;
+                    }
+                }
+                // This is an error condition.  The name was not found.  This
+                //  method must not match what we sent.
+                if (j == pars.Length)
+                    return false;
+            }
+
+            // Now we fill in the holes with the parameters that are unused.
+            int pos = 0;
+            for (int i = 0; i < pars.Length; i++)
+            {
+                if (paramOrder[i] == -1)
+                {
+                    for (; pos < pars.Length; pos++)
+                    {
+                        if (!used[pos])
+                        {
+                            paramOrder[i] = pos;
+                            pos++;
+                            break;
+                        }
+                    }
+                }
+            }
+            return true;
+        }
+
+        internal class BinderState
+        {
+            internal readonly int[] _argsMap;
+            internal readonly int _originalSize;
+            internal readonly bool _isParamArray;
+
+            internal BinderState(int[] argsMap, int originalSize, bool isParamArray)
+            {
+                _argsMap = argsMap;
+                _originalSize = originalSize;
+                _isParamArray = isParamArray;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/CodeAnalysis/SuppressMessageAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/CodeAnalysis/SuppressMessageAttribute.cs
new file mode 100644
index 0000000000..893d7b8bc9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/CodeAnalysis/SuppressMessageAttribute.cs
@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+**  An attribute to suppress violation messages/warnings   
+**  by static code analysis tools. 
+**
+** 
+===========================================================*/
+
+namespace System.Diagnostics.CodeAnalysis
+{
+    [AttributeUsage(
+     AttributeTargets.All,
+     Inherited = false,
+     AllowMultiple = true
+     )
+    ]
+    [Conditional("CODE_ANALYSIS")]
+    public sealed class SuppressMessageAttribute : Attribute
+    {
+        public SuppressMessageAttribute(string category, string checkId)
+        {
+            Category = category;
+            CheckId = checkId;
+        }
+
+        public string Category { get; }
+        public string CheckId { get; }
+        public string Scope { get; set; }
+        public string Target { get; set; }
+        public string MessageId { get; set; }
+        public string Justification { get; set; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/ConditionalAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/ConditionalAttribute.cs
new file mode 100644
index 0000000000..416625b779
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/ConditionalAttribute.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Diagnostics
+{
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, AllowMultiple = true)]
+    public sealed class ConditionalAttribute : Attribute
+    {
+        public ConditionalAttribute(string conditionString)
+        {
+            ConditionString = conditionString;
+        }
+
+        public string ConditionString { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Debug.Unix.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Debug.Unix.cs
new file mode 100644
index 0000000000..627ea4ab7e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Debug.Unix.cs
@@ -0,0 +1,107 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+
+namespace System.Diagnostics
+{
+    public static partial class Debug
+    {
+        private static readonly bool s_shouldWriteToStdErr = Environment.GetEnvironmentVariable("COMPlus_DebugWriteToStdErr") == "1";
+
+        private static void ShowDialog(string stackTrace, string message, string detailMessage, string errorSource)
+        {
+            if (Debugger.IsAttached)
+            {
+                Debugger.Break();
+            }
+            else
+            {
+                // In Core, we do not show a dialog.
+                // Fail in order to avoid anyone catching an exception and masking
+                // an assert failure.
+                DebugAssertException ex;
+                if (message == String.Empty) 
+                {
+                    ex = new DebugAssertException(stackTrace);
+                }
+                else if (detailMessage == String.Empty) 
+                {
+                    ex = new DebugAssertException(message, stackTrace);
+                }
+                else
+                {
+                    ex = new DebugAssertException(message, detailMessage, stackTrace);
+                }
+                Environment.FailFast(ex.Message, ex, errorSource);
+            }
+        }
+
+        private static void WriteCore(string message)
+        {
+            WriteToDebugger(message);
+
+            if (s_shouldWriteToStdErr)
+            {
+                WriteToStderr(message);
+            }
+        }
+
+        private static void WriteToDebugger(string message)
+        {
+            if (Debugger.IsLogging())
+            {
+                Debugger.Log(0, null, message);
+            }
+            else
+            {
+                Interop.Sys.SysLog(Interop.Sys.SysLogPriority.LOG_USER | Interop.Sys.SysLogPriority.LOG_DEBUG, "%s", message);
+            }
+        }
+
+        private static void WriteToStderr(string message)
+        {
+            // We don't want to write UTF-16 to a file like standard error.  Ideally we would transcode this
+            // to UTF8, but the downside of that is it pulls in a bunch of stuff into what is ideally
+            // a path with minimal dependencies (as to prevent re-entrency), so we'll take the strategy
+            // of just throwing away any non ASCII characters from the message and writing the rest
+
+            const int BufferLength = 256;
+
+            unsafe
+            {
+                byte* buf = stackalloc byte[BufferLength];
+                int bufCount;
+                int i = 0;
+
+                while (i < message.Length)
+                {
+                    for (bufCount = 0; bufCount < BufferLength && i < message.Length; i++)
+                    {
+                        if (message[i] <= 0x7F)
+                        {
+                            buf[bufCount] = (byte)message[i];
+                            bufCount++;
+                        }
+                    }
+
+                    int totalBytesWritten = 0;
+                    while (bufCount > 0)
+                    {
+                        int bytesWritten = Interop.Sys.Write(2 /* stderr */, buf + totalBytesWritten, bufCount);
+                        if (bytesWritten < 0)
+                        {
+                            // On error, simply stop writing the debug output.  This could commonly happen if stderr
+                            // was piped to a program that ended before this program did, resulting in EPIPE errors.
+                            return;
+                        }
+
+                        bufCount -= bytesWritten;
+                        totalBytesWritten += bytesWritten;
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Debug.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Debug.cs
new file mode 100644
index 0000000000..7bc43ccfcb
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Debug.cs
@@ -0,0 +1,350 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// Do not remove this, it is needed to retain calls to these conditional methods in release builds
+#define DEBUG
+using System.Diagnostics.Contracts;
+using System.Runtime.CompilerServices;
+
+namespace System.Diagnostics
+{
+    /// <summary>
+    /// Provides a set of properties and methods for debugging code.
+    /// </summary>
+    public static partial class Debug
+    {
+        private static readonly object s_lock = new object();
+
+        public static bool AutoFlush { get { return true; } set { } }
+
+        [ThreadStatic]
+        private static int s_indentLevel;
+        public static int IndentLevel
+        {
+            get
+            {
+                return s_indentLevel;
+            }
+            set
+            {
+                s_indentLevel = value < 0 ? 0 : value;
+            }
+        }
+
+        private static int s_indentSize = 4;
+        public static int IndentSize
+        {
+            get
+            {
+                return s_indentSize;
+            }
+            set
+            {
+                s_indentSize = value < 0 ? 0 : value;
+            }
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Close() { }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Flush() { }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Indent()
+        {
+            IndentLevel++;
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Unindent()
+        {
+            IndentLevel--;
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Print(string message)
+        {
+            Write(message);
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Print(string format, params object[] args)
+        {
+            Write(string.Format(null, format, args));
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Assert(bool condition)
+        {
+            Assert(condition, string.Empty, string.Empty);
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Assert(bool condition, string message)
+        {
+            Assert(condition, message, string.Empty);
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Assert(bool condition, string message, string detailMessage)
+        {
+            if (!condition)
+            {
+                string stackTrace;
+                try
+                {
+                    stackTrace = new StackTrace(0, true).ToString(System.Diagnostics.StackTrace.TraceFormat.Normal);
+                }
+                catch
+                {
+                    stackTrace = "";
+                }
+                WriteLine(FormatAssert(stackTrace, message, detailMessage));
+                s_ShowDialog(stackTrace, message, detailMessage, "Assertion Failed");
+            }
+        }
+
+        internal static void ContractFailure(bool condition, string message, string detailMessage, string failureKindMessage)
+        {
+            if (!condition)
+            {
+                string stackTrace;
+                try
+                {
+                    stackTrace = new StackTrace(2, true).ToString(System.Diagnostics.StackTrace.TraceFormat.Normal);
+                }
+                catch
+                {
+                    stackTrace = "";
+                }
+                WriteLine(FormatAssert(stackTrace, message, detailMessage));
+                s_ShowDialog(stackTrace, message, detailMessage, SR.GetResourceString(failureKindMessage));
+            }
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Fail(string message)
+        {
+            Assert(false, message, string.Empty);
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Fail(string message, string detailMessage)
+        {
+            Assert(false, message, detailMessage);
+        }
+
+        private static string FormatAssert(string stackTrace, string message, string detailMessage)
+        {
+            string newLine = GetIndentString() + Environment.NewLine;
+            return SR.DebugAssertBanner + newLine
+                   + SR.DebugAssertShortMessage + newLine
+                   + message + newLine
+                   + SR.DebugAssertLongMessage + newLine
+                   + detailMessage + newLine
+                   + stackTrace;
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Assert(bool condition, string message, string detailMessageFormat, params object[] args)
+        {
+            Assert(condition, message, string.Format(detailMessageFormat, args));
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void WriteLine(string message)
+        {
+            Write(message + Environment.NewLine);
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Write(string message)
+        {
+            lock (s_lock)
+            {
+                if (message == null)
+                {
+                    s_WriteCore(string.Empty);
+                    return;
+                }
+                if (s_needIndent)
+                {
+                    message = GetIndentString() + message;
+                    s_needIndent = false;
+                }
+                s_WriteCore(message);
+                if (message.EndsWith(Environment.NewLine))
+                {
+                    s_needIndent = true;
+                }
+            }
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void WriteLine(object value)
+        {
+            WriteLine(value?.ToString());
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void WriteLine(object value, string category)
+        {
+            WriteLine(value?.ToString(), category);
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void WriteLine(string format, params object[] args)
+        {
+            WriteLine(string.Format(null, format, args));
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void WriteLine(string message, string category)
+        {
+            if (category == null)
+            {
+                WriteLine(message);
+            }
+            else
+            {
+                WriteLine(category + ":" + message);
+            }
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Write(object value)
+        {
+            Write(value?.ToString());
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Write(string message, string category)
+        {
+            if (category == null)
+            {
+                Write(message);
+            }
+            else
+            {
+                Write(category + ":" + message);
+            }
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void Write(object value, string category)
+        {
+            Write(value?.ToString(), category);
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void WriteIf(bool condition, string message)
+        {
+            if (condition)
+            {
+                Write(message);
+            }
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void WriteIf(bool condition, object value)
+        {
+            if (condition)
+            {
+                Write(value);
+            }
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void WriteIf(bool condition, string message, string category)
+        {
+            if (condition)
+            {
+                Write(message, category);
+            }
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void WriteIf(bool condition, object value, string category)
+        {
+            if (condition)
+            {
+                Write(value, category);
+            }
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void WriteLineIf(bool condition, object value)
+        {
+            if (condition)
+            {
+                WriteLine(value);
+            }
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void WriteLineIf(bool condition, object value, string category)
+        {
+            if (condition)
+            {
+                WriteLine(value, category);
+            }
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void WriteLineIf(bool condition, string message)
+        {
+            if (condition)
+            {
+                WriteLine(message);
+            }
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        public static void WriteLineIf(bool condition, string message, string category)
+        {
+            if (condition)
+            {
+                WriteLine(message, category);
+            }
+        }
+
+        private static bool s_needIndent;
+
+        private static string s_indentString;
+
+        private static string GetIndentString()
+        {
+            int indentCount = IndentSize * IndentLevel;
+            if (s_indentString?.Length == indentCount)
+            {
+                return s_indentString;
+            }
+            return s_indentString = new string(' ', indentCount);
+        }
+
+        private sealed class DebugAssertException : Exception
+        {
+            internal DebugAssertException(string stackTrace) :
+                base(Environment.NewLine + stackTrace)
+            {
+            }
+
+            internal DebugAssertException(string message, string stackTrace) :
+                base(message + Environment.NewLine + Environment.NewLine + stackTrace)
+            {
+            }
+
+            internal DebugAssertException(string message, string detailMessage, string stackTrace) :
+                base(message + Environment.NewLine + detailMessage + Environment.NewLine + Environment.NewLine + stackTrace)
+            {
+            }
+        }
+
+        // internal and not readonly so that the tests can swap this out.
+        internal static Action<string, string, string, string> s_ShowDialog = ShowDialog;
+
+        internal static Action<string> s_WriteCore = WriteCore;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggableAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggableAttribute.cs
new file mode 100644
index 0000000000..d05f8471b3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggableAttribute.cs
@@ -0,0 +1,54 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Diagnostics
+{
+    // Attribute class used by the compiler to mark modules.  
+    // If present, then debugging information for everything in the
+    // assembly was generated by the compiler, and will be preserved
+    // by the Runtime so that the debugger can provide full functionality
+    // in the case of JIT attach. If not present, then the compiler may
+    // or may not have included debugging information, and the Runtime
+    // won't preserve the debugging info, which will make debugging after
+    // a JIT attach difficult.
+    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Module, AllowMultiple = false)]
+    public sealed class DebuggableAttribute : Attribute
+    {
+        [Flags]
+        public enum DebuggingModes
+        {
+            None = 0x0,
+            Default = 0x1,
+            DisableOptimizations = 0x100,
+            IgnoreSymbolStoreSequencePoints = 0x2,
+            EnableEditAndContinue = 0x4
+        }
+
+        public DebuggableAttribute(bool isJITTrackingEnabled, bool isJITOptimizerDisabled)
+        {
+            DebuggingFlags = 0;
+
+            if (isJITTrackingEnabled)
+            {
+                DebuggingFlags |= DebuggingModes.Default;
+            }
+
+            if (isJITOptimizerDisabled)
+            {
+                DebuggingFlags |= DebuggingModes.DisableOptimizations;
+            }
+        }
+
+        public DebuggableAttribute(DebuggingModes modes)
+        {
+            DebuggingFlags = modes;
+        }
+
+        public bool IsJITTrackingEnabled => (DebuggingFlags & DebuggingModes.Default) != 0;
+
+        public bool IsJITOptimizerDisabled => (DebuggingFlags & DebuggingModes.DisableOptimizations) != 0;
+
+        public DebuggingModes DebuggingFlags { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerBrowsableAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerBrowsableAttribute.cs
new file mode 100644
index 0000000000..b9d62225a9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerBrowsableAttribute.cs
@@ -0,0 +1,41 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Diagnostics
+{
+    //  DebuggerBrowsableState states are defined as follows:
+    //      Never       never show this element
+    //      Expanded    expansion of the class is done, so that all visible internal members are shown
+    //      Collapsed   expansion of the class is not performed. Internal visible members are hidden
+    //      RootHidden  The target element itself should not be shown, but should instead be 
+    //                  automatically expanded to have its members displayed.
+    //  Default value is collapsed
+
+    //  Please also change the code which validates DebuggerBrowsableState variable (in this file)
+    //  if you change this enum.
+    public enum DebuggerBrowsableState
+    {
+        Never = 0,
+        //Expanded is not supported in this release
+        //Expanded = 1, 
+        Collapsed = 2,
+        RootHidden = 3
+    }
+
+
+    // the one currently supported with the csee.dat 
+    // (mcee.dat, autoexp.dat) file. 
+    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false)]
+    public sealed class DebuggerBrowsableAttribute : Attribute
+    {
+        public DebuggerBrowsableAttribute(DebuggerBrowsableState state)
+        {
+            if (state < DebuggerBrowsableState.Never || state > DebuggerBrowsableState.RootHidden)
+                throw new ArgumentOutOfRangeException(nameof(state));
+
+            State = state;
+        }
+        public DebuggerBrowsableState State { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerDisplayAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerDisplayAttribute.cs
new file mode 100644
index 0000000000..7aae4b9397
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerDisplayAttribute.cs
@@ -0,0 +1,51 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Diagnostics
+{
+    // This attribute is used to control what is displayed for the given class or field 
+    // in the data windows in the debugger.  The single argument to this attribute is
+    // the string that will be displayed in the value column for instances of the type.  
+    // This string can include text between { and } which can be either a field, 
+    // property or method (as will be documented in mscorlib).  In the C# case, 
+    // a general expression will be allowed which only has implicit access to the this pointer 
+    // for the current instance of the target type. The expression will be limited, 
+    // however: there is no access to aliases, locals, or pointers. 
+    // In addition, attributes on properties referenced in the expression are not processed.
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Delegate | AttributeTargets.Enum | AttributeTargets.Field | AttributeTargets.Property | AttributeTargets.Assembly, AllowMultiple = true)]
+    public sealed class DebuggerDisplayAttribute : Attribute
+    {
+        private Type _target;
+
+        public DebuggerDisplayAttribute(string value)
+        {
+            Value = value ?? "";
+            Name = "";
+            Type = "";
+        }
+
+        public string Value { get; }
+
+        public string Name { get; set; }
+
+        public string Type { get; set; }
+
+        public Type Target
+        {
+            get => _target;
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value));
+                }
+
+                TargetTypeName = value.AssemblyQualifiedName;
+                _target = value;
+            }
+        }
+
+        public string TargetTypeName { get; set; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerHiddenAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerHiddenAttribute.cs
new file mode 100644
index 0000000000..ace452e911
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerHiddenAttribute.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Diagnostics
+{
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Property | AttributeTargets.Constructor, Inherited = false)]
+    public sealed class DebuggerHiddenAttribute : Attribute
+    {
+        public DebuggerHiddenAttribute() { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerNonUserCodeAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerNonUserCodeAttribute.cs
new file mode 100644
index 0000000000..1b61cb7262
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerNonUserCodeAttribute.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Diagnostics
+{
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method | AttributeTargets.Property | AttributeTargets.Constructor | AttributeTargets.Struct, Inherited = false)]
+    public sealed class DebuggerNonUserCodeAttribute : Attribute
+    {
+        public DebuggerNonUserCodeAttribute() { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerStepThroughAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerStepThroughAttribute.cs
new file mode 100644
index 0000000000..82a164771e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerStepThroughAttribute.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Diagnostics
+{
+#if PROJECTN
+    // Used by the IL2IL toolchain to mark generated code to control debugger stepping policy
+    [System.Runtime.CompilerServices.DependencyReductionRoot]
+#endif
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Method | AttributeTargets.Constructor, Inherited = false)]
+    public sealed class DebuggerStepThroughAttribute : Attribute
+    {
+        public DebuggerStepThroughAttribute() { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerStepperBoundaryAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerStepperBoundaryAttribute.cs
new file mode 100644
index 0000000000..647f2fdb00
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerStepperBoundaryAttribute.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Diagnostics
+{
+    /// <summary>Indicates the code following the attribute is to be executed in run, not step, mode.</summary>
+    [AttributeUsage(AttributeTargets.Constructor | AttributeTargets.Method, Inherited = false)]
+    public sealed class DebuggerStepperBoundaryAttribute : Attribute
+    {
+        public DebuggerStepperBoundaryAttribute() { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerTypeProxyAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerTypeProxyAttribute.cs
new file mode 100644
index 0000000000..445834e056
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerTypeProxyAttribute.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Diagnostics
+{
+    [AttributeUsage(AttributeTargets.Struct | AttributeTargets.Class | AttributeTargets.Assembly, AllowMultiple = true)]
+    public sealed class DebuggerTypeProxyAttribute : Attribute
+    {
+        private Type _target;
+
+        public DebuggerTypeProxyAttribute(Type type)
+        {
+            if (type == null)
+            {
+                throw new ArgumentNullException(nameof(type));
+            }
+
+            ProxyTypeName = type.AssemblyQualifiedName;
+        }
+
+        public DebuggerTypeProxyAttribute(string typeName)
+        {
+            ProxyTypeName = typeName;
+        }
+
+        public string ProxyTypeName { get; }
+
+        public Type Target
+        {
+            get => _target;
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value));
+                }
+
+                TargetTypeName = value.AssemblyQualifiedName;
+                _target = value;
+            }        
+        }
+
+        public string TargetTypeName { get; set; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerVisualizerAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerVisualizerAttribute.cs
new file mode 100644
index 0000000000..032eca8a15
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/DebuggerVisualizerAttribute.cs
@@ -0,0 +1,97 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Diagnostics
+{
+    /// <summary>
+    /// Signifies that the attributed type has a visualizer which is pointed
+    /// to by the parameter type name strings.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Struct | AttributeTargets.Class | AttributeTargets.Assembly, AllowMultiple = true)]
+    public sealed class DebuggerVisualizerAttribute : Attribute
+    {
+        private Type _target;
+
+        public DebuggerVisualizerAttribute(string visualizerTypeName)
+        {
+            VisualizerTypeName = visualizerTypeName;
+        }
+
+        public DebuggerVisualizerAttribute(string visualizerTypeName, string visualizerObjectSourceTypeName)
+        {
+            VisualizerTypeName = visualizerTypeName;
+            VisualizerObjectSourceTypeName = visualizerObjectSourceTypeName;
+        }
+
+        public DebuggerVisualizerAttribute(string visualizerTypeName, Type visualizerObjectSource)
+        {
+            if (visualizerObjectSource == null)
+            {
+                throw new ArgumentNullException(nameof(visualizerObjectSource));
+            }
+
+            VisualizerTypeName = visualizerTypeName;
+            VisualizerObjectSourceTypeName = visualizerObjectSource.AssemblyQualifiedName;
+        }
+
+        public DebuggerVisualizerAttribute(Type visualizer)
+        {
+            if (visualizer == null)
+            {
+                throw new ArgumentNullException(nameof(visualizer));
+            }
+
+            VisualizerTypeName = visualizer.AssemblyQualifiedName;
+        }
+
+        public DebuggerVisualizerAttribute(Type visualizer, Type visualizerObjectSource)
+        {
+            if (visualizer == null)
+            {
+                throw new ArgumentNullException(nameof(visualizer));
+            }
+            if (visualizerObjectSource == null)
+            {
+                throw new ArgumentNullException(nameof(visualizerObjectSource));
+            }
+
+            VisualizerTypeName = visualizer.AssemblyQualifiedName;
+            VisualizerObjectSourceTypeName = visualizerObjectSource.AssemblyQualifiedName;
+        }
+
+        public DebuggerVisualizerAttribute(Type visualizer, string visualizerObjectSourceTypeName)
+        {
+            if (visualizer == null)
+            {
+                throw new ArgumentNullException(nameof(visualizer));
+            }
+
+            VisualizerTypeName = visualizer.AssemblyQualifiedName;
+            VisualizerObjectSourceTypeName = visualizerObjectSourceTypeName;
+        }
+
+        public string VisualizerObjectSourceTypeName { get; }
+
+        public string VisualizerTypeName { get; }
+
+        public string Description { get; set; }
+        
+        public Type Target
+        {
+            get => _target;
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value));
+                }
+
+                TargetTypeName = value.AssemblyQualifiedName;
+                _target = value;
+            }
+        }
+
+        public string TargetTypeName { get; set; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/StackTraceHiddenAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/StackTraceHiddenAttribute.cs
new file mode 100644
index 0000000000..474274ac08
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/StackTraceHiddenAttribute.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Diagnostics
+{
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Struct, Inherited = false)]
+    internal sealed class StackTraceHiddenAttribute : Attribute
+    {
+        public StackTraceHiddenAttribute() { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/ActivityTracker.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/ActivityTracker.cs
new file mode 100644
index 0000000000..d9f9f081cb
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/ActivityTracker.cs
@@ -0,0 +1,661 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+using System.Threading;
+#if !ES_BUILD_AGAINST_DOTNET_V35
+using Contract = System.Diagnostics.Contracts.Contract;
+#else
+using Contract = Microsoft.Diagnostics.Contracts.Internal.Contract;
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+using System.Threading.Tasks;
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// Tracks activities.  This is meant to be a singleton (accessed by the ActivityTracer.Instance static property)
+    ///  
+    /// Logically this is simply holds the m_current variable that holds the async local that holds the current ActivityInfo
+    /// An ActivityInfo is represents a activity (which knows its creator and thus knows its path). 
+    ///
+    /// Most of the magic is in the async local (it gets copied to new tasks)
+    /// 
+    /// On every start event call OnStart 
+    /// 
+    ///     Guid activityID;
+    ///     Guid relatedActivityID;
+    ///     if (OnStart(activityName, out activityID, out relatedActivityID, ForceStop, options))
+    ///         // Log Start event with activityID and relatedActivityID
+    ///     
+    /// On every stop event call OnStop
+    /// 
+    ///     Guid activityID;
+    ///     if (OnStop(activityName, ref activityID  ForceStop))
+    ///         // Stop event with activityID
+    ///            
+    /// On any normal event log the event with activityTracker.CurrentActivityId
+    /// </summary>
+    internal class ActivityTracker
+    {
+
+        /// <summary>
+        /// Called on work item begins.  The activity name = providerName + activityName without 'Start' suffix.
+        /// It updates CurrentActivityId to track.   
+        /// 
+        /// It returns true if the Start should be logged, otherwise (if it is illegal recursion) it return false. 
+        /// 
+        /// The start event should use as its activity ID the CurrentActivityId AFTER calling this routine and its
+        /// RelatedActivityID the CurrentActivityId BEFORE calling this routine (the creator).  
+        /// 
+        /// If activity tracing is not on, then activityId and relatedActivityId are not set
+        /// </summary>
+        public void OnStart(string providerName, string activityName, int task, ref Guid activityId, ref Guid relatedActivityId, EventActivityOptions options)
+        {
+            if (m_current == null)        // We are not enabled
+            {
+                // We  used to rely on the TPL provider turning us on, but that has the disadvantage that you don't get Start-Stop tracking
+                // until you use Tasks for the first time (which you may never do).   Thus we change it to pull rather tan push for whether
+                // we are enabled.   
+                if (m_checkedForEnable)
+                    return;
+                m_checkedForEnable = true;
+                if (TplEtwProvider.Log.IsEnabled(EventLevel.Informational, TplEtwProvider.Keywords.TasksFlowActivityIds))
+                    Enable();
+                if (m_current == null)
+                    return;
+            }
+
+
+            Debug.Assert((options & EventActivityOptions.Disable) == 0);
+
+            var currentActivity = m_current.Value;
+            var fullActivityName = NormalizeActivityName(providerName, activityName, task);
+
+            var etwLog = TplEtwProvider.Log;
+            if (etwLog.Debug)
+            {
+                etwLog.DebugFacilityMessage("OnStartEnter", fullActivityName);
+                etwLog.DebugFacilityMessage("OnStartEnterActivityState", ActivityInfo.LiveActivities(currentActivity));
+            }
+
+            if (currentActivity != null)
+            {
+                // Stop activity tracking if we reached the maximum allowed depth 
+                if (currentActivity.m_level >= MAX_ACTIVITY_DEPTH)
+                {
+                    activityId = Guid.Empty;
+                    relatedActivityId = Guid.Empty;
+                    if (etwLog.Debug)
+                        etwLog.DebugFacilityMessage("OnStartRET", "Fail");
+                    return;
+                }
+                // Check for recursion, and force-stop any activities if the activity already started.
+                if ((options & EventActivityOptions.Recursive) == 0)
+                {
+                    ActivityInfo existingActivity = FindActiveActivity(fullActivityName, currentActivity);
+                    if (existingActivity != null)
+                    {
+                        OnStop(providerName, activityName, task, ref activityId);
+                        currentActivity = m_current.Value;
+                    }
+                }
+            }
+
+            // Get a unique ID for this activity.
+            long id;
+            if (currentActivity == null)
+                id = Interlocked.Increment(ref m_nextId);
+            else
+                id = Interlocked.Increment(ref currentActivity.m_lastChildID);
+
+            // The previous ID is my 'causer' and becomes my related activity ID
+            relatedActivityId = EventSource.CurrentThreadActivityId;
+
+            // Add to the list of started but not stopped activities. 
+            ActivityInfo newActivity = new ActivityInfo(fullActivityName, id, currentActivity, relatedActivityId, options);
+            m_current.Value = newActivity;
+
+            // Remember the current ID so we can log it 
+            activityId = newActivity.ActivityId;
+            
+            if (etwLog.Debug)
+            {
+                etwLog.DebugFacilityMessage("OnStartRetActivityState", ActivityInfo.LiveActivities(newActivity));
+                etwLog.DebugFacilityMessage1("OnStartRet", activityId.ToString(), relatedActivityId.ToString());
+            }
+        }
+
+        /// <summary>
+        /// Called when a work item stops.  The activity name = providerName + activityName without 'Stop' suffix.
+        /// It updates m_current variable to track this fact.   The Stop event associated with stop should log the ActivityID associated with the event.
+        ///
+        /// If activity tracing is not on, then activityId and relatedActivityId are not set
+        /// </summary>
+        public void OnStop(string providerName, string activityName, int task, ref Guid activityId)
+        {
+            if (m_current == null)        // We are not enabled
+                return;
+
+            var fullActivityName = NormalizeActivityName(providerName, activityName, task);
+            
+            var etwLog = TplEtwProvider.Log;
+            if (etwLog.Debug)
+            {
+                etwLog.DebugFacilityMessage("OnStopEnter", fullActivityName);
+                etwLog.DebugFacilityMessage("OnStopEnterActivityState", ActivityInfo.LiveActivities(m_current.Value));
+            }
+
+            for (; ; ) // This is a retry loop.
+            {
+                ActivityInfo currentActivity = m_current.Value;
+                ActivityInfo newCurrentActivity = null;               // if we have seen any live activities (orphans), at he first one we have seen.   
+
+                // Search to find the activity to stop in one pass.   This insures that we don't let one mistake
+                // (stopping something that was not started) cause all active starts to be stopped 
+                // By first finding the target start to stop we are more robust.  
+                ActivityInfo activityToStop = FindActiveActivity(fullActivityName, currentActivity);
+
+                // ignore stops where we can't find a start because we may have popped them previously.
+                if (activityToStop == null)
+                {
+                    activityId = Guid.Empty;
+                    // TODO add some logging about this. Basically could not find matching start.
+                    if (etwLog.Debug)
+                        etwLog.DebugFacilityMessage("OnStopRET", "Fail");
+                    return;
+                }
+
+                activityId = activityToStop.ActivityId;
+
+                // See if there are any orphans that need to be stopped.  
+                ActivityInfo orphan = currentActivity;
+                while (orphan != activityToStop && orphan != null)
+                {
+                    if (orphan.m_stopped != 0)      // Skip dead activities.
+                    {
+                        orphan = orphan.m_creator;
+                        continue;
+                    }
+                    if (orphan.CanBeOrphan())
+                    {
+                        // We can't pop anything after we see a valid orphan, remember this for later when we update m_current.  
+                        if (newCurrentActivity == null)
+                            newCurrentActivity = orphan;
+                    }
+                    else
+                    {
+                        orphan.m_stopped = 1;
+                        Debug.Assert(orphan.m_stopped != 0);
+                    }
+                    orphan = orphan.m_creator;
+                }
+
+                // try to Stop the activity atomically.  Other threads may be trying to do this as well.
+                if (Interlocked.CompareExchange(ref activityToStop.m_stopped, 1, 0) == 0)
+                {
+                    // I succeeded stopping this activity. Now we update our m_current pointer 
+
+                    // If I haven't yet determined the new current activity, it is my creator.
+                    if (newCurrentActivity == null)
+                        newCurrentActivity = activityToStop.m_creator;
+
+                    m_current.Value = newCurrentActivity;
+
+                    if (etwLog.Debug)
+                    {
+                        etwLog.DebugFacilityMessage("OnStopRetActivityState", ActivityInfo.LiveActivities(newCurrentActivity));
+                        etwLog.DebugFacilityMessage("OnStopRet", activityId.ToString());
+                    }
+                    return;
+                }
+                // We failed to stop it.  We must have hit a race to stop it.  Just start over and try again.  
+            }
+        }
+
+        /// <summary>
+        /// Turns on activity tracking.    It is sticky, once on it stays on (race issues otherwise)
+        /// </summary>
+        public void Enable()
+        {
+            if (m_current == null)
+            {
+                // Catch the not Implemented 
+                try
+                {
+                    m_current = new AsyncLocal<ActivityInfo>(ActivityChanging);
+                }
+                catch (NotImplementedException) {
+#if (!ES_BUILD_PCL && ! ES_BUILD_PN)
+                    // send message to debugger without delay
+                    System.Diagnostics.Debugger.Log(0, null, "Activity Enabled() called but AsyncLocals Not Supported (pre V4.6).  Ignoring Enable");
+#endif
+                } 
+            }
+        }
+
+        /// <summary>
+        /// An activity tracker is a singleton, this is how you get the one and only instance.
+        /// </summary>
+        public static ActivityTracker Instance { get { return s_activityTrackerInstance; } }
+
+
+        #region private
+
+        /// <summary>
+        /// Searched for a active (nonstopped) activity with the given name.  Returns null if not found.  
+        /// </summary>
+        private ActivityInfo FindActiveActivity(string name, ActivityInfo startLocation)
+        {
+            var activity = startLocation;
+            while (activity != null)
+            {
+                if (name == activity.m_name && activity.m_stopped == 0)
+                    return activity;
+                activity = activity.m_creator;
+            }
+            return null;
+        }
+
+        /// <summary>
+        /// Strip out "Start" or "End" suffix from activity name and add providerName prefix.
+        /// If 'task'  it does not end in Start or Stop and Task is non-zero use that as the name of the activity
+        /// </summary>
+        private string NormalizeActivityName(string providerName, string activityName, int task)
+        {
+            if (activityName.EndsWith(EventSource.s_ActivityStartSuffix, StringComparison.Ordinal))
+                activityName = activityName.Substring(0, activityName.Length - EventSource.s_ActivityStartSuffix.Length);
+            else if (activityName.EndsWith(EventSource.s_ActivityStopSuffix, StringComparison.Ordinal))
+                activityName = activityName.Substring(0, activityName.Length - EventSource.s_ActivityStopSuffix.Length);
+            else if (task != 0)
+                activityName = "task" + task.ToString();
+
+            // We use provider name to distinguish between activities from different providers.
+            return providerName + activityName;
+        }
+
+        // *******************************************************************************
+        /// <summary>
+        /// An ActivityInfo represents a particular activity.   It is almost read-only.   The only
+        /// fields that change after creation are
+        ///    m_lastChildID - used to generate unique IDs for the children activities and for the most part can be ignored.
+        ///    m_stopped - indicates that this activity is dead 
+        /// This read-only-ness is important because an activity's  m_creator chain forms the 
+        /// 'Path of creation' for the activity (which is also its unique ID) but is also used as
+        /// the 'list of live parents' which indicate of those ancestors, which are alive (if they
+        /// are not marked dead they are alive).   
+        /// </summary>
+        private class ActivityInfo
+        {
+            public ActivityInfo(string name, long uniqueId, ActivityInfo creator, Guid activityIDToRestore, EventActivityOptions options)
+            {
+                m_name = name;
+                m_eventOptions = options;
+                m_creator = creator;
+                m_uniqueId = uniqueId;
+                m_level = creator != null ? creator.m_level + 1 : 0;
+                m_activityIdToRestore = activityIDToRestore;
+
+                // Create a nice GUID that encodes the chain of activities that started this one.
+                CreateActivityPathGuid(out m_guid, out m_activityPathGuidOffset);
+            }
+
+            public Guid ActivityId
+            {
+                get
+                {
+                    return m_guid;
+                }
+            }
+
+            public static string Path(ActivityInfo activityInfo)
+            {
+                if (activityInfo == null)
+                    return ("");
+                return Path(activityInfo.m_creator) + "/" + activityInfo.m_uniqueId.ToString();
+            }
+
+            public override string ToString()
+            {
+                return m_name + "(" + Path(this) + (m_stopped != 0 ? ",DEAD)" : ")");
+            }
+
+            public static string LiveActivities(ActivityInfo list)
+            {
+                if (list == null)
+                    return "";
+                return list.ToString() + ";" + LiveActivities(list.m_creator);
+            }
+
+            public bool CanBeOrphan()
+            {
+                if ((m_eventOptions & EventActivityOptions.Detachable) != 0)
+                    return true;
+                return false;
+            }
+
+            #region private
+
+            #region CreateActivityPathGuid
+            /// <summary>
+            /// Logically every activity Path (see Path()) that describes the activities that caused this 
+            /// (rooted in an activity that predates activity tracking.  
+            ///
+            /// We wish to encode this path in the Guid to the extent that we can.  Many of the paths have
+            /// many small numbers in them and we take advantage of this in the encoding to output as long
+            /// a path in the GUID as possible.   
+            /// 
+            /// Because of the possibility of GUID collision, we only use 96 of the 128 bits of the GUID
+            /// for encoding the path.  The last 32 bits are a simple checksum (and random number) that 
+            /// identifies this as using the convention defined here.   
+            ///
+            /// It returns both the GUID which has the path as well as the offset that points just beyond
+            /// the end of the activity (so it can be appended to).  Note that if the end is in a nibble
+            /// (it uses nibbles instead of bytes as the unit of encoding, then it will point at the unfinished
+            /// byte (since the top nibble can't be zero you can determine if this is true by seeing if 
+            /// this byte is nonZero.   This offset is needed to efficiently create the ID for child activities. 
+            /// </summary>
+            private unsafe void CreateActivityPathGuid(out Guid idRet, out int activityPathGuidOffset)
+            {
+                fixed (Guid* outPtr = &idRet)
+                {
+                    int activityPathGuidOffsetStart = 0;
+                    if (m_creator != null)
+                    {
+                        activityPathGuidOffsetStart = m_creator.m_activityPathGuidOffset;
+                        idRet = m_creator.m_guid;
+                    }
+                    else
+                    {
+                        // TODO FIXME - differentiate between AD inside PCL
+                        int appDomainID = 0;
+#if (!ES_BUILD_STANDALONE && !ES_BUILD_PN)
+                        appDomainID = System.Threading.Thread.GetDomainID();
+#endif
+                        // We start with the appdomain number to make this unique among appdomains.
+                        activityPathGuidOffsetStart = AddIdToGuid(outPtr, activityPathGuidOffsetStart, (uint)appDomainID);
+                    }
+
+                    activityPathGuidOffset = AddIdToGuid(outPtr, activityPathGuidOffsetStart, (uint)m_uniqueId);
+
+
+                    // If the path does not fit, Make a GUID by incrementing rather than as a path, keeping as much of the path as possible
+                    if (12 < activityPathGuidOffset)
+                        CreateOverflowGuid(outPtr);
+                }
+            }
+
+            /// <summary>
+            /// If we can't fit the activity Path into the GUID we come here.   What we do is simply
+            /// generate a 4 byte number (s_nextOverflowId).  Then look for an ancestor that has  
+            /// sufficient space for this ID.   By doing this, we preserve the fact that this activity
+            /// is a child (of unknown depth) from that ancestor.
+            /// </summary>
+            private unsafe void CreateOverflowGuid(Guid* outPtr)
+            {
+                // Search backwards for an ancestor that has sufficient space to put the ID.  
+                for (ActivityInfo ancestor = m_creator; ancestor != null; ancestor = ancestor.m_creator)
+                {
+                    if (ancestor.m_activityPathGuidOffset <= 10)  // we need at least 2 bytes.  
+                    {
+                        uint id = unchecked((uint)Interlocked.Increment(ref ancestor.m_lastChildID));        // Get a unique ID 
+                        // Try to put the ID into the GUID
+                        *outPtr = ancestor.m_guid;
+                        int endId = AddIdToGuid(outPtr, ancestor.m_activityPathGuidOffset, id, true);
+
+                        // Does it fit?
+                        if (endId <= 12)
+                            break;
+                    }
+                }
+            }
+
+            /// <summary>
+            /// The encoding for a list of numbers used to make Activity  GUIDs.   Basically
+            /// we operate on nibbles (which are nice because they show up as hex digits).  The
+            /// list is ended with a end nibble (0) and depending on the nibble value (Below)
+            /// the value is either encoded into nibble itself or it can spill over into the
+            /// bytes that follow.   
+            /// </summary>
+            enum NumberListCodes : byte
+            {
+                End = 0x0,             // ends the list.   No valid value has this prefix.   
+                LastImmediateValue = 0xA,
+
+                PrefixCode = 0xB,      // all the 'long' encodings go here.  If the next nibble is MultiByte1-4
+                                       // than this is a 'overflow' id.   Unlike the hierarchical IDs these are 
+                                       // allocated densely but don't tell you anything about nesting. we use 
+                                       // these when we run out of space in the GUID to store the path.
+
+                MultiByte1 = 0xC,   // 1 byte follows.  If this Nibble is in the high bits, it the high bits of the number are stored in the low nibble.   
+                // commented out because the code does not explicitly reference the names (but they are logically defined).  
+                // MultiByte2 = 0xD,   // 2 bytes follow (we don't bother with the nibble optimization)
+                // MultiByte3 = 0xE,   // 3 bytes follow (we don't bother with the nibble optimization)
+                // MultiByte4 = 0xF,   // 4 bytes follow (we don't bother with the nibble optimization)
+            }
+
+            /// Add the activity id 'id' to the output Guid 'outPtr' starting at the offset 'whereToAddId'
+            /// Thus if this number is 6 that is where 'id' will be added.    This will return 13 (12
+            /// is the maximum number of bytes that fit in a GUID) if the path did not fit.  
+            /// If 'overflow' is true, then the number is encoded as an 'overflow number (which has a
+            /// special (longer prefix) that indicates that this ID is allocated differently 
+            private static unsafe int AddIdToGuid(Guid* outPtr, int whereToAddId, uint id, bool overflow = false)
+            {
+                byte* ptr = (byte*)outPtr;
+                byte* endPtr = ptr + 12;
+                ptr += whereToAddId;
+                if (endPtr <= ptr)
+                    return 13;                // 12 means we might exactly fit, 13 means we definately did not fit
+
+                if (0 < id && id <= (uint)NumberListCodes.LastImmediateValue && !overflow)
+                    WriteNibble(ref ptr, endPtr, id);
+                else
+                {
+                    uint len = 4;
+                    if (id <= 0xFF)
+                        len = 1;
+                    else if (id <= 0xFFFF)
+                        len = 2;
+                    else if (id <= 0xFFFFFF)
+                        len = 3;
+
+                    if (overflow)
+                    {
+                        if (endPtr <= ptr + 2)        // I need at least 2 bytes
+                            return 13;
+
+                        // Write out the prefix code nibble and the length nibble 
+                        WriteNibble(ref ptr, endPtr, (uint)NumberListCodes.PrefixCode);
+                    }
+                    // The rest is the same for overflow and non-overflow case
+                    WriteNibble(ref ptr, endPtr, (uint)NumberListCodes.MultiByte1 + (len - 1));
+
+                    // Do we have an odd nibble?   If so flush it or use it for the 12 byte case.   
+                    if (ptr < endPtr && *ptr != 0)
+                    {
+                        // If the value < 4096 we can use the nibble we are otherwise just outputting as padding. 
+                        if (id < 4096)
+                        {
+                            // Indicate this is a 1 byte multicode with 4 high order bits in the lower nibble.  
+                            *ptr = (byte)(((uint)NumberListCodes.MultiByte1 << 4) + (id >> 8));
+                            id &= 0xFF;     // Now we only want the low order bits.  
+                        }
+                        ptr++;
+                    }
+
+                    // Write out the bytes.
+                    while (0 < len)
+                    {
+                        if (endPtr <= ptr)
+                        {
+                            ptr++;        // Indicate that we have overflowed
+                            break;
+                        }
+                        *ptr++ = (byte)id;
+                        id = (id >> 8);
+                        --len;
+                    }
+                }
+
+                // Compute the checksum 
+                uint* sumPtr = (uint*)outPtr;
+                // We set the last DWORD the sum of the first 3 DWORDS in the GUID.   This 
+                // This last number is a random number (it identifies us as us)  the process ID to make it unique per process. 
+                sumPtr[3] = (sumPtr[0] + sumPtr[1] + sumPtr[2] + 0x599D99AD) ^ EventSource.s_currentPid;
+
+                return (int)(ptr - ((byte*)outPtr));
+            }
+
+            /// <summary>
+            /// Write a single Nible 'value' (must be 0-15) to the byte buffer represented by *ptr.  
+            /// Will not go past 'endPtr'.  Also it assumes that we never write 0 so we can detect
+            /// whether a nibble has already been written to ptr  because it will be nonzero.   
+            /// Thus if it is non-zero it adds to the current byte, otherwise it advances and writes
+            /// the new byte (in the high bits) of the next byte.  
+            /// </summary>
+            private static unsafe void WriteNibble(ref byte* ptr, byte* endPtr, uint value)
+            {
+                Debug.Assert(value < 16);
+                Debug.Assert(ptr < endPtr);
+
+                if (*ptr != 0)
+                    *ptr++ |= (byte)value;
+                else
+                    *ptr = (byte)(value << 4);
+            }
+
+            #endregion // CreateGuidForActivityPath
+
+            readonly internal string m_name;                        // The name used in the 'start' and 'stop' APIs to help match up
+            readonly long m_uniqueId;                               // a small number that makes this activity unique among its siblings
+            internal readonly Guid m_guid;                          // Activity Guid, it is basically an encoding of the Path() (see CreateActivityPathGuid)
+            internal readonly int m_activityPathGuidOffset;         // Keeps track of where in m_guid the causality path stops (used to generated child GUIDs)
+            internal readonly int m_level;                          // current depth of the Path() of the activity (used to keep recursion under control)
+            readonly internal EventActivityOptions m_eventOptions;  // Options passed to start. 
+            internal long m_lastChildID;                            // used to create a unique ID for my children activities
+            internal int m_stopped;                                 // This work item has stopped
+            readonly internal ActivityInfo m_creator;               // My parent (creator).  Forms the Path() for the activity.
+            readonly internal Guid m_activityIdToRestore;           // The Guid to restore after a stop.
+            #endregion
+        }
+
+        // This callback is used to initialize the m_current AsyncLocal Variable.   
+        // Its job is to keep the ETW Activity ID (part of thread local storage) in sync
+        // with m_current.ActivityID
+        void ActivityChanging(AsyncLocalValueChangedArgs<ActivityInfo> args)
+        {
+            ActivityInfo cur = args.CurrentValue;
+            ActivityInfo prev = args.PreviousValue;
+
+            // Are we popping off a value?   (we have a prev, and it creator is cur) 
+            // Then check if we should use the GUID at the time of the start event
+            if (prev != null && prev.m_creator == cur)
+            {
+                // If the saved activity ID is not the same as the creator activity
+                // that takes precedence (it means someone explicitly did a SetActivityID)
+                // Set it to that and get out
+                if (cur == null || prev.m_activityIdToRestore != cur.ActivityId)
+                {
+                    EventSource.SetCurrentThreadActivityId(prev.m_activityIdToRestore);
+                    return;
+                }
+            }
+
+            // OK we did not have an explicit SetActivityID set.   Then we should be 
+            // setting the activity to current ActivityInfo.  However that activity 
+            // might be dead, in which case we should skip it, so we never set 
+            // the ID to dead things.   
+            while (cur != null)
+            {
+                // We found a live activity (typically the first time), set it to that.  
+                if (cur.m_stopped == 0)
+                {
+                    EventSource.SetCurrentThreadActivityId(cur.ActivityId);
+                    return;
+                }
+                cur = cur.m_creator;
+            }
+            // we can get here if there is no information on our activity stack (everything is dead)
+            // currently we do nothing, as that seems better than setting to Guid.Emtpy.  
+        }
+
+        /// <summary>
+        /// Async local variables have the property that the are automatically copied whenever a task is created and used
+        /// while that task is running.   Thus m_current 'flows' to any task that is caused by the current thread that
+        /// last set it.   
+        /// 
+        /// This variable points a a linked list that represents all Activities that have started but have not stopped.  
+        /// </summary>
+        AsyncLocal<ActivityInfo> m_current;
+        bool m_checkedForEnable;
+
+        // Singleton
+        private static ActivityTracker s_activityTrackerInstance = new ActivityTracker();
+
+        // Used to create unique IDs at the top level.  Not used for nested Ids (each activity has its own id generator)
+        static long m_nextId = 0;
+        private const ushort MAX_ACTIVITY_DEPTH = 100;            // Limit maximum depth of activities to be tracked at 100. 
+                                                                  // This will avoid leaking memory in case of activities that are never stopped.
+
+        #endregion
+    }
+
+#if ES_BUILD_STANDALONE || ES_BUILD_PN
+    /******************************** SUPPORT *****************************/
+    /// <summary>
+    /// This is supplied by the framework.   It is has the semantics that the value is copied to any new Tasks that is created
+    /// by the current task.   Thus all causally related code gets this value.    Note that reads and writes to this VARIABLE 
+    /// (not what it points it) to this does not need to be protected by locks because it is inherently thread local (you always
+    /// only get your thread local copy which means that you never have races.  
+    /// </summary>
+    /// 
+#if ES_BUILD_STANDALONE
+    [EventSource(Name = "Microsoft.Tasks.Nuget")]
+#else
+    [EventSource(Name = "System.Diagnostics.Tracing.TplEtwProvider")]
+#endif
+    internal class TplEtwProvider : EventSource
+    {
+        public class Keywords
+        {
+            public const EventKeywords TasksFlowActivityIds = (EventKeywords)0x80;
+            public const EventKeywords Debug = (EventKeywords)0x20000;
+        }
+
+        public static TplEtwProvider Log = new TplEtwProvider();
+        public bool Debug { get { return IsEnabled(EventLevel.Verbose, Keywords.Debug); } }
+
+        public void DebugFacilityMessage(string Facility, string Message) { WriteEvent(1, Facility, Message); }
+        public void DebugFacilityMessage1(string Facility, string Message, string Arg) { WriteEvent(2, Facility, Message, Arg); }
+        public void SetActivityId(Guid Id) { WriteEvent(3, Id); }
+    }
+#endif
+
+#if ES_BUILD_AGAINST_DOTNET_V35 || ES_BUILD_PCL || NO_ASYNC_LOCAL
+    // In these cases we don't have any Async local support.   Do nothing.   
+    internal sealed class AsyncLocalValueChangedArgs<T>
+    {
+        public T PreviousValue { get { return default(T); } }
+        public T CurrentValue { get { return default(T); } }
+
+    }
+
+    internal sealed class AsyncLocal<T>
+    {
+        public AsyncLocal(Action<AsyncLocalValueChangedArgs<T>> valueChangedHandler) { 
+            throw new NotImplementedException("AsyncLocal only available on V4.6 and above");
+        }
+        public T Value
+        {
+            get { return default(T); }
+            set { }
+        }
+    }
+#endif
+
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventActivityOptions.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventActivityOptions.cs
new file mode 100644
index 0000000000..782afbf869
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventActivityOptions.cs
@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// EventActivityOptions flags allow to specify different activity related characteristics.
+    /// </summary>
+    [Flags]
+    public enum EventActivityOptions
+    {
+        /// <summary>
+        /// No special options are added to the event.
+        /// </summary>
+        None = 0,
+
+        /// <summary>
+        /// Disable Implicit Activity Tracking
+        /// </summary>
+        Disable = 0x2,
+
+        /// <summary>
+        /// Allow activity event to call itself (directly or indirectly)
+        /// </summary>
+        Recursive = 0x4,
+
+        /// <summary>
+        /// Allows event activity to live beyond its parent.
+        /// </summary>
+        Detachable = 0x8
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventDescriptor.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventDescriptor.cs
new file mode 100644
index 0000000000..0fed7b5c00
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventDescriptor.cs
@@ -0,0 +1,217 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+#if ES_BUILD_STANDALONE
+using Environment = Microsoft.Diagnostics.Tracing.Internal.Environment;
+#endif
+
+#if !ES_BUILD_AGAINST_DOTNET_V35
+using Contract = System.Diagnostics.Contracts.Contract;
+#else
+using Contract = Microsoft.Diagnostics.Contracts.Internal.Contract;
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    [StructLayout(LayoutKind.Explicit, Size = 16)]
+#if !CORECLR && !ES_BUILD_PN    
+    [System.Security.Permissions.HostProtection(MayLeakOnAbort = true)]
+#endif // !CORECLR && !ES_BUILD_PN
+
+    /*
+     EventDescriptor was public in the separate System.Diagnostics.Tracing assembly(pre NS2.0), 
+     now the move to CoreLib marked them as private.
+     While they are technically private (it's a contract used between the library and the ILC toolchain), 
+     we need them to be rooted and exported from shared library for the system to work.
+     For now I'm simply marking them as public again.A cleaner solution might be to use.rd.xml to 
+     root them and modify shared library definition to force export them.
+     */
+#if ES_BUILD_PN
+    public
+#else
+    internal
+#endif
+    struct EventDescriptor
+    {
+        # region private
+        [FieldOffset(0)]
+        private int m_traceloggingId;
+        [FieldOffset(0)]
+        private ushort m_id;
+        [FieldOffset(2)]
+        private byte m_version;
+        [FieldOffset(3)]
+        private byte m_channel;
+        [FieldOffset(4)]
+        private byte m_level;
+        [FieldOffset(5)]
+        private byte m_opcode;
+        [FieldOffset(6)]
+        private ushort m_task;
+        [FieldOffset(8)]
+        private long m_keywords;
+        #endregion
+
+        public EventDescriptor(
+                int traceloggingId,
+                byte level,
+                byte opcode,
+                long keywords
+                )
+        {
+            this.m_id = 0;
+            this.m_version = 0;
+            this.m_channel = 0;
+            this.m_traceloggingId = traceloggingId;
+            this.m_level = level;
+            this.m_opcode = opcode;
+            this.m_task = 0;
+            this.m_keywords = keywords;
+        }
+
+        public EventDescriptor(
+                int id,
+                byte version,
+                byte channel,
+                byte level,
+                byte opcode,
+                int task,
+                long keywords
+                )
+        {
+            if (id < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(id), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (id > ushort.MaxValue)
+            {
+                throw new ArgumentOutOfRangeException(nameof(id), SR.Format(SR.ArgumentOutOfRange_NeedValidId, 1, ushort.MaxValue));
+            }
+
+            m_traceloggingId = 0;
+            m_id = (ushort)id;
+            m_version = version;
+            m_channel = channel;
+            m_level = level;
+            m_opcode = opcode;
+            m_keywords = keywords;
+
+            if (task < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(task), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (task > ushort.MaxValue)
+            {
+                throw new ArgumentOutOfRangeException(nameof(task), SR.Format(SR.ArgumentOutOfRange_NeedValidId, 1, ushort.MaxValue));
+            }
+
+            m_task = (ushort)task;
+        }
+
+        public int EventId
+        {
+            get
+            {
+                return m_id;
+            }
+        }
+        public byte Version
+        {
+            get
+            {
+                return m_version;
+            }
+        }
+        public byte Channel
+        {
+            get
+            {
+                return m_channel;
+            }
+        }
+        public byte Level
+        {
+            get
+            {
+                return m_level;
+            }
+        }
+        public byte Opcode
+        {
+            get
+            {
+                return m_opcode;
+            }
+        }
+        public int Task
+        {
+            get
+            {
+                return m_task;
+            }
+        }
+        public long Keywords
+        {
+            get
+            {
+                return m_keywords;
+            }
+        }
+
+        internal int TraceLoggingId
+        {
+            get
+            {
+                return m_traceloggingId;
+            }
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (!(obj is EventDescriptor))
+                return false;
+
+            return Equals((EventDescriptor) obj);
+        }
+
+        public override int GetHashCode()
+        {
+            return m_id ^ m_version ^ m_channel ^ m_level ^ m_opcode ^ m_task ^ (int)m_keywords;
+        }
+
+        public bool Equals(EventDescriptor other)
+        {
+            if ((m_id != other.m_id) ||
+                (m_version != other.m_version) ||
+                (m_channel != other.m_channel) ||
+                (m_level != other.m_level) ||
+                (m_opcode != other.m_opcode) ||
+                (m_task != other.m_task) ||
+                (m_keywords != other.m_keywords))
+            {
+                return false;
+            }
+            return true;
+        }
+
+        public static bool operator ==(EventDescriptor event1, EventDescriptor event2)
+        {
+            return event1.Equals(event2);
+        }
+
+        public static bool operator !=(EventDescriptor event1, EventDescriptor event2)
+        {
+            return !event1.Equals(event2);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventProvider.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventProvider.cs
new file mode 100644
index 0000000000..c1e4298da8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventProvider.cs
@@ -0,0 +1,1323 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+using Microsoft.Win32;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Globalization;
+using System.Runtime.InteropServices;
+using System.Security;
+#if !CORECLR && !ES_BUILD_PN
+using System.Security.Permissions;
+#endif // !CORECLR && !ES_BUILD_PN
+using System.Threading;
+using System;
+
+#if !ES_BUILD_AGAINST_DOTNET_V35
+using Contract = System.Diagnostics.Contracts.Contract;
+#else
+using Contract = Microsoft.Diagnostics.Contracts.Internal.Contract;
+#endif
+
+#if ES_BUILD_AGAINST_DOTNET_V35
+using Microsoft.Internal;       // for Tuple (can't define alias for open generic types so we "use" the whole namespace)
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    // New in CLR4.0
+    internal enum ControllerCommand
+    {
+        // Strictly Positive numbers are for provider-specific commands, negative number are for 'shared' commands. 256
+        // The first 256 negative numbers are reserved for the framework.  
+        Update = 0,                 // Not used by EventPrividerBase.  
+        SendManifest = -1,
+        Enable = -2,
+        Disable = -3,
+    };
+
+    /// <summary>
+    /// Only here because System.Diagnostics.EventProvider needs one more extensibility hook (when it gets a 
+    /// controller callback)
+    /// </summary>
+#if !CORECLR && !ES_BUILD_PN
+    [System.Security.Permissions.HostProtection(MayLeakOnAbort = true)]
+#endif // !CORECLR && !ES_BUILD_PN
+    internal partial class EventProvider : IDisposable
+    {
+        // This is the windows EVENT_DATA_DESCRIPTOR structure.  We expose it because this is what
+        // subclasses of EventProvider use when creating efficient (but unsafe) version of
+        // EventWrite.   We do make it a nested type because we really don't expect anyone to use 
+        // it except subclasses (and then only rarely).  
+        [StructLayout(LayoutKind.Sequential)]
+        public struct EventData
+        {
+            internal unsafe ulong Ptr;
+            internal uint Size;
+            internal uint Reserved;
+        }
+
+        /// <summary>
+        /// A struct characterizing ETW sessions (identified by the etwSessionId) as
+        /// activity-tracing-aware or legacy. A session that's activity-tracing-aware
+        /// has specified one non-zero bit in the reserved range 44-47 in the 
+        /// 'allKeywords' value it passed in for a specific EventProvider.
+        /// </summary>
+        public struct SessionInfo
+        {
+            internal int sessionIdBit;      // the index of the bit used for tracing in the "reserved" field of AllKeywords
+            internal int etwSessionId;      // the machine-wide ETW session ID
+
+            internal SessionInfo(int sessionIdBit_, int etwSessionId_)
+            { sessionIdBit = sessionIdBit_; etwSessionId = etwSessionId_; }
+        }
+
+        private static bool m_setInformationMissing;
+
+        internal IEventProvider m_eventProvider;         // The interface that implements the specific logging mechanism functions.
+        UnsafeNativeMethods.ManifestEtw.EtwEnableCallback m_etwCallback;     // Trace Callback function
+        private long m_regHandle;                        // Trace Registration Handle
+        private byte m_level;                            // Tracing Level
+        private long m_anyKeywordMask;                   // Trace Enable Flags
+        private long m_allKeywordMask;                   // Match all keyword
+        private List<SessionInfo> m_liveSessions;        // current live sessions (Tuple<sessionIdBit, etwSessionId>)
+        private bool m_enabled;                          // Enabled flag from Trace callback
+        private string m_providerName;                   // Control name
+        private Guid m_providerId;                       // Control Guid
+        internal bool m_disposed;                        // when true provider has unregistered
+
+        [ThreadStatic]
+        private static WriteEventErrorCode s_returnCode; // The last return code 
+
+        private const int s_basicTypeAllocationBufferSize = 16;
+        private const int s_etwMaxNumberArguments = 128;
+        private const int s_etwAPIMaxRefObjCount = 8;
+        private const int s_maxEventDataDescriptors = 128;
+        private const int s_traceEventMaximumSize = 65482;
+        private const int s_traceEventMaximumStringSize = 32724;
+
+        [SuppressMessage("Microsoft.Design", "CA1034:NestedTypesShouldNotBeVisible")]
+        public enum WriteEventErrorCode : int
+        {
+            //check mapping to runtime codes
+            NoError = 0,
+            NoFreeBuffers = 1,
+            EventTooBig = 2,
+            NullInput = 3,
+            TooManyArgs = 4,
+            Other = 5,
+        };
+
+        // Because callbacks happen on registration, and we need the callbacks for those setup
+        // we can't call Register in the constructor.   
+        //
+        // Note that EventProvider should ONLY be used by EventSource.  In particular because
+        // it registers a callback from native code you MUST dispose it BEFORE shutdown, otherwise
+        // you may get native callbacks during shutdown when we have destroyed the delegate.  
+        // EventSource has special logic to do this, no one else should be calling EventProvider.  
+        internal EventProvider()
+        {
+#if PLATFORM_WINDOWS
+            m_eventProvider = new EtwEventProvider();
+#elif FEATURE_PERFTRACING
+            m_eventProvider = new EventPipeEventProvider();
+#else
+            m_eventProvider = new NoOpEventProvider();
+#endif
+        }
+
+        /// <summary>
+        /// This method registers the controlGuid of this class with ETW. We need to be running on
+        /// Vista or above. If not a PlatformNotSupported exception will be thrown. If for some 
+        /// reason the ETW Register call failed a NotSupported exception will be thrown. 
+        /// </summary>
+        // <SecurityKernel Critical="True" Ring="0">
+        // <CallsSuppressUnmanagedCode Name="UnsafeNativeMethods.ManifestEtw.EventRegister(System.Guid&,Microsoft.Win32.UnsafeNativeMethods.ManifestEtw+EtwEnableCallback,System.Void*,System.Int64&):System.UInt32" />
+        // <SatisfiesLinkDemand Name="Win32Exception..ctor(System.Int32)" />
+        // <ReferencesCritical Name="Method: EtwEnableCallBack(Guid&, Int32, Byte, Int64, Int64, Void*, Void*):Void" Ring="1" />
+        // </SecurityKernel>
+        internal unsafe void Register(EventSource eventSource)
+        {
+            uint status;
+            m_etwCallback = new UnsafeNativeMethods.ManifestEtw.EtwEnableCallback(EtwEnableCallBack);
+
+            status = EventRegister(eventSource, m_etwCallback);
+            if (status != 0)
+            {
+#if PLATFORM_WINDOWS && !ES_BUILD_STANDALONE
+                throw new ArgumentException(Interop.Kernel32.GetMessage(unchecked((int)status)));
+#else
+                throw new ArgumentException(Convert.ToString(unchecked((int)status)));
+#endif
+            }
+        }
+
+        //
+        // implement Dispose Pattern to early deregister from ETW insted of waiting for 
+        // the finalizer to call deregistration.
+        // Once the user is done with the provider it needs to call Close() or Dispose()
+        // If neither are called the finalizer will unregister the provider anyway
+        //
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        // <SecurityKernel Critical="True" TreatAsSafe="Does not expose critical resource" Ring="1">
+        // <ReferencesCritical Name="Method: Deregister():Void" Ring="1" />
+        // </SecurityKernel>
+        protected virtual void Dispose(bool disposing)
+        {
+            //
+            // explicit cleanup is done by calling Dispose with true from 
+            // Dispose() or Close(). The disposing arguement is ignored because there
+            // are no unmanaged resources.
+            // The finalizer calls Dispose with false.
+            //
+
+            //
+            // check if the object has been already disposed
+            //
+            if (m_disposed) return;
+
+            // Disable the provider.  
+            m_enabled = false;
+
+            // Do most of the work under a lock to avoid shutdown race.
+
+            long registrationHandle = 0;  
+            lock (EventListener.EventListenersLock)
+            {
+                // Double check
+                if (m_disposed)
+                    return;
+
+                registrationHandle = m_regHandle;
+                m_regHandle = 0;
+                m_disposed = true;
+            }
+
+            // We do the Unregistration outside the EventListenerLock because there is a lock
+            // inside the ETW routines.   This lock is taken before ETW issues commands
+            // Thus the ETW lock gets taken first and then our EventListenersLock gets taken
+            // in SendCommand(), and also here.  If we called EventUnregister after taking
+            // the EventListenersLock then the take-lock order is reversed and we can have
+            // deadlocks in race conditions (dispose racing with an ETW command).   
+            // 
+            // We solve by Unregistering after releasing the EventListenerLock.     
+            if (registrationHandle != 0)
+                EventUnregister(registrationHandle);
+
+        }
+
+        /// <summary>
+        /// This method deregisters the controlGuid of this class with ETW.
+        /// 
+        /// </summary>
+        public virtual void Close()
+        {
+            Dispose();
+        }
+
+        ~EventProvider()
+        {
+            Dispose(false);
+        }
+
+        // <SecurityKernel Critical="True" Ring="0">
+        // <UsesUnsafeCode Name="Parameter filterData of type: Void*" />
+        // <UsesUnsafeCode Name="Parameter callbackContext of type: Void*" />
+        // </SecurityKernel>
+        unsafe void EtwEnableCallBack(
+                        [In] ref System.Guid sourceId,
+                        [In] int controlCode,
+                        [In] byte setLevel,
+                        [In] long anyKeyword,
+                        [In] long allKeyword,
+                        [In] UnsafeNativeMethods.ManifestEtw.EVENT_FILTER_DESCRIPTOR* filterData,
+                        [In] void* callbackContext
+                        )
+        {
+            // This is an optional callback API. We will therefore ignore any failures that happen as a 
+            // result of turning on this provider as to not crash the app.
+            // EventSource has code to validate whether initialization it expected to occur actually occurred
+            try
+            {
+                ControllerCommand command = ControllerCommand.Update;
+                IDictionary<string, string> args = null;
+                bool skipFinalOnControllerCommand = false;
+                if (controlCode == UnsafeNativeMethods.ManifestEtw.EVENT_CONTROL_CODE_ENABLE_PROVIDER)
+                {
+                    m_enabled = true;
+                    m_level = setLevel;
+                    m_anyKeywordMask = anyKeyword;
+                    m_allKeywordMask = allKeyword;
+
+                    List<Tuple<SessionInfo, bool>> sessionsChanged = GetSessions();
+                    foreach (var session in sessionsChanged)
+                    {
+                        int sessionChanged = session.Item1.sessionIdBit;
+                        int etwSessionId = session.Item1.etwSessionId;
+                        bool bEnabling = session.Item2;
+
+                        skipFinalOnControllerCommand = true;
+                        args = null;                                // reinitialize args for every session...
+
+                        // if we get more than one session changed we have no way
+                        // of knowing which one "filterData" belongs to
+                        if (sessionsChanged.Count > 1)
+                            filterData = null;
+
+                        // read filter data only when a session is being *added*
+                        byte[] data;
+                        int keyIndex;
+                        if (bEnabling &&
+                            GetDataFromController(etwSessionId, filterData, out command, out data, out keyIndex))
+                        {
+                            args = new Dictionary<string, string>(4);
+                            while (keyIndex < data.Length)
+                            {
+                                int keyEnd = FindNull(data, keyIndex);
+                                int valueIdx = keyEnd + 1;
+                                int valueEnd = FindNull(data, valueIdx);
+                                if (valueEnd < data.Length)
+                                {
+                                    string key = System.Text.Encoding.UTF8.GetString(data, keyIndex, keyEnd - keyIndex);
+                                    string value = System.Text.Encoding.UTF8.GetString(data, valueIdx, valueEnd - valueIdx);
+                                    args[key] = value;
+                                }
+                                keyIndex = valueEnd + 1;
+                            }
+                        }
+
+                        // execute OnControllerCommand once for every session that has changed.
+                        OnControllerCommand(command, args, (bEnabling ? sessionChanged : -sessionChanged), etwSessionId);
+                    }
+                }
+                else if (controlCode == UnsafeNativeMethods.ManifestEtw.EVENT_CONTROL_CODE_DISABLE_PROVIDER)
+                {
+                    m_enabled = false;
+                    m_level = 0;
+                    m_anyKeywordMask = 0;
+                    m_allKeywordMask = 0;
+                    m_liveSessions = null;
+                }
+                else if (controlCode == UnsafeNativeMethods.ManifestEtw.EVENT_CONTROL_CODE_CAPTURE_STATE)
+                {
+                    command = ControllerCommand.SendManifest;
+                }
+                else
+                    return;     // per spec you ignore commands you don't recognize.  
+
+                if (!skipFinalOnControllerCommand)
+                    OnControllerCommand(command, args, 0, 0);
+            }
+            catch (Exception)
+            {
+                // We want to ignore any failures that happen as a result of turning on this provider as to
+                // not crash the app.
+            }
+        }
+
+        // New in CLR4.0
+        protected virtual void OnControllerCommand(ControllerCommand command, IDictionary<string, string> arguments, int sessionId, int etwSessionId) { }
+        protected EventLevel Level { get { return (EventLevel)m_level; } set { m_level = (byte)value; } }
+        protected EventKeywords MatchAnyKeyword { get { return (EventKeywords)m_anyKeywordMask; } set { m_anyKeywordMask = unchecked((long)value); } }
+        protected EventKeywords MatchAllKeyword { get { return (EventKeywords)m_allKeywordMask; } set { m_allKeywordMask = unchecked((long)value); } }
+
+        private static int FindNull(byte[] buffer, int idx)
+        {
+            while (idx < buffer.Length && buffer[idx] != 0)
+                idx++;
+            return idx;
+        }
+
+        /// <summary>
+        /// Determines the ETW sessions that have been added and/or removed to the set of
+        /// sessions interested in the current provider. It does so by (1) enumerating over all
+        /// ETW sessions that enabled 'this.m_Guid' for the current process ID, and (2)
+        /// comparing the current list with a list it cached on the previous invocation.
+        ///
+        /// The return value is a list of tuples, where the SessionInfo specifies the
+        /// ETW session that was added or remove, and the bool specifies whether the
+        /// session was added or whether it was removed from the set.
+        /// </summary>
+        private List<Tuple<SessionInfo, bool>> GetSessions()
+        {
+            List<SessionInfo> liveSessionList = null;
+
+            GetSessionInfo(
+                (int etwSessionId, long matchAllKeywords, ref List<SessionInfo> sessionList) =>
+                    GetSessionInfoCallback(etwSessionId, matchAllKeywords, ref sessionList),
+                ref liveSessionList);
+
+            List<Tuple<SessionInfo, bool>> changedSessionList = new List<Tuple<SessionInfo, bool>>();
+
+            // first look for sessions that have gone away (or have changed)
+            // (present in the m_liveSessions but not in the new liveSessionList)
+            if (m_liveSessions != null)
+            {
+                foreach (SessionInfo s in m_liveSessions)
+                {
+                    int idx;
+                    if ((idx = IndexOfSessionInList(liveSessionList, s.etwSessionId)) < 0 ||
+                        (liveSessionList[idx].sessionIdBit != s.sessionIdBit))
+                        changedSessionList.Add(Tuple.Create(s, false));
+
+                }
+            }
+            // next look for sessions that were created since the last callback  (or have changed)
+            // (present in the new liveSessionList but not in m_liveSessions)
+            if (liveSessionList != null)
+            {
+                foreach (SessionInfo s in liveSessionList)
+                {
+                    int idx;
+                    if ((idx = IndexOfSessionInList(m_liveSessions, s.etwSessionId)) < 0 ||
+                        (m_liveSessions[idx].sessionIdBit != s.sessionIdBit))
+                        changedSessionList.Add(Tuple.Create(s, true));
+                }
+            }
+
+            m_liveSessions = liveSessionList;
+            return changedSessionList;
+        }
+
+
+        /// <summary>
+        /// This method is the callback used by GetSessions() when it calls into GetSessionInfo(). 
+        /// It updates a List{SessionInfo} based on the etwSessionId and matchAllKeywords that 
+        /// GetSessionInfo() passes in.
+        /// </summary>
+        private static void GetSessionInfoCallback(int etwSessionId, long matchAllKeywords,
+                                ref List<SessionInfo> sessionList)
+        {
+            uint sessionIdBitMask = (uint)SessionMask.FromEventKeywords(unchecked((ulong)matchAllKeywords));
+            // an ETW controller that specifies more than the mandated bit for our EventSource
+            // will be ignored...
+            if (bitcount(sessionIdBitMask) > 1)
+                return;
+
+            if (sessionList == null)
+                sessionList = new List<SessionInfo>(8);
+
+            if (bitcount(sessionIdBitMask) == 1)
+            {
+                // activity-tracing-aware etw session
+                sessionList.Add(new SessionInfo(bitindex(sessionIdBitMask) + 1, etwSessionId));
+            }
+            else
+            {
+                // legacy etw session
+                sessionList.Add(new SessionInfo(bitcount((uint)SessionMask.All) + 1, etwSessionId));
+            }
+        }
+
+        private delegate void SessionInfoCallback(int etwSessionId, long matchAllKeywords, ref List<SessionInfo> sessionList);
+        
+        /// <summary>
+        /// This method enumerates over all active ETW sessions that have enabled 'this.m_Guid' 
+        /// for the current process ID, calling 'action' for each session, and passing it the
+        /// ETW session and the 'AllKeywords' the session enabled for the current provider.
+        /// </summary>
+        private unsafe void GetSessionInfo(SessionInfoCallback action, ref List<SessionInfo> sessionList)
+        {
+            // We wish the EventSource package to be legal for Windows Store applications.   
+            // Currently EnumerateTraceGuidsEx is not an allowed API, so we avoid its use here
+            // and use the information in the registry instead.  This means that ETW controllers
+            // that do not publish their intent to the registry (basically all controllers EXCEPT 
+            // TraceEventSesion) will not work properly 
+
+            // However the framework version of EventSource DOES have ES_SESSION_INFO defined and thus
+            // does not have this issue.  
+#if (PLATFORM_WINDOWS && (ES_SESSION_INFO || !ES_BUILD_STANDALONE))
+            int buffSize = 256;     // An initial guess that probably works most of the time.  
+            byte* buffer;
+            for (; ; )
+            {
+                var space = stackalloc byte[buffSize];
+                buffer = space;
+                var hr = 0;
+
+                fixed (Guid* provider = &m_providerId)
+                {
+                    hr = UnsafeNativeMethods.ManifestEtw.EnumerateTraceGuidsEx(UnsafeNativeMethods.ManifestEtw.TRACE_QUERY_INFO_CLASS.TraceGuidQueryInfo,
+                        provider, sizeof(Guid), buffer, buffSize, ref buffSize);
+                }
+                if (hr == 0)
+                    break;
+                if (hr != 122 /* ERROR_INSUFFICIENT_BUFFER */)
+                    return;
+            }
+
+            var providerInfos = (UnsafeNativeMethods.ManifestEtw.TRACE_GUID_INFO*)buffer;
+            var providerInstance = (UnsafeNativeMethods.ManifestEtw.TRACE_PROVIDER_INSTANCE_INFO*)&providerInfos[1];
+            int processId = unchecked((int)Win32Native.GetCurrentProcessId());
+            // iterate over the instances of the EventProvider in all processes
+            for (int i = 0; i < providerInfos->InstanceCount; i++)
+            {
+                if (providerInstance->Pid == processId)
+                {
+                    var enabledInfos = (UnsafeNativeMethods.ManifestEtw.TRACE_ENABLE_INFO*)&providerInstance[1];
+                    // iterate over the list of active ETW sessions "listening" to the current provider
+                    for (int j = 0; j < providerInstance->EnableCount; j++)
+                        action(enabledInfos[j].LoggerId, enabledInfos[j].MatchAllKeyword, ref sessionList);
+                }
+                if (providerInstance->NextOffset == 0)
+                    break;
+                Debug.Assert(0 <= providerInstance->NextOffset && providerInstance->NextOffset < buffSize);
+                var structBase = (byte*)providerInstance;
+                providerInstance = (UnsafeNativeMethods.ManifestEtw.TRACE_PROVIDER_INSTANCE_INFO*)&structBase[providerInstance->NextOffset];
+            }
+#else 
+#if !ES_BUILD_PCL && PLATFORM_WINDOWS  // TODO command arguments don't work on PCL builds...
+            // This code is only used in the Nuget Package Version of EventSource.  because
+            // the code above is using APIs baned from UWP apps.     
+            // 
+            // TODO: In addition to only working when TraceEventSession enables the provider, this code
+            // also has a problem because TraceEvent does not clean up if the registry is stale 
+            // It is unclear if it is worth keeping, but for now we leave it as it does work
+            // at least some of the time.  
+
+            // Determine our session from what is in the registry.  
+            string regKey = @"\Microsoft\Windows\CurrentVersion\Winevt\Publishers\{" + m_providerName + "}";
+            if (System.Runtime.InteropServices.Marshal.SizeOf(typeof(IntPtr)) == 8)
+                regKey = @"Software" + @"\Wow6432Node" + regKey;
+            else
+                regKey = @"Software" + regKey;
+
+            var key = Microsoft.Win32.Registry.LocalMachine.OpenSubKey(regKey);
+            if (key != null)
+            {
+                foreach (string valueName in key.GetValueNames())
+                {
+                    if (valueName.StartsWith("ControllerData_Session_", StringComparison.Ordinal))
+                    {
+                        string strId = valueName.Substring(23);      // strip of the ControllerData_Session_
+                        int etwSessionId;
+                        if (int.TryParse(strId, out etwSessionId))
+                        {
+                            // we need to assert this permission for partial trust scenarios
+                            (new RegistryPermission(RegistryPermissionAccess.Read, regKey)).Assert();
+                            var data = key.GetValue(valueName) as byte[];
+                            if (data != null)
+                            {
+                                var dataAsString = System.Text.Encoding.UTF8.GetString(data);
+                                int keywordIdx = dataAsString.IndexOf("EtwSessionKeyword", StringComparison.Ordinal);
+                                if (0 <= keywordIdx)
+                                {
+                                    int startIdx = keywordIdx + 18;
+                                    int endIdx = dataAsString.IndexOf('\0', startIdx);
+                                    string keywordBitString = dataAsString.Substring(startIdx, endIdx-startIdx);
+                                    int keywordBit;
+                                    if (0 < endIdx && int.TryParse(keywordBitString, out keywordBit))
+                                        action(etwSessionId, 1L << keywordBit, ref sessionList);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+#endif
+#endif
+        }
+
+        /// <summary>
+        /// Returns the index of the SesisonInfo from 'sessions' that has the specified 'etwSessionId'
+        /// or -1 if the value is not present.
+        /// </summary>
+        private static int IndexOfSessionInList(List<SessionInfo> sessions, int etwSessionId)
+        {
+            if (sessions == null)
+                return -1;
+            // for non-coreclr code we could use List<T>.FindIndex(Predicate<T>), but we need this to compile
+            // on coreclr as well
+            for (int i = 0; i < sessions.Count; ++i)
+                if (sessions[i].etwSessionId == etwSessionId)
+                    return i;
+
+            return -1;
+        }
+
+        /// <summary>
+        /// Gets any data to be passed from the controller to the provider.  It starts with what is passed
+        /// into the callback, but unfortunately this data is only present for when the provider is active
+        /// at the time the controller issues the command.  To allow for providers to activate after the
+        /// controller issued a command, we also check the registry and use that to get the data.  The function
+        /// returns an array of bytes representing the data, the index into that byte array where the data
+        /// starts, and the command being issued associated with that data.  
+        /// </summary>
+        private unsafe bool GetDataFromController(int etwSessionId,
+                UnsafeNativeMethods.ManifestEtw.EVENT_FILTER_DESCRIPTOR* filterData, out ControllerCommand command, out byte[] data, out int dataStart)
+        {
+            data = null;
+            dataStart = 0;
+            if (filterData == null)
+            {
+#if (!ES_BUILD_PCL && !ES_BUILD_PN && PLATFORM_WINDOWS)
+                string regKey = @"\Microsoft\Windows\CurrentVersion\Winevt\Publishers\{" + m_providerId + "}";
+                if (System.Runtime.InteropServices.Marshal.SizeOf(typeof(IntPtr)) == 8)
+                    regKey = @"HKEY_LOCAL_MACHINE\Software" + @"\Wow6432Node" + regKey;
+                else
+                    regKey = @"HKEY_LOCAL_MACHINE\Software" + regKey;
+
+                string valueName = "ControllerData_Session_" + etwSessionId.ToString(CultureInfo.InvariantCulture);
+
+                // we need to assert this permission for partial trust scenarios
+#if !CORECLR
+                (new RegistryPermission(RegistryPermissionAccess.Read, regKey)).Assert();
+#endif
+                data = Microsoft.Win32.Registry.GetValue(regKey, valueName, null) as byte[];
+                if (data != null)
+                {
+                    // We only used the persisted data from the registry for updates.   
+                    command = ControllerCommand.Update;
+                    return true;
+                }
+#endif
+            }
+            else
+            {
+                if (filterData->Ptr != 0 && 0 < filterData->Size && filterData->Size <= 1024)
+                {
+                    data = new byte[filterData->Size];
+                    Marshal.Copy((IntPtr)filterData->Ptr, data, 0, data.Length);
+                }
+                command = (ControllerCommand)filterData->Type;
+                return true;
+            }
+
+            command = ControllerCommand.Update;
+            return false;
+        }
+
+        /// <summary>
+        /// IsEnabled, method used to test if provider is enabled
+        /// </summary>
+        public bool IsEnabled()
+        {
+            return m_enabled;
+        }
+
+        /// <summary>
+        /// IsEnabled, method used to test if event is enabled
+        /// </summary>
+        /// <param name="level">
+        /// Level  to test
+        /// </param>
+        /// <param name="keywords">
+        /// Keyword  to test
+        /// </param>
+        public bool IsEnabled(byte level, long keywords)
+        {
+            //
+            // If not enabled at all, return false.
+            //
+            if (!m_enabled)
+            {
+                return false;
+            }
+
+            // This also covers the case of Level == 0.
+            if ((level <= m_level) ||
+                (m_level == 0))
+            {
+
+                //
+                // Check if Keyword is enabled
+                //
+
+                if ((keywords == 0) ||
+                    (((keywords & m_anyKeywordMask) != 0) &&
+                     ((keywords & m_allKeywordMask) == m_allKeywordMask)))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate")]
+        public static WriteEventErrorCode GetLastWriteEventError()
+        {
+            return s_returnCode;
+        }
+
+        //
+        // Helper function to set the last error on the thread
+        //
+        private static void SetLastError(int error)
+        {
+            switch (error)
+            {
+                case UnsafeNativeMethods.ManifestEtw.ERROR_ARITHMETIC_OVERFLOW:
+                case UnsafeNativeMethods.ManifestEtw.ERROR_MORE_DATA:
+                    s_returnCode = WriteEventErrorCode.EventTooBig;
+                    break;
+                case UnsafeNativeMethods.ManifestEtw.ERROR_NOT_ENOUGH_MEMORY:
+                    s_returnCode = WriteEventErrorCode.NoFreeBuffers;
+                    break;
+            }
+        }
+
+        // <SecurityKernel Critical="True" Ring="0">
+        // <UsesUnsafeCode Name="Local intptrPtr of type: IntPtr*" />
+        // <UsesUnsafeCode Name="Local intptrPtr of type: Int32*" />
+        // <UsesUnsafeCode Name="Local longptr of type: Int64*" />
+        // <UsesUnsafeCode Name="Local uintptr of type: UInt32*" />
+        // <UsesUnsafeCode Name="Local ulongptr of type: UInt64*" />
+        // <UsesUnsafeCode Name="Local charptr of type: Char*" />
+        // <UsesUnsafeCode Name="Local byteptr of type: Byte*" />
+        // <UsesUnsafeCode Name="Local shortptr of type: Int16*" />
+        // <UsesUnsafeCode Name="Local sbyteptr of type: SByte*" />
+        // <UsesUnsafeCode Name="Local ushortptr of type: UInt16*" />
+        // <UsesUnsafeCode Name="Local floatptr of type: Single*" />
+        // <UsesUnsafeCode Name="Local doubleptr of type: Double*" />
+        // <UsesUnsafeCode Name="Local boolptr of type: Boolean*" />
+        // <UsesUnsafeCode Name="Local guidptr of type: Guid*" />
+        // <UsesUnsafeCode Name="Local decimalptr of type: Decimal*" />
+        // <UsesUnsafeCode Name="Local booleanptr of type: Boolean*" />
+        // <UsesUnsafeCode Name="Parameter dataDescriptor of type: EventData*" />
+        // <UsesUnsafeCode Name="Parameter dataBuffer of type: Byte*" />
+        // </SecurityKernel>
+        private static unsafe object EncodeObject(ref object data, ref EventData* dataDescriptor, ref byte* dataBuffer, ref uint totalEventSize)
+        /*++
+
+        Routine Description:
+
+           This routine is used by WriteEvent to unbox the object type and
+           to fill the passed in ETW data descriptor. 
+
+        Arguments:
+
+           data - argument to be decoded
+
+           dataDescriptor - pointer to the descriptor to be filled (updated to point to the next empty entry)
+
+           dataBuffer - storage buffer for storing user data, needed because cant get the address of the object
+                        (updated to point to the next empty entry)
+
+        Return Value:
+
+           null if the object is a basic type other than string or byte[]. String otherwise
+
+        --*/
+        {
+        Again:
+            dataDescriptor->Reserved = 0;
+
+            string sRet = data as string;
+            byte[] blobRet = null;
+
+            if (sRet != null)
+            {
+                dataDescriptor->Size = ((uint)sRet.Length + 1) * 2;
+            }
+            else if ((blobRet = data as byte[]) != null)
+            {
+                // first store array length
+                *(int*)dataBuffer = blobRet.Length;
+                dataDescriptor->Ptr = (ulong)dataBuffer;
+                dataDescriptor->Size = 4;
+                totalEventSize += dataDescriptor->Size;
+
+                // then the array parameters
+                dataDescriptor++;
+                dataBuffer += s_basicTypeAllocationBufferSize;
+                dataDescriptor->Size = (uint)blobRet.Length;
+            }
+            else if (data is IntPtr)
+            {
+                dataDescriptor->Size = (uint)sizeof(IntPtr);
+                IntPtr* intptrPtr = (IntPtr*)dataBuffer;
+                *intptrPtr = (IntPtr)data;
+                dataDescriptor->Ptr = (ulong)intptrPtr;
+            }
+            else if (data is int)
+            {
+                dataDescriptor->Size = (uint)sizeof(int);
+                int* intptr = (int*)dataBuffer;
+                *intptr = (int)data;
+                dataDescriptor->Ptr = (ulong)intptr;
+            }
+            else if (data is long)
+            {
+                dataDescriptor->Size = (uint)sizeof(long);
+                long* longptr = (long*)dataBuffer;
+                *longptr = (long)data;
+                dataDescriptor->Ptr = (ulong)longptr;
+            }
+            else if (data is uint)
+            {
+                dataDescriptor->Size = (uint)sizeof(uint);
+                uint* uintptr = (uint*)dataBuffer;
+                *uintptr = (uint)data;
+                dataDescriptor->Ptr = (ulong)uintptr;
+            }
+            else if (data is UInt64)
+            {
+                dataDescriptor->Size = (uint)sizeof(ulong);
+                UInt64* ulongptr = (ulong*)dataBuffer;
+                *ulongptr = (ulong)data;
+                dataDescriptor->Ptr = (ulong)ulongptr;
+            }
+            else if (data is char)
+            {
+                dataDescriptor->Size = (uint)sizeof(char);
+                char* charptr = (char*)dataBuffer;
+                *charptr = (char)data;
+                dataDescriptor->Ptr = (ulong)charptr;
+            }
+            else if (data is byte)
+            {
+                dataDescriptor->Size = (uint)sizeof(byte);
+                byte* byteptr = (byte*)dataBuffer;
+                *byteptr = (byte)data;
+                dataDescriptor->Ptr = (ulong)byteptr;
+            }
+            else if (data is short)
+            {
+                dataDescriptor->Size = (uint)sizeof(short);
+                short* shortptr = (short*)dataBuffer;
+                *shortptr = (short)data;
+                dataDescriptor->Ptr = (ulong)shortptr;
+            }
+            else if (data is sbyte)
+            {
+                dataDescriptor->Size = (uint)sizeof(sbyte);
+                sbyte* sbyteptr = (sbyte*)dataBuffer;
+                *sbyteptr = (sbyte)data;
+                dataDescriptor->Ptr = (ulong)sbyteptr;
+            }
+            else if (data is ushort)
+            {
+                dataDescriptor->Size = (uint)sizeof(ushort);
+                ushort* ushortptr = (ushort*)dataBuffer;
+                *ushortptr = (ushort)data;
+                dataDescriptor->Ptr = (ulong)ushortptr;
+            }
+            else if (data is float)
+            {
+                dataDescriptor->Size = (uint)sizeof(float);
+                float* floatptr = (float*)dataBuffer;
+                *floatptr = (float)data;
+                dataDescriptor->Ptr = (ulong)floatptr;
+            }
+            else if (data is double)
+            {
+                dataDescriptor->Size = (uint)sizeof(double);
+                double* doubleptr = (double*)dataBuffer;
+                *doubleptr = (double)data;
+                dataDescriptor->Ptr = (ulong)doubleptr;
+            }
+            else if (data is bool)
+            {
+                // WIN32 Bool is 4 bytes
+                dataDescriptor->Size = 4;
+                int* intptr = (int*)dataBuffer;
+                if (((bool)data))
+                {
+                    *intptr = 1;
+                }
+                else
+                {
+                    *intptr = 0;
+                }
+                dataDescriptor->Ptr = (ulong)intptr;
+            }
+            else if (data is Guid)
+            {
+                dataDescriptor->Size = (uint)sizeof(Guid);
+                Guid* guidptr = (Guid*)dataBuffer;
+                *guidptr = (Guid)data;
+                dataDescriptor->Ptr = (ulong)guidptr;
+            }
+            else if (data is decimal)
+            {
+                dataDescriptor->Size = (uint)sizeof(decimal);
+                decimal* decimalptr = (decimal*)dataBuffer;
+                *decimalptr = (decimal)data;
+                dataDescriptor->Ptr = (ulong)decimalptr;
+            }
+            else if (data is DateTime)
+            {
+                const long UTCMinTicks = 504911232000000000;
+                long dateTimeTicks = 0;
+                // We cannot translate dates sooner than 1/1/1601 in UTC. 
+                // To avoid getting an ArgumentOutOfRangeException we compare with 1/1/1601 DateTime ticks
+                if (((DateTime)data).Ticks > UTCMinTicks)
+                    dateTimeTicks = ((DateTime)data).ToFileTimeUtc();
+                dataDescriptor->Size = (uint)sizeof(long);
+                long* longptr = (long*)dataBuffer;
+                *longptr = dateTimeTicks;
+                dataDescriptor->Ptr = (ulong)longptr;
+            }
+            else
+            {
+                if (data is System.Enum)
+                {
+                    Type underlyingType = Enum.GetUnderlyingType(data.GetType());
+                    if (underlyingType == typeof(int))
+                    {
+#if !ES_BUILD_PCL
+                        data = ((IConvertible)data).ToInt32(null);
+#else
+                        data = (int)data;
+#endif
+                        goto Again;
+                    }
+                    else if (underlyingType == typeof(long))
+                    {
+#if !ES_BUILD_PCL
+                        data = ((IConvertible)data).ToInt64(null);
+#else
+                        data = (long)data;
+#endif
+                        goto Again;
+                    }
+                }
+
+                // To our eyes, everything else is a just a string
+                if (data == null)
+                    sRet = "";
+                else
+                    sRet = data.ToString();
+                dataDescriptor->Size = ((uint)sRet.Length + 1) * 2;
+            }
+
+            totalEventSize += dataDescriptor->Size;
+
+            // advance buffers
+            dataDescriptor++;
+            dataBuffer += s_basicTypeAllocationBufferSize;
+
+            return (object)sRet ?? (object)blobRet;
+        }
+
+        /// <summary>
+        /// WriteEvent, method to write a parameters with event schema properties
+        /// </summary>
+        /// <param name="eventDescriptor">
+        /// Event Descriptor for this event. 
+        /// </param>
+        /// <param name="activityID">
+        /// A pointer to the activity ID GUID to log 
+        /// </param>
+        /// <param name="childActivityID">
+        /// childActivityID is marked as 'related' to the current activity ID. 
+        /// </param>
+        /// <param name="eventPayload">
+        /// Payload for the ETW event. 
+        /// </param>
+        // <SecurityKernel Critical="True" Ring="0">
+        // <CallsSuppressUnmanagedCode Name="UnsafeNativeMethods.ManifestEtw.EventWrite(System.Int64,EventDescriptor&,System.UInt32,System.Void*):System.UInt32" />
+        // <UsesUnsafeCode Name="Local dataBuffer of type: Byte*" />
+        // <UsesUnsafeCode Name="Local pdata of type: Char*" />
+        // <UsesUnsafeCode Name="Local userData of type: EventData*" />
+        // <UsesUnsafeCode Name="Local userDataPtr of type: EventData*" />
+        // <UsesUnsafeCode Name="Local currentBuffer of type: Byte*" />
+        // <UsesUnsafeCode Name="Local v0 of type: Char*" />
+        // <UsesUnsafeCode Name="Local v1 of type: Char*" />
+        // <UsesUnsafeCode Name="Local v2 of type: Char*" />
+        // <UsesUnsafeCode Name="Local v3 of type: Char*" />
+        // <UsesUnsafeCode Name="Local v4 of type: Char*" />
+        // <UsesUnsafeCode Name="Local v5 of type: Char*" />
+        // <UsesUnsafeCode Name="Local v6 of type: Char*" />
+        // <UsesUnsafeCode Name="Local v7 of type: Char*" />
+        // <ReferencesCritical Name="Method: EncodeObject(Object&, EventData*, Byte*):String" Ring="1" />
+        // </SecurityKernel>
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Maintainability", "CA1502:AvoidExcessiveComplexity", Justification = "Performance-critical code")]
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1045:DoNotPassTypesByReference")]
+        internal unsafe bool WriteEvent(ref EventDescriptor eventDescriptor, IntPtr eventHandle, Guid* activityID, Guid* childActivityID, params object[] eventPayload)
+        {
+            int status = 0;
+
+            if (IsEnabled(eventDescriptor.Level, eventDescriptor.Keywords))
+            {
+                int argCount = 0;
+                unsafe
+                {
+                    argCount = eventPayload.Length;
+
+                    if (argCount > s_etwMaxNumberArguments)
+                    {
+                        s_returnCode = WriteEventErrorCode.TooManyArgs;
+                        return false;
+                    }
+
+                    uint totalEventSize = 0;
+                    int index;
+                    int refObjIndex = 0;
+                    List<int> refObjPosition = new List<int>(s_etwAPIMaxRefObjCount);
+                    List<object> dataRefObj = new List<object>(s_etwAPIMaxRefObjCount);
+                    EventData* userData = stackalloc EventData[2 * argCount];
+                    for (int i = 0; i < 2 * argCount; i++)
+                        userData[i] = default(EventData);
+                    EventData* userDataPtr = (EventData*)userData;
+                    byte* dataBuffer = stackalloc byte[s_basicTypeAllocationBufferSize * 2 * argCount]; // Assume 16 chars for non-string argument
+                    byte* currentBuffer = dataBuffer;
+
+                    //
+                    // The loop below goes through all the arguments and fills in the data 
+                    // descriptors. For strings save the location in the dataString array.
+                    // Calculates the total size of the event by adding the data descriptor
+                    // size value set in EncodeObject method.
+                    //
+                    bool hasNonStringRefArgs = false;
+                    for (index = 0; index < eventPayload.Length; index++)
+                    {
+                        if (eventPayload[index] != null)
+                        {
+                            object supportedRefObj;
+                            supportedRefObj = EncodeObject(ref eventPayload[index], ref userDataPtr, ref currentBuffer, ref totalEventSize);
+
+                            if (supportedRefObj != null)
+                            {
+                                // EncodeObject advanced userDataPtr to the next empty slot
+                                int idx = (int)(userDataPtr - userData - 1);
+                                if (!(supportedRefObj is string))
+                                {
+                                    if (eventPayload.Length + idx + 1 - index > s_etwMaxNumberArguments)
+                                    {
+                                        s_returnCode = WriteEventErrorCode.TooManyArgs;
+                                        return false;
+                                    }
+                                    hasNonStringRefArgs = true;
+                                }
+                                dataRefObj.Add(supportedRefObj);
+                                refObjPosition.Add(idx);
+                                refObjIndex++;
+                            }
+                        }
+                        else
+                        {
+                            s_returnCode = WriteEventErrorCode.NullInput;
+                            return false;
+                        }
+                    }
+
+                    // update argCount based on actual number of arguments written to 'userData'
+                    argCount = (int)(userDataPtr - userData);
+
+                    if (totalEventSize > s_traceEventMaximumSize)
+                    {
+                        s_returnCode = WriteEventErrorCode.EventTooBig;
+                        return false;
+                    }
+
+                    // the optimized path (using "fixed" instead of allocating pinned GCHandles
+                    if (!hasNonStringRefArgs && (refObjIndex < s_etwAPIMaxRefObjCount))
+                    {
+                        // Fast path: at most 8 string arguments
+
+                        // ensure we have at least s_etwAPIMaxStringCount in dataString, so that
+                        // the "fixed" statement below works
+                        while (refObjIndex < s_etwAPIMaxRefObjCount)
+                        {
+                            dataRefObj.Add(null);
+                            ++refObjIndex;
+                        }
+
+                        //
+                        // now fix any string arguments and set the pointer on the data descriptor 
+                        //
+                        fixed (char* v0 = (string)dataRefObj[0], v1 = (string)dataRefObj[1], v2 = (string)dataRefObj[2], v3 = (string)dataRefObj[3],
+                                v4 = (string)dataRefObj[4], v5 = (string)dataRefObj[5], v6 = (string)dataRefObj[6], v7 = (string)dataRefObj[7])
+                        {
+                            userDataPtr = (EventData*)userData;
+                            if (dataRefObj[0] != null)
+                            {
+                                userDataPtr[refObjPosition[0]].Ptr = (ulong)v0;
+                            }
+                            if (dataRefObj[1] != null)
+                            {
+                                userDataPtr[refObjPosition[1]].Ptr = (ulong)v1;
+                            }
+                            if (dataRefObj[2] != null)
+                            {
+                                userDataPtr[refObjPosition[2]].Ptr = (ulong)v2;
+                            }
+                            if (dataRefObj[3] != null)
+                            {
+                                userDataPtr[refObjPosition[3]].Ptr = (ulong)v3;
+                            }
+                            if (dataRefObj[4] != null)
+                            {
+                                userDataPtr[refObjPosition[4]].Ptr = (ulong)v4;
+                            }
+                            if (dataRefObj[5] != null)
+                            {
+                                userDataPtr[refObjPosition[5]].Ptr = (ulong)v5;
+                            }
+                            if (dataRefObj[6] != null)
+                            {
+                                userDataPtr[refObjPosition[6]].Ptr = (ulong)v6;
+                            }
+                            if (dataRefObj[7] != null)
+                            {
+                                userDataPtr[refObjPosition[7]].Ptr = (ulong)v7;
+                            }
+
+                            status = m_eventProvider.EventWriteTransferWrapper(m_regHandle, ref eventDescriptor, eventHandle, activityID, childActivityID, argCount, userData);
+                        }
+                    }
+                    else
+                    {
+                        // Slow path: use pinned handles
+                        userDataPtr = (EventData*)userData;
+
+                        GCHandle[] rgGCHandle = new GCHandle[refObjIndex];
+                        for (int i = 0; i < refObjIndex; ++i)
+                        {
+                            // below we still use "fixed" to avoid taking dependency on the offset of the first field
+                            // in the object (the way we would need to if we used GCHandle.AddrOfPinnedObject)
+                            rgGCHandle[i] = GCHandle.Alloc(dataRefObj[i], GCHandleType.Pinned);
+                            if (dataRefObj[i] is string)
+                            {
+                                fixed (char* p = (string)dataRefObj[i])
+                                    userDataPtr[refObjPosition[i]].Ptr = (ulong)p;
+                            }
+                            else
+                            {
+                                fixed (byte* p = (byte[])dataRefObj[i])
+                                    userDataPtr[refObjPosition[i]].Ptr = (ulong)p;
+                            }
+                        }
+
+                        status = m_eventProvider.EventWriteTransferWrapper(m_regHandle, ref eventDescriptor, eventHandle, activityID, childActivityID, argCount, userData);
+
+                        for (int i = 0; i < refObjIndex; ++i)
+                        {
+                            rgGCHandle[i].Free();
+                        }
+                    }
+                }
+            }
+
+            if (status != 0)
+            {
+                SetLastError((int)status);
+                return false;
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// WriteEvent, method to be used by generated code on a derived class
+        /// </summary>
+        /// <param name="eventDescriptor">
+        /// Event Descriptor for this event. 
+        /// </param>
+        /// <param name="activityID">
+        /// A pointer to the activity ID to log 
+        /// </param>
+        /// <param name="childActivityID">
+        /// If this event is generating a child activity (WriteEventTransfer related activity) this is child activity
+        /// This can be null for events that do not generate a child activity.  
+        /// </param>
+        /// <param name="dataCount">
+        /// number of event descriptors 
+        /// </param>
+        /// <param name="data">
+        /// pointer  do the event data
+        /// </param>
+        // <SecurityKernel Critical="True" Ring="0">
+        // <CallsSuppressUnmanagedCode Name="UnsafeNativeMethods.ManifestEtw.EventWrite(System.Int64,EventDescriptor&,System.UInt32,System.Void*):System.UInt32" />
+        // </SecurityKernel>
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1045:DoNotPassTypesByReference")]
+        internal protected unsafe bool WriteEvent(ref EventDescriptor eventDescriptor, IntPtr eventHandle, Guid* activityID, Guid* childActivityID, int dataCount, IntPtr data)
+        {
+            if (childActivityID != null)
+            {
+                // activity transfers are supported only for events that specify the Send or Receive opcode
+                Debug.Assert((EventOpcode)eventDescriptor.Opcode == EventOpcode.Send ||
+                                (EventOpcode)eventDescriptor.Opcode == EventOpcode.Receive ||
+                                (EventOpcode)eventDescriptor.Opcode == EventOpcode.Start ||
+                                (EventOpcode)eventDescriptor.Opcode == EventOpcode.Stop);
+            }
+
+            int status = m_eventProvider.EventWriteTransferWrapper(m_regHandle, ref eventDescriptor, eventHandle, activityID, childActivityID, dataCount, (EventData*)data);
+
+            if (status != 0)
+            {
+                SetLastError(status);
+                return false;
+            }
+            return true;
+        }
+
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1045:DoNotPassTypesByReference")]
+        internal unsafe bool WriteEventRaw(
+            ref EventDescriptor eventDescriptor,
+            IntPtr eventHandle,
+            Guid* activityID,
+            Guid* relatedActivityID,
+            int dataCount,
+            IntPtr data)
+        {
+            int status;
+
+            status = m_eventProvider.EventWriteTransferWrapper(
+                m_regHandle,
+                ref eventDescriptor,
+                eventHandle,
+                activityID,
+                relatedActivityID,
+                dataCount,
+                (EventData*)data);
+
+            if (status != 0)
+            {
+                SetLastError(status);
+                return false;
+            }
+            return true;
+        }
+
+
+        // These are look-alikes to the Manifest based ETW OS APIs that have been shimmed to work
+        // either with Manifest ETW or Classic ETW (if Manifest based ETW is not available).  
+        private unsafe uint EventRegister(EventSource eventSource, UnsafeNativeMethods.ManifestEtw.EtwEnableCallback enableCallback)
+        {
+            m_providerName = eventSource.Name;
+            m_providerId = eventSource.Guid;
+            m_etwCallback = enableCallback;
+            return m_eventProvider.EventRegister(eventSource, enableCallback, null, ref m_regHandle);
+        }
+
+        private uint EventUnregister(long registrationHandle)
+        {
+            return m_eventProvider.EventUnregister(registrationHandle);
+        }
+
+        static int[] nibblebits = { 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4 };
+        private static int bitcount(uint n)
+        {
+            int count = 0;
+            for (; n != 0; n = n >> 4)
+                count += nibblebits[n & 0x0f];
+            return count;
+        }
+        private static int bitindex(uint n)
+        {
+            Debug.Assert(bitcount(n) == 1);
+            int idx = 0;
+            while ((n & (1 << idx)) == 0)
+                idx++;
+            return idx;
+        }
+    }
+
+#if PLATFORM_WINDOWS
+
+    // A wrapper around the ETW-specific API calls.
+    internal sealed class EtwEventProvider : IEventProvider
+    {
+        // Register an event provider.
+        unsafe uint IEventProvider.EventRegister(
+            EventSource eventSource,
+            UnsafeNativeMethods.ManifestEtw.EtwEnableCallback enableCallback,
+            void* callbackContext,
+            ref long registrationHandle)
+        {
+            Guid providerId = eventSource.Guid;
+            return UnsafeNativeMethods.ManifestEtw.EventRegister(
+                ref providerId,
+                enableCallback,
+                callbackContext,
+                ref registrationHandle);
+        }
+
+        // Unregister an event provider.
+        uint IEventProvider.EventUnregister(long registrationHandle)
+        {
+            return UnsafeNativeMethods.ManifestEtw.EventUnregister(registrationHandle);
+        }
+
+        // Write an event.
+        unsafe int IEventProvider.EventWriteTransferWrapper(
+            long registrationHandle,
+            ref EventDescriptor eventDescriptor,
+            IntPtr eventHandle,
+            Guid* activityId,
+            Guid* relatedActivityId,
+            int userDataCount,
+            EventProvider.EventData* userData)
+        {
+            return UnsafeNativeMethods.ManifestEtw.EventWriteTransferWrapper(
+                registrationHandle,
+                ref eventDescriptor,
+                activityId,
+                relatedActivityId,
+                userDataCount,
+                userData);
+        }
+
+        // Get or set the per-thread activity ID.
+        int IEventProvider.EventActivityIdControl(UnsafeNativeMethods.ManifestEtw.ActivityControl ControlCode, ref Guid ActivityId)
+        {
+            return UnsafeNativeMethods.ManifestEtw.EventActivityIdControl(
+                ControlCode,
+                ref ActivityId);
+        }
+
+        // Define an EventPipeEvent handle.
+        unsafe IntPtr IEventProvider.DefineEventHandle(uint eventID, string eventName, Int64 keywords, uint eventVersion, uint level, byte *pMetadata, uint metadataLength)
+        {
+            throw new System.NotSupportedException();
+        }
+    }
+
+#elif !FEATURE_PERFTRACING
+
+    internal sealed class NoOpEventProvider : IEventProvider
+    {
+        unsafe uint IEventProvider.EventRegister(
+            EventSource eventSource,
+            UnsafeNativeMethods.ManifestEtw.EtwEnableCallback enableCallback,
+            void* callbackContext,
+            ref long registrationHandle)
+        {
+            return 0;
+        }
+
+        uint IEventProvider.EventUnregister(long registrationHandle)
+        {
+            return 0;
+        }
+
+        unsafe int IEventProvider.EventWriteTransferWrapper(
+            long registrationHandle,
+            ref EventDescriptor eventDescriptor,
+            IntPtr eventHandle,
+            Guid* activityId,
+            Guid* relatedActivityId,
+            int userDataCount,
+            EventProvider.EventData* userData)
+        {
+            return 0;
+        }
+
+        int IEventProvider.EventActivityIdControl(UnsafeNativeMethods.ManifestEtw.ActivityControl ControlCode, ref Guid ActivityId)
+        {
+            return 0;
+        }
+
+        // Define an EventPipeEvent handle.
+        unsafe IntPtr IEventProvider.DefineEventHandle(uint eventID, string eventName, Int64 keywords, uint eventVersion, uint level, byte *pMetadata, uint metadataLength)
+        {
+            throw new System.NotSupportedException();
+        }
+    }
+
+#endif
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventSource.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventSource.cs
new file mode 100644
index 0000000000..1836a1f27d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventSource.cs
@@ -0,0 +1,5859 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// This program uses code hyperlinks available as part of the HyperAddin Visual Studio plug-in.
+// It is available from http://www.codeplex.com/hyperAddin 
+#if ES_BUILD_STANDALONE
+#define FEATURE_MANAGED_ETW_CHANNELS
+// #define FEATURE_ADVANCED_MANAGED_ETW_CHANNELS
+#endif
+
+/* DESIGN NOTES DESIGN NOTES DESIGN NOTES DESIGN NOTES */
+// DESIGN NOTES
+// Over the years EventSource has become more complex and so it is important to understand
+// the basic structure of the code to insure that it does not grow more complex.
+//
+// Basic Model
+//
+// PRINCIPLE: EventSource - ETW decoupling
+// 
+// Conceptually and EventSouce is something takes event logging data from the source methods 
+// To the EventListener that can subscribe them.  Note that CONCEPTUALLY EVENTSOURCES DON'T
+// KNOW ABOUT ETW!.   The MODEL of the system is that there is a special EventListener Which
+// we will call the EtwEventListener, that forwards commands from ETW to EventSources and
+// listeners to the EventSources and forwards on those events to ETW.   THus the model should
+// be that you DON'T NEED ETW.    
+//
+// Now in actual practice, EventSouce have rather intimate knowledge of ETW and send events
+// to it directly, but this can be VIEWED AS AN OPTIMIZATION.  
+//
+// Basic Event Data Flow:
+// 
+// There are two ways for event Data to enter the system
+//     1) WriteEvent* and friends.  This is called the 'contract' based approach because 
+//        you write a method per event which forms a contract that is know at compile time.
+//        In this scheme each event is given an EVENTID (small integer). which is its identity
+//     2) Write<T> methods.   This is called the 'dynamic' approach because new events 
+//        can be created on the fly.  Event identity is determined by the event NAME, and these
+//        are not quite as efficient at runtime since you have at least a hash table lookup
+//        on every event write.  
+//
+// EventSource-EventListener transfer fully support both ways of writing events (either contract
+// based (WriteEvent*) or dynamic (Write<T>).   Both way fully support the same set of data
+// types.   It is suggested, however, that you use the contract based approach when the event scheme 
+// is known at compile time (that is whenever possible).  It is more efficient, but more importantly
+// it makes the contract very explicit, and centralizes all policy about logging.  These are good 
+// things.    The Write<T> API is really meant for more ad-hoc 
+//
+// Allowed Data. 
+// 
+// Note that EventSource-EventListeners have a conceptual serialization-deserialization that happens
+// during the transfer.   In particular object identity is not preserved, some objects are morphed, 
+// and not all data types are supported.   In particular you can pass
+// 
+// A Valid type to log to an EventSource include
+//   * Primitive data types
+//   * IEnumerable<T> of valid types T (this include arrays)  (* New for V4.6)
+//   * Explicitly Opted in class or struct with public property Getters over Valid types.  (* New for V4.6)
+// 
+// This set of types is roughly a generalization of JSON support (Basically primitives, bags, and arrays).   
+//
+// Explicitly allowed structs include (* New for V4.6)
+//   * Marked with the EventData attribute
+//   * implicitly defined (e.g the C# new {x = 3, y = 5} syntax)
+//   * KeyValuePair<K,V>  (thus dictionaries can be passed since they are an IEnumerable of KeyValuePair)
+//         
+// When classes are returned in an EventListener, what is returned is something that implements 
+// IDictionary<string, T>.  Thus when objects are passed to an EventSource they are transformed
+// into a key-value bag (the IDictionary<string, T>) for consumption in the listener.   These 
+// are obvious NOT the original objects.  
+// 
+// ETWserialization formats:
+// 
+// As mentioned conceptually EventSource's send data to EventListeners and there is a conceptual 
+// copy/morph of that data as described above.   In addition the .NET framework supports a conceptual
+// ETWListener that will send the data to then ETW stream.   If you use this feature, the data needs 
+// to be serialized in a way that ETW supports.  ETW supports the following serialization formats 
+// 
+//     1) Manifest Based serialization. 
+//     2) SelfDescribing serialization (TraceLogging style in the TraceLogging directory)
+//
+// A key factor is that the Write<T> method, which support on the fly definition of events, can't
+// support the manifest based serialization because the manifest needs the schema of all events 
+// to be known before any events are emitted.  This implies the following
+//
+// If you use Write<T> and the output goes to ETW it will use the SelfDescribing format.
+// If you use the EventSource(string) constructor for an eventSource (in which you don't
+// create a subclass), the default is also to use Self-Describing serialization.  In addition
+// you can use the EventSoruce(EventSourceSettings) constructor to also explicitly specify
+// Self-Describing serialization format.   These effect the WriteEvent* APIs going to ETW.  
+//
+// Note that none of this ETW serialization logic affects EventListeners.   Only the ETW listener.  
+// 
+// *************************************************************************************
+// *** INTERNALS: Event Propagation
+//
+//   Data enters the system either though
+//
+// 1) A user defined method in the user defined subclass of EventSource which calls 
+//     A) A typesafe type specific overload of WriteEvent(ID, ...)  e.g. WriteEvent(ID, string, string) 
+//           * which calls into the unsafe WriteEventCore(ID COUNT EventData*) WriteEventWithRelatedActivityIdCore()
+//     B) The typesafe overload WriteEvent(ID, object[])  which calls the private helper WriteEventVarargs(ID, Guid* object[])
+//     C) Directly into the unsafe WriteEventCore(ID, COUNT EventData*) or WriteEventWithRelatedActivityIdCore()
+//
+//     All event data eventually flows to one of 
+//        * WriteEventWithRelatedActivityIdCore(ID, Guid*, COUNT, EventData*) 
+//        * WriteEventVarargs(ID, Guid*, object[])
+//
+// 2) A call to one of the overloads of Write<T>.   All these overloads end up in 
+//        * WriteImpl<T>(EventName, Options, Data, Guid*, Guid*)
+// 
+// On output there are the following routines
+//    Writing to all listeners that are NOT ETW, we have the following routines
+//       * WriteToAllListeners(ID, Guid*, Guid*, COUNT, EventData*)
+//       * WriteToAllListeners(ID, Guid*, Guid*, object[])
+//       * WriteToAllListeners(NAME, Guid*, Guid*, EventPayload)
+//
+//       EventPayload is the internal type that implements the IDictionary<string, object> interface
+//       The EventListeners will pass back for serialized classes for nested object, but  
+//       WriteToAllListeners(NAME, Guid*, Guid*, EventPayload) unpacks this uses the fields as if they
+//       were parameters to a method.  
+// 
+//       The first two are used for the WriteEvent* case, and the later is used for the Write<T> case.  
+// 
+//    Writing to ETW, Manifest Based 
+//          EventProvider.WriteEvent(EventDescriptor, Guid*, COUNT, EventData*)
+//          EventProvider.WriteEvent(EventDescriptor, Guid*, object[])
+//    Writing to ETW, Self-Describing format
+//          WriteMultiMerge(NAME, Options, Types, EventData*)
+//          WriteMultiMerge(NAME, Options, Types, object[])
+//          WriteImpl<T> has logic that knows how to serialize (like WriteMultiMerge) but also knows 
+//             will write it to 
+//
+//    All ETW writes eventually call
+//      EventWriteTransfer (native PINVOKE wrapper)
+//      EventWriteTransferWrapper (fixes compat problem if you pass null as the related activityID)
+//         EventProvider.WriteEventRaw   - sets last error
+//         EventSource.WriteEventRaw     - Does EventSource exception handling logic
+//            WriteMultiMerge
+//            WriteImpl<T>
+//         EventProvider.WriteEvent(EventDescriptor, Guid*, COUNT, EventData*)
+//         EventProvider.WriteEvent(EventDescriptor, Guid*, object[])
+// 
+// Serialization:  We have a bit of a hodge-podge of serializers right now.   Only the one for ETW knows
+// how to deal with nested classes or arrays.   I will call this serializer the 'TypeInfo' serializer
+// since it is the TraceLoggingTypeInfo structure that knows how to do this.   Effectively for a type you
+// can call one of these 
+//      WriteMetadata - transforms the type T into serialization meta data blob for that type
+//      WriteObjectData - transforms an object of T into serialization meta data blob for that type
+//      GetData - transforms an object of T into its deserialized form suitable for passing to EventListener. 
+// The first two are used to serialize something for ETW.   The second one is used to transform the object 
+// for use by the EventListener.    We also have a 'DecodeObject' method that will take a EventData* and
+// deserialize to pass to an EventListener, but it only works on primitive types (types supported in version V4.5). 
+// 
+// It is an important observation that while EventSource does support users directly calling with EventData* 
+// blobs, we ONLY support that for the primitive types (V4.5 level support).   Thus while there is a EventData*
+// path through the system it is only for some types.  The object[] path is the more general (but less efficient) path.  
+//
+// TODO There is cleanup needed There should be no divergence until WriteEventRaw.  
+// 
+// TODO: We should have a single choke point (right now we always have this parallel EventData* and object[] path.   This 
+// was historical (at one point we tried to pass object directly from EventSoruce to EventListener.  That was always 
+// fragile and a compatibility headache, but we have finally been forced into the idea that there is always a transformation.
+// This allows us to use the EventData* form to be the canonical data format in the low level APIs.  This also gives us the
+// opportunity to expose this format to EventListeners in the future.   
+// 
+using System;
+using System.Runtime.CompilerServices;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Globalization;
+using System.Reflection;
+using System.Resources;
+using System.Security;
+#if !CORECLR && !ES_BUILD_PN
+using System.Security.Permissions;
+#endif // !CORECLR && !ES_BUILD_PN
+
+using System.Text;
+using System.Threading;
+using Microsoft.Win32;
+
+#if ES_BUILD_STANDALONE
+using EventDescriptor = Microsoft.Diagnostics.Tracing.EventDescriptor;
+#else
+using System.Threading.Tasks;
+#endif
+
+using Microsoft.Reflection;
+
+#if !ES_BUILD_AGAINST_DOTNET_V35
+using Contract = System.Diagnostics.Contracts.Contract;
+#else
+using Contract = Microsoft.Diagnostics.Contracts.Internal.Contract;
+#endif
+
+#if CORECLR || ES_BUILD_PN
+using Internal.Runtime.Augments;
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// This class is meant to be inherited by a user-defined event source in order to define a managed
+    /// ETW provider.   Please See DESIGN NOTES above for the internal architecture.  
+    /// The minimal definition of an EventSource simply specifies a number of ETW event methods that
+    /// call one of the EventSource.WriteEvent overloads, <see cref="EventSource.WriteEventCore"/>, 
+    /// or <see cref="EventSource.WriteEventWithRelatedActivityIdCore"/> to log them. This functionality 
+    /// is sufficient for many users.
+    /// <para>
+    /// To achieve more control over the ETW provider manifest exposed by the event source type, the 
+    /// [<see cref="EventAttribute"/>] attributes can be specified for the ETW event methods.
+    /// </para><para>
+    /// For very advanced EventSources, it is possible to intercept the commands being given to the
+    /// eventSource and change what filtering is done (see EventListener.EnableEvents and 
+    /// <see cref="EventListener.DisableEvents"/>) or cause actions to be performed by the eventSource, 
+    /// e.g. dumping a data structure (see EventSource.SendCommand and
+    /// <see cref="EventSource.OnEventCommand"/>).
+    /// </para><para>
+    /// The eventSources can be turned on with Windows ETW controllers (e.g. logman), immediately. 
+    /// It is also possible to control and intercept the data dispatcher programmatically.  See 
+    /// <see cref="EventListener"/> for more.
+    /// </para>
+    /// </summary>
+    /// <remarks>
+    /// This is a minimal definition for a custom event source:
+    /// <code>
+    /// [EventSource(Name="Samples-Demos-Minimal")]
+    /// sealed class MinimalEventSource : EventSource
+    /// {
+    ///     public static MinimalEventSource Log = new MinimalEventSource();
+    ///     public void Load(long ImageBase, string Name) { WriteEvent(1, ImageBase, Name); }
+    ///     public void Unload(long ImageBase) { WriteEvent(2, ImageBase); }
+    ///     private MinimalEventSource() {}
+    /// }
+    /// </code>
+    /// </remarks>
+    public partial class EventSource : IDisposable
+    {
+
+#if FEATURE_EVENTSOURCE_XPLAT
+        private static readonly EventListener persistent_Xplat_Listener = XplatEventLogger.InitializePersistentListener();
+#endif //FEATURE_EVENTSOURCE_XPLAT
+
+        /// <summary>
+        /// The human-friendly name of the eventSource.  It defaults to the simple name of the class
+        /// </summary>
+        public string Name { get { return m_name; } }
+        /// <summary>
+        /// Every eventSource is assigned a GUID to uniquely identify it to the system. 
+        /// </summary>
+        public Guid Guid { get { return m_guid; } }
+
+        /// <summary>
+        /// Returns true if the eventSource has been enabled at all. This is the preferred test
+        /// to be performed before a relatively expensive EventSource operation.
+        /// </summary>
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        public bool IsEnabled()
+        {
+            return m_eventSourceEnabled;
+        }
+
+        /// <summary>
+        /// Returns true if events with greater than or equal 'level' and have one of 'keywords' set are enabled. 
+        /// 
+        /// Note that the result of this function is only an approximation on whether a particular
+        /// event is active or not. It is only meant to be used as way of avoiding expensive
+        /// computation for logging when logging is not on, therefore it sometimes returns false
+        /// positives (but is always accurate when returning false).  EventSources are free to 
+        /// have additional filtering.    
+        /// </summary>
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        public bool IsEnabled(EventLevel level, EventKeywords keywords)
+        {
+            return IsEnabled(level, keywords, EventChannel.None);
+        }
+
+        /// <summary>
+        /// Returns true if events with greater than or equal 'level' and have one of 'keywords' set are enabled, or
+        /// if 'keywords' specifies a channel bit for a channel that is enabled.
+        /// 
+        /// Note that the result of this function only an approximation on whether a particular
+        /// event is active or not. It is only meant to be used as way of avoiding expensive
+        /// computation for logging when logging is not on, therefore it sometimes returns false
+        /// positives (but is always accurate when returning false).  EventSources are free to 
+        /// have additional filtering.    
+        /// </summary>
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        public bool IsEnabled(EventLevel level, EventKeywords keywords, EventChannel channel)
+        {
+            if (!m_eventSourceEnabled)
+                return false;
+
+            if (!IsEnabledCommon(m_eventSourceEnabled, m_level, m_matchAnyKeyword, level, keywords, channel))
+                return false;
+
+            return true;
+        }
+
+        /// <summary>
+        /// Returns the settings for the event source instance
+        /// </summary>
+        public EventSourceSettings Settings
+        {
+            get { return m_config; }
+        }
+
+        // Manifest support 
+        /// <summary>
+        /// Returns the GUID that uniquely identifies the eventSource defined by 'eventSourceType'.  
+        /// This API allows you to compute this without actually creating an instance of the EventSource.   
+        /// It only needs to reflect over the type.  
+        /// </summary>
+        public static Guid GetGuid(Type eventSourceType)
+        {
+            if (eventSourceType == null)
+                throw new ArgumentNullException(nameof(eventSourceType));
+
+            EventSourceAttribute attrib = (EventSourceAttribute)GetCustomAttributeHelper(eventSourceType, typeof(EventSourceAttribute));
+            string name = eventSourceType.Name;
+            if (attrib != null)
+            {
+                if (attrib.Guid != null)
+                {
+                    Guid g = Guid.Empty;
+#if !ES_BUILD_AGAINST_DOTNET_V35
+                    if (Guid.TryParse(attrib.Guid, out g))
+                        return g;
+#else
+                    try { return new Guid(attrib.Guid); }
+                    catch (Exception) { }
+#endif
+                }
+
+                if (attrib.Name != null)
+                    name = attrib.Name;
+            }
+
+            if (name == null)
+            {
+                throw new ArgumentException(SR.Argument_InvalidTypeName, nameof(eventSourceType));
+            }
+            return GenerateGuidFromName(name.ToUpperInvariant());       // Make it case insensitive.  
+        }
+        /// <summary>
+        /// Returns the official ETW Provider name for the eventSource defined by 'eventSourceType'.  
+        /// This API allows you to compute this without actually creating an instance of the EventSource.   
+        /// It only needs to reflect over the type.  
+        /// </summary>
+        public static string GetName(Type eventSourceType)
+        {
+            return GetName(eventSourceType, EventManifestOptions.None);
+        }
+
+        /// <summary>
+        /// Returns a string of the XML manifest associated with the eventSourceType. The scheme for this XML is
+        /// documented at in EventManifest Schema http://msdn.microsoft.com/en-us/library/aa384043(VS.85).aspx.
+        /// This is the preferred way of generating a manifest to be embedded in the ETW stream as it is fast and
+        /// the fact that it only includes localized entries for the current UI culture is an acceptable tradeoff.
+        /// </summary>
+        /// <param name="eventSourceType">The type of the event source class for which the manifest is generated</param>
+        /// <param name="assemblyPathToIncludeInManifest">The manifest XML fragment contains the string name of the DLL name in
+        /// which it is embedded.  This parameter specifies what name will be used</param>
+        /// <returns>The XML data string</returns>
+        public static string GenerateManifest(Type eventSourceType, string assemblyPathToIncludeInManifest)
+        {
+            return GenerateManifest(eventSourceType, assemblyPathToIncludeInManifest, EventManifestOptions.None);
+        }
+        /// <summary>
+        /// Returns a string of the XML manifest associated with the eventSourceType. The scheme for this XML is
+        /// documented at in EventManifest Schema http://msdn.microsoft.com/en-us/library/aa384043(VS.85).aspx.
+        /// Pass EventManifestOptions.AllCultures when generating a manifest to be registered on the machine. This
+        /// ensures that the entries in the event log will be "optimally" localized.
+        /// </summary>
+        /// <param name="eventSourceType">The type of the event source class for which the manifest is generated</param>
+        /// <param name="assemblyPathToIncludeInManifest">The manifest XML fragment contains the string name of the DLL name in
+        /// which it is embedded.  This parameter specifies what name will be used</param>
+        /// <param name="flags">The flags to customize manifest generation. If flags has bit OnlyIfNeededForRegistration specified
+        /// this returns null when the eventSourceType does not require explicit registration</param>
+        /// <returns>The XML data string or null</returns>
+        public static string GenerateManifest(Type eventSourceType, string assemblyPathToIncludeInManifest, EventManifestOptions flags)
+        {
+            if (eventSourceType == null)
+                throw new ArgumentNullException(nameof(eventSourceType));
+
+            byte[] manifestBytes = EventSource.CreateManifestAndDescriptors(eventSourceType, assemblyPathToIncludeInManifest, null, flags);
+            return (manifestBytes == null) ? null : Encoding.UTF8.GetString(manifestBytes, 0, manifestBytes.Length);
+        }
+
+        // EventListener support
+        /// <summary>
+        /// returns a list (IEnumerable) of all sources in the appdomain).  EventListeners typically need this.  
+        /// </summary>
+        /// <returns></returns>
+        public static IEnumerable<EventSource> GetSources()
+        {
+            var ret = new List<EventSource>();
+            lock (EventListener.EventListenersLock)
+            {
+                foreach (WeakReference eventSourceRef in EventListener.s_EventSources)
+                {
+                    EventSource eventSource = eventSourceRef.Target as EventSource;
+                    if (eventSource != null && !eventSource.IsDisposed)
+                        ret.Add(eventSource);
+                }
+            }
+            return ret;
+        }
+
+        /// <summary>
+        /// Send a command to a particular EventSource identified by 'eventSource'.
+        /// Calling this routine simply forwards the command to the EventSource.OnEventCommand
+        /// callback.  What the EventSource does with the command and its arguments are from 
+        /// that point EventSource-specific.  
+        /// </summary>
+        /// <param name="eventSource">The instance of EventSource to send the command to</param>
+        /// <param name="command">A positive user-defined EventCommand, or EventCommand.SendManifest</param>
+        /// <param name="commandArguments">A set of (name-argument, value-argument) pairs associated with the command</param>
+        public static void SendCommand(EventSource eventSource, EventCommand command, IDictionary<string, string> commandArguments)
+        {
+            if (eventSource == null)
+                throw new ArgumentNullException(nameof(eventSource));
+
+            // User-defined EventCommands should not conflict with the reserved commands.
+            if ((int)command <= (int)EventCommand.Update && (int)command != (int)EventCommand.SendManifest)
+            {
+                throw new ArgumentException(SR.EventSource_InvalidCommand, nameof(command));
+            }
+
+            eventSource.SendCommand(null, 0, 0, command, true, EventLevel.LogAlways, EventKeywords.None, commandArguments);
+        }
+
+#if !ES_BUILD_STANDALONE
+        /// <summary>
+        /// This property allows EventSource code to appropriately handle as "different" 
+        /// activities started on different threads that have not had an activity created on them.
+        /// </summary>
+        internal static Guid InternalCurrentThreadActivityId
+        {
+            get
+            {
+                Guid retval = CurrentThreadActivityId;
+                if (retval == Guid.Empty)
+                {
+                    retval = FallbackActivityId;
+                }
+                return retval;
+            }
+        }
+
+        internal static Guid FallbackActivityId
+        {
+            get
+            {
+#pragma warning disable 612, 618
+                int threadID = AppDomain.GetCurrentThreadId();
+
+                // Managed thread IDs are more aggressively re-used than native thread IDs,
+                // so we'll use the latter...
+                return new Guid(unchecked((uint)threadID),
+                                unchecked((ushort)s_currentPid), unchecked((ushort)(s_currentPid >> 16)),
+                                0x94, 0x1b, 0x87, 0xd5, 0xa6, 0x5c, 0x36, 0x64);
+#pragma warning restore 612, 618
+            }
+        }
+#endif // !ES_BUILD_STANDALONE
+
+        // Error APIs.  (We don't throw by default, but you can probe for status)
+        /// <summary>
+        /// Because
+        /// 
+        ///     1) Logging is often optional and thus should not generate fatal errors (exceptions)
+        ///     2) EventSources are often initialized in class constructors (which propagate exceptions poorly)
+        ///     
+        /// The event source constructor does not throw exceptions.  Instead we remember any exception that 
+        /// was generated (it is also logged to Trace.WriteLine).
+        /// </summary>
+        public Exception ConstructionException { get { return m_constructionException; } }
+
+        /// <summary>
+        /// EventSources can have arbitrary string key-value pairs associated with them called Traits.  
+        /// These traits are not interpreted by the EventSource but may be interpreted by EventListeners
+        /// (e.g. like the built in ETW listener).   These traits are specified at EventSource 
+        /// construction time and can be retrieved by using this GetTrait API.  
+        /// </summary>
+        /// <param name="key">The key to look up in the set of key-value pairs passed to the EventSource constructor</param>
+        /// <returns>The value string associated with key.  Will return null if there is no such key.</returns>
+        public string GetTrait(string key)
+        {
+            if (m_traits != null)
+            {
+                for (int i = 0; i < m_traits.Length - 1; i += 2)
+                {
+                    if (m_traits[i] == key)
+                        return m_traits[i + 1];
+                }
+            }
+            return null;
+        }
+
+        /// <summary>
+        /// Displays the name and GUID for the eventSource for debugging purposes.  
+        /// </summary>
+        public override string ToString()
+        {
+            return SR.Format(SR.EventSource_ToString, Name, Guid);
+        }
+
+        /// <summary>
+        /// Fires when a Command (e.g. Enable) comes from a an EventListener.  
+        /// </summary>
+        public event EventHandler<EventCommandEventArgs> EventCommandExecuted
+        {
+            add
+            {
+                m_eventCommandExecuted += value;
+
+                // If we have an EventHandler<EventCommandEventArgs> attached to the EventSource before the first command arrives
+                // It should get a chance to handle the deferred commands.
+                EventCommandEventArgs deferredCommands = m_deferredCommands;
+                while (deferredCommands != null)
+                {
+                    value(this, deferredCommands);
+                    deferredCommands = deferredCommands.nextCommand;
+                }
+            }
+            remove
+            {
+                m_eventCommandExecuted -= value;
+            }
+        }
+
+#region protected
+        /// <summary>
+        /// This is the constructor that most users will use to create their eventSource.   It takes 
+        /// no parameters.  The ETW provider name and GUID of the EventSource are determined by the EventSource 
+        /// custom attribute (so you can determine these things declaratively).   If the GUID for the eventSource
+        /// is not specified in the EventSourceAttribute (recommended), it is Generated by hashing the name.
+        /// If the ETW provider name of the EventSource is not given, the name of the EventSource class is used as
+        /// the ETW provider name.
+        /// </summary>
+        protected EventSource()
+            : this(EventSourceSettings.EtwManifestEventFormat)
+        {
+        }
+
+        /// <summary>
+        /// By default calling the 'WriteEvent' methods do NOT throw on errors (they silently discard the event).  
+        /// This is because in most cases users assume logging is not 'precious' and do NOT wish to have logging failures
+        /// crash the program. However for those applications where logging is 'precious' and if it fails the caller
+        /// wishes to react, setting 'throwOnEventWriteErrors' will cause an exception to be thrown if WriteEvent
+        /// fails. Note the fact that EventWrite succeeds does not necessarily mean that the event reached its destination
+        /// only that operation of writing it did not fail. These EventSources will not generate self-describing ETW events.
+        /// 
+        /// For compatibility only use the EventSourceSettings.ThrowOnEventWriteErrors flag instead.  
+        /// </summary>
+        // [Obsolete("Use the EventSource(EventSourceSettings) overload")]
+        protected EventSource(bool throwOnEventWriteErrors)
+            : this(EventSourceSettings.EtwManifestEventFormat | (throwOnEventWriteErrors ? EventSourceSettings.ThrowOnEventWriteErrors : 0))
+        { }
+
+        /// <summary>
+        /// Construct an EventSource with additional non-default settings (see EventSourceSettings for more)  
+        /// </summary>
+        protected EventSource(EventSourceSettings settings) : this(settings, null) { }
+
+        /// <summary>
+        /// Construct an EventSource with additional non-default settings.  
+        /// 
+        /// Also specify a list of key-value pairs called traits (you must pass an even number of strings).   
+        /// The first string is the key and the second is the value.   These are not interpreted by EventSource
+        /// itself but may be interpreted the listeners.  Can be fetched with GetTrait(string).   
+        /// </summary>
+        /// <param name="settings">See EventSourceSettings for more.</param>
+        /// <param name="traits">A collection of key-value strings (must be an even number).</param>
+        protected EventSource(EventSourceSettings settings, params string[] traits)
+        {
+            m_config = ValidateSettings(settings);
+
+            Guid eventSourceGuid;
+            string eventSourceName;
+
+            EventMetadata[] eventDescriptors;
+            byte[] manifest;
+            GetMetadata(out eventSourceGuid, out eventSourceName, out eventDescriptors, out manifest);
+
+            if (eventSourceGuid.Equals(Guid.Empty) || eventSourceName == null)
+            {
+                var myType = this.GetType();
+                eventSourceGuid = GetGuid(myType);
+                eventSourceName = GetName(myType);
+            }
+
+            Initialize(eventSourceGuid, eventSourceName, traits);
+        }
+
+#if FEATURE_PERFTRACING
+        // Generate the serialized blobs that describe events for all strongly typed events (that is events that define strongly
+        // typed event methods. Dynamically defined events (that use Write) hare defined on the fly and are handled elsewhere.
+        private unsafe void DefineEventPipeEvents()
+        {
+            // If the EventSource is set to emit all events as TraceLogging events, skip this initialization.
+            // Events will be defined when they are emitted for the first time.
+            if(SelfDescribingEvents)
+            {
+                return;
+            }
+
+            Debug.Assert(m_eventData != null);
+            Debug.Assert(m_provider != null);
+            int cnt = m_eventData.Length;
+            for (int i = 0; i < cnt; i++)
+            {
+                uint eventID = (uint)m_eventData[i].Descriptor.EventId;
+                if (eventID == 0)
+                    continue;
+
+                byte[] metadata = EventPipeMetadataGenerator.Instance.GenerateEventMetadata(m_eventData[i]);
+                uint metadataLength = (metadata != null) ? (uint)metadata.Length : 0;
+
+                string eventName = m_eventData[i].Name;
+                Int64 keywords = m_eventData[i].Descriptor.Keywords;
+                uint eventVersion = m_eventData[i].Descriptor.Version;
+                uint level = m_eventData[i].Descriptor.Level;
+
+                fixed (byte *pMetadata = metadata)
+                {
+                    IntPtr eventHandle = m_provider.m_eventProvider.DefineEventHandle(
+                        eventID,
+                        eventName,
+                        keywords,
+                        eventVersion,
+                        level,
+                        pMetadata,
+                        metadataLength);
+
+                    Debug.Assert(eventHandle != IntPtr.Zero);
+                    m_eventData[i].EventHandle = eventHandle;
+                }
+            }
+        }
+#endif
+
+        internal virtual void GetMetadata(out Guid eventSourceGuid, out string eventSourceName, out EventMetadata[] eventData, out byte[] manifestBytes)
+        {
+            //
+            // In ProjectN subclasses need to override this method, and return the data from their EventSourceAttribute and EventAttribute annotations.
+            // On other architectures it is a no-op.
+            //
+            // eventDescriptors needs to contain one EventDescriptor for each event; the event's ID should be the same as its index in this array.
+            // manifestBytes is a UTF-8 encoding of the ETW manifest for the type.
+            //
+            // This will be implemented by an IL rewriter, so we can't make this method abstract or the initial build of the subclass would fail.
+            //
+            eventSourceGuid = Guid.Empty;
+            eventSourceName = null;
+            eventData = null;
+            manifestBytes = null;
+
+            return;
+        }
+
+        /// <summary>
+        /// This method is called when the eventSource is updated by the controller.  
+        /// </summary>
+        protected virtual void OnEventCommand(EventCommandEventArgs command) { }
+
+#pragma warning disable 1591
+        // optimized for common signatures (no args)
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId)
+        {
+            WriteEventCore(eventId, 0, null);
+        }
+
+        // optimized for common signatures (ints)
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, int arg1)
+        {
+            if (m_eventSourceEnabled)
+            {
+                EventSource.EventData* descrs = stackalloc EventSource.EventData[1];
+                descrs[0].DataPointer = (IntPtr)(&arg1);
+                descrs[0].Size = 4;
+                descrs[0].Reserved = 0;
+                WriteEventCore(eventId, 1, descrs);
+            }
+        }
+
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, int arg1, int arg2)
+        {
+            if (m_eventSourceEnabled)
+            {
+                EventSource.EventData* descrs = stackalloc EventSource.EventData[2];
+                descrs[0].DataPointer = (IntPtr)(&arg1);
+                descrs[0].Size = 4;
+                descrs[0].Reserved = 0;
+                descrs[1].DataPointer = (IntPtr)(&arg2);
+                descrs[1].Size = 4;
+                descrs[1].Reserved = 0;
+                WriteEventCore(eventId, 2, descrs);
+            }
+        }
+
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, int arg1, int arg2, int arg3)
+        {
+            if (m_eventSourceEnabled)
+            {
+                EventSource.EventData* descrs = stackalloc EventSource.EventData[3];
+                descrs[0].DataPointer = (IntPtr)(&arg1);
+                descrs[0].Size = 4;
+                descrs[0].Reserved = 0;
+                descrs[1].DataPointer = (IntPtr)(&arg2);
+                descrs[1].Size = 4;
+                descrs[1].Reserved = 0;
+                descrs[2].DataPointer = (IntPtr)(&arg3);
+                descrs[2].Size = 4;
+                descrs[2].Reserved = 0;
+                WriteEventCore(eventId, 3, descrs);
+            }
+        }
+
+        // optimized for common signatures (longs)
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, long arg1)
+        {
+            if (m_eventSourceEnabled)
+            {
+                EventSource.EventData* descrs = stackalloc EventSource.EventData[1];
+                descrs[0].DataPointer = (IntPtr)(&arg1);
+                descrs[0].Size = 8;
+                descrs[0].Reserved = 0;
+                WriteEventCore(eventId, 1, descrs);
+            }
+        }
+
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, long arg1, long arg2)
+        {
+            if (m_eventSourceEnabled)
+            {
+                EventSource.EventData* descrs = stackalloc EventSource.EventData[2];
+                descrs[0].DataPointer = (IntPtr)(&arg1);
+                descrs[0].Size = 8;
+                descrs[0].Reserved = 0;
+                descrs[1].DataPointer = (IntPtr)(&arg2);
+                descrs[1].Size = 8;
+                descrs[1].Reserved = 0;
+                WriteEventCore(eventId, 2, descrs);
+            }
+        }
+
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, long arg1, long arg2, long arg3)
+        {
+            if (m_eventSourceEnabled)
+            {
+                EventSource.EventData* descrs = stackalloc EventSource.EventData[3];
+                descrs[0].DataPointer = (IntPtr)(&arg1);
+                descrs[0].Size = 8;
+                descrs[0].Reserved = 0;
+                descrs[1].DataPointer = (IntPtr)(&arg2);
+                descrs[1].Size = 8;
+                descrs[1].Reserved = 0;
+                descrs[2].DataPointer = (IntPtr)(&arg3);
+                descrs[2].Size = 8;
+                descrs[2].Reserved = 0;
+                WriteEventCore(eventId, 3, descrs);
+            }
+        }
+
+        // optimized for common signatures (strings)
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, string arg1)
+        {
+            if (m_eventSourceEnabled)
+            {
+                if (arg1 == null) arg1 = "";
+                fixed (char* string1Bytes = arg1)
+                {
+                    EventSource.EventData* descrs = stackalloc EventSource.EventData[1];
+                    descrs[0].DataPointer = (IntPtr)string1Bytes;
+                    descrs[0].Size = ((arg1.Length + 1) * 2);
+                    descrs[0].Reserved = 0;
+                    WriteEventCore(eventId, 1, descrs);
+                }
+            }
+        }
+
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, string arg1, string arg2)
+        {
+            if (m_eventSourceEnabled)
+            {
+                if (arg1 == null) arg1 = "";
+                if (arg2 == null) arg2 = "";
+                fixed (char* string1Bytes = arg1)
+                fixed (char* string2Bytes = arg2)
+                {
+                    EventSource.EventData* descrs = stackalloc EventSource.EventData[2];
+                    descrs[0].DataPointer = (IntPtr)string1Bytes;
+                    descrs[0].Size = ((arg1.Length + 1) * 2);
+                    descrs[0].Reserved = 0;
+                    descrs[1].DataPointer = (IntPtr)string2Bytes;
+                    descrs[1].Size = ((arg2.Length + 1) * 2);
+                    descrs[1].Reserved = 0;
+                    WriteEventCore(eventId, 2, descrs);
+                }
+            }
+        }
+
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, string arg1, string arg2, string arg3)
+        {
+            if (m_eventSourceEnabled)
+            {
+                if (arg1 == null) arg1 = "";
+                if (arg2 == null) arg2 = "";
+                if (arg3 == null) arg3 = "";
+                fixed (char* string1Bytes = arg1)
+                fixed (char* string2Bytes = arg2)
+                fixed (char* string3Bytes = arg3)
+                {
+                    EventSource.EventData* descrs = stackalloc EventSource.EventData[3];
+                    descrs[0].DataPointer = (IntPtr)string1Bytes;
+                    descrs[0].Size = ((arg1.Length + 1) * 2);
+                    descrs[0].Reserved = 0;
+                    descrs[1].DataPointer = (IntPtr)string2Bytes;
+                    descrs[1].Size = ((arg2.Length + 1) * 2);
+                    descrs[1].Reserved = 0;
+                    descrs[2].DataPointer = (IntPtr)string3Bytes;
+                    descrs[2].Size = ((arg3.Length + 1) * 2);
+                    descrs[2].Reserved = 0;
+                    WriteEventCore(eventId, 3, descrs);
+                }
+            }
+        }
+
+        // optimized for common signatures (string and ints)
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, string arg1, int arg2)
+        {
+            if (m_eventSourceEnabled)
+            {
+                if (arg1 == null) arg1 = "";
+                fixed (char* string1Bytes = arg1)
+                {
+                    EventSource.EventData* descrs = stackalloc EventSource.EventData[2];
+                    descrs[0].DataPointer = (IntPtr)string1Bytes;
+                    descrs[0].Size = ((arg1.Length + 1) * 2);
+                    descrs[0].Reserved = 0;
+                    descrs[1].DataPointer = (IntPtr)(&arg2);
+                    descrs[1].Size = 4;
+                    descrs[1].Reserved = 0;
+                    WriteEventCore(eventId, 2, descrs);
+                }
+            }
+        }
+
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, string arg1, int arg2, int arg3)
+        {
+            if (m_eventSourceEnabled)
+            {
+                if (arg1 == null) arg1 = "";
+                fixed (char* string1Bytes = arg1)
+                {
+                    EventSource.EventData* descrs = stackalloc EventSource.EventData[3];
+                    descrs[0].DataPointer = (IntPtr)string1Bytes;
+                    descrs[0].Size = ((arg1.Length + 1) * 2);
+                    descrs[0].Reserved = 0;
+                    descrs[1].DataPointer = (IntPtr)(&arg2);
+                    descrs[1].Size = 4;
+                    descrs[1].Reserved = 0;
+                    descrs[2].DataPointer = (IntPtr)(&arg3);
+                    descrs[2].Size = 4;
+                    descrs[2].Reserved = 0;
+                    WriteEventCore(eventId, 3, descrs);
+                }
+            }
+        }
+
+        // optimized for common signatures (string and longs)
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, string arg1, long arg2)
+        {
+            if (m_eventSourceEnabled)
+            {
+                if (arg1 == null) arg1 = "";
+                fixed (char* string1Bytes = arg1)
+                {
+                    EventSource.EventData* descrs = stackalloc EventSource.EventData[2];
+                    descrs[0].DataPointer = (IntPtr)string1Bytes;
+                    descrs[0].Size = ((arg1.Length + 1) * 2);
+                    descrs[0].Reserved = 0;
+                    descrs[1].DataPointer = (IntPtr)(&arg2);
+                    descrs[1].Size = 8;
+                    descrs[1].Reserved = 0;
+                    WriteEventCore(eventId, 2, descrs);
+                }
+            }
+        }
+
+        // optimized for common signatures (long and string)
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, long arg1, string arg2)
+        {
+            if (m_eventSourceEnabled)
+            {
+                if (arg2 == null) arg2 = "";
+                fixed (char* string2Bytes = arg2)
+                {
+                    EventSource.EventData* descrs = stackalloc EventSource.EventData[2];
+                    descrs[0].DataPointer = (IntPtr)(&arg1);
+                    descrs[0].Size = 8;
+                    descrs[0].Reserved = 0;
+                    descrs[1].DataPointer = (IntPtr)string2Bytes;
+                    descrs[1].Size = ((arg2.Length + 1) * 2);
+                    descrs[1].Reserved = 0;
+                    WriteEventCore(eventId, 2, descrs);
+                }
+            }
+        }
+
+        // optimized for common signatures (int and string)
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, int arg1, string arg2)
+        {
+            if (m_eventSourceEnabled)
+            {
+                if (arg2 == null) arg2 = "";
+                fixed (char* string2Bytes = arg2)
+                {
+                    EventSource.EventData* descrs = stackalloc EventSource.EventData[2];
+                    descrs[0].DataPointer = (IntPtr)(&arg1);
+                    descrs[0].Size = 4;
+                    descrs[0].Reserved = 0;
+                    descrs[1].DataPointer = (IntPtr)string2Bytes;
+                    descrs[1].Size = ((arg2.Length + 1) * 2);
+                    descrs[1].Reserved = 0;
+                    WriteEventCore(eventId, 2, descrs);
+                }
+            }
+        }
+
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, byte[] arg1)
+        {
+            if (m_eventSourceEnabled)
+            {
+                EventSource.EventData* descrs = stackalloc EventSource.EventData[2];
+                if (arg1 == null || arg1.Length == 0)
+                {
+                    int blobSize = 0;
+                    descrs[0].DataPointer = (IntPtr)(&blobSize);
+                    descrs[0].Size = 4;
+                    descrs[0].Reserved = 0;
+                    descrs[1].DataPointer = (IntPtr)(&blobSize); // valid address instead of empty content 
+                    descrs[1].Size = 0;
+                    descrs[1].Reserved = 0;
+                    WriteEventCore(eventId, 2, descrs);
+                }
+                else
+                {
+                    int blobSize = arg1.Length;
+                    fixed (byte* blob = &arg1[0])
+                    {
+                        descrs[0].DataPointer = (IntPtr)(&blobSize);
+                        descrs[0].Size = 4;
+                        descrs[0].Reserved = 0;
+                        descrs[1].DataPointer = (IntPtr)blob;
+                        descrs[1].Size = blobSize;
+                        descrs[1].Reserved = 0;
+                        WriteEventCore(eventId, 2, descrs);
+                    }
+                }
+            }
+        }
+
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, long arg1, byte[] arg2)
+        {
+            if (m_eventSourceEnabled)
+            {
+                EventSource.EventData* descrs = stackalloc EventSource.EventData[3];
+                descrs[0].DataPointer = (IntPtr)(&arg1);
+                descrs[0].Size = 8;
+                descrs[0].Reserved = 0;
+                if (arg2 == null || arg2.Length == 0)
+                {
+                    int blobSize = 0;
+                    descrs[1].DataPointer = (IntPtr)(&blobSize);
+                    descrs[1].Size = 4;
+                    descrs[1].Reserved = 0;
+                    descrs[2].DataPointer = (IntPtr)(&blobSize); // valid address instead of empty contents 
+                    descrs[2].Size = 0;
+                    descrs[2].Reserved = 0;
+                    WriteEventCore(eventId, 3, descrs);
+                }
+                else
+                {
+                    int blobSize = arg2.Length;
+                    fixed (byte* blob = &arg2[0])
+                    {
+                        descrs[1].DataPointer = (IntPtr)(&blobSize);
+                        descrs[1].Size = 4;
+                        descrs[1].Reserved = 0;
+                        descrs[2].DataPointer = (IntPtr)blob;
+                        descrs[2].Size = blobSize;
+                        descrs[2].Reserved = 0;
+                        WriteEventCore(eventId, 3, descrs);
+                    }
+                }
+            }
+        }
+
+#pragma warning restore 1591
+
+        /// <summary>
+        /// Used to construct the data structure to be passed to the native ETW APIs - EventWrite and EventWriteTransfer.
+        /// </summary>
+        protected internal struct EventData
+        {
+            /// <summary>
+            /// Address where the one argument lives (if this points to managed memory you must ensure the
+            /// managed object is pinned.
+            /// </summary>
+            public unsafe IntPtr DataPointer { get { return (IntPtr)(void*)m_Ptr; } set { m_Ptr = unchecked((ulong)(void*)value); } }
+
+            /// <summary>
+            /// Size of the argument referenced by DataPointer
+            /// </summary>
+            public int Size { get { return m_Size; } set { m_Size = value; } }
+
+            /// <summary>
+            /// Reserved by ETW.  This property is present to ensure that we can zero it
+            /// since System.Private.CoreLib uses are not zero'd.
+            /// </summary>
+            internal int Reserved { get { return m_Reserved; } set { m_Reserved = value; } }
+
+#region private
+            /// <summary>
+            /// Initializes the members of this EventData object to point at a previously-pinned
+            /// tracelogging-compatible metadata blob.
+            /// </summary>
+            /// <param name="pointer">Pinned tracelogging-compatible metadata blob.</param>
+            /// <param name="size">The size of the metadata blob.</param>
+            /// <param name="reserved">Value for reserved: 2 for per-provider metadata, 1 for per-event metadata</param>
+            internal unsafe void SetMetadata(byte* pointer, int size, int reserved)
+            {
+                this.m_Ptr = (ulong)pointer;
+                this.m_Size = size;
+                this.m_Reserved = reserved; // Mark this descriptor as containing tracelogging-compatible metadata.
+            }
+
+            //Important, we pass this structure directly to the Win32 EventWrite API, so this structure must be layed out exactly
+            // the way EventWrite wants it.  
+            internal ulong m_Ptr;
+            internal int m_Size;
+#pragma warning disable 0649
+            internal int m_Reserved;       // Used to pad the size to match the Win32 API
+#pragma warning restore 0649
+#endregion
+        }
+
+        /// <summary>
+        /// This routine allows you to create efficient WriteEvent helpers, however the code that you use to
+        /// do this, while straightforward, is unsafe.
+        /// </summary>
+        /// <remarks>
+        /// <code>
+        ///    protected unsafe void WriteEvent(int eventId, string arg1, long arg2)
+        ///    {
+        ///        if (IsEnabled())
+        ///        {
+        ///            if (arg2 == null) arg2 = "";
+        ///            fixed (char* string2Bytes = arg2)
+        ///            {
+        ///                EventSource.EventData* descrs = stackalloc EventSource.EventData[2];
+        ///                descrs[0].DataPointer = (IntPtr)(&amp;arg1);
+        ///                descrs[0].Size = 8;
+        ///                descrs[0].Reserved = 0;
+        ///                descrs[1].DataPointer = (IntPtr)string2Bytes;
+        ///                descrs[1].Size = ((arg2.Length + 1) * 2);
+        ///                descrs[1].Reserved = 0;
+        ///                WriteEventCore(eventId, 2, descrs);
+        ///            }
+        ///        }
+        ///    }
+        /// </code>
+        /// </remarks>
+        [CLSCompliant(false)]
+        protected unsafe void WriteEventCore(int eventId, int eventDataCount, EventSource.EventData* data)
+        {
+            WriteEventWithRelatedActivityIdCore(eventId, null, eventDataCount, data);
+        }
+
+        /// <summary>
+        /// This routine allows you to create efficient WriteEventWithRelatedActivityId helpers, however the code 
+        /// that you use to do this, while straightforward, is unsafe. The only difference from
+        /// <see cref="WriteEventCore"/> is that you pass the relatedActivityId from caller through to this API
+        /// </summary>
+        /// <remarks>
+        /// <code>
+        ///    protected unsafe void WriteEventWithRelatedActivityId(int eventId, Guid relatedActivityId, string arg1, long arg2)
+        ///    {
+        ///        if (IsEnabled())
+        ///        {
+        ///            if (arg2 == null) arg2 = "";
+        ///            fixed (char* string2Bytes = arg2)
+        ///            {
+        ///                EventSource.EventData* descrs = stackalloc EventSource.EventData[2];
+        ///                descrs[0].DataPointer = (IntPtr)(&amp;arg1);
+        ///                descrs[0].Size = 8;
+        ///                descrs[1].DataPointer = (IntPtr)string2Bytes;
+        ///                descrs[1].Size = ((arg2.Length + 1) * 2);
+        ///                WriteEventWithRelatedActivityIdCore(eventId, relatedActivityId, 2, descrs);
+        ///            }
+        ///        }
+        ///    }
+        /// </code>
+        /// </remarks>
+        [CLSCompliant(false)]
+        protected unsafe void WriteEventWithRelatedActivityIdCore(int eventId, Guid* relatedActivityId, int eventDataCount, EventSource.EventData* data)
+        {
+            if (m_eventSourceEnabled)
+            {
+                try
+                {
+                    Debug.Assert(m_eventData != null);  // You must have initialized this if you enabled the source.
+                    if (relatedActivityId != null)
+                        ValidateEventOpcodeForTransfer(ref m_eventData[eventId], m_eventData[eventId].Name);
+
+                    EventOpcode opcode = (EventOpcode)m_eventData[eventId].Descriptor.Opcode;
+                    EventActivityOptions activityOptions = m_eventData[eventId].ActivityOptions;
+                    Guid* pActivityId = null;
+                    Guid activityId = Guid.Empty;
+                    Guid relActivityId = Guid.Empty;
+
+                    if (opcode != EventOpcode.Info && relatedActivityId == null &&
+                       ((activityOptions & EventActivityOptions.Disable) == 0))
+                    {
+                        if (opcode == EventOpcode.Start)
+                        {
+                            m_activityTracker.OnStart(m_name, m_eventData[eventId].Name, m_eventData[eventId].Descriptor.Task, ref activityId, ref relActivityId, m_eventData[eventId].ActivityOptions);
+                        }
+                        else if (opcode == EventOpcode.Stop)
+                        {
+                            m_activityTracker.OnStop(m_name, m_eventData[eventId].Name, m_eventData[eventId].Descriptor.Task, ref activityId);
+                        }
+
+                        if (activityId != Guid.Empty)
+                            pActivityId = &activityId;
+                        if (relActivityId != Guid.Empty)
+                            relatedActivityId = &relActivityId;
+                    }
+
+#if FEATURE_MANAGED_ETW
+                    if (m_eventData[eventId].EnabledForETW)
+                    {
+                        if (!SelfDescribingEvents)
+                        {
+                            if (!m_provider.WriteEvent(ref m_eventData[eventId].Descriptor, m_eventData[eventId].EventHandle, pActivityId, relatedActivityId, eventDataCount, (IntPtr)data))
+                                ThrowEventSourceException(m_eventData[eventId].Name);
+                        }
+                        else
+                        {
+                            TraceLoggingEventTypes tlet = m_eventData[eventId].TraceLoggingEventTypes;
+                            if (tlet == null)
+                            {
+                                tlet = new TraceLoggingEventTypes(m_eventData[eventId].Name,
+                                                                    m_eventData[eventId].Tags,
+                                                                    m_eventData[eventId].Parameters);
+                                Interlocked.CompareExchange(ref m_eventData[eventId].TraceLoggingEventTypes, tlet, null);
+
+                            }
+                            EventSourceOptions opt = new EventSourceOptions
+                            {
+                                Keywords = (EventKeywords)m_eventData[eventId].Descriptor.Keywords,
+                                Level = (EventLevel)m_eventData[eventId].Descriptor.Level,
+                                Opcode = (EventOpcode)m_eventData[eventId].Descriptor.Opcode
+                            };
+
+                            WriteMultiMerge(m_eventData[eventId].Name, ref opt, tlet, pActivityId, relatedActivityId, data);
+                        }
+                    }
+#endif // FEATURE_MANAGED_ETW
+
+                    if (m_Dispatchers != null && m_eventData[eventId].EnabledForAnyListener)
+                        WriteToAllListeners(eventId, pActivityId, relatedActivityId, eventDataCount, data);
+                }
+                catch (Exception ex)
+                {
+                    if (ex is EventSourceException)
+                        throw;
+                    else
+                        ThrowEventSourceException(m_eventData[eventId].Name, ex);
+                }
+            }
+        }
+
+        // fallback varags helpers. 
+        /// <summary>
+        /// This is the varargs helper for writing an event. It does create an array and box all the arguments so it is
+        /// relatively inefficient and should only be used for relatively rare events (e.g. less than 100 / sec). If your
+        /// rates are faster than that you should use <see cref="WriteEventCore"/> to create fast helpers for your particular 
+        /// method signature. Even if you use this for rare events, this call should be guarded by an <see cref="IsEnabled()"/> 
+        /// check so that the varargs call is not made when the EventSource is not active.  
+        /// </summary>
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        protected unsafe void WriteEvent(int eventId, params object[] args)
+        {
+            WriteEventVarargs(eventId, null, args);
+        }
+
+        /// <summary>
+        /// This is the varargs helper for writing an event which also specifies a related activity. It is completely analogous
+        /// to corresponding WriteEvent (they share implementation). It does create an array and box all the arguments so it is
+        /// relatively inefficient and should only be used for relatively rare events (e.g. less than 100 / sec).  If your
+        /// rates are faster than that you should use <see cref="WriteEventWithRelatedActivityIdCore"/> to create fast helpers for your 
+        /// particular method signature. Even if you use this for rare events, this call should be guarded by an <see cref="IsEnabled()"/>
+        /// check so that the varargs call is not made when the EventSource is not active.
+        /// </summary>
+        protected unsafe void WriteEventWithRelatedActivityId(int eventId, Guid relatedActivityId, params object[] args)
+        {
+            WriteEventVarargs(eventId, &relatedActivityId, args);
+        }
+
+#endregion
+
+#region IDisposable Members
+        /// <summary>
+        /// Disposes of an EventSource.
+        /// </summary>
+        public void Dispose()
+        {
+            this.Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+        /// <summary>
+        /// Disposes of an EventSource.
+        /// </summary>
+        /// <remarks>
+        /// Called from Dispose() with disposing=true, and from the finalizer (~EventSource) with disposing=false.
+        /// Guidelines:
+        /// 1. We may be called more than once: do nothing after the first call.
+        /// 2. Avoid throwing exceptions if disposing is false, i.e. if we're being finalized.
+        /// </remarks>
+        /// <param name="disposing">True if called from Dispose(), false if called from the finalizer.</param>
+        protected virtual void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+#if FEATURE_MANAGED_ETW
+#if !FEATURE_PERFTRACING
+                // Send the manifest one more time to ensure circular buffers have a chance to get to this information
+                // even in scenarios with a high volume of ETW events.
+                if (m_eventSourceEnabled)
+                {
+                    try
+                    {
+                        SendManifest(m_rawManifest);
+                    }
+                    catch (Exception)
+                    { }           // If it fails, simply give up.   
+                    m_eventSourceEnabled = false;
+                }
+#endif
+                if (m_provider != null)
+                {
+                    m_provider.Dispose();
+                    m_provider = null;
+                }
+#endif
+            }
+            m_eventSourceEnabled = false;
+            m_eventSourceDisposed = true;
+        }
+        /// <summary>
+        /// Finalizer for EventSource
+        /// </summary>
+        ~EventSource()
+        {
+            this.Dispose(false);
+        }
+#endregion
+
+#region private
+
+        private unsafe void WriteEventRaw(
+            string eventName,
+            ref EventDescriptor eventDescriptor,
+            IntPtr eventHandle,
+            Guid* activityID,
+            Guid* relatedActivityID,
+            int dataCount,
+            IntPtr data)
+        {
+#if FEATURE_MANAGED_ETW
+            if (m_provider == null)
+            {
+                ThrowEventSourceException(eventName);
+            }
+            else
+            {
+                if (!m_provider.WriteEventRaw(ref eventDescriptor, eventHandle, activityID, relatedActivityID, dataCount, data))
+                    ThrowEventSourceException(eventName);
+            }
+#endif // FEATURE_MANAGED_ETW
+        }
+
+        // FrameworkEventSource is on the startup path for the framework, so we have this internal overload that it can use
+        // to prevent the working set hit from looking at the custom attributes on the type to get the Guid.
+        internal EventSource(Guid eventSourceGuid, string eventSourceName)
+            : this(eventSourceGuid, eventSourceName, EventSourceSettings.EtwManifestEventFormat)
+        { }
+
+        // Used by the internal FrameworkEventSource constructor and the TraceLogging-style event source constructor
+        internal EventSource(Guid eventSourceGuid, string eventSourceName, EventSourceSettings settings, string[] traits = null)
+        {
+            m_config = ValidateSettings(settings);
+            Initialize(eventSourceGuid, eventSourceName, traits);
+        }
+
+        /// <summary>
+        /// This method is responsible for the common initialization path from our constructors. It must
+        /// not leak any exceptions (otherwise, since most EventSource classes define a static member, 
+        /// "Log", such an exception would become a cached exception for the initialization of the static
+        /// member, and any future access to the "Log" would throw the cached exception).
+        /// </summary>
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1720:IdentifiersShouldNotContainTypeNames", MessageId = "guid")]
+        private unsafe void Initialize(Guid eventSourceGuid, string eventSourceName, string[] traits)
+        {
+            try
+            {
+                m_traits = traits;
+                if (m_traits != null && m_traits.Length % 2 != 0)
+                {
+                    throw new ArgumentException(SR.EventSource_TraitEven, nameof(traits));
+                }
+
+                if (eventSourceGuid == Guid.Empty)
+                {
+                    throw new ArgumentException(SR.EventSource_NeedGuid);
+                }
+
+                if (eventSourceName == null)
+                {
+                    throw new ArgumentException(SR.EventSource_NeedName);
+                }
+
+                m_name = eventSourceName;
+                m_guid = eventSourceGuid;
+
+                //Enable Implicit Activity tracker
+                m_activityTracker = ActivityTracker.Instance;
+
+#if FEATURE_MANAGED_ETW
+                // Create and register our provider traits.  We do this early because it is needed to log errors 
+                // In the self-describing event case. 
+                this.InitializeProviderMetadata();
+
+                // Register the provider with ETW
+                var provider = new OverideEventProvider(this);
+                provider.Register(this);
+#endif
+                // Add the eventSource to the global (weak) list.  
+                // This also sets m_id, which is the index in the list. 
+                EventListener.AddEventSource(this);
+
+#if FEATURE_MANAGED_ETW
+                // OK if we get this far without an exception, then we can at least write out error messages. 
+                // Set m_provider, which allows this.  
+                m_provider = provider;
+
+#if PLATFORM_WINDOWS
+#if (!ES_BUILD_STANDALONE && !ES_BUILD_PN)
+                // API available on OS >= Win 8 and patched Win 7.
+                // Disable only for FrameworkEventSource to avoid recursion inside exception handling.
+                if (this.Name != "System.Diagnostics.Eventing.FrameworkEventSource" || Environment.IsWindows8OrAbove)
+#endif
+                {
+                    int setInformationResult;
+                    System.Runtime.InteropServices.GCHandle metadataHandle =
+                        System.Runtime.InteropServices.GCHandle.Alloc(this.providerMetadata, System.Runtime.InteropServices.GCHandleType.Pinned);
+                    IntPtr providerMetadata = metadataHandle.AddrOfPinnedObject();
+
+                    setInformationResult = m_provider.SetInformation(
+                        UnsafeNativeMethods.ManifestEtw.EVENT_INFO_CLASS.SetTraits,
+                        providerMetadata,
+                        (uint)this.providerMetadata.Length);
+
+                    metadataHandle.Free();
+                }
+#endif // PLATFORM_WINDOWS
+#endif // FEATURE_MANAGED_ETW
+                Debug.Assert(!m_eventSourceEnabled);     // We can't be enabled until we are completely initted.  
+                // We are logically completely initialized at this point.  
+                m_completelyInited = true;
+            }
+            catch (Exception e)
+            {
+                if (m_constructionException == null)
+                    m_constructionException = e;
+                ReportOutOfBandMessage("ERROR: Exception during construction of EventSource " + Name + ": " + e.Message, true);
+            }
+
+            // Once m_completelyInited is set, you can have concurrency, so all work is under the lock.  
+            lock (EventListener.EventListenersLock)
+            {
+                // If there are any deferred commands, we can do them now.   
+                // This is the most likely place for exceptions to happen.  
+                // Note that we are NOT resetting m_deferredCommands to NULL here, 
+                // We are giving for EventHandler<EventCommandEventArgs> that will be attached later
+                EventCommandEventArgs deferredCommands = m_deferredCommands;
+                while (deferredCommands != null)
+                {
+                    DoCommand(deferredCommands);      // This can never throw, it catches them and reports the errors.   
+                    deferredCommands = deferredCommands.nextCommand;
+                }
+            }
+        }
+
+        private static string GetName(Type eventSourceType, EventManifestOptions flags)
+        {
+            if (eventSourceType == null)
+                throw new ArgumentNullException(nameof(eventSourceType));
+
+            EventSourceAttribute attrib = (EventSourceAttribute)GetCustomAttributeHelper(eventSourceType, typeof(EventSourceAttribute), flags);
+            if (attrib != null && attrib.Name != null)
+                return attrib.Name;
+
+            return eventSourceType.Name;
+        }
+
+        /// <summary>
+        /// Implements the SHA1 hashing algorithm. Note that this
+        /// implementation is for hashing public information. Do not
+        /// use this code to hash private data, as this implementation does
+        /// not take any steps to avoid information disclosure.
+        /// </summary>
+        private struct Sha1ForNonSecretPurposes
+        {
+            private long length; // Total message length in bits
+            private uint[] w; // Workspace
+            private int pos; // Length of current chunk in bytes
+
+            /// <summary>
+            /// Call Start() to initialize the hash object.
+            /// </summary>
+            public void Start()
+            {
+                if (this.w == null)
+                {
+                    this.w = new uint[85];
+                }
+
+                this.length = 0;
+                this.pos = 0;
+                this.w[80] = 0x67452301;
+                this.w[81] = 0xEFCDAB89;
+                this.w[82] = 0x98BADCFE;
+                this.w[83] = 0x10325476;
+                this.w[84] = 0xC3D2E1F0;
+            }
+
+            /// <summary>
+            /// Adds an input byte to the hash.
+            /// </summary>
+            /// <param name="input">Data to include in the hash.</param>
+            public void Append(byte input)
+            {
+                this.w[this.pos / 4] = (this.w[this.pos / 4] << 8) | input;
+                if (64 == ++this.pos)
+                {
+                    this.Drain();
+                }
+            }
+
+            /// <summary>
+            /// Adds input bytes to the hash.
+            /// </summary>
+            /// <param name="input">
+            /// Data to include in the hash. Must not be null.
+            /// </param>
+            public void Append(byte[] input)
+            {
+                foreach (var b in input)
+                {
+                    this.Append(b);
+                }
+            }
+
+            /// <summary>
+            /// Retrieves the hash value.
+            /// Note that after calling this function, the hash object should
+            /// be considered uninitialized. Subsequent calls to Append or
+            /// Finish will produce useless results. Call Start() to
+            /// reinitialize.
+            /// </summary>
+            /// <param name="output">
+            /// Buffer to receive the hash value. Must not be null.
+            /// Up to 20 bytes of hash will be written to the output buffer.
+            /// If the buffer is smaller than 20 bytes, the remaining hash
+            /// bytes will be lost. If the buffer is larger than 20 bytes, the
+            /// rest of the buffer is left unmodified.
+            /// </param>
+            public void Finish(byte[] output)
+            {
+                long l = this.length + 8 * this.pos;
+                this.Append(0x80);
+                while (this.pos != 56)
+                {
+                    this.Append(0x00);
+                }
+
+                unchecked
+                {
+                    this.Append((byte)(l >> 56));
+                    this.Append((byte)(l >> 48));
+                    this.Append((byte)(l >> 40));
+                    this.Append((byte)(l >> 32));
+                    this.Append((byte)(l >> 24));
+                    this.Append((byte)(l >> 16));
+                    this.Append((byte)(l >> 8));
+                    this.Append((byte)l);
+
+                    int end = output.Length < 20 ? output.Length : 20;
+                    for (int i = 0; i != end; i++)
+                    {
+                        uint temp = this.w[80 + i / 4];
+                        output[i] = (byte)(temp >> 24);
+                        this.w[80 + i / 4] = temp << 8;
+                    }
+                }
+            }
+
+            /// <summary>
+            /// Called when this.pos reaches 64.
+            /// </summary>
+            private void Drain()
+            {
+                for (int i = 16; i != 80; i++)
+                {
+                    this.w[i] = Rol1((this.w[i - 3] ^ this.w[i - 8] ^ this.w[i - 14] ^ this.w[i - 16]));
+                }
+
+                unchecked
+                {
+                    uint a = this.w[80];
+                    uint b = this.w[81];
+                    uint c = this.w[82];
+                    uint d = this.w[83];
+                    uint e = this.w[84];
+
+                    for (int i = 0; i != 20; i++)
+                    {
+                        const uint k = 0x5A827999;
+                        uint f = (b & c) | ((~b) & d);
+                        uint temp = Rol5(a) + f + e + k + this.w[i]; e = d; d = c; c = Rol30(b); b = a; a = temp;
+                    }
+
+                    for (int i = 20; i != 40; i++)
+                    {
+                        uint f = b ^ c ^ d;
+                        const uint k = 0x6ED9EBA1;
+                        uint temp = Rol5(a) + f + e + k + this.w[i]; e = d; d = c; c = Rol30(b); b = a; a = temp;
+                    }
+
+                    for (int i = 40; i != 60; i++)
+                    {
+                        uint f = (b & c) | (b & d) | (c & d);
+                        const uint k = 0x8F1BBCDC;
+                        uint temp = Rol5(a) + f + e + k + this.w[i]; e = d; d = c; c = Rol30(b); b = a; a = temp;
+                    }
+
+                    for (int i = 60; i != 80; i++)
+                    {
+                        uint f = b ^ c ^ d;
+                        const uint k = 0xCA62C1D6;
+                        uint temp = Rol5(a) + f + e + k + this.w[i]; e = d; d = c; c = Rol30(b); b = a; a = temp;
+                    }
+
+                    this.w[80] += a;
+                    this.w[81] += b;
+                    this.w[82] += c;
+                    this.w[83] += d;
+                    this.w[84] += e;
+                }
+
+                this.length += 512; // 64 bytes == 512 bits
+                this.pos = 0;
+            }
+
+            private static uint Rol1(uint input)
+            {
+                return (input << 1) | (input >> 31);
+            }
+
+            private static uint Rol5(uint input)
+            {
+                return (input << 5) | (input >> 27);
+            }
+
+            private static uint Rol30(uint input)
+            {
+                return (input << 30) | (input >> 2);
+            }
+        }
+
+        private static Guid GenerateGuidFromName(string name)
+        {
+            byte[] bytes = Encoding.BigEndianUnicode.GetBytes(name);
+            var hash = new Sha1ForNonSecretPurposes();
+            hash.Start();
+            hash.Append(namespaceBytes);
+            hash.Append(bytes);
+            Array.Resize(ref bytes, 16);
+            hash.Finish(bytes);
+
+            bytes[7] = unchecked((byte)((bytes[7] & 0x0F) | 0x50));    // Set high 4 bits of octet 7 to 5, as per RFC 4122
+            return new Guid(bytes);
+        }
+
+        private unsafe object DecodeObject(int eventId, int parameterId, ref EventSource.EventData* data)
+        {
+            // TODO FIX : We use reflection which in turn uses EventSource, right now we carefully avoid
+            // the recursion, but can we do this in a robust way?  
+
+            IntPtr dataPointer = data->DataPointer;
+            // advance to next EventData in array
+            ++data;
+
+            Type dataType = GetDataType(m_eventData[eventId], parameterId);
+
+            Again:
+            if (dataType == typeof(IntPtr))
+            {
+                return *((IntPtr*)dataPointer);
+            }
+            else if (dataType == typeof(int))
+            {
+                return *((int*)dataPointer);
+            }
+            else if (dataType == typeof(uint))
+            {
+                return *((uint*)dataPointer);
+            }
+            else if (dataType == typeof(long))
+            {
+                return *((long*)dataPointer);
+            }
+            else if (dataType == typeof(ulong))
+            {
+                return *((ulong*)dataPointer);
+            }
+            else if (dataType == typeof(byte))
+            {
+                return *((byte*)dataPointer);
+            }
+            else if (dataType == typeof(sbyte))
+            {
+                return *((sbyte*)dataPointer);
+            }
+            else if (dataType == typeof(short))
+            {
+                return *((short*)dataPointer);
+            }
+            else if (dataType == typeof(ushort))
+            {
+                return *((ushort*)dataPointer);
+            }
+            else if (dataType == typeof(float))
+            {
+                return *((float*)dataPointer);
+            }
+            else if (dataType == typeof(double))
+            {
+                return *((double*)dataPointer);
+            }
+            else if (dataType == typeof(decimal))
+            {
+                return *((decimal*)dataPointer);
+            }
+            else if (dataType == typeof(bool))
+            {
+                // The manifest defines a bool as a 32bit type (WIN32 BOOL), not 1 bit as CLR Does.
+                if (*((int*)dataPointer) == 1)
+                {
+                    return true;
+                }
+                else
+                {
+                    return false;
+                }
+            }
+            else if (dataType == typeof(Guid))
+            {
+                return *((Guid*)dataPointer);
+            }
+            else if (dataType == typeof(char))
+            {
+                return *((char*)dataPointer);
+            }
+            else if (dataType == typeof(DateTime))
+            {
+                long dateTimeTicks = *((long*)dataPointer);
+                return DateTime.FromFileTimeUtc(dateTimeTicks);
+            }
+            else if (dataType == typeof(byte[]))
+            {
+                // byte[] are written to EventData* as an int followed by a blob
+                int cbSize = *((int*)dataPointer);
+                byte[] blob = new byte[cbSize];
+                dataPointer = data->DataPointer;
+                data++;
+                for (int i = 0; i < cbSize; ++i)
+                    blob[i] = *((byte*)(dataPointer + i));
+                return blob;
+            }
+            else if (dataType == typeof(byte*))
+            {
+                // TODO: how do we want to handle this? For now we ignore it...
+                return null;
+            }
+            else
+            {
+                if (m_EventSourcePreventRecursion && m_EventSourceInDecodeObject)
+                {
+                    return null;
+                }
+
+                try
+                {
+                    m_EventSourceInDecodeObject = true;
+
+                    if (dataType.IsEnum())
+                    {
+                        dataType = Enum.GetUnderlyingType(dataType);
+                        goto Again;
+                    }
+
+
+                    // Everything else is marshaled as a string.
+                    // ETW strings are NULL-terminated, so marshal everything up to the first
+                    // null in the string.
+                    //return System.Runtime.InteropServices.Marshal.PtrToStringUni(dataPointer);
+                    if(dataPointer == IntPtr.Zero)
+                    {
+                        return null;
+                    }
+
+                    return new string((char *)dataPointer);
+
+                }
+                finally
+                {
+                    m_EventSourceInDecodeObject = false;
+                }
+            }
+        }
+
+        // Finds the Dispatcher (which holds the filtering state), for a given dispatcher for the current
+        // eventSource).  
+        private EventDispatcher GetDispatcher(EventListener listener)
+        {
+            EventDispatcher dispatcher = m_Dispatchers;
+            while (dispatcher != null)
+            {
+                if (dispatcher.m_Listener == listener)
+                    return dispatcher;
+                dispatcher = dispatcher.m_Next;
+            }
+            return dispatcher;
+        }
+
+        private unsafe void WriteEventVarargs(int eventId, Guid* childActivityID, object[] args)
+        {
+            if (m_eventSourceEnabled)
+            {
+                try
+                {
+                    Debug.Assert(m_eventData != null);  // You must have initialized this if you enabled the source.  
+                    if (childActivityID != null)
+                    {
+                        ValidateEventOpcodeForTransfer(ref m_eventData[eventId], m_eventData[eventId].Name);
+
+                        // If you use WriteEventWithRelatedActivityID you MUST declare the first argument to be a GUID 
+                        // with the name 'relatedActivityID, and NOT pass this argument to the WriteEvent method.  
+                        // During manifest creation we modify the ParameterInfo[] that we store to strip out any
+                        // first parameter that is of type Guid and named "relatedActivityId." Thus, if you call
+                        // WriteEventWithRelatedActivityID from a method that doesn't name its first parameter correctly
+                        // we can end up in a state where the ParameterInfo[] doesn't have its first parameter stripped,
+                        // and this leads to a mismatch between the number of arguments and the number of ParameterInfos,
+                        // which would cause a cryptic IndexOutOfRangeException later if we don't catch it here.
+                        if (!m_eventData[eventId].HasRelatedActivityID)
+                        {
+                            throw new ArgumentException(SR.EventSource_NoRelatedActivityId);
+                        }
+                    }
+
+                    LogEventArgsMismatches(m_eventData[eventId].Parameters, args);
+
+                    Guid* pActivityId = null;
+                    Guid activityId = Guid.Empty;
+                    Guid relatedActivityId = Guid.Empty;
+                    EventOpcode opcode = (EventOpcode)m_eventData[eventId].Descriptor.Opcode;
+                    EventActivityOptions activityOptions = m_eventData[eventId].ActivityOptions;
+
+                    if (childActivityID == null &&
+                       ((activityOptions & EventActivityOptions.Disable) == 0))
+                    {
+                        if (opcode == EventOpcode.Start)
+                        {
+                            m_activityTracker.OnStart(m_name, m_eventData[eventId].Name, m_eventData[eventId].Descriptor.Task, ref activityId, ref relatedActivityId, m_eventData[eventId].ActivityOptions);
+                        }
+                        else if (opcode == EventOpcode.Stop)
+                        {
+                            m_activityTracker.OnStop(m_name, m_eventData[eventId].Name, m_eventData[eventId].Descriptor.Task, ref activityId);
+                        }
+
+                        if (activityId != Guid.Empty)
+                            pActivityId = &activityId;
+                        if (relatedActivityId != Guid.Empty)
+                            childActivityID = &relatedActivityId;
+                    }
+
+#if FEATURE_MANAGED_ETW
+                    if (m_eventData[eventId].EnabledForETW)
+                    {
+                        if (!SelfDescribingEvents)
+                        {
+                            if (!m_provider.WriteEvent(ref m_eventData[eventId].Descriptor, m_eventData[eventId].EventHandle, pActivityId, childActivityID, args))
+                                ThrowEventSourceException(m_eventData[eventId].Name);
+                        }
+                        else
+                        {
+                            TraceLoggingEventTypes tlet = m_eventData[eventId].TraceLoggingEventTypes;
+                            if (tlet == null)
+                            {
+                                tlet = new TraceLoggingEventTypes(m_eventData[eventId].Name,
+                                                                    EventTags.None,
+                                                                    m_eventData[eventId].Parameters);
+                                Interlocked.CompareExchange(ref m_eventData[eventId].TraceLoggingEventTypes, tlet, null);
+
+                            }
+                            // TODO: activity ID support
+                            EventSourceOptions opt = new EventSourceOptions
+                            {
+                                Keywords = (EventKeywords)m_eventData[eventId].Descriptor.Keywords,
+                                Level = (EventLevel)m_eventData[eventId].Descriptor.Level,
+                                Opcode = (EventOpcode)m_eventData[eventId].Descriptor.Opcode
+                            };
+
+                            WriteMultiMerge(m_eventData[eventId].Name, ref opt, tlet, pActivityId, childActivityID, args);
+                        }
+                    }
+#endif // FEATURE_MANAGED_ETW
+                    if (m_Dispatchers != null && m_eventData[eventId].EnabledForAnyListener)
+                    {
+#if (!ES_BUILD_STANDALONE && !ES_BUILD_PN)
+                        // Maintain old behavior - object identity is preserved
+                        if (AppContextSwitches.PreserveEventListnerObjectIdentity)
+                        {
+                            WriteToAllListeners(eventId, pActivityId, childActivityID, args);
+                        }
+                        else
+#endif // !ES_BUILD_STANDALONE
+                        {
+                            object[] serializedArgs = SerializeEventArgs(eventId, args);
+                            WriteToAllListeners(eventId, pActivityId, childActivityID, serializedArgs);
+                        }
+                    }
+                }
+                catch (Exception ex)
+                {
+                    if (ex is EventSourceException)
+                        throw;
+                    else
+                        ThrowEventSourceException(m_eventData[eventId].Name, ex);
+                }
+            }
+        }
+
+        private unsafe object[] SerializeEventArgs(int eventId, object[] args)
+        {
+            TraceLoggingEventTypes eventTypes = m_eventData[eventId].TraceLoggingEventTypes;
+            if (eventTypes == null)
+            {
+                eventTypes = new TraceLoggingEventTypes(m_eventData[eventId].Name,
+                                                        EventTags.None,
+                                                        m_eventData[eventId].Parameters);
+                Interlocked.CompareExchange(ref m_eventData[eventId].TraceLoggingEventTypes, eventTypes, null);
+            }
+            var eventData = new object[eventTypes.typeInfos.Length];
+            for (int i = 0; i < eventTypes.typeInfos.Length; i++)
+            {
+                eventData[i] = eventTypes.typeInfos[i].GetData(args[i]);
+            }
+            return eventData;
+        }
+
+        /// <summary>
+        /// We expect that the arguments to the Event method and the arguments to WriteEvent match. This function 
+        /// checks that they in fact match and logs a warning to the debugger if they don't.
+        /// </summary>
+        /// <param name="infos"></param>
+        /// <param name="args"></param>
+        private void LogEventArgsMismatches(ParameterInfo[] infos, object[] args)
+        {
+#if (!ES_BUILD_PCL && !ES_BUILD_PN)
+            // It would be nice to have this on PCL builds, but it would be pointless since there isn't support for 
+            // writing to the debugger log on PCL.
+            bool typesMatch = args.Length == infos.Length;
+
+            int i = 0;
+            while (typesMatch && i < args.Length)
+            {
+                Type pType = infos[i].ParameterType;
+
+                // Checking to see if the Parameter types (from the Event method) match the supplied argument types.
+                // Fail if one of two things hold : either the argument type is not equal to the parameter type, or the 
+                // argument is null and the parameter type is non-nullable.
+                if ((args[i] != null && (args[i].GetType() != pType))
+                    || (args[i] == null && (!(pType.IsGenericType && pType.GetGenericTypeDefinition() == typeof(Nullable<>))))
+                    )
+                {
+                    typesMatch = false;
+                    break;
+                }
+
+                ++i;
+            }
+
+            if (!typesMatch)
+            {
+                System.Diagnostics.Debugger.Log(0, null, SR.EventSource_VarArgsParameterMismatch + "\r\n");
+            }
+#endif //!ES_BUILD_PCL
+        }
+
+        private unsafe void WriteToAllListeners(int eventId, Guid* activityID, Guid* childActivityID, int eventDataCount, EventSource.EventData* data)
+        {
+            // We represent a byte[] as a integer denoting the length  and then a blob of bytes in the data pointer. This causes a spurious
+            // warning because eventDataCount is off by one for the byte[] case since a byte[] has 2 items associated it. So we want to check
+            // that the number of parameters is correct against the byte[] case, but also we the args array would be one too long if
+            // we just used the modifiedParamCount here -- so we need both.
+            int paramCount = GetParameterCount(m_eventData[eventId]);
+            int modifiedParamCount = 0;
+            for (int i = 0; i < paramCount; i++)
+            {
+                Type parameterType = GetDataType(m_eventData[eventId], i);
+                if (parameterType == typeof(byte[]))
+                {
+                    modifiedParamCount += 2;
+                }
+                else
+                {
+                    modifiedParamCount++;
+                }
+            }
+            if (eventDataCount != modifiedParamCount)
+            {
+                ReportOutOfBandMessage(SR.Format(SR.EventSource_EventParametersMismatch, eventId, eventDataCount, paramCount), true);
+                paramCount = Math.Min(paramCount, eventDataCount);
+            }
+
+            object[] args = new object[paramCount];
+
+            EventSource.EventData* dataPtr = data;
+            for (int i = 0; i < paramCount; i++)
+                args[i] = DecodeObject(eventId, i, ref dataPtr);
+            WriteToAllListeners(eventId, activityID, childActivityID, args);
+        }
+
+        // helper for writing to all EventListeners attached the current eventSource.  
+        private unsafe void WriteToAllListeners(int eventId, Guid* activityID, Guid* childActivityID, params object[] args)
+        {
+            EventWrittenEventArgs eventCallbackArgs = new EventWrittenEventArgs(this);
+            eventCallbackArgs.EventId = eventId;
+            if (activityID != null)
+                eventCallbackArgs.ActivityId = *activityID;
+            if (childActivityID != null)
+                eventCallbackArgs.RelatedActivityId = *childActivityID;
+            eventCallbackArgs.EventName = m_eventData[eventId].Name;
+            eventCallbackArgs.Message = m_eventData[eventId].Message;
+            eventCallbackArgs.Payload = new ReadOnlyCollection<object>(args);
+
+            DispatchToAllListeners(eventId, childActivityID, eventCallbackArgs);
+        }
+
+        private unsafe void DispatchToAllListeners(int eventId, Guid* childActivityID, EventWrittenEventArgs eventCallbackArgs)
+        {
+            Exception lastThrownException = null;
+            for (EventDispatcher dispatcher = m_Dispatchers; dispatcher != null; dispatcher = dispatcher.m_Next)
+            {
+                Debug.Assert(dispatcher.m_EventEnabled != null);
+                if (eventId == -1 || dispatcher.m_EventEnabled[eventId])
+                {
+                    {
+                        try
+                        {
+                            dispatcher.m_Listener.OnEventWritten(eventCallbackArgs);
+                        }
+                        catch (Exception e)
+                        {
+                            ReportOutOfBandMessage("ERROR: Exception during EventSource.OnEventWritten: "
+                                 + e.Message, false);
+                            lastThrownException = e;
+                        }
+                    }
+                }
+            }
+
+            if (lastThrownException != null)
+            {
+                throw new EventSourceException(lastThrownException);
+            }
+        }
+
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        private unsafe void WriteEventString(EventLevel level, long keywords, string msgString)
+        {
+#if FEATURE_MANAGED_ETW && !FEATURE_PERFTRACING
+            if (m_provider != null)
+            {
+                string eventName = "EventSourceMessage";
+                if (SelfDescribingEvents)
+                {
+                    EventSourceOptions opt = new EventSourceOptions
+                    {
+                        Keywords = (EventKeywords)unchecked(keywords),
+                        Level = level
+                    };
+                    var msg = new { message = msgString };
+                    var tlet = new TraceLoggingEventTypes(eventName, EventTags.None, new Type[] { msg.GetType() });
+                    WriteMultiMergeInner(eventName, ref opt, tlet, null, null, msg);
+                }
+                else
+                {
+                    // We want the name of the provider to show up so if we don't have a manifest we create 
+                    // on that at least has the provider name (I don't define any events).   
+                    if (m_rawManifest == null && m_outOfBandMessageCount == 1)
+                    {
+                        ManifestBuilder manifestBuilder = new ManifestBuilder(Name, Guid, Name, null, EventManifestOptions.None);
+                        manifestBuilder.StartEvent(eventName, new EventAttribute(0) { Level = EventLevel.LogAlways, Task = (EventTask)0xFFFE });
+                        manifestBuilder.AddEventParameter(typeof(string), "message");
+                        manifestBuilder.EndEvent();
+                        SendManifest(manifestBuilder.CreateManifest());
+                    }
+
+                    // We use this low level routine to to bypass the enabled checking, since the eventSource itself is only partially inited. 
+                    fixed (char* msgStringPtr = msgString)
+                    {
+                        EventDescriptor descr = new EventDescriptor(0, 0, 0, (byte)level, 0, 0, keywords);
+                        EventProvider.EventData data = new EventProvider.EventData();
+                        data.Ptr = (ulong)msgStringPtr;
+                        data.Size = (uint)(2 * (msgString.Length + 1));
+                        data.Reserved = 0;
+                        m_provider.WriteEvent(ref descr, IntPtr.Zero, null, null, 1, (IntPtr)((void*)&data));
+                    }
+                }
+            }
+#endif // FEATURE_MANAGED_ETW
+        }
+
+        /// <summary>
+        /// Since this is a means of reporting errors (see ReportoutOfBandMessage) any failure encountered 
+        /// while writing the message to any one of the listeners will be silently ignored.
+        /// </summary>
+        private void WriteStringToAllListeners(string eventName, string msg)
+        {
+            EventWrittenEventArgs eventCallbackArgs = new EventWrittenEventArgs(this);
+            eventCallbackArgs.EventId = 0;
+            eventCallbackArgs.Message = msg;
+            eventCallbackArgs.Payload = new ReadOnlyCollection<object>(new List<object>() { msg });
+            eventCallbackArgs.PayloadNames = new ReadOnlyCollection<string>(new List<string> { "message" });
+            eventCallbackArgs.EventName = eventName;
+
+            for (EventDispatcher dispatcher = m_Dispatchers; dispatcher != null; dispatcher = dispatcher.m_Next)
+            {
+                bool dispatcherEnabled = false;
+                if (dispatcher.m_EventEnabled == null)
+                {
+                    // if the listeners that weren't correctly initialized, we will send to it
+                    // since this is an error message and we want to see it go out. 
+                    dispatcherEnabled = true;
+                }
+                else
+                {
+                    // if there's *any* enabled event on the dispatcher we'll write out the string
+                    // otherwise we'll treat the listener as disabled and skip it
+                    for (int evtId = 0; evtId < dispatcher.m_EventEnabled.Length; ++evtId)
+                    {
+                        if (dispatcher.m_EventEnabled[evtId])
+                        {
+                            dispatcherEnabled = true;
+                            break;
+                        }
+                    }
+                }
+                try
+                {
+                    if (dispatcherEnabled)
+                        dispatcher.m_Listener.OnEventWritten(eventCallbackArgs);
+                }
+                catch
+                {
+                    // ignore any exceptions thrown by listeners' OnEventWritten
+                }
+            }
+        }
+
+        /// <summary>
+        /// Returns true if 'eventNum' is enabled if you only consider the level and matchAnyKeyword filters.
+        /// It is possible that eventSources turn off the event based on additional filtering criteria.  
+        /// </summary>
+        private bool IsEnabledByDefault(int eventNum, bool enable, EventLevel currentLevel, EventKeywords currentMatchAnyKeyword)
+        {
+            if (!enable)
+                return false;
+
+            EventLevel eventLevel = (EventLevel)m_eventData[eventNum].Descriptor.Level;
+            EventKeywords eventKeywords = unchecked((EventKeywords)((ulong)m_eventData[eventNum].Descriptor.Keywords & (~(SessionMask.All.ToEventKeywords()))));
+
+#if FEATURE_MANAGED_ETW_CHANNELS
+            EventChannel channel = unchecked((EventChannel)m_eventData[eventNum].Descriptor.Channel);
+#else
+            EventChannel channel = EventChannel.None;
+#endif
+
+            return IsEnabledCommon(enable, currentLevel, currentMatchAnyKeyword, eventLevel, eventKeywords, channel);
+        }
+
+        private bool IsEnabledCommon(bool enabled, EventLevel currentLevel, EventKeywords currentMatchAnyKeyword,
+                                                          EventLevel eventLevel, EventKeywords eventKeywords, EventChannel eventChannel)
+        {
+            if (!enabled)
+                return false;
+
+            // does is pass the level test?
+            if ((currentLevel != 0) && (currentLevel < eventLevel))
+                return false;
+
+            // if yes, does it pass the keywords test?
+            if (currentMatchAnyKeyword != 0 && eventKeywords != 0)
+            {
+#if FEATURE_MANAGED_ETW_CHANNELS
+                // is there a channel with keywords that match currentMatchAnyKeyword?
+                if (eventChannel != EventChannel.None && this.m_channelData != null && this.m_channelData.Length > (int)eventChannel)
+                {
+                    EventKeywords channel_keywords = unchecked((EventKeywords)(m_channelData[(int)eventChannel] | (ulong)eventKeywords));
+                    if (channel_keywords != 0 && (channel_keywords & currentMatchAnyKeyword) == 0)
+                        return false;
+                }
+                else
+#endif
+                {
+                    if ((unchecked((ulong)eventKeywords & (ulong)currentMatchAnyKeyword)) == 0)
+                        return false;
+                }
+            }
+            return true;
+
+        }
+        [System.Runtime.CompilerServices.MethodImpl(System.Runtime.CompilerServices.MethodImplOptions.NoInlining)]
+        private void ThrowEventSourceException(string eventName, Exception innerEx = null)
+        {
+            // If we fail during out of band logging we may end up trying 
+            // to throw another EventSourceException, thus hitting a StackOverflowException. 
+            // Avoid StackOverflow by making sure we do not recursively call this method.
+            if (m_EventSourceExceptionRecurenceCount > 0)
+                return;
+            try
+            {
+                m_EventSourceExceptionRecurenceCount++;
+
+                string errorPrefix = "EventSourceException";
+                if (eventName != null)
+                {
+                    errorPrefix += " while processing event \"" + eventName + "\"";
+                }
+
+                // TODO Create variations of EventSourceException that indicate more information using the error code.
+                switch (EventProvider.GetLastWriteEventError())
+                {
+                    case EventProvider.WriteEventErrorCode.EventTooBig:
+                        ReportOutOfBandMessage(errorPrefix + ": " + SR.EventSource_EventTooBig, true);
+                        if (ThrowOnEventWriteErrors) throw new EventSourceException(SR.EventSource_EventTooBig, innerEx);
+                        break;
+                    case EventProvider.WriteEventErrorCode.NoFreeBuffers:
+                        ReportOutOfBandMessage(errorPrefix + ": " + SR.EventSource_NoFreeBuffers, true);
+                        if (ThrowOnEventWriteErrors) throw new EventSourceException(SR.EventSource_NoFreeBuffers, innerEx);
+                        break;
+                    case EventProvider.WriteEventErrorCode.NullInput:
+                        ReportOutOfBandMessage(errorPrefix + ": " + SR.EventSource_NullInput, true);
+                        if (ThrowOnEventWriteErrors) throw new EventSourceException(SR.EventSource_NullInput, innerEx);
+                        break;
+                    case EventProvider.WriteEventErrorCode.TooManyArgs:
+                        ReportOutOfBandMessage(errorPrefix + ": " + SR.EventSource_TooManyArgs, true);
+                        if (ThrowOnEventWriteErrors) throw new EventSourceException(SR.EventSource_TooManyArgs, innerEx);
+                        break;
+                    default:
+                        if (innerEx != null)
+                            ReportOutOfBandMessage(errorPrefix + ": " + innerEx.GetType() + ":" + innerEx.Message, true);
+                        else
+                            ReportOutOfBandMessage(errorPrefix, true);
+                        if (ThrowOnEventWriteErrors) throw new EventSourceException(innerEx);
+                        break;
+                }
+            }
+            finally
+            {
+                m_EventSourceExceptionRecurenceCount--;
+            }
+        }
+
+        private void ValidateEventOpcodeForTransfer(ref EventMetadata eventData, string eventName)
+        {
+            if ((EventOpcode)eventData.Descriptor.Opcode != EventOpcode.Send &&
+                (EventOpcode)eventData.Descriptor.Opcode != EventOpcode.Receive &&
+                (EventOpcode)eventData.Descriptor.Opcode != EventOpcode.Start)
+            {
+                ThrowEventSourceException(eventName);
+            }
+        }
+
+        internal static EventOpcode GetOpcodeWithDefault(EventOpcode opcode, string eventName)
+        {
+            if (opcode == EventOpcode.Info && eventName != null)
+            {
+                if (eventName.EndsWith(s_ActivityStartSuffix, StringComparison.Ordinal))
+                {
+                    return EventOpcode.Start;
+                }
+                else if (eventName.EndsWith(s_ActivityStopSuffix, StringComparison.Ordinal))
+                {
+                    return EventOpcode.Stop;
+                }
+            }
+
+            return opcode;
+        }
+
+#if FEATURE_MANAGED_ETW
+        /// <summary>
+        /// This class lets us hook the 'OnEventCommand' from the eventSource.  
+        /// </summary>
+        private class OverideEventProvider : EventProvider
+        {
+            public OverideEventProvider(EventSource eventSource)
+            {
+                this.m_eventSource = eventSource;
+            }
+            protected override void OnControllerCommand(ControllerCommand command, IDictionary<string, string> arguments,
+                                                              int perEventSourceSessionId, int etwSessionId)
+            {
+                // We use null to represent the ETW EventListener.  
+                EventListener listener = null;
+                m_eventSource.SendCommand(listener, perEventSourceSessionId, etwSessionId,
+                                          (EventCommand)command, IsEnabled(), Level, MatchAnyKeyword, arguments);
+            }
+            private EventSource m_eventSource;
+        }
+#endif
+
+        /// <summary>
+        /// Used to hold all the static information about an event.  This includes everything in the event
+        /// descriptor as well as some stuff we added specifically for EventSource. see the
+        /// code:m_eventData for where we use this.  
+        /// </summary>
+
+        /*
+         EventMetadata was public in the separate System.Diagnostics.Tracing assembly(pre NS2.0), 
+         now the move to CoreLib marked them as private.
+         While they are technically private (it's a contract used between the library and the ILC toolchain), 
+         we need them to be rooted and exported from shared library for the system to work.
+         For now I'm simply marking them as public again.A cleaner solution might be to use.rd.xml to 
+         root them and modify shared library definition to force export them.
+         */
+#if ES_BUILD_PN
+       public
+#else
+       internal
+#endif
+        partial struct EventMetadata
+        {
+            public EventDescriptor Descriptor;
+            public IntPtr EventHandle;              // EventPipeEvent handle.
+            public EventTags Tags;
+            public bool EnabledForAnyListener;      // true if any dispatcher has this event turned on
+            public bool EnabledForETW;              // is this event on for the OS ETW data dispatcher?
+
+            public bool HasRelatedActivityID;       // Set if the event method's first parameter is a Guid named 'relatedActivityId'
+#pragma warning disable 0649
+            public byte TriggersActivityTracking;   // count of listeners that marked this event as trigger for start of activity logging.
+#pragma warning restore 0649
+            public string Name;                     // the name of the event
+            public string Message;                  // If the event has a message associated with it, this is it.  
+            public ParameterInfo[] Parameters;      // TODO can we remove? 
+
+            public TraceLoggingEventTypes TraceLoggingEventTypes;
+            public EventActivityOptions ActivityOptions;
+
+#if ES_BUILD_PN
+            public EventParameterType[] ParameterTypes;
+#endif
+        };
+
+        // This is the internal entry point that code:EventListeners call when wanting to send a command to a
+        // eventSource. The logic is as follows
+        // 
+        // * if Command == Update
+        //     * perEventSourceSessionId specifies the per-provider ETW session ID that the command applies 
+        //         to (if listener != null)
+        //         perEventSourceSessionId = 0 - reserved for EventListeners
+        //         perEventSourceSessionId = 1..SessionMask.MAX - reserved for activity tracing aware ETW sessions
+        //                  perEventSourceSessionId-1 represents the bit in the reserved field (bits 44..47) in 
+        //                  Keywords that identifies the session
+        //         perEventSourceSessionId = SessionMask.MAX+1 - reserved for legacy ETW sessions; these are 
+        //                  discriminated by etwSessionId
+        //     * etwSessionId specifies a machine-wide ETW session ID; this allows correlation of
+        //         activity tracing across different providers (which might have different sessionIds
+        //         for the same ETW session)
+        //     * enable, level, matchAnyKeywords are used to set a default for all events for the
+        //         eventSource.  In particular, if 'enabled' is false, 'level' and
+        //         'matchAnyKeywords' are not used.  
+        //     * OnEventCommand is invoked, which may cause calls to
+        //         code:EventSource.EnableEventForDispatcher which may cause changes in the filtering
+        //         depending on the logic in that routine.
+        // * else (command != Update)
+        //     * Simply call OnEventCommand. The expectation is that filtering is NOT changed.
+        //     * The 'enabled' 'level', matchAnyKeyword' arguments are ignored (must be true, 0, 0).  
+        // 
+        // dispatcher == null has special meaning. It is the 'ETW' dispatcher.
+        internal void SendCommand(EventListener listener, int perEventSourceSessionId, int etwSessionId,
+                                  EventCommand command, bool enable,
+                                  EventLevel level, EventKeywords matchAnyKeyword,
+                                  IDictionary<string, string> commandArguments)
+        {
+            var commandArgs = new EventCommandEventArgs(command, commandArguments, this, listener, perEventSourceSessionId, etwSessionId, enable, level, matchAnyKeyword);
+            lock (EventListener.EventListenersLock)
+            {
+                if (m_completelyInited)
+                {
+                    // After the first command arrive after construction, we are ready to get rid of the deferred commands
+                    this.m_deferredCommands = null;
+                    // We are fully initialized, do the command 
+                    DoCommand(commandArgs);
+                }
+                else
+                {
+                    // We can't do the command, simply remember it and we do it when we are fully constructed.  
+                    if (m_deferredCommands == null)
+                        m_deferredCommands = commandArgs;       // create the first entry
+                    else
+                    {
+                        // We have one or more entries, find the last one and add it to that.  
+                        EventCommandEventArgs lastCommand = m_deferredCommands;
+                        while (lastCommand.nextCommand != null)
+                            lastCommand = lastCommand.nextCommand;
+                        lastCommand.nextCommand = commandArgs;
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// We want the eventSource to be fully initialized when we do commands because that way we can send 
+        /// error messages and other logging directly to the event stream.   Unfortunately we can get callbacks
+        /// when we are not fully initialized.  In that case we store them in 'commandArgs' and do them later. 
+        /// This helper actually does all actual command logic. 
+        /// </summary>
+        internal void DoCommand(EventCommandEventArgs commandArgs)
+        {
+            // PRECONDITION: We should be holding the EventListener.EventListenersLock
+            // We defer commands until we are completely inited.  This allows error messages to be sent.  
+            Debug.Assert(m_completelyInited);
+
+#if FEATURE_MANAGED_ETW
+            if (m_provider == null)     // If we failed to construct
+                return;
+#endif // FEATURE_MANAGED_ETW
+
+            m_outOfBandMessageCount = 0;
+            bool shouldReport = (commandArgs.perEventSourceSessionId > 0) && (commandArgs.perEventSourceSessionId <= SessionMask.MAX);
+            try
+            {
+                EnsureDescriptorsInitialized();
+                Debug.Assert(m_eventData != null);
+
+                // Find the per-EventSource dispatcher corresponding to registered dispatcher
+                commandArgs.dispatcher = GetDispatcher(commandArgs.listener);
+                if (commandArgs.dispatcher == null && commandArgs.listener != null)     // dispatcher == null means ETW dispatcher
+                {
+                    throw new ArgumentException(SR.EventSource_ListenerNotFound);
+                }
+
+                if (commandArgs.Arguments == null)
+                    commandArgs.Arguments = new Dictionary<string, string>();
+
+                if (commandArgs.Command == EventCommand.Update)
+                {
+                    // Set it up using the 'standard' filtering bitfields (use the "global" enable, not session specific one)
+                    for (int i = 0; i < m_eventData.Length; i++)
+                        EnableEventForDispatcher(commandArgs.dispatcher, i, IsEnabledByDefault(i, commandArgs.enable, commandArgs.level, commandArgs.matchAnyKeyword));
+
+                    if (commandArgs.enable)
+                    {
+                        if (!m_eventSourceEnabled)
+                        {
+                            // EventSource turned on for the first time, simply copy the bits.  
+                            m_level = commandArgs.level;
+                            m_matchAnyKeyword = commandArgs.matchAnyKeyword;
+                        }
+                        else
+                        {
+                            // Already enabled, make it the most verbose of the existing and new filter
+                            if (commandArgs.level > m_level)
+                                m_level = commandArgs.level;
+                            if (commandArgs.matchAnyKeyword == 0)
+                                m_matchAnyKeyword = 0;
+                            else if (m_matchAnyKeyword != 0)
+                                m_matchAnyKeyword = unchecked(m_matchAnyKeyword | commandArgs.matchAnyKeyword);
+                        }
+                    }
+
+                    // interpret perEventSourceSessionId's sign, and adjust perEventSourceSessionId to 
+                    // represent 0-based positive values
+                    bool bSessionEnable = (commandArgs.perEventSourceSessionId >= 0);
+                    if (commandArgs.perEventSourceSessionId == 0 && commandArgs.enable == false)
+                        bSessionEnable = false;
+
+                    if (commandArgs.listener == null)
+                    {
+                        if (!bSessionEnable)
+                            commandArgs.perEventSourceSessionId = -commandArgs.perEventSourceSessionId;
+                        // for "global" enable/disable (passed in with listener == null and
+                        //  perEventSourceSessionId == 0) perEventSourceSessionId becomes -1
+                        --commandArgs.perEventSourceSessionId;
+                    }
+
+                    commandArgs.Command = bSessionEnable ? EventCommand.Enable : EventCommand.Disable;
+
+                    // perEventSourceSessionId = -1 when ETW sent a notification, but the set of active sessions
+                    // hasn't changed.
+                    // sesisonId = SessionMask.MAX when one of the legacy ETW sessions changed
+                    // 0 <= perEventSourceSessionId < SessionMask.MAX for activity-tracing aware sessions
+                    Debug.Assert(commandArgs.perEventSourceSessionId >= -1 && commandArgs.perEventSourceSessionId <= SessionMask.MAX);
+
+                    // Send the manifest if we are enabling an ETW session
+                    if (bSessionEnable && commandArgs.dispatcher == null)
+                    {
+                        // eventSourceDispatcher == null means this is the ETW manifest
+
+#if !FEATURE_PERFTRACING
+                        // Note that we unconditionally send the manifest whenever we are enabled, even if
+                        // we were already enabled.   This is because there may be multiple sessions active
+                        // and we can't know that all the sessions have seen the manifest.  
+                        if (!SelfDescribingEvents)
+                            SendManifest(m_rawManifest);
+#endif
+                    }
+
+                    // Turn on the enable bit before making the OnEventCommand callback  This allows you to do useful
+                    // things like log messages, or test if keywords are enabled in the callback.  
+                    if (commandArgs.enable)
+                    {
+                        Debug.Assert(m_eventData != null);
+                        m_eventSourceEnabled = true;
+                    }
+
+                    this.OnEventCommand(commandArgs);
+                    var eventCommandCallback = this.m_eventCommandExecuted;
+                    if (eventCommandCallback != null)
+                        eventCommandCallback(this, commandArgs);
+
+                    if (!commandArgs.enable)
+                    {
+                        // If we are disabling, maybe we can turn on 'quick checks' to filter
+                        // quickly.  These are all just optimizations (since later checks will still filter)
+
+                        // There is a good chance EnabledForAnyListener are not as accurate as
+                        // they could be, go ahead and get a better estimate.  
+                        for (int i = 0; i < m_eventData.Length; i++)
+                        {
+                            bool isEnabledForAnyListener = false;
+                            for (EventDispatcher dispatcher = m_Dispatchers; dispatcher != null; dispatcher = dispatcher.m_Next)
+                            {
+                                if (dispatcher.m_EventEnabled[i])
+                                {
+                                    isEnabledForAnyListener = true;
+                                    break;
+                                }
+                            }
+                            m_eventData[i].EnabledForAnyListener = isEnabledForAnyListener;
+                        }
+
+                        // If no events are enabled, disable the global enabled bit.
+                        if (!AnyEventEnabled())
+                        {
+                            m_level = 0;
+                            m_matchAnyKeyword = 0;
+                            m_eventSourceEnabled = false;
+                        }
+                    }
+                }
+                else
+                {
+#if !FEATURE_PERFTRACING
+                    if (commandArgs.Command == EventCommand.SendManifest)
+                    {
+                        // TODO: should we generate the manifest here if we hadn't already?
+                        if (m_rawManifest != null)
+                            SendManifest(m_rawManifest);
+                    }
+#endif
+
+                    // These are not used for non-update commands and thus should always be 'default' values
+                    // Debug.Assert(enable == true);
+                    // Debug.Assert(level == EventLevel.LogAlways);
+                    // Debug.Assert(matchAnyKeyword == EventKeywords.None);
+
+                    this.OnEventCommand(commandArgs);
+                    var eventCommandCallback = m_eventCommandExecuted;
+                    if (eventCommandCallback != null)
+                        eventCommandCallback(this, commandArgs);
+                }
+            }
+            catch (Exception e)
+            {
+                // When the ETW session is created after the EventSource has registered with the ETW system
+                // we can send any error messages here.
+                ReportOutOfBandMessage("ERROR: Exception in Command Processing for EventSource " + Name + ": " + e.Message, true);
+                // We never throw when doing a command.  
+            }
+        }
+
+        /// <summary>
+        /// If 'value is 'true' then set the eventSource so that 'dispatcher' will receive event with the eventId
+        /// of 'eventId.  If value is 'false' disable the event for that dispatcher.   If 'eventId' is out of
+        /// range return false, otherwise true.  
+        /// </summary>
+        internal bool EnableEventForDispatcher(EventDispatcher dispatcher, int eventId, bool value)
+        {
+            if (dispatcher == null)
+            {
+                if (eventId >= m_eventData.Length)
+                    return false;
+#if FEATURE_MANAGED_ETW
+                if (m_provider != null)
+                    m_eventData[eventId].EnabledForETW = value;
+#endif
+            }
+            else
+            {
+                if (eventId >= dispatcher.m_EventEnabled.Length)
+                    return false;
+                dispatcher.m_EventEnabled[eventId] = value;
+                if (value)
+                    m_eventData[eventId].EnabledForAnyListener = true;
+            }
+            return true;
+        }
+
+        /// <summary>
+        /// Returns true if any event at all is on.  
+        /// </summary>
+        private bool AnyEventEnabled()
+        {
+            for (int i = 0; i < m_eventData.Length; i++)
+                if (m_eventData[i].EnabledForETW || m_eventData[i].EnabledForAnyListener)
+                    return true;
+            return false;
+        }
+
+        private bool IsDisposed
+        {
+            get { return m_eventSourceDisposed; }
+        }
+
+        private void EnsureDescriptorsInitialized()
+        {
+#if !ES_BUILD_STANDALONE
+            Debug.Assert(Monitor.IsEntered(EventListener.EventListenersLock));
+#endif
+            if (m_eventData == null)
+            {
+                Guid eventSourceGuid = Guid.Empty;
+                string eventSourceName = null;
+                EventMetadata[] eventData = null;
+                byte[] manifest = null;
+
+                // Try the GetMetadata provided by the ILTransform in ProjectN. The default sets all to null, and in that case we fall back
+                // to the reflection approach.
+                GetMetadata(out eventSourceGuid, out eventSourceName, out eventData, out manifest);
+
+                if (eventSourceGuid.Equals(Guid.Empty) || eventSourceName == null || eventData == null || manifest == null)
+                {
+                    // GetMetadata failed, so we have to set it via reflection.
+                    Debug.Assert(m_rawManifest == null);
+
+                    m_rawManifest = CreateManifestAndDescriptors(this.GetType(), Name, this);
+                    Debug.Assert(m_eventData != null);
+
+                }
+                else
+                {
+                    // GetMetadata worked, so set the fields as appropriate.
+                    m_name = eventSourceName;
+                    m_guid = eventSourceGuid;
+                    m_eventData = eventData;
+                    m_rawManifest = manifest;
+                }
+                // TODO Enforce singleton pattern 
+                foreach (WeakReference eventSourceRef in EventListener.s_EventSources)
+                {
+                    EventSource eventSource = eventSourceRef.Target as EventSource;
+                    if (eventSource != null && eventSource.Guid == m_guid && !eventSource.IsDisposed)
+                    {
+                        if (eventSource != this)
+                        {
+                            throw new ArgumentException(SR.Format(SR.EventSource_EventSourceGuidInUse, m_guid));
+                        }
+                    }
+                }
+
+                // Make certain all dispatchers also have their arrays initialized
+                EventDispatcher dispatcher = m_Dispatchers;
+                while (dispatcher != null)
+                {
+                    if (dispatcher.m_EventEnabled == null)
+                        dispatcher.m_EventEnabled = new bool[m_eventData.Length];
+                    dispatcher = dispatcher.m_Next;
+                }
+#if FEATURE_PERFTRACING
+                // Initialize the EventPipe event handles.
+                DefineEventPipeEvents();
+#endif
+            }
+            if (s_currentPid == 0)
+            {
+#if ES_BUILD_STANDALONE && !ES_BUILD_PCL && !CORECLR
+                // for non-BCL EventSource we must assert SecurityPermission
+                new SecurityPermission(PermissionState.Unrestricted).Assert();
+#endif
+                s_currentPid = Win32Native.GetCurrentProcessId();
+            }
+        }
+
+        // Send out the ETW manifest XML out to ETW
+        // Today, we only send the manifest to ETW, custom listeners don't get it. 
+        private unsafe bool SendManifest(byte[] rawManifest)
+        {
+            bool success = true;
+
+            if (rawManifest == null)
+                return false;
+
+            Debug.Assert(!SelfDescribingEvents);
+
+#if FEATURE_MANAGED_ETW
+            fixed (byte* dataPtr = rawManifest)
+            {
+                // we don't want the manifest to show up in the event log channels so we specify as keywords 
+                // everything but the first 8 bits (reserved for the 8 channels)
+                var manifestDescr = new EventDescriptor(0xFFFE, 1, 0, 0, 0xFE, 0xFFFE, 0x00ffFFFFffffFFFF);
+                ManifestEnvelope envelope = new ManifestEnvelope();
+
+                envelope.Format = ManifestEnvelope.ManifestFormats.SimpleXmlFormat;
+                envelope.MajorVersion = 1;
+                envelope.MinorVersion = 0;
+                envelope.Magic = 0x5B;              // An unusual number that can be checked for consistency. 
+                int dataLeft = rawManifest.Length;
+                envelope.ChunkNumber = 0;
+
+                EventProvider.EventData* dataDescrs = stackalloc EventProvider.EventData[2];
+
+                dataDescrs[0].Ptr = (ulong)&envelope;
+                dataDescrs[0].Size = (uint)sizeof(ManifestEnvelope);
+                dataDescrs[0].Reserved = 0;
+
+                dataDescrs[1].Ptr = (ulong)dataPtr;
+                dataDescrs[1].Reserved = 0;
+
+                int chunkSize = ManifestEnvelope.MaxChunkSize;
+                TRY_AGAIN_WITH_SMALLER_CHUNK_SIZE:
+                envelope.TotalChunks = (ushort)((dataLeft + (chunkSize - 1)) / chunkSize);
+                while (dataLeft > 0)
+                {
+                    dataDescrs[1].Size = (uint)Math.Min(dataLeft, chunkSize);
+                    if (m_provider != null)
+                    {
+                        if (!m_provider.WriteEvent(ref manifestDescr, IntPtr.Zero, null, null, 2, (IntPtr)dataDescrs))
+                        {
+                            // Turns out that if users set the BufferSize to something less than 64K then WriteEvent
+                            // can fail.   If we get this failure on the first chunk try again with something smaller
+                            // The smallest BufferSize is 1K so if we get to 256 (to account for envelope overhead), we can give up making it smaller. 
+                            if (EventProvider.GetLastWriteEventError() == EventProvider.WriteEventErrorCode.EventTooBig)
+                            {
+                                if (envelope.ChunkNumber == 0 && chunkSize > 256)
+                                {
+                                    chunkSize = chunkSize / 2;
+                                    goto TRY_AGAIN_WITH_SMALLER_CHUNK_SIZE;
+                                }
+                            }
+                            success = false;
+                            if (ThrowOnEventWriteErrors)
+                                ThrowEventSourceException("SendManifest");
+                            break;
+                        }
+                    }
+                    dataLeft -= chunkSize;
+                    dataDescrs[1].Ptr += (uint)chunkSize;
+                    envelope.ChunkNumber++;
+
+                    // For large manifests we want to not overflow any receiver's buffer. Most manifests will fit within
+                    // 5 chunks, so only the largest manifests will hit the pause.
+                    if ((envelope.ChunkNumber % 5) == 0)
+                    {
+#if ES_BUILD_STANDALONE
+                        Thread.Sleep(15);
+#else
+                        RuntimeThread.Sleep(15);
+#endif
+                    }
+                }
+            }
+#endif // FEATURE_MANAGED_ETW
+            return success;
+        }
+
+#if (ES_BUILD_PCL)
+        internal static Attribute GetCustomAttributeHelper(Type type, Type attributeType, EventManifestOptions flags = EventManifestOptions.None)
+        {
+            return GetCustomAttributeHelper(type.GetTypeInfo(), attributeType, flags);
+        }
+#endif
+
+        // Helper to deal with the fact that the type we are reflecting over might be loaded in the ReflectionOnly context.
+        // When that is the case, we have the build the custom assemblies on a member by hand.         
+        internal static Attribute GetCustomAttributeHelper(MemberInfo member, Type attributeType, EventManifestOptions flags = EventManifestOptions.None)
+        {
+#if !ES_BUILD_PN
+            // On ProjectN, ReflectionOnly() always equals false.  AllowEventSourceOverride is an option that allows either Microsoft.Diagnostics.Tracing or
+            // System.Diagnostics.Tracing EventSource to be considered valid.  This should not mattter anywhere but in Microsoft.Diagnostics.Tracing (nuget package).
+            if (!member.Module.Assembly.ReflectionOnly() && (flags & EventManifestOptions.AllowEventSourceOverride) == 0)
+#endif // !ES_BUILD_PN
+            {
+                // Let the runtime to the work for us, since we can execute code in this context.
+                Attribute firstAttribute = null;
+                foreach (var attribute in member.GetCustomAttributes(attributeType, false))
+                {
+                    firstAttribute = (Attribute)attribute;
+                    break;
+                }
+                return firstAttribute;
+            }
+
+#if (!ES_BUILD_PCL && !ES_BUILD_PN)
+            // In the reflection only context, we have to do things by hand.
+            string fullTypeNameToFind = attributeType.FullName;
+
+#if EVENT_SOURCE_LEGACY_NAMESPACE_SUPPORT
+            fullTypeNameToFind = fullTypeNameToFind.Replace("System.Diagnostics.Eventing", "System.Diagnostics.Tracing");
+#endif
+
+            foreach (CustomAttributeData data in CustomAttributeData.GetCustomAttributes(member))
+            {
+                if (AttributeTypeNamesMatch(attributeType, data.Constructor.ReflectedType))
+                {
+                    Attribute attr = null;
+
+                    Debug.Assert(data.ConstructorArguments.Count <= 1);
+
+                    if (data.ConstructorArguments.Count == 1)
+                    {
+                        attr = (Attribute)Activator.CreateInstance(attributeType, new object[] { data.ConstructorArguments[0].Value });
+                    }
+                    else if (data.ConstructorArguments.Count == 0)
+                    {
+                        attr = (Attribute)Activator.CreateInstance(attributeType);
+                    }
+
+                    if (attr != null)
+                    {
+                        Type t = attr.GetType();
+
+                        foreach (CustomAttributeNamedArgument namedArgument in data.NamedArguments)
+                        {
+                            PropertyInfo p = t.GetProperty(namedArgument.MemberInfo.Name, BindingFlags.Public | BindingFlags.Instance);
+                            object value = namedArgument.TypedValue.Value;
+
+                            if (p.PropertyType.IsEnum)
+                            {
+                                value = Enum.Parse(p.PropertyType, value.ToString());
+                            }
+
+                            p.SetValue(attr, value, null);
+                        }
+
+                        return attr;
+                    }
+                }
+            }
+
+            return null;
+#else // ES_BUILD_PCL && ES_BUILD_PN
+            // Don't use nameof here because the resource doesn't exist on some platforms, which results in a compilation error.
+            throw new ArgumentException("EventSource_PCLPlatformNotSupportedReflection", "EventSource");
+#endif
+        }
+
+        /// <summary>
+        /// Evaluates if two related "EventSource"-domain types should be considered the same
+        /// </summary>
+        /// <param name="attributeType">The attribute type in the load context - it's associated with the running 
+        /// EventSource type. This type may be different fromt he base type of the user-defined EventSource.</param>
+        /// <param name="reflectedAttributeType">The attribute type in the reflection context - it's associated with
+        /// the user-defined EventSource, and is in the same assembly as the eventSourceType passed to 
+        /// </param>
+        /// <returns>True - if the types should be considered equivalent, False - otherwise</returns>
+        private static bool AttributeTypeNamesMatch(Type attributeType, Type reflectedAttributeType)
+        {
+            return
+                // are these the same type?
+                attributeType == reflectedAttributeType ||
+                // are the full typenames equal?
+                string.Equals(attributeType.FullName, reflectedAttributeType.FullName, StringComparison.Ordinal) ||
+                    // are the typenames equal and the namespaces under "Diagnostics.Tracing" (typically
+                    // either Microsoft.Diagnostics.Tracing or System.Diagnostics.Tracing)?
+                    string.Equals(attributeType.Name, reflectedAttributeType.Name, StringComparison.Ordinal) &&
+                    attributeType.Namespace.EndsWith("Diagnostics.Tracing", StringComparison.Ordinal) &&
+                    (reflectedAttributeType.Namespace.EndsWith("Diagnostics.Tracing", StringComparison.Ordinal)
+#if EVENT_SOURCE_LEGACY_NAMESPACE_SUPPORT
+                     || reflectedAttributeType.Namespace.EndsWith("Diagnostics.Eventing", StringComparison.Ordinal)
+#endif
+);
+        }
+
+        private static Type GetEventSourceBaseType(Type eventSourceType, bool allowEventSourceOverride, bool reflectionOnly)
+        {
+            // return false for "object" and interfaces
+            if (eventSourceType.BaseType() == null)
+                return null;
+
+            // now go up the inheritance chain until hitting a concrete type ("object" at worse)
+            do
+            {
+                eventSourceType = eventSourceType.BaseType();
+            }
+            while (eventSourceType != null && eventSourceType.IsAbstract());
+
+            if (eventSourceType != null)
+            {
+                if (!allowEventSourceOverride)
+                {
+                    if (reflectionOnly && eventSourceType.FullName != typeof(EventSource).FullName ||
+                        !reflectionOnly && eventSourceType != typeof(EventSource))
+                        return null;
+                }
+                else
+                {
+                    if (eventSourceType.Name != "EventSource")
+                        return null;
+                }
+            }
+            return eventSourceType;
+        }
+
+        // Use reflection to look at the attributes of a class, and generate a manifest for it (as UTF8) and
+        // return the UTF8 bytes.  It also sets up the code:EventData structures needed to dispatch events
+        // at run time.  'source' is the event source to place the descriptors.  If it is null,
+        // then the descriptors are not creaed, and just the manifest is generated.  
+        private static byte[] CreateManifestAndDescriptors(Type eventSourceType, string eventSourceDllName, EventSource source,
+            EventManifestOptions flags = EventManifestOptions.None)
+        {
+            ManifestBuilder manifest = null;
+            bool bNeedsManifest = source != null ? !source.SelfDescribingEvents : true;
+            Exception exception = null; // exception that might get raised during validation b/c we couldn't/didn't recover from a previous error
+            byte[] res = null;
+
+            if (eventSourceType.IsAbstract() && (flags & EventManifestOptions.Strict) == 0)
+                return null;
+
+#if DEBUG && ES_BUILD_STANDALONE && TEST_SUPPORT
+            TestSupport.TestHooks.MaybeThrow(eventSourceType,
+                                        TestSupport.Category.ManifestError,
+                                        "EventSource_CreateManifestAndDescriptors",
+                                        new ArgumentException("EventSource_CreateManifestAndDescriptors"));
+#endif
+
+            try
+            {
+                MethodInfo[] methods = eventSourceType.GetMethods(BindingFlags.DeclaredOnly | BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance);
+                EventAttribute defaultEventAttribute;
+                int eventId = 1;        // The number given to an event that does not have a explicitly given ID. 
+                EventMetadata[] eventData = null;
+                Dictionary<string, string> eventsByName = null;
+                if (source != null || (flags & EventManifestOptions.Strict) != 0)
+                {
+                    eventData = new EventMetadata[methods.Length + 1];
+                    eventData[0].Name = "";         // Event 0 is the 'write messages string' event, and has an empty name.
+                }
+
+                // See if we have localization information.  
+                ResourceManager resources = null;
+                EventSourceAttribute eventSourceAttrib = (EventSourceAttribute)GetCustomAttributeHelper(eventSourceType, typeof(EventSourceAttribute), flags);
+                if (eventSourceAttrib != null && eventSourceAttrib.LocalizationResources != null)
+                    resources = new ResourceManager(eventSourceAttrib.LocalizationResources, eventSourceType.Assembly());
+
+                manifest = new ManifestBuilder(GetName(eventSourceType, flags), GetGuid(eventSourceType), eventSourceDllName,
+                                               resources, flags);
+
+                // Add an entry unconditionally for event ID 0 which will be for a string message.  
+                manifest.StartEvent("EventSourceMessage", new EventAttribute(0) { Level = EventLevel.LogAlways, Task = (EventTask)0xFFFE });
+                manifest.AddEventParameter(typeof(string), "message");
+                manifest.EndEvent();
+
+                // eventSourceType must be sealed and must derive from this EventSource
+                if ((flags & EventManifestOptions.Strict) != 0)
+                {
+                    bool typeMatch = GetEventSourceBaseType(eventSourceType, (flags & EventManifestOptions.AllowEventSourceOverride) != 0, eventSourceType.Assembly().ReflectionOnly()) != null;
+
+                    if (!typeMatch)
+                    {
+                        manifest.ManifestError(SR.EventSource_TypeMustDeriveFromEventSource);
+                    }
+                    if (!eventSourceType.IsAbstract() && !eventSourceType.IsSealed())
+                    {
+                        manifest.ManifestError(SR.EventSource_TypeMustBeSealedOrAbstract);
+                    }
+                }
+
+                // Collect task, opcode, keyword and channel information
+#if FEATURE_MANAGED_ETW_CHANNELS && FEATURE_ADVANCED_MANAGED_ETW_CHANNELS
+                foreach (var providerEnumKind in new string[] { "Keywords", "Tasks", "Opcodes", "Channels" })
+#else
+                foreach (var providerEnumKind in new string[] { "Keywords", "Tasks", "Opcodes" })
+#endif
+                {
+                    Type nestedType = eventSourceType.GetNestedType(providerEnumKind);
+                    if (nestedType != null)
+                    {
+                        if (eventSourceType.IsAbstract())
+                        {
+                            manifest.ManifestError(SR.Format(SR.EventSource_AbstractMustNotDeclareKTOC, nestedType.Name));
+                        }
+                        else
+                        {
+                            foreach (FieldInfo staticField in nestedType.GetFields(BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static))
+                            {
+                                AddProviderEnumKind(manifest, staticField, providerEnumKind);
+                            }
+                        }
+                    }
+                }
+                // ensure we have keywords for the session-filtering reserved bits
+                {
+                    manifest.AddKeyword("Session3", (long)0x1000 << 32);
+                    manifest.AddKeyword("Session2", (long)0x2000 << 32);
+                    manifest.AddKeyword("Session1", (long)0x4000 << 32);
+                    manifest.AddKeyword("Session0", (long)0x8000 << 32);
+                }
+
+                if (eventSourceType != typeof(EventSource))
+                {
+                    for (int i = 0; i < methods.Length; i++)
+                    {
+                        MethodInfo method = methods[i];
+                        ParameterInfo[] args = method.GetParameters();
+
+                        // Get the EventDescriptor (from the Custom attributes)
+                        EventAttribute eventAttribute = (EventAttribute)GetCustomAttributeHelper(method, typeof(EventAttribute), flags);
+
+                        // Compat: until v4.5.1 we ignored any non-void returning methods as well as virtual methods for 
+                        // the only reason of limiting the number of methods considered to be events. This broke a common 
+                        // design of having event sources implement specific interfaces. To fix this in a compatible way
+                        // we will now allow both non-void returning and virtual methods to be Event methods, as long 
+                        // as they are marked with the [Event] attribute
+                        if (/* method.IsVirtual || */ method.IsStatic)
+                        {
+                            continue;
+                        }
+
+                        if (eventSourceType.IsAbstract())
+                        {
+                            if (eventAttribute != null)
+                            {
+                                manifest.ManifestError(SR.Format(SR.EventSource_AbstractMustNotDeclareEventMethods, method.Name, eventAttribute.EventId));
+                            }
+                            continue;
+                        }
+                        else if (eventAttribute == null)
+                        {
+                            // Methods that don't return void can't be events, if they're NOT marked with [Event].
+                            // (see Compat comment above)
+                            if (method.ReturnType != typeof(void))
+                            {
+                                continue;
+                            }
+
+                            // Continue to ignore virtual methods if they do NOT have the [Event] attribute
+                            // (see Compat comment above)
+                            if (method.IsVirtual)
+                            {
+                                continue;
+                            }
+
+                            // If we explicitly mark the method as not being an event, then honor that.  
+                            if (GetCustomAttributeHelper(method, typeof(NonEventAttribute), flags) != null)
+                                continue;
+
+                            defaultEventAttribute = new EventAttribute(eventId);
+                            eventAttribute = defaultEventAttribute;
+                        }
+                        else if (eventAttribute.EventId <= 0)
+                        {
+                            manifest.ManifestError(SR.Format(SR.EventSource_NeedPositiveId, method.Name), true);
+                            continue;   // don't validate anything else for this event
+                        }
+                        if (method.Name.LastIndexOf('.') >= 0)
+                        {
+                            manifest.ManifestError(SR.Format(SR.EventSource_EventMustNotBeExplicitImplementation, method.Name, eventAttribute.EventId));
+                        }
+
+                        eventId++;
+                        string eventName = method.Name;
+
+                        if (eventAttribute.Opcode == EventOpcode.Info)      // We are still using the default opcode. 
+                        {
+                            // By default pick a task ID derived from the EventID, starting with the highest task number and working back 
+                            bool noTask = (eventAttribute.Task == EventTask.None);
+                            if (noTask)
+                                eventAttribute.Task = (EventTask)(0xFFFE - eventAttribute.EventId);
+
+                            // Unless we explicitly set the opcode to Info (to override the auto-generate of Start or Stop opcodes, 
+                            // pick a default opcode based on the event name (either Info or start or stop if the name ends with that suffix).  
+                            if (!eventAttribute.IsOpcodeSet)
+                                eventAttribute.Opcode = GetOpcodeWithDefault(EventOpcode.Info, eventName);
+
+                            // Make the stop opcode have the same task as the start opcode.
+                            if (noTask)
+                            {
+                                if (eventAttribute.Opcode == EventOpcode.Start)
+                                {
+                                    string taskName = eventName.Substring(0, eventName.Length - s_ActivityStartSuffix.Length); // Remove the Stop suffix to get the task name
+                                    if (string.Compare(eventName, 0, taskName, 0, taskName.Length) == 0 &&
+                                        string.Compare(eventName, taskName.Length, s_ActivityStartSuffix, 0, Math.Max(eventName.Length - taskName.Length, s_ActivityStartSuffix.Length)) == 0)
+                                    {
+                                        // Add a task that is just the task name for the start event.   This suppress the auto-task generation
+                                        // That would otherwise happen (and create 'TaskName'Start as task name rather than just 'TaskName'
+                                        manifest.AddTask(taskName, (int)eventAttribute.Task);
+                                    }
+                                }
+                                else if (eventAttribute.Opcode == EventOpcode.Stop)
+                                {
+                                    // Find the start associated with this stop event.  We require start to be immediately before the stop
+                                    int startEventId = eventAttribute.EventId - 1;
+                                    if (eventData != null && startEventId < eventData.Length)
+                                    {
+                                        Debug.Assert(0 <= startEventId);                // Since we reserve id 0, we know that id-1 is <= 0
+                                        EventMetadata startEventMetadata = eventData[startEventId];
+
+                                        // If you remove the Stop and add a Start does that name match the Start Event's Name?
+                                        // Ideally we would throw an error 
+                                        string taskName = eventName.Substring(0, eventName.Length - s_ActivityStopSuffix.Length); // Remove the Stop suffix to get the task name
+                                        if (startEventMetadata.Descriptor.Opcode == (byte)EventOpcode.Start &&
+                                            string.Compare(startEventMetadata.Name, 0, taskName, 0, taskName.Length) == 0 &&
+                                            string.Compare(startEventMetadata.Name, taskName.Length, s_ActivityStartSuffix, 0, Math.Max(startEventMetadata.Name.Length - taskName.Length, s_ActivityStartSuffix.Length)) == 0)
+                                        {
+
+                                            // Make the stop event match the start event
+                                            eventAttribute.Task = (EventTask)startEventMetadata.Descriptor.Task;
+                                            noTask = false;
+                                        }
+                                    }
+                                    if (noTask && (flags & EventManifestOptions.Strict) != 0)        // Throw an error if we can compatibly.   
+                                    {
+                                        throw new ArgumentException(SR.EventSource_StopsFollowStarts);
+                                    }
+                                }
+                            }
+                        }
+
+                        bool hasRelatedActivityID = RemoveFirstArgIfRelatedActivityId(ref args);
+                        if (!(source != null && source.SelfDescribingEvents))
+                        {
+                            manifest.StartEvent(eventName, eventAttribute);
+                            for (int fieldIdx = 0; fieldIdx < args.Length; fieldIdx++)
+                            {
+                                manifest.AddEventParameter(args[fieldIdx].ParameterType, args[fieldIdx].Name);
+                            }
+                            manifest.EndEvent();
+                        }
+
+                        if (source != null || (flags & EventManifestOptions.Strict) != 0)
+                        {
+                            // Do checking for user errors (optional, but not a big deal so we do it).  
+                            DebugCheckEvent(ref eventsByName, eventData, method, eventAttribute, manifest, flags);
+
+#if FEATURE_MANAGED_ETW_CHANNELS
+                            // add the channel keyword for Event Viewer channel based filters. This is added for creating the EventDescriptors only
+                            // and is not required for the manifest
+                            if (eventAttribute.Channel != EventChannel.None)
+                            {
+                                unchecked
+                                {
+                                    eventAttribute.Keywords |= (EventKeywords)manifest.GetChannelKeyword(eventAttribute.Channel, (ulong)eventAttribute.Keywords);
+                                }
+                            }
+#endif
+                            string eventKey = "event_" + eventName;
+                            string msg = manifest.GetLocalizedMessage(eventKey, CultureInfo.CurrentUICulture, etwFormat: false);
+                            // overwrite inline message with the localized message
+                            if (msg != null) eventAttribute.Message = msg;
+
+                            AddEventDescriptor(ref eventData, eventName, eventAttribute, args, hasRelatedActivityID);
+                        }
+                    }
+                }
+
+                // Tell the TraceLogging stuff where to start allocating its own IDs.  
+                NameInfo.ReserveEventIDsBelow(eventId);
+
+                if (source != null)
+                {
+                    TrimEventDescriptors(ref eventData);
+                    source.m_eventData = eventData;     // officially initialize it. We do this at most once (it is racy otherwise). 
+#if FEATURE_MANAGED_ETW_CHANNELS
+                    source.m_channelData = manifest.GetChannelData();
+#endif
+                }
+
+                // if this is an abstract event source we've already performed all the validation we can
+                if (!eventSourceType.IsAbstract() && (source == null || !source.SelfDescribingEvents))
+                {
+                    bNeedsManifest = (flags & EventManifestOptions.OnlyIfNeededForRegistration) == 0
+#if FEATURE_MANAGED_ETW_CHANNELS
+                                            || manifest.GetChannelData().Length > 0
+#endif
+;
+
+                    // if the manifest is not needed and we're not requested to validate the event source return early
+                    if (!bNeedsManifest && (flags & EventManifestOptions.Strict) == 0)
+                        return null;
+
+                    res = manifest.CreateManifest();
+                }
+            }
+            catch (Exception e)
+            {
+                // if this is a runtime manifest generation let the exception propagate
+                if ((flags & EventManifestOptions.Strict) == 0)
+                    throw;
+                // else store it to include it in the Argument exception we raise below
+                exception = e;
+            }
+
+            if ((flags & EventManifestOptions.Strict) != 0 && (manifest.Errors.Count > 0 || exception != null))
+            {
+                string msg = String.Empty;
+                if (manifest.Errors.Count > 0)
+                {
+                    bool firstError = true;
+                    foreach (string error in manifest.Errors)
+                    {
+                        if (!firstError)
+                            msg += Environment.NewLine;
+                        firstError = false;
+                        msg += error;
+                    }
+                }
+                else
+                    msg = "Unexpected error: " + exception.Message;
+
+                throw new ArgumentException(msg, exception);
+            }
+
+            return bNeedsManifest ? res : null;
+        }
+
+        private static bool RemoveFirstArgIfRelatedActivityId(ref ParameterInfo[] args)
+        {
+            // If the first parameter is (case insensitive) 'relatedActivityId' then skip it.  
+            if (args.Length > 0 && args[0].ParameterType == typeof(Guid) &&
+                string.Compare(args[0].Name, "relatedActivityId", StringComparison.OrdinalIgnoreCase) == 0)
+            {
+                var newargs = new ParameterInfo[args.Length - 1];
+                Array.Copy(args, 1, newargs, 0, args.Length - 1);
+                args = newargs;
+
+                return true;
+            }
+
+            return false;
+        }
+
+        // adds a enumeration (keyword, opcode, task or channel) represented by 'staticField'
+        // to the manifest.  
+        private static void AddProviderEnumKind(ManifestBuilder manifest, FieldInfo staticField, string providerEnumKind)
+        {
+            bool reflectionOnly = staticField.Module.Assembly.ReflectionOnly();
+            Type staticFieldType = staticField.FieldType;
+            if (!reflectionOnly && (staticFieldType == typeof(EventOpcode)) || AttributeTypeNamesMatch(staticFieldType, typeof(EventOpcode)))
+            {
+                if (providerEnumKind != "Opcodes") goto Error;
+                int value = (int)staticField.GetRawConstantValue();
+                manifest.AddOpcode(staticField.Name, value);
+            }
+            else if (!reflectionOnly && (staticFieldType == typeof(EventTask)) || AttributeTypeNamesMatch(staticFieldType, typeof(EventTask)))
+            {
+                if (providerEnumKind != "Tasks") goto Error;
+                int value = (int)staticField.GetRawConstantValue();
+                manifest.AddTask(staticField.Name, value);
+            }
+            else if (!reflectionOnly && (staticFieldType == typeof(EventKeywords)) || AttributeTypeNamesMatch(staticFieldType, typeof(EventKeywords)))
+            {
+                if (providerEnumKind != "Keywords") goto Error;
+                ulong value = unchecked((ulong)(long)staticField.GetRawConstantValue());
+                manifest.AddKeyword(staticField.Name, value);
+            }
+#if FEATURE_MANAGED_ETW_CHANNELS && FEATURE_ADVANCED_MANAGED_ETW_CHANNELS
+            else if (!reflectionOnly && (staticFieldType == typeof(EventChannel)) || AttributeTypeNamesMatch(staticFieldType, typeof(EventChannel)))
+            {
+                if (providerEnumKind != "Channels") goto Error;
+                var channelAttribute = (EventChannelAttribute)GetCustomAttributeHelper(staticField, typeof(EventChannelAttribute));
+                manifest.AddChannel(staticField.Name, (byte)staticField.GetRawConstantValue(), channelAttribute);
+            }
+#endif
+            return;
+            Error:
+            manifest.ManifestError(SR.Format(SR.EventSource_EnumKindMismatch, staticField.Name, staticField.FieldType.Name, providerEnumKind));
+        }
+
+        // Helper used by code:CreateManifestAndDescriptors to add a code:EventData descriptor for a method
+        // with the code:EventAttribute 'eventAttribute'.  resourceManger may be null in which case we populate it
+        // it is populated if we need to look up message resources
+        private static void AddEventDescriptor(ref EventMetadata[] eventData, string eventName,
+                                EventAttribute eventAttribute, ParameterInfo[] eventParameters,
+                                bool hasRelatedActivityID)
+        {
+            if (eventData == null || eventData.Length <= eventAttribute.EventId)
+            {
+                EventMetadata[] newValues = new EventMetadata[Math.Max(eventData.Length + 16, eventAttribute.EventId + 1)];
+                Array.Copy(eventData, 0, newValues, 0, eventData.Length);
+                eventData = newValues;
+            }
+
+            eventData[eventAttribute.EventId].Descriptor = new EventDescriptor(
+                    eventAttribute.EventId,
+                    eventAttribute.Version,
+#if FEATURE_MANAGED_ETW_CHANNELS
+                    (byte)eventAttribute.Channel,
+#else
+                    (byte)0,
+#endif
+                    (byte)eventAttribute.Level,
+                    (byte)eventAttribute.Opcode,
+                    (int)eventAttribute.Task,
+                    unchecked((long)((ulong)eventAttribute.Keywords | SessionMask.All.ToEventKeywords())));
+
+            eventData[eventAttribute.EventId].Tags = eventAttribute.Tags;
+            eventData[eventAttribute.EventId].Name = eventName;
+            eventData[eventAttribute.EventId].Parameters = eventParameters;
+            eventData[eventAttribute.EventId].Message = eventAttribute.Message;
+            eventData[eventAttribute.EventId].ActivityOptions = eventAttribute.ActivityOptions;
+            eventData[eventAttribute.EventId].HasRelatedActivityID = hasRelatedActivityID;
+            eventData[eventAttribute.EventId].EventHandle = IntPtr.Zero;
+        }
+
+        // Helper used by code:CreateManifestAndDescriptors that trims the m_eventData array to the correct
+        // size after all event descriptors have been added. 
+        private static void TrimEventDescriptors(ref EventMetadata[] eventData)
+        {
+            int idx = eventData.Length;
+            while (0 < idx)
+            {
+                --idx;
+                if (eventData[idx].Descriptor.EventId != 0)
+                    break;
+            }
+            if (eventData.Length - idx > 2)      // allow one wasted slot. 
+            {
+                EventMetadata[] newValues = new EventMetadata[idx + 1];
+                Array.Copy(eventData, 0, newValues, 0, newValues.Length);
+                eventData = newValues;
+            }
+        }
+
+        // Helper used by code:EventListener.AddEventSource and code:EventListener.EventListener
+        // when a listener gets attached to a eventSource
+        internal void AddListener(EventListener listener)
+        {
+            lock (EventListener.EventListenersLock)
+            {
+                bool[] enabledArray = null;
+                if (m_eventData != null)
+                    enabledArray = new bool[m_eventData.Length];
+                m_Dispatchers = new EventDispatcher(m_Dispatchers, enabledArray, listener);
+                listener.OnEventSourceCreated(this);
+            }
+        }
+
+        // Helper used by code:CreateManifestAndDescriptors to find user mistakes like reusing an event
+        // index for two distinct events etc.  Throws exceptions when it finds something wrong. 
+        private static void DebugCheckEvent(ref Dictionary<string, string> eventsByName,
+            EventMetadata[] eventData, MethodInfo method, EventAttribute eventAttribute,
+            ManifestBuilder manifest, EventManifestOptions options)
+        {
+            int evtId = eventAttribute.EventId;
+            string evtName = method.Name;
+            int eventArg = GetHelperCallFirstArg(method);
+            if (eventArg >= 0 && evtId != eventArg)
+            {
+                manifest.ManifestError(SR.Format(SR.EventSource_MismatchIdToWriteEvent, evtName, evtId, eventArg), true);
+            }
+
+            if (evtId < eventData.Length && eventData[evtId].Descriptor.EventId != 0)
+            {
+                manifest.ManifestError(SR.Format(SR.EventSource_EventIdReused, evtName, evtId, eventData[evtId].Name), true);
+            }
+
+            // We give a task to things if they don't have one.  
+            // TODO this is moderately expensive (N*N).   We probably should not even bother....   
+            Debug.Assert(eventAttribute.Task != EventTask.None || eventAttribute.Opcode != EventOpcode.Info);
+            for (int idx = 0; idx < eventData.Length; ++idx)
+            {
+                // skip unused Event IDs. 
+                if (eventData[idx].Name == null)
+                    continue;
+
+                if (eventData[idx].Descriptor.Task == (int)eventAttribute.Task && eventData[idx].Descriptor.Opcode == (int)eventAttribute.Opcode)
+                {
+                    manifest.ManifestError(SR.Format(SR.EventSource_TaskOpcodePairReused,
+                                            evtName, evtId, eventData[idx].Name, idx));
+                    // If we are not strict stop on first error.   We have had problems with really large providers taking forever.  because of many errors.  
+                    if ((options & EventManifestOptions.Strict) == 0)
+                        break;
+                }
+            }
+
+            // for non-default event opcodes the user must define a task!
+            if (eventAttribute.Opcode != EventOpcode.Info)
+            {
+                bool failure = false;
+                if (eventAttribute.Task == EventTask.None)
+                    failure = true;
+                else
+                {
+                    // If you have the auto-assigned Task, then you did not explicitly set one.  
+                    // This is OK for Start events because we have special logic to assign the task to a prefix derived from the event name
+                    // But all other cases we want to catch the omission.  
+                    var autoAssignedTask = (EventTask)(0xFFFE - evtId);
+                    if ((eventAttribute.Opcode != EventOpcode.Start && eventAttribute.Opcode != EventOpcode.Stop) && eventAttribute.Task == autoAssignedTask)
+                        failure = true;
+                }
+                if (failure)
+                {
+                    manifest.ManifestError(SR.Format(SR.EventSource_EventMustHaveTaskIfNonDefaultOpcode, evtName, evtId));
+                }
+            }
+
+            // If we ever want to enforce the rule: MethodName = TaskName + OpcodeName here's how:
+            //  (the reason we don't is backwards compat and the need for handling this as a non-fatal error
+            //  by eventRegister.exe)
+            // taskName & opcodeName could be passed in by the caller which has opTab & taskTab handy
+            // if (!(((int)eventAttribute.Opcode == 0 && evtName == taskName) || (evtName == taskName+opcodeName)))
+            // {
+            //     throw new WarningException(SR.EventSource_EventNameDoesNotEqualTaskPlusOpcode);
+            // }
+
+            if (eventsByName == null)
+                eventsByName = new Dictionary<string, string>();
+
+            if (eventsByName.ContainsKey(evtName))
+            {
+                manifest.ManifestError(SR.Format(SR.EventSource_EventNameReused, evtName), true);
+            }
+
+            eventsByName[evtName] = evtName;
+        }
+
+        /// <summary>
+        /// This method looks at the IL and tries to pattern match against the standard
+        /// 'boilerplate' event body 
+        /// <code>
+        ///     { if (Enabled()) WriteEvent(#, ...) } 
+        /// </code>
+        /// If the pattern matches, it returns the literal number passed as the first parameter to
+        /// the WriteEvent.  This is used to find common user errors (mismatching this
+        /// number with the EventAttribute ID).  It is only used for validation.   
+        /// </summary>
+        /// <param name="method">The method to probe.</param>
+        /// <returns>The literal value or -1 if the value could not be determined. </returns>
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Maintainability", "CA1502:AvoidExcessiveComplexity", Justification = "Switch statement is clearer than alternatives")]
+        private static int GetHelperCallFirstArg(MethodInfo method)
+        {
+#if (!ES_BUILD_PCL && !ES_BUILD_PN)
+            // Currently searches for the following pattern
+            // 
+            // ...     // CAN ONLY BE THE INSTRUCTIONS BELOW
+            // LDARG0
+            // LDC.I4 XXX
+            // ...     // CAN ONLY BE THE INSTRUCTIONS BELOW CAN'T BE A BRANCH OR A CALL
+            // CALL 
+            // NOP     // 0 or more times
+            // RET
+            // 
+            // If we find this pattern we return the XXX.  Otherwise we return -1.  
+#if !CORECLR
+            (new ReflectionPermission(ReflectionPermissionFlag.MemberAccess)).Assert();
+#endif
+            byte[] instrs = method.GetMethodBody().GetILAsByteArray();
+            int retVal = -1;
+            for (int idx = 0; idx < instrs.Length;)
+            {
+                switch (instrs[idx])
+                {
+                    case 0: // NOP
+                    case 1: // BREAK
+                    case 2: // LDARG_0
+                    case 3: // LDARG_1
+                    case 4: // LDARG_2
+                    case 5: // LDARG_3
+                    case 6: // LDLOC_0
+                    case 7: // LDLOC_1
+                    case 8: // LDLOC_2
+                    case 9: // LDLOC_3
+                    case 10: // STLOC_0
+                    case 11: // STLOC_1
+                    case 12: // STLOC_2
+                    case 13: // STLOC_3
+                        break;
+                    case 14: // LDARG_S
+                    case 16: // STARG_S
+                        idx++;
+                        break;
+                    case 20: // LDNULL
+                        break;
+                    case 21: // LDC_I4_M1
+                    case 22: // LDC_I4_0
+                    case 23: // LDC_I4_1
+                    case 24: // LDC_I4_2
+                    case 25: // LDC_I4_3
+                    case 26: // LDC_I4_4
+                    case 27: // LDC_I4_5
+                    case 28: // LDC_I4_6
+                    case 29: // LDC_I4_7
+                    case 30: // LDC_I4_8
+                        if (idx > 0 && instrs[idx - 1] == 2)  // preceeded by LDARG0
+                            retVal = instrs[idx] - 22;
+                        break;
+                    case 31: // LDC_I4_S
+                        if (idx > 0 && instrs[idx - 1] == 2)  // preceeded by LDARG0
+                            retVal = instrs[idx + 1];
+                        idx++;
+                        break;
+                    case 32: // LDC_I4
+                        idx += 4;
+                        break;
+                    case 37: // DUP
+                        break;
+                    case 40: // CALL
+                        idx += 4;
+
+                        if (retVal >= 0)
+                        {
+                            // Is this call just before return?  
+                            for (int search = idx + 1; search < instrs.Length; search++)
+                            {
+                                if (instrs[search] == 42)  // RET
+                                    return retVal;
+                                if (instrs[search] != 0)   // NOP
+                                    break;
+                            }
+                        }
+                        retVal = -1;
+                        break;
+                    case 44: // BRFALSE_S
+                    case 45: // BRTRUE_S
+                        retVal = -1;
+                        idx++;
+                        break;
+                    case 57: // BRFALSE
+                    case 58: // BRTRUE
+                        retVal = -1;
+                        idx += 4;
+                        break;
+                    case 103: // CONV_I1
+                    case 104: // CONV_I2
+                    case 105: // CONV_I4
+                    case 106: // CONV_I8
+                    case 109: // CONV_U4
+                    case 110: // CONV_U8
+                        break;
+                    case 140: // BOX
+                    case 141: // NEWARR
+                        idx += 4;
+                        break;
+                    case 162: // STELEM_REF
+                        break;
+                    case 254: // PREFIX
+                        idx++;
+                        // Covers the CEQ instructions used in debug code for some reason.
+                        if (idx >= instrs.Length || instrs[idx] >= 6)
+                            goto default;
+                        break;
+                    default:
+                        /* Debug.Fail("Warning: User validation code sub-optimial: Unsuported opcode " + instrs[idx] +
+                            " at " + idx + " in method " + method.Name); */
+                        return -1;
+                }
+                idx++;
+            }
+#endif
+            return -1;
+        }
+
+#if false // This routine is not needed at all, it was used for unit test debugging. 
+        [Conditional("DEBUG")]
+        private static void OutputDebugString(string msg)
+        {
+#if !ES_BUILD_PCL
+            msg = msg.TrimEnd('\r', '\n') +
+                    string.Format(CultureInfo.InvariantCulture, ", Thrd({0})" + Environment.NewLine, Thread.CurrentThread.ManagedThreadId);
+            System.Diagnostics.Debugger.Log(0, null, msg);
+#endif
+        }
+#endif
+
+        /// <summary>
+        /// Sends an error message to the debugger (outputDebugString), as well as the EventListeners 
+        /// It will do this even if the EventSource is not enabled.  
+        /// TODO remove flush parameter it is not used.  
+        /// </summary>
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        internal void ReportOutOfBandMessage(string msg, bool flush)
+        {
+            try
+            {
+#if (!ES_BUILD_PCL && !ES_BUILD_PN)
+                // send message to debugger without delay
+                System.Diagnostics.Debugger.Log(0, null, String.Format("EventSource Error: {0}{1}", msg, Environment.NewLine));
+#endif
+
+                // Send it to all listeners.
+                if (m_outOfBandMessageCount < 16 - 1)     // Note this is only if size byte
+                    m_outOfBandMessageCount++;
+                else
+                {
+                    if (m_outOfBandMessageCount == 16)
+                        return;
+                    m_outOfBandMessageCount = 16;    // Mark that we hit the limit.  Notify them that this is the case. 
+                    msg = "Reached message limit.   End of EventSource error messages.";
+                }
+
+                WriteEventString(EventLevel.LogAlways, -1, msg);
+                WriteStringToAllListeners("EventSourceMessage", msg);
+            }
+            catch (Exception) { }      // If we fail during last chance logging, well, we have to give up....
+        }
+
+        private EventSourceSettings ValidateSettings(EventSourceSettings settings)
+        {
+            var evtFormatMask = EventSourceSettings.EtwManifestEventFormat |
+                                EventSourceSettings.EtwSelfDescribingEventFormat;
+            if ((settings & evtFormatMask) == evtFormatMask)
+            {
+                throw new ArgumentException(SR.EventSource_InvalidEventFormat, nameof(settings));
+            }
+
+            // If you did not explicitly ask for manifest, you get self-describing.  
+            if ((settings & evtFormatMask) == 0)
+                settings |= EventSourceSettings.EtwSelfDescribingEventFormat;
+            return settings;
+        }
+
+        private bool ThrowOnEventWriteErrors
+        {
+            get { return (m_config & EventSourceSettings.ThrowOnEventWriteErrors) != 0; }
+            set
+            {
+                if (value) m_config |= EventSourceSettings.ThrowOnEventWriteErrors;
+                else m_config &= ~EventSourceSettings.ThrowOnEventWriteErrors;
+            }
+        }
+
+        private bool SelfDescribingEvents
+        {
+            get
+            {
+                Debug.Assert(((m_config & EventSourceSettings.EtwManifestEventFormat) != 0) !=
+                                ((m_config & EventSourceSettings.EtwSelfDescribingEventFormat) != 0));
+                return (m_config & EventSourceSettings.EtwSelfDescribingEventFormat) != 0;
+            }
+            set
+            {
+                if (!value)
+                {
+                    m_config |= EventSourceSettings.EtwManifestEventFormat;
+                    m_config &= ~EventSourceSettings.EtwSelfDescribingEventFormat;
+                }
+                else
+                {
+                    m_config |= EventSourceSettings.EtwSelfDescribingEventFormat;
+                    m_config &= ~EventSourceSettings.EtwManifestEventFormat;
+                }
+            }
+        }
+
+        // private instance state 
+        private string m_name;                          // My friendly name (privided in ctor)
+        internal int m_id;                              // A small integer that is unique to this instance.  
+        private Guid m_guid;                            // GUID representing the ETW eventSource to the OS.  
+        internal volatile EventMetadata[] m_eventData;  // None per-event data
+        private volatile byte[] m_rawManifest;          // Bytes to send out representing the event schema
+
+        private EventHandler<EventCommandEventArgs> m_eventCommandExecuted;
+
+        private EventSourceSettings m_config;      // configuration information
+
+        private bool m_eventSourceDisposed;              // has Dispose been called.
+
+        // Enabling bits
+        private bool m_eventSourceEnabled;              // am I enabled (any of my events are enabled for any dispatcher)
+        internal EventLevel m_level;                    // highest level enabled by any output dispatcher
+        internal EventKeywords m_matchAnyKeyword;       // the logical OR of all levels enabled by any output dispatcher (zero is a special case) meaning 'all keywords'
+
+        // Dispatching state 
+        internal volatile EventDispatcher m_Dispatchers;    // Linked list of code:EventDispatchers we write the data to (we also do ETW specially)
+#if FEATURE_MANAGED_ETW
+        private volatile OverideEventProvider m_provider;   // This hooks up ETW commands to our 'OnEventCommand' callback
+#endif
+        private bool m_completelyInited;                // The EventSource constructor has returned without exception.   
+        private Exception m_constructionException;      // If there was an exception construction, this is it 
+        private byte m_outOfBandMessageCount;           // The number of out of band messages sent (we throttle them
+        private EventCommandEventArgs m_deferredCommands;// If we get commands before we are fully we store them here and run the when we are fully inited.  
+
+        private string[] m_traits;                      // Used to implement GetTraits
+
+        internal static uint s_currentPid;              // current process id, used in synthesizing quasi-GUIDs
+        [ThreadStatic]
+        private static byte m_EventSourceExceptionRecurenceCount = 0; // current recursion count inside ThrowEventSourceException
+
+        [ThreadStatic]
+        private static bool m_EventSourceInDecodeObject = false;
+
+#if FEATURE_MANAGED_ETW_CHANNELS
+        internal volatile ulong[] m_channelData;
+#endif
+
+        // We use a single instance of ActivityTracker for all EventSources instances to allow correlation between multiple event providers.
+        // We have m_activityTracker field simply because instance field is more efficient than static field fetch.
+        ActivityTracker m_activityTracker;
+        internal const string s_ActivityStartSuffix = "Start";
+        internal const string s_ActivityStopSuffix = "Stop";
+
+        // used for generating GUID from eventsource name
+        private static readonly byte[] namespaceBytes = new byte[] {
+            0x48, 0x2C, 0x2D, 0xB2, 0xC3, 0x90, 0x47, 0xC8,
+            0x87, 0xF8, 0x1A, 0x15, 0xBF, 0xC1, 0x30, 0xFB,
+        };
+
+#endregion
+    }
+
+    /// <summary>
+    /// Enables specifying event source configuration options to be used in the EventSource constructor.
+    /// </summary>
+    [Flags]
+    public enum EventSourceSettings
+    {
+        /// <summary>
+        /// This specifies none of the special configuration options should be enabled.
+        /// </summary>
+        Default = 0,
+        /// <summary>
+        /// Normally an EventSource NEVER throws; setting this option will tell it to throw when it encounters errors.  
+        /// </summary>
+        ThrowOnEventWriteErrors = 1,
+        /// <summary>
+        /// Setting this option is a directive to the ETW listener should use manifest-based format when
+        /// firing events. This is the default option when defining a type derived from EventSource 
+        /// (using the protected EventSource constructors).
+        /// Only one of EtwManifestEventFormat or EtwSelfDescribingEventFormat should be specified
+        /// </summary>
+        EtwManifestEventFormat = 4,
+        /// <summary>
+        /// Setting this option is a directive to the ETW listener should use self-describing event format
+        /// when firing events. This is the default option when creating a new instance of the EventSource
+        /// type (using the public EventSource constructors).  
+        /// Only one of EtwManifestEventFormat or EtwSelfDescribingEventFormat should be specified
+        /// </summary>
+        EtwSelfDescribingEventFormat = 8,
+    }
+
+    /// <summary>
+    /// An EventListener represents a target for the events generated by EventSources (that is subclasses
+    /// of <see cref="EventSource"/>), in the current appdomain. When a new EventListener is created
+    /// it is logically attached to all eventSources in that appdomain. When the EventListener is Disposed, then
+    /// it is disconnected from the event eventSources. Note that there is a internal list of STRONG references
+    /// to EventListeners, which means that relying on the lack of references to EventListeners to clean up
+    /// EventListeners will NOT work. You must call EventListener.Dispose explicitly when a dispatcher is no
+    /// longer needed.
+    /// <para>
+    /// Once created, EventListeners can enable or disable on a per-eventSource basis using verbosity levels
+    /// (<see cref="EventLevel"/>) and bitfields (<see cref="EventKeywords"/>) to further restrict the set of 
+    /// events to be sent to the dispatcher. The dispatcher can also send arbitrary commands to a particular 
+    /// eventSource using the 'SendCommand' method. The meaning of the commands are eventSource specific.
+    /// </para><para>
+    /// The Null Guid (that is (new Guid()) has special meaning as a wildcard for 'all current eventSources in
+    /// the appdomain'. Thus it is relatively easy to turn on all events in the appdomain if desired.
+    /// </para><para>
+    /// It is possible for there to be many EventListener's defined in a single appdomain. Each dispatcher is
+    /// logically independent of the other listeners. Thus when one dispatcher enables or disables events, it
+    /// affects only that dispatcher (other listeners get the events they asked for). It is possible that
+    /// commands sent with 'SendCommand' would do a semantic operation that would affect the other listeners
+    /// (like doing a GC, or flushing data ...), but this is the exception rather than the rule.
+    /// </para><para>
+    /// Thus the model is that each EventSource keeps a list of EventListeners that it is sending events
+    /// to. Associated with each EventSource-dispatcher pair is a set of filtering criteria that determine for
+    /// that eventSource what events that dispatcher will receive.
+    /// </para><para>
+    /// Listeners receive the events on their 'OnEventWritten' method. Thus subclasses of EventListener must
+    /// override this method to do something useful with the data.
+    /// </para><para>
+    /// In addition, when new eventSources are created, the 'OnEventSourceCreate' method is called. The
+    /// invariant associated with this callback is that every eventSource gets exactly one
+    /// 'OnEventSourceCreate' call for ever eventSource that can potentially send it log messages. In
+    /// particular when a EventListener is created, typically a series of OnEventSourceCreate' calls are
+    /// made to notify the new dispatcher of all the eventSources that existed before the EventListener was
+    /// created.
+    /// </para>
+    /// </summary>
+    public class EventListener : IDisposable
+    {
+        private event EventHandler<EventSourceCreatedEventArgs> _EventSourceCreated;
+
+        /// <summary>
+        /// This event is raised whenever a new eventSource is 'attached' to the dispatcher.
+        /// This can happen for all existing EventSources when the EventListener is created
+        /// as well as for any EventSources that come into existence after the EventListener
+        /// has been created.
+        /// 
+        /// These 'catch up' events are called during the construction of the EventListener.
+        /// Subclasses need to be prepared for that.
+        /// 
+        /// In a multi-threaded environment, it is possible that 'EventSourceEventWrittenCallback' 
+        /// events for a particular eventSource to occur BEFORE the EventSourceCreatedCallback is issued.
+        /// </summary>
+        public event EventHandler<EventSourceCreatedEventArgs> EventSourceCreated
+        {
+            add
+            {
+                CallBackForExistingEventSources(false, value);
+
+                this._EventSourceCreated = (EventHandler<EventSourceCreatedEventArgs>)Delegate.Combine(_EventSourceCreated, value);
+            }
+            remove
+            {
+                this._EventSourceCreated = (EventHandler<EventSourceCreatedEventArgs>)Delegate.Remove(_EventSourceCreated, value);
+            }
+        }
+
+        /// <summary>
+        /// This event is raised whenever an event has been written by a EventSource for which 
+        /// the EventListener has enabled events.  
+        /// </summary>
+        public event EventHandler<EventWrittenEventArgs> EventWritten;
+
+        /// <summary>
+        /// Create a new EventListener in which all events start off turned off (use EnableEvents to turn
+        /// them on).  
+        /// </summary>
+        public EventListener()
+        {
+            // This will cause the OnEventSourceCreated callback to fire. 
+            CallBackForExistingEventSources(true, (obj, args) => args.EventSource.AddListener((EventListener)obj));
+        }
+
+        /// <summary>
+        /// Dispose should be called when the EventListener no longer desires 'OnEvent*' callbacks. Because
+        /// there is an internal list of strong references to all EventListeners, calling 'Dispose' directly
+        /// is the only way to actually make the listen die. Thus it is important that users of EventListener
+        /// call Dispose when they are done with their logging.
+        /// </summary>
+#if ES_BUILD_STANDALONE
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1063:ImplementIDisposableCorrectly")]
+#endif
+        public virtual void Dispose()
+        {
+            lock (EventListenersLock)
+            {
+                if (s_Listeners != null)
+                {
+                    if (this == s_Listeners)
+                    {
+                        EventListener cur = s_Listeners;
+                        s_Listeners = this.m_Next;
+                        RemoveReferencesToListenerInEventSources(cur);
+                    }
+                    else
+                    {
+                        // Find 'this' from the s_Listeners linked list.  
+                        EventListener prev = s_Listeners;
+                        for (;;)
+                        {
+                            EventListener cur = prev.m_Next;
+                            if (cur == null)
+                                break;
+                            if (cur == this)
+                            {
+                                // Found our Listener, remove references to to it in the eventSources
+                                prev.m_Next = cur.m_Next;       // Remove entry. 
+                                RemoveReferencesToListenerInEventSources(cur);
+                                break;
+                            }
+                            prev = cur;
+                        }
+                    }
+                }
+                Validate();
+            }
+        }
+        // We don't expose a Dispose(bool), because the contract is that you don't have any non-syncronous
+        // 'cleanup' associated with this object
+
+        /// <summary>
+        /// Enable all events from the eventSource identified by 'eventSource' to the current 
+        /// dispatcher that have a verbosity level of 'level' or lower.
+        ///   
+        /// This call can have the effect of REDUCING the number of events sent to the 
+        /// dispatcher if 'level' indicates a less verbose level than was previously enabled.
+        /// 
+        /// This call never has an effect on other EventListeners.
+        ///
+        /// </summary>
+        public void EnableEvents(EventSource eventSource, EventLevel level)
+        {
+            EnableEvents(eventSource, level, EventKeywords.None);
+        }
+        /// <summary>
+        /// Enable all events from the eventSource identified by 'eventSource' to the current
+        /// dispatcher that have a verbosity level of 'level' or lower and have a event keyword
+        /// matching any of the bits in 'matchAnyKeyword'.
+        /// 
+        /// This call can have the effect of REDUCING the number of events sent to the 
+        /// dispatcher if 'level' indicates a less verbose level than was previously enabled or
+        /// if 'matchAnyKeyword' has fewer keywords set than where previously set.
+        /// 
+        /// This call never has an effect on other EventListeners.
+        /// </summary>
+        public void EnableEvents(EventSource eventSource, EventLevel level, EventKeywords matchAnyKeyword)
+        {
+            EnableEvents(eventSource, level, matchAnyKeyword, null);
+        }
+        /// <summary>
+        /// Enable all events from the eventSource identified by 'eventSource' to the current
+        /// dispatcher that have a verbosity level of 'level' or lower and have a event keyword
+        /// matching any of the bits in 'matchAnyKeyword' as well as any (eventSource specific)
+        /// effect passing additional 'key-value' arguments 'arguments' might have.  
+        /// 
+        /// This call can have the effect of REDUCING the number of events sent to the 
+        /// dispatcher if 'level' indicates a less verbose level than was previously enabled or
+        /// if 'matchAnyKeyword' has fewer keywords set than where previously set.
+        /// 
+        /// This call never has an effect on other EventListeners.
+        /// </summary>       
+        public void EnableEvents(EventSource eventSource, EventLevel level, EventKeywords matchAnyKeyword, IDictionary<string, string> arguments)
+        {
+            if (eventSource == null)
+            {
+                throw new ArgumentNullException(nameof(eventSource));
+            }
+
+            eventSource.SendCommand(this, 0, 0, EventCommand.Update, true, level, matchAnyKeyword, arguments);
+        }
+        /// <summary>
+        /// Disables all events coming from eventSource identified by 'eventSource'.  
+        /// 
+        /// This call never has an effect on other EventListeners.      
+        /// </summary>
+        public void DisableEvents(EventSource eventSource)
+        {
+            if (eventSource == null)
+            {
+                throw new ArgumentNullException(nameof(eventSource));
+            }
+
+            eventSource.SendCommand(this, 0, 0, EventCommand.Update, false, EventLevel.LogAlways, EventKeywords.None, null);
+        }
+
+        /// <summary>
+        /// EventSourceIndex is small non-negative integer (suitable for indexing in an array)
+        /// identifying EventSource. It is unique per-appdomain. Some EventListeners might find
+        /// it useful to store additional information about each eventSource connected to it,
+        /// and EventSourceIndex allows this extra information to be efficiently stored in a
+        /// (growable) array (eg List(T)).
+        /// </summary>
+        public static int EventSourceIndex(EventSource eventSource) { return eventSource.m_id; }
+
+        /// <summary>
+        /// This method is called whenever a new eventSource is 'attached' to the dispatcher.
+        /// This can happen for all existing EventSources when the EventListener is created
+        /// as well as for any EventSources that come into existence after the EventListener
+        /// has been created.
+        /// 
+        /// These 'catch up' events are called during the construction of the EventListener.
+        /// Subclasses need to be prepared for that.
+        /// 
+        /// In a multi-threaded environment, it is possible that 'OnEventWritten' callbacks
+        /// for a particular eventSource to occur BEFORE the OnEventSourceCreated is issued.
+        /// </summary>
+        /// <param name="eventSource"></param>
+        internal protected virtual void OnEventSourceCreated(EventSource eventSource)
+        {
+            EventHandler<EventSourceCreatedEventArgs> callBack = this._EventSourceCreated;
+            if (callBack != null)
+            {
+                EventSourceCreatedEventArgs args = new EventSourceCreatedEventArgs();
+                args.EventSource = eventSource;
+                callBack(this, args);
+            }
+        }
+
+        /// <summary>
+        /// This method is called whenever an event has been written by a EventSource for which 
+        /// the EventListener has enabled events.  
+        /// </summary>
+        /// <param name="eventData"></param>
+        internal protected virtual void OnEventWritten(EventWrittenEventArgs eventData)
+        {
+            EventHandler<EventWrittenEventArgs> callBack = this.EventWritten;
+            if (callBack != null)
+            {
+                callBack(this, eventData);
+            }
+        }
+
+
+#region private
+        /// <summary>
+        /// This routine adds newEventSource to the global list of eventSources, it also assigns the
+        /// ID to the eventSource (which is simply the ordinal in the global list).
+        /// 
+        /// EventSources currently do not pro-actively remove themselves from this list. Instead
+        /// when eventSources's are GCed, the weak handle in this list naturally gets nulled, and
+        /// we will reuse the slot. Today this list never shrinks (but we do reuse entries
+        /// that are in the list). This seems OK since the expectation is that EventSources
+        /// tend to live for the lifetime of the appdomain anyway (they tend to be used in
+        /// global variables).
+        /// </summary>
+        /// <param name="newEventSource"></param>
+        internal static void AddEventSource(EventSource newEventSource)
+        {
+            lock (EventListenersLock)
+            {
+                if (s_EventSources == null)
+                    s_EventSources = new List<WeakReference>(2);
+
+                if (!s_EventSourceShutdownRegistered)
+                {
+                    s_EventSourceShutdownRegistered = true;
+                }
+
+
+                // Periodically search the list for existing entries to reuse, this avoids
+                // unbounded memory use if we keep recycling eventSources (an unlikely thing). 
+                int newIndex = -1;
+                if (s_EventSources.Count % 64 == 63)   // on every block of 64, fill up the block before continuing
+                {
+                    int i = s_EventSources.Count;      // Work from the top down. 
+                    while (0 < i)
+                    {
+                        --i;
+                        WeakReference weakRef = s_EventSources[i];
+                        if (!weakRef.IsAlive)
+                        {
+                            newIndex = i;
+                            weakRef.Target = newEventSource;
+                            break;
+                        }
+                    }
+                }
+                if (newIndex < 0)
+                {
+                    newIndex = s_EventSources.Count;
+                    s_EventSources.Add(new WeakReference(newEventSource));
+                }
+                newEventSource.m_id = newIndex;
+
+                // Add every existing dispatcher to the new EventSource
+                for (EventListener listener = s_Listeners; listener != null; listener = listener.m_Next)
+                    newEventSource.AddListener(listener);
+
+                Validate();
+            }
+        }
+
+        // Whenver we have async callbacks from native code, there is an ugly issue where
+        // during .NET shutdown native code could be calling the callback, but the CLR
+        // has already prohibited callbacks to managed code in the appdomain, causing the CLR 
+        // to throw a COMPLUS_BOOT_EXCEPTION.   The guideline we give is that you must unregister
+        // such callbacks on process shutdown or appdomain so that unmanaged code will never 
+        // do this.  This is what this callback is for.  
+        // See bug 724140 for more
+        private static void DisposeOnShutdown(object sender, EventArgs e)
+        {
+            lock (EventListenersLock)
+            {
+                foreach (var esRef in s_EventSources)
+                {
+                    EventSource es = esRef.Target as EventSource;
+                    if (es != null)
+                        es.Dispose();
+                }
+            }
+        }
+
+        /// <summary>
+        /// Helper used in code:Dispose that removes any references to 'listenerToRemove' in any of the
+        /// eventSources in the appdomain.  
+        /// 
+        /// The EventListenersLock must be held before calling this routine. 
+        /// </summary>
+        private static void RemoveReferencesToListenerInEventSources(EventListener listenerToRemove)
+        {
+#if !ES_BUILD_STANDALONE
+            Debug.Assert(Monitor.IsEntered(EventListener.EventListenersLock));
+#endif
+            // Foreach existing EventSource in the appdomain
+            foreach (WeakReference eventSourceRef in s_EventSources)
+            {
+                EventSource eventSource = eventSourceRef.Target as EventSource;
+                if (eventSource != null)
+                {
+                    // Is the first output dispatcher the dispatcher we are removing?
+                    if (eventSource.m_Dispatchers.m_Listener == listenerToRemove)
+                        eventSource.m_Dispatchers = eventSource.m_Dispatchers.m_Next;
+                    else
+                    {
+                        // Remove 'listenerToRemove' from the eventSource.m_Dispatchers linked list.  
+                        EventDispatcher prev = eventSource.m_Dispatchers;
+                        for (;;)
+                        {
+                            EventDispatcher cur = prev.m_Next;
+                            if (cur == null)
+                            {
+                                Debug.Fail("EventSource did not have a registered EventListener!");
+                                break;
+                            }
+                            if (cur.m_Listener == listenerToRemove)
+                            {
+                                prev.m_Next = cur.m_Next;       // Remove entry. 
+                                break;
+                            }
+                            prev = cur;
+                        }
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Checks internal consistency of EventSources/Listeners. 
+        /// </summary>
+        [Conditional("DEBUG")]
+        internal static void Validate()
+        {
+            lock (EventListenersLock)
+            {
+                // Get all listeners 
+                Dictionary<EventListener, bool> allListeners = new Dictionary<EventListener, bool>();
+                EventListener cur = s_Listeners;
+                while (cur != null)
+                {
+                    allListeners.Add(cur, true);
+                    cur = cur.m_Next;
+                }
+
+                // For all eventSources 
+                int id = -1;
+                foreach (WeakReference eventSourceRef in s_EventSources)
+                {
+                    id++;
+                    EventSource eventSource = eventSourceRef.Target as EventSource;
+                    if (eventSource == null)
+                        continue;
+                    Debug.Assert(eventSource.m_id == id, "Unexpected event source ID.");
+
+                    // None listeners on eventSources exist in the dispatcher list.   
+                    EventDispatcher dispatcher = eventSource.m_Dispatchers;
+                    while (dispatcher != null)
+                    {
+                        Debug.Assert(allListeners.ContainsKey(dispatcher.m_Listener), "EventSource has a listener not on the global list.");
+                        dispatcher = dispatcher.m_Next;
+                    }
+
+                    // Every dispatcher is on Dispatcher List of every eventSource. 
+                    foreach (EventListener listener in allListeners.Keys)
+                    {
+                        dispatcher = eventSource.m_Dispatchers;
+                        for (;;)
+                        {
+                            Debug.Assert(dispatcher != null, "Listener is not on all eventSources.");
+                            if (dispatcher.m_Listener == listener)
+                                break;
+                            dispatcher = dispatcher.m_Next;
+                        }
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets a global lock that is intended to protect the code:s_Listeners linked list and the
+        /// code:s_EventSources WeakReference list.  (We happen to use the s_EventSources list as
+        /// the lock object)
+        /// </summary>
+        internal static object EventListenersLock
+        {
+            get
+            {
+                if (s_EventSources == null)
+                    Interlocked.CompareExchange(ref s_EventSources, new List<WeakReference>(2), null);
+                return s_EventSources;
+            }
+        }
+
+        private void CallBackForExistingEventSources(bool addToListenersList, EventHandler<EventSourceCreatedEventArgs> callback)
+        {
+            lock (EventListenersLock)
+            {
+                // Disallow creating EventListener reentrancy. 
+                if (s_CreatingListener)
+                {
+                    throw new InvalidOperationException(SR.EventSource_ListenerCreatedInsideCallback);
+                }
+
+                try
+                {
+                    s_CreatingListener = true;
+
+                    if (addToListenersList)
+                    {
+                        // Add to list of listeners in the system, do this BEFORE firing the 'OnEventSourceCreated' so that 
+                        // Those added sources see this listener.
+                        this.m_Next = s_Listeners;
+                        s_Listeners = this;
+                    }
+
+                    // Find all existing eventSources call OnEventSourceCreated to 'catchup'
+                    // Note that we DO have reentrancy here because 'AddListener' calls out to user code (via OnEventSourceCreated callback) 
+                    // We tolerate this by iterating over a copy of the list here. New event sources will take care of adding listeners themselves
+                    // EventSources are not guaranteed to be added at the end of the s_EventSource list -- We re-use slots when a new source
+                    // is created.
+                    WeakReference[] eventSourcesSnapshot = s_EventSources.ToArray();
+
+                    for (int i = 0; i < eventSourcesSnapshot.Length; i++)
+                    {
+                        WeakReference eventSourceRef = eventSourcesSnapshot[i];
+                        EventSource eventSource = eventSourceRef.Target as EventSource;
+                        if (eventSource != null)
+                        {
+                            EventSourceCreatedEventArgs args = new EventSourceCreatedEventArgs();
+                            args.EventSource = eventSource;
+                            callback(this, args);
+                        }
+                    }
+
+                    Validate();
+                }
+                finally
+                {
+                    s_CreatingListener = false;
+                }
+            }
+
+        }
+
+        // Instance fields
+        internal volatile EventListener m_Next;                         // These form a linked list in s_Listeners
+
+        // static fields
+
+        /// <summary>
+        /// The list of all listeners in the appdomain.  Listeners must be explicitly disposed to remove themselves 
+        /// from this list.   Note that EventSources point to their listener but NOT the reverse.  
+        /// </summary>
+        internal static EventListener s_Listeners;
+        /// <summary>
+        /// The list of all active eventSources in the appdomain.  Note that eventSources do NOT 
+        /// remove themselves from this list this is a weak list and the GC that removes them may
+        /// not have happened yet.  Thus it can contain event sources that are dead (thus you have 
+        /// to filter those out.  
+        /// </summary>
+        internal static List<WeakReference> s_EventSources;
+
+        /// <summary>
+        /// Used to disallow reentrancy.  
+        /// </summary>
+        private static bool s_CreatingListener = false;
+
+        /// <summary>
+        /// Used to register AD/Process shutdown callbacks.
+        /// </summary>
+        private static bool s_EventSourceShutdownRegistered = false;
+#endregion
+    }
+
+    /// <summary>
+    /// Passed to the code:EventSource.OnEventCommand callback
+    /// </summary>
+    public class EventCommandEventArgs : EventArgs
+    {
+        /// <summary>
+        /// Gets the command for the callback.
+        /// </summary>
+        public EventCommand Command { get; internal set; }
+
+        /// <summary>
+        /// Gets the arguments for the callback.
+        /// </summary>
+        public IDictionary<String, String> Arguments { get; internal set; }
+
+        /// <summary>
+        /// Enables the event that has the specified identifier.
+        /// </summary>
+        /// <param name="eventId">Event ID of event to be enabled</param>
+        /// <returns>true if eventId is in range</returns>
+        public bool EnableEvent(int eventId)
+        {
+            if (Command != EventCommand.Enable && Command != EventCommand.Disable)
+                throw new InvalidOperationException();
+            return eventSource.EnableEventForDispatcher(dispatcher, eventId, true);
+        }
+
+        /// <summary>
+        /// Disables the event that have the specified identifier.
+        /// </summary>
+        /// <param name="eventId">Event ID of event to be disabled</param>
+        /// <returns>true if eventId is in range</returns>
+        public bool DisableEvent(int eventId)
+        {
+            if (Command != EventCommand.Enable && Command != EventCommand.Disable)
+                throw new InvalidOperationException();
+            return eventSource.EnableEventForDispatcher(dispatcher, eventId, false);
+        }
+
+#region private
+
+        internal EventCommandEventArgs(EventCommand command, IDictionary<string, string> arguments, EventSource eventSource,
+            EventListener listener, int perEventSourceSessionId, int etwSessionId, bool enable, EventLevel level, EventKeywords matchAnyKeyword)
+        {
+            this.Command = command;
+            this.Arguments = arguments;
+            this.eventSource = eventSource;
+            this.listener = listener;
+            this.perEventSourceSessionId = perEventSourceSessionId;
+            this.etwSessionId = etwSessionId;
+            this.enable = enable;
+            this.level = level;
+            this.matchAnyKeyword = matchAnyKeyword;
+        }
+
+        internal EventSource eventSource;
+        internal EventDispatcher dispatcher;
+
+        // These are the arguments of sendCommand and are only used for deferring commands until after we are fully initialized. 
+        internal EventListener listener;
+        internal int perEventSourceSessionId;
+        internal int etwSessionId;
+        internal bool enable;
+        internal EventLevel level;
+        internal EventKeywords matchAnyKeyword;
+        internal EventCommandEventArgs nextCommand;     // We form a linked list of these deferred commands.      
+
+#endregion
+    }
+
+    /// <summary>
+    /// EventSourceCreatedEventArgs is passed to <see cref="EventListener.EventSourceCreated"/>
+    /// </summary>
+    public class EventSourceCreatedEventArgs : EventArgs
+    {
+        /// <summary>
+        /// The EventSource that is attaching to the listener.
+        /// </summary>
+        public EventSource EventSource
+        {
+            get;
+            internal set;
+        }
+    }
+
+    /// <summary>
+    /// EventWrittenEventArgs is passed to the user-provided override for
+    /// <see cref="EventListener.OnEventWritten"/> when an event is fired.
+    /// </summary>
+    public class EventWrittenEventArgs : EventArgs
+    {
+        /// <summary>
+        /// The name of the event.   
+        /// </summary>
+        public string EventName
+        {
+            get
+            {
+                if (m_eventName != null || EventId < 0)      // TraceLogging convention EventID == -1
+                {
+                    return m_eventName;
+                }
+                else
+                    return m_eventSource.m_eventData[EventId].Name;
+            }
+            internal set
+            {
+                m_eventName = value;
+            }
+        }
+
+        /// <summary>
+        /// Gets the event ID for the event that was written.
+        /// </summary>
+        public int EventId { get; internal set; }
+
+        /// <summary>
+        /// Gets the activity ID for the thread on which the event was written.
+        /// </summary>
+        public Guid ActivityId
+        {
+            get
+            {
+                Guid activityId = m_activityId;
+                if (activityId == Guid.Empty)
+                {
+                    activityId = EventSource.CurrentThreadActivityId;
+                }
+
+                return activityId;
+            }
+            internal set
+            {
+                m_activityId = value;
+            }
+        }
+
+        /// <summary>
+        /// Gets the related activity ID if one was specified when the event was written.
+        /// </summary>
+        public Guid RelatedActivityId
+        {
+            get;
+            internal set;
+        }
+
+        /// <summary>
+        /// Gets the payload for the event.
+        /// </summary>
+        public ReadOnlyCollection<Object> Payload { get; internal set; }
+
+        /// <summary>
+        /// Gets the payload argument names.
+        /// </summary>
+        public ReadOnlyCollection<string> PayloadNames
+        {
+            get
+            {
+                // For contract based events we create the list lazily.
+                // You can have m_payloadNames be null in the TraceLogging case (EventID < 0) so only
+                // do the lazy init if you know it is contract based (EventID >= 0)
+                if (EventId >= 0 && m_payloadNames == null)
+                {
+
+                    var names = new List<string>();
+                    foreach (var parameter in m_eventSource.m_eventData[EventId].Parameters)
+                    {
+                        names.Add(parameter.Name);
+                    }
+                    m_payloadNames = new ReadOnlyCollection<string>(names);
+                }
+
+                return m_payloadNames;
+            }
+
+            internal set
+            {
+                m_payloadNames = value;
+            }
+        }
+
+        /// <summary>
+        /// Gets the event source object.
+        /// </summary>
+        public EventSource EventSource { get { return m_eventSource; } }
+
+        /// <summary>
+        /// Gets the keywords for the event.
+        /// </summary>
+        public EventKeywords Keywords
+        {
+            get
+            {
+                if (EventId < 0)      // TraceLogging convention EventID == -1
+                    return m_keywords;
+
+                return (EventKeywords)m_eventSource.m_eventData[EventId].Descriptor.Keywords;
+            }
+        }
+
+        /// <summary>
+        /// Gets the operation code for the event.
+        /// </summary>
+        public EventOpcode Opcode
+        {
+            get
+            {
+                if (EventId <= 0)      // TraceLogging convention EventID == -1
+                    return m_opcode;
+                return (EventOpcode)m_eventSource.m_eventData[EventId].Descriptor.Opcode;
+            }
+        }
+
+        /// <summary>
+        /// Gets the task for the event.
+        /// </summary>
+        public EventTask Task
+        {
+            get
+            {
+                if (EventId <= 0)      // TraceLogging convention EventID == -1
+                    return EventTask.None;
+
+                return (EventTask)m_eventSource.m_eventData[EventId].Descriptor.Task;
+            }
+        }
+
+        /// <summary>
+        /// Any provider/user defined options associated with the event.  
+        /// </summary>
+        public EventTags Tags
+        {
+            get
+            {
+                if (EventId <= 0)      // TraceLogging convention EventID == -1
+                    return m_tags;
+                return m_eventSource.m_eventData[EventId].Tags;
+            }
+        }
+
+        /// <summary>
+        /// Gets the message for the event.  If the message has {N} parameters they are NOT substituted.  
+        /// </summary>
+        public string Message
+        {
+            get
+            {
+                if (EventId <= 0)      // TraceLogging convention EventID == -1
+                    return m_message;
+                else
+                    return m_eventSource.m_eventData[EventId].Message;
+            }
+            internal set
+            {
+                m_message = value;
+            }
+        }
+
+
+#if FEATURE_MANAGED_ETW_CHANNELS
+        /// <summary>
+        /// Gets the channel for the event.
+        /// </summary>
+        public EventChannel Channel
+        {
+            get
+            {
+                if (EventId <= 0)      // TraceLogging convention EventID == -1
+                    return EventChannel.None;
+                return (EventChannel)m_eventSource.m_eventData[EventId].Descriptor.Channel;
+            }
+        }
+#endif
+
+        /// <summary>
+        /// Gets the version of the event.
+        /// </summary>
+        public byte Version
+        {
+            get
+            {
+                if (EventId <= 0)      // TraceLogging convention EventID == -1
+                    return 0;
+                return m_eventSource.m_eventData[EventId].Descriptor.Version;
+            }
+        }
+
+        /// <summary>
+        /// Gets the level for the event.
+        /// </summary>
+        public EventLevel Level
+        {
+            get
+            {
+                if (EventId <= 0)      // TraceLogging convention EventID == -1
+                    return m_level;
+                return (EventLevel)m_eventSource.m_eventData[EventId].Descriptor.Level;
+            }
+        }
+
+#region private
+        internal EventWrittenEventArgs(EventSource eventSource)
+        {
+            m_eventSource = eventSource;
+        }
+        private string m_message;
+        private string m_eventName;
+        private EventSource m_eventSource;
+        private ReadOnlyCollection<string> m_payloadNames;
+        private Guid m_activityId;
+        internal EventTags m_tags;
+        internal EventOpcode m_opcode;
+        internal EventLevel m_level;
+        internal EventKeywords m_keywords;
+#endregion
+    }
+
+    /// <summary>
+    /// Allows customizing defaults and specifying localization support for the event source class to which it is applied. 
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Class)]
+    public sealed class EventSourceAttribute : Attribute
+    {
+        /// <summary>
+        /// Overrides the ETW name of the event source (which defaults to the class name)
+        /// </summary>
+        public string Name { get; set; }
+
+        /// <summary>
+        /// Overrides the default (calculated) Guid of an EventSource type. Explicitly defining a GUID is discouraged, 
+        /// except when upgrading existing ETW providers to using event sources.
+        /// </summary>
+        public string Guid { get; set; }
+
+        /// <summary>
+        /// <para>
+        /// EventSources support localization of events. The names used for events, opcodes, tasks, keywords and maps 
+        /// can be localized to several languages if desired. This works by creating a ResX style string table 
+        /// (by simply adding a 'Resource File' to your project). This resource file is given a name e.g. 
+        /// 'DefaultNameSpace.ResourceFileName' which can be passed to the ResourceManager constructor to read the 
+        /// resources. This name is the value of the LocalizationResources property. 
+        /// </para><para>
+        /// If LocalizationResources property is non-null, then EventSource will look up the localized strings for events by 
+        /// using the following resource naming scheme
+        /// </para>
+        ///     <para>* event_EVENTNAME</para>
+        ///     <para>* task_TASKNAME</para>
+        ///     <para>* keyword_KEYWORDNAME</para>
+        ///     <para>* map_MAPNAME</para>
+        /// <para>
+        /// where the capitalized name is the name of the event, task, keyword, or map value that should be localized.   
+        /// Note that the localized string for an event corresponds to the Message string, and can have {0} values 
+        /// which represent the payload values.  
+        /// </para>
+        /// </summary>
+        public string LocalizationResources { get; set; }
+    }
+
+    /// <summary>
+    /// Any instance methods in a class that subclasses <see cref="EventSource"/> and that return void are
+    /// assumed by default to be methods that generate an ETW event. Enough information can be deduced from the
+    /// name of the method and its signature to generate basic schema information for the event. The
+    /// <see cref="EventAttribute"/> class allows you to specify additional event schema information for an event if
+    /// desired.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Method)]
+    public sealed class EventAttribute : Attribute
+    {
+        /// <summary>Construct an EventAttribute with specified eventId</summary>
+        /// <param name="eventId">ID of the ETW event (an integer between 1 and 65535)</param>
+        public EventAttribute(int eventId) { this.EventId = eventId; Level = EventLevel.Informational; this.m_opcodeSet = false; }
+        /// <summary>Event's ID</summary>
+        public int EventId { get; private set; }
+        /// <summary>Event's severity level: indicates the severity or verbosity of the event</summary>
+        public EventLevel Level { get; set; }
+        /// <summary>Event's keywords: allows classification of events by "categories"</summary>
+        public EventKeywords Keywords { get; set; }
+        /// <summary>Event's operation code: allows defining operations, generally used with Tasks</summary>
+        public EventOpcode Opcode
+        {
+            get
+            {
+                return m_opcode;
+            }
+            set
+            {
+                this.m_opcode = value;
+                this.m_opcodeSet = true;
+            }
+        }
+
+        internal bool IsOpcodeSet
+        {
+            get
+            {
+                return m_opcodeSet;
+            }
+        }
+
+        /// <summary>Event's task: allows logical grouping of events</summary>
+        public EventTask Task { get; set; }
+#if FEATURE_MANAGED_ETW_CHANNELS
+        /// <summary>Event's channel: defines an event log as an additional destination for the event</summary>
+        public EventChannel Channel { get; set; }
+#endif
+        /// <summary>Event's version</summary>
+        public byte Version { get; set; }
+
+        /// <summary>
+        /// This can be specified to enable formatting and localization of the event's payload. You can 
+        /// use standard .NET substitution operators (eg {1}) in the string and they will be replaced 
+        /// with the 'ToString()' of the corresponding part of the  event payload.   
+        /// </summary>
+        public string Message { get; set; }
+
+        /// <summary>
+        /// User defined options associated with the event.  These do not have meaning to the EventSource but
+        /// are passed through to listeners which given them semantics.  
+        /// </summary>
+        public EventTags Tags { get; set; }
+
+        /// <summary>
+        /// Allows fine control over the Activity IDs generated by start and stop events
+        /// </summary>
+        public EventActivityOptions ActivityOptions { get; set; }
+
+#region private
+        EventOpcode m_opcode;
+        private bool m_opcodeSet;
+#endregion
+    }
+
+    /// <summary>
+    /// By default all instance methods in a class that subclasses code:EventSource that and return
+    /// void are assumed to be methods that generate an event. This default can be overridden by specifying
+    /// the code:NonEventAttribute
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Method)]
+    public sealed class NonEventAttribute : Attribute
+    {
+        /// <summary>
+        /// Constructs a default NonEventAttribute
+        /// </summary>
+        public NonEventAttribute() { }
+    }
+
+    // FUTURE we may want to expose this at some point once we have a partner that can help us validate the design.
+#if FEATURE_MANAGED_ETW_CHANNELS
+    /// <summary>
+    /// EventChannelAttribute allows customizing channels supported by an EventSource. This attribute must be
+    /// applied to an member of type EventChannel defined in a Channels class nested in the EventSource class:
+    /// <code>
+    ///     public static class Channels
+    ///     {
+    ///         [Channel(Enabled = true, EventChannelType = EventChannelType.Admin)]
+    ///         public const EventChannel Admin = (EventChannel)16;
+    ///     
+    ///         [Channel(Enabled = false, EventChannelType = EventChannelType.Operational)]
+    ///         public const EventChannel Operational = (EventChannel)17;
+    ///     }
+    /// </code>
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Field)]
+#if FEATURE_ADVANCED_MANAGED_ETW_CHANNELS
+    public 
+#endif
+    class EventChannelAttribute : Attribute
+    {
+        /// <summary>
+        /// Specified whether the channel is enabled by default
+        /// </summary>
+        public bool Enabled { get; set; }
+
+        /// <summary>
+        /// Legal values are in EventChannelType
+        /// </summary>
+        public EventChannelType EventChannelType { get; set; }
+
+#if FEATURE_ADVANCED_MANAGED_ETW_CHANNELS
+        /// <summary>
+        /// Specifies the isolation for the channel
+        /// </summary>
+        public EventChannelIsolation Isolation { get; set; }
+
+        /// <summary>
+        /// Specifies an SDDL access descriptor that controls access to the log file that backs the channel.
+        /// See MSDN ((http://msdn.microsoft.com/en-us/library/windows/desktop/aa382741.aspx) for details.
+        /// </summary>
+        public string Access { get; set; } 
+
+        /// <summary>
+        /// Allows importing channels defined in external manifests
+        /// </summary>
+        public string ImportChannel { get; set; }
+#endif
+
+        // TODO: there is a convention that the name is the Provider/Type   Should we provide an override?
+        // public string Name { get; set; }
+    }
+
+    /// <summary>
+    /// Allowed channel types
+    /// </summary>
+#if FEATURE_ADVANCED_MANAGED_ETW_CHANNELS
+    public 
+#endif
+    enum EventChannelType
+    {
+        /// <summary>The admin channel</summary>
+        Admin = 1,
+        /// <summary>The operational channel</summary>
+        Operational,
+        /// <summary>The Analytic channel</summary>
+        Analytic,
+        /// <summary>The debug channel</summary>
+        Debug,
+    }
+
+#if FEATURE_ADVANCED_MANAGED_ETW_CHANNELS
+    /// <summary>
+    /// Allowed isolation levels. See MSDN (http://msdn.microsoft.com/en-us/library/windows/desktop/aa382741.aspx) 
+    /// for the default permissions associated with each level. EventChannelIsolation and Access allows control over the 
+    /// access permissions for the channel and backing file.
+    /// </summary>
+    public 
+    enum EventChannelIsolation
+    {
+        /// <summary>
+        /// This is the default isolation level. All channels that specify Application isolation use the same ETW session
+        /// </summary>
+        Application = 1,
+        /// <summary>
+        /// All channels that specify System isolation use the same ETW session
+        /// </summary>
+        System,
+        /// <summary>
+        /// Use sparingly! When specifying Custom isolation, a separate ETW session is created for the channel.
+        /// Using Custom isolation lets you control the access permissions for the channel and backing file.
+        /// Because there are only 64 ETW sessions available, you should limit your use of Custom isolation.
+        /// </summary>
+        Custom,
+    }
+#endif
+#endif
+
+    /// <summary>
+    /// Describes the pre-defined command (EventCommandEventArgs.Command property) that is passed to the OnEventCommand callback.
+    /// </summary>
+    public enum EventCommand
+    {
+        /// <summary>
+        /// Update EventSource state
+        /// </summary>
+        Update = 0,
+        /// <summary>
+        /// Request EventSource to generate and send its manifest
+        /// </summary>
+        SendManifest = -1,
+        /// <summary>
+        /// Enable event
+        /// </summary>
+        Enable = -2,
+        /// <summary>
+        /// Disable event
+        /// </summary>
+        Disable = -3
+    };
+
+
+#region private classes
+
+    // holds a bitfield representing a session mask
+    /// <summary>
+    /// A SessionMask represents a set of (at most MAX) sessions as a bit mask. The perEventSourceSessionId
+    /// is the index in the SessionMask of the bit that will be set. These can translate to
+    /// EventSource's reserved keywords bits using the provided ToEventKeywords() and
+    /// FromEventKeywords() methods.
+    /// </summary>
+    internal struct SessionMask
+    {
+        public SessionMask(SessionMask m)
+        { m_mask = m.m_mask; }
+
+        public SessionMask(uint mask = 0)
+        { m_mask = mask & MASK; }
+
+        public bool IsEqualOrSupersetOf(SessionMask m)
+        {
+            return (this.m_mask | m.m_mask) == this.m_mask;
+        }
+
+        public static SessionMask All
+        {
+            get { return new SessionMask(MASK); }
+        }
+
+        public static SessionMask FromId(int perEventSourceSessionId)
+        {
+            Debug.Assert(perEventSourceSessionId < MAX);
+            return new SessionMask((uint)1 << perEventSourceSessionId);
+        }
+
+        public ulong ToEventKeywords()
+        {
+            return (ulong)m_mask << SHIFT_SESSION_TO_KEYWORD;
+        }
+
+        public static SessionMask FromEventKeywords(ulong m)
+        {
+            return new SessionMask((uint)(m >> SHIFT_SESSION_TO_KEYWORD));
+        }
+
+        public bool this[int perEventSourceSessionId]
+        {
+            get
+            {
+                Debug.Assert(perEventSourceSessionId < MAX);
+                return (m_mask & (1 << perEventSourceSessionId)) != 0;
+            }
+            set
+            {
+                Debug.Assert(perEventSourceSessionId < MAX);
+                if (value) m_mask |= ((uint)1 << perEventSourceSessionId);
+                else m_mask &= ~((uint)1 << perEventSourceSessionId);
+            }
+        }
+
+        public static SessionMask operator |(SessionMask m1, SessionMask m2)
+        {
+            return new SessionMask(m1.m_mask | m2.m_mask);
+        }
+
+        public static SessionMask operator &(SessionMask m1, SessionMask m2)
+        {
+            return new SessionMask(m1.m_mask & m2.m_mask);
+        }
+
+        public static SessionMask operator ^(SessionMask m1, SessionMask m2)
+        {
+            return new SessionMask(m1.m_mask ^ m2.m_mask);
+        }
+
+        public static SessionMask operator ~(SessionMask m)
+        {
+            return new SessionMask(MASK & ~(m.m_mask));
+        }
+
+        public static explicit operator ulong(SessionMask m)
+        { return m.m_mask; }
+
+        public static explicit operator uint(SessionMask m)
+        { return m.m_mask; }
+
+        private uint m_mask;
+
+        internal const int SHIFT_SESSION_TO_KEYWORD = 44;         // bits 44-47 inclusive are reserved
+        internal const uint MASK = 0x0fU;                         // the mask of 4 reserved bits
+        internal const uint MAX = 4;                              // maximum number of simultaneous ETW sessions supported
+    }
+
+    /// <summary>
+    /// code:EventDispatchers are a simple 'helper' structure that holds the filtering state
+    /// (m_EventEnabled) for a particular EventSource X EventListener tuple
+    /// 
+    /// Thus a single EventListener may have many EventDispatchers (one for every EventSource 
+    /// that EventListener has activate) and a Single EventSource may also have many
+    /// event Dispatchers (one for every EventListener that has activated it). 
+    /// 
+    /// Logically a particular EventDispatcher belongs to exactly one EventSource and exactly  
+    /// one EventListener (although EventDispatcher does not 'remember' the EventSource it is
+    /// associated with. 
+    /// </summary>
+    internal class EventDispatcher
+    {
+        internal EventDispatcher(EventDispatcher next, bool[] eventEnabled, EventListener listener)
+        {
+            m_Next = next;
+            m_EventEnabled = eventEnabled;
+            m_Listener = listener;
+        }
+
+        // Instance fields
+        readonly internal EventListener m_Listener;   // The dispatcher this entry is for
+        internal bool[] m_EventEnabled;               // For every event in a the eventSource, is it enabled?
+
+        // Only guaranteed to exist after a InsureInit()
+        internal EventDispatcher m_Next;              // These form a linked list in code:EventSource.m_Dispatchers
+        // Of all listeners for that eventSource.  
+    }
+
+    /// <summary>
+    /// Flags that can be used with EventSource.GenerateManifest to control how the ETW manifest for the EventSource is
+    /// generated.
+    /// </summary>
+    [Flags]
+    public enum EventManifestOptions
+    {
+        /// <summary>
+        /// Only the resources associated with current UI culture are included in the  manifest
+        /// </summary>
+        None = 0x0,
+        /// <summary>
+        /// Throw exceptions for any inconsistency encountered
+        /// </summary>
+        Strict = 0x1,
+        /// <summary>
+        /// Generate a "resources" node under "localization" for every satellite assembly provided
+        /// </summary>
+        AllCultures = 0x2,
+        /// <summary>
+        /// Generate the manifest only if the event source needs to be registered on the machine,
+        /// otherwise return null (but still perform validation if Strict is specified)
+        /// </summary>
+        OnlyIfNeededForRegistration = 0x4,
+        /// <summary>
+        /// When generating the manifest do *not* enforce the rule that the current EventSource class
+        /// must be the base class for the user-defined type passed in. This allows validation of .net
+        /// event sources using the new validation code
+        /// </summary>
+        AllowEventSourceOverride = 0x8,
+    }
+
+    /// <summary>
+    /// ManifestBuilder is designed to isolate the details of the message of the event from the
+    /// rest of EventSource.  This one happens to create XML. 
+    /// </summary>
+    internal partial class ManifestBuilder
+    {
+        /// <summary>
+        /// Build a manifest for 'providerName' with the given GUID, which will be packaged into 'dllName'.
+        /// 'resources, is a resource manager.  If specified all messages are localized using that manager.  
+        /// </summary>
+        public ManifestBuilder(string providerName, Guid providerGuid, string dllName, ResourceManager resources,
+                               EventManifestOptions flags)
+        {
+#if FEATURE_MANAGED_ETW_CHANNELS
+            this.providerName = providerName;
+#endif
+            this.flags = flags;
+
+            this.resources = resources;
+            sb = new StringBuilder();
+            events = new StringBuilder();
+            templates = new StringBuilder();
+            opcodeTab = new Dictionary<int, string>();
+            stringTab = new Dictionary<string, string>();
+            errors = new List<string>();
+            perEventByteArrayArgIndices = new Dictionary<string, List<int>>();
+
+            sb.AppendLine("<instrumentationManifest xmlns=\"http://schemas.microsoft.com/win/2004/08/events\">");
+            sb.AppendLine(" <instrumentation xmlns:xs=\"http://www.w3.org/2001/XMLSchema\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:win=\"http://manifests.microsoft.com/win/2004/08/windows/events\">");
+            sb.AppendLine("  <events xmlns=\"http://schemas.microsoft.com/win/2004/08/events\">");
+            sb.Append("<provider name=\"").Append(providerName).
+               Append("\" guid=\"{").Append(providerGuid.ToString()).Append("}");
+            if (dllName != null)
+                sb.Append("\" resourceFileName=\"").Append(dllName).Append("\" messageFileName=\"").Append(dllName);
+
+            var symbolsName = providerName.Replace("-", "").Replace(".", "_");  // Period and - are illegal replace them.
+            sb.Append("\" symbol=\"").Append(symbolsName);
+            sb.Append("\">").AppendLine();
+        }
+
+        public void AddOpcode(string name, int value)
+        {
+            if ((flags & EventManifestOptions.Strict) != 0)
+            {
+                if (value <= 10 || value >= 239)
+                {
+                    ManifestError(SR.Format(SR.EventSource_IllegalOpcodeValue, name, value));
+                }
+                string prevName;
+                if (opcodeTab.TryGetValue(value, out prevName) && !name.Equals(prevName, StringComparison.Ordinal))
+                {
+                    ManifestError(SR.Format(SR.EventSource_OpcodeCollision, name, prevName, value));
+                }
+            }
+            opcodeTab[value] = name;
+        }
+        public void AddTask(string name, int value)
+        {
+            if ((flags & EventManifestOptions.Strict) != 0)
+            {
+                if (value <= 0 || value >= 65535)
+                {
+                    ManifestError(SR.Format(SR.EventSource_IllegalTaskValue, name, value));
+                }
+                string prevName;
+                if (taskTab != null && taskTab.TryGetValue(value, out prevName) && !name.Equals(prevName, StringComparison.Ordinal))
+                {
+                    ManifestError(SR.Format(SR.EventSource_TaskCollision, name, prevName, value));
+                }
+            }
+            if (taskTab == null)
+                taskTab = new Dictionary<int, string>();
+            taskTab[value] = name;
+        }
+        public void AddKeyword(string name, ulong value)
+        {
+            if ((value & (value - 1)) != 0)   // Is it a power of 2?
+            {
+                ManifestError(SR.Format(SR.EventSource_KeywordNeedPowerOfTwo, "0x" + value.ToString("x", CultureInfo.CurrentCulture), name), true);
+            }
+            if ((flags & EventManifestOptions.Strict) != 0)
+            {
+                if (value >= 0x0000100000000000UL && !name.StartsWith("Session", StringComparison.Ordinal))
+                {
+                    ManifestError(SR.Format(SR.EventSource_IllegalKeywordsValue, name, "0x" + value.ToString("x", CultureInfo.CurrentCulture)));
+                }
+                string prevName;
+                if (keywordTab != null && keywordTab.TryGetValue(value, out prevName) && !name.Equals(prevName, StringComparison.Ordinal))
+                {
+                    ManifestError(SR.Format(SR.EventSource_KeywordCollision, name, prevName, "0x" + value.ToString("x", CultureInfo.CurrentCulture)));
+                }
+            }
+            if (keywordTab == null)
+                keywordTab = new Dictionary<ulong, string>();
+            keywordTab[value] = name;
+        }
+
+#if FEATURE_MANAGED_ETW_CHANNELS
+        /// <summary>
+        /// Add a channel.  channelAttribute can be null
+        /// </summary>
+        public void AddChannel(string name, int value, EventChannelAttribute channelAttribute)
+        {
+            EventChannel chValue = (EventChannel)value;
+            if (value < (int)EventChannel.Admin || value > 255)
+                ManifestError(SR.Format(SR.EventSource_EventChannelOutOfRange, name, value));
+            else if (chValue >= EventChannel.Admin && chValue <= EventChannel.Debug &&
+                     channelAttribute != null && EventChannelToChannelType(chValue) != channelAttribute.EventChannelType)
+            {
+                // we want to ensure developers do not define EventChannels that conflict with the builtin ones,
+                // but we want to allow them to override the default ones...
+                ManifestError(SR.Format(SR.EventSource_ChannelTypeDoesNotMatchEventChannelValue,
+                                                                            name, ((EventChannel)value).ToString()));
+            }
+
+            // TODO: validate there are no conflicting manifest exposed names (generally following the format "provider/type")
+
+            ulong kwd = GetChannelKeyword(chValue);
+
+            if (channelTab == null)
+                channelTab = new Dictionary<int, ChannelInfo>(4);
+            channelTab[value] = new ChannelInfo { Name = name, Keywords = kwd, Attribs = channelAttribute };
+        }
+
+        private EventChannelType EventChannelToChannelType(EventChannel channel)
+        {
+#if !ES_BUILD_STANDALONE
+            Debug.Assert(channel >= EventChannel.Admin && channel <= EventChannel.Debug);
+#endif
+            return (EventChannelType)((int)channel - (int)EventChannel.Admin + (int)EventChannelType.Admin);
+        }
+        private EventChannelAttribute GetDefaultChannelAttribute(EventChannel channel)
+        {
+            EventChannelAttribute attrib = new EventChannelAttribute();
+            attrib.EventChannelType = EventChannelToChannelType(channel);
+            if (attrib.EventChannelType <= EventChannelType.Operational)
+                attrib.Enabled = true;
+            return attrib;
+        }
+
+        public ulong[] GetChannelData()
+        {
+            if (this.channelTab == null)
+            {
+                return new ulong[0];
+            }
+
+            // We create an array indexed by the channel id for fast look up.
+            // E.g. channelMask[Admin] will give you the bit mask for Admin channel.
+            int maxkey = -1;
+            foreach (var item in this.channelTab.Keys)
+            {
+                if (item > maxkey)
+                {
+                    maxkey = item;
+                }
+            }
+
+            ulong[] channelMask = new ulong[maxkey + 1];
+            foreach (var item in this.channelTab)
+            {
+                channelMask[item.Key] = item.Value.Keywords;
+            }
+
+            return channelMask;
+        }
+
+#endif
+        public void StartEvent(string eventName, EventAttribute eventAttribute)
+        {
+            Debug.Assert(numParams == 0);
+            Debug.Assert(this.eventName == null);
+            this.eventName = eventName;
+            numParams = 0;
+            byteArrArgIndices = null;
+
+            events.Append("  <event").
+                 Append(" value=\"").Append(eventAttribute.EventId).Append("\"").
+                 Append(" version=\"").Append(eventAttribute.Version).Append("\"").
+                 Append(" level=\"").Append(GetLevelName(eventAttribute.Level)).Append("\"").
+                 Append(" symbol=\"").Append(eventName).Append("\"");
+
+            // at this point we add to the manifest's stringTab a message that is as-of-yet 
+            // "untranslated to manifest convention", b/c we don't have the number or position 
+            // of any byte[] args (which require string format index updates)
+            WriteMessageAttrib(events, "event", eventName, eventAttribute.Message);
+
+            if (eventAttribute.Keywords != 0)
+                events.Append(" keywords=\"").Append(GetKeywords((ulong)eventAttribute.Keywords, eventName)).Append("\"");
+            if (eventAttribute.Opcode != 0)
+                events.Append(" opcode=\"").Append(GetOpcodeName(eventAttribute.Opcode, eventName)).Append("\"");
+            if (eventAttribute.Task != 0)
+                events.Append(" task=\"").Append(GetTaskName(eventAttribute.Task, eventName)).Append("\"");
+#if FEATURE_MANAGED_ETW_CHANNELS
+            if (eventAttribute.Channel != 0)
+            {
+                events.Append(" channel=\"").Append(GetChannelName(eventAttribute.Channel, eventName, eventAttribute.Message)).Append("\"");
+            }
+#endif
+        }
+
+        public void AddEventParameter(Type type, string name)
+        {
+            if (numParams == 0)
+                templates.Append("  <template tid=\"").Append(eventName).Append("Args\">").AppendLine();
+            if (type == typeof(byte[]))
+            {
+                // mark this index as "extraneous" (it has no parallel in the managed signature)
+                // we use these values in TranslateToManifestConvention()
+                if (byteArrArgIndices == null)
+                    byteArrArgIndices = new List<int>(4);
+                byteArrArgIndices.Add(numParams);
+
+                // add an extra field to the template representing the length of the binary blob
+                numParams++;
+                templates.Append("   <data name=\"").Append(name).Append("Size\" inType=\"win:UInt32\"/>").AppendLine();
+            }
+            numParams++;
+            templates.Append("   <data name=\"").Append(name).Append("\" inType=\"").Append(GetTypeName(type)).Append("\"");
+            // TODO: for 'byte*' types it assumes the user provided length is named using the same naming convention
+            //       as for 'byte[]' args (blob_arg_name + "Size")
+            if ((type.IsArray || type.IsPointer) && type.GetElementType() == typeof(byte))
+            {
+                // add "length" attribute to the "blob" field in the template (referencing the field added above)
+                templates.Append(" length=\"").Append(name).Append("Size\"");
+            }
+            // ETW does not support 64-bit value maps, so we don't specify these as ETW maps
+            if (type.IsEnum() && Enum.GetUnderlyingType(type) != typeof(UInt64) && Enum.GetUnderlyingType(type) != typeof(Int64))
+            {
+                templates.Append(" map=\"").Append(type.Name).Append("\"");
+                if (mapsTab == null)
+                    mapsTab = new Dictionary<string, Type>();
+                if (!mapsTab.ContainsKey(type.Name))
+                    mapsTab.Add(type.Name, type);        // Remember that we need to dump the type enumeration  
+            }
+
+            templates.Append("/>").AppendLine();
+        }
+        public void EndEvent()
+        {
+            if (numParams > 0)
+            {
+                templates.Append("  </template>").AppendLine();
+                events.Append(" template=\"").Append(eventName).Append("Args\"");
+            }
+            events.Append("/>").AppendLine();
+
+            if (byteArrArgIndices != null)
+                perEventByteArrayArgIndices[eventName] = byteArrArgIndices;
+
+            // at this point we have all the information we need to translate the C# Message
+            // to the manifest string we'll put in the stringTab
+            string msg;
+            if (stringTab.TryGetValue("event_" + eventName, out msg))
+            {
+                msg = TranslateToManifestConvention(msg, eventName);
+                stringTab["event_" + eventName] = msg;
+            }
+
+            eventName = null;
+            numParams = 0;
+            byteArrArgIndices = null;
+        }
+
+#if FEATURE_MANAGED_ETW_CHANNELS
+        // Channel keywords are generated one per channel to allow channel based filtering in event viewer. These keywords are autogenerated
+        // by mc.exe for compiling a manifest and are based on the order of the channels (fields) in the Channels inner class (when advanced
+        // channel support is enabled), or based on the order the predefined channels appear in the EventAttribute properties (for simple 
+        // support). The manifest generated *MUST* have the channels specified in the same order (that's how our computed keywords are mapped
+        // to channels by the OS infrastructure).
+        // If channelKeyworkds is present, and has keywords bits in the ValidPredefinedChannelKeywords then it is 
+        // assumed that that the keyword for that channel should be that bit.   
+        // otherwise we allocate a channel bit for the channel.  
+        // explicit channel bits are only used by WCF to mimic an existing manifest, 
+        // so we don't dont do error checking.  
+        public ulong GetChannelKeyword(EventChannel channel, ulong channelKeyword = 0)
+        {
+            // strip off any non-channel keywords, since we are only interested in channels here.  
+            channelKeyword &= ValidPredefinedChannelKeywords;
+            if (channelTab == null)
+            {
+                channelTab = new Dictionary<int, ChannelInfo>(4);
+            }
+
+            if (channelTab.Count == MaxCountChannels)
+                ManifestError(SR.EventSource_MaxChannelExceeded);
+
+            ChannelInfo info;
+            if (!channelTab.TryGetValue((int)channel, out info))
+            {
+                // If we were not given an explicit channel, allocate one.  
+                if (channelKeyword != 0)
+                {
+                    channelKeyword = nextChannelKeywordBit;
+                    nextChannelKeywordBit >>= 1;
+                }
+            }
+            else
+            {
+                channelKeyword = info.Keywords;
+            }
+
+            return channelKeyword;
+        }
+#endif
+
+        public byte[] CreateManifest()
+        {
+            string str = CreateManifestString();
+            return Encoding.UTF8.GetBytes(str);
+        }
+
+        public IList<string> Errors { get { return errors; } }
+
+        /// <summary>
+        /// When validating an event source it adds the error to the error collection.
+        /// When not validating it throws an exception if runtimeCritical is "true".
+        /// Otherwise the error is ignored.
+        /// </summary>
+        /// <param name="msg"></param>
+        /// <param name="runtimeCritical"></param>
+        public void ManifestError(string msg, bool runtimeCritical = false)
+        {
+            if ((flags & EventManifestOptions.Strict) != 0)
+                errors.Add(msg);
+            else if (runtimeCritical)
+                throw new ArgumentException(msg);
+        }
+
+        private string CreateManifestString()
+        {
+
+#if FEATURE_MANAGED_ETW_CHANNELS
+            // Write out the channels
+            if (channelTab != null)
+            {
+                sb.Append(" <channels>").AppendLine();
+                var sortedChannels = new List<KeyValuePair<int, ChannelInfo>>();
+                foreach (KeyValuePair<int, ChannelInfo> p in channelTab) { sortedChannels.Add(p); }
+                sortedChannels.Sort((p1, p2) => -Comparer<ulong>.Default.Compare(p1.Value.Keywords, p2.Value.Keywords));
+                foreach (var kvpair in sortedChannels)
+                {
+                    int channel = kvpair.Key;
+                    ChannelInfo channelInfo = kvpair.Value;
+
+                    string channelType = null;
+                    string elementName = "channel";
+                    bool enabled = false;
+                    string fullName = null;
+#if FEATURE_ADVANCED_MANAGED_ETW_CHANNELS
+                    string isolation = null;
+                    string access = null;
+#endif
+                    if (channelInfo.Attribs != null)
+                    {
+                        var attribs = channelInfo.Attribs;
+                        if (Enum.IsDefined(typeof(EventChannelType), attribs.EventChannelType))
+                            channelType = attribs.EventChannelType.ToString();
+                        enabled = attribs.Enabled;
+#if FEATURE_ADVANCED_MANAGED_ETW_CHANNELS
+                        if (attribs.ImportChannel != null)
+                        {
+                            fullName = attribs.ImportChannel;
+                            elementName = "importChannel";
+                        }
+                        if (Enum.IsDefined(typeof(EventChannelIsolation), attribs.Isolation))
+                            isolation = attribs.Isolation.ToString();
+                        access = attribs.Access;
+#endif
+                    }
+                    if (fullName == null)
+                        fullName = providerName + "/" + channelInfo.Name;
+
+                    sb.Append("  <").Append(elementName);
+                    sb.Append(" chid=\"").Append(channelInfo.Name).Append("\"");
+                    sb.Append(" name=\"").Append(fullName).Append("\"");
+                    if (elementName == "channel")   // not applicable to importChannels.
+                    {
+                        WriteMessageAttrib(sb, "channel", channelInfo.Name, null);
+                        sb.Append(" value=\"").Append(channel).Append("\"");
+                        if (channelType != null)
+                            sb.Append(" type=\"").Append(channelType).Append("\"");
+                        sb.Append(" enabled=\"").Append(enabled.ToString().ToLower()).Append("\"");
+#if FEATURE_ADVANCED_MANAGED_ETW_CHANNELS
+                        if (access != null)
+                            sb.Append(" access=\"").Append(access).Append("\"");
+                        if (isolation != null)
+                            sb.Append(" isolation=\"").Append(isolation).Append("\"");
+#endif
+                    }
+                    sb.Append("/>").AppendLine();
+                }
+                sb.Append(" </channels>").AppendLine();
+            }
+#endif
+
+            // Write out the tasks
+            if (taskTab != null)
+            {
+
+                sb.Append(" <tasks>").AppendLine();
+                var sortedTasks = new List<int>(taskTab.Keys);
+                sortedTasks.Sort();
+                foreach (int task in sortedTasks)
+                {
+                    sb.Append("  <task");
+                    WriteNameAndMessageAttribs(sb, "task", taskTab[task]);
+                    sb.Append(" value=\"").Append(task).Append("\"/>").AppendLine();
+                }
+                sb.Append(" </tasks>").AppendLine();
+            }
+
+            // Write out the maps
+            if (mapsTab != null)
+            {
+                sb.Append(" <maps>").AppendLine();
+                foreach (Type enumType in mapsTab.Values)
+                {
+                    bool isbitmap = EventSource.GetCustomAttributeHelper(enumType, typeof(FlagsAttribute), flags) != null;
+                    string mapKind = isbitmap ? "bitMap" : "valueMap";
+                    sb.Append("  <").Append(mapKind).Append(" name=\"").Append(enumType.Name).Append("\">").AppendLine();
+
+                    // write out each enum value 
+                    FieldInfo[] staticFields = enumType.GetFields(BindingFlags.DeclaredOnly | BindingFlags.Public | BindingFlags.Static);
+                    foreach (FieldInfo staticField in staticFields)
+                    {
+                        object constantValObj = staticField.GetRawConstantValue();
+                        if (constantValObj != null)
+                        {
+                            long hexValue;
+                            if (constantValObj is int)
+                                hexValue = ((int)constantValObj);
+                            else if (constantValObj is long)
+                                hexValue = ((long)constantValObj);
+                            else
+                                continue;
+
+                            // ETW requires all bitmap values to be powers of 2.  Skip the ones that are not. 
+                            // TODO: Warn people about the dropping of values. 
+                            if (isbitmap && ((hexValue & (hexValue - 1)) != 0 || hexValue == 0))
+                                continue;
+
+                            sb.Append("   <map value=\"0x").Append(hexValue.ToString("x", CultureInfo.InvariantCulture)).Append("\"");
+                            WriteMessageAttrib(sb, "map", enumType.Name + "." + staticField.Name, staticField.Name);
+                            sb.Append("/>").AppendLine();
+                        }
+                    }
+                    sb.Append("  </").Append(mapKind).Append(">").AppendLine();
+                }
+                sb.Append(" </maps>").AppendLine();
+            }
+
+            // Write out the opcodes
+            sb.Append(" <opcodes>").AppendLine();
+            var sortedOpcodes = new List<int>(opcodeTab.Keys);
+            sortedOpcodes.Sort();
+            foreach (int opcode in sortedOpcodes)
+            {
+                sb.Append("  <opcode");
+                WriteNameAndMessageAttribs(sb, "opcode", opcodeTab[opcode]);
+                sb.Append(" value=\"").Append(opcode).Append("\"/>").AppendLine();
+            }
+            sb.Append(" </opcodes>").AppendLine();
+
+            // Write out the keywords
+            if (keywordTab != null)
+            {
+                sb.Append(" <keywords>").AppendLine();
+                var sortedKeywords = new List<ulong>(keywordTab.Keys);
+                sortedKeywords.Sort();
+                foreach (ulong keyword in sortedKeywords)
+                {
+                    sb.Append("  <keyword");
+                    WriteNameAndMessageAttribs(sb, "keyword", keywordTab[keyword]);
+                    sb.Append(" mask=\"0x").Append(keyword.ToString("x", CultureInfo.InvariantCulture)).Append("\"/>").AppendLine();
+                }
+                sb.Append(" </keywords>").AppendLine();
+            }
+
+            sb.Append(" <events>").AppendLine();
+            sb.Append(events);
+            sb.Append(" </events>").AppendLine();
+
+            sb.Append(" <templates>").AppendLine();
+            if (templates.Length > 0)
+            {
+                sb.Append(templates);
+            }
+            else
+            {
+                // Work around a cornercase ETW issue where a manifest with no templates causes 
+                // ETW events to not get sent to their associated channel.
+                sb.Append("    <template tid=\"_empty\"></template>").AppendLine();
+            }
+            sb.Append(" </templates>").AppendLine();
+
+            sb.Append("</provider>").AppendLine();
+            sb.Append("</events>").AppendLine();
+            sb.Append("</instrumentation>").AppendLine();
+
+            // Output the localization information.  
+            sb.Append("<localization>").AppendLine();
+
+            List<CultureInfo> cultures = null;
+            if (resources != null && (flags & EventManifestOptions.AllCultures) != 0)
+            {
+                cultures = GetSupportedCultures(resources);
+            }
+            else
+            {
+                cultures = new List<CultureInfo>();
+                cultures.Add(CultureInfo.CurrentUICulture);
+            }
+#if ES_BUILD_STANDALONE || ES_BUILD_PN
+            var sortedStrings = new List<string>(stringTab.Keys);
+            sortedStrings.Sort();
+#else
+            // DD 947936
+            var sortedStrings = new string[stringTab.Keys.Count];
+            stringTab.Keys.CopyTo(sortedStrings, 0);
+            // Avoid using public Array.Sort as that attempts to access BinaryCompatibility. Unfortunately FrameworkEventSource gets called 
+            // very early in the app domain creation, when _FusionStore is not set up yet, resulting in a failure to run the static constructory
+            // for BinaryCompatibility. This failure is then cached and a TypeInitializationException is thrown every time some code attampts to
+            // access BinaryCompatibility.
+            ArraySortHelper<string>.IntrospectiveSort(sortedStrings, 0, sortedStrings.Length, string.Compare);
+#endif
+            foreach (var ci in cultures)
+            {
+                sb.Append(" <resources culture=\"").Append(ci.Name).Append("\">").AppendLine();
+                sb.Append("  <stringTable>").AppendLine();
+
+                foreach (var stringKey in sortedStrings)
+                {
+                    string val = GetLocalizedMessage(stringKey, ci, etwFormat: true);
+                    sb.Append("   <string id=\"").Append(stringKey).Append("\" value=\"").Append(val).Append("\"/>").AppendLine();
+                }
+                sb.Append("  </stringTable>").AppendLine();
+                sb.Append(" </resources>").AppendLine();
+            }
+            sb.Append("</localization>").AppendLine();
+            sb.AppendLine("</instrumentationManifest>");
+            return sb.ToString();
+        }
+
+#region private
+        private void WriteNameAndMessageAttribs(StringBuilder stringBuilder, string elementName, string name)
+        {
+            stringBuilder.Append(" name=\"").Append(name).Append("\"");
+            WriteMessageAttrib(sb, elementName, name, name);
+        }
+        private void WriteMessageAttrib(StringBuilder stringBuilder, string elementName, string name, string value)
+        {
+            string key = elementName + "_" + name;
+            // See if the user wants things localized.  
+            if (resources != null)
+            {
+                // resource fallback: strings in the neutral culture will take precedence over inline strings
+                string localizedString = resources.GetString(key, CultureInfo.InvariantCulture);
+                if (localizedString != null)
+                    value = localizedString;
+            }
+            if (value == null)
+                return;
+
+            stringBuilder.Append(" message=\"$(string.").Append(key).Append(")\"");
+            string prevValue;
+            if (stringTab.TryGetValue(key, out prevValue) && !prevValue.Equals(value))
+            {
+                ManifestError(SR.Format(SR.EventSource_DuplicateStringKey, key), true);
+                return;
+            }
+
+            stringTab[key] = value;
+        }
+        internal string GetLocalizedMessage(string key, CultureInfo ci, bool etwFormat)
+        {
+            string value = null;
+            if (resources != null)
+            {
+                string localizedString = resources.GetString(key, ci);
+                if (localizedString != null)
+                {
+                    value = localizedString;
+                    if (etwFormat && key.StartsWith("event_", StringComparison.Ordinal))
+                    {
+                        var evtName = key.Substring("event_".Length);
+                        value = TranslateToManifestConvention(value, evtName);
+                    }
+                }
+            }
+            if (etwFormat && value == null)
+                stringTab.TryGetValue(key, out value);
+
+            return value;
+        }
+
+        /// <summary>
+        /// There's no API to enumerate all languages an assembly is localized into, so instead
+        /// we enumerate through all the "known" cultures and attempt to load a corresponding satellite 
+        /// assembly
+        /// </summary>
+        /// <param name="resources"></param>
+        /// <returns></returns>
+        private static List<CultureInfo> GetSupportedCultures(ResourceManager resources)
+        {
+            var cultures = new List<CultureInfo>();
+
+            if (!cultures.Contains(CultureInfo.CurrentUICulture))
+                cultures.Insert(0, CultureInfo.CurrentUICulture);
+            return cultures;
+        }
+
+        private static string GetLevelName(EventLevel level)
+        {
+            return (((int)level >= 16) ? "" : "win:") + level.ToString();
+        }
+
+#if FEATURE_MANAGED_ETW_CHANNELS
+        private string GetChannelName(EventChannel channel, string eventName, string eventMessage)
+        {
+            ChannelInfo info = null;
+            if (channelTab == null || !channelTab.TryGetValue((int)channel, out info))
+            {
+                if (channel < EventChannel.Admin) // || channel > EventChannel.Debug)
+                    ManifestError(SR.Format(SR.EventSource_UndefinedChannel, channel, eventName));
+
+                // allow channels to be auto-defined.  The well known ones get their well known names, and the
+                // rest get names Channel<N>.  This allows users to modify the Manifest if they want more advanced features. 
+                if (channelTab == null)
+                    channelTab = new Dictionary<int, ChannelInfo>(4);
+
+                string channelName = channel.ToString();        // For well know channels this is a nice name, otherwise a number 
+                if (EventChannel.Debug < channel)
+                    channelName = "Channel" + channelName;      // Add a 'Channel' prefix for numbers.  
+
+                AddChannel(channelName, (int)channel, GetDefaultChannelAttribute(channel));
+                if (!channelTab.TryGetValue((int)channel, out info))
+                    ManifestError(SR.Format(SR.EventSource_UndefinedChannel, channel, eventName));
+            }
+            // events that specify admin channels *must* have non-null "Message" attributes
+            if (resources != null && eventMessage == null)
+                eventMessage = resources.GetString("event_" + eventName, CultureInfo.InvariantCulture);
+            if (info.Attribs.EventChannelType == EventChannelType.Admin && eventMessage == null)
+                ManifestError(SR.Format(SR.EventSource_EventWithAdminChannelMustHaveMessage, eventName, info.Name));
+            return info.Name;
+        }
+#endif
+        private string GetTaskName(EventTask task, string eventName)
+        {
+            if (task == EventTask.None)
+                return "";
+
+            string ret;
+            if (taskTab == null)
+                taskTab = new Dictionary<int, string>();
+            if (!taskTab.TryGetValue((int)task, out ret))
+                ret = taskTab[(int)task] = eventName;
+            return ret;
+        }
+
+        private string GetOpcodeName(EventOpcode opcode, string eventName)
+        {
+            switch (opcode)
+            {
+                case EventOpcode.Info:
+                    return "win:Info";
+                case EventOpcode.Start:
+                    return "win:Start";
+                case EventOpcode.Stop:
+                    return "win:Stop";
+                case EventOpcode.DataCollectionStart:
+                    return "win:DC_Start";
+                case EventOpcode.DataCollectionStop:
+                    return "win:DC_Stop";
+                case EventOpcode.Extension:
+                    return "win:Extension";
+                case EventOpcode.Reply:
+                    return "win:Reply";
+                case EventOpcode.Resume:
+                    return "win:Resume";
+                case EventOpcode.Suspend:
+                    return "win:Suspend";
+                case EventOpcode.Send:
+                    return "win:Send";
+                case EventOpcode.Receive:
+                    return "win:Receive";
+            }
+
+            string ret;
+            if (opcodeTab == null || !opcodeTab.TryGetValue((int)opcode, out ret))
+            {
+                ManifestError(SR.Format(SR.EventSource_UndefinedOpcode, opcode, eventName), true);
+                ret = null;
+            }
+            return ret;
+        }
+
+        private string GetKeywords(ulong keywords, string eventName)
+        {
+#if FEATURE_MANAGED_ETW_CHANNELS
+            // ignore keywords associate with channels
+            // See ValidPredefinedChannelKeywords def for more. 
+            keywords &= ~ValidPredefinedChannelKeywords;
+#endif
+
+            string ret = "";
+            for (ulong bit = 1; bit != 0; bit <<= 1)
+            {
+                if ((keywords & bit) != 0)
+                {
+                    string keyword = null;
+                    if ((keywordTab == null || !keywordTab.TryGetValue(bit, out keyword)) &&
+                        (bit >= (ulong)0x1000000000000))
+                    {
+                        // do not report Windows reserved keywords in the manifest (this allows the code
+                        // to be resilient to potential renaming of these keywords)
+                        keyword = string.Empty;
+                    }
+                    if (keyword == null)
+                    {
+                        ManifestError(SR.Format(SR.EventSource_UndefinedKeyword, "0x" + bit.ToString("x", CultureInfo.CurrentCulture), eventName), true);
+                        keyword = string.Empty;
+                    }
+                    if (ret.Length != 0 && keyword.Length != 0)
+                        ret = ret + " ";
+                    ret = ret + keyword;
+                }
+            }
+            return ret;
+        }
+
+        private string GetTypeName(Type type)
+        {
+            if (type.IsEnum())
+            {
+                FieldInfo[] fields = type.GetFields(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance);
+                var typeName = GetTypeName(fields[0].FieldType);
+                return typeName.Replace("win:Int", "win:UInt"); // ETW requires enums to be unsigned.  
+            }
+
+            return GetTypeNameHelper(type);
+        }
+
+        private static void UpdateStringBuilder(ref StringBuilder stringBuilder, string eventMessage, int startIndex, int count)
+        {
+            if (stringBuilder == null)
+                stringBuilder = new StringBuilder();
+            stringBuilder.Append(eventMessage, startIndex, count);
+        }
+
+        private static readonly string[] s_escapes = { "&amp;", "&lt;", "&gt;", "&apos;", "&quot;", "%r", "%n", "%t" };
+        // Manifest messages use %N conventions for their message substitutions.   Translate from
+        // .NET conventions.   We can't use RegEx for this (we are in mscorlib), so we do it 'by hand' 
+        private string TranslateToManifestConvention(string eventMessage, string evtName)
+        {
+            StringBuilder stringBuilder = null;        // We lazily create this 
+            int writtenSoFar = 0;
+            int chIdx = -1;
+            for (int i = 0; ;)
+            {
+                if (i >= eventMessage.Length)
+                {
+                    if (stringBuilder == null)
+                        return eventMessage;
+                    UpdateStringBuilder(ref stringBuilder, eventMessage, writtenSoFar, i - writtenSoFar);
+                    return stringBuilder.ToString();
+                }
+
+                if (eventMessage[i] == '%')
+                {
+                    // handle format message escaping character '%' by escaping it
+                    UpdateStringBuilder(ref stringBuilder, eventMessage, writtenSoFar, i - writtenSoFar);
+                    stringBuilder.Append("%%");
+                    i++;
+                    writtenSoFar = i;
+                }
+                else if (i < eventMessage.Length - 1 &&
+                    (eventMessage[i] == '{' && eventMessage[i + 1] == '{' || eventMessage[i] == '}' && eventMessage[i + 1] == '}'))
+                {
+                    // handle C# escaped '{" and '}'
+                    UpdateStringBuilder(ref stringBuilder, eventMessage, writtenSoFar, i - writtenSoFar);
+                    stringBuilder.Append(eventMessage[i]);
+                    i++; i++;
+                    writtenSoFar = i;
+                }
+                else if (eventMessage[i] == '{')
+                {
+                    int leftBracket = i;
+                    i++;
+                    int argNum = 0;
+                    while (i < eventMessage.Length && Char.IsDigit(eventMessage[i]))
+                    {
+                        argNum = argNum * 10 + eventMessage[i] - '0';
+                        i++;
+                    }
+                    if (i < eventMessage.Length && eventMessage[i] == '}')
+                    {
+                        i++;
+                        UpdateStringBuilder(ref stringBuilder, eventMessage, writtenSoFar, leftBracket - writtenSoFar);
+                        int manIndex = TranslateIndexToManifestConvention(argNum, evtName);
+                        stringBuilder.Append('%').Append(manIndex);
+                        // An '!' after the insert specifier {n} will be interpreted as a literal.
+                        // We'll escape it so that mc.exe does not attempt to consider it the 
+                        // beginning of a format string.
+                        if (i < eventMessage.Length && eventMessage[i] == '!')
+                        {
+                            i++;
+                            stringBuilder.Append("%!");
+                        }
+                        writtenSoFar = i;
+                    }
+                    else
+                    {
+                        ManifestError(SR.Format(SR.EventSource_UnsupportedMessageProperty, evtName, eventMessage));
+                    }
+                }
+                else if ((chIdx = "&<>'\"\r\n\t".IndexOf(eventMessage[i])) >= 0)
+                {
+                    UpdateStringBuilder(ref stringBuilder, eventMessage, writtenSoFar, i - writtenSoFar);
+                    i++;
+                    stringBuilder.Append(s_escapes[chIdx]);
+                    writtenSoFar = i;
+                }
+                else
+                    i++;
+            }
+        }
+
+        private int TranslateIndexToManifestConvention(int idx, string evtName)
+        {
+            List<int> byteArrArgIndices;
+            if (perEventByteArrayArgIndices.TryGetValue(evtName, out byteArrArgIndices))
+            {
+                foreach (var byArrIdx in byteArrArgIndices)
+                {
+                    if (idx >= byArrIdx)
+                        ++idx;
+                    else
+                        break;
+                }
+            }
+            return idx + 1;
+        }
+
+#if FEATURE_MANAGED_ETW_CHANNELS
+        class ChannelInfo
+        {
+            public string Name;
+            public ulong Keywords;
+            public EventChannelAttribute Attribs;
+        }
+#endif
+
+        Dictionary<int, string> opcodeTab;
+        Dictionary<int, string> taskTab;
+#if FEATURE_MANAGED_ETW_CHANNELS
+        Dictionary<int, ChannelInfo> channelTab;
+#endif
+        Dictionary<ulong, string> keywordTab;
+        Dictionary<string, Type> mapsTab;
+
+        Dictionary<string, string> stringTab;       // Maps unlocalized strings to localized ones  
+
+#if FEATURE_MANAGED_ETW_CHANNELS
+        // WCF used EventSource to mimic a existing ETW manifest.   To support this
+        // in just their case, we allowed them to specify the keywords associated 
+        // with their channels explicitly.   ValidPredefinedChannelKeywords is 
+        // this set of channel keywords that we allow to be explicitly set.  You
+        // can ignore these bits otherwise.  
+        internal const ulong ValidPredefinedChannelKeywords = 0xF000000000000000;
+        ulong nextChannelKeywordBit = 0x8000000000000000;   // available Keyword bit to be used for next channel definition, grows down
+        const int MaxCountChannels = 8; // a manifest can defined at most 8 ETW channels
+#endif
+
+        StringBuilder sb;               // Holds the provider information. 
+        StringBuilder events;           // Holds the events. 
+        StringBuilder templates;
+
+#if FEATURE_MANAGED_ETW_CHANNELS
+        string providerName;
+#endif
+        ResourceManager resources;      // Look up localized strings here.  
+        EventManifestOptions flags;
+        IList<string> errors;           // list of currently encountered errors
+        Dictionary<string, List<int>> perEventByteArrayArgIndices;  // "event_name" -> List_of_Indices_of_Byte[]_Arg
+
+        // State we track between StartEvent and EndEvent.  
+        string eventName;               // Name of the event currently being processed. 
+        int numParams;                  // keeps track of the number of args the event has. 
+        List<int> byteArrArgIndices;    // keeps track of the index of each byte[] argument
+#endregion
+    }
+
+    /// <summary>
+    /// Used to send the m_rawManifest into the event dispatcher as a series of events.  
+    /// </summary>
+    internal struct ManifestEnvelope
+    {
+        public const int MaxChunkSize = 0xFF00;
+        public enum ManifestFormats : byte
+        {
+            SimpleXmlFormat = 1,          // simply dump the XML manifest as UTF8
+        }
+
+#if FEATURE_MANAGED_ETW
+        public ManifestFormats Format;
+        public byte MajorVersion;
+        public byte MinorVersion;
+        public byte Magic;
+        public ushort TotalChunks;
+        public ushort ChunkNumber;
+#endif
+    };
+
+#endregion
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventSourceException.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventSourceException.cs
new file mode 100644
index 0000000000..be1bf3940a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventSourceException.cs
@@ -0,0 +1,54 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Resources;
+using System.Runtime.Serialization;
+
+#if ES_BUILD_STANDALONE
+using Environment = Microsoft.Diagnostics.Tracing.Internal.Environment;
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// Exception that is thrown when an error occurs during EventSource operation.
+    /// </summary>
+#if !ES_BUILD_PCL
+    [Serializable]
+#endif
+    public class EventSourceException : Exception
+    {
+        /// <summary>
+        /// Initializes a new instance of the EventSourceException class.
+        /// </summary>
+        public EventSourceException() :
+            base(SR.EventSource_ListenerWriteFailure) { }
+
+        /// <summary>
+        /// Initializes a new instance of the EventSourceException class with a specified error message.
+        /// </summary>
+        public EventSourceException(string message) : base(message) { }
+
+        /// <summary>
+        /// Initializes a new instance of the EventSourceException class with a specified error message 
+        /// and a reference to the inner exception that is the cause of this exception.
+        /// </summary>
+        public EventSourceException(string message, Exception innerException) : base(message, innerException) { }
+
+#if !ES_BUILD_PCL
+        /// <summary>
+        /// Initializes a new instance of the EventSourceException class with serialized data.
+        /// </summary>
+        protected EventSourceException(SerializationInfo info, StreamingContext context) : base(info, context) { }
+#endif
+
+        internal EventSourceException(Exception innerException) :
+            base(SR.EventSource_ListenerWriteFailure, innerException) { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/IEventProvider.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/IEventProvider.cs
new file mode 100644
index 0000000000..d34f80eb51
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/IEventProvider.cs
@@ -0,0 +1,43 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using Microsoft.Win32;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    // Represents the interface between EventProvider and an external logging mechanism.
+    internal interface IEventProvider
+    {
+        // Register an event provider.
+        unsafe uint EventRegister(
+            EventSource eventSource,
+            UnsafeNativeMethods.ManifestEtw.EtwEnableCallback enableCallback,
+            void* callbackContext,
+            ref long registrationHandle);
+
+        // Unregister an event provider.
+        uint EventUnregister(long registrationHandle);
+
+        // Write an event.
+        unsafe int EventWriteTransferWrapper(
+            long registrationHandle,
+            ref EventDescriptor eventDescriptor,
+            IntPtr eventHandle,
+            Guid* activityId,
+            Guid* relatedActivityId,
+            int userDataCount,
+            EventProvider.EventData* userData);
+
+        // Get or set the per-thread activity ID.
+        int EventActivityIdControl(UnsafeNativeMethods.ManifestEtw.ActivityControl ControlCode, ref Guid ActivityId);
+
+        // Define an EventPipeEvent handle.
+        unsafe IntPtr DefineEventHandle(uint eventID, string eventName, Int64 keywords, uint eventVersion, uint level, byte *pMetadata, uint metadataLength);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/StubEnvironment.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/StubEnvironment.cs
new file mode 100644
index 0000000000..1b3ca8004c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/StubEnvironment.cs
@@ -0,0 +1,373 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing.Internal
+#else
+namespace System.Diagnostics.Tracing.Internal
+#endif
+{
+#if ES_BUILD_AGAINST_DOTNET_V35
+    using Microsoft.Internal;
+#endif
+    using Microsoft.Reflection;
+    using System.Reflection;
+
+    internal static class Environment
+    {
+        public static readonly string NewLine = System.Environment.NewLine;
+
+        public static int TickCount
+        { get { return System.Environment.TickCount; } }
+
+        public static string GetResourceString(string key, params object[] args)
+        {
+            string fmt = rm.GetString(key);
+            if (fmt != null)
+                return string.Format(fmt, args);
+
+            string sargs = String.Empty;
+            foreach(var arg in args)
+            {
+                if (sargs != String.Empty)
+                    sargs += ", ";
+                sargs += arg.ToString();
+            }
+
+            return key + " (" + sargs + ")";
+        }
+
+        public static string GetRuntimeResourceString(string key, params object[] args)
+        {
+            return GetResourceString(key, args);
+        }
+
+        private static System.Resources.ResourceManager rm = new System.Resources.ResourceManager("Microsoft.Diagnostics.Tracing.Messages", typeof(Environment).Assembly());
+    }
+}
+
+#if ES_BUILD_AGAINST_DOTNET_V35
+
+namespace Microsoft.Internal
+{
+    using System.Text;
+
+    internal static class Tuple
+    {
+        public static Tuple<T1> Create<T1>(T1 item1)
+        {
+            return new Tuple<T1>(item1);
+        }
+
+        public static Tuple<T1, T2> Create<T1, T2>(T1 item1, T2 item2)
+        {
+            return new Tuple<T1, T2>(item1, item2);
+        }
+    }
+
+    [Serializable]
+    internal class Tuple<T1>
+    {
+        private readonly T1 m_Item1;
+
+        public T1 Item1 { get { return m_Item1; } }
+
+        public Tuple(T1 item1)
+        {
+            m_Item1 = item1;
+        }
+
+        public override string ToString()
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append("(");
+            sb.Append(m_Item1);
+            sb.Append(")");
+            return sb.ToString();
+        }
+
+        int Size
+        {
+            get
+            {
+                return 1;
+            }
+        }
+    }
+
+    [Serializable]
+    public class Tuple<T1, T2>
+    {
+        private readonly T1 m_Item1;
+        private readonly T2 m_Item2;
+
+        public T1 Item1 { get { return m_Item1; } }
+        public T2 Item2 { get { return m_Item2; } }
+
+        public Tuple(T1 item1, T2 item2)
+        {
+            m_Item1 = item1;
+            m_Item2 = item2;
+        }
+
+        public override string ToString()
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append("(");
+            sb.Append(m_Item1);
+            sb.Append(", ");
+            sb.Append(m_Item2);
+            sb.Append(")");
+            return sb.ToString();
+        }
+
+        int Size
+        {
+            get
+            {
+                return 2;
+            }
+        }
+    }
+}
+
+#endif
+
+namespace Microsoft.Reflection
+{
+    using System.Reflection;
+
+#if ES_BUILD_PCL
+    [Flags]
+    public enum BindingFlags
+    {
+        DeclaredOnly = 0x02,        // Only look at the members declared on the Type
+        Instance     = 0x04,        // Include Instance members in search
+        Static       = 0x08,        // Include Static members in search
+        Public       = 0x10,        // Include Public members in search
+        NonPublic    = 0x20,        // Include Non-Public members in search
+    }
+    
+    public enum TypeCode {
+        Empty = 0,                  // Null reference
+        Object = 1,                 // Instance that isn't a value
+        DBNull = 2,                 // Database null value
+        Boolean = 3,                // Boolean
+        Char = 4,                   // Unicode character
+        SByte = 5,                  // Signed 8-bit integer
+        Byte = 6,                   // Unsigned 8-bit integer
+        Int16 = 7,                  // Signed 16-bit integer
+        UInt16 = 8,                 // Unsigned 16-bit integer
+        Int32 = 9,                  // Signed 32-bit integer
+        UInt32 = 10,                // Unsigned 32-bit integer
+        Int64 = 11,                 // Signed 64-bit integer
+        UInt64 = 12,                // Unsigned 64-bit integer
+        Single = 13,                // IEEE 32-bit float
+        Double = 14,                // IEEE 64-bit double
+        Decimal = 15,               // Decimal
+        DateTime = 16,              // DateTime
+        String = 18,                // Unicode character string
+    }
+#endif
+    static class ReflectionExtensions
+    {
+#if (!ES_BUILD_PCL && !ES_BUILD_PN)
+
+        //
+        // Type extension methods
+        //
+        public static bool IsEnum(this Type type) { return type.IsEnum; }
+        public static bool IsAbstract(this Type type) { return type.IsAbstract; }
+        public static bool IsSealed(this Type type) { return type.IsSealed; }
+        public static bool IsValueType(this Type type) { return type.IsValueType; }
+        public static bool IsGenericType(this Type type) { return type.IsGenericType; }
+        public static Type BaseType(this Type type) { return type.BaseType; }
+        public static Assembly Assembly(this Type type) { return type.Assembly; }
+        public static TypeCode GetTypeCode(this Type type) { return Type.GetTypeCode(type); }
+
+        public static bool ReflectionOnly(this Assembly assm) { return assm.ReflectionOnly; }
+
+#else // ES_BUILD_PCL
+
+        //
+        // Type extension methods
+        //
+        public static bool IsEnum(this Type type) { return type.GetTypeInfo().IsEnum; }
+        public static bool IsAbstract(this Type type) { return type.GetTypeInfo().IsAbstract; }
+        public static bool IsSealed(this Type type) { return type.GetTypeInfo().IsSealed; }
+        public static bool IsValueType(this Type type) { return type.GetTypeInfo().IsValueType; }
+        public static bool IsGenericType(this Type type) { return type.IsConstructedGenericType; }
+        public static Type BaseType(this Type type) { return type.GetTypeInfo().BaseType; }
+        public static Assembly Assembly(this Type type) { return type.GetTypeInfo().Assembly; }
+        public static IEnumerable<PropertyInfo> GetProperties(this Type type)
+        {
+#if ES_BUILD_PN
+            return type.GetProperties();
+#else
+            return type.GetRuntimeProperties();
+#endif
+        }
+        public static MethodInfo GetGetMethod(this PropertyInfo propInfo) { return propInfo.GetMethod; }
+        public static Type[] GetGenericArguments(this Type type) { return type.GenericTypeArguments; }
+        
+        public static MethodInfo[] GetMethods(this Type type, BindingFlags flags)
+        {
+            // Minimal implementation to cover only the cases we need
+            System.Diagnostics.Debug.Assert((flags & BindingFlags.DeclaredOnly) != 0);
+            System.Diagnostics.Debug.Assert((flags & ~(BindingFlags.DeclaredOnly|BindingFlags.Instance|BindingFlags.Static|BindingFlags.Public|BindingFlags.NonPublic)) == 0);
+            Func<MethodInfo, bool> visFilter;
+            Func<MethodInfo, bool> instFilter;
+            switch (flags & (BindingFlags.Public | BindingFlags.NonPublic))
+            {
+                case 0: visFilter = mi => false; break;
+                case BindingFlags.Public: visFilter = mi => mi.IsPublic; break;
+                case BindingFlags.NonPublic: visFilter = mi => !mi.IsPublic; break;
+                default: visFilter = mi => true; break;
+            }
+            switch (flags & (BindingFlags.Instance | BindingFlags.Static))
+            {
+                case 0: instFilter = mi => false; break;
+                case BindingFlags.Instance: instFilter = mi => !mi.IsStatic; break;
+                case BindingFlags.Static: instFilter = mi => mi.IsStatic; break;
+                default: instFilter = mi => true; break;
+            }
+            List<MethodInfo> methodInfos = new List<MethodInfo>();
+            foreach (var declaredMethod in type.GetTypeInfo().DeclaredMethods)
+            {
+                if (visFilter(declaredMethod) && instFilter(declaredMethod))
+                    methodInfos.Add(declaredMethod);
+            }
+            return methodInfos.ToArray();
+        }
+        public static FieldInfo[] GetFields(this Type type, BindingFlags flags)
+        {
+            // Minimal implementation to cover only the cases we need
+            System.Diagnostics.Debug.Assert((flags & BindingFlags.DeclaredOnly) != 0);
+            System.Diagnostics.Debug.Assert((flags & ~(BindingFlags.DeclaredOnly | BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic)) == 0);
+            Func<FieldInfo, bool> visFilter;
+            Func<FieldInfo, bool> instFilter;
+            switch (flags & (BindingFlags.Public | BindingFlags.NonPublic))
+            {
+                case 0: visFilter = fi => false; break;
+                case BindingFlags.Public: visFilter = fi => fi.IsPublic; break;
+                case BindingFlags.NonPublic: visFilter = fi => !fi.IsPublic; break;
+                default: visFilter = fi => true; break;
+            }
+            switch (flags & (BindingFlags.Instance | BindingFlags.Static))
+            {
+                case 0: instFilter = fi => false; break;
+                case BindingFlags.Instance: instFilter = fi => !fi.IsStatic; break;
+                case BindingFlags.Static: instFilter = fi => fi.IsStatic; break;
+                default: instFilter = fi => true; break;
+            }
+            List<FieldInfo> fieldInfos = new List<FieldInfo>();
+            foreach (var declaredField in type.GetTypeInfo().DeclaredFields)
+            {
+                if (visFilter(declaredField) && instFilter(declaredField))
+                    fieldInfos.Add(declaredField);
+            }
+            return fieldInfos.ToArray();
+        }
+        public static Type GetNestedType(this Type type, string nestedTypeName)
+        {
+            TypeInfo ti = null;
+            foreach(var nt in type.GetTypeInfo().DeclaredNestedTypes)
+            {
+                if (nt.Name == nestedTypeName)
+                {
+                    ti = nt;
+                    break;
+                }
+            }
+            return ti == null ? null : ti.AsType();
+        }
+        public static TypeCode GetTypeCode(this Type type) 
+        {
+            if (type == typeof(bool)) return TypeCode.Boolean;
+            else if (type == typeof(byte)) return TypeCode.Byte;
+            else if (type == typeof(char)) return TypeCode.Char;
+            else if (type == typeof(ushort)) return TypeCode.UInt16;
+            else if (type == typeof(uint)) return TypeCode.UInt32;
+            else if (type == typeof(ulong)) return TypeCode.UInt64;
+            else if (type == typeof(sbyte)) return TypeCode.SByte;
+            else if (type == typeof(short)) return TypeCode.Int16;
+            else if (type == typeof(int)) return TypeCode.Int32;
+            else if (type == typeof(long)) return TypeCode.Int64;
+            else if (type == typeof(string)) return TypeCode.String;
+            else if (type == typeof(float)) return TypeCode.Single;
+            else if (type == typeof(double)) return TypeCode.Double;
+            else if (type == typeof(DateTime)) return TypeCode.DateTime;
+            else if (type == (typeof(Decimal))) return TypeCode.Decimal;
+            else return TypeCode.Object;
+        }
+
+        //
+        // FieldInfo extension methods
+        //
+        public static object GetRawConstantValue(this FieldInfo fi)
+        { return fi.GetValue(null); }
+
+        //
+        // Assembly extension methods
+        //
+        public static bool ReflectionOnly(this Assembly assm)
+        {
+            // In PCL we can't load in reflection-only context
+            return false;
+        }
+
+#endif
+    }
+}
+
+// Defining some no-ops in PCL builds
+#if ES_BUILD_PCL
+namespace System.Security
+{
+    class SuppressUnmanagedCodeSecurityAttribute : Attribute { }
+
+    enum SecurityAction { Demand }
+}
+
+namespace System.Security.Permissions
+{
+    class HostProtectionAttribute : Attribute { public bool MayLeakOnAbort { get; set; } }
+    class PermissionSetAttribute : Attribute
+    { 
+        public PermissionSetAttribute(System.Security.SecurityAction action) { }
+        public bool Unrestricted { get; set; }
+    }
+}
+#endif
+
+#if ES_BUILD_PN
+namespace System
+{
+    internal static class AppDomain
+    {
+        public static int GetCurrentThreadId()
+        {
+            return Internal.Runtime.Augments.RuntimeThread.CurrentThread.ManagedThreadId;
+        }
+    }    
+}
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Win32
+{
+    using System.Runtime.InteropServices;
+    using System.Security;
+
+    [SuppressUnmanagedCodeSecurityAttribute()]
+    internal static class Win32Native
+    {
+        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
+        internal static extern uint GetCurrentProcessId();
+    }
+}
+#endif
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/ArrayTypeInfo.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/ArrayTypeInfo.cs
new file mode 100644
index 0000000000..5771354f67
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/ArrayTypeInfo.cs
@@ -0,0 +1,63 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    internal sealed class ArrayTypeInfo : TraceLoggingTypeInfo
+    {
+        private readonly TraceLoggingTypeInfo elementInfo;
+
+        public ArrayTypeInfo(Type type, TraceLoggingTypeInfo elementInfo)
+            : base(type)
+        {
+            this.elementInfo = elementInfo;
+        }
+
+        public override void WriteMetadata(
+            TraceLoggingMetadataCollector collector,
+            string name,
+            EventFieldFormat format)
+        {
+            collector.BeginBufferedArray();
+            this.elementInfo.WriteMetadata(collector, name, format);
+            collector.EndBufferedArray();
+        }
+
+        public override void WriteData(TraceLoggingDataCollector collector, PropertyValue value)
+        {
+            var bookmark = collector.BeginBufferedArray();
+
+            var count = 0;
+            Array array = (Array)value.ReferenceValue;
+            if (array != null)
+            {
+                count = array.Length;
+                for (int i = 0; i < array.Length; i++)
+                {
+                    this.elementInfo.WriteData(collector, elementInfo.PropertyValueFactory(array.GetValue(i)));
+                }
+            }
+
+            collector.EndBufferedArray(bookmark, count);
+        }
+
+        public override object GetData(object value)
+        {
+            var array = (Array)value;
+            var serializedArray = new object[array.Length];
+            for (int i = 0; i < array.Length; i++)
+            {
+                serializedArray[i] = this.elementInfo.GetData(array.GetValue(i));
+            }
+            return serializedArray;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/ConcurrentSet.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/ConcurrentSet.cs
new file mode 100644
index 0000000000..76c01c6c06
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/ConcurrentSet.cs
@@ -0,0 +1,127 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using Interlocked = System.Threading.Interlocked;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: A very simple lock-free add-only dictionary.
+    /// Warning: this is a copy-by-value type. Copying performs a snapshot.
+    /// Accessing a readonly field always makes a copy of the field, so the
+    /// GetOrAdd method will not work as expected if called on a readonly field.
+    /// </summary>
+    /// <typeparam name="KeyType">
+    /// The type of the key, used for TryGet.
+    /// </typeparam>
+    /// <typeparam name="ItemType">
+    /// The type of the item, used for GetOrAdd.
+    /// </typeparam>
+    internal struct ConcurrentSet<KeyType, ItemType>
+        where ItemType : ConcurrentSetItem<KeyType, ItemType>
+    {
+        private ItemType[] items;
+
+        public ItemType TryGet(KeyType key)
+        {
+            ItemType item;
+            var oldItems = this.items;
+
+            if (oldItems != null)
+            {
+                var lo = 0;
+                var hi = oldItems.Length;
+                do
+                {
+                    int i = (lo + hi) / 2;
+                    item = oldItems[i];
+
+                    int cmp = item.Compare(key);
+                    if (cmp == 0)
+                    {
+                        goto Done;
+                    }
+                    else if (cmp < 0)
+                    {
+                        lo = i + 1;
+                    }
+                    else
+                    {
+                        hi = i;
+                    }
+                }
+                while (lo != hi);
+            }
+
+            item = null;
+
+        Done:
+
+            return item;
+        }
+
+        public ItemType GetOrAdd(ItemType newItem)
+        {
+            ItemType item;
+            var oldItems = this.items;
+            ItemType[] newItems;
+
+        Retry:
+
+            if (oldItems == null)
+            {
+                newItems = new ItemType[] { newItem };
+            }
+            else
+            {
+                var lo = 0;
+                var hi = oldItems.Length;
+                do
+                {
+                    int i = (lo + hi) / 2;
+                    item = oldItems[i];
+
+                    int cmp = item.Compare(newItem);
+                    if (cmp == 0)
+                    {
+                        goto Done;
+                    }
+                    else if (cmp < 0)
+                    {
+                        lo = i + 1;
+                    }
+                    else
+                    {
+                        hi = i;
+                    }
+                }
+                while (lo != hi);
+
+                int oldLength = oldItems.Length;
+                newItems = new ItemType[oldLength + 1];
+                Array.Copy(oldItems, 0, newItems, 0, lo);
+                newItems[lo] = newItem;
+                Array.Copy(oldItems, lo, newItems, lo + 1, oldLength - lo);
+            }
+
+            newItems = Interlocked.CompareExchange(ref this.items, newItems, oldItems);
+            if (oldItems != newItems)
+            {
+                oldItems = newItems;
+                goto Retry;
+            }
+
+            item = newItem;
+
+        Done:
+
+            return item;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/ConcurrentSetItem.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/ConcurrentSetItem.cs
new file mode 100644
index 0000000000..558dbf670b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/ConcurrentSetItem.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: Abstract base class that must be inherited by items in a
+    /// ConcurrentSet.
+    /// </summary>
+    /// <typeparam name="KeyType">Type of the set's key.</typeparam>
+    /// <typeparam name="ItemType">Type of the derived class.</typeparam>
+    internal abstract class ConcurrentSetItem<KeyType, ItemType>
+        where ItemType : ConcurrentSetItem<KeyType, ItemType>
+    {
+        public abstract int Compare(ItemType other);
+        public abstract int Compare(KeyType key);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/DataCollector.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/DataCollector.cs
new file mode 100644
index 0000000000..11c18a260f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/DataCollector.cs
@@ -0,0 +1,358 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Resources;
+using System.Runtime.InteropServices;
+using System.Security;
+
+#if ES_BUILD_STANDALONE
+using Environment = Microsoft.Diagnostics.Tracing.Internal.Environment;
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: This is the implementation of the DataCollector
+    /// functionality. To enable safe access to the DataCollector from
+    /// untrusted code, there is one thread-local instance of this structure
+    /// per thread. The instance must be Enabled before any data is written to
+    /// it. The instance must be Finished before the data is passed to
+    /// EventWrite. The instance must be Disabled before the arrays referenced
+    /// by the pointers are freed or unpinned.
+    /// </summary>
+    internal unsafe struct DataCollector
+    {
+        [ThreadStatic]
+        internal static DataCollector ThreadInstance;
+
+        private byte* scratchEnd;
+        private EventSource.EventData* datasEnd;
+        private GCHandle* pinsEnd;
+        private EventSource.EventData* datasStart;
+        private byte* scratch;
+        private EventSource.EventData* datas;
+        private GCHandle* pins;
+        private byte[] buffer;
+        private int bufferPos;
+        private int bufferNesting;          // We may merge many fields int a single blob.   If we are doing this we increment this. 
+        private bool writingScalars;
+
+        internal void Enable(
+            byte* scratch,
+            int scratchSize,
+            EventSource.EventData* datas,
+            int dataCount,
+            GCHandle* pins,
+            int pinCount)
+        {
+            this.datasStart = datas;
+            this.scratchEnd = scratch + scratchSize;
+            this.datasEnd = datas + dataCount;
+            this.pinsEnd = pins + pinCount;
+            this.scratch = scratch;
+            this.datas = datas;
+            this.pins = pins;
+            this.writingScalars = false;
+        }
+
+        internal void Disable()
+        {
+            this = new DataCollector();
+        }
+
+        /// <summary>
+        /// Completes the list of scalars. Finish must be called before the data
+        /// descriptor array is passed to EventWrite.
+        /// </summary>
+        /// <returns>
+        /// A pointer to the next unused data descriptor, or datasEnd if they were
+        /// all used. (Descriptors may be unused if a string or array was null.)
+        /// </returns>
+        internal EventSource.EventData* Finish()
+        {
+            this.ScalarsEnd();
+            return this.datas;
+        }
+
+        internal void AddScalar(void* value, int size)
+        {
+            var pb = (byte*)value;
+            if (this.bufferNesting == 0)
+            {
+                var scratchOld = this.scratch;
+                var scratchNew = scratchOld + size;
+                if (this.scratchEnd < scratchNew)
+                {
+                    throw new IndexOutOfRangeException(SR.EventSource_AddScalarOutOfRange);
+                }
+
+                this.ScalarsBegin();
+                this.scratch = scratchNew;
+
+                for (int i = 0; i != size; i++)
+                {
+                    scratchOld[i] = pb[i];
+                }
+            }
+            else
+            {
+                var oldPos = this.bufferPos;
+                this.bufferPos = checked(this.bufferPos + size);
+                this.EnsureBuffer();
+                for (int i = 0; i != size; i++, oldPos++)
+                {
+                    this.buffer[oldPos] = pb[i];
+                }
+            }
+        }
+
+        internal void AddBinary(string value, int size)
+        {
+            if (size > ushort.MaxValue)
+            {
+                size = ushort.MaxValue - 1;
+            }
+
+            if (this.bufferNesting != 0)
+            {
+                this.EnsureBuffer(size + 2);
+            }
+
+            this.AddScalar(&size, 2);
+
+            if (size != 0)
+            {
+                if (this.bufferNesting == 0)
+                {
+                    this.ScalarsEnd();
+                    this.PinArray(value, size);
+                }
+                else
+                {
+                    var oldPos = this.bufferPos;
+                    this.bufferPos = checked(this.bufferPos + size);
+                    this.EnsureBuffer();
+                    fixed (void* p = value)
+                    {
+                        Marshal.Copy((IntPtr)p, buffer, oldPos, size);
+                    }
+                }
+            }
+        }
+
+        internal unsafe void AddNullTerminatedString(string value)
+        {
+            // Treat null strings as empty strings.
+            if (value == null)
+            {
+                value = string.Empty;
+            }
+
+            // Calculate the size of the string including the trailing NULL char.
+            // Don't use value.Length here because string allows for embedded NULL characters.
+            int nullCharIndex = value.IndexOf((char)0);
+            if (nullCharIndex < 0)
+            {
+                nullCharIndex = value.Length;
+            }
+            int size = (nullCharIndex + 1) * 2;
+
+            if (this.bufferNesting != 0)
+            {
+                this.EnsureBuffer(size);
+            }
+
+            if (this.bufferNesting == 0)
+            {
+                this.ScalarsEnd();
+                this.PinArray(value, size);
+            }
+            else
+            {
+                var oldPos = this.bufferPos;
+                this.bufferPos = checked(this.bufferPos + size);
+                this.EnsureBuffer();
+                fixed (void* p = value)
+                {
+                    Marshal.Copy((IntPtr)p, buffer, oldPos, size);
+                }
+            }
+        }
+
+        internal void AddBinary(Array value, int size)
+        {
+            this.AddArray(value, size, 1);
+        }
+
+        internal void AddArray(Array value, int length, int itemSize)
+        {
+            if (length > ushort.MaxValue)
+            {
+                length = ushort.MaxValue;
+            }
+
+            var size = length * itemSize;
+            if (this.bufferNesting != 0)
+            {
+                this.EnsureBuffer(size + 2);
+            }
+
+            this.AddScalar(&length, 2);
+
+            if (length != 0)
+            {
+                if (this.bufferNesting == 0)
+                {
+                    this.ScalarsEnd();
+                    this.PinArray(value, size);
+                }
+                else
+                {
+                    var oldPos = this.bufferPos;
+                    this.bufferPos = checked(this.bufferPos + size);
+                    this.EnsureBuffer();
+                    Buffer.BlockCopy(value, 0, this.buffer, oldPos, size);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Marks the start of a non-blittable array or enumerable.
+        /// </summary>
+        /// <returns>Bookmark to be passed to EndBufferedArray.</returns>
+        internal int BeginBufferedArray()
+        {
+            this.BeginBuffered();
+            this.bufferPos += 2; // Reserve space for the array length (filled in by EndEnumerable)
+            return this.bufferPos;
+        }
+
+        /// <summary>
+        /// Marks the end of a non-blittable array or enumerable.
+        /// </summary>
+        /// <param name="bookmark">The value returned by BeginBufferedArray.</param>
+        /// <param name="count">The number of items in the array.</param>
+        internal void EndBufferedArray(int bookmark, int count)
+        {
+            this.EnsureBuffer();
+            this.buffer[bookmark - 2] = unchecked((byte)count);
+            this.buffer[bookmark - 1] = unchecked((byte)(count >> 8));
+            this.EndBuffered();
+        }
+
+        /// <summary>
+        /// Marks the start of dynamically-buffered data.
+        /// </summary>
+        internal void BeginBuffered()
+        {
+            this.ScalarsEnd();
+            this.bufferNesting += 1;
+        }
+
+        /// <summary>
+        /// Marks the end of dynamically-buffered data.
+        /// </summary>
+        internal void EndBuffered()
+        {
+            this.bufferNesting -= 1;
+
+            if (this.bufferNesting == 0)
+            {
+                /*
+                TODO (perf): consider coalescing adjacent buffered regions into a
+                single buffer, similar to what we're already doing for adjacent
+                scalars. In addition, if a type contains a buffered region adjacent
+                to a blittable array, and the blittable array is small, it would be
+                more efficient to buffer the array instead of pinning it.
+                */
+
+                this.EnsureBuffer();
+                this.PinArray(this.buffer, this.bufferPos);
+                this.buffer = null;
+                this.bufferPos = 0;
+            }
+        }
+
+        private void EnsureBuffer()
+        {
+            var required = this.bufferPos;
+            if (this.buffer == null || this.buffer.Length < required)
+            {
+                this.GrowBuffer(required);
+            }
+        }
+
+        private void EnsureBuffer(int additionalSize)
+        {
+            var required = this.bufferPos + additionalSize;
+            if (this.buffer == null || this.buffer.Length < required)
+            {
+                this.GrowBuffer(required);
+            }
+        }
+
+        private void GrowBuffer(int required)
+        {
+            var newSize = this.buffer == null ? 64 : this.buffer.Length;
+
+            do
+            {
+                newSize *= 2;
+            }
+            while (newSize < required);
+
+            Array.Resize(ref this.buffer, newSize);
+        }
+
+        private void PinArray(object value, int size)
+        {
+            var pinsTemp = this.pins;
+            if (this.pinsEnd <= pinsTemp)
+            {
+                throw new IndexOutOfRangeException(SR.EventSource_PinArrayOutOfRange);
+            }
+
+            var datasTemp = this.datas;
+            if (this.datasEnd <= datasTemp)
+            {
+                throw new IndexOutOfRangeException(SR.EventSource_DataDescriptorsOutOfRange);
+            }
+
+            this.pins = pinsTemp + 1;
+            this.datas = datasTemp + 1;
+
+            *pinsTemp = GCHandle.Alloc(value, GCHandleType.Pinned);
+            datasTemp->DataPointer = pinsTemp->AddrOfPinnedObject();
+            datasTemp->m_Size = size;
+        }
+
+        private void ScalarsBegin()
+        {
+            if (!this.writingScalars)
+            {
+                var datasTemp = this.datas;
+                if (this.datasEnd <= datasTemp)
+                {
+                    throw new IndexOutOfRangeException(SR.EventSource_DataDescriptorsOutOfRange);
+                }
+
+                datasTemp->DataPointer = (IntPtr) this.scratch;
+                this.writingScalars = true;
+            }
+        }
+
+        private void ScalarsEnd()
+        {
+            if (this.writingScalars)
+            {
+                var datasTemp = this.datas;
+                datasTemp->m_Size = checked((int)(this.scratch - (byte*)datasTemp->m_Ptr));
+                this.datas = datasTemp + 1;
+                this.writingScalars = false;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EmptyStruct.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EmptyStruct.cs
new file mode 100644
index 0000000000..bc7fb8c346
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EmptyStruct.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: Empty struct indicating no payload data.
+    /// </summary>
+    internal struct EmptyStruct
+    {
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EnumHelper.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EnumHelper.cs
new file mode 100644
index 0000000000..7a23378bb1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EnumHelper.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+#if EVENTSOURCE_GENERICS
+?using System;
+using System.Reflection;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// Provides support for casting enums to their underlying type
+    /// from within generic context.
+    /// </summary>
+    /// <typeparam name="UnderlyingType">
+    /// The underlying type of the enum.
+    /// </typeparam>
+    internal static class EnumHelper<UnderlyingType>
+    {
+        public static UnderlyingType Cast<ValueType>(ValueType value)
+        {
+            return (UnderlyingType)(object)value;
+        }
+    }
+
+}
+#endif
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EnumerableTypeInfo.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EnumerableTypeInfo.cs
new file mode 100644
index 0000000000..74a3fa27b2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EnumerableTypeInfo.cs
@@ -0,0 +1,64 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    internal sealed class EnumerableTypeInfo : TraceLoggingTypeInfo
+    {
+        private readonly TraceLoggingTypeInfo elementInfo;
+
+        public EnumerableTypeInfo(Type type, TraceLoggingTypeInfo elementInfo)
+            : base(type)
+        {
+            this.elementInfo = elementInfo;
+        }
+
+        public override void WriteMetadata(
+            TraceLoggingMetadataCollector collector,
+            string name,
+            EventFieldFormat format)
+        {
+            collector.BeginBufferedArray();
+            this.elementInfo.WriteMetadata(collector, name, format);
+            collector.EndBufferedArray();
+        }
+
+        public override void WriteData(TraceLoggingDataCollector collector, PropertyValue value)
+        {
+            var bookmark = collector.BeginBufferedArray();
+
+            var count = 0;
+            IEnumerable enumerable = (IEnumerable)value.ReferenceValue;
+            if (enumerable != null)
+            {
+                foreach (var element in enumerable)
+                {
+                    this.elementInfo.WriteData(collector, elementInfo.PropertyValueFactory(element));
+                    count++;
+                }
+            }
+
+            collector.EndBufferedArray(bookmark, count);
+        }
+
+        public override object GetData(object value)
+        {
+            var iterType = (IEnumerable)value;
+            List<object> serializedEnumerable = new List<object>();
+            foreach (var element in iterType)
+            {
+                serializedEnumerable.Add(elementInfo.GetData(element));
+            }
+            return serializedEnumerable.ToArray();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventDataAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventDataAttribute.cs
new file mode 100644
index 0000000000..cdedf13c64
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventDataAttribute.cs
@@ -0,0 +1,146 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// Used when authoring types that will be passed to EventSource.Write.
+    /// EventSource.Write&lt;T> only works when T is either an anonymous type
+    /// or a type with an [EventData] attribute. In addition, the properties
+    /// of T must be supported property types. Supported property types include
+    /// simple built-in types (int, string, Guid, DateTime, DateTimeOffset,
+    /// KeyValuePair, etc.), anonymous types that only contain supported types,
+    /// types with an [EventData] attribute, arrays of the above, and IEnumerable
+    /// of the above.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct, Inherited = false)]
+    public class EventDataAttribute
+        : Attribute
+    {
+        private EventLevel level = (EventLevel)(-1);
+        private EventOpcode opcode = (EventOpcode)(-1);
+
+        /// <summary>
+        /// Gets or sets the name to use if this type is used for an
+        /// implicitly-named event or an implicitly-named property.
+        /// 
+        /// Example 1:
+        /// 
+        ///     EventSource.Write(null, new T()); // implicitly-named event
+        ///     
+        /// The name of the event will be determined as follows:
+        /// 
+        /// if (T has an EventData attribute and attribute.Name != null)
+        ///     eventName = attribute.Name;
+        /// else
+        ///     eventName = typeof(T).Name;
+        ///     
+        /// Example 2:
+        /// 
+        ///     EventSource.Write(name, new { _1 = new T() }); // implicitly-named field
+        ///     
+        /// The name of the field will be determined as follows:
+        /// 
+        /// if (T has an EventData attribute and attribute.Name != null)
+        ///     fieldName = attribute.Name;
+        /// else
+        ///     fieldName = typeof(T).Name;
+        /// </summary>
+        public string Name
+        {
+            get;
+            set;
+        }
+
+        /// <summary>
+        /// Gets or sets the level to use for the event.
+        /// Invalid levels (outside the range 0..255) are treated as unset.
+        /// Note that the Level attribute can bubble-up, i.e. if a type contains
+        /// a sub-object (a field or property), and the sub-object's type has a
+        /// TraceLoggingEvent attribute, the Level from the sub-object's attribute
+        /// can affect the event's level.
+        /// 
+        /// Example: for EventSource.Write(name, options, data), the level of the
+        /// event will be determined as follows:
+        /// 
+        /// if (options.Level has been set)
+        ///     eventLevel = options.Level;
+        /// else if (data.GetType() has a TraceLoggingEvent attribute and attribute.Level has been set)
+        ///     eventLevel = attribute.Level;
+        /// else if (a field/property contained in data has a TraceLoggingEvent attribute and attribute.Level has been set)
+        ///     eventLevel = attribute.Level;
+        /// else
+        ///     eventLevel = EventLevel.LogAlways;
+        /// </summary>
+        internal EventLevel Level
+        {
+            get { return this.level; }
+            set { this.level = value; }
+        }
+
+        /// <summary>
+        /// Gets or sets the opcode to use for the event.
+        /// Invalid opcodes (outside the range 0..255) are treated as unset.
+        /// Note that the Opcode attribute can bubble-up, i.e. if a type contains
+        /// a sub-object (a field or property), and the sub-object's type has a
+        /// TraceLoggingEvent attribute, the Opcode from the sub-object's attribute
+        /// can affect the event's opcode.
+        /// 
+        /// Example: for EventSource.Write(name, options, data), the opcode of the
+        /// event will be determined as follows:
+        /// 
+        /// if (options.Opcode has been set)
+        ///     eventOpcode = options.Opcode;
+        /// else if (data.GetType() has a TraceLoggingEvent attribute and attribute.Opcode has been set)
+        ///     eventOpcode = attribute.Opcode;
+        /// else if (a field/property contained in data has a TraceLoggingEvent attribute and attribute.Opcode has been set)
+        ///     eventOpcode = attribute.Opcode;
+        /// else
+        ///     eventOpcode = EventOpcode.Info;
+        /// </summary>
+        internal EventOpcode Opcode
+        {
+            get { return this.opcode; }
+            set { this.opcode = value; }
+        }
+
+        /// <summary>
+        /// Gets or sets the keywords to use for the event.
+        /// Note that the Keywords attribute can bubble-up, i.e. if a type contains
+        /// a sub-object (a field or property), and the sub-object's type has a
+        /// TraceLoggingEvent attribute, the Keywords from the sub-object's attribute
+        /// can affect the event's keywords.
+        /// 
+        /// Example: for EventSource.Write(name, options, data), the keywords of the
+        /// event will be determined as follows:
+        /// 
+        /// eventKeywords = options.Keywords;
+        /// if (data.GetType() has a TraceLoggingEvent attribute)
+        ///     eventKeywords |= attribute.Keywords;
+        /// if (a field/property contained in data has a TraceLoggingEvent attribute)
+        ///     eventKeywords |= attribute.Keywords;
+        /// </summary>
+        internal EventKeywords Keywords
+        {
+            get;
+            set;
+        }
+
+        /// <summary>
+        /// Gets or sets the flags for an event. These flags are ignored by ETW,
+        /// but can have meaning to the event consumer.
+        /// </summary>
+        internal EventTags Tags
+        {
+            get;
+            set;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventFieldAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventFieldAttribute.cs
new file mode 100644
index 0000000000..1a298c2851
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventFieldAttribute.cs
@@ -0,0 +1,76 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// Tags are flags that are not interpreted by EventSource but are passed along
+    /// to the EventListener. The EventListener determines the semantics of the flags.
+    /// </summary>
+    [Flags]
+    public enum EventFieldTags
+    {
+        /// <summary>
+        /// No special traits are added to the field.
+        /// </summary>
+        None = 0,
+
+        /* Bits below 0x10000 are available for any use by the provider. */
+        /* Bits at or above 0x10000 are reserved for definition by Microsoft. */
+    }
+
+    /// <summary>
+    /// TraceLogging: used when authoring types that will be passed to EventSource.Write.
+    /// Controls how a field or property is handled when it is written as a
+    /// field in a TraceLogging event. Apply this attribute to a field or
+    /// property if the default handling is not correct. (Apply the
+    /// TraceLoggingIgnore attribute if the property should not be
+    /// included as a field in the event.)
+    /// The default for Name is null, which means that the name of the
+    /// underlying field or property will be used as the event field's name.
+    /// The default for PiiTag is 0, which means that the event field does not
+    /// contain personally-identifiable information.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Property)]
+    public class EventFieldAttribute
+        : Attribute
+    {
+        /// <summary>
+        /// User defined options for the field. These are not interpreted by the EventSource
+        /// but are available to the Listener. See EventFieldSettings for details
+        /// </summary>
+        public EventFieldTags Tags
+        {
+            get;
+            set;
+        }
+
+        /// <summary>
+        /// Gets or sets the name to use for the field. This defaults to null.
+        /// If null, the name of the corresponding property will be used
+        /// as the event field's name.
+        /// TODO REMOVE
+        /// </summary>
+        internal string Name
+        {
+            get;
+            set;
+        }
+
+        /// <summary>
+        /// Gets or sets a field formatting hint.
+        /// </summary>
+        public EventFieldFormat Format
+        {
+            get;
+            set;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventFieldFormat.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventFieldFormat.cs
new file mode 100644
index 0000000000..fd77b07965
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventFieldFormat.cs
@@ -0,0 +1,130 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// Provides a hint that may be used by an event listener when formatting
+    /// an event field for display. Note that the event listener may ignore the
+    /// hint if it does not recognize a particular combination of type and format.
+    /// Similar to TDH_OUTTYPE.
+    /// </summary>
+    public enum EventFieldFormat
+    {
+        /// <summary>
+        /// Field receives default formatting based on the field's underlying type.
+        /// </summary>
+        Default = 0,
+#if false 
+        /// <summary>
+        /// Field should not be displayed.
+        /// </summary>
+        NoPrint = 1,
+#endif
+        /// <summary>
+        /// Field should be formatted as character or string data.
+        /// Typically applied to 8-bit or 16-bit integers.
+        /// This is the default format for String and Char types.
+        /// </summary>
+        String = 2,
+
+        /// <summary>
+        /// Field should be formatted as boolean data. Typically applied to 8-bit
+        /// or 32-bit integers. This is the default format for the Boolean type.
+        /// </summary>
+        Boolean = 3,
+
+        /// <summary>
+        /// Field should be formatted as hexadecimal data. Typically applied to
+        /// integer types.
+        /// </summary>
+        Hexadecimal = 4,
+
+#if false 
+        /// <summary>
+        /// Field should be formatted as a process identifier. Typically applied to
+        /// 32-bit integer types.
+        /// </summary>
+        ProcessId = 5,
+
+        /// <summary>
+        /// Field should be formatted as a thread identifier. Typically applied to
+        /// 32-bit integer types.
+        /// </summary>
+        ThreadId = 6,
+
+        /// <summary>
+        /// Field should be formatted as an Internet port. Typically applied to 16-bit integer
+        /// types.
+        /// </summary>
+        Port = 7,
+        /// <summary>
+        /// Field should be formatted as an Internet Protocol v4 address. Typically applied to
+        /// 32-bit integer types.
+        /// </summary>
+        Ipv4Address = 8,
+
+        /// <summary>
+        /// Field should be formatted as an Internet Protocol v6 address. Typically applied to
+        /// byte[] types.
+        /// </summary>
+        Ipv6Address = 9,
+        /// <summary>
+        /// Field should be formatted as a SOCKADDR. Typically applied to byte[] types.
+        /// </summary>
+        SocketAddress = 10,
+#endif
+        /// <summary>
+        /// Field should be formatted as XML string data. Typically applied to
+        /// strings or arrays of 8-bit or 16-bit integers.
+        /// </summary>
+        Xml = 11,
+
+        /// <summary>
+        /// Field should be formatted as JSON string data. Typically applied to
+        /// strings or arrays of 8-bit or 16-bit integers.
+        /// </summary>
+        Json = 12,
+#if false 
+        /// <summary>
+        /// Field should be formatted as a Win32 error code. Typically applied to
+        /// 32-bit integer types.
+        /// </summary>
+        Win32Error = 13,
+
+        /// <summary>
+        /// Field should be formatted as an NTSTATUS code. Typically applied to
+        /// 32-bit integer types.
+        /// </summary>
+        NTStatus = 14,
+#endif
+        /// <summary>
+        /// Field should be formatted as an HRESULT code. Typically applied to
+        /// 32-bit integer types.
+        /// </summary>
+        HResult = 15,
+#if false 
+        /// <summary>
+        /// Field should be formatted as a FILETIME. Typically applied to 64-bit
+        /// integer types. This is the default format for DateTime types.
+        /// </summary>
+        FileTime = 16,
+        /// <summary>
+        /// When applied to a numeric type, indicates that the type should be formatted
+        /// as a signed integer. This is the default format for signed integer types.
+        /// </summary>
+        Signed = 17,
+
+        /// <summary>
+        /// When applied to a numeric type, indicates that the type should be formatted
+        /// as an unsigned integer. This is the default format for unsigned integer types.
+        /// </summary>
+        Unsigned = 18,
+#endif
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventIgnoreAttribute.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventIgnoreAttribute.cs
new file mode 100644
index 0000000000..769345f78e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventIgnoreAttribute.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// Used when authoring types that will be passed to EventSource.Write.
+    /// By default, EventSource.Write will write all of an object's public
+    /// properties to the event payload. Apply [EventIgnore] to a public
+    /// property to prevent EventSource.Write from including the property in
+    /// the event.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Property)]
+    public class EventIgnoreAttribute
+        : Attribute
+    {
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventPayload.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventPayload.cs
new file mode 100644
index 0000000000..30a941195f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventPayload.cs
@@ -0,0 +1,156 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Collections;
+using System.Diagnostics;
+
+#if !ES_BUILD_AGAINST_DOTNET_V35
+using Contract = System.Diagnostics.Contracts.Contract;
+#else
+using Contract = Microsoft.Diagnostics.Contracts.Internal.Contract;
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// EventPayload class holds the list of parameters and their corresponding values for user defined types passed to 
+    /// EventSource APIs.
+    /// Preserving the order of the elements as they were found inside user defined types is the most important characteristic of this class.
+    /// </summary>
+    internal class EventPayload : IDictionary<string, object>
+    {
+        internal EventPayload(List<string> payloadNames, List<object> payloadValues) 
+        {
+            Debug.Assert(payloadNames.Count == payloadValues.Count);
+
+            m_names = payloadNames;
+            m_values = payloadValues;
+        }
+
+        public ICollection<string> Keys { get { return m_names; } }
+        public ICollection<object> Values { get { return m_values; } }
+
+        public object this[string key]
+        {
+            get
+            {
+                if (key == null)
+                    throw new System.ArgumentNullException(nameof(key));
+
+                int position = 0;
+                foreach(var name in m_names)
+                { 
+                    if (name == key)
+                    {
+                        return m_values[position];
+                    }
+                    position++;
+                }
+
+                throw new System.Collections.Generic.KeyNotFoundException(SR.Format(SR.Arg_KeyNotFoundWithKey, key.ToString()));
+            }
+            set
+            {
+                throw new System.NotSupportedException();
+            }
+        }
+
+        public void Add(string key, object value)
+        {
+            throw new System.NotSupportedException();
+        }
+
+        public void Add(KeyValuePair<string, object> payloadEntry)
+        {
+            throw new System.NotSupportedException();
+        }
+
+        public void Clear()
+        {
+            throw new System.NotSupportedException();
+        }
+
+        public bool Contains(KeyValuePair<string, object> entry)
+        {
+            return ContainsKey(entry.Key);
+        }
+
+        public bool ContainsKey(string key)
+        {
+            if (key == null)
+                throw new System.ArgumentNullException(nameof(key));
+
+            foreach (var item in m_names)
+            {
+                if (item == key)
+                    return true;
+            }
+            return false;
+        }
+
+        public int Count { get { return m_names.Count; } }
+
+        public bool IsReadOnly { get { return true; } }
+
+        public IEnumerator<KeyValuePair<string, object>> GetEnumerator()
+        {
+            for (int i = 0; i < Keys.Count; i++)
+            {
+                yield return new KeyValuePair<string, object>(this.m_names[i], this.m_values[i]);
+            }
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            var instance = this as IEnumerable<KeyValuePair<string, object>>;
+            return instance.GetEnumerator();
+        }
+
+        public void CopyTo(KeyValuePair<string, object>[] payloadEntries, int count)
+        {
+            throw new System.NotSupportedException();
+        }
+       
+        public bool Remove(string key)
+        {
+            throw new System.NotSupportedException();
+        }
+
+        public bool Remove(KeyValuePair<string, object> entry)
+        {
+            throw new System.NotSupportedException();
+        }
+       
+        public bool TryGetValue(string key, out object value)
+        {
+            if (key == null)
+                throw new System.ArgumentNullException(nameof(key));
+
+            int position = 0;
+            foreach (var name in m_names)
+            {
+                if (name == key)
+                {
+                    value =  m_values[position];
+                    return true;
+                }
+                position++;
+            }
+
+            value = default(object);
+            return false;
+        }
+
+        #region private
+        private List<string> m_names;
+        private List<object> m_values;
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventSourceActivity.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventSourceActivity.cs
new file mode 100644
index 0000000000..2d71550803
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventSourceActivity.cs
@@ -0,0 +1,320 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+#if !ES_BUILD_AGAINST_DOTNET_V35
+using Contract = System.Diagnostics.Contracts.Contract;
+#else
+using Contract = Microsoft.Diagnostics.Contracts.Internal.Contract;
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// Provides support for EventSource activities by marking the start and
+    /// end of a particular operation.
+    /// </summary>
+    internal sealed class EventSourceActivity
+        : IDisposable
+    {
+        /// <summary>
+        /// Initializes a new instance of the EventSourceActivity class that
+        /// is attached to the specified event source. The new activity will
+        /// not be attached to any related (parent) activity.
+        /// The activity is created in the Initialized state.
+        /// </summary>
+        /// <param name="eventSource">
+        /// The event source to which the activity information is written.
+        /// </param>
+        public EventSourceActivity(EventSource eventSource)
+        {
+            if (eventSource == null)
+                throw new ArgumentNullException(nameof(eventSource));
+
+            this.eventSource = eventSource;
+        }
+
+        /// <summary>
+        /// You can make an activity out of just an EventSource.  
+        /// </summary>
+        public static implicit operator EventSourceActivity(EventSource eventSource) { return new EventSourceActivity(eventSource); }
+
+        /* Properties */
+        /// <summary>
+        /// Gets the event source to which this activity writes events.
+        /// </summary>
+        public EventSource EventSource
+        {
+            get { return this.eventSource; }
+        }
+
+        /// <summary>
+        /// Gets this activity's unique identifier, or the default Guid if the
+        /// event source was disabled when the activity was initialized.
+        /// </summary>
+        public Guid Id
+        {
+            get { return this.activityId; }
+        }
+
+#if false // don't expose RelatedActivityId unless there is a need.   
+        /// <summary>
+        /// Gets the unique identifier of this activity's related (parent)
+        /// activity.
+        /// </summary>
+        public Guid RelatedId
+        {
+            get { return this.relatedActivityId; }
+        }
+#endif
+
+        /// <summary>
+        /// Writes a Start event with the specified name and data.   If the start event is not active (because the provider 
+        /// is not on or keyword-level indicates the event is off, then the returned activity is simply the 'this' pointer
+        /// and it is effectively like start did not get called.
+        /// 
+        /// A new activityID GUID is generated and the returned
+        /// EventSourceActivity remembers this activity and will mark every event (including the start stop and any writes)
+        /// with this activityID.   In addition the Start activity will log a 'relatedActivityID' that was the activity
+        /// ID before the start event.   This way event processors can form a linked list of all the activities that
+        /// caused this one (directly or indirectly).  
+        /// </summary>
+        /// <param name="eventName">
+        /// The name to use for the event.   It is strongly suggested that this name end in 'Start' (e.g. DownloadStart).  
+        /// If you do this, then the Stop() method will automatically replace the 'Start' suffix with a 'Stop' suffix.  
+        /// </param>
+        /// <param name="options">Allow options (keywords, level) to be set for the write associated with this start 
+        /// These will also be used for the stop event.</param>
+        /// <param name="data">The data to include in the event.</param>
+        public EventSourceActivity Start<T>(string eventName, EventSourceOptions options, T data)
+        {
+            return this.Start(eventName, ref options, ref data);
+        }
+        /// <summary>
+        /// Shortcut version see Start(string eventName, EventSourceOptions options, T data) Options is empty (no keywords 
+        /// and level==Info) Data payload is empty.  
+        /// </summary>
+        public EventSourceActivity Start(string eventName)
+        {
+            var options = new EventSourceOptions();
+            var data = new EmptyStruct();
+            return this.Start(eventName, ref options, ref data);
+        }
+        /// <summary>
+        /// Shortcut version see Start(string eventName, EventSourceOptions options, T data).  Data payload is empty. 
+        /// </summary>
+        public EventSourceActivity Start(string eventName, EventSourceOptions options)
+        {
+            var data = new EmptyStruct();
+            return this.Start(eventName, ref options, ref data);
+        }
+        /// <summary>
+        /// Shortcut version see Start(string eventName, EventSourceOptions options, T data) Options is empty (no keywords 
+        /// and level==Info) 
+        /// </summary>
+        public EventSourceActivity Start<T>(string eventName, T data)
+        {
+            var options = new EventSourceOptions();
+            return this.Start(eventName, ref options, ref data);
+        }
+
+        /// <summary>
+        /// Writes a Stop event with the specified data, and sets the activity
+        /// to the Stopped state.  The name is determined by the eventName used in Start.
+        /// If that Start event name is suffixed with 'Start' that is removed, and regardless
+        /// 'Stop' is appended to the result to form the Stop event name.  
+        /// May only be called when the activity is in the Started state.
+        /// </summary>
+        /// <param name="data">The data to include in the event.</param>
+        public void Stop<T>(T data)
+        {
+            this.Stop(null, ref data);
+        }
+        /// <summary>
+        /// Used if you wish to use the non-default stop name (which is the start name with Start replace with 'Stop')
+        /// This can be useful to indicate unusual ways of stopping (but it is still STRONGLY recommended that
+        /// you start with the same prefix used for the start event and you end with the 'Stop' suffix.   
+        /// </summary>
+        public void Stop<T>(string eventName)
+        {
+            var data = new EmptyStruct();
+            this.Stop(eventName, ref data);
+        }
+        /// <summary>
+        /// Used if you wish to use the non-default stop name (which is the start name with Start replace with 'Stop')
+        /// This can be useful to indicate unusual ways of stopping (but it is still STRONGLY recommended that
+        /// you start with the same prefix used for the start event and you end with the 'Stop' suffix.   
+        /// </summary>
+        public void Stop<T>(string eventName, T data)
+        {
+            this.Stop(eventName, ref data);
+        }
+
+        /// <summary>
+        /// Writes an event associated with this activity to the eventSource associated with this activity.  
+        /// May only be called when the activity is in the Started state.
+        /// </summary>
+        /// <param name="eventName">
+        /// The name to use for the event. If null, the name is determined from
+        /// data's type.
+        /// </param>
+        /// <param name="options">
+        /// The options to use for the event.
+        /// </param>
+        /// <param name="data">The data to include in the event.</param>
+        public void Write<T>(string eventName, EventSourceOptions options, T data)
+        {
+            this.Write(this.eventSource, eventName, ref options, ref data);
+        }
+        /// <summary>
+        /// Writes an event associated with this activity.
+        /// May only be called when the activity is in the Started state.
+        /// </summary>
+        /// <param name="eventName">
+        /// The name to use for the event. If null, the name is determined from
+        /// data's type.
+        /// </param>
+        /// <param name="data">The data to include in the event.</param>
+        public void Write<T>(string eventName, T data)
+        {
+            var options = new EventSourceOptions();
+            this.Write(this.eventSource, eventName, ref options, ref data);
+        }
+        /// <summary>
+        /// Writes a trivial event associated with this activity.
+        /// May only be called when the activity is in the Started state.
+        /// </summary>
+        /// <param name="eventName">
+        /// The name to use for the event. Must not be null.
+        /// </param>
+        /// <param name="options">
+        /// The options to use for the event.
+        /// </param>
+        public void Write(string eventName, EventSourceOptions options)
+        {
+            var data = new EmptyStruct();
+            this.Write(this.eventSource, eventName, ref options, ref data);
+        }
+        /// <summary>
+        /// Writes a trivial event associated with this activity.
+        /// May only be called when the activity is in the Started state.
+        /// </summary>
+        /// <param name="eventName">
+        /// The name to use for the event. Must not be null.
+        /// </param>
+        public void Write(string eventName)
+        {
+            var options = new EventSourceOptions();
+            var data = new EmptyStruct();
+            this.Write(this.eventSource, eventName, ref options, ref data);
+        }
+        /// <summary>
+        /// Writes an event to a arbitrary eventSource stamped with the activity ID of this activity.   
+        /// </summary>
+        public void Write<T>(EventSource source, string eventName, EventSourceOptions options, T data)
+        {
+            this.Write(source, eventName, ref options, ref data);
+        }
+
+        /// <summary>
+        /// Releases any unmanaged resources associated with this object.
+        /// If the activity is in the Started state, calls Stop().
+        /// </summary>
+        public void Dispose()
+        {
+            if (this.state == State.Started)
+            {
+                var data = new EmptyStruct();
+                this.Stop(null, ref data);
+            }
+        }
+
+        #region private
+        private EventSourceActivity Start<T>(string eventName, ref EventSourceOptions options, ref T data)
+        {
+            if (this.state != State.Started)
+                throw new InvalidOperationException();
+
+            // If the source is not on at all, then we don't need to do anything and we can simply return ourselves.  
+            if (!this.eventSource.IsEnabled())
+                return this;
+
+            var newActivity = new EventSourceActivity(eventSource);
+            if (!this.eventSource.IsEnabled(options.Level, options.Keywords))
+            {
+                // newActivity.relatedActivityId = this.Id;
+                Guid relatedActivityId = this.Id;
+                newActivity.activityId = Guid.NewGuid();
+                newActivity.startStopOptions = options;
+                newActivity.eventName = eventName;
+                newActivity.startStopOptions.Opcode = EventOpcode.Start;
+                this.eventSource.Write(eventName, ref newActivity.startStopOptions, ref newActivity.activityId, ref relatedActivityId, ref data);
+            }
+            else
+            {
+                // If we are not active, we don't set the eventName, which basically also turns off the Stop event as well.  
+                newActivity.activityId = this.Id;
+            }
+
+            return newActivity;
+        }
+
+        private void Write<T>(EventSource eventSource, string eventName, ref EventSourceOptions options, ref T data)
+        {
+            if (this.state != State.Started)
+                throw new InvalidOperationException();      // Write after stop. 
+            if (eventName == null)
+                throw new ArgumentNullException();
+
+            eventSource.Write(eventName, ref options, ref this.activityId, ref s_empty, ref data);
+        }
+
+        private void Stop<T>(string eventName, ref T data)
+        {
+            if (this.state != State.Started)
+                throw new InvalidOperationException();
+
+            // If start was not fired, then stop isn't as well.  
+            if (!StartEventWasFired)
+                return;
+
+            this.state = State.Stopped;
+            if (eventName == null)
+            {
+                eventName = this.eventName;
+                if (eventName.EndsWith("Start"))
+                    eventName = eventName.Substring(0, eventName.Length - 5);
+                eventName = eventName + "Stop";
+            }
+            this.startStopOptions.Opcode = EventOpcode.Stop;
+            this.eventSource.Write(eventName, ref this.startStopOptions, ref this.activityId, ref s_empty, ref data);
+        }
+
+        private enum State
+        {
+            Started,
+            Stopped
+        }
+
+        /// <summary>
+        /// If eventName is non-null then we logged a start event 
+        /// </summary>
+        private bool StartEventWasFired { get { return eventName != null; } }
+
+        private readonly EventSource eventSource;
+        private EventSourceOptions startStopOptions;
+        internal Guid activityId;
+        // internal Guid relatedActivityId;
+        private State state;
+        private string eventName;
+
+        internal static Guid s_empty;
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventSourceOptions.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventSourceOptions.cs
new file mode 100644
index 0000000000..26305a5708
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/EventSourceOptions.cs
@@ -0,0 +1,130 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// Used when calling EventSource.Write.
+    /// Optional overrides for event settings such as Level, Keywords, or Opcode.
+    /// If overrides are not provided for a setting, default values will be used.
+    /// </summary>
+    public struct EventSourceOptions
+    {
+        internal EventKeywords keywords;
+        internal EventTags tags;
+        internal EventActivityOptions activityOptions;
+        internal byte level;
+        internal byte opcode;
+        internal byte valuesSet;
+
+        internal const byte keywordsSet = 0x1;
+        internal const byte tagsSet = 0x2;
+        internal const byte levelSet = 0x4;
+        internal const byte opcodeSet = 0x8;
+        internal const byte activityOptionsSet = 0x10;
+
+        /// <summary>
+        /// Gets or sets the level to use for the specified event. If this property
+        /// is unset, the event's level will be 5 (Verbose).
+        /// </summary>
+        public EventLevel Level
+        {
+            get
+            {
+                return (EventLevel)this.level;
+            }
+
+            set
+            {
+                this.level = checked((byte)value);
+                this.valuesSet |= levelSet;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the opcode to use for the specified event. If this property
+        /// is unset, the event's opcode will 0 (Info).
+        /// </summary>
+        public EventOpcode Opcode
+        {
+            get
+            {
+                return (EventOpcode)this.opcode;
+            }
+
+            set
+            {
+                this.opcode = checked((byte)value);
+                this.valuesSet |= opcodeSet;
+            }
+        }
+
+        internal bool IsOpcodeSet
+        {
+            get
+            {
+                return (this.valuesSet & opcodeSet) != 0;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the keywords to use for the specified event. If this
+        /// property is unset, the event's keywords will be 0.
+        /// </summary>
+        public EventKeywords Keywords
+        {
+            get
+            {
+                return this.keywords;
+            }
+
+            set
+            {
+                this.keywords = value;
+                this.valuesSet |= keywordsSet;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the tags to use for the specified event. If this property is
+        /// unset, the event's tags will be 0.
+        /// </summary>
+        public EventTags Tags
+        {
+            get
+            {
+                return this.tags;
+            }
+
+            set
+            {
+                this.tags = value;
+                this.valuesSet |= tagsSet;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the activity options for this specified events. If this property is
+        /// unset, the event's activity options will be 0.
+        /// </summary>
+        public EventActivityOptions ActivityOptions
+        {
+            get
+            {
+                return this.activityOptions;
+            }
+            set
+            {
+                this.activityOptions = value;
+                this.valuesSet |= activityOptionsSet;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/FieldMetadata.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/FieldMetadata.cs
new file mode 100644
index 0000000000..f153734752
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/FieldMetadata.cs
@@ -0,0 +1,230 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Resources;
+using Encoding = System.Text.Encoding;
+
+#if ES_BUILD_STANDALONE
+using Environment = Microsoft.Diagnostics.Tracing.Internal.Environment;
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: Contains the information needed to generate tracelogging
+    /// metadata for an event field.
+    /// </summary>
+    internal class FieldMetadata
+    {
+        /// <summary>
+        /// Name of the field
+        /// </summary>
+        private readonly string name;
+
+        /// <summary>
+        /// The number of bytes in the UTF8 Encoding of 'name' INCLUDING a null terminator.  
+        /// </summary>
+        private readonly int nameSize;
+        private readonly EventFieldTags tags;
+        private readonly byte[] custom;
+
+        /// <summary>
+        /// ETW supports fixed sized arrays. If inType has the InTypeFixedCountFlag then this is the
+        /// statically known count for the array. It is also used to encode the number of bytes of
+        /// custom meta-data if InTypeCustomCountFlag set.
+        /// </summary>
+        private readonly ushort fixedCount;
+
+        private byte inType;
+        private byte outType;
+
+        /// <summary>
+        /// Scalar or variable-length array.
+        /// </summary>
+        public FieldMetadata(
+            string name,
+            TraceLoggingDataType type,
+            EventFieldTags tags,
+            bool variableCount)
+            : this(
+                name,
+                type,
+                tags,
+                variableCount ? Statics.InTypeVariableCountFlag : (byte)0,
+                0,
+                null)
+        {
+            return;
+        }
+
+        /// <summary>
+        /// Fixed-length array.
+        /// </summary>
+        public FieldMetadata(
+            string name,
+            TraceLoggingDataType type,
+            EventFieldTags tags,
+            ushort fixedCount)
+            : this(
+                name,
+                type,
+                tags,
+                Statics.InTypeFixedCountFlag,
+                fixedCount,
+                null)
+        {
+            return;
+        }
+
+        /// <summary>
+        /// Custom serializer
+        /// </summary>
+        public FieldMetadata(
+            string name,
+            TraceLoggingDataType type,
+            EventFieldTags tags,
+            byte[] custom)
+            : this(
+                name,
+                type,
+                tags,
+                Statics.InTypeCustomCountFlag,
+                checked((ushort)(custom == null ? 0 : custom.Length)),
+                custom)
+        {
+            return;
+        }
+
+        private FieldMetadata(
+            string name,
+            TraceLoggingDataType dataType,
+            EventFieldTags tags,
+            byte countFlags,
+            ushort fixedCount = 0,
+            byte[] custom = null)
+        {
+            if (name == null)
+            {
+                throw new ArgumentNullException(
+                    nameof(name),
+                    "This usually means that the object passed to Write is of a type that"
+                    + " does not support being used as the top-level object in an event,"
+                    + " e.g. a primitive or built-in type.");
+            }
+
+            Statics.CheckName(name);
+            var coreType = (int)dataType & Statics.InTypeMask;
+            this.name = name;
+            this.nameSize = Encoding.UTF8.GetByteCount(this.name) + 1;
+            this.inType = (byte)(coreType | countFlags);
+            this.outType = (byte)(((int)dataType >> 8) & Statics.OutTypeMask);
+            this.tags = tags;
+            this.fixedCount = fixedCount;
+            this.custom = custom;
+
+            if (countFlags != 0)
+            {
+                if (coreType == (int)TraceLoggingDataType.Nil)
+                {
+                    throw new NotSupportedException(SR.EventSource_NotSupportedArrayOfNil);
+                }
+                if (coreType == (int)TraceLoggingDataType.Binary)
+                {
+                    throw new NotSupportedException(SR.EventSource_NotSupportedArrayOfBinary);
+                }
+                if (coreType == (int)TraceLoggingDataType.Utf16String ||
+                    coreType == (int)TraceLoggingDataType.MbcsString)
+                {
+                    throw new NotSupportedException(SR.EventSource_NotSupportedArrayOfNullTerminatedString);
+                }
+            }
+
+            if (((int)this.tags & 0xfffffff) != 0)
+            {
+                this.outType |= Statics.OutTypeChainFlag;
+            }
+
+            if (this.outType != 0)
+            {
+                this.inType |= Statics.InTypeChainFlag;
+            }
+        }
+
+        public void IncrementStructFieldCount()
+        {
+            this.inType |= Statics.InTypeChainFlag;
+            this.outType++;
+            if ((this.outType & Statics.OutTypeMask) == 0)
+            {
+                throw new NotSupportedException(SR.EventSource_TooManyFields);
+            }
+        }
+
+        /// <summary>
+        /// This is the main routine for FieldMetaData.  Basically it will serialize the data in
+        /// this structure as TraceLogging style meta-data into the array 'metaArray' starting at
+        /// 'pos' (pos is updated to reflect the bytes written).  
+        /// 
+        /// Note that 'metaData' can be null, in which case it only updates 'pos'.  This is useful
+        /// for a 'two pass' approach where you figure out how big to make the array, and then you
+        /// fill it in.   
+        /// </summary>
+        public void Encode(ref int pos, byte[] metadata)
+        {
+            // Write out the null terminated UTF8 encoded name
+            if (metadata != null)
+            {
+                Encoding.UTF8.GetBytes(this.name, 0, this.name.Length, metadata, pos);
+            }
+            pos += this.nameSize;
+
+            // Write 1 byte for inType
+            if (metadata != null)
+            {
+                metadata[pos] = this.inType;
+            }
+            pos += 1;
+
+            // If InTypeChainFlag set, then write out the outType
+            if (0 != (this.inType & Statics.InTypeChainFlag))
+            {
+                if (metadata != null)
+                {
+                    metadata[pos] = this.outType;
+                }
+                pos += 1;
+
+                // If OutTypeChainFlag set, then write out tags
+                if (0 != (this.outType & Statics.OutTypeChainFlag))
+                {
+                    Statics.EncodeTags((int)this.tags, ref pos, metadata);
+                }
+            }
+
+            // If InTypeFixedCountFlag set, write out the fixedCount (2 bytes little endian)
+            if (0 != (this.inType & Statics.InTypeFixedCountFlag))
+            {
+                if (metadata != null)
+                {
+                    metadata[pos + 0] = unchecked((byte)this.fixedCount);
+                    metadata[pos + 1] = (byte)(this.fixedCount >> 8);
+                }
+                pos += 2;
+
+                // If InTypeCustomCountFlag set, write out the blob of custom meta-data.  
+                if (Statics.InTypeCustomCountFlag == (this.inType & Statics.InTypeCountMask) &&
+                    this.fixedCount != 0)
+                {
+                    if (metadata != null)
+                    {
+                        Buffer.BlockCopy(this.custom, 0, metadata, pos, this.fixedCount);
+                    }
+                    pos += this.fixedCount;
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/InvokeTypeInfo.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/InvokeTypeInfo.cs
new file mode 100644
index 0000000000..2a7113e5d7
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/InvokeTypeInfo.cs
@@ -0,0 +1,96 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: An implementation of TraceLoggingTypeInfo that works
+    /// for arbitrary types. It writes all public instance properties of
+    /// the type.
+    /// </summary>
+    /// <typeparam name="ContainerType">
+    /// Type from which to read values.
+    /// </typeparam>
+    internal sealed class InvokeTypeInfo : TraceLoggingTypeInfo
+    {
+        internal readonly PropertyAnalysis[] properties;
+
+        public InvokeTypeInfo(
+            Type type,
+            TypeAnalysis typeAnalysis)
+            : base(
+                type,
+                typeAnalysis.name,
+                typeAnalysis.level,
+                typeAnalysis.opcode,
+                typeAnalysis.keywords,
+                typeAnalysis.tags)
+        {
+            if (typeAnalysis.properties.Length != 0)
+                this.properties = typeAnalysis.properties;
+        }
+
+        public override void WriteMetadata(
+            TraceLoggingMetadataCollector collector,
+            string name,
+            EventFieldFormat format)
+        {
+            var groupCollector = collector.AddGroup(name);
+            if (this.properties != null)
+            {
+                foreach (var property in this.properties)
+                {
+                    var propertyFormat = EventFieldFormat.Default;
+                    var propertyAttribute = property.fieldAttribute;
+                    if (propertyAttribute != null)
+                    {
+                        groupCollector.Tags = propertyAttribute.Tags;
+                        propertyFormat = propertyAttribute.Format;
+                    }
+
+                    property.typeInfo.WriteMetadata(
+                        groupCollector,
+                        property.name,
+                        propertyFormat);
+                }
+            }
+        }
+
+        public override void WriteData(TraceLoggingDataCollector collector, PropertyValue value)
+        {
+            if (this.properties != null)
+            {
+                foreach (var property in this.properties)
+                {
+                    property.typeInfo.WriteData(collector, property.getter(value));
+                }
+            }
+        }
+
+        public override object GetData(object value)
+        {
+            if (this.properties != null)
+            {
+                var membersNames = new List<string>();
+                var memebersValues = new List<object>();
+                for (int i = 0; i < this.properties.Length; i++)
+                {
+                    var propertyValue = properties[i].propertyInfo.GetValue(value);
+                    membersNames.Add(properties[i].name);
+                    memebersValues.Add(properties[i].typeInfo.GetData(propertyValue));
+                }
+                return new EventPayload(membersNames, memebersValues);
+            }
+
+            return null;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/NameInfo.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/NameInfo.cs
new file mode 100644
index 0000000000..b1c7327c18
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/NameInfo.cs
@@ -0,0 +1,126 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Collections.Concurrent;
+using Interlocked = System.Threading.Interlocked;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: Stores the metadata and event identifier corresponding
+    /// to a tracelogging event type+name+tags combination.
+    /// </summary>
+    internal sealed class NameInfo
+        : ConcurrentSetItem<KeyValuePair<string, EventTags>, NameInfo>
+    {
+        /// <summary>
+        /// Insure that eventIds strictly less than 'eventId' will not be
+        /// used by the SelfDescribing events.   
+        /// </summary>
+        internal static void ReserveEventIDsBelow(int eventId)
+        {
+            for(;;)
+            {
+                int snapshot = lastIdentity;
+                int newIdentity = (lastIdentity & ~0xFFFFFF) + eventId;
+                newIdentity = Math.Max(newIdentity, snapshot);      // Should be redundant.  as we only create descriptors once.  
+                if (Interlocked.CompareExchange(ref lastIdentity, newIdentity, snapshot) == snapshot)
+                    break;
+            }
+        }
+
+        private static int lastIdentity = Statics.TraceLoggingChannel << 24;
+        internal readonly string name;
+        internal readonly EventTags tags;
+        internal readonly int identity;
+        internal readonly byte[] nameMetadata;
+
+#if FEATURE_PERFTRACING
+        private readonly object eventHandleCreationLock = new object();
+#endif
+
+        public NameInfo(string name, EventTags tags, int typeMetadataSize)
+        {
+            this.name = name;
+            this.tags = tags & Statics.EventTagsMask;
+            this.identity = Interlocked.Increment(ref lastIdentity);
+
+            int tagsPos = 0;
+            Statics.EncodeTags((int)this.tags, ref tagsPos, null);
+
+            this.nameMetadata = Statics.MetadataForString(name, tagsPos, 0, typeMetadataSize);
+
+            tagsPos = 2;
+            Statics.EncodeTags((int)this.tags, ref tagsPos, this.nameMetadata);
+        }
+
+        public override int Compare(NameInfo other)
+        {
+            return this.Compare(other.name, other.tags);
+        }
+
+        public override int Compare(KeyValuePair<string, EventTags> key)
+        {
+            return this.Compare(key.Key, key.Value & Statics.EventTagsMask);
+        }
+
+        private int Compare(string otherName, EventTags otherTags)
+        {
+            int result = StringComparer.Ordinal.Compare(this.name, otherName);
+            if (result == 0 && this.tags != otherTags)
+            {
+                result = this.tags < otherTags ? -1 : 1;
+            }
+            return result;
+        }
+
+#if FEATURE_PERFTRACING
+        public IntPtr GetOrCreateEventHandle(EventProvider provider, ConcurrentDictionary<int, IntPtr> eventHandleMap, EventDescriptor descriptor, TraceLoggingEventTypes eventTypes)
+        {
+            IntPtr eventHandle = IntPtr.Zero;
+            if(!eventHandleMap.TryGetValue(descriptor.EventId, out eventHandle))
+            {
+                lock (eventHandleCreationLock)
+                {
+                    if (!eventHandleMap.TryGetValue(descriptor.EventId, out eventHandle))
+                    {
+                        byte[] metadataBlob = EventPipeMetadataGenerator.Instance.GenerateEventMetadata(
+                            descriptor.EventId,
+                            name,
+                            (EventKeywords)descriptor.Keywords,
+                            (EventLevel)descriptor.Level,
+                            descriptor.Version,
+                            eventTypes);
+                        uint metadataLength = (metadataBlob != null) ? (uint)metadataBlob.Length : 0;
+
+                        unsafe
+                        {
+                            fixed (byte* pMetadataBlob = metadataBlob)
+                            {
+                                // Define the event.
+                                eventHandle = provider.m_eventProvider.DefineEventHandle(
+                                    (uint)descriptor.EventId,
+                                    name,
+                                    descriptor.Keywords,
+                                    descriptor.Version,
+                                    descriptor.Level,
+                                    pMetadataBlob,
+                                    metadataLength);
+                            }
+                        }
+                    }
+                }
+            }
+
+            return eventHandle;
+        }
+#endif
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/PropertyAnalysis.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/PropertyAnalysis.cs
new file mode 100644
index 0000000000..1f07539b52
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/PropertyAnalysis.cs
@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Reflection;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: stores the per-property information obtained by
+    /// reflecting over a type.
+    /// </summary>
+    internal sealed class PropertyAnalysis
+    {
+        internal readonly string name;
+        internal readonly PropertyInfo propertyInfo;
+        internal readonly Func<PropertyValue, PropertyValue> getter;
+        internal readonly TraceLoggingTypeInfo typeInfo;
+        internal readonly EventFieldAttribute fieldAttribute;
+
+        public PropertyAnalysis(
+            string name,
+            PropertyInfo propertyInfo,
+            TraceLoggingTypeInfo typeInfo,
+            EventFieldAttribute fieldAttribute)
+        {
+            this.name = name;
+            this.propertyInfo = propertyInfo;
+            this.getter = PropertyValue.GetPropertyGetter(propertyInfo);
+            this.typeInfo = typeInfo;
+            this.fieldAttribute = fieldAttribute;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/PropertyValue.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/PropertyValue.cs
new file mode 100644
index 0000000000..ae60888493
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/PropertyValue.cs
@@ -0,0 +1,277 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Reflection;
+using System.Runtime.InteropServices;
+using System.Diagnostics;
+
+#if !ES_BUILD_AGAINST_DOTNET_V35
+using Contract = System.Diagnostics.Contracts.Contract;
+#else
+using Contract = Microsoft.Diagnostics.Contracts.Internal.Contract;
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// Holds property values of any type.  For common value types, we have inline storage so that we don't need
+    /// to box the values.  For all other types, we store the value in a single object reference field.
+    /// 
+    /// To get the value of a property quickly, use a delegate produced by <see cref="PropertyValue.GetPropertyGetter(PropertyInfo)"/>.
+    /// </summary>
+#if ES_BUILD_PN
+    [CLSCompliant(false)]
+    public
+#else
+    internal
+#endif
+    unsafe readonly struct PropertyValue
+    {
+        /// <summary>
+        /// Union of well-known value types, to avoid boxing those types.
+        /// </summary>
+        [StructLayout(LayoutKind.Explicit)]
+        public struct Scalar
+        {
+            [FieldOffset(0)]
+            public Boolean AsBoolean;
+            [FieldOffset(0)]
+            public Byte AsByte;
+            [FieldOffset(0)]
+            public SByte AsSByte;
+            [FieldOffset(0)]
+            public Char AsChar;
+            [FieldOffset(0)]
+            public Int16 AsInt16;
+            [FieldOffset(0)]
+            public UInt16 AsUInt16;
+            [FieldOffset(0)]
+            public Int32 AsInt32;
+            [FieldOffset(0)]
+            public UInt32 AsUInt32;
+            [FieldOffset(0)]
+            public Int64 AsInt64;
+            [FieldOffset(0)]
+            public UInt64 AsUInt64;
+            [FieldOffset(0)]
+            public IntPtr AsIntPtr;
+            [FieldOffset(0)]
+            public UIntPtr AsUIntPtr;
+            [FieldOffset(0)]
+            public Single AsSingle;
+            [FieldOffset(0)]
+            public Double AsDouble;
+            [FieldOffset(0)]
+            public Guid AsGuid;
+            [FieldOffset(0)]
+            public DateTime AsDateTime;
+            [FieldOffset(0)]
+            public DateTimeOffset AsDateTimeOffset;
+            [FieldOffset(0)]
+            public TimeSpan AsTimeSpan;
+            [FieldOffset(0)]
+            public Decimal AsDecimal;
+        }
+
+        // Anything not covered by the Scalar union gets stored in this reference.
+        readonly object _reference;
+        readonly Scalar _scalar;
+        readonly int _scalarLength;
+
+        private PropertyValue(object value)
+        {
+            _reference = value;
+            _scalar = default(Scalar);
+            _scalarLength = 0;
+        }
+
+        private PropertyValue(Scalar scalar, int scalarLength)
+        {
+            _reference = null;
+            _scalar = scalar;
+            _scalarLength = scalarLength;
+        }
+
+        private PropertyValue(Boolean value) : this(new Scalar() { AsBoolean = value }, sizeof(Boolean)) { }
+        private PropertyValue(Byte value) : this(new Scalar() { AsByte = value }, sizeof(Byte)) { }
+        private PropertyValue(SByte value) : this(new Scalar() { AsSByte = value }, sizeof(SByte)) { }
+        private PropertyValue(Char value) : this(new Scalar() { AsChar = value }, sizeof(Char)) { }
+        private PropertyValue(Int16 value) : this(new Scalar() { AsInt16 = value }, sizeof(Int16)) { }
+        private PropertyValue(UInt16 value) : this(new Scalar() { AsUInt16 = value }, sizeof(UInt16)) { }
+        private PropertyValue(Int32 value) : this(new Scalar() { AsInt32 = value }, sizeof(Int32)) { }
+        private PropertyValue(UInt32 value) : this(new Scalar() { AsUInt32 = value }, sizeof(UInt32)) { }
+        private PropertyValue(Int64 value) : this(new Scalar() { AsInt64 = value }, sizeof(Int64)) { }
+        private PropertyValue(UInt64 value) : this(new Scalar() { AsUInt64 = value }, sizeof(UInt64)) { }
+        private PropertyValue(IntPtr value) : this(new Scalar() { AsIntPtr = value }, sizeof(IntPtr)) { }
+        private PropertyValue(UIntPtr value) : this(new Scalar() { AsUIntPtr = value }, sizeof(UIntPtr)) { }
+        private PropertyValue(Single value) : this(new Scalar() { AsSingle = value }, sizeof(Single)) { }
+        private PropertyValue(Double value) : this(new Scalar() { AsDouble = value }, sizeof(Double)) { }
+        private PropertyValue(Guid value) : this(new Scalar() { AsGuid = value }, sizeof(Guid)) { }
+        private PropertyValue(DateTime value) : this(new Scalar() { AsDateTime = value }, sizeof(DateTime)) { }
+        private PropertyValue(DateTimeOffset value) : this(new Scalar() { AsDateTimeOffset = value }, sizeof(DateTimeOffset)) { }
+        private PropertyValue(TimeSpan value) : this(new Scalar() { AsTimeSpan = value }, sizeof(TimeSpan)) { }
+        private PropertyValue(Decimal value) : this(new Scalar() { AsDecimal = value }, sizeof(Decimal)) { }
+
+        public static Func<object, PropertyValue> GetFactory(Type type)
+        {
+            if (type == typeof(Boolean)) return value => new PropertyValue((Boolean)value);
+            if (type == typeof(Byte)) return value => new PropertyValue((Byte)value);
+            if (type == typeof(SByte)) return value => new PropertyValue((SByte)value);
+            if (type == typeof(Char)) return value => new PropertyValue((Char)value);
+            if (type == typeof(Int16)) return value => new PropertyValue((Int16)value);
+            if (type == typeof(UInt16)) return value => new PropertyValue((UInt16)value);
+            if (type == typeof(Int32)) return value => new PropertyValue((Int32)value);
+            if (type == typeof(UInt32)) return value => new PropertyValue((UInt32)value);
+            if (type == typeof(Int64)) return value => new PropertyValue((Int64)value);
+            if (type == typeof(UInt64)) return value => new PropertyValue((UInt64)value);
+            if (type == typeof(IntPtr)) return value => new PropertyValue((IntPtr)value);
+            if (type == typeof(UIntPtr)) return value => new PropertyValue((UIntPtr)value);
+            if (type == typeof(Single)) return value => new PropertyValue((Single)value);
+            if (type == typeof(Double)) return value => new PropertyValue((Double)value);
+            if (type == typeof(Guid)) return value => new PropertyValue((Guid)value);
+            if (type == typeof(DateTime)) return value => new PropertyValue((DateTime)value);
+            if (type == typeof(DateTimeOffset)) return value => new PropertyValue((DateTimeOffset)value);
+            if (type == typeof(TimeSpan)) return value => new PropertyValue((TimeSpan)value);
+            if (type == typeof(Decimal)) return value => new PropertyValue((Decimal)value);
+
+            return value => new PropertyValue(value);
+        }
+
+
+        public object ReferenceValue
+        {
+            get
+            {
+                Debug.Assert(_scalarLength == 0, "This ReflectedValue refers to an unboxed value type, not a reference type or boxed value type.");
+                return _reference;
+            }
+        }
+
+        public Scalar ScalarValue
+        {
+            get
+            {
+                Debug.Assert(_scalarLength > 0, "This ReflectedValue refers to a reference type or boxed value type, not an unboxed value type");
+                return _scalar;
+            }
+        }
+
+        public int ScalarLength
+        {
+            get
+            {
+                Debug.Assert(_scalarLength > 0, "This ReflectedValue refers to a reference type or boxed value type, not an unboxed value type");
+                return _scalarLength;
+            }
+        }
+
+        /// <summary>
+        /// Gets a delegate that gets the value of a given property.
+        /// </summary>
+        public static Func<PropertyValue, PropertyValue> GetPropertyGetter(PropertyInfo property)
+        {
+            if (property.DeclaringType.GetTypeInfo().IsValueType)
+                return GetBoxedValueTypePropertyGetter(property);
+            else
+                return GetReferenceTypePropertyGetter(property);
+        }
+
+        /// <summary>
+        /// Gets a delegate that gets the value of a property of a value type.  We unfortunately cannot avoid boxing the value type,
+        /// without making this generic over the value type.  That would result in a large number of generic instantiations, and furthermore
+        /// does not work correctly on .Net Native (we cannot express the needed instantiations in an rd.xml file).  We expect that user-defined
+        /// value types will be rare, and in any case the boxing only happens for events that are actually enabled.
+        /// </summary>
+        private static Func<PropertyValue, PropertyValue> GetBoxedValueTypePropertyGetter(PropertyInfo property)
+        {
+            var type = property.PropertyType;
+
+            if (type.GetTypeInfo().IsEnum)
+                type = Enum.GetUnderlyingType(type);
+
+            var factory = GetFactory(type);
+
+            return container => factory(property.GetValue(container.ReferenceValue));
+        }
+
+        /// <summary>
+        /// For properties of reference types, we use a generic helper class to get the value.  This enables us to use MethodInfo.CreateDelegate
+        /// to build a fast getter.  We can get away with this on .Net Native, because we really only need one runtime instantiation of the
+        /// generic type, since it's only instantiated over reference types (and thus all instances are shared).
+        /// </summary>
+        /// <param name="property"></param>
+        /// <returns></returns>
+        private static Func<PropertyValue, PropertyValue> GetReferenceTypePropertyGetter(PropertyInfo property)
+        {
+            var helper = (TypeHelper)Activator.CreateInstance(typeof(ReferenceTypeHelper<>).MakeGenericType(property.DeclaringType));
+            return helper.GetPropertyGetter(property);
+        }
+
+#if ES_BUILD_PN
+        public
+#else
+        private
+#endif
+        abstract class TypeHelper
+        {
+            public abstract Func<PropertyValue, PropertyValue> GetPropertyGetter(PropertyInfo property);
+
+            protected Delegate GetGetMethod(PropertyInfo property, Type propertyType)
+            {
+                return property.GetMethod.CreateDelegate(typeof(Func<,>).MakeGenericType(property.DeclaringType, propertyType));
+            }
+        }
+
+#if ES_BUILD_PN
+        public
+#else
+        private
+#endif
+        sealed class ReferenceTypeHelper<TContainer> : TypeHelper where TContainer : class
+        {
+            public override Func<PropertyValue, PropertyValue> GetPropertyGetter(PropertyInfo property)
+            {
+                var type = property.PropertyType;
+
+                if (!Statics.IsValueType(type))
+                {
+                    var getter = (Func<TContainer, object>)GetGetMethod(property, type);
+                    return container => new PropertyValue(getter((TContainer)container.ReferenceValue));
+                }
+                else
+                {
+                    if (type.GetTypeInfo().IsEnum)
+                        type = Enum.GetUnderlyingType(type);
+
+                    if (type == typeof(Boolean)) { var f = (Func<TContainer, Boolean>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(Byte)) { var f = (Func<TContainer, Byte>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(SByte)) { var f = (Func<TContainer, SByte>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(Char)) { var f = (Func<TContainer, Char>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(Int16)) { var f = (Func<TContainer, Int16>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(UInt16)) { var f = (Func<TContainer, UInt16>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(Int32)) { var f = (Func<TContainer, Int32>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(UInt32)) { var f = (Func<TContainer, UInt32>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(Int64)) { var f = (Func<TContainer, Int64>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(UInt64)) { var f = (Func<TContainer, UInt64>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(IntPtr)) { var f = (Func<TContainer, IntPtr>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(UIntPtr)) { var f = (Func<TContainer, UIntPtr>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(Single)) { var f = (Func<TContainer, Single>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(Double)) { var f = (Func<TContainer, Double>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(Guid)) { var f = (Func<TContainer, Guid>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(DateTime)) { var f = (Func<TContainer, DateTime>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(DateTimeOffset)) { var f = (Func<TContainer, DateTimeOffset>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(TimeSpan)) { var f = (Func<TContainer, TimeSpan>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+                    if (type == typeof(Decimal)) { var f = (Func<TContainer, Decimal>)GetGetMethod(property, type); return container => new PropertyValue(f((TContainer)container.ReferenceValue)); }
+
+                    return container => new PropertyValue(property.GetValue(container.ReferenceValue));
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/SimpleEventTypes.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/SimpleEventTypes.cs
new file mode 100644
index 0000000000..cdced968f0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/SimpleEventTypes.cs
@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using Interlocked = System.Threading.Interlocked;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: Contains the metadata needed to emit an event, optimized
+    /// for events with one top-level compile-time-typed payload object.
+    /// </summary>
+    /// <typeparam name="T">
+    /// Type of the top-level payload object. Should be EmptyStruct if the
+    /// event has no payload.
+    /// </typeparam>
+    internal static class SimpleEventTypes<T>
+    {
+        private static TraceLoggingEventTypes instance;
+
+        public static TraceLoggingEventTypes Instance
+        {
+            get { return instance ?? InitInstance(); }
+        }
+
+        private static TraceLoggingEventTypes InitInstance()
+        {
+            var info = TraceLoggingTypeInfo.GetInstance(typeof(T), null);
+            var newInstance = new TraceLoggingEventTypes(info.Name, info.Tags, new TraceLoggingTypeInfo[] { info });
+            Interlocked.CompareExchange(ref instance, newInstance, null);
+            return instance;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/SimpleTypeInfos.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/SimpleTypeInfos.cs
new file mode 100644
index 0000000000..001a8e8f05
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/SimpleTypeInfos.cs
@@ -0,0 +1,303 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using System.Diagnostics;
+
+#if !ES_BUILD_AGAINST_DOTNET_V35
+using Contract = System.Diagnostics.Contracts.Contract;
+#else
+using Contract = Microsoft.Diagnostics.Contracts.Internal.Contract;
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: Type handler for empty or unsupported types.
+    /// </summary>
+    internal sealed class NullTypeInfo : TraceLoggingTypeInfo
+    {
+        public NullTypeInfo() : base(typeof(EmptyStruct)) { }
+
+        public override void WriteMetadata(
+            TraceLoggingMetadataCollector collector,
+            string name,
+            EventFieldFormat format)
+        {
+            collector.AddGroup(name);
+        }
+
+        public override void WriteData(TraceLoggingDataCollector collector, PropertyValue value)
+        {
+            return;
+        }
+
+        public override object GetData(object value)
+        {
+            return null;
+        }
+    }
+
+    /// <summary>
+    /// Type handler for simple scalar types.
+    /// </summary>
+    sealed class ScalarTypeInfo : TraceLoggingTypeInfo
+    {
+        Func<EventFieldFormat, TraceLoggingDataType, TraceLoggingDataType> formatFunc;
+        TraceLoggingDataType nativeFormat;
+
+        private ScalarTypeInfo(
+            Type type,
+            Func<EventFieldFormat, TraceLoggingDataType, TraceLoggingDataType> formatFunc,
+            TraceLoggingDataType nativeFormat) 
+            : base(type)
+        {
+            this.formatFunc = formatFunc;
+            this.nativeFormat = nativeFormat;
+        }
+
+        public override void WriteMetadata(TraceLoggingMetadataCollector collector, string name, EventFieldFormat format)
+        {
+            collector.AddScalar(name, formatFunc(format, nativeFormat));
+        }
+
+        public override void WriteData(TraceLoggingDataCollector collector, PropertyValue value)
+        {
+            collector.AddScalar(value);
+        }
+
+        public static TraceLoggingTypeInfo Boolean() { return new ScalarTypeInfo(typeof(Boolean), Statics.Format8, TraceLoggingDataType.Boolean8); }
+        public static TraceLoggingTypeInfo Byte() { return new ScalarTypeInfo(typeof(Byte), Statics.Format8, TraceLoggingDataType.UInt8); }
+        public static TraceLoggingTypeInfo SByte() { return new ScalarTypeInfo(typeof(SByte), Statics.Format8, TraceLoggingDataType.Int8); }
+        public static TraceLoggingTypeInfo Char() { return new ScalarTypeInfo(typeof(Char), Statics.Format16, TraceLoggingDataType.Char16); }
+        public static TraceLoggingTypeInfo Int16() { return new ScalarTypeInfo(typeof(Int16), Statics.Format16, TraceLoggingDataType.Int16); }
+        public static TraceLoggingTypeInfo UInt16() { return new ScalarTypeInfo(typeof(UInt16), Statics.Format16, TraceLoggingDataType.UInt16); }
+        public static TraceLoggingTypeInfo Int32() { return new ScalarTypeInfo(typeof(Int32), Statics.Format32, TraceLoggingDataType.Int32); }
+        public static TraceLoggingTypeInfo UInt32() { return new ScalarTypeInfo(typeof(UInt32), Statics.Format32, TraceLoggingDataType.UInt32); }
+        public static TraceLoggingTypeInfo Int64() { return new ScalarTypeInfo(typeof(Int64), Statics.Format64, TraceLoggingDataType.Int64); }
+        public static TraceLoggingTypeInfo UInt64() { return new ScalarTypeInfo(typeof(UInt64), Statics.Format64, TraceLoggingDataType.UInt64); }
+        public static TraceLoggingTypeInfo IntPtr() { return new ScalarTypeInfo(typeof(IntPtr), Statics.FormatPtr, Statics.IntPtrType); }
+        public static TraceLoggingTypeInfo UIntPtr() { return new ScalarTypeInfo(typeof(UIntPtr), Statics.FormatPtr, Statics.UIntPtrType); }
+        public static TraceLoggingTypeInfo Single() { return new ScalarTypeInfo(typeof(Single), Statics.Format32, TraceLoggingDataType.Float); }
+        public static TraceLoggingTypeInfo Double() { return new ScalarTypeInfo(typeof(Double), Statics.Format64, TraceLoggingDataType.Double); }
+        public static TraceLoggingTypeInfo Guid() { return new ScalarTypeInfo(typeof(Guid), (f, t) => Statics.MakeDataType(TraceLoggingDataType.Guid, f), TraceLoggingDataType.Guid); }
+    }
+
+
+    /// <summary>
+    /// Type handler for arrays of scalars
+    /// </summary>
+    internal sealed class ScalarArrayTypeInfo : TraceLoggingTypeInfo
+    {
+        Func<EventFieldFormat, TraceLoggingDataType, TraceLoggingDataType> formatFunc;
+        TraceLoggingDataType nativeFormat;
+        int elementSize;
+
+        private ScalarArrayTypeInfo(
+            Type type,
+            Func<EventFieldFormat, TraceLoggingDataType, TraceLoggingDataType> formatFunc,
+            TraceLoggingDataType nativeFormat,
+            int elementSize) 
+            : base(type)
+        {
+            this.formatFunc = formatFunc;
+            this.nativeFormat = nativeFormat;
+            this.elementSize = elementSize;
+        }
+
+        public override void WriteMetadata(TraceLoggingMetadataCollector collector, string name, EventFieldFormat format)
+        {
+            collector.AddArray(name, formatFunc(format, nativeFormat));
+        }
+
+        public override void WriteData(TraceLoggingDataCollector collector, PropertyValue value)
+        {
+            collector.AddArray(value, elementSize);
+        }
+
+        public static TraceLoggingTypeInfo Boolean() { return new ScalarArrayTypeInfo(typeof(Boolean[]), Statics.Format8, TraceLoggingDataType.Boolean8, sizeof(Boolean)); }
+        public static TraceLoggingTypeInfo Byte() { return new ScalarArrayTypeInfo(typeof(Byte[]), Statics.Format8, TraceLoggingDataType.UInt8, sizeof(Byte)); }
+        public static TraceLoggingTypeInfo SByte() { return new ScalarArrayTypeInfo(typeof(SByte[]), Statics.Format8, TraceLoggingDataType.Int8, sizeof(SByte)); }
+        public static TraceLoggingTypeInfo Char() { return new ScalarArrayTypeInfo(typeof(Char[]), Statics.Format16, TraceLoggingDataType.Char16, sizeof(Char)); }
+        public static TraceLoggingTypeInfo Int16() { return new ScalarArrayTypeInfo(typeof(Int16[]), Statics.Format16, TraceLoggingDataType.Int16, sizeof(Int16)); }
+        public static TraceLoggingTypeInfo UInt16() { return new ScalarArrayTypeInfo(typeof(UInt16[]), Statics.Format16, TraceLoggingDataType.UInt16, sizeof(UInt16)); }
+        public static TraceLoggingTypeInfo Int32() { return new ScalarArrayTypeInfo(typeof(Int32[]), Statics.Format32, TraceLoggingDataType.Int32, sizeof(Int32)); }
+        public static TraceLoggingTypeInfo UInt32() { return new ScalarArrayTypeInfo(typeof(UInt32[]), Statics.Format32, TraceLoggingDataType.UInt32, sizeof(UInt32)); }
+        public static TraceLoggingTypeInfo Int64() { return new ScalarArrayTypeInfo(typeof(Int64[]), Statics.Format64, TraceLoggingDataType.Int64, sizeof(Int64)); }
+        public static TraceLoggingTypeInfo UInt64() { return new ScalarArrayTypeInfo(typeof(UInt64[]), Statics.Format64, TraceLoggingDataType.UInt64, sizeof(UInt64)); }
+        public static TraceLoggingTypeInfo IntPtr() { return new ScalarArrayTypeInfo(typeof(IntPtr[]), Statics.FormatPtr, Statics.IntPtrType, System.IntPtr.Size); }
+        public static TraceLoggingTypeInfo UIntPtr() { return new ScalarArrayTypeInfo(typeof(UIntPtr[]), Statics.FormatPtr, Statics.UIntPtrType, System.IntPtr.Size); }
+        public static TraceLoggingTypeInfo Single() { return new ScalarArrayTypeInfo(typeof(Single[]), Statics.Format32, TraceLoggingDataType.Float, sizeof(Single)); }
+        public static TraceLoggingTypeInfo Double() { return new ScalarArrayTypeInfo(typeof(Double[]), Statics.Format64, TraceLoggingDataType.Double, sizeof(Double)); }
+        public static unsafe TraceLoggingTypeInfo Guid() { return new ScalarArrayTypeInfo(typeof(Guid), (f, t) => Statics.MakeDataType(TraceLoggingDataType.Guid, f), TraceLoggingDataType.Guid, sizeof(Guid)); }
+    }
+
+    /// <summary>
+    /// TraceLogging: Type handler for String.
+    /// </summary>
+    internal sealed class StringTypeInfo : TraceLoggingTypeInfo
+    {
+        public StringTypeInfo() : base(typeof(string)) { }
+
+        public override void WriteMetadata(
+            TraceLoggingMetadataCollector collector,
+            string name,
+            EventFieldFormat format)
+        {
+            collector.AddNullTerminatedString(name, Statics.MakeDataType(TraceLoggingDataType.Utf16String, format));
+        }
+
+        public override void WriteData(TraceLoggingDataCollector collector, PropertyValue value)
+        {
+            collector.AddNullTerminatedString((string)value.ReferenceValue);
+        }
+        
+        public override object GetData(object value)
+        {
+            if(value == null)
+            {
+                return "";
+            }
+            
+            return value;
+        }
+    }
+
+    /// <summary>
+    /// TraceLogging: Type handler for DateTime.
+    /// </summary>
+    internal sealed class DateTimeTypeInfo : TraceLoggingTypeInfo
+    {
+        public DateTimeTypeInfo() : base(typeof(DateTime)) { }
+
+        public override void WriteMetadata(
+            TraceLoggingMetadataCollector collector,
+            string name,
+            EventFieldFormat format)
+        {
+            collector.AddScalar(name, Statics.MakeDataType(TraceLoggingDataType.FileTime, format));
+        }
+
+        public override void WriteData(TraceLoggingDataCollector collector, PropertyValue value)
+        {
+            DateTime dateTime = value.ScalarValue.AsDateTime;
+            const long UTCMinTicks = 504911232000000000;
+            long dateTimeTicks = 0;
+            // We cannot translate dates sooner than 1/1/1601 in UTC.
+            // To avoid getting an ArgumentOutOfRangeException we compare with 1/1/1601 DateTime ticks
+            if (dateTime.Ticks > UTCMinTicks)
+                dateTimeTicks = dateTime.ToFileTimeUtc();
+            collector.AddScalar(dateTimeTicks);
+        }
+    }
+
+    /// <summary>
+    /// TraceLogging: Type handler for DateTimeOffset.
+    /// </summary>
+    internal sealed class DateTimeOffsetTypeInfo : TraceLoggingTypeInfo
+    {
+        public DateTimeOffsetTypeInfo() : base(typeof(DateTimeOffset)) { }
+
+        public override void WriteMetadata(TraceLoggingMetadataCollector collector, string name, EventFieldFormat format)
+        {
+            var group = collector.AddGroup(name);
+            group.AddScalar("Ticks", Statics.MakeDataType(TraceLoggingDataType.FileTime, format));
+            group.AddScalar("Offset", TraceLoggingDataType.Int64);
+        }
+
+        public override void WriteData(TraceLoggingDataCollector collector, PropertyValue value)
+        {
+            var dateTimeOffset = value.ScalarValue.AsDateTimeOffset;
+            var ticks = dateTimeOffset.Ticks;
+            collector.AddScalar(ticks < 504911232000000000 ? 0 : ticks - 504911232000000000);
+            collector.AddScalar(dateTimeOffset.Offset.Ticks);
+        }
+    }
+
+    /// <summary>
+    /// TraceLogging: Type handler for TimeSpan.
+    /// </summary>
+    internal sealed class TimeSpanTypeInfo : TraceLoggingTypeInfo
+    {
+        public TimeSpanTypeInfo() : base(typeof(TimeSpan)) { }
+
+        public override void WriteMetadata(
+            TraceLoggingMetadataCollector collector,
+            string name,
+            EventFieldFormat format)
+        {
+            collector.AddScalar(name, Statics.MakeDataType(TraceLoggingDataType.Int64, format));
+        }
+
+        public override void WriteData(TraceLoggingDataCollector collector, PropertyValue value)
+        {
+            collector.AddScalar(value.ScalarValue.AsTimeSpan.Ticks);
+        }
+    }
+
+    /// <summary>
+    /// TraceLogging: Type handler for Decimal. (Note: not full-fidelity, exposed as Double.)
+    /// </summary>
+    internal sealed class DecimalTypeInfo : TraceLoggingTypeInfo
+    {
+        public DecimalTypeInfo() : base(typeof(Decimal)) { }
+
+        public override void WriteMetadata(
+            TraceLoggingMetadataCollector collector,
+            string name,
+            EventFieldFormat format)
+        {
+            collector.AddScalar(name, Statics.MakeDataType(TraceLoggingDataType.Double, format));
+        }
+
+        public override void WriteData(TraceLoggingDataCollector collector, PropertyValue value)
+        {
+            collector.AddScalar((double)value.ScalarValue.AsDecimal);
+        }
+    }
+
+    /// <summary>
+    /// TraceLogging: Type handler for Nullable.
+    /// </summary>
+    internal sealed class NullableTypeInfo : TraceLoggingTypeInfo
+    {
+        private readonly TraceLoggingTypeInfo valueInfo;
+        private readonly Func<PropertyValue, PropertyValue> hasValueGetter;
+        private readonly Func<PropertyValue, PropertyValue> valueGetter;
+
+        public NullableTypeInfo(Type type, List<Type> recursionCheck)
+            : base(type)
+        {
+            var typeArgs = type.GenericTypeArguments;
+            Debug.Assert(typeArgs.Length == 1);
+            this.valueInfo = TraceLoggingTypeInfo.GetInstance(typeArgs[0], recursionCheck);
+            this.hasValueGetter = PropertyValue.GetPropertyGetter(type.GetTypeInfo().GetDeclaredProperty("HasValue"));
+            this.valueGetter = PropertyValue.GetPropertyGetter(type.GetTypeInfo().GetDeclaredProperty("Value"));
+        }
+
+        public override void WriteMetadata(
+            TraceLoggingMetadataCollector collector,
+            string name,
+            EventFieldFormat format)
+        {
+            var group = collector.AddGroup(name);
+            group.AddScalar("HasValue", TraceLoggingDataType.Boolean8);
+            this.valueInfo.WriteMetadata(group, "Value", format);
+        }
+
+        public override void WriteData(TraceLoggingDataCollector collector, PropertyValue value)
+        {
+            var hasValue = hasValueGetter(value);
+            collector.AddScalar(hasValue);
+            var val = hasValue.ScalarValue.AsBoolean ? valueGetter(value) : valueInfo.PropertyValueFactory(Activator.CreateInstance(valueInfo.DataType));
+            this.valueInfo.WriteData(collector, val);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/Statics.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/Statics.cs
new file mode 100644
index 0000000000..05539ab4fd
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/Statics.cs
@@ -0,0 +1,728 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using System.Resources;
+using System.Runtime.CompilerServices;
+using Encoding = System.Text.Encoding;
+
+using Microsoft.Reflection;
+
+#if ES_BUILD_STANDALONE
+using Environment = Microsoft.Diagnostics.Tracing.Internal.Environment;
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: Constants and utility functions.
+    /// </summary>
+    internal static class Statics
+    {
+        #region Constants
+
+        public const byte DefaultLevel = 5;
+        public const byte TraceLoggingChannel = 0xb;
+        public const byte InTypeMask = 31;
+        public const byte InTypeFixedCountFlag = 32;
+        public const byte InTypeVariableCountFlag = 64;
+        public const byte InTypeCustomCountFlag = 96;
+        public const byte InTypeCountMask = 96;
+        public const byte InTypeChainFlag = 128;
+        public const byte OutTypeMask = 127;
+        public const byte OutTypeChainFlag = 128;
+        public const EventTags EventTagsMask = (EventTags)0xfffffff;
+
+        public static readonly TraceLoggingDataType IntPtrType = IntPtr.Size == 8
+            ? TraceLoggingDataType.Int64
+            : TraceLoggingDataType.Int32;
+        public static readonly TraceLoggingDataType UIntPtrType = IntPtr.Size == 8
+            ? TraceLoggingDataType.UInt64
+            : TraceLoggingDataType.UInt32;
+        public static readonly TraceLoggingDataType HexIntPtrType = IntPtr.Size == 8
+            ? TraceLoggingDataType.HexInt64
+            : TraceLoggingDataType.HexInt32;
+
+        #endregion
+
+        #region Metadata helpers
+
+        /// <summary>
+        /// A complete metadata chunk can be expressed as:
+        /// length16 + prefix + null-terminated-utf8-name + suffix + additionalData.
+        /// We assume that excludedData will be provided by some other means,
+        /// but that its size is known. This function returns a blob containing
+        /// length16 + prefix + name + suffix, with prefix and suffix initialized
+        /// to 0's. The length16 value is initialized to the length of the returned
+        /// blob plus additionalSize, so that the concatenation of the returned blob
+        /// plus a blob of size additionalSize constitutes a valid metadata blob.
+        /// </summary>
+        /// <param name="name">
+        /// The name to include in the blob.
+        /// </param>
+        /// <param name="prefixSize">
+        /// Amount of space to reserve before name. For provider or field blobs, this
+        /// should be 0. For event blobs, this is used for the tags field and will vary
+        /// from 1 to 4, depending on how large the tags field needs to be.
+        /// </param>
+        /// <param name="suffixSize">
+        /// Amount of space to reserve after name. For example, a provider blob with no
+        /// traits would reserve 0 extra bytes, but a provider blob with a single GroupId
+        /// field would reserve 19 extra bytes.
+        /// </param>
+        /// <param name="additionalSize">
+        /// Amount of additional data in another blob. This value will be counted in the
+        /// blob's length field, but will not be included in the returned byte[] object.
+        /// The complete blob would then be the concatenation of the returned byte[] object
+        /// with another byte[] object of length additionalSize.
+        /// </param>
+        /// <returns>
+        /// A byte[] object with the length and name fields set, with room reserved for
+        /// prefix and suffix. If additionalSize was 0, the byte[] object is a complete
+        /// blob. Otherwise, another byte[] of size additionalSize must be concatenated
+        /// with this one to form a complete blob.
+        /// </returns>
+        public static byte[] MetadataForString(
+            string name,
+            int prefixSize,
+            int suffixSize,
+            int additionalSize)
+        {
+            Statics.CheckName(name);
+            int metadataSize = Encoding.UTF8.GetByteCount(name) + 3 + prefixSize + suffixSize;
+            var metadata = new byte[metadataSize];
+            ushort totalSize = checked((ushort)(metadataSize + additionalSize));
+            metadata[0] = unchecked((byte)totalSize);
+            metadata[1] = unchecked((byte)(totalSize >> 8));
+            Encoding.UTF8.GetBytes(name, 0, name.Length, metadata, 2 + prefixSize);
+            return metadata;
+        }
+
+        /// <summary>
+        /// Serialize the low 28 bits of the tags value into the metadata stream,
+        /// starting at the index given by pos. Updates pos. Writes 1 to 4 bytes,
+        /// depending on the value of the tags variable. Usable for event tags and
+        /// field tags.
+        /// 
+        /// Note that 'metadata' can be null, in which case it only updates 'pos'.
+        /// This is useful for a two pass approach where you figure out how big to
+        /// make the array, and then you fill it in.   
+        /// </summary>
+        public static void EncodeTags(int tags, ref int pos, byte[] metadata)
+        {
+            // We transmit the low 28 bits of tags, high bits first, 7 bits at a time.
+            var tagsLeft = tags & 0xfffffff;
+            bool more;
+            do
+            {
+                byte current = (byte)((tagsLeft >> 21) & 0x7f);
+                more = (tagsLeft & 0x1fffff) != 0;
+                current |= (byte)(more ? 0x80 : 0x00);
+                tagsLeft = tagsLeft << 7;
+
+                if (metadata != null)
+                {
+                    metadata[pos] = current;
+                }
+                pos += 1;
+            }
+            while (more);
+        }
+
+        public static byte Combine(
+            int settingValue,
+            byte defaultValue)
+        {
+            unchecked
+            {
+                return (byte)settingValue == settingValue
+                    ? (byte)settingValue
+                    : defaultValue;
+            }
+        }
+
+        public static byte Combine(
+            int settingValue1,
+            int settingValue2,
+            byte defaultValue)
+        {
+            unchecked
+            {
+                return (byte)settingValue1 == settingValue1
+                    ? (byte)settingValue1
+                    : (byte)settingValue2 == settingValue2
+                    ? (byte)settingValue2
+                    : defaultValue;
+            }
+        }
+
+        public static int Combine(
+            int settingValue1,
+            int settingValue2)
+        {
+            unchecked
+            {
+                return (byte)settingValue1 == settingValue1
+                    ? settingValue1
+                    : settingValue2;
+            }
+        }
+
+        public static void CheckName(string name)
+        {
+            if (name != null && 0 <= name.IndexOf('\0'))
+            {
+                throw new ArgumentOutOfRangeException(nameof(name));
+            }
+        }
+
+        public static bool ShouldOverrideFieldName(string fieldName)
+        {
+            return (fieldName.Length <= 2 && fieldName[0] == '_');
+        }
+
+        public static TraceLoggingDataType MakeDataType(
+            TraceLoggingDataType baseType,
+            EventFieldFormat format)
+        {
+            return (TraceLoggingDataType)(((int)baseType & 0x1f) | ((int)format << 8));
+        }
+
+        /// <summary>
+        /// Adjusts the native type based on format.
+        /// - If format is default, return native.
+        /// - If format is recognized, return the canonical type for that format.
+        /// - Otherwise remove existing format from native and apply the requested format.
+        /// </summary>
+        public static TraceLoggingDataType Format8(
+            EventFieldFormat format,
+            TraceLoggingDataType native)
+        {
+            switch (format)
+            {
+                case EventFieldFormat.Default:
+                    return native;
+                case EventFieldFormat.String:
+                    return TraceLoggingDataType.Char8;
+                case EventFieldFormat.Boolean:
+                    return TraceLoggingDataType.Boolean8;
+                case EventFieldFormat.Hexadecimal:
+                    return TraceLoggingDataType.HexInt8;
+#if false 
+                case EventSourceFieldFormat.Signed:
+                    return TraceLoggingDataType.Int8;
+                case EventSourceFieldFormat.Unsigned:
+                    return TraceLoggingDataType.UInt8;
+#endif
+                default:
+                    return MakeDataType(native, format);
+            }
+        }
+
+        /// <summary>
+        /// Adjusts the native type based on format.
+        /// - If format is default, return native.
+        /// - If format is recognized, return the canonical type for that format.
+        /// - Otherwise remove existing format from native and apply the requested format.
+        /// </summary>
+        public static TraceLoggingDataType Format16(
+            EventFieldFormat format,
+            TraceLoggingDataType native)
+        {
+            switch (format)
+            {
+                case EventFieldFormat.Default:
+                    return native;
+                case EventFieldFormat.String:
+                    return TraceLoggingDataType.Char16;
+                case EventFieldFormat.Hexadecimal:
+                    return TraceLoggingDataType.HexInt16;
+#if false
+                case EventSourceFieldFormat.Port:
+                    return TraceLoggingDataType.Port;
+                case EventSourceFieldFormat.Signed:
+                    return TraceLoggingDataType.Int16;
+                case EventSourceFieldFormat.Unsigned:
+                    return TraceLoggingDataType.UInt16;
+#endif
+                default:
+                    return MakeDataType(native, format);
+            }
+        }
+
+        /// <summary>
+        /// Adjusts the native type based on format.
+        /// - If format is default, return native.
+        /// - If format is recognized, return the canonical type for that format.
+        /// - Otherwise remove existing format from native and apply the requested format.
+        /// </summary>
+        public static TraceLoggingDataType Format32(
+            EventFieldFormat format,
+            TraceLoggingDataType native)
+        {
+            switch (format)
+            {
+                case EventFieldFormat.Default:
+                    return native;
+                case EventFieldFormat.Boolean:
+                    return TraceLoggingDataType.Boolean32;
+                case EventFieldFormat.Hexadecimal:
+                    return TraceLoggingDataType.HexInt32;
+#if false 
+                case EventSourceFieldFormat.Ipv4Address:
+                    return TraceLoggingDataType.Ipv4Address;
+                case EventSourceFieldFormat.ProcessId:
+                    return TraceLoggingDataType.ProcessId;
+                case EventSourceFieldFormat.ThreadId:
+                    return TraceLoggingDataType.ThreadId;
+                case EventSourceFieldFormat.Win32Error:
+                    return TraceLoggingDataType.Win32Error;
+                case EventSourceFieldFormat.NTStatus:
+                    return TraceLoggingDataType.NTStatus;
+#endif
+                case EventFieldFormat.HResult:
+                    return TraceLoggingDataType.HResult;
+#if false 
+                case EventSourceFieldFormat.Signed:
+                    return TraceLoggingDataType.Int32;
+                case EventSourceFieldFormat.Unsigned:
+                    return TraceLoggingDataType.UInt32;
+#endif
+                default:
+                    return MakeDataType(native, format);
+            }
+        }
+
+        /// <summary>
+        /// Adjusts the native type based on format.
+        /// - If format is default, return native.
+        /// - If format is recognized, return the canonical type for that format.
+        /// - Otherwise remove existing format from native and apply the requested format.
+        /// </summary>
+        public static TraceLoggingDataType Format64(
+            EventFieldFormat format,
+            TraceLoggingDataType native)
+        {
+            switch (format)
+            {
+                case EventFieldFormat.Default:
+                    return native;
+                case EventFieldFormat.Hexadecimal:
+                    return TraceLoggingDataType.HexInt64;
+#if false 
+                case EventSourceFieldFormat.FileTime:
+                    return TraceLoggingDataType.FileTime;
+                case EventSourceFieldFormat.Signed:
+                    return TraceLoggingDataType.Int64;
+                case EventSourceFieldFormat.Unsigned:
+                    return TraceLoggingDataType.UInt64;
+#endif
+                default:
+                    return MakeDataType(native, format);
+            }
+        }
+
+        /// <summary>
+        /// Adjusts the native type based on format.
+        /// - If format is default, return native.
+        /// - If format is recognized, return the canonical type for that format.
+        /// - Otherwise remove existing format from native and apply the requested format.
+        /// </summary>
+        public static TraceLoggingDataType FormatPtr(
+            EventFieldFormat format,
+            TraceLoggingDataType native)
+        {
+            switch (format)
+            {
+                case EventFieldFormat.Default:
+                    return native;
+                case EventFieldFormat.Hexadecimal:
+                    return HexIntPtrType;
+#if false 
+                case EventSourceFieldFormat.Signed:
+                    return IntPtrType;
+                case EventSourceFieldFormat.Unsigned:
+                    return UIntPtrType;
+#endif
+                default:
+                    return MakeDataType(native, format);
+            }
+        }
+
+        #endregion
+
+        #region Reflection helpers
+
+        /*
+        All TraceLogging use of reflection APIs should go through wrappers here.
+        This helps with portability, and it also makes it easier to audit what
+        kinds of reflection operations are being done.
+        */
+
+        public static object CreateInstance(Type type, params object[] parameters)
+        {
+            return Activator.CreateInstance(type, parameters);
+        }
+
+        public static bool IsValueType(Type type)
+        {
+            bool result = type.IsValueType();
+            return result;
+        }
+
+        public static bool IsEnum(Type type)
+        {
+            bool result = type.IsEnum();
+            return result;
+        }
+
+        public static IEnumerable<PropertyInfo> GetProperties(Type type)
+        {
+            IEnumerable<PropertyInfo> result = type.GetProperties();
+            return result;
+        }
+
+        public static MethodInfo GetGetMethod(PropertyInfo propInfo)
+        {
+            MethodInfo result = propInfo.GetGetMethod();
+            return result;
+        }
+
+        public static MethodInfo GetDeclaredStaticMethod(Type declaringType, string name)
+        {
+            MethodInfo result;
+#if (ES_BUILD_PCL || ES_BUILD_PN)
+            result = declaringType.GetTypeInfo().GetDeclaredMethod(name);
+#else
+            result = declaringType.GetMethod(
+                name,
+                BindingFlags.DeclaredOnly | BindingFlags.Static | BindingFlags.NonPublic);
+#endif
+            return result;
+        }
+
+        public static bool HasCustomAttribute(
+            PropertyInfo propInfo,
+            Type attributeType)
+        {
+            bool result;
+#if (ES_BUILD_PCL || ES_BUILD_PN)
+            result = propInfo.IsDefined(attributeType);
+#else
+            var attributes = propInfo.GetCustomAttributes(
+                attributeType,
+                false);
+            result = attributes.Length != 0;
+#endif
+            return result;
+        }
+
+        public static AttributeType GetCustomAttribute<AttributeType>(PropertyInfo propInfo)
+            where AttributeType : Attribute
+        {
+            AttributeType result = null;
+#if (ES_BUILD_PCL || ES_BUILD_PN)
+            foreach (var attrib in propInfo.GetCustomAttributes<AttributeType>(false))
+            {
+                result = attrib;
+                break;
+            }
+#else
+            var attributes = propInfo.GetCustomAttributes(typeof(AttributeType), false);
+            if (attributes.Length != 0)
+            {
+                result = (AttributeType)attributes[0];
+            }
+#endif
+            return result;
+        }
+
+        public static AttributeType GetCustomAttribute<AttributeType>(Type type)
+            where AttributeType : Attribute
+        {
+            AttributeType result = null;
+#if (ES_BUILD_PCL || ES_BUILD_PN)
+            foreach (var attrib in type.GetTypeInfo().GetCustomAttributes<AttributeType>(false))
+            {
+                result = attrib;
+                break;
+            }
+#else
+            var attributes = type.GetCustomAttributes(typeof(AttributeType), false);
+            if (attributes.Length != 0)
+            {
+                result = (AttributeType)attributes[0];
+            }
+#endif
+            return result;
+        }
+
+        public static Type[] GetGenericArguments(Type type)
+        {
+            return type.GetGenericArguments();
+        }
+
+        public static Type FindEnumerableElementType(Type type)
+        {
+            Type elementType = null;
+
+            if (IsGenericMatch(type, typeof(IEnumerable<>)))
+            {
+                elementType = GetGenericArguments(type)[0];
+            }
+            else
+            {
+#if (ES_BUILD_PCL || ES_BUILD_PN)
+                var ifaceTypes = type.GetTypeInfo().ImplementedInterfaces;
+#else
+                var ifaceTypes = type.FindInterfaces(IsGenericMatch, typeof(IEnumerable<>));
+#endif
+
+                foreach (var ifaceType in ifaceTypes)
+                {
+#if (ES_BUILD_PCL || ES_BUILD_PN)
+                    if (!IsGenericMatch(ifaceType, typeof(IEnumerable<>)))
+                    {
+                        continue;
+                    }
+#endif
+
+                    if (elementType != null)
+                    {
+                        // ambiguous match. report no match at all.
+                        elementType = null;
+                        break;
+                    }
+
+                    elementType = GetGenericArguments(ifaceType)[0];
+                }
+            }
+
+            return elementType;
+        }
+
+        public static bool IsGenericMatch(Type type, object openType)
+        {
+            return type.IsGenericType() && type.GetGenericTypeDefinition() == (Type)openType;
+        }
+
+        public static Delegate CreateDelegate(Type delegateType, MethodInfo methodInfo)
+        {
+            Delegate result;
+#if (ES_BUILD_PCL || ES_BUILD_PN)
+            result = methodInfo.CreateDelegate(
+                delegateType);
+#else
+            result = Delegate.CreateDelegate(
+                delegateType,
+                methodInfo);
+#endif
+            return result;
+        }
+
+        public static TraceLoggingTypeInfo CreateDefaultTypeInfo(
+            Type dataType,
+            List<Type> recursionCheck)
+        {
+            TraceLoggingTypeInfo result;
+
+            if (recursionCheck.Contains(dataType))
+            {
+                throw new NotSupportedException(SR.EventSource_RecursiveTypeDefinition);
+            }
+
+            recursionCheck.Add(dataType);
+
+            var eventAttrib = Statics.GetCustomAttribute<EventDataAttribute>(dataType);
+            if (eventAttrib != null ||
+                Statics.GetCustomAttribute<CompilerGeneratedAttribute>(dataType) != null ||
+                IsGenericMatch(dataType, typeof(KeyValuePair<,>)))
+            {
+                var analysis = new TypeAnalysis(dataType, eventAttrib, recursionCheck);
+                result = new InvokeTypeInfo(dataType, analysis);
+            }
+            else if (dataType.IsArray)
+            {
+                var elementType = dataType.GetElementType();
+                if (elementType == typeof(Boolean))
+                {
+                    result = ScalarArrayTypeInfo.Boolean();
+                }
+                else if (elementType == typeof(Byte))
+                {
+                    result = ScalarArrayTypeInfo.Byte();
+                }
+                else if (elementType == typeof(SByte))
+                {
+                    result = ScalarArrayTypeInfo.SByte();
+                }
+                else if (elementType == typeof(Int16))
+                {
+                    result = ScalarArrayTypeInfo.Int16();
+                }
+                else if (elementType == typeof(UInt16))
+                {
+                    result = ScalarArrayTypeInfo.UInt16();
+                }
+                else if (elementType == typeof(Int32))
+                {
+                    result = ScalarArrayTypeInfo.Int32();
+                }
+                else if (elementType == typeof(UInt32))
+                {
+                    result = ScalarArrayTypeInfo.UInt32();
+                }
+                else if (elementType == typeof(Int64))
+                {
+                    result = ScalarArrayTypeInfo.Int64();
+                }
+                else if (elementType == typeof(UInt64))
+                {
+                    result = ScalarArrayTypeInfo.UInt64();
+                }
+                else if (elementType == typeof(Char))
+                {
+                    result = ScalarArrayTypeInfo.Char();
+                }
+                else if (elementType == typeof(Double))
+                {
+                    result = ScalarArrayTypeInfo.Double();
+                }
+                else if (elementType == typeof(Single))
+                {
+                    result = ScalarArrayTypeInfo.Single();
+                }
+                else if (elementType == typeof(IntPtr))
+                {
+                    result = ScalarArrayTypeInfo.IntPtr();
+                }
+                else if (elementType == typeof(UIntPtr))
+                {
+                    result = ScalarArrayTypeInfo.UIntPtr();
+                }
+                else if (elementType == typeof(Guid))
+                {
+                    result = ScalarArrayTypeInfo.Guid();
+                }
+                else
+                {
+                    result = new ArrayTypeInfo(dataType, TraceLoggingTypeInfo.GetInstance(elementType, recursionCheck));
+                }
+            }
+            else
+            {
+                if (Statics.IsEnum(dataType))
+                    dataType = Enum.GetUnderlyingType(dataType);
+
+                if (dataType == typeof(String))
+                {
+                    result = new StringTypeInfo();
+                }
+                else if (dataType == typeof(Boolean))
+                {
+                    result = ScalarTypeInfo.Boolean();
+                }
+                else if (dataType == typeof(Byte))
+                {
+                    result = ScalarTypeInfo.Byte();
+                }
+                else if (dataType == typeof(SByte))
+                {
+                    result = ScalarTypeInfo.SByte();
+                }
+                else if (dataType == typeof(Int16))
+                {
+                    result = ScalarTypeInfo.Int16();
+                }
+                else if (dataType == typeof(UInt16))
+                {
+                    result = ScalarTypeInfo.UInt16();
+                }
+                else if (dataType == typeof(Int32))
+                {
+                    result = ScalarTypeInfo.Int32();
+                }
+                else if (dataType == typeof(UInt32))
+                {
+                    result = ScalarTypeInfo.UInt32();
+                }
+                else if (dataType == typeof(Int64))
+                {
+                    result = ScalarTypeInfo.Int64();
+                }
+                else if (dataType == typeof(UInt64))
+                {
+                    result = ScalarTypeInfo.UInt64();
+                }
+                else if (dataType == typeof(Char))
+                {
+                    result = ScalarTypeInfo.Char();
+                }
+                else if (dataType == typeof(Double))
+                {
+                    result = ScalarTypeInfo.Double();
+                }
+                else if (dataType == typeof(Single))
+                {
+                    result = ScalarTypeInfo.Single();
+                }
+                else if (dataType == typeof(DateTime))
+                {
+                    result = new DateTimeTypeInfo();
+                }
+                else if (dataType == typeof(Decimal))
+                {
+                    result = new DecimalTypeInfo();
+                }
+                else if (dataType == typeof(IntPtr))
+                {
+                    result = ScalarTypeInfo.IntPtr();
+                }
+                else if (dataType == typeof(UIntPtr))
+                {
+                    result = ScalarTypeInfo.UIntPtr();
+                }
+                else if (dataType == typeof(Guid))
+                {
+                    result = ScalarTypeInfo.Guid();
+                }
+                else if (dataType == typeof(TimeSpan))
+                {
+                    result = new TimeSpanTypeInfo();
+                }
+                else if (dataType == typeof(DateTimeOffset))
+                {
+                    result = new DateTimeOffsetTypeInfo();
+                }
+                else if (dataType == typeof(EmptyStruct))
+                {
+                    result = new NullTypeInfo();
+                }
+                else if (IsGenericMatch(dataType, typeof(Nullable<>)))
+                {
+                    result = new NullableTypeInfo(dataType, recursionCheck);
+                }
+                else
+                {
+                    var elementType = FindEnumerableElementType(dataType);
+                    if (elementType != null)
+                    {
+                        result = new EnumerableTypeInfo(dataType, TraceLoggingTypeInfo.GetInstance(elementType, recursionCheck));
+                    }
+                    else
+                    {
+                        throw new ArgumentException(SR.Format(SR.EventSource_NonCompliantTypeError, dataType.Name));
+                    }
+                }
+            }
+
+            return result;
+        }
+
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingDataCollector.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingDataCollector.cs
new file mode 100644
index 0000000000..f6d0a59aa6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingDataCollector.cs
@@ -0,0 +1,115 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Security;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: Used when implementing a custom TraceLoggingTypeInfo.
+    /// The instance of this type is provided to the TypeInfo.WriteData method.
+    /// All operations are forwarded to the current thread's DataCollector.
+    /// Note that this abstraction would allow us to expose the custom
+    /// serialization system to partially-trusted code. If we end up not
+    /// making custom serialization public, or if we only expose it to
+    /// full-trust code, this abstraction is unnecessary (though it probably
+    /// doesn't hurt anything).
+    /// </summary>
+    internal unsafe class TraceLoggingDataCollector
+    {
+        internal static readonly TraceLoggingDataCollector Instance = new TraceLoggingDataCollector();
+
+        private TraceLoggingDataCollector()
+        {
+            return;
+        }
+
+        /// <summary>
+        /// Marks the start of a non-blittable array or enumerable.
+        /// </summary>
+        /// <returns>Bookmark to be passed to EndBufferedArray.</returns>
+        public int BeginBufferedArray()
+        {
+            return DataCollector.ThreadInstance.BeginBufferedArray();
+        }
+
+        /// <summary>
+        /// Marks the end of a non-blittable array or enumerable.
+        /// </summary>
+        /// <param name="bookmark">The value returned by BeginBufferedArray.</param>
+        /// <param name="count">The number of items in the array.</param>
+        public void EndBufferedArray(int bookmark, int count)
+        {
+            DataCollector.ThreadInstance.EndBufferedArray(bookmark, count);
+        }
+
+        /// <summary>
+        /// Adds the start of a group to the event.
+        /// This has no effect on the event payload, but is provided to allow
+        /// WriteMetadata and WriteData implementations to have similar
+        /// sequences of calls, allowing for easier verification of correctness.
+        /// </summary>
+        public TraceLoggingDataCollector AddGroup()
+        {
+            return this;
+        }
+
+        public void AddScalar(PropertyValue value)
+        {
+            var scalar = value.ScalarValue;
+            DataCollector.ThreadInstance.AddScalar(&scalar, value.ScalarLength);
+        }
+
+        /// <summary>
+        /// Adds an Int64 value to the event payload.
+        /// </summary>
+        /// <param name="value">Value to be added.</param>
+        public void AddScalar(long value)
+        {
+            DataCollector.ThreadInstance.AddScalar(&value, sizeof(long));
+        }
+
+        /// <summary>
+        /// Adds a Double value to the event payload.
+        /// </summary>
+        /// <param name="value">Value to be added.</param>
+        public void AddScalar(double value)
+        {
+            DataCollector.ThreadInstance.AddScalar(&value, sizeof(double));
+        }
+
+        /// <summary>
+        /// Adds a null-terminated String value to the event payload.
+        /// </summary>
+        /// <param name="value">
+        /// Value to be added. A null value is treated as a zero-length string.
+        /// </param>
+        public void AddNullTerminatedString(string value)
+        {
+            DataCollector.ThreadInstance.AddNullTerminatedString(value);
+        }
+
+        /// <summary>
+        /// Adds a counted String value to the event payload.
+        /// </summary>
+        /// <param name="value">
+        /// Value to be added. A null value is treated as a zero-length string.
+        /// </param>
+        public void AddBinary(string value)
+        {
+            DataCollector.ThreadInstance.AddBinary(value, value == null ? 0 : value.Length * 2);
+        }
+
+        public void AddArray(PropertyValue value, int elementSize)
+        {
+            Array array = (Array)value.ReferenceValue;
+            DataCollector.ThreadInstance.AddArray(array, array == null ? 0 : array.Length, elementSize);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingDataType.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingDataType.cs
new file mode 100644
index 0000000000..cc416a96d9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingDataType.cs
@@ -0,0 +1,349 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: Used when implementing a custom TraceLoggingTypeInfo.
+    /// These are passed to metadataCollector.Add to specify the low-level
+    /// type of a field in the event payload. Note that a "formatted"
+    /// TraceLoggingDataType consists of a core TraceLoggingDataType value
+    /// (a TraceLoggingDataType with a value less than 32) plus an OutType.
+    /// Any combination of TraceLoggingDataType + OutType is valid, but not
+    /// all are useful. In particular, combinations not explicitly listed
+    /// below are unlikely to be recognized by decoders, and will typically
+    /// be decoded as the corresponding core type (i.e. the decoder will
+    /// mask off any unrecognized OutType value).
+    /// </summary>
+    internal enum TraceLoggingDataType
+    {
+        /// <summary>
+        /// Core type.
+        /// Data type with no value (0-length payload).
+        /// NOTE: arrays of Nil are illegal.
+        /// NOTE: a fixed-length array of Nil is interpreted by the decoder as
+        /// a struct (obsolete but retained for backwards-compatibility).
+        /// </summary>
+        Nil = 0,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes null-terminated Char16 string.
+        /// Decoding treats as UTF-16LE string.
+        /// </summary>
+        Utf16String = 1,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes null-terminated Char8 string.
+        /// Decoding treats as MBCS string.
+        /// </summary>
+        MbcsString = 2,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 8-bit value.
+        /// Decoding treats as signed integer.
+        /// </summary>
+        Int8 = 3,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 8-bit value.
+        /// Decoding treats as unsigned integer.
+        /// </summary>
+        UInt8 = 4,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 16-bit value.
+        /// Decoding treats as signed integer.
+        /// </summary>
+        Int16 = 5,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 16-bit value.
+        /// Decoding treats as unsigned integer.
+        /// </summary>
+        UInt16 = 6,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 32-bit value.
+        /// Decoding treats as signed integer.
+        /// </summary>
+        Int32 = 7,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 32-bit value.
+        /// Decoding treats as unsigned integer.
+        /// </summary>
+        UInt32 = 8,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 64-bit value.
+        /// Decoding treats as signed integer.
+        /// </summary>
+        Int64 = 9,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 64-bit value.
+        /// Decoding treats as unsigned integer.
+        /// </summary>
+        UInt64 = 10,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 32-bit value.
+        /// Decoding treats as Float.
+        /// </summary>
+        Float = 11,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 64-bit value.
+        /// Decoding treats as Double.
+        /// </summary>
+        Double = 12,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 32-bit value.
+        /// Decoding treats as Boolean.
+        /// </summary>
+        Boolean32 = 13,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 16-bit bytecount followed by binary data.
+        /// Decoding treats as binary data.
+        /// </summary>
+        Binary = 14,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 16-byte value.
+        /// Decoding treats as GUID.
+        /// </summary>
+        Guid = 15,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 64-bit value.
+        /// Decoding treats as FILETIME.
+        /// </summary>
+        FileTime = 17,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 16-byte value.
+        /// Decoding treats as SYSTEMTIME.
+        /// </summary>
+        SystemTime = 18,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 32-bit value.
+        /// Decoding treats as hexadecimal unsigned integer.
+        /// </summary>
+        HexInt32 = 20,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 64-bit value.
+        /// Decoding treats as hexadecimal unsigned integer.
+        /// </summary>
+        HexInt64 = 21,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 16-bit bytecount followed by Char16 data.
+        /// Decoding treats as UTF-16LE string.
+        /// </summary>
+        CountedUtf16String = 22,
+
+        /// <summary>
+        /// Core type.
+        /// Encoding assumes 16-bit bytecount followed by Char8 data.
+        /// Decoding treats as MBCS string.
+        /// </summary>
+        CountedMbcsString = 23,
+
+        /// <summary>
+        /// Core type.
+        /// Special case: Struct indicates that this field plus the
+        /// subsequent N logical fields are to be considered as one logical
+        /// field (i.e. a nested structure). The OutType is used to encode N.
+        /// The maximum value for N is 127. This field has no payload by
+        /// itself, but logically contains the payload of the following N
+        /// fields. It is legal to have an array of Struct.
+        /// </summary>
+        Struct = 24,
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 16-bit value.
+        /// Decoding treats as UTF-16LE character.
+        /// </summary>
+        Char16 = UInt16 + (EventFieldFormat.String << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 8-bit value.
+        /// Decoding treats as character.
+        /// </summary>
+        Char8 = UInt8 + (EventFieldFormat.String << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 8-bit value.
+        /// Decoding treats as Boolean.
+        /// </summary>
+        Boolean8 = UInt8 + (EventFieldFormat.Boolean << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 8-bit value.
+        /// Decoding treats as hexadecimal unsigned integer.
+        /// </summary>
+        HexInt8 = UInt8 + (EventFieldFormat.Hexadecimal << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 16-bit value.
+        /// Decoding treats as hexadecimal unsigned integer.
+        /// </summary>
+        HexInt16 = UInt16 + (EventFieldFormat.Hexadecimal << 8),
+
+#if false 
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 32-bit value.
+        /// Decoding treats as process identifier.
+        /// </summary>
+        ProcessId = UInt32 + (EventSourceFieldFormat.ProcessId << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 32-bit value.
+        /// Decoding treats as thread identifier.
+        /// </summary>
+        ThreadId = UInt32 + (EventSourceFieldFormat.ThreadId << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 16-bit value.
+        /// Decoding treats as IP port.
+        /// </summary>
+        Port = UInt16 + (EventSourceFieldFormat.Port << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 32-bit value.
+        /// Decoding treats as IPv4 address.
+        /// </summary>
+        Ipv4Address = UInt32 + (EventSourceFieldFormat.Ipv4Address << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 16-bit bytecount followed by binary data.
+        /// Decoding treats as IPv6 address.
+        /// </summary>
+        Ipv6Address = Binary + (EventSourceFieldFormat.Ipv6Address << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 16-bit bytecount followed by binary data.
+        /// Decoding treats as SOCKADDR.
+        /// </summary>
+        SocketAddress = Binary + (EventSourceFieldFormat.SocketAddress << 8),
+#endif
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes null-terminated Char16 string.
+        /// Decoding treats as UTF-16LE XML string.
+        /// </summary>
+        Utf16Xml = Utf16String + (EventFieldFormat.Xml << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes null-terminated Char8 string.
+        /// Decoding treats as MBCS XML string.
+        /// </summary>
+        MbcsXml = MbcsString + (EventFieldFormat.Xml << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 16-bit bytecount followed by Char16 data.
+        /// Decoding treats as UTF-16LE XML.
+        /// </summary>
+        CountedUtf16Xml = CountedUtf16String + (EventFieldFormat.Xml << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 16-bit bytecount followed by Char8 data.
+        /// Decoding treats as MBCS XML.
+        /// </summary>
+        CountedMbcsXml = CountedMbcsString + (EventFieldFormat.Xml << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes null-terminated Char16 string.
+        /// Decoding treats as UTF-16LE JSON string.
+        /// </summary>
+        Utf16Json = Utf16String + (EventFieldFormat.Json << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes null-terminated Char8 string.
+        /// Decoding treats as MBCS JSON string.
+        /// </summary>
+        MbcsJson = MbcsString + (EventFieldFormat.Json << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 16-bit bytecount followed by Char16 data.
+        /// Decoding treats as UTF-16LE JSON.
+        /// </summary>
+        CountedUtf16Json = CountedUtf16String + (EventFieldFormat.Json << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 16-bit bytecount followed by Char8 data.
+        /// Decoding treats as MBCS JSON.
+        /// </summary>
+        CountedMbcsJson = CountedMbcsString + (EventFieldFormat.Json << 8),
+#if false 
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 32-bit value.
+        /// Decoding treats as Win32 error.
+        /// </summary>
+        Win32Error = UInt32 + (EventSourceFieldFormat.Win32Error << 8),
+
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 32-bit value.
+        /// Decoding treats as NTSTATUS.
+        /// </summary>
+        NTStatus = UInt32 + (EventSourceFieldFormat.NTStatus << 8),
+#endif
+        /// <summary>
+        /// Formatted type.
+        /// Encoding assumes 32-bit value.
+        /// Decoding treats as HRESULT.
+        /// </summary>
+        HResult = Int32 + (EventFieldFormat.HResult << 8)
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingEventSource.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingEventSource.cs
new file mode 100644
index 0000000000..ccdc8bf7c4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingEventSource.cs
@@ -0,0 +1,910 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// This program uses code hyperlinks available as part of the HyperAddin Visual Studio plug-in.
+// It is available from http://www.codeplex.com/hyperAddin 
+
+#if PLATFORM_WINDOWS
+#define FEATURE_MANAGED_ETW
+#endif // PLATFORM_WINDOWS
+
+#if ES_BUILD_STANDALONE
+#define FEATURE_MANAGED_ETW_CHANNELS
+// #define FEATURE_ADVANCED_MANAGED_ETW_CHANNELS
+#endif
+
+#if ES_BUILD_STANDALONE
+using Environment = Microsoft.Diagnostics.Tracing.Internal.Environment;
+using EventDescriptor = Microsoft.Diagnostics.Tracing.EventDescriptor;
+#endif
+
+using System;
+using System.Resources;
+using System.Runtime.InteropServices;
+using System.Security;
+using System.Collections.ObjectModel;
+using System.Collections.Concurrent;
+
+#if !ES_BUILD_AGAINST_DOTNET_V35
+using Contract = System.Diagnostics.Contracts.Contract;
+using System.Collections.Generic;
+using System.Text;
+#else
+using Contract = Microsoft.Diagnostics.Contracts.Internal.Contract;
+using System.Collections.Generic;
+using System.Text;
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    public partial class EventSource
+    {
+#if FEATURE_MANAGED_ETW
+        private byte[] providerMetadata;
+#endif
+
+#if FEATURE_PERFTRACING
+        private ConcurrentDictionary<int, IntPtr> m_eventHandleMap = new ConcurrentDictionary<int, IntPtr>();
+#endif
+
+        /// <summary>
+        /// Construct an EventSource with a given name for non-contract based events (e.g. those using the Write() API).
+        /// </summary>
+        /// <param name="eventSourceName">
+        /// The name of the event source. Must not be null.
+        /// </param>
+        public EventSource(
+            string eventSourceName)
+            : this(eventSourceName, EventSourceSettings.EtwSelfDescribingEventFormat)
+        { }
+
+        /// <summary>
+        /// Construct an EventSource with a given name for non-contract based events (e.g. those using the Write() API).
+        /// </summary>
+        /// <param name="eventSourceName">
+        /// The name of the event source. Must not be null.
+        /// </param>
+        /// <param name="config">
+        /// Configuration options for the EventSource as a whole. 
+        /// </param>
+        public EventSource(
+            string eventSourceName,
+            EventSourceSettings config)
+            : this(eventSourceName, config, null) { }
+
+        /// <summary>
+        /// Construct an EventSource with a given name for non-contract based events (e.g. those using the Write() API).
+        /// 
+        /// Also specify a list of key-value pairs called traits (you must pass an even number of strings).   
+        /// The first string is the key and the second is the value.   These are not interpreted by EventSource
+        /// itself but may be interpreted the listeners.  Can be fetched with GetTrait(string).   
+        /// </summary>
+        /// <param name="eventSourceName">
+        /// The name of the event source. Must not be null.
+        /// </param>
+        /// <param name="config">
+        /// Configuration options for the EventSource as a whole. 
+        /// </param>
+        /// <param name="traits">A collection of key-value strings (must be an even number).</param>
+        public EventSource(
+            string eventSourceName,
+            EventSourceSettings config,
+            params string[] traits)
+            : this(
+                eventSourceName == null ? new Guid() : GenerateGuidFromName(eventSourceName.ToUpperInvariant()),
+                eventSourceName,
+                config, traits)
+        {
+            if (eventSourceName == null)
+            {
+                throw new ArgumentNullException(nameof(eventSourceName));
+            }
+        }
+
+        /// <summary>
+        /// Writes an event with no fields and default options.
+        /// (Native API: EventWriteTransfer)
+        /// </summary>
+        /// <param name="eventName">The name of the event. Must not be null.</param>
+        public unsafe void Write(string eventName)
+        {
+            if (eventName == null)
+            {
+                throw new ArgumentNullException(nameof(eventName));
+            }
+
+            if (!this.IsEnabled())
+            {
+                return;
+            }
+
+            var options = new EventSourceOptions();
+            this.WriteImpl(eventName, ref options, null, null, null, SimpleEventTypes<EmptyStruct>.Instance);
+        }
+
+        /// <summary>
+        /// Writes an event with no fields.
+        /// (Native API: EventWriteTransfer)
+        /// </summary>
+        /// <param name="eventName">The name of the event. Must not be null.</param>
+        /// <param name="options">
+        /// Options for the event, such as the level, keywords, and opcode. Unset
+        /// options will be set to default values.
+        /// </param>
+        public unsafe void Write(string eventName, EventSourceOptions options)
+        {
+            if (eventName == null)
+            {
+                throw new ArgumentNullException(nameof(eventName));
+            }
+
+            if (!this.IsEnabled())
+            {
+                return;
+            }
+
+            this.WriteImpl(eventName, ref options, null, null, null, SimpleEventTypes<EmptyStruct>.Instance);
+        }
+
+        /// <summary>
+        /// Writes an event.
+        /// (Native API: EventWriteTransfer)
+        /// </summary>
+        /// <typeparam name="T">
+        /// The type that defines the event and its payload. This must be an
+        /// anonymous type or a type with an [EventData] attribute.
+        /// </typeparam>
+        /// <param name="eventName">
+        /// The name for the event. If null, the event name is automatically
+        /// determined based on T, either from the Name property of T's EventData
+        /// attribute or from typeof(T).Name.
+        /// </param>
+        /// <param name="data">
+        /// The object containing the event payload data. The type T must be
+        /// an anonymous type or a type with an [EventData] attribute. The
+        /// public instance properties of data will be written recursively to
+        /// create the fields of the event.
+        /// </param>
+        public unsafe void Write<T>(
+            string eventName,
+            T data)
+        {
+            if (!this.IsEnabled())
+            {
+                return;
+            }
+
+            var options = new EventSourceOptions();
+            this.WriteImpl(eventName, ref options, data, null, null, SimpleEventTypes<T>.Instance);
+        }
+
+        /// <summary>
+        /// Writes an event.
+        /// (Native API: EventWriteTransfer)
+        /// </summary>
+        /// <typeparam name="T">
+        /// The type that defines the event and its payload. This must be an
+        /// anonymous type or a type with an [EventData] attribute.
+        /// </typeparam>
+        /// <param name="eventName">
+        /// The name for the event. If null, the event name is automatically
+        /// determined based on T, either from the Name property of T's EventData
+        /// attribute or from typeof(T).Name.
+        /// </param>
+        /// <param name="options">
+        /// Options for the event, such as the level, keywords, and opcode. Unset
+        /// options will be set to default values.
+        /// </param>
+        /// <param name="data">
+        /// The object containing the event payload data. The type T must be
+        /// an anonymous type or a type with an [EventData] attribute. The
+        /// public instance properties of data will be written recursively to
+        /// create the fields of the event.
+        /// </param>
+        public unsafe void Write<T>(
+            string eventName,
+            EventSourceOptions options,
+            T data)
+        {
+            if (!this.IsEnabled())
+            {
+                return;
+            }
+
+            this.WriteImpl(eventName, ref options, data, null, null, SimpleEventTypes<T>.Instance);
+        }
+
+        /// <summary>
+        /// Writes an event.
+        /// This overload is for use with extension methods that wish to efficiently
+        /// forward the options or data parameter without performing an extra copy.
+        /// (Native API: EventWriteTransfer)
+        /// </summary>
+        /// <typeparam name="T">
+        /// The type that defines the event and its payload. This must be an
+        /// anonymous type or a type with an [EventData] attribute.
+        /// </typeparam>
+        /// <param name="eventName">
+        /// The name for the event. If null, the event name is automatically
+        /// determined based on T, either from the Name property of T's EventData
+        /// attribute or from typeof(T).Name.
+        /// </param>
+        /// <param name="options">
+        /// Options for the event, such as the level, keywords, and opcode. Unset
+        /// options will be set to default values.
+        /// </param>
+        /// <param name="data">
+        /// The object containing the event payload data. The type T must be
+        /// an anonymous type or a type with an [EventData] attribute. The
+        /// public instance properties of data will be written recursively to
+        /// create the fields of the event.
+        /// </param>
+        public unsafe void Write<T>(
+            string eventName,
+            ref EventSourceOptions options,
+            ref T data)
+        {
+            if (!this.IsEnabled())
+            {
+                return;
+            }
+
+            this.WriteImpl(eventName, ref options, data, null, null, SimpleEventTypes<T>.Instance);
+        }
+
+        /// <summary>
+        /// Writes an event.
+        /// This overload is meant for clients that need to manipuate the activityId
+        /// and related ActivityId for the event.  
+        /// </summary>
+        /// <typeparam name="T">
+        /// The type that defines the event and its payload. This must be an
+        /// anonymous type or a type with an [EventData] attribute.
+        /// </typeparam>
+        /// <param name="eventName">
+        /// The name for the event. If null, the event name is automatically
+        /// determined based on T, either from the Name property of T's EventData
+        /// attribute or from typeof(T).Name.
+        /// </param>
+        /// <param name="options">
+        /// Options for the event, such as the level, keywords, and opcode. Unset
+        /// options will be set to default values.
+        /// </param>
+        /// <param name="activityId">
+        /// The GUID of the activity associated with this event.
+        /// </param>
+        /// <param name="relatedActivityId">
+        /// The GUID of another activity that is related to this activity, or Guid.Empty
+        /// if there is no related activity. Most commonly, the Start operation of a
+        /// new activity specifies a parent activity as its related activity.
+        /// </param>
+        /// <param name="data">
+        /// The object containing the event payload data. The type T must be
+        /// an anonymous type or a type with an [EventData] attribute. The
+        /// public instance properties of data will be written recursively to
+        /// create the fields of the event.
+        /// </param>
+        public unsafe void Write<T>(
+            string eventName,
+            ref EventSourceOptions options,
+            ref Guid activityId,
+            ref Guid relatedActivityId,
+            ref T data)
+        {
+            if (!this.IsEnabled())
+            {
+                return;
+            }
+
+            fixed (Guid* pActivity = &activityId, pRelated = &relatedActivityId)
+            {
+                this.WriteImpl(
+                    eventName,
+                    ref options,
+                    data,
+                    pActivity,
+                    relatedActivityId == Guid.Empty ? null : pRelated,
+                    SimpleEventTypes<T>.Instance);
+            }
+        }
+
+        /// <summary>
+        /// Writes an extended event, where the values of the event are the
+        /// combined properties of any number of values. This method is
+        /// intended for use in advanced logging scenarios that support a
+        /// dynamic set of event context providers.
+        /// This method does a quick check on whether this event is enabled.
+        /// </summary>
+        /// <param name="eventName">
+        /// The name for the event. If null, the name from eventTypes is used.
+        /// (Note that providing the event name via the name parameter is slightly
+        /// less efficient than using the name from eventTypes.)
+        /// </param>
+        /// <param name="options">
+        /// Optional overrides for the event, such as the level, keyword, opcode,
+        /// activityId, and relatedActivityId. Any settings not specified by options
+        /// are obtained from eventTypes.
+        /// </param>
+        /// <param name="eventTypes">
+        /// Information about the event and the types of the values in the event.
+        /// Must not be null. Note that the eventTypes object should be created once and
+        /// saved. It should not be recreated for each event.
+        /// </param>
+        /// <param name="activityID">
+        /// A pointer to the activity ID GUID to log 
+        /// </param>
+        /// <param name="childActivityID">
+        /// A pointer to the child activity ID to log (can be null) </param>
+        /// <param name="values">
+        /// The values to include in the event. Must not be null. The number and types of
+        /// the values must match the number and types of the fields described by the
+        /// eventTypes parameter.
+        /// </param>
+        private unsafe void WriteMultiMerge(
+            string eventName,
+            ref EventSourceOptions options,
+            TraceLoggingEventTypes eventTypes,
+             Guid* activityID,
+             Guid* childActivityID,
+            params object[] values)
+        {
+            if (!this.IsEnabled())
+            {
+                return;
+            }
+            byte level = (options.valuesSet & EventSourceOptions.levelSet) != 0
+                ? options.level
+                : eventTypes.level;
+            EventKeywords keywords = (options.valuesSet & EventSourceOptions.keywordsSet) != 0
+                ? options.keywords
+                : eventTypes.keywords;
+
+            if (this.IsEnabled((EventLevel)level, keywords))
+            {
+                WriteMultiMergeInner(eventName, ref options, eventTypes, activityID, childActivityID, values);
+            }
+        }
+
+        /// <summary>
+        /// Writes an extended event, where the values of the event are the
+        /// combined properties of any number of values. This method is
+        /// intended for use in advanced logging scenarios that support a
+        /// dynamic set of event context providers.
+        /// Attention: This API does not check whether the event is enabled or not. 
+        /// Please use WriteMultiMerge to avoid spending CPU cycles for events that are 
+        /// not enabled.
+        /// </summary>
+        /// <param name="eventName">
+        /// The name for the event. If null, the name from eventTypes is used.
+        /// (Note that providing the event name via the name parameter is slightly
+        /// less efficient than using the name from eventTypes.)
+        /// </param>
+        /// <param name="options">
+        /// Optional overrides for the event, such as the level, keyword, opcode,
+        /// activityId, and relatedActivityId. Any settings not specified by options
+        /// are obtained from eventTypes.
+        /// </param>
+        /// <param name="eventTypes">
+        /// Information about the event and the types of the values in the event.
+        /// Must not be null. Note that the eventTypes object should be created once and
+        /// saved. It should not be recreated for each event.
+        /// </param>
+        /// <param name="activityID">
+        /// A pointer to the activity ID GUID to log 
+        /// </param>
+        /// <param name="childActivityID">
+        /// A pointer to the child activity ID to log (can be null)
+        /// </param>
+        /// <param name="values">
+        /// The values to include in the event. Must not be null. The number and types of
+        /// the values must match the number and types of the fields described by the
+        /// eventTypes parameter.
+        /// </param>
+        private unsafe void WriteMultiMergeInner(
+            string eventName,
+            ref EventSourceOptions options,
+            TraceLoggingEventTypes eventTypes,
+            Guid* activityID,
+            Guid* childActivityID,
+            params object[] values)
+        {
+#if FEATURE_MANAGED_ETW
+            int identity = 0;
+            byte level = (options.valuesSet & EventSourceOptions.levelSet) != 0
+                ? options.level
+                : eventTypes.level;
+            byte opcode = (options.valuesSet & EventSourceOptions.opcodeSet) != 0
+                ? options.opcode
+                : eventTypes.opcode;
+            EventTags tags = (options.valuesSet & EventSourceOptions.tagsSet) != 0
+                ? options.tags
+                : eventTypes.Tags;
+            EventKeywords keywords = (options.valuesSet & EventSourceOptions.keywordsSet) != 0
+                ? options.keywords
+                : eventTypes.keywords;
+
+            var nameInfo = eventTypes.GetNameInfo(eventName ?? eventTypes.Name, tags);
+            if (nameInfo == null)
+            {
+                return;
+            }
+            identity = nameInfo.identity;
+            EventDescriptor descriptor = new EventDescriptor(identity, level, opcode, (long)keywords);
+
+#if FEATURE_PERFTRACING
+            IntPtr eventHandle = nameInfo.GetOrCreateEventHandle(m_provider, m_eventHandleMap, descriptor, eventTypes);
+            Debug.Assert(eventHandle != IntPtr.Zero);
+#else
+            IntPtr eventHandle = IntPtr.Zero;
+#endif
+
+            var pinCount = eventTypes.pinCount;
+            var scratch = stackalloc byte[eventTypes.scratchSize];
+            var descriptors = stackalloc EventData[eventTypes.dataCount + 3];
+            for(int i = 0; i < eventTypes.dataCount + 3; i++)
+                descriptors[i] = default(EventData);
+
+            var pins = stackalloc GCHandle[pinCount];
+            for (int i = 0; i < pinCount; i++)
+                pins[i] = default(GCHandle);
+
+            fixed (byte*
+                pMetadata0 = this.providerMetadata,
+                pMetadata1 = nameInfo.nameMetadata,
+                pMetadata2 = eventTypes.typeMetadata)
+            {
+                descriptors[0].SetMetadata(pMetadata0, this.providerMetadata.Length, 2);
+                descriptors[1].SetMetadata(pMetadata1, nameInfo.nameMetadata.Length, 1);
+                descriptors[2].SetMetadata(pMetadata2, eventTypes.typeMetadata.Length, 1);
+
+#if (!ES_BUILD_PCL && !ES_BUILD_PN)
+                System.Runtime.CompilerServices.RuntimeHelpers.PrepareConstrainedRegions();
+#endif
+                try
+                {
+                    DataCollector.ThreadInstance.Enable(
+                        scratch,
+                        eventTypes.scratchSize,
+                        descriptors + 3,
+                        eventTypes.dataCount,
+                        pins,
+                        pinCount);
+
+                    for (int i = 0; i < eventTypes.typeInfos.Length; i++)
+                    {
+                        var info = eventTypes.typeInfos[i];
+                        info.WriteData(TraceLoggingDataCollector.Instance, info.PropertyValueFactory(values[i]));
+                    }
+
+                    this.WriteEventRaw(
+                        eventName,
+                        ref descriptor,
+                        eventHandle,
+                        activityID,
+                        childActivityID,
+                        (int)(DataCollector.ThreadInstance.Finish() - descriptors),
+                        (IntPtr)descriptors);
+                }
+                finally
+                {
+                    this.WriteCleanup(pins, pinCount);
+                }
+            }
+#endif // FEATURE_MANAGED_ETW
+        }
+
+        /// <summary>
+        /// Writes an extended event, where the values of the event have already
+        /// been serialized in "data".
+        /// </summary>
+        /// <param name="eventName">
+        /// The name for the event. If null, the name from eventTypes is used.
+        /// (Note that providing the event name via the name parameter is slightly
+        /// less efficient than using the name from eventTypes.)
+        /// </param>
+        /// <param name="options">
+        /// Optional overrides for the event, such as the level, keyword, opcode,
+        /// activityId, and relatedActivityId. Any settings not specified by options
+        /// are obtained from eventTypes.
+        /// </param>
+        /// <param name="eventTypes">
+        /// Information about the event and the types of the values in the event.
+        /// Must not be null. Note that the eventTypes object should be created once and
+        /// saved. It should not be recreated for each event.
+        /// </param>
+        /// <param name="activityID">
+        /// A pointer to the activity ID GUID to log 
+        /// </param>
+        /// <param name="childActivityID">
+        /// A pointer to the child activity ID to log (can be null)
+        /// </param> 
+        /// <param name="data">
+        /// The previously serialized values to include in the event. Must not be null.
+        /// The number and types of the values must match the number and types of the 
+        /// fields described by the eventTypes parameter.
+        /// </param>
+        internal unsafe void WriteMultiMerge(
+            string eventName,
+            ref EventSourceOptions options,
+            TraceLoggingEventTypes eventTypes,
+            Guid* activityID,
+            Guid* childActivityID,
+            EventData* data)
+        {
+#if FEATURE_MANAGED_ETW
+            if (!this.IsEnabled())
+            {
+                return;
+            }
+
+            fixed (EventSourceOptions* pOptions = &options)
+            {
+                EventDescriptor descriptor;
+                var nameInfo = this.UpdateDescriptor(eventName, eventTypes, ref options, out descriptor);
+                if (nameInfo == null)
+                {
+                    return;
+                }
+
+#if FEATURE_PERFTRACING
+                    IntPtr eventHandle = nameInfo.GetOrCreateEventHandle(m_provider, m_eventHandleMap, descriptor, eventTypes);
+                    Debug.Assert(eventHandle != IntPtr.Zero);
+#else
+                    IntPtr eventHandle = IntPtr.Zero;
+#endif
+
+                // We make a descriptor for each EventData, and because we morph strings to counted strings
+                // we may have 2 for each arg, so we allocate enough for this.  
+                var descriptorsLength = eventTypes.dataCount + eventTypes.typeInfos.Length * 2 + 3;
+                var descriptors = stackalloc EventData[descriptorsLength];
+                for(int i = 0; i < descriptorsLength; i++)
+                    descriptors[i] = default(EventData);
+
+                fixed (byte*
+                    pMetadata0 = this.providerMetadata,
+                    pMetadata1 = nameInfo.nameMetadata,
+                    pMetadata2 = eventTypes.typeMetadata)
+                {
+                    descriptors[0].SetMetadata(pMetadata0, this.providerMetadata.Length, 2);
+                    descriptors[1].SetMetadata(pMetadata1, nameInfo.nameMetadata.Length, 1);
+                    descriptors[2].SetMetadata(pMetadata2, eventTypes.typeMetadata.Length, 1);
+                    int numDescrs = 3;
+
+                    for (int i = 0; i < eventTypes.typeInfos.Length; i++)
+                    {
+                        descriptors[numDescrs].m_Ptr = data[i].m_Ptr;
+                        descriptors[numDescrs].m_Size = data[i].m_Size;
+
+                        // old conventions for bool is 4 bytes, but meta-data assumes 1.
+                        if (data[i].m_Size == 4 && eventTypes.typeInfos[i].DataType == typeof(bool))
+                            descriptors[numDescrs].m_Size = 1;
+
+                        numDescrs++;
+                    }
+
+                    this.WriteEventRaw(
+                        eventName,
+                        ref descriptor,
+                        eventHandle,
+                        activityID,
+                        childActivityID,
+                        numDescrs,
+                        (IntPtr)descriptors);
+                }
+            }
+#endif // FEATURE_MANAGED_ETW
+        }
+
+        private unsafe void WriteImpl(
+            string eventName,
+            ref EventSourceOptions options,
+            object data,
+            Guid* pActivityId,
+            Guid* pRelatedActivityId,
+            TraceLoggingEventTypes eventTypes)
+        {
+            try
+            {
+                fixed (EventSourceOptions* pOptions = &options)
+                {
+                    EventDescriptor descriptor;
+                    options.Opcode = options.IsOpcodeSet ? options.Opcode : GetOpcodeWithDefault(options.Opcode, eventName);
+                    var nameInfo = this.UpdateDescriptor(eventName, eventTypes, ref options, out descriptor);
+                    if (nameInfo == null)
+                    {
+                        return;
+                    }
+
+#if FEATURE_PERFTRACING
+                    IntPtr eventHandle = nameInfo.GetOrCreateEventHandle(m_provider, m_eventHandleMap, descriptor, eventTypes);
+                    Debug.Assert(eventHandle != IntPtr.Zero);
+#else
+                    IntPtr eventHandle = IntPtr.Zero;
+#endif
+
+#if FEATURE_MANAGED_ETW
+                    var pinCount = eventTypes.pinCount;
+                    var scratch = stackalloc byte[eventTypes.scratchSize];
+                    var descriptors = stackalloc EventData[eventTypes.dataCount + 3];
+                    for(int i=0; i<eventTypes.dataCount + 3; i++)
+                        descriptors[i] = default(EventData);
+
+                    var pins = stackalloc GCHandle[pinCount];
+                    for (int i = 0; i < pinCount; i++)
+                        pins[i] = default(GCHandle);
+
+                    fixed (byte*
+                        pMetadata0 = this.providerMetadata,
+                        pMetadata1 = nameInfo.nameMetadata,
+                        pMetadata2 = eventTypes.typeMetadata)
+                    {
+                        descriptors[0].SetMetadata(pMetadata0, this.providerMetadata.Length, 2);
+                        descriptors[1].SetMetadata(pMetadata1, nameInfo.nameMetadata.Length, 1);
+                        descriptors[2].SetMetadata(pMetadata2, eventTypes.typeMetadata.Length, 1);
+#endif // FEATURE_MANAGED_ETW
+
+#if (!ES_BUILD_PCL && !ES_BUILD_PN)
+                    System.Runtime.CompilerServices.RuntimeHelpers.PrepareConstrainedRegions();
+#endif
+                        EventOpcode opcode = (EventOpcode)descriptor.Opcode;
+
+                        Guid activityId = Guid.Empty;
+                        Guid relatedActivityId = Guid.Empty;
+                        if (pActivityId == null && pRelatedActivityId == null &&
+                           ((options.ActivityOptions & EventActivityOptions.Disable) == 0))
+                        {
+                            if (opcode == EventOpcode.Start)
+                            {
+                                m_activityTracker.OnStart(m_name, eventName, 0, ref activityId, ref relatedActivityId, options.ActivityOptions);
+                            }
+                            else if (opcode == EventOpcode.Stop)
+                            {
+                                m_activityTracker.OnStop(m_name, eventName, 0, ref activityId);
+                            }
+                            if (activityId != Guid.Empty)
+                                pActivityId = &activityId;
+                            if (relatedActivityId != Guid.Empty)
+                                pRelatedActivityId = &relatedActivityId;
+                        }
+
+                        try
+                        {
+#if FEATURE_MANAGED_ETW
+                            DataCollector.ThreadInstance.Enable(
+                                scratch,
+                                eventTypes.scratchSize,
+                                descriptors + 3,
+                                eventTypes.dataCount,
+                                pins,
+                                pinCount);
+
+                            var info = eventTypes.typeInfos[0];
+                            info.WriteData(TraceLoggingDataCollector.Instance, info.PropertyValueFactory(data));
+
+                            this.WriteEventRaw(
+                                eventName,
+                                ref descriptor,
+                                eventHandle,
+                                pActivityId,
+                                pRelatedActivityId,
+                                (int)(DataCollector.ThreadInstance.Finish() - descriptors),
+                                (IntPtr)descriptors);
+#endif // FEATURE_MANAGED_ETW
+
+                            // TODO enable filtering for listeners.
+                            if (m_Dispatchers != null)
+                            {
+                                var eventData = (EventPayload)(eventTypes.typeInfos[0].GetData(data));
+                                WriteToAllListeners(eventName, ref descriptor, nameInfo.tags, pActivityId, pRelatedActivityId, eventData);
+                            }
+
+                        }
+                        catch (Exception ex)
+                        {
+                            if (ex is EventSourceException)
+                                throw;
+                            else
+                                ThrowEventSourceException(eventName, ex);
+                        }
+#if FEATURE_MANAGED_ETW
+                        finally
+                        {
+                            this.WriteCleanup(pins, pinCount);
+                        }
+                    }
+#endif // FEATURE_MANAGED_ETW
+                }
+            }
+            catch (Exception ex)
+            {
+                if (ex is EventSourceException)
+                    throw;
+                else
+                    ThrowEventSourceException(eventName, ex);
+            }
+        }
+
+        private unsafe void WriteToAllListeners(string eventName, ref EventDescriptor eventDescriptor, EventTags tags, Guid* pActivityId, Guid* pChildActivityId, EventPayload payload)
+        {
+            EventWrittenEventArgs eventCallbackArgs = new EventWrittenEventArgs(this);
+            eventCallbackArgs.EventName = eventName;
+            eventCallbackArgs.m_level = (EventLevel) eventDescriptor.Level;
+            eventCallbackArgs.m_keywords = (EventKeywords) eventDescriptor.Keywords;
+            eventCallbackArgs.m_opcode = (EventOpcode) eventDescriptor.Opcode;
+            eventCallbackArgs.m_tags = tags;
+
+            // Self described events do not have an id attached. We mark it internally with -1.
+            eventCallbackArgs.EventId = -1;
+            if (pActivityId != null)
+                eventCallbackArgs.ActivityId = *pActivityId;
+            if (pChildActivityId != null)
+                eventCallbackArgs.RelatedActivityId = *pChildActivityId;
+
+            if (payload != null)
+            {
+                eventCallbackArgs.Payload = new ReadOnlyCollection<object>((IList<object>)payload.Values);
+                eventCallbackArgs.PayloadNames = new ReadOnlyCollection<string>((IList<string>)payload.Keys);
+            }
+
+            DispatchToAllListeners(-1, pActivityId, eventCallbackArgs);
+        }
+
+#if (!ES_BUILD_PCL && !ES_BUILD_PN)
+        [System.Runtime.ConstrainedExecution.ReliabilityContract(
+            System.Runtime.ConstrainedExecution.Consistency.WillNotCorruptState,
+            System.Runtime.ConstrainedExecution.Cer.Success)]
+#endif
+        [NonEvent]
+        private unsafe void WriteCleanup(GCHandle* pPins, int cPins)
+        {
+            DataCollector.ThreadInstance.Disable();
+
+            for (int i = 0; i < cPins; i++)
+            {
+                if (pPins[i].IsAllocated)
+                {
+                    pPins[i].Free();
+                }
+            }
+        }
+
+        private void InitializeProviderMetadata()
+        {
+#if FEATURE_MANAGED_ETW
+            if (m_traits != null)
+            {
+                List<byte> traitMetaData = new List<byte>(100);
+                for (int i = 0; i < m_traits.Length - 1; i += 2)
+                {
+                    if (m_traits[i].StartsWith("ETW_", StringComparison.Ordinal))
+                    {
+                        string etwTrait = m_traits[i].Substring(4);
+                        byte traitNum;
+                        if (!byte.TryParse(etwTrait, out traitNum))
+                        {
+                            if (etwTrait == "GROUP")
+                            {
+                                traitNum = 1;
+                            }
+                            else
+                            {
+                                throw new ArgumentException(SR.Format(SR.EventSource_UnknownEtwTrait, etwTrait), "traits");
+                            }
+                        }
+                        string value = m_traits[i + 1];
+                        int lenPos = traitMetaData.Count;
+                        traitMetaData.Add(0);                                           // Emit size (to be filled in later) 
+                        traitMetaData.Add(0);
+                        traitMetaData.Add(traitNum);                                    // Emit Trait number
+                        var valueLen = AddValueToMetaData(traitMetaData, value) + 3;    // Emit the value bytes +3 accounts for 3 bytes we emited above.  
+                        traitMetaData[lenPos] = unchecked((byte)valueLen);              // Fill in size
+                        traitMetaData[lenPos + 1] = unchecked((byte)(valueLen >> 8));
+                    }
+                }
+                providerMetadata = Statics.MetadataForString(this.Name, 0, traitMetaData.Count, 0);
+                int startPos = providerMetadata.Length - traitMetaData.Count;
+                foreach (var b in traitMetaData)
+                    providerMetadata[startPos++] = b;
+            }
+            else
+                providerMetadata = Statics.MetadataForString(this.Name, 0, 0, 0);
+#endif //FEATURE_MANAGED_ETW
+        }
+
+        private static int AddValueToMetaData(List<byte> metaData, string value)
+        {
+            if (value.Length == 0)
+                return 0;
+
+            int startPos = metaData.Count;
+            char firstChar = value[0];
+
+            if (firstChar == '@')
+                metaData.AddRange(Encoding.UTF8.GetBytes(value.Substring(1)));
+            else if (firstChar == '{')
+                metaData.AddRange(new Guid(value).ToByteArray());
+            else if (firstChar == '#')
+            {
+                for (int i = 1; i < value.Length; i++)
+                {
+                    if (value[i] != ' ')        // Skip spaces between bytes.  
+                    {
+                        if (!(i + 1 < value.Length))
+                        {
+                            throw new ArgumentException(SR.EventSource_EvenHexDigits, "traits");
+                        }
+                        metaData.Add((byte)(HexDigit(value[i]) * 16 + HexDigit(value[i + 1])));
+                        i++;
+                    }
+                }
+            }
+            else if ('A' <= firstChar || ' ' == firstChar)  // Is it alphabetic or space (excludes digits and most punctuation). 
+            {
+                metaData.AddRange(Encoding.UTF8.GetBytes(value));
+            }
+            else
+            {
+                throw new ArgumentException(SR.Format(SR.EventSource_IllegalValue, value), "traits");
+            }
+
+            return metaData.Count - startPos;
+        }
+
+        /// <summary>
+        /// Returns a value 0-15 if 'c' is a hexadecimal digit.   If  it throws an argument exception.  
+        /// </summary>
+        private static int HexDigit(char c)
+        {
+            if ('0' <= c && c <= '9')
+            {
+                return (c - '0');
+            }
+            if ('a' <= c)
+            {
+                c = unchecked((char)(c - ('a' - 'A')));        // Convert to lower case
+            }
+            if ('A' <= c && c <= 'F')
+            {
+                return (c - 'A' + 10);
+            }
+            
+            throw new ArgumentException(SR.Format(SR.EventSource_BadHexDigit, c), "traits");
+        }
+
+        private NameInfo UpdateDescriptor(
+            string name,
+            TraceLoggingEventTypes eventInfo,
+            ref EventSourceOptions options,
+            out EventDescriptor descriptor)
+        {
+            NameInfo nameInfo = null;
+            int identity = 0;
+            byte level = (options.valuesSet & EventSourceOptions.levelSet) != 0
+                ? options.level
+                : eventInfo.level;
+            byte opcode = (options.valuesSet & EventSourceOptions.opcodeSet) != 0
+                ? options.opcode
+                : eventInfo.opcode;
+            EventTags tags = (options.valuesSet & EventSourceOptions.tagsSet) != 0
+                ? options.tags
+                : eventInfo.Tags;
+            EventKeywords keywords = (options.valuesSet & EventSourceOptions.keywordsSet) != 0
+                ? options.keywords
+                : eventInfo.keywords;
+
+            if (this.IsEnabled((EventLevel)level, keywords))
+            {
+                nameInfo = eventInfo.GetNameInfo(name ?? eventInfo.Name, tags);
+                identity = nameInfo.identity;
+            }
+
+            descriptor = new EventDescriptor(identity, level, opcode, (long)keywords);
+            return nameInfo;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingEventTraits.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingEventTraits.cs
new file mode 100644
index 0000000000..e808a8823c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingEventTraits.cs
@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// Tags are flags that are not interpreted by EventSource but are passed along
+    /// to the EventListener. The EventListener determines the semantics of the flags.
+    /// </summary>
+    [Flags]
+    public enum EventTags
+    {
+        /// <summary>
+        /// No special traits are added to the event.
+        /// </summary>
+        None = 0,
+
+        /* Bits below 0x10000 are available for any use by the provider. */
+        /* Bits at or above 0x10000 are reserved for definition by Microsoft. */
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingEventTypes.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingEventTypes.cs
new file mode 100644
index 0000000000..8887714fdb
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingEventTypes.cs
@@ -0,0 +1,272 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using Interlocked = System.Threading.Interlocked;
+
+#if !ES_BUILD_AGAINST_DOTNET_V35
+using Contract = System.Diagnostics.Contracts.Contract;
+#else
+using Contract = Microsoft.Diagnostics.Contracts.Internal.Contract;
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: Used when calling EventSource.WriteMultiMerge.
+    /// Stores the type information to use when writing the event fields.
+    /// </summary>
+    public class TraceLoggingEventTypes
+    {
+        internal readonly TraceLoggingTypeInfo[] typeInfos;
+#if FEATURE_PERFTRACING
+        internal readonly string[] paramNames;
+#endif
+        internal readonly string name;
+        internal readonly EventTags tags;
+        internal readonly byte level;
+        internal readonly byte opcode;
+        internal readonly EventKeywords keywords;
+        internal readonly byte[] typeMetadata;
+        internal readonly int scratchSize;
+        internal readonly int dataCount;
+        internal readonly int pinCount;
+        private ConcurrentSet<KeyValuePair<string, EventTags>, NameInfo> nameInfos;
+
+        /// <summary>
+        /// Initializes a new instance of TraceLoggingEventTypes corresponding
+        /// to the name, flags, and types provided. Always uses the default
+        /// TypeInfo for each Type.
+        /// </summary>
+        /// <param name="name">
+        /// The name to use when the name parameter passed to
+        /// EventSource.Write is null. This value must not be null.
+        /// </param>
+        /// <param name="tags">
+        /// Tags to add to the event if the tags are not set via options.
+        /// </param>
+        /// <param name="types">
+        /// The types of the fields in the event. This value must not be null.
+        /// </param>
+        internal TraceLoggingEventTypes(
+            string name,
+            EventTags tags,
+            params Type[] types)
+            : this(tags, name, MakeArray(types))
+        {
+            return;
+        }
+
+        /// <summary>
+        /// Returns a new instance of TraceLoggingEventInfo corresponding to the name,
+        /// flags, and typeInfos provided.
+        /// </summary>
+        /// <param name="name">
+        /// The name to use when the name parameter passed to
+        /// EventSource.Write is null. This value must not be null.
+        /// </param>
+        /// <param name="tags">
+        /// Tags to add to the event if the tags are not set via options.
+        /// </param>
+        /// <param name="typeInfos">
+        /// The types of the fields in the event. This value must not be null.
+        /// </param>
+        /// <returns>
+        /// An instance of TraceLoggingEventInfo with DefaultName set to the specified name
+        /// and with the specified typeInfos.
+        /// </returns>
+        internal TraceLoggingEventTypes(
+            string name,
+            EventTags tags,
+            params TraceLoggingTypeInfo[] typeInfos)
+            : this(tags, name, MakeArray(typeInfos))
+        {
+            return;
+        }
+
+        internal TraceLoggingEventTypes(
+            string name,
+            EventTags tags,
+            System.Reflection.ParameterInfo[] paramInfos)
+        {
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
+            this.typeInfos = MakeArray(paramInfos);
+#if FEATURE_PERFTRACING
+            this.paramNames = MakeParamNameArray(paramInfos);
+#endif
+            this.name = name;
+            this.tags = tags;
+            this.level = Statics.DefaultLevel;
+
+            var collector = new TraceLoggingMetadataCollector();
+            for (int i = 0; i < typeInfos.Length; ++i)
+            {
+                var typeInfo = typeInfos[i];
+                this.level = Statics.Combine((int)typeInfo.Level, this.level);
+                this.opcode = Statics.Combine((int)typeInfo.Opcode, this.opcode);
+                this.keywords |= typeInfo.Keywords;
+                var paramName = paramInfos[i].Name;
+                if (Statics.ShouldOverrideFieldName(paramName))
+                {
+                    paramName = typeInfo.Name;
+                }
+                typeInfo.WriteMetadata(collector, paramName, EventFieldFormat.Default);
+            }
+
+            this.typeMetadata = collector.GetMetadata();
+            this.scratchSize = collector.ScratchSize;
+            this.dataCount = collector.DataCount;
+            this.pinCount = collector.PinCount;
+        }
+
+        private TraceLoggingEventTypes(
+            EventTags tags,
+            string defaultName,
+            TraceLoggingTypeInfo[] typeInfos)
+        {
+            if (defaultName == null)
+            {
+                throw new ArgumentNullException(nameof(defaultName));
+            }
+
+            this.typeInfos = typeInfos;
+            this.name = defaultName;
+            this.tags = tags;
+            this.level = Statics.DefaultLevel;
+
+            var collector = new TraceLoggingMetadataCollector();
+            foreach (var typeInfo in typeInfos)
+            {
+                this.level = Statics.Combine((int)typeInfo.Level, this.level);
+                this.opcode = Statics.Combine((int)typeInfo.Opcode, this.opcode);
+                this.keywords |= typeInfo.Keywords;
+                typeInfo.WriteMetadata(collector, null, EventFieldFormat.Default);
+            }
+
+            this.typeMetadata = collector.GetMetadata();
+            this.scratchSize = collector.ScratchSize;
+            this.dataCount = collector.DataCount;
+            this.pinCount = collector.PinCount;
+        }
+
+        /// <summary>
+        /// Gets the default name that will be used for events with this descriptor.
+        /// </summary>
+        internal string Name
+        {
+            get { return this.name; }
+        }
+
+        /// <summary>
+        /// Gets the default level that will be used for events with this descriptor.
+        /// </summary>
+        internal EventLevel Level
+        {
+            get { return (EventLevel)this.level; }
+        }
+
+        /// <summary>
+        /// Gets the default opcode that will be used for events with this descriptor.
+        /// </summary>
+        internal EventOpcode Opcode
+        {
+            get { return (EventOpcode)this.opcode; }
+        }
+
+        /// <summary>
+        /// Gets the default set of keywords that will added to events with this descriptor.
+        /// </summary>
+        internal EventKeywords Keywords
+        {
+            get { return (EventKeywords)this.keywords; }
+        }
+
+        /// <summary>
+        /// Gets the default tags that will be added events with this descriptor.
+        /// </summary>
+        internal EventTags Tags
+        {
+            get { return this.tags; }
+        }
+
+        internal NameInfo GetNameInfo(string name, EventTags tags)
+        {
+            var ret = this.nameInfos.TryGet(new KeyValuePair<string, EventTags>(name, tags));
+            if (ret == null)
+            {
+                ret = this.nameInfos.GetOrAdd(new NameInfo(name, tags, this.typeMetadata.Length));
+            }
+
+            return ret;
+        }
+
+        private TraceLoggingTypeInfo[] MakeArray(System.Reflection.ParameterInfo[] paramInfos)
+        {
+            if (paramInfos == null)
+            {
+                throw new ArgumentNullException(nameof(paramInfos));
+            }
+
+            var recursionCheck = new List<Type>(paramInfos.Length);
+            var result = new TraceLoggingTypeInfo[paramInfos.Length];
+            for (int i = 0; i < paramInfos.Length; ++i)
+            {
+                result[i] = TraceLoggingTypeInfo.GetInstance(paramInfos[i].ParameterType, recursionCheck);
+            }
+
+            return result;
+        }
+
+        private static TraceLoggingTypeInfo[] MakeArray(Type[] types)
+        {
+            if (types == null)
+            {
+                throw new ArgumentNullException(nameof(types));
+            }
+
+            var recursionCheck = new List<Type>(types.Length);
+            var result = new TraceLoggingTypeInfo[types.Length];
+            for (int i = 0; i < types.Length; i++)
+            {
+                result[i] = TraceLoggingTypeInfo.GetInstance(types[i], recursionCheck);
+            }
+
+            return result;
+        }
+
+        private static TraceLoggingTypeInfo[] MakeArray(
+            TraceLoggingTypeInfo[] typeInfos)
+        {
+            if (typeInfos == null)
+            {
+                throw new ArgumentNullException(nameof(typeInfos));
+            }
+
+            return (TraceLoggingTypeInfo[])typeInfos.Clone(); ;
+        }
+
+#if FEATURE_PERFTRACING
+        private static string[] MakeParamNameArray(
+            System.Reflection.ParameterInfo[] paramInfos)
+        {
+            string[] paramNames = new string[paramInfos.Length];
+            for (int i = 0; i < paramNames.Length; i++)
+            {
+                paramNames[i] = paramInfos[i].Name;
+            }
+
+            return paramNames;
+        }
+#endif
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingMetadataCollector.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingMetadataCollector.cs
new file mode 100644
index 0000000000..b5b199dbca
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingMetadataCollector.cs
@@ -0,0 +1,391 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+
+#if ES_BUILD_STANDALONE
+using Environment = Microsoft.Diagnostics.Tracing.Internal.Environment;
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: used when implementing a custom TraceLoggingTypeInfo.
+    /// An instance of this type is provided to the TypeInfo.WriteMetadata method.
+    /// </summary>
+    internal class TraceLoggingMetadataCollector
+    {
+        private readonly Impl impl;
+        private readonly FieldMetadata currentGroup;
+        private int bufferedArrayFieldCount = int.MinValue;
+
+        /// <summary>
+        /// Creates a root-level collector.
+        /// </summary>
+        internal TraceLoggingMetadataCollector()
+        {
+            this.impl = new Impl();
+        }
+
+        /// <summary>
+        /// Creates a collector for a group.
+        /// </summary>
+        /// <param name="other">Parent collector</param>
+        /// <param name="group">The field that starts the group</param>
+        private TraceLoggingMetadataCollector(
+            TraceLoggingMetadataCollector other,
+            FieldMetadata group)
+        {
+            this.impl = other.impl;
+            this.currentGroup = group;
+        }
+
+        /// <summary>
+        /// The field tags to be used for the next field.
+        /// This will be reset to None each time a field is written.
+        /// </summary>
+        internal EventFieldTags Tags
+        {
+            get;
+            set;
+        }
+
+        internal int ScratchSize
+        {
+            get { return this.impl.scratchSize; }
+        }
+
+        internal int DataCount
+        {
+            get { return this.impl.dataCount; }
+        }
+
+        internal int PinCount
+        {
+            get { return this.impl.pinCount; }
+        }
+
+        private bool BeginningBufferedArray
+        {
+            get { return this.bufferedArrayFieldCount == 0; }
+        }
+
+        /// <summary>
+        /// Call this method to add a group to the event and to return
+        /// a new metadata collector that can be used to add fields to the
+        /// group. After all of the fields in the group have been written,
+        /// switch back to the original metadata collector to add fields
+        /// outside of the group.
+        /// Special-case: if name is null, no group is created, and AddGroup
+        /// returns the original metadata collector. This is useful when
+        /// adding the top-level group for an event.
+        /// Note: do not use the original metadata collector while the group's
+        /// metadata collector is in use, and do not use the group's metadata
+        /// collector after switching back to the original.
+        /// </summary>
+        /// <param name="name">
+        /// The name of the group. If name is null, the call to AddGroup is a
+        /// no-op (collector.AddGroup(null) returns collector).
+        /// </param>
+        /// <returns>
+        /// A new metadata collector that can be used to add fields to the group.
+        /// </returns>
+        public TraceLoggingMetadataCollector AddGroup(string name)
+        {
+            TraceLoggingMetadataCollector result = this;
+
+            if (name != null || // Normal.
+                this.BeginningBufferedArray) // Error, FieldMetadata's constructor will throw the appropriate exception.
+            {
+                var newGroup = new FieldMetadata(
+                    name,
+                    TraceLoggingDataType.Struct,
+                    this.Tags,
+                    this.BeginningBufferedArray);
+                this.AddField(newGroup);
+                result = new TraceLoggingMetadataCollector(this, newGroup);
+            }
+
+            return result;
+        }
+
+        /// <summary>
+        /// Adds a scalar field to an event.
+        /// </summary>
+        /// <param name="name">
+        /// The name to use for the added field. This value must not be null.
+        /// </param>
+        /// <param name="type">
+        /// The type code for the added field. This must be a fixed-size type
+        /// (e.g. string types are not supported).
+        /// </param>
+        public void AddScalar(string name, TraceLoggingDataType type)
+        {
+            int size;
+            switch ((TraceLoggingDataType)((int)type & Statics.InTypeMask))
+            {
+                case TraceLoggingDataType.Int8:
+                case TraceLoggingDataType.UInt8:
+                case TraceLoggingDataType.Char8:
+                    size = 1;
+                    break;
+                case TraceLoggingDataType.Int16:
+                case TraceLoggingDataType.UInt16:
+                case TraceLoggingDataType.Char16:
+                    size = 2;
+                    break;
+                case TraceLoggingDataType.Int32:
+                case TraceLoggingDataType.UInt32:
+                case TraceLoggingDataType.HexInt32:
+                case TraceLoggingDataType.Float:
+                case TraceLoggingDataType.Boolean32:
+                    size = 4;
+                    break;
+                case TraceLoggingDataType.Int64:
+                case TraceLoggingDataType.UInt64:
+                case TraceLoggingDataType.HexInt64:
+                case TraceLoggingDataType.Double:
+                case TraceLoggingDataType.FileTime:
+                    size = 8;
+                    break;
+                case TraceLoggingDataType.Guid:
+                case TraceLoggingDataType.SystemTime:
+                    size = 16;
+                    break;
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(type));
+            }
+
+            this.impl.AddScalar(size);
+            this.AddField(new FieldMetadata(name, type, this.Tags, this.BeginningBufferedArray));
+        }
+
+        /// <summary>
+        /// Adds a binary-format field to an event.
+        /// Compatible with core types: Binary, CountedUtf16String, CountedMbcsString.
+        /// Compatible with dataCollector methods: AddBinary(string), AddArray(Any8bitType[]).
+        /// </summary>
+        /// <param name="name">
+        /// The name to use for the added field. This value must not be null.
+        /// </param>
+        /// <param name="type">
+        /// The type code for the added field. This must be a Binary or CountedString type.
+        /// </param>
+        public void AddBinary(string name, TraceLoggingDataType type)
+        {
+            switch ((TraceLoggingDataType)((int)type & Statics.InTypeMask))
+            {
+                case TraceLoggingDataType.Binary:
+                case TraceLoggingDataType.CountedMbcsString:
+                case TraceLoggingDataType.CountedUtf16String:
+                    break;
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(type));
+            }
+
+            this.impl.AddScalar(2);
+            this.impl.AddNonscalar();
+            this.AddField(new FieldMetadata(name, type, this.Tags, this.BeginningBufferedArray));
+        }
+
+        /// <summary>
+        /// Adds a null-terminated string field to an event.
+        /// Compatible with core types: Utf16String, MbcsString.
+        /// Compatible with dataCollector method: AddNullTerminatedString(string).
+        /// </summary>
+        /// <param name="name">
+        /// The name to use for the added field. This value must not be null.
+        /// </param>
+        /// <param name="type">
+        /// The type code for the added field. This must be a null-terminated string type.
+        /// </param>
+        public void AddNullTerminatedString(string name, TraceLoggingDataType type)
+        {
+            switch ((TraceLoggingDataType)((int)type & Statics.InTypeMask))
+            {
+                case TraceLoggingDataType.Utf16String:
+                    break;
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(type));
+            }
+
+            this.impl.AddNonscalar();
+            this.AddField(new FieldMetadata(name, type, this.Tags, this.BeginningBufferedArray));
+        }
+
+        /// <summary>
+        /// Adds an array field to an event.
+        /// </summary>
+        /// <param name="name">
+        /// The name to use for the added field. This value must not be null.
+        /// </param>
+        /// <param name="type">
+        /// The type code for the added field. This must be a fixed-size type.
+        /// </param>
+        public void AddArray(string name, TraceLoggingDataType type)
+        {
+            switch ((TraceLoggingDataType)((int)type & Statics.InTypeMask))
+            {
+                case TraceLoggingDataType.Int8:
+                case TraceLoggingDataType.UInt8:
+                case TraceLoggingDataType.Int16:
+                case TraceLoggingDataType.UInt16:
+                case TraceLoggingDataType.Int32:
+                case TraceLoggingDataType.UInt32:
+                case TraceLoggingDataType.Int64:
+                case TraceLoggingDataType.UInt64:
+                case TraceLoggingDataType.Float:
+                case TraceLoggingDataType.Double:
+                case TraceLoggingDataType.Boolean32:
+                case TraceLoggingDataType.Guid:
+                case TraceLoggingDataType.FileTime:
+                case TraceLoggingDataType.HexInt32:
+                case TraceLoggingDataType.HexInt64:
+                case TraceLoggingDataType.Char16:
+                case TraceLoggingDataType.Char8:
+                    break;
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(type));
+            }
+
+            if (this.BeginningBufferedArray)
+            {
+                throw new NotSupportedException(SR.EventSource_NotSupportedNestedArraysEnums);
+            }
+
+            this.impl.AddScalar(2);
+            this.impl.AddNonscalar();
+            this.AddField(new FieldMetadata(name, type, this.Tags, true));
+        }
+
+        public void BeginBufferedArray()
+        {
+            if (this.bufferedArrayFieldCount >= 0)
+            {
+                throw new NotSupportedException(SR.EventSource_NotSupportedNestedArraysEnums);
+            }
+
+            this.bufferedArrayFieldCount = 0;
+            this.impl.BeginBuffered();
+        }
+
+        public void EndBufferedArray()
+        {
+            if (this.bufferedArrayFieldCount != 1)
+            {
+                throw new InvalidOperationException(SR.EventSource_IncorrentlyAuthoredTypeInfo);
+            }
+
+            this.bufferedArrayFieldCount = int.MinValue;
+            this.impl.EndBuffered();
+        }
+
+        /// <summary>
+        /// Adds a custom-serialized field to an event.
+        /// </summary>
+        /// <param name="name">
+        /// The name to use for the added field. This value must not be null.
+        /// </param>
+        /// <param name="type">The encoding type for the field.</param>
+        /// <param name="metadata">Additional information needed to decode the field, if any.</param>
+        public void AddCustom(string name, TraceLoggingDataType type, byte[] metadata)
+        {
+            if (this.BeginningBufferedArray)
+            {
+                throw new NotSupportedException(SR.EventSource_NotSupportedCustomSerializedData);
+            }
+
+            this.impl.AddScalar(2);
+            this.impl.AddNonscalar();
+            this.AddField(new FieldMetadata(
+                name,
+                type,
+                this.Tags,
+                metadata));
+        }
+
+        internal byte[] GetMetadata()
+        {
+            var size = this.impl.Encode(null);
+            var metadata = new byte[size];
+            this.impl.Encode(metadata);
+            return metadata;
+        }
+
+        private void AddField(FieldMetadata fieldMetadata)
+        {
+            this.Tags = EventFieldTags.None;
+            this.bufferedArrayFieldCount++;
+            this.impl.fields.Add(fieldMetadata);
+
+            if (this.currentGroup != null)
+            {
+                this.currentGroup.IncrementStructFieldCount();
+            }
+        }
+
+        private class Impl
+        {
+            internal readonly List<FieldMetadata> fields = new List<FieldMetadata>();
+            internal short scratchSize;
+            internal sbyte dataCount;
+            internal sbyte pinCount;
+            private int bufferNesting;
+            private bool scalar;
+
+            public void AddScalar(int size)
+            {
+                if (this.bufferNesting == 0)
+                {
+                    if (!this.scalar)
+                    {
+                        this.dataCount = checked((sbyte)(this.dataCount + 1));
+                    }
+
+                    this.scalar = true;
+                    this.scratchSize = checked((short)(this.scratchSize + size));
+                }
+            }
+
+            public void AddNonscalar()
+            {
+                if (this.bufferNesting == 0)
+                {
+                    this.scalar = false;
+                    this.pinCount = checked((sbyte)(this.pinCount + 1));
+                    this.dataCount = checked((sbyte)(this.dataCount + 1));
+                }
+            }
+
+            public void BeginBuffered()
+            {
+                if (this.bufferNesting == 0)
+                {
+                    this.AddNonscalar();
+                }
+
+                this.bufferNesting++;
+            }
+
+            public void EndBuffered()
+            {
+                this.bufferNesting--;
+            }
+
+            public int Encode(byte[] metadata)
+            {
+                int size = 0;
+
+                foreach (var field in this.fields)
+                {
+                    field.Encode(ref size, metadata);
+                }
+
+                return size;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingTypeInfo.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingTypeInfo.cs
new file mode 100644
index 0000000000..511a4fe480
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TraceLoggingTypeInfo.cs
@@ -0,0 +1,205 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+
+#if !ES_BUILD_AGAINST_DOTNET_V35
+using Contract = System.Diagnostics.Contracts.Contract;
+#else
+using Contract = Microsoft.Diagnostics.Contracts.Internal.Contract;
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: used when implementing a custom TraceLoggingTypeInfo.
+    /// Non-generic base class for TraceLoggingTypeInfo&lt;DataType>. Do not derive
+    /// from this class. Instead, derive from TraceLoggingTypeInfo&lt;DataType>.
+    /// </summary>
+    internal abstract class TraceLoggingTypeInfo
+    {
+        private readonly string name;
+        private readonly EventKeywords keywords;
+        private readonly EventLevel level = (EventLevel)(-1);
+        private readonly EventOpcode opcode = (EventOpcode)(-1);
+        private readonly EventTags tags;
+        private readonly Type dataType;
+        private readonly Func<object, PropertyValue> propertyValueFactory;
+
+        internal TraceLoggingTypeInfo(Type dataType)
+        {
+            if (dataType == null)
+            {
+                throw new ArgumentNullException(nameof(dataType));
+            }
+
+            this.name = dataType.Name;
+            this.dataType = dataType;
+            this.propertyValueFactory = PropertyValue.GetFactory(dataType);
+        }
+
+        internal TraceLoggingTypeInfo(
+            Type dataType,
+            string name,
+            EventLevel level,
+            EventOpcode opcode,
+            EventKeywords keywords,
+            EventTags tags)
+        {
+            if (dataType == null)
+            {
+                throw new ArgumentNullException(nameof(dataType));
+            }
+
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
+            Statics.CheckName(name);
+
+            this.name = name;
+            this.keywords = keywords;
+            this.level = level;
+            this.opcode = opcode;
+            this.tags = tags;
+            this.dataType = dataType;
+            this.propertyValueFactory = PropertyValue.GetFactory(dataType);
+        }
+
+        /// <summary>
+        /// Gets the name to use for the event if this type is the top-level type,
+        /// or the name to use for an implicitly-named field.
+        /// Never null.
+        /// </summary>
+        public string Name
+        {
+            get { return this.name; }
+        }
+
+        /// <summary>
+        /// Gets the event level associated with this type. Any value in the range 0..255
+        /// is an associated event level. Any value outside the range 0..255 is invalid and
+        /// indicates that this type has no associated event level.
+        /// </summary>
+        public EventLevel Level
+        {
+            get { return this.level; }
+        }
+
+        /// <summary>
+        /// Gets the event opcode associated with this type. Any value in the range 0..255
+        /// is an associated event opcode. Any value outside the range 0..255 is invalid and
+        /// indicates that this type has no associated event opcode.
+        /// </summary>
+        public EventOpcode Opcode
+        {
+            get { return this.opcode; }
+        }
+
+        /// <summary>
+        /// Gets the keyword(s) associated with this type.
+        /// </summary>
+        public EventKeywords Keywords
+        {
+            get { return this.keywords; }
+        }
+
+        /// <summary>
+        /// Gets the event tags associated with this type.
+        /// </summary>
+        public EventTags Tags
+        {
+            get { return this.tags; }
+        }
+
+        internal Type DataType
+        {
+            get { return this.dataType; }
+        }
+
+        internal Func<object, PropertyValue> PropertyValueFactory
+        {
+            get { return this.propertyValueFactory; }
+        }
+
+        /// <summary>
+        /// When overridden by a derived class, writes the metadata (schema) for
+        /// this type. Note that the sequence of operations in WriteMetadata should be
+        /// essentially identical to the sequence of operations in
+        /// WriteData/WriteObjectData. Otherwise, the metadata and data will not match,
+        /// which may cause trouble when decoding the event.
+        /// </summary>
+        /// <param name="collector">
+        /// The object that collects metadata for this object's type. Metadata is written
+        /// by calling methods on the collector object. Note that if the type contains
+        /// sub-objects, the implementation of this method may need to call the
+        /// WriteMetadata method for the type of the sub-object, e.g. by calling
+        /// TraceLoggingTypeInfo&lt;SubType&gt;.Instance.WriteMetadata(...).
+        /// </param>
+        /// <param name="name">
+        /// The name of the property that contains an object of this type, or null if this
+        /// object is being written as a top-level object of an event. Typical usage
+        /// is to pass this value to collector.AddGroup.
+        /// </param>
+        /// <param name="format">
+        /// The format attribute for the field that contains an object of this type.
+        /// </param>
+        public abstract void WriteMetadata(
+            TraceLoggingMetadataCollector collector,
+            string name,
+            EventFieldFormat format);
+
+        /// <summary>
+        /// Refer to TraceLoggingTypeInfo.WriteObjectData for information about this
+        /// method.
+        /// </summary>
+        /// <param name="collector">
+        /// Refer to TraceLoggingTypeInfo.WriteObjectData for information about this
+        /// method.
+        /// </param>
+        /// <param name="value">
+        /// Refer to TraceLoggingTypeInfo.WriteObjectData for information about this
+        /// method.
+        /// </param>
+        public abstract void WriteData(
+            TraceLoggingDataCollector collector,
+            PropertyValue value);
+
+        /// <summary>
+        /// Fetches the event parameter data for internal serialization. 
+        /// </summary>
+        /// <param name="value"></param>
+        /// <returns></returns>
+        public virtual object GetData(object value)
+        {
+            return value;
+        }
+
+        [ThreadStatic] // per-thread cache to avoid synchronization
+        private static Dictionary<Type, TraceLoggingTypeInfo> threadCache;
+
+        public static TraceLoggingTypeInfo GetInstance(Type type, List<Type> recursionCheck)
+        {
+            var cache = threadCache ?? (threadCache = new Dictionary<Type, TraceLoggingTypeInfo>());
+
+            TraceLoggingTypeInfo instance;
+            if (!cache.TryGetValue(type, out instance))
+            {
+                if (recursionCheck == null)
+                    recursionCheck = new List<Type>();
+                var recursionCheckCount = recursionCheck.Count;
+                instance = Statics.CreateDefaultTypeInfo(type, recursionCheck);
+                cache[type] = instance;
+                recursionCheck.RemoveRange(recursionCheckCount, recursionCheck.Count - recursionCheckCount);
+            }
+            return instance;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TypeAnalysis.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TypeAnalysis.cs
new file mode 100644
index 0000000000..42cdde5f6a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TypeAnalysis.cs
@@ -0,0 +1,103 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    /// <summary>
+    /// TraceLogging: stores the per-type information obtained by reflecting over a type.
+    /// </summary>
+    internal sealed class TypeAnalysis
+    {
+        internal readonly PropertyAnalysis[] properties;
+        internal readonly string name;
+        internal readonly EventKeywords keywords;
+        internal readonly EventLevel level = (EventLevel)(-1);
+        internal readonly EventOpcode opcode = (EventOpcode)(-1);
+        internal readonly EventTags tags;
+
+        public TypeAnalysis(
+            Type dataType,
+            EventDataAttribute eventAttrib,
+            List<Type> recursionCheck)
+        {
+            var propertyInfos = Statics.GetProperties(dataType);
+            var propertyList = new List<PropertyAnalysis>();
+
+            foreach (var propertyInfo in propertyInfos)
+            {
+                if (Statics.HasCustomAttribute(propertyInfo, typeof(EventIgnoreAttribute)))
+                {
+                    continue;
+                }
+
+                if (!propertyInfo.CanRead ||
+                    propertyInfo.GetIndexParameters().Length != 0)
+                {
+                    continue;
+                }
+
+                MethodInfo getterInfo = Statics.GetGetMethod(propertyInfo);
+                if (getterInfo == null)
+                {
+                    continue;
+                }
+
+                if (getterInfo.IsStatic || !getterInfo.IsPublic)
+                {
+                    continue;
+                }
+
+                var propertyType = propertyInfo.PropertyType;
+                var propertyTypeInfo = TraceLoggingTypeInfo.GetInstance(propertyType, recursionCheck);
+                var fieldAttribute = Statics.GetCustomAttribute<EventFieldAttribute>(propertyInfo);
+
+                string propertyName =
+                    fieldAttribute != null && fieldAttribute.Name != null
+                    ? fieldAttribute.Name
+                    : Statics.ShouldOverrideFieldName(propertyInfo.Name)
+                    ? propertyTypeInfo.Name
+                    : propertyInfo.Name;
+                propertyList.Add(new PropertyAnalysis(
+                    propertyName,
+                    propertyInfo,
+                    propertyTypeInfo,
+                    fieldAttribute));
+            }
+
+            this.properties = propertyList.ToArray();
+
+            foreach (var property in this.properties)
+            {
+                var typeInfo = property.typeInfo;
+                this.level = (EventLevel)Statics.Combine((int)typeInfo.Level, (int)this.level);
+                this.opcode = (EventOpcode)Statics.Combine((int)typeInfo.Opcode, (int)this.opcode);
+                this.keywords |= typeInfo.Keywords;
+                this.tags |= typeInfo.Tags;
+            }
+
+            if (eventAttrib != null)
+            {
+                this.level = (EventLevel)Statics.Combine((int)eventAttrib.Level, (int)this.level);
+                this.opcode = (EventOpcode)Statics.Combine((int)eventAttrib.Opcode, (int)this.opcode);
+                this.keywords |= eventAttrib.Keywords;
+                this.tags |= eventAttrib.Tags;
+                this.name = eventAttrib.Name;
+            }
+
+            if (this.name == null)
+            {
+                this.name = dataType.Name;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/Winmeta.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/Winmeta.cs
new file mode 100644
index 0000000000..c60ca5b365
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/Winmeta.cs
@@ -0,0 +1,187 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+** Purpose: 
+** Contains eventing constants defined by the Windows 
+** environment.
+** 
+============================================================*/
+#if ES_BUILD_STANDALONE
+#define FEATURE_MANAGED_ETW_CHANNELS
+#endif
+
+#if ES_BUILD_STANDALONE
+namespace Microsoft.Diagnostics.Tracing
+#else
+namespace System.Diagnostics.Tracing
+#endif
+{
+    using System;
+
+    /// <summary>
+    /// WindowsEventLevel. Custom values must be in the range from 16 through 255
+    /// </summary>
+    public enum EventLevel
+    {
+        /// <summary>
+        /// Log always
+        /// </summary>
+        LogAlways = 0,
+        /// <summary>
+        /// Only critical errors
+        /// </summary>
+        Critical,
+        /// <summary>
+        /// All errors, including previous levels
+        /// </summary>
+        Error,
+        /// <summary>
+        /// All warnings, including previous levels
+        /// </summary>
+        Warning,
+        /// <summary>
+        /// All informational events, including previous levels
+        /// </summary>
+        Informational,
+        /// <summary>
+        /// All events, including previous levels 
+        /// </summary>
+        Verbose
+    }
+    /// <summary>
+    /// WindowsEventTask. Custom values must be in the range from 1 through 65534
+    /// </summary>
+    public enum EventTask
+    {
+        /// <summary>
+        /// Undefined task
+        /// </summary>
+        None = 0
+    }
+    /// <summary>
+    /// EventOpcode. Custom values must be in the range from 11 through 239
+    /// </summary>
+    public enum EventOpcode
+    {
+        /// <summary>
+        /// An informational event
+        /// </summary>
+        Info = 0,
+        /// <summary>
+        /// An activity start event
+        /// </summary>
+        Start,
+        /// <summary>
+        /// An activity end event 
+        /// </summary>
+        Stop,
+        /// <summary>
+        /// A trace collection start event
+        /// </summary>
+        DataCollectionStart,
+        /// <summary>
+        /// A trace collection end event
+        /// </summary>
+        DataCollectionStop,
+        /// <summary>
+        /// An extensional event
+        /// </summary>
+        Extension,
+        /// <summary>
+        /// A reply event
+        /// </summary>
+        Reply,
+        /// <summary>
+        /// An event representing the activity resuming from the suspension
+        /// </summary>
+        Resume,
+        /// <summary>
+        /// An event representing the activity is suspended, pending another activity's completion
+        /// </summary>
+        Suspend,
+        /// <summary>
+        /// An event representing the activity is transferred to another component, and can continue to work
+        /// </summary>
+        Send,
+        /// <summary>
+        /// An event representing receiving an activity transfer from another component 
+        /// </summary>
+        Receive = 240
+    }
+
+    // Added for CLR V4
+    /// <summary>
+    /// EventChannel. Custom values must be in the range from 16 through 255. Currently only predefined values allowed.
+    /// </summary>
+    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1028:EnumStorageShouldBeInt32", Justification = "Backwards compatibility")]
+    public enum EventChannel : byte
+    {
+        /// <summary>
+        /// No channel
+        /// </summary>
+        None = 0,
+        // Channels 1 - 15 are reserved...
+        /// <summary>The admin channel</summary>
+        Admin = 16,
+        /// <summary>The operational channel</summary>
+        Operational = 17,
+        /// <summary>The analytic channel</summary>
+        Analytic = 18,
+        /// <summary>The debug channel</summary>
+        Debug = 19,
+
+    };
+
+    /// <summary>
+    /// EventOpcode
+    /// </summary>
+    [Flags]
+    public enum EventKeywords : long
+    {
+        /// <summary>
+        /// No events. 
+        /// </summary>
+        None = 0x0,
+        /// <summary>
+        /// All Events 
+        /// </summary>
+        All = ~0,
+        /// <summary>
+        /// Telemetry events
+        /// </summary>
+        MicrosoftTelemetry = 0x02000000000000,
+        /// <summary>
+        /// WDI context events
+        /// </summary>
+        WdiContext = 0x02000000000000,
+        /// <summary>
+        /// WDI diagnostic events
+        /// </summary>
+        WdiDiagnostic = 0x04000000000000,
+        /// <summary>
+        /// SQM events
+        /// </summary>
+        Sqm = 0x08000000000000,
+        /// <summary>
+        /// Failed security audits
+        /// </summary>
+        AuditFailure = 0x10000000000000,
+        /// <summary>
+        /// Successful security audits
+        /// </summary>
+        AuditSuccess = 0x20000000000000,
+        /// <summary>
+        /// Transfer events where the related Activity ID is a computed value and not a GUID
+        /// N.B. The correct value for this field is 0x40000000000000.
+        /// </summary>
+        CorrelationHint = 0x10000000000000,
+        /// <summary>
+        /// Events raised using classic eventlog API
+        /// </summary>
+        EventLogClassic = 0x80000000000000
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/DivideByZeroException.cs b/src/System.Private.CoreLib/shared/System/DivideByZeroException.cs
new file mode 100644
index 0000000000..b309695ff3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/DivideByZeroException.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception class for bad arithmetic conditions!
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class DivideByZeroException : ArithmeticException
+    {
+        public DivideByZeroException()
+            : base(SR.Arg_DivideByZero)
+        {
+            HResult = HResults.COR_E_DIVIDEBYZERO;
+        }
+
+        public DivideByZeroException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_DIVIDEBYZERO;
+        }
+
+        public DivideByZeroException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_DIVIDEBYZERO;
+        }
+
+        protected DivideByZeroException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/DllNotFoundException.cs b/src/System.Private.CoreLib/shared/System/DllNotFoundException.cs
new file mode 100644
index 0000000000..14fb50d9c5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/DllNotFoundException.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+** Class: DllNotFoundException
+**
+**
+** Purpose: The exception class for some failed P/Invoke calls.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class DllNotFoundException : TypeLoadException
+    {
+        public DllNotFoundException()
+            : base(SR.Arg_DllNotFoundException)
+        {
+            HResult = HResults.COR_E_DLLNOTFOUND;
+        }
+
+        public DllNotFoundException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_DLLNOTFOUND;
+        }
+
+        public DllNotFoundException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_DLLNOTFOUND;
+        }
+
+        protected DllNotFoundException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Double.cs b/src/System.Private.CoreLib/shared/System/Double.cs
new file mode 100644
index 0000000000..e466935953
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Double.cs
@@ -0,0 +1,453 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: A representation of an IEEE double precision
+**          floating point number.
+**
+**
+===========================================================*/
+
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+using Internal.Runtime.CompilerServices;
+
+namespace System
+{
+    [Serializable]
+    [StructLayout(LayoutKind.Sequential)]
+    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct Double : IComparable, IConvertible, IFormattable, IComparable<Double>, IEquatable<Double>, ISpanFormattable
+    {
+        private double m_value; // Do not rename (binary serialization)
+
+        //
+        // Public Constants
+        //
+        public const double MinValue = -1.7976931348623157E+308;
+        public const double MaxValue = 1.7976931348623157E+308;
+
+        // Note Epsilon should be a double whose hex representation is 0x1
+        // on little endian machines.
+        public const double Epsilon = 4.9406564584124654E-324;
+        public const double NegativeInfinity = (double)-1.0 / (double)(0.0);
+        public const double PositiveInfinity = (double)1.0 / (double)(0.0);
+        public const double NaN = (double)0.0 / (double)0.0;
+
+        // We use this explicit definition to avoid the confusion between 0.0 and -0.0.
+        internal const double NegativeZero = -0.0;
+
+        /// <summary>Determines whether the specified value is finite (zero, subnormal, or normal).</summary>
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe bool IsFinite(double d)
+        {
+            var bits = BitConverter.DoubleToInt64Bits(d);
+            return (bits & 0x7FFFFFFFFFFFFFFF) < 0x7FF0000000000000;
+        }
+
+        /// <summary>Determines whether the specified value is infinite.</summary>
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe bool IsInfinity(double d)
+        {
+            var bits = BitConverter.DoubleToInt64Bits(d);
+            return (bits & 0x7FFFFFFFFFFFFFFF) == 0x7FF0000000000000;
+        }
+
+        /// <summary>Determines whether the specified value is NaN.</summary>
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe bool IsNaN(double d)
+        {
+            var bits = BitConverter.DoubleToInt64Bits(d);
+            return (bits & 0x7FFFFFFFFFFFFFFF) > 0x7FF0000000000000;
+        }
+
+        /// <summary>Determines whether the specified value is negative.</summary>
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe bool IsNegative(double d)
+        {
+            var bits = unchecked((ulong)BitConverter.DoubleToInt64Bits(d));
+            return (bits & 0x8000000000000000) == 0x8000000000000000;
+        }
+
+        /// <summary>Determines whether the specified value is negative infinity.</summary>
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool IsNegativeInfinity(double d)
+        {
+            return (d == double.NegativeInfinity);
+        }
+
+        /// <summary>Determines whether the specified value is normal.</summary>
+        [NonVersionable]
+        // This is probably not worth inlining, it has branches and should be rarely called
+        public static unsafe bool IsNormal(double d)
+        {
+            var bits = BitConverter.DoubleToInt64Bits(d);
+            bits &= 0x7FFFFFFFFFFFFFFF;
+            return (bits < 0x7FF0000000000000) && (bits != 0) && ((bits & 0x7FF0000000000000) != 0);
+        }
+
+        /// <summary>Determines whether the specified value is positive infinity.</summary>
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool IsPositiveInfinity(double d)
+        {
+            return (d == double.PositiveInfinity);
+        }
+
+        /// <summary>Determines whether the specified value is subnormal.</summary>
+        [NonVersionable]
+        // This is probably not worth inlining, it has branches and should be rarely called
+        public static unsafe bool IsSubnormal(double d)
+        {
+            var bits = BitConverter.DoubleToInt64Bits(d);
+            bits &= 0x7FFFFFFFFFFFFFFF;
+            return (bits < 0x7FF0000000000000) && (bits != 0) && ((bits & 0x7FF0000000000000) == 0);
+        }
+
+        // Compares this object to another object, returning an instance of System.Relation.
+        // Null is considered less than any instance.
+        //
+        // If object is not of type Double, this method throws an ArgumentException.
+        //
+        // Returns a value less than zero if this  object
+        //
+        public int CompareTo(Object value)
+        {
+            if (value == null)
+            {
+                return 1;
+            }
+            if (value is Double)
+            {
+                double d = (double)value;
+                if (m_value < d) return -1;
+                if (m_value > d) return 1;
+                if (m_value == d) return 0;
+
+                // At least one of the values is NaN.
+                if (IsNaN(m_value))
+                    return (IsNaN(d) ? 0 : -1);
+                else
+                    return 1;
+            }
+            throw new ArgumentException(SR.Arg_MustBeDouble);
+        }
+
+        public int CompareTo(Double value)
+        {
+            if (m_value < value) return -1;
+            if (m_value > value) return 1;
+            if (m_value == value) return 0;
+
+            // At least one of the values is NaN.
+            if (IsNaN(m_value))
+                return (IsNaN(value) ? 0 : -1);
+            else
+                return 1;
+        }
+
+        // True if obj is another Double with the same value as the current instance.  This is
+        // a method of object equality, that only returns true if obj is also a double.
+        public override bool Equals(Object obj)
+        {
+            if (!(obj is Double))
+            {
+                return false;
+            }
+            double temp = ((Double)obj).m_value;
+            // This code below is written this way for performance reasons i.e the != and == check is intentional.
+            if (temp == m_value)
+            {
+                return true;
+            }
+            return IsNaN(temp) && IsNaN(m_value);
+        }
+
+        [NonVersionable]
+        public static bool operator ==(Double left, Double right)
+        {
+            return left == right;
+        }
+
+        [NonVersionable]
+        public static bool operator !=(Double left, Double right)
+        {
+            return left != right;
+        }
+
+        [NonVersionable]
+        public static bool operator <(Double left, Double right)
+        {
+            return left < right;
+        }
+
+        [NonVersionable]
+        public static bool operator >(Double left, Double right)
+        {
+            return left > right;
+        }
+
+        [NonVersionable]
+        public static bool operator <=(Double left, Double right)
+        {
+            return left <= right;
+        }
+
+        [NonVersionable]
+        public static bool operator >=(Double left, Double right)
+        {
+            return left >= right;
+        }
+
+        public bool Equals(Double obj)
+        {
+            if (obj == m_value)
+            {
+                return true;
+            }
+            return IsNaN(obj) && IsNaN(m_value);
+        }
+
+        //The hashcode for a double is the absolute value of the integer representation
+        //of that double.
+        //
+        [MethodImpl(MethodImplOptions.AggressiveInlining)] // 64-bit constants make the IL unusually large that makes the inliner to reject the method
+        public override int GetHashCode()
+        {
+            var bits = Unsafe.As<double, long>(ref m_value);
+
+            // Optimized check for IsNan() || IsZero()
+            if (((bits - 1) & 0x7FFFFFFFFFFFFFFF) >= 0x7FF0000000000000)
+            {
+                // Ensure that all NaNs and both zeros have the same hash code
+                bits &= 0x7FF0000000000000;
+            }
+
+            return unchecked((int)bits) ^ ((int)(bits >> 32));
+        }
+
+        public override String ToString()
+        {
+            return Number.FormatDouble(m_value, null, NumberFormatInfo.CurrentInfo);
+        }
+
+        public String ToString(String format)
+        {
+            return Number.FormatDouble(m_value, format, NumberFormatInfo.CurrentInfo);
+        }
+
+        public String ToString(IFormatProvider provider)
+        {
+            return Number.FormatDouble(m_value, null, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public String ToString(String format, IFormatProvider provider)
+        {
+            return Number.FormatDouble(m_value, format, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider provider = null)
+        {
+            return Number.TryFormatDouble(m_value, format, NumberFormatInfo.GetInstance(provider), destination, out charsWritten);
+        }
+
+        public static double Parse(String s)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseDouble(s, NumberStyles.Float | NumberStyles.AllowThousands, NumberFormatInfo.CurrentInfo);
+        }
+
+        public static double Parse(String s, NumberStyles style)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseDouble(s, style, NumberFormatInfo.CurrentInfo);
+        }
+
+        public static double Parse(String s, IFormatProvider provider)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseDouble(s, NumberStyles.Float | NumberStyles.AllowThousands, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public static double Parse(String s, NumberStyles style, IFormatProvider provider)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseDouble(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        // Parses a double from a String in the given style.  If
+        // a NumberFormatInfo isn't specified, the current culture's
+        // NumberFormatInfo is assumed.
+        //
+        // This method will not throw an OverflowException, but will return
+        // PositiveInfinity or NegativeInfinity for a number that is too
+        // large or too small.
+
+        public static double Parse(ReadOnlySpan<char> s, NumberStyles style = NumberStyles.Float | NumberStyles.AllowThousands, IFormatProvider provider = null)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            return Number.ParseDouble(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+
+
+        public static bool TryParse(String s, out double result)
+        {
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return TryParse((ReadOnlySpan<char>)s, NumberStyles.Float | NumberStyles.AllowThousands, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, out double result)
+        {
+            return TryParse(s, NumberStyles.Float | NumberStyles.AllowThousands, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        public static bool TryParse(String s, NumberStyles style, IFormatProvider provider, out double result)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return TryParse((ReadOnlySpan<char>)s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider provider, out double result)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            return TryParse(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        private static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info, out double result)
+        {
+            bool success = Number.TryParseDouble(s, style, info, out result);
+            if (!success)
+            {
+                ReadOnlySpan<char> sTrim = s.Trim();
+                if (sTrim.EqualsOrdinal(info.PositiveInfinitySymbol))
+                {
+                    result = PositiveInfinity;
+                }
+                else if (sTrim.EqualsOrdinal(info.NegativeInfinitySymbol))
+                {
+                    result = NegativeInfinity;
+                }
+                else if (sTrim.EqualsOrdinal(info.NaNSymbol))
+                {
+                    result = NaN;
+                }
+                else
+                {
+                    return false; // We really failed
+                }
+            }
+            return true;
+        }
+
+        //
+        // IConvertible implementation
+        //
+
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.Double;
+        }
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            return Convert.ToBoolean(m_value);
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Double", "Char"));
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return Convert.ToSByte(m_value);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return Convert.ToByte(m_value);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return Convert.ToInt16(m_value);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return Convert.ToUInt16(m_value);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return Convert.ToInt32(m_value);
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return Convert.ToUInt32(m_value);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return Convert.ToInt64(m_value);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return Convert.ToUInt64(m_value);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            return Convert.ToSingle(m_value);
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            return m_value;
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            return Convert.ToDecimal(m_value);
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Double", "DateTime"));
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/DuplicateWaitObjectException.cs b/src/System.Private.CoreLib/shared/System/DuplicateWaitObjectException.cs
new file mode 100644
index 0000000000..77303846a3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/DuplicateWaitObjectException.cs
@@ -0,0 +1,66 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception class for duplicate objects in WaitAll/WaitAny.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    // The DuplicateWaitObjectException is thrown when an object 
+    // appears more than once in the list of objects to WaitAll or WaitAny.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class DuplicateWaitObjectException : ArgumentException
+    {
+        private static volatile String s_duplicateWaitObjectMessage = null;
+
+        private static String DuplicateWaitObjectMessage
+        {
+            get
+            {
+                if (s_duplicateWaitObjectMessage == null)
+                    s_duplicateWaitObjectMessage = SR.Arg_DuplicateWaitObjectException;
+                return s_duplicateWaitObjectMessage;
+            }
+        }
+
+        // Creates a new DuplicateWaitObjectException with its message 
+        // string set to a default message.
+        public DuplicateWaitObjectException()
+            : base(DuplicateWaitObjectMessage)
+        {
+            HResult = HResults.COR_E_DUPLICATEWAITOBJECT;
+        }
+
+        public DuplicateWaitObjectException(String parameterName)
+            : base(DuplicateWaitObjectMessage, parameterName)
+        {
+            HResult = HResults.COR_E_DUPLICATEWAITOBJECT;
+        }
+
+        public DuplicateWaitObjectException(String parameterName, String message)
+            : base(message, parameterName)
+        {
+            HResult = HResults.COR_E_DUPLICATEWAITOBJECT;
+        }
+
+        public DuplicateWaitObjectException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_DUPLICATEWAITOBJECT;
+        }
+        
+        protected DuplicateWaitObjectException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Empty.cs b/src/System.Private.CoreLib/shared/System/Empty.cs
new file mode 100644
index 0000000000..186b92078e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Empty.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+#if CORERT
+    public // Needs to be public so that Reflection.Core can see it.
+#else
+    internal
+#endif
+    sealed class Empty
+    {
+        private Empty()
+        {
+        }
+
+        public static readonly Empty Value = new Empty();
+
+        public override string ToString()
+        {
+            return string.Empty;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/EntryPointNotFoundException.cs b/src/System.Private.CoreLib/shared/System/EntryPointNotFoundException.cs
new file mode 100644
index 0000000000..dac1cdb971
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/EntryPointNotFoundException.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: The exception class for some failed P/Invoke calls.
+**
+**
+=============================================================================*/
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class EntryPointNotFoundException : TypeLoadException
+    {
+        public EntryPointNotFoundException()
+            : base(SR.Arg_EntryPointNotFoundException)
+        {
+            HResult = HResults.COR_E_ENTRYPOINTNOTFOUND;
+        }
+
+        public EntryPointNotFoundException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_ENTRYPOINTNOTFOUND;
+        }
+
+        public EntryPointNotFoundException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_ENTRYPOINTNOTFOUND;
+        }
+
+        protected EntryPointNotFoundException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/EventArgs.cs b/src/System.Private.CoreLib/shared/System/EventArgs.cs
new file mode 100644
index 0000000000..f3561a8d0b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/EventArgs.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System
+{
+    // The base class for all event classes.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class EventArgs
+    {
+        public static readonly EventArgs Empty = new EventArgs();
+
+        public EventArgs()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/EventHandler.cs b/src/System.Private.CoreLib/shared/System/EventHandler.cs
new file mode 100644
index 0000000000..3d1cbfef26
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/EventHandler.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System
+{
+    public delegate void EventHandler(Object sender, EventArgs e);
+
+    public delegate void EventHandler<TEventArgs>(Object sender, TEventArgs e); // Removed TEventArgs constraint post-.NET 4
+}
diff --git a/src/System.Private.CoreLib/shared/System/ExecutionEngineException.cs b/src/System.Private.CoreLib/shared/System/ExecutionEngineException.cs
new file mode 100644
index 0000000000..5edd5cf19f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ExecutionEngineException.cs
@@ -0,0 +1,50 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+//
+/*=============================================================================
+**
+**
+**
+** Purpose: The exception class for misc execution engine exceptions.
+**          Currently, its only used as a placeholder type when the EE
+**          does a FailFast.
+**
+**
+=============================================================================*/
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Obsolete("This type previously indicated an unspecified fatal error in the runtime. The runtime no longer raises this exception so this type is obsolete.")]
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class ExecutionEngineException : SystemException
+    {
+        public ExecutionEngineException()
+            : base(SR.Arg_ExecutionEngineException)
+        {
+            HResult = HResults.COR_E_EXECUTIONENGINE;
+        }
+
+        public ExecutionEngineException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_EXECUTIONENGINE;
+        }
+
+        public ExecutionEngineException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_EXECUTIONENGINE;
+        }
+
+        internal ExecutionEngineException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/FieldAccessException.cs b/src/System.Private.CoreLib/shared/System/FieldAccessException.cs
new file mode 100644
index 0000000000..cb28264d61
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/FieldAccessException.cs
@@ -0,0 +1,42 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+** Purpose: The exception class for class loading failures.
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class FieldAccessException : MemberAccessException
+    {
+        public FieldAccessException()
+            : base(SR.Arg_FieldAccessException)
+        {
+            HResult = HResults.COR_E_FIELDACCESS;
+        }
+
+        public FieldAccessException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_FIELDACCESS;
+        }
+
+        public FieldAccessException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_FIELDACCESS;
+        }
+
+        protected FieldAccessException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/FlagsAttribute.cs b/src/System.Private.CoreLib/shared/System/FlagsAttribute.cs
new file mode 100644
index 0000000000..4f3ab36bfd
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/FlagsAttribute.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+
+namespace System
+{
+    // Custom attribute to indicate that the enum
+    // should be treated as a bitfield (or set of flags).
+    // An IDE may use this information to provide a richer
+    // development experience.
+    [AttributeUsage(AttributeTargets.Enum, Inherited = false)]
+    public class FlagsAttribute : Attribute
+    {
+        public FlagsAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/FormatException.cs b/src/System.Private.CoreLib/shared/System/FormatException.cs
new file mode 100644
index 0000000000..b0e273369c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/FormatException.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Exception to designate an illegal argument to FormatMessage.
+**
+** 
+===========================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class FormatException : SystemException
+    {
+        public FormatException()
+            : base(SR.Arg_FormatException)
+        {
+            HResult = HResults.COR_E_FORMAT;
+        }
+
+        public FormatException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_FORMAT;
+        }
+
+        public FormatException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_FORMAT;
+        }
+
+        protected FormatException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/FormattableString.cs b/src/System.Private.CoreLib/shared/System/FormattableString.cs
new file mode 100644
index 0000000000..6369363b5d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/FormattableString.cs
@@ -0,0 +1,81 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: implementation of the FormattableString
+** class.
+**
+===========================================================*/
+
+namespace System
+{
+    /// <summary>
+    /// A composite format string along with the arguments to be formatted. An instance of this
+    /// type may result from the use of the C# or VB language primitive "interpolated string".
+    /// </summary>
+    public abstract class FormattableString : IFormattable
+    {
+        /// <summary>
+        /// The composite format string.
+        /// </summary>
+        public abstract string Format { get; }
+
+        /// <summary>
+        /// Returns an object array that contains zero or more objects to format. Clients should not
+        /// mutate the contents of the array.
+        /// </summary>
+        public abstract object[] GetArguments();
+
+        /// <summary>
+        /// The number of arguments to be formatted.
+        /// </summary>
+        public abstract int ArgumentCount { get; }
+
+        /// <summary>
+        /// Returns one argument to be formatted from argument position <paramref name="index"/>.
+        /// </summary>
+        public abstract object GetArgument(int index);
+
+        /// <summary>
+        /// Format to a string using the given culture.
+        /// </summary>
+        public abstract string ToString(IFormatProvider formatProvider);
+
+        string IFormattable.ToString(string ignored, IFormatProvider formatProvider)
+        {
+            return ToString(formatProvider);
+        }
+
+        /// <summary>
+        /// Format the given object in the invariant culture. This static method may be
+        /// imported in C# by
+        /// <code>
+        /// using static System.FormattableString;
+        /// </code>.
+        /// Within the scope
+        /// of that import directive an interpolated string may be formatted in the
+        /// invariant culture by writing, for example,
+        /// <code>
+        /// Invariant($"{{ lat = {latitude}; lon = {longitude} }}")
+        /// </code>
+        /// </summary>
+        public static string Invariant(FormattableString formattable)
+        {
+            if (formattable == null)
+            {
+                throw new ArgumentNullException(nameof(formattable));
+            }
+
+            return formattable.ToString(Globalization.CultureInfo.InvariantCulture);
+        }
+
+        public override string ToString()
+        {
+            return ToString(Globalization.CultureInfo.CurrentCulture);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Gen2GcCallback.cs b/src/System.Private.CoreLib/shared/System/Gen2GcCallback.cs
new file mode 100644
index 0000000000..2252681224
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Gen2GcCallback.cs
@@ -0,0 +1,76 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.ConstrainedExecution;
+using System.Runtime.InteropServices;
+
+namespace System
+{
+    /// <summary>
+    /// Schedules a callback roughly every gen 2 GC (you may see a Gen 0 an Gen 1 but only once)
+    /// (We can fix this by capturing the Gen 2 count at startup and testing, but I mostly don't care)
+    /// </summary>
+    internal sealed class Gen2GcCallback : CriticalFinalizerObject
+    {
+        private Gen2GcCallback()
+            : base()
+        {
+        }
+
+        /// <summary>
+        /// Schedule 'callback' to be called in the next GC.  If the callback returns true it is 
+        /// rescheduled for the next Gen 2 GC.  Otherwise the callbacks stop. 
+        /// 
+        /// NOTE: This callback will be kept alive until either the callback function returns false,
+        /// or the target object dies.
+        /// </summary>
+        public static void Register(Func<object, bool> callback, object targetObj)
+        {
+            // Create a unreachable object that remembers the callback function and target object.
+            Gen2GcCallback gcCallback = new Gen2GcCallback();
+            gcCallback.Setup(callback, targetObj);
+        }
+
+        private Func<object, bool> _callback;
+        private GCHandle _weakTargetObj;
+
+        private void Setup(Func<object, bool> callback, object targetObj)
+        {
+            _callback = callback;
+            _weakTargetObj = GCHandle.Alloc(targetObj, GCHandleType.Weak);
+        }
+
+        ~Gen2GcCallback()
+        {
+            // Check to see if the target object is still alive.
+            object targetObj = _weakTargetObj.Target;
+            if (targetObj == null)
+            {
+                // The target object is dead, so this callback object is no longer needed.
+                _weakTargetObj.Free();
+                return;
+            }
+
+            // Execute the callback method.
+            try
+            {
+                if (!_callback(targetObj))
+                {
+                    // If the callback returns false, this callback object is no longer needed.
+                    return;
+                }
+            }
+            catch
+            {
+                // Ensure that we still get a chance to resurrect this object, even if the callback throws an exception.
+            }
+
+            // Resurrect ourselves by re-registering for finalization.
+            if (!Environment.HasShutdownStarted)
+            {
+                GC.ReRegisterForFinalize(this);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/BidiCategory.cs b/src/System.Private.CoreLib/shared/System/Globalization/BidiCategory.cs
new file mode 100644
index 0000000000..abe6950893
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/BidiCategory.cs
@@ -0,0 +1,33 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Globalization
+{
+    internal enum BidiCategory
+    {
+        LeftToRight = 0,
+        LeftToRightEmbedding = 1,
+        LeftToRightOverride = 2,
+        RightToLeft = 3,
+        RightToLeftArabic = 4,
+        RightToLeftEmbedding = 5,
+        RightToLeftOverride = 6,
+        PopDirectionalFormat = 7,
+        EuropeanNumber = 8,
+        EuropeanNumberSeparator = 9,
+        EuropeanNumberTerminator = 10,
+        ArabicNumber = 11,
+        CommonNumberSeparator = 12,
+        NonSpacingMark = 13,
+        BoundaryNeutral = 14,
+        ParagraphSeparator = 15,
+        SegmentSeparator = 16,
+        Whitespace = 17,
+        OtherNeutrals = 18,
+        LeftToRightIsolate = 19,
+        RightToLeftIsolate = 20,
+        FirstStrongIsolate = 21,
+        PopDirectionIsolate = 22,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/Calendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/Calendar.cs
new file mode 100644
index 0000000000..49ad597ceb
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/Calendar.cs
@@ -0,0 +1,840 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.Serialization;
+
+namespace System.Globalization
+{
+    // This abstract class represents a calendar. A calendar reckons time in
+    // divisions such as weeks, months and years. The number, length and start of
+    // the divisions vary in each calendar.
+    //
+    // Any instant in time can be represented as an n-tuple of numeric values using
+    // a particular calendar. For example, the next vernal equinox occurs at (0.0, 0
+    // , 46, 8, 20, 3, 1999) in the Gregorian calendar. An  implementation of
+    // Calendar can map any DateTime value to such an n-tuple and vice versa. The
+    // DateTimeFormat class can map between such n-tuples and a textual
+    // representation such as "8:46 AM March 20th 1999 AD".
+    //
+    // Most calendars identify a year which begins the current era. There may be any
+    // number of previous eras. The Calendar class identifies the eras as enumerated
+    // integers where the current era (CurrentEra) has the value zero.
+    //
+    // For consistency, the first unit in each interval, e.g. the first month, is
+    // assigned the value one.
+    // The calculation of hour/minute/second is moved to Calendar from GregorianCalendar,
+    // since most of the calendars (or all?) have the same way of calcuating hour/minute/second.
+
+    public abstract class Calendar : ICloneable
+    {
+        // Number of 100ns (10E-7 second) ticks per time unit
+        internal const long TicksPerMillisecond = 10000;
+        internal const long TicksPerSecond = TicksPerMillisecond * 1000;
+        internal const long TicksPerMinute = TicksPerSecond * 60;
+        internal const long TicksPerHour = TicksPerMinute * 60;
+        internal const long TicksPerDay = TicksPerHour * 24;
+
+        // Number of milliseconds per time unit
+        internal const int MillisPerSecond = 1000;
+        internal const int MillisPerMinute = MillisPerSecond * 60;
+        internal const int MillisPerHour = MillisPerMinute * 60;
+        internal const int MillisPerDay = MillisPerHour * 24;
+
+        // Number of days in a non-leap year
+        internal const int DaysPerYear = 365;
+        // Number of days in 4 years
+        internal const int DaysPer4Years = DaysPerYear * 4 + 1;
+        // Number of days in 100 years
+        internal const int DaysPer100Years = DaysPer4Years * 25 - 1;
+        // Number of days in 400 years
+        internal const int DaysPer400Years = DaysPer100Years * 4 + 1;
+
+        // Number of days from 1/1/0001 to 1/1/10000
+        internal const int DaysTo10000 = DaysPer400Years * 25 - 366;
+
+        internal const long MaxMillis = (long)DaysTo10000 * MillisPerDay;
+
+        private int _currentEraValue = -1;
+
+        private bool _isReadOnly = false;
+
+        // The minimum supported DateTime range for the calendar.
+
+        public virtual DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (DateTime.MinValue);
+            }
+        }
+
+        // The maximum supported DateTime range for the calendar.
+
+        public virtual DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (DateTime.MaxValue);
+            }
+        }
+
+        public virtual CalendarAlgorithmType AlgorithmType
+        {
+            get
+            {
+                return CalendarAlgorithmType.Unknown;
+            }
+        }
+
+        protected Calendar()
+        {
+            //Do-nothing constructor.
+        }
+
+        ///
+        // This can not be abstract, otherwise no one can create a subclass of Calendar.
+        //
+        internal virtual CalendarId ID
+        {
+            get
+            {
+                return CalendarId.UNINITIALIZED_VALUE;
+            }
+        }
+
+        ///
+        // Return the Base calendar ID for calendars that didn't have defined data in calendarData
+        //
+
+        internal virtual CalendarId BaseCalendarID
+        {
+            get { return ID; }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  IsReadOnly
+        //
+        //  Detect if the object is readonly.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public bool IsReadOnly
+        {
+            get { return (_isReadOnly); }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  Clone
+        //
+        //  Is the implementation of ICloneable.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual object Clone()
+        {
+            object o = MemberwiseClone();
+            ((Calendar)o).SetReadOnlyState(false);
+            return (o);
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  ReadOnly
+        //
+        //  Create a cloned readonly instance or return the input one if it is 
+        //  readonly.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public static Calendar ReadOnly(Calendar calendar)
+        {
+            if (calendar == null) { throw new ArgumentNullException(nameof(calendar)); }
+            if (calendar.IsReadOnly) { return (calendar); }
+
+            Calendar clonedCalendar = (Calendar)(calendar.MemberwiseClone());
+            clonedCalendar.SetReadOnlyState(true);
+
+            return (clonedCalendar);
+        }
+
+        internal void VerifyWritable()
+        {
+            if (_isReadOnly)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+            }
+        }
+
+        internal void SetReadOnlyState(bool readOnly)
+        {
+            _isReadOnly = readOnly;
+        }
+
+
+        /*=================================CurrentEraValue==========================
+        **Action: This is used to convert CurretEra(0) to an appropriate era value.
+        **Returns:
+        **Arguments:
+        **Exceptions:
+        **Notes:
+        ** The value is from calendar.nlp.
+        ============================================================================*/
+
+        internal virtual int CurrentEraValue
+        {
+            get
+            {
+                // The following code assumes that the current era value can not be -1.
+                if (_currentEraValue == -1)
+                {
+                    Debug.Assert(BaseCalendarID != CalendarId.UNINITIALIZED_VALUE, "[Calendar.CurrentEraValue] Expected a real calendar ID");
+                    _currentEraValue = CalendarData.GetCalendarData(BaseCalendarID).iCurrentEra;
+                }
+                return (_currentEraValue);
+            }
+        }
+
+        // The current era for a calendar.
+
+        public const int CurrentEra = 0;
+
+        internal int twoDigitYearMax = -1;
+
+        internal static void CheckAddResult(long ticks, DateTime minValue, DateTime maxValue)
+        {
+            if (ticks < minValue.Ticks || ticks > maxValue.Ticks)
+            {
+                throw new ArgumentException(
+                    String.Format(CultureInfo.InvariantCulture, SR.Format(SR.Argument_ResultCalendarRange,
+                        minValue, maxValue)));
+            }
+        }
+
+        internal DateTime Add(DateTime time, double value, int scale)
+        {
+            // From ECMA CLI spec, Partition III, section 3.27:
+            //
+            // If overflow occurs converting a floating-point type to an integer, or if the floating-point value 
+            // being converted to an integer is a NaN, the value returned is unspecified. 
+            //
+            // Based upon this, this method should be performing the comparison against the double
+            // before attempting a cast. Otherwise, the result is undefined.
+            double tempMillis = (value * scale + (value >= 0 ? 0.5 : -0.5));
+            if (!((tempMillis > -(double)MaxMillis) && (tempMillis < (double)MaxMillis)))
+            {
+                throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_AddValue);
+            }
+
+            long millis = (long)tempMillis;
+            long ticks = time.Ticks + millis * TicksPerMillisecond;
+            CheckAddResult(ticks, MinSupportedDateTime, MaxSupportedDateTime);
+            return (new DateTime(ticks));
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // milliseconds to the specified DateTime. The result is computed by rounding
+        // the number of milliseconds given by value to the nearest integer,
+        // and adding that interval to the specified DateTime. The value
+        // argument is permitted to be negative.
+        //
+
+        public virtual DateTime AddMilliseconds(DateTime time, double milliseconds)
+        {
+            return (Add(time, milliseconds, 1));
+        }
+
+
+        // Returns the DateTime resulting from adding a fractional number of
+        // days to the specified DateTime. The result is computed by rounding the
+        // fractional number of days given by value to the nearest
+        // millisecond, and adding that interval to the specified DateTime. The
+        // value argument is permitted to be negative.
+        //
+
+        public virtual DateTime AddDays(DateTime time, int days)
+        {
+            return (Add(time, days, MillisPerDay));
+        }
+
+        // Returns the DateTime resulting from adding a fractional number of
+        // hours to the specified DateTime. The result is computed by rounding the
+        // fractional number of hours given by value to the nearest
+        // millisecond, and adding that interval to the specified DateTime. The
+        // value argument is permitted to be negative.
+        //
+
+        public virtual DateTime AddHours(DateTime time, int hours)
+        {
+            return (Add(time, hours, MillisPerHour));
+        }
+
+
+        // Returns the DateTime resulting from adding a fractional number of
+        // minutes to the specified DateTime. The result is computed by rounding the
+        // fractional number of minutes given by value to the nearest
+        // millisecond, and adding that interval to the specified DateTime. The
+        // value argument is permitted to be negative.
+        //
+
+        public virtual DateTime AddMinutes(DateTime time, int minutes)
+        {
+            return (Add(time, minutes, MillisPerMinute));
+        }
+
+
+        // Returns the DateTime resulting from adding the given number of
+        // months to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year and month parts of the specified DateTime by
+        // value months, and, if required, adjusting the day part of the
+        // resulting date downwards to the last day of the resulting month in the
+        // resulting year. The time-of-day part of the result is the same as the
+        // time-of-day part of the specified DateTime.
+        //
+        // In more precise terms, considering the specified DateTime to be of the
+        // form y / m / d + t, where y is the
+        // year, m is the month, d is the day, and t is the
+        // time-of-day, the result is y1 / m1 / d1 + t,
+        // where y1 and m1 are computed by adding value months
+        // to y and m, and d1 is the largest value less than
+        // or equal to d that denotes a valid day in month m1 of year
+        // y1.
+        //
+
+        public abstract DateTime AddMonths(DateTime time, int months);
+
+        // Returns the DateTime resulting from adding a number of
+        // seconds to the specified DateTime. The result is computed by rounding the
+        // fractional number of seconds given by value to the nearest
+        // millisecond, and adding that interval to the specified DateTime. The
+        // value argument is permitted to be negative.
+        //
+
+        public virtual DateTime AddSeconds(DateTime time, int seconds)
+        {
+            return Add(time, seconds, MillisPerSecond);
+        }
+
+        // Returns the DateTime resulting from adding a number of
+        // weeks to the specified DateTime. The
+        // value argument is permitted to be negative.
+        //
+
+        public virtual DateTime AddWeeks(DateTime time, int weeks)
+        {
+            return (AddDays(time, weeks * 7));
+        }
+
+
+        // Returns the DateTime resulting from adding the given number of
+        // years to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year part of the specified DateTime by value
+        // years. If the month and day of the specified DateTime is 2/29, and if the
+        // resulting year is not a leap year, the month and day of the resulting
+        // DateTime becomes 2/28. Otherwise, the month, day, and time-of-day
+        // parts of the result are the same as those of the specified DateTime.
+        //
+
+        public abstract DateTime AddYears(DateTime time, int years);
+
+        // Returns the day-of-month part of the specified DateTime. The returned
+        // value is an integer between 1 and 31.
+        //
+
+        public abstract int GetDayOfMonth(DateTime time);
+
+        // Returns the day-of-week part of the specified DateTime. The returned value
+        // is an integer between 0 and 6, where 0 indicates Sunday, 1 indicates
+        // Monday, 2 indicates Tuesday, 3 indicates Wednesday, 4 indicates
+        // Thursday, 5 indicates Friday, and 6 indicates Saturday.
+        //
+
+        public abstract DayOfWeek GetDayOfWeek(DateTime time);
+
+        // Returns the day-of-year part of the specified DateTime. The returned value
+        // is an integer between 1 and 366.
+        //
+
+        public abstract int GetDayOfYear(DateTime time);
+
+        // Returns the number of days in the month given by the year and
+        // month arguments.
+        //
+
+        public virtual int GetDaysInMonth(int year, int month)
+        {
+            return (GetDaysInMonth(year, month, CurrentEra));
+        }
+
+        // Returns the number of days in the month given by the year and
+        // month arguments for the specified era.
+        //
+
+        public abstract int GetDaysInMonth(int year, int month, int era);
+
+        // Returns the number of days in the year given by the year argument for the current era.
+        //
+
+        public virtual int GetDaysInYear(int year)
+        {
+            return (GetDaysInYear(year, CurrentEra));
+        }
+
+        // Returns the number of days in the year given by the year argument for the current era.
+        //
+
+        public abstract int GetDaysInYear(int year, int era);
+
+        // Returns the era for the specified DateTime value.
+
+        public abstract int GetEra(DateTime time);
+
+        /*=================================Eras==========================
+        **Action: Get the list of era values.
+        **Returns: The int array of the era names supported in this calendar.
+        **      null if era is not used.
+        **Arguments: None.
+        **Exceptions: None.
+        ============================================================================*/
+
+
+        public abstract int[] Eras
+        {
+            get;
+        }
+
+
+        // Returns the hour part of the specified DateTime. The returned value is an
+        // integer between 0 and 23.
+        //
+
+        public virtual int GetHour(DateTime time)
+        {
+            return ((int)((time.Ticks / TicksPerHour) % 24));
+        }
+
+        // Returns the millisecond part of the specified DateTime. The returned value
+        // is an integer between 0 and 999.
+        //
+
+        public virtual double GetMilliseconds(DateTime time)
+        {
+            return (double)((time.Ticks / TicksPerMillisecond) % 1000);
+        }
+
+        // Returns the minute part of the specified DateTime. The returned value is
+        // an integer between 0 and 59.
+        //
+
+        public virtual int GetMinute(DateTime time)
+        {
+            return ((int)((time.Ticks / TicksPerMinute) % 60));
+        }
+
+        // Returns the month part of the specified DateTime. The returned value is an
+        // integer between 1 and 12.
+        //
+
+        public abstract int GetMonth(DateTime time);
+
+        // Returns the number of months in the specified year in the current era.
+
+        public virtual int GetMonthsInYear(int year)
+        {
+            return (GetMonthsInYear(year, CurrentEra));
+        }
+
+        // Returns the number of months in the specified year and era.
+
+        public abstract int GetMonthsInYear(int year, int era);
+
+        // Returns the second part of the specified DateTime. The returned value is
+        // an integer between 0 and 59.
+        //
+
+        public virtual int GetSecond(DateTime time)
+        {
+            return ((int)((time.Ticks / TicksPerSecond) % 60));
+        }
+
+        /*=================================GetFirstDayWeekOfYear==========================
+        **Action: Get the week of year using the FirstDay rule.
+        **Returns:  the week of year.
+        **Arguments:
+        **  time
+        **  firstDayOfWeek  the first day of week (0=Sunday, 1=Monday, ... 6=Saturday)
+        **Notes:
+        **  The CalendarWeekRule.FirstDay rule: Week 1 begins on the first day of the year.
+        **  Assume f is the specifed firstDayOfWeek,
+        **  and n is the day of week for January 1 of the specified year.
+        **  Assign offset = n - f;
+        **  Case 1: offset = 0
+        **      E.g.
+        **                     f=1
+        **          weekday 0  1  2  3  4  5  6  0  1
+        **          date       1/1
+        **          week#      1                    2
+        **      then week of year = (GetDayOfYear(time) - 1) / 7 + 1
+        **
+        **  Case 2: offset < 0
+        **      e.g.
+        **                     n=1   f=3
+        **          weekday 0  1  2  3  4  5  6  0
+        **          date       1/1
+        **          week#      1     2
+        **      This means that the first week actually starts 5 days before 1/1.
+        **      So week of year = (GetDayOfYear(time) + (7 + offset) - 1) / 7 + 1
+        **  Case 3: offset > 0
+        **      e.g.
+        **                  f=0   n=2
+        **          weekday 0  1  2  3  4  5  6  0  1  2
+        **          date          1/1
+        **          week#         1                    2
+        **      This means that the first week actually starts 2 days before 1/1.
+        **      So Week of year = (GetDayOfYear(time) + offset - 1) / 7 + 1
+        ============================================================================*/
+
+        internal int GetFirstDayWeekOfYear(DateTime time, int firstDayOfWeek)
+        {
+            int dayOfYear = GetDayOfYear(time) - 1;   // Make the day of year to be 0-based, so that 1/1 is day 0.
+            // Calculate the day of week for the first day of the year.
+            // dayOfWeek - (dayOfYear % 7) is the day of week for the first day of this year.  Note that
+            // this value can be less than 0.  It's fine since we are making it positive again in calculating offset.
+            int dayForJan1 = (int)GetDayOfWeek(time) - (dayOfYear % 7);
+            int offset = (dayForJan1 - firstDayOfWeek + 14) % 7;
+            Debug.Assert(offset >= 0, "Calendar.GetFirstDayWeekOfYear(): offset >= 0");
+            return ((dayOfYear + offset) / 7 + 1);
+        }
+
+        private int GetWeekOfYearFullDays(DateTime time, int firstDayOfWeek, int fullDays)
+        {
+            int dayForJan1;
+            int offset;
+            int day;
+
+            int dayOfYear = GetDayOfYear(time) - 1; // Make the day of year to be 0-based, so that 1/1 is day 0.
+            //
+            // Calculate the number of days between the first day of year (1/1) and the first day of the week.
+            // This value will be a positive value from 0 ~ 6.  We call this value as "offset".
+            //
+            // If offset is 0, it means that the 1/1 is the start of the first week.
+            //     Assume the first day of the week is Monday, it will look like this:
+            //     Sun      Mon     Tue     Wed     Thu     Fri     Sat
+            //     12/31    1/1     1/2     1/3     1/4     1/5     1/6
+            //              +--> First week starts here.
+            //
+            // If offset is 1, it means that the first day of the week is 1 day ahead of 1/1.
+            //     Assume the first day of the week is Monday, it will look like this:
+            //     Sun      Mon     Tue     Wed     Thu     Fri     Sat
+            //     1/1      1/2     1/3     1/4     1/5     1/6     1/7
+            //              +--> First week starts here.
+            //
+            // If offset is 2, it means that the first day of the week is 2 days ahead of 1/1.
+            //     Assume the first day of the week is Monday, it will look like this:
+            //     Sat      Sun     Mon     Tue     Wed     Thu     Fri     Sat
+            //     1/1      1/2     1/3     1/4     1/5     1/6     1/7     1/8
+            //                      +--> First week starts here.
+
+
+
+            // Day of week is 0-based.
+            // Get the day of week for 1/1.  This can be derived from the day of week of the target day.
+            // Note that we can get a negative value.  It's ok since we are going to make it a positive value when calculating the offset.
+            dayForJan1 = (int)GetDayOfWeek(time) - (dayOfYear % 7);
+
+            // Now, calculate the offset.  Subtract the first day of week from the dayForJan1.  And make it a positive value.
+            offset = (firstDayOfWeek - dayForJan1 + 14) % 7;
+            if (offset != 0 && offset >= fullDays)
+            {
+                //
+                // If the offset is greater than the value of fullDays, it means that
+                // the first week of the year starts on the week where Jan/1 falls on.
+                //
+                offset -= 7;
+            }
+            //
+            // Calculate the day of year for specified time by taking offset into account.
+            //
+            day = dayOfYear - offset;
+            if (day >= 0)
+            {
+                //
+                // If the day of year value is greater than zero, get the week of year.
+                //
+                return (day / 7 + 1);
+            }
+            //
+            // Otherwise, the specified time falls on the week of previous year.
+            // Call this method again by passing the last day of previous year.
+            //
+            // the last day of the previous year may "underflow" to no longer be a valid date time for
+            // this calendar if we just subtract so we need the subclass to provide us with 
+            // that information
+            if (time <= MinSupportedDateTime.AddDays(dayOfYear))
+            {
+                return GetWeekOfYearOfMinSupportedDateTime(firstDayOfWeek, fullDays);
+            }
+            return (GetWeekOfYearFullDays(time.AddDays(-(dayOfYear + 1)), firstDayOfWeek, fullDays));
+        }
+
+        private int GetWeekOfYearOfMinSupportedDateTime(int firstDayOfWeek, int minimumDaysInFirstWeek)
+        {
+            int dayOfYear = GetDayOfYear(MinSupportedDateTime) - 1;  // Make the day of year to be 0-based, so that 1/1 is day 0.
+            int dayOfWeekOfFirstOfYear = (int)GetDayOfWeek(MinSupportedDateTime) - dayOfYear % 7;
+
+            // Calculate the offset (how many days from the start of the year to the start of the week)
+            int offset = (firstDayOfWeek + 7 - dayOfWeekOfFirstOfYear) % 7;
+            if (offset == 0 || offset >= minimumDaysInFirstWeek)
+            {
+                // First of year falls in the first week of the year
+                return 1;
+            }
+
+            int daysInYearBeforeMinSupportedYear = DaysInYearBeforeMinSupportedYear - 1; // Make the day of year to be 0-based, so that 1/1 is day 0.
+            int dayOfWeekOfFirstOfPreviousYear = dayOfWeekOfFirstOfYear - 1 - (daysInYearBeforeMinSupportedYear % 7);
+
+            // starting from first day of the year, how many days do you have to go forward
+            // before getting to the first day of the week?
+            int daysInInitialPartialWeek = (firstDayOfWeek - dayOfWeekOfFirstOfPreviousYear + 14) % 7;
+            int day = daysInYearBeforeMinSupportedYear - daysInInitialPartialWeek;
+            if (daysInInitialPartialWeek >= minimumDaysInFirstWeek)
+            {
+                // If the offset is greater than the minimum Days in the first week, it means that
+                // First of year is part of the first week of the year even though it is only a partial week
+                // add another week
+                day += 7;
+            }
+
+            return (day / 7 + 1);
+        }
+
+        // it would be nice to make this abstract but we can't since that would break previous implementations
+        protected virtual int DaysInYearBeforeMinSupportedYear
+        {
+            get
+            {
+                return 365;
+            }
+        }
+
+
+        // Returns the week of year for the specified DateTime. The returned value is an
+        // integer between 1 and 53.
+        //
+
+        public virtual int GetWeekOfYear(DateTime time, CalendarWeekRule rule, DayOfWeek firstDayOfWeek)
+        {
+            if ((int)firstDayOfWeek < 0 || (int)firstDayOfWeek > 6)
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(firstDayOfWeek), SR.Format(SR.ArgumentOutOfRange_Range,
+                    DayOfWeek.Sunday, DayOfWeek.Saturday));
+            }
+            switch (rule)
+            {
+                case CalendarWeekRule.FirstDay:
+                    return (GetFirstDayWeekOfYear(time, (int)firstDayOfWeek));
+                case CalendarWeekRule.FirstFullWeek:
+                    return (GetWeekOfYearFullDays(time, (int)firstDayOfWeek, 7));
+                case CalendarWeekRule.FirstFourDayWeek:
+                    return (GetWeekOfYearFullDays(time, (int)firstDayOfWeek, 4));
+            }
+            throw new ArgumentOutOfRangeException(
+                nameof(rule), SR.Format(SR.ArgumentOutOfRange_Range,
+                CalendarWeekRule.FirstDay, CalendarWeekRule.FirstFourDayWeek));
+        }
+
+        // Returns the year part of the specified DateTime. The returned value is an
+        // integer between 1 and 9999.
+        //
+
+        public abstract int GetYear(DateTime time);
+
+        // Checks whether a given day in the current era is a leap day. This method returns true if
+        // the date is a leap day, or false if not.
+        //
+
+        public virtual bool IsLeapDay(int year, int month, int day)
+        {
+            return (IsLeapDay(year, month, day, CurrentEra));
+        }
+
+        // Checks whether a given day in the specified era is a leap day. This method returns true if
+        // the date is a leap day, or false if not.
+        //
+
+        public abstract bool IsLeapDay(int year, int month, int day, int era);
+
+        // Checks whether a given month in the current era is a leap month. This method returns true if
+        // month is a leap month, or false if not.
+        //
+
+        public virtual bool IsLeapMonth(int year, int month)
+        {
+            return (IsLeapMonth(year, month, CurrentEra));
+        }
+
+        // Checks whether a given month in the specified era is a leap month. This method returns true if
+        // month is a leap month, or false if not.
+        //
+
+        public abstract bool IsLeapMonth(int year, int month, int era);
+
+        // Returns  the leap month in a calendar year of the current era. This method returns 0
+        // if this calendar does not have leap month, or this year is not a leap year.
+        //
+
+        public virtual int GetLeapMonth(int year)
+        {
+            return (GetLeapMonth(year, CurrentEra));
+        }
+
+        // Returns  the leap month in a calendar year of the specified era. This method returns 0
+        // if this calendar does not have leap month, or this year is not a leap year.
+        //
+
+        public virtual int GetLeapMonth(int year, int era)
+        {
+            if (!IsLeapYear(year, era))
+                return 0;
+
+            int monthsCount = GetMonthsInYear(year, era);
+            for (int month = 1; month <= monthsCount; month++)
+            {
+                if (IsLeapMonth(year, month, era))
+                    return month;
+            }
+
+            return 0;
+        }
+
+        // Checks whether a given year in the current era is a leap year. This method returns true if
+        // year is a leap year, or false if not.
+        //
+
+        public virtual bool IsLeapYear(int year)
+        {
+            return (IsLeapYear(year, CurrentEra));
+        }
+
+        // Checks whether a given year in the specified era is a leap year. This method returns true if
+        // year is a leap year, or false if not.
+        //
+
+        public abstract bool IsLeapYear(int year, int era);
+
+        // Returns the date and time converted to a DateTime value.  Throws an exception if the n-tuple is invalid.
+        //
+
+        public virtual DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond)
+        {
+            return (ToDateTime(year, month, day, hour, minute, second, millisecond, CurrentEra));
+        }
+
+        // Returns the date and time converted to a DateTime value.  Throws an exception if the n-tuple is invalid.
+        //
+
+        public abstract DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era);
+
+        internal virtual Boolean TryToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era, out DateTime result)
+        {
+            result = DateTime.MinValue;
+            try
+            {
+                result = ToDateTime(year, month, day, hour, minute, second, millisecond, era);
+                return true;
+            }
+            catch (ArgumentException)
+            {
+                return false;
+            }
+        }
+
+        internal virtual bool IsValidYear(int year, int era)
+        {
+            return (year >= GetYear(MinSupportedDateTime) && year <= GetYear(MaxSupportedDateTime));
+        }
+
+        internal virtual bool IsValidMonth(int year, int month, int era)
+        {
+            return (IsValidYear(year, era) && month >= 1 && month <= GetMonthsInYear(year, era));
+        }
+
+        internal virtual bool IsValidDay(int year, int month, int day, int era)
+        {
+            return (IsValidMonth(year, month, era) && day >= 1 && day <= GetDaysInMonth(year, month, era));
+        }
+
+
+        // Returns and assigns the maximum value to represent a two digit year.  This
+        // value is the upper boundary of a 100 year range that allows a two digit year
+        // to be properly translated to a four digit year.  For example, if 2029 is the
+        // upper boundary, then a two digit value of 30 should be interpreted as 1930
+        // while a two digit value of 29 should be interpreted as 2029.  In this example
+        // , the 100 year range would be from 1930-2029.  See ToFourDigitYear().
+
+        public virtual int TwoDigitYearMax
+        {
+            get
+            {
+                return (twoDigitYearMax);
+            }
+
+            set
+            {
+                VerifyWritable();
+                twoDigitYearMax = value;
+            }
+        }
+
+        // Converts the year value to the appropriate century by using the
+        // TwoDigitYearMax property.  For example, if the TwoDigitYearMax value is 2029,
+        // then a two digit value of 30 will get converted to 1930 while a two digit
+        // value of 29 will get converted to 2029.
+
+        public virtual int ToFourDigitYear(int year)
+        {
+            if (year < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (year < 100)
+            {
+                return ((TwoDigitYearMax / 100 - (year > TwoDigitYearMax % 100 ? 1 : 0)) * 100 + year);
+            }
+            // If the year value is above 100, just return the year value.  Don't have to do
+            // the TwoDigitYearMax comparison.
+            return (year);
+        }
+
+        // Return the tick count corresponding to the given hour, minute, second.
+        // Will check the if the parameters are valid.
+        internal static long TimeToTicks(int hour, int minute, int second, int millisecond)
+        {
+            if (hour >= 0 && hour < 24 && minute >= 0 && minute < 60 && second >= 0 && second < 60)
+            {
+                if (millisecond < 0 || millisecond >= MillisPerSecond)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(millisecond),
+                                String.Format(
+                                    CultureInfo.InvariantCulture,
+                                    SR.Format(SR.ArgumentOutOfRange_Range, 0, MillisPerSecond - 1)));
+                }
+                return InternalGlobalizationHelper.TimeToTicks(hour, minute, second) + millisecond * TicksPerMillisecond;
+            }
+            throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadHourMinuteSecond);
+        }
+
+        internal static int GetSystemTwoDigitYearSetting(CalendarId CalID, int defaultYearValue)
+        {
+            int twoDigitYearMax = CalendarData.GetTwoDigitYearMax(CalID);
+            if (twoDigitYearMax < 0)
+            {
+                twoDigitYearMax = defaultYearValue;
+            }
+            return (twoDigitYearMax);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CalendarAlgorithmType.cs b/src/System.Private.CoreLib/shared/System/Globalization/CalendarAlgorithmType.cs
new file mode 100644
index 0000000000..4ddc307abf
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CalendarAlgorithmType.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Globalization
+{
+    public enum CalendarAlgorithmType
+    {
+        Unknown = 0,            // This is the default value to return in the Calendar base class.
+        SolarCalendar = 1,      // Solar-base calendar, such as GregorianCalendar, jaoaneseCalendar, JulianCalendar, etc.
+                                // Solar calendars are based on the solar year and seasons.
+        LunarCalendar = 2,      // Lunar-based calendar, such as Hijri and UmAlQuraCalendar.
+                                // Lunar calendars are based on the path of the moon.  The seasons are not accurately represented.
+        LunisolarCalendar = 3   // Lunisolar-based calendar which use leap month rule, such as HebrewCalendar and Asian Lunisolar calendars.
+                                // Lunisolar calendars are based on the cycle of the moon, but consider the seasons as a secondary consideration,
+                                // so they align with the seasons as well as lunar events.
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CalendarData.Unix.cs b/src/System.Private.CoreLib/shared/System/Globalization/CalendarData.Unix.cs
new file mode 100644
index 0000000000..17d6ed7a01
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CalendarData.Unix.cs
@@ -0,0 +1,363 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Security;
+using System.Text;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Globalization
+{
+    // needs to be kept in sync with CalendarDataType in System.Globalization.Native
+    internal enum CalendarDataType
+    {
+        Uninitialized = 0,
+        NativeName = 1,
+        MonthDay = 2,
+        ShortDates = 3,
+        LongDates = 4,
+        YearMonths = 5,
+        DayNames = 6,
+        AbbrevDayNames = 7,
+        MonthNames = 8,
+        AbbrevMonthNames = 9,
+        SuperShortDayNames = 10,
+        MonthGenitiveNames = 11,
+        AbbrevMonthGenitiveNames = 12,
+        EraNames = 13,
+        AbbrevEraNames = 14,
+    }
+
+    internal partial class CalendarData
+    {
+        private bool LoadCalendarDataFromSystem(String localeName, CalendarId calendarId)
+        {
+            bool result = true;
+            result &= GetCalendarInfo(localeName, calendarId, CalendarDataType.NativeName, out this.sNativeName);
+            result &= GetCalendarInfo(localeName, calendarId, CalendarDataType.MonthDay, out this.sMonthDay);
+            this.sMonthDay = NormalizeDatePattern(this.sMonthDay);
+
+            result &= EnumDatePatterns(localeName, calendarId, CalendarDataType.ShortDates, out this.saShortDates);
+            result &= EnumDatePatterns(localeName, calendarId, CalendarDataType.LongDates, out this.saLongDates);
+            result &= EnumDatePatterns(localeName, calendarId, CalendarDataType.YearMonths, out this.saYearMonths);
+            result &= EnumCalendarInfo(localeName, calendarId, CalendarDataType.DayNames, out this.saDayNames);
+            result &= EnumCalendarInfo(localeName, calendarId, CalendarDataType.AbbrevDayNames, out this.saAbbrevDayNames);
+            result &= EnumCalendarInfo(localeName, calendarId, CalendarDataType.SuperShortDayNames, out this.saSuperShortDayNames);
+
+            string leapHebrewMonthName = null;
+            result &= EnumMonthNames(localeName, calendarId, CalendarDataType.MonthNames, out this.saMonthNames, ref leapHebrewMonthName);
+            if (leapHebrewMonthName != null)
+            {              
+                // In Hebrew calendar, get the leap month name Adar II and override the non-leap month 7              
+                Debug.Assert(calendarId == CalendarId.HEBREW && saMonthNames.Length == 13);
+                saLeapYearMonthNames = (string[]) saMonthNames.Clone();
+                saLeapYearMonthNames[6] = leapHebrewMonthName;
+
+                // The returned data from ICU has 6th month name as 'Adar I' and 7th month name as 'Adar'
+                // We need to adjust that in the list used with non-leap year to have 6th month as 'Adar' and 7th month as 'Adar II'
+                // note that when formatting non-leap year dates, 7th month shouldn't get used at all.
+                saMonthNames[5] = saMonthNames[6];
+                saMonthNames[6] = leapHebrewMonthName;
+
+            }
+            result &= EnumMonthNames(localeName, calendarId, CalendarDataType.AbbrevMonthNames, out this.saAbbrevMonthNames, ref leapHebrewMonthName);
+            result &= EnumMonthNames(localeName, calendarId, CalendarDataType.MonthGenitiveNames, out this.saMonthGenitiveNames, ref leapHebrewMonthName);
+            result &= EnumMonthNames(localeName, calendarId, CalendarDataType.AbbrevMonthGenitiveNames, out this.saAbbrevMonthGenitiveNames, ref leapHebrewMonthName);
+
+            result &= EnumEraNames(localeName, calendarId, CalendarDataType.EraNames, out this.saEraNames);
+            result &= EnumEraNames(localeName, calendarId, CalendarDataType.AbbrevEraNames, out this.saAbbrevEraNames);
+
+            return result;
+        }
+
+        internal static int GetTwoDigitYearMax(CalendarId calendarId)
+        {
+            // There is no user override for this value on Linux or in ICU.
+            // So just return -1 to use the hard-coded defaults.
+            return -1;
+        }
+
+        // Call native side to figure out which calendars are allowed
+        internal static int GetCalendars(string localeName, bool useUserOverride, CalendarId[] calendars)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            // NOTE: there are no 'user overrides' on Linux
+            int count = Interop.Globalization.GetCalendars(localeName, calendars, calendars.Length);
+
+            // ensure there is at least 1 calendar returned
+            if (count == 0 && calendars.Length > 0)
+            {
+                calendars[0] = CalendarId.GREGORIAN;
+                count = 1;
+            }
+
+            return count;
+        }
+
+        private static bool SystemSupportsTaiwaneseCalendar()
+        {
+            return true;
+        }
+
+        // PAL Layer ends here
+
+        private static bool GetCalendarInfo(string localeName, CalendarId calendarId, CalendarDataType dataType, out string calendarString)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            return Interop.CallStringMethod(
+                (locale, calId, type, stringBuilder) =>
+                    Interop.Globalization.GetCalendarInfo(
+                        locale,
+                        calId,
+                        type,
+                        stringBuilder,
+                        stringBuilder.Capacity),
+                localeName,
+                calendarId,
+                dataType,
+                out calendarString);
+        }
+
+        private static bool EnumDatePatterns(string localeName, CalendarId calendarId, CalendarDataType dataType, out string[] datePatterns)
+        {
+            datePatterns = null;
+
+            EnumCalendarsData callbackContext = new EnumCalendarsData();
+            callbackContext.Results = new List<string>();
+            callbackContext.DisallowDuplicates = true;
+            bool result = EnumCalendarInfo(localeName, calendarId, dataType, ref callbackContext);
+            if (result)
+            {
+                List<string> datePatternsList = callbackContext.Results;
+
+                datePatterns = new string[datePatternsList.Count];
+                for (int i = 0; i < datePatternsList.Count; i++)
+                {
+                    datePatterns[i] = NormalizeDatePattern(datePatternsList[i]);
+                }
+            }
+
+            return result;
+        }
+
+        /// <summary>
+        /// The ICU date format characters are not exactly the same as the .NET date format characters.
+        /// NormalizeDatePattern will take in an ICU date pattern and return the equivalent .NET date pattern.
+        /// </summary>
+        /// <remarks>
+        /// see Date Field Symbol Table in http://userguide.icu-project.org/formatparse/datetime
+        /// and https://msdn.microsoft.com/en-us/library/8kb3ddd4(v=vs.110).aspx
+        /// </remarks>
+        private static string NormalizeDatePattern(string input)
+        {
+            StringBuilder destination = StringBuilderCache.Acquire(input.Length);
+
+            int index = 0;
+            while (index < input.Length)
+            {
+                switch (input[index])
+                {
+                    case '\'':
+                        // single quotes escape characters, like 'de' in es-SP
+                        // so read verbatim until the next single quote
+                        destination.Append(input[index++]);
+                        while (index < input.Length)
+                        {
+                            char current = input[index++];
+                            destination.Append(current);
+                            if (current == '\'')
+                            {
+                                break;
+                            }
+                        }
+                        break;
+                    case 'E':
+                    case 'e':
+                    case 'c':
+                        // 'E' in ICU is the day of the week, which maps to 3 or 4 'd's in .NET
+                        // 'e' in ICU is the local day of the week, which has no representation in .NET, but
+                        // maps closest to 3 or 4 'd's in .NET
+                        // 'c' in ICU is the stand-alone day of the week, which has no representation in .NET, but
+                        // maps closest to 3 or 4 'd's in .NET
+                        NormalizeDayOfWeek(input, destination, ref index);
+                        break;
+                    case 'L':
+                    case 'M':
+                        // 'L' in ICU is the stand-alone name of the month,
+                        // which maps closest to 'M' in .NET since it doesn't support stand-alone month names in patterns
+                        // 'M' in both ICU and .NET is the month,
+                        // but ICU supports 5 'M's, which is the super short month name
+                        int occurrences = CountOccurrences(input, input[index], ref index);
+                        if (occurrences > 4)
+                        {
+                            // 5 'L's or 'M's in ICU is the super short name, which maps closest to MMM in .NET
+                            occurrences = 3;
+                        }
+                        destination.Append('M', occurrences);
+                        break;
+                    case 'G':
+                        // 'G' in ICU is the era, which maps to 'g' in .NET
+                        occurrences = CountOccurrences(input, 'G', ref index);
+
+                        // it doesn't matter how many 'G's, since .NET only supports 'g' or 'gg', and they
+                        // have the same meaning
+                        destination.Append('g');
+                        break;
+                    case 'y':
+                        // a single 'y' in ICU is the year with no padding or trimming.
+                        // a single 'y' in .NET is the year with 1 or 2 digits
+                        // so convert any single 'y' to 'yyyy'
+                        occurrences = CountOccurrences(input, 'y', ref index);
+                        if (occurrences == 1)
+                        {
+                            occurrences = 4;
+                        }
+                        destination.Append('y', occurrences);
+                        break;
+                    default:
+                        const string unsupportedDateFieldSymbols = "YuUrQqwWDFg";
+                        Debug.Assert(unsupportedDateFieldSymbols.IndexOf(input[index]) == -1,
+                            string.Format(CultureInfo.InvariantCulture,
+                                "Encountered an unexpected date field symbol '{0}' from ICU which has no known corresponding .NET equivalent.", 
+                                input[index]));
+
+                        destination.Append(input[index++]);
+                        break;
+                }
+            }
+
+            return StringBuilderCache.GetStringAndRelease(destination);
+        }
+
+        private static void NormalizeDayOfWeek(string input, StringBuilder destination, ref int index)
+        {
+            char dayChar = input[index];
+            int occurrences = CountOccurrences(input, dayChar, ref index);
+            occurrences = Math.Max(occurrences, 3);
+            if (occurrences > 4)
+            {
+                // 5 and 6 E/e/c characters in ICU is the super short names, which maps closest to ddd in .NET
+                occurrences = 3;
+            }
+
+            destination.Append('d', occurrences);
+        }
+
+        private static int CountOccurrences(string input, char value, ref int index)
+        {
+            int startIndex = index;
+            while (index < input.Length && input[index] == value)
+            {
+                index++;
+            }
+
+            return index - startIndex;
+        }
+
+        private static bool EnumMonthNames(string localeName, CalendarId calendarId, CalendarDataType dataType, out string[] monthNames, ref string leapHebrewMonthName)
+        {
+            monthNames = null;
+
+            EnumCalendarsData callbackContext = new EnumCalendarsData();
+            callbackContext.Results = new List<string>();
+            bool result = EnumCalendarInfo(localeName, calendarId, dataType, ref callbackContext);
+            if (result)
+            {
+                // the month-name arrays are expected to have 13 elements.  If ICU only returns 12, add an
+                // extra empty string to fill the array.
+                if (callbackContext.Results.Count == 12)
+                {
+                    callbackContext.Results.Add(string.Empty);
+                }
+
+                if (callbackContext.Results.Count > 13)
+                {
+                    Debug.Assert(calendarId == CalendarId.HEBREW && callbackContext.Results.Count == 14);
+                    
+                    if (calendarId == CalendarId.HEBREW)
+                    {
+                        leapHebrewMonthName = callbackContext.Results[13];
+                    }
+                    callbackContext.Results.RemoveRange(13, callbackContext.Results.Count - 13);
+                }                
+
+                monthNames = callbackContext.Results.ToArray();
+            }
+
+            return result;
+        }
+
+        private static bool EnumEraNames(string localeName, CalendarId calendarId, CalendarDataType dataType, out string[] eraNames)
+        {
+            bool result = EnumCalendarInfo(localeName, calendarId, dataType, out eraNames);
+
+            // .NET expects that only the Japanese calendars have more than 1 era.
+            // So for other calendars, only return the latest era.
+            if (calendarId != CalendarId.JAPAN && calendarId != CalendarId.JAPANESELUNISOLAR && eraNames.Length > 0)
+            {
+                string[] latestEraName = new string[] { eraNames[eraNames.Length - 1] };
+                eraNames = latestEraName;
+            }
+
+            return result;
+        }
+
+        internal static bool EnumCalendarInfo(string localeName, CalendarId calendarId, CalendarDataType dataType, out string[] calendarData)
+        {
+            calendarData = null;
+
+            EnumCalendarsData callbackContext = new EnumCalendarsData();
+            callbackContext.Results = new List<string>();
+            bool result = EnumCalendarInfo(localeName, calendarId, dataType, ref callbackContext);
+            if (result)
+            {
+                calendarData = callbackContext.Results.ToArray();
+            }
+
+            return result;
+        }
+
+        private static unsafe bool EnumCalendarInfo(string localeName, CalendarId calendarId, CalendarDataType dataType, ref EnumCalendarsData callbackContext)
+        {
+            return Interop.Globalization.EnumCalendarInfo(EnumCalendarInfoCallback, localeName, calendarId, dataType, (IntPtr)Unsafe.AsPointer(ref callbackContext));
+        }
+
+        private static unsafe void EnumCalendarInfoCallback(string calendarString, IntPtr context)
+        {
+            try
+            {
+                ref EnumCalendarsData callbackContext = ref Unsafe.As<byte, EnumCalendarsData>(ref *(byte*)context);
+
+                if (callbackContext.DisallowDuplicates)
+                {
+                    foreach (string existingResult in callbackContext.Results)
+                    {
+                        if (string.Equals(calendarString, existingResult, StringComparison.Ordinal))
+                        {
+                            // the value is already in the results, so don't add it again
+                            return;
+                        }
+                    }
+                }
+
+                callbackContext.Results.Add(calendarString);
+            }
+            catch (Exception e)
+            {
+                Debug.Fail(e.ToString());
+                // we ignore the managed exceptions here because EnumCalendarInfoCallback will get called from the native code.
+                // If we don't ignore the exception here that can cause the runtime to fail fast.
+            }
+        }
+
+        private struct EnumCalendarsData
+        {
+            public List<string> Results;
+            public bool DisallowDuplicates;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CalendarData.Windows.cs b/src/System.Private.CoreLib/shared/System/Globalization/CalendarData.Windows.cs
new file mode 100644
index 0000000000..03f9088d62
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CalendarData.Windows.cs
@@ -0,0 +1,469 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Collections.Generic;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Globalization
+{
+    internal partial class CalendarData
+    {
+        private bool LoadCalendarDataFromSystem(String localeName, CalendarId calendarId)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            bool ret = true;
+
+            uint useOverrides = this.bUseUserOverrides ? 0 : CAL_NOUSEROVERRIDE;
+
+            //
+            // Windows doesn't support some calendars right now, so remap those.
+            //
+            switch (calendarId)
+            {
+                case CalendarId.JAPANESELUNISOLAR:    // Data looks like Japanese
+                    calendarId = CalendarId.JAPAN;
+                    break;
+                case CalendarId.JULIAN:               // Data looks like gregorian US
+                case CalendarId.CHINESELUNISOLAR:     // Algorithmic, so actual data is irrelevent
+                case CalendarId.SAKA:                 // reserved to match Office but not implemented in our code, so data is irrelevent
+                case CalendarId.LUNAR_ETO_CHN:        // reserved to match Office but not implemented in our code, so data is irrelevent
+                case CalendarId.LUNAR_ETO_KOR:        // reserved to match Office but not implemented in our code, so data is irrelevent
+                case CalendarId.LUNAR_ETO_ROKUYOU:    // reserved to match Office but not implemented in our code, so data is irrelevent
+                case CalendarId.KOREANLUNISOLAR:      // Algorithmic, so actual data is irrelevent
+                case CalendarId.TAIWANLUNISOLAR:      // Algorithmic, so actual data is irrelevent
+                    calendarId = CalendarId.GREGORIAN_US;
+                    break;
+            }
+
+            //
+            // Special handling for some special calendar due to OS limitation.
+            // This includes calendar like Taiwan calendar, UmAlQura calendar, etc.
+            //
+            CheckSpecialCalendar(ref calendarId, ref localeName);
+
+            // Numbers
+            ret &= CallGetCalendarInfoEx(localeName, calendarId, CAL_ITWODIGITYEARMAX | useOverrides, out this.iTwoDigitYearMax);
+
+            // Strings
+            ret &= CallGetCalendarInfoEx(localeName, calendarId, CAL_SCALNAME, out this.sNativeName);
+            ret &= CallGetCalendarInfoEx(localeName, calendarId, CAL_SMONTHDAY | useOverrides, out this.sMonthDay);
+
+            // String Arrays
+            // Formats
+            ret &= CallEnumCalendarInfo(localeName, calendarId, CAL_SSHORTDATE, LOCALE_SSHORTDATE | useOverrides, out this.saShortDates);
+            ret &= CallEnumCalendarInfo(localeName, calendarId, CAL_SLONGDATE, LOCALE_SLONGDATE | useOverrides, out this.saLongDates);
+
+            // Get the YearMonth pattern.
+            ret &= CallEnumCalendarInfo(localeName, calendarId, CAL_SYEARMONTH, LOCALE_SYEARMONTH, out this.saYearMonths);
+
+            // Day & Month Names
+            // These are all single calType entries, 1 per day, so we have to make 7 or 13 calls to collect all the names
+
+            // Day
+            // Note that we're off-by-one since managed starts on sunday and windows starts on monday
+            ret &= GetCalendarDayInfo(localeName, calendarId, CAL_SDAYNAME7, out this.saDayNames);
+            ret &= GetCalendarDayInfo(localeName, calendarId, CAL_SABBREVDAYNAME7, out this.saAbbrevDayNames);
+
+            // Month names
+            ret &= GetCalendarMonthInfo(localeName, calendarId, CAL_SMONTHNAME1, out this.saMonthNames);
+            ret &= GetCalendarMonthInfo(localeName, calendarId, CAL_SABBREVMONTHNAME1, out this.saAbbrevMonthNames);
+
+            //
+            // The following LCTYPE are not supported in some platforms.  If the call fails,
+            // don't return a failure.
+            //
+            GetCalendarDayInfo(localeName, calendarId, CAL_SSHORTESTDAYNAME7, out this.saSuperShortDayNames);
+
+            // Gregorian may have genitive month names
+            if (calendarId == CalendarId.GREGORIAN)
+            {
+                GetCalendarMonthInfo(localeName, calendarId, CAL_SMONTHNAME1 | CAL_RETURN_GENITIVE_NAMES, out this.saMonthGenitiveNames);
+                GetCalendarMonthInfo(localeName, calendarId, CAL_SABBREVMONTHNAME1 | CAL_RETURN_GENITIVE_NAMES, out this.saAbbrevMonthGenitiveNames);
+            }
+
+            // Calendar Parts Names
+            // This doesn't get always get localized names for gregorian (not available in windows < 7)
+            // so: eg: coreclr on win < 7 won't get these
+            CallEnumCalendarInfo(localeName, calendarId, CAL_SERASTRING, 0, out this.saEraNames);
+            CallEnumCalendarInfo(localeName, calendarId, CAL_SABBREVERASTRING, 0, out this.saAbbrevEraNames);
+
+            //
+            // Calendar Era Info
+            // Note that calendar era data (offsets, etc) is hard coded for each calendar since this
+            // data is implementation specific and not dynamic (except perhaps Japanese)
+            //
+
+            // Clean up the escaping of the formats
+            this.saShortDates = CultureData.ReescapeWin32Strings(this.saShortDates);
+            this.saLongDates = CultureData.ReescapeWin32Strings(this.saLongDates);
+            this.saYearMonths = CultureData.ReescapeWin32Strings(this.saYearMonths);
+            this.sMonthDay = CultureData.ReescapeWin32String(this.sMonthDay);
+
+            return ret;
+        }
+
+        // Get native two digit year max
+        internal static int GetTwoDigitYearMax(CalendarId calendarId)
+        {
+            if (GlobalizationMode.Invariant)
+            {
+                return Invariant.iTwoDigitYearMax;
+            }
+
+            int twoDigitYearMax = -1;
+
+            if (!CallGetCalendarInfoEx(null, calendarId, (uint)CAL_ITWODIGITYEARMAX, out twoDigitYearMax))
+            {
+                twoDigitYearMax = -1;
+            }
+
+            return twoDigitYearMax;
+        }
+
+        // Call native side to figure out which calendars are allowed
+        internal static int GetCalendars(String localeName, bool useUserOverride, CalendarId[] calendars)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            EnumCalendarsData data = new EnumCalendarsData();
+            data.userOverride = 0;
+            data.calendars = new List<int>();
+
+            // First call GetLocaleInfo if necessary
+            if (useUserOverride)
+            {
+                // They want user overrides, see if the user calendar matches the input calendar
+                int userCalendar = CultureData.GetLocaleInfoExInt(localeName, LOCALE_ICALENDARTYPE);
+
+                // If we got a default, then use it as the first calendar
+                if (userCalendar != 0)
+                {
+                    data.userOverride = userCalendar;
+                    data.calendars.Add(userCalendar);
+                }
+            }
+
+            unsafe
+            {
+                Interop.Kernel32.EnumCalendarInfoExEx(EnumCalendarsCallback, localeName, ENUM_ALL_CALENDARS, null, CAL_ICALINTVALUE, Unsafe.AsPointer(ref data));
+            }
+
+            // Copy to the output array
+            for (int i = 0; i < Math.Min(calendars.Length, data.calendars.Count); i++)
+                calendars[i] = (CalendarId)data.calendars[i];
+
+            // Now we have a list of data, return the count
+            return data.calendars.Count;
+        }
+
+        private static bool SystemSupportsTaiwaneseCalendar()
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            string data;
+            // Taiwanese calendar get listed as one of the optional zh-TW calendars only when having zh-TW UI 
+            return CallGetCalendarInfoEx("zh-TW", CalendarId.TAIWAN, CAL_SCALNAME, out data);
+        }
+
+        // PAL Layer ends here
+
+        private const uint CAL_RETURN_NUMBER = 0x20000000;
+        private const uint CAL_RETURN_GENITIVE_NAMES = 0x10000000;
+        private const uint CAL_NOUSEROVERRIDE = 0x80000000;
+        private const uint CAL_SCALNAME = 0x00000002;
+        private const uint CAL_SMONTHDAY = 0x00000038;
+        private const uint CAL_SSHORTDATE = 0x00000005;
+        private const uint CAL_SLONGDATE = 0x00000006;
+        private const uint CAL_SYEARMONTH = 0x0000002f;
+        private const uint CAL_SDAYNAME7 = 0x0000000d;
+        private const uint CAL_SABBREVDAYNAME7 = 0x00000014;
+        private const uint CAL_SMONTHNAME1 = 0x00000015;
+        private const uint CAL_SABBREVMONTHNAME1 = 0x00000022;
+        private const uint CAL_SSHORTESTDAYNAME7 = 0x00000037;
+        private const uint CAL_SERASTRING = 0x00000004;
+        private const uint CAL_SABBREVERASTRING = 0x00000039;
+        private const uint CAL_ICALINTVALUE = 0x00000001;
+        private const uint CAL_ITWODIGITYEARMAX = 0x00000030;
+
+        private const uint ENUM_ALL_CALENDARS = 0xffffffff;
+
+        private const uint LOCALE_SSHORTDATE = 0x0000001F;
+        private const uint LOCALE_SLONGDATE = 0x00000020;
+        private const uint LOCALE_SYEARMONTH = 0x00001006;
+        private const uint LOCALE_ICALENDARTYPE = 0x00001009;
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        // For calendars like Gregorain US/Taiwan/UmAlQura, they are not available
+        // in all OS or all localized versions of OS.
+        // If OS does not support these calendars, we will fallback by using the
+        // appropriate fallback calendar and locale combination to retrieve data from OS.
+        //
+        // Parameters:
+        //  __deref_inout pCalendarInt:
+        //    Pointer to the calendar ID. This will be updated to new fallback calendar ID if needed.
+        //  __in_out pLocaleNameStackBuffer
+        //    Pointer to the StackSString object which holds the locale name to be checked.
+        //    This will be updated to new fallback locale name if needed.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        private static void CheckSpecialCalendar(ref CalendarId calendar, ref string localeName)
+        {
+            string data;
+
+            // Gregorian-US isn't always available in the OS, however it is the same for all locales
+            switch (calendar)
+            {
+                case CalendarId.GREGORIAN_US:
+                    // See if this works
+                    if (!CallGetCalendarInfoEx(localeName, calendar, CAL_SCALNAME, out data))
+                    {
+                        // Failed, set it to a locale (fa-IR) that's alway has Gregorian US available in the OS
+                        localeName = "fa-IR";
+                    }
+                    // See if that works
+                    if (!CallGetCalendarInfoEx(localeName, calendar, CAL_SCALNAME, out data))
+                    {
+                        // Failed again, just use en-US with the gregorian calendar
+                        localeName = "en-US";
+                        calendar = CalendarId.GREGORIAN;
+                    }
+                    break;
+                case CalendarId.TAIWAN:
+                    // Taiwan calendar data is not always in all language version of OS due to Geopolical reasons.
+                    // It is only available in zh-TW localized versions of Windows.
+                    // Let's check if OS supports it.  If not, fallback to Greogrian localized for Taiwan calendar.
+                    if (!SystemSupportsTaiwaneseCalendar())
+                    {
+                        calendar = CalendarId.GREGORIAN;
+                    }
+                    break;
+            }
+        }
+
+        private static bool CallGetCalendarInfoEx(string localeName, CalendarId calendar, uint calType, out int data)
+        {
+            return (Interop.Kernel32.GetCalendarInfoEx(localeName, (uint)calendar, IntPtr.Zero, calType | CAL_RETURN_NUMBER, IntPtr.Zero, 0, out data) != 0);
+        }
+
+        private static unsafe bool CallGetCalendarInfoEx(string localeName, CalendarId calendar, uint calType, out string data)
+        {
+            const int BUFFER_LENGTH = 80;
+
+            // The maximum size for values returned from GetCalendarInfoEx is 80 characters.
+            char* buffer = stackalloc char[BUFFER_LENGTH];
+
+            int ret = Interop.Kernel32.GetCalendarInfoEx(localeName, (uint)calendar, IntPtr.Zero, calType, (IntPtr)buffer, BUFFER_LENGTH, IntPtr.Zero);
+            if (ret > 0)
+            {
+                if (buffer[ret - 1] == '\0')
+                {
+                    ret--; // don't include the null termination in the string
+                }
+                data = new string(buffer, 0, ret);
+                return true;
+            }
+            data = "";
+            return false;
+        }
+
+        // Context for EnumCalendarInfoExEx callback.
+        private struct EnumData
+        {
+            public string userOverride;
+            public List<string> strings;
+        }
+
+        // EnumCalendarInfoExEx callback itself.
+        // [NativeCallable(CallingConvention = CallingConvention.StdCall)]
+        private static unsafe Interop.BOOL EnumCalendarInfoCallback(char* lpCalendarInfoString, uint calendar, IntPtr pReserved, void* lParam)
+        {
+            ref EnumData context = ref Unsafe.As<byte, EnumData>(ref *(byte*)lParam);
+            try
+            {
+                string calendarInfo = new string(lpCalendarInfoString);
+
+                // If we had a user override, check to make sure this differs
+                if (context.userOverride != calendarInfo)
+                    context.strings.Add(calendarInfo);
+
+                return Interop.BOOL.TRUE;
+            }
+            catch (Exception)
+            {
+                return Interop.BOOL.FALSE;
+            }
+        }
+
+        private static unsafe bool CallEnumCalendarInfo(string localeName, CalendarId calendar, uint calType, uint lcType, out string[] data)
+        {
+            EnumData context = new EnumData();
+            context.userOverride = null;
+            context.strings = new List<string>();
+            // First call GetLocaleInfo if necessary
+            if (((lcType != 0) && ((lcType & CAL_NOUSEROVERRIDE) == 0)) &&
+                // Get user locale, see if it matches localeName.
+                // Note that they should match exactly, including letter case
+                GetUserDefaultLocaleName() == localeName)
+            {
+                // They want user overrides, see if the user calendar matches the input calendar
+                CalendarId userCalendar = (CalendarId)CultureData.GetLocaleInfoExInt(localeName, LOCALE_ICALENDARTYPE);
+
+                // If the calendars were the same, see if the locales were the same
+                if (userCalendar == calendar)
+                {
+                    // They matched, get the user override since locale & calendar match
+                    string res = CultureData.GetLocaleInfoEx(localeName, lcType);
+
+                    // if it succeeded remember the override for the later callers
+                    if (res != null)
+                    {
+                        // Remember this was the override (so we can look for duplicates later in the enum function)
+                        context.userOverride = res;
+
+                        // Add to the result strings.
+                        context.strings.Add(res);
+                    }
+                }
+            }
+
+            unsafe
+            {
+                // Now call the enumeration API. Work is done by our callback function
+                Interop.Kernel32.EnumCalendarInfoExEx(EnumCalendarInfoCallback, localeName, (uint)calendar, null, calType, Unsafe.AsPointer(ref context));
+            }
+
+            // Now we have a list of data, fail if we didn't find anything.
+            if (context.strings.Count == 0)
+            {
+                data = null;
+                return false;
+            }
+
+            string[] output = context.strings.ToArray();
+
+            if (calType == CAL_SABBREVERASTRING || calType == CAL_SERASTRING)
+            {
+                // Eras are enumerated backwards.  (oldest era name first, but
+                // Japanese calendar has newest era first in array, and is only
+                // calendar with multiple eras)
+                Array.Reverse(output, 0, output.Length);
+            }
+
+            data = output;
+
+            return true;
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        // Get the native day names
+        //
+        // NOTE: There's a disparity between .Net & windows day orders, the input day should
+        //           start with Sunday
+        //
+        // Parameters:
+        //      OUT pOutputStrings      The output string[] value.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        private static bool GetCalendarDayInfo(string localeName, CalendarId calendar, uint calType, out string[] outputStrings)
+        {
+            bool result = true;
+
+            //
+            // We'll need a new array of 7 items
+            //
+            string[] results = new string[7];
+
+            // Get each one of them
+            for (int i = 0; i < 7; i++, calType++)
+            {
+                result &= CallGetCalendarInfoEx(localeName, calendar, calType, out results[i]);
+
+                // On the first iteration we need to go from CAL_SDAYNAME7 to CAL_SDAYNAME1, so subtract 7 before the ++ happens
+                // This is because the framework starts on sunday and windows starts on monday when counting days
+                if (i == 0)
+                    calType -= 7;
+            }
+
+            outputStrings = results;
+
+            return result;
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        // Get the native month names
+        //
+        // Parameters:
+        //      OUT pOutputStrings      The output string[] value.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        private static bool GetCalendarMonthInfo(string localeName, CalendarId calendar, uint calType, out string[] outputStrings)
+        {
+            //
+            // We'll need a new array of 13 items
+            //
+            string[] results = new string[13];
+
+            // Get each one of them
+            for (int i = 0; i < 13; i++, calType++)
+            {
+                if (!CallGetCalendarInfoEx(localeName, calendar, calType, out results[i]))
+                    results[i] = "";
+            }
+
+            outputStrings = results;
+
+            return true;
+        }
+
+        //
+        // struct to help our calendar data enumaration callback
+        //
+        private struct EnumCalendarsData
+        {
+            public int userOverride;   // user override value (if found)
+            public List<int> calendars;      // list of calendars found so far
+        }
+
+        // [NativeCallable(CallingConvention = CallingConvention.StdCall)]
+        private static unsafe Interop.BOOL EnumCalendarsCallback(char* lpCalendarInfoString, uint calendar, IntPtr reserved, void* lParam)
+        {
+            ref EnumCalendarsData context = ref Unsafe.As<byte, EnumCalendarsData>(ref *(byte*)lParam);
+            try
+            {
+                // If we had a user override, check to make sure this differs
+                if (context.userOverride != calendar)
+                    context.calendars.Add((int)calendar);
+
+                return Interop.BOOL.TRUE;
+            }
+            catch (Exception)
+            {
+                return Interop.BOOL.FALSE;
+            }
+        }
+
+        private static unsafe String GetUserDefaultLocaleName()
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            const int LOCALE_NAME_MAX_LENGTH = 85;
+            const uint LOCALE_SNAME = 0x0000005c;
+            const string LOCALE_NAME_USER_DEFAULT = null;
+
+            int result;
+            char* localeName = stackalloc char[LOCALE_NAME_MAX_LENGTH];
+            result = CultureData.GetLocaleInfoEx(LOCALE_NAME_USER_DEFAULT, LOCALE_SNAME, localeName, LOCALE_NAME_MAX_LENGTH);
+
+            return result <= 0 ? "" : new String(localeName, 0, result - 1); // exclude the null termination
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CalendarData.cs b/src/System.Private.CoreLib/shared/System/Globalization/CalendarData.cs
new file mode 100644
index 0000000000..ea70a1ce9a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CalendarData.cs
@@ -0,0 +1,378 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    // List of calendar data
+    // Note the we cache overrides.
+    // Note that localized names (resource names) aren't available from here.
+    //
+    //  NOTE: Calendars depend on the locale name that creates it.  Only a few
+    //        properties are available without locales using CalendarData.GetCalendar(CalendarData)
+
+    internal partial class CalendarData
+    {
+        // Max calendars
+        internal const int MAX_CALENDARS = 23;
+
+        // Identity
+        internal String sNativeName; // Calendar Name for the locale
+
+        // Formats
+        internal String[] saShortDates; // Short Data format, default first
+        internal String[] saYearMonths; // Year/Month Data format, default first
+        internal String[] saLongDates; // Long Data format, default first
+        internal String sMonthDay; // Month/Day format
+
+        // Calendar Parts Names
+        internal String[] saEraNames; // Names of Eras
+        internal String[] saAbbrevEraNames; // Abbreviated Era Names
+        internal String[] saAbbrevEnglishEraNames; // Abbreviated Era Names in English
+        internal String[] saDayNames; // Day Names, null to use locale data, starts on Sunday
+        internal String[] saAbbrevDayNames; // Abbrev Day Names, null to use locale data, starts on Sunday
+        internal String[] saSuperShortDayNames; // Super short Day of week names
+        internal String[] saMonthNames; // Month Names (13)
+        internal String[] saAbbrevMonthNames; // Abbrev Month Names (13)
+        internal String[] saMonthGenitiveNames; // Genitive Month Names (13)
+        internal String[] saAbbrevMonthGenitiveNames; // Genitive Abbrev Month Names (13)
+        internal String[] saLeapYearMonthNames; // Multiple strings for the month names in a leap year.
+
+        // Integers at end to make marshaller happier
+        internal int iTwoDigitYearMax = 2029; // Max 2 digit year (for Y2K bug data entry)
+        internal int iCurrentEra = 0;  // current era # (usually 1)
+
+        // Use overrides?
+        internal bool bUseUserOverrides; // True if we want user overrides.
+
+        // Static invariant for the invariant locale
+        internal static readonly CalendarData Invariant = CreateInvariant();
+
+        // Private constructor
+        private CalendarData() { }
+
+        // Invariant factory
+        private static CalendarData CreateInvariant()
+        {
+            // Set our default/gregorian US calendar data
+            // Calendar IDs are 1-based, arrays are 0 based.
+            CalendarData invariant = new CalendarData();
+
+            // Set default data for calendar
+            // Note that we don't load resources since this IS NOT supposed to change (by definition)
+            invariant.sNativeName = "Gregorian Calendar";  // Calendar Name
+
+            // Year
+            invariant.iTwoDigitYearMax = 2029; // Max 2 digit year (for Y2K bug data entry)
+            invariant.iCurrentEra = 1; // Current era #
+
+            // Formats
+            invariant.saShortDates = new String[] { "MM/dd/yyyy", "yyyy-MM-dd" };          // short date format
+            invariant.saLongDates = new String[] { "dddd, dd MMMM yyyy" };                 // long date format
+            invariant.saYearMonths = new String[] { "yyyy MMMM" };                         // year month format
+            invariant.sMonthDay = "MMMM dd";                                            // Month day pattern
+
+            // Calendar Parts Names
+            invariant.saEraNames = new String[] { "A.D." };     // Era names
+            invariant.saAbbrevEraNames = new String[] { "AD" };      // Abbreviated Era names
+            invariant.saAbbrevEnglishEraNames = new String[] { "AD" };     // Abbreviated era names in English
+            invariant.saDayNames = new String[] { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" };// day names
+            invariant.saAbbrevDayNames = new String[] { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };     // abbreviated day names
+            invariant.saSuperShortDayNames = new String[] { "Su", "Mo", "Tu", "We", "Th", "Fr", "Sa" };      // The super short day names
+            invariant.saMonthNames = new String[] { "January", "February", "March", "April", "May", "June",
+                                                            "July", "August", "September", "October", "November", "December", String.Empty}; // month names
+            invariant.saAbbrevMonthNames = new String[] { "Jan", "Feb", "Mar", "Apr", "May", "Jun",
+                                                            "Jul", "Aug", "Sep", "Oct", "Nov", "Dec", String.Empty}; // abbreviated month names
+            invariant.saMonthGenitiveNames = invariant.saMonthNames;              // Genitive month names (same as month names for invariant)
+            invariant.saAbbrevMonthGenitiveNames = invariant.saAbbrevMonthNames;    // Abbreviated genitive month names (same as abbrev month names for invariant)
+            invariant.saLeapYearMonthNames = invariant.saMonthNames;              // leap year month names are unused in Gregorian English (invariant)
+
+            invariant.bUseUserOverrides = false;
+
+            return invariant;
+        }
+
+        //
+        // Get a bunch of data for a calendar
+        //
+        internal CalendarData(String localeName, CalendarId calendarId, bool bUseUserOverrides)
+        {
+            this.bUseUserOverrides = bUseUserOverrides;
+
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            if (!LoadCalendarDataFromSystem(localeName, calendarId))
+            {
+                Debug.Fail("[CalendarData] LoadCalendarDataFromSystem call isn't expected to fail for calendar " + calendarId + " locale " + localeName);
+
+                // Something failed, try invariant for missing parts
+                // This is really not good, but we don't want the callers to crash.
+                if (this.sNativeName == null) this.sNativeName = String.Empty;           // Calendar Name for the locale.
+
+                // Formats
+                if (this.saShortDates == null) this.saShortDates = Invariant.saShortDates; // Short Data format, default first
+                if (this.saYearMonths == null) this.saYearMonths = Invariant.saYearMonths; // Year/Month Data format, default first
+                if (this.saLongDates == null) this.saLongDates = Invariant.saLongDates;  // Long Data format, default first
+                if (this.sMonthDay == null) this.sMonthDay = Invariant.sMonthDay;    // Month/Day format
+
+                // Calendar Parts Names
+                if (this.saEraNames == null) this.saEraNames = Invariant.saEraNames;              // Names of Eras
+                if (this.saAbbrevEraNames == null) this.saAbbrevEraNames = Invariant.saAbbrevEraNames;        // Abbreviated Era Names
+                if (this.saAbbrevEnglishEraNames == null) this.saAbbrevEnglishEraNames = Invariant.saAbbrevEnglishEraNames; // Abbreviated Era Names in English
+                if (this.saDayNames == null) this.saDayNames = Invariant.saDayNames;              // Day Names, null to use locale data, starts on Sunday
+                if (this.saAbbrevDayNames == null) this.saAbbrevDayNames = Invariant.saAbbrevDayNames;        // Abbrev Day Names, null to use locale data, starts on Sunday
+                if (this.saSuperShortDayNames == null) this.saSuperShortDayNames = Invariant.saSuperShortDayNames;    // Super short Day of week names
+                if (this.saMonthNames == null) this.saMonthNames = Invariant.saMonthNames;            // Month Names (13)
+                if (this.saAbbrevMonthNames == null) this.saAbbrevMonthNames = Invariant.saAbbrevMonthNames;      // Abbrev Month Names (13)
+                // Genitive and Leap names can follow the fallback below
+            }
+
+            if (calendarId == CalendarId.TAIWAN)
+            {
+                if (SystemSupportsTaiwaneseCalendar())
+                {
+                    // We got the month/day names from the OS (same as gregorian), but the native name is wrong
+                    this.sNativeName = "\x4e2d\x83ef\x6c11\x570b\x66c6";
+                }
+                else
+                {
+                    this.sNativeName = String.Empty;
+                }
+            }
+
+            // Check for null genitive names (in case unmanaged side skips it for non-gregorian calendars, etc)
+            if (this.saMonthGenitiveNames == null || this.saMonthGenitiveNames.Length == 0 || String.IsNullOrEmpty(this.saMonthGenitiveNames[0]))
+                this.saMonthGenitiveNames = this.saMonthNames;              // Genitive month names (same as month names for invariant)
+            if (this.saAbbrevMonthGenitiveNames == null || this.saAbbrevMonthGenitiveNames.Length == 0 || String.IsNullOrEmpty(this.saAbbrevMonthGenitiveNames[0]))
+                this.saAbbrevMonthGenitiveNames = this.saAbbrevMonthNames;    // Abbreviated genitive month names (same as abbrev month names for invariant)
+            if (this.saLeapYearMonthNames == null || this.saLeapYearMonthNames.Length == 0 || String.IsNullOrEmpty(this.saLeapYearMonthNames[0]))
+                this.saLeapYearMonthNames = this.saMonthNames;
+
+            InitializeEraNames(localeName, calendarId);
+
+            InitializeAbbreviatedEraNames(localeName, calendarId);
+
+            // Abbreviated English Era Names are only used for the Japanese calendar.
+            if (calendarId == CalendarId.JAPAN)
+            {
+                this.saAbbrevEnglishEraNames = JapaneseCalendar.EnglishEraNames();
+            }
+            else
+            {
+                // For all others just use the an empty string (doesn't matter we'll never ask for it for other calendars)
+                this.saAbbrevEnglishEraNames = new String[] { "" };
+            }
+
+            // Japanese is the only thing with > 1 era.  Its current era # is how many ever 
+            // eras are in the array.  (And the others all have 1 string in the array)
+            this.iCurrentEra = this.saEraNames.Length;
+        }
+
+        private void InitializeEraNames(string localeName, CalendarId calendarId)
+        {
+            // Note that the saEraNames only include "A.D."  We don't have localized names for other calendars available from windows
+            switch (calendarId)
+            {
+                // For Localized Gregorian we really expect the data from the OS.
+                case CalendarId.GREGORIAN:
+                    // Fallback for CoreCLR < Win7 or culture.dll missing            
+                    if (this.saEraNames == null || this.saEraNames.Length == 0 || String.IsNullOrEmpty(this.saEraNames[0]))
+                    {
+                        this.saEraNames = new String[] { "A.D." };
+                    }
+                    break;
+
+                // The rest of the calendars have constant data, so we'll just use that
+                case CalendarId.GREGORIAN_US:
+                case CalendarId.JULIAN:
+                    this.saEraNames = new String[] { "A.D." };
+                    break;
+                case CalendarId.HEBREW:
+                    this.saEraNames = new String[] { "C.E." };
+                    break;
+                case CalendarId.HIJRI:
+                case CalendarId.UMALQURA:
+                    if (localeName == "dv-MV")
+                    {
+                        // Special case for Divehi
+                        this.saEraNames = new String[] { "\x0780\x07a8\x0796\x07b0\x0783\x07a9" };
+                    }
+                    else
+                    {
+                        this.saEraNames = new String[] { "\x0628\x0639\x062F \x0627\x0644\x0647\x062C\x0631\x0629" };
+                    }
+                    break;
+                case CalendarId.GREGORIAN_ARABIC:
+                case CalendarId.GREGORIAN_XLIT_ENGLISH:
+                case CalendarId.GREGORIAN_XLIT_FRENCH:
+                    // These are all the same:
+                    this.saEraNames = new String[] { "\x0645" };
+                    break;
+
+                case CalendarId.GREGORIAN_ME_FRENCH:
+                    this.saEraNames = new String[] { "ap. J.-C." };
+                    break;
+
+                case CalendarId.TAIWAN:
+                    if (SystemSupportsTaiwaneseCalendar())
+                    {
+                        this.saEraNames = new String[] { "\x4e2d\x83ef\x6c11\x570b" };
+                    }
+                    else
+                    {
+                        this.saEraNames = new String[] { String.Empty };
+                    }
+                    break;
+
+                case CalendarId.KOREA:
+                    this.saEraNames = new String[] { "\xb2e8\xae30" };
+                    break;
+
+                case CalendarId.THAI:
+                    this.saEraNames = new String[] { "\x0e1e\x002e\x0e28\x002e" };
+                    break;
+
+                case CalendarId.JAPAN:
+                case CalendarId.JAPANESELUNISOLAR:
+                    this.saEraNames = JapaneseCalendar.EraNames();
+                    break;
+
+                case CalendarId.PERSIAN:
+                    if (this.saEraNames == null || this.saEraNames.Length == 0 || String.IsNullOrEmpty(this.saEraNames[0]))
+                    {
+                        this.saEraNames = new String[] { "\x0647\x002e\x0634" };
+                    }
+                    break;
+
+                default:
+                    // Most calendars are just "A.D."
+                    this.saEraNames = Invariant.saEraNames;
+                    break;
+            }
+        }
+
+        private void InitializeAbbreviatedEraNames(string localeName, CalendarId calendarId)
+        {
+            // Note that the saAbbrevEraNames only include "AD"  We don't have localized names for other calendars available from windows
+            switch (calendarId)
+            {
+                // For Localized Gregorian we really expect the data from the OS.
+                case CalendarId.GREGORIAN:
+                    // Fallback for CoreCLR < Win7 or culture.dll missing            
+                    if (this.saAbbrevEraNames == null || this.saAbbrevEraNames.Length == 0 || String.IsNullOrEmpty(this.saAbbrevEraNames[0]))
+                    {
+                        this.saAbbrevEraNames = new String[] { "AD" };
+                    }
+                    break;
+
+                // The rest of the calendars have constant data, so we'll just use that
+                case CalendarId.GREGORIAN_US:
+                case CalendarId.JULIAN:
+                    this.saAbbrevEraNames = new String[] { "AD" };
+                    break;
+                case CalendarId.JAPAN:
+                case CalendarId.JAPANESELUNISOLAR:
+                    this.saAbbrevEraNames = JapaneseCalendar.AbbrevEraNames();
+                    break;
+                case CalendarId.HIJRI:
+                case CalendarId.UMALQURA:
+                    if (localeName == "dv-MV")
+                    {
+                        // Special case for Divehi
+                        this.saAbbrevEraNames = new String[] { "\x0780\x002e" };
+                    }
+                    else
+                    {
+                        this.saAbbrevEraNames = new String[] { "\x0647\x0640" };
+                    }
+                    break;
+                case CalendarId.TAIWAN:
+                    // Get era name and abbreviate it
+                    this.saAbbrevEraNames = new String[1];
+                    if (this.saEraNames[0].Length == 4)
+                    {
+                        this.saAbbrevEraNames[0] = this.saEraNames[0].Substring(2, 2);
+                    }
+                    else
+                    {
+                        this.saAbbrevEraNames[0] = this.saEraNames[0];
+                    }
+                    break;
+
+                case CalendarId.PERSIAN:
+                    if (this.saAbbrevEraNames == null || this.saAbbrevEraNames.Length == 0 || String.IsNullOrEmpty(this.saAbbrevEraNames[0]))
+                    {
+                        this.saAbbrevEraNames = this.saEraNames;
+                    }
+                    break;
+
+                default:
+                    // Most calendars just use the full name
+                    this.saAbbrevEraNames = this.saEraNames;
+                    break;
+            }
+        }
+
+        internal static CalendarData GetCalendarData(CalendarId calendarId)
+        {
+            //
+            // Get a calendar.
+            // Unfortunately we depend on the locale in the OS, so we need a locale
+            // no matter what.  So just get the appropriate calendar from the 
+            // appropriate locale here
+            //
+
+            // Get a culture name
+            // TODO: Note that this doesn't handle the new calendars (lunisolar, etc)
+            String culture = CalendarIdToCultureName(calendarId);
+
+            // Return our calendar
+            return CultureInfo.GetCultureInfo(culture)._cultureData.GetCalendar(calendarId);
+        }
+
+        private static String CalendarIdToCultureName(CalendarId calendarId)
+        {
+            switch (calendarId)
+            {
+                case CalendarId.GREGORIAN_US:
+                    return "fa-IR";             // "fa-IR" Iran
+
+                case CalendarId.JAPAN:
+                    return "ja-JP";             // "ja-JP" Japan
+
+                case CalendarId.TAIWAN:
+                    return "zh-TW";             // zh-TW Taiwan
+
+                case CalendarId.KOREA:
+                    return "ko-KR";             // "ko-KR" Korea
+
+                case CalendarId.HIJRI:
+                case CalendarId.GREGORIAN_ARABIC:
+                case CalendarId.UMALQURA:
+                    return "ar-SA";             // "ar-SA" Saudi Arabia
+
+                case CalendarId.THAI:
+                    return "th-TH";             // "th-TH" Thailand
+
+                case CalendarId.HEBREW:
+                    return "he-IL";             // "he-IL" Israel
+
+                case CalendarId.GREGORIAN_ME_FRENCH:
+                    return "ar-DZ";             // "ar-DZ" Algeria
+
+                case CalendarId.GREGORIAN_XLIT_ENGLISH:
+                case CalendarId.GREGORIAN_XLIT_FRENCH:
+                    return "ar-IQ";             // "ar-IQ"; Iraq
+
+                default:
+                    // Default to gregorian en-US
+                    break;
+            }
+
+            return "en-US";
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CalendarWeekRule.cs b/src/System.Private.CoreLib/shared/System/Globalization/CalendarWeekRule.cs
new file mode 100644
index 0000000000..f683ed05e7
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CalendarWeekRule.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Globalization
+{
+    public enum CalendarWeekRule
+    {
+        FirstDay = 0,           // Week 1 begins on the first day of the year
+
+        FirstFullWeek = 1,      // Week 1 begins on first FirstDayOfWeek not before the first day of the year
+
+        FirstFourDayWeek = 2    // Week 1 begins on first FirstDayOfWeek such that FirstDayOfWeek+3 is not before the first day of the year        
+    };
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CalendricalCalculationsHelper.cs b/src/System.Private.CoreLib/shared/System/Globalization/CalendricalCalculationsHelper.cs
new file mode 100644
index 0000000000..e0a3072b22
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CalendricalCalculationsHelper.cs
@@ -0,0 +1,412 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    internal class CalendricalCalculationsHelper
+    {
+        private const double FullCircleOfArc = 360.0; // 360.0;
+        private const int HalfCircleOfArc = 180;
+        private const double TwelveHours = 0.5; // half a day
+        private const double Noon2000Jan01 = 730120.5;
+        internal const double MeanTropicalYearInDays = 365.242189;
+        private const double MeanSpeedOfSun = MeanTropicalYearInDays / FullCircleOfArc;
+        private const double LongitudeSpring = 0.0;
+        private const double TwoDegreesAfterSpring = 2.0;
+        private const int SecondsPerDay = 24 * 60 * 60; // 24 hours * 60 minutes * 60 seconds
+
+        private const int DaysInUniformLengthCentury = 36525;
+        private const int SecondsPerMinute = 60;
+        private const int MinutesPerDegree = 60;
+
+        private static readonly long s_startOf1810 = GetNumberOfDays(new DateTime(1810, 1, 1));
+        private static readonly long s_startOf1900Century = GetNumberOfDays(new DateTime(1900, 1, 1));
+
+        private static readonly double[] s_coefficients1900to1987 = new double[] { -0.00002, 0.000297, 0.025184, -0.181133, 0.553040, -0.861938, 0.677066, -0.212591 };
+        private static readonly double[] s_coefficients1800to1899 = new double[] { -0.000009, 0.003844, 0.083563, 0.865736, 4.867575, 15.845535, 31.332267, 38.291999, 28.316289, 11.636204, 2.043794 };
+        private static readonly double[] s_coefficients1700to1799 = new double[] { 8.118780842, -0.005092142, 0.003336121, -0.0000266484 };
+        private static readonly double[] s_coefficients1620to1699 = new double[] { 196.58333, -4.0675, 0.0219167 };
+        private static readonly double[] s_lambdaCoefficients = new double[] { 280.46645, 36000.76983, 0.0003032 };
+        private static readonly double[] s_anomalyCoefficients = new double[] { 357.52910, 35999.05030, -0.0001559, -0.00000048 };
+        private static readonly double[] s_eccentricityCoefficients = new double[] { 0.016708617, -0.000042037, -0.0000001236 };
+        private static readonly double[] s_coefficients = new double[] { Angle(23, 26, 21.448), Angle(0, 0, -46.8150), Angle(0, 0, -0.00059), Angle(0, 0, 0.001813) };
+        private static readonly double[] s_coefficientsA = new double[] { 124.90, -1934.134, 0.002063 };
+        private static readonly double[] s_coefficientsB = new double[] { 201.11, 72001.5377, 0.00057 };
+
+        private static double RadiansFromDegrees(double degree)
+        {
+            return degree * Math.PI / 180;
+        }
+
+        private static double SinOfDegree(double degree)
+        {
+            return Math.Sin(RadiansFromDegrees(degree));
+        }
+
+        private static double CosOfDegree(double degree)
+        {
+            return Math.Cos(RadiansFromDegrees(degree));
+        }
+        private static double TanOfDegree(double degree)
+        {
+            return Math.Tan(RadiansFromDegrees(degree));
+        }
+
+        public static double Angle(int degrees, int minutes, double seconds)
+        {
+            return ((seconds / SecondsPerMinute + minutes) / MinutesPerDegree) + degrees;
+        }
+
+        private static double Obliquity(double julianCenturies)
+        {
+            return PolynomialSum(s_coefficients, julianCenturies);
+        }
+
+        internal static long GetNumberOfDays(DateTime date)
+        {
+            return date.Ticks / GregorianCalendar.TicksPerDay;
+        }
+
+        private static int GetGregorianYear(double numberOfDays)
+        {
+            return new DateTime(Math.Min((long)(Math.Floor(numberOfDays) * GregorianCalendar.TicksPerDay), DateTime.MaxValue.Ticks)).Year;
+        }
+
+        private enum CorrectionAlgorithm
+        {
+            Default,
+            Year1988to2019,
+            Year1900to1987,
+            Year1800to1899,
+            Year1700to1799,
+            Year1620to1699
+        }
+
+        private struct EphemerisCorrectionAlgorithmMap
+        {
+            public EphemerisCorrectionAlgorithmMap(int year, CorrectionAlgorithm algorithm)
+            {
+                _lowestYear = year;
+                _algorithm = algorithm;
+            }
+
+            internal int _lowestYear;
+            internal CorrectionAlgorithm _algorithm;
+        };
+
+        private static readonly EphemerisCorrectionAlgorithmMap[] s_ephemerisCorrectionTable = new EphemerisCorrectionAlgorithmMap[]
+        {
+            // lowest year that starts algorithm, algorithm to use
+            new EphemerisCorrectionAlgorithmMap(2020, CorrectionAlgorithm.Default),
+            new EphemerisCorrectionAlgorithmMap(1988, CorrectionAlgorithm.Year1988to2019),
+            new EphemerisCorrectionAlgorithmMap(1900, CorrectionAlgorithm.Year1900to1987),
+            new EphemerisCorrectionAlgorithmMap(1800, CorrectionAlgorithm.Year1800to1899),
+            new EphemerisCorrectionAlgorithmMap(1700, CorrectionAlgorithm.Year1700to1799),
+            new EphemerisCorrectionAlgorithmMap(1620, CorrectionAlgorithm.Year1620to1699),
+            new EphemerisCorrectionAlgorithmMap(int.MinValue, CorrectionAlgorithm.Default) // default must be last
+        };
+
+        private static double Reminder(double divisor, double dividend)
+        {
+            double whole = Math.Floor(divisor / dividend);
+            return divisor - (dividend * whole);
+        }
+
+        private static double NormalizeLongitude(double longitude)
+        {
+            longitude = Reminder(longitude, FullCircleOfArc);
+            if (longitude < 0)
+            {
+                longitude += FullCircleOfArc;
+            }
+            return longitude;
+        }
+
+        public static double AsDayFraction(double longitude)
+        {
+            return longitude / FullCircleOfArc;
+        }
+
+        private static double PolynomialSum(double[] coefficients, double indeterminate)
+        {
+            double sum = coefficients[0];
+            double indeterminateRaised = 1;
+            for (int i = 1; i < coefficients.Length; i++)
+            {
+                indeterminateRaised *= indeterminate;
+                sum += (coefficients[i] * indeterminateRaised);
+            }
+
+            return sum;
+        }
+
+        private static double CenturiesFrom1900(int gregorianYear)
+        {
+            long july1stOfYear = GetNumberOfDays(new DateTime(gregorianYear, 7, 1));
+            return (double)(july1stOfYear - s_startOf1900Century) / DaysInUniformLengthCentury;
+        }
+
+        // the following formulas defines a polynomial function which gives us the amount that the earth is slowing down for specific year ranges
+        private static double DefaultEphemerisCorrection(int gregorianYear)
+        {
+            Debug.Assert(gregorianYear < 1620 || 2020 <= gregorianYear);
+            long january1stOfYear = GetNumberOfDays(new DateTime(gregorianYear, 1, 1));
+            double daysSinceStartOf1810 = january1stOfYear - s_startOf1810;
+            double x = TwelveHours + daysSinceStartOf1810;
+            return ((Math.Pow(x, 2) / 41048480) - 15) / SecondsPerDay;
+        }
+
+        private static double EphemerisCorrection1988to2019(int gregorianYear)
+        {
+            Debug.Assert(1988 <= gregorianYear && gregorianYear <= 2019);
+            return (double)(gregorianYear - 1933) / SecondsPerDay;
+        }
+
+        private static double EphemerisCorrection1900to1987(int gregorianYear)
+        {
+            Debug.Assert(1900 <= gregorianYear && gregorianYear <= 1987);
+            double centuriesFrom1900 = CenturiesFrom1900(gregorianYear);
+            return PolynomialSum(s_coefficients1900to1987, centuriesFrom1900);
+        }
+
+        private static double EphemerisCorrection1800to1899(int gregorianYear)
+        {
+            Debug.Assert(1800 <= gregorianYear && gregorianYear <= 1899);
+            double centuriesFrom1900 = CenturiesFrom1900(gregorianYear);
+            return PolynomialSum(s_coefficients1800to1899, centuriesFrom1900);
+        }
+
+        private static double EphemerisCorrection1700to1799(int gregorianYear)
+        {
+            Debug.Assert(1700 <= gregorianYear && gregorianYear <= 1799);
+            double yearsSince1700 = gregorianYear - 1700;
+            return PolynomialSum(s_coefficients1700to1799, yearsSince1700) / SecondsPerDay;
+        }
+
+        private static double EphemerisCorrection1620to1699(int gregorianYear)
+        {
+            Debug.Assert(1620 <= gregorianYear && gregorianYear <= 1699);
+            double yearsSince1600 = gregorianYear - 1600;
+            return PolynomialSum(s_coefficients1620to1699, yearsSince1600) / SecondsPerDay;
+        }
+
+        // ephemeris-correction: correction to account for the slowing down of the rotation of the earth
+        private static double EphemerisCorrection(double time)
+        {
+            int year = GetGregorianYear(time);
+            foreach (EphemerisCorrectionAlgorithmMap map in s_ephemerisCorrectionTable)
+            {
+                if (map._lowestYear <= year)
+                {
+                    switch (map._algorithm)
+                    {
+                        case CorrectionAlgorithm.Default: return DefaultEphemerisCorrection(year);
+                        case CorrectionAlgorithm.Year1988to2019: return EphemerisCorrection1988to2019(year);
+                        case CorrectionAlgorithm.Year1900to1987: return EphemerisCorrection1900to1987(year);
+                        case CorrectionAlgorithm.Year1800to1899: return EphemerisCorrection1800to1899(year);
+                        case CorrectionAlgorithm.Year1700to1799: return EphemerisCorrection1700to1799(year);
+                        case CorrectionAlgorithm.Year1620to1699: return EphemerisCorrection1620to1699(year);
+                    }
+
+                    break; // break the loop and assert eventually 
+                }
+            }
+
+            Debug.Fail("Not expected to come here");
+            return DefaultEphemerisCorrection(year);
+        }
+
+        public static double JulianCenturies(double moment)
+        {
+            double dynamicalMoment = moment + EphemerisCorrection(moment);
+            return (dynamicalMoment - Noon2000Jan01) / DaysInUniformLengthCentury;
+        }
+
+        private static bool IsNegative(double value)
+        {
+            return Math.Sign(value) == -1;
+        }
+
+        private static double CopySign(double value, double sign)
+        {
+            return (IsNegative(value) == IsNegative(sign)) ? value : -value;
+        }
+
+        // equation-of-time; approximate the difference between apparent solar time and mean solar time
+        // formal definition is EOT = GHA - GMHA
+        // GHA is the Greenwich Hour Angle of the apparent (actual) Sun
+        // GMHA is the Greenwich Mean Hour Angle of the mean (fictitious) Sun
+        // http://www.esrl.noaa.gov/gmd/grad/solcalc/
+        // http://en.wikipedia.org/wiki/Equation_of_time
+        private static double EquationOfTime(double time)
+        {
+            double julianCenturies = JulianCenturies(time);
+            double lambda = PolynomialSum(s_lambdaCoefficients, julianCenturies);
+            double anomaly = PolynomialSum(s_anomalyCoefficients, julianCenturies);
+            double eccentricity = PolynomialSum(s_eccentricityCoefficients, julianCenturies);
+
+            double epsilon = Obliquity(julianCenturies);
+            double tanHalfEpsilon = TanOfDegree(epsilon / 2);
+            double y = tanHalfEpsilon * tanHalfEpsilon;
+
+            double dividend = ((y * SinOfDegree(2 * lambda))
+                - (2 * eccentricity * SinOfDegree(anomaly))
+                + (4 * eccentricity * y * SinOfDegree(anomaly) * CosOfDegree(2 * lambda))
+                - (0.5 * Math.Pow(y, 2) * SinOfDegree(4 * lambda))
+                - (1.25 * Math.Pow(eccentricity, 2) * SinOfDegree(2 * anomaly)));
+            double divisor = 2 * Math.PI;
+            double equation = dividend / divisor;
+
+            // approximation of equation of time is not valid for dates that are many millennia in the past or future
+            // thus limited to a half day
+            return CopySign(Math.Min(Math.Abs(equation), TwelveHours), equation);
+        }
+
+        private static double AsLocalTime(double apparentMidday, double longitude)
+        {
+            // slightly inaccurate since equation of time takes mean time not apparent time as its argument, but the difference is negligible
+            double universalTime = apparentMidday - AsDayFraction(longitude);
+            return apparentMidday - EquationOfTime(universalTime);
+        }
+
+        // midday
+        public static double Midday(double date, double longitude)
+        {
+            return AsLocalTime(date + TwelveHours, longitude) - AsDayFraction(longitude);
+        }
+
+        private static double InitLongitude(double longitude)
+        {
+            return NormalizeLongitude(longitude + HalfCircleOfArc) - HalfCircleOfArc;
+        }
+
+        // midday-in-tehran
+        public static double MiddayAtPersianObservationSite(double date)
+        {
+            return Midday(date, InitLongitude(52.5)); // 52.5 degrees east - longitude of UTC+3:30 which defines Iranian Standard Time
+        }
+
+        private static double PeriodicTerm(double julianCenturies, int x, double y, double z)
+        {
+            return x * SinOfDegree(y + z * julianCenturies);
+        }
+
+        private static double SumLongSequenceOfPeriodicTerms(double julianCenturies)
+        {
+            double sum = 0.0;
+            sum += PeriodicTerm(julianCenturies, 403406, 270.54861, 0.9287892);
+            sum += PeriodicTerm(julianCenturies, 195207, 340.19128, 35999.1376958);
+            sum += PeriodicTerm(julianCenturies, 119433, 63.91854, 35999.4089666);
+            sum += PeriodicTerm(julianCenturies, 112392, 331.2622, 35998.7287385);
+            sum += PeriodicTerm(julianCenturies, 3891, 317.843, 71998.20261);
+            sum += PeriodicTerm(julianCenturies, 2819, 86.631, 71998.4403);
+            sum += PeriodicTerm(julianCenturies, 1721, 240.052, 36000.35726);
+            sum += PeriodicTerm(julianCenturies, 660, 310.26, 71997.4812);
+            sum += PeriodicTerm(julianCenturies, 350, 247.23, 32964.4678);
+            sum += PeriodicTerm(julianCenturies, 334, 260.87, -19.441);
+            sum += PeriodicTerm(julianCenturies, 314, 297.82, 445267.1117);
+            sum += PeriodicTerm(julianCenturies, 268, 343.14, 45036.884);
+            sum += PeriodicTerm(julianCenturies, 242, 166.79, 3.1008);
+            sum += PeriodicTerm(julianCenturies, 234, 81.53, 22518.4434);
+            sum += PeriodicTerm(julianCenturies, 158, 3.5, -19.9739);
+            sum += PeriodicTerm(julianCenturies, 132, 132.75, 65928.9345);
+            sum += PeriodicTerm(julianCenturies, 129, 182.95, 9038.0293);
+            sum += PeriodicTerm(julianCenturies, 114, 162.03, 3034.7684);
+            sum += PeriodicTerm(julianCenturies, 99, 29.8, 33718.148);
+            sum += PeriodicTerm(julianCenturies, 93, 266.4, 3034.448);
+            sum += PeriodicTerm(julianCenturies, 86, 249.2, -2280.773);
+            sum += PeriodicTerm(julianCenturies, 78, 157.6, 29929.992);
+            sum += PeriodicTerm(julianCenturies, 72, 257.8, 31556.493);
+            sum += PeriodicTerm(julianCenturies, 68, 185.1, 149.588);
+            sum += PeriodicTerm(julianCenturies, 64, 69.9, 9037.75);
+            sum += PeriodicTerm(julianCenturies, 46, 8.0, 107997.405);
+            sum += PeriodicTerm(julianCenturies, 38, 197.1, -4444.176);
+            sum += PeriodicTerm(julianCenturies, 37, 250.4, 151.771);
+            sum += PeriodicTerm(julianCenturies, 32, 65.3, 67555.316);
+            sum += PeriodicTerm(julianCenturies, 29, 162.7, 31556.08);
+            sum += PeriodicTerm(julianCenturies, 28, 341.5, -4561.54);
+            sum += PeriodicTerm(julianCenturies, 27, 291.6, 107996.706);
+            sum += PeriodicTerm(julianCenturies, 27, 98.5, 1221.655);
+            sum += PeriodicTerm(julianCenturies, 25, 146.7, 62894.167);
+            sum += PeriodicTerm(julianCenturies, 24, 110.0, 31437.369);
+            sum += PeriodicTerm(julianCenturies, 21, 5.2, 14578.298);
+            sum += PeriodicTerm(julianCenturies, 21, 342.6, -31931.757);
+            sum += PeriodicTerm(julianCenturies, 20, 230.9, 34777.243);
+            sum += PeriodicTerm(julianCenturies, 18, 256.1, 1221.999);
+            sum += PeriodicTerm(julianCenturies, 17, 45.3, 62894.511);
+            sum += PeriodicTerm(julianCenturies, 14, 242.9, -4442.039);
+            sum += PeriodicTerm(julianCenturies, 13, 115.2, 107997.909);
+            sum += PeriodicTerm(julianCenturies, 13, 151.8, 119.066);
+            sum += PeriodicTerm(julianCenturies, 13, 285.3, 16859.071);
+            sum += PeriodicTerm(julianCenturies, 12, 53.3, -4.578);
+            sum += PeriodicTerm(julianCenturies, 10, 126.6, 26895.292);
+            sum += PeriodicTerm(julianCenturies, 10, 205.7, -39.127);
+            sum += PeriodicTerm(julianCenturies, 10, 85.9, 12297.536);
+            sum += PeriodicTerm(julianCenturies, 10, 146.1, 90073.778);
+            return sum;
+        }
+
+        private static double Aberration(double julianCenturies)
+        {
+            return (0.0000974 * CosOfDegree(177.63 + (35999.01848 * julianCenturies))) - 0.005575;
+        }
+
+        private static double Nutation(double julianCenturies)
+        {
+            double a = PolynomialSum(s_coefficientsA, julianCenturies);
+            double b = PolynomialSum(s_coefficientsB, julianCenturies);
+            return (-0.004778 * SinOfDegree(a)) - (0.0003667 * SinOfDegree(b));
+        }
+
+        public static double Compute(double time)
+        {
+            double julianCenturies = JulianCenturies(time);
+            double lambda = 282.7771834
+                + (36000.76953744 * julianCenturies)
+                + (0.000005729577951308232 * SumLongSequenceOfPeriodicTerms(julianCenturies));
+
+            double longitude = lambda + Aberration(julianCenturies) + Nutation(julianCenturies);
+            return InitLongitude(longitude);
+        }
+
+        public static double AsSeason(double longitude)
+        {
+            return (longitude < 0) ? (longitude + FullCircleOfArc) : longitude;
+        }
+
+        private static double EstimatePrior(double longitude, double time)
+        {
+            double timeSunLastAtLongitude = time - (MeanSpeedOfSun * AsSeason(InitLongitude(Compute(time) - longitude)));
+            double longitudeErrorDelta = InitLongitude(Compute(timeSunLastAtLongitude) - longitude);
+            return Math.Min(time, timeSunLastAtLongitude - (MeanSpeedOfSun * longitudeErrorDelta));
+        }
+
+        // persian-new-year-on-or-before
+        //  number of days is the absolute date. The absolute date is the number of days from January 1st, 1 A.D.
+        //  1/1/0001 is absolute date 1.
+        internal static long PersianNewYearOnOrBefore(long numberOfDays)
+        {
+            double date = (double)numberOfDays;
+
+            double approx = EstimatePrior(LongitudeSpring, MiddayAtPersianObservationSite(date));
+            long lowerBoundNewYearDay = (long)Math.Floor(approx) - 1;
+            long upperBoundNewYearDay = lowerBoundNewYearDay + 3; // estimate is generally within a day of the actual occurrance (at the limits, the error expands, since the calculations rely on the mean tropical year which changes...)
+            long day = lowerBoundNewYearDay;
+            for (; day != upperBoundNewYearDay; ++day)
+            {
+                double midday = MiddayAtPersianObservationSite((double)day);
+                double l = Compute(midday);
+                if ((LongitudeSpring <= l) && (l <= TwoDegreesAfterSpring))
+                {
+                    break;
+                }
+            }
+            Debug.Assert(day != upperBoundNewYearDay);
+
+            return day - 1;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CharUnicodeInfo.cs b/src/System.Private.CoreLib/shared/System/Globalization/CharUnicodeInfo.cs
new file mode 100644
index 0000000000..0cd8429bbc
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CharUnicodeInfo.cs
@@ -0,0 +1,397 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////
+//
+//
+//  Purpose:  This class implements a set of methods for retrieving
+//            character type information.  Character type information is
+//            independent of culture and region.
+//
+//
+////////////////////////////////////////////////////////////////////////////
+
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    public static partial class CharUnicodeInfo
+    {
+        //--------------------------------------------------------------------//
+        //                        Internal Information                        //
+        //--------------------------------------------------------------------//
+
+        //
+        // Native methods to access the Unicode category data tables in charinfo.nlp.
+        //
+        internal const char HIGH_SURROGATE_START = '\ud800';
+        internal const char HIGH_SURROGATE_END = '\udbff';
+        internal const char LOW_SURROGATE_START = '\udc00';
+        internal const char LOW_SURROGATE_END = '\udfff';
+
+        internal const int UNICODE_CATEGORY_OFFSET = 0;
+        internal const int BIDI_CATEGORY_OFFSET = 1;
+
+        // The starting codepoint for Unicode plane 1.  Plane 1 contains 0x010000 ~ 0x01ffff.
+        internal const int UNICODE_PLANE01_START = 0x10000;
+
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        // Actions:
+        // Convert the BMP character or surrogate pointed by index to a UTF32 value.
+        // This is similar to Char.ConvertToUTF32, but the difference is that
+        // it does not throw exceptions when invalid surrogate characters are passed in.
+        //
+        // WARNING: since it doesn't throw an exception it CAN return a value
+        //          in the surrogate range D800-DFFF, which are not legal unicode values.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        internal static int InternalConvertToUtf32(String s, int index)
+        {
+            Debug.Assert(s != null, "s != null");
+            Debug.Assert(index >= 0 && index < s.Length, "index < s.Length");
+            if (index < s.Length - 1)
+            {
+                int temp1 = (int)s[index] - HIGH_SURROGATE_START;
+                if (temp1 >= 0 && temp1 <= 0x3ff)
+                {
+                    int temp2 = (int)s[index + 1] - LOW_SURROGATE_START;
+                    if (temp2 >= 0 && temp2 <= 0x3ff)
+                    {
+                        // Convert the surrogate to UTF32 and get the result.
+                        return ((temp1 * 0x400) + temp2 + UNICODE_PLANE01_START);
+                    }
+                }
+            }
+            return ((int)s[index]);
+        }
+        ////////////////////////////////////////////////////////////////////////
+        //
+        // Convert a character or a surrogate pair starting at index of string s
+        // to UTF32 value.
+        //
+        //  Parameters:
+        //      s       The string
+        //      index   The starting index.  It can point to a BMP character or
+        //              a surrogate pair.
+        //      len     The length of the string.
+        //      charLength  [out]   If the index points to a BMP char, charLength
+        //              will be 1.  If the index points to a surrogate pair,
+        //              charLength will be 2.
+        //
+        // WARNING: since it doesn't throw an exception it CAN return a value
+        //          in the surrogate range D800-DFFF, which are not legal unicode values.
+        //
+        //  Returns:
+        //      The UTF32 value
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        internal static int InternalConvertToUtf32(String s, int index, out int charLength)
+        {
+            Debug.Assert(s != null, "s != null");
+            Debug.Assert(s.Length > 0, "s.Length > 0");
+            Debug.Assert(index >= 0 && index < s.Length, "index >= 0 && index < s.Length");
+            charLength = 1;
+            if (index < s.Length - 1)
+            {
+                int temp1 = (int)s[index] - HIGH_SURROGATE_START;
+                if (temp1 >= 0 && temp1 <= 0x3ff)
+                {
+                    int temp2 = (int)s[index + 1] - LOW_SURROGATE_START;
+                    if (temp2 >= 0 && temp2 <= 0x3ff)
+                    {
+                        // Convert the surrogate to UTF32 and get the result.
+                        charLength++;
+                        return ((temp1 * 0x400) + temp2 + UNICODE_PLANE01_START);
+                    }
+                }
+            }
+            return ((int)s[index]);
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  IsWhiteSpace
+        //
+        //  Determines if the given character is a white space character.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        internal static bool IsWhiteSpace(String s, int index)
+        {
+            Debug.Assert(s != null, "s!=null");
+            Debug.Assert(index >= 0 && index < s.Length, "index >= 0 && index < s.Length");
+
+            UnicodeCategory uc = GetUnicodeCategory(s, index);
+            // In Unicode 3.0, U+2028 is the only character which is under the category "LineSeparator".
+            // And U+2029 is th eonly character which is under the category "ParagraphSeparator".
+            switch (uc)
+            {
+                case (UnicodeCategory.SpaceSeparator):
+                case (UnicodeCategory.LineSeparator):
+                case (UnicodeCategory.ParagraphSeparator):
+                    return (true);
+            }
+            return (false);
+        }
+
+
+        internal static bool IsWhiteSpace(char c)
+        {
+            UnicodeCategory uc = GetUnicodeCategory(c);
+            // In Unicode 3.0, U+2028 is the only character which is under the category "LineSeparator".
+            // And U+2029 is th eonly character which is under the category "ParagraphSeparator".
+            switch (uc)
+            {
+                case (UnicodeCategory.SpaceSeparator):
+                case (UnicodeCategory.LineSeparator):
+                case (UnicodeCategory.ParagraphSeparator):
+                    return (true);
+            }
+
+            return (false);
+        }
+
+
+        //
+        // This is called by the public char and string, index versions
+        //
+        // Note that for ch in the range D800-DFFF we just treat it as any other non-numeric character
+        //
+        internal static unsafe double InternalGetNumericValue(int ch)
+        {
+            Debug.Assert(ch >= 0 && ch <= 0x10ffff, "ch is not in valid Unicode range.");
+            // Get the level 2 item from the highest 12 bit (8 - 19) of ch.
+            ushort index = s_pNumericLevel1Index[ch >> 8];
+            // Get the level 2 WORD offset from the 4 - 7 bit of ch.  This provides the base offset of the level 3 table.
+            // The offset is referred to an float item in m_pNumericFloatData.
+            // Note that & has the lower precedence than addition, so don't forget the parathesis.
+            index = s_pNumericLevel1Index[index + ((ch >> 4) & 0x000f)];
+
+            fixed (ushort* pUshortPtr = &(s_pNumericLevel1Index[index]))
+            {
+                byte* pBytePtr = (byte*)pUshortPtr;
+                fixed (byte* pByteNum = s_pNumericValues)
+                {
+                    double* pDouble = (double*)pByteNum;
+                    return pDouble[pBytePtr[(ch & 0x000f)]];
+                }
+            }
+        }
+
+        internal static unsafe ushort InternalGetDigitValues(int ch)
+        {
+            Debug.Assert(ch >= 0 && ch <= 0x10ffff, "ch is not in valid Unicode range.");
+            // Get the level 2 item from the highest 12 bit (8 - 19) of ch.
+            ushort index = s_pNumericLevel1Index[ch >> 8];
+            // Get the level 2 WORD offset from the 4 - 7 bit of ch.  This provides the base offset of the level 3 table.
+            // Note that & has the lower precedence than addition, so don't forget the parathesis.
+            index = s_pNumericLevel1Index[index + ((ch >> 4) & 0x000f)];
+
+            fixed (ushort* pUshortPtr = &(s_pNumericLevel1Index[index]))
+            {
+                byte* pBytePtr = (byte*)pUshortPtr;
+                return s_pDigitValues[pBytePtr[(ch & 0x000f)]];
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //Returns the numeric value associated with the character c. If the character is a fraction,
+        // the return value will not be an integer. If the character does not have a numeric value, the return value is -1.
+        //
+        //Returns:
+        //  the numeric value for the specified Unicode character.  If the character does not have a numeric value, the return value is -1.
+        //Arguments:
+        //      ch  a Unicode character
+        //Exceptions:
+        //      ArgumentNullException
+        //      ArgumentOutOfRangeException
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+
+        public static double GetNumericValue(char ch)
+        {
+            return (InternalGetNumericValue(ch));
+        }
+
+
+        public static double GetNumericValue(String s, int index)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+            if (index < 0 || index >= s.Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+            }
+            return (InternalGetNumericValue(InternalConvertToUtf32(s, index)));
+        }
+
+        public static int GetDecimalDigitValue(char ch)
+        {
+            return (sbyte)(InternalGetDigitValues(ch) >> 8);
+        }
+
+        public static int GetDecimalDigitValue(String s, int index)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+
+            if (index < 0 || index >= s.Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+            }
+
+            return (sbyte)(InternalGetDigitValues(InternalConvertToUtf32(s, index)) >> 8);
+        }
+
+        public static int GetDigitValue(char ch)
+        {
+            return (sbyte)(InternalGetDigitValues(ch) & 0x00FF);
+        }
+
+        public static int GetDigitValue(String s, int index)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+
+            if (index < 0 || index >= s.Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+            }
+
+            return (sbyte)(InternalGetDigitValues(InternalConvertToUtf32(s, index)) & 0x00FF);
+        }
+
+        public static UnicodeCategory GetUnicodeCategory(char ch)
+        {
+            return (GetUnicodeCategory((int)ch));
+        }
+
+        public static UnicodeCategory GetUnicodeCategory(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+            return InternalGetUnicodeCategory(s, index);
+        }
+
+        public static UnicodeCategory GetUnicodeCategory(int codePoint)
+        {
+            return ((UnicodeCategory)InternalGetCategoryValue(codePoint, UNICODE_CATEGORY_OFFSET));
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //Action: Returns the Unicode Category property for the character c.
+        //Returns:
+        //  an value in UnicodeCategory enum
+        //Arguments:
+        //  ch  a Unicode character
+        //Exceptions:
+        //  None
+        //
+        //Note that this API will return values for D800-DF00 surrogate halves.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        internal static unsafe byte InternalGetCategoryValue(int ch, int offset)
+        {
+            Debug.Assert(ch >= 0 && ch <= 0x10ffff, "ch is not in valid Unicode range.");
+            // Get the level 2 item from the highest 12 bit (8 - 19) of ch.
+            ushort index = s_pCategoryLevel1Index[ch >> 8];
+            // Get the level 2 WORD offset from the 4 - 7 bit of ch.  This provides the base offset of the level 3 table.
+            // Note that & has the lower precedence than addition, so don't forget the parathesis.
+            index = s_pCategoryLevel1Index[index + ((ch >> 4) & 0x000f)];
+
+            fixed (ushort* pUshortPtr = &(s_pCategoryLevel1Index[index]))
+            {
+                byte* pBytePtr = (byte*)pUshortPtr;
+                // Get the result from the 0 -3 bit of ch.
+                byte valueIndex = pBytePtr[(ch & 0x000f)];
+                byte uc = s_pCategoriesValue[valueIndex * 2 + offset];
+                //
+                // Make sure that OtherNotAssigned is the last category in UnicodeCategory.
+                // If that changes, change the following assertion as well.
+                //
+                //Debug.Assert(uc >= 0 && uc <= UnicodeCategory.OtherNotAssigned, "Table returns incorrect Unicode category");
+                return (uc);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //Action: Returns the Unicode Category property for the character c.
+        //Returns:
+        //  an value in UnicodeCategory enum
+        //Arguments:
+        //  value  a Unicode String
+        //  index  Index for the specified string.
+        //Exceptions:
+        //  None
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        internal static UnicodeCategory InternalGetUnicodeCategory(String value, int index)
+        {
+            Debug.Assert(value != null, "value can not be null");
+            Debug.Assert(index < value.Length, "index < value.Length");
+
+            return (GetUnicodeCategory(InternalConvertToUtf32(value, index)));
+        }
+
+        internal static BidiCategory GetBidiCategory(String s, int index)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+
+            if (((uint)index) >= ((uint)s.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index));
+            }
+
+            return ((BidiCategory) InternalGetCategoryValue(InternalConvertToUtf32(s, index), BIDI_CATEGORY_OFFSET));
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        // Get the Unicode category of the character starting at index.  If the character is in BMP, charLength will return 1.
+        // If the character is a valid surrogate pair, charLength will return 2.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        internal static UnicodeCategory InternalGetUnicodeCategory(String str, int index, out int charLength)
+        {
+            Debug.Assert(str != null, "str can not be null");
+            Debug.Assert(str.Length > 0, "str.Length > 0"); ;
+            Debug.Assert(index >= 0 && index < str.Length, "index >= 0 && index < str.Length");
+
+            return (GetUnicodeCategory(InternalConvertToUtf32(str, index, out charLength)));
+        }
+
+        internal static bool IsCombiningCategory(UnicodeCategory uc)
+        {
+            Debug.Assert(uc >= 0, "uc >= 0");
+            return (
+                uc == UnicodeCategory.NonSpacingMark ||
+                uc == UnicodeCategory.SpacingCombiningMark ||
+                uc == UnicodeCategory.EnclosingMark
+            );
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/ChineseLunisolarCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/ChineseLunisolarCalendar.cs
new file mode 100644
index 0000000000..d2b52b97be
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/ChineseLunisolarCalendar.cs
@@ -0,0 +1,386 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+namespace System.Globalization
+{
+    /*
+    **  Calendar support range:
+    **      Calendar               Minimum             Maximum
+    **      ==========     ==========  ==========
+    **      Gregorian              1901/02/19          2101/01/28
+    **      ChineseLunisolar   1901/01/01          2100/12/29
+    */
+
+    public class ChineseLunisolarCalendar : EastAsianLunisolarCalendar
+    {
+        //
+        // The era value for the current era.
+        //
+
+        public const int ChineseEra = 1;
+
+        internal const int MIN_LUNISOLAR_YEAR = 1901;
+        internal const int MAX_LUNISOLAR_YEAR = 2100;
+
+        internal const int MIN_GREGORIAN_YEAR = 1901;
+        internal const int MIN_GREGORIAN_MONTH = 2;
+        internal const int MIN_GREGORIAN_DAY = 19;
+
+        internal const int MAX_GREGORIAN_YEAR = 2101;
+        internal const int MAX_GREGORIAN_MONTH = 1;
+        internal const int MAX_GREGORIAN_DAY = 28;
+
+        internal static DateTime minDate = new DateTime(MIN_GREGORIAN_YEAR, MIN_GREGORIAN_MONTH, MIN_GREGORIAN_DAY);
+        internal static DateTime maxDate = new DateTime((new DateTime(MAX_GREGORIAN_YEAR, MAX_GREGORIAN_MONTH, MAX_GREGORIAN_DAY, 23, 59, 59, 999)).Ticks + 9999);
+
+        public override DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (minDate);
+            }
+        }
+
+
+        public override DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (maxDate);
+            }
+        }
+
+        protected override int DaysInYearBeforeMinSupportedYear
+        {
+            get
+            {
+                // 1900: 1-29 2-30 3-29 4-29 5-30 6-29 7-30 8-30 Leap8-29 9-30 10-30 11-29 12-30 from Calendrical Tabulations
+                return 384;
+            }
+        }
+
+
+        private static readonly int[,] s_yinfo =
+        {
+            /*Y            LM        Lmon    Lday        DaysPerMonth    D1    D2    D3    D4    D5    D6    D7    D8    D9    D10    D11    D12    D13    #Days
+           1901    */
+          {    0    ,    2    ,    19    ,    19168    },/*    29    30    29    29    30    29    30    29    30    30    30    29    0    354
+1902    */{    0    ,    2    ,    8    ,    42352    },/*    30    29    30    29    29    30    29    30    29    30    30    30    0    355
+1903    */{    5    ,    1    ,    29    ,    21096    },/*    29    30    29    30    29    29    30    29    29    30    30    29    30    383
+1904    */{    0    ,    2    ,    16    ,    53856    },/*    30    30    29    30    29    29    30    29    29    30    30    29    0    354
+1905    */{    0    ,    2    ,    4    ,    55632    },/*    30    30    29    30    30    29    29    30    29    30    29    30    0    355
+1906    */{    4    ,    1    ,    25    ,    27304    },/*    29    30    30    29    30    29    30    29    30    29    30    29    30    384
+1907    */{    0    ,    2    ,    13    ,    22176    },/*    29    30    29    30    29    30    30    29    30    29    30    29    0    354
+1908    */{    0    ,    2    ,    2    ,    39632    },/*    30    29    29    30    30    29    30    29    30    30    29    30    0    355
+1909    */{    2    ,    1    ,    22    ,    19176    },/*    29    30    29    29    30    29    30    29    30    30    30    29    30    384
+1910    */{    0    ,    2    ,    10    ,    19168    },/*    29    30    29    29    30    29    30    29    30    30    30    29    0    354
+1911    */{    6    ,    1    ,    30    ,    42200    },/*    30    29    30    29    29    30    29    29    30    30    29    30    30    384
+1912    */{    0    ,    2    ,    18    ,    42192    },/*    30    29    30    29    29    30    29    29    30    30    29    30    0    354
+1913    */{    0    ,    2    ,    6    ,    53840    },/*    30    30    29    30    29    29    30    29    29    30    29    30    0    354
+1914    */{    5    ,    1    ,    26    ,    54568    },/*    30    30    29    30    29    30    29    30    29    29    30    29    30    384
+1915    */{    0    ,    2    ,    14    ,    46400    },/*    30    29    30    30    29    30    29    30    29    30    29    29    0    354
+1916    */{    0    ,    2    ,    3    ,    54944    },/*    30    30    29    30    29    30    30    29    30    29    30    29    0    355
+1917    */{    2    ,    1    ,    23    ,    38608    },/*    30    29    29    30    29    30    30    29    30    30    29    30    29    384
+1918    */{    0    ,    2    ,    11    ,    38320    },/*    30    29    29    30    29    30    29    30    30    29    30    30    0    355
+1919    */{    7    ,    2    ,    1    ,    18872    },/*    29    30    29    29    30    29    29    30    30    29    30    30    30    384
+1920    */{    0    ,    2    ,    20    ,    18800    },/*    29    30    29    29    30    29    29    30    29    30    30    30    0    354
+1921    */{    0    ,    2    ,    8    ,    42160    },/*    30    29    30    29    29    30    29    29    30    29    30    30    0    354
+1922    */{    5    ,    1    ,    28    ,    45656    },/*    30    29    30    30    29    29    30    29    29    30    29    30    30    384
+1923    */{    0    ,    2    ,    16    ,    27216    },/*    29    30    30    29    30    29    30    29    29    30    29    30    0    354
+1924    */{    0    ,    2    ,    5    ,    27968    },/*    29    30    30    29    30    30    29    30    29    30    29    29    0    354
+1925    */{    4    ,    1    ,    24    ,    44456    },/*    30    29    30    29    30    30    29    30    30    29    30    29    30    385
+1926    */{    0    ,    2    ,    13    ,    11104    },/*    29    29    30    29    30    29    30    30    29    30    30    29    0    354
+1927    */{    0    ,    2    ,    2    ,    38256    },/*    30    29    29    30    29    30    29    30    29    30    30    30    0    355
+1928    */{    2    ,    1    ,    23    ,    18808    },/*    29    30    29    29    30    29    29    30    29    30    30    30    30    384
+1929    */{    0    ,    2    ,    10    ,    18800    },/*    29    30    29    29    30    29    29    30    29    30    30    30    0    354
+1930    */{    6    ,    1    ,    30    ,    25776    },/*    29    30    30    29    29    30    29    29    30    29    30    30    29    383
+1931    */{    0    ,    2    ,    17    ,    54432    },/*    30    30    29    30    29    30    29    29    30    29    30    29    0    354
+1932    */{    0    ,    2    ,    6    ,    59984    },/*    30    30    30    29    30    29    30    29    29    30    29    30    0    355
+1933    */{    5    ,    1    ,    26    ,    27976    },/*    29    30    30    29    30    30    29    30    29    30    29    29    30    384
+1934    */{    0    ,    2    ,    14    ,    23248    },/*    29    30    29    30    30    29    30    29    30    30    29    30    0    355
+1935    */{    0    ,    2    ,    4    ,    11104    },/*    29    29    30    29    30    29    30    30    29    30    30    29    0    354
+1936    */{    3    ,    1    ,    24    ,    37744    },/*    30    29    29    30    29    29    30    30    29    30    30    30    29    384
+1937    */{    0    ,    2    ,    11    ,    37600    },/*    30    29    29    30    29    29    30    29    30    30    30    29    0    354
+1938    */{    7    ,    1    ,    31    ,    51560    },/*    30    30    29    29    30    29    29    30    29    30    30    29    30    384
+1939    */{    0    ,    2    ,    19    ,    51536    },/*    30    30    29    29    30    29    29    30    29    30    29    30    0    354
+1940    */{    0    ,    2    ,    8    ,    54432    },/*    30    30    29    30    29    30    29    29    30    29    30    29    0    354
+1941    */{    6    ,    1    ,    27    ,    55888    },/*    30    30    29    30    30    29    30    29    29    30    29    30    29    384
+1942    */{    0    ,    2    ,    15    ,    46416    },/*    30    29    30    30    29    30    29    30    29    30    29    30    0    355
+1943    */{    0    ,    2    ,    5    ,    22176    },/*    29    30    29    30    29    30    30    29    30    29    30    29    0    354
+1944    */{    4    ,    1    ,    25    ,    43736    },/*    30    29    30    29    30    29    30    29    30    30    29    30    30    385
+1945    */{    0    ,    2    ,    13    ,    9680    },/*    29    29    30    29    29    30    29    30    30    30    29    30    0    354
+1946    */{    0    ,    2    ,    2    ,    37584    },/*    30    29    29    30    29    29    30    29    30    30    29    30    0    354
+1947    */{    2    ,    1    ,    22    ,    51544    },/*    30    30    29    29    30    29    29    30    29    30    29    30    30    384
+1948    */{    0    ,    2    ,    10    ,    43344    },/*    30    29    30    29    30    29    29    30    29    30    29    30    0    354
+1949    */{    7    ,    1    ,    29    ,    46248    },/*    30    29    30    30    29    30    29    29    30    29    30    29    30    384
+1950    */{    0    ,    2    ,    17    ,    27808    },/*    29    30    30    29    30    30    29    29    30    29    30    29    0    354
+1951    */{    0    ,    2    ,    6    ,    46416    },/*    30    29    30    30    29    30    29    30    29    30    29    30    0    355
+1952    */{    5    ,    1    ,    27    ,    21928    },/*    29    30    29    30    29    30    29    30    30    29    30    29    30    384
+1953    */{    0    ,    2    ,    14    ,    19872    },/*    29    30    29    29    30    30    29    30    30    29    30    29    0    354
+1954    */{    0    ,    2    ,    3    ,    42416    },/*    30    29    30    29    29    30    29    30    30    29    30    30    0    355
+1955    */{    3    ,    1    ,    24    ,    21176    },/*    29    30    29    30    29    29    30    29    30    29    30    30    30    384
+1956    */{    0    ,    2    ,    12    ,    21168    },/*    29    30    29    30    29    29    30    29    30    29    30    30    0    354
+1957    */{    8    ,    1    ,    31    ,    43344    },/*    30    29    30    29    30    29    29    30    29    30    29    30    29    383
+1958    */{    0    ,    2    ,    18    ,    59728    },/*    30    30    30    29    30    29    29    30    29    30    29    30    0    355
+1959    */{    0    ,    2    ,    8    ,    27296    },/*    29    30    30    29    30    29    30    29    30    29    30    29    0    354
+1960    */{    6    ,    1    ,    28    ,    44368    },/*    30    29    30    29    30    30    29    30    29    30    29    30    29    384
+1961    */{    0    ,    2    ,    15    ,    43856    },/*    30    29    30    29    30    29    30    30    29    30    29    30    0    355
+1962    */{    0    ,    2    ,    5    ,    19296    },/*    29    30    29    29    30    29    30    30    29    30    30    29    0    354
+1963    */{    4    ,    1    ,    25    ,    42352    },/*    30    29    30    29    29    30    29    30    29    30    30    30    29    384
+1964    */{    0    ,    2    ,    13    ,    42352    },/*    30    29    30    29    29    30    29    30    29    30    30    30    0    355
+1965    */{    0    ,    2    ,    2    ,    21088    },/*    29    30    29    30    29    29    30    29    29    30    30    29    0    353
+1966    */{    3    ,    1    ,    21    ,    59696    },/*    30    30    30    29    30    29    29    30    29    29    30    30    29    384
+1967    */{    0    ,    2    ,    9    ,    55632    },/*    30    30    29    30    30    29    29    30    29    30    29    30    0    355
+1968    */{    7    ,    1    ,    30    ,    23208    },/*    29    30    29    30    30    29    30    29    30    29    30    29    30    384
+1969    */{    0    ,    2    ,    17    ,    22176    },/*    29    30    29    30    29    30    30    29    30    29    30    29    0    354
+1970    */{    0    ,    2    ,    6    ,    38608    },/*    30    29    29    30    29    30    30    29    30    30    29    30    0    355
+1971    */{    5    ,    1    ,    27    ,    19176    },/*    29    30    29    29    30    29    30    29    30    30    30    29    30    384
+1972    */{    0    ,    2    ,    15    ,    19152    },/*    29    30    29    29    30    29    30    29    30    30    29    30    0    354
+1973    */{    0    ,    2    ,    3    ,    42192    },/*    30    29    30    29    29    30    29    29    30    30    29    30    0    354
+1974    */{    4    ,    1    ,    23    ,    53864    },/*    30    30    29    30    29    29    30    29    29    30    30    29    30    384
+1975    */{    0    ,    2    ,    11    ,    53840    },/*    30    30    29    30    29    29    30    29    29    30    29    30    0    354
+1976    */{    8    ,    1    ,    31    ,    54568    },/*    30    30    29    30    29    30    29    30    29    29    30    29    30    384
+1977    */{    0    ,    2    ,    18    ,    46400    },/*    30    29    30    30    29    30    29    30    29    30    29    29    0    354
+1978    */{    0    ,    2    ,    7    ,    46752    },/*    30    29    30    30    29    30    30    29    30    29    30    29    0    355
+1979    */{    6    ,    1    ,    28    ,    38608    },/*    30    29    29    30    29    30    30    29    30    30    29    30    29    384
+1980    */{    0    ,    2    ,    16    ,    38320    },/*    30    29    29    30    29    30    29    30    30    29    30    30    0    355
+1981    */{    0    ,    2    ,    5    ,    18864    },/*    29    30    29    29    30    29    29    30    30    29    30    30    0    354
+1982    */{    4    ,    1    ,    25    ,    42168    },/*    30    29    30    29    29    30    29    29    30    29    30    30    30    384
+1983    */{    0    ,    2    ,    13    ,    42160    },/*    30    29    30    29    29    30    29    29    30    29    30    30    0    354
+1984    */{    10    ,    2    ,    2    ,    45656    },/*    30    29    30    30    29    29    30    29    29    30    29    30    30    384
+1985    */{    0    ,    2    ,    20    ,    27216    },/*    29    30    30    29    30    29    30    29    29    30    29    30    0    354
+1986    */{    0    ,    2    ,    9    ,    27968    },/*    29    30    30    29    30    30    29    30    29    30    29    29    0    354
+1987    */{    6    ,    1    ,    29    ,    44448    },/*    30    29    30    29    30    30    29    30    30    29    30    29    29    384
+1988    */{    0    ,    2    ,    17    ,    43872    },/*    30    29    30    29    30    29    30    30    29    30    30    29    0    355
+1989    */{    0    ,    2    ,    6    ,    38256    },/*    30    29    29    30    29    30    29    30    29    30    30    30    0    355
+1990    */{    5    ,    1    ,    27    ,    18808    },/*    29    30    29    29    30    29    29    30    29    30    30    30    30    384
+1991    */{    0    ,    2    ,    15    ,    18800    },/*    29    30    29    29    30    29    29    30    29    30    30    30    0    354
+1992    */{    0    ,    2    ,    4    ,    25776    },/*    29    30    30    29    29    30    29    29    30    29    30    30    0    354
+1993    */{    3    ,    1    ,    23    ,    27216    },/*    29    30    30    29    30    29    30    29    29    30    29    30    29    383
+1994    */{    0    ,    2    ,    10    ,    59984    },/*    30    30    30    29    30    29    30    29    29    30    29    30    0    355
+1995    */{    8    ,    1    ,    31    ,    27432    },/*    29    30    30    29    30    29    30    30    29    29    30    29    30    384
+1996    */{    0    ,    2    ,    19    ,    23232    },/*    29    30    29    30    30    29    30    29    30    30    29    29    0    354
+1997    */{    0    ,    2    ,    7    ,    43872    },/*    30    29    30    29    30    29    30    30    29    30    30    29    0    355
+1998    */{    5    ,    1    ,    28    ,    37736    },/*    30    29    29    30    29    29    30    30    29    30    30    29    30    384
+1999    */{    0    ,    2    ,    16    ,    37600    },/*    30    29    29    30    29    29    30    29    30    30    30    29    0    354
+2000    */{    0    ,    2    ,    5    ,    51552    },/*    30    30    29    29    30    29    29    30    29    30    30    29    0    354
+2001    */{    4    ,    1    ,    24    ,    54440    },/*    30    30    29    30    29    30    29    29    30    29    30    29    30    384
+2002    */{    0    ,    2    ,    12    ,    54432    },/*    30    30    29    30    29    30    29    29    30    29    30    29    0    354
+2003    */{    0    ,    2    ,    1    ,    55888    },/*    30    30    29    30    30    29    30    29    29    30    29    30    0    355
+2004    */{    2    ,    1    ,    22    ,    23208    },/*    29    30    29    30    30    29    30    29    30    29    30    29    30    384
+2005    */{    0    ,    2    ,    9    ,    22176    },/*    29    30    29    30    29    30    30    29    30    29    30    29    0    354
+2006    */{    7    ,    1    ,    29    ,    43736    },/*    30    29    30    29    30    29    30    29    30    30    29    30    30    385
+2007    */{    0    ,    2    ,    18    ,    9680    },/*    29    29    30    29    29    30    29    30    30    30    29    30    0    354
+2008    */{    0    ,    2    ,    7    ,    37584    },/*    30    29    29    30    29    29    30    29    30    30    29    30    0    354
+2009    */{    5    ,    1    ,    26    ,    51544    },/*    30    30    29    29    30    29    29    30    29    30    29    30    30    384
+2010    */{    0    ,    2    ,    14    ,    43344    },/*    30    29    30    29    30    29    29    30    29    30    29    30    0    354
+2011    */{    0    ,    2    ,    3    ,    46240    },/*    30    29    30    30    29    30    29    29    30    29    30    29    0    354
+2012    */{    4    ,    1    ,    23    ,    46416    },/*    30    29    30    30    29    30    29    30    29    30    29    30    29    384
+2013    */{    0    ,    2    ,    10    ,    44368    },/*    30    29    30    29    30    30    29    30    29    30    29    30    0    355
+2014    */{    9    ,    1    ,    31    ,    21928    },/*    29    30    29    30    29    30    29    30    30    29    30    29    30    384
+2015    */{    0    ,    2    ,    19    ,    19360    },/*    29    30    29    29    30    29    30    30    30    29    30    29    0    354
+2016    */{    0    ,    2    ,    8    ,    42416    },/*    30    29    30    29    29    30    29    30    30    29    30    30    0    355
+2017    */{    6    ,    1    ,    28    ,    21176    },/*    29    30    29    30    29    29    30    29    30    29    30    30    30    384
+2018    */{    0    ,    2    ,    16    ,    21168    },/*    29    30    29    30    29    29    30    29    30    29    30    30    0    354
+2019    */{    0    ,    2    ,    5    ,    43312    },/*    30    29    30    29    30    29    29    30    29    29    30    30    0    354
+2020    */{    4    ,    1    ,    25    ,    29864    },/*    29    30    30    30    29    30    29    29    30    29    30    29    30    384
+2021    */{    0    ,    2    ,    12    ,    27296    },/*    29    30    30    29    30    29    30    29    30    29    30    29    0    354
+2022    */{    0    ,    2    ,    1    ,    44368    },/*    30    29    30    29    30    30    29    30    29    30    29    30    0    355
+2023    */{    2    ,    1    ,    22    ,    19880    },/*    29    30    29    29    30    30    29    30    30    29    30    29    30    384
+2024    */{    0    ,    2    ,    10    ,    19296    },/*    29    30    29    29    30    29    30    30    29    30    30    29    0    354
+2025    */{    6    ,    1    ,    29    ,    42352    },/*    30    29    30    29    29    30    29    30    29    30    30    30    29    384
+2026    */{    0    ,    2    ,    17    ,    42208    },/*    30    29    30    29    29    30    29    29    30    30    30    29    0    354
+2027    */{    0    ,    2    ,    6    ,    53856    },/*    30    30    29    30    29    29    30    29    29    30    30    29    0    354
+2028    */{    5    ,    1    ,    26    ,    59696    },/*    30    30    30    29    30    29    29    30    29    29    30    30    29    384
+2029    */{    0    ,    2    ,    13    ,    54576    },/*    30    30    29    30    29    30    29    30    29    29    30    30    0    355
+2030    */{    0    ,    2    ,    3    ,    23200    },/*    29    30    29    30    30    29    30    29    30    29    30    29    0    354
+2031    */{    3    ,    1    ,    23    ,    27472    },/*    29    30    30    29    30    29    30    30    29    30    29    30    29    384
+2032    */{    0    ,    2    ,    11    ,    38608    },/*    30    29    29    30    29    30    30    29    30    30    29    30    0    355
+2033    */{    11    ,    1    ,    31    ,    19176    },/*    29    30    29    29    30    29    30    29    30    30    30    29    30    384
+2034    */{    0    ,    2    ,    19    ,    19152    },/*    29    30    29    29    30    29    30    29    30    30    29    30    0    354
+2035    */{    0    ,    2    ,    8    ,    42192    },/*    30    29    30    29    29    30    29    29    30    30    29    30    0    354
+2036    */{    6    ,    1    ,    28    ,    53848    },/*    30    30    29    30    29    29    30    29    29    30    29    30    30    384
+2037    */{    0    ,    2    ,    15    ,    53840    },/*    30    30    29    30    29    29    30    29    29    30    29    30    0    354
+2038    */{    0    ,    2    ,    4    ,    54560    },/*    30    30    29    30    29    30    29    30    29    29    30    29    0    354
+2039    */{    5    ,    1    ,    24    ,    55968    },/*    30    30    29    30    30    29    30    29    30    29    30    29    29    384
+2040    */{    0    ,    2    ,    12    ,    46496    },/*    30    29    30    30    29    30    29    30    30    29    30    29    0    355
+2041    */{    0    ,    2    ,    1    ,    22224    },/*    29    30    29    30    29    30    30    29    30    30    29    30    0    355
+2042    */{    2    ,    1    ,    22    ,    19160    },/*    29    30    29    29    30    29    30    29    30    30    29    30    30    384
+2043    */{    0    ,    2    ,    10    ,    18864    },/*    29    30    29    29    30    29    29    30    30    29    30    30    0    354
+2044    */{    7    ,    1    ,    30    ,    42168    },/*    30    29    30    29    29    30    29    29    30    29    30    30    30    384
+2045    */{    0    ,    2    ,    17    ,    42160    },/*    30    29    30    29    29    30    29    29    30    29    30    30    0    354
+2046    */{    0    ,    2    ,    6    ,    43600    },/*    30    29    30    29    30    29    30    29    29    30    29    30    0    354
+2047    */{    5    ,    1    ,    26    ,    46376    },/*    30    29    30    30    29    30    29    30    29    29    30    29    30    384
+2048    */{    0    ,    2    ,    14    ,    27936    },/*    29    30    30    29    30    30    29    30    29    29    30    29    0    354
+2049    */{    0    ,    2    ,    2    ,    44448    },/*    30    29    30    29    30    30    29    30    30    29    30    29    0    355
+2050    */{    3    ,    1    ,    23    ,    21936    },/*    29    30    29    30    29    30    29    30    30    29    30    30    29    384
+2051    */{    0    ,    2    ,    11    ,    37744    },/*    30    29    29    30    29    29    30    30    29    30    30    30    0    355
+2052    */{    8    ,    2    ,    1    ,    18808    },/*    29    30    29    29    30    29    29    30    29    30    30    30    30    384
+2053    */{    0    ,    2    ,    19    ,    18800    },/*    29    30    29    29    30    29    29    30    29    30    30    30    0    354
+2054    */{    0    ,    2    ,    8    ,    25776    },/*    29    30    30    29    29    30    29    29    30    29    30    30    0    354
+2055    */{    6    ,    1    ,    28    ,    27216    },/*    29    30    30    29    30    29    30    29    29    30    29    30    29    383
+2056    */{    0    ,    2    ,    15    ,    59984    },/*    30    30    30    29    30    29    30    29    29    30    29    30    0    355
+2057    */{    0    ,    2    ,    4    ,    27424    },/*    29    30    30    29    30    29    30    30    29    29    30    29    0    354
+2058    */{    4    ,    1    ,    24    ,    43872    },/*    30    29    30    29    30    29    30    30    29    30    30    29    29    384
+2059    */{    0    ,    2    ,    12    ,    43744    },/*    30    29    30    29    30    29    30    29    30    30    30    29    0    355
+2060    */{    0    ,    2    ,    2    ,    37600    },/*    30    29    29    30    29    29    30    29    30    30    30    29    0    354
+2061    */{    3    ,    1    ,    21    ,    51568    },/*    30    30    29    29    30    29    29    30    29    30    30    30    29    384
+2062    */{    0    ,    2    ,    9    ,    51552    },/*    30    30    29    29    30    29    29    30    29    30    30    29    0    354
+2063    */{    7    ,    1    ,    29    ,    54440    },/*    30    30    29    30    29    30    29    29    30    29    30    29    30    384
+2064    */{    0    ,    2    ,    17    ,    54432    },/*    30    30    29    30    29    30    29    29    30    29    30    29    0    354
+2065    */{    0    ,    2    ,    5    ,    55888    },/*    30    30    29    30    30    29    30    29    29    30    29    30    0    355
+2066    */{    5    ,    1    ,    26    ,    23208    },/*    29    30    29    30    30    29    30    29    30    29    30    29    30    384
+2067    */{    0    ,    2    ,    14    ,    22176    },/*    29    30    29    30    29    30    30    29    30    29    30    29    0    354
+2068    */{    0    ,    2    ,    3    ,    42704    },/*    30    29    30    29    29    30    30    29    30    30    29    30    0    355
+2069    */{    4    ,    1    ,    23    ,    21224    },/*    29    30    29    30    29    29    30    29    30    30    30    29    30    384
+2070    */{    0    ,    2    ,    11    ,    21200    },/*    29    30    29    30    29    29    30    29    30    30    29    30    0    354
+2071    */{    8    ,    1    ,    31    ,    43352    },/*    30    29    30    29    30    29    29    30    29    30    29    30    30    384
+2072    */{    0    ,    2    ,    19    ,    43344    },/*    30    29    30    29    30    29    29    30    29    30    29    30    0    354
+2073    */{    0    ,    2    ,    7    ,    46240    },/*    30    29    30    30    29    30    29    29    30    29    30    29    0    354
+2074    */{    6    ,    1    ,    27    ,    46416    },/*    30    29    30    30    29    30    29    30    29    30    29    30    29    384
+2075    */{    0    ,    2    ,    15    ,    44368    },/*    30    29    30    29    30    30    29    30    29    30    29    30    0    355
+2076    */{    0    ,    2    ,    5    ,    21920    },/*    29    30    29    30    29    30    29    30    30    29    30    29    0    354
+2077    */{    4    ,    1    ,    24    ,    42448    },/*    30    29    30    29    29    30    29    30    30    30    29    30    29    384
+2078    */{    0    ,    2    ,    12    ,    42416    },/*    30    29    30    29    29    30    29    30    30    29    30    30    0    355
+2079    */{    0    ,    2    ,    2    ,    21168    },/*    29    30    29    30    29    29    30    29    30    29    30    30    0    354
+2080    */{    3    ,    1    ,    22    ,    43320    },/*    30    29    30    29    30    29    29    30    29    29    30    30    30    384
+2081    */{    0    ,    2    ,    9    ,    26928    },/*    29    30    30    29    30    29    29    30    29    29    30    30    0    354
+2082    */{    7    ,    1    ,    29    ,    29336    },/*    29    30    30    30    29    29    30    29    30    29    29    30    30    384
+2083    */{    0    ,    2    ,    17    ,    27296    },/*    29    30    30    29    30    29    30    29    30    29    30    29    0    354
+2084    */{    0    ,    2    ,    6    ,    44368    },/*    30    29    30    29    30    30    29    30    29    30    29    30    0    355
+2085    */{    5    ,    1    ,    26    ,    19880    },/*    29    30    29    29    30    30    29    30    30    29    30    29    30    384
+2086    */{    0    ,    2    ,    14    ,    19296    },/*    29    30    29    29    30    29    30    30    29    30    30    29    0    354
+2087    */{    0    ,    2    ,    3    ,    42352    },/*    30    29    30    29    29    30    29    30    29    30    30    30    0    355
+2088    */{    4    ,    1    ,    24    ,    21104    },/*    29    30    29    30    29    29    30    29    29    30    30    30    29    383
+2089    */{    0    ,    2    ,    10    ,    53856    },/*    30    30    29    30    29    29    30    29    29    30    30    29    0    354
+2090    */{    8    ,    1    ,    30    ,    59696    },/*    30    30    30    29    30    29    29    30    29    29    30    30    29    384
+2091    */{    0    ,    2    ,    18    ,    54560    },/*    30    30    29    30    29    30    29    30    29    29    30    29    0    354
+2092    */{    0    ,    2    ,    7    ,    55968    },/*    30    30    29    30    30    29    30    29    30    29    30    29    0    355
+2093    */{    6    ,    1    ,    27    ,    27472    },/*    29    30    30    29    30    29    30    30    29    30    29    30    29    384
+2094    */{    0    ,    2    ,    15    ,    22224    },/*    29    30    29    30    29    30    30    29    30    30    29    30    0    355
+2095    */{    0    ,    2    ,    5    ,    19168    },/*    29    30    29    29    30    29    30    29    30    30    30    29    0    354
+2096    */{    4    ,    1    ,    25    ,    42216    },/*    30    29    30    29    29    30    29    29    30    30    30    29    30    384
+2097    */{    0    ,    2    ,    12    ,    42192    },/*    30    29    30    29    29    30    29    29    30    30    29    30    0    354
+2098    */{    0    ,    2    ,    1    ,    53584    },/*    30    30    29    30    29    29    29    30    29    30    29    30    0    354
+2099    */{    2    ,    1    ,    21    ,    55592    },/*    30    30    29    30    30    29    29    30    29    29    30    29    30    384
+2100    */{    0    ,    2    ,    9    ,    54560    },/*    30    30    29    30    29    30    29    30    29    29    30    29    0    354
+        */};
+
+
+        internal override int MinCalendarYear
+        {
+            get
+            {
+                return (MIN_LUNISOLAR_YEAR);
+            }
+        }
+
+        internal override int MaxCalendarYear
+        {
+            get
+            {
+                return (MAX_LUNISOLAR_YEAR);
+            }
+        }
+
+        internal override DateTime MinDate
+        {
+            get
+            {
+                return (minDate);
+            }
+        }
+
+        internal override DateTime MaxDate
+        {
+            get
+            {
+                return (maxDate);
+            }
+        }
+
+        internal override EraInfo[] CalEraInfo
+        {
+            get
+            {
+                return (null);
+            }
+        }
+
+        internal override int GetYearInfo(int lunarYear, int index)
+        {
+            if ((lunarYear < MIN_LUNISOLAR_YEAR) || (lunarYear > MAX_LUNISOLAR_YEAR))
+            {
+                throw new ArgumentOutOfRangeException(
+                            "year",
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range, MIN_LUNISOLAR_YEAR, MAX_LUNISOLAR_YEAR));
+            }
+
+            return s_yinfo[lunarYear - MIN_LUNISOLAR_YEAR, index];
+        }
+
+        internal override int GetYear(int year, DateTime time)
+        {
+            return year;
+        }
+
+        internal override int GetGregorianYear(int year, int era)
+        {
+            if (era != CurrentEra && era != ChineseEra)
+            {
+                throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+            }
+
+            if (year < MIN_LUNISOLAR_YEAR || year > MAX_LUNISOLAR_YEAR)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range, MIN_LUNISOLAR_YEAR, MAX_LUNISOLAR_YEAR));
+            }
+
+            return year;
+        }
+
+        public ChineseLunisolarCalendar()
+        {
+        }
+
+        public override int GetEra(DateTime time)
+        {
+            CheckTicksRange(time.Ticks);
+            return (ChineseEra);
+        }
+
+        internal override CalendarId ID
+        {
+            get
+            {
+                return (CalendarId.CHINESELUNISOLAR);
+            }
+        }
+
+        internal override CalendarId BaseCalendarID
+        {
+            get
+            {
+                //Use CAL_GREGORIAN just to get CurrentEraValue as 1 since we do not have data under the ID CAL_ChineseLunisolar yet
+                return (CalendarId.GREGORIAN);
+            }
+        }
+
+
+        public override int[] Eras
+        {
+            get
+            {
+                return (new int[] { ChineseEra });
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CompareInfo.Invariant.cs b/src/System.Private.CoreLib/shared/System/Globalization/CompareInfo.Invariant.cs
new file mode 100644
index 0000000000..29e4f53212
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CompareInfo.Invariant.cs
@@ -0,0 +1,249 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System.Globalization
+{
+    public partial class CompareInfo
+    {
+        internal static unsafe int InvariantIndexOf(string source, string value, int startIndex, int count, bool ignoreCase)
+        {
+            Debug.Assert(source != null);
+            Debug.Assert(value != null);
+            Debug.Assert(startIndex >= 0 && startIndex < source.Length);
+
+            fixed (char* pSource = source) fixed (char* pValue = value)
+            {
+                char* pSrc = &pSource[startIndex];
+                int index = InvariantFindString(pSrc, count, pValue, value.Length, ignoreCase, start : true);
+                if (index >= 0)
+                {
+                    return index + startIndex;
+                }
+                return -1;
+            }
+        }
+
+        internal static unsafe int InvariantIndexOf(ReadOnlySpan<char> source, ReadOnlySpan<char> value, bool ignoreCase)
+        {
+            Debug.Assert(source.Length != 0);
+            Debug.Assert(value.Length != 0);
+
+            fixed (char* pSource = &MemoryMarshal.GetReference(source))
+            fixed (char* pValue = &MemoryMarshal.GetReference(value))
+            {
+                return InvariantFindString(pSource, source.Length, pValue, value.Length, ignoreCase, start: true);
+            }
+        }
+
+        internal static unsafe int InvariantLastIndexOf(string source, string value, int startIndex, int count, bool ignoreCase)
+        {
+            Debug.Assert(source != null);
+            Debug.Assert(value != null);
+            Debug.Assert(startIndex >= 0 && startIndex < source.Length);
+
+            fixed (char* pSource = source) fixed (char* pValue = value)
+            {
+                char* pSrc = &pSource[startIndex - count + 1];
+                int index = InvariantFindString(pSrc, count, pValue, value.Length, ignoreCase, start : false);
+                if (index >= 0)
+                {
+                    return index + startIndex - count + 1;
+                }
+                return -1;
+            }
+        }
+
+        private static unsafe int InvariantFindString(char* source, int sourceCount, char* value, int valueCount, bool ignoreCase, bool start)
+        {
+            int ctrSource = 0;  // index value into source
+            int ctrValue = 0;   // index value into value
+            char sourceChar;    // Character for case lookup in source
+            char valueChar;     // Character for case lookup in value
+            int lastSourceStart;
+
+            Debug.Assert(source != null);
+            Debug.Assert(value != null);
+            Debug.Assert(sourceCount >= 0);
+            Debug.Assert(valueCount >= 0);
+
+            if (valueCount == 0)
+            {
+                return start ? 0 : sourceCount - 1;
+            }
+
+            if (sourceCount < valueCount)
+            {
+                return -1;
+            }
+
+            if (start)
+            {
+                lastSourceStart = sourceCount - valueCount;
+                if (ignoreCase)
+                {
+                    char firstValueChar = InvariantToUpper(value[0]);
+                    for (ctrSource = 0; ctrSource <= lastSourceStart; ctrSource++)
+                    {
+                        sourceChar = InvariantToUpper(source[ctrSource]);
+                        if (sourceChar != firstValueChar)
+                        {
+                            continue;
+                        }
+
+                        for (ctrValue = 1; ctrValue < valueCount; ctrValue++)
+                        {
+                            sourceChar = InvariantToUpper(source[ctrSource + ctrValue]);
+                            valueChar = InvariantToUpper(value[ctrValue]);
+
+                            if (sourceChar != valueChar)
+                            {
+                                break;
+                            }
+                        }
+
+                        if (ctrValue == valueCount)
+                        {
+                            return ctrSource;
+                        }
+                    }
+                }
+                else
+                {
+                    char firstValueChar = value[0];
+                    for (ctrSource = 0; ctrSource <= lastSourceStart; ctrSource++)
+                    {
+                        sourceChar = source[ctrSource];
+                        if (sourceChar != firstValueChar)
+                        {
+                            continue;
+                        }
+
+                        for (ctrValue = 1; ctrValue < valueCount; ctrValue++)
+                        {
+                            sourceChar = source[ctrSource + ctrValue];
+                            valueChar = value[ctrValue];
+
+                            if (sourceChar != valueChar)
+                            {
+                                break;
+                            }
+                        }
+
+                        if (ctrValue == valueCount)
+                        {
+                            return ctrSource;
+                        }
+                    }
+                }
+            }
+            else
+            {
+                lastSourceStart = sourceCount - valueCount;
+                if (ignoreCase)
+                {
+                    char firstValueChar = InvariantToUpper(value[0]);
+                    for (ctrSource = lastSourceStart; ctrSource >= 0; ctrSource--)
+                    {
+                        sourceChar = InvariantToUpper(source[ctrSource]);
+                        if (sourceChar != firstValueChar)
+                        {
+                            continue;
+                        }
+                        for (ctrValue = 1; ctrValue < valueCount; ctrValue++)
+                        {
+                            sourceChar = InvariantToUpper(source[ctrSource + ctrValue]);
+                            valueChar = InvariantToUpper(value[ctrValue]);
+
+                            if (sourceChar != valueChar)
+                            {
+                                break;
+                            }
+                        }
+
+                        if (ctrValue == valueCount)
+                        {
+                            return ctrSource;
+                        }
+                    }
+                }
+                else
+                {
+                    char firstValueChar = value[0];
+                    for (ctrSource = lastSourceStart; ctrSource >= 0; ctrSource--)
+                    {
+                        sourceChar = source[ctrSource];
+                        if (sourceChar != firstValueChar)
+                        {
+                            continue;
+                        }
+
+                        for (ctrValue = 1; ctrValue < valueCount; ctrValue++)
+                        {
+                            sourceChar = source[ctrSource + ctrValue];
+                            valueChar = value[ctrValue];
+
+                            if (sourceChar != valueChar)
+                            {
+                                break;
+                            }
+                        }
+
+                        if (ctrValue == valueCount)
+                        {
+                            return ctrSource;
+                        }
+                    }
+                }
+            }
+
+            return -1;
+        }
+
+        private static char InvariantToUpper(char c)
+        {
+            return (uint)(c - 'a') <= (uint)('z' - 'a') ? (char)(c - 0x20) : c;
+        }
+
+        private unsafe SortKey InvariantCreateSortKey(string source, CompareOptions options)
+        {
+            if (source == null) { throw new ArgumentNullException(nameof(source)); }
+
+            if ((options & ValidSortkeyCtorMaskOffFlags) != 0)
+            {
+                throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
+            }
+
+            byte [] keyData;
+            if (source.Length == 0)
+            { 
+                keyData = Array.Empty<byte>();
+            }
+            else
+            {
+                // In the invariant mode, all string comparisons are done as ordinal so when generating the sort keys we generate it according to this fact
+                keyData = new byte[source.Length * sizeof(char)];
+
+                fixed (char* pChar = source) fixed (byte* pByte = keyData)
+                {
+                    if ((options & (CompareOptions.IgnoreCase | CompareOptions.OrdinalIgnoreCase)) != 0)
+                    {
+                        short *pShort = (short *) pByte;
+                        for (int i=0; i<source.Length; i++)
+                        {
+                            pShort[i] = (short) InvariantToUpper(source[i]);
+                        }
+                    } 
+                    else
+                    {
+                        Buffer.MemoryCopy(pChar, pByte, keyData.Length, keyData.Length);
+                    }
+                }
+            }
+            return new SortKey(Name, source, options, keyData);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CompareInfo.Unix.cs b/src/System.Private.CoreLib/shared/System/Globalization/CompareInfo.Unix.cs
new file mode 100644
index 0000000000..5a68492c69
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CompareInfo.Unix.cs
@@ -0,0 +1,1014 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Buffers;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Security;
+
+namespace System.Globalization
+{
+    public partial class CompareInfo
+    {
+        [NonSerialized]
+        private Interop.Globalization.SafeSortHandle _sortHandle;
+
+        [NonSerialized]
+        private bool _isAsciiEqualityOrdinal;
+
+        private void InitSort(CultureInfo culture)
+        {
+            _sortName = culture.SortName;
+
+            if (_invariantMode)
+            {
+                _isAsciiEqualityOrdinal = true;
+            }
+            else
+            {
+                Interop.Globalization.ResultCode resultCode = Interop.Globalization.GetSortHandle(GetNullTerminatedUtf8String(_sortName), out _sortHandle);
+                if (resultCode != Interop.Globalization.ResultCode.Success)
+                {
+                    _sortHandle.Dispose();
+
+                    if (resultCode == Interop.Globalization.ResultCode.OutOfMemory)
+                        throw new OutOfMemoryException();
+
+                    throw new ExternalException(SR.Arg_ExternalException);
+                }
+                _isAsciiEqualityOrdinal = (_sortName == "en-US" || _sortName == "");
+            }
+        }
+
+        internal static unsafe int IndexOfOrdinalCore(string source, string value, int startIndex, int count, bool ignoreCase)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            Debug.Assert(source != null);
+            Debug.Assert(value != null);
+
+            if (value.Length == 0)
+            {
+                return startIndex;
+            }
+
+            if (count < value.Length)
+            {
+                return -1;
+            }
+
+            if (ignoreCase)
+            {
+                fixed (char* pSource = source)
+                {
+                    int index = Interop.Globalization.IndexOfOrdinalIgnoreCase(value, value.Length, pSource + startIndex, count, findLast: false);
+                    return index != -1 ?
+                        startIndex + index :
+                        -1;
+                }
+            }
+
+            int endIndex = startIndex + (count - value.Length);
+            for (int i = startIndex; i <= endIndex; i++)
+            {
+                int valueIndex, sourceIndex;
+
+                for (valueIndex = 0, sourceIndex = i;
+                     valueIndex < value.Length && source[sourceIndex] == value[valueIndex];
+                     valueIndex++, sourceIndex++) ;
+
+                if (valueIndex == value.Length)
+                {
+                    return i;
+                }
+            }
+
+            return -1;
+        }
+
+        internal static unsafe int IndexOfOrdinalCore(ReadOnlySpan<char> source, ReadOnlySpan<char> value, bool ignoreCase)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            Debug.Assert(source.Length != 0);
+            Debug.Assert(value.Length != 0);
+
+            if (source.Length < value.Length)
+            {
+                return -1;
+            }
+
+            if (ignoreCase)
+            {
+                fixed (char* pSource = &MemoryMarshal.GetReference(source))
+                fixed (char* pValue = &MemoryMarshal.GetReference(value))
+                {
+                    int index = Interop.Globalization.IndexOfOrdinalIgnoreCase(pValue, value.Length, pSource, source.Length, findLast: false);
+                    return index;
+                }
+            }
+
+            int endIndex = source.Length - value.Length;
+            for (int i = 0; i <= endIndex; i++)
+            {
+                int valueIndex, sourceIndex;
+
+                for (valueIndex = 0, sourceIndex = i;
+                     valueIndex < value.Length && source[sourceIndex] == value[valueIndex];
+                     valueIndex++, sourceIndex++)
+                    ;
+
+                if (valueIndex == value.Length)
+                {
+                    return i;
+                }
+            }
+
+            return -1;
+        }
+
+        internal static unsafe int LastIndexOfOrdinalCore(string source, string value, int startIndex, int count, bool ignoreCase)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            Debug.Assert(source != null);
+            Debug.Assert(value != null);
+
+            if (value.Length == 0)
+            {
+                return startIndex;
+            }
+
+            if (count < value.Length)
+            {
+                return -1;
+            }
+
+            // startIndex is the index into source where we start search backwards from. 
+            // leftStartIndex is the index into source of the start of the string that is 
+            // count characters away from startIndex.
+            int leftStartIndex = startIndex - count + 1;
+
+            if (ignoreCase)
+            {
+                fixed (char* pSource = source)
+                {
+                    int lastIndex = Interop.Globalization.IndexOfOrdinalIgnoreCase(value, value.Length, pSource + leftStartIndex, count, findLast: true);
+                    return lastIndex != -1 ?
+                        leftStartIndex + lastIndex :
+                        -1;
+                }
+            }
+
+            for (int i = startIndex - value.Length + 1; i >= leftStartIndex; i--)
+            {
+                int valueIndex, sourceIndex;
+
+                for (valueIndex = 0, sourceIndex = i;
+                     valueIndex < value.Length && source[sourceIndex] == value[valueIndex];
+                     valueIndex++, sourceIndex++) ;
+
+                if (valueIndex == value.Length) {
+                    return i;
+                }
+            }
+
+            return -1;
+        }
+
+        private static unsafe int CompareStringOrdinalIgnoreCase(char* string1, int count1, char* string2, int count2)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            Debug.Assert(string1 != null);
+            Debug.Assert(string2 != null);
+
+            return Interop.Globalization.CompareStringOrdinalIgnoreCase(string1, count1, string2, count2);
+        }
+
+        // TODO https://github.com/dotnet/coreclr/issues/13827:
+        // This method shouldn't be necessary, as we should be able to just use the overload
+        // that takes two spans.  But due to this issue, that's adding significant overhead.
+        private unsafe int CompareString(ReadOnlySpan<char> string1, string string2, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+            Debug.Assert(string2 != null);
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+            fixed (char* pString1 = &MemoryMarshal.GetReference(string1))
+            fixed (char* pString2 = &string2.GetRawStringData())
+            {
+                return Interop.Globalization.CompareString(_sortHandle, pString1, string1.Length, pString2, string2.Length, options);
+            }
+        }
+
+        private unsafe int CompareString(ReadOnlySpan<char> string1, ReadOnlySpan<char> string2, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+            fixed (char* pString1 = &MemoryMarshal.GetReference(string1))
+            fixed (char* pString2 = &MemoryMarshal.GetReference(string2))
+            {
+                return Interop.Globalization.CompareString(_sortHandle, pString1, string1.Length, pString2, string2.Length, options);
+            }
+        }
+
+        internal unsafe int IndexOfCore(string source, string target, int startIndex, int count, CompareOptions options, int* matchLengthPtr)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!string.IsNullOrEmpty(source));
+            Debug.Assert(target != null);
+            Debug.Assert((options & CompareOptions.OrdinalIgnoreCase) == 0);
+
+            int index;
+
+            if (target.Length == 0)
+            {
+                if (matchLengthPtr != null)
+                    *matchLengthPtr = 0;
+                return startIndex;
+            }
+
+            if (options == CompareOptions.Ordinal)
+            {
+                index = IndexOfOrdinal(source, target, startIndex, count, ignoreCase: false);
+                if (index != -1)
+                {
+                    if (matchLengthPtr != null)
+                        *matchLengthPtr = target.Length;
+                }
+                return index;
+            }
+
+#if CORECLR
+            if (_isAsciiEqualityOrdinal && CanUseAsciiOrdinalForOptions(options) && source.IsFastSort() && target.IsFastSort())
+            {
+                index = IndexOf(source, target, startIndex, count, GetOrdinalCompareOptions(options));
+                if (index != -1)
+                {
+                    if (matchLengthPtr != null)
+                        *matchLengthPtr = target.Length;
+                }
+                return index;
+            }
+#endif
+
+            fixed (char* pSource = source)
+            {
+                index = Interop.Globalization.IndexOf(_sortHandle, target, target.Length, pSource + startIndex, count, options, matchLengthPtr);
+
+                return index != -1 ? index + startIndex : -1;
+            }
+        }
+
+        // For now, this method is only called from Span APIs with either options == CompareOptions.None or CompareOptions.IgnoreCase
+        internal unsafe int IndexOfCore(ReadOnlySpan<char> source, ReadOnlySpan<char> target, CompareOptions options, int* matchLengthPtr)
+        {
+            Debug.Assert(!_invariantMode);
+            Debug.Assert(source.Length != 0);
+            Debug.Assert(target.Length != 0);
+
+            if (_isAsciiEqualityOrdinal && CanUseAsciiOrdinalForOptions(options))
+            {
+                if ((options & CompareOptions.IgnoreCase) == CompareOptions.IgnoreCase)
+                {
+                    return IndexOfOrdinalIgnoreCaseHelper(source, target, options, matchLengthPtr);
+                }
+                else
+                {
+                    return IndexOfOrdinalHelper(source, target, options, matchLengthPtr);
+                }
+            }
+            else
+            {
+                fixed (char* pSource = &MemoryMarshal.GetReference(source))
+                fixed (char* pTarget = &MemoryMarshal.GetReference(target))
+                {
+                    return Interop.Globalization.IndexOf(_sortHandle, pTarget, target.Length, pSource, source.Length, options, matchLengthPtr);
+                }
+            }
+        }
+
+        private unsafe int IndexOfOrdinalIgnoreCaseHelper(ReadOnlySpan<char> source, ReadOnlySpan<char> target, CompareOptions options, int* matchLengthPtr)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!source.IsEmpty);
+            Debug.Assert(!target.IsEmpty);
+            Debug.Assert(_isAsciiEqualityOrdinal);
+
+            fixed (char* ap = &MemoryMarshal.GetReference(source))
+            fixed (char* bp = &MemoryMarshal.GetReference(target))
+            {
+                char* a = ap;
+                char* b = bp;
+                int endIndex = source.Length - target.Length;
+
+                if (endIndex < 0)
+                    goto InteropCall;
+
+                for (int j = 0; j < target.Length; j++)
+                {
+                    char targetChar = *(b + j);
+                    if (targetChar >= 0x80 || s_highCharTable[targetChar])
+                        goto InteropCall;
+                }
+
+                int i = 0;
+                for (; i <= endIndex; i++)
+                {
+                    int targetIndex = 0;
+                    int sourceIndex = i;
+
+                    for (; targetIndex < target.Length; targetIndex++)
+                    {
+                        char valueChar = *(a + sourceIndex);
+                        char targetChar = *(b + targetIndex);
+
+                        if (valueChar == targetChar && valueChar < 0x80 && !s_highCharTable[valueChar])
+                        {
+                            sourceIndex++;
+                            continue;
+                        }
+
+                        // uppercase both chars - notice that we need just one compare per char
+                        if ((uint)(valueChar - 'a') <= ('z' - 'a'))
+                            valueChar = (char)(valueChar - 0x20);
+                        if ((uint)(targetChar - 'a') <= ('z' - 'a'))
+                            targetChar = (char)(targetChar - 0x20);
+
+                        if (valueChar >= 0x80 || s_highCharTable[valueChar])
+                            goto InteropCall;
+                        else if (valueChar != targetChar)
+                            break;
+                        sourceIndex++;
+                    }
+
+                    if (targetIndex == target.Length)
+                    {
+                        if (matchLengthPtr != null)
+                            *matchLengthPtr = target.Length;
+                        return i;
+                    }
+                }
+                if (i > endIndex)
+                    return -1;
+            InteropCall:
+                return Interop.Globalization.IndexOf(_sortHandle, b, target.Length, a, source.Length, options, matchLengthPtr);
+            }
+        }
+
+        private unsafe int IndexOfOrdinalHelper(ReadOnlySpan<char> source, ReadOnlySpan<char> target, CompareOptions options, int* matchLengthPtr)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!source.IsEmpty);
+            Debug.Assert(!target.IsEmpty);
+            Debug.Assert(_isAsciiEqualityOrdinal);
+
+            fixed (char* ap = &MemoryMarshal.GetReference(source))
+            fixed (char* bp = &MemoryMarshal.GetReference(target))
+            {
+                char* a = ap;
+                char* b = bp;
+                int endIndex = source.Length - target.Length;
+
+                if (endIndex < 0)
+                    goto InteropCall;
+
+                for (int j = 0; j < target.Length; j++)
+                {
+                    char targetChar = *(b + j);
+                    if (targetChar >= 0x80 || s_highCharTable[targetChar])
+                        goto InteropCall;
+                }
+
+                int i = 0;
+                for (; i <= endIndex; i++)
+                {
+                    int targetIndex = 0;
+                    int sourceIndex = i;
+
+                    for (; targetIndex < target.Length; targetIndex++)
+                    {
+                        char valueChar = *(a + sourceIndex);
+                        char targetChar = *(b + targetIndex);
+                        if (valueChar >= 0x80 || s_highCharTable[valueChar])
+                            goto InteropCall;
+                        else if (valueChar != targetChar)
+                            break;
+                        sourceIndex++;
+                    }
+
+                    if (targetIndex == target.Length)
+                    {
+                        if (matchLengthPtr != null)
+                            *matchLengthPtr = target.Length;
+                        return i;
+                    }
+                }
+                if (i > endIndex)
+                    return -1;
+            InteropCall:
+                return Interop.Globalization.IndexOf(_sortHandle, b, target.Length, a, source.Length, options, matchLengthPtr);
+            }
+        }
+
+        private unsafe int LastIndexOfCore(string source, string target, int startIndex, int count, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!string.IsNullOrEmpty(source));
+            Debug.Assert(target != null);
+            Debug.Assert((options & CompareOptions.OrdinalIgnoreCase) == 0);
+
+            if (target.Length == 0)
+            {
+                return startIndex;
+            }
+
+            if (options == CompareOptions.Ordinal)
+            {
+                return LastIndexOfOrdinalCore(source, target, startIndex, count, ignoreCase: false);
+            }
+
+#if CORECLR
+            if (_isAsciiEqualityOrdinal && CanUseAsciiOrdinalForOptions(options) && source.IsFastSort() && target.IsFastSort())
+            {
+                return LastIndexOf(source, target, startIndex, count, GetOrdinalCompareOptions(options));
+            }
+#endif
+
+            // startIndex is the index into source where we start search backwards from. leftStartIndex is the index into source
+            // of the start of the string that is count characters away from startIndex.
+            int leftStartIndex = (startIndex - count + 1);
+
+            fixed (char* pSource = source)
+            {
+                int lastIndex = Interop.Globalization.LastIndexOf(_sortHandle, target, target.Length, pSource + (startIndex - count + 1), count, options);
+
+                return lastIndex != -1 ? lastIndex + leftStartIndex : -1;
+            }
+        }
+
+        private bool StartsWith(string source, string prefix, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!string.IsNullOrEmpty(source));
+            Debug.Assert(!string.IsNullOrEmpty(prefix));
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+#if CORECLR
+            if (_isAsciiEqualityOrdinal && CanUseAsciiOrdinalForOptions(options) && source.IsFastSort() && prefix.IsFastSort())
+            {
+                return IsPrefix(source, prefix, GetOrdinalCompareOptions(options));
+            }
+#endif
+
+            return Interop.Globalization.StartsWith(_sortHandle, prefix, prefix.Length, source, source.Length, options);
+        }
+
+        private unsafe bool StartsWith(ReadOnlySpan<char> source, ReadOnlySpan<char> prefix, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!source.IsEmpty);
+            Debug.Assert(!prefix.IsEmpty);
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+            if (_isAsciiEqualityOrdinal && CanUseAsciiOrdinalForOptions(options))
+            {
+                if (source.Length < prefix.Length)
+                {
+                    return false;
+                }
+
+                if ((options & CompareOptions.IgnoreCase) == CompareOptions.IgnoreCase)
+                {
+                    return StartsWithOrdinalIgnoreCaseHelper(source, prefix, options);
+                }
+                else
+                {
+                    return StartsWithOrdinalHelper(source, prefix, options);
+                }
+            }
+            else
+            {
+                fixed (char* pSource = &MemoryMarshal.GetReference(source))
+                fixed (char* pPrefix = &MemoryMarshal.GetReference(prefix))
+                {
+                    return Interop.Globalization.StartsWith(_sortHandle, pPrefix, prefix.Length, pSource, source.Length, options);
+                }
+            }
+        }
+
+        private unsafe bool StartsWithOrdinalIgnoreCaseHelper(ReadOnlySpan<char> source, ReadOnlySpan<char> prefix, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!source.IsEmpty);
+            Debug.Assert(!prefix.IsEmpty);
+            Debug.Assert(_isAsciiEqualityOrdinal);
+            Debug.Assert(source.Length >= prefix.Length);
+
+            int length = prefix.Length;
+
+            fixed (char* ap = &MemoryMarshal.GetReference(source))
+            fixed (char* bp = &MemoryMarshal.GetReference(prefix))
+            {
+                char* a = ap;
+                char* b = bp;
+
+                while (length != 0 && (*a < 0x80) && (*b < 0x80) && (!s_highCharTable[*a]) && (!s_highCharTable[*b]))
+                {
+                    int charA = *a;
+                    int charB = *b;
+
+                    if (charA == charB)
+                    {
+                        a++; b++;
+                        length--;
+                        continue;
+                    }
+
+                    // uppercase both chars - notice that we need just one compare per char
+                    if ((uint)(charA - 'a') <= (uint)('z' - 'a')) charA -= 0x20;
+                    if ((uint)(charB - 'a') <= (uint)('z' - 'a')) charB -= 0x20;
+                    
+                    if (charA != charB)
+                        return false;
+
+                    // Next char
+                    a++; b++;
+                    length--;
+                }
+
+                if (length == 0) return true;
+                return Interop.Globalization.StartsWith(_sortHandle, b, length, a, length, options);
+            }
+        }
+
+        private unsafe bool StartsWithOrdinalHelper(ReadOnlySpan<char> source, ReadOnlySpan<char> prefix, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!source.IsEmpty);
+            Debug.Assert(!prefix.IsEmpty);
+            Debug.Assert(_isAsciiEqualityOrdinal);
+            Debug.Assert(source.Length >= prefix.Length);
+
+            int length = prefix.Length;
+
+            fixed (char* ap = &MemoryMarshal.GetReference(source))
+            fixed (char* bp = &MemoryMarshal.GetReference(prefix))
+            {
+                char* a = ap;
+                char* b = bp;
+
+                while (length != 0 && (*a < 0x80) && (*b < 0x80) && (!s_highCharTable[*a]) && (!s_highCharTable[*b]))
+                {
+                    int charA = *a;
+                    int charB = *b;
+                    
+                    if (charA != charB)
+                        return false;
+
+                    // Next char
+                    a++; b++;
+                    length--;
+                }
+
+                if (length == 0) return true;
+                return Interop.Globalization.StartsWith(_sortHandle, b, length, a, length, options);
+            }
+        }
+
+        private bool EndsWith(string source, string suffix, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!string.IsNullOrEmpty(source));
+            Debug.Assert(!string.IsNullOrEmpty(suffix));
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+#if CORECLR
+            if (_isAsciiEqualityOrdinal && CanUseAsciiOrdinalForOptions(options) && source.IsFastSort() && suffix.IsFastSort())
+            {
+                return IsSuffix(source, suffix, GetOrdinalCompareOptions(options));
+            }
+#endif
+
+            return Interop.Globalization.EndsWith(_sortHandle, suffix, suffix.Length, source, source.Length, options);
+        }
+
+        private unsafe bool EndsWith(ReadOnlySpan<char> source, ReadOnlySpan<char> suffix, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!source.IsEmpty);
+            Debug.Assert(!suffix.IsEmpty);
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+            if (_isAsciiEqualityOrdinal && CanUseAsciiOrdinalForOptions(options))
+            {
+                if (source.Length < suffix.Length)
+                {
+                    return false;
+                }
+
+                if ((options & CompareOptions.IgnoreCase) == CompareOptions.IgnoreCase)
+                {
+                    return EndsWithOrdinalIgnoreCaseHelper(source, suffix, options);
+                }
+                else
+                {
+                    return EndsWithOrdinalHelper(source, suffix, options);
+                }
+            }
+            else
+            {
+                fixed (char* pSource = &MemoryMarshal.GetReference(source))
+                fixed (char* pSuffix = &MemoryMarshal.GetReference(suffix))
+                {
+                    return Interop.Globalization.EndsWith(_sortHandle, pSuffix, suffix.Length, pSource, source.Length, options);
+                }
+            }
+        }
+
+        private unsafe bool EndsWithOrdinalIgnoreCaseHelper(ReadOnlySpan<char> source, ReadOnlySpan<char> suffix, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!source.IsEmpty);
+            Debug.Assert(!suffix.IsEmpty);
+            Debug.Assert(_isAsciiEqualityOrdinal);
+            Debug.Assert(source.Length >= suffix.Length);
+
+            int length = suffix.Length;
+
+            fixed (char* ap = &MemoryMarshal.GetReference(source))
+            fixed (char* bp = &MemoryMarshal.GetReference(suffix))
+            {
+                char* a = ap + source.Length - 1;
+                char* b = bp + suffix.Length - 1;
+
+                while (length != 0 && (*a < 0x80) && (*b < 0x80) && (!s_highCharTable[*a]) && (!s_highCharTable[*b]))
+                {
+                    int charA = *a;
+                    int charB = *b;
+
+                    if (charA == charB)
+                    {
+                        a--; b--;
+                        length--;
+                        continue;
+                    }
+
+                    // uppercase both chars - notice that we need just one compare per char
+                    if ((uint)(charA - 'a') <= (uint)('z' - 'a')) charA -= 0x20;
+                    if ((uint)(charB - 'a') <= (uint)('z' - 'a')) charB -= 0x20;
+                    
+                    if (charA != charB)
+                        return false;
+
+                    // Next char
+                    a--; b--;
+                    length--;
+                }
+
+                if (length == 0) return true;
+                return Interop.Globalization.EndsWith(_sortHandle, b - length + 1, length, a - length + 1, length, options);
+            }
+        }
+
+        private unsafe bool EndsWithOrdinalHelper(ReadOnlySpan<char> source, ReadOnlySpan<char> suffix, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!source.IsEmpty);
+            Debug.Assert(!suffix.IsEmpty);
+            Debug.Assert(_isAsciiEqualityOrdinal);
+            Debug.Assert(source.Length >= suffix.Length);
+
+            int length = suffix.Length;
+
+            fixed (char* ap = &MemoryMarshal.GetReference(source))
+            fixed (char* bp = &MemoryMarshal.GetReference(suffix))
+            {
+                char* a = ap + source.Length - 1;
+                char* b = bp + suffix.Length - 1;
+
+                while (length != 0 && (*a < 0x80) && (*b < 0x80) && (!s_highCharTable[*a]) && (!s_highCharTable[*b]))
+                {
+                    int charA = *a;
+                    int charB = *b;
+                    
+                    if (charA != charB)
+                        return false;
+
+                    // Next char
+                    a--; b--;
+                    length--;
+                }
+
+                if (length == 0) return true;
+                return Interop.Globalization.EndsWith(_sortHandle, b - length + 1, length, a - length + 1, length, options);
+            }
+        }
+
+        private unsafe SortKey CreateSortKey(String source, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            if (source==null) { throw new ArgumentNullException(nameof(source)); }
+
+            if ((options & ValidSortkeyCtorMaskOffFlags) != 0)
+            {
+                throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
+            }
+            
+            byte [] keyData;
+            if (source.Length == 0)
+            { 
+                keyData = Array.Empty<Byte>();
+            }
+            else
+            {
+                int sortKeyLength = Interop.Globalization.GetSortKey(_sortHandle, source, source.Length, null, 0, options);
+                keyData = new byte[sortKeyLength];
+
+                fixed (byte* pSortKey = keyData)
+                {
+                    if (Interop.Globalization.GetSortKey(_sortHandle, source, source.Length, pSortKey, sortKeyLength, options) != sortKeyLength)
+                    {
+                        throw new ArgumentException(SR.Arg_ExternalException);
+                    }
+                }
+            }
+
+            return new SortKey(Name, source, options, keyData);
+        }       
+
+        private static unsafe bool IsSortable(char *text, int length)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            int index = 0;
+            UnicodeCategory uc;
+
+            while (index < length)
+            {
+                if (Char.IsHighSurrogate(text[index]))
+                {
+                    if (index == length - 1 || !Char.IsLowSurrogate(text[index+1]))
+                        return false; // unpaired surrogate
+
+                    uc = CharUnicodeInfo.GetUnicodeCategory(Char.ConvertToUtf32(text[index], text[index+1]));
+                    if (uc == UnicodeCategory.PrivateUse || uc == UnicodeCategory.OtherNotAssigned)
+                        return false;
+
+                    index += 2;
+                    continue;
+                }
+
+                if (Char.IsLowSurrogate(text[index]))
+                {
+                    return false; // unpaired surrogate
+                }
+
+                uc = CharUnicodeInfo.GetUnicodeCategory(text[index]);
+                if (uc == UnicodeCategory.PrivateUse || uc == UnicodeCategory.OtherNotAssigned)
+                {
+                    return false;
+                }
+
+                index++;
+            }
+
+            return true;
+        }
+
+        // -----------------------------
+        // ---- PAL layer ends here ----
+        // -----------------------------
+
+        internal unsafe int GetHashCodeOfStringCore(string source, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(source != null);
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+            if (source.Length == 0)
+            {
+                return 0;
+            }
+
+            int sortKeyLength = Interop.Globalization.GetSortKey(_sortHandle, source, source.Length, null, 0, options);
+
+            byte[] borrowedArr = null;
+            Span<byte> span = sortKeyLength <= 512 ?
+                stackalloc byte[512] :
+                (borrowedArr = ArrayPool<byte>.Shared.Rent(sortKeyLength));
+
+            fixed (byte* pSortKey = &MemoryMarshal.GetReference(span))
+            {
+                if (Interop.Globalization.GetSortKey(_sortHandle, source, source.Length, pSortKey, sortKeyLength, options) != sortKeyLength)
+                {
+                    throw new ArgumentException(SR.Arg_ExternalException);
+                }
+            }
+
+            int hash = Marvin.ComputeHash32(span.Slice(0, sortKeyLength), Marvin.DefaultSeed);
+
+            // Return the borrowed array if necessary.
+            if (borrowedArr != null)
+            {
+                ArrayPool<byte>.Shared.Return(borrowedArr);
+            }
+
+            return hash;
+        }
+
+        private static CompareOptions GetOrdinalCompareOptions(CompareOptions options)
+        {
+            if ((options & CompareOptions.IgnoreCase) == CompareOptions.IgnoreCase)
+            {
+                return CompareOptions.OrdinalIgnoreCase;
+            }
+            else
+            {
+                return CompareOptions.Ordinal;
+            }
+        }
+
+        private static bool CanUseAsciiOrdinalForOptions(CompareOptions options)
+        {
+            // Unlike the other Ignore options, IgnoreSymbols impacts ASCII characters (e.g. ').
+            return (options & CompareOptions.IgnoreSymbols) == 0;
+        }
+
+        private static byte[] GetNullTerminatedUtf8String(string s)
+        {
+            int byteLen = System.Text.Encoding.UTF8.GetByteCount(s);
+
+            // Allocate an extra byte (which defaults to 0) as the null terminator.
+            byte[] buffer = new byte[byteLen + 1];
+
+            int bytesWritten = System.Text.Encoding.UTF8.GetBytes(s, 0, s.Length, buffer, 0);
+
+            Debug.Assert(bytesWritten == byteLen);
+
+            return buffer;
+        }
+        
+        private SortVersion GetSortVersion()
+        {
+            Debug.Assert(!_invariantMode);
+
+            int sortVersion = Interop.Globalization.GetSortVersion(_sortHandle);
+            return new SortVersion(sortVersion, LCID, new Guid(sortVersion, 0, 0, 0, 0, 0, 0,
+                                                             (byte) (LCID >> 24),
+                                                             (byte) ((LCID  & 0x00FF0000) >> 16),
+                                                             (byte) ((LCID  & 0x0000FF00) >> 8),
+                                                             (byte) (LCID  & 0xFF)));
+        }
+
+        // See https://github.com/dotnet/coreclr/blob/master/src/utilcode/util_nodependencies.cpp#L970
+        private static readonly bool[] s_highCharTable = new bool[0x80]
+        {
+            true, /* 0x0, 0x0 */
+            true, /* 0x1, .*/
+            true, /* 0x2, .*/
+            true, /* 0x3, .*/
+            true, /* 0x4, .*/
+            true, /* 0x5, .*/
+            true, /* 0x6, .*/
+            true, /* 0x7, .*/
+            true, /* 0x8, .*/
+            false, /* 0x9,   */
+            true, /* 0xA,  */
+            false, /* 0xB, .*/
+            false, /* 0xC, .*/
+            true, /* 0xD,  */
+            true, /* 0xE, .*/
+            true, /* 0xF, .*/
+            true, /* 0x10, .*/
+            true, /* 0x11, .*/
+            true, /* 0x12, .*/
+            true, /* 0x13, .*/
+            true, /* 0x14, .*/
+            true, /* 0x15, .*/
+            true, /* 0x16, .*/
+            true, /* 0x17, .*/
+            true, /* 0x18, .*/
+            true, /* 0x19, .*/
+            true, /* 0x1A, */
+            true, /* 0x1B, .*/
+            true, /* 0x1C, .*/
+            true, /* 0x1D, .*/
+            true, /* 0x1E, .*/
+            true, /* 0x1F, .*/
+            false, /*0x20,  */
+            false, /*0x21, !*/
+            false, /*0x22, "*/
+            false, /*0x23,  #*/
+            false, /*0x24,  $*/
+            false, /*0x25,  %*/
+            false, /*0x26,  &*/
+            true,  /*0x27, '*/
+            false, /*0x28, (*/
+            false, /*0x29, )*/
+            false, /*0x2A **/
+            false, /*0x2B, +*/
+            false, /*0x2C, ,*/
+            true,  /*0x2D, -*/
+            false, /*0x2E, .*/
+            false, /*0x2F, /*/
+            false, /*0x30, 0*/
+            false, /*0x31, 1*/
+            false, /*0x32, 2*/
+            false, /*0x33, 3*/
+            false, /*0x34, 4*/
+            false, /*0x35, 5*/
+            false, /*0x36, 6*/
+            false, /*0x37, 7*/
+            false, /*0x38, 8*/
+            false, /*0x39, 9*/
+            false, /*0x3A, :*/
+            false, /*0x3B, ;*/
+            false, /*0x3C, <*/
+            false, /*0x3D, =*/
+            false, /*0x3E, >*/
+            false, /*0x3F, ?*/
+            false, /*0x40, @*/
+            false, /*0x41, A*/
+            false, /*0x42, B*/
+            false, /*0x43, C*/
+            false, /*0x44, D*/
+            false, /*0x45, E*/
+            false, /*0x46, F*/
+            false, /*0x47, G*/
+            false, /*0x48, H*/
+            false, /*0x49, I*/
+            false, /*0x4A, J*/
+            false, /*0x4B, K*/
+            false, /*0x4C, L*/
+            false, /*0x4D, M*/
+            false, /*0x4E, N*/
+            false, /*0x4F, O*/
+            false, /*0x50, P*/
+            false, /*0x51, Q*/
+            false, /*0x52, R*/
+            false, /*0x53, S*/
+            false, /*0x54, T*/
+            false, /*0x55, U*/
+            false, /*0x56, V*/
+            false, /*0x57, W*/
+            false, /*0x58, X*/
+            false, /*0x59, Y*/
+            false, /*0x5A, Z*/
+            false, /*0x5B, [*/
+            false, /*0x5C, \*/
+            false, /*0x5D, ]*/
+            false, /*0x5E, ^*/
+            false, /*0x5F, _*/
+            false, /*0x60, `*/
+            false, /*0x61, a*/
+            false, /*0x62, b*/
+            false, /*0x63, c*/
+            false, /*0x64, d*/
+            false, /*0x65, e*/
+            false, /*0x66, f*/
+            false, /*0x67, g*/
+            false, /*0x68, h*/
+            false, /*0x69, i*/
+            false, /*0x6A, j*/
+            false, /*0x6B, k*/
+            false, /*0x6C, l*/
+            false, /*0x6D, m*/
+            false, /*0x6E, n*/
+            false, /*0x6F, o*/
+            false, /*0x70, p*/
+            false, /*0x71, q*/
+            false, /*0x72, r*/
+            false, /*0x73, s*/
+            false, /*0x74, t*/
+            false, /*0x75, u*/
+            false, /*0x76, v*/
+            false, /*0x77, w*/
+            false, /*0x78, x*/
+            false, /*0x79, y*/
+            false, /*0x7A, z*/
+            false, /*0x7B, {*/
+            false, /*0x7C, |*/
+            false, /*0x7D, }*/
+            false, /*0x7E, ~*/
+            true, /*0x7F, */
+        };
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CompareInfo.Windows.cs b/src/System.Private.CoreLib/shared/System/Globalization/CompareInfo.Windows.cs
new file mode 100644
index 0000000000..37ed9469d9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CompareInfo.Windows.cs
@@ -0,0 +1,644 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Buffers;
+using System.Diagnostics;
+using System.Security;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace System.Globalization
+{
+    public partial class CompareInfo
+    {
+        private unsafe void InitSort(CultureInfo culture)
+        {
+            _sortName = culture.SortName;
+
+            if (_invariantMode)
+            {
+                _sortHandle = IntPtr.Zero;
+            }
+            else
+            {
+                const uint LCMAP_SORTHANDLE = 0x20000000;
+
+                IntPtr handle;
+                int ret = Interop.Kernel32.LCMapStringEx(_sortName, LCMAP_SORTHANDLE, null, 0, &handle, IntPtr.Size, null, null, IntPtr.Zero);
+                _sortHandle = ret > 0 ? handle : IntPtr.Zero;
+            }
+        }
+
+        private static unsafe int FindStringOrdinal(
+            uint dwFindStringOrdinalFlags,
+            string stringSource,
+            int offset,
+            int cchSource,
+            string value,
+            int cchValue,
+            bool bIgnoreCase)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            Debug.Assert(stringSource != null);
+            Debug.Assert(value != null);
+
+            fixed (char* pSource = stringSource)
+            fixed (char* pValue = value)
+            {
+                int ret = Interop.Kernel32.FindStringOrdinal(
+                            dwFindStringOrdinalFlags,
+                            pSource + offset,
+                            cchSource,
+                            pValue,
+                            cchValue,
+                            bIgnoreCase ? 1 : 0);
+                return ret < 0 ? ret : ret + offset;
+            }
+        }
+
+        private static unsafe int FindStringOrdinal(
+            uint dwFindStringOrdinalFlags,
+            ReadOnlySpan<char> source,
+            ReadOnlySpan<char> value,
+            bool bIgnoreCase)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            Debug.Assert(!source.IsEmpty);
+            Debug.Assert(!value.IsEmpty);
+
+            fixed (char* pSource = &MemoryMarshal.GetReference(source))
+            fixed (char* pValue = &MemoryMarshal.GetReference(value))
+            {
+                int ret = Interop.Kernel32.FindStringOrdinal(
+                            dwFindStringOrdinalFlags,
+                            pSource,
+                            source.Length,
+                            pValue,
+                            value.Length,
+                            bIgnoreCase ? 1 : 0);
+                return ret;
+            }
+        }
+
+        internal static int IndexOfOrdinalCore(string source, string value, int startIndex, int count, bool ignoreCase)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            Debug.Assert(source != null);
+            Debug.Assert(value != null);
+
+            return FindStringOrdinal(FIND_FROMSTART, source, startIndex, count, value, value.Length, ignoreCase);
+        }
+
+        internal static int IndexOfOrdinalCore(ReadOnlySpan<char> source, ReadOnlySpan<char> value, bool ignoreCase)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            Debug.Assert(source.Length != 0);
+            Debug.Assert(value.Length != 0);
+
+            return FindStringOrdinal(FIND_FROMSTART, source, value, ignoreCase);
+        }
+
+        internal static int LastIndexOfOrdinalCore(string source, string value, int startIndex, int count, bool ignoreCase)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            Debug.Assert(source != null);
+            Debug.Assert(value != null);
+
+            return FindStringOrdinal(FIND_FROMEND, source, startIndex - count + 1, count, value, value.Length, ignoreCase);
+        }
+
+        private unsafe int GetHashCodeOfStringCore(string source, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(source != null);
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+            if (source.Length == 0)
+            {
+                return 0;
+            }
+
+            uint flags = LCMAP_SORTKEY | (uint)GetNativeCompareFlags(options);
+
+            fixed (char* pSource = source)
+            {
+                int sortKeyLength = Interop.Kernel32.LCMapStringEx(_sortHandle != IntPtr.Zero ? null : _sortName,
+                                                  flags,
+                                                  pSource, source.Length,
+                                                  null, 0,
+                                                  null, null, _sortHandle);
+                if (sortKeyLength == 0)
+                {
+                    throw new ArgumentException(SR.Arg_ExternalException);
+                }
+
+                byte[] borrowedArr = null;
+                Span<byte> span = sortKeyLength <= 512 ?
+                    stackalloc byte[512] :
+                    (borrowedArr = ArrayPool<byte>.Shared.Rent(sortKeyLength));
+
+                fixed (byte* pSortKey = &MemoryMarshal.GetReference(span))
+                {
+                    if (Interop.Kernel32.LCMapStringEx(_sortHandle != IntPtr.Zero ? null : _sortName,
+                                                      flags,
+                                                      pSource, source.Length,
+                                                      pSortKey, sortKeyLength,
+                                                      null, null, _sortHandle) != sortKeyLength)
+                    {
+                        throw new ArgumentException(SR.Arg_ExternalException);
+                    }
+                }
+
+                int hash = Marvin.ComputeHash32(span.Slice(0, sortKeyLength), Marvin.DefaultSeed);
+
+                // Return the borrowed array if necessary.
+                if (borrowedArr != null)
+                {
+                    ArrayPool<byte>.Shared.Return(borrowedArr);
+                }
+
+                return hash;
+            }
+        }
+
+        private static unsafe int CompareStringOrdinalIgnoreCase(char* string1, int count1, char* string2, int count2)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            Debug.Assert(string1 != null);
+            Debug.Assert(string2 != null);
+
+            // Use the OS to compare and then convert the result to expected value by subtracting 2 
+            return Interop.Kernel32.CompareStringOrdinal(string1, count1, string2, count2, true) - 2;
+        }
+
+        // TODO https://github.com/dotnet/coreclr/issues/13827:
+        // This method shouldn't be necessary, as we should be able to just use the overload
+        // that takes two spans.  But due to this issue, that's adding significant overhead.
+        private unsafe int CompareString(ReadOnlySpan<char> string1, string string2, CompareOptions options)
+        {
+            Debug.Assert(string2 != null);
+            Debug.Assert(!_invariantMode);
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+            string localeName = _sortHandle != IntPtr.Zero ? null : _sortName;
+
+            fixed (char* pLocaleName = localeName)
+            fixed (char* pString1 = &MemoryMarshal.GetReference(string1))
+            fixed (char* pString2 = &string2.GetRawStringData())
+            {
+                Debug.Assert(pString1 != null);
+                int result = Interop.Kernel32.CompareStringEx(
+                                    pLocaleName,
+                                    (uint)GetNativeCompareFlags(options),
+                                    pString1,
+                                    string1.Length,
+                                    pString2,
+                                    string2.Length,
+                                    null,
+                                    null,
+                                    _sortHandle);
+
+                if (result == 0)
+                {
+                    throw new ArgumentException(SR.Arg_ExternalException);
+                }
+
+                // Map CompareStringEx return value to -1, 0, 1.
+                return result - 2;
+            }
+        }
+
+        private unsafe int CompareString(ReadOnlySpan<char> string1, ReadOnlySpan<char> string2, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+            string localeName = _sortHandle != IntPtr.Zero ? null : _sortName;
+
+            fixed (char* pLocaleName = localeName)
+            fixed (char* pString1 = &MemoryMarshal.GetReference(string1))
+            fixed (char* pString2 = &MemoryMarshal.GetReference(string2))
+            {
+                Debug.Assert(pString1 != null);
+                Debug.Assert(pString2 != null);
+                int result = Interop.Kernel32.CompareStringEx(
+                                    pLocaleName,
+                                    (uint)GetNativeCompareFlags(options),
+                                    pString1,
+                                    string1.Length,
+                                    pString2,
+                                    string2.Length,
+                                    null,
+                                    null,
+                                    _sortHandle);
+
+                if (result == 0)
+                {
+                    throw new ArgumentException(SR.Arg_ExternalException);
+                }
+
+                // Map CompareStringEx return value to -1, 0, 1.
+                return result - 2;
+            }
+        }
+
+        private unsafe int FindString(
+                    uint dwFindNLSStringFlags,
+                    ReadOnlySpan<char> lpStringSource,
+                    ReadOnlySpan<char> lpStringValue,
+                    int* pcchFound)
+        {
+            Debug.Assert(!_invariantMode);
+            Debug.Assert(!lpStringSource.IsEmpty);
+            Debug.Assert(!lpStringValue.IsEmpty);
+
+            string localeName = _sortHandle != IntPtr.Zero ? null : _sortName;
+
+            fixed (char* pLocaleName = localeName)
+            fixed (char* pSource = &MemoryMarshal.GetReference(lpStringSource))
+            fixed (char* pValue = &MemoryMarshal.GetReference(lpStringValue))
+            {
+                return Interop.Kernel32.FindNLSStringEx(
+                                    pLocaleName,
+                                    dwFindNLSStringFlags,
+                                    pSource,
+                                    lpStringSource.Length,
+                                    pValue,
+                                    lpStringValue.Length,
+                                    pcchFound,
+                                    null,
+                                    null,
+                                    _sortHandle);
+            }
+        }
+        
+        private unsafe int FindString(
+            uint dwFindNLSStringFlags,
+            string lpStringSource,
+            int startSource,
+            int cchSource,
+            string lpStringValue,
+            int startValue,
+            int cchValue,
+            int* pcchFound)
+        {
+            Debug.Assert(!_invariantMode);
+            Debug.Assert(lpStringSource != null);
+            Debug.Assert(lpStringValue != null);
+
+            string localeName = _sortHandle != IntPtr.Zero ? null : _sortName;
+
+            fixed (char* pLocaleName = localeName)
+            fixed (char* pSource = lpStringSource)
+            fixed (char* pValue = lpStringValue)
+            {
+                char* pS = pSource + startSource;
+                char* pV = pValue + startValue;
+
+                return Interop.Kernel32.FindNLSStringEx(
+                                    pLocaleName,
+                                    dwFindNLSStringFlags,
+                                    pS,
+                                    cchSource,
+                                    pV,
+                                    cchValue,
+                                    pcchFound,
+                                    null,
+                                    null,
+                                    _sortHandle);
+            }
+        }
+
+        internal unsafe int IndexOfCore(String source, String target, int startIndex, int count, CompareOptions options, int* matchLengthPtr)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(source != null);
+            Debug.Assert(target != null);
+            Debug.Assert((options & CompareOptions.OrdinalIgnoreCase) == 0);
+
+            if (target.Length == 0)
+            {
+                if (matchLengthPtr != null)
+                    *matchLengthPtr = 0;
+                return startIndex;
+            }
+
+            if (source.Length == 0)
+            {
+                return -1;
+            }
+
+            if ((options & CompareOptions.Ordinal) != 0)
+            {
+                int retValue = FastIndexOfString(source, target, startIndex, count, target.Length, findLastIndex: false);
+                if (retValue >= 0)
+                {
+                    if (matchLengthPtr != null)
+                        *matchLengthPtr = target.Length;
+                }
+                return retValue;
+            }
+            else
+            {
+                int retValue = FindString(FIND_FROMSTART | (uint)GetNativeCompareFlags(options), source, startIndex, count,
+                                                               target, 0, target.Length, matchLengthPtr);
+                if (retValue >= 0)
+                {
+                    return retValue + startIndex;
+                }
+            }
+
+            return -1;
+        }
+
+        internal unsafe int IndexOfCore(ReadOnlySpan<char> source, ReadOnlySpan<char> target, CompareOptions options, int* matchLengthPtr)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(source.Length != 0);
+            Debug.Assert(target.Length != 0);
+            Debug.Assert((options == CompareOptions.None || options == CompareOptions.IgnoreCase));
+
+            int retValue = FindString(FIND_FROMSTART | (uint)GetNativeCompareFlags(options), source, target, matchLengthPtr);
+            return retValue;
+        }
+
+        private unsafe int LastIndexOfCore(string source, string target, int startIndex, int count, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!string.IsNullOrEmpty(source));
+            Debug.Assert(target != null);
+            Debug.Assert((options & CompareOptions.OrdinalIgnoreCase) == 0);
+
+            if (target.Length == 0)
+                return startIndex;
+
+            if ((options & CompareOptions.Ordinal) != 0)
+            {
+                return FastIndexOfString(source, target, startIndex, count, target.Length, findLastIndex: true);
+            }
+            else
+            {
+                int retValue = FindString(FIND_FROMEND | (uint)GetNativeCompareFlags(options), source, startIndex - count + 1,
+                                                               count, target, 0, target.Length, null);
+
+                if (retValue >= 0)
+                {
+                    return retValue + startIndex - (count - 1);
+                }
+            }
+
+            return -1;
+        }
+
+        private unsafe bool StartsWith(string source, string prefix, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!string.IsNullOrEmpty(source));
+            Debug.Assert(!string.IsNullOrEmpty(prefix));
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+            return FindString(FIND_STARTSWITH | (uint)GetNativeCompareFlags(options), source, 0, source.Length,
+                                                   prefix, 0, prefix.Length, null) >= 0;
+        }
+
+        private unsafe bool StartsWith(ReadOnlySpan<char> source, ReadOnlySpan<char> prefix, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!source.IsEmpty);
+            Debug.Assert(!prefix.IsEmpty);
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+            return FindString(FIND_STARTSWITH | (uint)GetNativeCompareFlags(options), source, prefix, null) >= 0;
+        }
+
+        private unsafe bool EndsWith(string source, string suffix, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!string.IsNullOrEmpty(source));
+            Debug.Assert(!string.IsNullOrEmpty(suffix));
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+            return FindString(FIND_ENDSWITH | (uint)GetNativeCompareFlags(options), source, 0, source.Length,
+                                                   suffix, 0, suffix.Length, null) >= 0;
+        }
+
+        private unsafe bool EndsWith(ReadOnlySpan<char> source, ReadOnlySpan<char> suffix, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            Debug.Assert(!source.IsEmpty);
+            Debug.Assert(!suffix.IsEmpty);
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+            return FindString(FIND_ENDSWITH | (uint)GetNativeCompareFlags(options), source, suffix, null) >= 0;
+        }
+
+        // PAL ends here
+        [NonSerialized]
+        private IntPtr _sortHandle;
+
+        private const uint LCMAP_SORTKEY = 0x00000400;
+        private const uint LCMAP_HASH    = 0x00040000;
+
+        private const int FIND_STARTSWITH = 0x00100000;
+        private const int FIND_ENDSWITH = 0x00200000;
+        private const int FIND_FROMSTART = 0x00400000;
+        private const int FIND_FROMEND = 0x00800000;
+
+        // TODO: Instead of this method could we just have upstack code call IndexOfOrdinal with ignoreCase = false?
+        private static unsafe int FastIndexOfString(string source, string target, int startIndex, int sourceCount, int targetCount, bool findLastIndex)
+        {
+            int retValue = -1;
+
+            int sourceStartIndex = findLastIndex ? startIndex - sourceCount + 1 : startIndex;
+
+            fixed (char* pSource = source, spTarget = target)
+            {
+                char* spSubSource = pSource + sourceStartIndex;
+
+                if (findLastIndex)
+                {
+                    int startPattern = (sourceCount - 1) - targetCount + 1;
+                    if (startPattern < 0)
+                        return -1;
+
+                    char patternChar0 = spTarget[0];
+                    for (int ctrSrc = startPattern; ctrSrc >= 0; ctrSrc--)
+                    {
+                        if (spSubSource[ctrSrc] != patternChar0)
+                            continue;
+
+                        int ctrPat;
+                        for (ctrPat = 1; ctrPat < targetCount; ctrPat++)
+                        {
+                            if (spSubSource[ctrSrc + ctrPat] != spTarget[ctrPat])
+                                break;
+                        }
+                        if (ctrPat == targetCount)
+                        {
+                            retValue = ctrSrc;
+                            break;
+                        }
+                    }
+
+                    if (retValue >= 0)
+                    {
+                        retValue += startIndex - sourceCount + 1;
+                    }
+                }
+                else
+                {
+                    int endPattern = (sourceCount - 1) - targetCount + 1;
+                    if (endPattern < 0)
+                        return -1;
+
+                    char patternChar0 = spTarget[0];
+                    for (int ctrSrc = 0; ctrSrc <= endPattern; ctrSrc++)
+                    {
+                        if (spSubSource[ctrSrc] != patternChar0)
+                            continue;
+                        int ctrPat;
+                        for (ctrPat = 1; ctrPat < targetCount; ctrPat++)
+                        {
+                            if (spSubSource[ctrSrc + ctrPat] != spTarget[ctrPat])
+                                break;
+                        }
+                        if (ctrPat == targetCount)
+                        {
+                            retValue = ctrSrc;
+                            break;
+                        }
+                    }
+
+                    if (retValue >= 0)
+                    {
+                        retValue += startIndex;
+                    }
+                }
+            }
+
+            return retValue;
+        }
+
+        private unsafe SortKey CreateSortKey(String source, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+
+            if (source == null) { throw new ArgumentNullException(nameof(source)); }
+
+            if ((options & ValidSortkeyCtorMaskOffFlags) != 0)
+            {
+                throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
+            }
+
+            byte [] keyData = null;
+            if (source.Length == 0)
+            { 
+                keyData = Array.Empty<byte>();
+            }
+            else
+            {
+                uint flags = LCMAP_SORTKEY | (uint)GetNativeCompareFlags(options);
+
+                fixed (char *pSource = source)
+                {
+                    int sortKeyLength = Interop.Kernel32.LCMapStringEx(_sortHandle != IntPtr.Zero ? null : _sortName,
+                                                flags,
+                                                pSource, source.Length,
+                                                null, 0,
+                                                null, null, _sortHandle);
+                    if (sortKeyLength == 0)
+                    {
+                        throw new ArgumentException(SR.Arg_ExternalException);
+                    }
+
+                    keyData = new byte[sortKeyLength];
+
+                    fixed (byte* pBytes =  keyData)
+                    {
+                        if (Interop.Kernel32.LCMapStringEx(_sortHandle != IntPtr.Zero ? null : _sortName,
+                                                flags,
+                                                pSource, source.Length,
+                                                pBytes, keyData.Length,
+                                                null, null, _sortHandle) != sortKeyLength)
+                        {
+                            throw new ArgumentException(SR.Arg_ExternalException);
+                        }
+                    }
+                }
+            }
+
+            return new SortKey(Name, source, options, keyData);
+        }
+
+        private static unsafe bool IsSortable(char* text, int length)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            Debug.Assert(text != null);
+
+            return Interop.Kernel32.IsNLSDefinedString(Interop.Kernel32.COMPARE_STRING, 0, IntPtr.Zero, text, length);
+        }
+
+        private const int COMPARE_OPTIONS_ORDINAL = 0x40000000;       // Ordinal
+        private const int NORM_IGNORECASE = 0x00000001;       // Ignores case.  (use LINGUISTIC_IGNORECASE instead)
+        private const int NORM_IGNOREKANATYPE = 0x00010000;       // Does not differentiate between Hiragana and Katakana characters. Corresponding Hiragana and Katakana will compare as equal.
+        private const int NORM_IGNORENONSPACE = 0x00000002;       // Ignores nonspacing. This flag also removes Japanese accent characters.  (use LINGUISTIC_IGNOREDIACRITIC instead)
+        private const int NORM_IGNORESYMBOLS = 0x00000004;       // Ignores symbols.
+        private const int NORM_IGNOREWIDTH = 0x00020000;       // Does not differentiate between a single-byte character and the same character as a double-byte character.
+        private const int NORM_LINGUISTIC_CASING = 0x08000000;       // use linguistic rules for casing
+        private const int SORT_STRINGSORT = 0x00001000;       // Treats punctuation the same as symbols.
+
+        private static int GetNativeCompareFlags(CompareOptions options)
+        {
+            // Use "linguistic casing" by default (load the culture's casing exception tables)
+            int nativeCompareFlags = NORM_LINGUISTIC_CASING;
+
+            if ((options & CompareOptions.IgnoreCase) != 0) { nativeCompareFlags |= NORM_IGNORECASE; }
+            if ((options & CompareOptions.IgnoreKanaType) != 0) { nativeCompareFlags |= NORM_IGNOREKANATYPE; }
+            if ((options & CompareOptions.IgnoreNonSpace) != 0) { nativeCompareFlags |= NORM_IGNORENONSPACE; }
+            if ((options & CompareOptions.IgnoreSymbols) != 0) { nativeCompareFlags |= NORM_IGNORESYMBOLS; }
+            if ((options & CompareOptions.IgnoreWidth) != 0) { nativeCompareFlags |= NORM_IGNOREWIDTH; }
+            if ((options & CompareOptions.StringSort) != 0) { nativeCompareFlags |= SORT_STRINGSORT; }
+
+            // TODO: Can we try for GetNativeCompareFlags to never
+            // take Ordinal or OrdinalIgnoreCase.  This value is not part of Win32, we just handle it special
+            // in some places.
+            // Suffix & Prefix shouldn't use this, make sure to turn off the NORM_LINGUISTIC_CASING flag
+            if (options == CompareOptions.Ordinal) { nativeCompareFlags = COMPARE_OPTIONS_ORDINAL; }
+
+            Debug.Assert(((options & ~(CompareOptions.IgnoreCase |
+                                          CompareOptions.IgnoreKanaType |
+                                          CompareOptions.IgnoreNonSpace |
+                                          CompareOptions.IgnoreSymbols |
+                                          CompareOptions.IgnoreWidth |
+                                          CompareOptions.StringSort)) == 0) ||
+                             (options == CompareOptions.Ordinal), "[CompareInfo.GetNativeCompareFlags]Expected all flags to be handled");
+
+            return nativeCompareFlags;
+        }
+
+        private unsafe SortVersion GetSortVersion()
+        {
+            Debug.Assert(!_invariantMode);
+
+            Interop.Kernel32.NlsVersionInfoEx nlsVersion = new Interop.Kernel32.NlsVersionInfoEx();
+            nlsVersion.dwNLSVersionInfoSize = sizeof(Interop.Kernel32.NlsVersionInfoEx);
+            Interop.Kernel32.GetNLSVersionEx(Interop.Kernel32.COMPARE_STRING, _sortName, &nlsVersion);
+            return new SortVersion(
+                        nlsVersion.dwNLSVersion,
+                        nlsVersion.dwEffectiveId == 0 ? LCID : nlsVersion.dwEffectiveId,
+                        nlsVersion.guidCustomVersion);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CompareInfo.cs b/src/System.Private.CoreLib/shared/System/Globalization/CompareInfo.cs
new file mode 100644
index 0000000000..079b8afbc0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CompareInfo.cs
@@ -0,0 +1,1368 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////
+//
+//
+//
+//  Purpose:  This class implements a set of methods for comparing
+//            strings.
+//
+//
+////////////////////////////////////////////////////////////////////////////
+
+using System.Reflection;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.Serialization;
+using System.Buffers;
+using System.Text;
+
+namespace System.Globalization
+{
+    [Flags]
+    public enum CompareOptions
+    {
+        None = 0x00000000,
+        IgnoreCase = 0x00000001,
+        IgnoreNonSpace = 0x00000002,
+        IgnoreSymbols = 0x00000004,
+        IgnoreKanaType = 0x00000008,   // ignore kanatype
+        IgnoreWidth = 0x00000010,   // ignore width
+        OrdinalIgnoreCase = 0x10000000,   // This flag can not be used with other flags.
+        StringSort = 0x20000000,   // use string sort method
+        Ordinal = 0x40000000,   // This flag can not be used with other flags.
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public partial class CompareInfo : IDeserializationCallback
+    {
+        // Mask used to check if IndexOf()/LastIndexOf()/IsPrefix()/IsPostfix() has the right flags.
+        private const CompareOptions ValidIndexMaskOffFlags =
+            ~(CompareOptions.IgnoreCase | CompareOptions.IgnoreSymbols | CompareOptions.IgnoreNonSpace |
+              CompareOptions.IgnoreWidth | CompareOptions.IgnoreKanaType);
+
+        // Mask used to check if Compare() has the right flags.
+        private const CompareOptions ValidCompareMaskOffFlags =
+            ~(CompareOptions.IgnoreCase | CompareOptions.IgnoreSymbols | CompareOptions.IgnoreNonSpace |
+              CompareOptions.IgnoreWidth | CompareOptions.IgnoreKanaType | CompareOptions.StringSort);
+
+        // Mask used to check if GetHashCodeOfString() has the right flags.
+        private const CompareOptions ValidHashCodeOfStringMaskOffFlags =
+            ~(CompareOptions.IgnoreCase | CompareOptions.IgnoreSymbols | CompareOptions.IgnoreNonSpace |
+              CompareOptions.IgnoreWidth | CompareOptions.IgnoreKanaType);
+
+        // Mask used to check if we have the right flags.
+        private const CompareOptions ValidSortkeyCtorMaskOffFlags =
+            ~(CompareOptions.IgnoreCase | CompareOptions.IgnoreSymbols | CompareOptions.IgnoreNonSpace |
+              CompareOptions.IgnoreWidth | CompareOptions.IgnoreKanaType | CompareOptions.StringSort);
+
+        // Cache the invariant CompareInfo
+        internal static readonly CompareInfo Invariant = CultureInfo.InvariantCulture.CompareInfo;
+
+        //
+        // CompareInfos have an interesting identity.  They are attached to the locale that created them,
+        // ie: en-US would have an en-US sort.  For haw-US (custom), then we serialize it as haw-US.
+        // The interesting part is that since haw-US doesn't have its own sort, it has to point at another
+        // locale, which is what SCOMPAREINFO does.
+        [OptionalField(VersionAdded = 2)]
+        private string m_name;  // The name used to construct this CompareInfo. Do not rename (binary serialization)
+
+        [NonSerialized]
+        private string _sortName; // The name that defines our behavior
+
+        [OptionalField(VersionAdded = 3)]
+        private SortVersion m_SortVersion; // Do not rename (binary serialization)
+
+        // _invariantMode is defined for the perf reason as accessing the instance field is faster than access the static property GlobalizationMode.Invariant
+        [NonSerialized]
+        private readonly bool _invariantMode = GlobalizationMode.Invariant;
+
+        private int culture; // Do not rename (binary serialization). The fields sole purpose is to support Desktop serialization.
+
+        internal CompareInfo(CultureInfo culture)
+        {
+            m_name = culture._name;
+            InitSort(culture);
+        }
+
+        /*=================================GetCompareInfo==========================
+        **Action: Get the CompareInfo constructed from the data table in the specified assembly for the specified culture.
+        **       Warning: The assembly versioning mechanism is dead!
+        **Returns: The CompareInfo for the specified culture.
+        **Arguments:
+        **   culture    the ID of the culture
+        **   assembly   the assembly which contains the sorting table.
+        **Exceptions:
+        **  ArgumentNullException when the assembly is null
+        **  ArgumentException if culture is invalid.
+        ============================================================================*/
+        // Assembly constructor should be deprecated, we don't act on the assembly information any more
+        public static CompareInfo GetCompareInfo(int culture, Assembly assembly)
+        {
+            // Parameter checking.
+            if (assembly == null)
+            {
+                throw new ArgumentNullException(nameof(assembly));
+            }
+            if (assembly != typeof(Object).Module.Assembly)
+            {
+                throw new ArgumentException(SR.Argument_OnlyMscorlib);
+            }
+
+            return GetCompareInfo(culture);
+        }
+
+        /*=================================GetCompareInfo==========================
+        **Action: Get the CompareInfo constructed from the data table in the specified assembly for the specified culture.
+        **       The purpose of this method is to provide version for CompareInfo tables.
+        **Returns: The CompareInfo for the specified culture.
+        **Arguments:
+        **   name      the name of the culture
+        **   assembly  the assembly which contains the sorting table.
+        **Exceptions:
+        **  ArgumentNullException when the assembly is null
+        **  ArgumentException if name is invalid.
+        ============================================================================*/
+        // Assembly constructor should be deprecated, we don't act on the assembly information any more
+        public static CompareInfo GetCompareInfo(string name, Assembly assembly)
+        {
+            if (name == null || assembly == null)
+            {
+                throw new ArgumentNullException(name == null ? nameof(name) : nameof(assembly));
+            }
+
+            if (assembly != typeof(Object).Module.Assembly)
+            {
+                throw new ArgumentException(SR.Argument_OnlyMscorlib);
+            }
+
+            return GetCompareInfo(name);
+        }
+
+        /*=================================GetCompareInfo==========================
+        **Action: Get the CompareInfo for the specified culture.
+        ** This method is provided for ease of integration with NLS-based software.
+        **Returns: The CompareInfo for the specified culture.
+        **Arguments:
+        **   culture    the ID of the culture.
+        **Exceptions:
+        **  ArgumentException if culture is invalid.
+        ============================================================================*/
+        // People really shouldn't be calling LCID versions, no custom support
+        public static CompareInfo GetCompareInfo(int culture)
+        {
+            if (CultureData.IsCustomCultureId(culture))
+            {
+                // Customized culture cannot be created by the LCID.
+                throw new ArgumentException(SR.Argument_CustomCultureCannotBePassedByNumber, nameof(culture));
+            }
+
+            return CultureInfo.GetCultureInfo(culture).CompareInfo;
+        }
+
+        /*=================================GetCompareInfo==========================
+        **Action: Get the CompareInfo for the specified culture.
+        **Returns: The CompareInfo for the specified culture.
+        **Arguments:
+        **   name    the name of the culture.
+        **Exceptions:
+        **  ArgumentException if name is invalid.
+        ============================================================================*/
+
+        public static CompareInfo GetCompareInfo(string name)
+        {
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
+            return CultureInfo.GetCultureInfo(name).CompareInfo;
+        }
+
+        public static unsafe bool IsSortable(char ch)
+        {
+            if (GlobalizationMode.Invariant)
+            {
+                return true;
+            }
+            char *pChar = &ch;
+            return IsSortable(pChar, 1);
+        }
+
+        public static unsafe bool IsSortable(string text)
+        {
+            if (text == null)
+            {
+                // A null param is invalid here.
+                throw new ArgumentNullException(nameof(text));
+            }
+
+            if (text.Length == 0)
+            {
+                // A zero length string is not invalid, but it is also not sortable.
+                return (false);
+            }
+
+            if (GlobalizationMode.Invariant)
+            {
+                return true;
+            }
+
+            fixed (char *pChar = text)
+            {
+                return IsSortable(pChar, text.Length);
+            }
+        }
+
+        [OnDeserializing]
+        private void OnDeserializing(StreamingContext ctx)
+        {
+            m_name = null;
+        }
+
+        void IDeserializationCallback.OnDeserialization(object sender)
+        {
+            OnDeserialized();
+        }
+
+        [OnDeserialized]
+        private void OnDeserialized(StreamingContext ctx)
+        {
+            OnDeserialized();
+        }
+
+        private void OnDeserialized()
+        {
+            // If we didn't have a name, use the LCID
+            if (m_name == null)
+            {
+                // From whidbey, didn't have a name
+                CultureInfo ci = CultureInfo.GetCultureInfo(this.culture);
+                m_name = ci._name;
+            }
+            else
+            {
+                InitSort(CultureInfo.GetCultureInfo(m_name));
+            }
+        }
+
+        [OnSerializing]
+        private void OnSerializing(StreamingContext ctx)
+        {
+            // This is merely for serialization compatibility with Whidbey/Orcas, it can go away when we don't want that compat any more.
+            culture = CultureInfo.GetCultureInfo(this.Name).LCID; // This is the lcid of the constructing culture (still have to dereference to get target sort)
+            Debug.Assert(m_name != null, "CompareInfo.OnSerializing - expected m_name to be set already");
+        }
+
+        ///////////////////////////----- Name -----/////////////////////////////////
+        //
+        //  Returns the name of the culture (well actually, of the sort).
+        //  Very important for providing a non-LCID way of identifying
+        //  what the sort is.
+        //
+        //  Note that this name isn't dereferenced in case the CompareInfo is a different locale
+        //  which is consistent with the behaviors of earlier versions.  (so if you ask for a sort
+        //  and the locale's changed behavior, then you'll get changed behavior, which is like
+        //  what happens for a version update)
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        public virtual string Name
+        {
+            get
+            {
+                Debug.Assert(m_name != null, "CompareInfo.Name Expected _name to be set");
+                if (m_name == "zh-CHT" || m_name == "zh-CHS")
+                {
+                    return m_name;
+                }
+
+                return _sortName;
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  Compare
+        //
+        //  Compares the two strings with the given options.  Returns 0 if the
+        //  two strings are equal, a number less than 0 if string1 is less
+        //  than string2, and a number greater than 0 if string1 is greater
+        //  than string2.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        public virtual int Compare(string string1, string string2)
+        {
+            return (Compare(string1, string2, CompareOptions.None));
+        }
+
+        public virtual int Compare(string string1, string string2, CompareOptions options)
+        {
+            if (options == CompareOptions.OrdinalIgnoreCase)
+            {
+                return String.Compare(string1, string2, StringComparison.OrdinalIgnoreCase);
+            }
+
+            // Verify the options before we do any real comparison.
+            if ((options & CompareOptions.Ordinal) != 0)
+            {
+                if (options != CompareOptions.Ordinal)
+                {
+                    throw new ArgumentException(SR.Argument_CompareOptionOrdinal, nameof(options));
+                }
+
+                return String.CompareOrdinal(string1, string2);
+            }
+
+            if ((options & ValidCompareMaskOffFlags) != 0)
+            {
+                throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
+            }
+
+            //Our paradigm is that null sorts less than any other string and
+            //that two nulls sort as equal.
+            if (string1 == null)
+            {
+                if (string2 == null)
+                {
+                    return (0);     // Equal
+                }
+                return (-1);    // null < non-null
+            }
+            if (string2 == null)
+            {
+                return (1);     // non-null > null
+            }
+
+            if (_invariantMode)
+            {
+                if ((options & CompareOptions.IgnoreCase) != 0)
+                    return CompareOrdinalIgnoreCase(string1, string2);
+
+                return String.CompareOrdinal(string1, string2);
+            }
+
+            return CompareString(string1.AsSpan(), string2.AsSpan(), options);
+        }
+
+        // TODO https://github.com/dotnet/coreclr/issues/13827:
+        // This method shouldn't be necessary, as we should be able to just use the overload
+        // that takes two spans.  But due to this issue, that's adding significant overhead.
+        internal int Compare(ReadOnlySpan<char> string1, string string2, CompareOptions options)
+        {
+            if (options == CompareOptions.OrdinalIgnoreCase)
+            {
+                return CompareOrdinalIgnoreCase(string1, string2.AsSpan());
+            }
+
+            // Verify the options before we do any real comparison.
+            if ((options & CompareOptions.Ordinal) != 0)
+            {
+                if (options != CompareOptions.Ordinal)
+                {
+                    throw new ArgumentException(SR.Argument_CompareOptionOrdinal, nameof(options));
+                }
+
+                return string.CompareOrdinal(string1, string2.AsSpan());
+            }
+
+            if ((options & ValidCompareMaskOffFlags) != 0)
+            {
+                throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
+            }
+
+            // null sorts less than any other string.
+            if (string2 == null)
+            {
+                return 1;
+            }
+
+            if (_invariantMode)
+            {
+                return (options & CompareOptions.IgnoreCase) != 0 ?
+                    CompareOrdinalIgnoreCase(string1, string2.AsSpan()) :
+                    string.CompareOrdinal(string1, string2.AsSpan());
+            }
+
+            return CompareString(string1, string2, options);
+        }
+
+        internal int CompareOptionNone(ReadOnlySpan<char> string1, ReadOnlySpan<char> string2)
+        {
+            // Check for empty span or span from a null string
+            if (string1.Length == 0 || string2.Length == 0)
+                return string1.Length - string2.Length;
+
+            return _invariantMode ?
+                string.CompareOrdinal(string1, string2) :
+                CompareString(string1, string2, CompareOptions.None);
+        }
+
+        internal int CompareOptionIgnoreCase(ReadOnlySpan<char> string1, ReadOnlySpan<char> string2)
+        {
+            // Check for empty span or span from a null string
+            if (string1.Length == 0 || string2.Length == 0)
+                return string1.Length - string2.Length;
+
+            return _invariantMode ?
+                CompareOrdinalIgnoreCase(string1, string2) :
+                CompareString(string1, string2, CompareOptions.IgnoreCase);
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  Compare
+        //
+        //  Compares the specified regions of the two strings with the given
+        //  options.
+        //  Returns 0 if the two strings are equal, a number less than 0 if
+        //  string1 is less than string2, and a number greater than 0 if
+        //  string1 is greater than string2.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+
+        public virtual int Compare(string string1, int offset1, int length1, string string2, int offset2, int length2)
+        {
+            return Compare(string1, offset1, length1, string2, offset2, length2, 0);
+        }
+
+
+        public virtual int Compare(string string1, int offset1, string string2, int offset2, CompareOptions options)
+        {
+            return Compare(string1, offset1, string1 == null ? 0 : string1.Length - offset1,
+                           string2, offset2, string2 == null ? 0 : string2.Length - offset2, options);
+        }
+
+
+        public virtual int Compare(string string1, int offset1, string string2, int offset2)
+        {
+            return Compare(string1, offset1, string2, offset2, 0);
+        }
+
+
+        public virtual int Compare(string string1, int offset1, int length1, string string2, int offset2, int length2, CompareOptions options)
+        {
+            if (options == CompareOptions.OrdinalIgnoreCase)
+            {
+                int result = String.Compare(string1, offset1, string2, offset2, length1 < length2 ? length1 : length2, StringComparison.OrdinalIgnoreCase);
+                if ((length1 != length2) && result == 0)
+                    return (length1 > length2 ? 1 : -1);
+                return (result);
+            }
+
+            // Verify inputs
+            if (length1 < 0 || length2 < 0)
+            {
+                throw new ArgumentOutOfRangeException((length1 < 0) ? nameof(length1) : nameof(length2), SR.ArgumentOutOfRange_NeedPosNum);
+            }
+            if (offset1 < 0 || offset2 < 0)
+            {
+                throw new ArgumentOutOfRangeException((offset1 < 0) ? nameof(offset1) : nameof(offset2), SR.ArgumentOutOfRange_NeedPosNum);
+            }
+            if (offset1 > (string1 == null ? 0 : string1.Length) - length1)
+            {
+                throw new ArgumentOutOfRangeException(nameof(string1), SR.ArgumentOutOfRange_OffsetLength);
+            }
+            if (offset2 > (string2 == null ? 0 : string2.Length) - length2)
+            {
+                throw new ArgumentOutOfRangeException(nameof(string2), SR.ArgumentOutOfRange_OffsetLength);
+            }
+            if ((options & CompareOptions.Ordinal) != 0)
+            {
+                if (options != CompareOptions.Ordinal)
+                {
+                    throw new ArgumentException(SR.Argument_CompareOptionOrdinal,
+                                                nameof(options));
+                }
+            }
+            else if ((options & ValidCompareMaskOffFlags) != 0)
+            {
+                throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
+            }
+
+            //
+            // Check for the null case.
+            //
+            if (string1 == null)
+            {
+                if (string2 == null)
+                {
+                    return (0);
+                }
+                return (-1);
+            }
+            if (string2 == null)
+            {
+                return (1);
+            }
+
+            ReadOnlySpan<char> span1 = string1.AsSpan(offset1, length1);
+            ReadOnlySpan<char> span2 = string2.AsSpan(offset2, length2);
+
+            if (options == CompareOptions.Ordinal)
+            {
+                return string.CompareOrdinal(span1, span2);
+            }
+
+            if (_invariantMode)
+            {
+                if ((options & CompareOptions.IgnoreCase) != 0)
+                    return CompareOrdinalIgnoreCase(span1, span2);
+
+                return string.CompareOrdinal(span1, span2);
+            }
+
+            return CompareString(span1, span2, options);
+        }
+
+        //
+        // CompareOrdinalIgnoreCase compare two string ordinally with ignoring the case.
+        // it assumes the strings are Ascii string till we hit non Ascii character in strA or strB and then we continue the comparison by
+        // calling the OS.
+        //
+        internal static int CompareOrdinalIgnoreCase(string strA, int indexA, int lengthA, string strB, int indexB, int lengthB)
+        {
+            Debug.Assert(indexA + lengthA <= strA.Length);
+            Debug.Assert(indexB + lengthB <= strB.Length);
+            return CompareOrdinalIgnoreCase(strA.AsSpan(indexA, lengthA), strB.AsSpan(indexB, lengthB));
+        }
+
+        internal static unsafe int CompareOrdinalIgnoreCase(ReadOnlySpan<char> strA, ReadOnlySpan<char> strB)
+        {
+            int length = Math.Min(strA.Length, strB.Length);
+            int range = length;
+
+            fixed (char* ap = &MemoryMarshal.GetReference(strA))
+            fixed (char* bp = &MemoryMarshal.GetReference(strB))
+            {
+                char* a = ap;
+                char* b = bp;
+
+                // in InvariantMode we support all range and not only the ascii characters.
+                char maxChar = (char) (GlobalizationMode.Invariant ? 0xFFFF : 0x7F);
+
+                while (length != 0 && (*a <= maxChar) && (*b <= maxChar))
+                {
+                    int charA = *a;
+                    int charB = *b;
+
+                    if (charA == charB)
+                    {
+                        a++; b++;
+                        length--;
+                        continue;
+                    }
+
+                    // uppercase both chars - notice that we need just one compare per char
+                    if ((uint)(charA - 'a') <= 'z' - 'a') charA -= 0x20;
+                    if ((uint)(charB - 'a') <= 'z' - 'a') charB -= 0x20;
+
+                    // Return the (case-insensitive) difference between them.
+                    if (charA != charB)
+                        return charA - charB;
+
+                    // Next char
+                    a++; b++;
+                    length--;
+                }
+
+                if (length == 0)
+                    return strA.Length - strB.Length;
+
+                Debug.Assert(!GlobalizationMode.Invariant);
+
+                range -= length;
+
+                return CompareStringOrdinalIgnoreCase(a, strA.Length - range, b, strB.Length - range);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  IsPrefix
+        //
+        //  Determines whether prefix is a prefix of string.  If prefix equals
+        //  String.Empty, true is returned.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual bool IsPrefix(string source, string prefix, CompareOptions options)
+        {
+            if (source == null || prefix == null)
+            {
+                throw new ArgumentNullException((source == null ? nameof(source) : nameof(prefix)),
+                    SR.ArgumentNull_String);
+            }
+
+            if (prefix.Length == 0)
+            {
+                return (true);
+            }
+
+            if (source.Length == 0)
+            {
+                return false;
+            }
+
+            if (options == CompareOptions.OrdinalIgnoreCase)
+            {
+                return source.StartsWith(prefix, StringComparison.OrdinalIgnoreCase);
+            }
+
+            if (options == CompareOptions.Ordinal)
+            {
+                return source.StartsWith(prefix, StringComparison.Ordinal);
+            }
+
+            if ((options & ValidIndexMaskOffFlags) != 0)
+            {
+                throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
+            }
+
+            if (_invariantMode)
+            {
+                return source.StartsWith(prefix, (options & CompareOptions.IgnoreCase) != 0 ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal);
+            }
+
+            return StartsWith(source, prefix, options);
+        }
+
+        internal bool IsPrefix(ReadOnlySpan<char> source, ReadOnlySpan<char> prefix, CompareOptions options)
+        {
+            Debug.Assert(prefix.Length != 0);
+            Debug.Assert(source.Length != 0);
+            Debug.Assert((options & ValidIndexMaskOffFlags) == 0);
+            Debug.Assert(!_invariantMode);
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+            return StartsWith(source, prefix, options);
+        }
+
+        public virtual bool IsPrefix(string source, string prefix)
+        {
+            return (IsPrefix(source, prefix, 0));
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  IsSuffix
+        //
+        //  Determines whether suffix is a suffix of string.  If suffix equals
+        //  String.Empty, true is returned.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual bool IsSuffix(string source, string suffix, CompareOptions options)
+        {
+            if (source == null || suffix == null)
+            {
+                throw new ArgumentNullException((source == null ? nameof(source) : nameof(suffix)),
+                    SR.ArgumentNull_String);
+            }
+
+            if (suffix.Length == 0)
+            {
+                return (true);
+            }
+
+            if (source.Length == 0)
+            {
+                return false;
+            }
+
+            if (options == CompareOptions.OrdinalIgnoreCase)
+            {
+                return source.EndsWith(suffix, StringComparison.OrdinalIgnoreCase);
+            }
+
+            if (options == CompareOptions.Ordinal)
+            {
+                return source.EndsWith(suffix, StringComparison.Ordinal);
+            }
+
+            if ((options & ValidIndexMaskOffFlags) != 0)
+            {
+                throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
+            }
+
+            if (_invariantMode)
+            {
+                return source.EndsWith(suffix, (options & CompareOptions.IgnoreCase) != 0 ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal);
+            }
+
+            return EndsWith(source, suffix, options);
+        }
+
+        internal bool IsSuffix(ReadOnlySpan<char> source, ReadOnlySpan<char> suffix, CompareOptions options)
+        {
+            Debug.Assert(suffix.Length != 0);
+            Debug.Assert(source.Length != 0);
+            Debug.Assert((options & ValidIndexMaskOffFlags) == 0);
+            Debug.Assert(!_invariantMode);
+            Debug.Assert((options & (CompareOptions.Ordinal | CompareOptions.OrdinalIgnoreCase)) == 0);
+
+            return EndsWith(source, suffix, options);
+        }
+
+
+        public virtual bool IsSuffix(string source, string suffix)
+        {
+            return (IsSuffix(source, suffix, 0));
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  IndexOf
+        //
+        //  Returns the first index where value is found in string.  The
+        //  search starts from startIndex and ends at endIndex.  Returns -1 if
+        //  the specified value is not found.  If value equals String.Empty,
+        //  startIndex is returned.  Throws IndexOutOfRange if startIndex or
+        //  endIndex is less than zero or greater than the length of string.
+        //  Throws ArgumentException if value is null.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+
+        public virtual int IndexOf(string source, char value)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            return IndexOf(source, value, 0, source.Length, CompareOptions.None);
+        }
+
+
+        public virtual int IndexOf(string source, string value)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            return IndexOf(source, value, 0, source.Length, CompareOptions.None);
+        }
+
+
+        public virtual int IndexOf(string source, char value, CompareOptions options)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            return IndexOf(source, value, 0, source.Length, options);
+        }
+
+
+        public virtual int IndexOf(string source, string value, CompareOptions options)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            return IndexOf(source, value, 0, source.Length, options);
+        }
+
+        public virtual int IndexOf(string source, char value, int startIndex)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            return IndexOf(source, value, startIndex, source.Length - startIndex, CompareOptions.None);
+        }
+
+        public virtual int IndexOf(string source, string value, int startIndex)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            return IndexOf(source, value, startIndex, source.Length - startIndex, CompareOptions.None);
+        }
+
+        public virtual int IndexOf(string source, char value, int startIndex, CompareOptions options)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            return IndexOf(source, value, startIndex, source.Length - startIndex, options);
+        }
+
+
+        public virtual int IndexOf(string source, string value, int startIndex, CompareOptions options)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            return IndexOf(source, value, startIndex, source.Length - startIndex, options);
+        }
+
+
+        public virtual int IndexOf(string source, char value, int startIndex, int count)
+        {
+            return IndexOf(source, value, startIndex, count, CompareOptions.None);
+        }
+
+
+        public virtual int IndexOf(string source, string value, int startIndex, int count)
+        {
+            return IndexOf(source, value, startIndex, count, CompareOptions.None);
+        }
+
+        public unsafe virtual int IndexOf(string source, char value, int startIndex, int count, CompareOptions options)
+        {
+            // Validate inputs
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            if (startIndex < 0 || startIndex > source.Length)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+
+            if (count < 0 || startIndex > source.Length - count)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Count);
+
+            if (source.Length == 0)
+            {
+                return -1;
+            }
+
+            if (options == CompareOptions.OrdinalIgnoreCase)
+            {
+                return source.IndexOf(value.ToString(), startIndex, count, StringComparison.OrdinalIgnoreCase);
+            }
+
+            // Validate CompareOptions
+            // Ordinal can't be selected with other flags
+            if ((options & ValidIndexMaskOffFlags) != 0 && (options != CompareOptions.Ordinal))
+                throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
+
+            if (_invariantMode)
+                return IndexOfOrdinal(source, new string(value, 1), startIndex, count, ignoreCase: (options & (CompareOptions.IgnoreCase | CompareOptions.OrdinalIgnoreCase)) != 0);
+
+            return IndexOfCore(source, new string(value, 1), startIndex, count, options, null);
+        }
+
+        public unsafe virtual int IndexOf(string source, string value, int startIndex, int count, CompareOptions options)
+        {
+            // Validate inputs
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            if (startIndex > source.Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+            }
+
+            // In Everett we used to return -1 for empty string even if startIndex is negative number so we keeping same behavior here.
+            // We return 0 if both source and value are empty strings for Everett compatibility too.
+            if (source.Length == 0)
+            {
+                if (value.Length == 0)
+                {
+                    return 0;
+                }
+                return -1;
+            }
+
+            if (startIndex < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+            }
+
+            if (count < 0 || startIndex > source.Length - count)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Count);
+
+            if (options == CompareOptions.OrdinalIgnoreCase)
+            {
+                return IndexOfOrdinal(source, value, startIndex, count, ignoreCase: true);
+            }
+
+            // Validate CompareOptions
+            // Ordinal can't be selected with other flags
+            if ((options & ValidIndexMaskOffFlags) != 0 && (options != CompareOptions.Ordinal))
+                throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
+
+            if (_invariantMode)
+                return IndexOfOrdinal(source, value, startIndex, count, ignoreCase: (options & (CompareOptions.IgnoreCase | CompareOptions.OrdinalIgnoreCase)) != 0);
+
+            return IndexOfCore(source, value, startIndex, count, options, null);
+        }
+
+        internal int IndexOfOrdinal(ReadOnlySpan<char> source, ReadOnlySpan<char> value, bool ignoreCase)
+        {
+            Debug.Assert(!_invariantMode);
+            Debug.Assert(!source.IsEmpty);
+            Debug.Assert(!value.IsEmpty);
+            return IndexOfOrdinalCore(source, value, ignoreCase);
+        }
+
+        internal unsafe int IndexOf(ReadOnlySpan<char> source, ReadOnlySpan<char> value, CompareOptions options)
+        {
+            Debug.Assert(!_invariantMode);
+            Debug.Assert(!source.IsEmpty);
+            Debug.Assert(!value.IsEmpty);
+            return IndexOfCore(source, value, options, null);
+        }
+
+        // The following IndexOf overload is mainly used by String.Replace. This overload assumes the parameters are already validated
+        // and the caller is passing a valid matchLengthPtr pointer.
+        internal unsafe int IndexOf(string source, string value, int startIndex, int count, CompareOptions options, int* matchLengthPtr)
+        {
+            Debug.Assert(source != null);
+            Debug.Assert(value != null);
+            Debug.Assert(startIndex >= 0);
+            Debug.Assert(matchLengthPtr != null);
+            *matchLengthPtr = 0;
+
+            if (source.Length == 0)
+            {
+                if (value.Length == 0)
+                {
+                    return 0;
+                }
+                return -1;
+            }
+
+            if (startIndex >= source.Length)
+            {
+                return -1;
+            }
+
+            if (options == CompareOptions.OrdinalIgnoreCase)
+            {
+                int res = IndexOfOrdinal(source, value, startIndex, count, ignoreCase: true);
+                if (res >= 0)
+                {
+                    *matchLengthPtr = value.Length;
+                }
+                return res;
+            }
+
+            if (_invariantMode)
+            {
+                int res = IndexOfOrdinal(source, value, startIndex, count, ignoreCase: (options & (CompareOptions.IgnoreCase | CompareOptions.OrdinalIgnoreCase)) != 0);
+                if (res >= 0)
+                {
+                    *matchLengthPtr = value.Length;
+                }
+                return res;
+            }
+
+            return IndexOfCore(source, value, startIndex, count, options, matchLengthPtr);
+        }
+
+        internal int IndexOfOrdinal(string source, string value, int startIndex, int count, bool ignoreCase)
+        {
+            if (_invariantMode)
+            {
+                return InvariantIndexOf(source, value, startIndex, count, ignoreCase);
+            }
+
+            return IndexOfOrdinalCore(source, value, startIndex, count, ignoreCase);
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  LastIndexOf
+        //
+        //  Returns the last index where value is found in string.  The
+        //  search starts from startIndex and ends at endIndex.  Returns -1 if
+        //  the specified value is not found.  If value equals String.Empty,
+        //  endIndex is returned.  Throws IndexOutOfRange if startIndex or
+        //  endIndex is less than zero or greater than the length of string.
+        //  Throws ArgumentException if value is null.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+
+        public virtual int LastIndexOf(String source, char value)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            // Can't start at negative index, so make sure we check for the length == 0 case.
+            return LastIndexOf(source, value, source.Length - 1, source.Length, CompareOptions.None);
+        }
+
+
+        public virtual int LastIndexOf(string source, string value)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            // Can't start at negative index, so make sure we check for the length == 0 case.
+            return LastIndexOf(source, value, source.Length - 1,
+                source.Length, CompareOptions.None);
+        }
+
+
+        public virtual int LastIndexOf(string source, char value, CompareOptions options)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            // Can't start at negative index, so make sure we check for the length == 0 case.
+            return LastIndexOf(source, value, source.Length - 1,
+                source.Length, options);
+        }
+
+        public virtual int LastIndexOf(string source, string value, CompareOptions options)
+        {
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            // Can't start at negative index, so make sure we check for the length == 0 case.
+            return LastIndexOf(source, value, source.Length - 1, source.Length, options);
+        }
+
+        public virtual int LastIndexOf(string source, char value, int startIndex)
+        {
+            return LastIndexOf(source, value, startIndex, startIndex + 1, CompareOptions.None);
+        }
+
+
+        public virtual int LastIndexOf(string source, string value, int startIndex)
+        {
+            return LastIndexOf(source, value, startIndex, startIndex + 1, CompareOptions.None);
+        }
+
+        public virtual int LastIndexOf(string source, char value, int startIndex, CompareOptions options)
+        {
+            return LastIndexOf(source, value, startIndex, startIndex + 1, options);
+        }
+
+
+        public virtual int LastIndexOf(string source, string value, int startIndex, CompareOptions options)
+        {
+            return LastIndexOf(source, value, startIndex, startIndex + 1, options);
+        }
+
+
+        public virtual int LastIndexOf(string source, char value, int startIndex, int count)
+        {
+            return LastIndexOf(source, value, startIndex, count, CompareOptions.None);
+        }
+
+
+        public virtual int LastIndexOf(string source, string value, int startIndex, int count)
+        {
+            return LastIndexOf(source, value, startIndex, count, CompareOptions.None);
+        }
+
+
+        public virtual int LastIndexOf(string source, char value, int startIndex, int count, CompareOptions options)
+        {
+            // Verify Arguments
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+
+            // Validate CompareOptions
+            // Ordinal can't be selected with other flags
+            if ((options & ValidIndexMaskOffFlags) != 0 &&
+                (options != CompareOptions.Ordinal) &&
+                (options != CompareOptions.OrdinalIgnoreCase))
+                throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
+
+            // Special case for 0 length input strings
+            if (source.Length == 0 && (startIndex == -1 || startIndex == 0))
+                return -1;
+
+            // Make sure we're not out of range
+            if (startIndex < 0 || startIndex > source.Length)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+
+            // Make sure that we allow startIndex == source.Length
+            if (startIndex == source.Length)
+            {
+                startIndex--;
+                if (count > 0)
+                    count--;
+            }
+
+            // 2nd have of this also catches when startIndex == MAXINT, so MAXINT - 0 + 1 == -1, which is < 0.
+            if (count < 0 || startIndex - count + 1 < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Count);
+
+            if (options == CompareOptions.OrdinalIgnoreCase)
+            {
+                return source.LastIndexOf(value.ToString(), startIndex, count, StringComparison.OrdinalIgnoreCase);
+            }
+
+            if (_invariantMode)
+                return InvariantLastIndexOf(source, new string(value, 1), startIndex, count, (options & (CompareOptions.IgnoreCase | CompareOptions.OrdinalIgnoreCase)) != 0);
+
+            return LastIndexOfCore(source, value.ToString(), startIndex, count, options);
+        }
+
+
+        public virtual int LastIndexOf(string source, string value, int startIndex, int count, CompareOptions options)
+        {
+            // Verify Arguments
+            if (source == null)
+                throw new ArgumentNullException(nameof(source));
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            // Validate CompareOptions
+            // Ordinal can't be selected with other flags
+            if ((options & ValidIndexMaskOffFlags) != 0 &&
+                (options != CompareOptions.Ordinal) &&
+                (options != CompareOptions.OrdinalIgnoreCase))
+                throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
+
+            // Special case for 0 length input strings
+            if (source.Length == 0 && (startIndex == -1 || startIndex == 0))
+                return (value.Length == 0) ? 0 : -1;
+
+            // Make sure we're not out of range
+            if (startIndex < 0 || startIndex > source.Length)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+
+            // Make sure that we allow startIndex == source.Length
+            if (startIndex == source.Length)
+            {
+                startIndex--;
+                if (count > 0)
+                    count--;
+
+                // If we are looking for nothing, just return 0
+                if (value.Length == 0 && count >= 0 && startIndex - count + 1 >= 0)
+                    return startIndex;
+            }
+
+            // 2nd half of this also catches when startIndex == MAXINT, so MAXINT - 0 + 1 == -1, which is < 0.
+            if (count < 0 || startIndex - count + 1 < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Count);
+
+            if (options == CompareOptions.OrdinalIgnoreCase)
+            {
+                return LastIndexOfOrdinal(source, value, startIndex, count, ignoreCase: true);
+            }
+
+            if (_invariantMode)
+                return InvariantLastIndexOf(source, value, startIndex, count, (options & (CompareOptions.IgnoreCase | CompareOptions.OrdinalIgnoreCase)) != 0);
+
+            return LastIndexOfCore(source, value, startIndex, count, options);
+        }
+
+        internal int LastIndexOfOrdinal(string source, string value, int startIndex, int count, bool ignoreCase)
+        {
+            if (_invariantMode)
+            {
+                return InvariantLastIndexOf(source, value, startIndex, count, ignoreCase);
+            }
+
+            return LastIndexOfOrdinalCore(source, value, startIndex, count, ignoreCase);
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetSortKey
+        //
+        //  Gets the SortKey for the given string with the given options.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual SortKey GetSortKey(string source, CompareOptions options)
+        {
+            if (_invariantMode)
+                return InvariantCreateSortKey(source, options);
+
+            return CreateSortKey(source, options);
+        }
+
+
+        public virtual SortKey GetSortKey(string source)
+        {
+            if (_invariantMode)
+                return InvariantCreateSortKey(source, CompareOptions.None);
+
+            return CreateSortKey(source, CompareOptions.None);
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  Equals
+        //
+        //  Implements Object.Equals().  Returns a boolean indicating whether
+        //  or not object refers to the same CompareInfo as the current
+        //  instance.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+
+        public override bool Equals(Object value)
+        {
+            CompareInfo that = value as CompareInfo;
+
+            if (that != null)
+            {
+                return this.Name == that.Name;
+            }
+
+            return (false);
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetHashCode
+        //
+        //  Implements Object.GetHashCode().  Returns the hash code for the
+        //  CompareInfo.  The hash code is guaranteed to be the same for
+        //  CompareInfo A and B where A.Equals(B) is true.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+
+        public override int GetHashCode()
+        {
+            return (this.Name.GetHashCode());
+        }
+
+        internal static unsafe int GetIgnoreCaseHash(string source)
+        {
+            Debug.Assert(source != null, "source must not be null");
+
+            // Do not allocate on the stack if string is empty
+            if (source.Length == 0)
+            {
+                return source.GetHashCode();
+            }
+
+            char[] borrowedArr = null;
+            Span<char> span = source.Length <= 255 ?
+                stackalloc char[255] :
+                (borrowedArr = ArrayPool<char>.Shared.Rent(source.Length));
+
+            int charsWritten = source.AsSpan().ToUpperInvariant(span);
+
+            // Slice the array to the size returned by ToUpperInvariant.
+            int hash = Marvin.ComputeHash32(MemoryMarshal.AsBytes(span.Slice(0, charsWritten)), Marvin.DefaultSeed);
+
+            // Return the borrowed array if necessary.
+            if (borrowedArr != null)
+            {
+                ArrayPool<char>.Shared.Return(borrowedArr);
+            }
+
+            return hash;
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetHashCodeOfString
+        //
+        //  This internal method allows a method that allows the equivalent of creating a Sortkey for a
+        //  string from CompareInfo, and generate a hashcode value from it.  It is not very convenient
+        //  to use this method as is and it creates an unnecessary Sortkey object that will be GC'ed.
+        //
+        //  The hash code is guaranteed to be the same for string A and B where A.Equals(B) is true and both
+        //  the CompareInfo and the CompareOptions are the same. If two different CompareInfo objects
+        //  treat the string the same way, this implementation will treat them differently (the same way that
+        //  Sortkey does at the moment).
+        //
+        //  This method will never be made public itself, but public consumers of it could be created, e.g.:
+        //
+        //      string.GetHashCode(CultureInfo)
+        //      string.GetHashCode(CompareInfo)
+        //      string.GetHashCode(CultureInfo, CompareOptions)
+        //      string.GetHashCode(CompareInfo, CompareOptions)
+        //      etc.
+        //
+        //  (the methods above that take a CultureInfo would use CultureInfo.CompareInfo)
+        //
+        ////////////////////////////////////////////////////////////////////////
+        internal int GetHashCodeOfString(string source, CompareOptions options)
+        {
+            //
+            //  Parameter validation
+            //
+            if (null == source)
+            {
+                throw new ArgumentNullException(nameof(source));
+            }
+
+            if ((options & ValidHashCodeOfStringMaskOffFlags) != 0)
+            {
+                throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
+            }
+
+            if (_invariantMode)
+            {
+                return ((options & CompareOptions.IgnoreCase) != 0) ? GetIgnoreCaseHash(source) : source.GetHashCode();
+            }
+
+            return GetHashCodeOfStringCore(source, options);
+        }
+
+        public virtual int GetHashCode(string source, CompareOptions options)
+        {
+            if (source == null)
+            {
+                throw new ArgumentNullException(nameof(source));
+            }
+
+            if (options == CompareOptions.Ordinal)
+            {
+                return source.GetHashCode();
+            }
+
+            if (options == CompareOptions.OrdinalIgnoreCase)
+            {
+                return GetIgnoreCaseHash(source);
+            }
+
+            //
+            // GetHashCodeOfString does more parameters validation. basically will throw when
+            // having Ordinal, OrdinalIgnoreCase and StringSort
+            //
+
+            return GetHashCodeOfString(source, options);
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  ToString
+        //
+        //  Implements Object.ToString().  Returns a string describing the
+        //  CompareInfo.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public override string ToString()
+        {
+            return ("CompareInfo - " + this.Name);
+        }
+
+        public SortVersion Version
+        {
+            get
+            {
+                if (m_SortVersion == null)
+                {
+                    if (_invariantMode)
+                    {
+                        m_SortVersion = new SortVersion(0, CultureInfo.LOCALE_INVARIANT, new Guid(0, 0, 0, 0, 0, 0, 0,
+                                                                        (byte) (CultureInfo.LOCALE_INVARIANT >> 24),
+                                                                        (byte) ((CultureInfo.LOCALE_INVARIANT  & 0x00FF0000) >> 16),
+                                                                        (byte) ((CultureInfo.LOCALE_INVARIANT  & 0x0000FF00) >> 8),
+                                                                        (byte) (CultureInfo.LOCALE_INVARIANT  & 0xFF)));
+                    }
+                    else
+                    {
+                        m_SortVersion = GetSortVersion();
+                    }
+                }
+
+                return m_SortVersion;
+            }
+        }
+
+        public int LCID
+        {
+            get
+            {
+                return CultureInfo.GetCultureInfo(Name).LCID;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CultureData.Unix.cs b/src/System.Private.CoreLib/shared/System/Globalization/CultureData.Unix.cs
new file mode 100644
index 0000000000..3fce527929
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CultureData.Unix.cs
@@ -0,0 +1,430 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Security;
+using System.Text;
+
+namespace System.Globalization
+{
+    internal partial class CultureData
+    {
+        // ICU constants
+        const int ICU_ULOC_KEYWORD_AND_VALUES_CAPACITY = 100; // max size of keyword or value
+        const int ICU_ULOC_FULLNAME_CAPACITY = 157;           // max size of locale name
+        const string ICU_COLLATION_KEYWORD = "@collation=";
+        
+        
+        /// <summary>
+        /// This method uses the sRealName field (which is initialized by the constructor before this is called) to
+        /// initialize the rest of the state of CultureData based on the underlying OS globalization library.
+        /// </summary>
+        private unsafe bool InitCultureData()
+        {
+            Debug.Assert(_sRealName != null);
+
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            string alternateSortName = string.Empty;
+            string realNameBuffer = _sRealName;
+
+            // Basic validation
+            if (realNameBuffer.Contains('@'))
+            {
+                return false; // don't allow ICU variants to come in directly
+            }
+
+            // Replace _ (alternate sort) with @collation= for ICU
+            int index = realNameBuffer.IndexOf('_');
+            if (index > 0)
+            {
+                if (index >= (realNameBuffer.Length - 1) // must have characters after _
+                    || realNameBuffer.Substring(index + 1).Contains('_')) // only one _ allowed
+                {
+                    return false; // fail
+                }
+                alternateSortName = realNameBuffer.Substring(index + 1);
+                realNameBuffer = realNameBuffer.Substring(0, index) + ICU_COLLATION_KEYWORD + alternateSortName;
+            }
+
+            // Get the locale name from ICU
+            if (!GetLocaleName(realNameBuffer, out _sWindowsName))
+            {
+                return false; // fail
+            }
+
+            // Replace the ICU collation keyword with an _
+            index = _sWindowsName.IndexOf(ICU_COLLATION_KEYWORD, StringComparison.Ordinal);
+            if (index >= 0)
+            {
+                _sName = _sWindowsName.Substring(0, index) + "_" + alternateSortName;
+            }
+            else
+            {
+                _sName = _sWindowsName;
+            }
+            _sRealName = _sName;
+
+            _iLanguage = this.ILANGUAGE;
+            if (_iLanguage == 0)
+            {
+                _iLanguage = CultureInfo.LOCALE_CUSTOM_UNSPECIFIED;
+            }
+
+            _bNeutral = (this.SISO3166CTRYNAME.Length == 0);
+            
+            _sSpecificCulture = _bNeutral ? LocaleData.GetSpecificCultureName(_sRealName) : _sRealName;   
+            
+            // Remove the sort from sName unless custom culture
+            if (index>0 && !_bNeutral && !IsCustomCultureId(_iLanguage))
+            {
+                _sName = _sWindowsName.Substring(0, index);
+            }
+            return true;
+        }
+
+        internal static bool GetLocaleName(string localeName, out string windowsName)
+        {
+            // Get the locale name from ICU
+            StringBuilder sb = StringBuilderCache.Acquire(ICU_ULOC_FULLNAME_CAPACITY);
+            if (!Interop.Globalization.GetLocaleName(localeName, sb, sb.Capacity))
+            {
+                StringBuilderCache.Release(sb);
+                windowsName = null;
+                return false; // fail
+            }
+
+            // Success - use the locale name returned which may be different than realNameBuffer (casing)
+            windowsName = StringBuilderCache.GetStringAndRelease(sb); // the name passed to subsequent ICU calls
+            return true;
+        }
+
+        internal static bool GetDefaultLocaleName(out string windowsName)
+        {
+            // Get the default (system) locale name from ICU
+            StringBuilder sb = StringBuilderCache.Acquire(ICU_ULOC_FULLNAME_CAPACITY);
+            if (!Interop.Globalization.GetDefaultLocaleName(sb, sb.Capacity))
+            {
+                StringBuilderCache.Release(sb);
+                windowsName = null;
+                return false; // fail
+            }
+
+            // Success - use the locale name returned which may be different than realNameBuffer (casing)
+            windowsName = StringBuilderCache.GetStringAndRelease(sb); // the name passed to subsequent ICU calls
+            return true;
+        }
+        
+        private string GetLocaleInfo(LocaleStringData type)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            
+            Debug.Assert(_sWindowsName != null, "[CultureData.GetLocaleInfo] Expected _sWindowsName to be populated already");
+            return GetLocaleInfo(_sWindowsName, type);
+        }
+
+        // For LOCALE_SPARENT we need the option of using the "real" name (forcing neutral names) instead of the
+        // "windows" name, which can be specific for downlevel (< windows 7) os's.
+        private string GetLocaleInfo(string localeName, LocaleStringData type)
+        {
+            Debug.Assert(localeName != null, "[CultureData.GetLocaleInfo] Expected localeName to be not be null");
+
+            switch (type)
+            {
+                case LocaleStringData.NegativeInfinitySymbol:
+                    // not an equivalent in ICU; prefix the PositiveInfinitySymbol with NegativeSign
+                    return GetLocaleInfo(localeName, LocaleStringData.NegativeSign) +
+                        GetLocaleInfo(localeName, LocaleStringData.PositiveInfinitySymbol);
+            }
+
+            StringBuilder sb = StringBuilderCache.Acquire(ICU_ULOC_KEYWORD_AND_VALUES_CAPACITY);
+
+            bool result = Interop.Globalization.GetLocaleInfoString(localeName, (uint)type, sb, sb.Capacity);
+            if (!result)
+            {
+                // Failed, just use empty string
+                StringBuilderCache.Release(sb);
+                Debug.Fail("[CultureData.GetLocaleInfo(LocaleStringData)] Failed");
+                return String.Empty;
+            }
+            return StringBuilderCache.GetStringAndRelease(sb);
+        }
+
+        private int GetLocaleInfo(LocaleNumberData type)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            Debug.Assert(_sWindowsName != null, "[CultureData.GetLocaleInfo(LocaleNumberData)] Expected _sWindowsName to be populated already");
+
+            switch (type)
+            {
+                case LocaleNumberData.CalendarType:
+                    // returning 0 will cause the first supported calendar to be returned, which is the preferred calendar
+                    return 0;
+            }
+            
+
+            int value = 0;
+            bool result = Interop.Globalization.GetLocaleInfoInt(_sWindowsName, (uint)type, ref value);
+            if (!result)
+            {
+                // Failed, just use 0
+                Debug.Fail("[CultureData.GetLocaleInfo(LocaleNumberData)] failed");
+            }
+
+            return value;
+        }
+
+        private int[] GetLocaleInfo(LocaleGroupingData type)
+        {
+            Debug.Assert(_sWindowsName != null, "[CultureData.GetLocaleInfo(LocaleGroupingData)] Expected _sWindowsName to be populated already");
+
+            int primaryGroupingSize = 0;
+            int secondaryGroupingSize = 0;
+            bool result = Interop.Globalization.GetLocaleInfoGroupingSizes(_sWindowsName, (uint)type, ref primaryGroupingSize, ref secondaryGroupingSize);
+            if (!result)
+            {
+                Debug.Fail("[CultureData.GetLocaleInfo(LocaleGroupingData type)] failed");
+            }
+
+            if (secondaryGroupingSize == 0)
+            {
+                return new int[] { primaryGroupingSize };
+            }
+
+            return new int[] { primaryGroupingSize, secondaryGroupingSize };
+        }
+
+        private string GetTimeFormatString()
+        {
+            return GetTimeFormatString(false);
+        }
+
+        private string GetTimeFormatString(bool shortFormat)
+        {
+            Debug.Assert(_sWindowsName != null, "[CultureData.GetTimeFormatString(bool shortFormat)] Expected _sWindowsName to be populated already");
+
+            StringBuilder sb = StringBuilderCache.Acquire(ICU_ULOC_KEYWORD_AND_VALUES_CAPACITY);
+
+            bool result = Interop.Globalization.GetLocaleTimeFormat(_sWindowsName, shortFormat, sb, sb.Capacity);
+            if (!result)
+            {
+                // Failed, just use empty string
+                StringBuilderCache.Release(sb);
+                Debug.Fail("[CultureData.GetTimeFormatString(bool shortFormat)] Failed");
+                return String.Empty;
+            }
+
+            return ConvertIcuTimeFormatString(StringBuilderCache.GetStringAndRelease(sb));
+        }
+
+        private int GetFirstDayOfWeek()
+        {
+            return this.GetLocaleInfo(LocaleNumberData.FirstDayOfWeek);
+        }
+
+        private String[] GetTimeFormats()
+        {
+            string format = GetTimeFormatString(false);
+            return new string[] { format };
+        }
+
+        private String[] GetShortTimeFormats()
+        {
+            string format = GetTimeFormatString(true);
+            return new string[] { format };
+        }
+
+        private static CultureData GetCultureDataFromRegionName(String regionName)
+        {
+            // no support to lookup by region name, other than the hard-coded list in CultureData
+            return null;
+        }
+
+        private static string GetLanguageDisplayName(string cultureName)
+        {
+            return new CultureInfo(cultureName)._cultureData.GetLocaleInfo(cultureName, LocaleStringData.LocalizedDisplayName);
+        }
+
+        private static string GetRegionDisplayName(string isoCountryCode)
+        {
+            // use the fallback which is to return NativeName
+            return null;
+        }
+
+        private static CultureInfo GetUserDefaultCulture()
+        {
+            return CultureInfo.GetUserDefaultCulture();
+        }
+
+        private static string ConvertIcuTimeFormatString(string icuFormatString)
+        {
+            StringBuilder sb = StringBuilderCache.Acquire(ICU_ULOC_FULLNAME_CAPACITY);
+            bool amPmAdded = false;
+
+            for (int i = 0; i < icuFormatString.Length; i++)
+            {
+                switch(icuFormatString[i])
+                {
+                    case ':':
+                    case '.':
+                    case 'H':
+                    case 'h':
+                    case 'm':
+                    case 's':
+                        sb.Append(icuFormatString[i]);
+                        break;
+
+                    case ' ':
+                    case '\u00A0':
+                        // Convert nonbreaking spaces into regular spaces
+                        sb.Append(' ');
+                        break;
+
+                    case 'a': // AM/PM
+                        if (!amPmAdded)
+                        {
+                            amPmAdded = true;
+                            sb.Append("tt");
+                        }
+                        break;
+
+                }
+            }
+
+            return StringBuilderCache.GetStringAndRelease(sb);
+        }
+        
+        private static string LCIDToLocaleName(int culture)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            return LocaleData.LCIDToLocaleName(culture);
+        }
+
+        private static int LocaleNameToLCID(string cultureName)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            
+            int lcid = LocaleData.GetLocaleDataNumericPart(cultureName, LocaleDataParts.Lcid);
+            return lcid == -1 ? CultureInfo.LOCALE_CUSTOM_UNSPECIFIED : lcid; 
+        }
+        
+        private static int GetAnsiCodePage(string cultureName)
+        {
+            int ansiCodePage = LocaleData.GetLocaleDataNumericPart(cultureName, LocaleDataParts.AnsiCodePage);
+            return ansiCodePage == -1 ? CultureData.Invariant.IDEFAULTANSICODEPAGE : ansiCodePage; 
+        }
+
+        private static int GetOemCodePage(string cultureName)
+        {
+            int oemCodePage = LocaleData.GetLocaleDataNumericPart(cultureName, LocaleDataParts.OemCodePage);
+            return oemCodePage == -1 ? CultureData.Invariant.IDEFAULTOEMCODEPAGE : oemCodePage; 
+        }
+
+        private static int GetMacCodePage(string cultureName)
+        {
+            int macCodePage = LocaleData.GetLocaleDataNumericPart(cultureName, LocaleDataParts.MacCodePage);
+            return macCodePage == -1 ? CultureData.Invariant.IDEFAULTMACCODEPAGE : macCodePage; 
+        }
+
+        private static int GetEbcdicCodePage(string cultureName)
+        {
+            int ebcdicCodePage = LocaleData.GetLocaleDataNumericPart(cultureName, LocaleDataParts.EbcdicCodePage);
+            return ebcdicCodePage == -1 ? CultureData.Invariant.IDEFAULTEBCDICCODEPAGE : ebcdicCodePage; 
+        }
+
+        private static int GetGeoId(string cultureName)
+        {
+            int geoId = LocaleData.GetLocaleDataNumericPart(cultureName, LocaleDataParts.GeoId);
+            return geoId == -1 ? CultureData.Invariant.IGEOID : geoId; 
+        }
+        
+        private static int GetDigitSubstitution(string cultureName)
+        {
+            int digitSubstitution = LocaleData.GetLocaleDataNumericPart(cultureName, LocaleDataParts.DigitSubstitution);
+            return digitSubstitution == -1 ? (int) DigitShapes.None : digitSubstitution; 
+        }
+
+        private static string GetThreeLetterWindowsLanguageName(string cultureName)
+        {
+            string langName = LocaleData.GetThreeLetterWindowsLangageName(cultureName);
+            return langName == null ? "ZZZ" /* default lang name */ : langName; 
+        }
+
+        private static CultureInfo[] EnumCultures(CultureTypes types)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            
+            if ((types & (CultureTypes.NeutralCultures | CultureTypes.SpecificCultures)) == 0)
+            {
+                return Array.Empty<CultureInfo>();
+            }
+            
+            int bufferLength = Interop.Globalization.GetLocales(null, 0);
+            if (bufferLength <= 0)
+            {
+                return Array.Empty<CultureInfo>();
+            }
+            
+            Char [] chars = new Char[bufferLength];
+            
+            bufferLength = Interop.Globalization.GetLocales(chars, bufferLength);
+            if (bufferLength <= 0)
+            {
+                return Array.Empty<CultureInfo>();
+            }
+            
+            bool enumNeutrals   = (types & CultureTypes.NeutralCultures) != 0; 
+            bool enumSpecificss = (types & CultureTypes.SpecificCultures) != 0; 
+            
+            List<CultureInfo> list = new List<CultureInfo>();
+            if (enumNeutrals) 
+            {
+                list.Add(CultureInfo.InvariantCulture);
+            }
+            
+            int index = 0;
+            while (index < bufferLength)
+            {
+                int length = (int) chars[index++];
+                if (index + length <= bufferLength)
+                {
+                    CultureInfo ci = CultureInfo.GetCultureInfo(new String(chars, index, length));
+                    if ((enumNeutrals && ci.IsNeutralCulture) || (enumSpecificss && !ci.IsNeutralCulture))
+                    {
+                        list.Add(ci);
+                    }
+                }
+                
+                index += length;
+            }
+            
+            return list.ToArray();
+        }
+        
+        private static string GetConsoleFallbackName(string cultureName)
+        {
+            return LocaleData.GetConsoleUICulture(cultureName);
+        }
+        
+        internal bool IsFramework // not applicable on Linux based systems 
+        {
+            get { return false; }
+        }
+        
+        internal bool IsWin32Installed // not applicable on Linux based systems
+        {
+            get { return false; }
+        }
+        
+        internal bool IsReplacementCulture // not applicable on Linux based systems
+        {
+            get { return false; }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CultureData.Windows.cs b/src/System.Private.CoreLib/shared/System/Globalization/CultureData.Windows.cs
new file mode 100644
index 0000000000..393f983bba
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CultureData.Windows.cs
@@ -0,0 +1,774 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Text;
+using Internal.Runtime.CompilerServices;
+
+#if ENABLE_WINRT
+using Internal.Runtime.Augments;
+#endif
+
+namespace System.Globalization
+{
+    internal partial class CultureData
+    {
+        private const uint LOCALE_NOUSEROVERRIDE = 0x80000000;
+        private const uint LOCALE_RETURN_NUMBER = 0x20000000;
+        private const uint LOCALE_SISO3166CTRYNAME = 0x0000005A;
+
+        private const uint TIME_NOSECONDS = 0x00000002;
+
+        /// <summary>
+        /// Check with the OS to see if this is a valid culture.
+        /// If so we populate a limited number of fields.  If its not valid we return false.
+        ///
+        /// The fields we populate:
+        ///
+        /// sWindowsName -- The name that windows thinks this culture is, ie:
+        ///                            en-US if you pass in en-US
+        ///                            de-DE_phoneb if you pass in de-DE_phoneb
+        ///                            fj-FJ if you pass in fj (neutral, on a pre-Windows 7 machine)
+        ///                            fj if you pass in fj (neutral, post-Windows 7 machine)
+        ///
+        /// sRealName -- The name you used to construct the culture, in pretty form
+        ///                       en-US if you pass in EN-us
+        ///                       en if you pass in en
+        ///                       de-DE_phoneb if you pass in de-DE_phoneb
+        ///
+        /// sSpecificCulture -- The specific culture for this culture
+        ///                             en-US for en-US
+        ///                             en-US for en
+        ///                             de-DE_phoneb for alt sort
+        ///                             fj-FJ for fj (neutral)
+        ///
+        /// sName -- The IETF name of this culture (ie: no sort info, could be neutral)
+        ///                en-US if you pass in en-US
+        ///                en if you pass in en
+        ///                de-DE if you pass in de-DE_phoneb
+        ///
+        /// bNeutral -- TRUE if it is a neutral locale
+        ///
+        /// For a neutral we just populate the neutral name, but we leave the windows name pointing to the
+        /// windows locale that's going to provide data for us.
+        /// </summary>
+        private unsafe bool InitCultureData()
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            const uint LOCALE_ILANGUAGE = 0x00000001;
+            const uint LOCALE_INEUTRAL = 0x00000071;
+            const uint LOCALE_SNAME = 0x0000005c;
+
+            int result;
+            string realNameBuffer = _sRealName;
+            char* pBuffer = stackalloc char[LOCALE_NAME_MAX_LENGTH];
+
+            result = GetLocaleInfoEx(realNameBuffer, LOCALE_SNAME, pBuffer, LOCALE_NAME_MAX_LENGTH);
+
+            // Did it fail?
+            if (result == 0)
+            {
+                return false;
+            }
+
+            // It worked, note that the name is the locale name, so use that (even for neutrals)
+            // We need to clean up our "real" name, which should look like the windows name right now
+            // so overwrite the input with the cleaned up name
+            _sRealName = new string(pBuffer, 0, result - 1);
+            realNameBuffer = _sRealName;
+
+            // Check for neutrality, don't expect to fail
+            // (buffer has our name in it, so we don't have to do the gc. stuff)
+
+            result = GetLocaleInfoEx(realNameBuffer, LOCALE_INEUTRAL | LOCALE_RETURN_NUMBER, pBuffer, sizeof(int) / sizeof(char));
+            if (result == 0)
+            {
+                return false;
+            }
+
+            // Remember our neutrality
+            _bNeutral = *((uint*)pBuffer) != 0;
+
+            // Note: Parents will be set dynamically
+
+            // Start by assuming the windows name will be the same as the specific name since windows knows
+            // about specifics on all versions. Only for downlevel Neutral locales does this have to change.
+            _sWindowsName = realNameBuffer;
+
+            // Neutrals and non-neutrals are slightly different
+            if (_bNeutral)
+            {
+                // Neutral Locale
+
+                // IETF name looks like neutral name
+                _sName = realNameBuffer;
+
+                // Specific locale name is whatever ResolveLocaleName (win7+) returns.
+                // (Buffer has our name in it, and we can recycle that because windows resolves it before writing to the buffer)
+                result = Interop.Kernel32.ResolveLocaleName(realNameBuffer, pBuffer, LOCALE_NAME_MAX_LENGTH);
+
+                // 0 is failure, 1 is invariant (""), which we expect
+                if (result < 1)
+                {
+                    return false;
+                }
+                // We found a locale name, so use it.
+                // In vista this should look like a sort name (de-DE_phoneb) or a specific culture (en-US) and be in the "pretty" form
+                _sSpecificCulture = new string(pBuffer, 0, result - 1);
+            }
+            else
+            {
+                // Specific Locale
+
+                // Specific culture's the same as the locale name since we know its not neutral
+                // On mac we'll use this as well, even for neutrals. There's no obvious specific
+                // culture to use and this isn't exposed, but behaviorally this is correct on mac.
+                // Note that specifics include the sort name (de-DE_phoneb)
+                _sSpecificCulture = realNameBuffer;
+
+                _sName = realNameBuffer;
+
+                // We need the IETF name (sname)
+                // If we aren't an alt sort locale then this is the same as the windows name.
+                // If we are an alt sort locale then this is the same as the part before the _ in the windows name
+                // This is for like de-DE_phoneb and es-ES_tradnl that hsouldn't have the _ part
+
+                result = GetLocaleInfoEx(realNameBuffer, LOCALE_ILANGUAGE | LOCALE_RETURN_NUMBER, pBuffer, sizeof(int) / sizeof(char));
+                if (result == 0)
+                {
+                    return false;
+                }
+
+                _iLanguage = *((int*)pBuffer);
+
+                if (!IsCustomCultureId(_iLanguage))
+                {
+                    // not custom locale
+                    int index = realNameBuffer.IndexOf('_');
+                    if (index > 0 && index < realNameBuffer.Length)
+                    {
+                        _sName = realNameBuffer.Substring(0, index);
+                    }
+                }
+            }
+
+            // It succeeded.
+            return true;
+        }
+
+        // Wrappers around the GetLocaleInfoEx APIs which handle marshalling the returned
+        // data as either and Int or string.
+        internal static unsafe string GetLocaleInfoEx(string localeName, uint field)
+        {
+            // REVIEW: Determine the maximum size for the buffer
+            const int BUFFER_SIZE = 530;
+
+            char* pBuffer = stackalloc char[BUFFER_SIZE];
+            int resultCode = GetLocaleInfoEx(localeName, field, pBuffer, BUFFER_SIZE);
+            if (resultCode > 0)
+            {
+                return new string(pBuffer);
+            }
+
+            return null;
+        }
+
+        internal static unsafe int GetLocaleInfoExInt(string localeName, uint field)
+        {
+            const uint LOCALE_RETURN_NUMBER = 0x20000000;
+            field |= LOCALE_RETURN_NUMBER;
+            int value = 0;
+            GetLocaleInfoEx(localeName, field, (char*) &value, sizeof(int));
+            return value;
+        }
+
+        internal static unsafe int GetLocaleInfoEx(string lpLocaleName, uint lcType, char* lpLCData, int cchData)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            return Interop.Kernel32.GetLocaleInfoEx(lpLocaleName, lcType, lpLCData, cchData);
+        }
+
+        private string GetLocaleInfo(LocaleStringData type)
+        {
+            Debug.Assert(_sWindowsName != null, "[CultureData.DoGetLocaleInfo] Expected _sWindowsName to be populated by already");
+            return GetLocaleInfo(_sWindowsName, type);
+        }
+
+        // For LOCALE_SPARENT we need the option of using the "real" name (forcing neutral names) instead of the
+        // "windows" name, which can be specific for downlevel (< windows 7) os's.
+        private string GetLocaleInfo(string localeName, LocaleStringData type)
+        {
+            uint lctype = (uint)type;
+
+            return GetLocaleInfoFromLCType(localeName, lctype, UseUserOverride);
+        }
+
+        private int GetLocaleInfo(LocaleNumberData type)
+        {
+            uint lctype = (uint)type;
+
+            // Fix lctype if we don't want overrides
+            if (!UseUserOverride)
+            {
+                lctype |= LOCALE_NOUSEROVERRIDE;
+            }
+
+            // Ask OS for data, note that we presume it returns success, so we have to know that
+            // sWindowsName is valid before calling.
+            Debug.Assert(_sWindowsName != null, "[CultureData.DoGetLocaleInfoInt] Expected _sWindowsName to be populated by already");
+            return  GetLocaleInfoExInt(_sWindowsName, lctype);
+        }
+
+        private int[] GetLocaleInfo(LocaleGroupingData type)
+        {
+            return ConvertWin32GroupString(GetLocaleInfoFromLCType(_sWindowsName, (uint)type, UseUserOverride));
+        }
+
+        private string GetTimeFormatString()
+        {
+            const uint LOCALE_STIMEFORMAT = 0x00001003;
+
+            return ReescapeWin32String(GetLocaleInfoFromLCType(_sWindowsName, LOCALE_STIMEFORMAT, UseUserOverride));
+        }
+
+        private int GetFirstDayOfWeek()
+        {
+            Debug.Assert(_sWindowsName != null, "[CultureData.DoGetLocaleInfoInt] Expected _sWindowsName to be populated by already");
+
+            const uint LOCALE_IFIRSTDAYOFWEEK = 0x0000100C;
+
+            int result = GetLocaleInfoExInt(_sWindowsName, LOCALE_IFIRSTDAYOFWEEK | (!UseUserOverride ? LOCALE_NOUSEROVERRIDE : 0));
+
+            // Win32 and .NET disagree on the numbering for days of the week, so we have to convert.
+            return ConvertFirstDayOfWeekMonToSun(result);
+        }
+
+        private string[] GetTimeFormats()
+        {
+            // Note that this gets overrides for us all the time
+            Debug.Assert(_sWindowsName != null, "[CultureData.DoEnumTimeFormats] Expected _sWindowsName to be populated by already");
+            string[] result = ReescapeWin32Strings(nativeEnumTimeFormats(_sWindowsName, 0, UseUserOverride));
+
+            return result;
+        }
+
+        private string[] GetShortTimeFormats()
+        {
+            // Note that this gets overrides for us all the time
+            Debug.Assert(_sWindowsName != null, "[CultureData.DoEnumShortTimeFormats] Expected _sWindowsName to be populated by already");
+            string[] result = ReescapeWin32Strings(nativeEnumTimeFormats(_sWindowsName, TIME_NOSECONDS, UseUserOverride));
+
+            return result;
+        }
+
+        // Enumerate all system cultures and then try to find out which culture has
+        // region name match the requested region name
+        private static CultureData GetCultureDataFromRegionName(string regionName)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            Debug.Assert(regionName != null);
+
+            const uint LOCALE_SUPPLEMENTAL = 0x00000002;
+            const uint LOCALE_SPECIFICDATA = 0x00000020;
+
+            EnumLocaleData context = new EnumLocaleData();
+            context.cultureName = null;
+            context.regionName = regionName;
+
+            unsafe
+            {
+                Interop.Kernel32.EnumSystemLocalesEx(EnumSystemLocalesProc, LOCALE_SPECIFICDATA | LOCALE_SUPPLEMENTAL, Unsafe.AsPointer(ref context), IntPtr.Zero);
+            }
+
+            if (context.cultureName != null)
+            {
+                // we got a matched culture
+                return GetCultureData(context.cultureName, true);
+            }
+
+            return null;
+        }
+
+        private string GetLanguageDisplayName(string cultureName)
+        {
+#if ENABLE_WINRT
+            return WinRTInterop.Callbacks.GetLanguageDisplayName(cultureName);
+#else
+            // Usually the UI culture shouldn't be different than what we got from WinRT except
+            // if DefaultThreadCurrentUICulture was set
+            CultureInfo ci;
+
+            if (CultureInfo.DefaultThreadCurrentUICulture != null &&
+                ((ci = GetUserDefaultCulture()) != null) &&
+                !CultureInfo.DefaultThreadCurrentUICulture.Name.Equals(ci.Name))
+            {
+                return SNATIVEDISPLAYNAME;
+            }
+            else
+            {
+                return GetLocaleInfo(cultureName, LocaleStringData.LocalizedDisplayName);
+            }
+#endif // ENABLE_WINRT
+        }
+
+        private string GetRegionDisplayName(string isoCountryCode)
+        {
+#if ENABLE_WINRT
+            return WinRTInterop.Callbacks.GetRegionDisplayName(isoCountryCode);
+#else
+            // If the current UI culture matching the OS UI language, we'll get the display name from the OS.
+            // otherwise, we use the native name as we don't carry resources for the region display names anyway.
+            if (CultureInfo.CurrentUICulture.Name.Equals(CultureInfo.UserDefaultUICulture.Name))
+            {
+                return GetLocaleInfo(LocaleStringData.LocalizedCountryName);
+            }
+
+            return SNATIVECOUNTRY;
+#endif // ENABLE_WINRT
+        }
+
+        private static CultureInfo GetUserDefaultCulture()
+        {
+#if ENABLE_WINRT
+            return (CultureInfo)WinRTInterop.Callbacks.GetUserDefaultCulture();
+#else
+            return CultureInfo.GetUserDefaultCulture();
+#endif // ENABLE_WINRT
+        }
+
+        // PAL methods end here.
+
+        private static string GetLocaleInfoFromLCType(string localeName, uint lctype, bool useUserOveride)
+        {
+            Debug.Assert(localeName != null, "[CultureData.GetLocaleInfoFromLCType] Expected localeName to be not be null");
+
+            // Fix lctype if we don't want overrides
+            if (!useUserOveride)
+            {
+                lctype |= LOCALE_NOUSEROVERRIDE;
+            }
+
+            // Ask OS for data
+            string result = GetLocaleInfoEx(localeName, lctype);
+            if (result == null)
+            {
+                // Failed, just use empty string
+                result = string.Empty;
+            }
+
+            return result;
+        }
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // Reescape a Win32 style quote string as a NLS+ style quoted string
+        //
+        // This is also the escaping style used by custom culture data files
+        //
+        // NLS+ uses \ to escape the next character, whether in a quoted string or
+        // not, so we always have to change \ to \\.
+        //
+        // NLS+ uses \' to escape a quote inside a quoted string so we have to change
+        // '' to \' (if inside a quoted string)
+        //
+        // We don't build the stringbuilder unless we find something to change
+        ////////////////////////////////////////////////////////////////////////////
+        internal static string ReescapeWin32String(string str)
+        {
+            // If we don't have data, then don't try anything
+            if (str == null)
+                return null;
+
+            StringBuilder result = null;
+
+            bool inQuote = false;
+            for (int i = 0; i < str.Length; i++)
+            {
+                // Look for quote
+                if (str[i] == '\'')
+                {
+                    // Already in quote?
+                    if (inQuote)
+                    {
+                        // See another single quote.  Is this '' of 'fred''s' or '''', or is it an ending quote?
+                        if (i + 1 < str.Length && str[i + 1] == '\'')
+                        {
+                            // Found another ', so we have ''.  Need to add \' instead.
+                            // 1st make sure we have our stringbuilder
+                            if (result == null)
+                                result = new StringBuilder(str, 0, i, str.Length * 2);
+
+                            // Append a \' and keep going (so we don't turn off quote mode)
+                            result.Append("\\'");
+                            i++;
+                            continue;
+                        }
+
+                        // Turning off quote mode, fall through to add it
+                        inQuote = false;
+                    }
+                    else
+                    {
+                        // Found beginning quote, fall through to add it
+                        inQuote = true;
+                    }
+                }
+                // Is there a single \ character?
+                else if (str[i] == '\\')
+                {
+                    // Found a \, need to change it to \\
+                    // 1st make sure we have our stringbuilder
+                    if (result == null)
+                        result = new StringBuilder(str, 0, i, str.Length * 2);
+
+                    // Append our \\ to the string & continue
+                    result.Append("\\\\");
+                    continue;
+                }
+
+                // If we have a builder we need to add our character
+                if (result != null)
+                    result.Append(str[i]);
+            }
+
+            // Unchanged string? , just return input string
+            if (result == null)
+                return str;
+
+            // String changed, need to use the builder
+            return result.ToString();
+        }
+
+        internal static string[] ReescapeWin32Strings(string[] array)
+        {
+            if (array != null)
+            {
+                for (int i = 0; i < array.Length; i++)
+                {
+                    array[i] = ReescapeWin32String(array[i]);
+                }
+            }
+
+            return array;
+        }
+
+        // If we get a group from windows, then its in 3;0 format with the 0 backwards
+        // of how NLS+ uses it (ie: if the string has a 0, then the int[] shouldn't and vice versa)
+        // EXCEPT in the case where the list only contains 0 in which NLS and NLS+ have the same meaning.
+        private static int[] ConvertWin32GroupString(string win32Str)
+        {
+            // None of these cases make any sense
+            if (win32Str == null || win32Str.Length == 0)
+            {
+                return (new int[] { 3 });
+            }
+
+            if (win32Str[0] == '0')
+            {
+                return (new int[] { 0 });
+            }
+
+            // Since its in n;n;n;n;n format, we can always get the length quickly
+            int[] values;
+            if (win32Str[win32Str.Length - 1] == '0')
+            {
+                // Trailing 0 gets dropped. 1;0 -> 1
+                values = new int[(win32Str.Length / 2)];
+            }
+            else
+            {
+                // Need extra space for trailing zero 1 -> 1;0
+                values = new int[(win32Str.Length / 2) + 2];
+                values[values.Length - 1] = 0;
+            }
+
+            int i;
+            int j;
+            for (i = 0, j = 0; i < win32Str.Length && j < values.Length; i += 2, j++)
+            {
+                // Note that this # shouldn't ever be zero, 'cause 0 is only at end
+                // But we'll test because its registry that could be anything
+                if (win32Str[i] < '1' || win32Str[i] > '9')
+                    return new int[] { 3 };
+
+                values[j] = (int)(win32Str[i] - '0');
+            }
+
+            return (values);
+        }
+
+        private static int ConvertFirstDayOfWeekMonToSun(int iTemp)
+        {
+            // Convert Mon-Sun to Sun-Sat format
+            iTemp++;
+            if (iTemp > 6)
+            {
+                // Wrap Sunday and convert invalid data to Sunday
+                iTemp = 0;
+            }
+            return iTemp;
+        }
+
+
+        // Context for EnumCalendarInfoExEx callback.
+        private class EnumLocaleData
+        {
+            public string regionName;
+            public string cultureName;
+        }
+
+        // EnumSystemLocaleEx callback.
+        // [NativeCallable(CallingConvention = CallingConvention.StdCall)]
+        private static unsafe Interop.BOOL EnumSystemLocalesProc(char* lpLocaleString, uint flags, void* contextHandle)
+        {
+            ref EnumLocaleData context = ref Unsafe.As<byte, EnumLocaleData>(ref *(byte*)contextHandle);
+            try
+            {
+                string cultureName = new string(lpLocaleString);
+                string regionName = GetLocaleInfoEx(cultureName, LOCALE_SISO3166CTRYNAME);
+                if (regionName != null && regionName.Equals(context.regionName, StringComparison.OrdinalIgnoreCase))
+                {
+                    context.cultureName = cultureName;
+                    return Interop.BOOL.FALSE; // we found a match, then stop the enumeration
+                }
+
+                return Interop.BOOL.TRUE;
+            }
+            catch (Exception)
+            {
+                return Interop.BOOL.FALSE;
+            }
+        }
+
+        // EnumSystemLocaleEx callback.
+        // [NativeCallable(CallingConvention = CallingConvention.StdCall)]
+        private static unsafe Interop.BOOL EnumAllSystemLocalesProc(char* lpLocaleString, uint flags, void* contextHandle)
+        {
+            ref EnumData context = ref Unsafe.As<byte, EnumData>(ref *(byte*)contextHandle);
+            try
+            {
+                context.strings.Add(new string(lpLocaleString));
+                return Interop.BOOL.TRUE;
+            }
+            catch (Exception)
+            {
+                return Interop.BOOL.FALSE;
+            }
+        }
+
+        // Context for EnumTimeFormatsEx callback.
+        private struct EnumData
+        {
+            public List<string> strings;
+        }
+
+        // EnumTimeFormatsEx callback itself.
+        // [NativeCallable(CallingConvention = CallingConvention.StdCall)]
+        private static unsafe Interop.BOOL EnumTimeCallback(char* lpTimeFormatString, void* lParam)
+        {
+            ref EnumData context = ref Unsafe.As<byte, EnumData>(ref *(byte*)lParam);
+            try
+            {
+                context.strings.Add(new string(lpTimeFormatString));
+                return Interop.BOOL.TRUE;
+            }
+            catch (Exception)
+            {
+                return Interop.BOOL.FALSE;
+            }
+        }
+
+        private static unsafe string[] nativeEnumTimeFormats(string localeName, uint dwFlags, bool useUserOverride)
+        {
+            const uint LOCALE_SSHORTTIME = 0x00000079;
+            const uint LOCALE_STIMEFORMAT = 0x00001003;
+
+            EnumData data = new EnumData();
+            data.strings = new List<string>();
+
+            // Now call the enumeration API. Work is done by our callback function
+            Interop.Kernel32.EnumTimeFormatsEx(EnumTimeCallback, localeName, (uint)dwFlags, Unsafe.AsPointer(ref data));
+
+            if (data.strings.Count > 0)
+            {
+                // Now we need to allocate our stringarray and populate it
+                string[] results = data.strings.ToArray();
+
+                if (!useUserOverride && data.strings.Count > 1)
+                {
+                    // Since there is no "NoUserOverride" aware EnumTimeFormatsEx, we always get an override
+                    // The override is the first entry if it is overriden.
+                    // We can check if we have overrides by checking the GetLocaleInfo with no override
+                    // If we do have an override, we don't know if it is a user defined override or if the
+                    // user has just selected one of the predefined formats so we can't just remove it
+                    // but we can move it down.
+                    uint lcType = (dwFlags == TIME_NOSECONDS) ? LOCALE_SSHORTTIME : LOCALE_STIMEFORMAT;
+                    string timeFormatNoUserOverride = GetLocaleInfoFromLCType(localeName, lcType, useUserOverride);
+                    if (timeFormatNoUserOverride != "")
+                    {
+                        string firstTimeFormat = results[0];
+                        if (timeFormatNoUserOverride != firstTimeFormat)
+                        {
+                            results[0] = results[1];
+                            results[1] = firstTimeFormat;
+                        }
+                    }
+                }
+
+                return results;
+            }
+
+            return null;
+        }
+
+        private static int LocaleNameToLCID(string cultureName)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            return Interop.Kernel32.LocaleNameToLCID(cultureName, Interop.Kernel32.LOCALE_ALLOW_NEUTRAL_NAMES);
+        }
+
+        private static unsafe string LCIDToLocaleName(int culture)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            char *pBuffer = stackalloc char[Interop.Kernel32.LOCALE_NAME_MAX_LENGTH + 1]; // +1 for the null termination
+            int length = Interop.Kernel32.LCIDToLocaleName(culture, pBuffer, Interop.Kernel32.LOCALE_NAME_MAX_LENGTH + 1, Interop.Kernel32.LOCALE_ALLOW_NEUTRAL_NAMES);
+
+            if (length > 0)
+            {
+                return new string(pBuffer);
+            }
+
+            return null;
+        }
+
+        private int GetAnsiCodePage(string cultureName)
+        {
+            return GetLocaleInfo(LocaleNumberData.AnsiCodePage);
+        }
+
+        private int GetOemCodePage(string cultureName)
+        {
+            return GetLocaleInfo(LocaleNumberData.OemCodePage);
+        }
+
+        private int GetMacCodePage(string cultureName)
+        {
+            return GetLocaleInfo(LocaleNumberData.MacCodePage);
+        }
+
+        private int GetEbcdicCodePage(string cultureName)
+        {
+            return GetLocaleInfo(LocaleNumberData.EbcdicCodePage);
+        }
+
+        private int GetGeoId(string cultureName)
+        {
+            return GetLocaleInfo(LocaleNumberData.GeoId);
+        }
+
+        private int GetDigitSubstitution(string cultureName)
+        {
+            return GetLocaleInfo(LocaleNumberData.DigitSubstitution);
+        }
+
+        private string GetThreeLetterWindowsLanguageName(string cultureName)
+        {
+            return GetLocaleInfo(cultureName, LocaleStringData.AbbreviatedWindowsLanguageName);
+        }
+
+        private static CultureInfo[] EnumCultures(CultureTypes types)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            uint flags = 0;
+
+#pragma warning disable 618
+            if ((types & (CultureTypes.FrameworkCultures | CultureTypes.InstalledWin32Cultures | CultureTypes.ReplacementCultures)) != 0)
+            {
+                flags |= Interop.Kernel32.LOCALE_NEUTRALDATA | Interop.Kernel32.LOCALE_SPECIFICDATA;
+            }
+#pragma warning restore 618
+
+            if ((types & CultureTypes.NeutralCultures) != 0)
+            {
+                flags |= Interop.Kernel32.LOCALE_NEUTRALDATA;
+            }
+
+            if ((types & CultureTypes.SpecificCultures) != 0)
+            {
+                flags |= Interop.Kernel32.LOCALE_SPECIFICDATA;
+            }
+
+            if ((types & CultureTypes.UserCustomCulture) != 0)
+            {
+                flags |= Interop.Kernel32.LOCALE_SUPPLEMENTAL;
+            }
+
+            if ((types & CultureTypes.ReplacementCultures) != 0)
+            {
+                flags |= Interop.Kernel32.LOCALE_SUPPLEMENTAL;
+            }
+
+            EnumData context = new EnumData();
+            context.strings = new List<string>();
+
+            unsafe
+            {
+                Interop.Kernel32.EnumSystemLocalesEx(EnumAllSystemLocalesProc, flags, Unsafe.AsPointer(ref context), IntPtr.Zero);
+            }
+
+            CultureInfo [] cultures = new CultureInfo[context.strings.Count];
+            for (int i = 0; i < cultures.Length; i++)
+            {
+                cultures[i] = new CultureInfo(context.strings[i]);
+            }
+
+            return cultures;
+        }
+
+        private string GetConsoleFallbackName(string cultureName)
+        {
+            return GetLocaleInfo(cultureName, LocaleStringData.ConsoleFallbackName);
+        }
+
+        internal bool IsFramework
+        {
+            get { return false; }
+        }
+
+        internal bool IsWin32Installed
+        {
+            get { return true; }
+        }
+
+        internal bool IsReplacementCulture
+        {
+            get
+            {
+                EnumData context = new EnumData();
+                context.strings = new List<string>();
+
+                unsafe
+                {
+                    Interop.Kernel32.EnumSystemLocalesEx(EnumAllSystemLocalesProc, Interop.Kernel32.LOCALE_REPLACEMENT, Unsafe.AsPointer(ref context), IntPtr.Zero);
+                }
+
+                for (int i=0; i<context.strings.Count; i++)
+                {
+                    if (string.Compare(context.strings[i], _sWindowsName, StringComparison.OrdinalIgnoreCase) == 0)
+                        return true;
+                }
+
+                return false;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CultureData.cs b/src/System.Private.CoreLib/shared/System/Globalization/CultureData.cs
new file mode 100644
index 0000000000..fda239c518
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CultureData.cs
@@ -0,0 +1,2574 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Text;
+using System.Threading;
+
+namespace System.Globalization
+{
+#if CORERT
+    using StringStringDictionary = LowLevelDictionary<string, string>;
+    using StringCultureDataDictionary = LowLevelDictionary<string, CultureData>;
+    using LcidToCultureNameDictionary = LowLevelDictionary<int, string>;
+#else
+    using StringStringDictionary = Dictionary<string, string>;
+    using StringCultureDataDictionary = Dictionary<string, CultureData>;
+    using LcidToCultureNameDictionary = Dictionary<int, string>;
+#endif
+
+    //
+    // List of culture data
+    // Note the we cache overrides.
+    // Note that localized names (resource names) aren't available from here.
+    //
+
+    //
+    // Our names are a tad confusing.
+    //
+    // sWindowsName -- The name that windows thinks this culture is, ie:
+    //                            en-US if you pass in en-US
+    //                            de-DE_phoneb if you pass in de-DE_phoneb
+    //                            fj-FJ if you pass in fj (neutral, on a pre-Windows 7 machine)
+    //                            fj if you pass in fj (neutral, post-Windows 7 machine)
+    //
+    // sRealName -- The name you used to construct the culture, in pretty form
+    //                       en-US if you pass in EN-us
+    //                       en if you pass in en
+    //                       de-DE_phoneb if you pass in de-DE_phoneb
+    //
+    // sSpecificCulture -- The specific culture for this culture
+    //                             en-US for en-US
+    //                             en-US for en
+    //                             de-DE_phoneb for alt sort
+    //                             fj-FJ for fj (neutral)
+    //
+    // sName -- The IETF name of this culture (ie: no sort info, could be neutral)
+    //                en-US if you pass in en-US
+    //                en if you pass in en
+    //                de-DE if you pass in de-DE_phoneb
+    //
+    internal partial class CultureData
+    {
+        private const int LOCALE_NAME_MAX_LENGTH = 85;
+        private const int undef = -1;
+
+        // Override flag
+        private string _sRealName; // Name you passed in (ie: en-US, en, or de-DE_phoneb)
+        private string _sWindowsName; // Name OS thinks the object is (ie: de-DE_phoneb, or en-US (even if en was passed in))
+
+        // Identity
+        private string _sName; // locale name (ie: en-us, NO sort info, but could be neutral)
+        private string _sParent; // Parent name (which may be a custom locale/culture)
+        private string _sLocalizedDisplayName; // Localized pretty name for this locale
+        private string _sEnglishDisplayName; // English pretty name for this locale
+        private string _sNativeDisplayName; // Native pretty name for this locale
+        private string _sSpecificCulture; // The culture name to be used in CultureInfo.CreateSpecificCulture(), en-US form if neutral, sort name if sort
+
+        // Language
+        private string _sISO639Language; // ISO 639 Language Name
+        private string _sISO639Language2; // ISO 639 Language Name
+        private string _sLocalizedLanguage; // Localized name for this language
+        private string _sEnglishLanguage; // English name for this language
+        private string _sNativeLanguage; // Native name of this language
+        private string _sAbbrevLang; // abbreviated language name (Windows Language Name) ex: ENU
+        private string _sConsoleFallbackName; // The culture name for the console fallback UI culture
+        private int    _iInputLanguageHandle=undef;// input language handle
+
+        // Region
+        private string _sRegionName; // (RegionInfo)
+        private string _sLocalizedCountry; // localized country name
+        private string _sEnglishCountry; // english country name (RegionInfo)
+        private string _sNativeCountry; // native country name
+        private string _sISO3166CountryName; // ISO 3166 (RegionInfo), ie: US
+        private string _sISO3166CountryName2; // 3 char ISO 3166 country name 2 2(RegionInfo) ex: USA (ISO)
+        private int    _iGeoId = undef; // GeoId
+
+        // Numbers
+        private string _sPositiveSign; // (user can override) positive sign
+        private string _sNegativeSign; // (user can override) negative sign
+        // (nfi populates these 5, don't have to be = undef)
+        private int _iDigits; // (user can override) number of fractional digits
+        private int _iNegativeNumber; // (user can override) negative number format
+        private int[] _waGrouping; // (user can override) grouping of digits
+        private string _sDecimalSeparator; // (user can override) decimal separator
+        private string _sThousandSeparator; // (user can override) thousands separator
+        private string _sNaN; // Not a Number
+        private string _sPositiveInfinity; // + Infinity
+        private string _sNegativeInfinity; // - Infinity
+
+        // Percent
+        private int _iNegativePercent = undef; // Negative Percent (0-3)
+        private int _iPositivePercent = undef; // Positive Percent (0-11)
+        private string _sPercent; // Percent (%) symbol
+        private string _sPerMille; // PerMille symbol
+
+        // Currency
+        private string _sCurrency; // (user can override) local monetary symbol
+        private string _sIntlMonetarySymbol; // international monetary symbol (RegionInfo)
+        private string _sEnglishCurrency; // English name for this currency
+        private string _sNativeCurrency; // Native name for this currency
+        // (nfi populates these 4, don't have to be = undef)
+        private int _iCurrencyDigits; // (user can override) # local monetary fractional digits
+        private int _iCurrency; // (user can override) positive currency format
+        private int _iNegativeCurrency; // (user can override) negative currency format
+        private int[] _waMonetaryGrouping; // (user can override) monetary grouping of digits
+        private string _sMonetaryDecimal; // (user can override) monetary decimal separator
+        private string _sMonetaryThousand; // (user can override) monetary thousands separator
+
+        // Misc
+        private int _iMeasure = undef; // (user can override) system of measurement 0=metric, 1=US (RegionInfo)
+        private string _sListSeparator; // (user can override) list separator
+
+        // Time
+        private string _sAM1159; // (user can override) AM designator
+        private string _sPM2359; // (user can override) PM designator
+        private string _sTimeSeparator;
+        private volatile string[] _saLongTimes; // (user can override) time format
+        private volatile string[] _saShortTimes; // short time format
+        private volatile string[] _saDurationFormats; // time duration format
+
+        // Calendar specific data
+        private int _iFirstDayOfWeek = undef; // (user can override) first day of week (gregorian really)
+        private int _iFirstWeekOfYear = undef; // (user can override) first week of year (gregorian really)
+        private volatile CalendarId[] _waCalendars; // all available calendar type(s).  The first one is the default calendar
+
+        // Store for specific data about each calendar
+        private CalendarData[] _calendars; // Store for specific calendar data
+
+        // Text information
+        private int _iReadingLayout = undef; // Reading layout data
+        // 0 - Left to right (eg en-US)
+        // 1 - Right to left (eg arabic locales)
+        // 2 - Vertical top to bottom with columns to the left and also left to right (ja-JP locales)
+        // 3 - Vertical top to bottom with columns proceeding to the right
+
+        // CoreCLR depends on this even though its not exposed publicly.
+
+        private int _iDefaultAnsiCodePage = undef; // default ansi code page ID (ACP)
+        private int _iDefaultOemCodePage = undef; // default oem code page ID (OCP or OEM)
+        private int _iDefaultMacCodePage = undef; // default macintosh code page
+        private int _iDefaultEbcdicCodePage = undef; // default EBCDIC code page
+
+        private int _iLanguage; // locale ID (0409) - NO sort information
+        private bool _bUseOverrides; // use user overrides?
+        private bool _bNeutral; // Flags for the culture (ie: neutral or not right now)
+
+        // Region Name to Culture Name mapping table
+        // (In future would be nice to be in registry or something)
+
+        //Using a property so we avoid creating the dictionary until we need it
+        private static StringStringDictionary RegionNames
+        {
+            get
+            {
+                if (s_RegionNames == null)
+                {
+                    StringStringDictionary regionNames = new StringStringDictionary(211 /* prime */);
+
+                    regionNames.Add("029", "en-029");
+                    regionNames.Add("AE", "ar-AE");
+                    regionNames.Add("AF", "prs-AF");
+                    regionNames.Add("AL", "sq-AL");
+                    regionNames.Add("AM", "hy-AM");
+                    regionNames.Add("AR", "es-AR");
+                    regionNames.Add("AT", "de-AT");
+                    regionNames.Add("AU", "en-AU");
+                    regionNames.Add("AZ", "az-Cyrl-AZ");
+                    regionNames.Add("BA", "bs-Latn-BA");
+                    regionNames.Add("BD", "bn-BD");
+                    regionNames.Add("BE", "nl-BE");
+                    regionNames.Add("BG", "bg-BG");
+                    regionNames.Add("BH", "ar-BH");
+                    regionNames.Add("BN", "ms-BN");
+                    regionNames.Add("BO", "es-BO");
+                    regionNames.Add("BR", "pt-BR");
+                    regionNames.Add("BY", "be-BY");
+                    regionNames.Add("BZ", "en-BZ");
+                    regionNames.Add("CA", "en-CA");
+                    regionNames.Add("CH", "it-CH");
+                    regionNames.Add("CL", "es-CL");
+                    regionNames.Add("CN", "zh-CN");
+                    regionNames.Add("CO", "es-CO");
+                    regionNames.Add("CR", "es-CR");
+                    regionNames.Add("CS", "sr-Cyrl-CS");
+                    regionNames.Add("CZ", "cs-CZ");
+                    regionNames.Add("DE", "de-DE");
+                    regionNames.Add("DK", "da-DK");
+                    regionNames.Add("DO", "es-DO");
+                    regionNames.Add("DZ", "ar-DZ");
+                    regionNames.Add("EC", "es-EC");
+                    regionNames.Add("EE", "et-EE");
+                    regionNames.Add("EG", "ar-EG");
+                    regionNames.Add("ES", "es-ES");
+                    regionNames.Add("ET", "am-ET");
+                    regionNames.Add("FI", "fi-FI");
+                    regionNames.Add("FO", "fo-FO");
+                    regionNames.Add("FR", "fr-FR");
+                    regionNames.Add("GB", "en-GB");
+                    regionNames.Add("GE", "ka-GE");
+                    regionNames.Add("GL", "kl-GL");
+                    regionNames.Add("GR", "el-GR");
+                    regionNames.Add("GT", "es-GT");
+                    regionNames.Add("HK", "zh-HK");
+                    regionNames.Add("HN", "es-HN");
+                    regionNames.Add("HR", "hr-HR");
+                    regionNames.Add("HU", "hu-HU");
+                    regionNames.Add("ID", "id-ID");
+                    regionNames.Add("IE", "en-IE");
+                    regionNames.Add("IL", "he-IL");
+                    regionNames.Add("IN", "hi-IN");
+                    regionNames.Add("IQ", "ar-IQ");
+                    regionNames.Add("IR", "fa-IR");
+                    regionNames.Add("IS", "is-IS");
+                    regionNames.Add("IT", "it-IT");
+                    regionNames.Add("IV", "");
+                    regionNames.Add("JM", "en-JM");
+                    regionNames.Add("JO", "ar-JO");
+                    regionNames.Add("JP", "ja-JP");
+                    regionNames.Add("KE", "sw-KE");
+                    regionNames.Add("KG", "ky-KG");
+                    regionNames.Add("KH", "km-KH");
+                    regionNames.Add("KR", "ko-KR");
+                    regionNames.Add("KW", "ar-KW");
+                    regionNames.Add("KZ", "kk-KZ");
+                    regionNames.Add("LA", "lo-LA");
+                    regionNames.Add("LB", "ar-LB");
+                    regionNames.Add("LI", "de-LI");
+                    regionNames.Add("LK", "si-LK");
+                    regionNames.Add("LT", "lt-LT");
+                    regionNames.Add("LU", "lb-LU");
+                    regionNames.Add("LV", "lv-LV");
+                    regionNames.Add("LY", "ar-LY");
+                    regionNames.Add("MA", "ar-MA");
+                    regionNames.Add("MC", "fr-MC");
+                    regionNames.Add("ME", "sr-Latn-ME");
+                    regionNames.Add("MK", "mk-MK");
+                    regionNames.Add("MN", "mn-MN");
+                    regionNames.Add("MO", "zh-MO");
+                    regionNames.Add("MT", "mt-MT");
+                    regionNames.Add("MV", "dv-MV");
+                    regionNames.Add("MX", "es-MX");
+                    regionNames.Add("MY", "ms-MY");
+                    regionNames.Add("NG", "ig-NG");
+                    regionNames.Add("NI", "es-NI");
+                    regionNames.Add("NL", "nl-NL");
+                    regionNames.Add("NO", "nn-NO");
+                    regionNames.Add("NP", "ne-NP");
+                    regionNames.Add("NZ", "en-NZ");
+                    regionNames.Add("OM", "ar-OM");
+                    regionNames.Add("PA", "es-PA");
+                    regionNames.Add("PE", "es-PE");
+                    regionNames.Add("PH", "en-PH");
+                    regionNames.Add("PK", "ur-PK");
+                    regionNames.Add("PL", "pl-PL");
+                    regionNames.Add("PR", "es-PR");
+                    regionNames.Add("PT", "pt-PT");
+                    regionNames.Add("PY", "es-PY");
+                    regionNames.Add("QA", "ar-QA");
+                    regionNames.Add("RO", "ro-RO");
+                    regionNames.Add("RS", "sr-Latn-RS");
+                    regionNames.Add("RU", "ru-RU");
+                    regionNames.Add("RW", "rw-RW");
+                    regionNames.Add("SA", "ar-SA");
+                    regionNames.Add("SE", "sv-SE");
+                    regionNames.Add("SG", "zh-SG");
+                    regionNames.Add("SI", "sl-SI");
+                    regionNames.Add("SK", "sk-SK");
+                    regionNames.Add("SN", "wo-SN");
+                    regionNames.Add("SV", "es-SV");
+                    regionNames.Add("SY", "ar-SY");
+                    regionNames.Add("TH", "th-TH");
+                    regionNames.Add("TJ", "tg-Cyrl-TJ");
+                    regionNames.Add("TM", "tk-TM");
+                    regionNames.Add("TN", "ar-TN");
+                    regionNames.Add("TR", "tr-TR");
+                    regionNames.Add("TT", "en-TT");
+                    regionNames.Add("TW", "zh-TW");
+                    regionNames.Add("UA", "uk-UA");
+                    regionNames.Add("US", "en-US");
+                    regionNames.Add("UY", "es-UY");
+                    regionNames.Add("UZ", "uz-Cyrl-UZ");
+                    regionNames.Add("VE", "es-VE");
+                    regionNames.Add("VN", "vi-VN");
+                    regionNames.Add("YE", "ar-YE");
+                    regionNames.Add("ZA", "af-ZA");
+                    regionNames.Add("ZW", "en-ZW");
+
+                    s_RegionNames = regionNames;
+                }
+
+                return s_RegionNames;
+            }
+        }
+
+        // Cache of regions we've already looked up
+        private static volatile StringCultureDataDictionary s_cachedRegions;
+        private static volatile StringStringDictionary s_RegionNames;
+
+        internal static CultureData GetCultureDataForRegion(string cultureName, bool useUserOverride)
+        {
+            // First do a shortcut for Invariant
+            if (string.IsNullOrEmpty(cultureName))
+            {
+                return CultureData.Invariant;
+            }
+
+            //
+            // First check if GetCultureData() can find it (ie: its a real culture)
+            //
+            CultureData retVal = GetCultureData(cultureName, useUserOverride);
+            if (retVal != null && (retVal.IsNeutralCulture == false)) return retVal;
+
+            //
+            // Not a specific culture, perhaps it's region-only name
+            // (Remember this isn't a core clr path where that's not supported)
+            //
+
+            // If it was neutral remember that so that RegionInfo() can throw the right exception
+            CultureData neutral = retVal;
+
+            // Try the hash table next
+            string hashName = AnsiToLower(useUserOverride ? cultureName : cultureName + '*');
+            StringCultureDataDictionary tempHashTable = s_cachedRegions;
+            if (tempHashTable == null)
+            {
+                // No table yet, make a new one
+                tempHashTable = new StringCultureDataDictionary();
+            }
+            else
+            {
+                // Check the hash table
+                lock (s_lock)
+                {
+                    tempHashTable.TryGetValue(hashName, out retVal);
+                }
+                if (retVal != null)
+                {
+                    return retVal;
+                }
+            }
+
+            //
+            // Not found in the hash table, look it up the hard way
+            //
+
+            // If not a valid mapping from the registry we'll have to try the hard coded table
+            if (retVal == null || (retVal.IsNeutralCulture == true))
+            {
+                // Not a valid mapping, try the hard coded table
+                string name;
+                if (RegionNames.TryGetValue(cultureName, out name))
+                {
+                    // Make sure we can get culture data for it
+                    retVal = GetCultureData(name, useUserOverride);
+                }
+            }
+
+            // If not found in the hard coded table we'll have to find a culture that works for us
+            if (!GlobalizationMode.Invariant && (retVal == null || (retVal.IsNeutralCulture == true)))
+            {
+                retVal = GetCultureDataFromRegionName(cultureName);
+            }
+
+            // If we found one we can use, then cache it for next time
+            if (retVal != null && (retVal.IsNeutralCulture == false))
+            {
+                // first add it to the cache
+                lock (s_lock)
+                {
+                    tempHashTable[hashName] = retVal;
+                }
+
+                // Copy the hashtable to the corresponding member variables.  This will potentially overwrite
+                // new tables simultaneously created by a new thread, but maximizes thread safety.
+                s_cachedRegions = tempHashTable;
+            }
+            else
+            {
+                // Unable to find a matching culture/region, return null or neutral
+                // (regionInfo throws a more specific exception on neutrals)
+                retVal = neutral;
+            }
+
+            // Return the found culture to use, null, or the neutral culture.
+            return retVal;
+        }
+
+        // Clear our internal caches
+        internal static void ClearCachedData()
+        {
+            s_cachedCultures = null;
+            s_cachedRegions = null;
+        }
+
+        internal static CultureInfo[] GetCultures(CultureTypes types)
+        {
+            // Disable  warning 618: System.Globalization.CultureTypes.FrameworkCultures' is obsolete
+#pragma warning disable 618
+            // Validate flags
+            if ((int)types <= 0 || ((int)types & (int)~(CultureTypes.NeutralCultures | CultureTypes.SpecificCultures |
+                                                        CultureTypes.InstalledWin32Cultures | CultureTypes.UserCustomCulture |
+                                                        CultureTypes.ReplacementCultures | CultureTypes.WindowsOnlyCultures |
+                                                        CultureTypes.FrameworkCultures)) != 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(types),
+                              SR.Format(SR.ArgumentOutOfRange_Range, CultureTypes.NeutralCultures, CultureTypes.FrameworkCultures));
+            }
+
+            // We have deprecated CultureTypes.FrameworkCultures.
+            // When this enum is used, we will enumerate Whidbey framework cultures (for compatibility).
+
+            // We have deprecated CultureTypes.WindowsOnlyCultures.
+            // When this enum is used, we will return an empty array for this enum.
+            if ((types & CultureTypes.WindowsOnlyCultures) != 0)
+            {
+                // Remove the enum as it is an no-op.
+                types &= (~CultureTypes.WindowsOnlyCultures);
+            }
+
+            if (GlobalizationMode.Invariant)
+            {
+                // in invariant mode we always return invariant culture only from the enumeration
+                return new CultureInfo[1] { new CultureInfo("") };
+            }
+
+#pragma warning restore 618
+            return EnumCultures(types);
+        }
+
+        private static CultureData CreateCultureWithInvariantData()
+        {
+            // Make a new culturedata
+            CultureData invariant = new CultureData();
+
+            // Basics
+            // Note that we override the resources since this IS NOT supposed to change (by definition)
+            invariant._bUseOverrides = false;
+            invariant._sRealName = "";                     // Name you passed in (ie: en-US, en, or de-DE_phoneb)
+            invariant._sWindowsName = "";                     // Name OS thinks the object is (ie: de-DE_phoneb, or en-US (even if en was passed in))
+
+            // Identity
+            invariant._sName = "";                     // locale name (ie: en-us)
+            invariant._sParent = "";                     // Parent name (which may be a custom locale/culture)
+            invariant._bNeutral = false;                   // Flags for the culture (ie: neutral or not right now)
+            invariant._sEnglishDisplayName = "Invariant Language (Invariant Country)"; // English pretty name for this locale
+            invariant._sNativeDisplayName = "Invariant Language (Invariant Country)";  // Native pretty name for this locale
+            invariant._sSpecificCulture = "";                     // The culture name to be used in CultureInfo.CreateSpecificCulture()
+
+            // Language
+            invariant._sISO639Language = "iv";                   // ISO 639 Language Name
+            invariant._sISO639Language2 = "ivl";                  // 3 char ISO 639 lang name 2
+            invariant._sLocalizedLanguage = "Invariant Language";   // Display name for this Language
+            invariant._sEnglishLanguage = "Invariant Language";   // English name for this language
+            invariant._sNativeLanguage = "Invariant Language";   // Native name of this language
+            invariant._sAbbrevLang = "IVL";                  // abbreviated language name (Windows Language Name)
+            invariant._sConsoleFallbackName = "";            // The culture name for the console fallback UI culture
+            invariant._iInputLanguageHandle = 0x07F;         // input language handle
+
+            // Region
+            invariant._sRegionName = "IV";                    // (RegionInfo)
+            invariant._sEnglishCountry = "Invariant Country"; // english country name (RegionInfo)
+            invariant._sNativeCountry = "Invariant Country";  // native country name (Windows Only)
+            invariant._sISO3166CountryName = "IV";            // (RegionInfo), ie: US
+            invariant._sISO3166CountryName2 = "ivc";          // 3 char ISO 3166 country name 2 2(RegionInfo)
+            invariant._iGeoId = 244;                          // GeoId (Windows Only)
+
+            // Numbers
+            invariant._sPositiveSign = "+";                    // positive sign
+            invariant._sNegativeSign = "-";                    // negative sign
+            invariant._iDigits = 2;                      // number of fractional digits
+            invariant._iNegativeNumber = 1;                      // negative number format
+            invariant._waGrouping = new int[] { 3 };          // grouping of digits
+            invariant._sDecimalSeparator = ".";                    // decimal separator
+            invariant._sThousandSeparator = ",";                    // thousands separator
+            invariant._sNaN = "NaN";                  // Not a Number
+            invariant._sPositiveInfinity = "Infinity";             // + Infinity
+            invariant._sNegativeInfinity = "-Infinity";            // - Infinity
+
+            // Percent
+            invariant._iNegativePercent = 0;                      // Negative Percent (0-3)
+            invariant._iPositivePercent = 0;                      // Positive Percent (0-11)
+            invariant._sPercent = "%";                    // Percent (%) symbol
+            invariant._sPerMille = "\x2030";               // PerMille symbol
+
+            // Currency
+            invariant._sCurrency = "\x00a4";                // local monetary symbol: for international monetary symbol
+            invariant._sIntlMonetarySymbol = "XDR";                  // international monetary symbol (RegionInfo)
+            invariant._sEnglishCurrency = "International Monetary Fund"; // English name for this currency (Windows Only)
+            invariant._sNativeCurrency = "International Monetary Fund"; // Native name for this currency (Windows Only)
+            invariant._iCurrencyDigits = 2;                      // # local monetary fractional digits
+            invariant._iCurrency = 0;                      // positive currency format
+            invariant._iNegativeCurrency = 0;                      // negative currency format
+            invariant._waMonetaryGrouping = new int[] { 3 };          // monetary grouping of digits
+            invariant._sMonetaryDecimal = ".";                    // monetary decimal separator
+            invariant._sMonetaryThousand = ",";                    // monetary thousands separator
+
+            // Misc
+            invariant._iMeasure = 0;                      // system of measurement 0=metric, 1=US (RegionInfo)
+            invariant._sListSeparator = ",";                    // list separator
+
+            // Time
+            invariant._sTimeSeparator = ":";
+            invariant._sAM1159 = "AM";                   // AM designator
+            invariant._sPM2359 = "PM";                   // PM designator
+            invariant._saLongTimes = new string[] { "HH:mm:ss" };                             // time format
+            invariant._saShortTimes = new string[] { "HH:mm", "hh:mm tt", "H:mm", "h:mm tt" }; // short time format
+            invariant._saDurationFormats = new string[] { "HH:mm:ss" };                             // time duration format
+
+
+            // Calendar specific data
+            invariant._iFirstDayOfWeek = 0;                      // first day of week
+            invariant._iFirstWeekOfYear = 0;                      // first week of year
+            invariant._waCalendars = new CalendarId[] { CalendarId.GREGORIAN };       // all available calendar type(s).  The first one is the default calendar
+
+            // Store for specific data about each calendar
+            invariant._calendars = new CalendarData[CalendarData.MAX_CALENDARS];
+            invariant._calendars[0] = CalendarData.Invariant;
+
+            // Text information
+            invariant._iReadingLayout = 0;
+
+            // These are desktop only, not coreclr
+
+            invariant._iLanguage = CultureInfo.LOCALE_INVARIANT;   // locale ID (0409) - NO sort information
+            invariant._iDefaultAnsiCodePage = 1252;         // default ansi code page ID (ACP)
+            invariant._iDefaultOemCodePage = 437;           // default oem code page ID (OCP or OEM)
+            invariant._iDefaultMacCodePage = 10000;         // default macintosh code page
+            invariant._iDefaultEbcdicCodePage = 037;        // default EBCDIC code page
+
+            if (GlobalizationMode.Invariant)
+            {
+                invariant._sLocalizedDisplayName = invariant._sNativeDisplayName;
+                invariant._sLocalizedCountry = invariant._sNativeCountry;
+            }
+
+            return invariant;
+        }
+
+        /////////////////////////////////////////////////////////////////////////
+        // Build our invariant information
+        //
+        // We need an invariant instance, which we build hard-coded
+        /////////////////////////////////////////////////////////////////////////
+        internal static CultureData Invariant
+        {
+            get
+            {
+                if (s_Invariant == null)
+                {
+                    // Remember it
+                    s_Invariant = CreateCultureWithInvariantData();
+                }
+                return s_Invariant;
+            }
+        }
+        private volatile static CultureData s_Invariant;
+
+        ///////////////
+        // Constructors //
+        ///////////////
+        // Cache of cultures we've already looked up
+        private static volatile StringCultureDataDictionary s_cachedCultures;
+        private static readonly object s_lock = new object();
+
+        internal static CultureData GetCultureData(string cultureName, bool useUserOverride)
+        {
+            // First do a shortcut for Invariant
+            if (string.IsNullOrEmpty(cultureName))
+            {
+                return CultureData.Invariant;
+            }
+
+            // Try the hash table first
+            string hashName = AnsiToLower(useUserOverride ? cultureName : cultureName + '*');
+            StringCultureDataDictionary tempHashTable = s_cachedCultures;
+            if (tempHashTable == null)
+            {
+                // No table yet, make a new one
+                tempHashTable = new StringCultureDataDictionary();
+            }
+            else
+            {
+                // Check the hash table
+                bool ret;
+                CultureData retVal;
+                lock (s_lock)
+                {
+                    ret = tempHashTable.TryGetValue(hashName, out retVal);
+                }
+                if (ret && retVal != null)
+                {
+                    return retVal;
+                }
+            }
+
+            // Not found in the hash table, need to see if we can build one that works for us
+            CultureData culture = CreateCultureData(cultureName, useUserOverride);
+            if (culture == null)
+            {
+                return null;
+            }
+
+            // Found one, add it to the cache
+            lock (s_lock)
+            {
+                tempHashTable[hashName] = culture;
+            }
+
+            // Copy the hashtable to the corresponding member variables.  This will potentially overwrite
+            // new tables simultaneously created by a new thread, but maximizes thread safety.
+            s_cachedCultures = tempHashTable;
+
+            return culture;
+        }
+
+        private static string NormalizeCultureName(string name, out bool isNeutralName)
+        {
+            isNeutralName = true;
+            int i = 0;
+
+            if (name.Length > LOCALE_NAME_MAX_LENGTH)
+            {
+                // Theoretically we shouldn't hit this exception.
+                throw new ArgumentException(SR.Format(SR.Argument_InvalidId, nameof(name)));
+            }
+
+            Span<char> normalizedName = stackalloc char[name.Length];
+
+            bool changed = false;
+
+            while (i < name.Length && name[i] != '-' && name[i] != '_')
+            {
+                if (name[i] >= 'A' && name[i] <= 'Z')
+                {
+                    // lowercase characters before '-'
+                    normalizedName[i] = (char) (((int)name[i]) + 0x20);
+                    changed = true;
+                }
+                else
+                {
+                    normalizedName[i] = name[i];
+                }
+                i++;
+            }
+
+            if (i < name.Length)
+            {
+                // this is not perfect to detect the non neutral cultures but it is good enough when we are running in invariant mode
+                isNeutralName = false;
+            }
+
+            while (i < name.Length)
+            {
+                if (name[i] >= 'a' && name[i] <= 'z')
+                {
+                    normalizedName[i] = (char) (((int)name[i]) - 0x20);
+                    changed = true;
+                }
+                else
+                {
+                    normalizedName[i] = name[i];
+                }
+                i++;
+            }
+
+            if (changed)
+                return new string(normalizedName);
+
+            return name;
+        }
+
+        private static CultureData CreateCultureData(string cultureName, bool useUserOverride)
+        {
+            if (GlobalizationMode.Invariant)
+            {
+                if (cultureName.Length > LOCALE_NAME_MAX_LENGTH || !CultureInfo.VerifyCultureName(cultureName, false))
+                {
+                    return null;
+                }
+                CultureData cd = CreateCultureWithInvariantData();
+                cd._bUseOverrides = useUserOverride;
+                cd._sName = NormalizeCultureName(cultureName, out cd._bNeutral);
+                cd._sRealName = cd._sName;
+                cd._sWindowsName = cd._sName;
+                cd._iLanguage = CultureInfo.LOCALE_CUSTOM_UNSPECIFIED;
+
+                return cd;
+            }
+
+            CultureData culture = new CultureData();
+            culture._bUseOverrides = useUserOverride;
+            culture._sRealName = cultureName;
+
+            // Ask native code if that one's real
+            if (culture.InitCultureData() == false)
+            {
+                if (culture.InitCompatibilityCultureData() == false)
+                {
+                    return null;
+                }
+            }
+
+            return culture;
+        }
+
+        private bool InitCompatibilityCultureData()
+        {
+            // for compatibility handle the deprecated ids: zh-chs, zh-cht
+            string cultureName = _sRealName;
+
+            string fallbackCultureName;
+            string realCultureName;
+            switch (AnsiToLower(cultureName))
+            {
+                case "zh-chs":
+                    fallbackCultureName = "zh-Hans";
+                    realCultureName = "zh-CHS";
+                    break;
+                case "zh-cht":
+                    fallbackCultureName = "zh-Hant";
+                    realCultureName = "zh-CHT";
+                    break;
+                default:
+                    return false;
+            }
+
+            _sRealName = fallbackCultureName;
+            if (InitCultureData() == false)
+            {
+                return false;
+            }
+            // fixup our data
+            _sName = realCultureName; // the name that goes back to the user
+            _sParent = fallbackCultureName;
+
+            return true;
+        }
+
+        // We'd rather people use the named version since this doesn't allow custom locales
+        internal static CultureData GetCultureData(int culture, bool bUseUserOverride)
+        {
+            string localeName = null;
+            CultureData retVal = null;
+
+            if (culture == CultureInfo.LOCALE_INVARIANT)
+                return Invariant;
+
+            if (GlobalizationMode.Invariant)
+            {
+                // LCID is not supported in the InvariantMode
+                throw new CultureNotFoundException(nameof(culture), culture, SR.Argument_CultureNotSupported);
+            }
+
+            // Convert the lcid to a name, then use that
+            // Note that this will return neutral names (unlike Vista native API)
+            localeName = LCIDToLocaleName(culture);
+
+            if (!string.IsNullOrEmpty(localeName))
+            {
+                // Valid name, use it
+                retVal = GetCultureData(localeName, bUseUserOverride);
+            }
+
+            // If not successful, throw
+            if (retVal == null)
+                throw new CultureNotFoundException(nameof(culture), culture, SR.Argument_CultureNotSupported);
+
+            // Return the one we found
+            return retVal;
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  All the accessors
+        //
+        //  Accessors for our data object items
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        ///////////
+        // Identity //
+        ///////////
+
+        // The real name used to construct the locale (ie: de-DE_phoneb)
+        internal string CultureName
+        {
+            get
+            {
+                Debug.Assert(_sRealName != null, "[CultureData.CultureName] Expected _sRealName to be populated by already");
+                // since windows doesn't know about zh-CHS and zh-CHT,
+                // we leave sRealName == zh-Hanx but we still need to
+                // pretend that it was zh-CHX.
+                switch (_sName)
+                {
+                    case "zh-CHS":
+                    case "zh-CHT":
+                        return _sName;
+                }
+                return _sRealName;
+            }
+        }
+
+        // Are overrides enabled?
+        internal bool UseUserOverride
+        {
+            get
+            {
+                return _bUseOverrides;
+            }
+        }
+
+        // locale name (ie: de-DE, NO sort information)
+        internal string SNAME
+        {
+            get
+            {
+                if (_sName == null)
+                {
+                    _sName = string.Empty;
+                }
+                return _sName;
+            }
+        }
+
+        // Parent name (which may be a custom locale/culture)
+        internal string SPARENT
+        {
+            get
+            {
+                if (_sParent == null)
+                {
+                    // Ask using the real name, so that we get parents of neutrals
+                    _sParent = GetLocaleInfo(_sRealName, LocaleStringData.ParentName);
+                }
+                return _sParent;
+            }
+        }
+
+        // Localized pretty name for this locale (ie: Inglis (estados Unitos))
+        internal string SLOCALIZEDDISPLAYNAME
+        {
+            get
+            {
+                if (_sLocalizedDisplayName == null)
+                {
+                    if (this.IsSupplementalCustomCulture)
+                    {
+                        if (this.IsNeutralCulture)
+                        {
+                            _sLocalizedDisplayName = this.SNATIVELANGUAGE;
+                        }
+                        else
+                        {
+                            _sLocalizedDisplayName = this.SNATIVEDISPLAYNAME;
+                        }
+                    }
+                    else
+                    {
+                        try
+                        {
+                            const string ZH_CHT = "zh-CHT";
+                            const string ZH_CHS = "zh-CHS";
+
+                            if (SNAME.Equals(ZH_CHT, StringComparison.OrdinalIgnoreCase))
+                            {
+                                _sLocalizedDisplayName = GetLanguageDisplayName("zh-Hant");
+                            }
+                            else if (SNAME.Equals(ZH_CHS, StringComparison.OrdinalIgnoreCase))
+                            {
+                                _sLocalizedDisplayName = GetLanguageDisplayName("zh-Hans");
+                            }
+                            else
+                            {
+                                _sLocalizedDisplayName = GetLanguageDisplayName(SNAME);
+                            }
+                        }
+                        catch (Exception)
+                        {
+                            // do nothing
+                        }
+                    }
+                    // If it hasn't been found (Windows 8 and up), fallback to the system
+                    if (string.IsNullOrEmpty(_sLocalizedDisplayName))
+                    {
+                        // If its neutral use the language name
+                        if (this.IsNeutralCulture)
+                        {
+                            _sLocalizedDisplayName = this.SLOCALIZEDLANGUAGE;
+                        }
+                        else
+                        {
+                            // Usually the UI culture shouldn't be different than what we got from WinRT except
+                            // if DefaultThreadCurrentUICulture was set
+                            CultureInfo ci;
+
+                            if (CultureInfo.DefaultThreadCurrentUICulture != null &&
+                                ((ci = GetUserDefaultCulture()) != null) &&
+                                !CultureInfo.DefaultThreadCurrentUICulture.Name.Equals(ci.Name))
+                            {
+                                _sLocalizedDisplayName = this.SNATIVEDISPLAYNAME;
+                            }
+                            else
+                            {
+                                _sLocalizedDisplayName = GetLocaleInfo(LocaleStringData.LocalizedDisplayName);
+                            }
+                        }
+                    }
+                }
+
+                return _sLocalizedDisplayName;
+            }
+        }
+
+        // English pretty name for this locale (ie: English (United States))
+        internal string SENGDISPLAYNAME
+        {
+            get
+            {
+                if (_sEnglishDisplayName == null)
+                {
+                    // If its neutral use the language name
+                    if (this.IsNeutralCulture)
+                    {
+                        _sEnglishDisplayName = this.SENGLISHLANGUAGE;
+                        // differentiate the legacy display names
+                        switch (_sName)
+                        {
+                            case "zh-CHS":
+                            case "zh-CHT":
+                                _sEnglishDisplayName += " Legacy";
+                                break;
+                        }
+                    }
+                    else
+                    {
+                        _sEnglishDisplayName = GetLocaleInfo(LocaleStringData.EnglishDisplayName);
+
+                        // if it isn't found build one:
+                        if (string.IsNullOrEmpty(_sEnglishDisplayName))
+                        {
+                            // Our existing names mostly look like:
+                            // "English" + "United States" -> "English (United States)"
+                            // "Azeri (Latin)" + "Azerbaijan" -> "Azeri (Latin, Azerbaijan)"
+                            if (this.SENGLISHLANGUAGE[this.SENGLISHLANGUAGE.Length - 1] == ')')
+                            {
+                                // "Azeri (Latin)" + "Azerbaijan" -> "Azeri (Latin, Azerbaijan)"
+                                _sEnglishDisplayName =
+                                    this.SENGLISHLANGUAGE.Substring(0, _sEnglishLanguage.Length - 1) +
+                                    ", " + this.SENGCOUNTRY + ")";
+                            }
+                            else
+                            {
+                                // "English" + "United States" -> "English (United States)"
+                                _sEnglishDisplayName = this.SENGLISHLANGUAGE + " (" + this.SENGCOUNTRY + ")";
+                            }
+                        }
+                    }
+                }
+                return _sEnglishDisplayName;
+            }
+        }
+
+        // Native pretty name for this locale (ie: Deutsch (Deutschland))
+        internal string SNATIVEDISPLAYNAME
+        {
+            get
+            {
+                if (_sNativeDisplayName == null)
+                {
+                    // If its neutral use the language name
+                    if (this.IsNeutralCulture)
+                    {
+                        _sNativeDisplayName = this.SNATIVELANGUAGE;
+                        // differentiate the legacy display names
+                        switch (_sName)
+                        {
+                            case "zh-CHS":
+                                _sNativeDisplayName += " \u65E7\u7248";
+                                break;
+                            case "zh-CHT":
+                                _sNativeDisplayName += " \u820A\u7248";
+                                break;
+                        }
+                    }
+                    else
+                    {
+                        _sNativeDisplayName = GetLocaleInfo(LocaleStringData.NativeDisplayName);
+
+                        // if it isn't found build one:
+                        if (string.IsNullOrEmpty(_sNativeDisplayName))
+                        {
+                            // These should primarily be "Deutsch (Deutschland)" type names
+                            _sNativeDisplayName = this.SNATIVELANGUAGE + " (" + this.SNATIVECOUNTRY + ")";
+                        }
+                    }
+                }
+                return _sNativeDisplayName;
+            }
+        }
+
+        // The culture name to be used in CultureInfo.CreateSpecificCulture()
+        internal string SSPECIFICCULTURE
+        {
+            get
+            {
+                // This got populated during the culture initialization
+                Debug.Assert(_sSpecificCulture != null, "[CultureData.SSPECIFICCULTURE] Expected this.sSpecificCulture to be populated by culture data initialization already");
+                return _sSpecificCulture;
+            }
+        }
+
+        /////////////
+        // Language //
+        /////////////
+
+        // iso 639 language name, ie: en
+        internal string SISO639LANGNAME
+        {
+            get
+            {
+                if (_sISO639Language == null)
+                {
+                    _sISO639Language = GetLocaleInfo(LocaleStringData.Iso639LanguageTwoLetterName);
+                }
+                return _sISO639Language;
+            }
+        }
+
+        // iso 639 language name, ie: eng
+        internal string SISO639LANGNAME2
+        {
+            get
+            {
+                if (_sISO639Language2 == null)
+                {
+                    _sISO639Language2 = GetLocaleInfo(LocaleStringData.Iso639LanguageThreeLetterName);
+                }
+                return _sISO639Language2;
+            }
+        }
+
+        // abbreviated windows language name (ie: enu) (non-standard, avoid this)
+        internal string SABBREVLANGNAME
+        {
+            get
+            {
+                if (_sAbbrevLang == null)
+                {
+                    _sAbbrevLang = GetThreeLetterWindowsLanguageName(_sRealName);
+                }
+                return _sAbbrevLang;
+            }
+        }
+
+        // Localized name for this language (Windows Only) ie: Inglis
+        // This is only valid for Windows 8 and higher neutrals:
+        internal string SLOCALIZEDLANGUAGE
+        {
+            get
+            {
+                if (_sLocalizedLanguage == null)
+                {
+                    // Usually the UI culture shouldn't be different than what we got from WinRT except
+                    // if DefaultThreadCurrentUICulture was set
+                    CultureInfo ci;
+
+                    if (CultureInfo.DefaultThreadCurrentUICulture != null &&
+                        ((ci = GetUserDefaultCulture()) != null) &&
+                        !CultureInfo.DefaultThreadCurrentUICulture.Name.Equals(ci.Name))
+                    {
+                        _sLocalizedLanguage = SNATIVELANGUAGE;
+                    }
+                    else
+                    {
+                        _sLocalizedLanguage = GetLocaleInfo(LocaleStringData.LocalizedLanguageName);
+                    }
+                }
+
+                return _sLocalizedLanguage;
+            }
+        }
+
+        // English name for this language (Windows Only) ie: German
+        internal string SENGLISHLANGUAGE
+        {
+            get
+            {
+                if (_sEnglishLanguage == null)
+                {
+                    _sEnglishLanguage = GetLocaleInfo(LocaleStringData.EnglishLanguageName);
+                }
+                return _sEnglishLanguage;
+            }
+        }
+
+        // Native name of this language (Windows Only) ie: Deutsch
+        internal string SNATIVELANGUAGE
+        {
+            get
+            {
+                if (_sNativeLanguage == null)
+                {
+                    _sNativeLanguage = GetLocaleInfo(LocaleStringData.NativeLanguageName);
+                }
+                return _sNativeLanguage;
+            }
+        }
+
+        ///////////
+        // Region //
+        ///////////
+
+        // region name (eg US)
+        internal string SREGIONNAME
+        {
+            get
+            {
+                if (_sRegionName == null)
+                {
+                    _sRegionName = GetLocaleInfo(LocaleStringData.Iso3166CountryName);
+                }
+                return _sRegionName;
+            }
+        }
+
+        internal int IGEOID
+        {
+            get
+            {
+                if (_iGeoId == undef)
+                {
+                    _iGeoId = GetGeoId(_sRealName);
+                }
+                return _iGeoId;
+            }
+        }
+
+        // localized name for the country
+        internal string SLOCALIZEDCOUNTRY
+        {
+            get
+            {
+                if (_sLocalizedCountry == null)
+                {
+                    try
+                    {
+                        _sLocalizedCountry = GetRegionDisplayName(SISO3166CTRYNAME);
+                    }
+                    catch (Exception)
+                    {
+                        // do nothing. we'll fallback
+                    }
+
+                    if (_sLocalizedCountry == null)
+                    {
+                        _sLocalizedCountry = SNATIVECOUNTRY;
+                    }
+                }
+                return _sLocalizedCountry;
+            }
+        }
+
+        // english country name (RegionInfo) ie: Germany
+        internal string SENGCOUNTRY
+        {
+            get
+            {
+                if (_sEnglishCountry == null)
+                {
+                    _sEnglishCountry = GetLocaleInfo(LocaleStringData.EnglishCountryName);
+                }
+                return _sEnglishCountry;
+            }
+        }
+
+        // native country name (RegionInfo) ie: Deutschland
+        internal string SNATIVECOUNTRY
+        {
+            get
+            {
+                if (_sNativeCountry == null)
+                {
+                    _sNativeCountry = GetLocaleInfo(LocaleStringData.NativeCountryName);
+                }
+                return _sNativeCountry;
+            }
+        }
+
+        // ISO 3166 Country Name
+        internal string SISO3166CTRYNAME
+        {
+            get
+            {
+                if (_sISO3166CountryName == null)
+                {
+                    _sISO3166CountryName = GetLocaleInfo(LocaleStringData.Iso3166CountryName);
+                }
+                return _sISO3166CountryName;
+            }
+        }
+
+        // 3 letter ISO 3166 country code
+        internal string SISO3166CTRYNAME2
+        {
+            get
+            {
+                if (_sISO3166CountryName2 == null)
+                {
+                    _sISO3166CountryName2 = GetLocaleInfo(LocaleStringData.Iso3166CountryName2);
+                }
+                return _sISO3166CountryName2;
+            }
+        }
+
+        internal int IINPUTLANGUAGEHANDLE
+        {
+            get
+            {
+                if (_iInputLanguageHandle == undef)
+                {
+                    if (IsSupplementalCustomCulture)
+                    {
+                        _iInputLanguageHandle = 0x0409;
+                    }
+                    else
+                    {
+                        // Input Language is same as LCID for built-in cultures
+                        _iInputLanguageHandle = this.ILANGUAGE;
+                    }
+                }
+                return _iInputLanguageHandle;
+            }
+        }
+
+        // Console fallback name (ie: locale to use for console apps for unicode-only locales)
+        internal string SCONSOLEFALLBACKNAME
+        {
+            get
+            {
+                if (_sConsoleFallbackName == null)
+                {
+                    _sConsoleFallbackName = GetConsoleFallbackName(_sRealName);
+                }
+                return _sConsoleFallbackName;
+            }
+        }
+
+        // (user can override) grouping of digits
+        internal int[] WAGROUPING
+        {
+            get
+            {
+                if (_waGrouping == null)
+                {
+                    _waGrouping = GetLocaleInfo(LocaleGroupingData.Digit);
+                }
+                return _waGrouping;
+            }
+        }
+
+
+        //                internal string _sDecimalSeparator        ; // (user can override) decimal separator
+        //                internal string _sThousandSeparator       ; // (user can override) thousands separator
+
+        // Not a Number
+        internal string SNAN
+        {
+            get
+            {
+                if (_sNaN == null)
+                {
+                    _sNaN = GetLocaleInfo(LocaleStringData.NaNSymbol);
+                }
+                return _sNaN;
+            }
+        }
+
+        // + Infinity
+        internal string SPOSINFINITY
+        {
+            get
+            {
+                if (_sPositiveInfinity == null)
+                {
+                    _sPositiveInfinity = GetLocaleInfo(LocaleStringData.PositiveInfinitySymbol);
+                }
+                return _sPositiveInfinity;
+            }
+        }
+
+        // - Infinity
+        internal string SNEGINFINITY
+        {
+            get
+            {
+                if (_sNegativeInfinity == null)
+                {
+                    _sNegativeInfinity = GetLocaleInfo(LocaleStringData.NegativeInfinitySymbol);
+                }
+                return _sNegativeInfinity;
+            }
+        }
+
+
+        ////////////
+        // Percent //
+        ///////////
+
+        // Negative Percent (0-3)
+        internal int INEGATIVEPERCENT
+        {
+            get
+            {
+                if (_iNegativePercent == undef)
+                {
+                    // Note that <= Windows Vista this is synthesized by native code
+                    _iNegativePercent = GetLocaleInfo(LocaleNumberData.NegativePercentFormat);
+                }
+                return _iNegativePercent;
+            }
+        }
+
+        // Positive Percent (0-11)
+        internal int IPOSITIVEPERCENT
+        {
+            get
+            {
+                if (_iPositivePercent == undef)
+                {
+                    // Note that <= Windows Vista this is synthesized by native code
+                    _iPositivePercent = GetLocaleInfo(LocaleNumberData.PositivePercentFormat);
+                }
+                return _iPositivePercent;
+            }
+        }
+
+        // Percent (%) symbol
+        internal string SPERCENT
+        {
+            get
+            {
+                if (_sPercent == null)
+                {
+                    _sPercent = GetLocaleInfo(LocaleStringData.PercentSymbol);
+                }
+                return _sPercent;
+            }
+        }
+
+        // PerMille symbol
+        internal string SPERMILLE
+        {
+            get
+            {
+                if (_sPerMille == null)
+                {
+                    _sPerMille = GetLocaleInfo(LocaleStringData.PerMilleSymbol);
+                }
+                return _sPerMille;
+            }
+        }
+
+        /////////////
+        // Currency //
+        /////////////
+
+        // (user can override) local monetary symbol, eg: $
+        internal string SCURRENCY
+        {
+            get
+            {
+                if (_sCurrency == null)
+                {
+                    _sCurrency = GetLocaleInfo(LocaleStringData.MonetarySymbol);
+                }
+                return _sCurrency;
+            }
+        }
+
+        // international monetary symbol (RegionInfo), eg: USD
+        internal string SINTLSYMBOL
+        {
+            get
+            {
+                if (_sIntlMonetarySymbol == null)
+                {
+                    _sIntlMonetarySymbol = GetLocaleInfo(LocaleStringData.Iso4217MonetarySymbol);
+                }
+                return _sIntlMonetarySymbol;
+            }
+        }
+
+        // English name for this currency (RegionInfo), eg: US Dollar
+        internal string SENGLISHCURRENCY
+        {
+            get
+            {
+                if (_sEnglishCurrency == null)
+                {
+                    _sEnglishCurrency = GetLocaleInfo(LocaleStringData.CurrencyEnglishName);
+                }
+                return _sEnglishCurrency;
+            }
+        }
+
+        // Native name for this currency (RegionInfo), eg: Schweiz Frank
+        internal string SNATIVECURRENCY
+        {
+            get
+            {
+                if (_sNativeCurrency == null)
+                {
+                    _sNativeCurrency = GetLocaleInfo(LocaleStringData.CurrencyNativeName);
+                }
+                return _sNativeCurrency;
+            }
+        }
+
+        //                internal int iCurrencyDigits          ; // (user can override) # local monetary fractional digits
+        //                internal int iCurrency                ; // (user can override) positive currency format
+        //                internal int iNegativeCurrency        ; // (user can override) negative currency format
+
+        // (user can override) monetary grouping of digits
+        internal int[] WAMONGROUPING
+        {
+            get
+            {
+                if (_waMonetaryGrouping == null)
+                {
+                    _waMonetaryGrouping = GetLocaleInfo(LocaleGroupingData.Monetary);
+                }
+                return _waMonetaryGrouping;
+            }
+        }
+
+        // (user can override) system of measurement 0=metric, 1=US (RegionInfo)
+        internal int IMEASURE
+        {
+            get
+            {
+                if (_iMeasure == undef)
+                {
+                    _iMeasure = GetLocaleInfo(LocaleNumberData.MeasurementSystem);
+                }
+                return _iMeasure;
+            }
+        }
+
+        // (user can override) list Separator
+        internal string SLIST
+        {
+            get
+            {
+                if (_sListSeparator == null)
+                {
+                    _sListSeparator = GetLocaleInfo(LocaleStringData.ListSeparator);
+                }
+                return _sListSeparator;
+            }
+        }
+
+
+        ////////////////////////////
+        // Calendar/Time (Gregorian) //
+        ////////////////////////////
+
+        // (user can override) AM designator
+        internal string SAM1159
+        {
+            get
+            {
+                if (_sAM1159 == null)
+                {
+                    _sAM1159 = GetLocaleInfo(LocaleStringData.AMDesignator);
+                }
+                return _sAM1159;
+            }
+        }
+
+        // (user can override) PM designator
+        internal string SPM2359
+        {
+            get
+            {
+                if (_sPM2359 == null)
+                {
+                    _sPM2359 = GetLocaleInfo(LocaleStringData.PMDesignator);
+                }
+                return _sPM2359;
+            }
+        }
+
+        // (user can override) time format
+        internal string[] LongTimes
+        {
+            get
+            {
+                if (_saLongTimes == null)
+                {
+                    Debug.Assert(!GlobalizationMode.Invariant);
+
+                    string[] longTimes = GetTimeFormats();
+                    if (longTimes == null || longTimes.Length == 0)
+                    {
+                        _saLongTimes = Invariant._saLongTimes;
+                    }
+                    else
+                    {
+                        _saLongTimes = longTimes;
+                    }
+                }
+                return _saLongTimes;
+            }
+        }
+
+        // short time format
+        // Short times (derived from long times format)
+        // TODO: NLS Arrowhead -  On Windows 7 we should have short times so this isn't necessary
+        internal string[] ShortTimes
+        {
+            get
+            {
+                if (_saShortTimes == null)
+                {
+                    Debug.Assert(!GlobalizationMode.Invariant);
+
+                    // Try to get the short times from the OS/culture.dll
+                    string[] shortTimes = null;
+                    shortTimes = GetShortTimeFormats();
+
+                    if (shortTimes == null || shortTimes.Length == 0)
+                    {
+                        //
+                        // If we couldn't find short times, then compute them from long times
+                        // (eg: CORECLR on < Win7 OS & fallback for missing culture.dll)
+                        //
+                        shortTimes = DeriveShortTimesFromLong();
+                    }
+
+                    /* The above logic doesn't make sense on Mac, since the OS can provide us a "short time pattern".
+                     * currently this is the 4th element in the array returned by LongTimes.  We'll add this to our array
+                     * if it doesn't exist.
+                     */
+                    shortTimes = AdjustShortTimesForMac(shortTimes);
+
+                    // Found short times, use them
+                    _saShortTimes = shortTimes;
+                }
+                return _saShortTimes;
+            }
+        }
+
+        private string[] AdjustShortTimesForMac(string[] shortTimes)
+        {
+            return shortTimes;
+        }
+
+        private string[] DeriveShortTimesFromLong()
+        {
+            // Our logic is to look for h,H,m,s,t.  If we find an s, then we check the string
+            // between it and the previous marker, if any.  If its a short, unescaped separator,
+            // then we don't retain that part.
+            // We then check after the ss and remove anything before the next h,H,m,t...
+            string[] longTimes = LongTimes;
+            string[] shortTimes = new string[longTimes.Length];
+
+            for (int i = 0; i < longTimes.Length; i++)
+            {
+                shortTimes[i] = StripSecondsFromPattern(longTimes[i]);
+            }
+            return shortTimes;
+        }
+
+        private static string StripSecondsFromPattern(string time)
+        {
+            bool bEscape = false;
+            int iLastToken = -1;
+
+            // Find the seconds
+            for (int j = 0; j < time.Length; j++)
+            {
+                // Change escape mode?
+                if (time[j] == '\'')
+                {
+                    // Continue
+                    bEscape = !bEscape;
+                    continue;
+                }
+
+                // See if there was a single \
+                if (time[j] == '\\')
+                {
+                    // Skip next char
+                    j++;
+                    continue;
+                }
+
+                if (bEscape)
+                {
+                    continue;
+                }
+
+                switch (time[j])
+                {
+                    // Check for seconds
+                    case 's':
+                        // Found seconds, see if there was something unescaped and short between
+                        // the last marker and the seconds.  Windows says separator can be a
+                        // maximum of three characters (without null)
+                        // If 1st or last characters were ', then ignore it
+                        if ((j - iLastToken) <= 4 && (j - iLastToken) > 1 &&
+                            (time[iLastToken + 1] != '\'') &&
+                            (time[j - 1] != '\''))
+                        {
+                            // There was something there we want to remember
+                            if (iLastToken >= 0)
+                            {
+                                j = iLastToken + 1;
+                            }
+                        }
+
+                        bool containsSpace;
+                        int endIndex = GetIndexOfNextTokenAfterSeconds(time, j, out containsSpace);
+
+                        string sep;
+
+                        if (containsSpace)
+                        {
+                            sep = " ";
+                        }
+                        else
+                        {
+                            sep = "";
+                        }
+
+                        time = time.Substring(0, j) + sep + time.Substring(endIndex);
+                        break;
+                    case 'm':
+                    case 'H':
+                    case 'h':
+                        iLastToken = j;
+                        break;
+                }
+            }
+            return time;
+        }
+
+        private static int GetIndexOfNextTokenAfterSeconds(string time, int index, out bool containsSpace)
+        {
+            bool bEscape = false;
+            containsSpace = false;
+            for (; index < time.Length; index++)
+            {
+                switch (time[index])
+                {
+                    case '\'':
+                        bEscape = !bEscape;
+                        continue;
+                    case '\\':
+                        index++;
+                        if (time[index] == ' ')
+                        {
+                            containsSpace = true;
+                        }
+                        continue;
+                    case ' ':
+                        containsSpace = true;
+                        break;
+                    case 't':
+                    case 'm':
+                    case 'H':
+                    case 'h':
+                        if (bEscape)
+                        {
+                            continue;
+                        }
+                        return index;
+                }
+            }
+            containsSpace = false;
+            return index;
+        }
+
+        // (user can override) first day of week
+        internal int IFIRSTDAYOFWEEK
+        {
+            get
+            {
+                if (_iFirstDayOfWeek == undef)
+                {
+                    _iFirstDayOfWeek = GetFirstDayOfWeek();
+                }
+                return _iFirstDayOfWeek;
+            }
+        }
+
+        // (user can override) first week of year
+        internal int IFIRSTWEEKOFYEAR
+        {
+            get
+            {
+                if (_iFirstWeekOfYear == undef)
+                {
+                    _iFirstWeekOfYear = GetLocaleInfo(LocaleNumberData.FirstWeekOfYear);
+                }
+                return _iFirstWeekOfYear;
+            }
+        }
+
+        // (user can override default only) short date format
+        internal string[] ShortDates(CalendarId calendarId)
+        {
+            return GetCalendar(calendarId).saShortDates;
+        }
+
+        // (user can override default only) long date format
+        internal string[] LongDates(CalendarId calendarId)
+        {
+            return GetCalendar(calendarId).saLongDates;
+        }
+
+        // (user can override) date year/month format.
+        internal string[] YearMonths(CalendarId calendarId)
+        {
+            return GetCalendar(calendarId).saYearMonths;
+        }
+
+        // day names
+        internal string[] DayNames(CalendarId calendarId)
+        {
+            return GetCalendar(calendarId).saDayNames;
+        }
+
+        // abbreviated day names
+        internal string[] AbbreviatedDayNames(CalendarId calendarId)
+        {
+            // Get abbreviated day names for this calendar from the OS if necessary
+            return GetCalendar(calendarId).saAbbrevDayNames;
+        }
+
+        // The super short day names
+        internal string[] SuperShortDayNames(CalendarId calendarId)
+        {
+            return GetCalendar(calendarId).saSuperShortDayNames;
+        }
+
+        // month names
+        internal string[] MonthNames(CalendarId calendarId)
+        {
+            return GetCalendar(calendarId).saMonthNames;
+        }
+
+        // Genitive month names
+        internal string[] GenitiveMonthNames(CalendarId calendarId)
+        {
+            return GetCalendar(calendarId).saMonthGenitiveNames;
+        }
+
+        // month names
+        internal string[] AbbreviatedMonthNames(CalendarId calendarId)
+        {
+            return GetCalendar(calendarId).saAbbrevMonthNames;
+        }
+
+        // Genitive month names
+        internal string[] AbbreviatedGenitiveMonthNames(CalendarId calendarId)
+        {
+            return GetCalendar(calendarId).saAbbrevMonthGenitiveNames;
+        }
+
+        // Leap year month names
+        // Note: This only applies to Hebrew, and it basically adds a "1" to the 6th month name
+        // the non-leap names skip the 7th name in the normal month name array
+        internal string[] LeapYearMonthNames(CalendarId calendarId)
+        {
+            return GetCalendar(calendarId).saLeapYearMonthNames;
+        }
+
+        // month/day format (single string, no override)
+        internal string MonthDay(CalendarId calendarId)
+        {
+            return GetCalendar(calendarId).sMonthDay;
+        }
+
+
+
+        /////////////
+        // Calendars //
+        /////////////
+
+        // all available calendar type(s), The first one is the default calendar.
+        internal CalendarId[] CalendarIds
+        {
+            get
+            {
+                if (_waCalendars == null)
+                {
+                    // We pass in an array of ints, and native side fills it up with count calendars.
+                    // We then have to copy that list to a new array of the right size.
+                    // Default calendar should be first
+                    CalendarId[] calendars = new CalendarId[23];
+                    Debug.Assert(_sWindowsName != null, "[CultureData.CalendarIds] Expected _sWindowsName to be populated by already");
+                    int count = CalendarData.GetCalendars(_sWindowsName, _bUseOverrides, calendars);
+
+                    // See if we had a calendar to add.
+                    if (count == 0)
+                    {
+                        // Failed for some reason, just grab Gregorian from Invariant
+                        _waCalendars = Invariant._waCalendars;
+                    }
+                    else
+                    {
+                        // The OS may not return calendar 4 for zh-TW, but we've always allowed it.
+                        // TODO: Is this hack necessary long-term?
+                        if (_sWindowsName == "zh-TW")
+                        {
+                            bool found = false;
+
+                            // Do we need to insert calendar 4?
+                            for (int i = 0; i < count; i++)
+                            {
+                                // Stop if we found calendar four
+                                if (calendars[i] == CalendarId.TAIWAN)
+                                {
+                                    found = true;
+                                    break;
+                                }
+                            }
+
+                            // If not found then insert it
+                            if (!found)
+                            {
+                                // Insert it as the 2nd calendar
+                                count++;
+                                // Copy them from the 2nd position to the end, -1 for skipping 1st, -1 for one being added.
+                                Array.Copy(calendars, 1, calendars, 2, 23 - 1 - 1);
+                                calendars[1] = CalendarId.TAIWAN;
+                            }
+                        }
+
+                        // It worked, remember the list
+                        CalendarId[] temp = new CalendarId[count];
+                        Array.Copy(calendars, temp, count);
+
+                        // Want 1st calendar to be default
+                        // Prior to Vista the enumeration didn't have default calendar first
+                        if (temp.Length > 1)
+                        {
+                            CalendarId i = (CalendarId)GetLocaleInfo(LocaleNumberData.CalendarType);
+                            if (temp[1] == i)
+                            {
+                                temp[1] = temp[0];
+                                temp[0] = i;
+                            }
+                        }
+
+                        _waCalendars = temp;
+                    }
+                }
+
+                return _waCalendars;
+            }
+        }
+
+        // Native calendar names.  index of optional calendar - 1, empty if no optional calendar at that number
+        internal string CalendarName(CalendarId calendarId)
+        {
+            // Get the calendar
+            return GetCalendar(calendarId).sNativeName;
+        }
+
+        internal CalendarData GetCalendar(CalendarId calendarId)
+        {
+            Debug.Assert(calendarId > 0 && calendarId <= CalendarId.LAST_CALENDAR,
+                "[CultureData.GetCalendar] Expect calendarId to be in a valid range");
+
+            // arrays are 0 based, calendarIds are 1 based
+            int calendarIndex = (int)calendarId - 1;
+
+            // Have to have calendars
+            if (_calendars == null)
+            {
+                _calendars = new CalendarData[CalendarData.MAX_CALENDARS];
+            }
+
+            // we need the following local variable to avoid returning null
+            // when another thread creates a new array of CalendarData (above)
+            // right after we insert the newly created CalendarData (below)
+            CalendarData calendarData = _calendars[calendarIndex];
+            // Make sure that calendar has data
+            if (calendarData == null)
+            {
+                Debug.Assert(_sWindowsName != null, "[CultureData.GetCalendar] Expected _sWindowsName to be populated by already");
+                calendarData = new CalendarData(_sWindowsName, calendarId, this.UseUserOverride);
+                _calendars[calendarIndex] = calendarData;
+            }
+
+            return calendarData;
+        }
+
+        ///////////////////
+        // Text Information //
+        ///////////////////
+
+        // IsRightToLeft
+        internal bool IsRightToLeft
+        {
+            get
+            {
+                // Returns one of the following 4 reading layout values:
+                // 0 - Left to right (eg en-US)
+                // 1 - Right to left (eg arabic locales)
+                // 2 - Vertical top to bottom with columns to the left and also left to right (ja-JP locales)
+                // 3 - Vertical top to bottom with columns proceeding to the right
+                return (this.IREADINGLAYOUT == 1);
+            }
+        }
+
+        // IREADINGLAYOUT
+        // Returns one of the following 4 reading layout values:
+        // 0 - Left to right (eg en-US)
+        // 1 - Right to left (eg arabic locales)
+        // 2 - Vertical top to bottom with columns to the left and also left to right (ja-JP locales)
+        // 3 - Vertical top to bottom with columns proceeding to the right
+        //
+        // If exposed as a public API, we'd have an enum with those 4 values
+        private int IREADINGLAYOUT
+        {
+            get
+            {
+                if (_iReadingLayout == undef)
+                {
+                    Debug.Assert(_sRealName != null, "[CultureData.IsRightToLeft] Expected _sRealName to be populated by already");
+                    _iReadingLayout = GetLocaleInfo(LocaleNumberData.ReadingLayout);
+                }
+
+                return (_iReadingLayout);
+            }
+        }
+
+        // The TextInfo name never includes that alternate sort and is always specific
+        // For customs, it uses the SortLocale (since the textinfo is not exposed in Win7)
+        // en -> en-US
+        // en-US -> en-US
+        // fj (custom neutral) -> en-US (assuming that en-US is the sort locale for fj)
+        // fj_FJ (custom specific) -> en-US (assuming that en-US is the sort locale for fj-FJ)
+        // es-ES_tradnl -> es-ES
+        internal string STEXTINFO               // Text info name to use for text information
+        {
+            get
+            {
+                // Note: Custom cultures might point at another culture's textinfo, however windows knows how
+                // to redirect it to the desired textinfo culture, so this is OK.
+                Debug.Assert(_sRealName != null, "[CultureData.STEXTINFO] Expected _sRealName to be populated by already");
+                return (_sRealName);
+            }
+        }
+
+        // Compare info name (including sorting key) to use if custom
+        internal string SCOMPAREINFO
+        {
+            get
+            {
+                Debug.Assert(_sRealName != null, "[CultureData.SCOMPAREINFO] Expected _sRealName to be populated by already");
+                return (_sRealName);
+            }
+        }
+
+        internal bool IsSupplementalCustomCulture
+        {
+            get
+            {
+                return IsCustomCultureId(this.ILANGUAGE);
+            }
+        }
+
+        internal int IDEFAULTANSICODEPAGE   // default ansi code page ID (ACP)
+        {
+            get
+            {
+                if (_iDefaultAnsiCodePage == undef)
+                {
+                    _iDefaultAnsiCodePage = GetAnsiCodePage(_sRealName);
+                }
+                return _iDefaultAnsiCodePage;
+            }
+        }
+
+        internal int IDEFAULTOEMCODEPAGE   // default oem code page ID (OCP or OEM)
+        {
+            get
+            {
+                if (_iDefaultOemCodePage == undef)
+                {
+                    _iDefaultOemCodePage = GetOemCodePage(_sRealName);
+                }
+                return _iDefaultOemCodePage;
+            }
+        }
+
+        internal int IDEFAULTMACCODEPAGE   // default macintosh code page
+        {
+            get
+            {
+                if (_iDefaultMacCodePage == undef)
+                {
+                    _iDefaultMacCodePage = GetMacCodePage(_sRealName);
+                }
+                return _iDefaultMacCodePage;
+            }
+        }
+
+        internal int IDEFAULTEBCDICCODEPAGE   // default EBCDIC code page
+        {
+            get
+            {
+                if (_iDefaultEbcdicCodePage == undef)
+                {
+                    _iDefaultEbcdicCodePage = GetEbcdicCodePage(_sRealName);
+                }
+                return _iDefaultEbcdicCodePage;
+            }
+        }
+
+        internal int ILANGUAGE
+        {
+            get
+            {
+                if (_iLanguage == 0)
+                {
+                    Debug.Assert(_sRealName != null, "[CultureData.ILANGUAGE] Expected this.sRealName to be populated already");
+                    _iLanguage = LocaleNameToLCID(_sRealName);
+                }
+                return _iLanguage;
+            }
+        }
+
+        internal bool IsNeutralCulture
+        {
+            get
+            {
+                // InitCultureData told us if we're neutral or not
+                return _bNeutral;
+            }
+        }
+
+        internal bool IsInvariantCulture
+        {
+            get
+            {
+                return string.IsNullOrEmpty(this.SNAME);
+            }
+        }
+
+        // Get an instance of our default calendar
+        internal Calendar DefaultCalendar
+        {
+            get
+            {
+                if (GlobalizationMode.Invariant)
+                {
+                    return CultureInfo.GetCalendarInstance(CalendarIds[0]);
+                }
+
+                CalendarId defaultCalId = (CalendarId)GetLocaleInfo(LocaleNumberData.CalendarType);
+
+                if (defaultCalId == 0)
+                {
+                    defaultCalId = this.CalendarIds[0];
+                }
+
+                return CultureInfo.GetCalendarInstance(defaultCalId);
+            }
+        }
+
+        // All of our era names
+        internal string[] EraNames(CalendarId calendarId)
+        {
+            Debug.Assert(calendarId > 0, "[CultureData.saEraNames] Expected Calendar.ID > 0");
+
+            return this.GetCalendar(calendarId).saEraNames;
+        }
+
+        internal string[] AbbrevEraNames(CalendarId calendarId)
+        {
+            Debug.Assert(calendarId > 0, "[CultureData.saAbbrevEraNames] Expected Calendar.ID > 0");
+
+            return this.GetCalendar(calendarId).saAbbrevEraNames;
+        }
+
+        internal string[] AbbreviatedEnglishEraNames(CalendarId calendarId)
+        {
+            Debug.Assert(calendarId > 0, "[CultureData.saAbbrevEraNames] Expected Calendar.ID > 0");
+
+            return this.GetCalendar(calendarId).saAbbrevEnglishEraNames;
+        }
+
+        //// string array DEFAULTS
+        //// Note: GetDTFIOverrideValues does the user overrides for these, so we don't have to.
+
+
+        // Time separator (derived from time format)
+        internal string TimeSeparator
+        {
+            get
+            {
+                if (_sTimeSeparator == null)
+                {
+                    string longTimeFormat = GetTimeFormatString();
+                    if (string.IsNullOrEmpty(longTimeFormat))
+                    {
+                        longTimeFormat = LongTimes[0];
+                    }
+
+                    // Compute STIME from time format
+                    _sTimeSeparator = GetTimeSeparator(longTimeFormat);
+                }
+                return _sTimeSeparator;
+            }
+        }
+
+        // Date separator (derived from short date format)
+        internal string DateSeparator(CalendarId calendarId)
+        {
+            return GetDateSeparator(ShortDates(calendarId)[0]);
+        }
+
+        //////////////////////////////////////
+        // Helper Functions to get derived properties //
+        //////////////////////////////////////
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // Unescape a NLS style quote string
+        //
+        // This removes single quotes:
+        //      'fred' -> fred
+        //      'fred -> fred
+        //      fred' -> fred
+        //      fred's -> freds
+        //
+        // This removes the first \ of escaped characters:
+        //      fred\'s -> fred's
+        //      a\\b -> a\b
+        //      a\b -> ab
+        //
+        // We don't build the stringbuilder unless we find a ' or a \.  If we find a ' or a \, we
+        // always build a stringbuilder because we need to remove the ' or \.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+        private static string UnescapeNlsString(string str, int start, int end)
+        {
+            Debug.Assert(str != null);
+            Debug.Assert(start >= 0);
+            Debug.Assert(end >= 0);
+            StringBuilder result = null;
+
+            for (int i = start; i < str.Length && i <= end; i++)
+            {
+                switch (str[i])
+                {
+                    case '\'':
+                        if (result == null)
+                        {
+                            result = new StringBuilder(str, start, i - start, str.Length);
+                        }
+                        break;
+                    case '\\':
+                        if (result == null)
+                        {
+                            result = new StringBuilder(str, start, i - start, str.Length);
+                        }
+                        ++i;
+                        if (i < str.Length)
+                        {
+                            result.Append(str[i]);
+                        }
+                        break;
+                    default:
+                        if (result != null)
+                        {
+                            result.Append(str[i]);
+                        }
+                        break;
+                }
+            }
+
+            if (result == null)
+                return (str.Substring(start, end - start + 1));
+
+            return (result.ToString());
+        }
+
+        private static string GetTimeSeparator(string format)
+        {
+            // Time format separator (ie: : in 12:39:00)
+            //
+            // We calculate this from the provided time format
+            //
+
+            //
+            //  Find the time separator so that we can pretend we know STIME.
+            //
+            return GetSeparator(format, "Hhms");
+        }
+
+        private static string GetDateSeparator(string format)
+        {
+            // Date format separator (ie: / in 9/1/03)
+            //
+            // We calculate this from the provided short date
+            //
+
+            //
+            //  Find the date separator so that we can pretend we know SDATE.
+            //
+            return GetSeparator(format, "dyM");
+        }
+
+        private static string GetSeparator(string format, string timeParts)
+        {
+            int index = IndexOfTimePart(format, 0, timeParts);
+
+            if (index != -1)
+            {
+                // Found a time part, find out when it changes
+                char cTimePart = format[index];
+
+                do
+                {
+                    index++;
+                } while (index < format.Length && format[index] == cTimePart);
+
+                int separatorStart = index;
+
+                // Now we need to find the end of the separator
+                if (separatorStart < format.Length)
+                {
+                    int separatorEnd = IndexOfTimePart(format, separatorStart, timeParts);
+                    if (separatorEnd != -1)
+                    {
+                        // From [separatorStart, count) is our string, except we need to unescape
+                        return UnescapeNlsString(format, separatorStart, separatorEnd - 1);
+                    }
+                }
+            }
+
+            return string.Empty;
+        }
+
+        private static int IndexOfTimePart(string format, int startIndex, string timeParts)
+        {
+            Debug.Assert(startIndex >= 0, "startIndex cannot be negative");
+            Debug.Assert(timeParts.IndexOfAny(new char[] { '\'', '\\' }) == -1, "timeParts cannot include quote characters");
+            bool inQuote = false;
+            for (int i = startIndex; i < format.Length; ++i)
+            {
+                // See if we have a time Part
+                if (!inQuote && timeParts.IndexOf(format[i]) != -1)
+                {
+                    return i;
+                }
+                switch (format[i])
+                {
+                    case '\\':
+                        if (i + 1 < format.Length)
+                        {
+                            ++i;
+                            switch (format[i])
+                            {
+                                case '\'':
+                                case '\\':
+                                    break;
+                                default:
+                                    --i; //backup since we will move over this next
+                                    break;
+                            }
+                        }
+                        break;
+                    case '\'':
+                        inQuote = !inQuote;
+                        break;
+                }
+            }
+
+            return -1;
+        }
+
+        internal static bool IsCustomCultureId(int cultureId)
+        {
+            return (cultureId == CultureInfo.LOCALE_CUSTOM_DEFAULT || cultureId == CultureInfo.LOCALE_CUSTOM_UNSPECIFIED);
+        }
+
+        internal void GetNFIValues(NumberFormatInfo nfi)
+        {
+            if (GlobalizationMode.Invariant || this.IsInvariantCulture)
+            {
+                // FUTURE: NumberFormatInfo already has default values for many of these fields.  Can we not do this?
+                nfi.positiveSign = _sPositiveSign;
+                nfi.negativeSign = _sNegativeSign;
+
+                nfi.numberGroupSeparator = _sThousandSeparator;
+                nfi.numberDecimalSeparator = _sDecimalSeparator;
+                nfi.numberDecimalDigits = _iDigits;
+                nfi.numberNegativePattern = _iNegativeNumber;
+
+                nfi.currencySymbol = _sCurrency;
+                nfi.currencyGroupSeparator = _sMonetaryThousand;
+                nfi.currencyDecimalSeparator = _sMonetaryDecimal;
+                nfi.currencyDecimalDigits = _iCurrencyDigits;
+                nfi.currencyNegativePattern = _iNegativeCurrency;
+                nfi.currencyPositivePattern = _iCurrency;
+            }
+            else
+            {
+                Debug.Assert(_sWindowsName != null, "[CultureData.GetNFIValues] Expected _sWindowsName to be populated by already");
+                // String values
+                nfi.positiveSign = GetLocaleInfo(LocaleStringData.PositiveSign);
+                nfi.negativeSign = GetLocaleInfo(LocaleStringData.NegativeSign);
+
+                nfi.numberDecimalSeparator = GetLocaleInfo(LocaleStringData.DecimalSeparator);
+                nfi.numberGroupSeparator = GetLocaleInfo(LocaleStringData.ThousandSeparator);
+                nfi.currencyGroupSeparator = GetLocaleInfo(LocaleStringData.MonetaryThousandSeparator);
+                nfi.currencyDecimalSeparator = GetLocaleInfo(LocaleStringData.MonetaryDecimalSeparator);
+                nfi.currencySymbol = GetLocaleInfo(LocaleStringData.MonetarySymbol);
+
+                // Numeric values
+                nfi.numberDecimalDigits = GetLocaleInfo(LocaleNumberData.FractionalDigitsCount);
+                nfi.currencyDecimalDigits = GetLocaleInfo(LocaleNumberData.MonetaryFractionalDigitsCount);
+                nfi.currencyPositivePattern = GetLocaleInfo(LocaleNumberData.PositiveMonetaryNumberFormat);
+                nfi.currencyNegativePattern = GetLocaleInfo(LocaleNumberData.NegativeMonetaryNumberFormat);
+                nfi.numberNegativePattern = GetLocaleInfo(LocaleNumberData.NegativeNumberFormat);
+
+                // LOCALE_SNATIVEDIGITS (array of 10 single character strings).
+                string digits = GetLocaleInfo(LocaleStringData.Digits);
+                nfi.nativeDigits = new string[10];
+                for (int i = 0; i < nfi.nativeDigits.Length; i++)
+                {
+                    nfi.nativeDigits[i] = new string(digits[i], 1);
+                }
+
+                nfi.digitSubstitution = GetDigitSubstitution(_sRealName);
+            }
+
+            //
+            // Gather additional data
+            //
+            nfi.numberGroupSizes = this.WAGROUPING;
+            nfi.currencyGroupSizes = this.WAMONGROUPING;
+
+            // prefer the cached value since these do not have user overrides
+            nfi.percentNegativePattern = this.INEGATIVEPERCENT;
+            nfi.percentPositivePattern = this.IPOSITIVEPERCENT;
+            nfi.percentSymbol = this.SPERCENT;
+            nfi.perMilleSymbol = this.SPERMILLE;
+
+            nfi.negativeInfinitySymbol = this.SNEGINFINITY;
+            nfi.positiveInfinitySymbol = this.SPOSINFINITY;
+            nfi.nanSymbol = this.SNAN;
+
+            //
+            // We don't have percent values, so use the number values
+            //
+            nfi.percentDecimalDigits = nfi.numberDecimalDigits;
+            nfi.percentDecimalSeparator = nfi.numberDecimalSeparator;
+            nfi.percentGroupSizes = nfi.numberGroupSizes;
+            nfi.percentGroupSeparator = nfi.numberGroupSeparator;
+
+            //
+            // Clean up a few odd values
+            //
+
+            // Windows usually returns an empty positive sign, but we like it to be "+"
+            if (nfi.positiveSign == null || nfi.positiveSign.Length == 0) nfi.positiveSign = "+";
+
+            //Special case for Italian.  The currency decimal separator in the control panel is the empty string. When the user
+            //specifies C4 as the currency format, this results in the number apparently getting multiplied by 10000 because the
+            //decimal point doesn't show up.  We'll just hack this here because our default currency format will never use nfi.
+            if (nfi.currencyDecimalSeparator == null || nfi.currencyDecimalSeparator.Length == 0)
+            {
+                nfi.currencyDecimalSeparator = nfi.numberDecimalSeparator;
+            }
+        }
+
+        // Helper
+        // This is ONLY used for caching names and shouldn't be used for anything else
+        internal static string AnsiToLower(string testString)
+        {
+            int index = 0;
+
+            while (index<testString.Length && (testString[index]<'A' || testString[index]>'Z' ))
+            {
+                index++;
+            }
+            if (index >= testString.Length)
+            {
+                return testString; // we didn't really change the string
+            }
+
+            StringBuilder sb = new StringBuilder(testString.Length);
+            for (int i=0; i<index; i++)
+            {
+                sb.Append(testString[i]);
+            }
+
+            sb.Append((char) (testString[index] -'A' + 'a'));
+
+            for (int ich = index+1; ich < testString.Length; ich++)
+            {
+                char ch = testString[ich];
+                sb.Append(ch <= 'Z' && ch >= 'A' ? (char)(ch - 'A' + 'a') : ch);
+            }
+
+            return (sb.ToString());
+        }
+
+        /// <remarks>
+        /// The numeric values of the enum members match their Win32 counterparts.  The CultureData Win32 PAL implementation
+        /// takes a dependency on this fact, in order to prevent having to construct a mapping from internal values to LCTypes.
+        /// </remarks>
+        private enum LocaleStringData : uint
+        {
+            /// <summary>localized name of locale, eg "German (Germany)" in UI language (corresponds to LOCALE_SLOCALIZEDDISPLAYNAME)</summary>
+            LocalizedDisplayName = 0x00000002,
+            /// <summary>Display name (language + country usually) in English, eg "German (Germany)" (corresponds to LOCALE_SENGLISHDISPLAYNAME)</summary>
+            EnglishDisplayName = 0x00000072,
+            /// <summary>Display name in native locale language, eg "Deutsch (Deutschland) (corresponds to LOCALE_SNATIVEDISPLAYNAME)</summary>
+            NativeDisplayName = 0x00000073,
+            /// <summary>Language Display Name for a language, eg "German" in UI language (corresponds to LOCALE_SLOCALIZEDLANGUAGENAME)</summary>
+            LocalizedLanguageName = 0x0000006f,
+            /// <summary>English name of language, eg "German" (corresponds to LOCALE_SENGLISHLANGUAGENAME)</summary>
+            EnglishLanguageName = 0x00001001,
+            /// <summary>native name of language, eg "Deutsch" (corresponds to LOCALE_SNATIVELANGUAGENAME)</summary>
+            NativeLanguageName = 0x00000004,
+            /// <summary>localized name of country, eg "Germany" in UI language (corresponds to LOCALE_SLOCALIZEDCOUNTRYNAME)</summary>
+            LocalizedCountryName = 0x00000006,
+            /// <summary>English name of country, eg "Germany" (corresponds to LOCALE_SENGLISHCOUNTRYNAME)</summary>
+            EnglishCountryName = 0x00001002,
+            /// <summary>native name of country, eg "Deutschland" (corresponds to LOCALE_SNATIVECOUNTRYNAME)</summary>
+            NativeCountryName = 0x00000008,
+            /// <summary>abbreviated language name (corresponds to LOCALE_SABBREVLANGNAME)</summary>
+            AbbreviatedWindowsLanguageName = 0x00000003,
+            /// <summary>list item separator (corresponds to LOCALE_SLIST)</summary>
+            ListSeparator = 0x0000000C,
+            /// <summary>decimal separator (corresponds to LOCALE_SDECIMAL)</summary>
+            DecimalSeparator = 0x0000000E,
+            /// <summary>thousand separator (corresponds to LOCALE_STHOUSAND)</summary>
+            ThousandSeparator = 0x0000000F,
+            /// <summary>digit grouping (corresponds to LOCALE_SGROUPING)</summary>
+            Digits = 0x00000013,
+            /// <summary>local monetary symbol (corresponds to LOCALE_SCURRENCY)</summary>
+            MonetarySymbol = 0x00000014,
+            /// <summary>English currency name (corresponds to LOCALE_SENGCURRNAME)</summary>
+            CurrencyEnglishName = 0x00001007,
+            /// <summary>Native currency name (corresponds to LOCALE_SNATIVECURRNAME)</summary>
+            CurrencyNativeName = 0x00001008,
+            /// <summary>uintl monetary symbol (corresponds to LOCALE_SINTLSYMBOL)</summary>
+            Iso4217MonetarySymbol = 0x00000015,
+            /// <summary>monetary decimal separator (corresponds to LOCALE_SMONDECIMALSEP)</summary>
+            MonetaryDecimalSeparator = 0x00000016,
+            /// <summary>monetary thousand separator (corresponds to LOCALE_SMONTHOUSANDSEP)</summary>
+            MonetaryThousandSeparator = 0x00000017,
+            /// <summary>AM designator (corresponds to LOCALE_S1159)</summary>
+            AMDesignator = 0x00000028,
+            /// <summary>PM designator (corresponds to LOCALE_S2359)</summary>
+            PMDesignator = 0x00000029,
+            /// <summary>positive sign (corresponds to LOCALE_SPOSITIVESIGN)</summary>
+            PositiveSign = 0x00000050,
+            /// <summary>negative sign (corresponds to LOCALE_SNEGATIVESIGN)</summary>
+            NegativeSign = 0x00000051,
+            /// <summary>ISO abbreviated language name (corresponds to LOCALE_SISO639LANGNAME)</summary>
+            Iso639LanguageTwoLetterName = 0x00000059,
+            /// <summary>ISO abbreviated country name (corresponds to LOCALE_SISO639LANGNAME2)</summary>
+            Iso639LanguageThreeLetterName = 0x00000067,
+            /// <summary>ISO abbreviated language name (corresponds to LOCALE_SISO639LANGNAME)</summary>
+            Iso639LanguageName = 0x00000059,
+            /// <summary>ISO abbreviated country name (corresponds to LOCALE_SISO3166CTRYNAME)</summary>
+            Iso3166CountryName = 0x0000005A,
+            /// <summary>3 letter ISO country code (corresponds to LOCALE_SISO3166CTRYNAME2)</summary>
+            Iso3166CountryName2 = 0x00000068,   // 3 character ISO country name
+            /// <summary>Not a Number (corresponds to LOCALE_SNAN)</summary>
+            NaNSymbol = 0x00000069,
+            /// <summary>+ Infinity (corresponds to LOCALE_SPOSINFINITY)</summary>
+            PositiveInfinitySymbol = 0x0000006a,
+            /// <summary>- Infinity (corresponds to LOCALE_SNEGINFINITY)</summary>
+            NegativeInfinitySymbol = 0x0000006b,
+            /// <summary>Fallback name for resources (corresponds to LOCALE_SPARENT)</summary>
+            ParentName = 0x0000006d,
+            /// <summary>Fallback name for within the console (corresponds to LOCALE_SCONSOLEFALLBACKNAME)</summary>
+            ConsoleFallbackName = 0x0000006e,
+            /// <summary>Returns the percent symbol (corresponds to LOCALE_SPERCENT)</summary>
+            PercentSymbol = 0x00000076,
+            /// <summary>Returns the permille (U+2030) symbol (corresponds to LOCALE_SPERMILLE)</summary>
+            PerMilleSymbol = 0x00000077
+        }
+
+        /// <remarks>
+        /// The numeric values of the enum members match their Win32 counterparts.  The CultureData Win32 PAL implementation
+        /// takes a dependency on this fact, in order to prevent having to construct a mapping from internal values to LCTypes.
+        /// </remarks>
+        private enum LocaleGroupingData : uint
+        {
+            /// <summary>digit grouping (corresponds to LOCALE_SGROUPING)</summary>
+            Digit = 0x00000010,
+            /// <summary>monetary grouping (corresponds to LOCALE_SMONGROUPING)</summary>
+            Monetary = 0x00000018,
+        }
+
+        /// <remarks>
+        /// The numeric values of the enum members match their Win32 counterparts.  The CultureData Win32 PAL implementation
+        /// takes a dependency on this fact, in order to prevent having to construct a mapping from internal values to LCTypes.
+        /// </remarks>
+        private enum LocaleNumberData : uint
+        {
+            /// <summary>language id (corresponds to LOCALE_ILANGUAGE)</summary>
+            LanguageId = 0x00000001,
+            /// <summary>geographical location id, (corresponds to LOCALE_IGEOID)</summary>
+            GeoId = 0x0000005B,
+            /// <summary>0 = context, 1 = none, 2 = national (corresponds to LOCALE_IDIGITSUBSTITUTION)</summary>
+            DigitSubstitution = 0x00001014,
+            /// <summary>0 = metric, 1 = US (corresponds to LOCALE_IMEASURE)</summary>
+            MeasurementSystem = 0x0000000D,
+            /// <summary>number of fractional digits (corresponds to LOCALE_IDIGITS)</summary>
+            FractionalDigitsCount = 0x00000011,
+            /// <summary>negative number mode (corresponds to LOCALE_INEGNUMBER)</summary>
+            NegativeNumberFormat = 0x00001010,
+            /// <summary># local monetary digits (corresponds to LOCALE_ICURRDIGITS)</summary>
+            MonetaryFractionalDigitsCount = 0x00000019,
+            /// <summary>positive currency mode (corresponds to LOCALE_ICURRENCY)</summary>
+            PositiveMonetaryNumberFormat = 0x0000001B,
+            /// <summary>negative currency mode (corresponds to LOCALE_INEGCURR)</summary>
+            NegativeMonetaryNumberFormat = 0x0000001C,
+            /// <summary>type of calendar specifier (corresponds to LOCALE_ICALENDARTYPE)</summary>
+            CalendarType = 0x00001009,
+            /// <summary>first day of week specifier (corresponds to LOCALE_IFIRSTDAYOFWEEK)</summary>
+            FirstDayOfWeek = 0x0000100C,
+            /// <summary>first week of year specifier (corresponds to LOCALE_IFIRSTWEEKOFYEAR)</summary>
+            FirstWeekOfYear = 0x0000100D,
+            /// <summary>
+            /// Returns one of the following 4 reading layout values:
+            ///  0 - Left to right (eg en-US)
+            ///  1 - Right to left (eg arabic locales)
+            ///  2 - Vertical top to bottom with columns to the left and also left to right (ja-JP locales)
+            ///  3 - Vertical top to bottom with columns proceeding to the right
+            /// (corresponds to LOCALE_IREADINGLAYOUT)
+            /// </summary>
+            ReadingLayout = 0x00000070,
+            /// <summary>Returns 0-11 for the negative percent format (corresponds to LOCALE_INEGATIVEPERCENT)</summary>
+            NegativePercentFormat = 0x00000074,
+            /// <summary>Returns 0-3 for the positive percent format (corresponds to LOCALE_IPOSITIVEPERCENT)</summary>
+            PositivePercentFormat = 0x00000075,
+            /// <summary>default ansi code page (corresponds to LOCALE_IDEFAULTCODEPAGE)</summary>
+            OemCodePage = 0x0000000B,
+            /// <summary>default ansi code page (corresponds to LOCALE_IDEFAULTANSICODEPAGE)</summary>
+            AnsiCodePage = 0x00001004,
+            /// <summary>default mac code page (corresponds to LOCALE_IDEFAULTMACCODEPAGE)</summary>
+            MacCodePage = 0x00001011,
+            /// <summary>default ebcdic code page (corresponds to LOCALE_IDEFAULTEBCDICCODEPAGE)</summary>
+            EbcdicCodePage = 0x00001012,
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CultureNotFoundException.cs b/src/System.Private.CoreLib/shared/System/Globalization/CultureNotFoundException.cs
new file mode 100644
index 0000000000..10e8b1f836
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CultureNotFoundException.cs
@@ -0,0 +1,121 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Globalization
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class CultureNotFoundException : ArgumentException
+    {
+        private string _invalidCultureName; // unrecognized culture name
+        private int? _invalidCultureId;     // unrecognized culture Lcid
+
+        public CultureNotFoundException()
+            : base(DefaultMessage)
+        {
+        }
+
+        public CultureNotFoundException(String message)
+            : base(message)
+        {
+        }
+
+        public CultureNotFoundException(String paramName, String message)
+            : base(message, paramName)
+        {
+        }
+
+        public CultureNotFoundException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
+
+        public CultureNotFoundException(String paramName, string invalidCultureName, String message)
+            : base(message, paramName)
+        {
+            _invalidCultureName = invalidCultureName;
+        }
+
+        public CultureNotFoundException(String message, string invalidCultureName, Exception innerException)
+            : base(message, innerException)
+        {
+            _invalidCultureName = invalidCultureName;
+        }
+
+        public CultureNotFoundException(string message, int invalidCultureId, Exception innerException)
+            : base(message, innerException)
+        {
+            _invalidCultureId = invalidCultureId;
+        }
+
+        public CultureNotFoundException(string paramName, int invalidCultureId, string message)
+            : base(message, paramName)
+        {
+            _invalidCultureId = invalidCultureId;
+        }
+
+        protected CultureNotFoundException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            _invalidCultureId = (int?)info.GetValue("InvalidCultureId", typeof(int?));
+            _invalidCultureName = (string)info.GetValue("InvalidCultureName", typeof(string));
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("InvalidCultureId", _invalidCultureId, typeof(int?));
+            info.AddValue("InvalidCultureName", _invalidCultureName, typeof(string));
+        }
+
+        public virtual Nullable<int> InvalidCultureId
+        {
+            get { return _invalidCultureId; }
+        }
+
+        public virtual string InvalidCultureName
+        {
+            get { return _invalidCultureName; }
+        }
+
+        private static String DefaultMessage
+        {
+            get
+            {
+                return SR.Argument_CultureNotSupported;
+            }
+        }
+
+        private String FormatedInvalidCultureId
+        {
+            get
+            {
+                return InvalidCultureId != null ?
+                    String.Format(CultureInfo.InvariantCulture, "{0} (0x{0:x4})", (int)InvalidCultureId) :
+                    InvalidCultureName;
+            }
+        }
+
+        public override String Message
+        {
+            get
+            {
+                String s = base.Message;
+                if (_invalidCultureId != null || _invalidCultureName != null)
+                {
+                    String valueMessage = SR.Format(SR.Argument_CultureInvalidIdentifier, FormatedInvalidCultureId);
+                    if (s == null)
+                    {
+                        return valueMessage;
+                    }
+
+                    return s + Environment.NewLine + valueMessage;
+                }
+                return s;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/CultureTypes.cs b/src/System.Private.CoreLib/shared/System/Globalization/CultureTypes.cs
new file mode 100644
index 0000000000..f52ac82a83
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/CultureTypes.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// The enumeration constants used in CultureInfo.GetCultures().
+// On Linux platforms, the only enum values used there is NeutralCultures and SpecificCultures 
+// the rest are obsolete or not valid on Linux
+
+namespace System.Globalization
+{
+    [Flags]
+    public enum CultureTypes
+    {
+        NeutralCultures = 0x0001, // Neutral cultures are cultures like "en", "de", "zh", etc, for enumeration this includes ALL neutrals regardless of other flags
+        SpecificCultures = 0x0002, // Non-netural cultuers.  Examples are "en-us", "zh-tw", etc., for enumeration this includes ALL specifics regardless of other flags
+        InstalledWin32Cultures = 0x0004, // Win32 installed cultures in the system and exists in the framework too., this is effectively all cultures
+
+        AllCultures = NeutralCultures | SpecificCultures | InstalledWin32Cultures,
+
+        UserCustomCulture = 0x0008, // User defined custom culture
+        ReplacementCultures = 0x0010, // User defined replacement custom culture.
+        [Obsolete("This value has been deprecated.  Please use other values in CultureTypes.")]
+        WindowsOnlyCultures = 0x0020, // this will always return empty list.
+        [Obsolete("This value has been deprecated.  Please use other values in CultureTypes.")]
+        FrameworkCultures = 0x0040, // will return only the v2 cultures marked as Framework culture.
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/DateTimeFormat.cs b/src/System.Private.CoreLib/shared/System/Globalization/DateTimeFormat.cs
new file mode 100644
index 0000000000..092ad0365d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/DateTimeFormat.cs
@@ -0,0 +1,1393 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using System.Text;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    /*  
+     Customized format patterns:
+     P.S. Format in the table below is the internal number format used to display the pattern.
+
+     Patterns   Format      Description                           Example
+     =========  ==========  ===================================== ========
+        "h"     "0"         hour (12-hour clock)w/o leading zero  3
+        "hh"    "00"        hour (12-hour clock)with leading zero 03
+        "hh*"   "00"        hour (12-hour clock)with leading zero 03
+
+        "H"     "0"         hour (24-hour clock)w/o leading zero  8
+        "HH"    "00"        hour (24-hour clock)with leading zero 08
+        "HH*"   "00"        hour (24-hour clock)                  08
+
+        "m"     "0"         minute w/o leading zero
+        "mm"    "00"        minute with leading zero
+        "mm*"   "00"        minute with leading zero
+
+        "s"     "0"         second w/o leading zero
+        "ss"    "00"        second with leading zero
+        "ss*"   "00"        second with leading zero
+
+        "f"     "0"         second fraction (1 digit)
+        "ff"    "00"        second fraction (2 digit)
+        "fff"   "000"       second fraction (3 digit)
+        "ffff"  "0000"      second fraction (4 digit)
+        "fffff" "00000"         second fraction (5 digit)
+        "ffffff"    "000000"    second fraction (6 digit)
+        "fffffff"   "0000000"   second fraction (7 digit)
+
+        "F"     "0"         second fraction (up to 1 digit)
+        "FF"    "00"        second fraction (up to 2 digit)
+        "FFF"   "000"       second fraction (up to 3 digit)
+        "FFFF"  "0000"      second fraction (up to 4 digit)
+        "FFFFF" "00000"         second fraction (up to 5 digit)
+        "FFFFFF"    "000000"    second fraction (up to 6 digit)
+        "FFFFFFF"   "0000000"   second fraction (up to 7 digit)
+
+        "t"                 first character of AM/PM designator   A
+        "tt"                AM/PM designator                      AM
+        "tt*"               AM/PM designator                      PM
+
+        "d"     "0"         day w/o leading zero                  1
+        "dd"    "00"        day with leading zero                 01
+        "ddd"               short weekday name (abbreviation)     Mon
+        "dddd"              full weekday name                     Monday
+        "dddd*"             full weekday name                     Monday
+        
+
+        "M"     "0"         month w/o leading zero                2
+        "MM"    "00"        month with leading zero               02
+        "MMM"               short month name (abbreviation)       Feb
+        "MMMM"              full month name                       Febuary
+        "MMMM*"             full month name                       Febuary
+       
+        "y"     "0"         two digit year (year % 100) w/o leading zero           0
+        "yy"    "00"        two digit year (year % 100) with leading zero          00
+        "yyy"   "D3"        year                                  2000
+        "yyyy"  "D4"        year                                  2000
+        "yyyyy" "D5"        year                                  2000
+        ...
+
+        "z"     "+0;-0"     timezone offset w/o leading zero      -8
+        "zz"    "+00;-00"   timezone offset with leading zero     -08
+        "zzz"      "+00;-00" for hour offset, "00" for minute offset  full timezone offset   -07:30
+        "zzz*"  "+00;-00" for hour offset, "00" for minute offset   full timezone offset   -08:00
+        
+        "K"    -Local       "zzz", e.g. -08:00
+               -Utc         "'Z'", representing UTC
+               -Unspecified ""               
+               -DateTimeOffset      "zzzzz" e.g -07:30:15
+
+        "g*"                the current era name                  A.D.
+
+        ":"                 time separator                        : -- DEPRECATED - Insert separator directly into pattern (eg: "H.mm.ss")
+        "/"                 date separator                        /-- DEPRECATED - Insert separator directly into pattern (eg: "M-dd-yyyy")
+        "'"                 quoted string                         'ABC' will insert ABC into the formatted string.
+        '"'                 quoted string                         "ABC" will insert ABC into the formatted string.
+        "%"                 used to quote a single pattern characters      E.g.The format character "%y" is to print two digit year.
+        "\"                 escaped character                     E.g. '\d' insert the character 'd' into the format string.
+        other characters    insert the character into the format string. 
+
+    Pre-defined format characters: 
+        (U) to indicate Universal time is used.
+        (G) to indicate Gregorian calendar is used.
+    
+        Format              Description                             Real format                             Example
+        =========           =================================       ======================                  =======================
+        "d"                 short date                              culture-specific                        10/31/1999
+        "D"                 long data                               culture-specific                        Sunday, October 31, 1999
+        "f"                 full date (long date + short time)      culture-specific                        Sunday, October 31, 1999 2:00 AM
+        "F"                 full date (long date + long time)       culture-specific                        Sunday, October 31, 1999 2:00:00 AM
+        "g"                 general date (short date + short time)  culture-specific                        10/31/1999 2:00 AM
+        "G"                 general date (short date + long time)   culture-specific                        10/31/1999 2:00:00 AM
+        "m"/"M"             Month/Day date                          culture-specific                        October 31
+(G)     "o"/"O"             Round Trip XML                          "yyyy-MM-ddTHH:mm:ss.fffffffK"          1999-10-31 02:00:00.0000000Z
+(G)     "r"/"R"             RFC 1123 date,                          "ddd, dd MMM yyyy HH':'mm':'ss 'GMT'"   Sun, 31 Oct 1999 10:00:00 GMT
+(G)     "s"                 Sortable format, based on ISO 8601.     "yyyy-MM-dd'T'HH:mm:ss"                 1999-10-31T02:00:00
+                                                                    ('T' for local time)
+        "t"                 short time                              culture-specific                        2:00 AM
+        "T"                 long time                               culture-specific                        2:00:00 AM
+(G)     "u"                 Universal time with sortable format,    "yyyy'-'MM'-'dd HH':'mm':'ss'Z'"        1999-10-31 10:00:00Z
+                            based on ISO 8601.
+(U)     "U"                 Universal time with full                culture-specific                        Sunday, October 31, 1999 10:00:00 AM
+                            (long date + long time) format
+                            "y"/"Y"             Year/Month day                          culture-specific                        October, 1999
+
+    */
+
+    //This class contains only static members and does not require the serializable attribute.    
+    internal static
+    class DateTimeFormat
+    {
+        internal const int MaxSecondsFractionDigits = 7;
+        internal static readonly TimeSpan NullOffset = TimeSpan.MinValue;
+
+        internal static char[] allStandardFormats =
+        {
+            'd', 'D', 'f', 'F', 'g', 'G',
+            'm', 'M', 'o', 'O', 'r', 'R',
+            's', 't', 'T', 'u', 'U', 'y', 'Y',
+        };
+
+        internal const String RoundtripFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss.fffffffK";
+        internal const String RoundtripDateTimeUnfixed = "yyyy'-'MM'-'ddTHH':'mm':'ss zzz";
+
+        private const int DEFAULT_ALL_DATETIMES_SIZE = 132;
+
+        internal static readonly DateTimeFormatInfo InvariantFormatInfo = CultureInfo.InvariantCulture.DateTimeFormat;
+        internal static readonly string[] InvariantAbbreviatedMonthNames = InvariantFormatInfo.AbbreviatedMonthNames;
+        internal static readonly string[] InvariantAbbreviatedDayNames = InvariantFormatInfo.AbbreviatedDayNames;
+        internal const string Gmt = "GMT";
+
+        internal static String[] fixedNumberFormats = new String[] {
+            "0",
+            "00",
+            "000",
+            "0000",
+            "00000",
+            "000000",
+            "0000000",
+        };
+
+        ////////////////////////////////////////////////////////////////////////////
+        // 
+        // Format the positive integer value to a string and perfix with assigned 
+        // length of leading zero.
+        //
+        // Parameters:
+        //  value: The value to format
+        //  len: The maximum length for leading zero.  
+        //  If the digits of the value is greater than len, no leading zero is added.
+        //
+        // Notes: 
+        //  The function can format to Int32.MaxValue.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+        internal static void FormatDigits(StringBuilder outputBuffer, int value, int len)
+        {
+            Debug.Assert(value >= 0, "DateTimeFormat.FormatDigits(): value >= 0");
+            FormatDigits(outputBuffer, value, len, false);
+        }
+
+        internal static unsafe void FormatDigits(StringBuilder outputBuffer, int value, int len, bool overrideLengthLimit)
+        {
+            Debug.Assert(value >= 0, "DateTimeFormat.FormatDigits(): value >= 0");
+
+            // Limit the use of this function to be two-digits, so that we have the same behavior
+            // as RTM bits.
+            if (!overrideLengthLimit && len > 2)
+            {
+                len = 2;
+            }
+
+            char* buffer = stackalloc char[16];
+            char* p = buffer + 16;
+            int n = value;
+            do
+            {
+                *--p = (char)(n % 10 + '0');
+                n /= 10;
+            } while ((n != 0) && (p > buffer));
+
+            int digits = (int)(buffer + 16 - p);
+
+            //If the repeat count is greater than 0, we're trying
+            //to emulate the "00" format, so we have to prepend
+            //a zero if the string only has one character.
+            while ((digits < len) && (p > buffer))
+            {
+                *--p = '0';
+                digits++;
+            }
+            outputBuffer.Append(p, digits);
+        }
+
+        private static void HebrewFormatDigits(StringBuilder outputBuffer, int digits)
+        {
+            outputBuffer.Append(HebrewNumber.ToString(digits));
+        }
+
+        internal static int ParseRepeatPattern(ReadOnlySpan<char> format, int pos, char patternChar)
+        {
+            int len = format.Length;
+            int index = pos + 1;
+            while ((index < len) && (format[index] == patternChar))
+            {
+                index++;
+            }
+            return (index - pos);
+        }
+
+        private static String FormatDayOfWeek(int dayOfWeek, int repeat, DateTimeFormatInfo dtfi)
+        {
+            Debug.Assert(dayOfWeek >= 0 && dayOfWeek <= 6, "dayOfWeek >= 0 && dayOfWeek <= 6");
+            if (repeat == 3)
+            {
+                return (dtfi.GetAbbreviatedDayName((DayOfWeek)dayOfWeek));
+            }
+            // Call dtfi.GetDayName() here, instead of accessing DayNames property, because we don't
+            // want a clone of DayNames, which will hurt perf.
+            return (dtfi.GetDayName((DayOfWeek)dayOfWeek));
+        }
+
+        private static String FormatMonth(int month, int repeatCount, DateTimeFormatInfo dtfi)
+        {
+            Debug.Assert(month >= 1 && month <= 12, "month >=1 && month <= 12");
+            if (repeatCount == 3)
+            {
+                return (dtfi.GetAbbreviatedMonthName(month));
+            }
+            // Call GetMonthName() here, instead of accessing MonthNames property, because we don't
+            // want a clone of MonthNames, which will hurt perf.
+            return (dtfi.GetMonthName(month));
+        }
+
+        //
+        //  FormatHebrewMonthName
+        //
+        //  Action: Return the Hebrew month name for the specified DateTime.
+        //  Returns: The month name string for the specified DateTime.
+        //  Arguments: 
+        //        time   the time to format
+        //        month  The month is the value of HebrewCalendar.GetMonth(time).         
+        //        repeat Return abbreviated month name if repeat=3, or full month name if repeat=4
+        //        dtfi    The DateTimeFormatInfo which uses the Hebrew calendars as its calendar.
+        //  Exceptions: None.
+        // 
+
+        /* Note:
+            If DTFI is using Hebrew calendar, GetMonthName()/GetAbbreviatedMonthName() will return month names like this:            
+            1   Hebrew 1st Month
+            2   Hebrew 2nd Month
+            ..  ...
+            6   Hebrew 6th Month
+            7   Hebrew 6th Month II (used only in a leap year)
+            8   Hebrew 7th Month
+            9   Hebrew 8th Month
+            10  Hebrew 9th Month
+            11  Hebrew 10th Month
+            12  Hebrew 11th Month
+            13  Hebrew 12th Month
+
+            Therefore, if we are in a regular year, we have to increment the month name if moth is greater or eqaul to 7.            
+        */
+        private static String FormatHebrewMonthName(DateTime time, int month, int repeatCount, DateTimeFormatInfo dtfi)
+        {
+            Debug.Assert(repeatCount != 3 || repeatCount != 4, "repeateCount should be 3 or 4");
+            if (dtfi.Calendar.IsLeapYear(dtfi.Calendar.GetYear(time)))
+            {
+                // This month is in a leap year
+                return (dtfi.internalGetMonthName(month, MonthNameStyles.LeapYear, (repeatCount == 3)));
+            }
+            // This is in a regular year.
+            if (month >= 7)
+            {
+                month++;
+            }
+            if (repeatCount == 3)
+            {
+                return (dtfi.GetAbbreviatedMonthName(month));
+            }
+            return (dtfi.GetMonthName(month));
+        }
+
+        //
+        // The pos should point to a quote character. This method will
+        // append to the result StringBuilder the string encloed by the quote character.
+        //
+        internal static int ParseQuoteString(ReadOnlySpan<char> format, int pos, StringBuilder result)
+        {
+            //
+            // NOTE : pos will be the index of the quote character in the 'format' string.
+            //
+            int formatLen = format.Length;
+            int beginPos = pos;
+            char quoteChar = format[pos++]; // Get the character used to quote the following string.
+
+            bool foundQuote = false;
+            while (pos < formatLen)
+            {
+                char ch = format[pos++];
+                if (ch == quoteChar)
+                {
+                    foundQuote = true;
+                    break;
+                }
+                else if (ch == '\\')
+                {
+                    // The following are used to support escaped character.
+                    // Escaped character is also supported in the quoted string.
+                    // Therefore, someone can use a format like "'minute:' mm\"" to display:
+                    //  minute: 45"
+                    // because the second double quote is escaped.
+                    if (pos < formatLen)
+                    {
+                        result.Append(format[pos++]);
+                    }
+                    else
+                    {
+                        //
+                        // This means that '\' is at the end of the formatting string.
+                        //
+                        throw new FormatException(SR.Format_InvalidString);
+                    }
+                }
+                else
+                {
+                    result.Append(ch);
+                }
+            }
+
+            if (!foundQuote)
+            {
+                // Here we can't find the matching quote.
+                throw new FormatException(
+                        String.Format(
+                            CultureInfo.CurrentCulture,
+                            SR.Format_BadQuote, quoteChar));
+            }
+
+            //
+            // Return the character count including the begin/end quote characters and enclosed string.
+            //
+            return (pos - beginPos);
+        }
+
+        //
+        // Get the next character at the index of 'pos' in the 'format' string.
+        // Return value of -1 means 'pos' is already at the end of the 'format' string.
+        // Otherwise, return value is the int value of the next character.
+        //
+        internal static int ParseNextChar(ReadOnlySpan<char> format, int pos)
+        {
+            if (pos >= format.Length - 1)
+            {
+                return (-1);
+            }
+            return ((int)format[pos + 1]);
+        }
+
+        //
+        //  IsUseGenitiveForm
+        //
+        //  Actions: Check the format to see if we should use genitive month in the formatting.
+        //      Starting at the position (index) in the (format) string, look back and look ahead to
+        //      see if there is "d" or "dd".  In the case like "d MMMM" or "MMMM dd", we can use 
+        //      genitive form.  Genitive form is not used if there is more than two "d".
+        //  Arguments:
+        //      format      The format string to be scanned.
+        //      index       Where we should start the scanning.  This is generally where "M" starts.
+        //      tokenLen    The len of the current pattern character.  This indicates how many "M" that we have.
+        //      patternToMatch  The pattern that we want to search. This generally uses "d"
+        //
+        private static bool IsUseGenitiveForm(ReadOnlySpan<char> format, int index, int tokenLen, char patternToMatch)
+        {
+            int i;
+            int repeat = 0;
+            //
+            // Look back to see if we can find "d" or "ddd"
+            //
+
+            // Find first "d".
+            for (i = index - 1; i >= 0 && format[i] != patternToMatch; i--) {  /*Do nothing here */ };
+
+            if (i >= 0)
+            {
+                // Find a "d", so look back to see how many "d" that we can find.
+                while (--i >= 0 && format[i] == patternToMatch)
+                {
+                    repeat++;
+                }
+                //
+                // repeat == 0 means that we have one (patternToMatch)
+                // repeat == 1 means that we have two (patternToMatch)
+                //
+                if (repeat <= 1)
+                {
+                    return (true);
+                }
+                // Note that we can't just stop here.  We may find "ddd" while looking back, and we have to look
+                // ahead to see if there is "d" or "dd".
+            }
+
+            //
+            // If we can't find "d" or "dd" by looking back, try look ahead.
+            //
+
+            // Find first "d"
+            for (i = index + tokenLen; i < format.Length && format[i] != patternToMatch; i++) { /* Do nothing here */ };
+
+            if (i < format.Length)
+            {
+                repeat = 0;
+                // Find a "d", so contine the walk to see how may "d" that we can find.
+                while (++i < format.Length && format[i] == patternToMatch)
+                {
+                    repeat++;
+                }
+                //
+                // repeat == 0 means that we have one (patternToMatch)
+                // repeat == 1 means that we have two (patternToMatch)
+                //
+                if (repeat <= 1)
+                {
+                    return (true);
+                }
+            }
+            return (false);
+        }
+
+
+        //
+        //  FormatCustomized
+        //
+        //  Actions: Format the DateTime instance using the specified format.
+        // 
+        private static StringBuilder FormatCustomized(
+            DateTime dateTime, ReadOnlySpan<char> format, DateTimeFormatInfo dtfi, TimeSpan offset, StringBuilder result)
+        {
+            Calendar cal = dtfi.Calendar;
+
+            bool resultBuilderIsPooled = false;
+            if (result == null)
+            {
+                resultBuilderIsPooled = true;
+                result = StringBuilderCache.Acquire();
+            }
+            
+            // This is a flag to indicate if we are format the dates using Hebrew calendar.
+            bool isHebrewCalendar = (cal.ID == CalendarId.HEBREW);
+            // This is a flag to indicate if we are formating hour/minute/second only.
+            bool bTimeOnly = true;
+
+            int i = 0;
+            int tokenLen, hour12;
+
+            while (i < format.Length)
+            {
+                char ch = format[i];
+                int nextChar;
+                switch (ch)
+                {
+                    case 'g':
+                        tokenLen = ParseRepeatPattern(format, i, ch);
+                        result.Append(dtfi.GetEraName(cal.GetEra(dateTime)));
+                        break;
+                    case 'h':
+                        tokenLen = ParseRepeatPattern(format, i, ch);
+                        hour12 = dateTime.Hour % 12;
+                        if (hour12 == 0)
+                        {
+                            hour12 = 12;
+                        }
+                        FormatDigits(result, hour12, tokenLen);
+                        break;
+                    case 'H':
+                        tokenLen = ParseRepeatPattern(format, i, ch);
+                        FormatDigits(result, dateTime.Hour, tokenLen);
+                        break;
+                    case 'm':
+                        tokenLen = ParseRepeatPattern(format, i, ch);
+                        FormatDigits(result, dateTime.Minute, tokenLen);
+                        break;
+                    case 's':
+                        tokenLen = ParseRepeatPattern(format, i, ch);
+                        FormatDigits(result, dateTime.Second, tokenLen);
+                        break;
+                    case 'f':
+                    case 'F':
+                        tokenLen = ParseRepeatPattern(format, i, ch);
+                        if (tokenLen <= MaxSecondsFractionDigits)
+                        {
+                            long fraction = (dateTime.Ticks % Calendar.TicksPerSecond);
+                            fraction = fraction / (long)Math.Pow(10, 7 - tokenLen);
+                            if (ch == 'f')
+                            {
+                                result.Append(((int)fraction).ToString(fixedNumberFormats[tokenLen - 1], CultureInfo.InvariantCulture));
+                            }
+                            else
+                            {
+                                int effectiveDigits = tokenLen;
+                                while (effectiveDigits > 0)
+                                {
+                                    if (fraction % 10 == 0)
+                                    {
+                                        fraction = fraction / 10;
+                                        effectiveDigits--;
+                                    }
+                                    else
+                                    {
+                                        break;
+                                    }
+                                }
+                                if (effectiveDigits > 0)
+                                {
+                                    result.Append(((int)fraction).ToString(fixedNumberFormats[effectiveDigits - 1], CultureInfo.InvariantCulture));
+                                }
+                                else
+                                {
+                                    // No fraction to emit, so see if we should remove decimal also.
+                                    if (result.Length > 0 && result[result.Length - 1] == '.')
+                                    {
+                                        result.Remove(result.Length - 1, 1);
+                                    }
+                                }
+                            }
+                        }
+                        else
+                        {
+                            if (resultBuilderIsPooled)
+                            {
+                                StringBuilderCache.Release(result);
+                            }
+                            throw new FormatException(SR.Format_InvalidString);
+                        }
+                        break;
+                    case 't':
+                        tokenLen = ParseRepeatPattern(format, i, ch);
+                        if (tokenLen == 1)
+                        {
+                            if (dateTime.Hour < 12)
+                            {
+                                if (dtfi.AMDesignator.Length >= 1)
+                                {
+                                    result.Append(dtfi.AMDesignator[0]);
+                                }
+                            }
+                            else
+                            {
+                                if (dtfi.PMDesignator.Length >= 1)
+                                {
+                                    result.Append(dtfi.PMDesignator[0]);
+                                }
+                            }
+                        }
+                        else
+                        {
+                            result.Append((dateTime.Hour < 12 ? dtfi.AMDesignator : dtfi.PMDesignator));
+                        }
+                        break;
+                    case 'd':
+                        //
+                        // tokenLen == 1 : Day of month as digits with no leading zero.
+                        // tokenLen == 2 : Day of month as digits with leading zero for single-digit months.
+                        // tokenLen == 3 : Day of week as a three-leter abbreviation.
+                        // tokenLen >= 4 : Day of week as its full name.
+                        //
+                        tokenLen = ParseRepeatPattern(format, i, ch);
+                        if (tokenLen <= 2)
+                        {
+                            int day = cal.GetDayOfMonth(dateTime);
+                            if (isHebrewCalendar)
+                            {
+                                // For Hebrew calendar, we need to convert numbers to Hebrew text for yyyy, MM, and dd values.
+                                HebrewFormatDigits(result, day);
+                            }
+                            else
+                            {
+                                FormatDigits(result, day, tokenLen);
+                            }
+                        }
+                        else
+                        {
+                            int dayOfWeek = (int)cal.GetDayOfWeek(dateTime);
+                            result.Append(FormatDayOfWeek(dayOfWeek, tokenLen, dtfi));
+                        }
+                        bTimeOnly = false;
+                        break;
+                    case 'M':
+                        // 
+                        // tokenLen == 1 : Month as digits with no leading zero.
+                        // tokenLen == 2 : Month as digits with leading zero for single-digit months.
+                        // tokenLen == 3 : Month as a three-letter abbreviation.
+                        // tokenLen >= 4 : Month as its full name.
+                        //
+                        tokenLen = ParseRepeatPattern(format, i, ch);
+                        int month = cal.GetMonth(dateTime);
+                        if (tokenLen <= 2)
+                        {
+                            if (isHebrewCalendar)
+                            {
+                                // For Hebrew calendar, we need to convert numbers to Hebrew text for yyyy, MM, and dd values.
+                                HebrewFormatDigits(result, month);
+                            }
+                            else
+                            {
+                                FormatDigits(result, month, tokenLen);
+                            }
+                        }
+                        else
+                        {
+                            if (isHebrewCalendar)
+                            {
+                                result.Append(FormatHebrewMonthName(dateTime, month, tokenLen, dtfi));
+                            }
+                            else
+                            {
+                                if ((dtfi.FormatFlags & DateTimeFormatFlags.UseGenitiveMonth) != 0 && tokenLen >= 4)
+                                {
+                                    result.Append(
+                                        dtfi.internalGetMonthName(
+                                            month,
+                                            IsUseGenitiveForm(format, i, tokenLen, 'd') ? MonthNameStyles.Genitive : MonthNameStyles.Regular,
+                                            false));
+                                }
+                                else
+                                {
+                                    result.Append(FormatMonth(month, tokenLen, dtfi));
+                                }
+                            }
+                        }
+                        bTimeOnly = false;
+                        break;
+                    case 'y':
+                        // Notes about OS behavior:
+                        // y: Always print (year % 100). No leading zero.
+                        // yy: Always print (year % 100) with leading zero.
+                        // yyy/yyyy/yyyyy/... : Print year value.  No leading zero.
+
+                        int year = cal.GetYear(dateTime);
+                        tokenLen = ParseRepeatPattern(format, i, ch);
+                        if (dtfi.HasForceTwoDigitYears)
+                        {
+                            FormatDigits(result, year, tokenLen <= 2 ? tokenLen : 2);
+                        }
+                        else if (cal.ID == CalendarId.HEBREW)
+                        {
+                            HebrewFormatDigits(result, year);
+                        }
+                        else
+                        {
+                            if (tokenLen <= 2)
+                            {
+                                FormatDigits(result, year % 100, tokenLen);
+                            }
+                            else
+                            {
+                                String fmtPattern = "D" + tokenLen.ToString();
+                                result.Append(year.ToString(fmtPattern, CultureInfo.InvariantCulture));
+                            }
+                        }
+                        bTimeOnly = false;
+                        break;
+                    case 'z':
+                        tokenLen = ParseRepeatPattern(format, i, ch);
+                        FormatCustomizedTimeZone(dateTime, offset, format, tokenLen, bTimeOnly, result);
+                        break;
+                    case 'K':
+                        tokenLen = 1;
+                        FormatCustomizedRoundripTimeZone(dateTime, offset, result);
+                        break;
+                    case ':':
+                        result.Append(dtfi.TimeSeparator);
+                        tokenLen = 1;
+                        break;
+                    case '/':
+                        result.Append(dtfi.DateSeparator);
+                        tokenLen = 1;
+                        break;
+                    case '\'':
+                    case '\"':
+                        tokenLen = ParseQuoteString(format, i, result);
+                        break;
+                    case '%':
+                        // Optional format character.
+                        // For example, format string "%d" will print day of month 
+                        // without leading zero.  Most of the cases, "%" can be ignored.
+                        nextChar = ParseNextChar(format, i);
+                        // nextChar will be -1 if we already reach the end of the format string.
+                        // Besides, we will not allow "%%" appear in the pattern.
+                        if (nextChar >= 0 && nextChar != '%')
+                        {
+                            char nextCharChar = (char)nextChar;
+                            StringBuilder origStringBuilder = FormatCustomized(dateTime, MemoryMarshal.CreateReadOnlySpan<char>(ref nextCharChar, 1), dtfi, offset, result);
+                            Debug.Assert(ReferenceEquals(origStringBuilder, result));
+                            tokenLen = 2;
+                        }
+                        else
+                        {
+                            //
+                            // This means that '%' is at the end of the format string or
+                            // "%%" appears in the format string.
+                            //
+                            if (resultBuilderIsPooled)
+                            {
+                                StringBuilderCache.Release(result);
+                            }
+                            throw new FormatException(SR.Format_InvalidString);
+                        }
+                        break;
+                    case '\\':
+                        // Escaped character.  Can be used to insert character into the format string.
+                        // For exmple, "\d" will insert the character 'd' into the string.
+                        //
+                        // NOTENOTE : we can remove this format character if we enforce the enforced quote 
+                        // character rule.
+                        // That is, we ask everyone to use single quote or double quote to insert characters,
+                        // then we can remove this character.
+                        //
+                        nextChar = ParseNextChar(format, i);
+                        if (nextChar >= 0)
+                        {
+                            result.Append(((char)nextChar));
+                            tokenLen = 2;
+                        }
+                        else
+                        {
+                            //
+                            // This means that '\' is at the end of the formatting string.
+                            //
+                            if (resultBuilderIsPooled)
+                            {
+                                StringBuilderCache.Release(result);
+                            }
+                            throw new FormatException(SR.Format_InvalidString);
+                        }
+                        break;
+                    default:
+                        // NOTENOTE : we can remove this rule if we enforce the enforced quote
+                        // character rule.
+                        // That is, if we ask everyone to use single quote or double quote to insert characters,
+                        // then we can remove this default block.
+                        result.Append(ch);
+                        tokenLen = 1;
+                        break;
+                }
+                i += tokenLen;
+            }
+            return result;
+        }
+
+
+        // output the 'z' famliy of formats, which output a the offset from UTC, e.g. "-07:30"
+        private static void FormatCustomizedTimeZone(DateTime dateTime, TimeSpan offset, ReadOnlySpan<char> format, Int32 tokenLen, Boolean timeOnly, StringBuilder result)
+        {
+            // See if the instance already has an offset
+            Boolean dateTimeFormat = (offset == NullOffset);
+            if (dateTimeFormat)
+            {
+                // No offset. The instance is a DateTime and the output should be the local time zone
+
+                if (timeOnly && dateTime.Ticks < Calendar.TicksPerDay)
+                {
+                    // For time only format and a time only input, the time offset on 0001/01/01 is less 
+                    // accurate than the system's current offset because of daylight saving time.
+                    offset = TimeZoneInfo.GetLocalUtcOffset(DateTime.Now, TimeZoneInfoOptions.NoThrowOnInvalidTime);
+                }
+                else if (dateTime.Kind == DateTimeKind.Utc)
+                {
+                    offset = TimeSpan.Zero;
+                }
+                else
+                {
+                    offset = TimeZoneInfo.GetLocalUtcOffset(dateTime, TimeZoneInfoOptions.NoThrowOnInvalidTime);
+                }
+            }
+            if (offset >= TimeSpan.Zero)
+            {
+                result.Append('+');
+            }
+            else
+            {
+                result.Append('-');
+                // get a positive offset, so that you don't need a separate code path for the negative numbers.
+                offset = offset.Negate();
+            }
+
+            if (tokenLen <= 1)
+            {
+                // 'z' format e.g "-7"
+                result.AppendFormat(CultureInfo.InvariantCulture, "{0:0}", offset.Hours);
+            }
+            else
+            {
+                // 'zz' or longer format e.g "-07"
+                result.AppendFormat(CultureInfo.InvariantCulture, "{0:00}", offset.Hours);
+                if (tokenLen >= 3)
+                {
+                    // 'zzz*' or longer format e.g "-07:30"
+                    result.AppendFormat(CultureInfo.InvariantCulture, ":{0:00}", offset.Minutes);
+                }
+            }
+        }
+
+        // output the 'K' format, which is for round-tripping the data
+        private static void FormatCustomizedRoundripTimeZone(DateTime dateTime, TimeSpan offset, StringBuilder result)
+        {
+            // The objective of this format is to round trip the data in the type
+            // For DateTime it should round-trip the Kind value and preserve the time zone. 
+            // DateTimeOffset instance, it should do so by using the internal time zone.                        
+
+            if (offset == NullOffset)
+            {
+                // source is a date time, so behavior depends on the kind.
+                switch (dateTime.Kind)
+                {
+                    case DateTimeKind.Local:
+                        // This should output the local offset, e.g. "-07:30"
+                        offset = TimeZoneInfo.GetLocalUtcOffset(dateTime, TimeZoneInfoOptions.NoThrowOnInvalidTime);
+                        // fall through to shared time zone output code
+                        break;
+                    case DateTimeKind.Utc:
+                        // The 'Z' constant is a marker for a UTC date
+                        result.Append("Z");
+                        return;
+                    default:
+                        // If the kind is unspecified, we output nothing here
+                        return;
+                }
+            }
+            if (offset >= TimeSpan.Zero)
+            {
+                result.Append('+');
+            }
+            else
+            {
+                result.Append('-');
+                // get a positive offset, so that you don't need a separate code path for the negative numbers.
+                offset = offset.Negate();
+            }
+
+            Append2DigitNumber(result, offset.Hours);
+            result.Append(':');
+            Append2DigitNumber(result, offset.Minutes);
+        }
+
+        private static void Append2DigitNumber(StringBuilder result, int val)
+        {
+            result.Append((char)('0' + (val / 10)));
+            result.Append((char)('0' + (val % 10)));
+        }
+
+        internal static String GetRealFormat(ReadOnlySpan<char> format, DateTimeFormatInfo dtfi)
+        {
+            String realFormat = null;
+
+            switch (format[0])
+            {
+                case 'd':       // Short Date
+                    realFormat = dtfi.ShortDatePattern;
+                    break;
+                case 'D':       // Long Date
+                    realFormat = dtfi.LongDatePattern;
+                    break;
+                case 'f':       // Full (long date + short time)
+                    realFormat = dtfi.LongDatePattern + " " + dtfi.ShortTimePattern;
+                    break;
+                case 'F':       // Full (long date + long time)
+                    realFormat = dtfi.FullDateTimePattern;
+                    break;
+                case 'g':       // General (short date + short time)
+                    realFormat = dtfi.GeneralShortTimePattern;
+                    break;
+                case 'G':       // General (short date + long time)
+                    realFormat = dtfi.GeneralLongTimePattern;
+                    break;
+                case 'm':
+                case 'M':       // Month/Day Date
+                    realFormat = dtfi.MonthDayPattern;
+                    break;
+                case 'o':
+                case 'O':
+                    realFormat = RoundtripFormat;
+                    break;
+                case 'r':
+                case 'R':       // RFC 1123 Standard                    
+                    realFormat = dtfi.RFC1123Pattern;
+                    break;
+                case 's':       // Sortable without Time Zone Info
+                    realFormat = dtfi.SortableDateTimePattern;
+                    break;
+                case 't':       // Short Time
+                    realFormat = dtfi.ShortTimePattern;
+                    break;
+                case 'T':       // Long Time
+                    realFormat = dtfi.LongTimePattern;
+                    break;
+                case 'u':       // Universal with Sortable format
+                    realFormat = dtfi.UniversalSortableDateTimePattern;
+                    break;
+                case 'U':       // Universal with Full (long date + long time) format
+                    realFormat = dtfi.FullDateTimePattern;
+                    break;
+                case 'y':
+                case 'Y':       // Year/Month Date
+                    realFormat = dtfi.YearMonthPattern;
+                    break;
+                default:
+                    throw new FormatException(SR.Format_InvalidString);
+            }
+            return (realFormat);
+        }
+
+
+        // Expand a pre-defined format string (like "D" for long date) to the real format that
+        // we are going to use in the date time parsing.
+        // This method also convert the dateTime if necessary (e.g. when the format is in Universal time),
+        // and change dtfi if necessary (e.g. when the format should use invariant culture).
+        //
+        private static String ExpandPredefinedFormat(ReadOnlySpan<char> format, ref DateTime dateTime, ref DateTimeFormatInfo dtfi, ref TimeSpan offset)
+        {
+            switch (format[0])
+            {
+                case 'o':
+                case 'O':       // Round trip format
+                    dtfi = DateTimeFormatInfo.InvariantInfo;
+                    break;
+                case 'r':
+                case 'R':       // RFC 1123 Standard                    
+                    if (offset != NullOffset)
+                    {
+                        // Convert to UTC invariants mean this will be in range
+                        dateTime = dateTime - offset;
+                    }
+                    else if (dateTime.Kind == DateTimeKind.Local)
+                    {
+                        InvalidFormatForLocal(format, dateTime);
+                    }
+                    dtfi = DateTimeFormatInfo.InvariantInfo;
+                    break;
+                case 's':       // Sortable without Time Zone Info                
+                    dtfi = DateTimeFormatInfo.InvariantInfo;
+                    break;
+                case 'u':       // Universal time in sortable format.
+                    if (offset != NullOffset)
+                    {
+                        // Convert to UTC invariants mean this will be in range
+                        dateTime = dateTime - offset;
+                    }
+                    else if (dateTime.Kind == DateTimeKind.Local)
+                    {
+                        InvalidFormatForLocal(format, dateTime);
+                    }
+                    dtfi = DateTimeFormatInfo.InvariantInfo;
+                    break;
+                case 'U':       // Universal time in culture dependent format.
+                    if (offset != NullOffset)
+                    {
+                        // This format is not supported by DateTimeOffset
+                        throw new FormatException(SR.Format_InvalidString);
+                    }
+                    // Universal time is always in Greogrian calendar.
+                    //
+                    // Change the Calendar to be Gregorian Calendar.
+                    //
+                    dtfi = (DateTimeFormatInfo)dtfi.Clone();
+                    if (dtfi.Calendar.GetType() != typeof(GregorianCalendar))
+                    {
+                        dtfi.Calendar = GregorianCalendar.GetDefaultInstance();
+                    }
+                    dateTime = dateTime.ToUniversalTime();
+                    break;
+            }
+            return GetRealFormat(format, dtfi);
+        }
+
+        internal static String Format(DateTime dateTime, String format, IFormatProvider provider)
+        {
+            return Format(dateTime, format, provider, NullOffset);
+        }
+
+        internal static string Format(DateTime dateTime, String format, IFormatProvider provider, TimeSpan offset)
+        {
+            if (format != null && format.Length == 1)
+            {
+                // Optimize for these standard formats that are not affected by culture.
+                switch (format[0])
+                {
+                    // Round trip format
+                    case 'o':
+                    case 'O':
+                        const int MinFormatOLength = 27, MaxFormatOLength = 33;
+                        Span<char> span = stackalloc char[MaxFormatOLength];
+                        TryFormatO(dateTime, offset, span, out int ochars);
+                        Debug.Assert(ochars >= MinFormatOLength && ochars <= MaxFormatOLength);
+                        return span.Slice(0, ochars).ToString();
+
+                    // RFC1123
+                    case 'r':
+                    case 'R':
+                        const int FormatRLength = 29;
+                        string str = string.FastAllocateString(FormatRLength);
+                        TryFormatR(dateTime, offset, new Span<char>(ref str.GetRawStringData(), str.Length), out int rchars);
+                        Debug.Assert(rchars == str.Length);
+                        return str;
+                }
+            }
+
+            DateTimeFormatInfo dtfi = DateTimeFormatInfo.GetInstance(provider);
+            return StringBuilderCache.GetStringAndRelease(FormatStringBuilder(dateTime, format, dtfi, offset));
+        }
+
+        internal static bool TryFormat(DateTime dateTime, Span<char> destination, out int charsWritten, ReadOnlySpan<char> format, IFormatProvider provider) =>
+            TryFormat(dateTime, destination, out charsWritten, format, provider, NullOffset);
+
+        internal static bool TryFormat(DateTime dateTime, Span<char> destination, out int charsWritten, ReadOnlySpan<char> format, IFormatProvider provider, TimeSpan offset)
+        {
+            if (format.Length == 1)
+            {
+                // Optimize for these standard formats that are not affected by culture.
+                switch (format[0])
+                {
+                    // Round trip format
+                    case 'o':
+                    case 'O':
+                        return TryFormatO(dateTime, offset, destination, out charsWritten);
+
+                    // RFC1123
+                    case 'r':
+                    case 'R':
+                        return TryFormatR(dateTime, offset, destination, out charsWritten);
+                }
+            }
+
+            DateTimeFormatInfo dtfi = DateTimeFormatInfo.GetInstance(provider);
+            StringBuilder sb = FormatStringBuilder(dateTime, format, dtfi, offset);
+
+            bool success = sb.Length <= destination.Length;
+            if (success)
+            {
+                sb.CopyTo(0, destination, sb.Length);
+                charsWritten = sb.Length;
+            }
+            else
+            {
+                charsWritten = 0;
+            }
+
+            StringBuilderCache.Release(sb);
+            return success;
+        }
+
+        private static StringBuilder FormatStringBuilder(DateTime dateTime, ReadOnlySpan<char> format, DateTimeFormatInfo dtfi, TimeSpan offset)
+        {
+            Debug.Assert(dtfi != null);
+            if (format.Length == 0)
+            {
+                Boolean timeOnlySpecialCase = false;
+                if (dateTime.Ticks < Calendar.TicksPerDay)
+                {
+                    // If the time is less than 1 day, consider it as time of day.
+                    // Just print out the short time format.
+                    //
+                    // This is a workaround for VB, since they use ticks less then one day to be 
+                    // time of day.  In cultures which use calendar other than Gregorian calendar, these
+                    // alternative calendar may not support ticks less than a day.
+                    // For example, Japanese calendar only supports date after 1868/9/8.
+                    // This will pose a problem when people in VB get the time of day, and use it
+                    // to call ToString(), which will use the general format (short date + long time).
+                    // Since Japanese calendar does not support Gregorian year 0001, an exception will be
+                    // thrown when we try to get the Japanese year for Gregorian year 0001.
+                    // Therefore, the workaround allows them to call ToString() for time of day from a DateTime by
+                    // formatting as ISO 8601 format.
+                    switch (dtfi.Calendar.ID)
+                    {
+                        case CalendarId.JAPAN:
+                        case CalendarId.TAIWAN:
+                        case CalendarId.HIJRI:
+                        case CalendarId.HEBREW:
+                        case CalendarId.JULIAN:
+                        case CalendarId.UMALQURA:
+                        case CalendarId.PERSIAN:
+                            timeOnlySpecialCase = true;
+                            dtfi = DateTimeFormatInfo.InvariantInfo;
+                            break;
+                    }
+                }
+                if (offset == NullOffset)
+                {
+                    // Default DateTime.ToString case.
+                    format = timeOnlySpecialCase ? "s" : "G";
+                }
+                else
+                {
+                    // Default DateTimeOffset.ToString case.
+                    format = timeOnlySpecialCase ? RoundtripDateTimeUnfixed : dtfi.DateTimeOffsetPattern;
+                }
+            }
+
+            if (format.Length == 1)
+            {
+                format = ExpandPredefinedFormat(format, ref dateTime, ref dtfi, ref offset);
+            }
+
+            return FormatCustomized(dateTime, format, dtfi, offset, result: null);
+        }
+
+        // Roundtrippable format. One of
+        //   012345678901234567890123456789012
+        //   ---------------------------------
+        //   2017-06-12T05:30:45.7680000-07:00
+        //   2017-06-12T05:30:45.7680000Z           (Z is short for "+00:00" but also distinguishes DateTimeKind.Utc from DateTimeKind.Local)
+        //   2017-06-12T05:30:45.7680000            (interpreted as local time wrt to current time zone)
+        private static bool TryFormatO(DateTime dateTime, TimeSpan offset, Span<char> destination, out int charsWritten)
+        {
+            const int MinimumBytesNeeded = 27;
+
+            int charsRequired = MinimumBytesNeeded;
+            DateTimeKind kind = DateTimeKind.Local;
+
+            if (offset == NullOffset)
+            {
+                kind = dateTime.Kind;
+                if (kind == DateTimeKind.Local)
+                {
+                    offset = TimeZoneInfo.Local.GetUtcOffset(dateTime);
+                    charsRequired += 6;
+                }
+                else if (kind == DateTimeKind.Utc)
+                {
+                    charsRequired += 1;
+                }
+            }
+            else
+            {
+                charsRequired += 6;
+            }
+
+            if (destination.Length < charsRequired)
+            {
+                charsWritten = 0;
+                return false;
+            }
+            charsWritten = charsRequired;
+
+            // Hoist most of the bounds checks on destination.
+            { var unused = destination[MinimumBytesNeeded - 1]; }
+
+            WriteFourDecimalDigits((uint)dateTime.Year, destination, 0);
+            destination[4] = '-';
+            WriteTwoDecimalDigits((uint)dateTime.Month, destination, 5);
+            destination[7] = '-';
+            WriteTwoDecimalDigits((uint)dateTime.Day, destination, 8);
+            destination[10] = 'T';
+            WriteTwoDecimalDigits((uint)dateTime.Hour, destination, 11);
+            destination[13] = ':';
+            WriteTwoDecimalDigits((uint)dateTime.Minute, destination, 14);
+            destination[16] = ':';
+            WriteTwoDecimalDigits((uint)dateTime.Second, destination, 17);
+            destination[19] = '.';
+            WriteDigits((uint)((ulong)dateTime.Ticks % (ulong)TimeSpan.TicksPerSecond), destination.Slice(20, 7));
+
+            if (kind == DateTimeKind.Local)
+            {
+                char sign;
+                if (offset < default(TimeSpan) /* a "const" version of TimeSpan.Zero */)
+                {
+                    sign = '-';
+                    offset = TimeSpan.FromTicks(-offset.Ticks);
+                }
+                else
+                {
+                    sign = '+';
+                }
+
+                // Writing the value backward allows the JIT to optimize by
+                // performing a single bounds check against buffer.
+                WriteTwoDecimalDigits((uint)offset.Minutes, destination, 31);
+                destination[30] = ':';
+                WriteTwoDecimalDigits((uint)offset.Hours, destination, 28);
+                destination[27] = sign;
+            }
+            else if (kind == DateTimeKind.Utc)
+            {
+                destination[27] = 'Z';
+            }
+
+            return true;
+        }
+
+        // Rfc1123
+        //   01234567890123456789012345678
+        //   -----------------------------
+        //   Tue, 03 Jan 2017 08:08:05 GMT
+        private static bool TryFormatR(DateTime dateTime, TimeSpan offset, Span<char> destination, out int charsWritten)
+        {
+            // Writing the check in this fashion elides all bounds checks on 'destination'
+            // for the remainder of the method.
+            if (28 >= (uint)destination.Length)
+            {
+                charsWritten = 0;
+                return false;
+            }
+
+            if (offset != NullOffset)
+            {
+                // Convert to UTC invariants.
+                dateTime = dateTime - offset;
+            }
+
+            dateTime.GetDatePart(out int year, out int month, out int day);
+
+            string dayAbbrev = InvariantAbbreviatedDayNames[(int)dateTime.DayOfWeek];
+            Debug.Assert(dayAbbrev.Length == 3);
+
+            string monthAbbrev = InvariantAbbreviatedMonthNames[month - 1];
+            Debug.Assert(monthAbbrev.Length == 3);
+
+            destination[0] = dayAbbrev[0];
+            destination[1] = dayAbbrev[1];
+            destination[2] = dayAbbrev[2];
+            destination[3] = ',';
+            destination[4] = ' ';
+            WriteTwoDecimalDigits((uint)day, destination, 5);
+            destination[7] = ' ';
+            destination[8] = monthAbbrev[0];
+            destination[9] = monthAbbrev[1];
+            destination[10] = monthAbbrev[2];
+            destination[11] = ' ';
+            WriteFourDecimalDigits((uint)year, destination, 12);
+            destination[16] = ' ';
+            WriteTwoDecimalDigits((uint)dateTime.Hour, destination, 17);
+            destination[19] = ':';
+            WriteTwoDecimalDigits((uint)dateTime.Minute, destination, 20);
+            destination[22] = ':';
+            WriteTwoDecimalDigits((uint)dateTime.Second, destination, 23);
+            destination[25] = ' ';
+            destination[26] = 'G';
+            destination[27] = 'M';
+            destination[28] = 'T';
+
+            charsWritten = 29;
+            return true;
+        }
+
+        /// <summary>
+        /// Writes a value [ 00 .. 99 ] to the buffer starting at the specified offset.
+        /// This method performs best when the starting index is a constant literal.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void WriteTwoDecimalDigits(uint value, Span<char> destination, int offset)
+        {
+            Debug.Assert(0 <= value && value <= 99);
+
+            uint temp = '0' + value;
+            value /= 10;
+            destination[offset + 1] = (char)(temp - (value * 10));
+            destination[offset] = (char)('0' + value);
+        }
+
+        /// <summary>
+        /// Writes a value [ 0000 .. 9999 ] to the buffer starting at the specified offset.
+        /// This method performs best when the starting index is a constant literal.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void WriteFourDecimalDigits(uint value, Span<char> buffer, int startingIndex = 0)
+        {
+            Debug.Assert(0 <= value && value <= 9999);
+
+            uint temp = '0' + value;
+            value /= 10;
+            buffer[startingIndex + 3] = (char)(temp - (value * 10));
+
+            temp = '0' + value;
+            value /= 10;
+            buffer[startingIndex + 2] = (char)(temp - (value * 10));
+
+            temp = '0' + value;
+            value /= 10;
+            buffer[startingIndex + 1] = (char)(temp - (value * 10));
+
+            buffer[startingIndex] = (char)('0' + value);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void WriteDigits(ulong value, Span<char> buffer)
+        {
+            // We can mutate the 'value' parameter since it's a copy-by-value local.
+            // It'll be used to represent the value left over after each division by 10.
+
+            for (int i = buffer.Length - 1; i >= 1; i--)
+            {
+                ulong temp = '0' + value;
+                value /= 10;
+                buffer[i] = (char)(temp - (value * 10));
+            }
+
+            Debug.Assert(value < 10);
+            buffer[0] = (char)('0' + value);
+        }
+
+        internal static String[] GetAllDateTimes(DateTime dateTime, char format, DateTimeFormatInfo dtfi)
+        {
+            Debug.Assert(dtfi != null);
+            String[] allFormats = null;
+            String[] results = null;
+
+            switch (format)
+            {
+                case 'd':
+                case 'D':
+                case 'f':
+                case 'F':
+                case 'g':
+                case 'G':
+                case 'm':
+                case 'M':
+                case 't':
+                case 'T':
+                case 'y':
+                case 'Y':
+                    allFormats = dtfi.GetAllDateTimePatterns(format);
+                    results = new String[allFormats.Length];
+                    for (int i = 0; i < allFormats.Length; i++)
+                    {
+                        results[i] = Format(dateTime, allFormats[i], dtfi);
+                    }
+                    break;
+                case 'U':
+                    DateTime universalTime = dateTime.ToUniversalTime();
+                    allFormats = dtfi.GetAllDateTimePatterns(format);
+                    results = new String[allFormats.Length];
+                    for (int i = 0; i < allFormats.Length; i++)
+                    {
+                        results[i] = Format(universalTime, allFormats[i], dtfi);
+                    }
+                    break;
+                //
+                // The following ones are special cases because these patterns are read-only in
+                // DateTimeFormatInfo.
+                //
+                case 'r':
+                case 'R':
+                case 'o':
+                case 'O':
+                case 's':
+                case 'u':
+                    results = new String[] { Format(dateTime, new String(format, 1), dtfi) };
+                    break;
+                default:
+                    throw new FormatException(SR.Format_InvalidString);
+            }
+            return (results);
+        }
+
+        internal static String[] GetAllDateTimes(DateTime dateTime, DateTimeFormatInfo dtfi)
+        {
+            List<String> results = new List<String>(DEFAULT_ALL_DATETIMES_SIZE);
+
+            for (int i = 0; i < allStandardFormats.Length; i++)
+            {
+                String[] strings = GetAllDateTimes(dateTime, allStandardFormats[i], dtfi);
+                for (int j = 0; j < strings.Length; j++)
+                {
+                    results.Add(strings[j]);
+                }
+            }
+            String[] value = new String[results.Count];
+            results.CopyTo(0, value, 0, results.Count);
+            return (value);
+        }
+
+        // This is a placeholder for an MDA to detect when the user is using a
+        // local DateTime with a format that will be interpreted as UTC.
+        internal static void InvalidFormatForLocal(ReadOnlySpan<char> format, DateTime dateTime)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/DateTimeFormatInfo.cs b/src/System.Private.CoreLib/shared/System/Globalization/DateTimeFormatInfo.cs
new file mode 100644
index 0000000000..edec75ac85
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/DateTimeFormatInfo.cs
@@ -0,0 +1,2875 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+
+namespace System.Globalization
+{
+    //
+    // Flags used to indicate different styles of month names.
+    // This is an internal flag used by internalGetMonthName().
+    // Use flag here in case that we need to provide a combination of these styles
+    // (such as month name of a leap year in genitive form.  Not likely for now,
+    // but would like to keep the option open).
+    //
+
+    [Flags]
+    internal enum MonthNameStyles
+    {
+        Regular = 0x00000000,
+        Genitive = 0x00000001,
+        LeapYear = 0x00000002,
+    }
+
+    //
+    // Flags used to indicate special rule used in parsing/formatting
+    // for a specific DateTimeFormatInfo instance.
+    // This is an internal flag.
+    //
+    // This flag is different from MonthNameStyles because this flag
+    // can be expanded to accommodate parsing behaviors like CJK month names
+    // or alternative month names, etc.
+
+    [Flags]
+    internal enum DateTimeFormatFlags
+    {
+        None = 0x00000000,
+        UseGenitiveMonth = 0x00000001,
+        UseLeapYearMonth = 0x00000002,
+        UseSpacesInMonthNames = 0x00000004, // Has spaces or non-breaking space in the month names.
+        UseHebrewRule = 0x00000008,   // Format/Parse using the Hebrew calendar rule.
+        UseSpacesInDayNames = 0x00000010,   // Has spaces or non-breaking space in the day names.
+        UseDigitPrefixInTokens = 0x00000020,   // Has token starting with numbers.
+
+        NotInitialized = -1,
+    }
+
+
+    public sealed class DateTimeFormatInfo : IFormatProvider, ICloneable
+    {
+        // cache for the invariant culture.
+        // invariantInfo is constant irrespective of your current culture.
+        private static volatile DateTimeFormatInfo s_invariantInfo;
+
+        // an index which points to a record in Culture Data Table.
+        private CultureData _cultureData;
+
+        // The culture name used to create this DTFI.
+        private String _name = null;
+
+        // The language name of the culture used to create this DTFI.
+        private String _langName = null;
+
+        // CompareInfo usually used by the parser.
+        private CompareInfo _compareInfo = null;
+
+        // Culture matches current DTFI. mainly used for string comparisons during parsing.
+        private CultureInfo _cultureInfo = null;
+
+        //
+        // Caches for various properties.
+        //
+
+        private String amDesignator = null;
+        private String pmDesignator = null;
+
+        private String dateSeparator = null;            // derived from short date (whidbey expects, arrowhead doesn't)
+
+        private String generalShortTimePattern = null;     // short date + short time (whidbey expects, arrowhead doesn't)
+
+        private String generalLongTimePattern = null;     // short date + long time (whidbey expects, arrowhead doesn't)
+
+        private String timeSeparator = null;            // derived from long time (whidbey expects, arrowhead doesn't)
+        private String monthDayPattern = null;
+        // added in .NET Framework Release {2.0SP1/3.0SP1/3.5RTM}
+        private String dateTimeOffsetPattern = null;
+
+        //
+        // The following are constant values.
+        //
+        private const String rfc1123Pattern = "ddd, dd MMM yyyy HH':'mm':'ss 'GMT'";
+
+        // The sortable pattern is based on ISO 8601.
+        private const String sortableDateTimePattern = "yyyy'-'MM'-'dd'T'HH':'mm':'ss";
+        private const String universalSortableDateTimePattern = "yyyy'-'MM'-'dd HH':'mm':'ss'Z'";
+
+        //
+        // The following are affected by calendar settings.
+        //
+        private Calendar calendar = null;
+
+        private int firstDayOfWeek = -1;
+        private int calendarWeekRule = -1;
+
+
+        private String fullDateTimePattern = null;        // long date + long time (whidbey expects, arrowhead doesn't)
+
+        private String[] abbreviatedDayNames = null;
+
+
+        private String[] m_superShortDayNames = null;
+
+        private String[] dayNames = null;
+        private String[] abbreviatedMonthNames = null;
+        private String[] monthNames = null;
+        // Cache the genitive month names that we retrieve from the data table.
+
+        private String[] genitiveMonthNames = null;
+
+        // Cache the abbreviated genitive month names that we retrieve from the data table.
+
+        private String[] m_genitiveAbbreviatedMonthNames = null;
+
+        // Cache the month names of a leap year that we retrieve from the data table.
+
+        private String[] leapYearMonthNames = null;
+
+        // For our "patterns" arrays we have 2 variables, a string and a string[]
+        //
+        // The string[] contains the list of patterns, EXCEPT the default may not be included.
+        // The string contains the default pattern.
+        // When we initially construct our string[], we set the string to string[0]
+
+        // The "default" Date/time patterns 
+        private String longDatePattern = null;
+        private String shortDatePattern = null;
+        private String yearMonthPattern = null;
+        private String longTimePattern = null;
+        private String shortTimePattern = null;
+
+        private String[] allYearMonthPatterns = null;
+
+        private String[] allShortDatePatterns = null;
+        private String[] allLongDatePatterns = null;
+        private String[] allShortTimePatterns = null;
+        private String[] allLongTimePatterns = null;
+
+        // Cache the era names for this DateTimeFormatInfo instance.
+        private String[] m_eraNames = null;
+        private String[] m_abbrevEraNames = null;
+        private String[] m_abbrevEnglishEraNames = null;
+
+        private CalendarId[] optionalCalendars = null;
+
+        private const int DEFAULT_ALL_DATETIMES_SIZE = 132;
+
+        // CultureInfo updates this
+        internal bool _isReadOnly = false;
+
+        // This flag gives hints about if formatting/parsing should perform special code path for things like
+        // genitive form or leap year month names.
+
+        private DateTimeFormatFlags formatFlags = DateTimeFormatFlags.NotInitialized;
+
+        private String CultureName
+        {
+            get
+            {
+                if (_name == null)
+                {
+                    _name = _cultureData.CultureName;
+                }
+                return (_name);
+            }
+        }
+
+        private CultureInfo Culture
+        {
+            get
+            {
+                if (_cultureInfo == null)
+                {
+                    _cultureInfo = CultureInfo.GetCultureInfo(this.CultureName);
+                }
+                return _cultureInfo;
+            }
+        }
+
+        // TODO: This ignores other cultures that might want to do something similar
+        private String LanguageName
+        {
+            get
+            {
+                if (_langName == null)
+                {
+                    _langName = _cultureData.SISO639LANGNAME;
+                }
+                return (_langName);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // Create an array of string which contains the abbreviated day names.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+
+        private string[] internalGetAbbreviatedDayOfWeekNames() => this.abbreviatedDayNames ?? internalGetAbbreviatedDayOfWeekNamesCore();
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private string[] internalGetAbbreviatedDayOfWeekNamesCore()
+        {
+            // Get the abbreviated day names for our current calendar
+            this.abbreviatedDayNames = _cultureData.AbbreviatedDayNames(Calendar.ID);
+            Debug.Assert(this.abbreviatedDayNames.Length == 7, "[DateTimeFormatInfo.GetAbbreviatedDayOfWeekNames] Expected 7 day names in a week");
+            return this.abbreviatedDayNames;
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        // Action: Returns the string array of the one-letter day of week names.
+        // Returns:
+        //  an array of one-letter day of week names
+        // Arguments:
+        //  None
+        // Exceptions:
+        //  None
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        private string[] internalGetSuperShortDayNames() => this.m_superShortDayNames ?? internalGetSuperShortDayNamesCore();
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private string[] internalGetSuperShortDayNamesCore()
+        {
+            // Get the super short day names for our current calendar
+            this.m_superShortDayNames = _cultureData.SuperShortDayNames(Calendar.ID);
+            Debug.Assert(this.m_superShortDayNames.Length == 7, "[DateTimeFormatInfo.internalGetSuperShortDayNames] Expected 7 day names in a week");
+            return this.m_superShortDayNames;
+        }
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // Create an array of string which contains the day names.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+
+        private string[] internalGetDayOfWeekNames() => this.dayNames ?? internalGetDayOfWeekNamesCore();
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private string[] internalGetDayOfWeekNamesCore()
+        {
+            // Get the day names for our current calendar
+            this.dayNames = _cultureData.DayNames(Calendar.ID);
+            Debug.Assert(this.dayNames.Length == 7, "[DateTimeFormatInfo.GetDayOfWeekNames] Expected 7 day names in a week");
+            return this.dayNames;
+        }
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // Create an array of string which contains the abbreviated month names.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+
+        private String[] internalGetAbbreviatedMonthNames() => this.abbreviatedMonthNames ?? internalGetAbbreviatedMonthNamesCore();
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private String[] internalGetAbbreviatedMonthNamesCore()
+        {
+            // Get the month names for our current calendar
+            this.abbreviatedMonthNames = _cultureData.AbbreviatedMonthNames(Calendar.ID);
+            Debug.Assert(this.abbreviatedMonthNames.Length == 12 || this.abbreviatedMonthNames.Length == 13,
+                "[DateTimeFormatInfo.GetAbbreviatedMonthNames] Expected 12 or 13 month names in a year");
+            return this.abbreviatedMonthNames;
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // Create an array of string which contains the month names.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+
+        private string[] internalGetMonthNames() => this.monthNames ?? internalGetMonthNamesCore();
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private string[] internalGetMonthNamesCore()
+        {
+            // Get the month names for our current calendar
+            this.monthNames = _cultureData.MonthNames(Calendar.ID);
+            Debug.Assert(this.monthNames.Length == 12 || this.monthNames.Length == 13,
+                "[DateTimeFormatInfo.GetMonthNames] Expected 12 or 13 month names in a year");
+            return this.monthNames;
+        }
+
+
+        //
+        // Invariant DateTimeFormatInfo doesn't have user-overriden values
+        // Default calendar is gregorian
+        public DateTimeFormatInfo()
+            : this(CultureInfo.InvariantCulture._cultureData, GregorianCalendar.GetDefaultInstance())
+        {
+        }
+
+        internal DateTimeFormatInfo(CultureData cultureData, Calendar cal)
+        {
+            Debug.Assert(cultureData != null);
+            Debug.Assert(cal != null);
+
+            // Remember our culture
+            _cultureData = cultureData;
+
+            this.Calendar = cal;
+        }
+
+        private void InitializeOverridableProperties(CultureData cultureData, CalendarId calendarId)
+        {
+            Debug.Assert(cultureData != null);
+            Debug.Assert(calendarId != CalendarId.UNINITIALIZED_VALUE, "[DateTimeFormatInfo.Populate] Expected initalized calendarId");
+
+            if (this.firstDayOfWeek == -1) { this.firstDayOfWeek = cultureData.IFIRSTDAYOFWEEK; }
+            if (this.calendarWeekRule == -1) { this.calendarWeekRule = cultureData.IFIRSTWEEKOFYEAR; }
+
+            if (this.amDesignator == null) { this.amDesignator = cultureData.SAM1159; }
+            if (this.pmDesignator == null) { this.pmDesignator = cultureData.SPM2359; }
+            if (this.timeSeparator == null) { this.timeSeparator = cultureData.TimeSeparator; }
+            if (this.dateSeparator == null) { this.dateSeparator = cultureData.DateSeparator(calendarId); }
+
+            this.allLongTimePatterns = _cultureData.LongTimes;
+            Debug.Assert(this.allLongTimePatterns.Length > 0, "[DateTimeFormatInfo.Populate] Expected some long time patterns");
+
+            this.allShortTimePatterns = _cultureData.ShortTimes;
+            Debug.Assert(this.allShortTimePatterns.Length > 0, "[DateTimeFormatInfo.Populate] Expected some short time patterns");
+
+            this.allLongDatePatterns = cultureData.LongDates(calendarId);
+            Debug.Assert(this.allLongDatePatterns.Length > 0, "[DateTimeFormatInfo.Populate] Expected some long date patterns");
+
+            this.allShortDatePatterns = cultureData.ShortDates(calendarId);
+            Debug.Assert(this.allShortDatePatterns.Length > 0, "[DateTimeFormatInfo.Populate] Expected some short date patterns");
+
+            this.allYearMonthPatterns = cultureData.YearMonths(calendarId);
+            Debug.Assert(this.allYearMonthPatterns.Length > 0, "[DateTimeFormatInfo.Populate] Expected some year month patterns");
+        }
+
+        // Returns a default DateTimeFormatInfo that will be universally
+        // supported and constant irrespective of the current culture.
+        // Used by FromString methods.
+        //
+
+        public static DateTimeFormatInfo InvariantInfo
+        {
+            get
+            {
+                if (s_invariantInfo == null)
+                {
+                    DateTimeFormatInfo info = new DateTimeFormatInfo();
+                    info.Calendar.SetReadOnlyState(true);
+                    info._isReadOnly = true;
+                    s_invariantInfo = info;
+                }
+                return (s_invariantInfo);
+            }
+        }
+
+        // Returns the current culture's DateTimeFormatInfo.  Used by Parse methods.
+        //
+
+        public static DateTimeFormatInfo CurrentInfo
+        {
+            get
+            {
+                System.Globalization.CultureInfo culture = System.Globalization.CultureInfo.CurrentCulture;
+                if (!culture._isInherited)
+                {
+                    DateTimeFormatInfo info = culture.dateTimeInfo;
+                    if (info != null)
+                    {
+                        return info;
+                    }
+                }
+                return (DateTimeFormatInfo)culture.GetFormat(typeof(DateTimeFormatInfo));
+            }
+        }
+
+        public static DateTimeFormatInfo GetInstance(IFormatProvider provider) =>
+            provider == null ? CurrentInfo :
+            provider is CultureInfo cultureProvider && !cultureProvider._isInherited ? cultureProvider.DateTimeFormat :
+            provider is DateTimeFormatInfo info ? info :
+            provider.GetFormat(typeof(DateTimeFormatInfo)) is DateTimeFormatInfo info2 ? info2 :
+            CurrentInfo; // Couldn't get anything, just use currentInfo as fallback
+
+        public Object GetFormat(Type formatType)
+        {
+            return (formatType == typeof(DateTimeFormatInfo) ? this : null);
+        }
+
+
+        public Object Clone()
+        {
+            DateTimeFormatInfo n = (DateTimeFormatInfo)MemberwiseClone();
+            // We can use the data member calendar in the setter, instead of the property Calendar,
+            // since the cloned copy should have the same state as the original copy.
+            n.calendar = (Calendar)this.Calendar.Clone();
+            n._isReadOnly = false;
+            return n;
+        }
+
+
+        public String AMDesignator
+        {
+            get
+            {
+                if (this.amDesignator == null)
+                {
+                    this.amDesignator = _cultureData.SAM1159;
+                }
+                Debug.Assert(this.amDesignator != null, "DateTimeFormatInfo.AMDesignator, amDesignator != null");
+                return (this.amDesignator);
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_String);
+                }
+                ClearTokenHashTable();
+                amDesignator = value;
+            }
+        }
+
+
+        public Calendar Calendar
+        {
+            get
+            {
+                Debug.Assert(this.calendar != null, "DateTimeFormatInfo.Calendar: calendar != null");
+                return (this.calendar);
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value), SR.ArgumentNull_Obj);
+                }
+                if (value == calendar)
+                {
+                    return;
+                }
+
+                for (int i = 0; i < this.OptionalCalendars.Length; i++)
+                {
+                    if (this.OptionalCalendars[i] == value.ID)
+                    {
+                        // We can use this one, so do so.
+
+                        // Clean related properties if we already had a calendar set
+                        if (calendar != null)
+                        {
+                            // clean related properties which are affected by the calendar setting,
+                            // so that they will be refreshed when they are accessed next time.
+                            //
+
+                            // These properites are in the order as appearing in calendar.xml.
+                            m_eraNames = null;
+                            m_abbrevEraNames = null;
+                            m_abbrevEnglishEraNames = null;
+
+                            monthDayPattern = null;
+
+                            dayNames = null;
+                            abbreviatedDayNames = null;
+                            m_superShortDayNames = null;
+                            monthNames = null;
+                            abbreviatedMonthNames = null;
+                            genitiveMonthNames = null;
+                            m_genitiveAbbreviatedMonthNames = null;
+                            leapYearMonthNames = null;
+                            formatFlags = DateTimeFormatFlags.NotInitialized;
+
+                            allShortDatePatterns = null;
+                            allLongDatePatterns = null;
+                            allYearMonthPatterns = null;
+                            dateTimeOffsetPattern = null;
+
+                            // The defaults need reset as well:
+                            longDatePattern = null;
+                            shortDatePattern = null;
+                            yearMonthPattern = null;
+
+                            // These properies are not in the OS data, but they are dependent on the values like shortDatePattern.
+                            fullDateTimePattern = null; // Long date + long time
+                            generalShortTimePattern = null; // short date + short time
+                            generalLongTimePattern = null; // short date + long time
+
+                            // Derived item that changes
+                            dateSeparator = null;
+
+                            // We don't need to do these because they are not changed by changing calendar
+                            //      amDesignator
+                            //      pmDesignator
+                            //      timeSeparator
+                            //      longTimePattern
+                            //      firstDayOfWeek
+                            //      calendarWeekRule
+
+                            // remember to reload tokens
+                            ClearTokenHashTable();
+                        }
+
+                        // Remember the new calendar
+                        calendar = value;
+                        InitializeOverridableProperties(_cultureData, calendar.ID);
+
+                        // We succeeded, return
+                        return;
+                    }
+                }
+
+                // The assigned calendar is not a valid calendar for this culture, throw
+                throw new ArgumentOutOfRangeException(nameof(value), SR.Argument_InvalidCalendar);
+            }
+        }
+
+        private CalendarId[] OptionalCalendars
+        {
+            get
+            {
+                if (this.optionalCalendars == null)
+                {
+                    this.optionalCalendars = _cultureData.CalendarIds;
+                }
+                return (this.optionalCalendars);
+            }
+        }
+
+        /*=================================GetEra==========================
+        **Action: Get the era value by parsing the name of the era.
+        **Returns: The era value for the specified era name.
+        **      -1 if the name of the era is not valid or not supported.
+        **Arguments: eraName    the name of the era.
+        **Exceptions: None.
+        ============================================================================*/
+
+
+        public int GetEra(String eraName)
+        {
+            if (eraName == null)
+            {
+                throw new ArgumentNullException(nameof(eraName),
+                    SR.ArgumentNull_String);
+            }
+
+            // The Era Name and Abbreviated Era Name 
+            // for Taiwan Calendar on non-Taiwan SKU returns empty string (which 
+            // would be matched below) but we don't want the empty string to give
+            // us an Era number
+            // confer 85900 DTFI.GetEra("") should fail on all cultures
+            if (eraName.Length == 0)
+            {
+                return (-1);
+            }
+
+            // The following is based on the assumption that the era value is starting from 1, and has a
+            // serial values.
+            // If that ever changes, the code has to be changed.
+
+            // The calls to String.Compare should use the current culture for the string comparisons, but the
+            // invariant culture when comparing against the english names.
+            for (int i = 0; i < EraNames.Length; i++)
+            {
+                // Compare the era name in a case-insensitive way for the appropriate culture.
+                if (m_eraNames[i].Length > 0)
+                {
+                    if (this.Culture.CompareInfo.Compare(eraName, m_eraNames[i], CompareOptions.IgnoreCase) == 0)
+                    {
+                        return (i + 1);
+                    }
+                }
+            }
+            for (int i = 0; i < AbbreviatedEraNames.Length; i++)
+            {
+                // Compare the abbreviated era name in a case-insensitive way for the appropriate culture.              
+                if (this.Culture.CompareInfo.Compare(eraName, m_abbrevEraNames[i], CompareOptions.IgnoreCase) == 0)
+                {
+                    return (i + 1);
+                }
+            }
+            for (int i = 0; i < AbbreviatedEnglishEraNames.Length; i++)
+            {
+                // this comparison should use the InvariantCulture.  The English name could have linguistically
+                // interesting characters.
+                if (CompareInfo.Invariant.Compare(eraName, m_abbrevEnglishEraNames[i], CompareOptions.IgnoreCase) == 0)
+                {
+                    return (i + 1);
+                }
+            }
+            return (-1);
+        }
+
+
+        internal String[] EraNames
+        {
+            get
+            {
+                if (this.m_eraNames == null)
+                {
+                    this.m_eraNames = _cultureData.EraNames(Calendar.ID); ;
+                }
+                return (this.m_eraNames);
+            }
+        }
+
+        /*=================================GetEraName==========================
+        **Action: Get the name of the era for the specified era value.
+        **Returns: The name of the specified era.
+        **Arguments:
+        **      era the era value.
+        **Exceptions:
+        **      ArguementException if the era valie is invalid.
+        ============================================================================*/
+
+        // Era names are 1 indexed
+        public String GetEraName(int era)
+        {
+            if (era == Calendar.CurrentEra)
+            {
+                era = Calendar.CurrentEraValue;
+            }
+
+            // The following is based on the assumption that the era value is starting from 1, and has a
+            // serial values.
+            // If that ever changes, the code has to be changed.
+            if ((--era) < EraNames.Length && (era >= 0))
+            {
+                return (m_eraNames[era]);
+            }
+            throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+        }
+
+        internal String[] AbbreviatedEraNames
+        {
+            get
+            {
+                if (this.m_abbrevEraNames == null)
+                {
+                    this.m_abbrevEraNames = _cultureData.AbbrevEraNames(Calendar.ID);
+                }
+                return (this.m_abbrevEraNames);
+            }
+        }
+
+        // Era names are 1 indexed
+        public String GetAbbreviatedEraName(int era)
+        {
+            if (AbbreviatedEraNames.Length == 0)
+            {
+                // If abbreviation era name is not used in this culture,
+                // return the full era name.
+                return (GetEraName(era));
+            }
+            if (era == Calendar.CurrentEra)
+            {
+                era = Calendar.CurrentEraValue;
+            }
+            if ((--era) < m_abbrevEraNames.Length && (era >= 0))
+            {
+                return (m_abbrevEraNames[era]);
+            }
+            throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+        }
+
+        internal String[] AbbreviatedEnglishEraNames
+        {
+            get
+            {
+                if (this.m_abbrevEnglishEraNames == null)
+                {
+                    Debug.Assert(Calendar.ID > 0, "[DateTimeFormatInfo.AbbreviatedEnglishEraNames] Expected Calendar.ID > 0");
+                    this.m_abbrevEnglishEraNames = _cultureData.AbbreviatedEnglishEraNames(Calendar.ID);
+                }
+                return (this.m_abbrevEnglishEraNames);
+            }
+        }
+
+        // Note that cultureData derives this from the short date format (unless someone's set this previously)
+        // Note that this property is quite undesirable.
+        public string DateSeparator
+        {
+            get
+            {
+                if (dateSeparator == null)
+                {
+                    dateSeparator = _cultureData.DateSeparator(Calendar.ID);
+                }
+                Debug.Assert(this.dateSeparator != null, "DateTimeFormatInfo.DateSeparator, dateSeparator != null");
+                return dateSeparator;
+            }
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value), SR.ArgumentNull_String);
+                }
+                ClearTokenHashTable();
+                dateSeparator = value;
+            }
+        }
+
+        public DayOfWeek FirstDayOfWeek
+        {
+            get
+            {
+                if (this.firstDayOfWeek == -1)
+                {
+                    this.firstDayOfWeek = _cultureData.IFIRSTDAYOFWEEK;
+                }
+                Debug.Assert(this.firstDayOfWeek != -1, "DateTimeFormatInfo.FirstDayOfWeek, firstDayOfWeek != -1");
+
+                return ((DayOfWeek)this.firstDayOfWeek);
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value >= DayOfWeek.Sunday && value <= DayOfWeek.Saturday)
+                {
+                    firstDayOfWeek = (int)value;
+                }
+                else
+                {
+                    throw new ArgumentOutOfRangeException(
+                        nameof(value), SR.Format(SR.ArgumentOutOfRange_Range,
+                        DayOfWeek.Sunday, DayOfWeek.Saturday));
+                }
+            }
+        }
+
+        public CalendarWeekRule CalendarWeekRule
+        {
+            get
+            {
+                if (this.calendarWeekRule == -1)
+                {
+                    this.calendarWeekRule = _cultureData.IFIRSTWEEKOFYEAR;
+                }
+                Debug.Assert(this.calendarWeekRule != -1, "DateTimeFormatInfo.CalendarWeekRule, calendarWeekRule != -1");
+                return ((CalendarWeekRule)this.calendarWeekRule);
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value >= CalendarWeekRule.FirstDay && value <= CalendarWeekRule.FirstFourDayWeek)
+                {
+                    calendarWeekRule = (int)value;
+                }
+                else
+                {
+                    throw new ArgumentOutOfRangeException(
+                        nameof(value), SR.Format(SR.ArgumentOutOfRange_Range,
+                        CalendarWeekRule.FirstDay, CalendarWeekRule.FirstFourDayWeek));
+                }
+            }
+        }
+
+        public String FullDateTimePattern
+        {
+            get
+            {
+                if (fullDateTimePattern == null)
+                {
+                    fullDateTimePattern = LongDatePattern + " " + LongTimePattern;
+                }
+                return (fullDateTimePattern);
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_String);
+                }
+                fullDateTimePattern = value;
+            }
+        }
+
+
+        // For our "patterns" arrays we have 2 variables, a string and a string[]
+        //
+        // The string[] contains the list of patterns, EXCEPT the default may not be included.
+        // The string contains the default pattern.
+        // When we initially construct our string[], we set the string to string[0]
+        public String LongDatePattern
+        {
+            get
+            {
+                // Initialize our long date pattern from the 1st array value if not set
+                if (this.longDatePattern == null)
+                {
+                    // Initialize our data
+                    this.longDatePattern = this.UnclonedLongDatePatterns[0];
+                }
+
+                return this.longDatePattern;
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_String);
+                }
+
+                // Remember the new string
+                this.longDatePattern = value;
+
+                // Clear the token hash table
+                ClearTokenHashTable();
+
+                // Clean up cached values that will be affected by this property.
+                this.fullDateTimePattern = null;
+            }
+        }
+
+        // For our "patterns" arrays we have 2 variables, a string and a string[]
+        //
+        // The string[] contains the list of patterns, EXCEPT the default may not be included.
+        // The string contains the default pattern.
+        // When we initially construct our string[], we set the string to string[0]
+        public String LongTimePattern
+        {
+            get
+            {
+                // Initialize our long time pattern from the 1st array value if not set
+                if (this.longTimePattern == null)
+                {
+                    // Initialize our data
+                    this.longTimePattern = this.UnclonedLongTimePatterns[0];
+                }
+
+                return this.longTimePattern;
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_String);
+                }
+
+                // Remember the new string
+                this.longTimePattern = value;
+
+                // Clear the token hash table
+                ClearTokenHashTable();
+
+                // Clean up cached values that will be affected by this property.
+                this.fullDateTimePattern = null;     // Full date = long date + long Time
+                this.generalLongTimePattern = null;  // General long date = short date + long Time
+                this.dateTimeOffsetPattern = null;
+            }
+        }
+
+
+        // Note: just to be confusing there's only 1 month day pattern, not a whole list
+        public String MonthDayPattern
+        {
+            get
+            {
+                if (this.monthDayPattern == null)
+                {
+                    Debug.Assert(Calendar.ID > 0, "[DateTimeFormatInfo.MonthDayPattern] Expected calID > 0");
+                    this.monthDayPattern = _cultureData.MonthDay(Calendar.ID);
+                }
+                Debug.Assert(this.monthDayPattern != null, "DateTimeFormatInfo.MonthDayPattern, monthDayPattern != null");
+                return (this.monthDayPattern);
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_String);
+                }
+
+                this.monthDayPattern = value;
+            }
+        }
+
+
+        public String PMDesignator
+        {
+            get
+            {
+                if (this.pmDesignator == null)
+                {
+                    this.pmDesignator = _cultureData.SPM2359;
+                }
+                Debug.Assert(this.pmDesignator != null, "DateTimeFormatInfo.PMDesignator, pmDesignator != null");
+                return (this.pmDesignator);
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_String);
+                }
+                ClearTokenHashTable();
+
+                pmDesignator = value;
+            }
+        }
+
+
+        public String RFC1123Pattern
+        {
+            get
+            {
+                return (rfc1123Pattern);
+            }
+        }
+
+        // For our "patterns" arrays we have 2 variables, a string and a string[]
+        //
+        // The string[] contains the list of patterns, EXCEPT the default may not be included.
+        // The string contains the default pattern.
+        // When we initially construct our string[], we set the string to string[0]
+        public String ShortDatePattern
+        {
+            get
+            {
+                // Initialize our short date pattern from the 1st array value if not set
+                if (this.shortDatePattern == null)
+                {
+                    // Initialize our data
+                    this.shortDatePattern = this.UnclonedShortDatePatterns[0];
+                }
+
+                return this.shortDatePattern;
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_String);
+
+                // Remember the new string
+                this.shortDatePattern = value;
+
+                // Clear the token hash table, note that even short dates could require this
+                ClearTokenHashTable();
+
+                // Clean up cached values that will be affected by this property.
+                generalLongTimePattern = null;   // General long time = short date + long time
+                generalShortTimePattern = null;  // General short time = short date + short Time
+                dateTimeOffsetPattern = null;
+            }
+        }
+
+
+        // For our "patterns" arrays we have 2 variables, a string and a string[]
+        //
+        // The string[] contains the list of patterns, EXCEPT the default may not be included.
+        // The string contains the default pattern.
+        // When we initially construct our string[], we set the string to string[0]
+        public String ShortTimePattern
+        {
+            get
+            {
+                // Initialize our short time pattern from the 1st array value if not set
+                if (this.shortTimePattern == null)
+                {
+                    // Initialize our data
+                    this.shortTimePattern = this.UnclonedShortTimePatterns[0];
+                }
+                return this.shortTimePattern;
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_String);
+                }
+
+                // Remember the new string
+                this.shortTimePattern = value;
+
+                // Clear the token hash table, note that even short times could require this
+                ClearTokenHashTable();
+
+                // Clean up cached values that will be affected by this property.
+                generalShortTimePattern = null; // General short date = short date + short time.
+            }
+        }
+
+
+        public String SortableDateTimePattern
+        {
+            get
+            {
+                return (sortableDateTimePattern);
+            }
+        }
+
+        /*=================================GeneralShortTimePattern=====================
+        **Property: Return the pattern for 'g' general format: shortDate + short time
+        **Note: This is used by DateTimeFormat.cs to get the pattern for 'g'
+        **      We put this internal property here so that we can avoid doing the
+        **      concatation every time somebody asks for the general format.
+        ==============================================================================*/
+
+        internal String GeneralShortTimePattern
+        {
+            get
+            {
+                if (generalShortTimePattern == null)
+                {
+                    generalShortTimePattern = ShortDatePattern + " " + ShortTimePattern;
+                }
+                return (generalShortTimePattern);
+            }
+        }
+
+        /*=================================GeneralLongTimePattern=====================
+        **Property: Return the pattern for 'g' general format: shortDate + Long time
+        **Note: This is used by DateTimeFormat.cs to get the pattern for 'g'
+        **      We put this internal property here so that we can avoid doing the
+        **      concatation every time somebody asks for the general format.
+        ==============================================================================*/
+
+        internal String GeneralLongTimePattern
+        {
+            get
+            {
+                if (generalLongTimePattern == null)
+                {
+                    generalLongTimePattern = ShortDatePattern + " " + LongTimePattern;
+                }
+                return (generalLongTimePattern);
+            }
+        }
+
+        /*=================================DateTimeOffsetPattern==========================
+        **Property: Return the default pattern DateTimeOffset : shortDate + long time + time zone offset
+        **Note: This is used by DateTimeFormat.cs to get the pattern for short Date + long time +  time zone offset
+        **      We put this internal property here so that we can avoid doing the
+        **      concatation every time somebody uses this form
+        ==============================================================================*/
+
+        internal String DateTimeOffsetPattern
+        {
+            get
+            {
+                if (dateTimeOffsetPattern == null)
+                {
+                    string dateTimePattern = ShortDatePattern + " " + LongTimePattern;
+
+                    /* LongTimePattern might contain a "z" as part of the format string in which case we don't want to append a time zone offset */
+
+                    bool foundZ = false;
+                    bool inQuote = false;
+                    char quote = '\'';
+                    for (int i = 0; !foundZ && i < LongTimePattern.Length; i++)
+                    {
+                        switch (LongTimePattern[i])
+                        {
+                            case 'z':
+                                /* if we aren't in a quote, we've found a z */
+                                foundZ = !inQuote;
+                                /* we'll fall out of the loop now because the test includes !foundZ */
+                                break;
+                            case '\'':
+                            case '\"':
+                                if (inQuote && (quote == LongTimePattern[i]))
+                                {
+                                    /* we were in a quote and found a matching exit quote, so we are outside a quote now */
+                                    inQuote = false;
+                                }
+                                else if (!inQuote)
+                                {
+                                    quote = LongTimePattern[i];
+                                    inQuote = true;
+                                }
+                                else
+                                {
+                                    /* we were in a quote and saw the other type of quote character, so we are still in a quote */
+                                }
+                                break;
+                            case '%':
+                            case '\\':
+                                i++; /* skip next character that is escaped by this backslash */
+                                break;
+                            default:
+                                break;
+                        }
+                    }
+
+                    if (!foundZ)
+                    {
+                        dateTimePattern = dateTimePattern + " zzz";
+                    }
+
+                    dateTimeOffsetPattern = dateTimePattern;
+                }
+                return (dateTimeOffsetPattern);
+            }
+        }
+
+        // Note that cultureData derives this from the long time format (unless someone's set this previously)
+        // Note that this property is quite undesirable.
+        public string TimeSeparator
+        {
+            get
+            {
+                if (timeSeparator == null)
+                {
+                    timeSeparator = _cultureData.TimeSeparator;
+                }
+                Debug.Assert(this.timeSeparator != null, "DateTimeFormatInfo.TimeSeparator, timeSeparator != null");
+                return (timeSeparator);
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value), SR.ArgumentNull_String);
+                }
+
+                ClearTokenHashTable();
+
+                timeSeparator = value;
+            }
+        }
+
+        public String UniversalSortableDateTimePattern
+        {
+            get
+            {
+                return (universalSortableDateTimePattern);
+            }
+        }
+
+        // For our "patterns" arrays we have 2 variables, a string and a string[]
+        //
+        // The string[] contains the list of patterns, EXCEPT the default may not be included.
+        // The string contains the default pattern.
+        // When we initially construct our string[], we set the string to string[0]
+        public String YearMonthPattern
+        {
+            get
+            {
+                // Initialize our year/month pattern from the 1st array value if not set
+                if (this.yearMonthPattern == null)
+                {
+                    // Initialize our data
+                    this.yearMonthPattern = this.UnclonedYearMonthPatterns[0];
+                }
+                return this.yearMonthPattern;
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_String);
+                }
+
+                // Remember the new string
+                this.yearMonthPattern = value;
+
+                // Clear the token hash table, note that even short times could require this
+                ClearTokenHashTable();
+            }
+        }
+
+        //
+        // Check if a string array contains a null value, and throw ArgumentNullException with parameter name "value"
+        //
+        private static void CheckNullValue(String[] values, int length)
+        {
+            Debug.Assert(values != null, "value != null");
+            Debug.Assert(values.Length >= length);
+            for (int i = 0; i < length; i++)
+            {
+                if (values[i] == null)
+                {
+                    throw new ArgumentNullException("value",
+                        SR.ArgumentNull_ArrayValue);
+                }
+            }
+        }
+
+
+        public String[] AbbreviatedDayNames
+        {
+            get
+            {
+                return ((String[])internalGetAbbreviatedDayOfWeekNames().Clone());
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_Array);
+                }
+                if (value.Length != 7)
+                {
+                    throw new ArgumentException(SR.Format(SR.Argument_InvalidArrayLength, 7), nameof(value));
+                }
+                CheckNullValue(value, value.Length);
+                ClearTokenHashTable();
+
+                abbreviatedDayNames = value;
+            }
+        }
+
+        // Returns the string array of the one-letter day of week names.
+        public String[] ShortestDayNames
+        {
+            get
+            {
+                return ((String[])internalGetSuperShortDayNames().Clone());
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_Array);
+                }
+                if (value.Length != 7)
+                {
+                    throw new ArgumentException(SR.Format(SR.Argument_InvalidArrayLength, 7), nameof(value));
+                }
+                CheckNullValue(value, value.Length);
+                this.m_superShortDayNames = value;
+            }
+        }
+
+
+        public String[] DayNames
+        {
+            get
+            {
+                return ((String[])internalGetDayOfWeekNames().Clone());
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_Array);
+                }
+                if (value.Length != 7)
+                {
+                    throw new ArgumentException(SR.Format(SR.Argument_InvalidArrayLength, 7), nameof(value));
+                }
+                CheckNullValue(value, value.Length);
+                ClearTokenHashTable();
+
+                dayNames = value;
+            }
+        }
+
+
+        public String[] AbbreviatedMonthNames
+        {
+            get
+            {
+                return ((String[])internalGetAbbreviatedMonthNames().Clone());
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_Array);
+                }
+                if (value.Length != 13)
+                {
+                    throw new ArgumentException(SR.Format(SR.Argument_InvalidArrayLength, 13), nameof(value));
+                }
+                CheckNullValue(value, value.Length - 1);
+                ClearTokenHashTable();
+                abbreviatedMonthNames = value;
+            }
+        }
+
+
+        public String[] MonthNames
+        {
+            get
+            {
+                return ((String[])internalGetMonthNames().Clone());
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_Array);
+                }
+                if (value.Length != 13)
+                {
+                    throw new ArgumentException(SR.Format(SR.Argument_InvalidArrayLength, 13), nameof(value));
+                }
+                CheckNullValue(value, value.Length - 1);
+                monthNames = value;
+                ClearTokenHashTable();
+            }
+        }
+
+        // Whitespaces that we allow in the month names.
+        // U+00a0 is non-breaking space.
+        private static readonly char[] s_monthSpaces = { ' ', '\u00a0' };
+
+        internal bool HasSpacesInMonthNames
+        {
+            get
+            {
+                return (FormatFlags & DateTimeFormatFlags.UseSpacesInMonthNames) != 0;
+            }
+        }
+
+        internal bool HasSpacesInDayNames
+        {
+            get
+            {
+                return (FormatFlags & DateTimeFormatFlags.UseSpacesInDayNames) != 0;
+            }
+        }
+
+
+        //
+        //  internalGetMonthName
+        //
+        // Actions: Return the month name using the specified MonthNameStyles in either abbreviated form
+        //      or full form.
+        // Arguments:
+        //      month
+        //      style           To indicate a form like regular/genitive/month name in a leap year.
+        //      abbreviated     When true, return abbreviated form.  Otherwise, return a full form.
+        //  Exceptions:
+        //      ArgumentOutOfRangeException When month name is invalid.
+        //
+        internal String internalGetMonthName(int month, MonthNameStyles style, bool abbreviated)
+        {
+            //
+            // Right now, style is mutual exclusive, but I make the style to be flag so that
+            // maybe we can combine flag if there is such a need.
+            //
+            String[] monthNamesArray = null;
+            switch (style)
+            {
+                case MonthNameStyles.Genitive:
+                    monthNamesArray = internalGetGenitiveMonthNames(abbreviated);
+                    break;
+                case MonthNameStyles.LeapYear:
+                    monthNamesArray = internalGetLeapYearMonthNames(/*abbreviated*/);
+                    break;
+                default:
+                    monthNamesArray = (abbreviated ? internalGetAbbreviatedMonthNames() : internalGetMonthNames());
+                    break;
+            }
+            // The month range is from 1 ~ this.m_monthNames.Length
+            // (actually is 13 right now for all cases)
+            if ((month < 1) || (month > monthNamesArray.Length))
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(month), SR.Format(SR.ArgumentOutOfRange_Range,
+                    1, monthNamesArray.Length));
+            }
+            return (monthNamesArray[month - 1]);
+        }
+
+        //
+        //  internalGetGenitiveMonthNames
+        //
+        //  Action: Retrieve the array which contains the month names in genitive form.
+        //      If this culture does not use the gentive form, the normal month name is returned.
+        //  Arguments:
+        //      abbreviated     When true, return abbreviated form.  Otherwise, return a full form.
+        //
+        private String[] internalGetGenitiveMonthNames(bool abbreviated)
+        {
+            if (abbreviated)
+            {
+                if (this.m_genitiveAbbreviatedMonthNames == null)
+                {
+                    this.m_genitiveAbbreviatedMonthNames = _cultureData.AbbreviatedGenitiveMonthNames(this.Calendar.ID);
+                    Debug.Assert(this.m_genitiveAbbreviatedMonthNames.Length == 13,
+                        "[DateTimeFormatInfo.GetGenitiveMonthNames] Expected 13 abbreviated genitive month names in a year");
+                }
+                return (this.m_genitiveAbbreviatedMonthNames);
+            }
+
+            if (this.genitiveMonthNames == null)
+            {
+                this.genitiveMonthNames = _cultureData.GenitiveMonthNames(this.Calendar.ID);
+                Debug.Assert(this.genitiveMonthNames.Length == 13,
+                    "[DateTimeFormatInfo.GetGenitiveMonthNames] Expected 13 genitive month names in a year");
+            }
+            return (this.genitiveMonthNames);
+        }
+
+        //
+        //  internalGetLeapYearMonthNames
+        //
+        //  Actions: Retrieve the month names used in a leap year.
+        //      If this culture does not have different month names in a leap year, the normal month name is returned.
+        //  Arguments: None. (can use abbreviated later if needed)
+        //
+        internal String[] internalGetLeapYearMonthNames(/*bool abbreviated*/)
+        {
+            if (this.leapYearMonthNames == null)
+            {
+                Debug.Assert(Calendar.ID > 0, "[DateTimeFormatInfo.internalGetLeapYearMonthNames] Expected Calendar.ID > 0");
+                this.leapYearMonthNames = _cultureData.LeapYearMonthNames(Calendar.ID);
+                Debug.Assert(this.leapYearMonthNames.Length == 13,
+                    "[DateTimeFormatInfo.internalGetLeapYearMonthNames] Expepcted 13 leap year month names");
+            }
+            return (leapYearMonthNames);
+        }
+
+
+        public String GetAbbreviatedDayName(DayOfWeek dayofweek)
+        {
+            if ((int)dayofweek < 0 || (int)dayofweek > 6)
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(dayofweek), SR.Format(SR.ArgumentOutOfRange_Range,
+                    DayOfWeek.Sunday, DayOfWeek.Saturday));
+            }
+            //
+            // Don't call the public property AbbreviatedDayNames here since a clone is needed in that
+            // property, so it will be slower.  Instead, use GetAbbreviatedDayOfWeekNames() directly.
+            //
+            return (internalGetAbbreviatedDayOfWeekNames()[(int)dayofweek]);
+        }
+
+        // Returns the super short day of week names for the specified day of week.
+        public string GetShortestDayName(DayOfWeek dayOfWeek)
+        {
+            if ((int)dayOfWeek < 0 || (int)dayOfWeek > 6)
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(dayOfWeek), SR.Format(SR.ArgumentOutOfRange_Range,
+                    DayOfWeek.Sunday, DayOfWeek.Saturday));
+            }
+            //
+            // Don't call the public property SuperShortDayNames here since a clone is needed in that
+            // property, so it will be slower.  Instead, use internalGetSuperShortDayNames() directly.
+            //
+            return (internalGetSuperShortDayNames()[(int)dayOfWeek]);
+        }
+
+        // Get all possible combination of inputs
+        private static String[] GetCombinedPatterns(String[] patterns1, String[] patterns2, String connectString)
+        {
+            Debug.Assert(patterns1 != null);
+            Debug.Assert(patterns2 != null);
+
+            // Get array size
+            String[] result = new String[patterns1.Length * patterns2.Length];
+
+            // Counter of actual results
+            int k = 0;
+            for (int i = 0; i < patterns1.Length; i++)
+            {
+                for (int j = 0; j < patterns2.Length; j++)
+                {
+                    // Can't combine if null or empty
+                    result[k++] = patterns1[i] + connectString + patterns2[j];
+                }
+            }
+
+            // Return the combinations
+            return (result);
+        }
+
+        public string[] GetAllDateTimePatterns()
+        {
+            List<String> results = new List<String>(DEFAULT_ALL_DATETIMES_SIZE);
+
+            for (int i = 0; i < DateTimeFormat.allStandardFormats.Length; i++)
+            {
+                String[] strings = GetAllDateTimePatterns(DateTimeFormat.allStandardFormats[i]);
+                for (int j = 0; j < strings.Length; j++)
+                {
+                    results.Add(strings[j]);
+                }
+            }
+            return results.ToArray();
+        }
+
+        public string[] GetAllDateTimePatterns(char format)
+        {
+            String[] result = null;
+
+            switch (format)
+            {
+                case 'd':
+                    result = this.AllShortDatePatterns;
+                    break;
+                case 'D':
+                    result = this.AllLongDatePatterns;
+                    break;
+                case 'f':
+                    result = GetCombinedPatterns(AllLongDatePatterns, AllShortTimePatterns, " ");
+                    break;
+                case 'F':
+                case 'U':
+                    result = GetCombinedPatterns(AllLongDatePatterns, AllLongTimePatterns, " ");
+                    break;
+                case 'g':
+                    result = GetCombinedPatterns(AllShortDatePatterns, AllShortTimePatterns, " ");
+                    break;
+                case 'G':
+                    result = GetCombinedPatterns(AllShortDatePatterns, AllLongTimePatterns, " ");
+                    break;
+                case 'm':
+                case 'M':
+                    result = new String[] { MonthDayPattern };
+                    break;
+                case 'o':
+                case 'O':
+                    result = new String[] { RoundtripFormat };
+                    break;
+                case 'r':
+                case 'R':
+                    result = new String[] { rfc1123Pattern };
+                    break;
+                case 's':
+                    result = new String[] { sortableDateTimePattern };
+                    break;
+                case 't':
+                    result = this.AllShortTimePatterns;
+                    break;
+                case 'T':
+                    result = this.AllLongTimePatterns;
+                    break;
+                case 'u':
+                    result = new String[] { UniversalSortableDateTimePattern };
+                    break;
+                case 'y':
+                case 'Y':
+                    result = this.AllYearMonthPatterns;
+                    break;
+                default:
+                    throw new ArgumentException(SR.Format(SR.Format_BadFormatSpecifier, format), nameof(format));
+            }
+            return (result);
+        }
+
+
+        public String GetDayName(DayOfWeek dayofweek)
+        {
+            if ((int)dayofweek < 0 || (int)dayofweek > 6)
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(dayofweek), SR.Format(SR.ArgumentOutOfRange_Range,
+                    DayOfWeek.Sunday, DayOfWeek.Saturday));
+            }
+
+            // Use the internal one so that we don't clone the array unnecessarily
+            return (internalGetDayOfWeekNames()[(int)dayofweek]);
+        }
+
+        public String GetAbbreviatedMonthName(int month)
+        {
+            if (month < 1 || month > 13)
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(month), SR.Format(SR.ArgumentOutOfRange_Range,
+                    1, 13));
+            }
+            // Use the internal one so we don't clone the array unnecessarily
+            return (internalGetAbbreviatedMonthNames()[month - 1]);
+        }
+
+        public String GetMonthName(int month)
+        {
+            if (month < 1 || month > 13)
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(month), SR.Format(SR.ArgumentOutOfRange_Range,
+                    1, 13));
+            }
+            // Use the internal one so we don't clone the array unnecessarily
+            return (internalGetMonthNames()[month - 1]);
+        }
+
+        // For our "patterns" arrays we have 2 variables, a string and a string[]
+        //
+        // The string[] contains the list of patterns, EXCEPT the default may not be included.
+        // The string contains the default pattern.
+        // When we initially construct our string[], we set the string to string[0]
+        //
+        // The resulting [] can get returned to the calling app, so clone it.
+        private static string[] GetMergedPatterns(string[] patterns, string defaultPattern)
+        {
+            Debug.Assert(patterns != null && patterns.Length > 0,
+                            "[DateTimeFormatInfo.GetMergedPatterns]Expected array of at least one pattern");
+            Debug.Assert(defaultPattern != null,
+                            "[DateTimeFormatInfo.GetMergedPatterns]Expected non null default string");
+
+            // If the default happens to be the first in the list just return (a cloned) copy
+            if (defaultPattern == patterns[0])
+            {
+                return (string[])patterns.Clone();
+            }
+
+            // We either need a bigger list, or the pattern from the list.
+            int i;
+            for (i = 0; i < patterns.Length; i++)
+            {
+                // Stop if we found it
+                if (defaultPattern == patterns[i])
+                    break;
+            }
+
+            // Either way we're going to need a new array
+            string[] newPatterns;
+
+            // Did we find it
+            if (i < patterns.Length)
+            {
+                // Found it, output will be same size
+                newPatterns = (string[])patterns.Clone();
+
+                // Have to move [0] item to [i] so we can re-write default at [0]
+                // (remember defaultPattern == [i] so this is OK)
+                newPatterns[i] = newPatterns[0];
+            }
+            else
+            {
+                // Not found, make room for it
+                newPatterns = new String[patterns.Length + 1];
+
+                // Copy existing array
+                Array.Copy(patterns, 0, newPatterns, 1, patterns.Length);
+            }
+
+            // Remember the default
+            newPatterns[0] = defaultPattern;
+
+            // Return the reconstructed list
+            return newPatterns;
+        }
+
+        // Needed by DateTimeFormatInfo and DateTimeFormat
+        internal const String RoundtripFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss.fffffffK";
+        internal const String RoundtripDateTimeUnfixed = "yyyy'-'MM'-'ddTHH':'mm':'ss zzz";
+
+        // Default string isn't necessarily in our string array, so get the 
+        // merged patterns of both
+        private String[] AllYearMonthPatterns
+        {
+            get
+            {
+                return GetMergedPatterns(this.UnclonedYearMonthPatterns, this.YearMonthPattern);
+            }
+        }
+
+        private String[] AllShortDatePatterns
+        {
+            get
+            {
+                return GetMergedPatterns(this.UnclonedShortDatePatterns, this.ShortDatePattern);
+            }
+        }
+
+        private String[] AllShortTimePatterns
+        {
+            get
+            {
+                return GetMergedPatterns(this.UnclonedShortTimePatterns, this.ShortTimePattern);
+            }
+        }
+
+        private String[] AllLongDatePatterns
+        {
+            get
+            {
+                return GetMergedPatterns(this.UnclonedLongDatePatterns, this.LongDatePattern);
+            }
+        }
+
+        private String[] AllLongTimePatterns
+        {
+            get
+            {
+                return GetMergedPatterns(this.UnclonedLongTimePatterns, this.LongTimePattern);
+            }
+        }
+
+        // NOTE: Clone this string array if you want to return it to user.  Otherwise, you are returning a writable cache copy.
+        // This won't include default, call AllYearMonthPatterns
+        private String[] UnclonedYearMonthPatterns
+        {
+            get
+            {
+                if (allYearMonthPatterns == null)
+                {
+                    Debug.Assert(Calendar.ID > 0, "[DateTimeFormatInfo.UnclonedYearMonthPatterns] Expected Calendar.ID > 0");
+                    this.allYearMonthPatterns = _cultureData.YearMonths(this.Calendar.ID);
+                    Debug.Assert(this.allYearMonthPatterns.Length > 0,
+                        "[DateTimeFormatInfo.UnclonedYearMonthPatterns] Expected some year month patterns");
+                }
+
+                return allYearMonthPatterns;
+            }
+        }
+
+
+        // NOTE: Clone this string array if you want to return it to user.  Otherwise, you are returning a writable cache copy.
+        // This won't include default, call AllShortDatePatterns
+        private String[] UnclonedShortDatePatterns
+        {
+            get
+            {
+                if (allShortDatePatterns == null)
+                {
+                    Debug.Assert(Calendar.ID > 0, "[DateTimeFormatInfo.UnclonedShortDatePatterns] Expected Calendar.ID > 0");
+                    this.allShortDatePatterns = _cultureData.ShortDates(this.Calendar.ID);
+                    Debug.Assert(this.allShortDatePatterns.Length > 0,
+                        "[DateTimeFormatInfo.UnclonedShortDatePatterns] Expected some short date patterns");
+                }
+
+                return this.allShortDatePatterns;
+            }
+        }
+
+        // NOTE: Clone this string array if you want to return it to user.  Otherwise, you are returning a writable cache copy.
+        // This won't include default, call AllLongDatePatterns
+        private String[] UnclonedLongDatePatterns
+        {
+            get
+            {
+                if (allLongDatePatterns == null)
+                {
+                    Debug.Assert(Calendar.ID > 0, "[DateTimeFormatInfo.UnclonedLongDatePatterns] Expected Calendar.ID > 0");
+                    this.allLongDatePatterns = _cultureData.LongDates(this.Calendar.ID);
+                    Debug.Assert(this.allLongDatePatterns.Length > 0,
+                        "[DateTimeFormatInfo.UnclonedLongDatePatterns] Expected some long date patterns");
+                }
+
+                return this.allLongDatePatterns;
+            }
+        }
+
+        // NOTE: Clone this string array if you want to return it to user.  Otherwise, you are returning a writable cache copy.
+        // This won't include default, call AllShortTimePatterns
+        private String[] UnclonedShortTimePatterns
+        {
+            get
+            {
+                if (this.allShortTimePatterns == null)
+                {
+                    this.allShortTimePatterns = _cultureData.ShortTimes;
+                    Debug.Assert(this.allShortTimePatterns.Length > 0,
+                        "[DateTimeFormatInfo.UnclonedShortTimePatterns] Expected some short time patterns");
+                }
+
+                return this.allShortTimePatterns;
+            }
+        }
+
+        // NOTE: Clone this string array if you want to return it to user.  Otherwise, you are returning a writable cache copy.
+        // This won't include default, call AllLongTimePatterns
+        private String[] UnclonedLongTimePatterns
+        {
+            get
+            {
+                if (this.allLongTimePatterns == null)
+                {
+                    this.allLongTimePatterns = _cultureData.LongTimes;
+                    Debug.Assert(this.allLongTimePatterns.Length > 0,
+                        "[DateTimeFormatInfo.UnclonedLongTimePatterns] Expected some long time patterns");
+                }
+
+                return this.allLongTimePatterns;
+            }
+        }
+
+        public static DateTimeFormatInfo ReadOnly(DateTimeFormatInfo dtfi)
+        {
+            if (dtfi == null)
+            {
+                throw new ArgumentNullException(nameof(dtfi),
+                    SR.ArgumentNull_Obj);
+            }
+            if (dtfi.IsReadOnly)
+            {
+                return (dtfi);
+            }
+            DateTimeFormatInfo newInfo = (DateTimeFormatInfo)(dtfi.MemberwiseClone());
+            // We can use the data member calendar in the setter, instead of the property Calendar,
+            // since the cloned copy should have the same state as the original copy.
+            newInfo.calendar = Calendar.ReadOnly(dtfi.Calendar);
+            newInfo._isReadOnly = true;
+            return (newInfo);
+        }
+
+        public bool IsReadOnly
+        {
+            get
+            {
+                return (_isReadOnly);
+            }
+        }
+
+        // Return the native name for the calendar in DTFI.Calendar.  The native name is referred to
+        // the culture used to create the DTFI.  E.g. in the following example, the native language is Japanese.
+        // DateTimeFormatInfo dtfi = new CultureInfo("ja-JP", false).DateTimeFormat.Calendar = new JapaneseCalendar();
+        // String nativeName = dtfi.NativeCalendarName; // Get the Japanese name for the Japanese calendar.
+        // DateTimeFormatInfo dtfi = new CultureInfo("ja-JP", false).DateTimeFormat.Calendar = new GregorianCalendar(GregorianCalendarTypes.Localized);
+        // String nativeName = dtfi.NativeCalendarName; // Get the Japanese name for the Gregorian calendar.
+        public string NativeCalendarName
+        {
+            get
+            {
+                return _cultureData.CalendarName(Calendar.ID);
+            }
+        }
+
+        //
+        // Used by custom cultures and others to set the list of available formats. Note that none of them are
+        // explicitly used unless someone calls GetAllDateTimePatterns and subsequently uses one of the items
+        // from the list.
+        //
+        // Most of the format characters that can be used in GetAllDateTimePatterns are
+        // not really needed since they are one of the following:
+        //
+        //  r/R/s/u     locale-independent constants -- cannot be changed!
+        //  m/M/y/Y     fields with a single string in them -- that can be set through props directly
+        //  f/F/g/G/U   derived fields based on combinations of various of the below formats
+        //
+        // NOTE: No special validation is done here beyond what is done when the actual respective fields
+        // are used (what would be the point of disallowing here what we allow in the appropriate property?)
+        //
+        // WARNING: If more validation is ever done in one place, it should be done in the other.
+        //
+        public void SetAllDateTimePatterns(String[] patterns, char format)
+        {
+            if (IsReadOnly)
+                throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+
+            if (patterns == null)
+            {
+                throw new ArgumentNullException(nameof(patterns), SR.ArgumentNull_Array);
+            }
+
+            if (patterns.Length == 0)
+            {
+                throw new ArgumentException(SR.Arg_ArrayZeroError, nameof(patterns));
+            }
+
+
+            for (int i = 0; i < patterns.Length; i++)
+            {
+                if (patterns[i] == null)
+                {
+                    throw new ArgumentNullException("patterns[" + i + "]", SR.ArgumentNull_ArrayValue);
+                }
+            }
+
+            // Remember the patterns, and use the 1st as default
+            switch (format)
+            {
+                case 'd':
+                    allShortDatePatterns = patterns;
+                    shortDatePattern = allShortDatePatterns[0];
+                    break;
+
+                case 'D':
+                    allLongDatePatterns = patterns;
+                    longDatePattern = allLongDatePatterns[0];
+                    break;
+
+                case 't':
+                    allShortTimePatterns = patterns;
+                    shortTimePattern = allShortTimePatterns[0];
+                    break;
+
+                case 'T':
+                    allLongTimePatterns = patterns;
+                    longTimePattern = allLongTimePatterns[0];
+                    break;
+
+                case 'y':
+                case 'Y':
+                    allYearMonthPatterns = patterns;
+                    yearMonthPattern = allYearMonthPatterns[0];
+                    break;
+
+                default:
+                    throw new ArgumentException(SR.Format(SR.Format_BadFormatSpecifier, format), nameof(format));
+            }
+
+            // Clear the token hash table, note that even short dates could require this
+            ClearTokenHashTable();
+        }
+
+        public String[] AbbreviatedMonthGenitiveNames
+        {
+            get
+            {
+                return ((String[])internalGetGenitiveMonthNames(true).Clone());
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_Array);
+                }
+                if (value.Length != 13)
+                {
+                    throw new ArgumentException(SR.Format(SR.Argument_InvalidArrayLength, 13), nameof(value));
+                }
+                CheckNullValue(value, value.Length - 1);
+                ClearTokenHashTable();
+                this.m_genitiveAbbreviatedMonthNames = value;
+            }
+        }
+
+        public String[] MonthGenitiveNames
+        {
+            get
+            {
+                return ((String[])internalGetGenitiveMonthNames(false).Clone());
+            }
+
+            set
+            {
+                if (IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value),
+                        SR.ArgumentNull_Array);
+                }
+                if (value.Length != 13)
+                {
+                    throw new ArgumentException(SR.Format(SR.Argument_InvalidArrayLength, 13), nameof(value));
+                }
+                CheckNullValue(value, value.Length - 1);
+                genitiveMonthNames = value;
+                ClearTokenHashTable();
+            }
+        }
+
+        //
+        // Positive TimeSpan Pattern
+        //
+        private string _fullTimeSpanPositivePattern;
+        internal String FullTimeSpanPositivePattern
+        {
+            get
+            {
+                if (_fullTimeSpanPositivePattern == null)
+                {
+                    CultureData cultureDataWithoutUserOverrides;
+                    if (_cultureData.UseUserOverride)
+                        cultureDataWithoutUserOverrides = CultureData.GetCultureData(_cultureData.CultureName, false);
+                    else
+                        cultureDataWithoutUserOverrides = _cultureData;
+                    String decimalSeparator = new NumberFormatInfo(cultureDataWithoutUserOverrides).NumberDecimalSeparator;
+
+                    _fullTimeSpanPositivePattern = "d':'h':'mm':'ss'" + decimalSeparator + "'FFFFFFF";
+                }
+                return _fullTimeSpanPositivePattern;
+            }
+        }
+
+        //
+        // Negative TimeSpan Pattern
+        //
+        private string _fullTimeSpanNegativePattern;
+        internal String FullTimeSpanNegativePattern
+        {
+            get
+            {
+                if (_fullTimeSpanNegativePattern == null)
+                    _fullTimeSpanNegativePattern = "'-'" + FullTimeSpanPositivePattern;
+                return _fullTimeSpanNegativePattern;
+            }
+        }
+
+        //
+        // Get suitable CompareInfo from current DTFI object.
+        //
+        internal CompareInfo CompareInfo
+        {
+            get
+            {
+                if (_compareInfo == null)
+                {
+                    // We use the regular GetCompareInfo here to make sure the created CompareInfo object is stored in the
+                    // CompareInfo cache. otherwise we would just create CompareInfo using _cultureData.
+                    _compareInfo = CompareInfo.GetCompareInfo(_cultureData.SCOMPAREINFO);
+                }
+
+                return _compareInfo;
+            }
+        }
+
+
+        internal const DateTimeStyles InvalidDateTimeStyles = ~(DateTimeStyles.AllowLeadingWhite | DateTimeStyles.AllowTrailingWhite
+                                                               | DateTimeStyles.AllowInnerWhite | DateTimeStyles.NoCurrentDateDefault
+                                                               | DateTimeStyles.AdjustToUniversal | DateTimeStyles.AssumeLocal
+                                                               | DateTimeStyles.AssumeUniversal | DateTimeStyles.RoundtripKind);
+
+        internal static void ValidateStyles(DateTimeStyles style, String parameterName)
+        {
+            if ((style & InvalidDateTimeStyles) != 0)
+            {
+                throw new ArgumentException(SR.Argument_InvalidDateTimeStyles, parameterName);
+            }
+            if (((style & (DateTimeStyles.AssumeLocal)) != 0) && ((style & (DateTimeStyles.AssumeUniversal)) != 0))
+            {
+                throw new ArgumentException(SR.Argument_ConflictingDateTimeStyles, parameterName);
+            }
+            if (((style & DateTimeStyles.RoundtripKind) != 0)
+                && ((style & (DateTimeStyles.AssumeLocal | DateTimeStyles.AssumeUniversal | DateTimeStyles.AdjustToUniversal)) != 0))
+            {
+                throw new ArgumentException(SR.Argument_ConflictingDateTimeRoundtripStyles, parameterName);
+            }
+        }
+
+        //
+        // Actions: Return the internal flag used in formatting and parsing.
+        //  The flag can be used to indicate things like if genitive forms is used in this DTFi, or if leap year gets different month names.
+        //
+        internal DateTimeFormatFlags FormatFlags => formatFlags != DateTimeFormatFlags.NotInitialized ? formatFlags : InitializeFormatFlags();
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private DateTimeFormatFlags InitializeFormatFlags()
+        {
+            // Build the format flags from the data in this DTFI
+            formatFlags = 
+                (DateTimeFormatFlags)DateTimeFormatInfoScanner.GetFormatFlagGenitiveMonth(
+                    MonthNames, internalGetGenitiveMonthNames(false), AbbreviatedMonthNames, internalGetGenitiveMonthNames(true)) |
+                (DateTimeFormatFlags)DateTimeFormatInfoScanner.GetFormatFlagUseSpaceInMonthNames(
+                    MonthNames, internalGetGenitiveMonthNames(false), AbbreviatedMonthNames, internalGetGenitiveMonthNames(true)) |
+                (DateTimeFormatFlags)DateTimeFormatInfoScanner.GetFormatFlagUseSpaceInDayNames(DayNames, AbbreviatedDayNames) |
+                (DateTimeFormatFlags)DateTimeFormatInfoScanner.GetFormatFlagUseHebrewCalendar((int)Calendar.ID);
+            return formatFlags;
+        }
+
+        internal Boolean HasForceTwoDigitYears
+        {
+            get
+            {
+                switch (calendar.ID)
+                {
+                    // Handle Japanese and Taiwan cases.
+                    // If is y/yy, do not get (year % 100). "y" will print
+                    // year without leading zero.  "yy" will print year with two-digit in leading zero.
+                    // If pattern is yyy/yyyy/..., print year value with two-digit in leading zero.
+                    // So year 5 is "05", and year 125 is "125".
+                    // The reason for not doing (year % 100) is for Taiwan calendar.
+                    // If year 125, then output 125 and not 25.
+                    // Note: OS uses "yyyy" for Taiwan calendar by default.
+                    case (CalendarId.JAPAN):
+                    case (CalendarId.TAIWAN):
+                        return true;
+                }
+                return false;
+            }
+        }
+
+        // Returns whether the YearMonthAdjustment function has any fix-up work to do for this culture/calendar.
+        internal Boolean HasYearMonthAdjustment
+        {
+            get
+            {
+                return ((FormatFlags & DateTimeFormatFlags.UseHebrewRule) != 0);
+            }
+        }
+
+        // This is a callback that the parser can make back into the DTFI to let it fiddle with special
+        // cases associated with that culture or calendar. Currently this only has special cases for
+        // the Hebrew calendar, but this could be extended to other cultures.
+        //
+        // The return value is whether the year and month are actually valid for this calendar.
+        internal Boolean YearMonthAdjustment(ref int year, ref int month, Boolean parsedMonthName)
+        {
+            if ((FormatFlags & DateTimeFormatFlags.UseHebrewRule) != 0)
+            {
+                // Special rules to fix up the Hebrew year/month
+
+                // When formatting, we only format up to the hundred digit of the Hebrew year, although Hebrew year is now over 5000.
+                // E.g. if the year is 5763, we only format as 763.
+                if (year < 1000)
+                {
+                    year += 5000;
+                }
+
+                // Because we need to calculate leap year, we should fall out now for an invalid year.
+                if (year < Calendar.GetYear(Calendar.MinSupportedDateTime) || year > Calendar.GetYear(Calendar.MaxSupportedDateTime))
+                {
+                    return false;
+                }
+
+                // To handle leap months, the set of month names in the symbol table does not always correspond to the numbers.
+                // For non-leap years, month 7 (Adar Bet) is not present, so we need to make using this month invalid and
+                // shuffle the other months down.
+                if (parsedMonthName)
+                {
+                    if (!Calendar.IsLeapYear(year))
+                    {
+                        if (month >= 8)
+                        {
+                            month--;
+                        }
+                        else if (month == 7)
+                        {
+                            return false;
+                        }
+                    }
+                }
+            }
+            return true;
+        }
+
+        //
+        // DateTimeFormatInfo tokenizer.  This is used by DateTime.Parse() to break input string into tokens.
+        //
+        private TokenHashValue[] _dtfiTokenHash;
+
+        private const int TOKEN_HASH_SIZE = 199;
+        private const int SECOND_PRIME = 197;
+        private const String dateSeparatorOrTimeZoneOffset = "-";
+        private const String invariantDateSeparator = "/";
+        private const String invariantTimeSeparator = ":";
+
+        //
+        // Common Ignorable Symbols
+        //
+        internal const String IgnorablePeriod = ".";
+        internal const String IgnorableComma = ",";
+
+        //
+        // Year/Month/Day suffixes
+        //
+        internal const String CJKYearSuff = "\u5e74";
+        internal const String CJKMonthSuff = "\u6708";
+        internal const String CJKDaySuff = "\u65e5";
+
+        internal const String KoreanYearSuff = "\ub144";
+        internal const String KoreanMonthSuff = "\uc6d4";
+        internal const String KoreanDaySuff = "\uc77c";
+
+        internal const String KoreanHourSuff = "\uc2dc";
+        internal const String KoreanMinuteSuff = "\ubd84";
+        internal const String KoreanSecondSuff = "\ucd08";
+
+        internal const String CJKHourSuff = "\u6642";
+        internal const String ChineseHourSuff = "\u65f6";
+
+        internal const String CJKMinuteSuff = "\u5206";
+        internal const String CJKSecondSuff = "\u79d2";
+
+        internal const String LocalTimeMark = "T";
+
+        internal const String GMTName = "GMT";
+        internal const String ZuluName = "Z";
+
+        internal const String KoreanLangName = "ko";
+        internal const String JapaneseLangName = "ja";
+        internal const String EnglishLangName = "en";
+
+        private static volatile DateTimeFormatInfo s_jajpDTFI;
+        private static volatile DateTimeFormatInfo s_zhtwDTFI;
+
+        //
+        // Create a Japanese DTFI which uses JapaneseCalendar.  This is used to parse
+        // date string with Japanese era name correctly even when the supplied DTFI
+        // does not use Japanese calendar.
+        // The created instance is stored in global s_jajpDTFI.
+        //
+        internal static DateTimeFormatInfo GetJapaneseCalendarDTFI()
+        {
+            DateTimeFormatInfo temp = s_jajpDTFI;
+            if (temp == null)
+            {
+                temp = new CultureInfo("ja-JP", false).DateTimeFormat;
+                temp.Calendar = JapaneseCalendar.GetDefaultInstance();
+                s_jajpDTFI = temp;
+            }
+            return (temp);
+        }
+
+        // Create a Taiwan DTFI which uses TaiwanCalendar.  This is used to parse
+        // date string with era name correctly even when the supplied DTFI
+        // does not use Taiwan calendar.
+        // The created instance is stored in global s_zhtwDTFI.
+        internal static DateTimeFormatInfo GetTaiwanCalendarDTFI()
+        {
+            DateTimeFormatInfo temp = s_zhtwDTFI;
+            if (temp == null)
+            {
+                temp = new CultureInfo("zh-TW", false).DateTimeFormat;
+                temp.Calendar = TaiwanCalendar.GetDefaultInstance();
+                s_zhtwDTFI = temp;
+            }
+            return (temp);
+        }
+
+
+        // DTFI properties should call this when the setter are called.
+        private void ClearTokenHashTable()
+        {
+            _dtfiTokenHash = null;
+            formatFlags = DateTimeFormatFlags.NotInitialized;
+        }
+
+        internal TokenHashValue[] CreateTokenHashTable()
+        {
+            TokenHashValue[] temp = _dtfiTokenHash;
+            if (temp == null)
+            {
+                temp = new TokenHashValue[TOKEN_HASH_SIZE];
+
+                bool koreanLanguage = LanguageName.Equals(KoreanLangName);
+
+                string sep = this.TimeSeparator.Trim();
+                if (IgnorableComma != sep) InsertHash(temp, IgnorableComma, TokenType.IgnorableSymbol, 0);
+                if (IgnorablePeriod != sep) InsertHash(temp, IgnorablePeriod, TokenType.IgnorableSymbol, 0);
+
+                if (KoreanHourSuff != sep && CJKHourSuff != sep && ChineseHourSuff != sep)
+                {
+                    //
+                    // On the Macintosh, the default TimeSeparator is identical to the KoreanHourSuff, CJKHourSuff, or ChineseHourSuff for some cultures like
+                    // ja-JP and ko-KR.  In these cases having the same symbol inserted into the hash table with multiple TokenTypes causes undesirable
+                    // DateTime.Parse behavior.  For instance, the DateTimeFormatInfo.Tokenize() method might return SEP_DateOrOffset for KoreanHourSuff
+                    // instead of SEP_HourSuff.
+                    //
+                    InsertHash(temp, this.TimeSeparator, TokenType.SEP_Time, 0);
+                }
+
+                InsertHash(temp, this.AMDesignator, TokenType.SEP_Am | TokenType.Am, 0);
+                InsertHash(temp, this.PMDesignator, TokenType.SEP_Pm | TokenType.Pm, 1);
+
+                // TODO: This ignores similar custom cultures
+                if (LanguageName.Equals("sq"))
+                {
+                    // Albanian allows time formats like "12:00.PD"
+                    InsertHash(temp, IgnorablePeriod + this.AMDesignator, TokenType.SEP_Am | TokenType.Am, 0);
+                    InsertHash(temp, IgnorablePeriod + this.PMDesignator, TokenType.SEP_Pm | TokenType.Pm, 1);
+                }
+
+                // CJK suffix
+                InsertHash(temp, CJKYearSuff, TokenType.SEP_YearSuff, 0);
+                InsertHash(temp, KoreanYearSuff, TokenType.SEP_YearSuff, 0);
+                InsertHash(temp, CJKMonthSuff, TokenType.SEP_MonthSuff, 0);
+                InsertHash(temp, KoreanMonthSuff, TokenType.SEP_MonthSuff, 0);
+                InsertHash(temp, CJKDaySuff, TokenType.SEP_DaySuff, 0);
+                InsertHash(temp, KoreanDaySuff, TokenType.SEP_DaySuff, 0);
+
+                InsertHash(temp, CJKHourSuff, TokenType.SEP_HourSuff, 0);
+                InsertHash(temp, ChineseHourSuff, TokenType.SEP_HourSuff, 0);
+                InsertHash(temp, CJKMinuteSuff, TokenType.SEP_MinuteSuff, 0);
+                InsertHash(temp, CJKSecondSuff, TokenType.SEP_SecondSuff, 0);
+
+                // TODO: This ignores other custom cultures that might want to do something similar
+                if (koreanLanguage)
+                {
+                    // Korean suffix
+                    InsertHash(temp, KoreanHourSuff, TokenType.SEP_HourSuff, 0);
+                    InsertHash(temp, KoreanMinuteSuff, TokenType.SEP_MinuteSuff, 0);
+                    InsertHash(temp, KoreanSecondSuff, TokenType.SEP_SecondSuff, 0);
+                }
+
+                if (LanguageName.Equals("ky"))
+                {
+                    // For some cultures, the date separator works more like a comma, being allowed before or after any date part
+                    InsertHash(temp, dateSeparatorOrTimeZoneOffset, TokenType.IgnorableSymbol, 0);
+                }
+                else
+                {
+                    InsertHash(temp, dateSeparatorOrTimeZoneOffset, TokenType.SEP_DateOrOffset, 0);
+                }
+
+                String[] dateWords = null;
+                DateTimeFormatInfoScanner scanner = null;
+
+                // We need to rescan the date words since we're always synthetic
+                scanner = new DateTimeFormatInfoScanner();
+                dateWords = scanner.GetDateWordsOfDTFI(this);
+                // Ensure the formatflags is initialized.
+                DateTimeFormatFlags flag = FormatFlags;
+
+                // For some cultures, the date separator works more like a comma, being allowed before or after any date part.
+                // In these cultures, we do not use normal date separator since we disallow date separator after a date terminal state.
+                // This is determined in DateTimeFormatInfoScanner.  Use this flag to determine if we should treat date separator as ignorable symbol.
+                bool useDateSepAsIgnorableSymbol = false;
+
+                String monthPostfix = null;
+                if (dateWords != null)
+                {
+                    // There are DateWords.  It could be a real date word (such as "de"), or a monthPostfix.
+                    // The monthPostfix starts with '\xfffe' (MonthPostfixChar), followed by the real monthPostfix.
+                    for (int i = 0; i < dateWords.Length; i++)
+                    {
+                        switch (dateWords[i][0])
+                        {
+                            // This is a month postfix
+                            case DateTimeFormatInfoScanner.MonthPostfixChar:
+                                // Get the real month postfix.
+                                monthPostfix = dateWords[i].Substring(1);
+                                // Add the month name + postfix into the token.
+                                AddMonthNames(temp, monthPostfix);
+                                break;
+                            case DateTimeFormatInfoScanner.IgnorableSymbolChar:
+                                String symbol = dateWords[i].Substring(1);
+                                InsertHash(temp, symbol, TokenType.IgnorableSymbol, 0);
+                                if (this.DateSeparator.Trim(null).Equals(symbol))
+                                {
+                                    // The date separator is the same as the ignorable symbol.
+                                    useDateSepAsIgnorableSymbol = true;
+                                }
+                                break;
+                            default:
+                                InsertHash(temp, dateWords[i], TokenType.DateWordToken, 0);
+                                // TODO: This ignores similar custom cultures
+                                if (LanguageName.Equals("eu"))
+                                {
+                                    // Basque has date words with leading dots
+                                    InsertHash(temp, IgnorablePeriod + dateWords[i], TokenType.DateWordToken, 0);
+                                }
+                                break;
+                        }
+                    }
+                }
+
+                if (!useDateSepAsIgnorableSymbol)
+                {
+                    // Use the normal date separator.
+                    InsertHash(temp, this.DateSeparator, TokenType.SEP_Date, 0);
+                }
+                // Add the regular month names.
+                AddMonthNames(temp, null);
+
+                // Add the abbreviated month names.
+                for (int i = 1; i <= 13; i++)
+                {
+                    InsertHash(temp, GetAbbreviatedMonthName(i), TokenType.MonthToken, i);
+                }
+
+
+                if ((FormatFlags & DateTimeFormatFlags.UseGenitiveMonth) != 0)
+                {
+                    for (int i = 1; i <= 13; i++)
+                    {
+                        String str;
+                        str = internalGetMonthName(i, MonthNameStyles.Genitive, false);
+                        InsertHash(temp, str, TokenType.MonthToken, i);
+                    }
+                }
+
+                if ((FormatFlags & DateTimeFormatFlags.UseLeapYearMonth) != 0)
+                {
+                    for (int i = 1; i <= 13; i++)
+                    {
+                        String str;
+                        str = internalGetMonthName(i, MonthNameStyles.LeapYear, false);
+                        InsertHash(temp, str, TokenType.MonthToken, i);
+                    }
+                }
+
+                for (int i = 0; i < 7; i++)
+                {
+                    //String str = GetDayOfWeekNames()[i];
+                    // We have to call public methods here to work with inherited DTFI.
+                    String str = GetDayName((DayOfWeek)i);
+                    InsertHash(temp, str, TokenType.DayOfWeekToken, i);
+
+                    str = GetAbbreviatedDayName((DayOfWeek)i);
+                    InsertHash(temp, str, TokenType.DayOfWeekToken, i);
+                }
+
+                int[] eras = calendar.Eras;
+                for (int i = 1; i <= eras.Length; i++)
+                {
+                    InsertHash(temp, GetEraName(i), TokenType.EraToken, i);
+                    InsertHash(temp, GetAbbreviatedEraName(i), TokenType.EraToken, i);
+                }
+
+                // TODO: This ignores other cultures that might want to do something similar
+                if (LanguageName.Equals(JapaneseLangName))
+                {
+                    // Japanese allows day of week forms like: "(Tue)"
+                    for (int i = 0; i < 7; i++)
+                    {
+                        String specialDayOfWeek = "(" + GetAbbreviatedDayName((DayOfWeek)i) + ")";
+                        InsertHash(temp, specialDayOfWeek, TokenType.DayOfWeekToken, i);
+                    }
+                    if (this.Calendar.GetType() != typeof(JapaneseCalendar))
+                    {
+                        // Special case for Japanese.  If this is a Japanese DTFI, and the calendar is not Japanese calendar,
+                        // we will check Japanese Era name as well when the calendar is Gregorian.
+                        DateTimeFormatInfo jaDtfi = GetJapaneseCalendarDTFI();
+                        for (int i = 1; i <= jaDtfi.Calendar.Eras.Length; i++)
+                        {
+                            InsertHash(temp, jaDtfi.GetEraName(i), TokenType.JapaneseEraToken, i);
+                            InsertHash(temp, jaDtfi.GetAbbreviatedEraName(i), TokenType.JapaneseEraToken, i);
+                            // m_abbrevEnglishEraNames[0] contains the name for era 1, so the token value is i+1.
+                            InsertHash(temp, jaDtfi.AbbreviatedEnglishEraNames[i - 1], TokenType.JapaneseEraToken, i);
+                        }
+                    }
+                }
+                // TODO: This prohibits similar custom cultures, but we hard coded the name
+                else if (CultureName.Equals("zh-TW"))
+                {
+                    DateTimeFormatInfo twDtfi = GetTaiwanCalendarDTFI();
+                    for (int i = 1; i <= twDtfi.Calendar.Eras.Length; i++)
+                    {
+                        if (twDtfi.GetEraName(i).Length > 0)
+                        {
+                            InsertHash(temp, twDtfi.GetEraName(i), TokenType.TEraToken, i);
+                        }
+                    }
+                }
+
+                InsertHash(temp, InvariantInfo.AMDesignator, TokenType.SEP_Am | TokenType.Am, 0);
+                InsertHash(temp, InvariantInfo.PMDesignator, TokenType.SEP_Pm | TokenType.Pm, 1);
+
+                // Add invariant month names and day names.
+                for (int i = 1; i <= 12; i++)
+                {
+                    String str;
+                    // We have to call public methods here to work with inherited DTFI.
+                    // Insert the month name first, so that they are at the front of abbreviated
+                    // month names.
+                    str = InvariantInfo.GetMonthName(i);
+                    InsertHash(temp, str, TokenType.MonthToken, i);
+                    str = InvariantInfo.GetAbbreviatedMonthName(i);
+                    InsertHash(temp, str, TokenType.MonthToken, i);
+                }
+
+                for (int i = 0; i < 7; i++)
+                {
+                    // We have to call public methods here to work with inherited DTFI.
+                    String str = InvariantInfo.GetDayName((DayOfWeek)i);
+                    InsertHash(temp, str, TokenType.DayOfWeekToken, i);
+
+                    str = InvariantInfo.GetAbbreviatedDayName((DayOfWeek)i);
+                    InsertHash(temp, str, TokenType.DayOfWeekToken, i);
+                }
+
+                for (int i = 0; i < AbbreviatedEnglishEraNames.Length; i++)
+                {
+                    // m_abbrevEnglishEraNames[0] contains the name for era 1, so the token value is i+1.
+                    InsertHash(temp, AbbreviatedEnglishEraNames[i], TokenType.EraToken, i + 1);
+                }
+
+                InsertHash(temp, LocalTimeMark, TokenType.SEP_LocalTimeMark, 0);
+                InsertHash(temp, GMTName, TokenType.TimeZoneToken, 0);
+                InsertHash(temp, ZuluName, TokenType.TimeZoneToken, 0);
+
+                InsertHash(temp, invariantDateSeparator, TokenType.SEP_Date, 0);
+                InsertHash(temp, invariantTimeSeparator, TokenType.SEP_Time, 0);
+
+                _dtfiTokenHash = temp;
+            }
+            return (temp);
+        }
+
+        private void AddMonthNames(TokenHashValue[] temp, String monthPostfix)
+        {
+            for (int i = 1; i <= 13; i++)
+            {
+                String str;
+                //str = internalGetMonthName(i, MonthNameStyles.Regular, false);
+                // We have to call public methods here to work with inherited DTFI.
+                // Insert the month name first, so that they are at the front of abbreviated
+                // month names.
+                str = GetMonthName(i);
+                if (str.Length > 0)
+                {
+                    if (monthPostfix != null)
+                    {
+                        // Insert the month name with the postfix first, so it can be matched first.
+                        InsertHash(temp, str + monthPostfix, TokenType.MonthToken, i);
+                    }
+                    else
+                    {
+                        InsertHash(temp, str, TokenType.MonthToken, i);
+                    }
+                }
+                str = GetAbbreviatedMonthName(i);
+                InsertHash(temp, str, TokenType.MonthToken, i);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        // Actions:
+        // Try to parse the current word to see if it is a Hebrew number.
+        // Tokens will be updated accordingly.
+        // This is called by the Lexer of DateTime.Parse().
+        //
+        // Unlike most of the functions in this class, the return value indicates
+        // whether or not it started to parse. The badFormat parameter indicates
+        // if parsing began, but the format was bad.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        private static bool TryParseHebrewNumber(
+            ref __DTString str,
+            out Boolean badFormat,
+            out int number)
+        {
+            number = -1;
+            badFormat = false;
+
+            int i = str.Index;
+            if (!HebrewNumber.IsDigit(str.Value[i]))
+            {
+                // If the current character is not a Hebrew digit, just return false.
+                // There is no chance that we can parse a valid Hebrew number from here.
+                return (false);
+            }
+            // The current character is a Hebrew digit.  Try to parse this word as a Hebrew number.
+            HebrewNumberParsingContext context = new HebrewNumberParsingContext(0);
+            HebrewNumberParsingState state;
+
+            do
+            {
+                state = HebrewNumber.ParseByChar(str.Value[i++], ref context);
+                switch (state)
+                {
+                    case HebrewNumberParsingState.InvalidHebrewNumber:    // Not a valid Hebrew number.
+                    case HebrewNumberParsingState.NotHebrewDigit:         // The current character is not a Hebrew digit character.
+                        // Break out so that we don't continue to try parse this as a Hebrew number.
+                        return (false);
+                }
+            } while (i < str.Value.Length && (state != HebrewNumberParsingState.FoundEndOfHebrewNumber));
+
+            // When we are here, we are either at the end of the string, or we find a valid Hebrew number.
+            Debug.Assert(state == HebrewNumberParsingState.ContinueParsing || state == HebrewNumberParsingState.FoundEndOfHebrewNumber,
+                "Invalid returned state from HebrewNumber.ParseByChar()");
+
+            if (state != HebrewNumberParsingState.FoundEndOfHebrewNumber)
+            {
+                // We reach end of the string but we can't find a terminal state in parsing Hebrew number.
+                return (false);
+            }
+
+            // We have found a valid Hebrew number.  Update the index.
+            str.Advance(i - str.Index);
+
+            // Get the final Hebrew number value from the HebrewNumberParsingContext.
+            number = context.result;
+
+            return (true);
+        }
+
+        private static bool IsHebrewChar(char ch)
+        {
+            return (ch >= '\x0590' && ch <= '\x05ff');
+        }
+
+        internal bool Tokenize(TokenType TokenMask, out TokenType tokenType, out int tokenValue,
+                               ref __DTString str)
+        {
+            tokenType = TokenType.UnknownToken;
+            tokenValue = 0;
+
+            TokenHashValue value;
+            Debug.Assert(str.Index < str.Value.Length, "DateTimeFormatInfo.Tokenize(): start < value.Length");
+
+            char ch = str.m_current;
+            bool isLetter = Char.IsLetter(ch);
+            if (isLetter)
+            {
+                ch = this.Culture.TextInfo.ToLower(ch);
+                if (IsHebrewChar(ch) && TokenMask == TokenType.RegularTokenMask)
+                {
+                    bool badFormat;
+                    if (TryParseHebrewNumber(ref str, out badFormat, out tokenValue))
+                    {
+                        if (badFormat)
+                        {
+                            tokenType = TokenType.UnknownToken;
+                            return (false);
+                        }
+                        // This is a Hebrew number.
+                        // Do nothing here.  TryParseHebrewNumber() will update token accordingly.
+                        tokenType = TokenType.HebrewNumber;
+                        return (true);
+                    }
+                }
+            }
+
+
+            int hashcode = ch % TOKEN_HASH_SIZE;
+            int hashProbe = 1 + ch % SECOND_PRIME;
+            int remaining = str.Length - str.Index;
+            int i = 0;
+
+            TokenHashValue[] hashTable = _dtfiTokenHash;
+            if (hashTable == null)
+            {
+                hashTable = CreateTokenHashTable();
+            }
+            do
+            {
+                value = hashTable[hashcode];
+                if (value == null)
+                {
+                    // Not found.
+                    break;
+                }
+                // Check this value has the right category (regular token or separator token) that we are looking for.
+                if (((int)value.tokenType & (int)TokenMask) > 0 && value.tokenString.Length <= remaining)
+                {
+                    bool compareStrings = true;
+                    if (isLetter)
+                    {
+                        // If this token starts with a letter, make sure that we won't allow partial match.  So you can't tokenize "MarchWed" separately.
+                        // Also an optimization to avoid string comparison
+                        int nextCharIndex = str.Index + value.tokenString.Length;
+                        if (nextCharIndex > str.Length)
+                        {
+                            compareStrings = false;
+                        }
+                        else if (nextCharIndex < str.Length)
+                        {
+                            // Check word boundary.  The next character should NOT be a letter.
+                            char nextCh = str.Value[nextCharIndex];
+                            compareStrings = !(Char.IsLetter(nextCh));
+                        }
+                    }
+                    
+                    if (compareStrings &&
+                        ((value.tokenString.Length == 1 && str.Value[str.Index] == value.tokenString[0]) ||
+                         Culture.CompareInfo.Compare(str.Value.Slice(str.Index, value.tokenString.Length), value.tokenString, CompareOptions.IgnoreCase) == 0))
+                    {
+                        tokenType = value.tokenType & TokenMask;
+                        tokenValue = value.tokenValue;
+                        str.Advance(value.tokenString.Length);
+                        return (true);
+                    }
+                    else if ((value.tokenType == TokenType.MonthToken && HasSpacesInMonthNames) ||
+                             (value.tokenType == TokenType.DayOfWeekToken && HasSpacesInDayNames))
+                    {
+                        // For month or day token, we will match the names which have spaces.
+                        int matchStrLen = 0;
+                        if (str.MatchSpecifiedWords(value.tokenString, true, ref matchStrLen))
+                        {
+                            tokenType = value.tokenType & TokenMask;
+                            tokenValue = value.tokenValue;
+                            str.Advance(matchStrLen);
+                            return (true);
+                        }
+                    }
+                }
+                i++;
+                hashcode += hashProbe;
+                if (hashcode >= TOKEN_HASH_SIZE) hashcode -= TOKEN_HASH_SIZE;
+            } while (i < TOKEN_HASH_SIZE);
+
+            return (false);
+        }
+
+        private void InsertAtCurrentHashNode(TokenHashValue[] hashTable, String str, char ch, TokenType tokenType, int tokenValue, int pos, int hashcode, int hashProbe)
+        {
+            // Remember the current slot.
+            TokenHashValue previousNode = hashTable[hashcode];
+
+            //// Console.WriteLine("   Insert Key: {0} in {1}", str, slotToInsert);
+            // Insert the new node into the current slot.
+            hashTable[hashcode] = new TokenHashValue(str, tokenType, tokenValue); ;
+
+            while (++pos < TOKEN_HASH_SIZE)
+            {
+                hashcode += hashProbe;
+                if (hashcode >= TOKEN_HASH_SIZE) hashcode -= TOKEN_HASH_SIZE;
+                // Remember this slot
+                TokenHashValue temp = hashTable[hashcode];
+
+                if (temp != null && this.Culture.TextInfo.ToLower(temp.tokenString[0]) != ch)
+                {
+                    continue;
+                }
+                // Put the previous slot into this slot.
+                hashTable[hashcode] = previousNode;
+                //// Console.WriteLine("  Move {0} to slot {1}", previousNode.tokenString, hashcode);
+                if (temp == null)
+                {
+                    // Done
+                    return;
+                }
+                previousNode = temp;
+            };
+            Debug.Fail("The hashtable is full.  This should not happen.");
+        }
+
+        private void InsertHash(TokenHashValue[] hashTable, String str, TokenType tokenType, int tokenValue)
+        {
+            // The month of the 13th month is allowed to be null, so make sure that we ignore null value here.
+            if (str == null || str.Length == 0)
+            {
+                return;
+            }
+            TokenHashValue value;
+            int i = 0;
+            // If there is whitespace characters in the beginning and end of the string, trim them since whitespaces are skipped by
+            // DateTime.Parse().
+            if (Char.IsWhiteSpace(str[0]) || Char.IsWhiteSpace(str[str.Length - 1]))
+            {
+                str = str.Trim(null);   // Trim white space characters.
+                // Could have space for separators
+                if (str.Length == 0)
+                    return;
+            }
+            char ch = this.Culture.TextInfo.ToLower(str[0]);
+            int hashcode = ch % TOKEN_HASH_SIZE;
+            int hashProbe = 1 + ch % SECOND_PRIME;
+            do
+            {
+                value = hashTable[hashcode];
+                if (value == null)
+                {
+                    //// Console.WriteLine("   Put Key: {0} in {1}", str, hashcode);
+                    hashTable[hashcode] = new TokenHashValue(str, tokenType, tokenValue);
+                    return;
+                }
+                else
+                {
+                    // Collision happens. Find another slot.
+                    if (str.Length >= value.tokenString.Length)
+                    {
+                        // If there are two tokens with the same prefix, we have to make sure that the longer token should be at the front of
+                        // the shorter ones.
+                        if (this.CompareStringIgnoreCaseOptimized(str, 0, value.tokenString.Length, value.tokenString, 0, value.tokenString.Length))
+                        {
+                            if (str.Length > value.tokenString.Length)
+                            {
+                                // The str to be inserted has the same prefix as the current token, and str is longer.
+                                // Insert str into this node, and shift every node behind it.
+                                InsertAtCurrentHashNode(hashTable, str, ch, tokenType, tokenValue, i, hashcode, hashProbe);
+                                return;
+                            }
+                            else
+                            {
+                                // Same token.  If they have different types (regular token vs separator token).  Add them.
+                                // If we have the same regular token or separator token in the hash already, do NOT update the hash.
+                                // Therefore, the order of inserting token is significant here regarding what tokenType will be kept in the hash.
+
+
+                                //
+                                // Check the current value of RegularToken (stored in the lower 8-bit of tokenType) , and insert the tokenType into the hash ONLY when we don't have a RegularToken yet.
+                                // Also check the current value of SeparatorToken (stored in the upper 8-bit of token), and insert the tokenType into the hash ONLY when we don't have the SeparatorToken yet.
+                                //
+
+                                int nTokenType = (int)tokenType;
+                                int nCurrentTokenTypeInHash = (int)value.tokenType;
+
+                                //
+                                // The folowing is the fix for the issue of throwing FormatException when "mar" is passed in string of the short date format dd/MMM/yyyy for es-MX
+                                //
+
+                                if (((nCurrentTokenTypeInHash & (int)TokenType.RegularTokenMask) == 0) && ((nTokenType & (int)TokenType.RegularTokenMask) != 0) ||
+                                    ((nCurrentTokenTypeInHash & (int)TokenType.SeparatorTokenMask) == 0) && ((nTokenType & (int)TokenType.SeparatorTokenMask) != 0))
+                                {
+                                    value.tokenType |= tokenType;
+                                    if (tokenValue != 0)
+                                    {
+                                        value.tokenValue = tokenValue;
+                                    }
+                                }
+                                // The token to be inserted is already in the table.  Skip it.
+                                return;
+                            }
+                        }
+                    }
+                }
+                //// Console.WriteLine("  COLLISION. Old Key: {0}, New Key: {1}", hashTable[hashcode].tokenString, str);
+                i++;
+                hashcode += hashProbe;
+                if (hashcode >= TOKEN_HASH_SIZE) hashcode -= TOKEN_HASH_SIZE;
+            } while (i < TOKEN_HASH_SIZE);
+            Debug.Fail("The hashtable is full.  This should not happen.");
+        }
+
+        private bool CompareStringIgnoreCaseOptimized(string string1, int offset1, int length1, string string2, int offset2, int length2)
+        {
+            // Optimize for one character cases which are common due to date and time separators (/ and :)
+            if (length1 == 1 && length2 == 1 && string1[offset1] == string2[offset2])
+            {
+                return true;
+            }
+
+            return (this.Culture.CompareInfo.Compare(string1, offset1, length1, string2, offset2, length2, CompareOptions.IgnoreCase) == 0);
+        }
+
+        // class DateTimeFormatInfo
+
+        internal class TokenHashValue
+        {
+            internal String tokenString;
+            internal TokenType tokenType;
+            internal int tokenValue;
+
+            internal TokenHashValue(String tokenString, TokenType tokenType, int tokenValue)
+            {
+                this.tokenString = tokenString;
+                this.tokenType = tokenType;
+                this.tokenValue = tokenValue;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/DateTimeFormatInfoScanner.cs b/src/System.Private.CoreLib/shared/System/Globalization/DateTimeFormatInfoScanner.cs
new file mode 100644
index 0000000000..d3c3aac84e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/DateTimeFormatInfoScanner.cs
@@ -0,0 +1,729 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////
+//
+// DateTimeFormatInfoScanner
+//
+//  Scan a specified DateTimeFormatInfo to search for data used in DateTime.Parse()
+//
+//  The data includes:
+//
+//      DateWords: such as "de" used in es-ES (Spanish) LongDatePattern.
+//      Postfix: such as "ta" used in fi-FI after the month name.
+//
+//  This class is shared among mscorlib.dll and sysglobl.dll.
+//  Use conditional CULTURE_AND_REGIONINFO_BUILDER_ONLY to differentiate between
+//  methods for mscorlib.dll and sysglobl.dll.
+//
+////////////////////////////////////////////////////////////////////////////
+
+using System.Collections.Generic;
+using System.Text;
+
+namespace System.Globalization
+{
+    //
+    // from LocaleEx.txt header
+    //
+    //; IFORMATFLAGS
+    //;       Parsing/formatting flags.
+    internal enum FORMATFLAGS
+    {
+        None = 0x00000000,
+        UseGenitiveMonth = 0x00000001,
+        UseLeapYearMonth = 0x00000002,
+        UseSpacesInMonthNames = 0x00000004,
+        UseHebrewParsing = 0x00000008,
+        UseSpacesInDayNames = 0x00000010,   // Has spaces or non-breaking space in the day names.
+        UseDigitPrefixInTokens = 0x00000020,   // Has token starting with numbers.        
+    }
+
+    internal enum CalendarId : ushort
+    {
+        UNINITIALIZED_VALUE = 0,
+        GREGORIAN = 1,     // Gregorian (localized) calendar
+        GREGORIAN_US = 2,     // Gregorian (U.S.) calendar
+        JAPAN = 3,     // Japanese Emperor Era calendar
+                       /* SSS_WARNINGS_OFF */
+        TAIWAN = 4,     // Taiwan Era calendar /* SSS_WARNINGS_ON */ 
+        KOREA = 5,     // Korean Tangun Era calendar
+        HIJRI = 6,     // Hijri (Arabic Lunar) calendar
+        THAI = 7,     // Thai calendar
+        HEBREW = 8,     // Hebrew (Lunar) calendar
+        GREGORIAN_ME_FRENCH = 9,     // Gregorian Middle East French calendar
+        GREGORIAN_ARABIC = 10,     // Gregorian Arabic calendar
+        GREGORIAN_XLIT_ENGLISH = 11,     // Gregorian Transliterated English calendar
+        GREGORIAN_XLIT_FRENCH = 12,
+        // Note that all calendars after this point are MANAGED ONLY for now.
+        JULIAN = 13,
+        JAPANESELUNISOLAR = 14,
+        CHINESELUNISOLAR = 15,
+        SAKA = 16,     // reserved to match Office but not implemented in our code
+        LUNAR_ETO_CHN = 17,     // reserved to match Office but not implemented in our code
+        LUNAR_ETO_KOR = 18,     // reserved to match Office but not implemented in our code
+        LUNAR_ETO_ROKUYOU = 19,     // reserved to match Office but not implemented in our code
+        KOREANLUNISOLAR = 20,
+        TAIWANLUNISOLAR = 21,
+        PERSIAN = 22,
+        UMALQURA = 23,
+        LAST_CALENDAR = 23      // Last calendar ID
+    }
+
+    internal class DateTimeFormatInfoScanner
+    {
+        // Special prefix-like flag char in DateWord array.
+
+        // Use char in PUA area since we won't be using them in real data.
+        // The char used to tell a read date word or a month postfix.  A month postfix
+        // is "ta" in the long date pattern like "d. MMMM'ta 'yyyy" for fi-FI.
+        // In this case, it will be stored as "\xfffeta" in the date word array.
+        internal const char MonthPostfixChar = '\xe000';
+
+        // Add ignorable symbol in a DateWord array.
+
+        // hu-HU has:
+        //      shrot date pattern: yyyy. MM. dd.;yyyy-MM-dd;yy-MM-dd
+        //      long date pattern: yyyy. MMMM d.
+        // Here, "." is the date separator (derived from short date pattern). However,
+        // "." also appear at the end of long date pattern.  In this case, we just
+        // "." as ignorable symbol so that the DateTime.Parse() state machine will not
+        // treat the additional date separator at the end of y,m,d pattern as an error
+        // condition.
+        internal const char IgnorableSymbolChar = '\xe001';
+
+        // Known CJK suffix
+        internal const String CJKYearSuff = "\u5e74";
+        internal const String CJKMonthSuff = "\u6708";
+        internal const String CJKDaySuff = "\u65e5";
+
+        internal const String KoreanYearSuff = "\ub144";
+        internal const String KoreanMonthSuff = "\uc6d4";
+        internal const String KoreanDaySuff = "\uc77c";
+
+        internal const String KoreanHourSuff = "\uc2dc";
+        internal const String KoreanMinuteSuff = "\ubd84";
+        internal const String KoreanSecondSuff = "\ucd08";
+
+        internal const String CJKHourSuff = "\u6642";
+        internal const String ChineseHourSuff = "\u65f6";
+
+        internal const String CJKMinuteSuff = "\u5206";
+        internal const String CJKSecondSuff = "\u79d2";
+
+        // The collection fo date words & postfix.
+        internal List<string> m_dateWords = new List<string>();
+        // Hashtable for the known words.
+        private static volatile Dictionary<string, string> s_knownWords;
+
+        static Dictionary<string, string> KnownWords
+        {
+            get
+            {
+                if (s_knownWords == null)
+                {
+                    Dictionary<string, string> temp = new Dictionary<string, string>();
+                    // Add known words into the hash table.
+
+                    // Skip these special symbols.                        
+                    temp.Add("/", String.Empty);
+                    temp.Add("-", String.Empty);
+                    temp.Add(".", String.Empty);
+                    // Skip known CJK suffixes.
+                    temp.Add(CJKYearSuff, String.Empty);
+                    temp.Add(CJKMonthSuff, String.Empty);
+                    temp.Add(CJKDaySuff, String.Empty);
+                    temp.Add(KoreanYearSuff, String.Empty);
+                    temp.Add(KoreanMonthSuff, String.Empty);
+                    temp.Add(KoreanDaySuff, String.Empty);
+                    temp.Add(KoreanHourSuff, String.Empty);
+                    temp.Add(KoreanMinuteSuff, String.Empty);
+                    temp.Add(KoreanSecondSuff, String.Empty);
+                    temp.Add(CJKHourSuff, String.Empty);
+                    temp.Add(ChineseHourSuff, String.Empty);
+                    temp.Add(CJKMinuteSuff, String.Empty);
+                    temp.Add(CJKSecondSuff, String.Empty);
+
+                    s_knownWords = temp;
+                }
+                return (s_knownWords);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        //  Parameters:
+        //      pattern: The pattern to be scanned.
+        //      currentIndex: the current index to start the scan.
+        //
+        //  Returns:
+        //      Return the index with the first character that is a letter, which will
+        //      be the start of a date word.
+        //      Note that the index can be pattern.Length if we reach the end of the string.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+        internal static int SkipWhiteSpacesAndNonLetter(String pattern, int currentIndex)
+        {
+            while (currentIndex < pattern.Length)
+            {
+                char ch = pattern[currentIndex];
+                if (ch == '\\')
+                {
+                    // Escaped character. Look ahead one character.
+                    currentIndex++;
+                    if (currentIndex < pattern.Length)
+                    {
+                        ch = pattern[currentIndex];
+                        if (ch == '\'')
+                        {
+                            // Skip the leading single quote.  We will
+                            // stop at the first letter.
+                            continue;
+                        }
+                        // Fall thru to check if this is a letter.
+                    }
+                    else
+                    {
+                        // End of string
+                        break;
+                    }
+                }
+                if (Char.IsLetter(ch) || ch == '\'' || ch == '.')
+                {
+                    break;
+                }
+                // Skip the current char since it is not a letter.
+                currentIndex++;
+            }
+            return (currentIndex);
+        }
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // A helper to add the found date word or month postfix into ArrayList for date words.
+        //
+        // Parameters:
+        //      formatPostfix: What kind of postfix this is.  
+        //          Possible values:
+        //              null: This is a regular date word
+        //              "MMMM": month postfix
+        //      word: The date word or postfix to be added.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+        internal void AddDateWordOrPostfix(String formatPostfix, String str)
+        {
+            if (str.Length > 0)
+            {
+                // Some cultures use . like an abbreviation
+                if (str.Equals("."))
+                {
+                    AddIgnorableSymbols(".");
+                    return;
+                }
+                String words;
+                if (KnownWords.TryGetValue(str, out words) == false)
+                {
+                    if (m_dateWords == null)
+                    {
+                        m_dateWords = new List<string>();
+                    }
+                    if (formatPostfix == "MMMM")
+                    {
+                        // Add the word into the ArrayList as "\xfffe" + real month postfix.
+                        String temp = MonthPostfixChar + str;
+                        if (!m_dateWords.Contains(temp))
+                        {
+                            m_dateWords.Add(temp);
+                        }
+                    }
+                    else
+                    {
+                        if (!m_dateWords.Contains(str))
+                        {
+                            m_dateWords.Add(str);
+                        }
+                        if (str[str.Length - 1] == '.')
+                        {
+                            // Old version ignore the trialing dot in the date words. Support this as well.
+                            String strWithoutDot = str.Substring(0, str.Length - 1);
+                            if (!m_dateWords.Contains(strWithoutDot))
+                            {
+                                m_dateWords.Add(strWithoutDot);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // Scan the pattern from the specified index and add the date word/postfix
+        // when appropriate.
+        //
+        //  Parameters:
+        //      pattern: The pattern to be scanned.
+        //      index: The starting index to be scanned.
+        //      formatPostfix: The kind of postfix to be scanned.
+        //          Possible values:
+        //              null: This is a regular date word
+        //              "MMMM": month postfix
+        //          
+        //
+        ////////////////////////////////////////////////////////////////////////////
+        internal int AddDateWords(String pattern, int index, String formatPostfix)
+        {
+            // Skip any whitespaces so we will start from a letter.
+            int newIndex = SkipWhiteSpacesAndNonLetter(pattern, index);
+            if (newIndex != index && formatPostfix != null)
+            {
+                // There are whitespaces. This will not be a postfix.
+                formatPostfix = null;
+            }
+            index = newIndex;
+
+            // This is the first char added into dateWord.  
+            // Skip all non-letter character.  We will add the first letter into DateWord.
+            StringBuilder dateWord = new StringBuilder();
+            // We assume that date words should start with a letter. 
+            // Skip anything until we see a letter.
+
+            while (index < pattern.Length)
+            {
+                char ch = pattern[index];
+                if (ch == '\'')
+                {
+                    // We have seen the end of quote.  Add the word if we do not see it before, 
+                    // and break the while loop.                    
+                    AddDateWordOrPostfix(formatPostfix, dateWord.ToString());
+                    index++;
+                    break;
+                }
+                else if (ch == '\\')
+                {
+                    //
+                    // Escaped character.  Look ahead one character
+                    //
+
+                    // Skip escaped backslash.
+                    index++;
+                    if (index < pattern.Length)
+                    {
+                        dateWord.Append(pattern[index]);
+                        index++;
+                    }
+                }
+                else if (Char.IsWhiteSpace(ch))
+                {
+                    // Found a whitespace.  We have to add the current date word/postfix.
+                    AddDateWordOrPostfix(formatPostfix, dateWord.ToString());
+                    if (formatPostfix != null)
+                    {
+                        // Done with postfix.  The rest will be regular date word.
+                        formatPostfix = null;
+                    }
+                    // Reset the dateWord.
+                    dateWord.Length = 0;
+                    index++;
+                }
+                else
+                {
+                    dateWord.Append(ch);
+                    index++;
+                }
+            }
+            return (index);
+        }
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // A simple helper to find the repeat count for a specified char.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+        internal static int ScanRepeatChar(String pattern, char ch, int index, out int count)
+        {
+            count = 1;
+            while (++index < pattern.Length && pattern[index] == ch)
+            {
+                count++;
+            }
+            // Return the updated position.
+            return (index);
+        }
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // Add the text that is a date separator but is treated like ignroable symbol.
+        // E.g.
+        // hu-HU has:
+        //      shrot date pattern: yyyy. MM. dd.;yyyy-MM-dd;yy-MM-dd
+        //      long date pattern: yyyy. MMMM d.
+        // Here, "." is the date separator (derived from short date pattern). However,
+        // "." also appear at the end of long date pattern.  In this case, we just
+        // "." as ignorable symbol so that the DateTime.Parse() state machine will not
+        // treat the additional date separator at the end of y,m,d pattern as an error
+        // condition.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+
+        internal void AddIgnorableSymbols(String text)
+        {
+            if (m_dateWords == null)
+            {
+                // Create the date word array.
+                m_dateWords = new List<string>();
+            }
+            // Add the ignorable symbol into the ArrayList.
+            String temp = IgnorableSymbolChar + text;
+            if (!m_dateWords.Contains(temp))
+            {
+                m_dateWords.Add(temp);
+            }
+        }
+
+
+        //
+        // Flag used to trace the date patterns (yy/yyyyy/M/MM/MMM/MMM/d/dd) that we have seen.
+        //
+        private enum FoundDatePattern
+        {
+            None = 0x0000,
+            FoundYearPatternFlag = 0x0001,
+            FoundMonthPatternFlag = 0x0002,
+            FoundDayPatternFlag = 0x0004,
+            FoundYMDPatternFlag = 0x0007, // FoundYearPatternFlag | FoundMonthPatternFlag | FoundDayPatternFlag;
+        }
+
+        // Check if we have found all of the year/month/day pattern.
+        private FoundDatePattern _ymdFlags = FoundDatePattern.None;
+
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // Given a date format pattern, scan for date word or postfix.
+        //
+        // A date word should be always put in a single quoted string.  And it will
+        // start from a letter, so whitespace and symbols will be ignored before
+        // the first letter.
+        //
+        // Examples of date word:
+        //  'de' in es-SP: dddd, dd' de 'MMMM' de 'yyyy
+        //  "\x0443." in bg-BG: dd.M.yyyy '\x0433.'
+        //
+        // Example of postfix:
+        //  month postfix: 
+        //      "ta" in fi-FI: d. MMMM'ta 'yyyy
+        //  Currently, only month postfix is supported.
+        //
+        // Usage:
+        //  Always call this with Framework-style pattern, instead of Windows style pattern.
+        //  Windows style pattern uses '' for single quote, while .NET uses \'
+        //
+        ////////////////////////////////////////////////////////////////////////////        
+        internal void ScanDateWord(String pattern)
+        {
+            // Check if we have found all of the year/month/day pattern.
+            _ymdFlags = FoundDatePattern.None;
+
+            int i = 0;
+            while (i < pattern.Length)
+            {
+                char ch = pattern[i];
+                int chCount;
+
+                switch (ch)
+                {
+                    case '\'':
+                        // Find a beginning quote.  Search until the end quote.
+                        i = AddDateWords(pattern, i + 1, null);
+                        break;
+                    case 'M':
+                        i = ScanRepeatChar(pattern, 'M', i, out chCount);
+                        if (chCount >= 4)
+                        {
+                            if (i < pattern.Length && pattern[i] == '\'')
+                            {
+                                i = AddDateWords(pattern, i + 1, "MMMM");
+                            }
+                        }
+                        _ymdFlags |= FoundDatePattern.FoundMonthPatternFlag;
+                        break;
+                    case 'y':
+                        i = ScanRepeatChar(pattern, 'y', i, out chCount);
+                        _ymdFlags |= FoundDatePattern.FoundYearPatternFlag;
+                        break;
+                    case 'd':
+                        i = ScanRepeatChar(pattern, 'd', i, out chCount);
+                        if (chCount <= 2)
+                        {
+                            // Only count "d" & "dd".
+                            // ddd, dddd are day names.  Do not count them.
+                            _ymdFlags |= FoundDatePattern.FoundDayPatternFlag;
+                        }
+                        break;
+                    case '\\':
+                        // Found a escaped char not in a quoted string.  Skip the current backslash
+                        // and its next character.
+                        i += 2;
+                        break;
+                    case '.':
+                        if (_ymdFlags == FoundDatePattern.FoundYMDPatternFlag)
+                        {
+                            // If we find a dot immediately after the we have seen all of the y, m, d pattern.
+                            // treat it as a ignroable symbol.  Check for comments in AddIgnorableSymbols for
+                            // more details.
+                            AddIgnorableSymbols(".");
+                            _ymdFlags = FoundDatePattern.None;
+                        }
+                        i++;
+                        break;
+                    default:
+                        if (_ymdFlags == FoundDatePattern.FoundYMDPatternFlag && !Char.IsWhiteSpace(ch))
+                        {
+                            // We are not seeing "." after YMD. Clear the flag.
+                            _ymdFlags = FoundDatePattern.None;
+                        }
+                        // We are not in quote.  Skip the current character.
+                        i++;
+                        break;
+                }
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // Given a DTFI, get all of the date words from date patterns and time patterns.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+
+        internal String[] GetDateWordsOfDTFI(DateTimeFormatInfo dtfi)
+        {
+            // Enumarate all LongDatePatterns, and get the DateWords and scan for month postfix.
+            String[] datePatterns = dtfi.GetAllDateTimePatterns('D');
+            int i;
+
+            // Scan the long date patterns
+            for (i = 0; i < datePatterns.Length; i++)
+            {
+                ScanDateWord(datePatterns[i]);
+            }
+
+            // Scan the short date patterns
+            datePatterns = dtfi.GetAllDateTimePatterns('d');
+            for (i = 0; i < datePatterns.Length; i++)
+            {
+                ScanDateWord(datePatterns[i]);
+            }
+            // Scan the YearMonth patterns.
+            datePatterns = dtfi.GetAllDateTimePatterns('y');
+            for (i = 0; i < datePatterns.Length; i++)
+            {
+                ScanDateWord(datePatterns[i]);
+            }
+
+            // Scan the month/day pattern
+            ScanDateWord(dtfi.MonthDayPattern);
+
+            // Scan the long time patterns.
+            datePatterns = dtfi.GetAllDateTimePatterns('T');
+            for (i = 0; i < datePatterns.Length; i++)
+            {
+                ScanDateWord(datePatterns[i]);
+            }
+
+            // Scan the short time patterns.
+            datePatterns = dtfi.GetAllDateTimePatterns('t');
+            for (i = 0; i < datePatterns.Length; i++)
+            {
+                ScanDateWord(datePatterns[i]);
+            }
+
+            String[] result = null;
+            if (m_dateWords != null && m_dateWords.Count > 0)
+            {
+                result = new String[m_dateWords.Count];
+                for (i = 0; i < m_dateWords.Count; i++)
+                {
+                    result[i] = m_dateWords[i];
+                }
+            }
+            return (result);
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////////        
+        //
+        // Scan the month names to see if genitive month names are used, and return
+        // the format flag.
+        //
+        ////////////////////////////////////////////////////////////////////////////        
+        internal static FORMATFLAGS GetFormatFlagGenitiveMonth(String[] monthNames, String[] genitveMonthNames, String[] abbrevMonthNames, String[] genetiveAbbrevMonthNames)
+        {
+            // If we have different names in regular and genitive month names, use genitive month flag.
+            return ((!EqualStringArrays(monthNames, genitveMonthNames) || !EqualStringArrays(abbrevMonthNames, genetiveAbbrevMonthNames))
+                ? FORMATFLAGS.UseGenitiveMonth : 0);
+        }
+
+        ////////////////////////////////////////////////////////////////////////////        
+        //
+        // Scan the month names to see if spaces are used or start with a digit, and return the format flag
+        //
+        ////////////////////////////////////////////////////////////////////////////        
+        internal static FORMATFLAGS GetFormatFlagUseSpaceInMonthNames(String[] monthNames, String[] genitveMonthNames, String[] abbrevMonthNames, String[] genetiveAbbrevMonthNames)
+        {
+            FORMATFLAGS formatFlags = 0;
+            formatFlags |= (ArrayElementsBeginWithDigit(monthNames) ||
+                    ArrayElementsBeginWithDigit(genitveMonthNames) ||
+                    ArrayElementsBeginWithDigit(abbrevMonthNames) ||
+                    ArrayElementsBeginWithDigit(genetiveAbbrevMonthNames)
+                    ? FORMATFLAGS.UseDigitPrefixInTokens : 0);
+
+            formatFlags |= (ArrayElementsHaveSpace(monthNames) ||
+                    ArrayElementsHaveSpace(genitveMonthNames) ||
+                    ArrayElementsHaveSpace(abbrevMonthNames) ||
+                    ArrayElementsHaveSpace(genetiveAbbrevMonthNames)
+                    ? FORMATFLAGS.UseSpacesInMonthNames : 0);
+            return (formatFlags);
+        }
+
+        ////////////////////////////////////////////////////////////////////////////        
+        //
+        // Scan the day names and set the correct format flag.
+        //
+        ////////////////////////////////////////////////////////////////////////////        
+        internal static FORMATFLAGS GetFormatFlagUseSpaceInDayNames(String[] dayNames, String[] abbrevDayNames)
+        {
+            return ((ArrayElementsHaveSpace(dayNames) ||
+                    ArrayElementsHaveSpace(abbrevDayNames))
+                    ? FORMATFLAGS.UseSpacesInDayNames : 0);
+        }
+
+        ////////////////////////////////////////////////////////////////////////////        
+        //
+        // Check the calendar to see if it is HebrewCalendar and set the Hebrew format flag if necessary.
+        //
+        ////////////////////////////////////////////////////////////////////////////                
+        internal static FORMATFLAGS GetFormatFlagUseHebrewCalendar(int calID)
+        {
+            return (calID == (int)CalendarId.HEBREW ?
+                FORMATFLAGS.UseHebrewParsing | FORMATFLAGS.UseLeapYearMonth : 0);
+        }
+
+
+        //-----------------------------------------------------------------------------
+        // EqualStringArrays 
+        //      compares two string arrays and return true if all elements of the first  
+        //      array equals to all elmentsof the second array. 
+        //      otherwise it returns false.
+        //-----------------------------------------------------------------------------
+
+        private static bool EqualStringArrays(string[] array1, string[] array2)
+        {
+            // Shortcut if they're the same array
+            if (array1 == array2)
+            {
+                return true;
+            }
+
+            // This is effectively impossible
+            if (array1.Length != array2.Length)
+            {
+                return false;
+            }
+
+            // Check each string 
+            for (int i = 0; i < array1.Length; i++)
+            {
+                if (!array1[i].Equals(array2[i]))
+                {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
+        //-----------------------------------------------------------------------------
+        // ArrayElementsHaveSpace 
+        //      It checks all input array elements if any of them has space character
+        //      returns true if found space character in one of the array elements.
+        //      otherwise returns false.
+        //-----------------------------------------------------------------------------
+
+        private static bool ArrayElementsHaveSpace(string[] array)
+        {
+            for (int i = 0; i < array.Length; i++)
+            {
+                // it is faster to check for space character manually instead of calling IndexOf
+                // so we don't have to go to native code side.
+                for (int j = 0; j < array[i].Length; j++)
+                {
+                    if (Char.IsWhiteSpace(array[i][j]))
+                    {
+                        return true;
+                    }
+                }
+            }
+
+            return false;
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////////        
+        //
+        // Check if any element of the array start with a digit.
+        //
+        ////////////////////////////////////////////////////////////////////////////        
+        private static bool ArrayElementsBeginWithDigit(string[] array)
+        {
+            for (int i = 0; i < array.Length; i++)
+            {
+                // it is faster to check for space character manually instead of calling IndexOf
+                // so we don't have to go to native code side.
+                if (array[i].Length > 0 &&
+                   array[i][0] >= '0' && array[i][0] <= '9')
+                {
+                    int index = 1;
+                    while (index < array[i].Length && array[i][index] >= '0' && array[i][index] <= '9')
+                    {
+                        // Skip other digits.
+                        index++;
+                    }
+                    if (index == array[i].Length)
+                    {
+                        return (false);
+                    }
+
+                    if (index == array[i].Length - 1)
+                    {
+                        // Skip known CJK month suffix.
+                        // CJK uses month name like "1\x6708", since \x6708 is a known month suffix,
+                        // we don't need the UseDigitPrefixInTokens since it is slower.
+                        switch (array[i][index])
+                        {
+                            case '\x6708': // CJKMonthSuff
+                            case '\xc6d4': // KoreanMonthSuff
+                                return (false);
+                        }
+                    }
+
+                    if (index == array[i].Length - 4)
+                    {
+                        // Skip known CJK month suffix.
+                        // Starting with Windows 8, the CJK months for some cultures looks like: "1' \x6708'" 
+                        // instead of just "1\x6708"
+                        if (array[i][index] == '\'' && array[i][index + 1] == ' ' &&
+                           array[i][index + 2] == '\x6708' && array[i][index + 3] == '\'')
+                        {
+                            return (false);
+                        }
+                    }
+                    return (true);
+                }
+            }
+
+            return false;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/DateTimeParse.cs b/src/System.Private.CoreLib/shared/System/Globalization/DateTimeParse.cs
new file mode 100644
index 0000000000..970d1765bb
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/DateTimeParse.cs
@@ -0,0 +1,5668 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Text;
+
+namespace System
+{
+    internal static class DateTimeParse
+    {
+        internal const Int32 MaxDateTimeNumberDigits = 8;
+
+        internal delegate bool MatchNumberDelegate(ref __DTString str, int digitLen, out int result);
+
+        internal static MatchNumberDelegate m_hebrewNumberParser = new MatchNumberDelegate(DateTimeParse.MatchHebrewDigits);
+
+        internal static DateTime ParseExact(ReadOnlySpan<char> s, ReadOnlySpan<char> format, DateTimeFormatInfo dtfi, DateTimeStyles style)
+        {
+            DateTimeResult result = new DateTimeResult();       // The buffer to store the parsing result.
+            result.Init(s);
+            if (TryParseExact(s, format, dtfi, style, ref result))
+            {
+                return result.parsedDate;
+            }
+            else
+            {
+                throw GetDateTimeParseException(ref result);
+            }
+        }
+
+        internal static DateTime ParseExact(ReadOnlySpan<char> s, ReadOnlySpan<char> format, DateTimeFormatInfo dtfi, DateTimeStyles style, out TimeSpan offset)
+        {
+            DateTimeResult result = new DateTimeResult();       // The buffer to store the parsing result.
+            offset = TimeSpan.Zero;
+            result.Init(s);
+            result.flags |= ParseFlags.CaptureOffset;
+            if (TryParseExact(s, format, dtfi, style, ref result))
+            {
+                offset = result.timeZoneOffset;
+                return result.parsedDate;
+            }
+            else
+            {
+                throw GetDateTimeParseException(ref result);
+            }
+        }
+
+        internal static bool TryParseExact(ReadOnlySpan<char> s, ReadOnlySpan<char> format, DateTimeFormatInfo dtfi, DateTimeStyles style, out DateTime result)
+        {
+            result = DateTime.MinValue;
+            DateTimeResult resultData = new DateTimeResult();       // The buffer to store the parsing result.
+            resultData.Init(s);
+            if (TryParseExact(s, format, dtfi, style, ref resultData))
+            {
+                result = resultData.parsedDate;
+                return true;
+            }
+            return false;
+        }
+
+        internal static bool TryParseExact(ReadOnlySpan<char> s, ReadOnlySpan<char> format, DateTimeFormatInfo dtfi, DateTimeStyles style, out DateTime result, out TimeSpan offset)
+        {
+            result = DateTime.MinValue;
+            offset = TimeSpan.Zero;
+            DateTimeResult resultData = new DateTimeResult();       // The buffer to store the parsing result.
+            resultData.Init(s);
+            resultData.flags |= ParseFlags.CaptureOffset;
+            if (TryParseExact(s, format, dtfi, style, ref resultData))
+            {
+                result = resultData.parsedDate;
+                offset = resultData.timeZoneOffset;
+                return true;
+            }
+            return false;
+        }
+
+        internal static bool TryParseExact(ReadOnlySpan<char> s, ReadOnlySpan<char> format, DateTimeFormatInfo dtfi, DateTimeStyles style, ref DateTimeResult result)
+        {
+            if (s.Length == 0)
+            {
+                result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_BadDateTime));
+                return false;
+            }
+
+            if (format.Length == 0)
+            {
+                result.SetBadFormatSpecifierFailure();
+                return false;
+            }
+
+            Debug.Assert(dtfi != null, "dtfi == null");
+
+            return DoStrictParse(s, format, style, dtfi, ref result);
+        }
+
+        internal static DateTime ParseExactMultiple(ReadOnlySpan<char> s, String[] formats,
+                                                DateTimeFormatInfo dtfi, DateTimeStyles style)
+        {
+            DateTimeResult result = new DateTimeResult();       // The buffer to store the parsing result.
+            result.Init(s);
+            if (TryParseExactMultiple(s, formats, dtfi, style, ref result))
+            {
+                return result.parsedDate;
+            }
+            else
+            {
+                throw GetDateTimeParseException(ref result);
+            }
+        }
+
+
+        internal static DateTime ParseExactMultiple(ReadOnlySpan<char> s, String[] formats,
+                                                DateTimeFormatInfo dtfi, DateTimeStyles style, out TimeSpan offset)
+        {
+            DateTimeResult result = new DateTimeResult();       // The buffer to store the parsing result.
+            offset = TimeSpan.Zero;
+            result.Init(s);
+            result.flags |= ParseFlags.CaptureOffset;
+            if (TryParseExactMultiple(s, formats, dtfi, style, ref result))
+            {
+                offset = result.timeZoneOffset;
+                return result.parsedDate;
+            }
+            else
+            {
+                throw GetDateTimeParseException(ref result);
+            }
+        }
+
+        internal static bool TryParseExactMultiple(ReadOnlySpan<char> s, String[] formats,
+                                                   DateTimeFormatInfo dtfi, DateTimeStyles style, out DateTime result, out TimeSpan offset)
+        {
+            result = DateTime.MinValue;
+            offset = TimeSpan.Zero;
+            DateTimeResult resultData = new DateTimeResult();       // The buffer to store the parsing result.
+            resultData.Init(s);
+            resultData.flags |= ParseFlags.CaptureOffset;
+            if (TryParseExactMultiple(s, formats, dtfi, style, ref resultData))
+            {
+                result = resultData.parsedDate;
+                offset = resultData.timeZoneOffset;
+                return true;
+            }
+            return false;
+        }
+
+
+        internal static bool TryParseExactMultiple(ReadOnlySpan<char> s, String[] formats,
+                                                   DateTimeFormatInfo dtfi, DateTimeStyles style, out DateTime result)
+        {
+            result = DateTime.MinValue;
+            DateTimeResult resultData = new DateTimeResult();       // The buffer to store the parsing result.
+            resultData.Init(s);
+            if (TryParseExactMultiple(s, formats, dtfi, style, ref resultData))
+            {
+                result = resultData.parsedDate;
+                return true;
+            }
+            return false;
+        }
+
+        internal static bool TryParseExactMultiple(ReadOnlySpan<char> s, String[] formats,
+                                                DateTimeFormatInfo dtfi, DateTimeStyles style, ref DateTimeResult result)
+        {
+            if (formats == null)
+            {
+                result.SetFailure(ParseFailureKind.ArgumentNull, nameof(SR.ArgumentNull_String), null, nameof(formats));
+                return false;
+            }
+
+            if (s.Length == 0)
+            {
+                result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_BadDateTime));
+                return false;
+            }
+
+            if (formats.Length == 0)
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_NoFormatSpecifier));
+                return false;
+            }
+
+            Debug.Assert(dtfi != null, "dtfi == null");
+
+            //
+            // Do a loop through the provided formats and see if we can parse succesfully in
+            // one of the formats.
+            //
+            for (int i = 0; i < formats.Length; i++)
+            {
+                if (formats[i] == null || formats[i].Length == 0)
+                {
+                    result.SetBadFormatSpecifierFailure();
+                    return false;
+                }
+                // Create a new result each time to ensure the runs are independent. Carry through
+                // flags from the caller and return the result.
+                DateTimeResult innerResult = new DateTimeResult();       // The buffer to store the parsing result.
+                innerResult.Init(s);
+                innerResult.flags = result.flags;
+                if (TryParseExact(s, formats[i], dtfi, style, ref innerResult))
+                {
+                    result.parsedDate = innerResult.parsedDate;
+                    result.timeZoneOffset = innerResult.timeZoneOffset;
+                    return (true);
+                }
+            }
+            result.SetBadDateTimeFailure();
+            return (false);
+        }
+
+        ////////////////////////////////////////////////////////////////////////////
+        // Date Token Types
+        //
+        // Following is the set of tokens that can be generated from a date
+        // string. Notice that the legal set of trailing separators have been
+        // folded in with the date number, and month name tokens. This set
+        // of tokens is chosen to reduce the number of date parse states.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+
+        internal enum DTT : int
+        {
+            End = 0,    // '\0'
+            NumEnd = 1,    // Num[ ]*[\0]
+            NumAmpm = 2,    // Num[ ]+AmPm
+            NumSpace = 3,    // Num[ ]+^[Dsep|Tsep|'0\']
+            NumDatesep = 4,    // Num[ ]*Dsep
+            NumTimesep = 5,    // Num[ ]*Tsep
+            MonthEnd = 6,    // Month[ ]*'\0'
+            MonthSpace = 7,    // Month[ ]+^[Dsep|Tsep|'\0']
+            MonthDatesep = 8,    // Month[ ]*Dsep
+            NumDatesuff = 9,    // Month[ ]*DSuff
+            NumTimesuff = 10,   // Month[ ]*TSuff
+            DayOfWeek = 11,   // Day of week name
+            YearSpace = 12,   // Year+^[Dsep|Tsep|'0\']
+            YearDateSep = 13,  // Year+Dsep
+            YearEnd = 14,  // Year+['\0']
+            TimeZone = 15,  // timezone name
+            Era = 16,  // era name
+            NumUTCTimeMark = 17,      // Num + 'Z'
+            // When you add a new token which will be in the
+            // state table, add it after NumLocalTimeMark.
+            Unk = 18,   // unknown
+            NumLocalTimeMark = 19,    // Num + 'T'
+            Max = 20,   // marker
+        }
+
+        internal enum TM
+        {
+            NotSet = -1,
+            AM = 0,
+            PM = 1,
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // DateTime parsing state enumeration (DS.*)
+        //
+        ////////////////////////////////////////////////////////////////////////////
+
+        internal enum DS
+        {
+            BEGIN = 0,
+            N = 1,        // have one number
+            NN = 2,        // have two numbers
+
+            // The following are known to be part of a date
+
+            D_Nd = 3,        // date string: have number followed by date separator
+            D_NN = 4,        // date string: have two numbers
+            D_NNd = 5,        // date string: have two numbers followed by date separator
+
+            D_M = 6,        // date string: have a month
+            D_MN = 7,        // date string: have a month and a number
+            D_NM = 8,        // date string: have a number and a month
+            D_MNd = 9,        // date string: have a month and number followed by date separator
+            D_NDS = 10,       // date string: have one number followed a date suffix.
+
+            D_Y = 11,        // date string: have a year.
+            D_YN = 12,        // date string: have a year and a number
+            D_YNd = 13,        // date string: have a year and a number and a date separator
+            D_YM = 14,        // date string: have a year and a month
+            D_YMd = 15,        // date string: have a year and a month and a date separator
+            D_S = 16,       // have numbers followed by a date suffix.
+            T_S = 17,       // have numbers followed by a time suffix.
+
+            // The following are known to be part of a time
+
+            T_Nt = 18,          // have num followed by time separator
+            T_NNt = 19,       // have two numbers followed by time separator
+
+
+            ERROR = 20,
+
+            // The following are terminal states. These all have an action
+            // associated with them; and transition back to BEGIN.
+
+            DX_NN = 21,       // day from two numbers
+            DX_NNN = 22,       // day from three numbers
+            DX_MN = 23,       // day from month and one number
+            DX_NM = 24,       // day from month and one number
+            DX_MNN = 25,       // day from month and two numbers
+            DX_DS = 26,       // a set of date suffixed numbers.
+            DX_DSN = 27,       // day from date suffixes and one number.
+            DX_NDS = 28,       // day from one number and date suffixes .
+            DX_NNDS = 29,       // day from one number and date suffixes .
+
+            DX_YNN = 30,       // date string: have a year and two number
+            DX_YMN = 31,       // date string: have a year, a month, and a number.
+            DX_YN = 32,       // date string: have a year and one number
+            DX_YM = 33,       // date string: have a year, a month.
+            TX_N = 34,       // time from one number (must have ampm)
+            TX_NN = 35,       // time from two numbers
+            TX_NNN = 36,       // time from three numbers
+            TX_TS = 37,       // a set of time suffixed numbers.
+            DX_NNY = 38,
+        }
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // NOTE: The following state machine table is dependent on the order of the
+        // DS and DTT enumerations.
+        //
+        // For each non terminal state, the following table defines the next state
+        // for each given date token type.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+
+        //          End       NumEnd      NumAmPm     NumSpace    NumDaySep   NumTimesep  MonthEnd    MonthSpace  MonthDSep   NumDateSuff NumTimeSuff     DayOfWeek     YearSpace   YearDateSep YearEnd     TimeZone   Era         UTCTimeMark
+        private static DS[][] dateParsingStates = {
+// DS.BEGIN                                                                             // DS.BEGIN
+new DS[] { DS.BEGIN, DS.ERROR,   DS.TX_N,    DS.N,       DS.D_Nd,    DS.T_Nt,    DS.ERROR,   DS.D_M,     DS.D_M,     DS.D_S,     DS.T_S,         DS.BEGIN,     DS.D_Y,     DS.D_Y,     DS.ERROR,   DS.BEGIN,  DS.BEGIN,    DS.ERROR},
+
+// DS.N                                                                                 // DS.N
+new DS[] { DS.ERROR, DS.DX_NN,   DS.ERROR,   DS.NN,      DS.D_NNd,   DS.ERROR,   DS.DX_NM,   DS.D_NM,    DS.D_MNd,   DS.D_NDS,   DS.ERROR,       DS.N,         DS.D_YN,    DS.D_YNd,   DS.DX_YN,   DS.N,      DS.N,        DS.ERROR},
+
+// DS.NN                                                                                // DS.NN
+new DS[] { DS.DX_NN, DS.DX_NNN,  DS.TX_N,    DS.DX_NNN,  DS.ERROR,   DS.T_Nt,    DS.DX_MNN,  DS.DX_MNN,  DS.ERROR,   DS.ERROR,   DS.T_S,         DS.NN,        DS.DX_NNY,  DS.ERROR,   DS.DX_NNY,  DS.NN,     DS.NN,       DS.ERROR},
+
+// DS.D_Nd                                                                              // DS.D_Nd
+new DS[] { DS.ERROR, DS.DX_NN,   DS.ERROR,   DS.D_NN,    DS.D_NNd,   DS.ERROR,   DS.DX_NM,   DS.D_MN,    DS.D_MNd,   DS.ERROR,   DS.ERROR,       DS.D_Nd,      DS.D_YN,    DS.D_YNd,   DS.DX_YN,   DS.ERROR,  DS.D_Nd,     DS.ERROR},
+
+// DS.D_NN                                                                              // DS.D_NN
+new DS[] { DS.DX_NN, DS.DX_NNN,  DS.TX_N,    DS.DX_NNN,  DS.ERROR,   DS.T_Nt,    DS.DX_MNN,  DS.DX_MNN,  DS.ERROR,   DS.DX_DS,   DS.T_S,         DS.D_NN,     DS.DX_NNY,   DS.ERROR,   DS.DX_NNY,  DS.ERROR,  DS.D_NN,     DS.ERROR},
+
+// DS.D_NNd                                                                             // DS.D_NNd
+new DS[] { DS.ERROR, DS.DX_NNN,  DS.DX_NNN,  DS.DX_NNN,  DS.ERROR,   DS.ERROR,   DS.DX_MNN,  DS.DX_MNN,  DS.ERROR,   DS.DX_DS,   DS.ERROR,       DS.D_NNd,     DS.DX_NNY,  DS.ERROR,   DS.DX_NNY,  DS.ERROR,  DS.D_NNd,    DS.ERROR},
+
+// DS.D_M                                                                               // DS.D_M
+new DS[] { DS.ERROR, DS.DX_MN,   DS.ERROR,   DS.D_MN,    DS.D_MNd,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,       DS.D_M,       DS.D_YM,    DS.D_YMd,   DS.DX_YM,   DS.ERROR,  DS.D_M,      DS.ERROR},
+
+// DS.D_MN                                                                              // DS.D_MN
+new DS[] { DS.DX_MN, DS.DX_MNN,  DS.DX_MNN,  DS.DX_MNN,  DS.ERROR,   DS.T_Nt,    DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.DX_DS,   DS.T_S,         DS.D_MN,      DS.DX_YMN,  DS.ERROR,   DS.DX_YMN,  DS.ERROR,  DS.D_MN,     DS.ERROR},
+
+// DS.D_NM                                                                              // DS.D_NM
+new DS[] { DS.DX_NM, DS.DX_MNN,  DS.DX_MNN,  DS.DX_MNN,  DS.ERROR,   DS.T_Nt,    DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.DX_DS,   DS.T_S,         DS.D_NM,      DS.DX_YMN,  DS.ERROR,   DS.DX_YMN,  DS.ERROR,   DS.D_NM,    DS.ERROR},
+
+// DS.D_MNd                                                                             // DS.D_MNd
+new DS[] { DS.ERROR, DS.DX_MNN,  DS.ERROR,   DS.DX_MNN,  DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,       DS.D_MNd,     DS.DX_YMN,  DS.ERROR,   DS.DX_YMN,  DS.ERROR,   DS.D_MNd,   DS.ERROR},
+
+// DS.D_NDS,                                                                            // DS.D_NDS,
+new DS[] { DS.DX_NDS,DS.DX_NNDS, DS.DX_NNDS, DS.DX_NNDS, DS.ERROR,   DS.T_Nt,    DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.D_NDS,   DS.T_S,         DS.D_NDS,     DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.D_NDS,   DS.ERROR},
+
+// DS.D_Y                                                                               // DS.D_Y
+new DS[] { DS.ERROR, DS.DX_YN,   DS.ERROR,   DS.D_YN,    DS.D_YNd,   DS.ERROR,   DS.DX_YM,   DS.D_YM,    DS.D_YMd,   DS.D_YM,    DS.ERROR,       DS.D_Y,       DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.D_Y,     DS.ERROR},
+
+// DS.D_YN                                                                              // DS.D_YN
+new DS[] { DS.DX_YN, DS.DX_YNN,  DS.DX_YNN,  DS.DX_YNN,  DS.ERROR,   DS.ERROR,   DS.DX_YMN,  DS.DX_YMN,  DS.ERROR,   DS.ERROR,   DS.ERROR,       DS.D_YN,      DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.D_YN,    DS.ERROR},
+
+// DS.D_YNd                                                                             // DS.D_YNd
+new DS[] { DS.ERROR, DS.DX_YNN,  DS.DX_YNN,  DS.DX_YNN,  DS.ERROR,   DS.ERROR,   DS.DX_YMN,  DS.DX_YMN,  DS.ERROR,   DS.ERROR,   DS.ERROR,       DS.D_YN,      DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.D_YN,    DS.ERROR},
+
+// DS.D_YM                                                                              // DS.D_YM
+new DS[] { DS.DX_YM, DS.DX_YMN,  DS.DX_YMN,  DS.DX_YMN,  DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,       DS.D_YM,      DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.D_YM,    DS.ERROR},
+
+// DS.D_YMd                                                                             // DS.D_YMd
+new DS[] { DS.ERROR, DS.DX_YMN,  DS.DX_YMN,  DS.DX_YMN,  DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,       DS.D_YM,      DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.D_YM,    DS.ERROR},
+
+// DS.D_S                                                                               // DS.D_S
+new DS[] { DS.DX_DS, DS.DX_DSN,  DS.TX_N,    DS.T_Nt,    DS.ERROR,   DS.T_Nt,    DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.D_S,     DS.T_S,         DS.D_S,       DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.D_S,     DS.ERROR},
+
+// DS.T_S                                                                               // DS.T_S
+new DS[] { DS.TX_TS, DS.TX_TS,   DS.TX_TS,   DS.T_Nt,    DS.D_Nd,    DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.D_S,     DS.T_S,         DS.T_S,       DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.T_S,     DS.T_S,     DS.ERROR},
+
+// DS.T_Nt                                                                              // DS.T_Nt
+new DS[] { DS.ERROR, DS.TX_NN,   DS.TX_NN,   DS.TX_NN,   DS.ERROR,   DS.T_NNt,   DS.DX_NM,   DS.D_NM,    DS.ERROR,   DS.ERROR,   DS.T_S,         DS.ERROR,     DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.T_Nt,    DS.T_Nt,    DS.TX_NN},
+
+// DS.T_NNt                                                                             // DS.T_NNt
+new DS[] { DS.ERROR, DS.TX_NNN,  DS.TX_NNN,  DS.TX_NNN,  DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.T_S,         DS.T_NNt,     DS.ERROR,   DS.ERROR,   DS.ERROR,   DS.T_NNt,   DS.T_NNt,   DS.TX_NNN},
+};
+        //          End       NumEnd      NumAmPm     NumSpace    NumDaySep   NumTimesep  MonthEnd    MonthSpace  MonthDSep   NumDateSuff NumTimeSuff     DayOfWeek     YearSpace   YearDateSep YearEnd     TimeZone    Era        UTCMark
+
+        internal const String GMTName = "GMT";
+        internal const String ZuluName = "Z";
+
+        //
+        // Search from the index of str at str.Index to see if the target string exists in the str.
+        //
+        private static bool MatchWord(ref __DTString str, String target)
+        {
+            if (target.Length > (str.Value.Length - str.Index))
+            {
+                return false;
+            }
+
+            if (str.CompareInfo.Compare(str.Value.Slice(str.Index, target.Length), target, CompareOptions.IgnoreCase) != 0)
+            {
+                return (false);
+            }
+
+            int nextCharIndex = str.Index + target.Length;
+
+            if (nextCharIndex < str.Value.Length)
+            {
+                char nextCh = str.Value[nextCharIndex];
+                if (Char.IsLetter(nextCh))
+                {
+                    return (false);
+                }
+            }
+            str.Index = nextCharIndex;
+            if (str.Index < str.Length)
+            {
+                str.m_current = str.Value[str.Index];
+            }
+
+            return (true);
+        }
+
+
+        //
+        // Check the word at the current index to see if it matches GMT name or Zulu name.
+        //
+        private static bool GetTimeZoneName(ref __DTString str)
+        {
+            if (MatchWord(ref str, GMTName))
+            {
+                return (true);
+            }
+
+            if (MatchWord(ref str, ZuluName))
+            {
+                return (true);
+            }
+
+            return (false);
+        }
+
+        internal static bool IsDigit(char ch) => (uint)(ch - '0') <= 9;
+
+        /*=================================ParseFraction==========================
+        **Action: Starting at the str.Index, which should be a decimal symbol.
+        ** if the current character is a digit, parse the remaining
+        **      numbers as fraction.  For example, if the sub-string starting at str.Index is "123", then
+        **      the method will return 0.123
+        **Returns:      The fraction number.
+        **Arguments:
+        **      str the parsing string
+        **Exceptions:
+        ============================================================================*/
+
+        private static bool ParseFraction(ref __DTString str, out double result)
+        {
+            result = 0;
+            double decimalBase = 0.1;
+            int digits = 0;
+            char ch;
+            while (str.GetNext()
+                   && IsDigit(ch = str.m_current))
+            {
+                result += (ch - '0') * decimalBase;
+                decimalBase *= 0.1;
+                digits++;
+            }
+            return (digits > 0);
+        }
+
+        /*=================================ParseTimeZone==========================
+        **Action: Parse the timezone offset in the following format:
+        **          "+8", "+08", "+0800", "+0800"
+        **        This method is used by DateTime.Parse().
+        **Returns:      The TimeZone offset.
+        **Arguments:
+        **      str the parsing string
+        **Exceptions:
+        **      FormatException if invalid timezone format is found.
+        ============================================================================*/
+
+        private static bool ParseTimeZone(ref __DTString str, ref TimeSpan result)
+        {
+            // The hour/minute offset for timezone.
+            int hourOffset = 0;
+            int minuteOffset = 0;
+            DTSubString sub;
+
+            // Consume the +/- character that has already been read
+            sub = str.GetSubString();
+            if (sub.length != 1)
+            {
+                return false;
+            }
+            char offsetChar = sub[0];
+            if (offsetChar != '+' && offsetChar != '-')
+            {
+                return false;
+            }
+            str.ConsumeSubString(sub);
+
+            sub = str.GetSubString();
+            if (sub.type != DTSubStringType.Number)
+            {
+                return false;
+            }
+            int value = sub.value;
+            int length = sub.length;
+            if (length == 1 || length == 2)
+            {
+                // Parsing "+8" or "+08"
+                hourOffset = value;
+                str.ConsumeSubString(sub);
+                // See if we have minutes
+                sub = str.GetSubString();
+                if (sub.length == 1 && sub[0] == ':')
+                {
+                    // Parsing "+8:00" or "+08:00"
+                    str.ConsumeSubString(sub);
+                    sub = str.GetSubString();
+                    if (sub.type != DTSubStringType.Number || sub.length < 1 || sub.length > 2)
+                    {
+                        return false;
+                    }
+                    minuteOffset = sub.value;
+                    str.ConsumeSubString(sub);
+                }
+            }
+            else if (length == 3 || length == 4)
+            {
+                // Parsing "+800" or "+0800"
+                hourOffset = value / 100;
+                minuteOffset = value % 100;
+                str.ConsumeSubString(sub);
+            }
+            else
+            {
+                // Wrong number of digits
+                return false;
+            }
+            Debug.Assert(hourOffset >= 0 && hourOffset <= 99, "hourOffset >= 0 && hourOffset <= 99");
+            Debug.Assert(minuteOffset >= 0 && minuteOffset <= 99, "minuteOffset >= 0 && minuteOffset <= 99");
+            if (minuteOffset < 0 || minuteOffset >= 60)
+            {
+                return false;
+            }
+
+            result = new TimeSpan(hourOffset, minuteOffset, 0);
+            if (offsetChar == '-')
+            {
+                result = result.Negate();
+            }
+            return true;
+        }
+
+        // This is the helper function to handle timezone in string in the format like +/-0800
+        private static bool HandleTimeZone(ref __DTString str, ref DateTimeResult result)
+        {
+            if ((str.Index < str.Length - 1))
+            {
+                char nextCh = str.Value[str.Index];
+                // Skip whitespace, but don't update the index unless we find a time zone marker
+                int whitespaceCount = 0;
+                while (Char.IsWhiteSpace(nextCh) && str.Index + whitespaceCount < str.Length - 1)
+                {
+                    whitespaceCount++;
+                    nextCh = str.Value[str.Index + whitespaceCount];
+                }
+                if (nextCh == '+' || nextCh == '-')
+                {
+                    str.Index += whitespaceCount;
+                    if ((result.flags & ParseFlags.TimeZoneUsed) != 0)
+                    {
+                        // Should not have two timezone offsets.
+                        result.SetBadDateTimeFailure();
+                        return false;
+                    }
+                    result.flags |= ParseFlags.TimeZoneUsed;
+                    if (!ParseTimeZone(ref str, ref result.timeZoneOffset))
+                    {
+                        result.SetBadDateTimeFailure();
+                        return false;
+                    }
+                }
+            }
+            return true;
+        }
+
+        //
+        // This is the lexer. Check the character at the current index, and put the found token in dtok and
+        // some raw date/time information in raw.
+        //
+        private static Boolean Lex(DS dps, ref __DTString str, ref DateTimeToken dtok, ref DateTimeRawInfo raw, ref DateTimeResult result, ref DateTimeFormatInfo dtfi, DateTimeStyles styles)
+        {
+            TokenType tokenType;
+            int tokenValue;
+            int indexBeforeSeparator;
+            char charBeforeSeparator;
+
+            TokenType sep;
+            dtok.dtt = DTT.Unk;     // Assume the token is unkown.
+
+            str.GetRegularToken(out tokenType, out tokenValue, dtfi);
+
+#if _LOGGING
+            if (_tracingEnabled)
+            {
+                Trace($"Lex({Hex(str.Value)})\tpos:{str.Index}({Hex(str.m_current)}), {tokenType}, DS.{dps}");
+            }
+#endif // _LOGGING
+
+            // Look at the regular token.
+            switch (tokenType)
+            {
+                case TokenType.NumberToken:
+                case TokenType.YearNumberToken:
+                    if (raw.numCount == 3 || tokenValue == -1)
+                    {
+                        result.SetBadDateTimeFailure();
+                        LexTraceExit("0010", dps);
+                        return false;
+                    }
+                    //
+                    // This is a digit.
+                    //
+                    // If the previous parsing state is DS.T_NNt (like 12:01), and we got another number,
+                    // so we will have a terminal state DS.TX_NNN (like 12:01:02).
+                    // If the previous parsing state is DS.T_Nt (like 12:), and we got another number,
+                    // so we will have a terminal state DS.TX_NN (like 12:01).
+                    //
+                    // Look ahead to see if the following character is a decimal point or timezone offset.
+                    // This enables us to parse time in the forms of:
+                    //  "11:22:33.1234" or "11:22:33-08".
+                    if (dps == DS.T_NNt)
+                    {
+                        if ((str.Index < str.Length - 1))
+                        {
+                            char nextCh = str.Value[str.Index];
+                            if (nextCh == '.')
+                            {
+                                // While ParseFraction can fail, it just means that there were no digits after
+                                // the dot. In this case ParseFraction just removes the dot. This is actually
+                                // valid for cultures like Albanian, that join the time marker to the time with
+                                // with a dot: e.g. "9:03.MD"
+                                ParseFraction(ref str, out raw.fraction);
+                            }
+                        }
+                    }
+                    if (dps == DS.T_NNt || dps == DS.T_Nt)
+                    {
+                        if ((str.Index < str.Length - 1))
+                        {
+                            if (false == HandleTimeZone(ref str, ref result))
+                            {
+                                LexTraceExit("0020 (value like \"12:01\" or \"12:\" followed by a non-TZ number", dps);
+                                return false;
+                            }
+                        }
+                    }
+
+                    dtok.num = tokenValue;
+                    if (tokenType == TokenType.YearNumberToken)
+                    {
+                        if (raw.year == -1)
+                        {
+                            raw.year = tokenValue;
+                            //
+                            // If we have number which has 3 or more digits (like "001" or "0001"),
+                            // we assume this number is a year. Save the currnet raw.numCount in
+                            // raw.year.
+                            //
+                            switch (sep = str.GetSeparatorToken(dtfi, out indexBeforeSeparator, out charBeforeSeparator))
+                            {
+                                case TokenType.SEP_End:
+                                    dtok.dtt = DTT.YearEnd;
+                                    break;
+                                case TokenType.SEP_Am:
+                                case TokenType.SEP_Pm:
+                                    if (raw.timeMark == TM.NotSet)
+                                    {
+                                        raw.timeMark = (sep == TokenType.SEP_Am ? TM.AM : TM.PM);
+                                        dtok.dtt = DTT.YearSpace;
+                                    }
+                                    else
+                                    {
+                                        result.SetBadDateTimeFailure();
+                                        LexTraceExit("0030 (TM.AM/TM.PM Happened more than 1x)", dps);
+                                    }
+                                    break;
+                                case TokenType.SEP_Space:
+                                    dtok.dtt = DTT.YearSpace;
+                                    break;
+                                case TokenType.SEP_Date:
+                                    dtok.dtt = DTT.YearDateSep;
+                                    break;
+                                case TokenType.SEP_Time:
+                                    if (!raw.hasSameDateAndTimeSeparators)
+                                    {
+                                        result.SetBadDateTimeFailure();
+                                        LexTraceExit("0040 (Invalid separator after number)", dps);
+                                        return false;
+                                    }
+
+                                    // we have the date and time separators are same and getting a year number, then change the token to YearDateSep as
+                                    // we are sure we are not parsing time.
+                                    dtok.dtt = DTT.YearDateSep;
+                                    break;
+                                case TokenType.SEP_DateOrOffset:
+                                    // The separator is either a date separator or the start of a time zone offset. If the token will complete the date then
+                                    // process just the number and roll back the index so that the outer loop can attempt to parse the time zone offset.
+                                    if ((dateParsingStates[(int)dps][(int)DTT.YearDateSep] == DS.ERROR)
+                                        && (dateParsingStates[(int)dps][(int)DTT.YearSpace] > DS.ERROR))
+                                    {
+                                        str.Index = indexBeforeSeparator;
+                                        str.m_current = charBeforeSeparator;
+                                        dtok.dtt = DTT.YearSpace;
+                                    }
+                                    else
+                                    {
+                                        dtok.dtt = DTT.YearDateSep;
+                                    }
+                                    break;
+                                case TokenType.SEP_YearSuff:
+                                case TokenType.SEP_MonthSuff:
+                                case TokenType.SEP_DaySuff:
+                                    dtok.dtt = DTT.NumDatesuff;
+                                    dtok.suffix = sep;
+                                    break;
+                                case TokenType.SEP_HourSuff:
+                                case TokenType.SEP_MinuteSuff:
+                                case TokenType.SEP_SecondSuff:
+                                    dtok.dtt = DTT.NumTimesuff;
+                                    dtok.suffix = sep;
+                                    break;
+                                default:
+                                    // Invalid separator after number number.
+                                    result.SetBadDateTimeFailure();
+                                    LexTraceExit("0040 (Invalid separator after number)", dps);
+                                    return false;
+                            }
+                            //
+                            // Found the token already. Return now.
+                            //
+                            LexTraceExit("0050 (success)", dps);
+                            return true;
+                        }
+                        result.SetBadDateTimeFailure();
+                        LexTraceExit("0060", dps);
+                        return false;
+                    }
+                    switch (sep = str.GetSeparatorToken(dtfi, out indexBeforeSeparator, out charBeforeSeparator))
+                    {
+                        //
+                        // Note here we check if the numCount is less than three.
+                        // When we have more than three numbers, it will be caught as error in the state machine.
+                        //
+                        case TokenType.SEP_End:
+                            dtok.dtt = DTT.NumEnd;
+                            raw.AddNumber(dtok.num);
+                            break;
+                        case TokenType.SEP_Am:
+                        case TokenType.SEP_Pm:
+                            if (raw.timeMark == TM.NotSet)
+                            {
+                                raw.timeMark = (sep == TokenType.SEP_Am ? TM.AM : TM.PM);
+                                dtok.dtt = DTT.NumAmpm;
+                                // Fix AM/PM parsing case, e.g. "1/10 5 AM"
+                                if (dps == DS.D_NN)
+                                {
+                                    if (!ProcessTerminalState(DS.DX_NN, ref str, ref result, ref styles, ref raw, dtfi))
+                                    {
+                                        return false;
+                                    }
+                                }
+
+                                raw.AddNumber(dtok.num);
+                            }
+                            else
+                            {
+                                result.SetBadDateTimeFailure();
+                                break;
+                            }
+                            if (dps == DS.T_NNt || dps == DS.T_Nt)
+                            {
+                                if (false == HandleTimeZone(ref str, ref result))
+                                {
+                                    LexTraceExit("0070 (HandleTimeZone returned false)", dps);
+                                    return false;
+                                }
+                            }
+                            break;
+                        case TokenType.SEP_Space:
+                            dtok.dtt = DTT.NumSpace;
+                            raw.AddNumber(dtok.num);
+                            break;
+                        case TokenType.SEP_Date:
+                            dtok.dtt = DTT.NumDatesep;
+                            raw.AddNumber(dtok.num);
+                            break;
+                        case TokenType.SEP_DateOrOffset:
+                            // The separator is either a date separator or the start of a time zone offset. If the token will complete the date then
+                            // process just the number and roll back the index so that the outer loop can attempt to parse the time zone offset.
+                            if ((dateParsingStates[(int)dps][(int)DTT.NumDatesep] == DS.ERROR)
+                                && (dateParsingStates[(int)dps][(int)DTT.NumSpace] > DS.ERROR))
+                            {
+                                str.Index = indexBeforeSeparator;
+                                str.m_current = charBeforeSeparator;
+                                dtok.dtt = DTT.NumSpace;
+                            }
+                            else
+                            {
+                                dtok.dtt = DTT.NumDatesep;
+                            }
+                            raw.AddNumber(dtok.num);
+                            break;
+                        case TokenType.SEP_Time:
+                            if (raw.hasSameDateAndTimeSeparators &&
+                                (dps == DS.D_Y || dps == DS.D_YN || dps == DS.D_YNd || dps == DS.D_YM || dps == DS.D_YMd))
+                            {
+                                // we are parsing a date and we have the time separator same as date separator, so we mark the token as date separator
+                                dtok.dtt = DTT.NumDatesep;
+                                raw.AddNumber(dtok.num);
+                                break;
+                            }
+                            dtok.dtt = DTT.NumTimesep;
+                            raw.AddNumber(dtok.num);
+                            break;
+                        case TokenType.SEP_YearSuff:
+                            try
+                            {
+                                dtok.num = dtfi.Calendar.ToFourDigitYear(tokenValue);
+                            }
+                            catch (ArgumentOutOfRangeException)
+                            {
+                                result.SetBadDateTimeFailure();
+                                LexTraceExit("0075 (Calendar.ToFourDigitYear failed)", dps);
+                                return false;
+                            }
+                            dtok.dtt = DTT.NumDatesuff;
+                            dtok.suffix = sep;
+                            break;
+                        case TokenType.SEP_MonthSuff:
+                        case TokenType.SEP_DaySuff:
+                            dtok.dtt = DTT.NumDatesuff;
+                            dtok.suffix = sep;
+                            break;
+                        case TokenType.SEP_HourSuff:
+                        case TokenType.SEP_MinuteSuff:
+                        case TokenType.SEP_SecondSuff:
+                            dtok.dtt = DTT.NumTimesuff;
+                            dtok.suffix = sep;
+                            break;
+                        case TokenType.SEP_LocalTimeMark:
+                            dtok.dtt = DTT.NumLocalTimeMark;
+                            raw.AddNumber(dtok.num);
+                            break;
+                        default:
+                            // Invalid separator after number number.
+                            result.SetBadDateTimeFailure();
+                            LexTraceExit("0080", dps);
+                            return false;
+                    }
+                    break;
+                case TokenType.HebrewNumber:
+                    if (tokenValue >= 100)
+                    {
+                        // This is a year number
+                        if (raw.year == -1)
+                        {
+                            raw.year = tokenValue;
+                            //
+                            // If we have number which has 3 or more digits (like "001" or "0001"),
+                            // we assume this number is a year. Save the currnet raw.numCount in
+                            // raw.year.
+                            //
+                            switch (sep = str.GetSeparatorToken(dtfi, out indexBeforeSeparator, out charBeforeSeparator))
+                            {
+                                case TokenType.SEP_End:
+                                    dtok.dtt = DTT.YearEnd;
+                                    break;
+                                case TokenType.SEP_Space:
+                                    dtok.dtt = DTT.YearSpace;
+                                    break;
+                                case TokenType.SEP_DateOrOffset:
+                                    // The separator is either a date separator or the start of a time zone offset. If the token will complete the date then
+                                    // process just the number and roll back the index so that the outer loop can attempt to parse the time zone offset.
+                                    if (dateParsingStates[(int)dps][(int)DTT.YearSpace] > DS.ERROR)
+                                    {
+                                        str.Index = indexBeforeSeparator;
+                                        str.m_current = charBeforeSeparator;
+                                        dtok.dtt = DTT.YearSpace;
+                                        break;
+                                    }
+                                    goto default;
+                                default:
+                                    // Invalid separator after number number.
+                                    result.SetBadDateTimeFailure();
+                                    LexTraceExit("0090", dps);
+                                    return false;
+                            }
+                        }
+                        else
+                        {
+                            // Invalid separator after number number.
+                            result.SetBadDateTimeFailure();
+                            LexTraceExit("0100", dps);
+                            return false;
+                        }
+                    }
+                    else
+                    {
+                        // This is a day number
+                        dtok.num = tokenValue;
+                        raw.AddNumber(dtok.num);
+
+                        switch (sep = str.GetSeparatorToken(dtfi, out indexBeforeSeparator, out charBeforeSeparator))
+                        {
+                            //
+                            // Note here we check if the numCount is less than three.
+                            // When we have more than three numbers, it will be caught as error in the state machine.
+                            //
+                            case TokenType.SEP_End:
+                                dtok.dtt = DTT.NumEnd;
+                                break;
+                            case TokenType.SEP_Space:
+                            case TokenType.SEP_Date:
+                                dtok.dtt = DTT.NumDatesep;
+                                break;
+                            case TokenType.SEP_DateOrOffset:
+                                // The separator is either a date separator or the start of a time zone offset. If the token will complete the date then
+                                // process just the number and roll back the index so that the outer loop can attempt to parse the time zone offset.
+                                if ((dateParsingStates[(int)dps][(int)DTT.NumDatesep] == DS.ERROR)
+                                    && (dateParsingStates[(int)dps][(int)DTT.NumSpace] > DS.ERROR))
+                                {
+                                    str.Index = indexBeforeSeparator;
+                                    str.m_current = charBeforeSeparator;
+                                    dtok.dtt = DTT.NumSpace;
+                                }
+                                else
+                                {
+                                    dtok.dtt = DTT.NumDatesep;
+                                }
+                                break;
+                            default:
+                                // Invalid separator after number number.
+                                result.SetBadDateTimeFailure();
+                                LexTraceExit("0110", dps);
+                                return false;
+                        }
+                    }
+                    break;
+                case TokenType.DayOfWeekToken:
+                    if (raw.dayOfWeek == -1)
+                    {
+                        //
+                        // This is a day of week name.
+                        //
+                        raw.dayOfWeek = tokenValue;
+                        dtok.dtt = DTT.DayOfWeek;
+                    }
+                    else
+                    {
+                        result.SetBadDateTimeFailure();
+                        LexTraceExit("0120 (DayOfWeek seen more than 1x)", dps);
+                        return false;
+                    }
+                    break;
+                case TokenType.MonthToken:
+                    if (raw.month == -1)
+                    {
+                        //
+                        // This is a month name
+                        //
+                        switch (sep = str.GetSeparatorToken(dtfi, out indexBeforeSeparator, out charBeforeSeparator))
+                        {
+                            case TokenType.SEP_End:
+                                dtok.dtt = DTT.MonthEnd;
+                                break;
+                            case TokenType.SEP_Space:
+                                dtok.dtt = DTT.MonthSpace;
+                                break;
+                            case TokenType.SEP_Date:
+                                dtok.dtt = DTT.MonthDatesep;
+                                break;
+                            case TokenType.SEP_Time:
+                                if (!raw.hasSameDateAndTimeSeparators)
+                                {
+                                    result.SetBadDateTimeFailure();
+                                    LexTraceExit("0130 (Invalid separator after month name)", dps);
+                                    return false;
+                                }
+
+                                // we have the date and time separators are same and getting a Month name, then change the token to MonthDatesep as
+                                // we are sure we are not parsing time.
+                                dtok.dtt = DTT.MonthDatesep;
+                                break;
+                            case TokenType.SEP_DateOrOffset:
+                                // The separator is either a date separator or the start of a time zone offset. If the token will complete the date then
+                                // process just the number and roll back the index so that the outer loop can attempt to parse the time zone offset.
+                                if ((dateParsingStates[(int)dps][(int)DTT.MonthDatesep] == DS.ERROR)
+                                    && (dateParsingStates[(int)dps][(int)DTT.MonthSpace] > DS.ERROR))
+                                {
+                                    str.Index = indexBeforeSeparator;
+                                    str.m_current = charBeforeSeparator;
+                                    dtok.dtt = DTT.MonthSpace;
+                                }
+                                else
+                                {
+                                    dtok.dtt = DTT.MonthDatesep;
+                                }
+                                break;
+                            default:
+                                //Invalid separator after month name
+                                result.SetBadDateTimeFailure();
+                                LexTraceExit("0130 (Invalid separator after month name)", dps);
+                                return false;
+                        }
+                        raw.month = tokenValue;
+                    }
+                    else
+                    {
+                        result.SetBadDateTimeFailure();
+                        LexTraceExit("0140 (MonthToken seen more than 1x)", dps);
+                        return false;
+                    }
+                    break;
+                case TokenType.EraToken:
+                    if (result.era != -1)
+                    {
+                        result.era = tokenValue;
+                        dtok.dtt = DTT.Era;
+                    }
+                    else
+                    {
+                        result.SetBadDateTimeFailure();
+                        LexTraceExit("0150 (EraToken seen when result.era already set)", dps);
+                        return false;
+                    }
+                    break;
+                case TokenType.JapaneseEraToken:
+                    // Special case for Japanese.  We allow Japanese era name to be used even if the calendar is not Japanese Calendar.
+                    result.calendar = JapaneseCalendar.GetDefaultInstance();
+                    dtfi = DateTimeFormatInfo.GetJapaneseCalendarDTFI();
+                    if (result.era != -1)
+                    {
+                        result.era = tokenValue;
+                        dtok.dtt = DTT.Era;
+                    }
+                    else
+                    {
+                        result.SetBadDateTimeFailure();
+                        LexTraceExit("0160 (JapaneseEraToken seen when result.era already set)", dps);
+                        return false;
+                    }
+                    break;
+                case TokenType.TEraToken:
+                    result.calendar = TaiwanCalendar.GetDefaultInstance();
+                    dtfi = DateTimeFormatInfo.GetTaiwanCalendarDTFI();
+                    if (result.era != -1)
+                    {
+                        result.era = tokenValue;
+                        dtok.dtt = DTT.Era;
+                    }
+                    else
+                    {
+                        result.SetBadDateTimeFailure();
+                        LexTraceExit("0170 (TEraToken seen when result.era already set)", dps);
+                        return false;
+                    }
+                    break;
+                case TokenType.TimeZoneToken:
+                    //
+                    // This is a timezone designator
+                    //
+                    // NOTENOTE : for now, we only support "GMT" and "Z" (for Zulu time).
+                    //
+                    if ((result.flags & ParseFlags.TimeZoneUsed) != 0)
+                    {
+                        // Should not have two timezone offsets.
+                        result.SetBadDateTimeFailure();
+                        LexTraceExit("0180 (seen GMT or Z more than 1x)", dps);
+                        return false;
+                    }
+                    dtok.dtt = DTT.TimeZone;
+                    result.flags |= ParseFlags.TimeZoneUsed;
+                    result.timeZoneOffset = new TimeSpan(0);
+                    result.flags |= ParseFlags.TimeZoneUtc;
+                    break;
+                case TokenType.EndOfString:
+                    dtok.dtt = DTT.End;
+                    break;
+                case TokenType.DateWordToken:
+                case TokenType.IgnorableSymbol:
+                    // Date words and ignorable symbols can just be skipped over
+                    break;
+                case TokenType.Am:
+                case TokenType.Pm:
+                    if (raw.timeMark == TM.NotSet)
+                    {
+                        raw.timeMark = (TM)tokenValue;
+                    }
+                    else
+                    {
+                        result.SetBadDateTimeFailure();
+                        LexTraceExit("0190 (AM/PM timeMark already set)", dps);
+                        return false;
+                    }
+                    break;
+                case TokenType.UnknownToken:
+                    if (Char.IsLetter(str.m_current))
+                    {
+                        result.SetFailure(ParseFailureKind.FormatWithOriginalDateTimeAndParameter, nameof(SR.Format_UnknownDateTimeWord), str.Index);
+                        LexTraceExit("0200", dps);
+                        return (false);
+                    }
+
+                    if ((str.m_current == '-' || str.m_current == '+') && ((result.flags & ParseFlags.TimeZoneUsed) == 0))
+                    {
+                        Int32 originalIndex = str.Index;
+                        if (ParseTimeZone(ref str, ref result.timeZoneOffset))
+                        {
+                            result.flags |= ParseFlags.TimeZoneUsed;
+                            LexTraceExit("0220 (success)", dps);
+                            return true;
+                        }
+                        else
+                        {
+                            // Time zone parse attempt failed. Fall through to punctuation handling.
+                            str.Index = originalIndex;
+                        }
+                    }
+
+                    // Visual Basic implements string to date conversions on top of DateTime.Parse:
+                    //   CDate("#10/10/95#")
+                    //
+                    if (VerifyValidPunctuation(ref str))
+                    {
+                        LexTraceExit("0230 (success)", dps);
+                        return true;
+                    }
+
+                    result.SetBadDateTimeFailure();
+                    LexTraceExit("0240", dps);
+                    return false;
+            }
+
+            LexTraceExit("0250 (success)", dps);
+            return true;
+        }
+
+        private static Boolean VerifyValidPunctuation(ref __DTString str)
+        {
+            // Compatability Behavior. Allow trailing nulls and surrounding hashes
+            Char ch = str.Value[str.Index];
+            if (ch == '#')
+            {
+                bool foundStart = false;
+                bool foundEnd = false;
+                for (int i = 0; i < str.Length; i++)
+                {
+                    ch = str.Value[i];
+                    if (ch == '#')
+                    {
+                        if (foundStart)
+                        {
+                            if (foundEnd)
+                            {
+                                // Having more than two hashes is invalid
+                                return false;
+                            }
+                            else
+                            {
+                                foundEnd = true;
+                            }
+                        }
+                        else
+                        {
+                            foundStart = true;
+                        }
+                    }
+                    else if (ch == '\0')
+                    {
+                        // Allow nulls only at the end
+                        if (!foundEnd)
+                        {
+                            return false;
+                        }
+                    }
+                    else if ((!Char.IsWhiteSpace(ch)))
+                    {
+                        // Anything other than whitespace outside hashes is invalid
+                        if (!foundStart || foundEnd)
+                        {
+                            return false;
+                        }
+                    }
+                }
+                if (!foundEnd)
+                {
+                    // The has was un-paired
+                    return false;
+                }
+                // Valid Hash usage: eat the hash and continue.
+                str.GetNext();
+                return true;
+            }
+            else if (ch == '\0')
+            {
+                for (int i = str.Index; i < str.Length; i++)
+                {
+                    if (str.Value[i] != '\0')
+                    {
+                        // Nulls are only valid if they are the only trailing character
+                        return false;
+                    }
+                }
+                // Move to the end of the string
+                str.Index = str.Length;
+                return true;
+            }
+            return false;
+        }
+
+        private const int ORDER_YMD = 0;     // The order of date is Year/Month/Day.
+        private const int ORDER_MDY = 1;     // The order of date is Month/Day/Year.
+        private const int ORDER_DMY = 2;     // The order of date is Day/Month/Year.
+        private const int ORDER_YDM = 3;     // The order of date is Year/Day/Month
+        private const int ORDER_YM = 4;     // Year/Month order.
+        private const int ORDER_MY = 5;     // Month/Year order.
+        private const int ORDER_MD = 6;     // Month/Day order.
+        private const int ORDER_DM = 7;     // Day/Month order.
+
+        //
+        // Decide the year/month/day order from the datePattern.
+        //
+        // Return 0 for YMD, 1 for MDY, 2 for DMY, otherwise -1.
+        //
+        private static Boolean GetYearMonthDayOrder(String datePattern, DateTimeFormatInfo dtfi, out int order)
+        {
+            int yearOrder = -1;
+            int monthOrder = -1;
+            int dayOrder = -1;
+            int orderCount = 0;
+
+            bool inQuote = false;
+
+            for (int i = 0; i < datePattern.Length && orderCount < 3; i++)
+            {
+                char ch = datePattern[i];
+                if (ch == '\\' || ch == '%')
+                {
+                    i++;
+                    continue;  // Skip next character that is escaped by this backslash
+                }
+
+                if (ch == '\'' || ch == '"')
+                {
+                    inQuote = !inQuote;
+                }
+
+                if (!inQuote)
+                {
+                    if (ch == 'y')
+                    {
+                        yearOrder = orderCount++;
+
+                        //
+                        // Skip all year pattern charaters.
+                        //
+                        for (; i + 1 < datePattern.Length && datePattern[i + 1] == 'y'; i++)
+                        {
+                            // Do nothing here.
+                        }
+                    }
+                    else if (ch == 'M')
+                    {
+                        monthOrder = orderCount++;
+                        //
+                        // Skip all month pattern characters.
+                        //
+                        for (; i + 1 < datePattern.Length && datePattern[i + 1] == 'M'; i++)
+                        {
+                            // Do nothing here.
+                        }
+                    }
+                    else if (ch == 'd')
+                    {
+                        int patternCount = 1;
+                        //
+                        // Skip all day pattern characters.
+                        //
+                        for (; i + 1 < datePattern.Length && datePattern[i + 1] == 'd'; i++)
+                        {
+                            patternCount++;
+                        }
+                        //
+                        // Make sure this is not "ddd" or "dddd", which means day of week.
+                        //
+                        if (patternCount <= 2)
+                        {
+                            dayOrder = orderCount++;
+                        }
+                    }
+                }
+            }
+
+            if (yearOrder == 0 && monthOrder == 1 && dayOrder == 2)
+            {
+                order = ORDER_YMD;
+                return true;
+            }
+            if (monthOrder == 0 && dayOrder == 1 && yearOrder == 2)
+            {
+                order = ORDER_MDY;
+                return true;
+            }
+            if (dayOrder == 0 && monthOrder == 1 && yearOrder == 2)
+            {
+                order = ORDER_DMY;
+                return true;
+            }
+            if (yearOrder == 0 && dayOrder == 1 && monthOrder == 2)
+            {
+                order = ORDER_YDM;
+                return true;
+            }
+            order = -1;
+            return false;
+        }
+
+        //
+        // Decide the year/month order from the pattern.
+        //
+        // Return 0 for YM, 1 for MY, otherwise -1.
+        //
+        private static Boolean GetYearMonthOrder(String pattern, DateTimeFormatInfo dtfi, out int order)
+        {
+            int yearOrder = -1;
+            int monthOrder = -1;
+            int orderCount = 0;
+
+            bool inQuote = false;
+            for (int i = 0; i < pattern.Length && orderCount < 2; i++)
+            {
+                char ch = pattern[i];
+                if (ch == '\\' || ch == '%')
+                {
+                    i++;
+                    continue;  // Skip next character that is escaped by this backslash
+                }
+
+                if (ch == '\'' || ch == '"')
+                {
+                    inQuote = !inQuote;
+                }
+
+                if (!inQuote)
+                {
+                    if (ch == 'y')
+                    {
+                        yearOrder = orderCount++;
+
+                        //
+                        // Skip all year pattern charaters.
+                        //
+                        for (; i + 1 < pattern.Length && pattern[i + 1] == 'y'; i++)
+                        {
+                        }
+                    }
+                    else if (ch == 'M')
+                    {
+                        monthOrder = orderCount++;
+                        //
+                        // Skip all month pattern characters.
+                        //
+                        for (; i + 1 < pattern.Length && pattern[i + 1] == 'M'; i++)
+                        {
+                        }
+                    }
+                }
+            }
+
+            if (yearOrder == 0 && monthOrder == 1)
+            {
+                order = ORDER_YM;
+                return true;
+            }
+            if (monthOrder == 0 && yearOrder == 1)
+            {
+                order = ORDER_MY;
+                return true;
+            }
+            order = -1;
+            return false;
+        }
+
+        //
+        // Decide the month/day order from the pattern.
+        //
+        // Return 0 for MD, 1 for DM, otherwise -1.
+        //
+        private static Boolean GetMonthDayOrder(String pattern, DateTimeFormatInfo dtfi, out int order)
+        {
+            int monthOrder = -1;
+            int dayOrder = -1;
+            int orderCount = 0;
+
+            bool inQuote = false;
+            for (int i = 0; i < pattern.Length && orderCount < 2; i++)
+            {
+                char ch = pattern[i];
+                if (ch == '\\' || ch == '%')
+                {
+                    i++;
+                    continue;  // Skip next character that is escaped by this backslash
+                }
+
+                if (ch == '\'' || ch == '"')
+                {
+                    inQuote = !inQuote;
+                }
+
+                if (!inQuote)
+                {
+                    if (ch == 'd')
+                    {
+                        int patternCount = 1;
+                        //
+                        // Skip all day pattern charaters.
+                        //
+                        for (; i + 1 < pattern.Length && pattern[i + 1] == 'd'; i++)
+                        {
+                            patternCount++;
+                        }
+
+                        //
+                        // Make sure this is not "ddd" or "dddd", which means day of week.
+                        //
+                        if (patternCount <= 2)
+                        {
+                            dayOrder = orderCount++;
+                        }
+                    }
+                    else if (ch == 'M')
+                    {
+                        monthOrder = orderCount++;
+                        //
+                        // Skip all month pattern characters.
+                        //
+                        for (; i + 1 < pattern.Length && pattern[i + 1] == 'M'; i++)
+                        {
+                        }
+                    }
+                }
+            }
+
+            if (monthOrder == 0 && dayOrder == 1)
+            {
+                order = ORDER_MD;
+                return true;
+            }
+            if (dayOrder == 0 && monthOrder == 1)
+            {
+                order = ORDER_DM;
+                return true;
+            }
+            order = -1;
+            return false;
+        }
+
+        //
+        // Adjust the two-digit year if necessary.
+        //
+        private static bool TryAdjustYear(ref DateTimeResult result, int year, out int adjustedYear)
+        {
+            if (year < 100)
+            {
+                try
+                {
+                    // the Calendar classes need some real work.  Many of the calendars that throw
+                    // don't implement a fast/non-allocating (and non-throwing) IsValid{Year|Day|Month} method.
+                    // we are making a targeted try/catch fix in the in-place release but will revisit this code
+                    // in the next side-by-side release.
+                    year = result.calendar.ToFourDigitYear(year);
+                }
+                catch (ArgumentOutOfRangeException)
+                {
+                    adjustedYear = -1;
+                    return false;
+                }
+            }
+            adjustedYear = year;
+            return true;
+        }
+
+        private static bool SetDateYMD(ref DateTimeResult result, int year, int month, int day)
+        {
+            // Note, longer term these checks should be done at the end of the parse. This current
+            // way of checking creates order dependence with parsing the era name.
+            if (result.calendar.IsValidDay(year, month, day, result.era))
+            {
+                result.SetDate(year, month, day);                           // YMD
+                return (true);
+            }
+            return (false);
+        }
+
+        private static bool SetDateMDY(ref DateTimeResult result, int month, int day, int year)
+        {
+            return (SetDateYMD(ref result, year, month, day));
+        }
+
+        private static bool SetDateDMY(ref DateTimeResult result, int day, int month, int year)
+        {
+            return (SetDateYMD(ref result, year, month, day));
+        }
+
+        private static bool SetDateYDM(ref DateTimeResult result, int year, int day, int month)
+        {
+            return (SetDateYMD(ref result, year, month, day));
+        }
+
+        private static void GetDefaultYear(ref DateTimeResult result, ref DateTimeStyles styles)
+        {
+            result.Year = result.calendar.GetYear(GetDateTimeNow(ref result, ref styles));
+            result.flags |= ParseFlags.YearDefault;
+        }
+
+        // Processing teriminal case: DS.DX_NN
+        private static Boolean GetDayOfNN(ref DateTimeResult result, ref DateTimeStyles styles, ref DateTimeRawInfo raw, DateTimeFormatInfo dtfi)
+        {
+            if ((result.flags & ParseFlags.HaveDate) != 0)
+            {
+                // Multiple dates in the input string
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+
+            int n1 = raw.GetNumber(0);
+            int n2 = raw.GetNumber(1);
+
+            GetDefaultYear(ref result, ref styles);
+
+            int order;
+            if (!GetMonthDayOrder(dtfi.MonthDayPattern, dtfi, out order))
+            {
+                result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_BadDatePattern), dtfi.MonthDayPattern);
+                return false;
+            }
+
+            if (order == ORDER_MD)
+            {
+                if (SetDateYMD(ref result, result.Year, n1, n2))                           // MD
+                {
+                    result.flags |= ParseFlags.HaveDate;
+                    return true;
+                }
+            }
+            else
+            {
+                // ORDER_DM
+                if (SetDateYMD(ref result, result.Year, n2, n1))                           // DM
+                {
+                    result.flags |= ParseFlags.HaveDate;
+                    return true;
+                }
+            }
+            result.SetBadDateTimeFailure();
+            return false;
+        }
+
+        // Processing teriminal case: DS.DX_NNN
+        private static Boolean GetDayOfNNN(ref DateTimeResult result, ref DateTimeRawInfo raw, DateTimeFormatInfo dtfi)
+        {
+            if ((result.flags & ParseFlags.HaveDate) != 0)
+            {
+                // Multiple dates in the input string
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+
+            int n1 = raw.GetNumber(0);
+            int n2 = raw.GetNumber(1); ;
+            int n3 = raw.GetNumber(2);
+
+            int order;
+            if (!GetYearMonthDayOrder(dtfi.ShortDatePattern, dtfi, out order))
+            {
+                result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_BadDatePattern), dtfi.ShortDatePattern);
+                return false;
+            }
+            int year;
+
+            if (order == ORDER_YMD)
+            {
+                if (TryAdjustYear(ref result, n1, out year) && SetDateYMD(ref result, year, n2, n3))         // YMD
+                {
+                    result.flags |= ParseFlags.HaveDate;
+                    return true;
+                }
+            }
+            else if (order == ORDER_MDY)
+            {
+                if (TryAdjustYear(ref result, n3, out year) && SetDateMDY(ref result, n1, n2, year))         // MDY
+                {
+                    result.flags |= ParseFlags.HaveDate;
+                    return true;
+                }
+            }
+            else if (order == ORDER_DMY)
+            {
+                if (TryAdjustYear(ref result, n3, out year) && SetDateDMY(ref result, n1, n2, year))         // DMY
+                {
+                    result.flags |= ParseFlags.HaveDate;
+                    return true;
+                }
+            }
+            else if (order == ORDER_YDM)
+            {
+                if (TryAdjustYear(ref result, n1, out year) && SetDateYDM(ref result, year, n2, n3))         // YDM
+                {
+                    result.flags |= ParseFlags.HaveDate;
+                    return true;
+                }
+            }
+            result.SetBadDateTimeFailure();
+            return false;
+        }
+
+        private static Boolean GetDayOfMN(ref DateTimeResult result, ref DateTimeStyles styles, ref DateTimeRawInfo raw, DateTimeFormatInfo dtfi)
+        {
+            if ((result.flags & ParseFlags.HaveDate) != 0)
+            {
+                // Multiple dates in the input string
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+
+            // The interpretation is based on the MonthDayPattern and YearMonthPattern
+            //
+            //    MonthDayPattern   YearMonthPattern  Interpretation
+            //    ---------------   ----------------  ---------------
+            //    MMMM dd           MMMM yyyy         Day
+            //    MMMM dd           yyyy MMMM         Day
+            //    dd MMMM           MMMM yyyy         Year
+            //    dd MMMM           yyyy MMMM         Day
+            //
+            // In the first and last cases, it could be either or neither, but a day is a better default interpretation
+            // than a 2 digit year.
+
+            int monthDayOrder;
+            if (!GetMonthDayOrder(dtfi.MonthDayPattern, dtfi, out monthDayOrder))
+            {
+                result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_BadDatePattern), dtfi.MonthDayPattern);
+                return false;
+            }
+            if (monthDayOrder == ORDER_DM)
+            {
+                int yearMonthOrder;
+                if (!GetYearMonthOrder(dtfi.YearMonthPattern, dtfi, out yearMonthOrder))
+                {
+                    result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_BadDatePattern), dtfi.YearMonthPattern);
+                    return false;
+                }
+                if (yearMonthOrder == ORDER_MY)
+                {
+                    int year;
+                    if (!TryAdjustYear(ref result, raw.GetNumber(0), out year) || !SetDateYMD(ref result, year, raw.month, 1))
+                    {
+                        result.SetBadDateTimeFailure();
+                        return false;
+                    }
+                    return true;
+                }
+            }
+
+            GetDefaultYear(ref result, ref styles);
+            if (!SetDateYMD(ref result, result.Year, raw.month, raw.GetNumber(0)))
+            {
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+            return true;
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //  Actions:
+        //  Deal with the terminal state for Hebrew Month/Day pattern
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        private static Boolean GetHebrewDayOfNM(ref DateTimeResult result, ref DateTimeRawInfo raw, DateTimeFormatInfo dtfi)
+        {
+            int monthDayOrder;
+            if (!GetMonthDayOrder(dtfi.MonthDayPattern, dtfi, out monthDayOrder))
+            {
+                result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_BadDatePattern), dtfi.MonthDayPattern);
+                return false;
+            }
+            result.Month = raw.month;
+            if (monthDayOrder == ORDER_DM || monthDayOrder == ORDER_MD)
+            {
+                if (result.calendar.IsValidDay(result.Year, result.Month, raw.GetNumber(0), result.era))
+                {
+                    result.Day = raw.GetNumber(0);
+                    return true;
+                }
+            }
+            result.SetBadDateTimeFailure();
+            return false;
+        }
+
+        private static Boolean GetDayOfNM(ref DateTimeResult result, ref DateTimeStyles styles, ref DateTimeRawInfo raw, DateTimeFormatInfo dtfi)
+        {
+            if ((result.flags & ParseFlags.HaveDate) != 0)
+            {
+                // Multiple dates in the input string
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+
+            // The interpretation is based on the MonthDayPattern and YearMonthPattern
+            //
+            //    MonthDayPattern   YearMonthPattern  Interpretation
+            //    ---------------   ----------------  ---------------
+            //    MMMM dd           MMMM yyyy         Day
+            //    MMMM dd           yyyy MMMM         Year
+            //    dd MMMM           MMMM yyyy         Day
+            //    dd MMMM           yyyy MMMM         Day
+            //
+            // In the first and last cases, it could be either or neither, but a day is a better default interpretation
+            // than a 2 digit year.
+
+            int monthDayOrder;
+            if (!GetMonthDayOrder(dtfi.MonthDayPattern, dtfi, out monthDayOrder))
+            {
+                result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_BadDatePattern), dtfi.MonthDayPattern);
+                return false;
+            }
+            if (monthDayOrder == ORDER_MD)
+            {
+                int yearMonthOrder;
+                if (!GetYearMonthOrder(dtfi.YearMonthPattern, dtfi, out yearMonthOrder))
+                {
+                    result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_BadDatePattern), dtfi.YearMonthPattern);
+                    return false;
+                }
+                if (yearMonthOrder == ORDER_YM)
+                {
+                    int year;
+                    if (!TryAdjustYear(ref result, raw.GetNumber(0), out year) || !SetDateYMD(ref result, year, raw.month, 1))
+                    {
+                        result.SetBadDateTimeFailure();
+                        return false;
+                    }
+                    return true;
+                }
+            }
+
+            GetDefaultYear(ref result, ref styles);
+            if (!SetDateYMD(ref result, result.Year, raw.month, raw.GetNumber(0)))
+            {
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+            return true;
+        }
+
+        private static Boolean GetDayOfMNN(ref DateTimeResult result, ref DateTimeRawInfo raw, DateTimeFormatInfo dtfi)
+        {
+            if ((result.flags & ParseFlags.HaveDate) != 0)
+            {
+                // Multiple dates in the input string
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+
+            int n1 = raw.GetNumber(0);
+            int n2 = raw.GetNumber(1);
+
+            int order;
+            if (!GetYearMonthDayOrder(dtfi.ShortDatePattern, dtfi, out order))
+            {
+                result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_BadDatePattern), dtfi.ShortDatePattern);
+                return false;
+            }
+            int year;
+
+            if (order == ORDER_MDY)
+            {
+                if (TryAdjustYear(ref result, n2, out year) && result.calendar.IsValidDay(year, raw.month, n1, result.era))
+                {
+                    result.SetDate(year, raw.month, n1);      // MDY
+                    result.flags |= ParseFlags.HaveDate;
+                    return true;
+                }
+                else if (TryAdjustYear(ref result, n1, out year) && result.calendar.IsValidDay(year, raw.month, n2, result.era))
+                {
+                    result.SetDate(year, raw.month, n2);      // YMD
+                    result.flags |= ParseFlags.HaveDate;
+                    return true;
+                }
+            }
+            else if (order == ORDER_YMD)
+            {
+                if (TryAdjustYear(ref result, n1, out year) && result.calendar.IsValidDay(year, raw.month, n2, result.era))
+                {
+                    result.SetDate(year, raw.month, n2);      // YMD
+                    result.flags |= ParseFlags.HaveDate;
+                    return true;
+                }
+                else if (TryAdjustYear(ref result, n2, out year) && result.calendar.IsValidDay(year, raw.month, n1, result.era))
+                {
+                    result.SetDate(year, raw.month, n1);      // DMY
+                    result.flags |= ParseFlags.HaveDate;
+                    return true;
+                }
+            }
+            else if (order == ORDER_DMY)
+            {
+                if (TryAdjustYear(ref result, n2, out year) && result.calendar.IsValidDay(year, raw.month, n1, result.era))
+                {
+                    result.SetDate(year, raw.month, n1);      // DMY
+                    result.flags |= ParseFlags.HaveDate;
+                    return true;
+                }
+                else if (TryAdjustYear(ref result, n1, out year) && result.calendar.IsValidDay(year, raw.month, n2, result.era))
+                {
+                    result.SetDate(year, raw.month, n2);      // YMD
+                    result.flags |= ParseFlags.HaveDate;
+                    return true;
+                }
+            }
+
+            result.SetBadDateTimeFailure();
+            return false;
+        }
+
+        private static Boolean GetDayOfYNN(ref DateTimeResult result, ref DateTimeRawInfo raw, DateTimeFormatInfo dtfi)
+        {
+            if ((result.flags & ParseFlags.HaveDate) != 0)
+            {
+                // Multiple dates in the input string
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+
+            int n1 = raw.GetNumber(0);
+            int n2 = raw.GetNumber(1);
+            String pattern = dtfi.ShortDatePattern;
+
+            // For compatibility, don't throw if we can't determine the order, but default to YMD instead
+            int order;
+            if (GetYearMonthDayOrder(pattern, dtfi, out order) && order == ORDER_YDM)
+            {
+                if (SetDateYMD(ref result, raw.year, n2, n1))
+                {
+                    result.flags |= ParseFlags.HaveDate;
+                    return true; // Year + DM
+                }
+            }
+            else
+            {
+                if (SetDateYMD(ref result, raw.year, n1, n2))
+                {
+                    result.flags |= ParseFlags.HaveDate;
+                    return true; // Year + MD
+                }
+            }
+            result.SetBadDateTimeFailure();
+            return false;
+        }
+
+        private static Boolean GetDayOfNNY(ref DateTimeResult result, ref DateTimeRawInfo raw, DateTimeFormatInfo dtfi)
+        {
+            if ((result.flags & ParseFlags.HaveDate) != 0)
+            {
+                // Multiple dates in the input string
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+
+            int n1 = raw.GetNumber(0);
+            int n2 = raw.GetNumber(1);
+
+            int order;
+            if (!GetYearMonthDayOrder(dtfi.ShortDatePattern, dtfi, out order))
+            {
+                result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_BadDatePattern), dtfi.ShortDatePattern);
+                return false;
+            }
+
+            if (order == ORDER_MDY || order == ORDER_YMD)
+            {
+                if (SetDateYMD(ref result, raw.year, n1, n2))
+                {
+                    result.flags |= ParseFlags.HaveDate;
+                    return true; // MD + Year
+                }
+            }
+            else
+            {
+                if (SetDateYMD(ref result, raw.year, n2, n1))
+                {
+                    result.flags |= ParseFlags.HaveDate;
+                    return true; // DM + Year
+                }
+            }
+            result.SetBadDateTimeFailure();
+            return false;
+        }
+
+
+        private static Boolean GetDayOfYMN(ref DateTimeResult result, ref DateTimeRawInfo raw)
+        {
+            if ((result.flags & ParseFlags.HaveDate) != 0)
+            {
+                // Multiple dates in the input string
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+
+            if (SetDateYMD(ref result, raw.year, raw.month, raw.GetNumber(0)))
+            {
+                result.flags |= ParseFlags.HaveDate;
+                return true;
+            }
+            result.SetBadDateTimeFailure();
+            return false;
+        }
+
+        private static Boolean GetDayOfYN(ref DateTimeResult result, ref DateTimeRawInfo raw)
+        {
+            if ((result.flags & ParseFlags.HaveDate) != 0)
+            {
+                // Multiple dates in the input string
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+
+            if (SetDateYMD(ref result, raw.year, raw.GetNumber(0), 1))
+            {
+                result.flags |= ParseFlags.HaveDate;
+                return true;
+            }
+            result.SetBadDateTimeFailure();
+            return false;
+        }
+
+        private static Boolean GetDayOfYM(ref DateTimeResult result, ref DateTimeRawInfo raw)
+        {
+            if ((result.flags & ParseFlags.HaveDate) != 0)
+            {
+                // Multiple dates in the input string
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+
+            if (SetDateYMD(ref result, raw.year, raw.month, 1))
+            {
+                result.flags |= ParseFlags.HaveDate;
+                return true;
+            }
+            result.SetBadDateTimeFailure();
+            return false;
+        }
+
+        private static void AdjustTimeMark(DateTimeFormatInfo dtfi, ref DateTimeRawInfo raw)
+        {
+            // Specail case for culture which uses AM as empty string.
+            // E.g. af-ZA (0x0436)
+            //    S1159                  \x0000
+            //    S2359                  nm
+            // In this case, if we are parsing a string like "2005/09/14 12:23", we will assume this is in AM.
+
+            if (raw.timeMark == TM.NotSet)
+            {
+                if (dtfi.AMDesignator != null && dtfi.PMDesignator != null)
+                {
+                    if (dtfi.AMDesignator.Length == 0 && dtfi.PMDesignator.Length != 0)
+                    {
+                        raw.timeMark = TM.AM;
+                    }
+                    if (dtfi.PMDesignator.Length == 0 && dtfi.AMDesignator.Length != 0)
+                    {
+                        raw.timeMark = TM.PM;
+                    }
+                }
+            }
+        }
+
+        //
+        // Adjust hour according to the time mark.
+        //
+        private static Boolean AdjustHour(ref int hour, TM timeMark)
+        {
+            if (timeMark != TM.NotSet)
+            {
+                if (timeMark == TM.AM)
+                {
+                    if (hour < 0 || hour > 12)
+                    {
+                        return false;
+                    }
+                    hour = (hour == 12) ? 0 : hour;
+                }
+                else
+                {
+                    if (hour < 0 || hour > 23)
+                    {
+                        return false;
+                    }
+                    if (hour < 12)
+                    {
+                        hour += 12;
+                    }
+                }
+            }
+            return true;
+        }
+
+        private static Boolean GetTimeOfN(ref DateTimeResult result, ref DateTimeRawInfo raw)
+        {
+            if ((result.flags & ParseFlags.HaveTime) != 0)
+            {
+                // Multiple times in the input string
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+            //
+            // In this case, we need a time mark. Check if so.
+            //
+            if (raw.timeMark == TM.NotSet)
+            {
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+            result.Hour = raw.GetNumber(0);
+            result.flags |= ParseFlags.HaveTime;
+            return true;
+        }
+
+        private static Boolean GetTimeOfNN(ref DateTimeResult result, ref DateTimeRawInfo raw)
+        {
+            Debug.Assert(raw.numCount >= 2, "raw.numCount >= 2");
+            if ((result.flags & ParseFlags.HaveTime) != 0)
+            {
+                // Multiple times in the input string
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+
+            result.Hour = raw.GetNumber(0);
+            result.Minute = raw.GetNumber(1);
+            result.flags |= ParseFlags.HaveTime;
+            return true;
+        }
+
+        private static Boolean GetTimeOfNNN(ref DateTimeResult result, ref DateTimeRawInfo raw)
+        {
+            if ((result.flags & ParseFlags.HaveTime) != 0)
+            {
+                // Multiple times in the input string
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+            Debug.Assert(raw.numCount >= 3, "raw.numCount >= 3");
+            result.Hour = raw.GetNumber(0);
+            result.Minute = raw.GetNumber(1);
+            result.Second = raw.GetNumber(2);
+            result.flags |= ParseFlags.HaveTime;
+            return true;
+        }
+
+        //
+        // Processing terminal state: A Date suffix followed by one number.
+        //
+        private static Boolean GetDateOfDSN(ref DateTimeResult result, ref DateTimeRawInfo raw)
+        {
+            if (raw.numCount != 1 || result.Day != -1)
+            {
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+            result.Day = raw.GetNumber(0);
+            return true;
+        }
+
+        private static Boolean GetDateOfNDS(ref DateTimeResult result, ref DateTimeRawInfo raw)
+        {
+            if (result.Month == -1)
+            {
+                //Should have a month suffix
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+            if (result.Year != -1)
+            {
+                // Already has a year suffix
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+            if (!TryAdjustYear(ref result, raw.GetNumber(0), out result.Year))
+            {
+                // the year value is out of range
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+            result.Day = 1;
+            return true;
+        }
+
+        private static Boolean GetDateOfNNDS(ref DateTimeResult result, ref DateTimeRawInfo raw, DateTimeFormatInfo dtfi)
+        {
+            // For partial CJK Dates, the only valid formats are with a specified year, followed by two numbers, which
+            // will be the Month and Day, and with a specified Month, when the numbers are either the year and day or
+            // day and year, depending on the short date pattern.
+
+            if ((result.flags & ParseFlags.HaveYear) != 0)
+            {
+                if (((result.flags & ParseFlags.HaveMonth) == 0) && ((result.flags & ParseFlags.HaveDay) == 0))
+                {
+                    if (TryAdjustYear(ref result, raw.year, out result.Year) && SetDateYMD(ref result, result.Year, raw.GetNumber(0), raw.GetNumber(1)))
+                    {
+                        return true;
+                    }
+                }
+            }
+            else if ((result.flags & ParseFlags.HaveMonth) != 0)
+            {
+                if (((result.flags & ParseFlags.HaveYear) == 0) && ((result.flags & ParseFlags.HaveDay) == 0))
+                {
+                    int order;
+                    if (!GetYearMonthDayOrder(dtfi.ShortDatePattern, dtfi, out order))
+                    {
+                        result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_BadDatePattern), dtfi.ShortDatePattern);
+                        return false;
+                    }
+                    int year;
+                    if (order == ORDER_YMD)
+                    {
+                        if (TryAdjustYear(ref result, raw.GetNumber(0), out year) && SetDateYMD(ref result, year, result.Month, raw.GetNumber(1)))
+                        {
+                            return true;
+                        }
+                    }
+                    else
+                    {
+                        if (TryAdjustYear(ref result, raw.GetNumber(1), out year) && SetDateYMD(ref result, year, result.Month, raw.GetNumber(0)))
+                        {
+                            return true;
+                        }
+                    }
+                }
+            }
+            result.SetBadDateTimeFailure();
+            return false;
+        }
+
+        //
+        // A date suffix is found, use this method to put the number into the result.
+        //
+        private static bool ProcessDateTimeSuffix(ref DateTimeResult result, ref DateTimeRawInfo raw, ref DateTimeToken dtok)
+        {
+            switch (dtok.suffix)
+            {
+                case TokenType.SEP_YearSuff:
+                    if ((result.flags & ParseFlags.HaveYear) != 0)
+                    {
+                        return false;
+                    }
+                    result.flags |= ParseFlags.HaveYear;
+                    result.Year = raw.year = dtok.num;
+                    break;
+                case TokenType.SEP_MonthSuff:
+                    if ((result.flags & ParseFlags.HaveMonth) != 0)
+                    {
+                        return false;
+                    }
+                    result.flags |= ParseFlags.HaveMonth;
+                    result.Month = raw.month = dtok.num;
+                    break;
+                case TokenType.SEP_DaySuff:
+                    if ((result.flags & ParseFlags.HaveDay) != 0)
+                    {
+                        return false;
+                    }
+                    result.flags |= ParseFlags.HaveDay;
+                    result.Day = dtok.num;
+                    break;
+                case TokenType.SEP_HourSuff:
+                    if ((result.flags & ParseFlags.HaveHour) != 0)
+                    {
+                        return false;
+                    }
+                    result.flags |= ParseFlags.HaveHour;
+                    result.Hour = dtok.num;
+                    break;
+                case TokenType.SEP_MinuteSuff:
+                    if ((result.flags & ParseFlags.HaveMinute) != 0)
+                    {
+                        return false;
+                    }
+                    result.flags |= ParseFlags.HaveMinute;
+                    result.Minute = dtok.num;
+                    break;
+                case TokenType.SEP_SecondSuff:
+                    if ((result.flags & ParseFlags.HaveSecond) != 0)
+                    {
+                        return false;
+                    }
+                    result.flags |= ParseFlags.HaveSecond;
+                    result.Second = dtok.num;
+                    break;
+            }
+            return true;
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        // Actions:
+        // This is used by DateTime.Parse().
+        // Process the terminal state for the Hebrew calendar parsing.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        internal static Boolean ProcessHebrewTerminalState(DS dps, ref __DTString str, ref DateTimeResult result, ref DateTimeStyles styles, ref DateTimeRawInfo raw, DateTimeFormatInfo dtfi)
+        {
+            // The following are accepted terminal state for Hebrew date.
+            switch (dps)
+            {
+                case DS.DX_MNN:
+                    // Deal with the default long/short date format when the year number is ambigous (i.e. year < 100).
+                    raw.year = raw.GetNumber(1);
+                    if (!dtfi.YearMonthAdjustment(ref raw.year, ref raw.month, true))
+                    {
+                        result.SetFailure(ParseFailureKind.FormatBadDateTimeCalendar, nameof(SR.Format_BadDateTimeCalendar));
+                        return false;
+                    }
+                    if (!GetDayOfMNN(ref result, ref raw, dtfi))
+                    {
+                        return false;
+                    }
+                    break;
+                case DS.DX_YMN:
+                    // Deal with the default long/short date format when the year number is NOT ambigous (i.e. year >= 100).
+                    if (!dtfi.YearMonthAdjustment(ref raw.year, ref raw.month, true))
+                    {
+                        result.SetFailure(ParseFailureKind.FormatBadDateTimeCalendar, nameof(SR.Format_BadDateTimeCalendar));
+                        return false;
+                    }
+                    if (!GetDayOfYMN(ref result, ref raw))
+                    {
+                        return false;
+                    }
+                    break;
+                case DS.DX_NNY:
+                    // When formatting, we only format up to the hundred digit of the Hebrew year, although Hebrew year is now over 5000.
+                    // E.g. if the year is 5763, we only format as 763. so we do the reverse when parsing.
+                    if (raw.year < 1000)
+                    {
+                        raw.year += 5000;
+                    }
+                    if (!GetDayOfNNY(ref result, ref raw, dtfi))
+                    {
+                        return false;
+                    }
+                    if (!dtfi.YearMonthAdjustment(ref result.Year, ref raw.month, true))
+                    {
+                        result.SetFailure(ParseFailureKind.FormatBadDateTimeCalendar, nameof(SR.Format_BadDateTimeCalendar));
+                        return false;
+                    }
+                    break;
+                case DS.DX_NM:
+                case DS.DX_MN:
+                    // Deal with Month/Day pattern.
+                    GetDefaultYear(ref result, ref styles);
+                    if (!dtfi.YearMonthAdjustment(ref result.Year, ref raw.month, true))
+                    {
+                        result.SetFailure(ParseFailureKind.FormatBadDateTimeCalendar, nameof(SR.Format_BadDateTimeCalendar));
+                        return false;
+                    }
+                    if (!GetHebrewDayOfNM(ref result, ref raw, dtfi))
+                    {
+                        return false;
+                    }
+                    break;
+                case DS.DX_YM:
+                    // Deal with Year/Month pattern.
+                    if (!dtfi.YearMonthAdjustment(ref raw.year, ref raw.month, true))
+                    {
+                        result.SetFailure(ParseFailureKind.FormatBadDateTimeCalendar, nameof(SR.Format_BadDateTimeCalendar));
+                        return false;
+                    }
+                    if (!GetDayOfYM(ref result, ref raw))
+                    {
+                        return false;
+                    }
+                    break;
+                case DS.TX_N:
+                    // Deal hour + AM/PM
+                    if (!GetTimeOfN(ref result, ref raw))
+                    {
+                        return false;
+                    }
+                    break;
+                case DS.TX_NN:
+                    if (!GetTimeOfNN(ref result, ref raw))
+                    {
+                        return false;
+                    }
+                    break;
+                case DS.TX_NNN:
+                    if (!GetTimeOfNNN(ref result, ref raw))
+                    {
+                        return false;
+                    }
+                    break;
+                default:
+                    result.SetBadDateTimeFailure();
+                    return false;
+            }
+            if (dps > DS.ERROR)
+            {
+                //
+                // We have reached a terminal state. Reset the raw num count.
+                //
+                raw.numCount = 0;
+            }
+            return true;
+        }
+
+        //
+        // A terminal state has been reached, call the appropriate function to fill in the parsing result.
+        // Return true if the state is a terminal state.
+        //
+        internal static Boolean ProcessTerminalState(DS dps, ref __DTString str, ref DateTimeResult result, ref DateTimeStyles styles, ref DateTimeRawInfo raw, DateTimeFormatInfo dtfi)
+        {
+            bool passed = true;
+            switch (dps)
+            {
+                case DS.DX_NN:
+                    passed = GetDayOfNN(ref result, ref styles, ref raw, dtfi);
+                    break;
+                case DS.DX_NNN:
+                    passed = GetDayOfNNN(ref result, ref raw, dtfi);
+                    break;
+                case DS.DX_MN:
+                    passed = GetDayOfMN(ref result, ref styles, ref raw, dtfi);
+                    break;
+                case DS.DX_NM:
+                    passed = GetDayOfNM(ref result, ref styles, ref raw, dtfi);
+                    break;
+                case DS.DX_MNN:
+                    passed = GetDayOfMNN(ref result, ref raw, dtfi);
+                    break;
+                case DS.DX_DS:
+                    // The result has got the correct value. No need to process.
+                    passed = true;
+                    break;
+                case DS.DX_YNN:
+                    passed = GetDayOfYNN(ref result, ref raw, dtfi);
+                    break;
+                case DS.DX_NNY:
+                    passed = GetDayOfNNY(ref result, ref raw, dtfi);
+                    break;
+                case DS.DX_YMN:
+                    passed = GetDayOfYMN(ref result, ref raw);
+                    break;
+                case DS.DX_YN:
+                    passed = GetDayOfYN(ref result, ref raw);
+                    break;
+                case DS.DX_YM:
+                    passed = GetDayOfYM(ref result, ref raw);
+                    break;
+                case DS.TX_N:
+                    passed = GetTimeOfN(ref result, ref raw);
+                    break;
+                case DS.TX_NN:
+                    passed = GetTimeOfNN(ref result, ref raw);
+                    break;
+                case DS.TX_NNN:
+                    passed = GetTimeOfNNN(ref result, ref raw);
+                    break;
+                case DS.TX_TS:
+                    // The result has got the correct value. Nothing to do.
+                    passed = true;
+                    break;
+                case DS.DX_DSN:
+                    passed = GetDateOfDSN(ref result, ref raw);
+                    break;
+                case DS.DX_NDS:
+                    passed = GetDateOfNDS(ref result, ref raw);
+                    break;
+                case DS.DX_NNDS:
+                    passed = GetDateOfNNDS(ref result, ref raw, dtfi);
+                    break;
+            }
+
+            PTSTraceExit(dps, passed);
+            if (!passed)
+            {
+                return false;
+            }
+
+            if (dps > DS.ERROR)
+            {
+                //
+                // We have reached a terminal state. Reset the raw num count.
+                //
+                raw.numCount = 0;
+            }
+            return true;
+        }
+
+        internal static DateTime Parse(ReadOnlySpan<char> s, DateTimeFormatInfo dtfi, DateTimeStyles styles)
+        {
+            DateTimeResult result = new DateTimeResult();       // The buffer to store the parsing result.
+            result.Init(s);
+            if (TryParse(s, dtfi, styles, ref result))
+            {
+                return result.parsedDate;
+            }
+            else
+            {
+                throw GetDateTimeParseException(ref result);
+            }
+        }
+
+        internal static DateTime Parse(ReadOnlySpan<char> s, DateTimeFormatInfo dtfi, DateTimeStyles styles, out TimeSpan offset)
+        {
+            DateTimeResult result = new DateTimeResult();       // The buffer to store the parsing result.
+            result.Init(s);
+            result.flags |= ParseFlags.CaptureOffset;
+            if (TryParse(s, dtfi, styles, ref result))
+            {
+                offset = result.timeZoneOffset;
+                return result.parsedDate;
+            }
+            else
+            {
+                throw GetDateTimeParseException(ref result);
+            }
+        }
+
+
+        internal static bool TryParse(ReadOnlySpan<char> s, DateTimeFormatInfo dtfi, DateTimeStyles styles, out DateTime result)
+        {
+            result = DateTime.MinValue;
+            DateTimeResult resultData = new DateTimeResult();       // The buffer to store the parsing result.
+            resultData.Init(s);
+            if (TryParse(s, dtfi, styles, ref resultData))
+            {
+                result = resultData.parsedDate;
+                return true;
+            }
+            return false;
+        }
+
+        internal static bool TryParse(ReadOnlySpan<char> s, DateTimeFormatInfo dtfi, DateTimeStyles styles, out DateTime result, out TimeSpan offset)
+        {
+            result = DateTime.MinValue;
+            offset = TimeSpan.Zero;
+            DateTimeResult parseResult = new DateTimeResult();       // The buffer to store the parsing result.
+            parseResult.Init(s);
+            parseResult.flags |= ParseFlags.CaptureOffset;
+            if (TryParse(s, dtfi, styles, ref parseResult))
+            {
+                result = parseResult.parsedDate;
+                offset = parseResult.timeZoneOffset;
+                return true;
+            }
+            return false;
+        }
+
+
+        //
+        // This is the real method to do the parsing work.
+        //
+        internal static bool TryParse(ReadOnlySpan<char> s, DateTimeFormatInfo dtfi, DateTimeStyles styles, ref DateTimeResult result)
+        {
+            if (s.Length == 0)
+            {
+                result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_BadDateTime));
+                return false;
+            }
+
+            Debug.Assert(dtfi != null, "dtfi == null");
+
+#if _LOGGING
+            DTFITrace(dtfi);
+#endif
+
+            DateTime time;
+            //
+            // First try the predefined format.
+            //
+
+            DS dps = DS.BEGIN;     // Date Parsing State.
+            bool reachTerminalState = false;
+
+            DateTimeToken dtok = new DateTimeToken();      // The buffer to store the parsing token.
+            dtok.suffix = TokenType.SEP_Unk;
+            DateTimeRawInfo raw = new DateTimeRawInfo();    // The buffer to store temporary parsing information.
+            unsafe
+            {
+                Int32* numberPointer = stackalloc Int32[3];
+                raw.Init(numberPointer);
+            }
+            raw.hasSameDateAndTimeSeparators = dtfi.DateSeparator.Equals(dtfi.TimeSeparator, StringComparison.Ordinal);
+
+            result.calendar = dtfi.Calendar;
+            result.era = Calendar.CurrentEra;
+
+            //
+            // The string to be parsed. Use a __DTString wrapper so that we can trace the index which
+            // indicates the begining of next token.
+            //
+            __DTString str = new __DTString(s, dtfi);
+
+            str.GetNext();
+
+            //
+            // The following loop will break out when we reach the end of the str.
+            //
+            do
+            {
+                //
+                // Call the lexer to get the next token.
+                //
+                // If we find a era in Lex(), the era value will be in raw.era.
+                if (!Lex(dps, ref str, ref dtok, ref raw, ref result, ref dtfi, styles))
+                {
+                    TPTraceExit("0000", dps);
+                    return false;
+                }
+
+                //
+                // If the token is not unknown, process it.
+                // Otherwise, just discard it.
+                //
+                if (dtok.dtt != DTT.Unk)
+                {
+                    //
+                    // Check if we got any CJK Date/Time suffix.
+                    // Since the Date/Time suffix tells us the number belongs to year/month/day/hour/minute/second,
+                    // store the number in the appropriate field in the result.
+                    //
+                    if (dtok.suffix != TokenType.SEP_Unk)
+                    {
+                        if (!ProcessDateTimeSuffix(ref result, ref raw, ref dtok))
+                        {
+                            result.SetBadDateTimeFailure();
+                            TPTraceExit("0010", dps);
+                            return false;
+                        }
+
+                        dtok.suffix = TokenType.SEP_Unk;  // Reset suffix to SEP_Unk;
+                    }
+
+                    if (dtok.dtt == DTT.NumLocalTimeMark)
+                    {
+                        if (dps == DS.D_YNd || dps == DS.D_YN)
+                        {
+                            // Consider this as ISO 8601 format:
+                            // "yyyy-MM-dd'T'HH:mm:ss"                 1999-10-31T02:00:00
+                            TPTraceExit("0020", dps);
+                            return (ParseISO8601(ref raw, ref str, styles, ref result));
+                        }
+                        else
+                        {
+                            result.SetBadDateTimeFailure();
+                            TPTraceExit("0030", dps);
+                            return false;
+                        }
+                    }
+
+                    if (raw.hasSameDateAndTimeSeparators)
+                    {
+                        if (dtok.dtt == DTT.YearEnd || dtok.dtt == DTT.YearSpace || dtok.dtt == DTT.YearDateSep)
+                        {
+                            // When time and date separators are same and we are hitting a year number while the first parsed part of the string was recognized
+                            // as part of time (and not a date) DS.T_Nt, DS.T_NNt then change the state to be a date so we try to parse it as a date instead
+                            if (dps == DS.T_Nt)
+                            {
+                                dps = DS.D_Nd;
+                            }
+                            if (dps == DS.T_NNt)
+                            {
+                                dps = DS.D_NNd;
+                            }
+                        }
+
+                        bool atEnd = str.AtEnd();
+                        if (dateParsingStates[(int)dps][(int)dtok.dtt] == DS.ERROR || atEnd)
+                        {
+                            switch (dtok.dtt)
+                            {
+                                // we have the case of Serbia have dates in forms 'd.M.yyyy.' so we can expect '.' after the date parts.
+                                // changing the token to end with space instead of Date Separator will avoid failing the parsing.
+
+                                case DTT.YearDateSep: dtok.dtt = atEnd ? DTT.YearEnd : DTT.YearSpace; break;
+                                case DTT.NumDatesep: dtok.dtt = atEnd ? DTT.NumEnd : DTT.NumSpace; break;
+                                case DTT.NumTimesep: dtok.dtt = atEnd ? DTT.NumEnd : DTT.NumSpace; break;
+                                case DTT.MonthDatesep: dtok.dtt = atEnd ? DTT.MonthEnd : DTT.MonthSpace; break;
+                            }
+                        }
+                    }
+
+                    //
+                    // Advance to the next state, and continue
+                    //
+                    dps = dateParsingStates[(int)dps][(int)dtok.dtt];
+
+                    if (dps == DS.ERROR)
+                    {
+                        result.SetBadDateTimeFailure();
+                        TPTraceExit("0040 (invalid state transition)", dps);
+                        return false;
+                    }
+                    else if (dps > DS.ERROR)
+                    {
+                        if ((dtfi.FormatFlags & DateTimeFormatFlags.UseHebrewRule) != 0)
+                        {
+                            if (!ProcessHebrewTerminalState(dps, ref str, ref result, ref styles, ref raw, dtfi))
+                            {
+                                TPTraceExit("0050 (ProcessHebrewTerminalState)", dps);
+                                return false;
+                            }
+                        }
+                        else
+                        {
+                            if (!ProcessTerminalState(dps, ref str, ref result, ref styles, ref raw, dtfi))
+                            {
+                                TPTraceExit("0060 (ProcessTerminaltState)", dps);
+                                return false;
+                            }
+                        }
+                        reachTerminalState = true;
+
+                        //
+                        // If we have reached a terminal state, start over from DS.BEGIN again.
+                        // For example, when we parsed "1999-12-23 13:30", we will reach a terminal state at "1999-12-23",
+                        // and we start over so we can continue to parse "12:30".
+                        //
+                        dps = DS.BEGIN;
+                    }
+                }
+            } while (dtok.dtt != DTT.End && dtok.dtt != DTT.NumEnd && dtok.dtt != DTT.MonthEnd);
+
+            if (!reachTerminalState)
+            {
+                result.SetBadDateTimeFailure();
+                TPTraceExit("0070 (did not reach terminal state)", dps);
+                return false;
+            }
+
+            AdjustTimeMark(dtfi, ref raw);
+            if (!AdjustHour(ref result.Hour, raw.timeMark))
+            {
+                result.SetBadDateTimeFailure();
+                TPTraceExit("0080 (AdjustHour)", dps);
+                return false;
+            }
+
+            // Check if the parased string only contains hour/minute/second values.
+            bool bTimeOnly = (result.Year == -1 && result.Month == -1 && result.Day == -1);
+
+            //
+            // Check if any year/month/day is missing in the parsing string.
+            // If yes, get the default value from today's date.
+            //
+            if (!CheckDefaultDateTime(ref result, ref result.calendar, styles))
+            {
+                TPTraceExit("0090 (failed to fill in missing year/month/day defaults)", dps);
+                return false;
+            }
+
+            if (!result.calendar.TryToDateTime(result.Year, result.Month, result.Day,
+                    result.Hour, result.Minute, result.Second, 0, result.era, out time))
+            {
+                result.SetFailure(ParseFailureKind.FormatBadDateTimeCalendar, nameof(SR.Format_BadDateTimeCalendar));
+                TPTraceExit("0100 (result.calendar.TryToDateTime)", dps);
+                return false;
+            }
+            if (raw.fraction > 0)
+            {
+                time = time.AddTicks((long)Math.Round(raw.fraction * Calendar.TicksPerSecond));
+            }
+
+            //
+            // We have to check day of week before we adjust to the time zone.
+            // Otherwise, the value of day of week may change after adjusting to the time zone.
+            //
+            if (raw.dayOfWeek != -1)
+            {
+                //
+                // Check if day of week is correct.
+                //
+                if (raw.dayOfWeek != (int)result.calendar.GetDayOfWeek(time))
+                {
+                    result.SetFailure(ParseFailureKind.FormatWithOriginalDateTime, nameof(SR.Format_BadDayOfWeek));
+                    TPTraceExit("0110 (dayOfWeek check)", dps);
+                    return false;
+                }
+            }
+
+            result.parsedDate = time;
+
+            if (!DetermineTimeZoneAdjustments(ref str, ref result, styles, bTimeOnly))
+            {
+                TPTraceExit("0120 (DetermineTimeZoneAdjustments)", dps);
+                return false;
+            }
+            TPTraceExit("0130 (success)", dps);
+            return true;
+        }
+
+
+        // Handles time zone adjustments and sets DateTimeKind values as required by the styles
+        private static Boolean DetermineTimeZoneAdjustments(ref __DTString str, ref DateTimeResult result, DateTimeStyles styles, Boolean bTimeOnly)
+        {
+            if ((result.flags & ParseFlags.CaptureOffset) != 0)
+            {
+                // This is a DateTimeOffset parse, so the offset will actually be captured directly, and
+                // no adjustment is required in most cases
+                return DateTimeOffsetTimeZonePostProcessing(ref str, ref result, styles);
+            }
+            else
+            {
+                Int64 offsetTicks = result.timeZoneOffset.Ticks;
+
+                // the DateTime offset must be within +- 14:00 hours.
+                if (offsetTicks < DateTimeOffset.MinOffset || offsetTicks > DateTimeOffset.MaxOffset)
+                {
+                    result.SetFailure(ParseFailureKind.FormatWithOriginalDateTime, nameof(SR.Format_OffsetOutOfRange));
+                    return false;
+                }
+            }
+
+            // The flags AssumeUniveral and AssumeLocal only apply when the input does not have a time zone
+            if ((result.flags & ParseFlags.TimeZoneUsed) == 0)
+            {
+                // If AssumeLocal or AssumeLocal is used, there will always be a kind specified. As in the
+                // case when a time zone is present, it will default to being local unless AdjustToUniversal
+                // is present. These comparisons determine whether setting the kind is sufficient, or if a
+                // time zone adjustment is required. For consistentcy with the rest of parsing, it is desirable
+                // to fall through to the Adjust methods below, so that there is consist handling of boundary
+                // cases like wrapping around on time-only dates and temporarily allowing an adjusted date
+                // to exceed DateTime.MaxValue
+                if ((styles & DateTimeStyles.AssumeLocal) != 0)
+                {
+                    if ((styles & DateTimeStyles.AdjustToUniversal) != 0)
+                    {
+                        result.flags |= ParseFlags.TimeZoneUsed;
+                        result.timeZoneOffset = TimeZoneInfo.GetLocalUtcOffset(result.parsedDate, TimeZoneInfoOptions.NoThrowOnInvalidTime);
+                    }
+                    else
+                    {
+                        result.parsedDate = DateTime.SpecifyKind(result.parsedDate, DateTimeKind.Local);
+                        return true;
+                    }
+                }
+                else if ((styles & DateTimeStyles.AssumeUniversal) != 0)
+                {
+                    if ((styles & DateTimeStyles.AdjustToUniversal) != 0)
+                    {
+                        result.parsedDate = DateTime.SpecifyKind(result.parsedDate, DateTimeKind.Utc);
+                        return true;
+                    }
+                    else
+                    {
+                        result.flags |= ParseFlags.TimeZoneUsed;
+                        result.timeZoneOffset = TimeSpan.Zero;
+                    }
+                }
+                else
+                {
+                    // No time zone and no Assume flags, so DateTimeKind.Unspecified is fine
+                    Debug.Assert(result.parsedDate.Kind == DateTimeKind.Unspecified, "result.parsedDate.Kind == DateTimeKind.Unspecified");
+                    return true;
+                }
+            }
+
+            if (((styles & DateTimeStyles.RoundtripKind) != 0) && ((result.flags & ParseFlags.TimeZoneUtc) != 0))
+            {
+                result.parsedDate = DateTime.SpecifyKind(result.parsedDate, DateTimeKind.Utc);
+                return true;
+            }
+
+            if ((styles & DateTimeStyles.AdjustToUniversal) != 0)
+            {
+                return (AdjustTimeZoneToUniversal(ref result));
+            }
+            return (AdjustTimeZoneToLocal(ref result, bTimeOnly));
+        }
+
+        // Apply validation and adjustments specific to DateTimeOffset
+        private static Boolean DateTimeOffsetTimeZonePostProcessing(ref __DTString str, ref DateTimeResult result, DateTimeStyles styles)
+        {
+            // For DateTimeOffset, default to the Utc or Local offset when an offset was not specified by
+            // the input string.
+            if ((result.flags & ParseFlags.TimeZoneUsed) == 0)
+            {
+                if ((styles & DateTimeStyles.AssumeUniversal) != 0)
+                {
+                    // AssumeUniversal causes the offset to default to zero (0)
+                    result.timeZoneOffset = TimeSpan.Zero;
+                }
+                else
+                {
+                    // AssumeLocal causes the offset to default to Local.  This flag is on by default for DateTimeOffset.
+                    result.timeZoneOffset = TimeZoneInfo.GetLocalUtcOffset(result.parsedDate, TimeZoneInfoOptions.NoThrowOnInvalidTime);
+                }
+            }
+
+            Int64 offsetTicks = result.timeZoneOffset.Ticks;
+
+            // there should be no overflow, because the offset can be no more than -+100 hours and the date already
+            // fits within a DateTime.
+            Int64 utcTicks = result.parsedDate.Ticks - offsetTicks;
+
+            // For DateTimeOffset, both the parsed time and the corresponding UTC value must be within the boundaries
+            // of a DateTime instance.
+            if (utcTicks < DateTime.MinTicks || utcTicks > DateTime.MaxTicks)
+            {
+                result.SetFailure(ParseFailureKind.FormatWithOriginalDateTime, nameof(SR.Format_UTCOutOfRange));
+                return false;
+            }
+
+            // the offset must be within +- 14:00 hours.
+            if (offsetTicks < DateTimeOffset.MinOffset || offsetTicks > DateTimeOffset.MaxOffset)
+            {
+                result.SetFailure(ParseFailureKind.FormatWithOriginalDateTime, nameof(SR.Format_OffsetOutOfRange));
+                return false;
+            }
+
+            // DateTimeOffset should still honor the AdjustToUniversal flag for consistency with DateTime. It means you
+            // want to return an adjusted UTC value, so store the utcTicks in the DateTime and set the offset to zero
+            if ((styles & DateTimeStyles.AdjustToUniversal) != 0)
+            {
+                if (((result.flags & ParseFlags.TimeZoneUsed) == 0) && ((styles & DateTimeStyles.AssumeUniversal) == 0))
+                {
+                    // Handle the special case where the timeZoneOffset was defaulted to Local
+                    Boolean toUtcResult = AdjustTimeZoneToUniversal(ref result);
+                    result.timeZoneOffset = TimeSpan.Zero;
+                    return toUtcResult;
+                }
+
+                // The constructor should always succeed because of the range check earlier in the function
+                // Although it is UTC, internally DateTimeOffset does not use this flag
+                result.parsedDate = new DateTime(utcTicks, DateTimeKind.Utc);
+                result.timeZoneOffset = TimeSpan.Zero;
+            }
+
+            return true;
+        }
+
+
+        //
+        // Adjust the specified time to universal time based on the supplied timezone.
+        // E.g. when parsing "2001/06/08 14:00-07:00",
+        // the time is 2001/06/08 14:00, and timeZoneOffset = -07:00.
+        // The result will be "2001/06/08 21:00"
+        //
+        private static Boolean AdjustTimeZoneToUniversal(ref DateTimeResult result)
+        {
+            long resultTicks = result.parsedDate.Ticks;
+            resultTicks -= result.timeZoneOffset.Ticks;
+            if (resultTicks < 0)
+            {
+                resultTicks += Calendar.TicksPerDay;
+            }
+
+            if (resultTicks < DateTime.MinTicks || resultTicks > DateTime.MaxTicks)
+            {
+                result.SetFailure(ParseFailureKind.FormatWithOriginalDateTime, nameof(SR.Format_DateOutOfRange));
+                return false;
+            }
+            result.parsedDate = new DateTime(resultTicks, DateTimeKind.Utc);
+            return true;
+        }
+
+        //
+        // Adjust the specified time to universal time based on the supplied timezone,
+        // and then convert to local time.
+        // E.g. when parsing "2001/06/08 14:00-04:00", and local timezone is GMT-7.
+        // the time is 2001/06/08 14:00, and timeZoneOffset = -05:00.
+        // The result will be "2001/06/08 11:00"
+        //
+        private static Boolean AdjustTimeZoneToLocal(ref DateTimeResult result, bool bTimeOnly)
+        {
+            long resultTicks = result.parsedDate.Ticks;
+            // Convert to local ticks
+            TimeZoneInfo tz = TimeZoneInfo.Local;
+            Boolean isAmbiguousLocalDst = false;
+            if (resultTicks < Calendar.TicksPerDay)
+            {
+                //
+                // This is time of day.
+                //
+
+                // Adjust timezone.
+                resultTicks -= result.timeZoneOffset.Ticks;
+                // If the time is time of day, use the current timezone offset.
+                resultTicks += tz.GetUtcOffset(bTimeOnly ? DateTime.Now : result.parsedDate, TimeZoneInfoOptions.NoThrowOnInvalidTime).Ticks;
+
+                if (resultTicks < 0)
+                {
+                    resultTicks += Calendar.TicksPerDay;
+                }
+            }
+            else
+            {
+                // Adjust timezone to GMT.
+                resultTicks -= result.timeZoneOffset.Ticks;
+                if (resultTicks < DateTime.MinTicks || resultTicks > DateTime.MaxTicks)
+                {
+                    // If the result ticks is greater than DateTime.MaxValue, we can not create a DateTime from this ticks.
+                    // In this case, keep using the old code.
+                    resultTicks += tz.GetUtcOffset(result.parsedDate, TimeZoneInfoOptions.NoThrowOnInvalidTime).Ticks;
+                }
+                else
+                {
+                    // Convert the GMT time to local time.
+                    DateTime utcDt = new DateTime(resultTicks, DateTimeKind.Utc);
+                    Boolean isDaylightSavings = false;
+                    resultTicks += TimeZoneInfo.GetUtcOffsetFromUtc(utcDt, TimeZoneInfo.Local, out isDaylightSavings, out isAmbiguousLocalDst).Ticks;
+                }
+            }
+            if (resultTicks < DateTime.MinTicks || resultTicks > DateTime.MaxTicks)
+            {
+                result.parsedDate = DateTime.MinValue;
+                result.SetFailure(ParseFailureKind.FormatWithOriginalDateTime, nameof(SR.Format_DateOutOfRange));
+                return false;
+            }
+            result.parsedDate = new DateTime(resultTicks, DateTimeKind.Local, isAmbiguousLocalDst);
+            return true;
+        }
+
+        //
+        // Parse the ISO8601 format string found during Parse();
+        //
+        //
+        private static bool ParseISO8601(ref DateTimeRawInfo raw, ref __DTString str, DateTimeStyles styles, ref DateTimeResult result)
+        {
+            if (raw.year < 0 || raw.GetNumber(0) < 0 || raw.GetNumber(1) < 0)
+            {
+            }
+            str.Index--;
+            int hour, minute;
+            int second = 0;
+            double partSecond = 0;
+
+            str.SkipWhiteSpaces();
+            if (!ParseDigits(ref str, 2, out hour))
+            {
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+            str.SkipWhiteSpaces();
+            if (!str.Match(':'))
+            {
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+            str.SkipWhiteSpaces();
+            if (!ParseDigits(ref str, 2, out minute))
+            {
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+            str.SkipWhiteSpaces();
+            if (str.Match(':'))
+            {
+                str.SkipWhiteSpaces();
+                if (!ParseDigits(ref str, 2, out second))
+                {
+                    result.SetBadDateTimeFailure();
+                    return false;
+                }
+                if (str.Match('.'))
+                {
+                    if (!ParseFraction(ref str, out partSecond))
+                    {
+                        result.SetBadDateTimeFailure();
+                        return false;
+                    }
+                    str.Index--;
+                }
+                str.SkipWhiteSpaces();
+            }
+            if (str.GetNext())
+            {
+                char ch = str.GetChar();
+                if (ch == '+' || ch == '-')
+                {
+                    result.flags |= ParseFlags.TimeZoneUsed;
+                    if (!ParseTimeZone(ref str, ref result.timeZoneOffset))
+                    {
+                        result.SetBadDateTimeFailure();
+                        return false;
+                    }
+                }
+                else if (ch == 'Z' || ch == 'z')
+                {
+                    result.flags |= ParseFlags.TimeZoneUsed;
+                    result.timeZoneOffset = TimeSpan.Zero;
+                    result.flags |= ParseFlags.TimeZoneUtc;
+                }
+                else
+                {
+                    str.Index--;
+                }
+                str.SkipWhiteSpaces();
+                if (str.Match('#'))
+                {
+                    if (!VerifyValidPunctuation(ref str))
+                    {
+                        result.SetBadDateTimeFailure();
+                        return false;
+                    }
+                    str.SkipWhiteSpaces();
+                }
+                if (str.Match('\0'))
+                {
+                    if (!VerifyValidPunctuation(ref str))
+                    {
+                        result.SetBadDateTimeFailure();
+                        return false;
+                    }
+                }
+                if (str.GetNext())
+                {
+                    // If this is true, there were non-white space characters remaining in the DateTime
+                    result.SetBadDateTimeFailure();
+                    return false;
+                }
+            }
+
+            DateTime time;
+            Calendar calendar = GregorianCalendar.GetDefaultInstance();
+            if (!calendar.TryToDateTime(raw.year, raw.GetNumber(0), raw.GetNumber(1),
+                    hour, minute, second, 0, result.era, out time))
+            {
+                result.SetFailure(ParseFailureKind.FormatBadDateTimeCalendar, nameof(SR.Format_BadDateTimeCalendar));
+                return false;
+            }
+
+            time = time.AddTicks((long)Math.Round(partSecond * Calendar.TicksPerSecond));
+            result.parsedDate = time;
+            if (!DetermineTimeZoneAdjustments(ref str, ref result, styles, false))
+            {
+                return false;
+            }
+            return true;
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        // Actions:
+        //    Parse the current word as a Hebrew number.
+        //      This is used by DateTime.ParseExact().
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        internal static bool MatchHebrewDigits(ref __DTString str, int digitLen, out int number)
+        {
+            number = 0;
+
+            // Create a context object so that we can parse the Hebrew number text character by character.
+            HebrewNumberParsingContext context = new HebrewNumberParsingContext(0);
+
+            // Set this to ContinueParsing so that we will run the following while loop in the first time.
+            HebrewNumberParsingState state = HebrewNumberParsingState.ContinueParsing;
+
+            while (state == HebrewNumberParsingState.ContinueParsing && str.GetNext())
+            {
+                state = HebrewNumber.ParseByChar(str.GetChar(), ref context);
+            }
+
+            if (state == HebrewNumberParsingState.FoundEndOfHebrewNumber)
+            {
+                // If we have reached a terminal state, update the result and returns.
+                number = context.result;
+                return (true);
+            }
+
+            // If we run out of the character before reaching FoundEndOfHebrewNumber, or
+            // the state is InvalidHebrewNumber or ContinueParsing, we fail to match a Hebrew number.
+            // Return an error.
+            return false;
+        }
+
+        /*=================================ParseDigits==================================
+        **Action: Parse the number string in __DTString that are formatted using
+        **        the following patterns:
+        **        "0", "00", and "000..0"
+        **Returns: the integer value
+        **Arguments:    str: a __DTString.  The parsing will start from the
+        **              next character after str.Index.
+        **Exceptions: FormatException if error in parsing number.
+        ==============================================================================*/
+
+        internal static bool ParseDigits(ref __DTString str, int digitLen, out int result)
+        {
+            if (digitLen == 1)
+            {
+                // 1 really means 1 or 2 for this call
+                return ParseDigits(ref str, 1, 2, out result);
+            }
+            else
+            {
+                return ParseDigits(ref str, digitLen, digitLen, out result);
+            }
+        }
+
+        internal static bool ParseDigits(ref __DTString str, int minDigitLen, int maxDigitLen, out int result)
+        {
+            Debug.Assert(minDigitLen > 0, "minDigitLen > 0");
+            Debug.Assert(maxDigitLen < 9, "maxDigitLen < 9");
+            Debug.Assert(minDigitLen <= maxDigitLen, "minDigitLen <= maxDigitLen");
+            int localResult = 0;
+            int startingIndex = str.Index;
+            int tokenLength = 0;
+            while (tokenLength < maxDigitLen)
+            {
+                if (!str.GetNextDigit())
+                {
+                    str.Index--;
+                    break;
+                }
+                localResult = localResult * 10 + str.GetDigit();
+                tokenLength++;
+            }
+            result = localResult;
+            if (tokenLength < minDigitLen)
+            {
+                str.Index = startingIndex;
+                return false;
+            }
+            return true;
+        }
+
+        /*=================================ParseFractionExact==================================
+        **Action: Parse the number string in __DTString that are formatted using
+        **        the following patterns:
+        **        "0", "00", and "000..0"
+        **Returns: the fraction value
+        **Arguments:    str: a __DTString.  The parsing will start from the
+        **              next character after str.Index.
+        **Exceptions: FormatException if error in parsing number.
+        ==============================================================================*/
+
+        private static bool ParseFractionExact(ref __DTString str, int maxDigitLen, ref double result)
+        {
+            if (!str.GetNextDigit())
+            {
+                str.Index--;
+                return false;
+            }
+            result = str.GetDigit();
+
+            int digitLen = 1;
+            for (; digitLen < maxDigitLen; digitLen++)
+            {
+                if (!str.GetNextDigit())
+                {
+                    str.Index--;
+                    break;
+                }
+                result = result * 10 + str.GetDigit();
+            }
+
+            result /= TimeSpanParse.Pow10(digitLen);
+            return (digitLen == maxDigitLen);
+        }
+
+        /*=================================ParseSign==================================
+        **Action: Parse a positive or a negative sign.
+        **Returns:      true if postive sign.  flase if negative sign.
+        **Arguments:    str: a __DTString.  The parsing will start from the
+        **              next character after str.Index.
+        **Exceptions:   FormatException if end of string is encountered or a sign
+        **              symbol is not found.
+        ==============================================================================*/
+
+        private static bool ParseSign(ref __DTString str, ref bool result)
+        {
+            if (!str.GetNext())
+            {
+                // A sign symbol ('+' or '-') is expected. However, end of string is encountered.
+                return false;
+            }
+            char ch = str.GetChar();
+            if (ch == '+')
+            {
+                result = true;
+                return (true);
+            }
+            else if (ch == '-')
+            {
+                result = false;
+                return (true);
+            }
+            // A sign symbol ('+' or '-') is expected.
+            return false;
+        }
+
+        /*=================================ParseTimeZoneOffset==================================
+        **Action: Parse the string formatted using "z", "zz", "zzz" in DateTime.Format().
+        **Returns: the TimeSpan for the parsed timezone offset.
+        **Arguments:    str: a __DTString.  The parsing will start from the
+        **              next character after str.Index.
+        **              len: the repeated number of the "z"
+        **Exceptions: FormatException if errors in parsing.
+        ==============================================================================*/
+
+        private static bool ParseTimeZoneOffset(ref __DTString str, int len, ref TimeSpan result)
+        {
+            bool isPositive = true;
+            int hourOffset;
+            int minuteOffset = 0;
+
+            switch (len)
+            {
+                case 1:
+                case 2:
+                    if (!ParseSign(ref str, ref isPositive))
+                    {
+                        return (false);
+                    }
+                    if (!ParseDigits(ref str, len, out hourOffset))
+                    {
+                        return (false);
+                    }
+                    break;
+                default:
+                    if (!ParseSign(ref str, ref isPositive))
+                    {
+                        return (false);
+                    }
+
+                    // Parsing 1 digit will actually parse 1 or 2.
+                    if (!ParseDigits(ref str, 1, out hourOffset))
+                    {
+                        return (false);
+                    }
+                    // ':' is optional.
+                    if (str.Match(":"))
+                    {
+                        // Found ':'
+                        if (!ParseDigits(ref str, 2, out minuteOffset))
+                        {
+                            return (false);
+                        }
+                    }
+                    else
+                    {
+                        // Since we can not match ':', put the char back.
+                        str.Index--;
+                        if (!ParseDigits(ref str, 2, out minuteOffset))
+                        {
+                            return (false);
+                        }
+                    }
+                    break;
+            }
+            if (minuteOffset < 0 || minuteOffset >= 60)
+            {
+                return false;
+            }
+
+            result = (new TimeSpan(hourOffset, minuteOffset, 0));
+            if (!isPositive)
+            {
+                result = result.Negate();
+            }
+            return (true);
+        }
+
+        /*=================================MatchAbbreviatedMonthName==================================
+        **Action: Parse the abbreviated month name from string starting at str.Index.
+        **Returns: A value from 1 to 12 for the first month to the twelveth month.
+        **Arguments:    str: a __DTString.  The parsing will start from the
+        **              next character after str.Index.
+        **Exceptions: FormatException if an abbreviated month name can not be found.
+        ==============================================================================*/
+
+        private static bool MatchAbbreviatedMonthName(ref __DTString str, DateTimeFormatInfo dtfi, ref int result)
+        {
+            int maxMatchStrLen = 0;
+            result = -1;
+            if (str.GetNext())
+            {
+                //
+                // Scan the month names (note that some calendars has 13 months) and find
+                // the matching month name which has the max string length.
+                // We need to do this because some cultures (e.g. "cs-CZ") which have
+                // abbreviated month names with the same prefix.
+                //
+                int monthsInYear = (dtfi.GetMonthName(13).Length == 0 ? 12 : 13);
+                for (int i = 1; i <= monthsInYear; i++)
+                {
+                    String searchStr = dtfi.GetAbbreviatedMonthName(i);
+                    int matchStrLen = searchStr.Length;
+                    if (dtfi.HasSpacesInMonthNames
+                            ? str.MatchSpecifiedWords(searchStr, false, ref matchStrLen)
+                            : str.MatchSpecifiedWord(searchStr))
+                    {
+                        if (matchStrLen > maxMatchStrLen)
+                        {
+                            maxMatchStrLen = matchStrLen;
+                            result = i;
+                        }
+                    }
+                }
+
+                // Search leap year form.
+                if ((dtfi.FormatFlags & DateTimeFormatFlags.UseLeapYearMonth) != 0)
+                {
+                    int tempResult = str.MatchLongestWords(dtfi.internalGetLeapYearMonthNames(), ref maxMatchStrLen);
+                    // We found a longer match in the leap year month name.  Use this as the result.
+                    // The result from MatchLongestWords is 0 ~ length of word array.
+                    // So we increment the result by one to become the month value.
+                    if (tempResult >= 0)
+                    {
+                        result = tempResult + 1;
+                    }
+                }
+            }
+            if (result > 0)
+            {
+                str.Index += (maxMatchStrLen - 1);
+                return (true);
+            }
+            return false;
+        }
+
+        /*=================================MatchMonthName==================================
+        **Action: Parse the month name from string starting at str.Index.
+        **Returns: A value from 1 to 12 indicating the first month to the twelveth month.
+        **Arguments:    str: a __DTString.  The parsing will start from the
+        **              next character after str.Index.
+        **Exceptions: FormatException if a month name can not be found.
+        ==============================================================================*/
+
+        private static bool MatchMonthName(ref __DTString str, DateTimeFormatInfo dtfi, ref int result)
+        {
+            int maxMatchStrLen = 0;
+            result = -1;
+            if (str.GetNext())
+            {
+                //
+                // Scan the month names (note that some calendars has 13 months) and find
+                // the matching month name which has the max string length.
+                // We need to do this because some cultures (e.g. "vi-VN") which have
+                // month names with the same prefix.
+                //
+                int monthsInYear = (dtfi.GetMonthName(13).Length == 0 ? 12 : 13);
+                for (int i = 1; i <= monthsInYear; i++)
+                {
+                    String searchStr = dtfi.GetMonthName(i);
+                    int matchStrLen = searchStr.Length;
+                    if (dtfi.HasSpacesInMonthNames
+                            ? str.MatchSpecifiedWords(searchStr, false, ref matchStrLen)
+                            : str.MatchSpecifiedWord(searchStr))
+                    {
+                        if (matchStrLen > maxMatchStrLen)
+                        {
+                            maxMatchStrLen = matchStrLen;
+                            result = i;
+                        }
+                    }
+                }
+
+                // Search genitive form.
+                if ((dtfi.FormatFlags & DateTimeFormatFlags.UseGenitiveMonth) != 0)
+                {
+                    int tempResult = str.MatchLongestWords(dtfi.MonthGenitiveNames, ref maxMatchStrLen);
+                    // We found a longer match in the genitive month name.  Use this as the result.
+                    // The result from MatchLongestWords is 0 ~ length of word array.
+                    // So we increment the result by one to become the month value.
+                    if (tempResult >= 0)
+                    {
+                        result = tempResult + 1;
+                    }
+                }
+
+                // Search leap year form.
+                if ((dtfi.FormatFlags & DateTimeFormatFlags.UseLeapYearMonth) != 0)
+                {
+                    int tempResult = str.MatchLongestWords(dtfi.internalGetLeapYearMonthNames(), ref maxMatchStrLen);
+                    // We found a longer match in the leap year month name.  Use this as the result.
+                    // The result from MatchLongestWords is 0 ~ length of word array.
+                    // So we increment the result by one to become the month value.
+                    if (tempResult >= 0)
+                    {
+                        result = tempResult + 1;
+                    }
+                }
+            }
+
+            if (result > 0)
+            {
+                str.Index += (maxMatchStrLen - 1);
+                return (true);
+            }
+            return false;
+        }
+
+        /*=================================MatchAbbreviatedDayName==================================
+        **Action: Parse the abbreviated day of week name from string starting at str.Index.
+        **Returns: A value from 0 to 6 indicating Sunday to Saturday.
+        **Arguments:    str: a __DTString.  The parsing will start from the
+        **              next character after str.Index.
+        **Exceptions: FormatException if a abbreviated day of week name can not be found.
+        ==============================================================================*/
+
+        private static bool MatchAbbreviatedDayName(ref __DTString str, DateTimeFormatInfo dtfi, ref int result)
+        {
+            int maxMatchStrLen = 0;
+            result = -1;
+            if (str.GetNext())
+            {
+                for (DayOfWeek i = DayOfWeek.Sunday; i <= DayOfWeek.Saturday; i++)
+                {
+                    String searchStr = dtfi.GetAbbreviatedDayName(i);
+                    int matchStrLen = searchStr.Length;
+                    if (dtfi.HasSpacesInDayNames
+                            ? str.MatchSpecifiedWords(searchStr, false, ref matchStrLen)
+                            : str.MatchSpecifiedWord(searchStr))
+                    {
+                        if (matchStrLen > maxMatchStrLen)
+                        {
+                            maxMatchStrLen = matchStrLen;
+                            result = (int)i;
+                        }
+                    }
+                }
+            }
+            if (result >= 0)
+            {
+                str.Index += maxMatchStrLen - 1;
+                return (true);
+            }
+            return false;
+        }
+
+        /*=================================MatchDayName==================================
+        **Action: Parse the day of week name from string starting at str.Index.
+        **Returns: A value from 0 to 6 indicating Sunday to Saturday.
+        **Arguments:    str: a __DTString.  The parsing will start from the
+        **              next character after str.Index.
+        **Exceptions: FormatException if a day of week name can not be found.
+        ==============================================================================*/
+
+        private static bool MatchDayName(ref __DTString str, DateTimeFormatInfo dtfi, ref int result)
+        {
+            // Turkish (tr-TR) got day names with the same prefix.
+            int maxMatchStrLen = 0;
+            result = -1;
+            if (str.GetNext())
+            {
+                for (DayOfWeek i = DayOfWeek.Sunday; i <= DayOfWeek.Saturday; i++)
+                {
+                    String searchStr = dtfi.GetDayName(i);
+                    int matchStrLen = searchStr.Length;
+                    if (dtfi.HasSpacesInDayNames
+                            ? str.MatchSpecifiedWords(searchStr, false, ref matchStrLen)
+                            : str.MatchSpecifiedWord(searchStr))
+                    {
+                        if (matchStrLen > maxMatchStrLen)
+                        {
+                            maxMatchStrLen = matchStrLen;
+                            result = (int)i;
+                        }
+                    }
+                }
+            }
+            if (result >= 0)
+            {
+                str.Index += maxMatchStrLen - 1;
+                return (true);
+            }
+            return false;
+        }
+
+        /*=================================MatchEraName==================================
+        **Action: Parse era name from string starting at str.Index.
+        **Returns: An era value.
+        **Arguments:    str: a __DTString.  The parsing will start from the
+        **              next character after str.Index.
+        **Exceptions: FormatException if an era name can not be found.
+        ==============================================================================*/
+
+        private static bool MatchEraName(ref __DTString str, DateTimeFormatInfo dtfi, ref int result)
+        {
+            if (str.GetNext())
+            {
+                int[] eras = dtfi.Calendar.Eras;
+
+                if (eras != null)
+                {
+                    for (int i = 0; i < eras.Length; i++)
+                    {
+                        String searchStr = dtfi.GetEraName(eras[i]);
+                        if (str.MatchSpecifiedWord(searchStr))
+                        {
+                            str.Index += (searchStr.Length - 1);
+                            result = eras[i];
+                            return (true);
+                        }
+                        searchStr = dtfi.GetAbbreviatedEraName(eras[i]);
+                        if (str.MatchSpecifiedWord(searchStr))
+                        {
+                            str.Index += (searchStr.Length - 1);
+                            result = eras[i];
+                            return (true);
+                        }
+                    }
+                }
+            }
+            return false;
+        }
+
+        /*=================================MatchTimeMark==================================
+        **Action: Parse the time mark (AM/PM) from string starting at str.Index.
+        **Returns: TM_AM or TM_PM.
+        **Arguments:    str: a __DTString.  The parsing will start from the
+        **              next character after str.Index.
+        **Exceptions: FormatException if a time mark can not be found.
+        ==============================================================================*/
+
+        private static bool MatchTimeMark(ref __DTString str, DateTimeFormatInfo dtfi, ref TM result)
+        {
+            result = TM.NotSet;
+            // In some cultures have empty strings in AM/PM mark. E.g. af-ZA (0x0436), the AM mark is "", and PM mark is "nm".
+            if (dtfi.AMDesignator.Length == 0)
+            {
+                result = TM.AM;
+            }
+            if (dtfi.PMDesignator.Length == 0)
+            {
+                result = TM.PM;
+            }
+
+            if (str.GetNext())
+            {
+                String searchStr = dtfi.AMDesignator;
+                if (searchStr.Length > 0)
+                {
+                    if (str.MatchSpecifiedWord(searchStr))
+                    {
+                        // Found an AM timemark with length > 0.
+                        str.Index += (searchStr.Length - 1);
+                        result = TM.AM;
+                        return (true);
+                    }
+                }
+                searchStr = dtfi.PMDesignator;
+                if (searchStr.Length > 0)
+                {
+                    if (str.MatchSpecifiedWord(searchStr))
+                    {
+                        // Found a PM timemark with length > 0.
+                        str.Index += (searchStr.Length - 1);
+                        result = TM.PM;
+                        return (true);
+                    }
+                }
+                str.Index--; // Undo the GetNext call.
+            }
+            if (result != TM.NotSet)
+            {
+                // If one of the AM/PM marks is empty string, return the result.
+                return (true);
+            }
+            return false;
+        }
+
+        /*=================================MatchAbbreviatedTimeMark==================================
+        **Action: Parse the abbreviated time mark (AM/PM) from string starting at str.Index.
+        **Returns: TM_AM or TM_PM.
+        **Arguments:    str: a __DTString.  The parsing will start from the
+        **              next character after str.Index.
+        **Exceptions: FormatException if a abbreviated time mark can not be found.
+        ==============================================================================*/
+
+        private static bool MatchAbbreviatedTimeMark(ref __DTString str, DateTimeFormatInfo dtfi, ref TM result)
+        {
+            // NOTENOTE : the assumption here is that abbreviated time mark is the first
+            // character of the AM/PM designator.  If this invariant changes, we have to
+            // change the code below.
+            if (str.GetNext())
+            {
+                string amDesignator = dtfi.AMDesignator;
+                if (amDesignator.Length > 0 && str.GetChar() == amDesignator[0])
+                {
+                    result = TM.AM;
+                    return true;
+                }
+
+                string pmDesignator = dtfi.PMDesignator;
+                if (pmDesignator.Length > 0 && str.GetChar() == pmDesignator[0])
+                {
+                    result = TM.PM;
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        /*=================================CheckNewValue==================================
+        **Action: Check if currentValue is initialized.  If not, return the newValue.
+        **        If yes, check if the current value is equal to newValue.  Return false
+        **        if they are not equal.  This is used to check the case like "d" and "dd" are both
+        **        used to format a string.
+        **Returns: the correct value for currentValue.
+        **Arguments:
+        **Exceptions:
+        ==============================================================================*/
+
+        private static bool CheckNewValue(ref int currentValue, int newValue, char patternChar, ref DateTimeResult result)
+        {
+            if (currentValue == -1)
+            {
+                currentValue = newValue;
+                return (true);
+            }
+            else
+            {
+                if (newValue != currentValue)
+                {
+                    result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_RepeatDateTimePattern), patternChar);
+                    return (false);
+                }
+            }
+            return (true);
+        }
+
+        private static DateTime GetDateTimeNow(ref DateTimeResult result, ref DateTimeStyles styles)
+        {
+            if ((result.flags & ParseFlags.CaptureOffset) != 0)
+            {
+                if ((result.flags & ParseFlags.TimeZoneUsed) != 0)
+                {
+                    // use the supplied offset to calculate 'Now'
+                    return new DateTime(DateTime.UtcNow.Ticks + result.timeZoneOffset.Ticks, DateTimeKind.Unspecified);
+                }
+                else if ((styles & DateTimeStyles.AssumeUniversal) != 0)
+                {
+                    // assume the offset is Utc
+                    return DateTime.UtcNow;
+                }
+            }
+
+            // assume the offset is Local
+            return DateTime.Now;
+        }
+
+        private static bool CheckDefaultDateTime(ref DateTimeResult result, ref Calendar cal, DateTimeStyles styles)
+        {
+            if ((result.flags & ParseFlags.CaptureOffset) != 0)
+            {
+                // DateTimeOffset.Parse should allow dates without a year, but only if there is also no time zone marker;
+                // e.g. "May 1 5pm" is OK, but "May 1 5pm -08:30" is not.  This is somewhat pragmatic, since we would
+                // have to rearchitect parsing completely to allow this one case to correctly handle things like leap
+                // years and leap months.  Is is an extremely corner case, and DateTime is basically incorrect in that
+                // case today.
+                //
+                // values like "11:00Z" or "11:00 -3:00" are also acceptable
+                //
+                // if ((month or day is set) and (year is not set and time zone is set))
+                //
+                if (((result.Month != -1) || (result.Day != -1))
+                    && ((result.Year == -1 || ((result.flags & ParseFlags.YearDefault) != 0)) && (result.flags & ParseFlags.TimeZoneUsed) != 0))
+                {
+                    result.SetFailure(ParseFailureKind.FormatWithOriginalDateTime, nameof(SR.Format_MissingIncompleteDate));
+                    return false;
+                }
+            }
+
+
+            if ((result.Year == -1) || (result.Month == -1) || (result.Day == -1))
+            {
+                /*
+                The following table describes the behaviors of getting the default value
+                when a certain year/month/day values are missing.
+
+                An "X" means that the value exists.  And "--" means that value is missing.
+
+                Year    Month   Day =>  ResultYear  ResultMonth     ResultDay       Note
+
+                X       X       X       Parsed year Parsed month    Parsed day
+                X       X       --      Parsed Year Parsed month    First day       If we have year and month, assume the first day of that month.
+                X       --      X       Parsed year First month     Parsed day      If the month is missing, assume first month of that year.
+                X       --      --      Parsed year First month     First day       If we have only the year, assume the first day of that year.
+
+                --      X       X       CurrentYear Parsed month    Parsed day      If the year is missing, assume the current year.
+                --      X       --      CurrentYear Parsed month    First day       If we have only a month value, assume the current year and current day.
+                --      --      X       CurrentYear First month     Parsed day      If we have only a day value, assume current year and first month.
+                --      --      --      CurrentYear Current month   Current day     So this means that if the date string only contains time, you will get current date.
+
+                */
+
+                DateTime now = GetDateTimeNow(ref result, ref styles);
+                if (result.Month == -1 && result.Day == -1)
+                {
+                    if (result.Year == -1)
+                    {
+                        if ((styles & DateTimeStyles.NoCurrentDateDefault) != 0)
+                        {
+                            // If there is no year/month/day values, and NoCurrentDateDefault flag is used,
+                            // set the year/month/day value to the beginning year/month/day of DateTime().
+                            // Note we should be using Gregorian for the year/month/day.
+                            cal = GregorianCalendar.GetDefaultInstance();
+                            result.Year = result.Month = result.Day = 1;
+                        }
+                        else
+                        {
+                            // Year/Month/Day are all missing.
+                            result.Year = cal.GetYear(now);
+                            result.Month = cal.GetMonth(now);
+                            result.Day = cal.GetDayOfMonth(now);
+                        }
+                    }
+                    else
+                    {
+                        // Month/Day are both missing.
+                        result.Month = 1;
+                        result.Day = 1;
+                    }
+                }
+                else
+                {
+                    if (result.Year == -1)
+                    {
+                        result.Year = cal.GetYear(now);
+                    }
+                    if (result.Month == -1)
+                    {
+                        result.Month = 1;
+                    }
+                    if (result.Day == -1)
+                    {
+                        result.Day = 1;
+                    }
+                }
+            }
+            // Set Hour/Minute/Second to zero if these value are not in str.
+            if (result.Hour == -1) result.Hour = 0;
+            if (result.Minute == -1) result.Minute = 0;
+            if (result.Second == -1) result.Second = 0;
+            if (result.era == -1) result.era = Calendar.CurrentEra;
+            return true;
+        }
+
+        // Expand a pre-defined format string (like "D" for long date) to the real format that
+        // we are going to use in the date time parsing.
+        // This method also set the dtfi according/parseInfo to some special pre-defined
+        // formats.
+        //
+        private static String ExpandPredefinedFormat(ReadOnlySpan<char> format, ref DateTimeFormatInfo dtfi, ref ParsingInfo parseInfo, ref DateTimeResult result)
+        {
+            //
+            // Check the format to see if we need to override the dtfi to be InvariantInfo,
+            // and see if we need to set up the userUniversalTime flag.
+            //
+            switch (format[0])
+            {
+                case 'o':
+                case 'O':       // Round Trip Format
+                    parseInfo.calendar = GregorianCalendar.GetDefaultInstance();
+                    dtfi = DateTimeFormatInfo.InvariantInfo;
+                    break;
+                case 'r':
+                case 'R':       // RFC 1123 Standard.  (in Universal time)
+                    parseInfo.calendar = GregorianCalendar.GetDefaultInstance();
+                    dtfi = DateTimeFormatInfo.InvariantInfo;
+
+                    if ((result.flags & ParseFlags.CaptureOffset) != 0)
+                    {
+                        result.flags |= ParseFlags.Rfc1123Pattern;
+                    }
+                    break;
+                case 's':       // Sortable format (in local time)
+                    dtfi = DateTimeFormatInfo.InvariantInfo;
+                    parseInfo.calendar = GregorianCalendar.GetDefaultInstance();
+                    break;
+                case 'u':       // Universal time format in sortable format.
+                    parseInfo.calendar = GregorianCalendar.GetDefaultInstance();
+                    dtfi = DateTimeFormatInfo.InvariantInfo;
+
+                    if ((result.flags & ParseFlags.CaptureOffset) != 0)
+                    {
+                        result.flags |= ParseFlags.UtcSortPattern;
+                    }
+                    break;
+                case 'U':       // Universal time format with culture-dependent format.
+                    parseInfo.calendar = GregorianCalendar.GetDefaultInstance();
+                    result.flags |= ParseFlags.TimeZoneUsed;
+                    result.timeZoneOffset = new TimeSpan(0);
+                    result.flags |= ParseFlags.TimeZoneUtc;
+                    if (dtfi.Calendar.GetType() != typeof(GregorianCalendar))
+                    {
+                        dtfi = (DateTimeFormatInfo)dtfi.Clone();
+                        dtfi.Calendar = GregorianCalendar.GetDefaultInstance();
+                    }
+                    break;
+            }
+
+            //
+            // Expand the pre-defined format character to the real format from DateTimeFormatInfo.
+            //
+            return (DateTimeFormat.GetRealFormat(format, dtfi));
+        }
+
+
+
+
+
+        // Given a specified format character, parse and update the parsing result.
+        //
+        private static bool ParseByFormat(
+            ref __DTString str,
+            ref __DTString format,
+            ref ParsingInfo parseInfo,
+            DateTimeFormatInfo dtfi,
+            ref DateTimeResult result)
+        {
+            int tokenLen = 0;
+            int tempYear = 0, tempMonth = 0, tempDay = 0, tempDayOfWeek = 0, tempHour = 0, tempMinute = 0, tempSecond = 0;
+            double tempFraction = 0;
+            TM tempTimeMark = 0;
+
+            char ch = format.GetChar();
+
+            switch (ch)
+            {
+                case 'y':
+                    tokenLen = format.GetRepeatCount();
+                    bool parseResult;
+                    if (dtfi.HasForceTwoDigitYears)
+                    {
+                        parseResult = ParseDigits(ref str, 1, 4, out tempYear);
+                    }
+                    else
+                    {
+                        if (tokenLen <= 2)
+                        {
+                            parseInfo.fUseTwoDigitYear = true;
+                        }
+                        parseResult = ParseDigits(ref str, tokenLen, out tempYear);
+                    }
+                    if (!parseResult && parseInfo.fCustomNumberParser)
+                    {
+                        parseResult = parseInfo.parseNumberDelegate(ref str, tokenLen, out tempYear);
+                    }
+                    if (!parseResult)
+                    {
+                        result.SetBadDateTimeFailure();
+                        return (false);
+                    }
+                    if (!CheckNewValue(ref result.Year, tempYear, ch, ref result))
+                    {
+                        return (false);
+                    }
+                    break;
+                case 'M':
+                    tokenLen = format.GetRepeatCount();
+                    if (tokenLen <= 2)
+                    {
+                        if (!ParseDigits(ref str, tokenLen, out tempMonth))
+                        {
+                            if (!parseInfo.fCustomNumberParser ||
+                                !parseInfo.parseNumberDelegate(ref str, tokenLen, out tempMonth))
+                            {
+                                result.SetBadDateTimeFailure();
+                                return (false);
+                            }
+                        }
+                    }
+                    else
+                    {
+                        if (tokenLen == 3)
+                        {
+                            if (!MatchAbbreviatedMonthName(ref str, dtfi, ref tempMonth))
+                            {
+                                result.SetBadDateTimeFailure();
+                                return (false);
+                            }
+                        }
+                        else
+                        {
+                            if (!MatchMonthName(ref str, dtfi, ref tempMonth))
+                            {
+                                result.SetBadDateTimeFailure();
+                                return (false);
+                            }
+                        }
+                        result.flags |= ParseFlags.ParsedMonthName;
+                    }
+                    if (!CheckNewValue(ref result.Month, tempMonth, ch, ref result))
+                    {
+                        return (false);
+                    }
+                    break;
+                case 'd':
+                    // Day & Day of week
+                    tokenLen = format.GetRepeatCount();
+                    if (tokenLen <= 2)
+                    {
+                        // "d" & "dd"
+
+                        if (!ParseDigits(ref str, tokenLen, out tempDay))
+                        {
+                            if (!parseInfo.fCustomNumberParser ||
+                                !parseInfo.parseNumberDelegate(ref str, tokenLen, out tempDay))
+                            {
+                                result.SetBadDateTimeFailure();
+                                return (false);
+                            }
+                        }
+                        if (!CheckNewValue(ref result.Day, tempDay, ch, ref result))
+                        {
+                            return (false);
+                        }
+                    }
+                    else
+                    {
+                        if (tokenLen == 3)
+                        {
+                            // "ddd"
+                            if (!MatchAbbreviatedDayName(ref str, dtfi, ref tempDayOfWeek))
+                            {
+                                result.SetBadDateTimeFailure();
+                                return (false);
+                            }
+                        }
+                        else
+                        {
+                            // "dddd*"
+                            if (!MatchDayName(ref str, dtfi, ref tempDayOfWeek))
+                            {
+                                result.SetBadDateTimeFailure();
+                                return (false);
+                            }
+                        }
+                        if (!CheckNewValue(ref parseInfo.dayOfWeek, tempDayOfWeek, ch, ref result))
+                        {
+                            return (false);
+                        }
+                    }
+                    break;
+                case 'g':
+                    tokenLen = format.GetRepeatCount();
+                    // Put the era value in result.era.
+                    if (!MatchEraName(ref str, dtfi, ref result.era))
+                    {
+                        result.SetBadDateTimeFailure();
+                        return (false);
+                    }
+                    break;
+                case 'h':
+                    parseInfo.fUseHour12 = true;
+                    tokenLen = format.GetRepeatCount();
+                    if (!ParseDigits(ref str, (tokenLen < 2 ? 1 : 2), out tempHour))
+                    {
+                        result.SetBadDateTimeFailure();
+                        return (false);
+                    }
+                    if (!CheckNewValue(ref result.Hour, tempHour, ch, ref result))
+                    {
+                        return (false);
+                    }
+                    break;
+                case 'H':
+                    tokenLen = format.GetRepeatCount();
+                    if (!ParseDigits(ref str, (tokenLen < 2 ? 1 : 2), out tempHour))
+                    {
+                        result.SetBadDateTimeFailure();
+                        return (false);
+                    }
+                    if (!CheckNewValue(ref result.Hour, tempHour, ch, ref result))
+                    {
+                        return (false);
+                    }
+                    break;
+                case 'm':
+                    tokenLen = format.GetRepeatCount();
+                    if (!ParseDigits(ref str, (tokenLen < 2 ? 1 : 2), out tempMinute))
+                    {
+                        result.SetBadDateTimeFailure();
+                        return (false);
+                    }
+                    if (!CheckNewValue(ref result.Minute, tempMinute, ch, ref result))
+                    {
+                        return (false);
+                    }
+                    break;
+                case 's':
+                    tokenLen = format.GetRepeatCount();
+                    if (!ParseDigits(ref str, (tokenLen < 2 ? 1 : 2), out tempSecond))
+                    {
+                        result.SetBadDateTimeFailure();
+                        return (false);
+                    }
+                    if (!CheckNewValue(ref result.Second, tempSecond, ch, ref result))
+                    {
+                        return (false);
+                    }
+                    break;
+                case 'f':
+                case 'F':
+                    tokenLen = format.GetRepeatCount();
+                    if (tokenLen <= DateTimeFormat.MaxSecondsFractionDigits)
+                    {
+                        if (!ParseFractionExact(ref str, tokenLen, ref tempFraction))
+                        {
+                            if (ch == 'f')
+                            {
+                                result.SetBadDateTimeFailure();
+                                return (false);
+                            }
+                        }
+                        if (result.fraction < 0)
+                        {
+                            result.fraction = tempFraction;
+                        }
+                        else
+                        {
+                            if (tempFraction != result.fraction)
+                            {
+                                result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_RepeatDateTimePattern), ch);
+                                return (false);
+                            }
+                        }
+                    }
+                    else
+                    {
+                        result.SetBadDateTimeFailure();
+                        return (false);
+                    }
+                    break;
+                case 't':
+                    // AM/PM designator
+                    tokenLen = format.GetRepeatCount();
+                    if (tokenLen == 1)
+                    {
+                        if (!MatchAbbreviatedTimeMark(ref str, dtfi, ref tempTimeMark))
+                        {
+                            result.SetBadDateTimeFailure();
+                            return (false);
+                        }
+                    }
+                    else
+                    {
+                        if (!MatchTimeMark(ref str, dtfi, ref tempTimeMark))
+                        {
+                            result.SetBadDateTimeFailure();
+                            return (false);
+                        }
+                    }
+
+                    if (parseInfo.timeMark == TM.NotSet)
+                    {
+                        parseInfo.timeMark = tempTimeMark;
+                    }
+                    else
+                    {
+                        if (parseInfo.timeMark != tempTimeMark)
+                        {
+                            result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_RepeatDateTimePattern), ch);
+                            return (false);
+                        }
+                    }
+                    break;
+                case 'z':
+                    // timezone offset
+                    tokenLen = format.GetRepeatCount();
+                    {
+                        TimeSpan tempTimeZoneOffset = new TimeSpan(0);
+                        if (!ParseTimeZoneOffset(ref str, tokenLen, ref tempTimeZoneOffset))
+                        {
+                            result.SetBadDateTimeFailure();
+                            return (false);
+                        }
+                        if ((result.flags & ParseFlags.TimeZoneUsed) != 0 && tempTimeZoneOffset != result.timeZoneOffset)
+                        {
+                            result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_RepeatDateTimePattern), 'z');
+                            return (false);
+                        }
+                        result.timeZoneOffset = tempTimeZoneOffset;
+                        result.flags |= ParseFlags.TimeZoneUsed;
+                    }
+                    break;
+                case 'Z':
+                    if ((result.flags & ParseFlags.TimeZoneUsed) != 0 && result.timeZoneOffset != TimeSpan.Zero)
+                    {
+                        result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_RepeatDateTimePattern), 'Z');
+                        return (false);
+                    }
+
+                    result.flags |= ParseFlags.TimeZoneUsed;
+                    result.timeZoneOffset = new TimeSpan(0);
+                    result.flags |= ParseFlags.TimeZoneUtc;
+
+                    // The updating of the indexes is to reflect that ParseExact MatchXXX methods assume that
+                    // they need to increment the index and Parse GetXXX do not. Since we are calling a Parse
+                    // method from inside ParseExact we need to adjust this. Long term, we should try to
+                    // eliminate this discrepancy.
+                    str.Index++;
+                    if (!GetTimeZoneName(ref str))
+                    {
+                        result.SetBadDateTimeFailure();
+                        return false;
+                    }
+                    str.Index--;
+                    break;
+                case 'K':
+                    // This should parse either as a blank, the 'Z' character or a local offset like "-07:00"
+                    if (str.Match('Z'))
+                    {
+                        if ((result.flags & ParseFlags.TimeZoneUsed) != 0 && result.timeZoneOffset != TimeSpan.Zero)
+                        {
+                            result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_RepeatDateTimePattern), 'K');
+                            return (false);
+                        }
+
+                        result.flags |= ParseFlags.TimeZoneUsed;
+                        result.timeZoneOffset = new TimeSpan(0);
+                        result.flags |= ParseFlags.TimeZoneUtc;
+                    }
+                    else if (str.Match('+') || str.Match('-'))
+                    {
+                        str.Index--; // Put the character back for the parser
+                        TimeSpan tempTimeZoneOffset = new TimeSpan(0);
+                        if (!ParseTimeZoneOffset(ref str, 3, ref tempTimeZoneOffset))
+                        {
+                            result.SetBadDateTimeFailure();
+                            return (false);
+                        }
+                        if ((result.flags & ParseFlags.TimeZoneUsed) != 0 && tempTimeZoneOffset != result.timeZoneOffset)
+                        {
+                            result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_RepeatDateTimePattern), 'K');
+                            return (false);
+                        }
+                        result.timeZoneOffset = tempTimeZoneOffset;
+                        result.flags |= ParseFlags.TimeZoneUsed;
+                    }
+                    // Otherwise it is unspecified and we consume no characters
+                    break;
+                case ':':
+                    // We match the separator in time pattern with the character in the time string if both equal to ':' or the date separator is matching the characters in the date string
+                    // We have to exclude the case when the time separator is more than one character and starts with ':' something like "::" for instance.
+                    if (((dtfi.TimeSeparator.Length > 1 && dtfi.TimeSeparator[0] == ':') || !str.Match(':')) &&
+                        !str.Match(dtfi.TimeSeparator))
+                    {
+                        // A time separator is expected.
+                        result.SetBadDateTimeFailure();
+                        return false;
+                    }
+                    break;
+                case '/':
+                    // We match the separator in date pattern with the character in the date string if both equal to '/' or the date separator is matching the characters in the date string
+                    // We have to exclude the case when the date separator is more than one character and starts with '/' something like "//" for instance.
+                    if (((dtfi.DateSeparator.Length > 1 && dtfi.DateSeparator[0] == '/') || !str.Match('/')) &&
+                        !str.Match(dtfi.DateSeparator))
+                    {
+                        // A date separator is expected.
+                        result.SetBadDateTimeFailure();
+                        return false;
+                    }
+                    break;
+                case '\"':
+                case '\'':
+                    StringBuilder enquotedString = StringBuilderCache.Acquire();
+                    // Use ParseQuoteString so that we can handle escape characters within the quoted string.
+                    if (!TryParseQuoteString(format.Value, format.Index, enquotedString, out tokenLen))
+                    {
+                        result.SetFailure(ParseFailureKind.FormatWithParameter, nameof(SR.Format_BadQuote), ch);
+                        StringBuilderCache.Release(enquotedString);
+                        return (false);
+                    }
+                    format.Index += tokenLen - 1;
+
+                    // Some cultures uses space in the quoted string.  E.g. Spanish has long date format as:
+                    // "dddd, dd' de 'MMMM' de 'yyyy".  When inner spaces flag is set, we should skip whitespaces if there is space
+                    // in the quoted string.
+                    String quotedStr = StringBuilderCache.GetStringAndRelease(enquotedString);
+
+                    for (int i = 0; i < quotedStr.Length; i++)
+                    {
+                        if (quotedStr[i] == ' ' && parseInfo.fAllowInnerWhite)
+                        {
+                            str.SkipWhiteSpaces();
+                        }
+                        else if (!str.Match(quotedStr[i]))
+                        {
+                            // Can not find the matching quoted string.
+                            result.SetBadDateTimeFailure();
+                            return false;
+                        }
+                    }
+
+                    // The "r" and "u" formats incorrectly quoted 'GMT' and 'Z', respectively.  We cannot
+                    // correct this mistake for DateTime.ParseExact for compatibility reasons, but we can
+                    // fix it for DateTimeOffset.ParseExact as DateTimeOffset has not been publically released
+                    // with this issue.
+                    if ((result.flags & ParseFlags.CaptureOffset) != 0)
+                    {
+                        if ((result.flags & ParseFlags.Rfc1123Pattern) != 0 && quotedStr == GMTName)
+                        {
+                            result.flags |= ParseFlags.TimeZoneUsed;
+                            result.timeZoneOffset = TimeSpan.Zero;
+                        }
+                        else if ((result.flags & ParseFlags.UtcSortPattern) != 0 && quotedStr == ZuluName)
+                        {
+                            result.flags |= ParseFlags.TimeZoneUsed;
+                            result.timeZoneOffset = TimeSpan.Zero;
+                        }
+                    }
+
+                    break;
+                case '%':
+                    // Skip this so we can get to the next pattern character.
+                    // Used in case like "%d", "%y"
+
+                    // Make sure the next character is not a '%' again.
+                    if (format.Index >= format.Value.Length - 1 || format.Value[format.Index + 1] == '%')
+                    {
+                        result.SetBadFormatSpecifierFailure(format.Value);
+                        return false;
+                    }
+                    break;
+                case '\\':
+                    // Escape character. For example, "\d".
+                    // Get the next character in format, and see if we can
+                    // find a match in str.
+                    if (format.GetNext())
+                    {
+                        if (!str.Match(format.GetChar()))
+                        {
+                            // Can not find a match for the escaped character.
+                            result.SetBadDateTimeFailure();
+                            return false;
+                        }
+                    }
+                    else
+                    {
+                        result.SetBadFormatSpecifierFailure(format.Value);
+                        return false;
+                    }
+                    break;
+                case '.':
+                    if (!str.Match(ch))
+                    {
+                        if (format.GetNext())
+                        {
+                            // If we encounter the pattern ".F", and the dot is not present, it is an optional
+                            // second fraction and we can skip this format.
+                            if (format.Match('F'))
+                            {
+                                format.GetRepeatCount();
+                                break;
+                            }
+                        }
+                        result.SetBadDateTimeFailure();
+                        return false;
+                    }
+                    break;
+                default:
+                    if (ch == ' ')
+                    {
+                        if (parseInfo.fAllowInnerWhite)
+                        {
+                            // Skip whitespaces if AllowInnerWhite.
+                            // Do nothing here.
+                        }
+                        else
+                        {
+                            if (!str.Match(ch))
+                            {
+                                // If the space does not match, and trailing space is allowed, we do
+                                // one more step to see if the next format character can lead to
+                                // successful parsing.
+                                // This is used to deal with special case that a empty string can match
+                                // a specific pattern.
+                                // The example here is af-ZA, which has a time format like "hh:mm:ss tt".  However,
+                                // its AM symbol is "" (empty string).  If fAllowTrailingWhite is used, and time is in
+                                // the AM, we will trim the whitespaces at the end, which will lead to a failure
+                                // when we are trying to match the space before "tt".
+                                if (parseInfo.fAllowTrailingWhite)
+                                {
+                                    if (format.GetNext())
+                                    {
+                                        if (ParseByFormat(ref str, ref format, ref parseInfo, dtfi, ref result))
+                                        {
+                                            return (true);
+                                        }
+                                    }
+                                }
+                                result.SetBadDateTimeFailure();
+                                return false;
+                            }
+                            // Found a macth.
+                        }
+                    }
+                    else
+                    {
+                        if (format.MatchSpecifiedWord(GMTName))
+                        {
+                            format.Index += (GMTName.Length - 1);
+                            // Found GMT string in format.  This means the DateTime string
+                            // is in GMT timezone.
+                            result.flags |= ParseFlags.TimeZoneUsed;
+                            result.timeZoneOffset = TimeSpan.Zero;
+                            if (!str.Match(GMTName))
+                            {
+                                result.SetBadDateTimeFailure();
+                                return false;
+                            }
+                        }
+                        else if (!str.Match(ch))
+                        {
+                            // ch is expected.
+                            result.SetBadDateTimeFailure();
+                            return false;
+                        }
+                    }
+                    break;
+            } // switch
+            return (true);
+        }
+
+        //
+        // The pos should point to a quote character. This method will
+        // get the string enclosed by the quote character.
+        //
+        internal static bool TryParseQuoteString(ReadOnlySpan<char> format, int pos, StringBuilder result, out int returnValue)
+        {
+            //
+            // NOTE : pos will be the index of the quote character in the 'format' string.
+            //
+            returnValue = 0;
+            int formatLen = format.Length;
+            int beginPos = pos;
+            char quoteChar = format[pos++]; // Get the character used to quote the following string.
+
+            bool foundQuote = false;
+            while (pos < formatLen)
+            {
+                char ch = format[pos++];
+                if (ch == quoteChar)
+                {
+                    foundQuote = true;
+                    break;
+                }
+                else if (ch == '\\')
+                {
+                    // The following are used to support escaped character.
+                    // Escaped character is also supported in the quoted string.
+                    // Therefore, someone can use a format like "'minute:' mm\"" to display:
+                    //  minute: 45"
+                    // because the second double quote is escaped.
+                    if (pos < formatLen)
+                    {
+                        result.Append(format[pos++]);
+                    }
+                    else
+                    {
+                        //
+                        // This means that '\' is at the end of the formatting string.
+                        //
+                        return false;
+                    }
+                }
+                else
+                {
+                    result.Append(ch);
+                }
+            }
+
+            if (!foundQuote)
+            {
+                // Here we can't find the matching quote.
+                return false;
+            }
+
+            //
+            // Return the character count including the begin/end quote characters and enclosed string.
+            //
+            returnValue = (pos - beginPos);
+            return true;
+        }
+
+
+
+
+        /*=================================DoStrictParse==================================
+        **Action: Do DateTime parsing using the format in formatParam.
+        **Returns: The parsed DateTime.
+        **Arguments:
+        **Exceptions:
+        **
+        **Notes:
+        **  When the following general formats are used, InvariantInfo is used in dtfi:
+        **      'r', 'R', 's'.
+        **  When the following general formats are used, the time is assumed to be in Universal time.
+        **
+        **Limitations:
+        **  Only GregarianCalendar is supported for now.
+        **  Only support GMT timezone.
+        ==============================================================================*/
+
+        private static bool DoStrictParse(
+            ReadOnlySpan<char> s,
+            ReadOnlySpan<char> formatParam,
+            DateTimeStyles styles,
+            DateTimeFormatInfo dtfi,
+            ref DateTimeResult result)
+        {
+            ParsingInfo parseInfo = new ParsingInfo();
+            parseInfo.Init();
+
+            parseInfo.calendar = dtfi.Calendar;
+            parseInfo.fAllowInnerWhite = ((styles & DateTimeStyles.AllowInnerWhite) != 0);
+            parseInfo.fAllowTrailingWhite = ((styles & DateTimeStyles.AllowTrailingWhite) != 0);
+
+            if (formatParam.Length == 1)
+            {
+                if (((result.flags & ParseFlags.CaptureOffset) != 0) && formatParam[0] == 'U')
+                {
+                    // The 'U' format is not allowed for DateTimeOffset
+                    result.SetBadFormatSpecifierFailure(formatParam);
+                    return false;
+                }
+                formatParam = ExpandPredefinedFormat(formatParam, ref dtfi, ref parseInfo, ref result);
+            }
+
+            bool bTimeOnly = false;
+            result.calendar = parseInfo.calendar;
+
+            if (parseInfo.calendar.ID == CalendarId.HEBREW)
+            {
+                parseInfo.parseNumberDelegate = m_hebrewNumberParser;
+                parseInfo.fCustomNumberParser = true;
+            }
+
+            // Reset these values to negative one so that we could throw exception
+            // if we have parsed every item twice.
+            result.Hour = result.Minute = result.Second = -1;
+
+            __DTString format = new __DTString(formatParam, dtfi, false);
+            __DTString str = new __DTString(s, dtfi, false);
+
+            if (parseInfo.fAllowTrailingWhite)
+            {
+                // Trim trailing spaces if AllowTrailingWhite.
+                format.TrimTail();
+                format.RemoveTrailingInQuoteSpaces();
+                str.TrimTail();
+            }
+
+            if ((styles & DateTimeStyles.AllowLeadingWhite) != 0)
+            {
+                format.SkipWhiteSpaces();
+                format.RemoveLeadingInQuoteSpaces();
+                str.SkipWhiteSpaces();
+            }
+
+            //
+            // Scan every character in format and match the pattern in str.
+            //
+            while (format.GetNext())
+            {
+                // We trim inner spaces here, so that we will not eat trailing spaces when
+                // AllowTrailingWhite is not used.
+                if (parseInfo.fAllowInnerWhite)
+                {
+                    str.SkipWhiteSpaces();
+                }
+                if (!ParseByFormat(ref str, ref format, ref parseInfo, dtfi, ref result))
+                {
+                    return (false);
+                }
+            }
+
+            if (str.Index < str.Value.Length - 1)
+            {
+                // There are still remaining character in str.
+                result.SetBadDateTimeFailure();
+                return false;
+            }
+
+            if (parseInfo.fUseTwoDigitYear && ((dtfi.FormatFlags & DateTimeFormatFlags.UseHebrewRule) == 0))
+            {
+                // A two digit year value is expected. Check if the parsed year value is valid.
+                if (result.Year >= 100)
+                {
+                    result.SetBadDateTimeFailure();
+                    return false;
+                }
+                try
+                {
+                    result.Year = parseInfo.calendar.ToFourDigitYear(result.Year);
+                }
+                catch (ArgumentOutOfRangeException)
+                {
+                    result.SetBadDateTimeFailure();
+                    return false;
+                }
+            }
+
+            if (parseInfo.fUseHour12)
+            {
+                if (parseInfo.timeMark == TM.NotSet)
+                {
+                    // hh is used, but no AM/PM designator is specified.
+                    // Assume the time is AM.
+                    // Don't throw exceptions in here becasue it is very confusing for the caller.
+                    // I always got confused myself when I use "hh:mm:ss" to parse a time string,
+                    // and ParseExact() throws on me (because I didn't use the 24-hour clock 'HH').
+                    parseInfo.timeMark = TM.AM;
+                }
+                if (result.Hour > 12)
+                {
+                    // AM/PM is used, but the value for HH is too big.
+                    result.SetBadDateTimeFailure();
+                    return false;
+                }
+                if (parseInfo.timeMark == TM.AM)
+                {
+                    if (result.Hour == 12)
+                    {
+                        result.Hour = 0;
+                    }
+                }
+                else
+                {
+                    result.Hour = (result.Hour == 12) ? 12 : result.Hour + 12;
+                }
+            }
+            else
+            {
+                // Military (24-hour time) mode
+                //
+                // AM cannot be set with a 24-hour time like 17:15.
+                // PM cannot be set with a 24-hour time like 03:15.
+                if ((parseInfo.timeMark == TM.AM && result.Hour >= 12)
+                    || (parseInfo.timeMark == TM.PM && result.Hour < 12))
+                {
+                    result.SetBadDateTimeFailure();
+                    return false;
+                }
+            }
+
+
+            // Check if the parased string only contains hour/minute/second values.
+            bTimeOnly = (result.Year == -1 && result.Month == -1 && result.Day == -1);
+            if (!CheckDefaultDateTime(ref result, ref parseInfo.calendar, styles))
+            {
+                return false;
+            }
+
+            if (!bTimeOnly && dtfi.HasYearMonthAdjustment)
+            {
+                if (!dtfi.YearMonthAdjustment(ref result.Year, ref result.Month, ((result.flags & ParseFlags.ParsedMonthName) != 0)))
+                {
+                    result.SetFailure(ParseFailureKind.FormatBadDateTimeCalendar, nameof(SR.Format_BadDateTimeCalendar));
+                    return false;
+                }
+            }
+            if (!parseInfo.calendar.TryToDateTime(result.Year, result.Month, result.Day,
+                    result.Hour, result.Minute, result.Second, 0, result.era, out result.parsedDate))
+            {
+                result.SetFailure(ParseFailureKind.FormatBadDateTimeCalendar, nameof(SR.Format_BadDateTimeCalendar));
+                return false;
+            }
+            if (result.fraction > 0)
+            {
+                result.parsedDate = result.parsedDate.AddTicks((long)Math.Round(result.fraction * Calendar.TicksPerSecond));
+            }
+
+            //
+            // We have to check day of week before we adjust to the time zone.
+            // It is because the value of day of week may change after adjusting
+            // to the time zone.
+            //
+            if (parseInfo.dayOfWeek != -1)
+            {
+                //
+                // Check if day of week is correct.
+                //
+                if (parseInfo.dayOfWeek != (int)parseInfo.calendar.GetDayOfWeek(result.parsedDate))
+                {
+                    result.SetFailure(ParseFailureKind.FormatWithOriginalDateTime, nameof(SR.Format_BadDayOfWeek));
+                    return false;
+                }
+            }
+
+
+            if (!DetermineTimeZoneAdjustments(ref str, ref result, styles, bTimeOnly))
+            {
+                return false;
+            }
+            return true;
+        }
+
+        private static Exception GetDateTimeParseException(ref DateTimeResult result)
+        {
+            switch (result.failure)
+            {
+                case ParseFailureKind.ArgumentNull:
+                    return new ArgumentNullException(result.failureArgumentName, SR.GetResourceString(result.failureMessageID));
+                case ParseFailureKind.Format:
+                    return new FormatException(SR.GetResourceString(result.failureMessageID));
+                case ParseFailureKind.FormatWithParameter:
+                    return new FormatException(SR.Format(SR.GetResourceString(result.failureMessageID), result.failureMessageFormatArgument));
+                case ParseFailureKind.FormatBadDateTimeCalendar:
+                    return new FormatException(SR.Format(SR.GetResourceString(result.failureMessageID), new string(result.originalDateTimeString), result.calendar));
+                case ParseFailureKind.FormatWithOriginalDateTime:
+                    return new FormatException(SR.Format(SR.GetResourceString(result.failureMessageID), new string(result.originalDateTimeString)));
+                case ParseFailureKind.FormatWithFormatSpecifier:
+                    return new FormatException(SR.Format(SR.GetResourceString(result.failureMessageID), new string(result.failedFormatSpecifier)));
+                case ParseFailureKind.FormatWithOriginalDateTimeAndParameter:
+                    return new FormatException(SR.Format(SR.GetResourceString(result.failureMessageID), new string(result.originalDateTimeString), result.failureMessageFormatArgument));
+                default:
+                    Debug.Fail("Unknown DateTimeParseFailure: " + result.failure.ToString());
+                    return null;
+            }
+        }
+
+        [Conditional("_LOGGING")]
+        private static void LexTraceExit(string message, DS dps)
+        {
+#if _LOGGING
+            if (!_tracingEnabled)
+                return;
+            Trace($"Lex return {message}, DS.{dps}");
+#endif // _LOGGING
+        }
+        [Conditional("_LOGGING")]
+        private static void PTSTraceExit(DS dps, bool passed)
+        {
+#if _LOGGING
+            if (!_tracingEnabled)
+                return;
+            Trace($"ProcessTerminalState {(passed ? "passed" : "failed")} @ DS.{dps}");
+#endif // _LOGGING
+        }
+        [Conditional("_LOGGING")]
+        private static void TPTraceExit(string message, DS dps)
+        {
+#if _LOGGING
+            if (!_tracingEnabled)
+                return;
+            Trace($"TryParse return {message}, DS.{dps}");
+#endif // _LOGGING
+        }
+        [Conditional("_LOGGING")]
+        private static void DTFITrace(DateTimeFormatInfo dtfi)
+        {
+#if _LOGGING
+            if (!_tracingEnabled)
+                return;
+
+            Trace("DateTimeFormatInfo Properties");
+#if !FEATURE_COREFX_GLOBALIZATION
+            Trace($" NativeCalendarName {Hex(dtfi.NativeCalendarName)}");
+#endif
+            Trace($"       AMDesignator {Hex(dtfi.AMDesignator)}");
+            Trace($"       PMDesignator {Hex(dtfi.PMDesignator)}");
+            Trace($"      TimeSeparator {Hex(dtfi.TimeSeparator)}");
+            Trace($"      AbbrvDayNames {Hex(dtfi.AbbreviatedDayNames)}");
+            Trace($"   ShortestDayNames {Hex(dtfi.ShortestDayNames)}");
+            Trace($"           DayNames {Hex(dtfi.DayNames)}");
+            Trace($"    AbbrvMonthNames {Hex(dtfi.AbbreviatedMonthNames)}");
+            Trace($"         MonthNames {Hex(dtfi.MonthNames)}");
+            Trace($" AbbrvMonthGenNames {Hex(dtfi.AbbreviatedMonthGenitiveNames)}");
+            Trace($"      MonthGenNames {Hex(dtfi.MonthGenitiveNames)}");
+#endif // _LOGGING
+        }
+#if _LOGGING
+        // return a string in the form: "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
+        private static string Hex(string[] strs)
+        {
+            if (strs == null || strs.Length == 0)
+                return String.Empty;
+            if (strs.Length == 1)
+                return Hex(strs[0]);
+
+            int curLineLength = 0;
+            int maxLineLength = 55;
+            int newLinePadding = 20;
+
+
+            //invariant: strs.Length >= 2
+            StringBuilder buffer = new StringBuilder();
+            buffer.Append(Hex(strs[0]));
+            curLineLength = buffer.Length;
+            String s;
+
+            for (int i = 1; i < strs.Length - 1; i++)
+            {
+                s = Hex(strs[i]);
+
+                if (s.Length > maxLineLength || (curLineLength + s.Length + 2) > maxLineLength)
+                {
+                    buffer.Append(',');
+                    buffer.Append(Environment.NewLine);
+                    buffer.Append(' ', newLinePadding);
+                    curLineLength = 0;
+                }
+                else
+                {
+                    buffer.Append(", ");
+                    curLineLength += 2;
+                }
+                buffer.Append(s);
+                curLineLength += s.Length;
+            }
+
+            buffer.Append(',');
+            s = Hex(strs[strs.Length - 1]);
+            if (s.Length > maxLineLength || (curLineLength + s.Length + 6) > maxLineLength)
+            {
+                buffer.Append(Environment.NewLine);
+                buffer.Append(' ', newLinePadding);
+            }
+            else
+            {
+                buffer.Append(' ');
+            }
+            buffer.Append(s);
+            return buffer.ToString();
+        }
+        // return a string in the form: "Sun"
+        private static string Hex(string str) => Hex((ReadOnlySpan<char>)str);
+        private static string Hex(ReadOnlySpan<char> str)
+        {
+            StringBuilder buffer = new StringBuilder();
+            buffer.Append("\"");
+            for (int i = 0; i < str.Length; i++)
+            {
+                if (str[i] <= '\x007f')
+                    buffer.Append(str[i]);
+                else
+                    buffer.Append("\\u" + ((int)str[i]).ToString("x4", CultureInfo.InvariantCulture));
+            }
+            buffer.Append("\"");
+            return buffer.ToString();
+        }
+        // return an unicode escaped string form of char c
+        private static String Hex(char c)
+        {
+            if (c <= '\x007f')
+                return c.ToString(CultureInfo.InvariantCulture);
+            else
+                return "\\u" + ((int)c).ToString("x4", CultureInfo.InvariantCulture);
+        }
+
+        private static void Trace(string s)
+        {
+            // Internal.Console.WriteLine(s);
+        }
+
+        private static bool _tracingEnabled = false;
+#endif // _LOGGING
+    }
+
+
+    //
+    // This is a string parsing helper which wraps a String object.
+    // It has a Index property which tracks
+    // the current parsing pointer of the string.
+    //
+    internal ref struct __DTString
+    {
+        //
+        // Value propery: stores the real string to be parsed.
+        //
+        internal ReadOnlySpan<char> Value;
+
+        //
+        // Index property: points to the character that we are currently parsing.
+        //
+        internal int Index;
+
+        // The length of Value string.
+        internal int Length => Value.Length;
+
+        // The current chracter to be looked at.
+        internal char m_current;
+
+        private CompareInfo m_info;
+        // Flag to indicate if we encouter an digit, we should check for token or not.
+        // In some cultures, such as mn-MN, it uses "\x0031\x00a0\x0434\x04af\x0433\x044d\x044d\x0440\x00a0\x0441\x0430\x0440" in month names.
+        private bool m_checkDigitToken;
+
+        internal __DTString(ReadOnlySpan<char> str, DateTimeFormatInfo dtfi, bool checkDigitToken) : this(str, dtfi)
+        {
+            m_checkDigitToken = checkDigitToken;
+        }
+
+        internal __DTString(ReadOnlySpan<char> str, DateTimeFormatInfo dtfi)
+        {
+            Index = -1;
+            Value = str;
+
+            m_current = '\0';
+            if (dtfi != null)
+            {
+                m_info = dtfi.CompareInfo;
+                m_checkDigitToken = ((dtfi.FormatFlags & DateTimeFormatFlags.UseDigitPrefixInTokens) != 0);
+            }
+            else
+            {
+                m_info = CultureInfo.CurrentCulture.CompareInfo;
+                m_checkDigitToken = false;
+            }
+        }
+
+        internal CompareInfo CompareInfo
+        {
+            get { return m_info; }
+        }
+
+        //
+        // Advance the Index.
+        // Return true if Index is NOT at the end of the string.
+        //
+        // Typical usage:
+        // while (str.GetNext())
+        // {
+        //     char ch = str.GetChar()
+        // }
+        internal bool GetNext()
+        {
+            Index++;
+            if (Index < Length)
+            {
+                m_current = Value[Index];
+                return (true);
+            }
+            return (false);
+        }
+
+        internal bool AtEnd()
+        {
+            return Index < Length ? false : true;
+        }
+
+        internal bool Advance(int count)
+        {
+            Debug.Assert(Index + count <= Length, "__DTString::Advance: Index + count <= len");
+            Index += count;
+            if (Index < Length)
+            {
+                m_current = Value[Index];
+                return (true);
+            }
+            return (false);
+        }
+
+
+        // Used by DateTime.Parse() to get the next token.
+        internal void GetRegularToken(out TokenType tokenType, out int tokenValue, DateTimeFormatInfo dtfi)
+        {
+            tokenValue = 0;
+            if (Index >= Length)
+            {
+                tokenType = TokenType.EndOfString;
+                return;
+            }
+
+            tokenType = TokenType.UnknownToken;
+
+        Start:
+            if (DateTimeParse.IsDigit(m_current))
+            {
+                // This is a digit.
+                tokenValue = m_current - '0';
+                int value;
+                int start = Index;
+
+                //
+                // Collect other digits.
+                //
+                while (++Index < Length)
+                {
+                    m_current = Value[Index];
+                    value = m_current - '0';
+                    if (value >= 0 && value <= 9)
+                    {
+                        tokenValue = tokenValue * 10 + value;
+                    }
+                    else
+                    {
+                        break;
+                    }
+                }
+                if (Index - start > DateTimeParse.MaxDateTimeNumberDigits)
+                {
+                    tokenType = TokenType.NumberToken;
+                    tokenValue = -1;
+                }
+                else if (Index - start < 3)
+                {
+                    tokenType = TokenType.NumberToken;
+                }
+                else
+                {
+                    // If there are more than 3 digits, assume that it's a year value.
+                    tokenType = TokenType.YearNumberToken;
+                }
+                if (m_checkDigitToken)
+                {
+                    int save = Index;
+                    char saveCh = m_current;
+                    // Re-scan using the staring Index to see if this is a token.
+                    Index = start;  // To include the first digit.
+                    m_current = Value[Index];
+                    TokenType tempType;
+                    int tempValue;
+                    // This DTFI has tokens starting with digits.
+                    // E.g. mn-MN has month name like "\x0031\x00a0\x0434\x04af\x0433\x044d\x044d\x0440\x00a0\x0441\x0430\x0440"
+                    if (dtfi.Tokenize(TokenType.RegularTokenMask, out tempType, out tempValue, ref this))
+                    {
+                        tokenType = tempType;
+                        tokenValue = tempValue;
+                        // This is a token, so the Index has been advanced propertly in DTFI.Tokenizer().
+                    }
+                    else
+                    {
+                        // Use the number token value.
+                        // Restore the index.
+                        Index = save;
+                        m_current = saveCh;
+                    }
+                }
+            }
+            else if (Char.IsWhiteSpace(m_current))
+            {
+                // Just skip to the next character.
+                while (++Index < Length)
+                {
+                    m_current = Value[Index];
+                    if (!(Char.IsWhiteSpace(m_current)))
+                    {
+                        goto Start;
+                    }
+                }
+                // We have reached the end of string.
+                tokenType = TokenType.EndOfString;
+            }
+            else
+            {
+                dtfi.Tokenize(TokenType.RegularTokenMask, out tokenType, out tokenValue, ref this);
+            }
+        }
+
+        internal TokenType GetSeparatorToken(DateTimeFormatInfo dtfi, out int indexBeforeSeparator, out char charBeforeSeparator)
+        {
+            indexBeforeSeparator = Index;
+            charBeforeSeparator = m_current;
+            TokenType tokenType;
+            if (!SkipWhiteSpaceCurrent())
+            {
+                // Reach the end of the string.
+                return (TokenType.SEP_End);
+            }
+            if (!DateTimeParse.IsDigit(m_current))
+            {
+                // Not a digit.  Tokenize it.
+                int tokenValue;
+                bool found = dtfi.Tokenize(TokenType.SeparatorTokenMask, out tokenType, out tokenValue, ref this);
+                if (!found)
+                {
+                    tokenType = TokenType.SEP_Space;
+                }
+            }
+            else
+            {
+                // Do nothing here.  If we see a number, it will not be a separator. There is no need wasting time trying to find the
+                // separator token.
+                tokenType = TokenType.SEP_Space;
+            }
+            return (tokenType);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal bool MatchSpecifiedWord(String target) =>
+            Index + target.Length <= Length &&
+            m_info.Compare(Value.Slice(Index, target.Length), target, CompareOptions.IgnoreCase) == 0;
+
+        private static readonly Char[] WhiteSpaceChecks = new Char[] { ' ', '\u00A0' };
+
+        internal bool MatchSpecifiedWords(String target, bool checkWordBoundary, ref int matchLength)
+        {
+            int valueRemaining = Value.Length - Index;
+            matchLength = target.Length;
+
+            if (matchLength > valueRemaining || m_info.Compare(Value.Slice(Index, matchLength), target, CompareOptions.IgnoreCase) != 0)
+            {
+                // Check word by word
+                int targetPosition = 0;                 // Where we are in the target string
+                int thisPosition = Index;         // Where we are in this string
+                int wsIndex = target.IndexOfAny(WhiteSpaceChecks, targetPosition);
+                if (wsIndex == -1)
+                {
+                    return false;
+                }
+                do
+                {
+                    int segmentLength = wsIndex - targetPosition;
+                    if (thisPosition >= Value.Length - segmentLength)
+                    { // Subtraction to prevent overflow.
+                        return false;
+                    }
+                    if (segmentLength == 0)
+                    {
+                        // If segmentLength == 0, it means that we have leading space in the target string.
+                        // In that case, skip the leading spaces in the target and this string.
+                        matchLength--;
+                    }
+                    else
+                    {
+                        // Make sure we also have whitespace in the input string
+                        if (!Char.IsWhiteSpace(Value[thisPosition + segmentLength]))
+                        {
+                            return false;
+                        }
+                        if (m_info.CompareOptionIgnoreCase(Value.Slice(thisPosition, segmentLength), target.AsSpan(targetPosition, segmentLength)) != 0)
+                        {
+                            return false;
+                        }
+                        // Advance the input string
+                        thisPosition = thisPosition + segmentLength + 1;
+                    }
+                    // Advance our target string
+                    targetPosition = wsIndex + 1;
+
+
+                    // Skip past multiple whitespace
+                    while (thisPosition < Value.Length && Char.IsWhiteSpace(Value[thisPosition]))
+                    {
+                        thisPosition++;
+                        matchLength++;
+                    }
+                } while ((wsIndex = target.IndexOfAny(WhiteSpaceChecks, targetPosition)) >= 0);
+                // now check the last segment;
+                if (targetPosition < target.Length)
+                {
+                    int segmentLength = target.Length - targetPosition;
+                    if (thisPosition > Value.Length - segmentLength)
+                    {
+                        return false;
+                    }
+                    if (m_info.CompareOptionIgnoreCase(Value.Slice(thisPosition, segmentLength), target.AsSpan(targetPosition, segmentLength)) != 0)
+                    {
+                        return false;
+                    }
+                }
+            }
+
+            if (checkWordBoundary)
+            {
+                int nextCharIndex = Index + matchLength;
+                if (nextCharIndex < Value.Length)
+                {
+                    if (Char.IsLetter(Value[nextCharIndex]))
+                    {
+                        return (false);
+                    }
+                }
+            }
+            return (true);
+        }
+
+        //
+        // Check to see if the string starting from Index is a prefix of
+        // str.
+        // If a match is found, true value is returned and Index is updated to the next character to be parsed.
+        // Otherwise, Index is unchanged.
+        //
+        internal bool Match(String str)
+        {
+            if (++Index >= Length)
+            {
+                return (false);
+            }
+
+            if (str.Length > (Value.Length - Index))
+            {
+                return false;
+            }
+
+            if (m_info.Compare(Value.Slice(Index, str.Length), str, CompareOptions.Ordinal) == 0)
+            {
+                // Update the Index to the end of the matching string.
+                // So the following GetNext()/Match() opeartion will get
+                // the next character to be parsed.
+                Index += (str.Length - 1);
+                return (true);
+            }
+            return (false);
+        }
+
+        internal bool Match(char ch)
+        {
+            if (++Index >= Length)
+            {
+                return (false);
+            }
+            if (Value[Index] == ch)
+            {
+                m_current = ch;
+                return (true);
+            }
+            Index--;
+            return (false);
+        }
+
+        //
+        //  Actions: From the current position, try matching the longest word in the specified string array.
+        //      E.g. words[] = {"AB", "ABC", "ABCD"}, if the current position points to a substring like "ABC DEF",
+        //          MatchLongestWords(words, ref MaxMatchStrLen) will return 1 (the index), and maxMatchLen will be 3.
+        //  Returns:
+        //      The index that contains the longest word to match
+        //  Arguments:
+        //      words   The string array that contains words to search.
+        //      maxMatchStrLen  [in/out] the initailized maximum length.  This parameter can be used to
+        //          find the longest match in two string arrays.
+        //
+        internal int MatchLongestWords(String[] words, ref int maxMatchStrLen)
+        {
+            int result = -1;
+            for (int i = 0; i < words.Length; i++)
+            {
+                String word = words[i];
+                int matchLength = word.Length;
+                if (MatchSpecifiedWords(word, false, ref matchLength))
+                {
+                    if (matchLength > maxMatchStrLen)
+                    {
+                        maxMatchStrLen = matchLength;
+                        result = i;
+                    }
+                }
+            }
+
+            return (result);
+        }
+
+        //
+        // Get the number of repeat character after the current character.
+        // For a string "hh:mm:ss" at Index of 3. GetRepeatCount() = 2, and Index
+        // will point to the second ':'.
+        //
+        internal int GetRepeatCount()
+        {
+            char repeatChar = Value[Index];
+            int pos = Index + 1;
+            while ((pos < Length) && (Value[pos] == repeatChar))
+            {
+                pos++;
+            }
+            int repeatCount = (pos - Index);
+            // Update the Index to the end of the repeated characters.
+            // So the following GetNext() opeartion will get
+            // the next character to be parsed.
+            Index = pos - 1;
+            return (repeatCount);
+        }
+
+        // Return false when end of string is encountered or a non-digit character is found.
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal bool GetNextDigit() =>
+            ++Index < Length &&
+            DateTimeParse.IsDigit(Value[Index]);
+
+        //
+        // Get the current character.
+        //
+        internal char GetChar()
+        {
+            Debug.Assert(Index >= 0 && Index < Length, "Index >= 0 && Index < len");
+            return (Value[Index]);
+        }
+
+        //
+        // Convert the current character to a digit, and return it.
+        //
+        internal int GetDigit()
+        {
+            Debug.Assert(Index >= 0 && Index < Length, "Index >= 0 && Index < len");
+            Debug.Assert(DateTimeParse.IsDigit(Value[Index]), "IsDigit(Value[Index])");
+            return (Value[Index] - '0');
+        }
+
+        //
+        // Eat White Space ahead of the current position
+        //
+        // Return false if end of string is encountered.
+        //
+        internal void SkipWhiteSpaces()
+        {
+            // Look ahead to see if the next character
+            // is a whitespace.
+            while (Index + 1 < Length)
+            {
+                char ch = Value[Index + 1];
+                if (!Char.IsWhiteSpace(ch))
+                {
+                    return;
+                }
+                Index++;
+            }
+            return;
+        }
+
+        //
+        // Skip white spaces from the current position
+        //
+        // Return false if end of string is encountered.
+        //
+        internal bool SkipWhiteSpaceCurrent()
+        {
+            if (Index >= Length)
+            {
+                return (false);
+            }
+
+            if (!Char.IsWhiteSpace(m_current))
+            {
+                return (true);
+            }
+
+            while (++Index < Length)
+            {
+                m_current = Value[Index];
+                if (!Char.IsWhiteSpace(m_current))
+                {
+                    return (true);
+                }
+                // Nothing here.
+            }
+            return (false);
+        }
+
+        internal void TrimTail()
+        {
+            int i = Length - 1;
+            while (i >= 0 && Char.IsWhiteSpace(Value[i]))
+            {
+                i--;
+            }
+            Value = Value.Slice(0, i + 1);
+        }
+
+        // Trim the trailing spaces within a quoted string.
+        // Call this after TrimTail() is done.
+        internal void RemoveTrailingInQuoteSpaces()
+        {
+            int i = Length - 1;
+            if (i <= 1)
+            {
+                return;
+            }
+            char ch = Value[i];
+            // Check if the last character is a quote.
+            if (ch == '\'' || ch == '\"')
+            {
+                if (char.IsWhiteSpace(Value[i - 1]))
+                {
+                    i--;
+                    while (i >= 1 && char.IsWhiteSpace(Value[i - 1]))
+                    {
+                        i--;
+                    }
+                    Span<char> result = new char[i + 1];
+                    result[i] = ch;
+                    Value.Slice(0, i).CopyTo(result);
+                    Value = result;
+                }
+            }
+        }
+
+        // Trim the leading spaces within a quoted string.
+        // Call this after the leading spaces before quoted string are trimmed.
+        internal void RemoveLeadingInQuoteSpaces()
+        {
+            if (Length <= 2)
+            {
+                return;
+            }
+            int i = 0;
+            char ch = Value[i];
+            // Check if the last character is a quote.
+            if (ch == '\'' || ch == '\"')
+            {
+                while ((i + 1) < Length && char.IsWhiteSpace(Value[i + 1]))
+                {
+                    i++;
+                }
+                if (i != 0)
+                {
+                    Span<char> result = new char[Value.Length - i];
+                    result[0] = ch;
+                    Value.Slice(i + 1).CopyTo(result.Slice(1));
+                    Value = result;
+                }
+            }
+        }
+
+        internal DTSubString GetSubString()
+        {
+            DTSubString sub = new DTSubString();
+            sub.index = Index;
+            sub.s = Value;
+            while (Index + sub.length < Length)
+            {
+                DTSubStringType currentType;
+                Char ch = Value[Index + sub.length];
+                if (ch >= '0' && ch <= '9')
+                {
+                    currentType = DTSubStringType.Number;
+                }
+                else
+                {
+                    currentType = DTSubStringType.Other;
+                }
+
+                if (sub.length == 0)
+                {
+                    sub.type = currentType;
+                }
+                else
+                {
+                    if (sub.type != currentType)
+                    {
+                        break;
+                    }
+                }
+                sub.length++;
+                if (currentType == DTSubStringType.Number)
+                {
+                    // Incorporate the number into the value
+                    // Limit the digits to prevent overflow
+                    if (sub.length > DateTimeParse.MaxDateTimeNumberDigits)
+                    {
+                        sub.type = DTSubStringType.Invalid;
+                        return sub;
+                    }
+                    int number = ch - '0';
+                    Debug.Assert(number >= 0 && number <= 9, "number >= 0 && number <= 9");
+                    sub.value = sub.value * 10 + number;
+                }
+                else
+                {
+                    // For non numbers, just return this length 1 token. This should be expanded
+                    // to more types of thing if this parsing approach is used for things other
+                    // than numbers and single characters
+                    break;
+                }
+            }
+            if (sub.length == 0)
+            {
+                sub.type = DTSubStringType.End;
+                return sub;
+            }
+
+            return sub;
+        }
+
+        internal void ConsumeSubString(DTSubString sub)
+        {
+            Debug.Assert(sub.index == Index, "sub.index == Index");
+            Debug.Assert(sub.index + sub.length <= Length, "sub.index + sub.length <= len");
+            Index = sub.index + sub.length;
+            if (Index < Length)
+            {
+                m_current = Value[Index];
+            }
+        }
+    }
+
+    internal enum DTSubStringType
+    {
+        Unknown = 0,
+        Invalid = 1,
+        Number = 2,
+        End = 3,
+        Other = 4,
+    }
+
+    internal ref struct DTSubString
+    {
+        internal ReadOnlySpan<char> s;
+        internal Int32 index;
+        internal Int32 length;
+        internal DTSubStringType type;
+        internal Int32 value;
+
+        internal Char this[Int32 relativeIndex]
+        {
+            get
+            {
+                return s[index + relativeIndex];
+            }
+        }
+    }
+
+    //
+    // The buffer to store the parsing token.
+    //
+    internal
+    struct DateTimeToken
+    {
+        internal DateTimeParse.DTT dtt;    // Store the token
+        internal TokenType suffix; // Store the CJK Year/Month/Day suffix (if any)
+        internal int num;    // Store the number that we are parsing (if any)
+    }
+
+    //
+    // The buffer to store temporary parsing information.
+    //
+    internal
+    unsafe struct DateTimeRawInfo
+    {
+        private int* num;
+        internal int numCount;
+        internal int month;
+        internal int year;
+        internal int dayOfWeek;
+        internal int era;
+        internal DateTimeParse.TM timeMark;
+        internal double fraction;
+        internal bool hasSameDateAndTimeSeparators;
+
+        internal void Init(int* numberBuffer)
+        {
+            month = -1;
+            year = -1;
+            dayOfWeek = -1;
+            era = -1;
+            timeMark = DateTimeParse.TM.NotSet;
+            fraction = -1;
+            num = numberBuffer;
+        }
+        internal unsafe void AddNumber(int value)
+        {
+            num[numCount++] = value;
+        }
+        internal unsafe int GetNumber(int index)
+        {
+            return num[index];
+        }
+    }
+
+    internal enum ParseFailureKind
+    {
+        None = 0,
+        ArgumentNull = 1,
+        Format = 2,
+        FormatWithParameter = 3,
+        FormatWithOriginalDateTime = 4,
+        FormatWithFormatSpecifier = 5,
+        FormatWithOriginalDateTimeAndParameter = 6,
+        FormatBadDateTimeCalendar = 7,  // FormatException when ArgumentOutOfRange is thrown by a Calendar.TryToDateTime().
+    };
+
+    [Flags]
+    internal enum ParseFlags
+    {
+        HaveYear = 0x00000001,
+        HaveMonth = 0x00000002,
+        HaveDay = 0x00000004,
+        HaveHour = 0x00000008,
+        HaveMinute = 0x00000010,
+        HaveSecond = 0x00000020,
+        HaveTime = 0x00000040,
+        HaveDate = 0x00000080,
+        TimeZoneUsed = 0x00000100,
+        TimeZoneUtc = 0x00000200,
+        ParsedMonthName = 0x00000400,
+        CaptureOffset = 0x00000800,
+        YearDefault = 0x00001000,
+        Rfc1123Pattern = 0x00002000,
+        UtcSortPattern = 0x00004000,
+    }
+
+    //
+    // This will store the result of the parsing.  And it will be eventually
+    // used to construct a DateTime instance.
+    //
+    internal
+    ref struct DateTimeResult
+    {
+        internal int Year;
+        internal int Month;
+        internal int Day;
+        //
+        // Set time defualt to 00:00:00.
+        //
+        internal int Hour;
+        internal int Minute;
+        internal int Second;
+        internal double fraction;
+
+        internal int era;
+
+        internal ParseFlags flags;
+
+        internal TimeSpan timeZoneOffset;
+
+        internal Calendar calendar;
+
+        internal DateTime parsedDate;
+
+        internal ParseFailureKind failure;
+        internal string failureMessageID;
+        internal object failureMessageFormatArgument;
+        internal string failureArgumentName;
+        internal ReadOnlySpan<char> originalDateTimeString;
+        internal ReadOnlySpan<char> failedFormatSpecifier;
+
+        internal void Init(ReadOnlySpan<char> originalDateTimeString)
+        {
+            this.originalDateTimeString = originalDateTimeString;
+            Year = -1;
+            Month = -1;
+            Day = -1;
+            fraction = -1;
+            era = -1;
+        }
+
+        internal void SetDate(int year, int month, int day)
+        {
+            Year = year;
+            Month = month;
+            Day = day;
+        }
+
+        internal void SetBadFormatSpecifierFailure()
+        {
+            SetBadFormatSpecifierFailure(ReadOnlySpan<char>.Empty);
+        }
+
+        internal void SetBadFormatSpecifierFailure(ReadOnlySpan<char> failedFormatSpecifier)
+        {
+            this.failure = ParseFailureKind.FormatWithFormatSpecifier;
+            this.failureMessageID = nameof(SR.Format_BadFormatSpecifier);
+            this.failedFormatSpecifier = failedFormatSpecifier;
+        }
+
+        internal void SetBadDateTimeFailure()
+        {
+            this.failure = ParseFailureKind.FormatWithOriginalDateTime;
+            this.failureMessageID = nameof(SR.Format_BadDateTime);
+            this.failureMessageFormatArgument = null;
+        }
+
+        internal void SetFailure(ParseFailureKind failure, string failureMessageID)
+        {
+            this.failure = failure;
+            this.failureMessageID = failureMessageID;
+            this.failureMessageFormatArgument = null;
+        }
+
+        internal void SetFailure(ParseFailureKind failure, string failureMessageID, object failureMessageFormatArgument)
+        {
+            this.failure = failure;
+            this.failureMessageID = failureMessageID;
+            this.failureMessageFormatArgument = failureMessageFormatArgument;
+        }
+
+        internal void SetFailure(ParseFailureKind failure, string failureMessageID, object failureMessageFormatArgument, string failureArgumentName)
+        {
+            this.failure = failure;
+            this.failureMessageID = failureMessageID;
+            this.failureMessageFormatArgument = failureMessageFormatArgument;
+            this.failureArgumentName = failureArgumentName;
+        }
+    }
+
+    // This is the helper data structure used in ParseExact().
+    internal struct ParsingInfo
+    {
+        internal Calendar calendar;
+        internal int dayOfWeek;
+        internal DateTimeParse.TM timeMark;
+
+        internal bool fUseHour12;
+        internal bool fUseTwoDigitYear;
+        internal bool fAllowInnerWhite;
+        internal bool fAllowTrailingWhite;
+        internal bool fCustomNumberParser;
+        internal DateTimeParse.MatchNumberDelegate parseNumberDelegate;
+
+        internal void Init()
+        {
+            dayOfWeek = -1;
+            timeMark = DateTimeParse.TM.NotSet;
+        }
+    }
+
+    //
+    // The type of token that will be returned by DateTimeFormatInfo.Tokenize().
+    //
+    internal enum TokenType
+    {
+        // The valid token should start from 1.
+
+        // Regular tokens. The range is from 0x00 ~ 0xff.
+        NumberToken = 1,    // The number.  E.g. "12"
+        YearNumberToken = 2,    // The number which is considered as year number, which has 3 or more digits.  E.g. "2003"
+        Am = 3,    // AM timemark. E.g. "AM"
+        Pm = 4,    // PM timemark. E.g. "PM"
+        MonthToken = 5,    // A word (or words) that represents a month name.  E.g. "March"
+        EndOfString = 6,    // End of string
+        DayOfWeekToken = 7,    // A word (or words) that represents a day of week name.  E.g. "Monday" or "Mon"
+        TimeZoneToken = 8,    // A word that represents a timezone name. E.g. "GMT"
+        EraToken = 9,    // A word that represents a era name. E.g. "A.D."
+        DateWordToken = 10,   // A word that can appear in a DateTime string, but serves no parsing semantics.  E.g. "de" in Spanish culture.
+        UnknownToken = 11,   // An unknown word, which signals an error in parsing.
+        HebrewNumber = 12,   // A number that is composed of Hebrew text.  Hebrew calendar uses Hebrew digits for year values, month values, and day values.
+        JapaneseEraToken = 13,   // Era name for JapaneseCalendar
+        TEraToken = 14,   // Era name for TaiwanCalendar
+        IgnorableSymbol = 15,   // A separator like "," that is equivalent to whitespace
+
+
+        // Separator tokens.
+        SEP_Unk = 0x100,         // Unknown separator.
+        SEP_End = 0x200,    // The end of the parsing string.
+        SEP_Space = 0x300,    // Whitespace (including comma).
+        SEP_Am = 0x400,    // AM timemark. E.g. "AM"
+        SEP_Pm = 0x500,    // PM timemark. E.g. "PM"
+        SEP_Date = 0x600,    // date separator. E.g. "/"
+        SEP_Time = 0x700,    // time separator. E.g. ":"
+        SEP_YearSuff = 0x800,    // Chinese/Japanese/Korean year suffix.
+        SEP_MonthSuff = 0x900,    // Chinese/Japanese/Korean month suffix.
+        SEP_DaySuff = 0xa00,    // Chinese/Japanese/Korean day suffix.
+        SEP_HourSuff = 0xb00,   // Chinese/Japanese/Korean hour suffix.
+        SEP_MinuteSuff = 0xc00,   // Chinese/Japanese/Korean minute suffix.
+        SEP_SecondSuff = 0xd00,   // Chinese/Japanese/Korean second suffix.
+        SEP_LocalTimeMark = 0xe00,   // 'T', used in ISO 8601 format.
+        SEP_DateOrOffset = 0xf00,   // '-' which could be a date separator or start of a time zone offset
+
+        RegularTokenMask = 0x00ff,
+        SeparatorTokenMask = 0xff00,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/DateTimeStyles.cs b/src/System.Private.CoreLib/shared/System/Globalization/DateTimeStyles.cs
new file mode 100644
index 0000000000..bf68ac91d5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/DateTimeStyles.cs
@@ -0,0 +1,49 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Contains valid formats for DateTime recognized by
+** the DateTime class' parsing code.
+**
+**
+===========================================================*/
+
+namespace System.Globalization
+{
+    [Flags]
+    public enum DateTimeStyles
+    {
+        // Bit flag indicating that leading whitespace is allowed. Character values
+        // 0x0009, 0x000A, 0x000B, 0x000C, 0x000D, and 0x0020 are considered to be
+        // whitespace.
+
+
+        None = 0x00000000,
+
+        AllowLeadingWhite = 0x00000001,
+
+        AllowTrailingWhite = 0x00000002, //Bitflag indicating trailing whitespace is allowed.
+
+        AllowInnerWhite = 0x00000004,
+
+        AllowWhiteSpaces = AllowLeadingWhite | AllowInnerWhite | AllowTrailingWhite,
+        // When parsing a date/time string, if all year/month/day are missing, set the default date
+        // to 0001/1/1, instead of the current year/month/day.
+
+        NoCurrentDateDefault = 0x00000008,
+        // When parsing a date/time string, if a timezone specifier ("GMT","Z","+xxxx", "-xxxx" exists), we will
+        // adjust the parsed time based to GMT.
+
+        AdjustToUniversal = 0x00000010,
+
+        AssumeLocal = 0x00000020,
+
+        AssumeUniversal = 0x00000040,
+        // Attempt to preserve whether the input is unspecified, local or UTC
+        RoundtripKind = 0x00000080,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/DaylightTime.cs b/src/System.Private.CoreLib/shared/System/Globalization/DaylightTime.cs
new file mode 100644
index 0000000000..72a572c97d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/DaylightTime.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Globalization
+{
+    // This class represents a starting/ending time for a period of daylight saving time.
+    public class DaylightTime
+    {
+        private readonly DateTime _start;
+        private readonly DateTime _end;
+        private readonly TimeSpan _delta;
+
+        public DaylightTime(DateTime start, DateTime end, TimeSpan delta)
+        {
+            _start = start;
+            _end = end;
+            _delta = delta;
+        }
+
+        // The start date of a daylight saving period.
+        public DateTime Start => _start;
+
+        // The end date of a daylight saving period.
+        public DateTime End => _end;
+
+        // Delta to stardard offset in ticks.
+        public TimeSpan Delta => _delta;
+    }
+
+    // Value type version of DaylightTime
+    internal readonly struct DaylightTimeStruct
+    {
+        public DaylightTimeStruct(DateTime start, DateTime end, TimeSpan delta)
+        {
+            Start = start;
+            End = end;
+            Delta = delta;
+        }
+
+        public readonly DateTime Start;
+        public readonly DateTime End;
+        public readonly TimeSpan Delta;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/DigitShapes.cs b/src/System.Private.CoreLib/shared/System/Globalization/DigitShapes.cs
new file mode 100644
index 0000000000..1ce45dbeb6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/DigitShapes.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Globalization
+{
+    public enum DigitShapes : int
+    {
+        Context         = 0x0000,   // The shape depends on the previous text in the same output.
+        None            = 0x0001,   // Gives full Unicode compatibility.
+        NativeNational  = 0x0002    // National shapes 
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/EastAsianLunisolarCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/EastAsianLunisolarCalendar.cs
new file mode 100644
index 0000000000..358f4df182
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/EastAsianLunisolarCalendar.cs
@@ -0,0 +1,703 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+namespace System.Globalization
+{
+    public abstract class EastAsianLunisolarCalendar : Calendar
+    {
+        internal const int LeapMonth = 0;
+        internal const int Jan1Month = 1;
+        internal const int Jan1Date = 2;
+        internal const int nDaysPerMonth = 3;
+
+        // # of days so far in the solar year
+        internal static readonly int[] DaysToMonth365 =
+        {
+            0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
+        };
+
+        internal static readonly int[] DaysToMonth366 =
+        {
+            0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335
+        };
+
+        internal const int DatePartYear = 0;
+        internal const int DatePartDayOfYear = 1;
+        internal const int DatePartMonth = 2;
+        internal const int DatePartDay = 3;
+
+        public override CalendarAlgorithmType AlgorithmType
+        {
+            get
+            {
+                return CalendarAlgorithmType.LunisolarCalendar;
+            }
+        }
+
+        // Return the year number in the 60-year cycle.
+        //
+
+        public virtual int GetSexagenaryYear(DateTime time)
+        {
+            CheckTicksRange(time.Ticks);
+
+            int year = 0, month = 0, day = 0;
+            TimeToLunar(time, ref year, ref month, ref day);
+
+            return ((year - 4) % 60) + 1;
+        }
+
+        // Return the celestial year from the 60-year cycle.
+        // The returned value is from 1 ~ 10.
+        //
+
+        public int GetCelestialStem(int sexagenaryYear)
+        {
+            if ((sexagenaryYear < 1) || (sexagenaryYear > 60))
+            {
+                throw new ArgumentOutOfRangeException(
+                                nameof(sexagenaryYear),
+                                SR.Format(SR.ArgumentOutOfRange_Range, 1, 60));
+            }
+
+            return ((sexagenaryYear - 1) % 10) + 1;
+        }
+
+        // Return the Terrestial Branch from the 60-year cycle.
+        // The returned value is from 1 ~ 12.
+        //
+
+        public int GetTerrestrialBranch(int sexagenaryYear)
+        {
+            if ((sexagenaryYear < 1) || (sexagenaryYear > 60))
+            {
+                throw new ArgumentOutOfRangeException(
+                                nameof(sexagenaryYear),
+                                SR.Format(SR.ArgumentOutOfRange_Range, 1, 60));
+            }
+
+            return ((sexagenaryYear - 1) % 12) + 1;
+        }
+
+        internal abstract int GetYearInfo(int LunarYear, int Index);
+        internal abstract int GetYear(int year, DateTime time);
+        internal abstract int GetGregorianYear(int year, int era);
+
+        internal abstract int MinCalendarYear { get; }
+        internal abstract int MaxCalendarYear { get; }
+        internal abstract EraInfo[] CalEraInfo { get; }
+        internal abstract DateTime MinDate { get; }
+        internal abstract DateTime MaxDate { get; }
+
+        internal const int MaxCalendarMonth = 13;
+        internal const int MaxCalendarDay = 30;
+
+        internal int MinEraCalendarYear(int era)
+        {
+            EraInfo[] mEraInfo = CalEraInfo;
+            //ChineseLunisolarCalendar does not has m_EraInfo it is going to retuen null
+            if (mEraInfo == null)
+            {
+                return MinCalendarYear;
+            }
+
+            if (era == Calendar.CurrentEra)
+            {
+                era = CurrentEraValue;
+            }
+            //era has to be in the supported range otherwise we will throw exception in CheckEraRange()
+            if (era == GetEra(MinDate))
+            {
+                return (GetYear(MinCalendarYear, MinDate));
+            }
+
+            for (int i = 0; i < mEraInfo.Length; i++)
+            {
+                if (era == mEraInfo[i].era)
+                {
+                    return (mEraInfo[i].minEraYear);
+                }
+            }
+            throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+        }
+
+        internal int MaxEraCalendarYear(int era)
+        {
+            EraInfo[] mEraInfo = CalEraInfo;
+            //ChineseLunisolarCalendar does not has m_EraInfo it is going to retuen null
+            if (mEraInfo == null)
+            {
+                return MaxCalendarYear;
+            }
+
+            if (era == Calendar.CurrentEra)
+            {
+                era = CurrentEraValue;
+            }
+            //era has to be in the supported range otherwise we will throw exception in CheckEraRange()
+            if (era == GetEra(MaxDate))
+            {
+                return (GetYear(MaxCalendarYear, MaxDate));
+            }
+
+            for (int i = 0; i < mEraInfo.Length; i++)
+            {
+                if (era == mEraInfo[i].era)
+                {
+                    return (mEraInfo[i].maxEraYear);
+                }
+            }
+            throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+        }
+
+        internal EastAsianLunisolarCalendar()
+        {
+        }
+
+        internal void CheckTicksRange(long ticks)
+        {
+            if (ticks < MinSupportedDateTime.Ticks || ticks > MaxSupportedDateTime.Ticks)
+            {
+                throw new ArgumentOutOfRangeException(
+                                "time",
+                                String.Format(CultureInfo.InvariantCulture, SR.ArgumentOutOfRange_CalendarRange,
+                                MinSupportedDateTime, MaxSupportedDateTime));
+            }
+        }
+
+        internal void CheckEraRange(int era)
+        {
+            if (era == Calendar.CurrentEra)
+            {
+                era = CurrentEraValue;
+            }
+
+            if ((era < GetEra(MinDate)) || (era > GetEra(MaxDate)))
+            {
+                throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+            }
+        }
+
+        internal int CheckYearRange(int year, int era)
+        {
+            CheckEraRange(era);
+            year = GetGregorianYear(year, era);
+
+            if ((year < MinCalendarYear) || (year > MaxCalendarYear))
+            {
+                throw new ArgumentOutOfRangeException(
+                                nameof(year),
+                                SR.Format(SR.ArgumentOutOfRange_Range, MinEraCalendarYear(era), MaxEraCalendarYear(era)));
+            }
+            return year;
+        }
+
+        internal int CheckYearMonthRange(int year, int month, int era)
+        {
+            year = CheckYearRange(year, era);
+
+            if (month == 13)
+            {
+                //Reject if there is no leap month this year
+                if (GetYearInfo(year, LeapMonth) == 0)
+                    throw new ArgumentOutOfRangeException(nameof(month), SR.ArgumentOutOfRange_Month);
+            }
+
+            if (month < 1 || month > 13)
+            {
+                throw new ArgumentOutOfRangeException(nameof(month), SR.ArgumentOutOfRange_Month);
+            }
+            return year;
+        }
+
+        internal int InternalGetDaysInMonth(int year, int month)
+        {
+            int nDays;
+            int mask;        // mask for extracting bits
+
+            mask = 0x8000;
+            // convert the lunar day into a lunar month/date
+            mask >>= (month - 1);
+            if ((GetYearInfo(year, nDaysPerMonth) & mask) == 0)
+                nDays = 29;
+            else
+                nDays = 30;
+            return nDays;
+        }
+
+        // Returns the number of days in the month given by the year and
+        // month arguments.
+        //
+
+        public override int GetDaysInMonth(int year, int month, int era)
+        {
+            year = CheckYearMonthRange(year, month, era);
+            return InternalGetDaysInMonth(year, month);
+        }
+
+        private static int GregorianIsLeapYear(int y)
+        {
+            return ((((y) % 4) != 0) ? 0 : ((((y) % 100) != 0) ? 1 : ((((y) % 400) != 0) ? 0 : 1)));
+        }
+
+        // Returns the date and time converted to a DateTime value.  Throws an exception if the n-tuple is invalid.
+        //
+
+        public override DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era)
+        {
+            year = CheckYearMonthRange(year, month, era);
+            int daysInMonth = InternalGetDaysInMonth(year, month);
+            if (day < 1 || day > daysInMonth)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(day),
+                            SR.Format(SR.ArgumentOutOfRange_Day, daysInMonth, month));
+            }
+
+            int gy = 0; int gm = 0; int gd = 0;
+
+            if (LunarToGregorian(year, month, day, ref gy, ref gm, ref gd))
+            {
+                return new DateTime(gy, gm, gd, hour, minute, second, millisecond);
+            }
+            else
+            {
+                throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadYearMonthDay);
+            }
+        }
+
+
+        //
+        // GregorianToLunar calculates lunar calendar info for the given gregorian year, month, date.
+        // The input date should be validated before calling this method.
+        //
+        internal void GregorianToLunar(int nSYear, int nSMonth, int nSDate, ref int nLYear, ref int nLMonth, ref int nLDate)
+        {
+            //    unsigned int nLYear, nLMonth, nLDate;    // lunar ymd
+            int nSolarDay;        // day # in solar year
+            int nLunarDay;        // day # in lunar year
+            int fLeap;                    // is it a solar leap year?
+            int LDpM;        // lunar days/month bitfield
+            int mask;        // mask for extracting bits
+            int nDays;        // # days this lunar month
+            int nJan1Month, nJan1Date;
+
+            // calc the solar day of year
+            fLeap = GregorianIsLeapYear(nSYear);
+            nSolarDay = (fLeap == 1) ? DaysToMonth366[nSMonth - 1] : DaysToMonth365[nSMonth - 1];
+            nSolarDay += nSDate;
+
+            // init lunar year info
+            nLunarDay = nSolarDay;
+            nLYear = nSYear;
+            if (nLYear == (MaxCalendarYear + 1))
+            {
+                nLYear--;
+                nLunarDay += ((GregorianIsLeapYear(nLYear) == 1) ? 366 : 365);
+                nJan1Month = GetYearInfo(nLYear, Jan1Month);
+                nJan1Date = GetYearInfo(nLYear, Jan1Date);
+            }
+            else
+            {
+                nJan1Month = GetYearInfo(nLYear, Jan1Month);
+                nJan1Date = GetYearInfo(nLYear, Jan1Date);
+
+                // check if this solar date is actually part of the previous
+                // lunar year
+                if ((nSMonth < nJan1Month) ||
+                    (nSMonth == nJan1Month && nSDate < nJan1Date))
+                {
+                    // the corresponding lunar day is actually part of the previous
+                    // lunar year
+                    nLYear--;
+
+                    // add a solar year to the lunar day #
+                    nLunarDay += ((GregorianIsLeapYear(nLYear) == 1) ? 366 : 365);
+
+                    // update the new start of year
+                    nJan1Month = GetYearInfo(nLYear, Jan1Month);
+                    nJan1Date = GetYearInfo(nLYear, Jan1Date);
+                }
+            }
+
+            // convert solar day into lunar day.
+            // subtract off the beginning part of the solar year which is not
+            // part of the lunar year.  since this part is always in Jan or Feb,
+            // we don't need to handle Leap Year (LY only affects March
+            // and later).
+            nLunarDay -= DaysToMonth365[nJan1Month - 1];
+            nLunarDay -= (nJan1Date - 1);
+
+            // convert the lunar day into a lunar month/date
+            mask = 0x8000;
+            LDpM = GetYearInfo(nLYear, nDaysPerMonth);
+            nDays = ((LDpM & mask) != 0) ? 30 : 29;
+            nLMonth = 1;
+            while (nLunarDay > nDays)
+            {
+                nLunarDay -= nDays;
+                nLMonth++;
+                mask >>= 1;
+                nDays = ((LDpM & mask) != 0) ? 30 : 29;
+            }
+            nLDate = nLunarDay;
+        }
+
+        /*
+        //Convert from Lunar to Gregorian
+        //Highly inefficient, but it works based on the forward conversion
+        */
+        internal bool LunarToGregorian(int nLYear, int nLMonth, int nLDate, ref int nSolarYear, ref int nSolarMonth, ref int nSolarDay)
+        {
+            int numLunarDays;
+
+            if (nLDate < 1 || nLDate > 30)
+                return false;
+
+            numLunarDays = nLDate - 1;
+
+            //Add previous months days to form the total num of days from the first of the month.
+            for (int i = 1; i < nLMonth; i++)
+            {
+                numLunarDays += InternalGetDaysInMonth(nLYear, i);
+            }
+
+            //Get Gregorian First of year
+            int nJan1Month = GetYearInfo(nLYear, Jan1Month);
+            int nJan1Date = GetYearInfo(nLYear, Jan1Date);
+
+            // calc the solar day of year of 1 Lunar day
+            int fLeap = GregorianIsLeapYear(nLYear);
+            int[] days = (fLeap == 1) ? DaysToMonth366 : DaysToMonth365;
+
+            nSolarDay = nJan1Date;
+
+            if (nJan1Month > 1)
+                nSolarDay += days[nJan1Month - 1];
+
+            // Add the actual lunar day to get the solar day we want
+            nSolarDay = nSolarDay + numLunarDays;// - 1;
+
+            if (nSolarDay > (fLeap + 365))
+            {
+                nSolarYear = nLYear + 1;
+                nSolarDay -= (fLeap + 365);
+            }
+            else
+            {
+                nSolarYear = nLYear;
+            }
+
+            for (nSolarMonth = 1; nSolarMonth < 12; nSolarMonth++)
+            {
+                if (days[nSolarMonth] >= nSolarDay)
+                    break;
+            }
+
+            nSolarDay -= days[nSolarMonth - 1];
+            return true;
+        }
+
+        internal DateTime LunarToTime(DateTime time, int year, int month, int day)
+        {
+            int gy = 0; int gm = 0; int gd = 0;
+            LunarToGregorian(year, month, day, ref gy, ref gm, ref gd);
+            return (GregorianCalendar.GetDefaultInstance().ToDateTime(gy, gm, gd, time.Hour, time.Minute, time.Second, time.Millisecond));
+        }
+
+        internal void TimeToLunar(DateTime time, ref int year, ref int month, ref int day)
+        {
+            int gy = 0; int gm = 0; int gd = 0;
+
+            Calendar Greg = GregorianCalendar.GetDefaultInstance();
+            gy = Greg.GetYear(time);
+            gm = Greg.GetMonth(time);
+            gd = Greg.GetDayOfMonth(time);
+
+            GregorianToLunar(gy, gm, gd, ref year, ref month, ref day);
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // months to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year and month parts of the specified DateTime by
+        // value months, and, if required, adjusting the day part of the
+        // resulting date downwards to the last day of the resulting month in the
+        // resulting year. The time-of-day part of the result is the same as the
+        // time-of-day part of the specified DateTime.
+        //
+
+        public override DateTime AddMonths(DateTime time, int months)
+        {
+            if (months < -120000 || months > 120000)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(months),
+                            SR.Format(SR.ArgumentOutOfRange_Range, -120000, 120000));
+            }
+
+            CheckTicksRange(time.Ticks);
+
+            int y = 0; int m = 0; int d = 0;
+            TimeToLunar(time, ref y, ref m, ref d);
+
+            int i = m + months;
+            if (i > 0)
+            {
+                int monthsInYear = InternalIsLeapYear(y) ? 13 : 12;
+
+                while (i - monthsInYear > 0)
+                {
+                    i -= monthsInYear;
+                    y++;
+                    monthsInYear = InternalIsLeapYear(y) ? 13 : 12;
+                }
+                m = i;
+            }
+            else
+            {
+                int monthsInYear;
+                while (i <= 0)
+                {
+                    monthsInYear = InternalIsLeapYear(y - 1) ? 13 : 12;
+                    i += monthsInYear;
+                    y--;
+                }
+                m = i;
+            }
+
+            int days = InternalGetDaysInMonth(y, m);
+            if (d > days)
+            {
+                d = days;
+            }
+            DateTime dt = LunarToTime(time, y, m, d);
+
+            CheckAddResult(dt.Ticks, MinSupportedDateTime, MaxSupportedDateTime);
+            return (dt);
+        }
+
+
+        public override DateTime AddYears(DateTime time, int years)
+        {
+            CheckTicksRange(time.Ticks);
+
+            int y = 0; int m = 0; int d = 0;
+            TimeToLunar(time, ref y, ref m, ref d);
+
+            y += years;
+
+            if (m == 13 && !InternalIsLeapYear(y))
+            {
+                m = 12;
+                d = InternalGetDaysInMonth(y, m);
+            }
+            int DaysInMonths = InternalGetDaysInMonth(y, m);
+            if (d > DaysInMonths)
+            {
+                d = DaysInMonths;
+            }
+
+            DateTime dt = LunarToTime(time, y, m, d);
+            CheckAddResult(dt.Ticks, MinSupportedDateTime, MaxSupportedDateTime);
+            return (dt);
+        }
+
+        // Returns the day-of-year part of the specified DateTime. The returned value
+        // is an integer between 1 and [354|355 |383|384].
+        //
+
+        public override int GetDayOfYear(DateTime time)
+        {
+            CheckTicksRange(time.Ticks);
+
+            int y = 0; int m = 0; int d = 0;
+            TimeToLunar(time, ref y, ref m, ref d);
+
+            for (int i = 1; i < m; i++)
+            {
+                d = d + InternalGetDaysInMonth(y, i);
+            }
+            return d;
+        }
+
+        // Returns the day-of-month part of the specified DateTime. The returned
+        // value is an integer between 1 and 29 or 30.
+        //
+
+        public override int GetDayOfMonth(DateTime time)
+        {
+            CheckTicksRange(time.Ticks);
+
+            int y = 0; int m = 0; int d = 0;
+            TimeToLunar(time, ref y, ref m, ref d);
+
+            return d;
+        }
+
+        // Returns the number of days in the year given by the year argument for the current era.
+        //
+
+        public override int GetDaysInYear(int year, int era)
+        {
+            year = CheckYearRange(year, era);
+
+            int Days = 0;
+            int monthsInYear = InternalIsLeapYear(year) ? 13 : 12;
+
+            while (monthsInYear != 0)
+                Days += InternalGetDaysInMonth(year, monthsInYear--);
+
+            return Days;
+        }
+
+        // Returns the month part of the specified DateTime. The returned value is an
+        // integer between 1 and 13.
+        //
+
+        public override int GetMonth(DateTime time)
+        {
+            CheckTicksRange(time.Ticks);
+
+            int y = 0; int m = 0; int d = 0;
+            TimeToLunar(time, ref y, ref m, ref d);
+
+            return m;
+        }
+
+        // Returns the year part of the specified DateTime. The returned value is an
+        // integer between 1 and MaxCalendarYear.
+        //
+
+        public override int GetYear(DateTime time)
+        {
+            CheckTicksRange(time.Ticks);
+
+            int y = 0; int m = 0; int d = 0;
+            TimeToLunar(time, ref y, ref m, ref d);
+
+            return GetYear(y, time);
+        }
+
+        // Returns the day-of-week part of the specified DateTime. The returned value
+        // is an integer between 0 and 6, where 0 indicates Sunday, 1 indicates
+        // Monday, 2 indicates Tuesday, 3 indicates Wednesday, 4 indicates
+        // Thursday, 5 indicates Friday, and 6 indicates Saturday.
+        //
+
+        public override DayOfWeek GetDayOfWeek(DateTime time)
+        {
+            CheckTicksRange(time.Ticks);
+            return ((DayOfWeek)((int)(time.Ticks / Calendar.TicksPerDay + 1) % 7));
+        }
+
+        // Returns the number of months in the specified year and era.
+
+        public override int GetMonthsInYear(int year, int era)
+        {
+            year = CheckYearRange(year, era);
+            return (InternalIsLeapYear(year) ? 13 : 12);
+        }
+
+        // Checks whether a given day in the specified era is a leap day. This method returns true if
+        // the date is a leap day, or false if not.
+        //
+
+        public override bool IsLeapDay(int year, int month, int day, int era)
+        {
+            year = CheckYearMonthRange(year, month, era);
+            int daysInMonth = InternalGetDaysInMonth(year, month);
+
+            if (day < 1 || day > daysInMonth)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(day),
+                            SR.Format(SR.ArgumentOutOfRange_Day, daysInMonth, month));
+            }
+            int m = GetYearInfo(year, LeapMonth);
+            return ((m != 0) && (month == (m + 1)));
+        }
+
+        // Checks whether a given month in the specified era is a leap month. This method returns true if
+        // month is a leap month, or false if not.
+        //
+
+        public override bool IsLeapMonth(int year, int month, int era)
+        {
+            year = CheckYearMonthRange(year, month, era);
+            int m = GetYearInfo(year, LeapMonth);
+            return ((m != 0) && (month == (m + 1)));
+        }
+
+        // Returns  the leap month in a calendar year of the specified era. This method returns 0
+        // if this this year is not a leap year.
+        //
+
+        public override int GetLeapMonth(int year, int era)
+        {
+            year = CheckYearRange(year, era);
+            int month = GetYearInfo(year, LeapMonth);
+            if (month > 0)
+            {
+                return (month + 1);
+            }
+            return 0;
+        }
+
+        internal bool InternalIsLeapYear(int year)
+        {
+            return (GetYearInfo(year, LeapMonth) != 0);
+        }
+        // Checks whether a given year in the specified era is a leap year. This method returns true if
+        // year is a leap year, or false if not.
+        //
+
+        public override bool IsLeapYear(int year, int era)
+        {
+            year = CheckYearRange(year, era);
+            return InternalIsLeapYear(year);
+        }
+
+        private const int DEFAULT_GREGORIAN_TWO_DIGIT_YEAR_MAX = 2029;
+
+
+        public override int TwoDigitYearMax
+        {
+            get
+            {
+                if (twoDigitYearMax == -1)
+                {
+                    twoDigitYearMax = GetSystemTwoDigitYearSetting(BaseCalendarID, GetYear(new DateTime(DEFAULT_GREGORIAN_TWO_DIGIT_YEAR_MAX, 1, 1)));
+                }
+                return (twoDigitYearMax);
+            }
+
+            set
+            {
+                VerifyWritable();
+                if (value < 99 || value > MaxCalendarYear)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(value),
+                                SR.Format(SR.ArgumentOutOfRange_Range, 99, MaxCalendarYear));
+                }
+                twoDigitYearMax = value;
+            }
+        }
+
+
+        public override int ToFourDigitYear(int year)
+        {
+            if (year < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            year = base.ToFourDigitYear(year);
+            CheckYearRange(year, CurrentEra);
+            return (year);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/GlobalizationExtensions.cs b/src/System.Private.CoreLib/shared/System/Globalization/GlobalizationExtensions.cs
new file mode 100644
index 0000000000..007283aa6b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/GlobalizationExtensions.cs
@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    public static class GlobalizationExtensions
+    {
+        public static StringComparer GetStringComparer(this CompareInfo compareInfo, CompareOptions options)
+        {
+            if (compareInfo == null)
+            {
+                throw new ArgumentNullException(nameof(compareInfo));
+            }
+
+            if (options == CompareOptions.Ordinal)
+            {
+                return StringComparer.Ordinal;
+            }
+
+            if (options == CompareOptions.OrdinalIgnoreCase)
+            {
+                return StringComparer.OrdinalIgnoreCase;
+            }
+
+            return new CultureAwareComparer(compareInfo, options);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/GregorianCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/GregorianCalendar.cs
new file mode 100644
index 0000000000..94963a19cc
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/GregorianCalendar.cs
@@ -0,0 +1,584 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Globalization;
+using System.Threading;
+
+namespace System.Globalization
+{
+    // This calendar recognizes two era values:
+    // 0 CurrentEra (AD)
+    // 1 BeforeCurrentEra (BC)
+    public class GregorianCalendar : Calendar
+    {
+        /*
+            A.D. = anno Domini
+         */
+
+        public const int ADEra = 1;
+
+        //
+        // This is the max Gregorian year can be represented by DateTime class.  The limitation
+        // is derived from DateTime class.
+        //
+        internal const int MaxYear = 9999;
+
+        internal GregorianCalendarTypes m_type;
+
+        internal static readonly int[] DaysToMonth365 =
+        {
+            0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365
+        };
+
+        internal static readonly int[] DaysToMonth366 =
+        {
+            0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366
+        };
+
+        private static volatile Calendar s_defaultInstance;
+
+
+        public override DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (DateTime.MinValue);
+            }
+        }
+
+        public override DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (DateTime.MaxValue);
+            }
+        }
+
+        public override CalendarAlgorithmType AlgorithmType
+        {
+            get
+            {
+                return CalendarAlgorithmType.SolarCalendar;
+            }
+        }
+
+        /*=================================GetDefaultInstance==========================
+        **Action: Internal method to provide a default intance of GregorianCalendar.  Used by NLS+ implementation
+        **       and other calendars.
+        **Returns:
+        **Arguments:
+        **Exceptions:
+        ============================================================================*/
+
+        internal static Calendar GetDefaultInstance()
+        {
+            if (s_defaultInstance == null)
+            {
+                s_defaultInstance = new GregorianCalendar();
+            }
+            return (s_defaultInstance);
+        }
+
+        // Construct an instance of gregorian calendar.
+
+        public GregorianCalendar() :
+            this(GregorianCalendarTypes.Localized)
+        {
+        }
+
+
+        public GregorianCalendar(GregorianCalendarTypes type)
+        {
+            if ((int)type < (int)GregorianCalendarTypes.Localized || (int)type > (int)GregorianCalendarTypes.TransliteratedFrench)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(type),
+                            SR.Format(SR.ArgumentOutOfRange_Range,
+                    GregorianCalendarTypes.Localized, GregorianCalendarTypes.TransliteratedFrench));
+            }
+            this.m_type = type;
+        }
+
+        public virtual GregorianCalendarTypes CalendarType
+        {
+            get
+            {
+                return (m_type);
+            }
+
+            set
+            {
+                VerifyWritable();
+
+                switch (value)
+                {
+                    case GregorianCalendarTypes.Localized:
+                    case GregorianCalendarTypes.USEnglish:
+                    case GregorianCalendarTypes.MiddleEastFrench:
+                    case GregorianCalendarTypes.Arabic:
+                    case GregorianCalendarTypes.TransliteratedEnglish:
+                    case GregorianCalendarTypes.TransliteratedFrench:
+                        m_type = value;
+                        break;
+
+                    default:
+                        throw new ArgumentOutOfRangeException("m_type", SR.ArgumentOutOfRange_Enum);
+                }
+            }
+        }
+
+        internal override CalendarId ID
+        {
+            get
+            {
+                // By returning different ID for different variations of GregorianCalendar,
+                // we can support the Transliterated Gregorian calendar.
+                // DateTimeFormatInfo will use this ID to get formatting information about
+                // the calendar.
+                return ((CalendarId)m_type);
+            }
+        }
+
+
+        /*=================================GetAbsoluteDate==========================
+        **Action: Gets the absolute date for the given Gregorian date.  The absolute date means
+        **       the number of days from January 1st, 1 A.D.
+        **Returns:  the absolute date
+        **Arguments:
+        **      year    the Gregorian year
+        **      month   the Gregorian month
+        **      day     the day
+        **Exceptions:
+        **      ArgumentOutOfRangException  if year, month, day value is valid.
+        **Note:
+        **      This is an internal method used by DateToTicks() and the calculations of Hijri and Hebrew calendars.
+        **      Number of Days in Prior Years (both common and leap years) +
+        **      Number of Days in Prior Months of Current Year +
+        **      Number of Days in Current Month
+        **
+        ============================================================================*/
+
+        internal static long GetAbsoluteDate(int year, int month, int day)
+        {
+            if (year >= 1 && year <= MaxYear && month >= 1 && month <= 12)
+            {
+                int[] days = ((year % 4 == 0 && (year % 100 != 0 || year % 400 == 0))) ? DaysToMonth366 : DaysToMonth365;
+                if (day >= 1 && (day <= days[month] - days[month - 1]))
+                {
+                    int y = year - 1;
+                    int absoluteDate = y * 365 + y / 4 - y / 100 + y / 400 + days[month - 1] + day - 1;
+                    return (absoluteDate);
+                }
+            }
+            throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadYearMonthDay);
+        }
+
+        // Returns the tick count corresponding to the given year, month, and day.
+        // Will check the if the parameters are valid.
+        internal virtual long DateToTicks(int year, int month, int day)
+        {
+            return (GetAbsoluteDate(year, month, day) * TicksPerDay);
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // months to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year and month parts of the specified DateTime by
+        // value months, and, if required, adjusting the day part of the
+        // resulting date downwards to the last day of the resulting month in the
+        // resulting year. The time-of-day part of the result is the same as the
+        // time-of-day part of the specified DateTime.
+        //
+        // In more precise terms, considering the specified DateTime to be of the
+        // form y / m / d + t, where y is the
+        // year, m is the month, d is the day, and t is the
+        // time-of-day, the result is y1 / m1 / d1 + t,
+        // where y1 and m1 are computed by adding value months
+        // to y and m, and d1 is the largest value less than
+        // or equal to d that denotes a valid day in month m1 of year
+        // y1.
+        //
+
+        public override DateTime AddMonths(DateTime time, int months)
+        {
+            if (months < -120000 || months > 120000)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(months),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                -120000,
+                                120000));
+            }
+            time.GetDatePart(out int y, out int m, out int d);
+            int i = m - 1 + months;
+            if (i >= 0)
+            {
+                m = i % 12 + 1;
+                y = y + i / 12;
+            }
+            else
+            {
+                m = 12 + (i + 1) % 12;
+                y = y + (i - 11) / 12;
+            }
+            int[] daysArray = (y % 4 == 0 && (y % 100 != 0 || y % 400 == 0)) ? DaysToMonth366 : DaysToMonth365;
+            int days = (daysArray[m] - daysArray[m - 1]);
+
+            if (d > days)
+            {
+                d = days;
+            }
+            long ticks = DateToTicks(y, m, d) + time.Ticks % TicksPerDay;
+            Calendar.CheckAddResult(ticks, MinSupportedDateTime, MaxSupportedDateTime);
+
+            return (new DateTime(ticks));
+        }
+
+
+        // Returns the DateTime resulting from adding the given number of
+        // years to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year part of the specified DateTime by value
+        // years. If the month and day of the specified DateTime is 2/29, and if the
+        // resulting year is not a leap year, the month and day of the resulting
+        // DateTime becomes 2/28. Otherwise, the month, day, and time-of-day
+        // parts of the result are the same as those of the specified DateTime.
+        //
+
+        public override DateTime AddYears(DateTime time, int years)
+        {
+            return (AddMonths(time, years * 12));
+        }
+
+        // Returns the day-of-month part of the specified DateTime. The returned
+        // value is an integer between 1 and 31.
+        //
+
+        public override int GetDayOfMonth(DateTime time)
+        {
+            return time.Day;
+        }
+
+        // Returns the day-of-week part of the specified DateTime. The returned value
+        // is an integer between 0 and 6, where 0 indicates Sunday, 1 indicates
+        // Monday, 2 indicates Tuesday, 3 indicates Wednesday, 4 indicates
+        // Thursday, 5 indicates Friday, and 6 indicates Saturday.
+        //
+
+        public override DayOfWeek GetDayOfWeek(DateTime time)
+        {
+            return ((DayOfWeek)((int)(time.Ticks / TicksPerDay + 1) % 7));
+        }
+
+        // Returns the day-of-year part of the specified DateTime. The returned value
+        // is an integer between 1 and 366.
+        //
+
+        public override int GetDayOfYear(DateTime time)
+        {
+            return time.DayOfYear;
+        }
+
+        // Returns the number of days in the month given by the year and
+        // month arguments.
+        //
+
+        public override int GetDaysInMonth(int year, int month, int era)
+        {
+            if (era == CurrentEra || era == ADEra)
+            {
+                if (year < 1 || year > MaxYear)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(year), SR.Format(SR.ArgumentOutOfRange_Range,
+                        1, MaxYear));
+                }
+                if (month < 1 || month > 12)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(month), SR.ArgumentOutOfRange_Month);
+                }
+                int[] days = ((year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)) ? DaysToMonth366 : DaysToMonth365);
+                return (days[month] - days[month - 1]);
+            }
+            throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+        }
+
+        // Returns the number of days in the year given by the year argument for the current era.
+        //
+
+        public override int GetDaysInYear(int year, int era)
+        {
+            if (era == CurrentEra || era == ADEra)
+            {
+                if (year >= 1 && year <= MaxYear)
+                {
+                    return ((year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)) ? 366 : 365);
+                }
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                1,
+                                MaxYear));
+            }
+            throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+        }
+
+        // Returns the era for the specified DateTime value.
+
+        public override int GetEra(DateTime time)
+        {
+            return (ADEra);
+        }
+
+
+        public override int[] Eras
+        {
+            get
+            {
+                return (new int[] { ADEra });
+            }
+        }
+
+
+        // Returns the month part of the specified DateTime. The returned value is an
+        // integer between 1 and 12.
+        //
+
+        public override int GetMonth(DateTime time)
+        {
+            return time.Month;
+        }
+
+        // Returns the number of months in the specified year and era.
+
+        public override int GetMonthsInYear(int year, int era)
+        {
+            if (era == CurrentEra || era == ADEra)
+            {
+                if (year >= 1 && year <= MaxYear)
+                {
+                    return (12);
+                }
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                1,
+                                MaxYear));
+            }
+            throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+        }
+
+        // Returns the year part of the specified DateTime. The returned value is an
+        // integer between 1 and 9999.
+        //
+
+        public override int GetYear(DateTime time)
+        {
+            return time.Year;
+        }
+
+        internal override bool IsValidYear(int year, int era) => year >= 1 && year <= MaxYear;
+
+        internal override bool IsValidDay(int year, int month, int day, int era)
+        {
+            if ((era != CurrentEra && era != ADEra) || 
+                year < 1 || year > MaxYear ||
+                month < 1 || month > 12 ||
+                day < 1)
+            {
+                return false;
+            }
+
+            int[] days = (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)) ? DaysToMonth366 : DaysToMonth365;
+            return day <= (days[month] - days[month - 1]);
+        }
+
+        // Checks whether a given day in the specified era is a leap day. This method returns true if
+        // the date is a leap day, or false if not.
+        //
+
+        public override bool IsLeapDay(int year, int month, int day, int era)
+        {
+            if (month < 1 || month > 12)
+            {
+                throw new ArgumentOutOfRangeException(nameof(month), SR.Format(SR.ArgumentOutOfRange_Range,
+                    1, 12));
+            }
+
+            if (era != CurrentEra && era != ADEra)
+            {
+                throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+            }
+            if (year < 1 || year > MaxYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                                nameof(year),
+                                SR.Format(SR.ArgumentOutOfRange_Range, 1, MaxYear));
+            }
+
+            if (day < 1 || day > GetDaysInMonth(year, month))
+            {
+                throw new ArgumentOutOfRangeException(nameof(day), SR.Format(SR.ArgumentOutOfRange_Range,
+                    1, GetDaysInMonth(year, month)));
+            }
+            if (!IsLeapYear(year))
+            {
+                return (false);
+            }
+            if (month == 2 && day == 29)
+            {
+                return (true);
+            }
+            return (false);
+        }
+
+        // Returns  the leap month in a calendar year of the specified era. This method returns 0
+        // if this calendar does not have leap month, or this year is not a leap year.
+        //
+
+        public override int GetLeapMonth(int year, int era)
+        {
+            if (era != CurrentEra && era != ADEra)
+            {
+                throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+            }
+            if (year < 1 || year > MaxYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range, 1, MaxYear));
+            }
+            return (0);
+        }
+
+        // Checks whether a given month in the specified era is a leap month. This method returns true if
+        // month is a leap month, or false if not.
+        //
+
+        public override bool IsLeapMonth(int year, int month, int era)
+        {
+            if (era != CurrentEra && era != ADEra)
+            {
+                throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+            }
+
+            if (year < 1 || year > MaxYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range, 1, MaxYear));
+            }
+
+            if (month < 1 || month > 12)
+            {
+                throw new ArgumentOutOfRangeException(nameof(month), SR.Format(SR.ArgumentOutOfRange_Range,
+                    1, 12));
+            }
+            return (false);
+        }
+
+        // Checks whether a given year in the specified era is a leap year. This method returns true if
+        // year is a leap year, or false if not.
+        //
+
+        public override bool IsLeapYear(int year, int era)
+        {
+            if (era == CurrentEra || era == ADEra)
+            {
+                if (year >= 1 && year <= MaxYear)
+                {
+                    return (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0));
+                }
+
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range, 1, MaxYear));
+            }
+            throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+        }
+
+        // Returns the date and time converted to a DateTime value.  Throws an exception if the n-tuple is invalid.
+        //
+
+        public override DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era)
+        {
+            if (era == CurrentEra || era == ADEra)
+            {
+                return new DateTime(year, month, day, hour, minute, second, millisecond);
+            }
+            throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+        }
+
+        internal override bool TryToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era, out DateTime result)
+        {
+            if (era == CurrentEra || era == ADEra)
+            {
+                return DateTime.TryCreate(year, month, day, hour, minute, second, millisecond, out result);
+            }
+            result = DateTime.MinValue;
+            return false;
+        }
+
+        private const int DEFAULT_TWO_DIGIT_YEAR_MAX = 2029;
+
+
+        public override int TwoDigitYearMax
+        {
+            get
+            {
+                if (twoDigitYearMax == -1)
+                {
+                    twoDigitYearMax = GetSystemTwoDigitYearSetting(ID, DEFAULT_TWO_DIGIT_YEAR_MAX);
+                }
+                return (twoDigitYearMax);
+            }
+
+            set
+            {
+                VerifyWritable();
+                if (value < 99 || value > MaxYear)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                "year",
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    99,
+                                    MaxYear));
+                }
+                twoDigitYearMax = value;
+            }
+        }
+
+
+        public override int ToFourDigitYear(int year)
+        {
+            if (year < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (year > MaxYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range, 1, MaxYear));
+            }
+            return (base.ToFourDigitYear(year));
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/GregorianCalendarHelper.cs b/src/System.Private.CoreLib/shared/System/Globalization/GregorianCalendarHelper.cs
new file mode 100644
index 0000000000..2842bd3a16
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/GregorianCalendarHelper.cs
@@ -0,0 +1,651 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading;
+
+namespace System.Globalization
+{
+    // Gregorian Calendars use Era Info
+    internal class EraInfo
+    {
+        internal int era;          // The value of the era.
+        internal long ticks;    // The time in ticks when the era starts
+        internal int yearOffset;   // The offset to Gregorian year when the era starts.
+                                   // Gregorian Year = Era Year + yearOffset
+                                   // Era Year = Gregorian Year - yearOffset
+        internal int minEraYear;   // Min year value in this era. Generally, this value is 1, but this may
+                                   // be affected by the DateTime.MinValue;
+        internal int maxEraYear;   // Max year value in this era. (== the year length of the era + 1)
+
+        internal String eraName;    // The era name
+        internal String abbrevEraName;  // Abbreviated Era Name
+        internal String englishEraName; // English era name
+
+        internal EraInfo(int era, int startYear, int startMonth, int startDay, int yearOffset, int minEraYear, int maxEraYear)
+        {
+            this.era = era;
+            this.yearOffset = yearOffset;
+            this.minEraYear = minEraYear;
+            this.maxEraYear = maxEraYear;
+            this.ticks = new DateTime(startYear, startMonth, startDay).Ticks;
+        }
+
+        internal EraInfo(int era, int startYear, int startMonth, int startDay, int yearOffset, int minEraYear, int maxEraYear,
+                          String eraName, String abbrevEraName, String englishEraName)
+        {
+            this.era = era;
+            this.yearOffset = yearOffset;
+            this.minEraYear = minEraYear;
+            this.maxEraYear = maxEraYear;
+            this.ticks = new DateTime(startYear, startMonth, startDay).Ticks;
+            this.eraName = eraName;
+            this.abbrevEraName = abbrevEraName;
+            this.englishEraName = englishEraName;
+        }
+    }
+
+    // This calendar recognizes two era values:
+    // 0 CurrentEra (AD) 
+    // 1 BeforeCurrentEra (BC) 
+    internal class GregorianCalendarHelper
+    {
+        // 1 tick = 100ns = 10E-7 second
+        // Number of ticks per time unit
+        internal const long TicksPerMillisecond = 10000;
+        internal const long TicksPerSecond = TicksPerMillisecond * 1000;
+        internal const long TicksPerMinute = TicksPerSecond * 60;
+        internal const long TicksPerHour = TicksPerMinute * 60;
+        internal const long TicksPerDay = TicksPerHour * 24;
+
+        // Number of milliseconds per time unit
+        internal const int MillisPerSecond = 1000;
+        internal const int MillisPerMinute = MillisPerSecond * 60;
+        internal const int MillisPerHour = MillisPerMinute * 60;
+        internal const int MillisPerDay = MillisPerHour * 24;
+
+        // Number of days in a non-leap year
+        internal const int DaysPerYear = 365;
+        // Number of days in 4 years
+        internal const int DaysPer4Years = DaysPerYear * 4 + 1;
+        // Number of days in 100 years
+        internal const int DaysPer100Years = DaysPer4Years * 25 - 1;
+        // Number of days in 400 years
+        internal const int DaysPer400Years = DaysPer100Years * 4 + 1;
+
+        // Number of days from 1/1/0001 to 1/1/10000
+        internal const int DaysTo10000 = DaysPer400Years * 25 - 366;
+
+        internal const long MaxMillis = (long)DaysTo10000 * MillisPerDay;
+
+        internal const int DatePartYear = 0;
+        internal const int DatePartDayOfYear = 1;
+        internal const int DatePartMonth = 2;
+        internal const int DatePartDay = 3;
+
+        //
+        // This is the max Gregorian year can be represented by DateTime class.  The limitation
+        // is derived from DateTime class.
+        // 
+        internal int MaxYear
+        {
+            get
+            {
+                return (m_maxYear);
+            }
+        }
+
+        internal static readonly int[] DaysToMonth365 =
+        {
+            0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365
+        };
+
+        internal static readonly int[] DaysToMonth366 =
+        {
+            0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366
+        };
+
+        internal int m_maxYear = 9999;
+        internal int m_minYear;
+        internal Calendar m_Cal;
+
+        internal EraInfo[] m_EraInfo;
+        internal int[] m_eras = null;
+
+
+        // Construct an instance of gregorian calendar.
+        internal GregorianCalendarHelper(Calendar cal, EraInfo[] eraInfo)
+        {
+            m_Cal = cal;
+            m_EraInfo = eraInfo;
+            m_maxYear = m_EraInfo[0].maxEraYear;
+            m_minYear = m_EraInfo[0].minEraYear; ;
+        }
+
+        /*=================================GetGregorianYear==========================
+        **Action: Get the Gregorian year value for the specified year in an era.
+        **Returns: The Gregorian year value.
+        **Arguments:
+        **      year    the year value in Japanese calendar
+        **      era     the Japanese emperor era value.
+        **Exceptions:
+        **      ArgumentOutOfRangeException if year value is invalid or era value is invalid.
+        ============================================================================*/
+
+        internal int GetGregorianYear(int year, int era)
+        {
+            if (year < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (era == Calendar.CurrentEra)
+            {
+                era = m_Cal.CurrentEraValue;
+            }
+
+            for (int i = 0; i < m_EraInfo.Length; i++)
+            {
+                if (era == m_EraInfo[i].era)
+                {
+                    if (year < m_EraInfo[i].minEraYear || year > m_EraInfo[i].maxEraYear)
+                    {
+                        throw new ArgumentOutOfRangeException(
+                                    nameof(year),
+                                    String.Format(
+                                        CultureInfo.CurrentCulture,
+                                        SR.ArgumentOutOfRange_Range,
+                                        m_EraInfo[i].minEraYear,
+                                        m_EraInfo[i].maxEraYear));
+                    }
+                    return (m_EraInfo[i].yearOffset + year);
+                }
+            }
+            throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+        }
+
+        internal bool IsValidYear(int year, int era)
+        {
+            if (year < 0)
+            {
+                return false;
+            }
+
+            if (era == Calendar.CurrentEra)
+            {
+                era = m_Cal.CurrentEraValue;
+            }
+
+            for (int i = 0; i < m_EraInfo.Length; i++)
+            {
+                if (era == m_EraInfo[i].era)
+                {
+                    if (year < m_EraInfo[i].minEraYear || year > m_EraInfo[i].maxEraYear)
+                    {
+                        return false;
+                    }
+                    return true;
+                }
+            }
+            return false;
+        }
+
+
+        // Returns a given date part of this DateTime. This method is used
+        // to compute the year, day-of-year, month, or day part.
+        internal virtual int GetDatePart(long ticks, int part)
+        {
+            CheckTicksRange(ticks);
+            // n = number of days since 1/1/0001
+            int n = (int)(ticks / TicksPerDay);
+            // y400 = number of whole 400-year periods since 1/1/0001
+            int y400 = n / DaysPer400Years;
+            // n = day number within 400-year period
+            n -= y400 * DaysPer400Years;
+            // y100 = number of whole 100-year periods within 400-year period
+            int y100 = n / DaysPer100Years;
+            // Last 100-year period has an extra day, so decrement result if 4
+            if (y100 == 4) y100 = 3;
+            // n = day number within 100-year period
+            n -= y100 * DaysPer100Years;
+            // y4 = number of whole 4-year periods within 100-year period
+            int y4 = n / DaysPer4Years;
+            // n = day number within 4-year period
+            n -= y4 * DaysPer4Years;
+            // y1 = number of whole years within 4-year period
+            int y1 = n / DaysPerYear;
+            // Last year has an extra day, so decrement result if 4
+            if (y1 == 4) y1 = 3;
+            // If year was requested, compute and return it
+            if (part == DatePartYear)
+            {
+                return (y400 * 400 + y100 * 100 + y4 * 4 + y1 + 1);
+            }
+            // n = day number within year
+            n -= y1 * DaysPerYear;
+            // If day-of-year was requested, return it
+            if (part == DatePartDayOfYear)
+            {
+                return (n + 1);
+            }
+            // Leap year calculation looks different from IsLeapYear since y1, y4,
+            // and y100 are relative to year 1, not year 0
+            bool leapYear = (y1 == 3 && (y4 != 24 || y100 == 3));
+            int[] days = leapYear ? DaysToMonth366 : DaysToMonth365;
+            // All months have less than 32 days, so n >> 5 is a good conservative
+            // estimate for the month
+            int m = (n >> 5) + 1;
+            // m = 1-based month number
+            while (n >= days[m]) m++;
+            // If month was requested, return it
+            if (part == DatePartMonth) return (m);
+            // Return 1-based day-of-month
+            return (n - days[m - 1] + 1);
+        }
+
+        /*=================================GetAbsoluteDate==========================
+        **Action: Gets the absolute date for the given Gregorian date.  The absolute date means
+        **       the number of days from January 1st, 1 A.D.
+        **Returns:  the absolute date
+        **Arguments:
+        **      year    the Gregorian year
+        **      month   the Gregorian month
+        **      day     the day
+        **Exceptions:
+        **      ArgumentOutOfRangException  if year, month, day value is valid.
+        **Note:
+        **      This is an internal method used by DateToTicks() and the calculations of Hijri and Hebrew calendars.
+        **      Number of Days in Prior Years (both common and leap years) +
+        **      Number of Days in Prior Months of Current Year +
+        **      Number of Days in Current Month
+        **
+        ============================================================================*/
+
+        internal static long GetAbsoluteDate(int year, int month, int day)
+        {
+            if (year >= 1 && year <= 9999 && month >= 1 && month <= 12)
+            {
+                int[] days = ((year % 4 == 0 && (year % 100 != 0 || year % 400 == 0))) ? DaysToMonth366 : DaysToMonth365;
+                if (day >= 1 && (day <= days[month] - days[month - 1]))
+                {
+                    int y = year - 1;
+                    int absoluteDate = y * 365 + y / 4 - y / 100 + y / 400 + days[month - 1] + day - 1;
+                    return (absoluteDate);
+                }
+            }
+            throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadYearMonthDay);
+        }
+
+        // Returns the tick count corresponding to the given year, month, and day.
+        // Will check the if the parameters are valid.
+        internal static long DateToTicks(int year, int month, int day)
+        {
+            return (GetAbsoluteDate(year, month, day) * TicksPerDay);
+        }
+
+        // Return the tick count corresponding to the given hour, minute, second.
+        // Will check the if the parameters are valid.
+        internal static long TimeToTicks(int hour, int minute, int second, int millisecond)
+        {
+            //TimeSpan.TimeToTicks is a family access function which does no error checking, so
+            //we need to put some error checking out here.
+            if (hour >= 0 && hour < 24 && minute >= 0 && minute < 60 && second >= 0 && second < 60)
+            {
+                if (millisecond < 0 || millisecond >= MillisPerSecond)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(millisecond),
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    0,
+                                    MillisPerSecond - 1));
+                }
+                return (InternalGlobalizationHelper.TimeToTicks(hour, minute, second) + millisecond * TicksPerMillisecond); ;
+            }
+            throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadHourMinuteSecond);
+        }
+
+
+        internal void CheckTicksRange(long ticks)
+        {
+            if (ticks < m_Cal.MinSupportedDateTime.Ticks || ticks > m_Cal.MaxSupportedDateTime.Ticks)
+            {
+                throw new ArgumentOutOfRangeException(
+                            "time",
+                            String.Format(
+                                CultureInfo.InvariantCulture,
+                                SR.ArgumentOutOfRange_CalendarRange,
+                                m_Cal.MinSupportedDateTime,
+                                m_Cal.MaxSupportedDateTime));
+            }
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // months to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year and month parts of the specified DateTime by
+        // value months, and, if required, adjusting the day part of the
+        // resulting date downwards to the last day of the resulting month in the
+        // resulting year. The time-of-day part of the result is the same as the
+        // time-of-day part of the specified DateTime.
+        //
+        // In more precise terms, considering the specified DateTime to be of the
+        // form y / m / d + t, where y is the
+        // year, m is the month, d is the day, and t is the
+        // time-of-day, the result is y1 / m1 / d1 + t,
+        // where y1 and m1 are computed by adding value months
+        // to y and m, and d1 is the largest value less than
+        // or equal to d that denotes a valid day in month m1 of year
+        // y1.
+        //
+        public DateTime AddMonths(DateTime time, int months)
+        {
+            if (months < -120000 || months > 120000)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(months),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                -120000,
+                                120000));
+            }
+            CheckTicksRange(time.Ticks);
+
+            int y = GetDatePart(time.Ticks, DatePartYear);
+            int m = GetDatePart(time.Ticks, DatePartMonth);
+            int d = GetDatePart(time.Ticks, DatePartDay);
+            int i = m - 1 + months;
+            if (i >= 0)
+            {
+                m = i % 12 + 1;
+                y = y + i / 12;
+            }
+            else
+            {
+                m = 12 + (i + 1) % 12;
+                y = y + (i - 11) / 12;
+            }
+            int[] daysArray = (y % 4 == 0 && (y % 100 != 0 || y % 400 == 0)) ? DaysToMonth366 : DaysToMonth365;
+            int days = (daysArray[m] - daysArray[m - 1]);
+
+            if (d > days)
+            {
+                d = days;
+            }
+            long ticks = DateToTicks(y, m, d) + (time.Ticks % TicksPerDay);
+            Calendar.CheckAddResult(ticks, m_Cal.MinSupportedDateTime, m_Cal.MaxSupportedDateTime);
+            return (new DateTime(ticks));
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // years to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year part of the specified DateTime by value
+        // years. If the month and day of the specified DateTime is 2/29, and if the
+        // resulting year is not a leap year, the month and day of the resulting
+        // DateTime becomes 2/28. Otherwise, the month, day, and time-of-day
+        // parts of the result are the same as those of the specified DateTime.
+        //
+        public DateTime AddYears(DateTime time, int years)
+        {
+            return (AddMonths(time, years * 12));
+        }
+
+        // Returns the day-of-month part of the specified DateTime. The returned
+        // value is an integer between 1 and 31.
+        //
+        public int GetDayOfMonth(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartDay));
+        }
+
+        // Returns the day-of-week part of the specified DateTime. The returned value
+        // is an integer between 0 and 6, where 0 indicates Sunday, 1 indicates
+        // Monday, 2 indicates Tuesday, 3 indicates Wednesday, 4 indicates
+        // Thursday, 5 indicates Friday, and 6 indicates Saturday.
+        //
+        public DayOfWeek GetDayOfWeek(DateTime time)
+        {
+            CheckTicksRange(time.Ticks);
+            return ((DayOfWeek)((time.Ticks / TicksPerDay + 1) % 7));
+        }
+
+        // Returns the day-of-year part of the specified DateTime. The returned value
+        // is an integer between 1 and 366.
+        //
+        public int GetDayOfYear(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartDayOfYear));
+        }
+
+        // Returns the number of days in the month given by the year and
+        // month arguments.
+        //
+        public int GetDaysInMonth(int year, int month, int era)
+        {
+            //
+            // Convert year/era value to Gregorain year value.
+            //
+            year = GetGregorianYear(year, era);
+            if (month < 1 || month > 12)
+            {
+                throw new ArgumentOutOfRangeException(nameof(month), SR.ArgumentOutOfRange_Month);
+            }
+            int[] days = ((year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)) ? DaysToMonth366 : DaysToMonth365);
+            return (days[month] - days[month - 1]);
+        }
+
+        // Returns the number of days in the year given by the year argument for the current era.
+        //
+
+        public int GetDaysInYear(int year, int era)
+        {
+            //
+            // Convert year/era value to Gregorain year value.
+            //
+            year = GetGregorianYear(year, era);
+            return ((year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)) ? 366 : 365);
+        }
+
+        // Returns the era for the specified DateTime value.
+        public int GetEra(DateTime time)
+        {
+            long ticks = time.Ticks;
+            // The assumption here is that m_EraInfo is listed in reverse order.
+            for (int i = 0; i < m_EraInfo.Length; i++)
+            {
+                if (ticks >= m_EraInfo[i].ticks)
+                {
+                    return (m_EraInfo[i].era);
+                }
+            }
+            throw new ArgumentOutOfRangeException(nameof(time), SR.ArgumentOutOfRange_Era);
+        }
+
+
+        public int[] Eras
+        {
+            get
+            {
+                if (m_eras == null)
+                {
+                    m_eras = new int[m_EraInfo.Length];
+                    for (int i = 0; i < m_EraInfo.Length; i++)
+                    {
+                        m_eras[i] = m_EraInfo[i].era;
+                    }
+                }
+                return ((int[])m_eras.Clone());
+            }
+        }
+
+        // Returns the month part of the specified DateTime. The returned value is an
+        // integer between 1 and 12.
+        //
+        public int GetMonth(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartMonth));
+        }
+
+        // Returns the number of months in the specified year and era.
+        public int GetMonthsInYear(int year, int era)
+        {
+            year = GetGregorianYear(year, era);
+            return (12);
+        }
+
+        // Returns the year part of the specified DateTime. The returned value is an
+        // integer between 1 and 9999.
+        //
+        public int GetYear(DateTime time)
+        {
+            long ticks = time.Ticks;
+            int year = GetDatePart(ticks, DatePartYear);
+            for (int i = 0; i < m_EraInfo.Length; i++)
+            {
+                if (ticks >= m_EraInfo[i].ticks)
+                {
+                    return (year - m_EraInfo[i].yearOffset);
+                }
+            }
+            throw new ArgumentException(SR.Argument_NoEra);
+        }
+
+        // Returns the year that match the specified Gregorian year. The returned value is an
+        // integer between 1 and 9999.
+        //
+        public int GetYear(int year, DateTime time)
+        {
+            long ticks = time.Ticks;
+            for (int i = 0; i < m_EraInfo.Length; i++)
+            {
+                // while calculating dates with JapaneseLuniSolarCalendar, we can run into cases right after the start of the era
+                // and still belong to the month which is started in previous era. Calculating equivalent calendar date will cause
+                // using the new era info which will have the year offset equal to the year we are calculating year = m_EraInfo[i].yearOffset
+                // which will end up with zero as calendar year.
+                // We should use the previous era info instead to get the right year number. Example of such date is Feb 2nd 1989
+                if (ticks >= m_EraInfo[i].ticks && year > m_EraInfo[i].yearOffset)
+                {
+                    return (year - m_EraInfo[i].yearOffset);
+                }
+            }
+            throw new ArgumentException(SR.Argument_NoEra);
+        }
+
+        // Checks whether a given day in the specified era is a leap day. This method returns true if
+        // the date is a leap day, or false if not.
+        //
+        public bool IsLeapDay(int year, int month, int day, int era)
+        {
+            // year/month/era checking is done in GetDaysInMonth()
+            if (day < 1 || day > GetDaysInMonth(year, month, era))
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(day),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                1,
+                                GetDaysInMonth(year, month, era)));
+            }
+
+            if (!IsLeapYear(year, era))
+            {
+                return (false);
+            }
+
+            if (month == 2 && day == 29)
+            {
+                return (true);
+            }
+
+            return (false);
+        }
+
+        // Returns  the leap month in a calendar year of the specified era. This method returns 0
+        // if this calendar does not have leap month, or this year is not a leap year.
+        //
+        public int GetLeapMonth(int year, int era)
+        {
+            year = GetGregorianYear(year, era);
+            return (0);
+        }
+
+        // Checks whether a given month in the specified era is a leap month. This method returns true if
+        // month is a leap month, or false if not.
+        //
+        public bool IsLeapMonth(int year, int month, int era)
+        {
+            year = GetGregorianYear(year, era);
+            if (month < 1 || month > 12)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(month),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                1,
+                                12));
+            }
+            return (false);
+        }
+
+        // Checks whether a given year in the specified era is a leap year. This method returns true if
+        // year is a leap year, or false if not.
+        //
+        public bool IsLeapYear(int year, int era)
+        {
+            year = GetGregorianYear(year, era);
+            return (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0));
+        }
+
+        // Returns the date and time converted to a DateTime value.  Throws an exception if the n-tuple is invalid.
+        //
+        public DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era)
+        {
+            year = GetGregorianYear(year, era);
+            long ticks = DateToTicks(year, month, day) + TimeToTicks(hour, minute, second, millisecond);
+            CheckTicksRange(ticks);
+            return (new DateTime(ticks));
+        }
+
+        public virtual int GetWeekOfYear(DateTime time, CalendarWeekRule rule, DayOfWeek firstDayOfWeek)
+        {
+            CheckTicksRange(time.Ticks);
+            // Use GregorianCalendar to get around the problem that the implmentation in Calendar.GetWeekOfYear()
+            // can call GetYear() that exceeds the supported range of the Gregorian-based calendars.
+            return (GregorianCalendar.GetDefaultInstance().GetWeekOfYear(time, rule, firstDayOfWeek));
+        }
+
+
+        public int ToFourDigitYear(int year, int twoDigitYearMax)
+        {
+            if (year < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year),
+                    SR.ArgumentOutOfRange_NeedPosNum);
+            }
+
+            if (year < 100)
+            {
+                int y = year % 100;
+                return ((twoDigitYearMax / 100 - (y > twoDigitYearMax % 100 ? 1 : 0)) * 100 + y);
+            }
+
+            if (year < m_minYear || year > m_maxYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range, m_minYear, m_maxYear));
+            }
+            // If the year value is above 100, just return the year value.  Don't have to do
+            // the TwoDigitYearMax comparison.
+            return (year);
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/GregorianCalendarTypes.cs b/src/System.Private.CoreLib/shared/System/Globalization/GregorianCalendarTypes.cs
new file mode 100644
index 0000000000..46f13b00e0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/GregorianCalendarTypes.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Globalization
+{
+    // Note: The values of the members of this enum must match the coresponding values
+    // in the CalendarId enum (since we cast between GregorianCalendarTypes and CalendarId).
+    public enum GregorianCalendarTypes
+    {
+        Localized = CalendarId.GREGORIAN,
+        USEnglish = CalendarId.GREGORIAN_US,
+        MiddleEastFrench = CalendarId.GREGORIAN_ME_FRENCH,
+        Arabic = CalendarId.GREGORIAN_ARABIC,
+        TransliteratedEnglish = CalendarId.GREGORIAN_XLIT_ENGLISH,
+        TransliteratedFrench = CalendarId.GREGORIAN_XLIT_FRENCH,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/HebrewCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/HebrewCalendar.cs
new file mode 100644
index 0000000000..533d3831bf
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/HebrewCalendar.cs
@@ -0,0 +1,1124 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    ////////////////////////////////////////////////////////////////////////////
+    //
+    //  Rules for the Hebrew calendar:
+    //    - The Hebrew calendar is both a Lunar (months) and Solar (years)
+    //        calendar, but allows for a week of seven days.
+    //    - Days begin at sunset.
+    //    - Leap Years occur in the 3, 6, 8, 11, 14, 17, & 19th years of a
+    //        19-year cycle.  Year = leap iff ((7y+1) mod 19 < 7).
+    //    - There are 12 months in a common year and 13 months in a leap year.
+    //    - In a common year, the 6th month, Adar, has 29 days.  In a leap
+    //        year, the 6th month, Adar I, has 30 days and the leap month,
+    //        Adar II, has 29 days.
+    //    - Common years have 353-355 days.  Leap years have 383-385 days.
+    //    - The Hebrew new year (Rosh HaShanah) begins on the 1st of Tishri,
+    //        the 7th month in the list below.
+    //        - The new year may not begin on Sunday, Wednesday, or Friday.
+    //        - If the new year would fall on a Tuesday and the conjunction of
+    //            the following year were at midday or later, the new year is
+    //            delayed until Thursday.
+    //        - If the new year would fall on a Monday after a leap year, the
+    //            new year is delayed until Tuesday.
+    //    - The length of the 8th and 9th months vary from year to year,
+    //        depending on the overall length of the year.
+    //        - The length of a year is determined by the dates of the new
+    //            years (Tishri 1) preceding and following the year in question.
+    //        - The 2th month is long (30 days) if the year has 355 or 385 days.
+    //        - The 3th month is short (29 days) if the year has 353 or 383 days.
+    //    - The Hebrew months are:
+    //        1.  Tishri        (30 days)
+    //        2.  Heshvan       (29 or 30 days)
+    //        3.  Kislev        (29 or 30 days)
+    //        4.  Teveth        (29 days)
+    //        5.  Shevat        (30 days)
+    //        6.  Adar I        (30 days)
+    //        7.  Adar {II}     (29 days, this only exists if that year is a leap year)
+    //        8.  Nisan         (30 days)
+    //        9.  Iyyar         (29 days)
+    //        10. Sivan         (30 days)
+    //        11. Tammuz        (29 days)
+    //        12. Av            (30 days)
+    //        13. Elul          (29 days)
+    //
+    ////////////////////////////////////////////////////////////////////////////
+    /*
+    **  Calendar support range:
+    **      Calendar    Minimum     Maximum
+    **      ==========  ==========  ==========
+    **      Gregorian   1583/01/01  2239/09/29
+    **      Hebrew      5343/04/07  5999/13/29
+    */
+
+    // Includes CHebrew implemetation;i.e All the code necessary for converting
+    // Gregorian to Hebrew Lunar from 1583 to 2239.
+
+
+    public class HebrewCalendar : Calendar
+    {
+        public static readonly int HebrewEra = 1;
+
+        internal const int DatePartYear = 0;
+        internal const int DatePartDayOfYear = 1;
+        internal const int DatePartMonth = 2;
+        internal const int DatePartDay = 3;
+        internal const int DatePartDayOfWeek = 4;
+
+        //
+        //  Hebrew Translation Table.
+        //
+        //  This table is used to get the following Hebrew calendar information for a
+        //  given Gregorian year:
+        //      1. The day of the Hebrew month corresponding to Gregorian January 1st
+        //         for a given Gregorian year.
+        //      2. The month of the Hebrew month corresponding to Gregorian January 1st
+        //         for a given Gregorian year.
+        //         The information is not directly in the table.  Instead, the info is decoded
+        //          by special values (numbers above 29 and below 1).
+        //      3. The type of the Hebrew year for a given Gregorian year.
+        //
+
+        /*
+            More notes:
+
+            This table includes 2 numbers for each year.
+            The offset into the table determines the year. (offset 0 is Gregorian year 1500)
+            1st number determines the day of the Hebrew month coresponeds to January 1st.
+            2nd number determines the type of the Hebrew year. (the type determines how
+             many days are there in the year.)
+
+             normal years : 1 = 353 days   2 = 354 days   3 = 355 days.
+             Leap years   : 4 = 383        5   384        6 = 385 days.
+
+             A 99 means the year is not supported for translation.
+             for convenience the table was defined for 750 year,
+             but only 640 years are supported. (from 1583 to 2239)
+             the years before 1582 (starting of Georgian calander)
+             and after 2239, are filled with 99.
+
+             Greogrian January 1st falls usually in Tevet (4th month). Tevet has always 29 days.
+             That's why, there no nead to specify the lunar month in the table.
+             There are exceptions, these are coded by giving numbers above 29 and below 1.
+             Actual decoding is takenig place whenever fetching information from the table.
+             The function for decoding is in GetLunarMonthDay().
+
+             Example:
+                The data for 2000 - 2005 A.D. is:
+
+                    23,6,6,1,17,2,27,6,7,3,         // 2000 - 2004
+
+                For year 2000, we know it has a Hebrew year type 6, which means it has 385 days.
+                And 1/1/2000 A.D. is Hebrew year 5760, 23rd day of 4th month.
+        */
+
+        //
+        //  Jewish Era in use today is dated from the supposed year of the
+        //  Creation with its beginning in 3761 B.C.
+        //
+
+        // The Hebrew year of Gregorian 1st year AD.
+        // 0001/01/01 AD is Hebrew 3760/01/01
+        private const int HebrewYearOf1AD = 3760;
+
+        // The first Gregorian year in HebrewTable.
+        private const int FirstGregorianTableYear = 1583;   // == Hebrew Year 5343
+        // The last Gregorian year in HebrewTable.
+        private const int LastGregorianTableYear = 2239;    // == Hebrew Year 5999
+        private const int TABLESIZE = (LastGregorianTableYear - FirstGregorianTableYear);
+
+        private const int MinHebrewYear = HebrewYearOf1AD + FirstGregorianTableYear;   // == 5343
+        private const int MaxHebrewYear = HebrewYearOf1AD + LastGregorianTableYear;    // == 5999
+
+        private static readonly byte[] s_hebrewTable = {
+            7,3,17,3,         // 1583-1584  (Hebrew year: 5343 - 5344)
+            0,4,11,2,21,6,1,3,13,2,             // 1585-1589
+            25,4,5,3,16,2,27,6,9,1,             // 1590-1594
+            20,2,0,6,11,3,23,4,4,2,             // 1595-1599
+            14,3,27,4,8,2,18,3,28,6,            // 1600
+            11,1,22,5,2,3,12,3,25,4,      // 1605
+            6,2,16,3,26,6,8,2,20,1,      // 1610
+            0,6,11,2,24,4,4,3,15,2,      // 1615
+            25,6,8,1,19,2,29,6,9,3,      // 1620
+            22,4,3,2,13,3,25,4,6,3,      // 1625
+            17,2,27,6,7,3,19,2,31,4,      // 1630
+            11,3,23,4,5,2,15,3,25,6,      // 1635
+            6,2,19,1,29,6,10,2,22,4,      // 1640
+            3,3,14,2,24,6,6,1,17,3,      // 1645
+            28,5,8,3,20,1,32,5,12,3,      // 1650
+            22,6,4,1,16,2,26,6,6,3,      // 1655
+            17,2,0,4,10,3,22,4,3,2,      // 1660
+            14,3,24,6,5,2,17,1,28,6,      // 1665
+            9,2,19,3,31,4,13,2,23,6,      // 1670
+            3,3,15,1,27,5,7,3,17,3,      // 1675
+            29,4,11,2,21,6,3,1,14,2,      // 1680
+            25,6,5,3,16,2,28,4,9,3,      // 1685
+            20,2,0,6,12,1,23,6,4,2,      // 1690
+            14,3,26,4,8,2,18,3,0,4,      // 1695
+            10,3,21,5,1,3,13,1,24,5,      // 1700
+            5,3,15,3,27,4,8,2,19,3,      // 1705
+            29,6,10,2,22,4,3,3,14,2,      // 1710
+            26,4,6,3,18,2,28,6,10,1,      // 1715
+            20,6,2,2,12,3,24,4,5,2,      // 1720
+            16,3,28,4,8,3,19,2,0,6,      // 1725
+            12,1,23,5,3,3,14,3,26,4,      // 1730
+            7,2,17,3,28,6,9,2,21,4,      // 1735
+            1,3,13,2,25,4,5,3,16,2,      // 1740
+            27,6,9,1,19,3,0,5,11,3,      // 1745
+            23,4,4,2,14,3,25,6,7,1,      // 1750
+            18,2,28,6,9,3,21,4,2,2,      // 1755
+            12,3,25,4,6,2,16,3,26,6,      // 1760
+            8,2,20,1,0,6,11,2,22,6,      // 1765
+            4,1,15,2,25,6,6,3,18,1,      // 1770
+            29,5,9,3,22,4,2,3,13,2,      // 1775
+            23,6,4,3,15,2,27,4,7,3,      // 1780
+            19,2,31,4,11,3,21,6,3,2,      // 1785
+            15,1,25,6,6,2,17,3,29,4,      // 1790
+            10,2,20,6,3,1,13,3,24,5,      // 1795
+            4,3,16,1,27,5,7,3,17,3,      // 1800
+            0,4,11,2,21,6,1,3,13,2,      // 1805
+            25,4,5,3,16,2,29,4,9,3,      // 1810
+            19,6,30,2,13,1,23,6,4,2,      // 1815
+            14,3,27,4,8,2,18,3,0,4,      // 1820
+            11,3,22,5,2,3,14,1,26,5,      // 1825
+            6,3,16,3,28,4,10,2,20,6,      // 1830
+            30,3,11,2,24,4,4,3,15,2,      // 1835
+            25,6,8,1,19,2,29,6,9,3,      // 1840
+            22,4,3,2,13,3,25,4,7,2,      // 1845
+            17,3,27,6,9,1,21,5,1,3,      // 1850
+            11,3,23,4,5,2,15,3,25,6,      // 1855
+            6,2,19,1,29,6,10,2,22,4,      // 1860
+            3,3,14,2,24,6,6,1,18,2,      // 1865
+            28,6,8,3,20,4,2,2,12,3,      // 1870
+            24,4,4,3,16,2,26,6,6,3,      // 1875
+            17,2,0,4,10,3,22,4,3,2,      // 1880
+            14,3,24,6,5,2,17,1,28,6,      // 1885
+            9,2,21,4,1,3,13,2,23,6,      // 1890
+            5,1,15,3,27,5,7,3,19,1,      // 1895
+            0,5,10,3,22,4,2,3,13,2,      // 1900
+            24,6,4,3,15,2,27,4,8,3,      // 1905
+            20,4,1,2,11,3,22,6,3,2,      // 1910
+            15,1,25,6,7,2,17,3,29,4,      // 1915
+            10,2,21,6,1,3,13,1,24,5,      // 1920
+            5,3,15,3,27,4,8,2,19,6,      // 1925
+            1,1,12,2,22,6,3,3,14,2,      // 1930
+            26,4,6,3,18,2,28,6,10,1,      // 1935
+            20,6,2,2,12,3,24,4,5,2,      // 1940
+            16,3,28,4,9,2,19,6,30,3,      // 1945
+            12,1,23,5,3,3,14,3,26,4,      // 1950
+            7,2,17,3,28,6,9,2,21,4,      // 1955
+            1,3,13,2,25,4,5,3,16,2,      // 1960
+            27,6,9,1,19,6,30,2,11,3,      // 1965
+            23,4,4,2,14,3,27,4,7,3,      // 1970
+            18,2,28,6,11,1,22,5,2,3,      // 1975
+            12,3,25,4,6,2,16,3,26,6,      // 1980
+            8,2,20,4,30,3,11,2,24,4,      // 1985
+            4,3,15,2,25,6,8,1,18,3,      // 1990
+            29,5,9,3,22,4,3,2,13,3,      // 1995
+            23,6,6,1,17,2,27,6,7,3,         // 2000 - 2004
+            20,4,1,2,11,3,23,4,5,2,         // 2005 - 2009
+            15,3,25,6,6,2,19,1,29,6,        // 2010
+            10,2,20,6,3,1,14,2,24,6,      // 2015
+            4,3,17,1,28,5,8,3,20,4,      // 2020
+            1,3,12,2,22,6,2,3,14,2,      // 2025
+            26,4,6,3,17,2,0,4,10,3,      // 2030
+            20,6,1,2,14,1,24,6,5,2,      // 2035
+            15,3,28,4,9,2,19,6,1,1,      // 2040
+            12,3,23,5,3,3,15,1,27,5,      // 2045
+            7,3,17,3,29,4,11,2,21,6,      // 2050
+            1,3,12,2,25,4,5,3,16,2,      // 2055
+            28,4,9,3,19,6,30,2,12,1,      // 2060
+            23,6,4,2,14,3,26,4,8,2,      // 2065
+            18,3,0,4,10,3,22,5,2,3,      // 2070
+            14,1,25,5,6,3,16,3,28,4,      // 2075
+            9,2,20,6,30,3,11,2,23,4,      // 2080
+            4,3,15,2,27,4,7,3,19,2,      // 2085
+            29,6,11,1,21,6,3,2,13,3,      // 2090
+            25,4,6,2,17,3,27,6,9,1,      // 2095
+            20,5,30,3,10,3,22,4,3,2,      // 2100
+            14,3,24,6,5,2,17,1,28,6,      // 2105
+            9,2,21,4,1,3,13,2,23,6,      // 2110
+            5,1,16,2,27,6,7,3,19,4,      // 2115
+            30,2,11,3,23,4,3,3,14,2,      // 2120
+            25,6,5,3,16,2,28,4,9,3,      // 2125
+            21,4,2,2,12,3,23,6,4,2,      // 2130
+            16,1,26,6,8,2,20,4,30,3,      // 2135
+            11,2,22,6,4,1,14,3,25,5,      // 2140
+            6,3,18,1,29,5,9,3,22,4,      // 2145
+            2,3,13,2,23,6,4,3,15,2,      // 2150
+            27,4,7,3,20,4,1,2,11,3,      // 2155
+            21,6,3,2,15,1,25,6,6,2,      // 2160
+            17,3,29,4,10,2,20,6,3,1,      // 2165
+            13,3,24,5,4,3,17,1,28,5,      // 2170
+            8,3,18,6,1,1,12,2,22,6,      // 2175
+            2,3,14,2,26,4,6,3,17,2,      // 2180
+            28,6,10,1,20,6,1,2,12,3,    // 2185
+            24,4,5,2,15,3,28,4,9,2,     // 2190
+            19,6,33,3,12,1,23,5,3,3,    // 2195
+            13,3,25,4,6,2,16,3,26,6,    // 2200
+            8,2,20,4,30,3,11,2,24,4,    // 2205
+            4,3,15,2,25,6,8,1,18,6,     // 2210
+            33,2,9,3,22,4,3,2,13,3,     // 2215
+            25,4,6,3,17,2,27,6,9,1,     // 2220
+            21,5,1,3,11,3,23,4,5,2,     // 2225
+            15,3,25,6,6,2,19,4,33,3,    // 2230
+            10,2,22,4,3,3,14,2,24,6,    // 2235
+            6,1    // 2240 (Hebrew year: 6000)
+        };
+
+        private const int MaxMonthPlusOne = 14;
+
+        //
+        //  The lunar calendar has 6 different variations of month lengths
+        //  within a year.
+        //
+        private static readonly byte[] s_lunarMonthLen = {
+            0,00,00,00,00,00,00,00,00,00,00,00,00,0,
+            0,30,29,29,29,30,29,30,29,30,29,30,29,0,     // 3 common year variations
+            0,30,29,30,29,30,29,30,29,30,29,30,29,0,
+            0,30,30,30,29,30,29,30,29,30,29,30,29,0,
+            0,30,29,29,29,30,30,29,30,29,30,29,30,29,    // 3 leap year variations
+            0,30,29,30,29,30,30,29,30,29,30,29,30,29,
+            0,30,30,30,29,30,30,29,30,29,30,29,30,29
+        };
+
+        internal static readonly DateTime calendarMinValue = new DateTime(1583, 1, 1);
+        // Gregorian 2239/9/29 = Hebrew 5999/13/29 (last day in Hebrew year 5999).
+        // We can only format/parse Hebrew numbers up to 999, so we limit the max range to Hebrew year 5999.
+        internal static readonly DateTime calendarMaxValue = new DateTime((new DateTime(2239, 9, 29, 23, 59, 59, 999)).Ticks + 9999);
+
+
+
+        public override DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (calendarMinValue);
+            }
+        }
+
+
+
+        public override DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (calendarMaxValue);
+            }
+        }
+
+        public override CalendarAlgorithmType AlgorithmType
+        {
+            get
+            {
+                return CalendarAlgorithmType.LunisolarCalendar;
+            }
+        }
+
+        public HebrewCalendar()
+        {
+        }
+
+        internal override CalendarId ID
+        {
+            get
+            {
+                return (CalendarId.HEBREW);
+            }
+        }
+
+
+        /*=================================CheckHebrewYearValue==========================
+        **Action: Check if the Hebrew year value is supported in this class.
+        **Returns:  None.
+        **Arguments: y  Hebrew year value
+        **          ear Hebrew era value
+        **Exceptions: ArgumentOutOfRange_Range if the year value is not supported.
+        **Note:
+        **  We use a table for the Hebrew calendar calculation, so the year supported is limited.
+        ============================================================================*/
+
+        private static void CheckHebrewYearValue(int y, int era, String varName)
+        {
+            CheckEraRange(era);
+            if (y > MaxHebrewYear || y < MinHebrewYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            varName,
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                MinHebrewYear,
+                                MaxHebrewYear));
+            }
+        }
+
+        /*=================================CheckHebrewMonthValue==========================
+        **Action: Check if the Hebrew month value is valid.
+        **Returns:  None.
+        **Arguments: year  Hebrew year value
+        **          month Hebrew month value
+        **Exceptions: ArgumentOutOfRange_Range if the month value is not valid.
+        **Note:
+        **  Call CheckHebrewYearValue() before calling this to verify the year value is supported.
+        ============================================================================*/
+
+        private void CheckHebrewMonthValue(int year, int month, int era)
+        {
+            int monthsInYear = GetMonthsInYear(year, era);
+            if (month < 1 || month > monthsInYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(month),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                1,
+                                monthsInYear));
+            }
+        }
+
+        /*=================================CheckHebrewDayValue==========================
+        **Action: Check if the Hebrew day value is valid.
+        **Returns:  None.
+        **Arguments: year  Hebrew year value
+        **          month Hebrew month value
+        **          day     Hebrew day value.
+        **Exceptions: ArgumentOutOfRange_Range if the day value is not valid.
+        **Note:
+        **  Call CheckHebrewYearValue()/CheckHebrewMonthValue() before calling this to verify the year/month values are valid.
+        ============================================================================*/
+
+        private void CheckHebrewDayValue(int year, int month, int day, int era)
+        {
+            int daysInMonth = GetDaysInMonth(year, month, era);
+            if (day < 1 || day > daysInMonth)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(day),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                1,
+                                daysInMonth));
+            }
+        }
+
+        internal static void CheckEraRange(int era)
+        {
+            if (era != CurrentEra && era != HebrewEra)
+            {
+                throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+            }
+        }
+
+        private static void CheckTicksRange(long ticks)
+        {
+            if (ticks < calendarMinValue.Ticks || ticks > calendarMaxValue.Ticks)
+            {
+                throw new ArgumentOutOfRangeException(
+                            "time",
+                            // Print out the date in Gregorian using InvariantCulture since the DateTime is based on GreograinCalendar.
+                            String.Format(
+                                CultureInfo.InvariantCulture,
+                                SR.ArgumentOutOfRange_CalendarRange,
+                                calendarMinValue,
+                                calendarMaxValue));
+            }
+        }
+
+        internal static int GetResult(__DateBuffer result, int part)
+        {
+            switch (part)
+            {
+                case DatePartYear:
+                    return (result.year);
+                case DatePartMonth:
+                    return (result.month);
+                case DatePartDay:
+                    return (result.day);
+            }
+
+            throw new InvalidOperationException(SR.InvalidOperation_DateTimeParsing);
+        }
+
+        /*=================================GetLunarMonthDay==========================
+        **Action: Using the Hebrew table (HebrewTable) to get the Hebrew month/day value for Gregorian January 1st
+        ** in a given Gregorian year.
+        ** Greogrian January 1st falls usually in Tevet (4th month). Tevet has always 29 days.
+        **     That's why, there no nead to specify the lunar month in the table.  There are exceptions, and these
+        **     are coded by giving numbers above 29 and below 1.
+        **     Actual decoding is takenig place in the switch statement below.
+        **Returns:
+        **     The Hebrew year type. The value is from 1 to 6.
+        **     normal years : 1 = 353 days   2 = 354 days   3 = 355 days.
+        **     Leap years   : 4 = 383        5   384        6 = 385 days.
+        **Arguments:
+        **      gregorianYear   The year value in Gregorian calendar.  The value should be between 1500 and 2239.
+        **      lunarDate       Object to take the result of the Hebrew year/month/day.
+        **Exceptions:
+        ============================================================================*/
+
+        internal static int GetLunarMonthDay(int gregorianYear, __DateBuffer lunarDate)
+        {
+            //
+            //  Get the offset into the LunarMonthLen array and the lunar day
+            //  for January 1st.
+            //
+            int index = gregorianYear - FirstGregorianTableYear;
+            if (index < 0 || index > TABLESIZE)
+            {
+                throw new ArgumentOutOfRangeException(nameof(gregorianYear));
+            }
+
+            index *= 2;
+            lunarDate.day = s_hebrewTable[index];
+
+            // Get the type of the year. The value is from 1 to 6
+            int LunarYearType = s_hebrewTable[index + 1];
+
+            //
+            //  Get the Lunar Month.
+            //
+            switch (lunarDate.day)
+            {
+                case (0):                   // 1/1 is on Shvat 1
+                    lunarDate.month = 5;
+                    lunarDate.day = 1;
+                    break;
+                case (30):                  // 1/1 is on Kislev 30
+                    lunarDate.month = 3;
+                    break;
+                case (31):                  // 1/1 is on Shvat 2
+                    lunarDate.month = 5;
+                    lunarDate.day = 2;
+                    break;
+                case (32):                  // 1/1 is on Shvat 3
+                    lunarDate.month = 5;
+                    lunarDate.day = 3;
+                    break;
+                case (33):                  // 1/1 is on Kislev 29
+                    lunarDate.month = 3;
+                    lunarDate.day = 29;
+                    break;
+                default:                      // 1/1 is on Tevet (This is the general case)
+                    lunarDate.month = 4;
+                    break;
+            }
+            return (LunarYearType);
+        }
+
+        // Returns a given date part of this DateTime. This method is used
+        // to compute the year, day-of-year, month, or day part.
+
+        internal virtual int GetDatePart(long ticks, int part)
+        {
+            // The Gregorian year, month, day value for ticks.
+            int gregorianYear, gregorianMonth, gregorianDay;
+            int hebrewYearType;                // lunar year type
+            long AbsoluteDate;                // absolute date - absolute date 1/1/1600
+
+            //
+            //  Make sure we have a valid Gregorian date that will fit into our
+            //  Hebrew conversion limits.
+            //
+            CheckTicksRange(ticks);
+
+            DateTime time = new DateTime(ticks);
+
+            //
+            //  Save the Gregorian date values.
+            //
+            time.GetDatePart(out gregorianYear, out gregorianMonth, out gregorianDay);
+
+            __DateBuffer lunarDate = new __DateBuffer();    // lunar month and day for Jan 1
+
+            // From the table looking-up value of HebrewTable[index] (stored in lunarDate.day), we get the the
+            // lunar month and lunar day where the Gregorian date 1/1 falls.
+            lunarDate.year = gregorianYear + HebrewYearOf1AD;
+            hebrewYearType = GetLunarMonthDay(gregorianYear, lunarDate);
+
+            // This is the buffer used to store the result Hebrew date.
+            __DateBuffer result = new __DateBuffer();
+
+            //
+            //  Store the values for the start of the new year - 1/1.
+            //
+            result.year = lunarDate.year;
+            result.month = lunarDate.month;
+            result.day = lunarDate.day;
+
+            //
+            //  Get the absolute date from 1/1/1600.
+            //
+            AbsoluteDate = GregorianCalendar.GetAbsoluteDate(gregorianYear, gregorianMonth, gregorianDay);
+
+            //
+            //  If the requested date was 1/1, then we're done.
+            //
+            if ((gregorianMonth == 1) && (gregorianDay == 1))
+            {
+                return (GetResult(result, part));
+            }
+
+            //
+            //  Calculate the number of days between 1/1 and the requested date.
+            //
+            long NumDays;                      // number of days since 1/1
+            NumDays = AbsoluteDate - GregorianCalendar.GetAbsoluteDate(gregorianYear, 1, 1);
+
+            //
+            //  If the requested date is within the current lunar month, then
+            //  we're done.
+            //
+            if ((NumDays + (long)lunarDate.day) <= (long)(s_lunarMonthLen[hebrewYearType * MaxMonthPlusOne + lunarDate.month]))
+            {
+                result.day += (int)NumDays;
+                return (GetResult(result, part));
+            }
+
+            //
+            //  Adjust for the current partial month.
+            //
+            result.month++;
+            result.day = 1;
+
+            //
+            //  Adjust the Lunar Month and Year (if necessary) based on the number
+            //  of days between 1/1 and the requested date.
+            //
+            //  Assumes Jan 1 can never translate to the last Lunar month, which
+            //  is true.
+            //
+            NumDays -= (long)(s_lunarMonthLen[hebrewYearType * MaxMonthPlusOne + lunarDate.month] - lunarDate.day);
+            Debug.Assert(NumDays >= 1, "NumDays >= 1");
+
+            // If NumDays is 1, then we are done.  Otherwise, find the correct Hebrew month
+            // and day.
+            if (NumDays > 1)
+            {
+                //
+                //  See if we're on the correct Lunar month.
+                //
+                while (NumDays > (long)(s_lunarMonthLen[hebrewYearType * MaxMonthPlusOne + result.month]))
+                {
+                    //
+                    //  Adjust the number of days and move to the next month.
+                    //
+                    NumDays -= (long)(s_lunarMonthLen[hebrewYearType * MaxMonthPlusOne + result.month++]);
+
+                    //
+                    //  See if we need to adjust the Year.
+                    //  Must handle both 12 and 13 month years.
+                    //
+                    if ((result.month > 13) || (s_lunarMonthLen[hebrewYearType * MaxMonthPlusOne + result.month] == 0))
+                    {
+                        //
+                        //  Adjust the Year.
+                        //
+                        result.year++;
+                        hebrewYearType = s_hebrewTable[(gregorianYear + 1 - FirstGregorianTableYear) * 2 + 1];
+
+                        //
+                        //  Adjust the Month.
+                        //
+                        result.month = 1;
+                    }
+                }
+                //
+                //  Found the right Lunar month.
+                //
+                result.day += (int)(NumDays - 1);
+            }
+            return (GetResult(result, part));
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // months to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year and month parts of the specified DateTime by
+        // value months, and, if required, adjusting the day part of the
+        // resulting date downwards to the last day of the resulting month in the
+        // resulting year. The time-of-day part of the result is the same as the
+        // time-of-day part of the specified DateTime.
+        //
+        // In more precise terms, considering the specified DateTime to be of the
+        // form y / m / d + t, where y is the
+        // year, m is the month, d is the day, and t is the
+        // time-of-day, the result is y1 / m1 / d1 + t,
+        // where y1 and m1 are computed by adding value months
+        // to y and m, and d1 is the largest value less than
+        // or equal to d that denotes a valid day in month m1 of year
+        // y1.
+        //
+
+        public override DateTime AddMonths(DateTime time, int months)
+        {
+            try
+            {
+                int y = GetDatePart(time.Ticks, DatePartYear);
+                int m = GetDatePart(time.Ticks, DatePartMonth);
+                int d = GetDatePart(time.Ticks, DatePartDay);
+
+
+                int monthsInYear;
+                int i;
+                if (months >= 0)
+                {
+                    i = m + months;
+                    while (i > (monthsInYear = GetMonthsInYear(y, CurrentEra)))
+                    {
+                        y++;
+                        i -= monthsInYear;
+                    }
+                }
+                else
+                {
+                    if ((i = m + months) <= 0)
+                    {
+                        months = -months;
+                        months -= m;
+                        y--;
+
+                        while (months > (monthsInYear = GetMonthsInYear(y, CurrentEra)))
+                        {
+                            y--;
+                            months -= monthsInYear;
+                        }
+                        monthsInYear = GetMonthsInYear(y, CurrentEra);
+                        i = monthsInYear - months;
+                    }
+                }
+
+                int days = GetDaysInMonth(y, i);
+                if (d > days)
+                {
+                    d = days;
+                }
+                return (new DateTime(ToDateTime(y, i, d, 0, 0, 0, 0).Ticks + (time.Ticks % TicksPerDay)));
+            }
+            // We expect ArgumentException and ArgumentOutOfRangeException (which is subclass of ArgumentException)
+            // If exception is thrown in the calls above, we are out of the supported range of this calendar.
+            catch (ArgumentException)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(months),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_AddValue));
+            }
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // years to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year part of the specified DateTime by value
+        // years. If the month and day of the specified DateTime is 2/29, and if the
+        // resulting year is not a leap year, the month and day of the resulting
+        // DateTime becomes 2/28. Otherwise, the month, day, and time-of-day
+        // parts of the result are the same as those of the specified DateTime.
+        //
+
+        public override DateTime AddYears(DateTime time, int years)
+        {
+            int y = GetDatePart(time.Ticks, DatePartYear);
+            int m = GetDatePart(time.Ticks, DatePartMonth);
+            int d = GetDatePart(time.Ticks, DatePartDay);
+
+            y += years;
+            CheckHebrewYearValue(y, Calendar.CurrentEra, nameof(years));
+
+            int months = GetMonthsInYear(y, CurrentEra);
+            if (m > months)
+            {
+                m = months;
+            }
+
+            int days = GetDaysInMonth(y, m);
+            if (d > days)
+            {
+                d = days;
+            }
+
+            long ticks = ToDateTime(y, m, d, 0, 0, 0, 0).Ticks + (time.Ticks % TicksPerDay);
+            Calendar.CheckAddResult(ticks, MinSupportedDateTime, MaxSupportedDateTime);
+            return (new DateTime(ticks));
+        }
+
+        // Returns the day-of-month part of the specified DateTime. The returned
+        // value is an integer between 1 and 31.
+        //
+
+        public override int GetDayOfMonth(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartDay));
+        }
+
+        // Returns the day-of-week part of the specified DateTime. The returned value
+        // is an integer between 0 and 6, where 0 indicates Sunday, 1 indicates
+        // Monday, 2 indicates Tuesday, 3 indicates Wednesday, 4 indicates
+        // Thursday, 5 indicates Friday, and 6 indicates Saturday.
+        //
+
+        public override DayOfWeek GetDayOfWeek(DateTime time)
+        {
+            // If we calculate back, the Hebrew day of week for Gregorian 0001/1/1 is Monday (1).
+            // Therfore, the fomula is:
+            return ((DayOfWeek)((int)(time.Ticks / TicksPerDay + 1) % 7));
+        }
+
+        internal static int GetHebrewYearType(int year, int era)
+        {
+            CheckHebrewYearValue(year, era, nameof(year));
+            // The HebrewTable is indexed by Gregorian year and starts from FirstGregorianYear.
+            // So we need to convert year (Hebrew year value) to Gregorian Year below.
+            return (s_hebrewTable[(year - HebrewYearOf1AD - FirstGregorianTableYear) * 2 + 1]);
+        }
+
+        // Returns the day-of-year part of the specified DateTime. The returned value
+        // is an integer between 1 and 366.
+        //
+
+        public override int GetDayOfYear(DateTime time)
+        {
+            // Get Hebrew year value of the specified time.
+            int year = GetYear(time);
+            DateTime beginOfYearDate;
+            if (year == 5343)
+            {
+                // Gregorian 1583/01/01 corresponds to Hebrew 5343/04/07 (MinSupportedDateTime)
+                // To figure out the Gregorian date associated with Hebrew 5343/01/01, we need to
+                // count the days from 5343/01/01 to 5343/04/07 and subtract that from Gregorian 
+                // 1583/01/01.
+                //        1.  Tishri        (30 days)
+                //        2.  Heshvan       (30 days since 5343 has 355 days)
+                //        3.  Kislev        (30 days since 5343 has 355 days)
+                // 96 days to get from 5343/01/01 to 5343/04/07
+                // Gregorian 1583/01/01 - 96 days = 1582/9/27
+
+                // the beginning of Hebrew year 5343 corresponds to Gregorian September 27, 1582.
+                beginOfYearDate = new DateTime(1582, 9, 27);
+            }
+            else
+            {
+                // following line will fail when year is 5343 (first supported year)
+                beginOfYearDate = ToDateTime(year, 1, 1, 0, 0, 0, 0, CurrentEra);
+            }
+            return ((int)((time.Ticks - beginOfYearDate.Ticks) / TicksPerDay) + 1);
+        }
+
+        // Returns the number of days in the month given by the year and
+        // month arguments.
+        //
+
+        public override int GetDaysInMonth(int year, int month, int era)
+        {
+            CheckEraRange(era);
+            int hebrewYearType = GetHebrewYearType(year, era);
+            CheckHebrewMonthValue(year, month, era);
+
+            Debug.Assert(hebrewYearType >= 1 && hebrewYearType <= 6,
+                "hebrewYearType should be from  1 to 6, but now hebrewYearType = " + hebrewYearType + " for hebrew year " + year);
+            int monthDays = s_lunarMonthLen[hebrewYearType * MaxMonthPlusOne + month];
+            if (monthDays == 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(month), SR.ArgumentOutOfRange_Month);
+            }
+            return (monthDays);
+        }
+
+        // Returns the number of days in the year given by the year argument for the current era.
+        //
+
+        public override int GetDaysInYear(int year, int era)
+        {
+            CheckEraRange(era);
+            // normal years : 1 = 353 days   2 = 354 days   3 = 355 days.
+            // Leap years   : 4 = 383        5   384        6 = 385 days.
+
+            // LunarYearType is from 1 to 6
+            int LunarYearType = GetHebrewYearType(year, era);
+            if (LunarYearType < 4)
+            {
+                // common year: LunarYearType = 1, 2, 3
+                return (352 + LunarYearType);
+            }
+            return (382 + (LunarYearType - 3));
+        }
+
+        // Returns the era for the specified DateTime value.
+
+        public override int GetEra(DateTime time)
+        {
+            return (HebrewEra);
+        }
+
+
+        public override int[] Eras
+        {
+            get
+            {
+                return (new int[] { HebrewEra });
+            }
+        }
+
+        // Returns the month part of the specified DateTime. The returned value is an
+        // integer between 1 and 12.
+        //
+
+        public override int GetMonth(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartMonth));
+        }
+
+        // Returns the number of months in the specified year and era.
+
+        public override int GetMonthsInYear(int year, int era)
+        {
+            return (IsLeapYear(year, era) ? 13 : 12);
+        }
+
+        // Returns the year part of the specified DateTime. The returned value is an
+        // integer between 1 and 9999.
+        //
+
+        public override int GetYear(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartYear));
+        }
+
+        // Checks whether a given day in the specified era is a leap day. This method returns true if
+        // the date is a leap day, or false if not.
+        //
+
+        public override bool IsLeapDay(int year, int month, int day, int era)
+        {
+            if (IsLeapMonth(year, month, era))
+            {
+                // Every day in a leap month is a leap day.
+                CheckHebrewDayValue(year, month, day, era);
+                return (true);
+            }
+            else if (IsLeapYear(year, Calendar.CurrentEra))
+            {
+                // There is an additional day in the 6th month in the leap year (the extra day is the 30th day in the 6th month),
+                // so we should return true for 6/30 if that's in a leap year.
+                if (month == 6 && day == 30)
+                {
+                    return (true);
+                }
+            }
+            CheckHebrewDayValue(year, month, day, era);
+            return (false);
+        }
+
+        // Returns  the leap month in a calendar year of the specified era. This method returns 0
+        // if this calendar does not have leap month, or this year is not a leap year.
+        //
+
+
+        public override int GetLeapMonth(int year, int era)
+        {
+            // Year/era values are checked in IsLeapYear().
+            if (IsLeapYear(year, era))
+            {
+                // The 7th month in a leap year is a leap month.
+                return (7);
+            }
+            return (0);
+        }
+
+        // Checks whether a given month in the specified era is a leap month. This method returns true if
+        // month is a leap month, or false if not.
+        //
+
+        public override bool IsLeapMonth(int year, int month, int era)
+        {
+            // Year/era values are checked in IsLeapYear().
+            bool isLeapYear = IsLeapYear(year, era);
+            CheckHebrewMonthValue(year, month, era);
+            // The 7th month in a leap year is a leap month.
+            if (isLeapYear)
+            {
+                if (month == 7)
+                {
+                    return (true);
+                }
+            }
+            return (false);
+        }
+
+        // Checks whether a given year in the specified era is a leap year. This method returns true if
+        // year is a leap year, or false if not.
+        //
+
+        public override bool IsLeapYear(int year, int era)
+        {
+            CheckHebrewYearValue(year, era, nameof(year));
+            return (((7 * (long)year + 1) % 19) < 7);
+        }
+
+        // (month1, day1) - (month2, day2)
+        private static int GetDayDifference(int lunarYearType, int month1, int day1, int month2, int day2)
+        {
+            if (month1 == month2)
+            {
+                return (day1 - day2);
+            }
+
+            // Make sure that (month1, day1) < (month2, day2)
+            bool swap = (month1 > month2);
+            if (swap)
+            {
+                // (month1, day1) < (month2, day2).  Swap the values.
+                // The result will be a negative number.
+                int tempMonth, tempDay;
+                tempMonth = month1; tempDay = day1;
+                month1 = month2; day1 = day2;
+                month2 = tempMonth; day2 = tempDay;
+            }
+
+            // Get the number of days from (month1,day1) to (month1, end of month1)
+            int days = s_lunarMonthLen[lunarYearType * MaxMonthPlusOne + month1] - day1;
+
+            // Move to next month.
+            month1++;
+
+            // Add up the days.
+            while (month1 < month2)
+            {
+                days += s_lunarMonthLen[lunarYearType * MaxMonthPlusOne + month1++];
+            }
+            days += day2;
+
+            return (swap ? days : -days);
+        }
+
+        /*=================================HebrewToGregorian==========================
+        **Action: Convert Hebrew date to Gregorian date.
+        **Returns:
+        **Arguments:
+        **Exceptions:
+        **  The algorithm is like this:
+        **      The hebrew year has an offset to the Gregorian year, so we can guess the Gregorian year for
+        **      the specified Hebrew year.  That is, GreogrianYear = HebrewYear - FirstHebrewYearOf1AD.
+        **
+        **      From the Gregorian year and HebrewTable, we can get the Hebrew month/day value
+        **      of the Gregorian date January 1st.  Let's call this month/day value [hebrewDateForJan1]
+        **
+        **      If the requested Hebrew month/day is less than [hebrewDateForJan1], we know the result
+        **      Gregorian date falls in previous year.  So we decrease the Gregorian year value, and
+        **      retrieve the Hebrew month/day value of the Gregorian date january 1st again.
+        **
+        **      Now, we get the answer of the Gregorian year.
+        **
+        **      The next step is to get the number of days between the requested Hebrew month/day
+        **      and [hebrewDateForJan1].  When we get that, we can create the DateTime by adding/subtracting
+        **      the ticks value of the number of days.
+        **
+        ============================================================================*/
+
+
+        private static DateTime HebrewToGregorian(int hebrewYear, int hebrewMonth, int hebrewDay, int hour, int minute, int second, int millisecond)
+        {
+            // Get the rough Gregorian year for the specified hebrewYear.
+            //
+            int gregorianYear = hebrewYear - HebrewYearOf1AD;
+
+            __DateBuffer hebrewDateOfJan1 = new __DateBuffer(); // year value is unused.
+            int lunarYearType = GetLunarMonthDay(gregorianYear, hebrewDateOfJan1);
+
+            if ((hebrewMonth == hebrewDateOfJan1.month) && (hebrewDay == hebrewDateOfJan1.day))
+            {
+                return (new DateTime(gregorianYear, 1, 1, hour, minute, second, millisecond));
+            }
+
+            int days = GetDayDifference(lunarYearType, hebrewMonth, hebrewDay, hebrewDateOfJan1.month, hebrewDateOfJan1.day);
+
+            DateTime gregorianNewYear = new DateTime(gregorianYear, 1, 1);
+            return (new DateTime(gregorianNewYear.Ticks + days * TicksPerDay
+                + TimeToTicks(hour, minute, second, millisecond)));
+        }
+
+        // Returns the date and time converted to a DateTime value.  Throws an exception if the n-tuple is invalid.
+        //
+
+        public override DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era)
+        {
+            CheckHebrewYearValue(year, era, nameof(year));
+            CheckHebrewMonthValue(year, month, era);
+            CheckHebrewDayValue(year, month, day, era);
+            DateTime dt = HebrewToGregorian(year, month, day, hour, minute, second, millisecond);
+            CheckTicksRange(dt.Ticks);
+            return (dt);
+        }
+
+        private const int DEFAULT_TWO_DIGIT_YEAR_MAX = 5790;
+
+
+        public override int TwoDigitYearMax
+        {
+            get
+            {
+                if (twoDigitYearMax == -1)
+                {
+                    twoDigitYearMax = GetSystemTwoDigitYearSetting(ID, DEFAULT_TWO_DIGIT_YEAR_MAX);
+                }
+                return (twoDigitYearMax);
+            }
+
+            set
+            {
+                VerifyWritable();
+                if (value == 99)
+                {
+                    // Do nothing here.  Year 99 is allowed so that TwoDitYearMax is disabled.
+                }
+                else
+                {
+                    CheckHebrewYearValue(value, HebrewEra, nameof(value));
+                }
+                twoDigitYearMax = value;
+            }
+        }
+
+
+        public override int ToFourDigitYear(int year)
+        {
+            if (year < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (year < 100)
+            {
+                return (base.ToFourDigitYear(year));
+            }
+
+            if (year > MaxHebrewYear || year < MinHebrewYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                MinHebrewYear,
+                                MaxHebrewYear));
+            }
+            return (year);
+        }
+
+        internal class __DateBuffer
+        {
+            internal int year;
+            internal int month;
+            internal int day;
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/HebrewNumber.cs b/src/System.Private.CoreLib/shared/System/Globalization/HebrewNumber.cs
new file mode 100644
index 0000000000..1e8fff2bcb
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/HebrewNumber.cs
@@ -0,0 +1,457 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text;
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    ////////////////////////////////////////////////////////////////////////////
+    //
+    // Used in HebrewNumber.ParseByChar to maintain the context information (
+    // the state in the state machine and current Hebrew number values, etc.)
+    // when parsing Hebrew number character by character.
+    //
+    ////////////////////////////////////////////////////////////////////////////
+
+    internal struct HebrewNumberParsingContext
+    {
+        // The current state of the state machine for parsing Hebrew numbers.
+        internal HebrewNumber.HS state;
+        // The current value of the Hebrew number.
+        // The final value is determined when state is FoundEndOfHebrewNumber.
+        internal int result;
+
+        public HebrewNumberParsingContext(int result)
+        {
+            // Set the start state of the state machine for parsing Hebrew numbers.
+            state = HebrewNumber.HS.Start;
+            this.result = result;
+        }
+    }
+
+    ////////////////////////////////////////////////////////////////////////////
+    //
+    // Please see ParseByChar() for comments about different states defined here.
+    //
+    ////////////////////////////////////////////////////////////////////////////
+
+    internal enum HebrewNumberParsingState
+    {
+        InvalidHebrewNumber,
+        NotHebrewDigit,
+        FoundEndOfHebrewNumber,
+        ContinueParsing,
+    }
+
+    ////////////////////////////////////////////////////////////////////////////
+    //
+    // class HebrewNumber
+    //
+    //  Provides static methods for formatting integer values into
+    //  Hebrew text and parsing Hebrew number text.
+    //
+    //  Limitations:
+    //      Parse can only handles value 1 ~ 999.
+    //      ToString() can only handles 1 ~ 999. If value is greater than 5000,
+    //      5000 will be subtracted from the value.
+    //
+    ////////////////////////////////////////////////////////////////////////////
+
+    internal class HebrewNumber
+    {
+        // This class contains only static methods.  Add a private ctor so that
+        // compiler won't generate a default one for us.
+        private HebrewNumber()
+        {
+        }
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        //  ToString
+        //
+        //  Converts the given number to Hebrew letters according to the numeric
+        //  value of each Hebrew letter.  Basically, this converts the lunar year
+        //  and the lunar month to letters.
+        //
+        //  The character of a year is described by three letters of the Hebrew
+        //  alphabet, the first and third giving, respectively, the days of the
+        //  weeks on which the New Year occurs and Passover begins, while the
+        //  second is the initial of the Hebrew word for defective, normal, or
+        //  complete.
+        //
+        //  Defective Year : Both Heshvan and Kislev are defective (353 or 383 days)
+        //  Normal Year    : Heshvan is defective, Kislev is full  (354 or 384 days)
+        //  Complete Year  : Both Heshvan and Kislev are full      (355 or 385 days)
+        //
+        ////////////////////////////////////////////////////////////////////////////
+
+        internal static String ToString(int Number)
+        {
+            char cTens = '\x0';
+            char cUnits;               // tens and units chars
+            int Hundreds, Tens;              // hundreds and tens values
+            StringBuilder szHebrew = new StringBuilder();
+
+
+            //
+            //  Adjust the number if greater than 5000.
+            //
+            if (Number > 5000)
+            {
+                Number -= 5000;
+            }
+
+            Debug.Assert(Number > 0 && Number <= 999, "Number is out of range."); ;
+
+            //
+            //  Get the Hundreds.
+            //
+            Hundreds = Number / 100;
+
+            if (Hundreds > 0)
+            {
+                Number -= Hundreds * 100;
+                // \x05e7 = 100
+                // \x05e8 = 200
+                // \x05e9 = 300
+                // \x05ea = 400
+                // If the number is greater than 400, use the multiples of 400.
+                for (int i = 0; i < (Hundreds / 4); i++)
+                {
+                    szHebrew.Append('\x05ea');
+                }
+
+                int remains = Hundreds % 4;
+                if (remains > 0)
+                {
+                    szHebrew.Append((char)((int)'\x05e6' + remains));
+                }
+            }
+
+            //
+            //  Get the Tens.
+            //
+            Tens = Number / 10;
+            Number %= 10;
+
+            switch (Tens)
+            {
+                case (0):
+                    cTens = '\x0';
+                    break;
+                case (1):
+                    cTens = '\x05d9';          // Hebrew Letter Yod
+                    break;
+                case (2):
+                    cTens = '\x05db';          // Hebrew Letter Kaf
+                    break;
+                case (3):
+                    cTens = '\x05dc';          // Hebrew Letter Lamed
+                    break;
+                case (4):
+                    cTens = '\x05de';          // Hebrew Letter Mem
+                    break;
+                case (5):
+                    cTens = '\x05e0';          // Hebrew Letter Nun
+                    break;
+                case (6):
+                    cTens = '\x05e1';          // Hebrew Letter Samekh
+                    break;
+                case (7):
+                    cTens = '\x05e2';          // Hebrew Letter Ayin
+                    break;
+                case (8):
+                    cTens = '\x05e4';          // Hebrew Letter Pe
+                    break;
+                case (9):
+                    cTens = '\x05e6';          // Hebrew Letter Tsadi
+                    break;
+            }
+
+            //
+            //  Get the Units.
+            //
+            cUnits = (char)(Number > 0 ? ((int)'\x05d0' + Number - 1) : 0);
+
+            if ((cUnits == '\x05d4') &&            // Hebrew Letter He  (5)
+                (cTens == '\x05d9'))
+            {              // Hebrew Letter Yod (10)
+                cUnits = '\x05d5';                 // Hebrew Letter Vav (6)
+                cTens = '\x05d8';                 // Hebrew Letter Tet (9)
+            }
+
+            if ((cUnits == '\x05d5') &&            // Hebrew Letter Vav (6)
+                (cTens == '\x05d9'))
+            {               // Hebrew Letter Yod (10)
+                cUnits = '\x05d6';                 // Hebrew Letter Zayin (7)
+                cTens = '\x05d8';                 // Hebrew Letter Tet (9)
+            }
+
+            //
+            //  Copy the appropriate info to the given buffer.
+            //
+
+            if (cTens != '\x0')
+            {
+                szHebrew.Append(cTens);
+            }
+
+            if (cUnits != '\x0')
+            {
+                szHebrew.Append(cUnits);
+            }
+
+            if (szHebrew.Length > 1)
+            {
+                szHebrew.Insert(szHebrew.Length - 1, '"');
+            }
+            else
+            {
+                szHebrew.Append('\'');
+            }
+
+            //
+            //  Return success.
+            //
+            return (szHebrew.ToString());
+        }
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // Token used to tokenize a Hebrew word into tokens so that we can use in the
+        // state machine.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+
+        private enum HebrewToken : short
+        {
+            Invalid = -1,
+            Digit400 = 0,
+            Digit200_300 = 1,
+            Digit100 = 2,
+            Digit10 = 3,    // 10 ~ 90
+            Digit1 = 4,     // 1, 2, 3, 4, 5, 8, 
+            Digit6_7 = 5,
+            Digit7 = 6,
+            Digit9 = 7,
+            SingleQuote = 8,
+            DoubleQuote = 9,
+        };
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // This class is used to map a token into its Hebrew digit value.
+        //
+        ////////////////////////////////////////////////////////////////////////////
+
+        private struct HebrewValue
+        {
+            internal HebrewToken token;
+            internal short value;
+            internal HebrewValue(HebrewToken token, short value)
+            {
+                this.token = token;
+                this.value = value;
+            }
+        }
+
+        //
+        // Map a Hebrew character from U+05D0 ~ U+05EA to its digit value.
+        // The value is -1 if the Hebrew character does not have a associated value.
+        //
+        private static readonly HebrewValue[] s_hebrewValues = {
+            new HebrewValue(HebrewToken.Digit1, 1) , // '\x05d0
+            new HebrewValue(HebrewToken.Digit1, 2) , // '\x05d1
+            new HebrewValue(HebrewToken.Digit1, 3) , // '\x05d2
+            new HebrewValue(HebrewToken.Digit1, 4) , // '\x05d3
+            new HebrewValue(HebrewToken.Digit1, 5) , // '\x05d4
+            new HebrewValue(HebrewToken.Digit6_7,6) , // '\x05d5
+            new HebrewValue(HebrewToken.Digit6_7,7) , // '\x05d6
+            new HebrewValue(HebrewToken.Digit1, 8) , // '\x05d7
+            new HebrewValue(HebrewToken.Digit9, 9) , // '\x05d8
+            new HebrewValue(HebrewToken.Digit10, 10) , // '\x05d9;          // Hebrew Letter Yod
+            new HebrewValue(HebrewToken.Invalid, -1) , // '\x05da; 
+            new HebrewValue(HebrewToken.Digit10, 20) , // '\x05db;          // Hebrew Letter Kaf
+            new HebrewValue(HebrewToken.Digit10, 30) , // '\x05dc;          // Hebrew Letter Lamed
+            new HebrewValue(HebrewToken.Invalid, -1) , // '\x05dd;
+            new HebrewValue(HebrewToken.Digit10, 40) , // '\x05de;          // Hebrew Letter Mem
+            new HebrewValue(HebrewToken.Invalid, -1) , // '\x05df;
+            new HebrewValue(HebrewToken.Digit10, 50) , // '\x05e0;          // Hebrew Letter Nun
+            new HebrewValue(HebrewToken.Digit10, 60) , // '\x05e1;          // Hebrew Letter Samekh
+            new HebrewValue(HebrewToken.Digit10, 70) , // '\x05e2;          // Hebrew Letter Ayin
+            new HebrewValue(HebrewToken.Invalid, -1) , // '\x05e3;
+            new HebrewValue(HebrewToken.Digit10, 80) , // '\x05e4;          // Hebrew Letter Pe
+            new HebrewValue(HebrewToken.Invalid, -1) , // '\x05e5;
+            new HebrewValue(HebrewToken.Digit10, 90) , // '\x05e6;          // Hebrew Letter Tsadi
+            new HebrewValue(HebrewToken.Digit100, 100) , // '\x05e7;
+            new HebrewValue(HebrewToken.Digit200_300, 200) , // '\x05e8;
+            new HebrewValue(HebrewToken.Digit200_300, 300) , // '\x05e9;
+            new HebrewValue(HebrewToken.Digit400, 400) , // '\x05ea;
+        };
+
+        private const int minHebrewNumberCh = 0x05d0;
+        private static char s_maxHebrewNumberCh = (char)(minHebrewNumberCh + s_hebrewValues.Length - 1);
+
+        ////////////////////////////////////////////////////////////////////////////
+        //
+        // Hebrew number parsing State
+        // The current state and the next token will lead to the next state in the state machine.
+        // DQ = Double Quote
+        //
+        ////////////////////////////////////////////////////////////////////////////
+
+        internal enum HS : sbyte
+        {
+            _err = -1,          // an error state
+            Start = 0,
+            S400 = 1,           // a Hebrew digit 400
+            S400_400 = 2,       // Two Hebrew digit 400
+            S400_X00 = 3,       // Two Hebrew digit 400 and followed by 100
+            S400_X0 = 4,       // Hebrew digit 400 and followed by 10 ~ 90
+            X00_DQ = 5,         // A hundred number and followed by a double quote.
+            S400_X00_X0 = 6,
+            X0_DQ = 7,          // A two-digit number and followed by a double quote.
+            X = 8,              // A single digit Hebrew number.
+            X0 = 9,            // A two-digit Hebrew number
+            X00 = 10,           // A three-digit Hebrew number
+            S400_DQ = 11,       // A Hebrew digit 400 and followed by a double quote.
+            S400_400_DQ = 12,
+            S400_400_100 = 13,
+            S9 = 14,            // Hebrew digit 9
+            X00_S9 = 15,        // A hundered number and followed by a digit 9
+            S9_DQ = 16,         // Hebrew digit 9 and followed by a double quote
+            END = 100,          // A terminial state is reached.
+        }
+
+        // 
+        // The state machine for Hebrew number pasing.
+        //
+        private static readonly HS[] s_numberPasingState =
+        {
+            // 400            300/200         100             90~10           8~1      6,       7,       9,          '           "
+            /* 0 */
+                             HS.S400,       HS.X00,         HS.X00,         HS.X0,          HS.X,    HS.X,    HS.X,    HS.S9,      HS._err,    HS._err,
+            /* 1: S400 */
+                             HS.S400_400,   HS.S400_X00,    HS.S400_X00,    HS.S400_X0,     HS._err, HS._err, HS._err, HS.X00_S9  ,HS.END,     HS.S400_DQ,
+            /* 2: S400_400 */
+                             HS._err,       HS._err,        HS.S400_400_100,HS.S400_X0,     HS._err, HS._err, HS._err, HS.X00_S9  ,HS._err,    HS.S400_400_DQ,
+            /* 3: S400_X00 */
+                             HS._err,       HS._err,        HS._err,        HS.S400_X00_X0, HS._err, HS._err, HS._err, HS.X00_S9  ,HS._err,    HS.X00_DQ,
+            /* 4: S400_X0 */
+                             HS._err,       HS._err,        HS._err,        HS._err,        HS._err, HS._err, HS._err, HS._err,    HS._err,    HS.X0_DQ,
+            /* 5: X00_DQ */
+                             HS._err,       HS._err,        HS._err,        HS.END,         HS.END,  HS.END,  HS.END,  HS.END,     HS._err,    HS._err,
+            /* 6: S400_X00_X0 */
+                             HS._err,       HS._err,        HS._err,        HS._err,        HS._err, HS._err, HS._err, HS._err,    HS._err,    HS.X0_DQ,
+            /* 7: X0_DQ */
+                             HS._err,       HS._err,        HS._err,        HS._err,        HS.END,  HS.END,  HS.END,  HS.END,     HS._err,    HS._err,
+            /* 8: X */
+                             HS._err,       HS._err,        HS._err,        HS._err,        HS._err, HS._err, HS._err, HS._err,    HS.END,     HS._err,
+            /* 9: X0 */
+                             HS._err,       HS._err,        HS._err,        HS._err,        HS._err, HS._err, HS._err, HS._err,    HS.END,     HS.X0_DQ,
+            /* 10: X00 */
+                             HS._err,       HS._err,        HS._err,        HS.S400_X0,     HS._err, HS._err, HS._err, HS.X00_S9,  HS.END,     HS.X00_DQ,
+            /* 11: S400_DQ */
+                             HS.END,        HS.END,         HS.END,         HS.END,         HS.END,  HS.END,  HS.END,  HS.END,     HS._err,    HS._err,
+            /* 12: S400_400_DQ*/
+                             HS._err,       HS._err,        HS.END,         HS.END,         HS.END,  HS.END,  HS.END,  HS.END,     HS._err,    HS._err,
+            /* 13: S400_400_100*/
+                             HS._err,       HS._err,        HS._err,        HS.S400_X00_X0, HS._err, HS._err, HS._err, HS.X00_S9,  HS._err,    HS.X00_DQ,
+            /* 14: S9 */
+                             HS._err,       HS._err,        HS._err,        HS._err,        HS._err, HS._err, HS._err, HS._err,    HS.END,     HS.S9_DQ,
+            /* 15: X00_S9 */
+                             HS._err,       HS._err,        HS._err,        HS._err,        HS._err, HS._err, HS._err, HS._err,    HS._err,    HS.S9_DQ,
+            /* 16: S9_DQ */
+                             HS._err,       HS._err,        HS._err,        HS._err,        HS._err, HS.END,  HS.END,  HS._err,    HS._err,    HS._err
+        };
+
+        // Count of valid HebrewToken, column count in the NumberPasingState array
+        private const int HebrewTokenCount = 10;
+
+        ////////////////////////////////////////////////////////////////////////
+        //  
+        //  Actions:
+        //      Parse the Hebrew number by passing one character at a time.
+        //      The state between characters are maintained at HebrewNumberPasingContext.
+        //  Returns:
+        //      Return a enum of HebrewNumberParsingState.
+        //          NotHebrewDigit: The specified ch is not a valid Hebrew digit.
+        //          InvalidHebrewNumber: After parsing the specified ch, it will lead into
+        //              an invalid Hebrew number text.
+        //          FoundEndOfHebrewNumber: A terminal state is reached.  This means that
+        //              we find a valid Hebrew number text after the specified ch is parsed.
+        //          ContinueParsing: The specified ch is a valid Hebrew digit, and
+        //              it will lead into a valid state in the state machine, we should
+        //              continue to parse incoming characters.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        internal static HebrewNumberParsingState ParseByChar(char ch, ref HebrewNumberParsingContext context)
+        {
+            Debug.Assert(s_numberPasingState.Length == HebrewTokenCount * ((int)HS.S9_DQ + 1));
+
+            HebrewToken token;
+            if (ch == '\'')
+            {
+                token = HebrewToken.SingleQuote;
+            }
+            else if (ch == '\"')
+            {
+                token = HebrewToken.DoubleQuote;
+            }
+            else
+            {
+                int index = (int)ch - minHebrewNumberCh;
+                if (index >= 0 && index < s_hebrewValues.Length)
+                {
+                    token = s_hebrewValues[index].token;
+                    if (token == HebrewToken.Invalid)
+                    {
+                        return (HebrewNumberParsingState.NotHebrewDigit);
+                    }
+                    context.result += s_hebrewValues[index].value;
+                }
+                else
+                {
+                    // Not in valid Hebrew digit range.
+                    return (HebrewNumberParsingState.NotHebrewDigit);
+                }
+            }
+            context.state = s_numberPasingState[(int)context.state * (int)HebrewTokenCount + (int)token];
+            if (context.state == HS._err)
+            {
+                // Invalid Hebrew state.  This indicates an incorrect Hebrew number.
+                return (HebrewNumberParsingState.InvalidHebrewNumber);
+            }
+            if (context.state == HS.END)
+            {
+                // Reach a terminal state.
+                return (HebrewNumberParsingState.FoundEndOfHebrewNumber);
+            }
+            // We should continue to parse.
+            return (HebrewNumberParsingState.ContinueParsing);
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        // Actions:
+        //  Check if the ch is a valid Hebrew number digit.
+        //  This function will return true if the specified char is a legal Hebrew
+        //  digit character, single quote, or double quote.
+        // Returns:
+        //  true if the specified character is a valid Hebrew number character.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        internal static bool IsDigit(char ch)
+        {
+            if (ch >= minHebrewNumberCh && ch <= s_maxHebrewNumberCh)
+            {
+                return (s_hebrewValues[ch - minHebrewNumberCh].value >= 0);
+            }
+            return (ch == '\'' || ch == '\"');
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/HijriCalendar.Unix.cs b/src/System.Private.CoreLib/shared/System/Globalization/HijriCalendar.Unix.cs
new file mode 100644
index 0000000000..a6e8f73d3e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/HijriCalendar.Unix.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Globalization
+{
+    public partial class HijriCalendar : Calendar
+    {
+        private static int GetHijriDateAdjustment()
+        {
+            // this setting is not supported on Unix, so always return 0
+            return 0;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/HijriCalendar.Win32.cs b/src/System.Private.CoreLib/shared/System/Globalization/HijriCalendar.Win32.cs
new file mode 100644
index 0000000000..64a73fb81d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/HijriCalendar.Win32.cs
@@ -0,0 +1,94 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32;
+
+namespace System.Globalization
+{
+    public partial class HijriCalendar : Calendar
+    {
+        private int GetHijriDateAdjustment()
+        {
+            if (_hijriAdvance == Int32.MinValue)
+            {
+                // Never been set before.  Use the system value from registry.
+                _hijriAdvance = GetAdvanceHijriDate();
+            }
+            return (_hijriAdvance);
+        }
+
+        private const String InternationalRegKey = "Control Panel\\International";
+        private const String HijriAdvanceRegKeyEntry = "AddHijriDate";
+
+        /*=================================GetAdvanceHijriDate==========================
+        **Action: Gets the AddHijriDate value from the registry.
+        **Returns:
+        **Arguments:    None.
+        **Exceptions:
+        **Note:
+        **  The HijriCalendar has a user-overidable calculation.  That is, use can set a value from the control
+        **  panel, so that the calculation of the Hijri Calendar can move ahead or backwards from -2 to +2 days.
+        **
+        **  The valid string values in the registry are:
+        **      "AddHijriDate-2"  =>  Add -2 days to the current calculated Hijri date.
+        **      "AddHijriDate"    =>  Add -1 day to the current calculated Hijri date.
+        **      ""              =>  Add 0 day to the current calculated Hijri date.
+        **      "AddHijriDate+1"  =>  Add +1 days to the current calculated Hijri date.
+        **      "AddHijriDate+2"  =>  Add +2 days to the current calculated Hijri date.
+        ============================================================================*/
+        private static int GetAdvanceHijriDate()
+        {
+            int hijriAdvance = 0;
+            Microsoft.Win32.RegistryKey key = null;
+
+            try
+            {
+                // Open in read-only mode.
+                key = RegistryKey.GetBaseKey(RegistryKey.HKEY_CURRENT_USER).OpenSubKey(InternationalRegKey, false);
+            }
+            //If this fails for any reason, we'll just return 0.
+            catch (ObjectDisposedException) { return 0; }
+            catch (ArgumentException) { return 0; }
+
+            if (key != null)
+            {
+                try
+                {
+                    Object value = key.InternalGetValue(HijriAdvanceRegKeyEntry, null, false, false);
+                    if (value == null)
+                    {
+                        return (0);
+                    }
+                    String str = value.ToString();
+                    if (String.Compare(str, 0, HijriAdvanceRegKeyEntry, 0, HijriAdvanceRegKeyEntry.Length, StringComparison.OrdinalIgnoreCase) == 0)
+                    {
+                        if (str.Length == HijriAdvanceRegKeyEntry.Length)
+                            hijriAdvance = -1;
+                        else
+                        {
+                            try
+                            {
+                                int advance = Int32.Parse(str.AsSpan(HijriAdvanceRegKeyEntry.Length), provider:CultureInfo.InvariantCulture);
+                                if ((advance >= MinAdvancedHijri) && (advance <= MaxAdvancedHijri))
+                                {
+                                    hijriAdvance = advance;
+                                }
+                            }
+                            // If we got garbage from registry just ignore it.
+                            // hijriAdvance = 0 because of declaraction assignment up above.
+                            catch (ArgumentException) { }
+                            catch (FormatException) { }
+                            catch (OverflowException) { }
+                        }
+                    }
+                }
+                finally
+                {
+                    key.Close();
+                }
+            }
+            return (hijriAdvance);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/HijriCalendar.WinRT.cs b/src/System.Private.CoreLib/shared/System/Globalization/HijriCalendar.WinRT.cs
new file mode 100644
index 0000000000..fb91c27ef6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/HijriCalendar.WinRT.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Internal.Runtime.Augments;
+
+namespace System.Globalization
+{
+    public partial class HijriCalendar : Calendar
+    {
+        private static int GetHijriDateAdjustment()
+        {
+            return WinRTInterop.Callbacks.GetHijriDateAdjustment();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/HijriCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/HijriCalendar.cs
new file mode 100644
index 0000000000..6755844620
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/HijriCalendar.cs
@@ -0,0 +1,671 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+namespace System.Globalization
+{
+    ////////////////////////////////////////////////////////////////////////////
+    //
+    //  Rules for the Hijri calendar:
+    //    - The Hijri calendar is a strictly Lunar calendar.
+    //    - Days begin at sunset.
+    //    - Islamic Year 1 (Muharram 1, 1 A.H.) is equivalent to absolute date
+    //        227015 (Friday, July 16, 622 C.E. - Julian).
+    //    - Leap Years occur in the 2, 5, 7, 10, 13, 16, 18, 21, 24, 26, & 29th
+    //        years of a 30-year cycle.  Year = leap iff ((11y+14) mod 30 < 11).
+    //    - There are 12 months which contain alternately 30 and 29 days.
+    //    - The 12th month, Dhu al-Hijjah, contains 30 days instead of 29 days
+    //        in a leap year.
+    //    - Common years have 354 days.  Leap years have 355 days.
+    //    - There are 10,631 days in a 30-year cycle.
+    //    - The Islamic months are:
+    //        1.  Muharram   (30 days)     7.  Rajab          (30 days)
+    //        2.  Safar      (29 days)     8.  Sha'ban        (29 days)
+    //        3.  Rabi I     (30 days)     9.  Ramadan        (30 days)
+    //        4.  Rabi II    (29 days)     10. Shawwal        (29 days)
+    //        5.  Jumada I   (30 days)     11. Dhu al-Qada    (30 days)
+    //        6.  Jumada II  (29 days)     12. Dhu al-Hijjah  (29 days) {30}
+    //
+    //  NOTENOTE
+    //      The calculation of the HijriCalendar is based on the absolute date.  And the
+    //      absolute date means the number of days from January 1st, 1 A.D.
+    //      Therefore, we do not support the days before the January 1st, 1 A.D.
+    //
+    ////////////////////////////////////////////////////////////////////////////
+    /*
+    **  Calendar support range:
+    **      Calendar    Minimum     Maximum
+    **      ==========  ==========  ==========
+    **      Gregorian   0622/07/18   9999/12/31
+    **      Hijri       0001/01/01   9666/04/03
+    */
+
+    public partial class HijriCalendar : Calendar
+    {
+        public static readonly int HijriEra = 1;
+
+        internal const int DatePartYear = 0;
+        internal const int DatePartDayOfYear = 1;
+        internal const int DatePartMonth = 2;
+        internal const int DatePartDay = 3;
+
+        internal const int MinAdvancedHijri = -2;
+        internal const int MaxAdvancedHijri = 2;
+
+        internal static readonly int[] HijriMonthDays = { 0, 30, 59, 89, 118, 148, 177, 207, 236, 266, 295, 325, 355 };
+
+        private int _hijriAdvance = Int32.MinValue;
+
+        // DateTime.MaxValue = Hijri calendar (year:9666, month: 4, day: 3).
+        internal const int MaxCalendarYear = 9666;
+        internal const int MaxCalendarMonth = 4;
+        internal const int MaxCalendarDay = 3;
+        // Hijri calendar (year: 1, month: 1, day:1 ) = Gregorian (year: 622, month: 7, day: 18)
+        // This is the minimal Gregorian date that we support in the HijriCalendar.
+        internal static readonly DateTime calendarMinValue = new DateTime(622, 7, 18);
+        internal static readonly DateTime calendarMaxValue = DateTime.MaxValue;
+
+
+        public override DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (calendarMinValue);
+            }
+        }
+
+
+        public override DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (calendarMaxValue);
+            }
+        }
+
+        public override CalendarAlgorithmType AlgorithmType
+        {
+            get
+            {
+                return CalendarAlgorithmType.LunarCalendar;
+            }
+        }
+
+        public HijriCalendar()
+        {
+        }
+
+        internal override CalendarId ID
+        {
+            get
+            {
+                return CalendarId.HIJRI;
+            }
+        }
+
+        protected override int DaysInYearBeforeMinSupportedYear
+        {
+            get
+            {
+                // the year before the 1st year of the cycle would have been the 30th year
+                // of the previous cycle which is not a leap year. Common years have 354 days.
+                return 354;
+            }
+        }
+
+
+
+        /*=================================GetAbsoluteDateHijri==========================
+        **Action: Gets the Absolute date for the given Hijri date.  The absolute date means
+        **       the number of days from January 1st, 1 A.D.
+        **Returns:
+        **Arguments:
+        **Exceptions:
+        ============================================================================*/
+
+        private long GetAbsoluteDateHijri(int y, int m, int d)
+        {
+            return (long)(DaysUpToHijriYear(y) + HijriMonthDays[m - 1] + d - 1 - HijriAdjustment);
+        }
+
+        /*=================================DaysUpToHijriYear==========================
+        **Action: Gets the total number of days (absolute date) up to the given Hijri Year.
+        **       The absolute date means the number of days from January 1st, 1 A.D.
+        **Returns: Gets the total number of days (absolute date) up to the given Hijri Year.
+        **Arguments: HijriYear year value in Hijri calendar.
+        **Exceptions: None
+        **Notes:
+        ============================================================================*/
+
+        private long DaysUpToHijriYear(int HijriYear)
+        {
+            long NumDays;           // number of absolute days
+            int NumYear30;         // number of years up to current 30 year cycle
+            int NumYearsLeft;      // number of years into 30 year cycle
+
+            //
+            //  Compute the number of years up to the current 30 year cycle.
+            //
+            NumYear30 = ((HijriYear - 1) / 30) * 30;
+
+            //
+            //  Compute the number of years left.  This is the number of years
+            //  into the 30 year cycle for the given year.
+            //
+            NumYearsLeft = HijriYear - NumYear30 - 1;
+
+            //
+            //  Compute the number of absolute days up to the given year.
+            //
+            NumDays = ((NumYear30 * 10631L) / 30L) + 227013L;
+            while (NumYearsLeft > 0)
+            {
+                // Common year is 354 days, and leap year is 355 days.
+                NumDays += 354 + (IsLeapYear(NumYearsLeft, CurrentEra) ? 1 : 0);
+                NumYearsLeft--;
+            }
+
+            //
+            //  Return the number of absolute days.
+            //
+            return (NumDays);
+        }
+
+        public int HijriAdjustment
+        {
+            get
+            {
+                if (_hijriAdvance == Int32.MinValue)
+                {
+                    // Never been set before.  Use the system value from registry.
+                    _hijriAdvance = GetHijriDateAdjustment();
+                }
+                return (_hijriAdvance);
+            }
+
+            set
+            {
+                // NOTE: Check the value of Min/MaxAdvancedHijri with Arabic speakers to see if the assumption is good.
+                if (value < MinAdvancedHijri || value > MaxAdvancedHijri)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                "HijriAdjustment",
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Bounds_Lower_Upper,
+                                    MinAdvancedHijri,
+                                    MaxAdvancedHijri));
+                }
+                VerifyWritable();
+
+                _hijriAdvance = value;
+            }
+        }
+
+        internal static void CheckTicksRange(long ticks)
+        {
+            if (ticks < calendarMinValue.Ticks || ticks > calendarMaxValue.Ticks)
+            {
+                throw new ArgumentOutOfRangeException(
+                            "time",
+                            String.Format(
+                                CultureInfo.InvariantCulture,
+                                SR.ArgumentOutOfRange_CalendarRange,
+                                calendarMinValue,
+                                calendarMaxValue));
+            }
+        }
+
+        internal static void CheckEraRange(int era)
+        {
+            if (era != CurrentEra && era != HijriEra)
+            {
+                throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+            }
+        }
+
+        internal static void CheckYearRange(int year, int era)
+        {
+            CheckEraRange(era);
+            if (year < 1 || year > MaxCalendarYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                1,
+                                MaxCalendarYear));
+            }
+        }
+
+        internal static void CheckYearMonthRange(int year, int month, int era)
+        {
+            CheckYearRange(year, era);
+            if (year == MaxCalendarYear)
+            {
+                if (month > MaxCalendarMonth)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(month),
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    1,
+                                    MaxCalendarMonth));
+                }
+            }
+
+            if (month < 1 || month > 12)
+            {
+                throw new ArgumentOutOfRangeException(nameof(month), SR.ArgumentOutOfRange_Month);
+            }
+        }
+
+        /*=================================GetDatePart==========================
+        **Action: Returns a given date part of this <i>DateTime</i>. This method is used
+        **       to compute the year, day-of-year, month, or day part.
+        **Returns:
+        **Arguments:
+        **Exceptions:  ArgumentException if part is incorrect.
+        **Notes:
+        **      First, we get the absolute date (the number of days from January 1st, 1 A.C) for the given ticks.
+        **      Use the formula (((AbsoluteDate - 227013) * 30) / 10631) + 1, we can a rough value for the Hijri year.
+        **      In order to get the exact Hijri year, we compare the exact absolute date for HijriYear and (HijriYear + 1).
+        **      From here, we can get the correct Hijri year.
+        ============================================================================*/
+
+        internal virtual int GetDatePart(long ticks, int part)
+        {
+            int HijriYear;                   // Hijri year
+            int HijriMonth;                  // Hijri month
+            int HijriDay;                    // Hijri day
+            long NumDays;                 // The calculation buffer in number of days.
+
+            CheckTicksRange(ticks);
+
+            //
+            //  Get the absolute date.  The absolute date is the number of days from January 1st, 1 A.D.
+            //  1/1/0001 is absolute date 1.
+            //
+            NumDays = ticks / GregorianCalendar.TicksPerDay + 1;
+
+            //
+            //  See how much we need to backup or advance
+            //
+            NumDays += HijriAdjustment;
+
+            //
+            //  Calculate the appromixate Hijri Year from this magic formula.
+            //
+            HijriYear = (int)(((NumDays - 227013) * 30) / 10631) + 1;
+
+            long daysToHijriYear = DaysUpToHijriYear(HijriYear);            // The absolute date for HijriYear
+            long daysOfHijriYear = GetDaysInYear(HijriYear, CurrentEra);    // The number of days for (HijriYear+1) year.
+
+            if (NumDays < daysToHijriYear)
+            {
+                daysToHijriYear -= daysOfHijriYear;
+                HijriYear--;
+            }
+            else if (NumDays == daysToHijriYear)
+            {
+                HijriYear--;
+                daysToHijriYear -= GetDaysInYear(HijriYear, CurrentEra);
+            }
+            else
+            {
+                if (NumDays > daysToHijriYear + daysOfHijriYear)
+                {
+                    daysToHijriYear += daysOfHijriYear;
+                    HijriYear++;
+                }
+            }
+            if (part == DatePartYear)
+            {
+                return (HijriYear);
+            }
+
+            //
+            //  Calculate the Hijri Month.
+            //
+
+            HijriMonth = 1;
+            NumDays -= daysToHijriYear;
+
+            if (part == DatePartDayOfYear)
+            {
+                return ((int)NumDays);
+            }
+
+            while ((HijriMonth <= 12) && (NumDays > HijriMonthDays[HijriMonth - 1]))
+            {
+                HijriMonth++;
+            }
+            HijriMonth--;
+
+            if (part == DatePartMonth)
+            {
+                return (HijriMonth);
+            }
+
+            //
+            //  Calculate the Hijri Day.
+            //
+            HijriDay = (int)(NumDays - HijriMonthDays[HijriMonth - 1]);
+
+            if (part == DatePartDay)
+            {
+                return (HijriDay);
+            }
+            // Incorrect part value.
+            throw new InvalidOperationException(SR.InvalidOperation_DateTimeParsing);
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // months to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year and month parts of the specified DateTime by
+        // value months, and, if required, adjusting the day part of the
+        // resulting date downwards to the last day of the resulting month in the
+        // resulting year. The time-of-day part of the result is the same as the
+        // time-of-day part of the specified DateTime.
+        //
+        // In more precise terms, considering the specified DateTime to be of the
+        // form y / m / d + t, where y is the
+        // year, m is the month, d is the day, and t is the
+        // time-of-day, the result is y1 / m1 / d1 + t,
+        // where y1 and m1 are computed by adding value months
+        // to y and m, and d1 is the largest value less than
+        // or equal to d that denotes a valid day in month m1 of year
+        // y1.
+        //
+
+        public override DateTime AddMonths(DateTime time, int months)
+        {
+            if (months < -120000 || months > 120000)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(months),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                -120000,
+                                120000));
+            }
+            // Get the date in Hijri calendar.
+            int y = GetDatePart(time.Ticks, DatePartYear);
+            int m = GetDatePart(time.Ticks, DatePartMonth);
+            int d = GetDatePart(time.Ticks, DatePartDay);
+            int i = m - 1 + months;
+            if (i >= 0)
+            {
+                m = i % 12 + 1;
+                y = y + i / 12;
+            }
+            else
+            {
+                m = 12 + (i + 1) % 12;
+                y = y + (i - 11) / 12;
+            }
+            int days = GetDaysInMonth(y, m);
+            if (d > days)
+            {
+                d = days;
+            }
+            long ticks = GetAbsoluteDateHijri(y, m, d) * TicksPerDay + (time.Ticks % TicksPerDay);
+            Calendar.CheckAddResult(ticks, MinSupportedDateTime, MaxSupportedDateTime);
+            return (new DateTime(ticks));
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // years to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year part of the specified DateTime by value
+        // years. If the month and day of the specified DateTime is 2/29, and if the
+        // resulting year is not a leap year, the month and day of the resulting
+        // DateTime becomes 2/28. Otherwise, the month, day, and time-of-day
+        // parts of the result are the same as those of the specified DateTime.
+        //
+
+        public override DateTime AddYears(DateTime time, int years)
+        {
+            return (AddMonths(time, years * 12));
+        }
+
+        // Returns the day-of-month part of the specified DateTime. The returned
+        // value is an integer between 1 and 31.
+        //
+
+        public override int GetDayOfMonth(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartDay));
+        }
+
+        // Returns the day-of-week part of the specified DateTime. The returned value
+        // is an integer between 0 and 6, where 0 indicates Sunday, 1 indicates
+        // Monday, 2 indicates Tuesday, 3 indicates Wednesday, 4 indicates
+        // Thursday, 5 indicates Friday, and 6 indicates Saturday.
+        //
+
+        public override DayOfWeek GetDayOfWeek(DateTime time)
+        {
+            return ((DayOfWeek)((int)(time.Ticks / TicksPerDay + 1) % 7));
+        }
+
+        // Returns the day-of-year part of the specified DateTime. The returned value
+        // is an integer between 1 and 366.
+        //
+
+        public override int GetDayOfYear(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartDayOfYear));
+        }
+
+        // Returns the number of days in the month given by the year and
+        // month arguments.
+        //
+        public override int GetDaysInMonth(int year, int month, int era)
+        {
+            CheckYearMonthRange(year, month, era);
+            if (month == 12)
+            {
+                // For the 12th month, leap year has 30 days, and common year has 29 days.
+                return (IsLeapYear(year, CurrentEra) ? 30 : 29);
+            }
+            // Other months contain 30 and 29 days alternatively.  The 1st month has 30 days.
+            return (((month % 2) == 1) ? 30 : 29);
+        }
+
+        // Returns the number of days in the year given by the year argument for the current era.
+        //
+
+        public override int GetDaysInYear(int year, int era)
+        {
+            CheckYearRange(year, era);
+            // Common years have 354 days.  Leap years have 355 days.
+            return (IsLeapYear(year, CurrentEra) ? 355 : 354);
+        }
+
+        // Returns the era for the specified DateTime value.
+
+        public override int GetEra(DateTime time)
+        {
+            CheckTicksRange(time.Ticks);
+            return (HijriEra);
+        }
+
+
+        public override int[] Eras
+        {
+            get
+            {
+                return (new int[] { HijriEra });
+            }
+        }
+
+        // Returns the month part of the specified DateTime. The returned value is an
+        // integer between 1 and 12.
+        //
+
+        public override int GetMonth(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartMonth));
+        }
+
+        // Returns the number of months in the specified year and era.
+
+        public override int GetMonthsInYear(int year, int era)
+        {
+            CheckYearRange(year, era);
+            return (12);
+        }
+
+        // Returns the year part of the specified DateTime. The returned value is an
+        // integer between 1 and MaxCalendarYear.
+        //
+
+        public override int GetYear(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartYear));
+        }
+
+        // Checks whether a given day in the specified era is a leap day. This method returns true if
+        // the date is a leap day, or false if not.
+        //
+
+        public override bool IsLeapDay(int year, int month, int day, int era)
+        {
+            // The year/month/era value checking is done in GetDaysInMonth().
+            int daysInMonth = GetDaysInMonth(year, month, era);
+            if (day < 1 || day > daysInMonth)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(day),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Day,
+                                daysInMonth,
+                                month));
+            }
+            return (IsLeapYear(year, era) && month == 12 && day == 30);
+        }
+
+        // Returns  the leap month in a calendar year of the specified era. This method returns 0
+        // if this calendar does not have leap month, or this year is not a leap year.
+        //
+
+        public override int GetLeapMonth(int year, int era)
+        {
+            CheckYearRange(year, era);
+            return (0);
+        }
+
+        // Checks whether a given month in the specified era is a leap month. This method returns true if
+        // month is a leap month, or false if not.
+        //
+
+        public override bool IsLeapMonth(int year, int month, int era)
+        {
+            CheckYearMonthRange(year, month, era);
+            return (false);
+        }
+
+        // Checks whether a given year in the specified era is a leap year. This method returns true if
+        // year is a leap year, or false if not.
+        //
+
+        public override bool IsLeapYear(int year, int era)
+        {
+            CheckYearRange(year, era);
+            return ((((year * 11) + 14) % 30) < 11);
+        }
+
+        // Returns the date and time converted to a DateTime value.  Throws an exception if the n-tuple is invalid.
+        //
+
+        public override DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era)
+        {
+            // The year/month/era checking is done in GetDaysInMonth().
+            int daysInMonth = GetDaysInMonth(year, month, era);
+            if (day < 1 || day > daysInMonth)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(day),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Day,
+                                daysInMonth,
+                                month));
+            }
+
+            long lDate = GetAbsoluteDateHijri(year, month, day);
+
+            if (lDate >= 0)
+            {
+                return (new DateTime(lDate * GregorianCalendar.TicksPerDay + TimeToTicks(hour, minute, second, millisecond)));
+            }
+            else
+            {
+                throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadYearMonthDay);
+            }
+        }
+
+        private const int DEFAULT_TWO_DIGIT_YEAR_MAX = 1451;
+
+
+        public override int TwoDigitYearMax
+        {
+            get
+            {
+                if (twoDigitYearMax == -1)
+                {
+                    twoDigitYearMax = GetSystemTwoDigitYearSetting(ID, DEFAULT_TWO_DIGIT_YEAR_MAX);
+                }
+                return (twoDigitYearMax);
+            }
+
+            set
+            {
+                VerifyWritable();
+                if (value < 99 || value > MaxCalendarYear)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(value),
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    99,
+                                    MaxCalendarYear));
+                }
+                twoDigitYearMax = value;
+            }
+        }
+
+
+        public override int ToFourDigitYear(int year)
+        {
+            if (year < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (year < 100)
+            {
+                return (base.ToFourDigitYear(year));
+            }
+
+            if (year > MaxCalendarYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                1,
+                                MaxCalendarYear));
+            }
+            return (year);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/IdnMapping.Unix.cs b/src/System.Private.CoreLib/shared/System/Globalization/IdnMapping.Unix.cs
new file mode 100644
index 0000000000..20f753e986
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/IdnMapping.Unix.cs
@@ -0,0 +1,145 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    sealed partial class IdnMapping
+    {
+        private unsafe string GetAsciiCore(string unicodeString, char* unicode, int count)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            Debug.Assert(unicodeString != null && unicodeString.Length >= count);
+
+            uint flags = Flags;
+            CheckInvalidIdnCharacters(unicode, count, flags, nameof(unicode));
+
+            const int StackallocThreshold = 512;
+            // Each unicode character is represented by up to 3 ASCII chars
+            // and the whole string is prefixed by "xn--" (length 4)
+            int estimatedLength = (int)Math.Min(count * 3L + 4, StackallocThreshold);
+            int actualLength;
+            if (estimatedLength < StackallocThreshold)
+            {
+                char* outputStack = stackalloc char[estimatedLength];
+                actualLength = Interop.Globalization.ToAscii(flags, unicode, count, outputStack, estimatedLength);
+                if (actualLength > 0 && actualLength <= estimatedLength)
+                {
+                    return GetStringForOutput(unicodeString, unicode, count, outputStack, actualLength);
+                }
+            }
+            else
+            {
+                actualLength = Interop.Globalization.ToAscii(flags, unicode, count, null, 0);
+            }
+            if (actualLength == 0)
+            {
+                throw new ArgumentException(SR.Argument_IdnIllegalName, nameof(unicode));
+            }
+
+            char[] outputHeap = new char[actualLength];
+            fixed (char* pOutputHeap = &outputHeap[0])
+            {
+                actualLength = Interop.Globalization.ToAscii(flags, unicode, count, pOutputHeap, actualLength);
+                if (actualLength == 0 || actualLength > outputHeap.Length)
+                {
+                    throw new ArgumentException(SR.Argument_IdnIllegalName, nameof(unicode));
+                }
+                return GetStringForOutput(unicodeString, unicode, count, pOutputHeap, actualLength);
+            }
+        }
+
+        private unsafe string GetUnicodeCore(string asciiString, char* ascii, int count)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            Debug.Assert(asciiString != null && asciiString.Length >= count);
+
+            uint flags = Flags;
+            CheckInvalidIdnCharacters(ascii, count, flags, nameof(ascii));
+
+            const int StackAllocThreshold = 512;
+            if (count < StackAllocThreshold)
+            {
+                char* output = stackalloc char[count];
+                return GetUnicodeCore(asciiString, ascii, count, flags, output, count, reattempt: true);
+            }
+            else
+            {
+                char[] output = new char[count];
+                fixed (char* pOutput = &output[0])
+                {
+                    return GetUnicodeCore(asciiString, ascii, count, flags, pOutput, count, reattempt: true);
+                }
+            }
+        }
+
+        private unsafe string GetUnicodeCore(string asciiString, char* ascii, int count, uint flags, char* output, int outputLength, bool reattempt)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            Debug.Assert(asciiString != null && asciiString.Length >= count);
+
+            int realLen = Interop.Globalization.ToUnicode(flags, ascii, count, output, outputLength);
+
+            if (realLen == 0)
+            {
+                throw new ArgumentException(SR.Argument_IdnIllegalName, nameof(ascii));
+            }
+            else if (realLen <= outputLength)
+            {
+                return GetStringForOutput(asciiString, ascii, count, output, realLen);
+            }
+            else if (reattempt)
+            {
+                char[] newOutput = new char[realLen];
+                fixed (char* pNewOutput = newOutput)
+                {
+                    return GetUnicodeCore(asciiString, ascii, count, flags, pNewOutput, realLen, reattempt: false);
+                }
+            }
+
+            throw new ArgumentException(SR.Argument_IdnIllegalName, nameof(ascii));
+        }
+
+        // -----------------------------
+        // ---- PAL layer ends here ----
+        // -----------------------------
+
+        private uint Flags
+        {
+            get
+            {
+                int flags =
+                    (AllowUnassigned ? Interop.Globalization.AllowUnassigned : 0) |
+                    (UseStd3AsciiRules ? Interop.Globalization.UseStd3AsciiRules : 0);
+                return (uint)flags;
+            }
+        }
+
+        /// <summary>
+        /// ICU doesn't check for invalid characters unless the STD3 rules option
+        /// is enabled.
+        ///
+        /// To match Windows behavior, we walk the string ourselves looking for these
+        /// bad characters so we can continue to throw ArgumentException in these cases. 
+        /// </summary>
+        private static unsafe void CheckInvalidIdnCharacters(char* s, int count, uint flags, string paramName)
+        {
+            if ((flags & Interop.Globalization.UseStd3AsciiRules) == 0)
+            {
+                for (int i = 0; i < count; i++)
+                {
+                    char c = s[i];
+
+                    // These characters are prohibited regardless of the UseStd3AsciiRules property.
+                    // See https://msdn.microsoft.com/en-us/library/system.globalization.idnmapping.usestd3asciirules(v=vs.110).aspx
+                    if (c <= 0x1F || c == 0x7F)
+                    {
+                        throw new ArgumentException(SR.Argument_IdnIllegalName, paramName);
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/IdnMapping.Windows.cs b/src/System.Private.CoreLib/shared/System/Globalization/IdnMapping.Windows.cs
new file mode 100644
index 0000000000..9d491dfbb8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/IdnMapping.Windows.cs
@@ -0,0 +1,128 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System.Globalization
+{
+    public sealed partial class IdnMapping
+    {
+        private unsafe string GetAsciiCore(string unicodeString, char* unicode, int count)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            Debug.Assert(unicodeString != null && unicodeString.Length >= count);
+
+            uint flags = Flags;
+
+            // Determine the required length
+            int length = Interop.Normaliz.IdnToAscii(flags, unicode, count, null, 0);
+            if (length == 0)
+            {
+                ThrowForZeroLength(unicode: true);
+            }
+
+            // Do the conversion
+            const int StackAllocThreshold = 512; // arbitrary limit to switch from stack to heap allocation
+            if (length < StackAllocThreshold)
+            {
+                char* output = stackalloc char[length];
+                return GetAsciiCore(unicodeString, unicode, count, flags, output, length);
+            }
+            else
+            {
+                char[] output = new char[length];
+                fixed (char* pOutput = &output[0])
+                {
+                    return GetAsciiCore(unicodeString, unicode, count, flags, pOutput, length);
+                }
+            }
+        }
+
+        private unsafe string GetAsciiCore(string unicodeString, char* unicode, int count, uint flags, char* output, int outputLength)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            Debug.Assert(unicodeString != null && unicodeString.Length >= count);
+
+            int length = Interop.Normaliz.IdnToAscii(flags, unicode, count, output, outputLength);
+            if (length == 0)
+            {
+                ThrowForZeroLength(unicode: true);
+            }
+            Debug.Assert(length == outputLength);
+            return GetStringForOutput(unicodeString, unicode, count, output, length);
+        }
+
+        private unsafe string GetUnicodeCore(string asciiString, char* ascii, int count)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            Debug.Assert(asciiString != null && asciiString.Length >= count);
+
+            uint flags = Flags;
+
+            // Determine the required length
+            int length = Interop.Normaliz.IdnToUnicode(flags, ascii, count, null, 0);
+            if (length == 0)
+            {
+                ThrowForZeroLength(unicode: false);
+            }
+
+            // Do the conversion
+            const int StackAllocThreshold = 512; // arbitrary limit to switch from stack to heap allocation
+            if (length < StackAllocThreshold)
+            {
+                char* output = stackalloc char[length];
+                return GetUnicodeCore(asciiString, ascii, count, flags, output, length);
+            }
+            else
+            {
+                char[] output = new char[length];
+                fixed (char* pOutput = &output[0])
+                {
+                    return GetUnicodeCore(asciiString, ascii, count, flags, pOutput, length);
+                }
+            }
+        }
+
+        private unsafe string GetUnicodeCore(string asciiString, char* ascii, int count, uint flags, char* output, int outputLength)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+            Debug.Assert(asciiString != null && asciiString.Length >= count);
+
+            int length = Interop.Normaliz.IdnToUnicode(flags, ascii, count, output, outputLength);
+            if (length == 0)
+            {
+                ThrowForZeroLength(unicode: false);
+            }
+            Debug.Assert(length == outputLength);
+            return GetStringForOutput(asciiString, ascii, count, output, length);
+        }
+
+        // -----------------------------
+        // ---- PAL layer ends here ----
+        // -----------------------------
+
+        private uint Flags
+        {
+            get
+            {
+                int flags =
+                    (AllowUnassigned ? Interop.Normaliz.IDN_ALLOW_UNASSIGNED : 0) |
+                    (UseStd3AsciiRules ? Interop.Normaliz.IDN_USE_STD3_ASCII_RULES : 0);
+                return (uint)flags;
+            }
+        }
+
+        private static void ThrowForZeroLength(bool unicode)
+        {
+            int lastError = Marshal.GetLastWin32Error();
+
+            throw new ArgumentException(
+                lastError == Interop.Errors.ERROR_INVALID_NAME ? SR.Argument_IdnIllegalName : 
+                    (unicode ? SR.Argument_InvalidCharSequenceNoIndex : SR.Argument_IdnBadPunycode),
+                unicode ? "unicode" : "ascii");
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/IdnMapping.cs b/src/System.Private.CoreLib/shared/System/Globalization/IdnMapping.cs
new file mode 100644
index 0000000000..6da6f79f24
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/IdnMapping.cs
@@ -0,0 +1,902 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// This file contains the IDN functions and implementation.
+//
+// This allows encoding of non-ASCII domain names in a "punycode" form,
+// for example:
+//
+//     \u5B89\u5BA4\u5948\u7F8E\u6075-with-SUPER-MONKEYS
+//
+// is encoded as:
+//
+//     xn---with-SUPER-MONKEYS-pc58ag80a8qai00g7n9n
+//
+// Additional options are provided to allow unassigned IDN characters and
+// to validate according to the Std3ASCII Rules (like DNS names).
+//
+// There are also rules regarding bidirectionality of text and the length
+// of segments.
+//
+// For additional rules see also:
+//  RFC 3490 - Internationalizing Domain Names in Applications (IDNA)
+//  RFC 3491 - Nameprep: A Stringprep Profile for Internationalized Domain Names (IDN)
+//  RFC 3492 - Punycode: A Bootstring encoding of Unicode for Internationalized Domain Names in Applications (IDNA)
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Text;
+
+namespace System.Globalization
+{
+    // IdnMapping class used to map names to Punycode
+    public sealed partial class IdnMapping
+    {
+        private bool _allowUnassigned;
+        private bool _useStd3AsciiRules;
+
+        public IdnMapping()
+        {
+        }
+
+        public bool AllowUnassigned
+        {
+            get { return _allowUnassigned; }
+            set { _allowUnassigned = value; }
+        }
+
+        public bool UseStd3AsciiRules
+        {
+            get { return _useStd3AsciiRules; }
+            set { _useStd3AsciiRules = value; }
+        }
+
+        // Gets ASCII (Punycode) version of the string
+        public string GetAscii(string unicode)
+        {
+            return GetAscii(unicode, 0);
+        }
+
+        public string GetAscii(string unicode, int index)
+        {
+            if (unicode == null)
+                throw new ArgumentNullException(nameof(unicode));
+            return GetAscii(unicode, index, unicode.Length - index);
+        }
+
+        public string GetAscii(string unicode, int index, int count)
+        {
+            if (unicode == null)
+                throw new ArgumentNullException(nameof(unicode));
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0) ? nameof(index) : nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (index > unicode.Length)
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+            if (index > unicode.Length - count)
+                throw new ArgumentOutOfRangeException(nameof(unicode), SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (count == 0)
+            {
+                throw new ArgumentException(SR.Argument_IdnBadLabelSize, nameof(unicode));
+            }
+            if (unicode[index + count - 1] == 0)
+            {
+                throw new ArgumentException(SR.Format(SR.Argument_InvalidCharSequence, index + count - 1), nameof(unicode));
+            }
+
+            if (GlobalizationMode.Invariant)
+            {
+                return GetAsciiInvariant(unicode, index, count);
+            }
+
+            unsafe
+            {
+                fixed (char* pUnicode = unicode)
+                {
+                    return GetAsciiCore(unicode, pUnicode + index, count);
+                }
+            }
+        }
+
+        // Gets Unicode version of the string.  Normalized and limited to IDNA characters.
+        public string GetUnicode(string ascii)
+        {
+            return GetUnicode(ascii, 0);
+        }
+
+        public string GetUnicode(string ascii, int index)
+        {
+            if (ascii == null)
+                throw new ArgumentNullException(nameof(ascii));
+            return GetUnicode(ascii, index, ascii.Length - index);
+        }
+
+        public string GetUnicode(string ascii, int index, int count)
+        {
+            if (ascii == null)
+                throw new ArgumentNullException(nameof(ascii));
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0) ? nameof(index) : nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (index > ascii.Length)
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+            if (index > ascii.Length - count)
+                throw new ArgumentOutOfRangeException(nameof(ascii), SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // This is a case (i.e. explicitly null-terminated input) where behavior in .NET and Win32 intentionally differ.
+            // The .NET APIs should (and did in v4.0 and earlier) throw an ArgumentException on input that includes a terminating null.
+            // The Win32 APIs fail on an embedded null, but not on a terminating null.
+            if (count > 0 && ascii[index + count - 1] == (char)0)
+                throw new ArgumentException(SR.Argument_IdnBadPunycode, nameof(ascii));
+
+            if (GlobalizationMode.Invariant)
+            {
+                return GetUnicodeInvariant(ascii, index, count);
+            }
+
+            unsafe
+            {
+                fixed (char* pAscii = ascii)
+                {
+                    return GetUnicodeCore(ascii, pAscii + index, count);
+                }
+            }
+        }
+
+        public override bool Equals(object obj)
+        {
+            IdnMapping that = obj as IdnMapping;
+            return
+                that != null &&
+                _allowUnassigned == that._allowUnassigned &&
+                _useStd3AsciiRules == that._useStd3AsciiRules;
+        }
+
+        public override int GetHashCode()
+        {
+            return (_allowUnassigned ? 100 : 200) + (_useStd3AsciiRules ? 1000 : 2000);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static unsafe string GetStringForOutput(string originalString, char* input, int inputLength, char* output, int outputLength)
+        {
+            return originalString.Length == inputLength && new ReadOnlySpan<char>(input, inputLength).SequenceEqual(new ReadOnlySpan<char>(output, outputLength)) ?
+                originalString :
+                new string(output, 0, outputLength);
+        }
+
+        //
+        // Invariant implementation
+        //
+
+        private const char c_delimiter = '-';
+        private const string c_strAcePrefix = "xn--";
+        private const int c_labelLimit = 63;          // Not including dots
+        private const int c_defaultNameLimit = 255;   // Including dots
+        private const int c_initialN = 0x80;
+        private const int c_maxint = 0x7ffffff;
+        private const int c_initialBias = 72;
+        private const int c_punycodeBase = 36;
+        private const int c_tmin = 1;
+        private const int c_tmax = 26;
+        private const int c_skew = 38;
+        private const int c_damp = 700;
+
+
+        // Legal "dot" separators (i.e: . in www.microsoft.com)
+        private static char[] c_Dots = { '.', '\u3002', '\uFF0E', '\uFF61' };
+
+        private string GetAsciiInvariant(string unicode, int index, int count)
+        {
+            if (index > 0 || count < unicode.Length)
+            {
+                unicode = unicode.Substring(index, count);
+            }
+
+            // Check for ASCII only string, which will be unchanged
+            if (ValidateStd3AndAscii(unicode, UseStd3AsciiRules, true))
+            {
+                return unicode;
+            }
+
+            // Cannot be null terminated (normalization won't help us with this one, and
+            // may have returned false before checking the whole string above)
+            Debug.Assert(count >= 1, "[IdnMapping.GetAscii] Expected 0 length strings to fail before now.");
+            if (unicode[unicode.Length - 1] <= 0x1f)
+            {
+                throw new ArgumentException(SR.Format(SR.Argument_InvalidCharSequence, unicode.Length - 1), nameof(unicode));
+            }
+
+            // Have to correctly IDNA normalize the string and Unassigned flags
+            bool bHasLastDot = (unicode.Length > 0) && IsDot(unicode[unicode.Length - 1]);
+
+            // Make sure we didn't normalize away something after a last dot
+            if ((!bHasLastDot) && unicode.Length > 0 && IsDot(unicode[unicode.Length - 1]))
+            {
+                throw new ArgumentException(SR.Argument_IdnBadLabelSize, nameof(unicode));
+            }
+
+            // May need to check Std3 rules again for non-ascii
+            if (UseStd3AsciiRules)
+            {
+                ValidateStd3AndAscii(unicode, true, false);
+            }
+
+            // Go ahead and encode it
+            return PunycodeEncode(unicode);
+        }
+
+        // See if we're only ASCII
+        static bool ValidateStd3AndAscii(string unicode, bool bUseStd3, bool bCheckAscii)
+        {
+            // If its empty, then its too small
+            if (unicode.Length == 0)
+                throw new ArgumentException(SR.Argument_IdnBadLabelSize, nameof(unicode));
+
+            int iLastDot = -1;
+
+            // Loop the whole string
+            for (int i = 0; i < unicode.Length; i++)
+            {
+                // Aren't allowing control chars (or 7f, but idn tables catch that, they don't catch \0 at end though)
+                if (unicode[i] <= 0x1f)
+                {
+                    throw new ArgumentException(SR.Format(SR.Argument_InvalidCharSequence, i ), nameof(unicode));
+                }
+
+                // If its Unicode or a control character, return false (non-ascii)
+                if (bCheckAscii && unicode[i] >= 0x7f)
+                    return false;
+
+                // Check for dots
+                if (IsDot(unicode[i]))
+                {
+                    // Can't have 2 dots in a row
+                    if (i == iLastDot + 1)
+                        throw new ArgumentException(SR.Argument_IdnBadLabelSize, nameof(unicode));
+
+                    // If its too far between dots then fail
+                    if (i - iLastDot > c_labelLimit + 1)
+                        throw new ArgumentException(SR.Argument_IdnBadLabelSize, nameof(unicode));
+
+                    // If validating Std3, then char before dot can't be - char
+                    if (bUseStd3 && i > 0)
+                        ValidateStd3(unicode[i - 1], true);
+
+                    // Remember where the last dot is
+                    iLastDot = i;
+                    continue;
+                }
+
+                // If necessary, make sure its a valid std3 character
+                if (bUseStd3)
+                {
+                    ValidateStd3(unicode[i], (i == iLastDot + 1));
+                }
+            }
+
+            // If we never had a dot, then we need to be shorter than the label limit
+            if (iLastDot == -1 && unicode.Length > c_labelLimit)
+                throw new ArgumentException(SR.Argument_IdnBadLabelSize, nameof(unicode));
+
+            // Need to validate entire string length, 1 shorter if last char wasn't a dot
+            if (unicode.Length > c_defaultNameLimit - (IsDot(unicode[unicode.Length - 1]) ? 0 : 1))
+                throw new ArgumentException(SR.Format(SR.Argument_IdnBadNameSize, 
+                                                        c_defaultNameLimit - (IsDot(unicode[unicode.Length - 1]) ? 0 : 1)), nameof(unicode));
+
+            // If last char wasn't a dot we need to check for trailing -
+            if (bUseStd3 && !IsDot(unicode[unicode.Length - 1]))
+                ValidateStd3(unicode[unicode.Length - 1], true);
+
+            return true;
+        }
+
+        /* PunycodeEncode() converts Unicode to Punycode.  The input     */
+        /* is represented as an array of Unicode code points (not code    */
+        /* units; surrogate pairs are not allowed), and the output        */
+        /* will be represented as an array of ASCII code points.  The     */
+        /* output string is *not* null-terminated; it will contain        */
+        /* zeros if and only if the input contains zeros.  (Of course     */
+        /* the caller can leave room for a terminator and add one if      */
+        /* needed.)  The input_length is the number of code points in     */
+        /* the input.  The output_length is an in/out argument: the       */
+        /* caller passes in the maximum number of code points that it     */
+
+        /* can receive, and on successful return it will contain the      */
+        /* number of code points actually output.  The case_flags array   */
+        /* holds input_length boolean values, where nonzero suggests that */
+        /* the corresponding Unicode character be forced to uppercase     */
+        /* after being decoded (if possible), and zero suggests that      */
+        /* it be forced to lowercase (if possible).  ASCII code points    */
+        /* are encoded literally, except that ASCII letters are forced    */
+        /* to uppercase or lowercase according to the corresponding       */
+        /* uppercase flags.  If case_flags is a null pointer then ASCII   */
+        /* letters are left as they are, and other code points are        */
+        /* treated as if their uppercase flags were zero.  The return     */
+        /* value can be any of the punycode_status values defined above   */
+        /* except punycode_bad_input; if not punycode_success, then       */
+        /* output_size and output might contain garbage.                  */
+        static string PunycodeEncode(string unicode)
+        {
+            // 0 length strings aren't allowed
+            if (unicode.Length == 0)
+                throw new ArgumentException(SR.Argument_IdnBadLabelSize, nameof(unicode));
+
+            StringBuilder output = new StringBuilder(unicode.Length);
+            int iNextDot = 0;
+            int iAfterLastDot = 0;
+            int iOutputAfterLastDot = 0;
+
+            // Find the next dot
+            while (iNextDot < unicode.Length)
+            {
+                // Find end of this segment
+                iNextDot = unicode.IndexOfAny(c_Dots, iAfterLastDot);
+                Debug.Assert(iNextDot <= unicode.Length, "[IdnMapping.punycode_encode]IndexOfAny is broken");
+                if (iNextDot < 0)
+                    iNextDot = unicode.Length;
+
+                // Only allowed to have empty . section at end (www.microsoft.com.)
+                if (iNextDot == iAfterLastDot)
+                {
+                    // Only allowed to have empty sections as trailing .
+                    if (iNextDot != unicode.Length)
+                        throw new ArgumentException(SR.Argument_IdnBadLabelSize, nameof(unicode));
+                    // Last dot, stop
+                    break;
+                }
+
+                // We'll need an Ace prefix
+                output.Append(c_strAcePrefix);
+
+                // Everything resets every segment.
+                bool bRightToLeft = false;
+
+                // Check for RTL.  If right-to-left, then 1st & last chars must be RTL
+                BidiCategory eBidi = CharUnicodeInfo.GetBidiCategory(unicode, iAfterLastDot);
+                if (eBidi == BidiCategory.RightToLeft || eBidi == BidiCategory.RightToLeftArabic)
+                {
+                    // It has to be right to left.
+                    bRightToLeft = true;
+
+                    // Check last char
+                    int iTest = iNextDot - 1;
+                    if (Char.IsLowSurrogate(unicode, iTest))
+                    {
+                        iTest--;
+                    }
+
+                    eBidi = CharUnicodeInfo.GetBidiCategory(unicode, iTest);
+                    if (eBidi != BidiCategory.RightToLeft && eBidi != BidiCategory.RightToLeftArabic)
+                    {
+                        // Oops, last wasn't RTL, last should be RTL if first is RTL
+                        throw new ArgumentException(SR.Argument_IdnBadBidi, nameof(unicode));
+                    }
+                }
+
+                // Handle the basic code points
+                int basicCount;
+                int numProcessed = 0;           // Num code points that have been processed so far (this segment)
+                for (basicCount = iAfterLastDot; basicCount < iNextDot; basicCount++)
+                {
+                    // Can't be lonely surrogate because it would've thrown in normalization
+                    Debug.Assert(Char.IsLowSurrogate(unicode, basicCount) == false, "[IdnMapping.punycode_encode]Unexpected low surrogate");
+
+                    // Double check our bidi rules
+                    BidiCategory testBidi = CharUnicodeInfo.GetBidiCategory(unicode, basicCount);
+
+                    // If we're RTL, we can't have LTR chars
+                    if (bRightToLeft && testBidi == BidiCategory.LeftToRight)
+                    {
+                        // Oops, throw error
+                        throw new ArgumentException(SR.Argument_IdnBadBidi, nameof(unicode));
+                    }
+
+                    // If we're not RTL we can't have RTL chars
+                    if (!bRightToLeft && (testBidi == BidiCategory.RightToLeft || testBidi == BidiCategory.RightToLeftArabic))
+                    {
+                        // Oops, throw error
+                        throw new ArgumentException(SR.Argument_IdnBadBidi, nameof(unicode));
+                    }
+
+                    // If its basic then add it
+                    if (Basic(unicode[basicCount]))
+                    {
+                        output.Append(EncodeBasic(unicode[basicCount]));
+                        numProcessed++;
+                    }
+                    // If its a surrogate, skip the next since our bidi category tester doesn't handle it.
+                    else if (Char.IsSurrogatePair(unicode, basicCount))
+                        basicCount++;
+                }
+
+                int numBasicCodePoints = numProcessed;     // number of basic code points
+
+                // Stop if we ONLY had basic code points
+                if (numBasicCodePoints == iNextDot - iAfterLastDot)
+                {
+                    // Get rid of xn-- and this segments done
+                    output.Remove(iOutputAfterLastDot, c_strAcePrefix.Length);
+                }
+                else
+                {
+                    // If it has some non-basic code points the input cannot start with xn--
+                    if (unicode.Length - iAfterLastDot >= c_strAcePrefix.Length &&
+                        unicode.Substring(iAfterLastDot, c_strAcePrefix.Length).Equals(
+                            c_strAcePrefix, StringComparison.OrdinalIgnoreCase))
+                        throw new ArgumentException(SR.Argument_IdnBadPunycode, nameof(unicode));
+
+                    // Need to do ACE encoding
+                    int numSurrogatePairs = 0;            // number of surrogate pairs so far
+
+                    // Add a delimiter (-) if we had any basic code points (between basic and encoded pieces)
+                    if (numBasicCodePoints > 0)
+                    {
+                        output.Append(c_delimiter);
+                    }
+
+                    // Initialize the state
+                    int n = c_initialN;
+                    int delta = 0;
+                    int bias = c_initialBias;
+
+                    // Main loop
+                    while (numProcessed < (iNextDot - iAfterLastDot))
+                    {
+                        /* All non-basic code points < n have been     */
+                        /* handled already.  Find the next larger one: */
+                        int j;
+                        int m;
+                        int test = 0;
+                        for (m = c_maxint, j = iAfterLastDot;
+                             j < iNextDot;
+                             j += IsSupplementary(test) ? 2 : 1)
+                        {
+                            test = Char.ConvertToUtf32(unicode, j);
+                            if (test >= n && test < m) m = test;
+                        }
+
+                        /* Increase delta enough to advance the decoder's    */
+                        /* <n,i> state to <m,0>, but guard against overflow: */
+                        delta += (int)((m - n) * ((numProcessed - numSurrogatePairs) + 1));
+                        Debug.Assert(delta > 0, "[IdnMapping.cs]1 punycode_encode - delta overflowed int");
+                        n = m;
+
+                        for (j = iAfterLastDot;  j < iNextDot;  j+= IsSupplementary(test) ? 2 : 1)
+                        {
+                            // Make sure we're aware of surrogates
+                            test = Char.ConvertToUtf32(unicode, j);
+
+                            // Adjust for character position (only the chars in our string already, some
+                            // haven't been processed.
+
+                            if (test < n)
+                            {
+                                delta++;
+                                Debug.Assert(delta > 0, "[IdnMapping.cs]2 punycode_encode - delta overflowed int");
+                            }
+
+                            if (test == n)
+                            {
+                                // Represent delta as a generalized variable-length integer:
+                                int q, k;
+                                for (q = delta, k = c_punycodeBase;  ; k += c_punycodeBase)
+                                {
+                                    int t = k <= bias ? c_tmin : k >= bias + c_tmax ? c_tmax : k - bias;
+                                    if (q < t) break;
+                                    Debug.Assert(c_punycodeBase != t, "[IdnMapping.punycode_encode]Expected c_punycodeBase (36) to be != t");
+                                    output.Append(EncodeDigit(t + (q - t) % (c_punycodeBase - t)));
+                                    q = (q - t) / (c_punycodeBase - t);
+                                }
+
+                                output.Append(EncodeDigit(q));
+                                bias = Adapt(delta, (numProcessed - numSurrogatePairs) + 1, numProcessed == numBasicCodePoints);
+                                delta = 0;
+                                numProcessed++;
+
+                                if (IsSupplementary(m))
+                                {
+                                    numProcessed++;
+                                    numSurrogatePairs++;
+                                }
+                            }
+                        }
+                        ++delta;
+                        ++n;
+                        Debug.Assert(delta > 0, "[IdnMapping.cs]3 punycode_encode - delta overflowed int");
+                    }
+                }
+
+                // Make sure its not too big
+                if (output.Length - iOutputAfterLastDot > c_labelLimit)
+                    throw new ArgumentException(SR.Argument_IdnBadLabelSize, nameof(unicode));
+
+                // Done with this segment, add dot if necessary
+                if (iNextDot != unicode.Length)
+                    output.Append('.');
+
+                iAfterLastDot = iNextDot + 1;
+                iOutputAfterLastDot = output.Length;
+            }
+
+            // Throw if we're too long
+            if (output.Length > c_defaultNameLimit - (IsDot(unicode[unicode.Length-1]) ? 0 : 1))
+                throw new ArgumentException(SR.Format(SR.Argument_IdnBadNameSize, 
+                                                c_defaultNameLimit - (IsDot(unicode[unicode.Length-1]) ? 0 : 1)), nameof(unicode));
+            // Return our output string
+            return output.ToString();
+        }
+
+        // Is it a dot?
+        // are we U+002E (., full stop), U+3002 (ideographic full stop), U+FF0E (fullwidth full stop), or
+        // U+FF61 (halfwidth ideographic full stop).
+        // Note: IDNA Normalization gets rid of dots now, but testing for last dot is before normalization
+        private static bool IsDot(char c)
+        {
+            return c == '.' || c == '\u3002' || c == '\uFF0E' || c == '\uFF61';
+        }
+
+        private static bool IsSupplementary(int cTest)
+        {
+            return cTest >= 0x10000;
+        }
+
+        private static bool Basic(uint cp)
+        {
+            // Is it in ASCII range?
+            return cp < 0x80;
+        }
+
+        // Validate Std3 rules for a character
+        private static void ValidateStd3(char c, bool bNextToDot)
+        {
+            // Check for illegal characters
+            if ((c <= ',' || c == '/' || (c >= ':' && c <= '@') ||      // Lots of characters not allowed
+                (c >= '[' && c <= '`') || (c >= '{' && c <= (char)0x7F)) ||
+                (c == '-' && bNextToDot))
+                    throw new ArgumentException(SR.Format(SR.Argument_IdnBadStd3, c), nameof(c));
+        }
+
+        private string GetUnicodeInvariant(string ascii, int index, int count)
+        {
+            if (index > 0 || count < ascii.Length)
+            {
+                // We're only using part of the string
+                ascii = ascii.Substring(index, count);
+            }
+            // Convert Punycode to Unicode
+            string strUnicode = PunycodeDecode(ascii);
+
+            // Output name MUST obey IDNA rules & round trip (casing differences are allowed)
+            if (!ascii.Equals(GetAscii(strUnicode), StringComparison.OrdinalIgnoreCase))
+                throw new ArgumentException(SR.Argument_IdnIllegalName, nameof(ascii));
+
+            return strUnicode;
+        }
+
+        /* PunycodeDecode() converts Punycode to Unicode.  The input is  */
+        /* represented as an array of ASCII code points, and the output   */
+        /* will be represented as an array of Unicode code points.  The   */
+        /* input_length is the number of code points in the input.  The   */
+        /* output_length is an in/out argument: the caller passes in      */
+        /* the maximum number of code points that it can receive, and     */
+        /* on successful return it will contain the actual number of      */
+        /* code points output.  The case_flags array needs room for at    */
+        /* least output_length values, or it can be a null pointer if the */
+        /* case information is not needed.  A nonzero flag suggests that  */
+        /* the corresponding Unicode character be forced to uppercase     */
+        /* by the caller (if possible), while zero suggests that it be    */
+        /* forced to lowercase (if possible).  ASCII code points are      */
+        /* output already in the proper case, but their flags will be set */
+        /* appropriately so that applying the flags would be harmless.    */
+        /* The return value can be any of the punycode_status values      */
+        /* defined above; if not punycode_success, then output_length,    */
+        /* output, and case_flags might contain garbage.  On success, the */
+        /* decoder will never need to write an output_length greater than */
+        /* input_length, because of how the encoding is defined.          */
+
+        private static string PunycodeDecode(string ascii)
+        {
+            // 0 length strings aren't allowed
+            if (ascii.Length == 0)
+                throw new ArgumentException(SR.Argument_IdnBadLabelSize, nameof(ascii));
+
+            // Throw if we're too long
+            if (ascii.Length > c_defaultNameLimit - (IsDot(ascii[ascii.Length-1]) ? 0 : 1))
+                throw new ArgumentException(SR.Format(SR.Argument_IdnBadNameSize, 
+                                            c_defaultNameLimit - (IsDot(ascii[ascii.Length-1]) ? 0 : 1)), nameof(ascii));
+
+            // output stringbuilder
+            StringBuilder output = new StringBuilder(ascii.Length);
+
+            // Dot searching
+            int iNextDot = 0;
+            int iAfterLastDot = 0;
+            int iOutputAfterLastDot = 0;
+
+            while (iNextDot < ascii.Length)
+            {
+                // Find end of this segment
+                iNextDot = ascii.IndexOf('.', iAfterLastDot);
+                if (iNextDot < 0 || iNextDot > ascii.Length)
+                    iNextDot = ascii.Length;
+
+                // Only allowed to have empty . section at end (www.microsoft.com.)
+                if (iNextDot == iAfterLastDot)
+                {
+                    // Only allowed to have empty sections as trailing .
+                    if (iNextDot != ascii.Length)
+                        throw new ArgumentException(SR.Argument_IdnBadLabelSize, nameof(ascii));
+
+                    // Last dot, stop
+                    break;
+                }
+
+                // In either case it can't be bigger than segment size
+                if (iNextDot - iAfterLastDot > c_labelLimit)
+                    throw new ArgumentException(SR.Argument_IdnBadLabelSize, nameof(ascii));
+
+                // See if this section's ASCII or ACE
+                if (ascii.Length < c_strAcePrefix.Length + iAfterLastDot || 
+                    !ascii.Substring(iAfterLastDot,c_strAcePrefix.Length).Equals(c_strAcePrefix, StringComparison.OrdinalIgnoreCase))
+                {
+                    // Its ASCII, copy it
+                    output.Append(ascii.Substring(iAfterLastDot, iNextDot - iAfterLastDot));
+                }
+                else
+                {
+                    // Not ASCII, bump up iAfterLastDot to be after ACE Prefix
+                    iAfterLastDot += c_strAcePrefix.Length;
+
+                    // Get number of basic code points (where delimiter is)
+                    // numBasicCodePoints < 0 if there're no basic code points
+                    int iTemp = ascii.LastIndexOf(c_delimiter, iNextDot - 1);
+
+                    // Trailing - not allowed
+                    if (iTemp == iNextDot - 1)
+                        throw new ArgumentException(SR.Argument_IdnBadPunycode, nameof(ascii));
+
+                    int numBasicCodePoints;
+                    if (iTemp <= iAfterLastDot)
+                        numBasicCodePoints = 0;
+                    else
+                    {
+                        numBasicCodePoints = iTemp - iAfterLastDot;
+
+                        // Copy all the basic code points, making sure they're all in the allowed range,
+                        // and losing the casing for all of them.
+                        for (int copyAscii = iAfterLastDot; copyAscii < iAfterLastDot + numBasicCodePoints; copyAscii++)
+                        {
+                            // Make sure we don't allow unicode in the ascii part
+                            if (ascii[copyAscii] > 0x7f)
+                                throw new ArgumentException(SR.Argument_IdnBadPunycode, nameof(ascii));
+
+                            // When appending make sure they get lower cased
+                            output.Append((char)(ascii[copyAscii] >= 'A' && ascii[copyAscii] <='Z' ? ascii[copyAscii] - 'A' + 'a' : ascii[copyAscii]));
+                        }
+                    }
+
+                    // Get ready for main loop.  Start at beginning if we didn't have any
+                    // basic code points, otherwise start after the -.
+                    // asciiIndex will be next character to read from ascii
+                    int asciiIndex = iAfterLastDot + (numBasicCodePoints > 0 ? numBasicCodePoints + 1 : 0);
+
+                    // initialize our state
+                    int n = c_initialN;
+                    int bias = c_initialBias;
+                    int i = 0;
+
+                    int w, k;
+
+                    // no Supplementary characters yet
+                    int numSurrogatePairs = 0;
+
+                    // Main loop, read rest of ascii
+                    while (asciiIndex < iNextDot)
+                    {
+                        /* Decode a generalized variable-length integer into delta,  */
+                        /* which gets added to i.  The overflow checking is easier   */
+                        /* if we increase i as we go, then subtract off its starting */
+                        /* value at the end to obtain delta.                         */
+                        int oldi = i;
+
+                        for (w = 1, k = c_punycodeBase;  ;  k += c_punycodeBase)
+                        {
+                            // Check to make sure we aren't overrunning our ascii string
+                            if (asciiIndex >= iNextDot)
+                                throw new ArgumentException(SR.Argument_IdnBadPunycode, nameof(ascii));
+
+                            // decode the digit from the next char
+                            int digit = DecodeDigit(ascii[asciiIndex++]);
+
+                            Debug.Assert(w > 0, "[IdnMapping.punycode_decode]Expected w > 0");
+                            if (digit > (c_maxint - i) / w)
+                                throw new ArgumentException(SR.Argument_IdnBadPunycode, nameof(ascii));
+
+                            i += (int)(digit * w);
+                            int t = k <= bias ? c_tmin : k >= bias + c_tmax ? c_tmax : k - bias;
+                            if (digit < t) 
+                                break;
+                            Debug.Assert(c_punycodeBase != t, "[IdnMapping.punycode_decode]Expected t != c_punycodeBase (36)");
+                            if (w > c_maxint / (c_punycodeBase - t))
+                                throw new ArgumentException(SR.Argument_IdnBadPunycode, nameof(ascii));
+                            w *= (c_punycodeBase - t);
+                        }
+
+                        bias = Adapt(i - oldi, (output.Length - iOutputAfterLastDot - numSurrogatePairs) + 1, oldi == 0);
+
+                        /* i was supposed to wrap around from output.Length to 0,   */
+                        /* incrementing n each time, so we'll fix that now: */
+                        Debug.Assert((output.Length - iOutputAfterLastDot - numSurrogatePairs) + 1 > 0,
+                            "[IdnMapping.punycode_decode]Expected to have added > 0 characters this segment");
+                        if (i / ((output.Length - iOutputAfterLastDot - numSurrogatePairs) + 1) > c_maxint - n)
+                            throw new ArgumentException(SR.Argument_IdnBadPunycode, nameof(ascii));
+                        n += (int)(i / (output.Length - iOutputAfterLastDot - numSurrogatePairs + 1));
+                        i %= (output.Length - iOutputAfterLastDot - numSurrogatePairs + 1);
+
+                        // Make sure n is legal
+                        if ((n < 0 || n > 0x10ffff) || (n >= 0xD800 && n <= 0xDFFF))
+                            throw new ArgumentException(SR.Argument_IdnBadPunycode, nameof(ascii));
+
+                        // insert n at position i of the output:  Really tricky if we have surrogates
+                        int iUseInsertLocation;
+                        String strTemp = Char.ConvertFromUtf32(n);
+
+                        // If we have supplimentary characters
+                        if (numSurrogatePairs > 0)
+                        {
+                            // Hard way, we have supplimentary characters
+                            int iCount;
+                            for (iCount = i, iUseInsertLocation = iOutputAfterLastDot; iCount > 0; iCount--, iUseInsertLocation++)
+                            {
+                                // If its a surrogate, we have to go one more
+                                if (iUseInsertLocation >= output.Length)
+                                    throw new ArgumentException(SR.Argument_IdnBadPunycode, nameof(ascii));
+                                if (Char.IsSurrogate(output[iUseInsertLocation]))
+                                    iUseInsertLocation++;
+                            }
+                        }
+                        else
+                        {
+                            // No Supplementary chars yet, just add i
+                            iUseInsertLocation = iOutputAfterLastDot + i;
+                        }
+
+                        // Insert it
+                        output.Insert(iUseInsertLocation, strTemp);
+
+                        // If it was a surrogate increment our counter
+                        if (IsSupplementary(n))
+                            numSurrogatePairs++;
+
+                        // Index gets updated
+                        i++;
+                    }
+
+                    // Do BIDI testing
+                    bool bRightToLeft = false;
+
+                    // Check for RTL.  If right-to-left, then 1st & last chars must be RTL
+                    BidiCategory eBidi = CharUnicodeInfo.GetBidiCategory(output.ToString(), iOutputAfterLastDot);
+                    if (eBidi == BidiCategory.RightToLeft || eBidi == BidiCategory.RightToLeftArabic)
+                    {
+                        // It has to be right to left.
+                        bRightToLeft = true;
+                    }
+
+                    // Check the rest of them to make sure RTL/LTR is consistent
+                    for (int iTest = iOutputAfterLastDot; iTest < output.Length; iTest++)
+                    {
+                        // This might happen if we run into a pair
+                        if (Char.IsLowSurrogate(output.ToString(), iTest)) 
+                            continue;
+
+                        // Check to see if its LTR
+                        eBidi = CharUnicodeInfo.GetBidiCategory(output.ToString(), iTest);
+                        if ((bRightToLeft && eBidi == BidiCategory.LeftToRight) ||
+                            (!bRightToLeft && (eBidi == BidiCategory.RightToLeft || eBidi == BidiCategory.RightToLeftArabic)))
+                            throw new ArgumentException(SR.Argument_IdnBadBidi, nameof(ascii));
+                    }
+
+                    // Its also a requirement that the last one be RTL if 1st is RTL
+                    if (bRightToLeft && eBidi != BidiCategory.RightToLeft && eBidi != BidiCategory.RightToLeftArabic)
+                    {
+                        // Oops, last wasn't RTL, last should be RTL if first is RTL
+                        throw new ArgumentException(SR.Argument_IdnBadBidi, nameof(ascii));
+                    }
+                }
+
+                // See if this label was too long
+                if (iNextDot - iAfterLastDot > c_labelLimit)
+                    throw new ArgumentException(SR.Argument_IdnBadLabelSize, nameof(ascii));
+
+                // Done with this segment, add dot if necessary
+                if (iNextDot != ascii.Length)
+                    output.Append('.');
+
+                iAfterLastDot = iNextDot + 1;
+                iOutputAfterLastDot = output.Length;
+            }
+
+            // Throw if we're too long
+            if (output.Length > c_defaultNameLimit - (IsDot(output[output.Length-1]) ? 0 : 1))
+                throw new ArgumentException(SR.Format(SR.Argument_IdnBadNameSize, c_defaultNameLimit - (IsDot(output[output.Length-1]) ? 0 : 1)), nameof(ascii));
+
+            // Return our output string
+            return output.ToString();
+        }
+
+        // DecodeDigit(cp) returns the numeric value of a basic code */
+        // point (for use in representing integers) in the range 0 to */
+        // c_punycodeBase-1, or <0 if cp is does not represent a value. */
+
+        private static int DecodeDigit(char cp)
+        {
+            if (cp >= '0' && cp <= '9')
+                return cp - '0' + 26;
+
+            // Two flavors for case differences
+            if (cp >= 'a' && cp <= 'z')
+                return cp - 'a';
+
+            if (cp >= 'A' && cp <= 'Z')
+                return cp - 'A';
+
+            // Expected 0-9, A-Z or a-z, everything else is illegal
+            throw new ArgumentException(SR.Argument_IdnBadPunycode, nameof(cp));
+        }
+
+        private static int Adapt(int delta, int numpoints, bool firsttime)
+        {
+            uint k;
+
+            delta = firsttime ? delta / c_damp : delta / 2;
+            Debug.Assert(numpoints != 0, "[IdnMapping.adapt]Expected non-zero numpoints.");
+            delta += delta / numpoints;
+
+            for (k = 0;  delta > ((c_punycodeBase - c_tmin) * c_tmax) / 2;  k += c_punycodeBase)
+            {
+              delta /= c_punycodeBase - c_tmin;
+            }
+
+            Debug.Assert(delta + c_skew != 0, "[IdnMapping.adapt]Expected non-zero delta+skew.");
+            return (int)(k + (c_punycodeBase - c_tmin + 1) * delta / (delta + c_skew));
+        }
+
+        /* EncodeBasic(bcp,flag) forces a basic code point to lowercase */
+        /* if flag is false, uppercase if flag is true, and returns    */
+        /* the resulting code point.  The code point is unchanged if it  */
+        /* is caseless.  The behavior is undefined if bcp is not a basic */
+        /* code point.                                                   */
+
+        static char EncodeBasic(char bcp)
+        {
+            if (HasUpperCaseFlag(bcp))
+                bcp += (char)('a' - 'A');
+
+            return bcp;
+        }
+
+        // Return whether a punycode code point is flagged as being upper case.
+        private static bool HasUpperCaseFlag(char punychar)
+        {
+            return (punychar >= 'A' && punychar <= 'Z');
+        }
+
+        /* EncodeDigit(d,flag) returns the basic code point whose value      */
+        /* (when used for representing integers) is d, which needs to be in   */
+        /* the range 0 to punycodeBase-1.  The lowercase form is used unless flag is  */
+        /* true, in which case the uppercase form is used. */
+
+        private static char EncodeDigit(int d)
+        {
+            Debug.Assert(d >= 0 && d < c_punycodeBase, "[IdnMapping.encode_digit]Expected 0 <= d < punycodeBase");
+            // 26-35 map to ASCII 0-9
+            if (d > 25) return (char)(d - 26 + '0');
+
+            //  0-25 map to a-z or A-Z
+            return (char)(d + 'a');
+        }
+        
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/InternalGlobalizationHelper.cs b/src/System.Private.CoreLib/shared/System/Globalization/InternalGlobalizationHelper.cs
new file mode 100644
index 0000000000..60abcecf61
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/InternalGlobalizationHelper.cs
@@ -0,0 +1,48 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Globalization
+{
+    internal class InternalGlobalizationHelper
+    {
+        // Copied from the TimeSpan to be used inside the globalization code and avoid internal dependency on TimeSpan class
+        internal static long TimeToTicks(int hour, int minute, int second)
+        {
+            // totalSeconds is bounded by 2^31 * 2^12 + 2^31 * 2^8 + 2^31,
+            // which is less than 2^44, meaning we won't overflow totalSeconds.
+            long totalSeconds = (long)hour * 3600 + (long)minute * 60 + (long)second;
+            if (totalSeconds > MaxSeconds || totalSeconds < MinSeconds)
+                throw new ArgumentOutOfRangeException(null, SR.Overflow_TimeSpanTooLong);
+            return totalSeconds * TicksPerSecond;
+        }
+
+
+        //
+        // Define needed constants so globalization code can be independant from any other types
+        //
+
+        internal const long TicksPerMillisecond = 10000;
+        internal const long TicksPerTenthSecond = TicksPerMillisecond * 100;
+        internal const long TicksPerSecond = TicksPerMillisecond * 1000;   // 10,000,000
+        internal const long MaxSeconds = Int64.MaxValue / TicksPerSecond;
+        internal const long MinSeconds = Int64.MinValue / TicksPerSecond;
+        private const int DaysPerYear = 365;
+        private const int DaysPer4Years = DaysPerYear * 4 + 1;       // 1461
+        private const int DaysPer100Years = DaysPer4Years * 25 - 1;  // 36524
+        private const int DaysPer400Years = DaysPer100Years * 4 + 1; // 146097
+        private const int DaysTo10000 = DaysPer400Years * 25 - 366;  // 3652059
+        private const long TicksPerMinute = TicksPerSecond * 60;
+        private const long TicksPerHour = TicksPerMinute * 60;
+        private const long TicksPerDay = TicksPerHour * 24;
+        internal const long MaxTicks = DaysTo10000 * TicksPerDay - 1;
+        internal const long MinTicks = 0;
+        internal const long MaxMilliSeconds = Int64.MaxValue / TicksPerMillisecond;
+        internal const long MinMilliSeconds = Int64.MinValue / TicksPerMillisecond;
+
+        internal const int StringBuilderDefaultCapacity = 16;
+
+        internal const Int64 MaxOffset = TimeSpan.TicksPerHour * 14;
+        internal const Int64 MinOffset = -MaxOffset;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/JapaneseCalendar.Unix.cs b/src/System.Private.CoreLib/shared/System/Globalization/JapaneseCalendar.Unix.cs
new file mode 100644
index 0000000000..5e66c94b2c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/JapaneseCalendar.Unix.cs
@@ -0,0 +1,96 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    public partial class JapaneseCalendar : Calendar
+    {
+        private static EraInfo[] GetJapaneseEras()
+        {
+            if (GlobalizationMode.Invariant)
+            {
+                return null;
+            }
+
+            string[] eraNames;
+            if (!CalendarData.EnumCalendarInfo("ja-JP", CalendarId.JAPAN, CalendarDataType.EraNames, out eraNames))
+            {
+                return null;
+            }
+
+            string[] abbrevEnglishEraNames;
+            if (!CalendarData.EnumCalendarInfo("en", CalendarId.JAPAN, CalendarDataType.AbbrevEraNames, out abbrevEnglishEraNames))
+            {
+                return null;
+            }
+
+            List<EraInfo> eras = new List<EraInfo>();
+            int lastMaxYear = GregorianCalendar.MaxYear;
+
+            int latestEra = Interop.Globalization.GetLatestJapaneseEra();
+            for (int i = latestEra; i >= 0; i--)
+            {
+                DateTime dt;
+                if (!GetJapaneseEraStartDate(i, out dt))
+                {
+                    return null;
+                }
+
+                if (dt < JapaneseCalendar.calendarMinValue)
+                {
+                    // only populate the Eras that are valid JapaneseCalendar date times
+                    break;
+                }
+
+                eras.Add(new EraInfo(i, dt.Year, dt.Month, dt.Day, dt.Year - 1, 1, lastMaxYear - dt.Year + 1,
+                    eraNames[i], GetAbbreviatedEraName(eraNames, i), abbrevEnglishEraNames[i]));
+
+                lastMaxYear = dt.Year;
+            }
+
+            // remap the Era numbers, now that we know how many there will be
+            for (int i = 0; i < eras.Count; i++)
+            {
+                eras[i].era = eras.Count - i;
+            }
+
+            return eras.ToArray();
+        }
+
+        // PAL Layer ends here
+
+        private static string GetAbbreviatedEraName(string[] eraNames, int eraIndex)
+        {
+            // This matches the behavior on Win32 - only returning the first character of the era name.
+            // See Calendar.EraAsString(Int32) - https://msdn.microsoft.com/en-us/library/windows/apps/br206751.aspx
+            return eraNames[eraIndex].Substring(0, 1);
+        }
+
+        private static bool GetJapaneseEraStartDate(int era, out DateTime dateTime)
+        {
+            Debug.Assert(!GlobalizationMode.Invariant);
+
+            dateTime = default(DateTime);
+
+            int startYear;
+            int startMonth;
+            int startDay;
+            bool result = Interop.Globalization.GetJapaneseEraStartDate(
+                era,
+                out startYear,
+                out startMonth,
+                out startDay);
+
+            if (result)
+            {
+                dateTime = new DateTime(startYear, startMonth, startDay);
+            }
+
+            return result;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/JapaneseCalendar.Win32.cs b/src/System.Private.CoreLib/shared/System/Globalization/JapaneseCalendar.Win32.cs
new file mode 100644
index 0000000000..1d0180b00e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/JapaneseCalendar.Win32.cs
@@ -0,0 +1,210 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+using Microsoft.Win32;
+
+namespace System.Globalization
+{
+    public partial class JapaneseCalendar : Calendar
+    {
+        private const string c_japaneseErasHive = @"System\CurrentControlSet\Control\Nls\Calendars\Japanese\Eras";
+        private const string c_japaneseErasHivePermissionList = @"HKEY_LOCAL_MACHINE\" + c_japaneseErasHive;
+
+        // We know about 4 built-in eras, however users may add additional era(s) from the
+        // registry, by adding values to HKLM\SYSTEM\CurrentControlSet\Control\Nls\Calendars\Japanese\Eras
+        //
+        // Registry values look like:
+        //      yyyy.mm.dd=era_abbrev_english_englishabbrev
+        //
+        // Where yyyy.mm.dd is the registry value name, and also the date of the era start.
+        // yyyy, mm, and dd are the year, month & day the era begins (4, 2 & 2 digits long)
+        // era is the Japanese Era name
+        // abbrev is the Abbreviated Japanese Era Name
+        // english is the English name for the Era (unused)
+        // englishabbrev is the Abbreviated English name for the era.
+        // . is a delimiter, but the value of . doesn't matter.
+        // '_' marks the space between the japanese era name, japanese abbreviated era name
+        //     english name, and abbreviated english names.
+        private static EraInfo[] GetJapaneseEras()
+        {
+            // Look in the registry key and see if we can find any ranges
+            int iFoundEras = 0;
+            EraInfo[] registryEraRanges = null;
+
+            try
+            {
+                // Need to access registry
+                RegistryKey key = RegistryKey.GetBaseKey(RegistryKey.HKEY_LOCAL_MACHINE).OpenSubKey(c_japaneseErasHive, false);
+
+                // Abort if we didn't find anything
+                if (key == null) return null;
+
+                // Look up the values in our reg key
+                String[] valueNames = key.GetValueNames();
+                if (valueNames != null && valueNames.Length > 0)
+                {
+                    registryEraRanges = new EraInfo[valueNames.Length];
+
+                    // Loop through the registry and read in all the values
+                    for (int i = 0; i < valueNames.Length; i++)
+                    {
+                        // See if the era is a valid date
+                        EraInfo era = GetEraFromValue(valueNames[i], key.GetValue(valueNames[i]).ToString());
+
+                        // continue if not valid
+                        if (era == null) continue;
+
+                        // Remember we found one.
+                        registryEraRanges[iFoundEras] = era;
+                        iFoundEras++;
+                    }
+                }
+            }
+            catch (System.Security.SecurityException)
+            {
+                // If we weren't allowed to read, then just ignore the error
+                return null;
+            }
+            catch (System.IO.IOException)
+            {
+                // If key is being deleted just ignore the error
+                return null;
+            }
+            catch (System.UnauthorizedAccessException)
+            {
+                // Registry access rights permissions, just ignore the error
+                return null;
+            }
+
+            //
+            // If we didn't have valid eras, then fail
+            // should have at least 4 eras
+            //
+            if (iFoundEras < 4) return null;
+
+            //
+            // Now we have eras, clean them up.
+            //
+            // Clean up array length
+            Array.Resize(ref registryEraRanges, iFoundEras);
+
+            // Sort them
+            Array.Sort(registryEraRanges, CompareEraRanges);
+
+            // Clean up era information
+            for (int i = 0; i < registryEraRanges.Length; i++)
+            {
+                // eras count backwards from length to 1 (and are 1 based indexes into string arrays)
+                registryEraRanges[i].era = registryEraRanges.Length - i;
+
+                // update max era year
+                if (i == 0)
+                {
+                    // First range is 'til the end of the calendar
+                    registryEraRanges[0].maxEraYear = GregorianCalendar.MaxYear - registryEraRanges[0].yearOffset;
+                }
+                else
+                {
+                    // Rest are until the next era (remember most recent era is first in array)
+                    registryEraRanges[i].maxEraYear = registryEraRanges[i - 1].yearOffset + 1 - registryEraRanges[i].yearOffset;
+                }
+            }
+
+            // Return our ranges
+            return registryEraRanges;
+        }
+
+        //
+        // Compare two era ranges, eg just the ticks
+        // Remember the era array is supposed to be in reverse chronological order
+        //
+        private static int CompareEraRanges(EraInfo a, EraInfo b)
+        {
+            return b.ticks.CompareTo(a.ticks);
+        }
+
+        //
+        // GetEraFromValue
+        //
+        // Parse the registry value name/data pair into an era
+        //
+        // Registry values look like:
+        //      yyyy.mm.dd=era_abbrev_english_englishabbrev
+        //
+        // Where yyyy.mm.dd is the registry value name, and also the date of the era start.
+        // yyyy, mm, and dd are the year, month & day the era begins (4, 2 & 2 digits long)
+        // era is the Japanese Era name
+        // abbrev is the Abbreviated Japanese Era Name
+        // english is the English name for the Era (unused)
+        // englishabbrev is the Abbreviated English name for the era.
+        // . is a delimiter, but the value of . doesn't matter.
+        // '_' marks the space between the japanese era name, japanese abbreviated era name
+        //     english name, and abbreviated english names.
+        private static EraInfo GetEraFromValue(String value, String data)
+        {
+            // Need inputs
+            if (value == null || data == null) return null;
+
+            //
+            // Get Date
+            //
+            // Need exactly 10 characters in name for date
+            // yyyy.mm.dd although the . can be any character
+            if (value.Length != 10) return null;
+
+            int year;
+            int month;
+            int day;
+
+            ReadOnlySpan<char> valueSpan = value.AsSpan();
+            if (!Int32.TryParse(valueSpan.Slice(0, 4), NumberStyles.None, NumberFormatInfo.InvariantInfo, out year) ||
+                !Int32.TryParse(valueSpan.Slice(5, 2), NumberStyles.None, NumberFormatInfo.InvariantInfo, out month) ||
+                !Int32.TryParse(valueSpan.Slice(8, 2), NumberStyles.None, NumberFormatInfo.InvariantInfo, out day))
+            {
+                // Couldn't convert integer, fail
+                return null;
+            }
+
+            //
+            // Get Strings
+            //
+            // Needs to be a certain length e_a_E_A at least (7 chars, exactly 4 groups)
+            String[] names = data.Split('_');
+
+            // Should have exactly 4 parts
+            // 0 - Era Name
+            // 1 - Abbreviated Era Name
+            // 2 - English Era Name
+            // 3 - Abbreviated English Era Name
+            if (names.Length != 4) return null;
+
+            // Each part should have data in it
+            if (names[0].Length == 0 ||
+                names[1].Length == 0 ||
+                names[2].Length == 0 ||
+                names[3].Length == 0)
+                return null;
+
+            //
+            // Now we have an era we can build
+            // Note that the era # and max era year need cleaned up after sorting
+            // Don't use the full English Era Name (names[2])
+            //
+            return new EraInfo(0, year, month, day, year - 1, 1, 0,
+                                names[0], names[1], names[3]);
+        }
+
+        // PAL Layer ends here
+
+        private static string[] s_japaneseErasEnglishNames = new String[] { "M", "T", "S", "H" };
+
+        private static string GetJapaneseEnglishEraName(int era)
+        {
+            Debug.Assert(era > 0);
+            return era <= s_japaneseErasEnglishNames.Length ? s_japaneseErasEnglishNames[era - 1] : " ";
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/JapaneseCalendar.WinRT.cs b/src/System.Private.CoreLib/shared/System/Globalization/JapaneseCalendar.WinRT.cs
new file mode 100644
index 0000000000..6a9df97200
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/JapaneseCalendar.WinRT.cs
@@ -0,0 +1,62 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+using Internal.Runtime.Augments;
+
+namespace System.Globalization
+{
+    public partial class JapaneseCalendar : Calendar
+    {
+        private static EraInfo[] GetJapaneseEras()
+        {
+            int erasCount = WinRTInterop.Callbacks.GetJapaneseEraCount();
+            if (erasCount < 4)
+            {
+                return null;
+            }
+
+            EraInfo[] eras = new EraInfo[erasCount];
+            int lastMaxYear = GregorianCalendar.MaxYear;
+
+            for (int i = erasCount; i > 0; i--)
+            {
+                DateTimeOffset dateOffset;
+
+                string eraName;
+                string abbreviatedEraName;
+
+                if (!GetJapaneseEraInfo(i, out dateOffset, out eraName, out abbreviatedEraName))
+                {
+                    return null;
+                }
+
+                DateTime dt = new DateTime(dateOffset.Ticks);
+
+                eras[erasCount - i] = new EraInfo(i, dt.Year, dt.Month, dt.Day, dt.Year - 1, 1, lastMaxYear - dt.Year + 1,
+                                                   eraName, abbreviatedEraName, GetJapaneseEnglishEraName(i));    // era #4 start year/month/day, yearOffset, minEraYear
+
+                lastMaxYear = dt.Year;
+            }
+
+            return eras;
+        }
+
+        // PAL Layer ends here
+
+        private static string[] JapaneseErasEnglishNames = new String[] { "M", "T", "S", "H" };
+
+        private static string GetJapaneseEnglishEraName(int era)
+        {
+            Debug.Assert(era > 0);
+            return era <= JapaneseErasEnglishNames.Length ? JapaneseErasEnglishNames[era - 1] : " ";
+        }
+
+        private static bool GetJapaneseEraInfo(int era, out DateTimeOffset dateOffset, out string eraName, out string abbreviatedEraName)
+        {
+            return  WinRTInterop.Callbacks.GetJapaneseEraInfo(era, out dateOffset, out eraName, out abbreviatedEraName);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/JapaneseCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/JapaneseCalendar.cs
new file mode 100644
index 0000000000..50195d7f1c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/JapaneseCalendar.cs
@@ -0,0 +1,405 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics.CodeAnalysis;
+
+namespace System.Globalization
+{
+    /*=================================JapaneseCalendar==========================
+    **
+    ** JapaneseCalendar is based on Gregorian calendar.  The month and day values are the same as
+    ** Gregorian calendar.  However, the year value is an offset to the Gregorian
+    ** year based on the era.
+    **
+    ** This system is adopted by Emperor Meiji in 1868. The year value is counted based on the reign of an emperor,
+    ** and the era begins on the day an emperor ascends the throne and continues until his death.
+    ** The era changes at 12:00AM.
+    **
+    ** For example, the current era is Heisei.  It started on 1989/1/8 A.D.  Therefore, Gregorian year 1989 is also Heisei 1st.
+    ** 1989/1/8 A.D. is also Heisei 1st 1/8.
+    **
+    ** Any date in the year during which era is changed can be reckoned in either era.  For example,
+    ** 1989/1/1 can be 1/1 Heisei 1st year or 1/1 Showa 64th year.
+    **
+    ** Note:
+    **  The DateTime can be represented by the JapaneseCalendar are limited to two factors:
+    **      1. The min value and max value of DateTime class.
+    **      2. The available era information.
+    **
+    **  Calendar support range:
+    **      Calendar    Minimum     Maximum
+    **      ==========  ==========  ==========
+    **      Gregorian   1868/09/08  9999/12/31
+    **      Japanese    Meiji 01/01 Heisei 8011/12/31
+    ============================================================================*/
+
+
+    public partial class JapaneseCalendar : Calendar
+    {
+        internal static readonly DateTime calendarMinValue = new DateTime(1868, 9, 8);
+
+
+        public override DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (calendarMinValue);
+            }
+        }
+
+        public override DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (DateTime.MaxValue);
+            }
+        }
+
+        public override CalendarAlgorithmType AlgorithmType
+        {
+            get
+            {
+                return CalendarAlgorithmType.SolarCalendar;
+            }
+        }
+
+        //
+        // Using a field initializer rather than a static constructor so that the whole class can be lazy
+        // init.
+        internal static volatile EraInfo[] japaneseEraInfo;
+
+        //
+        // Read our era info
+        //
+        // m_EraInfo must be listed in reverse chronological order.  The most recent era
+        // should be the first element.
+        // That is, m_EraInfo[0] contains the most recent era.
+        //
+        // We know about 4 built-in eras, however users may add additional era(s) from the
+        // registry, by adding values to HKLM\SYSTEM\CurrentControlSet\Control\Nls\Calendars\Japanese\Eras
+        // we don't read the registry and instead we call WinRT to get the needed informatio
+        //
+        // Registry values look like:
+        //      yyyy.mm.dd=era_abbrev_english_englishabbrev
+        //
+        // Where yyyy.mm.dd is the registry value name, and also the date of the era start.
+        // yyyy, mm, and dd are the year, month & day the era begins (4, 2 & 2 digits long)
+        // era is the Japanese Era name
+        // abbrev is the Abbreviated Japanese Era Name
+        // english is the English name for the Era (unused)
+        // englishabbrev is the Abbreviated English name for the era.
+        // . is a delimiter, but the value of . doesn't matter.
+        // '_' marks the space between the japanese era name, japanese abbreviated era name
+        //     english name, and abbreviated english names.
+        //
+        internal static EraInfo[] GetEraInfo()
+        {
+            // See if we need to build it
+            if (japaneseEraInfo == null)
+            {
+                japaneseEraInfo = GetJapaneseEras();
+                // See if we have to use the built-in eras
+                if (japaneseEraInfo == null)
+                {
+                    // We know about some built-in ranges
+                    EraInfo[] defaultEraRanges = new EraInfo[4];
+                    defaultEraRanges[0] = new EraInfo(4, 1989, 1, 8, 1988, 1, GregorianCalendar.MaxYear - 1988,
+                                                       "\x5e73\x6210", "\x5e73", "H");    // era #4 start year/month/day, yearOffset, minEraYear
+                    defaultEraRanges[1] = new EraInfo(3, 1926, 12, 25, 1925, 1, 1989 - 1925,
+                                                       "\x662d\x548c", "\x662d", "S");    // era #3,start year/month/day, yearOffset, minEraYear
+                    defaultEraRanges[2] = new EraInfo(2, 1912, 7, 30, 1911, 1, 1926 - 1911,
+                                                       "\x5927\x6b63", "\x5927", "T");    // era #2,start year/month/day, yearOffset, minEraYear
+                    defaultEraRanges[3] = new EraInfo(1, 1868, 1, 1, 1867, 1, 1912 - 1867,
+                                                       "\x660e\x6cbb", "\x660e", "M");    // era #1,start year/month/day, yearOffset, minEraYear
+
+                    // Remember the ranges we built
+                    japaneseEraInfo = defaultEraRanges;
+                }
+            }
+
+            // return the era we found/made
+            return japaneseEraInfo;
+        }
+
+        internal static volatile Calendar s_defaultInstance;
+        internal GregorianCalendarHelper helper;
+
+        /*=================================GetDefaultInstance==========================
+        **Action: Internal method to provide a default intance of JapaneseCalendar.  Used by NLS+ implementation
+        **       and other calendars.
+        **Returns:
+        **Arguments:
+        **Exceptions:
+        ============================================================================*/
+
+        internal static Calendar GetDefaultInstance()
+        {
+            if (s_defaultInstance == null)
+            {
+                s_defaultInstance = new JapaneseCalendar();
+            }
+            return (s_defaultInstance);
+        }
+
+
+        public JapaneseCalendar()
+        {
+            try
+            {
+                new CultureInfo("ja-JP");
+            }
+            catch (ArgumentException e)
+            {
+                throw new TypeInitializationException(this.GetType().ToString(), e);
+            }
+            helper = new GregorianCalendarHelper(this, GetEraInfo());
+        }
+
+        internal override CalendarId ID
+        {
+            get
+            {
+                return CalendarId.JAPAN;
+            }
+        }
+
+
+        public override DateTime AddMonths(DateTime time, int months)
+        {
+            return (helper.AddMonths(time, months));
+        }
+
+
+        public override DateTime AddYears(DateTime time, int years)
+        {
+            return (helper.AddYears(time, years));
+        }
+
+        /*=================================GetDaysInMonth==========================
+        **Action: Returns the number of days in the month given by the year and month arguments.
+        **Returns: The number of days in the given month.
+        **Arguments:
+        **      year The year in Japanese calendar.
+        **      month The month
+        **      era     The Japanese era value.
+        **Exceptions
+        **  ArgumentException  If month is less than 1 or greater * than 12.
+        ============================================================================*/
+
+
+        public override int GetDaysInMonth(int year, int month, int era)
+        {
+            return (helper.GetDaysInMonth(year, month, era));
+        }
+
+
+        public override int GetDaysInYear(int year, int era)
+        {
+            return (helper.GetDaysInYear(year, era));
+        }
+
+
+        public override int GetDayOfMonth(DateTime time)
+        {
+            return (helper.GetDayOfMonth(time));
+        }
+
+
+        public override DayOfWeek GetDayOfWeek(DateTime time)
+        {
+            return (helper.GetDayOfWeek(time));
+        }
+
+
+        public override int GetDayOfYear(DateTime time)
+        {
+            return (helper.GetDayOfYear(time));
+        }
+
+
+        public override int GetMonthsInYear(int year, int era)
+        {
+            return (helper.GetMonthsInYear(year, era));
+        }
+
+
+        public override int GetWeekOfYear(DateTime time, CalendarWeekRule rule, DayOfWeek firstDayOfWeek)
+        {
+            return (helper.GetWeekOfYear(time, rule, firstDayOfWeek));
+        }
+
+        /*=================================GetEra==========================
+        **Action: Get the era value of the specified time.
+        **Returns: The era value for the specified time.
+        **Arguments:
+        **      time the specified date time.
+        **Exceptions: ArgumentOutOfRangeException if time is out of the valid era ranges.
+        ============================================================================*/
+
+
+        public override int GetEra(DateTime time)
+        {
+            return (helper.GetEra(time));
+        }
+
+
+        public override int GetMonth(DateTime time)
+        {
+            return (helper.GetMonth(time));
+        }
+
+
+        public override int GetYear(DateTime time)
+        {
+            return (helper.GetYear(time));
+        }
+
+
+        public override bool IsLeapDay(int year, int month, int day, int era)
+        {
+            return (helper.IsLeapDay(year, month, day, era));
+        }
+
+
+        public override bool IsLeapYear(int year, int era)
+        {
+            return (helper.IsLeapYear(year, era));
+        }
+
+        // Returns  the leap month in a calendar year of the specified era. This method returns 0
+        // if this calendar does not have leap month, or this year is not a leap year.
+        //
+
+        public override int GetLeapMonth(int year, int era)
+        {
+            return (helper.GetLeapMonth(year, era));
+        }
+
+
+        public override bool IsLeapMonth(int year, int month, int era)
+        {
+            return (helper.IsLeapMonth(year, month, era));
+        }
+
+
+        public override DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era)
+        {
+            return (helper.ToDateTime(year, month, day, hour, minute, second, millisecond, era));
+        }
+
+        // For Japanese calendar, four digit year is not used.  Few emperors will live for more than one hundred years.
+        // Therefore, for any two digit number, we just return the original number.
+
+        public override int ToFourDigitYear(int year)
+        {
+            if (year <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year),
+                    SR.ArgumentOutOfRange_NeedPosNum);
+            }
+
+            if (year > helper.MaxYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                1,
+                                helper.MaxYear));
+            }
+            return (year);
+        }
+
+
+        public override int[] Eras
+        {
+            get
+            {
+                return (helper.Eras);
+            }
+        }
+
+        //
+        // Return the various era strings
+        // Note: The arrays are backwards of the eras
+        //
+        internal static String[] EraNames()
+        {
+            EraInfo[] eras = GetEraInfo();
+            String[] eraNames = new String[eras.Length];
+
+            for (int i = 0; i < eras.Length; i++)
+            {
+                // Strings are in chronological order, eras are backwards order.
+                eraNames[i] = eras[eras.Length - i - 1].eraName;
+            }
+
+            return eraNames;
+        }
+
+        internal static String[] AbbrevEraNames()
+        {
+            EraInfo[] eras = GetEraInfo();
+            String[] erasAbbrev = new String[eras.Length];
+
+            for (int i = 0; i < eras.Length; i++)
+            {
+                // Strings are in chronological order, eras are backwards order.
+                erasAbbrev[i] = eras[eras.Length - i - 1].abbrevEraName;
+            }
+
+            return erasAbbrev;
+        }
+
+        internal static String[] EnglishEraNames()
+        {
+            EraInfo[] eras = GetEraInfo();
+            String[] erasEnglish = new String[eras.Length];
+
+            for (int i = 0; i < eras.Length; i++)
+            {
+                // Strings are in chronological order, eras are backwards order.
+                erasEnglish[i] = eras[eras.Length - i - 1].englishEraName;
+            }
+
+            return erasEnglish;
+        }
+
+        private const int DEFAULT_TWO_DIGIT_YEAR_MAX = 99;
+
+        internal override bool IsValidYear(int year, int era)
+        {
+            return helper.IsValidYear(year, era);
+        }
+
+        public override int TwoDigitYearMax
+        {
+            get
+            {
+                if (twoDigitYearMax == -1)
+                {
+                    twoDigitYearMax = GetSystemTwoDigitYearSetting(ID, DEFAULT_TWO_DIGIT_YEAR_MAX);
+                }
+                return (twoDigitYearMax);
+            }
+
+            set
+            {
+                VerifyWritable();
+                if (value < 99 || value > helper.MaxYear)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                "year",
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    99,
+                                    helper.MaxYear));
+                }
+                twoDigitYearMax = value;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/JapaneseLunisolarCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/JapaneseLunisolarCalendar.cs
new file mode 100644
index 0000000000..e8a2dcd637
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/JapaneseLunisolarCalendar.cs
@@ -0,0 +1,302 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+namespace System.Globalization
+{
+    /*
+    **  Calendar support range:
+    **      Calendar               Minimum             Maximum
+    **      ==========             ==========          ==========
+    **      Gregorian              1960/01/28          2050/01/22
+    **      JapaneseLunisolar      1960/01/01          2049/12/29
+    */
+
+    public class JapaneseLunisolarCalendar : EastAsianLunisolarCalendar
+    {
+        //
+        // The era value for the current era.
+        //
+
+        public const int JapaneseEra = 1;
+
+        internal GregorianCalendarHelper helper;
+
+        internal const int MIN_LUNISOLAR_YEAR = 1960;
+        internal const int MAX_LUNISOLAR_YEAR = 2049;
+
+        internal const int MIN_GREGORIAN_YEAR = 1960;
+        internal const int MIN_GREGORIAN_MONTH = 1;
+        internal const int MIN_GREGORIAN_DAY = 28;
+
+        internal const int MAX_GREGORIAN_YEAR = 2050;
+        internal const int MAX_GREGORIAN_MONTH = 1;
+        internal const int MAX_GREGORIAN_DAY = 22;
+
+        internal static DateTime minDate = new DateTime(MIN_GREGORIAN_YEAR, MIN_GREGORIAN_MONTH, MIN_GREGORIAN_DAY);
+        internal static DateTime maxDate = new DateTime((new DateTime(MAX_GREGORIAN_YEAR, MAX_GREGORIAN_MONTH, MAX_GREGORIAN_DAY, 23, 59, 59, 999)).Ticks + 9999);
+
+        public override DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (minDate);
+            }
+        }
+
+
+        public override DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (maxDate);
+            }
+        }
+        protected override int DaysInYearBeforeMinSupportedYear
+        {
+            get
+            {
+                // 1959 from ChineseLunisolarCalendar
+                return 354;
+            }
+        }
+
+        private static readonly int[,] s_yinfo =
+        {
+            /*Y            LM        Lmon    Lday        DaysPerMonth    D1    D2    D3    D4    D5    D6    D7    D8    D9    D10    D11    D12    D13    #Days
+            1960    */
+          {    6    ,    1    ,    28    ,    44368    },/*    30    29    30    29    30    30    29    30    29    30    29    30    29    384
+1961    */{    0    ,    2    ,    15    ,    43856    },/*    30    29    30    29    30    29    30    30    29    30    29    30    0    355
+1962    */{    0    ,    2    ,    5     ,    19808    },/*    29    30    29    29    30    30    29    30    29    30    30    29    0    354
+1963    */{    4    ,    1    ,    25    ,    42352    },/*    30    29    30    29    29    30    29    30    29    30    30    30    29    384
+1964    */{    0    ,    2    ,    13    ,    42352    },/*    30    29    30    29    29    30    29    30    29    30    30    30    0    355
+1965    */{    0    ,    2    ,    2     ,    21104    },/*    29    30    29    30    29    29    30    29    29    30    30    30    0    354
+1966    */{    3    ,    1    ,    22    ,    26928    },/*    29    30    30    29    30    29    29    30    29    29    30    30    29    383
+1967    */{    0    ,    2    ,    9     ,    55632    },/*    30    30    29    30    30    29    29    30    29    30    29    30    0    355
+1968    */{    7    ,    1    ,    30    ,    27304    },/*    29    30    30    29    30    29    30    29    30    29    30    29    30    384
+1969    */{    0    ,    2    ,    17    ,    22176    },/*    29    30    29    30    29    30    30    29    30    29    30    29    0    354
+1970    */{    0    ,    2    ,    6     ,    39632    },/*    30    29    29    30    30    29    30    29    30    30    29    30    0    355
+1971    */{    5    ,    1    ,    27    ,    19176    },/*    29    30    29    29    30    29    30    29    30    30    30    29    30    384
+1972    */{    0    ,    2    ,    15    ,    19168    },/*    29    30    29    29    30    29    30    29    30    30    30    29    0    354
+1973    */{    0    ,    2    ,    3     ,    42208    },/*    30    29    30    29    29    30    29    29    30    30    30    29    0    354
+1974    */{    4    ,    1    ,    23    ,    53864    },/*    30    30    29    30    29    29    30    29    29    30    30    29    30    384
+1975    */{    0    ,    2    ,    11    ,    53840    },/*    30    30    29    30    29    29    30    29    29    30    29    30    0    354
+1976    */{    8    ,    1    ,    31    ,    54600    },/*    30    30    29    30    29    30    29    30    29    30    29    29    30    384
+1977    */{    0    ,    2    ,    18    ,    46400    },/*    30    29    30    30    29    30    29    30    29    30    29    29    0    354
+1978    */{    0    ,    2    ,    7     ,    54944    },/*    30    30    29    30    29    30    30    29    30    29    30    29    0    355
+1979    */{    6    ,    1    ,    28    ,    38608    },/*    30    29    29    30    29    30    30    29    30    30    29    30    29    384
+1980    */{    0    ,    2    ,    16    ,    38320    },/*    30    29    29    30    29    30    29    30    30    29    30    30    0    355
+1981    */{    0    ,    2    ,    5     ,    18864    },/*    29    30    29    29    30    29    29    30    30    29    30    30    0    354
+1982    */{    4    ,    1    ,    25    ,    42200    },/*    30    29    30    29    29    30    29    29    30    30    29    30    30    384
+1983    */{    0    ,    2    ,    13    ,    42160    },/*    30    29    30    29    29    30    29    29    30    29    30    30    0    354
+1984    */{    10   ,    2    ,    2     ,    45656    },/*    30    29    30    30    29    29    30    29    29    30    29    30    30    384
+1985    */{    0    ,    2    ,    20    ,    27216    },/*    29    30    30    29    30    29    30    29    29    30    29    30    0    354
+1986    */{    0    ,    2    ,    9     ,    27968    },/*    29    30    30    29    30    30    29    30    29    30    29    29    0    354
+1987    */{    6    ,    1    ,    29    ,    46504    },/*    30    29    30    30    29    30    29    30    30    29    30    29    30    385
+1988    */{    0    ,    2    ,    18    ,    11104    },/*    29    29    30    29    30    29    30    30    29    30    30    29    0    354
+1989    */{    0    ,    2    ,    6     ,    38320    },/*    30    29    29    30    29    30    29    30    30    29    30    30    0    355
+1990    */{    5    ,    1    ,    27    ,    18872    },/*    29    30    29    29    30    29    29    30    30    29    30    30    30    384
+1991    */{    0    ,    2    ,    15    ,    18800    },/*    29    30    29    29    30    29    29    30    29    30    30    30    0    354
+1992    */{    0    ,    2    ,    4     ,    25776    },/*    29    30    30    29    29    30    29    29    30    29    30    30    0    354
+1993    */{    3    ,    1    ,    23    ,    27216    },/*    29    30    30    29    30    29    30    29    29    30    29    30    29    383
+1994    */{    0    ,    2    ,    10    ,    59984    },/*    30    30    30    29    30    29    30    29    29    30    29    30    0    355
+1995    */{    8    ,    1    ,    31    ,    27976    },/*    29    30    30    29    30    30    29    30    29    30    29    29    30    384
+1996    */{    0    ,    2    ,    19    ,    23248    },/*    29    30    29    30    30    29    30    29    30    30    29    30    0    355
+1997    */{    0    ,    2    ,    8     ,    11104    },/*    29    29    30    29    30    29    30    30    29    30    30    29    0    354
+1998    */{    5    ,    1    ,    28    ,    37744    },/*    30    29    29    30    29    29    30    30    29    30    30    30    29    384
+1999    */{    0    ,    2    ,    16    ,    37600    },/*    30    29    29    30    29    29    30    29    30    30    30    29    0    354
+2000    */{    0    ,    2    ,    5     ,    51552    },/*    30    30    29    29    30    29    29    30    29    30    30    29    0    354
+2001    */{    4    ,    1    ,    24    ,    58536    },/*    30    30    30    29    29    30    29    29    30    29    30    29    30    384
+2002    */{    0    ,    2    ,    12    ,    54432    },/*    30    30    29    30    29    30    29    29    30    29    30    29    0    354
+2003    */{    0    ,    2    ,    1     ,    55888    },/*    30    30    29    30    30    29    30    29    29    30    29    30    0    355
+2004    */{    2    ,    1    ,    22    ,    23208    },/*    29    30    29    30    30    29    30    29    30    29    30    29    30    384
+2005    */{    0    ,    2    ,    9     ,    22208    },/*    29    30    29    30    29    30    30    29    30    30    29    29    0    354
+2006    */{    7    ,    1    ,    29    ,    43736    },/*    30    29    30    29    30    29    30    29    30    30    29    30    30    385
+2007    */{    0    ,    2    ,    18    ,    9680     },/*    29    29    30    29    29    30    29    30    30    30    29    30    0    354
+2008    */{    0    ,    2    ,    7     ,    37584    },/*    30    29    29    30    29    29    30    29    30    30    29    30    0    354
+2009    */{    5    ,    1    ,    26    ,    51544    },/*    30    30    29    29    30    29    29    30    29    30    29    30    30    384
+2010    */{    0    ,    2    ,    14    ,    43344    },/*    30    29    30    29    30    29    29    30    29    30    29    30    0    354
+2011    */{    0    ,    2    ,    3     ,    46240    },/*    30    29    30    30    29    30    29    29    30    29    30    29    0    354
+2012    */{    3    ,    1    ,    23    ,    47696    },/*    30    29    30    30    30    29    30    29    29    30    29    30    29    384
+2013    */{    0    ,    2    ,    10    ,    46416    },/*    30    29    30    30    29    30    29    30    29    30    29    30    0    355
+2014    */{    9    ,    1    ,    31    ,    21928    },/*    29    30    29    30    29    30    29    30    30    29    30    29    30    384
+2015    */{    0    ,    2    ,    19    ,    19360    },/*    29    30    29    29    30    29    30    30    30    29    30    29    0    354
+2016    */{    0    ,    2    ,    8     ,    42416    },/*    30    29    30    29    29    30    29    30    30    29    30    30    0    355
+2017    */{    5    ,    1    ,    28    ,    21176    },/*    29    30    29    30    29    29    30    29    30    29    30    30    30    384
+2018    */{    0    ,    2    ,    16    ,    21168    },/*    29    30    29    30    29    29    30    29    30    29    30    30    0    354
+2019    */{    0    ,    2    ,    5     ,    43344    },/*    30    29    30    29    30    29    29    30    29    30    29    30    0    354
+2020    */{    4    ,    1    ,    25    ,    46248    },/*    30    29    30    30    29    30    29    29    30    29    30    29    30    384
+2021    */{    0    ,    2    ,    12    ,    27296    },/*    29    30    30    29    30    29    30    29    30    29    30    29    0    354
+2022    */{    0    ,    2    ,    1     ,    44368    },/*    30    29    30    29    30    30    29    30    29    30    29    30    0    355
+2023    */{    2    ,    1    ,    22    ,    21928    },/*    29    30    29    30    29    30    29    30    30    29    30    29    30    384
+2024    */{    0    ,    2    ,    10    ,    19296    },/*    29    30    29    29    30    29    30    30    29    30    30    29    0    354
+2025    */{    6    ,    1    ,    29    ,    42352    },/*    30    29    30    29    29    30    29    30    29    30    30    30    29    384
+2026    */{    0    ,    2    ,    17    ,    42352    },/*    30    29    30    29    29    30    29    30    29    30    30    30    0    355
+2027    */{    0    ,    2    ,    7     ,    21104    },/*    29    30    29    30    29    29    30    29    29    30    30    30    0    354
+2028    */{    5    ,    1    ,    27    ,    26928    },/*    29    30    30    29    30    29    29    30    29    29    30    30    29    383
+2029    */{    0    ,    2    ,    13    ,    55600    },/*    30    30    29    30    30    29    29    30    29    29    30    30    0    355
+2030    */{    0    ,    2    ,    3     ,    23200    },/*    29    30    29    30    30    29    30    29    30    29    30    29    0    354
+2031    */{    3    ,    1    ,    23    ,    43856    },/*    30    29    30    29    30    29    30    30    29    30    29    30    29    384
+2032    */{    0    ,    2    ,    11    ,    38608    },/*    30    29    29    30    29    30    30    29    30    30    29    30    0    355
+2033    */{    11   ,    1    ,    31    ,    19176    },/*    29    30    29    29    30    29    30    29    30    30    30    29    30    384
+2034    */{    0    ,    2    ,    19    ,    19168    },/*    29    30    29    29    30    29    30    29    30    30    30    29    0    354
+2035    */{    0    ,    2    ,    8     ,    42192    },/*    30    29    30    29    29    30    29    29    30    30    29    30    0    354
+2036    */{    6    ,    1    ,    28    ,    53864    },/*    30    30    29    30    29    29    30    29    29    30    30    29    30    384
+2037    */{    0    ,    2    ,    15    ,    53840    },/*    30    30    29    30    29    29    30    29    29    30    29    30    0    354
+2038    */{    0    ,    2    ,    4     ,    54560    },/*    30    30    29    30    29    30    29    30    29    29    30    29    0    354
+2039    */{    5    ,    1    ,    24    ,    55968    },/*    30    30    29    30    30    29    30    29    30    29    30    29    29    384
+2040    */{    0    ,    2    ,    12    ,    46752    },/*    30    29    30    30    29    30    30    29    30    29    30    29    0    355
+2041    */{    0    ,    2    ,    1     ,    38608    },/*    30    29    29    30    29    30    30    29    30    30    29    30    0    355
+2042    */{    2    ,    1    ,    22    ,    19160    },/*    29    30    29    29    30    29    30    29    30    30    29    30    30    384
+2043    */{    0    ,    2    ,    10    ,    18864    },/*    29    30    29    29    30    29    29    30    30    29    30    30    0    354
+2044    */{    7    ,    1    ,    30    ,    42168    },/*    30    29    30    29    29    30    29    29    30    29    30    30    30    384
+2045    */{    0    ,    2    ,    17    ,    42160    },/*    30    29    30    29    29    30    29    29    30    29    30    30    0    354
+2046    */{    0    ,    2    ,    6     ,    45648    },/*    30    29    30    30    29    29    30    29    29    30    29    30    0    354
+2047    */{    5    ,    1    ,    26    ,    46376    },/*    30    29    30    30    29    30    29    30    29    29    30    29    30    384
+2048    */{    0    ,    2    ,    14    ,    27968    },/*    29    30    30    29    30    30    29    30    29    30    29    29    0    354
+2049    */{    0    ,    2    ,    2     ,    44448    },/*    30    29    30    29    30    30    29    30    30    29    30    29    0    355
+     */ };
+
+        internal override int MinCalendarYear
+        {
+            get
+            {
+                return (MIN_LUNISOLAR_YEAR);
+            }
+        }
+
+        internal override int MaxCalendarYear
+        {
+            get
+            {
+                return (MAX_LUNISOLAR_YEAR);
+            }
+        }
+
+        internal override DateTime MinDate
+        {
+            get
+            {
+                return (minDate);
+            }
+        }
+
+        internal override DateTime MaxDate
+        {
+            get
+            {
+                return (maxDate);
+            }
+        }
+
+        internal override EraInfo[] CalEraInfo
+        {
+            get
+            {
+                return (JapaneseCalendar.GetEraInfo());
+            }
+        }
+
+        internal override int GetYearInfo(int lunarYear, int index)
+        {
+            if ((lunarYear < MIN_LUNISOLAR_YEAR) || (lunarYear > MAX_LUNISOLAR_YEAR))
+            {
+                throw new ArgumentOutOfRangeException(
+                            "year",
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                MIN_LUNISOLAR_YEAR,
+                                MAX_LUNISOLAR_YEAR));
+            }
+
+            return s_yinfo[lunarYear - MIN_LUNISOLAR_YEAR, index];
+        }
+
+        internal override int GetYear(int year, DateTime time)
+        {
+            return helper.GetYear(year, time);
+        }
+
+        internal override int GetGregorianYear(int year, int era)
+        {
+            return helper.GetGregorianYear(year, era);
+        }
+
+        // Trim off the eras that are before our date range
+        private static EraInfo[] TrimEras(EraInfo[] baseEras)
+        {
+            EraInfo[] newEras = new EraInfo[baseEras.Length];
+            int newIndex = 0;
+
+            // Eras have most recent first, so start with that
+            for (int i = 0; i < baseEras.Length; i++)
+            {
+                // If this one's minimum year is bigger than our maximum year
+                // then we can't use it.
+                if (baseEras[i].yearOffset + baseEras[i].minEraYear >= MAX_LUNISOLAR_YEAR)
+                {
+                    // skip this one.
+                    continue;
+                }
+
+                // If this one's maximum era is less than our minimum era
+                // then we've gotten too low in the era #s, so we're done
+                if (baseEras[i].yearOffset + baseEras[i].maxEraYear < MIN_LUNISOLAR_YEAR)
+                {
+                    break;
+                }
+
+                // Wasn't too large or too small, can use this one
+                newEras[newIndex] = baseEras[i];
+                newIndex++;
+            }
+
+            // If we didn't copy any then something was wrong, just return base
+            if (newIndex == 0) return baseEras;
+
+            // Resize the output array
+            Array.Resize(ref newEras, newIndex);
+            return newEras;
+        }
+
+
+        // Construct an instance of JapaneseLunisolar calendar.
+        public JapaneseLunisolarCalendar()
+        {
+            helper = new GregorianCalendarHelper(this, TrimEras(JapaneseCalendar.GetEraInfo()));
+        }
+
+
+        public override int GetEra(DateTime time)
+        {
+            return (helper.GetEra(time));
+        }
+
+        internal override CalendarId BaseCalendarID
+        {
+            get
+            {
+                return (CalendarId.JAPAN);
+            }
+        }
+
+        internal override CalendarId ID
+        {
+            get
+            {
+                return (CalendarId.JAPANESELUNISOLAR);
+            }
+        }
+
+
+        public override int[] Eras
+        {
+            get
+            {
+                return (helper.Eras);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/JulianCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/JulianCalendar.cs
new file mode 100644
index 0000000000..82e4d589d3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/JulianCalendar.cs
@@ -0,0 +1,439 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+namespace System.Globalization
+{
+    //
+    // This class implements the Julian calendar. In 48 B.C. Julius Caesar ordered a calendar reform, and this calendar
+    // is called Julian calendar. It consisted of a solar year of twelve months and of 365 days with an extra day
+    // every fourth year.
+    //*
+    //*  Calendar support range:
+    //*      Calendar    Minimum     Maximum
+    //*      ==========  ==========  ==========
+    //*      Gregorian   0001/01/01   9999/12/31
+    //*      Julia       0001/01/03   9999/10/19
+
+    public class JulianCalendar : Calendar
+    {
+        public static readonly int JulianEra = 1;
+
+        private const int DatePartYear = 0;
+        private const int DatePartDayOfYear = 1;
+        private const int DatePartMonth = 2;
+        private const int DatePartDay = 3;
+
+        // Number of days in a non-leap year
+        private const int JulianDaysPerYear = 365;
+        // Number of days in 4 years
+        private const int JulianDaysPer4Years = JulianDaysPerYear * 4 + 1;
+
+        private static readonly int[] s_daysToMonth365 =
+        {
+            0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365
+        };
+
+        private static readonly int[] s_daysToMonth366 =
+        {
+            0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366
+        };
+
+        // Gregorian Calendar 9999/12/31 = Julian Calendar 9999/10/19
+        // keep it as variable field for serialization compat.
+        internal int MaxYear = 9999;
+
+
+        public override DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (DateTime.MinValue);
+            }
+        }
+
+        public override DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (DateTime.MaxValue);
+            }
+        }
+
+        public override CalendarAlgorithmType AlgorithmType
+        {
+            get
+            {
+                return CalendarAlgorithmType.SolarCalendar;
+            }
+        }
+
+        public JulianCalendar()
+        {
+            // There is no system setting of TwoDigitYear max, so set the value here.
+            twoDigitYearMax = 2029;
+        }
+
+        internal override CalendarId ID
+        {
+            get
+            {
+                return CalendarId.JULIAN;
+            }
+        }
+
+        internal static void CheckEraRange(int era)
+        {
+            if (era != CurrentEra && era != JulianEra)
+            {
+                throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+            }
+        }
+
+        internal void CheckYearEraRange(int year, int era)
+        {
+            CheckEraRange(era);
+            if (year <= 0 || year > MaxYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                1,
+                                MaxYear));
+            }
+        }
+
+        internal static void CheckMonthRange(int month)
+        {
+            if (month < 1 || month > 12)
+            {
+                throw new ArgumentOutOfRangeException(nameof(month), SR.ArgumentOutOfRange_Month);
+            }
+        }
+
+        /*===================================CheckDayRange============================
+        **Action: Check for if the day value is valid.
+        **Returns:
+        **Arguments:
+        **Exceptions:
+        **Notes:
+        **  Before calling this method, call CheckYearEraRange()/CheckMonthRange() to make
+        **  sure year/month values are correct.
+        ============================================================================*/
+
+        internal static void CheckDayRange(int year, int month, int day)
+        {
+            if (year == 1 && month == 1)
+            {
+                // The mimimum supported Julia date is Julian 0001/01/03.
+                if (day < 3)
+                {
+                    throw new ArgumentOutOfRangeException(null,
+                        SR.ArgumentOutOfRange_BadYearMonthDay);
+                }
+            }
+            bool isLeapYear = (year % 4) == 0;
+            int[] days = isLeapYear ? s_daysToMonth366 : s_daysToMonth365;
+            int monthDays = days[month] - days[month - 1];
+            if (day < 1 || day > monthDays)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(day),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                1,
+                                monthDays));
+            }
+        }
+
+
+        // Returns a given date part of this DateTime. This method is used
+        // to compute the year, day-of-year, month, or day part.
+        internal static int GetDatePart(long ticks, int part)
+        {
+            // Gregorian 1/1/0001 is Julian 1/3/0001. Remember DateTime(0) is refered to Gregorian 1/1/0001.
+            // The following line convert Gregorian ticks to Julian ticks.
+            long julianTicks = ticks + TicksPerDay * 2;
+            // n = number of days since 1/1/0001
+            int n = (int)(julianTicks / TicksPerDay);
+            // y4 = number of whole 4-year periods within 100-year period
+            int y4 = n / JulianDaysPer4Years;
+            // n = day number within 4-year period
+            n -= y4 * JulianDaysPer4Years;
+            // y1 = number of whole years within 4-year period
+            int y1 = n / JulianDaysPerYear;
+            // Last year has an extra day, so decrement result if 4
+            if (y1 == 4) y1 = 3;
+            // If year was requested, compute and return it
+            if (part == DatePartYear)
+            {
+                return (y4 * 4 + y1 + 1);
+            }
+            // n = day number within year
+            n -= y1 * JulianDaysPerYear;
+            // If day-of-year was requested, return it
+            if (part == DatePartDayOfYear)
+            {
+                return (n + 1);
+            }
+            // Leap year calculation looks different from IsLeapYear since y1, y4,
+            // and y100 are relative to year 1, not year 0
+            bool leapYear = (y1 == 3);
+            int[] days = leapYear ? s_daysToMonth366 : s_daysToMonth365;
+            // All months have less than 32 days, so n >> 5 is a good conservative
+            // estimate for the month
+            int m = (n >> 5) + 1;
+            // m = 1-based month number
+            while (n >= days[m]) m++;
+            // If month was requested, return it
+            if (part == DatePartMonth) return (m);
+            // Return 1-based day-of-month
+            return (n - days[m - 1] + 1);
+        }
+
+        // Returns the tick count corresponding to the given year, month, and day.
+        internal static long DateToTicks(int year, int month, int day)
+        {
+            int[] days = (year % 4 == 0) ? s_daysToMonth366 : s_daysToMonth365;
+            int y = year - 1;
+            int n = y * 365 + y / 4 + days[month - 1] + day - 1;
+            // Gregorian 1/1/0001 is Julian 1/3/0001. n * TicksPerDay is the ticks in JulianCalendar.
+            // Therefore, we subtract two days in the following to convert the ticks in JulianCalendar
+            // to ticks in Gregorian calendar.
+            return ((n - 2) * TicksPerDay);
+        }
+
+
+        public override DateTime AddMonths(DateTime time, int months)
+        {
+            if (months < -120000 || months > 120000)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(months),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                -120000,
+                                120000));
+            }
+            int y = GetDatePart(time.Ticks, DatePartYear);
+            int m = GetDatePart(time.Ticks, DatePartMonth);
+            int d = GetDatePart(time.Ticks, DatePartDay);
+            int i = m - 1 + months;
+            if (i >= 0)
+            {
+                m = i % 12 + 1;
+                y = y + i / 12;
+            }
+            else
+            {
+                m = 12 + (i + 1) % 12;
+                y = y + (i - 11) / 12;
+            }
+            int[] daysArray = (y % 4 == 0 && (y % 100 != 0 || y % 400 == 0)) ? s_daysToMonth366 : s_daysToMonth365;
+            int days = (daysArray[m] - daysArray[m - 1]);
+
+            if (d > days)
+            {
+                d = days;
+            }
+            long ticks = DateToTicks(y, m, d) + time.Ticks % TicksPerDay;
+            Calendar.CheckAddResult(ticks, MinSupportedDateTime, MaxSupportedDateTime);
+            return (new DateTime(ticks));
+        }
+
+
+        public override DateTime AddYears(DateTime time, int years)
+        {
+            return (AddMonths(time, years * 12));
+        }
+
+
+        public override int GetDayOfMonth(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartDay));
+        }
+
+
+        public override DayOfWeek GetDayOfWeek(DateTime time)
+        {
+            return ((DayOfWeek)((int)(time.Ticks / TicksPerDay + 1) % 7));
+        }
+
+
+        public override int GetDayOfYear(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartDayOfYear));
+        }
+
+
+        public override int GetDaysInMonth(int year, int month, int era)
+        {
+            CheckYearEraRange(year, era);
+            CheckMonthRange(month);
+            int[] days = (year % 4 == 0) ? s_daysToMonth366 : s_daysToMonth365;
+            return (days[month] - days[month - 1]);
+        }
+
+
+        public override int GetDaysInYear(int year, int era)
+        {
+            // Year/Era range is done in IsLeapYear().
+            return (IsLeapYear(year, era) ? 366 : 365);
+        }
+
+
+        public override int GetEra(DateTime time)
+        {
+            return (JulianEra);
+        }
+
+
+        public override int GetMonth(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartMonth));
+        }
+
+
+        public override int[] Eras
+        {
+            get
+            {
+                return (new int[] { JulianEra });
+            }
+        }
+
+
+        public override int GetMonthsInYear(int year, int era)
+        {
+            CheckYearEraRange(year, era);
+            return (12);
+        }
+
+
+        public override int GetYear(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartYear));
+        }
+
+
+        public override bool IsLeapDay(int year, int month, int day, int era)
+        {
+            CheckMonthRange(month);
+            // Year/Era range check is done in IsLeapYear().
+            if (IsLeapYear(year, era))
+            {
+                CheckDayRange(year, month, day);
+                return (month == 2 && day == 29);
+            }
+            CheckDayRange(year, month, day);
+            return (false);
+        }
+
+        // Returns  the leap month in a calendar year of the specified era. This method returns 0
+        // if this calendar does not have leap month, or this year is not a leap year.
+        //
+
+        public override int GetLeapMonth(int year, int era)
+        {
+            CheckYearEraRange(year, era);
+            return (0);
+        }
+
+
+        public override bool IsLeapMonth(int year, int month, int era)
+        {
+            CheckYearEraRange(year, era);
+            CheckMonthRange(month);
+            return (false);
+        }
+
+        // Checks whether a given year in the specified era is a leap year. This method returns true if
+        // year is a leap year, or false if not.
+        //
+
+        public override bool IsLeapYear(int year, int era)
+        {
+            CheckYearEraRange(year, era);
+            return (year % 4 == 0);
+        }
+
+
+        public override DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era)
+        {
+            CheckYearEraRange(year, era);
+            CheckMonthRange(month);
+            CheckDayRange(year, month, day);
+            if (millisecond < 0 || millisecond >= MillisPerSecond)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(millisecond),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                0,
+                                MillisPerSecond - 1));
+            }
+
+            if (hour >= 0 && hour < 24 && minute >= 0 && minute < 60 && second >= 0 && second < 60)
+            {
+                return new DateTime(DateToTicks(year, month, day) + (new TimeSpan(0, hour, minute, second, millisecond)).Ticks);
+            }
+            else
+            {
+                throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadHourMinuteSecond);
+            }
+        }
+
+
+        public override int TwoDigitYearMax
+        {
+            get
+            {
+                return (twoDigitYearMax);
+            }
+
+            set
+            {
+                VerifyWritable();
+                if (value < 99 || value > MaxYear)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                "year",
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    99,
+                                    MaxYear));
+                }
+                twoDigitYearMax = value;
+            }
+        }
+
+
+        public override int ToFourDigitYear(int year)
+        {
+            if (year < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (year > MaxYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Bounds_Lower_Upper,
+                                1,
+                                MaxYear));
+            }
+            return (base.ToFourDigitYear(year));
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/KoreanCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/KoreanCalendar.cs
new file mode 100644
index 0000000000..9168b664e0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/KoreanCalendar.cs
@@ -0,0 +1,262 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics.CodeAnalysis;
+
+namespace System.Globalization
+{
+    /*=================================KoreanCalendar==========================
+    **
+    ** Korean calendar is based on the Gregorian calendar.  And the year is an offset to Gregorian calendar.
+    ** That is,
+    **      Korean year = Gregorian year + 2333.  So 2000/01/01 A.D. is Korean 4333/01/01
+    **
+    ** 0001/1/1 A.D. is Korean year 2334.
+    **
+    **  Calendar support range:
+    **      Calendar    Minimum     Maximum
+    **      ==========  ==========  ==========
+    **      Gregorian   0001/01/01   9999/12/31
+    **      Korean      2334/01/01  12332/12/31
+    ============================================================================*/
+
+
+    public class KoreanCalendar : Calendar
+    {
+        //
+        // The era value for the current era.
+        //
+
+        public const int KoreanEra = 1;
+
+        // Since
+        //    Gregorian Year = Era Year + yearOffset
+        // Gregorian Year 1 is Korean year 2334, so that
+        //    1 = 2334 + yearOffset
+        //  So yearOffset = -2333
+        // Gregorian year 2001 is Korean year 4334.
+
+        //m_EraInfo[0] = new EraInfo(1, new DateTime(1, 1, 1).Ticks, -2333, 2334, GregorianCalendar.MaxYear + 2333);
+
+        // Initialize our era info.
+        internal static EraInfo[] koreanEraInfo = new EraInfo[] {
+            new EraInfo( 1, 1, 1, 1, -2333, 2334, GregorianCalendar.MaxYear + 2333)   // era #, start year/month/day, yearOffset, minEraYear 
+        };
+
+        internal GregorianCalendarHelper helper;
+
+
+        public override DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (DateTime.MinValue);
+            }
+        }
+
+        public override DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (DateTime.MaxValue);
+            }
+        }
+
+        public override CalendarAlgorithmType AlgorithmType
+        {
+            get
+            {
+                return CalendarAlgorithmType.SolarCalendar;
+            }
+        }
+
+        public KoreanCalendar()
+        {
+            try
+            {
+                new CultureInfo("ko-KR");
+            }
+            catch (ArgumentException e)
+            {
+                throw new TypeInitializationException(this.GetType().ToString(), e);
+            }
+            helper = new GregorianCalendarHelper(this, koreanEraInfo);
+        }
+
+        internal override CalendarId ID
+        {
+            get
+            {
+                return CalendarId.KOREA;
+            }
+        }
+
+
+        public override DateTime AddMonths(DateTime time, int months)
+        {
+            return (helper.AddMonths(time, months));
+        }
+
+
+        public override DateTime AddYears(DateTime time, int years)
+        {
+            return (helper.AddYears(time, years));
+        }
+
+        /*=================================GetDaysInMonth==========================
+        **Action: Returns the number of days in the month given by the year and month arguments.
+        **Returns: The number of days in the given month.
+        **Arguments:
+        **      year The year in Korean calendar.
+        **      month The month
+        **      era     The Japanese era value.
+        **Exceptions
+        **  ArgumentException  If month is less than 1 or greater * than 12.
+        ============================================================================*/
+
+
+        public override int GetDaysInMonth(int year, int month, int era)
+        {
+            return (helper.GetDaysInMonth(year, month, era));
+        }
+
+
+        public override int GetDaysInYear(int year, int era)
+        {
+            return (helper.GetDaysInYear(year, era));
+        }
+
+
+        public override int GetDayOfMonth(DateTime time)
+        {
+            return (helper.GetDayOfMonth(time));
+        }
+
+
+        public override DayOfWeek GetDayOfWeek(DateTime time)
+        {
+            return (helper.GetDayOfWeek(time));
+        }
+
+
+        public override int GetDayOfYear(DateTime time)
+        {
+            return (helper.GetDayOfYear(time));
+        }
+
+
+        public override int GetMonthsInYear(int year, int era)
+        {
+            return (helper.GetMonthsInYear(year, era));
+        }
+
+
+        public override int GetWeekOfYear(DateTime time, CalendarWeekRule rule, DayOfWeek firstDayOfWeek)
+        {
+            return (helper.GetWeekOfYear(time, rule, firstDayOfWeek));
+        }
+
+
+        public override int GetEra(DateTime time)
+        {
+            return (helper.GetEra(time));
+        }
+
+        public override int GetMonth(DateTime time)
+        {
+            return (helper.GetMonth(time));
+        }
+
+
+        public override int GetYear(DateTime time)
+        {
+            return (helper.GetYear(time));
+        }
+
+
+        public override bool IsLeapDay(int year, int month, int day, int era)
+        {
+            return (helper.IsLeapDay(year, month, day, era));
+        }
+
+
+        public override bool IsLeapYear(int year, int era)
+        {
+            return (helper.IsLeapYear(year, era));
+        }
+
+        // Returns  the leap month in a calendar year of the specified era. This method returns 0
+        // if this calendar does not have leap month, or this year is not a leap year.
+        //
+
+        public override int GetLeapMonth(int year, int era)
+        {
+            return (helper.GetLeapMonth(year, era));
+        }
+
+
+        public override bool IsLeapMonth(int year, int month, int era)
+        {
+            return (helper.IsLeapMonth(year, month, era));
+        }
+
+
+        public override DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era)
+        {
+            return (helper.ToDateTime(year, month, day, hour, minute, second, millisecond, era));
+        }
+
+
+        public override int[] Eras
+        {
+            get
+            {
+                return (helper.Eras);
+            }
+        }
+
+        private const int DEFAULT_TWO_DIGIT_YEAR_MAX = 4362;
+
+
+        public override int TwoDigitYearMax
+        {
+            get
+            {
+                if (twoDigitYearMax == -1)
+                {
+                    twoDigitYearMax = GetSystemTwoDigitYearSetting(ID, DEFAULT_TWO_DIGIT_YEAR_MAX);
+                }
+                return (twoDigitYearMax);
+            }
+
+            set
+            {
+                VerifyWritable();
+                if (value < 99 || value > helper.MaxYear)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                "year",
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    99,
+                                    helper.MaxYear));
+                }
+                twoDigitYearMax = value;
+            }
+        }
+
+
+        public override int ToFourDigitYear(int year)
+        {
+            if (year < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            return (helper.ToFourDigitYear(year, this.TwoDigitYearMax));
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/KoreanLunisolarCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/KoreanLunisolarCalendar.cs
new file mode 100644
index 0000000000..0f71b5f687
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/KoreanLunisolarCalendar.cs
@@ -0,0 +1,1316 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+namespace System.Globalization
+{
+    /*
+    **  Calendar support range:
+    **      Calendar           Minimum     Maximum
+    **      ==========         ==========  ==========
+    **      Gregorian          918/02/19   2051/02/10
+    **      KoreanLunisolar    918/01/01   2050/13/29
+    */
+
+    public class KoreanLunisolarCalendar : EastAsianLunisolarCalendar
+    {
+        //
+        // The era value for the current era.
+        //
+
+        public const int GregorianEra = 1;
+
+        internal const int MIN_LUNISOLAR_YEAR = 918;
+        internal const int MAX_LUNISOLAR_YEAR = 2050;
+
+        internal const int MIN_GREGORIAN_YEAR = 918;
+        internal const int MIN_GREGORIAN_MONTH = 2;
+        internal const int MIN_GREGORIAN_DAY = 19;
+
+        internal const int MAX_GREGORIAN_YEAR = 2051;
+        internal const int MAX_GREGORIAN_MONTH = 2;
+        internal const int MAX_GREGORIAN_DAY = 10;
+
+        internal static DateTime minDate = new DateTime(MIN_GREGORIAN_YEAR, MIN_GREGORIAN_MONTH, MIN_GREGORIAN_DAY);
+        internal static DateTime maxDate = new DateTime((new DateTime(MAX_GREGORIAN_YEAR, MAX_GREGORIAN_MONTH, MAX_GREGORIAN_DAY, 23, 59, 59, 999)).Ticks + 9999);
+
+        public override DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (minDate);
+            }
+        }
+
+        public override DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (maxDate);
+            }
+        }
+
+        protected override int DaysInYearBeforeMinSupportedYear
+        {
+            get
+            {
+                // 917  -- From http://emr.cs.iit.edu/home/reingold/calendar-book/Calendrica.html
+                //              using ChineseLunisolar
+                return 384;
+            }
+        }
+
+// Data for years 1391-2050 matches that available from
+// Korea Astronomy and Space Science Institute (KASI)
+// https://astro.kasi.re.kr:444/life/pageView/5
+        private static readonly int[,] s_yinfo =
+        {
+/*Y           LM  Lmon  Lday    DaysPerMonth               D1   D2   D3   D4   D5   D6   D7   D8   D9   D10  D11  D12  D13  #Days
+0918     */ { 00,   02,   19,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30        355 
+0919     */ { 00,   02,   09,   0b0100010111010000 }, /*   29   30   29   29   29   30   29   30   30   30   29   30        354 
+0920     */ { 06,   01,   29,   0b1010001011011000 }, /*   30   29   30   29   29   29   30   29   30   30   29   30   30   384 
+0921     */ { 00,   02,   16,   0b1010001010110000 }, /*   30   29   30   29   29   29   30   29   30   29   30   30        354 
+0922     */ { 00,   02,   05,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354 
+0923     */ { 04,   01,   25,   0b1011010010101000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29   30   384 
+0924     */ { 00,   02,   13,   0b0110110100100000 }, /*   29   30   30   29   30   30   29   30   29   29   30   29        354 
+0925     */ { 12,   02,   01,   0b1010110101100000 }, /*   30   29   30   29   30   30   29   30   29   30   30   29   29   384 
+0926     */ { 00,   02,   20,   0b1010101101100000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29        355 
+0927     */ { 00,   02,   10,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30        355 
+0928     */ { 08,   01,   31,   0b0100010110111000 }, /*   29   30   29   29   29   30   29   30   30   29   30   30   30   384 
+0929     */ { 00,   02,   18,   0b0100010101110000 }, /*   29   30   29   29   29   30   29   30   29   30   30   30        354 
+0930     */ { 00,   02,   07,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354 
+0931     */ { 05,   01,   27,   0b0110100101010000 }, /*   29   30   30   29   30   29   29   30   29   30   29   30   29   383 
+0932     */ { 00,   02,   14,   0b1110100101010000 }, /*   30   30   30   29   30   29   29   30   29   30   29   30        355 
+0933     */ { 00,   02,   03,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354 
+0934     */ { 01,   01,   23,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30   29   384 
+0935     */ { 00,   02,   11,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30        355 
+0936     */ { 11,   02,   01,   0b0101001101100000 }, /*   29   30   29   30   29   29   30   30   29   30   30   29   29   383 
+0937     */ { 00,   02,   18,   0b1100101011000000 }, /*   30   30   29   29   30   29   30   29   30   30   29   29        354 
+0938     */ { 00,   02,   07,   0b1110010101100000 }, /*   30   30   30   29   29   30   29   30   29   30   30   29        355 
+0939     */ { 07,   01,   28,   0b1101001010101000 }, /*   30   30   29   30   29   29   30   29   30   29   30   29   30   384 
+0940     */ { 00,   02,   16,   0b1101001010100000 }, /*   30   30   29   30   29   29   30   29   30   29   30   29        354 
+0941     */ { 00,   02,   04,   0b1101100101010000 }, /*   30   30   29   30   30   29   29   30   29   30   29   30        355 
+0942     */ { 03,   01,   25,   0b0101101010101000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29   30   384 
+0943     */ { 00,   02,   13,   0b0101011010100000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29        354 
+0944     */ { 12,   02,   02,   0b1010011011010000 }, /*   30   29   30   29   29   30   30   29   30   30   29   30   29   384 
+0945     */ { 00,   02,   20,   0b1001010111010000 }, /*   30   29   29   30   29   30   29   30   30   30   29   30        355 
+0946     */ { 00,   02,   10,   0b0100101011010000 }, /*   29   30   29   29   30   29   30   29   30   30   29   30        354 
+0947     */ { 07,   01,   30,   0b1010010011011000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30   30   384 
+0948     */ { 00,   02,   18,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354 
+0949     */ { 00,   02,   06,   0b1011001001100000 }, /*   30   29   30   30   29   29   30   29   29   30   30   29        354 
+0950     */ { 05,   01,   26,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30   29   384 
+0951     */ { 00,   02,   14,   0b1011001101110000 }, /*   30   29   30   30   29   29   30   30   29   30   30   30        356 
+0953     */ { 00,   01,   05,   0b1010101011010000 }, /*   30   29   30   29   30   29   30   29   30   30   29   30        355 
+0953     */ { 01,   01,   23,   0b1001010111010000 }, /*   30   29   29   30   29   30   29   30   30   30   29   30   29   384 
+0954     */ { 00,   02,   11,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30        355 
+0955     */ { 09,   02,   01,   0b0100101010111000 }, /*   29   30   29   29   30   29   30   29   30   29   30   30   30   384 
+0956     */ { 00,   02,   20,   0b0100100110110000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30        354 
+0957     */ { 00,   02,   08,   0b1010010010110000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30        354 
+0958     */ { 07,   01,   28,   0b1010101010011000 }, /*   30   29   30   29   30   29   30   29   30   29   29   30   30   384 
+0959     */ { 00,   02,   16,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354 
+0960     */ { 00,   02,   05,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30        355 
+0961     */ { 03,   01,   25,   0b0100110110101000 }, /*   29   30   29   29   30   30   29   30   30   29   30   29   30   384 
+0962     */ { 00,   02,   13,   0b0010101101100000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29        354 
+0963     */ { 12,   02,   02,   0b1001010101110000 }, /*   30   29   29   30   29   30   29   30   29   30   30   30   29   384 
+0964     */ { 00,   02,   21,   0b1010001101110000 }, /*   30   29   30   29   29   29   30   30   29   30   30   30        355 
+0965     */ { 00,   02,   10,   0b0101000101110000 }, /*   29   30   29   30   29   29   29   30   29   30   30   30        354 
+0966     */ { 08,   01,   30,   0b0110010010110000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30   29   383 
+0967     */ { 00,   02,   17,   0b1101010010110000 }, /*   30   30   29   30   29   30   29   29   30   29   30   30        355 
+0968     */ { 00,   02,   07,   0b0101101010010000 }, /*   29   30   29   30   30   29   30   29   30   29   29   30        354 
+0969     */ { 05,   01,   26,   0b0110101101010000 }, /*   29   30   30   29   30   29   30   30   29   30   29   30   29   384 
+0970     */ { 00,   02,   14,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30        355 
+0971     */ { 00,   02,   04,   0b0010101011100000 }, /*   29   29   30   29   30   29   30   29   30   30   30   29        354 
+0972     */ { 02,   01,   24,   0b1001001101110000 }, /*   30   29   29   30   29   29   30   30   29   30   30   30   29   384 
+0973     */ { 00,   02,   11,   0b1010001011100000 }, /*   30   29   30   29   29   29   30   29   30   30   30   29        354 
+0974     */ { 10,   01,   31,   0b1100100101101000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29   30   384 
+0975     */ { 00,   02,   19,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354 
+0976     */ { 00,   02,   08,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354 
+0977     */ { 07,   01,   27,   0b1101101010010000 }, /*   30   30   29   30   30   29   30   29   30   29   29   30   29   384 
+0978     */ { 00,   02,   15,   0b1011010110100000 }, /*   30   29   30   30   29   30   29   30   30   29   30   29        355 
+0979     */ { 00,   02,   05,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30        355 
+0980     */ { 03,   01,   26,   0b0010101011011000 }, /*   29   29   30   29   30   29   30   29   30   30   29   30   30   384 
+0981     */ { 00,   02,   13,   0b0010010111010000 }, /*   29   29   30   29   29   30   29   30   30   30   29   30        354 
+0982     */ { 12,   02,   02,   0b1001001011011000 }, /*   30   29   29   30   29   29   30   29   30   30   29   30   30   384 
+0983     */ { 00,   02,   21,   0b1001001010110000 }, /*   30   29   29   30   29   29   30   29   30   29   30   30        354 
+0984     */ { 00,   02,   10,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354 
+0985     */ { 09,   01,   29,   0b1011010010101000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29   30   384 
+0986     */ { 00,   02,   17,   0b1010110010100000 }, /*   30   29   30   29   30   30   29   29   30   29   30   29        354 
+0987     */ { 00,   02,   06,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30        355 
+0988     */ { 05,   01,   27,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30   29   384 
+0989     */ { 00,   02,   14,   0b0100101110110000 }, /*   29   30   29   29   30   29   30   30   30   29   30   30        355 
+0990     */ { 00,   02,   04,   0b0010010110110000 }, /*   29   29   30   29   29   30   29   30   30   29   30   30        354 
+0991     */ { 02,   01,   24,   0b1001001010111000 }, /*   30   29   29   30   29   29   30   29   30   29   30   30   30   384 
+0992     */ { 00,   02,   12,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354 
+0993     */ { 10,   01,   31,   0b0110100101011000 }, /*   29   30   30   29   30   29   29   30   29   30   29   30   30   384 
+0994     */ { 00,   02,   19,   0b0101100101010000 }, /*   29   30   29   30   30   29   29   30   29   30   29   30        354 
+0995     */ { 00,   02,   08,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354 
+0996     */ { 07,   01,   28,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30   29   384 
+0997     */ { 00,   02,   15,   0b1010101101100000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29        355 
+0998     */ { 00,   02,   05,   0b0100101101100000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29        354 
+0999     */ { 03,   01,   25,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30   29   384 
+1000     */ { 00,   02,   13,   0b0010010101110000 }, /*   29   29   30   29   29   30   29   30   29   30   30   30        354 
+1001     */ { 12,   02,   03,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30   29   383 
+1002     */ { 00,   02,   21,   0b1101001010100000 }, /*   30   30   29   30   29   29   30   29   30   29   30   29        354 
+1003     */ { 00,   02,   10,   0b1101010101010000 }, /*   30   30   29   30   29   30   29   30   29   30   29   30        355 
+1004     */ { 09,   01,   31,   0b0101101010101000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29   30   384 
+1005     */ { 00,   02,   18,   0b0101011010100000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29        354 
+1006     */ { 00,   02,   07,   0b1001011011010000 }, /*   30   29   29   30   29   30   30   29   30   30   29   30        355 
+1007     */ { 05,   01,   28,   0b0100101011101000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29   30   384 
+1008     */ { 00,   02,   16,   0b0100101011010000 }, /*   29   30   29   29   30   29   30   29   30   30   29   30        354 
+1009     */ { 00,   02,   04,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354 
+1010     */ { 02,   01,   24,   0b1101001001101000 }, /*   30   30   29   30   29   29   30   29   29   30   30   29   30   384 
+1011     */ { 00,   02,   12,   0b1011001001100000 }, /*   30   29   30   30   29   29   30   29   29   30   30   29        354 
+1012     */ { 10,   02,   01,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30   29   384 
+1013     */ { 00,   02,   19,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30        355 
+1014     */ { 00,   02,   09,   0b0011010110100000 }, /*   29   29   30   30   29   30   29   30   30   29   30   29        354 
+1015     */ { 06,   01,   29,   0b1001010111010000 }, /*   30   29   29   30   29   30   29   30   30   30   29   30   29   384 
+1016     */ { 00,   02,   17,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30        355 
+1017     */ { 00,   02,   06,   0b0100100110110000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30        354 
+1018     */ { 04,   01,   26,   0b1010010011011000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30   30   384 
+1019     */ { 00,   02,   14,   0b1010010010110000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30        354 
+1020     */ { 12,   02,   03,   0b1010101001011000 }, /*   30   29   30   29   30   29   30   29   29   30   29   30   30   384 
+1021     */ { 00,   02,   21,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354 
+1022     */ { 00,   02,   10,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30        355 
+1023     */ { 09,   01,   31,   0b0010110110101000 }, /*   29   29   30   29   30   30   29   30   30   29   30   29   30   384 
+1024     */ { 00,   02,   19,   0b0010101101010000 }, /*   29   29   30   29   30   29   30   30   29   30   29   30        354 
+1025     */ { 00,   02,   07,   0b1001010101110000 }, /*   30   29   29   30   29   30   29   30   29   30   30   30        355 
+1026     */ { 05,   01,   28,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30   29   383 
+1027     */ { 00,   02,   15,   0b1100100101110000 }, /*   30   30   29   29   30   29   29   30   29   30   30   30        355 
+1028     */ { 00,   02,   05,   0b0110010010110000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30        354 
+1029     */ { 02,   01,   24,   0b0110101001010000 }, /*   29   30   30   29   30   29   30   29   29   30   29   30   29   383 
+1030     */ { 00,   02,   11,   0b1101101010010000 }, /*   30   30   29   30   30   29   30   29   30   29   29   30        355 
+1031     */ { 10,   02,   01,   0b0110101101010000 }, /*   29   30   30   29   30   29   30   30   29   30   29   30   29   384 
+1032     */ { 00,   02,   20,   0b0110011011010000 }, /*   29   30   30   29   29   30   30   29   30   30   29   30        355 
+1033     */ { 00,   02,   09,   0b0010011011100000 }, /*   29   29   30   29   29   30   30   29   30   30   30   29        354 
+1034     */ { 06,   01,   29,   0b1001001101110000 }, /*   30   29   29   30   29   29   30   30   29   30   30   30   29   384 
+1035     */ { 00,   02,   17,   0b1001001011100000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29        354 
+1036     */ { 00,   02,   06,   0b1100100101100000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29        354 
+1037     */ { 04,   01,   25,   0b1101010010101000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29   30   384 
+1038     */ { 00,   02,   13,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354 
+1039     */ { 12,   02,   02,   0b1101011010010000 }, /*   30   30   29   30   29   30   30   29   30   29   29   30   29   384 
+1040     */ { 00,   02,   21,   0b1011010110000000 }, /*   30   29   30   30   29   30   29   30   30   29   29   29        354 
+1041     */ { 00,   02,   09,   0b1101011010110000 }, /*   30   30   29   30   29   30   30   29   30   29   30   30        356 
+1042     */ { 09,   01,   31,   0b0010011011011000 }, /*   29   29   30   29   29   30   30   29   30   30   29   30   30   384 
+1043     */ { 00,   02,   19,   0b0010010111010000 }, /*   29   29   30   29   29   30   29   30   30   30   29   30        354 
+1044     */ { 00,   02,   08,   0b1001001010110000 }, /*   30   29   29   30   29   29   30   29   30   29   30   30        354 
+1045     */ { 05,   01,   27,   0b1010100101011000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30   30   384 
+1046     */ { 00,   02,   15,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354 
+1047     */ { 00,   02,   04,   0b1011010010100000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29        354 
+1048     */ { 01,   01,   24,   0b1011010101011000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30   30   385 
+1049     */ { 00,   02,   12,   0b0010110101010000 }, /*   29   29   30   29   30   30   29   30   29   30   29   30        354 
+1050     */ { 11,   02,   01,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30   29   384 
+1051     */ { 00,   02,   20,   0b0100101110110000 }, /*   29   30   29   29   30   29   30   30   30   29   30   30        355 
+1052     */ { 00,   02,   10,   0b0010010110110000 }, /*   29   29   30   29   29   30   29   30   30   29   30   30        354 
+1053     */ { 07,   01,   29,   0b0101001010111000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30   30   384 
+1054     */ { 00,   02,   17,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354 
+1055     */ { 00,   02,   06,   0b0110100101010000 }, /*   29   30   30   29   30   29   29   30   29   30   29   30        354 
+1056     */ { 03,   01,   26,   0b0110101010101000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29   30   384 
+1057     */ { 00,   02,   13,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354 
+1058     */ { 12,   02,   02,   0b1010101101011000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30   30   385 
+1059     */ { 00,   02,   22,   0b0010011101010000 }, /*   29   29   30   29   29   30   30   30   29   30   29   30        354 
+1060     */ { 00,   02,   11,   0b0100101101100000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29        354 
+1061     */ { 08,   01,   30,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30   29   384 
+1062     */ { 00,   02,   18,   0b1010010101100000 }, /*   30   29   30   29   29   30   29   30   29   30   30   29        354 
+1063     */ { 00,   02,   07,   0b1101001001100000 }, /*   30   30   29   30   29   29   30   29   29   30   30   29        354 
+1064     */ { 05,   01,   27,   0b1110100100110000 }, /*   30   30   30   29   30   29   29   30   29   29   30   30   29   384 
+1065     */ { 00,   02,   14,   0b1101010101010000 }, /*   30   30   29   30   29   30   29   30   29   30   29   30        355 
+1066     */ { 00,   02,   04,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354 
+1067     */ { 01,   01,   24,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30   29   384 
+1068     */ { 00,   02,   12,   0b1001011011010000 }, /*   30   29   29   30   29   30   30   29   30   30   29   30        355 
+1069     */ { 11,   02,   01,   0b0100101011101000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29   30   384 
+1070     */ { 00,   02,   20,   0b0100100111010000 }, /*   29   30   29   29   30   29   29   30   30   30   29   30        354 
+1071     */ { 00,   02,   09,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354 
+1072     */ { 07,   01,   29,   0b1101001001101000 }, /*   30   30   29   30   29   29   30   29   29   30   30   29   30   384 
+1073     */ { 00,   02,   16,   0b1010101001100000 }, /*   30   29   30   29   30   29   30   29   29   30   30   29        354 
+1074     */ { 00,   02,   05,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30        355 
+1075     */ { 04,   01,   26,   0b0101011010101000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29   30   384 
+1076     */ { 00,   02,   14,   0b0011010110100000 }, /*   29   29   30   30   29   30   29   30   30   29   30   29        354 
+1077     */ { 00,   02,   02,   0b1001010111010000 }, /*   30   29   29   30   29   30   29   30   30   30   29   30        355 
+1078     */ { 01,   01,   23,   0b0100101110011000 }, /*   29   30   29   29   30   29   30   30   30   29   29   30   30   384 
+1079     */ { 00,   02,   11,   0b0100010110110000 }, /*   29   30   29   29   29   30   29   30   30   29   30   30        354 
+1080     */ { 09,   01,   31,   0b1010010010111000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30   30   384 
+1081     */ { 00,   02,   18,   0b0110010010110000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30        354 
+1082     */ { 00,   02,   07,   0b1010101001010000 }, /*   30   29   30   29   30   29   30   29   29   30   29   30        354 
+1083     */ { 06,   01,   27,   0b1011010101001000 }, /*   30   29   30   30   29   30   29   30   29   30   29   29   30   384 
+1084     */ { 00,   02,   15,   0b0110101101010000 }, /*   29   30   30   29   30   29   30   30   29   30   29   30        355 
+1085     */ { 00,   02,   04,   0b0010110110100000 }, /*   29   29   30   29   30   30   29   30   30   29   30   29        354 
+1086     */ { 02,   01,   24,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30   29   384 
+1087     */ { 00,   02,   12,   0b1001001101110000 }, /*   30   29   29   30   29   29   30   30   29   30   30   30        355 
+1088     */ { 12,   02,   02,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30   29   383 
+1089     */ { 00,   02,   19,   0b1100100101110000 }, /*   30   30   29   29   30   29   29   30   29   30   30   30        355 
+1090     */ { 00,   02,   09,   0b0110010010110000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30        354 
+1091     */ { 08,   01,   29,   0b0110101001010000 }, /*   29   30   30   29   30   29   30   29   29   30   29   30   29   383 
+1092     */ { 00,   02,   16,   0b1101101001010000 }, /*   30   30   29   30   30   29   30   29   29   30   29   30        355 
+1093     */ { 00,   02,   05,   0b0101101101000000 }, /*   29   30   29   30   30   29   30   30   29   30   29   29        354 
+1094     */ { 04,   01,   25,   0b1010101101101000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29   30   385 
+1095     */ { 00,   02,   14,   0b0010101011100000 }, /*   29   29   30   29   30   29   30   29   30   30   30   29        354 
+1096     */ { 00,   02,   03,   0b1110011000010000 }, /*   30   30   30   29   29   30   30   29   29   29   29   30        354 
+1097     */ { 02,   01,   22,   0b1100100101110000 }, /*   30   30   29   29   30   29   29   30   29   30   30   30   29   384 
+1098     */ { 00,   02,   10,   0b1100100101100000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29        354 
+1099     */ { 09,   01,   30,   0b1101010010101000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29   30   384 
+1100     */ { 00,   02,   18,   0b0101010010100000 }, /*   29   30   29   30   29   30   29   29   30   29   30   29        353 
+1101     */ { 00,   02,   07,   0b1101011001010000 }, /*   30   30   29   30   29   30   30   29   29   30   29   30        355 
+1102     */ { 06,   01,   28,   0b0101101010101000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29   30   384 
+1103     */ { 00,   02,   16,   0b0101010111010000 }, /*   29   30   29   30   29   30   29   30   30   30   29   30        355 
+1104     */ { 00,   02,   06,   0b0010011011010000 }, /*   29   29   30   29   29   30   30   29   30   30   29   30        354 
+1105     */ { 02,   01,   25,   0b1001001011101000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29   30   384 
+1106     */ { 00,   02,   13,   0b1001001010110000 }, /*   30   29   29   30   29   29   30   29   30   29   30   30        354 
+1107     */ { 10,   02,   02,   0b1010100101011000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30   30   384 
+1108     */ { 00,   02,   21,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354 
+1109     */ { 00,   02,   09,   0b1011010010100000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29        354 
+1110     */ { 08,   01,   29,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30   29   384 
+1111     */ { 00,   02,   17,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30        355 
+1112     */ { 00,   02,   07,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30        355 
+1113     */ { 04,   01,   27,   0b0010010110111000 }, /*   29   29   30   29   29   30   29   30   30   29   30   30   30   384 
+1114     */ { 00,   02,   15,   0b0100010101110000 }, /*   29   30   29   29   29   30   29   30   29   30   30   30        354 
+1115     */ { 00,   02,   04,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354 
+1116     */ { 01,   01,   24,   0b1010100101011000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30   30   384 
+1117     */ { 00,   02,   11,   0b0110100101010000 }, /*   29   30   30   29   30   29   29   30   29   30   29   30        354 
+1118     */ { 09,   01,   31,   0b0111001010101000 }, /*   29   30   30   30   29   29   30   29   30   29   30   29   30   384 
+1119     */ { 00,   02,   19,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354 
+1120     */ { 00,   02,   08,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30        355 
+1121     */ { 05,   01,   28,   0b0100101101101000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29   30   384 
+1122     */ { 00,   02,   16,   0b0100101101100000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29        354 
+1123     */ { 00,   02,   05,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30        355 
+1124     */ { 03,   01,   26,   0b0101001001110000 }, /*   29   30   29   30   29   29   30   29   29   30   30   30   29   383 
+1125     */ { 00,   02,   12,   0b1101001001100000 }, /*   30   30   29   30   29   29   30   29   29   30   30   29        354 
+1126     */ { 11,   02,   01,   0b1110100100110000 }, /*   30   30   30   29   30   29   29   30   29   29   30   30   29   384 
+1127     */ { 00,   02,   20,   0b1101010101010000 }, /*   30   30   29   30   29   30   29   30   29   30   29   30        355 
+1128     */ { 00,   02,   10,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354 
+1129     */ { 08,   01,   29,   0b1001101110010000 }, /*   30   29   29   30   30   29   30   30   30   29   29   30   29   384 
+1130     */ { 00,   02,   17,   0b1001011011010000 }, /*   30   29   29   30   29   30   30   29   30   30   29   30        355 
+1131     */ { 00,   02,   07,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354 
+1132     */ { 04,   01,   27,   0b1010010011101000 }, /*   30   29   30   29   29   30   29   29   30   30   30   29   30   384 
+1133     */ { 00,   02,   14,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354 
+1134     */ { 00,   02,   03,   0b1101001001010000 }, /*   30   30   29   30   29   29   30   29   29   30   29   30        354 
+1135     */ { 02,   01,   23,   0b1101100100101000 }, /*   30   30   29   30   30   29   29   30   29   29   30   29   30   384 
+1136     */ { 00,   02,   11,   0b1011010101000000 }, /*   30   29   30   30   29   30   29   30   29   30   29   29        354 
+1137     */ { 10,   01,   30,   0b1101011010101000 }, /*   30   30   29   30   29   30   30   29   30   29   30   29   30   385 
+1138     */ { 00,   02,   19,   0b0010110110100000 }, /*   29   29   30   29   30   30   29   30   30   29   30   29        354 
+1139     */ { 00,   02,   08,   0b1001010111010000 }, /*   30   29   29   30   29   30   29   30   30   30   29   30        355 
+1140     */ { 06,   01,   29,   0b0100101011011000 }, /*   29   30   29   29   30   29   30   29   30   30   29   30   30   384 
+1141     */ { 00,   02,   16,   0b0100100110110000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30        354 
+1142     */ { 00,   02,   05,   0b1010010010110000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30        354 
+1143     */ { 04,   01,   25,   0b1011001001011000 }, /*   30   29   30   30   29   29   30   29   29   30   29   30   30   384 
+1144     */ { 00,   02,   13,   0b0110101001010000 }, /*   29   30   30   29   30   29   30   29   29   30   29   30        354 
+1145     */ { 11,   02,   01,   0b1011010100101000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29   30   384 
+1146     */ { 00,   02,   20,   0b0110101101000000 }, /*   29   30   30   29   30   29   30   30   29   30   29   29        354 
+1147     */ { 00,   02,   09,   0b1010101101100000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29        355 
+1148     */ { 08,   01,   30,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30   29   384 
+1149     */ { 00,   02,   17,   0b1001100101110000 }, /*   30   29   29   30   30   29   29   30   29   30   30   30        355 
+1150     */ { 00,   02,   07,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30        354 
+1151     */ { 04,   01,   27,   0b0110010010111000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30   30   384 
+1152     */ { 00,   02,   15,   0b0101010010110000 }, /*   29   30   29   30   29   30   29   29   30   29   30   30        354 
+1153     */ { 12,   02,   03,   0b0110101001010000 }, /*   29   30   30   29   30   29   30   29   29   30   29   30   29   383 
+1154     */ { 00,   02,   21,   0b1101101001010000 }, /*   30   30   29   30   30   29   30   29   29   30   29   30        355 
+1155     */ { 00,   02,   11,   0b0101101011000000 }, /*   29   30   29   30   30   29   30   29   30   30   29   29        354 
+1156     */ { 10,   01,   31,   0b1010101101101000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29   30   385 
+1157     */ { 00,   02,   19,   0b0010011011100000 }, /*   29   29   30   29   29   30   30   29   30   30   30   29        354 
+1158     */ { 00,   02,   08,   0b1001001011100000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29        354 
+1159     */ { 06,   01,   28,   0b1100100101110000 }, /*   30   30   29   29   30   29   29   30   29   30   30   30   29   384 
+1160     */ { 00,   02,   16,   0b1100100101100000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29        354 
+1161     */ { 00,   02,   04,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354 
+1162     */ { 02,   01,   24,   0b1101101001010000 }, /*   30   30   29   30   30   29   30   29   29   30   29   30   29   384 
+1163     */ { 00,   02,   12,   0b1101010101010000 }, /*   30   30   29   30   29   30   29   30   29   30   29   30        355 
+1164     */ { 11,   02,   02,   0b0101011010101000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29   30   384 
+1165     */ { 00,   02,   20,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30        355 
+1166     */ { 00,   02,   10,   0b0010010111010000 }, /*   29   29   30   29   29   30   29   30   30   30   29   30        354 
+1167     */ { 07,   01,   30,   0b1001001011101000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29   30   384 
+1168     */ { 00,   02,   18,   0b1001001001110000 }, /*   30   29   29   30   29   29   30   29   29   30   30   30        354 
+1169     */ { 00,   02,   06,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354 
+1170     */ { 05,   01,   26,   0b1101010010101000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29   30   384 
+1171     */ { 00,   02,   14,   0b1011010010100000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29        354 
+1172     */ { 00,   02,   03,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30        355 
+1173     */ { 01,   01,   23,   0b0101011010101000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29   30   384 
+1174     */ { 00,   02,   11,   0b0100110110110000 }, /*   29   30   29   29   30   30   29   30   30   29   30   30        355 
+1175     */ { 09,   02,   01,   0b0010010110110000 }, /*   29   29   30   29   29   30   29   30   30   29   30   30   29   383 
+1176     */ { 00,   02,   19,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30        355 
+1177     */ { 00,   02,   08,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354 
+1178     */ { 06,   01,   28,   0b1010100101011000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30   30   384 
+1179     */ { 00,   02,   16,   0b0110100101010000 }, /*   29   30   30   29   30   29   29   30   29   30   29   30        354 
+1180     */ { 00,   02,   05,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354 
+1181     */ { 03,   01,   24,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30   29   384 
+1182     */ { 00,   02,   12,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30        355 
+1183     */ { 11,   02,   02,   0b0100101101101000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29   30   384 
+1184     */ { 00,   02,   21,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354 
+1185     */ { 00,   02,   09,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30        355 
+1186     */ { 07,   01,   30,   0b0101001001110000 }, /*   29   30   29   30   29   29   30   29   29   30   30   30   29   383 
+1187     */ { 00,   02,   17,   0b1101000010010000 }, /*   30   30   29   30   29   29   29   29   30   29   29   30        353 
+1188     */ { 00,   01,   08,   0b0111010010011000 }, /*   29   30   30   30   29   30   29   29   30   29   29   30        354 
+1189     */ { 05,   01,   26,   0b0110101010101000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29   30   384 
+1190     */ { 00,   02,   14,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354 
+1191     */ { 00,   02,   03,   0b1001101101010000 }, /*   30   29   29   30   30   29   30   30   29   30   29   30        355 
+1192     */ { 02,   01,   24,   0b0100101101101000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29   30   384 
+1193     */ { 00,   02,   11,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354 
+1194     */ { 10,   01,   31,   0b1010010011101000 }, /*   30   29   30   29   29   30   29   29   30   30   30   29   30   384 
+1195     */ { 00,   02,   19,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354 
+1196     */ { 00,   02,   08,   0b1101001001100000 }, /*   30   30   29   30   29   29   30   29   29   30   30   29        354 
+1197     */ { 06,   01,   27,   0b1101010100101000 }, /*   30   30   29   30   29   30   29   30   29   29   30   29   30   384 
+1198     */ { 00,   02,   15,   0b1011010100100000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29        354 
+1199     */ { 00,   02,   04,   0b1101011010100000 }, /*   30   30   29   30   29   30   30   29   30   29   30   29        355 
+1200     */ { 02,   01,   25,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30   29   384 
+1201     */ { 00,   02,   12,   0b1001010111010000 }, /*   30   29   29   30   29   30   29   30   30   30   29   30        355 
+1202     */ { 12,   02,   02,   0b0100100111011000 }, /*   29   30   29   29   30   29   29   30   30   30   29   30   30   384 
+1203     */ { 00,   02,   21,   0b0100100110110000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30        354 
+1204     */ { 00,   02,   10,   0b1010010010110000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30        354 
+1205     */ { 08,   01,   29,   0b1010101001011000 }, /*   30   29   30   29   30   29   30   29   29   30   29   30   30   384 
+1206     */ { 00,   02,   17,   0b0110101001010000 }, /*   29   30   30   29   30   29   30   29   29   30   29   30        354 
+1207     */ { 00,   02,   06,   0b1011010101000000 }, /*   30   29   30   30   29   30   29   30   29   30   29   29        354 
+1208     */ { 04,   01,   26,   0b1011010110100000 }, /*   30   29   30   30   29   30   29   30   30   29   30   29   29   384 
+1209     */ { 00,   02,   13,   0b1010101101100000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29        355 
+1210     */ { 00,   02,   03,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30        355 
+1211     */ { 02,   01,   24,   0b0100100110111000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30   30   384 
+1212     */ { 00,   02,   12,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30        354 
+1213     */ { 09,   01,   31,   0b0110010010111000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30   30   384 
+1214     */ { 00,   02,   19,   0b0101010010110000 }, /*   29   30   29   30   29   30   29   29   30   29   30   30        354 
+1215     */ { 00,   02,   08,   0b0110101001010000 }, /*   29   30   30   29   30   29   30   29   29   30   29   30        354 
+1216     */ { 07,   01,   28,   0b0110110100101000 }, /*   29   30   30   29   30   30   29   30   29   29   30   29   30   384 
+1217     */ { 00,   02,   15,   0b0101101011000000 }, /*   29   30   29   30   30   29   30   29   30   30   29   29        354 
+1218     */ { 00,   02,   04,   0b1010101101100000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29        355 
+1219     */ { 03,   01,   25,   0b1001001101110000 }, /*   30   29   29   30   29   29   30   30   29   30   30   30   29   384 
+1220     */ { 00,   02,   13,   0b1001001011100000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29        354 
+1221     */ { 12,   02,   01,   0b1100100101110000 }, /*   30   30   29   29   30   29   29   30   29   30   30   30   29   384 
+1222     */ { 00,   02,   20,   0b1100100101100000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29        354 
+1223     */ { 00,   02,   09,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354 
+1224     */ { 08,   01,   29,   0b1101101001010000 }, /*   30   30   29   30   30   29   30   29   29   30   29   30   29   384 
+1225     */ { 00,   02,   16,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30        355 
+1226     */ { 00,   02,   06,   0b0101011010100000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29        354 
+1227     */ { 05,   01,   26,   0b1010101011011000 }, /*   30   29   30   29   30   29   30   29   30   30   29   30   30   385 
+1228     */ { 00,   02,   15,   0b0010010111010000 }, /*   29   29   30   29   29   30   29   30   30   30   29   30        354 
+1229     */ { 00,   02,   03,   0b1001001011100000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29        354 
+1230     */ { 02,   01,   23,   0b1100100101011000 }, /*   30   30   29   29   30   29   29   30   29   30   29   30   30   384 
+1231     */ { 00,   02,   11,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354 
+1232     */ { 09,   01,   31,   0b1101010010101000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29   30   384 
+1233     */ { 00,   02,   18,   0b1011001010100000 }, /*   30   29   30   30   29   29   30   29   30   29   30   29        354 
+1234     */ { 00,   02,   07,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30        355 
+1235     */ { 07,   01,   28,   0b0101011010101000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29   30   384 
+1236     */ { 00,   02,   16,   0b0100110110100000 }, /*   29   30   29   29   30   30   29   30   30   29   30   29        354 
+1237     */ { 00,   02,   04,   0b1010010110110000 }, /*   30   29   30   29   29   30   29   30   30   29   30   30        355 
+1238     */ { 04,   01,   25,   0b0101001010111000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30   30   384 
+1239     */ { 00,   02,   13,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354 
+1240     */ { 12,   02,   02,   0b1010100100111000 }, /*   30   29   30   29   30   29   29   30   29   29   30   30   30   384 
+1241     */ { 00,   02,   20,   0b0110100100110000 }, /*   29   30   30   29   30   29   29   30   29   29   30   30        354 
+1242     */ { 00,   02,   09,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354 
+1243     */ { 08,   01,   29,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30   29   384 
+1244     */ { 00,   02,   17,   0b1010111001010000 }, /*   30   29   30   29   30   30   30   29   29   30   29   30        355 
+1245     */ { 00,   02,   06,   0b0100101101100000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29        354 
+1246     */ { 04,   01,   26,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30   29   384 
+1247     */ { 00,   02,   14,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30        355 
+1248     */ { 00,   02,   04,   0b0101001001110000 }, /*   29   30   29   30   29   29   30   29   29   30   30   30        354 
+1249     */ { 02,   01,   23,   0b0110100100110000 }, /*   29   30   30   29   30   29   29   30   29   29   30   30   29   383 
+1250     */ { 00,   02,   10,   0b1110010100110000 }, /*   30   30   30   29   29   30   29   30   29   29   30   30        355 
+1251     */ { 10,   01,   31,   0b0110110010011000 }, /*   29   30   30   29   30   30   29   29   30   29   29   30   30   384 
+1252     */ { 00,   02,   19,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354 
+1253     */ { 00,   02,   07,   0b0101101011010000 }, /*   29   30   29   30   30   29   30   29   30   30   29   30        355 
+1254     */ { 06,   01,   28,   0b0100101101101000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29   30   384 
+1255     */ { 00,   02,   16,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354 
+1256     */ { 00,   02,   05,   0b1010010011100000 }, /*   30   29   30   29   29   30   29   29   30   30   30   29        354 
+1257     */ { 04,   01,   24,   0b1101001001101000 }, /*   30   30   29   30   29   29   30   29   29   30   30   29   30   384 
+1258     */ { 00,   02,   12,   0b1101001001100000 }, /*   30   30   29   30   29   29   30   29   29   30   30   29        354 
+1259     */ { 11,   02,   01,   0b1101010100101000 }, /*   30   30   29   30   29   30   29   30   29   29   30   29   30   384 
+1260     */ { 00,   02,   20,   0b1011010100100000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29        354 
+1261     */ { 00,   02,   08,   0b1011011010100000 }, /*   30   29   30   30   29   30   30   29   30   29   30   29        355 
+1262     */ { 09,   01,   29,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30   29   384 
+1263     */ { 00,   02,   17,   0b0101010101110000 }, /*   29   30   29   30   29   30   29   30   29   30   30   30        355 
+1264     */ { 00,   02,   07,   0b0100100111010000 }, /*   29   30   29   29   30   29   29   30   30   30   29   30        354 
+1265     */ { 05,   01,   26,   0b1010010011011000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30   30   384 
+1266     */ { 00,   02,   14,   0b1010010010110000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30        354 
+1267     */ { 00,   02,   03,   0b1010101001010000 }, /*   30   29   30   29   30   29   30   29   29   30   29   30        354 
+1268     */ { 01,   01,   23,   0b1011010100101000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29   30   384 
+1269     */ { 00,   02,   10,   0b1011010100100000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29        354 
+1270     */ { 11,   01,   30,   0b1011010111000000 }, /*   30   29   30   30   29   30   29   30   30   30   29   29   29   384 
+1271     */ { 00,   02,   18,   0b1010101101100000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29        355 
+1272     */ { 00,   02,   08,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30        355 
+1273     */ { 06,   01,   28,   0b0100100110111000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30   30   384 
+1274     */ { 00,   02,   16,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30        354 
+1275     */ { 00,   02,   05,   0b0110010010110000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30        354 
+1276     */ { 03,   01,   25,   0b0110101001011000 }, /*   29   30   30   29   30   29   30   29   29   30   29   30   30   384 
+1277     */ { 00,   02,   12,   0b0110101001010000 }, /*   29   30   30   29   30   29   30   29   29   30   29   30        354 
+1278     */ { 11,   02,   01,   0b0110101100101000 }, /*   29   30   30   29   30   29   30   30   29   29   30   29   30   384 
+1279     */ { 00,   02,   20,   0b0101101011000000 }, /*   29   30   29   30   30   29   30   29   30   30   29   29        354 
+1280     */ { 00,   02,   09,   0b1010101101100000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29        355 
+1281     */ { 08,   01,   29,   0b0010101011101000 }, /*   29   29   30   29   30   29   30   29   30   30   30   29   30   384 
+1282     */ { 00,   02,   17,   0b0100100111100000 }, /*   29   30   29   29   30   29   29   30   30   30   30   29        354 
+1283     */ { 00,   02,   06,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354 
+1284     */ { 05,   01,   26,   0b1101001001011000 }, /*   30   30   29   30   29   29   30   29   29   30   29   30   30   384 
+1285     */ { 00,   02,   13,   0b1011001001010000 }, /*   30   29   30   30   29   29   30   29   29   30   29   30        354 
+1286     */ { 00,   02,   02,   0b1011010100100000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29        354 
+1287     */ { 02,   01,   22,   0b1111001010010000 }, /*   30   30   30   30   29   29   30   29   30   29   29   30   29   384 
+1288     */ { 00,   02,   10,   0b1011010110100000 }, /*   30   29   30   30   29   30   29   30   30   29   30   29        355 
+1289     */ { 10,   01,   30,   0b1001010111010000 }, /*   30   29   29   30   29   30   29   30   30   30   29   30   29   384 
+1290     */ { 00,   02,   18,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30        355 
+1291     */ { 00,   02,   08,   0b0100100110110000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30        354 
+1292     */ { 06,   01,   28,   0b1010010010111000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30   30   384 
+1293     */ { 00,   02,   15,   0b1010010010110000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30        354 
+1294     */ { 00,   02,   04,   0b1010101001010000 }, /*   30   29   30   29   30   29   30   29   29   30   29   30        354 
+1295     */ { 04,   01,   24,   0b1011010100101000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29   30   384 
+1296     */ { 00,   02,   12,   0b0110110101000000 }, /*   29   30   30   29   30   30   29   30   29   30   29   29        354 
+1297     */ { 12,   01,   31,   0b1010110101100000 }, /*   30   29   30   29   30   30   29   30   29   30   30   29   29   384 
+1298     */ { 00,   02,   19,   0b1010101101100000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29        355 
+1299     */ { 00,   02,   09,   0b1001001101110000 }, /*   30   29   29   30   29   29   30   30   29   30   30   30        355 
+1300     */ { 08,   01,   30,   0b0000100101111000 }, /*   29   29   29   29   30   29   29   30   29   30   30   30   30   383 
+1301     */ { 00,   02,   18,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30        354 
+1302     */ { 00,   02,   07,   0b0110010010110000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30        354 
+1303     */ { 05,   01,   27,   0b0110101001010000 }, /*   29   30   30   29   30   29   30   29   29   30   29   30   29   383 
+1304     */ { 00,   02,   14,   0b1101101001010000 }, /*   30   30   29   30   30   29   30   29   29   30   29   30        355 
+1305     */ { 00,   02,   03,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354 
+1306     */ { 01,   01,   23,   0b1010101101100000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29   29   384 
+1307     */ { 00,   02,   11,   0b1010011011100000 }, /*   30   29   30   29   29   30   30   29   30   30   30   29        355 
+1308     */ { 11,   02,   01,   0b1001001011101000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29   30   384 
+1309     */ { 00,   02,   19,   0b1001001011100000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29        354 
+1310     */ { 00,   02,   08,   0b1100100101100000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29        354 
+1311     */ { 07,   01,   28,   0b1101010010101000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29   30   384 
+1312     */ { 00,   02,   16,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354 
+1313     */ { 00,   02,   04,   0b1101010101010000 }, /*   30   30   29   30   29   30   29   30   29   30   29   30        355 
+1314     */ { 03,   01,   25,   0b0101101010101000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29   30   384 
+1315     */ { 00,   02,   13,   0b0101011010100000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29        354 
+1316     */ { 00,   02,   02,   0b1010011011010000 }, /*   30   29   30   29   29   30   30   29   30   30   29   30        355 
+1317     */ { 01,   01,   22,   0b1001001011101000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29   30   384 
+1318     */ { 00,   02,   10,   0b1001001010110000 }, /*   30   29   29   30   29   29   30   29   30   29   30   30        354 
+1319     */ { 08,   01,   30,   0b1010010101011000 }, /*   30   29   30   29   29   30   29   30   29   30   29   30   30   384 
+1320     */ { 00,   02,   18,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354 
+1321     */ { 00,   02,   06,   0b1011001010100000 }, /*   30   29   30   30   29   29   30   29   30   29   30   29        354 
+1322     */ { 05,   01,   26,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30   29   384 
+1323     */ { 00,   02,   14,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30        355 
+1324     */ { 00,   02,   04,   0b0100110110100000 }, /*   29   30   29   29   30   30   29   30   30   29   30   29        354 
+1325     */ { 01,   01,   23,   0b1010010111010000 }, /*   30   29   30   29   29   30   29   30   30   30   29   30   29   384 
+1326     */ { 00,   02,   11,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30        355 
+1327     */ { 09,   02,   01,   0b0101001010111000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30   30   384 
+1328     */ { 00,   02,   20,   0b0101001001110000 }, /*   29   30   29   30   29   29   30   29   29   30   30   30        354 
+1329     */ { 00,   02,   08,   0b0110100100110000 }, /*   29   30   30   29   30   29   29   30   29   29   30   30        354 
+1330     */ { 07,   01,   28,   0b0110101010011000 }, /*   29   30   30   29   30   29   30   29   30   29   29   30   30   384 
+1331     */ { 00,   02,   16,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354 
+1332     */ { 00,   02,   05,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30        355 
+1333     */ { 03,   01,   25,   0b0100101110101000 }, /*   29   30   29   29   30   29   30   30   30   29   30   29   30   384 
+1334     */ { 00,   02,   13,   0b0100101101100000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29        354 
+1335     */ { 12,   02,   02,   0b1010011001110000 }, /*   30   29   30   29   29   30   30   29   29   30   30   30   29   384 
+1336     */ { 00,   02,   21,   0b1010001011100000 }, /*   30   29   30   29   29   29   30   29   30   30   30   29        354 
+1337     */ { 00,   02,   09,   0b1101000101100000 }, /*   30   30   29   30   29   29   29   30   29   30   30   29        354 
+1338     */ { 08,   01,   29,   0b1110100100110000 }, /*   30   30   30   29   30   29   29   30   29   29   30   30   29   384 
+1339     */ { 00,   02,   17,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354 
+1340     */ { 00,   02,   06,   0b1101101010100000 }, /*   30   30   29   30   30   29   30   29   30   29   30   29        355 
+1341     */ { 05,   01,   26,   0b0101101101010000 }, /*   29   30   29   30   30   29   30   30   29   30   29   30   29   384 
+1342     */ { 00,   02,   14,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30        355 
+1343     */ { 00,   02,   04,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354 
+1344     */ { 02,   01,   24,   0b1010001011101000 }, /*   30   29   30   29   29   29   30   29   30   30   30   29   30   384 
+1345     */ { 00,   02,   11,   0b1010001011010000 }, /*   30   29   30   29   29   29   30   29   30   30   29   30        354 
+1346     */ { 10,   01,   31,   0b1101000101011000 }, /*   30   30   29   30   29   29   29   30   29   30   29   30   30   384 
+1347     */ { 00,   02,   19,   0b1010101001010000 }, /*   30   29   30   29   30   29   30   29   29   30   29   30        354 
+1348     */ { 00,   02,   08,   0b1011010100100000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29        354 
+1349     */ { 07,   01,   27,   0b1101011010100000 }, /*   30   30   29   30   29   30   30   29   30   29   30   29   29   384 
+1350     */ { 00,   02,   15,   0b1010110110100000 }, /*   30   29   30   29   30   30   29   30   30   29   30   29        355 
+1351     */ { 00,   02,   05,   0b0101010111010000 }, /*   29   30   29   30   29   30   29   30   30   30   29   30        355 
+1352     */ { 03,   01,   26,   0b0100100111011000 }, /*   29   30   29   29   30   29   29   30   30   30   29   30   30   384 
+1353     */ { 00,   02,   13,   0b0100010110110000 }, /*   29   30   29   29   29   30   29   30   30   29   30   30        354 
+1354     */ { 00,   02,   02,   0b1010001010110000 }, /*   30   29   30   29   29   29   30   29   30   29   30   30        354 
+1355     */ { 01,   01,   22,   0b1101000101011000 }, /*   30   30   29   30   29   29   29   30   29   30   29   30   30   384 
+1356     */ { 00,   02,   10,   0b1010101001010000 }, /*   30   29   30   29   30   29   30   29   29   30   29   30        354 
+1357     */ { 09,   01,   29,   0b1011010100101000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29   30   384 
+1358     */ { 00,   02,   17,   0b0110101100100000 }, /*   29   30   30   29   30   29   30   30   29   29   30   29        354 
+1359     */ { 00,   02,   06,   0b1010110101100000 }, /*   30   29   30   29   30   30   29   30   29   30   30   29        355 
+1360     */ { 05,   01,   27,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30   29   384 
+1361     */ { 00,   02,   14,   0b1001001101110000 }, /*   30   29   29   30   29   29   30   30   29   30   30   30        355 
+1362     */ { 00,   02,   04,   0b0100010101110000 }, /*   29   30   29   29   29   30   29   30   29   30   30   30        354 
+1363     */ { 03,   01,   24,   0b1010001010111000 }, /*   30   29   30   29   29   29   30   29   30   29   30   30   30   384 
+1364     */ { 00,   02,   12,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354 
+1365     */ { 10,   01,   31,   0b1010101001010000 }, /*   30   29   30   29   30   29   30   29   29   30   29   30   29   383 
+1366     */ { 00,   02,   18,   0b1101100101010000 }, /*   30   30   29   30   30   29   29   30   29   30   29   30        355 
+1367     */ { 00,   02,   08,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354 
+1368     */ { 07,   01,   28,   0b1010101101100000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29   29   384 
+1369     */ { 00,   02,   15,   0b1010011011100000 }, /*   30   29   30   29   29   30   30   29   30   30   30   29        355 
+1370     */ { 00,   02,   05,   0b0101001011100000 }, /*   29   30   29   30   29   29   30   29   30   30   30   29        354 
+1371     */ { 03,   01,   25,   0b1100010101110000 }, /*   30   30   29   29   29   30   29   30   29   30   30   30   29   384 
+1372     */ { 00,   02,   13,   0b1010010101100000 }, /*   30   29   30   29   29   30   29   30   29   30   30   29        354 
+1373     */ { 11,   02,   01,   0b1101001010101000 }, /*   30   30   29   30   29   29   30   29   30   29   30   29   30   384 
+1374     */ { 00,   02,   20,   0b1101001010100000 }, /*   30   30   29   30   29   29   30   29   30   29   30   29        354 
+1375     */ { 00,   02,   09,   0b1101010101010000 }, /*   30   30   29   30   29   30   29   30   29   30   29   30        355 
+1376     */ { 09,   01,   30,   0b0101101010101000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29   30   384 
+1377     */ { 00,   02,   17,   0b0101011010100000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29        354 
+1378     */ { 00,   02,   06,   0b1010011011010000 }, /*   30   29   30   29   29   30   30   29   30   30   29   30        355 
+1379     */ { 05,   01,   27,   0b0101001011101000 }, /*   29   30   29   30   29   29   30   29   30   30   30   29   30   384 
+1380     */ { 00,   02,   15,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354 
+1381     */ { 00,   02,   03,   0b1010100011010000 }, /*   30   29   30   29   30   29   29   29   30   30   29   30        354 
+1382     */ { 02,   01,   23,   0b1101001010101000 }, /*   30   30   29   30   29   29   30   29   30   29   30   29   30   384 
+1383     */ { 00,   02,   11,   0b1011001010100000 }, /*   30   29   30   30   29   29   30   29   30   29   30   29        354 
+1384     */ { 10,   01,   31,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30   29   384 
+1385     */ { 00,   02,   18,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30        355 
+1386     */ { 00,   02,   08,   0b0100110110100000 }, /*   29   30   29   29   30   30   29   30   30   29   30   29        354 
+1387     */ { 06,   01,   28,   0b1010010111010000 }, /*   30   29   30   29   29   30   29   30   30   30   29   30   29   384 
+1388     */ { 00,   02,   16,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30        355 
+1389     */ { 00,   02,   05,   0b0101000110110000 }, /*   29   30   29   30   29   29   29   30   30   29   30   30        354 
+1390     */ { 04,   01,   25,   0b1010100010111000 }, /*   30   29   30   29   30   29   29   29   30   29   30   30   30   384             
+1391     */ { 00,   02,   13,   0b0110010100110000 }, /*   29   30   30   29   29   30   29   30   29   29   30   30        354
+1392     */ { 12,   02,   02,   0b0110101010011000 }, /*   29   30   30   29   30   29   30   29   30   29   29   30   30   384
+1393     */ { 00,   02,   20,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354
+1394     */ { 00,   02,   09,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30        355
+1395     */ { 09,   01,   30,   0b0010101110101000 }, /*   29   29   30   29   30   29   30   30   30   29   30   29   30   384
+1396     */ { 00,   02,   18,   0b0010101101100000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29        354
+1397     */ { 00,   02,   06,   0b1100001101110000 }, /*   30   30   29   29   29   29   30   30   29   30   30   30        355
+1398     */ { 05,   01,   27,   0b0101000101110000 }, /*   29   30   29   30   29   29   29   30   29   30   30   30   29   383
+1399     */ { 00,   02,   14,   0b1100100101100000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29        354
+1400     */ { 00,   02,   03,   0b1110010010110000 }, /*   30   30   30   29   29   30   29   29   30   29   30   30        355
+1401     */ { 03,   01,   24,   0b0110101010010000 }, /*   29   30   30   29   30   29   30   29   30   29   29   30   29   383
+1402     */ { 00,   02,   11,   0b1101101010100000 }, /*   30   30   29   30   30   29   30   29   30   29   30   29        355
+1403     */ { 11,   02,   01,   0b0101101101010000 }, /*   29   30   29   30   30   29   30   30   29   30   29   30   29   384
+1404     */ { 00,   02,   20,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30        355
+1405     */ { 00,   02,   09,   0b0010101011100000 }, /*   29   29   30   29   30   29   30   29   30   30   30   29        354
+1406     */ { 07,   01,   29,   0b1010001011101000 }, /*   30   29   30   29   29   29   30   29   30   30   30   29   30   384
+1407     */ { 00,   02,   17,   0b1010001011010000 }, /*   30   29   30   29   29   29   30   29   30   30   29   30        354
+1408     */ { 00,   02,   06,   0b1101000101010000 }, /*   30   30   29   30   29   29   29   30   29   30   29   30        354
+1409     */ { 04,   01,   25,   0b1101010010101000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29   30   384
+1410     */ { 00,   02,   13,   0b1011010100100000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29        354
+1411     */ { 12,   02,   02,   0b1011011010010000 }, /*   30   29   30   30   29   30   30   29   30   29   29   30   29   384
+1412     */ { 00,   02,   21,   0b1010110110100000 }, /*   30   29   30   29   30   30   29   30   30   29   30   29        355
+1413     */ { 00,   02,   10,   0b0101010111010000 }, /*   29   30   29   30   29   30   29   30   30   30   29   30        355
+1414     */ { 09,   01,   31,   0b0010010111011000 }, /*   29   29   30   29   29   30   29   30   30   30   29   30   30   384
+1415     */ { 00,   02,   19,   0b0100010110110000 }, /*   29   30   29   29   29   30   29   30   30   29   30   30        354
+1416     */ { 00,   02,   08,   0b1010001010110000 }, /*   30   29   30   29   29   29   30   29   30   29   30   30        354
+1417     */ { 05,   01,   27,   0b1010100101011000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30   30   384
+1418     */ { 00,   02,   15,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354
+1419     */ { 00,   02,   04,   0b1011010100100000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29        354
+1420     */ { 01,   01,   24,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30   29   384
+1421     */ { 00,   02,   11,   0b1010101101100000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29        355
+1422     */ { 12,   02,   01,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30   29   384
+1423     */ { 00,   02,   20,   0b0100101101110000 }, /*   29   30   29   29   30   29   30   30   29   30   30   30        355
+1424     */ { 00,   02,   10,   0b0100010101110000 }, /*   29   30   29   29   29   30   29   30   29   30   30   30        354
+1425     */ { 07,   01,   29,   0b0101001010111000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30   30   384
+1426     */ { 00,   02,   17,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354
+1427     */ { 00,   02,   06,   0b0110100101010000 }, /*   29   30   30   29   30   29   29   30   29   30   29   30        354
+1428     */ { 04,   01,   26,   0b0110110010101000 }, /*   29   30   30   29   30   30   29   29   30   29   30   29   30   384
+1429     */ { 00,   02,   13,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354
+1430     */ { 12,   02,   02,   0b1001101101010000 }, /*   30   29   29   30   30   29   30   30   29   30   29   30   29   384
+1431     */ { 00,   02,   21,   0b1010011011100000 }, /*   30   29   30   29   29   30   30   29   30   30   30   29        355
+1432     */ { 00,   02,   11,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354
+1433     */ { 08,   01,   30,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30   29   384
+1434     */ { 00,   02,   18,   0b1010010101100000 }, /*   30   29   30   29   29   30   29   30   29   30   30   29        354
+1435     */ { 00,   02,   07,   0b1101001010100000 }, /*   30   30   29   30   29   29   30   29   30   29   30   29        354
+1436     */ { 06,   01,   27,   0b1110100101010000 }, /*   30   30   30   29   30   29   29   30   29   30   29   30   29   384
+1437     */ { 00,   02,   14,   0b1101010101010000 }, /*   30   30   29   30   29   30   29   30   29   30   29   30        355
+1438     */ { 00,   02,   04,   0b0101011010100000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29        354
+1439     */ { 02,   01,   24,   0b1010101011010000 }, /*   30   29   30   29   30   29   30   29   30   30   29   30   29   384
+1440     */ { 00,   02,   12,   0b1001010111100000 }, /*   30   29   29   30   29   30   29   30   30   30   30   29        355
+1441     */ { 11,   02,   01,   0b0100101011101000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29   30   384
+1442     */ { 00,   02,   20,   0b0100100110110000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30        354
+1443     */ { 00,   02,   09,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354
+1444     */ { 07,   01,   29,   0b1101001001110000 }, /*   30   30   29   30   29   29   30   29   29   30   30   30   29   384
+1445     */ { 00,   02,   16,   0b1011001010100000 }, /*   30   29   30   30   29   29   30   29   30   29   30   29        354
+1446     */ { 00,   02,   05,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30        355
+1447     */ { 04,   01,   26,   0b0101011010101000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29   30   384
+1448     */ { 00,   02,   14,   0b0010110110100000 }, /*   29   29   30   29   30   30   29   30   30   29   30   29        354
+1449     */ { 00,   02,   02,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30        355
+1450     */ { 01,   01,   23,   0b0100101010111000 }, /*   29   30   29   29   30   29   30   29   30   29   30   30   30   384
+1451     */ { 00,   02,   11,   0b0100100110110000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30        354
+1452     */ { 09,   01,   31,   0b1010010010111000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30   30   384
+1453     */ { 00,   02,   18,   0b0110010010110000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30        354
+1454     */ { 00,   02,   07,   0b0110101010010000 }, /*   29   30   30   29   30   29   30   29   30   29   29   30        354
+1455     */ { 06,   01,   27,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30   29   384
+1456     */ { 00,   02,   15,   0b0110101101010000 }, /*   29   30   30   29   30   29   30   30   29   30   29   30        355
+1457     */ { 00,   02,   04,   0b0010101101100000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29        354
+1458     */ { 02,   01,   24,   0b1001010101110000 }, /*   30   29   29   30   29   30   29   30   29   30   30   30   29   384
+1459     */ { 00,   02,   12,   0b1001001101110000 }, /*   30   29   29   30   29   29   30   30   29   30   30   30        355
+1460     */ { 11,   02,   02,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30   29   383
+1461     */ { 00,   02,   19,   0b1100100101100000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29        354
+1462     */ { 00,   02,   08,   0b1110010010110000 }, /*   30   30   30   29   29   30   29   29   30   29   30   30        355
+1463     */ { 07,   01,   29,   0b0110101010010000 }, /*   29   30   30   29   30   29   30   29   30   29   29   30   29   383
+1464     */ { 00,   02,   16,   0b1101101010100000 }, /*   30   30   29   30   30   29   30   29   30   29   30   29        355
+1465     */ { 00,   02,   05,   0b0101101011010000 }, /*   29   30   29   30   30   29   30   29   30   30   29   30        355
+1466     */ { 03,   01,   26,   0b0010101101101000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29   30   384
+1467     */ { 00,   02,   14,   0b0010011011100000 }, /*   29   29   30   29   29   30   30   29   30   30   30   29        354
+1468     */ { 00,   02,   03,   0b1001001011100000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29        354
+1469     */ { 02,   01,   22,   0b1100100101101000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29   30   384
+1470     */ { 00,   02,   10,   0b1100100101010000 }, /*   30   30   29   29   30   29   29   30   29   30   29   30        354
+1471     */ { 09,   01,   30,   0b1101010010101000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29   30   384
+1472     */ { 00,   02,   18,   0b1011010010100000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29        354
+1473     */ { 00,   02,   06,   0b1011011010010000 }, /*   30   29   30   30   29   30   30   29   30   29   29   30        355
+1474     */ { 06,   01,   27,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30   29   384
+1475     */ { 00,   02,   15,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30        355
+1476     */ { 00,   02,   05,   0b0010010111010000 }, /*   29   29   30   29   29   30   29   30   30   30   29   30        354
+1477     */ { 02,   01,   24,   0b1001001011011000 }, /*   30   29   29   30   29   29   30   29   30   30   29   30   30   384
+1478     */ { 00,   02,   12,   0b1001001010110000 }, /*   30   29   29   30   29   29   30   29   30   29   30   30        354
+1479     */ { 10,   02,   01,   0b1010100101011000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30   30   384
+1480     */ { 00,   02,   20,   0b0110100101010000 }, /*   29   30   30   29   30   29   29   30   29   30   29   30        354
+1481     */ { 00,   02,   08,   0b0111010010100000 }, /*   29   30   30   30   29   30   29   29   30   29   30   29        354
+1482     */ { 08,   01,   28,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30   29   384
+1483     */ { 00,   02,   16,   0b1010101101100000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29        355
+1484     */ { 00,   02,   06,   0b0101001110110000 }, /*   29   30   29   30   29   29   30   30   30   29   30   30        355
+1485     */ { 04,   01,   26,   0b0010010110111000 }, /*   29   29   30   29   29   30   29   30   30   29   30   30   30   384
+1486     */ { 00,   02,   14,   0b0010010101110000 }, /*   29   29   30   29   29   30   29   30   29   30   30   30        354
+1487     */ { 00,   02,   03,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354
+1488     */ { 01,   01,   23,   0b1010100101011000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30   30   384
+1489     */ { 00,   02,   10,   0b0110100101010000 }, /*   29   30   30   29   30   29   29   30   29   30   29   30        354
+1490     */ { 09,   01,   30,   0b0110101010101000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29   30   384
+1491     */ { 00,   02,   18,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354
+1492     */ { 00,   02,   07,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30        355
+1493     */ { 05,   01,   27,   0b0100101101101000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29   30   384
+1494     */ { 00,   02,   15,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354
+1495     */ { 00,   02,   04,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30        355
+1496     */ { 03,   01,   25,   0b0101001001110000 }, /*   29   30   29   30   29   29   30   29   29   30   30   30   29   383
+1497     */ { 00,   02,   11,   0b1101001010100000 }, /*   30   30   29   30   29   29   30   29   30   29   30   29        354
+1498     */ { 11,   01,   31,   0b1101100101010000 }, /*   30   30   29   30   30   29   29   30   29   30   29   30   29   384
+1499     */ { 00,   02,   19,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30        355
+1500     */ { 00,   02,   09,   0b0101011010100000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29        354
+1501     */ { 07,   01,   29,   0b1001011011010000 }, /*   30   29   29   30   29   30   30   29   30   30   29   30   29   384
+1502     */ { 00,   02,   17,   0b1001010111010000 }, /*   30   29   29   30   29   30   29   30   30   30   29   30        355
+1503     */ { 00,   02,   07,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354
+1504     */ { 04,   01,   27,   0b1010010011011000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30   30   384
+1505     */ { 00,   02,   14,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354
+1506     */ { 00,   02,   03,   0b1101001001010000 }, /*   30   30   29   30   29   29   30   29   29   30   29   30        354
+1507     */ { 01,   01,   23,   0b1101010101010000 }, /*   30   30   29   30   29   30   29   30   29   30   29   30   29   384
+1508     */ { 00,   02,   11,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30        355
+1509     */ { 09,   01,   31,   0b0101011010101000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29   30   384
+1510     */ { 00,   02,   19,   0b0010110110100000 }, /*   29   29   30   29   30   30   29   30   30   29   30   29        354
+1511     */ { 00,   02,   08,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30        355
+1512     */ { 05,   01,   29,   0b0100100110111000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30   30   384
+1513     */ { 00,   02,   16,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30        354
+1514     */ { 00,   02,   05,   0b1010010010110000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30        354
+1515     */ { 04,   01,   25,   0b1011001001011000 }, /*   30   29   30   30   29   29   30   29   29   30   29   30   30   384
+1516     */ { 00,   02,   13,   0b0110101010010000 }, /*   29   30   30   29   30   29   30   29   30   29   29   30        354
+1517     */ { 12,   02,   01,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30   29   384
+1518     */ { 00,   02,   20,   0b0101101101010000 }, /*   29   30   29   30   30   29   30   30   29   30   29   30        355
+1519     */ { 00,   02,   10,   0b0010101101100000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29        354
+1520     */ { 08,   01,   30,   0b1001010101110000 }, /*   30   29   29   30   29   30   29   30   29   30   30   30   29   384
+1521     */ { 00,   02,   17,   0b1001001011110000 }, /*   30   29   29   30   29   29   30   29   30   30   30   30        355
+1522     */ { 00,   02,   07,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30        354
+1523     */ { 04,   01,   27,   0b0110010010110000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30   29   383
+1524     */ { 00,   02,   14,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354
+1525     */ { 12,   02,   02,   0b1110101001010000 }, /*   30   30   30   29   30   29   30   29   29   30   29   30   29   384
+1526     */ { 00,   02,   21,   0b1101011010010000 }, /*   30   30   29   30   29   30   30   29   30   29   29   30        355
+1527     */ { 00,   02,   11,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30        355
+1528     */ { 10,   02,   01,   0b0010101101101000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29   30   384
+1529     */ { 00,   02,   19,   0b0010011011100000 }, /*   29   29   30   29   29   30   30   29   30   30   30   29        354
+1530     */ { 00,   02,   08,   0b0101001011100000 }, /*   29   30   29   30   29   29   30   29   30   30   30   29        354
+1531     */ { 06,   01,   28,   0b1100100101101000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29   30   384
+1532     */ { 00,   02,   16,   0b1100100101010000 }, /*   30   30   29   29   30   29   29   30   29   30   29   30        354
+1533     */ { 00,   02,   04,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354
+1534     */ { 02,   01,   24,   0b1101101001010000 }, /*   30   30   29   30   30   29   30   29   29   30   29   30   29   384
+1535     */ { 00,   02,   12,   0b1011010110010000 }, /*   30   29   30   30   29   30   29   30   30   29   29   30        355
+1536     */ { 12,   02,   02,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30   29   384
+1537     */ { 00,   02,   20,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30        355
+1538     */ { 00,   02,   10,   0b0010010111010000 }, /*   29   29   30   29   29   30   29   30   30   30   29   30        354
+1539     */ { 07,   01,   30,   0b1001001011011000 }, /*   30   29   29   30   29   29   30   29   30   30   29   30   30   384
+1540     */ { 00,   02,   18,   0b1001001010110000 }, /*   30   29   29   30   29   29   30   29   30   29   30   30        354
+1541     */ { 00,   02,   06,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354
+1542     */ { 05,   01,   26,   0b1011010010101000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29   30   384
+1543     */ { 00,   02,   14,   0b0110110010100000 }, /*   29   30   30   29   30   30   29   29   30   29   30   29        354
+1544     */ { 00,   02,   03,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30        355
+1545     */ { 01,   01,   23,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30   29   384
+1546     */ { 00,   02,   11,   0b0100101110110000 }, /*   29   30   29   29   30   29   30   30   30   29   30   30        355
+1547     */ { 09,   02,   01,   0b0010010110111000 }, /*   29   29   30   29   29   30   29   30   30   29   30   30   30   384
+1548     */ { 00,   02,   20,   0b0010010101110000 }, /*   29   29   30   29   29   30   29   30   29   30   30   30        354
+1549     */ { 00,   02,   08,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354
+1550     */ { 06,   01,   28,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30   29   383
+1551     */ { 00,   02,   15,   0b1110100101010000 }, /*   30   30   30   29   30   29   29   30   29   30   29   30        355
+1552     */ { 00,   02,   05,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354
+1553     */ { 03,   01,   24,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30   29   384
+1554     */ { 00,   02,   12,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30        355
+1555     */ { 11,   02,   02,   0b0100101101101000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29   30   384
+1556     */ { 00,   02,   21,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354
+1557     */ { 00,   02,   09,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30        355
+1558     */ { 07,   01,   30,   0b0101001001101000 }, /*   29   30   29   30   29   29   30   29   29   30   30   29   30   383
+1559     */ { 00,   02,   17,   0b1101001001100000 }, /*   30   30   29   30   29   29   30   29   29   30   30   29        354
+1560     */ { 00,   02,   06,   0b1101100101010000 }, /*   30   30   29   30   30   29   29   30   29   30   29   30        355
+1561     */ { 05,   01,   26,   0b0101101010101000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29   30   384
+1562     */ { 00,   02,   14,   0b0101011010100000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29        354
+1563     */ { 00,   02,   03,   0b1001011011010000 }, /*   30   29   29   30   29   30   30   29   30   30   29   30        355
+1564     */ { 02,   01,   24,   0b0100101011101000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29   30   384
+1565     */ { 00,   02,   11,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354
+1566     */ { 10,   01,   31,   0b1010010011011000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30   30   384
+1567     */ { 00,   02,   19,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354
+1568     */ { 00,   02,   08,   0b1101001001010000 }, /*   30   30   29   30   29   29   30   29   29   30   29   30        354
+1569     */ { 06,   01,   27,   0b1101010101001000 }, /*   30   30   29   30   29   30   29   30   29   30   29   29   30   384
+1570     */ { 00,   02,   15,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30        355
+1571     */ { 00,   02,   05,   0b0011010110100000 }, /*   29   29   30   30   29   30   29   30   30   29   30   29        354
+1572     */ { 02,   01,   25,   0b1001010111010000 }, /*   30   29   29   30   29   30   29   30   30   30   29   30   29   384
+1573     */ { 00,   02,   12,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30        355
+1574     */ { 12,   02,   02,   0b0100100110111000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30   30   384
+1575     */ { 00,   02,   21,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30        354
+1576     */ { 00,   02,   10,   0b1010010010110000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30        354
+1577     */ { 08,   01,   29,   0b1011001001011000 }, /*   30   29   30   30   29   29   30   29   29   30   29   30   30   384
+1578     */ { 00,   02,   17,   0b0110101001010000 }, /*   29   30   30   29   30   29   30   29   29   30   29   30        354
+1579     */ { 00,   02,   06,   0b0110110101000000 }, /*   29   30   30   29   30   30   29   30   29   30   29   29        354
+1580     */ { 04,   01,   26,   0b1010110110101000 }, /*   30   29   30   29   30   30   29   30   30   29   30   29   30   385
+1581     */ { 00,   02,   14,   0b0010101101100000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29        354
+1582     */ { 00,   02,   03,   0b1001001101110000 }, /*   30   29   29   30   29   29   30   30   29   30   30   30        355
+1583     */ { 02,   01,   24,   0b0100100101111000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30   30   384
+1584     */ { 00,   02,   12,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30        354
+1585     */ { 09,   01,   31,   0b0110010010110000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30   29   383
+1586     */ { 00,   02,   18,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354
+1587     */ { 00,   02,   07,   0b1110101001010000 }, /*   30   30   30   29   30   29   30   29   29   30   29   30        355
+1588     */ { 06,   01,   28,   0b0110101101001000 }, /*   29   30   30   29   30   29   30   30   29   30   29   29   30   384
+1589     */ { 00,   02,   15,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30        355
+1590     */ { 00,   02,   05,   0b0010101101100000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29        354
+1591     */ { 03,   01,   25,   0b1001001011110000 }, /*   30   29   29   30   29   29   30   29   30   30   30   30   29   384
+1592     */ { 00,   02,   13,   0b1001001011100000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29        354
+1593     */ { 11,   02,   01,   0b1100100101101000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29   30   384
+1594     */ { 00,   02,   20,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354
+1595     */ { 00,   02,   09,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354
+1596     */ { 08,   01,   29,   0b1101101001010000 }, /*   30   30   29   30   30   29   30   29   29   30   29   30   29   384
+1597     */ { 00,   02,   16,   0b1011010011010000 }, /*   30   29   30   30   29   30   29   29   30   30   29   30        355
+1598     */ { 00,   02,   06,   0b0101011010110000 }, /*   29   30   29   30   29   30   30   29   30   29   30   30        355
+1599     */ { 04,   01,   27,   0b0010011011011000 }, /*   29   29   30   29   29   30   30   29   30   30   29   30   30   384
+1600     */ { 00,   02,   15,   0b0010010111010000 }, /*   29   29   30   29   29   30   29   30   30   30   29   30        354
+1601     */ { 00,   02,   03,   0b1001001011010000 }, /*   30   29   29   30   29   29   30   29   30   30   29   30        354
+1602     */ { 02,   01,   23,   0b1100100110011000 }, /*   30   30   29   29   30   29   29   30   30   29   29   30   30   384
+1603     */ { 00,   02,   11,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354
+1604     */ { 09,   01,   31,   0b1011010010101000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29   30   384
+1605     */ { 00,   02,   18,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354
+1606     */ { 00,   02,   07,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30        355
+1607     */ { 06,   01,   28,   0b0101010110101000 }, /*   29   30   29   30   29   30   29   30   30   29   30   29   30   384
+1608     */ { 00,   02,   16,   0b0100101110110000 }, /*   29   30   29   29   30   29   30   30   30   29   30   30        355
+1609     */ { 00,   02,   05,   0b0010010110110000 }, /*   29   29   30   29   29   30   29   30   30   29   30   30        354
+1610     */ { 03,   01,   25,   0b0101001010111000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30   30   384
+1611     */ { 00,   02,   13,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354
+1612     */ { 11,   02,   02,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30   29   383
+1613     */ { 00,   02,   19,   0b1110100101010000 }, /*   30   30   30   29   30   29   29   30   29   30   29   30        355
+1614     */ { 00,   02,   09,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354
+1615     */ { 08,   01,   29,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30   29   384
+1616     */ { 00,   02,   17,   0b1001101101010000 }, /*   30   29   29   30   30   29   30   30   29   30   29   30        355
+1617     */ { 00,   02,   06,   0b0100101101100000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29        354
+1618     */ { 04,   01,   26,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30   29   384
+1619     */ { 00,   02,   14,   0b1010010011110000 }, /*   30   29   30   29   29   30   29   29   30   30   30   30        355
+1620     */ { 00,   02,   04,   0b0101001001100000 }, /*   29   30   29   30   29   29   30   29   29   30   30   29        353
+1621     */ { 02,   01,   22,   0b1110100100110000 }, /*   30   30   30   29   30   29   29   30   29   29   30   30   29   384
+1622     */ { 00,   02,   10,   0b1101010101010000 }, /*   30   30   29   30   29   30   29   30   29   30   29   30        355
+1623     */ { 10,   01,   31,   0b0101101010101000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29   30   384
+1624     */ { 00,   02,   19,   0b0101011010100000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29        354
+1625     */ { 00,   02,   07,   0b1001011011010000 }, /*   30   29   29   30   29   30   30   29   30   30   29   30        355
+1626     */ { 06,   01,   28,   0b0100101011101000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29   30   384
+1627     */ { 00,   02,   16,   0b0100100111100000 }, /*   29   30   29   29   30   29   29   30   30   30   30   29        354
+1628     */ { 00,   02,   05,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354
+1629     */ { 04,   01,   24,   0b1101001001101000 }, /*   30   30   29   30   29   29   30   29   29   30   30   29   30   384
+1630     */ { 00,   02,   12,   0b1101001001010000 }, /*   30   30   29   30   29   29   30   29   29   30   29   30        354
+1631     */ { 11,   02,   01,   0b1101010100101000 }, /*   30   30   29   30   29   30   29   30   29   29   30   29   30   384
+1632     */ { 00,   02,   20,   0b1011010101000000 }, /*   30   29   30   30   29   30   29   30   29   30   29   29        354
+1633     */ { 00,   02,   08,   0b1011010110100000 }, /*   30   29   30   30   29   30   29   30   30   29   30   29        355
+1634     */ { 08,   01,   29,   0b1001010111010000 }, /*   30   29   29   30   29   30   29   30   30   30   29   30   29   384
+1635     */ { 00,   02,   17,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30        355
+1636     */ { 00,   02,   07,   0b0100100110110000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30        354
+1637     */ { 04,   01,   26,   0b1010010010111000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30   30   384
+1638     */ { 00,   02,   14,   0b1010010010110000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30        354
+1639     */ { 00,   02,   03,   0b1010101001010000 }, /*   30   29   30   29   30   29   30   29   29   30   29   30        354
+1640     */ { 01,   01,   23,   0b1011010100101000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29   30   384
+1641     */ { 00,   02,   10,   0b0110110101000000 }, /*   29   30   30   29   30   30   29   30   29   30   29   29        354
+1642     */ { 11,   01,   30,   0b1010110110101000 }, /*   30   29   30   29   30   30   29   30   30   29   30   29   30   385
+1643     */ { 00,   02,   19,   0b0010101101100000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29        354
+1644     */ { 00,   02,   08,   0b1001001101110000 }, /*   30   29   29   30   29   29   30   30   29   30   30   30        355
+1645     */ { 06,   01,   28,   0b0100100101111000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30   30   384
+1646     */ { 00,   02,   16,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30        354
+1647     */ { 00,   02,   05,   0b0110010010110000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30        354
+1648     */ { 03,   01,   25,   0b0110101001010000 }, /*   29   30   30   29   30   29   30   29   29   30   29   30   29   383
+1649     */ { 00,   02,   11,   0b1101101001010000 }, /*   30   30   29   30   30   29   30   29   29   30   29   30        355
+1650     */ { 11,   02,   01,   0b0110101101001000 }, /*   29   30   30   29   30   29   30   30   29   30   29   29   30   384
+1651     */ { 00,   02,   20,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30        355
+1652     */ { 00,   02,   10,   0b0010101110100000 }, /*   29   29   30   29   30   29   30   30   30   29   30   29        354
+1653     */ { 07,   01,   29,   0b1001001011110000 }, /*   30   29   29   30   29   29   30   29   30   30   30   30   29   384
+1654     */ { 00,   02,   17,   0b1001001011100000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29        354
+1655     */ { 00,   02,   06,   0b1100100101100000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29        354
+1656     */ { 05,   01,   26,   0b1101010010101000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29   30   384
+1657     */ { 00,   02,   13,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354
+1658     */ { 00,   02,   02,   0b1101101001010000 }, /*   30   30   29   30   30   29   30   29   29   30   29   30        355
+1659     */ { 03,   01,   23,   0b0101101010101000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29   30   384
+1660     */ { 00,   02,   11,   0b0101011010100000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29        354
+1661     */ { 07,   01,   30,   0b1010011011010000 }, /*   30   29   30   29   29   30   30   29   30   30   29   30   29   384
+1662     */ { 00,   02,   18,   0b1010010111010000 }, /*   30   29   30   29   29   30   29   30   30   30   29   30        355
+1663     */ { 00,   02,   08,   0b1001001011010000 }, /*   30   29   29   30   29   29   30   29   30   30   29   30        354
+1664     */ { 06,   01,   28,   0b1010100101011000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30   30   384
+1665     */ { 00,   02,   15,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354
+1666     */ { 00,   02,   04,   0b1011010010100000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29        354
+1667     */ { 04,   01,   24,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30   29   384
+1668     */ { 00,   02,   12,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30        355
+1669     */ { 00,   02,   01,   0b0101010110100000 }, /*   29   30   29   30   29   30   29   30   30   29   30   29        354
+1670     */ { 02,   01,   21,   0b1010010111010000 }, /*   30   29   30   29   29   30   29   30   30   30   29   30   29   384
+1671     */ { 00,   02,   09,   0b1010010110110000 }, /*   30   29   30   29   29   30   29   30   30   29   30   30        355
+1672     */ { 07,   01,   30,   0b0101001010111000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30   30   384
+1673     */ { 00,   02,   17,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354
+1674     */ { 00,   02,   06,   0b0110100100110000 }, /*   29   30   30   29   30   29   29   30   29   29   30   30        354
+1675     */ { 05,   01,   26,   0b0111010010101000 }, /*   29   30   30   30   29   30   29   29   30   29   30   29   30   384
+1676     */ { 00,   02,   14,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354
+1677     */ { 00,   02,   02,   0b1010110110010000 }, /*   30   29   30   29   30   30   29   30   30   29   29   30        355
+1678     */ { 03,   01,   23,   0b0100110110101000 }, /*   29   30   29   29   30   30   29   30   30   29   30   29   30   384
+1679     */ { 00,   02,   11,   0b0100101101100000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29        354
+1680     */ { 08,   01,   31,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30   29   384
+1681     */ { 00,   02,   18,   0b1010010011100000 }, /*   30   29   30   29   29   30   29   29   30   30   30   29        354
+1682     */ { 00,   02,   07,   0b1101001001100000 }, /*   30   30   29   30   29   29   30   29   29   30   30   29        354
+1683     */ { 06,   01,   27,   0b1110100100110000 }, /*   30   30   30   29   30   29   29   30   29   29   30   30   29   384
+1684     */ { 00,   02,   15,   0b1101010100100000 }, /*   30   30   29   30   29   30   29   30   29   29   30   29        354
+1685     */ { 00,   02,   03,   0b1101101010100000 }, /*   30   30   29   30   30   29   30   29   30   29   30   29        355
+1686     */ { 04,   01,   24,   0b0110101101010000 }, /*   29   30   30   29   30   29   30   30   29   30   29   30   29   384
+1687     */ { 00,   02,   12,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30        355
+1688     */ { 00,   02,   02,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354
+1689     */ { 03,   01,   21,   0b1010010011101000 }, /*   30   29   30   29   29   30   29   29   30   30   30   29   30   384
+1690     */ { 00,   02,   09,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354
+1691     */ { 07,   01,   29,   0b1101001001011000 }, /*   30   30   29   30   29   29   30   29   29   30   29   30   30   384
+1692     */ { 00,   02,   17,   0b1011001001010000 }, /*   30   29   30   30   29   29   30   29   29   30   29   30        354
+1693     */ { 00,   02,   05,   0b1101010100100000 }, /*   30   30   29   30   29   30   29   30   29   29   30   29        354
+1694     */ { 05,   01,   25,   0b1101011010100000 }, /*   30   30   29   30   29   30   30   29   30   29   30   29   29   384
+1695     */ { 00,   02,   13,   0b1011010110100000 }, /*   30   29   30   30   29   30   29   30   30   29   30   29        355
+1696     */ { 00,   02,   03,   0b0101010111010000 }, /*   29   30   29   30   29   30   29   30   30   30   29   30        355
+1697     */ { 03,   01,   23,   0b0100101011011000 }, /*   29   30   29   29   30   29   30   29   30   30   29   30   30   384
+1698     */ { 00,   02,   11,   0b0100100111010000 }, /*   29   30   29   29   30   29   29   30   30   30   29   30        354
+1699     */ { 07,   01,   31,   0b1010010010111000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30   30   384
+1700     */ { 00,   02,   19,   0b1010010010110000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30        354
+1701     */ { 00,   02,   08,   0b1010101001010000 }, /*   30   29   30   29   30   29   30   29   29   30   29   30        354
+1702     */ { 06,   01,   28,   0b1011010100101000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29   30   384
+1703     */ { 00,   02,   16,   0b0110110100100000 }, /*   29   30   30   29   30   30   29   30   29   29   30   29        354
+1704     */ { 00,   02,   05,   0b1010110110100000 }, /*   30   29   30   29   30   30   29   30   30   29   30   29        355
+1705     */ { 04,   01,   25,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30   29   384
+1706     */ { 00,   02,   13,   0b1001001101110000 }, /*   30   29   29   30   29   29   30   30   29   30   30   30        355
+1707     */ { 00,   02,   03,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30        354
+1708     */ { 03,   01,   23,   0b0110010010111000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30   30   384
+1709     */ { 00,   02,   10,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354
+1710     */ { 07,   01,   30,   0b0110101001010000 }, /*   29   30   30   29   30   29   30   29   29   30   29   30   29   383
+1711     */ { 00,   02,   17,   0b1101101001010000 }, /*   30   30   29   30   30   29   30   29   29   30   29   30        355
+1712     */ { 00,   02,   07,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354
+1713     */ { 05,   01,   26,   0b1010101101100000 }, /*   30   29   30   29   30   29   30   30   29   30   30   29   29   384
+1714     */ { 00,   02,   14,   0b1010101011100000 }, /*   30   29   30   29   30   29   30   29   30   30   30   29        355
+1715     */ { 00,   02,   04,   0b1001001011100000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29        354
+1716     */ { 03,   01,   24,   0b1100100101110000 }, /*   30   30   29   29   30   29   29   30   29   30   30   30   29   384
+1717     */ { 00,   02,   11,   0b1100100101100000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29        354
+1718     */ { 08,   01,   31,   0b1101010010101000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29   30   384
+1719     */ { 00,   02,   19,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354
+1720     */ { 00,   02,   08,   0b1101010101010000 }, /*   30   30   29   30   29   30   29   30   29   30   29   30        355
+1721     */ { 06,   01,   28,   0b0101101010101000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29   30   384
+1722     */ { 00,   02,   16,   0b0101011010100000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29        354
+1723     */ { 00,   02,   05,   0b1010011011010000 }, /*   30   29   30   29   29   30   30   29   30   30   29   30        355
+1724     */ { 04,   01,   26,   0b0101001011101000 }, /*   29   30   29   30   29   29   30   29   30   30   30   29   30   384
+1725     */ { 00,   02,   13,   0b0101001011010000 }, /*   29   30   29   30   29   29   30   29   30   30   29   30        354
+1726     */ { 00,   02,   02,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354
+1727     */ { 03,   01,   22,   0b1110010010101000 }, /*   30   30   30   29   29   30   29   29   30   29   30   29   30   384
+1728     */ { 00,   02,   10,   0b1011010010100000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29        354
+1729     */ { 07,   01,   29,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30   29   384
+1730     */ { 00,   02,   17,   0b1001110101010000 }, /*   30   29   29   30   30   30   29   30   29   30   29   30        355
+1731     */ { 00,   02,   07,   0b0101010110100000 }, /*   29   30   29   30   29   30   29   30   30   29   30   29        354
+1732     */ { 05,   01,   27,   0b1010010111010000 }, /*   30   29   30   29   29   30   29   30   30   30   29   30   29   384
+1733     */ { 00,   02,   14,   0b1010010110110000 }, /*   30   29   30   29   29   30   29   30   30   29   30   30        355
+1734     */ { 00,   02,   04,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354
+1735     */ { 04,   01,   24,   0b1010100010111000 }, /*   30   29   30   29   30   29   29   29   30   29   30   30   30   384
+1736     */ { 00,   02,   12,   0b0110100100110000 }, /*   29   30   30   29   30   29   29   30   29   29   30   30        354
+1737     */ { 09,   01,   31,   0b0110101010011000 }, /*   29   30   30   29   30   29   30   29   30   29   29   30   30   384
+1738     */ { 00,   02,   19,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354
+1739     */ { 00,   02,   08,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30        355
+1740     */ { 06,   01,   29,   0b0100110110101000 }, /*   29   30   29   29   30   30   29   30   30   29   30   29   30   384
+1741     */ { 00,   02,   16,   0b0100101101100000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29        354
+1742     */ { 00,   02,   05,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30        355
+1743     */ { 04,   01,   26,   0b0101000101110000 }, /*   29   30   29   30   29   29   29   30   29   30   30   30   29   383
+1744     */ { 00,   02,   13,   0b1101000101100000 }, /*   30   30   29   30   29   29   29   30   29   30   30   29        354
+1745     */ { 00,   02,   01,   0b1110100100110000 }, /*   30   30   30   29   30   29   29   30   29   29   30   30        355
+1746     */ { 03,   01,   22,   0b0110101010010000 }, /*   29   30   30   29   30   29   30   29   30   29   29   30   29   383
+1747     */ { 00,   02,   09,   0b1101101010100000 }, /*   30   30   29   30   30   29   30   29   30   29   30   29        355
+1748     */ { 07,   01,   30,   0b0101101101010000 }, /*   29   30   29   30   30   29   30   30   29   30   29   30   29   384
+1749     */ { 00,   02,   17,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30        355
+1750     */ { 00,   02,   07,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354
+1751     */ { 05,   01,   27,   0b1010010011011000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30   30   384
+1752     */ { 00,   02,   15,   0b1010001011010000 }, /*   30   29   30   29   29   29   30   29   30   30   29   30        354
+1753     */ { 00,   02,   03,   0b1101000101010000 }, /*   30   30   29   30   29   29   29   30   29   30   29   30        354
+1754     */ { 04,   01,   23,   0b1101010100101000 }, /*   30   30   29   30   29   30   29   30   29   29   30   29   30   384
+1755     */ { 00,   02,   11,   0b1011010100100000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29        354
+1756     */ { 09,   01,   31,   0b1101011010010000 }, /*   30   30   29   30   29   30   30   29   30   29   29   30   29   384
+1757     */ { 00,   02,   18,   0b1010110110100000 }, /*   30   29   30   29   30   30   29   30   30   29   30   29        355
+1758     */ { 00,   02,   08,   0b0101010111010000 }, /*   29   30   29   30   29   30   29   30   30   30   29   30        355
+1759     */ { 06,   01,   29,   0b0010101011011000 }, /*   29   29   30   29   30   29   30   29   30   30   29   30   30   384
+1760     */ { 00,   02,   17,   0b0100010110110000 }, /*   29   30   29   29   29   30   29   30   30   29   30   30        354
+1761     */ { 00,   02,   05,   0b1010001010110000 }, /*   30   29   30   29   29   29   30   29   30   29   30   30        354
+1762     */ { 05,   01,   25,   0b1011000101011000 }, /*   30   29   30   30   29   29   29   30   29   30   29   30   30   384
+1763     */ { 00,   02,   13,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354
+1764     */ { 00,   02,   02,   0b1011010100100000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29        354
+1765     */ { 02,   01,   21,   0b1011010110010000 }, /*   30   29   30   30   29   30   29   30   30   29   29   30   29   384
+1766     */ { 00,   02,   09,   0b1010110101100000 }, /*   30   29   30   29   30   30   29   30   29   30   30   29        355
+1767     */ { 07,   01,   30,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30   29   384
+1768     */ { 00,   02,   18,   0b0101001101110000 }, /*   29   30   29   30   29   29   30   30   29   30   30   30        355
+1769     */ { 00,   02,   07,   0b0100010101110000 }, /*   29   30   29   29   29   30   29   30   29   30   30   30        354
+1770     */ { 05,   01,   27,   0b0110001010111000 }, /*   29   30   30   29   29   29   30   29   30   29   30   30   30   384
+1771     */ { 00,   02,   15,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354
+1772     */ { 00,   02,   04,   0b0110100101010000 }, /*   29   30   30   29   30   29   29   30   29   30   29   30        354
+1773     */ { 03,   01,   23,   0b0110110010101000 }, /*   29   30   30   29   30   30   29   29   30   29   30   29   30   384
+1774     */ { 00,   02,   11,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354
+1775     */ { 10,   01,   31,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30   29   384
+1776     */ { 00,   02,   19,   0b1010011011010000 }, /*   30   29   30   29   29   30   30   29   30   30   29   30        355
+1777     */ { 00,   02,   08,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354
+1778     */ { 06,   01,   28,   0b1001010101110000 }, /*   30   29   29   30   29   30   29   30   29   30   30   30   29   384
+1779     */ { 00,   02,   16,   0b1010010101100000 }, /*   30   29   30   29   29   30   29   30   29   30   30   29        354
+1780     */ { 00,   02,   05,   0b1101001010100000 }, /*   30   30   29   30   29   29   30   29   30   29   30   29        354
+1781     */ { 05,   01,   24,   0b1110100101010000 }, /*   30   30   30   29   30   29   29   30   29   30   29   30   29   384
+1782     */ { 00,   02,   12,   0b1101010101010000 }, /*   30   30   29   30   29   30   29   30   29   30   29   30        355
+1783     */ { 00,   02,   02,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354
+1784     */ { 03,   01,   22,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30   29   384
+1785     */ { 00,   02,   09,   0b1010011011010000 }, /*   30   29   30   29   29   30   30   29   30   30   29   30        355
+1786     */ { 07,   01,   30,   0b0100101011101000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29   30   384
+1787     */ { 00,   02,   18,   0b0100101010110000 }, /*   29   30   29   29   30   29   30   29   30   29   30   30        354
+1788     */ { 00,   02,   07,   0b1010100011010000 }, /*   30   29   30   29   30   29   29   29   30   30   29   30        354
+1789     */ { 05,   01,   26,   0b1101001010101000 }, /*   30   30   29   30   29   29   30   29   30   29   30   29   30   384
+1790     */ { 00,   02,   14,   0b1011001010100000 }, /*   30   29   30   30   29   29   30   29   30   29   30   29        354
+1791     */ { 00,   02,   03,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30        355
+1792     */ { 04,   01,   24,   0b0101011010101000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29   30   384
+1793     */ { 00,   02,   11,   0b0100110110100000 }, /*   29   30   29   29   30   30   29   30   30   29   30   29        354
+1794     */ { 00,   01,   31,   0b1001010111010000 }, /*   30   29   29   30   29   30   29   30   30   30   29   30        355
+1795     */ { 02,   01,   21,   0b0100101010111000 }, /*   29   30   29   29   30   29   30   29   30   29   30   30   30   384
+1796     */ { 00,   02,   09,   0b0100100110110000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30        354
+1797     */ { 06,   01,   28,   0b1010100010111000 }, /*   30   29   30   29   30   29   29   29   30   29   30   30   30   384
+1798     */ { 00,   02,   16,   0b0110010010110000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30        354
+1799     */ { 00,   02,   05,   0b0110101010010000 }, /*   29   30   30   29   30   29   30   29   30   29   29   30        354
+1800     */ { 04,   01,   25,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30   29   384
+1801     */ { 00,   02,   13,   0b0110101101010000 }, /*   29   30   30   29   30   29   30   30   29   30   29   30        355
+1802     */ { 00,   02,   03,   0b0010101110100000 }, /*   29   29   30   29   30   29   30   30   30   29   30   29        354
+1803     */ { 02,   01,   23,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30   29   384
+1804     */ { 00,   02,   11,   0b1001001101110000 }, /*   30   29   29   30   29   29   30   30   29   30   30   30        355
+1805     */ { 06,   01,   31,   0b0101000101110000 }, /*   29   30   29   30   29   29   29   30   29   30   30   30   29   383
+1806     */ { 00,   02,   18,   0b1101000101100000 }, /*   30   30   29   30   29   29   29   30   29   30   30   29        354
+1807     */ { 00,   02,   07,   0b1110010010110000 }, /*   30   30   30   29   29   30   29   29   30   29   30   30        355
+1808     */ { 05,   01,   28,   0b0110101010010000 }, /*   29   30   30   29   30   29   30   29   30   29   29   30   29   383
+1809     */ { 00,   02,   14,   0b1101101010010000 }, /*   30   30   29   30   30   29   30   29   30   29   29   30        355
+1810     */ { 00,   02,   04,   0b0101101101010000 }, /*   29   30   29   30   30   29   30   30   29   30   29   30        355
+1811     */ { 03,   01,   25,   0b0010101101101000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29   30   384
+1812     */ { 00,   02,   13,   0b0010101011100000 }, /*   29   29   30   29   30   29   30   29   30   30   30   29        354
+1813     */ { 00,   02,   01,   0b1010001011100000 }, /*   30   29   30   29   29   29   30   29   30   30   30   29        354
+1814     */ { 02,   01,   21,   0b1101000101101000 }, /*   30   30   29   30   29   29   29   30   29   30   30   29   30   384
+1815     */ { 00,   02,   09,   0b1100100101010000 }, /*   30   30   29   29   30   29   29   30   29   30   29   30        354
+1816     */ { 06,   01,   29,   0b1101010010101000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29   30   384
+1817     */ { 00,   02,   16,   0b1011010100100000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29        354
+1818     */ { 00,   02,   05,   0b1011011010010000 }, /*   30   29   30   30   29   30   30   29   30   29   29   30        355
+1819     */ { 04,   01,   26,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30   29   384
+1820     */ { 00,   02,   14,   0b0101010111010000 }, /*   29   30   29   30   29   30   29   30   30   30   29   30        355
+1821     */ { 00,   02,   03,   0b0010010111010000 }, /*   29   29   30   29   29   30   29   30   30   30   29   30        354
+1822     */ { 03,   01,   23,   0b1010001011011000 }, /*   30   29   30   29   29   29   30   29   30   30   29   30   30   384
+1823     */ { 00,   02,   11,   0b1010001010110000 }, /*   30   29   30   29   29   29   30   29   30   29   30   30        354
+1824     */ { 07,   01,   31,   0b1010100101011000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30   30   384
+1825     */ { 00,   02,   18,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354
+1826     */ { 00,   02,   07,   0b1011010010100000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29        354
+1827     */ { 05,   01,   27,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30   29   384
+1828     */ { 00,   02,   15,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30        355
+1829     */ { 00,   02,   04,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30        355
+1830     */ { 04,   01,   25,   0b0010010110111000 }, /*   29   29   30   29   29   30   29   30   30   29   30   30   30   384
+1831     */ { 00,   02,   13,   0b0010010101110000 }, /*   29   29   30   29   29   30   29   30   29   30   30   30        354
+1832     */ { 09,   02,   02,   0b0101001010111000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30   30   384
+1833     */ { 00,   02,   20,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354
+1834     */ { 00,   02,   09,   0b0110100101010000 }, /*   29   30   30   29   30   29   29   30   29   30   29   30        354
+1835     */ { 06,   01,   29,   0b0110110010101000 }, /*   29   30   30   29   30   30   29   29   30   29   30   29   30   384
+1836     */ { 00,   02,   17,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354
+1837     */ { 00,   02,   05,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30        355
+1838     */ { 04,   01,   26,   0b0101001101101000 }, /*   29   30   29   30   29   29   30   30   29   30   30   29   30   384
+1839     */ { 00,   02,   14,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354
+1840     */ { 00,   02,   03,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30        355
+1841     */ { 03,   01,   23,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30   29   383
+1842     */ { 00,   02,   10,   0b1101001010100000 }, /*   30   30   29   30   29   29   30   29   30   29   30   29        354
+1843     */ { 07,   01,   30,   0b1110100101010000 }, /*   30   30   30   29   30   29   29   30   29   30   29   30   29   384
+1844     */ { 00,   02,   18,   0b1101010101010000 }, /*   30   30   29   30   29   30   29   30   29   30   29   30        355
+1845     */ { 00,   02,   07,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354
+1846     */ { 05,   01,   27,   0b1010101011010000 }, /*   30   29   30   29   30   29   30   29   30   30   29   30   29   384
+1847     */ { 00,   02,   15,   0b1001010111010000 }, /*   30   29   29   30   29   30   29   30   30   30   29   30        355
+1848     */ { 00,   02,   05,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354
+1849     */ { 04,   01,   24,   0b1010010101011000 }, /*   30   29   30   29   29   30   29   30   29   30   29   30   30   384
+1850     */ { 00,   02,   12,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354
+1851     */ { 08,   02,   01,   0b1101001001011000 }, /*   30   30   29   30   29   29   30   29   29   30   29   30   30   384
+1852     */ { 00,   02,   20,   0b1011001010010000 }, /*   30   29   30   30   29   29   30   29   30   29   29   30        354
+1853     */ { 00,   02,   08,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30        355
+1854     */ { 07,   01,   29,   0b0101011010101000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29   30   384
+1855     */ { 00,   02,   17,   0b0010110110100000 }, /*   29   29   30   29   30   30   29   30   30   29   30   29        354
+1856     */ { 00,   02,   06,   0b1001010111010000 }, /*   30   29   29   30   29   30   29   30   30   30   29   30        355
+1857     */ { 05,   01,   26,   0b0100101010111000 }, /*   29   30   29   29   30   29   30   29   30   29   30   30   30   384
+1858     */ { 00,   02,   14,   0b0100100110110000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30        354
+1859     */ { 00,   02,   03,   0b1010010010110000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30        354
+1860     */ { 03,   01,   23,   0b1011001001011000 }, /*   30   29   30   30   29   29   30   29   29   30   29   30   30   384
+1861     */ { 00,   02,   10,   0b0110101010010000 }, /*   29   30   30   29   30   29   30   29   30   29   29   30        354
+1862     */ { 08,   01,   30,   0b1010110101001000 }, /*   30   29   30   29   30   30   29   30   29   30   29   29   30   384
+1863     */ { 00,   02,   18,   0b0110101101010000 }, /*   29   30   30   29   30   29   30   30   29   30   29   30        355
+1864     */ { 00,   02,   08,   0b0010101101100000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29        354
+1865     */ { 05,   01,   27,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30   29   384
+1866     */ { 00,   02,   15,   0b1001001101110000 }, /*   30   29   29   30   29   29   30   30   29   30   30   30        355
+1867     */ { 00,   02,   05,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30        354
+1868     */ { 04,   01,   25,   0b0110010010110000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30   29   383
+1869     */ { 00,   02,   11,   0b1110010010100000 }, /*   30   30   30   29   29   30   29   29   30   29   30   29        354
+1870     */ { 10,   01,   31,   0b1110101001010000 }, /*   30   30   30   29   30   29   30   29   29   30   29   30   29   384
+1871     */ { 00,   02,   19,   0b1101101010010000 }, /*   30   30   29   30   30   29   30   29   30   29   29   30        355
+1872     */ { 00,   02,   09,   0b0101101011010000 }, /*   29   30   29   30   30   29   30   29   30   30   29   30        355
+1873     */ { 06,   01,   29,   0b0010101101101000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29   30   384
+1874     */ { 00,   02,   17,   0b0010101011100000 }, /*   29   29   30   29   30   29   30   29   30   30   30   29        354
+1875     */ { 00,   02,   06,   0b1001001011100000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29        354
+1876     */ { 05,   01,   26,   0b1100100101101000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29   30   384
+1877     */ { 00,   02,   13,   0b1100100101010000 }, /*   30   30   29   29   30   29   29   30   29   30   29   30        354
+1878     */ { 00,   02,   02,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354
+1879     */ { 03,   01,   22,   0b1101101001010000 }, /*   30   30   29   30   30   29   30   29   29   30   29   30   29   384
+1880     */ { 00,   02,   10,   0b1011011010010000 }, /*   30   29   30   30   29   30   30   29   30   29   29   30        355
+1881     */ { 07,   01,   30,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30   29   384
+1882     */ { 00,   02,   18,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30        355
+1883     */ { 00,   02,   08,   0b0010010111010000 }, /*   29   29   30   29   29   30   29   30   30   30   29   30        354
+1884     */ { 05,   01,   28,   0b1001001011011000 }, /*   30   29   29   30   29   29   30   29   30   30   29   30   30   384
+1885     */ { 00,   02,   15,   0b1001001010110000 }, /*   30   29   29   30   29   29   30   29   30   29   30   30        354
+1886     */ { 00,   02,   04,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354
+1887     */ { 04,   01,   24,   0b1101010010101000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29   30   384
+1888     */ { 00,   02,   12,   0b1011010010100000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29        354
+1889     */ { 00,   01,   31,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30        355
+1890     */ { 02,   01,   21,   0b0101011010101000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29   30   384
+1891     */ { 00,   02,   09,   0b0101010110110000 }, /*   29   30   29   30   29   30   29   30   30   29   30   30        355
+1892     */ { 06,   01,   30,   0b0010010110111000 }, /*   29   29   30   29   29   30   29   30   30   29   30   30   30   384
+1893     */ { 00,   02,   17,   0b0010010101110000 }, /*   29   29   30   29   29   30   29   30   29   30   30   30        354
+1894     */ { 00,   02,   06,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354
+1895     */ { 05,   01,   26,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30   29   383
+1896     */ { 00,   02,   13,   0b1110100101010000 }, /*   30   30   30   29   30   29   29   30   29   30   29   30        355
+1897     */ { 00,   02,   02,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354
+1898     */ { 03,   01,   22,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30   29   384
+1899     */ { 00,   02,   10,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30        355
+1900     */ { 08,   01,   31,   0b0100101101101000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29   30   384
+1901     */ { 00,   02,   19,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354
+1902     */ { 00,   02,   08,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30        355
+1903     */ { 05,   01,   29,   0b0101001001101000 }, /*   29   30   29   30   29   29   30   29   29   30   30   29   30   383
+1904     */ { 00,   02,   16,   0b1101001001100000 }, /*   30   30   29   30   29   29   30   29   29   30   30   29        354
+1905     */ { 00,   02,   04,   0b1101100101010000 }, /*   30   30   29   30   30   29   29   30   29   30   29   30        355
+1906     */ { 04,   01,   25,   0b0110101010101000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29   30   384
+1907     */ { 00,   02,   13,   0b0101011010100000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29        354
+1908     */ { 00,   02,   02,   0b1001101011010000 }, /*   30   29   29   30   30   29   30   29   30   30   29   30        355
+1909     */ { 02,   01,   22,   0b0100101011101000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29   30   384
+1910     */ { 00,   02,   10,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354
+1911     */ { 06,   01,   30,   0b1010010011011000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30   30   384
+1912     */ { 00,   02,   18,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354
+1913     */ { 00,   02,   06,   0b1101001001010000 }, /*   30   30   29   30   29   29   30   29   29   30   29   30        354
+1914     */ { 05,   01,   26,   0b1101100101001000 }, /*   30   30   29   30   30   29   29   30   29   30   29   29   30   384
+1915     */ { 00,   02,   14,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30        355
+1916     */ { 00,   02,   04,   0b0101011010100000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29        354
+1917     */ { 02,   01,   23,   0b1001011011010000 }, /*   30   29   29   30   29   30   30   29   30   30   29   30   29   384
+1918     */ { 00,   02,   11,   0b1001010111010000 }, /*   30   29   29   30   29   30   29   30   30   30   29   30        355
+1919     */ { 07,   02,   01,   0b0100101011011000 }, /*   29   30   29   29   30   29   30   29   30   30   29   30   30   384
+1920     */ { 00,   02,   20,   0b0100100110110000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30        354
+1921     */ { 00,   02,   08,   0b1010010010110000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30        354
+1922     */ { 05,   01,   28,   0b1011001001011000 }, /*   30   29   30   30   29   29   30   29   29   30   29   30   30   384
+1923     */ { 00,   02,   16,   0b0110101010010000 }, /*   29   30   30   29   30   29   30   29   30   29   29   30        354
+1924     */ { 00,   02,   05,   0b1010110101000000 }, /*   30   29   30   29   30   30   29   30   29   30   29   29        354
+1925     */ { 04,   01,   24,   0b1011010110101000 }, /*   30   29   30   30   29   30   29   30   30   29   30   29   30   385
+1926     */ { 00,   02,   13,   0b0010101101100000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29        354
+1927     */ { 00,   02,   02,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30        355
+1928     */ { 02,   01,   23,   0b0100100110111000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30   30   384
+1929     */ { 00,   02,   10,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30        354
+1930     */ { 06,   01,   30,   0b0110010010110000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30   29   383
+1931     */ { 00,   02,   17,   0b1110010010100000 }, /*   30   30   30   29   29   30   29   29   30   29   30   29        354
+1932     */ { 00,   02,   06,   0b1110101001010000 }, /*   30   30   30   29   30   29   30   29   29   30   29   30        355
+1933     */ { 05,   01,   26,   0b0110110101001000 }, /*   29   30   30   29   30   30   29   30   29   30   29   29   30   384
+1934     */ { 00,   02,   14,   0b0101101101010000 }, /*   29   30   29   30   30   29   30   30   29   30   29   30        355
+1935     */ { 00,   02,   04,   0b0010101101100000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29        354
+1936     */ { 03,   01,   24,   0b1001010101110000 }, /*   30   29   29   30   29   30   29   30   29   30   30   30   29   384
+1937     */ { 00,   02,   11,   0b1001001011100000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29        354
+1938     */ { 07,   01,   31,   0b1100100101101000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29   30   384
+1939     */ { 00,   02,   19,   0b1100100101010000 }, /*   30   30   29   29   30   29   29   30   29   30   29   30        354
+1940     */ { 00,   02,   08,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354
+1941     */ { 06,   01,   27,   0b1101101001010000 }, /*   30   30   29   30   30   29   30   29   29   30   29   30   29   384
+1942     */ { 00,   02,   15,   0b1011011010010000 }, /*   30   29   30   30   29   30   30   29   30   29   29   30        355
+1943     */ { 00,   02,   05,   0b0101011011010000 }, /*   29   30   29   30   29   30   30   29   30   30   29   30        355
+1944     */ { 04,   01,   26,   0b0010101011011000 }, /*   29   29   30   29   30   29   30   29   30   30   29   30   30   384
+1945     */ { 00,   02,   13,   0b0010010111010000 }, /*   29   29   30   29   29   30   29   30   30   30   29   30        354
+1946     */ { 00,   02,   02,   0b1001001011010000 }, /*   30   29   29   30   29   29   30   29   30   30   29   30        354
+1947     */ { 02,   01,   22,   0b1100100101011000 }, /*   30   30   29   29   30   29   29   30   29   30   29   30   30   384
+1948     */ { 00,   02,   10,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354
+1949     */ { 07,   01,   29,   0b1101010010101000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29   30   384
+1950     */ { 00,   02,   17,   0b1011010010100000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29        354
+1951     */ { 00,   02,   06,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30        355
+1952     */ { 05,   01,   27,   0b0101011010101000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29   30   384
+1953     */ { 00,   02,   14,   0b0100110110110000 }, /*   29   30   29   29   30   30   29   30   30   29   30   30        355
+1954     */ { 00,   02,   04,   0b0010010110110000 }, /*   29   29   30   29   29   30   29   30   30   29   30   30        354
+1955     */ { 03,   01,   24,   0b1001001010111000 }, /*   30   29   29   30   29   29   30   29   30   29   30   30   30   384
+1956     */ { 00,   02,   12,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354
+1957     */ { 08,   01,   31,   0b1010100101011000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30   30   384
+1958     */ { 00,   02,   19,   0b0110100101010000 }, /*   29   30   30   29   30   29   29   30   29   30   29   30        354
+1959     */ { 00,   02,   08,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354
+1960     */ { 06,   01,   28,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30   29   384
+1961     */ { 00,   02,   15,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30        355
+1962     */ { 00,   02,   05,   0b0100101101100000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29        354
+1963     */ { 04,   01,   25,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30   29   384
+1964     */ { 00,   02,   13,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30        355
+1965     */ { 00,   02,   02,   0b0101001001110000 }, /*   29   30   29   30   29   29   30   29   29   30   30   30        354
+1966     */ { 03,   01,   22,   0b0110100100110000 }, /*   29   30   30   29   30   29   29   30   29   29   30   30   29   383
+1967     */ { 00,   02,   09,   0b1101100101010000 }, /*   30   30   29   30   30   29   29   30   29   30   29   30        355
+1968     */ { 07,   01,   30,   0b0110101010101000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29   30   384
+1969     */ { 00,   02,   17,   0b0101011010100000 }, /*   29   30   29   30   29   30   30   29   30   29   30   29        354
+1970     */ { 00,   02,   06,   0b1001101011010000 }, /*   30   29   29   30   30   29   30   29   30   30   29   30        355
+1971     */ { 05,   01,   27,   0b0100101011101000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29   30   384
+1972     */ { 00,   02,   15,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354
+1973     */ { 00,   02,   03,   0b1010010011100000 }, /*   30   29   30   29   29   30   29   29   30   30   30   29        354
+1974     */ { 04,   01,   23,   0b1101001001101000 }, /*   30   30   29   30   29   29   30   29   29   30   30   29   30   384
+1975     */ { 00,   02,   11,   0b1101001001010000 }, /*   30   30   29   30   29   29   30   29   29   30   29   30        354
+1976     */ { 08,   01,   31,   0b1101010101001000 }, /*   30   30   29   30   29   30   29   30   29   30   29   29   30   384
+1977     */ { 00,   02,   18,   0b1011010101000000 }, /*   30   29   30   30   29   30   29   30   29   30   29   29        354
+1978     */ { 00,   02,   07,   0b1101011010100000 }, /*   30   30   29   30   29   30   30   29   30   29   30   29        355
+1979     */ { 06,   01,   28,   0b1001011011010000 }, /*   30   29   29   30   29   30   30   29   30   30   29   30   29   384
+1980     */ { 00,   02,   16,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30        355
+1981     */ { 00,   02,   05,   0b0100100110110000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30        354
+1982     */ { 04,   01,   25,   0b1010010011011000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30   30   384
+1983     */ { 00,   02,   13,   0b1010010010110000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30        354
+1984     */ { 10,   02,   02,   0b1011001001011000 }, /*   30   29   30   30   29   29   30   29   29   30   29   30   30   384
+1985     */ { 00,   02,   20,   0b0110101001010000 }, /*   29   30   30   29   30   29   30   29   29   30   29   30        354
+1986     */ { 00,   02,   09,   0b0110110101000000 }, /*   29   30   30   29   30   30   29   30   29   30   29   29        354
+1987     */ { 06,   01,   29,   0b1011010110101000 }, /*   30   29   30   30   29   30   29   30   30   29   30   29   30   385
+1988     */ { 00,   02,   18,   0b0010101101100000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29        354
+1989     */ { 00,   02,   06,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30        355
+1990     */ { 05,   01,   27,   0b0100100110111000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30   30   384
+1991     */ { 00,   02,   15,   0b0100100101110000 }, /*   29   30   29   29   30   29   29   30   29   30   30   30        354
+1992     */ { 00,   02,   04,   0b0110010010110000 }, /*   29   30   30   29   29   30   29   29   30   29   30   30        354
+1993     */ { 03,   01,   23,   0b0110101001010000 }, /*   29   30   30   29   30   29   30   29   29   30   29   30   29   383
+1994     */ { 00,   02,   10,   0b1110101001010000 }, /*   30   30   30   29   30   29   30   29   29   30   29   30        355
+1995     */ { 08,   01,   31,   0b0110110101001000 }, /*   29   30   30   29   30   30   29   30   29   30   29   29   30   384
+1996     */ { 00,   02,   19,   0b0101101011010000 }, /*   29   30   29   30   30   29   30   29   30   30   29   30        355
+1997     */ { 00,   02,   08,   0b0010101101100000 }, /*   29   29   30   29   30   29   30   30   29   30   30   29        354
+1998     */ { 05,   01,   28,   0b1001001101110000 }, /*   30   29   29   30   29   29   30   30   29   30   30   30   29   384
+1999     */ { 00,   02,   16,   0b1001001011100000 }, /*   30   29   29   30   29   29   30   29   30   30   30   29        354
+2000     */ { 00,   02,   05,   0b1100100101100000 }, /*   30   30   29   29   30   29   29   30   29   30   30   29        354
+2001     */ { 04,   01,   24,   0b1110010010101000 }, /*   30   30   30   29   29   30   29   29   30   29   30   29   30   384
+2002     */ { 00,   02,   12,   0b1101010010100000 }, /*   30   30   29   30   29   30   29   29   30   29   30   29        354
+2003     */ { 00,   02,   01,   0b1101101001010000 }, /*   30   30   29   30   30   29   30   29   29   30   29   30        355
+2004     */ { 02,   01,   22,   0b0101101010101000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29   30   384
+2005     */ { 00,   02,   09,   0b0101011011000000 }, /*   29   30   29   30   29   30   30   29   30   30   29   29        354
+2006     */ { 07,   01,   29,   0b1010101011011000 }, /*   30   29   30   29   30   29   30   29   30   30   29   30   30   385
+2007     */ { 00,   02,   18,   0b0010010111010000 }, /*   29   29   30   29   29   30   29   30   30   30   29   30        354
+2008     */ { 00,   02,   07,   0b1001001011010000 }, /*   30   29   29   30   29   29   30   29   30   30   29   30        354
+2009     */ { 05,   01,   26,   0b1100100101011000 }, /*   30   30   29   29   30   29   29   30   29   30   29   30   30   384
+2010     */ { 00,   02,   14,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354
+2011     */ { 00,   02,   03,   0b1011010010100000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29        354
+2012     */ { 03,   01,   23,   0b1011101001010000 }, /*   30   29   30   30   30   29   30   29   29   30   29   30   29   384
+2013     */ { 00,   02,   10,   0b1011010101010000 }, /*   30   29   30   30   29   30   29   30   29   30   29   30        355
+2014     */ { 09,   01,   31,   0b0101010110101000 }, /*   29   30   29   30   29   30   29   30   30   29   30   29   30   384
+2015     */ { 00,   02,   19,   0b0100101110100000 }, /*   29   30   29   29   30   29   30   30   30   29   30   29        354
+2016     */ { 00,   02,   08,   0b1010010110110000 }, /*   30   29   30   29   29   30   29   30   30   29   30   30        355
+2017     */ { 05,   01,   28,   0b0101001010111000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30   30   384
+2018     */ { 00,   02,   16,   0b0101001010110000 }, /*   29   30   29   30   29   29   30   29   30   29   30   30        354
+2019     */ { 00,   02,   05,   0b1010100101010000 }, /*   30   29   30   29   30   29   29   30   29   30   29   30        354
+2020     */ { 04,   01,   25,   0b1011010010101000 }, /*   30   29   30   30   29   30   29   29   30   29   30   29   30   384
+2021     */ { 00,   02,   12,   0b0110101010100000 }, /*   29   30   30   29   30   29   30   29   30   29   30   29        354
+2022     */ { 00,   02,   01,   0b1010110101010000 }, /*   30   29   30   29   30   30   29   30   29   30   29   30        355
+2023     */ { 02,   01,   22,   0b0101010110101000 }, /*   29   30   29   30   29   30   29   30   30   29   30   29   30   384
+2024     */ { 00,   02,   10,   0b0100101101100000 }, /*   29   30   29   29   30   29   30   30   29   30   30   29        354
+2025     */ { 06,   01,   29,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30   29   384
+2026     */ { 00,   02,   17,   0b1010010101110000 }, /*   30   29   30   29   29   30   29   30   29   30   30   30        355
+2027     */ { 00,   02,   07,   0b0101001001110000 }, /*   29   30   29   30   29   29   30   29   29   30   30   30        354
+2028     */ { 05,   01,   27,   0b0110100100110000 }, /*   29   30   30   29   30   29   29   30   29   29   30   30   29   383
+2029     */ { 00,   02,   13,   0b1101100100110000 }, /*   30   30   29   30   30   29   29   30   29   29   30   30        355
+2030     */ { 00,   02,   03,   0b0101101010100000 }, /*   29   30   29   30   30   29   30   29   30   29   30   29        354
+2031     */ { 03,   01,   23,   0b1010101101010000 }, /*   30   29   30   29   30   29   30   30   29   30   29   30   29   384
+2032     */ { 00,   02,   11,   0b1001011011010000 }, /*   30   29   29   30   29   30   30   29   30   30   29   30        355
+2033     */ { 11,   01,   31,   0b0100101011101000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29   30   384
+2034     */ { 00,   02,   19,   0b0100101011100000 }, /*   29   30   29   29   30   29   30   29   30   30   30   29        354
+2035     */ { 00,   02,   08,   0b1010010011010000 }, /*   30   29   30   29   29   30   29   29   30   30   29   30        354
+2036     */ { 06,   01,   28,   0b1101001001101000 }, /*   30   30   29   30   29   29   30   29   29   30   30   29   30   384
+2037     */ { 00,   02,   15,   0b1101001001010000 }, /*   30   30   29   30   29   29   30   29   29   30   29   30        354
+2038     */ { 00,   02,   04,   0b1101010100100000 }, /*   30   30   29   30   29   30   29   30   29   29   30   29        354
+2039     */ { 05,   01,   24,   0b1101101010100000 }, /*   30   30   29   30   30   29   30   29   30   29   30   29   29   384
+2040     */ { 00,   02,   12,   0b1011011010100000 }, /*   30   29   30   30   29   30   30   29   30   29   30   29        355
+2041     */ { 00,   02,   01,   0b1001011011010000 }, /*   30   29   29   30   29   30   30   29   30   30   29   30        355
+2042     */ { 02,   01,   22,   0b0100101011011000 }, /*   29   30   29   29   30   29   30   29   30   30   29   30   30   384
+2043     */ { 00,   02,   10,   0b0100100110110000 }, /*   29   30   29   29   30   29   29   30   30   29   30   30        354
+2044     */ { 07,   01,   30,   0b1010010010111000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30   30   384
+2045     */ { 00,   02,   17,   0b1010010010110000 }, /*   30   29   30   29   29   30   29   29   30   29   30   30        354
+2046     */ { 00,   02,   06,   0b1011001001010000 }, /*   30   29   30   30   29   29   30   29   29   30   29   30        354
+2047     */ { 05,   01,   26,   0b1011010100101000 }, /*   30   29   30   30   29   30   29   30   29   29   30   29   30   384
+2048     */ { 00,   02,   14,   0b0110110101000000 }, /*   29   30   30   29   30   30   29   30   29   30   29   29        354
+2049     */ { 00,   02,   02,   0b1010110110100000 }, /*   30   29   30   29   30   30   29   30   30   29   30   29        355
+2050     */ { 03,   01,   23,   0b1001010110110000 }, /*   30   29   29   30   29   30   29   30   30   29   30   30   29   384
+         */ };
+
+        internal override int MinCalendarYear
+        {
+            get
+            {
+                return (MIN_LUNISOLAR_YEAR);
+            }
+        }
+
+        internal override int MaxCalendarYear
+        {
+            get
+            {
+                return (MAX_LUNISOLAR_YEAR);
+            }
+        }
+
+        internal override DateTime MinDate
+        {
+            get
+            {
+                return (minDate);
+            }
+        }
+
+        internal override DateTime MaxDate
+        {
+            get
+            {
+                return (maxDate);
+            }
+        }
+
+        internal override EraInfo[] CalEraInfo
+        {
+            get
+            {
+                return null;
+            }
+        }
+
+        internal override int GetYearInfo(int lunarYear, int index)
+        {
+            if ((lunarYear < MIN_LUNISOLAR_YEAR) || (lunarYear > MAX_LUNISOLAR_YEAR))
+            {
+                throw new ArgumentOutOfRangeException(
+                            "year",
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                MIN_LUNISOLAR_YEAR,
+                                MAX_LUNISOLAR_YEAR));
+            }
+            return s_yinfo[lunarYear - MIN_LUNISOLAR_YEAR, index];
+        }
+
+        internal override int GetYear(int year, DateTime time)
+        {
+            return year;
+        }
+
+        internal override int GetGregorianYear(int year, int era)
+        {
+            if (era != CurrentEra && era != GregorianEra)
+                throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+
+            if (year < MIN_LUNISOLAR_YEAR || year > MAX_LUNISOLAR_YEAR)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range, MIN_LUNISOLAR_YEAR, MAX_LUNISOLAR_YEAR));
+            }
+
+            return year;
+        }
+
+        public KoreanLunisolarCalendar()
+        {
+        }
+
+        public override int GetEra(DateTime time)
+        {
+            CheckTicksRange(time.Ticks);
+            return (GregorianEra);
+        }
+
+        internal override CalendarId BaseCalendarID
+        {
+            get
+            {
+                return (CalendarId.KOREA);
+            }
+        }
+
+        internal override CalendarId ID
+        {
+            get
+            {
+                return (CalendarId.KOREANLUNISOLAR);
+            }
+        }
+
+        public override int[] Eras
+        {
+            get
+            {
+                return (new int[] { GregorianEra });
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/LocaleData.Unix.cs b/src/System.Private.CoreLib/shared/System/Globalization/LocaleData.Unix.cs
new file mode 100644
index 0000000000..ccf1078ac6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/LocaleData.Unix.cs
@@ -0,0 +1,4571 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+// This file contains the handling of Windows OS specific culture features.  
+
+namespace System.Globalization
+{
+    internal enum LocaleDataParts
+    {
+        Lcid = 0,
+        AnsiCodePage = 1,
+        OemCodePage = 2,
+        MacCodePage = 3,
+        EbcdicCodePage = 4,
+        GeoId = 5, 
+        DigitSubstitution = 6, 
+        SpecificLocaleIndex = 7, 
+        ConsoleLocaleIndex = 8
+    }
+    
+    internal partial class LocaleData
+    {
+        // this is done rather than using a large readonly array of strings to avoid
+        // generating a large amount of code in the static constructor.
+        // Using indices from s_localeNamesIndices, we binary search this string when mapping
+        // an culture name to Lcid. Note that these names are all lowercase and are
+        // sorted alphabetically (ordinal).
+        private const string c_localeNames =
+        //  culture name                    Lcid
+            "aa"                      + //  01000 - 0
+            "aa-dj"                   + //  01000 - 2
+            "aa-er"                   + //  01000 - 7
+            "aa-et"                   + //  01000 - 12
+            "af"                      + //  00036 - 17
+            "af-na"                   + //  01000 - 19
+            "af-za"                   + //  00436 - 24
+            "agq"                     + //  01000 - 29
+            "agq-cm"                  + //  01000 - 32
+            "ak"                      + //  01000 - 38
+            "ak-gh"                   + //  01000 - 40
+            "am"                      + //  0005e - 45
+            "am-et"                   + //  0045e - 47
+            "ar"                      + //  00001 - 52
+            "ar-001"                  + //  01000 - 54
+            "ar-ae"                   + //  03801 - 60
+            "ar-bh"                   + //  03c01 - 65
+            "ar-dj"                   + //  01000 - 70
+            "ar-dz"                   + //  01401 - 75
+            "ar-eg"                   + //  00c01 - 80
+            "ar-er"                   + //  01000 - 85
+            "ar-il"                   + //  01000 - 90
+            "ar-iq"                   + //  00801 - 95
+            "ar-jo"                   + //  02c01 - 100
+            "ar-km"                   + //  01000 - 105
+            "ar-kw"                   + //  03401 - 110
+            "ar-lb"                   + //  03001 - 115
+            "ar-ly"                   + //  01001 - 120
+            "ar-ma"                   + //  01801 - 125
+            "ar-mr"                   + //  01000 - 130
+            "ar-om"                   + //  02001 - 135
+            "ar-ps"                   + //  01000 - 140
+            "ar-qa"                   + //  04001 - 145
+            "ar-sa"                   + //  00401 - 150
+            "ar-sd"                   + //  01000 - 155
+            "ar-so"                   + //  01000 - 160
+            "ar-ss"                   + //  01000 - 165
+            "ar-sy"                   + //  02801 - 170
+            "ar-td"                   + //  01000 - 175
+            "ar-tn"                   + //  01c01 - 180
+            "ar-ye"                   + //  02401 - 185
+            "arn"                     + //  0007a - 190
+            "arn-cl"                  + //  0047a - 193
+            "as"                      + //  0004d - 199
+            "as-in"                   + //  0044d - 201
+            "asa"                     + //  01000 - 206
+            "asa-tz"                  + //  01000 - 209
+            "ast"                     + //  01000 - 215
+            "ast-es"                  + //  01000 - 218
+            "az"                      + //  0002c - 224
+            "az-cyrl"                 + //  0742c - 226
+            "az-cyrl-az"              + //  0082c - 233
+            "az-latn"                 + //  0782c - 243
+            "az-latn-az"              + //  0042c - 250
+            "ba"                      + //  0006d - 260
+            "ba-ru"                   + //  0046d - 262
+            "bas"                     + //  01000 - 267
+            "bas-cm"                  + //  01000 - 270
+            "be"                      + //  00023 - 276
+            "be-by"                   + //  00423 - 278
+            "bem"                     + //  01000 - 283
+            "bem-zm"                  + //  01000 - 286
+            "bez"                     + //  01000 - 292
+            "bez-tz"                  + //  01000 - 295
+            "bg"                      + //  00002 - 301
+            "bg-bg"                   + //  00402 - 303
+            "bin"                     + //  00066 - 308
+            "bin-ng"                  + //  00466 - 311
+            "bm"                      + //  01000 - 317
+            "bm-latn"                 + //  01000 - 319
+            "bm-latn-ml"              + //  01000 - 326
+            "bn"                      + //  00045 - 336
+            "bn-bd"                   + //  00845 - 338
+            "bn-in"                   + //  00445 - 343
+            "bo"                      + //  00051 - 348
+            "bo-cn"                   + //  00451 - 350
+            "bo-in"                   + //  01000 - 355
+            "br"                      + //  0007e - 360
+            "br-fr"                   + //  0047e - 362
+            "brx"                     + //  01000 - 367
+            "brx-in"                  + //  01000 - 370
+            "bs"                      + //  0781a - 376
+            "bs-cyrl"                 + //  0641a - 378
+            "bs-cyrl-ba"              + //  0201a - 385
+            "bs-latn"                 + //  0681a - 395
+            "bs-latn-ba"              + //  0141a - 402
+            "byn"                     + //  01000 - 412
+            "byn-er"                  + //  01000 - 415
+            "ca"                      + //  00003 - 421
+            "ca-ad"                   + //  01000 - 423
+            "ca-es"                   + //  00403 - 428
+            "ca-es-valencia"          + //  00803 - 433
+            "ca-fr"                   + //  01000 - 447
+            "ca-it"                   + //  01000 - 452
+            "ce"                      + //  01000 - 457
+            "ce-ru"                   + //  01000 - 459
+            "cgg"                     + //  01000 - 464
+            "cgg-ug"                  + //  01000 - 467
+            "chr"                     + //  0005c - 473
+            "chr-cher"                + //  07c5c - 476
+            "chr-cher-us"             + //  0045c - 484
+            "co"                      + //  00083 - 495
+            "co-fr"                   + //  00483 - 497
+            "cs"                      + //  00005 - 502
+            "cs-cz"                   + //  00405 - 504
+            "cu"                      + //  01000 - 509
+            "cu-ru"                   + //  01000 - 511
+            "cy"                      + //  00052 - 516
+            "cy-gb"                   + //  00452 - 518
+            "da"                      + //  00006 - 523
+            "da-dk"                   + //  00406 - 525
+            "da-gl"                   + //  01000 - 530
+            "dav"                     + //  01000 - 535
+            "dav-ke"                  + //  01000 - 538
+            "de"                      + //  00007 - 544
+            "de-at"                   + //  00c07 - 546
+            "de-be"                   + //  01000 - 551
+            "de-ch"                   + //  00807 - 556
+            "de-de"                   + //  00407 - 561
+            "de-de_phoneb"            + //  10407 - 566
+            "de-it"                   + //  01000 - 578
+            "de-li"                   + //  01407 - 583
+            "de-lu"                   + //  01007 - 588
+            "dje"                     + //  01000 - 593
+            "dje-ne"                  + //  01000 - 596
+            "dsb"                     + //  07c2e - 602
+            "dsb-de"                  + //  0082e - 605
+            "dua"                     + //  01000 - 611
+            "dua-cm"                  + //  01000 - 614
+            "dv"                      + //  00065 - 620
+            "dv-mv"                   + //  00465 - 622
+            "dyo"                     + //  01000 - 627
+            "dyo-sn"                  + //  01000 - 630
+            "dz"                      + //  01000 - 636
+            "dz-bt"                   + //  00c51 - 638
+            "ebu"                     + //  01000 - 643
+            "ebu-ke"                  + //  01000 - 646
+            "ee"                      + //  01000 - 652
+            "ee-gh"                   + //  01000 - 654
+            "ee-tg"                   + //  01000 - 659
+            "el"                      + //  00008 - 664
+            "el-cy"                   + //  01000 - 666
+            "el-gr"                   + //  00408 - 671
+            "en"                      + //  00009 - 676
+            "en-001"                  + //  01000 - 678
+            "en-029"                  + //  02409 - 684
+            "en-150"                  + //  01000 - 690
+            "en-ag"                   + //  01000 - 696
+            "en-ai"                   + //  01000 - 701
+            "en-as"                   + //  01000 - 706
+            "en-at"                   + //  01000 - 711
+            "en-au"                   + //  00c09 - 716
+            "en-bb"                   + //  01000 - 721
+            "en-be"                   + //  01000 - 726
+            "en-bi"                   + //  01000 - 731
+            "en-bm"                   + //  01000 - 736
+            "en-bs"                   + //  01000 - 741
+            "en-bw"                   + //  01000 - 746
+            "en-bz"                   + //  02809 - 751
+            "en-ca"                   + //  01009 - 756
+            "en-cc"                   + //  01000 - 761
+            "en-ch"                   + //  01000 - 766
+            "en-ck"                   + //  01000 - 771
+            "en-cm"                   + //  01000 - 776
+            "en-cx"                   + //  01000 - 781
+            "en-cy"                   + //  01000 - 786
+            "en-de"                   + //  01000 - 791
+            "en-dk"                   + //  01000 - 796
+            "en-dm"                   + //  01000 - 801
+            "en-er"                   + //  01000 - 806
+            "en-fi"                   + //  01000 - 811
+            "en-fj"                   + //  01000 - 816
+            "en-fk"                   + //  01000 - 821
+            "en-fm"                   + //  01000 - 826
+            "en-gb"                   + //  00809 - 831
+            "en-gd"                   + //  01000 - 836
+            "en-gg"                   + //  01000 - 841
+            "en-gh"                   + //  01000 - 846
+            "en-gi"                   + //  01000 - 851
+            "en-gm"                   + //  01000 - 856
+            "en-gu"                   + //  01000 - 861
+            "en-gy"                   + //  01000 - 866
+            "en-hk"                   + //  03c09 - 871
+            "en-id"                   + //  03809 - 876
+            "en-ie"                   + //  01809 - 881
+            "en-il"                   + //  01000 - 886
+            "en-im"                   + //  01000 - 891
+            "en-in"                   + //  04009 - 896
+            "en-io"                   + //  01000 - 901
+            "en-je"                   + //  01000 - 906
+            "en-jm"                   + //  02009 - 911
+            "en-ke"                   + //  01000 - 916
+            "en-ki"                   + //  01000 - 921
+            "en-kn"                   + //  01000 - 926
+            "en-ky"                   + //  01000 - 931
+            "en-lc"                   + //  01000 - 936
+            "en-lr"                   + //  01000 - 941
+            "en-ls"                   + //  01000 - 946
+            "en-mg"                   + //  01000 - 951
+            "en-mh"                   + //  01000 - 956
+            "en-mo"                   + //  01000 - 961
+            "en-mp"                   + //  01000 - 966
+            "en-ms"                   + //  01000 - 971
+            "en-mt"                   + //  01000 - 976
+            "en-mu"                   + //  01000 - 981
+            "en-mw"                   + //  01000 - 986
+            "en-my"                   + //  04409 - 991
+            "en-na"                   + //  01000 - 996
+            "en-nf"                   + //  01000 - 1001
+            "en-ng"                   + //  01000 - 1006
+            "en-nl"                   + //  01000 - 1011
+            "en-nr"                   + //  01000 - 1016
+            "en-nu"                   + //  01000 - 1021
+            "en-nz"                   + //  01409 - 1026
+            "en-pg"                   + //  01000 - 1031
+            "en-ph"                   + //  03409 - 1036
+            "en-pk"                   + //  01000 - 1041
+            "en-pn"                   + //  01000 - 1046
+            "en-pr"                   + //  01000 - 1051
+            "en-pw"                   + //  01000 - 1056
+            "en-rw"                   + //  01000 - 1061
+            "en-sb"                   + //  01000 - 1066
+            "en-sc"                   + //  01000 - 1071
+            "en-sd"                   + //  01000 - 1076
+            "en-se"                   + //  01000 - 1081
+            "en-sg"                   + //  04809 - 1086
+            "en-sh"                   + //  01000 - 1091
+            "en-si"                   + //  01000 - 1096
+            "en-sl"                   + //  01000 - 1101
+            "en-ss"                   + //  01000 - 1106
+            "en-sx"                   + //  01000 - 1111
+            "en-sz"                   + //  01000 - 1116
+            "en-tc"                   + //  01000 - 1121
+            "en-tk"                   + //  01000 - 1126
+            "en-to"                   + //  01000 - 1131
+            "en-tt"                   + //  02c09 - 1136
+            "en-tv"                   + //  01000 - 1141
+            "en-tz"                   + //  01000 - 1146
+            "en-ug"                   + //  01000 - 1151
+            "en-um"                   + //  01000 - 1156
+            "en-us"                   + //  00409 - 1161
+            "en-vc"                   + //  01000 - 1166
+            "en-vg"                   + //  01000 - 1171
+            "en-vi"                   + //  01000 - 1176
+            "en-vu"                   + //  01000 - 1181
+            "en-ws"                   + //  01000 - 1186
+            "en-za"                   + //  01c09 - 1191
+            "en-zm"                   + //  01000 - 1196
+            "en-zw"                   + //  03009 - 1201
+            "eo"                      + //  01000 - 1206
+            "eo-001"                  + //  01000 - 1208
+            "es"                      + //  0000a - 1214
+            "es-419"                  + //  0580a - 1216
+            "es-ar"                   + //  02c0a - 1222
+            "es-bo"                   + //  0400a - 1227
+            "es-br"                   + //  01000 - 1232
+            "es-cl"                   + //  0340a - 1237
+            "es-co"                   + //  0240a - 1242
+            "es-cr"                   + //  0140a - 1247
+            "es-cu"                   + //  05c0a - 1252
+            "es-do"                   + //  01c0a - 1257
+            "es-ec"                   + //  0300a - 1262
+            "es-es"                   + //  00c0a - 1267
+            "es-es_tradnl"            + //  0040a - 1272
+            "es-gq"                   + //  01000 - 1284
+            "es-gt"                   + //  0100a - 1289
+            "es-hn"                   + //  0480a - 1294
+            "es-mx"                   + //  0080a - 1299
+            "es-ni"                   + //  04c0a - 1304
+            "es-pa"                   + //  0180a - 1309
+            "es-pe"                   + //  0280a - 1314
+            "es-ph"                   + //  01000 - 1319
+            "es-pr"                   + //  0500a - 1324
+            "es-py"                   + //  03c0a - 1329
+            "es-sv"                   + //  0440a - 1334
+            "es-us"                   + //  0540a - 1339
+            "es-uy"                   + //  0380a - 1344
+            "es-ve"                   + //  0200a - 1349
+            "et"                      + //  00025 - 1354
+            "et-ee"                   + //  00425 - 1356
+            "eu"                      + //  0002d - 1361
+            "eu-es"                   + //  0042d - 1363
+            "ewo"                     + //  01000 - 1368
+            "ewo-cm"                  + //  01000 - 1371
+            "fa"                      + //  00029 - 1377
+            "fa-ir"                   + //  00429 - 1379
+            "ff"                      + //  00067 - 1384
+            "ff-cm"                   + //  01000 - 1386
+            "ff-gn"                   + //  01000 - 1391
+            "ff-latn"                 + //  07c67 - 1396
+            "ff-latn-sn"              + //  00867 - 1403
+            "ff-mr"                   + //  01000 - 1413
+            "ff-ng"                   + //  00467 - 1418
+            "fi"                      + //  0000b - 1423
+            "fi-fi"                   + //  0040b - 1425
+            "fil"                     + //  00064 - 1430
+            "fil-ph"                  + //  00464 - 1433
+            "fo"                      + //  00038 - 1439
+            "fo-dk"                   + //  01000 - 1441
+            "fo-fo"                   + //  00438 - 1446
+            "fr"                      + //  0000c - 1451
+            "fr-029"                  + //  01c0c - 1453
+            "fr-be"                   + //  0080c - 1459
+            "fr-bf"                   + //  01000 - 1464
+            "fr-bi"                   + //  01000 - 1469
+            "fr-bj"                   + //  01000 - 1474
+            "fr-bl"                   + //  01000 - 1479
+            "fr-ca"                   + //  00c0c - 1484
+            "fr-cd"                   + //  0240c - 1489
+            "fr-cf"                   + //  01000 - 1494
+            "fr-cg"                   + //  01000 - 1499
+            "fr-ch"                   + //  0100c - 1504
+            "fr-ci"                   + //  0300c - 1509
+            "fr-cm"                   + //  02c0c - 1514
+            "fr-dj"                   + //  01000 - 1519
+            "fr-dz"                   + //  01000 - 1524
+            "fr-fr"                   + //  0040c - 1529
+            "fr-ga"                   + //  01000 - 1534
+            "fr-gf"                   + //  01000 - 1539
+            "fr-gn"                   + //  01000 - 1544
+            "fr-gp"                   + //  01000 - 1549
+            "fr-gq"                   + //  01000 - 1554
+            "fr-ht"                   + //  03c0c - 1559
+            "fr-km"                   + //  01000 - 1564
+            "fr-lu"                   + //  0140c - 1569
+            "fr-ma"                   + //  0380c - 1574
+            "fr-mc"                   + //  0180c - 1579
+            "fr-mf"                   + //  01000 - 1584
+            "fr-mg"                   + //  01000 - 1589
+            "fr-ml"                   + //  0340c - 1594
+            "fr-mq"                   + //  01000 - 1599
+            "fr-mr"                   + //  01000 - 1604
+            "fr-mu"                   + //  01000 - 1609
+            "fr-nc"                   + //  01000 - 1614
+            "fr-ne"                   + //  01000 - 1619
+            "fr-pf"                   + //  01000 - 1624
+            "fr-pm"                   + //  01000 - 1629
+            "fr-re"                   + //  0200c - 1634
+            "fr-rw"                   + //  01000 - 1639
+            "fr-sc"                   + //  01000 - 1644
+            "fr-sn"                   + //  0280c - 1649
+            "fr-sy"                   + //  01000 - 1654
+            "fr-td"                   + //  01000 - 1659
+            "fr-tg"                   + //  01000 - 1664
+            "fr-tn"                   + //  01000 - 1669
+            "fr-vu"                   + //  01000 - 1674
+            "fr-wf"                   + //  01000 - 1679
+            "fr-yt"                   + //  01000 - 1684
+            "fur"                     + //  01000 - 1689
+            "fur-it"                  + //  01000 - 1692
+            "fy"                      + //  00062 - 1698
+            "fy-nl"                   + //  00462 - 1700
+            "ga"                      + //  0003c - 1705
+            "ga-ie"                   + //  0083c - 1707
+            "gd"                      + //  00091 - 1712
+            "gd-gb"                   + //  00491 - 1714
+            "gl"                      + //  00056 - 1719
+            "gl-es"                   + //  00456 - 1721
+            "gn"                      + //  00074 - 1726
+            "gn-py"                   + //  00474 - 1728
+            "gsw"                     + //  00084 - 1733
+            "gsw-ch"                  + //  01000 - 1736
+            "gsw-fr"                  + //  00484 - 1742
+            "gsw-li"                  + //  01000 - 1748
+            "gu"                      + //  00047 - 1754
+            "gu-in"                   + //  00447 - 1756
+            "guz"                     + //  01000 - 1761
+            "guz-ke"                  + //  01000 - 1764
+            "gv"                      + //  01000 - 1770
+            "gv-im"                   + //  01000 - 1772
+            "ha"                      + //  00068 - 1777
+            "ha-latn"                 + //  07c68 - 1779
+            "ha-latn-gh"              + //  01000 - 1786
+            "ha-latn-ne"              + //  01000 - 1796
+            "ha-latn-ng"              + //  00468 - 1806
+            "haw"                     + //  00075 - 1816
+            "haw-us"                  + //  00475 - 1819
+            "he"                      + //  0000d - 1825
+            "he-il"                   + //  0040d - 1827
+            "hi"                      + //  00039 - 1832
+            "hi-in"                   + //  00439 - 1834
+            "hr"                      + //  0001a - 1839
+            "hr-ba"                   + //  0101a - 1841
+            "hr-hr"                   + //  0041a - 1846
+            "hsb"                     + //  0002e - 1851
+            "hsb-de"                  + //  0042e - 1854
+            "hu"                      + //  0000e - 1860
+            "hu-hu"                   + //  0040e - 1862
+            "hu-hu_technl"            + //  1040e - 1867
+            "hy"                      + //  0002b - 1879
+            "hy-am"                   + //  0042b - 1881
+            "ia"                      + //  01000 - 1886
+            "ia-001"                  + //  01000 - 1888
+            "ia-fr"                   + //  01000 - 1894
+            "ibb"                     + //  00069 - 1899
+            "ibb-ng"                  + //  00469 - 1902
+            "id"                      + //  00021 - 1908
+            "id-id"                   + //  00421 - 1910
+            "ig"                      + //  00070 - 1915
+            "ig-ng"                   + //  00470 - 1917
+            "ii"                      + //  00078 - 1922
+            "ii-cn"                   + //  00478 - 1924
+            "is"                      + //  0000f - 1929
+            "is-is"                   + //  0040f - 1931
+            "it"                      + //  00010 - 1936
+            "it-ch"                   + //  00810 - 1938
+            "it-it"                   + //  00410 - 1943
+            "it-sm"                   + //  01000 - 1948
+            "iu"                      + //  0005d - 1953
+            "iu-cans"                 + //  0785d - 1955
+            "iu-cans-ca"              + //  0045d - 1962
+            "iu-latn"                 + //  07c5d - 1972
+            "iu-latn-ca"              + //  0085d - 1979
+            "ja"                      + //  00011 - 1989
+            "ja-jp"                   + //  00411 - 1991
+            "ja-jp_radstr"            + //  40411 - 1996
+            "jgo"                     + //  01000 - 2008
+            "jgo-cm"                  + //  01000 - 2011
+            "jmc"                     + //  01000 - 2017
+            "jmc-tz"                  + //  01000 - 2020
+            "jv"                      + //  01000 - 2026
+            "jv-java"                 + //  01000 - 2028
+            "jv-java-id"              + //  01000 - 2035
+            "jv-latn"                 + //  01000 - 2045
+            "jv-latn-id"              + //  01000 - 2052
+            "ka"                      + //  00037 - 2062
+            "ka-ge"                   + //  00437 - 2064
+            "ka-ge_modern"            + //  10437 - 2069
+            "kab"                     + //  01000 - 2081
+            "kab-dz"                  + //  01000 - 2084
+            "kam"                     + //  01000 - 2090
+            "kam-ke"                  + //  01000 - 2093
+            "kde"                     + //  01000 - 2099
+            "kde-tz"                  + //  01000 - 2102
+            "kea"                     + //  01000 - 2108
+            "kea-cv"                  + //  01000 - 2111
+            "khq"                     + //  01000 - 2117
+            "khq-ml"                  + //  01000 - 2120
+            "ki"                      + //  01000 - 2126
+            "ki-ke"                   + //  01000 - 2128
+            "kk"                      + //  0003f - 2133
+            "kk-kz"                   + //  0043f - 2135
+            "kkj"                     + //  01000 - 2140
+            "kkj-cm"                  + //  01000 - 2143
+            "kl"                      + //  0006f - 2149
+            "kl-gl"                   + //  0046f - 2151
+            "kln"                     + //  01000 - 2156
+            "kln-ke"                  + //  01000 - 2159
+            "km"                      + //  00053 - 2165
+            "km-kh"                   + //  00453 - 2167
+            "kn"                      + //  0004b - 2172
+            "kn-in"                   + //  0044b - 2174
+            "ko"                      + //  00012 - 2179
+            "ko-kp"                   + //  01000 - 2181
+            "ko-kr"                   + //  00412 - 2186
+            "kok"                     + //  00057 - 2191
+            "kok-in"                  + //  00457 - 2194
+            "kr"                      + //  00071 - 2200
+            "kr-ng"                   + //  00471 - 2202
+            "ks"                      + //  00060 - 2207
+            "ks-arab"                 + //  00460 - 2209
+            "ks-arab-in"              + //  01000 - 2216
+            "ks-deva"                 + //  01000 - 2226
+            "ks-deva-in"              + //  00860 - 2233
+            "ksb"                     + //  01000 - 2243
+            "ksb-tz"                  + //  01000 - 2246
+            "ksf"                     + //  01000 - 2252
+            "ksf-cm"                  + //  01000 - 2255
+            "ksh"                     + //  01000 - 2261
+            "ksh-de"                  + //  01000 - 2264
+            "ku"                      + //  00092 - 2270
+            "ku-arab"                 + //  07c92 - 2272
+            "ku-arab-iq"              + //  00492 - 2279
+            "ku-arab-ir"              + //  01000 - 2289
+            "kw"                      + //  01000 - 2299
+            "kw-gb"                   + //  01000 - 2301
+            "ky"                      + //  00040 - 2306
+            "ky-kg"                   + //  00440 - 2308
+            "la"                      + //  00076 - 2313
+            "la-001"                  + //  00476 - 2315
+            "lag"                     + //  01000 - 2321
+            "lag-tz"                  + //  01000 - 2324
+            "lb"                      + //  0006e - 2330
+            "lb-lu"                   + //  0046e - 2332
+            "lg"                      + //  01000 - 2337
+            "lg-ug"                   + //  01000 - 2339
+            "lkt"                     + //  01000 - 2344
+            "lkt-us"                  + //  01000 - 2347
+            "ln"                      + //  01000 - 2353
+            "ln-ao"                   + //  01000 - 2355
+            "ln-cd"                   + //  01000 - 2360
+            "ln-cf"                   + //  01000 - 2365
+            "ln-cg"                   + //  01000 - 2370
+            "lo"                      + //  00054 - 2375
+            "lo-la"                   + //  00454 - 2377
+            "lrc"                     + //  01000 - 2382
+            "lrc-iq"                  + //  01000 - 2385
+            "lrc-ir"                  + //  01000 - 2391
+            "lt"                      + //  00027 - 2397
+            "lt-lt"                   + //  00427 - 2399
+            "lu"                      + //  01000 - 2404
+            "lu-cd"                   + //  01000 - 2406
+            "luo"                     + //  01000 - 2411
+            "luo-ke"                  + //  01000 - 2414
+            "luy"                     + //  01000 - 2420
+            "luy-ke"                  + //  01000 - 2423
+            "lv"                      + //  00026 - 2429
+            "lv-lv"                   + //  00426 - 2431
+            "mas"                     + //  01000 - 2436
+            "mas-ke"                  + //  01000 - 2439
+            "mas-tz"                  + //  01000 - 2445
+            "mer"                     + //  01000 - 2451
+            "mer-ke"                  + //  01000 - 2454
+            "mfe"                     + //  01000 - 2460
+            "mfe-mu"                  + //  01000 - 2463
+            "mg"                      + //  01000 - 2469
+            "mg-mg"                   + //  01000 - 2471
+            "mgh"                     + //  01000 - 2476
+            "mgh-mz"                  + //  01000 - 2479
+            "mgo"                     + //  01000 - 2485
+            "mgo-cm"                  + //  01000 - 2488
+            "mi"                      + //  00081 - 2494
+            "mi-nz"                   + //  00481 - 2496
+            "mk"                      + //  0002f - 2501
+            "mk-mk"                   + //  0042f - 2503
+            "ml"                      + //  0004c - 2508
+            "ml-in"                   + //  0044c - 2510
+            "mn"                      + //  00050 - 2515
+            "mn-cyrl"                 + //  07850 - 2517
+            "mn-mn"                   + //  00450 - 2524
+            "mn-mong"                 + //  07c50 - 2529
+            "mn-mong-cn"              + //  00850 - 2536
+            "mn-mong-mn"              + //  00c50 - 2546
+            "mni"                     + //  00058 - 2556
+            "mni-in"                  + //  00458 - 2559
+            "moh"                     + //  0007c - 2565
+            "moh-ca"                  + //  0047c - 2568
+            "mr"                      + //  0004e - 2574
+            "mr-in"                   + //  0044e - 2576
+            "ms"                      + //  0003e - 2581
+            "ms-bn"                   + //  0083e - 2583
+            "ms-my"                   + //  0043e - 2588
+            "ms-sg"                   + //  01000 - 2593
+            "mt"                      + //  0003a - 2598
+            "mt-mt"                   + //  0043a - 2600
+            "mua"                     + //  01000 - 2605
+            "mua-cm"                  + //  01000 - 2608
+            "my"                      + //  00055 - 2614
+            "my-mm"                   + //  00455 - 2616
+            "mzn"                     + //  01000 - 2621
+            "mzn-ir"                  + //  01000 - 2624
+            "naq"                     + //  01000 - 2630
+            "naq-na"                  + //  01000 - 2633
+            "nb"                      + //  07c14 - 2639
+            "nb-no"                   + //  00414 - 2641
+            "nb-sj"                   + //  01000 - 2646
+            "nd"                      + //  01000 - 2651
+            "nd-zw"                   + //  01000 - 2653
+            "nds"                     + //  01000 - 2658
+            "nds-de"                  + //  01000 - 2661
+            "nds-nl"                  + //  01000 - 2667
+            "ne"                      + //  00061 - 2673
+            "ne-in"                   + //  00861 - 2675
+            "ne-np"                   + //  00461 - 2680
+            "nl"                      + //  00013 - 2685
+            "nl-aw"                   + //  01000 - 2687
+            "nl-be"                   + //  00813 - 2692
+            "nl-bq"                   + //  01000 - 2697
+            "nl-cw"                   + //  01000 - 2702
+            "nl-nl"                   + //  00413 - 2707
+            "nl-sr"                   + //  01000 - 2712
+            "nl-sx"                   + //  01000 - 2717
+            "nmg"                     + //  01000 - 2722
+            "nmg-cm"                  + //  01000 - 2725
+            "nn"                      + //  07814 - 2731
+            "nn-no"                   + //  00814 - 2733
+            "nnh"                     + //  01000 - 2738
+            "nnh-cm"                  + //  01000 - 2741
+            "no"                      + //  00014 - 2747
+            "nqo"                     + //  01000 - 2749
+            "nqo-gn"                  + //  01000 - 2752
+            "nr"                      + //  01000 - 2758
+            "nr-za"                   + //  01000 - 2760
+            "nso"                     + //  0006c - 2765
+            "nso-za"                  + //  0046c - 2768
+            "nus"                     + //  01000 - 2774
+            "nus-ss"                  + //  01000 - 2777
+            "nyn"                     + //  01000 - 2783
+            "nyn-ug"                  + //  01000 - 2786
+            "oc"                      + //  00082 - 2792
+            "oc-fr"                   + //  00482 - 2794
+            "om"                      + //  00072 - 2799
+            "om-et"                   + //  00472 - 2801
+            "om-ke"                   + //  01000 - 2806
+            "or"                      + //  00048 - 2811
+            "or-in"                   + //  00448 - 2813
+            "os"                      + //  01000 - 2818
+            "os-ge"                   + //  01000 - 2820
+            "os-ru"                   + //  01000 - 2825
+            "pa"                      + //  00046 - 2830
+            "pa-arab"                 + //  07c46 - 2832
+            "pa-arab-pk"              + //  00846 - 2839
+            "pa-in"                   + //  00446 - 2849
+            "pap"                     + //  00079 - 2854
+            "pap-029"                 + //  00479 - 2857
+            "pl"                      + //  00015 - 2864
+            "pl-pl"                   + //  00415 - 2866
+            "prg"                     + //  01000 - 2871
+            "prg-001"                 + //  01000 - 2874
+            "prs"                     + //  0008c - 2881
+            "prs-af"                  + //  0048c - 2884
+            "ps"                      + //  00063 - 2890
+            "ps-af"                   + //  00463 - 2892
+            "pt"                      + //  00016 - 2897
+            "pt-ao"                   + //  01000 - 2899
+            "pt-br"                   + //  00416 - 2904
+            "pt-ch"                   + //  01000 - 2909
+            "pt-cv"                   + //  01000 - 2914
+            "pt-gq"                   + //  01000 - 2919
+            "pt-gw"                   + //  01000 - 2924
+            "pt-lu"                   + //  01000 - 2929
+            "pt-mo"                   + //  01000 - 2934
+            "pt-mz"                   + //  01000 - 2939
+            "pt-pt"                   + //  00816 - 2944
+            "pt-st"                   + //  01000 - 2949
+            "pt-tl"                   + //  01000 - 2954
+            "qps-latn-x-sh"           + //  00901 - 2959
+            "qps-ploc"                + //  00501 - 2972
+            "qps-ploca"               + //  005fe - 2980
+            "qps-plocm"               + //  009ff - 2989
+            "quc"                     + //  00086 - 2998
+            "quc-latn"                + //  07c86 - 3001
+            "quc-latn-gt"             + //  00486 - 3009
+            "quz"                     + //  0006b - 3020
+            "quz-bo"                  + //  0046b - 3023
+            "quz-ec"                  + //  0086b - 3029
+            "quz-pe"                  + //  00c6b - 3035
+            "rm"                      + //  00017 - 3041
+            "rm-ch"                   + //  00417 - 3043
+            "rn"                      + //  01000 - 3048
+            "rn-bi"                   + //  01000 - 3050
+            "ro"                      + //  00018 - 3055
+            "ro-md"                   + //  00818 - 3057
+            "ro-ro"                   + //  00418 - 3062
+            "rof"                     + //  01000 - 3067
+            "rof-tz"                  + //  01000 - 3070
+            "ru"                      + //  00019 - 3076
+            "ru-by"                   + //  01000 - 3078
+            "ru-kg"                   + //  01000 - 3083
+            "ru-kz"                   + //  01000 - 3088
+            "ru-md"                   + //  00819 - 3093
+            "ru-ru"                   + //  00419 - 3098
+            "ru-ua"                   + //  01000 - 3103
+            "rw"                      + //  00087 - 3108
+            "rw-rw"                   + //  00487 - 3110
+            "rwk"                     + //  01000 - 3115
+            "rwk-tz"                  + //  01000 - 3118
+            "sa"                      + //  0004f - 3124
+            "sa-in"                   + //  0044f - 3126
+            "sah"                     + //  00085 - 3131
+            "sah-ru"                  + //  00485 - 3134
+            "saq"                     + //  01000 - 3140
+            "saq-ke"                  + //  01000 - 3143
+            "sbp"                     + //  01000 - 3149
+            "sbp-tz"                  + //  01000 - 3152
+            "sd"                      + //  00059 - 3158
+            "sd-arab"                 + //  07c59 - 3160
+            "sd-arab-pk"              + //  00859 - 3167
+            "sd-deva"                 + //  01000 - 3177
+            "sd-deva-in"              + //  00459 - 3184
+            "se"                      + //  0003b - 3194
+            "se-fi"                   + //  00c3b - 3196
+            "se-no"                   + //  0043b - 3201
+            "se-se"                   + //  0083b - 3206
+            "seh"                     + //  01000 - 3211
+            "seh-mz"                  + //  01000 - 3214
+            "ses"                     + //  01000 - 3220
+            "ses-ml"                  + //  01000 - 3223
+            "sg"                      + //  01000 - 3229
+            "sg-cf"                   + //  01000 - 3231
+            "shi"                     + //  01000 - 3236
+            "shi-latn"                + //  01000 - 3239
+            "shi-latn-ma"             + //  01000 - 3247
+            "shi-tfng"                + //  01000 - 3258
+            "shi-tfng-ma"             + //  01000 - 3266
+            "si"                      + //  0005b - 3277
+            "si-lk"                   + //  0045b - 3279
+            "sk"                      + //  0001b - 3284
+            "sk-sk"                   + //  0041b - 3286
+            "sl"                      + //  00024 - 3291
+            "sl-si"                   + //  00424 - 3293
+            "sma"                     + //  0783b - 3298
+            "sma-no"                  + //  0183b - 3301
+            "sma-se"                  + //  01c3b - 3307
+            "smj"                     + //  07c3b - 3313
+            "smj-no"                  + //  0103b - 3316
+            "smj-se"                  + //  0143b - 3322
+            "smn"                     + //  0703b - 3328
+            "smn-fi"                  + //  0243b - 3331
+            "sms"                     + //  0743b - 3337
+            "sms-fi"                  + //  0203b - 3340
+            "sn"                      + //  01000 - 3346
+            "sn-latn"                 + //  01000 - 3348
+            "sn-latn-zw"              + //  01000 - 3355
+            "so"                      + //  00077 - 3365
+            "so-dj"                   + //  01000 - 3367
+            "so-et"                   + //  01000 - 3372
+            "so-ke"                   + //  01000 - 3377
+            "so-so"                   + //  00477 - 3382
+            "sq"                      + //  0001c - 3387
+            "sq-al"                   + //  0041c - 3389
+            "sq-mk"                   + //  01000 - 3394
+            "sq-xk"                   + //  01000 - 3399
+            "sr"                      + //  07c1a - 3404
+            "sr-cyrl"                 + //  06c1a - 3406
+            "sr-cyrl-ba"              + //  01c1a - 3413
+            "sr-cyrl-cs"              + //  00c1a - 3423
+            "sr-cyrl-me"              + //  0301a - 3433
+            "sr-cyrl-rs"              + //  0281a - 3443
+            "sr-cyrl-xk"              + //  01000 - 3453
+            "sr-latn"                 + //  0701a - 3463
+            "sr-latn-ba"              + //  0181a - 3470
+            "sr-latn-cs"              + //  0081a - 3480
+            "sr-latn-me"              + //  02c1a - 3490
+            "sr-latn-rs"              + //  0241a - 3500
+            "sr-latn-xk"              + //  01000 - 3510
+            "ss"                      + //  01000 - 3520
+            "ss-sz"                   + //  01000 - 3522
+            "ss-za"                   + //  01000 - 3527
+            "ssy"                     + //  01000 - 3532
+            "ssy-er"                  + //  01000 - 3535
+            "st"                      + //  00030 - 3541
+            "st-ls"                   + //  01000 - 3543
+            "st-za"                   + //  00430 - 3548
+            "sv"                      + //  0001d - 3553
+            "sv-ax"                   + //  01000 - 3555
+            "sv-fi"                   + //  0081d - 3560
+            "sv-se"                   + //  0041d - 3565
+            "sw"                      + //  00041 - 3570
+            "sw-cd"                   + //  01000 - 3572
+            "sw-ke"                   + //  00441 - 3577
+            "sw-tz"                   + //  01000 - 3582
+            "sw-ug"                   + //  01000 - 3587
+            "swc"                     + //  01000 - 3592
+            "swc-cd"                  + //  01000 - 3595
+            "syr"                     + //  0005a - 3601
+            "syr-sy"                  + //  0045a - 3604
+            "ta"                      + //  00049 - 3610
+            "ta-in"                   + //  00449 - 3612
+            "ta-lk"                   + //  00849 - 3617
+            "ta-my"                   + //  01000 - 3622
+            "ta-sg"                   + //  01000 - 3627
+            "te"                      + //  0004a - 3632
+            "te-in"                   + //  0044a - 3634
+            "teo"                     + //  01000 - 3639
+            "teo-ke"                  + //  01000 - 3642
+            "teo-ug"                  + //  01000 - 3648
+            "tg"                      + //  00028 - 3654
+            "tg-cyrl"                 + //  07c28 - 3656
+            "tg-cyrl-tj"              + //  00428 - 3663
+            "th"                      + //  0001e - 3673
+            "th-th"                   + //  0041e - 3675
+            "ti"                      + //  00073 - 3680
+            "ti-er"                   + //  00873 - 3682
+            "ti-et"                   + //  00473 - 3687
+            "tig"                     + //  01000 - 3692
+            "tig-er"                  + //  01000 - 3695
+            "tk"                      + //  00042 - 3701
+            "tk-tm"                   + //  00442 - 3703
+            "tn"                      + //  00032 - 3708
+            "tn-bw"                   + //  00832 - 3710
+            "tn-za"                   + //  00432 - 3715
+            "to"                      + //  01000 - 3720
+            "to-to"                   + //  01000 - 3722
+            "tr"                      + //  0001f - 3727
+            "tr-cy"                   + //  01000 - 3729
+            "tr-tr"                   + //  0041f - 3734
+            "ts"                      + //  00031 - 3739
+            "ts-za"                   + //  00431 - 3741
+            "tt"                      + //  00044 - 3746
+            "tt-ru"                   + //  00444 - 3748
+            "twq"                     + //  01000 - 3753
+            "twq-ne"                  + //  01000 - 3756
+            "tzm"                     + //  0005f - 3762
+            "tzm-arab"                + //  01000 - 3765
+            "tzm-arab-ma"             + //  0045f - 3773
+            "tzm-latn"                + //  07c5f - 3784
+            "tzm-latn-dz"             + //  0085f - 3792
+            "tzm-latn-ma"             + //  01000 - 3803
+            "tzm-tfng"                + //  0785f - 3814
+            "tzm-tfng-ma"             + //  0105f - 3822
+            "ug"                      + //  00080 - 3833
+            "ug-cn"                   + //  00480 - 3835
+            "uk"                      + //  00022 - 3840
+            "uk-ua"                   + //  00422 - 3842
+            "ur"                      + //  00020 - 3847
+            "ur-in"                   + //  00820 - 3849
+            "ur-pk"                   + //  00420 - 3854
+            "uz"                      + //  00043 - 3859
+            "uz-arab"                 + //  01000 - 3861
+            "uz-arab-af"              + //  01000 - 3868
+            "uz-cyrl"                 + //  07843 - 3878
+            "uz-cyrl-uz"              + //  00843 - 3885
+            "uz-latn"                 + //  07c43 - 3895
+            "uz-latn-uz"              + //  00443 - 3902
+            "vai"                     + //  01000 - 3912
+            "vai-latn"                + //  01000 - 3915
+            "vai-latn-lr"             + //  01000 - 3923
+            "vai-vaii"                + //  01000 - 3934
+            "vai-vaii-lr"             + //  01000 - 3942
+            "ve"                      + //  00033 - 3953
+            "ve-za"                   + //  00433 - 3955
+            "vi"                      + //  0002a - 3960
+            "vi-vn"                   + //  0042a - 3962
+            "vo"                      + //  01000 - 3967
+            "vo-001"                  + //  01000 - 3969
+            "vun"                     + //  01000 - 3975
+            "vun-tz"                  + //  01000 - 3978
+            "wae"                     + //  01000 - 3984
+            "wae-ch"                  + //  01000 - 3987
+            "wal"                     + //  01000 - 3993
+            "wal-et"                  + //  01000 - 3996
+            "wo"                      + //  00088 - 4002
+            "wo-sn"                   + //  00488 - 4004
+            "x-iv_mathan"             + //  1007f - 4009
+            "xh"                      + //  00034 - 4020
+            "xh-za"                   + //  00434 - 4022
+            "xog"                     + //  01000 - 4027
+            "xog-ug"                  + //  01000 - 4030
+            "yav"                     + //  01000 - 4036
+            "yav-cm"                  + //  01000 - 4039
+            "yi"                      + //  0003d - 4045
+            "yi-001"                  + //  0043d - 4047
+            "yo"                      + //  0006a - 4053
+            "yo-bj"                   + //  01000 - 4055
+            "yo-ng"                   + //  0046a - 4060
+            "yue"                     + //  01000 - 4065
+            "yue-hk"                  + //  01000 - 4068
+            "zgh"                     + //  01000 - 4074
+            "zgh-tfng"                + //  01000 - 4077
+            "zgh-tfng-ma"             + //  01000 - 4085
+            "zh"                      + //  07804 - 4096
+            "zh-chs"                  + //  00004 - 4098
+            "zh-cht"                  + //  07c04 - 4104
+            "zh-cn"                   + //  00804 - 4110
+            "zh-cn_phoneb"            + //  50804 - 4115
+            "zh-cn_stroke"            + //  20804 - 4127
+            "zh-hans"                 + //  00004 - 4139
+            "zh-hans-hk"              + //  01000 - 4146
+            "zh-hans-mo"              + //  01000 - 4156
+            "zh-hant"                 + //  07c04 - 4166
+            "zh-hk"                   + //  00c04 - 4173
+            "zh-hk_radstr"            + //  40c04 - 4178
+            "zh-mo"                   + //  01404 - 4190
+            "zh-mo_radstr"            + //  41404 - 4195
+            "zh-mo_stroke"            + //  21404 - 4207
+            "zh-sg"                   + //  01004 - 4219
+            "zh-sg_phoneb"            + //  51004 - 4224
+            "zh-sg_stroke"            + //  21004 - 4236
+            "zh-tw"                   + //  00404 - 4248
+            "zh-tw_pronun"            + //  30404 - 4253
+            "zh-tw_radstr"            + //  40404 - 4265
+            "zu"                      + //  00035 - 4277
+            "zu-za";                    //  00435 - 4279
+        
+        // c_threeLetterWindowsLanguageName is string containing 3-letter Windows language names
+        // every 3-characters entry is matching locale name entry in c_localeNames 
+        
+        private const string c_threeLetterWindowsLanguageName =
+            "ZZZ" + // aa
+            "ZZZ" + // aa-dj
+            "ZZZ" + // aa-er
+            "ZZZ" + // aa-et
+            "AFK" + // af
+            "ZZZ" + // af-na
+            "AFK" + // af-za
+            "ZZZ" + // agq
+            "ZZZ" + // agq-cm
+            "ZZZ" + // ak
+            "ZZZ" + // ak-gh
+            "AMH" + // am
+            "AMH" + // am-et
+            "ARA" + // ar
+            "ZZZ" + // ar-001
+            "ARU" + // ar-ae
+            "ARH" + // ar-bh
+            "ZZZ" + // ar-dj
+            "ARG" + // ar-dz
+            "ARE" + // ar-eg
+            "ZZZ" + // ar-er
+            "ZZZ" + // ar-il
+            "ARI" + // ar-iq
+            "ARJ" + // ar-jo
+            "ZZZ" + // ar-km
+            "ARK" + // ar-kw
+            "ARB" + // ar-lb
+            "ARL" + // ar-ly
+            "ARM" + // ar-ma
+            "ZZZ" + // ar-mr
+            "ARO" + // ar-om
+            "ZZZ" + // ar-ps
+            "ARQ" + // ar-qa
+            "ARA" + // ar-sa
+            "ZZZ" + // ar-sd
+            "ZZZ" + // ar-so
+            "ZZZ" + // ar-ss
+            "ARS" + // ar-sy
+            "ZZZ" + // ar-td
+            "ART" + // ar-tn
+            "ARY" + // ar-ye
+            "MPD" + // arn
+            "MPD" + // arn-cl
+            "ASM" + // as
+            "ASM" + // as-in
+            "ZZZ" + // asa
+            "ZZZ" + // asa-tz
+            "ZZZ" + // ast
+            "ZZZ" + // ast-es
+            "AZE" + // az
+            "AZC" + // az-cyrl
+            "AZC" + // az-cyrl-az
+            "AZE" + // az-latn
+            "AZE" + // az-latn-az
+            "BAS" + // ba
+            "BAS" + // ba-ru
+            "ZZZ" + // bas
+            "ZZZ" + // bas-cm
+            "BEL" + // be
+            "BEL" + // be-by
+            "ZZZ" + // bem
+            "ZZZ" + // bem-zm
+            "ZZZ" + // bez
+            "ZZZ" + // bez-tz
+            "BGR" + // bg
+            "BGR" + // bg-bg
+            "ZZZ" + // bin
+            "ZZZ" + // bin-ng
+            "ZZZ" + // bm
+            "ZZZ" + // bm-latn
+            "ZZZ" + // bm-latn-ml
+            "BNB" + // bn
+            "BNB" + // bn-bd
+            "BNG" + // bn-in
+            "BOB" + // bo
+            "BOB" + // bo-cn
+            "ZZZ" + // bo-in
+            "BRE" + // br
+            "BRE" + // br-fr
+            "ZZZ" + // brx
+            "ZZZ" + // brx-in
+            "BSB" + // bs
+            "BSC" + // bs-cyrl
+            "BSC" + // bs-cyrl-ba
+            "BSB" + // bs-latn
+            "BSB" + // bs-latn-ba
+            "ZZZ" + // byn
+            "ZZZ" + // byn-er
+            "CAT" + // ca
+            "ZZZ" + // ca-ad
+            "CAT" + // ca-es
+            "VAL" + // ca-es-valencia
+            "ZZZ" + // ca-fr
+            "ZZZ" + // ca-it
+            "ZZZ" + // ce
+            "ZZZ" + // ce-ru
+            "ZZZ" + // cgg
+            "ZZZ" + // cgg-ug
+            "CRE" + // chr
+            "CRE" + // chr-cher
+            "CRE" + // chr-cher-us
+            "COS" + // co
+            "COS" + // co-fr
+            "CSY" + // cs
+            "CSY" + // cs-cz
+            "ZZZ" + // cu
+            "ZZZ" + // cu-ru
+            "CYM" + // cy
+            "CYM" + // cy-gb
+            "DAN" + // da
+            "DAN" + // da-dk
+            "ZZZ" + // da-gl
+            "ZZZ" + // dav
+            "ZZZ" + // dav-ke
+            "DEU" + // de
+            "DEA" + // de-at
+            "ZZZ" + // de-be
+            "DES" + // de-ch
+            "DEU" + // de-de
+            "DEU" + // de-de_phoneb
+            "ZZZ" + // de-it
+            "DEC" + // de-li
+            "DEL" + // de-lu
+            "ZZZ" + // dje
+            "ZZZ" + // dje-ne
+            "DSB" + // dsb
+            "DSB" + // dsb-de
+            "ZZZ" + // dua
+            "ZZZ" + // dua-cm
+            "DIV" + // dv
+            "DIV" + // dv-mv
+            "ZZZ" + // dyo
+            "ZZZ" + // dyo-sn
+            "ZZZ" + // dz
+            "ZZZ" + // dz-bt
+            "ZZZ" + // ebu
+            "ZZZ" + // ebu-ke
+            "ZZZ" + // ee
+            "ZZZ" + // ee-gh
+            "ZZZ" + // ee-tg
+            "ELL" + // el
+            "ZZZ" + // el-cy
+            "ELL" + // el-gr
+            "ENU" + // en
+            "ZZZ" + // en-001
+            "ENB" + // en-029
+            "ZZZ" + // en-150
+            "ZZZ" + // en-ag
+            "ZZZ" + // en-ai
+            "ZZZ" + // en-as
+            "ZZZ" + // en-at
+            "ENA" + // en-au
+            "ZZZ" + // en-bb
+            "ZZZ" + // en-be
+            "ZZZ" + // en-bi
+            "ZZZ" + // en-bm
+            "ZZZ" + // en-bs
+            "ZZZ" + // en-bw
+            "ENL" + // en-bz
+            "ENC" + // en-ca
+            "ZZZ" + // en-cc
+            "ZZZ" + // en-ch
+            "ZZZ" + // en-ck
+            "ZZZ" + // en-cm
+            "ZZZ" + // en-cx
+            "ZZZ" + // en-cy
+            "ZZZ" + // en-de
+            "ZZZ" + // en-dk
+            "ZZZ" + // en-dm
+            "ZZZ" + // en-er
+            "ZZZ" + // en-fi
+            "ZZZ" + // en-fj
+            "ZZZ" + // en-fk
+            "ZZZ" + // en-fm
+            "ENG" + // en-gb
+            "ZZZ" + // en-gd
+            "ZZZ" + // en-gg
+            "ZZZ" + // en-gh
+            "ZZZ" + // en-gi
+            "ZZZ" + // en-gm
+            "ZZZ" + // en-gu
+            "ZZZ" + // en-gy
+            "ENH" + // en-hk
+            "ZZZ" + // en-id
+            "ENI" + // en-ie
+            "ZZZ" + // en-il
+            "ZZZ" + // en-im
+            "ENN" + // en-in
+            "ZZZ" + // en-io
+            "ZZZ" + // en-je
+            "ENJ" + // en-jm
+            "ZZZ" + // en-ke
+            "ZZZ" + // en-ki
+            "ZZZ" + // en-kn
+            "ZZZ" + // en-ky
+            "ZZZ" + // en-lc
+            "ZZZ" + // en-lr
+            "ZZZ" + // en-ls
+            "ZZZ" + // en-mg
+            "ZZZ" + // en-mh
+            "ZZZ" + // en-mo
+            "ZZZ" + // en-mp
+            "ZZZ" + // en-ms
+            "ZZZ" + // en-mt
+            "ZZZ" + // en-mu
+            "ZZZ" + // en-mw
+            "ENM" + // en-my
+            "ZZZ" + // en-na
+            "ZZZ" + // en-nf
+            "ZZZ" + // en-ng
+            "ZZZ" + // en-nl
+            "ZZZ" + // en-nr
+            "ZZZ" + // en-nu
+            "ENZ" + // en-nz
+            "ZZZ" + // en-pg
+            "ENP" + // en-ph
+            "ZZZ" + // en-pk
+            "ZZZ" + // en-pn
+            "ZZZ" + // en-pr
+            "ZZZ" + // en-pw
+            "ZZZ" + // en-rw
+            "ZZZ" + // en-sb
+            "ZZZ" + // en-sc
+            "ZZZ" + // en-sd
+            "ZZZ" + // en-se
+            "ENE" + // en-sg
+            "ZZZ" + // en-sh
+            "ZZZ" + // en-si
+            "ZZZ" + // en-sl
+            "ZZZ" + // en-ss
+            "ZZZ" + // en-sx
+            "ZZZ" + // en-sz
+            "ZZZ" + // en-tc
+            "ZZZ" + // en-tk
+            "ZZZ" + // en-to
+            "ENT" + // en-tt
+            "ZZZ" + // en-tv
+            "ZZZ" + // en-tz
+            "ZZZ" + // en-ug
+            "ZZZ" + // en-um
+            "ENU" + // en-us
+            "ZZZ" + // en-vc
+            "ZZZ" + // en-vg
+            "ZZZ" + // en-vi
+            "ZZZ" + // en-vu
+            "ZZZ" + // en-ws
+            "ENS" + // en-za
+            "ZZZ" + // en-zm
+            "ENW" + // en-zw
+            "ZZZ" + // eo
+            "ZZZ" + // eo-001
+            "ESN" + // es
+            "ESJ" + // es-419
+            "ESS" + // es-ar
+            "ESB" + // es-bo
+            "ZZZ" + // es-br
+            "ESL" + // es-cl
+            "ESO" + // es-co
+            "ESC" + // es-cr
+            "ESK" + // es-cu
+            "ESD" + // es-do
+            "ESF" + // es-ec
+            "ESN" + // es-es
+            "ESP" + // es-es_tradnl
+            "ZZZ" + // es-gq
+            "ESG" + // es-gt
+            "ESH" + // es-hn
+            "ESM" + // es-mx
+            "ESI" + // es-ni
+            "ESA" + // es-pa
+            "ESR" + // es-pe
+            "ZZZ" + // es-ph
+            "ESU" + // es-pr
+            "ESZ" + // es-py
+            "ESE" + // es-sv
+            "EST" + // es-us
+            "ESY" + // es-uy
+            "ESV" + // es-ve
+            "ETI" + // et
+            "ETI" + // et-ee
+            "EUQ" + // eu
+            "EUQ" + // eu-es
+            "ZZZ" + // ewo
+            "ZZZ" + // ewo-cm
+            "FAR" + // fa
+            "FAR" + // fa-ir
+            "FUL" + // ff
+            "ZZZ" + // ff-cm
+            "ZZZ" + // ff-gn
+            "FUL" + // ff-latn
+            "FUL" + // ff-latn-sn
+            "ZZZ" + // ff-mr
+            "ZZZ" + // ff-ng
+            "FIN" + // fi
+            "FIN" + // fi-fi
+            "FPO" + // fil
+            "FPO" + // fil-ph
+            "FOS" + // fo
+            "ZZZ" + // fo-dk
+            "FOS" + // fo-fo
+            "FRA" + // fr
+            "ZZZ" + // fr-029
+            "FRB" + // fr-be
+            "ZZZ" + // fr-bf
+            "ZZZ" + // fr-bi
+            "ZZZ" + // fr-bj
+            "ZZZ" + // fr-bl
+            "FRC" + // fr-ca
+            "FRD" + // fr-cd
+            "ZZZ" + // fr-cf
+            "ZZZ" + // fr-cg
+            "FRS" + // fr-ch
+            "FRI" + // fr-ci
+            "FRE" + // fr-cm
+            "ZZZ" + // fr-dj
+            "ZZZ" + // fr-dz
+            "FRA" + // fr-fr
+            "ZZZ" + // fr-ga
+            "ZZZ" + // fr-gf
+            "ZZZ" + // fr-gn
+            "ZZZ" + // fr-gp
+            "ZZZ" + // fr-gq
+            "FRH" + // fr-ht
+            "ZZZ" + // fr-km
+            "FRL" + // fr-lu
+            "FRO" + // fr-ma
+            "FRM" + // fr-mc
+            "ZZZ" + // fr-mf
+            "ZZZ" + // fr-mg
+            "FRF" + // fr-ml
+            "ZZZ" + // fr-mq
+            "ZZZ" + // fr-mr
+            "ZZZ" + // fr-mu
+            "ZZZ" + // fr-nc
+            "ZZZ" + // fr-ne
+            "ZZZ" + // fr-pf
+            "ZZZ" + // fr-pm
+            "FRR" + // fr-re
+            "ZZZ" + // fr-rw
+            "ZZZ" + // fr-sc
+            "FRN" + // fr-sn
+            "ZZZ" + // fr-sy
+            "ZZZ" + // fr-td
+            "ZZZ" + // fr-tg
+            "ZZZ" + // fr-tn
+            "ZZZ" + // fr-vu
+            "ZZZ" + // fr-wf
+            "ZZZ" + // fr-yt
+            "ZZZ" + // fur
+            "ZZZ" + // fur-it
+            "FYN" + // fy
+            "FYN" + // fy-nl
+            "IRE" + // ga
+            "IRE" + // ga-ie
+            "GLA" + // gd
+            "GLA" + // gd-gb
+            "GLC" + // gl
+            "GLC" + // gl-es
+            "GRN" + // gn
+            "GRN" + // gn-py
+            "ZZZ" + // gsw
+            "ZZZ" + // gsw-ch
+            "GSW" + // gsw-fr
+            "ZZZ" + // gsw-li
+            "GUJ" + // gu
+            "GUJ" + // gu-in
+            "ZZZ" + // guz
+            "ZZZ" + // guz-ke
+            "ZZZ" + // gv
+            "ZZZ" + // gv-im
+            "HAU" + // ha
+            "HAU" + // ha-latn
+            "ZZZ" + // ha-latn-gh
+            "ZZZ" + // ha-latn-ne
+            "HAU" + // ha-latn-ng
+            "HAW" + // haw
+            "HAW" + // haw-us
+            "HEB" + // he
+            "HEB" + // he-il
+            "HIN" + // hi
+            "HIN" + // hi-in
+            "HRV" + // hr
+            "HRB" + // hr-ba
+            "HRV" + // hr-hr
+            "HSB" + // hsb
+            "HSB" + // hsb-de
+            "HUN" + // hu
+            "HUN" + // hu-hu
+            "HUN" + // hu-hu_technl
+            "HYE" + // hy
+            "HYE" + // hy-am
+            "ZZZ" + // ia
+            "ZZZ" + // ia-001
+            "ZZZ" + // ia-fr
+            "ZZZ" + // ibb
+            "ZZZ" + // ibb-ng
+            "IND" + // id
+            "IND" + // id-id
+            "IBO" + // ig
+            "IBO" + // ig-ng
+            "III" + // ii
+            "III" + // ii-cn
+            "ISL" + // is
+            "ISL" + // is-is
+            "ITA" + // it
+            "ITS" + // it-ch
+            "ITA" + // it-it
+            "ZZZ" + // it-sm
+            "IUK" + // iu
+            "IUS" + // iu-cans
+            "IUS" + // iu-cans-ca
+            "IUK" + // iu-latn
+            "IUK" + // iu-latn-ca
+            "JPN" + // ja
+            "JPN" + // ja-jp
+            "JPN" + // ja-jp_radstr
+            "ZZZ" + // jgo
+            "ZZZ" + // jgo-cm
+            "ZZZ" + // jmc
+            "ZZZ" + // jmc-tz
+            "JAV" + // jv
+            "ZZZ" + // jv-java
+            "ZZZ" + // jv-java-id
+            "JAV" + // jv-latn
+            "JAV" + // jv-latn-id
+            "KAT" + // ka
+            "KAT" + // ka-ge
+            "KAT" + // ka-ge_modern
+            "ZZZ" + // kab
+            "ZZZ" + // kab-dz
+            "ZZZ" + // kam
+            "ZZZ" + // kam-ke
+            "ZZZ" + // kde
+            "ZZZ" + // kde-tz
+            "ZZZ" + // kea
+            "ZZZ" + // kea-cv
+            "ZZZ" + // khq
+            "ZZZ" + // khq-ml
+            "ZZZ" + // ki
+            "ZZZ" + // ki-ke
+            "KKZ" + // kk
+            "KKZ" + // kk-kz
+            "ZZZ" + // kkj
+            "ZZZ" + // kkj-cm
+            "KAL" + // kl
+            "KAL" + // kl-gl
+            "ZZZ" + // kln
+            "ZZZ" + // kln-ke
+            "KHM" + // km
+            "KHM" + // km-kh
+            "KDI" + // kn
+            "KDI" + // kn-in
+            "KOR" + // ko
+            "ZZZ" + // ko-kp
+            "KOR" + // ko-kr
+            "KNK" + // kok
+            "KNK" + // kok-in
+            "ZZZ" + // kr
+            "ZZZ" + // kr-ng
+            "ZZZ" + // ks
+            "ZZZ" + // ks-arab
+            "ZZZ" + // ks-arab-in
+            "ZZZ" + // ks-deva
+            "ZZZ" + // ks-deva-in
+            "ZZZ" + // ksb
+            "ZZZ" + // ksb-tz
+            "ZZZ" + // ksf
+            "ZZZ" + // ksf-cm
+            "ZZZ" + // ksh
+            "ZZZ" + // ksh-de
+            "KUR" + // ku
+            "KUR" + // ku-arab
+            "KUR" + // ku-arab-iq
+            "ZZZ" + // ku-arab-ir
+            "ZZZ" + // kw
+            "ZZZ" + // kw-gb
+            "KYR" + // ky
+            "KYR" + // ky-kg
+            "ZZZ" + // la
+            "ZZZ" + // la-001
+            "ZZZ" + // lag
+            "ZZZ" + // lag-tz
+            "LBX" + // lb
+            "LBX" + // lb-lu
+            "ZZZ" + // lg
+            "ZZZ" + // lg-ug
+            "ZZZ" + // lkt
+            "ZZZ" + // lkt-us
+            "ZZZ" + // ln
+            "ZZZ" + // ln-ao
+            "ZZZ" + // ln-cd
+            "ZZZ" + // ln-cf
+            "ZZZ" + // ln-cg
+            "LAO" + // lo
+            "LAO" + // lo-la
+            "ZZZ" + // lrc
+            "ZZZ" + // lrc-iq
+            "ZZZ" + // lrc-ir
+            "LTH" + // lt
+            "LTH" + // lt-lt
+            "ZZZ" + // lu
+            "ZZZ" + // lu-cd
+            "ZZZ" + // luo
+            "ZZZ" + // luo-ke
+            "ZZZ" + // luy
+            "ZZZ" + // luy-ke
+            "LVI" + // lv
+            "LVI" + // lv-lv
+            "ZZZ" + // mas
+            "ZZZ" + // mas-ke
+            "ZZZ" + // mas-tz
+            "ZZZ" + // mer
+            "ZZZ" + // mer-ke
+            "ZZZ" + // mfe
+            "ZZZ" + // mfe-mu
+            "MLG" + // mg
+            "MLG" + // mg-mg
+            "ZZZ" + // mgh
+            "ZZZ" + // mgh-mz
+            "ZZZ" + // mgo
+            "ZZZ" + // mgo-cm
+            "MRI" + // mi
+            "MRI" + // mi-nz
+            "MKI" + // mk
+            "MKI" + // mk-mk
+            "MYM" + // ml
+            "MYM" + // ml-in
+            "MNN" + // mn
+            "MNN" + // mn-cyrl
+            "MNN" + // mn-mn
+            "MNG" + // mn-mong
+            "MNG" + // mn-mong-cn
+            "MNM" + // mn-mong-mn
+            "ZZZ" + // mni
+            "ZZZ" + // mni-in
+            "MWK" + // moh
+            "MWK" + // moh-ca
+            "MAR" + // mr
+            "MAR" + // mr-in
+            "MSL" + // ms
+            "MSB" + // ms-bn
+            "MSL" + // ms-my
+            "ZZZ" + // ms-sg
+            "MLT" + // mt
+            "MLT" + // mt-mt
+            "ZZZ" + // mua
+            "ZZZ" + // mua-cm
+            "MYA" + // my
+            "MYA" + // my-mm
+            "ZZZ" + // mzn
+            "ZZZ" + // mzn-ir
+            "ZZZ" + // naq
+            "ZZZ" + // naq-na
+            "NOR" + // nb
+            "NOR" + // nb-no
+            "ZZZ" + // nb-sj
+            "ZZZ" + // nd
+            "ZZZ" + // nd-zw
+            "ZZZ" + // nds
+            "ZZZ" + // nds-de
+            "ZZZ" + // nds-nl
+            "NEP" + // ne
+            "NEI" + // ne-in
+            "NEP" + // ne-np
+            "NLD" + // nl
+            "ZZZ" + // nl-aw
+            "NLB" + // nl-be
+            "ZZZ" + // nl-bq
+            "ZZZ" + // nl-cw
+            "NLD" + // nl-nl
+            "ZZZ" + // nl-sr
+            "ZZZ" + // nl-sx
+            "ZZZ" + // nmg
+            "ZZZ" + // nmg-cm
+            "NON" + // nn
+            "NON" + // nn-no
+            "ZZZ" + // nnh
+            "ZZZ" + // nnh-cm
+            "NOR" + // no
+            "NQO" + // nqo
+            "NQO" + // nqo-gn
+            "ZZZ" + // nr
+            "ZZZ" + // nr-za
+            "NSO" + // nso
+            "NSO" + // nso-za
+            "ZZZ" + // nus
+            "ZZZ" + // nus-ss
+            "ZZZ" + // nyn
+            "ZZZ" + // nyn-ug
+            "OCI" + // oc
+            "OCI" + // oc-fr
+            "ORM" + // om
+            "ORM" + // om-et
+            "ZZZ" + // om-ke
+            "ORI" + // or
+            "ORI" + // or-in
+            "ZZZ" + // os
+            "ZZZ" + // os-ge
+            "ZZZ" + // os-ru
+            "PAN" + // pa
+            "PAP" + // pa-arab
+            "PAP" + // pa-arab-pk
+            "PAN" + // pa-in
+            "ZZZ" + // pap
+            "ZZZ" + // pap-029
+            "PLK" + // pl
+            "PLK" + // pl-pl
+            "ZZZ" + // prg
+            "ZZZ" + // prg-001
+            "PRS" + // prs
+            "PRS" + // prs-af
+            "PAS" + // ps
+            "PAS" + // ps-af
+            "PTB" + // pt
+            "PTA" + // pt-ao
+            "PTB" + // pt-br
+            "ZZZ" + // pt-ch
+            "ZZZ" + // pt-cv
+            "ZZZ" + // pt-gq
+            "ZZZ" + // pt-gw
+            "ZZZ" + // pt-lu
+            "ZZZ" + // pt-mo
+            "ZZZ" + // pt-mz
+            "PTG" + // pt-pt
+            "ZZZ" + // pt-st
+            "ZZZ" + // pt-tl
+            "ENJ" + // qps-latn-x-sh
+            "ENU" + // qps-ploc
+            "JPN" + // qps-ploca
+            "ARA" + // qps-plocm
+            "QUT" + // quc
+            "QUT" + // quc-latn
+            "QUT" + // quc-latn-gt
+            "QUB" + // quz
+            "QUB" + // quz-bo
+            "QUE" + // quz-ec
+            "QUP" + // quz-pe
+            "RMC" + // rm
+            "RMC" + // rm-ch
+            "ZZZ" + // rn
+            "ZZZ" + // rn-bi
+            "ROM" + // ro
+            "ROD" + // ro-md
+            "ROM" + // ro-ro
+            "ZZZ" + // rof
+            "ZZZ" + // rof-tz
+            "RUS" + // ru
+            "ZZZ" + // ru-by
+            "ZZZ" + // ru-kg
+            "ZZZ" + // ru-kz
+            "RUM" + // ru-md
+            "RUS" + // ru-ru
+            "ZZZ" + // ru-ua
+            "KIN" + // rw
+            "KIN" + // rw-rw
+            "ZZZ" + // rwk
+            "ZZZ" + // rwk-tz
+            "SAN" + // sa
+            "SAN" + // sa-in
+            "SAH" + // sah
+            "SAH" + // sah-ru
+            "ZZZ" + // saq
+            "ZZZ" + // saq-ke
+            "ZZZ" + // sbp
+            "ZZZ" + // sbp-tz
+            "SIP" + // sd
+            "SIP" + // sd-arab
+            "SIP" + // sd-arab-pk
+            "ZZZ" + // sd-deva
+            "ZZZ" + // sd-deva-in
+            "SME" + // se
+            "SMG" + // se-fi
+            "SME" + // se-no
+            "SMF" + // se-se
+            "ZZZ" + // seh
+            "ZZZ" + // seh-mz
+            "ZZZ" + // ses
+            "ZZZ" + // ses-ml
+            "ZZZ" + // sg
+            "ZZZ" + // sg-cf
+            "ZZZ" + // shi
+            "ZZZ" + // shi-latn
+            "ZZZ" + // shi-latn-ma
+            "ZZZ" + // shi-tfng
+            "ZZZ" + // shi-tfng-ma
+            "SIN" + // si
+            "SIN" + // si-lk
+            "SKY" + // sk
+            "SKY" + // sk-sk
+            "SLV" + // sl
+            "SLV" + // sl-si
+            "SMB" + // sma
+            "SMA" + // sma-no
+            "SMB" + // sma-se
+            "SMK" + // smj
+            "SMJ" + // smj-no
+            "SMK" + // smj-se
+            "SMN" + // smn
+            "SMN" + // smn-fi
+            "SMS" + // sms
+            "SMS" + // sms-fi
+            "SNA" + // sn
+            "SNA" + // sn-latn
+            "SNA" + // sn-latn-zw
+            "SOM" + // so
+            "ZZZ" + // so-dj
+            "ZZZ" + // so-et
+            "ZZZ" + // so-ke
+            "SOM" + // so-so
+            "SQI" + // sq
+            "SQI" + // sq-al
+            "ZZZ" + // sq-mk
+            "ZZZ" + // sq-xk
+            "SRM" + // sr
+            "SRO" + // sr-cyrl
+            "SRN" + // sr-cyrl-ba
+            "SRB" + // sr-cyrl-cs
+            "SRQ" + // sr-cyrl-me
+            "SRO" + // sr-cyrl-rs
+            "ZZZ" + // sr-cyrl-xk
+            "SRM" + // sr-latn
+            "SRS" + // sr-latn-ba
+            "SRL" + // sr-latn-cs
+            "SRP" + // sr-latn-me
+            "SRM" + // sr-latn-rs
+            "ZZZ" + // sr-latn-xk
+            "ZZZ" + // ss
+            "ZZZ" + // ss-sz
+            "ZZZ" + // ss-za
+            "ZZZ" + // ssy
+            "ZZZ" + // ssy-er
+            "SOT" + // st
+            "ZZZ" + // st-ls
+            "SOT" + // st-za
+            "SVE" + // sv
+            "ZZZ" + // sv-ax
+            "SVF" + // sv-fi
+            "SVE" + // sv-se
+            "SWK" + // sw
+            "ZZZ" + // sw-cd
+            "SWK" + // sw-ke
+            "ZZZ" + // sw-tz
+            "ZZZ" + // sw-ug
+            "ZZZ" + // swc
+            "ZZZ" + // swc-cd
+            "SYR" + // syr
+            "SYR" + // syr-sy
+            "TAI" + // ta
+            "TAI" + // ta-in
+            "TAM" + // ta-lk
+            "ZZZ" + // ta-my
+            "ZZZ" + // ta-sg
+            "TEL" + // te
+            "TEL" + // te-in
+            "ZZZ" + // teo
+            "ZZZ" + // teo-ke
+            "ZZZ" + // teo-ug
+            "TAJ" + // tg
+            "TAJ" + // tg-cyrl
+            "TAJ" + // tg-cyrl-tj
+            "THA" + // th
+            "THA" + // th-th
+            "TIR" + // ti
+            "TIR" + // ti-er
+            "TIE" + // ti-et
+            "ZZZ" + // tig
+            "ZZZ" + // tig-er
+            "TUK" + // tk
+            "TUK" + // tk-tm
+            "TSN" + // tn
+            "TSB" + // tn-bw
+            "TSN" + // tn-za
+            "ZZZ" + // to
+            "ZZZ" + // to-to
+            "TRK" + // tr
+            "ZZZ" + // tr-cy
+            "TRK" + // tr-tr
+            "TSO" + // ts
+            "TSO" + // ts-za
+            "TTT" + // tt
+            "TTT" + // tt-ru
+            "ZZZ" + // twq
+            "ZZZ" + // twq-ne
+            "TZA" + // tzm
+            "ZZZ" + // tzm-arab
+            "ZZZ" + // tzm-arab-ma
+            "TZA" + // tzm-latn
+            "TZA" + // tzm-latn-dz
+            "ZZZ" + // tzm-latn-ma
+            "TZM" + // tzm-tfng
+            "TZM" + // tzm-tfng-ma
+            "UIG" + // ug
+            "UIG" + // ug-cn
+            "UKR" + // uk
+            "UKR" + // uk-ua
+            "URD" + // ur
+            "URI" + // ur-in
+            "URD" + // ur-pk
+            "UZB" + // uz
+            "ZZZ" + // uz-arab
+            "ZZZ" + // uz-arab-af
+            "UZC" + // uz-cyrl
+            "UZC" + // uz-cyrl-uz
+            "UZB" + // uz-latn
+            "UZB" + // uz-latn-uz
+            "ZZZ" + // vai
+            "ZZZ" + // vai-latn
+            "ZZZ" + // vai-latn-lr
+            "ZZZ" + // vai-vaii
+            "ZZZ" + // vai-vaii-lr
+            "ZZZ" + // ve
+            "ZZZ" + // ve-za
+            "VIT" + // vi
+            "VIT" + // vi-vn
+            "ZZZ" + // vo
+            "ZZZ" + // vo-001
+            "ZZZ" + // vun
+            "ZZZ" + // vun-tz
+            "ZZZ" + // wae
+            "ZZZ" + // wae-ch
+            "ZZZ" + // wal
+            "ZZZ" + // wal-et
+            "WOL" + // wo
+            "WOL" + // wo-sn
+            "IVL" + // x-iv_mathan
+            "XHO" + // xh
+            "XHO" + // xh-za
+            "ZZZ" + // xog
+            "ZZZ" + // xog-ug
+            "ZZZ" + // yav
+            "ZZZ" + // yav-cm
+            "ZZZ" + // yi
+            "ZZZ" + // yi-001
+            "YOR" + // yo
+            "ZZZ" + // yo-bj
+            "YOR" + // yo-ng
+            "ZZZ" + // yue
+            "ZZZ" + // yue-hk
+            "ZHG" + // zgh
+            "ZHG" + // zgh-tfng
+            "ZHG" + // zgh-tfng-ma
+            "CHS" + // zh
+            "CHS" + // zh-chs
+            "CHT" + // zh-cht
+            "CHS" + // zh-cn
+            "CHS" + // zh-cn_phoneb
+            "CHS" + // zh-cn_stroke
+            "CHS" + // zh-hans
+            "ZZZ" + // zh-hans-hk
+            "ZZZ" + // zh-hans-mo
+            "ZHH" + // zh-hant
+            "ZHH" + // zh-hk
+            "ZHH" + // zh-hk_radstr
+            "ZHM" + // zh-mo
+            "ZHM" + // zh-mo_radstr
+            "ZHM" + // zh-mo_stroke
+            "ZHI" + // zh-sg
+            "ZHI" + // zh-sg_phoneb
+            "ZHI" + // zh-sg_stroke
+            "CHT" + // zh-tw
+            "CHT" + // zh-tw_pronun
+            "CHT" + // zh-tw_radstr
+            "ZUL" + // zu
+            "ZUL";  // zu-za
+
+        // s_localeNamesIndices contains the start index of every culture name in the string
+        // s_localeNames. We infer the length of each string by looking at the start index
+        // of the next string.
+        private static readonly int[] s_localeNamesIndices = new int[]
+        {
+            // c_localeNames index, // index to this array - culture name
+            0   , // 0    - aa
+            2   , // 1    - aa-dj
+            7   , // 2    - aa-er
+            12  , // 3    - aa-et
+            17  , // 4    - af
+            19  , // 5    - af-na
+            24  , // 6    - af-za
+            29  , // 7    - agq
+            32  , // 8    - agq-cm
+            38  , // 9    - ak
+            40  , // 10   - ak-gh
+            45  , // 11   - am
+            47  , // 12   - am-et
+            52  , // 13   - ar
+            54  , // 14   - ar-001
+            60  , // 15   - ar-ae
+            65  , // 16   - ar-bh
+            70  , // 17   - ar-dj
+            75  , // 18   - ar-dz
+            80  , // 19   - ar-eg
+            85  , // 20   - ar-er
+            90  , // 21   - ar-il
+            95  , // 22   - ar-iq
+            100 , // 23   - ar-jo
+            105 , // 24   - ar-km
+            110 , // 25   - ar-kw
+            115 , // 26   - ar-lb
+            120 , // 27   - ar-ly
+            125 , // 28   - ar-ma
+            130 , // 29   - ar-mr
+            135 , // 30   - ar-om
+            140 , // 31   - ar-ps
+            145 , // 32   - ar-qa
+            150 , // 33   - ar-sa
+            155 , // 34   - ar-sd
+            160 , // 35   - ar-so
+            165 , // 36   - ar-ss
+            170 , // 37   - ar-sy
+            175 , // 38   - ar-td
+            180 , // 39   - ar-tn
+            185 , // 40   - ar-ye
+            190 , // 41   - arn
+            193 , // 42   - arn-cl
+            199 , // 43   - as
+            201 , // 44   - as-in
+            206 , // 45   - asa
+            209 , // 46   - asa-tz
+            215 , // 47   - ast
+            218 , // 48   - ast-es
+            224 , // 49   - az
+            226 , // 50   - az-cyrl
+            233 , // 51   - az-cyrl-az
+            243 , // 52   - az-latn
+            250 , // 53   - az-latn-az
+            260 , // 54   - ba
+            262 , // 55   - ba-ru
+            267 , // 56   - bas
+            270 , // 57   - bas-cm
+            276 , // 58   - be
+            278 , // 59   - be-by
+            283 , // 60   - bem
+            286 , // 61   - bem-zm
+            292 , // 62   - bez
+            295 , // 63   - bez-tz
+            301 , // 64   - bg
+            303 , // 65   - bg-bg
+            308 , // 66   - bin
+            311 , // 67   - bin-ng
+            317 , // 68   - bm
+            319 , // 69   - bm-latn
+            326 , // 70   - bm-latn-ml
+            336 , // 71   - bn
+            338 , // 72   - bn-bd
+            343 , // 73   - bn-in
+            348 , // 74   - bo
+            350 , // 75   - bo-cn
+            355 , // 76   - bo-in
+            360 , // 77   - br
+            362 , // 78   - br-fr
+            367 , // 79   - brx
+            370 , // 80   - brx-in
+            376 , // 81   - bs
+            378 , // 82   - bs-cyrl
+            385 , // 83   - bs-cyrl-ba
+            395 , // 84   - bs-latn
+            402 , // 85   - bs-latn-ba
+            412 , // 86   - byn
+            415 , // 87   - byn-er
+            421 , // 88   - ca
+            423 , // 89   - ca-ad
+            428 , // 90   - ca-es
+            433 , // 91   - ca-es-valencia
+            447 , // 92   - ca-fr
+            452 , // 93   - ca-it
+            457 , // 94   - ce
+            459 , // 95   - ce-ru
+            464 , // 96   - cgg
+            467 , // 97   - cgg-ug
+            473 , // 98   - chr
+            476 , // 99   - chr-cher
+            484 , // 100  - chr-cher-us
+            495 , // 101  - co
+            497 , // 102  - co-fr
+            502 , // 103  - cs
+            504 , // 104  - cs-cz
+            509 , // 105  - cu
+            511 , // 106  - cu-ru
+            516 , // 107  - cy
+            518 , // 108  - cy-gb
+            523 , // 109  - da
+            525 , // 110  - da-dk
+            530 , // 111  - da-gl
+            535 , // 112  - dav
+            538 , // 113  - dav-ke
+            544 , // 114  - de
+            546 , // 115  - de-at
+            551 , // 116  - de-be
+            556 , // 117  - de-ch
+            561 , // 118  - de-de
+            566 , // 119  - de-de_phoneb
+            578 , // 120  - de-it
+            583 , // 121  - de-li
+            588 , // 122  - de-lu
+            593 , // 123  - dje
+            596 , // 124  - dje-ne
+            602 , // 125  - dsb
+            605 , // 126  - dsb-de
+            611 , // 127  - dua
+            614 , // 128  - dua-cm
+            620 , // 129  - dv
+            622 , // 130  - dv-mv
+            627 , // 131  - dyo
+            630 , // 132  - dyo-sn
+            636 , // 133  - dz
+            638 , // 134  - dz-bt
+            643 , // 135  - ebu
+            646 , // 136  - ebu-ke
+            652 , // 137  - ee
+            654 , // 138  - ee-gh
+            659 , // 139  - ee-tg
+            664 , // 140  - el
+            666 , // 141  - el-cy
+            671 , // 142  - el-gr
+            676 , // 143  - en
+            678 , // 144  - en-001
+            684 , // 145  - en-029
+            690 , // 146  - en-150
+            696 , // 147  - en-ag
+            701 , // 148  - en-ai
+            706 , // 149  - en-as
+            711 , // 150  - en-at
+            716 , // 151  - en-au
+            721 , // 152  - en-bb
+            726 , // 153  - en-be
+            731 , // 154  - en-bi
+            736 , // 155  - en-bm
+            741 , // 156  - en-bs
+            746 , // 157  - en-bw
+            751 , // 158  - en-bz
+            756 , // 159  - en-ca
+            761 , // 160  - en-cc
+            766 , // 161  - en-ch
+            771 , // 162  - en-ck
+            776 , // 163  - en-cm
+            781 , // 164  - en-cx
+            786 , // 165  - en-cy
+            791 , // 166  - en-de
+            796 , // 167  - en-dk
+            801 , // 168  - en-dm
+            806 , // 169  - en-er
+            811 , // 170  - en-fi
+            816 , // 171  - en-fj
+            821 , // 172  - en-fk
+            826 , // 173  - en-fm
+            831 , // 174  - en-gb
+            836 , // 175  - en-gd
+            841 , // 176  - en-gg
+            846 , // 177  - en-gh
+            851 , // 178  - en-gi
+            856 , // 179  - en-gm
+            861 , // 180  - en-gu
+            866 , // 181  - en-gy
+            871 , // 182  - en-hk
+            876 , // 183  - en-id
+            881 , // 184  - en-ie
+            886 , // 185  - en-il
+            891 , // 186  - en-im
+            896 , // 187  - en-in
+            901 , // 188  - en-io
+            906 , // 189  - en-je
+            911 , // 190  - en-jm
+            916 , // 191  - en-ke
+            921 , // 192  - en-ki
+            926 , // 193  - en-kn
+            931 , // 194  - en-ky
+            936 , // 195  - en-lc
+            941 , // 196  - en-lr
+            946 , // 197  - en-ls
+            951 , // 198  - en-mg
+            956 , // 199  - en-mh
+            961 , // 200  - en-mo
+            966 , // 201  - en-mp
+            971 , // 202  - en-ms
+            976 , // 203  - en-mt
+            981 , // 204  - en-mu
+            986 , // 205  - en-mw
+            991 , // 206  - en-my
+            996 , // 207  - en-na
+            1001, // 208  - en-nf
+            1006, // 209  - en-ng
+            1011, // 210  - en-nl
+            1016, // 211  - en-nr
+            1021, // 212  - en-nu
+            1026, // 213  - en-nz
+            1031, // 214  - en-pg
+            1036, // 215  - en-ph
+            1041, // 216  - en-pk
+            1046, // 217  - en-pn
+            1051, // 218  - en-pr
+            1056, // 219  - en-pw
+            1061, // 220  - en-rw
+            1066, // 221  - en-sb
+            1071, // 222  - en-sc
+            1076, // 223  - en-sd
+            1081, // 224  - en-se
+            1086, // 225  - en-sg
+            1091, // 226  - en-sh
+            1096, // 227  - en-si
+            1101, // 228  - en-sl
+            1106, // 229  - en-ss
+            1111, // 230  - en-sx
+            1116, // 231  - en-sz
+            1121, // 232  - en-tc
+            1126, // 233  - en-tk
+            1131, // 234  - en-to
+            1136, // 235  - en-tt
+            1141, // 236  - en-tv
+            1146, // 237  - en-tz
+            1151, // 238  - en-ug
+            1156, // 239  - en-um
+            1161, // 240  - en-us
+            1166, // 241  - en-vc
+            1171, // 242  - en-vg
+            1176, // 243  - en-vi
+            1181, // 244  - en-vu
+            1186, // 245  - en-ws
+            1191, // 246  - en-za
+            1196, // 247  - en-zm
+            1201, // 248  - en-zw
+            1206, // 249  - eo
+            1208, // 250  - eo-001
+            1214, // 251  - es
+            1216, // 252  - es-419
+            1222, // 253  - es-ar
+            1227, // 254  - es-bo
+            1232, // 255  - es-br
+            1237, // 256  - es-cl
+            1242, // 257  - es-co
+            1247, // 258  - es-cr
+            1252, // 259  - es-cu
+            1257, // 260  - es-do
+            1262, // 261  - es-ec
+            1267, // 262  - es-es
+            1272, // 263  - es-es_tradnl
+            1284, // 264  - es-gq
+            1289, // 265  - es-gt
+            1294, // 266  - es-hn
+            1299, // 267  - es-mx
+            1304, // 268  - es-ni
+            1309, // 269  - es-pa
+            1314, // 270  - es-pe
+            1319, // 271  - es-ph
+            1324, // 272  - es-pr
+            1329, // 273  - es-py
+            1334, // 274  - es-sv
+            1339, // 275  - es-us
+            1344, // 276  - es-uy
+            1349, // 277  - es-ve
+            1354, // 278  - et
+            1356, // 279  - et-ee
+            1361, // 280  - eu
+            1363, // 281  - eu-es
+            1368, // 282  - ewo
+            1371, // 283  - ewo-cm
+            1377, // 284  - fa
+            1379, // 285  - fa-ir
+            1384, // 286  - ff
+            1386, // 287  - ff-cm
+            1391, // 288  - ff-gn
+            1396, // 289  - ff-latn
+            1403, // 290  - ff-latn-sn
+            1413, // 291  - ff-mr
+            1418, // 292  - ff-ng
+            1423, // 293  - fi
+            1425, // 294  - fi-fi
+            1430, // 295  - fil
+            1433, // 296  - fil-ph
+            1439, // 297  - fo
+            1441, // 298  - fo-dk
+            1446, // 299  - fo-fo
+            1451, // 300  - fr
+            1453, // 301  - fr-029
+            1459, // 302  - fr-be
+            1464, // 303  - fr-bf
+            1469, // 304  - fr-bi
+            1474, // 305  - fr-bj
+            1479, // 306  - fr-bl
+            1484, // 307  - fr-ca
+            1489, // 308  - fr-cd
+            1494, // 309  - fr-cf
+            1499, // 310  - fr-cg
+            1504, // 311  - fr-ch
+            1509, // 312  - fr-ci
+            1514, // 313  - fr-cm
+            1519, // 314  - fr-dj
+            1524, // 315  - fr-dz
+            1529, // 316  - fr-fr
+            1534, // 317  - fr-ga
+            1539, // 318  - fr-gf
+            1544, // 319  - fr-gn
+            1549, // 320  - fr-gp
+            1554, // 321  - fr-gq
+            1559, // 322  - fr-ht
+            1564, // 323  - fr-km
+            1569, // 324  - fr-lu
+            1574, // 325  - fr-ma
+            1579, // 326  - fr-mc
+            1584, // 327  - fr-mf
+            1589, // 328  - fr-mg
+            1594, // 329  - fr-ml
+            1599, // 330  - fr-mq
+            1604, // 331  - fr-mr
+            1609, // 332  - fr-mu
+            1614, // 333  - fr-nc
+            1619, // 334  - fr-ne
+            1624, // 335  - fr-pf
+            1629, // 336  - fr-pm
+            1634, // 337  - fr-re
+            1639, // 338  - fr-rw
+            1644, // 339  - fr-sc
+            1649, // 340  - fr-sn
+            1654, // 341  - fr-sy
+            1659, // 342  - fr-td
+            1664, // 343  - fr-tg
+            1669, // 344  - fr-tn
+            1674, // 345  - fr-vu
+            1679, // 346  - fr-wf
+            1684, // 347  - fr-yt
+            1689, // 348  - fur
+            1692, // 349  - fur-it
+            1698, // 350  - fy
+            1700, // 351  - fy-nl
+            1705, // 352  - ga
+            1707, // 353  - ga-ie
+            1712, // 354  - gd
+            1714, // 355  - gd-gb
+            1719, // 356  - gl
+            1721, // 357  - gl-es
+            1726, // 358  - gn
+            1728, // 359  - gn-py
+            1733, // 360  - gsw
+            1736, // 361  - gsw-ch
+            1742, // 362  - gsw-fr
+            1748, // 363  - gsw-li
+            1754, // 364  - gu
+            1756, // 365  - gu-in
+            1761, // 366  - guz
+            1764, // 367  - guz-ke
+            1770, // 368  - gv
+            1772, // 369  - gv-im
+            1777, // 370  - ha
+            1779, // 371  - ha-latn
+            1786, // 372  - ha-latn-gh
+            1796, // 373  - ha-latn-ne
+            1806, // 374  - ha-latn-ng
+            1816, // 375  - haw
+            1819, // 376  - haw-us
+            1825, // 377  - he
+            1827, // 378  - he-il
+            1832, // 379  - hi
+            1834, // 380  - hi-in
+            1839, // 381  - hr
+            1841, // 382  - hr-ba
+            1846, // 383  - hr-hr
+            1851, // 384  - hsb
+            1854, // 385  - hsb-de
+            1860, // 386  - hu
+            1862, // 387  - hu-hu
+            1867, // 388  - hu-hu_technl
+            1879, // 389  - hy
+            1881, // 390  - hy-am
+            1886, // 391  - ia
+            1888, // 392  - ia-001
+            1894, // 393  - ia-fr
+            1899, // 394  - ibb
+            1902, // 395  - ibb-ng
+            1908, // 396  - id
+            1910, // 397  - id-id
+            1915, // 398  - ig
+            1917, // 399  - ig-ng
+            1922, // 400  - ii
+            1924, // 401  - ii-cn
+            1929, // 402  - is
+            1931, // 403  - is-is
+            1936, // 404  - it
+            1938, // 405  - it-ch
+            1943, // 406  - it-it
+            1948, // 407  - it-sm
+            1953, // 408  - iu
+            1955, // 409  - iu-cans
+            1962, // 410  - iu-cans-ca
+            1972, // 411  - iu-latn
+            1979, // 412  - iu-latn-ca
+            1989, // 413  - ja
+            1991, // 414  - ja-jp
+            1996, // 415  - ja-jp_radstr
+            2008, // 416  - jgo
+            2011, // 417  - jgo-cm
+            2017, // 418  - jmc
+            2020, // 419  - jmc-tz
+            2026, // 420  - jv
+            2028, // 421  - jv-java
+            2035, // 422  - jv-java-id
+            2045, // 423  - jv-latn
+            2052, // 424  - jv-latn-id
+            2062, // 425  - ka
+            2064, // 426  - ka-ge
+            2069, // 427  - ka-ge_modern
+            2081, // 428  - kab
+            2084, // 429  - kab-dz
+            2090, // 430  - kam
+            2093, // 431  - kam-ke
+            2099, // 432  - kde
+            2102, // 433  - kde-tz
+            2108, // 434  - kea
+            2111, // 435  - kea-cv
+            2117, // 436  - khq
+            2120, // 437  - khq-ml
+            2126, // 438  - ki
+            2128, // 439  - ki-ke
+            2133, // 440  - kk
+            2135, // 441  - kk-kz
+            2140, // 442  - kkj
+            2143, // 443  - kkj-cm
+            2149, // 444  - kl
+            2151, // 445  - kl-gl
+            2156, // 446  - kln
+            2159, // 447  - kln-ke
+            2165, // 448  - km
+            2167, // 449  - km-kh
+            2172, // 450  - kn
+            2174, // 451  - kn-in
+            2179, // 452  - ko
+            2181, // 453  - ko-kp
+            2186, // 454  - ko-kr
+            2191, // 455  - kok
+            2194, // 456  - kok-in
+            2200, // 457  - kr
+            2202, // 458  - kr-ng
+            2207, // 459  - ks
+            2209, // 460  - ks-arab
+            2216, // 461  - ks-arab-in
+            2226, // 462  - ks-deva
+            2233, // 463  - ks-deva-in
+            2243, // 464  - ksb
+            2246, // 465  - ksb-tz
+            2252, // 466  - ksf
+            2255, // 467  - ksf-cm
+            2261, // 468  - ksh
+            2264, // 469  - ksh-de
+            2270, // 470  - ku
+            2272, // 471  - ku-arab
+            2279, // 472  - ku-arab-iq
+            2289, // 473  - ku-arab-ir
+            2299, // 474  - kw
+            2301, // 475  - kw-gb
+            2306, // 476  - ky
+            2308, // 477  - ky-kg
+            2313, // 478  - la
+            2315, // 479  - la-001
+            2321, // 480  - lag
+            2324, // 481  - lag-tz
+            2330, // 482  - lb
+            2332, // 483  - lb-lu
+            2337, // 484  - lg
+            2339, // 485  - lg-ug
+            2344, // 486  - lkt
+            2347, // 487  - lkt-us
+            2353, // 488  - ln
+            2355, // 489  - ln-ao
+            2360, // 490  - ln-cd
+            2365, // 491  - ln-cf
+            2370, // 492  - ln-cg
+            2375, // 493  - lo
+            2377, // 494  - lo-la
+            2382, // 495  - lrc
+            2385, // 496  - lrc-iq
+            2391, // 497  - lrc-ir
+            2397, // 498  - lt
+            2399, // 499  - lt-lt
+            2404, // 500  - lu
+            2406, // 501  - lu-cd
+            2411, // 502  - luo
+            2414, // 503  - luo-ke
+            2420, // 504  - luy
+            2423, // 505  - luy-ke
+            2429, // 506  - lv
+            2431, // 507  - lv-lv
+            2436, // 508  - mas
+            2439, // 509  - mas-ke
+            2445, // 510  - mas-tz
+            2451, // 511  - mer
+            2454, // 512  - mer-ke
+            2460, // 513  - mfe
+            2463, // 514  - mfe-mu
+            2469, // 515  - mg
+            2471, // 516  - mg-mg
+            2476, // 517  - mgh
+            2479, // 518  - mgh-mz
+            2485, // 519  - mgo
+            2488, // 520  - mgo-cm
+            2494, // 521  - mi
+            2496, // 522  - mi-nz
+            2501, // 523  - mk
+            2503, // 524  - mk-mk
+            2508, // 525  - ml
+            2510, // 526  - ml-in
+            2515, // 527  - mn
+            2517, // 528  - mn-cyrl
+            2524, // 529  - mn-mn
+            2529, // 530  - mn-mong
+            2536, // 531  - mn-mong-cn
+            2546, // 532  - mn-mong-mn
+            2556, // 533  - mni
+            2559, // 534  - mni-in
+            2565, // 535  - moh
+            2568, // 536  - moh-ca
+            2574, // 537  - mr
+            2576, // 538  - mr-in
+            2581, // 539  - ms
+            2583, // 540  - ms-bn
+            2588, // 541  - ms-my
+            2593, // 542  - ms-sg
+            2598, // 543  - mt
+            2600, // 544  - mt-mt
+            2605, // 545  - mua
+            2608, // 546  - mua-cm
+            2614, // 547  - my
+            2616, // 548  - my-mm
+            2621, // 549  - mzn
+            2624, // 550  - mzn-ir
+            2630, // 551  - naq
+            2633, // 552  - naq-na
+            2639, // 553  - nb
+            2641, // 554  - nb-no
+            2646, // 555  - nb-sj
+            2651, // 556  - nd
+            2653, // 557  - nd-zw
+            2658, // 558  - nds
+            2661, // 559  - nds-de
+            2667, // 560  - nds-nl
+            2673, // 561  - ne
+            2675, // 562  - ne-in
+            2680, // 563  - ne-np
+            2685, // 564  - nl
+            2687, // 565  - nl-aw
+            2692, // 566  - nl-be
+            2697, // 567  - nl-bq
+            2702, // 568  - nl-cw
+            2707, // 569  - nl-nl
+            2712, // 570  - nl-sr
+            2717, // 571  - nl-sx
+            2722, // 572  - nmg
+            2725, // 573  - nmg-cm
+            2731, // 574  - nn
+            2733, // 575  - nn-no
+            2738, // 576  - nnh
+            2741, // 577  - nnh-cm
+            2747, // 578  - no
+            2749, // 579  - nqo
+            2752, // 580  - nqo-gn
+            2758, // 581  - nr
+            2760, // 582  - nr-za
+            2765, // 583  - nso
+            2768, // 584  - nso-za
+            2774, // 585  - nus
+            2777, // 586  - nus-ss
+            2783, // 587  - nyn
+            2786, // 588  - nyn-ug
+            2792, // 589  - oc
+            2794, // 590  - oc-fr
+            2799, // 591  - om
+            2801, // 592  - om-et
+            2806, // 593  - om-ke
+            2811, // 594  - or
+            2813, // 595  - or-in
+            2818, // 596  - os
+            2820, // 597  - os-ge
+            2825, // 598  - os-ru
+            2830, // 599  - pa
+            2832, // 600  - pa-arab
+            2839, // 601  - pa-arab-pk
+            2849, // 602  - pa-in
+            2854, // 603  - pap
+            2857, // 604  - pap-029
+            2864, // 605  - pl
+            2866, // 606  - pl-pl
+            2871, // 607  - prg
+            2874, // 608  - prg-001
+            2881, // 609  - prs
+            2884, // 610  - prs-af
+            2890, // 611  - ps
+            2892, // 612  - ps-af
+            2897, // 613  - pt
+            2899, // 614  - pt-ao
+            2904, // 615  - pt-br
+            2909, // 616  - pt-ch
+            2914, // 617  - pt-cv
+            2919, // 618  - pt-gq
+            2924, // 619  - pt-gw
+            2929, // 620  - pt-lu
+            2934, // 621  - pt-mo
+            2939, // 622  - pt-mz
+            2944, // 623  - pt-pt
+            2949, // 624  - pt-st
+            2954, // 625  - pt-tl
+            2959, // 626  - qps-latn-x-sh
+            2972, // 627  - qps-ploc
+            2980, // 628  - qps-ploca
+            2989, // 629  - qps-plocm
+            2998, // 630  - quc
+            3001, // 631  - quc-latn
+            3009, // 632  - quc-latn-gt
+            3020, // 633  - quz
+            3023, // 634  - quz-bo
+            3029, // 635  - quz-ec
+            3035, // 636  - quz-pe
+            3041, // 637  - rm
+            3043, // 638  - rm-ch
+            3048, // 639  - rn
+            3050, // 640  - rn-bi
+            3055, // 641  - ro
+            3057, // 642  - ro-md
+            3062, // 643  - ro-ro
+            3067, // 644  - rof
+            3070, // 645  - rof-tz
+            3076, // 646  - ru
+            3078, // 647  - ru-by
+            3083, // 648  - ru-kg
+            3088, // 649  - ru-kz
+            3093, // 650  - ru-md
+            3098, // 651  - ru-ru
+            3103, // 652  - ru-ua
+            3108, // 653  - rw
+            3110, // 654  - rw-rw
+            3115, // 655  - rwk
+            3118, // 656  - rwk-tz
+            3124, // 657  - sa
+            3126, // 658  - sa-in
+            3131, // 659  - sah
+            3134, // 660  - sah-ru
+            3140, // 661  - saq
+            3143, // 662  - saq-ke
+            3149, // 663  - sbp
+            3152, // 664  - sbp-tz
+            3158, // 665  - sd
+            3160, // 666  - sd-arab
+            3167, // 667  - sd-arab-pk
+            3177, // 668  - sd-deva
+            3184, // 669  - sd-deva-in
+            3194, // 670  - se
+            3196, // 671  - se-fi
+            3201, // 672  - se-no
+            3206, // 673  - se-se
+            3211, // 674  - seh
+            3214, // 675  - seh-mz
+            3220, // 676  - ses
+            3223, // 677  - ses-ml
+            3229, // 678  - sg
+            3231, // 679  - sg-cf
+            3236, // 680  - shi
+            3239, // 681  - shi-latn
+            3247, // 682  - shi-latn-ma
+            3258, // 683  - shi-tfng
+            3266, // 684  - shi-tfng-ma
+            3277, // 685  - si
+            3279, // 686  - si-lk
+            3284, // 687  - sk
+            3286, // 688  - sk-sk
+            3291, // 689  - sl
+            3293, // 690  - sl-si
+            3298, // 691  - sma
+            3301, // 692  - sma-no
+            3307, // 693  - sma-se
+            3313, // 694  - smj
+            3316, // 695  - smj-no
+            3322, // 696  - smj-se
+            3328, // 697  - smn
+            3331, // 698  - smn-fi
+            3337, // 699  - sms
+            3340, // 700  - sms-fi
+            3346, // 701  - sn
+            3348, // 702  - sn-latn
+            3355, // 703  - sn-latn-zw
+            3365, // 704  - so
+            3367, // 705  - so-dj
+            3372, // 706  - so-et
+            3377, // 707  - so-ke
+            3382, // 708  - so-so
+            3387, // 709  - sq
+            3389, // 710  - sq-al
+            3394, // 711  - sq-mk
+            3399, // 712  - sq-xk
+            3404, // 713  - sr
+            3406, // 714  - sr-cyrl
+            3413, // 715  - sr-cyrl-ba
+            3423, // 716  - sr-cyrl-cs
+            3433, // 717  - sr-cyrl-me
+            3443, // 718  - sr-cyrl-rs
+            3453, // 719  - sr-cyrl-xk
+            3463, // 720  - sr-latn
+            3470, // 721  - sr-latn-ba
+            3480, // 722  - sr-latn-cs
+            3490, // 723  - sr-latn-me
+            3500, // 724  - sr-latn-rs
+            3510, // 725  - sr-latn-xk
+            3520, // 726  - ss
+            3522, // 727  - ss-sz
+            3527, // 728  - ss-za
+            3532, // 729  - ssy
+            3535, // 730  - ssy-er
+            3541, // 731  - st
+            3543, // 732  - st-ls
+            3548, // 733  - st-za
+            3553, // 734  - sv
+            3555, // 735  - sv-ax
+            3560, // 736  - sv-fi
+            3565, // 737  - sv-se
+            3570, // 738  - sw
+            3572, // 739  - sw-cd
+            3577, // 740  - sw-ke
+            3582, // 741  - sw-tz
+            3587, // 742  - sw-ug
+            3592, // 743  - swc
+            3595, // 744  - swc-cd
+            3601, // 745  - syr
+            3604, // 746  - syr-sy
+            3610, // 747  - ta
+            3612, // 748  - ta-in
+            3617, // 749  - ta-lk
+            3622, // 750  - ta-my
+            3627, // 751  - ta-sg
+            3632, // 752  - te
+            3634, // 753  - te-in
+            3639, // 754  - teo
+            3642, // 755  - teo-ke
+            3648, // 756  - teo-ug
+            3654, // 757  - tg
+            3656, // 758  - tg-cyrl
+            3663, // 759  - tg-cyrl-tj
+            3673, // 760  - th
+            3675, // 761  - th-th
+            3680, // 762  - ti
+            3682, // 763  - ti-er
+            3687, // 764  - ti-et
+            3692, // 765  - tig
+            3695, // 766  - tig-er
+            3701, // 767  - tk
+            3703, // 768  - tk-tm
+            3708, // 769  - tn
+            3710, // 770  - tn-bw
+            3715, // 771  - tn-za
+            3720, // 772  - to
+            3722, // 773  - to-to
+            3727, // 774  - tr
+            3729, // 775  - tr-cy
+            3734, // 776  - tr-tr
+            3739, // 777  - ts
+            3741, // 778  - ts-za
+            3746, // 779  - tt
+            3748, // 780  - tt-ru
+            3753, // 781  - twq
+            3756, // 782  - twq-ne
+            3762, // 783  - tzm
+            3765, // 784  - tzm-arab
+            3773, // 785  - tzm-arab-ma
+            3784, // 786  - tzm-latn
+            3792, // 787  - tzm-latn-dz
+            3803, // 788  - tzm-latn-ma
+            3814, // 789  - tzm-tfng
+            3822, // 790  - tzm-tfng-ma
+            3833, // 791  - ug
+            3835, // 792  - ug-cn
+            3840, // 793  - uk
+            3842, // 794  - uk-ua
+            3847, // 795  - ur
+            3849, // 796  - ur-in
+            3854, // 797  - ur-pk
+            3859, // 798  - uz
+            3861, // 799  - uz-arab
+            3868, // 800  - uz-arab-af
+            3878, // 801  - uz-cyrl
+            3885, // 802  - uz-cyrl-uz
+            3895, // 803  - uz-latn
+            3902, // 804  - uz-latn-uz
+            3912, // 805  - vai
+            3915, // 806  - vai-latn
+            3923, // 807  - vai-latn-lr
+            3934, // 808  - vai-vaii
+            3942, // 809  - vai-vaii-lr
+            3953, // 810  - ve
+            3955, // 811  - ve-za
+            3960, // 812  - vi
+            3962, // 813  - vi-vn
+            3967, // 814  - vo
+            3969, // 815  - vo-001
+            3975, // 816  - vun
+            3978, // 817  - vun-tz
+            3984, // 818  - wae
+            3987, // 819  - wae-ch
+            3993, // 820  - wal
+            3996, // 821  - wal-et
+            4002, // 822  - wo
+            4004, // 823  - wo-sn
+            4009, // 824  - x-iv_mathan
+            4020, // 825  - xh
+            4022, // 826  - xh-za
+            4027, // 827  - xog
+            4030, // 828  - xog-ug
+            4036, // 829  - yav
+            4039, // 830  - yav-cm
+            4045, // 831  - yi
+            4047, // 832  - yi-001
+            4053, // 833  - yo
+            4055, // 834  - yo-bj
+            4060, // 835  - yo-ng
+            4065, // 836  - yue
+            4068, // 837  - yue-hk
+            4074, // 838  - zgh
+            4077, // 839  - zgh-tfng
+            4085, // 840  - zgh-tfng-ma
+            4096, // 841  - zh
+            4098, // 842  - zh-chs
+            4104, // 843  - zh-cht
+            4110, // 844  - zh-cn
+            4115, // 845  - zh-cn_phoneb
+            4127, // 846  - zh-cn_stroke
+            4139, // 847  - zh-hans
+            4146, // 848  - zh-hans-hk
+            4156, // 849  - zh-hans-mo
+            4166, // 850  - zh-hant
+            4173, // 851  - zh-hk
+            4178, // 852  - zh-hk_radstr
+            4190, // 853  - zh-mo
+            4195, // 854  - zh-mo_radstr
+            4207, // 855  - zh-mo_stroke
+            4219, // 856  - zh-sg
+            4224, // 857  - zh-sg_phoneb
+            4236, // 858  - zh-sg_stroke
+            4248, // 859  - zh-tw
+            4253, // 860  - zh-tw_pronun
+            4265, // 861  - zh-tw_radstr
+            4277, // 862  - zu
+            4279,  // 863  - zu-za
+            4284
+        };
+               
+        private const int NUMERIC_LOCALE_DATA_COUNT_PER_ROW = 9;
+        // s_nameIndexToNumericData is mapping from index in s_localeNamesIndices to locale data.
+        // each row in the table will have the following data:
+        //      Lcid, Ansi codepage, Oem codepage, MAC codepage, EBCDIC codepage, Geo Id, Digit Substitution, specific locale index, Console locale index
+        private static readonly int[] s_nameIndexToNumericData = new int[]
+        {
+         // Lcid,  Ansi CP, Oem CP, MAC CP, EBCDIC CP, Geo Id, digit substitution, Specific culture index, keyboard Id, Console locale index  // index - locale name
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x49  , 1 , 3   , 240 , // 0    - aa
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x3e  , 1 , 1   , 240 , // 1    - aa-dj
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x47  , 1 , 2   , 240 , // 2    - aa-er
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x49  , 1 , 3   , 240 , // 3    - aa-et
+            0x36   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd1  , 1 , 6   , 6   , // 4    - af
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xfe  , 1 , 5   , 240 , // 5    - af-na
+            0x436  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd1  , 1 , 6   , 6   , // 6    - af-za
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 8   , 240 , // 7    - agq
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 8   , 240 , // 8    - agq-cm
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x59  , 1 , 10  , 240 , // 9    - ak
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x59  , 1 , 10  , 240 , // 10   - ak-gh
+            0x5e   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x49  , 1 , 12  , 143 , // 11   - am
+            0x45e  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x49  , 1 , 12  , 143 , // 12   - am-et
+            0x1    , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xcd  , 0 , 33  , 143 , // 13   - ar
+            0x1000 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x989e, 0 , 14  , 240 , // 14   - ar-001
+            0x3801 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xe0  , 0 , 15  , 143 , // 15   - ar-ae
+            0x3c01 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x11  , 0 , 16  , 143 , // 16   - ar-bh
+            0x1000 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x3e  , 0 , 17  , 240 , // 17   - ar-dj
+            0x1401 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x4   , 1 , 18  , 300 , // 18   - ar-dz
+            0xc01  , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x43  , 0 , 19  , 143 , // 19   - ar-eg
+            0x1000 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x47  , 0 , 20  , 240 , // 20   - ar-er
+            0x1000 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x75  , 0 , 21  , 240 , // 21   - ar-il
+            0x801  , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x79  , 0 , 22  , 143 , // 22   - ar-iq
+            0x2c01 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x7e  , 0 , 23  , 143 , // 23   - ar-jo
+            0x1000 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x32  , 0 , 24  , 240 , // 24   - ar-km
+            0x3401 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x88  , 0 , 25  , 143 , // 25   - ar-kw
+            0x3001 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x8b  , 0 , 26  , 143 , // 26   - ar-lb
+            0x1001 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x94  , 1 , 27  , 143 , // 27   - ar-ly
+            0x1801 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x9f  , 1 , 28  , 300 , // 28   - ar-ma
+            0x1000 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xa2  , 0 , 29  , 240 , // 29   - ar-mr
+            0x2001 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xa4  , 0 , 30  , 143 , // 30   - ar-om
+            0x1000 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xb8  , 0 , 31  , 240 , // 31   - ar-ps
+            0x4001 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xc5  , 0 , 32  , 143 , // 32   - ar-qa
+            0x401  , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xcd  , 0 , 33  , 143 , // 33   - ar-sa
+            0x1000 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xdb  , 0 , 34  , 240 , // 34   - ar-sd
+            0x1000 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xd8  , 0 , 35  , 240 , // 35   - ar-so
+            0x1000 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x114 , 0 , 36  , 240 , // 36   - ar-ss
+            0x2801 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xde  , 0 , 37  , 143 , // 37   - ar-sy
+            0x1000 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x29  , 0 , 38  , 240 , // 38   - ar-td
+            0x1c01 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xea  , 1 , 39  , 300 , // 39   - ar-tn
+            0x2401 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x105 , 0 , 40  , 143 , // 40   - ar-ye
+            0x7a   , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x2e  , 1 , 42  , 42  , // 41   - arn
+            0x47a  , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x2e  , 1 , 42  , 42  , // 42   - arn-cl
+            0x4d   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 44  , 143 , // 43   - as
+            0x44d  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 44  , 143 , // 44   - as-in
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 46  , 240 , // 45   - asa
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 46  , 240 , // 46   - asa-tz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd9  , 1 , 48  , 240 , // 47   - ast
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd9  , 1 , 48  , 240 , // 48   - ast-es
+            0x2c   , 0x4e6 , 0x359 , 0x2761, 0x51a9, 0x5   , 1 , 53  , 53  , // 49   - az
+            0x742c , 0x4e3 , 0x362 , 0x2717, 0x5190, 0x5   , 1 , 51  , 51  , // 50   - az-cyrl
+            0x82c  , 0x4e3 , 0x362 , 0x2717, 0x5190, 0x5   , 1 , 51  , 51  , // 51   - az-cyrl-az
+            0x782c , 0x4e6 , 0x359 , 0x2761, 0x51a9, 0x5   , 1 , 53  , 53  , // 52   - az-latn
+            0x42c  , 0x4e6 , 0x359 , 0x2761, 0x51a9, 0x5   , 1 , 53  , 53  , // 53   - az-latn-az
+            0x6d   , 0x4e3 , 0x362 , 0x2717, 0x5190, 0xcb  , 1 , 55  , 55  , // 54   - ba
+            0x46d  , 0x4e3 , 0x362 , 0x2717, 0x5190, 0xcb  , 1 , 55  , 55  , // 55   - ba-ru
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 57  , 240 , // 56   - bas
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 57  , 240 , // 57   - bas-cm
+            0x23   , 0x4e3 , 0x362 , 0x2717, 0x1f4 , 0x1d  , 1 , 59  , 59  , // 58   - be
+            0x423  , 0x4e3 , 0x362 , 0x2717, 0x1f4 , 0x1d  , 1 , 59  , 59  , // 59   - be-by
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x107 , 1 , 61  , 240 , // 60   - bem
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x107 , 1 , 61  , 240 , // 61   - bem-zm
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 63  , 240 , // 62   - bez
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 63  , 240 , // 63   - bez-tz
+            0x2    , 0x4e3 , 0x362 , 0x2717, 0x5221, 0x23  , 1 , 65  , 65  , // 64   - bg
+            0x402  , 0x4e3 , 0x362 , 0x2717, 0x5221, 0x23  , 1 , 65  , 65  , // 65   - bg-bg
+            0x66   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xaf  , 1 , 67  , 240 , // 66   - bin
+            0x466  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xaf  , 1 , 67  , 240 , // 67   - bin-ng
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9d  , 1 , 70  , 240 , // 68   - bm
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9d  , 1 , 70  , 240 , // 69   - bm-latn
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9d  , 1 , 70  , 240 , // 70   - bm-latn-ml
+            0x45   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x17  , 1 , 72  , 143 , // 71   - bn
+            0x845  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x17  , 1 , 72  , 143 , // 72   - bn-bd
+            0x445  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 73  , 143 , // 73   - bn-in
+            0x51   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x2d  , 1 , 75  , 143 , // 74   - bo
+            0x451  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x2d  , 1 , 75  , 143 , // 75   - bo-cn
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 76  , 240 , // 76   - bo-in
+            0x7e   , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x54  , 1 , 78  , 78  , // 77   - br
+            0x47e  , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x54  , 1 , 78  , 78  , // 78   - br-fr
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 80  , 240 , // 79   - brx
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 80  , 240 , // 80   - brx-in
+            0x781a , 0x4e2 , 0x354 , 0x2762, 0x366 , 0x19  , 1 , 85  , 85  , // 81   - bs
+            0x641a , 0x4e3 , 0x357 , 0x2762, 0x366 , 0x19  , 1 , 83  , 83  , // 82   - bs-cyrl
+            0x201a , 0x4e3 , 0x357 , 0x2762, 0x366 , 0x19  , 1 , 83  , 83  , // 83   - bs-cyrl-ba
+            0x681a , 0x4e2 , 0x354 , 0x2762, 0x366 , 0x19  , 1 , 85  , 85  , // 84   - bs-latn
+            0x141a , 0x4e2 , 0x354 , 0x2762, 0x366 , 0x19  , 1 , 85  , 85  , // 85   - bs-latn-ba
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x47  , 1 , 87  , 240 , // 86   - byn
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x47  , 1 , 87  , 240 , // 87   - byn-er
+            0x3    , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd9  , 1 , 90  , 90  , // 88   - ca
+            0x1000 , 0x4e4 , 0x352 , 0x2   , 0x1f4 , 0x8   , 1 , 89  , 240 , // 89   - ca-ad
+            0x403  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd9  , 1 , 90  , 90  , // 90   - ca-es
+            0x803  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd9  , 1 , 91  , 90  , // 91   - ca-es-valencia
+            0x1000 , 0x4e4 , 0x352 , 0x2   , 0x1f4 , 0x54  , 1 , 92  , 240 , // 92   - ca-fr
+            0x1000 , 0x4e4 , 0x352 , 0x2   , 0x1f4 , 0x76  , 1 , 93  , 240 , // 93   - ca-it
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xcb  , 1 , 95  , 240 , // 94   - ce
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xcb  , 1 , 95  , 240 , // 95   - ce-ru
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf0  , 1 , 97  , 240 , // 96   - cgg
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf0  , 1 , 97  , 240 , // 97   - cgg-ug
+            0x5c   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf4  , 1 , 100 , 240 , // 98   - chr
+            0x7c5c , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf4  , 1 , 100 , 240 , // 99   - chr-cher
+            0x45c  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf4  , 1 , 100 , 240 , // 100  - chr-cher-us
+            0x83   , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x54  , 1 , 102 , 102 , // 101  - co
+            0x483  , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x54  , 1 , 102 , 102 , // 102  - co-fr
+            0x5    , 0x4e2 , 0x354 , 0x272d, 0x1f4 , 0x4b  , 1 , 104 , 104 , // 103  - cs
+            0x405  , 0x4e2 , 0x354 , 0x272d, 0x1f4 , 0x4b  , 1 , 104 , 104 , // 104  - cs-cz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xcb  , 1 , 106 , 240 , // 105  - cu
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xcb  , 1 , 106 , 240 , // 106  - cu-ru
+            0x52   , 0x4e4 , 0x352 , 0x2710, 0x4f3d, 0xf2  , 1 , 108 , 108 , // 107  - cy
+            0x452  , 0x4e4 , 0x352 , 0x2710, 0x4f3d, 0xf2  , 1 , 108 , 108 , // 108  - cy-gb
+            0x6    , 0x4e4 , 0x352 , 0x2710, 0x4f35, 0x3d  , 1 , 110 , 110 , // 109  - da
+            0x406  , 0x4e4 , 0x352 , 0x2710, 0x4f35, 0x3d  , 1 , 110 , 110 , // 110  - da-dk
+            0x1000 , 0x4e4 , 0x352 , 0x2   , 0x1f4 , 0x5d  , 1 , 111 , 240 , // 111  - da-gl
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 113 , 240 , // 112  - dav
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 113 , 240 , // 113  - dav-ke
+            0x7    , 0x4e4 , 0x352 , 0x2710, 0x4f31, 0x5e  , 1 , 118 , 118 , // 114  - de
+            0xc07  , 0x4e4 , 0x352 , 0x2710, 0x4f31, 0xe   , 1 , 115 , 115 , // 115  - de-at
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f31, 0x15  , 1 , 116 , 240 , // 116  - de-be
+            0x807  , 0x4e4 , 0x352 , 0x2710, 0x4f31, 0xdf  , 1 , 117 , 117 , // 117  - de-ch
+            0x407  , 0x4e4 , 0x352 , 0x2710, 0x4f31, 0x5e  , 1 , 118 , 118 , // 118  - de-de
+            0x10407, 0x4e4 , 0x352 , 0x2710, 0x4f31, 0x5e  , 1 , 118 , 118 , // 119  - de-de_phoneb
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x76  , 1 , 120 , 240 , // 120  - de-it
+            0x1407 , 0x4e4 , 0x352 , 0x2710, 0x4f31, 0x91  , 1 , 121 , 121 , // 121  - de-li
+            0x1007 , 0x4e4 , 0x352 , 0x2710, 0x4f31, 0x93  , 1 , 122 , 122 , // 122  - de-lu
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xad  , 1 , 124 , 240 , // 123  - dje
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xad  , 1 , 124 , 240 , // 124  - dje-ne
+            0x7c2e , 0x4e4 , 0x352 , 0x2710, 0x366 , 0x5e  , 1 , 126 , 126 , // 125  - dsb
+            0x82e  , 0x4e4 , 0x352 , 0x2710, 0x366 , 0x5e  , 1 , 126 , 126 , // 126  - dsb-de
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 128 , 240 , // 127  - dua
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 128 , 240 , // 128  - dua-cm
+            0x65   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xa5  , 1 , 130 , 143 , // 129  - dv
+            0x465  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xa5  , 1 , 130 , 143 , // 130  - dv-mv
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd2  , 1 , 132 , 240 , // 131  - dyo
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd2  , 1 , 132 , 240 , // 132  - dyo-sn
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x22  , 2 , 134 , 240 , // 133  - dz
+            0xc51  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x22  , 2 , 134 , 240 , // 134  - dz-bt
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 136 , 240 , // 135  - ebu
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 136 , 240 , // 136  - ebu-ke
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x59  , 1 , 138 , 240 , // 137  - ee
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x59  , 1 , 138 , 240 , // 138  - ee-gh
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xe8  , 1 , 139 , 240 , // 139  - ee-tg
+            0x8    , 0x4e5 , 0x2e1 , 0x2716, 0x4f31, 0x62  , 1 , 142 , 142 , // 140  - el
+            0x1000 , 0x4e5 , 0x2e1 , 0x2716, 0x4f31, 0x3b  , 1 , 141 , 240 , // 141  - el-cy
+            0x408  , 0x4e5 , 0x2e1 , 0x2716, 0x4f31, 0x62  , 1 , 142 , 142 , // 142  - el-gr
+            0x9    , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xf4  , 1 , 240 , 240 , // 143  - en
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x989e, 1 , 144 , 240 , // 144  - en-001
+            0x2409 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x993248, 1 , 145 , 145 , // 145  - en-029
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x292d, 1 , 146 , 240 , // 146  - en-150
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x2   , 1 , 147 , 240 , // 147  - en-ag
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x12c , 1 , 148 , 240 , // 148  - en-ai
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xa   , 1 , 149 , 240 , // 149  - en-as
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xe   , 1 , 150 , 240 , // 150  - en-at
+            0xc09  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xc   , 1 , 151 , 151 , // 151  - en-au
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x12  , 1 , 152 , 240 , // 152  - en-bb
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x15  , 1 , 153 , 240 , // 153  - en-be
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x26  , 1 , 154 , 240 , // 154  - en-bi
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x14  , 1 , 155 , 240 , // 155  - en-bm
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x16  , 1 , 156 , 240 , // 156  - en-bs
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x13  , 1 , 157 , 240 , // 157  - en-bw
+            0x2809 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x18  , 1 , 158 , 158 , // 158  - en-bz
+            0x1009 , 0x4e4 , 0x352 , 0x2710, 0x25  , 0x27  , 1 , 159 , 159 , // 159  - en-ca
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x137 , 1 , 160 , 240 , // 160  - en-cc
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xdf  , 1 , 161 , 240 , // 161  - en-ch
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x138 , 1 , 162 , 240 , // 162  - en-ck
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x31  , 1 , 163 , 240 , // 163  - en-cm
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x135 , 1 , 164 , 240 , // 164  - en-cx
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x3b  , 1 , 165 , 240 , // 165  - en-cy
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x5e  , 1 , 166 , 240 , // 166  - en-de
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x3d  , 1 , 167 , 240 , // 167  - en-dk
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x3f  , 1 , 168 , 240 , // 168  - en-dm
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x47  , 1 , 169 , 240 , // 169  - en-er
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x4d  , 1 , 170 , 240 , // 170  - en-fi
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x4e  , 1 , 171 , 240 , // 171  - en-fj
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x13b , 1 , 172 , 240 , // 172  - en-fk
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x50  , 1 , 173 , 240 , // 173  - en-fm
+            0x809  , 0x4e4 , 0x352 , 0x2710, 0x4f3d, 0xf2  , 1 , 174 , 174 , // 174  - en-gb
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x5b  , 1 , 175 , 240 , // 175  - en-gd
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x144 , 1 , 176 , 240 , // 176  - en-gg
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x59  , 1 , 177 , 240 , // 177  - en-gh
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x5a  , 1 , 178 , 240 , // 178  - en-gi
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x56  , 1 , 179 , 240 , // 179  - en-gm
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x142 , 1 , 180 , 240 , // 180  - en-gu
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x65  , 1 , 181 , 240 , // 181  - en-gy
+            0x3c09 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x68  , 1 , 182 , 240 , // 182  - en-hk
+            0x3809 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x6f  , 1 , 183 , 240 , // 183  - en-id
+            0x1809 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x44  , 1 , 184 , 184 , // 184  - en-ie
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x75  , 1 , 185 , 240 , // 185  - en-il
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x3b16, 1 , 186 , 240 , // 186  - en-im
+            0x4009 , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0x71  , 1 , 187 , 187 , // 187  - en-in
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x72  , 1 , 188 , 240 , // 188  - en-io
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x148 , 1 , 189 , 240 , // 189  - en-je
+            0x2009 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x7c  , 1 , 190 , 190 , // 190  - en-jm
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x81  , 1 , 191 , 240 , // 191  - en-ke
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x85  , 1 , 192 , 240 , // 192  - en-ki
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xcf  , 1 , 193 , 240 , // 193  - en-kn
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x133 , 1 , 194 , 240 , // 194  - en-ky
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xda  , 1 , 195 , 240 , // 195  - en-lc
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x8e  , 1 , 196 , 240 , // 196  - en-lr
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x92  , 1 , 197 , 240 , // 197  - en-ls
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x95  , 1 , 198 , 240 , // 198  - en-mg
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xc7  , 1 , 199 , 240 , // 199  - en-mh
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x97  , 1 , 200 , 240 , // 200  - en-mo
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x151 , 1 , 201 , 240 , // 201  - en-mp
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x14c , 1 , 202 , 240 , // 202  - en-ms
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xa3  , 1 , 203 , 240 , // 203  - en-mt
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xa0  , 1 , 204 , 240 , // 204  - en-mu
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x9c  , 1 , 205 , 240 , // 205  - en-mw
+            0x4409 , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xa7  , 1 , 206 , 206 , // 206  - en-my
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xfe  , 1 , 207 , 240 , // 207  - en-na
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x150 , 1 , 208 , 240 , // 208  - en-nf
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xaf  , 1 , 209 , 240 , // 209  - en-ng
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xb0  , 1 , 210 , 240 , // 210  - en-nl
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xb4  , 1 , 211 , 240 , // 211  - en-nr
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x14f , 1 , 212 , 240 , // 212  - en-nu
+            0x1409 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xb7  , 1 , 213 , 213 , // 213  - en-nz
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xc2  , 1 , 214 , 240 , // 214  - en-pg
+            0x3409 , 0x4e4 , 0x1b5 , 0x2710, 0x1f4 , 0xc9  , 1 , 215 , 215 , // 215  - en-ph
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xbe  , 1 , 216 , 240 , // 216  - en-pk
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x153 , 1 , 217 , 240 , // 217  - en-pn
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xca  , 1 , 218 , 240 , // 218  - en-pr
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xc3  , 1 , 219 , 240 , // 219  - en-pw
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xcc  , 1 , 220 , 240 , // 220  - en-rw
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x1e  , 1 , 221 , 240 , // 221  - en-sb
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd0  , 1 , 222 , 240 , // 222  - en-sc
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xdb  , 1 , 223 , 240 , // 223  - en-sd
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xdd  , 1 , 224 , 240 , // 224  - en-se
+            0x4809 , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xd7  , 1 , 225 , 225 , // 225  - en-sg
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x157 , 1 , 226 , 240 , // 226  - en-sh
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd4  , 1 , 227 , 240 , // 227  - en-si
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd5  , 1 , 228 , 240 , // 228  - en-sl
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x114 , 1 , 229 , 240 , // 229  - en-ss
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x78f7, 1 , 230 , 240 , // 230  - en-sx
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x104 , 1 , 231 , 240 , // 231  - en-sz
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x15d , 1 , 232 , 240 , // 232  - en-tc
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x15b , 1 , 233 , 240 , // 233  - en-tk
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xe7  , 1 , 234 , 240 , // 234  - en-to
+            0x2c09 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xe1  , 1 , 235 , 235 , // 235  - en-tt
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xec  , 1 , 236 , 240 , // 236  - en-tv
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xef  , 1 , 237 , 240 , // 237  - en-tz
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xf0  , 1 , 238 , 240 , // 238  - en-ug
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x9a55d40, 1 , 239 , 240 , // 239  - en-um
+            0x409  , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xf4  , 1 , 240 , 240 , // 240  - en-us
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xf8  , 1 , 241 , 240 , // 241  - en-vc
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x15f , 1 , 242 , 240 , // 242  - en-vg
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xfc  , 1 , 243 , 240 , // 243  - en-vi
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xae  , 1 , 244 , 240 , // 244  - en-vu
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x103 , 1 , 245 , 240 , // 245  - en-ws
+            0x1c09 , 0x4e4 , 0x1b5 , 0x2710, 0x1f4 , 0xd1  , 1 , 246 , 246 , // 246  - en-za
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x107 , 1 , 247 , 240 , // 247  - en-zm
+            0x3009 , 0x4e4 , 0x1b5 , 0x2710, 0x1f4 , 0x108 , 1 , 248 , 248 , // 248  - en-zw
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x989e, 1 , 250 , 240 , // 249  - eo
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x989e, 1 , 250 , 240 , // 250  - eo-001
+            0xa    , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xd9  , 1 , 262 , 262 , // 251  - es
+            0x580a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x9a55d41, 1 , 252 , 240 , // 252  - es-419
+            0x2c0a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xb   , 1 , 253 , 253 , // 253  - es-ar
+            0x400a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x1a  , 1 , 254 , 254 , // 254  - es-bo
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x20  , 1 , 255 , 240 , // 255  - es-br
+            0x340a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x2e  , 1 , 256 , 256 , // 256  - es-cl
+            0x240a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x33  , 1 , 257 , 257 , // 257  - es-co
+            0x140a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x36  , 1 , 258 , 258 , // 258  - es-cr
+            0x5c0a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x38  , 1 , 259 , 240 , // 259  - es-cu
+            0x1c0a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x41  , 1 , 260 , 260 , // 260  - es-do
+            0x300a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x42  , 1 , 261 , 261 , // 261  - es-ec
+            0xc0a  , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xd9  , 1 , 262 , 262 , // 262  - es-es
+            0x40a  , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xd9  , 1 , 263 , 263 , // 263  - es-es_tradnl
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x45  , 1 , 264 , 240 , // 264  - es-gq
+            0x100a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x63  , 1 , 265 , 265 , // 265  - es-gt
+            0x480a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x6a  , 1 , 266 , 266 , // 266  - es-hn
+            0x80a  , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xa6  , 1 , 267 , 267 , // 267  - es-mx
+            0x4c0a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xb6  , 1 , 268 , 268 , // 268  - es-ni
+            0x180a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xc0  , 1 , 269 , 269 , // 269  - es-pa
+            0x280a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xbb  , 1 , 270 , 270 , // 270  - es-pe
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xc9  , 1 , 271 , 240 , // 271  - es-ph
+            0x500a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xca  , 1 , 272 , 272 , // 272  - es-pr
+            0x3c0a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xb9  , 1 , 273 , 273 , // 273  - es-py
+            0x440a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x48  , 1 , 274 , 274 , // 274  - es-sv
+            0x540a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xf4  , 1 , 275 , 275 , // 275  - es-us
+            0x380a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xf6  , 1 , 276 , 276 , // 276  - es-uy
+            0x200a , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xf9  , 1 , 277 , 277 , // 277  - es-ve
+            0x25   , 0x4e9 , 0x307 , 0x272d, 0x1f4 , 0x46  , 1 , 279 , 279 , // 278  - et
+            0x425  , 0x4e9 , 0x307 , 0x272d, 0x1f4 , 0x46  , 1 , 279 , 279 , // 279  - et-ee
+            0x2d   , 0x4e4 , 0x352 , 0x2   , 0x1f4 , 0xd9  , 1 , 281 , 240 , // 280  - eu
+            0x42d  , 0x4e4 , 0x352 , 0x2   , 0x1f4 , 0xd9  , 1 , 281 , 240 , // 281  - eu-es
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 283 , 240 , // 282  - ewo
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 283 , 240 , // 283  - ewo-cm
+            0x29   , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x74  , 0 , 285 , 143 , // 284  - fa
+            0x429  , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x74  , 0 , 285 , 143 , // 285  - fa-ir
+            0x67   , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xd2  , 1 , 290 , 290 , // 286  - ff
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x31  , 1 , 287 , 240 , // 287  - ff-cm
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x64  , 1 , 288 , 240 , // 288  - ff-gn
+            0x7c67 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xd2  , 1 , 290 , 290 , // 289  - ff-latn
+            0x867  , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xd2  , 1 , 290 , 290 , // 290  - ff-latn-sn
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xa2  , 1 , 291 , 240 , // 291  - ff-mr
+            0x467  , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xaf  , 1 , 292 , 240 , // 292  - ff-ng
+            0xb    , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0x4d  , 1 , 294 , 294 , // 293  - fi
+            0x40b  , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0x4d  , 1 , 294 , 294 , // 294  - fi-fi
+            0x64   , 0x4e4 , 0x1b5 , 0x2710, 0x1f4 , 0xc9  , 1 , 296 , 296 , // 295  - fil
+            0x464  , 0x4e4 , 0x1b5 , 0x2710, 0x1f4 , 0xc9  , 1 , 296 , 296 , // 296  - fil-ph
+            0x38   , 0x4e4 , 0x352 , 0x275f, 0x4f35, 0x51  , 1 , 299 , 299 , // 297  - fo
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x3d  , 1 , 298 , 240 , // 298  - fo-dk
+            0x438  , 0x4e4 , 0x352 , 0x275f, 0x4f35, 0x51  , 1 , 299 , 299 , // 299  - fo-fo
+            0xc    , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x54  , 1 , 316 , 316 , // 300  - fr
+            0x1c0c , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x993248, 1 , 301 , 316 , // 301  - fr-029
+            0x80c  , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x15  , 1 , 302 , 302 , // 302  - fr-be
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xf5  , 1 , 303 , 240 , // 303  - fr-bf
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x26  , 1 , 304 , 240 , // 304  - fr-bi
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x1c  , 1 , 305 , 240 , // 305  - fr-bj
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x9a55c4f, 1 , 306 , 240 , // 306  - fr-bl
+            0xc0c  , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x27  , 1 , 307 , 307 , // 307  - fr-ca
+            0x240c , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x2c  , 1 , 308 , 240 , // 308  - fr-cd
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x37  , 1 , 309 , 240 , // 309  - fr-cf
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x2b  , 1 , 310 , 240 , // 310  - fr-cg
+            0x100c , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xdf  , 1 , 311 , 311 , // 311  - fr-ch
+            0x300c , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x77  , 1 , 312 , 240 , // 312  - fr-ci
+            0x2c0c , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x31  , 1 , 313 , 240 , // 313  - fr-cm
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x3e  , 1 , 314 , 240 , // 314  - fr-dj
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x4   , 1 , 315 , 240 , // 315  - fr-dz
+            0x40c  , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x54  , 1 , 316 , 316 , // 316  - fr-fr
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x57  , 1 , 317 , 240 , // 317  - fr-ga
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x13d , 1 , 318 , 240 , // 318  - fr-gf
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x64  , 1 , 319 , 240 , // 319  - fr-gn
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x141 , 1 , 320 , 240 , // 320  - fr-gp
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x45  , 1 , 321 , 240 , // 321  - fr-gq
+            0x3c0c , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x67  , 1 , 322 , 240 , // 322  - fr-ht
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x32  , 1 , 323 , 240 , // 323  - fr-km
+            0x140c , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x93  , 1 , 324 , 324 , // 324  - fr-lu
+            0x380c , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x9f  , 1 , 325 , 240 , // 325  - fr-ma
+            0x180c , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x9e  , 1 , 326 , 326 , // 326  - fr-mc
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x7bda, 1 , 327 , 240 , // 327  - fr-mf
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x95  , 1 , 328 , 240 , // 328  - fr-mg
+            0x340c , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x9d  , 1 , 329 , 240 , // 329  - fr-ml
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x14a , 1 , 330 , 240 , // 330  - fr-mq
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xa2  , 1 , 331 , 240 , // 331  - fr-mr
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xa0  , 1 , 332 , 240 , // 332  - fr-mu
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x14e , 1 , 333 , 240 , // 333  - fr-nc
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xad  , 1 , 334 , 240 , // 334  - fr-ne
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x13e , 1 , 335 , 240 , // 335  - fr-pf
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xce  , 1 , 336 , 240 , // 336  - fr-pm
+            0x200c , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xc6  , 1 , 337 , 240 , // 337  - fr-re
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xcc  , 1 , 338 , 240 , // 338  - fr-rw
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xd0  , 1 , 339 , 240 , // 339  - fr-sc
+            0x280c , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xd2  , 1 , 340 , 240 , // 340  - fr-sn
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xde  , 1 , 341 , 240 , // 341  - fr-sy
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x29  , 1 , 342 , 240 , // 342  - fr-td
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xe8  , 1 , 343 , 240 , // 343  - fr-tg
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xea  , 1 , 344 , 240 , // 344  - fr-tn
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xae  , 1 , 345 , 240 , // 345  - fr-vu
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x160 , 1 , 346 , 240 , // 346  - fr-wf
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x14b , 1 , 347 , 240 , // 347  - fr-yt
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x76  , 1 , 349 , 240 , // 348  - fur
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x76  , 1 , 349 , 240 , // 349  - fur-it
+            0x62   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xb0  , 1 , 351 , 351 , // 350  - fy
+            0x462  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xb0  , 1 , 351 , 351 , // 351  - fy-nl
+            0x3c   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x44  , 1 , 353 , 353 , // 352  - ga
+            0x83c  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x44  , 1 , 353 , 353 , // 353  - ga-ie
+            0x91   , 0x4e4 , 0x352 , 0x2710, 0x4f3d, 0xf2  , 1 , 355 , 355 , // 354  - gd
+            0x491  , 0x4e4 , 0x352 , 0x2710, 0x4f3d, 0xf2  , 1 , 355 , 355 , // 355  - gd-gb
+            0x56   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd9  , 1 , 357 , 357 , // 356  - gl
+            0x456  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd9  , 1 , 357 , 357 , // 357  - gl-es
+            0x74   , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xb9  , 1 , 359 , 359 , // 358  - gn
+            0x474  , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xb9  , 1 , 359 , 359 , // 359  - gn-py
+            0x84   , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xdf  , 1 , 361 , 240 , // 360  - gsw
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xdf  , 1 , 361 , 240 , // 361  - gsw-ch
+            0x484  , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x54  , 1 , 362 , 362 , // 362  - gsw-fr
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x91  , 1 , 363 , 240 , // 363  - gsw-li
+            0x47   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 365 , 143 , // 364  - gu
+            0x447  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 365 , 143 , // 365  - gu-in
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 367 , 240 , // 366  - guz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 367 , 240 , // 367  - guz-ke
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x3b16, 1 , 369 , 240 , // 368  - gv
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x3b16, 1 , 369 , 240 , // 369  - gv-im
+            0x68   , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xaf  , 1 , 374 , 374 , // 370  - ha
+            0x7c68 , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xaf  , 1 , 374 , 374 , // 371  - ha-latn
+            0x1000 , 0x4e4 , 0x1b5 , 0x2710, 0x1f4 , 0x59  , 1 , 372 , 240 , // 372  - ha-latn-gh
+            0x1000 , 0x4e4 , 0x1b5 , 0x2710, 0x1f4 , 0xad  , 1 , 373 , 240 , // 373  - ha-latn-ne
+            0x468  , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xaf  , 1 , 374 , 374 , // 374  - ha-latn-ng
+            0x75   , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xf4  , 1 , 376 , 376 , // 375  - haw
+            0x475  , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xf4  , 1 , 376 , 376 , // 376  - haw-us
+            0xd    , 0x4e7 , 0x35e , 0x2715, 0x1f4 , 0x75  , 1 , 378 , 143 , // 377  - he
+            0x40d  , 0x4e7 , 0x35e , 0x2715, 0x1f4 , 0x75  , 1 , 378 , 143 , // 378  - he-il
+            0x39   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 380 , 143 , // 379  - hi
+            0x439  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 380 , 143 , // 380  - hi-in
+            0x1a   , 0x4e2 , 0x354 , 0x2762, 0x1f4 , 0x6c  , 1 , 383 , 383 , // 381  - hr
+            0x101a , 0x4e2 , 0x354 , 0x2762, 0x366 , 0x19  , 1 , 382 , 382 , // 382  - hr-ba
+            0x41a  , 0x4e2 , 0x354 , 0x2762, 0x1f4 , 0x6c  , 1 , 383 , 383 , // 383  - hr-hr
+            0x2e   , 0x4e4 , 0x352 , 0x2710, 0x366 , 0x5e  , 1 , 385 , 385 , // 384  - hsb
+            0x42e  , 0x4e4 , 0x352 , 0x2710, 0x366 , 0x5e  , 1 , 385 , 385 , // 385  - hsb-de
+            0xe    , 0x4e2 , 0x354 , 0x272d, 0x1f4 , 0x6d  , 1 , 387 , 387 , // 386  - hu
+            0x40e  , 0x4e2 , 0x354 , 0x272d, 0x1f4 , 0x6d  , 1 , 387 , 387 , // 387  - hu-hu
+            0x1040e, 0x4e2 , 0x354 , 0x272d, 0x1f4 , 0x6d  , 1 , 387 , 387 , // 388  - hu-hu_technl
+            0x2b   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x7   , 1 , 390 , 390 , // 389  - hy
+            0x42b  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x7   , 1 , 390 , 390 , // 390  - hy-am
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x54  , 1 , 393 , 240 , // 391  - ia
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x989e, 1 , 392 , 240 , // 392  - ia-001
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x54  , 1 , 393 , 240 , // 393  - ia-fr
+            0x69   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xaf  , 1 , 395 , 240 , // 394  - ibb
+            0x469  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xaf  , 1 , 395 , 240 , // 395  - ibb-ng
+            0x21   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x6f  , 1 , 397 , 397 , // 396  - id
+            0x421  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x6f  , 1 , 397 , 397 , // 397  - id-id
+            0x70   , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xaf  , 1 , 399 , 399 , // 398  - ig
+            0x470  , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xaf  , 1 , 399 , 399 , // 399  - ig-ng
+            0x78   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x2d  , 1 , 401 , 143 , // 400  - ii
+            0x478  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x2d  , 1 , 401 , 143 , // 401  - ii-cn
+            0xf    , 0x4e4 , 0x352 , 0x275f, 0x5187, 0x6e  , 1 , 403 , 403 , // 402  - is
+            0x40f  , 0x4e4 , 0x352 , 0x275f, 0x5187, 0x6e  , 1 , 403 , 403 , // 403  - is-is
+            0x10   , 0x4e4 , 0x352 , 0x2710, 0x4f38, 0x76  , 1 , 406 , 406 , // 404  - it
+            0x810  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xdf  , 1 , 405 , 405 , // 405  - it-ch
+            0x410  , 0x4e4 , 0x352 , 0x2710, 0x4f38, 0x76  , 1 , 406 , 406 , // 406  - it-it
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f38, 0xd6  , 1 , 407 , 240 , // 407  - it-sm
+            0x5d   , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0x27  , 1 , 412 , 412 , // 408  - iu
+            0x785d , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x27  , 1 , 410 , 143 , // 409  - iu-cans
+            0x45d  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x27  , 1 , 410 , 143 , // 410  - iu-cans-ca
+            0x7c5d , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0x27  , 1 , 412 , 412 , // 411  - iu-latn
+            0x85d  , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0x27  , 1 , 412 , 412 , // 412  - iu-latn-ca
+            0x11   , 0x3a4 , 0x3a4 , 0x2711, 0x4f42, 0x7a  , 1 , 414 , 414 , // 413  - ja
+            0x411  , 0x3a4 , 0x3a4 , 0x2711, 0x4f42, 0x7a  , 1 , 414 , 414 , // 414  - ja-jp
+            0x40411, 0x3a4 , 0x3a4 , 0x2711, 0x4f42, 0x7a  , 1 , 414 , 414 , // 415  - ja-jp_radstr
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 417 , 240 , // 416  - jgo
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 417 , 240 , // 417  - jgo-cm
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 419 , 240 , // 418  - jmc
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 419 , 240 , // 419  - jmc-tz
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x6f  , 1 , 424 , 424 , // 420  - jv
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x6f  , 1 , 422 , 424 , // 421  - jv-java
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x6f  , 1 , 422 , 424 , // 422  - jv-java-id
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x6f  , 1 , 424 , 424 , // 423  - jv-latn
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x6f  , 1 , 424 , 424 , // 424  - jv-latn-id
+            0x37   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x58  , 1 , 426 , 426 , // 425  - ka
+            0x437  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x58  , 1 , 426 , 426 , // 426  - ka-ge
+            0x10437, 0x0   , 0x1   , 0x2   , 0x1f4 , 0x58  , 1 , 426 , 426 , // 427  - ka-ge_modern
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x4   , 1 , 429 , 240 , // 428  - kab
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x4   , 1 , 429 , 240 , // 429  - kab-dz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 431 , 240 , // 430  - kam
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 431 , 240 , // 431  - kam-ke
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 433 , 240 , // 432  - kde
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 433 , 240 , // 433  - kde-tz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x39  , 1 , 435 , 240 , // 434  - kea
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x39  , 1 , 435 , 240 , // 435  - kea-cv
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9d  , 1 , 437 , 240 , // 436  - khq
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9d  , 1 , 437 , 240 , // 437  - khq-ml
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 439 , 240 , // 438  - ki
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 439 , 240 , // 439  - ki-ke
+            0x3f   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x89  , 1 , 441 , 441 , // 440  - kk
+            0x43f  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x89  , 1 , 441 , 441 , // 441  - kk-kz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 443 , 240 , // 442  - kkj
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 443 , 240 , // 443  - kkj-cm
+            0x6f   , 0x4e4 , 0x352 , 0x2710, 0x4f35, 0x5d  , 1 , 445 , 445 , // 444  - kl
+            0x46f  , 0x4e4 , 0x352 , 0x2710, 0x4f35, 0x5d  , 1 , 445 , 445 , // 445  - kl-gl
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 447 , 240 , // 446  - kln
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 447 , 240 , // 447  - kln-ke
+            0x53   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x28  , 2 , 449 , 143 , // 448  - km
+            0x453  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x28  , 2 , 449 , 143 , // 449  - km-kh
+            0x4b   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 451 , 143 , // 450  - kn
+            0x44b  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 451 , 143 , // 451  - kn-in
+            0x12   , 0x3b5 , 0x3b5 , 0x2713, 0x5161, 0x86  , 1 , 454 , 454 , // 452  - ko
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x83  , 1 , 453 , 240 , // 453  - ko-kp
+            0x412  , 0x3b5 , 0x3b5 , 0x2713, 0x5161, 0x86  , 1 , 454 , 454 , // 454  - ko-kr
+            0x57   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 456 , 143 , // 455  - kok
+            0x457  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 456 , 143 , // 456  - kok-in
+            0x71   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xaf  , 1 , 458 , 240 , // 457  - kr
+            0x471  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xaf  , 1 , 458 , 240 , // 458  - kr-ng
+            0x60   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 2 , 461 , 240 , // 459  - ks
+            0x460  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 2 , 461 , 240 , // 460  - ks-arab
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 2 , 461 , 240 , // 461  - ks-arab-in
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 463 , 187 , // 462  - ks-deva
+            0x860  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 463 , 187 , // 463  - ks-deva-in
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 465 , 240 , // 464  - ksb
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 465 , 240 , // 465  - ksb-tz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 467 , 240 , // 466  - ksf
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 467 , 240 , // 467  - ksf-cm
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x5e  , 1 , 469 , 240 , // 468  - ksh
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x5e  , 1 , 469 , 240 , // 469  - ksh-de
+            0x92   , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x79  , 0 , 472 , 143 , // 470  - ku
+            0x7c92 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x79  , 0 , 472 , 143 , // 471  - ku-arab
+            0x492  , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x79  , 0 , 472 , 143 , // 472  - ku-arab-iq
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x74  , 0 , 473 , 240 , // 473  - ku-arab-ir
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf2  , 1 , 475 , 240 , // 474  - kw
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf2  , 1 , 475 , 240 , // 475  - kw-gb
+            0x40   , 0x4e3 , 0x362 , 0x2717, 0x5190, 0x82  , 1 , 477 , 477 , // 476  - ky
+            0x440  , 0x4e3 , 0x362 , 0x2717, 0x5190, 0x82  , 1 , 477 , 477 , // 477  - ky-kg
+            0x76   , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0x989e, 1 , 479 , 143 , // 478  - la
+            0x476  , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0x989e, 1 , 479 , 143 , // 479  - la-001
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 481 , 240 , // 480  - lag
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 481 , 240 , // 481  - lag-tz
+            0x6e   , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x93  , 1 , 483 , 483 , // 482  - lb
+            0x46e  , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x93  , 1 , 483 , 483 , // 483  - lb-lu
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf0  , 1 , 485 , 240 , // 484  - lg
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf0  , 1 , 485 , 240 , // 485  - lg-ug
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf4  , 1 , 487 , 240 , // 486  - lkt
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf4  , 1 , 487 , 240 , // 487  - lkt-us
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x2c  , 1 , 490 , 240 , // 488  - ln
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9   , 1 , 489 , 240 , // 489  - ln-ao
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x2c  , 1 , 490 , 240 , // 490  - ln-cd
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x37  , 1 , 491 , 240 , // 491  - ln-cf
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x2b  , 1 , 492 , 240 , // 492  - ln-cg
+            0x54   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x8a  , 1 , 494 , 143 , // 493  - lo
+            0x454  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x8a  , 1 , 494 , 143 , // 494  - lo-la
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x74  , 2 , 497 , 240 , // 495  - lrc
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x79  , 2 , 496 , 240 , // 496  - lrc-iq
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x74  , 2 , 497 , 240 , // 497  - lrc-ir
+            0x27   , 0x4e9 , 0x307 , 0x272d, 0x1f4 , 0x8d  , 1 , 499 , 499 , // 498  - lt
+            0x427  , 0x4e9 , 0x307 , 0x272d, 0x1f4 , 0x8d  , 1 , 499 , 499 , // 499  - lt-lt
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x2c  , 1 , 501 , 240 , // 500  - lu
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x2c  , 1 , 501 , 240 , // 501  - lu-cd
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 503 , 240 , // 502  - luo
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 503 , 240 , // 503  - luo-ke
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 505 , 240 , // 504  - luy
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 505 , 240 , // 505  - luy-ke
+            0x26   , 0x4e9 , 0x307 , 0x272d, 0x1f4 , 0x8c  , 1 , 507 , 507 , // 506  - lv
+            0x426  , 0x4e9 , 0x307 , 0x272d, 0x1f4 , 0x8c  , 1 , 507 , 507 , // 507  - lv-lv
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 509 , 240 , // 508  - mas
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 509 , 240 , // 509  - mas-ke
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 510 , 240 , // 510  - mas-tz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 512 , 240 , // 511  - mer
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 512 , 240 , // 512  - mer-ke
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xa0  , 1 , 514 , 240 , // 513  - mfe
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xa0  , 1 , 514 , 240 , // 514  - mfe-mu
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x95  , 1 , 516 , 240 , // 515  - mg
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x95  , 1 , 516 , 240 , // 516  - mg-mg
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xa8  , 1 , 518 , 240 , // 517  - mgh
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xa8  , 1 , 518 , 240 , // 518  - mgh-mz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 520 , 240 , // 519  - mgo
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 520 , 240 , // 520  - mgo-cm
+            0x81   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xb7  , 1 , 522 , 522 , // 521  - mi
+            0x481  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xb7  , 1 , 522 , 522 , // 522  - mi-nz
+            0x2f   , 0x4e3 , 0x362 , 0x2717, 0x1f4 , 0x4ca2, 1 , 524 , 524 , // 523  - mk
+            0x42f  , 0x4e3 , 0x362 , 0x2717, 0x1f4 , 0x4ca2, 1 , 524 , 524 , // 524  - mk-mk
+            0x4c   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 526 , 143 , // 525  - ml
+            0x44c  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 526 , 143 , // 526  - ml-in
+            0x50   , 0x4e3 , 0x362 , 0x2717, 0x5190, 0x9a  , 1 , 529 , 529 , // 527  - mn
+            0x7850 , 0x4e3 , 0x362 , 0x2717, 0x5190, 0x9a  , 1 , 529 , 529 , // 528  - mn-cyrl
+            0x450  , 0x4e3 , 0x362 , 0x2717, 0x5190, 0x9a  , 1 , 529 , 529 , // 529  - mn-mn
+            0x7c50 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x2d  , 1 , 531 , 531 , // 530  - mn-mong
+            0x850  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x2d  , 1 , 531 , 531 , // 531  - mn-mong-cn
+            0xc50  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9a  , 1 , 532 , 532 , // 532  - mn-mong-mn
+            0x58   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 534 , 187 , // 533  - mni
+            0x458  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 534 , 187 , // 534  - mni-in
+            0x7c   , 0x4e4 , 0x352 , 0x2710, 0x25  , 0x27  , 1 , 536 , 240 , // 535  - moh
+            0x47c  , 0x4e4 , 0x352 , 0x2710, 0x25  , 0x27  , 1 , 536 , 240 , // 536  - moh-ca
+            0x4e   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 538 , 143 , // 537  - mr
+            0x44e  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 538 , 143 , // 538  - mr-in
+            0x3e   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xa7  , 1 , 541 , 541 , // 539  - ms
+            0x83e  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x25  , 1 , 540 , 540 , // 540  - ms-bn
+            0x43e  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xa7  , 1 , 541 , 541 , // 541  - ms-my
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd7  , 1 , 542 , 240 , // 542  - ms-sg
+            0x3a   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xa3  , 1 , 544 , 544 , // 543  - mt
+            0x43a  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xa3  , 1 , 544 , 544 , // 544  - mt-mt
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 546 , 240 , // 545  - mua
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 546 , 240 , // 546  - mua-cm
+            0x55   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x1b  , 2 , 548 , 240 , // 547  - my
+            0x455  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x1b  , 2 , 548 , 240 , // 548  - my-mm
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x74  , 2 , 550 , 240 , // 549  - mzn
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x74  , 2 , 550 , 240 , // 550  - mzn-ir
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xfe  , 1 , 552 , 240 , // 551  - naq
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xfe  , 1 , 552 , 240 , // 552  - naq-na
+            0x7c14 , 0x4e4 , 0x352 , 0x2710, 0x4f35, 0xb1  , 1 , 554 , 554 , // 553  - nb
+            0x414  , 0x4e4 , 0x352 , 0x2710, 0x4f35, 0xb1  , 1 , 554 , 554 , // 554  - nb-no
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f35, 0xdc  , 1 , 555 , 240 , // 555  - nb-sj
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x108 , 1 , 557 , 240 , // 556  - nd
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x108 , 1 , 557 , 240 , // 557  - nd-zw
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x5e  , 1 , 559 , 240 , // 558  - nds
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x5e  , 1 , 559 , 240 , // 559  - nds-de
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xb0  , 1 , 560 , 240 , // 560  - nds-nl
+            0x61   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xb2  , 1 , 563 , 143 , // 561  - ne
+            0x861  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 2 , 562 , 240 , // 562  - ne-in
+            0x461  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xb2  , 1 , 563 , 143 , // 563  - ne-np
+            0x13   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xb0  , 1 , 569 , 569 , // 564  - nl
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x12e , 1 , 565 , 240 , // 565  - nl-aw
+            0x813  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x15  , 1 , 566 , 566 , // 566  - nl-be
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x9a55d42, 1 , 567 , 240 , // 567  - nl-bq
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x111 , 1 , 568 , 240 , // 568  - nl-cw
+            0x413  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xb0  , 1 , 569 , 569 , // 569  - nl-nl
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xb5  , 1 , 570 , 240 , // 570  - nl-sr
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x78f7, 1 , 571 , 240 , // 571  - nl-sx
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 573 , 240 , // 572  - nmg
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 573 , 240 , // 573  - nmg-cm
+            0x7814 , 0x4e4 , 0x352 , 0x2710, 0x4f35, 0xb1  , 1 , 575 , 575 , // 574  - nn
+            0x814  , 0x4e4 , 0x352 , 0x2710, 0x4f35, 0xb1  , 1 , 575 , 575 , // 575  - nn-no
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 577 , 240 , // 576  - nnh
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 577 , 240 , // 577  - nnh-cm
+            0x14   , 0x4e4 , 0x352 , 0x2710, 0x4f35, 0xb1  , 1 , 554 , 554 , // 578  - no
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x64  , 2 , 580 , 143 , // 579  - nqo
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x64  , 2 , 580 , 143 , // 580  - nqo-gn
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd1  , 1 , 582 , 240 , // 581  - nr
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd1  , 1 , 582 , 240 , // 582  - nr-za
+            0x6c   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd1  , 1 , 584 , 584 , // 583  - nso
+            0x46c  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd1  , 1 , 584 , 584 , // 584  - nso-za
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x114 , 1 , 586 , 240 , // 585  - nus
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x114 , 1 , 586 , 240 , // 586  - nus-ss
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf0  , 1 , 588 , 240 , // 587  - nyn
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf0  , 1 , 588 , 240 , // 588  - nyn-ug
+            0x82   , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x54  , 1 , 590 , 590 , // 589  - oc
+            0x482  , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x54  , 1 , 590 , 590 , // 590  - oc-fr
+            0x72   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x49  , 1 , 592 , 240 , // 591  - om
+            0x472  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x49  , 1 , 592 , 240 , // 592  - om-et
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 593 , 240 , // 593  - om-ke
+            0x48   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 595 , 143 , // 594  - or
+            0x448  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 595 , 143 , // 595  - or-in
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x58  , 1 , 597 , 240 , // 596  - os
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x58  , 1 , 597 , 240 , // 597  - os-ge
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xcb  , 1 , 598 , 240 , // 598  - os-ru
+            0x46   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 602 , 143 , // 599  - pa
+            0x7c46 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xbe  , 2 , 601 , 143 , // 600  - pa-arab
+            0x846  , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xbe  , 2 , 601 , 143 , // 601  - pa-arab-pk
+            0x446  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 602 , 143 , // 602  - pa-in
+            0x79   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x993248, 1 , 604 , 145 , // 603  - pap
+            0x479  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x993248, 1 , 604 , 145 , // 604  - pap-029
+            0x15   , 0x4e2 , 0x354 , 0x272d, 0x5190, 0xbf  , 1 , 606 , 606 , // 605  - pl
+            0x415  , 0x4e2 , 0x354 , 0x272d, 0x5190, 0xbf  , 1 , 606 , 606 , // 606  - pl-pl
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x989e, 1 , 608 , 240 , // 607  - prg
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x989e, 1 , 608 , 240 , // 608  - prg-001
+            0x8c   , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x3   , 2 , 610 , 143 , // 609  - prs
+            0x48c  , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x3   , 2 , 610 , 143 , // 610  - prs-af
+            0x63   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x3   , 2 , 612 , 143 , // 611  - ps
+            0x463  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x3   , 2 , 612 , 143 , // 612  - ps-af
+            0x16   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x20  , 1 , 615 , 615 , // 613  - pt
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x9   , 1 , 614 , 240 , // 614  - pt-ao
+            0x416  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x20  , 1 , 615 , 615 , // 615  - pt-br
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xdf  , 1 , 616 , 240 , // 616  - pt-ch
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x39  , 1 , 617 , 240 , // 617  - pt-cv
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x45  , 1 , 618 , 240 , // 618  - pt-gq
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xc4  , 1 , 619 , 240 , // 619  - pt-gw
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x93  , 1 , 620 , 240 , // 620  - pt-lu
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x97  , 1 , 621 , 240 , // 621  - pt-mo
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xa8  , 1 , 622 , 240 , // 622  - pt-mz
+            0x816  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xc1  , 1 , 623 , 623 , // 623  - pt-pt
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xe9  , 1 , 624 , 240 , // 624  - pt-st
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x6f60e7, 1 , 625 , 240 , // 625  - pt-tl
+            0x901  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x7c  , 1 , 626 , 190 , // 626  - qps-latn-x-sh
+            0x501  , 0x4e2 , 0x354 , 0x272d, 0x5190, 0xf4  , 1 , 627 , 627 , // 627  - qps-ploc
+            0x5fe  , 0x3a4 , 0x3a4 , 0x2711, 0x4f42, 0x7a  , 1 , 628 , 628 , // 628  - qps-ploca
+            0x9ff  , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xcd  , 0 , 629 , 143 , // 629  - qps-plocm
+            0x86   , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x63  , 1 , 632 , 632 , // 630  - quc
+            0x7c86 , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x63  , 1 , 632 , 632 , // 631  - quc-latn
+            0x486  , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x63  , 1 , 632 , 632 , // 632  - quc-latn-gt
+            0x6b   , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x1a  , 1 , 634 , 634 , // 633  - quz
+            0x46b  , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x1a  , 1 , 634 , 634 , // 634  - quz-bo
+            0x86b  , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0x42  , 1 , 635 , 635 , // 635  - quz-ec
+            0xc6b  , 0x4e4 , 0x352 , 0x2710, 0x4f3c, 0xbb  , 1 , 636 , 636 , // 636  - quz-pe
+            0x17   , 0x4e4 , 0x352 , 0x2710, 0x4f31, 0xdf  , 1 , 638 , 638 , // 637  - rm
+            0x417  , 0x4e4 , 0x352 , 0x2710, 0x4f31, 0xdf  , 1 , 638 , 638 , // 638  - rm-ch
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x26  , 1 , 640 , 240 , // 639  - rn
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x26  , 1 , 640 , 240 , // 640  - rn-bi
+            0x18   , 0x4e2 , 0x354 , 0x272d, 0x5190, 0xc8  , 1 , 643 , 643 , // 641  - ro
+            0x818  , 0x4e2 , 0x354 , 0x2   , 0x1f4 , 0x98  , 1 , 642 , 240 , // 642  - ro-md
+            0x418  , 0x4e2 , 0x354 , 0x272d, 0x5190, 0xc8  , 1 , 643 , 643 , // 643  - ro-ro
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 645 , 240 , // 644  - rof
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 645 , 240 , // 645  - rof-tz
+            0x19   , 0x4e3 , 0x362 , 0x2717, 0x5190, 0xcb  , 1 , 651 , 651 , // 646  - ru
+            0x1000 , 0x4e3 , 0x362 , 0x2   , 0x1f4 , 0x1d  , 1 , 647 , 240 , // 647  - ru-by
+            0x1000 , 0x4e3 , 0x362 , 0x2   , 0x1f4 , 0x82  , 1 , 648 , 240 , // 648  - ru-kg
+            0x1000 , 0x4e3 , 0x362 , 0x2   , 0x1f4 , 0x89  , 1 , 649 , 240 , // 649  - ru-kz
+            0x819  , 0x4e3 , 0x362 , 0x2   , 0x1f4 , 0x98  , 1 , 650 , 240 , // 650  - ru-md
+            0x419  , 0x4e3 , 0x362 , 0x2717, 0x5190, 0xcb  , 1 , 651 , 651 , // 651  - ru-ru
+            0x1000 , 0x4e3 , 0x362 , 0x2   , 0x1f4 , 0xf1  , 1 , 652 , 240 , // 652  - ru-ua
+            0x87   , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xcc  , 1 , 654 , 654 , // 653  - rw
+            0x487  , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xcc  , 1 , 654 , 654 , // 654  - rw-rw
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 656 , 240 , // 655  - rwk
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 656 , 240 , // 656  - rwk-tz
+            0x4f   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 658 , 143 , // 657  - sa
+            0x44f  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 658 , 143 , // 658  - sa-in
+            0x85   , 0x4e3 , 0x362 , 0x2717, 0x5190, 0xcb  , 1 , 660 , 660 , // 659  - sah
+            0x485  , 0x4e3 , 0x362 , 0x2717, 0x5190, 0xcb  , 1 , 660 , 660 , // 660  - sah-ru
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 662 , 240 , // 661  - saq
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 662 , 240 , // 662  - saq-ke
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 664 , 240 , // 663  - sbp
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 664 , 240 , // 664  - sbp-tz
+            0x59   , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xbe  , 2 , 667 , 143 , // 665  - sd
+            0x7c59 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xbe  , 2 , 667 , 143 , // 666  - sd-arab
+            0x859  , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xbe  , 2 , 667 , 143 , // 667  - sd-arab-pk
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 669 , 187 , // 668  - sd-deva
+            0x459  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 669 , 187 , // 669  - sd-deva-in
+            0x3b   , 0x4e4 , 0x352 , 0x2710, 0x4f35, 0xb1  , 1 , 672 , 672 , // 670  - se
+            0xc3b  , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0x4d  , 1 , 671 , 671 , // 671  - se-fi
+            0x43b  , 0x4e4 , 0x352 , 0x2710, 0x4f35, 0xb1  , 1 , 672 , 672 , // 672  - se-no
+            0x83b  , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0xdd  , 1 , 673 , 673 , // 673  - se-se
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xa8  , 1 , 675 , 240 , // 674  - seh
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xa8  , 1 , 675 , 240 , // 675  - seh-mz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9d  , 1 , 677 , 240 , // 676  - ses
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9d  , 1 , 677 , 240 , // 677  - ses-ml
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x37  , 1 , 679 , 240 , // 678  - sg
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x37  , 1 , 679 , 240 , // 679  - sg-cf
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9f  , 1 , 684 , 240 , // 680  - shi
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9f  , 1 , 682 , 240 , // 681  - shi-latn
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9f  , 1 , 682 , 240 , // 682  - shi-latn-ma
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9f  , 1 , 684 , 240 , // 683  - shi-tfng
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9f  , 1 , 684 , 240 , // 684  - shi-tfng-ma
+            0x5b   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x2a  , 1 , 686 , 143 , // 685  - si
+            0x45b  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x2a  , 1 , 686 , 143 , // 686  - si-lk
+            0x1b   , 0x4e2 , 0x354 , 0x272d, 0x5190, 0x8f  , 1 , 688 , 688 , // 687  - sk
+            0x41b  , 0x4e2 , 0x354 , 0x272d, 0x5190, 0x8f  , 1 , 688 , 688 , // 688  - sk-sk
+            0x24   , 0x4e2 , 0x354 , 0x272d, 0x5190, 0xd4  , 1 , 690 , 690 , // 689  - sl
+            0x424  , 0x4e2 , 0x354 , 0x272d, 0x5190, 0xd4  , 1 , 690 , 690 , // 690  - sl-si
+            0x783b , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0xdd  , 1 , 693 , 693 , // 691  - sma
+            0x183b , 0x4e4 , 0x352 , 0x2710, 0x4f35, 0xb1  , 1 , 692 , 692 , // 692  - sma-no
+            0x1c3b , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0xdd  , 1 , 693 , 693 , // 693  - sma-se
+            0x7c3b , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0xdd  , 1 , 696 , 696 , // 694  - smj
+            0x103b , 0x4e4 , 0x352 , 0x2710, 0x4f35, 0xb1  , 1 , 695 , 695 , // 695  - smj-no
+            0x143b , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0xdd  , 1 , 696 , 696 , // 696  - smj-se
+            0x703b , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0x4d  , 1 , 698 , 698 , // 697  - smn
+            0x243b , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0x4d  , 1 , 698 , 698 , // 698  - smn-fi
+            0x743b , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0x4d  , 1 , 700 , 700 , // 699  - sms
+            0x203b , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0x4d  , 1 , 700 , 700 , // 700  - sms-fi
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x108 , 1 , 703 , 240 , // 701  - sn
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x108 , 1 , 703 , 240 , // 702  - sn-latn
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x108 , 1 , 703 , 240 , // 703  - sn-latn-zw
+            0x77   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd8  , 1 , 708 , 240 , // 704  - so
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x3e  , 1 , 705 , 240 , // 705  - so-dj
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x49  , 1 , 706 , 240 , // 706  - so-et
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 707 , 240 , // 707  - so-ke
+            0x477  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd8  , 1 , 708 , 240 , // 708  - so-so
+            0x1c   , 0x4e2 , 0x354 , 0x272d, 0x5190, 0x6   , 1 , 710 , 710 , // 709  - sq
+            0x41c  , 0x4e2 , 0x354 , 0x272d, 0x5190, 0x6   , 1 , 710 , 710 , // 710  - sq-al
+            0x1000 , 0x4e2 , 0x354 , 0x272d, 0x5190, 0x4ca2, 1 , 711 , 240 , // 711  - sq-mk
+            0x1000 , 0x4e2 , 0x354 , 0x272d, 0x5190, 0x974941, 1 , 712 , 240 , // 712  - sq-xk
+            0x7c1a , 0x4e2 , 0x354 , 0x272d, 0x1f4 , 0x10f , 1 , 724 , 724 , // 713  - sr
+            0x6c1a , 0x4e3 , 0x357 , 0x2717, 0x5221, 0x10f , 1 , 718 , 718 , // 714  - sr-cyrl
+            0x1c1a , 0x4e3 , 0x357 , 0x2717, 0x5221, 0x19  , 1 , 715 , 715 , // 715  - sr-cyrl-ba
+            0xc1a  , 0x4e3 , 0x357 , 0x2717, 0x5221, 0x10d , 1 , 716 , 716 , // 716  - sr-cyrl-cs
+            0x301a , 0x4e3 , 0x357 , 0x2717, 0x5221, 0x10e , 1 , 717 , 717 , // 717  - sr-cyrl-me
+            0x281a , 0x4e3 , 0x357 , 0x2717, 0x5221, 0x10f , 1 , 718 , 718 , // 718  - sr-cyrl-rs
+            0x1000 , 0x4e3 , 0x357 , 0x2717, 0x5221, 0x974941, 1 , 719 , 240 , // 719  - sr-cyrl-xk
+            0x701a , 0x4e2 , 0x354 , 0x272d, 0x1f4 , 0x10f , 1 , 724 , 724 , // 720  - sr-latn
+            0x181a , 0x4e2 , 0x354 , 0x2762, 0x366 , 0x19  , 1 , 721 , 721 , // 721  - sr-latn-ba
+            0x81a  , 0x4e2 , 0x354 , 0x272d, 0x1f4 , 0x10d , 1 , 722 , 722 , // 722  - sr-latn-cs
+            0x2c1a , 0x4e2 , 0x354 , 0x272d, 0x1f4 , 0x10e , 1 , 723 , 723 , // 723  - sr-latn-me
+            0x241a , 0x4e2 , 0x354 , 0x272d, 0x1f4 , 0x10f , 1 , 724 , 724 , // 724  - sr-latn-rs
+            0x1000 , 0x4e2 , 0x354 , 0x272d, 0x1f4 , 0x974941, 1 , 725 , 240 , // 725  - sr-latn-xk
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd1  , 1 , 728 , 240 , // 726  - ss
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x104 , 1 , 727 , 240 , // 727  - ss-sz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd1  , 1 , 728 , 240 , // 728  - ss-za
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x47  , 1 , 730 , 240 , // 729  - ssy
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x47  , 1 , 730 , 240 , // 730  - ssy-er
+            0x30   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd1  , 1 , 733 , 240 , // 731  - st
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x92  , 1 , 732 , 240 , // 732  - st-ls
+            0x430  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd1  , 1 , 733 , 240 , // 733  - st-za
+            0x1d   , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0xdd  , 1 , 737 , 737 , // 734  - sv
+            0x1000 , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0x9906f5, 1 , 735 , 240 , // 735  - sv-ax
+            0x81d  , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0x4d  , 1 , 736 , 736 , // 736  - sv-fi
+            0x41d  , 0x4e4 , 0x352 , 0x2710, 0x4f36, 0xdd  , 1 , 737 , 737 , // 737  - sv-se
+            0x41   , 0x4e4 , 0x1b5 , 0x2710, 0x1f4 , 0x81  , 1 , 740 , 740 , // 738  - sw
+            0x1000 , 0x4e4 , 0x1b5 , 0x2710, 0x1f4 , 0x2c  , 1 , 739 , 740 , // 739  - sw-cd
+            0x441  , 0x4e4 , 0x1b5 , 0x2710, 0x1f4 , 0x81  , 1 , 740 , 740 , // 740  - sw-ke
+            0x1000 , 0x4e4 , 0x1b5 , 0x2710, 0x1f4 , 0xef  , 1 , 741 , 240 , // 741  - sw-tz
+            0x1000 , 0x4e4 , 0x1b5 , 0x2710, 0x1f4 , 0xf0  , 1 , 742 , 240 , // 742  - sw-ug
+            0x1000 , 0x0   , 0x1   , 0x0   , 0x1f4 , 0x2c  , 1 , 744 , 240 , // 743  - swc
+            0x1000 , 0x0   , 0x1   , 0x0   , 0x1f4 , 0x2c  , 1 , 744 , 240 , // 744  - swc-cd
+            0x5a   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xde  , 1 , 746 , 143 , // 745  - syr
+            0x45a  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xde  , 1 , 746 , 143 , // 746  - syr-sy
+            0x49   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 748 , 143 , // 747  - ta
+            0x449  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 748 , 143 , // 748  - ta-in
+            0x849  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x2a  , 1 , 749 , 143 , // 749  - ta-lk
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xa7  , 1 , 750 , 240 , // 750  - ta-my
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd7  , 1 , 751 , 240 , // 751  - ta-sg
+            0x4a   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 753 , 143 , // 752  - te
+            0x44a  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x71  , 1 , 753 , 143 , // 753  - te-in
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf0  , 1 , 756 , 240 , // 754  - teo
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x81  , 1 , 755 , 240 , // 755  - teo-ke
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf0  , 1 , 756 , 240 , // 756  - teo-ug
+            0x28   , 0x4e3 , 0x362 , 0x2717, 0x5190, 0xe4  , 1 , 759 , 759 , // 757  - tg
+            0x7c28 , 0x4e3 , 0x362 , 0x2717, 0x5190, 0xe4  , 1 , 759 , 759 , // 758  - tg-cyrl
+            0x428  , 0x4e3 , 0x362 , 0x2717, 0x5190, 0xe4  , 1 , 759 , 759 , // 759  - tg-cyrl-tj
+            0x1e   , 0x36a , 0x36a , 0x2725, 0x5166, 0xe3  , 1 , 761 , 143 , // 760  - th
+            0x41e  , 0x36a , 0x36a , 0x2725, 0x5166, 0xe3  , 1 , 761 , 143 , // 761  - th-th
+            0x73   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x47  , 1 , 763 , 143 , // 762  - ti
+            0x873  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x47  , 1 , 763 , 143 , // 763  - ti-er
+            0x473  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x49  , 1 , 764 , 143 , // 764  - ti-et
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x47  , 1 , 766 , 240 , // 765  - tig
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x47  , 1 , 766 , 240 , // 766  - tig-er
+            0x42   , 0x4e2 , 0x354 , 0x272d, 0x5190, 0xee  , 1 , 768 , 768 , // 767  - tk
+            0x442  , 0x4e2 , 0x354 , 0x272d, 0x5190, 0xee  , 1 , 768 , 768 , // 768  - tk-tm
+            0x32   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd1  , 1 , 771 , 771 , // 769  - tn
+            0x832  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0x13  , 1 , 770 , 770 , // 770  - tn-bw
+            0x432  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd1  , 1 , 771 , 771 , // 771  - tn-za
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xe7  , 1 , 773 , 240 , // 772  - to
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xe7  , 1 , 773 , 240 , // 773  - to-to
+            0x1f   , 0x4e6 , 0x359 , 0x2761, 0x51a9, 0xeb  , 1 , 776 , 776 , // 774  - tr
+            0x1000 , 0x4e6 , 0x359 , 0x2761, 0x51a9, 0x3b  , 1 , 775 , 240 , // 775  - tr-cy
+            0x41f  , 0x4e6 , 0x359 , 0x2761, 0x51a9, 0xeb  , 1 , 776 , 776 , // 776  - tr-tr
+            0x31   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd1  , 1 , 778 , 240 , // 777  - ts
+            0x431  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd1  , 1 , 778 , 240 , // 778  - ts-za
+            0x44   , 0x4e3 , 0x362 , 0x2717, 0x5190, 0xcb  , 1 , 780 , 780 , // 779  - tt
+            0x444  , 0x4e3 , 0x362 , 0x2717, 0x5190, 0xcb  , 1 , 780 , 780 , // 780  - tt-ru
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xad  , 1 , 782 , 240 , // 781  - twq
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xad  , 1 , 782 , 240 , // 782  - twq-ne
+            0x5f   , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x4   , 1 , 787 , 787 , // 783  - tzm
+            0x1000 , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x9f  , 1 , 785 , 240 , // 784  - tzm-arab
+            0x45f  , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x9f  , 1 , 785 , 240 , // 785  - tzm-arab-ma
+            0x7c5f , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x4   , 1 , 787 , 787 , // 786  - tzm-latn
+            0x85f  , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0x4   , 1 , 787 , 787 , // 787  - tzm-latn-dz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9f  , 1 , 788 , 240 , // 788  - tzm-latn-ma
+            0x785f , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9f  , 1 , 790 , 316 , // 789  - tzm-tfng
+            0x105f , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9f  , 1 , 790 , 316 , // 790  - tzm-tfng-ma
+            0x80   , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x2d  , 1 , 792 , 143 , // 791  - ug
+            0x480  , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0x2d  , 1 , 792 , 143 , // 792  - ug-cn
+            0x22   , 0x4e3 , 0x362 , 0x2721, 0x1f4 , 0xf1  , 1 , 794 , 794 , // 793  - uk
+            0x422  , 0x4e3 , 0x362 , 0x2721, 0x1f4 , 0xf1  , 1 , 794 , 794 , // 794  - uk-ua
+            0x20   , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xbe  , 1 , 797 , 143 , // 795  - ur
+            0x820  , 0x4e8 , 0x2d0 , 0x2   , 0x1f4 , 0x71  , 2 , 796 , 240 , // 796  - ur-in
+            0x420  , 0x4e8 , 0x2d0 , 0x2714, 0x4fc4, 0xbe  , 1 , 797 , 143 , // 797  - ur-pk
+            0x43   , 0x4e6 , 0x359 , 0x272d, 0x1f4 , 0xf7  , 1 , 804 , 804 , // 798  - uz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x3   , 2 , 800 , 240 , // 799  - uz-arab
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x3   , 2 , 800 , 240 , // 800  - uz-arab-af
+            0x7843 , 0x4e3 , 0x362 , 0x2717, 0x5190, 0xf7  , 1 , 802 , 802 , // 801  - uz-cyrl
+            0x843  , 0x4e3 , 0x362 , 0x2717, 0x5190, 0xf7  , 1 , 802 , 802 , // 802  - uz-cyrl-uz
+            0x7c43 , 0x4e6 , 0x359 , 0x272d, 0x1f4 , 0xf7  , 1 , 804 , 804 , // 803  - uz-latn
+            0x443  , 0x4e6 , 0x359 , 0x272d, 0x1f4 , 0xf7  , 1 , 804 , 804 , // 804  - uz-latn-uz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x8e  , 1 , 809 , 240 , // 805  - vai
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x8e  , 1 , 807 , 240 , // 806  - vai-latn
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x8e  , 1 , 807 , 240 , // 807  - vai-latn-lr
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x8e  , 1 , 809 , 240 , // 808  - vai-vaii
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x8e  , 1 , 809 , 240 , // 809  - vai-vaii-lr
+            0x33   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd1  , 1 , 811 , 240 , // 810  - ve
+            0x433  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xd1  , 1 , 811 , 240 , // 811  - ve-za
+            0x2a   , 0x4ea , 0x4ea , 0x2710, 0x1f4 , 0xfb  , 1 , 813 , 143 , // 812  - vi
+            0x42a  , 0x4ea , 0x4ea , 0x2710, 0x1f4 , 0xfb  , 1 , 813 , 143 , // 813  - vi-vn
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x989e, 1 , 815 , 240 , // 814  - vo
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x989e, 1 , 815 , 240 , // 815  - vo-001
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 817 , 240 , // 816  - vun
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xef  , 1 , 817 , 240 , // 817  - vun-tz
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xdf  , 1 , 819 , 240 , // 818  - wae
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xdf  , 1 , 819 , 240 , // 819  - wae-ch
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x49  , 1 , 821 , 240 , // 820  - wal
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x49  , 1 , 821 , 240 , // 821  - wal-et
+            0x88   , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xd2  , 1 , 823 , 823 , // 822  - wo
+            0x488  , 0x4e4 , 0x352 , 0x2710, 0x4f49, 0xd2  , 1 , 823 , 823 , // 823  - wo-sn
+            0x1007f, 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xf4  , 1 , -1  , -1  , // 824  - x-iv_mathan
+            0x34   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd1  , 1 , 826 , 826 , // 825  - xh
+            0x434  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd1  , 1 , 826 , 826 , // 826  - xh-za
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf0  , 1 , 828 , 240 , // 827  - xog
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0xf0  , 1 , 828 , 240 , // 828  - xog-ug
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 830 , 240 , // 829  - yav
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x31  , 1 , 830 , 240 , // 830  - yav-cm
+            0x3d   , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x989e, 1 , 832 , 240 , // 831  - yi
+            0x43d  , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x989e, 1 , 832 , 240 , // 832  - yi-001
+            0x6a   , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xaf  , 1 , 835 , 835 , // 833  - yo
+            0x1000 , 0x4e4 , 0x1b5 , 0x2710, 0x1f4 , 0x1c  , 1 , 834 , 240 , // 834  - yo-bj
+            0x46a  , 0x4e4 , 0x1b5 , 0x2710, 0x25  , 0xaf  , 1 , 835 , 835 , // 835  - yo-ng
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x68  , 1 , 837 , 240 , // 836  - yue
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x68  , 1 , 837 , 240 , // 837  - yue-hk
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9f  , 1 , 840 , 316 , // 838  - zgh
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9f  , 1 , 840 , 316 , // 839  - zgh-tfng
+            0x1000 , 0x0   , 0x1   , 0x2   , 0x1f4 , 0x9f  , 1 , 840 , 316 , // 840  - zgh-tfng-ma
+            0x7804 , 0x3a8 , 0x3a8 , 0x2718, 0x1f4 , 0x2d  , 1 , 844 , 844 , // 841  - zh
+            0x4    , 0x3a8 , 0x3a8 , 0x0   , 0x1f4 , 0x2d  , 1 , 844 , 844 , // 842  - zh-chs
+            0x7c04 , 0x3b6 , 0x3b6 , 0x0   , 0x1f4 , 0x68  , 1 , 851 , 851 , // 843  - zh-cht
+            0x804  , 0x3a8 , 0x3a8 , 0x2718, 0x1f4 , 0x2d  , 1 , 844 , 844 , // 844  - zh-cn
+            0x50804, 0x3a8 , 0x3a8 , 0x2718, 0x1f4 , 0x2d  , 1 , 844 , 844 , // 845  - zh-cn_phoneb
+            0x20804, 0x3a8 , 0x3a8 , 0x2718, 0x1f4 , 0x2d  , 1 , 844 , 844 , // 846  - zh-cn_stroke
+            0x4    , 0x3a8 , 0x3a8 , 0x2718, 0x1f4 , 0x2d  , 1 , 844 , 844 , // 847  - zh-hans
+            0x1000 , 0x3a8 , 0x3a8 , 0x2718, 0x1f4 , 0x68  , 1 , 848 , 240 , // 848  - zh-hans-hk
+            0x1000 , 0x3a8 , 0x3a8 , 0x2718, 0x1f4 , 0x97  , 1 , 849 , 240 , // 849  - zh-hans-mo
+            0x7c04 , 0x3b6 , 0x3b6 , 0x2712, 0x1f4 , 0x68  , 1 , 851 , 851 , // 850  - zh-hant
+            0xc04  , 0x3b6 , 0x3b6 , 0x2712, 0x1f4 , 0x68  , 1 , 851 , 851 , // 851  - zh-hk
+            0x40c04, 0x3b6 , 0x3b6 , 0x2712, 0x1f4 , 0x68  , 1 , 851 , 851 , // 852  - zh-hk_radstr
+            0x1404 , 0x3b6 , 0x3b6 , 0x2712, 0x1f4 , 0x97  , 1 , 853 , 853 , // 853  - zh-mo
+            0x41404, 0x3b6 , 0x3b6 , 0x2712, 0x1f4 , 0x97  , 1 , 853 , 853 , // 854  - zh-mo_radstr
+            0x21404, 0x3b6 , 0x3b6 , 0x2712, 0x1f4 , 0x97  , 1 , 853 , 853 , // 855  - zh-mo_stroke
+            0x1004 , 0x3a8 , 0x3a8 , 0x2718, 0x1f4 , 0xd7  , 1 , 856 , 856 , // 856  - zh-sg
+            0x51004, 0x3a8 , 0x3a8 , 0x2718, 0x1f4 , 0xd7  , 1 , 856 , 856 , // 857  - zh-sg_phoneb
+            0x21004, 0x3a8 , 0x3a8 , 0x2718, 0x1f4 , 0xd7  , 1 , 856 , 856 , // 858  - zh-sg_stroke
+            0x404  , 0x3b6 , 0x3b6 , 0x2712, 0x1f4 , 0xed  , 1 , 859 , 859 , // 859  - zh-tw
+            0x30404, 0x3b6 , 0x3b6 , 0x2712, 0x1f4 , 0xed  , 1 , 859 , 859 , // 860  - zh-tw_pronun
+            0x40404, 0x3b6 , 0x3b6 , 0x2712, 0x1f4 , 0xed  , 1 , 859 , 859 , // 861  - zh-tw_radstr
+            0x35   , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd1  , 1 , 863 , 863 , // 862  - zu
+            0x435  , 0x4e4 , 0x352 , 0x2710, 0x1f4 , 0xd1  , 1 , 863 , 863 , // 863  - zu-za
+        };
+
+        // s_lcids list all supported lcids. used to binary search and we use the index of the matched lcid to 
+        // get the index in s_localeNamesIndices using s_lcidToCultureNameIndices
+        private static readonly int[] s_lcids = new int[]
+        {
+            // Lcid , index   - index in c_localeNames
+            0x1    , // 0    - 52
+            0x2    , // 1    - 301
+            0x3    , // 2    - 421
+            0x4    , // 3    - 4139
+            0x5    , // 4    - 502
+            0x6    , // 5    - 523
+            0x7    , // 6    - 544
+            0x8    , // 7    - 664
+            0x9    , // 8    - 676
+            0xa    , // 9    - 1214
+            0xb    , // 10   - 1423
+            0xc    , // 11   - 1451
+            0xd    , // 12   - 1825
+            0xe    , // 13   - 1860
+            0xf    , // 14   - 1929
+            0x10   , // 15   - 1936
+            0x11   , // 16   - 1989
+            0x12   , // 17   - 2179
+            0x13   , // 18   - 2685
+            0x14   , // 19   - 2747
+            0x15   , // 20   - 2864
+            0x16   , // 21   - 2897
+            0x17   , // 22   - 3041
+            0x18   , // 23   - 3055
+            0x19   , // 24   - 3076
+            0x1a   , // 25   - 1839
+            0x1b   , // 26   - 3284
+            0x1c   , // 27   - 3387
+            0x1d   , // 28   - 3553
+            0x1e   , // 29   - 3673
+            0x1f   , // 30   - 3727
+            0x20   , // 31   - 3847
+            0x21   , // 32   - 1908
+            0x22   , // 33   - 3840
+            0x23   , // 34   - 276
+            0x24   , // 35   - 3291
+            0x25   , // 36   - 1354
+            0x26   , // 37   - 2429
+            0x27   , // 38   - 2397
+            0x28   , // 39   - 3654
+            0x29   , // 40   - 1377
+            0x2a   , // 41   - 3960
+            0x2b   , // 42   - 1879
+            0x2c   , // 43   - 224
+            0x2d   , // 44   - 1361
+            0x2e   , // 45   - 1851
+            0x2f   , // 46   - 2501
+            0x30   , // 47   - 3541
+            0x31   , // 48   - 3739
+            0x32   , // 49   - 3708
+            0x33   , // 50   - 3953
+            0x34   , // 51   - 4020
+            0x35   , // 52   - 4277
+            0x36   , // 53   - 17
+            0x37   , // 54   - 2062
+            0x38   , // 55   - 1439
+            0x39   , // 56   - 1832
+            0x3a   , // 57   - 2598
+            0x3b   , // 58   - 3194
+            0x3c   , // 59   - 1705
+            0x3d   , // 60   - 4045
+            0x3e   , // 61   - 2581
+            0x3f   , // 62   - 2133
+            0x40   , // 63   - 2306
+            0x41   , // 64   - 3570
+            0x42   , // 65   - 3701
+            0x43   , // 66   - 3859
+            0x44   , // 67   - 3746
+            0x45   , // 68   - 336
+            0x46   , // 69   - 2830
+            0x47   , // 70   - 1754
+            0x48   , // 71   - 2811
+            0x49   , // 72   - 3610
+            0x4a   , // 73   - 3632
+            0x4b   , // 74   - 2172
+            0x4c   , // 75   - 2508
+            0x4d   , // 76   - 199
+            0x4e   , // 77   - 2574
+            0x4f   , // 78   - 3124
+            0x50   , // 79   - 2515
+            0x51   , // 80   - 348
+            0x52   , // 81   - 516
+            0x53   , // 82   - 2165
+            0x54   , // 83   - 2375
+            0x55   , // 84   - 2614
+            0x56   , // 85   - 1719
+            0x57   , // 86   - 2191
+            0x58   , // 87   - 2556
+            0x59   , // 88   - 3158
+            0x5a   , // 89   - 3601
+            0x5b   , // 90   - 3277
+            0x5c   , // 91   - 473
+            0x5d   , // 92   - 1953
+            0x5e   , // 93   - 45
+            0x5f   , // 94   - 3762
+            0x60   , // 95   - 2207
+            0x61   , // 96   - 2673
+            0x62   , // 97   - 1698
+            0x63   , // 98   - 2890
+            0x64   , // 99   - 1430
+            0x65   , // 100  - 620
+            0x66   , // 101  - 308
+            0x67   , // 102  - 1384
+            0x68   , // 103  - 1777
+            0x69   , // 104  - 1899
+            0x6a   , // 105  - 4053
+            0x6b   , // 106  - 3020
+            0x6c   , // 107  - 2765
+            0x6d   , // 108  - 260
+            0x6e   , // 109  - 2330
+            0x6f   , // 110  - 2149
+            0x70   , // 111  - 1915
+            0x71   , // 112  - 2200
+            0x72   , // 113  - 2799
+            0x73   , // 114  - 3680
+            0x74   , // 115  - 1726
+            0x75   , // 116  - 1816
+            0x76   , // 117  - 2313
+            0x77   , // 118  - 3365
+            0x78   , // 119  - 1922
+            0x79   , // 120  - 2854
+            0x7a   , // 121  - 190
+            0x7c   , // 122  - 2565
+            0x7e   , // 123  - 360
+            0x80   , // 124  - 3833
+            0x81   , // 125  - 2494
+            0x82   , // 126  - 2792
+            0x83   , // 127  - 495
+            0x84   , // 128  - 1733
+            0x85   , // 129  - 3131
+            0x86   , // 130  - 2998
+            0x87   , // 131  - 3108
+            0x88   , // 132  - 4002
+            0x8c   , // 133  - 2881
+            0x91   , // 134  - 1712
+            0x92   , // 135  - 2270
+            0x401  , // 136  - 150
+            0x402  , // 137  - 303
+            0x403  , // 138  - 428
+            0x404  , // 139  - 4248
+            0x405  , // 140  - 504
+            0x406  , // 141  - 525
+            0x407  , // 142  - 561
+            0x408  , // 143  - 671
+            0x409  , // 144  - 1161
+            0x40a  , // 145  - 1272
+            0x40b  , // 146  - 1425
+            0x40c  , // 147  - 1529
+            0x40d  , // 148  - 1827
+            0x40e  , // 149  - 1862
+            0x40f  , // 150  - 1931
+            0x410  , // 151  - 1943
+            0x411  , // 152  - 1991
+            0x412  , // 153  - 2186
+            0x413  , // 154  - 2707
+            0x414  , // 155  - 2641
+            0x415  , // 156  - 2866
+            0x416  , // 157  - 2904
+            0x417  , // 158  - 3043
+            0x418  , // 159  - 3062
+            0x419  , // 160  - 3098
+            0x41a  , // 161  - 1846
+            0x41b  , // 162  - 3286
+            0x41c  , // 163  - 3389
+            0x41d  , // 164  - 3565
+            0x41e  , // 165  - 3675
+            0x41f  , // 166  - 3734
+            0x420  , // 167  - 3854
+            0x421  , // 168  - 1910
+            0x422  , // 169  - 3842
+            0x423  , // 170  - 278
+            0x424  , // 171  - 3293
+            0x425  , // 172  - 1356
+            0x426  , // 173  - 2431
+            0x427  , // 174  - 2399
+            0x428  , // 175  - 3663
+            0x429  , // 176  - 1379
+            0x42a  , // 177  - 3962
+            0x42b  , // 178  - 1881
+            0x42c  , // 179  - 250
+            0x42d  , // 180  - 1363
+            0x42e  , // 181  - 1854
+            0x42f  , // 182  - 2503
+            0x430  , // 183  - 3548
+            0x431  , // 184  - 3741
+            0x432  , // 185  - 3715
+            0x433  , // 186  - 3955
+            0x434  , // 187  - 4022
+            0x435  , // 188  - 4279
+            0x436  , // 189  - 24
+            0x437  , // 190  - 2064
+            0x438  , // 191  - 1446
+            0x439  , // 192  - 1834
+            0x43a  , // 193  - 2600
+            0x43b  , // 194  - 3201
+            0x43d  , // 195  - 4047
+            0x43e  , // 196  - 2588
+            0x43f  , // 197  - 2135
+            0x440  , // 198  - 2308
+            0x441  , // 199  - 3577
+            0x442  , // 200  - 3703
+            0x443  , // 201  - 3902
+            0x444  , // 202  - 3748
+            0x445  , // 203  - 343
+            0x446  , // 204  - 2849
+            0x447  , // 205  - 1756
+            0x448  , // 206  - 2813
+            0x449  , // 207  - 3612
+            0x44a  , // 208  - 3634
+            0x44b  , // 209  - 2174
+            0x44c  , // 210  - 2510
+            0x44d  , // 211  - 201
+            0x44e  , // 212  - 2576
+            0x44f  , // 213  - 3126
+            0x450  , // 214  - 2524
+            0x451  , // 215  - 350
+            0x452  , // 216  - 518
+            0x453  , // 217  - 2167
+            0x454  , // 218  - 2377
+            0x455  , // 219  - 2616
+            0x456  , // 220  - 1721
+            0x457  , // 221  - 2194
+            0x458  , // 222  - 2559
+            0x459  , // 223  - 3184
+            0x45a  , // 224  - 3604
+            0x45b  , // 225  - 3279
+            0x45c  , // 226  - 484
+            0x45d  , // 227  - 1962
+            0x45e  , // 228  - 47
+            0x45f  , // 229  - 3773
+            0x460  , // 230  - 2209
+            0x461  , // 231  - 2680
+            0x462  , // 232  - 1700
+            0x463  , // 233  - 2892
+            0x464  , // 234  - 1433
+            0x465  , // 235  - 622
+            0x466  , // 236  - 311
+            0x467  , // 237  - 1418
+            0x468  , // 238  - 1806
+            0x469  , // 239  - 1902
+            0x46a  , // 240  - 4060
+            0x46b  , // 241  - 3023
+            0x46c  , // 242  - 2768
+            0x46d  , // 243  - 262
+            0x46e  , // 244  - 2332
+            0x46f  , // 245  - 2151
+            0x470  , // 246  - 1917
+            0x471  , // 247  - 2202
+            0x472  , // 248  - 2801
+            0x473  , // 249  - 3687
+            0x474  , // 250  - 1728
+            0x475  , // 251  - 1819
+            0x476  , // 252  - 2315
+            0x477  , // 253  - 3382
+            0x478  , // 254  - 1924
+            0x479  , // 255  - 2857
+            0x47a  , // 256  - 193
+            0x47c  , // 257  - 2568
+            0x47e  , // 258  - 362
+            0x480  , // 259  - 3835
+            0x481  , // 260  - 2496
+            0x482  , // 261  - 2794
+            0x483  , // 262  - 497
+            0x484  , // 263  - 1742
+            0x485  , // 264  - 3134
+            0x486  , // 265  - 3009
+            0x487  , // 266  - 3110
+            0x488  , // 267  - 4004
+            0x48c  , // 268  - 2884
+            0x491  , // 269  - 1714
+            0x492  , // 270  - 2279
+            0x501  , // 271  - 2972
+            0x5fe  , // 272  - 2980
+            0x801  , // 273  - 95
+            0x803  , // 274  - 433
+            0x804  , // 275  - 4110
+            0x807  , // 276  - 556
+            0x809  , // 277  - 831
+            0x80a  , // 278  - 1299
+            0x80c  , // 279  - 1459
+            0x810  , // 280  - 1938
+            0x813  , // 281  - 2692
+            0x814  , // 282  - 2733
+            0x816  , // 283  - 2944
+            0x818  , // 284  - 3057
+            0x819  , // 285  - 3093
+            0x81a  , // 286  - 3480
+            0x81d  , // 287  - 3560
+            0x820  , // 288  - 3849
+            0x82c  , // 289  - 233
+            0x82e  , // 290  - 605
+            0x832  , // 291  - 3710
+            0x83b  , // 292  - 3206
+            0x83c  , // 293  - 1707
+            0x83e  , // 294  - 2583
+            0x843  , // 295  - 3885
+            0x845  , // 296  - 338
+            0x846  , // 297  - 2839
+            0x849  , // 298  - 3617
+            0x850  , // 299  - 2536
+            0x859  , // 300  - 3167
+            0x85d  , // 301  - 1979
+            0x85f  , // 302  - 3792
+            0x860  , // 303  - 2233
+            0x861  , // 304  - 2675
+            0x867  , // 305  - 1403
+            0x86b  , // 306  - 3029
+            0x873  , // 307  - 3682
+            0x901  , // 308  - 2959
+            0x9ff  , // 309  - 2989
+            0xc01  , // 310  - 80
+            0xc04  , // 311  - 4173
+            0xc07  , // 312  - 546
+            0xc09  , // 313  - 716
+            0xc0a  , // 314  - 1267
+            0xc0c  , // 315  - 1484
+            0xc1a  , // 316  - 3423
+            0xc3b  , // 317  - 3196
+            0xc50  , // 318  - 2546
+            0xc51  , // 319  - 638
+            0xc6b  , // 320  - 3035
+            0x1001 , // 321  - 120
+            0x1004 , // 322  - 4219
+            0x1007 , // 323  - 588
+            0x1009 , // 324  - 756
+            0x100a , // 325  - 1289
+            0x100c , // 326  - 1504
+            0x101a , // 327  - 1841
+            0x103b , // 328  - 3316
+            0x105f , // 329  - 3822
+            0x1401 , // 330  - 75
+            0x1404 , // 331  - 4190
+            0x1407 , // 332  - 583
+            0x1409 , // 333  - 1026
+            0x140a , // 334  - 1247
+            0x140c , // 335  - 1569
+            0x141a , // 336  - 402
+            0x143b , // 337  - 3322
+            0x1801 , // 338  - 125
+            0x1809 , // 339  - 881
+            0x180a , // 340  - 1309
+            0x180c , // 341  - 1579
+            0x181a , // 342  - 3470
+            0x183b , // 343  - 3301
+            0x1c01 , // 344  - 180
+            0x1c09 , // 345  - 1191
+            0x1c0a , // 346  - 1257
+            0x1c0c , // 347  - 1453
+            0x1c1a , // 348  - 3413
+            0x1c3b , // 349  - 3307
+            0x2001 , // 350  - 135
+            0x2009 , // 351  - 911
+            0x200a , // 352  - 1349
+            0x200c , // 353  - 1634
+            0x201a , // 354  - 385
+            0x203b , // 355  - 3340
+            0x2401 , // 356  - 185
+            0x2409 , // 357  - 684
+            0x240a , // 358  - 1242
+            0x240c , // 359  - 1489
+            0x241a , // 360  - 3500
+            0x243b , // 361  - 3331
+            0x2801 , // 362  - 170
+            0x2809 , // 363  - 751
+            0x280a , // 364  - 1314
+            0x280c , // 365  - 1649
+            0x281a , // 366  - 3443
+            0x2c01 , // 367  - 100
+            0x2c09 , // 368  - 1136
+            0x2c0a , // 369  - 1222
+            0x2c0c , // 370  - 1514
+            0x2c1a , // 371  - 3490
+            0x3001 , // 372  - 115
+            0x3009 , // 373  - 1201
+            0x300a , // 374  - 1262
+            0x300c , // 375  - 1509
+            0x301a , // 376  - 3433
+            0x3401 , // 377  - 110
+            0x3409 , // 378  - 1036
+            0x340a , // 379  - 1237
+            0x340c , // 380  - 1594
+            0x3801 , // 381  - 60
+            0x3809 , // 382  - 876
+            0x380a , // 383  - 1344
+            0x380c , // 384  - 1574
+            0x3c01 , // 385  - 65
+            0x3c09 , // 386  - 871
+            0x3c0a , // 387  - 1329
+            0x3c0c , // 388  - 1559
+            0x4001 , // 389  - 145
+            0x4009 , // 390  - 896
+            0x400a , // 391  - 1227
+            0x4409 , // 392  - 991
+            0x440a , // 393  - 1334
+            0x4809 , // 394  - 1086
+            0x480a , // 395  - 1294
+            0x4c0a , // 396  - 1304
+            0x500a , // 397  - 1324
+            0x540a , // 398  - 1339
+            0x580a , // 399  - 1216
+            0x5c0a , // 400  - 1252
+            0x641a , // 401  - 378
+            0x681a , // 402  - 395
+            0x6c1a , // 403  - 3406
+            0x701a , // 404  - 3463
+            0x703b , // 405  - 3328
+            0x742c , // 406  - 226
+            0x743b , // 407  - 3337
+            0x7804 , // 408  - 4096
+            0x7814 , // 409  - 2731
+            0x781a , // 410  - 376
+            0x782c , // 411  - 243
+            0x783b , // 412  - 3298
+            0x7843 , // 413  - 3878
+            0x7850 , // 414  - 2517
+            0x785d , // 415  - 1955
+            0x785f , // 416  - 3814
+            0x7c04 , // 417  - 4166
+            0x7c14 , // 418  - 2639
+            0x7c1a , // 419  - 3404
+            0x7c28 , // 420  - 3656
+            0x7c2e , // 421  - 602
+            0x7c3b , // 422  - 3313
+            0x7c43 , // 423  - 3895
+            0x7c46 , // 424  - 2832
+            0x7c50 , // 425  - 2529
+            0x7c59 , // 426  - 3160
+            0x7c5c , // 427  - 476
+            0x7c5d , // 428  - 1972
+            0x7c5f , // 429  - 3784
+            0x7c67 , // 430  - 1396
+            0x7c68 , // 431  - 1779
+            0x7c86 , // 432  - 3001
+            0x7c92 , // 433  - 2272
+            0x1007f, // 434  - 4009
+            0x10407, // 435  - 566
+            0x1040e, // 436  - 1867
+            0x10437, // 437  - 2069
+            0x20804, // 438  - 4127
+            0x21004, // 439  - 4236
+            0x21404, // 440  - 4207
+            0x30404, // 441  - 4253
+            0x40404, // 442  - 4265
+            0x40411, // 443  - 1996
+            0x40c04, // 444  - 4178
+            0x41404, // 445  - 4195
+            0x50804, // 446  - 4115
+            0x51004  // 447  - 4224
+        };        
+        // each element in s_lcidToCultureNameIndices is index to s_localeNamesIndices
+        private static readonly int[] s_lcidToCultureNameIndices = new int[]
+        {
+        // Index to s_localeNamesIndices, index to this array - lcid  - index to the c_localeNames
+            13   , // 0    - 1     - 52
+            64   , // 1    - 2     - 301
+            88   , // 2    - 3     - 421
+            847  , // 3    - 4     - 4139
+            103  , // 4    - 5     - 502
+            109  , // 5    - 6     - 523
+            114  , // 6    - 7     - 544
+            140  , // 7    - 8     - 664
+            143  , // 8    - 9     - 676
+            251  , // 9    - a     - 1214
+            293  , // 10   - b     - 1423
+            300  , // 11   - c     - 1451
+            377  , // 12   - d     - 1825
+            386  , // 13   - e     - 1860
+            402  , // 14   - f     - 1929
+            404  , // 15   - 10    - 1936
+            413  , // 16   - 11    - 1989
+            452  , // 17   - 12    - 2179
+            564  , // 18   - 13    - 2685
+            578  , // 19   - 14    - 2747
+            605  , // 20   - 15    - 2864
+            613  , // 21   - 16    - 2897
+            637  , // 22   - 17    - 3041
+            641  , // 23   - 18    - 3055
+            646  , // 24   - 19    - 3076
+            381  , // 25   - 1a    - 1839
+            687  , // 26   - 1b    - 3284
+            709  , // 27   - 1c    - 3387
+            734  , // 28   - 1d    - 3553
+            760  , // 29   - 1e    - 3673
+            774  , // 30   - 1f    - 3727
+            795  , // 31   - 20    - 3847
+            396  , // 32   - 21    - 1908
+            793  , // 33   - 22    - 3840
+            58   , // 34   - 23    - 276
+            689  , // 35   - 24    - 3291
+            278  , // 36   - 25    - 1354
+            506  , // 37   - 26    - 2429
+            498  , // 38   - 27    - 2397
+            757  , // 39   - 28    - 3654
+            284  , // 40   - 29    - 1377
+            812  , // 41   - 2a    - 3960
+            389  , // 42   - 2b    - 1879
+            49   , // 43   - 2c    - 224
+            280  , // 44   - 2d    - 1361
+            384  , // 45   - 2e    - 1851
+            523  , // 46   - 2f    - 2501
+            731  , // 47   - 30    - 3541
+            777  , // 48   - 31    - 3739
+            769  , // 49   - 32    - 3708
+            810  , // 50   - 33    - 3953
+            825  , // 51   - 34    - 4020
+            862  , // 52   - 35    - 4277
+            4    , // 53   - 36    - 17
+            425  , // 54   - 37    - 2062
+            297  , // 55   - 38    - 1439
+            379  , // 56   - 39    - 1832
+            543  , // 57   - 3a    - 2598
+            670  , // 58   - 3b    - 3194
+            352  , // 59   - 3c    - 1705
+            831  , // 60   - 3d    - 4045
+            539  , // 61   - 3e    - 2581
+            440  , // 62   - 3f    - 2133
+            476  , // 63   - 40    - 2306
+            738  , // 64   - 41    - 3570
+            767  , // 65   - 42    - 3701
+            798  , // 66   - 43    - 3859
+            779  , // 67   - 44    - 3746
+            71   , // 68   - 45    - 336
+            599  , // 69   - 46    - 2830
+            364  , // 70   - 47    - 1754
+            594  , // 71   - 48    - 2811
+            747  , // 72   - 49    - 3610
+            752  , // 73   - 4a    - 3632
+            450  , // 74   - 4b    - 2172
+            525  , // 75   - 4c    - 2508
+            43   , // 76   - 4d    - 199
+            537  , // 77   - 4e    - 2574
+            657  , // 78   - 4f    - 3124
+            527  , // 79   - 50    - 2515
+            74   , // 80   - 51    - 348
+            107  , // 81   - 52    - 516
+            448  , // 82   - 53    - 2165
+            493  , // 83   - 54    - 2375
+            547  , // 84   - 55    - 2614
+            356  , // 85   - 56    - 1719
+            455  , // 86   - 57    - 2191
+            533  , // 87   - 58    - 2556
+            665  , // 88   - 59    - 3158
+            745  , // 89   - 5a    - 3601
+            685  , // 90   - 5b    - 3277
+            98   , // 91   - 5c    - 473
+            408  , // 92   - 5d    - 1953
+            11   , // 93   - 5e    - 45
+            783  , // 94   - 5f    - 3762
+            459  , // 95   - 60    - 2207
+            561  , // 96   - 61    - 2673
+            350  , // 97   - 62    - 1698
+            611  , // 98   - 63    - 2890
+            295  , // 99   - 64    - 1430
+            129  , // 100  - 65    - 620
+            66   , // 101  - 66    - 308
+            286  , // 102  - 67    - 1384
+            370  , // 103  - 68    - 1777
+            394  , // 104  - 69    - 1899
+            833  , // 105  - 6a    - 4053
+            633  , // 106  - 6b    - 3020
+            583  , // 107  - 6c    - 2765
+            54   , // 108  - 6d    - 260
+            482  , // 109  - 6e    - 2330
+            444  , // 110  - 6f    - 2149
+            398  , // 111  - 70    - 1915
+            457  , // 112  - 71    - 2200
+            591  , // 113  - 72    - 2799
+            762  , // 114  - 73    - 3680
+            358  , // 115  - 74    - 1726
+            375  , // 116  - 75    - 1816
+            478  , // 117  - 76    - 2313
+            704  , // 118  - 77    - 3365
+            400  , // 119  - 78    - 1922
+            603  , // 120  - 79    - 2854
+            41   , // 121  - 7a    - 190
+            535  , // 122  - 7c    - 2565
+            77   , // 123  - 7e    - 360
+            791  , // 124  - 80    - 3833
+            521  , // 125  - 81    - 2494
+            589  , // 126  - 82    - 2792
+            101  , // 127  - 83    - 495
+            360  , // 128  - 84    - 1733
+            659  , // 129  - 85    - 3131
+            630  , // 130  - 86    - 2998
+            653  , // 131  - 87    - 3108
+            822  , // 132  - 88    - 4002
+            609  , // 133  - 8c    - 2881
+            354  , // 134  - 91    - 1712
+            470  , // 135  - 92    - 2270
+            33   , // 136  - 401   - 150
+            65   , // 137  - 402   - 303
+            90   , // 138  - 403   - 428
+            859  , // 139  - 404   - 4248
+            104  , // 140  - 405   - 504
+            110  , // 141  - 406   - 525
+            118  , // 142  - 407   - 561
+            142  , // 143  - 408   - 671
+            240  , // 144  - 409   - 1161
+            263  , // 145  - 40a   - 1272
+            294  , // 146  - 40b   - 1425
+            316  , // 147  - 40c   - 1529
+            378  , // 148  - 40d   - 1827
+            387  , // 149  - 40e   - 1862
+            403  , // 150  - 40f   - 1931
+            406  , // 151  - 410   - 1943
+            414  , // 152  - 411   - 1991
+            454  , // 153  - 412   - 2186
+            569  , // 154  - 413   - 2707
+            554  , // 155  - 414   - 2641
+            606  , // 156  - 415   - 2866
+            615  , // 157  - 416   - 2904
+            638  , // 158  - 417   - 3043
+            643  , // 159  - 418   - 3062
+            651  , // 160  - 419   - 3098
+            383  , // 161  - 41a   - 1846
+            688  , // 162  - 41b   - 3286
+            710  , // 163  - 41c   - 3389
+            737  , // 164  - 41d   - 3565
+            761  , // 165  - 41e   - 3675
+            776  , // 166  - 41f   - 3734
+            797  , // 167  - 420   - 3854
+            397  , // 168  - 421   - 1910
+            794  , // 169  - 422   - 3842
+            59   , // 170  - 423   - 278
+            690  , // 171  - 424   - 3293
+            279  , // 172  - 425   - 1356
+            507  , // 173  - 426   - 2431
+            499  , // 174  - 427   - 2399
+            759  , // 175  - 428   - 3663
+            285  , // 176  - 429   - 1379
+            813  , // 177  - 42a   - 3962
+            390  , // 178  - 42b   - 1881
+            53   , // 179  - 42c   - 250
+            281  , // 180  - 42d   - 1363
+            385  , // 181  - 42e   - 1854
+            524  , // 182  - 42f   - 2503
+            733  , // 183  - 430   - 3548
+            778  , // 184  - 431   - 3741
+            771  , // 185  - 432   - 3715
+            811  , // 186  - 433   - 3955
+            826  , // 187  - 434   - 4022
+            863  , // 188  - 435   - 4279
+            6    , // 189  - 436   - 24
+            426  , // 190  - 437   - 2064
+            299  , // 191  - 438   - 1446
+            380  , // 192  - 439   - 1834
+            544  , // 193  - 43a   - 2600
+            672  , // 194  - 43b   - 3201
+            832  , // 195  - 43d   - 4047
+            541  , // 196  - 43e   - 2588
+            441  , // 197  - 43f   - 2135
+            477  , // 198  - 440   - 2308
+            740  , // 199  - 441   - 3577
+            768  , // 200  - 442   - 3703
+            804  , // 201  - 443   - 3902
+            780  , // 202  - 444   - 3748
+            73   , // 203  - 445   - 343
+            602  , // 204  - 446   - 2849
+            365  , // 205  - 447   - 1756
+            595  , // 206  - 448   - 2813
+            748  , // 207  - 449   - 3612
+            753  , // 208  - 44a   - 3634
+            451  , // 209  - 44b   - 2174
+            526  , // 210  - 44c   - 2510
+            44   , // 211  - 44d   - 201
+            538  , // 212  - 44e   - 2576
+            658  , // 213  - 44f   - 3126
+            529  , // 214  - 450   - 2524
+            75   , // 215  - 451   - 350
+            108  , // 216  - 452   - 518
+            449  , // 217  - 453   - 2167
+            494  , // 218  - 454   - 2377
+            548  , // 219  - 455   - 2616
+            357  , // 220  - 456   - 1721
+            456  , // 221  - 457   - 2194
+            534  , // 222  - 458   - 2559
+            669  , // 223  - 459   - 3184
+            746  , // 224  - 45a   - 3604
+            686  , // 225  - 45b   - 3279
+            100  , // 226  - 45c   - 484
+            410  , // 227  - 45d   - 1962
+            12   , // 228  - 45e   - 47
+            785  , // 229  - 45f   - 3773
+            460  , // 230  - 460   - 2209
+            563  , // 231  - 461   - 2680
+            351  , // 232  - 462   - 1700
+            612  , // 233  - 463   - 2892
+            296  , // 234  - 464   - 1433
+            130  , // 235  - 465   - 622
+            67   , // 236  - 466   - 311
+            292  , // 237  - 467   - 1418
+            374  , // 238  - 468   - 1806
+            395  , // 239  - 469   - 1902
+            835  , // 240  - 46a   - 4060
+            634  , // 241  - 46b   - 3023
+            584  , // 242  - 46c   - 2768
+            55   , // 243  - 46d   - 262
+            483  , // 244  - 46e   - 2332
+            445  , // 245  - 46f   - 2151
+            399  , // 246  - 470   - 1917
+            458  , // 247  - 471   - 2202
+            592  , // 248  - 472   - 2801
+            764  , // 249  - 473   - 3687
+            359  , // 250  - 474   - 1728
+            376  , // 251  - 475   - 1819
+            479  , // 252  - 476   - 2315
+            708  , // 253  - 477   - 3382
+            401  , // 254  - 478   - 1924
+            604  , // 255  - 479   - 2857
+            42   , // 256  - 47a   - 193
+            536  , // 257  - 47c   - 2568
+            78   , // 258  - 47e   - 362
+            792  , // 259  - 480   - 3835
+            522  , // 260  - 481   - 2496
+            590  , // 261  - 482   - 2794
+            102  , // 262  - 483   - 497
+            362  , // 263  - 484   - 1742
+            660  , // 264  - 485   - 3134
+            632  , // 265  - 486   - 3009
+            654  , // 266  - 487   - 3110
+            823  , // 267  - 488   - 4004
+            610  , // 268  - 48c   - 2884
+            355  , // 269  - 491   - 1714
+            472  , // 270  - 492   - 2279
+            627  , // 271  - 501   - 2972
+            628  , // 272  - 5fe   - 2980
+            22   , // 273  - 801   - 95
+            91   , // 274  - 803   - 433
+            844  , // 275  - 804   - 4110
+            117  , // 276  - 807   - 556
+            174  , // 277  - 809   - 831
+            267  , // 278  - 80a   - 1299
+            302  , // 279  - 80c   - 1459
+            405  , // 280  - 810   - 1938
+            566  , // 281  - 813   - 2692
+            575  , // 282  - 814   - 2733
+            623  , // 283  - 816   - 2944
+            642  , // 284  - 818   - 3057
+            650  , // 285  - 819   - 3093
+            722  , // 286  - 81a   - 3480
+            736  , // 287  - 81d   - 3560
+            796  , // 288  - 820   - 3849
+            51   , // 289  - 82c   - 233
+            126  , // 290  - 82e   - 605
+            770  , // 291  - 832   - 3710
+            673  , // 292  - 83b   - 3206
+            353  , // 293  - 83c   - 1707
+            540  , // 294  - 83e   - 2583
+            802  , // 295  - 843   - 3885
+            72   , // 296  - 845   - 338
+            601  , // 297  - 846   - 2839
+            749  , // 298  - 849   - 3617
+            531  , // 299  - 850   - 2536
+            667  , // 300  - 859   - 3167
+            412  , // 301  - 85d   - 1979
+            787  , // 302  - 85f   - 3792
+            463  , // 303  - 860   - 2233
+            562  , // 304  - 861   - 2675
+            290  , // 305  - 867   - 1403
+            635  , // 306  - 86b   - 3029
+            763  , // 307  - 873   - 3682
+            626  , // 308  - 901   - 2959
+            629  , // 309  - 9ff   - 2989
+            19   , // 310  - c01   - 80
+            851  , // 311  - c04   - 4173
+            115  , // 312  - c07   - 546
+            151  , // 313  - c09   - 716
+            262  , // 314  - c0a   - 1267
+            307  , // 315  - c0c   - 1484
+            716  , // 316  - c1a   - 3423
+            671  , // 317  - c3b   - 3196
+            532  , // 318  - c50   - 2546
+            134  , // 319  - c51   - 638
+            636  , // 320  - c6b   - 3035
+            27   , // 321  - 1001  - 120
+            856  , // 322  - 1004  - 4219
+            122  , // 323  - 1007  - 588
+            159  , // 324  - 1009  - 756
+            265  , // 325  - 100a  - 1289
+            311  , // 326  - 100c  - 1504
+            382  , // 327  - 101a  - 1841
+            695  , // 328  - 103b  - 3316
+            790  , // 329  - 105f  - 3822
+            18   , // 330  - 1401  - 75
+            853  , // 331  - 1404  - 4190
+            121  , // 332  - 1407  - 583
+            213  , // 333  - 1409  - 1026
+            258  , // 334  - 140a  - 1247
+            324  , // 335  - 140c  - 1569
+            85   , // 336  - 141a  - 402
+            696  , // 337  - 143b  - 3322
+            28   , // 338  - 1801  - 125
+            184  , // 339  - 1809  - 881
+            269  , // 340  - 180a  - 1309
+            326  , // 341  - 180c  - 1579
+            721  , // 342  - 181a  - 3470
+            692  , // 343  - 183b  - 3301
+            39   , // 344  - 1c01  - 180
+            246  , // 345  - 1c09  - 1191
+            260  , // 346  - 1c0a  - 1257
+            301  , // 347  - 1c0c  - 1453
+            715  , // 348  - 1c1a  - 3413
+            693  , // 349  - 1c3b  - 3307
+            30   , // 350  - 2001  - 135
+            190  , // 351  - 2009  - 911
+            277  , // 352  - 200a  - 1349
+            337  , // 353  - 200c  - 1634
+            83   , // 354  - 201a  - 385
+            700  , // 355  - 203b  - 3340
+            40   , // 356  - 2401  - 185
+            145  , // 357  - 2409  - 684
+            257  , // 358  - 240a  - 1242
+            308  , // 359  - 240c  - 1489
+            724  , // 360  - 241a  - 3500
+            698  , // 361  - 243b  - 3331
+            37   , // 362  - 2801  - 170
+            158  , // 363  - 2809  - 751
+            270  , // 364  - 280a  - 1314
+            340  , // 365  - 280c  - 1649
+            718  , // 366  - 281a  - 3443
+            23   , // 367  - 2c01  - 100
+            235  , // 368  - 2c09  - 1136
+            253  , // 369  - 2c0a  - 1222
+            313  , // 370  - 2c0c  - 1514
+            723  , // 371  - 2c1a  - 3490
+            26   , // 372  - 3001  - 115
+            248  , // 373  - 3009  - 1201
+            261  , // 374  - 300a  - 1262
+            312  , // 375  - 300c  - 1509
+            717  , // 376  - 301a  - 3433
+            25   , // 377  - 3401  - 110
+            215  , // 378  - 3409  - 1036
+            256  , // 379  - 340a  - 1237
+            329  , // 380  - 340c  - 1594
+            15   , // 381  - 3801  - 60
+            183  , // 382  - 3809  - 876
+            276  , // 383  - 380a  - 1344
+            325  , // 384  - 380c  - 1574
+            16   , // 385  - 3c01  - 65
+            182  , // 386  - 3c09  - 871
+            273  , // 387  - 3c0a  - 1329
+            322  , // 388  - 3c0c  - 1559
+            32   , // 389  - 4001  - 145
+            187  , // 390  - 4009  - 896
+            254  , // 391  - 400a  - 1227
+            206  , // 392  - 4409  - 991
+            274  , // 393  - 440a  - 1334
+            225  , // 394  - 4809  - 1086
+            266  , // 395  - 480a  - 1294
+            268  , // 396  - 4c0a  - 1304
+            272  , // 397  - 500a  - 1324
+            275  , // 398  - 540a  - 1339
+            252  , // 399  - 580a  - 1216
+            259  , // 400  - 5c0a  - 1252
+            82   , // 401  - 641a  - 378
+            84   , // 402  - 681a  - 395
+            714  , // 403  - 6c1a  - 3406
+            720  , // 404  - 701a  - 3463
+            697  , // 405  - 703b  - 3328
+            50   , // 406  - 742c  - 226
+            699  , // 407  - 743b  - 3337
+            841  , // 408  - 7804  - 4096
+            574  , // 409  - 7814  - 2731
+            81   , // 410  - 781a  - 376
+            52   , // 411  - 782c  - 243
+            691  , // 412  - 783b  - 3298
+            801  , // 413  - 7843  - 3878
+            528  , // 414  - 7850  - 2517
+            409  , // 415  - 785d  - 1955
+            789  , // 416  - 785f  - 3814
+            850  , // 417  - 7c04  - 4166
+            553  , // 418  - 7c14  - 2639
+            713  , // 419  - 7c1a  - 3404
+            758  , // 420  - 7c28  - 3656
+            125  , // 421  - 7c2e  - 602
+            694  , // 422  - 7c3b  - 3313
+            803  , // 423  - 7c43  - 3895
+            600  , // 424  - 7c46  - 2832
+            530  , // 425  - 7c50  - 2529
+            666  , // 426  - 7c59  - 3160
+            99   , // 427  - 7c5c  - 476
+            411  , // 428  - 7c5d  - 1972
+            786  , // 429  - 7c5f  - 3784
+            289  , // 430  - 7c67  - 1396
+            371  , // 431  - 7c68  - 1779
+            631  , // 432  - 7c86  - 3001
+            471  , // 433  - 7c92  - 2272
+            824  , // 434  - 1007f - 4009
+            119  , // 435  - 10407 - 566
+            388  , // 436  - 1040e - 1867
+            427  , // 437  - 10437 - 2069
+            846  , // 438  - 20804 - 4127
+            858  , // 439  - 21004 - 4236
+            855  , // 440  - 21404 - 4207
+            860  , // 441  - 30404 - 4253
+            861  , // 442  - 40404 - 4265
+            415  , // 443  - 40411 - 1996
+            852  , // 444  - 40c04 - 4178
+            854  , // 445  - 41404 - 4195
+            845  , // 446  - 50804 - 4115
+            857    // 447  - 51004 - 4224
+        };
+          
+        internal static string LCIDToLocaleName(int culture)
+        {
+            int left = 0;
+            int right = s_lcids.Length - 1;
+            int index;
+
+            Debug.Assert(s_lcids.Length == s_lcidToCultureNameIndices.Length);
+
+            while (left <= right)
+            {
+                index = (right + left) / 2;
+
+                if (culture == s_lcids[index])
+                {
+                    int indexToLocaleNamesIndices = s_lcidToCultureNameIndices[index];
+                    Debug.Assert(indexToLocaleNamesIndices < s_localeNamesIndices.Length - 1);
+                    
+                    return c_localeNames.Substring(s_localeNamesIndices[indexToLocaleNamesIndices], 
+                                                                         s_localeNamesIndices[indexToLocaleNamesIndices + 1] - 
+                                                                         s_localeNamesIndices[indexToLocaleNamesIndices]);
+                }
+                else if (culture < s_lcids[index])
+                {
+                    right = index - 1;
+                }
+                else
+                {
+                    left = index + 1;
+                }
+            }
+
+            return null;
+        }
+
+        internal static int GetLocaleDataNumericPart(string cultureName, LocaleDataParts part)
+        {
+            int index = SearchCultureName(cultureName);
+            if (index < 0)
+            {
+                return -1; 
+            }
+            
+            Debug.Assert((s_localeNamesIndices.Length-1 == (s_nameIndexToNumericData.Length/NUMERIC_LOCALE_DATA_COUNT_PER_ROW)) && 
+                            index < s_localeNamesIndices.Length);
+            
+            return s_nameIndexToNumericData[index * NUMERIC_LOCALE_DATA_COUNT_PER_ROW + (int) part];
+        }
+        
+        internal static string GetThreeLetterWindowsLangageName(string cultureName)
+        {
+            int index = SearchCultureName(cultureName);
+            if (index < 0)
+            {
+                return null;
+            }
+            
+            Debug.Assert(s_localeNamesIndices.Length-1 == (c_threeLetterWindowsLanguageName.Length / 3));
+            return c_threeLetterWindowsLanguageName.Substring(index * 3, 3); 
+        }
+        
+        internal static string GetLocaleDataMappedCulture(string cultureName, LocaleDataParts part)
+        {
+            int indexToIndicesTable = GetLocaleDataNumericPart(cultureName, part);
+            if (indexToIndicesTable < 0)
+            {
+                return ""; // fallback to invariant
+            }
+            
+            Debug.Assert(indexToIndicesTable < s_localeNamesIndices.Length-1);
+            
+            return c_localeNames.Substring(s_localeNamesIndices[indexToIndicesTable], 
+                                           s_localeNamesIndices[indexToIndicesTable+1] - s_localeNamesIndices[indexToIndicesTable]);
+        }
+        
+        internal static string GetSpecificCultureName(string cultureName)
+        {
+            return GetLocaleDataMappedCulture(cultureName, LocaleDataParts.SpecificLocaleIndex);
+        }
+        
+        internal static string GetConsoleUICulture(string cultureName)
+        {
+            return GetLocaleDataMappedCulture(cultureName, LocaleDataParts.ConsoleLocaleIndex);
+        }
+        
+        // SearchCultureName will binary search c_localeNames using s_localeNamesIndices.
+        // return index in s_localeNamesIndices, or -1 if it fail finding any match   
+        private static int SearchCultureName(string name)
+        {
+            int left = 0;
+            int right = s_localeNamesIndices.Length - 2;
+            int index;
+            int result;
+
+            Debug.Assert(s_localeNamesIndices[s_localeNamesIndices.Length - 1] == c_localeNames.Length);
+
+            name = CultureData.AnsiToLower(name);
+
+            // Binary search the array until we have only a couple of elements left and then
+            // just walk those elements.
+            while ((right - left) > 3)
+            {
+                index = ((right - left) / 2) + left;
+
+                Debug.Assert(index < s_localeNamesIndices.Length - 1);
+                result = CompareOrdinal(name, c_localeNames, s_localeNamesIndices[index], s_localeNamesIndices[index + 1] - s_localeNamesIndices[index]);
+                if (result == 0)
+                {
+                    return index;
+                }
+                else if (result < 0)
+                {
+                    right = index;
+                }
+                else
+                {
+                    left = index;
+                }
+            }
+
+            // Walk the remaining elements (it'll be 3 or fewer).
+            for (; left <= right; left++)
+            {
+                Debug.Assert(left < s_localeNamesIndices.Length - 1);
+                if (CompareOrdinal(name, c_localeNames, s_localeNamesIndices[left], s_localeNamesIndices[left + 1] - s_localeNamesIndices[left]) == 0)
+                {
+                    return (left);
+                }
+            }
+
+            // couldn't find culture name
+            return -1;
+        }
+        
+        // optimized to avoid parameters checking
+        private static int CompareOrdinal(string s1, string s2, int index, int length)
+        {
+            int count = s1.Length;
+            if (count > length)
+                count = length;
+
+            int i = 0;
+            while (i < count && s1[i] == s2[index + i])
+                i++;
+
+            if (i < count)
+                return (int)(s1[i] - s2[index + i]);
+
+            return s1.Length - length;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/Normalization.Unix.cs b/src/System.Private.CoreLib/shared/System/Globalization/Normalization.Unix.cs
new file mode 100644
index 0000000000..443dbae530
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/Normalization.Unix.cs
@@ -0,0 +1,134 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Text;
+
+namespace System.Globalization
+{
+    internal static partial class Normalization
+    {
+        internal static bool IsNormalized(string strInput, NormalizationForm normalizationForm)
+        {
+            if (GlobalizationMode.Invariant)
+            {
+                // In Invariant mode we assume all characters are normalized. 
+                // This is because we don't support any linguistic operation on the strings
+                return true;
+            }
+
+            ValidateArguments(strInput, normalizationForm);
+
+            int ret = Interop.Globalization.IsNormalized(normalizationForm, strInput, strInput.Length);
+
+            if (ret == -1)
+            {
+                throw new ArgumentException(SR.Argument_InvalidCharSequenceNoIndex, nameof(strInput));
+            }
+
+            return ret == 1;
+        }
+
+        internal static string Normalize(string strInput, NormalizationForm normalizationForm)
+        {
+            if (GlobalizationMode.Invariant)
+            {
+                // In Invariant mode we assume all characters are normalized. 
+                // This is because we don't support any linguistic operation on the strings
+                return strInput;
+            }
+
+            ValidateArguments(strInput, normalizationForm);
+
+            char[] buf = new char[strInput.Length];
+
+            for (int attempts = 2; attempts > 0; attempts--)
+            {
+                int realLen = Interop.Globalization.NormalizeString(normalizationForm, strInput, strInput.Length, buf, buf.Length);
+
+                if (realLen == -1)
+                {
+                    throw new ArgumentException(SR.Argument_InvalidCharSequenceNoIndex, nameof(strInput));
+                }
+
+                if (realLen <= buf.Length)
+                {
+                    return new string(buf, 0, realLen);
+                }
+
+                buf = new char[realLen];
+            }
+
+            throw new ArgumentException(SR.Argument_InvalidCharSequenceNoIndex, nameof(strInput));
+        }
+
+        // -----------------------------
+        // ---- PAL layer ends here ----
+        // -----------------------------
+
+        private static void ValidateArguments(string strInput, NormalizationForm normalizationForm)
+        {
+            Debug.Assert(strInput != null);
+
+            if (normalizationForm != NormalizationForm.FormC && normalizationForm != NormalizationForm.FormD &&
+                normalizationForm != NormalizationForm.FormKC && normalizationForm != NormalizationForm.FormKD)
+            {
+                throw new ArgumentException(SR.Argument_InvalidNormalizationForm, nameof(normalizationForm));
+            }
+
+            if (HasInvalidUnicodeSequence(strInput))
+            {
+                throw new ArgumentException(SR.Argument_InvalidCharSequenceNoIndex, nameof(strInput));
+            }
+        }
+
+        /// <summary>
+        /// ICU does not signal an error during normalization if the input string has invalid unicode,
+        /// unlike Windows (which uses the ERROR_NO_UNICODE_TRANSLATION error value to signal an error).
+        ///
+        /// We walk the string ourselves looking for these bad sequences so we can continue to throw
+        /// ArgumentException in these cases.
+        /// </summary>
+        private static bool HasInvalidUnicodeSequence(string s)
+        {
+            for (int i = 0; i < s.Length; i++)
+            {
+                char c = s[i];
+                
+                if (c < '\ud800')
+                {
+                    continue;
+                }
+
+                if (c == '\uFFFE')
+                {
+                    return true;
+                }
+
+                // If we see low surrogate before a high one, the string is invalid.
+                if (char.IsLowSurrogate(c))
+                {
+                    return true;
+                }
+
+                if (char.IsHighSurrogate(c))
+                {
+                    if (i + 1 >= s.Length || !char.IsLowSurrogate(s[i + 1]))
+                    {
+                        // A high surrogate at the end of the string or a high surrogate
+                        // not followed by a low surrogate
+                        return true;
+                    }
+                    else
+                    {
+                        i++; // consume the low surrogate.
+                        continue;
+                    }
+                }
+            }
+
+            return false;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/Normalization.Windows.cs b/src/System.Private.CoreLib/shared/System/Globalization/Normalization.Windows.cs
new file mode 100644
index 0000000000..8418c53b6c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/Normalization.Windows.cs
@@ -0,0 +1,148 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace System.Globalization
+{
+    internal static partial class Normalization
+    {
+        internal static bool IsNormalized(string strInput, NormalizationForm normalizationForm)
+        {
+            if (GlobalizationMode.Invariant)
+            {
+                // In Invariant mode we assume all characters are normalized. 
+                // This is because we don't support any linguistic operation on the strings
+                return true;
+            }
+
+            Debug.Assert(strInput != null);
+
+            // The only way to know if IsNormalizedString failed is through checking the Win32 last error
+            // IsNormalizedString pinvoke has SetLastError attribute property which will set the last error 
+            // to 0 (ERROR_SUCCESS) before executing the calls.
+            bool result = Interop.Normaliz.IsNormalizedString((int)normalizationForm, strInput, strInput.Length);
+
+            int lastError = Marshal.GetLastWin32Error();
+            switch (lastError)
+            {
+                case Interop.Errors.ERROR_SUCCESS:
+                    break;
+
+                case Interop.Errors.ERROR_INVALID_PARAMETER:
+                case Interop.Errors.ERROR_NO_UNICODE_TRANSLATION:
+                    if (normalizationForm != NormalizationForm.FormC && 
+                        normalizationForm != NormalizationForm.FormD && 
+                        normalizationForm != NormalizationForm.FormKC && 
+                        normalizationForm != NormalizationForm.FormKD)
+                    {
+                        throw new ArgumentException(SR.Argument_InvalidNormalizationForm, nameof(normalizationForm));
+                    }
+
+                    throw new ArgumentException(SR.Argument_InvalidCharSequenceNoIndex, nameof(strInput));
+
+                case Interop.Errors.ERROR_NOT_ENOUGH_MEMORY:
+                    throw new OutOfMemoryException();
+
+                default:
+                    throw new InvalidOperationException(SR.Format(SR.UnknownError_Num, lastError));
+            }
+
+            return result;
+        }
+
+        internal static string Normalize(string strInput, NormalizationForm normalizationForm)
+        {
+            if (GlobalizationMode.Invariant)
+            {
+                // In Invariant mode we assume all characters are normalized. 
+                // This is because we don't support any linguistic operation on the strings
+                return strInput;
+            }
+
+            Debug.Assert(strInput != null);
+
+            // we depend on Win32 last error when calling NormalizeString
+            // NormalizeString pinvoke has SetLastError attribute property which will set the last error 
+            // to 0 (ERROR_SUCCESS) before executing the calls.
+
+            // Guess our buffer size first
+            int iLength = Interop.Normaliz.NormalizeString((int)normalizationForm, strInput, strInput.Length, null, 0);
+
+            int lastError = Marshal.GetLastWin32Error();
+            // Could have an error (actually it'd be quite hard to have an error here)
+            if ((lastError != Interop.Errors.ERROR_SUCCESS) || iLength < 0)
+            {
+                if (lastError == Interop.Errors.ERROR_INVALID_PARAMETER)
+                {
+                    if (normalizationForm != NormalizationForm.FormC && 
+                        normalizationForm != NormalizationForm.FormD && 
+                        normalizationForm != NormalizationForm.FormKC && 
+                        normalizationForm != NormalizationForm.FormKD)
+                    {
+                        throw new ArgumentException(SR.Argument_InvalidNormalizationForm, nameof(normalizationForm));
+                    }
+
+                    throw new ArgumentException(SR.Argument_InvalidCharSequenceNoIndex, nameof(strInput));
+                }
+
+                // We shouldn't really be able to get here..., guessing length is
+                // a trivial math function...
+                // Can't really be Out of Memory, but just in case:
+                if (lastError == Interop.Errors.ERROR_NOT_ENOUGH_MEMORY)
+                    throw new OutOfMemoryException();
+
+                // Who knows what happened?  Not us!
+                throw new InvalidOperationException(SR.Format(SR.UnknownError_Num, lastError));
+            }
+
+            // Don't break for empty strings (only possible for D & KD and not really possible at that)
+            if (iLength == 0) return string.Empty;
+
+            // Someplace to stick our buffer
+            char[] cBuffer = null;
+
+            for (;;)
+            {
+                // (re)allocation buffer and normalize string
+                cBuffer = new char[iLength];
+
+                // NormalizeString pinvoke has SetLastError attribute property which will set the last error 
+                // to 0 (ERROR_SUCCESS) before executing the calls.
+                iLength = Interop.Normaliz.NormalizeString((int)normalizationForm, strInput, strInput.Length, cBuffer, cBuffer.Length);
+                lastError = Marshal.GetLastWin32Error();
+
+                if (lastError == Interop.Errors.ERROR_SUCCESS)
+                    break;
+
+                // Could have an error (actually it'd be quite hard to have an error here)
+                switch (lastError)
+                {
+                    // Do appropriate stuff for the individual errors:
+                    case Interop.Errors.ERROR_INSUFFICIENT_BUFFER:
+                        iLength = Math.Abs(iLength);
+                        Debug.Assert(iLength > cBuffer.Length, "Buffer overflow should have iLength > cBuffer.Length");
+                        continue;
+
+                    case Interop.Errors.ERROR_INVALID_PARAMETER:
+                    case Interop.Errors.ERROR_NO_UNICODE_TRANSLATION:
+                        // Illegal code point or order found.  Ie: FFFE or D800 D800, etc.
+                        throw new ArgumentException(SR.Argument_InvalidCharSequenceNoIndex, nameof(strInput));
+
+                    case Interop.Errors.ERROR_NOT_ENOUGH_MEMORY:
+                        throw new OutOfMemoryException();
+
+                    default:
+                        // We shouldn't get here...
+                        throw new InvalidOperationException(SR.Format(SR.UnknownError_Num, lastError));
+                }
+            }
+
+            // Copy our buffer into our new string, which will be the appropriate size
+            return new string(cBuffer, 0, iLength);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/NumberFormatInfo.cs b/src/System.Private.CoreLib/shared/System/Globalization/NumberFormatInfo.cs
new file mode 100644
index 0000000000..a98023dc96
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/NumberFormatInfo.cs
@@ -0,0 +1,842 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Text;
+
+namespace System.Globalization
+{
+    //
+    // Property             Default Description
+    // PositiveSign           '+'   Character used to indicate positive values.
+    // NegativeSign           '-'   Character used to indicate negative values.
+    // NumberDecimalSeparator '.'   The character used as the decimal separator.
+    // NumberGroupSeparator   ','   The character used to separate groups of
+    //                              digits to the left of the decimal point.
+    // NumberDecimalDigits    2     The default number of decimal places.
+    // NumberGroupSizes       3     The number of digits in each group to the
+    //                              left of the decimal point.
+    // NaNSymbol             "NaN"  The string used to represent NaN values.
+    // PositiveInfinitySymbol"Infinity" The string used to represent positive
+    //                              infinities.
+    // NegativeInfinitySymbol"-Infinity" The string used to represent negative
+    //                              infinities.
+    //
+    //
+    //
+    // Property                  Default  Description
+    // CurrencyDecimalSeparator  '.'      The character used as the decimal
+    //                                    separator.
+    // CurrencyGroupSeparator    ','      The character used to separate groups
+    //                                    of digits to the left of the decimal
+    //                                    point.
+    // CurrencyDecimalDigits     2        The default number of decimal places.
+    // CurrencyGroupSizes        3        The number of digits in each group to
+    //                                    the left of the decimal point.
+    // CurrencyPositivePattern   0        The format of positive values.
+    // CurrencyNegativePattern   0        The format of negative values.
+    // CurrencySymbol            "$"      String used as local monetary symbol.
+    //
+
+    sealed public class NumberFormatInfo : IFormatProvider, ICloneable
+    {
+        // invariantInfo is constant irrespective of your current culture.
+        private static volatile NumberFormatInfo s_invariantInfo;
+
+        // READTHIS READTHIS READTHIS
+        // This class has an exact mapping onto a native structure defined in COMNumber.cpp
+        // DO NOT UPDATE THIS WITHOUT UPDATING THAT STRUCTURE. IF YOU ADD BOOL, ADD THEM AT THE END.
+        // ALSO MAKE SURE TO UPDATE mscorlib.h in the VM directory to check field offsets.
+        // READTHIS READTHIS READTHIS
+        internal int[] numberGroupSizes = new int[] { 3 };
+        internal int[] currencyGroupSizes = new int[] { 3 };
+        internal int[] percentGroupSizes = new int[] { 3 };
+        internal String positiveSign = "+";
+        internal String negativeSign = "-";
+        internal String numberDecimalSeparator = ".";
+        internal String numberGroupSeparator = ",";
+        internal String currencyGroupSeparator = ",";
+        internal String currencyDecimalSeparator = ".";
+        internal String currencySymbol = "\x00a4";  // U+00a4 is the symbol for International Monetary Fund.
+        internal String nanSymbol = "NaN";
+        internal String positiveInfinitySymbol = "Infinity";
+        internal String negativeInfinitySymbol = "-Infinity";
+        internal String percentDecimalSeparator = ".";
+        internal String percentGroupSeparator = ",";
+        internal String percentSymbol = "%";
+        internal String perMilleSymbol = "\u2030";
+
+
+        internal String[] nativeDigits = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" };
+
+        internal int numberDecimalDigits = 2;
+        internal int currencyDecimalDigits = 2;
+        internal int currencyPositivePattern = 0;
+        internal int currencyNegativePattern = 0;
+        internal int numberNegativePattern = 1;
+        internal int percentPositivePattern = 0;
+        internal int percentNegativePattern = 0;
+        internal int percentDecimalDigits = 2;
+
+        internal int digitSubstitution = (int)DigitShapes.None;
+
+        internal bool isReadOnly = false;
+
+        // Is this NumberFormatInfo for invariant culture?
+        internal bool m_isInvariant = false;
+
+        public NumberFormatInfo() : this(null)
+        {
+        }
+
+        private static void VerifyDecimalSeparator(String decSep, String propertyName)
+        {
+            if (decSep == null)
+            {
+                throw new ArgumentNullException(propertyName,
+                        SR.ArgumentNull_String);
+            }
+
+            if (decSep.Length == 0)
+            {
+                throw new ArgumentException(SR.Argument_EmptyDecString);
+            }
+        }
+
+        private static void VerifyGroupSeparator(String groupSep, String propertyName)
+        {
+            if (groupSep == null)
+            {
+                throw new ArgumentNullException(propertyName,
+                        SR.ArgumentNull_String);
+            }
+        }
+
+        private static void VerifyNativeDigits(string[] nativeDig, string propertyName)
+        {
+            if (nativeDig == null)
+            {
+                throw new ArgumentNullException(propertyName, SR.ArgumentNull_Array);
+            }
+
+            if (nativeDig.Length != 10)
+            {
+                throw new ArgumentException(SR.Argument_InvalidNativeDigitCount, propertyName);
+            }
+
+            for (int i = 0; i < nativeDig.Length; i++)
+            {
+                if (nativeDig[i] == null)
+                {
+                    throw new ArgumentNullException(propertyName, SR.ArgumentNull_ArrayValue);
+                }
+
+                if (nativeDig[i].Length != 1)
+                {
+                    if (nativeDig[i].Length != 2)
+                    {
+                        // Not 1 or 2 UTF-16 code points
+                        throw new ArgumentException(SR.Argument_InvalidNativeDigitValue, propertyName);
+                    }
+                    else if (!char.IsSurrogatePair(nativeDig[i][0], nativeDig[i][1]))
+                    {
+                        // 2 UTF-6 code points, but not a surrogate pair
+                        throw new ArgumentException(SR.Argument_InvalidNativeDigitValue, propertyName);
+                    }
+                }
+
+                if (CharUnicodeInfo.GetDecimalDigitValue(nativeDig[i], 0) != i &&
+                    CharUnicodeInfo.GetUnicodeCategory(nativeDig[i], 0) != UnicodeCategory.PrivateUse)
+                {
+                    // Not the appropriate digit according to the Unicode data properties
+                    // (Digit 0 must be a 0, etc.).
+                    throw new ArgumentException(SR.Argument_InvalidNativeDigitValue, propertyName);
+                }
+            }
+        }
+
+        private static void VerifyDigitSubstitution(DigitShapes digitSub, string propertyName)
+        {
+            switch (digitSub)
+            {
+                case DigitShapes.Context:
+                case DigitShapes.None:
+                case DigitShapes.NativeNational:
+                    // Success.
+                    break;
+
+                default:
+                    throw new ArgumentException(SR.Argument_InvalidDigitSubstitution, propertyName);
+            }
+        }
+
+        internal NumberFormatInfo(CultureData cultureData)
+        {
+            if (cultureData != null)
+            {
+                // We directly use fields here since these data is coming from data table or Win32, so we
+                // don't need to verify their values (except for invalid parsing situations).
+                cultureData.GetNFIValues(this);
+
+                if (cultureData.IsInvariantCulture)
+                {
+                    // For invariant culture
+                    this.m_isInvariant = true;
+                }
+            }
+        }
+
+        private void VerifyWritable()
+        {
+            if (isReadOnly)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+            }
+        }
+
+        // Returns a default NumberFormatInfo that will be universally
+        // supported and constant irrespective of the current culture.
+        // Used by FromString methods.
+        //
+
+        public static NumberFormatInfo InvariantInfo
+        {
+            get
+            {
+                if (s_invariantInfo == null)
+                {
+                    // Lazy create the invariant info. This cannot be done in a .cctor because exceptions can
+                    // be thrown out of a .cctor stack that will need this.
+                    NumberFormatInfo nfi = new NumberFormatInfo();
+                    nfi.m_isInvariant = true;
+                    s_invariantInfo = ReadOnly(nfi);
+                }
+                return s_invariantInfo;
+            }
+        }
+
+        public static NumberFormatInfo GetInstance(IFormatProvider formatProvider)
+        {
+            return formatProvider == null ?
+                CurrentInfo : // Fast path for a null provider
+                GetProviderNonNull(formatProvider);
+
+            NumberFormatInfo GetProviderNonNull(IFormatProvider provider)
+            {
+                // Fast path for a regular CultureInfo
+                if (provider is CultureInfo cultureProvider && !cultureProvider._isInherited)
+                {
+                    return cultureProvider.numInfo ?? cultureProvider.NumberFormat;
+                }
+
+                return
+                    provider as NumberFormatInfo ?? // Fast path for an NFI
+                    provider.GetFormat(typeof(NumberFormatInfo)) as NumberFormatInfo ??
+                    CurrentInfo;
+            }
+        }
+
+        public Object Clone()
+        {
+            NumberFormatInfo n = (NumberFormatInfo)MemberwiseClone();
+            n.isReadOnly = false;
+            return n;
+        }
+
+
+        public int CurrencyDecimalDigits
+        {
+            get { return currencyDecimalDigits; }
+            set
+            {
+                if (value < 0 || value > 99)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(CurrencyDecimalDigits),
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    0,
+                                    99));
+                }
+                VerifyWritable();
+                currencyDecimalDigits = value;
+            }
+        }
+
+
+        public String CurrencyDecimalSeparator
+        {
+            get { return currencyDecimalSeparator; }
+            set
+            {
+                VerifyWritable();
+                VerifyDecimalSeparator(value, nameof(CurrencyDecimalSeparator));
+                currencyDecimalSeparator = value;
+            }
+        }
+
+
+        public bool IsReadOnly
+        {
+            get
+            {
+                return isReadOnly;
+            }
+        }
+
+        //
+        // Check the values of the groupSize array.
+        //
+        // Every element in the groupSize array should be between 1 and 9
+        // excpet the last element could be zero.
+        //
+        internal static void CheckGroupSize(String propName, int[] groupSize)
+        {
+            for (int i = 0; i < groupSize.Length; i++)
+            {
+                if (groupSize[i] < 1)
+                {
+                    if (i == groupSize.Length - 1 && groupSize[i] == 0)
+                        return;
+                    throw new ArgumentException(SR.Argument_InvalidGroupSize, propName);
+                }
+                else if (groupSize[i] > 9)
+                {
+                    throw new ArgumentException(SR.Argument_InvalidGroupSize, propName);
+                }
+            }
+        }
+
+
+        public int[] CurrencyGroupSizes
+        {
+            get
+            {
+                return ((int[])currencyGroupSizes.Clone());
+            }
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(CurrencyGroupSizes),
+                        SR.ArgumentNull_Obj);
+                }
+                VerifyWritable();
+
+                Int32[] inputSizes = (Int32[])value.Clone();
+                CheckGroupSize(nameof(CurrencyGroupSizes), inputSizes);
+                currencyGroupSizes = inputSizes;
+            }
+        }
+
+
+
+        public int[] NumberGroupSizes
+        {
+            get
+            {
+                return ((int[])numberGroupSizes.Clone());
+            }
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(NumberGroupSizes),
+                        SR.ArgumentNull_Obj);
+                }
+                VerifyWritable();
+
+                Int32[] inputSizes = (Int32[])value.Clone();
+                CheckGroupSize(nameof(NumberGroupSizes), inputSizes);
+                numberGroupSizes = inputSizes;
+            }
+        }
+
+
+        public int[] PercentGroupSizes
+        {
+            get
+            {
+                return ((int[])percentGroupSizes.Clone());
+            }
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(PercentGroupSizes),
+                        SR.ArgumentNull_Obj);
+                }
+                VerifyWritable();
+                Int32[] inputSizes = (Int32[])value.Clone();
+                CheckGroupSize(nameof(PercentGroupSizes), inputSizes);
+                percentGroupSizes = inputSizes;
+            }
+        }
+
+
+        public String CurrencyGroupSeparator
+        {
+            get { return currencyGroupSeparator; }
+            set
+            {
+                VerifyWritable();
+                VerifyGroupSeparator(value, nameof(CurrencyGroupSeparator));
+                currencyGroupSeparator = value;
+            }
+        }
+
+
+        public String CurrencySymbol
+        {
+            get { return currencySymbol; }
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(CurrencySymbol),
+                        SR.ArgumentNull_String);
+                }
+                VerifyWritable();
+                currencySymbol = value;
+            }
+        }
+
+        // Returns the current culture's NumberFormatInfo.  Used by Parse methods.
+        //
+
+        public static NumberFormatInfo CurrentInfo
+        {
+            get
+            {
+                System.Globalization.CultureInfo culture = CultureInfo.CurrentCulture;
+                if (!culture._isInherited)
+                {
+                    NumberFormatInfo info = culture.numInfo;
+                    if (info != null)
+                    {
+                        return info;
+                    }
+                }
+                return ((NumberFormatInfo)culture.GetFormat(typeof(NumberFormatInfo)));
+            }
+        }
+
+
+        public String NaNSymbol
+        {
+            get
+            {
+                return nanSymbol;
+            }
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(NaNSymbol),
+                        SR.ArgumentNull_String);
+                }
+                VerifyWritable();
+                nanSymbol = value;
+            }
+        }
+
+
+
+        public int CurrencyNegativePattern
+        {
+            get { return currencyNegativePattern; }
+            set
+            {
+                if (value < 0 || value > 15)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(CurrencyNegativePattern),
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    0,
+                                    15));
+                }
+                VerifyWritable();
+                currencyNegativePattern = value;
+            }
+        }
+
+
+        public int NumberNegativePattern
+        {
+            get { return numberNegativePattern; }
+            set
+            {
+                //
+                // NOTENOTE: the range of value should correspond to negNumberFormats[] in vm\COMNumber.cpp.
+                //
+                if (value < 0 || value > 4)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(NumberNegativePattern),
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    0,
+                                    4));
+                }
+                VerifyWritable();
+                numberNegativePattern = value;
+            }
+        }
+
+
+        public int PercentPositivePattern
+        {
+            get { return percentPositivePattern; }
+            set
+            {
+                //
+                // NOTENOTE: the range of value should correspond to posPercentFormats[] in vm\COMNumber.cpp.
+                //
+                if (value < 0 || value > 3)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(PercentPositivePattern),
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    0,
+                                    3));
+                }
+                VerifyWritable();
+                percentPositivePattern = value;
+            }
+        }
+
+
+        public int PercentNegativePattern
+        {
+            get { return percentNegativePattern; }
+            set
+            {
+                //
+                // NOTENOTE: the range of value should correspond to posPercentFormats[] in vm\COMNumber.cpp.
+                //
+                if (value < 0 || value > 11)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(PercentNegativePattern),
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    0,
+                                    11));
+                }
+                VerifyWritable();
+                percentNegativePattern = value;
+            }
+        }
+
+
+        public String NegativeInfinitySymbol
+        {
+            get
+            {
+                return negativeInfinitySymbol;
+            }
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(NegativeInfinitySymbol),
+                        SR.ArgumentNull_String);
+                }
+                VerifyWritable();
+                negativeInfinitySymbol = value;
+            }
+        }
+
+
+        public String NegativeSign
+        {
+            get { return negativeSign; }
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(NegativeSign),
+                        SR.ArgumentNull_String);
+                }
+                VerifyWritable();
+                negativeSign = value;
+            }
+        }
+
+
+        public int NumberDecimalDigits
+        {
+            get { return numberDecimalDigits; }
+            set
+            {
+                if (value < 0 || value > 99)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(NumberDecimalDigits),
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    0,
+                                    99));
+                }
+                VerifyWritable();
+                numberDecimalDigits = value;
+            }
+        }
+
+
+        public String NumberDecimalSeparator
+        {
+            get { return numberDecimalSeparator; }
+            set
+            {
+                VerifyWritable();
+                VerifyDecimalSeparator(value, nameof(NumberDecimalSeparator));
+                numberDecimalSeparator = value;
+            }
+        }
+
+
+        public String NumberGroupSeparator
+        {
+            get { return numberGroupSeparator; }
+            set
+            {
+                VerifyWritable();
+                VerifyGroupSeparator(value, nameof(NumberGroupSeparator));
+                numberGroupSeparator = value;
+            }
+        }
+
+
+        public int CurrencyPositivePattern
+        {
+            get { return currencyPositivePattern; }
+            set
+            {
+                if (value < 0 || value > 3)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(CurrencyPositivePattern),
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    0,
+                                    3));
+                }
+                VerifyWritable();
+                currencyPositivePattern = value;
+            }
+        }
+
+
+        public String PositiveInfinitySymbol
+        {
+            get
+            {
+                return positiveInfinitySymbol;
+            }
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(PositiveInfinitySymbol),
+                        SR.ArgumentNull_String);
+                }
+                VerifyWritable();
+                positiveInfinitySymbol = value;
+            }
+        }
+
+
+        public String PositiveSign
+        {
+            get { return positiveSign; }
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(PositiveSign),
+                        SR.ArgumentNull_String);
+                }
+                VerifyWritable();
+                positiveSign = value;
+            }
+        }
+
+
+        public int PercentDecimalDigits
+        {
+            get { return percentDecimalDigits; }
+            set
+            {
+                if (value < 0 || value > 99)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(PercentDecimalDigits),
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    0,
+                                    99));
+                }
+                VerifyWritable();
+                percentDecimalDigits = value;
+            }
+        }
+
+
+        public String PercentDecimalSeparator
+        {
+            get { return percentDecimalSeparator; }
+            set
+            {
+                VerifyWritable();
+                VerifyDecimalSeparator(value, nameof(PercentDecimalSeparator));
+                percentDecimalSeparator = value;
+            }
+        }
+
+
+        public String PercentGroupSeparator
+        {
+            get { return percentGroupSeparator; }
+            set
+            {
+                VerifyWritable();
+                VerifyGroupSeparator(value, nameof(PercentGroupSeparator));
+                percentGroupSeparator = value;
+            }
+        }
+
+
+        public String PercentSymbol
+        {
+            get
+            {
+                return percentSymbol;
+            }
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(PercentSymbol),
+                        SR.ArgumentNull_String);
+                }
+                VerifyWritable();
+                percentSymbol = value;
+            }
+        }
+
+
+        public String PerMilleSymbol
+        {
+            get { return perMilleSymbol; }
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(PerMilleSymbol),
+                        SR.ArgumentNull_String);
+                }
+                VerifyWritable();
+                perMilleSymbol = value;
+            }
+        }
+
+        public string[] NativeDigits
+        {
+            get { return (String[])nativeDigits.Clone(); }
+            set
+            {
+                VerifyWritable();
+                VerifyNativeDigits(value, nameof(NativeDigits));
+                nativeDigits = value;
+            }
+        }
+
+        public DigitShapes DigitSubstitution
+        {
+            get { return (DigitShapes)digitSubstitution; }
+            set
+            {
+                VerifyWritable();
+                VerifyDigitSubstitution(value, nameof(DigitSubstitution));
+                digitSubstitution = (int)value;
+            }
+        }
+
+        public Object GetFormat(Type formatType)
+        {
+            return formatType == typeof(NumberFormatInfo) ? this : null;
+        }
+
+        public static NumberFormatInfo ReadOnly(NumberFormatInfo nfi)
+        {
+            if (nfi == null)
+            {
+                throw new ArgumentNullException(nameof(nfi));
+            }
+            if (nfi.IsReadOnly)
+            {
+                return (nfi);
+            }
+            NumberFormatInfo info = (NumberFormatInfo)(nfi.MemberwiseClone());
+            info.isReadOnly = true;
+            return info;
+        }
+
+        // private const NumberStyles InvalidNumberStyles = unchecked((NumberStyles) 0xFFFFFC00);
+        private const NumberStyles InvalidNumberStyles = ~(NumberStyles.AllowLeadingWhite | NumberStyles.AllowTrailingWhite
+                                                           | NumberStyles.AllowLeadingSign | NumberStyles.AllowTrailingSign
+                                                           | NumberStyles.AllowParentheses | NumberStyles.AllowDecimalPoint
+                                                           | NumberStyles.AllowThousands | NumberStyles.AllowExponent
+                                                           | NumberStyles.AllowCurrencySymbol | NumberStyles.AllowHexSpecifier);
+
+        internal static void ValidateParseStyleInteger(NumberStyles style)
+        {
+            // Check for undefined flags
+            if ((style & InvalidNumberStyles) != 0)
+            {
+                throw new ArgumentException(SR.Argument_InvalidNumberStyles, nameof(style));
+            }
+            if ((style & NumberStyles.AllowHexSpecifier) != 0)
+            { // Check for hex number
+                if ((style & ~NumberStyles.HexNumber) != 0)
+                {
+                    throw new ArgumentException(SR.Arg_InvalidHexStyle);
+                }
+            }
+        }
+
+        internal static void ValidateParseStyleFloatingPoint(NumberStyles style)
+        {
+            // Check for undefined flags
+            if ((style & InvalidNumberStyles) != 0)
+            {
+                throw new ArgumentException(SR.Argument_InvalidNumberStyles, nameof(style));
+            }
+            if ((style & NumberStyles.AllowHexSpecifier) != 0)
+            { // Check for hex number
+                throw new ArgumentException(SR.Arg_HexStyleNotSupported);
+            }
+        }
+    } // NumberFormatInfo
+}
+
+
+
+
+
+
+
+
+
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/NumberStyles.cs b/src/System.Private.CoreLib/shared/System/Globalization/NumberStyles.cs
new file mode 100644
index 0000000000..5909d65a2c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/NumberStyles.cs
@@ -0,0 +1,65 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Contains valid formats for Numbers recognized by
+** the Number class' parsing code.
+**
+**
+===========================================================*/
+
+namespace System.Globalization
+{
+    [Flags]
+    public enum NumberStyles
+    {
+        // Bit flag indicating that leading whitespace is allowed. Character values
+        // 0x0009, 0x000A, 0x000B, 0x000C, 0x000D, and 0x0020 are considered to be
+        // whitespace.
+
+        None = 0x00000000,
+
+        AllowLeadingWhite = 0x00000001,
+
+        AllowTrailingWhite = 0x00000002, //Bitflag indicating trailing whitespace is allowed.
+
+        AllowLeadingSign = 0x00000004, //Can the number start with a sign char.  
+                                       //Specified by NumberFormatInfo.PositiveSign and NumberFormatInfo.NegativeSign
+
+        AllowTrailingSign = 0x00000008, //Allow the number to end with a sign char
+
+        AllowParentheses = 0x00000010, //Allow the number to be enclosed in parens
+
+        AllowDecimalPoint = 0x00000020, //Allow a decimal point
+
+        AllowThousands = 0x00000040, //Allow thousands separators (more properly, allow group separators)
+
+        AllowExponent = 0x00000080, //Allow an exponent
+
+        AllowCurrencySymbol = 0x00000100, //Allow a currency symbol.
+
+        AllowHexSpecifier = 0x00000200, //Allow specifiying hexadecimal.
+                                        //Common uses.  These represent some of the most common combinations of these flags.
+
+
+        Integer = AllowLeadingWhite | AllowTrailingWhite | AllowLeadingSign,
+
+        HexNumber = AllowLeadingWhite | AllowTrailingWhite | AllowHexSpecifier,
+
+        Number = AllowLeadingWhite | AllowTrailingWhite | AllowLeadingSign | AllowTrailingSign |
+                   AllowDecimalPoint | AllowThousands,
+
+        Float = AllowLeadingWhite | AllowTrailingWhite | AllowLeadingSign |
+                   AllowDecimalPoint | AllowExponent,
+
+        Currency = AllowLeadingWhite | AllowTrailingWhite | AllowLeadingSign | AllowTrailingSign |
+                   AllowParentheses | AllowDecimalPoint | AllowThousands | AllowCurrencySymbol,
+
+        Any = AllowLeadingWhite | AllowTrailingWhite | AllowLeadingSign | AllowTrailingSign |
+                   AllowParentheses | AllowDecimalPoint | AllowThousands | AllowCurrencySymbol | AllowExponent,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/PersianCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/PersianCalendar.cs
new file mode 100644
index 0000000000..10912f85b1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/PersianCalendar.cs
@@ -0,0 +1,601 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    // Modern Persian calendar is a solar observation based calendar. Each new year begins on the day when the vernal equinox occurs before noon.
+    // The epoch is the date of the vernal equinox prior to the epoch of the Islamic calendar (March 19, 622 Julian or March 22, 622 Gregorian)
+
+    // There is no Persian year 0. Ordinary years have 365 days. Leap years have 366 days with the last month (Esfand) gaining the extra day.
+    /*
+     **  Calendar support range:
+     **      Calendar    Minimum     Maximum
+     **      ==========  ==========  ==========
+     **      Gregorian   0622/03/22   9999/12/31
+     **      Persian     0001/01/01   9378/10/13
+     */
+
+    public class PersianCalendar : Calendar
+    {
+        public static readonly int PersianEra = 1;
+
+        internal static long PersianEpoch = new DateTime(622, 3, 22).Ticks / GregorianCalendar.TicksPerDay;
+        private const int ApproximateHalfYear = 180;
+
+        internal const int DatePartYear = 0;
+        internal const int DatePartDayOfYear = 1;
+        internal const int DatePartMonth = 2;
+        internal const int DatePartDay = 3;
+        internal const int MonthsPerYear = 12;
+
+        internal static int[] DaysToMonth = { 0, 31, 62, 93, 124, 155, 186, 216, 246, 276, 306, 336, 366 };
+
+        internal const int MaxCalendarYear = 9378;
+        internal const int MaxCalendarMonth = 10;
+        internal const int MaxCalendarDay = 13;
+
+        // Persian calendar (year: 1, month: 1, day:1 ) = Gregorian (year: 622, month: 3, day: 22)
+        // This is the minimal Gregorian date that we support in the PersianCalendar.
+        internal static DateTime minDate = new DateTime(622, 3, 22);
+        internal static DateTime maxDate = DateTime.MaxValue;
+
+        public override DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (minDate);
+            }
+        }
+
+        public override DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (maxDate);
+            }
+        }
+
+        public override CalendarAlgorithmType AlgorithmType
+        {
+            get
+            {
+                return CalendarAlgorithmType.SolarCalendar;
+            }
+        }
+
+        // Construct an instance of Persian calendar.
+
+        public PersianCalendar()
+        {
+        }
+
+
+        internal override CalendarId BaseCalendarID
+        {
+            get
+            {
+                return CalendarId.GREGORIAN;
+            }
+        }
+
+        internal override CalendarId ID
+        {
+            get
+            {
+                return CalendarId.PERSIAN;
+            }
+        }
+
+
+        /*=================================GetAbsoluteDatePersian==========================
+        **Action: Gets the Absolute date for the given Persian date.  The absolute date means
+        **       the number of days from January 1st, 1 A.D.
+        **Returns:
+        **Arguments:
+        **Exceptions:
+        ============================================================================*/
+
+        private long GetAbsoluteDatePersian(int year, int month, int day)
+        {
+            if (year >= 1 && year <= MaxCalendarYear && month >= 1 && month <= 12)
+            {
+                int ordinalDay = DaysInPreviousMonths(month) + day - 1; // day is one based, make 0 based since this will be the number of days we add to beginning of year below
+                int approximateDaysFromEpochForYearStart = (int)(CalendricalCalculationsHelper.MeanTropicalYearInDays * (year - 1));
+                long yearStart = CalendricalCalculationsHelper.PersianNewYearOnOrBefore(PersianEpoch + approximateDaysFromEpochForYearStart + ApproximateHalfYear);
+                yearStart += ordinalDay;
+                return yearStart;
+            }
+            throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadYearMonthDay);
+        }
+
+        internal static void CheckTicksRange(long ticks)
+        {
+            if (ticks < minDate.Ticks || ticks > maxDate.Ticks)
+            {
+                throw new ArgumentOutOfRangeException(
+                            "time",
+                            String.Format(
+                                CultureInfo.InvariantCulture,
+                                SR.ArgumentOutOfRange_CalendarRange,
+                                minDate,
+                                maxDate));
+            }
+        }
+
+        internal static void CheckEraRange(int era)
+        {
+            if (era != CurrentEra && era != PersianEra)
+            {
+                throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+            }
+        }
+
+        internal static void CheckYearRange(int year, int era)
+        {
+            CheckEraRange(era);
+            if (year < 1 || year > MaxCalendarYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                1,
+                                MaxCalendarYear));
+            }
+        }
+
+        internal static void CheckYearMonthRange(int year, int month, int era)
+        {
+            CheckYearRange(year, era);
+            if (year == MaxCalendarYear)
+            {
+                if (month > MaxCalendarMonth)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(month),
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    1,
+                                    MaxCalendarMonth));
+                }
+            }
+
+            if (month < 1 || month > 12)
+            {
+                throw new ArgumentOutOfRangeException(nameof(month), SR.ArgumentOutOfRange_Month);
+            }
+        }
+
+        private static int MonthFromOrdinalDay(int ordinalDay)
+        {
+            Debug.Assert(ordinalDay <= 366);
+            int index = 0;
+            while (ordinalDay > DaysToMonth[index])
+                index++;
+
+            return index;
+        }
+
+        private static int DaysInPreviousMonths(int month)
+        {
+            Debug.Assert(1 <= month && month <= 12);
+            --month; // months are one based but for calculations use 0 based
+            return DaysToMonth[month];
+        }
+
+        /*=================================GetDatePart==========================
+        **Action: Returns a given date part of this <i>DateTime</i>. This method is used
+        **       to compute the year, day-of-year, month, or day part.
+        **Returns:
+        **Arguments:
+        **Exceptions:  ArgumentException if part is incorrect.
+        ============================================================================*/
+
+        internal int GetDatePart(long ticks, int part)
+        {
+            long NumDays;                 // The calculation buffer in number of days.
+
+            CheckTicksRange(ticks);
+
+            //
+            //  Get the absolute date.  The absolute date is the number of days from January 1st, 1 A.D.
+            //  1/1/0001 is absolute date 1.
+            //
+            NumDays = ticks / GregorianCalendar.TicksPerDay + 1;
+
+            //
+            //  Calculate the appromixate Persian Year.
+            //
+
+            long yearStart = CalendricalCalculationsHelper.PersianNewYearOnOrBefore(NumDays);
+            int y = (int)(Math.Floor(((yearStart - PersianEpoch) / CalendricalCalculationsHelper.MeanTropicalYearInDays) + 0.5)) + 1;
+            Debug.Assert(y >= 1);
+
+            if (part == DatePartYear)
+            {
+                return y;
+            }
+
+            //
+            //  Calculate the Persian Month.
+            //
+
+            int ordinalDay = (int)(NumDays - CalendricalCalculationsHelper.GetNumberOfDays(this.ToDateTime(y, 1, 1, 0, 0, 0, 0, 1)));
+
+            if (part == DatePartDayOfYear)
+            {
+                return ordinalDay;
+            }
+
+            int m = MonthFromOrdinalDay(ordinalDay);
+            Debug.Assert(ordinalDay >= 1);
+            Debug.Assert(m >= 1 && m <= 12);
+            if (part == DatePartMonth)
+            {
+                return m;
+            }
+
+            int d = ordinalDay - DaysInPreviousMonths(m);
+            Debug.Assert(1 <= d);
+            Debug.Assert(d <= 31);
+
+            //
+            //  Calculate the Persian Day.
+            //
+
+            if (part == DatePartDay)
+            {
+                return (d);
+            }
+
+            // Incorrect part value.
+            throw new InvalidOperationException(SR.InvalidOperation_DateTimeParsing);
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // months to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year and month parts of the specified DateTime by
+        // value months, and, if required, adjusting the day part of the
+        // resulting date downwards to the last day of the resulting month in the
+        // resulting year. The time-of-day part of the result is the same as the
+        // time-of-day part of the specified DateTime.
+        //
+        // In more precise terms, considering the specified DateTime to be of the
+        // form y / m / d + t, where y is the
+        // year, m is the month, d is the day, and t is the
+        // time-of-day, the result is y1 / m1 / d1 + t,
+        // where y1 and m1 are computed by adding value months
+        // to y and m, and d1 is the largest value less than
+        // or equal to d that denotes a valid day in month m1 of year
+        // y1.
+        //
+
+
+        public override DateTime AddMonths(DateTime time, int months)
+        {
+            if (months < -120000 || months > 120000)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(months),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                -120000,
+                                120000));
+            }
+            // Get the date in Persian calendar.
+            int y = GetDatePart(time.Ticks, DatePartYear);
+            int m = GetDatePart(time.Ticks, DatePartMonth);
+            int d = GetDatePart(time.Ticks, DatePartDay);
+            int i = m - 1 + months;
+            if (i >= 0)
+            {
+                m = i % 12 + 1;
+                y = y + i / 12;
+            }
+            else
+            {
+                m = 12 + (i + 1) % 12;
+                y = y + (i - 11) / 12;
+            }
+            int days = GetDaysInMonth(y, m);
+            if (d > days)
+            {
+                d = days;
+            }
+            long ticks = GetAbsoluteDatePersian(y, m, d) * TicksPerDay + time.Ticks % TicksPerDay;
+            Calendar.CheckAddResult(ticks, MinSupportedDateTime, MaxSupportedDateTime);
+            return (new DateTime(ticks));
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // years to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year part of the specified DateTime by value
+        // years. If the month and day of the specified DateTime is 2/29, and if the
+        // resulting year is not a leap year, the month and day of the resulting
+        // DateTime becomes 2/28. Otherwise, the month, day, and time-of-day
+        // parts of the result are the same as those of the specified DateTime.
+        //
+
+
+        public override DateTime AddYears(DateTime time, int years)
+        {
+            return (AddMonths(time, years * 12));
+        }
+
+        // Returns the day-of-month part of the specified DateTime. The returned
+        // value is an integer between 1 and 31.
+        //
+
+
+        public override int GetDayOfMonth(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartDay));
+        }
+
+        // Returns the day-of-week part of the specified DateTime. The returned value
+        // is an integer between 0 and 6, where 0 indicates Sunday, 1 indicates
+        // Monday, 2 indicates Tuesday, 3 indicates Wednesday, 4 indicates
+        // Thursday, 5 indicates Friday, and 6 indicates Saturday.
+        //
+
+
+        public override DayOfWeek GetDayOfWeek(DateTime time)
+        {
+            return ((DayOfWeek)((int)(time.Ticks / TicksPerDay + 1) % 7));
+        }
+
+        // Returns the day-of-year part of the specified DateTime. The returned value
+        // is an integer between 1 and 366.
+        //
+
+
+        public override int GetDayOfYear(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartDayOfYear));
+        }
+
+        // Returns the number of days in the month given by the year and
+        // month arguments.
+        //
+
+
+        public override int GetDaysInMonth(int year, int month, int era)
+        {
+            CheckYearMonthRange(year, month, era);
+
+            if ((month == MaxCalendarMonth) && (year == MaxCalendarYear))
+            {
+                return MaxCalendarDay;
+            }
+
+            int daysInMonth = DaysToMonth[month] - DaysToMonth[month - 1];
+            if ((month == MonthsPerYear) && !IsLeapYear(year))
+            {
+                Debug.Assert(daysInMonth == 30);
+                --daysInMonth;
+            }
+            return daysInMonth;
+        }
+
+        // Returns the number of days in the year given by the year argument for the current era.
+        //
+
+        public override int GetDaysInYear(int year, int era)
+        {
+            CheckYearRange(year, era);
+            if (year == MaxCalendarYear)
+            {
+                return DaysToMonth[MaxCalendarMonth - 1] + MaxCalendarDay;
+            }
+            // Common years have 365 days.  Leap years have 366 days.
+            return (IsLeapYear(year, CurrentEra) ? 366 : 365);
+        }
+
+        // Returns the era for the specified DateTime value.
+
+
+        public override int GetEra(DateTime time)
+        {
+            CheckTicksRange(time.Ticks);
+            return (PersianEra);
+        }
+
+
+
+        public override int[] Eras
+        {
+            get
+            {
+                return (new int[] { PersianEra });
+            }
+        }
+
+        // Returns the month part of the specified DateTime. The returned value is an
+        // integer between 1 and 12.
+        //
+
+
+        public override int GetMonth(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartMonth));
+        }
+
+        // Returns the number of months in the specified year and era.
+
+
+        public override int GetMonthsInYear(int year, int era)
+        {
+            CheckYearRange(year, era);
+            if (year == MaxCalendarYear)
+            {
+                return MaxCalendarMonth;
+            }
+            return (12);
+        }
+
+        // Returns the year part of the specified DateTime. The returned value is an
+        // integer between 1 and MaxCalendarYear.
+        //
+
+
+        public override int GetYear(DateTime time)
+        {
+            return (GetDatePart(time.Ticks, DatePartYear));
+        }
+
+        // Checks whether a given day in the specified era is a leap day. This method returns true if
+        // the date is a leap day, or false if not.
+        //
+
+
+        public override bool IsLeapDay(int year, int month, int day, int era)
+        {
+            // The year/month/era value checking is done in GetDaysInMonth().
+            int daysInMonth = GetDaysInMonth(year, month, era);
+            if (day < 1 || day > daysInMonth)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(day),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Day,
+                                daysInMonth,
+                                month));
+            }
+            return (IsLeapYear(year, era) && month == 12 && day == 30);
+        }
+
+        // Returns  the leap month in a calendar year of the specified era. This method returns 0
+        // if this calendar does not have leap month, or this year is not a leap year.
+        //
+
+
+        public override int GetLeapMonth(int year, int era)
+        {
+            CheckYearRange(year, era);
+            return (0);
+        }
+
+        // Checks whether a given month in the specified era is a leap month. This method returns true if
+        // month is a leap month, or false if not.
+        //
+
+
+        public override bool IsLeapMonth(int year, int month, int era)
+        {
+            CheckYearMonthRange(year, month, era);
+            return (false);
+        }
+
+        // Checks whether a given year in the specified era is a leap year. This method returns true if
+        // year is a leap year, or false if not.
+        //
+
+        public override bool IsLeapYear(int year, int era)
+        {
+            CheckYearRange(year, era);
+
+            if (year == MaxCalendarYear)
+            {
+                return false;
+            }
+
+            return (GetAbsoluteDatePersian(year + 1, 1, 1) - GetAbsoluteDatePersian(year, 1, 1)) == 366;
+        }
+
+        // Returns the date and time converted to a DateTime value.  Throws an exception if the n-tuple is invalid.
+        //
+
+
+        public override DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era)
+        {
+            // The year/month/era checking is done in GetDaysInMonth().
+            int daysInMonth = GetDaysInMonth(year, month, era);
+            if (day < 1 || day > daysInMonth)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(day),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Day,
+                                daysInMonth,
+                                month));
+            }
+
+            long lDate = GetAbsoluteDatePersian(year, month, day);
+
+            if (lDate >= 0)
+            {
+                return (new DateTime(lDate * GregorianCalendar.TicksPerDay + TimeToTicks(hour, minute, second, millisecond)));
+            }
+            else
+            {
+                throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadYearMonthDay);
+            }
+        }
+
+        private const int DEFAULT_TWO_DIGIT_YEAR_MAX = 1410;
+
+        public override int TwoDigitYearMax
+        {
+            get
+            {
+                if (twoDigitYearMax == -1)
+                {
+                    twoDigitYearMax = GetSystemTwoDigitYearSetting(ID, DEFAULT_TWO_DIGIT_YEAR_MAX);
+                }
+                return (twoDigitYearMax);
+            }
+
+            set
+            {
+                VerifyWritable();
+                if (value < 99 || value > MaxCalendarYear)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(value),
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    99,
+                                    MaxCalendarYear));
+                }
+                twoDigitYearMax = value;
+            }
+        }
+
+
+
+        public override int ToFourDigitYear(int year)
+        {
+            if (year < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (year < 100)
+            {
+                return (base.ToFourDigitYear(year));
+            }
+
+            if (year > MaxCalendarYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                1,
+                                MaxCalendarYear));
+            }
+            return (year);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/RegionInfo.cs b/src/System.Private.CoreLib/shared/System/Globalization/RegionInfo.cs
new file mode 100644
index 0000000000..2cad7bb31c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/RegionInfo.cs
@@ -0,0 +1,399 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////
+//
+//
+//  Purpose:  This class represents settings specified by de jure or
+//            de facto standards for a particular country/region.  In
+//            contrast to CultureInfo, the RegionInfo does not represent
+//            preferences of the user and does not depend on the user's
+//            language or culture.
+//
+//
+////////////////////////////////////////////////////////////////////////////
+
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    public class RegionInfo
+    {
+        //--------------------------------------------------------------------//
+        //                        Internal Information                        //
+        //--------------------------------------------------------------------//
+
+        //
+        //  Variables.
+        //
+
+        //
+        // Name of this region (ie: es-US): serialized, the field used for deserialization
+        //
+        internal String _name;
+
+        //
+        // The CultureData instance that we are going to read data from.
+        //
+        internal CultureData _cultureData;
+
+        //
+        // The RegionInfo for our current region
+        //
+        internal static volatile RegionInfo s_currentRegionInfo;
+
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  RegionInfo Constructors
+        //
+        //  Note: We prefer that a region be created with a full culture name (ie: en-US)
+        //  because otherwise the native strings won't be right.
+        //
+        //  In Silverlight we enforce that RegionInfos must be created with a full culture name
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public RegionInfo(String name)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            if (name.Length == 0) //The InvariantCulture has no matching region
+            {
+                throw new ArgumentException(SR.Argument_NoRegionInvariantCulture, nameof(name));
+            }
+
+
+            //
+            // For CoreCLR we only want the region names that are full culture names
+            //
+            _cultureData = CultureData.GetCultureDataForRegion(name, true);
+            if (_cultureData == null)
+                throw new ArgumentException(
+                    String.Format(
+                        CultureInfo.CurrentCulture,
+                        SR.Argument_InvalidCultureName, name), nameof(name));
+
+
+            // Not supposed to be neutral
+            if (_cultureData.IsNeutralCulture)
+                throw new ArgumentException(SR.Format(SR.Argument_InvalidNeutralRegionName, name), nameof(name));
+
+            SetName(name);
+        }
+
+        public RegionInfo(int culture)
+        {
+            if (culture == CultureInfo.LOCALE_INVARIANT) //The InvariantCulture has no matching region
+            { 
+                throw new ArgumentException(SR.Argument_NoRegionInvariantCulture);
+            }
+
+            if (culture == CultureInfo.LOCALE_NEUTRAL)
+            {
+                // Not supposed to be neutral
+                throw new ArgumentException(SR.Format(SR.Argument_CultureIsNeutral, culture), nameof(culture));
+            }
+
+            if (culture == CultureInfo.LOCALE_CUSTOM_DEFAULT)
+            {
+                // Not supposed to be neutral
+                throw new ArgumentException(SR.Format(SR.Argument_CustomCultureCannotBePassedByNumber, culture), nameof(culture));
+            }
+            
+            _cultureData = CultureData.GetCultureData(culture, true);
+            _name = _cultureData.SREGIONNAME;
+
+            if (_cultureData.IsNeutralCulture)
+            {
+                // Not supposed to be neutral
+                throw new ArgumentException(SR.Format(SR.Argument_CultureIsNeutral, culture), nameof(culture));
+            }
+        }
+
+        internal RegionInfo(CultureData cultureData)
+        {
+            _cultureData = cultureData;
+            _name = _cultureData.SREGIONNAME;
+        }
+
+        private void SetName(string name)
+        {
+            // Use the name of the region we found
+            _name = _cultureData.SREGIONNAME;
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetCurrentRegion
+        //
+        //  This instance provides methods based on the current user settings.
+        //  These settings are volatile and may change over the lifetime of the
+        //  thread.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public static RegionInfo CurrentRegion
+        {
+            get
+            {
+                RegionInfo temp = s_currentRegionInfo;
+                if (temp == null)
+                {
+                    temp = new RegionInfo(CultureInfo.CurrentCulture._cultureData);
+
+                    // Need full name for custom cultures
+                    temp._name = temp._cultureData.SREGIONNAME;
+                    s_currentRegionInfo = temp;
+                }
+                return temp;
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetName
+        //
+        //  Returns the name of the region (ie: en-US)
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String Name
+        {
+            get
+            {
+                Debug.Assert(_name != null, "Expected RegionInfo._name to be populated already");
+                return (_name);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetEnglishName
+        //
+        //  Returns the name of the region in English. (ie: United States)
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String EnglishName
+        {
+            get
+            {
+                return (_cultureData.SENGCOUNTRY);
+            }
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetDisplayName
+        //
+        //  Returns the display name (localized) of the region. (ie: United States
+        //  if the current UI language is en-US)
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String DisplayName
+        {
+            get
+            {
+                return (_cultureData.SLOCALIZEDCOUNTRY);
+            }
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetNativeName
+        //
+        //  Returns the native name of the region. (ie: Deutschland)
+        //  WARNING: You need a full locale name for this to make sense.        
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String NativeName
+        {
+            get
+            {
+                return (_cultureData.SNATIVECOUNTRY);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  TwoLetterISORegionName
+        //
+        //  Returns the two letter ISO region name (ie: US)
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String TwoLetterISORegionName
+        {
+            get
+            {
+                return (_cultureData.SISO3166CTRYNAME);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  ThreeLetterISORegionName
+        //
+        //  Returns the three letter ISO region name (ie: USA)
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String ThreeLetterISORegionName
+        {
+            get
+            {
+                return (_cultureData.SISO3166CTRYNAME2);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  ThreeLetterWindowsRegionName
+        //
+        //  Returns the three letter windows region name (ie: USA)
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String ThreeLetterWindowsRegionName
+        {
+            get
+            {
+                // ThreeLetterWindowsRegionName is really same as ThreeLetterISORegionName 
+                return ThreeLetterISORegionName;
+            }
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  IsMetric
+        //
+        //  Returns true if this region uses the metric measurement system
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual bool IsMetric
+        {
+            get
+            {
+                int value = _cultureData.IMEASURE;
+                return (value == 0);
+            }
+        }
+
+        public virtual int GeoId 
+        {
+            get
+            {
+                return (_cultureData.IGEOID);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  CurrencyEnglishName
+        //
+        //  English name for this region's currency, ie: Swiss Franc
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual string CurrencyEnglishName
+        {
+            get
+            {
+                return (_cultureData.SENGLISHCURRENCY);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  CurrencyNativeName
+        //
+        //  Native name for this region's currency, ie: Schweizer Franken
+        //  WARNING: You need a full locale name for this to make sense.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual string CurrencyNativeName
+        {
+            get
+            {
+                return (_cultureData.SNATIVECURRENCY);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  CurrencySymbol
+        //
+        //  Currency Symbol for this locale, ie: Fr. or $
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String CurrencySymbol
+        {
+            get
+            {
+                return (_cultureData.SCURRENCY);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  ISOCurrencySymbol
+        //
+        //  ISO Currency Symbol for this locale, ie: CHF
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String ISOCurrencySymbol
+        {
+            get
+            {
+                return (_cultureData.SINTLSYMBOL);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  Equals
+        //
+        //  Implements Object.Equals().  Returns a boolean indicating whether
+        //  or not object refers to the same RegionInfo as the current instance.
+        //
+        //  RegionInfos are considered equal if and only if they have the same name
+        //  (ie: en-US)
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public override bool Equals(Object value)
+        {
+            RegionInfo that = value as RegionInfo;
+            if (that != null)
+            {
+                return this.Name.Equals(that.Name);
+            }
+
+            return (false);
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetHashCode
+        //
+        //  Implements Object.GetHashCode().  Returns the hash code for the
+        //  CultureInfo.  The hash code is guaranteed to be the same for RegionInfo
+        //  A and B where A.Equals(B) is true.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public override int GetHashCode()
+        {
+            return (this.Name.GetHashCode());
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  ToString
+        //
+        //  Implements Object.ToString().  Returns the name of the Region, ie: es-US
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public override String ToString()
+        {
+            return (Name);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/SortKey.cs b/src/System.Private.CoreLib/shared/System/Globalization/SortKey.cs
new file mode 100644
index 0000000000..647db75b63
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/SortKey.cs
@@ -0,0 +1,175 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////
+//
+//
+//  Purpose:  This class implements a set of methods for retrieving
+//            sort key information.
+//
+//
+////////////////////////////////////////////////////////////////////////////
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    public partial class SortKey
+    {
+        //--------------------------------------------------------------------//
+        //                        Internal Information                        //
+        //--------------------------------------------------------------------//
+
+        internal string _localeName;       // locale identifier
+
+        internal CompareOptions _options;  // options
+        internal string _string;         // original string
+        internal byte[] _keyData;        // sortkey data
+
+        //
+        // The following constructor is designed to be called from CompareInfo to get the 
+        // the sort key of specific string for synthetic culture
+        //
+        internal SortKey(String localeName, String str, CompareOptions options, byte[] keyData)
+        {
+            _keyData = keyData;
+            _localeName = localeName;
+            _options = options;
+            _string = str;
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetOriginalString
+        //
+        //  Returns the original string used to create the current instance
+        //  of SortKey.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String OriginalString
+        {
+            get
+            {
+                return (_string);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetKeyData
+        //
+        //  Returns a byte array representing the current instance of the
+        //  sort key.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual byte[] KeyData
+        {
+            get
+            {
+                return (byte[])(_keyData.Clone());
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  Compare
+        //
+        //  Compares the two sort keys.  Returns 0 if the two sort keys are
+        //  equal, a number less than 0 if sortkey1 is less than sortkey2,
+        //  and a number greater than 0 if sortkey1 is greater than sortkey2.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public static int Compare(SortKey sortkey1, SortKey sortkey2)
+        {
+            if (sortkey1 == null || sortkey2 == null)
+            {
+                throw new ArgumentNullException((sortkey1 == null ? nameof(sortkey1) : nameof(sortkey2)));
+            }
+
+            byte[] key1Data = sortkey1._keyData;
+            byte[] key2Data = sortkey2._keyData;
+
+            Debug.Assert(key1Data != null, "key1Data != null");
+            Debug.Assert(key2Data != null, "key2Data != null");
+
+            if (key1Data.Length == 0)
+            {
+                if (key2Data.Length == 0)
+                {
+                    return (0);
+                }
+                return (-1);
+            }
+            if (key2Data.Length == 0)
+            {
+                return (1);
+            }
+
+            int compLen = (key1Data.Length < key2Data.Length) ? key1Data.Length : key2Data.Length;
+
+            for (int i = 0; i < compLen; i++)
+            {
+                if (key1Data[i] > key2Data[i])
+                {
+                    return (1);
+                }
+                if (key1Data[i] < key2Data[i])
+                {
+                    return (-1);
+                }
+            }
+
+            return 0;
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  Equals
+        //
+        //  Implements Object.Equals().  Returns a boolean indicating whether
+        //  or not object refers to the same SortKey as the current instance.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public override bool Equals(Object value)
+        {
+            SortKey that = value as SortKey;
+
+            if (that != null)
+            {
+                return Compare(this, that) == 0;
+            }
+
+            return (false);
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetHashCode
+        //
+        //  Implements Object.GetHashCode().  Returns the hash code for the
+        //  SortKey.  The hash code is guaranteed to be the same for
+        //  SortKey A and B where A.Equals(B) is true.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public override int GetHashCode()
+        {
+            return (CompareInfo.GetCompareInfo(_localeName).GetHashCodeOfString(_string, _options));
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  ToString
+        //
+        //  Implements Object.ToString().  Returns a string describing the
+        //  SortKey.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public override String ToString()
+        {
+            return ("SortKey - " + _localeName + ", " + _options + ", " + _string);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/SortVersion.cs b/src/System.Private.CoreLib/shared/System/Globalization/SortVersion.cs
new file mode 100644
index 0000000000..46e9a833ec
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/SortVersion.cs
@@ -0,0 +1,99 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Globalization
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class SortVersion : IEquatable<SortVersion>
+    {
+        private int m_NlsVersion; // Do not rename (binary serialization)
+        private Guid m_SortId; // Do not rename (binary serialization)
+
+        public int FullVersion
+        {
+            get
+            {
+                return m_NlsVersion;
+            }
+        }
+
+        public Guid SortId
+        {
+            get
+            {
+                return m_SortId;
+            }
+        }
+
+        public SortVersion(int fullVersion, Guid sortId)
+        {
+            m_SortId = sortId;
+            m_NlsVersion = fullVersion;
+        }
+
+        internal SortVersion(int nlsVersion, int effectiveId, Guid customVersion)
+        {
+            m_NlsVersion = nlsVersion;
+
+            if (customVersion == Guid.Empty)
+            {
+                byte b1 = (byte)(effectiveId >> 24);
+                byte b2 = (byte)((effectiveId & 0x00FF0000) >> 16);
+                byte b3 = (byte)((effectiveId & 0x0000FF00) >> 8);
+                byte b4 = (byte)(effectiveId & 0xFF);
+                customVersion = new Guid(0, 0, 0, 0, 0, 0, 0, b1, b2, b3, b4);
+            }
+
+            m_SortId = customVersion;
+        }
+
+        public override bool Equals(object obj)
+        {
+            SortVersion n = obj as SortVersion;
+            if (n != null)
+            {
+                return this.Equals(n);
+            }
+
+            return false;
+        }
+
+        public bool Equals(SortVersion other)
+        {
+            if (other == null)
+            {
+                return false;
+            }
+
+            return m_NlsVersion == other.m_NlsVersion && m_SortId == other.m_SortId;
+        }
+
+        public override int GetHashCode()
+        {
+            return m_NlsVersion * 7 | m_SortId.GetHashCode();
+        }
+
+        public static bool operator ==(SortVersion left, SortVersion right)
+        {
+            if (((object)left) != null)
+            {
+                return left.Equals(right);
+            }
+
+            if (((object)right) != null)
+            {
+                return right.Equals(left);
+            }
+
+            // Both null.
+            return true;
+        }
+
+        public static bool operator !=(SortVersion left, SortVersion right)
+        {
+            return !(left == right);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/StringInfo.cs b/src/System.Private.CoreLib/shared/System/Globalization/StringInfo.cs
new file mode 100644
index 0000000000..aa62b2c474
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/StringInfo.cs
@@ -0,0 +1,350 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////
+//
+//
+//  Purpose:  This class defines behaviors specific to a writing system.
+//            A writing system is the collection of scripts and
+//            orthographic rules required to represent a language as text.
+//
+//
+////////////////////////////////////////////////////////////////////////////
+
+using System;
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    public class StringInfo
+    {
+        private string _str;
+
+        private int[] _indexes;
+
+        // Legacy constructor
+        public StringInfo() : this("") { }
+
+        // Primary, useful constructor
+        public StringInfo(string value)
+        {
+            this.String = value;
+        }
+
+        public override bool Equals(Object value)
+        {
+            StringInfo that = value as StringInfo;
+            if (that != null)
+            {
+                return (_str.Equals(that._str));
+            }
+            return (false);
+        }
+
+        public override int GetHashCode()
+        {
+            return _str.GetHashCode();
+        }
+
+
+        // Our zero-based array of index values into the string. Initialize if 
+        // our private array is not yet, in fact, initialized.
+        private int[] Indexes
+        {
+            get
+            {
+                if ((null == _indexes) && (0 < this.String.Length))
+                {
+                    _indexes = StringInfo.ParseCombiningCharacters(this.String);
+                }
+
+                return (_indexes);
+            }
+        }
+
+        public string String
+        {
+            get
+            {
+                return (_str);
+            }
+            set
+            {
+                if (null == value)
+                {
+                    throw new ArgumentNullException(nameof(String),
+                        SR.ArgumentNull_String);
+                }
+
+                _str = value;
+                _indexes = null;
+            }
+        }
+
+        public int LengthInTextElements
+        {
+            get
+            {
+                if (null == this.Indexes)
+                {
+                    // Indexes not initialized, so assume length zero
+                    return (0);
+                }
+
+                return (this.Indexes.Length);
+            }
+        }
+
+        public string SubstringByTextElements(int startingTextElement)
+        {
+            // If the string is empty, no sense going further. 
+            if (null == this.Indexes)
+            {
+                // Just decide which error to give depending on the param they gave us....
+                if (startingTextElement < 0)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(startingTextElement), SR.ArgumentOutOfRange_NeedPosNum);
+                }
+                else
+                {
+                    throw new ArgumentOutOfRangeException(nameof(startingTextElement), SR.Arg_ArgumentOutOfRangeException);
+                }
+            }
+            return (SubstringByTextElements(startingTextElement, Indexes.Length - startingTextElement));
+        }
+
+        public string SubstringByTextElements(int startingTextElement, int lengthInTextElements)
+        {
+            if (startingTextElement < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startingTextElement), SR.ArgumentOutOfRange_NeedPosNum);
+            }
+
+            if (this.String.Length == 0 || startingTextElement >= Indexes.Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startingTextElement), SR.Arg_ArgumentOutOfRangeException);
+            }
+
+            if (lengthInTextElements < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(lengthInTextElements), SR.ArgumentOutOfRange_NeedPosNum);
+            }
+
+            if (startingTextElement > Indexes.Length - lengthInTextElements)
+            {
+                throw new ArgumentOutOfRangeException(nameof(lengthInTextElements), SR.Arg_ArgumentOutOfRangeException);
+            }
+
+            int start = Indexes[startingTextElement];
+
+            if (startingTextElement + lengthInTextElements == Indexes.Length)
+            {
+                // We are at the last text element in the string and because of that
+                // must handle the call differently.
+                return (this.String.Substring(start));
+            }
+            else
+            {
+                return (this.String.Substring(start, (Indexes[lengthInTextElements + startingTextElement] - start)));
+            }
+        }
+
+        public static string GetNextTextElement(string str)
+        {
+            return (GetNextTextElement(str, 0));
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        // Get the code point count of the current text element.
+        //
+        // A combining class is defined as:
+        //      A character/surrogate that has the following Unicode category:
+        //      * NonSpacingMark (e.g. U+0300 COMBINING GRAVE ACCENT)
+        //      * SpacingCombiningMark (e.g. U+ 0903 DEVANGARI SIGN VISARGA)
+        //      * EnclosingMark (e.g. U+20DD COMBINING ENCLOSING CIRCLE)
+        //
+        // In the context of GetNextTextElement() and ParseCombiningCharacters(), a text element is defined as:
+        //
+        //  1. If a character/surrogate is in the following category, it is a text element.  
+        //     It can NOT further combine with characters in the combinging class to form a text element.
+        //      * one of the Unicode category in the combinging class
+        //      * UnicodeCategory.Format
+        //      * UnicodeCateogry.Control
+        //      * UnicodeCategory.OtherNotAssigned
+        //  2. Otherwise, the character/surrogate can be combined with characters in the combinging class to form a text element.
+        //
+        //  Return:
+        //      The length of the current text element
+        //
+        //  Parameters:
+        //      String str
+        //      index   The starting index
+        //      len     The total length of str (to define the upper boundary)
+        //      ucCurrent   The Unicode category pointed by Index.  It will be updated to the uc of next character if this is not the last text element.
+        //      currentCharCount    The char count of an abstract char pointed by Index.  It will be updated to the char count of next abstract character if this is not the last text element.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        internal static int GetCurrentTextElementLen(string str, int index, int len, ref UnicodeCategory ucCurrent, ref int currentCharCount)
+        {
+            Debug.Assert(index >= 0 && len >= 0, "StringInfo.GetCurrentTextElementLen() : index = " + index + ", len = " + len);
+            Debug.Assert(index < len, "StringInfo.GetCurrentTextElementLen() : index = " + index + ", len = " + len);
+            if (index + currentCharCount == len)
+            {
+                // This is the last character/surrogate in the string.
+                return (currentCharCount);
+            }
+
+            // Call an internal GetUnicodeCategory, which will tell us both the unicode category, and also tell us if it is a surrogate pair or not.
+            int nextCharCount;
+            UnicodeCategory ucNext = CharUnicodeInfo.InternalGetUnicodeCategory(str, index + currentCharCount, out nextCharCount);
+            if (CharUnicodeInfo.IsCombiningCategory(ucNext))
+            {
+                // The next element is a combining class.
+                // Check if the current text element to see if it is a valid base category (i.e. it should not be a combining category,
+                // not a format character, and not a control character).
+
+                if (CharUnicodeInfo.IsCombiningCategory(ucCurrent)
+                    || (ucCurrent == UnicodeCategory.Format)
+                    || (ucCurrent == UnicodeCategory.Control)
+                    || (ucCurrent == UnicodeCategory.OtherNotAssigned)
+                    || (ucCurrent == UnicodeCategory.Surrogate))    // An unpair high surrogate or low surrogate
+                {
+                    // Will fall thru and return the currentCharCount
+                }
+                else
+                {
+                    int startIndex = index; // Remember the current index.
+
+                    // We have a valid base characters, and we have a character (or surrogate) that is combining.
+                    // Check if there are more combining characters to follow.
+                    // Check if the next character is a nonspacing character.
+                    index += currentCharCount + nextCharCount;
+
+                    while (index < len)
+                    {
+                        ucNext = CharUnicodeInfo.InternalGetUnicodeCategory(str, index, out nextCharCount);
+                        if (!CharUnicodeInfo.IsCombiningCategory(ucNext))
+                        {
+                            ucCurrent = ucNext;
+                            currentCharCount = nextCharCount;
+                            break;
+                        }
+                        index += nextCharCount;
+                    }
+                    return (index - startIndex);
+                }
+            }
+            // The return value will be the currentCharCount.
+            int ret = currentCharCount;
+            ucCurrent = ucNext;
+            // Update currentCharCount.
+            currentCharCount = nextCharCount;
+            return (ret);
+        }
+
+        // Returns the str containing the next text element in str starting at 
+        // index index.  If index is not supplied, then it will start at the beginning 
+        // of str.  It recognizes a base character plus one or more combining 
+        // characters or a properly formed surrogate pair as a text element.  See also 
+        // the ParseCombiningCharacters() and the ParseSurrogates() methods.
+        public static string GetNextTextElement(string str, int index)
+        {
+            //
+            // Validate parameters.
+            //
+            if (str == null)
+            {
+                throw new ArgumentNullException(nameof(str));
+            }
+
+            int len = str.Length;
+            if (index < 0 || index >= len)
+            {
+                if (index == len)
+                {
+                    return (String.Empty);
+                }
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+            }
+
+            int charLen;
+            UnicodeCategory uc = CharUnicodeInfo.InternalGetUnicodeCategory(str, index, out charLen);
+            return (str.Substring(index, GetCurrentTextElementLen(str, index, len, ref uc, ref charLen)));
+        }
+
+        public static TextElementEnumerator GetTextElementEnumerator(string str)
+        {
+            return (GetTextElementEnumerator(str, 0));
+        }
+
+        public static TextElementEnumerator GetTextElementEnumerator(string str, int index)
+        {
+            //
+            // Validate parameters.
+            //
+            if (str == null)
+            {
+                throw new ArgumentNullException(nameof(str));
+            }
+
+            int len = str.Length;
+            if (index < 0 || (index > len))
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+            }
+
+            return (new TextElementEnumerator(str, index, len));
+        }
+
+        /*
+         * Returns the indices of each base character or properly formed surrogate pair 
+         * within the str.  It recognizes a base character plus one or more combining 
+         * characters or a properly formed surrogate pair as a text element and returns 
+         * the index of the base character or high surrogate.  Each index is the 
+         * beginning of a text element within a str.  The length of each element is 
+         * easily computed as the difference between successive indices.  The length of 
+         * the array will always be less than or equal to the length of the str.  For 
+         * example, given the str \u4f00\u302a\ud800\udc00\u4f01, this method would 
+         * return the indices: 0, 2, 4.
+         */
+
+        public static int[] ParseCombiningCharacters(string str)
+        {
+            if (str == null)
+            {
+                throw new ArgumentNullException(nameof(str));
+            }
+
+            int len = str.Length;
+            int[] result = new int[len];
+            if (len == 0)
+            {
+                return (result);
+            }
+
+            int resultCount = 0;
+
+            int i = 0;
+            int currentCharLen;
+            UnicodeCategory currentCategory = CharUnicodeInfo.InternalGetUnicodeCategory(str, 0, out currentCharLen);
+
+            while (i < len)
+            {
+                result[resultCount++] = i;
+                i += GetCurrentTextElementLen(str, i, len, ref currentCategory, ref currentCharLen);
+            }
+
+            if (resultCount < len)
+            {
+                int[] returnArray = new int[resultCount];
+                Array.Copy(result, returnArray, resultCount);
+                return (returnArray);
+            }
+            return (result);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/TaiwanCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/TaiwanCalendar.cs
new file mode 100644
index 0000000000..c5161138de
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/TaiwanCalendar.cs
@@ -0,0 +1,281 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics.CodeAnalysis;
+
+namespace System.Globalization
+{
+    /*=================================TaiwanCalendar==========================
+    **
+    ** Taiwan calendar is based on the Gregorian calendar.  And the year is an offset to Gregorian calendar.
+    ** That is,
+    **      Taiwan year = Gregorian year - 1911.  So 1912/01/01 A.D. is Taiwan 1/01/01
+    **
+    **  Calendar support range:
+    **      Calendar    Minimum     Maximum
+    **      ==========  ==========  ==========
+    **      Gregorian   1912/01/01  9999/12/31
+    **      Taiwan      01/01/01    8088/12/31
+    ============================================================================*/
+
+    public class TaiwanCalendar : Calendar
+    {
+        //
+        // The era value for the current era.
+        //
+
+        // Since
+        //    Gregorian Year = Era Year + yearOffset
+        // When Gregorian Year 1912 is year 1, so that
+        //    1912 = 1 + yearOffset
+        //  So yearOffset = 1911
+        //m_EraInfo[0] = new EraInfo(1, new DateTime(1912, 1, 1).Ticks, 1911, 1, GregorianCalendar.MaxYear - 1911);
+
+        // Initialize our era info.
+        internal static EraInfo[] taiwanEraInfo = new EraInfo[] {
+            new EraInfo( 1, 1912, 1, 1, 1911, 1, GregorianCalendar.MaxYear - 1911)    // era #, start year/month/day, yearOffset, minEraYear 
+        };
+
+        internal static volatile Calendar s_defaultInstance;
+
+        internal GregorianCalendarHelper helper;
+
+        /*=================================GetDefaultInstance==========================
+        **Action: Internal method to provide a default intance of TaiwanCalendar.  Used by NLS+ implementation
+        **       and other calendars.
+        **Returns:
+        **Arguments:
+        **Exceptions:
+        ============================================================================*/
+
+        internal static Calendar GetDefaultInstance()
+        {
+            if (s_defaultInstance == null)
+            {
+                s_defaultInstance = new TaiwanCalendar();
+            }
+            return (s_defaultInstance);
+        }
+
+        internal static readonly DateTime calendarMinValue = new DateTime(1912, 1, 1);
+
+
+        public override DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (calendarMinValue);
+            }
+        }
+
+        public override DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (DateTime.MaxValue);
+            }
+        }
+
+        public override CalendarAlgorithmType AlgorithmType
+        {
+            get
+            {
+                return CalendarAlgorithmType.SolarCalendar;
+            }
+        }
+
+        // Return the type of the Taiwan calendar.
+        //
+
+        public TaiwanCalendar()
+        {
+            try
+            {
+                new CultureInfo("zh-TW");
+            }
+            catch (ArgumentException e)
+            {
+                throw new TypeInitializationException(this.GetType().ToString(), e);
+            }
+            helper = new GregorianCalendarHelper(this, taiwanEraInfo);
+        }
+
+        internal override CalendarId ID
+        {
+            get
+            {
+                return CalendarId.TAIWAN;
+            }
+        }
+
+
+        public override DateTime AddMonths(DateTime time, int months)
+        {
+            return (helper.AddMonths(time, months));
+        }
+
+
+        public override DateTime AddYears(DateTime time, int years)
+        {
+            return (helper.AddYears(time, years));
+        }
+
+
+        public override int GetDaysInMonth(int year, int month, int era)
+        {
+            return (helper.GetDaysInMonth(year, month, era));
+        }
+
+
+        public override int GetDaysInYear(int year, int era)
+        {
+            return (helper.GetDaysInYear(year, era));
+        }
+
+
+        public override int GetDayOfMonth(DateTime time)
+        {
+            return (helper.GetDayOfMonth(time));
+        }
+
+
+        public override DayOfWeek GetDayOfWeek(DateTime time)
+        {
+            return (helper.GetDayOfWeek(time));
+        }
+
+
+        public override int GetDayOfYear(DateTime time)
+        {
+            return (helper.GetDayOfYear(time));
+        }
+
+
+        public override int GetMonthsInYear(int year, int era)
+        {
+            return (helper.GetMonthsInYear(year, era));
+        }
+
+
+        public override int GetWeekOfYear(DateTime time, CalendarWeekRule rule, DayOfWeek firstDayOfWeek)
+        {
+            return (helper.GetWeekOfYear(time, rule, firstDayOfWeek));
+        }
+
+
+        public override int GetEra(DateTime time)
+        {
+            return (helper.GetEra(time));
+        }
+
+        public override int GetMonth(DateTime time)
+        {
+            return (helper.GetMonth(time));
+        }
+
+
+        public override int GetYear(DateTime time)
+        {
+            return (helper.GetYear(time));
+        }
+
+
+        public override bool IsLeapDay(int year, int month, int day, int era)
+        {
+            return (helper.IsLeapDay(year, month, day, era));
+        }
+
+
+        public override bool IsLeapYear(int year, int era)
+        {
+            return (helper.IsLeapYear(year, era));
+        }
+
+        // Returns  the leap month in a calendar year of the specified era. This method returns 0
+        // if this calendar does not have leap month, or this year is not a leap year.
+        //
+
+        public override int GetLeapMonth(int year, int era)
+        {
+            return (helper.GetLeapMonth(year, era));
+        }
+
+
+        public override bool IsLeapMonth(int year, int month, int era)
+        {
+            return (helper.IsLeapMonth(year, month, era));
+        }
+
+
+        public override DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era)
+        {
+            return (helper.ToDateTime(year, month, day, hour, minute, second, millisecond, era));
+        }
+
+
+        public override int[] Eras
+        {
+            get
+            {
+                return (helper.Eras);
+            }
+        }
+
+        private const int DEFAULT_TWO_DIGIT_YEAR_MAX = 99;
+
+        public override int TwoDigitYearMax
+        {
+            get
+            {
+                if (twoDigitYearMax == -1)
+                {
+                    twoDigitYearMax = GetSystemTwoDigitYearSetting(ID, DEFAULT_TWO_DIGIT_YEAR_MAX);
+                }
+                return (twoDigitYearMax);
+            }
+
+            set
+            {
+                VerifyWritable();
+                if (value < 99 || value > helper.MaxYear)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                "year",
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    99,
+                                    helper.MaxYear));
+                }
+                twoDigitYearMax = value;
+            }
+        }
+
+        // For Taiwan calendar, four digit year is not used.
+        // Therefore, for any two digit number, we just return the original number.
+
+        public override int ToFourDigitYear(int year)
+        {
+            if (year <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year),
+                    SR.ArgumentOutOfRange_NeedPosNum);
+            }
+
+            if (year > helper.MaxYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                1,
+                                helper.MaxYear));
+            }
+            return (year);
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/TaiwanLunisolarCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/TaiwanLunisolarCalendar.cs
new file mode 100644
index 0000000000..60e84f7f33
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/TaiwanLunisolarCalendar.cs
@@ -0,0 +1,322 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Globalization
+{
+    /*
+    **  Calendar support range:
+    **      Calendar            Minimum     Maximum
+    **      ==========          ==========  ==========
+    **      Gregorian           1912/02/18  2051/02/10
+    **      TaiwanLunisolar     1912/01/01  2050/13/29
+    */
+
+    public class TaiwanLunisolarCalendar : EastAsianLunisolarCalendar
+    {
+        // Since
+        //    Gregorian Year = Era Year + yearOffset
+        // When Gregorian Year 1912 is year 1, so that
+        //    1912 = 1 + yearOffset
+        //  So yearOffset = 1911
+        //m_EraInfo[0] = new EraInfo(1, new DateTime(1912, 1, 1).Ticks, 1911, 1, GregorianCalendar.MaxYear - 1911);
+
+        // Initialize our era info.
+        internal static EraInfo[] taiwanLunisolarEraInfo = new EraInfo[] {
+            new EraInfo( 1, 1912, 1, 1, 1911, 1, GregorianCalendar.MaxYear - 1911)    // era #, start year/month/day, yearOffset, minEraYear 
+        };
+
+        internal GregorianCalendarHelper helper;
+
+        internal const int MIN_LUNISOLAR_YEAR = 1912;
+        internal const int MAX_LUNISOLAR_YEAR = 2050;
+
+        internal const int MIN_GREGORIAN_YEAR = 1912;
+        internal const int MIN_GREGORIAN_MONTH = 2;
+        internal const int MIN_GREGORIAN_DAY = 18;
+
+        internal const int MAX_GREGORIAN_YEAR = 2051;
+        internal const int MAX_GREGORIAN_MONTH = 2;
+        internal const int MAX_GREGORIAN_DAY = 10;
+
+        internal static DateTime minDate = new DateTime(MIN_GREGORIAN_YEAR, MIN_GREGORIAN_MONTH, MIN_GREGORIAN_DAY);
+        internal static DateTime maxDate = new DateTime((new DateTime(MAX_GREGORIAN_YEAR, MAX_GREGORIAN_MONTH, MAX_GREGORIAN_DAY, 23, 59, 59, 999)).Ticks + 9999);
+
+        public override DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (minDate);
+            }
+        }
+
+
+
+        public override DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (maxDate);
+            }
+        }
+
+        protected override int DaysInYearBeforeMinSupportedYear
+        {
+            get
+            {
+                // 1911 from ChineseLunisolarCalendar
+                return 384;
+            }
+        }
+
+        private static readonly int[,] s_yinfo =
+        {
+            /*Y            LM        Lmon    Lday        DaysPerMonth    D1    D2    D3    D4    D5    D6    D7    D8    D9    D10    D11    D12    D13    #Days
+            1912    */
+          {    0    ,    2    ,    18    ,    42192    },/*    30    29    30    29    29    30    29    29    30    30    29    30    0    354
+1913    */{    0    ,    2    ,    6    ,    53840    },/*    30    30    29    30    29    29    30    29    29    30    29    30    0    354
+1914    */{    5    ,    1    ,    26    ,    54568    },/*    30    30    29    30    29    30    29    30    29    29    30    29    30    384
+1915    */{    0    ,    2    ,    14    ,    46400    },/*    30    29    30    30    29    30    29    30    29    30    29    29    0    354
+1916    */{    0    ,    2    ,    3    ,    54944    },/*    30    30    29    30    29    30    30    29    30    29    30    29    0    355
+1917    */{    2    ,    1    ,    23    ,    38608    },/*    30    29    29    30    29    30    30    29    30    30    29    30    29    384
+1918    */{    0    ,    2    ,    11    ,    38320    },/*    30    29    29    30    29    30    29    30    30    29    30    30    0    355
+1919    */{    7    ,    2    ,    1    ,    18872    },/*    29    30    29    29    30    29    29    30    30    29    30    30    30    384
+1920    */{    0    ,    2    ,    20    ,    18800    },/*    29    30    29    29    30    29    29    30    29    30    30    30    0    354
+1921    */{    0    ,    2    ,    8    ,    42160    },/*    30    29    30    29    29    30    29    29    30    29    30    30    0    354
+1922    */{    5    ,    1    ,    28    ,    45656    },/*    30    29    30    30    29    29    30    29    29    30    29    30    30    384
+1923    */{    0    ,    2    ,    16    ,    27216    },/*    29    30    30    29    30    29    30    29    29    30    29    30    0    354
+1924    */{    0    ,    2    ,    5    ,    27968    },/*    29    30    30    29    30    30    29    30    29    30    29    29    0    354
+1925    */{    4    ,    1    ,    24    ,    44456    },/*    30    29    30    29    30    30    29    30    30    29    30    29    30    385
+1926    */{    0    ,    2    ,    13    ,    11104    },/*    29    29    30    29    30    29    30    30    29    30    30    29    0    354
+1927    */{    0    ,    2    ,    2    ,    38256    },/*    30    29    29    30    29    30    29    30    29    30    30    30    0    355
+1928    */{    2    ,    1    ,    23    ,    18808    },/*    29    30    29    29    30    29    29    30    29    30    30    30    30    384
+1929    */{    0    ,    2    ,    10    ,    18800    },/*    29    30    29    29    30    29    29    30    29    30    30    30    0    354
+1930    */{    6    ,    1    ,    30    ,    25776    },/*    29    30    30    29    29    30    29    29    30    29    30    30    29    383
+1931    */{    0    ,    2    ,    17    ,    54432    },/*    30    30    29    30    29    30    29    29    30    29    30    29    0    354
+1932    */{    0    ,    2    ,    6    ,    59984    },/*    30    30    30    29    30    29    30    29    29    30    29    30    0    355
+1933    */{    5    ,    1    ,    26    ,    27976    },/*    29    30    30    29    30    30    29    30    29    30    29    29    30    384
+1934    */{    0    ,    2    ,    14    ,    23248    },/*    29    30    29    30    30    29    30    29    30    30    29    30    0    355
+1935    */{    0    ,    2    ,    4    ,    11104    },/*    29    29    30    29    30    29    30    30    29    30    30    29    0    354
+1936    */{    3    ,    1    ,    24    ,    37744    },/*    30    29    29    30    29    29    30    30    29    30    30    30    29    384
+1937    */{    0    ,    2    ,    11    ,    37600    },/*    30    29    29    30    29    29    30    29    30    30    30    29    0    354
+1938    */{    7    ,    1    ,    31    ,    51560    },/*    30    30    29    29    30    29    29    30    29    30    30    29    30    384
+1939    */{    0    ,    2    ,    19    ,    51536    },/*    30    30    29    29    30    29    29    30    29    30    29    30    0    354
+1940    */{    0    ,    2    ,    8    ,    54432    },/*    30    30    29    30    29    30    29    29    30    29    30    29    0    354
+1941    */{    6    ,    1    ,    27    ,    55888    },/*    30    30    29    30    30    29    30    29    29    30    29    30    29    384
+1942    */{    0    ,    2    ,    15    ,    46416    },/*    30    29    30    30    29    30    29    30    29    30    29    30    0    355
+1943    */{    0    ,    2    ,    5    ,    22176    },/*    29    30    29    30    29    30    30    29    30    29    30    29    0    354
+1944    */{    4    ,    1    ,    25    ,    43736    },/*    30    29    30    29    30    29    30    29    30    30    29    30    30    385
+1945    */{    0    ,    2    ,    13    ,    9680    },/*    29    29    30    29    29    30    29    30    30    30    29    30    0    354
+1946    */{    0    ,    2    ,    2    ,    37584    },/*    30    29    29    30    29    29    30    29    30    30    29    30    0    354
+1947    */{    2    ,    1    ,    22    ,    51544    },/*    30    30    29    29    30    29    29    30    29    30    29    30    30    384
+1948    */{    0    ,    2    ,    10    ,    43344    },/*    30    29    30    29    30    29    29    30    29    30    29    30    0    354
+1949    */{    7    ,    1    ,    29    ,    46248    },/*    30    29    30    30    29    30    29    29    30    29    30    29    30    384
+1950    */{    0    ,    2    ,    17    ,    27808    },/*    29    30    30    29    30    30    29    29    30    29    30    29    0    354
+1951    */{    0    ,    2    ,    6    ,    46416    },/*    30    29    30    30    29    30    29    30    29    30    29    30    0    355
+1952    */{    5    ,    1    ,    27    ,    21928    },/*    29    30    29    30    29    30    29    30    30    29    30    29    30    384
+1953    */{    0    ,    2    ,    14    ,    19872    },/*    29    30    29    29    30    30    29    30    30    29    30    29    0    354
+1954    */{    0    ,    2    ,    3    ,    42416    },/*    30    29    30    29    29    30    29    30    30    29    30    30    0    355
+1955    */{    3    ,    1    ,    24    ,    21176    },/*    29    30    29    30    29    29    30    29    30    29    30    30    30    384
+1956    */{    0    ,    2    ,    12    ,    21168    },/*    29    30    29    30    29    29    30    29    30    29    30    30    0    354
+1957    */{    8    ,    1    ,    31    ,    43344    },/*    30    29    30    29    30    29    29    30    29    30    29    30    29    383
+1958    */{    0    ,    2    ,    18    ,    59728    },/*    30    30    30    29    30    29    29    30    29    30    29    30    0    355
+1959    */{    0    ,    2    ,    8    ,    27296    },/*    29    30    30    29    30    29    30    29    30    29    30    29    0    354
+1960    */{    6    ,    1    ,    28    ,    44368    },/*    30    29    30    29    30    30    29    30    29    30    29    30    29    384
+1961    */{    0    ,    2    ,    15    ,    43856    },/*    30    29    30    29    30    29    30    30    29    30    29    30    0    355
+1962    */{    0    ,    2    ,    5    ,    19296    },/*    29    30    29    29    30    29    30    30    29    30    30    29    0    354
+1963    */{    4    ,    1    ,    25    ,    42352    },/*    30    29    30    29    29    30    29    30    29    30    30    30    29    384
+1964    */{    0    ,    2    ,    13    ,    42352    },/*    30    29    30    29    29    30    29    30    29    30    30    30    0    355
+1965    */{    0    ,    2    ,    2    ,    21088    },/*    29    30    29    30    29    29    30    29    29    30    30    29    0    353
+1966    */{    3    ,    1    ,    21    ,    59696    },/*    30    30    30    29    30    29    29    30    29    29    30    30    29    384
+1967    */{    0    ,    2    ,    9    ,    55632    },/*    30    30    29    30    30    29    29    30    29    30    29    30    0    355
+1968    */{    7    ,    1    ,    30    ,    23208    },/*    29    30    29    30    30    29    30    29    30    29    30    29    30    384
+1969    */{    0    ,    2    ,    17    ,    22176    },/*    29    30    29    30    29    30    30    29    30    29    30    29    0    354
+1970    */{    0    ,    2    ,    6    ,    38608    },/*    30    29    29    30    29    30    30    29    30    30    29    30    0    355
+1971    */{    5    ,    1    ,    27    ,    19176    },/*    29    30    29    29    30    29    30    29    30    30    30    29    30    384
+1972    */{    0    ,    2    ,    15    ,    19152    },/*    29    30    29    29    30    29    30    29    30    30    29    30    0    354
+1973    */{    0    ,    2    ,    3    ,    42192    },/*    30    29    30    29    29    30    29    29    30    30    29    30    0    354
+1974    */{    4    ,    1    ,    23    ,    53864    },/*    30    30    29    30    29    29    30    29    29    30    30    29    30    384
+1975    */{    0    ,    2    ,    11    ,    53840    },/*    30    30    29    30    29    29    30    29    29    30    29    30    0    354
+1976    */{    8    ,    1    ,    31    ,    54568    },/*    30    30    29    30    29    30    29    30    29    29    30    29    30    384
+1977    */{    0    ,    2    ,    18    ,    46400    },/*    30    29    30    30    29    30    29    30    29    30    29    29    0    354
+1978    */{    0    ,    2    ,    7    ,    46752    },/*    30    29    30    30    29    30    30    29    30    29    30    29    0    355
+1979    */{    6    ,    1    ,    28    ,    38608    },/*    30    29    29    30    29    30    30    29    30    30    29    30    29    384
+1980    */{    0    ,    2    ,    16    ,    38320    },/*    30    29    29    30    29    30    29    30    30    29    30    30    0    355
+1981    */{    0    ,    2    ,    5    ,    18864    },/*    29    30    29    29    30    29    29    30    30    29    30    30    0    354
+1982    */{    4    ,    1    ,    25    ,    42168    },/*    30    29    30    29    29    30    29    29    30    29    30    30    30    384
+1983    */{    0    ,    2    ,    13    ,    42160    },/*    30    29    30    29    29    30    29    29    30    29    30    30    0    354
+1984    */{    10    ,    2    ,    2    ,    45656    },/*    30    29    30    30    29    29    30    29    29    30    29    30    30    384
+1985    */{    0    ,    2    ,    20    ,    27216    },/*    29    30    30    29    30    29    30    29    29    30    29    30    0    354
+1986    */{    0    ,    2    ,    9    ,    27968    },/*    29    30    30    29    30    30    29    30    29    30    29    29    0    354
+1987    */{    6    ,    1    ,    29    ,    44448    },/*    30    29    30    29    30    30    29    30    30    29    30    29    29    384
+1988    */{    0    ,    2    ,    17    ,    43872    },/*    30    29    30    29    30    29    30    30    29    30    30    29    0    355
+1989    */{    0    ,    2    ,    6    ,    38256    },/*    30    29    29    30    29    30    29    30    29    30    30    30    0    355
+1990    */{    5    ,    1    ,    27    ,    18808    },/*    29    30    29    29    30    29    29    30    29    30    30    30    30    384
+1991    */{    0    ,    2    ,    15    ,    18800    },/*    29    30    29    29    30    29    29    30    29    30    30    30    0    354
+1992    */{    0    ,    2    ,    4    ,    25776    },/*    29    30    30    29    29    30    29    29    30    29    30    30    0    354
+1993    */{    3    ,    1    ,    23    ,    27216    },/*    29    30    30    29    30    29    30    29    29    30    29    30    29    383
+1994    */{    0    ,    2    ,    10    ,    59984    },/*    30    30    30    29    30    29    30    29    29    30    29    30    0    355
+1995    */{    8    ,    1    ,    31    ,    27432    },/*    29    30    30    29    30    29    30    30    29    29    30    29    30    384
+1996    */{    0    ,    2    ,    19    ,    23232    },/*    29    30    29    30    30    29    30    29    30    30    29    29    0    354
+1997    */{    0    ,    2    ,    7    ,    43872    },/*    30    29    30    29    30    29    30    30    29    30    30    29    0    355
+1998    */{    5    ,    1    ,    28    ,    37736    },/*    30    29    29    30    29    29    30    30    29    30    30    29    30    384
+1999    */{    0    ,    2    ,    16    ,    37600    },/*    30    29    29    30    29    29    30    29    30    30    30    29    0    354
+2000    */{    0    ,    2    ,    5    ,    51552    },/*    30    30    29    29    30    29    29    30    29    30    30    29    0    354
+2001    */{    4    ,    1    ,    24    ,    54440    },/*    30    30    29    30    29    30    29    29    30    29    30    29    30    384
+2002    */{    0    ,    2    ,    12    ,    54432    },/*    30    30    29    30    29    30    29    29    30    29    30    29    0    354
+2003    */{    0    ,    2    ,    1    ,    55888    },/*    30    30    29    30    30    29    30    29    29    30    29    30    0    355
+2004    */{    2    ,    1    ,    22    ,    23208    },/*    29    30    29    30    30    29    30    29    30    29    30    29    30    384
+2005    */{    0    ,    2    ,    9    ,    22176    },/*    29    30    29    30    29    30    30    29    30    29    30    29    0    354
+2006    */{    7    ,    1    ,    29    ,    43736    },/*    30    29    30    29    30    29    30    29    30    30    29    30    30    385
+2007    */{    0    ,    2    ,    18    ,    9680    },/*    29    29    30    29    29    30    29    30    30    30    29    30    0    354
+2008    */{    0    ,    2    ,    7    ,    37584    },/*    30    29    29    30    29    29    30    29    30    30    29    30    0    354
+2009    */{    5    ,    1    ,    26    ,    51544    },/*    30    30    29    29    30    29    29    30    29    30    29    30    30    384
+2010    */{    0    ,    2    ,    14    ,    43344    },/*    30    29    30    29    30    29    29    30    29    30    29    30    0    354
+2011    */{    0    ,    2    ,    3    ,    46240    },/*    30    29    30    30    29    30    29    29    30    29    30    29    0    354
+2012    */{    4    ,    1    ,    23    ,    46416    },/*    30    29    30    30    29    30    29    30    29    30    29    30    29    384
+2013    */{    0    ,    2    ,    10    ,    44368    },/*    30    29    30    29    30    30    29    30    29    30    29    30    0    355
+2014    */{    9    ,    1    ,    31    ,    21928    },/*    29    30    29    30    29    30    29    30    30    29    30    29    30    384
+2015    */{    0    ,    2    ,    19    ,    19360    },/*    29    30    29    29    30    29    30    30    30    29    30    29    0    354
+2016    */{    0    ,    2    ,    8    ,    42416    },/*    30    29    30    29    29    30    29    30    30    29    30    30    0    355
+2017    */{    6    ,    1    ,    28    ,    21176    },/*    29    30    29    30    29    29    30    29    30    29    30    30    30    384
+2018    */{    0    ,    2    ,    16    ,    21168    },/*    29    30    29    30    29    29    30    29    30    29    30    30    0    354
+2019    */{    0    ,    2    ,    5    ,    43312    },/*    30    29    30    29    30    29    29    30    29    29    30    30    0    354
+2020    */{    4    ,    1    ,    25    ,    29864    },/*    29    30    30    30    29    30    29    29    30    29    30    29    30    384
+2021    */{    0    ,    2    ,    12    ,    27296    },/*    29    30    30    29    30    29    30    29    30    29    30    29    0    354
+2022    */{    0    ,    2    ,    1    ,    44368    },/*    30    29    30    29    30    30    29    30    29    30    29    30    0    355
+2023    */{    2    ,    1    ,    22    ,    19880    },/*    29    30    29    29    30    30    29    30    30    29    30    29    30    384
+2024    */{    0    ,    2    ,    10    ,    19296    },/*    29    30    29    29    30    29    30    30    29    30    30    29    0    354
+2025    */{    6    ,    1    ,    29    ,    42352    },/*    30    29    30    29    29    30    29    30    29    30    30    30    29    384
+2026    */{    0    ,    2    ,    17    ,    42208    },/*    30    29    30    29    29    30    29    29    30    30    30    29    0    354
+2027    */{    0    ,    2    ,    6    ,    53856    },/*    30    30    29    30    29    29    30    29    29    30    30    29    0    354
+2028    */{    5    ,    1    ,    26    ,    59696    },/*    30    30    30    29    30    29    29    30    29    29    30    30    29    384
+2029    */{    0    ,    2    ,    13    ,    54576    },/*    30    30    29    30    29    30    29    30    29    29    30    30    0    355
+2030    */{    0    ,    2    ,    3    ,    23200    },/*    29    30    29    30    30    29    30    29    30    29    30    29    0    354
+2031    */{    3    ,    1    ,    23    ,    27472    },/*    29    30    30    29    30    29    30    30    29    30    29    30    29    384
+2032    */{    0    ,    2    ,    11    ,    38608    },/*    30    29    29    30    29    30    30    29    30    30    29    30    0    355
+2033    */{    11    ,    1    ,    31    ,    19176    },/*    29    30    29    29    30    29    30    29    30    30    30    29    30    384
+2034    */{    0    ,    2    ,    19    ,    19152    },/*    29    30    29    29    30    29    30    29    30    30    29    30    0    354
+2035    */{    0    ,    2    ,    8    ,    42192    },/*    30    29    30    29    29    30    29    29    30    30    29    30    0    354
+2036    */{    6    ,    1    ,    28    ,    53848    },/*    30    30    29    30    29    29    30    29    29    30    29    30    30    384
+2037    */{    0    ,    2    ,    15    ,    53840    },/*    30    30    29    30    29    29    30    29    29    30    29    30    0    354
+2038    */{    0    ,    2    ,    4    ,    54560    },/*    30    30    29    30    29    30    29    30    29    29    30    29    0    354
+2039    */{    5    ,    1    ,    24    ,    55968    },/*    30    30    29    30    30    29    30    29    30    29    30    29    29    384
+2040    */{    0    ,    2    ,    12    ,    46496    },/*    30    29    30    30    29    30    29    30    30    29    30    29    0    355
+2041    */{    0    ,    2    ,    1    ,    22224    },/*    29    30    29    30    29    30    30    29    30    30    29    30    0    355
+2042    */{    2    ,    1    ,    22    ,    19160    },/*    29    30    29    29    30    29    30    29    30    30    29    30    30    384
+2043    */{    0    ,    2    ,    10    ,    18864    },/*    29    30    29    29    30    29    29    30    30    29    30    30    0    354
+2044    */{    7    ,    1    ,    30    ,    42168    },/*    30    29    30    29    29    30    29    29    30    29    30    30    30    384
+2045    */{    0    ,    2    ,    17    ,    42160    },/*    30    29    30    29    29    30    29    29    30    29    30    30    0    354
+2046    */{    0    ,    2    ,    6    ,    43600    },/*    30    29    30    29    30    29    30    29    29    30    29    30    0    354
+2047    */{    5    ,    1    ,    26    ,    46376    },/*    30    29    30    30    29    30    29    30    29    29    30    29    30    384
+2048    */{    0    ,    2    ,    14    ,    27936    },/*    29    30    30    29    30    30    29    30    29    29    30    29    0    354
+2049    */{    0    ,    2    ,    2    ,    44448    },/*    30    29    30    29    30    30    29    30    30    29    30    29    0    355
+2050    */{    3    ,    1    ,    23    ,    21936    },/*    29    30    29    30    29    30    29    30    30    29    30    30    29    384
+        */};
+
+
+        internal override int MinCalendarYear
+        {
+            get
+            {
+                return (MIN_LUNISOLAR_YEAR);
+            }
+        }
+
+        internal override int MaxCalendarYear
+        {
+            get
+            {
+                return (MAX_LUNISOLAR_YEAR);
+            }
+        }
+
+        internal override DateTime MinDate
+        {
+            get
+            {
+                return (minDate);
+            }
+        }
+
+        internal override DateTime MaxDate
+        {
+            get
+            {
+                return (maxDate);
+            }
+        }
+
+        internal override EraInfo[] CalEraInfo
+        {
+            get
+            {
+                return (taiwanLunisolarEraInfo);
+            }
+        }
+
+        internal override int GetYearInfo(int lunarYear, int index)
+        {
+            if ((lunarYear < MIN_LUNISOLAR_YEAR) || (lunarYear > MAX_LUNISOLAR_YEAR))
+            {
+                throw new ArgumentOutOfRangeException(
+                            "year",
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                MIN_LUNISOLAR_YEAR,
+                                MAX_LUNISOLAR_YEAR));
+            }
+
+            return s_yinfo[lunarYear - MIN_LUNISOLAR_YEAR, index];
+        }
+
+        internal override int GetYear(int year, DateTime time)
+        {
+            return helper.GetYear(year, time);
+        }
+
+        internal override int GetGregorianYear(int year, int era)
+        {
+            return helper.GetGregorianYear(year, era);
+        }
+
+        public TaiwanLunisolarCalendar()
+        {
+            helper = new GregorianCalendarHelper(this, taiwanLunisolarEraInfo);
+        }
+
+        public override int GetEra(DateTime time)
+        {
+            return (helper.GetEra(time));
+        }
+
+        internal override CalendarId BaseCalendarID
+        {
+            get
+            {
+                return (CalendarId.TAIWAN);
+            }
+        }
+
+        internal override CalendarId ID
+        {
+            get
+            {
+                return (CalendarId.TAIWANLUNISOLAR);
+            }
+        }
+
+
+
+        public override int[] Eras
+        {
+            get
+            {
+                return (helper.Eras);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/TextElementEnumerator.cs b/src/System.Private.CoreLib/shared/System/Globalization/TextElementEnumerator.cs
new file mode 100644
index 0000000000..8b0f102a77
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/TextElementEnumerator.cs
@@ -0,0 +1,117 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////
+//
+//
+//  Purpose:  
+//
+//
+////////////////////////////////////////////////////////////////////////////
+
+using System.Collections;
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    //
+    // This is public because GetTextElement() is public.
+    //
+
+    public class TextElementEnumerator : IEnumerator
+    {
+        private String _str;
+        private int _index;
+        private int _startIndex;
+
+        private int _strLen;                // This is the length of the total string, counting from the beginning of string.
+
+        private int _currTextElementLen; // The current text element lenght after MoveNext() is called.
+
+        private UnicodeCategory _uc;
+
+        private int _charLen;            // The next abstract char to look at after MoveNext() is called.  It could be 1 or 2, depending on if it is a surrogate or not.
+
+        internal TextElementEnumerator(String str, int startIndex, int strLen)
+        {
+            Debug.Assert(str != null, "TextElementEnumerator(): str != null");
+            Debug.Assert(startIndex >= 0 && strLen >= 0, "TextElementEnumerator(): startIndex >= 0 && strLen >= 0");
+            Debug.Assert(strLen >= startIndex, "TextElementEnumerator(): strLen >= startIndex");
+            _str = str;
+            _startIndex = startIndex;
+            _strLen = strLen;
+            Reset();
+        }
+
+        public bool MoveNext()
+        {
+            if (_index >= _strLen)
+            {
+                // Make the _index to be greater than _strLen so that we can throw exception if GetTextElement() is called.
+                _index = _strLen + 1;
+                return (false);
+            }
+            _currTextElementLen = StringInfo.GetCurrentTextElementLen(_str, _index, _strLen, ref _uc, ref _charLen);
+            _index += _currTextElementLen;
+            return (true);
+        }
+
+        //
+        // Get the current text element.
+        //
+
+        public Object Current
+        {
+            get
+            {
+                return (GetTextElement());
+            }
+        }
+
+        //
+        // Get the current text element.
+        //
+
+        public String GetTextElement()
+        {
+            if (_index == _startIndex)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_EnumNotStarted);
+            }
+            if (_index > _strLen)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_EnumEnded);
+            }
+
+            return (_str.Substring(_index - _currTextElementLen, _currTextElementLen));
+        }
+
+        //
+        // Get the starting index of the current text element.
+        //
+
+        public int ElementIndex
+        {
+            get
+            {
+                if (_index == _startIndex)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumNotStarted);
+                }
+                return (_index - _currTextElementLen);
+            }
+        }
+
+
+        public void Reset()
+        {
+            _index = _startIndex;
+            if (_index < _strLen)
+            {
+                // If we have more than 1 character, get the category of the current char.
+                _uc = CharUnicodeInfo.InternalGetUnicodeCategory(_str, _index, out _charLen);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/TextInfo.Unix.cs b/src/System.Private.CoreLib/shared/System/Globalization/TextInfo.Unix.cs
new file mode 100644
index 0000000000..c431e462b5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/TextInfo.Unix.cs
@@ -0,0 +1,57 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Security;
+using System.Text;
+
+namespace System.Globalization
+{
+    public partial class TextInfo
+    {
+        private Tristate _needsTurkishCasing = Tristate.NotInitialized;
+
+        private void FinishInitialization() { }
+
+        // -----------------------------
+        // ---- PAL layer ends here ----
+        // -----------------------------
+
+        private bool NeedsTurkishCasing(string localeName)
+        {
+            Debug.Assert(localeName != null);
+
+            return CultureInfo.GetCultureInfo(localeName).CompareInfo.Compare("\u0131", "I", CompareOptions.IgnoreCase) == 0;
+        }
+
+        private bool IsInvariant { get { return _cultureName.Length == 0; } }
+
+        internal unsafe void ChangeCase(char* src, int srcLen, char* dstBuffer, int dstBufferCapacity, bool bToUpper)
+        {
+            Debug.Assert(!_invariantMode);
+
+            if (IsInvariant)
+            {
+                Interop.Globalization.ChangeCaseInvariant(src, srcLen, dstBuffer, dstBufferCapacity, bToUpper);
+            }
+            else
+            {
+                if (_needsTurkishCasing == Tristate.NotInitialized)
+                {
+                    _needsTurkishCasing = NeedsTurkishCasing(_textInfoName) ? Tristate.True : Tristate.False;
+                }
+                if (_needsTurkishCasing == Tristate.True)
+                {
+                    Interop.Globalization.ChangeCaseTurkish(src, srcLen, dstBuffer, dstBufferCapacity, bToUpper);
+                }
+                else
+                {
+                    Interop.Globalization.ChangeCase(src, srcLen, dstBuffer, dstBufferCapacity, bToUpper);
+                }
+            }
+        }
+
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/TextInfo.Windows.cs b/src/System.Private.CoreLib/shared/System/Globalization/TextInfo.Windows.cs
new file mode 100644
index 0000000000..6e5e321002
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/TextInfo.Windows.cs
@@ -0,0 +1,65 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    public partial class TextInfo
+    {
+        private unsafe void FinishInitialization()
+        {
+            if (_invariantMode)
+            {
+                _sortHandle = IntPtr.Zero;
+                return;
+            }
+
+            const uint LCMAP_SORTHANDLE = 0x20000000;
+
+            IntPtr handle;
+            int ret = Interop.Kernel32.LCMapStringEx(_textInfoName, LCMAP_SORTHANDLE, null, 0, &handle, IntPtr.Size, null, null, IntPtr.Zero);
+            _sortHandle = ret > 0 ? handle : IntPtr.Zero;
+        }
+
+        private unsafe void ChangeCase(char* pSource, int pSourceLen, char* pResult, int pResultLen, bool toUpper)
+        {
+            Debug.Assert(!_invariantMode);
+            Debug.Assert(pSource != null);
+            Debug.Assert(pResult != null);
+            Debug.Assert(pSourceLen >= 0);
+            Debug.Assert(pResultLen >= 0);
+            Debug.Assert(pSourceLen <= pResultLen);
+
+            // Check for Invariant to avoid A/V in LCMapStringEx
+            uint linguisticCasing = IsInvariantLocale(_textInfoName) ? 0 : LCMAP_LINGUISTIC_CASING;
+
+            int ret = Interop.Kernel32.LCMapStringEx(_sortHandle != IntPtr.Zero ? null : _textInfoName,
+                                                     linguisticCasing | (toUpper ? LCMAP_UPPERCASE : LCMAP_LOWERCASE),
+                                                     pSource,
+                                                     pSourceLen,
+                                                     pResult,
+                                                     pSourceLen,
+                                                     null,
+                                                     null,
+                                                     _sortHandle);
+            if (ret == 0)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+            }
+
+            Debug.Assert(ret == pSourceLen, "Expected getting the same length of the original string");
+        }
+
+        // PAL Ends here
+
+        private IntPtr _sortHandle;
+
+        private const uint LCMAP_LINGUISTIC_CASING = 0x01000000;
+        private const uint LCMAP_LOWERCASE = 0x00000100;
+        private const uint LCMAP_UPPERCASE = 0x00000200;
+
+        private static bool IsInvariantLocale(string localeName) => localeName == "";
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/TextInfo.cs b/src/System.Private.CoreLib/shared/System/Globalization/TextInfo.cs
new file mode 100644
index 0000000000..183f02ccce
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/TextInfo.cs
@@ -0,0 +1,904 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////
+//
+//
+//  Purpose:  This Class defines behaviors specific to a writing system.
+//            A writing system is the collection of scripts and
+//            orthographic rules required to represent a language as text.
+//
+//
+////////////////////////////////////////////////////////////////////////////
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.Serialization;
+using System.Text;
+
+namespace System.Globalization
+{
+    public partial class TextInfo : ICloneable, IDeserializationCallback
+    {
+        private enum Tristate : byte
+        {
+            NotInitialized,
+            True,
+            False,
+        }
+
+        private string _listSeparator;
+        private bool _isReadOnly = false;
+
+        /*    _cultureName is the name of the creating culture.
+              _cultureData is the data that backs this class.
+              _textInfoName is the actual name of the textInfo (from cultureData.STEXTINFO)
+                      In the desktop, when we call the sorting dll, it doesn't
+                      know how to resolve custom locle names to sort ids so we have to have already resolved this.
+        */
+
+        private readonly string _cultureName;      // Name of the culture that created this text info
+        private readonly CultureData _cultureData; // Data record for the culture that made us, not for this textinfo
+        private readonly string _textInfoName;     // Name of the text info we're using (ie: _cultureData.STEXTINFO)
+
+        private Tristate _isAsciiCasingSameAsInvariant = Tristate.NotInitialized;
+
+        // _invariantMode is defined for the perf reason as accessing the instance field is faster than access the static property GlobalizationMode.Invariant
+        private readonly bool _invariantMode = GlobalizationMode.Invariant;
+
+        // Invariant text info
+        internal static TextInfo Invariant
+        {
+            get
+            {
+                if (s_Invariant == null)
+                    s_Invariant = new TextInfo(CultureData.Invariant);
+                return s_Invariant;
+            }
+        }
+        internal volatile static TextInfo s_Invariant;
+
+        //////////////////////////////////////////////////////////////////////////
+        ////
+        ////  TextInfo Constructors
+        ////
+        ////  Implements CultureInfo.TextInfo.
+        ////
+        //////////////////////////////////////////////////////////////////////////
+        internal TextInfo(CultureData cultureData)
+        {
+            // This is our primary data source, we don't need most of the rest of this
+            _cultureData = cultureData;
+            _cultureName = _cultureData.CultureName;
+            _textInfoName = _cultureData.STEXTINFO;
+
+            FinishInitialization();
+        }
+
+        void IDeserializationCallback.OnDeserialization(Object sender)
+        {
+            throw new PlatformNotSupportedException();
+        }
+
+        public virtual int ANSICodePage => _cultureData.IDEFAULTANSICODEPAGE;
+
+        public virtual int OEMCodePage => _cultureData.IDEFAULTOEMCODEPAGE;
+
+        public virtual int MacCodePage => _cultureData.IDEFAULTMACCODEPAGE;
+
+        public virtual int EBCDICCodePage => _cultureData.IDEFAULTEBCDICCODEPAGE;
+
+        // Just use the LCID from our text info name
+        public int LCID => CultureInfo.GetCultureInfo(_textInfoName).LCID;
+
+        public string CultureName => _textInfoName;
+
+        public bool IsReadOnly => _isReadOnly;
+
+        //////////////////////////////////////////////////////////////////////////
+        ////
+        ////  Clone
+        ////
+        ////  Is the implementation of ICloneable.
+        ////
+        //////////////////////////////////////////////////////////////////////////
+        public virtual object Clone()
+        {
+            object o = MemberwiseClone();
+            ((TextInfo)o).SetReadOnlyState(false);
+            return o;
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  ReadOnly
+        //
+        //  Create a cloned readonly instance or return the input one if it is 
+        //  readonly.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public static TextInfo ReadOnly(TextInfo textInfo)
+        {
+            if (textInfo == null) { throw new ArgumentNullException(nameof(textInfo)); }
+            if (textInfo.IsReadOnly) { return textInfo; }
+
+            TextInfo clonedTextInfo = (TextInfo)(textInfo.MemberwiseClone());
+            clonedTextInfo.SetReadOnlyState(true);
+
+            return clonedTextInfo;
+        }
+
+        private void VerifyWritable()
+        {
+            if (_isReadOnly)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+            }
+        }
+
+        internal void SetReadOnlyState(bool readOnly)
+        {
+            _isReadOnly = readOnly;
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  ListSeparator
+        //
+        //  Returns the string used to separate items in a list.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual string ListSeparator
+        {
+            get
+            {
+                if (_listSeparator == null)
+                {
+                    _listSeparator = _cultureData.SLIST;
+                }
+                return _listSeparator;
+            }
+
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value), SR.ArgumentNull_String);
+                }
+                VerifyWritable();
+                _listSeparator = value;
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  ToLower
+        //
+        //  Converts the character or string to lower case.  Certain locales
+        //  have different casing semantics from the file systems in Win32.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public unsafe virtual char ToLower(char c)
+        {
+            if (_invariantMode || (IsAscii(c) && IsAsciiCasingSameAsInvariant))
+            {
+                return ToLowerAsciiInvariant(c);
+            }
+
+            return ChangeCase(c, toUpper: false);
+        }
+
+        public unsafe virtual string ToLower(string str)
+        {
+            if (str == null) { throw new ArgumentNullException(nameof(str)); }
+
+            if (_invariantMode)
+            {
+                return ToLowerAsciiInvariant(str);
+            }
+
+            return ChangeCase(str, toUpper: false);
+        }
+
+        private unsafe char ChangeCase(char c, bool toUpper)
+        {
+            Debug.Assert(!_invariantMode);
+            
+            char dst = default;
+            ChangeCase(&c, 1, &dst, 1, toUpper);
+            return dst;
+        }
+
+        private unsafe string ChangeCase(string source, bool toUpper)
+        {
+            Debug.Assert(!_invariantMode);
+            Debug.Assert(source != null);
+
+            // If the string is empty, we're done.
+            if (source.Length == 0)
+            {
+                return string.Empty;
+            }
+
+            int sourcePos = 0;
+            string result = null;
+
+            // If this culture's casing for ASCII is the same as invariant, try to take
+            // a fast path that'll work in managed code and ASCII rather than calling out
+            // to the OS for culture-aware casing.
+            if (IsAsciiCasingSameAsInvariant)
+            {
+                if (toUpper)
+                {
+                    // Loop through each character.
+                    for (sourcePos = 0; sourcePos < source.Length; sourcePos++)
+                    {
+                        // If the character is lower-case, we're going to need to allocate a string.
+                        char c = source[sourcePos];
+                        if ((uint)(c - 'a') <= 'z' - 'a')
+                        {
+                            // Allocate the result string.
+                            result = string.FastAllocateString(source.Length);
+                            fixed (char* pResult = result)
+                            {
+                                // Store all of characters examined thus far.
+                                if (sourcePos > 0)
+                                {
+                                    source.AsSpan(0, sourcePos).CopyTo(new Span<char>(pResult, sourcePos));
+                                }
+
+                                // And store the current character, upper-cased.
+                                char* d = pResult + sourcePos;
+                                *d++ = (char)(c & ~0x20);
+                                sourcePos++;
+
+                                // Then continue looping through the remainder of the characters. If we hit
+                                // a non-ASCII character, bail to fall back to culture-aware casing.
+                                for (; sourcePos < source.Length; sourcePos++)
+                                {
+                                    c = source[sourcePos];
+                                    if ((uint)(c - 'a') <= 'z' - 'a')
+                                    {
+                                        *d++ = (char)(c & ~0x20);
+                                    }
+                                    else if (!IsAscii(c))
+                                    {
+                                        break;
+                                    }
+                                    else
+                                    {
+                                        *d++ = c;
+                                    }
+                                }
+                            }
+
+                            break;
+                        }
+                        else if (!IsAscii(c))
+                        {
+                            // The character isn't ASCII; bail to fall back to a culture-aware casing.
+                            break;
+                        }
+                    }
+                }
+                else // toUpper == false
+                {
+                    // Loop through each character.
+                    for (sourcePos = 0; sourcePos < source.Length; sourcePos++)
+                    {
+                        // If the character is upper-case, we're going to need to allocate a string.
+                        char c = source[sourcePos];
+                        if ((uint)(c - 'A') <= 'Z' - 'A')
+                        {
+                            // Allocate the result string.
+                            result = string.FastAllocateString(source.Length);
+                            fixed (char* pResult = result)
+                            {
+                                // Store all of characters examined thus far.
+                                if (sourcePos > 0)
+                                {
+                                    source.AsSpan(0, sourcePos).CopyTo(new Span<char>(pResult, sourcePos));
+                                }
+
+                                // And store the current character, upper-cased.
+                                char* d = pResult + sourcePos;
+                                *d++ = (char)(c | 0x20);
+                                sourcePos++;
+
+                                // Then continue looping through the remainder of the characters. If we hit
+                                // a non-ASCII character, bail to fall back to culture-aware casing.
+                                for (; sourcePos < source.Length; sourcePos++)
+                                {
+                                    c = source[sourcePos];
+                                    if ((uint)(c - 'A') <= 'Z' - 'A')
+                                    {
+                                       *d++ = (char)(c | 0x20);
+                                    }
+                                    else if (!IsAscii(c))
+                                    {
+                                        break;
+                                    }
+                                    else
+                                    {
+                                        *d++ = c;
+                                    }
+                                }
+                            }
+
+                            break;
+                        }
+                        else if (!IsAscii(c))
+                        {
+                            // The character isn't ASCII; bail to fall back to a culture-aware casing.
+                            break;
+                        }
+                    }
+                }
+
+                // If we successfully iterated through all of the characters, we didn't need to fall back
+                // to culture-aware casing.  In that case, if we allocated a result string, use it, otherwise
+                // just return the original string, as no modifications were necessary.
+                if (sourcePos == source.Length)
+                {
+                    return result ?? source;
+                }
+            }
+
+            // Falling back to culture-aware casing.  Make sure we have a result string to write into.
+            // If we need to allocate the result string, we'll also need to copy over to it any
+            // characters already examined.
+            if (result == null)
+            {
+                result = string.FastAllocateString(source.Length);
+                if (sourcePos > 0)
+                {
+                    fixed (char* pResult = result)
+                    {
+                        source.AsSpan(0, sourcePos).CopyTo(new Span<char>(pResult, sourcePos));
+                    }
+                }
+            }
+
+            // Do the casing operation on everything after what we already processed.
+            fixed (char* pSource = source)
+            {
+                fixed (char* pResult = result)
+                {
+                    ChangeCase(pSource + sourcePos, source.Length - sourcePos, pResult + sourcePos, result.Length - sourcePos, toUpper);
+                }
+            }
+
+            return result;
+        }
+
+        internal unsafe void ChangeCase(ReadOnlySpan<char> source, Span<char> destination, bool toUpper)
+        {
+            Debug.Assert(!_invariantMode);
+            Debug.Assert(destination.Length >= source.Length);
+
+            if (source.IsEmpty)
+            {
+                return;
+            }
+
+            fixed (char* pSource = &MemoryMarshal.GetReference(source))
+            fixed (char* pResult = &MemoryMarshal.GetReference(destination))
+            {
+                if (IsAsciiCasingSameAsInvariant)
+                {
+                    int length = 0;
+                    char* a = pSource, b = pResult;
+                    if (toUpper)
+                    {
+                        while (length < source.Length && *a < 0x80)
+                        {
+                            *b++ = ToUpperAsciiInvariant(*a++);
+                            length++;
+                        }
+                    }
+                    else
+                    {
+                        while (length < source.Length && *a < 0x80)
+                        {
+                            *b++ = ToLowerAsciiInvariant(*a++);
+                            length++;
+                        }
+                    }
+
+                    if (length != source.Length)
+                    {
+                        ChangeCase(a, source.Length - length, b, destination.Length - length, toUpper);
+                    }
+                }
+                else
+                {
+                    ChangeCase(pSource, source.Length, pResult, destination.Length, toUpper);
+                }
+            }
+        }
+
+        private static unsafe string ToLowerAsciiInvariant(string s)
+        {
+            if (s.Length == 0)
+            {
+                return string.Empty;
+            }
+            
+            fixed (char* pSource = s)
+            {
+                int i = 0;
+                while (i < s.Length)
+                {
+                    if ((uint)(pSource[i] - 'A') <= (uint)('Z' - 'A'))
+                    {
+                        break;
+                    }
+                    i++;
+                }
+                
+                if (i >= s.Length)
+                {
+                    return s;
+                }
+
+                string result = string.FastAllocateString(s.Length);
+                fixed (char* pResult = result)
+                {
+                    for (int j = 0; j < i; j++)
+                    {
+                        pResult[j] = pSource[j];
+                    }
+                    
+                    pResult[i] = (char)(pSource[i] | 0x20);
+                    i++;
+
+                    while (i < s.Length)
+                    {
+                        pResult[i] = ToLowerAsciiInvariant(pSource[i]);
+                        i++;
+                    }
+                }
+
+                return result;
+            }
+        }
+
+        internal static void ToLowerAsciiInvariant(ReadOnlySpan<char> source, Span<char> destination)
+        {
+            Debug.Assert(destination.Length >= source.Length);
+
+            for (int i = 0; i < source.Length; i++)
+            {
+                destination[i] = ToLowerAsciiInvariant(source[i]);
+            }
+        }
+
+        private static unsafe string ToUpperAsciiInvariant(string s)
+        {
+            if (s.Length == 0)
+            {
+                return string.Empty;
+            }
+            
+            fixed (char* pSource = s)
+            {
+                int i = 0;
+                while (i < s.Length)
+                {
+                    if ((uint)(pSource[i] - 'a') <= (uint)('z' - 'a'))
+                    {
+                        break;
+                    }
+                    i++;
+                }
+                
+                if (i >= s.Length)
+                {
+                    return s;
+                }
+
+                string result = string.FastAllocateString(s.Length);
+                fixed (char* pResult = result)
+                {
+                    for (int j = 0; j < i; j++)
+                    {
+                        pResult[j] = pSource[j];
+                    }
+                    
+                    pResult[i] = (char)(pSource[i] & ~0x20);
+                    i++;
+
+                    while (i < s.Length)
+                    {
+                        pResult[i] = ToUpperAsciiInvariant(pSource[i]);
+                        i++;
+                    }
+                }
+
+                return result;
+            }
+        }
+
+        internal static void ToUpperAsciiInvariant(ReadOnlySpan<char> source, Span<char> destination)
+        {
+            Debug.Assert(destination.Length >= source.Length);
+
+            for (int i = 0; i < source.Length; i++)
+            {
+                destination[i] = ToUpperAsciiInvariant(source[i]);
+            }
+        }
+
+        private static char ToLowerAsciiInvariant(char c)
+        {
+            if ((uint)(c - 'A') <= (uint)('Z' - 'A'))
+            {
+                c = (char)(c | 0x20);
+            }
+            return c;
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  ToUpper
+        //
+        //  Converts the character or string to upper case.  Certain locales
+        //  have different casing semantics from the file systems in Win32.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public unsafe virtual char ToUpper(char c)
+        {
+            if (_invariantMode || (IsAscii(c) && IsAsciiCasingSameAsInvariant))
+            {
+                return ToUpperAsciiInvariant(c);
+            }
+            
+            return ChangeCase(c, toUpper: true);
+        }
+
+        public unsafe virtual string ToUpper(string str)
+        {
+            if (str == null) { throw new ArgumentNullException(nameof(str)); }
+
+            if (_invariantMode)
+            {
+                return ToUpperAsciiInvariant(str);
+            }
+
+            return ChangeCase(str, toUpper: true);
+        }
+
+        internal static char ToUpperAsciiInvariant(char c)
+        {
+            if ((uint)(c - 'a') <= (uint)('z' - 'a'))
+            {
+                c = (char)(c & ~0x20);
+            }
+            return c;
+        }
+
+        private static bool IsAscii(char c)
+        {
+            return c < 0x80;
+        }
+
+        private bool IsAsciiCasingSameAsInvariant
+        {
+            get
+            {
+                if (_isAsciiCasingSameAsInvariant == Tristate.NotInitialized)
+                {
+                    _isAsciiCasingSameAsInvariant = CultureInfo.GetCultureInfo(_textInfoName).CompareInfo.Compare("abcdefghijklmnopqrstuvwxyz",
+                                                                             "ABCDEFGHIJKLMNOPQRSTUVWXYZ",
+                                                                             CompareOptions.IgnoreCase) == 0 ? Tristate.True : Tristate.False;
+                }
+                return _isAsciiCasingSameAsInvariant == Tristate.True;
+            }
+        }
+
+        // IsRightToLeft
+        //
+        // Returns true if the dominant direction of text and UI such as the relative position of buttons and scroll bars
+        //
+        public bool IsRightToLeft => _cultureData.IsRightToLeft;
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  Equals
+        //
+        //  Implements Object.Equals().  Returns a boolean indicating whether
+        //  or not object refers to the same CultureInfo as the current instance.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public override bool Equals(Object obj)
+        {
+            TextInfo that = obj as TextInfo;
+
+            if (that != null)
+            {
+                return CultureName.Equals(that.CultureName);
+            }
+
+            return false;
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetHashCode
+        //
+        //  Implements Object.GetHashCode().  Returns the hash code for the
+        //  CultureInfo.  The hash code is guaranteed to be the same for CultureInfo A
+        //  and B where A.Equals(B) is true.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public override int GetHashCode()
+        {
+            return CultureName.GetHashCode();
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  ToString
+        //
+        //  Implements Object.ToString().  Returns a string describing the
+        //  TextInfo.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public override string ToString()
+        {
+            return "TextInfo - " + _cultureData.CultureName;
+        }
+
+        //
+        // Titlecasing:
+        // -----------
+        // Titlecasing refers to a casing practice wherein the first letter of a word is an uppercase letter
+        // and the rest of the letters are lowercase.  The choice of which words to titlecase in headings
+        // and titles is dependent on language and local conventions.  For example, "The Merry Wives of Windor"
+        // is the appropriate titlecasing of that play's name in English, with the word "of" not titlecased.
+        // In German, however, the title is "Die lustigen Weiber von Windsor," and both "lustigen" and "von"
+        // are not titlecased.  In French even fewer words are titlecased: "Les joyeuses commeres de Windsor."
+        //
+        // Moreover, the determination of what actually constitutes a word is language dependent, and this can
+        // influence which letter or letters of a "word" are uppercased when titlecasing strings.  For example
+        // "l'arbre" is considered two words in French, whereas "can't" is considered one word in English.
+        //
+        public unsafe string ToTitleCase(string str)
+        {
+            if (str == null)
+            {
+                throw new ArgumentNullException(nameof(str));
+            }
+            if (str.Length == 0)
+            {
+                return str;
+            }
+
+            StringBuilder result = new StringBuilder();
+            string lowercaseData = null;
+            // Store if the current culture is Dutch (special case)
+            bool isDutchCulture = CultureName.StartsWith("nl-", StringComparison.OrdinalIgnoreCase);
+
+            for (int i = 0; i < str.Length; i++)
+            {
+                UnicodeCategory charType;
+                int charLen;
+
+                charType = CharUnicodeInfo.InternalGetUnicodeCategory(str, i, out charLen);
+                if (char.CheckLetter(charType))
+                {
+                    // Special case to check for Dutch specific titlecasing with "IJ" characters 
+                    // at the beginning of a word
+                    if (isDutchCulture && i < str.Length - 1 && (str[i] == 'i' || str[i] == 'I') && (str[i+1] == 'j' || str[i+1] == 'J'))
+                    {
+                        result.Append("IJ");
+                        i += 2;
+                    }
+                    else
+                    {
+                        // Do the titlecasing for the first character of the word.
+                        i = AddTitlecaseLetter(ref result, ref str, i, charLen) + 1;
+                    }
+
+                    //
+                    // Convert the characters until the end of the this word
+                    // to lowercase.
+                    //
+                    int lowercaseStart = i;
+
+                    //
+                    // Use hasLowerCase flag to prevent from lowercasing acronyms (like "URT", "USA", etc)
+                    // This is in line with Word 2000 behavior of titlecasing.
+                    //
+                    bool hasLowerCase = (charType == UnicodeCategory.LowercaseLetter);
+                    // Use a loop to find all of the other letters following this letter.
+                    while (i < str.Length)
+                    {
+                        charType = CharUnicodeInfo.InternalGetUnicodeCategory(str, i, out charLen);
+                        if (IsLetterCategory(charType))
+                        {
+                            if (charType == UnicodeCategory.LowercaseLetter)
+                            {
+                                hasLowerCase = true;
+                            }
+                            i += charLen;
+                        }
+                        else if (str[i] == '\'')
+                        {
+                            i++;
+                            if (hasLowerCase)
+                            {
+                                if (lowercaseData == null)
+                                {
+                                    lowercaseData = ToLower(str);
+                                }
+                                result.Append(lowercaseData, lowercaseStart, i - lowercaseStart);
+                            }
+                            else
+                            {
+                                result.Append(str, lowercaseStart, i - lowercaseStart);
+                            }
+                            lowercaseStart = i;
+                            hasLowerCase = true;
+                        }
+                        else if (!IsWordSeparator(charType))
+                        {
+                            // This category is considered to be part of the word.
+                            // This is any category that is marked as false in wordSeprator array.
+                            i+= charLen;
+                        }
+                        else
+                        {
+                            // A word separator. Break out of the loop.
+                            break;
+                        }
+                    }
+
+                    int count = i - lowercaseStart;
+
+                    if (count > 0)
+                    {
+                        if (hasLowerCase)
+                        {
+                            if (lowercaseData == null)
+                            {
+                                lowercaseData = ToLower(str);
+                            }
+                            result.Append(lowercaseData, lowercaseStart, count);
+                        }
+                        else
+                        {
+                            result.Append(str, lowercaseStart, count);
+                        }
+                    }
+
+                    if (i < str.Length)
+                    {
+                        // not a letter, just append it
+                        i = AddNonLetter(ref result, ref str, i, charLen);
+                    }
+                }
+                else
+                {
+                    // not a letter, just append it
+                    i = AddNonLetter(ref result, ref str, i, charLen);
+                }
+            }
+            return result.ToString();
+        }
+
+        private static int AddNonLetter(ref StringBuilder result, ref string input, int inputIndex, int charLen)
+        {
+            Debug.Assert(charLen == 1 || charLen == 2, "[TextInfo.AddNonLetter] CharUnicodeInfo.InternalGetUnicodeCategory returned an unexpected charLen!");
+            if (charLen == 2)
+            {
+                // Surrogate pair
+                result.Append(input[inputIndex++]);
+                result.Append(input[inputIndex]);
+            }
+            else
+            {
+                result.Append(input[inputIndex]);
+            }
+            return inputIndex;
+        }
+
+        private int AddTitlecaseLetter(ref StringBuilder result, ref string input, int inputIndex, int charLen)
+        {
+            Debug.Assert(charLen == 1 || charLen == 2, "[TextInfo.AddTitlecaseLetter] CharUnicodeInfo.InternalGetUnicodeCategory returned an unexpected charLen!");
+
+            // for surrogate pairs do a simple ToUpper operation on the substring
+            if (charLen == 2)
+            {
+                // Surrogate pair
+                result.Append(ToUpper(input.Substring(inputIndex, charLen)));
+                inputIndex++;
+            }
+            else
+            {
+                switch (input[inputIndex])
+                {
+                    //
+                    // For AppCompat, the Titlecase Case Mapping data from NDP 2.0 is used below.
+                    case (char) 0x01C4:  // DZ with Caron -> Dz with Caron
+                    case (char) 0x01C5:  // Dz with Caron -> Dz with Caron
+                    case (char) 0x01C6:  // dz with Caron -> Dz with Caron
+                        result.Append((char) 0x01C5);
+                        break;
+                    case (char) 0x01C7:  // LJ -> Lj
+                    case (char) 0x01C8:  // Lj -> Lj
+                    case (char) 0x01C9:  // lj -> Lj
+                        result.Append((char) 0x01C8);
+                        break;
+                    case (char) 0x01CA:  // NJ -> Nj
+                    case (char) 0x01CB:  // Nj -> Nj
+                    case (char) 0x01CC:  // nj -> Nj
+                        result.Append((char) 0x01CB);
+                        break;
+                    case (char) 0x01F1:  // DZ -> Dz
+                    case (char) 0x01F2:  // Dz -> Dz
+                    case (char) 0x01F3:  // dz -> Dz
+                        result.Append((char) 0x01F2);
+                        break;
+                    default:
+                        result.Append(ToUpper(input[inputIndex]));
+                        break;
+                }
+            }
+            return inputIndex;
+        }
+
+        //
+        // Used in ToTitleCase():
+        // When we find a starting letter, the following array decides if a category should be
+        // considered as word seprator or not.
+        //
+        private const int c_wordSeparatorMask = 
+            /* false */ (0 <<  0) | // UppercaseLetter = 0,
+            /* false */ (0 <<  1) | // LowercaseLetter = 1,
+            /* false */ (0 <<  2) | // TitlecaseLetter = 2,
+            /* false */ (0 <<  3) | // ModifierLetter = 3,
+            /* false */ (0 <<  4) | // OtherLetter = 4,
+            /* false */ (0 <<  5) | // NonSpacingMark = 5,
+            /* false */ (0 <<  6) | // SpacingCombiningMark = 6,
+            /* false */ (0 <<  7) | // EnclosingMark = 7,
+            /* false */ (0 <<  8) | // DecimalDigitNumber = 8,
+            /* false */ (0 <<  9) | // LetterNumber = 9,
+            /* false */ (0 << 10) | // OtherNumber = 10,
+            /* true  */ (1 << 11) | // SpaceSeparator = 11,
+            /* true  */ (1 << 12) | // LineSeparator = 12,
+            /* true  */ (1 << 13) | // ParagraphSeparator = 13,
+            /* true  */ (1 << 14) | // Control = 14,
+            /* true  */ (1 << 15) | // Format = 15,
+            /* false */ (0 << 16) | // Surrogate = 16,
+            /* false */ (0 << 17) | // PrivateUse = 17,
+            /* true  */ (1 << 18) | // ConnectorPunctuation = 18,
+            /* true  */ (1 << 19) | // DashPunctuation = 19,
+            /* true  */ (1 << 20) | // OpenPunctuation = 20,
+            /* true  */ (1 << 21) | // ClosePunctuation = 21,
+            /* true  */ (1 << 22) | // InitialQuotePunctuation = 22,
+            /* true  */ (1 << 23) | // FinalQuotePunctuation = 23,
+            /* true  */ (1 << 24) | // OtherPunctuation = 24,
+            /* true  */ (1 << 25) | // MathSymbol = 25,
+            /* true  */ (1 << 26) | // CurrencySymbol = 26,
+            /* true  */ (1 << 27) | // ModifierSymbol = 27,
+            /* true  */ (1 << 28) | // OtherSymbol = 28,
+            /* false */ (0 << 29);  // OtherNotAssigned = 29;
+        
+        private static bool IsWordSeparator(UnicodeCategory category) 
+        {
+            return (c_wordSeparatorMask & (1 << (int) category)) != 0;
+        }
+
+        private static bool IsLetterCategory(UnicodeCategory uc)
+        {
+            return (uc == UnicodeCategory.UppercaseLetter
+                 || uc == UnicodeCategory.LowercaseLetter
+                 || uc == UnicodeCategory.TitlecaseLetter
+                 || uc == UnicodeCategory.ModifierLetter
+                 || uc == UnicodeCategory.OtherLetter);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/ThaiBuddhistCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/ThaiBuddhistCalendar.cs
new file mode 100644
index 0000000000..4f8fd8f019
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/ThaiBuddhistCalendar.cs
@@ -0,0 +1,232 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics.CodeAnalysis;
+
+namespace System.Globalization
+{
+    /*=================================ThaiBuddhistCalendar==========================
+    **
+    ** ThaiBuddhistCalendar is based on Gregorian calendar.  Its year value has
+    ** an offset to the Gregorain calendar.
+    **
+    **  Calendar support range:
+    **      Calendar    Minimum     Maximum
+    **      ==========  ==========  ==========
+    **      Gregorian   0001/01/01   9999/12/31
+    **      Thai        0544/01/01  10542/12/31
+    ============================================================================*/
+
+    public class ThaiBuddhistCalendar : Calendar
+    {
+        // Initialize our era info.
+        internal static EraInfo[] thaiBuddhistEraInfo = new EraInfo[] {
+            new EraInfo( 1, 1, 1, 1, -543, 544, GregorianCalendar.MaxYear + 543)     // era #, start year/month/day, yearOffset, minEraYear 
+        };
+
+        //
+        // The era value for the current era.
+        //
+
+        public const int ThaiBuddhistEra = 1;
+
+        internal GregorianCalendarHelper helper;
+
+
+        public override DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (DateTime.MinValue);
+            }
+        }
+
+        public override DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (DateTime.MaxValue);
+            }
+        }
+
+        public override CalendarAlgorithmType AlgorithmType
+        {
+            get
+            {
+                return CalendarAlgorithmType.SolarCalendar;
+            }
+        }
+
+        public ThaiBuddhistCalendar()
+        {
+            helper = new GregorianCalendarHelper(this, thaiBuddhistEraInfo);
+        }
+
+        internal override CalendarId ID
+        {
+            get
+            {
+                return (CalendarId.THAI);
+            }
+        }
+
+
+        public override DateTime AddMonths(DateTime time, int months)
+        {
+            return (helper.AddMonths(time, months));
+        }
+
+
+        public override DateTime AddYears(DateTime time, int years)
+        {
+            return (helper.AddYears(time, years));
+        }
+
+
+        public override int GetDaysInMonth(int year, int month, int era)
+        {
+            return (helper.GetDaysInMonth(year, month, era));
+        }
+
+
+        public override int GetDaysInYear(int year, int era)
+        {
+            return (helper.GetDaysInYear(year, era));
+        }
+
+
+        public override int GetDayOfMonth(DateTime time)
+        {
+            return (helper.GetDayOfMonth(time));
+        }
+
+
+        public override DayOfWeek GetDayOfWeek(DateTime time)
+        {
+            return (helper.GetDayOfWeek(time));
+        }
+
+
+        public override int GetDayOfYear(DateTime time)
+        {
+            return (helper.GetDayOfYear(time));
+        }
+
+
+        public override int GetMonthsInYear(int year, int era)
+        {
+            return (helper.GetMonthsInYear(year, era));
+        }
+
+
+        public override int GetWeekOfYear(DateTime time, CalendarWeekRule rule, DayOfWeek firstDayOfWeek)
+        {
+            return (helper.GetWeekOfYear(time, rule, firstDayOfWeek));
+        }
+
+
+        public override int GetEra(DateTime time)
+        {
+            return (helper.GetEra(time));
+        }
+
+        public override int GetMonth(DateTime time)
+        {
+            return (helper.GetMonth(time));
+        }
+
+
+        public override int GetYear(DateTime time)
+        {
+            return (helper.GetYear(time));
+        }
+
+
+        public override bool IsLeapDay(int year, int month, int day, int era)
+        {
+            return (helper.IsLeapDay(year, month, day, era));
+        }
+
+
+        public override bool IsLeapYear(int year, int era)
+        {
+            return (helper.IsLeapYear(year, era));
+        }
+
+        // Returns  the leap month in a calendar year of the specified era. This method returns 0
+        // if this calendar does not have leap month, or this year is not a leap year.
+        //
+
+        public override int GetLeapMonth(int year, int era)
+        {
+            return (helper.GetLeapMonth(year, era));
+        }
+
+
+        public override bool IsLeapMonth(int year, int month, int era)
+        {
+            return (helper.IsLeapMonth(year, month, era));
+        }
+
+
+        public override DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era)
+        {
+            return (helper.ToDateTime(year, month, day, hour, minute, second, millisecond, era));
+        }
+
+
+        public override int[] Eras
+        {
+            get
+            {
+                return (helper.Eras);
+            }
+        }
+
+        private const int DEFAULT_TWO_DIGIT_YEAR_MAX = 2572;
+
+
+        public override int TwoDigitYearMax
+        {
+            get
+            {
+                if (twoDigitYearMax == -1)
+                {
+                    twoDigitYearMax = GetSystemTwoDigitYearSetting(ID, DEFAULT_TWO_DIGIT_YEAR_MAX);
+                }
+                return (twoDigitYearMax);
+            }
+
+            set
+            {
+                VerifyWritable();
+                if (value < 99 || value > helper.MaxYear)
+                {
+                    throw new ArgumentOutOfRangeException(
+                                "year",
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    99,
+                                    helper.MaxYear));
+                }
+                twoDigitYearMax = value;
+            }
+        }
+
+
+        public override int ToFourDigitYear(int year)
+        {
+            if (year < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            return (helper.ToFourDigitYear(year, this.TwoDigitYearMax));
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/TimeSpanFormat.cs b/src/System.Private.CoreLib/shared/System/Globalization/TimeSpanFormat.cs
new file mode 100644
index 0000000000..a66e4600aa
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/TimeSpanFormat.cs
@@ -0,0 +1,537 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System.Globalization
+{
+    internal static class TimeSpanFormat
+    {
+        private static unsafe void AppendNonNegativeInt32(StringBuilder sb, int n, int digits)
+        {
+            Debug.Assert(n >= 0);
+            uint value = (uint)n;
+
+            const int MaxUInt32Digits = 10;
+            char* buffer = stackalloc char[MaxUInt32Digits];
+
+            int index = 0;
+            do
+            {
+                uint div = value / 10;
+                buffer[index++] = (char)(value - (div * 10) + '0');
+                value = div;
+            }
+            while (value != 0);
+            Debug.Assert(index <= MaxUInt32Digits);
+
+            for (int i = digits - index; i > 0; --i) sb.Append('0');
+            for (int i = index - 1; i >= 0; --i) sb.Append(buffer[i]);
+        }
+
+        internal static readonly FormatLiterals PositiveInvariantFormatLiterals = TimeSpanFormat.FormatLiterals.InitInvariant(isNegative: false);
+        internal static readonly FormatLiterals NegativeInvariantFormatLiterals = TimeSpanFormat.FormatLiterals.InitInvariant(isNegative: true);
+
+        internal enum Pattern
+        {
+            None = 0,
+            Minimum = 1,
+            Full = 2,
+        }
+
+        /// <summary>Main method called from TimeSpan.ToString.</summary>
+        internal static string Format(TimeSpan value, string format, IFormatProvider formatProvider) =>
+            StringBuilderCache.GetStringAndRelease(FormatToBuilder(value, format, formatProvider));
+
+        /// <summary>Main method called from TimeSpan.TryFormat.</summary>
+        internal static bool TryFormat(TimeSpan value, Span<char> destination, out int charsWritten, ReadOnlySpan<char> format, IFormatProvider formatProvider)
+        {
+            StringBuilder sb = FormatToBuilder(value, format, formatProvider);
+            if (sb.Length <= destination.Length)
+            {
+                charsWritten = sb.Length;
+                sb.CopyTo(0, destination, sb.Length);
+                StringBuilderCache.Release(sb);
+                return true;
+            }
+            else
+            {
+                StringBuilderCache.Release(sb);
+                charsWritten = 0;
+                return false;
+            }
+        }
+
+        private static StringBuilder FormatToBuilder(TimeSpan value, ReadOnlySpan<char> format, IFormatProvider formatProvider)
+        {
+            if (format.Length == 0)
+            {
+                format = "c";
+            }
+
+            // Standard formats
+            if (format.Length == 1)
+            {
+                char f = format[0];
+                switch (f)
+                {
+                    case 'c':
+                    case 't':
+                    case 'T':
+                        return FormatStandard(
+                            value,
+                            isInvariant: true,
+                            format: format,
+                            pattern: Pattern.Minimum);
+
+                    case 'g':
+                    case 'G':
+                        DateTimeFormatInfo dtfi = DateTimeFormatInfo.GetInstance(formatProvider);
+                        return FormatStandard(
+                            value, 
+                            isInvariant: false,
+                            format: value.Ticks < 0 ? dtfi.FullTimeSpanNegativePattern : dtfi.FullTimeSpanPositivePattern,
+                            pattern: f == 'g' ? Pattern.Minimum : Pattern.Full);
+
+                    default:
+                        throw new FormatException(SR.Format_InvalidString);
+                }
+            }
+
+            // Custom formats
+            return FormatCustomized(value, format, DateTimeFormatInfo.GetInstance(formatProvider), result: null);
+        }
+
+        /// <summary>Format the TimeSpan instance using the specified format.</summary>
+        private static StringBuilder FormatStandard(TimeSpan value, bool isInvariant, ReadOnlySpan<char> format, Pattern pattern)
+        {
+            StringBuilder sb = StringBuilderCache.Acquire(InternalGlobalizationHelper.StringBuilderDefaultCapacity);
+            int day = (int)(value.Ticks / TimeSpan.TicksPerDay);
+            long time = value.Ticks % TimeSpan.TicksPerDay;
+
+            if (value.Ticks < 0)
+            {
+                day = -day;
+                time = -time;
+            }
+            int hours = (int)(time / TimeSpan.TicksPerHour % 24);
+            int minutes = (int)(time / TimeSpan.TicksPerMinute % 60);
+            int seconds = (int)(time / TimeSpan.TicksPerSecond % 60);
+            int fraction = (int)(time % TimeSpan.TicksPerSecond);
+
+            FormatLiterals literal;
+            if (isInvariant)
+            {
+                literal = value.Ticks < 0 ?
+                    NegativeInvariantFormatLiterals :
+                    PositiveInvariantFormatLiterals;
+            }
+            else
+            {
+                literal = new FormatLiterals();
+                literal.Init(format, pattern == Pattern.Full);
+            }
+
+            if (fraction != 0)
+            {
+                // truncate the partial second to the specified length
+                fraction = (int)(fraction / TimeSpanParse.Pow10(DateTimeFormat.MaxSecondsFractionDigits - literal.ff));
+            }
+
+            // Pattern.Full: [-]dd.hh:mm:ss.fffffff
+            // Pattern.Minimum: [-][d.]hh:mm:ss[.fffffff] 
+
+            sb.Append(literal.Start);                           // [-]
+            if (pattern == Pattern.Full || day != 0)
+            {
+                sb.Append(day);                                 // [dd]
+                sb.Append(literal.DayHourSep);                  // [.]
+            }                                                   //
+            AppendNonNegativeInt32(sb, hours, literal.hh);      // hh
+            sb.Append(literal.HourMinuteSep);                   // :
+            AppendNonNegativeInt32(sb, minutes, literal.mm);    // mm
+            sb.Append(literal.MinuteSecondSep);                 // :
+            AppendNonNegativeInt32(sb, seconds, literal.ss);    // ss
+            if (!isInvariant && pattern == Pattern.Minimum)
+            {
+                int effectiveDigits = literal.ff;
+                while (effectiveDigits > 0)
+                {
+                    if (fraction % 10 == 0)
+                    {
+                        fraction = fraction / 10;
+                        effectiveDigits--;
+                    }
+                    else
+                    {
+                        break;
+                    }
+                }
+                if (effectiveDigits > 0)
+                {
+                    sb.Append(literal.SecondFractionSep);           // [.FFFFFFF]
+                    sb.Append((fraction).ToString(DateTimeFormat.fixedNumberFormats[effectiveDigits - 1], CultureInfo.InvariantCulture));
+                }
+            }
+            else if (pattern == Pattern.Full || fraction != 0)
+            {
+                sb.Append(literal.SecondFractionSep);             // [.]
+                AppendNonNegativeInt32(sb, fraction, literal.ff); // [fffffff]
+            }
+            sb.Append(literal.End);
+
+            return sb;
+        }
+
+        /// <summary>Format the TimeSpan instance using the specified format.</summary>
+        private static StringBuilder FormatCustomized(TimeSpan value, ReadOnlySpan<char> format, DateTimeFormatInfo dtfi, StringBuilder result)
+        {
+            Debug.Assert(dtfi != null);
+
+            bool resultBuilderIsPooled = false;
+            if (result == null)
+            {
+                result = StringBuilderCache.Acquire(InternalGlobalizationHelper.StringBuilderDefaultCapacity);
+                resultBuilderIsPooled = true;
+            }
+
+            int day = (int)(value.Ticks / TimeSpan.TicksPerDay);
+            long time = value.Ticks % TimeSpan.TicksPerDay;
+
+            if (value.Ticks < 0)
+            {
+                day = -day;
+                time = -time;
+            }
+            int hours = (int)(time / TimeSpan.TicksPerHour % 24);
+            int minutes = (int)(time / TimeSpan.TicksPerMinute % 60);
+            int seconds = (int)(time / TimeSpan.TicksPerSecond % 60);
+            int fraction = (int)(time % TimeSpan.TicksPerSecond);
+
+            long tmp = 0;
+            int i = 0;
+            int tokenLen;
+
+            while (i < format.Length)
+            {
+                char ch = format[i];
+                int nextChar;
+                switch (ch)
+                {
+                    case 'h':
+                        tokenLen = DateTimeFormat.ParseRepeatPattern(format, i, ch);
+                        if (tokenLen > 2)
+                        {
+                            goto default; // to release the builder and throw
+                        }
+                        DateTimeFormat.FormatDigits(result, hours, tokenLen);
+                        break;
+                    case 'm':
+                        tokenLen = DateTimeFormat.ParseRepeatPattern(format, i, ch);
+                        if (tokenLen > 2)
+                        {
+                            goto default; // to release the builder and throw
+                        }
+                        DateTimeFormat.FormatDigits(result, minutes, tokenLen);
+                        break;
+                    case 's':
+                        tokenLen = DateTimeFormat.ParseRepeatPattern(format, i, ch);
+                        if (tokenLen > 2)
+                        {
+                            goto default; // to release the builder and throw
+                        }
+                        DateTimeFormat.FormatDigits(result, seconds, tokenLen);
+                        break;
+                    case 'f':
+                        //
+                        // The fraction of a second in single-digit precision. The remaining digits are truncated. 
+                        //
+                        tokenLen = DateTimeFormat.ParseRepeatPattern(format, i, ch);
+                        if (tokenLen > DateTimeFormat.MaxSecondsFractionDigits)
+                        {
+                            goto default; // to release the builder and throw
+                        }
+
+                        tmp = fraction;
+                        tmp /= TimeSpanParse.Pow10(DateTimeFormat.MaxSecondsFractionDigits - tokenLen);
+                        result.Append((tmp).ToString(DateTimeFormat.fixedNumberFormats[tokenLen - 1], CultureInfo.InvariantCulture));
+                        break;
+                    case 'F':
+                        //
+                        // Displays the most significant digit of the seconds fraction. Nothing is displayed if the digit is zero.
+                        //
+                        tokenLen = DateTimeFormat.ParseRepeatPattern(format, i, ch);
+                        if (tokenLen > DateTimeFormat.MaxSecondsFractionDigits)
+                        {
+                            goto default; // to release the builder and throw
+                        }
+
+                        tmp = fraction;
+                        tmp /= TimeSpanParse.Pow10(DateTimeFormat.MaxSecondsFractionDigits - tokenLen);
+                        int effectiveDigits = tokenLen;
+                        while (effectiveDigits > 0)
+                        {
+                            if (tmp % 10 == 0)
+                            {
+                                tmp = tmp / 10;
+                                effectiveDigits--;
+                            }
+                            else
+                            {
+                                break;
+                            }
+                        }
+                        if (effectiveDigits > 0)
+                        {
+                            result.Append((tmp).ToString(DateTimeFormat.fixedNumberFormats[effectiveDigits - 1], CultureInfo.InvariantCulture));
+                        }
+                        break;
+                    case 'd':
+                        //
+                        // tokenLen == 1 : Day as digits with no leading zero.
+                        // tokenLen == 2+: Day as digits with leading zero for single-digit days.
+                        //
+                        tokenLen = DateTimeFormat.ParseRepeatPattern(format, i, ch);
+                        if (tokenLen > 8)
+                        {
+                            goto default; // to release the builder and throw
+                        }
+
+                        DateTimeFormat.FormatDigits(result, day, tokenLen, true);
+                        break;
+                    case '\'':
+                    case '\"':
+                        tokenLen = DateTimeFormat.ParseQuoteString(format, i, result);
+                        break;
+                    case '%':
+                        // Optional format character.
+                        // For example, format string "%d" will print day 
+                        // Most of the cases, "%" can be ignored.
+                        nextChar = DateTimeFormat.ParseNextChar(format, i);
+                        // nextChar will be -1 if we already reach the end of the format string.
+                        // Besides, we will not allow "%%" appear in the pattern.
+                        if (nextChar >= 0 && nextChar != (int)'%')
+                        {
+                            char nextCharChar = (char)nextChar;
+                            StringBuilder origStringBuilder = FormatCustomized(value, MemoryMarshal.CreateReadOnlySpan<char>(ref nextCharChar, 1), dtfi, result);
+                            Debug.Assert(ReferenceEquals(origStringBuilder, result));
+                            tokenLen = 2;
+                        }
+                        else
+                        {
+                            //
+                            // This means that '%' is at the end of the format string or
+                            // "%%" appears in the format string.
+                            //
+                            goto default; // to release the builder and throw
+                        }
+                        break;
+                    case '\\':
+                        // Escaped character.  Can be used to insert character into the format string.
+                        // For example, "\d" will insert the character 'd' into the string.
+                        //
+                        nextChar = DateTimeFormat.ParseNextChar(format, i);
+                        if (nextChar >= 0)
+                        {
+                            result.Append(((char)nextChar));
+                            tokenLen = 2;
+                        }
+                        else
+                        {
+                            //
+                            // This means that '\' is at the end of the formatting string.
+                            //
+                            goto default; // to release the builder and throw
+                        }
+                        break;
+                    default:
+                        // Invalid format string
+                        if (resultBuilderIsPooled)
+                        {
+                            StringBuilderCache.Release(result);
+                        }
+                        throw new FormatException(SR.Format_InvalidString);
+                }
+                i += tokenLen;
+            }
+            return result;
+        }
+
+        internal struct FormatLiterals
+        {
+            internal string AppCompatLiteral;
+            internal int dd;
+            internal int hh;
+            internal int mm;
+            internal int ss;
+            internal int ff;
+
+            private string[] _literals;
+
+            internal string Start => _literals[0];
+            internal string DayHourSep => _literals[1];
+            internal string HourMinuteSep => _literals[2];
+            internal string MinuteSecondSep => _literals[3];
+            internal string SecondFractionSep => _literals[4];
+            internal string End => _literals[5];
+
+            /* factory method for static invariant FormatLiterals */
+            internal static FormatLiterals InitInvariant(bool isNegative)
+            {
+                FormatLiterals x = new FormatLiterals();
+                x._literals = new string[6];
+                x._literals[0] = isNegative ? "-" : string.Empty;
+                x._literals[1] = ".";
+                x._literals[2] = ":";
+                x._literals[3] = ":";
+                x._literals[4] = ".";
+                x._literals[5] = string.Empty;
+                x.AppCompatLiteral = ":."; // MinuteSecondSep+SecondFractionSep;       
+                x.dd = 2;
+                x.hh = 2;
+                x.mm = 2;
+                x.ss = 2;
+                x.ff = DateTimeFormat.MaxSecondsFractionDigits;
+                return x;
+            }
+
+            // For the "v1" TimeSpan localized patterns, the data is simply literal field separators with
+            // the constants guaranteed to include DHMSF ordered greatest to least significant.
+            // Once the data becomes more complex than this we will need to write a proper tokenizer for
+            // parsing and formatting
+            internal void Init(ReadOnlySpan<char> format, bool useInvariantFieldLengths)
+            {
+                dd = hh = mm = ss = ff = 0;
+                _literals = new string[6];
+                for (int i = 0; i < _literals.Length; i++)
+                {
+                    _literals[i] = string.Empty;
+                }
+
+                StringBuilder sb = StringBuilderCache.Acquire(InternalGlobalizationHelper.StringBuilderDefaultCapacity);
+                bool inQuote = false;
+                char quote = '\'';
+                int field = 0;
+
+                for (int i = 0; i < format.Length; i++)
+                {
+                    switch (format[i])
+                    {
+                        case '\'':
+                        case '\"':
+                            if (inQuote && (quote == format[i]))
+                            {
+                                /* we were in a quote and found a matching exit quote, so we are outside a quote now */
+                                if (field >= 0 && field <= 5)
+                                {
+                                    _literals[field] = sb.ToString();
+                                    sb.Length = 0;
+                                    inQuote = false;
+                                }
+                                else
+                                {
+                                    Debug.Fail($"Unexpected field value: {field}");
+                                    return; // how did we get here?
+                                }
+                            }
+                            else if (!inQuote)
+                            {
+                                /* we are at the start of a new quote block */
+                                quote = format[i];
+                                inQuote = true;
+                            }
+                            else
+                            {
+                                /* we were in a quote and saw the other type of quote character, so we are still in a quote */
+                            }
+                            break;
+                        case '%':
+                            Debug.Fail("Unexpected special token '%', Bug in DateTimeFormatInfo.FullTimeSpan[Positive|Negative]Pattern");
+                            goto default;
+                        case '\\':
+                            if (!inQuote)
+                            {
+                                i++; /* skip next character that is escaped by this backslash or percent sign */
+                                break;
+                            }
+                            goto default;
+                        case 'd':
+                            if (!inQuote)
+                            {
+                                Debug.Assert((field == 0 && sb.Length == 0) || field == 1, "field == 0 || field == 1, Bug in DateTimeFormatInfo.FullTimeSpan[Positive|Negative]Pattern");
+                                field = 1; // DayHourSep
+                                dd++;
+                            }
+                            break;
+                        case 'h':
+                            if (!inQuote)
+                            {
+                                Debug.Assert((field == 1 && sb.Length == 0) || field == 2, "field == 1 || field == 2, Bug in DateTimeFormatInfo.FullTimeSpan[Positive|Negative]Pattern");
+                                field = 2; // HourMinuteSep
+                                hh++;
+                            }
+                            break;
+                        case 'm':
+                            if (!inQuote)
+                            {
+                                Debug.Assert((field == 2 && sb.Length == 0) || field == 3, "field == 2 || field == 3, Bug in DateTimeFormatInfo.FullTimeSpan[Positive|Negative]Pattern");
+                                field = 3; // MinuteSecondSep
+                                mm++;
+                            }
+                            break;
+                        case 's':
+                            if (!inQuote)
+                            {
+                                Debug.Assert((field == 3 && sb.Length == 0) || field == 4, "field == 3 || field == 4, Bug in DateTimeFormatInfo.FullTimeSpan[Positive|Negative]Pattern");
+                                field = 4; // SecondFractionSep
+                                ss++;
+                            }
+                            break;
+                        case 'f':
+                        case 'F':
+                            if (!inQuote)
+                            {
+                                Debug.Assert((field == 4 && sb.Length == 0) || field == 5, "field == 4 || field == 5, Bug in DateTimeFormatInfo.FullTimeSpan[Positive|Negative]Pattern");
+                                field = 5; // End
+                                ff++;
+                            }
+                            break;
+                        default:
+                            sb.Append(format[i]);
+                            break;
+                    }
+                }
+
+                Debug.Assert(field == 5);
+                AppCompatLiteral = MinuteSecondSep + SecondFractionSep;
+
+                Debug.Assert(0 < dd && dd < 3, "0 < dd && dd < 3, Bug in System.Globalization.DateTimeFormatInfo.FullTimeSpan[Positive|Negative]Pattern");
+                Debug.Assert(0 < hh && hh < 3, "0 < hh && hh < 3, Bug in System.Globalization.DateTimeFormatInfo.FullTimeSpan[Positive|Negative]Pattern");
+                Debug.Assert(0 < mm && mm < 3, "0 < mm && mm < 3, Bug in System.Globalization.DateTimeFormatInfo.FullTimeSpan[Positive|Negative]Pattern");
+                Debug.Assert(0 < ss && ss < 3, "0 < ss && ss < 3, Bug in System.Globalization.DateTimeFormatInfo.FullTimeSpan[Positive|Negative]Pattern");
+                Debug.Assert(0 < ff && ff < 8, "0 < ff && ff < 8, Bug in System.Globalization.DateTimeFormatInfo.FullTimeSpan[Positive|Negative]Pattern");
+
+                if (useInvariantFieldLengths)
+                {
+                    dd = 2;
+                    hh = 2;
+                    mm = 2;
+                    ss = 2;
+                    ff = DateTimeFormat.MaxSecondsFractionDigits;
+                }
+                else
+                {
+                    if (dd < 1 || dd > 2) dd = 2;   // The DTFI property has a problem. let's try to make the best of the situation.
+                    if (hh < 1 || hh > 2) hh = 2;
+                    if (mm < 1 || mm > 2) mm = 2;
+                    if (ss < 1 || ss > 2) ss = 2;
+                    if (ff < 1 || ff > 7) ff = 7;
+                }
+                StringBuilderCache.Release(sb);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/TimeSpanParse.cs b/src/System.Private.CoreLib/shared/System/Globalization/TimeSpanParse.cs
new file mode 100644
index 0000000000..b1e104550e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/TimeSpanParse.cs
@@ -0,0 +1,1704 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////
+//
+//  Purpose:  Used by TimeSpan to parse a time interval string.
+//
+//  Standard Format:
+//  -=-=-=-=-=-=-=-
+//  "c":  Constant format.  [-][d'.']hh':'mm':'ss['.'fffffff]  
+//  Not culture sensitive.  Default format (and null/empty format string) map to this format.
+//
+//  "g":  General format, short:  [-][d':']h':'mm':'ss'.'FFFFFFF  
+//  Only print what's needed.  Localized (if you want Invariant, pass in Invariant).
+//  The fractional seconds separator is localized, equal to the culture's DecimalSeparator.
+//
+//  "G":  General format, long:  [-]d':'hh':'mm':'ss'.'fffffff
+//  Always print days and 7 fractional digits.  Localized (if you want Invariant, pass in Invariant).
+//  The fractional seconds separator is localized, equal to the culture's DecimalSeparator.
+//
+//  * "TryParseTimeSpan" is the main method for Parse/TryParse
+//
+//  - TimeSpanTokenizer.GetNextToken() is used to split the input string into number and literal tokens.
+//  - TimeSpanRawInfo.ProcessToken() adds the next token into the parsing intermediary state structure
+//  - ProcessTerminalState() uses the fully initialized TimeSpanRawInfo to find a legal parse match.
+//    The terminal states are attempted as follows:
+//    foreach (+InvariantPattern, -InvariantPattern, +LocalizedPattern, -LocalizedPattern) try
+//       1 number  => d
+//       2 numbers => h:m
+//       3 numbers => h:m:s     | d.h:m   | h:m:.f
+//       4 numbers => h:m:s.f   | d.h:m:s | d.h:m:.f
+//       5 numbers => d.h:m:s.f
+//
+// Custom Format:
+// -=-=-=-=-=-=-=
+//
+// * "TryParseExactTimeSpan" is the main method for ParseExact/TryParseExact methods
+// * "TryParseExactMultipleTimeSpan" is the main method for ParseExact/TryparseExact
+//    methods that take a string[] of formats
+//
+// - For single-letter formats "TryParseTimeSpan" is called (see above)
+// - For multi-letter formats "TryParseByFormat" is called
+// - TryParseByFormat uses helper methods (ParseExactLiteral, ParseExactDigits, etc)
+//   which drive the underlying TimeSpanTokenizer.  However, unlike standard formatting which
+//   operates on whole-tokens, ParseExact operates at the character-level.  As such, 
+//   TimeSpanTokenizer.NextChar and TimeSpanTokenizer.BackOne() are called directly. 
+//
+////////////////////////////////////////////////////////////////////////////
+
+using System.Diagnostics;
+using System.Text;
+
+namespace System.Globalization
+{
+    internal static class TimeSpanParse
+    {
+        private const int MaxFractionDigits = 7;
+        private const int MaxDays = 10675199;
+        private const int MaxHours = 23;
+        private const int MaxMinutes = 59;
+        private const int MaxSeconds = 59;
+        private const int MaxFraction = 9999999;
+
+        [Flags]
+        private enum TimeSpanStandardStyles : byte
+        {
+            // Standard Format Styles
+            None = 0x00000000,
+            Invariant = 0x00000001, //Allow Invariant Culture
+            Localized = 0x00000002, //Allow Localized Culture
+            RequireFull = 0x00000004, //Require the input to be in DHMSF format
+            Any = Invariant | Localized,
+        }
+
+        // TimeSpan Token Types
+        private enum TTT : byte
+        {
+            None = 0,         // None of the TimeSpanToken fields are set
+            End = 1,          // '\0'
+            Num = 2,          // Number
+            Sep = 3,          // literal
+            NumOverflow = 4,  // Number that overflowed
+        }
+
+        private ref struct TimeSpanToken
+        {
+            internal TTT _ttt;
+            internal int _num;                // Store the number that we are parsing (if any)
+            internal int _zeroes;             // Store the number of leading zeroes (if any)
+            internal ReadOnlySpan<char> _sep; // Store the literal that we are parsing (if any)
+
+            public TimeSpanToken(TTT type) : this(type, 0, 0, default(ReadOnlySpan<char>)) { }
+
+            public TimeSpanToken(int number) : this(TTT.Num, number, 0, default(ReadOnlySpan<char>)) { }
+
+            public TimeSpanToken(int number, int leadingZeroes) : this(TTT.Num, number, leadingZeroes, default(ReadOnlySpan<char>)) { }
+
+            public TimeSpanToken(TTT type, int number, int leadingZeroes, ReadOnlySpan<char> separator)
+            {
+                _ttt = type;
+                _num = number;
+                _zeroes = leadingZeroes;
+                _sep = separator;
+            }
+
+            public bool IsInvalidFraction()
+            {
+                Debug.Assert(_ttt == TTT.Num);
+                Debug.Assert(_num > -1);
+
+                if (_num > MaxFraction || _zeroes > MaxFractionDigits)
+                    return true;
+
+                if (_num == 0 || _zeroes == 0)
+                    return false;
+
+                // num > 0 && zeroes > 0 && num <= maxValue && zeroes <= maxPrecision
+                return _num >= MaxFraction / Pow10(_zeroes - 1);
+            }
+        }
+
+        private ref struct TimeSpanTokenizer
+        {
+            private ReadOnlySpan<char> _value;
+            private int _pos;
+
+            internal TimeSpanTokenizer(ReadOnlySpan<char> input) : this(input, 0) { }
+
+            internal TimeSpanTokenizer(ReadOnlySpan<char> input, int startPosition)
+            {
+                _value = input;
+                _pos = startPosition;
+            }
+
+            /// <summary>Returns the next token in the input string</summary>
+            /// <remarks>Used by the parsing routines that operate on standard-formats.</remarks>
+            internal TimeSpanToken GetNextToken()
+            {
+                // Get the position of the next character to be processed.  If there is no
+                // next character, we're at the end.
+                int pos = _pos;
+                Debug.Assert(pos > -1);
+                if (pos >= _value.Length)
+                {
+                    return new TimeSpanToken(TTT.End);
+                }
+
+                // Now retrieve that character. If it's a digit, we're processing a number.
+                int num = _value[pos] - '0';
+                if ((uint)num <= 9)
+                {
+                    int zeroes = 0;
+                    if (num == 0)
+                    {
+                        // Read all leading zeroes.
+                        zeroes = 1;
+                        while (true)
+                        {
+                            int digit;
+                            if (++_pos >= _value.Length || (uint)(digit = _value[_pos] - '0') > 9)
+                            {
+                                return new TimeSpanToken(TTT.Num, 0, zeroes, default(ReadOnlySpan<char>));
+                            }
+
+                            if (digit == 0)
+                            {
+                                zeroes++;
+                                continue;
+                            }
+
+                            num = digit;
+                            break;
+                        }
+                    }
+
+                    // Continue to read as long as we're reading digits.
+                    while (++_pos < _value.Length)
+                    {
+                        int digit = _value[_pos] - '0';
+                        if ((uint)digit > 9)
+                        {
+                            break;
+                        }
+
+                        num = num * 10 + digit;
+                        if ((num & 0xF0000000) != 0)
+                        {
+                            return new TimeSpanToken(TTT.NumOverflow);
+                        }
+                    }
+
+                    return new TimeSpanToken(TTT.Num, num, zeroes, default(ReadOnlySpan<char>));
+                }
+
+                // Otherwise, we're processing a separator, and we've already processed the first
+                // character of it.  Continue processing characters as long as they're not digits.
+                int length = 1;
+                while (true)
+                {
+                    if (++_pos >= _value.Length || (uint)(_value[_pos] - '0') <= 9)
+                    {
+                        break;
+                    }
+                    length++;
+                }
+
+                // Return the separator.
+                return new TimeSpanToken(TTT.Sep, 0, 0, _value.Slice(pos, length));
+            }
+
+            internal bool EOL => _pos >= (_value.Length - 1);
+
+            internal void BackOne()
+            {
+                if (_pos > 0) --_pos;
+            }
+
+            internal char NextChar
+            {
+                get
+                {
+                    int pos = ++_pos;
+                    return (uint)pos < (uint)_value.Length ?
+                        _value[pos] :
+                        (char)0;
+                }
+            }
+        }
+
+        /// <summary>Stores intermediary parsing state for the standard formats.</summary>
+        private ref struct TimeSpanRawInfo
+        {
+            internal TimeSpanFormat.FormatLiterals PositiveInvariant => TimeSpanFormat.PositiveInvariantFormatLiterals;
+            internal TimeSpanFormat.FormatLiterals NegativeInvariant => TimeSpanFormat.NegativeInvariantFormatLiterals;
+
+            internal TimeSpanFormat.FormatLiterals PositiveLocalized
+            {
+                get
+                {
+                    if (!_posLocInit)
+                    {
+                        _posLoc = new TimeSpanFormat.FormatLiterals();
+                        _posLoc.Init(_fullPosPattern, false);
+                        _posLocInit = true;
+                    }
+                    return _posLoc;
+                }
+            }
+
+            internal TimeSpanFormat.FormatLiterals NegativeLocalized
+            {
+                get
+                {
+                    if (!_negLocInit)
+                    {
+                        _negLoc = new TimeSpanFormat.FormatLiterals();
+                        _negLoc.Init(_fullNegPattern, false);
+                        _negLocInit = true;
+                    }
+                    return _negLoc;
+                }
+            }
+
+            internal bool FullAppCompatMatch(TimeSpanFormat.FormatLiterals pattern) =>
+                _sepCount == 5
+                && _numCount == 4
+                && _literals0.EqualsOrdinal(pattern.Start)
+                && _literals1.EqualsOrdinal(pattern.DayHourSep)
+                && _literals2.EqualsOrdinal(pattern.HourMinuteSep)
+                && _literals3.EqualsOrdinal(pattern.AppCompatLiteral)
+                && _literals4.EqualsOrdinal(pattern.End);
+
+            internal bool PartialAppCompatMatch(TimeSpanFormat.FormatLiterals pattern) =>
+                _sepCount == 4
+                && _numCount == 3
+                && _literals0.EqualsOrdinal(pattern.Start)
+                && _literals1.EqualsOrdinal(pattern.HourMinuteSep)
+                && _literals2.EqualsOrdinal(pattern.AppCompatLiteral)
+                && _literals3.EqualsOrdinal(pattern.End);
+
+            /// <summary>DHMSF (all values matched)</summary>
+            internal bool FullMatch(TimeSpanFormat.FormatLiterals pattern) =>
+                _sepCount == MaxLiteralTokens
+                && _numCount == MaxNumericTokens
+                && _literals0.EqualsOrdinal(pattern.Start)
+                && _literals1.EqualsOrdinal(pattern.DayHourSep)
+                && _literals2.EqualsOrdinal(pattern.HourMinuteSep)
+                && _literals3.EqualsOrdinal(pattern.MinuteSecondSep)
+                && _literals4.EqualsOrdinal(pattern.SecondFractionSep)
+                && _literals5.EqualsOrdinal(pattern.End);
+
+            /// <summary>D (no hours, minutes, seconds, or fractions)</summary>
+            internal bool FullDMatch(TimeSpanFormat.FormatLiterals pattern) =>
+                _sepCount == 2
+                && _numCount == 1
+                && _literals0.EqualsOrdinal(pattern.Start)
+                && _literals1.EqualsOrdinal(pattern.End);
+
+            /// <summary>HM (no days, seconds, or fractions)</summary>
+            internal bool FullHMMatch(TimeSpanFormat.FormatLiterals pattern) =>
+                _sepCount == 3
+                && _numCount == 2
+                && _literals0.EqualsOrdinal(pattern.Start)
+                && _literals1.EqualsOrdinal(pattern.HourMinuteSep)
+                && _literals2.EqualsOrdinal(pattern.End);
+
+            /// <summary>DHM (no seconds or fraction)</summary>
+            internal bool FullDHMMatch(TimeSpanFormat.FormatLiterals pattern) =>
+                _sepCount == 4
+                && _numCount == 3
+                && _literals0.EqualsOrdinal(pattern.Start)
+                && _literals1.EqualsOrdinal(pattern.DayHourSep)
+                && _literals2.EqualsOrdinal(pattern.HourMinuteSep)
+                && _literals3.EqualsOrdinal(pattern.End);
+
+            /// <summary>HMS (no days or fraction)</summary>
+            internal bool FullHMSMatch(TimeSpanFormat.FormatLiterals pattern) =>
+                _sepCount == 4
+                && _numCount == 3
+                && _literals0.EqualsOrdinal(pattern.Start)
+                && _literals1.EqualsOrdinal(pattern.HourMinuteSep)
+                && _literals2.EqualsOrdinal(pattern.MinuteSecondSep)
+                && _literals3.EqualsOrdinal(pattern.End);
+
+            /// <summary>DHMS (no fraction)</summary>
+            internal bool FullDHMSMatch(TimeSpanFormat.FormatLiterals pattern) =>
+                _sepCount == 5
+                && _numCount == 4
+                && _literals0.EqualsOrdinal(pattern.Start)
+                && _literals1.EqualsOrdinal(pattern.DayHourSep)
+                && _literals2.EqualsOrdinal(pattern.HourMinuteSep)
+                && _literals3.EqualsOrdinal(pattern.MinuteSecondSep)
+                && _literals4.EqualsOrdinal(pattern.End);
+
+            /// <summary>HMSF (no days)</summary>
+            internal bool FullHMSFMatch(TimeSpanFormat.FormatLiterals pattern) =>
+                _sepCount == 5
+                && _numCount == 4
+                && _literals0.EqualsOrdinal(pattern.Start)
+                && _literals1.EqualsOrdinal(pattern.HourMinuteSep)
+                && _literals2.EqualsOrdinal(pattern.MinuteSecondSep)
+                && _literals3.EqualsOrdinal(pattern.SecondFractionSep)
+                && _literals4.EqualsOrdinal(pattern.End);
+
+            internal TTT _lastSeenTTT;
+            internal int _tokenCount;
+            internal int _sepCount;
+            internal int _numCount;
+
+            private TimeSpanFormat.FormatLiterals _posLoc;
+            private TimeSpanFormat.FormatLiterals _negLoc;
+            private bool _posLocInit;
+            private bool _negLocInit;
+            private string _fullPosPattern;
+            private string _fullNegPattern;
+
+            private const int MaxTokens = 11;
+            private const int MaxLiteralTokens = 6;
+            private const int MaxNumericTokens = 5;
+
+            internal TimeSpanToken _numbers0, _numbers1, _numbers2, _numbers3, _numbers4; // MaxNumbericTokens = 5
+            internal ReadOnlySpan<char> _literals0, _literals1, _literals2, _literals3, _literals4, _literals5; // MaxLiteralTokens=6
+
+            internal void Init(DateTimeFormatInfo dtfi)
+            {
+                Debug.Assert(dtfi != null);
+
+                _lastSeenTTT = TTT.None;
+                _tokenCount = 0;
+                _sepCount = 0;
+                _numCount = 0;
+
+                _fullPosPattern = dtfi.FullTimeSpanPositivePattern;
+                _fullNegPattern = dtfi.FullTimeSpanNegativePattern;
+                _posLocInit = false;
+                _negLocInit = false;
+            }
+
+            internal bool ProcessToken(ref TimeSpanToken tok, ref TimeSpanResult result)
+            {
+                switch (tok._ttt)
+                {
+                    case TTT.Num:
+                        if ((_tokenCount == 0 && !AddSep(default(ReadOnlySpan<char>), ref result)) || !AddNum(tok, ref result))
+                        {
+                            return false;
+                        }
+                        break;
+
+                    case TTT.Sep:
+                        if (!AddSep(tok._sep, ref result))
+                        {
+                            return false;
+                        }
+                        break;
+
+                    case TTT.NumOverflow:
+                        return result.SetOverflowFailure();
+
+                    default:
+                        // Some unknown token or a repeat token type in the input
+                        return result.SetBadTimeSpanFailure();
+                }
+
+                _lastSeenTTT = tok._ttt;
+                Debug.Assert(_tokenCount == (_sepCount + _numCount), "tokenCount == (SepCount + NumCount)");
+                return true;
+            }
+
+            private bool AddSep(ReadOnlySpan<char> sep, ref TimeSpanResult result)
+            {
+                if (_sepCount >= MaxLiteralTokens || _tokenCount >= MaxTokens)
+                {
+                    return result.SetBadTimeSpanFailure();
+                }
+
+                switch (_sepCount++)
+                {
+                    case 0: _literals0 = sep; break;
+                    case 1: _literals1 = sep; break;
+                    case 2: _literals2 = sep; break;
+                    case 3: _literals3 = sep; break;
+                    case 4: _literals4 = sep; break;
+                    default: _literals5 = sep; break;
+                }
+
+                _tokenCount++;
+                return true;
+            }
+            private bool AddNum(TimeSpanToken num, ref TimeSpanResult result)
+            {
+                if (_numCount >= MaxNumericTokens || _tokenCount >= MaxTokens)
+                {
+                    return result.SetBadTimeSpanFailure();
+                }
+
+                switch (_numCount++)
+                {
+                    case 0: _numbers0 = num; break;
+                    case 1: _numbers1 = num; break;
+                    case 2: _numbers2 = num; break;
+                    case 3: _numbers3 = num; break;
+                    default: _numbers4 = num; break;
+                }
+
+                _tokenCount++;
+                return true;
+            }
+        }
+
+        /// <summary>Store the result of the parsing.</summary>
+        private ref struct TimeSpanResult
+        {
+            internal TimeSpan parsedTimeSpan;
+            private readonly bool _throwOnFailure;
+            private readonly ReadOnlySpan<char> _originalTimeSpanString;
+
+            internal TimeSpanResult(bool throwOnFailure, ReadOnlySpan<char> originalTimeSpanString)
+            {
+                parsedTimeSpan = default(TimeSpan);
+                _throwOnFailure = throwOnFailure;
+                _originalTimeSpanString = originalTimeSpanString;
+            }
+
+            internal bool SetNoFormatSpecifierFailure()
+            {
+                if (!_throwOnFailure)
+                {
+                    return false;
+                }
+
+                throw new FormatException(SR.Format_NoFormatSpecifier);
+            }
+
+            internal bool SetBadQuoteFailure(char failingCharacter)
+            {
+                if (!_throwOnFailure)
+                {
+                    return false;
+                }
+
+                throw new FormatException(SR.Format(SR.Format_BadQuote, failingCharacter));
+            }
+
+            internal bool SetInvalidStringFailure()
+            {
+                if (!_throwOnFailure)
+                {
+                    return false;
+                }
+
+                throw new FormatException(SR.Format_InvalidString);
+            }
+
+            internal bool SetArgumentNullFailure(string argumentName)
+            {
+                if (!_throwOnFailure)
+                {
+                    return false;
+                }
+
+                Debug.Assert(argumentName != null);
+                throw new ArgumentNullException(argumentName, SR.ArgumentNull_String);
+            }
+
+            internal bool SetOverflowFailure()
+            {
+                if (!_throwOnFailure)
+                {
+                    return false;
+                }
+
+                throw new OverflowException(SR.Format(SR.Overflow_TimeSpanElementTooLarge, new string(_originalTimeSpanString)));
+            }
+
+            internal bool SetBadTimeSpanFailure()
+            {
+                if (!_throwOnFailure)
+                {
+                    return false;
+                }
+
+                throw new FormatException(SR.Format(SR.Format_BadTimeSpan, new string(_originalTimeSpanString)));
+            }
+
+            internal bool SetBadFormatSpecifierFailure(char? formatSpecifierCharacter = null)
+            {
+                if (!_throwOnFailure)
+                {
+                    return false;
+                }
+
+                throw new FormatException(SR.Format(SR.Format_BadFormatSpecifier, formatSpecifierCharacter));
+            }
+        }
+
+        internal static long Pow10(int pow)
+        {
+            switch (pow)
+            {
+                case 0:  return 1;
+                case 1:  return 10;
+                case 2:  return 100;
+                case 3:  return 1000;
+                case 4:  return 10000;
+                case 5:  return 100000;
+                case 6:  return 1000000;
+                case 7:  return 10000000;
+                default: return (long)Math.Pow(10, pow);
+            }
+        }
+
+        private static bool TryTimeToTicks(bool positive, TimeSpanToken days, TimeSpanToken hours, TimeSpanToken minutes, TimeSpanToken seconds, TimeSpanToken fraction, out long result)
+        {
+            if (days._num > MaxDays ||
+                hours._num > MaxHours ||
+                minutes._num > MaxMinutes ||
+                seconds._num > MaxSeconds ||
+                fraction.IsInvalidFraction())
+            {
+                result = 0;
+                return false;
+            }
+
+            long ticks = ((long)days._num * 3600 * 24 + (long)hours._num * 3600 + (long)minutes._num * 60 + seconds._num) * 1000;
+            if (ticks > InternalGlobalizationHelper.MaxMilliSeconds || ticks < InternalGlobalizationHelper.MinMilliSeconds)
+            {
+                result = 0;
+                return false;
+            }
+
+            // Normalize the fraction component
+            //
+            // string representation => (zeroes,num) => resultant fraction ticks
+            // ---------------------    ------------    ------------------------
+            // ".9999999"            => (0,9999999)  => 9,999,999 ticks (same as constant maxFraction)
+            // ".1"                  => (0,1)        => 1,000,000 ticks
+            // ".01"                 => (1,1)        =>   100,000 ticks
+            // ".001"                => (2,1)        =>    10,000 ticks
+            long f = fraction._num;
+            if (f != 0)
+            {
+                long lowerLimit = InternalGlobalizationHelper.TicksPerTenthSecond;
+                if (fraction._zeroes > 0)
+                {
+                    long divisor = Pow10(fraction._zeroes);
+                    lowerLimit = lowerLimit / divisor;
+                }
+
+                while (f < lowerLimit)
+                {
+                    f *= 10;
+                }
+            }
+
+            result = ticks * TimeSpan.TicksPerMillisecond + f;
+            if (positive && result < 0)
+            {
+                result = 0;
+                return false;
+            }
+
+            return true;
+        }
+
+        internal static TimeSpan Parse(ReadOnlySpan<char> input, IFormatProvider formatProvider)
+        {
+            var parseResult = new TimeSpanResult(throwOnFailure: true, originalTimeSpanString: input);
+            bool success = TryParseTimeSpan(input, TimeSpanStandardStyles.Any, formatProvider, ref parseResult);
+            Debug.Assert(success, "Should have thrown on failure");
+            return parseResult.parsedTimeSpan;
+        }
+
+        internal static bool TryParse(ReadOnlySpan<char> input, IFormatProvider formatProvider, out TimeSpan result)
+        {
+            var parseResult = new TimeSpanResult(throwOnFailure: false, originalTimeSpanString: input);
+
+            if (TryParseTimeSpan(input, TimeSpanStandardStyles.Any, formatProvider, ref parseResult))
+            {
+                result = parseResult.parsedTimeSpan;
+                return true;
+            }
+
+            result = default(TimeSpan);
+            return false;
+        }
+
+        internal static TimeSpan ParseExact(ReadOnlySpan<char> input, ReadOnlySpan<char> format, IFormatProvider formatProvider, TimeSpanStyles styles)
+        {
+            var parseResult = new TimeSpanResult(throwOnFailure: true, originalTimeSpanString: input);
+            bool success = TryParseExactTimeSpan(input, format, formatProvider, styles, ref parseResult);
+            Debug.Assert(success, "Should have thrown on failure");
+            return parseResult.parsedTimeSpan;
+        }
+
+        internal static bool TryParseExact(ReadOnlySpan<char> input, ReadOnlySpan<char> format, IFormatProvider formatProvider, TimeSpanStyles styles, out TimeSpan result)
+        {
+            var parseResult = new TimeSpanResult(throwOnFailure: false, originalTimeSpanString: input);
+
+            if (TryParseExactTimeSpan(input, format, formatProvider, styles, ref parseResult))
+            {
+                result = parseResult.parsedTimeSpan;
+                return true;
+            }
+
+            result = default(TimeSpan);
+            return false;
+        }
+
+        internal static TimeSpan ParseExactMultiple(ReadOnlySpan<char> input, string[] formats, IFormatProvider formatProvider, TimeSpanStyles styles)
+        {
+            var parseResult = new TimeSpanResult(throwOnFailure: true, originalTimeSpanString: input);
+            bool success = TryParseExactMultipleTimeSpan(input, formats, formatProvider, styles, ref parseResult);
+            Debug.Assert(success, "Should have thrown on failure");
+            return parseResult.parsedTimeSpan;
+        }
+
+        internal static bool TryParseExactMultiple(ReadOnlySpan<char> input, string[] formats, IFormatProvider formatProvider, TimeSpanStyles styles, out TimeSpan result)
+        {
+            var parseResult = new TimeSpanResult(throwOnFailure: false, originalTimeSpanString: input);
+
+            if (TryParseExactMultipleTimeSpan(input, formats, formatProvider, styles, ref parseResult))
+            {
+                result = parseResult.parsedTimeSpan;
+                return true;
+            }
+
+            result = default(TimeSpan);
+            return false;
+        }
+
+        /// <summary>Common private Parse method called by both Parse and TryParse.</summary>
+        private static bool TryParseTimeSpan(ReadOnlySpan<char> input, TimeSpanStandardStyles style, IFormatProvider formatProvider, ref TimeSpanResult result)
+        {
+            input = input.Trim();
+            if (input.IsEmpty)
+            {
+                return result.SetBadTimeSpanFailure();
+            }
+
+            var tokenizer = new TimeSpanTokenizer(input);
+
+            var raw = new TimeSpanRawInfo();
+            raw.Init(DateTimeFormatInfo.GetInstance(formatProvider));
+
+            TimeSpanToken tok = tokenizer.GetNextToken();
+
+            // The following loop will break out when we reach the end of the str or
+            // when we can determine that the input is invalid.
+            while (tok._ttt != TTT.End)
+            {
+                if (!raw.ProcessToken(ref tok, ref result))
+                {
+                    return result.SetBadTimeSpanFailure();
+                }
+                tok = tokenizer.GetNextToken();
+            }
+            Debug.Assert(tokenizer.EOL);
+
+            if (!ProcessTerminalState(ref raw, style, ref result))
+            {
+                return result.SetBadTimeSpanFailure();
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// Validate the terminal state of a standard format parse.
+        /// Sets result.parsedTimeSpan on success.
+        /// Calculates the resultant TimeSpan from the TimeSpanRawInfo.
+        /// </summary>
+        /// <remarks>
+        /// try => +InvariantPattern, -InvariantPattern, +LocalizedPattern, -LocalizedPattern
+        /// 1) Verify Start matches
+        /// 2) Verify End matches
+        /// 3) 1 number  => d
+        ///    2 numbers => h:m
+        ///    3 numbers => h:m:s | d.h:m | h:m:.f
+        ///    4 numbers => h:m:s.f | d.h:m:s | d.h:m:.f
+        ///    5 numbers => d.h:m:s.f
+        /// </remarks>
+        private static bool ProcessTerminalState(ref TimeSpanRawInfo raw, TimeSpanStandardStyles style, ref TimeSpanResult result)
+        {
+            if (raw._lastSeenTTT == TTT.Num)
+            {
+                TimeSpanToken tok = new TimeSpanToken();
+                tok._ttt = TTT.Sep;
+                if (!raw.ProcessToken(ref tok, ref result))
+                {
+                    return result.SetBadTimeSpanFailure();
+                }
+            }
+
+            switch (raw._numCount)
+            {
+                case 1: return ProcessTerminal_D(ref raw, style, ref result);
+                case 2: return ProcessTerminal_HM(ref raw, style, ref result);
+                case 3: return ProcessTerminal_HM_S_D(ref raw, style, ref result);
+                case 4: return ProcessTerminal_HMS_F_D(ref raw, style, ref result);
+                case 5: return ProcessTerminal_DHMSF(ref raw, style, ref result);
+                default: return result.SetBadTimeSpanFailure();
+            }
+        }
+
+        /// <summary>Validate the 5-number "Days.Hours:Minutes:Seconds.Fraction" terminal case.</summary>
+        private static bool ProcessTerminal_DHMSF(ref TimeSpanRawInfo raw, TimeSpanStandardStyles style, ref TimeSpanResult result)
+        {
+            if (raw._sepCount != 6)
+            {
+                return result.SetBadTimeSpanFailure();
+            }
+            Debug.Assert(raw._numCount == 5);
+
+            bool inv = (style & TimeSpanStandardStyles.Invariant) != 0;
+            bool loc = (style & TimeSpanStandardStyles.Localized) != 0;
+            bool positive = false;
+            bool match = false;
+
+            if (inv)
+            {
+                if (raw.FullMatch(raw.PositiveInvariant))
+                {
+                    match = true;
+                    positive = true;
+                }
+                if (!match && raw.FullMatch(raw.NegativeInvariant))
+                {
+                    match = true;
+                    positive = false;
+                }
+            }
+
+            if (loc)
+            {
+                if (!match && raw.FullMatch(raw.PositiveLocalized))
+                {
+                    match = true;
+                    positive = true;
+                }
+                if (!match && raw.FullMatch(raw.NegativeLocalized))
+                {
+                    match = true;
+                    positive = false;
+                }
+            }
+
+            if (match)
+            {
+                long ticks;
+
+                if (!TryTimeToTicks(positive, raw._numbers0, raw._numbers1, raw._numbers2, raw._numbers3, raw._numbers4, out ticks))
+                {
+                    return result.SetOverflowFailure();
+                }
+
+                if (!positive)
+                {
+                    ticks = -ticks;
+                    if (ticks > 0)
+                    {
+                        return result.SetOverflowFailure();
+                    }
+                }
+
+                result.parsedTimeSpan._ticks = ticks;
+                return true;
+            }
+
+            return result.SetBadTimeSpanFailure();
+        }
+
+
+        /// <summary>
+        /// Validate the ambiguous 4-number "Hours:Minutes:Seconds.Fraction", "Days.Hours:Minutes:Seconds",
+        /// or "Days.Hours:Minutes:.Fraction" terminal case.
+        /// </summary>
+        private static bool ProcessTerminal_HMS_F_D(ref TimeSpanRawInfo raw, TimeSpanStandardStyles style, ref TimeSpanResult result)
+        {
+            if (raw._sepCount != 5 || (style & TimeSpanStandardStyles.RequireFull) != 0)
+            {
+                return result.SetBadTimeSpanFailure();
+            }
+            Debug.Assert(raw._numCount == 4);
+
+            bool inv = ((style & TimeSpanStandardStyles.Invariant) != 0);
+            bool loc = ((style & TimeSpanStandardStyles.Localized) != 0);
+
+            long ticks = 0;
+            bool positive = false, match = false, overflow = false;
+            var zero = new TimeSpanToken(0);
+
+            if (inv)
+            {
+                if (raw.FullHMSFMatch(raw.PositiveInvariant))
+                {
+                    positive = true;
+                    match = TryTimeToTicks(positive, zero, raw._numbers0, raw._numbers1, raw._numbers2, raw._numbers3, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullDHMSMatch(raw.PositiveInvariant))
+                {
+                    positive = true;
+                    match = TryTimeToTicks(positive, raw._numbers0, raw._numbers1, raw._numbers2, raw._numbers3, zero, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullAppCompatMatch(raw.PositiveInvariant))
+                {
+                    positive = true;
+                    match = TryTimeToTicks(positive, raw._numbers0, raw._numbers1, raw._numbers2, zero, raw._numbers3, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullHMSFMatch(raw.NegativeInvariant))
+                {
+                    positive = false;
+                    match = TryTimeToTicks(positive, zero, raw._numbers0, raw._numbers1, raw._numbers2, raw._numbers3, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullDHMSMatch(raw.NegativeInvariant))
+                {
+                    positive = false;
+                    match = TryTimeToTicks(positive, raw._numbers0, raw._numbers1, raw._numbers2, raw._numbers3, zero, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullAppCompatMatch(raw.NegativeInvariant))
+                {
+                    positive = false;
+                    match = TryTimeToTicks(positive, raw._numbers0, raw._numbers1, raw._numbers2, zero, raw._numbers3, out ticks);
+                    overflow = overflow || !match;
+                }
+            }
+
+            if (loc)
+            {
+                if (!match && raw.FullHMSFMatch(raw.PositiveLocalized))
+                {
+                    positive = true;
+                    match = TryTimeToTicks(positive, zero, raw._numbers0, raw._numbers1, raw._numbers2, raw._numbers3, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullDHMSMatch(raw.PositiveLocalized))
+                {
+                    positive = true;
+                    match = TryTimeToTicks(positive, raw._numbers0, raw._numbers1, raw._numbers2, raw._numbers3, zero, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullAppCompatMatch(raw.PositiveLocalized))
+                {
+                    positive = true;
+                    match = TryTimeToTicks(positive, raw._numbers0, raw._numbers1, raw._numbers2, zero, raw._numbers3, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullHMSFMatch(raw.NegativeLocalized))
+                {
+                    positive = false;
+                    match = TryTimeToTicks(positive, zero, raw._numbers0, raw._numbers1, raw._numbers2, raw._numbers3, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullDHMSMatch(raw.NegativeLocalized))
+                {
+                    positive = false;
+                    match = TryTimeToTicks(positive, raw._numbers0, raw._numbers1, raw._numbers2, raw._numbers3, zero, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullAppCompatMatch(raw.NegativeLocalized))
+                {
+                    positive = false;
+                    match = TryTimeToTicks(positive, raw._numbers0, raw._numbers1, raw._numbers2, zero, raw._numbers3, out ticks);
+                    overflow = overflow || !match;
+                }
+            }
+
+            if (match)
+            {
+                if (!positive)
+                {
+                    ticks = -ticks;
+                    if (ticks > 0)
+                    {
+                        return result.SetOverflowFailure();
+                    }
+                }
+
+                result.parsedTimeSpan._ticks = ticks;
+                return true;
+            }
+
+            return overflow ?
+                result.SetOverflowFailure() : // we found at least one literal pattern match but the numbers just didn't fit
+                result.SetBadTimeSpanFailure(); // we couldn't find a thing
+        }
+
+        /// <summary>Validate the ambiguous 3-number "Hours:Minutes:Seconds", "Days.Hours:Minutes", or "Hours:Minutes:.Fraction" terminal case.</summary>
+        private static bool ProcessTerminal_HM_S_D(ref TimeSpanRawInfo raw, TimeSpanStandardStyles style, ref TimeSpanResult result)
+        {
+            if (raw._sepCount != 4 || (style & TimeSpanStandardStyles.RequireFull) != 0)
+            {
+                return result.SetBadTimeSpanFailure();
+            }
+            Debug.Assert(raw._numCount == 3);
+
+            bool inv = ((style & TimeSpanStandardStyles.Invariant) != 0);
+            bool loc = ((style & TimeSpanStandardStyles.Localized) != 0);
+
+            bool positive = false, match = false, overflow = false;
+            var zero = new TimeSpanToken(0);
+            long ticks = 0;
+
+            if (inv)
+            {
+                if (raw.FullHMSMatch(raw.PositiveInvariant))
+                {
+                    positive = true;
+                    match = TryTimeToTicks(positive, zero, raw._numbers0, raw._numbers1, raw._numbers2, zero, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullDHMMatch(raw.PositiveInvariant))
+                {
+                    positive = true;
+                    match = TryTimeToTicks(positive, raw._numbers0, raw._numbers1, raw._numbers2, zero, zero, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.PartialAppCompatMatch(raw.PositiveInvariant))
+                {
+                    positive = true;
+                    match = TryTimeToTicks(positive, zero, raw._numbers0, raw._numbers1, zero, raw._numbers2, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullHMSMatch(raw.NegativeInvariant))
+                {
+                    positive = false;
+                    match = TryTimeToTicks(positive, zero, raw._numbers0, raw._numbers1, raw._numbers2, zero, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullDHMMatch(raw.NegativeInvariant))
+                {
+                    positive = false;
+                    match = TryTimeToTicks(positive, raw._numbers0, raw._numbers1, raw._numbers2, zero, zero, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.PartialAppCompatMatch(raw.NegativeInvariant))
+                {
+                    positive = false;
+                    match = TryTimeToTicks(positive, zero, raw._numbers0, raw._numbers1, zero, raw._numbers2, out ticks);
+                    overflow = overflow || !match;
+                }
+            }
+
+            if (loc)
+            {
+                if (!match && raw.FullHMSMatch(raw.PositiveLocalized))
+                {
+                    positive = true;
+                    match = TryTimeToTicks(positive, zero, raw._numbers0, raw._numbers1, raw._numbers2, zero, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullDHMMatch(raw.PositiveLocalized))
+                {
+                    positive = true;
+                    match = TryTimeToTicks(positive, raw._numbers0, raw._numbers1, raw._numbers2, zero, zero, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.PartialAppCompatMatch(raw.PositiveLocalized))
+                {
+                    positive = true;
+                    match = TryTimeToTicks(positive, zero, raw._numbers0, raw._numbers1, zero, raw._numbers2, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullHMSMatch(raw.NegativeLocalized))
+                {
+                    positive = false;
+                    match = TryTimeToTicks(positive, zero, raw._numbers0, raw._numbers1, raw._numbers2, zero, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.FullDHMMatch(raw.NegativeLocalized))
+                {
+                    positive = false;
+                    match = TryTimeToTicks(positive, raw._numbers0, raw._numbers1, raw._numbers2, zero, zero, out ticks);
+                    overflow = overflow || !match;
+                }
+
+                if (!match && raw.PartialAppCompatMatch(raw.NegativeLocalized))
+                {
+                    positive = false;
+                    match = TryTimeToTicks(positive, zero, raw._numbers0, raw._numbers1, zero, raw._numbers2, out ticks);
+                    overflow = overflow || !match;
+                }
+            }
+
+            if (match)
+            {
+                if (!positive)
+                {
+                    ticks = -ticks;
+                    if (ticks > 0)
+                    {
+                        return result.SetOverflowFailure();
+                    }
+                }
+
+                result.parsedTimeSpan._ticks = ticks;
+                return true;
+            }
+
+            return overflow ?
+                result.SetOverflowFailure() : // we found at least one literal pattern match but the numbers just didn't fit
+                result.SetBadTimeSpanFailure(); // we couldn't find a thing
+        }
+
+        /// <summary>Validate the 2-number "Hours:Minutes" terminal case.</summary>
+        private static bool ProcessTerminal_HM(ref TimeSpanRawInfo raw, TimeSpanStandardStyles style, ref TimeSpanResult result)
+        {
+            if (raw._sepCount != 3 || (style & TimeSpanStandardStyles.RequireFull) != 0)
+            {
+                return result.SetBadTimeSpanFailure();
+            }
+            Debug.Assert(raw._numCount == 2);
+
+            bool inv = ((style & TimeSpanStandardStyles.Invariant) != 0);
+            bool loc = ((style & TimeSpanStandardStyles.Localized) != 0);
+
+            bool positive = false, match = false;
+
+            if (inv)
+            {
+                if (raw.FullHMMatch(raw.PositiveInvariant))
+                {
+                    match = true;
+                    positive = true;
+                }
+
+                if (!match && raw.FullHMMatch(raw.NegativeInvariant))
+                {
+                    match = true;
+                    positive = false;
+                }
+            }
+
+            if (loc)
+            {
+                if (!match && raw.FullHMMatch(raw.PositiveLocalized))
+                {
+                    match = true;
+                    positive = true;
+                }
+
+                if (!match && raw.FullHMMatch(raw.NegativeLocalized))
+                {
+                    match = true;
+                    positive = false;
+                }
+            }
+
+            if (match)
+            {
+                long ticks = 0;
+                var zero = new TimeSpanToken(0);
+
+                if (!TryTimeToTicks(positive, zero, raw._numbers0, raw._numbers1, zero, zero, out ticks))
+                {
+                    return result.SetOverflowFailure();
+                }
+
+                if (!positive)
+                {
+                    ticks = -ticks;
+                    if (ticks > 0)
+                    {
+                        return result.SetOverflowFailure();
+                    }
+                }
+
+                result.parsedTimeSpan._ticks = ticks;
+                return true;
+            }
+
+            return result.SetBadTimeSpanFailure();
+        }
+
+        /// <summary>Validate the 1-number "Days" terminal case.</summary>
+        private static bool ProcessTerminal_D(ref TimeSpanRawInfo raw, TimeSpanStandardStyles style, ref TimeSpanResult result)
+        {
+            if (raw._sepCount != 2 || (style & TimeSpanStandardStyles.RequireFull) != 0)
+            {
+                return result.SetBadTimeSpanFailure();
+            }
+            Debug.Assert(raw._numCount == 1);
+
+            bool inv = ((style & TimeSpanStandardStyles.Invariant) != 0);
+            bool loc = ((style & TimeSpanStandardStyles.Localized) != 0);
+
+            bool positive = false, match = false;
+
+            if (inv)
+            {
+                if (raw.FullDMatch(raw.PositiveInvariant))
+                {
+                    match = true;
+                    positive = true;
+                }
+
+                if (!match && raw.FullDMatch(raw.NegativeInvariant))
+                {
+                    match = true;
+                    positive = false;
+                }
+            }
+
+            if (loc)
+            {
+                if (!match && raw.FullDMatch(raw.PositiveLocalized))
+                {
+                    match = true;
+                    positive = true;
+                }
+
+                if (!match && raw.FullDMatch(raw.NegativeLocalized))
+                {
+                    match = true;
+                    positive = false;
+                }
+            }
+
+            if (match)
+            {
+                long ticks = 0;
+                var zero = new TimeSpanToken(0);
+
+                if (!TryTimeToTicks(positive, raw._numbers0, zero, zero, zero, zero, out ticks))
+                {
+                    return result.SetOverflowFailure();
+                }
+
+                if (!positive)
+                {
+                    ticks = -ticks;
+                    if (ticks > 0)
+                    {
+                        return result.SetOverflowFailure();
+                    }
+                }
+
+                result.parsedTimeSpan._ticks = ticks;
+                return true;
+            }
+
+            return result.SetBadTimeSpanFailure();
+        }
+
+        /// <summary>Common private ParseExact method called by both ParseExact and TryParseExact.</summary>
+        private static bool TryParseExactTimeSpan(ReadOnlySpan<char> input, ReadOnlySpan<char> format, IFormatProvider formatProvider, TimeSpanStyles styles, ref TimeSpanResult result)
+        {
+            if (format.Length == 0)
+            {
+                return result.SetBadFormatSpecifierFailure();
+            }
+
+            if (format.Length == 1)
+            {
+                switch (format[0])
+                {
+                    case 'c':
+                    case 't':
+                    case 'T':
+                        return TryParseTimeSpanConstant(input, ref result); // fast path for legacy style TimeSpan formats.
+
+                    case 'g':
+                        return TryParseTimeSpan(input, TimeSpanStandardStyles.Localized, formatProvider, ref result);
+
+                    case 'G':
+                        return TryParseTimeSpan(input, TimeSpanStandardStyles.Localized | TimeSpanStandardStyles.RequireFull, formatProvider, ref result);
+
+                    default:
+                        return result.SetBadFormatSpecifierFailure(format[0]);
+                }
+            }
+
+            return TryParseByFormat(input, format, styles, ref result);
+        }
+
+        /// <summary>Parse the TimeSpan instance using the specified format.  Used by TryParseExactTimeSpan.</summary>
+        private static bool TryParseByFormat(ReadOnlySpan<char> input, ReadOnlySpan<char> format, TimeSpanStyles styles, ref TimeSpanResult result)
+        {
+            bool seenDD = false;      // already processed days?
+            bool seenHH = false;      // already processed hours?
+            bool seenMM = false;      // already processed minutes?
+            bool seenSS = false;      // already processed seconds?
+            bool seenFF = false;      // already processed fraction?
+
+            int dd = 0;               // parsed days
+            int hh = 0;               // parsed hours
+            int mm = 0;               // parsed minutes
+            int ss = 0;               // parsed seconds
+            int leadingZeroes = 0;    // number of leading zeroes in the parsed fraction
+            int ff = 0;               // parsed fraction
+            int i = 0;                // format string position
+            int tokenLen = 0;         // length of current format token, used to update index 'i'
+
+            var tokenizer = new TimeSpanTokenizer(input, -1);
+
+            while (i < format.Length)
+            {
+                char ch = format[i];
+                int nextFormatChar;
+                switch (ch)
+                {
+                    case 'h':
+                        tokenLen = DateTimeFormat.ParseRepeatPattern(format, i, ch);
+                        if (tokenLen > 2 || seenHH || !ParseExactDigits(ref tokenizer, tokenLen, out hh))
+                        {
+                            return result.SetInvalidStringFailure();
+                        }
+                        seenHH = true;
+                        break;
+
+                    case 'm':
+                        tokenLen = DateTimeFormat.ParseRepeatPattern(format, i, ch);
+                        if (tokenLen > 2 || seenMM || !ParseExactDigits(ref tokenizer, tokenLen, out mm))
+                        {
+                            return result.SetInvalidStringFailure();
+                        }
+                        seenMM = true;
+                        break;
+
+                    case 's':
+                        tokenLen = DateTimeFormat.ParseRepeatPattern(format, i, ch);
+                        if (tokenLen > 2 || seenSS || !ParseExactDigits(ref tokenizer, tokenLen, out ss))
+                        {
+                            return result.SetInvalidStringFailure();
+                        }
+                        seenSS = true;
+                        break;
+
+                    case 'f':
+                        tokenLen = DateTimeFormat.ParseRepeatPattern(format, i, ch);
+                        if (tokenLen > DateTimeFormat.MaxSecondsFractionDigits || seenFF || !ParseExactDigits(ref tokenizer, tokenLen, tokenLen, out leadingZeroes, out ff))
+                        {
+                            return result.SetInvalidStringFailure();
+                        }
+                        seenFF = true;
+                        break;
+
+                    case 'F':
+                        tokenLen = DateTimeFormat.ParseRepeatPattern(format, i, ch);
+                        if (tokenLen > DateTimeFormat.MaxSecondsFractionDigits || seenFF)
+                        {
+                            return result.SetInvalidStringFailure();
+                        }
+                        ParseExactDigits(ref tokenizer, tokenLen, tokenLen, out leadingZeroes, out ff);
+                        seenFF = true;
+                        break;
+
+                    case 'd':
+                        tokenLen = DateTimeFormat.ParseRepeatPattern(format, i, ch);
+                        int tmp = 0;
+                        if (tokenLen > 8 || seenDD || !ParseExactDigits(ref tokenizer, (tokenLen < 2) ? 1 : tokenLen, (tokenLen < 2) ? 8 : tokenLen, out tmp, out dd))
+                        {
+                            return result.SetInvalidStringFailure();
+                        }
+                        seenDD = true;
+                        break;
+
+                    case '\'':
+                    case '\"':
+                        StringBuilder enquotedString = StringBuilderCache.Acquire();
+                        if (!DateTimeParse.TryParseQuoteString(format, i, enquotedString, out tokenLen))
+                        {
+                            StringBuilderCache.Release(enquotedString);
+                            return result.SetBadQuoteFailure(ch);
+                        }
+                        if (!ParseExactLiteral(ref tokenizer, enquotedString))
+                        {
+                            StringBuilderCache.Release(enquotedString);
+                            return result.SetInvalidStringFailure();
+                        }
+                        StringBuilderCache.Release(enquotedString);
+                        break;
+
+                    case '%':
+                        // Optional format character.
+                        // For example, format string "%d" will print day 
+                        // Most of the cases, "%" can be ignored.
+                        nextFormatChar = DateTimeFormat.ParseNextChar(format, i);
+
+                        // nextFormatChar will be -1 if we already reach the end of the format string.
+                        // Besides, we will not allow "%%" appear in the pattern.
+                        if (nextFormatChar >= 0 && nextFormatChar != '%')
+                        {
+                            tokenLen = 1; // skip the '%' and process the format character
+                            break;
+                        }
+                        else
+                        {
+                            // This means that '%' is at the end of the format string or
+                            // "%%" appears in the format string.
+                            return result.SetInvalidStringFailure();
+                        }
+
+                    case '\\':
+                        // Escaped character.  Can be used to insert character into the format string.
+                        // For example, "\d" will insert the character 'd' into the string.
+                        //
+                        nextFormatChar = DateTimeFormat.ParseNextChar(format, i);
+                        if (nextFormatChar >= 0 && tokenizer.NextChar == (char)nextFormatChar)
+                        {
+                            tokenLen = 2;
+                        }
+                        else
+                        {
+                            // This means that '\' is at the end of the format string or the literal match failed.
+                            return result.SetInvalidStringFailure();
+                        }
+                        break;
+
+                    default:
+                        return result.SetInvalidStringFailure();
+                }
+
+                i += tokenLen;
+            }
+
+
+            if (!tokenizer.EOL)
+            {
+                // the custom format didn't consume the entire input
+                return result.SetBadTimeSpanFailure();
+            }
+
+            bool positive = (styles & TimeSpanStyles.AssumeNegative) == 0;
+            if (TryTimeToTicks(positive, new TimeSpanToken(dd),
+                                         new TimeSpanToken(hh),
+                                         new TimeSpanToken(mm),
+                                         new TimeSpanToken(ss),
+                                         new TimeSpanToken(ff, leadingZeroes),
+                                         out long ticks))
+            {
+                if (!positive)
+                {
+                    ticks = -ticks;
+                }
+
+                result.parsedTimeSpan._ticks = ticks;
+                return true;
+            }
+            else
+            {
+                return result.SetOverflowFailure();
+            }
+        }
+
+        private static bool ParseExactDigits(ref TimeSpanTokenizer tokenizer, int minDigitLength, out int result)
+        {
+            result = 0;
+            int zeroes = 0;
+            int maxDigitLength = (minDigitLength == 1) ? 2 : minDigitLength;
+            return ParseExactDigits(ref tokenizer, minDigitLength, maxDigitLength, out zeroes, out result);
+        }
+
+        private static bool ParseExactDigits(ref TimeSpanTokenizer tokenizer, int minDigitLength, int maxDigitLength, out int zeroes, out int result)
+        {
+            int tmpResult = 0, tmpZeroes = 0;
+
+            int tokenLength = 0;
+            while (tokenLength < maxDigitLength)
+            {
+                char ch = tokenizer.NextChar;
+                if (ch < '0' || ch > '9')
+                {
+                    tokenizer.BackOne();
+                    break;
+                }
+
+                tmpResult = tmpResult * 10 + (ch - '0');
+                if (tmpResult == 0) tmpZeroes++;
+                tokenLength++;
+            }
+
+            zeroes = tmpZeroes;
+            result = tmpResult;
+            return tokenLength >= minDigitLength;
+        }
+
+        private static bool ParseExactLiteral(ref TimeSpanTokenizer tokenizer, StringBuilder enquotedString)
+        {
+            for (int i = 0; i < enquotedString.Length; i++)
+            {
+                if (enquotedString[i] != tokenizer.NextChar)
+                {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// Parses the "c" (constant) format.  This code is 100% identical to the non-globalized v1.0-v3.5 TimeSpan.Parse() routine
+        /// and exists for performance/appcompat with legacy callers who cannot move onto the globalized Parse overloads. 
+        /// </summary>
+        private static bool TryParseTimeSpanConstant(ReadOnlySpan<char> input, ref TimeSpanResult result) =>
+            new StringParser().TryParse(input, ref result);
+
+        private ref struct StringParser
+        {
+            private ReadOnlySpan<char> _str;
+            private char _ch;
+            private int _pos;
+            private int _len;
+
+            internal void NextChar()
+            {
+                if (_pos < _len)
+                {
+                    _pos++;
+                }
+
+                _ch = _pos < _len ?
+                    _str[_pos] :
+                    (char)0;
+            }
+
+            internal char NextNonDigit()
+            {
+                int i = _pos;
+                while (i < _len)
+                {
+                    char ch = _str[i];
+                    if (ch < '0' || ch > '9') return ch;
+                    i++;
+                }
+
+                return (char)0;
+            }
+
+            internal bool TryParse(ReadOnlySpan<char> input, ref TimeSpanResult result)
+            {
+                result.parsedTimeSpan._ticks = 0;
+
+                _str = input;
+                _len = input.Length;
+                _pos = -1;
+                NextChar();
+                SkipBlanks();
+
+                bool negative = false;
+                if (_ch == '-')
+                {
+                    negative = true;
+                    NextChar();
+                }
+
+                long time;
+                if (NextNonDigit() == ':')
+                {
+                    if (!ParseTime(out time, ref result))
+                    {
+                        return false;
+                    };
+                }
+                else
+                {
+                    int days;
+                    if (!ParseInt((int)(0x7FFFFFFFFFFFFFFFL / TimeSpan.TicksPerDay), out days, ref result))
+                    {
+                        return false;
+                    }
+
+                    time = days * TimeSpan.TicksPerDay;
+
+                    if (_ch == '.')
+                    {
+                        NextChar();
+                        long remainingTime;
+                        if (!ParseTime(out remainingTime, ref result))
+                        {
+                            return false;
+                        };
+                        time += remainingTime;
+                    }
+                }
+
+                if (negative)
+                {
+                    time = -time;
+                    // Allow -0 as well
+                    if (time > 0)
+                    {
+                        return result.SetOverflowFailure();
+                    }
+                }
+                else
+                {
+                    if (time < 0)
+                    {
+                        return result.SetOverflowFailure();
+                    }
+                }
+
+                SkipBlanks();
+
+                if (_pos < _len)
+                {
+                    return result.SetBadTimeSpanFailure();
+                }
+
+                result.parsedTimeSpan._ticks = time;
+                return true;
+            }
+
+            internal bool ParseInt(int max, out int i, ref TimeSpanResult result)
+            {
+                i = 0;
+                int p = _pos;
+                while (_ch >= '0' && _ch <= '9')
+                {
+                    if ((i & 0xF0000000) != 0)
+                    {
+                        return result.SetOverflowFailure();
+                    }
+
+                    i = i * 10 + _ch - '0';
+                    if (i < 0)
+                    {
+                        return result.SetOverflowFailure();
+                    }
+
+                    NextChar();
+                }
+
+                if (p == _pos)
+                {
+                    return result.SetBadTimeSpanFailure();
+                }
+
+                if (i > max)
+                {
+                    return result.SetOverflowFailure();
+                }
+
+                return true;
+            }
+
+            internal bool ParseTime(out long time, ref TimeSpanResult result)
+            {
+                time = 0;
+                int unit;
+
+                if (!ParseInt(23, out unit, ref result))
+                {
+                    return false;
+                }
+
+                time = unit * TimeSpan.TicksPerHour;
+                if (_ch != ':')
+                {
+                    return result.SetBadTimeSpanFailure();
+                }
+
+                NextChar();
+
+                if (!ParseInt(59, out unit, ref result))
+                {
+                    return false;
+                }
+
+                time += unit * TimeSpan.TicksPerMinute;
+
+                if (_ch == ':')
+                {
+                    NextChar();
+                    
+                    // allow seconds with the leading zero
+                    if (_ch != '.')
+                    {
+                        if (!ParseInt(59, out unit, ref result))
+                        {
+                            return false;
+                        }
+                        time += unit * TimeSpan.TicksPerSecond;
+                    }
+
+                    if (_ch == '.')
+                    {
+                        NextChar();
+                        int f = (int)TimeSpan.TicksPerSecond;
+                        while (f > 1 && _ch >= '0' && _ch <= '9')
+                        {
+                            f /= 10;
+                            time += (_ch - '0') * f;
+                            NextChar();
+                        }
+                    }
+                }
+
+                return true;
+            }
+
+            internal void SkipBlanks()
+            {
+                while (_ch == ' ' || _ch == '\t') NextChar();
+            }
+        }
+
+        /// <summary>Common private ParseExactMultiple method called by both ParseExactMultiple and TryParseExactMultiple.</summary>
+        private static bool TryParseExactMultipleTimeSpan(ReadOnlySpan<char> input, string[] formats, IFormatProvider formatProvider, TimeSpanStyles styles, ref TimeSpanResult result)
+        {
+            if (formats == null)
+            {
+                return result.SetArgumentNullFailure(nameof(formats));
+            }
+
+            if (input.Length == 0)
+            {
+                return result.SetBadTimeSpanFailure();
+            }
+
+            if (formats.Length == 0)
+            {
+                return result.SetNoFormatSpecifierFailure();
+            }
+
+            // Do a loop through the provided formats and see if we can parse succesfully in
+            // one of the formats.
+            for (int i = 0; i < formats.Length; i++)
+            {
+                if (formats[i] == null || formats[i].Length == 0)
+                {
+                    return result.SetBadFormatSpecifierFailure();
+                }
+
+                // Create a new non-throwing result each time to ensure the runs are independent.
+                TimeSpanResult innerResult = new TimeSpanResult(throwOnFailure: false, originalTimeSpanString: input);
+
+                if (TryParseExactTimeSpan(input, formats[i], formatProvider, styles, ref innerResult))
+                {
+                    result.parsedTimeSpan = innerResult.parsedTimeSpan;
+                    return true;
+                }
+            }
+
+            return result.SetBadTimeSpanFailure();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/TimeSpanStyles.cs b/src/System.Private.CoreLib/shared/System/Globalization/TimeSpanStyles.cs
new file mode 100644
index 0000000000..68a47bcbe6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/TimeSpanStyles.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Globalization
+{
+    [Flags]
+    public enum TimeSpanStyles
+    {
+        None = 0x00000000,
+        AssumeNegative = 0x00000001,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/UmAlQuraCalendar.cs b/src/System.Private.CoreLib/shared/System/Globalization/UmAlQuraCalendar.cs
new file mode 100644
index 0000000000..21a938f8f1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/UmAlQuraCalendar.cs
@@ -0,0 +1,858 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Globalization
+{
+    /*
+    **  Calendar support range:
+    **      Calendar    Minimum     Maximum
+    **      ==========  ==========  ==========
+    **      Gregorian   1900/04/30   2077/05/13
+    **      UmAlQura    1318/01/01   1500/12/30
+    */
+
+    public partial class UmAlQuraCalendar : Calendar
+    {
+        internal const int MinCalendarYear = 1318;
+        internal const int MaxCalendarYear = 1500;
+
+        internal struct DateMapping
+        {
+            internal DateMapping(int MonthsLengthFlags, int GYear, int GMonth, int GDay)
+            {
+                HijriMonthsLengthFlags = MonthsLengthFlags;
+                GregorianDate = new DateTime(GYear, GMonth, GDay);
+            }
+            internal int HijriMonthsLengthFlags;
+            internal DateTime GregorianDate;
+        }
+
+        private static readonly DateMapping[] s_hijriYearInfo = InitDateMapping();
+
+        private static DateMapping[] InitDateMapping()
+        {
+            short[] rawData = new short[]
+            {
+                //These data is taken from Tables/Excel/UmAlQura.xls please make sure that the two places are in sync
+                /*  DaysPerM     GY      GM     GD     D1   D2   D3   D4   D5   D6   D7   D8   D9   D10  D11  D12    
+                1318*/0x02EA,    1900,     4,    30,/* 0    1    0    1    0    1    1    1    0    1    0    0    4/30/1900
+                1319*/0x06E9,    1901,     4,    19,/* 1    0    0    1    0    1    1    1    0    1    1    0    4/19/1901
+                1320*/0x0ED2,    1902,     4,     9,/* 0    1    0    0    1    0    1    1    0    1    1    1    4/9/1902
+                1321*/0x0EA4,    1903,     3,    30,/* 0    0    1    0    0    1    0    1    0    1    1    1    3/30/1903
+                1322*/0x0D4A,    1904,     3,    18,/* 0    1    0    1    0    0    1    0    1    0    1    1    3/18/1904
+                1323*/0x0A96,    1905,     3,     7,/* 0    1    1    0    1    0    0    1    0    1    0    1    3/7/1905
+                1324*/0x0536,    1906,     2,    24,/* 0    1    1    0    1    1    0    0    1    0    1    0    2/24/1906
+                1325*/0x0AB5,    1907,     2,    13,/* 1    0    1    0    1    1    0    1    0    1    0    1    2/13/1907
+                1326*/0x0DAA,    1908,     2,     3,/* 0    1    0    1    0    1    0    1    1    0    1    1    2/3/1908
+                1327*/0x0BA4,    1909,     1,    23,/* 0    0    1    0    0    1    0    1    1    1    0    1    1/23/1909
+                1328*/0x0B49,    1910,     1,    12,/* 1    0    0    1    0    0    1    0    1    1    0    1    1/12/1910
+                1329*/0x0A93,    1911,     1,     1,/* 1    1    0    0    1    0    0    1    0    1    0    1    1/1/1911
+                1330*/0x052B,    1911,    12,    21,/* 1    1    0    1    0    1    0    0    1    0    1    0    12/21/1911
+                1331*/0x0A57,    1912,    12,     9,/* 1    1    1    0    1    0    1    0    0    1    0    1    12/9/1912
+                1332*/0x04B6,    1913,    11,    29,/* 0    1    1    0    1    1    0    1    0    0    1    0    11/29/1913
+                1333*/0x0AB5,    1914,    11,    18,/* 1    0    1    0    1    1    0    1    0    1    0    1    11/18/1914
+                1334*/0x05AA,    1915,    11,     8,/* 0    1    0    1    0    1    0    1    1    0    1    0    11/8/1915
+                1335*/0x0D55,    1916,    10,    27,/* 1    0    1    0    1    0    1    0    1    0    1    1    10/27/1916
+                1336*/0x0D2A,    1917,    10,    17,/* 0    1    0    1    0    1    0    0    1    0    1    1    10/17/1917
+                1337*/0x0A56,    1918,    10,     6,/* 0    1    1    0    1    0    1    0    0    1    0    1    10/6/1918
+                1338*/0x04AE,    1919,     9,    25,/* 0    1    1    1    0    1    0    1    0    0    1    0    9/25/1919
+                1339*/0x095D,    1920,     9,    13,/* 1    0    1    1    1    0    1    0    1    0    0    1    9/13/1920
+                1340*/0x02EC,    1921,     9,     3,/* 0    0    1    1    0    1    1    1    0    1    0    0    9/3/1921
+                1341*/0x06D5,    1922,     8,    23,/* 1    0    1    0    1    0    1    1    0    1    1    0    8/23/1922
+                1342*/0x06AA,    1923,     8,    13,/* 0    1    0    1    0    1    0    1    0    1    1    0    8/13/1923
+                1343*/0x0555,    1924,     8,     1,/* 1    0    1    0    1    0    1    0    1    0    1    0    8/1/1924
+                1344*/0x04AB,    1925,     7,    21,/* 1    1    0    1    0    1    0    1    0    0    1    0    7/21/1925
+                1345*/0x095B,    1926,     7,    10,/* 1    1    0    1    1    0    1    0    1    0    0    1    7/10/1926
+                1346*/0x02BA,    1927,     6,    30,/* 0    1    0    1    1    1    0    1    0    1    0    0    6/30/1927
+                1347*/0x0575,    1928,     6,    18,/* 1    0    1    0    1    1    1    0    1    0    1    0    6/18/1928
+                1348*/0x0BB2,    1929,     6,     8,/* 0    1    0    0    1    1    0    1    1    1    0    1    6/8/1929
+                1349*/0x0764,    1930,     5,    29,/* 0    0    1    0    0    1    1    0    1    1    1    0    5/29/1930
+                1350*/0x0749,    1931,     5,    18,/* 1    0    0    1    0    0    1    0    1    1    1    0    5/18/1931
+                1351*/0x0655,    1932,     5,     6,/* 1    0    1    0    1    0    1    0    0    1    1    0    5/6/1932
+                1352*/0x02AB,    1933,     4,    25,/* 1    1    0    1    0    1    0    1    0    1    0    0    4/25/1933
+                1353*/0x055B,    1934,     4,    14,/* 1    1    0    1    1    0    1    0    1    0    1    0    4/14/1934
+                1354*/0x0ADA,    1935,     4,     4,/* 0    1    0    1    1    0    1    1    0    1    0    1    4/4/1935
+                1355*/0x06D4,    1936,     3,    24,/* 0    0    1    0    1    0    1    1    0    1    1    0    3/24/1936
+                1356*/0x0EC9,    1937,     3,    13,/* 1    0    0    1    0    0    1    1    0    1    1    1    3/13/1937
+                1357*/0x0D92,    1938,     3,     3,/* 0    1    0    0    1    0    0    1    1    0    1    1    3/3/1938
+                1358*/0x0D25,    1939,     2,    20,/* 1    0    1    0    0    1    0    0    1    0    1    1    2/20/1939
+                1359*/0x0A4D,    1940,     2,     9,/* 1    0    1    1    0    0    1    0    0    1    0    1    2/9/1940
+                1360*/0x02AD,    1941,     1,    28,/* 1    0    1    1    0    1    0    1    0    1    0    0    1/28/1941
+                1361*/0x056D,    1942,     1,    17,/* 1    0    1    1    0    1    1    0    1    0    1    0    1/17/1942
+                1362*/0x0B6A,    1943,     1,     7,/* 0    1    0    1    0    1    1    0    1    1    0    1    1/7/1943
+                1363*/0x0B52,    1943,    12,    28,/* 0    1    0    0    1    0    1    0    1    1    0    1    12/28/1943
+                1364*/0x0AA5,    1944,    12,    16,/* 1    0    1    0    0    1    0    1    0    1    0    1    12/16/1944
+                1365*/0x0A4B,    1945,    12,     5,/* 1    1    0    1    0    0    1    0    0    1    0    1    12/5/1945
+                1366*/0x0497,    1946,    11,    24,/* 1    1    1    0    1    0    0    1    0    0    1    0    11/24/1946
+                1367*/0x0937,    1947,    11,    13,/* 1    1    1    0    1    1    0    0    1    0    0    1    11/13/1947
+                1368*/0x02B6,    1948,    11,     2,/* 0    1    1    0    1    1    0    1    0    1    0    0    11/2/1948
+                1369*/0x0575,    1949,    10,    22,/* 1    0    1    0    1    1    1    0    1    0    1    0    10/22/1949
+                1370*/0x0D6A,    1950,    10,    12,/* 0    1    0    1    0    1    1    0    1    0    1    1    10/12/1950
+                1371*/0x0D52,    1951,    10,     2,/* 0    1    0    0    1    0    1    0    1    0    1    1    10/2/1951
+                1372*/0x0A96,    1952,     9,    20,/* 0    1    1    0    1    0    0    1    0    1    0    1    9/20/1952
+                1373*/0x092D,    1953,     9,     9,/* 1    0    1    1    0    1    0    0    1    0    0    1    9/9/1953
+                1374*/0x025D,    1954,     8,    29,/* 1    0    1    1    1    0    1    0    0    1    0    0    8/29/1954
+                1375*/0x04DD,    1955,     8,    18,/* 1    0    1    1    1    0    1    1    0    0    1    0    8/18/1955
+                1376*/0x0ADA,    1956,     8,     7,/* 0    1    0    1    1    0    1    1    0    1    0    1    8/7/1956
+                1377*/0x05D4,    1957,     7,    28,/* 0    0    1    0    1    0    1    1    1    0    1    0    7/28/1957
+                1378*/0x0DA9,    1958,     7,    17,/* 1    0    0    1    0    1    0    1    1    0    1    1    7/17/1958
+                1379*/0x0D52,    1959,     7,     7,/* 0    1    0    0    1    0    1    0    1    0    1    1    7/7/1959
+                1380*/0x0AAA,    1960,     6,    25,/* 0    1    0    1    0    1    0    1    0    1    0    1    6/25/1960
+                1381*/0x04D6,    1961,     6,    14,/* 0    1    1    0    1    0    1    1    0    0    1    0    6/14/1961
+                1382*/0x09B6,    1962,     6,     3,/* 0    1    1    0    1    1    0    1    1    0    0    1    6/3/1962
+                1383*/0x0374,    1963,     5,    24,/* 0    0    1    0    1    1    1    0    1    1    0    0    5/24/1963
+                1384*/0x0769,    1964,     5,    12,/* 1    0    0    1    0    1    1    0    1    1    1    0    5/12/1964
+                1385*/0x0752,    1965,     5,     2,/* 0    1    0    0    1    0    1    0    1    1    1    0    5/2/1965
+                1386*/0x06A5,    1966,     4,    21,/* 1    0    1    0    0    1    0    1    0    1    1    0    4/21/1966
+                1387*/0x054B,    1967,     4,    10,/* 1    1    0    1    0    0    1    0    1    0    1    0    4/10/1967
+                1388*/0x0AAB,    1968,     3,    29,/* 1    1    0    1    0    1    0    1    0    1    0    1    3/29/1968
+                1389*/0x055A,    1969,     3,    19,/* 0    1    0    1    1    0    1    0    1    0    1    0    3/19/1969
+                1390*/0x0AD5,    1970,     3,     8,/* 1    0    1    0    1    0    1    1    0    1    0    1    3/8/1970
+                1391*/0x0DD2,    1971,     2,    26,/* 0    1    0    0    1    0    1    1    1    0    1    1    2/26/1971
+                1392*/0x0DA4,    1972,     2,    16,/* 0    0    1    0    0    1    0    1    1    0    1    1    2/16/1972
+                1393*/0x0D49,    1973,     2,     4,/* 1    0    0    1    0    0    1    0    1    0    1    1    2/4/1973
+                1394*/0x0A95,    1974,     1,    24,/* 1    0    1    0    1    0    0    1    0    1    0    1    1/24/1974
+                1395*/0x052D,    1975,     1,    13,/* 1    0    1    1    0    1    0    0    1    0    1    0    1/13/1975
+                1396*/0x0A5D,    1976,     1,     2,/* 1    0    1    1    1    0    1    0    0    1    0    1    1/2/1976
+                1397*/0x055A,    1976,    12,    22,/* 0    1    0    1    1    0    1    0    1    0    1    0    12/22/1976
+                1398*/0x0AD5,    1977,    12,    11,/* 1    0    1    0    1    0    1    1    0    1    0    1    12/11/1977
+                1399*/0x06AA,    1978,    12,     1,/* 0    1    0    1    0    1    0    1    0    1    1    0    12/1/1978
+                1400*/0x0695,    1979,    11,    20,/* 1    0    1    0    1    0    0    1    0    1    1    0    11/20/1979
+                1401*/0x052B,    1980,    11,     8,/* 1    1    0    1    0    1    0    0    1    0    1    0    11/8/1980
+                1402*/0x0A57,    1981,    10,    28,/* 1    1    1    0    1    0    1    0    0    1    0    1    10/28/1981
+                1403*/0x04AE,    1982,    10,    18,/* 0    1    1    1    0    1    0    1    0    0    1    0    10/18/1982
+                1404*/0x0976,    1983,    10,     7,/* 0    1    1    0    1    1    1    0    1    0    0    1    10/7/1983
+                1405*/0x056C,    1984,     9,    26,/* 0    0    1    1    0    1    1    0    1    0    1    0    9/26/1984
+                1406*/0x0B55,    1985,     9,    15,/* 1    0    1    0    1    0    1    0    1    1    0    1    9/15/1985
+                1407*/0x0AAA,    1986,     9,     5,/* 0    1    0    1    0    1    0    1    0    1    0    1    9/5/1986
+                1408*/0x0A55,    1987,     8,    25,/* 1    0    1    0    1    0    1    0    0    1    0    1    8/25/1987
+                1409*/0x04AD,    1988,     8,    13,/* 1    0    1    1    0    1    0    1    0    0    1    0    8/13/1988
+                1410*/0x095D,    1989,     8,     2,/* 1    0    1    1    1    0    1    0    1    0    0    1    8/2/1989
+                1411*/0x02DA,    1990,     7,    23,/* 0    1    0    1    1    0    1    1    0    1    0    0    7/23/1990
+                1412*/0x05D9,    1991,     7,    12,/* 1    0    0    1    1    0    1    1    1    0    1    0    7/12/1991
+                1413*/0x0DB2,    1992,     7,     1,/* 0    1    0    0    1    1    0    1    1    0    1    1    7/1/1992
+                1414*/0x0BA4,    1993,     6,    21,/* 0    0    1    0    0    1    0    1    1    1    0    1    6/21/1993
+                1415*/0x0B4A,    1994,     6,    10,/* 0    1    0    1    0    0    1    0    1    1    0    1    6/10/1994
+                1416*/0x0A55,    1995,     5,    30,/* 1    0    1    0    1    0    1    0    0    1    0    1    5/30/1995
+                1417*/0x02B5,    1996,     5,    18,/* 1    0    1    0    1    1    0    1    0    1    0    0    5/18/1996
+                1418*/0x0575,    1997,     5,     7,/* 1    0    1    0    1    1    1    0    1    0    1    0    5/7/1997
+                1419*/0x0B6A,    1998,     4,    27,/* 0    1    0    1    0    1    1    0    1    1    0    1    4/27/1998
+                1420*/0x0BD2,    1999,     4,    17,/* 0    1    0    0    1    0    1    1    1    1    0    1    4/17/1999
+                1421*/0x0BC4,    2000,     4,     6,/* 0    0    1    0    0    0    1    1    1    1    0    1    4/6/2000
+                1422*/0x0B89,    2001,     3,    26,/* 1    0    0    1    0    0    0    1    1    1    0    1    3/26/2001
+                1423*/0x0A95,    2002,     3,    15,/* 1    0    1    0    1    0    0    1    0    1    0    1    3/15/2002
+                1424*/0x052D,    2003,     3,     4,/* 1    0    1    1    0    1    0    0    1    0    1    0    3/4/2003
+                1425*/0x05AD,    2004,     2,    21,/* 1    0    1    1    0    1    0    1    1    0    1    0    2/21/2004
+                1426*/0x0B6A,    2005,     2,    10,/* 0    1    0    1    0    1    1    0    1    1    0    1    2/10/2005
+                1427*/0x06D4,    2006,     1,    31,/* 0    0    1    0    1    0    1    1    0    1    1    0    1/31/2006
+                1428*/0x0DC9,    2007,     1,    20,/* 1    0    0    1    0    0    1    1    1    0    1    1    1/20/2007
+                1429*/0x0D92,    2008,     1,    10,/* 0    1    0    0    1    0    0    1    1    0    1    1    1/10/2008
+                1430*/0x0AA6,    2008,    12,    29,/* 0    1    1    0    0    1    0    1    0    1    0    1    12/29/2008
+                1431*/0x0956,    2009,    12,    18,/* 0    1    1    0    1    0    1    0    1    0    0    1    12/18/2009
+                1432*/0x02AE,    2010,    12,     7,/* 0    1    1    1    0    1    0    1    0    1    0    0    12/7/2010
+                1433*/0x056D,    2011,    11,    26,/* 1    0    1    1    0    1    1    0    1    0    1    0    11/26/2011
+                1434*/0x036A,    2012,    11,    15,/* 0    1    0    1    0    1    1    0    1    1    0    0    11/15/2012
+                1435*/0x0B55,    2013,    11,     4,/* 1    0    1    0    1    0    1    0    1    1    0    1    11/4/2013
+                1436*/0x0AAA,    2014,    10,    25,/* 0    1    0    1    0    1    0    1    0    1    0    1    10/25/2014
+                1437*/0x094D,    2015,    10,    14,/* 1    0    1    1    0    0    1    0    1    0    0    1    10/14/2015
+                1438*/0x049D,    2016,    10,     2,/* 1    0    1    1    1    0    0    1    0    0    1    0    10/2/2016
+                1439*/0x095D,    2017,     9,    21,/* 1    0    1    1    1    0    1    0    1    0    0    1    9/21/2017
+                1440*/0x02BA,    2018,     9,    11,/* 0    1    0    1    1    1    0    1    0    1    0    0    9/11/2018
+                1441*/0x05B5,    2019,     8,    31,/* 1    0    1    0    1    1    0    1    1    0    1    0    8/31/2019
+                1442*/0x05AA,    2020,     8,    20,/* 0    1    0    1    0    1    0    1    1    0    1    0    8/20/2020
+                1443*/0x0D55,    2021,     8,     9,/* 1    0    1    0    1    0    1    0    1    0    1    1    8/9/2021
+                1444*/0x0A9A,    2022,     7,    30,/* 0    1    0    1    1    0    0    1    0    1    0    1    7/30/2022
+                1445*/0x092E,    2023,     7,    19,/* 0    1    1    1    0    1    0    0    1    0    0    1    7/19/2023
+                1446*/0x026E,    2024,     7,     7,/* 0    1    1    1    0    1    1    0    0    1    0    0    7/7/2024
+                1447*/0x055D,    2025,     6,    26,/* 1    0    1    1    1    0    1    0    1    0    1    0    6/26/2025
+                1448*/0x0ADA,    2026,     6,    16,/* 0    1    0    1    1    0    1    1    0    1    0    1    6/16/2026
+                1449*/0x06D4,    2027,     6,     6,/* 0    0    1    0    1    0    1    1    0    1    1    0    6/6/2027
+                1450*/0x06A5,    2028,     5,    25,/* 1    0    1    0    0    1    0    1    0    1    1    0    5/25/2028
+                1451*/0x054B,    2029,     5,    14,/* 1    1    0    1    0    0    1    0    1    0    1    0    5/14/2029
+                1452*/0x0A97,    2030,     5,     3,/* 1    1    1    0    1    0    0    1    0    1    0    1    5/3/2030
+                1453*/0x054E,    2031,     4,    23,/* 0    1    1    1    0    0    1    0    1    0    1    0    4/23/2031
+                1454*/0x0AAE,    2032,     4,    11,/* 0    1    1    1    0    1    0    1    0    1    0    1    4/11/2032
+                1455*/0x05AC,    2033,     4,     1,/* 0    0    1    1    0    1    0    1    1    0    1    0    4/1/2033
+                1456*/0x0BA9,    2034,     3,    21,/* 1    0    0    1    0    1    0    1    1    1    0    1    3/21/2034
+                1457*/0x0D92,    2035,     3,    11,/* 0    1    0    0    1    0    0    1    1    0    1    1    3/11/2035
+                1458*/0x0B25,    2036,     2,    28,/* 1    0    1    0    0    1    0    0    1    1    0    1    2/28/2036
+                1459*/0x064B,    2037,     2,    16,/* 1    1    0    1    0    0    1    0    0    1    1    0    2/16/2037
+                1460*/0x0CAB,    2038,     2,     5,/* 1    1    0    1    0    1    0    1    0    0    1    1    2/5/2038
+                1461*/0x055A,    2039,     1,    26,/* 0    1    0    1    1    0    1    0    1    0    1    0    1/26/2039
+                1462*/0x0B55,    2040,     1,    15,/* 1    0    1    0    1    0    1    0    1    1    0    1    1/15/2040
+                1463*/0x06D2,    2041,     1,     4,/* 0    1    0    0    1    0    1    1    0    1    1    0    1/4/2041
+                1464*/0x0EA5,    2041,     12,   24,/* 1    0    1    0    0    1    0    1    0    1    1    1    12/24/2041
+                1465*/0x0E4A,    2042,     12,   14,/* 0    1    0    1    0    0    1    0    0    1    1    1    12/14/2042
+                1466*/0x0A95,    2043,     12,    3,/* 1    0    1    0    1    0    0    1    0    1    0    1    12/3/2043
+                1467*/0x052D,    2044,     11,   21,/* 1    0    1    1    0    1    0    0    1    0    1    0    11/21/2044
+                1468*/0x0AAD,    2045,     11,   10,/* 1    0    1    1    0    1    0    1    0    1    0    1    11/10/2045
+                1469*/0x036C,    2046,     10,   31,/* 0    0    1    1    0    1    1    0    1    1    0    0    10/31/2046
+                1470*/0x0759,    2047,     10,   20,/* 1    0    0    1    1    0    1    0    1    1    1    0    10/20/2047
+                1471*/0x06D2,    2048,     10,    9,/* 0    1    0    0    1    0    1    1    0    1    1    0    10/9/2048
+                1472*/0x0695,    2049,     9,    28,/* 1    0    1    0    1    0    0    1    0    1    1    0    9/28/2049
+                1473*/0x052D,    2050,     9,    17,/* 1    0    1    1    0    1    0    0    1    0    1    0    9/17/2050
+                1474*/0x0A5B,    2051,     9,     6,/* 1    1    0    1    1    0    1    0    0    1    0    1    9/6/2051
+                1475*/0x04BA,    2052,     8,    26,/* 0    1    0    1    1    1    0    1    0    0    1    0    8/26/2052
+                1476*/0x09BA,    2053,     8,    15,/* 0    1    0    1    1    1    0    1    1    0    0    1    8/15/2053
+                1477*/0x03B4,    2054,     8,     5,/* 0    0    1    0    1    1    0    1    1    1    0    0    8/5/2054
+                1478*/0x0B69,    2055,     7,    25,/* 1    0    0    1    0    1    1    0    1    1    0    1    7/25/2055
+                1479*/0x0B52,    2056,     7,    14,/* 0    1    0    0    1    0    1    0    1    1    0    1    7/14/2056
+                1480*/0x0AA6,    2057,     7,     3,/* 0    1    1    0    0    1    0    1    0    1    0    1    7/3/2057
+                1481*/0x04B6,    2058,     6,    22,/* 0    1    1    0    1    1    0    1    0    0    1    0    6/22/2058
+                1482*/0x096D,    2059,     6,    11,/* 1    0    1    1    0    1    1    0    1    0    0    1    6/11/2059
+                1483*/0x02EC,    2060,     5,    31,/* 0    0    1    1    0    1    1    1    0    1    0    0    5/31/2060
+                1484*/0x06D9,    2061,     5,    20,/* 1    0    0    1    1    0    1    1    0    1    1    0    5/20/2061
+                1485*/0x0EB2,    2062,     5,    10,/* 0    1    0    0    1    1    0    1    0    1    1    1    5/10/2062
+                1486*/0x0D54,    2063,     4,    30,/* 0    0    1    0    1    0    1    0    1    0    1    1    4/30/2063
+                1487*/0x0D2A,    2064,     4,    18,/* 0    1    0    1    0    1    0    0    1    0    1    1    4/18/2064
+                1488*/0x0A56,    2065,     4,     7,/* 0    1    1    0    1    0    1    0    0    1    0    1    4/7/2065
+                1489*/0x04AE,    2066,     3,    27,/* 0    1    1    1    0    1    0    1    0    0    1    0    3/27/2066
+                1490*/0x096D,    2067,     3,    16,/* 1    0    1    1    0    1    1    0    1    0    0    1    3/16/2067
+                1491*/0x0D6A,    2068,     3,     5,/* 0    1    0    1    0    1    1    0    1    0    1    1    3/5/2068
+                1492*/0x0B54,    2069,     2,    23,/* 0    0    1    0    1    0    1    0    1    1    0    1    2/23/2069
+                1493*/0x0B29,    2070,     2,    12,/* 1    0    0    1    0    1    0    0    1    1    0    1    2/12/2070
+                1494*/0x0A93,    2071,     2,     1,/* 1    1    0    0    1    0    0    1    0    1    0    1    2/1/2071
+                1495*/0x052B,    2072,     1,    21,/* 1    1    0    1    0    1    0    0    1    0    1    0    1/21/2072
+                1496*/0x0A57,    2073,     1,     9,/* 1    1    1    0    1    0    1    0    0    1    0    1    1/9/2073
+                1497*/0x0536,    2073,     12,   30,/* 0    1    1    0    1    1    0    0    1    0    1    0    12/30/2073
+                1498*/0x0AB5,    2074,     12,   19,/* 1    0    1    0    1    1    0    1    0    1    0    1    12/19/2074
+                1499*/0x06AA,    2075,     12,    9,/* 0    1    0    1    0    1    0    1    0    1    1    0    12/9/2075
+                1500*/0x0E93,    2076,     11,   27,/* 1    1    0    0    1    0    0    1    0    1    1    1    11/27/2076
+                1501*/     0,    2077,     11,   17,/* 0    0    0    0    0    0    0    0    0    0    0    0    11/17/2077
+    */      };
+            // Direct inline initialization of DateMapping array would produce a lot of code bloat.
+
+            // We take advantage of C# compiler compiles inline initialization of primitive type array into very compact code.
+            // So we start with raw data stored in primitive type array, and initialize the DateMapping out of it
+
+            DateMapping[] mapping = new DateMapping[rawData.Length / 4];
+            for (int i = 0; i < mapping.Length; i++)
+                mapping[i] = new DateMapping(rawData[i * 4], rawData[i * 4 + 1], rawData[i * 4 + 2], rawData[i * 4 + 3]);
+            return mapping;
+        }
+
+        public const int UmAlQuraEra = 1;
+
+        internal const int DateCycle = 30;
+        internal const int DatePartYear = 0;
+        internal const int DatePartDayOfYear = 1;
+        internal const int DatePartMonth = 2;
+        internal const int DatePartDay = 3;
+
+
+        // This is the minimal Gregorian date that we support in the UmAlQuraCalendar.
+        internal static DateTime minDate = new DateTime(1900, 4, 30);
+        internal static DateTime maxDate = new DateTime((new DateTime(2077, 11, 16, 23, 59, 59, 999)).Ticks + 9999);
+
+        public override DateTime MinSupportedDateTime
+        {
+            get
+            {
+                return (minDate);
+            }
+        }
+
+        public override DateTime MaxSupportedDateTime
+        {
+            get
+            {
+                return (maxDate);
+            }
+        }
+
+        public override CalendarAlgorithmType AlgorithmType
+        {
+            get
+            {
+                return CalendarAlgorithmType.LunarCalendar;
+            }
+        }
+
+        public UmAlQuraCalendar()
+        {
+        }
+
+        internal override CalendarId BaseCalendarID
+        {
+            get
+            {
+                return (CalendarId.HIJRI);
+            }
+        }
+
+        internal override CalendarId ID
+        {
+            get
+            {
+                return (CalendarId.UMALQURA);
+            }
+        }
+
+        protected override int DaysInYearBeforeMinSupportedYear
+        {
+            get
+            {
+                // HijriCalendar has same number of days as UmAlQuraCalendar for any given year
+                // HijriCalendar says year 1317 has 355 days.
+                return 355;
+            }
+        }
+
+        /*==========================ConvertHijriToGregorian==========================
+        ** Purpose: convert Hdate(year,month,day) to Gdate(year,month,day)                               
+        ** Arguments:                                                                                                                
+        ** Input/Ouput: Hijrah  date: year:yh, month:mh, day:dh                                                  
+        ** Output: Gregorian date: year:yg, month:mg, day:dg , day of week:dayweek                   
+        **       and returns flag found:1 not found:0                                                                      
+        =========================ConvertHijriToGregorian============================*/
+        private static void ConvertHijriToGregorian(int HijriYear, int HijriMonth, int HijriDay, ref int yg, ref int mg, ref int dg)
+        {
+            Debug.Assert((HijriYear >= MinCalendarYear) && (HijriYear <= MaxCalendarYear), "Hijri year is out of range.");
+            Debug.Assert(HijriMonth >= 1, "Hijri month is out of range.");
+            Debug.Assert(HijriDay >= 1, "Hijri day is out of range.");
+            int index, b, nDays = HijriDay - 1;
+            DateTime dt;
+
+
+            index = HijriYear - MinCalendarYear;
+            dt = s_hijriYearInfo[index].GregorianDate;
+
+
+            b = s_hijriYearInfo[index].HijriMonthsLengthFlags;
+
+            for (int m = 1; m < HijriMonth; m++)
+            {
+                nDays = nDays + 29 + (b & 1);   /* Add the months lengths before mh */
+                b = b >> 1;
+            }
+
+            dt = dt.AddDays(nDays);
+            dt.GetDatePart(out yg, out mg, out dg);
+        }
+
+        /*=================================GetAbsoluteDateUmAlQura==========================
+        **Action: Gets the Absolute date for the given UmAlQura date.  The absolute date means
+        **       the number of days from January 1st, 1 A.D.
+        **Returns:
+        **Arguments:
+        **Exceptions:
+        ============================================================================*/
+        private static long GetAbsoluteDateUmAlQura(int year, int month, int day)
+        {
+            //Caller should check the validaty of year, month and day.
+
+            int yg = 0, mg = 0, dg = 0;
+            ConvertHijriToGregorian(year, month, day, ref yg, ref mg, ref dg);
+            return GregorianCalendar.GetAbsoluteDate(yg, mg, dg);
+        }
+
+        internal static void CheckTicksRange(long ticks)
+        {
+            if (ticks < minDate.Ticks || ticks > maxDate.Ticks)
+            {
+                throw new ArgumentOutOfRangeException(
+                            "time",
+                            String.Format(
+                                CultureInfo.InvariantCulture,
+                                SR.ArgumentOutOfRange_CalendarRange,
+                                minDate,
+                                maxDate));
+            }
+        }
+
+        internal static void CheckEraRange(int era)
+        {
+            if (era != CurrentEra && era != UmAlQuraEra)
+            {
+                throw new ArgumentOutOfRangeException(nameof(era), SR.ArgumentOutOfRange_InvalidEraValue);
+            }
+        }
+
+        internal static void CheckYearRange(int year, int era)
+        {
+            CheckEraRange(era);
+            if (year < MinCalendarYear || year > MaxCalendarYear)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                MinCalendarYear,
+                                MaxCalendarYear));
+            }
+        }
+
+        internal static void CheckYearMonthRange(int year, int month, int era)
+        {
+            CheckYearRange(year, era);
+            if (month < 1 || month > 12)
+            {
+                throw new ArgumentOutOfRangeException(nameof(month), SR.ArgumentOutOfRange_Month);
+            }
+        }
+
+        /*========================ConvertGregorianToHijri============================
+        ** Purpose: convert DateTime to Hdate(year,month,day)                                                   
+        ** Arguments:                                                                                                                
+        ** Input: DateTime                                                                                                         
+        ** Output: Hijrah  date: year:yh, month:mh, day:dh                                                          
+        ============================================================================*/
+        private static void ConvertGregorianToHijri(DateTime time, ref int HijriYear, ref int HijriMonth, ref int HijriDay)
+        {
+            int index, b, DaysPerThisMonth;
+            double nDays;
+            TimeSpan ts;
+            int yh1 = 0, mh1 = 0, dh1 = 0;
+
+            Debug.Assert((time.Ticks >= minDate.Ticks) && (time.Ticks <= maxDate.Ticks), "Gregorian date is out of range.");
+
+            // Find the index where we should start our search by quessing the Hijri year that we will be in HijriYearInfo.
+            // A Hijri year is 354 or 355 days.  Use 355 days so that we will search from a lower index.
+
+            index = (int)((time.Ticks - minDate.Ticks) / Calendar.TicksPerDay) / 355;
+            do
+            {
+            } while (time.CompareTo(s_hijriYearInfo[++index].GregorianDate) > 0); //while greater
+
+            if (time.CompareTo(s_hijriYearInfo[index].GregorianDate) != 0)
+            {
+                index--;
+            }
+
+            ts = time.Subtract(s_hijriYearInfo[index].GregorianDate);
+            yh1 = index + MinCalendarYear;
+
+            mh1 = 1;
+            dh1 = 1;
+            nDays = ts.TotalDays;
+            b = s_hijriYearInfo[index].HijriMonthsLengthFlags;
+            DaysPerThisMonth = 29 + (b & 1);
+
+            while (nDays >= DaysPerThisMonth)
+            {
+                nDays -= DaysPerThisMonth;
+                b = b >> 1;
+                DaysPerThisMonth = 29 + (b & 1);
+                mh1++;
+            }
+            dh1 += (int)nDays;
+
+            HijriDay = dh1;
+            HijriMonth = mh1;
+            HijriYear = yh1;
+        }
+
+        /*=================================GetDatePart==========================
+        **Action: Returns a given date part of this <i>DateTime</i>. This method is used
+        **       to compute the year, day-of-year, month, or day part.
+        **Returns:
+        **Arguments:
+        **Exceptions:  ArgumentException if part is incorrect.
+        **Notes:
+        **      First, we get the absolute date (the number of days from January 1st, 1 A.C) for the given ticks.
+        **      Use the formula (((AbsoluteDate - 226894) * 33) / (33 * 365 + 8)) + 1, we can a rough value for the UmAlQura year.
+        **      In order to get the exact UmAlQura year, we compare the exact absolute date for UmAlQuraYear and (UmAlQuraYear + 1).
+        **      From here, we can get the correct UmAlQura year.
+        ============================================================================*/
+
+        internal virtual int GetDatePart(DateTime time, int part)
+        {
+            int UmAlQuraYear = 0;              // UmAlQura year
+            int UmAlQuraMonth = 0;             // UmAlQura month
+            int UmAlQuraDay = 0;               // UmAlQura day
+            long ticks = time.Ticks;
+            CheckTicksRange(ticks);
+
+            ConvertGregorianToHijri(time, ref UmAlQuraYear, ref UmAlQuraMonth, ref UmAlQuraDay);
+
+            if (part == DatePartYear)
+                return (UmAlQuraYear);
+
+            if (part == DatePartMonth)
+                return (UmAlQuraMonth);
+
+            if (part == DatePartDay)
+                return (UmAlQuraDay);
+
+            if (part == DatePartDayOfYear)
+                return (int)(GetAbsoluteDateUmAlQura(UmAlQuraYear, UmAlQuraMonth, UmAlQuraDay) - GetAbsoluteDateUmAlQura(UmAlQuraYear, 1, 1) + 1);
+
+            // Incorrect part value.
+            throw new InvalidOperationException(SR.InvalidOperation_DateTimeParsing);
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // months to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year and month parts of the specified DateTime by
+        // value months, and, if required, adjusting the day part of the
+        // resulting date downwards to the last day of the resulting month in the
+        // resulting year. The time-of-day part of the result is the same as the
+        // time-of-day part of the specified DateTime.
+        //
+        // In more precise terms, considering the specified DateTime to be of the
+        // form y / m / d + t, where y is the
+        // year, m is the month, d is the day, and t is the
+        // time-of-day, the result is y1 / m1 / d1 + t,
+        // where y1 and m1 are computed by adding value months
+        // to y and m, and d1 is the largest value less than
+        // or equal to d that denotes a valid day in month m1 of year
+        // y1.
+        //
+
+
+        public override DateTime AddMonths(DateTime time, int months)
+        {
+            if (months < -120000 || months > 120000)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(months),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Range,
+                                -120000,
+                                120000));
+            }
+            // Get the date in UmAlQura calendar.
+            int y = GetDatePart(time, DatePartYear);
+            int m = GetDatePart(time, DatePartMonth);
+            int d = GetDatePart(time, DatePartDay);
+            int i = m - 1 + months;
+
+            if (i >= 0)
+            {
+                m = i % 12 + 1;
+                y = y + i / 12;
+            }
+            else
+            {
+                m = 12 + (i + 1) % 12;
+                y = y + (i - 11) / 12;
+            }
+
+            if (d > 29)
+            {
+                int days = GetDaysInMonth(y, m);
+                if (d > days)
+                {
+                    d = days;
+                }
+            }
+            CheckYearRange(y, UmAlQuraEra);
+            DateTime dt = new DateTime(GetAbsoluteDateUmAlQura(y, m, d) * TicksPerDay + time.Ticks % TicksPerDay);
+            Calendar.CheckAddResult(dt.Ticks, MinSupportedDateTime, MaxSupportedDateTime);
+            return (dt);
+        }
+
+        // Returns the DateTime resulting from adding the given number of
+        // years to the specified DateTime. The result is computed by incrementing
+        // (or decrementing) the year part of the specified DateTime by value
+        // years. If the month and day of the specified DateTime is 2/29, and if the
+        // resulting year is not a leap year, the month and day of the resulting
+        // DateTime becomes 2/28. Otherwise, the month, day, and time-of-day
+        // parts of the result are the same as those of the specified DateTime.
+        //
+
+
+        public override DateTime AddYears(DateTime time, int years)
+        {
+            return (AddMonths(time, years * 12));
+        }
+
+        // Returns the day-of-month part of the specified DateTime. The returned
+        // value is an integer between 1 and 31.
+        //
+
+
+        public override int GetDayOfMonth(DateTime time)
+        {
+            return (GetDatePart(time, DatePartDay));
+        }
+
+        // Returns the day-of-week part of the specified DateTime. The returned value
+        // is an integer between 0 and 6, where 0 indicates Sunday, 1 indicates
+        // Monday, 2 indicates Tuesday, 3 indicates Wednesday, 4 indicates
+        // Thursday, 5 indicates Friday, and 6 indicates Saturday.
+        //
+
+
+        public override DayOfWeek GetDayOfWeek(DateTime time)
+        {
+            return ((DayOfWeek)((int)(time.Ticks / TicksPerDay + 1) % 7));
+        }
+
+        // Returns the day-of-year part of the specified DateTime. The returned value
+        // is an integer between 1 and 354 or 355.
+        //
+
+
+        public override int GetDayOfYear(DateTime time)
+        {
+            return (GetDatePart(time, DatePartDayOfYear));
+        }
+
+        /*
+        internal bool CouldBeLeapYear(int year)
+        {
+            return ((((year * 11) + 14) % 30) < 11);
+        }
+        */
+
+        // Returns the number of days in the month given by the year and
+        // month arguments.
+        //
+
+
+        public override int GetDaysInMonth(int year, int month, int era)
+        {
+            CheckYearMonthRange(year, month, era);
+
+            if ((s_hijriYearInfo[year - MinCalendarYear].HijriMonthsLengthFlags & (1 << month - 1)) == 0)
+                return 29;
+            else
+                return 30;
+        }
+
+        internal static int RealGetDaysInYear(int year)
+        {
+            int days = 0, b;
+
+            Debug.Assert((year >= MinCalendarYear) && (year <= MaxCalendarYear), "Hijri year is out of range.");
+
+            b = s_hijriYearInfo[year - MinCalendarYear].HijriMonthsLengthFlags;
+
+            for (int m = 1; m <= 12; m++)
+            {
+                days = days + 29 + (b & 1);   /* Add the months lengths before mh */
+                b = b >> 1;
+            }
+            Debug.Assert((days == 354) || (days == 355), "Hijri year has to be 354 or 355 days.");
+            return days;
+        }
+
+        // Returns the number of days in the year given by the year argument for the current era.
+        //
+
+
+        public override int GetDaysInYear(int year, int era)
+        {
+            CheckYearRange(year, era);
+            return (RealGetDaysInYear(year));
+        }
+
+        // Returns the era for the specified DateTime value.
+
+
+        public override int GetEra(DateTime time)
+        {
+            CheckTicksRange(time.Ticks);
+            return (UmAlQuraEra);
+        }
+
+
+
+        public override int[] Eras
+        {
+            get
+            {
+                return (new int[] { UmAlQuraEra });
+            }
+        }
+
+        // Returns the month part of the specified DateTime. The returned value is an
+        // integer between 1 and 12.
+        //
+
+
+        public override int GetMonth(DateTime time)
+        {
+            return (GetDatePart(time, DatePartMonth));
+        }
+
+        // Returns the number of months in the specified year and era.
+
+
+        public override int GetMonthsInYear(int year, int era)
+        {
+            CheckYearRange(year, era);
+            return (12);
+        }
+
+        // Returns the year part of the specified DateTime. The returned value is an
+        // integer between MinCalendarYear and MaxCalendarYear.
+        //
+
+
+        public override int GetYear(DateTime time)
+        {
+            return (GetDatePart(time, DatePartYear));
+        }
+
+        // Checks whether a given day in the specified era is a leap day. This method returns true if
+        // the date is a leap day, or false if not.
+        //
+
+
+        public override bool IsLeapDay(int year, int month, int day, int era)
+        {
+            if (day >= 1 && day <= 29)
+            {
+                CheckYearMonthRange(year, month, era);
+                return (false);
+            }
+
+            // The year/month/era value checking is done in GetDaysInMonth().
+            int daysInMonth = GetDaysInMonth(year, month, era);
+            if (day < 1 || day > daysInMonth)
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(day),
+                            String.Format(
+                                CultureInfo.CurrentCulture,
+                                SR.ArgumentOutOfRange_Day,
+                                daysInMonth,
+                                month));
+            }
+            return (false);
+        }
+
+        // Returns  the leap month in a calendar year of the specified era. This method returns 0
+        // if this calendar does not have leap month, or this year is not a leap year.
+        //
+
+
+        public override int GetLeapMonth(int year, int era)
+        {
+            CheckYearRange(year, era);
+            return (0);
+        }
+
+        // Checks whether a given month in the specified era is a leap month. This method returns true if
+        // month is a leap month, or false if not.
+        //
+
+
+        public override bool IsLeapMonth(int year, int month, int era)
+        {
+            CheckYearMonthRange(year, month, era);
+            return (false);
+        }
+
+        // Checks whether a given year in the specified era is a leap year. This method returns true if
+        // year is a leap year, or false if not.
+        //
+
+
+        public override bool IsLeapYear(int year, int era)
+        {
+            CheckYearRange(year, era);
+            if (RealGetDaysInYear(year) == 355)
+                return true;
+            else
+                return false;
+        }
+
+        // Returns the date and time converted to a DateTime value.  Throws an exception if the n-tuple is invalid.
+        //
+
+
+        public override DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era)
+        {
+            if (day >= 1 && day <= 29)
+            {
+                CheckYearMonthRange(year, month, era);
+                goto DayInRang;
+            }
+
+            // The year/month/era value checking is done in GetDaysInMonth().
+            int daysInMonth = GetDaysInMonth(year, month, era);
+
+            if (day < 1 || day > daysInMonth)
+            {
+                throw new ArgumentOutOfRangeException(
+                           nameof(day),
+                           String.Format(
+                               CultureInfo.CurrentCulture,
+                               SR.ArgumentOutOfRange_Day,
+                               daysInMonth,
+                               month));
+            }
+        DayInRang:
+            long lDate = GetAbsoluteDateUmAlQura(year, month, day);
+
+            if (lDate >= 0)
+            {
+                return (new DateTime(lDate * GregorianCalendar.TicksPerDay + TimeToTicks(hour, minute, second, millisecond)));
+            }
+            else
+            {
+                throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadYearMonthDay);
+            }
+        }
+
+        private const int DEFAULT_TWO_DIGIT_YEAR_MAX = 1451;
+
+
+
+        public override int TwoDigitYearMax
+        {
+            get
+            {
+                if (twoDigitYearMax == -1)
+                {
+                    twoDigitYearMax = GetSystemTwoDigitYearSetting(ID, DEFAULT_TWO_DIGIT_YEAR_MAX);
+                }
+                return (twoDigitYearMax);
+            }
+
+            set
+            {
+                if (value != 99 && (value < MinCalendarYear || value > MaxCalendarYear))
+                {
+                    throw new ArgumentOutOfRangeException(
+                                nameof(value),
+                                String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    MinCalendarYear,
+                                    MaxCalendarYear));
+                }
+                VerifyWritable();
+                // We allow year 99 to be set so that one can make ToFourDigitYearMax a no-op by setting TwoDigitYearMax to 99.
+                twoDigitYearMax = value;
+            }
+        }
+
+
+
+        public override int ToFourDigitYear(int year)
+        {
+            if (year < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(year),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (year < 100)
+            {
+                return (base.ToFourDigitYear(year));
+            }
+
+            if ((year < MinCalendarYear) || (year > MaxCalendarYear))
+            {
+                throw new ArgumentOutOfRangeException(
+                            nameof(year),
+                            String.Format(
+                                    CultureInfo.CurrentCulture,
+                                    SR.ArgumentOutOfRange_Range,
+                                    MinCalendarYear,
+                                    MaxCalendarYear));
+            }
+            return (year);
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Globalization/UnicodeCategory.cs b/src/System.Private.CoreLib/shared/System/Globalization/UnicodeCategory.cs
new file mode 100644
index 0000000000..f0ae1fdfd9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Globalization/UnicodeCategory.cs
@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Globalization
+{
+    public enum UnicodeCategory
+    {
+        UppercaseLetter = 0,
+        LowercaseLetter = 1,
+        TitlecaseLetter = 2,
+        ModifierLetter = 3,
+        OtherLetter = 4,
+        NonSpacingMark = 5,
+        SpacingCombiningMark = 6,
+        EnclosingMark = 7,
+        DecimalDigitNumber = 8,
+        LetterNumber = 9,
+        OtherNumber = 10,
+        SpaceSeparator = 11,
+        LineSeparator = 12,
+        ParagraphSeparator = 13,
+        Control = 14,
+        Format = 15,
+        Surrogate = 16,
+        PrivateUse = 17,
+        ConnectorPunctuation = 18,
+        DashPunctuation = 19,
+        OpenPunctuation = 20,
+        ClosePunctuation = 21,
+        InitialQuotePunctuation = 22,
+        FinalQuotePunctuation = 23,
+        OtherPunctuation = 24,
+        MathSymbol = 25,
+        CurrencySymbol = 26,
+        ModifierSymbol = 27,
+        OtherSymbol = 28,
+        OtherNotAssigned = 29,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Guid.Unix.cs b/src/System.Private.CoreLib/shared/System/Guid.Unix.cs
new file mode 100644
index 0000000000..442e7f8837
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Guid.Unix.cs
@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System
+{
+    partial struct Guid
+    {
+        // This will create a new random guid based on the https://www.ietf.org/rfc/rfc4122.txt 
+        public static unsafe Guid NewGuid()
+        {
+            Guid g;
+            Interop.GetRandomBytes((byte*)&g, sizeof(Guid));
+            
+            const ushort VersionMask = 0xF000;
+            const ushort RandomGuidVersion = 0x4000;
+
+            const byte ClockSeqHiAndReservedMask = 0xC0;
+            const byte ClockSeqHiAndReservedValue = 0x80;
+
+            // Modify bits indicating the type of the GUID
+
+            unchecked
+            {
+                // time_hi_and_version
+                g._c = (short)((g._c & ~VersionMask) | RandomGuidVersion);
+                // clock_seq_hi_and_reserved
+                g._d = (byte)((g._d & ~ClockSeqHiAndReservedMask) | ClockSeqHiAndReservedValue);
+            }
+
+            return g;
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Guid.Windows.cs b/src/System.Private.CoreLib/shared/System/Guid.Windows.cs
new file mode 100644
index 0000000000..f00fbe45b3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Guid.Windows.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    partial struct Guid
+    {
+        public static Guid NewGuid()
+        {
+            // CoCreateGuid should never return Guid.Empty, since it attempts to maintain some
+            // uniqueness guarantees.
+
+            Guid g;
+            int hr = Interop.Ole32.CoCreateGuid(out g);
+            // We don't expect that this will ever throw an error, none are even documented, and so we don't want to pull 
+            // in the HR to ComException mappings into the core library just for this so we will try a generic exception if 
+            // we ever hit this condition.
+            if (hr != 0)
+            {
+                Exception ex = new Exception();
+                ex.SetErrorCode(hr);
+                throw ex;
+            }
+            return g;
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Guid.cs b/src/System.Private.CoreLib/shared/System/Guid.cs
new file mode 100644
index 0000000000..37a8dce94c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Guid.cs
@@ -0,0 +1,1436 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+using Internal.Runtime.CompilerServices;
+
+namespace System
+{
+    // Represents a Globally Unique Identifier.
+    [StructLayout(LayoutKind.Sequential)]
+    [Serializable]
+    [Runtime.Versioning.NonVersionable] // This only applies to field layout
+    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public partial struct Guid : IFormattable, IComparable, IComparable<Guid>, IEquatable<Guid>, ISpanFormattable
+    {
+        public static readonly Guid Empty = new Guid();
+
+        ////////////////////////////////////////////////////////////////////////////////
+        //  Member variables
+        ////////////////////////////////////////////////////////////////////////////////
+        private int _a; // Do not rename (binary serialization)
+        private short _b; // Do not rename (binary serialization)
+        private short _c; // Do not rename (binary serialization)
+        private byte _d; // Do not rename (binary serialization)
+        private byte _e; // Do not rename (binary serialization)
+        private byte _f; // Do not rename (binary serialization)
+        private byte _g; // Do not rename (binary serialization)
+        private byte _h; // Do not rename (binary serialization)
+        private byte _i; // Do not rename (binary serialization)
+        private byte _j; // Do not rename (binary serialization)
+        private byte _k; // Do not rename (binary serialization)
+
+        ////////////////////////////////////////////////////////////////////////////////
+        //  Constructors
+        ////////////////////////////////////////////////////////////////////////////////
+
+        // Creates a new guid from an array of bytes.
+        public Guid(byte[] b) :
+            this(new ReadOnlySpan<byte>(b ?? throw new ArgumentNullException(nameof(b))))
+        {
+        }
+
+        // Creates a new guid from a read-only span.
+        public Guid(ReadOnlySpan<byte> b)
+        {
+            if (b.Length != 16)
+                throw new ArgumentException(SR.Format(SR.Arg_GuidArrayCtor, "16"), nameof(b));
+
+            _a = b[3] << 24 | b[2] << 16 | b[1] << 8 | b[0];
+            _b = (short)(b[5] << 8 | b[4]);
+            _c = (short)(b[7] << 8 | b[6]);
+            _d = b[8];
+            _e = b[9];
+            _f = b[10];
+            _g = b[11];
+            _h = b[12];
+            _i = b[13];
+            _j = b[14];
+            _k = b[15];
+        }
+
+        [CLSCompliant(false)]
+        public Guid(uint a, ushort b, ushort c, byte d, byte e, byte f, byte g, byte h, byte i, byte j, byte k)
+        {
+            _a = (int)a;
+            _b = (short)b;
+            _c = (short)c;
+            _d = d;
+            _e = e;
+            _f = f;
+            _g = g;
+            _h = h;
+            _i = i;
+            _j = j;
+            _k = k;
+        }
+
+        // Creates a new GUID initialized to the value represented by the arguments.
+        //
+        public Guid(int a, short b, short c, byte[] d)
+        {
+            if (d == null)
+                throw new ArgumentNullException(nameof(d));
+            // Check that array is not too big
+            if (d.Length != 8)
+                throw new ArgumentException(SR.Format(SR.Arg_GuidArrayCtor, "8"), nameof(d));
+
+            _a = a;
+            _b = b;
+            _c = c;
+            _d = d[0];
+            _e = d[1];
+            _f = d[2];
+            _g = d[3];
+            _h = d[4];
+            _i = d[5];
+            _j = d[6];
+            _k = d[7];
+        }
+
+        // Creates a new GUID initialized to the value represented by the
+        // arguments.  The bytes are specified like this to avoid endianness issues.
+        //
+        public Guid(int a, short b, short c, byte d, byte e, byte f, byte g, byte h, byte i, byte j, byte k)
+        {
+            _a = a;
+            _b = b;
+            _c = c;
+            _d = d;
+            _e = e;
+            _f = f;
+            _g = g;
+            _h = h;
+            _i = i;
+            _j = j;
+            _k = k;
+        }
+
+        [Flags]
+        private enum GuidStyles
+        {
+            None = 0x00000000,
+            AllowParenthesis = 0x00000001, //Allow the guid to be enclosed in parens
+            AllowBraces = 0x00000002, //Allow the guid to be enclosed in braces
+            AllowDashes = 0x00000004, //Allow the guid to contain dash group separators
+            AllowHexPrefix = 0x00000008, //Allow the guid to contain {0xdd,0xdd}
+            RequireParenthesis = 0x00000010, //Require the guid to be enclosed in parens
+            RequireBraces = 0x00000020, //Require the guid to be enclosed in braces
+            RequireDashes = 0x00000040, //Require the guid to contain dash group separators
+            RequireHexPrefix = 0x00000080, //Require the guid to contain {0xdd,0xdd}
+
+            HexFormat = RequireBraces | RequireHexPrefix,                      /* X */
+            NumberFormat = None,                                                  /* N */
+            DigitFormat = RequireDashes,                                         /* D */
+            BraceFormat = RequireBraces | RequireDashes,                         /* B */
+            ParenthesisFormat = RequireParenthesis | RequireDashes,                    /* P */
+
+            Any = AllowParenthesis | AllowBraces | AllowDashes | AllowHexPrefix,
+        }
+        private enum GuidParseThrowStyle
+        {
+            None = 0,
+            All = 1,
+            AllButOverflow = 2
+        }
+        private enum ParseFailureKind
+        {
+            None = 0,
+            ArgumentNull = 1,
+            Format = 2,
+            FormatWithParameter = 3,
+            NativeException = 4,
+            FormatWithInnerException = 5
+        }
+
+        // This will store the result of the parsing.  And it will eventually be used to construct a Guid instance.
+        private struct GuidResult
+        {
+            internal Guid _parsedGuid;
+            internal GuidParseThrowStyle _throwStyle;
+
+            private ParseFailureKind _failure;
+            private string _failureMessageID;
+            private object _failureMessageFormatArgument;
+            private string _failureArgumentName;
+            private Exception _innerException;
+
+            internal void Init(GuidParseThrowStyle canThrow)
+            {
+                _throwStyle = canThrow;
+            }
+
+            internal void SetFailure(Exception nativeException)
+            {
+                _failure = ParseFailureKind.NativeException;
+                _innerException = nativeException;
+            }
+
+            internal void SetFailure(ParseFailureKind failure, string failureMessageID)
+            {
+                SetFailure(failure, failureMessageID, null, null, null);
+            }
+
+            internal void SetFailure(ParseFailureKind failure, string failureMessageID, object failureMessageFormatArgument)
+            {
+                SetFailure(failure, failureMessageID, failureMessageFormatArgument, null, null);
+            }
+
+            internal void SetFailure(ParseFailureKind failure, string failureMessageID, object failureMessageFormatArgument,
+                                     string failureArgumentName, Exception innerException)
+            {
+                Debug.Assert(failure != ParseFailureKind.NativeException, "ParseFailureKind.NativeException should not be used with this overload");
+                _failure = failure;
+                _failureMessageID = failureMessageID;
+                _failureMessageFormatArgument = failureMessageFormatArgument;
+                _failureArgumentName = failureArgumentName;
+                _innerException = innerException;
+                if (_throwStyle != GuidParseThrowStyle.None)
+                {
+                    throw GetGuidParseException();
+                }
+            }
+
+            internal Exception GetGuidParseException()
+            {
+                switch (_failure)
+                {
+                    case ParseFailureKind.ArgumentNull:
+                        return new ArgumentNullException(_failureArgumentName, SR.GetResourceString(_failureMessageID));
+
+                    case ParseFailureKind.FormatWithInnerException:
+                        return new FormatException(SR.GetResourceString(_failureMessageID), _innerException);
+
+                    case ParseFailureKind.FormatWithParameter:
+                        return new FormatException(SR.Format(SR.GetResourceString(_failureMessageID), _failureMessageFormatArgument));
+
+                    case ParseFailureKind.Format:
+                        return new FormatException(SR.GetResourceString(_failureMessageID));
+
+                    case ParseFailureKind.NativeException:
+                        return _innerException;
+
+                    default:
+                        Debug.Fail("Unknown GuidParseFailure: " + _failure);
+                        return new FormatException(SR.Format_GuidUnrecognized);
+                }
+            }
+        }
+
+        // Creates a new guid based on the value in the string.  The value is made up
+        // of hex digits speared by the dash ("-"). The string may begin and end with
+        // brackets ("{", "}").
+        //
+        // The string must be of the form dddddddd-dddd-dddd-dddd-dddddddddddd. where
+        // d is a hex digit. (That is 8 hex digits, followed by 4, then 4, then 4,
+        // then 12) such as: "CA761232-ED42-11CE-BACD-00AA0057B223"
+        //
+        public Guid(string g)
+        {
+            if (g == null)
+            {
+                throw new ArgumentNullException(nameof(g));
+            }
+
+            GuidResult result = new GuidResult();
+            result.Init(GuidParseThrowStyle.All);
+            if (TryParseGuid(g, GuidStyles.Any, ref result))
+            {
+                this = result._parsedGuid;
+            }
+            else
+            {
+                throw result.GetGuidParseException();
+            }
+        }
+
+        public static Guid Parse(string input) =>
+            Parse(input != null ? (ReadOnlySpan<char>)input : throw new ArgumentNullException(nameof(input)));
+
+        public static Guid Parse(ReadOnlySpan<char> input)
+        {
+            GuidResult result = new GuidResult();
+            result.Init(GuidParseThrowStyle.AllButOverflow);
+            if (TryParseGuid(input, GuidStyles.Any, ref result))
+            {
+                return result._parsedGuid;
+            }
+            else
+            {
+                throw result.GetGuidParseException();
+            }
+        }
+
+        public static bool TryParse(string input, out Guid result)
+        {
+            if (input == null)
+            {
+                result = default(Guid);
+                return false;
+            }
+
+            return TryParse((ReadOnlySpan<char>)input, out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> input, out Guid result)
+        {
+            GuidResult parseResult = new GuidResult();
+            parseResult.Init(GuidParseThrowStyle.None);
+            if (TryParseGuid(input, GuidStyles.Any, ref parseResult))
+            {
+                result = parseResult._parsedGuid;
+                return true;
+            }
+            else
+            {
+                result = default(Guid);
+                return false;
+            }
+        }
+
+        public static Guid ParseExact(string input, string format) =>
+            ParseExact(
+                input != null ? (ReadOnlySpan<char>)input : throw new ArgumentNullException(nameof(input)),
+                format != null ? (ReadOnlySpan<char>)format : throw new ArgumentNullException(nameof(format)));
+
+        public static Guid ParseExact(ReadOnlySpan<char> input, ReadOnlySpan<char> format)
+        {
+            if (format.Length != 1)
+            {
+                // all acceptable format strings are of length 1
+                throw new FormatException(SR.Format_InvalidGuidFormatSpecification);
+            }
+
+            GuidStyles style;
+            switch (format[0])
+            {
+                case 'D':
+                case 'd':
+                    style = GuidStyles.DigitFormat;
+                    break;
+                case 'N':
+                case 'n':
+                    style = GuidStyles.NumberFormat;
+                    break;
+                case 'B':
+                case 'b':
+                    style = GuidStyles.BraceFormat;
+                    break;
+                case 'P':
+                case 'p':
+                    style = GuidStyles.ParenthesisFormat;
+                    break;
+                case 'X':
+                case 'x':
+                    style = GuidStyles.HexFormat;
+                    break;
+                default:
+                    throw new FormatException(SR.Format_InvalidGuidFormatSpecification);
+            }
+
+            GuidResult result = new GuidResult();
+            result.Init(GuidParseThrowStyle.AllButOverflow);
+            if (TryParseGuid(input, style, ref result))
+            {
+                return result._parsedGuid;
+            }
+            else
+            {
+                throw result.GetGuidParseException();
+            }
+        }
+
+        public static bool TryParseExact(string input, string format, out Guid result)
+        {
+            if (input == null)
+            {
+                result = default(Guid);
+                return false;
+            }
+
+            return TryParseExact((ReadOnlySpan<char>)input, format, out result);
+        }
+
+        public static bool TryParseExact(ReadOnlySpan<char> input, ReadOnlySpan<char> format, out Guid result)
+        {
+            if (format.Length != 1)
+            {
+                result = default(Guid);
+                return false;
+            }
+
+            GuidStyles style;
+            switch (format[0])
+            {
+                case 'D':
+                case 'd':
+                    style = GuidStyles.DigitFormat;
+                    break;
+                case 'N':
+                case 'n':
+                    style = GuidStyles.NumberFormat;
+                    break;
+                case 'B':
+                case 'b':
+                    style = GuidStyles.BraceFormat;
+                    break;
+                case 'P':
+                case 'p':
+                    style = GuidStyles.ParenthesisFormat;
+                    break;
+                case 'X':
+                case 'x':
+                    style = GuidStyles.HexFormat;
+                    break;
+                default:
+                    // invalid guid format specification
+                    result = default(Guid);
+                    return false;
+            }
+
+            GuidResult parseResult = new GuidResult();
+            parseResult.Init(GuidParseThrowStyle.None);
+            if (TryParseGuid(input, style, ref parseResult))
+            {
+                result = parseResult._parsedGuid;
+                return true;
+            }
+            else
+            {
+                result = default(Guid);
+                return false;
+            }
+        }
+
+        private static bool TryParseGuid(ReadOnlySpan<char> guidString, GuidStyles flags, ref GuidResult result)
+        {
+            guidString = guidString.Trim(); // Remove whitespace from beginning and end
+
+            if (guidString.Length == 0)
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidUnrecognized));
+                return false;
+            }
+
+            // Check for dashes
+            bool dashesExistInString = guidString.IndexOf('-') >= 0;
+
+            if (dashesExistInString)
+            {
+                if ((flags & (GuidStyles.AllowDashes | GuidStyles.RequireDashes)) == 0)
+                {
+                    // dashes are not allowed
+                    result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidUnrecognized));
+                    return false;
+                }
+            }
+            else
+            {
+                if ((flags & GuidStyles.RequireDashes) != 0)
+                {
+                    // dashes are required
+                    result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidUnrecognized));
+                    return false;
+                }
+            }
+
+            // Check for braces
+            bool bracesExistInString = (guidString.IndexOf('{') >= 0);
+
+            if (bracesExistInString)
+            {
+                if ((flags & (GuidStyles.AllowBraces | GuidStyles.RequireBraces)) == 0)
+                {
+                    // braces are not allowed
+                    result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidUnrecognized));
+                    return false;
+                }
+            }
+            else
+            {
+                if ((flags & GuidStyles.RequireBraces) != 0)
+                {
+                    // braces are required
+                    result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidUnrecognized));
+                    return false;
+                }
+            }
+
+            // Check for parenthesis
+            bool parenthesisExistInString = (guidString.IndexOf('(') >= 0);
+
+            if (parenthesisExistInString)
+            {
+                if ((flags & (GuidStyles.AllowParenthesis | GuidStyles.RequireParenthesis)) == 0)
+                {
+                    // parenthesis are not allowed
+                    result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidUnrecognized));
+                    return false;
+                }
+            }
+            else
+            {
+                if ((flags & GuidStyles.RequireParenthesis) != 0)
+                {
+                    // parenthesis are required
+                    result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidUnrecognized));
+                    return false;
+                }
+            }
+
+            try
+            {
+                // let's get on with the parsing
+                if (dashesExistInString)
+                {
+                    // Check if it's of the form [{|(]dddddddd-dddd-dddd-dddd-dddddddddddd[}|)]
+                    return TryParseGuidWithDashes(guidString, ref result);
+                }
+                else if (bracesExistInString)
+                {
+                    // Check if it's of the form {0xdddddddd,0xdddd,0xdddd,{0xdd,0xdd,0xdd,0xdd,0xdd,0xdd,0xdd,0xdd}}
+                    return TryParseGuidWithHexPrefix(guidString, ref result);
+                }
+                else
+                {
+                    // Check if it's of the form dddddddddddddddddddddddddddddddd
+                    return TryParseGuidWithNoStyle(guidString, ref result);
+                }
+            }
+            catch (IndexOutOfRangeException ex)
+            {
+                result.SetFailure(ParseFailureKind.FormatWithInnerException, nameof(SR.Format_GuidUnrecognized), null, null, ex);
+                return false;
+            }
+            catch (ArgumentException ex)
+            {
+                result.SetFailure(ParseFailureKind.FormatWithInnerException, nameof(SR.Format_GuidUnrecognized), null, null, ex);
+                return false;
+            }
+        }
+
+        // Check if it's of the form {0xdddddddd,0xdddd,0xdddd,{0xdd,0xdd,0xdd,0xdd,0xdd,0xdd,0xdd,0xdd}}
+        private static bool TryParseGuidWithHexPrefix(ReadOnlySpan<char> guidString, ref GuidResult result)
+        {
+            int numStart = 0;
+            int numLen = 0;
+
+            // Eat all of the whitespace
+            guidString = EatAllWhitespace(guidString);
+
+            // Check for leading '{'
+            if (guidString.Length == 0 || guidString[0] != '{')
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidBrace));
+                return false;
+            }
+
+            // Check for '0x'
+            if (!IsHexPrefix(guidString, 1))
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidHexPrefix), "{0xdddddddd, etc}");
+                return false;
+            }
+
+            // Find the end of this hex number (since it is not fixed length)
+            numStart = 3;
+            numLen = guidString.Slice(numStart).IndexOf(',');
+            if (numLen <= 0)
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidComma));
+                return false;
+            }
+
+            if (!StringToInt(guidString.Slice(numStart, numLen) /*first DWORD*/, -1, ParseNumbers.IsTight, out result._parsedGuid._a, ref result))
+                return false;
+
+            // Check for '0x'
+            if (!IsHexPrefix(guidString, numStart + numLen + 1))
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidHexPrefix), "{0xdddddddd, 0xdddd, etc}");
+                return false;
+            }
+            // +3 to get by ',0x'
+            numStart = numStart + numLen + 3;
+            numLen = guidString.Slice(numStart).IndexOf(',');
+            if (numLen <= 0)
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidComma));
+                return false;
+            }
+
+            // Read in the number
+            if (!StringToShort(guidString.Slice(numStart, numLen) /*first DWORD*/, -1, ParseNumbers.IsTight, out result._parsedGuid._b, ref result))
+                return false;
+            // Check for '0x'
+            if (!IsHexPrefix(guidString, numStart + numLen + 1))
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidHexPrefix), "{0xdddddddd, 0xdddd, 0xdddd, etc}");
+                return false;
+            }
+            // +3 to get by ',0x'
+            numStart = numStart + numLen + 3;
+            numLen = guidString.Slice(numStart).IndexOf(',');
+            if (numLen <= 0)
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidComma));
+                return false;
+            }
+
+            // Read in the number
+            if (!StringToShort(guidString.Slice(numStart, numLen) /*first DWORD*/, -1, ParseNumbers.IsTight, out result._parsedGuid._c, ref result))
+                return false;
+
+            // Check for '{'
+            if (guidString.Length <= numStart + numLen + 1 || guidString[numStart + numLen + 1] != '{')
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidBrace));
+                return false;
+            }
+
+            // Prepare for loop
+            numLen++;
+            Span<byte> bytes = stackalloc byte[8];
+
+            for (int i = 0; i < bytes.Length; i++)
+            {
+                // Check for '0x'
+                if (!IsHexPrefix(guidString, numStart + numLen + 1))
+                {
+                    result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidHexPrefix), "{... { ... 0xdd, ...}}");
+                    return false;
+                }
+
+                // +3 to get by ',0x' or '{0x' for first case
+                numStart = numStart + numLen + 3;
+
+                // Calculate number length
+                if (i < 7)  // first 7 cases
+                {
+                    numLen = guidString.Slice(numStart).IndexOf(',');
+                    if (numLen <= 0)
+                    {
+                        result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidComma));
+                        return false;
+                    }
+                }
+                else       // last case ends with '}', not ','
+                {
+                    numLen = guidString.Slice(numStart).IndexOf('}');
+                    if (numLen <= 0)
+                    {
+                        result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidBraceAfterLastNumber));
+                        return false;
+                    }
+                }
+
+                // Read in the number
+                int signedNumber;
+                if (!StringToInt(guidString.Slice(numStart, numLen), -1, ParseNumbers.IsTight, out signedNumber, ref result))
+                {
+                    return false;
+                }
+                uint number = (uint)signedNumber;
+
+                // check for overflow
+                if (number > 255)
+                {
+                    result.SetFailure(ParseFailureKind.Format, nameof(SR.Overflow_Byte));
+                    return false;
+                }
+                bytes[i] = (byte)number;
+            }
+
+            result._parsedGuid._d = bytes[0];
+            result._parsedGuid._e = bytes[1];
+            result._parsedGuid._f = bytes[2];
+            result._parsedGuid._g = bytes[3];
+            result._parsedGuid._h = bytes[4];
+            result._parsedGuid._i = bytes[5];
+            result._parsedGuid._j = bytes[6];
+            result._parsedGuid._k = bytes[7];
+
+            // Check for last '}'
+            if (numStart + numLen + 1 >= guidString.Length || guidString[numStart + numLen + 1] != '}')
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidEndBrace));
+                return false;
+            }
+
+            // Check if we have extra characters at the end
+            if (numStart + numLen + 1 != guidString.Length - 1)
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_ExtraJunkAtEnd));
+                return false;
+            }
+
+            return true;
+        }
+
+        // Check if it's of the form dddddddddddddddddddddddddddddddd
+        private static bool TryParseGuidWithNoStyle(ReadOnlySpan<char> guidString, ref GuidResult result)
+        {
+            int startPos = 0;
+            int temp;
+            long templ;
+            int currentPos = 0;
+
+            if (guidString.Length != 32)
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidInvLen));
+                return false;
+            }
+
+            for (int i = 0; i < guidString.Length; i++)
+            {
+                char ch = guidString[i];
+                if (ch >= '0' && ch <= '9')
+                {
+                    continue;
+                }
+                else
+                {
+                    char upperCaseCh = char.ToUpperInvariant(ch);
+                    if (upperCaseCh >= 'A' && upperCaseCh <= 'F')
+                    {
+                        continue;
+                    }
+                }
+
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidInvalidChar));
+                return false;
+            }
+
+            if (!StringToInt(guidString.Slice(startPos, 8) /*first DWORD*/, -1, ParseNumbers.IsTight, out result._parsedGuid._a, ref result))
+                return false;
+
+            startPos += 8;
+            if (!StringToShort(guidString.Slice(startPos, 4), -1, ParseNumbers.IsTight, out result._parsedGuid._b, ref result))
+                return false;
+
+            startPos += 4;
+            if (!StringToShort(guidString.Slice(startPos, 4), -1, ParseNumbers.IsTight, out result._parsedGuid._c, ref result))
+                return false;
+
+            startPos += 4;
+            if (!StringToInt(guidString.Slice(startPos, 4), -1, ParseNumbers.IsTight, out temp, ref result))
+                return false;
+
+            startPos += 4;
+            currentPos = startPos;
+
+            if (!StringToLong(guidString, ref currentPos, ParseNumbers.NoSpace, out templ, ref result))
+                return false;
+
+            if (currentPos - startPos != 12)
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidInvLen));
+                return false;
+            }
+
+            result._parsedGuid._d = (byte)(temp >> 8);
+            result._parsedGuid._e = (byte)(temp);
+            temp = (int)(templ >> 32);
+            result._parsedGuid._f = (byte)(temp >> 8);
+            result._parsedGuid._g = (byte)(temp);
+            temp = (int)(templ);
+            result._parsedGuid._h = (byte)(temp >> 24);
+            result._parsedGuid._i = (byte)(temp >> 16);
+            result._parsedGuid._j = (byte)(temp >> 8);
+            result._parsedGuid._k = (byte)(temp);
+
+            return true;
+        }
+
+        // Check if it's of the form [{|(]dddddddd-dddd-dddd-dddd-dddddddddddd[}|)]
+        private static bool TryParseGuidWithDashes(ReadOnlySpan<char> guidString, ref GuidResult result)
+        {
+            int startPos = 0;
+            int temp;
+            long templ;
+            int currentPos = 0;
+
+            // check to see that it's the proper length
+            if (guidString[0] == '{')
+            {
+                if (guidString.Length != 38 || guidString[37] != '}')
+                {
+                    result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidInvLen));
+                    return false;
+                }
+                startPos = 1;
+            }
+            else if (guidString[0] == '(')
+            {
+                if (guidString.Length != 38 || guidString[37] != ')')
+                {
+                    result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidInvLen));
+                    return false;
+                }
+                startPos = 1;
+            }
+            else if (guidString.Length != 36)
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidInvLen));
+                return false;
+            }
+
+            if (guidString[8 + startPos] != '-' ||
+                guidString[13 + startPos] != '-' ||
+                guidString[18 + startPos] != '-' ||
+                guidString[23 + startPos] != '-')
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidDashes));
+                return false;
+            }
+
+            currentPos = startPos;
+            if (!StringToInt(guidString, ref currentPos, 8, ParseNumbers.NoSpace, out temp, ref result))
+                return false;
+            result._parsedGuid._a = temp;
+            ++currentPos; //Increment past the '-';
+
+            if (!StringToInt(guidString, ref currentPos, 4, ParseNumbers.NoSpace, out temp, ref result))
+                return false;
+            result._parsedGuid._b = (short)temp;
+            ++currentPos; //Increment past the '-';
+
+            if (!StringToInt(guidString, ref currentPos, 4, ParseNumbers.NoSpace, out temp, ref result))
+                return false;
+            result._parsedGuid._c = (short)temp;
+            ++currentPos; //Increment past the '-';
+
+            if (!StringToInt(guidString, ref currentPos, 4, ParseNumbers.NoSpace, out temp, ref result))
+                return false;
+            ++currentPos; //Increment past the '-';
+            startPos = currentPos;
+
+            if (!StringToLong(guidString, ref currentPos, ParseNumbers.NoSpace, out templ, ref result))
+                return false;
+
+            if (currentPos - startPos != 12)
+            {
+                result.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidInvLen));
+                return false;
+            }
+            result._parsedGuid._d = (byte)(temp >> 8);
+            result._parsedGuid._e = (byte)(temp);
+            temp = (int)(templ >> 32);
+            result._parsedGuid._f = (byte)(temp >> 8);
+            result._parsedGuid._g = (byte)(temp);
+            temp = (int)(templ);
+            result._parsedGuid._h = (byte)(temp >> 24);
+            result._parsedGuid._i = (byte)(temp >> 16);
+            result._parsedGuid._j = (byte)(temp >> 8);
+            result._parsedGuid._k = (byte)(temp);
+
+            return true;
+        }
+
+        private static bool StringToShort(ReadOnlySpan<char> str, int requiredLength, int flags, out short result, ref GuidResult parseResult)
+        {
+            int parsePos = 0;
+            return StringToShort(str, ref parsePos, requiredLength, flags, out result, ref parseResult);
+        }
+
+        private static bool StringToShort(ReadOnlySpan<char> str, ref int parsePos, int requiredLength, int flags, out short result, ref GuidResult parseResult)
+        {
+            result = 0;
+            int x;
+            bool retValue = StringToInt(str, ref parsePos, requiredLength, flags, out x, ref parseResult);
+            result = (short)x;
+            return retValue;
+        }
+
+        private static bool StringToInt(ReadOnlySpan<char> str, int requiredLength, int flags, out int result, ref GuidResult parseResult)
+        {
+            int parsePos = 0;
+            return StringToInt(str, ref parsePos, requiredLength, flags, out result, ref parseResult);
+        }
+
+        private static bool StringToInt(ReadOnlySpan<char> str, ref int parsePos, int requiredLength, int flags, out int result, ref GuidResult parseResult)
+        {
+            result = 0;
+
+            int currStart = parsePos;
+            try
+            {
+                result = ParseNumbers.StringToInt(str, 16, flags, ref parsePos);
+            }
+            catch (OverflowException ex)
+            {
+                if (parseResult._throwStyle == GuidParseThrowStyle.All)
+                {
+                    throw;
+                }
+                else if (parseResult._throwStyle == GuidParseThrowStyle.AllButOverflow)
+                {
+                    throw new FormatException(SR.Format_GuidUnrecognized, ex);
+                }
+                else
+                {
+                    parseResult.SetFailure(ex);
+                    return false;
+                }
+            }
+            catch (Exception ex)
+            {
+                if (parseResult._throwStyle == GuidParseThrowStyle.None)
+                {
+                    parseResult.SetFailure(ex);
+                    return false;
+                }
+                else
+                {
+                    throw;
+                }
+            }
+
+            //If we didn't parse enough characters, there's clearly an error.
+            if (requiredLength != -1 && parsePos - currStart != requiredLength)
+            {
+                parseResult.SetFailure(ParseFailureKind.Format, nameof(SR.Format_GuidInvalidChar));
+                return false;
+            }
+            return true;
+        }
+
+        private static unsafe bool StringToLong(ReadOnlySpan<char> str, ref int parsePos, int flags, out long result, ref GuidResult parseResult)
+        {
+            result = 0;
+
+            try
+            {
+                result = ParseNumbers.StringToLong(str, 16, flags, ref parsePos);
+            }
+            catch (OverflowException ex)
+            {
+                if (parseResult._throwStyle == GuidParseThrowStyle.All)
+                {
+                    throw;
+                }
+                else if (parseResult._throwStyle == GuidParseThrowStyle.AllButOverflow)
+                {
+                    throw new FormatException(SR.Format_GuidUnrecognized, ex);
+                }
+                else
+                {
+                    parseResult.SetFailure(ex);
+                    return false;
+                }
+            }
+            catch (Exception ex)
+            {
+                if (parseResult._throwStyle == GuidParseThrowStyle.None)
+                {
+                    parseResult.SetFailure(ex);
+                    return false;
+                }
+                else
+                {
+                    throw;
+                }
+            }
+            return true;
+        }
+
+        private static ReadOnlySpan<char> EatAllWhitespace(ReadOnlySpan<char> str)
+        {
+            // Find the first whitespace character.  If there is none, just return the input.
+            int i;
+            for (i = 0; i < str.Length && !char.IsWhiteSpace(str[i]); i++) ;
+            if (i == str.Length)
+            {
+                return str;
+            }
+
+            // There was at least one whitespace.  Copy over everything prior to it to a new array.
+            var chArr = new char[str.Length];
+            int newLength = 0;
+            if (i > 0)
+            {
+                newLength = i;
+                str.Slice(0, i).CopyTo(chArr);
+            }
+
+            // Loop through the remaining chars, copying over non-whitespace.
+            for (; i < str.Length; i++)
+            {
+                char c = str[i];
+                if (!char.IsWhiteSpace(c))
+                {
+                    chArr[newLength++] = c;
+                }
+            }
+
+            // Return the string with the whitespace removed.
+            return new ReadOnlySpan<char>(chArr, 0, newLength);
+        }
+
+        private static bool IsHexPrefix(ReadOnlySpan<char> str, int i) =>
+            i + 1 < str.Length &&
+            str[i] == '0' &&
+            (str[i + 1] == 'x' || char.ToLowerInvariant(str[i + 1]) == 'x');
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private void WriteByteHelper(Span<byte> destination)
+        {
+            destination[0] = (byte)(_a);
+            destination[1] = (byte)(_a >> 8);
+            destination[2] = (byte)(_a >> 16);
+            destination[3] = (byte)(_a >> 24);
+            destination[4] = (byte)(_b);
+            destination[5] = (byte)(_b >> 8);
+            destination[6] = (byte)(_c);
+            destination[7] = (byte)(_c >> 8);
+            destination[8] = _d;
+            destination[9] = _e;
+            destination[10] = _f;
+            destination[11] = _g;
+            destination[12] = _h;
+            destination[13] = _i;
+            destination[14] = _j;
+            destination[15] = _k;
+        }
+
+        // Returns an unsigned byte array containing the GUID.
+        public byte[] ToByteArray()
+        {
+            var g = new byte[16];
+            WriteByteHelper(g);
+            return g;
+        }
+
+        // Returns whether bytes are sucessfully written to given span.
+        public bool TryWriteBytes(Span<byte> destination)
+        {
+            if (destination.Length < 16)
+                return false;
+
+            WriteByteHelper(destination);
+            return true;
+        }
+
+        // Returns the guid in "registry" format.
+        public override string ToString()
+        {
+            return ToString("D", null);
+        }
+
+        public override int GetHashCode()
+        {
+            // Simply XOR all the bits of the GUID 32 bits at a time.
+            return _a ^ Unsafe.Add(ref _a, 1) ^ Unsafe.Add(ref _a, 2) ^ Unsafe.Add(ref _a, 3);
+        }
+
+        // Returns true if and only if the guid represented
+        //  by o is the same as this instance.
+        public override bool Equals(object o)
+        {
+            Guid g;
+            // Check that o is a Guid first
+            if (o == null || !(o is Guid))
+                return false;
+            else g = (Guid)o;
+
+            // Now compare each of the elements
+            return g._a == _a &&
+                Unsafe.Add(ref g._a, 1) == Unsafe.Add(ref _a, 1) &&
+                Unsafe.Add(ref g._a, 2) == Unsafe.Add(ref _a, 2) &&
+                Unsafe.Add(ref g._a, 3) == Unsafe.Add(ref _a, 3);
+        }
+
+        public bool Equals(Guid g)
+        {
+            // Now compare each of the elements
+            return g._a == _a &&
+                Unsafe.Add(ref g._a, 1) == Unsafe.Add(ref _a, 1) &&
+                Unsafe.Add(ref g._a, 2) == Unsafe.Add(ref _a, 2) &&
+                Unsafe.Add(ref g._a, 3) == Unsafe.Add(ref _a, 3);
+        }
+
+        private int GetResult(uint me, uint them)
+        {
+            if (me < them)
+            {
+                return -1;
+            }
+            return 1;
+        }
+
+        public int CompareTo(object value)
+        {
+            if (value == null)
+            {
+                return 1;
+            }
+            if (!(value is Guid))
+            {
+                throw new ArgumentException(SR.Arg_MustBeGuid, nameof(value));
+            }
+            Guid g = (Guid)value;
+
+            if (g._a != _a)
+            {
+                return GetResult((uint)_a, (uint)g._a);
+            }
+
+            if (g._b != _b)
+            {
+                return GetResult((uint)_b, (uint)g._b);
+            }
+
+            if (g._c != _c)
+            {
+                return GetResult((uint)_c, (uint)g._c);
+            }
+
+            if (g._d != _d)
+            {
+                return GetResult(_d, g._d);
+            }
+
+            if (g._e != _e)
+            {
+                return GetResult(_e, g._e);
+            }
+
+            if (g._f != _f)
+            {
+                return GetResult(_f, g._f);
+            }
+
+            if (g._g != _g)
+            {
+                return GetResult(_g, g._g);
+            }
+
+            if (g._h != _h)
+            {
+                return GetResult(_h, g._h);
+            }
+
+            if (g._i != _i)
+            {
+                return GetResult(_i, g._i);
+            }
+
+            if (g._j != _j)
+            {
+                return GetResult(_j, g._j);
+            }
+
+            if (g._k != _k)
+            {
+                return GetResult(_k, g._k);
+            }
+
+            return 0;
+        }
+
+        public int CompareTo(Guid value)
+        {
+            if (value._a != _a)
+            {
+                return GetResult((uint)_a, (uint)value._a);
+            }
+
+            if (value._b != _b)
+            {
+                return GetResult((uint)_b, (uint)value._b);
+            }
+
+            if (value._c != _c)
+            {
+                return GetResult((uint)_c, (uint)value._c);
+            }
+
+            if (value._d != _d)
+            {
+                return GetResult(_d, value._d);
+            }
+
+            if (value._e != _e)
+            {
+                return GetResult(_e, value._e);
+            }
+
+            if (value._f != _f)
+            {
+                return GetResult(_f, value._f);
+            }
+
+            if (value._g != _g)
+            {
+                return GetResult(_g, value._g);
+            }
+
+            if (value._h != _h)
+            {
+                return GetResult(_h, value._h);
+            }
+
+            if (value._i != _i)
+            {
+                return GetResult(_i, value._i);
+            }
+
+            if (value._j != _j)
+            {
+                return GetResult(_j, value._j);
+            }
+
+            if (value._k != _k)
+            {
+                return GetResult(_k, value._k);
+            }
+
+            return 0;
+        }
+
+        public static bool operator ==(Guid a, Guid b)
+        {
+            // Now compare each of the elements
+            return a._a == b._a &&
+                Unsafe.Add(ref a._a, 1) == Unsafe.Add(ref b._a, 1) &&
+                Unsafe.Add(ref a._a, 2) == Unsafe.Add(ref b._a, 2) &&
+                Unsafe.Add(ref a._a, 3) == Unsafe.Add(ref b._a, 3);
+        }
+
+        public static bool operator !=(Guid a, Guid b)
+        {
+            // Now compare each of the elements
+            return a._a != b._a ||
+                Unsafe.Add(ref a._a, 1) != Unsafe.Add(ref b._a, 1) ||
+                Unsafe.Add(ref a._a, 2) != Unsafe.Add(ref b._a, 2) ||
+                Unsafe.Add(ref a._a, 3) != Unsafe.Add(ref b._a, 3);
+        }
+
+        public string ToString(string format)
+        {
+            return ToString(format, null);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static char HexToChar(int a)
+        {
+            a = a & 0xf;
+            return (char)((a > 9) ? a - 10 + 0x61 : a + 0x30);
+        }
+
+        private static unsafe int HexsToChars(char* guidChars, int a, int b)
+        {
+            guidChars[0] = HexToChar(a >> 4);
+            guidChars[1] = HexToChar(a);
+
+            guidChars[2] = HexToChar(b >> 4);
+            guidChars[3] = HexToChar(b);
+
+            return 4;
+        }
+
+        private static unsafe int HexsToCharsHexOutput(char* guidChars, int a, int b)
+        {
+            guidChars[0] = '0';
+            guidChars[1] = 'x';
+
+            guidChars[2] = HexToChar(a >> 4);
+            guidChars[3] = HexToChar(a);
+
+            guidChars[4] = ',';
+            guidChars[5] = '0';
+            guidChars[6] = 'x';
+
+            guidChars[7] = HexToChar(b >> 4);
+            guidChars[8] = HexToChar(b);
+
+            return 9;
+        }
+
+        // IFormattable interface
+        // We currently ignore provider
+        public string ToString(string format, IFormatProvider provider)
+        {
+            if (format == null || format.Length == 0)
+                format = "D";
+
+            // all acceptable format strings are of length 1
+            if (format.Length != 1)
+                throw new FormatException(SR.Format_InvalidGuidFormatSpecification);
+
+            int guidSize;
+            switch (format[0])
+            {
+                case 'D':
+                case 'd':
+                    guidSize = 36;
+                    break;
+                case 'N':
+                case 'n':
+                    guidSize = 32;
+                    break;
+                case 'B':
+                case 'b':
+                case 'P':
+                case 'p':
+                    guidSize = 38;
+                    break;
+                case 'X':
+                case 'x':
+                    guidSize = 68;
+                    break;
+                default:
+                    throw new FormatException(SR.Format_InvalidGuidFormatSpecification);
+            }
+
+            string guidString = string.FastAllocateString(guidSize);
+
+            int bytesWritten;
+            bool result = TryFormat(new Span<char>(ref guidString.GetRawStringData(), guidString.Length), out bytesWritten, format);
+            Debug.Assert(result && bytesWritten == guidString.Length, "Formatting guid should have succeeded.");
+
+            return guidString;
+        }
+
+        // Returns whether the guid is successfully formatted as a span. 
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default)
+        {
+            if (format.Length == 0)
+                format = "D";
+
+            // all acceptable format strings are of length 1
+            if (format.Length != 1) 
+                throw new FormatException(SR.Format_InvalidGuidFormatSpecification);
+
+            bool dash = true;
+            bool hex = false;
+            int braces = 0;
+
+            int guidSize;
+
+            switch (format[0])
+            {
+                case 'D':
+                case 'd':
+                    guidSize = 36;
+                    break;
+                case 'N':
+                case 'n':
+                    dash = false;
+                    guidSize = 32;
+                    break;
+                case 'B':
+                case 'b':
+                    braces = '{' + ('}' << 16);
+                    guidSize = 38;
+                    break;
+                case 'P':
+                case 'p':
+                    braces = '(' + (')' << 16);
+                    guidSize = 38;
+                    break;
+                case 'X':
+                case 'x':
+                    braces = '{' + ('}' << 16);
+                    dash = false;
+                    hex = true;
+                    guidSize = 68;
+                    break;
+                default:
+                    throw new FormatException(SR.Format_InvalidGuidFormatSpecification);
+            }
+
+            if (destination.Length < guidSize)
+            {
+                charsWritten = 0;
+                return false;
+            }
+
+            unsafe
+            {
+                fixed (char* guidChars = &MemoryMarshal.GetReference(destination))
+                {
+                    char * p = guidChars;
+
+                    if (braces != 0)
+                        *p++ = (char)braces;
+
+                    if (hex)
+                    {
+                        // {0xdddddddd,0xdddd,0xdddd,{0xdd,0xdd,0xdd,0xdd,0xdd,0xdd,0xdd,0xdd}}
+                        *p++ = '0';
+                        *p++ = 'x';
+                        p += HexsToChars(p, _a >> 24, _a >> 16);
+                        p += HexsToChars(p, _a >> 8, _a);
+                        *p++ = ',';
+                        *p++ = '0';
+                        *p++ = 'x';
+                        p += HexsToChars(p, _b >> 8, _b);
+                        *p++ = ',';
+                        *p++ = '0';
+                        *p++ = 'x';
+                        p += HexsToChars(p, _c >> 8, _c);
+                        *p++ = ',';
+                        *p++ = '{';
+                        p += HexsToCharsHexOutput(p, _d, _e);
+                        *p++ = ',';
+                        p += HexsToCharsHexOutput(p, _f, _g);
+                        *p++ = ',';
+                        p += HexsToCharsHexOutput(p, _h, _i);
+                        *p++ = ',';
+                        p += HexsToCharsHexOutput(p, _j, _k);
+                        *p++ = '}';
+                    }
+                    else
+                    {
+                        // [{|(]dddddddd[-]dddd[-]dddd[-]dddd[-]dddddddddddd[}|)]
+                        p += HexsToChars(p, _a >> 24, _a >> 16);
+                        p += HexsToChars(p, _a >> 8, _a);
+                        if (dash)
+                            *p++ = '-';
+                        p += HexsToChars(p, _b >> 8, _b);
+                        if (dash)
+                            *p++ = '-';
+                        p += HexsToChars(p, _c >> 8, _c);
+                        if (dash)
+                            *p++ = '-';
+                        p += HexsToChars(p, _d, _e);
+                        if (dash)
+                            *p++ = '-';
+                        p += HexsToChars(p, _f, _g);
+                        p += HexsToChars(p, _h, _i);
+                        p += HexsToChars(p, _j, _k);
+                    }
+
+                    if (braces != 0)
+                        *p++ = (char)(braces >> 16);
+
+                    Debug.Assert(p - guidChars == guidSize);
+                }
+            }
+
+            charsWritten = guidSize;
+            return true;
+        }
+
+        bool ISpanFormattable.TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format, IFormatProvider provider)
+        {
+            // Like with the IFormattable implementation, provider is ignored.
+            return TryFormat(destination, out charsWritten, format);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/HResults.cs b/src/System.Private.CoreLib/shared/System/HResults.cs
new file mode 100644
index 0000000000..c242389db3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/HResults.cs
@@ -0,0 +1,128 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//=============================================================================
+//
+//
+// Purpose: Define HResult constants. Every exception has one of these.
+//
+//
+//===========================================================================*/
+// Note: FACILITY_URT is defined as 0x13 (0x8013xxxx).  Within that
+// range, 0x1yyy is for Runtime errors (used for Security, Metadata, etc).
+// In that subrange, 0x15zz and 0x16zz have been allocated for classlib-type 
+// HResults. Also note that some of our HResults have to map to certain 
+// COM HR's, etc.
+
+// Reflection will use 0x1600 -> 0x161f.  IO will use 0x1620 -> 0x163f.
+// Security will use 0x1640 -> 0x165f
+
+
+using System;
+
+namespace System
+{
+    internal static partial class HResults
+    {
+        internal const int S_OK = unchecked((int)0x00000000);
+        internal const int COR_E_ABANDONEDMUTEX = unchecked((int)0x8013152D);
+        internal const int COR_E_AMBIGUOUSMATCH = unchecked((int)0x8000211D);
+        internal const int COR_E_APPDOMAINUNLOADED = unchecked((int)0x80131014);
+        internal const int COR_E_APPLICATION = unchecked((int)0x80131600);
+        internal const int COR_E_ARGUMENT = unchecked((int)0x80070057);
+        internal const int COR_E_ARGUMENTOUTOFRANGE = unchecked((int)0x80131502);
+        internal const int COR_E_ARITHMETIC = unchecked((int)0x80070216);
+        internal const int COR_E_ARRAYTYPEMISMATCH = unchecked((int)0x80131503);
+        internal const int COR_E_BADEXEFORMAT = unchecked((int)0x800700C1);
+        internal const int COR_E_BADIMAGEFORMAT = unchecked((int)0x8007000B);
+        internal const int COR_E_CANNOTUNLOADAPPDOMAIN = unchecked((int)0x80131015);
+        internal const int COR_E_COMEMULATE = unchecked((int)0x80131535);
+        internal const int COR_E_CONTEXTMARSHAL = unchecked((int)0x80131504);
+        internal const int COR_E_CUSTOMATTRIBUTEFORMAT = unchecked((int)0x80131605);
+        internal const int COR_E_DATAMISALIGNED = unchecked((int)0x80131541);
+        internal const int COR_E_DIRECTORYNOTFOUND = unchecked((int)0x80070003);
+        internal const int COR_E_DIVIDEBYZERO = unchecked((int)0x80020012); // DISP_E_DIVBYZERO
+        internal const int COR_E_DLLNOTFOUND = unchecked((int)0x80131524);
+        internal const int COR_E_DUPLICATEWAITOBJECT = unchecked((int)0x80131529);
+        internal const int COR_E_ENDOFSTREAM = unchecked((int)0x80070026);  // OS defined
+        internal const int COR_E_ENTRYPOINTNOTFOUND = unchecked((int)0x80131523);
+        internal const int COR_E_EXCEPTION = unchecked((int)0x80131500);
+        internal const int COR_E_EXECUTIONENGINE = unchecked((int)0x80131506);
+        internal const int COR_E_FIELDACCESS = unchecked((int)0x80131507);
+        internal const int COR_E_FILELOAD = unchecked((int)0x80131621);
+        internal const int COR_E_FILENOTFOUND = unchecked((int)0x80070002);
+        internal const int COR_E_FORMAT = unchecked((int)0x80131537);
+        internal const int COR_E_HOSTPROTECTION = unchecked((int)0x80131640);
+        internal const int COR_E_INDEXOUTOFRANGE = unchecked((int)0x80131508);
+        internal const int COR_E_INSUFFICIENTEXECUTIONSTACK = unchecked((int)0x80131578);
+        internal const int COR_E_INSUFFICIENTMEMORY = unchecked((int)0x8013153D);
+        internal const int COR_E_INVALIDCAST = unchecked((int)0x80004002);
+        internal const int COR_E_INVALIDCOMOBJECT = unchecked((int)0x80131527);
+        internal const int COR_E_INVALIDFILTERCRITERIA = unchecked((int)0x80131601);
+        internal const int COR_E_INVALIDOLEVARIANTTYPE = unchecked((int)0x80131531);
+        internal const int COR_E_INVALIDOPERATION = unchecked((int)0x80131509);
+        internal const int COR_E_INVALIDPROGRAM = unchecked((int)0x8013153A);
+        internal const int COR_E_IO = unchecked((int)0x80131620);
+        internal const int COR_E_KEYNOTFOUND = unchecked((int)0x80131577);
+        internal const int COR_E_MARSHALDIRECTIVE = unchecked((int)0x80131535);
+        internal const int COR_E_MEMBERACCESS = unchecked((int)0x8013151A);
+        internal const int COR_E_METHODACCESS = unchecked((int)0x80131510);
+        internal const int COR_E_MISSINGFIELD = unchecked((int)0x80131511);
+        internal const int COR_E_MISSINGMANIFESTRESOURCE = unchecked((int)0x80131532);
+        internal const int COR_E_MISSINGMEMBER = unchecked((int)0x80131512);
+        internal const int COR_E_MISSINGMETHOD = unchecked((int)0x80131513);
+        internal const int COR_E_MISSINGSATELLITEASSEMBLY = unchecked((int)0x80131536);
+        internal const int COR_E_MULTICASTNOTSUPPORTED = unchecked((int)0x80131514);
+        internal const int COR_E_NOTFINITENUMBER = unchecked((int)0x80131528);
+        internal const int COR_E_NOTSUPPORTED = unchecked((int)0x80131515);
+        internal const int COR_E_NULLREFERENCE = unchecked((int)0x80004003);
+        internal const int COR_E_OBJECTDISPOSED = unchecked((int)0x80131622);
+        internal const int COR_E_OPERATIONCANCELED = unchecked((int)0x8013153B);
+        internal const int COR_E_OUTOFMEMORY = unchecked((int)0x8007000E);
+        internal const int COR_E_OVERFLOW = unchecked((int)0x80131516);
+        internal const int COR_E_PATHTOOLONG = unchecked((int)0x800700CE);
+        internal const int COR_E_PLATFORMNOTSUPPORTED = unchecked((int)0x80131539);
+        internal const int COR_E_RANK = unchecked((int)0x80131517);
+        internal const int COR_E_REFLECTIONTYPELOAD = unchecked((int)0x80131602);
+        internal const int COR_E_RUNTIMEWRAPPED = unchecked((int)0x8013153E);
+        internal const int COR_E_SAFEARRAYRANKMISMATCH = unchecked((int)0x80131538);
+        internal const int COR_E_SAFEARRAYTYPEMISMATCH = unchecked((int)0x80131533);
+        internal const int COR_E_SAFEHANDLEMISSINGATTRIBUTE = unchecked((int)0x80131623);
+        internal const int COR_E_SECURITY = unchecked((int)0x8013150A);
+        internal const int COR_E_SEMAPHOREFULL = unchecked((int)0x8013152B);
+        internal const int COR_E_SERIALIZATION = unchecked((int)0x8013150C);
+        internal const int COR_E_STACKOVERFLOW = unchecked((int)0x800703E9);
+        internal const int COR_E_SYNCHRONIZATIONLOCK = unchecked((int)0x80131518);
+        internal const int COR_E_SYSTEM = unchecked((int)0x80131501);
+        internal const int COR_E_TARGET = unchecked((int)0x80131603);
+        internal const int COR_E_TARGETINVOCATION = unchecked((int)0x80131604);
+        internal const int COR_E_TARGETPARAMCOUNT = unchecked((int)0x8002000E);
+        internal const int COR_E_THREADABORTED = unchecked((int)0x80131530);
+        internal const int COR_E_THREADINTERRUPTED = unchecked((int)0x80131519);
+        internal const int COR_E_THREADSTART = unchecked((int)0x80131525);
+        internal const int COR_E_THREADSTATE = unchecked((int)0x80131520);
+        internal const int COR_E_THREADSTOP = unchecked((int)0x80131521);
+        internal const int COR_E_TIMEOUT = unchecked((int)0x80131505);
+        internal const int COR_E_TYPEACCESS = unchecked((int)0x80131543);
+        internal const int COR_E_TYPEINITIALIZATION = unchecked((int)0x80131534);
+        internal const int COR_E_TYPELOAD = unchecked((int)0x80131522);
+        internal const int COR_E_TYPEUNLOADED = unchecked((int)0x80131013);
+        internal const int COR_E_UNAUTHORIZEDACCESS = unchecked((int)0x80070005);
+        internal const int COR_E_UNSUPPORTEDFORMAT = unchecked((int)0x80131523);
+        internal const int COR_E_VERIFICATION = unchecked((int)0x8013150D);
+        internal const int COR_E_WAITHANDLECANNOTBEOPENED = unchecked((int)0x8013152C);
+        internal const int DISP_E_OVERFLOW = unchecked((int)0x8002000A);
+        internal const int E_BOUNDS = unchecked((int)0x8000000B);
+        internal const int E_CHANGED_STATE = unchecked((int)0x8000000C);
+        internal const int E_FAIL = unchecked((int)0x80004005);
+        internal const int E_HANDLE = unchecked((int)0x80070006);
+        internal const int E_INVALIDARG = unchecked((int)0x80070057);
+        internal const int E_NOTIMPL = unchecked((int)0x80004001);
+        internal const int E_POINTER = unchecked((int)0x80004003);
+        internal const int ERROR_MRM_MAP_NOT_FOUND = unchecked((int)0x80073B1F);
+        internal const int RO_E_CLOSED = unchecked((int)0x80000013);
+        internal const int TYPE_E_TYPEMISMATCH = unchecked((int)0x80028CA0);
+        internal const int CO_E_NOTINITIALIZED = unchecked((int)0x800401F0);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/HashCode.cs b/src/System.Private.CoreLib/shared/System/HashCode.cs
new file mode 100644
index 0000000000..4be57be02a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/HashCode.cs
@@ -0,0 +1,430 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*
+
+The xxHash32 implementation is based on the code published by Yann Collet:
+https://raw.githubusercontent.com/Cyan4973/xxHash/5c174cfa4e45a42f94082dc0d4539b39696afea1/xxhash.c
+
+  xxHash - Fast Hash algorithm
+  Copyright (C) 2012-2016, Yann Collet
+  
+  BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
+  
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions are
+  met:
+  
+  * Redistributions of source code must retain the above copyright
+  notice, this list of conditions and the following disclaimer.
+  * Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the following disclaimer
+  in the documentation and/or other materials provided with the
+  distribution.
+  
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+  
+  You can contact the author at :
+  - xxHash homepage: http://www.xxhash.com
+  - xxHash source repository : https://github.com/Cyan4973/xxHash
+
+*/
+
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    // xxHash32 is used for the hash code.
+    // https://github.com/Cyan4973/xxHash
+
+    public struct HashCode
+    {
+        private static readonly uint s_seed = GenerateGlobalSeed();
+
+        private const uint Prime1 = 2654435761U;
+        private const uint Prime2 = 2246822519U;
+        private const uint Prime3 = 3266489917U;
+        private const uint Prime4 = 668265263U;
+        private const uint Prime5 = 374761393U;
+
+        private uint _v1, _v2, _v3, _v4;
+        private uint _queue1, _queue2, _queue3;
+        private uint _length;
+
+        private static unsafe uint GenerateGlobalSeed()
+        {
+            uint result;
+            Interop.GetRandomBytes((byte*)&result, sizeof(uint));
+            return result;
+        }
+
+        public static int Combine<T1>(T1 value1)
+        {
+            // Provide a way of diffusing bits from something with a limited
+            // input hash space. For example, many enums only have a few
+            // possible hashes, only using the bottom few bits of the code. Some
+            // collections are built on the assumption that hashes are spread
+            // over a larger space, so diffusing the bits may help the
+            // collection work more efficiently.
+
+            var hc1 = (uint)(value1?.GetHashCode() ?? 0);
+
+            uint hash = MixEmptyState();
+            hash += 4;
+
+            hash = QueueRound(hash, hc1);
+
+            hash = MixFinal(hash);
+            return (int)hash;
+        }
+
+        public static int Combine<T1, T2>(T1 value1, T2 value2)
+        {
+            var hc1 = (uint)(value1?.GetHashCode() ?? 0);
+            var hc2 = (uint)(value2?.GetHashCode() ?? 0);
+
+            uint hash = MixEmptyState();
+            hash += 8;
+
+            hash = QueueRound(hash, hc1);
+            hash = QueueRound(hash, hc2);
+
+            hash = MixFinal(hash);
+            return (int)hash;
+        }
+
+        public static int Combine<T1, T2, T3>(T1 value1, T2 value2, T3 value3)
+        {
+            var hc1 = (uint)(value1?.GetHashCode() ?? 0);
+            var hc2 = (uint)(value2?.GetHashCode() ?? 0);
+            var hc3 = (uint)(value3?.GetHashCode() ?? 0);
+
+            uint hash = MixEmptyState();
+            hash += 12;
+
+            hash = QueueRound(hash, hc1);
+            hash = QueueRound(hash, hc2);
+            hash = QueueRound(hash, hc3);
+
+            hash = MixFinal(hash);
+            return (int)hash;
+        }
+
+        public static int Combine<T1, T2, T3, T4>(T1 value1, T2 value2, T3 value3, T4 value4)
+        {
+            var hc1 = (uint)(value1?.GetHashCode() ?? 0);
+            var hc2 = (uint)(value2?.GetHashCode() ?? 0);
+            var hc3 = (uint)(value3?.GetHashCode() ?? 0);
+            var hc4 = (uint)(value4?.GetHashCode() ?? 0);
+
+            Initialize(out uint v1, out uint v2, out uint v3, out uint v4);
+
+            v1 = Round(v1, hc1);
+            v2 = Round(v2, hc2);
+            v3 = Round(v3, hc3);
+            v4 = Round(v4, hc4);
+
+            uint hash = MixState(v1, v2, v3, v4);
+            hash += 16;
+
+            hash = MixFinal(hash);
+            return (int)hash;
+        }
+
+        public static int Combine<T1, T2, T3, T4, T5>(T1 value1, T2 value2, T3 value3, T4 value4, T5 value5)
+        {
+            var hc1 = (uint)(value1?.GetHashCode() ?? 0);
+            var hc2 = (uint)(value2?.GetHashCode() ?? 0);
+            var hc3 = (uint)(value3?.GetHashCode() ?? 0);
+            var hc4 = (uint)(value4?.GetHashCode() ?? 0);
+            var hc5 = (uint)(value5?.GetHashCode() ?? 0);
+
+            Initialize(out uint v1, out uint v2, out uint v3, out uint v4);
+
+            v1 = Round(v1, hc1);
+            v2 = Round(v2, hc2);
+            v3 = Round(v3, hc3);
+            v4 = Round(v4, hc4);
+
+            uint hash = MixState(v1, v2, v3, v4);
+            hash += 20;
+
+            hash = QueueRound(hash, hc5);
+
+            hash = MixFinal(hash);
+            return (int)hash;
+        }
+
+        public static int Combine<T1, T2, T3, T4, T5, T6>(T1 value1, T2 value2, T3 value3, T4 value4, T5 value5, T6 value6)
+        {
+            var hc1 = (uint)(value1?.GetHashCode() ?? 0);
+            var hc2 = (uint)(value2?.GetHashCode() ?? 0);
+            var hc3 = (uint)(value3?.GetHashCode() ?? 0);
+            var hc4 = (uint)(value4?.GetHashCode() ?? 0);
+            var hc5 = (uint)(value5?.GetHashCode() ?? 0);
+            var hc6 = (uint)(value6?.GetHashCode() ?? 0);
+
+            Initialize(out uint v1, out uint v2, out uint v3, out uint v4);
+
+            v1 = Round(v1, hc1);
+            v2 = Round(v2, hc2);
+            v3 = Round(v3, hc3);
+            v4 = Round(v4, hc4);
+
+            uint hash = MixState(v1, v2, v3, v4);
+            hash += 24;
+
+            hash = QueueRound(hash, hc5);
+            hash = QueueRound(hash, hc6);
+
+            hash = MixFinal(hash);
+            return (int)hash;
+        }
+
+        public static int Combine<T1, T2, T3, T4, T5, T6, T7>(T1 value1, T2 value2, T3 value3, T4 value4, T5 value5, T6 value6, T7 value7)
+        {
+            var hc1 = (uint)(value1?.GetHashCode() ?? 0);
+            var hc2 = (uint)(value2?.GetHashCode() ?? 0);
+            var hc3 = (uint)(value3?.GetHashCode() ?? 0);
+            var hc4 = (uint)(value4?.GetHashCode() ?? 0);
+            var hc5 = (uint)(value5?.GetHashCode() ?? 0);
+            var hc6 = (uint)(value6?.GetHashCode() ?? 0);
+            var hc7 = (uint)(value7?.GetHashCode() ?? 0);
+
+            Initialize(out uint v1, out uint v2, out uint v3, out uint v4);
+
+            v1 = Round(v1, hc1);
+            v2 = Round(v2, hc2);
+            v3 = Round(v3, hc3);
+            v4 = Round(v4, hc4);
+
+            uint hash = MixState(v1, v2, v3, v4);
+            hash += 28;
+
+            hash = QueueRound(hash, hc5);
+            hash = QueueRound(hash, hc6);
+            hash = QueueRound(hash, hc7);
+
+            hash = MixFinal(hash);
+            return (int)hash;
+        }
+
+        public static int Combine<T1, T2, T3, T4, T5, T6, T7, T8>(T1 value1, T2 value2, T3 value3, T4 value4, T5 value5, T6 value6, T7 value7, T8 value8)
+        {
+            var hc1 = (uint)(value1?.GetHashCode() ?? 0);
+            var hc2 = (uint)(value2?.GetHashCode() ?? 0);
+            var hc3 = (uint)(value3?.GetHashCode() ?? 0);
+            var hc4 = (uint)(value4?.GetHashCode() ?? 0);
+            var hc5 = (uint)(value5?.GetHashCode() ?? 0);
+            var hc6 = (uint)(value6?.GetHashCode() ?? 0);
+            var hc7 = (uint)(value7?.GetHashCode() ?? 0);
+            var hc8 = (uint)(value8?.GetHashCode() ?? 0);
+
+            Initialize(out uint v1, out uint v2, out uint v3, out uint v4);
+
+            v1 = Round(v1, hc1);
+            v2 = Round(v2, hc2);
+            v3 = Round(v3, hc3);
+            v4 = Round(v4, hc4);
+
+            v1 = Round(v1, hc5);
+            v2 = Round(v2, hc6);
+            v3 = Round(v3, hc7);
+            v4 = Round(v4, hc8);
+
+            uint hash = MixState(v1, v2, v3, v4);
+            hash += 32;
+
+            hash = MixFinal(hash);
+            return (int)hash;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static uint Rol(uint value, int count)
+            => (value << count) | (value >> (32 - count));
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void Initialize(out uint v1, out uint v2, out uint v3, out uint v4)
+        {
+            v1 = s_seed + Prime1 + Prime2;
+            v2 = s_seed + Prime2;
+            v3 = s_seed;
+            v4 = s_seed - Prime1;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static uint Round(uint hash, uint input)
+        {
+            hash += input * Prime2;
+            hash = Rol(hash, 13);
+            hash *= Prime1;
+            return hash;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static uint QueueRound(uint hash, uint queuedValue)
+        {
+            hash += queuedValue * Prime3;
+            return Rol(hash, 17) * Prime4;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static uint MixState(uint v1, uint v2, uint v3, uint v4)
+        {
+            return Rol(v1, 1) + Rol(v2, 7) + Rol(v3, 12) + Rol(v4, 18);
+        }
+
+        private static uint MixEmptyState()
+        {
+            return s_seed + Prime5;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static uint MixFinal(uint hash)
+        {
+            hash ^= hash >> 15;
+            hash *= Prime2;
+            hash ^= hash >> 13;
+            hash *= Prime3;
+            hash ^= hash >> 16;
+            return hash;
+        }
+
+        public void Add<T>(T value)
+        {
+            Add(value?.GetHashCode() ?? 0);
+        }
+
+        public void Add<T>(T value, IEqualityComparer<T> comparer)
+        {
+            Add(comparer != null ? comparer.GetHashCode(value) : (value?.GetHashCode() ?? 0));
+        }
+
+        private void Add(int value)
+        {
+            // The original xxHash works as follows:
+            // 0. Initialize immediately. We can't do this in a struct (no
+            //    default ctor).
+            // 1. Accumulate blocks of length 16 (4 uints) into 4 accumulators.
+            // 2. Accumulate remaining blocks of length 4 (1 uint) into the
+            //    hash.
+            // 3. Accumulate remaining blocks of length 1 into the hash.
+
+            // There is no need for #3 as this type only accepts ints. _queue1,
+            // _queue2 and _queue3 are basically a buffer so that when
+            // ToHashCode is called we can execute #2 correctly.
+
+            // We need to initialize the xxHash32 state (_v1 to _v4) lazily (see
+            // #0) nd the last place that can be done if you look at the
+            // original code is just before the first block of 16 bytes is mixed
+            // in. The xxHash32 state is never used for streams containing fewer
+            // than 16 bytes.
+
+            // To see what's really going on here, have a look at the Combine
+            // methods.
+            
+            var val = (uint)value;
+            
+            // Storing the value of _length locally shaves of quite a few bytes
+            // in the resulting machine code.
+            uint previousLength = _length++;
+            uint position = previousLength % 4;
+
+            // Switch can't be inlined.
+
+            if (position == 0)
+                _queue1 = val;
+            else if (position == 1)
+                _queue2 = val;
+            else if (position == 2)
+                _queue3 = val;
+            else // position == 3
+            {
+                if (previousLength == 3)
+                    Initialize(out _v1, out _v2, out _v3, out _v4);
+
+                _v1 = Round(_v1, _queue1);
+                _v2 = Round(_v2, _queue2);
+                _v3 = Round(_v3, _queue3);
+                _v4 = Round(_v4, val);
+            }
+        }
+
+        public int ToHashCode()
+        {
+            // Storing the value of _length locally shaves of quite a few bytes
+            // in the resulting machine code.
+            uint length = _length;
+            
+            // position refers to the *next* queue position in this method, so
+            // position == 1 means that _queue1 is populated; _queue2 would have
+            // been populated on the next call to Add.
+            uint position = length % 4;
+
+            // If the length is less than 4, _v1 to _v4 don't contain anything
+            // yet. xxHash32 treats this differently.
+
+            uint hash = length < 4 ? MixEmptyState() : MixState(_v1, _v2, _v3, _v4);
+
+            // _length is incremented once per Add(Int32) and is therefore 4
+            // times too small (xxHash length is in bytes, not ints).
+
+            hash += length * 4;
+
+            // Mix what remains in the queue
+
+            // Switch can't be inlined right now, so use as few branches as
+            // possible by manually excluding impossible scenarios (position > 1
+            // is always false if position is not > 0).
+            if (position > 0)
+            {
+                hash = QueueRound(hash, _queue1);
+                if (position > 1)
+                {
+                    hash = QueueRound(hash, _queue2);
+                    if (position > 2)
+                        hash = QueueRound(hash, _queue3);
+                }
+            }
+
+            hash = MixFinal(hash);
+            return (int)hash;
+        }
+
+#pragma warning disable 0809
+        // Obsolete member 'memberA' overrides non-obsolete member 'memberB'. 
+        // Disallowing GetHashCode and Equals is by design
+
+        // * We decided to not override GetHashCode() to produce the hash code 
+        //   as this would be weird, both naming-wise as well as from a
+        //   behavioral standpoint (GetHashCode() should return the object's
+        //   hash code, not the one being computed).
+
+        // * Even though ToHashCode() can be called safely multiple times on
+        //   this implementation, it is not part of the contract. If the
+        //   implementation has to change in the future we don't want to worry
+        //   about people who might have incorrectly used this type.
+
+        [Obsolete("HashCode is a mutable struct and should not be compared with other HashCodes. Use ToHashCode to retrieve the computed hash code.", error: true)]
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public override int GetHashCode() => throw new NotSupportedException(SR.HashCode_HashCodeNotSupported);
+
+        [Obsolete("HashCode is a mutable struct and should not be compared with other HashCodes.", error: true)]
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public override bool Equals(object obj) => throw new NotSupportedException(SR.HashCode_EqualityNotSupported);
+#pragma warning restore 0809
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IAsyncResult.cs b/src/System.Private.CoreLib/shared/System/IAsyncResult.cs
new file mode 100644
index 0000000000..0abeaca525
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IAsyncResult.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Interface: IAsyncResult
+**
+** Purpose: Interface to encapsulate the results of an async
+**          operation
+**
+===========================================================*/
+
+using System;
+using System.Threading;
+
+namespace System
+{
+    public interface IAsyncResult
+    {
+        bool IsCompleted { get; }
+
+        WaitHandle AsyncWaitHandle { get; }
+
+
+        Object AsyncState { get; }
+
+        bool CompletedSynchronously { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ICloneable.cs b/src/System.Private.CoreLib/shared/System/ICloneable.cs
new file mode 100644
index 0000000000..9f123e45c8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ICloneable.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    public interface ICloneable
+    {
+        object Clone();
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IComparable.cs b/src/System.Private.CoreLib/shared/System/IComparable.cs
new file mode 100644
index 0000000000..72aeeb027c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IComparable.cs
@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    // The IComparable interface is implemented by classes that support an
+    // ordering of instances of the class. The ordering represented by
+    // IComparable can be used to sort arrays and collections of objects
+    // that implement the interface.
+    // 
+    public interface IComparable
+    {
+        // Interface does not need to be marked with the serializable attribute
+        // Compares this object to another object, returning an integer that
+        // indicates the relationship. An implementation of this method must return
+        // a value less than zero if this is less than object, zero
+        // if this is equal to object, or a value greater than zero
+        // if this is greater than object.
+        // 
+        int CompareTo(Object obj);
+    }
+
+    // Generic version of IComparable.
+
+    public interface IComparable<in T>
+    {
+        // Interface does not need to be marked with the serializable attribute
+        // Compares this object to another object, returning an integer that
+        // indicates the relationship. An implementation of this method must return
+        // a value less than zero if this is less than object, zero
+        // if this is equal to object, or a value greater than zero
+        // if this is greater than object.
+        // 
+        int CompareTo(T other);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IConvertible.cs b/src/System.Private.CoreLib/shared/System/IConvertible.cs
new file mode 100644
index 0000000000..87351127f2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IConvertible.cs
@@ -0,0 +1,63 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    // The IConvertible interface represents an object that contains a value. This
+    // interface is implemented by the following types in the System namespace:
+    // Boolean, Char, SByte, Byte, Int16, UInt16, Int32, UInt32, Int64, UInt64,
+    // Single, Double, Decimal, DateTime, and String. The interface may
+    // be implemented by other types that are to be considered values. For example,
+    // a library of nullable database types could implement IConvertible.
+    //
+    // Note: The interface was originally proposed as IValue.
+    //
+    // The implementations of IConvertible provided by the System.XXX value classes
+    // simply forward to the appropriate Value.ToXXX(YYY) methods (a description of
+    // the Value class follows below). In cases where a Value.ToXXX(YYY) method
+    // does not exist (because the particular conversion is not supported), the
+    // IConvertible implementation should simply throw an InvalidCastException.
+
+    [CLSCompliant(false)]
+    public interface IConvertible
+    {
+        // Returns the type code of this object. An implementation of this method
+        // must not return TypeCode.Empty (which represents a null reference) or
+        // TypeCode.Object (which represents an object that doesn't implement the
+        // IConvertible interface). An implementation of this method should return
+        // TypeCode.DBNull if the value of this object is a database null. For
+        // example, a nullable integer type should return TypeCode.DBNull if the
+        // value of the object is the database null. Otherwise, an implementation
+        // of this method should return the TypeCode that best describes the
+        // internal representation of the object.
+
+        TypeCode GetTypeCode();
+
+        // The ToXXX methods convert the value of the underlying object to the
+        // given type. If a particular conversion is not supported, the
+        // implementation must throw an InvalidCastException. If the value of the
+        // underlying object is not within the range of the target type, the
+        // implementation must throw an OverflowException.  The 
+        // IFormatProvider will be used to get a NumberFormatInfo or similar
+        // appropriate service object, and may safely be null.
+
+        bool ToBoolean(IFormatProvider provider);
+        char ToChar(IFormatProvider provider);
+        sbyte ToSByte(IFormatProvider provider);
+        byte ToByte(IFormatProvider provider);
+        short ToInt16(IFormatProvider provider);
+        ushort ToUInt16(IFormatProvider provider);
+        int ToInt32(IFormatProvider provider);
+        uint ToUInt32(IFormatProvider provider);
+        long ToInt64(IFormatProvider provider);
+        ulong ToUInt64(IFormatProvider provider);
+        float ToSingle(IFormatProvider provider);
+        double ToDouble(IFormatProvider provider);
+        Decimal ToDecimal(IFormatProvider provider);
+        DateTime ToDateTime(IFormatProvider provider);
+        String ToString(IFormatProvider provider);
+        Object ToType(Type conversionType, IFormatProvider provider);
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/ICustomFormatter.cs b/src/System.Private.CoreLib/shared/System/ICustomFormatter.cs
new file mode 100644
index 0000000000..47340f3093
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ICustomFormatter.cs
@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Interface:  ICustomFormatter
+**
+**
+** Purpose: Marks a class as providing special formatting
+**
+**
+===========================================================*/
+
+using System;
+
+namespace System
+{
+    public interface ICustomFormatter
+    {
+        // Interface does not need to be marked with the serializable attribute
+        String Format(String format, Object arg, IFormatProvider formatProvider);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IDisposable.cs b/src/System.Private.CoreLib/shared/System/IDisposable.cs
new file mode 100644
index 0000000000..24f0740edc
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IDisposable.cs
@@ -0,0 +1,60 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Interface:  IDisposable
+**
+**
+** Purpose: Interface for assisting with deterministic finalization.
+**
+** 
+===========================================================*/
+
+namespace System
+{
+    // IDisposable is an attempt at helping to solve problems with deterministic
+    // finalization.  The GC of course doesn't leave any way to deterministically
+    // know when a finalizer will run.  This forces classes that hold onto OS
+    // resources or some sort of important state (such as a FileStream or a 
+    // network connection) to provide a Close or Dispose method so users can 
+    // run clean up code deterministically.  We have formalized this into an 
+    // interface with one method.  Classes may privately implement IDisposable and
+    // provide a Close method instead, if that name is by far the expected name
+    // for objects in that domain (ie, you don't Dispose of a FileStream, you Close
+    // it).
+    //
+    // This interface could be theoretically used as a marker by a compiler to 
+    // ensure a disposable object has been cleaned up along all code paths if it's 
+    // been allocated in that method, though in practice any compiler that 
+    // draconian may tick off any number of people.  Perhaps an external tool (like
+    // like Purify or BoundsChecker) could do this.  Instead, C# has added a using 
+    // clause, which will generate a try/finally statement where the resource 
+    // passed into the using clause will always have it's Dispose method called.  
+    // Syntax is using(FileStream fs = ...) { .. };
+    //
+    // Dispose should meet the following conditions:
+    // 1) Be safely callable multiple times
+    // 2) Release any resources associated with the instance
+    // 3) Call the base class's Dispose method, if necessary
+    // 4) Suppress finalization of this class to help the GC by reducing the
+    //    number of objects on the finalization queue.
+    // 5) Dispose shouldn't generally throw exceptions, except for very serious 
+    //    errors that are particularly unexpected. (ie, OutOfMemoryException)  
+    //    Ideally, nothing should go wrong with your object by calling Dispose.
+    //
+    // If possible, a class should define a finalizer that calls Dispose.
+    // However, in many situations, this is impractical.  For instance, take the
+    // classic example of a Stream and a StreamWriter (which has an internal 
+    // buffer of data to write to the Stream).  If both objects are collected 
+    // before Close or Dispose has been called on either, then the GC may run the
+    // finalizer for the Stream first, before the StreamWriter.  At that point, any
+    // data buffered by the StreamWriter cannot be written to the Stream.  In this
+    // case, it doesn't make much sense to provide a finalizer on the StreamWriter
+    // since you cannot solve this problem correctly.  
+    public interface IDisposable
+    {
+        void Dispose();
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IEquatable.cs b/src/System.Private.CoreLib/shared/System/IEquatable.cs
new file mode 100644
index 0000000000..1264fdd57a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IEquatable.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System
+{
+    public interface IEquatable<T>
+    {
+        bool Equals(T other);
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/IFormatProvider.cs b/src/System.Private.CoreLib/shared/System/IFormatProvider.cs
new file mode 100644
index 0000000000..0c17354af3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IFormatProvider.cs
@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Notes a class which knows how to return formatting information
+**
+**
+============================================================*/
+
+using System;
+
+namespace System
+{
+    public interface IFormatProvider
+    {
+        // Interface does not need to be marked with the serializable attribute
+        Object GetFormat(Type formatType);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IFormattable.cs b/src/System.Private.CoreLib/shared/System/IFormattable.cs
new file mode 100644
index 0000000000..1f2f7022cc
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IFormattable.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System
+{
+    public interface IFormattable
+    {
+        String ToString(String format, IFormatProvider formatProvider);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/BinaryWriter.cs b/src/System.Private.CoreLib/shared/System/IO/BinaryWriter.cs
new file mode 100644
index 0000000000..ad1d31f577
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/BinaryWriter.cs
@@ -0,0 +1,441 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text;
+using System.Diagnostics;
+using System.Buffers;
+
+namespace System.IO
+{
+    // This abstract base class represents a writer that can write
+    // primitives to an arbitrary stream. A subclass can override methods to
+    // give unique encodings.
+    //
+    public class BinaryWriter : IDisposable
+    {
+        public static readonly BinaryWriter Null = new BinaryWriter();
+
+        protected Stream OutStream;
+        private byte[] _buffer;    // temp space for writing primitives to.
+        private Encoding _encoding;
+        private Encoder _encoder;
+
+        private bool _leaveOpen;
+
+        // Perf optimization stuff
+        private byte[] _largeByteBuffer;  // temp space for writing chars.
+        private int _maxChars;   // max # of chars we can put in _largeByteBuffer
+        // Size should be around the max number of chars/string * Encoding's max bytes/char
+        private const int LargeByteBufferSize = 256;
+
+        // Protected default constructor that sets the output stream
+        // to a null stream (a bit bucket).
+        protected BinaryWriter()
+        {
+            OutStream = Stream.Null;
+            _buffer = new byte[16];
+            _encoding = EncodingCache.UTF8NoBOM;
+            _encoder = _encoding.GetEncoder();
+        }
+
+        public BinaryWriter(Stream output) : this(output, EncodingCache.UTF8NoBOM, false)
+        {
+        }
+
+        public BinaryWriter(Stream output, Encoding encoding) : this(output, encoding, false)
+        {
+        }
+
+        public BinaryWriter(Stream output, Encoding encoding, bool leaveOpen)
+        {
+            if (output == null)
+                throw new ArgumentNullException(nameof(output));
+            if (encoding == null)
+                throw new ArgumentNullException(nameof(encoding));
+            if (!output.CanWrite)
+                throw new ArgumentException(SR.Argument_StreamNotWritable);
+
+            OutStream = output;
+            _buffer = new byte[16];
+            _encoding = encoding;
+            _encoder = _encoding.GetEncoder();
+            _leaveOpen = leaveOpen;
+        }
+
+        // Closes this writer and releases any system resources associated with the
+        // writer. Following a call to Close, any operations on the writer
+        // may raise exceptions. 
+        public virtual void Close()
+        {
+            Dispose(true);
+        }
+
+        protected virtual void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                if (_leaveOpen)
+                    OutStream.Flush();
+                else
+                    OutStream.Close();
+            }
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+        }
+
+        // Returns the stream associated with the writer. It flushes all pending
+        // writes before returning. All subclasses should override Flush to
+        // ensure that all buffered data is sent to the stream.
+        public virtual Stream BaseStream
+        {
+            get
+            {
+                Flush();
+                return OutStream;
+            }
+        }
+
+        // Clears all buffers for this writer and causes any buffered data to be
+        // written to the underlying device. 
+        public virtual void Flush()
+        {
+            OutStream.Flush();
+        }
+
+        public virtual long Seek(int offset, SeekOrigin origin)
+        {
+            return OutStream.Seek(offset, origin);
+        }
+
+        // Writes a boolean to this stream. A single byte is written to the stream
+        // with the value 0 representing false or the value 1 representing true.
+        // 
+        public virtual void Write(bool value)
+        {
+            _buffer[0] = (byte)(value ? 1 : 0);
+            OutStream.Write(_buffer, 0, 1);
+        }
+
+        // Writes a byte to this stream. The current position of the stream is
+        // advanced by one.
+        // 
+        public virtual void Write(byte value)
+        {
+            OutStream.WriteByte(value);
+        }
+
+        // Writes a signed byte to this stream. The current position of the stream 
+        // is advanced by one.
+        // 
+        [CLSCompliant(false)]
+        public virtual void Write(sbyte value)
+        {
+            OutStream.WriteByte((byte)value);
+        }
+
+        // Writes a byte array to this stream.
+        // 
+        // This default implementation calls the Write(Object, int, int)
+        // method to write the byte array.
+        // 
+        public virtual void Write(byte[] buffer)
+        {
+            if (buffer == null)
+                throw new ArgumentNullException(nameof(buffer));
+            OutStream.Write(buffer, 0, buffer.Length);
+        }
+
+        // Writes a section of a byte array to this stream.
+        //
+        // This default implementation calls the Write(Object, int, int)
+        // method to write the byte array.
+        // 
+        public virtual void Write(byte[] buffer, int index, int count)
+        {
+            OutStream.Write(buffer, index, count);
+        }
+
+
+        // Writes a character to this stream. The current position of the stream is
+        // advanced by two.
+        // Note this method cannot handle surrogates properly in UTF-8.
+        // 
+        public unsafe virtual void Write(char ch)
+        {
+            if (Char.IsSurrogate(ch))
+                throw new ArgumentException(SR.Arg_SurrogatesNotAllowedAsSingleChar);
+
+            Debug.Assert(_encoding.GetMaxByteCount(1) <= 16, "_encoding.GetMaxByteCount(1) <= 16)");
+            int numBytes = 0;
+            fixed (byte* pBytes = &_buffer[0])
+            {
+                numBytes = _encoder.GetBytes(&ch, 1, pBytes, _buffer.Length, flush: true);
+            }
+            OutStream.Write(_buffer, 0, numBytes);
+        }
+
+        // Writes a character array to this stream.
+        // 
+        // This default implementation calls the Write(Object, int, int)
+        // method to write the character array.
+        // 
+        public virtual void Write(char[] chars)
+        {
+            if (chars == null)
+                throw new ArgumentNullException(nameof(chars));
+
+            byte[] bytes = _encoding.GetBytes(chars, 0, chars.Length);
+            OutStream.Write(bytes, 0, bytes.Length);
+        }
+
+        // Writes a section of a character array to this stream.
+        //
+        // This default implementation calls the Write(Object, int, int)
+        // method to write the character array.
+        // 
+        public virtual void Write(char[] chars, int index, int count)
+        {
+            byte[] bytes = _encoding.GetBytes(chars, index, count);
+            OutStream.Write(bytes, 0, bytes.Length);
+        }
+
+
+        // Writes a double to this stream. The current position of the stream is
+        // advanced by eight.
+        // 
+        public unsafe virtual void Write(double value)
+        {
+            ulong TmpValue = *(ulong*)&value;
+            _buffer[0] = (byte)TmpValue;
+            _buffer[1] = (byte)(TmpValue >> 8);
+            _buffer[2] = (byte)(TmpValue >> 16);
+            _buffer[3] = (byte)(TmpValue >> 24);
+            _buffer[4] = (byte)(TmpValue >> 32);
+            _buffer[5] = (byte)(TmpValue >> 40);
+            _buffer[6] = (byte)(TmpValue >> 48);
+            _buffer[7] = (byte)(TmpValue >> 56);
+            OutStream.Write(_buffer, 0, 8);
+        }
+
+        public virtual void Write(decimal value)
+        {
+            Decimal.GetBytes(value, _buffer);
+            OutStream.Write(_buffer, 0, 16);
+        }
+
+        // Writes a two-byte signed integer to this stream. The current position of
+        // the stream is advanced by two.
+        // 
+        public virtual void Write(short value)
+        {
+            _buffer[0] = (byte)value;
+            _buffer[1] = (byte)(value >> 8);
+            OutStream.Write(_buffer, 0, 2);
+        }
+
+        // Writes a two-byte unsigned integer to this stream. The current position
+        // of the stream is advanced by two.
+        // 
+        [CLSCompliant(false)]
+        public virtual void Write(ushort value)
+        {
+            _buffer[0] = (byte)value;
+            _buffer[1] = (byte)(value >> 8);
+            OutStream.Write(_buffer, 0, 2);
+        }
+
+        // Writes a four-byte signed integer to this stream. The current position
+        // of the stream is advanced by four.
+        // 
+        public virtual void Write(int value)
+        {
+            _buffer[0] = (byte)value;
+            _buffer[1] = (byte)(value >> 8);
+            _buffer[2] = (byte)(value >> 16);
+            _buffer[3] = (byte)(value >> 24);
+            OutStream.Write(_buffer, 0, 4);
+        }
+
+        // Writes a four-byte unsigned integer to this stream. The current position
+        // of the stream is advanced by four.
+        // 
+        [CLSCompliant(false)]
+        public virtual void Write(uint value)
+        {
+            _buffer[0] = (byte)value;
+            _buffer[1] = (byte)(value >> 8);
+            _buffer[2] = (byte)(value >> 16);
+            _buffer[3] = (byte)(value >> 24);
+            OutStream.Write(_buffer, 0, 4);
+        }
+
+        // Writes an eight-byte signed integer to this stream. The current position
+        // of the stream is advanced by eight.
+        // 
+        public virtual void Write(long value)
+        {
+            _buffer[0] = (byte)value;
+            _buffer[1] = (byte)(value >> 8);
+            _buffer[2] = (byte)(value >> 16);
+            _buffer[3] = (byte)(value >> 24);
+            _buffer[4] = (byte)(value >> 32);
+            _buffer[5] = (byte)(value >> 40);
+            _buffer[6] = (byte)(value >> 48);
+            _buffer[7] = (byte)(value >> 56);
+            OutStream.Write(_buffer, 0, 8);
+        }
+
+        // Writes an eight-byte unsigned integer to this stream. The current 
+        // position of the stream is advanced by eight.
+        // 
+        [CLSCompliant(false)]
+        public virtual void Write(ulong value)
+        {
+            _buffer[0] = (byte)value;
+            _buffer[1] = (byte)(value >> 8);
+            _buffer[2] = (byte)(value >> 16);
+            _buffer[3] = (byte)(value >> 24);
+            _buffer[4] = (byte)(value >> 32);
+            _buffer[5] = (byte)(value >> 40);
+            _buffer[6] = (byte)(value >> 48);
+            _buffer[7] = (byte)(value >> 56);
+            OutStream.Write(_buffer, 0, 8);
+        }
+
+        // Writes a float to this stream. The current position of the stream is
+        // advanced by four.
+        // 
+        public unsafe virtual void Write(float value)
+        {
+            uint TmpValue = *(uint*)&value;
+            _buffer[0] = (byte)TmpValue;
+            _buffer[1] = (byte)(TmpValue >> 8);
+            _buffer[2] = (byte)(TmpValue >> 16);
+            _buffer[3] = (byte)(TmpValue >> 24);
+            OutStream.Write(_buffer, 0, 4);
+        }
+
+
+        // Writes a length-prefixed string to this stream in the BinaryWriter's
+        // current Encoding. This method first writes the length of the string as 
+        // a four-byte unsigned integer, and then writes that many characters 
+        // to the stream.
+        // 
+        public unsafe virtual void Write(String value)
+        {
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            int len = _encoding.GetByteCount(value);
+            Write7BitEncodedInt(len);
+
+            if (_largeByteBuffer == null)
+            {
+                _largeByteBuffer = new byte[LargeByteBufferSize];
+                _maxChars = _largeByteBuffer.Length / _encoding.GetMaxByteCount(1);
+            }
+
+            if (len <= _largeByteBuffer.Length)
+            {
+                //Debug.Assert(len == _encoding.GetBytes(chars, 0, chars.Length, _largeByteBuffer, 0), "encoding's GetByteCount & GetBytes gave different answers!  encoding type: "+_encoding.GetType().Name);
+                _encoding.GetBytes(value, 0, value.Length, _largeByteBuffer, 0);
+                OutStream.Write(_largeByteBuffer, 0, len);
+            }
+            else
+            {
+                // Aggressively try to not allocate memory in this loop for
+                // runtime performance reasons.  Use an Encoder to write out 
+                // the string correctly (handling surrogates crossing buffer
+                // boundaries properly).  
+                int charStart = 0;
+                int numLeft = value.Length;
+#if DEBUG
+                int totalBytes = 0;
+#endif
+                while (numLeft > 0)
+                {
+                    // Figure out how many chars to process this round.
+                    int charCount = (numLeft > _maxChars) ? _maxChars : numLeft;
+                    int byteLen;
+
+                    checked
+                    {
+                        if (charStart < 0 || charCount < 0 || charStart > value.Length - charCount)
+                        {
+                            throw new ArgumentOutOfRangeException(nameof(charCount));
+                        }
+                        fixed (char* pChars = value)
+                        {
+                            fixed (byte* pBytes = &_largeByteBuffer[0])
+                            {
+                                byteLen = _encoder.GetBytes(pChars + charStart, charCount, pBytes, _largeByteBuffer.Length, charCount == numLeft);
+                            }
+                        }
+                    }
+#if DEBUG
+                    totalBytes += byteLen;
+                    Debug.Assert(totalBytes <= len && byteLen <= _largeByteBuffer.Length, "BinaryWriter::Write(String) - More bytes encoded than expected!");
+#endif
+                    OutStream.Write(_largeByteBuffer, 0, byteLen);
+                    charStart += charCount;
+                    numLeft -= charCount;
+                }
+#if DEBUG
+                Debug.Assert(totalBytes == len, "BinaryWriter::Write(String) - Didn't write out all the bytes!");
+#endif
+            }
+        }
+
+        public virtual void Write(ReadOnlySpan<byte> buffer)
+        {
+            if (GetType() == typeof(BinaryWriter))
+            {
+                OutStream.Write(buffer);
+            }
+            else
+            {
+                byte[] array = ArrayPool<byte>.Shared.Rent(buffer.Length);
+                try
+                {
+                    buffer.CopyTo(array);
+                    Write(array, 0, buffer.Length);
+                }
+                finally
+                {
+                    ArrayPool<byte>.Shared.Return(array);
+                }
+            }
+        }
+
+        public virtual void Write(ReadOnlySpan<char> chars)
+        {
+            byte[] bytes = ArrayPool<byte>.Shared.Rent(_encoding.GetMaxByteCount(chars.Length));
+            try
+            {
+                int bytesWritten = _encoding.GetBytes(chars, bytes);
+                Write(bytes, 0, bytesWritten);
+            }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(bytes);
+            }
+        }
+
+        protected void Write7BitEncodedInt(int value)
+        {
+            // Write out an int 7 bits at a time.  The high bit of the byte,
+            // when on, tells reader to continue reading more bytes.
+            uint v = (uint)value;   // support negative numbers
+            while (v >= 0x80)
+            {
+                Write((byte)(v | 0x80));
+                v >>= 7;
+            }
+            Write((byte)v);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/DirectoryNotFoundException.cs b/src/System.Private.CoreLib/shared/System/IO/DirectoryNotFoundException.cs
new file mode 100644
index 0000000000..d7c6eacb9a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/DirectoryNotFoundException.cs
@@ -0,0 +1,42 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.IO
+{
+    /*
+     * Thrown when trying to access a directory that doesn't exist on disk.
+     * From COM Interop, this exception is thrown for 2 HRESULTS: 
+     * the Win32 errorcode-as-HRESULT ERROR_PATH_NOT_FOUND (0x80070003) 
+     * and STG_E_PATHNOTFOUND (0x80030003).
+     */
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class DirectoryNotFoundException : IOException
+    {
+        public DirectoryNotFoundException()
+            : base(SR.Arg_DirectoryNotFoundException)
+        {
+            HResult = HResults.COR_E_DIRECTORYNOTFOUND;
+        }
+
+        public DirectoryNotFoundException(string message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_DIRECTORYNOTFOUND;
+        }
+
+        public DirectoryNotFoundException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_DIRECTORYNOTFOUND;
+        }
+
+        protected DirectoryNotFoundException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/DisableMediaInsertionPrompt.cs b/src/System.Private.CoreLib/shared/System/IO/DisableMediaInsertionPrompt.cs
new file mode 100644
index 0000000000..aa10e8d883
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/DisableMediaInsertionPrompt.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.IO
+{
+    /// <summary>
+    /// Simple wrapper to safely disable the normal media insertion prompt for
+    /// removable media (floppies, cds, memory cards, etc.)
+    /// </summary>
+    /// <remarks>
+    /// Note that removable media file systems lazily load. After starting the OS
+    /// they won't be loaded until you have media in the drive- and as such the
+    /// prompt won't happen. You have to have had media in at least once to get
+    /// the file system to load and then have removed it.
+    /// </remarks>
+    internal struct DisableMediaInsertionPrompt : IDisposable
+    {
+        private bool _disableSuccess;
+        private uint _oldMode;
+
+        public static DisableMediaInsertionPrompt Create()
+        {
+            DisableMediaInsertionPrompt prompt = new DisableMediaInsertionPrompt();
+            prompt._disableSuccess = Interop.Kernel32.SetThreadErrorMode(Interop.Kernel32.SEM_FAILCRITICALERRORS, out prompt._oldMode);
+            return prompt;
+        }
+
+        public void Dispose()
+        {
+            uint ignore;
+            if (_disableSuccess)
+                Interop.Kernel32.SetThreadErrorMode(_oldMode, out ignore);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/EncodingCache.cs b/src/System.Private.CoreLib/shared/System/IO/EncodingCache.cs
new file mode 100644
index 0000000000..53379bc77f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/EncodingCache.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text;
+
+namespace System.IO
+{
+    internal static class EncodingCache
+    {
+        internal static readonly Encoding UTF8NoBOM = new UTF8Encoding(encoderShouldEmitUTF8Identifier: false, throwOnInvalidBytes: true);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/EndOfStreamException.cs b/src/System.Private.CoreLib/shared/System/IO/EndOfStreamException.cs
new file mode 100644
index 0000000000..606073ad9a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/EndOfStreamException.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.IO
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class EndOfStreamException : IOException
+    {
+        public EndOfStreamException()
+            : base(SR.Arg_EndOfStreamException)
+        {
+            HResult = HResults.COR_E_ENDOFSTREAM;
+        }
+
+        public EndOfStreamException(string message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_ENDOFSTREAM;
+        }
+
+        public EndOfStreamException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_ENDOFSTREAM;
+        }
+
+        protected EndOfStreamException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/Error.cs b/src/System.Private.CoreLib/shared/System/IO/Error.cs
new file mode 100644
index 0000000000..1e319a0680
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/Error.cs
@@ -0,0 +1,47 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Globalization;
+
+namespace System.IO
+{
+    /// <summary>
+    ///     Provides centralized methods for creating exceptions for System.IO.FileSystem.
+    /// </summary>
+    internal static class Error
+    {
+        internal static Exception GetStreamIsClosed()
+        {
+            return new ObjectDisposedException(null, SR.ObjectDisposed_StreamClosed);
+        }
+
+        internal static Exception GetEndOfFile()
+        {
+            return new EndOfStreamException(SR.IO_EOF_ReadBeyondEOF);
+        }
+
+        internal static Exception GetFileNotOpen()
+        {
+            return new ObjectDisposedException(null, SR.ObjectDisposed_FileClosed);
+        }
+
+        internal static Exception GetReadNotSupported()
+        {
+            return new NotSupportedException(SR.NotSupported_UnreadableStream);
+        }
+
+        internal static Exception GetSeekNotSupported()
+        {
+            return new NotSupportedException(SR.NotSupported_UnseekableStream);
+        }
+
+        internal static Exception GetWriteNotSupported()
+        {
+            return new NotSupportedException(SR.NotSupported_UnwritableStream);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/FileAccess.cs b/src/System.Private.CoreLib/shared/System/IO/FileAccess.cs
new file mode 100644
index 0000000000..1b70bae172
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/FileAccess.cs
@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.IO
+{
+    // Contains constants for specifying the access you want for a file.
+    // You can have Read, Write or ReadWrite access.
+    // 
+    [Flags]
+    public enum FileAccess
+    {
+        // Specifies read access to the file. Data can be read from the file and
+        // the file pointer can be moved. Combine with WRITE for read-write access.
+        Read = 1,
+
+        // Specifies write access to the file. Data can be written to the file and
+        // the file pointer can be moved. Combine with READ for read-write access.
+        Write = 2,
+
+        // Specifies read and write access to the file. Data can be written to the
+        // file and the file pointer can be moved. Data can also be read from the 
+        // file.
+        ReadWrite = 3,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/FileLoadException.cs b/src/System.Private.CoreLib/shared/System/IO/FileLoadException.cs
new file mode 100644
index 0000000000..8c31244e1d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/FileLoadException.cs
@@ -0,0 +1,98 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.IO
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public partial class FileLoadException : IOException
+    {
+        public FileLoadException()
+            : base(SR.IO_FileLoad)
+        {
+            HResult = HResults.COR_E_FILELOAD;
+        }
+
+        public FileLoadException(string message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_FILELOAD;
+        }
+
+        public FileLoadException(string message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_FILELOAD;
+        }
+
+        public FileLoadException(string message, string fileName) : base(message)
+        {
+            HResult = HResults.COR_E_FILELOAD;
+            FileName = fileName;
+        }
+
+        public FileLoadException(string message, string fileName, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_FILELOAD;
+            FileName = fileName;
+        }
+
+        public override string Message
+        {
+            get
+            {
+                if (_message == null)
+                {
+                    _message = FormatFileLoadExceptionMessage(FileName, HResult);
+                }
+                return _message;
+            }
+        }
+
+        public string FileName { get; }
+        public string FusionLog { get; }
+
+        public override string ToString()
+        {
+            string s = GetType().ToString() + ": " + Message;
+
+            if (FileName != null && FileName.Length != 0)
+                s += Environment.NewLine + SR.Format(SR.IO_FileName_Name, FileName);
+
+            if (InnerException != null)
+                s = s + " ---> " + InnerException.ToString();
+
+            if (StackTrace != null)
+                s += Environment.NewLine + StackTrace;
+
+            if (FusionLog != null)
+            {
+                if (s == null)
+                    s = " ";
+                s += Environment.NewLine;
+                s += Environment.NewLine;
+                s += FusionLog;
+            }
+
+            return s;
+        }
+
+        protected FileLoadException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            FileName = info.GetString("FileLoad_FileName");
+            FusionLog = info.GetString("FileLoad_FusionLog");
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("FileLoad_FileName", FileName, typeof(string));
+            info.AddValue("FileLoad_FusionLog", FusionLog, typeof(string));
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/FileMode.cs b/src/System.Private.CoreLib/shared/System/IO/FileMode.cs
new file mode 100644
index 0000000000..77f2fe6f20
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/FileMode.cs
@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.IO
+{
+    // Contains constants for specifying how the OS should open a file.
+    // These will control whether you overwrite a file, open an existing
+    // file, or some combination thereof.
+    // 
+    // To append to a file, use Append (which maps to OpenOrCreate then we seek
+    // to the end of the file).  To truncate a file or create it if it doesn't 
+    // exist, use Create.
+    // 
+    public enum FileMode
+    {
+        // Creates a new file. An exception is raised if the file already exists.
+        CreateNew = 1,
+
+        // Creates a new file. If the file already exists, it is overwritten.
+        Create = 2,
+
+        // Opens an existing file. An exception is raised if the file does not exist.
+        Open = 3,
+
+        // Opens the file if it exists. Otherwise, creates a new file.
+        OpenOrCreate = 4,
+
+        // Opens an existing file. Once opened, the file is truncated so that its
+        // size is zero bytes. The calling process must open the file with at least
+        // WRITE access. An exception is raised if the file does not exist.
+        Truncate = 5,
+
+        // Opens the file if it exists and seeks to the end.  Otherwise, 
+        // creates a new file.
+        Append = 6,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/FileNotFoundException.cs b/src/System.Private.CoreLib/shared/System/IO/FileNotFoundException.cs
new file mode 100644
index 0000000000..72cff4cfc0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/FileNotFoundException.cs
@@ -0,0 +1,110 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.IO
+{
+    // Thrown when trying to access a file that doesn't exist on disk.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public partial class FileNotFoundException : IOException
+    {
+        public FileNotFoundException()
+            : base(SR.IO_FileNotFound)
+        {
+            HResult = HResults.COR_E_FILENOTFOUND;
+        }
+
+        public FileNotFoundException(string message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_FILENOTFOUND;
+        }
+
+        public FileNotFoundException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_FILENOTFOUND;
+        }
+
+        public FileNotFoundException(string message, string fileName) 
+            : base(message)
+        {
+            HResult = HResults.COR_E_FILENOTFOUND;
+            FileName = fileName;
+        }
+
+        public FileNotFoundException(string message, string fileName, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_FILENOTFOUND;
+            FileName = fileName;
+        }
+
+        public override string Message
+        {
+            get
+            {
+                SetMessageField();
+                return _message;
+            }
+        }
+
+        private void SetMessageField()
+        {
+            if (_message == null)
+            {
+                if ((FileName == null) &&
+                    (HResult == System.HResults.COR_E_EXCEPTION))
+                    _message = SR.IO_FileNotFound;
+
+                else if (FileName != null)
+                    _message = FileLoadException.FormatFileLoadExceptionMessage(FileName, HResult);
+            }
+        }
+
+        public string FileName { get; }
+        public string FusionLog { get; }
+
+        public override string ToString()
+        {
+            string s = GetType().ToString() + ": " + Message;
+
+            if (FileName != null && FileName.Length != 0)
+                s += Environment.NewLine + SR.Format(SR.IO_FileName_Name, FileName);
+
+            if (InnerException != null)
+                s = s + " ---> " + InnerException.ToString();
+
+            if (StackTrace != null)
+                s += Environment.NewLine + StackTrace;
+
+            if (FusionLog != null)
+            {
+                if (s == null)
+                    s = " ";
+                s += Environment.NewLine;
+                s += Environment.NewLine;
+                s += FusionLog;
+            }
+            return s;
+        }
+
+        protected FileNotFoundException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            FileName = info.GetString("FileNotFound_FileName");
+            FusionLog = info.GetString("FileNotFound_FusionLog");
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("FileNotFound_FileName", FileName, typeof(string));
+            info.AddValue("FileNotFound_FusionLog", FusionLog, typeof(string));
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/IO/FileOptions.cs b/src/System.Private.CoreLib/shared/System/IO/FileOptions.cs
new file mode 100644
index 0000000000..ae8396a588
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/FileOptions.cs
@@ -0,0 +1,33 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace System.IO
+{
+    // Maps to FILE_FLAG_DELETE_ON_CLOSE and similar values from winbase.h.
+    // We didn't expose a number of these values because we didn't believe 
+    // a number of them made sense in managed code, at least not yet.
+    [Flags]
+    public enum FileOptions
+    {
+        // NOTE: any change to FileOptions enum needs to be 
+        // matched in the FileStream ctor for error validation
+        None = 0,
+        WriteThrough = unchecked((int)0x80000000),
+        Asynchronous = unchecked((int)0x40000000), // FILE_FLAG_OVERLAPPED
+        // NoBuffering = 0x20000000,
+        RandomAccess = 0x10000000,
+        DeleteOnClose = 0x04000000,
+        SequentialScan = 0x08000000,
+        // AllowPosix = 0x01000000,  // FILE_FLAG_POSIX_SEMANTICS
+        // BackupOrRestore,
+        // DisallowReparsePoint = 0x00200000, // FILE_FLAG_OPEN_REPARSE_POINT
+        // NoRemoteRecall = 0x00100000, // FILE_FLAG_OPEN_NO_RECALL
+        // FirstPipeInstance = 0x00080000, // FILE_FLAG_FIRST_PIPE_INSTANCE
+        Encrypted = 0x00004000, // FILE_ATTRIBUTE_ENCRYPTED
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/IO/FileShare.cs b/src/System.Private.CoreLib/shared/System/IO/FileShare.cs
new file mode 100644
index 0000000000..e9b9b5e32f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/FileShare.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.IO
+{
+    // Contains constants for controlling file sharing options while
+    // opening files.  You can specify what access other processes trying
+    // to open the same file concurrently can have.
+    //
+    // Note these values currently match the values for FILE_SHARE_READ,
+    // FILE_SHARE_WRITE, and FILE_SHARE_DELETE in winnt.h
+    // 
+    [Flags]
+    public enum FileShare
+    {
+        // No sharing. Any request to open the file (by this process or another
+        // process) will fail until the file is closed.
+        None = 0,
+
+        // Allows subsequent opening of the file for reading. If this flag is not
+        // specified, any request to open the file for reading (by this process or
+        // another process) will fail until the file is closed.
+        Read = 1,
+
+        // Allows subsequent opening of the file for writing. If this flag is not
+        // specified, any request to open the file for writing (by this process or
+        // another process) will fail until the file is closed.
+        Write = 2,
+
+        // Allows subsequent opening of the file for writing or reading. If this flag
+        // is not specified, any request to open the file for writing or reading (by
+        // this process or another process) will fail until the file is closed.
+        ReadWrite = 3,
+
+        // Open the file, but allow someone else to delete the file.
+        Delete = 4,
+
+        // Whether the file handle should be inheritable by child processes.
+        // Note this is not directly supported like this by Win32.
+        Inheritable = 0x10,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/FileStream.Linux.cs b/src/System.Private.CoreLib/shared/System/IO/FileStream.Linux.cs
new file mode 100644
index 0000000000..873c4eb559
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/FileStream.Linux.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.IO
+{
+    public partial class FileStream : Stream
+    {
+        /// <summary>Prevents other processes from reading from or writing to the FileStream.</summary>
+        /// <param name="position">The beginning of the range to lock.</param>
+        /// <param name="length">The range to be locked.</param>
+        private void LockInternal(long position, long length)
+        {
+            CheckFileCall(Interop.Sys.LockFileRegion(_fileHandle, position, length, Interop.Sys.LockType.F_WRLCK));
+        }
+
+        /// <summary>Allows access by other processes to all or part of a file that was previously locked.</summary>
+        /// <param name="position">The beginning of the range to unlock.</param>
+        /// <param name="length">The range to be unlocked.</param>
+        private void UnlockInternal(long position, long length)
+        {
+            CheckFileCall(Interop.Sys.LockFileRegion(_fileHandle, position, length, Interop.Sys.LockType.F_UNLCK));
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/FileStream.OSX.cs b/src/System.Private.CoreLib/shared/System/IO/FileStream.OSX.cs
new file mode 100644
index 0000000000..f29e922337
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/FileStream.OSX.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.IO
+{
+    public partial class FileStream : Stream
+    {
+        private void LockInternal(long position, long length)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_OSXFileLocking);
+        }
+
+        private void UnlockInternal(long position, long length)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_OSXFileLocking);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/FileStream.Unix.cs b/src/System.Private.CoreLib/shared/System/IO/FileStream.Unix.cs
new file mode 100644
index 0000000000..d9fcf65711
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/FileStream.Unix.cs
@@ -0,0 +1,813 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.IO
+{
+    /// <summary>Provides an implementation of a file stream for Unix files.</summary>
+    public partial class FileStream : Stream
+    {
+        /// <summary>File mode.</summary>
+        private FileMode _mode;
+
+        /// <summary>Advanced options requested when opening the file.</summary>
+        private FileOptions _options;
+
+        /// <summary>If the file was opened with FileMode.Append, the length of the file when opened; otherwise, -1.</summary>
+        private long _appendStart = -1;
+
+        /// <summary>
+        /// Extra state used by the file stream when _useAsyncIO is true.  This includes
+        /// the semaphore used to serialize all operation, the buffer/offset/count provided by the
+        /// caller for ReadAsync/WriteAsync operations, and the last successful task returned
+        /// synchronously from ReadAsync which can be reused if the count matches the next request.
+        /// Only initialized when <see cref="_useAsyncIO"/> is true.
+        /// </summary>
+        private AsyncState _asyncState;
+
+        /// <summary>Lazily-initialized value for whether the file supports seeking.</summary>
+        private bool? _canSeek;
+
+        private SafeFileHandle OpenHandle(FileMode mode, FileShare share, FileOptions options)
+        {
+            // FileStream performs most of the general argument validation.  We can assume here that the arguments
+            // are all checked and consistent (e.g. non-null-or-empty path; valid enums in mode, access, share, and options; etc.)
+            // Store the arguments
+            _mode = mode;
+            _options = options;
+
+            if (_useAsyncIO)
+                _asyncState = new AsyncState();
+
+            // Translate the arguments into arguments for an open call.
+            Interop.Sys.OpenFlags openFlags = PreOpenConfigurationFromOptions(mode, _access, share, options);
+
+            // If the file gets created a new, we'll select the permissions for it.  Most Unix utilities by default use 666 (read and 
+            // write for all), so we do the same (even though this doesn't match Windows, where by default it's possible to write out
+            // a file and then execute it). No matter what we choose, it'll be subject to the umask applied by the system, such that the
+            // actual permissions will typically be less than what we select here.
+            const Interop.Sys.Permissions OpenPermissions =
+                Interop.Sys.Permissions.S_IRUSR | Interop.Sys.Permissions.S_IWUSR |
+                Interop.Sys.Permissions.S_IRGRP | Interop.Sys.Permissions.S_IWGRP |
+                Interop.Sys.Permissions.S_IROTH | Interop.Sys.Permissions.S_IWOTH;
+
+            // Open the file and store the safe handle.
+            return SafeFileHandle.Open(_path, openFlags, (int)OpenPermissions);
+        }
+
+        /// <summary>Initializes a stream for reading or writing a Unix file.</summary>
+        /// <param name="mode">How the file should be opened.</param>
+        /// <param name="share">What other access to the file should be allowed.  This is currently ignored.</param>
+        private void Init(FileMode mode, FileShare share)
+        {
+            _fileHandle.IsAsync = _useAsyncIO;
+
+            // Lock the file if requested via FileShare.  This is only advisory locking. FileShare.None implies an exclusive 
+            // lock on the file and all other modes use a shared lock.  While this is not as granular as Windows, not mandatory, 
+            // and not atomic with file opening, it's better than nothing.
+            Interop.Sys.LockOperations lockOperation = (share == FileShare.None) ? Interop.Sys.LockOperations.LOCK_EX : Interop.Sys.LockOperations.LOCK_SH;
+            if (Interop.Sys.FLock(_fileHandle, lockOperation | Interop.Sys.LockOperations.LOCK_NB) < 0)
+            {
+                // The only error we care about is EWOULDBLOCK, which indicates that the file is currently locked by someone
+                // else and we would block trying to access it.  Other errors, such as ENOTSUP (locking isn't supported) or
+                // EACCES (the file system doesn't allow us to lock), will only hamper FileStream's usage without providing value,
+                // given again that this is only advisory / best-effort.
+                Interop.ErrorInfo errorInfo = Interop.Sys.GetLastErrorInfo();
+                if (errorInfo.Error == Interop.Error.EWOULDBLOCK)
+                {
+                    throw Interop.GetExceptionForIoErrno(errorInfo, _path, isDirectory: false);
+                }
+            }
+
+            // These provide hints around how the file will be accessed.  Specifying both RandomAccess
+            // and Sequential together doesn't make sense as they are two competing options on the same spectrum,
+            // so if both are specified, we prefer RandomAccess (behavior on Windows is unspecified if both are provided).
+            Interop.Sys.FileAdvice fadv =
+                (_options & FileOptions.RandomAccess) != 0 ? Interop.Sys.FileAdvice.POSIX_FADV_RANDOM :
+                (_options & FileOptions.SequentialScan) != 0 ? Interop.Sys.FileAdvice.POSIX_FADV_SEQUENTIAL :
+                0;
+            if (fadv != 0)
+            {
+                CheckFileCall(Interop.Sys.PosixFAdvise(_fileHandle, 0, 0, fadv),
+                    ignoreNotSupported: true); // just a hint.
+            }
+
+            if (_mode == FileMode.Append)
+            {
+                // Jump to the end of the file if opened as Append.
+                _appendStart = SeekCore(_fileHandle, 0, SeekOrigin.End);
+            }
+            else if (mode == FileMode.Create || mode == FileMode.Truncate)
+            {
+                // Truncate the file now if the file mode requires it. This ensures that the file only will be truncated
+                // if opened successfully.
+                CheckFileCall(Interop.Sys.FTruncate(_fileHandle, 0));
+            }
+        }
+
+        /// <summary>Initializes a stream from an already open file handle (file descriptor).</summary>
+        private void InitFromHandle(SafeFileHandle handle, FileAccess access, bool useAsyncIO)
+        {
+            if (useAsyncIO)
+                _asyncState = new AsyncState();
+
+            if (CanSeekCore(handle)) // use non-virtual CanSeekCore rather than CanSeek to avoid making virtual call during ctor
+                SeekCore(handle, 0, SeekOrigin.Current);
+        }
+
+        /// <summary>Translates the FileMode, FileAccess, and FileOptions values into flags to be passed when opening the file.</summary>
+        /// <param name="mode">The FileMode provided to the stream's constructor.</param>
+        /// <param name="access">The FileAccess provided to the stream's constructor</param>
+        /// <param name="share">The FileShare provided to the stream's constructor</param>
+        /// <param name="options">The FileOptions provided to the stream's constructor</param>
+        /// <returns>The flags value to be passed to the open system call.</returns>
+        private static Interop.Sys.OpenFlags PreOpenConfigurationFromOptions(FileMode mode, FileAccess access, FileShare share, FileOptions options)
+        {
+            // Translate FileMode.  Most of the values map cleanly to one or more options for open.
+            Interop.Sys.OpenFlags flags = default(Interop.Sys.OpenFlags);
+            switch (mode)
+            {
+                default:
+                case FileMode.Open: // Open maps to the default behavior for open(...).  No flags needed.
+                case FileMode.Truncate: // We truncate the file after getting the lock
+                    break;
+
+                case FileMode.Append: // Append is the same as OpenOrCreate, except that we'll also separately jump to the end later
+                case FileMode.OpenOrCreate:
+                case FileMode.Create: // We truncate the file after getting the lock
+                    flags |= Interop.Sys.OpenFlags.O_CREAT;
+                    break;
+
+                case FileMode.CreateNew:
+                    flags |= (Interop.Sys.OpenFlags.O_CREAT | Interop.Sys.OpenFlags.O_EXCL);
+                    break;
+            }
+
+            // Translate FileAccess.  All possible values map cleanly to corresponding values for open.
+            switch (access)
+            {
+                case FileAccess.Read:
+                    flags |= Interop.Sys.OpenFlags.O_RDONLY;
+                    break;
+
+                case FileAccess.ReadWrite:
+                    flags |= Interop.Sys.OpenFlags.O_RDWR;
+                    break;
+
+                case FileAccess.Write:
+                    flags |= Interop.Sys.OpenFlags.O_WRONLY;
+                    break;
+            }
+
+            // Handle Inheritable, other FileShare flags are handled by Init
+            if ((share & FileShare.Inheritable) == 0)
+            {
+                flags |= Interop.Sys.OpenFlags.O_CLOEXEC;
+            }
+
+            // Translate some FileOptions; some just aren't supported, and others will be handled after calling open.
+            // - Asynchronous: Handled in ctor, setting _useAsync and SafeFileHandle.IsAsync to true
+            // - DeleteOnClose: Doesn't have a Unix equivalent, but we approximate it in Dispose
+            // - Encrypted: No equivalent on Unix and is ignored
+            // - RandomAccess: Implemented after open if posix_fadvise is available
+            // - SequentialScan: Implemented after open if posix_fadvise is available
+            // - WriteThrough: Handled here
+            if ((options & FileOptions.WriteThrough) != 0)
+            {
+                flags |= Interop.Sys.OpenFlags.O_SYNC;
+            }
+
+            return flags;
+        }
+
+        /// <summary>Gets a value indicating whether the current stream supports seeking.</summary>
+        public override bool CanSeek => CanSeekCore(_fileHandle);
+
+        /// <summary>Gets a value indicating whether the current stream supports seeking.</summary>
+        /// <remarks>
+        /// Separated out of CanSeek to enable making non-virtual call to this logic.
+        /// We also pass in the file handle to allow the constructor to use this before it stashes the handle.
+        /// </remarks>
+        private bool CanSeekCore(SafeFileHandle fileHandle)
+        {
+            if (fileHandle.IsClosed)
+            {
+                return false;
+            }
+
+            if (!_canSeek.HasValue)
+            {
+                // Lazily-initialize whether we're able to seek, tested by seeking to our current location.
+                _canSeek = Interop.Sys.LSeek(fileHandle, 0, Interop.Sys.SeekWhence.SEEK_CUR) >= 0;
+            }
+
+            return _canSeek.Value;
+        }
+
+        private long GetLengthInternal()
+        {
+            // Get the length of the file as reported by the OS
+            Interop.Sys.FileStatus status;
+            CheckFileCall(Interop.Sys.FStat(_fileHandle, out status));
+            long length = status.Size;
+
+            // But we may have buffered some data to be written that puts our length
+            // beyond what the OS is aware of.  Update accordingly.
+            if (_writePos > 0 && _filePosition + _writePos > length)
+            {
+                length = _writePos + _filePosition;
+            }
+
+            return length;
+        }
+
+        /// <summary>Releases the unmanaged resources used by the stream.</summary>
+        /// <param name="disposing">true to release both managed and unmanaged resources; false to release only unmanaged resources.</param>
+        protected override void Dispose(bool disposing)
+        {
+            try
+            {
+                if (_fileHandle != null && !_fileHandle.IsClosed)
+                {
+                    // Flush any remaining data in the file
+                    try
+                    {
+                        FlushWriteBuffer();
+                    }
+                    catch (Exception e) when (IsIoRelatedException(e) && !disposing)
+                    {
+                        // On finalization, ignore failures from trying to flush the write buffer,
+                        // e.g. if this stream is wrapping a pipe and the pipe is now broken.
+                    }
+
+                    // If DeleteOnClose was requested when constructed, delete the file now.
+                    // (Unix doesn't directly support DeleteOnClose, so we mimic it here.)
+                    if (_path != null && (_options & FileOptions.DeleteOnClose) != 0)
+                    {
+                        // Since we still have the file open, this will end up deleting
+                        // it (assuming we're the only link to it) once it's closed, but the
+                        // name will be removed immediately.
+                        Interop.Sys.Unlink(_path); // ignore errors; it's valid that the path may no longer exist
+                    }
+                }
+            }
+            finally
+            {
+                if (_fileHandle != null && !_fileHandle.IsClosed)
+                {
+                    _fileHandle.Dispose();
+                }
+                base.Dispose(disposing);
+            }
+        }
+
+        /// <summary>Flushes the OS buffer.  This does not flush the internal read/write buffer.</summary>
+        private void FlushOSBuffer()
+        {
+            if (Interop.Sys.FSync(_fileHandle) < 0)
+            {
+                Interop.ErrorInfo errorInfo = Interop.Sys.GetLastErrorInfo();
+                switch (errorInfo.Error)
+                {
+                    case Interop.Error.EROFS:
+                    case Interop.Error.EINVAL:
+                    case Interop.Error.ENOTSUP:
+                        // Ignore failures due to the FileStream being bound to a special file that
+                        // doesn't support synchronization.  In such cases there's nothing to flush.
+                        break;
+                    default:
+                        throw Interop.GetExceptionForIoErrno(errorInfo, _path, isDirectory: false);
+                }
+            }
+        }
+
+        private void FlushWriteBufferForWriteByte()
+        {
+            _asyncState?.Wait();
+            try { FlushWriteBuffer(); }
+            finally { _asyncState?.Release(); }
+        }
+
+        /// <summary>Writes any data in the write buffer to the underlying stream and resets the buffer.</summary>
+        private void FlushWriteBuffer()
+        {
+            AssertBufferInvariants();
+            if (_writePos > 0)
+            {
+                WriteNative(new ReadOnlySpan<byte>(GetBuffer(), 0, _writePos));
+                _writePos = 0;
+            }
+        }
+
+        /// <summary>Asynchronously clears all buffers for this stream, causing any buffered data to be written to the underlying device.</summary>
+        /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
+        /// <returns>A task that represents the asynchronous flush operation.</returns>
+        private Task FlushAsyncInternal(CancellationToken cancellationToken)
+        {
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return Task.FromCanceled(cancellationToken);
+            }
+            if (_fileHandle.IsClosed)
+            {
+                throw Error.GetFileNotOpen();
+            }
+
+            // As with Win32FileStream, flush the buffers synchronously to avoid race conditions.
+            try
+            {
+                FlushInternalBuffer();
+            }
+            catch (Exception e)
+            {
+                return Task.FromException(e);
+            }
+
+            // We then separately flush to disk asynchronously.  This is only 
+            // necessary if we support writing; otherwise, we're done.
+            if (CanWrite)
+            {
+                return Task.Factory.StartNew(
+                    state => ((FileStream)state).FlushOSBuffer(),
+                    this,
+                    cancellationToken,
+                    TaskCreationOptions.DenyChildAttach,
+                    TaskScheduler.Default);
+            }
+            else
+            {
+                return Task.CompletedTask;
+            }
+        }
+
+        /// <summary>Sets the length of this stream to the given value.</summary>
+        /// <param name="value">The new length of the stream.</param>
+        private void SetLengthInternal(long value)
+        {
+            FlushInternalBuffer();
+
+            if (_appendStart != -1 && value < _appendStart)
+            {
+                throw new IOException(SR.IO_SetLengthAppendTruncate);
+            }
+
+            long origPos = _filePosition;
+
+            VerifyOSHandlePosition();
+
+            if (_filePosition != value)
+            {
+                SeekCore(_fileHandle, value, SeekOrigin.Begin);
+            }
+
+            CheckFileCall(Interop.Sys.FTruncate(_fileHandle, value));
+
+            // Return file pointer to where it was before setting length
+            if (origPos != value)
+            {
+                if (origPos < value)
+                {
+                    SeekCore(_fileHandle, origPos, SeekOrigin.Begin);
+                }
+                else
+                {
+                    SeekCore(_fileHandle, 0, SeekOrigin.End);
+                }
+            }
+        }
+
+        /// <summary>Reads a block of bytes from the stream and writes the data in a given buffer.</summary>
+        private int ReadSpan(Span<byte> destination)
+        {
+            PrepareForReading();
+
+            // Are there any bytes available in the read buffer? If yes,
+            // we can just return from the buffer.  If the buffer is empty
+            // or has no more available data in it, we can either refill it
+            // (and then read from the buffer into the user's buffer) or
+            // we can just go directly into the user's buffer, if they asked
+            // for more data than we'd otherwise buffer.
+            int numBytesAvailable = _readLength - _readPos;
+            bool readFromOS = false;
+            if (numBytesAvailable == 0)
+            {
+                // If we're not able to seek, then we're not able to rewind the stream (i.e. flushing
+                // a read buffer), in which case we don't want to use a read buffer.  Similarly, if
+                // the user has asked for more data than we can buffer, we also want to skip the buffer.
+                if (!CanSeek || (destination.Length >= _bufferLength))
+                {
+                    // Read directly into the user's buffer
+                    _readPos = _readLength = 0;
+                    return ReadNative(destination);
+                }
+                else
+                {
+                    // Read into our buffer.
+                    _readLength = numBytesAvailable = ReadNative(GetBuffer());
+                    _readPos = 0;
+                    if (numBytesAvailable == 0)
+                    {
+                        return 0;
+                    }
+
+                    // Note that we did an OS read as part of this Read, so that later
+                    // we don't try to do one again if what's in the buffer doesn't
+                    // meet the user's request.
+                    readFromOS = true;
+                }
+            }
+
+            // Now that we know there's data in the buffer, read from it into the user's buffer.
+            Debug.Assert(numBytesAvailable > 0, "Data must be in the buffer to be here");
+            int bytesRead = Math.Min(numBytesAvailable, destination.Length);
+            new Span<byte>(GetBuffer(), _readPos, bytesRead).CopyTo(destination);
+            _readPos += bytesRead;
+
+            // We may not have had enough data in the buffer to completely satisfy the user's request.
+            // While Read doesn't require that we return as much data as the user requested (any amount
+            // up to the requested count is fine), FileStream on Windows tries to do so by doing a 
+            // subsequent read from the file if we tried to satisfy the request with what was in the 
+            // buffer but the buffer contained less than the requested count. To be consistent with that 
+            // behavior, we do the same thing here on Unix.  Note that we may still get less the requested 
+            // amount, as the OS may give us back fewer than we request, either due to reaching the end of 
+            // file, or due to its own whims.
+            if (!readFromOS && bytesRead < destination.Length)
+            {
+                Debug.Assert(_readPos == _readLength, "bytesToRead should only be < destination.Length if numBytesAvailable < destination.Length");
+                _readPos = _readLength = 0; // no data left in the read buffer
+                bytesRead += ReadNative(destination.Slice(bytesRead));
+            }
+
+            return bytesRead;
+        }
+
+        /// <summary>Unbuffered, reads a block of bytes from the file handle into the given buffer.</summary>
+        /// <param name="buffer">The buffer into which data from the file is read.</param>
+        /// <returns>
+        /// The total number of bytes read into the buffer. This might be less than the number of bytes requested 
+        /// if that number of bytes are not currently available, or zero if the end of the stream is reached.
+        /// </returns>
+        private unsafe int ReadNative(Span<byte> buffer)
+        {
+            FlushWriteBuffer(); // we're about to read; dump the write buffer
+
+            VerifyOSHandlePosition();
+
+            int bytesRead;
+            fixed (byte* bufPtr = &MemoryMarshal.GetReference(buffer))
+            {
+                bytesRead = CheckFileCall(Interop.Sys.Read(_fileHandle, bufPtr, buffer.Length));
+                Debug.Assert(bytesRead <= buffer.Length);
+            }
+            _filePosition += bytesRead;
+            return bytesRead;
+        }
+
+        /// <summary>
+        /// Asynchronously reads a sequence of bytes from the current stream and advances
+        /// the position within the stream by the number of bytes read.
+        /// </summary>
+        /// <param name="destination">The buffer to write the data into.</param>
+        /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
+        /// <param name="synchronousResult">If the operation completes synchronously, the number of bytes read.</param>
+        /// <returns>A task that represents the asynchronous read operation.</returns>
+        private Task<int> ReadAsyncInternal(Memory<byte> destination, CancellationToken cancellationToken, out int synchronousResult)
+        {
+            Debug.Assert(_useAsyncIO);
+
+            if (!CanRead) // match Windows behavior; this gets thrown synchronously
+            {
+                throw Error.GetReadNotSupported();
+            }
+
+            // Serialize operations using the semaphore.
+            Task waitTask = _asyncState.WaitAsync();
+
+            // If we got ownership immediately, and if there's enough data in our buffer
+            // to satisfy the full request of the caller, hand back the buffered data.
+            // While it would be a legal implementation of the Read contract, we don't
+            // hand back here less than the amount requested so as to match the behavior
+            // in ReadCore that will make a native call to try to fulfill the remainder
+            // of the request.
+            if (waitTask.Status == TaskStatus.RanToCompletion)
+            {
+                int numBytesAvailable = _readLength - _readPos;
+                if (numBytesAvailable >= destination.Length)
+                {
+                    try
+                    {
+                        PrepareForReading();
+
+                        new Span<byte>(GetBuffer(), _readPos, destination.Length).CopyTo(destination.Span);
+                        _readPos += destination.Length;
+
+                        synchronousResult = destination.Length;
+                        return null;
+                    }
+                    catch (Exception exc)
+                    {
+                        synchronousResult = 0;
+                        return Task.FromException<int>(exc);
+                    }
+                    finally
+                    {
+                        _asyncState.Release();
+                    }
+                }
+            }
+
+            // Otherwise, issue the whole request asynchronously.
+            synchronousResult = 0;
+            _asyncState.Memory = destination;
+            return waitTask.ContinueWith((t, s) =>
+            {
+                // The options available on Unix for writing asynchronously to an arbitrary file 
+                // handle typically amount to just using another thread to do the synchronous write, 
+                // which is exactly  what this implementation does. This does mean there are subtle
+                // differences in certain FileStream behaviors between Windows and Unix when multiple 
+                // asynchronous operations are issued against the stream to execute concurrently; on 
+                // Unix the operations will be serialized due to the usage of a semaphore, but the 
+                // position /length information won't be updated until after the write has completed, 
+                // whereas on Windows it may happen before the write has completed.
+
+                Debug.Assert(t.Status == TaskStatus.RanToCompletion);
+                var thisRef = (FileStream)s;
+                try
+                {
+                    Memory<byte> memory = thisRef._asyncState.Memory;
+                    thisRef._asyncState.Memory = default(Memory<byte>);
+                    return thisRef.ReadSpan(memory.Span);
+                }
+                finally { thisRef._asyncState.Release(); }
+            }, this, CancellationToken.None, TaskContinuationOptions.DenyChildAttach, TaskScheduler.Default);
+        }
+
+        /// <summary>Reads from the file handle into the buffer, overwriting anything in it.</summary>
+        private int FillReadBufferForReadByte()
+        {
+            _asyncState?.Wait();
+            try { return ReadNative(_buffer); }
+            finally { _asyncState?.Release(); }
+        }
+
+        /// <summary>Writes a block of bytes to the file stream.</summary>
+        /// <param name="source">The buffer containing data to write to the stream.</param>
+        private void WriteSpan(ReadOnlySpan<byte> source)
+        {
+            PrepareForWriting();
+
+            // If no data is being written, nothing more to do.
+            if (source.Length == 0)
+            {
+                return;
+            }
+
+            // If there's already data in our write buffer, then we need to go through
+            // our buffer to ensure data isn't corrupted.
+            if (_writePos > 0)
+            {
+                // If there's space remaining in the buffer, then copy as much as
+                // we can from the user's buffer into ours.
+                int spaceRemaining = _bufferLength - _writePos;
+                if (spaceRemaining >= source.Length)
+                {
+                    source.CopyTo(new Span<byte>(GetBuffer()).Slice(_writePos));
+                    _writePos += source.Length;
+                    return;
+                }
+                else if (spaceRemaining > 0)
+                {
+                    source.Slice(0, spaceRemaining).CopyTo(new Span<byte>(GetBuffer()).Slice(_writePos));
+                    _writePos += spaceRemaining;
+                    source = source.Slice(spaceRemaining);
+                }
+
+                // At this point, the buffer is full, so flush it out.
+                FlushWriteBuffer();
+            }
+
+            // Our buffer is now empty.  If using the buffer would slow things down (because
+            // the user's looking to write more data than we can store in the buffer),
+            // skip the buffer.  Otherwise, put the remaining data into the buffer.
+            Debug.Assert(_writePos == 0);
+            if (source.Length >= _bufferLength)
+            {
+                WriteNative(source);
+            }
+            else
+            {
+                source.CopyTo(new Span<byte>(GetBuffer()));
+                _writePos = source.Length;
+            }
+        }
+
+        /// <summary>Unbuffered, writes a block of bytes to the file stream.</summary>
+        /// <param name="source">The buffer containing data to write to the stream.</param>
+        private unsafe void WriteNative(ReadOnlySpan<byte> source)
+        {
+            VerifyOSHandlePosition();
+
+            fixed (byte* bufPtr = &MemoryMarshal.GetReference(source))
+            {
+                int offset = 0;
+                int count = source.Length;
+                while (count > 0)
+                {
+                    int bytesWritten = CheckFileCall(Interop.Sys.Write(_fileHandle, bufPtr + offset, count));
+                    _filePosition += bytesWritten;
+                    offset += bytesWritten;
+                    count -= bytesWritten;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Asynchronously writes a sequence of bytes to the current stream, advances
+        /// the current position within this stream by the number of bytes written, and
+        /// monitors cancellation requests.
+        /// </summary>
+        /// <param name="source">The buffer to write data from.</param>
+        /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
+        /// <returns>A task that represents the asynchronous write operation.</returns>
+        private ValueTask WriteAsyncInternal(ReadOnlyMemory<byte> source, CancellationToken cancellationToken)
+        {
+            Debug.Assert(_useAsyncIO);
+
+            if (cancellationToken.IsCancellationRequested)
+                return new ValueTask(Task.FromCanceled(cancellationToken));
+
+            if (_fileHandle.IsClosed)
+                throw Error.GetFileNotOpen();
+
+            if (!CanWrite) // match Windows behavior; this gets thrown synchronously
+            {
+                throw Error.GetWriteNotSupported();
+            }
+
+            // Serialize operations using the semaphore.
+            Task waitTask = _asyncState.WaitAsync();
+
+            // If we got ownership immediately, and if there's enough space in our buffer
+            // to buffer the entire write request, then do so and we're done.
+            if (waitTask.Status == TaskStatus.RanToCompletion)
+            {
+                int spaceRemaining = _bufferLength - _writePos;
+                if (spaceRemaining >= source.Length)
+                {
+                    try
+                    {
+                        PrepareForWriting();
+
+                        source.Span.CopyTo(new Span<byte>(GetBuffer(), _writePos, source.Length));
+                        _writePos += source.Length;
+
+                        return default;
+                    }
+                    catch (Exception exc)
+                    {
+                        return new ValueTask(Task.FromException(exc));
+                    }
+                    finally
+                    {
+                        _asyncState.Release();
+                    }
+                }
+            }
+
+            // Otherwise, issue the whole request asynchronously.
+            _asyncState.ReadOnlyMemory = source;
+            return new ValueTask(waitTask.ContinueWith((t, s) =>
+            {
+                // The options available on Unix for writing asynchronously to an arbitrary file 
+                // handle typically amount to just using another thread to do the synchronous write, 
+                // which is exactly  what this implementation does. This does mean there are subtle
+                // differences in certain FileStream behaviors between Windows and Unix when multiple 
+                // asynchronous operations are issued against the stream to execute concurrently; on 
+                // Unix the operations will be serialized due to the usage of a semaphore, but the 
+                // position/length information won't be updated until after the write has completed, 
+                // whereas on Windows it may happen before the write has completed.
+
+                Debug.Assert(t.Status == TaskStatus.RanToCompletion);
+                var thisRef = (FileStream)s;
+                try
+                {
+                    ReadOnlyMemory<byte> readOnlyMemory = thisRef._asyncState.ReadOnlyMemory;
+                    thisRef._asyncState.ReadOnlyMemory = default(ReadOnlyMemory<byte>);
+                    thisRef.WriteSpan(readOnlyMemory.Span);
+                }
+                finally { thisRef._asyncState.Release(); }
+            }, this, CancellationToken.None, TaskContinuationOptions.DenyChildAttach, TaskScheduler.Default));
+        }
+
+        /// <summary>Sets the current position of this stream to the given value.</summary>
+        /// <param name="offset">The point relative to origin from which to begin seeking. </param>
+        /// <param name="origin">
+        /// Specifies the beginning, the end, or the current position as a reference 
+        /// point for offset, using a value of type SeekOrigin.
+        /// </param>
+        /// <returns>The new position in the stream.</returns>
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            if (origin < SeekOrigin.Begin || origin > SeekOrigin.End)
+            {
+                throw new ArgumentException(SR.Argument_InvalidSeekOrigin, nameof(origin));
+            }
+            if (_fileHandle.IsClosed)
+            {
+                throw Error.GetFileNotOpen();
+            }
+            if (!CanSeek)
+            {
+                throw Error.GetSeekNotSupported();
+            }
+
+            VerifyOSHandlePosition();
+
+            // Flush our write/read buffer.  FlushWrite will output any write buffer we have and reset _bufferWritePos.
+            // We don't call FlushRead, as that will do an unnecessary seek to rewind the read buffer, and since we're 
+            // about to seek and update our position, we can simply update the offset as necessary and reset our read 
+            // position and length to 0. (In the future, for some simple cases we could potentially add an optimization 
+            // here to just move data around in the buffer for short jumps, to avoid re-reading the data from disk.)
+            FlushWriteBuffer();
+            if (origin == SeekOrigin.Current)
+            {
+                offset -= (_readLength - _readPos);
+            }
+            _readPos = _readLength = 0;
+
+            // Keep track of where we were, in case we're in append mode and need to verify
+            long oldPos = 0;
+            if (_appendStart >= 0)
+            {
+                oldPos = SeekCore(_fileHandle, 0, SeekOrigin.Current);
+            }
+
+            // Jump to the new location
+            long pos = SeekCore(_fileHandle, offset, origin);
+
+            // Prevent users from overwriting data in a file that was opened in append mode.
+            if (_appendStart != -1 && pos < _appendStart)
+            {
+                SeekCore(_fileHandle, oldPos, SeekOrigin.Begin);
+                throw new IOException(SR.IO_SeekAppendOverwrite);
+            }
+
+            // Return the new position
+            return pos;
+        }
+
+        /// <summary>Sets the current position of this stream to the given value.</summary>
+        /// <param name="offset">The point relative to origin from which to begin seeking. </param>
+        /// <param name="origin">
+        /// Specifies the beginning, the end, or the current position as a reference 
+        /// point for offset, using a value of type SeekOrigin.
+        /// </param>
+        /// <returns>The new position in the stream.</returns>
+        private long SeekCore(SafeFileHandle fileHandle, long offset, SeekOrigin origin)
+        {
+            Debug.Assert(!fileHandle.IsClosed && (GetType() != typeof(FileStream) || CanSeekCore(fileHandle))); // verify that we can seek, but only if CanSeek won't be a virtual call (which could happen in the ctor)
+            Debug.Assert(origin >= SeekOrigin.Begin && origin <= SeekOrigin.End);
+
+            long pos = CheckFileCall(Interop.Sys.LSeek(fileHandle, offset, (Interop.Sys.SeekWhence)(int)origin)); // SeekOrigin values are the same as Interop.libc.SeekWhence values
+            _filePosition = pos;
+            return pos;
+        }
+
+        private long CheckFileCall(long result, bool ignoreNotSupported = false)
+        {
+            if (result < 0)
+            {
+                Interop.ErrorInfo errorInfo = Interop.Sys.GetLastErrorInfo();
+                if (!(ignoreNotSupported && errorInfo.Error == Interop.Error.ENOTSUP))
+                {
+                    throw Interop.GetExceptionForIoErrno(errorInfo, _path, isDirectory: false);
+                }
+            }
+
+            return result;
+        }
+
+        private int CheckFileCall(int result, bool ignoreNotSupported = false)
+        {
+            CheckFileCall((long)result, ignoreNotSupported);
+
+            return result;
+        }
+
+        /// <summary>State used when the stream is in async mode.</summary>
+        private sealed class AsyncState : SemaphoreSlim
+        {
+            internal ReadOnlyMemory<byte> ReadOnlyMemory;
+            internal Memory<byte> Memory;
+
+            /// <summary>Initialize the AsyncState.</summary>
+            internal AsyncState() : base(initialCount: 1, maxCount: 1) { }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/FileStream.Win32.cs b/src/System.Private.CoreLib/shared/System/IO/FileStream.Win32.cs
new file mode 100644
index 0000000000..4b75ad6dad
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/FileStream.Win32.cs
@@ -0,0 +1,47 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+
+namespace System.IO
+{
+    public partial class FileStream : Stream
+    {
+        private SafeFileHandle OpenHandle(FileMode mode, FileShare share, FileOptions options)
+        {
+            return CreateFileOpenHandle(mode, share, options);
+        }
+
+        private unsafe SafeFileHandle CreateFileOpenHandle(FileMode mode, FileShare share, FileOptions options)
+        {
+            Interop.Kernel32.SECURITY_ATTRIBUTES secAttrs = GetSecAttrs(share);
+
+            int fAccess =
+                ((_access & FileAccess.Read) == FileAccess.Read ? GENERIC_READ : 0) |
+                ((_access & FileAccess.Write) == FileAccess.Write ? GENERIC_WRITE : 0);
+
+            // Our Inheritable bit was stolen from Windows, but should be set in
+            // the security attributes class.  Don't leave this bit set.
+            share &= ~FileShare.Inheritable;
+
+            // Must use a valid Win32 constant here...
+            if (mode == FileMode.Append)
+                mode = FileMode.OpenOrCreate;
+
+            int flagsAndAttributes = (int)options;
+
+            // For mitigating local elevation of privilege attack through named pipes
+            // make sure we always call CreateFile with SECURITY_ANONYMOUS so that the
+            // named pipe server can't impersonate a high privileged client security context
+            // (note that this is the effective default on CreateFile2)
+            flagsAndAttributes |= (Interop.Kernel32.SecurityOptions.SECURITY_SQOS_PRESENT | Interop.Kernel32.SecurityOptions.SECURITY_ANONYMOUS);
+
+            using (DisableMediaInsertionPrompt.Create())
+            {
+                return ValidateFileHandle(
+                    Interop.Kernel32.CreateFile(_path, fAccess, share, ref secAttrs, mode, flagsAndAttributes, IntPtr.Zero));
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/FileStream.WinRT.cs b/src/System.Private.CoreLib/shared/System/IO/FileStream.WinRT.cs
new file mode 100644
index 0000000000..304088eea7
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/FileStream.WinRT.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32.SafeHandles;
+using System.Runtime.InteropServices;
+
+namespace System.IO
+{
+    public partial class FileStream : Stream
+    {
+        private unsafe SafeFileHandle OpenHandle(FileMode mode, FileShare share, FileOptions options)
+        {
+            Interop.Kernel32.SECURITY_ATTRIBUTES secAttrs = GetSecAttrs(share);
+
+            int access =
+                ((_access & FileAccess.Read) == FileAccess.Read ? GENERIC_READ : 0) |
+                ((_access & FileAccess.Write) == FileAccess.Write ? GENERIC_WRITE : 0);
+
+            // Our Inheritable bit was stolen from Windows, but should be set in
+            // the security attributes class.  Don't leave this bit set.
+            share &= ~FileShare.Inheritable;
+
+            // Must use a valid Win32 constant here...
+            if (mode == FileMode.Append)
+                mode = FileMode.OpenOrCreate;
+
+            Interop.Kernel32.CREATEFILE2_EXTENDED_PARAMETERS parameters = new Interop.Kernel32.CREATEFILE2_EXTENDED_PARAMETERS();
+            parameters.dwSize = (uint)sizeof(Interop.Kernel32.CREATEFILE2_EXTENDED_PARAMETERS);
+            parameters.dwFileFlags = (uint)options;
+            parameters.lpSecurityAttributes = &secAttrs;
+
+            using (DisableMediaInsertionPrompt.Create())
+            {
+                return ValidateFileHandle(Interop.Kernel32.CreateFile2(
+                    lpFileName: _path,
+                    dwDesiredAccess: access,
+                    dwShareMode: share,
+                    dwCreationDisposition: mode,
+                    pCreateExParams: ref parameters));
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/FileStream.Windows.cs b/src/System.Private.CoreLib/shared/System/IO/FileStream.Windows.cs
new file mode 100644
index 0000000000..80c07dfdf4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/FileStream.Windows.cs
@@ -0,0 +1,1657 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Buffers;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Win32.SafeHandles;
+using System.Runtime.CompilerServices;
+
+/*
+ * Win32FileStream supports different modes of accessing the disk - async mode
+ * and sync mode.  They are two completely different codepaths in the
+ * sync & async methods (i.e. Read/Write vs. ReadAsync/WriteAsync).  File
+ * handles in NT can be opened in only sync or overlapped (async) mode,
+ * and we have to deal with this pain.  Stream has implementations of
+ * the sync methods in terms of the async ones, so we'll
+ * call through to our base class to get those methods when necessary.
+ *
+ * Also buffering is added into Win32FileStream as well. Folded in the
+ * code from BufferedStream, so all the comments about it being mostly
+ * aggressive (and the possible perf improvement) apply to Win32FileStream as 
+ * well.  Also added some buffering to the async code paths.
+ *
+ * Class Invariants:
+ * The class has one buffer, shared for reading & writing.  It can only be
+ * used for one or the other at any point in time - not both.  The following
+ * should be true:
+ *   0 <= _readPos <= _readLen < _bufferSize
+ *   0 <= _writePos < _bufferSize
+ *   _readPos == _readLen && _readPos > 0 implies the read buffer is valid, 
+ *     but we're at the end of the buffer.
+ *   _readPos == _readLen == 0 means the read buffer contains garbage.
+ *   Either _writePos can be greater than 0, or _readLen & _readPos can be
+ *     greater than zero, but neither can be greater than zero at the same time.
+ *
+ */
+
+namespace System.IO
+{
+    public partial class FileStream : Stream
+    {
+        private bool _canSeek;
+        private bool _isPipe;      // Whether to disable async buffering code.
+        private long _appendStart; // When appending, prevent overwriting file.
+
+        private static unsafe IOCompletionCallback s_ioCallback = FileStreamCompletionSource.IOCallback;
+
+        private Task _activeBufferOperation = null;                 // tracks in-progress async ops using the buffer
+        private PreAllocatedOverlapped _preallocatedOverlapped;     // optimization for async ops to avoid per-op allocations
+        private FileStreamCompletionSource _currentOverlappedOwner; // async op currently using the preallocated overlapped
+
+        private void Init(FileMode mode, FileShare share)
+        {
+            // Disallow access to all non-file devices from the Win32FileStream
+            // constructors that take a String.  Everyone else can call 
+            // CreateFile themselves then use the constructor that takes an 
+            // IntPtr.  Disallows "con:", "com1:", "lpt1:", etc.
+            int fileType = Interop.Kernel32.GetFileType(_fileHandle);
+            if (fileType != Interop.Kernel32.FileTypes.FILE_TYPE_DISK)
+            {
+                _fileHandle.Dispose();
+                throw new NotSupportedException(SR.NotSupported_FileStreamOnNonFiles);
+            }
+
+            // This is necessary for async IO using IO Completion ports via our 
+            // managed Threadpool API's.  This (theoretically) calls the OS's 
+            // BindIoCompletionCallback method, and passes in a stub for the 
+            // LPOVERLAPPED_COMPLETION_ROUTINE.  This stub looks at the Overlapped
+            // struct for this request and gets a delegate to a managed callback 
+            // from there, which it then calls on a threadpool thread.  (We allocate
+            // our native OVERLAPPED structs 2 pointers too large and store EE state
+            // & GC handles there, one to an IAsyncResult, the other to a delegate.)
+            if (_useAsyncIO)
+            {
+                try
+                {
+                    _fileHandle.ThreadPoolBinding = ThreadPoolBoundHandle.BindHandle(_fileHandle);
+                }
+                catch (ArgumentException ex)
+                {
+                    throw new IOException(SR.IO_BindHandleFailed, ex);
+                }
+                finally
+                {
+                    if (_fileHandle.ThreadPoolBinding == null)
+                    {
+                        // We should close the handle so that the handle is not open until SafeFileHandle GC
+                        Debug.Assert(!_exposedHandle, "Are we closing handle that we exposed/not own, how?");
+                        _fileHandle.Dispose();
+                    }
+                }
+            }
+
+            _canSeek = true;
+
+            // For Append mode...
+            if (mode == FileMode.Append)
+            {
+                _appendStart = SeekCore(_fileHandle, 0, SeekOrigin.End);
+            }
+            else
+            {
+                _appendStart = -1;
+            }
+        }
+
+        private void InitFromHandle(SafeFileHandle handle, FileAccess access, bool useAsyncIO)
+        {
+#if DEBUG
+            bool hadBinding = handle.ThreadPoolBinding != null;
+
+            try
+            {
+#endif
+                InitFromHandleImpl(handle, access, useAsyncIO);
+#if DEBUG
+            }
+            catch
+            {
+                Debug.Assert(hadBinding || handle.ThreadPoolBinding == null, "We should never error out with a ThreadPoolBinding we've added");
+                throw;
+            }
+#endif
+        }
+
+        private void InitFromHandleImpl(SafeFileHandle handle, FileAccess access, bool useAsyncIO)
+        {
+            int handleType = Interop.Kernel32.GetFileType(handle);
+            Debug.Assert(handleType == Interop.Kernel32.FileTypes.FILE_TYPE_DISK || handleType == Interop.Kernel32.FileTypes.FILE_TYPE_PIPE || handleType == Interop.Kernel32.FileTypes.FILE_TYPE_CHAR, "FileStream was passed an unknown file type!");
+
+            _canSeek = handleType == Interop.Kernel32.FileTypes.FILE_TYPE_DISK;
+            _isPipe = handleType == Interop.Kernel32.FileTypes.FILE_TYPE_PIPE;
+
+            // This is necessary for async IO using IO Completion ports via our 
+            // managed Threadpool API's.  This calls the OS's 
+            // BindIoCompletionCallback method, and passes in a stub for the 
+            // LPOVERLAPPED_COMPLETION_ROUTINE.  This stub looks at the Overlapped
+            // struct for this request and gets a delegate to a managed callback 
+            // from there, which it then calls on a threadpool thread.  (We allocate
+            // our native OVERLAPPED structs 2 pointers too large and store EE 
+            // state & a handle to a delegate there.)
+            // 
+            // If, however, we've already bound this file handle to our completion port,
+            // don't try to bind it again because it will fail.  A handle can only be
+            // bound to a single completion port at a time.
+            if (useAsyncIO && !(handle.IsAsync ?? false))
+            {
+                try
+                {
+                    handle.ThreadPoolBinding = ThreadPoolBoundHandle.BindHandle(handle);
+                }
+                catch (Exception ex)
+                {
+                    // If you passed in a synchronous handle and told us to use
+                    // it asynchronously, throw here.
+                    throw new ArgumentException(SR.Arg_HandleNotAsync, nameof(handle), ex);
+                }
+            }
+            else if (!useAsyncIO)
+            {
+                if (handleType != Interop.Kernel32.FileTypes.FILE_TYPE_PIPE)
+                    VerifyHandleIsSync(handle, access);
+            }
+
+            if (_canSeek)
+                SeekCore(handle, 0, SeekOrigin.Current);
+            else
+                _filePosition = 0;
+        }
+
+        private static unsafe Interop.Kernel32.SECURITY_ATTRIBUTES GetSecAttrs(FileShare share)
+        {
+            Interop.Kernel32.SECURITY_ATTRIBUTES secAttrs = default;
+            if ((share & FileShare.Inheritable) != 0)
+            {
+                secAttrs = new Interop.Kernel32.SECURITY_ATTRIBUTES
+                {
+                    nLength = (uint)sizeof(Interop.Kernel32.SECURITY_ATTRIBUTES),
+                    bInheritHandle = Interop.BOOL.TRUE
+                };
+            }
+            return secAttrs;
+        }
+
+        // Verifies that this handle supports synchronous IO operations (unless you
+        // didn't open it for either reading or writing).
+        private static unsafe void VerifyHandleIsSync(SafeFileHandle handle, FileAccess access)
+        {
+            // Do NOT use this method on pipes.  Reading or writing to a pipe may
+            // cause an app to block incorrectly, introducing a deadlock (depending
+            // on whether a write will wake up an already-blocked thread or this
+            // Win32FileStream's thread).
+            Debug.Assert(Interop.Kernel32.GetFileType(handle) != Interop.Kernel32.FileTypes.FILE_TYPE_PIPE);
+
+            byte* bytes = stackalloc byte[1];
+            int numBytesReadWritten;
+            int r = -1;
+
+            // If the handle is a pipe, ReadFile will block until there
+            // has been a write on the other end.  We'll just have to deal with it,
+            // For the read end of a pipe, you can mess up and 
+            // accidentally read synchronously from an async pipe.
+            if ((access & FileAccess.Read) != 0) // don't use the virtual CanRead or CanWrite, as this may be used in the ctor
+            {
+                r = Interop.Kernel32.ReadFile(handle, bytes, 0, out numBytesReadWritten, IntPtr.Zero);
+            }
+            else if ((access & FileAccess.Write) != 0) // don't use the virtual CanRead or CanWrite, as this may be used in the ctor
+            {
+                r = Interop.Kernel32.WriteFile(handle, bytes, 0, out numBytesReadWritten, IntPtr.Zero);
+            }
+
+            if (r == 0)
+            {
+                int errorCode = Marshal.GetLastWin32Error();
+                switch (errorCode)
+                {
+                    case Interop.Errors.ERROR_INVALID_PARAMETER:
+                        throw new ArgumentException(SR.Arg_HandleNotSync, "handle");
+                    case Interop.Errors.ERROR_INVALID_HANDLE:
+                        throw Win32Marshal.GetExceptionForWin32Error(errorCode);
+                }
+            }
+        }
+
+        private bool HasActiveBufferOperation
+            => _activeBufferOperation != null && !_activeBufferOperation.IsCompleted;
+
+        public override bool CanSeek => _canSeek;
+
+        private unsafe long GetLengthInternal()
+        {
+            Interop.Kernel32.FILE_STANDARD_INFO info = new Interop.Kernel32.FILE_STANDARD_INFO();
+
+            if (!Interop.Kernel32.GetFileInformationByHandleEx(_fileHandle, Interop.Kernel32.FILE_INFO_BY_HANDLE_CLASS.FileStandardInfo, out info, (uint)sizeof(Interop.Kernel32.FILE_STANDARD_INFO)))
+                throw Win32Marshal.GetExceptionForLastWin32Error(_path);
+            long len = info.EndOfFile;
+            // If we're writing near the end of the file, we must include our
+            // internal buffer in our Length calculation.  Don't flush because
+            // we use the length of the file in our async write method.
+            if (_writePos > 0 && _filePosition + _writePos > len)
+                len = _writePos + _filePosition;
+            return len;
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            // Nothing will be done differently based on whether we are 
+            // disposing vs. finalizing.  This is taking advantage of the
+            // weak ordering between normal finalizable objects & critical
+            // finalizable objects, which I included in the SafeHandle 
+            // design for Win32FileStream, which would often "just work" when 
+            // finalized.
+            try
+            {
+                if (_fileHandle != null && !_fileHandle.IsClosed)
+                {
+                    // Flush data to disk iff we were writing.  After 
+                    // thinking about this, we also don't need to flush
+                    // our read position, regardless of whether the handle
+                    // was exposed to the user.  They probably would NOT 
+                    // want us to do this.
+                    if (_writePos > 0)
+                    {
+                        try
+                        {
+                            FlushWriteBuffer(!disposing);
+                        }
+                        catch (Exception e) when (IsIoRelatedException(e) && !disposing)
+                        {
+                            // On finalization, ignore failures from trying to flush the write buffer,
+                            // e.g. if this stream is wrapping a pipe and the pipe is now broken.
+                        }
+                    }
+                }
+            }
+            finally
+            {
+                if (_fileHandle != null && !_fileHandle.IsClosed)
+                {
+                    if (_fileHandle.ThreadPoolBinding != null)
+                        _fileHandle.ThreadPoolBinding.Dispose();
+
+                    _fileHandle.Dispose();
+                }
+
+                if (_preallocatedOverlapped != null)
+                    _preallocatedOverlapped.Dispose();
+
+                _canSeek = false;
+
+                // Don't set the buffer to null, to avoid a NullReferenceException
+                // when users have a race condition in their code (i.e. they call
+                // Close when calling another method on Stream like Read).
+                //_buffer = null;
+                base.Dispose(disposing);
+            }
+        }
+
+        private void FlushOSBuffer()
+        {
+            if (!Interop.Kernel32.FlushFileBuffers(_fileHandle))
+            {
+                throw Win32Marshal.GetExceptionForLastWin32Error(_path);
+            }
+        }
+
+        // Returns a task that flushes the internal write buffer
+        private Task FlushWriteAsync(CancellationToken cancellationToken)
+        {
+            Debug.Assert(_useAsyncIO);
+            Debug.Assert(_readPos == 0 && _readLength == 0, "FileStream: Read buffer must be empty in FlushWriteAsync!");
+
+            // If the buffer is already flushed, don't spin up the OS write
+            if (_writePos == 0) return Task.CompletedTask;
+
+            Task flushTask = WriteAsyncInternalCore(new ReadOnlyMemory<byte>(GetBuffer(), 0, _writePos), cancellationToken);
+            _writePos = 0;
+
+            // Update the active buffer operation
+            _activeBufferOperation = HasActiveBufferOperation ?
+                Task.WhenAll(_activeBufferOperation, flushTask) :
+                flushTask;
+
+            return flushTask;
+        }
+
+        private void FlushWriteBufferForWriteByte() => FlushWriteBuffer();
+
+        // Writes are buffered.  Anytime the buffer fills up 
+        // (_writePos + delta > _bufferSize) or the buffer switches to reading
+        // and there is left over data (_writePos > 0), this function must be called.
+        private void FlushWriteBuffer(bool calledFromFinalizer = false)
+        {
+            if (_writePos == 0) return;
+            Debug.Assert(_readPos == 0 && _readLength == 0, "FileStream: Read buffer must be empty in FlushWrite!");
+
+            if (_useAsyncIO)
+            {
+                Task writeTask = FlushWriteAsync(CancellationToken.None);
+                // With our Whidbey async IO & overlapped support for AD unloads,
+                // we don't strictly need to block here to release resources
+                // since that support takes care of the pinning & freeing the 
+                // overlapped struct.  We need to do this when called from
+                // Close so that the handle is closed when Close returns, but
+                // we don't need to call EndWrite from the finalizer.  
+                // Additionally, if we do call EndWrite, we block forever 
+                // because AD unloads prevent us from running the managed 
+                // callback from the IO completion port.  Blocking here when 
+                // called from the finalizer during AD unload is clearly wrong, 
+                // but we can't use any sort of test for whether the AD is 
+                // unloading because if we weren't unloading, an AD unload 
+                // could happen on a separate thread before we call EndWrite.
+                if (!calledFromFinalizer)
+                {
+                    writeTask.GetAwaiter().GetResult();
+                }
+            }
+            else
+            {
+                WriteCore(new ReadOnlySpan<byte>(GetBuffer(), 0, _writePos));
+            }
+
+            _writePos = 0;
+        }
+
+        private void SetLengthInternal(long value)
+        {
+            // Handle buffering updates.
+            if (_writePos > 0)
+            {
+                FlushWriteBuffer();
+            }
+            else if (_readPos < _readLength)
+            {
+                FlushReadBuffer();
+            }
+            _readPos = 0;
+            _readLength = 0;
+
+            if (_appendStart != -1 && value < _appendStart)
+                throw new IOException(SR.IO_SetLengthAppendTruncate);
+            SetLengthCore(value);
+        }
+
+        // We absolutely need this method broken out so that WriteInternalCoreAsync can call
+        // a method without having to go through buffering code that might call FlushWrite.
+        private void SetLengthCore(long value)
+        {
+            Debug.Assert(value >= 0, "value >= 0");
+            long origPos = _filePosition;
+
+            VerifyOSHandlePosition();
+            if (_filePosition != value)
+                SeekCore(_fileHandle, value, SeekOrigin.Begin);
+            if (!Interop.Kernel32.SetEndOfFile(_fileHandle))
+            {
+                int errorCode = Marshal.GetLastWin32Error();
+                if (errorCode == Interop.Errors.ERROR_INVALID_PARAMETER)
+                    throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_FileLengthTooBig);
+                throw Win32Marshal.GetExceptionForWin32Error(errorCode, _path);
+            }
+            // Return file pointer to where it was before setting length
+            if (origPos != value)
+            {
+                if (origPos < value)
+                    SeekCore(_fileHandle, origPos, SeekOrigin.Begin);
+                else
+                    SeekCore(_fileHandle, 0, SeekOrigin.End);
+            }
+        }
+
+        // Instance method to help code external to this MarshalByRefObject avoid
+        // accessing its fields by ref.  This avoids a compiler warning.
+        private FileStreamCompletionSource CompareExchangeCurrentOverlappedOwner(FileStreamCompletionSource newSource, FileStreamCompletionSource existingSource) => Interlocked.CompareExchange(ref _currentOverlappedOwner, newSource, existingSource);
+
+        private int ReadSpan(Span<byte> destination)
+        {
+            Debug.Assert(!_useAsyncIO, "Must only be used when in synchronous mode");
+            Debug.Assert((_readPos == 0 && _readLength == 0 && _writePos >= 0) || (_writePos == 0 && _readPos <= _readLength),
+                "We're either reading or writing, but not both.");
+
+            bool isBlocked = false;
+            int n = _readLength - _readPos;
+            // if the read buffer is empty, read into either user's array or our
+            // buffer, depending on number of bytes user asked for and buffer size.
+            if (n == 0)
+            {
+                if (!CanRead) throw Error.GetReadNotSupported();
+                if (_writePos > 0) FlushWriteBuffer();
+                if (!CanSeek || (destination.Length >= _bufferLength))
+                {
+                    n = ReadNative(destination);
+                    // Throw away read buffer.
+                    _readPos = 0;
+                    _readLength = 0;
+                    return n;
+                }
+                n = ReadNative(GetBuffer());
+                if (n == 0) return 0;
+                isBlocked = n < _bufferLength;
+                _readPos = 0;
+                _readLength = n;
+            }
+            // Now copy min of count or numBytesAvailable (i.e. near EOF) to array.
+            if (n > destination.Length) n = destination.Length;
+            new ReadOnlySpan<byte>(GetBuffer(), _readPos, n).CopyTo(destination);
+            _readPos += n;
+
+            // We may have read less than the number of bytes the user asked 
+            // for, but that is part of the Stream contract.  Reading again for
+            // more data may cause us to block if we're using a device with 
+            // no clear end of file, such as a serial port or pipe.  If we
+            // blocked here & this code was used with redirected pipes for a
+            // process's standard output, this can lead to deadlocks involving
+            // two processes. But leave this here for files to avoid what would
+            // probably be a breaking change.         -- 
+
+            // If we are reading from a device with no clear EOF like a 
+            // serial port or a pipe, this will cause us to block incorrectly.
+            if (!_isPipe)
+            {
+                // If we hit the end of the buffer and didn't have enough bytes, we must
+                // read some more from the underlying stream.  However, if we got
+                // fewer bytes from the underlying stream than we asked for (i.e. we're 
+                // probably blocked), don't ask for more bytes.
+                if (n < destination.Length && !isBlocked)
+                {
+                    Debug.Assert(_readPos == _readLength, "Read buffer should be empty!");
+                    int moreBytesRead = ReadNative(destination.Slice(n));
+                    n += moreBytesRead;
+                    // We've just made our buffer inconsistent with our position 
+                    // pointer.  We must throw away the read buffer.
+                    _readPos = 0;
+                    _readLength = 0;
+                }
+            }
+
+            return n;
+        }
+
+        [Conditional("DEBUG")]
+        private void AssertCanRead()
+        {
+            Debug.Assert(!_fileHandle.IsClosed, "!_fileHandle.IsClosed");
+            Debug.Assert(CanRead, "CanRead");
+        }
+
+        /// <summary>Reads from the file handle into the buffer, overwriting anything in it.</summary>
+        private int FillReadBufferForReadByte() =>
+            _useAsyncIO ?
+                ReadNativeAsync(new Memory<byte>(_buffer), 0, CancellationToken.None).GetAwaiter().GetResult() :
+                ReadNative(_buffer);
+
+        private unsafe int ReadNative(Span<byte> buffer)
+        {
+            Debug.Assert(!_useAsyncIO, $"{nameof(ReadNative)} doesn't work on asynchronous file streams.");
+            AssertCanRead();
+
+            // Make sure we are reading from the right spot
+            VerifyOSHandlePosition();
+
+            int r = ReadFileNative(_fileHandle, buffer, null, out int errorCode);
+
+            if (r == -1)
+            {
+                // For pipes, ERROR_BROKEN_PIPE is the normal end of the pipe.
+                if (errorCode == ERROR_BROKEN_PIPE)
+                {
+                    r = 0;
+                }
+                else
+                {
+                    if (errorCode == ERROR_INVALID_PARAMETER)
+                        throw new ArgumentException(SR.Arg_HandleNotSync, "_fileHandle");
+
+                    throw Win32Marshal.GetExceptionForWin32Error(errorCode, _path);
+                }
+            }
+            Debug.Assert(r >= 0, "FileStream's ReadNative is likely broken.");
+            _filePosition += r;
+
+            return r;
+        }
+
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            if (origin < SeekOrigin.Begin || origin > SeekOrigin.End)
+                throw new ArgumentException(SR.Argument_InvalidSeekOrigin, nameof(origin));
+            if (_fileHandle.IsClosed) throw Error.GetFileNotOpen();
+            if (!CanSeek) throw Error.GetSeekNotSupported();
+
+            Debug.Assert((_readPos == 0 && _readLength == 0 && _writePos >= 0) || (_writePos == 0 && _readPos <= _readLength), "We're either reading or writing, but not both.");
+
+            // If we've got bytes in our buffer to write, write them out.
+            // If we've read in and consumed some bytes, we'll have to adjust
+            // our seek positions ONLY IF we're seeking relative to the current
+            // position in the stream.  This simulates doing a seek to the new
+            // position, then a read for the number of bytes we have in our buffer.
+            if (_writePos > 0)
+            {
+                FlushWriteBuffer();
+            }
+            else if (origin == SeekOrigin.Current)
+            {
+                // Don't call FlushRead here, which would have caused an infinite
+                // loop.  Simply adjust the seek origin.  This isn't necessary
+                // if we're seeking relative to the beginning or end of the stream.
+                offset -= (_readLength - _readPos);
+            }
+            _readPos = _readLength = 0;
+
+            // Verify that internal position is in sync with the handle
+            VerifyOSHandlePosition();
+
+            long oldPos = _filePosition + (_readPos - _readLength);
+            long pos = SeekCore(_fileHandle, offset, origin);
+
+            // Prevent users from overwriting data in a file that was opened in
+            // append mode.
+            if (_appendStart != -1 && pos < _appendStart)
+            {
+                SeekCore(_fileHandle, oldPos, SeekOrigin.Begin);
+                throw new IOException(SR.IO_SeekAppendOverwrite);
+            }
+
+            // We now must update the read buffer.  We can in some cases simply
+            // update _readPos within the buffer, copy around the buffer so our 
+            // Position property is still correct, and avoid having to do more 
+            // reads from the disk.  Otherwise, discard the buffer's contents.
+            if (_readLength > 0)
+            {
+                // We can optimize the following condition:
+                // oldPos - _readPos <= pos < oldPos + _readLen - _readPos
+                if (oldPos == pos)
+                {
+                    if (_readPos > 0)
+                    {
+                        Buffer.BlockCopy(GetBuffer(), _readPos, GetBuffer(), 0, _readLength - _readPos);
+                        _readLength -= _readPos;
+                        _readPos = 0;
+                    }
+                    // If we still have buffered data, we must update the stream's 
+                    // position so our Position property is correct.
+                    if (_readLength > 0)
+                        SeekCore(_fileHandle, _readLength, SeekOrigin.Current);
+                }
+                else if (oldPos - _readPos < pos && pos < oldPos + _readLength - _readPos)
+                {
+                    int diff = (int)(pos - oldPos);
+                    Buffer.BlockCopy(GetBuffer(), _readPos + diff, GetBuffer(), 0, _readLength - (_readPos + diff));
+                    _readLength -= (_readPos + diff);
+                    _readPos = 0;
+                    if (_readLength > 0)
+                        SeekCore(_fileHandle, _readLength, SeekOrigin.Current);
+                }
+                else
+                {
+                    // Lose the read buffer.
+                    _readPos = 0;
+                    _readLength = 0;
+                }
+                Debug.Assert(_readLength >= 0 && _readPos <= _readLength, "_readLen should be nonnegative, and _readPos should be less than or equal _readLen");
+                Debug.Assert(pos == Position, "Seek optimization: pos != Position!  Buffer math was mangled.");
+            }
+            return pos;
+        }
+
+        // This doesn't do argument checking.  Necessary for SetLength, which must
+        // set the file pointer beyond the end of the file. This will update the 
+        // internal position
+        private long SeekCore(SafeFileHandle fileHandle, long offset, SeekOrigin origin, bool closeInvalidHandle = false)
+        {
+            Debug.Assert(!fileHandle.IsClosed && _canSeek, "!fileHandle.IsClosed && _canSeek");
+            Debug.Assert(origin >= SeekOrigin.Begin && origin <= SeekOrigin.End, "origin >= SeekOrigin.Begin && origin <= SeekOrigin.End");
+
+            if (!Interop.Kernel32.SetFilePointerEx(fileHandle, offset, out long ret, (uint)origin))
+            {
+                if (closeInvalidHandle)
+                {
+                    throw Win32Marshal.GetExceptionForWin32Error(GetLastWin32ErrorAndDisposeHandleIfInvalid(throwIfInvalidHandle: false), _path);
+                }
+                else
+                {
+                    throw Win32Marshal.GetExceptionForLastWin32Error(_path);
+                }
+            }
+
+            _filePosition = ret;
+            return ret;
+        }
+
+        partial void OnBufferAllocated()
+        {
+            Debug.Assert(_buffer != null);
+            Debug.Assert(_preallocatedOverlapped == null);
+
+            if (_useAsyncIO)
+                _preallocatedOverlapped = new PreAllocatedOverlapped(s_ioCallback, this, _buffer);
+        }
+
+        private void WriteSpan(ReadOnlySpan<byte> source)
+        {
+            Debug.Assert(!_useAsyncIO, "Must only be used when in synchronous mode");
+
+            if (_writePos == 0)
+            {
+                // Ensure we can write to the stream, and ready buffer for writing.
+                if (!CanWrite) throw Error.GetWriteNotSupported();
+                if (_readPos < _readLength) FlushReadBuffer();
+                _readPos = 0;
+                _readLength = 0;
+            }
+
+            // If our buffer has data in it, copy data from the user's array into
+            // the buffer, and if we can fit it all there, return.  Otherwise, write
+            // the buffer to disk and copy any remaining data into our buffer.
+            // The assumption here is memcpy is cheaper than disk (or net) IO.
+            // (10 milliseconds to disk vs. ~20-30 microseconds for a 4K memcpy)
+            // So the extra copying will reduce the total number of writes, in 
+            // non-pathological cases (i.e. write 1 byte, then write for the buffer 
+            // size repeatedly)
+            if (_writePos > 0)
+            {
+                int numBytes = _bufferLength - _writePos;   // space left in buffer
+                if (numBytes > 0)
+                {
+                    if (numBytes >= source.Length)
+                    {
+                        source.CopyTo(new Span<byte>(GetBuffer()).Slice(_writePos));
+                        _writePos += source.Length;
+                        return;
+                    }
+                    else
+                    {
+                        source.Slice(0, numBytes).CopyTo(new Span<byte>(GetBuffer()).Slice(_writePos));
+                        _writePos += numBytes;
+                        source = source.Slice(numBytes);
+                    }
+                }
+                // Reset our buffer.  We essentially want to call FlushWrite
+                // without calling Flush on the underlying Stream.
+
+                WriteCore(new ReadOnlySpan<byte>(GetBuffer(), 0, _writePos));
+                _writePos = 0;
+            }
+
+            // If the buffer would slow writes down, avoid buffer completely.
+            if (source.Length >= _bufferLength)
+            {
+                Debug.Assert(_writePos == 0, "FileStream cannot have buffered data to write here!  Your stream will be corrupted.");
+                WriteCore(source);
+                return;
+            }
+            else if (source.Length == 0)
+            {
+                return;  // Don't allocate a buffer then call memcpy for 0 bytes.
+            }
+
+            // Copy remaining bytes into buffer, to write at a later date.
+            source.CopyTo(new Span<byte>(GetBuffer()).Slice(_writePos));
+            _writePos = source.Length;
+            return;
+        }
+
+        private unsafe void WriteCore(ReadOnlySpan<byte> source)
+        {
+            Debug.Assert(!_useAsyncIO);
+            Debug.Assert(!_fileHandle.IsClosed, "!_handle.IsClosed");
+            Debug.Assert(CanWrite, "_parent.CanWrite");
+            Debug.Assert(_readPos == _readLength, "_readPos == _readLen");
+
+            // Make sure we are writing to the position that we think we are
+            VerifyOSHandlePosition();
+
+            int errorCode = 0;
+            int r = WriteFileNative(_fileHandle, source, null, out errorCode);
+
+            if (r == -1)
+            {
+                // For pipes, ERROR_NO_DATA is not an error, but the pipe is closing.
+                if (errorCode == ERROR_NO_DATA)
+                {
+                    r = 0;
+                }
+                else
+                {
+                    // ERROR_INVALID_PARAMETER may be returned for writes
+                    // where the position is too large or for synchronous writes 
+                    // to a handle opened asynchronously.
+                    if (errorCode == ERROR_INVALID_PARAMETER)
+                        throw new IOException(SR.IO_FileTooLongOrHandleNotSync);
+                    throw Win32Marshal.GetExceptionForWin32Error(errorCode, _path);
+                }
+            }
+            Debug.Assert(r >= 0, "FileStream's WriteCore is likely broken.");
+            _filePosition += r;
+            return;
+        }
+
+        private Task<int> ReadAsyncInternal(Memory<byte> destination, CancellationToken cancellationToken, out int synchronousResult)
+        {
+            Debug.Assert(_useAsyncIO);
+            if (!CanRead) throw Error.GetReadNotSupported();
+
+            Debug.Assert((_readPos == 0 && _readLength == 0 && _writePos >= 0) || (_writePos == 0 && _readPos <= _readLength), "We're either reading or writing, but not both.");
+
+            if (_isPipe)
+            {
+                // Pipes are tricky, at least when you have 2 different pipes
+                // that you want to use simultaneously.  When redirecting stdout
+                // & stderr with the Process class, it's easy to deadlock your
+                // parent & child processes when doing writes 4K at a time.  The
+                // OS appears to use a 4K buffer internally.  If you write to a
+                // pipe that is full, you will block until someone read from 
+                // that pipe.  If you try reading from an empty pipe and 
+                // Win32FileStream's ReadAsync blocks waiting for data to fill it's 
+                // internal buffer, you will be blocked.  In a case where a child
+                // process writes to stdout & stderr while a parent process tries
+                // reading from both, you can easily get into a deadlock here.
+                // To avoid this deadlock, don't buffer when doing async IO on
+                // pipes.  But don't completely ignore buffered data either.  
+                if (_readPos < _readLength)
+                {
+                    int n = Math.Min(_readLength - _readPos, destination.Length);
+                    new Span<byte>(GetBuffer(), _readPos, n).CopyTo(destination.Span);
+                    _readPos += n;
+                    synchronousResult = n;
+                    return null;
+                }
+                else
+                {
+                    Debug.Assert(_writePos == 0, "Win32FileStream must not have buffered write data here!  Pipes should be unidirectional.");
+                    synchronousResult = 0;
+                    return ReadNativeAsync(destination, 0, cancellationToken);
+                }
+            }
+
+            Debug.Assert(!_isPipe, "Should not be a pipe.");
+
+            // Handle buffering.
+            if (_writePos > 0) FlushWriteBuffer();
+            if (_readPos == _readLength)
+            {
+                // I can't see how to handle buffering of async requests when 
+                // filling the buffer asynchronously, without a lot of complexity.
+                // The problems I see are issuing an async read, we do an async 
+                // read to fill the buffer, then someone issues another read 
+                // (either synchronously or asynchronously) before the first one 
+                // returns.  This would involve some sort of complex buffer locking
+                // that we probably don't want to get into, at least not in V1.
+                // If we did a sync read to fill the buffer, we could avoid the
+                // problem, and any async read less than 64K gets turned into a
+                // synchronous read by NT anyways...       -- 
+
+                if (destination.Length < _bufferLength)
+                {
+                    Task<int> readTask = ReadNativeAsync(new Memory<byte>(GetBuffer()), 0, cancellationToken);
+                    _readLength = readTask.GetAwaiter().GetResult();
+                    int n = Math.Min(_readLength, destination.Length);
+                    new Span<byte>(GetBuffer(), 0, n).CopyTo(destination.Span);
+                    _readPos = n;
+
+                    synchronousResult = n;
+                    return null;
+                }
+                else
+                {
+                    // Here we're making our position pointer inconsistent
+                    // with our read buffer.  Throw away the read buffer's contents.
+                    _readPos = 0;
+                    _readLength = 0;
+                    synchronousResult = 0;
+                    return ReadNativeAsync(destination, 0, cancellationToken);
+                }
+            }
+            else
+            {
+                int n = Math.Min(_readLength - _readPos, destination.Length);
+                new Span<byte>(GetBuffer(), _readPos, n).CopyTo(destination.Span);
+                _readPos += n;
+
+                if (n == destination.Length)
+                {
+                    // Return a completed task
+                    synchronousResult = n;
+                    return null;
+                }
+                else
+                {
+                    // For streams with no clear EOF like serial ports or pipes
+                    // we cannot read more data without causing an app to block
+                    // incorrectly.  Pipes don't go down this path 
+                    // though.  This code needs to be fixed.
+                    // Throw away read buffer.
+                    _readPos = 0;
+                    _readLength = 0;
+                    synchronousResult = 0;
+                    return ReadNativeAsync(destination.Slice(n), n, cancellationToken);
+                }
+            }
+        }
+
+        private unsafe Task<int> ReadNativeAsync(Memory<byte> destination, int numBufferedBytesRead, CancellationToken cancellationToken)
+        {
+            AssertCanRead();
+            Debug.Assert(_useAsyncIO, "ReadNativeAsync doesn't work on synchronous file streams!");
+
+            // Create and store async stream class library specific data in the async result
+            FileStreamCompletionSource completionSource = FileStreamCompletionSource.Create(this, numBufferedBytesRead, destination);
+            NativeOverlapped* intOverlapped = completionSource.Overlapped;
+
+            // Calculate position in the file we should be at after the read is done
+            if (CanSeek)
+            {
+                long len = Length;
+
+                // Make sure we are reading from the position that we think we are
+                VerifyOSHandlePosition();
+
+                if (_filePosition + destination.Length > len)
+                {
+                    if (_filePosition <= len)
+                    {
+                        destination = destination.Slice(0, (int)(len - _filePosition));
+                    }
+                    else
+                    {
+                        destination = default(Memory<byte>);
+                    }
+                }
+
+                // Now set the position to read from in the NativeOverlapped struct
+                // For pipes, we should leave the offset fields set to 0.
+                intOverlapped->OffsetLow = unchecked((int)_filePosition);
+                intOverlapped->OffsetHigh = (int)(_filePosition >> 32);
+
+                // When using overlapped IO, the OS is not supposed to 
+                // touch the file pointer location at all.  We will adjust it 
+                // ourselves. This isn't threadsafe.
+
+                // WriteFile should not update the file pointer when writing
+                // in overlapped mode, according to MSDN.  But it does update 
+                // the file pointer when writing to a UNC path!   
+                // So changed the code below to seek to an absolute 
+                // location, not a relative one.  ReadFile seems consistent though.
+                SeekCore(_fileHandle, destination.Length, SeekOrigin.Current);
+            }
+
+            // queue an async ReadFile operation and pass in a packed overlapped
+            int errorCode = 0;
+            int r = ReadFileNative(_fileHandle, destination.Span, intOverlapped, out errorCode);
+
+            // ReadFile, the OS version, will return 0 on failure.  But
+            // my ReadFileNative wrapper returns -1.  My wrapper will return
+            // the following:
+            // On error, r==-1.
+            // On async requests that are still pending, r==-1 w/ errorCode==ERROR_IO_PENDING
+            // on async requests that completed sequentially, r==0
+            // You will NEVER RELIABLY be able to get the number of bytes
+            // read back from this call when using overlapped structures!  You must
+            // not pass in a non-null lpNumBytesRead to ReadFile when using 
+            // overlapped structures!  This is by design NT behavior.
+            if (r == -1)
+            {
+                // For pipes, when they hit EOF, they will come here.
+                if (errorCode == ERROR_BROKEN_PIPE)
+                {
+                    // Not an error, but EOF.  AsyncFSCallback will NOT be 
+                    // called.  Call the user callback here.
+
+                    // We clear the overlapped status bit for this special case.
+                    // Failure to do so looks like we are freeing a pending overlapped later.
+                    intOverlapped->InternalLow = IntPtr.Zero;
+                    completionSource.SetCompletedSynchronously(0);
+                }
+                else if (errorCode != ERROR_IO_PENDING)
+                {
+                    if (!_fileHandle.IsClosed && CanSeek)  // Update Position - It could be anywhere.
+                    {
+                        SeekCore(_fileHandle, 0, SeekOrigin.Current);
+                    }
+
+                    completionSource.ReleaseNativeResource();
+
+                    if (errorCode == ERROR_HANDLE_EOF)
+                    {
+                        throw Error.GetEndOfFile();
+                    }
+                    else
+                    {
+                        throw Win32Marshal.GetExceptionForWin32Error(errorCode, _path);
+                    }
+                }
+                else if (cancellationToken.CanBeCanceled) // ERROR_IO_PENDING
+                {
+                    // Only once the IO is pending do we register for cancellation
+                    completionSource.RegisterForCancellation(cancellationToken);
+                }
+            }
+            else
+            {
+                // Due to a workaround for a race condition in NT's ReadFile & 
+                // WriteFile routines, we will always be returning 0 from ReadFileNative
+                // when we do async IO instead of the number of bytes read, 
+                // irregardless of whether the operation completed 
+                // synchronously or asynchronously.  We absolutely must not
+                // set asyncResult._numBytes here, since will never have correct
+                // results.  
+            }
+
+            return completionSource.Task;
+        }
+
+        private ValueTask WriteAsyncInternal(ReadOnlyMemory<byte> source, CancellationToken cancellationToken)
+        {
+            Debug.Assert(_useAsyncIO);
+            Debug.Assert((_readPos == 0 && _readLength == 0 && _writePos >= 0) || (_writePos == 0 && _readPos <= _readLength), "We're either reading or writing, but not both.");
+            Debug.Assert(!_isPipe || (_readPos == 0 && _readLength == 0), "Win32FileStream must not have buffered data here!  Pipes should be unidirectional.");
+
+            if (!CanWrite) throw Error.GetWriteNotSupported();
+
+            bool writeDataStoredInBuffer = false;
+            if (!_isPipe) // avoid async buffering with pipes, as doing so can lead to deadlocks (see comments in ReadInternalAsyncCore)
+            {
+                // Ensure the buffer is clear for writing
+                if (_writePos == 0)
+                {
+                    if (_readPos < _readLength)
+                    {
+                        FlushReadBuffer();
+                    }
+                    _readPos = 0;
+                    _readLength = 0;
+                }
+
+                // Determine how much space remains in the buffer
+                int remainingBuffer = _bufferLength - _writePos;
+                Debug.Assert(remainingBuffer >= 0);
+
+                // Simple/common case:
+                // - The write is smaller than our buffer, such that it's worth considering buffering it.
+                // - There's no active flush operation, such that we don't have to worry about the existing buffer being in use.
+                // - And the data we're trying to write fits in the buffer, meaning it wasn't already filled by previous writes.
+                // In that case, just store it in the buffer.
+                if (source.Length < _bufferLength && !HasActiveBufferOperation && source.Length <= remainingBuffer)
+                {
+                    source.Span.CopyTo(new Span<byte>(GetBuffer(), _writePos, source.Length));
+                    _writePos += source.Length;
+                    writeDataStoredInBuffer = true;
+
+                    // There is one special-but-common case, common because devs often use
+                    // byte[] sizes that are powers of 2 and thus fit nicely into our buffer, which is
+                    // also a power of 2. If after our write the buffer still has remaining space,
+                    // then we're done and can return a completed task now.  But if we filled the buffer
+                    // completely, we want to do the asynchronous flush/write as part of this operation 
+                    // rather than waiting until the next write that fills the buffer.
+                    if (source.Length != remainingBuffer)
+                        return default;
+
+                    Debug.Assert(_writePos == _bufferLength);
+                }
+            }
+
+            // At this point, at least one of the following is true:
+            // 1. There was an active flush operation (it could have completed by now, though).
+            // 2. The data doesn't fit in the remaining buffer (or it's a pipe and we chose not to try).
+            // 3. We wrote all of the data to the buffer, filling it.
+            //
+            // If there's an active operation, we can't touch the current buffer because it's in use.
+            // That gives us a choice: we can either allocate a new buffer, or we can skip the buffer
+            // entirely (even if the data would otherwise fit in it).  For now, for simplicity, we do
+            // the latter; it could also have performance wins due to OS-level optimizations, and we could
+            // potentially add support for PreAllocatedOverlapped due to having a single buffer. (We can
+            // switch to allocating a new buffer, potentially experimenting with buffer pooling, should
+            // performance data suggest it's appropriate.)
+            //
+            // If the data doesn't fit in the remaining buffer, it could be because it's so large
+            // it's greater than the entire buffer size, in which case we'd always skip the buffer,
+            // or it could be because there's more data than just the space remaining.  For the latter
+            // case, we need to issue an asynchronous write to flush that data, which then turns this into
+            // the first case above with an active operation.
+            //
+            // If we already stored the data, then we have nothing additional to write beyond what
+            // we need to flush.
+            //
+            // In any of these cases, we have the same outcome:
+            // - If there's data in the buffer, flush it by writing it out asynchronously.
+            // - Then, if there's any data to be written, issue a write for it concurrently.
+            // We return a Task that represents one or both.
+
+            // Flush the buffer asynchronously if there's anything to flush
+            Task flushTask = null;
+            if (_writePos > 0)
+            {
+                flushTask = FlushWriteAsync(cancellationToken);
+
+                // If we already copied all of the data into the buffer,
+                // simply return the flush task here.  Same goes for if the task has 
+                // already completed and was unsuccessful.
+                if (writeDataStoredInBuffer ||
+                    flushTask.IsFaulted ||
+                    flushTask.IsCanceled)
+                {
+                    return new ValueTask(flushTask);
+                }
+            }
+
+            Debug.Assert(!writeDataStoredInBuffer);
+            Debug.Assert(_writePos == 0);
+
+            // Finally, issue the write asynchronously, and return a Task that logically
+            // represents the write operation, including any flushing done.
+            Task writeTask = WriteAsyncInternalCore(source, cancellationToken);
+            return new ValueTask(
+                (flushTask == null || flushTask.Status == TaskStatus.RanToCompletion) ? writeTask :
+                (writeTask.Status == TaskStatus.RanToCompletion) ? flushTask :
+                Task.WhenAll(flushTask, writeTask));
+        }
+
+        private unsafe Task WriteAsyncInternalCore(ReadOnlyMemory<byte> source, CancellationToken cancellationToken)
+        {
+            Debug.Assert(!_fileHandle.IsClosed, "!_handle.IsClosed");
+            Debug.Assert(CanWrite, "_parent.CanWrite");
+            Debug.Assert(_readPos == _readLength, "_readPos == _readLen");
+            Debug.Assert(_useAsyncIO, "WriteInternalCoreAsync doesn't work on synchronous file streams!");
+
+            // Create and store async stream class library specific data in the async result
+            FileStreamCompletionSource completionSource = FileStreamCompletionSource.Create(this, 0, source);
+            NativeOverlapped* intOverlapped = completionSource.Overlapped;
+
+            if (CanSeek)
+            {
+                // Make sure we set the length of the file appropriately.
+                long len = Length;
+
+                // Make sure we are writing to the position that we think we are
+                VerifyOSHandlePosition();
+
+                if (_filePosition + source.Length > len)
+                {
+                    SetLengthCore(_filePosition + source.Length);
+                }
+
+                // Now set the position to read from in the NativeOverlapped struct
+                // For pipes, we should leave the offset fields set to 0.
+                intOverlapped->OffsetLow = (int)_filePosition;
+                intOverlapped->OffsetHigh = (int)(_filePosition >> 32);
+
+                // When using overlapped IO, the OS is not supposed to 
+                // touch the file pointer location at all.  We will adjust it 
+                // ourselves.  This isn't threadsafe.
+                SeekCore(_fileHandle, source.Length, SeekOrigin.Current);
+            }
+
+            int errorCode = 0;
+            // queue an async WriteFile operation and pass in a packed overlapped
+            int r = WriteFileNative(_fileHandle, source.Span, intOverlapped, out errorCode);
+
+            // WriteFile, the OS version, will return 0 on failure.  But
+            // my WriteFileNative wrapper returns -1.  My wrapper will return
+            // the following:
+            // On error, r==-1.
+            // On async requests that are still pending, r==-1 w/ errorCode==ERROR_IO_PENDING
+            // On async requests that completed sequentially, r==0
+            // You will NEVER RELIABLY be able to get the number of bytes
+            // written back from this call when using overlapped IO!  You must
+            // not pass in a non-null lpNumBytesWritten to WriteFile when using 
+            // overlapped structures!  This is ByDesign NT behavior.
+            if (r == -1)
+            {
+                // For pipes, when they are closed on the other side, they will come here.
+                if (errorCode == ERROR_NO_DATA)
+                {
+                    // Not an error, but EOF. AsyncFSCallback will NOT be called.
+                    // Completing TCS and return cached task allowing the GC to collect TCS.
+                    completionSource.SetCompletedSynchronously(0);
+                    return Task.CompletedTask;
+                }
+                else if (errorCode != ERROR_IO_PENDING)
+                {
+                    if (!_fileHandle.IsClosed && CanSeek)  // Update Position - It could be anywhere.
+                    {
+                        SeekCore(_fileHandle, 0, SeekOrigin.Current);
+                    }
+
+                    completionSource.ReleaseNativeResource();
+
+                    if (errorCode == ERROR_HANDLE_EOF)
+                    {
+                        throw Error.GetEndOfFile();
+                    }
+                    else
+                    {
+                        throw Win32Marshal.GetExceptionForWin32Error(errorCode, _path);
+                    }
+                }
+                else if (cancellationToken.CanBeCanceled) // ERROR_IO_PENDING
+                {
+                    // Only once the IO is pending do we register for cancellation
+                    completionSource.RegisterForCancellation(cancellationToken);
+                }
+            }
+            else
+            {
+                // Due to a workaround for a race condition in NT's ReadFile & 
+                // WriteFile routines, we will always be returning 0 from WriteFileNative
+                // when we do async IO instead of the number of bytes written, 
+                // irregardless of whether the operation completed 
+                // synchronously or asynchronously.  We absolutely must not
+                // set asyncResult._numBytes here, since will never have correct
+                // results.  
+            }
+
+            return completionSource.Task;
+        }
+
+        // Windows API definitions, from winbase.h and others
+
+        private const int FILE_ATTRIBUTE_NORMAL = 0x00000080;
+        private const int FILE_ATTRIBUTE_ENCRYPTED = 0x00004000;
+        private const int FILE_FLAG_OVERLAPPED = 0x40000000;
+        internal const int GENERIC_READ = unchecked((int)0x80000000);
+        private const int GENERIC_WRITE = 0x40000000;
+
+        private const int FILE_BEGIN = 0;
+        private const int FILE_CURRENT = 1;
+        private const int FILE_END = 2;
+
+        // Error codes (not HRESULTS), from winerror.h
+        internal const int ERROR_BROKEN_PIPE = 109;
+        internal const int ERROR_NO_DATA = 232;
+        private const int ERROR_HANDLE_EOF = 38;
+        private const int ERROR_INVALID_PARAMETER = 87;
+        private const int ERROR_IO_PENDING = 997;
+
+        // __ConsoleStream also uses this code. 
+        private unsafe int ReadFileNative(SafeFileHandle handle, Span<byte> bytes, NativeOverlapped* overlapped, out int errorCode)
+        {
+            Debug.Assert(handle != null, "handle != null");
+            Debug.Assert((_useAsyncIO && overlapped != null) || (!_useAsyncIO && overlapped == null), "Async IO and overlapped parameters inconsistent in call to ReadFileNative.");
+
+            int r;
+            int numBytesRead = 0;
+
+            fixed (byte* p = &MemoryMarshal.GetReference(bytes))
+            {
+                r = _useAsyncIO ?
+                    Interop.Kernel32.ReadFile(handle, p, bytes.Length, IntPtr.Zero, overlapped) :
+                    Interop.Kernel32.ReadFile(handle, p, bytes.Length, out numBytesRead, IntPtr.Zero);
+            }
+
+            if (r == 0)
+            {
+                errorCode = GetLastWin32ErrorAndDisposeHandleIfInvalid();
+                return -1;
+            }
+            else
+            {
+                errorCode = 0;
+                return numBytesRead;
+            }
+        }
+
+        private unsafe int WriteFileNative(SafeFileHandle handle, ReadOnlySpan<byte> buffer, NativeOverlapped* overlapped, out int errorCode)
+        {
+            Debug.Assert(handle != null, "handle != null");
+            Debug.Assert((_useAsyncIO && overlapped != null) || (!_useAsyncIO && overlapped == null), "Async IO and overlapped parameters inconsistent in call to WriteFileNative.");
+
+            int numBytesWritten = 0;
+            int r;
+
+            fixed (byte* p = &MemoryMarshal.GetReference(buffer))
+            {
+                r = _useAsyncIO ?
+                    Interop.Kernel32.WriteFile(handle, p, buffer.Length, IntPtr.Zero, overlapped) :
+                    Interop.Kernel32.WriteFile(handle, p, buffer.Length, out numBytesWritten, IntPtr.Zero);
+            }
+
+            if (r == 0)
+            {
+                errorCode = GetLastWin32ErrorAndDisposeHandleIfInvalid();
+                return -1;
+            }
+            else
+            {
+                errorCode = 0;
+                return numBytesWritten;
+            }
+        }
+
+        private int GetLastWin32ErrorAndDisposeHandleIfInvalid(bool throwIfInvalidHandle = false)
+        {
+            int errorCode = Marshal.GetLastWin32Error();
+
+            // If ERROR_INVALID_HANDLE is returned, it doesn't suffice to set
+            // the handle as invalid; the handle must also be closed.
+            //
+            // Marking the handle as invalid but not closing the handle
+            // resulted in exceptions during finalization and locked column
+            // values (due to invalid but unclosed handle) in SQL Win32FileStream
+            // scenarios.
+            //
+            // A more mainstream scenario involves accessing a file on a
+            // network share. ERROR_INVALID_HANDLE may occur because the network
+            // connection was dropped and the server closed the handle. However,
+            // the client side handle is still open and even valid for certain
+            // operations.
+            //
+            // Note that _parent.Dispose doesn't throw so we don't need to special case.
+            // SetHandleAsInvalid only sets _closed field to true (without
+            // actually closing handle) so we don't need to call that as well.
+            if (errorCode == Interop.Errors.ERROR_INVALID_HANDLE)
+            {
+                _fileHandle.Dispose();
+
+                if (throwIfInvalidHandle)
+                    throw Win32Marshal.GetExceptionForWin32Error(errorCode, _path);
+            }
+
+            return errorCode;
+        }
+
+        public override Task CopyToAsync(Stream destination, int bufferSize, CancellationToken cancellationToken)
+        {
+            // If we're in sync mode, just use the shared CopyToAsync implementation that does
+            // typical read/write looping.  We also need to take this path if this is a derived
+            // instance from FileStream, as a derived type could have overridden ReadAsync, in which
+            // case our custom CopyToAsync implementation isn't necessarily correct.
+            if (!_useAsyncIO || GetType() != typeof(FileStream))
+            {
+                return base.CopyToAsync(destination, bufferSize, cancellationToken);
+            }
+
+            StreamHelpers.ValidateCopyToArgs(this, destination, bufferSize);
+
+            // Bail early for cancellation if cancellation has been requested
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return Task.FromCanceled<int>(cancellationToken);
+            }
+
+            // Fail if the file was closed
+            if (_fileHandle.IsClosed)
+            {
+                throw Error.GetFileNotOpen();
+            }
+
+            // Do the async copy, with differing implementations based on whether the FileStream was opened as async or sync
+            Debug.Assert((_readPos == 0 && _readLength == 0 && _writePos >= 0) || (_writePos == 0 && _readPos <= _readLength), "We're either reading or writing, but not both.");
+            return AsyncModeCopyToAsync(destination, bufferSize, cancellationToken);
+        }
+
+        private async Task AsyncModeCopyToAsync(Stream destination, int bufferSize, CancellationToken cancellationToken)
+        {
+            Debug.Assert(_useAsyncIO, "This implementation is for async mode only");
+            Debug.Assert(!_fileHandle.IsClosed, "!_handle.IsClosed");
+            Debug.Assert(CanRead, "_parent.CanRead");
+
+            // Make sure any pending writes have been flushed before we do a read.
+            if (_writePos > 0)
+            {
+                await FlushWriteAsync(cancellationToken).ConfigureAwait(false);
+            }
+
+            // Typically CopyToAsync would be invoked as the only "read" on the stream, but it's possible some reading is
+            // done and then the CopyToAsync is issued.  For that case, see if we have any data available in the buffer.
+            if (GetBuffer() != null)
+            {
+                int bufferedBytes = _readLength - _readPos;
+                if (bufferedBytes > 0)
+                {
+                    await destination.WriteAsync(new ReadOnlyMemory<byte>(GetBuffer(), _readPos, bufferedBytes), cancellationToken).ConfigureAwait(false);
+                    _readPos = _readLength = 0;
+                }
+            }
+
+            // For efficiency, we avoid creating a new task and associated state for each asynchronous read.
+            // Instead, we create a single reusable awaitable object that will be triggered when an await completes
+            // and reset before going again.
+            var readAwaitable = new AsyncCopyToAwaitable(this);
+
+            // Make sure we are reading from the position that we think we are.
+            // Only set the position in the awaitable if we can seek (e.g. not for pipes).
+            bool canSeek = CanSeek;
+            if (canSeek)
+            {
+                VerifyOSHandlePosition();
+                readAwaitable._position = _filePosition;
+            }
+
+            // Get the buffer to use for the copy operation, as the base CopyToAsync does. We don't try to use
+            // _buffer here, even if it's not null, as concurrent operations are allowed, and another operation may
+            // actually be using the buffer already. Plus, it'll be rare for _buffer to be non-null, as typically
+            // CopyToAsync is used as the only operation performed on the stream, and the buffer is lazily initialized.
+            // Further, typically the CopyToAsync buffer size will be larger than that used by the FileStream, such that
+            // we'd likely be unable to use it anyway.  Instead, we rent the buffer from a pool.
+            byte[] copyBuffer = ArrayPool<byte>.Shared.Rent(bufferSize);
+
+            // Allocate an Overlapped we can use repeatedly for all operations
+            var awaitableOverlapped = new PreAllocatedOverlapped(AsyncCopyToAwaitable.s_callback, readAwaitable, copyBuffer);
+            var cancellationReg = default(CancellationTokenRegistration);
+            try
+            {
+                // Register for cancellation.  We do this once for the whole copy operation, and just try to cancel
+                // whatever read operation may currently be in progress, if there is one.  It's possible the cancellation
+                // request could come in between operations, in which case we flag that with explicit calls to ThrowIfCancellationRequested
+                // in the read/write copy loop.
+                if (cancellationToken.CanBeCanceled)
+                {
+                    cancellationReg = cancellationToken.Register(s =>
+                    {
+                        var innerAwaitable = (AsyncCopyToAwaitable)s;
+                        unsafe
+                        {
+                            lock (innerAwaitable.CancellationLock) // synchronize with cleanup of the overlapped
+                            {
+                                if (innerAwaitable._nativeOverlapped != null)
+                                {
+                                    // Try to cancel the I/O.  We ignore the return value, as cancellation is opportunistic and we
+                                    // don't want to fail the operation because we couldn't cancel it.
+                                    Interop.Kernel32.CancelIoEx(innerAwaitable._fileStream._fileHandle, innerAwaitable._nativeOverlapped);
+                                }
+                            }
+                        }
+                    }, readAwaitable);
+                }
+
+                // Repeatedly read from this FileStream and write the results to the destination stream.
+                while (true)
+                {
+                    cancellationToken.ThrowIfCancellationRequested();
+                    readAwaitable.ResetForNextOperation();
+
+                    try
+                    {
+                        bool synchronousSuccess;
+                        int errorCode;
+                        unsafe
+                        {
+                            // Allocate a native overlapped for our reusable overlapped, and set position to read based on the next
+                            // desired address stored in the awaitable.  (This position may be 0, if either we're at the beginning or
+                            // if the stream isn't seekable.)
+                            readAwaitable._nativeOverlapped = _fileHandle.ThreadPoolBinding.AllocateNativeOverlapped(awaitableOverlapped);
+                            if (canSeek)
+                            {
+                                readAwaitable._nativeOverlapped->OffsetLow = unchecked((int)readAwaitable._position);
+                                readAwaitable._nativeOverlapped->OffsetHigh = (int)(readAwaitable._position >> 32);
+                            }
+
+                            // Kick off the read.
+                            synchronousSuccess = ReadFileNative(_fileHandle, copyBuffer, readAwaitable._nativeOverlapped, out errorCode) >= 0;
+                        }
+
+                        // If the operation did not synchronously succeed, it either failed or initiated the asynchronous operation.
+                        if (!synchronousSuccess)
+                        {
+                            switch (errorCode)
+                            {
+                                case ERROR_IO_PENDING:
+                                    // Async operation in progress.
+                                    break;
+                                case ERROR_BROKEN_PIPE:
+                                case ERROR_HANDLE_EOF:
+                                    // We're at or past the end of the file, and the overlapped callback
+                                    // won't be raised in these cases. Mark it as completed so that the await
+                                    // below will see it as such.
+                                    readAwaitable.MarkCompleted();
+                                    break;
+                                default:
+                                    // Everything else is an error (and there won't be a callback).
+                                    throw Win32Marshal.GetExceptionForWin32Error(errorCode, _path);
+                            }
+                        }
+
+                        // Wait for the async operation (which may or may not have already completed), then throw if it failed.
+                        await readAwaitable;
+                        switch (readAwaitable._errorCode)
+                        {
+                            case 0: // success
+                                Debug.Assert(readAwaitable._numBytes >= 0, $"Expected non-negative numBytes, got {readAwaitable._numBytes}");
+                                break;
+                            case ERROR_BROKEN_PIPE: // logically success with 0 bytes read (write end of pipe closed)
+                            case ERROR_HANDLE_EOF:  // logically success with 0 bytes read (read at end of file)
+                                Debug.Assert(readAwaitable._numBytes == 0, $"Expected 0 bytes read, got {readAwaitable._numBytes}");
+                                break;
+                            case Interop.Errors.ERROR_OPERATION_ABORTED: // canceled
+                                throw new OperationCanceledException(cancellationToken.IsCancellationRequested ? cancellationToken : new CancellationToken(true));
+                            default: // error
+                                throw Win32Marshal.GetExceptionForWin32Error((int)readAwaitable._errorCode, _path);
+                        }
+
+                        // Successful operation.  If we got zero bytes, we're done: exit the read/write loop.
+                        int numBytesRead = (int)readAwaitable._numBytes;
+                        if (numBytesRead == 0)
+                        {
+                            break;
+                        }
+
+                        // Otherwise, update the read position for next time accordingly.
+                        if (canSeek)
+                        {
+                            readAwaitable._position += numBytesRead;
+                        }
+                    }
+                    finally
+                    {
+                        // Free the resources for this read operation
+                        unsafe
+                        {
+                            NativeOverlapped* overlapped;
+                            lock (readAwaitable.CancellationLock) // just an Exchange, but we need this to be synchronized with cancellation, so using the same lock
+                            {
+                                overlapped = readAwaitable._nativeOverlapped;
+                                readAwaitable._nativeOverlapped = null;
+                            }
+                            if (overlapped != null)
+                            {
+                                _fileHandle.ThreadPoolBinding.FreeNativeOverlapped(overlapped);
+                            }
+                        }
+                    }
+
+                    // Write out the read data.
+                    await destination.WriteAsync(new ReadOnlyMemory<byte>(copyBuffer, 0, (int)readAwaitable._numBytes), cancellationToken).ConfigureAwait(false);
+                }
+            }
+            finally
+            {
+                // Cleanup from the whole copy operation
+                cancellationReg.Dispose();
+                awaitableOverlapped.Dispose();
+
+                ArrayPool<byte>.Shared.Return(copyBuffer);
+
+                // Make sure the stream's current position reflects where we ended up
+                if (!_fileHandle.IsClosed && CanSeek)
+                {
+                    SeekCore(_fileHandle, 0, SeekOrigin.End);
+                }
+            }
+        }
+
+        /// <summary>Used by CopyToAsync to enable awaiting the result of an overlapped I/O operation with minimal overhead.</summary>
+        private sealed unsafe class AsyncCopyToAwaitable : ICriticalNotifyCompletion
+        {
+            /// <summary>Sentinel object used to indicate that the I/O operation has completed before being awaited.</summary>
+            private readonly static Action s_sentinel = () => { };
+            /// <summary>Cached delegate to IOCallback.</summary>
+            internal static readonly IOCompletionCallback s_callback = IOCallback;
+
+            /// <summary>The FileStream that owns this instance.</summary>
+            internal readonly FileStream _fileStream;
+
+            /// <summary>Tracked position representing the next location from which to read.</summary>
+            internal long _position;
+            /// <summary>The current native overlapped pointer.  This changes for each operation.</summary>
+            internal NativeOverlapped* _nativeOverlapped;
+            /// <summary>
+            /// null if the operation is still in progress,
+            /// s_sentinel if the I/O operation completed before the await,
+            /// s_callback if it completed after the await yielded.
+            /// </summary>
+            internal Action _continuation;
+            /// <summary>Last error code from completed operation.</summary>
+            internal uint _errorCode;
+            /// <summary>Last number of read bytes from completed operation.</summary>
+            internal uint _numBytes;
+
+            /// <summary>Lock object used to protect cancellation-related access to _nativeOverlapped.</summary>
+            internal object CancellationLock => this;
+
+            /// <summary>Initialize the awaitable.</summary>
+            internal unsafe AsyncCopyToAwaitable(FileStream fileStream)
+            {
+                _fileStream = fileStream;
+            }
+
+            /// <summary>Reset state to prepare for the next read operation.</summary>
+            internal void ResetForNextOperation()
+            {
+                Debug.Assert(_position >= 0, $"Expected non-negative position, got {_position}");
+                _continuation = null;
+                _errorCode = 0;
+                _numBytes = 0;
+            }
+
+            /// <summary>Overlapped callback: store the results, then invoke the continuation delegate.</summary>
+            internal static unsafe void IOCallback(uint errorCode, uint numBytes, NativeOverlapped* pOVERLAP)
+            {
+                var awaitable = (AsyncCopyToAwaitable)ThreadPoolBoundHandle.GetNativeOverlappedState(pOVERLAP);
+
+                Debug.Assert(!ReferenceEquals(awaitable._continuation, s_sentinel), "Sentinel must not have already been set as the continuation");
+                awaitable._errorCode = errorCode;
+                awaitable._numBytes = numBytes;
+
+                (awaitable._continuation ?? Interlocked.CompareExchange(ref awaitable._continuation, s_sentinel, null))?.Invoke();
+            }
+
+            /// <summary>
+            /// Called when it's known that the I/O callback for an operation will not be invoked but we'll
+            /// still be awaiting the awaitable.
+            /// </summary>
+            internal void MarkCompleted()
+            {
+                Debug.Assert(_continuation == null, "Expected null continuation");
+                _continuation = s_sentinel;
+            }
+
+            public AsyncCopyToAwaitable GetAwaiter() => this;
+            public bool IsCompleted => ReferenceEquals(_continuation, s_sentinel);
+            public void GetResult() { }
+            public void OnCompleted(Action continuation) => UnsafeOnCompleted(continuation);
+            public void UnsafeOnCompleted(Action continuation)
+            {
+                if (ReferenceEquals(_continuation, s_sentinel) ||
+                    Interlocked.CompareExchange(ref _continuation, continuation, null) != null)
+                {
+                    Debug.Assert(ReferenceEquals(_continuation, s_sentinel), $"Expected continuation set to s_sentinel, got ${_continuation}");
+                    Task.Run(continuation);
+                }
+            }
+        }
+
+        // Unlike Flush(), FlushAsync() always flushes to disk. This is intentional.
+        // Legend is that we chose not to flush the OS file buffers in Flush() in fear of 
+        // perf problems with frequent, long running FlushFileBuffers() calls. But we don't 
+        // have that problem with FlushAsync() because we will call FlushFileBuffers() in the background.
+        private Task FlushAsyncInternal(CancellationToken cancellationToken)
+        {
+            if (cancellationToken.IsCancellationRequested)
+                return Task.FromCanceled(cancellationToken);
+
+            if (_fileHandle.IsClosed)
+                throw Error.GetFileNotOpen();
+
+            // The always synchronous data transfer between the OS and the internal buffer is intentional 
+            // because this is needed to allow concurrent async IO requests. Concurrent data transfer
+            // between the OS and the internal buffer will result in race conditions. Since FlushWrite and
+            // FlushRead modify internal state of the stream and transfer data between the OS and the 
+            // internal buffer, they cannot be truly async. We will, however, flush the OS file buffers
+            // asynchronously because it doesn't modify any internal state of the stream and is potentially 
+            // a long running process.
+            try
+            {
+                FlushInternalBuffer();
+            }
+            catch (Exception e)
+            {
+                return Task.FromException(e);
+            }
+
+            if (CanWrite)
+            {
+                return Task.Factory.StartNew(
+                    state => ((FileStream)state).FlushOSBuffer(),
+                    this,
+                    cancellationToken,
+                    TaskCreationOptions.DenyChildAttach,
+                    TaskScheduler.Default);
+            }
+            else
+            {
+                return Task.CompletedTask;
+            }
+        }
+
+        private void LockInternal(long position, long length)
+        {
+            int positionLow = unchecked((int)(position));
+            int positionHigh = unchecked((int)(position >> 32));
+            int lengthLow = unchecked((int)(length));
+            int lengthHigh = unchecked((int)(length >> 32));
+
+            if (!Interop.Kernel32.LockFile(_fileHandle, positionLow, positionHigh, lengthLow, lengthHigh))
+            {
+                throw Win32Marshal.GetExceptionForLastWin32Error(_path);
+            }
+        }
+
+        private void UnlockInternal(long position, long length)
+        {
+            int positionLow = unchecked((int)(position));
+            int positionHigh = unchecked((int)(position >> 32));
+            int lengthLow = unchecked((int)(length));
+            int lengthHigh = unchecked((int)(length >> 32));
+
+            if (!Interop.Kernel32.UnlockFile(_fileHandle, positionLow, positionHigh, lengthLow, lengthHigh))
+            {
+                throw Win32Marshal.GetExceptionForLastWin32Error(_path);
+            }
+        }
+
+        private SafeFileHandle ValidateFileHandle(SafeFileHandle fileHandle)
+        {
+            if (fileHandle.IsInvalid)
+            {
+                // Return a meaningful exception with the full path.
+
+                // NT5 oddity - when trying to open "C:\" as a Win32FileStream,
+                // we usually get ERROR_PATH_NOT_FOUND from the OS.  We should
+                // probably be consistent w/ every other directory.
+                int errorCode = Marshal.GetLastWin32Error();
+
+                if (errorCode == Interop.Errors.ERROR_PATH_NOT_FOUND && _path.Length == PathInternal.GetRootLength(_path))
+                    errorCode = Interop.Errors.ERROR_ACCESS_DENIED;
+
+                throw Win32Marshal.GetExceptionForWin32Error(errorCode, _path);
+            }
+
+            fileHandle.IsAsync = _useAsyncIO;
+            return fileHandle;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/FileStream.cs b/src/System.Private.CoreLib/shared/System/IO/FileStream.cs
new file mode 100644
index 0000000000..a6ad63c6eb
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/FileStream.cs
@@ -0,0 +1,881 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Win32.SafeHandles;
+using System.Diagnostics;
+using System.Security;
+
+namespace System.IO
+{
+    public partial class FileStream : Stream
+    {
+        private const FileShare DefaultShare = FileShare.Read;
+        private const bool DefaultIsAsync = false;
+        internal const int DefaultBufferSize = 4096;
+
+        private byte[] _buffer;
+        private int _bufferLength;
+        private readonly SafeFileHandle _fileHandle;
+
+        /// <summary>Whether the file is opened for reading, writing, or both.</summary>
+        private readonly FileAccess _access;
+
+        /// <summary>The path to the opened file.</summary>
+        private readonly string _path;
+
+        /// <summary>The next available byte to be read from the _buffer.</summary>
+        private int _readPos;
+
+        /// <summary>The number of valid bytes in _buffer.</summary>
+        private int _readLength;
+
+        /// <summary>The next location in which a write should occur to the buffer.</summary>
+        private int _writePos;
+
+        /// <summary>
+        /// Whether asynchronous read/write/flush operations should be performed using async I/O.
+        /// On Windows FileOptions.Asynchronous controls how the file handle is configured, 
+        /// and then as a result how operations are issued against that file handle.  On Unix, 
+        /// there isn't any distinction around how file descriptors are created for async vs 
+        /// sync, but we still differentiate how the operations are issued in order to provide
+        /// similar behavioral semantics and performance characteristics as on Windows.  On
+        /// Windows, if non-async, async read/write requests just delegate to the base stream,
+        /// and no attempt is made to synchronize between sync and async operations on the stream;
+        /// if async, then async read/write requests are implemented specially, and sync read/write
+        /// requests are coordinated with async ones by implementing the sync ones over the async
+        /// ones.  On Unix, we do something similar.  If non-async, async read/write requests just
+        /// delegate to the base stream, and no attempt is made to synchronize.  If async, we use
+        /// a semaphore to coordinate both sync and async operations.
+        /// </summary>
+        private readonly bool _useAsyncIO;
+
+        /// <summary>cached task for read ops that complete synchronously</summary>
+        private Task<int> _lastSynchronouslyCompletedTask = null;
+
+        /// <summary>
+        /// Currently cached position in the stream.  This should always mirror the underlying file's actual position,
+        /// and should only ever be out of sync if another stream with access to this same file manipulates it, at which
+        /// point we attempt to error out.
+        /// </summary>
+        private long _filePosition;
+
+        /// <summary>Whether the file stream's handle has been exposed.</summary>
+        private bool _exposedHandle;
+
+        [Obsolete("This constructor has been deprecated.  Please use new FileStream(SafeFileHandle handle, FileAccess access) instead.  http://go.microsoft.com/fwlink/?linkid=14202")]
+        public FileStream(IntPtr handle, FileAccess access)
+            : this(handle, access, true, DefaultBufferSize, false)
+        {
+        }
+
+        [Obsolete("This constructor has been deprecated.  Please use new FileStream(SafeFileHandle handle, FileAccess access) instead, and optionally make a new SafeFileHandle with ownsHandle=false if needed.  http://go.microsoft.com/fwlink/?linkid=14202")]
+        public FileStream(IntPtr handle, FileAccess access, bool ownsHandle)
+            : this(handle, access, ownsHandle, DefaultBufferSize, false)
+        {
+        }
+
+        [Obsolete("This constructor has been deprecated.  Please use new FileStream(SafeFileHandle handle, FileAccess access, int bufferSize) instead, and optionally make a new SafeFileHandle with ownsHandle=false if needed.  http://go.microsoft.com/fwlink/?linkid=14202")]
+        public FileStream(IntPtr handle, FileAccess access, bool ownsHandle, int bufferSize)
+            : this(handle, access, ownsHandle, bufferSize, false)
+        {
+        }
+
+        [Obsolete("This constructor has been deprecated.  Please use new FileStream(SafeFileHandle handle, FileAccess access, int bufferSize, bool isAsync) instead, and optionally make a new SafeFileHandle with ownsHandle=false if needed.  http://go.microsoft.com/fwlink/?linkid=14202")]
+        public FileStream(IntPtr handle, FileAccess access, bool ownsHandle, int bufferSize, bool isAsync)
+        {
+            SafeFileHandle safeHandle = new SafeFileHandle(handle, ownsHandle: ownsHandle);
+            try
+            {
+                ValidateAndInitFromHandle(safeHandle, access, bufferSize, isAsync);
+            }
+            catch
+            {
+                // We don't want to take ownership of closing passed in handles
+                // *unless* the constructor completes successfully.
+                GC.SuppressFinalize(safeHandle);
+
+                // This would also prevent Close from being called, but is unnecessary
+                // as we've removed the object from the finalizer queue.
+                //
+                // safeHandle.SetHandleAsInvalid();
+                throw;
+            }
+
+            // Note: Cleaner to set the following fields in ValidateAndInitFromHandle,
+            // but we can't as they're readonly.
+            _access = access;
+            _useAsyncIO = isAsync;
+
+            // As the handle was passed in, we must set the handle field at the very end to
+            // avoid the finalizer closing the handle when we throw errors.
+            _fileHandle = safeHandle;
+        }
+
+        public FileStream(SafeFileHandle handle, FileAccess access)
+            : this(handle, access, DefaultBufferSize)
+        {
+        }
+
+        public FileStream(SafeFileHandle handle, FileAccess access, int bufferSize)
+            : this(handle, access, bufferSize, GetDefaultIsAsync(handle))
+        {
+        }
+
+        private void ValidateAndInitFromHandle(SafeFileHandle handle, FileAccess access, int bufferSize, bool isAsync)
+        {
+            if (handle.IsInvalid)
+                throw new ArgumentException(SR.Arg_InvalidHandle, nameof(handle));
+
+            if (access < FileAccess.Read || access > FileAccess.ReadWrite)
+                throw new ArgumentOutOfRangeException(nameof(access), SR.ArgumentOutOfRange_Enum);
+            if (bufferSize <= 0)
+                throw new ArgumentOutOfRangeException(nameof(bufferSize), SR.ArgumentOutOfRange_NeedPosNum);
+
+            if (handle.IsClosed)
+                throw new ObjectDisposedException(SR.ObjectDisposed_FileClosed);
+            if (handle.IsAsync.HasValue && isAsync != handle.IsAsync.Value)
+                throw new ArgumentException(SR.Arg_HandleNotAsync, nameof(handle));
+
+            _exposedHandle = true;
+            _bufferLength = bufferSize;
+
+            InitFromHandle(handle, access, isAsync);
+        }
+
+        public FileStream(SafeFileHandle handle, FileAccess access, int bufferSize, bool isAsync)
+        {
+            ValidateAndInitFromHandle(handle, access, bufferSize, isAsync);
+
+            // Note: Cleaner to set the following fields in ValidateAndInitFromHandle,
+            // but we can't as they're readonly.
+            _access = access;
+            _useAsyncIO = isAsync;
+
+            // As the handle was passed in, we must set the handle field at the very end to
+            // avoid the finalizer closing the handle when we throw errors.
+            _fileHandle = handle;
+        }
+
+        public FileStream(string path, FileMode mode) :
+            this(path, mode, (mode == FileMode.Append ? FileAccess.Write : FileAccess.ReadWrite), DefaultShare, DefaultBufferSize, DefaultIsAsync)
+        { }
+
+        public FileStream(string path, FileMode mode, FileAccess access) :
+            this(path, mode, access, DefaultShare, DefaultBufferSize, DefaultIsAsync)
+        { }
+
+        public FileStream(string path, FileMode mode, FileAccess access, FileShare share) :
+            this(path, mode, access, share, DefaultBufferSize, DefaultIsAsync)
+        { }
+
+        public FileStream(string path, FileMode mode, FileAccess access, FileShare share, int bufferSize) :
+            this(path, mode, access, share, bufferSize, DefaultIsAsync)
+        { }
+
+        public FileStream(string path, FileMode mode, FileAccess access, FileShare share, int bufferSize, bool useAsync) :
+            this(path, mode, access, share, bufferSize, useAsync ? FileOptions.Asynchronous : FileOptions.None)
+        { }
+
+        public FileStream(string path, FileMode mode, FileAccess access, FileShare share, int bufferSize, FileOptions options)
+        {
+            if (path == null)
+                throw new ArgumentNullException(nameof(path), SR.ArgumentNull_Path);
+            if (path.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyPath, nameof(path));
+
+            // don't include inheritable in our bounds check for share
+            FileShare tempshare = share & ~FileShare.Inheritable;
+            string badArg = null;
+
+            if (mode < FileMode.CreateNew || mode > FileMode.Append)
+                badArg = nameof(mode);
+            else if (access < FileAccess.Read || access > FileAccess.ReadWrite)
+                badArg = nameof(access);
+            else if (tempshare < FileShare.None || tempshare > (FileShare.ReadWrite | FileShare.Delete))
+                badArg = nameof(share);
+
+            if (badArg != null)
+                throw new ArgumentOutOfRangeException(badArg, SR.ArgumentOutOfRange_Enum);
+
+            // NOTE: any change to FileOptions enum needs to be matched here in the error validation
+            if (options != FileOptions.None && (options & ~(FileOptions.WriteThrough | FileOptions.Asynchronous | FileOptions.RandomAccess | FileOptions.DeleteOnClose | FileOptions.SequentialScan | FileOptions.Encrypted | (FileOptions)0x20000000 /* NoBuffering */)) != 0)
+                throw new ArgumentOutOfRangeException(nameof(options), SR.ArgumentOutOfRange_Enum);
+
+            if (bufferSize <= 0)
+                throw new ArgumentOutOfRangeException(nameof(bufferSize), SR.ArgumentOutOfRange_NeedPosNum);
+
+            // Write access validation
+            if ((access & FileAccess.Write) == 0)
+            {
+                if (mode == FileMode.Truncate || mode == FileMode.CreateNew || mode == FileMode.Create || mode == FileMode.Append)
+                {
+                    // No write access, mode and access disagree but flag access since mode comes first
+                    throw new ArgumentException(SR.Format(SR.Argument_InvalidFileModeAndAccessCombo, mode, access), nameof(access));
+                }
+            }
+
+            if ((access & FileAccess.Read) != 0 && mode == FileMode.Append)
+                throw new ArgumentException(SR.Argument_InvalidAppendMode, nameof(access));
+
+            string fullPath = Path.GetFullPath(path);
+
+            _path = fullPath;
+            _access = access;
+            _bufferLength = bufferSize;
+
+            if ((options & FileOptions.Asynchronous) != 0)
+                _useAsyncIO = true;
+
+            _fileHandle = OpenHandle(mode, share, options);
+
+            try
+            {
+                Init(mode, share);
+            }
+            catch
+            {
+                // If anything goes wrong while setting up the stream, make sure we deterministically dispose
+                // of the opened handle.
+                _fileHandle.Dispose();
+                _fileHandle = null;
+                throw;
+            }
+        }
+
+        private static bool GetDefaultIsAsync(SafeFileHandle handle)
+        {
+            // This will eventually get more complicated as we can actually check the underlying handle type on Windows
+            return handle.IsAsync.HasValue ? handle.IsAsync.Value : false;
+        }
+
+        [Obsolete("This property has been deprecated.  Please use FileStream's SafeFileHandle property instead.  http://go.microsoft.com/fwlink/?linkid=14202")]
+        public virtual IntPtr Handle { get { return SafeFileHandle.DangerousGetHandle(); } }
+
+        public virtual void Lock(long position, long length)
+        {
+            if (position < 0 || length < 0)
+            {
+                throw new ArgumentOutOfRangeException(position < 0 ? nameof(position) : nameof(length), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (_fileHandle.IsClosed)
+            {
+                throw Error.GetFileNotOpen();
+            }
+
+            LockInternal(position, length);
+        }
+
+        public virtual void Unlock(long position, long length)
+        {
+            if (position < 0 || length < 0)
+            {
+                throw new ArgumentOutOfRangeException(position < 0 ? nameof(position) : nameof(length), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (_fileHandle.IsClosed)
+            {
+                throw Error.GetFileNotOpen();
+            }
+
+            UnlockInternal(position, length);
+        }
+
+        public override Task FlushAsync(CancellationToken cancellationToken)
+        {
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Flush() which a subclass might have overridden.  To be safe 
+            // we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Flush) when we are not sure.
+            if (GetType() != typeof(FileStream))
+                return base.FlushAsync(cancellationToken);
+
+            return FlushAsyncInternal(cancellationToken);
+        }
+
+        public override int Read(byte[] array, int offset, int count)
+        {
+            ValidateReadWriteArgs(array, offset, count);
+            return _useAsyncIO ?
+                ReadAsyncTask(array, offset, count, CancellationToken.None).GetAwaiter().GetResult() :
+                ReadSpan(new Span<byte>(array, offset, count));
+        }
+
+        public override int Read(Span<byte> buffer)
+        {
+            if (GetType() == typeof(FileStream) && !_useAsyncIO)
+            {
+                if (_fileHandle.IsClosed)
+                {
+                    throw Error.GetFileNotOpen();
+                }
+                return ReadSpan(buffer);
+            }
+            else
+            {
+                // This type is derived from FileStream and/or the stream is in async mode.  If this is a 
+                // derived type, it may have overridden Read(byte[], int, int) prior to this Read(Span<byte>)
+                // overload being introduced.  In that case, this Read(Span<byte>) overload should use the behavior
+                // of Read(byte[],int,int) overload.  Or if the stream is in async mode, we can't call the
+                // synchronous ReadSpan, so we similarly call the base Read, which will turn delegate to
+                // Read(byte[],int,int), which will do the right thing if we're in async mode.
+                return base.Read(buffer);
+            }
+        }
+
+        public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            if (buffer == null)
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (buffer.Length - offset < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen /*, no good single parameter name to pass*/);
+
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Read() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Read/ReadAsync) when we are not sure.
+            // Similarly, if we weren't opened for asynchronous I/O, call to the base implementation so that
+            // Read is invoked asynchronously.
+            if (GetType() != typeof(FileStream) || !_useAsyncIO)
+                return base.ReadAsync(buffer, offset, count, cancellationToken);
+
+            if (cancellationToken.IsCancellationRequested)
+                return Task.FromCanceled<int>(cancellationToken);
+
+            if (IsClosed)
+                throw Error.GetFileNotOpen();
+
+            return ReadAsyncTask(buffer, offset, count, cancellationToken);
+        }
+
+        public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            if (!_useAsyncIO || GetType() != typeof(FileStream))
+            {
+                // If we're not using async I/O, delegate to the base, which will queue a call to Read.
+                // Or if this isn't a concrete FileStream, a derived type may have overridden ReadAsync(byte[],...),
+                // which was introduced first, so delegate to the base which will delegate to that.
+                return base.ReadAsync(buffer, cancellationToken);
+            }
+
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return new ValueTask<int>(Task.FromCanceled<int>(cancellationToken));
+            }
+
+            if (IsClosed)
+            {
+                throw Error.GetFileNotOpen();
+            }
+
+            Task<int> t = ReadAsyncInternal(buffer, cancellationToken, out int synchronousResult);
+            return t != null ?
+                new ValueTask<int>(t) :
+                new ValueTask<int>(synchronousResult);
+        }
+
+        private Task<int> ReadAsyncTask(byte[] array, int offset, int count, CancellationToken cancellationToken)
+        {
+            Task<int> t = ReadAsyncInternal(new Memory<byte>(array, offset, count), cancellationToken, out int synchronousResult);
+
+            if (t == null)
+            {
+                t = _lastSynchronouslyCompletedTask;
+                Debug.Assert(t == null || t.IsCompletedSuccessfully, "Cached task should have completed successfully");
+
+                if (t == null || t.Result != synchronousResult)
+                {
+                    _lastSynchronouslyCompletedTask = t = Task.FromResult(synchronousResult);
+                }
+            }
+
+            return t;
+        }
+
+        public override void Write(byte[] array, int offset, int count)
+        {
+            ValidateReadWriteArgs(array, offset, count);
+            if (_useAsyncIO)
+            {
+                WriteAsyncInternal(new ReadOnlyMemory<byte>(array, offset, count), CancellationToken.None).GetAwaiter().GetResult();
+            }
+            else
+            {
+                WriteSpan(new ReadOnlySpan<byte>(array, offset, count));
+            }
+        }
+
+        public override void Write(ReadOnlySpan<byte> buffer)
+        {
+            if (GetType() == typeof(FileStream) && !_useAsyncIO)
+            {
+                if (_fileHandle.IsClosed)
+                {
+                    throw Error.GetFileNotOpen();
+                }
+                WriteSpan(buffer);
+            }
+            else
+            {
+                // This type is derived from FileStream and/or the stream is in async mode.  If this is a 
+                // derived type, it may have overridden Write(byte[], int, int) prior to this Write(ReadOnlySpan<byte>)
+                // overload being introduced.  In that case, this Write(ReadOnlySpan<byte>) overload should use the behavior
+                // of Write(byte[],int,int) overload.  Or if the stream is in async mode, we can't call the
+                // synchronous WriteSpan, so we similarly call the base Write, which will turn delegate to
+                // Write(byte[],int,int), which will do the right thing if we're in async mode.
+                base.Write(buffer);
+            }
+        }
+
+        public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            if (buffer == null)
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (buffer.Length - offset < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen /*, no good single parameter name to pass*/);
+
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Write() or WriteAsync() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Write/WriteAsync) when we are not sure.
+            if (!_useAsyncIO || GetType() != typeof(FileStream))
+                return base.WriteAsync(buffer, offset, count, cancellationToken);
+
+            if (cancellationToken.IsCancellationRequested)
+                return Task.FromCanceled(cancellationToken);
+
+            if (IsClosed)
+                throw Error.GetFileNotOpen();
+
+            return WriteAsyncInternal(new ReadOnlyMemory<byte>(buffer, offset, count), cancellationToken).AsTask();
+        }
+
+        public override ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            if (!_useAsyncIO || GetType() != typeof(FileStream))
+            {
+                // If we're not using async I/O, delegate to the base, which will queue a call to Write.
+                // Or if this isn't a concrete FileStream, a derived type may have overridden WriteAsync(byte[],...),
+                // which was introduced first, so delegate to the base which will delegate to that.
+                return base.WriteAsync(buffer, cancellationToken);
+            }
+
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return new ValueTask(Task.FromCanceled<int>(cancellationToken));
+            }
+
+            if (IsClosed)
+            {
+                throw Error.GetFileNotOpen();
+            }
+
+            return WriteAsyncInternal(buffer, cancellationToken);
+        }
+
+        /// <summary>
+        /// Clears buffers for this stream and causes any buffered data to be written to the file.
+        /// </summary>
+        public override void Flush()
+        {
+            // Make sure that we call through the public virtual API
+            Flush(flushToDisk: false);
+        }
+
+        /// <summary>
+        /// Clears buffers for this stream, and if <param name="flushToDisk"/> is true, 
+        /// causes any buffered data to be written to the file.
+        /// </summary>
+        public virtual void Flush(bool flushToDisk)
+        {
+            if (IsClosed) throw Error.GetFileNotOpen();
+
+            FlushInternalBuffer();
+
+            if (flushToDisk && CanWrite)
+            {
+                FlushOSBuffer();
+            }
+        }
+
+        /// <summary>Gets a value indicating whether the current stream supports reading.</summary>
+        public override bool CanRead
+        {
+            get { return !_fileHandle.IsClosed && (_access & FileAccess.Read) != 0; }
+        }
+
+        /// <summary>Gets a value indicating whether the current stream supports writing.</summary>
+        public override bool CanWrite
+        {
+            get { return !_fileHandle.IsClosed && (_access & FileAccess.Write) != 0; }
+        }
+
+        /// <summary>Validates arguments to Read and Write and throws resulting exceptions.</summary>
+        /// <param name="array">The buffer to read from or write to.</param>
+        /// <param name="offset">The zero-based offset into the array.</param>
+        /// <param name="count">The maximum number of bytes to read or write.</param>
+        private void ValidateReadWriteArgs(byte[] array, int offset, int count)
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array), SR.ArgumentNull_Buffer);
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (array.Length - offset < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen /*, no good single parameter name to pass*/);
+            if (_fileHandle.IsClosed)
+                throw Error.GetFileNotOpen();
+        }
+
+        /// <summary>Sets the length of this stream to the given value.</summary>
+        /// <param name="value">The new length of the stream.</param>
+        public override void SetLength(long value)
+        {
+            if (value < 0)
+                throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (_fileHandle.IsClosed)
+                throw Error.GetFileNotOpen();
+            if (!CanSeek)
+                throw Error.GetSeekNotSupported();
+            if (!CanWrite)
+                throw Error.GetWriteNotSupported();
+
+            SetLengthInternal(value);
+        }
+
+        public virtual SafeFileHandle SafeFileHandle
+        {
+            get
+            {
+                Flush();
+                _exposedHandle = true;
+                return _fileHandle;
+            }
+        }
+
+        /// <summary>Gets the path that was passed to the constructor.</summary>
+        public virtual string Name { get { return _path ?? SR.IO_UnknownFileName; } }
+
+        /// <summary>Gets a value indicating whether the stream was opened for I/O to be performed synchronously or asynchronously.</summary>
+        public virtual bool IsAsync
+        {
+            get { return _useAsyncIO; }
+        }
+
+        /// <summary>Gets the length of the stream in bytes.</summary>
+        public override long Length
+        {
+            get
+            {
+                if (_fileHandle.IsClosed) throw Error.GetFileNotOpen();
+                if (!CanSeek) throw Error.GetSeekNotSupported();
+                return GetLengthInternal();
+            }
+        }
+
+        /// <summary>
+        /// Verify that the actual position of the OS's handle equals what we expect it to.
+        /// This will fail if someone else moved the UnixFileStream's handle or if
+        /// our position updating code is incorrect.
+        /// </summary>
+        private void VerifyOSHandlePosition()
+        {
+            bool verifyPosition = _exposedHandle; // in release, only verify if we've given out the handle such that someone else could be manipulating it
+#if DEBUG
+            verifyPosition = true; // in debug, always make sure our position matches what the OS says it should be
+#endif
+            if (verifyPosition && CanSeek)
+            {
+                long oldPos = _filePosition; // SeekCore will override the current _position, so save it now
+                long curPos = SeekCore(_fileHandle, 0, SeekOrigin.Current);
+                if (oldPos != curPos)
+                {
+                    // For reads, this is non-fatal but we still could have returned corrupted 
+                    // data in some cases, so discard the internal buffer. For writes, 
+                    // this is a problem; discard the buffer and error out.
+                    _readPos = _readLength = 0;
+                    if (_writePos > 0)
+                    {
+                        _writePos = 0;
+                        throw new IOException(SR.IO_FileStreamHandlePosition);
+                    }
+                }
+            }
+        }
+
+        /// <summary>Verifies that state relating to the read/write buffer is consistent.</summary>
+        [Conditional("DEBUG")]
+        private void AssertBufferInvariants()
+        {
+            // Read buffer values must be in range: 0 <= _bufferReadPos <= _bufferReadLength <= _bufferLength
+            Debug.Assert(0 <= _readPos && _readPos <= _readLength && _readLength <= _bufferLength);
+
+            // Write buffer values must be in range: 0 <= _bufferWritePos <= _bufferLength
+            Debug.Assert(0 <= _writePos && _writePos <= _bufferLength);
+
+            // Read buffering and write buffering can't both be active
+            Debug.Assert((_readPos == 0 && _readLength == 0) || _writePos == 0);
+        }
+
+        /// <summary>Validates that we're ready to read from the stream.</summary>
+        private void PrepareForReading()
+        {
+            if (_fileHandle.IsClosed)
+                throw Error.GetFileNotOpen();
+            if (_readLength == 0 && !CanRead)
+                throw Error.GetReadNotSupported();
+
+            AssertBufferInvariants();
+        }
+
+        /// <summary>Gets or sets the position within the current stream</summary>
+        public override long Position
+        {
+            get
+            {
+                if (_fileHandle.IsClosed)
+                    throw Error.GetFileNotOpen();
+
+                if (!CanSeek)
+                    throw Error.GetSeekNotSupported();
+
+                AssertBufferInvariants();
+                VerifyOSHandlePosition();
+
+                // We may have read data into our buffer from the handle, such that the handle position
+                // is artificially further along than the consumer's view of the stream's position.
+                // Thus, when reading, our position is really starting from the handle position negatively
+                // offset by the number of bytes in the buffer and positively offset by the number of
+                // bytes into that buffer we've read.  When writing, both the read length and position
+                // must be zero, and our position is just the handle position offset positive by how many
+                // bytes we've written into the buffer.
+                return (_filePosition - _readLength) + _readPos + _writePos;
+            }
+            set
+            {
+                if (value < 0)
+                    throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+                Seek(value, SeekOrigin.Begin);
+            }
+        }
+
+        internal virtual bool IsClosed => _fileHandle.IsClosed;
+
+        private static bool IsIoRelatedException(Exception e) =>
+            // These all derive from IOException
+            //     DirectoryNotFoundException
+            //     DriveNotFoundException
+            //     EndOfStreamException
+            //     FileLoadException
+            //     FileNotFoundException
+            //     PathTooLongException
+            //     PipeException 
+            e is IOException ||
+            // Note that SecurityException is only thrown on runtimes that support CAS
+            // e is SecurityException || 
+            e is UnauthorizedAccessException ||
+            e is NotSupportedException ||
+            (e is ArgumentException && !(e is ArgumentNullException));
+
+        /// <summary>
+        /// Gets the array used for buffering reading and writing.  
+        /// If the array hasn't been allocated, this will lazily allocate it.
+        /// </summary>
+        /// <returns>The buffer.</returns>
+        private byte[] GetBuffer()
+        {
+            Debug.Assert(_buffer == null || _buffer.Length == _bufferLength);
+            if (_buffer == null)
+            {
+                _buffer = new byte[_bufferLength];
+                OnBufferAllocated();
+            }
+
+            return _buffer;
+        }
+
+        partial void OnBufferAllocated();
+
+        /// <summary>
+        /// Flushes the internal read/write buffer for this stream.  If write data has been buffered,
+        /// that data is written out to the underlying file.  Or if data has been buffered for 
+        /// reading from the stream, the data is dumped and our position in the underlying file 
+        /// is rewound as necessary.  This does not flush the OS buffer.
+        /// </summary>
+        private void FlushInternalBuffer()
+        {
+            AssertBufferInvariants();
+            if (_writePos > 0)
+            {
+                FlushWriteBuffer();
+            }
+            else if (_readPos < _readLength && CanSeek)
+            {
+                FlushReadBuffer();
+            }
+        }
+
+        /// <summary>Dumps any read data in the buffer and rewinds our position in the stream, accordingly, as necessary.</summary>
+        private void FlushReadBuffer()
+        {
+            // Reading is done by blocks from the file, but someone could read
+            // 1 byte from the buffer then write.  At that point, the OS's file
+            // pointer is out of sync with the stream's position.  All write 
+            // functions should call this function to preserve the position in the file.
+
+            AssertBufferInvariants();
+            Debug.Assert(_writePos == 0, "FileStream: Write buffer must be empty in FlushReadBuffer!");
+
+            int rewind = _readPos - _readLength;
+            if (rewind != 0)
+            {
+                Debug.Assert(CanSeek, "FileStream will lose buffered read data now.");
+                SeekCore(_fileHandle, rewind, SeekOrigin.Current);
+            }
+            _readPos = _readLength = 0;
+        }
+
+        /// <summary>
+        /// Reads a byte from the file stream.  Returns the byte cast to an int
+        /// or -1 if reading from the end of the stream.
+        /// </summary>
+        public override int ReadByte()
+        {
+            PrepareForReading();
+
+            byte[] buffer = GetBuffer();
+            if (_readPos == _readLength)
+            {
+                FlushWriteBuffer();
+                _readLength = FillReadBufferForReadByte();
+                _readPos = 0;
+                if (_readLength == 0)
+                {
+                    return -1;
+                }
+            }
+
+            return buffer[_readPos++];
+        }
+
+        /// <summary>
+        /// Writes a byte to the current position in the stream and advances the position
+        /// within the stream by one byte.
+        /// </summary>
+        /// <param name="value">The byte to write to the stream.</param>
+        public override void WriteByte(byte value)
+        {
+            PrepareForWriting();
+
+            // Flush the write buffer if it's full
+            if (_writePos == _bufferLength)
+                FlushWriteBufferForWriteByte();
+
+            // We now have space in the buffer. Store the byte.
+            GetBuffer()[_writePos++] = value;
+        }
+
+        /// <summary>
+        /// Validates that we're ready to write to the stream,
+        /// including flushing a read buffer if necessary.
+        /// </summary>
+        private void PrepareForWriting()
+        {
+            if (_fileHandle.IsClosed)
+                throw Error.GetFileNotOpen();
+
+            // Make sure we're good to write.  We only need to do this if there's nothing already
+            // in our write buffer, since if there is something in the buffer, we've already done 
+            // this checking and flushing.
+            if (_writePos == 0)
+            {
+                if (!CanWrite) throw Error.GetWriteNotSupported();
+                FlushReadBuffer();
+                Debug.Assert(_bufferLength > 0, "_bufferSize > 0");
+            }
+        }
+
+        ~FileStream()
+        {
+            // Preserved for compatibility since FileStream has defined a 
+            // finalizer in past releases and derived classes may depend
+            // on Dispose(false) call.
+            Dispose(false);
+        }
+
+        public override IAsyncResult BeginRead(byte[] array, int offset, int numBytes, AsyncCallback callback, object state)
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array));
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (numBytes < 0)
+                throw new ArgumentOutOfRangeException(nameof(numBytes), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (array.Length - offset < numBytes)
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+            if (IsClosed) throw new ObjectDisposedException(SR.ObjectDisposed_FileClosed);
+            if (!CanRead) throw new NotSupportedException(SR.NotSupported_UnreadableStream);
+
+            if (!IsAsync)
+                return base.BeginRead(array, offset, numBytes, callback, state);
+            else
+                return TaskToApm.Begin(ReadAsyncTask(array, offset, numBytes, CancellationToken.None), callback, state);
+        }
+
+        public override IAsyncResult BeginWrite(byte[] array, int offset, int numBytes, AsyncCallback callback, object state)
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array));
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (numBytes < 0)
+                throw new ArgumentOutOfRangeException(nameof(numBytes), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (array.Length - offset < numBytes)
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+            if (IsClosed) throw new ObjectDisposedException(SR.ObjectDisposed_FileClosed);
+            if (!CanWrite) throw new NotSupportedException(SR.NotSupported_UnwritableStream);
+
+            if (!IsAsync)
+                return base.BeginWrite(array, offset, numBytes, callback, state);
+            else
+                return TaskToApm.Begin(WriteAsyncInternal(new ReadOnlyMemory<byte>(array, offset, numBytes), CancellationToken.None).AsTask(), callback, state);
+        }
+
+        public override int EndRead(IAsyncResult asyncResult)
+        {
+            if (asyncResult == null)
+                throw new ArgumentNullException(nameof(asyncResult));
+
+            if (!IsAsync)
+                return base.EndRead(asyncResult);
+            else
+                return TaskToApm.End<int>(asyncResult);
+        }
+
+        public override void EndWrite(IAsyncResult asyncResult)
+        {
+            if (asyncResult == null)
+                throw new ArgumentNullException(nameof(asyncResult));
+
+            if (!IsAsync)
+                base.EndWrite(asyncResult);
+            else
+                TaskToApm.End(asyncResult);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/FileStreamCompletionSource.Win32.cs b/src/System.Private.CoreLib/shared/System/IO/FileStreamCompletionSource.Win32.cs
new file mode 100644
index 0000000000..62ace0918d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/FileStreamCompletionSource.Win32.cs
@@ -0,0 +1,259 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Buffers;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.IO
+{
+    public partial class FileStream : Stream
+    {
+        // This is an internal object extending TaskCompletionSource with fields
+        // for all of the relevant data necessary to complete the IO operation.
+        // This is used by IOCallback and all of the async methods.
+        private unsafe class FileStreamCompletionSource : TaskCompletionSource<int>
+        {
+            private const long NoResult = 0;
+            private const long ResultSuccess = (long)1 << 32;
+            private const long ResultError = (long)2 << 32;
+            private const long RegisteringCancellation = (long)4 << 32;
+            private const long CompletedCallback = (long)8 << 32;
+            private const ulong ResultMask = ((ulong)uint.MaxValue) << 32;
+
+            private static Action<object> s_cancelCallback;
+
+            private readonly FileStream _stream;
+            private readonly int _numBufferedBytes;
+            private CancellationTokenRegistration _cancellationRegistration;
+#if DEBUG
+            private bool _cancellationHasBeenRegistered;
+#endif
+            private NativeOverlapped* _overlapped; // Overlapped class responsible for operations in progress when an appdomain unload occurs
+            private long _result; // Using long since this needs to be used in Interlocked APIs
+
+            // Using RunContinuationsAsynchronously for compat reasons (old API used Task.Factory.StartNew for continuations)
+            protected FileStreamCompletionSource(FileStream stream, int numBufferedBytes, byte[] bytes)
+                : base(TaskCreationOptions.RunContinuationsAsynchronously)
+            {
+                _numBufferedBytes = numBufferedBytes;
+                _stream = stream;
+                _result = NoResult;
+
+                // Create the native overlapped. We try to use the preallocated overlapped if possible: it's possible if the byte
+                // buffer is null (there's nothing to pin) or the same one that's associated with the preallocated overlapped (and
+                // thus is already pinned) and if no one else is currently using the preallocated overlapped.  This is the fast-path
+                // for cases where the user-provided buffer is smaller than the FileStream's buffer (such that the FileStream's
+                // buffer is used) and where operations on the FileStream are not being performed concurrently.
+                Debug.Assert((bytes == null || ReferenceEquals(bytes, _stream._buffer)));
+
+                // The _preallocatedOverlapped is null if the internal buffer was never created, so we check for 
+                // a non-null bytes before using the stream's _preallocatedOverlapped
+                _overlapped = bytes != null && _stream.CompareExchangeCurrentOverlappedOwner(this, null) == null ?
+                    _stream._fileHandle.ThreadPoolBinding.AllocateNativeOverlapped(_stream._preallocatedOverlapped) :
+                    _stream._fileHandle.ThreadPoolBinding.AllocateNativeOverlapped(s_ioCallback, this, bytes);
+                Debug.Assert(_overlapped != null, "AllocateNativeOverlapped returned null");
+            }
+
+            internal NativeOverlapped* Overlapped
+            {
+                get { return _overlapped; }
+            }
+
+            public void SetCompletedSynchronously(int numBytes)
+            {
+                ReleaseNativeResource();
+                TrySetResult(numBytes + _numBufferedBytes);
+            }
+
+            public void RegisterForCancellation(CancellationToken cancellationToken)
+            {
+#if DEBUG
+                Debug.Assert(cancellationToken.CanBeCanceled);
+                Debug.Assert(!_cancellationHasBeenRegistered, "Cannot register for cancellation twice");
+                _cancellationHasBeenRegistered = true;
+#endif
+
+                // Quick check to make sure the IO hasn't completed
+                if (_overlapped != null)
+                {
+                    var cancelCallback = s_cancelCallback;
+                    if (cancelCallback == null) s_cancelCallback = cancelCallback = Cancel;
+
+                    // Register the cancellation only if the IO hasn't completed
+                    long packedResult = Interlocked.CompareExchange(ref _result, RegisteringCancellation, NoResult);
+                    if (packedResult == NoResult)
+                    {
+                        _cancellationRegistration = cancellationToken.Register(cancelCallback, this);
+
+                        // Switch the result, just in case IO completed while we were setting the registration
+                        packedResult = Interlocked.Exchange(ref _result, NoResult);
+                    }
+                    else if (packedResult != CompletedCallback)
+                    {
+                        // Failed to set the result, IO is in the process of completing
+                        // Attempt to take the packed result
+                        packedResult = Interlocked.Exchange(ref _result, NoResult);
+                    }
+
+                    // If we have a callback that needs to be completed
+                    if ((packedResult != NoResult) && (packedResult != CompletedCallback) && (packedResult != RegisteringCancellation))
+                    {
+                        CompleteCallback((ulong)packedResult);
+                    }
+                }
+            }
+
+            internal virtual void ReleaseNativeResource()
+            {
+                // Ensure that cancellation has been completed and cleaned up.
+                _cancellationRegistration.Dispose();
+
+                // Free the overlapped.
+                // NOTE: The cancellation must *NOT* be running at this point, or it may observe freed memory
+                // (this is why we disposed the registration above).
+                if (_overlapped != null)
+                {
+                    _stream._fileHandle.ThreadPoolBinding.FreeNativeOverlapped(_overlapped);
+                    _overlapped = null;
+                }
+
+                // Ensure we're no longer set as the current completion source (we may not have been to begin with).
+                // Only one operation at a time is eligible to use the preallocated overlapped, 
+                _stream.CompareExchangeCurrentOverlappedOwner(null, this);
+            }
+
+            // When doing IO asynchronously (i.e. _isAsync==true), this callback is 
+            // called by a free thread in the threadpool when the IO operation 
+            // completes.  
+            internal static unsafe void IOCallback(uint errorCode, uint numBytes, NativeOverlapped* pOverlapped)
+            {
+                // Extract the completion source from the overlapped.  The state in the overlapped
+                // will either be a Win32FileStream (in the case where the preallocated overlapped was used),
+                // in which case the operation being completed is its _currentOverlappedOwner, or it'll
+                // be directly the FileStreamCompletion that's completing (in the case where the preallocated
+                // overlapped was already in use by another operation).
+                object state = ThreadPoolBoundHandle.GetNativeOverlappedState(pOverlapped);
+                FileStream fs = state as FileStream;
+                FileStreamCompletionSource completionSource = fs != null ?
+                    fs._currentOverlappedOwner :
+                    (FileStreamCompletionSource)state;
+                Debug.Assert(completionSource._overlapped == pOverlapped, "Overlaps don't match");
+
+                // Handle reading from & writing to closed pipes.  While I'm not sure
+                // this is entirely necessary anymore, maybe it's possible for 
+                // an async read on a pipe to be issued and then the pipe is closed, 
+                // returning this error.  This may very well be necessary.
+                ulong packedResult;
+                if (errorCode != 0 && errorCode != ERROR_BROKEN_PIPE && errorCode != ERROR_NO_DATA)
+                {
+                    packedResult = ((ulong)ResultError | errorCode);
+                }
+                else
+                {
+                    packedResult = ((ulong)ResultSuccess | numBytes);
+                }
+
+                // Stow the result so that other threads can observe it
+                // And, if no other thread is registering cancellation, continue
+                if (NoResult == Interlocked.Exchange(ref completionSource._result, (long)packedResult))
+                {
+                    // Successfully set the state, attempt to take back the callback
+                    if (Interlocked.Exchange(ref completionSource._result, CompletedCallback) != NoResult)
+                    {
+                        // Successfully got the callback, finish the callback
+                        completionSource.CompleteCallback(packedResult);
+                    }
+                    // else: Some other thread stole the result, so now it is responsible to finish the callback
+                }
+                // else: Some other thread is registering a cancellation, so it *must* finish the callback
+            }
+
+            private void CompleteCallback(ulong packedResult)
+            {
+                // Free up the native resource and cancellation registration
+                CancellationToken cancellationToken = _cancellationRegistration.Token; // access before disposing registration
+                ReleaseNativeResource();
+
+                // Unpack the result and send it to the user
+                long result = (long)(packedResult & ResultMask);
+                if (result == ResultError)
+                {
+                    int errorCode = unchecked((int)(packedResult & uint.MaxValue));
+                    if (errorCode == Interop.Errors.ERROR_OPERATION_ABORTED)
+                    {
+                        TrySetCanceled(cancellationToken.IsCancellationRequested ? cancellationToken : new CancellationToken(true));
+                    }
+                    else
+                    {
+                        TrySetException(Win32Marshal.GetExceptionForWin32Error(errorCode));
+                    }
+                }
+                else
+                {
+                    Debug.Assert(result == ResultSuccess, "Unknown result");
+                    TrySetResult((int)(packedResult & uint.MaxValue) + _numBufferedBytes);
+                }
+            }
+
+            private static void Cancel(object state)
+            {
+                // WARNING: This may potentially be called under a lock (during cancellation registration)
+
+                FileStreamCompletionSource completionSource = state as FileStreamCompletionSource;
+                Debug.Assert(completionSource != null, "Unknown state passed to cancellation");
+                Debug.Assert(completionSource._overlapped != null && !completionSource.Task.IsCompleted, "IO should not have completed yet");
+
+                // If the handle is still valid, attempt to cancel the IO
+                if (!completionSource._stream._fileHandle.IsInvalid &&
+                    !Interop.Kernel32.CancelIoEx(completionSource._stream._fileHandle, completionSource._overlapped))
+                {
+                    int errorCode = Marshal.GetLastWin32Error();
+
+                    // ERROR_NOT_FOUND is returned if CancelIoEx cannot find the request to cancel.
+                    // This probably means that the IO operation has completed.
+                    if (errorCode != Interop.Errors.ERROR_NOT_FOUND)
+                    {
+                        throw Win32Marshal.GetExceptionForWin32Error(errorCode);
+                    }
+                }
+            }
+
+            public static FileStreamCompletionSource Create(FileStream stream, int numBufferedBytesRead, ReadOnlyMemory<byte> memory)
+            {
+                // If the memory passed in is the stream's internal buffer, we can use the base FileStreamCompletionSource,
+                // which has a PreAllocatedOverlapped with the memory already pinned.  Otherwise, we use the derived
+                // MemoryFileStreamCompletionSource, which Retains the memory, which will result in less pinning in the case
+                // where the underlying memory is backed by pre-pinned buffers.
+                return MemoryMarshal.TryGetArray(memory, out ArraySegment<byte> buffer) && ReferenceEquals(buffer.Array, stream._buffer) ?
+                    new FileStreamCompletionSource(stream, numBufferedBytesRead, buffer.Array) :
+                    new MemoryFileStreamCompletionSource(stream, numBufferedBytesRead, memory);
+            }
+        }
+
+        /// <summary>
+        /// Extends <see cref="FileStreamCompletionSource"/> with to support disposing of a
+        /// <see cref="MemoryHandle"/> when the operation has completed.  This should only be used
+        /// when memory doesn't wrap a byte[].
+        /// </summary>
+        private sealed class MemoryFileStreamCompletionSource : FileStreamCompletionSource
+        {
+            private MemoryHandle _handle; // mutable struct; do not make this readonly
+
+            internal MemoryFileStreamCompletionSource(FileStream stream, int numBufferedBytes, ReadOnlyMemory<byte> memory) :
+                base(stream, numBufferedBytes, bytes: null) // this type handles the pinning, so null is passed for bytes
+            {
+                _handle = memory.Pin();
+            }
+
+            internal override void ReleaseNativeResource()
+            {
+                _handle.Dispose();
+                base.ReleaseNativeResource();
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/IOException.cs b/src/System.Private.CoreLib/shared/System/IO/IOException.cs
new file mode 100644
index 0000000000..89b25d5142
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/IOException.cs
@@ -0,0 +1,42 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System.IO
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class IOException : SystemException
+    {
+        public IOException()
+            : base(SR.Arg_IOException)
+        {
+            HResult = HResults.COR_E_IO;
+        }
+
+        public IOException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_IO;
+        }
+
+        public IOException(String message, int hresult)
+            : base(message)
+        {
+            HResult = hresult;
+        }
+
+        public IOException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_IO;
+        }
+
+        protected IOException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/MemoryStream.cs b/src/System.Private.CoreLib/shared/System/IO/MemoryStream.cs
new file mode 100644
index 0000000000..fb319de7c2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/MemoryStream.cs
@@ -0,0 +1,823 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.IO
+{
+    // A MemoryStream represents a Stream in memory (ie, it has no backing store).
+    // This stream may reduce the need for temporary buffers and files in 
+    // an application.  
+    // 
+    // There are two ways to create a MemoryStream.  You can initialize one
+    // from an unsigned byte array, or you can create an empty one.  Empty 
+    // memory streams are resizable, while ones created with a byte array provide
+    // a stream "view" of the data.
+    public class MemoryStream : Stream
+    {
+        private byte[] _buffer;    // Either allocated internally or externally.
+        private int _origin;       // For user-provided arrays, start at this origin
+        private int _position;     // read/write head.
+        private int _length;       // Number of bytes within the memory stream
+        private int _capacity;     // length of usable portion of buffer for stream
+        // Note that _capacity == _buffer.Length for non-user-provided byte[]'s
+
+        private bool _expandable;  // User-provided buffers aren't expandable.
+        private bool _writable;    // Can user write to this stream?
+        private bool _exposable;   // Whether the array can be returned to the user.
+        private bool _isOpen;      // Is this stream open or closed?
+
+        private Task<int> _lastReadTask; // The last successful task returned from ReadAsync
+
+        private const int MemStreamMaxLength = int.MaxValue;
+
+        public MemoryStream()
+            : this(0)
+        {
+        }
+
+        public MemoryStream(int capacity)
+        {
+            if (capacity < 0)
+                throw new ArgumentOutOfRangeException(nameof(capacity), SR.ArgumentOutOfRange_NegativeCapacity);
+
+            _buffer = capacity != 0 ? new byte[capacity] : Array.Empty<byte>();
+            _capacity = capacity;
+            _expandable = true;
+            _writable = true;
+            _exposable = true;
+            _origin = 0;      // Must be 0 for byte[]'s created by MemoryStream
+            _isOpen = true;
+        }
+
+        public MemoryStream(byte[] buffer)
+            : this(buffer, true)
+        {
+        }
+
+        public MemoryStream(byte[] buffer, bool writable)
+        {
+            if (buffer == null)
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+
+            _buffer = buffer;
+            _length = _capacity = buffer.Length;
+            _writable = writable;
+            _exposable = false;
+            _origin = 0;
+            _isOpen = true;
+        }
+
+        public MemoryStream(byte[] buffer, int index, int count)
+            : this(buffer, index, count, true, false)
+        {
+        }
+
+        public MemoryStream(byte[] buffer, int index, int count, bool writable)
+            : this(buffer, index, count, writable, false)
+        {
+        }
+
+        public MemoryStream(byte[] buffer, int index, int count, bool writable, bool publiclyVisible)
+        {
+            if (buffer == null)
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (buffer.Length - index < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+            _buffer = buffer;
+            _origin = _position = index;
+            _length = _capacity = index + count;
+            _writable = writable;
+            _exposable = publiclyVisible;  // Can TryGetBuffer/GetBuffer return the array?
+            _expandable = false;
+            _isOpen = true;
+        }
+
+        public override bool CanRead => _isOpen;
+
+        public override bool CanSeek => _isOpen;
+
+        public override bool CanWrite => _writable;
+
+        private void EnsureNotClosed()
+        {
+            if (!_isOpen)
+                throw Error.GetStreamIsClosed();
+        }
+
+        private void EnsureWriteable()
+        {
+            if (!CanWrite)
+                throw Error.GetWriteNotSupported();
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            try
+            {
+                if (disposing)
+                {
+                    _isOpen = false;
+                    _writable = false;
+                    _expandable = false;
+                    // Don't set buffer to null - allow TryGetBuffer, GetBuffer & ToArray to work.
+                    _lastReadTask = null;
+                }
+            }
+            finally
+            {
+                // Call base.Close() to cleanup async IO resources
+                base.Dispose(disposing);
+            }
+        }
+
+        // returns a bool saying whether we allocated a new array.
+        private bool EnsureCapacity(int value)
+        {
+            // Check for overflow
+            if (value < 0)
+                throw new IOException(SR.IO_StreamTooLong);
+
+            if (value > _capacity)
+            {
+                int newCapacity = value;
+                if (newCapacity < 256)
+                {
+                    newCapacity = 256;
+                }
+
+                // We are ok with this overflowing since the next statement will deal
+                // with the cases where _capacity*2 overflows.
+                if (newCapacity < _capacity * 2)
+                {
+                    newCapacity = _capacity * 2;
+                }
+
+                // We want to expand the array up to Array.MaxByteArrayLength
+                // And we want to give the user the value that they asked for
+                if ((uint)(_capacity * 2) > Array.MaxByteArrayLength)
+                {
+                    newCapacity = value > Array.MaxByteArrayLength ? value : Array.MaxByteArrayLength;
+                }
+
+                Capacity = newCapacity;
+                return true;
+            }
+            return false;
+        }
+
+        public override void Flush()
+        {
+        }
+
+        public override Task FlushAsync(CancellationToken cancellationToken)
+        {
+            if (cancellationToken.IsCancellationRequested)
+                return Task.FromCanceled(cancellationToken);
+
+            try
+            {
+                Flush();
+                return Task.CompletedTask;
+            }
+            catch (Exception ex)
+            {
+                return Task.FromException(ex);
+            }
+        }
+
+
+        public virtual byte[] GetBuffer()
+        {
+            if (!_exposable)
+                throw new UnauthorizedAccessException(SR.UnauthorizedAccess_MemStreamBuffer);
+            return _buffer;
+        }
+
+        public virtual bool TryGetBuffer(out ArraySegment<byte> buffer)
+        {
+            if (!_exposable)
+            {
+                buffer = default(ArraySegment<byte>);
+                return false;
+            }
+
+            buffer = new ArraySegment<byte>(_buffer, offset: _origin, count: (_length - _origin));
+            return true;
+        }
+
+        // -------------- PERF: Internal functions for fast direct access of MemoryStream buffer (cf. BinaryReader for usage) ---------------
+
+        // PERF: Internal sibling of GetBuffer, always returns a buffer (cf. GetBuffer())
+        internal byte[] InternalGetBuffer()
+        {
+            return _buffer;
+        }
+
+        // PERF: True cursor position, we don't need _origin for direct access
+        internal int InternalGetPosition()
+        {
+            return _position;
+        }
+
+        // PERF: Takes out Int32 as fast as possible
+        internal int InternalReadInt32()
+        {
+            EnsureNotClosed();
+
+            int pos = (_position += 4); // use temp to avoid a race condition
+            if (pos > _length)
+            {
+                _position = _length;
+                throw Error.GetEndOfFile();
+            }
+            return (int)(_buffer[pos - 4] | _buffer[pos - 3] << 8 | _buffer[pos - 2] << 16 | _buffer[pos - 1] << 24);
+        }
+
+        // PERF: Get actual length of bytes available for read; do sanity checks; shift position - i.e. everything except actual copying bytes
+        internal int InternalEmulateRead(int count)
+        {
+            EnsureNotClosed();
+
+            int n = _length - _position;
+            if (n > count)
+                n = count;
+            if (n < 0)
+                n = 0;
+
+            Debug.Assert(_position + n >= 0, "_position + n >= 0");  // len is less than 2^31 -1.
+            _position += n;
+            return n;
+        }
+
+        // Gets & sets the capacity (number of bytes allocated) for this stream.
+        // The capacity cannot be set to a value less than the current length
+        // of the stream.
+        // 
+        public virtual int Capacity
+        {
+            get
+            {
+                EnsureNotClosed();
+                return _capacity - _origin;
+            }
+            set
+            {
+                // Only update the capacity if the MS is expandable and the value is different than the current capacity.
+                // Special behavior if the MS isn't expandable: we don't throw if value is the same as the current capacity
+                if (value < Length)
+                    throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_SmallCapacity);
+
+                EnsureNotClosed();
+
+                if (!_expandable && (value != Capacity))
+                    throw new NotSupportedException(SR.NotSupported_MemStreamNotExpandable);
+
+                // MemoryStream has this invariant: _origin > 0 => !expandable (see ctors)
+                if (_expandable && value != _capacity)
+                {
+                    if (value > 0)
+                    {
+                        byte[] newBuffer = new byte[value];
+                        if (_length > 0)
+                        {
+                            Buffer.BlockCopy(_buffer, 0, newBuffer, 0, _length);
+                        }
+                        _buffer = newBuffer;
+                    }
+                    else
+                    {
+                        _buffer = null;
+                    }
+                    _capacity = value;
+                }
+            }
+        }
+
+        public override long Length
+        {
+            get
+            {
+                EnsureNotClosed();
+                return _length - _origin;
+            }
+        }
+
+        public override long Position
+        {
+            get
+            {
+                EnsureNotClosed();
+                return _position - _origin;
+            }
+            set
+            {
+                if (value < 0)
+                    throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+                EnsureNotClosed();
+
+                if (value > MemStreamMaxLength)
+                    throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_StreamLength);
+                _position = _origin + (int)value;
+            }
+        }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            if (buffer == null)
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (buffer.Length - offset < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+            EnsureNotClosed();
+
+            int n = _length - _position;
+            if (n > count)
+                n = count;
+            if (n <= 0)
+                return 0;
+
+            Debug.Assert(_position + n >= 0, "_position + n >= 0");  // len is less than 2^31 -1.
+
+            if (n <= 8)
+            {
+                int byteCount = n;
+                while (--byteCount >= 0)
+                    buffer[offset + byteCount] = _buffer[_position + byteCount];
+            }
+            else
+                Buffer.BlockCopy(_buffer, _position, buffer, offset, n);
+            _position += n;
+
+            return n;
+        }
+
+        public override int Read(Span<byte> buffer)
+        {
+            if (GetType() != typeof(MemoryStream))
+            {
+                // MemoryStream is not sealed, and a derived type may have overridden Read(byte[], int, int) prior
+                // to this Read(Span<byte>) overload being introduced.  In that case, this Read(Span<byte>) overload
+                // should use the behavior of Read(byte[],int,int) overload.
+                return base.Read(buffer);
+            }
+
+            EnsureNotClosed();
+
+            int n = Math.Min(_length - _position, buffer.Length);
+            if (n <= 0)
+                return 0;
+
+            // TODO https://github.com/dotnet/coreclr/issues/15076:
+            // Read(byte[], int, int) has an n <= 8 optimization, presumably based
+            // on benchmarking.  Determine if/where such a cut-off is here and add
+            // an equivalent optimization if necessary.
+            new Span<byte>(_buffer, _position, n).CopyTo(buffer);
+
+            _position += n;
+            return n;
+        }
+
+        public override Task<int> ReadAsync(Byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            if (buffer == null)
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (buffer.Length - offset < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+            // If cancellation was requested, bail early
+            if (cancellationToken.IsCancellationRequested)
+                return Task.FromCanceled<int>(cancellationToken);
+
+            try
+            {
+                int n = Read(buffer, offset, count);
+                var t = _lastReadTask;
+                Debug.Assert(t == null || t.Status == TaskStatus.RanToCompletion,
+                    "Expected that a stored last task completed successfully");
+                return (t != null && t.Result == n) ? t : (_lastReadTask = Task.FromResult<int>(n));
+            }
+            catch (OperationCanceledException oce)
+            {
+                return Task.FromCancellation<int>(oce);
+            }
+            catch (Exception exception)
+            {
+                return Task.FromException<int>(exception);
+            }
+        }
+
+        public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return new ValueTask<int>(Task.FromCanceled<int>(cancellationToken));
+            }
+
+            try
+            {
+                // ReadAsync(Memory<byte>,...) needs to delegate to an existing virtual to do the work, in case an existing derived type
+                // has changed or augmented the logic associated with reads.  If the Memory wraps an array, we could delegate to
+                // ReadAsync(byte[], ...), but that would defeat part of the purpose, as ReadAsync(byte[], ...) often needs to allocate
+                // a Task<int> for the return value, so we want to delegate to one of the synchronous methods.  We could always
+                // delegate to the Read(Span<byte>) method, and that's the most efficient solution when dealing with a concrete
+                // MemoryStream, but if we're dealing with a type derived from MemoryStream, Read(Span<byte>) will end up delegating
+                // to Read(byte[], ...), which requires it to get a byte[] from ArrayPool and copy the data.  So, we special-case the
+                // very common case of the Memory<byte> wrapping an array: if it does, we delegate to Read(byte[], ...) with it,
+                // as that will be efficient in both cases, and we fall back to Read(Span<byte>) if the Memory<byte> wrapped something
+                // else; if this is a concrete MemoryStream, that'll be efficient, and only in the case where the Memory<byte> wrapped
+                // something other than an array and this is a MemoryStream-derived type that doesn't override Read(Span<byte>) will
+                // it then fall back to doing the ArrayPool/copy behavior.
+                return new ValueTask<int>(
+                    MemoryMarshal.TryGetArray(buffer, out ArraySegment<byte> destinationArray) ?
+                        Read(destinationArray.Array, destinationArray.Offset, destinationArray.Count) :
+                        Read(buffer.Span));
+            }
+            catch (OperationCanceledException oce)
+            {
+                return new ValueTask<int>(Task.FromCancellation<int>(oce));
+            }
+            catch (Exception exception)
+            {
+                return new ValueTask<int>(Task.FromException<int>(exception));
+            }
+        }
+
+        public override int ReadByte()
+        {
+            EnsureNotClosed();
+
+            if (_position >= _length)
+                return -1;
+
+            return _buffer[_position++];
+        }
+
+        public override void CopyTo(Stream destination, int bufferSize)
+        {
+            // Since we did not originally override this method, validate the arguments
+            // the same way Stream does for back-compat.
+            StreamHelpers.ValidateCopyToArgs(this, destination, bufferSize);
+
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Read() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Read) when we are not sure.
+            if (GetType() != typeof(MemoryStream))
+            {
+                base.CopyTo(destination, bufferSize);
+                return;
+            }
+
+            int originalPosition = _position;
+
+            // Seek to the end of the MemoryStream.
+            int remaining = InternalEmulateRead(_length - originalPosition);
+
+            // If we were already at or past the end, there's no copying to do so just quit.
+            if (remaining > 0)
+            {
+                // Call Write() on the other Stream, using our internal buffer and avoiding any
+                // intermediary allocations.
+                destination.Write(_buffer, originalPosition, remaining);
+            }
+        }
+
+        public override Task CopyToAsync(Stream destination, int bufferSize, CancellationToken cancellationToken)
+        {
+            // This implementation offers better performance compared to the base class version.
+
+            StreamHelpers.ValidateCopyToArgs(this, destination, bufferSize);
+
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to ReadAsync() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into ReadAsync) when we are not sure.
+            if (GetType() != typeof(MemoryStream))
+                return base.CopyToAsync(destination, bufferSize, cancellationToken);
+
+            // If cancelled - return fast:
+            if (cancellationToken.IsCancellationRequested)
+                return Task.FromCanceled(cancellationToken);
+
+            // Avoid copying data from this buffer into a temp buffer:
+            //   (require that InternalEmulateRead does not throw,
+            //    otherwise it needs to be wrapped into try-catch-Task.FromException like memStrDest.Write below)
+
+            int pos = _position;
+            int n = InternalEmulateRead(_length - _position);
+
+            // If we were already at or past the end, there's no copying to do so just quit.
+            if (n == 0)
+                return Task.CompletedTask;
+
+            // If destination is not a memory stream, write there asynchronously:
+            MemoryStream memStrDest = destination as MemoryStream;
+            if (memStrDest == null)
+                return destination.WriteAsync(_buffer, pos, n, cancellationToken);
+
+            try
+            {
+                // If destination is a MemoryStream, CopyTo synchronously:
+                memStrDest.Write(_buffer, pos, n);
+                return Task.CompletedTask;
+            }
+            catch (Exception ex)
+            {
+                return Task.FromException(ex);
+            }
+        }
+
+
+        public override long Seek(long offset, SeekOrigin loc)
+        {
+            EnsureNotClosed();
+
+            if (offset > MemStreamMaxLength)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_StreamLength);
+
+            switch (loc)
+            {
+                case SeekOrigin.Begin:
+                    {
+                        int tempPosition = unchecked(_origin + (int)offset);
+                        if (offset < 0 || tempPosition < _origin)
+                            throw new IOException(SR.IO_SeekBeforeBegin);
+                        _position = tempPosition;
+                        break;
+                    }
+                case SeekOrigin.Current:
+                    {
+                        int tempPosition = unchecked(_position + (int)offset);
+                        if (unchecked(_position + offset) < _origin || tempPosition < _origin)
+                            throw new IOException(SR.IO_SeekBeforeBegin);
+                        _position = tempPosition;
+                        break;
+                    }
+                case SeekOrigin.End:
+                    {
+                        int tempPosition = unchecked(_length + (int)offset);
+                        if (unchecked(_length + offset) < _origin || tempPosition < _origin)
+                            throw new IOException(SR.IO_SeekBeforeBegin);
+                        _position = tempPosition;
+                        break;
+                    }
+                default:
+                    throw new ArgumentException(SR.Argument_InvalidSeekOrigin);
+            }
+
+            Debug.Assert(_position >= 0, "_position >= 0");
+            return _position;
+        }
+
+        // Sets the length of the stream to a given value.  The new
+        // value must be nonnegative and less than the space remaining in
+        // the array, int.MaxValue - origin
+        // Origin is 0 in all cases other than a MemoryStream created on
+        // top of an existing array and a specific starting offset was passed 
+        // into the MemoryStream constructor.  The upper bounds prevents any 
+        // situations where a stream may be created on top of an array then 
+        // the stream is made longer than the maximum possible length of the 
+        // array (int.MaxValue).
+        // 
+        public override void SetLength(long value)
+        {
+            if (value < 0 || value > int.MaxValue)
+                throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_StreamLength);
+
+            EnsureWriteable();
+
+            // Origin wasn't publicly exposed above.
+            Debug.Assert(MemStreamMaxLength == int.MaxValue);  // Check parameter validation logic in this method if this fails.
+            if (value > (int.MaxValue - _origin))
+                throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_StreamLength);
+
+            int newLength = _origin + (int)value;
+            bool allocatedNewArray = EnsureCapacity(newLength);
+            if (!allocatedNewArray && newLength > _length)
+                Array.Clear(_buffer, _length, newLength - _length);
+            _length = newLength;
+            if (_position > newLength)
+                _position = newLength;
+        }
+
+        public virtual byte[] ToArray()
+        {
+            int count = _length - _origin;
+            if (count == 0)
+                return Array.Empty<byte>();
+            byte[] copy = new byte[count];
+            Buffer.BlockCopy(_buffer, _origin, copy, 0, count);
+            return copy;
+        }
+
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            if (buffer == null)
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (buffer.Length - offset < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+            EnsureNotClosed();
+            EnsureWriteable();
+
+            int i = _position + count;
+            // Check for overflow
+            if (i < 0)
+                throw new IOException(SR.IO_StreamTooLong);
+
+            if (i > _length)
+            {
+                bool mustZero = _position > _length;
+                if (i > _capacity)
+                {
+                    bool allocatedNewArray = EnsureCapacity(i);
+                    if (allocatedNewArray)
+                    {
+                        mustZero = false;
+                    }
+                }
+                if (mustZero)
+                {
+                    Array.Clear(_buffer, _length, i - _length);
+                }
+                _length = i;
+            }
+            if ((count <= 8) && (buffer != _buffer))
+            {
+                int byteCount = count;
+                while (--byteCount >= 0)
+                {
+                    _buffer[_position + byteCount] = buffer[offset + byteCount];
+                }
+            }
+            else
+            {
+                Buffer.BlockCopy(buffer, offset, _buffer, _position, count);
+            }
+            _position = i;
+        }
+
+        public override void Write(ReadOnlySpan<byte> buffer)
+        {
+            if (GetType() != typeof(MemoryStream))
+            {
+                // MemoryStream is not sealed, and a derived type may have overridden Write(byte[], int, int) prior
+                // to this Write(Span<byte>) overload being introduced.  In that case, this Write(Span<byte>) overload
+                // should use the behavior of Write(byte[],int,int) overload.
+                base.Write(buffer);
+                return;
+            }
+
+            EnsureNotClosed();
+            EnsureWriteable();
+
+            // Check for overflow
+            int i = _position + buffer.Length;
+            if (i < 0)
+                throw new IOException(SR.IO_StreamTooLong);
+
+            if (i > _length)
+            {
+                bool mustZero = _position > _length;
+                if (i > _capacity)
+                {
+                    bool allocatedNewArray = EnsureCapacity(i);
+                    if (allocatedNewArray)
+                    {
+                        mustZero = false;
+                    }
+                }
+                if (mustZero)
+                {
+                    Array.Clear(_buffer, _length, i - _length);
+                }
+                _length = i;
+            }
+
+            buffer.CopyTo(new Span<byte>(_buffer, _position, buffer.Length));
+            _position = i;
+        }
+
+        public override Task WriteAsync(Byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            if (buffer == null)
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (buffer.Length - offset < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+            // If cancellation is already requested, bail early
+            if (cancellationToken.IsCancellationRequested)
+                return Task.FromCanceled(cancellationToken);
+
+            try
+            {
+                Write(buffer, offset, count);
+                return Task.CompletedTask;
+            }
+            catch (OperationCanceledException oce)
+            {
+                return Task.FromCancellation<VoidTaskResult>(oce);
+            }
+            catch (Exception exception)
+            {
+                return Task.FromException(exception);
+            }
+        }
+
+        public override ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return new ValueTask(Task.FromCanceled(cancellationToken));
+            }
+
+            try
+            {
+                // See corresponding comment in ReadAsync for why we don't just always use Write(ReadOnlySpan<byte>).
+                // Unlike ReadAsync, we could delegate to WriteAsync(byte[], ...) here, but we don't for consistency.
+                if (MemoryMarshal.TryGetArray(buffer, out ArraySegment<byte> sourceArray))
+                {
+                    Write(sourceArray.Array, sourceArray.Offset, sourceArray.Count);
+                }
+                else
+                {
+                    Write(buffer.Span);
+                }
+                return default;
+            }
+            catch (OperationCanceledException oce)
+            {
+                return new ValueTask(Task.FromCancellation<VoidTaskResult>(oce));
+            }
+            catch (Exception exception)
+            {
+                return new ValueTask(Task.FromException(exception));
+            }
+        }
+
+        public override void WriteByte(byte value)
+        {
+            EnsureNotClosed();
+            EnsureWriteable();
+
+            if (_position >= _length)
+            {
+                int newLength = _position + 1;
+                bool mustZero = _position > _length;
+                if (newLength >= _capacity)
+                {
+                    bool allocatedNewArray = EnsureCapacity(newLength);
+                    if (allocatedNewArray)
+                    {
+                        mustZero = false;
+                    }
+                }
+                if (mustZero)
+                {
+                    Array.Clear(_buffer, _length, _position - _length);
+                }
+                _length = newLength;
+            }
+            _buffer[_position++] = value;
+        }
+
+        // Writes this MemoryStream to another stream.
+        public virtual void WriteTo(Stream stream)
+        {
+            if (stream == null)
+                throw new ArgumentNullException(nameof(stream), SR.ArgumentNull_Stream);
+
+            EnsureNotClosed();
+
+            stream.Write(_buffer, _origin, _length - _origin);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/Path.Unix.cs b/src/System.Private.CoreLib/shared/System/IO/Path.Unix.cs
new file mode 100644
index 0000000000..f364b84df0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/Path.Unix.cs
@@ -0,0 +1,147 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace System.IO
+{
+    public static partial class Path
+    {
+        public static char[] GetInvalidFileNameChars() => new char[] { '\0', '/' };
+
+        public static char[] GetInvalidPathChars() => new char[] { '\0' };
+
+        // Expands the given path to a fully qualified path. 
+        public static string GetFullPath(string path)
+        {
+            if (path == null)
+                throw new ArgumentNullException(nameof(path));
+
+            if (path.Length == 0)
+                throw new ArgumentException(SR.Arg_PathEmpty, nameof(path));
+
+            if (path.IndexOf('\0') != -1)
+                throw new ArgumentException(SR.Argument_InvalidPathChars, nameof(path)); 
+            
+            // Expand with current directory if necessary
+            if (!IsPathRooted(path))
+            {
+                path = Combine(Interop.Sys.GetCwd(), path);
+            }
+
+            // We would ideally use realpath to do this, but it resolves symlinks, requires that the file actually exist,
+            // and turns it into a full path, which we only want if fullCheck is true.
+            string collapsedString = PathInternal.RemoveRelativeSegments(path, PathInternal.GetRootLength(path));
+
+            Debug.Assert(collapsedString.Length < path.Length || collapsedString.ToString() == path,
+                "Either we've removed characters, or the string should be unmodified from the input path.");
+
+            string result = collapsedString.Length == 0 ? PathInternal.DirectorySeparatorCharAsString : collapsedString;
+
+            return result;
+        }
+
+        public static string GetFullPath(string path, string basePath)
+        {
+            if (path == null)
+                throw new ArgumentNullException(nameof(path));
+
+            if (basePath == null)
+                throw new ArgumentNullException(nameof(basePath));
+
+            if (!IsPathFullyQualified(basePath))
+                throw new ArgumentException(SR.Arg_BasePathNotFullyQualified, nameof(basePath));
+
+            if (basePath.Contains('\0') || path.Contains('\0'))
+                throw new ArgumentException(SR.Argument_InvalidPathChars);
+
+            if (IsPathFullyQualified(path))
+                return GetFullPath(path);
+
+            return GetFullPath(CombineInternal(basePath, path));
+        }
+
+        private static string RemoveLongPathPrefix(string path)
+        {
+            return path; // nop.  There's nothing special about "long" paths on Unix.
+        }
+
+        public static string GetTempPath()
+        {
+            const string TempEnvVar = "TMPDIR";
+            const string DefaultTempPath = "/tmp/";
+
+            // Get the temp path from the TMPDIR environment variable.
+            // If it's not set, just return the default path.
+            // If it is, return it, ensuring it ends with a slash.
+            string path = Environment.GetEnvironmentVariable(TempEnvVar);
+            return
+                string.IsNullOrEmpty(path) ? DefaultTempPath :
+                PathInternal.IsDirectorySeparator(path[path.Length - 1]) ? path :
+                path + PathInternal.DirectorySeparatorChar;
+        }
+
+        public static string GetTempFileName()
+        {
+            const string Suffix = ".tmp";
+            const int SuffixByteLength = 4;
+
+            // mkstemps takes a char* and overwrites the XXXXXX with six characters
+            // that'll result in a unique file name.
+            string template = GetTempPath() + "tmpXXXXXX" + Suffix + "\0";
+            byte[] name = Encoding.UTF8.GetBytes(template);
+
+            // Create, open, and close the temp file.
+            IntPtr fd = Interop.CheckIo(Interop.Sys.MksTemps(name, SuffixByteLength));
+            Interop.Sys.Close(fd); // ignore any errors from close; nothing to do if cleanup isn't possible
+
+            // 'name' is now the name of the file
+            Debug.Assert(name[name.Length - 1] == '\0');
+            return Encoding.UTF8.GetString(name, 0, name.Length - 1); // trim off the trailing '\0'
+        }
+
+        public static bool IsPathRooted(string path)
+        {
+            if (path == null)
+                return false;
+
+            return IsPathRooted(path.AsSpan());
+        }
+
+        public static bool IsPathRooted(ReadOnlySpan<char> path)
+        {
+            return path.Length > 0 && path[0] == PathInternal.DirectorySeparatorChar;
+        }
+
+        /// <summary>
+        /// Returns the path root or null if path is empty or null.
+        /// </summary>
+        public static string GetPathRoot(string path)
+        {
+            if (PathInternal.IsEffectivelyEmpty(path)) return null;
+
+            return IsPathRooted(path) ? PathInternal.DirectorySeparatorCharAsString : string.Empty;
+        }
+
+        public static ReadOnlySpan<char> GetPathRoot(ReadOnlySpan<char> path)
+        {
+            return PathInternal.IsEffectivelyEmpty(path) && IsPathRooted(path) ? PathInternal.DirectorySeparatorCharAsString.AsSpan() : ReadOnlySpan<char>.Empty;
+        }
+
+        /// <summary>Gets whether the system is case-sensitive.</summary>
+        internal static bool IsCaseSensitive
+        {
+            get
+            {
+                #if PLATFORM_OSX
+                    return false;
+                #else
+                    return true;
+                #endif
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/Path.Windows.cs b/src/System.Private.CoreLib/shared/System/IO/Path.Windows.cs
new file mode 100644
index 0000000000..f22a9913ea
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/Path.Windows.cs
@@ -0,0 +1,286 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Text;
+
+namespace System.IO
+{
+    public static partial class Path
+    {
+        public static char[] GetInvalidFileNameChars() => new char[]
+        {
+            '\"', '<', '>', '|', '\0',
+            (char)1, (char)2, (char)3, (char)4, (char)5, (char)6, (char)7, (char)8, (char)9, (char)10,
+            (char)11, (char)12, (char)13, (char)14, (char)15, (char)16, (char)17, (char)18, (char)19, (char)20,
+            (char)21, (char)22, (char)23, (char)24, (char)25, (char)26, (char)27, (char)28, (char)29, (char)30,
+            (char)31, ':', '*', '?', '\\', '/'
+        };
+
+        public static char[] GetInvalidPathChars() => new char[]
+        {
+            '|', '\0',
+            (char)1, (char)2, (char)3, (char)4, (char)5, (char)6, (char)7, (char)8, (char)9, (char)10,
+            (char)11, (char)12, (char)13, (char)14, (char)15, (char)16, (char)17, (char)18, (char)19, (char)20,
+            (char)21, (char)22, (char)23, (char)24, (char)25, (char)26, (char)27, (char)28, (char)29, (char)30,
+            (char)31
+        };
+
+        // Expands the given path to a fully qualified path.
+        public static string GetFullPath(string path)
+        {
+            if (path == null)
+                throw new ArgumentNullException(nameof(path));
+
+            // If the path would normalize to string empty, we'll consider it empty
+            if (PathInternal.IsEffectivelyEmpty(path))
+                throw new ArgumentException(SR.Arg_PathEmpty, nameof(path));
+
+            // Embedded null characters are the only invalid character case we trully care about.
+            // This is because the nulls will signal the end of the string to Win32 and therefore have
+            // unpredictable results.
+            if (path.IndexOf('\0') != -1)
+                throw new ArgumentException(SR.Argument_InvalidPathChars, nameof(path));
+
+            if (PathInternal.IsExtended(path))
+            {
+                // \\?\ paths are considered normalized by definition. Windows doesn't normalize \\?\
+                // paths and neither should we. Even if we wanted to GetFullPathName does not work
+                // properly with device paths. If one wants to pass a \\?\ path through normalization
+                // one can chop off the prefix, pass it to GetFullPath and add it again.
+                return path;
+            }
+
+            return PathHelper.Normalize(path);
+        }
+
+        public static string GetFullPath(string path, string basePath)
+        {
+            if (path == null)
+                throw new ArgumentNullException(nameof(path));
+
+            if (basePath == null)
+                throw new ArgumentNullException(nameof(basePath));
+
+            if (!IsPathFullyQualified(basePath))
+                throw new ArgumentException(SR.Arg_BasePathNotFullyQualified, nameof(basePath));
+
+            if (basePath.Contains('\0') || path.Contains('\0'))
+                throw new ArgumentException(SR.Argument_InvalidPathChars);
+
+            if (IsPathFullyQualified(path))
+                return GetFullPath(path);
+
+            if (PathInternal.IsEffectivelyEmpty(path))
+                return basePath;
+
+            int length = path.Length;
+            string combinedPath = null;
+
+            if ((length >= 1 && PathInternal.IsDirectorySeparator(path[0])))
+            {
+                // Path is current drive rooted i.e. starts with \:
+                // "\Foo" and "C:\Bar" => "C:\Foo"
+                // "\Foo" and "\\?\C:\Bar" => "\\?\C:\Foo"
+                combinedPath = Join(GetPathRoot(basePath.AsSpan()), path.AsSpan(1)); // Cut the separator to ensure we don't end up with two separators when joining with the root.
+            }
+            else if (length >= 2 && PathInternal.IsValidDriveChar(path[0]) && path[1] == PathInternal.VolumeSeparatorChar)
+            {
+                // Drive relative paths
+                Debug.Assert(length == 2 || !PathInternal.IsDirectorySeparator(path[2]));
+
+                if (GetVolumeName(path).EqualsOrdinal(GetVolumeName(basePath)))
+                {
+                    // Matching root
+                    // "C:Foo" and "C:\Bar" => "C:\Bar\Foo"
+                    // "C:Foo" and "\\?\C:\Bar" => "\\?\C:\Bar\Foo"
+                    combinedPath = Join(basePath, path.AsSpan(2));
+                }
+                else
+                {
+                    // No matching root, root to specified drive
+                    // "D:Foo" and "C:\Bar" => "D:Foo"
+                    // "D:Foo" and "\\?\C:\Bar" => "\\?\D:\Foo"
+                    combinedPath = !PathInternal.IsDevice(basePath)
+                        ? path.Insert(2, @"\")
+                        : length == 2
+                            ? JoinInternal(basePath.AsSpan(0, 4), path, @"\")
+                            : JoinInternal(basePath.AsSpan(0, 4), path.AsSpan(0, 2), @"\", path.AsSpan(2));
+                }
+            }
+            else
+            {
+                // "Simple" relative path
+                // "Foo" and "C:\Bar" => "C:\Bar\Foo"
+                // "Foo" and "\\?\C:\Bar" => "\\?\C:\Bar\Foo"
+                combinedPath = JoinInternal(basePath, path);
+            }
+
+            // Device paths are normalized by definition, so passing something of this format (i.e. \\?\C:\.\tmp, \\.\C:\foo)
+            // to Windows APIs won't do anything by design. Additionally, GetFullPathName() in Windows doesn't root
+            // them properly. As such we need to manually remove segments and not use GetFullPath().
+
+            return PathInternal.IsDevice(combinedPath)
+                ? PathInternal.RemoveRelativeSegments(combinedPath, PathInternal.GetRootLength(combinedPath))
+                : GetFullPath(combinedPath);
+        }
+
+        public static string GetTempPath()
+        {
+            Span<char> initialBuffer = stackalloc char[PathInternal.MaxShortPath];
+            var builder = new ValueStringBuilder(initialBuffer);
+
+            GetTempPath(ref builder);
+
+            string path = PathHelper.Normalize(ref builder);
+            builder.Dispose();
+            return path;
+        }
+
+        private static void GetTempPath(ref ValueStringBuilder builder)
+        {
+            uint result = 0;
+            while ((result = Interop.Kernel32.GetTempPathW(builder.Capacity, ref builder.GetPinnableReference())) > builder.Capacity)
+            {
+                // Reported size is greater than the buffer size. Increase the capacity.
+                builder.EnsureCapacity(checked((int)result));
+            }
+
+            if (result == 0)
+                throw Win32Marshal.GetExceptionForLastWin32Error();
+
+            builder.Length = (int)result;
+        }
+
+        // Returns a unique temporary file name, and creates a 0-byte file by that
+        // name on disk.
+        public static string GetTempFileName()
+        {
+            Span<char> initialTempPathBuffer = stackalloc char[PathInternal.MaxShortPath];
+            ValueStringBuilder tempPathBuilder = new ValueStringBuilder(initialTempPathBuffer);
+
+            GetTempPath(ref tempPathBuilder);
+
+            Span<char> initialBuffer = stackalloc char[PathInternal.MaxShortPath];
+            var builder = new ValueStringBuilder(initialBuffer);
+
+            uint result = Interop.Kernel32.GetTempFileNameW(
+                ref tempPathBuilder.GetPinnableReference(), "tmp", 0, ref builder.GetPinnableReference());
+
+            tempPathBuilder.Dispose();
+
+            if (result == 0)
+                throw Win32Marshal.GetExceptionForLastWin32Error();
+
+            builder.Length = builder.RawChars.IndexOf('\0');
+
+            string path = PathHelper.Normalize(ref builder);
+            builder.Dispose();
+            return path;
+        }
+
+        // Tests if the given path contains a root. A path is considered rooted
+        // if it starts with a backslash ("\") or a valid drive letter and a colon (":").
+        public static bool IsPathRooted(string path)
+        {
+            return path != null && IsPathRooted(path.AsSpan());
+        }
+
+        public static bool IsPathRooted(ReadOnlySpan<char> path)
+        {
+            int length = path.Length;
+            return (length >= 1 && PathInternal.IsDirectorySeparator(path[0]))
+                || (length >= 2 && PathInternal.IsValidDriveChar(path[0]) && path[1] == PathInternal.VolumeSeparatorChar);
+        }
+
+        // Returns the root portion of the given path. The resulting string
+        // consists of those rightmost characters of the path that constitute the
+        // root of the path. Possible patterns for the resulting string are: An
+        // empty string (a relative path on the current drive), "\" (an absolute
+        // path on the current drive), "X:" (a relative path on a given drive,
+        // where X is the drive letter), "X:\" (an absolute path on a given drive),
+        // and "\\server\share" (a UNC path for a given server and share name).
+        // The resulting string is null if path is null. If the path is empty or
+        // only contains whitespace characters an ArgumentException gets thrown.
+        public static string GetPathRoot(string path)
+        {
+            if (PathInternal.IsEffectivelyEmpty(path))
+                return null;
+
+            ReadOnlySpan<char> result = GetPathRoot(path.AsSpan());
+            if (path.Length == result.Length)
+                return PathInternal.NormalizeDirectorySeparators(path);
+
+            return PathInternal.NormalizeDirectorySeparators(new string(result));
+        }
+
+        /// <remarks>
+        /// Unlike the string overload, this method will not normalize directory separators.
+        /// </remarks>
+        public static ReadOnlySpan<char> GetPathRoot(ReadOnlySpan<char> path)
+        {
+            if (PathInternal.IsEffectivelyEmpty(path))
+                return ReadOnlySpan<char>.Empty;
+
+            int pathRoot = PathInternal.GetRootLength(path);
+            return pathRoot <= 0 ? ReadOnlySpan<char>.Empty : path.Slice(0, pathRoot);
+        }
+
+        /// <summary>Gets whether the system is case-sensitive.</summary>
+        internal static bool IsCaseSensitive { get { return false; } }
+
+        /// <summary>
+        /// Returns the volume name for dos, UNC and device paths.
+        /// </summary>
+        internal static ReadOnlySpan<char> GetVolumeName(ReadOnlySpan<char> path)
+        {
+            // 3 cases: UNC ("\\server\share"), Device ("\\?\C:\"), or Dos ("C:\")
+            ReadOnlySpan<char> root = GetPathRoot(path);
+            if (root.Length == 0)
+                return root;
+
+            int offset = GetUncRootLength(path);
+            if (offset >= 0)
+            {
+                // Cut from "\\?\UNC\Server\Share" to "Server\Share"
+                // Cut from  "\\Server\Share" to "Server\Share"
+                return TrimEndingDirectorySeparator(root.Slice(offset));
+            }
+            else if (PathInternal.IsDevice(path))
+            {
+                return TrimEndingDirectorySeparator(root.Slice(4)); // Cut from "\\?\C:\" to "C:"
+            }
+
+            return TrimEndingDirectorySeparator(root); // e.g. "C:"
+        }
+
+        /// <summary>
+        /// Trims the ending directory separator if present.
+        /// </summary>
+        /// <param name="path"></param>
+        internal static ReadOnlySpan<char> TrimEndingDirectorySeparator(ReadOnlySpan<char> path) =>
+            PathInternal.EndsInDirectorySeparator(path) ?
+                path.Slice(0, path.Length - 1) :
+                path;
+
+        /// <summary>
+        /// Returns offset as -1 if the path is not in Unc format, otherwise returns the root length.
+        /// </summary>
+        /// <param name="path"></param>
+        /// <returns></returns>
+        internal static int GetUncRootLength(ReadOnlySpan<char> path)
+        {
+            bool isDevice = PathInternal.IsDevice(path);
+
+            if (!isDevice && path.Slice(0, 2).EqualsOrdinal(@"\\") )
+                return 2;
+            else if (isDevice && path.Length >= 8
+                && (path.Slice(0, 8).EqualsOrdinal(PathInternal.UncExtendedPathPrefix)
+                || path.Slice(5, 4).EqualsOrdinal(@"UNC\")))
+                return 8;
+
+            return -1;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/Path.cs b/src/System.Private.CoreLib/shared/System/IO/Path.cs
new file mode 100644
index 0000000000..1e40ab5e60
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/Path.cs
@@ -0,0 +1,771 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace System.IO
+{
+    // Provides methods for processing file system strings in a cross-platform manner.
+    // Most of the methods don't do a complete parsing (such as examining a UNC hostname), 
+    // but they will handle most string operations.
+    public static partial class Path
+    {
+        // Public static readonly variant of the separators. The Path implementation itself is using
+        // internal const variant of the separators for better performance.
+        public static readonly char DirectorySeparatorChar = PathInternal.DirectorySeparatorChar;
+        public static readonly char AltDirectorySeparatorChar = PathInternal.AltDirectorySeparatorChar;
+        public static readonly char VolumeSeparatorChar = PathInternal.VolumeSeparatorChar;
+        public static readonly char PathSeparator = PathInternal.PathSeparator;
+
+        // For generating random file names
+        // 8 random bytes provides 12 chars in our encoding for the 8.3 name.
+        private const int KeyLength = 8;
+
+        [Obsolete("Please use GetInvalidPathChars or GetInvalidFileNameChars instead.")]
+        public static readonly char[] InvalidPathChars = GetInvalidPathChars();
+
+        // Changes the extension of a file path. The path parameter
+        // specifies a file path, and the extension parameter
+        // specifies a file extension (with a leading period, such as
+        // ".exe" or ".cs").
+        //
+        // The function returns a file path with the same root, directory, and base
+        // name parts as path, but with the file extension changed to
+        // the specified extension. If path is null, the function
+        // returns null. If path does not contain a file extension,
+        // the new file extension is appended to the path. If extension
+        // is null, any existing extension is removed from path.
+        public static string ChangeExtension(string path, string extension)
+        {
+            if (path != null)
+            {
+                string s = path;
+                for (int i = path.Length - 1; i >= 0; i--)
+                {
+                    char ch = path[i];
+                    if (ch == '.')
+                    {
+                        s = path.Substring(0, i);
+                        break;
+                    }
+                    if (PathInternal.IsDirectorySeparator(ch)) break;
+                }
+
+                if (extension != null && path.Length != 0)
+                {
+                    s = (extension.Length == 0 || extension[0] != '.') ?
+                        s + "." + extension :
+                        s + extension;
+                }
+
+                return s;
+            }
+            return null;
+        }
+
+        /// <summary>
+        /// Returns the directory portion of a file path. This method effectively
+        /// removes the last segment of the given file path, i.e. it returns a
+        /// string consisting of all characters up to but not including the last
+        /// backslash ("\") in the file path. The returned value is null if the
+        /// specified path is null, empty, or a root (such as "\", "C:", or
+        /// "\\server\share").
+        /// </summary>
+        /// <remarks>
+        /// Directory separators are normalized in the returned string.
+        /// </remarks>
+        public static string GetDirectoryName(string path)
+        {
+            if (path == null || PathInternal.IsEffectivelyEmpty(path))
+                return null;
+
+            int end = GetDirectoryNameOffset(path);
+            return end >= 0 ? PathInternal.NormalizeDirectorySeparators(path.Substring(0, end)) : null;
+        }
+
+        /// <summary>
+        /// Returns the directory portion of a file path. The returned value is empty
+        /// if the specified path is null, empty, or a root (such as "\", "C:", or
+        /// "\\server\share").
+        /// </summary>
+        /// <remarks>
+        /// Unlike the string overload, this method will not normalize directory separators.
+        /// </remarks>
+        public static ReadOnlySpan<char> GetDirectoryName(ReadOnlySpan<char> path)
+        {
+            if (PathInternal.IsEffectivelyEmpty(path))
+                return ReadOnlySpan<char>.Empty;
+
+            int end = GetDirectoryNameOffset(path);
+            return end >= 0 ? path.Slice(0, end) : ReadOnlySpan<char>.Empty;
+        }
+
+        private static int GetDirectoryNameOffset(ReadOnlySpan<char> path)
+        {
+            int rootLength = PathInternal.GetRootLength(path);
+            int end = path.Length;
+            if (end <= rootLength)
+                return -1;
+
+            while (end > rootLength && !PathInternal.IsDirectorySeparator(path[--end]));
+
+            // Trim off any remaining separators (to deal with C:\foo\\bar)
+            while (end > rootLength && PathInternal.IsDirectorySeparator(path[end - 1]))
+                end--;
+
+            return end;
+        }
+
+        /// <summary>
+        /// Returns the extension of the given path. The returned value includes the period (".") character of the
+        /// extension except when you have a terminal period when you get string.Empty, such as ".exe" or ".cpp".
+        /// The returned value is null if the given path is null or empty if the given path does not include an
+        /// extension.
+        /// </summary>
+        public static string GetExtension(string path)
+        {
+            if (path == null)
+                return null;
+
+            return new string(GetExtension(path.AsSpan()));
+        }
+
+        /// <summary>
+        /// Returns the extension of the given path.
+        /// </summary>
+        /// <remarks> 
+        /// The returned value is an empty ReadOnlySpan if the given path does not include an extension.
+        /// </remarks>
+        public static ReadOnlySpan<char> GetExtension(ReadOnlySpan<char> path)
+        {
+            int length = path.Length;
+
+            for (int i = length - 1; i >= 0; i--)
+            {
+                char ch = path[i];
+                if (ch == '.')
+                {
+                    if (i != length - 1)
+                        return path.Slice(i, length - i);
+                    else
+                        return ReadOnlySpan<char>.Empty;
+                }
+                if (PathInternal.IsDirectorySeparator(ch))
+                    break;
+            }
+            return ReadOnlySpan<char>.Empty;
+        }
+
+        /// <summary>
+        /// Returns the name and extension parts of the given path. The resulting string contains
+        /// the characters of path that follow the last separator in path. The resulting string is
+        /// null if path is null.
+        /// </summary>
+        public static string GetFileName(string path)
+        {
+            if (path == null)
+                return null;
+
+            ReadOnlySpan<char> result = GetFileName(path.AsSpan());
+            if (path.Length == result.Length)
+                return path;
+
+            return new string(result);
+        }
+
+        /// <summary>
+        /// The returned ReadOnlySpan contains the characters of the path that follows the last separator in path.
+        /// </summary>
+        public static ReadOnlySpan<char> GetFileName(ReadOnlySpan<char> path)
+        {
+            int root = GetPathRoot(path).Length;
+
+            // We don't want to cut off "C:\file.txt:stream" (i.e. should be "file.txt:stream")
+            // but we *do* want "C:Foo" => "Foo". This necessitates checking for the root.
+
+            for (int i = path.Length; --i >= 0;)
+            {
+                if (i < root || PathInternal.IsDirectorySeparator(path[i]))
+                    return path.Slice(i + 1, path.Length - i - 1);
+            }
+
+            return path;
+        }
+
+        public static string GetFileNameWithoutExtension(string path)
+        {
+            if (path == null)
+                return null;
+
+            ReadOnlySpan<char> result = GetFileNameWithoutExtension(path.AsSpan());
+            if (path.Length == result.Length)
+                return path;
+
+            return new string(result);
+        }
+
+        /// <summary>
+        /// Returns the characters between the last separator and last (.) in the path.
+        /// </summary>
+        public static ReadOnlySpan<char> GetFileNameWithoutExtension(ReadOnlySpan<char> path)
+        {
+            ReadOnlySpan<char> fileName = GetFileName(path);
+            int lastPeriod = fileName.LastIndexOf('.');
+            return lastPeriod == -1 ?
+                fileName : // No extension was found
+                fileName.Slice(0, lastPeriod);
+        }
+
+        /// <summary>
+        /// Returns a cryptographically strong random 8.3 string that can be
+        /// used as either a folder name or a file name.
+        /// </summary>
+        public static unsafe string GetRandomFileName()
+        {
+            byte* pKey = stackalloc byte[KeyLength];
+            Interop.GetRandomBytes(pKey, KeyLength);
+
+            const int RandomFileNameLength = 12;
+            char* pRandomFileName = stackalloc char[RandomFileNameLength];
+            Populate83FileNameFromRandomBytes(pKey, KeyLength, pRandomFileName, RandomFileNameLength);
+            return new string(pRandomFileName, 0, RandomFileNameLength);
+        }
+
+        /// <summary>
+        /// Returns true if the path is fixed to a specific drive or UNC path. This method does no
+        /// validation of the path (URIs will be returned as relative as a result).
+        /// Returns false if the path specified is relative to the current drive or working directory.
+        /// </summary>
+        /// <remarks>
+        /// Handles paths that use the alternate directory separator.  It is a frequent mistake to
+        /// assume that rooted paths <see cref="Path.IsPathRooted(string)"/> are not relative.  This isn't the case.
+        /// "C:a" is drive relative- meaning that it will be resolved against the current directory
+        /// for C: (rooted, but relative). "C:\a" is rooted and not relative (the current directory
+        /// will not be used to modify the path).
+        /// </remarks>
+        /// <exception cref="ArgumentNullException">
+        /// Thrown if <paramref name="path"/> is null.
+        /// </exception>
+        public static bool IsPathFullyQualified(string path)
+        {
+            if (path == null)
+                throw new ArgumentNullException(nameof(path));
+
+            return IsPathFullyQualified(path.AsSpan());
+        }
+
+        public static bool IsPathFullyQualified(ReadOnlySpan<char> path)
+        {
+            return !PathInternal.IsPartiallyQualified(path);
+        }
+
+        /// <summary>
+        /// Tests if a path's file name includes a file extension. A trailing period
+        /// is not considered an extension.
+        /// </summary>
+        public static bool HasExtension(string path)
+        {
+            if (path != null)
+            {
+                return HasExtension(path.AsSpan());
+            }
+            return false;
+        }
+
+        public static bool HasExtension(ReadOnlySpan<char> path)
+        {
+            for (int i = path.Length - 1; i >= 0; i--)
+            {
+                char ch = path[i];
+                if (ch == '.')
+                {
+                    return i != path.Length - 1;
+                }
+                if (PathInternal.IsDirectorySeparator(ch))
+                    break;
+            }
+            return false;
+        }
+
+        public static string Combine(string path1, string path2)
+        {
+            if (path1 == null || path2 == null)
+                throw new ArgumentNullException((path1 == null) ? nameof(path1) : nameof(path2));
+
+            return CombineInternal(path1, path2);
+        }
+
+        public static string Combine(string path1, string path2, string path3)
+        {
+            if (path1 == null || path2 == null || path3 == null)
+                throw new ArgumentNullException((path1 == null) ? nameof(path1) : (path2 == null) ? nameof(path2) : nameof(path3));
+
+            return CombineInternal(path1, path2, path3);
+        }
+
+        public static string Combine(string path1, string path2, string path3, string path4)
+        {
+            if (path1 == null || path2 == null || path3 == null || path4 == null)
+                throw new ArgumentNullException((path1 == null) ? nameof(path1) : (path2 == null) ? nameof(path2) : (path3 == null) ? nameof(path3) : nameof(path4));
+
+            return CombineInternal(path1, path2, path3, path4);
+        }
+
+        public static string Combine(params string[] paths)
+        {
+            if (paths == null)
+            {
+                throw new ArgumentNullException(nameof(paths));
+            }
+
+            int finalSize = 0;
+            int firstComponent = 0;
+
+            // We have two passes, the first calculates how large a buffer to allocate and does some precondition
+            // checks on the paths passed in.  The second actually does the combination.
+
+            for (int i = 0; i < paths.Length; i++)
+            {
+                if (paths[i] == null)
+                {
+                    throw new ArgumentNullException(nameof(paths));
+                }
+
+                if (paths[i].Length == 0)
+                {
+                    continue;
+                }
+
+                if (IsPathRooted(paths[i]))
+                {
+                    firstComponent = i;
+                    finalSize = paths[i].Length;
+                }
+                else
+                {
+                    finalSize += paths[i].Length;
+                }
+
+                char ch = paths[i][paths[i].Length - 1];
+                if (!PathInternal.IsDirectorySeparator(ch))
+                    finalSize++;
+            }
+
+            StringBuilder finalPath = StringBuilderCache.Acquire(finalSize);
+
+            for (int i = firstComponent; i < paths.Length; i++)
+            {
+                if (paths[i].Length == 0)
+                {
+                    continue;
+                }
+
+                if (finalPath.Length == 0)
+                {
+                    finalPath.Append(paths[i]);
+                }
+                else
+                {
+                    char ch = finalPath[finalPath.Length - 1];
+                    if (!PathInternal.IsDirectorySeparator(ch))
+                    {
+                        finalPath.Append(PathInternal.DirectorySeparatorChar);
+                    }
+
+                    finalPath.Append(paths[i]);
+                }
+            }
+
+            return StringBuilderCache.GetStringAndRelease(finalPath);
+        }
+
+        // Unlike Combine(), Join() methods do not consider rooting. They simply combine paths, ensuring that there
+        // is a directory separator between them.
+
+        public static string Join(ReadOnlySpan<char> path1, ReadOnlySpan<char> path2)
+        {
+            if (path1.Length == 0)
+                return new string(path2);
+            if (path2.Length == 0)
+                return new string(path1);
+
+            return JoinInternal(path1, path2);
+        }
+
+        public static string Join(ReadOnlySpan<char> path1, ReadOnlySpan<char> path2, ReadOnlySpan<char> path3)
+        {
+            if (path1.Length == 0)
+                return Join(path2, path3);
+
+            if (path2.Length == 0)
+                return Join(path1, path3);
+
+            if (path3.Length == 0)
+                return Join(path1, path2);
+
+            return JoinInternal(path1, path2, path3);
+        }
+
+        public static bool TryJoin(ReadOnlySpan<char> path1, ReadOnlySpan<char> path2, Span<char> destination, out int charsWritten)
+        {
+            charsWritten = 0;
+            if (path1.Length == 0 && path2.Length == 0)
+                return true;
+
+            if (path1.Length == 0 || path2.Length == 0)
+            {
+                ref ReadOnlySpan<char> pathToUse = ref path1.Length == 0 ? ref path2 : ref path1;
+                if (destination.Length < pathToUse.Length)
+                {
+                    return false;
+                }
+
+                pathToUse.CopyTo(destination);
+                charsWritten = pathToUse.Length;
+                return true;
+            }
+
+            bool needsSeparator = !(PathInternal.EndsInDirectorySeparator(path1) || PathInternal.StartsWithDirectorySeparator(path2));
+            int charsNeeded = path1.Length + path2.Length + (needsSeparator ? 1 : 0);
+            if (destination.Length < charsNeeded)
+                return false;
+
+            path1.CopyTo(destination);
+            if (needsSeparator)
+                destination[path1.Length] = DirectorySeparatorChar;
+
+            path2.CopyTo(destination.Slice(path1.Length + (needsSeparator ? 1 : 0)));
+
+            charsWritten = charsNeeded;
+            return true;
+        }
+
+        public static bool TryJoin(ReadOnlySpan<char> path1, ReadOnlySpan<char> path2, ReadOnlySpan<char> path3, Span<char> destination, out int charsWritten)
+        {
+            charsWritten = 0;
+            if (path1.Length == 0 && path2.Length == 0 && path3.Length == 0)
+                return true;
+
+            if (path1.Length == 0)
+                return TryJoin(path2, path3, destination, out charsWritten);
+            if (path2.Length == 0)
+                return TryJoin(path1, path3, destination, out charsWritten);
+            if (path3.Length == 0)
+                return TryJoin(path1, path2, destination, out charsWritten);
+
+            int neededSeparators = PathInternal.EndsInDirectorySeparator(path1) || PathInternal.StartsWithDirectorySeparator(path2) ? 0 : 1;
+            bool needsSecondSeparator = !(PathInternal.EndsInDirectorySeparator(path2) || PathInternal.StartsWithDirectorySeparator(path3));
+            if (needsSecondSeparator)
+                neededSeparators++;
+
+            int charsNeeded = path1.Length + path2.Length + path3.Length + neededSeparators;
+            if (destination.Length < charsNeeded)
+                return false;
+
+            bool result = TryJoin(path1, path2, destination, out charsWritten);
+            Debug.Assert(result, "should never fail joining first two paths");
+
+            if (needsSecondSeparator)
+                destination[charsWritten++] = DirectorySeparatorChar;
+
+            path3.CopyTo(destination.Slice(charsWritten));
+            charsWritten += path3.Length;
+
+            return true;
+        }
+
+        private static string CombineInternal(string first, string second)
+        {
+            if (string.IsNullOrEmpty(first))
+                return second;
+
+            if (string.IsNullOrEmpty(second))
+                return first;
+
+            if (IsPathRooted(second.AsSpan()))
+                return second;
+
+            return JoinInternal(first, second);
+        }
+
+        private static string CombineInternal(string first, string second, string third)
+        {
+            if (string.IsNullOrEmpty(first))
+                return CombineInternal(second, third);
+            if (string.IsNullOrEmpty(second))
+                return CombineInternal(first, third);
+            if (string.IsNullOrEmpty(third))
+                return CombineInternal(first, second);
+
+            if (IsPathRooted(third.AsSpan()))
+                return third;
+            if (IsPathRooted(second.AsSpan()))
+                return CombineInternal(second, third);
+
+            return JoinInternal(first, second, third);
+        }
+
+        private static string CombineInternal(string first, string second, string third, string fourth)
+        {
+            if (string.IsNullOrEmpty(first))
+                return CombineInternal(second, third, fourth);
+            if (string.IsNullOrEmpty(second))
+                return CombineInternal(first, third, fourth);
+            if (string.IsNullOrEmpty(third))
+                return CombineInternal(first, second, fourth);
+            if (string.IsNullOrEmpty(fourth))
+                return CombineInternal(first, second, third);
+
+            if (IsPathRooted(fourth.AsSpan()))
+                return fourth;
+            if (IsPathRooted(third.AsSpan()))
+                return CombineInternal(third, fourth);
+            if (IsPathRooted(second.AsSpan()))
+                return CombineInternal(second, third, fourth);
+
+            return JoinInternal(first, second, third, fourth);
+        }
+
+        private static unsafe string JoinInternal(ReadOnlySpan<char> first, ReadOnlySpan<char> second)
+        {
+            Debug.Assert(first.Length > 0 && second.Length > 0, "should have dealt with empty paths");
+
+            bool hasSeparator = PathInternal.IsDirectorySeparator(first[first.Length - 1])
+                || PathInternal.IsDirectorySeparator(second[0]);
+
+            fixed (char* f = &MemoryMarshal.GetReference(first), s = &MemoryMarshal.GetReference(second))
+            {
+                return string.Create(
+                    first.Length + second.Length + (hasSeparator ? 0 : 1),
+                    (First: (IntPtr)f, FirstLength: first.Length, Second: (IntPtr)s, SecondLength: second.Length, HasSeparator: hasSeparator),
+                    (destination, state) =>
+                    {
+                        new Span<char>((char*)state.First, state.FirstLength).CopyTo(destination);
+                        if (!state.HasSeparator)
+                            destination[state.FirstLength] = PathInternal.DirectorySeparatorChar;
+                        new Span<char>((char*)state.Second, state.SecondLength).CopyTo(destination.Slice(state.FirstLength + (state.HasSeparator ? 0 : 1)));
+                    });
+            }
+        }
+
+        private static unsafe string JoinInternal(ReadOnlySpan<char> first, ReadOnlySpan<char> second, ReadOnlySpan<char> third)
+        {
+            Debug.Assert(first.Length > 0 && second.Length > 0 && third.Length > 0, "should have dealt with empty paths");
+
+            bool firstHasSeparator = PathInternal.IsDirectorySeparator(first[first.Length - 1])
+                || PathInternal.IsDirectorySeparator(second[0]);
+            bool thirdHasSeparator = PathInternal.IsDirectorySeparator(second[second.Length - 1])
+                || PathInternal.IsDirectorySeparator(third[0]);
+
+            fixed (char* f = &MemoryMarshal.GetReference(first), s = &MemoryMarshal.GetReference(second), t = &MemoryMarshal.GetReference(third))
+            {
+                return string.Create(
+                    first.Length + second.Length + third.Length + (firstHasSeparator ? 0 : 1) + (thirdHasSeparator ? 0 : 1),
+                    (First: (IntPtr)f, FirstLength: first.Length, Second: (IntPtr)s, SecondLength: second.Length,
+                        Third: (IntPtr)t, ThirdLength: third.Length, FirstHasSeparator: firstHasSeparator, ThirdHasSeparator: thirdHasSeparator),
+                    (destination, state) =>
+                    {
+                        new Span<char>((char*)state.First, state.FirstLength).CopyTo(destination);
+                        if (!state.FirstHasSeparator)
+                            destination[state.FirstLength] = PathInternal.DirectorySeparatorChar;
+                        new Span<char>((char*)state.Second, state.SecondLength).CopyTo(destination.Slice(state.FirstLength + (state.FirstHasSeparator ? 0 : 1)));
+                        if (!state.ThirdHasSeparator)
+                            destination[destination.Length - state.ThirdLength - 1] = PathInternal.DirectorySeparatorChar;
+                        new Span<char>((char*)state.Third, state.ThirdLength).CopyTo(destination.Slice(destination.Length - state.ThirdLength));
+                    });
+            }
+        }
+
+        private static unsafe string JoinInternal(ReadOnlySpan<char> first, ReadOnlySpan<char> second, ReadOnlySpan<char> third, ReadOnlySpan<char> fourth)
+        {
+            Debug.Assert(first.Length > 0 && second.Length > 0 && third.Length > 0 && fourth.Length > 0, "should have dealt with empty paths");
+
+            bool firstHasSeparator = PathInternal.IsDirectorySeparator(first[first.Length - 1])
+                || PathInternal.IsDirectorySeparator(second[0]);
+            bool thirdHasSeparator = PathInternal.IsDirectorySeparator(second[second.Length - 1])
+                || PathInternal.IsDirectorySeparator(third[0]);
+            bool fourthHasSeparator = PathInternal.IsDirectorySeparator(third[third.Length - 1])
+                || PathInternal.IsDirectorySeparator(fourth[0]);
+
+            fixed (char* f = &MemoryMarshal.GetReference(first), s = &MemoryMarshal.GetReference(second), t = &MemoryMarshal.GetReference(third), u = &MemoryMarshal.GetReference(fourth))
+            {
+                return string.Create(
+                    first.Length + second.Length + third.Length + fourth.Length + (firstHasSeparator ? 0 : 1) + (thirdHasSeparator ? 0 : 1) + (fourthHasSeparator ? 0 : 1),
+                    (First: (IntPtr)f, FirstLength: first.Length, Second: (IntPtr)s, SecondLength: second.Length,
+                        Third: (IntPtr)t, ThirdLength: third.Length, Fourth: (IntPtr)u, FourthLength:fourth.Length,
+                        FirstHasSeparator: firstHasSeparator, ThirdHasSeparator: thirdHasSeparator, FourthHasSeparator: fourthHasSeparator),
+                    (destination, state) =>
+                    {
+                        new Span<char>((char*)state.First, state.FirstLength).CopyTo(destination);
+                        if (!state.FirstHasSeparator)
+                            destination[state.FirstLength] = PathInternal.DirectorySeparatorChar;
+                        new Span<char>((char*)state.Second, state.SecondLength).CopyTo(destination.Slice(state.FirstLength + (state.FirstHasSeparator ? 0 : 1)));
+                        if (!state.ThirdHasSeparator)
+                            destination[state.FirstLength + state.SecondLength + (state.FirstHasSeparator ? 0 : 1)] = PathInternal.DirectorySeparatorChar;
+                        new Span<char>((char*)state.Third, state.ThirdLength).CopyTo(destination.Slice(state.FirstLength + state.SecondLength + (state.FirstHasSeparator ? 0 : 1) + (state.ThirdHasSeparator ? 0 : 1)));
+                        if (!state.FourthHasSeparator)
+                            destination[destination.Length - state.FourthLength - 1] = PathInternal.DirectorySeparatorChar;
+                        new Span<char>((char*)state.Fourth, state.FourthLength).CopyTo(destination.Slice(destination.Length - state.FourthLength));
+                    });
+            }
+        }
+
+        private static readonly char[] s_base32Char = {
+                'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h',
+                'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p',
+                'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
+                'y', 'z', '0', '1', '2', '3', '4', '5'};
+
+        private static unsafe void Populate83FileNameFromRandomBytes(byte* bytes, int byteCount, char* chars, int charCount)
+        {
+            Debug.Assert(bytes != null);
+            Debug.Assert(chars != null);
+
+            // This method requires bytes of length 8 and chars of length 12.
+            Debug.Assert(byteCount == 8, $"Unexpected {nameof(byteCount)}");
+            Debug.Assert(charCount == 12, $"Unexpected {nameof(charCount)}");
+
+            byte b0 = bytes[0];
+            byte b1 = bytes[1];
+            byte b2 = bytes[2];
+            byte b3 = bytes[3];
+            byte b4 = bytes[4];
+
+            // Consume the 5 Least significant bits of the first 5 bytes
+            chars[0] = s_base32Char[b0 & 0x1F];
+            chars[1] = s_base32Char[b1 & 0x1F];
+            chars[2] = s_base32Char[b2 & 0x1F];
+            chars[3] = s_base32Char[b3 & 0x1F];
+            chars[4] = s_base32Char[b4 & 0x1F];
+
+            // Consume 3 MSB of b0, b1, MSB bits 6, 7 of b3, b4
+            chars[5] = s_base32Char[(
+                    ((b0 & 0xE0) >> 5) |
+                    ((b3 & 0x60) >> 2))];
+
+            chars[6] = s_base32Char[(
+                    ((b1 & 0xE0) >> 5) |
+                    ((b4 & 0x60) >> 2))];
+
+            // Consume 3 MSB bits of b2, 1 MSB bit of b3, b4
+            b2 >>= 5;
+
+            Debug.Assert(((b2 & 0xF8) == 0), "Unexpected set bits");
+
+            if ((b3 & 0x80) != 0)
+                b2 |= 0x08;
+            if ((b4 & 0x80) != 0)
+                b2 |= 0x10;
+
+            chars[7] = s_base32Char[b2];
+
+            // Set the file extension separator
+            chars[8] = '.';
+
+            // Consume the 5 Least significant bits of the remaining 3 bytes
+            chars[9] = s_base32Char[(bytes[5] & 0x1F)];
+            chars[10] = s_base32Char[(bytes[6] & 0x1F)];
+            chars[11] = s_base32Char[(bytes[7] & 0x1F)];
+        }
+
+        /// <summary>
+        /// Create a relative path from one path to another. Paths will be resolved before calculating the difference.
+        /// Default path comparison for the active platform will be used (OrdinalIgnoreCase for Windows or Mac, Ordinal for Unix).
+        /// </summary>
+        /// <param name="relativeTo">The source path the output should be relative to. This path is always considered to be a directory.</param>
+        /// <param name="path">The destination path.</param>
+        /// <returns>The relative path or <paramref name="path"/> if the paths don't share the same root.</returns>
+        /// <exception cref="ArgumentNullException">Thrown if <paramref name="relativeTo"/> or <paramref name="path"/> is <c>null</c> or an empty string.</exception>
+        public static string GetRelativePath(string relativeTo, string path)
+        {
+            return GetRelativePath(relativeTo, path, StringComparison);
+        }
+
+        private static string GetRelativePath(string relativeTo, string path, StringComparison comparisonType)
+        {
+            if (string.IsNullOrEmpty(relativeTo)) throw new ArgumentNullException(nameof(relativeTo));
+            if (PathInternal.IsEffectivelyEmpty(path)) throw new ArgumentNullException(nameof(path));
+            Debug.Assert(comparisonType == StringComparison.Ordinal || comparisonType == StringComparison.OrdinalIgnoreCase);
+
+            relativeTo = GetFullPath(relativeTo);
+            path = GetFullPath(path);
+
+            // Need to check if the roots are different- if they are we need to return the "to" path.
+            if (!PathInternal.AreRootsEqual(relativeTo, path, comparisonType))
+                return path;
+
+            int commonLength = PathInternal.GetCommonPathLength(relativeTo, path, ignoreCase: comparisonType == StringComparison.OrdinalIgnoreCase);
+
+            // If there is nothing in common they can't share the same root, return the "to" path as is.
+            if (commonLength == 0)
+                return path;
+
+            // Trailing separators aren't significant for comparison
+            int relativeToLength = relativeTo.Length;
+            if (PathInternal.EndsInDirectorySeparator(relativeTo))
+                relativeToLength--;
+
+            bool pathEndsInSeparator = PathInternal.EndsInDirectorySeparator(path);
+            int pathLength = path.Length;
+            if (pathEndsInSeparator)
+                pathLength--;
+
+            // If we have effectively the same path, return "."
+            if (relativeToLength == pathLength && commonLength >= relativeToLength) return ".";
+
+            // We have the same root, we need to calculate the difference now using the
+            // common Length and Segment count past the length.
+            //
+            // Some examples:
+            //
+            //  C:\Foo C:\Bar L3, S1 -> ..\Bar
+            //  C:\Foo C:\Foo\Bar L6, S0 -> Bar
+            //  C:\Foo\Bar C:\Bar\Bar L3, S2 -> ..\..\Bar\Bar
+            //  C:\Foo\Foo C:\Foo\Bar L7, S1 -> ..\Bar
+
+            StringBuilder sb = StringBuilderCache.Acquire(Math.Max(relativeTo.Length, path.Length));
+
+            // Add parent segments for segments past the common on the "from" path
+            if (commonLength < relativeToLength)
+            {
+                sb.Append(PathInternal.ParentDirectoryPrefix);
+
+                for (int i = commonLength; i < relativeToLength; i++)
+                {
+                    if (PathInternal.IsDirectorySeparator(relativeTo[i]))
+                    {
+                        sb.Append(PathInternal.ParentDirectoryPrefix);
+                    }
+                }
+            }
+            else if (PathInternal.IsDirectorySeparator(path[commonLength]))
+            {
+                // No parent segments and we need to eat the initial separator
+                //  (C:\Foo C:\Foo\Bar case)
+                commonLength++;
+            }
+
+            // Now add the rest of the "to" path, adding back the trailing separator
+            int count = pathLength - commonLength;
+            if (pathEndsInSeparator)
+                count++;
+
+            sb.Append(path, commonLength, count);
+            return StringBuilderCache.GetStringAndRelease(sb);
+        }
+
+        /// <summary>Returns a comparison that can be used to compare file and directory names for equality.</summary>
+        internal static StringComparison StringComparison
+        {
+            get
+            {
+                return IsCaseSensitive ?
+                    StringComparison.Ordinal :
+                    StringComparison.OrdinalIgnoreCase;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/PathHelper.Windows.cs b/src/System.Private.CoreLib/shared/System/IO/PathHelper.Windows.cs
new file mode 100644
index 0000000000..ed49422c1a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/PathHelper.Windows.cs
@@ -0,0 +1,252 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace System.IO
+{
+    /// <summary>
+    /// Wrapper to help with path normalization.
+    /// </summary>
+    internal class PathHelper
+    {
+        /// <summary>
+        /// Normalize the given path.
+        /// </summary>
+        /// <remarks>
+        /// Normalizes via Win32 GetFullPathName().
+        /// </remarks>
+        /// <param name="path">Path to normalize</param>
+        /// <exception cref="PathTooLongException">Thrown if we have a string that is too large to fit into a UNICODE_STRING.</exception>
+        /// <exception cref="IOException">Thrown if the path is empty.</exception>
+        /// <returns>Normalized path</returns>
+        internal static string Normalize(string path)
+        {
+            Span<char> initialBuffer = stackalloc char[PathInternal.MaxShortPath];
+            var builder = new ValueStringBuilder(initialBuffer);
+
+            // Get the full path
+            GetFullPathName(path.AsSpan(), ref builder);
+
+            // If we have the exact same string we were passed in, don't allocate another string.
+            // TryExpandShortName does this input identity check.
+            string result = builder.AsSpan().IndexOf('~') >= 0
+                ? TryExpandShortFileName(ref builder, originalPath: path)
+                : builder.AsSpan().Equals(path.AsSpan(), StringComparison.Ordinal) ? path : builder.ToString();
+
+            // Clear the buffer
+            builder.Dispose();
+            return result;
+        }
+
+        /// <summary>
+        /// Normalize the given path.
+        /// </summary>
+        /// <remarks>
+        /// Exceptions are the same as the string overload.
+        /// </remarks>
+        internal static string Normalize(ref ValueStringBuilder path)
+        {
+            Span<char> initialBuffer = stackalloc char[PathInternal.MaxShortPath];
+            var builder = new ValueStringBuilder(initialBuffer);
+
+            // Get the full path
+            GetFullPathName(path.AsSpan(terminate: true), ref builder);
+
+            string result = builder.AsSpan().IndexOf('~') >= 0
+                ? TryExpandShortFileName(ref builder, originalPath: null)
+                : builder.ToString();
+
+            // Clear the buffer
+            builder.Dispose();
+            return result;
+        }
+
+        /// <summary>
+        /// Calls GetFullPathName on the given path.
+        /// </summary>
+        /// <param name="path">The path name. MUST be null terminated after the span.</param>
+        private static void GetFullPathName(ReadOnlySpan<char> path, ref ValueStringBuilder builder)
+        {
+            // If the string starts with an extended prefix we would need to remove it from the path before we call GetFullPathName as
+            // it doesn't root extended paths correctly. We don't currently resolve extended paths, so we'll just assert here.
+            Debug.Assert(PathInternal.IsPartiallyQualified(path) || !PathInternal.IsExtended(path));
+
+            uint result = 0;
+            while ((result = Interop.Kernel32.GetFullPathNameW(ref MemoryMarshal.GetReference(path), (uint)builder.Capacity, ref builder.GetPinnableReference(), IntPtr.Zero)) > builder.Capacity)
+            {
+                // Reported size is greater than the buffer size. Increase the capacity.
+                builder.EnsureCapacity(checked((int)result));
+            }
+
+            if (result == 0)
+            {
+                // Failure, get the error and throw
+                int errorCode = Marshal.GetLastWin32Error();
+                if (errorCode == 0)
+                    errorCode = Interop.Errors.ERROR_BAD_PATHNAME;
+                throw Win32Marshal.GetExceptionForWin32Error(errorCode, path.ToString());
+            }
+
+            builder.Length = (int)result;
+        }
+
+        internal static int PrependDevicePathChars(ref ValueStringBuilder content, bool isDosUnc, ref ValueStringBuilder buffer)
+        {
+            int length = content.Length;
+
+            length += isDosUnc
+                ? PathInternal.UncExtendedPrefixLength - PathInternal.UncPrefixLength
+                : PathInternal.DevicePrefixLength;
+
+            buffer.EnsureCapacity(length + 1);
+            buffer.Length = 0;
+
+            if (isDosUnc)
+            {
+                // Is a \\Server\Share, put \\?\UNC\ in the front
+                buffer.Append(PathInternal.UncExtendedPathPrefix);
+
+                // Copy Server\Share\... over to the buffer
+                buffer.Append(content.AsSpan(PathInternal.UncPrefixLength));
+
+                // Return the prefix difference
+                return PathInternal.UncExtendedPrefixLength - PathInternal.UncPrefixLength;
+            }
+            else
+            {
+                // Not an UNC, put the \\?\ prefix in front, then the original string
+                buffer.Append(PathInternal.ExtendedPathPrefix);
+                buffer.Append(content.AsSpan());
+                return PathInternal.DevicePrefixLength;
+            }
+        }
+
+        internal static string TryExpandShortFileName(ref ValueStringBuilder outputBuilder, string originalPath)
+        {
+            // We guarantee we'll expand short names for paths that only partially exist. As such, we need to find the part of the path that actually does exist. To
+            // avoid allocating like crazy we'll create only one input array and modify the contents with embedded nulls.
+
+            Debug.Assert(!PathInternal.IsPartiallyQualified(outputBuilder.AsSpan()), "should have resolved by now");
+
+            // We'll have one of a few cases by now (the normalized path will have already:
+            //
+            //  1. Dos path (C:\)
+            //  2. Dos UNC (\\Server\Share)
+            //  3. Dos device path (\\.\C:\, \\?\C:\)
+            //
+            // We want to put the extended syntax on the front if it doesn't already have it (for long path support and speed), which may mean switching from \\.\.
+            //
+            // Note that we will never get \??\ here as GetFullPathName() does not recognize \??\ and will return it as C:\??\ (or whatever the current drive is).
+
+            int rootLength = PathInternal.GetRootLength(outputBuilder.AsSpan());
+            bool isDevice = PathInternal.IsDevice(outputBuilder.AsSpan());
+
+            // As this is a corner case we're not going to add a stackalloc here to keep the stack pressure down.
+            var inputBuilder = new ValueStringBuilder();
+
+            bool isDosUnc = false;
+            int rootDifference = 0;
+            bool wasDotDevice = false;
+
+            // Add the extended prefix before expanding to allow growth over MAX_PATH
+            if (isDevice)
+            {
+                // We have one of the following (\\?\ or \\.\)
+                inputBuilder.Append(outputBuilder.AsSpan());
+
+                if (outputBuilder[2] == '.')
+                {
+                    wasDotDevice = true;
+                    inputBuilder[2] = '?';
+                }
+            }
+            else
+            {
+                isDosUnc = !PathInternal.IsDevice(outputBuilder.AsSpan()) && outputBuilder.Length > 1 && outputBuilder[0] == '\\' && outputBuilder[1] == '\\';
+                rootDifference = PrependDevicePathChars(ref outputBuilder, isDosUnc, ref inputBuilder);
+            }
+
+            rootLength += rootDifference;
+            int inputLength = inputBuilder.Length;
+
+            bool success = false;
+            int foundIndex = inputBuilder.Length - 1;
+
+            while (!success)
+            {
+                uint result = Interop.Kernel32.GetLongPathNameW(
+                    ref inputBuilder.GetPinnableReference(terminate: true), ref outputBuilder.GetPinnableReference(), (uint)outputBuilder.Capacity);
+
+                // Replace any temporary null we added
+                if (inputBuilder[foundIndex] == '\0') inputBuilder[foundIndex] = '\\';
+
+                if (result == 0)
+                {
+                    // Look to see if we couldn't find the file
+                    int error = Marshal.GetLastWin32Error();
+                    if (error != Interop.Errors.ERROR_FILE_NOT_FOUND && error != Interop.Errors.ERROR_PATH_NOT_FOUND)
+                    {
+                        // Some other failure, give up
+                        break;
+                    }
+
+                    // We couldn't find the path at the given index, start looking further back in the string.
+                    foundIndex--;
+
+                    for (; foundIndex > rootLength && inputBuilder[foundIndex] != '\\'; foundIndex--) ;
+                    if (foundIndex == rootLength)
+                    {
+                        // Can't trim the path back any further
+                        break;
+                    }
+                    else
+                    {
+                        // Temporarily set a null in the string to get Windows to look further up the path
+                        inputBuilder[foundIndex] = '\0';
+                    }
+                }
+                else if (result > outputBuilder.Capacity)
+                {
+                    // Not enough space. The result count for this API does not include the null terminator.
+                    outputBuilder.EnsureCapacity(checked((int)result));
+                    result = Interop.Kernel32.GetLongPathNameW(ref inputBuilder.GetPinnableReference(), ref outputBuilder.GetPinnableReference(), (uint)outputBuilder.Capacity);
+                }
+                else
+                {
+                    // Found the path
+                    success = true;
+                    outputBuilder.Length = checked((int)result);
+                    if (foundIndex < inputLength - 1)
+                    {
+                        // It was a partial find, put the non-existent part of the path back
+                        outputBuilder.Append(inputBuilder.AsSpan(foundIndex, inputBuilder.Length - foundIndex));
+                    }
+                }
+            }
+
+            // If we were able to expand the path, use it, otherwise use the original full path result
+            ref ValueStringBuilder builderToUse = ref (success ? ref outputBuilder : ref inputBuilder);
+
+            // Switch back from \\?\ to \\.\ if necessary
+            if (wasDotDevice)
+                builderToUse[2] = '.';
+
+            // Change from \\?\UNC\ to \\?\UN\\ if needed
+            if (isDosUnc)
+                builderToUse[PathInternal.UncExtendedPrefixLength - PathInternal.UncPrefixLength] = '\\';
+
+            // Strip out any added characters at the front of the string
+            ReadOnlySpan<char> output = builderToUse.AsSpan(rootDifference);
+
+            string returnValue = ((originalPath != null) && output.Equals(originalPath.AsSpan(), StringComparison.Ordinal))
+                ? originalPath : new string(output);
+
+            inputBuilder.Dispose();
+            return returnValue;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/PathInternal.Unix.cs b/src/System.Private.CoreLib/shared/System/IO/PathInternal.Unix.cs
new file mode 100644
index 0000000000..fae309be56
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/PathInternal.Unix.cs
@@ -0,0 +1,102 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Text;
+using System.Runtime.InteropServices;
+
+namespace System.IO
+{
+    /// <summary>Contains internal path helpers that are shared between many projects.</summary>
+    internal static partial class PathInternal
+    {
+        internal const char DirectorySeparatorChar = '/';
+        internal const char AltDirectorySeparatorChar = '/';
+        internal const char VolumeSeparatorChar = '/';
+        internal const char PathSeparator = ':';
+
+        internal const string DirectorySeparatorCharAsString = "/";
+
+        // There is only one invalid path character in Unix
+        private const char InvalidPathChar = '\0';
+
+        internal const string ParentDirectoryPrefix = @"../";
+
+        internal static int GetRootLength(ReadOnlySpan<char> path)
+        {
+            return path.Length > 0 && IsDirectorySeparator(path[0]) ? 1 : 0;
+        }
+
+        internal static bool IsDirectorySeparator(char c)
+        {
+            // The alternate directory separator char is the same as the directory separator,
+            // so we only need to check one.
+            Debug.Assert(DirectorySeparatorChar == AltDirectorySeparatorChar);
+            return c == DirectorySeparatorChar;
+        }
+
+        /// <summary>
+        /// Normalize separators in the given path. Compresses forward slash runs.
+        /// </summary>
+        internal static string NormalizeDirectorySeparators(string path)
+        {
+            if (string.IsNullOrEmpty(path))
+                return path;
+
+            // Make a pass to see if we need to normalize so we can potentially skip allocating
+            bool normalized = true;
+
+            for (int i = 0; i < path.Length; i++)
+            {
+                if (IsDirectorySeparator(path[i])
+                    && (i + 1 < path.Length && IsDirectorySeparator(path[i + 1])))
+                {
+                    normalized = false;
+                    break;
+                }
+            }
+
+            if (normalized)
+                return path;
+
+            StringBuilder builder = new StringBuilder(path.Length);
+
+            for (int i = 0; i < path.Length; i++)
+            {
+                char current = path[i];
+
+                // Skip if we have another separator following
+                if (IsDirectorySeparator(current)
+                    && (i + 1 < path.Length && IsDirectorySeparator(path[i + 1])))
+                    continue;
+
+                builder.Append(current);
+            }
+
+            return builder.ToString();
+        }
+
+        internal static bool IsPartiallyQualified(ReadOnlySpan<char> path)
+        {
+            // This is much simpler than Windows where paths can be rooted, but not fully qualified (such as Drive Relative)
+            // As long as the path is rooted in Unix it doesn't use the current directory and therefore is fully qualified.
+            return !Path.IsPathRooted(path);
+        }
+
+        /// <summary>
+        /// Returns true if the path is effectively empty for the current OS.
+        /// For unix, this is empty or null. For Windows, this is empty, null, or 
+        /// just spaces ((char)32).
+        /// </summary>
+        internal static bool IsEffectivelyEmpty(string path)
+        {
+            return string.IsNullOrEmpty(path);
+        }
+
+        internal static bool IsEffectivelyEmpty(ReadOnlySpan<char> path)
+        {
+            return path.IsEmpty;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/PathInternal.Windows.cs b/src/System.Private.CoreLib/shared/System/IO/PathInternal.Windows.cs
new file mode 100644
index 0000000000..b01482abd2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/PathInternal.Windows.cs
@@ -0,0 +1,428 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+using System.Text;
+
+namespace System.IO
+{
+    /// <summary>Contains internal path helpers that are shared between many projects.</summary>
+    internal static partial class PathInternal
+    {
+        // All paths in Win32 ultimately end up becoming a path to a File object in the Windows object manager. Passed in paths get mapped through
+        // DosDevice symbolic links in the object tree to actual File objects under \Devices. To illustrate, this is what happens with a typical
+        // path "Foo" passed as a filename to any Win32 API:
+        //
+        //  1. "Foo" is recognized as a relative path and is appended to the current directory (say, "C:\" in our example)
+        //  2. "C:\Foo" is prepended with the DosDevice namespace "\??\"
+        //  3. CreateFile tries to create an object handle to the requested file "\??\C:\Foo"
+        //  4. The Object Manager recognizes the DosDevices prefix and looks
+        //      a. First in the current session DosDevices ("\Sessions\1\DosDevices\" for example, mapped network drives go here)
+        //      b. If not found in the session, it looks in the Global DosDevices ("\GLOBAL??\")
+        //  5. "C:" is found in DosDevices (in our case "\GLOBAL??\C:", which is a symbolic link to "\Device\HarddiskVolume6")
+        //  6. The full path is now "\Device\HarddiskVolume6\Foo", "\Device\HarddiskVolume6" is a File object and parsing is handed off
+        //      to the registered parsing method for Files
+        //  7. The registered open method for File objects is invoked to create the file handle which is then returned
+        //
+        // There are multiple ways to directly specify a DosDevices path. The final format of "\??\" is one way. It can also be specified
+        // as "\\.\" (the most commonly documented way) and "\\?\". If the question mark syntax is used the path will skip normalization
+        // (essentially GetFullPathName()) and path length checks.
+
+        // Windows Kernel-Mode Object Manager
+        // https://msdn.microsoft.com/en-us/library/windows/hardware/ff565763.aspx
+        // https://channel9.msdn.com/Shows/Going+Deep/Windows-NT-Object-Manager
+        //
+        // Introduction to MS-DOS Device Names
+        // https://msdn.microsoft.com/en-us/library/windows/hardware/ff548088.aspx
+        //
+        // Local and Global MS-DOS Device Names
+        // https://msdn.microsoft.com/en-us/library/windows/hardware/ff554302.aspx
+
+        internal const char DirectorySeparatorChar = '\\';
+        internal const char AltDirectorySeparatorChar = '/';
+        internal const char VolumeSeparatorChar = ':';
+        internal const char PathSeparator = ';';
+
+        internal const string DirectorySeparatorCharAsString = "\\";
+
+        internal const string ExtendedPathPrefix = @"\\?\";
+        internal const string UncPathPrefix = @"\\";
+        internal const string UncExtendedPrefixToInsert = @"?\UNC\";
+        internal const string UncExtendedPathPrefix = @"\\?\UNC\";
+        internal const string DevicePathPrefix = @"\\.\";
+        internal const string ParentDirectoryPrefix = @"..\";
+
+        internal const int MaxShortPath = 260;
+        internal const int MaxShortDirectoryPath = 248;
+        // \\?\, \\.\, \??\
+        internal const int DevicePrefixLength = 4;
+        // \\
+        internal const int UncPrefixLength = 2;
+        // \\?\UNC\, \\.\UNC\
+        internal const int UncExtendedPrefixLength = 8;
+
+        /// <summary>
+        /// Returns true if the given character is a valid drive letter
+        /// </summary>
+        internal static bool IsValidDriveChar(char value)
+        {
+            return ((value >= 'A' && value <= 'Z') || (value >= 'a' && value <= 'z'));
+        }
+
+        internal static bool EndsWithPeriodOrSpace(string path)
+        {
+            if (string.IsNullOrEmpty(path))
+                return false;
+
+            char c = path[path.Length - 1];
+            return c == ' ' || c == '.';
+        }
+
+        /// <summary>
+        /// Adds the extended path prefix (\\?\) if not already a device path, IF the path is not relative,
+        /// AND the path is more than 259 characters. (> MAX_PATH + null). This will also insert the extended
+        /// prefix if the path ends with a period or a space. Trailing periods and spaces are normally eaten
+        /// away from paths during normalization, but if we see such a path at this point it should be
+        /// normalized and has retained the final characters. (Typically from one of the *Info classes)
+        /// </summary>
+        internal static string EnsureExtendedPrefixIfNeeded(string path)
+        {
+            if (path != null && (path.Length >= MaxShortPath || EndsWithPeriodOrSpace(path)))
+            {
+                return EnsureExtendedPrefix(path);
+            }
+            else
+            {
+                return path;
+            }
+        }
+
+        /// <summary>
+        /// DO NOT USE- Use EnsureExtendedPrefixIfNeeded. This will be removed shortly.
+        /// Adds the extended path prefix (\\?\) if not already a device path, IF the path is not relative,
+        /// AND the path is more than 259 characters. (> MAX_PATH + null)
+        /// </summary>
+        internal static string EnsureExtendedPrefixOverMaxPath(string path)
+        {
+            if (path != null && path.Length >= MaxShortPath)
+            {
+                return EnsureExtendedPrefix(path);
+            }
+            else
+            {
+                return path;
+            }
+        }
+
+        /// <summary>
+        /// Adds the extended path prefix (\\?\) if not relative or already a device path.
+        /// </summary>
+        internal static string EnsureExtendedPrefix(string path)
+        {
+            // Putting the extended prefix on the path changes the processing of the path. It won't get normalized, which
+            // means adding to relative paths will prevent them from getting the appropriate current directory inserted.
+
+            // If it already has some variant of a device path (\??\, \\?\, \\.\, //./, etc.) we don't need to change it
+            // as it is either correct or we will be changing the behavior. When/if Windows supports long paths implicitly
+            // in the future we wouldn't want normalization to come back and break existing code.
+
+            // In any case, all internal usages should be hitting normalize path (Path.GetFullPath) before they hit this
+            // shimming method. (Or making a change that doesn't impact normalization, such as adding a filename to a
+            // normalized base path.)
+            if (IsPartiallyQualified(path) || IsDevice(path))
+                return path;
+
+            // Given \\server\share in longpath becomes \\?\UNC\server\share
+            if (path.StartsWith(UncPathPrefix, StringComparison.OrdinalIgnoreCase))
+                return path.Insert(2, UncExtendedPrefixToInsert);
+
+            return ExtendedPathPrefix + path;
+        }
+
+        /// <summary>
+        /// Returns true if the path uses any of the DOS device path syntaxes. ("\\.\", "\\?\", or "\??\")
+        /// </summary>
+        internal static bool IsDevice(ReadOnlySpan<char> path)
+        {
+            // If the path begins with any two separators is will be recognized and normalized and prepped with
+            // "\??\" for internal usage correctly. "\??\" is recognized and handled, "/??/" is not.
+            return IsExtended(path)
+                ||
+                (
+                    path.Length >= DevicePrefixLength
+                    && IsDirectorySeparator(path[0])
+                    && IsDirectorySeparator(path[1])
+                    && (path[2] == '.' || path[2] == '?')
+                    && IsDirectorySeparator(path[3])
+                );
+        }
+
+        /// <summary>
+        /// Returns true if the path is a device UNC (\\?\UNC\, \\.\UNC\)
+        /// </summary>
+        internal static bool IsDeviceUNC(ReadOnlySpan<char> path)
+        {
+            return path.Length >= UncExtendedPrefixLength
+                && IsDevice(path)
+                && IsDirectorySeparator(path[7])
+                && path[4] == 'U'
+                && path[5] == 'N'
+                && path[6] == 'C';
+        }
+
+        /// <summary>
+        /// Returns true if the path uses the canonical form of extended syntax ("\\?\" or "\??\"). If the
+        /// path matches exactly (cannot use alternate directory separators) Windows will skip normalization
+        /// and path length checks.
+        /// </summary>
+        internal static bool IsExtended(ReadOnlySpan<char> path)
+        {
+            // While paths like "//?/C:/" will work, they're treated the same as "\\.\" paths.
+            // Skipping of normalization will *only* occur if back slashes ('\') are used.
+            return path.Length >= DevicePrefixLength
+                && path[0] == '\\'
+                && (path[1] == '\\' || path[1] == '?')
+                && path[2] == '?'
+                && path[3] == '\\';
+        }
+
+        /// <summary>
+        /// Check for known wildcard characters. '*' and '?' are the most common ones.
+        /// </summary>
+        internal static bool HasWildCardCharacters(ReadOnlySpan<char> path)
+        {
+            // Question mark is part of dos device syntax so we have to skip if we are
+            int startIndex = IsDevice(path) ? ExtendedPathPrefix.Length : 0;
+
+            // [MS - FSA] 2.1.4.4 Algorithm for Determining if a FileName Is in an Expression
+            // https://msdn.microsoft.com/en-us/library/ff469270.aspx
+            for (int i = startIndex; i < path.Length; i++)
+            {
+                char c = path[i];
+                if (c <= '?') // fast path for common case - '?' is highest wildcard character
+                {
+                    if (c == '\"' || c == '<' || c == '>' || c == '*' || c == '?')
+                        return true;
+                }
+            }
+
+            return false;
+        }
+
+        /// <summary>
+        /// Gets the length of the root of the path (drive, share, etc.).
+        /// </summary>
+        internal static int GetRootLength(ReadOnlySpan<char> path)
+        {
+            int pathLength = path.Length;
+            int i = 0;
+
+            bool deviceSyntax = IsDevice(path);
+            bool deviceUnc = deviceSyntax && IsDeviceUNC(path);
+
+            if ((!deviceSyntax || deviceUnc) && pathLength > 0 && IsDirectorySeparator(path[0]))
+            {
+                // UNC or simple rooted path (e.g. "\foo", NOT "\\?\C:\foo")
+                if (deviceUnc || (pathLength > 1 && IsDirectorySeparator(path[1])))
+                {
+                    // UNC (\\?\UNC\ or \\), scan past server\share
+
+                    // Start past the prefix ("\\" or "\\?\UNC\")
+                    i = deviceUnc ? UncExtendedPrefixLength : UncPrefixLength;
+
+                    // Skip two separators at most
+                    int n = 2;
+                    while (i < pathLength && (!IsDirectorySeparator(path[i]) || --n > 0))
+                        i++;
+                }
+                else
+                {
+                    // Current drive rooted (e.g. "\foo")
+                    i = 1;
+                }
+            }
+            else if (deviceSyntax)
+            {
+                // Device path (e.g. "\\?\.", "\\.\")
+                // Skip any characters following the prefix that aren't a separator
+                i = DevicePrefixLength;
+                while (i < pathLength && !IsDirectorySeparator(path[i]))
+                    i++;
+
+                // If there is another separator take it, as long as we have had at least one
+                // non-separator after the prefix (e.g. don't take "\\?\\", but take "\\?\a\")
+                if (i < pathLength && i > DevicePrefixLength && IsDirectorySeparator(path[i]))
+                    i++;
+            }
+            else if (pathLength >= 2
+                && path[1] == VolumeSeparatorChar
+                && IsValidDriveChar(path[0]))
+            {
+                // Valid drive specified path ("C:", "D:", etc.)
+                i = 2;
+
+                // If the colon is followed by a directory separator, move past it (e.g "C:\")
+                if (pathLength > 2 && IsDirectorySeparator(path[2]))
+                    i++;
+            }
+
+            return i;
+        }
+
+        /// <summary>
+        /// Returns true if the path specified is relative to the current drive or working directory.
+        /// Returns false if the path is fixed to a specific drive or UNC path.  This method does no
+        /// validation of the path (URIs will be returned as relative as a result).
+        /// </summary>
+        /// <remarks>
+        /// Handles paths that use the alternate directory separator.  It is a frequent mistake to
+        /// assume that rooted paths (Path.IsPathRooted) are not relative.  This isn't the case.
+        /// "C:a" is drive relative- meaning that it will be resolved against the current directory
+        /// for C: (rooted, but relative). "C:\a" is rooted and not relative (the current directory
+        /// will not be used to modify the path).
+        /// </remarks>
+        internal static bool IsPartiallyQualified(ReadOnlySpan<char> path)
+        {
+            if (path.Length < 2)
+            {
+                // It isn't fixed, it must be relative.  There is no way to specify a fixed
+                // path with one character (or less).
+                return true;
+            }
+
+            if (IsDirectorySeparator(path[0]))
+            {
+                // There is no valid way to specify a relative path with two initial slashes or
+                // \? as ? isn't valid for drive relative paths and \??\ is equivalent to \\?\
+                return !(path[1] == '?' || IsDirectorySeparator(path[1]));
+            }
+
+            // The only way to specify a fixed path that doesn't begin with two slashes
+            // is the drive, colon, slash format- i.e. C:\
+            return !((path.Length >= 3)
+                && (path[1] == VolumeSeparatorChar)
+                && IsDirectorySeparator(path[2])
+                // To match old behavior we'll check the drive character for validity as the path is technically
+                // not qualified if you don't have a valid drive. "=:\" is the "=" file's default data stream.
+                && IsValidDriveChar(path[0]));
+        }
+
+        /// <summary>
+        /// True if the given character is a directory separator.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static bool IsDirectorySeparator(char c)
+        {
+            return c == DirectorySeparatorChar || c == AltDirectorySeparatorChar;
+        }
+
+        /// <summary>
+        /// Normalize separators in the given path. Converts forward slashes into back slashes and compresses slash runs, keeping initial 2 if present.
+        /// Also trims initial whitespace in front of "rooted" paths (see PathStartSkip).
+        /// 
+        /// This effectively replicates the behavior of the legacy NormalizePath when it was called with fullCheck=false and expandShortpaths=false.
+        /// The current NormalizePath gets directory separator normalization from Win32's GetFullPathName(), which will resolve relative paths and as
+        /// such can't be used here (and is overkill for our uses).
+        /// 
+        /// Like the current NormalizePath this will not try and analyze periods/spaces within directory segments.
+        /// </summary>
+        /// <remarks>
+        /// The only callers that used to use Path.Normalize(fullCheck=false) were Path.GetDirectoryName() and Path.GetPathRoot(). Both usages do
+        /// not need trimming of trailing whitespace here.
+        /// 
+        /// GetPathRoot() could technically skip normalizing separators after the second segment- consider as a future optimization.
+        /// 
+        /// For legacy desktop behavior with ExpandShortPaths:
+        ///  - It has no impact on GetPathRoot() so doesn't need consideration.
+        ///  - It could impact GetDirectoryName(), but only if the path isn't relative (C:\ or \\Server\Share).
+        /// 
+        /// In the case of GetDirectoryName() the ExpandShortPaths behavior was undocumented and provided inconsistent results if the path was
+        /// fixed/relative. For example: "C:\PROGRA~1\A.TXT" would return "C:\Program Files" while ".\PROGRA~1\A.TXT" would return ".\PROGRA~1". If you
+        /// ultimately call GetFullPath() this doesn't matter, but if you don't or have any intermediate string handling could easily be tripped up by
+        /// this undocumented behavior.
+        /// 
+        /// We won't match this old behavior because:
+        /// 
+        ///   1. It was undocumented
+        ///   2. It was costly (extremely so if it actually contained '~')
+        ///   3. Doesn't play nice with string logic
+        ///   4. Isn't a cross-plat friendly concept/behavior
+        /// </remarks>
+        internal static string NormalizeDirectorySeparators(string path)
+        {
+            if (string.IsNullOrEmpty(path))
+                return path;
+
+            char current;
+
+            // Make a pass to see if we need to normalize so we can potentially skip allocating
+            bool normalized = true;
+
+            for (int i = 0; i < path.Length; i++)
+            {
+                current = path[i];
+                if (IsDirectorySeparator(current)
+                    && (current != DirectorySeparatorChar
+                        // Check for sequential separators past the first position (we need to keep initial two for UNC/extended)
+                        || (i > 0 && i + 1 < path.Length && IsDirectorySeparator(path[i + 1]))))
+                {
+                    normalized = false;
+                    break;
+                }
+            }
+
+            if (normalized)
+                return path;
+
+            StringBuilder builder = new StringBuilder(path.Length);
+
+            int start = 0;
+            if (IsDirectorySeparator(path[start]))
+            {
+                start++;
+                builder.Append(DirectorySeparatorChar);
+            }
+
+            for (int i = start; i < path.Length; i++)
+            {
+                current = path[i];
+
+                // If we have a separator
+                if (IsDirectorySeparator(current))
+                {
+                    // If the next is a separator, skip adding this
+                    if (i + 1 < path.Length && IsDirectorySeparator(path[i + 1]))
+                    {
+                        continue;
+                    }
+
+                    // Ensure it is the primary separator
+                    current = DirectorySeparatorChar;
+                }
+
+                builder.Append(current);
+            }
+
+            return builder.ToString();
+        }
+
+        /// <summary>
+        /// Returns true if the path is effectively empty for the current OS.
+        /// For unix, this is empty or null. For Windows, this is empty, null, or 
+        /// just spaces ((char)32).
+        /// </summary>
+        internal static bool IsEffectivelyEmpty(ReadOnlySpan<char> path)
+        {
+            if (path.IsEmpty)
+                return true;
+
+            foreach (char c in path)
+            {
+                if (c != ' ')
+                    return false;
+            }
+            return true;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/PathInternal.cs b/src/System.Private.CoreLib/shared/System/IO/PathInternal.cs
new file mode 100644
index 0000000000..00cb12e920
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/PathInternal.cs
@@ -0,0 +1,208 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Text;
+
+namespace System.IO
+{
+    /// <summary>Contains internal path helpers that are shared between many projects.</summary>
+    internal static partial class PathInternal
+    {
+        /// <summary>
+        /// Returns true if the path ends in a directory separator.
+        /// </summary>
+        internal static bool EndsInDirectorySeparator(ReadOnlySpan<char> path)
+            => path.Length > 0 && IsDirectorySeparator(path[path.Length - 1]);
+
+        /// <summary>
+        /// Returns true if the path starts in a directory separator.
+        /// </summary>
+        internal static bool StartsWithDirectorySeparator(ReadOnlySpan<char> path) => path.Length > 0 && IsDirectorySeparator(path[0]);
+
+        internal static string EnsureTrailingSeparator(string path)
+            => EndsInDirectorySeparator(path) ? path : path + DirectorySeparatorCharAsString;
+
+        internal static string TrimEndingDirectorySeparator(string path) =>
+            EndsInDirectorySeparator(path) && !IsRoot(path) ?
+                path.Substring(0, path.Length - 1) :
+                path;
+
+        internal static ReadOnlySpan<char> TrimEndingDirectorySeparator(ReadOnlySpan<char> path) =>
+            EndsInDirectorySeparator(path) && !IsRoot(path) ?
+                path.Slice(0, path.Length - 1) :
+                path;
+
+        internal static bool IsRoot(ReadOnlySpan<char> path)
+            => path.Length == GetRootLength(path);
+
+        /// <summary>
+        /// Get the common path length from the start of the string.
+        /// </summary>
+        internal static int GetCommonPathLength(string first, string second, bool ignoreCase)
+        {
+            int commonChars = EqualStartingCharacterCount(first, second, ignoreCase: ignoreCase);
+
+            // If nothing matches
+            if (commonChars == 0)
+                return commonChars;
+
+            // Or we're a full string and equal length or match to a separator
+            if (commonChars == first.Length
+                && (commonChars == second.Length || IsDirectorySeparator(second[commonChars])))
+                return commonChars;
+
+            if (commonChars == second.Length && IsDirectorySeparator(first[commonChars]))
+                return commonChars;
+
+            // It's possible we matched somewhere in the middle of a segment e.g. C:\Foodie and C:\Foobar.
+            while (commonChars > 0 && !IsDirectorySeparator(first[commonChars - 1]))
+                commonChars--;
+
+            return commonChars;
+        }
+
+        /// <summary>
+        /// Gets the count of common characters from the left optionally ignoring case
+        /// </summary>
+        internal static unsafe int EqualStartingCharacterCount(string first, string second, bool ignoreCase)
+        {
+            if (string.IsNullOrEmpty(first) || string.IsNullOrEmpty(second)) return 0;
+
+            int commonChars = 0;
+
+            fixed (char* f = first)
+            fixed (char* s = second)
+            {
+                char* l = f;
+                char* r = s;
+                char* leftEnd = l + first.Length;
+                char* rightEnd = r + second.Length;
+
+                while (l != leftEnd && r != rightEnd
+                    && (*l == *r || (ignoreCase && char.ToUpperInvariant((*l)) == char.ToUpperInvariant((*r)))))
+                {
+                    commonChars++;
+                    l++;
+                    r++;
+                }
+            }
+
+            return commonChars;
+        }
+
+        /// <summary>
+        /// Returns true if the two paths have the same root
+        /// </summary>
+        internal static bool AreRootsEqual(string first, string second, StringComparison comparisonType)
+        {
+            int firstRootLength = GetRootLength(first);
+            int secondRootLength = GetRootLength(second);
+
+            return firstRootLength == secondRootLength
+                && string.Compare(
+                    strA: first,
+                    indexA: 0,
+                    strB: second,
+                    indexB: 0,
+                    length: firstRootLength,
+                    comparisonType: comparisonType) == 0;
+        }
+
+        /// <summary>
+        /// Try to remove relative segments from the given path (without combining with a root).
+        /// </summary>
+        /// <param name="rootLength">The length of the root of the given path</param>
+        internal static string RemoveRelativeSegments(string path, int rootLength)
+        {
+            Debug.Assert(rootLength > 0);
+            bool flippedSeparator = false;
+
+            int skip = rootLength;
+            // We treat "\.." , "\." and "\\" as a relative segment. We want to collapse the first separator past the root presuming
+            // the root actually ends in a separator. Otherwise the first segment for RemoveRelativeSegments
+            // in cases like "\\?\C:\.\" and "\\?\C:\..\", the first segment after the root will be ".\" and "..\" which is not considered as a relative segment and hence not be removed.
+            if (PathInternal.IsDirectorySeparator(path[skip - 1]))
+                skip--;
+
+            Span<char> initialBuffer = stackalloc char[260 /* PathInternal.MaxShortPath */];
+            ValueStringBuilder sb = new ValueStringBuilder(initialBuffer);
+
+            // Remove "//", "/./", and "/../" from the path by copying each character to the output, 
+            // except the ones we're removing, such that the builder contains the normalized path 
+            // at the end.
+            if (skip > 0)
+            {
+                sb.Append(path.AsSpan(0, skip));
+            }
+
+            for (int i = skip; i < path.Length; i++)
+            {
+                char c = path[i];
+
+                if (PathInternal.IsDirectorySeparator(c) && i + 1 < path.Length)
+                {
+                    // Skip this character if it's a directory separator and if the next character is, too,
+                    // e.g. "parent//child" => "parent/child"
+                    if (PathInternal.IsDirectorySeparator(path[i + 1]))
+                    {
+                        continue;
+                    }
+
+                    // Skip this character and the next if it's referring to the current directory,
+                    // e.g. "parent/./child" => "parent/child"
+                    if ((i + 2 == path.Length || PathInternal.IsDirectorySeparator(path[i + 2])) &&
+                        path[i + 1] == '.')
+                    {
+                        i++;
+                        continue;
+                    }
+
+                    // Skip this character and the next two if it's referring to the parent directory,
+                    // e.g. "parent/child/../grandchild" => "parent/grandchild"
+                    if (i + 2 < path.Length &&
+                        (i + 3 == path.Length || PathInternal.IsDirectorySeparator(path[i + 3])) &&
+                        path[i + 1] == '.' && path[i + 2] == '.')
+                    {
+                        // Unwind back to the last slash (and if there isn't one, clear out everything).
+                        int s;
+                        for (s = sb.Length - 1; s >= skip; s--)
+                        {
+                            if (PathInternal.IsDirectorySeparator(sb[s]))
+                            {
+                                sb.Length = (i + 3 >= path.Length && s == skip) ? s + 1 : s; // to avoid removing the complete "\tmp\" segment in cases like \\?\C:\tmp\..\, C:\tmp\..
+                                break;
+                            }
+                        }
+                        if (s < skip)
+                        {
+                            sb.Length = skip;
+                        }
+
+                        i += 2;
+                        continue;
+                    }
+                }
+
+                // Normalize the directory separator if needed
+                if (c != PathInternal.DirectorySeparatorChar && c == PathInternal.AltDirectorySeparatorChar)
+                {
+                    c = PathInternal.DirectorySeparatorChar;
+                    flippedSeparator = true;
+                }
+
+                sb.Append(c);
+            }
+
+            // If we haven't changed the source path, return the original
+            if (!flippedSeparator && sb.Length == path.Length)
+            {
+                sb.Dispose();
+                return path;
+            }
+
+            return sb.Length < rootLength ? path.Substring(0, rootLength) : sb.ToString();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/PathTooLongException.cs b/src/System.Private.CoreLib/shared/System/IO/PathTooLongException.cs
new file mode 100644
index 0000000000..7af2452736
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/PathTooLongException.cs
@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System.IO
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class PathTooLongException : IOException
+    {
+        public PathTooLongException()
+            : base(SR.IO_PathTooLong)
+        {
+            HResult = HResults.COR_E_PATHTOOLONG;
+        }
+
+        public PathTooLongException(string message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_PATHTOOLONG;
+        }
+
+        public PathTooLongException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_PATHTOOLONG;
+        }
+
+        protected PathTooLongException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/PinnedBufferMemoryStream.cs b/src/System.Private.CoreLib/shared/System/IO/PinnedBufferMemoryStream.cs
new file mode 100644
index 0000000000..94331a2ef8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/PinnedBufferMemoryStream.cs
@@ -0,0 +1,60 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Pins a byte[], exposing it as an unmanaged memory 
+**          stream.  Used in ResourceReader for corner cases.
+**
+**
+===========================================================*/
+
+using System;
+using System.Runtime.InteropServices;
+using System.Diagnostics;
+
+namespace System.IO
+{
+    internal sealed unsafe class PinnedBufferMemoryStream : UnmanagedMemoryStream
+    {
+        private byte[] _array;
+        private GCHandle _pinningHandle;
+
+        internal PinnedBufferMemoryStream(byte[] array)
+        {
+            Debug.Assert(array != null, "Array can't be null");
+
+            _array = array;
+            _pinningHandle = GCHandle.Alloc(array, GCHandleType.Pinned);
+            // Now the byte[] is pinned for the lifetime of this instance.
+            // But I also need to get a pointer to that block of memory...
+            int len = array.Length;
+            fixed (byte* ptr = &MemoryMarshal.GetReference((Span<byte>)array))
+                Initialize(ptr, len, len, FileAccess.Read);
+        }
+
+        public override int Read(Span<byte> buffer) => ReadCore(buffer);
+
+        public override void Write(ReadOnlySpan<byte> buffer) => WriteCore(buffer);
+
+        ~PinnedBufferMemoryStream()
+        {
+            Dispose(false);
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            if (_pinningHandle.IsAllocated)
+            {
+                _pinningHandle.Free();
+            }
+
+            base.Dispose(disposing);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/SeekOrigin.cs b/src/System.Private.CoreLib/shared/System/IO/SeekOrigin.cs
new file mode 100644
index 0000000000..3798a0ce70
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/SeekOrigin.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.IO
+{
+    // Provides seek reference points.  To seek to the end of a stream,
+    // call stream.Seek(0, SeekOrigin.End).
+    public enum SeekOrigin
+    {
+        // These constants match Win32's FILE_BEGIN, FILE_CURRENT, and FILE_END
+        Begin = 0,
+        Current = 1,
+        End = 2,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/StreamHelpers.CopyValidation.cs b/src/System.Private.CoreLib/shared/System/IO/StreamHelpers.CopyValidation.cs
new file mode 100644
index 0000000000..45bbd816df
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/StreamHelpers.CopyValidation.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.IO
+{
+    /// <summary>Provides methods to help in the implementation of Stream-derived types.</summary>
+    internal static partial class StreamHelpers
+    {
+        /// <summary>Validate the arguments to CopyTo, as would Stream.CopyTo.</summary>
+        public static void ValidateCopyToArgs(Stream source, Stream destination, int bufferSize)
+        {
+            if (destination == null)
+            {
+                throw new ArgumentNullException(nameof(destination));
+            }
+
+            if (bufferSize <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(bufferSize), bufferSize, SR.ArgumentOutOfRange_NeedPosNum);
+            }
+
+            bool sourceCanRead = source.CanRead;
+            if (!sourceCanRead && !source.CanWrite)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_StreamClosed);
+            }
+
+            bool destinationCanWrite = destination.CanWrite;
+            if (!destinationCanWrite && !destination.CanRead)
+            {
+                throw new ObjectDisposedException(nameof(destination), SR.ObjectDisposed_StreamClosed);
+            }
+
+            if (!sourceCanRead)
+            {
+                throw new NotSupportedException(SR.NotSupported_UnreadableStream);
+            }
+
+            if (!destinationCanWrite)
+            {
+                throw new NotSupportedException(SR.NotSupported_UnwritableStream);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/StreamReader.cs b/src/System.Private.CoreLib/shared/System/IO/StreamReader.cs
new file mode 100644
index 0000000000..ea30541f5a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/StreamReader.cs
@@ -0,0 +1,1422 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.IO
+{
+    // This class implements a TextReader for reading characters to a Stream.
+    // This is designed for character input in a particular Encoding, 
+    // whereas the Stream class is designed for byte input and output.  
+    public class StreamReader : TextReader
+    {
+        // StreamReader.Null is threadsafe.
+        public new static readonly StreamReader Null = new NullStreamReader();
+
+        // Using a 1K byte buffer and a 4K FileStream buffer works out pretty well
+        // perf-wise.  On even a 40 MB text file, any perf loss by using a 4K
+        // buffer is negated by the win of allocating a smaller byte[], which 
+        // saves construction time.  This does break adaptive buffering,
+        // but this is slightly faster.
+        private const int DefaultBufferSize = 1024;  // Byte buffer size
+        private const int DefaultFileStreamBufferSize = 4096;
+        private const int MinBufferSize = 128;
+
+        private Stream _stream;
+        private Encoding _encoding;
+        private Decoder _decoder;
+        private byte[] _byteBuffer;
+        private char[] _charBuffer;
+        private int _charPos;
+        private int _charLen;
+        // Record the number of valid bytes in the byteBuffer, for a few checks.
+        private int _byteLen;
+        // This is used only for preamble detection
+        private int _bytePos;
+
+        // This is the maximum number of chars we can get from one call to 
+        // ReadBuffer.  Used so ReadBuffer can tell when to copy data into
+        // a user's char[] directly, instead of our internal char[].
+        private int _maxCharsPerBuffer;
+
+        // We will support looking for byte order marks in the stream and trying
+        // to decide what the encoding might be from the byte order marks, IF they
+        // exist.  But that's all we'll do.  
+        private bool _detectEncoding;
+
+        // Whether we must still check for the encoding's given preamble at the
+        // beginning of this file.
+        private bool _checkPreamble;
+
+        // Whether the stream is most likely not going to give us back as much 
+        // data as we want the next time we call it.  We must do the computation
+        // before we do any byte order mark handling and save the result.  Note
+        // that we need this to allow users to handle streams used for an 
+        // interactive protocol, where they block waiting for the remote end 
+        // to send a response, like logging in on a Unix machine.
+        private bool _isBlocked;
+
+        // The intent of this field is to leave open the underlying stream when 
+        // disposing of this StreamReader.  A name like _leaveOpen is better, 
+        // but this type is serializable, and this field's name was _closable.
+        private bool _closable;  // Whether to close the underlying stream.
+
+        // We don't guarantee thread safety on StreamReader, but we should at 
+        // least prevent users from trying to read anything while an Async
+        // read from the same thread is in progress.
+        private Task _asyncReadTask = Task.CompletedTask;
+
+        private void CheckAsyncTaskInProgress()
+        {
+            // We are not locking the access to _asyncReadTask because this is not meant to guarantee thread safety. 
+            // We are simply trying to deter calling any Read APIs while an async Read from the same thread is in progress.
+            if (!_asyncReadTask.IsCompleted)
+            {
+                ThrowAsyncIOInProgress();
+            }
+        }
+
+        private static void ThrowAsyncIOInProgress() =>
+            throw new InvalidOperationException(SR.InvalidOperation_AsyncIOInProgress);
+
+        // StreamReader by default will ignore illegal UTF8 characters. We don't want to 
+        // throw here because we want to be able to read ill-formed data without choking. 
+        // The high level goal is to be tolerant of encoding errors when we read and very strict 
+        // when we write. Hence, default StreamWriter encoding will throw on error.   
+
+        internal StreamReader()
+        {
+        }
+
+        public StreamReader(Stream stream)
+            : this(stream, true)
+        {
+        }
+
+        public StreamReader(Stream stream, bool detectEncodingFromByteOrderMarks)
+            : this(stream, Encoding.UTF8, detectEncodingFromByteOrderMarks, DefaultBufferSize, false)
+        {
+        }
+
+        public StreamReader(Stream stream, Encoding encoding)
+            : this(stream, encoding, true, DefaultBufferSize, false)
+        {
+        }
+
+        public StreamReader(Stream stream, Encoding encoding, bool detectEncodingFromByteOrderMarks)
+            : this(stream, encoding, detectEncodingFromByteOrderMarks, DefaultBufferSize, false)
+        {
+        }
+
+        // Creates a new StreamReader for the given stream.  The 
+        // character encoding is set by encoding and the buffer size, 
+        // in number of 16-bit characters, is set by bufferSize.  
+        // 
+        // Note that detectEncodingFromByteOrderMarks is a very
+        // loose attempt at detecting the encoding by looking at the first
+        // 3 bytes of the stream.  It will recognize UTF-8, little endian
+        // unicode, and big endian unicode text, but that's it.  If neither
+        // of those three match, it will use the Encoding you provided.
+        // 
+        public StreamReader(Stream stream, Encoding encoding, bool detectEncodingFromByteOrderMarks, int bufferSize)
+            : this(stream, encoding, detectEncodingFromByteOrderMarks, bufferSize, false)
+        {
+        }
+
+        public StreamReader(Stream stream, Encoding encoding, bool detectEncodingFromByteOrderMarks, int bufferSize, bool leaveOpen)
+        {
+            if (stream == null || encoding == null)
+            {
+                throw new ArgumentNullException(stream == null ? nameof(stream) : nameof(encoding));
+            }
+            if (!stream.CanRead)
+            {
+                throw new ArgumentException(SR.Argument_StreamNotReadable);
+            }
+            if (bufferSize <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(bufferSize), SR.ArgumentOutOfRange_NeedPosNum);
+            }
+
+            Init(stream, encoding, detectEncodingFromByteOrderMarks, bufferSize, leaveOpen);
+        }
+
+        public StreamReader(string path)
+            : this(path, true)
+        {
+        }
+
+        public StreamReader(string path, bool detectEncodingFromByteOrderMarks)
+            : this(path, Encoding.UTF8, detectEncodingFromByteOrderMarks, DefaultBufferSize)
+        {
+        }
+
+        public StreamReader(string path, Encoding encoding)
+            : this(path, encoding, true, DefaultBufferSize)
+        {
+        }
+
+        public StreamReader(string path, Encoding encoding, bool detectEncodingFromByteOrderMarks)
+            : this(path, encoding, detectEncodingFromByteOrderMarks, DefaultBufferSize)
+        {
+        }
+
+        public StreamReader(string path, Encoding encoding, bool detectEncodingFromByteOrderMarks, int bufferSize)
+        {
+            if (path == null)
+                throw new ArgumentNullException(nameof(path));
+            if (encoding == null)
+                throw new ArgumentNullException(nameof(encoding));
+            if (path.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyPath);
+            if (bufferSize <= 0)
+                throw new ArgumentOutOfRangeException(nameof(bufferSize), SR.ArgumentOutOfRange_NeedPosNum);
+
+            Stream stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, 
+                DefaultFileStreamBufferSize, FileOptions.SequentialScan);
+            Init(stream, encoding, detectEncodingFromByteOrderMarks, bufferSize, leaveOpen: false);
+        }
+
+        private void Init(Stream stream, Encoding encoding, bool detectEncodingFromByteOrderMarks, int bufferSize, bool leaveOpen)
+        {
+            _stream = stream;
+            _encoding = encoding;
+            _decoder = encoding.GetDecoder();
+            if (bufferSize < MinBufferSize)
+            {
+                bufferSize = MinBufferSize;
+            }
+
+            _byteBuffer = new byte[bufferSize];
+            _maxCharsPerBuffer = encoding.GetMaxCharCount(bufferSize);
+            _charBuffer = new char[_maxCharsPerBuffer];
+            _byteLen = 0;
+            _bytePos = 0;
+            _detectEncoding = detectEncodingFromByteOrderMarks;
+            _checkPreamble = encoding.Preamble.Length > 0;
+            _isBlocked = false;
+            _closable = !leaveOpen;
+        }
+
+        // Init used by NullStreamReader, to delay load encoding
+        internal void Init(Stream stream)
+        {
+            _stream = stream;
+            _closable = true;
+        }
+
+        public override void Close()
+        {
+            Dispose(true);
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            // Dispose of our resources if this StreamReader is closable.
+            // Note that Console.In should be left open.
+            try
+            {
+                // Note that Stream.Close() can potentially throw here. So we need to 
+                // ensure cleaning up internal resources, inside the finally block.  
+                if (!LeaveOpen && disposing && (_stream != null))
+                {
+                    _stream.Close();
+                }
+            }
+            finally
+            {
+                if (!LeaveOpen && (_stream != null))
+                {
+                    _stream = null;
+                    _encoding = null;
+                    _decoder = null;
+                    _byteBuffer = null;
+                    _charBuffer = null;
+                    _charPos = 0;
+                    _charLen = 0;
+                    base.Dispose(disposing);
+                }
+            }
+        }
+
+        public virtual Encoding CurrentEncoding
+        {
+            get { return _encoding; }
+        }
+
+        public virtual Stream BaseStream
+        {
+            get { return _stream; }
+        }
+
+        internal bool LeaveOpen
+        {
+            get { return !_closable; }
+        }
+
+        // DiscardBufferedData tells StreamReader to throw away its internal
+        // buffer contents.  This is useful if the user needs to seek on the
+        // underlying stream to a known location then wants the StreamReader
+        // to start reading from this new point.  This method should be called
+        // very sparingly, if ever, since it can lead to very poor performance.
+        // However, it may be the only way of handling some scenarios where 
+        // users need to re-read the contents of a StreamReader a second time.
+        public void DiscardBufferedData()
+        {
+            CheckAsyncTaskInProgress();
+
+            _byteLen = 0;
+            _charLen = 0;
+            _charPos = 0;
+            // in general we'd like to have an invariant that encoding isn't null. However,
+            // for startup improvements for NullStreamReader, we want to delay load encoding. 
+            if (_encoding != null)
+            {
+                _decoder = _encoding.GetDecoder();
+            }
+            _isBlocked = false;
+        }
+
+        public bool EndOfStream
+        {
+            get
+            {
+                if (_stream == null)
+                {
+                    throw new ObjectDisposedException(null, SR.ObjectDisposed_ReaderClosed);
+                }
+
+                CheckAsyncTaskInProgress();
+
+                if (_charPos < _charLen)
+                {
+                    return false;
+                }
+
+                // This may block on pipes!
+                int numRead = ReadBuffer();
+                return numRead == 0;
+            }
+        }
+
+        public override int Peek()
+        {
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ReaderClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            if (_charPos == _charLen)
+            {
+                if (_isBlocked || ReadBuffer() == 0)
+                {
+                    return -1;
+                }
+            }
+            return _charBuffer[_charPos];
+        }
+
+        public override int Read()
+        {
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ReaderClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            if (_charPos == _charLen)
+            {
+                if (ReadBuffer() == 0)
+                {
+                    return -1;
+                }
+            }
+            int result = _charBuffer[_charPos];
+            _charPos++;
+            return result;
+        }
+
+        public override int Read(char[] buffer, int index, int count)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            }
+            if (index < 0 || count < 0)
+            {
+                throw new ArgumentOutOfRangeException(index < 0 ? nameof(index) : nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (buffer.Length - index < count)
+            {
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+            }
+
+            return ReadSpan(new Span<char>(buffer, index, count));
+        }
+
+        public override int Read(Span<char> buffer) =>
+            GetType() == typeof(StreamReader) ? ReadSpan(buffer) :
+            base.Read(buffer); // Defer to Read(char[], ...) if a derived type may have previously overridden it
+        
+        private int ReadSpan(Span<char> buffer)
+        {
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ReaderClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            int charsRead = 0;
+            // As a perf optimization, if we had exactly one buffer's worth of 
+            // data read in, let's try writing directly to the user's buffer.
+            bool readToUserBuffer = false;
+            int count = buffer.Length;
+            while (count > 0)
+            {
+                int n = _charLen - _charPos;
+                if (n == 0)
+                {
+                    n = ReadBuffer(buffer.Slice(charsRead), out readToUserBuffer);
+                }
+                if (n == 0)
+                {
+                    break;  // We're at EOF
+                }
+                if (n > count)
+                {
+                    n = count;
+                }
+                if (!readToUserBuffer)
+                {
+                    new Span<char>(_charBuffer, _charPos, n).CopyTo(buffer.Slice(charsRead));
+                    _charPos += n;
+                }
+
+                charsRead += n;
+                count -= n;
+                // This function shouldn't block for an indefinite amount of time,
+                // or reading from a network stream won't work right.  If we got
+                // fewer bytes than we requested, then we want to break right here.
+                if (_isBlocked)
+                {
+                    break;
+                }
+            }
+
+            return charsRead;
+        }
+
+        public override string ReadToEnd()
+        {
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ReaderClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            // Call ReadBuffer, then pull data out of charBuffer.
+            StringBuilder sb = new StringBuilder(_charLen - _charPos);
+            do
+            {
+                sb.Append(_charBuffer, _charPos, _charLen - _charPos);
+                _charPos = _charLen;  // Note we consumed these characters
+                ReadBuffer();
+            } while (_charLen > 0);
+            return sb.ToString();
+        }
+
+        public override int ReadBlock(char[] buffer, int index, int count)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            }
+            if (index < 0 || count < 0)
+            {
+                throw new ArgumentOutOfRangeException(index < 0 ? nameof(index) : nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (buffer.Length - index < count)
+            {
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+            }
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ReaderClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            return base.ReadBlock(buffer, index, count);
+        }
+
+        public override int ReadBlock(Span<char> buffer)
+        {
+            if (GetType() != typeof(StreamReader))
+            {
+                // Defer to Read(char[], ...) if a derived type may have previously overridden it.
+                return base.ReadBlock(buffer);
+            }
+
+            int i, n = 0;
+            do
+            {
+                i = ReadSpan(buffer.Slice(n));
+                n += i;
+            } while (i > 0 && n < buffer.Length);
+            return n;
+        }
+
+        // Trims n bytes from the front of the buffer.
+        private void CompressBuffer(int n)
+        {
+            Debug.Assert(_byteLen >= n, "CompressBuffer was called with a number of bytes greater than the current buffer length.  Are two threads using this StreamReader at the same time?");
+            Buffer.BlockCopy(_byteBuffer, n, _byteBuffer, 0, _byteLen - n);
+            _byteLen -= n;
+        }
+
+        private void DetectEncoding()
+        {
+            if (_byteLen < 2)
+            {
+                return;
+            }
+            _detectEncoding = false;
+            bool changedEncoding = false;
+            if (_byteBuffer[0] == 0xFE && _byteBuffer[1] == 0xFF)
+            {
+                // Big Endian Unicode
+
+                _encoding = Encoding.BigEndianUnicode;
+                CompressBuffer(2);
+                changedEncoding = true;
+            }
+
+            else if (_byteBuffer[0] == 0xFF && _byteBuffer[1] == 0xFE)
+            {
+                // Little Endian Unicode, or possibly little endian UTF32
+                if (_byteLen < 4 || _byteBuffer[2] != 0 || _byteBuffer[3] != 0)
+                {
+                    _encoding = Encoding.Unicode;
+                    CompressBuffer(2);
+                    changedEncoding = true;
+                }
+                else
+                {
+                    _encoding = Encoding.UTF32;
+                    CompressBuffer(4);
+                    changedEncoding = true;
+                }
+            }
+
+            else if (_byteLen >= 3 && _byteBuffer[0] == 0xEF && _byteBuffer[1] == 0xBB && _byteBuffer[2] == 0xBF)
+            {
+                // UTF-8
+                _encoding = Encoding.UTF8;
+                CompressBuffer(3);
+                changedEncoding = true;
+            }
+            else if (_byteLen >= 4 && _byteBuffer[0] == 0 && _byteBuffer[1] == 0 &&
+                _byteBuffer[2] == 0xFE && _byteBuffer[3] == 0xFF)
+            {
+                // Big Endian UTF32
+                _encoding = new UTF32Encoding(bigEndian: true, byteOrderMark: true);
+                CompressBuffer(4);
+                changedEncoding = true;
+            }
+            else if (_byteLen == 2)
+            {
+                _detectEncoding = true;
+            }
+            // Note: in the future, if we change this algorithm significantly,
+            // we can support checking for the preamble of the given encoding.
+
+            if (changedEncoding)
+            {
+                _decoder = _encoding.GetDecoder();
+                int newMaxCharsPerBuffer = _encoding.GetMaxCharCount(_byteBuffer.Length);
+                if (newMaxCharsPerBuffer > _maxCharsPerBuffer)
+                {
+                    _charBuffer = new char[newMaxCharsPerBuffer];
+                }
+                _maxCharsPerBuffer = newMaxCharsPerBuffer;
+            }
+        }
+
+        // Trims the preamble bytes from the byteBuffer. This routine can be called multiple times
+        // and we will buffer the bytes read until the preamble is matched or we determine that
+        // there is no match. If there is no match, every byte read previously will be available 
+        // for further consumption. If there is a match, we will compress the buffer for the 
+        // leading preamble bytes
+        private bool IsPreamble()
+        {
+            if (!_checkPreamble)
+            {
+                return _checkPreamble;
+            }
+
+            ReadOnlySpan<byte> preamble = _encoding.Preamble;
+
+            Debug.Assert(_bytePos <= preamble.Length, "_compressPreamble was called with the current bytePos greater than the preamble buffer length.  Are two threads using this StreamReader at the same time?");
+            int len = (_byteLen >= (preamble.Length)) ? (preamble.Length - _bytePos) : (_byteLen - _bytePos);
+
+            for (int i = 0; i < len; i++, _bytePos++)
+            {
+                if (_byteBuffer[_bytePos] != preamble[_bytePos])
+                {
+                    _bytePos = 0;
+                    _checkPreamble = false;
+                    break;
+                }
+            }
+
+            Debug.Assert(_bytePos <= preamble.Length, "possible bug in _compressPreamble.  Are two threads using this StreamReader at the same time?");
+
+            if (_checkPreamble)
+            {
+                if (_bytePos == preamble.Length)
+                {
+                    // We have a match
+                    CompressBuffer(preamble.Length);
+                    _bytePos = 0;
+                    _checkPreamble = false;
+                    _detectEncoding = false;
+                }
+            }
+
+            return _checkPreamble;
+        }
+
+        internal virtual int ReadBuffer()
+        {
+            _charLen = 0;
+            _charPos = 0;
+
+            if (!_checkPreamble)
+            {
+                _byteLen = 0;
+            }
+
+            do
+            {
+                if (_checkPreamble)
+                {
+                    Debug.Assert(_bytePos <= _encoding.Preamble.Length, "possible bug in _compressPreamble.  Are two threads using this StreamReader at the same time?");
+                    int len = _stream.Read(_byteBuffer, _bytePos, _byteBuffer.Length - _bytePos);
+                    Debug.Assert(len >= 0, "Stream.Read returned a negative number!  This is a bug in your stream class.");
+
+                    if (len == 0)
+                    {
+                        // EOF but we might have buffered bytes from previous 
+                        // attempt to detect preamble that needs to be decoded now
+                        if (_byteLen > 0)
+                        {
+                            _charLen += _decoder.GetChars(_byteBuffer, 0, _byteLen, _charBuffer, _charLen);
+                            // Need to zero out the byteLen after we consume these bytes so that we don't keep infinitely hitting this code path
+                            _bytePos = _byteLen = 0;
+                        }
+
+                        return _charLen;
+                    }
+
+                    _byteLen += len;
+                }
+                else
+                {
+                    Debug.Assert(_bytePos == 0, "bytePos can be non zero only when we are trying to _checkPreamble.  Are two threads using this StreamReader at the same time?");
+                    _byteLen = _stream.Read(_byteBuffer, 0, _byteBuffer.Length);
+                    Debug.Assert(_byteLen >= 0, "Stream.Read returned a negative number!  This is a bug in your stream class.");
+
+                    if (_byteLen == 0)  // We're at EOF
+                    {
+                        return _charLen;
+                    }
+                }
+
+                // _isBlocked == whether we read fewer bytes than we asked for.
+                // Note we must check it here because CompressBuffer or 
+                // DetectEncoding will change byteLen.
+                _isBlocked = (_byteLen < _byteBuffer.Length);
+
+                // Check for preamble before detect encoding. This is not to override the
+                // user supplied Encoding for the one we implicitly detect. The user could
+                // customize the encoding which we will loose, such as ThrowOnError on UTF8
+                if (IsPreamble())
+                {
+                    continue;
+                }
+
+                // If we're supposed to detect the encoding and haven't done so yet,
+                // do it.  Note this may need to be called more than once.
+                if (_detectEncoding && _byteLen >= 2)
+                {
+                    DetectEncoding();
+                }
+
+                _charLen += _decoder.GetChars(_byteBuffer, 0, _byteLen, _charBuffer, _charLen);
+            } while (_charLen == 0);
+            //Console.WriteLine("ReadBuffer called.  chars: "+charLen);
+            return _charLen;
+        }
+
+
+        // This version has a perf optimization to decode data DIRECTLY into the 
+        // user's buffer, bypassing StreamReader's own buffer.
+        // This gives a > 20% perf improvement for our encodings across the board,
+        // but only when asking for at least the number of characters that one
+        // buffer's worth of bytes could produce.
+        // This optimization, if run, will break SwitchEncoding, so we must not do 
+        // this on the first call to ReadBuffer.  
+        private int ReadBuffer(Span<char> userBuffer, out bool readToUserBuffer)
+        {
+            _charLen = 0;
+            _charPos = 0;
+
+            if (!_checkPreamble)
+            {
+                _byteLen = 0;
+            }
+
+            int charsRead = 0;
+
+            // As a perf optimization, we can decode characters DIRECTLY into a
+            // user's char[].  We absolutely must not write more characters 
+            // into the user's buffer than they asked for.  Calculating 
+            // encoding.GetMaxCharCount(byteLen) each time is potentially very 
+            // expensive - instead, cache the number of chars a full buffer's 
+            // worth of data may produce.  Yes, this makes the perf optimization 
+            // less aggressive, in that all reads that asked for fewer than AND 
+            // returned fewer than _maxCharsPerBuffer chars won't get the user 
+            // buffer optimization.  This affects reads where the end of the
+            // Stream comes in the middle somewhere, and when you ask for 
+            // fewer chars than your buffer could produce.
+            readToUserBuffer = userBuffer.Length >= _maxCharsPerBuffer;
+
+            do
+            {
+                Debug.Assert(charsRead == 0);
+
+                if (_checkPreamble)
+                {
+                    Debug.Assert(_bytePos <= _encoding.Preamble.Length, "possible bug in _compressPreamble.  Are two threads using this StreamReader at the same time?");
+                    int len = _stream.Read(_byteBuffer, _bytePos, _byteBuffer.Length - _bytePos);
+                    Debug.Assert(len >= 0, "Stream.Read returned a negative number!  This is a bug in your stream class.");
+
+                    if (len == 0)
+                    {
+                        // EOF but we might have buffered bytes from previous 
+                        // attempt to detect preamble that needs to be decoded now
+                        if (_byteLen > 0)
+                        {
+                            if (readToUserBuffer)
+                            {
+                                charsRead = _decoder.GetChars(new ReadOnlySpan<byte>(_byteBuffer, 0, _byteLen), userBuffer.Slice(charsRead), flush: false);
+                                _charLen = 0;  // StreamReader's buffer is empty.
+                            }
+                            else
+                            {
+                                charsRead = _decoder.GetChars(_byteBuffer, 0, _byteLen, _charBuffer, charsRead);
+                                _charLen += charsRead;  // Number of chars in StreamReader's buffer.
+                            }
+                        }
+
+                        return charsRead;
+                    }
+
+                    _byteLen += len;
+                }
+                else
+                {
+                    Debug.Assert(_bytePos == 0, "bytePos can be non zero only when we are trying to _checkPreamble.  Are two threads using this StreamReader at the same time?");
+
+                    _byteLen = _stream.Read(_byteBuffer, 0, _byteBuffer.Length);
+
+                    Debug.Assert(_byteLen >= 0, "Stream.Read returned a negative number!  This is a bug in your stream class.");
+
+                    if (_byteLen == 0)  // EOF
+                    {
+                        break;
+                    }
+                }
+
+                // _isBlocked == whether we read fewer bytes than we asked for.
+                // Note we must check it here because CompressBuffer or 
+                // DetectEncoding will change byteLen.
+                _isBlocked = (_byteLen < _byteBuffer.Length);
+
+                // Check for preamble before detect encoding. This is not to override the
+                // user supplied Encoding for the one we implicitly detect. The user could
+                // customize the encoding which we will loose, such as ThrowOnError on UTF8
+                // Note: we don't need to recompute readToUserBuffer optimization as IsPreamble
+                // doesn't change the encoding or affect _maxCharsPerBuffer
+                if (IsPreamble())
+                {
+                    continue;
+                }
+
+                // On the first call to ReadBuffer, if we're supposed to detect the encoding, do it.
+                if (_detectEncoding && _byteLen >= 2)
+                {
+                    DetectEncoding();
+                    // DetectEncoding changes some buffer state.  Recompute this.
+                    readToUserBuffer = userBuffer.Length >= _maxCharsPerBuffer;
+                }
+
+                _charPos = 0;
+                if (readToUserBuffer)
+                {
+                    charsRead += _decoder.GetChars(new ReadOnlySpan<byte>(_byteBuffer, 0, _byteLen), userBuffer.Slice(charsRead), flush:false);
+                    _charLen = 0;  // StreamReader's buffer is empty.
+                }
+                else
+                {
+                    charsRead = _decoder.GetChars(_byteBuffer, 0, _byteLen, _charBuffer, charsRead);
+                    _charLen += charsRead;  // Number of chars in StreamReader's buffer.
+                }
+            } while (charsRead == 0);
+
+            _isBlocked &= charsRead < userBuffer.Length;
+
+            //Console.WriteLine("ReadBuffer: charsRead: "+charsRead+"  readToUserBuffer: "+readToUserBuffer);
+            return charsRead;
+        }
+
+
+        // Reads a line. A line is defined as a sequence of characters followed by
+        // a carriage return ('\r'), a line feed ('\n'), or a carriage return
+        // immediately followed by a line feed. The resulting string does not
+        // contain the terminating carriage return and/or line feed. The returned
+        // value is null if the end of the input stream has been reached.
+        //
+        public override string ReadLine()
+        {
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ReaderClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            if (_charPos == _charLen)
+            {
+                if (ReadBuffer() == 0)
+                {
+                    return null;
+                }
+            }
+
+            StringBuilder sb = null;
+            do
+            {
+                int i = _charPos;
+                do
+                {
+                    char ch = _charBuffer[i];
+                    // Note the following common line feed chars:
+                    // \n - UNIX   \r\n - DOS   \r - Mac
+                    if (ch == '\r' || ch == '\n')
+                    {
+                        string s;
+                        if (sb != null)
+                        {
+                            sb.Append(_charBuffer, _charPos, i - _charPos);
+                            s = sb.ToString();
+                        }
+                        else
+                        {
+                            s = new string(_charBuffer, _charPos, i - _charPos);
+                        }
+                        _charPos = i + 1;
+                        if (ch == '\r' && (_charPos < _charLen || ReadBuffer() > 0))
+                        {
+                            if (_charBuffer[_charPos] == '\n')
+                            {
+                                _charPos++;
+                            }
+                        }
+                        return s;
+                    }
+                    i++;
+                } while (i < _charLen);
+                i = _charLen - _charPos;
+                if (sb == null)
+                {
+                    sb = new StringBuilder(i + 80);
+                }
+                sb.Append(_charBuffer, _charPos, i);
+            } while (ReadBuffer() > 0);
+            return sb.ToString();
+        }
+
+        #region Task based Async APIs
+        public override Task<string> ReadLineAsync()
+        {
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Read() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Read) when we are not sure.
+            if (GetType() != typeof(StreamReader))
+            {
+                return base.ReadLineAsync();
+            }
+
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ReaderClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            Task<string> task = ReadLineAsyncInternal();
+            _asyncReadTask = task;
+
+            return task;
+        }
+
+        private async Task<string> ReadLineAsyncInternal()
+        {
+            if (_charPos == _charLen && (await ReadBufferAsync().ConfigureAwait(false)) == 0)
+            {
+                return null;
+            }
+
+            StringBuilder sb = null;
+
+            do
+            {
+                char[] tmpCharBuffer = _charBuffer;
+                int tmpCharLen = _charLen;
+                int tmpCharPos = _charPos;
+                int i = tmpCharPos;
+
+                do
+                {
+                    char ch = tmpCharBuffer[i];
+
+                    // Note the following common line feed chars:
+                    // \n - UNIX   \r\n - DOS   \r - Mac
+                    if (ch == '\r' || ch == '\n')
+                    {
+                        string s;
+
+                        if (sb != null)
+                        {
+                            sb.Append(tmpCharBuffer, tmpCharPos, i - tmpCharPos);
+                            s = sb.ToString();
+                        }
+                        else
+                        {
+                            s = new string(tmpCharBuffer, tmpCharPos, i - tmpCharPos);
+                        }
+
+                        _charPos = tmpCharPos = i + 1;
+
+                        if (ch == '\r' && (tmpCharPos < tmpCharLen || (await ReadBufferAsync().ConfigureAwait(false)) > 0))
+                        {
+                            tmpCharPos = _charPos;
+                            if (_charBuffer[tmpCharPos] == '\n')
+                            {
+                                _charPos = ++tmpCharPos;
+                            }
+                        }
+
+                        return s;
+                    }
+
+                    i++;
+                } while (i < tmpCharLen);
+
+                i = tmpCharLen - tmpCharPos;
+                if (sb == null)
+                {
+                    sb = new StringBuilder(i + 80);
+                }
+                sb.Append(tmpCharBuffer, tmpCharPos, i);
+            } while (await ReadBufferAsync().ConfigureAwait(false) > 0);
+
+            return sb.ToString();
+        }
+
+        public override Task<string> ReadToEndAsync()
+        {
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Read() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Read) when we are not sure.
+            if (GetType() != typeof(StreamReader))
+            {
+                return base.ReadToEndAsync();
+            }
+
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ReaderClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            Task<string> task = ReadToEndAsyncInternal();
+            _asyncReadTask = task;
+
+            return task;
+        }
+
+        private async Task<string> ReadToEndAsyncInternal()
+        {
+            // Call ReadBuffer, then pull data out of charBuffer.
+            StringBuilder sb = new StringBuilder(_charLen - _charPos);
+            do
+            {
+                int tmpCharPos = _charPos;
+                sb.Append(_charBuffer, tmpCharPos, _charLen - tmpCharPos);
+                _charPos = _charLen;  // We consumed these characters
+                await ReadBufferAsync().ConfigureAwait(false);
+            } while (_charLen > 0);
+
+            return sb.ToString();
+        }
+
+        public override Task<int> ReadAsync(char[] buffer, int index, int count)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            }
+            if (index < 0 || count < 0)
+            {
+                throw new ArgumentOutOfRangeException(index < 0 ? nameof(index) : nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (buffer.Length - index < count)
+            {
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+            }
+
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Read() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Read) when we are not sure.
+            if (GetType() != typeof(StreamReader))
+            {
+                return base.ReadAsync(buffer, index, count);
+            }
+
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ReaderClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            Task<int> task = ReadAsyncInternal(new Memory<char>(buffer, index, count), default).AsTask();
+            _asyncReadTask = task;
+
+            return task;
+        }
+
+        public override ValueTask<int> ReadAsync(Memory<char> buffer, CancellationToken cancellationToken = default)
+        {
+            if (GetType() != typeof(StreamReader))
+            {
+                // Ensure we use existing overrides if a class already overrode existing overloads.
+                return base.ReadAsync(buffer, cancellationToken);
+            }
+
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ReaderClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return new ValueTask<int>(Task.FromCanceled<int>(cancellationToken));
+            }
+
+            return ReadAsyncInternal(buffer, cancellationToken);
+        }
+
+        internal override async ValueTask<int> ReadAsyncInternal(Memory<char> buffer, CancellationToken cancellationToken)
+        {
+            if (_charPos == _charLen && (await ReadBufferAsync().ConfigureAwait(false)) == 0)
+            {
+                return 0;
+            }
+
+            int charsRead = 0;
+
+            // As a perf optimization, if we had exactly one buffer's worth of 
+            // data read in, let's try writing directly to the user's buffer.
+            bool readToUserBuffer = false;
+
+            Byte[] tmpByteBuffer = _byteBuffer;
+            Stream tmpStream = _stream;
+
+            int count = buffer.Length;
+            while (count > 0)
+            {
+                // n is the characters available in _charBuffer
+                int n = _charLen - _charPos;
+
+                // charBuffer is empty, let's read from the stream
+                if (n == 0)
+                {
+                    _charLen = 0;
+                    _charPos = 0;
+
+                    if (!_checkPreamble)
+                    {
+                        _byteLen = 0;
+                    }
+
+                    readToUserBuffer = count >= _maxCharsPerBuffer;
+
+                    // We loop here so that we read in enough bytes to yield at least 1 char.
+                    // We break out of the loop if the stream is blocked (EOF is reached).
+                    do
+                    {
+                        Debug.Assert(n == 0);
+
+                        if (_checkPreamble)
+                        {
+                            Debug.Assert(_bytePos <= _encoding.Preamble.Length, "possible bug in _compressPreamble.  Are two threads using this StreamReader at the same time?");
+                            int tmpBytePos = _bytePos;
+                            int len = await tmpStream.ReadAsync(new Memory<byte>(tmpByteBuffer, tmpBytePos, tmpByteBuffer.Length - tmpBytePos), cancellationToken).ConfigureAwait(false);
+                            Debug.Assert(len >= 0, "Stream.Read returned a negative number!  This is a bug in your stream class.");
+
+                            if (len == 0)
+                            {
+                                // EOF but we might have buffered bytes from previous 
+                                // attempts to detect preamble that needs to be decoded now
+                                if (_byteLen > 0)
+                                {
+                                    if (readToUserBuffer)
+                                    {
+                                        n = _decoder.GetChars(new ReadOnlySpan<byte>(tmpByteBuffer, 0, _byteLen), buffer.Span.Slice(charsRead), flush: false);
+                                        _charLen = 0;  // StreamReader's buffer is empty.
+                                    }
+                                    else
+                                    {
+                                        n = _decoder.GetChars(tmpByteBuffer, 0, _byteLen, _charBuffer, 0);
+                                        _charLen += n;  // Number of chars in StreamReader's buffer.
+                                    }
+                                }
+
+                                // How can part of the preamble yield any chars?
+                                Debug.Assert(n == 0);
+
+                                _isBlocked = true;
+                                break;
+                            }
+                            else
+                            {
+                                _byteLen += len;
+                            }
+                        }
+                        else
+                        {
+                            Debug.Assert(_bytePos == 0, "_bytePos can be non zero only when we are trying to _checkPreamble.  Are two threads using this StreamReader at the same time?");
+
+                            _byteLen = await tmpStream.ReadAsync(new Memory<byte>(tmpByteBuffer), cancellationToken).ConfigureAwait(false);
+
+                            Debug.Assert(_byteLen >= 0, "Stream.Read returned a negative number!  This is a bug in your stream class.");
+
+                            if (_byteLen == 0)  // EOF
+                            {
+                                _isBlocked = true;
+                                break;
+                            }
+                        }
+
+                        // _isBlocked == whether we read fewer bytes than we asked for.
+                        // Note we must check it here because CompressBuffer or 
+                        // DetectEncoding will change _byteLen.
+                        _isBlocked = (_byteLen < tmpByteBuffer.Length);
+
+                        // Check for preamble before detect encoding. This is not to override the
+                        // user supplied Encoding for the one we implicitly detect. The user could
+                        // customize the encoding which we will loose, such as ThrowOnError on UTF8
+                        // Note: we don't need to recompute readToUserBuffer optimization as IsPreamble
+                        // doesn't change the encoding or affect _maxCharsPerBuffer
+                        if (IsPreamble())
+                        {
+                            continue;
+                        }
+
+                        // On the first call to ReadBuffer, if we're supposed to detect the encoding, do it.
+                        if (_detectEncoding && _byteLen >= 2)
+                        {
+                            DetectEncoding();
+                            // DetectEncoding changes some buffer state.  Recompute this.
+                            readToUserBuffer = count >= _maxCharsPerBuffer;
+                        }
+
+                        Debug.Assert(n == 0);
+
+                        _charPos = 0;
+                        if (readToUserBuffer)
+                        {
+                            n += _decoder.GetChars(new ReadOnlySpan<byte>(tmpByteBuffer, 0, _byteLen), buffer.Span.Slice(charsRead), flush: false);
+
+                            // Why did the bytes yield no chars?
+                            Debug.Assert(n > 0);
+
+                            _charLen = 0;  // StreamReader's buffer is empty.
+                        }
+                        else
+                        {
+                            n = _decoder.GetChars(tmpByteBuffer, 0, _byteLen, _charBuffer, 0);
+
+                            // Why did the bytes yield no chars?
+                            Debug.Assert(n > 0);
+
+                            _charLen += n;  // Number of chars in StreamReader's buffer.
+                        }
+                    } while (n == 0);
+
+                    if (n == 0)
+                    {
+                        break;  // We're at EOF
+                    }
+                }  // if (n == 0)
+
+                // Got more chars in charBuffer than the user requested
+                if (n > count)
+                {
+                    n = count;
+                }
+
+                if (!readToUserBuffer)
+                {
+                    new Span<char>(_charBuffer, _charPos, n).CopyTo(buffer.Span.Slice(charsRead));
+                    _charPos += n;
+                }
+
+                charsRead += n;
+                count -= n;
+
+                // This function shouldn't block for an indefinite amount of time,
+                // or reading from a network stream won't work right.  If we got
+                // fewer bytes than we requested, then we want to break right here.
+                if (_isBlocked)
+                {
+                    break;
+                }
+            }  // while (count > 0)
+
+            return charsRead;
+        }
+
+        public override Task<int> ReadBlockAsync(char[] buffer, int index, int count)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            }
+            if (index < 0 || count < 0)
+            {
+                throw new ArgumentOutOfRangeException(index < 0 ? nameof(index) : nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (buffer.Length - index < count)
+            {
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+            }
+
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Read() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Read) when we are not sure.
+            if (GetType() != typeof(StreamReader))
+            {
+                return base.ReadBlockAsync(buffer, index, count);
+            }
+
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ReaderClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            Task<int> task = base.ReadBlockAsync(buffer, index, count);
+            _asyncReadTask = task;
+
+            return task;
+        }
+
+        public override ValueTask<int> ReadBlockAsync(Memory<char> buffer, CancellationToken cancellationToken = default)
+        {
+            if (GetType() != typeof(StreamReader))
+            {
+                // If a derived type may have overridden ReadBlockAsync(char[], ...) before this overload
+                // was introduced, defer to it.
+                return base.ReadBlockAsync(buffer, cancellationToken);
+            }
+
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ReaderClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return new ValueTask<int>(Task.FromCanceled<int>(cancellationToken));
+            }
+
+            ValueTask<int> vt = ReadBlockAsyncInternal(buffer, cancellationToken);
+            if (vt.IsCompletedSuccessfully)
+            {
+                return vt;
+            }
+
+            Task<int> t = vt.AsTask();
+            _asyncReadTask = t;
+            return new ValueTask<int>(t);
+        }
+
+        private async Task<int> ReadBufferAsync()
+        {
+            _charLen = 0;
+            _charPos = 0;
+            Byte[] tmpByteBuffer = _byteBuffer;
+            Stream tmpStream = _stream;
+
+            if (!_checkPreamble)
+            {
+                _byteLen = 0;
+            }
+            do
+            {
+                if (_checkPreamble)
+                {
+                    Debug.Assert(_bytePos <= _encoding.Preamble.Length, "possible bug in _compressPreamble. Are two threads using this StreamReader at the same time?");
+                    int tmpBytePos = _bytePos;
+                    int len = await tmpStream.ReadAsync(new Memory<byte>(tmpByteBuffer, tmpBytePos, tmpByteBuffer.Length - tmpBytePos)).ConfigureAwait(false);
+                    Debug.Assert(len >= 0, "Stream.Read returned a negative number!  This is a bug in your stream class.");
+
+                    if (len == 0)
+                    {
+                        // EOF but we might have buffered bytes from previous 
+                        // attempt to detect preamble that needs to be decoded now
+                        if (_byteLen > 0)
+                        {
+                            _charLen += _decoder.GetChars(tmpByteBuffer, 0, _byteLen, _charBuffer, _charLen);
+                            // Need to zero out the _byteLen after we consume these bytes so that we don't keep infinitely hitting this code path
+                            _bytePos = 0; _byteLen = 0;
+                        }
+
+                        return _charLen;
+                    }
+
+                    _byteLen += len;
+                }
+                else
+                {
+                    Debug.Assert(_bytePos == 0, "_bytePos can be non zero only when we are trying to _checkPreamble. Are two threads using this StreamReader at the same time?");
+                    _byteLen = await tmpStream.ReadAsync(new Memory<byte>(tmpByteBuffer)).ConfigureAwait(false);
+                    Debug.Assert(_byteLen >= 0, "Stream.Read returned a negative number!  Bug in stream class.");
+
+                    if (_byteLen == 0)  // We're at EOF
+                    {
+                        return _charLen;
+                    }
+                }
+
+                // _isBlocked == whether we read fewer bytes than we asked for.
+                // Note we must check it here because CompressBuffer or 
+                // DetectEncoding will change _byteLen.
+                _isBlocked = (_byteLen < tmpByteBuffer.Length);
+
+                // Check for preamble before detect encoding. This is not to override the
+                // user supplied Encoding for the one we implicitly detect. The user could
+                // customize the encoding which we will loose, such as ThrowOnError on UTF8
+                if (IsPreamble())
+                {
+                    continue;
+                }
+
+                // If we're supposed to detect the encoding and haven't done so yet,
+                // do it.  Note this may need to be called more than once.
+                if (_detectEncoding && _byteLen >= 2)
+                {
+                    DetectEncoding();
+                }
+
+                _charLen += _decoder.GetChars(tmpByteBuffer, 0, _byteLen, _charBuffer, _charLen);
+            } while (_charLen == 0);
+
+            return _charLen;
+        }
+#endregion
+
+
+        // No data, class doesn't need to be serializable.
+        // Note this class is threadsafe.
+        private class NullStreamReader : StreamReader
+        {
+            // Instantiating Encoding causes unnecessary perf hit. 
+            internal NullStreamReader()
+            {
+                Init(Stream.Null);
+            }
+
+            public override Stream BaseStream
+            {
+                get { return Stream.Null; }
+            }
+
+            public override Encoding CurrentEncoding
+            {
+                get { return Encoding.Unicode; }
+            }
+
+            protected override void Dispose(bool disposing)
+            {
+                // Do nothing - this is essentially unclosable.
+            }
+
+            public override int Peek()
+            {
+                return -1;
+            }
+
+            public override int Read()
+            {
+                return -1;
+            }
+
+            [SuppressMessage("Microsoft.Contracts", "CC1055")]  // Skip extra error checking to avoid *potential* AppCompat problems.
+            public override int Read(char[] buffer, int index, int count)
+            {
+                return 0;
+            }
+
+            public override string ReadLine()
+            {
+                return null;
+            }
+
+            public override string ReadToEnd()
+            {
+                return string.Empty;
+            }
+
+            internal override int ReadBuffer()
+            {
+                return 0;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/StreamWriter.cs b/src/System.Private.CoreLib/shared/System/IO/StreamWriter.cs
new file mode 100644
index 0000000000..06d94d2385
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/StreamWriter.cs
@@ -0,0 +1,996 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.IO
+{
+    // This class implements a TextWriter for writing characters to a Stream.
+    // This is designed for character output in a particular Encoding, 
+    // whereas the Stream class is designed for byte input and output.  
+    public class StreamWriter : TextWriter
+    {
+        // For UTF-8, the values of 1K for the default buffer size and 4K for the
+        // file stream buffer size are reasonable & give very reasonable
+        // performance for in terms of construction time for the StreamWriter and
+        // write perf.  Note that for UTF-8, we end up allocating a 4K byte buffer,
+        // which means we take advantage of adaptive buffering code.
+        // The performance using UnicodeEncoding is acceptable.  
+        private const int DefaultBufferSize = 1024;   // char[]
+        private const int DefaultFileStreamBufferSize = 4096;
+        private const int MinBufferSize = 128;
+
+        private const int DontCopyOnWriteLineThreshold = 512;
+
+        // Bit bucket - Null has no backing store. Non closable.
+        public new static readonly StreamWriter Null = new StreamWriter(Stream.Null, UTF8NoBOM, MinBufferSize, true);
+
+        private Stream _stream;
+        private Encoding _encoding;
+        private Encoder _encoder;
+        private byte[] _byteBuffer;
+        private char[] _charBuffer;
+        private int _charPos;
+        private int _charLen;
+        private bool _autoFlush;
+        private bool _haveWrittenPreamble;
+        private bool _closable;
+
+        // We don't guarantee thread safety on StreamWriter, but we should at 
+        // least prevent users from trying to write anything while an Async
+        // write from the same thread is in progress.
+        private Task _asyncWriteTask = Task.CompletedTask;
+
+        private void CheckAsyncTaskInProgress()
+        {
+            // We are not locking the access to _asyncWriteTask because this is not meant to guarantee thread safety. 
+            // We are simply trying to deter calling any Write APIs while an async Write from the same thread is in progress.
+            if (!_asyncWriteTask.IsCompleted)
+            {
+                ThrowAsyncIOInProgress();
+            }
+        }
+
+        private static void ThrowAsyncIOInProgress() =>
+            throw new InvalidOperationException(SR.InvalidOperation_AsyncIOInProgress);
+
+        // The high level goal is to be tolerant of encoding errors when we read and very strict 
+        // when we write. Hence, default StreamWriter encoding will throw on encoding error.   
+        // Note: when StreamWriter throws on invalid encoding chars (for ex, high surrogate character 
+        // D800-DBFF without a following low surrogate character DC00-DFFF), it will cause the 
+        // internal StreamWriter's state to be irrecoverable as it would have buffered the 
+        // illegal chars and any subsequent call to Flush() would hit the encoding error again. 
+        // Even Close() will hit the exception as it would try to flush the unwritten data. 
+        // Maybe we can add a DiscardBufferedData() method to get out of such situation (like 
+        // StreamReader though for different reason). Either way, the buffered data will be lost!
+        private static Encoding UTF8NoBOM => EncodingCache.UTF8NoBOM;
+
+
+        internal StreamWriter() : base(null)
+        { // Ask for CurrentCulture all the time 
+        }
+
+        public StreamWriter(Stream stream)
+            : this(stream, UTF8NoBOM, DefaultBufferSize, false)
+        {
+        }
+
+        public StreamWriter(Stream stream, Encoding encoding)
+            : this(stream, encoding, DefaultBufferSize, false)
+        {
+        }
+
+        // Creates a new StreamWriter for the given stream.  The 
+        // character encoding is set by encoding and the buffer size, 
+        // in number of 16-bit characters, is set by bufferSize.  
+        // 
+        public StreamWriter(Stream stream, Encoding encoding, int bufferSize)
+            : this(stream, encoding, bufferSize, false)
+        {
+        }
+
+        public StreamWriter(Stream stream, Encoding encoding, int bufferSize, bool leaveOpen)
+            : base(null) // Ask for CurrentCulture all the time
+        {
+            if (stream == null || encoding == null)
+            {
+                throw new ArgumentNullException(stream == null ? nameof(stream) : nameof(encoding));
+            }
+            if (!stream.CanWrite)
+            {
+                throw new ArgumentException(SR.Argument_StreamNotWritable);
+            }
+            if (bufferSize <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(bufferSize), SR.ArgumentOutOfRange_NeedPosNum);
+            }
+
+            Init(stream, encoding, bufferSize, leaveOpen);
+        }
+
+        public StreamWriter(string path)
+            : this(path, false, UTF8NoBOM, DefaultBufferSize)
+        {
+        }
+
+        public StreamWriter(string path, bool append)
+            : this(path, append, UTF8NoBOM, DefaultBufferSize)
+        {
+        }
+
+        public StreamWriter(string path, bool append, Encoding encoding)
+            : this(path, append, encoding, DefaultBufferSize)
+        {
+        }
+
+        public StreamWriter(string path, bool append, Encoding encoding, int bufferSize)
+        { 
+            if (path == null)
+                throw new ArgumentNullException(nameof(path));
+            if (encoding == null)
+                throw new ArgumentNullException(nameof(encoding));
+            if (path.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyPath);
+            if (bufferSize <= 0)
+                throw new ArgumentOutOfRangeException(nameof(bufferSize), SR.ArgumentOutOfRange_NeedPosNum);
+
+            Stream stream = new FileStream(path, append ? FileMode.Append : FileMode.Create, FileAccess.Write, FileShare.Read,
+                DefaultFileStreamBufferSize, FileOptions.SequentialScan);
+            Init(stream, encoding, bufferSize, shouldLeaveOpen: false);
+        }
+
+        private void Init(Stream streamArg, Encoding encodingArg, int bufferSize, bool shouldLeaveOpen)
+        {
+            _stream = streamArg;
+            _encoding = encodingArg;
+            _encoder = _encoding.GetEncoder();
+            if (bufferSize < MinBufferSize)
+            {
+                bufferSize = MinBufferSize;
+            }
+
+            _charBuffer = new char[bufferSize];
+            _byteBuffer = new byte[_encoding.GetMaxByteCount(bufferSize)];
+            _charLen = bufferSize;
+            // If we're appending to a Stream that already has data, don't write
+            // the preamble.
+            if (_stream.CanSeek && _stream.Position > 0)
+            {
+                _haveWrittenPreamble = true;
+            }
+
+            _closable = !shouldLeaveOpen;
+        }
+
+        public override void Close()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            try
+            {
+                // We need to flush any buffered data if we are being closed/disposed.
+                // Also, we never close the handles for stdout & friends.  So we can safely 
+                // write any buffered data to those streams even during finalization, which 
+                // is generally the right thing to do.
+                if (_stream != null)
+                {
+                    // Note: flush on the underlying stream can throw (ex., low disk space)
+                    if (disposing /* || (LeaveOpen && stream is __ConsoleStream) */)
+                    {
+                        CheckAsyncTaskInProgress();
+
+                        Flush(true, true);
+                    }
+                }
+            }
+            finally
+            {
+                // Dispose of our resources if this StreamWriter is closable. 
+                // Note: Console.Out and other such non closable streamwriters should be left alone 
+                if (!LeaveOpen && _stream != null)
+                {
+                    try
+                    {
+                        // Attempt to close the stream even if there was an IO error from Flushing.
+                        // Note that Stream.Close() can potentially throw here (may or may not be
+                        // due to the same Flush error). In this case, we still need to ensure 
+                        // cleaning up internal resources, hence the finally block.  
+                        if (disposing)
+                        {
+                            _stream.Close();
+                        }
+                    }
+                    finally
+                    {
+                        _stream = null;
+                        _byteBuffer = null;
+                        _charBuffer = null;
+                        _encoding = null;
+                        _encoder = null;
+                        _charLen = 0;
+                        base.Dispose(disposing);
+                    }
+                }
+            }
+        }
+
+        public override void Flush()
+        {
+            CheckAsyncTaskInProgress();
+
+            Flush(true, true);
+        }
+
+        private void Flush(bool flushStream, bool flushEncoder)
+        {
+            // flushEncoder should be true at the end of the file and if
+            // the user explicitly calls Flush (though not if AutoFlush is true).
+            // This is required to flush any dangling characters from our UTF-7 
+            // and UTF-8 encoders.  
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_WriterClosed);
+            }
+
+            // Perf boost for Flush on non-dirty writers.
+            if (_charPos == 0 && !flushStream && !flushEncoder)
+            {
+                return;
+            }
+
+            if (!_haveWrittenPreamble)
+            {
+                _haveWrittenPreamble = true;
+                ReadOnlySpan<byte> preamble = _encoding.Preamble;
+                if (preamble.Length > 0)
+                {
+                    _stream.Write(preamble);
+                }
+            }
+
+            int count = _encoder.GetBytes(_charBuffer, 0, _charPos, _byteBuffer, 0, flushEncoder);
+            _charPos = 0;
+            if (count > 0)
+            {
+                _stream.Write(_byteBuffer, 0, count);
+            }
+            // By definition, calling Flush should flush the stream, but this is
+            // only necessary if we passed in true for flushStream.  The Web
+            // Services guys have some perf tests where flushing needlessly hurts.
+            if (flushStream)
+            {
+                _stream.Flush();
+            }
+        }
+
+        public virtual bool AutoFlush
+        {
+            get { return _autoFlush; }
+
+            set
+            {
+                CheckAsyncTaskInProgress();
+
+                _autoFlush = value;
+                if (value)
+                {
+                    Flush(true, false);
+                }
+            }
+        }
+
+        public virtual Stream BaseStream
+        {
+            get { return _stream; }
+        }
+
+        internal bool LeaveOpen
+        {
+            get { return !_closable; }
+        }
+
+        internal bool HaveWrittenPreamble
+        {
+            set { _haveWrittenPreamble = value; }
+        }
+
+        public override Encoding Encoding
+        {
+            get { return _encoding; }
+        }
+
+        public override void Write(char value)
+        {
+            CheckAsyncTaskInProgress();
+
+            if (_charPos == _charLen)
+            {
+                Flush(false, false);
+            }
+
+            _charBuffer[_charPos] = value;
+            _charPos++;
+            if (_autoFlush)
+            {
+                Flush(true, false);
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)] // prevent WriteSpan from bloating call sites
+        public override void Write(char[] buffer)
+        {
+            WriteSpan(buffer, appendNewLine: false);
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)] // prevent WriteSpan from bloating call sites
+        public override void Write(char[] buffer, int index, int count)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            }
+            if (index < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (buffer.Length - index < count)
+            {
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+            }
+
+            WriteSpan(buffer.AsSpan(index, count), appendNewLine: false);
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)] // prevent WriteSpan from bloating call sites
+        public override void Write(ReadOnlySpan<char> buffer)
+        {
+            if (GetType() == typeof(StreamWriter))
+            {
+                WriteSpan(buffer, appendNewLine: false);
+            }
+            else
+            {
+                // If a derived class may have overridden existing Write behavior,
+                // we need to make sure we use it.
+                base.Write(buffer);
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private unsafe void WriteSpan(ReadOnlySpan<char> buffer, bool appendNewLine)
+        {
+            CheckAsyncTaskInProgress();
+
+            if (buffer.Length <= 4 && // Threshold of 4 chosen based on perf experimentation
+                buffer.Length <= _charLen - _charPos)
+            {
+                // For very short buffers and when we don't need to worry about running out of space
+                // in the char buffer, just copy the chars individually.
+                for (int i = 0; i < buffer.Length; i++)
+                {
+                    _charBuffer[_charPos++] = buffer[i];
+                }
+            }
+            else
+            {
+                // For larger buffers or when we may run out of room in the internal char buffer, copy in chunks.
+                // Use unsafe code until https://github.com/dotnet/coreclr/issues/13827 is addressed, as spans are
+                // resulting in significant overhead (even when the if branch above is taken rather than this
+                // else) due to temporaries that need to be cleared.  Given the use of unsafe code, we also
+                // make local copies of instance state to protect against potential concurrent misuse.
+
+                char[] charBuffer = _charBuffer;
+                if (charBuffer == null)
+                {
+                    throw new ObjectDisposedException(null, SR.ObjectDisposed_WriterClosed);
+                }
+
+                fixed (char* bufferPtr = &MemoryMarshal.GetReference(buffer))
+                fixed (char* dstPtr = &charBuffer[0])
+                {
+                    char* srcPtr = bufferPtr;
+                    int count = buffer.Length;
+                    int dstPos = _charPos; // use a local copy of _charPos for safety
+                    while (count > 0)
+                    {
+                        if (dstPos == charBuffer.Length)
+                        {
+                            Flush(false, false);
+                            dstPos = 0;
+                        }
+
+                        int n = Math.Min(charBuffer.Length - dstPos, count);
+                        int bytesToCopy = n * sizeof(char);
+
+                        Buffer.MemoryCopy(srcPtr, dstPtr + dstPos, bytesToCopy, bytesToCopy);
+
+                        _charPos += n;
+                        dstPos += n;
+                        srcPtr += n;
+                        count -= n;
+                    }
+                }
+            }
+
+            if (appendNewLine)
+            {
+                char[] coreNewLine = CoreNewLine;
+                for (int i = 0; i < coreNewLine.Length; i++) // Generally 1 (\n) or 2 (\r\n) iterations
+                {
+                    if (_charPos == _charLen)
+                    {
+                        Flush(false, false);
+                    }
+
+                    _charBuffer[_charPos] = coreNewLine[i];
+                    _charPos++;
+                }
+            }
+
+            if (_autoFlush)
+            {
+                Flush(true, false);
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)] // prevent WriteSpan from bloating call sites
+        public override void Write(string value)
+        {
+            WriteSpan(value, appendNewLine: false);
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)] // prevent WriteSpan from bloating call sites
+        public override void WriteLine(string value)
+        {
+            CheckAsyncTaskInProgress();
+            WriteSpan(value, appendNewLine: true);
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)] // prevent WriteSpan from bloating call sites
+        public override void WriteLine(ReadOnlySpan<char> value)
+        {
+            if (GetType() == typeof(StreamWriter))
+            {
+                CheckAsyncTaskInProgress();
+                WriteSpan(value, appendNewLine: true);
+            }
+            else
+            {
+                // If a derived class may have overridden existing WriteLine behavior,
+                // we need to make sure we use it.
+                base.WriteLine(value);
+            }
+        }
+
+        #region Task based Async APIs
+        public override Task WriteAsync(char value)
+        {
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Write() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Write) when we are not sure.
+            if (GetType() != typeof(StreamWriter))
+            {
+                return base.WriteAsync(value);
+            }
+
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_WriterClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            Task task = WriteAsyncInternal(this, value, _charBuffer, _charPos, _charLen, CoreNewLine, _autoFlush, appendNewLine: false);
+            _asyncWriteTask = task;
+
+            return task;
+        }
+
+        // We pass in private instance fields of this MarshalByRefObject-derived type as local params
+        // to ensure performant access inside the state machine that corresponds this async method.
+        // Fields that are written to must be assigned at the end of the method *and* before instance invocations.
+        private static async Task WriteAsyncInternal(StreamWriter _this, char value,
+                                                     char[] charBuffer, int charPos, int charLen, char[] coreNewLine,
+                                                     bool autoFlush, bool appendNewLine)
+        {
+            if (charPos == charLen)
+            {
+                await _this.FlushAsyncInternal(false, false, charBuffer, charPos).ConfigureAwait(false);
+                Debug.Assert(_this._charPos == 0);
+                charPos = 0;
+            }
+
+            charBuffer[charPos] = value;
+            charPos++;
+
+            if (appendNewLine)
+            {
+                for (int i = 0; i < coreNewLine.Length; i++)   // Expect 2 iterations, no point calling BlockCopy
+                {
+                    if (charPos == charLen)
+                    {
+                        await _this.FlushAsyncInternal(false, false, charBuffer, charPos).ConfigureAwait(false);
+                        Debug.Assert(_this._charPos == 0);
+                        charPos = 0;
+                    }
+
+                    charBuffer[charPos] = coreNewLine[i];
+                    charPos++;
+                }
+            }
+
+            if (autoFlush)
+            {
+                await _this.FlushAsyncInternal(true, false, charBuffer, charPos).ConfigureAwait(false);
+                Debug.Assert(_this._charPos == 0);
+                charPos = 0;
+            }
+
+            _this.CharPos_Prop = charPos;
+        }
+
+        public override Task WriteAsync(string value)
+        {
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Write() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Write) when we are not sure.
+            if (GetType() != typeof(StreamWriter))
+            {
+                return base.WriteAsync(value);
+            }
+
+            if (value != null)
+            {
+                if (_stream == null)
+                {
+                    throw new ObjectDisposedException(null, SR.ObjectDisposed_WriterClosed);
+                }
+
+                CheckAsyncTaskInProgress();
+
+                Task task = WriteAsyncInternal(this, value, _charBuffer, _charPos, _charLen, CoreNewLine, _autoFlush, appendNewLine: false);
+                _asyncWriteTask = task;
+
+                return task;
+            }
+            else
+            {
+                return Task.CompletedTask;
+            }
+        }
+
+        // We pass in private instance fields of this MarshalByRefObject-derived type as local params
+        // to ensure performant access inside the state machine that corresponds this async method.
+        // Fields that are written to must be assigned at the end of the method *and* before instance invocations.
+        private static async Task WriteAsyncInternal(StreamWriter _this, string value,
+                                                     char[] charBuffer, int charPos, int charLen, char[] coreNewLine,
+                                                     bool autoFlush, bool appendNewLine)
+        {
+            Debug.Assert(value != null);
+
+            int count = value.Length;
+            int index = 0;
+
+            while (count > 0)
+            {
+                if (charPos == charLen)
+                {
+                    await _this.FlushAsyncInternal(false, false, charBuffer, charPos).ConfigureAwait(false);
+                    Debug.Assert(_this._charPos == 0);
+                    charPos = 0;
+                }
+
+                int n = charLen - charPos;
+                if (n > count)
+                {
+                    n = count;
+                }
+
+                Debug.Assert(n > 0, "StreamWriter::Write(String) isn't making progress!  This is most likely a race condition in user code.");
+
+                value.CopyTo(index, charBuffer, charPos, n);
+
+                charPos += n;
+                index += n;
+                count -= n;
+            }
+
+            if (appendNewLine)
+            {
+                for (int i = 0; i < coreNewLine.Length; i++)   // Expect 2 iterations, no point calling BlockCopy
+                {
+                    if (charPos == charLen)
+                    {
+                        await _this.FlushAsyncInternal(false, false, charBuffer, charPos).ConfigureAwait(false);
+                        Debug.Assert(_this._charPos == 0);
+                        charPos = 0;
+                    }
+
+                    charBuffer[charPos] = coreNewLine[i];
+                    charPos++;
+                }
+            }
+
+            if (autoFlush)
+            {
+                await _this.FlushAsyncInternal(true, false, charBuffer, charPos).ConfigureAwait(false);
+                Debug.Assert(_this._charPos == 0);
+                charPos = 0;
+            }
+
+            _this.CharPos_Prop = charPos;
+        }
+
+        public override Task WriteAsync(char[] buffer, int index, int count)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            }
+            if (index < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (buffer.Length - index < count)
+            {
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+            }
+
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Write() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Write) when we are not sure.
+            if (GetType() != typeof(StreamWriter))
+            {
+                return base.WriteAsync(buffer, index, count);
+            }
+
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_WriterClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            Task task = WriteAsyncInternal(this, new ReadOnlyMemory<char>(buffer, index, count), _charBuffer, _charPos, _charLen, CoreNewLine, _autoFlush, appendNewLine: false, cancellationToken: default);
+            _asyncWriteTask = task;
+
+            return task;
+        }
+
+        public override Task WriteAsync(ReadOnlyMemory<char> buffer, CancellationToken cancellationToken = default)
+        {
+            if (GetType() != typeof(StreamWriter))
+            {
+                // If a derived type may have overridden existing WriteASync(char[], ...) behavior, make sure we use it.
+                return base.WriteAsync(buffer, cancellationToken);
+            }
+
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_WriterClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return Task.FromCanceled(cancellationToken);
+            }
+
+            Task task = WriteAsyncInternal(this, buffer, _charBuffer, _charPos, _charLen, CoreNewLine, _autoFlush, appendNewLine: false, cancellationToken: cancellationToken);
+            _asyncWriteTask = task;
+            return task;
+        }
+
+        // We pass in private instance fields of this MarshalByRefObject-derived type as local params
+        // to ensure performant access inside the state machine that corresponds this async method.
+        // Fields that are written to must be assigned at the end of the method *and* before instance invocations.
+        private static async Task WriteAsyncInternal(StreamWriter _this, ReadOnlyMemory<char> source,
+                                                     char[] charBuffer, int charPos, int charLen, char[] coreNewLine,
+                                                     bool autoFlush, bool appendNewLine, CancellationToken cancellationToken)
+        {
+            int copied = 0;
+            while (copied < source.Length)
+            {
+                if (charPos == charLen)
+                {
+                    await _this.FlushAsyncInternal(false, false, charBuffer, charPos, cancellationToken).ConfigureAwait(false);
+                    Debug.Assert(_this._charPos == 0);
+                    charPos = 0;
+                }
+
+                int n = Math.Min(charLen - charPos, source.Length - copied);
+                Debug.Assert(n > 0, "StreamWriter::Write(char[], int, int) isn't making progress!  This is most likely a race condition in user code.");
+
+                source.Span.Slice(copied, n).CopyTo(new Span<char>(charBuffer, charPos, n));
+                charPos += n;
+                copied += n;
+            }
+
+            if (appendNewLine)
+            {
+                for (int i = 0; i < coreNewLine.Length; i++)   // Expect 2 iterations, no point calling BlockCopy
+                {
+                    if (charPos == charLen)
+                    {
+                        await _this.FlushAsyncInternal(false, false, charBuffer, charPos, cancellationToken).ConfigureAwait(false);
+                        Debug.Assert(_this._charPos == 0);
+                        charPos = 0;
+                    }
+
+                    charBuffer[charPos] = coreNewLine[i];
+                    charPos++;
+                }
+            }
+
+            if (autoFlush)
+            {
+                await _this.FlushAsyncInternal(true, false, charBuffer, charPos, cancellationToken).ConfigureAwait(false);
+                Debug.Assert(_this._charPos == 0);
+                charPos = 0;
+            }
+
+            _this.CharPos_Prop = charPos;
+        }
+
+        public override Task WriteLineAsync()
+        {
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Write() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Write) when we are not sure.
+            if (GetType() != typeof(StreamWriter))
+            {
+                return base.WriteLineAsync();
+            }
+
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_WriterClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            Task task = WriteAsyncInternal(this, ReadOnlyMemory<char>.Empty, _charBuffer, _charPos, _charLen, CoreNewLine, _autoFlush, appendNewLine: true, cancellationToken: default);
+            _asyncWriteTask = task;
+
+            return task;
+        }
+
+
+        public override Task WriteLineAsync(char value)
+        {
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Write() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Write) when we are not sure.
+            if (GetType() != typeof(StreamWriter))
+            {
+                return base.WriteLineAsync(value);
+            }
+
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_WriterClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            Task task = WriteAsyncInternal(this, value, _charBuffer, _charPos, _charLen, CoreNewLine, _autoFlush, appendNewLine: true);
+            _asyncWriteTask = task;
+
+            return task;
+        }
+
+
+        public override Task WriteLineAsync(string value)
+        {
+            if (value == null)
+            {
+                return WriteLineAsync();
+            }
+
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Write() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Write) when we are not sure.
+            if (GetType() != typeof(StreamWriter))
+            {
+                return base.WriteLineAsync(value);
+            }
+
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_WriterClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            Task task = WriteAsyncInternal(this, value, _charBuffer, _charPos, _charLen, CoreNewLine, _autoFlush, appendNewLine: true);
+            _asyncWriteTask = task;
+
+            return task;
+        }
+
+
+        public override Task WriteLineAsync(char[] buffer, int index, int count)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            }
+            if (index < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (buffer.Length - index < count)
+            {
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+            }
+
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Write() which a subclass might have overridden.  
+            // To be safe we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Write) when we are not sure.
+            if (GetType() != typeof(StreamWriter))
+            {
+                return base.WriteLineAsync(buffer, index, count);
+            }
+
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_WriterClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            Task task = WriteAsyncInternal(this, new ReadOnlyMemory<char>(buffer, index, count), _charBuffer, _charPos, _charLen, CoreNewLine, _autoFlush, appendNewLine: true, cancellationToken: default);
+            _asyncWriteTask = task;
+
+            return task;
+        }
+
+        public override Task WriteLineAsync(ReadOnlyMemory<char> buffer, CancellationToken cancellationToken = default)
+        {
+            if (GetType() != typeof(StreamWriter))
+            {
+                return base.WriteLineAsync(buffer, cancellationToken);
+            }
+
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_WriterClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return Task.FromCanceled(cancellationToken);
+            }
+
+            Task task = WriteAsyncInternal(this, buffer, _charBuffer, _charPos, _charLen, CoreNewLine, _autoFlush, appendNewLine: true, cancellationToken: cancellationToken);
+            _asyncWriteTask = task;
+
+            return task;
+        }
+
+
+        public override Task FlushAsync()
+        {
+            // If we have been inherited into a subclass, the following implementation could be incorrect
+            // since it does not call through to Flush() which a subclass might have overridden.  To be safe 
+            // we will only use this implementation in cases where we know it is safe to do so,
+            // and delegate to our base class (which will call into Flush) when we are not sure.
+            if (GetType() != typeof(StreamWriter))
+            {
+                return base.FlushAsync();
+            }
+
+            // flushEncoder should be true at the end of the file and if
+            // the user explicitly calls Flush (though not if AutoFlush is true).
+            // This is required to flush any dangling characters from our UTF-7 
+            // and UTF-8 encoders.  
+            if (_stream == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_WriterClosed);
+            }
+
+            CheckAsyncTaskInProgress();
+
+            Task task = FlushAsyncInternal(true, true, _charBuffer, _charPos);
+            _asyncWriteTask = task;
+
+            return task;
+        }
+
+        private int CharPos_Prop
+        {
+            set { _charPos = value; }
+        }
+
+        private bool HaveWrittenPreamble_Prop
+        {
+            set { _haveWrittenPreamble = value; }
+        }
+
+        private Task FlushAsyncInternal(bool flushStream, bool flushEncoder,
+                                        char[] sCharBuffer, int sCharPos, CancellationToken cancellationToken = default)
+        {
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return Task.FromCanceled(cancellationToken);
+            }
+
+            // Perf boost for Flush on non-dirty writers.
+            if (sCharPos == 0 && !flushStream && !flushEncoder)
+            {
+                return Task.CompletedTask;
+            }
+
+            Task flushTask = FlushAsyncInternal(this, flushStream, flushEncoder, sCharBuffer, sCharPos, _haveWrittenPreamble,
+                                                _encoding, _encoder, _byteBuffer, _stream, cancellationToken);
+
+            _charPos = 0;
+            return flushTask;
+        }
+
+
+        // We pass in private instance fields of this MarshalByRefObject-derived type as local params
+        // to ensure performant access inside the state machine that corresponds this async method.
+        private static async Task FlushAsyncInternal(StreamWriter _this, bool flushStream, bool flushEncoder,
+                                                     char[] charBuffer, int charPos, bool haveWrittenPreamble,
+                                                     Encoding encoding, Encoder encoder, Byte[] byteBuffer, Stream stream, CancellationToken cancellationToken)
+        {
+            if (!haveWrittenPreamble)
+            {
+                _this.HaveWrittenPreamble_Prop = true;
+                byte[] preamble = encoding.GetPreamble();
+                if (preamble.Length > 0)
+                {
+                    await stream.WriteAsync(new ReadOnlyMemory<byte>(preamble), cancellationToken).ConfigureAwait(false);
+                }
+            }
+
+            int count = encoder.GetBytes(charBuffer, 0, charPos, byteBuffer, 0, flushEncoder);
+            if (count > 0)
+            {
+                await stream.WriteAsync(new ReadOnlyMemory<byte>(byteBuffer, 0, count), cancellationToken).ConfigureAwait(false);
+            }
+
+            // By definition, calling Flush should flush the stream, but this is
+            // only necessary if we passed in true for flushStream.  The Web
+            // Services guys have some perf tests where flushing needlessly hurts.
+            if (flushStream)
+            {
+                await stream.FlushAsync(cancellationToken).ConfigureAwait(false);
+            }
+        }
+        #endregion
+    }  // class StreamWriter
+}  // namespace
diff --git a/src/System.Private.CoreLib/shared/System/IO/TextReader.cs b/src/System.Private.CoreLib/shared/System/IO/TextReader.cs
new file mode 100644
index 0000000000..eb94dd7594
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/TextReader.cs
@@ -0,0 +1,412 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Buffers;
+
+namespace System.IO
+{
+    // This abstract base class represents a reader that can read a sequential
+    // stream of characters.  This is not intended for reading bytes -
+    // there are methods on the Stream class to read bytes.
+    // A subclass must minimally implement the Peek() and Read() methods.
+    //
+    // This class is intended for character input, not bytes.  
+    // There are methods on the Stream class for reading bytes. 
+    public abstract partial class TextReader : MarshalByRefObject, IDisposable
+    {
+        public static readonly TextReader Null = new NullTextReader();
+
+        protected TextReader() { }
+
+        public virtual void Close()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        protected virtual void Dispose(bool disposing)
+        {
+        }
+
+        // Returns the next available character without actually reading it from
+        // the input stream. The current position of the TextReader is not changed by
+        // this operation. The returned value is -1 if no further characters are
+        // available.
+        // 
+        // This default method simply returns -1.
+        //
+        public virtual int Peek()
+        {
+            return -1;
+        }
+
+        // Reads the next character from the input stream. The returned value is
+        // -1 if no further characters are available.
+        // 
+        // This default method simply returns -1.
+        //
+        public virtual int Read()
+        {
+            return -1;
+        }
+
+        // Reads a block of characters. This method will read up to
+        // count characters from this TextReader into the
+        // buffer character array starting at position
+        // index. Returns the actual number of characters read.
+        //
+        public virtual int Read(char[] buffer, int index, int count)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            }
+            if (index < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (buffer.Length - index < count)
+            {
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+            }
+
+            int n;
+            for (n = 0; n < count; n++)
+            {
+                int ch = Read();
+                if (ch == -1) break;
+                buffer[index + n] = (char)ch;
+            }
+            
+            return n;
+        }
+
+        // Reads a span of characters. This method will read up to
+        // count characters from this TextReader into the
+        // span of characters Returns the actual number of characters read.
+        //
+        public virtual int Read(Span<char> buffer)
+        {
+            char[] array = ArrayPool<char>.Shared.Rent(buffer.Length);
+
+            try
+            {
+                int numRead = Read(array, 0, buffer.Length);
+                if ((uint)numRead > buffer.Length)
+                {
+                    throw new IOException(SR.IO_InvalidReadLength);
+                }
+                new Span<char>(array, 0, numRead).CopyTo(buffer);
+                return numRead;
+            }
+            finally
+            {
+                ArrayPool<char>.Shared.Return(array);
+            }
+        }
+
+        // Reads all characters from the current position to the end of the 
+        // TextReader, and returns them as one string.
+        public virtual string ReadToEnd()
+        {
+            char[] chars = new char[4096];
+            int len;
+            StringBuilder sb = new StringBuilder(4096);
+            while ((len = Read(chars, 0, chars.Length)) != 0)
+            {
+                sb.Append(chars, 0, len);
+            }
+            return sb.ToString();
+        }
+
+        // Blocking version of read.  Returns only when count
+        // characters have been read or the end of the file was reached.
+        // 
+        public virtual int ReadBlock(char[] buffer, int index, int count)
+        {
+            int i, n = 0;
+            do
+            {
+                n += (i = Read(buffer, index + n, count - n));
+            } while (i > 0 && n < count);
+            return n;
+        }
+
+        // Blocking version of read for span of characters.  Returns only when count
+        // characters have been read or the end of the file was reached.
+        //
+        public virtual int ReadBlock(Span<char> buffer)
+        {
+            char[] array = ArrayPool<char>.Shared.Rent(buffer.Length);
+
+            try
+            {
+                int numRead = ReadBlock(array, 0, buffer.Length);
+                if ((uint)numRead > buffer.Length)
+                {
+                    throw new IOException(SR.IO_InvalidReadLength);
+                }
+                new Span<char>(array, 0, numRead).CopyTo(buffer);
+                return numRead;
+            }
+            finally
+            {
+                ArrayPool<char>.Shared.Return(array);
+            }
+        }
+
+        // Reads a line. A line is defined as a sequence of characters followed by
+        // a carriage return ('\r'), a line feed ('\n'), or a carriage return
+        // immediately followed by a line feed. The resulting string does not
+        // contain the terminating carriage return and/or line feed. The returned
+        // value is null if the end of the input stream has been reached.
+        //
+        public virtual string ReadLine()
+        {
+            StringBuilder sb = new StringBuilder();
+            while (true)
+            {
+                int ch = Read();
+                if (ch == -1) break;
+                if (ch == '\r' || ch == '\n')
+                {
+                    if (ch == '\r' && Peek() == '\n')
+                    {
+                        Read();
+                    }
+
+                    return sb.ToString();
+                }
+                sb.Append((char)ch);
+            }
+            if (sb.Length > 0)
+            {
+                return sb.ToString();
+            }
+
+            return null;
+        }
+
+        #region Task based Async APIs
+        public virtual Task<string> ReadLineAsync()
+        {
+            return Task<String>.Factory.StartNew(state =>
+            {
+                return ((TextReader)state).ReadLine();
+            },
+            this, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+        }
+
+        public async virtual Task<string> ReadToEndAsync()
+        {
+            var sb = new StringBuilder(4096);
+            char[] chars = ArrayPool<char>.Shared.Rent(4096);
+            try
+            {
+                int len;
+                while ((len = await ReadAsyncInternal(chars, default).ConfigureAwait(false)) != 0)
+                {
+                    sb.Append(chars, 0, len);
+                }
+            }
+            finally
+            {
+                ArrayPool<char>.Shared.Return(chars);
+            }
+            return sb.ToString();
+        }
+
+        public virtual Task<int> ReadAsync(char[] buffer, int index, int count)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            }
+            if (index < 0 || count < 0)
+            {
+                throw new ArgumentOutOfRangeException((index < 0 ? nameof(index): nameof(count)), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (buffer.Length - index < count)
+            {
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+            }
+
+            return ReadAsyncInternal(new Memory<char>(buffer, index, count), default).AsTask();
+        }
+
+        public virtual ValueTask<int> ReadAsync(Memory<char> buffer, CancellationToken cancellationToken = default(CancellationToken)) =>
+            new ValueTask<int>(MemoryMarshal.TryGetArray(buffer, out ArraySegment<char> array) ?
+                ReadAsync(array.Array, array.Offset, array.Count) :
+                Task<int>.Factory.StartNew(state =>
+                {
+                    var t = (Tuple<TextReader, Memory<char>>)state;
+                    return t.Item1.Read(t.Item2.Span);
+                }, Tuple.Create(this, buffer), cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default));
+
+        internal virtual ValueTask<int> ReadAsyncInternal(Memory<char> buffer, CancellationToken cancellationToken)
+        {
+            var tuple = new Tuple<TextReader, Memory<char>>(this, buffer);
+            return new ValueTask<int>(Task<int>.Factory.StartNew(state =>
+            {
+                var t = (Tuple<TextReader, Memory<char>>)state;
+                return t.Item1.Read(t.Item2.Span);
+            },
+            tuple, cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default));
+        }
+
+        public virtual Task<int> ReadBlockAsync(char[] buffer, int index, int count)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            }
+            if (index < 0 || count < 0)
+            {
+                throw new ArgumentOutOfRangeException((index < 0 ? nameof(index): nameof(count)), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (buffer.Length - index < count)
+            {
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+            }
+
+            return ReadBlockAsyncInternal(new Memory<char>(buffer, index, count), default).AsTask();
+        }
+
+        public virtual ValueTask<int> ReadBlockAsync(Memory<char> buffer, CancellationToken cancellationToken = default(CancellationToken)) =>
+            new ValueTask<int>(MemoryMarshal.TryGetArray(buffer, out ArraySegment<char> array) ?
+                ReadBlockAsync(array.Array, array.Offset, array.Count) :
+                Task<int>.Factory.StartNew(state =>
+                {
+                    var t = (Tuple<TextReader, Memory<char>>)state;
+                    return t.Item1.ReadBlock(t.Item2.Span);
+                }, Tuple.Create(this, buffer), cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default));
+
+        internal async ValueTask<int> ReadBlockAsyncInternal(Memory<char> buffer, CancellationToken cancellationToken)
+        {
+            int n = 0, i;
+            do
+            {
+                i = await ReadAsyncInternal(buffer.Slice(n), cancellationToken).ConfigureAwait(false);
+                n += i;
+            } while (i > 0 && n < buffer.Length);
+
+            return n;
+        }
+        #endregion
+
+        private sealed class NullTextReader : TextReader
+        {
+            public NullTextReader() { }
+
+            public override int Read(char[] buffer, int index, int count)
+            {
+                return 0;
+            }
+
+            public override string ReadLine()
+            {
+                return null;
+            }
+        }
+
+        public static TextReader Synchronized(TextReader reader)
+        {
+            if (reader == null)
+                throw new ArgumentNullException(nameof(reader));
+
+            return reader is SyncTextReader ? reader : new SyncTextReader(reader);
+        }
+
+        internal sealed class SyncTextReader : TextReader
+        {
+            internal readonly TextReader _in;
+
+            internal SyncTextReader(TextReader t)
+            {
+                _in = t;
+            }
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Close() => _in.Close();
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            protected override void Dispose(bool disposing)
+            {
+                // Explicitly pick up a potentially methodimpl'ed Dispose
+                if (disposing)
+                    ((IDisposable)_in).Dispose();
+            }
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override int Peek() => _in.Peek();
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override int Read() => _in.Read();
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override int Read(char[] buffer, int index, int count) => _in.Read(buffer, index, count);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override int ReadBlock(char[] buffer, int index, int count) => _in.ReadBlock(buffer, index, count);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override string ReadLine() => _in.ReadLine();
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override string ReadToEnd() => _in.ReadToEnd();
+
+            //
+            // On SyncTextReader all APIs should run synchronously, even the async ones.
+            //
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override Task<string> ReadLineAsync() => Task.FromResult(ReadLine());
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override Task<string> ReadToEndAsync() => Task.FromResult(ReadToEnd());
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override Task<int> ReadBlockAsync(char[] buffer, int index, int count)
+            {
+                if (buffer == null)
+                    throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+                if (index < 0 || count < 0)
+                    throw new ArgumentOutOfRangeException((index < 0 ? nameof(index) : nameof(count)), SR.ArgumentOutOfRange_NeedNonNegNum);
+                if (buffer.Length - index < count)
+                    throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+                return Task.FromResult(ReadBlock(buffer, index, count));
+            }
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override Task<int> ReadAsync(char[] buffer, int index, int count)
+            {
+                if (buffer == null)
+                    throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+                if (index < 0 || count < 0)
+                    throw new ArgumentOutOfRangeException((index < 0 ? nameof(index) : nameof(count)), SR.ArgumentOutOfRange_NeedNonNegNum);
+                if (buffer.Length - index < count)
+                    throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+                return Task.FromResult(Read(buffer, index, count));
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/TextWriter.cs b/src/System.Private.CoreLib/shared/System/IO/TextWriter.cs
new file mode 100644
index 0000000000..48e702be67
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/TextWriter.cs
@@ -0,0 +1,870 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text;
+using System.Threading;
+using System.Globalization;
+using System.Threading.Tasks;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Buffers;
+
+namespace System.IO
+{
+    // This abstract base class represents a writer that can write a sequential
+    // stream of characters. A subclass must minimally implement the 
+    // Write(char) method.
+    //
+    // This class is intended for character output, not bytes.  
+    // There are methods on the Stream class for writing bytes. 
+    public abstract partial class TextWriter : MarshalByRefObject, IDisposable
+    {
+        public static readonly TextWriter Null = new NullTextWriter();
+
+        // We don't want to allocate on every TextWriter creation, so cache the char array.  
+        private static readonly char[] s_coreNewLine = Environment.NewLine.ToCharArray();
+
+        /// <summary>
+        /// This is the 'NewLine' property expressed as a char[].   
+        /// It is exposed to subclasses as a protected field for read-only
+        /// purposes.  You should only modify it by using the 'NewLine' property.  
+        /// In particular you should never modify the elements of the array 
+        /// as they are shared among many instances of TextWriter.  
+        /// </summary>
+        protected char[] CoreNewLine = s_coreNewLine;
+        private string CoreNewLineStr = Environment.NewLine;
+
+        // Can be null - if so, ask for the Thread's CurrentCulture every time.
+        private IFormatProvider _internalFormatProvider;
+
+        protected TextWriter()
+        {
+            _internalFormatProvider = null;  // Ask for CurrentCulture all the time.
+        }
+
+        protected TextWriter(IFormatProvider formatProvider)
+        {
+            _internalFormatProvider = formatProvider;
+        }
+
+        public virtual IFormatProvider FormatProvider
+        {
+            get
+            {
+                if (_internalFormatProvider == null)
+                {
+                    return CultureInfo.CurrentCulture;
+                }
+                else
+                {
+                    return _internalFormatProvider;
+                }
+            }
+        }
+
+        public virtual void Close()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        protected virtual void Dispose(bool disposing)
+        {
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        // Clears all buffers for this TextWriter and causes any buffered data to be
+        // written to the underlying device. This default method is empty, but
+        // descendant classes can override the method to provide the appropriate
+        // functionality.
+        public virtual void Flush()
+        {
+        }
+
+        public abstract Encoding Encoding
+        {
+            get;
+        }
+
+        /// <summary>
+        /// Returns the line terminator string used by this TextWriter. The default line
+        /// terminator string is Environment.NewLine, which is platform specific. 
+        /// On Windows this is a carriage return followed by a line feed ("\r\n").
+        /// On OSX and Linux this is a line feed ("\n").
+        /// </summary>
+        /// <remarks>
+        /// The line terminator string is written to the text stream whenever one of the
+        /// WriteLine methods are called. In order for text written by
+        /// the TextWriter to be readable by a TextReader, only one of the following line
+        /// terminator strings should be used: "\r", "\n", or "\r\n".
+        /// </remarks>
+        public virtual string NewLine
+        {
+            get { return CoreNewLineStr; }
+            set
+            {
+                if (value == null)
+                {
+                    value = Environment.NewLine;
+                }
+
+                CoreNewLineStr = value;
+                CoreNewLine = value.ToCharArray();
+            }
+        }
+
+
+        // Writes a character to the text stream. This default method is empty,
+        // but descendant classes can override the method to provide the
+        // appropriate functionality.
+        //
+        public virtual void Write(char value)
+        {
+        }
+
+        // Writes a character array to the text stream. This default method calls
+        // Write(char) for each of the characters in the character array.
+        // If the character array is null, nothing is written.
+        //
+        public virtual void Write(char[] buffer)
+        {
+            if (buffer != null)
+            {
+                Write(buffer, 0, buffer.Length);
+            }
+        }
+
+        // Writes a range of a character array to the text stream. This method will
+        // write count characters of data into this TextWriter from the
+        // buffer character array starting at position index.
+        //
+        public virtual void Write(char[] buffer, int index, int count)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            }
+            if (index < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (buffer.Length - index < count)
+            {
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+            }
+
+            for (int i = 0; i < count; i++) Write(buffer[index + i]);
+        }
+
+        // Writes a span of characters to the text stream.
+        //
+        public virtual void Write(ReadOnlySpan<char> buffer)
+        {
+            char[] array = ArrayPool<char>.Shared.Rent(buffer.Length);
+
+            try
+            {
+                buffer.CopyTo(new Span<char>(array));
+                Write(array, 0, buffer.Length);
+            }
+            finally
+            {
+                ArrayPool<char>.Shared.Return(array);
+            }
+        }
+
+        // Writes the text representation of a boolean to the text stream. This
+        // method outputs either Boolean.TrueString or Boolean.FalseString.
+        //
+        public virtual void Write(bool value)
+        {
+            Write(value ? "True" : "False");
+        }
+
+        // Writes the text representation of an integer to the text stream. The
+        // text representation of the given value is produced by calling the
+        // Int32.ToString() method.
+        //
+        public virtual void Write(int value)
+        {
+            Write(value.ToString(FormatProvider));
+        }
+
+        // Writes the text representation of an integer to the text stream. The
+        // text representation of the given value is produced by calling the
+        // UInt32.ToString() method.
+        //
+        [CLSCompliant(false)]
+        public virtual void Write(uint value)
+        {
+            Write(value.ToString(FormatProvider));
+        }
+
+        // Writes the text representation of a long to the text stream. The
+        // text representation of the given value is produced by calling the
+        // Int64.ToString() method.
+        //
+        public virtual void Write(long value)
+        {
+            Write(value.ToString(FormatProvider));
+        }
+
+        // Writes the text representation of an unsigned long to the text 
+        // stream. The text representation of the given value is produced 
+        // by calling the UInt64.ToString() method.
+        //
+        [CLSCompliant(false)]
+        public virtual void Write(ulong value)
+        {
+            Write(value.ToString(FormatProvider));
+        }
+
+        // Writes the text representation of a float to the text stream. The
+        // text representation of the given value is produced by calling the
+        // Float.toString(float) method.
+        //
+        public virtual void Write(float value)
+        {
+            Write(value.ToString(FormatProvider));
+        }
+
+        // Writes the text representation of a double to the text stream. The
+        // text representation of the given value is produced by calling the
+        // Double.toString(double) method.
+        //
+        public virtual void Write(double value)
+        {
+            Write(value.ToString(FormatProvider));
+        }
+
+        public virtual void Write(decimal value)
+        {
+            Write(value.ToString(FormatProvider));
+        }
+
+        // Writes a string to the text stream. If the given string is null, nothing
+        // is written to the text stream.
+        //
+        public virtual void Write(string value)
+        {
+            if (value != null)
+            {
+                Write(value.ToCharArray());
+            }
+        }
+
+        // Writes the text representation of an object to the text stream. If the
+        // given object is null, nothing is written to the text stream.
+        // Otherwise, the object's ToString method is called to produce the
+        // string representation, and the resulting string is then written to the
+        // output stream.
+        //
+        public virtual void Write(object value)
+        {
+            if (value != null)
+            {
+                IFormattable f = value as IFormattable;
+                if (f != null)
+                {
+                    Write(f.ToString(null, FormatProvider));
+                }
+                else
+                    Write(value.ToString());
+            }
+        }
+
+        // Writes out a formatted string.  Uses the same semantics as
+        // String.Format.
+        // 
+        public virtual void Write(string format, object arg0)
+        {
+            Write(string.Format(FormatProvider, format, arg0));
+        }
+
+        // Writes out a formatted string.  Uses the same semantics as
+        // String.Format.
+        // 
+        public virtual void Write(string format, object arg0, object arg1)
+        {
+            Write(string.Format(FormatProvider, format, arg0, arg1));
+        }
+
+        // Writes out a formatted string.  Uses the same semantics as
+        // String.Format.
+        // 
+        public virtual void Write(string format, object arg0, object arg1, object arg2)
+        {
+            Write(string.Format(FormatProvider, format, arg0, arg1, arg2));
+        }
+
+        // Writes out a formatted string.  Uses the same semantics as
+        // String.Format.
+        // 
+        public virtual void Write(string format, params object[] arg)
+        {
+            Write(string.Format(FormatProvider, format, arg));
+        }
+
+
+        // Writes a line terminator to the text stream. The default line terminator
+        // is Environment.NewLine, but this value can be changed by setting the NewLine property.
+        //
+        public virtual void WriteLine()
+        {
+            Write(CoreNewLine);
+        }
+
+        // Writes a character followed by a line terminator to the text stream.
+        //
+        public virtual void WriteLine(char value)
+        {
+            Write(value);
+            WriteLine();
+        }
+
+        // Writes an array of characters followed by a line terminator to the text
+        // stream.
+        //
+        public virtual void WriteLine(char[] buffer)
+        {
+            Write(buffer);
+            WriteLine();
+        }
+
+        // Writes a range of a character array followed by a line terminator to the
+        // text stream.
+        //
+        public virtual void WriteLine(char[] buffer, int index, int count)
+        {
+            Write(buffer, index, count);
+            WriteLine();
+        }
+
+        public virtual void WriteLine(ReadOnlySpan<char> buffer)
+        {
+            char[] array = ArrayPool<char>.Shared.Rent(buffer.Length);
+
+            try
+            {
+                buffer.CopyTo(new Span<char>(array));
+                WriteLine(array, 0, buffer.Length);
+            }
+            finally
+            {
+                ArrayPool<char>.Shared.Return(array);
+            }
+        }
+
+        // Writes the text representation of a boolean followed by a line
+        // terminator to the text stream.
+        //
+        public virtual void WriteLine(bool value)
+        {
+            Write(value);
+            WriteLine();
+        }
+
+        // Writes the text representation of an integer followed by a line
+        // terminator to the text stream.
+        //
+        public virtual void WriteLine(int value)
+        {
+            Write(value);
+            WriteLine();
+        }
+
+        // Writes the text representation of an unsigned integer followed by 
+        // a line terminator to the text stream.
+        //
+        [CLSCompliant(false)]
+        public virtual void WriteLine(uint value)
+        {
+            Write(value);
+            WriteLine();
+        }
+
+        // Writes the text representation of a long followed by a line terminator
+        // to the text stream.
+        //
+        public virtual void WriteLine(long value)
+        {
+            Write(value);
+            WriteLine();
+        }
+
+        // Writes the text representation of an unsigned long followed by 
+        // a line terminator to the text stream.
+        //
+        [CLSCompliant(false)]
+        public virtual void WriteLine(ulong value)
+        {
+            Write(value);
+            WriteLine();
+        }
+
+        // Writes the text representation of a float followed by a line terminator
+        // to the text stream.
+        //
+        public virtual void WriteLine(float value)
+        {
+            Write(value);
+            WriteLine();
+        }
+
+        // Writes the text representation of a double followed by a line terminator
+        // to the text stream.
+        //
+        public virtual void WriteLine(double value)
+        {
+            Write(value);
+            WriteLine();
+        }
+
+        public virtual void WriteLine(decimal value)
+        {
+            Write(value);
+            WriteLine();
+        }
+
+        // Writes a string followed by a line terminator to the text stream.
+        //
+        public virtual void WriteLine(string value)
+        {
+            if (value != null)
+            {
+                Write(value);
+            }
+            Write(CoreNewLineStr);
+        }
+
+        // Writes the text representation of an object followed by a line
+        // terminator to the text stream.
+        //
+        public virtual void WriteLine(object value)
+        {
+            if (value == null)
+            {
+                WriteLine();
+            }
+            else
+            {
+                // Call WriteLine(value.ToString), not Write(Object), WriteLine().
+                // This makes calls to WriteLine(Object) atomic.
+                IFormattable f = value as IFormattable;
+                if (f != null)
+                {
+                    WriteLine(f.ToString(null, FormatProvider));
+                }
+                else
+                {
+                    WriteLine(value.ToString());
+                }
+            }
+        }
+
+        // Writes out a formatted string and a new line.  Uses the same 
+        // semantics as String.Format.
+        // 
+        public virtual void WriteLine(string format, object arg0)
+        {
+            WriteLine(string.Format(FormatProvider, format, arg0));
+        }
+
+        // Writes out a formatted string and a new line.  Uses the same 
+        // semantics as String.Format.
+        // 
+        public virtual void WriteLine(string format, object arg0, object arg1)
+        {
+            WriteLine(string.Format(FormatProvider, format, arg0, arg1));
+        }
+
+        // Writes out a formatted string and a new line.  Uses the same 
+        // semantics as String.Format.
+        // 
+        public virtual void WriteLine(string format, object arg0, object arg1, object arg2)
+        {
+            WriteLine(string.Format(FormatProvider, format, arg0, arg1, arg2));
+        }
+
+        // Writes out a formatted string and a new line.  Uses the same 
+        // semantics as String.Format.
+        // 
+        public virtual void WriteLine(string format, params object[] arg)
+        {
+            WriteLine(string.Format(FormatProvider, format, arg));
+        }
+
+        #region Task based Async APIs
+        public virtual Task WriteAsync(char value)
+        {
+            var tuple = new Tuple<TextWriter, char>(this, value);
+            return Task.Factory.StartNew(state =>
+            {
+                var t = (Tuple<TextWriter, char>)state;
+                t.Item1.Write(t.Item2);
+            },
+            tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+        }
+
+        public virtual Task WriteAsync(string value)
+        {
+            var tuple = new Tuple<TextWriter, string>(this, value);
+            return Task.Factory.StartNew(state =>
+            {
+                var t = (Tuple<TextWriter, string>)state;
+                t.Item1.Write(t.Item2);
+            },
+            tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+        }
+
+        public Task WriteAsync(char[] buffer)
+        {
+            if (buffer == null)
+            {
+                return Task.CompletedTask;
+            }
+
+            return WriteAsync(buffer, 0, buffer.Length);
+        }
+
+        public virtual Task WriteAsync(char[] buffer, int index, int count)
+        {
+            var tuple = new Tuple<TextWriter, char[], int, int>(this, buffer, index, count);
+            return Task.Factory.StartNew(state =>
+            {
+                var t = (Tuple<TextWriter, char[], int, int>)state;
+                t.Item1.Write(t.Item2, t.Item3, t.Item4);
+            },
+            tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+        }
+
+        public virtual Task WriteAsync(ReadOnlyMemory<char> buffer, CancellationToken cancellationToken = default(CancellationToken)) =>
+            MemoryMarshal.TryGetArray(buffer, out ArraySegment<char> array) ?
+                WriteAsync(array.Array, array.Offset, array.Count) :
+                Task.Factory.StartNew(state =>
+                {
+                    var t = (Tuple<TextWriter, ReadOnlyMemory<char>>)state;
+                    t.Item1.Write(t.Item2.Span);
+                }, Tuple.Create(this, buffer), cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+
+        public virtual Task WriteLineAsync(char value)
+        {
+            var tuple = new Tuple<TextWriter, char>(this, value);
+            return Task.Factory.StartNew(state =>
+            {
+                var t = (Tuple<TextWriter, char>)state;
+                t.Item1.WriteLine(t.Item2);
+            },
+            tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+        }
+
+        public virtual Task WriteLineAsync(string value)
+        {
+            var tuple = new Tuple<TextWriter, string>(this, value);
+            return Task.Factory.StartNew(state =>
+            {
+                var t = (Tuple<TextWriter, string>)state;
+                t.Item1.WriteLine(t.Item2);
+            },
+            tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+        }
+
+        public Task WriteLineAsync(char[] buffer)
+        {
+            if (buffer == null)
+            {
+                return WriteLineAsync();
+            }
+
+            return WriteLineAsync(buffer, 0, buffer.Length);
+        }
+
+        public virtual Task WriteLineAsync(char[] buffer, int index, int count)
+        {
+            var tuple = new Tuple<TextWriter, char[], int, int>(this, buffer, index, count);
+            return Task.Factory.StartNew(state =>
+            {
+                var t = (Tuple<TextWriter, char[], int, int>)state;
+                t.Item1.WriteLine(t.Item2, t.Item3, t.Item4);
+            },
+            tuple, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+        }
+
+        public virtual Task WriteLineAsync(ReadOnlyMemory<char> buffer, CancellationToken cancellationToken = default(CancellationToken)) =>
+            MemoryMarshal.TryGetArray(buffer, out ArraySegment<char> array) ?
+                WriteLineAsync(array.Array, array.Offset, array.Count) :
+                Task.Factory.StartNew(state =>
+                {
+                    var t = (Tuple<TextWriter, ReadOnlyMemory<char>>)state;
+                    t.Item1.WriteLine(t.Item2.Span);
+                }, Tuple.Create(this, buffer), cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+
+        public virtual Task WriteLineAsync()
+        {
+            return WriteAsync(CoreNewLine);
+        }
+
+        public virtual Task FlushAsync()
+        {
+            return Task.Factory.StartNew(state =>
+            {
+                ((TextWriter)state).Flush();
+            },
+            this, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+        }
+        #endregion
+
+        private sealed class NullTextWriter : TextWriter
+        {
+            internal NullTextWriter() : base(CultureInfo.InvariantCulture)
+            {
+            }
+
+            public override Encoding Encoding
+            {
+                get
+                {
+                    return Encoding.Unicode;
+                }
+            }
+
+            public override void Write(char[] buffer, int index, int count)
+            {
+            }
+
+            public override void Write(string value)
+            {
+            }
+
+            // Not strictly necessary, but for perf reasons
+            public override void WriteLine()
+            {
+            }
+
+            // Not strictly necessary, but for perf reasons
+            public override void WriteLine(string value)
+            {
+            }
+
+            public override void WriteLine(object value)
+            {
+            }
+
+            public override void Write(char value)
+            {
+            }
+        }
+
+        public static TextWriter Synchronized(TextWriter writer)
+        {
+            if (writer == null)
+                throw new ArgumentNullException(nameof(writer));
+
+            return writer is SyncTextWriter ? writer : new SyncTextWriter(writer);
+        }
+
+        internal sealed class SyncTextWriter : TextWriter, IDisposable
+        {
+            private readonly TextWriter _out;
+
+            internal SyncTextWriter(TextWriter t) : base(t.FormatProvider)
+            {
+                _out = t;
+            }
+
+            public override Encoding Encoding =>  _out.Encoding;
+
+            public override IFormatProvider FormatProvider => _out.FormatProvider;
+
+            public override string NewLine
+            {
+                [MethodImpl(MethodImplOptions.Synchronized)]
+                get { return _out.NewLine; }
+                [MethodImpl(MethodImplOptions.Synchronized)]
+                set { _out.NewLine = value; }
+            }
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Close() => _out.Close();
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            protected override void Dispose(bool disposing)
+            {
+                // Explicitly pick up a potentially methodimpl'ed Dispose
+                if (disposing)
+                    ((IDisposable)_out).Dispose();
+            }
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Flush() => _out.Flush();
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(char value) => _out.Write(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(char[] buffer) => _out.Write(buffer);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(char[] buffer, int index, int count) => _out.Write(buffer, index, count);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(bool value) => _out.Write(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(int value) => _out.Write(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(uint value) => _out.Write(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(long value) => _out.Write(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(ulong value) => _out.Write(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(float value) => _out.Write(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(double value) => _out.Write(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(Decimal value) => _out.Write(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(string value) => _out.Write(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(object value) => _out.Write(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(string format, object arg0) => _out.Write(format, arg0);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(string format, object arg0, object arg1) => _out.Write(format, arg0, arg1);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(string format, object arg0, object arg1, object arg2) => _out.Write(format, arg0, arg1, arg2);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void Write(string format, object[] arg) => _out.Write(format, arg);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine() => _out.WriteLine();
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(char value) => _out.WriteLine(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(decimal value) => _out.WriteLine(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(char[] buffer) => _out.WriteLine(buffer);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(char[] buffer, int index, int count) => _out.WriteLine(buffer, index, count);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(bool value) => _out.WriteLine(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(int value) => _out.WriteLine(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(uint value) => _out.WriteLine(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(long value) => _out.WriteLine(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(ulong value) => _out.WriteLine(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(float value) => _out.WriteLine(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(double value) => _out.WriteLine(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(string value) => _out.WriteLine(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(object value) => _out.WriteLine(value);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(string format, object arg0) => _out.WriteLine(format, arg0);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(string format, object arg0, object arg1) => _out.WriteLine(format, arg0, arg1);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(string format, object arg0, object arg1, object arg2) => _out.WriteLine(format, arg0, arg1, arg2);
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override void WriteLine(string format, object[] arg) => _out.WriteLine(format, arg);
+
+            //
+            // On SyncTextWriter all APIs should run synchronously, even the async ones.
+            //
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override Task WriteAsync(char value)
+            {
+                Write(value);
+                return Task.CompletedTask;
+            }
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override Task WriteAsync(string value)
+            {
+                Write(value);
+                return Task.CompletedTask;
+            }
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override Task WriteAsync(char[] buffer, int index, int count)
+            {
+                Write(buffer, index, count);
+                return Task.CompletedTask;
+            }
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override Task WriteLineAsync(char value)
+            {
+                WriteLine(value);
+                return Task.CompletedTask;
+            }
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override Task WriteLineAsync(string value)
+            {
+                WriteLine(value);
+                return Task.CompletedTask;
+            }
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override Task WriteLineAsync(char[] buffer, int index, int count)
+            {
+                WriteLine(buffer, index, count);
+                return Task.CompletedTask;
+            }
+
+            [MethodImpl(MethodImplOptions.Synchronized)]
+            public override Task FlushAsync()
+            {
+                Flush();
+                return Task.CompletedTask;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/UnmanagedMemoryAccessor.cs b/src/System.Private.CoreLib/shared/System/IO/UnmanagedMemoryAccessor.cs
new file mode 100644
index 0000000000..1247ad6d5d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/UnmanagedMemoryAccessor.cs
@@ -0,0 +1,670 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+** Purpose: Provides a fast, AV free, cross-language way of 
+**          accessing unmanaged memory in a random fashion.
+**
+**
+===========================================================*/
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.IO
+{
+    /// Perf notes: ReadXXX, WriteXXX (for basic types) acquire and release the 
+    /// SafeBuffer pointer rather than relying on generic Read(T) from SafeBuffer because
+    /// this gives better throughput; benchmarks showed about 12-15% better.
+    public class UnmanagedMemoryAccessor : IDisposable
+    {
+        private SafeBuffer _buffer;
+        private long _offset;
+        private long _capacity;
+        private FileAccess _access;
+        private bool _isOpen;
+        private bool _canRead;
+        private bool _canWrite;
+
+        protected UnmanagedMemoryAccessor()
+        {
+            _isOpen = false;
+        }
+
+        public UnmanagedMemoryAccessor(SafeBuffer buffer, long offset, long capacity)
+        {
+            Initialize(buffer, offset, capacity, FileAccess.Read);
+        }
+
+        public UnmanagedMemoryAccessor(SafeBuffer buffer, long offset, long capacity, FileAccess access)
+        {
+            Initialize(buffer, offset, capacity, access);
+        }
+
+        protected void Initialize(SafeBuffer buffer, long offset, long capacity, FileAccess access)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer));
+            }
+            if (offset < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (capacity < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(capacity), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (buffer.ByteLength < (ulong)(offset + capacity))
+            {
+                throw new ArgumentException(SR.Argument_OffsetAndCapacityOutOfBounds);
+            }
+            if (access < FileAccess.Read || access > FileAccess.ReadWrite)
+            {
+                throw new ArgumentOutOfRangeException(nameof(access));
+            }
+
+            if (_isOpen)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_CalledTwice);
+            }
+
+            unsafe
+            {
+                byte* pointer = null;
+
+                try
+                {
+                    buffer.AcquirePointer(ref pointer);
+                    if (((byte*)((long)pointer + offset + capacity)) < pointer)
+                    {
+                        throw new ArgumentException(SR.Argument_UnmanagedMemAccessorWrapAround);
+                    }
+                }
+                finally
+                {
+                    if (pointer != null)
+                    {
+                        buffer.ReleasePointer();
+                    }
+                }
+            }
+
+            _offset = offset;
+            _buffer = buffer;
+            _capacity = capacity;
+            _access = access;
+            _isOpen = true;
+            _canRead = (_access & FileAccess.Read) != 0;
+            _canWrite = (_access & FileAccess.Write) != 0;
+        }
+
+        public long Capacity => _capacity;
+
+        public bool CanRead => _isOpen && _canRead;
+
+        public bool CanWrite => _isOpen && _canWrite;
+
+        protected virtual void Dispose(bool disposing)
+        {
+            _isOpen = false;
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        protected bool IsOpen => _isOpen;
+
+        // ************** Read Methods ****************/
+
+        public bool ReadBoolean(long position) => ReadByte(position) != 0;
+
+        public byte ReadByte(long position)
+        {
+            EnsureSafeToRead(position, sizeof(byte));
+
+            byte result;
+            unsafe
+            {
+                byte* pointer = null;
+
+                try
+                {
+                    _buffer.AcquirePointer(ref pointer);
+                    result = *((byte*)(pointer + _offset + position));
+                }
+                finally
+                {
+                    if (pointer != null)
+                    {
+                        _buffer.ReleasePointer();
+                    }
+                }
+            }
+            return result;
+        }
+
+        public char ReadChar(long position) => unchecked((char)ReadInt16(position));
+
+        public short ReadInt16(long position)
+        {
+            EnsureSafeToRead(position, sizeof(short));
+
+            short result;
+            unsafe
+            {
+                byte* pointer = null;
+
+                try
+                {
+                    _buffer.AcquirePointer(ref pointer);
+                    result = Unsafe.ReadUnaligned<short>(pointer + _offset + position);
+                }
+                finally
+                {
+                    if (pointer != null)
+                    {
+                        _buffer.ReleasePointer();
+                    }
+                }
+            }
+            return result;
+        }
+
+        public int ReadInt32(long position)
+        {
+            EnsureSafeToRead(position, sizeof(int));
+
+            int result;
+            unsafe
+            {
+                byte* pointer = null;
+
+                try
+                {
+                    _buffer.AcquirePointer(ref pointer);
+                    result = Unsafe.ReadUnaligned<int>(pointer + _offset + position);
+                }
+                finally
+                {
+                    if (pointer != null)
+                    {
+                        _buffer.ReleasePointer();
+                    }
+                }
+            }
+            return result;
+        }
+
+        public long ReadInt64(long position)
+        {
+            EnsureSafeToRead(position, sizeof(long));
+
+            long result;
+            unsafe
+            {
+                byte* pointer = null;
+
+                try
+                {
+                    _buffer.AcquirePointer(ref pointer);
+                    result = Unsafe.ReadUnaligned<long>(pointer + _offset + position);
+                }
+                finally
+                {
+                    if (pointer != null)
+                    {
+                        _buffer.ReleasePointer();
+                    }
+                }
+            }
+            return result;
+        }
+
+        public decimal ReadDecimal(long position)
+        {
+            const int ScaleMask = 0x00FF0000;
+            const int SignMask = unchecked((int)0x80000000);
+
+            EnsureSafeToRead(position, sizeof(decimal));
+
+            int lo, mid, hi, flags;
+
+            unsafe
+            {
+                byte* pointer = null;
+                try
+                {
+                    _buffer.AcquirePointer(ref pointer);
+                    pointer += (_offset + position);
+
+                    lo = Unsafe.ReadUnaligned<int>(pointer);
+                    mid = Unsafe.ReadUnaligned<int>(pointer + 4);
+                    hi = Unsafe.ReadUnaligned<int>(pointer + 8);
+                    flags = Unsafe.ReadUnaligned<int>(pointer + 12);
+                }
+                finally
+                {
+                    if (pointer != null)
+                    {
+                        _buffer.ReleasePointer();
+                    }
+                }
+            }
+
+            // Check for invalid Decimal values
+            if (!((flags & ~(SignMask | ScaleMask)) == 0 && (flags & ScaleMask) <= (28 << 16)))
+            {
+                throw new ArgumentException(SR.Arg_BadDecimal); // Throw same Exception type as Decimal(int[]) ctor for compat
+            }
+
+            bool isNegative = (flags & SignMask) != 0;
+            byte scale = (byte)(flags >> 16);
+
+            return new decimal(lo, mid, hi, isNegative, scale);
+        }
+
+        public float ReadSingle(long position) => BitConverter.Int32BitsToSingle(ReadInt32(position));
+
+        public double ReadDouble(long position) => BitConverter.Int64BitsToDouble(ReadInt64(position));
+
+        [CLSCompliant(false)]
+        public sbyte ReadSByte(long position) => unchecked((sbyte)ReadByte(position));
+
+        [CLSCompliant(false)]
+        public ushort ReadUInt16(long position) => unchecked((ushort)ReadInt16(position));
+
+        [CLSCompliant(false)]
+        public uint ReadUInt32(long position) => unchecked((uint)ReadInt32(position));
+
+        [CLSCompliant(false)]
+        public ulong ReadUInt64(long position) => unchecked((ulong)ReadInt64(position));
+
+        // Reads a struct of type T from unmanaged memory, into the reference pointed to by ref value.  
+        // Note: this method is not safe, since it overwrites the contents of a structure, it can be 
+        // used to modify the private members of a struct.
+        // This method is most performant when used with medium to large sized structs
+        // (larger than 8 bytes -- though this is number is JIT and architecture dependent).   As 
+        // such, it is best to use the ReadXXX methods for small standard types such as ints, longs, 
+        // bools, etc.
+        public void Read<T>(long position, out T structure) where T : struct
+        {
+            if (position < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(position), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (!_isOpen)
+            {
+                throw new ObjectDisposedException(nameof(UnmanagedMemoryAccessor), SR.ObjectDisposed_ViewAccessorClosed);
+            }
+            if (!_canRead)
+            {
+                throw new NotSupportedException(SR.NotSupported_Reading);
+            }
+
+            uint sizeOfT = SafeBuffer.SizeOf<T>();
+            if (position > _capacity - sizeOfT)
+            {
+                if (position >= _capacity)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(position), SR.ArgumentOutOfRange_PositionLessThanCapacityRequired);
+                }
+                else
+                {
+                    throw new ArgumentException(SR.Format(SR.Argument_NotEnoughBytesToRead, typeof(T)), nameof(position));
+                }
+            }
+
+            structure = _buffer.Read<T>((ulong)(_offset + position));
+        }
+
+        // Reads 'count' structs of type T from unmanaged memory, into 'array' starting at 'offset'.  
+        // Note: this method is not safe, since it overwrites the contents of structures, it can 
+        // be used to modify the private members of a struct.
+        public int ReadArray<T>(long position, T[] array, int offset, int count) where T : struct
+        {
+            if (array == null)
+            {
+                throw new ArgumentNullException(nameof(array), SR.ArgumentNull_Buffer);
+            }
+            if (offset < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (array.Length - offset < count)
+            {
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+            }
+            if (!_isOpen)
+            {
+                throw new ObjectDisposedException(nameof(UnmanagedMemoryAccessor), SR.ObjectDisposed_ViewAccessorClosed);
+            }
+            if (!_canRead)
+            {
+                throw new NotSupportedException(SR.NotSupported_Reading);
+            }
+            if (position < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(position), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            uint sizeOfT = SafeBuffer.AlignedSizeOf<T>();
+
+            // only check position and ask for fewer Ts if count is too big
+            if (position >= _capacity)
+            {
+                throw new ArgumentOutOfRangeException(nameof(position), SR.ArgumentOutOfRange_PositionLessThanCapacityRequired);
+            }
+
+            int n = count;
+            long spaceLeft = _capacity - position;
+            if (spaceLeft < 0)
+            {
+                n = 0;
+            }
+            else
+            {
+                ulong spaceNeeded = (ulong)(sizeOfT * count);
+                if ((ulong)spaceLeft < spaceNeeded)
+                {
+                    n = (int)(spaceLeft / sizeOfT);
+                }
+            }
+
+            _buffer.ReadArray<T>((ulong)(_offset + position), array, offset, n);
+
+            return n;
+        }
+
+        // ************** Write Methods ****************/
+
+        public void Write(long position, bool value) => Write(position, (byte)(value ? 1 : 0));
+
+        public void Write(long position, byte value)
+        {
+            EnsureSafeToWrite(position, sizeof(byte));
+
+            unsafe
+            {
+                byte* pointer = null;
+
+                try
+                {
+                    _buffer.AcquirePointer(ref pointer);
+                    *((byte*)(pointer + _offset + position)) = value;
+                }
+                finally
+                {
+                    if (pointer != null)
+                    {
+                        _buffer.ReleasePointer();
+                    }
+                }
+            }
+        }
+
+        public void Write(long position, char value) => Write(position, unchecked((short)value));
+
+        public void Write(long position, short value)
+        {
+            EnsureSafeToWrite(position, sizeof(short));
+
+            unsafe
+            {
+                byte* pointer = null;
+
+                try
+                {
+                    _buffer.AcquirePointer(ref pointer);
+                    Unsafe.WriteUnaligned<short>(pointer + _offset + position, value);
+                }
+                finally
+                {
+                    if (pointer != null)
+                    {
+                        _buffer.ReleasePointer();
+                    }
+                }
+            }
+        }
+
+        public void Write(long position, int value)
+        {
+            EnsureSafeToWrite(position, sizeof(int));
+
+            unsafe
+            {
+                byte* pointer = null;
+
+                try
+                {
+                    _buffer.AcquirePointer(ref pointer);
+                    Unsafe.WriteUnaligned<int>(pointer + _offset + position, value);
+                }
+                finally
+                {
+                    if (pointer != null)
+                    {
+                        _buffer.ReleasePointer();
+                    }
+                }
+            }
+        }
+
+        public void Write(long position, long value)
+        {
+            EnsureSafeToWrite(position, sizeof(long));
+
+            unsafe
+            {
+                byte* pointer = null;
+
+                try
+                {
+                    _buffer.AcquirePointer(ref pointer);
+                    Unsafe.WriteUnaligned<long>(pointer + _offset + position, value);
+                }
+                finally
+                {
+                    if (pointer != null)
+                    {
+                        _buffer.ReleasePointer();
+                    }
+                }
+            }
+        }
+
+        public void Write(long position, decimal value)
+        {
+            EnsureSafeToWrite(position, sizeof(decimal));
+
+            unsafe
+            {
+                int* valuePtr = (int*)(&value);
+                int flags = *valuePtr;
+                int hi = *(valuePtr + 1);
+                int lo = *(valuePtr + 2);
+                int mid = *(valuePtr + 3);
+
+                byte* pointer = null;
+                try
+                {
+                    _buffer.AcquirePointer(ref pointer);
+                    pointer += (_offset + position);
+
+                    Unsafe.WriteUnaligned<int>(pointer, lo);
+                    Unsafe.WriteUnaligned<int>(pointer + 4, mid);
+                    Unsafe.WriteUnaligned<int>(pointer + 8, hi);
+                    Unsafe.WriteUnaligned<int>(pointer + 12, flags);
+                }
+                finally
+                {
+                    if (pointer != null)
+                    {
+                        _buffer.ReleasePointer();
+                    }
+                }
+            }
+        }
+
+        public void Write(long position, float value) => Write(position, BitConverter.SingleToInt32Bits(value));
+
+        public void Write(long position, double value) => Write(position, BitConverter.DoubleToInt64Bits(value));
+
+        [CLSCompliant(false)]
+        public void Write(long position, sbyte value) => Write(position, unchecked((byte)value));
+
+        [CLSCompliant(false)]
+        public void Write(long position, ushort value) => Write(position, unchecked((short)value));
+
+        [CLSCompliant(false)]
+        public void Write(long position, uint value) => Write(position, unchecked((int)value));
+
+        [CLSCompliant(false)]
+        public void Write(long position, ulong value) => Write(position, unchecked((long)value));
+
+        // Writes the struct pointed to by ref value into unmanaged memory.  Note that this method
+        // is most performant when used with medium to large sized structs (larger than 8 bytes 
+        // though this is number is JIT and architecture dependent).   As such, it is best to use 
+        // the WriteX methods for small standard types such as ints, longs, bools, etc.
+        public void Write<T>(long position, ref T structure) where T : struct
+        {
+            if (position < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(position), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (!_isOpen)
+            {
+                throw new ObjectDisposedException(nameof(UnmanagedMemoryAccessor), SR.ObjectDisposed_ViewAccessorClosed);
+            }
+            if (!_canWrite)
+            {
+                throw new NotSupportedException(SR.NotSupported_Writing);
+            }
+
+            uint sizeOfT = SafeBuffer.SizeOf<T>();
+            if (position > _capacity - sizeOfT)
+            {
+                if (position >= _capacity)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(position), SR.ArgumentOutOfRange_PositionLessThanCapacityRequired);
+                }
+                else
+                {
+                    throw new ArgumentException(SR.Format(SR.Argument_NotEnoughBytesToWrite, typeof(T)), nameof(position));
+                }
+            }
+
+            _buffer.Write<T>((ulong)(_offset + position), structure);
+        }
+
+        // Writes 'count' structs of type T from 'array' (starting at 'offset') into unmanaged memory. 
+        public void WriteArray<T>(long position, T[] array, int offset, int count) where T : struct
+        {
+            if (array == null)
+            {
+                throw new ArgumentNullException(nameof(array), SR.ArgumentNull_Buffer);
+            }
+            if (offset < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (array.Length - offset < count)
+            {
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+            }
+            if (position < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(position), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (position >= Capacity)
+            {
+                throw new ArgumentOutOfRangeException(nameof(position), SR.ArgumentOutOfRange_PositionLessThanCapacityRequired);
+            }
+
+            if (!_isOpen)
+            {
+                throw new ObjectDisposedException(nameof(UnmanagedMemoryAccessor), SR.ObjectDisposed_ViewAccessorClosed);
+            }
+            if (!_canWrite)
+            {
+                throw new NotSupportedException(SR.NotSupported_Writing);
+            }
+
+            _buffer.WriteArray<T>((ulong)(_offset + position), array, offset, count);
+        }
+
+        private void EnsureSafeToRead(long position, int sizeOfType)
+        {
+            if (!_isOpen)
+            {
+                throw new ObjectDisposedException(nameof(UnmanagedMemoryAccessor), SR.ObjectDisposed_ViewAccessorClosed);
+            }
+            if (!_canRead)
+            {
+                throw new NotSupportedException(SR.NotSupported_Reading);
+            }
+            if (position < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(position), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (position > _capacity - sizeOfType)
+            {
+                if (position >= _capacity)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(position), SR.ArgumentOutOfRange_PositionLessThanCapacityRequired);
+                }
+                else
+                {
+                    throw new ArgumentException(SR.Argument_NotEnoughBytesToRead, nameof(position));
+                }
+            }
+        }
+
+        private void EnsureSafeToWrite(long position, int sizeOfType)
+        {
+            if (!_isOpen)
+            {
+                throw new ObjectDisposedException(nameof(UnmanagedMemoryAccessor), SR.ObjectDisposed_ViewAccessorClosed);
+            }
+            if (!_canWrite)
+            {
+                throw new NotSupportedException(SR.NotSupported_Writing);
+            }
+            if (position < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(position), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (position > _capacity - sizeOfType)
+            {
+                if (position >= _capacity)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(position), SR.ArgumentOutOfRange_PositionLessThanCapacityRequired);
+                }
+                else
+                {
+                    throw new ArgumentException(SR.Argument_NotEnoughBytesToWrite, nameof(position));
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/UnmanagedMemoryStream.cs b/src/System.Private.CoreLib/shared/System/IO/UnmanagedMemoryStream.cs
new file mode 100644
index 0000000000..2bcb16f24e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/UnmanagedMemoryStream.cs
@@ -0,0 +1,882 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.IO
+{
+    /*
+     * This class is used to access a contiguous block of memory, likely outside 
+     * the GC heap (or pinned in place in the GC heap, but a MemoryStream may 
+     * make more sense in those cases).  It's great if you have a pointer and
+     * a length for a section of memory mapped in by someone else and you don't
+     * want to copy this into the GC heap.  UnmanagedMemoryStream assumes these 
+     * two things:
+     *
+     * 1) All the memory in the specified block is readable or writable,
+     *    depending on the values you pass to the constructor.
+     * 2) The lifetime of the block of memory is at least as long as the lifetime
+     *    of the UnmanagedMemoryStream.
+     * 3) You clean up the memory when appropriate.  The UnmanagedMemoryStream 
+     *    currently will do NOTHING to free this memory.
+     * 4) All calls to Write and WriteByte may not be threadsafe currently.
+     *
+     * It may become necessary to add in some sort of 
+     * DeallocationMode enum, specifying whether we unmap a section of memory, 
+     * call free, run a user-provided delegate to free the memory, etc.  
+     * We'll suggest user write a subclass of UnmanagedMemoryStream that uses
+     * a SafeHandle subclass to hold onto the memory.
+     * 
+     */
+
+    /// <summary>
+    /// Stream over a memory pointer or over a SafeBuffer
+    /// </summary>
+    public class UnmanagedMemoryStream : Stream
+    {
+        private SafeBuffer _buffer;
+        private unsafe byte* _mem;
+        private long _length;
+        private long _capacity;
+        private long _position;
+        private long _offset;
+        private FileAccess _access;
+        private bool _isOpen;
+        private Task<Int32> _lastReadTask; // The last successful task returned from ReadAsync 
+
+        /// <summary>
+        /// Creates a closed stream.
+        /// </summary>
+        // Needed for subclasses that need to map a file, etc.
+        protected UnmanagedMemoryStream()
+        {
+            unsafe
+            {
+                _mem = null;
+            }
+            _isOpen = false;
+        }
+
+        /// <summary>
+        /// Creates a stream over a SafeBuffer.
+        /// </summary>
+        /// <param name="buffer"></param>
+        /// <param name="offset"></param>
+        /// <param name="length"></param>
+        public UnmanagedMemoryStream(SafeBuffer buffer, long offset, long length)
+        {
+            Initialize(buffer, offset, length, FileAccess.Read);
+        }
+
+        /// <summary>
+        /// Creates a stream over a SafeBuffer.
+        /// </summary>
+        public UnmanagedMemoryStream(SafeBuffer buffer, long offset, long length, FileAccess access)
+        {
+            Initialize(buffer, offset, length, access);
+        }
+
+        /// <summary>
+        /// Subclasses must call this method (or the other overload) to properly initialize all instance fields.
+        /// </summary>
+        /// <param name="buffer"></param>
+        /// <param name="offset"></param>
+        /// <param name="length"></param>
+        /// <param name="access"></param>
+        protected void Initialize(SafeBuffer buffer, long offset, long length, FileAccess access)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer));
+            }
+            if (offset < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (length < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (buffer.ByteLength < (ulong)(offset + length))
+            {
+                throw new ArgumentException(SR.Argument_InvalidSafeBufferOffLen);
+            }
+            if (access < FileAccess.Read || access > FileAccess.ReadWrite)
+            {
+                throw new ArgumentOutOfRangeException(nameof(access));
+            }
+
+            if (_isOpen)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_CalledTwice);
+            }
+
+            // check for wraparound
+            unsafe
+            {
+                byte* pointer = null;
+                RuntimeHelpers.PrepareConstrainedRegions();
+                try
+                {
+                    buffer.AcquirePointer(ref pointer);
+                    if ((pointer + offset + length) < pointer)
+                    {
+                        throw new ArgumentException(SR.ArgumentOutOfRange_UnmanagedMemStreamWrapAround);
+                    }
+                }
+                finally
+                {
+                    if (pointer != null)
+                    {
+                        buffer.ReleasePointer();
+                    }
+                }
+            }
+
+            _offset = offset;
+            _buffer = buffer;
+            _length = length;
+            _capacity = length;
+            _access = access;
+            _isOpen = true;
+        }
+
+        /// <summary>
+        /// Creates a stream over a byte*.
+        /// </summary>
+        [CLSCompliant(false)]
+        public unsafe UnmanagedMemoryStream(byte* pointer, long length)
+        {
+            Initialize(pointer, length, length, FileAccess.Read);
+        }
+
+        /// <summary>
+        /// Creates a stream over a byte*.
+        /// </summary>
+        [CLSCompliant(false)]
+        public unsafe UnmanagedMemoryStream(byte* pointer, long length, long capacity, FileAccess access)
+        {
+            Initialize(pointer, length, capacity, access);
+        }
+
+        /// <summary>
+        /// Subclasses must call this method (or the other overload) to properly initialize all instance fields.
+        /// </summary>
+        [CLSCompliant(false)]
+        protected unsafe void Initialize(byte* pointer, long length, long capacity, FileAccess access)
+        {
+            if (pointer == null)
+                throw new ArgumentNullException(nameof(pointer));
+            if (length < 0 || capacity < 0)
+                throw new ArgumentOutOfRangeException((length < 0) ? nameof(length) : nameof(capacity), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (length > capacity)
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_LengthGreaterThanCapacity);
+            // Check for wraparound.
+            if (((byte*)((long)pointer + capacity)) < pointer)
+                throw new ArgumentOutOfRangeException(nameof(capacity), SR.ArgumentOutOfRange_UnmanagedMemStreamWrapAround);
+            if (access < FileAccess.Read || access > FileAccess.ReadWrite)
+                throw new ArgumentOutOfRangeException(nameof(access), SR.ArgumentOutOfRange_Enum);
+            if (_isOpen)
+                throw new InvalidOperationException(SR.InvalidOperation_CalledTwice);
+
+            _mem = pointer;
+            _offset = 0;
+            _length = length;
+            _capacity = capacity;
+            _access = access;
+            _isOpen = true;
+        }
+
+        /// <summary>
+        /// Returns true if the stream can be read; otherwise returns false.
+        /// </summary>
+        public override bool CanRead
+        {
+            get { return _isOpen && (_access & FileAccess.Read) != 0; }
+        }
+
+        /// <summary>
+        /// Returns true if the stream can seek; otherwise returns false.
+        /// </summary>
+        public override bool CanSeek
+        {
+            get { return _isOpen; }
+        }
+
+        /// <summary>
+        /// Returns true if the stream can be written to; otherwise returns false.
+        /// </summary>
+        public override bool CanWrite
+        {
+            get { return _isOpen && (_access & FileAccess.Write) != 0; }
+        }
+
+        /// <summary>
+        /// Closes the stream. The stream's memory needs to be dealt with separately.
+        /// </summary>
+        /// <param name="disposing"></param>
+        protected override void Dispose(bool disposing)
+        {
+            _isOpen = false;
+            unsafe { _mem = null; }
+
+            // Stream allocates WaitHandles for async calls. So for correctness 
+            // call base.Dispose(disposing) for better perf, avoiding waiting
+            // for the finalizers to run on those types.
+            base.Dispose(disposing);
+        }
+
+        private void EnsureNotClosed()
+        {
+            if (!_isOpen)
+                throw Error.GetStreamIsClosed();
+        }
+
+        private void EnsureReadable()
+        {
+            if (!CanRead)
+                throw Error.GetReadNotSupported();
+        }
+
+        private void EnsureWriteable()
+        {
+            if (!CanWrite)
+                throw Error.GetWriteNotSupported();
+        }
+
+        /// <summary>
+        /// Since it's a memory stream, this method does nothing.
+        /// </summary>
+        public override void Flush()
+        {
+            EnsureNotClosed();
+        }
+
+        /// <summary>
+        /// Since it's a memory stream, this method does nothing specific.
+        /// </summary>
+        /// <param name="cancellationToken"></param>
+        /// <returns></returns>
+        public override Task FlushAsync(CancellationToken cancellationToken)
+        {
+            if (cancellationToken.IsCancellationRequested)
+                return Task.FromCanceled(cancellationToken);
+
+            try
+            {
+                Flush();
+                return Task.CompletedTask;
+            }
+            catch (Exception ex)
+            {
+                return Task.FromException(ex);
+            }
+        }
+
+        /// <summary>
+        /// Number of bytes in the stream.
+        /// </summary>
+        public override long Length
+        {
+            get
+            {
+                EnsureNotClosed();
+                return Interlocked.Read(ref _length);
+            }
+        }
+
+        /// <summary>
+        /// Number of bytes that can be written to the stream.
+        /// </summary>
+        public long Capacity
+        {
+            get
+            {
+                EnsureNotClosed();
+                return _capacity;
+            }
+        }
+
+        /// <summary>
+        /// ReadByte will read byte at the Position in the stream
+        /// </summary>
+        public override long Position
+        {
+            get
+            {
+                if (!CanSeek) throw Error.GetStreamIsClosed();
+                return Interlocked.Read(ref _position);
+            }
+            set
+            {
+                if (value < 0) throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_NeedNonNegNum);
+                if (!CanSeek) throw Error.GetStreamIsClosed();
+
+                Interlocked.Exchange(ref _position, value);
+            }
+        }
+
+        /// <summary>
+        /// Pointer to memory at the current Position in the stream. 
+        /// </summary>
+        [CLSCompliant(false)]
+        public unsafe byte* PositionPointer
+        {
+            get
+            {
+                if (_buffer != null)
+                    throw new NotSupportedException(SR.NotSupported_UmsSafeBuffer);
+
+                EnsureNotClosed();
+
+                // Use a temp to avoid a race
+                long pos = Interlocked.Read(ref _position);
+                if (pos > _capacity)
+                    throw new IndexOutOfRangeException(SR.IndexOutOfRange_UMSPosition);
+                byte* ptr = _mem + pos;
+                return ptr;
+            }
+            set
+            {
+                if (_buffer != null)
+                    throw new NotSupportedException(SR.NotSupported_UmsSafeBuffer);
+
+                EnsureNotClosed();
+
+                if (value < _mem)
+                    throw new IOException(SR.IO_SeekBeforeBegin);
+                long newPosition = (long)value - (long)_mem;
+                if (newPosition < 0)
+                    throw new ArgumentOutOfRangeException("offset", SR.ArgumentOutOfRange_UnmanagedMemStreamLength);
+
+                Interlocked.Exchange(ref _position, newPosition);
+            }
+        }
+
+        /// <summary>
+        /// Reads bytes from stream and puts them into the buffer
+        /// </summary>
+        /// <param name="buffer">Buffer to read the bytes to.</param>
+        /// <param name="offset">Starting index in the buffer.</param>
+        /// <param name="count">Maximum number of bytes to read.</param>
+        /// <returns>Number of bytes actually read.</returns>
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            if (buffer == null)
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (buffer.Length - offset < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+            return ReadCore(new Span<byte>(buffer, offset, count));
+        }
+
+        public override int Read(Span<byte> buffer)
+        {
+            if (GetType() == typeof(UnmanagedMemoryStream))
+            {
+                return ReadCore(buffer);
+            }
+            else
+            {
+                // UnmanagedMemoryStream is not sealed, and a derived type may have overridden Read(byte[], int, int) prior
+                // to this Read(Span<byte>) overload being introduced.  In that case, this Read(Span<byte>) overload
+                // should use the behavior of Read(byte[],int,int) overload.
+                return base.Read(buffer);
+            }
+        }
+
+        internal int ReadCore(Span<byte> buffer)
+        {
+            EnsureNotClosed();
+            EnsureReadable();
+
+            // Use a local variable to avoid a race where another thread 
+            // changes our position after we decide we can read some bytes.
+            long pos = Interlocked.Read(ref _position);
+            long len = Interlocked.Read(ref _length);
+            long n = Math.Min(len - pos, buffer.Length);
+            if (n <= 0)
+            {
+                return 0;
+            }
+
+            int nInt = (int)n; // Safe because n <= count, which is an Int32
+            if (nInt < 0)
+            {
+                return 0;  // _position could be beyond EOF
+            }
+            Debug.Assert(pos + nInt >= 0, "_position + n >= 0");  // len is less than 2^63 -1.
+
+            unsafe
+            {
+                fixed (byte* pBuffer = &MemoryMarshal.GetReference(buffer))
+                {
+                    if (_buffer != null)
+                    {
+                        byte* pointer = null;
+
+                        RuntimeHelpers.PrepareConstrainedRegions();
+                        try
+                        {
+                            _buffer.AcquirePointer(ref pointer);
+                            Buffer.Memcpy(pBuffer, pointer + pos + _offset, nInt);
+                        }
+                        finally
+                        {
+                            if (pointer != null)
+                            {
+                                _buffer.ReleasePointer();
+                            }
+                        }
+                    }
+                    else
+                    {
+                        Buffer.Memcpy(pBuffer, _mem + pos, nInt);
+                    }
+                }
+            }
+            Interlocked.Exchange(ref _position, pos + n);
+            return nInt;
+        }
+
+        /// <summary>
+        /// Reads bytes from stream and puts them into the buffer
+        /// </summary>
+        /// <param name="buffer">Buffer to read the bytes to.</param>
+        /// <param name="offset">Starting index in the buffer.</param>
+        /// <param name="count">Maximum number of bytes to read.</param>       
+        /// <param name="cancellationToken">Token that can be used to cancel this operation.</param>
+        /// <returns>Task that can be used to access the number of bytes actually read.</returns>
+        public override Task<Int32> ReadAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken)
+        {
+            if (buffer == null)
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (buffer.Length - offset < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+            if (cancellationToken.IsCancellationRequested)
+                return Task.FromCanceled<Int32>(cancellationToken);
+
+            try
+            {
+                Int32 n = Read(buffer, offset, count);
+                Task<Int32> t = _lastReadTask;
+                return (t != null && t.Result == n) ? t : (_lastReadTask = Task.FromResult<Int32>(n));
+            }
+            catch (Exception ex)
+            {
+                Debug.Assert(!(ex is OperationCanceledException));
+                return Task.FromException<Int32>(ex);
+            }
+        }
+
+        /// <summary>
+        /// Reads bytes from stream and puts them into the buffer
+        /// </summary>
+        /// <param name="buffer">Buffer to read the bytes to.</param>
+        /// <param name="cancellationToken">Token that can be used to cancel this operation.</param>
+        public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return new ValueTask<int>(Task.FromCanceled<int>(cancellationToken));
+            }
+
+            try
+            {
+                // ReadAsync(Memory<byte>,...) needs to delegate to an existing virtual to do the work, in case an existing derived type
+                // has changed or augmented the logic associated with reads.  If the Memory wraps an array, we could delegate to
+                // ReadAsync(byte[], ...), but that would defeat part of the purpose, as ReadAsync(byte[], ...) often needs to allocate
+                // a Task<int> for the return value, so we want to delegate to one of the synchronous methods.  We could always
+                // delegate to the Read(Span<byte>) method, and that's the most efficient solution when dealing with a concrete
+                // UnmanagedMemoryStream, but if we're dealing with a type derived from UnmanagedMemoryStream, Read(Span<byte>) will end up delegating
+                // to Read(byte[], ...), which requires it to get a byte[] from ArrayPool and copy the data.  So, we special-case the
+                // very common case of the Memory<byte> wrapping an array: if it does, we delegate to Read(byte[], ...) with it,
+                // as that will be efficient in both cases, and we fall back to Read(Span<byte>) if the Memory<byte> wrapped something
+                // else; if this is a concrete UnmanagedMemoryStream, that'll be efficient, and only in the case where the Memory<byte> wrapped
+                // something other than an array and this is an UnmanagedMemoryStream-derived type that doesn't override Read(Span<byte>) will
+                // it then fall back to doing the ArrayPool/copy behavior.
+                return new ValueTask<int>(
+                    MemoryMarshal.TryGetArray(buffer, out ArraySegment<byte> destinationArray) ?
+                        Read(destinationArray.Array, destinationArray.Offset, destinationArray.Count) :
+                        Read(buffer.Span));
+            }
+            catch (Exception ex)
+            {
+                return new ValueTask<int>(Task.FromException<int>(ex));
+            }
+        }
+
+        /// <summary>
+        /// Returns the byte at the stream current Position and advances the Position.
+        /// </summary>
+        /// <returns></returns>
+        public override int ReadByte()
+        {
+            EnsureNotClosed();
+            EnsureReadable();
+
+            long pos = Interlocked.Read(ref _position);  // Use a local to avoid a race condition
+            long len = Interlocked.Read(ref _length);
+            if (pos >= len)
+                return -1;
+            Interlocked.Exchange(ref _position, pos + 1);
+            int result;
+            if (_buffer != null)
+            {
+                unsafe
+                {
+                    byte* pointer = null;
+                    RuntimeHelpers.PrepareConstrainedRegions();
+                    try
+                    {
+                        _buffer.AcquirePointer(ref pointer);
+                        result = *(pointer + pos + _offset);
+                    }
+                    finally
+                    {
+                        if (pointer != null)
+                        {
+                            _buffer.ReleasePointer();
+                        }
+                    }
+                }
+            }
+            else
+            {
+                unsafe
+                {
+                    result = _mem[pos];
+                }
+            }
+            return result;
+        }
+
+        /// <summary>
+        /// Advanced the Position to specific location in the stream.
+        /// </summary>
+        /// <param name="offset">Offset from the loc parameter.</param>
+        /// <param name="loc">Origin for the offset parameter.</param>
+        /// <returns></returns>
+        public override long Seek(long offset, SeekOrigin loc)
+        {
+            EnsureNotClosed();
+
+            switch (loc)
+            {
+                case SeekOrigin.Begin:
+                    if (offset < 0)
+                        throw new IOException(SR.IO_SeekBeforeBegin);
+                    Interlocked.Exchange(ref _position, offset);
+                    break;
+
+                case SeekOrigin.Current:
+                    long pos = Interlocked.Read(ref _position);
+                    if (offset + pos < 0)
+                        throw new IOException(SR.IO_SeekBeforeBegin);
+                    Interlocked.Exchange(ref _position, offset + pos);
+                    break;
+
+                case SeekOrigin.End:
+                    long len = Interlocked.Read(ref _length);
+                    if (len + offset < 0)
+                        throw new IOException(SR.IO_SeekBeforeBegin);
+                    Interlocked.Exchange(ref _position, len + offset);
+                    break;
+
+                default:
+                    throw new ArgumentException(SR.Argument_InvalidSeekOrigin);
+            }
+
+            long finalPos = Interlocked.Read(ref _position);
+            Debug.Assert(finalPos >= 0, "_position >= 0");
+            return finalPos;
+        }
+
+        /// <summary>
+        /// Sets the Length of the stream.
+        /// </summary>
+        /// <param name="value"></param>
+        public override void SetLength(long value)
+        {
+            if (value < 0)
+                throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (_buffer != null)
+                throw new NotSupportedException(SR.NotSupported_UmsSafeBuffer);
+
+            EnsureNotClosed();
+            EnsureWriteable();
+
+            if (value > _capacity)
+                throw new IOException(SR.IO_FixedCapacity);
+
+            long pos = Interlocked.Read(ref _position);
+            long len = Interlocked.Read(ref _length);
+            if (value > len)
+            {
+                unsafe
+                {
+                    Buffer.ZeroMemory(_mem + len, value - len);
+                }
+            }
+            Interlocked.Exchange(ref _length, value);
+            if (pos > value)
+            {
+                Interlocked.Exchange(ref _position, value);
+            }
+        }
+
+        /// <summary>
+        /// Writes buffer into the stream
+        /// </summary>
+        /// <param name="buffer">Buffer that will be written.</param>
+        /// <param name="offset">Starting index in the buffer.</param>
+        /// <param name="count">Number of bytes to write.</param>
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            if (buffer == null)
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (buffer.Length - offset < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+            WriteCore(new Span<byte>(buffer, offset, count));
+        }
+
+        public override void Write(ReadOnlySpan<byte> buffer)
+        {
+            if (GetType() == typeof(UnmanagedMemoryStream))
+            {
+                WriteCore(buffer);
+            }
+            else
+            {
+                // UnmanagedMemoryStream is not sealed, and a derived type may have overridden Write(byte[], int, int) prior
+                // to this Write(Span<byte>) overload being introduced.  In that case, this Write(Span<byte>) overload
+                // should use the behavior of Write(byte[],int,int) overload.
+                base.Write(buffer);
+            }
+        }
+
+        internal unsafe void WriteCore(ReadOnlySpan<byte> buffer)
+        {
+            EnsureNotClosed();
+            EnsureWriteable();
+
+            long pos = Interlocked.Read(ref _position);  // Use a local to avoid a race condition
+            long len = Interlocked.Read(ref _length);
+            long n = pos + buffer.Length;
+            // Check for overflow
+            if (n < 0)
+            {
+                throw new IOException(SR.IO_StreamTooLong);
+            }
+
+            if (n > _capacity)
+            {
+                throw new NotSupportedException(SR.IO_FixedCapacity);
+            }
+
+            if (_buffer == null)
+            {
+                // Check to see whether we are now expanding the stream and must 
+                // zero any memory in the middle.
+                if (pos > len)
+                {
+                    Buffer.ZeroMemory(_mem + len, pos - len);
+                }
+
+                // set length after zeroing memory to avoid race condition of accessing unzeroed memory
+                if (n > len)
+                {
+                    Interlocked.Exchange(ref _length, n);
+                }
+            }
+
+            fixed (byte* pBuffer = &MemoryMarshal.GetReference(buffer))
+            {
+                if (_buffer != null)
+                {
+                    long bytesLeft = _capacity - pos;
+                    if (bytesLeft < buffer.Length)
+                    {
+                        throw new ArgumentException(SR.Arg_BufferTooSmall);
+                    }
+
+                    byte* pointer = null;
+                    RuntimeHelpers.PrepareConstrainedRegions();
+                    try
+                    {
+                        _buffer.AcquirePointer(ref pointer);
+                        Buffer.Memcpy(pointer + pos + _offset, pBuffer, buffer.Length);
+                    }
+                    finally
+                    {
+                        if (pointer != null)
+                        {
+                            _buffer.ReleasePointer();
+                        }
+                    }
+                }
+                else
+                {
+                    Buffer.Memcpy(_mem + pos, pBuffer, buffer.Length);
+                }
+            }
+
+            Interlocked.Exchange(ref _position, n);
+            return;
+        }
+
+        /// <summary>
+        /// Writes buffer into the stream. The operation completes synchronously.
+        /// </summary>
+        /// <param name="buffer">Buffer that will be written.</param>
+        /// <param name="offset">Starting index in the buffer.</param>
+        /// <param name="count">Number of bytes to write.</param>
+        /// <param name="cancellationToken">Token that can be used to cancel the operation.</param>
+        /// <returns>Task that can be awaited </returns>
+        public override Task WriteAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken)
+        {
+            if (buffer == null)
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            if (offset < 0)
+                throw new ArgumentOutOfRangeException(nameof(offset), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (buffer.Length - offset < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+            if (cancellationToken.IsCancellationRequested)
+                return Task.FromCanceled(cancellationToken);
+
+            try
+            {
+                Write(buffer, offset, count);
+                return Task.CompletedTask;
+            }
+            catch (Exception ex)
+            {
+                Debug.Assert(!(ex is OperationCanceledException));
+                return Task.FromException(ex);
+            }
+        }
+
+        /// <summary>
+        /// Writes buffer into the stream. The operation completes synchronously.
+        /// </summary>
+        /// <param name="buffer">Buffer that will be written.</param>
+        /// <param name="cancellationToken">Token that can be used to cancel the operation.</param>
+        public override ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return new ValueTask(Task.FromCanceled(cancellationToken));
+            }
+
+            try
+            {
+                // See corresponding comment in ReadAsync for why we don't just always use Write(ReadOnlySpan<byte>).
+                // Unlike ReadAsync, we could delegate to WriteAsync(byte[], ...) here, but we don't for consistency.
+                if (MemoryMarshal.TryGetArray(buffer, out ArraySegment<byte> sourceArray))
+                {
+                    Write(sourceArray.Array, sourceArray.Offset, sourceArray.Count);
+                }
+                else
+                {
+                    Write(buffer.Span);
+                }
+                return default;
+            }
+            catch (Exception ex)
+            {
+                return new ValueTask(Task.FromException(ex));
+            }
+        }
+
+        /// <summary>
+        /// Writes a byte to the stream and advances the current Position.
+        /// </summary>
+        /// <param name="value"></param>
+        public override void WriteByte(byte value)
+        {
+            EnsureNotClosed();
+            EnsureWriteable();
+
+            long pos = Interlocked.Read(ref _position);  // Use a local to avoid a race condition
+            long len = Interlocked.Read(ref _length);
+            long n = pos + 1;
+            if (pos >= len)
+            {
+                // Check for overflow
+                if (n < 0)
+                    throw new IOException(SR.IO_StreamTooLong);
+
+                if (n > _capacity)
+                    throw new NotSupportedException(SR.IO_FixedCapacity);
+
+                // Check to see whether we are now expanding the stream and must 
+                // zero any memory in the middle.
+                // don't do if created from SafeBuffer
+                if (_buffer == null)
+                {
+                    if (pos > len)
+                    {
+                        unsafe
+                        {
+                            Buffer.ZeroMemory(_mem + len, pos - len);
+                        }
+                    }
+
+                    // set length after zeroing memory to avoid race condition of accessing unzeroed memory
+                    Interlocked.Exchange(ref _length, n);
+                }
+            }
+
+            if (_buffer != null)
+            {
+                unsafe
+                {
+                    byte* pointer = null;
+                    RuntimeHelpers.PrepareConstrainedRegions();
+                    try
+                    {
+                        _buffer.AcquirePointer(ref pointer);
+                        *(pointer + pos + _offset) = value;
+                    }
+                    finally
+                    {
+                        if (pointer != null)
+                        {
+                            _buffer.ReleasePointer();
+                        }
+                    }
+                }
+            }
+            else
+            {
+                unsafe
+                {
+                    _mem[pos] = value;
+                }
+            }
+            Interlocked.Exchange(ref _position, n);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IO/UnmanagedMemoryStreamWrapper.cs b/src/System.Private.CoreLib/shared/System/IO/UnmanagedMemoryStreamWrapper.cs
new file mode 100644
index 0000000000..65a33961db
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/UnmanagedMemoryStreamWrapper.cs
@@ -0,0 +1,226 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+** Purpose: Create a Memorystream over an UnmanagedMemoryStream
+**
+===========================================================*/
+
+using System;
+using System.Runtime.InteropServices;
+using System.Diagnostics.CodeAnalysis;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.IO
+{
+    // Needed for backwards compatibility with V1.x usages of the
+    // ResourceManager, where a MemoryStream is now returned as an 
+    // UnmanagedMemoryStream from ResourceReader.
+    internal sealed class UnmanagedMemoryStreamWrapper : MemoryStream
+    {
+        private UnmanagedMemoryStream _unmanagedStream;
+
+        internal UnmanagedMemoryStreamWrapper(UnmanagedMemoryStream stream)
+        {
+            _unmanagedStream = stream;
+        }
+
+        public override bool CanRead
+        {
+            get { return _unmanagedStream.CanRead; }
+        }
+
+        public override bool CanSeek
+        {
+            get { return _unmanagedStream.CanSeek; }
+        }
+
+        public override bool CanWrite
+        {
+            get { return _unmanagedStream.CanWrite; }
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            try
+            {
+                if (disposing)
+                    _unmanagedStream.Dispose();
+            }
+            finally
+            {
+                base.Dispose(disposing);
+            }
+        }
+
+        public override void Flush()
+        {
+            _unmanagedStream.Flush();
+        }
+
+        public override byte[] GetBuffer()
+        {
+            throw new UnauthorizedAccessException(SR.UnauthorizedAccess_MemStreamBuffer);
+        }
+
+        public override bool TryGetBuffer(out ArraySegment<byte> buffer)
+        {
+            buffer = default(ArraySegment<byte>);
+            return false;
+        }
+
+        public override int Capacity
+        {
+            get
+            {
+                return (int)_unmanagedStream.Capacity;
+            }
+            set
+            {
+                throw new IOException(SR.IO_FixedCapacity);
+            }
+        }
+
+        public override long Length
+        {
+            get
+            {
+                return _unmanagedStream.Length;
+            }
+        }
+
+        public override long Position
+        {
+            get
+            {
+                return _unmanagedStream.Position;
+            }
+            set
+            {
+                _unmanagedStream.Position = value;
+            }
+        }
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            return _unmanagedStream.Read(buffer, offset, count);
+        }
+
+        public override int Read(Span<byte> buffer)
+        {
+            return _unmanagedStream.Read(buffer);
+        }
+
+        public override int ReadByte()
+        {
+            return _unmanagedStream.ReadByte();
+        }
+
+        public override long Seek(long offset, SeekOrigin loc)
+        {
+            return _unmanagedStream.Seek(offset, loc);
+        }
+
+        public unsafe override byte[] ToArray()
+        {
+            byte[] buffer = new byte[_unmanagedStream.Length];
+            _unmanagedStream.Read(buffer, 0, (int)_unmanagedStream.Length);
+            return buffer;
+        }
+
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            _unmanagedStream.Write(buffer, offset, count);
+        }
+
+        public override void Write(ReadOnlySpan<byte> buffer)
+        {
+            _unmanagedStream.Write(buffer);
+        }
+
+        public override void WriteByte(byte value)
+        {
+            _unmanagedStream.WriteByte(value);
+        }
+
+        // Writes this MemoryStream to another stream.
+        public unsafe override void WriteTo(Stream stream)
+        {
+            if (stream == null)
+                throw new ArgumentNullException(nameof(stream), SR.ArgumentNull_Stream);
+
+            byte[] buffer = ToArray();
+
+            stream.Write(buffer, 0, buffer.Length);
+        }
+
+        public override void SetLength(Int64 value)
+        {
+            // This was probably meant to call _unmanagedStream.SetLength(value), but it was forgotten in V.4.0.
+            // Now this results in a call to the base which touches the underlying array which is never actually used.
+            // We cannot fix it due to compat now, but we should fix this at the next SxS release oportunity.
+            base.SetLength(value);
+        }
+
+
+        public override Task CopyToAsync(Stream destination, Int32 bufferSize, CancellationToken cancellationToken)
+        {
+            // The parameter checks must be in sync with the base version:
+            if (destination == null)
+                throw new ArgumentNullException(nameof(destination));
+
+            if (bufferSize <= 0)
+                throw new ArgumentOutOfRangeException(nameof(bufferSize), SR.ArgumentOutOfRange_NeedPosNum);
+
+            if (!CanRead && !CanWrite)
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_StreamClosed);
+
+            if (!destination.CanRead && !destination.CanWrite)
+                throw new ObjectDisposedException(nameof(destination), SR.ObjectDisposed_StreamClosed);
+
+            if (!CanRead)
+                throw new NotSupportedException(SR.NotSupported_UnreadableStream);
+
+            if (!destination.CanWrite)
+                throw new NotSupportedException(SR.NotSupported_UnwritableStream);
+
+
+            return _unmanagedStream.CopyToAsync(destination, bufferSize, cancellationToken);
+        }
+
+
+        public override Task FlushAsync(CancellationToken cancellationToken)
+        {
+            return _unmanagedStream.FlushAsync(cancellationToken);
+        }
+
+
+        public override Task<Int32> ReadAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken)
+        {
+            return _unmanagedStream.ReadAsync(buffer, offset, count, cancellationToken);
+        }
+
+        public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            return _unmanagedStream.ReadAsync(buffer, cancellationToken);
+        }
+
+
+        public override Task WriteAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken)
+        {
+            return _unmanagedStream.WriteAsync(buffer, offset, count, cancellationToken);
+        }
+
+        public override ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            return _unmanagedStream.WriteAsync(buffer, cancellationToken);
+        }
+    }  // class UnmanagedMemoryStreamWrapper
+}  // namespace
+
diff --git a/src/System.Private.CoreLib/shared/System/IO/Win32Marshal.cs b/src/System.Private.CoreLib/shared/System/IO/Win32Marshal.cs
new file mode 100644
index 0000000000..7888d8d61b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IO/Win32Marshal.cs
@@ -0,0 +1,95 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+
+namespace System.IO
+{
+    /// <summary>
+    /// Provides static methods for converting from Win32 errors codes to exceptions, HRESULTS and error messages.
+    /// </summary>
+    internal static class Win32Marshal
+    {
+        /// <summary>
+        /// Converts, resetting it, the last Win32 error into a corresponding <see cref="Exception"/> object, optionally
+        /// including the specified path in the error message.
+        /// </summary>
+        internal static Exception GetExceptionForLastWin32Error(string path = "")
+            => GetExceptionForWin32Error(Marshal.GetLastWin32Error(), path);
+
+        /// <summary>
+        /// Converts the specified Win32 error into a corresponding <see cref="Exception"/> object, optionally
+        /// including the specified path in the error message.
+        /// </summary>
+        internal static Exception GetExceptionForWin32Error(int errorCode, string path = "")
+        {
+            switch (errorCode)
+            {
+                case Interop.Errors.ERROR_FILE_NOT_FOUND:
+                    return new FileNotFoundException(
+                        string.IsNullOrEmpty(path) ? SR.IO_FileNotFound : SR.Format(SR.IO_FileNotFound_FileName, path), path);
+                case Interop.Errors.ERROR_PATH_NOT_FOUND:
+                    return new DirectoryNotFoundException(
+                        string.IsNullOrEmpty(path) ? SR.IO_PathNotFound_NoPathName : SR.Format(SR.IO_PathNotFound_Path, path));
+                case Interop.Errors.ERROR_ACCESS_DENIED:
+                    return new UnauthorizedAccessException(
+                        string.IsNullOrEmpty(path) ? SR.UnauthorizedAccess_IODenied_NoPathName : SR.Format(SR.UnauthorizedAccess_IODenied_Path, path));
+                case Interop.Errors.ERROR_ALREADY_EXISTS:
+                    if (string.IsNullOrEmpty(path))
+                        goto default;
+                    return new IOException(SR.Format(SR.IO_AlreadyExists_Name, path), MakeHRFromErrorCode(errorCode));
+                case Interop.Errors.ERROR_FILENAME_EXCED_RANGE:
+                    return new PathTooLongException(
+                        string.IsNullOrEmpty(path) ? SR.IO_PathTooLong : SR.Format(SR.IO_PathTooLong_Path, path));
+                case Interop.Errors.ERROR_SHARING_VIOLATION:
+                    return new IOException(
+                        string.IsNullOrEmpty(path) ? SR.IO_SharingViolation_NoFileName : SR.Format(SR.IO_SharingViolation_File, path),
+                        MakeHRFromErrorCode(errorCode));
+                case Interop.Errors.ERROR_FILE_EXISTS:
+                    if (string.IsNullOrEmpty(path))
+                        goto default;
+                    return new IOException(SR.Format(SR.IO_FileExists_Name, path), MakeHRFromErrorCode(errorCode));
+                case Interop.Errors.ERROR_OPERATION_ABORTED:
+                    return new OperationCanceledException();
+                case Interop.Errors.ERROR_INVALID_PARAMETER:
+                default:
+                    return new IOException(
+                        string.IsNullOrEmpty(path) ? GetMessage(errorCode) : $"{GetMessage(errorCode)} : '{path}'",
+                        MakeHRFromErrorCode(errorCode));
+            }
+        }
+
+        /// <summary>
+        /// If not already an HRESULT, returns an HRESULT for the specified Win32 error code.
+        /// </summary>
+        internal static int MakeHRFromErrorCode(int errorCode)
+        {
+            // Don't convert it if it is already an HRESULT
+            if ((0xFFFF0000 & errorCode) != 0)
+                return errorCode;
+
+            return unchecked(((int)0x80070000) | errorCode);
+        }
+
+        /// <summary>
+        /// Returns a Win32 error code for the specified HRESULT if it came from FACILITY_WIN32
+        /// If not, returns the HRESULT unchanged
+        /// </summary>
+        internal static int TryMakeWin32ErrorCodeFromHR(int hr)
+        {
+            if ((0xFFFF0000 & hr) == 0x80070000)
+            {
+                // Win32 error, Win32Marshal.GetExceptionForWin32Error expects the Win32 format
+                hr &= 0x0000FFFF;
+            }
+
+            return hr;
+        }
+
+        /// <summary>
+        /// Returns a string message for the specified Win32 error code.
+        /// </summary>
+        internal static string GetMessage(int errorCode) => Interop.Kernel32.GetMessage(errorCode);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IObservable.cs b/src/System.Private.CoreLib/shared/System/IObservable.cs
new file mode 100644
index 0000000000..aabb0b8fb4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IObservable.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    public interface IObservable<out T>
+    {
+        IDisposable Subscribe(IObserver<T> observer);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IObserver.cs b/src/System.Private.CoreLib/shared/System/IObserver.cs
new file mode 100644
index 0000000000..39e123de8d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IObserver.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    public interface IObserver<in T>
+    {
+        void OnNext(T value);
+        void OnError(Exception error);
+        void OnCompleted();
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IProgress.cs b/src/System.Private.CoreLib/shared/System/IProgress.cs
new file mode 100644
index 0000000000..724c7bdce9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IProgress.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    /// <summary>Defines a provider for progress updates.</summary>
+    /// <typeparam name="T">The type of progress update value.</typeparam>
+    public interface IProgress<in T>
+    {
+        /// <summary>Reports a progress update.</summary>
+        /// <param name="value">The value of the updated progress.</param>
+        void Report(T value);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ISpanFormattable.cs b/src/System.Private.CoreLib/shared/System/ISpanFormattable.cs
new file mode 100644
index 0000000000..df46b5bcd1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ISpanFormattable.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    internal interface ISpanFormattable
+    {
+        bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format, IFormatProvider provider);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IndexOutOfRangeException.cs b/src/System.Private.CoreLib/shared/System/IndexOutOfRangeException.cs
new file mode 100644
index 0000000000..b6d93ef568
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IndexOutOfRangeException.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception class for invalid array indices.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class IndexOutOfRangeException : SystemException
+    {
+        public IndexOutOfRangeException()
+            : base(SR.Arg_IndexOutOfRangeException)
+        {
+            HResult = HResults.COR_E_INDEXOUTOFRANGE;
+        }
+
+        public IndexOutOfRangeException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_INDEXOUTOFRANGE;
+        }
+
+        public IndexOutOfRangeException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_INDEXOUTOFRANGE;
+        }
+
+        internal IndexOutOfRangeException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/InsufficientExecutionStackException.cs b/src/System.Private.CoreLib/shared/System/InsufficientExecutionStackException.cs
new file mode 100644
index 0000000000..4822028f85
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/InsufficientExecutionStackException.cs
@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class InsufficientExecutionStackException : SystemException
+    {
+        public InsufficientExecutionStackException()
+            : base(SR.Arg_InsufficientExecutionStackException)
+        {
+            HResult = HResults.COR_E_INSUFFICIENTEXECUTIONSTACK;
+        }
+
+        public InsufficientExecutionStackException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_INSUFFICIENTEXECUTIONSTACK;
+        }
+
+        public InsufficientExecutionStackException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_INSUFFICIENTEXECUTIONSTACK;
+        }
+
+        internal InsufficientExecutionStackException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Int16.cs b/src/System.Private.CoreLib/shared/System/Int16.cs
new file mode 100644
index 0000000000..fecc87e9fe
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Int16.cs
@@ -0,0 +1,314 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    [Serializable]
+    [StructLayout(LayoutKind.Sequential)]
+    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct Int16 : IComparable, IConvertible, IFormattable, IComparable<Int16>, IEquatable<Int16>, ISpanFormattable
+    {
+        private short m_value; // Do not rename (binary serialization)
+
+        public const short MaxValue = (short)0x7FFF;
+        public const short MinValue = unchecked((short)0x8000);
+
+        // Compares this object to another object, returning an integer that
+        // indicates the relationship. 
+        // Returns a value less than zero if this  object
+        // null is considered to be less than any instance.
+        // If object is not of type Int16, this method throws an ArgumentException.
+        // 
+        public int CompareTo(Object value)
+        {
+            if (value == null)
+            {
+                return 1;
+            }
+
+            if (value is Int16)
+            {
+                return m_value - ((Int16)value).m_value;
+            }
+
+            throw new ArgumentException(SR.Arg_MustBeInt16);
+        }
+
+        public int CompareTo(Int16 value)
+        {
+            return m_value - value;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (!(obj is Int16))
+            {
+                return false;
+            }
+            return m_value == ((Int16)obj).m_value;
+        }
+
+        [NonVersionable]
+        public bool Equals(Int16 obj)
+        {
+            return m_value == obj;
+        }
+
+        // Returns a HashCode for the Int16
+        public override int GetHashCode()
+        {
+            return ((int)((ushort)m_value) | (((int)m_value) << 16));
+        }
+
+
+        public override String ToString()
+        {
+            return Number.FormatInt32(m_value, null, null);
+        }
+
+        public String ToString(IFormatProvider provider)
+        {
+            return Number.FormatInt32(m_value, null, provider);
+        }
+
+        public String ToString(String format)
+        {
+            return ToString(format, null);
+        }
+
+        public String ToString(String format, IFormatProvider provider)
+        {
+            if (m_value < 0 && format != null && format.Length > 0 && (format[0] == 'X' || format[0] == 'x'))
+            {
+                uint temp = (uint)(m_value & 0x0000FFFF);
+                return Number.FormatUInt32(temp, format, provider);
+            }
+
+            return Number.FormatInt32(m_value, format, provider);
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider provider = null)
+        {
+            if (m_value < 0 && format.Length > 0 && (format[0] == 'X' || format[0] == 'x'))
+            {
+                uint temp = (uint)(m_value & 0x0000FFFF);
+                return Number.TryFormatUInt32(temp, format, provider, destination, out charsWritten);
+            }
+            return Number.TryFormatInt32(m_value, format, provider, destination, out charsWritten);
+        }
+
+        public static short Parse(String s)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo);
+        }
+
+        public static short Parse(String s, NumberStyles style)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, style, NumberFormatInfo.CurrentInfo);
+        }
+
+        public static short Parse(String s, IFormatProvider provider)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public static short Parse(String s, NumberStyles style, IFormatProvider provider)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public static short Parse(ReadOnlySpan<char> s, NumberStyles style = NumberStyles.Integer, IFormatProvider provider = null)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return Parse(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        private static short Parse(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info)
+        {
+            int i = 0;
+            try
+            {
+                i = Number.ParseInt32(s, style, info);
+            }
+            catch (OverflowException e)
+            {
+                throw new OverflowException(SR.Overflow_Int16, e);
+            }
+
+            // We need this check here since we don't allow signs to specified in hex numbers. So we fixup the result
+            // for negative numbers
+            if ((style & NumberStyles.AllowHexSpecifier) != 0)
+            { // We are parsing a hexadecimal number
+                if ((i < 0) || (i > UInt16.MaxValue))
+                {
+                    throw new OverflowException(SR.Overflow_Int16);
+                }
+                return (short)i;
+            }
+
+            if (i < MinValue || i > MaxValue) throw new OverflowException(SR.Overflow_Int16);
+            return (short)i;
+        }
+
+        public static bool TryParse(String s, out Int16 result)
+        {
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return TryParse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, out short result)
+        {
+            return TryParse(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        public static bool TryParse(String s, NumberStyles style, IFormatProvider provider, out Int16 result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return TryParse((ReadOnlySpan<char>)s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider provider, out short result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return TryParse(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        private static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info, out Int16 result)
+        {
+            result = 0;
+            int i;
+            if (!Number.TryParseInt32(s, style, info, out i))
+            {
+                return false;
+            }
+
+            // We need this check here since we don't allow signs to specified in hex numbers. So we fixup the result
+            // for negative numbers
+            if ((style & NumberStyles.AllowHexSpecifier) != 0)
+            { // We are parsing a hexadecimal number
+                if ((i < 0) || i > UInt16.MaxValue)
+                {
+                    return false;
+                }
+                result = (Int16)i;
+                return true;
+            }
+
+            if (i < MinValue || i > MaxValue)
+            {
+                return false;
+            }
+            result = (Int16)i;
+            return true;
+        }
+
+        //
+        // IConvertible implementation
+        // 
+
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.Int16;
+        }
+
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            return Convert.ToBoolean(m_value);
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            return Convert.ToChar(m_value);
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return Convert.ToSByte(m_value);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return Convert.ToByte(m_value);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return m_value;
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return Convert.ToUInt16(m_value);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return Convert.ToInt32(m_value);
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return Convert.ToUInt32(m_value);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return Convert.ToInt64(m_value);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return Convert.ToUInt64(m_value);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            return Convert.ToSingle(m_value);
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            return Convert.ToDouble(m_value);
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            return Convert.ToDecimal(m_value);
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Int16", "DateTime"));
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Int32.cs b/src/System.Private.CoreLib/shared/System/Int32.cs
new file mode 100644
index 0000000000..b573e950e4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Int32.cs
@@ -0,0 +1,269 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    [Serializable]
+    [StructLayout(LayoutKind.Sequential)]
+    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct Int32 : IComparable, IConvertible, IFormattable, IComparable<Int32>, IEquatable<Int32>, ISpanFormattable
+    {
+        private int m_value; // Do not rename (binary serialization)
+
+        public const int MaxValue = 0x7fffffff;
+        public const int MinValue = unchecked((int)0x80000000);
+
+        // Compares this object to another object, returning an integer that
+        // indicates the relationship. 
+        // Returns :
+        // 0 if the values are equal
+        // Negative number if _value is less than value
+        // Positive number if _value is more than value
+        // null is considered to be less than any instance, hence returns positive number
+        // If object is not of type Int32, this method throws an ArgumentException.
+        // 
+        public int CompareTo(Object value)
+        {
+            if (value == null)
+            {
+                return 1;
+            }
+            if (value is Int32)
+            {
+                // NOTE: Cannot use return (_value - value) as this causes a wrap
+                // around in cases where _value - value > MaxValue.
+                int i = (int)value;
+                if (m_value < i) return -1;
+                if (m_value > i) return 1;
+                return 0;
+            }
+            throw new ArgumentException(SR.Arg_MustBeInt32);
+        }
+
+        public int CompareTo(int value)
+        {
+            // NOTE: Cannot use return (_value - value) as this causes a wrap
+            // around in cases where _value - value > MaxValue.
+            if (m_value < value) return -1;
+            if (m_value > value) return 1;
+            return 0;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (!(obj is Int32))
+            {
+                return false;
+            }
+            return m_value == ((Int32)obj).m_value;
+        }
+
+        [NonVersionable]
+        public bool Equals(Int32 obj)
+        {
+            return m_value == obj;
+        }
+
+        // The absolute value of the int contained.
+        public override int GetHashCode()
+        {
+            return m_value;
+        }
+
+        public override String ToString()
+        {
+            return Number.FormatInt32(m_value, null, null);
+        }
+
+        public String ToString(String format)
+        {
+            return Number.FormatInt32(m_value, format, null);
+        }
+
+        public String ToString(IFormatProvider provider)
+        {
+            return Number.FormatInt32(m_value, null, provider);
+        }
+
+        public String ToString(String format, IFormatProvider provider)
+        {
+            return Number.FormatInt32(m_value, format, provider);
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider provider = null)
+        {
+            return Number.TryFormatInt32(m_value, format, provider, destination, out charsWritten);
+        }
+
+        public static int Parse(String s)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseInt32(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo);
+        }
+
+        public static int Parse(String s, NumberStyles style)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseInt32(s, style, NumberFormatInfo.CurrentInfo);
+        }
+
+        // Parses an integer from a String in the given style.  If
+        // a NumberFormatInfo isn't specified, the current culture's 
+        // NumberFormatInfo is assumed.
+        // 
+        public static int Parse(String s, IFormatProvider provider)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseInt32(s, NumberStyles.Integer, NumberFormatInfo.GetInstance(provider));
+        }
+
+        // Parses an integer from a String in the given style.  If
+        // a NumberFormatInfo isn't specified, the current culture's 
+        // NumberFormatInfo is assumed.
+        // 
+        public static int Parse(String s, NumberStyles style, IFormatProvider provider)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseInt32(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public static int Parse(ReadOnlySpan<char> s, NumberStyles style = NumberStyles.Integer, IFormatProvider provider = null)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return Number.ParseInt32(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        // Parses an integer from a String. Returns false rather
+        // than throwing exceptin if input is invalid
+        // 
+        public static bool TryParse(String s, out Int32 result)
+        {
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return Number.TryParseInt32(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, out int result)
+        {
+            return Number.TryParseInt32(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        // Parses an integer from a String in the given style. Returns false rather
+        // than throwing exceptin if input is invalid
+        // 
+        public static bool TryParse(String s, NumberStyles style, IFormatProvider provider, out Int32 result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return Number.TryParseInt32(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider provider, out int result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return Number.TryParseInt32(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        //
+        // IConvertible implementation
+        // 
+
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.Int32;
+        }
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            return Convert.ToBoolean(m_value);
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            return Convert.ToChar(m_value);
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return Convert.ToSByte(m_value);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return Convert.ToByte(m_value);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return Convert.ToInt16(m_value);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return Convert.ToUInt16(m_value);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return m_value;
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return Convert.ToUInt32(m_value);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return Convert.ToInt64(m_value);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return Convert.ToUInt64(m_value);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            return Convert.ToSingle(m_value);
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            return Convert.ToDouble(m_value);
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            return Convert.ToDecimal(m_value);
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Int32", "DateTime"));
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Int64.cs b/src/System.Private.CoreLib/shared/System/Int64.cs
new file mode 100644
index 0000000000..0bcca87309
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Int64.cs
@@ -0,0 +1,257 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    [Serializable]
+    [StructLayout(LayoutKind.Sequential)]
+    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct Int64 : IComparable, IConvertible, IFormattable, IComparable<Int64>, IEquatable<Int64>, ISpanFormattable
+    {
+        private long m_value; // Do not rename (binary serialization)
+
+        public const long MaxValue = 0x7fffffffffffffffL;
+        public const long MinValue = unchecked((long)0x8000000000000000L);
+
+        // Compares this object to another object, returning an integer that
+        // indicates the relationship. 
+        // Returns a value less than zero if this  object
+        // null is considered to be less than any instance.
+        // If object is not of type Int64, this method throws an ArgumentException.
+        // 
+        public int CompareTo(Object value)
+        {
+            if (value == null)
+            {
+                return 1;
+            }
+            if (value is Int64)
+            {
+                // Need to use compare because subtraction will wrap
+                // to positive for very large neg numbers, etc.
+                long i = (long)value;
+                if (m_value < i) return -1;
+                if (m_value > i) return 1;
+                return 0;
+            }
+            throw new ArgumentException(SR.Arg_MustBeInt64);
+        }
+
+        public int CompareTo(Int64 value)
+        {
+            // Need to use compare because subtraction will wrap
+            // to positive for very large neg numbers, etc.
+            if (m_value < value) return -1;
+            if (m_value > value) return 1;
+            return 0;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (!(obj is Int64))
+            {
+                return false;
+            }
+            return m_value == ((Int64)obj).m_value;
+        }
+
+        [NonVersionable]
+        public bool Equals(Int64 obj)
+        {
+            return m_value == obj;
+        }
+
+        // The value of the lower 32 bits XORed with the uppper 32 bits.
+        public override int GetHashCode()
+        {
+            return (unchecked((int)((long)m_value)) ^ (int)(m_value >> 32));
+        }
+
+        public override String ToString()
+        {
+            return Number.FormatInt64(m_value, null, null);
+        }
+
+        public String ToString(IFormatProvider provider)
+        {
+            return Number.FormatInt64(m_value, null, provider);
+        }
+
+        public String ToString(String format)
+        {
+            return Number.FormatInt64(m_value, format, null);
+        }
+
+        public String ToString(String format, IFormatProvider provider)
+        {
+            return Number.FormatInt64(m_value, format, provider);
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider provider = null)
+        {
+            return Number.TryFormatInt64(m_value, format, provider, destination, out charsWritten);
+        }
+
+        public static long Parse(String s)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseInt64(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo);
+        }
+
+        public static long Parse(String s, NumberStyles style)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseInt64(s, style, NumberFormatInfo.CurrentInfo);
+        }
+
+        public static long Parse(String s, IFormatProvider provider)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseInt64(s, NumberStyles.Integer, NumberFormatInfo.GetInstance(provider));
+        }
+
+
+        // Parses a long from a String in the given style.  If
+        // a NumberFormatInfo isn't specified, the current culture's 
+        // NumberFormatInfo is assumed.
+        // 
+        public static long Parse(String s, NumberStyles style, IFormatProvider provider)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseInt64(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public static long Parse(ReadOnlySpan<char> s, NumberStyles style = NumberStyles.Integer, IFormatProvider provider = null)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return Number.ParseInt64(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public static Boolean TryParse(String s, out Int64 result)
+        {
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return Number.TryParseInt64(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, out long result)
+        {
+            return Number.TryParseInt64(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        public static Boolean TryParse(String s, NumberStyles style, IFormatProvider provider, out Int64 result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return Number.TryParseInt64(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider provider, out long result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return Number.TryParseInt64(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        //
+        // IConvertible implementation
+        // 
+
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.Int64;
+        }
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            return Convert.ToBoolean(m_value);
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            return Convert.ToChar(m_value);
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return Convert.ToSByte(m_value);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return Convert.ToByte(m_value);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return Convert.ToInt16(m_value);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return Convert.ToUInt16(m_value);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return Convert.ToInt32(m_value);
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return Convert.ToUInt32(m_value);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return m_value;
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return Convert.ToUInt64(m_value);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            return Convert.ToSingle(m_value);
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            return Convert.ToDouble(m_value);
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            return Convert.ToDecimal(m_value);
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Int64", "DateTime"));
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/IntPtr.cs b/src/System.Private.CoreLib/shared/System/IntPtr.cs
new file mode 100644
index 0000000000..44638ddd8e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/IntPtr.cs
@@ -0,0 +1,235 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.Serialization;
+using System.Runtime.Versioning;
+
+#if BIT64
+using nint = System.Int64;
+#else
+using nint = System.Int32;
+#endif
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct IntPtr : IEquatable<IntPtr>, ISerializable
+    {
+        // WARNING: We allow diagnostic tools to directly inspect this member (_value). 
+        // See https://github.com/dotnet/corert/blob/master/Documentation/design-docs/diagnostics/diagnostics-tools-contract.md for more details. 
+        // Please do not change the type, the name, or the semantic usage of this member without understanding the implication for tools. 
+        // Get in touch with the diagnostics team if you have questions.
+        private unsafe void* _value; // Do not rename (binary serialization)
+
+        [Intrinsic]
+        public static readonly IntPtr Zero;
+
+        [Intrinsic]
+        [NonVersionable]
+        public unsafe IntPtr(int value)
+        {
+            _value = (void*)value;
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public unsafe IntPtr(long value)
+        {
+#if BIT64
+            _value = (void*)value;
+#else
+            _value = (void*)checked((int)value);
+#endif
+        }
+
+        [CLSCompliant(false)]
+        [Intrinsic]
+        [NonVersionable]
+        public unsafe IntPtr(void* value)
+        {
+            _value = value;
+        }
+
+        private unsafe IntPtr(SerializationInfo info, StreamingContext context)
+        {
+            long l = info.GetInt64("value");
+
+            if (Size == 4 && (l > int.MaxValue || l < int.MinValue))
+                throw new ArgumentException(SR.Serialization_InvalidPtrValue);
+
+            _value = (void*)l;
+        }
+
+        unsafe void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+                throw new ArgumentNullException(nameof(info));
+
+            info.AddValue("value", ToInt64());
+        }
+
+        public unsafe override bool Equals(Object obj)
+        {
+            if (obj is IntPtr)
+            {
+                return (_value == ((IntPtr)obj)._value);
+            }
+            return false;
+        }
+
+        unsafe bool IEquatable<IntPtr>.Equals(IntPtr other)
+        {
+            return _value == other._value;
+        }
+
+        public unsafe override int GetHashCode()
+        {
+#if BIT64
+            long l = (long)_value;
+            return (unchecked((int)l) ^ (int)(l >> 32));
+#else
+            return unchecked((int)_value);
+#endif
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public unsafe int ToInt32()
+        {
+#if BIT64
+            long l = (long)_value;
+            return checked((int)l);
+#else
+            return (int)_value;
+#endif
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public unsafe long ToInt64()
+        {
+            return (nint)_value;
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe explicit operator IntPtr(int value)
+        {
+            return new IntPtr(value);
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe explicit operator IntPtr(long value)
+        {
+            return new IntPtr(value);
+        }
+
+        [CLSCompliant(false)]
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe explicit operator IntPtr(void* value)
+        {
+            return new IntPtr(value);
+        }
+
+        [CLSCompliant(false)]
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe explicit operator void* (IntPtr value)
+        {
+            return value._value;
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe explicit operator int(IntPtr value)
+        {
+#if BIT64
+            long l = (long)value._value;
+            return checked((int)l);
+#else
+            return (int)value._value;
+#endif
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe explicit operator long(IntPtr value)
+        {
+            return (nint)value._value;
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe bool operator ==(IntPtr value1, IntPtr value2)
+        {
+            return value1._value == value2._value;
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe bool operator !=(IntPtr value1, IntPtr value2)
+        {
+            return value1._value != value2._value;
+        }
+
+        [NonVersionable]
+        public static IntPtr Add(IntPtr pointer, int offset)
+        {
+            return pointer + offset;
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe IntPtr operator +(IntPtr pointer, int offset)
+        {
+            return new IntPtr((nint)pointer._value + offset);
+        }
+
+        [NonVersionable]
+        public static IntPtr Subtract(IntPtr pointer, int offset)
+        {
+            return pointer - offset;
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe IntPtr operator -(IntPtr pointer, int offset)
+        {
+            return new IntPtr((nint)pointer._value - offset);
+        }
+
+        public static int Size
+        {
+            [Intrinsic]
+            [NonVersionable]
+            get
+            {
+                return sizeof(nint);
+            }
+        }
+
+        [CLSCompliant(false)]
+        [Intrinsic]
+        [NonVersionable]
+        public unsafe void* ToPointer()
+        {
+            return _value;
+        }
+
+        public unsafe override string ToString()
+        {
+            return ((nint)_value).ToString(CultureInfo.InvariantCulture);
+        }
+
+        public unsafe string ToString(string format)
+        {
+            return ((nint)_value).ToString(format, CultureInfo.InvariantCulture);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/InvalidCastException.cs b/src/System.Private.CoreLib/shared/System/InvalidCastException.cs
new file mode 100644
index 0000000000..055643278a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/InvalidCastException.cs
@@ -0,0 +1,47 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+** Purpose: Exception class for invalid cast conditions!
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class InvalidCastException : SystemException
+    {
+        public InvalidCastException()
+            : base(SR.Arg_InvalidCastException)
+        {
+            HResult = HResults.COR_E_INVALIDCAST;
+        }
+
+        public InvalidCastException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_INVALIDCAST;
+        }
+
+        public InvalidCastException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_INVALIDCAST;
+        }
+
+        public InvalidCastException(String message, int errorCode)
+            : base(message)
+        {
+            HResult = errorCode;
+        }
+
+        protected InvalidCastException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/InvalidOperationException.cs b/src/System.Private.CoreLib/shared/System/InvalidOperationException.cs
new file mode 100644
index 0000000000..62c222af40
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/InvalidOperationException.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception class for denoting an object was in a state that
+** made calling a method illegal.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class InvalidOperationException : SystemException
+    {
+        public InvalidOperationException()
+            : base(SR.Arg_InvalidOperationException)
+        {
+            HResult = HResults.COR_E_INVALIDOPERATION;
+        }
+
+        public InvalidOperationException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_INVALIDOPERATION;
+        }
+
+        public InvalidOperationException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_INVALIDOPERATION;
+        }
+
+        protected InvalidOperationException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/InvalidProgramException.cs b/src/System.Private.CoreLib/shared/System/InvalidProgramException.cs
new file mode 100644
index 0000000000..c8047c548b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/InvalidProgramException.cs
@@ -0,0 +1,42 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: The exception class for programs with invalid IL or bad metadata.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class InvalidProgramException : SystemException
+    {
+        public InvalidProgramException()
+            : base(SR.InvalidProgram_Default)
+        {
+            HResult = HResults.COR_E_INVALIDPROGRAM;
+        }
+
+        public InvalidProgramException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_INVALIDPROGRAM;
+        }
+
+        public InvalidProgramException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_INVALIDPROGRAM;
+        }
+
+        internal InvalidProgramException(SerializationInfo info, StreamingContext context) : base(info, context) { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/InvalidTimeZoneException.cs b/src/System.Private.CoreLib/shared/System/InvalidTimeZoneException.cs
new file mode 100644
index 0000000000..25b155e8d1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/InvalidTimeZoneException.cs
@@ -0,0 +1,31 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class InvalidTimeZoneException : Exception
+    {
+        public InvalidTimeZoneException()
+        {
+        }
+
+        public InvalidTimeZoneException(String message)
+            : base(message)
+        {
+        }
+
+        public InvalidTimeZoneException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
+
+        protected InvalidTimeZoneException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Lazy.cs b/src/System.Private.CoreLib/shared/System/Lazy.cs
new file mode 100644
index 0000000000..6410c2e285
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Lazy.cs
@@ -0,0 +1,548 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// --------------------------------------------------------------------------------------
+//
+// A class that provides a simple, lightweight implementation of lazy initialization, 
+// obviating the need for a developer to implement a custom, thread-safe lazy initialization 
+// solution.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+#pragma warning disable 0420
+
+using System.Diagnostics;
+using System.Runtime.ExceptionServices;
+using System.Runtime.InteropServices;
+using System.Threading;
+
+namespace System
+{
+    internal enum LazyState
+    {
+        NoneViaConstructor = 0,
+        NoneViaFactory     = 1,
+        NoneException      = 2,
+
+        PublicationOnlyViaConstructor = 3,
+        PublicationOnlyViaFactory     = 4,
+        PublicationOnlyWait           = 5,
+        PublicationOnlyException      = 6,
+
+        ExecutionAndPublicationViaConstructor = 7,
+        ExecutionAndPublicationViaFactory     = 8,
+        ExecutionAndPublicationException      = 9,
+    }
+
+    /// <summary>
+    /// LazyHelper serves multiples purposes
+    /// - minimizing code size of Lazy&lt;T&gt; by implementing as much of the code that is not generic
+    ///   this reduces generic code bloat, making faster class initialization
+    /// - contains singleton objects that are used to handle threading primitives for PublicationOnly mode
+    /// - allows for instantiation for ExecutionAndPublication so as to create an object for locking on
+    /// - holds exception information.
+    /// </summary>
+    internal class LazyHelper
+    {
+        internal readonly static LazyHelper NoneViaConstructor            = new LazyHelper(LazyState.NoneViaConstructor);
+        internal readonly static LazyHelper NoneViaFactory                = new LazyHelper(LazyState.NoneViaFactory);
+        internal readonly static LazyHelper PublicationOnlyViaConstructor = new LazyHelper(LazyState.PublicationOnlyViaConstructor);
+        internal readonly static LazyHelper PublicationOnlyViaFactory     = new LazyHelper(LazyState.PublicationOnlyViaFactory);
+        internal readonly static LazyHelper PublicationOnlyWaitForOtherThreadToPublish       = new LazyHelper(LazyState.PublicationOnlyWait);
+
+        internal LazyState State { get; }
+
+        private readonly ExceptionDispatchInfo _exceptionDispatch;
+
+        /// <summary>
+        /// Constructor that defines the state
+        /// </summary>
+        internal LazyHelper(LazyState state)
+        {
+            State = state;
+        }
+
+        /// <summary>
+        /// Constructor used for exceptions
+        /// </summary>
+        internal LazyHelper(LazyThreadSafetyMode mode, Exception exception)
+        {
+            switch(mode)
+            {
+                case LazyThreadSafetyMode.ExecutionAndPublication:
+                    State = LazyState.ExecutionAndPublicationException;
+                    break;
+
+                case LazyThreadSafetyMode.None:
+                    State = LazyState.NoneException;
+                    break;
+
+                case LazyThreadSafetyMode.PublicationOnly:
+                    State = LazyState.PublicationOnlyException;
+                    break;
+
+                default:
+                    Debug.Fail("internal constructor, this should never occur");
+                    break;
+            }
+
+            _exceptionDispatch = ExceptionDispatchInfo.Capture(exception);
+        }
+
+        internal void ThrowException()
+        {
+            Debug.Assert(_exceptionDispatch != null, "execution path is invalid");
+
+            _exceptionDispatch.Throw();
+        }
+
+        private LazyThreadSafetyMode GetMode()
+        {
+            switch (State)
+            {
+                case LazyState.NoneViaConstructor:
+                case LazyState.NoneViaFactory:
+                case LazyState.NoneException:
+                    return LazyThreadSafetyMode.None;
+
+                case LazyState.PublicationOnlyViaConstructor:
+                case LazyState.PublicationOnlyViaFactory:
+                case LazyState.PublicationOnlyWait:
+                case LazyState.PublicationOnlyException:
+                    return LazyThreadSafetyMode.PublicationOnly;
+
+                case LazyState.ExecutionAndPublicationViaConstructor:
+                case LazyState.ExecutionAndPublicationViaFactory:
+                case LazyState.ExecutionAndPublicationException:
+                    return LazyThreadSafetyMode.ExecutionAndPublication;
+
+                default:
+                    Debug.Fail("Invalid logic; State should always have a valid value");
+                    return default(LazyThreadSafetyMode);
+            }
+        }
+
+        internal static LazyThreadSafetyMode? GetMode(LazyHelper state)
+        {
+            if (state == null)
+                return null; // we don't know the mode anymore
+            return state.GetMode();
+        }
+
+        internal static bool GetIsValueFaulted(LazyHelper state) => state?._exceptionDispatch != null;
+
+        internal static LazyHelper Create(LazyThreadSafetyMode mode, bool useDefaultConstructor)
+        {
+            switch (mode)
+            {
+                case LazyThreadSafetyMode.None:
+                    return useDefaultConstructor ? NoneViaConstructor : NoneViaFactory;
+
+                case LazyThreadSafetyMode.PublicationOnly:
+                    return useDefaultConstructor ? PublicationOnlyViaConstructor : PublicationOnlyViaFactory;
+
+                case LazyThreadSafetyMode.ExecutionAndPublication:
+                    // we need to create an object for ExecutionAndPublication because we use Monitor-based locking
+                    var state = useDefaultConstructor ? LazyState.ExecutionAndPublicationViaConstructor : LazyState.ExecutionAndPublicationViaFactory;
+                    return new LazyHelper(state);
+
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(mode), SR.Lazy_ctor_ModeInvalid);
+            }
+        }
+
+        internal static object CreateViaDefaultConstructor(Type type)
+        {
+            try
+            {
+                return Activator.CreateInstance(type);
+            }
+            catch (MissingMethodException)
+            {
+                throw new MissingMemberException(SR.Lazy_CreateValue_NoParameterlessCtorForT);
+            }
+        }
+
+        internal static LazyThreadSafetyMode GetModeFromIsThreadSafe(bool isThreadSafe)
+        {
+            return isThreadSafe ? LazyThreadSafetyMode.ExecutionAndPublication : LazyThreadSafetyMode.None;
+        }
+    }
+
+    /// <summary>
+    /// Provides support for lazy initialization.
+    /// </summary>
+    /// <typeparam name="T">Specifies the type of element being lazily initialized.</typeparam>
+    /// <remarks>
+    /// <para>
+    /// By default, all public and protected members of <see cref="Lazy{T}"/> are thread-safe and may be used
+    /// concurrently from multiple threads.  These thread-safety guarantees may be removed optionally and per instance
+    /// using parameters to the type's constructors.
+    /// </para>
+    /// </remarks>
+    [DebuggerTypeProxy(typeof(LazyDebugView<>))]
+    [DebuggerDisplay("ThreadSafetyMode={Mode}, IsValueCreated={IsValueCreated}, IsValueFaulted={IsValueFaulted}, Value={ValueForDebugDisplay}")]
+    public class Lazy<T>
+    {
+        private static T CreateViaDefaultConstructor()
+        {
+            return (T)LazyHelper.CreateViaDefaultConstructor(typeof(T));
+        }
+
+        // _state, a volatile reference, is set to null after _value has been set
+        private volatile LazyHelper _state;
+
+        // we ensure that _factory when finished is set to null to allow garbage collector to clean up
+        // any referenced items
+        private Func<T> _factory;
+
+        // _value eventually stores the lazily created value. It is valid when _state = null.
+        private T _value;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Lazy{T}"/> class that 
+        /// uses <typeparamref name="T"/>'s default constructor for lazy initialization.
+        /// </summary>
+        /// <remarks>
+        /// An instance created with this constructor may be used concurrently from multiple threads.
+        /// </remarks>
+        public Lazy()
+            : this(null, LazyThreadSafetyMode.ExecutionAndPublication, useDefaultConstructor:true)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Lazy{T}"/> class that
+        /// uses a pre-initialized specified value.
+        /// </summary>
+        /// <remarks>
+        /// An instance created with this constructor should be usable by multiple threads
+        //  concurrently.
+        /// </remarks>
+        public Lazy(T value)
+        {
+            _value = value;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Lazy{T}"/> class that uses a
+        /// specified initialization function.
+        /// </summary>
+        /// <param name="valueFactory">
+        /// The <see cref="T:System.Func{T}"/> invoked to produce the lazily-initialized value when it is
+        /// needed.
+        /// </param>
+        /// <exception cref="System.ArgumentNullException"><paramref name="valueFactory"/> is a null
+        /// reference (Nothing in Visual Basic).</exception>
+        /// <remarks>
+        /// An instance created with this constructor may be used concurrently from multiple threads.
+        /// </remarks>
+        public Lazy(Func<T> valueFactory)
+            : this(valueFactory, LazyThreadSafetyMode.ExecutionAndPublication, useDefaultConstructor:false)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Lazy{T}"/>
+        /// class that uses <typeparamref name="T"/>'s default constructor and a specified thread-safety mode.
+        /// </summary>
+        /// <param name="isThreadSafe">true if this instance should be usable by multiple threads concurrently; false if the instance will only be used by one thread at a time.
+        /// </param>
+        public Lazy(bool isThreadSafe) :
+            this(null, LazyHelper.GetModeFromIsThreadSafe(isThreadSafe), useDefaultConstructor:true)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Lazy{T}"/>
+        /// class that uses <typeparamref name="T"/>'s default constructor and a specified thread-safety mode.
+        /// </summary>
+        /// <param name="mode">The lazy thread-safety mode</param>
+        /// <exception cref="System.ArgumentOutOfRangeException"><paramref name="mode"/> mode contains an invalid valuee</exception>
+        public Lazy(LazyThreadSafetyMode mode) :
+            this(null, mode, useDefaultConstructor:true)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Lazy{T}"/> class
+        /// that uses a specified initialization function and a specified thread-safety mode.
+        /// </summary>
+        /// <param name="valueFactory">
+        /// The <see cref="T:System.Func{T}"/> invoked to produce the lazily-initialized value when it is needed.
+        /// </param>
+        /// <param name="isThreadSafe">true if this instance should be usable by multiple threads concurrently; false if the instance will only be used by one thread at a time.
+        /// </param>
+        /// <exception cref="System.ArgumentNullException"><paramref name="valueFactory"/> is
+        /// a null reference (Nothing in Visual Basic).</exception>
+        public Lazy(Func<T> valueFactory, bool isThreadSafe) :
+            this(valueFactory, LazyHelper.GetModeFromIsThreadSafe(isThreadSafe), useDefaultConstructor:false)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Lazy{T}"/> class
+        /// that uses a specified initialization function and a specified thread-safety mode.
+        /// </summary>
+        /// <param name="valueFactory">
+        /// The <see cref="T:System.Func{T}"/> invoked to produce the lazily-initialized value when it is needed.
+        /// </param>
+        /// <param name="mode">The lazy thread-safety mode.</param>
+        /// <exception cref="System.ArgumentNullException"><paramref name="valueFactory"/> is
+        /// a null reference (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.ArgumentOutOfRangeException"><paramref name="mode"/> mode contains an invalid value.</exception>
+        public Lazy(Func<T> valueFactory, LazyThreadSafetyMode mode)
+            : this(valueFactory, mode, useDefaultConstructor:false)
+        {
+        }
+
+        private Lazy(Func<T> valueFactory, LazyThreadSafetyMode mode, bool useDefaultConstructor)
+        {
+            if (valueFactory == null && !useDefaultConstructor)
+                throw new ArgumentNullException(nameof(valueFactory));
+
+            _factory = valueFactory;
+            _state = LazyHelper.Create(mode, useDefaultConstructor);
+        }
+
+        private void ViaConstructor()
+        {
+            _value = CreateViaDefaultConstructor();
+            _state = null; // volatile write, must occur after setting _value
+        }
+
+        private void ViaFactory(LazyThreadSafetyMode mode)
+        {
+            try
+            {
+                Func<T> factory = _factory;
+                if (factory == null)
+                    throw new InvalidOperationException(SR.Lazy_Value_RecursiveCallsToValue);
+                _factory = null;
+
+                _value = factory();
+                _state = null; // volatile write, must occur after setting _value
+            }
+            catch (Exception exception)
+            {
+                _state = new LazyHelper(mode, exception);
+                throw;
+            }
+        }
+
+        private void ExecutionAndPublication(LazyHelper executionAndPublication, bool useDefaultConstructor)
+        {
+            lock (executionAndPublication)
+            {
+                // it's possible for multiple calls to have piled up behind the lock, so we need to check
+                // to see if the ExecutionAndPublication object is still the current implementation.
+                if (ReferenceEquals(_state, executionAndPublication))
+                {
+                    if (useDefaultConstructor)
+                    {
+                        ViaConstructor();
+                    }
+                    else
+                    {
+                        ViaFactory(LazyThreadSafetyMode.ExecutionAndPublication);
+                    }
+                }
+            }
+        }
+
+        private void PublicationOnly(LazyHelper publicationOnly, T possibleValue)
+        {
+            LazyHelper previous = Interlocked.CompareExchange(ref _state, LazyHelper.PublicationOnlyWaitForOtherThreadToPublish, publicationOnly);
+            if (previous == publicationOnly)
+            {
+                _factory = null;
+                _value = possibleValue;
+                _state = null; // volatile write, must occur after setting _value
+            }
+        }
+
+        private void PublicationOnlyViaConstructor(LazyHelper initializer)
+        {
+            PublicationOnly(initializer, CreateViaDefaultConstructor());
+        }
+
+        private void PublicationOnlyViaFactory(LazyHelper initializer)
+        {
+            Func<T> factory = _factory;
+            if (factory == null)
+            {
+                PublicationOnlyWaitForOtherThreadToPublish();
+            }
+            else
+            {
+                PublicationOnly(initializer, factory());
+            }
+        }
+
+        private void PublicationOnlyWaitForOtherThreadToPublish()
+        {
+            var spinWait = new SpinWait();
+            while (!ReferenceEquals(_state, null))
+            {
+                // We get here when PublicationOnly temporarily sets _state to LazyHelper.PublicationOnlyWaitForOtherThreadToPublish.
+                // This temporary state should be quickly followed by _state being set to null.
+                spinWait.SpinOnce();
+            }
+        }
+
+        private T CreateValue()
+        {
+            // we have to create a copy of state here, and use the copy exclusively from here on in
+            // so as to ensure thread safety.
+            var state = _state;
+            if (state != null) 
+            {
+                switch (state.State)
+                {
+                    case LazyState.NoneViaConstructor:
+                        ViaConstructor();
+                        break;
+
+                    case LazyState.NoneViaFactory:
+                        ViaFactory(LazyThreadSafetyMode.None);
+                        break;
+
+                    case LazyState.PublicationOnlyViaConstructor:
+                        PublicationOnlyViaConstructor(state);
+                        break;
+
+                    case LazyState.PublicationOnlyViaFactory:
+                        PublicationOnlyViaFactory(state);
+                        break;
+
+                    case LazyState.PublicationOnlyWait:
+                        PublicationOnlyWaitForOtherThreadToPublish();
+                        break;
+
+                    case LazyState.ExecutionAndPublicationViaConstructor:
+                        ExecutionAndPublication(state, useDefaultConstructor:true);
+                        break;
+
+                    case LazyState.ExecutionAndPublicationViaFactory:
+                        ExecutionAndPublication(state, useDefaultConstructor:false);
+                        break;
+
+                    default:
+                        state.ThrowException();
+                        break;
+                }
+            }
+            return Value;
+        }
+
+        /// <summary>Creates and returns a string representation of this instance.</summary>
+        /// <returns>The result of calling <see cref="System.Object.ToString"/> on the <see
+        /// cref="Value"/>.</returns>
+        /// <exception cref="T:System.NullReferenceException">
+        /// The <see cref="Value"/> is null.
+        /// </exception>
+        public override string ToString()
+        {
+            return IsValueCreated ? Value.ToString() : SR.Lazy_ToString_ValueNotCreated;
+        }
+
+        /// <summary>Gets the value of the Lazy&lt;T&gt; for debugging display purposes.</summary>
+        internal T ValueForDebugDisplay
+        {
+            get
+            {
+                if (!IsValueCreated)
+                {
+                    return default(T);
+                }
+                return _value;
+            }
+        }
+
+        /// <summary>
+        /// Gets a value indicating whether this instance may be used concurrently from multiple threads.
+        /// </summary>
+        internal LazyThreadSafetyMode? Mode => LazyHelper.GetMode(_state);
+
+        /// <summary>
+        /// Gets whether the value creation is faulted or not
+        /// </summary>
+        internal bool IsValueFaulted => LazyHelper.GetIsValueFaulted(_state);
+
+        /// <summary>Gets a value indicating whether the <see cref="T:System.Lazy{T}"/> has been initialized.
+        /// </summary>
+        /// <value>true if the <see cref="T:System.Lazy{T}"/> instance has been initialized;
+        /// otherwise, false.</value>
+        /// <remarks>
+        /// The initialization of a <see cref="T:System.Lazy{T}"/> instance may result in either
+        /// a value being produced or an exception being thrown.  If an exception goes unhandled during initialization, 
+        /// <see cref="IsValueCreated"/> will return false.
+        /// </remarks>
+        public bool IsValueCreated => _state == null;
+
+        /// <summary>Gets the lazily initialized value of the current <see
+        /// cref="T:System.Threading.Lazy{T}"/>.</summary>
+        /// <value>The lazily initialized value of the current <see
+        /// cref="T:System.Threading.Lazy{T}"/>.</value>
+        /// <exception cref="T:System.MissingMemberException">
+        /// The <see cref="T:System.Threading.Lazy{T}"/> was initialized to use the default constructor 
+        /// of the type being lazily initialized, and that type does not have a public, parameterless constructor.
+        /// </exception>
+        /// <exception cref="T:System.MemberAccessException">
+        /// The <see cref="T:System.Threading.Lazy{T}"/> was initialized to use the default constructor 
+        /// of the type being lazily initialized, and permissions to access the constructor were missing.
+        /// </exception>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The <see cref="T:System.Threading.Lazy{T}"/> was constructed with the <see cref="T:System.Threading.LazyThreadSafetyMode.ExecutionAndPublication"/> or
+        /// <see cref="T:System.Threading.LazyThreadSafetyMode.None"/>  and the initialization function attempted to access <see cref="Value"/> on this instance.
+        /// </exception>
+        /// <remarks>
+        /// If <see cref="IsValueCreated"/> is false, accessing <see cref="Value"/> will force initialization.
+        /// Please <see cref="System.Threading.LazyThreadSafetyMode"> for more information on how <see cref="T:System.Threading.Lazy{T}"/> will behave if an exception is thrown
+        /// from initialization delegate.
+        /// </remarks>
+        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
+        public T Value => _state == null ? _value : CreateValue();
+    }
+
+    /// <summary>A debugger view of the Lazy&lt;T&gt; to surface additional debugging properties and 
+    /// to ensure that the Lazy&lt;T&gt; does not become initialized if it was not already.</summary>
+    internal sealed class LazyDebugView<T>
+    {
+        //The Lazy object being viewed.
+        private readonly Lazy<T> _lazy;
+
+        /// <summary>Constructs a new debugger view object for the provided Lazy object.</summary>
+        /// <param name="lazy">A Lazy object to browse in the debugger.</param>
+        public LazyDebugView(Lazy<T> lazy)
+        {
+            _lazy = lazy;
+        }
+
+        /// <summary>Returns whether the Lazy object is initialized or not.</summary>
+        public bool IsValueCreated
+        {
+            get { return _lazy.IsValueCreated; }
+        }
+
+        /// <summary>Returns the value of the Lazy object.</summary>
+        public T Value
+        {
+            get
+            { return _lazy.ValueForDebugDisplay; }
+        }
+
+        /// <summary>Returns the execution mode of the Lazy object</summary>
+        public LazyThreadSafetyMode? Mode
+        {
+            get { return _lazy.Mode; }
+        }
+
+        /// <summary>Returns the execution mode of the Lazy object</summary>
+        public bool IsValueFaulted
+        {
+            get { return _lazy.IsValueFaulted; }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/MarshalByRefObject.cs b/src/System.Private.CoreLib/shared/System/MarshalByRefObject.cs
new file mode 100644
index 0000000000..390b728329
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/MarshalByRefObject.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    public abstract class MarshalByRefObject
+    {
+        protected MarshalByRefObject()
+        {
+        }
+
+        public object GetLifetimeService()
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_Remoting);
+        }
+
+        public virtual object InitializeLifetimeService()
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_Remoting);
+        }
+
+        protected MarshalByRefObject MemberwiseClone(bool cloneIdentity)
+        {
+            MarshalByRefObject mbr = (MarshalByRefObject)base.MemberwiseClone();
+            return mbr;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Marvin.cs b/src/System.Private.CoreLib/shared/System/Marvin.cs
new file mode 100644
index 0000000000..e51ad9c552
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Marvin.cs
@@ -0,0 +1,139 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using Internal.Runtime.CompilerServices;
+
+#if BIT64
+using nuint = System.UInt64;
+#else
+using nuint = System.UInt32;
+#endif
+
+namespace System
+{
+    internal static class Marvin
+    {
+        /// <summary>
+        /// Compute a Marvin hash and collapse it into a 32-bit hash.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int ComputeHash32(ReadOnlySpan<byte> data, ulong seed) => ComputeHash32(ref MemoryMarshal.GetReference(data), data.Length, seed);
+
+        /// <summary>
+        /// Compute a Marvin hash and collapse it into a 32-bit hash.
+        /// </summary>
+        public static int ComputeHash32(ref byte data, int count, ulong seed)
+        {
+            nuint ucount = (nuint)count;
+            uint p0 = (uint)seed;
+            uint p1 = (uint)(seed >> 32);
+
+            nuint byteOffset = 0;
+
+            while (ucount >= 8)
+            {
+                p0 += Unsafe.ReadUnaligned<uint>(ref Unsafe.AddByteOffset(ref data, byteOffset));
+                Block(ref p0, ref p1);
+
+                p0 += Unsafe.ReadUnaligned<uint>(ref Unsafe.AddByteOffset(ref data, byteOffset + 4));
+                Block(ref p0, ref p1);
+
+                byteOffset += 8;
+                ucount -= 8;
+            }
+
+            switch (ucount)
+            {
+                case 4:
+                    p0 += Unsafe.ReadUnaligned<uint>(ref Unsafe.AddByteOffset(ref data, byteOffset));
+                    Block(ref p0, ref p1);
+                    goto case 0;
+
+                case 0:
+                    p0 += 0x80u;
+                    break;
+
+                case 5:
+                    p0 += Unsafe.ReadUnaligned<uint>(ref Unsafe.AddByteOffset(ref data, byteOffset));
+                    byteOffset += 4;
+                    Block(ref p0, ref p1);
+                    goto case 1;
+
+                case 1:
+                    p0 += 0x8000u | Unsafe.AddByteOffset(ref data, byteOffset);
+                    break;
+
+                case 6:
+                    p0 += Unsafe.ReadUnaligned<uint>(ref Unsafe.AddByteOffset(ref data, byteOffset));
+                    byteOffset += 4;
+                    Block(ref p0, ref p1);
+                    goto case 2;
+
+                case 2:
+                    p0 += 0x800000u | Unsafe.ReadUnaligned<ushort>(ref Unsafe.AddByteOffset(ref data, byteOffset));
+                    break;
+
+                case 7:
+                    p0 += Unsafe.ReadUnaligned<uint>(ref Unsafe.AddByteOffset(ref data, byteOffset));
+                    byteOffset += 4;
+                    Block(ref p0, ref p1);
+                    goto case 3;
+
+                case 3:
+                    p0 += 0x80000000u | (((uint)(Unsafe.AddByteOffset(ref data, byteOffset + 2))) << 16)| (uint)(Unsafe.ReadUnaligned<ushort>(ref Unsafe.AddByteOffset(ref data, byteOffset)));
+                    break;
+
+                default:
+                    Debug.Fail("Should not get here.");
+                    break;
+            }
+
+            Block(ref p0, ref p1);
+            Block(ref p0, ref p1);
+
+            return (int)(p1 ^ p0);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void Block(ref uint rp0, ref uint rp1)
+        {
+            uint p0 = rp0;
+            uint p1 = rp1;
+
+            p1 ^= p0;
+            p0 = _rotl(p0, 20);
+
+            p0 += p1;
+            p1 = _rotl(p1, 9);
+
+            p1 ^= p0;
+            p0 = _rotl(p0, 27);
+
+            p0 += p1;
+            p1 = _rotl(p1, 19);
+
+            rp0 = p0;
+            rp1 = p1;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static uint _rotl(uint value, int shift)
+        {
+            // This is expected to be optimized into a single rol (or ror with negated shift value) instruction
+            return (value << shift) | (value >> (32 - shift));
+        }
+
+        public static ulong DefaultSeed { get; } = GenerateSeed();
+
+        private static unsafe ulong GenerateSeed()
+        {
+            ulong seed;
+            Interop.GetRandomBytes((byte*)&seed, sizeof(ulong));
+            return seed;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Math.cs b/src/System.Private.CoreLib/shared/System/Math.cs
new file mode 100644
index 0000000000..a175103f81
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Math.cs
@@ -0,0 +1,825 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Some floating-point math operations
+**
+** 
+===========================================================*/
+
+//This class contains only static members and doesn't require serialization.
+
+using System.Diagnostics;
+using System.Runtime;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    public static partial class Math
+    {
+        public const double E = 2.7182818284590452354;
+
+        public const double PI = 3.14159265358979323846;
+
+        private const int maxRoundingDigits = 15;
+
+        private static double doubleRoundLimit = 1e16d;
+
+        // This table is required for the Round function which can specify the number of digits to round to
+        private static double[] roundPower10Double = new double[] {
+          1E0, 1E1, 1E2, 1E3, 1E4, 1E5, 1E6, 1E7, 1E8,
+          1E9, 1E10, 1E11, 1E12, 1E13, 1E14, 1E15
+        };
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static short Abs(short value)
+        {
+            if (value < 0)
+            {
+                value = (short)-value;
+                if (value < 0)
+                {
+                    ThrowAbsOverflow();
+                }
+            }
+            return value;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int Abs(int value)
+        {
+            if (value < 0)
+            {
+                value = -value;
+                if (value < 0)
+                {
+                    ThrowAbsOverflow();
+                }
+            }
+            return value;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static long Abs(long value)
+        {
+            if (value < 0)
+            {
+                value = -value;
+                if (value < 0)
+                {
+                    ThrowAbsOverflow();
+                }
+            }
+            return value;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        [CLSCompliant(false)]
+        public static sbyte Abs(sbyte value)
+        {
+            if (value < 0)
+            {
+                value = (sbyte)-value;
+                if (value < 0)
+                {
+                    ThrowAbsOverflow();
+                }
+            }
+            return value;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static decimal Abs(decimal value)
+        {
+            return decimal.Abs(ref value);
+        }
+
+        [StackTraceHidden]
+        private static void ThrowAbsOverflow()
+        {
+            throw new OverflowException(SR.Overflow_NegateTwosCompNum);
+        }
+
+        public static long BigMul(int a, int b)
+        {
+            return ((long)a) * b;
+        }
+
+        public static int DivRem(int a, int b, out int result)
+        {
+            // TODO https://github.com/dotnet/coreclr/issues/3439:
+            // Restore to using % and / when the JIT is able to eliminate one of the idivs.
+            // In the meantime, a * and - is measurably faster than an extra /.
+
+            int div = a / b;
+            result = a - (div * b);
+            return div;
+        }
+
+        public static long DivRem(long a, long b, out long result)
+        {
+            // TODO https://github.com/dotnet/coreclr/issues/3439:
+            // Restore to using % and / when the JIT is able to eliminate one of the idivs.
+            // In the meantime, a * and - is measurably faster than an extra /.
+
+            long div = a / b;
+            result = a - (div * b);
+            return div;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static decimal Ceiling(decimal d)
+        {
+            return decimal.Ceiling(d);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static byte Clamp(byte value, byte min, byte max)
+        {
+            if (min > max)
+            {
+                ThrowMinMaxException(min, max);
+            }
+
+            if (value < min)
+            {
+                return min;
+            }
+            else if (value > max)
+            {
+                return max;
+            }
+
+            return value;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static decimal Clamp(decimal value, decimal min, decimal max)
+        {
+            if (min > max)
+            {
+                ThrowMinMaxException(min, max);
+            }
+
+            if (value < min)
+            {
+                return min;
+            }
+            else if (value > max)
+            {
+                return max;
+            }
+
+            return value;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static double Clamp(double value, double min, double max)
+        {
+            if (min > max)
+            {
+                ThrowMinMaxException(min, max);
+            }
+
+            if (value < min)
+            {
+                return min;
+            }
+            else if (value > max)
+            {
+                return max;
+            }
+
+            return value;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static short Clamp(short value, short min, short max)
+        {
+            if (min > max)
+            {
+                ThrowMinMaxException(min, max);
+            }
+
+            if (value < min)
+            {
+                return min;
+            }
+            else if (value > max)
+            {
+                return max;
+            }
+
+            return value;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int Clamp(int value, int min, int max)
+        {
+            if (min > max)
+            {
+                ThrowMinMaxException(min, max);
+            }
+
+            if (value < min)
+            {
+                return min;
+            }
+            else if (value > max)
+            {
+                return max;
+            }
+            
+            return value;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static long Clamp(long value, long min, long max)
+        {
+            if (min > max)
+            {
+                ThrowMinMaxException(min, max);
+            }
+
+            if (value < min)
+            {
+                return min;
+            }
+            else if (value > max)
+            {
+                return max;
+            }
+
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static sbyte Clamp(sbyte value, sbyte min, sbyte max)
+        {
+            if (min > max)
+            {
+                ThrowMinMaxException(min, max);
+            }
+
+            if (value < min)
+            {
+                return min;
+            }
+            else if (value > max)
+            {
+                return max;
+            }
+
+            return value;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static float Clamp(float value, float min, float max)
+        {
+            if (min > max)
+            {
+                ThrowMinMaxException(min, max);
+            }
+
+            if (value < min)
+            {
+                return min;
+            }
+            else if (value > max)
+            {
+                return max;
+            }
+
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ushort Clamp(ushort value, ushort min, ushort max)
+        {
+            if (min > max)
+            {
+                ThrowMinMaxException(min, max);
+            }
+
+            if (value < min)
+            {
+                return min;
+            }
+            else if (value > max)
+            {
+                return max;
+            }
+
+            return value;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        [CLSCompliant(false)]
+        public static uint Clamp(uint value, uint min, uint max)
+        {
+            if (min > max)
+            {
+                ThrowMinMaxException(min, max);
+            }
+
+            if (value < min)
+            {
+                return min;
+            }
+            else if (value > max)
+            {
+                return max;
+            }
+
+            return value;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        [CLSCompliant(false)]
+        public static ulong Clamp(ulong value, ulong min, ulong max)
+        {
+            if (min > max)
+            {
+                ThrowMinMaxException(min, max);
+            }
+
+            if (value < min)
+            {
+                return min;
+            }
+            else if (value > max)
+            {
+                return max;
+            }
+
+            return value;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static decimal Floor(decimal d)
+        {
+            return decimal.Floor(d);
+        }
+
+        public static double IEEERemainder(double x, double y)
+        {
+            if (double.IsNaN(x))
+            {
+                return x; // IEEE 754-2008: NaN payload must be preserved
+            }
+
+            if (double.IsNaN(y))
+            {
+                return y; // IEEE 754-2008: NaN payload must be preserved
+            }
+
+            var regularMod = x % y;
+
+            if (double.IsNaN(regularMod))
+            {
+                return double.NaN;
+            }
+
+            if ((regularMod == 0) && double.IsNegative(x))
+            {
+                return double.NegativeZero;
+            }
+
+            var alternativeResult = (regularMod - (Abs(y) * Sign(x)));
+
+            if (Abs(alternativeResult) == Abs(regularMod))
+            {
+                var divisionResult = x / y;
+                var roundedResult = Round(divisionResult);
+
+                if (Abs(roundedResult) > Abs(divisionResult))
+                {
+                    return alternativeResult;
+                }
+                else
+                {
+                    return regularMod;
+                }
+            }
+
+            if (Abs(alternativeResult) < Abs(regularMod))
+            {
+                return alternativeResult;
+            }
+            else
+            {
+                return regularMod;
+            }
+        }
+
+        public static double Log(double a, double newBase)
+        {
+            if (double.IsNaN(a))
+            {
+                return a; // IEEE 754-2008: NaN payload must be preserved
+            }
+
+            if (double.IsNaN(newBase))
+            {
+                return newBase; // IEEE 754-2008: NaN payload must be preserved
+            }
+
+            if (newBase == 1)
+            {
+                return double.NaN;
+            }
+
+            if ((a != 1) && ((newBase == 0) || double.IsPositiveInfinity(newBase)))
+            {
+                return double.NaN;
+            }
+
+            return (Log(a) / Log(newBase));
+        }
+
+        [NonVersionable]
+        public static byte Max(byte val1, byte val2)
+        {
+            return (val1 >= val2) ? val1 : val2;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static decimal Max(decimal val1, decimal val2)
+        {
+            return decimal.Max(ref val1, ref val2);
+        }
+
+        public static double Max(double val1, double val2)
+        {
+            if (val1 > val2)
+            {
+                return val1;
+            }
+
+            if (double.IsNaN(val1))
+            {
+                return val1;
+            }
+
+            return val2;
+        }
+
+        [NonVersionable]
+        public static short Max(short val1, short val2)
+        {
+            return (val1 >= val2) ? val1 : val2;
+        }
+
+        [NonVersionable]
+        public static int Max(int val1, int val2)
+        {
+            return (val1 >= val2) ? val1 : val2;
+        }
+
+        [NonVersionable]
+        public static long Max(long val1, long val2)
+        {
+            return (val1 >= val2) ? val1 : val2;
+        }
+
+        [CLSCompliant(false)]
+        [NonVersionable]
+        public static sbyte Max(sbyte val1, sbyte val2)
+        {
+            return (val1 >= val2) ? val1 : val2;
+        }
+        
+        public static float Max(float val1, float val2)
+        {
+            if (val1 > val2)
+            {
+                return val1;
+            }
+
+            if (float.IsNaN(val1))
+            {
+                return val1;
+            }
+
+            return val2;
+        }
+
+        [CLSCompliant(false)]
+        [NonVersionable]
+        public static ushort Max(ushort val1, ushort val2)
+        {
+            return (val1 >= val2) ? val1 : val2;
+        }
+
+        [CLSCompliant(false)]
+        [NonVersionable]
+        public static uint Max(uint val1, uint val2)
+        {
+            return (val1 >= val2) ? val1 : val2;
+        }
+
+        [CLSCompliant(false)]
+        [NonVersionable]
+        public static ulong Max(ulong val1, ulong val2)
+        {
+            return (val1 >= val2) ? val1 : val2;
+        }
+
+        [NonVersionable]
+        public static byte Min(byte val1, byte val2)
+        {
+            return (val1 <= val2) ? val1 : val2;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static decimal Min(decimal val1, decimal val2)
+        {
+            return decimal.Min(ref val1, ref val2);
+        }
+
+        public static double Min(double val1, double val2)
+        {
+            if (val1 < val2)
+            {
+                return val1;
+            }
+
+            if (double.IsNaN(val1))
+            {
+                return val1;
+            }
+
+            return val2;
+        }
+
+        [NonVersionable]
+        public static short Min(short val1, short val2)
+        {
+            return (val1 <= val2) ? val1 : val2;
+        }
+
+        [NonVersionable]
+        public static int Min(int val1, int val2)
+        {
+            return (val1 <= val2) ? val1 : val2;
+        }
+
+        [NonVersionable]
+        public static long Min(long val1, long val2)
+        {
+            return (val1 <= val2) ? val1 : val2;
+        }
+
+        [CLSCompliant(false)]
+        [NonVersionable]
+        public static sbyte Min(sbyte val1, sbyte val2)
+        {
+            return (val1 <= val2) ? val1 : val2;
+        }
+
+        public static float Min(float val1, float val2)
+        {
+            if (val1 < val2)
+            {
+                return val1;
+            }
+
+            if (float.IsNaN(val1))
+            {
+                return val1;
+            }
+
+            return val2;
+        }
+
+        [CLSCompliant(false)]
+        [NonVersionable]
+        public static ushort Min(ushort val1, ushort val2)
+        {
+            return (val1 <= val2) ? val1 : val2;
+        }
+
+        [CLSCompliant(false)]
+        [NonVersionable]
+        public static uint Min(uint val1, uint val2)
+        {
+            return (val1 <= val2) ? val1 : val2;
+        }
+
+        [CLSCompliant(false)]
+        [NonVersionable]
+        public static ulong Min(ulong val1, ulong val2)
+        {
+            return (val1 <= val2) ? val1 : val2;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static decimal Round(decimal d)
+        {
+            return decimal.Round(d, 0);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static decimal Round(decimal d, int decimals)
+        {
+            return decimal.Round(d, decimals);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static decimal Round(decimal d, MidpointRounding mode)
+        {
+            return decimal.Round(d, 0, mode);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static decimal Round(decimal d, int decimals, MidpointRounding mode)
+        {
+            return decimal.Round(d, decimals, mode);
+        }
+
+        [Intrinsic]
+        public static double Round(double a)
+        {
+            // ************************************************************************************
+            // IMPORTANT: Do not change this implementation without also updating Math.Round(double),
+            //            FloatingPointUtils::round(double), and FloatingPointUtils::round(float)
+            // ************************************************************************************
+
+            // If the number has no fractional part do nothing
+            // This shortcut is necessary to workaround precision loss in borderline cases on some platforms
+
+            if (a == (double)((long)a))
+            {
+                return a;
+            }
+
+            // We had a number that was equally close to 2 integers.
+            // We need to return the even one.
+
+            double flrTempVal = Floor(a + 0.5);
+
+            if ((a == (Floor(a) + 0.5)) && (FMod(flrTempVal, 2.0) != 0))
+            {
+                flrTempVal -= 1.0;
+            }
+
+            return copysign(flrTempVal, a);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static double Round(double value, int digits)
+        {
+            return Round(value, digits, MidpointRounding.ToEven);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static double Round(double value, MidpointRounding mode)
+        {
+            return Round(value, 0, mode);
+        }
+
+        public static unsafe double Round(double value, int digits, MidpointRounding mode)
+        {
+            if ((digits < 0) || (digits > maxRoundingDigits))
+            {
+                throw new ArgumentOutOfRangeException(nameof(digits), SR.ArgumentOutOfRange_RoundingDigits);
+            }
+
+            if (mode < MidpointRounding.ToEven || mode > MidpointRounding.AwayFromZero)
+            {
+                throw new ArgumentException(SR.Format(SR.Argument_InvalidEnumValue, mode, nameof(MidpointRounding)), nameof(mode));
+            }
+
+            if (Abs(value) < doubleRoundLimit)
+            {
+                var power10 = roundPower10Double[digits];
+
+                value *= power10;
+
+                if (mode == MidpointRounding.AwayFromZero)
+                {
+                    var fraction = ModF(value, &value);
+
+                    if (Abs(fraction) >= 0.5)
+                    {
+                        value += Sign(fraction);
+                    }
+                }
+                else
+                {
+                    value = Round(value);
+                }
+
+                value /= power10;
+            }
+
+            return value;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int Sign(decimal value)
+        {
+            return decimal.Sign(ref value);
+        }
+
+        public static int Sign(double value)
+        {
+            if (value < 0)
+            {
+                return -1;
+            }
+            else if (value > 0)
+            {
+                return 1;
+            }
+            else if (value == 0)
+            {
+                return 0;
+            }
+
+            throw new ArithmeticException(SR.Arithmetic_NaN);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int Sign(short value)
+        {
+            return Sign((int)value);
+        }
+
+        public static int Sign(int value)
+        {
+            return unchecked(value >> 31 | (int)((uint)-value >> 31));
+        }
+
+        public static int Sign(long value)
+        {
+            return unchecked((int)(value >> 63 | (long)((ulong)-value >> 63)));
+        }
+
+        [CLSCompliant(false)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int Sign(sbyte value)
+        {
+            return Sign((int)value);
+        }
+
+        public static int Sign(float value)
+        {
+            if (value < 0)
+            {
+                return -1;
+            }
+            else if (value > 0)
+            {
+                return 1;
+            }
+            else if (value == 0)
+            {
+                return 0;
+            }
+
+            throw new ArithmeticException(SR.Arithmetic_NaN);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static decimal Truncate(decimal d)
+        {
+            return decimal.Truncate(d);
+        }
+
+        public static unsafe double Truncate(double d)
+        {
+            ModF(d, &d);
+            return d;
+        }
+
+        private static unsafe double copysign(double x, double y)
+        {
+            var xbits = BitConverter.DoubleToInt64Bits(x);
+            var ybits = BitConverter.DoubleToInt64Bits(y);
+
+            // If the sign bits of x and y are not the same,
+            // flip the sign bit of x and return the new value;
+            // otherwise, just return x
+
+            if (((xbits ^ ybits) >> 63) != 0)
+            {
+                return BitConverter.Int64BitsToDouble(xbits ^ long.MinValue);
+            }
+
+            return x;
+        }
+
+        private static void ThrowMinMaxException<T>(T min, T max)
+        {
+            throw new ArgumentException(SR.Format(SR.Argument_MinMaxValue, min, max));
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/MathF.cs b/src/System.Private.CoreLib/shared/System/MathF.cs
new file mode 100644
index 0000000000..5b7e48b062
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/MathF.cs
@@ -0,0 +1,235 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Purpose: Some single-precision floating-point math operations
+**
+===========================================================*/
+
+//This class contains only static members and doesn't require serialization.
+
+using System.Runtime;
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    public static partial class MathF
+    {
+        public const float E = 2.71828183f;
+
+        public const float PI = 3.14159265f;
+
+        private const int maxRoundingDigits = 6;
+
+        // This table is required for the Round function which can specify the number of digits to round to
+        private static float[] roundPower10Single = new float[] {
+            1e0f, 1e1f, 1e2f, 1e3f, 1e4f, 1e5f, 1e6f
+        };
+
+        private static float singleRoundLimit = 1e8f;
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static float Abs(float x)
+        {
+            return Math.Abs(x);
+        }
+
+        public static float IEEERemainder(float x, float y)
+        {
+            if (float.IsNaN(x))
+            {
+                return x; // IEEE 754-2008: NaN payload must be preserved
+            }
+
+            if (float.IsNaN(y))
+            {
+                return y; // IEEE 754-2008: NaN payload must be preserved
+            }
+
+            var regularMod = x % y;
+
+            if (float.IsNaN(regularMod))
+            {
+                return float.NaN;
+            }
+
+            if ((regularMod == 0) && float.IsNegative(x))
+            {
+                return float.NegativeZero;
+            }
+
+            var alternativeResult = (regularMod - (Abs(y) * Sign(x)));
+
+            if (Abs(alternativeResult) == Abs(regularMod))
+            {
+                var divisionResult = x / y;
+                var roundedResult = Round(divisionResult);
+
+                if (Abs(roundedResult) > Abs(divisionResult))
+                {
+                    return alternativeResult;
+                }
+                else
+                {
+                    return regularMod;
+                }
+            }
+
+            if (Abs(alternativeResult) < Abs(regularMod))
+            {
+                return alternativeResult;
+            }
+            else
+            {
+                return regularMod;
+            }
+        }
+
+        public static float Log(float x, float y)
+        {
+            if (float.IsNaN(x))
+            {
+                return x; // IEEE 754-2008: NaN payload must be preserved
+            }
+
+            if (float.IsNaN(y))
+            {
+                return y; // IEEE 754-2008: NaN payload must be preserved
+            }
+
+            if (y == 1)
+            {
+                return float.NaN;
+            }
+
+            if ((x != 1) && ((y == 0) || float.IsPositiveInfinity(y)))
+            {
+                return float.NaN;
+            }
+
+            return Log(x) / Log(y);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static float Max(float x, float y)
+        {
+            return Math.Max(x, y);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static float Min(float x, float y)
+        {
+            return Math.Min(x, y);
+        }
+
+        [Intrinsic]
+        public static float Round(float x)
+        {
+            // ************************************************************************************
+            // IMPORTANT: Do not change this implementation without also updating Math.Round(double),
+            //            FloatingPointUtils::round(double), and FloatingPointUtils::round(float)
+            // ************************************************************************************
+    
+            // If the number has no fractional part do nothing
+            // This shortcut is necessary to workaround precision loss in borderline cases on some platforms
+
+            if (x == (float)((int)x))
+            {
+                return x;
+            }
+
+            // We had a number that was equally close to 2 integers.
+            // We need to return the even one.
+
+            float flrTempVal = Floor(x + 0.5f);
+
+            if ((x == (Floor(x) + 0.5f)) && (FMod(flrTempVal, 2.0f) != 0))
+            {
+                flrTempVal -= 1.0f;
+            }
+
+            return CopySign(flrTempVal, x);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static float Round(float x, int digits)
+        {
+            return Round(x, digits, MidpointRounding.ToEven);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static float Round(float x, MidpointRounding mode)
+        {
+            return Round(x, 0, mode);
+        }
+
+        public static unsafe float Round(float x, int digits, MidpointRounding mode)
+        {
+            if ((digits < 0) || (digits > maxRoundingDigits))
+            {
+                throw new ArgumentOutOfRangeException(nameof(digits), SR.ArgumentOutOfRange_RoundingDigits);
+            }
+
+            if (mode < MidpointRounding.ToEven || mode > MidpointRounding.AwayFromZero)
+            {
+                throw new ArgumentException(SR.Format(SR.Argument_InvalidEnum, mode, nameof(MidpointRounding)), nameof(mode));
+            }
+
+            if (Abs(x) < singleRoundLimit)
+            {
+                var power10 = roundPower10Single[digits];
+
+                x *= power10;
+
+                if (mode == MidpointRounding.AwayFromZero)
+                {
+                    var fraction = ModF(x, &x);
+
+                    if (Abs(fraction) >= 0.5f)
+                    {
+                        x += Sign(fraction);
+                    }
+                }
+                else
+                {
+                    x = Round(x);
+                }
+
+                x /= power10;
+            }
+
+            return x;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int Sign(float x)
+        {
+            return Math.Sign(x);
+        }
+
+        public static unsafe float Truncate(float x)
+        {
+            ModF(x, &x);
+            return x;
+        }
+
+        private static unsafe float CopySign(float x, float y)
+        {
+            var xbits = BitConverter.SingleToInt32Bits(x);
+            var ybits = BitConverter.SingleToInt32Bits(y);
+
+            // If the sign bits of x and y are not the same,
+            // flip the sign bit of x and return the new value;
+            // otherwise, just return x
+
+            if (((xbits ^ ybits) >> 31) != 0)
+            {
+                return BitConverter.Int32BitsToSingle(xbits ^ int.MinValue);
+            }
+
+            return x;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/MemberAccessException.cs b/src/System.Private.CoreLib/shared/System/MemberAccessException.cs
new file mode 100644
index 0000000000..dfea52dbed
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/MemberAccessException.cs
@@ -0,0 +1,50 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////////
+// MemberAccessException
+// Thrown when we try accessing a member that we cannot
+// access, due to it being removed, private or something similar.
+////////////////////////////////////////////////////////////////////////////////
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    // The MemberAccessException is thrown when trying to access a class
+    // member fails.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class MemberAccessException : SystemException
+    {
+        // Creates a new MemberAccessException with its message string set to
+        // the empty string, its HRESULT set to COR_E_MEMBERACCESS, 
+        // and its ExceptionInfo reference set to null. 
+        public MemberAccessException()
+            : base(SR.Arg_AccessException)
+        {
+            HResult = HResults.COR_E_MEMBERACCESS;
+        }
+
+        // Creates a new MemberAccessException with its message string set to
+        // message, its HRESULT set to COR_E_ACCESS, 
+        // and its ExceptionInfo reference set to null. 
+        // 
+        public MemberAccessException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_MEMBERACCESS;
+        }
+
+        public MemberAccessException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_MEMBERACCESS;
+        }
+
+        protected MemberAccessException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Memory.cs b/src/System.Private.CoreLib/shared/System/Memory.cs
new file mode 100644
index 0000000000..0abe3634ae
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Memory.cs
@@ -0,0 +1,441 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Buffers;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using EditorBrowsableAttribute = System.ComponentModel.EditorBrowsableAttribute;
+using EditorBrowsableState = System.ComponentModel.EditorBrowsableState;
+#if !FEATURE_PORTABLE_SPAN
+using Internal.Runtime.CompilerServices;
+#endif // FEATURE_PORTABLE_SPAN
+
+namespace System
+{
+    /// <summary>
+    /// Memory represents a contiguous region of arbitrary memory similar to <see cref="Span{T}"/>.
+    /// Unlike <see cref="Span{T}"/>, it is not a byref-like type.
+    /// </summary>
+    [DebuggerTypeProxy(typeof(MemoryDebugView<>))]
+    [DebuggerDisplay("{ToString(),raw}")]
+    public readonly struct Memory<T>
+    {
+        // NOTE: With the current implementation, Memory<T> and ReadOnlyMemory<T> must have the same layout,
+        // as code uses Unsafe.As to cast between them.
+
+        // The highest order bit of _index is used to discern whether _object is an array/string or an owned memory
+        // if (_index >> 31) == 1, object _object is an MemoryManager<T>
+        // else, object _object is a T[] or a string.
+        //     if (_length >> 31) == 1, _object is a pre-pinned array, so Pin() will not allocate a new GCHandle
+        //     else, Pin() needs to allocate a new GCHandle to pin the object.
+        // It can only be a string if the Memory<T> was created by
+        // using unsafe / marshaling code to reinterpret a ReadOnlyMemory<char> wrapped around a string as
+        // a Memory<T>.
+        private readonly object _object;
+        private readonly int _index;
+        private readonly int _length;
+
+        private const int RemoveFlagsBitMask = 0x7FFFFFFF;
+
+        /// <summary>
+        /// Creates a new memory over the entirety of the target array.
+        /// </summary>
+        /// <param name="array">The target array.</param>
+        /// <remarks>Returns default when <paramref name="array"/> is null.</remarks>
+        /// <exception cref="System.ArrayTypeMismatchException">Thrown when <paramref name="array"/> is covariant and array's type is not exactly T[].</exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public Memory(T[] array)
+        {
+            if (array == null)
+            {
+                this = default;
+                return; // returns default
+            }
+            if (default(T) == null && array.GetType() != typeof(T[]))
+                ThrowHelper.ThrowArrayTypeMismatchException();
+
+            _object = array;
+            _index = 0;
+            _length = array.Length;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal Memory(T[] array, int start)
+        {
+            if (array == null)
+            {
+                if (start != 0)
+                    ThrowHelper.ThrowArgumentOutOfRangeException();
+                this = default;
+                return; // returns default
+            }
+            if (default(T) == null && array.GetType() != typeof(T[]))
+                ThrowHelper.ThrowArrayTypeMismatchException();
+            if ((uint)start > (uint)array.Length)
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            _object = array;
+            _index = start;
+            _length = array.Length - start;
+        }
+
+        /// <summary>
+        /// Creates a new memory over the portion of the target array beginning
+        /// at 'start' index and ending at 'end' index (exclusive).
+        /// </summary>
+        /// <param name="array">The target array.</param>
+        /// <param name="start">The index at which to begin the memory.</param>
+        /// <param name="length">The number of items in the memory.</param>
+        /// <remarks>Returns default when <paramref name="array"/> is null.</remarks>
+        /// <exception cref="System.ArrayTypeMismatchException">Thrown when <paramref name="array"/> is covariant and array's type is not exactly T[].</exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in the range (&lt;0 or &gt;=Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public Memory(T[] array, int start, int length)
+        {
+            if (array == null)
+            {
+                if (start != 0 || length != 0)
+                    ThrowHelper.ThrowArgumentOutOfRangeException();
+                this = default;
+                return; // returns default
+            }
+            if (default(T) == null && array.GetType() != typeof(T[]))
+                ThrowHelper.ThrowArrayTypeMismatchException();
+            if ((uint)start > (uint)array.Length || (uint)length > (uint)(array.Length - start))
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            _object = array;
+            _index = start;
+            _length = length;
+        }
+
+        /// <summary>
+        /// Creates a new memory from a memory manager that provides specific method implementations beginning
+        /// at 0 index and ending at 'end' index (exclusive).
+        /// </summary>
+        /// <param name="manager">The memory manager.</param>
+        /// <param name="length">The number of items in the memory.</param>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="length"/> is negative.
+        /// </exception>
+        /// <remarks>For internal infrastructure only</remarks>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal Memory(MemoryManager<T> manager, int length)
+        {
+            Debug.Assert(manager != null);
+
+            if (length < 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            _object = manager;
+            _index = (1 << 31); // Mark as MemoryManager type
+            // Before using _index, check if _index < 0, then 'and' it with RemoveFlagsBitMask
+            _length = length;
+        }
+
+        /// <summary>
+        /// Creates a new memory from a memory manager that provides specific method implementations beginning
+        /// at 'start' index and ending at 'end' index (exclusive).
+        /// </summary>
+        /// <param name="manager">The memory manager.</param>
+        /// <param name="start">The index at which to begin the memory.</param>
+        /// <param name="length">The number of items in the memory.</param>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or <paramref name="length"/> is negative.
+        /// </exception>
+        /// <remarks>For internal infrastructure only</remarks>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal Memory(MemoryManager<T> manager, int start, int length)
+        {
+            Debug.Assert(manager != null);
+
+            if (length < 0 || start < 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            _object = manager;
+            _index = start | (1 << 31); // Mark as MemoryManager type
+            // Before using _index, check if _index < 0, then 'and' it with RemoveFlagsBitMask
+            _length = length;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal Memory(object obj, int start, int length)
+        {
+            // No validation performed; caller must provide any necessary validation.
+            _object = obj;
+            _index = start;
+            _length = length;
+        }
+
+        /// <summary>
+        /// Defines an implicit conversion of an array to a <see cref="Memory{T}"/>
+        /// </summary>
+        public static implicit operator Memory<T>(T[] array) => new Memory<T>(array);
+
+        /// <summary>
+        /// Defines an implicit conversion of a <see cref="ArraySegment{T}"/> to a <see cref="Memory{T}"/>
+        /// </summary>
+        public static implicit operator Memory<T>(ArraySegment<T> segment) => new Memory<T>(segment.Array, segment.Offset, segment.Count);
+
+        /// <summary>
+        /// Defines an implicit conversion of a <see cref="Memory{T}"/> to a <see cref="ReadOnlyMemory{T}"/>
+        /// </summary>
+        public static implicit operator ReadOnlyMemory<T>(Memory<T> memory) =>
+            Unsafe.As<Memory<T>, ReadOnlyMemory<T>>(ref memory);
+
+        /// <summary>
+        /// Returns an empty <see cref="Memory{T}"/>
+        /// </summary>
+        public static Memory<T> Empty => default;
+
+        /// <summary>
+        /// The number of items in the memory.
+        /// </summary>
+        public int Length => _length & RemoveFlagsBitMask;
+
+        /// <summary>
+        /// Returns true if Length is 0.
+        /// </summary>
+        public bool IsEmpty => (_length & RemoveFlagsBitMask) == 0;
+
+        /// <summary>
+        /// For <see cref="Memory{Char}"/>, returns a new instance of string that represents the characters pointed to by the memory.
+        /// Otherwise, returns a <see cref="string"/> with the name of the type and the number of elements.
+        /// </summary>
+        public override string ToString()
+        {
+            if (typeof(T) == typeof(char))
+            {
+                return (_object is string str) ? str.Substring(_index, _length & RemoveFlagsBitMask) : Span.ToString();
+            }
+            return string.Format("System.Memory<{0}>[{1}]", typeof(T).Name, _length & RemoveFlagsBitMask);
+        }
+
+        /// <summary>
+        /// Forms a slice out of the given memory, beginning at 'start'.
+        /// </summary>
+        /// <param name="start">The index at which to begin this slice.</param>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> index is not in range (&lt;0 or &gt;=Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public Memory<T> Slice(int start)
+        {
+            // Used to maintain the high-bit which indicates whether the Memory has been pre-pinned or not.
+            int capturedLength = _length;
+            int actualLength = capturedLength & RemoveFlagsBitMask;
+            if ((uint)start > (uint)actualLength)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+            }
+
+            // It is expected for (capturedLength - start) to be negative if the memory is already pre-pinned.
+            return new Memory<T>(_object, _index + start, capturedLength - start);
+        }
+
+        /// <summary>
+        /// Forms a slice out of the given memory, beginning at 'start', of given length
+        /// </summary>
+        /// <param name="start">The index at which to begin this slice.</param>
+        /// <param name="length">The desired length for the slice (exclusive).</param>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in range (&lt;0 or &gt;=Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public Memory<T> Slice(int start, int length)
+        {
+            // Used to maintain the high-bit which indicates whether the Memory has been pre-pinned or not.
+            int capturedLength = _length;
+            int actualLength = capturedLength & RemoveFlagsBitMask;
+            if ((uint)start > (uint)actualLength || (uint)length > (uint)(actualLength - start))
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+            }
+
+            // Set the high-bit to match the this._length high bit (1 for pre-pinned, 0 for unpinned).
+            return new Memory<T>(_object, _index + start, length | (capturedLength & ~RemoveFlagsBitMask));
+        }
+
+        /// <summary>
+        /// Returns a span from the memory.
+        /// </summary>
+        public Span<T> Span
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                if (_index < 0)
+                {
+                    Debug.Assert(_length >= 0);
+                    Debug.Assert(_object != null);
+                    return ((MemoryManager<T>)_object).GetSpan().Slice(_index & RemoveFlagsBitMask, _length);
+                }
+                else if (typeof(T) == typeof(char) && _object is string s)
+                {
+                    Debug.Assert(_length >= 0);
+                    // This is dangerous, returning a writable span for a string that should be immutable.
+                    // However, we need to handle the case where a ReadOnlyMemory<char> was created from a string
+                    // and then cast to a Memory<T>. Such a cast can only be done with unsafe or marshaling code,
+                    // in which case that's the dangerous operation performed by the dev, and we're just following
+                    // suit here to make it work as best as possible.
+#if FEATURE_PORTABLE_SPAN
+                    return new Span<T>(Unsafe.As<Pinnable<T>>(s), MemoryExtensions.StringAdjustment, s.Length).Slice(_index, _length);
+#else
+                    return new Span<T>(ref Unsafe.As<char, T>(ref s.GetRawStringData()), s.Length).Slice(_index, _length);
+#endif // FEATURE_PORTABLE_SPAN
+                }
+                else if (_object != null)
+                {
+                    return new Span<T>((T[])_object, _index, _length & RemoveFlagsBitMask);
+                }
+                else
+                {
+                    return default;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Copies the contents of the memory into the destination. If the source
+        /// and destination overlap, this method behaves as if the original values are in
+        /// a temporary location before the destination is overwritten.
+        ///
+        /// <param name="destination">The Memory to copy items into.</param>
+        /// <exception cref="System.ArgumentException">
+        /// Thrown when the destination is shorter than the source.
+        /// </exception>
+        /// </summary>
+        public void CopyTo(Memory<T> destination) => Span.CopyTo(destination.Span);
+
+        /// <summary>
+        /// Copies the contents of the memory into the destination. If the source
+        /// and destination overlap, this method behaves as if the original values are in
+        /// a temporary location before the destination is overwritten.
+        ///
+        /// <returns>If the destination is shorter than the source, this method
+        /// return false and no data is written to the destination.</returns>
+        /// </summary>
+        /// <param name="destination">The span to copy items into.</param>
+        public bool TryCopyTo(Memory<T> destination) => Span.TryCopyTo(destination.Span);
+
+        /// <summary>
+        /// Creates a handle for the memory.
+        /// The GC will not move the memory until the returned <see cref="MemoryHandle"/>
+        /// is disposed, enabling taking and using the memory's address.
+        /// <exception cref="System.ArgumentException">
+        /// An instance with nonprimitive (non-blittable) members cannot be pinned.
+        /// </exception>
+        /// </summary>
+        public unsafe MemoryHandle Pin()
+        {
+            if (_index < 0)
+            {
+                Debug.Assert(_object != null);
+                return ((MemoryManager<T>)_object).Pin((_index & RemoveFlagsBitMask));
+            }
+            else if (typeof(T) == typeof(char) && _object is string s)
+            {
+                // This case can only happen if a ReadOnlyMemory<char> was created around a string
+                // and then that was cast to a Memory<char> using unsafe / marshaling code.  This needs
+                // to work, however, so that code that uses a single Memory<char> field to store either
+                // a readable ReadOnlyMemory<char> or a writable Memory<char> can still be pinned and
+                // used for interop purposes.
+                GCHandle handle = GCHandle.Alloc(s, GCHandleType.Pinned);
+#if FEATURE_PORTABLE_SPAN
+                void* pointer = Unsafe.Add<T>((void*)handle.AddrOfPinnedObject(), _index);
+#else
+                void* pointer = Unsafe.Add<T>(Unsafe.AsPointer(ref s.GetRawStringData()), _index);
+#endif // FEATURE_PORTABLE_SPAN
+                return new MemoryHandle(pointer, handle);
+            }
+            else if (_object is T[] array)
+            {
+                // Array is already pre-pinned
+                if (_length < 0)
+                {
+#if FEATURE_PORTABLE_SPAN
+                    void* pointer = Unsafe.Add<T>(Unsafe.AsPointer(ref MemoryMarshal.GetReference<T>(array)), _index);
+#else
+                    void* pointer = Unsafe.Add<T>(Unsafe.AsPointer(ref array.GetRawSzArrayData()), _index);
+#endif // FEATURE_PORTABLE_SPAN
+                    return new MemoryHandle(pointer);
+                }
+                else
+                {
+                    GCHandle handle = GCHandle.Alloc(array, GCHandleType.Pinned);
+#if FEATURE_PORTABLE_SPAN
+                    void* pointer = Unsafe.Add<T>((void*)handle.AddrOfPinnedObject(), _index);
+#else
+                    void* pointer = Unsafe.Add<T>(Unsafe.AsPointer(ref array.GetRawSzArrayData()), _index);
+#endif // FEATURE_PORTABLE_SPAN
+                    return new MemoryHandle(pointer, handle);
+                }
+            }
+            return default;
+        }
+
+        /// <summary>
+        /// Copies the contents from the memory into a new array.  This heap
+        /// allocates, so should generally be avoided, however it is sometimes
+        /// necessary to bridge the gap with APIs written in terms of arrays.
+        /// </summary>
+        public T[] ToArray() => Span.ToArray();
+
+        /// <summary>
+        /// Determines whether the specified object is equal to the current object.
+        /// Returns true if the object is Memory or ReadOnlyMemory and if both objects point to the same array and have the same length.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public override bool Equals(object obj)
+        {
+            if (obj is ReadOnlyMemory<T>)
+            {
+                return ((ReadOnlyMemory<T>)obj).Equals(this);
+            }
+            else if (obj is Memory<T> memory)
+            {
+                return Equals(memory);
+            }
+            else
+            {
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// Returns true if the memory points to the same array and has the same length.  Note that
+        /// this does *not* check to see if the *contents* are equal.
+        /// </summary>
+        public bool Equals(Memory<T> other)
+        {
+            return
+                _object == other._object &&
+                _index == other._index &&
+                _length == other._length;
+        }
+
+        /// <summary>
+        /// Serves as the default hash function.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public override int GetHashCode()
+        {
+            return _object != null ? CombineHashCodes(_object.GetHashCode(), _index.GetHashCode(), _length.GetHashCode()) : 0;
+        }
+
+        private static int CombineHashCodes(int left, int right)
+        {
+            return ((left << 5) + left) ^ right;
+        }
+
+        private static int CombineHashCodes(int h1, int h2, int h3)
+        {
+            return CombineHashCodes(CombineHashCodes(h1, h2), h3);
+        }
+
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/MemoryDebugView.cs b/src/System.Private.CoreLib/shared/System/MemoryDebugView.cs
new file mode 100644
index 0000000000..f56a67c636
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/MemoryDebugView.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System
+{
+    internal sealed class MemoryDebugView<T>
+    {
+        private readonly ReadOnlyMemory<T> _memory;
+
+        public MemoryDebugView(Memory<T> memory)
+        {
+            _memory = memory;
+        }
+
+        public MemoryDebugView(ReadOnlyMemory<T> memory)
+        {
+            _memory = memory;
+        }
+
+        [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+        public T[] Items => _memory.ToArray();
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/MemoryExtensions.Fast.cs b/src/System.Private.CoreLib/shared/System/MemoryExtensions.Fast.cs
new file mode 100644
index 0000000000..a9a755aa80
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/MemoryExtensions.Fast.cs
@@ -0,0 +1,487 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+using Internal.Runtime.CompilerServices;
+
+namespace System
+{
+    /// <summary>
+    /// Extension methods for Span{T}, Memory{T}, and friends.
+    /// </summary>
+    public static partial class MemoryExtensions
+    {
+        /// <summary>
+        /// Returns a value indicating whether the specified <paramref name="value"/> occurs within the <paramref name="span"/>.
+        /// <param name="span">The source span.</param>
+        /// <param name="value">The value to seek within the source span.</param>
+        /// <param name="comparisonType">One of the enumeration values that determines how the <paramref name="span"/> and <paramref name="value"/> are compared.</param>
+        /// </summary>
+        public static bool Contains(this ReadOnlySpan<char> span, ReadOnlySpan<char> value, StringComparison comparisonType)
+        {
+            return (IndexOf(span, value, comparisonType) >= 0);
+        }
+
+        /// <summary>
+        /// Determines whether this <paramref name="span"/> and the specified <paramref name="other"/> span have the same characters
+        /// when compared using the specified <paramref name="comparisonType"/> option.
+        /// <param name="span">The source span.</param>
+        /// <param name="other">The value to compare with the source span.</param>
+        /// <param name="comparisonType">One of the enumeration values that determines how the <paramref name="span"/> and <paramref name="other"/> are compared.</param>
+        /// </summary>
+        public static bool Equals(this ReadOnlySpan<char> span, ReadOnlySpan<char> other, StringComparison comparisonType)
+        {
+            string.CheckStringComparison(comparisonType);
+
+            switch (comparisonType)
+            {
+                case StringComparison.CurrentCulture:
+                    return (CultureInfo.CurrentCulture.CompareInfo.CompareOptionNone(span, other) == 0);
+
+                case StringComparison.CurrentCultureIgnoreCase:
+                    return (CultureInfo.CurrentCulture.CompareInfo.CompareOptionIgnoreCase(span, other) == 0);
+
+                case StringComparison.InvariantCulture:
+                    return (CompareInfo.Invariant.CompareOptionNone(span, other) == 0);
+
+                case StringComparison.InvariantCultureIgnoreCase:
+                    return (CompareInfo.Invariant.CompareOptionIgnoreCase(span, other) == 0);
+
+                case StringComparison.Ordinal:
+                    return EqualsOrdinal(span, other);
+
+                case StringComparison.OrdinalIgnoreCase:
+                    return EqualsOrdinalIgnoreCase(span, other);
+            }
+
+            Debug.Fail("StringComparison outside range");
+            return false;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static bool EqualsOrdinal(this ReadOnlySpan<char> span, ReadOnlySpan<char> value)
+        {
+            if (span.Length != value.Length)
+                return false;
+            if (value.Length == 0)  // span.Length == value.Length == 0
+                return true;
+            return span.SequenceEqual(value);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static bool EqualsOrdinalIgnoreCase(this ReadOnlySpan<char> span, ReadOnlySpan<char> value)
+        {
+            if (span.Length != value.Length)
+                return false;
+            if (value.Length == 0)  // span.Length == value.Length == 0
+                return true;
+            return (CompareInfo.CompareOrdinalIgnoreCase(span, value) == 0);
+        }
+
+        // TODO https://github.com/dotnet/corefx/issues/27526
+        internal static bool Contains(this ReadOnlySpan<char> source, char value)
+        {
+            for (int i = 0; i < source.Length; i++)
+            {
+                if (source[i] == value)
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        /// <summary>
+        /// Compares the specified <paramref name="span"/> and <paramref name="other"/> using the specified <paramref name="comparisonType"/>,
+        /// and returns an integer that indicates their relative position in the sort order.
+        /// <param name="span">The source span.</param>
+        /// <param name="other">The value to compare with the source span.</param>
+        /// <param name="comparisonType">One of the enumeration values that determines how the <paramref name="span"/> and <paramref name="other"/> are compared.</param>
+        /// </summary>
+        public static int CompareTo(this ReadOnlySpan<char> span, ReadOnlySpan<char> other, StringComparison comparisonType)
+        {
+            string.CheckStringComparison(comparisonType);
+
+            switch (comparisonType)
+            {
+                case StringComparison.CurrentCulture:
+                    return CultureInfo.CurrentCulture.CompareInfo.CompareOptionNone(span, other);
+
+                case StringComparison.CurrentCultureIgnoreCase:
+                    return CultureInfo.CurrentCulture.CompareInfo.CompareOptionIgnoreCase(span, other);
+
+                case StringComparison.InvariantCulture:
+                    return CompareInfo.Invariant.CompareOptionNone(span, other);
+
+                case StringComparison.InvariantCultureIgnoreCase:
+                    return CompareInfo.Invariant.CompareOptionIgnoreCase(span, other);
+
+                case StringComparison.Ordinal:
+                    if (span.Length == 0 || other.Length == 0)
+                        return span.Length - other.Length;
+                    return string.CompareOrdinal(span, other);
+
+                case StringComparison.OrdinalIgnoreCase:
+                    return CompareInfo.CompareOrdinalIgnoreCase(span, other);
+            }
+
+            Debug.Fail("StringComparison outside range");
+            return 0;
+        }
+
+        /// <summary>
+        /// Reports the zero-based index of the first occurrence of the specified <paramref name="value"/> in the current <paramref name="span"/>.
+        /// <param name="span">The source span.</param>
+        /// <param name="value">The value to seek within the source span.</param>
+        /// <param name="comparisonType">One of the enumeration values that determines how the <paramref name="span"/> and <paramref name="value"/> are compared.</param>
+        /// </summary>
+        public static int IndexOf(this ReadOnlySpan<char> span, ReadOnlySpan<char> value, StringComparison comparisonType)
+        {
+            string.CheckStringComparison(comparisonType);
+
+            if (value.Length == 0)
+            {
+                return 0;
+            }
+
+            if (span.Length == 0)
+            {
+                return -1;
+            }
+
+            if (GlobalizationMode.Invariant)
+            {
+                return CompareInfo.InvariantIndexOf(span, value, string.GetCaseCompareOfComparisonCulture(comparisonType) != CompareOptions.None);
+            }
+
+            switch (comparisonType)
+            {
+                case StringComparison.CurrentCulture:
+                case StringComparison.CurrentCultureIgnoreCase:
+                    return CultureInfo.CurrentCulture.CompareInfo.IndexOf(span, value, string.GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.InvariantCulture:
+                case StringComparison.InvariantCultureIgnoreCase:
+                    return CompareInfo.Invariant.IndexOf(span, value, string.GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.Ordinal:
+                case StringComparison.OrdinalIgnoreCase:
+                    return CompareInfo.Invariant.IndexOfOrdinal(span, value, string.GetCaseCompareOfComparisonCulture(comparisonType) != CompareOptions.None);
+            }
+
+            Debug.Fail("StringComparison outside range");
+            return -1;
+        }
+
+        /// <summary>
+        /// Copies the characters from the source span into the destination, converting each character to lowercase,
+        /// using the casing rules of the specified culture.
+        /// </summary>
+        /// <param name="source">The source span.</param>
+        /// <param name="destination">The destination span which contains the transformed characters.</param>
+        /// <param name="culture">An object that supplies culture-specific casing rules.</param>
+        /// <remarks>If the source and destinations overlap, this method behaves as if the original values are in
+        /// a temporary location before the destination is overwritten.</remarks>
+        /// <exception cref="System.ArgumentNullException">
+        /// Thrown when <paramref name="culture"/> is null.
+        /// </exception>
+        public static int ToLower(this ReadOnlySpan<char> source, Span<char> destination, CultureInfo culture)
+        {
+            if (culture == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.culture);
+
+            // Assuming that changing case does not affect length
+            if (destination.Length < source.Length)
+                return -1;
+
+            if (GlobalizationMode.Invariant)
+                TextInfo.ToLowerAsciiInvariant(source, destination);
+            else
+                culture.TextInfo.ChangeCase(source, destination, toUpper: false);
+            return source.Length;
+        }
+
+        /// <summary>
+        /// Copies the characters from the source span into the destination, converting each character to lowercase,
+        /// using the casing rules of the invariant culture.
+        /// </summary>
+        /// <param name="source">The source span.</param>
+        /// <param name="destination">The destination span which contains the transformed characters.</param>
+        /// <remarks>If the source and destinations overlap, this method behaves as if the original values are in
+        /// a temporary location before the destination is overwritten.</remarks>
+        public static int ToLowerInvariant(this ReadOnlySpan<char> source, Span<char> destination)
+        {
+            // Assuming that changing case does not affect length
+            if (destination.Length < source.Length)
+                return -1;
+
+            if (GlobalizationMode.Invariant)
+                TextInfo.ToLowerAsciiInvariant(source, destination);
+            else
+                CultureInfo.InvariantCulture.TextInfo.ChangeCase(source, destination, toUpper: false);
+            return source.Length;
+        }
+
+        /// <summary>
+        /// Copies the characters from the source span into the destination, converting each character to uppercase,
+        /// using the casing rules of the specified culture.
+        /// </summary>
+        /// <param name="source">The source span.</param>
+        /// <param name="destination">The destination span which contains the transformed characters.</param>
+        /// <param name="culture">An object that supplies culture-specific casing rules.</param>
+        /// <remarks>If the source and destinations overlap, this method behaves as if the original values are in
+        /// a temporary location before the destination is overwritten.</remarks>
+        /// <exception cref="System.ArgumentNullException">
+        /// Thrown when <paramref name="culture"/> is null.
+        /// </exception>
+        public static int ToUpper(this ReadOnlySpan<char> source, Span<char> destination, CultureInfo culture)
+        {
+            if (culture == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.culture);
+
+            // Assuming that changing case does not affect length
+            if (destination.Length < source.Length)
+                return -1;
+
+            if (GlobalizationMode.Invariant)
+                TextInfo.ToUpperAsciiInvariant(source, destination);
+            else
+                culture.TextInfo.ChangeCase(source, destination, toUpper: true);
+            return source.Length;
+        }
+
+        /// <summary>
+        /// Copies the characters from the source span into the destination, converting each character to uppercase
+        /// using the casing rules of the invariant culture.
+        /// </summary>
+        /// <param name="source">The source span.</param>
+        /// <param name="destination">The destination span which contains the transformed characters.</param>
+        /// <remarks>If the source and destinations overlap, this method behaves as if the original values are in
+        /// a temporary location before the destination is overwritten.</remarks>
+        public static int ToUpperInvariant(this ReadOnlySpan<char> source, Span<char> destination)
+        {
+            // Assuming that changing case does not affect length
+            if (destination.Length < source.Length)
+                return -1;
+
+            if (GlobalizationMode.Invariant)
+                TextInfo.ToUpperAsciiInvariant(source, destination);
+            else
+                CultureInfo.InvariantCulture.TextInfo.ChangeCase(source, destination, toUpper: true);
+            return source.Length;
+        }
+
+        /// <summary>
+        /// Determines whether the end of the <paramref name="span"/> matches the specified <paramref name="value"/> when compared using the specified <paramref name="comparisonType"/> option.
+        /// </summary>
+        /// <param name="span">The source span.</param>
+        /// <param name="value">The sequence to compare to the end of the source span.</param>
+        /// <param name="comparisonType">One of the enumeration values that determines how the <paramref name="span"/> and <paramref name="value"/> are compared.</param>
+        public static bool EndsWith(this ReadOnlySpan<char> span, ReadOnlySpan<char> value, StringComparison comparisonType)
+        {
+            string.CheckStringComparison(comparisonType);
+
+            if (value.Length == 0)
+            {
+                return true;
+            }
+
+            if (comparisonType >= StringComparison.Ordinal || GlobalizationMode.Invariant)
+            {
+                if (string.GetCaseCompareOfComparisonCulture(comparisonType) == CompareOptions.None)
+                    return span.EndsWith(value);
+
+                return (span.Length >= value.Length) ? (CompareInfo.CompareOrdinalIgnoreCase(span.Slice(span.Length - value.Length), value) == 0) : false;
+            }
+
+            if (span.Length == 0)
+            {
+                return false;
+            }
+
+            return (comparisonType >= StringComparison.InvariantCulture) ?
+                CompareInfo.Invariant.IsSuffix(span, value, string.GetCaseCompareOfComparisonCulture(comparisonType)) :
+                    CultureInfo.CurrentCulture.CompareInfo.IsSuffix(span, value, string.GetCaseCompareOfComparisonCulture(comparisonType));
+        }
+
+        /// <summary>
+        /// Determines whether the beginning of the <paramref name="span"/> matches the specified <paramref name="value"/> when compared using the specified <paramref name="comparisonType"/> option.
+        /// </summary>
+        /// <param name="span">The source span.</param>
+        /// <param name="value">The sequence to compare to the beginning of the source span.</param>
+        /// <param name="comparisonType">One of the enumeration values that determines how the <paramref name="span"/> and <paramref name="value"/> are compared.</param>
+        public static bool StartsWith(this ReadOnlySpan<char> span, ReadOnlySpan<char> value, StringComparison comparisonType)
+        {
+            string.CheckStringComparison(comparisonType);
+
+            if (value.Length == 0)
+            {
+                return true;
+            }
+
+            if (comparisonType >= StringComparison.Ordinal || GlobalizationMode.Invariant)
+            {
+                if (string.GetCaseCompareOfComparisonCulture(comparisonType) == CompareOptions.None)
+                    return span.StartsWith(value);
+
+                return (span.Length >= value.Length) ? (CompareInfo.CompareOrdinalIgnoreCase(span.Slice(0, value.Length), value) == 0) : false;
+            }
+
+            if (span.Length == 0)
+            {
+                return false;
+            }
+
+            return (comparisonType >= StringComparison.InvariantCulture) ?
+                CompareInfo.Invariant.IsPrefix(span, value, string.GetCaseCompareOfComparisonCulture(comparisonType)) :
+                    CultureInfo.CurrentCulture.CompareInfo.IsPrefix(span, value, string.GetCaseCompareOfComparisonCulture(comparisonType));
+        }
+
+        /// <summary>
+        /// Creates a new span over the portion of the target array.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Span<T> AsSpan<T>(this T[] array, int start)
+        {
+            if (array == null)
+            {
+                if (start != 0)
+                    ThrowHelper.ThrowArgumentOutOfRangeException();
+                return default;
+            }
+            if (default(T) == null && array.GetType() != typeof(T[]))
+                ThrowHelper.ThrowArrayTypeMismatchException();
+            if ((uint)start > (uint)array.Length)
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            return new Span<T>(ref Unsafe.Add(ref Unsafe.As<byte, T>(ref array.GetRawSzArrayData()), start), array.Length - start);
+        }
+
+        /// <summary>
+        /// Creates a new readonly span over the portion of the target string.
+        /// </summary>
+        /// <param name="text">The target string.</param>
+        /// <remarks>Returns default when <paramref name="text"/> is null.</remarks>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ReadOnlySpan<char> AsSpan(this string text)
+        {
+            if (text == null)
+                return default;
+
+            return new ReadOnlySpan<char>(ref text.GetRawStringData(), text.Length);
+        }
+
+        /// <summary>
+        /// Creates a new readonly span over the portion of the target string.
+        /// </summary>
+        /// <param name="text">The target string.</param>
+        /// <param name="start">The index at which to begin this slice.</param>
+        /// <exception cref="System.ArgumentNullException">Thrown when <paramref name="text"/> is null.</exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> index is not in range (&lt;0 or &gt;text.Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ReadOnlySpan<char> AsSpan(this string text, int start)
+        {
+            if (text == null)
+            {
+                if (start != 0)
+                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+                return default;
+            }
+
+            if ((uint)start > (uint)text.Length)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+
+            return new ReadOnlySpan<char>(ref Unsafe.Add(ref text.GetRawStringData(), start), text.Length - start);
+        }
+
+        /// <summary>
+        /// Creates a new readonly span over the portion of the target string.
+        /// </summary>
+        /// <param name="text">The target string.</param>
+        /// <param name="start">The index at which to begin this slice.</param>
+        /// <param name="length">The desired length for the slice (exclusive).</param>
+        /// <remarks>Returns default when <paramref name="text"/> is null.</remarks>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> index or <paramref name="length"/> is not in range.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ReadOnlySpan<char> AsSpan(this string text, int start, int length)
+        {
+            if (text == null)
+            {
+                if (start != 0 || length != 0)
+                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+                return default;
+            }
+
+            if ((uint)start > (uint)text.Length || (uint)length > (uint)(text.Length - start))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+
+            return new ReadOnlySpan<char>(ref Unsafe.Add(ref text.GetRawStringData(), start), length);
+        }
+
+        /// <summary>Creates a new <see cref="ReadOnlyMemory{T}"/> over the portion of the target string.</summary>
+        /// <param name="text">The target string.</param>
+        /// <remarks>Returns default when <paramref name="text"/> is null.</remarks>
+        public static ReadOnlyMemory<char> AsMemory(this string text)
+        {
+            if (text == null)
+                return default;
+
+            return new ReadOnlyMemory<char>(text, 0, text.Length);
+        }
+
+        /// <summary>Creates a new <see cref="ReadOnlyMemory{T}"/> over the portion of the target string.</summary>
+        /// <param name="text">The target string.</param>
+        /// <param name="start">The index at which to begin this slice.</param>
+        /// <remarks>Returns default when <paramref name="text"/> is null.</remarks>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> index is not in range (&lt;0 or &gt;text.Length).
+        /// </exception>
+        public static ReadOnlyMemory<char> AsMemory(this string text, int start)
+        {
+            if (text == null)
+            {
+                if (start != 0)
+                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+                return default;
+            }
+
+            if ((uint)start > (uint)text.Length)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+
+            return new ReadOnlyMemory<char>(text, start, text.Length - start);
+        }
+
+        /// <summary>Creates a new <see cref="ReadOnlyMemory{T}"/> over the portion of the target string.</summary>
+        /// <param name="text">The target string.</param>
+        /// <param name="start">The index at which to begin this slice.</param>
+        /// <param name="length">The desired length for the slice (exclusive).</param>
+        /// <remarks>Returns default when <paramref name="text"/> is null.</remarks>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> index or <paramref name="length"/> is not in range.
+        /// </exception>
+        public static ReadOnlyMemory<char> AsMemory(this string text, int start, int length)
+        {
+            if (text == null)
+            {
+                if (start != 0 || length != 0)
+                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+                return default;
+            }
+
+            if ((uint)start > (uint)text.Length || (uint)length > (uint)(text.Length - start))
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+
+            return new ReadOnlyMemory<char>(text, start, length);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/MemoryExtensions.cs b/src/System.Private.CoreLib/shared/System/MemoryExtensions.cs
new file mode 100644
index 0000000000..b4782dcaf0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/MemoryExtensions.cs
@@ -0,0 +1,1389 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+#if !netstandard
+using Internal.Runtime.CompilerServices;
+#endif
+
+#if netstandard
+using nuint = System.NUInt;
+#else
+#if BIT64
+using nuint = System.UInt64;
+#else
+using nuint = System.UInt32;
+#endif // BIT64
+#endif // netstandard
+
+namespace System
+{
+    /// <summary>
+    /// Extension methods for Span{T}, Memory{T}, and friends.
+    /// </summary>
+    public static partial class MemoryExtensions
+    {
+        /// <summary>
+        /// Removes all leading and trailing white-space characters from the span.
+        /// </summary>
+        public static ReadOnlySpan<char> Trim(this ReadOnlySpan<char> span)
+        {
+            return span.TrimStart().TrimEnd();
+        }
+
+        /// <summary>
+        /// Removes all leading white-space characters from the span.
+        /// </summary>
+        public static ReadOnlySpan<char> TrimStart(this ReadOnlySpan<char> span)
+        {
+            int start = 0;
+            for (; start < span.Length; start++)
+            {
+                if (!char.IsWhiteSpace(span[start]))
+                    break;
+            }
+            return span.Slice(start);
+        }
+
+        /// <summary>
+        /// Removes all trailing white-space characters from the span.
+        /// </summary>
+        public static ReadOnlySpan<char> TrimEnd(this ReadOnlySpan<char> span)
+        {
+            int end = span.Length - 1;
+            for (; end >= 0; end--)
+            {
+                if (!char.IsWhiteSpace(span[end]))
+                    break;
+            }
+            return span.Slice(0, end + 1);
+        }
+
+        /// <summary>
+        /// Removes all leading and trailing occurrences of a specified character.
+        /// </summary>
+        /// <param name="span">The source span from which the character is removed.</param>
+        /// <param name="trimChar">The specified character to look for and remove.</param>
+        public static ReadOnlySpan<char> Trim(this ReadOnlySpan<char> span, char trimChar)
+        {
+            return span.TrimStart(trimChar).TrimEnd(trimChar);
+        }
+
+        /// <summary>
+        /// Removes all leading occurrences of a specified character.
+        /// </summary>
+        /// <param name="span">The source span from which the character is removed.</param>
+        /// <param name="trimChar">The specified character to look for and remove.</param>
+        public static ReadOnlySpan<char> TrimStart(this ReadOnlySpan<char> span, char trimChar)
+        {
+            int start = 0;
+            for (; start < span.Length; start++)
+            {
+                if (span[start] != trimChar)
+                    break;
+            }
+            return span.Slice(start);
+        }
+
+        /// <summary>
+        /// Removes all trailing occurrences of a specified character.
+        /// </summary>
+        /// <param name="span">The source span from which the character is removed.</param>
+        /// <param name="trimChar">The specified character to look for and remove.</param>
+        public static ReadOnlySpan<char> TrimEnd(this ReadOnlySpan<char> span, char trimChar)
+        {
+            int end = span.Length - 1;
+            for (; end >= 0; end--)
+            {
+                if (span[end] != trimChar)
+                    break;
+            }
+            return span.Slice(0, end + 1);
+        }
+
+        /// <summary>
+        /// Removes all leading and trailing occurrences of a set of characters specified 
+        /// in a readonly span from the span.
+        /// </summary>
+        /// <param name="span">The source span from which the characters are removed.</param>
+        /// <param name="trimChars">The span which contains the set of characters to remove.</param>
+        /// <remarks>If <paramref name="trimChars"/> is empty, white-space characters are removed instead.</remarks>
+        public static ReadOnlySpan<char> Trim(this ReadOnlySpan<char> span, ReadOnlySpan<char> trimChars)
+        {
+            return span.TrimStart(trimChars).TrimEnd(trimChars);
+        }
+
+        /// <summary>
+        /// Removes all leading occurrences of a set of characters specified 
+        /// in a readonly span from the span.
+        /// </summary>
+        /// <param name="span">The source span from which the characters are removed.</param>
+        /// <param name="trimChars">The span which contains the set of characters to remove.</param>
+        /// <remarks>If <paramref name="trimChars"/> is empty, white-space characters are removed instead.</remarks>
+        public static ReadOnlySpan<char> TrimStart(this ReadOnlySpan<char> span, ReadOnlySpan<char> trimChars)
+        {
+            if (trimChars.IsEmpty)
+            {
+                return span.TrimStart();
+            }
+
+            int start = 0;
+            for (; start < span.Length; start++)
+            {
+                for (int i = 0; i < trimChars.Length; i++)
+                {
+                    if (span[start] == trimChars[i])
+                        goto Next;
+                }
+                break;
+            Next:
+                ;
+            }
+            return span.Slice(start);
+        }
+
+        /// <summary>
+        /// Removes all trailing occurrences of a set of characters specified 
+        /// in a readonly span from the span.
+        /// </summary>
+        /// <param name="span">The source span from which the characters are removed.</param>
+        /// <param name="trimChars">The span which contains the set of characters to remove.</param>
+        /// <remarks>If <paramref name="trimChars"/> is empty, white-space characters are removed instead.</remarks>
+        public static ReadOnlySpan<char> TrimEnd(this ReadOnlySpan<char> span, ReadOnlySpan<char> trimChars)
+        {
+            if (trimChars.IsEmpty)
+            {
+                return span.TrimEnd();
+            }
+
+            int end = span.Length - 1;
+            for (; end >= 0; end--)
+            {
+                for (int i = 0; i < trimChars.Length; i++)
+                {
+                    if (span[end] == trimChars[i])
+                        goto Next;
+                }
+                break;
+            Next:
+                ;
+            }
+            return span.Slice(0, end + 1);
+        }
+
+        /// <summary>
+        /// Indicates whether the specified span contains only white-space characters.
+        /// </summary>
+        public static bool IsWhiteSpace(this ReadOnlySpan<char> span)
+        {
+            for (int i = 0; i < span.Length; i++)
+            {
+                if (!char.IsWhiteSpace(span[i]))
+                    return false;
+            }
+            return true;
+        }
+
+        /// <summary>
+        /// Searches for the specified value and returns the index of its first occurrence. If not found, returns -1. Values are compared using IEquatable{T}.Equals(T). 
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value">The value to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int IndexOf<T>(this Span<T> span, T value)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.IndexOf(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, byte>(ref value),
+                    span.Length);
+            if (typeof(T) == typeof(char))
+                return SpanHelpers.IndexOf(
+                    ref Unsafe.As<T, char>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, char>(ref value),
+                    span.Length);
+
+            return SpanHelpers.IndexOf(ref MemoryMarshal.GetReference(span), value, span.Length);
+        }
+
+        /// <summary>
+        /// Searches for the specified sequence and returns the index of its first occurrence. If not found, returns -1. Values are compared using IEquatable{T}.Equals(T). 
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value">The sequence to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int IndexOf<T>(this Span<T> span, ReadOnlySpan<T> value)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.IndexOf(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    span.Length,
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(value)),
+                    value.Length);
+
+            return SpanHelpers.IndexOf(ref MemoryMarshal.GetReference(span), span.Length, ref MemoryMarshal.GetReference(value), value.Length);
+        }
+
+        /// <summary>
+        /// Searches for the specified value and returns the index of its last occurrence. If not found, returns -1. Values are compared using IEquatable{T}.Equals(T). 
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value">The value to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int LastIndexOf<T>(this Span<T> span, T value)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.LastIndexOf(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, byte>(ref value),
+                    span.Length);
+            if (typeof(T) == typeof(char))
+                return SpanHelpers.LastIndexOf(
+                    ref Unsafe.As<T, char>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, char>(ref value),
+                    span.Length);
+
+            return SpanHelpers.LastIndexOf<T>(ref MemoryMarshal.GetReference(span), value, span.Length);
+        }
+
+        /// <summary>
+        /// Searches for the specified sequence and returns the index of its last occurrence. If not found, returns -1. Values are compared using IEquatable{T}.Equals(T). 
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value">The sequence to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int LastIndexOf<T>(this Span<T> span, ReadOnlySpan<T> value)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.LastIndexOf(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    span.Length,
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(value)),
+                    value.Length);
+
+            return SpanHelpers.LastIndexOf<T>(ref MemoryMarshal.GetReference(span), span.Length, ref MemoryMarshal.GetReference(value), value.Length);
+        }
+
+        /// <summary>
+        /// Determines whether two sequences are equal by comparing the elements using IEquatable{T}.Equals(T). 
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool SequenceEqual<T>(this Span<T> span, ReadOnlySpan<T> other)
+            where T : IEquatable<T>
+        {
+            int length = span.Length;
+
+            if (default(T) != null && IsTypeComparableAsBytes<T>(out nuint size))
+                return length == other.Length &&
+                SpanHelpers.SequenceEqual(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(other)),
+                    ((nuint)length) * size);  // If this multiplication overflows, the Span we got overflows the entire address range. There's no happy outcome for this api in such a case so we choose not to take the overhead of checking.
+
+            return length == other.Length && SpanHelpers.SequenceEqual(ref MemoryMarshal.GetReference(span), ref MemoryMarshal.GetReference(other), length);
+        }
+
+        /// <summary>
+        /// Determines the relative order of the sequences being compared by comparing the elements using IComparable{T}.CompareTo(T). 
+        /// </summary>
+        public static int SequenceCompareTo<T>(this Span<T> span, ReadOnlySpan<T> other)
+            where T : IComparable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.SequenceCompareTo(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    span.Length,
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(other)),
+                    other.Length);
+
+            if (typeof(T) == typeof(char))
+                return SpanHelpers.SequenceCompareTo(
+                    ref Unsafe.As<T, char>(ref MemoryMarshal.GetReference(span)),
+                    span.Length,
+                    ref Unsafe.As<T, char>(ref MemoryMarshal.GetReference(other)),
+                    other.Length);
+
+            return SpanHelpers.SequenceCompareTo(ref MemoryMarshal.GetReference(span), span.Length, ref MemoryMarshal.GetReference(other), other.Length);
+        }
+
+        /// <summary>
+        /// Searches for the specified value and returns the index of its first occurrence. If not found, returns -1. Values are compared using IEquatable{T}.Equals(T). 
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value">The value to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int IndexOf<T>(this ReadOnlySpan<T> span, T value)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.IndexOf(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, byte>(ref value),
+                    span.Length);
+            if (typeof(T) == typeof(char))
+                return SpanHelpers.IndexOf(
+                    ref Unsafe.As<T, char>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, char>(ref value),
+                    span.Length);
+
+            return SpanHelpers.IndexOf(ref MemoryMarshal.GetReference(span), value, span.Length);
+        }
+
+        /// <summary>
+        /// Searches for the specified sequence and returns the index of its first occurrence. If not found, returns -1. Values are compared using IEquatable{T}.Equals(T). 
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value">The sequence to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int IndexOf<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> value)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.IndexOf(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    span.Length,
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(value)),
+                    value.Length);
+
+            return SpanHelpers.IndexOf(ref MemoryMarshal.GetReference(span), span.Length, ref MemoryMarshal.GetReference(value), value.Length);
+        }
+
+        /// <summary>
+        /// Searches for the specified value and returns the index of its last occurrence. If not found, returns -1. Values are compared using IEquatable{T}.Equals(T). 
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value">The value to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int LastIndexOf<T>(this ReadOnlySpan<T> span, T value)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.LastIndexOf(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, byte>(ref value),
+                    span.Length);
+            if (typeof(T) == typeof(char))
+                return SpanHelpers.LastIndexOf(
+                    ref Unsafe.As<T, char>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, char>(ref value),
+                    span.Length);
+
+            return SpanHelpers.LastIndexOf<T>(ref MemoryMarshal.GetReference(span), value, span.Length);
+        }
+
+        /// <summary>
+        /// Searches for the specified sequence and returns the index of its last occurrence. If not found, returns -1. Values are compared using IEquatable{T}.Equals(T). 
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value">The sequence to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int LastIndexOf<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> value)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.LastIndexOf(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    span.Length,
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(value)),
+                    value.Length);
+
+            return SpanHelpers.LastIndexOf<T>(ref MemoryMarshal.GetReference(span), span.Length, ref MemoryMarshal.GetReference(value), value.Length);
+        }
+
+        /// <summary>
+        /// Searches for the first index of any of the specified values similar to calling IndexOf several times with the logical OR operator. If not found, returns -1.
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value0">One of the values to search for.</param>
+        /// <param name="value1">One of the values to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int IndexOfAny<T>(this Span<T> span, T value0, T value1)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.IndexOfAny(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, byte>(ref value0),
+                    Unsafe.As<T, byte>(ref value1),
+                    span.Length);
+
+            return SpanHelpers.IndexOfAny(ref MemoryMarshal.GetReference(span), value0, value1, span.Length);
+        }
+
+        /// <summary>
+        /// Searches for the first index of any of the specified values similar to calling IndexOf several times with the logical OR operator. If not found, returns -1.
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value0">One of the values to search for.</param>
+        /// <param name="value1">One of the values to search for.</param>
+        /// <param name="value2">One of the values to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int IndexOfAny<T>(this Span<T> span, T value0, T value1, T value2)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.IndexOfAny(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, byte>(ref value0),
+                    Unsafe.As<T, byte>(ref value1),
+                    Unsafe.As<T, byte>(ref value2),
+                    span.Length);
+
+            return SpanHelpers.IndexOfAny(ref MemoryMarshal.GetReference(span), value0, value1, value2, span.Length);
+        }
+
+        /// <summary>
+        /// Searches for the first index of any of the specified values similar to calling IndexOf several times with the logical OR operator. If not found, returns -1. 
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="values">The set of values to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int IndexOfAny<T>(this Span<T> span, ReadOnlySpan<T> values)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.IndexOfAny(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    span.Length,
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(values)),
+                    values.Length);
+
+            return SpanHelpers.IndexOfAny(ref MemoryMarshal.GetReference(span), span.Length, ref MemoryMarshal.GetReference(values), values.Length);
+        }
+
+        /// <summary>
+        /// Searches for the first index of any of the specified values similar to calling IndexOf several times with the logical OR operator. If not found, returns -1.
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value0">One of the values to search for.</param>
+        /// <param name="value1">One of the values to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int IndexOfAny<T>(this ReadOnlySpan<T> span, T value0, T value1)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.IndexOfAny(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, byte>(ref value0),
+                    Unsafe.As<T, byte>(ref value1),
+                    span.Length);
+
+            return SpanHelpers.IndexOfAny(ref MemoryMarshal.GetReference(span), value0, value1, span.Length);
+        }
+
+        /// <summary>
+        /// Searches for the first index of any of the specified values similar to calling IndexOf several times with the logical OR operator. If not found, returns -1. 
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value0">One of the values to search for.</param>
+        /// <param name="value1">One of the values to search for.</param>
+        /// <param name="value2">One of the values to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int IndexOfAny<T>(this ReadOnlySpan<T> span, T value0, T value1, T value2)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.IndexOfAny(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, byte>(ref value0),
+                    Unsafe.As<T, byte>(ref value1),
+                    Unsafe.As<T, byte>(ref value2),
+                    span.Length);
+
+            return SpanHelpers.IndexOfAny(ref MemoryMarshal.GetReference(span), value0, value1, value2, span.Length);
+        }
+
+        /// <summary>
+        /// Searches for the first index of any of the specified values similar to calling IndexOf several times with the logical OR operator. If not found, returns -1. 
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="values">The set of values to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int IndexOfAny<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> values)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.IndexOfAny(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    span.Length,
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(values)),
+                    values.Length);
+
+            return SpanHelpers.IndexOfAny(ref MemoryMarshal.GetReference(span), span.Length, ref MemoryMarshal.GetReference(values), values.Length);
+        }
+
+        /// <summary>
+        /// Searches for the last index of any of the specified values similar to calling LastIndexOf several times with the logical OR operator. If not found, returns -1.
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value0">One of the values to search for.</param>
+        /// <param name="value1">One of the values to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int LastIndexOfAny<T>(this Span<T> span, T value0, T value1)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.LastIndexOfAny(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, byte>(ref value0),
+                    Unsafe.As<T, byte>(ref value1),
+                    span.Length);
+
+            return SpanHelpers.LastIndexOfAny(ref MemoryMarshal.GetReference(span), value0, value1, span.Length);
+        }
+
+        /// <summary>
+        /// Searches for the last index of any of the specified values similar to calling LastIndexOf several times with the logical OR operator. If not found, returns -1.
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value0">One of the values to search for.</param>
+        /// <param name="value1">One of the values to search for.</param>
+        /// <param name="value2">One of the values to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int LastIndexOfAny<T>(this Span<T> span, T value0, T value1, T value2)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.LastIndexOfAny(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, byte>(ref value0),
+                    Unsafe.As<T, byte>(ref value1),
+                    Unsafe.As<T, byte>(ref value2),
+                    span.Length);
+
+            return SpanHelpers.LastIndexOfAny(ref MemoryMarshal.GetReference(span), value0, value1, value2, span.Length);
+        }
+
+        /// <summary>
+        /// Searches for the last index of any of the specified values similar to calling LastIndexOf several times with the logical OR operator. If not found, returns -1. 
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="values">The set of values to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int LastIndexOfAny<T>(this Span<T> span, ReadOnlySpan<T> values)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.LastIndexOfAny(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    span.Length,
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(values)),
+                    values.Length);
+
+            return SpanHelpers.LastIndexOfAny(ref MemoryMarshal.GetReference(span), span.Length, ref MemoryMarshal.GetReference(values), values.Length);
+        }
+
+        /// <summary>
+        /// Searches for the last index of any of the specified values similar to calling LastIndexOf several times with the logical OR operator. If not found, returns -1.
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value0">One of the values to search for.</param>
+        /// <param name="value1">One of the values to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int LastIndexOfAny<T>(this ReadOnlySpan<T> span, T value0, T value1)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.LastIndexOfAny(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, byte>(ref value0),
+                    Unsafe.As<T, byte>(ref value1),
+                    span.Length);
+
+            return SpanHelpers.LastIndexOfAny(ref MemoryMarshal.GetReference(span), value0, value1, span.Length);
+        }
+
+        /// <summary>
+        /// Searches for the last index of any of the specified values similar to calling LastIndexOf several times with the logical OR operator. If not found, returns -1. 
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="value0">One of the values to search for.</param>
+        /// <param name="value1">One of the values to search for.</param>
+        /// <param name="value2">One of the values to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int LastIndexOfAny<T>(this ReadOnlySpan<T> span, T value0, T value1, T value2)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.LastIndexOfAny(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    Unsafe.As<T, byte>(ref value0),
+                    Unsafe.As<T, byte>(ref value1),
+                    Unsafe.As<T, byte>(ref value2),
+                    span.Length);
+
+            return SpanHelpers.LastIndexOfAny(ref MemoryMarshal.GetReference(span), value0, value1, value2, span.Length);
+        }
+
+        /// <summary>
+        /// Searches for the last index of any of the specified values similar to calling LastIndexOf several times with the logical OR operator. If not found, returns -1. 
+        /// </summary>
+        /// <param name="span">The span to search.</param>
+        /// <param name="values">The set of values to search for.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int LastIndexOfAny<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> values)
+            where T : IEquatable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.LastIndexOfAny(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    span.Length,
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(values)),
+                    values.Length);
+
+            return SpanHelpers.LastIndexOfAny<T>(ref MemoryMarshal.GetReference(span), span.Length, ref MemoryMarshal.GetReference(values), values.Length);
+        }
+
+        /// <summary>
+        /// Determines whether two sequences are equal by comparing the elements using IEquatable{T}.Equals(T). 
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool SequenceEqual<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> other)
+            where T : IEquatable<T>
+        {
+            int length = span.Length;
+            if (default(T) != null && IsTypeComparableAsBytes<T>(out nuint size))
+                return length == other.Length &&
+                SpanHelpers.SequenceEqual(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(other)),
+                    ((nuint)length) * size);  // If this multiplication overflows, the Span we got overflows the entire address range. There's no happy outcome for this api in such a case so we choose not to take the overhead of checking.
+
+            return length == other.Length && SpanHelpers.SequenceEqual(ref MemoryMarshal.GetReference(span), ref MemoryMarshal.GetReference(other), length);
+        }
+
+        /// <summary>
+        /// Determines the relative order of the sequences being compared by comparing the elements using IComparable{T}.CompareTo(T). 
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int SequenceCompareTo<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> other)
+            where T : IComparable<T>
+        {
+            if (typeof(T) == typeof(byte))
+                return SpanHelpers.SequenceCompareTo(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    span.Length,
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(other)),
+                    other.Length);
+
+            if (typeof(T) == typeof(char))
+                return SpanHelpers.SequenceCompareTo(
+                    ref Unsafe.As<T, char>(ref MemoryMarshal.GetReference(span)),
+                    span.Length,
+                    ref Unsafe.As<T, char>(ref MemoryMarshal.GetReference(other)),
+                    other.Length);
+
+            return SpanHelpers.SequenceCompareTo(ref MemoryMarshal.GetReference(span), span.Length, ref MemoryMarshal.GetReference(other), other.Length);
+        }
+
+        /// <summary>
+        /// Determines whether the specified sequence appears at the start of the span.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool StartsWith<T>(this Span<T> span, ReadOnlySpan<T> value)
+            where T : IEquatable<T>
+        {
+            int valueLength = value.Length;
+            if (default(T) != null && IsTypeComparableAsBytes<T>(out nuint size))
+                return valueLength <= span.Length &&
+                SpanHelpers.SequenceEqual(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(value)),
+                    ((nuint)valueLength) * size);  // If this multiplication overflows, the Span we got overflows the entire address range. There's no happy outcome for this api in such a case so we choose not to take the overhead of checking.
+
+            return valueLength <= span.Length && SpanHelpers.SequenceEqual(ref MemoryMarshal.GetReference(span), ref MemoryMarshal.GetReference(value), valueLength);
+        }
+
+        /// <summary>
+        /// Determines whether the specified sequence appears at the start of the span.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool StartsWith<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> value)
+            where T : IEquatable<T>
+        {
+            int valueLength = value.Length;
+            if (default(T) != null && IsTypeComparableAsBytes<T>(out nuint size))
+                return valueLength <= span.Length &&
+                SpanHelpers.SequenceEqual(
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(span)),
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(value)),
+                    ((nuint)valueLength) * size);  // If this multiplication overflows, the Span we got overflows the entire address range. There's no happy outcome for this api in such a case so we choose not to take the overhead of checking.
+
+            return valueLength <= span.Length && SpanHelpers.SequenceEqual(ref MemoryMarshal.GetReference(span), ref MemoryMarshal.GetReference(value), valueLength);
+        }
+
+        /// <summary>
+        /// Determines whether the specified sequence appears at the end of the span.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool EndsWith<T>(this Span<T> span, ReadOnlySpan<T> value)
+            where T : IEquatable<T>
+        {
+            int spanLength = span.Length;
+            int valueLength = value.Length;
+            if (default(T) != null && IsTypeComparableAsBytes<T>(out nuint size))
+                return valueLength <= spanLength &&
+                SpanHelpers.SequenceEqual(
+                    ref Unsafe.As<T, byte>(ref Unsafe.Add(ref MemoryMarshal.GetReference(span), spanLength - valueLength)),
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(value)),
+                    ((nuint)valueLength) * size);  // If this multiplication overflows, the Span we got overflows the entire address range. There's no happy outcome for this api in such a case so we choose not to take the overhead of checking.
+
+            return valueLength <= spanLength &&
+                SpanHelpers.SequenceEqual(
+                    ref Unsafe.Add(ref MemoryMarshal.GetReference(span), spanLength - valueLength),
+                    ref MemoryMarshal.GetReference(value),
+                    valueLength);
+        }
+
+        /// <summary>
+        /// Determines whether the specified sequence appears at the end of the span.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool EndsWith<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> value)
+            where T : IEquatable<T>
+        {
+            int spanLength = span.Length;
+            int valueLength = value.Length;
+            if (default(T) != null && IsTypeComparableAsBytes<T>(out nuint size))
+                return valueLength <= spanLength &&
+                SpanHelpers.SequenceEqual(
+                    ref Unsafe.As<T, byte>(ref Unsafe.Add(ref MemoryMarshal.GetReference(span), spanLength - valueLength)),
+                    ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(value)),
+                    ((nuint)valueLength) * size);  // If this multiplication overflows, the Span we got overflows the entire address range. There's no happy outcome for this api in such a case so we choose not to take the overhead of checking.
+
+            return valueLength <= spanLength &&
+                SpanHelpers.SequenceEqual(
+                    ref Unsafe.Add(ref MemoryMarshal.GetReference(span), spanLength - valueLength),
+                    ref MemoryMarshal.GetReference(value),
+                    valueLength);
+        }
+
+        /// <summary>
+        /// Reverses the sequence of the elements in the entire span.
+        /// </summary>
+        public static void Reverse<T>(this Span<T> span)
+        {
+            if (span.Length <= 1)
+            {
+                return;
+            }
+
+            ref T first = ref MemoryMarshal.GetReference(span);
+            ref T last = ref Unsafe.Add(ref Unsafe.Add(ref first, span.Length), -1);
+            do
+            {
+                T temp = first;
+                first = last;
+                last = temp;
+                first = ref Unsafe.Add(ref first, 1);
+                last = ref Unsafe.Add(ref last, -1);
+            } while (Unsafe.IsAddressLessThan(ref first, ref last));
+        }
+
+        /// <summary>
+        /// Creates a new span over the target array.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Span<T> AsSpan<T>(this T[] array)
+        {
+            return new Span<T>(array);
+        }
+
+        /// <summary>
+        /// Creates a new Span over the portion of the target array beginning
+        /// at 'start' index and ending at 'end' index (exclusive).
+        /// </summary>
+        /// <param name="array">The target array.</param>
+        /// <param name="start">The index at which to begin the Span.</param>
+        /// <param name="length">The number of items in the Span.</param>
+        /// <remarks>Returns default when <paramref name="array"/> is null.</remarks>
+        /// <exception cref="System.ArrayTypeMismatchException">Thrown when <paramref name="array"/> is covariant and array's type is not exactly T[].</exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in the range (&lt;0 or &gt;=Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Span<T> AsSpan<T>(this T[] array, int start, int length)
+        {
+            return new Span<T>(array, start, length);
+        }
+
+        /// <summary>
+        /// Creates a new span over the portion of the target array segment.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Span<T> AsSpan<T>(this ArraySegment<T> segment)
+        {
+            return new Span<T>(segment.Array, segment.Offset, segment.Count);
+        }
+
+        /// <summary>
+        /// Creates a new Span over the portion of the target array beginning
+        /// at 'start' index and ending at 'end' index (exclusive).
+        /// </summary>
+        /// <param name="segment">The target array.</param>
+        /// <param name="start">The index at which to begin the Span.</param>
+        /// <remarks>Returns default when <paramref name="segment"/> is null.</remarks>
+        /// <exception cref="System.ArrayTypeMismatchException">Thrown when <paramref name="segment"/> is covariant and array's type is not exactly T[].</exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in the range (&lt;0 or &gt;=segment.Count).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Span<T> AsSpan<T>(this ArraySegment<T> segment, int start)
+        {
+            if (((uint)start) > segment.Count)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+
+            return new Span<T>(segment.Array, segment.Offset + start, segment.Count - start);
+        }
+
+        /// <summary>
+        /// Creates a new Span over the portion of the target array beginning
+        /// at 'start' index and ending at 'end' index (exclusive).
+        /// </summary>
+        /// <param name="segment">The target array.</param>
+        /// <param name="start">The index at which to begin the Span.</param>
+        /// <param name="length">The number of items in the Span.</param>
+        /// <remarks>Returns default when <paramref name="segment"/> is null.</remarks>
+        /// <exception cref="System.ArrayTypeMismatchException">Thrown when <paramref name="segment"/> is covariant and array's type is not exactly T[].</exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in the range (&lt;0 or &gt;=segment.Count).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Span<T> AsSpan<T>(this ArraySegment<T> segment, int start, int length)
+        {
+            if (((uint)start) > segment.Count)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+            if (((uint)length) > segment.Count - start)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.length);
+
+            return new Span<T>(segment.Array, segment.Offset + start, length);
+        }
+
+        /// <summary>
+        /// Creates a new memory over the target array.
+        /// </summary>
+        public static Memory<T> AsMemory<T>(this T[] array) => new Memory<T>(array);
+
+        /// <summary>
+        /// Creates a new memory over the portion of the target array beginning
+        /// at 'start' index and ending at 'end' index (exclusive).
+        /// </summary>
+        /// <param name="array">The target array.</param>
+        /// <param name="start">The index at which to begin the memory.</param>
+        /// <remarks>Returns default when <paramref name="array"/> is null.</remarks>
+        /// <exception cref="System.ArrayTypeMismatchException">Thrown when <paramref name="array"/> is covariant and array's type is not exactly T[].</exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in the range (&lt;0 or &gt;=array.Length).
+        /// </exception>
+        public static Memory<T> AsMemory<T>(this T[] array, int start) => new Memory<T>(array, start);
+
+        /// <summary>
+        /// Creates a new memory over the portion of the target array beginning
+        /// at 'start' index and ending at 'end' index (exclusive).
+        /// </summary>
+        /// <param name="array">The target array.</param>
+        /// <param name="start">The index at which to begin the memory.</param>
+        /// <param name="length">The number of items in the memory.</param>
+        /// <remarks>Returns default when <paramref name="array"/> is null.</remarks>
+        /// <exception cref="System.ArrayTypeMismatchException">Thrown when <paramref name="array"/> is covariant and array's type is not exactly T[].</exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in the range (&lt;0 or &gt;=Length).
+        /// </exception>
+        public static Memory<T> AsMemory<T>(this T[] array, int start, int length) => new Memory<T>(array, start, length);
+
+        /// <summary>
+        /// Creates a new memory over the portion of the target array.
+        /// </summary>
+        public static Memory<T> AsMemory<T>(this ArraySegment<T> segment) => new Memory<T>(segment.Array, segment.Offset, segment.Count);
+
+        /// <summary>
+        /// Creates a new memory over the portion of the target array beginning
+        /// at 'start' index and ending at 'end' index (exclusive).
+        /// </summary>
+        /// <param name="segment">The target array.</param>
+        /// <param name="start">The index at which to begin the memory.</param>
+        /// <remarks>Returns default when <paramref name="segment"/> is null.</remarks>
+        /// <exception cref="System.ArrayTypeMismatchException">Thrown when <paramref name="segment"/> is covariant and array's type is not exactly T[].</exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in the range (&lt;0 or &gt;=segment.Count).
+        /// </exception>
+        public static Memory<T> AsMemory<T>(this ArraySegment<T> segment, int start)
+        {
+            if (((uint)start) > segment.Count)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+
+            return new Memory<T>(segment.Array, segment.Offset + start, segment.Count - start);
+        }
+
+        /// <summary>
+        /// Creates a new memory over the portion of the target array beginning
+        /// at 'start' index and ending at 'end' index (exclusive).
+        /// </summary>
+        /// <param name="segment">The target array.</param>
+        /// <param name="start">The index at which to begin the memory.</param>
+        /// <param name="length">The number of items in the memory.</param>
+        /// <remarks>Returns default when <paramref name="segment"/> is null.</remarks>
+        /// <exception cref="System.ArrayTypeMismatchException">Thrown when <paramref name="segment"/> is covariant and array's type is not exactly T[].</exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in the range (&lt;0 or &gt;=segment.Count).
+        /// </exception>
+        public static Memory<T> AsMemory<T>(this ArraySegment<T> segment, int start, int length)
+        {
+            if (((uint)start) > segment.Count)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+            if (((uint)length) > segment.Count - start)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.length);
+
+            return new Memory<T>(segment.Array, segment.Offset + start, length);
+        }
+
+        /// <summary>
+        /// Copies the contents of the array into the span. If the source
+        /// and destinations overlap, this method behaves as if the original values in
+        /// a temporary location before the destination is overwritten.
+        /// 
+        ///<param name="source">The array to copy items from.</param>
+        /// <param name="destination">The span to copy items into.</param>
+        /// <exception cref="System.ArgumentException">
+        /// Thrown when the destination Span is shorter than the source array.
+        /// </exception>
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void CopyTo<T>(this T[] source, Span<T> destination)
+        {
+            new ReadOnlySpan<T>(source).CopyTo(destination);
+        }
+
+        /// <summary>
+        /// Copies the contents of the array into the memory. If the source
+        /// and destinations overlap, this method behaves as if the original values are in
+        /// a temporary location before the destination is overwritten.
+        /// 
+        ///<param name="source">The array to copy items from.</param>
+        /// <param name="destination">The memory to copy items into.</param>
+        /// <exception cref="System.ArgumentException">
+        /// Thrown when the destination is shorter than the source array.
+        /// </exception>
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void CopyTo<T>(this T[] source, Memory<T> destination)
+        {
+            source.CopyTo(destination.Span);
+        }
+
+        //
+        //  Overlaps
+        //  ========
+        //
+        //  The following methods can be used to determine if two sequences
+        //  overlap in memory.
+        //
+        //  Two sequences overlap if they have positions in common and neither
+        //  is empty. Empty sequences do not overlap with any other sequence.
+        //
+        //  If two sequences overlap, the element offset is the number of
+        //  elements by which the second sequence is offset from the first
+        //  sequence (i.e., second minus first). An exception is thrown if the
+        //  number is not a whole number, which can happen when a sequence of a
+        //  smaller type is cast to a sequence of a larger type with unsafe code
+        //  or NonPortableCast. If the sequences do not overlap, the offset is
+        //  meaningless and arbitrarily set to zero.
+        //
+        //  Implementation
+        //  --------------
+        //
+        //  Implementing this correctly is quite tricky due of two problems:
+        //
+        //  * If the sequences refer to two different objects on the managed
+        //    heap, the garbage collector can move them freely around or change
+        //    their relative order in memory.
+        //
+        //  * The distance between two sequences can be greater than
+        //    int.MaxValue (on a 32-bit system) or long.MaxValue (on a 64-bit
+        //    system).
+        //
+        //  (For simplicity, the following text assumes a 32-bit system, but
+        //  everything also applies to a 64-bit system if every 32 is replaced a
+        //  64.)
+        //
+        //  The first problem is solved by calculating the distance with exactly
+        //  one atomic operation. If the garbage collector happens to move the
+        //  sequences afterwards and the sequences overlapped before, they will
+        //  still overlap after the move and their distance hasn't changed. If
+        //  the sequences did not overlap, the distance can change but the
+        //  sequences still won't overlap.
+        //
+        //  The second problem is solved by making all addresses relative to the
+        //  start of the first sequence and performing all operations in
+        //  unsigned integer arithmetic modulo 2³².
+        //
+        //  Example
+        //  -------
+        //
+        //  Let's say there are two sequences, x and y. Let
+        //
+        //      ref T xRef = MemoryMarshal.GetReference(x)
+        //      uint xLength = x.Length * Unsafe.SizeOf<T>()
+        //      ref T yRef = MemoryMarshal.GetReference(y)
+        //      uint yLength = y.Length * Unsafe.SizeOf<T>()
+        //
+        //  Visually, the two sequences are located somewhere in the 32-bit
+        //  address space as follows:
+        //
+        //      [----------------------------------------------)                            normal address space
+        //      0                                             2³²
+        //                            [------------------)                                  first sequence
+        //                            xRef            xRef + xLength
+        //              [--------------------------)     .                                  second sequence
+        //              yRef          .         yRef + yLength
+        //              :             .            .     .
+        //              :             .            .     .
+        //                            .            .     .
+        //                            .            .     .
+        //                            .            .     .
+        //                            [----------------------------------------------)      relative address space
+        //                            0            .     .                          2³²
+        //                            [------------------)             :                    first sequence
+        //                            x1           .     x2            :
+        //                            -------------)                   [-------------       second sequence
+        //                                         y2                  y1
+        //
+        //  The idea is to make all addresses relative to xRef: Let x1 be the
+        //  start address of x in this relative address space, x2 the end
+        //  address of x, y1 the start address of y, and y2 the end address of
+        //  y:
+        //
+        //      nuint x1 = 0
+        //      nuint x2 = xLength
+        //      nuint y1 = (nuint)Unsafe.ByteOffset(xRef, yRef)
+        //      nuint y2 = y1 + yLength
+        //  
+        //  xRef relative to xRef is 0.
+        //  
+        //  x2 is simply x1 + xLength. This cannot overflow.
+        //  
+        //  yRef relative to xRef is (yRef - xRef). If (yRef - xRef) is
+        //  negative, casting it to an unsigned 32-bit integer turns it into
+        //  (yRef - xRef + 2³²). So, in the example above, y1 moves to the right
+        //  of x2.
+        //  
+        //  y2 is simply y1 + yLength. Note that this can overflow, as in the
+        //  example above, which must be avoided.
+        //
+        //  The two sequences do *not* overlap if y is entirely in the space
+        //  right of x in the relative address space. (It can't be left of it!)
+        //
+        //          (y1 >= x2) && (y2 <= 2³²)
+        //
+        //  Inversely, they do overlap if
+        //
+        //          (y1 < x2) || (y2 > 2³²)
+        //
+        //  After substituting x2 and y2 with their respective definition:
+        //
+        //      == (y1 < xLength) || (y1 + yLength > 2³²)
+        //
+        //  Since yLength can't be greater than the size of the address space,
+        //  the overflow can be avoided as follows:
+        //
+        //      == (y1 < xLength) || (y1 > 2³² - yLength)
+        //
+        //  However, 2³² cannot be stored in an unsigned 32-bit integer, so one
+        //  more change is needed to keep doing everything with unsigned 32-bit
+        //  integers:
+        //
+        //      == (y1 < xLength) || (y1 > -yLength)
+        //  
+        //  Due to modulo arithmetic, this gives exactly same result *except* if
+        //  yLength is zero, since 2³² - 0 is 0 and not 2³². So the case
+        //  y.IsEmpty must be handled separately first.
+        //  
+
+        /// <summary>
+        /// Determines whether two sequences overlap in memory.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool Overlaps<T>(this Span<T> span, ReadOnlySpan<T> other)
+        {
+            return Overlaps((ReadOnlySpan<T>)span, other);
+        }
+
+        /// <summary>
+        /// Determines whether two sequences overlap in memory and outputs the element offset.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool Overlaps<T>(this Span<T> span, ReadOnlySpan<T> other, out int elementOffset)
+        {
+            return Overlaps((ReadOnlySpan<T>)span, other, out elementOffset);
+        }
+
+        /// <summary>
+        /// Determines whether two sequences overlap in memory.
+        /// </summary>
+        public static bool Overlaps<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> other)
+        {
+            if (span.IsEmpty || other.IsEmpty)
+            {
+                return false;
+            }
+
+            IntPtr byteOffset = Unsafe.ByteOffset(
+                ref MemoryMarshal.GetReference(span),
+                ref MemoryMarshal.GetReference(other));
+
+            if (Unsafe.SizeOf<IntPtr>() == sizeof(int))
+            {
+                return (uint)byteOffset < (uint)(span.Length * Unsafe.SizeOf<T>()) ||
+                       (uint)byteOffset > (uint)-(other.Length * Unsafe.SizeOf<T>());
+            }
+            else
+            {
+                return (ulong)byteOffset < (ulong)((long)span.Length * Unsafe.SizeOf<T>()) ||
+                       (ulong)byteOffset > (ulong)-((long)other.Length * Unsafe.SizeOf<T>());
+            }
+        }
+
+        /// <summary>
+        /// Determines whether two sequences overlap in memory and outputs the element offset.
+        /// </summary>
+        public static bool Overlaps<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> other, out int elementOffset)
+        {
+            if (span.IsEmpty || other.IsEmpty)
+            {
+                elementOffset = 0;
+                return false;
+            }
+
+            IntPtr byteOffset = Unsafe.ByteOffset(
+                ref MemoryMarshal.GetReference(span),
+                ref MemoryMarshal.GetReference(other));
+
+            if (Unsafe.SizeOf<IntPtr>() == sizeof(int))
+            {
+                if ((uint)byteOffset < (uint)(span.Length * Unsafe.SizeOf<T>()) ||
+                    (uint)byteOffset > (uint)-(other.Length * Unsafe.SizeOf<T>()))
+                {
+                    if ((int)byteOffset % Unsafe.SizeOf<T>() != 0)
+                        ThrowHelper.ThrowArgumentException_OverlapAlignmentMismatch();
+
+                    elementOffset = (int)byteOffset / Unsafe.SizeOf<T>();
+                    return true;
+                }
+                else
+                {
+                    elementOffset = 0;
+                    return false;
+                }
+            }
+            else
+            {
+                if ((ulong)byteOffset < (ulong)((long)span.Length * Unsafe.SizeOf<T>()) ||
+                    (ulong)byteOffset > (ulong)-((long)other.Length * Unsafe.SizeOf<T>()))
+                {
+                    if ((long)byteOffset % Unsafe.SizeOf<T>() != 0)
+                        ThrowHelper.ThrowArgumentException_OverlapAlignmentMismatch();
+
+                    elementOffset = (int)((long)byteOffset / Unsafe.SizeOf<T>());
+                    return true;
+                }
+                else
+                {
+                    elementOffset = 0;
+                    return false;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Searches an entire sorted <see cref="Span{T}"/> for a value
+        /// using the specified <see cref="IComparable{T}"/> generic interface.
+        /// </summary>
+        /// <typeparam name="T">The element type of the span.</typeparam>
+        /// <param name="span">The sorted <see cref="Span{T}"/> to search.</param>
+        /// <param name="comparable">The <see cref="IComparable{T}"/> to use when comparing.</param>
+        /// <returns>
+        /// The zero-based index of <paramref name="comparable"/> in the sorted <paramref name="span"/>,
+        /// if <paramref name="comparable"/> is found; otherwise, a negative number that is the bitwise complement
+        /// of the index of the next element that is larger than <paramref name="comparable"/> or, if there is
+        /// no larger element, the bitwise complement of <see cref="Span{T}.Length"/>.
+        /// </returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// <paramref name = "comparable" /> is <see langword="null"/> .
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int BinarySearch<T>(
+            this Span<T> span, IComparable<T> comparable)
+        {
+            return BinarySearch<T, IComparable<T>>(span, comparable);
+        }
+
+        /// <summary>
+        /// Searches an entire sorted <see cref="Span{T}"/> for a value
+        /// using the specified <typeparamref name="TComparable"/> generic type.
+        /// </summary>
+        /// <typeparam name="T">The element type of the span.</typeparam>
+        /// <typeparam name="TComparable">The specific type of <see cref="IComparable{T}"/>.</typeparam>
+        /// <param name="span">The sorted <see cref="Span{T}"/> to search.</param>
+        /// <param name="comparable">The <typeparamref name="TComparable"/> to use when comparing.</param>
+        /// <returns>
+        /// The zero-based index of <paramref name="comparable"/> in the sorted <paramref name="span"/>,
+        /// if <paramref name="comparable"/> is found; otherwise, a negative number that is the bitwise complement
+        /// of the index of the next element that is larger than <paramref name="comparable"/> or, if there is
+        /// no larger element, the bitwise complement of <see cref="Span{T}.Length"/>.
+        /// </returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// <paramref name = "comparable" /> is <see langword="null"/> .
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int BinarySearch<T, TComparable>(
+            this Span<T> span, TComparable comparable)
+            where TComparable : IComparable<T>
+        {
+            return BinarySearch((ReadOnlySpan<T>)span, comparable);
+        }
+
+        /// <summary>
+        /// Searches an entire sorted <see cref="Span{T}"/> for the specified <paramref name="value"/>
+        /// using the specified <typeparamref name="TComparer"/> generic type.
+        /// </summary>
+        /// <typeparam name="T">The element type of the span.</typeparam>
+        /// <typeparam name="TComparer">The specific type of <see cref="IComparer{T}"/>.</typeparam>
+        /// <param name="span">The sorted <see cref="Span{T}"/> to search.</param>
+        /// <param name="value">The object to locate. The value can be null for reference types.</param>
+        /// <param name="comparer">The <typeparamref name="TComparer"/> to use when comparing.</param>
+        /// /// <returns>
+        /// The zero-based index of <paramref name="value"/> in the sorted <paramref name="span"/>,
+        /// if <paramref name="value"/> is found; otherwise, a negative number that is the bitwise complement
+        /// of the index of the next element that is larger than <paramref name="value"/> or, if there is
+        /// no larger element, the bitwise complement of <see cref="Span{T}.Length"/>.
+        /// </returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// <paramref name = "comparer" /> is <see langword="null"/> .
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int BinarySearch<T, TComparer>(
+            this Span<T> span, T value, TComparer comparer)
+            where TComparer : IComparer<T>
+        {
+            return BinarySearch((ReadOnlySpan<T>)span, value, comparer);
+        }
+
+        /// <summary>
+        /// Searches an entire sorted <see cref="ReadOnlySpan{T}"/> for a value
+        /// using the specified <see cref="IComparable{T}"/> generic interface.
+        /// </summary>
+        /// <typeparam name="T">The element type of the span.</typeparam>
+        /// <param name="span">The sorted <see cref="ReadOnlySpan{T}"/> to search.</param>
+        /// <param name="comparable">The <see cref="IComparable{T}"/> to use when comparing.</param>
+        /// <returns>
+        /// The zero-based index of <paramref name="comparable"/> in the sorted <paramref name="span"/>,
+        /// if <paramref name="comparable"/> is found; otherwise, a negative number that is the bitwise complement
+        /// of the index of the next element that is larger than <paramref name="comparable"/> or, if there is
+        /// no larger element, the bitwise complement of <see cref="ReadOnlySpan{T}.Length"/>.
+        /// </returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// <paramref name = "comparable" /> is <see langword="null"/> .
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int BinarySearch<T>(
+            this ReadOnlySpan<T> span, IComparable<T> comparable)
+        {
+            return BinarySearch<T, IComparable<T>>(span, comparable);
+        }
+
+        /// <summary>
+        /// Searches an entire sorted <see cref="ReadOnlySpan{T}"/> for a value
+        /// using the specified <typeparamref name="TComparable"/> generic type.
+        /// </summary>
+        /// <typeparam name="T">The element type of the span.</typeparam>
+        /// <typeparam name="TComparable">The specific type of <see cref="IComparable{T}"/>.</typeparam>
+        /// <param name="span">The sorted <see cref="ReadOnlySpan{T}"/> to search.</param>
+        /// <param name="comparable">The <typeparamref name="TComparable"/> to use when comparing.</param>
+        /// <returns>
+        /// The zero-based index of <paramref name="comparable"/> in the sorted <paramref name="span"/>,
+        /// if <paramref name="comparable"/> is found; otherwise, a negative number that is the bitwise complement
+        /// of the index of the next element that is larger than <paramref name="comparable"/> or, if there is
+        /// no larger element, the bitwise complement of <see cref="ReadOnlySpan{T}.Length"/>.
+        /// </returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// <paramref name = "comparable" /> is <see langword="null"/> .
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int BinarySearch<T, TComparable>(
+            this ReadOnlySpan<T> span, TComparable comparable)
+            where TComparable : IComparable<T>
+        {
+            return SpanHelpers.BinarySearch(span, comparable);
+        }
+
+        /// <summary>
+        /// Searches an entire sorted <see cref="ReadOnlySpan{T}"/> for the specified <paramref name="value"/>
+        /// using the specified <typeparamref name="TComparer"/> generic type.
+        /// </summary>
+        /// <typeparam name="T">The element type of the span.</typeparam>
+        /// <typeparam name="TComparer">The specific type of <see cref="IComparer{T}"/>.</typeparam>
+        /// <param name="span">The sorted <see cref="ReadOnlySpan{T}"/> to search.</param>
+        /// <param name="value">The object to locate. The value can be null for reference types.</param>
+        /// <param name="comparer">The <typeparamref name="TComparer"/> to use when comparing.</param>
+        /// /// <returns>
+        /// The zero-based index of <paramref name="value"/> in the sorted <paramref name="span"/>,
+        /// if <paramref name="value"/> is found; otherwise, a negative number that is the bitwise complement
+        /// of the index of the next element that is larger than <paramref name="value"/> or, if there is
+        /// no larger element, the bitwise complement of <see cref="ReadOnlySpan{T}.Length"/>.
+        /// </returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// <paramref name = "comparer" /> is <see langword="null"/> .
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int BinarySearch<T, TComparer>(
+            this ReadOnlySpan<T> span, T value, TComparer comparer)
+            where TComparer : IComparer<T>
+        {
+            if (comparer == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.comparer);
+
+            var comparable = new SpanHelpers.ComparerComparable<T, TComparer>(
+                value, comparer);
+            return BinarySearch(span, comparable);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static bool IsTypeComparableAsBytes<T>(out nuint size)
+        {
+            if (typeof(T) == typeof(byte) || typeof(T) == typeof(sbyte))
+            {
+                size = (nuint)sizeof(byte);
+                return true;
+            }
+
+            if (typeof(T) == typeof(char) || typeof(T) == typeof(short) || typeof(T) == typeof(ushort))
+            {
+                size = (nuint)sizeof(char);
+                return true;
+            }
+
+            if (typeof(T) == typeof(int) || typeof(T) == typeof(uint))
+            {
+                size = (nuint)sizeof(int);
+                return true;
+            }
+
+            if (typeof(T) == typeof(long) || typeof(T) == typeof(ulong))
+            {
+                size = (nuint)sizeof(long);
+                return true;
+            }
+
+            size = default;
+            return false;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/MethodAccessException.cs b/src/System.Private.CoreLib/shared/System/MethodAccessException.cs
new file mode 100644
index 0000000000..1ca0297b94
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/MethodAccessException.cs
@@ -0,0 +1,42 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+** Purpose: The exception class for class loading failures.
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class MethodAccessException : MemberAccessException
+    {
+        public MethodAccessException()
+            : base(SR.Arg_MethodAccessException)
+        {
+            HResult = HResults.COR_E_METHODACCESS;
+        }
+
+        public MethodAccessException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_METHODACCESS;
+        }
+
+        public MethodAccessException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_METHODACCESS;
+        }
+
+        protected MethodAccessException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/MidpointRounding.cs b/src/System.Private.CoreLib/shared/System/MidpointRounding.cs
new file mode 100644
index 0000000000..a75de43e65
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/MidpointRounding.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    public enum MidpointRounding
+    {
+        ToEven = 0,
+        AwayFromZero = 1,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/MissingMethodException.cs b/src/System.Private.CoreLib/shared/System/MissingMethodException.cs
new file mode 100644
index 0000000000..abb6c0e97b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/MissingMethodException.cs
@@ -0,0 +1,61 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: The exception class for class loading failures.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class MissingMethodException : MissingMemberException
+    {
+        public MissingMethodException()
+            : base(SR.Arg_MissingMethodException)
+        {
+            HResult = HResults.COR_E_MISSINGMETHOD;
+        }
+
+        public MissingMethodException(string message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_MISSINGMETHOD;
+        }
+
+        public MissingMethodException(string message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_MISSINGMETHOD;
+        }
+
+        public MissingMethodException(string className, string methodName)
+        {
+            ClassName = className;
+            MemberName = methodName;
+        }
+
+        protected MissingMethodException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+
+        public override string Message
+        {
+            get
+            {
+                return ClassName == null ? base.Message : 
+                    SR.Format(SR.MissingMethod_Name, ClassName + "." + MemberName + 
+                        (Signature != null ? " " + FormatSignature(Signature) : string.Empty));
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/MulticastNotSupportedException.cs b/src/System.Private.CoreLib/shared/System/MulticastNotSupportedException.cs
new file mode 100644
index 0000000000..cc6c77023e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/MulticastNotSupportedException.cs
@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////////
+// MulticastNotSupportedException
+// This is thrown when you add multiple callbacks to a non-multicast delegate.
+////////////////////////////////////////////////////////////////////////////////
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class MulticastNotSupportedException : SystemException
+    {
+        public MulticastNotSupportedException()
+            : base(SR.Arg_MulticastNotSupportedException)
+        {
+            HResult = HResults.COR_E_MULTICASTNOTSUPPORTED;
+        }
+
+        public MulticastNotSupportedException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_MULTICASTNOTSUPPORTED;
+        }
+
+        public MulticastNotSupportedException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_MULTICASTNOTSUPPORTED;
+        }
+
+        internal MulticastNotSupportedException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/NonSerializedAttribute.cs b/src/System.Private.CoreLib/shared/System/NonSerializedAttribute.cs
new file mode 100644
index 0000000000..cabd5a2aa2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/NonSerializedAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    [AttributeUsage(AttributeTargets.Field, Inherited = false)]
+    public sealed class NonSerializedAttribute : Attribute
+    {
+        public NonSerializedAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/NotFiniteNumberException.cs b/src/System.Private.CoreLib/shared/System/NotFiniteNumberException.cs
new file mode 100644
index 0000000000..b9c9af06d3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/NotFiniteNumberException.cs
@@ -0,0 +1,72 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class NotFiniteNumberException : ArithmeticException
+    {
+        private double _offendingNumber;
+
+        public NotFiniteNumberException()
+            : base(SR.Arg_NotFiniteNumberException)
+        {
+            _offendingNumber = 0;
+            HResult = HResults.COR_E_NOTFINITENUMBER;
+        }
+
+        public NotFiniteNumberException(double offendingNumber)
+            : base()
+        {
+            _offendingNumber = offendingNumber;
+            HResult = HResults.COR_E_NOTFINITENUMBER;
+        }
+
+        public NotFiniteNumberException(string message)
+            : base(message)
+        {
+            _offendingNumber = 0;
+            HResult = HResults.COR_E_NOTFINITENUMBER;
+        }
+
+        public NotFiniteNumberException(string message, double offendingNumber)
+            : base(message)
+        {
+            _offendingNumber = offendingNumber;
+            HResult = HResults.COR_E_NOTFINITENUMBER;
+        }
+
+        public NotFiniteNumberException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_NOTFINITENUMBER;
+        }
+
+        public NotFiniteNumberException(string message, double offendingNumber, Exception innerException)
+            : base(message, innerException)
+        {
+            _offendingNumber = offendingNumber;
+            HResult = HResults.COR_E_NOTFINITENUMBER;
+        }
+
+        protected NotFiniteNumberException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+            _offendingNumber = info.GetInt32("OffendingNumber");
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("OffendingNumber", _offendingNumber, typeof(int));
+        }
+
+        public double OffendingNumber
+        {
+            get { return _offendingNumber; }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/NotImplementedException.cs b/src/System.Private.CoreLib/shared/System/NotImplementedException.cs
new file mode 100644
index 0000000000..1a3b6afcd4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/NotImplementedException.cs
@@ -0,0 +1,43 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception thrown when a requested method or operation is not 
+**            implemented.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class NotImplementedException : SystemException
+    {
+        public NotImplementedException()
+            : base(SR.Arg_NotImplementedException)
+        {
+            HResult = HResults.E_NOTIMPL;
+        }
+        public NotImplementedException(String message)
+            : base(message)
+        {
+            HResult = HResults.E_NOTIMPL;
+        }
+        public NotImplementedException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.E_NOTIMPL;
+        }
+
+        protected NotImplementedException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/NotSupportedException.cs b/src/System.Private.CoreLib/shared/System/NotSupportedException.cs
new file mode 100644
index 0000000000..3180bc2837
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/NotSupportedException.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: For methods that should be implemented on subclasses.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class NotSupportedException : SystemException
+    {
+        public NotSupportedException()
+            : base(SR.Arg_NotSupportedException)
+        {
+            HResult = HResults.COR_E_NOTSUPPORTED;
+        }
+
+        public NotSupportedException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_NOTSUPPORTED;
+        }
+
+        public NotSupportedException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_NOTSUPPORTED;
+        }
+
+        protected NotSupportedException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/NullReferenceException.cs b/src/System.Private.CoreLib/shared/System/NullReferenceException.cs
new file mode 100644
index 0000000000..c2e722470c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/NullReferenceException.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception class for dereferencing a null reference.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class NullReferenceException : SystemException
+    {
+        public NullReferenceException()
+            : base(SR.Arg_NullReferenceException)
+        {
+            HResult = HResults.COR_E_NULLREFERENCE;
+        }
+
+        public NullReferenceException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_NULLREFERENCE;
+        }
+
+        public NullReferenceException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_NULLREFERENCE;
+        }
+
+        protected NullReferenceException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Nullable.cs b/src/System.Private.CoreLib/shared/System/Nullable.cs
new file mode 100644
index 0000000000..73ad6056c2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Nullable.cs
@@ -0,0 +1,152 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    // Because we have special type system support that says a a boxed Nullable<T>
+    // can be used where a boxed<T> is use, Nullable<T> can not implement any intefaces
+    // at all (since T may not).   Do NOT add any interfaces to Nullable!
+    //
+    [Serializable]
+    [NonVersionable] // This only applies to field layout
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct Nullable<T> where T : struct
+    {
+        private readonly bool hasValue; // Do not rename (binary serialization)
+        internal T value; // Do not rename (binary serialization) or make readonly (can be mutated in ToString, etc.)
+
+        [NonVersionable]
+        public Nullable(T value)
+        {
+            this.value = value;
+            hasValue = true;
+        }
+
+        public bool HasValue
+        {
+            [NonVersionable]
+            get
+            {
+                return hasValue;
+            }
+        }
+
+        public T Value
+        {
+            get
+            {
+                if (!hasValue)
+                {
+                    ThrowHelper.ThrowInvalidOperationException_InvalidOperation_NoValue();
+                }
+                return value;
+            }
+        }
+
+        [NonVersionable]
+        public T GetValueOrDefault()
+        {
+            return value;
+        }
+
+        [NonVersionable]
+        public T GetValueOrDefault(T defaultValue)
+        {
+            return hasValue ? value : defaultValue;
+        }
+
+        public override bool Equals(object other)
+        {
+            if (!hasValue) return other == null;
+            if (other == null) return false;
+            return value.Equals(other);
+        }
+
+        public override int GetHashCode()
+        {
+            return hasValue ? value.GetHashCode() : 0;
+        }
+
+        public override string ToString()
+        {
+            return hasValue ? value.ToString() : "";
+        }
+
+        [NonVersionable]
+        public static implicit operator Nullable<T>(T value)
+        {
+            return new Nullable<T>(value);
+        }
+
+        [NonVersionable]
+        public static explicit operator T(Nullable<T> value)
+        {
+            return value.Value;
+        }
+    }
+
+    public static class Nullable
+    {
+        public static int Compare<T>(Nullable<T> n1, Nullable<T> n2) where T : struct
+        {
+            if (n1.HasValue)
+            {
+                if (n2.HasValue) return Comparer<T>.Default.Compare(n1.value, n2.value);
+                return 1;
+            }
+            if (n2.HasValue) return -1;
+            return 0;
+        }
+
+        public static bool Equals<T>(Nullable<T> n1, Nullable<T> n2) where T : struct
+        {
+            if (n1.HasValue)
+            {
+                if (n2.HasValue) return EqualityComparer<T>.Default.Equals(n1.value, n2.value);
+                return false;
+            }
+            if (n2.HasValue) return false;
+            return true;
+        }
+
+        // If the type provided is not a Nullable Type, return null.
+        // Otherwise, returns the underlying type of the Nullable type
+        public static Type GetUnderlyingType(Type nullableType)
+        {
+            if ((object)nullableType == null)
+            {
+                throw new ArgumentNullException(nameof(nullableType));
+            }
+
+#if CORERT
+            // This is necessary to handle types without reflection metadata
+            if (nullableType.TryGetEEType(out EETypePtr nullableEEType))
+            {
+                if (nullableEEType.IsGeneric)
+                {
+                    if (nullableEEType.IsNullable)
+                    {
+                        return Internal.Reflection.Core.NonPortable.RuntimeTypeUnifier.GetRuntimeTypeForEEType(nullableEEType.NullableType);
+                    }
+                }
+                return null;
+            }
+#endif
+
+            if (nullableType.IsGenericType && !nullableType.IsGenericTypeDefinition)
+            {
+                // instantiated generic type only                
+                Type genericType = nullableType.GetGenericTypeDefinition();
+                if (Object.ReferenceEquals(genericType, typeof(Nullable<>)))
+                {
+                    return nullableType.GetGenericArguments()[0];
+                }
+            }
+            return null;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Number.Formatting.cs b/src/System.Private.CoreLib/shared/System/Number.Formatting.cs
new file mode 100644
index 0000000000..74395ab2f5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Number.Formatting.cs
@@ -0,0 +1,2291 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Buffers.Text;
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace System
+{
+    // The Format methods provided by the numeric classes convert
+    // the numeric value to a string using the format string given by the
+    // format parameter. If the format parameter is null or
+    // an empty string, the number is formatted as if the string "G" (general
+    // format) was specified. The info parameter specifies the
+    // NumberFormatInfo instance to use when formatting the number. If the
+    // info parameter is null or omitted, the numeric formatting information
+    // is obtained from the current culture. The NumberFormatInfo supplies
+    // such information as the characters to use for decimal and thousand
+    // separators, and the spelling and placement of currency symbols in monetary
+    // values.
+    //
+    // Format strings fall into two categories: Standard format strings and
+    // user-defined format strings. A format string consisting of a single
+    // alphabetic character (A-Z or a-z), optionally followed by a sequence of
+    // digits (0-9), is a standard format string. All other format strings are
+    // used-defined format strings.
+    //
+    // A standard format string takes the form Axx, where A is an
+    // alphabetic character called the format specifier and xx is a
+    // sequence of digits called the precision specifier. The format
+    // specifier controls the type of formatting applied to the number and the
+    // precision specifier controls the number of significant digits or decimal
+    // places of the formatting operation. The following table describes the
+    // supported standard formats.
+    //
+    // C c - Currency format. The number is
+    // converted to a string that represents a currency amount. The conversion is
+    // controlled by the currency format information of the NumberFormatInfo
+    // used to format the number. The precision specifier indicates the desired
+    // number of decimal places. If the precision specifier is omitted, the default
+    // currency precision given by the NumberFormatInfo is used.
+    //
+    // D d - Decimal format. This format is
+    // supported for integral types only. The number is converted to a string of
+    // decimal digits, prefixed by a minus sign if the number is negative. The
+    // precision specifier indicates the minimum number of digits desired in the
+    // resulting string. If required, the number will be left-padded with zeros to
+    // produce the number of digits given by the precision specifier.
+    //
+    // E e Engineering (scientific) format.
+    // The number is converted to a string of the form
+    // "-d.ddd...E+ddd" or "-d.ddd...e+ddd", where each
+    // 'd' indicates a digit (0-9). The string starts with a minus sign if the
+    // number is negative, and one digit always precedes the decimal point. The
+    // precision specifier indicates the desired number of digits after the decimal
+    // point. If the precision specifier is omitted, a default of 6 digits after
+    // the decimal point is used. The format specifier indicates whether to prefix
+    // the exponent with an 'E' or an 'e'. The exponent is always consists of a
+    // plus or minus sign and three digits.
+    //
+    // F f Fixed point format. The number is
+    // converted to a string of the form "-ddd.ddd....", where each
+    // 'd' indicates a digit (0-9). The string starts with a minus sign if the
+    // number is negative. The precision specifier indicates the desired number of
+    // decimal places. If the precision specifier is omitted, the default numeric
+    // precision given by the NumberFormatInfo is used.
+    //
+    // G g - General format. The number is
+    // converted to the shortest possible decimal representation using fixed point
+    // or scientific format. The precision specifier determines the number of
+    // significant digits in the resulting string. If the precision specifier is
+    // omitted, the number of significant digits is determined by the type of the
+    // number being converted (10 for int, 19 for long, 7 for
+    // float, 15 for double, 19 for Currency, and 29 for
+    // Decimal). Trailing zeros after the decimal point are removed, and the
+    // resulting string contains a decimal point only if required. The resulting
+    // string uses fixed point format if the exponent of the number is less than
+    // the number of significant digits and greater than or equal to -4. Otherwise,
+    // the resulting string uses scientific format, and the case of the format
+    // specifier controls whether the exponent is prefixed with an 'E' or an 'e'.
+    //
+    // N n Number format. The number is
+    // converted to a string of the form "-d,ddd,ddd.ddd....", where
+    // each 'd' indicates a digit (0-9). The string starts with a minus sign if the
+    // number is negative. Thousand separators are inserted between each group of
+    // three digits to the left of the decimal point. The precision specifier
+    // indicates the desired number of decimal places. If the precision specifier
+    // is omitted, the default numeric precision given by the
+    // NumberFormatInfo is used.
+    //
+    // X x - Hexadecimal format. This format is
+    // supported for integral types only. The number is converted to a string of
+    // hexadecimal digits. The format specifier indicates whether to use upper or
+    // lower case characters for the hexadecimal digits above 9 ('X' for 'ABCDEF',
+    // and 'x' for 'abcdef'). The precision specifier indicates the minimum number
+    // of digits desired in the resulting string. If required, the number will be
+    // left-padded with zeros to produce the number of digits given by the
+    // precision specifier.
+    //
+    // Some examples of standard format strings and their results are shown in the
+    // table below. (The examples all assume a default NumberFormatInfo.)
+    //
+    // Value        Format  Result
+    // 12345.6789   C       $12,345.68
+    // -12345.6789  C       ($12,345.68)
+    // 12345        D       12345
+    // 12345        D8      00012345
+    // 12345.6789   E       1.234568E+004
+    // 12345.6789   E10     1.2345678900E+004
+    // 12345.6789   e4      1.2346e+004
+    // 12345.6789   F       12345.68
+    // 12345.6789   F0      12346
+    // 12345.6789   F6      12345.678900
+    // 12345.6789   G       12345.6789
+    // 12345.6789   G7      12345.68
+    // 123456789    G7      1.234568E8
+    // 12345.6789   N       12,345.68
+    // 123456789    N4      123,456,789.0000
+    // 0x2c45e      x       2c45e
+    // 0x2c45e      X       2C45E
+    // 0x2c45e      X8      0002C45E
+    //
+    // Format strings that do not start with an alphabetic character, or that start
+    // with an alphabetic character followed by a non-digit, are called
+    // user-defined format strings. The following table describes the formatting
+    // characters that are supported in user defined format strings.
+    //
+    // 
+    // 0 - Digit placeholder. If the value being
+    // formatted has a digit in the position where the '0' appears in the format
+    // string, then that digit is copied to the output string. Otherwise, a '0' is
+    // stored in that position in the output string. The position of the leftmost
+    // '0' before the decimal point and the rightmost '0' after the decimal point
+    // determines the range of digits that are always present in the output
+    // string.
+    //
+    // # - Digit placeholder. If the value being
+    // formatted has a digit in the position where the '#' appears in the format
+    // string, then that digit is copied to the output string. Otherwise, nothing
+    // is stored in that position in the output string.
+    //
+    // . - Decimal point. The first '.' character
+    // in the format string determines the location of the decimal separator in the
+    // formatted value; any additional '.' characters are ignored. The actual
+    // character used as a the decimal separator in the output string is given by
+    // the NumberFormatInfo used to format the number.
+    //
+    // , - Thousand separator and number scaling.
+    // The ',' character serves two purposes. First, if the format string contains
+    // a ',' character between two digit placeholders (0 or #) and to the left of
+    // the decimal point if one is present, then the output will have thousand
+    // separators inserted between each group of three digits to the left of the
+    // decimal separator. The actual character used as a the decimal separator in
+    // the output string is given by the NumberFormatInfo used to format the
+    // number. Second, if the format string contains one or more ',' characters
+    // immediately to the left of the decimal point, or after the last digit
+    // placeholder if there is no decimal point, then the number will be divided by
+    // 1000 times the number of ',' characters before it is formatted. For example,
+    // the format string '0,,' will represent 100 million as just 100. Use of the
+    // ',' character to indicate scaling does not also cause the formatted number
+    // to have thousand separators. Thus, to scale a number by 1 million and insert
+    // thousand separators you would use the format string '#,##0,,'.
+    //
+    // % - Percentage placeholder. The presence of
+    // a '%' character in the format string causes the number to be multiplied by
+    // 100 before it is formatted. The '%' character itself is inserted in the
+    // output string where it appears in the format string.
+    //
+    // E+ E- e+ e-   - Scientific notation.
+    // If any of the strings 'E+', 'E-', 'e+', or 'e-' are present in the format
+    // string and are immediately followed by at least one '0' character, then the
+    // number is formatted using scientific notation with an 'E' or 'e' inserted
+    // between the number and the exponent. The number of '0' characters following
+    // the scientific notation indicator determines the minimum number of digits to
+    // output for the exponent. The 'E+' and 'e+' formats indicate that a sign
+    // character (plus or minus) should always precede the exponent. The 'E-' and
+    // 'e-' formats indicate that a sign character should only precede negative
+    // exponents.
+    //
+    // \ - Literal character. A backslash character
+    // causes the next character in the format string to be copied to the output
+    // string as-is. The backslash itself isn't copied, so to place a backslash
+    // character in the output string, use two backslashes (\\) in the format
+    // string.
+    //
+    // 'ABC' "ABC" - Literal string. Characters
+    // enclosed in single or double quotation marks are copied to the output string
+    // as-is and do not affect formatting.
+    //
+    // ; - Section separator. The ';' character is
+    // used to separate sections for positive, negative, and zero numbers in the
+    // format string.
+    //
+    // Other - All other characters are copied to
+    // the output string in the position they appear.
+    //
+    // For fixed point formats (formats not containing an 'E+', 'E-', 'e+', or
+    // 'e-'), the number is rounded to as many decimal places as there are digit
+    // placeholders to the right of the decimal point. If the format string does
+    // not contain a decimal point, the number is rounded to the nearest
+    // integer. If the number has more digits than there are digit placeholders to
+    // the left of the decimal point, the extra digits are copied to the output
+    // string immediately before the first digit placeholder.
+    //
+    // For scientific formats, the number is rounded to as many significant digits
+    // as there are digit placeholders in the format string.
+    //
+    // To allow for different formatting of positive, negative, and zero values, a
+    // user-defined format string may contain up to three sections separated by
+    // semicolons. The results of having one, two, or three sections in the format
+    // string are described in the table below.
+    //
+    // Sections:
+    //
+    // One - The format string applies to all values.
+    //
+    // Two - The first section applies to positive values
+    // and zeros, and the second section applies to negative values. If the number
+    // to be formatted is negative, but becomes zero after rounding according to
+    // the format in the second section, then the resulting zero is formatted
+    // according to the first section.
+    //
+    // Three - The first section applies to positive
+    // values, the second section applies to negative values, and the third section
+    // applies to zeros. The second section may be left empty (by having no
+    // characters between the semicolons), in which case the first section applies
+    // to all non-zero values. If the number to be formatted is non-zero, but
+    // becomes zero after rounding according to the format in the first or second
+    // section, then the resulting zero is formatted according to the third
+    // section.
+    //
+    // For both standard and user-defined formatting operations on values of type
+    // float and double, if the value being formatted is a NaN (Not
+    // a Number) or a positive or negative infinity, then regardless of the format
+    // string, the resulting string is given by the NaNSymbol,
+    // PositiveInfinitySymbol, or NegativeInfinitySymbol property of
+    // the NumberFormatInfo used to format the number.
+
+    internal static partial class Number
+    {
+        internal const int DecimalPrecision = 29; // Decimal.DecCalc also uses this value
+        private const int FloatPrecision = 7;
+        private const int DoublePrecision = 15;
+        private const int ScaleNAN = unchecked((int)0x80000000);
+        private const int ScaleINF = 0x7FFFFFFF;
+        private const int MaxUInt32DecDigits = 10;
+        private const int CharStackBufferSize = 32;
+        private const string PosNumberFormat = "#";
+
+        private static readonly string[] s_posCurrencyFormats =
+        {
+            "$#", "#$", "$ #", "# $"
+        };
+
+        private static readonly string[] s_negCurrencyFormats =
+        {
+            "($#)", "-$#", "$-#", "$#-",
+            "(#$)", "-#$", "#-$", "#$-",
+            "-# $", "-$ #", "# $-", "$ #-",
+            "$ -#", "#- $", "($ #)", "(# $)"
+        };
+
+        private static readonly string[] s_posPercentFormats =
+        {
+            "# %", "#%", "%#", "% #"
+        };
+
+        private static readonly string[] s_negPercentFormats =
+        {
+            "-# %", "-#%", "-%#",
+            "%-#", "%#-",
+            "#-%", "#%-",
+            "-% #", "# %-", "% #-",
+            "% -#", "#- %"
+        };
+
+        private static readonly string[] s_negNumberFormats =
+        {
+            "(#)", "-#", "- #", "#-", "# -",
+        };
+
+        public static string FormatDecimal(decimal value, ReadOnlySpan<char> format, NumberFormatInfo info)
+        {
+            char fmt = ParseFormatSpecifier(format, out int digits);
+
+            NumberBuffer number = default;
+            DecimalToNumber(value, ref number);
+
+            ValueStringBuilder sb;
+            unsafe
+            {
+                char* stackPtr = stackalloc char[CharStackBufferSize];
+                sb = new ValueStringBuilder(new Span<char>(stackPtr, CharStackBufferSize));
+            }
+
+            if (fmt != 0)
+            {
+                NumberToString(ref sb, ref number, fmt, digits, info, isDecimal:true);
+            }
+            else
+            {
+                NumberToStringFormat(ref sb, ref number, format, info);
+            }
+
+            return sb.ToString();
+        }
+
+        public static bool TryFormatDecimal(decimal value, ReadOnlySpan<char> format, NumberFormatInfo info, Span<char> destination, out int charsWritten)
+        {
+            char fmt = ParseFormatSpecifier(format, out int digits);
+
+            NumberBuffer number = default;
+            DecimalToNumber(value, ref number);
+
+            ValueStringBuilder sb;
+            unsafe
+            {
+                char* stackPtr = stackalloc char[CharStackBufferSize];
+                sb = new ValueStringBuilder(new Span<char>(stackPtr, CharStackBufferSize));
+            }
+
+            if (fmt != 0)
+            {
+                NumberToString(ref sb, ref number, fmt, digits, info, isDecimal: true);
+            }
+            else
+            {
+                NumberToStringFormat(ref sb, ref number, format, info);
+            }
+
+            return sb.TryCopyTo(destination, out charsWritten);
+        }
+
+        private static unsafe void DecimalToNumber(decimal value, ref NumberBuffer number)
+        {
+            decimal d = value;
+
+            char* buffer = number.digits;
+            number.precision = DecimalPrecision;
+            number.sign = d.IsNegative;
+
+            char* p = buffer + DecimalPrecision;
+            while ((d.Mid | d.High) != 0)
+            {
+                p = UInt32ToDecChars(p, decimal.DecDivMod1E9(ref d), 9);
+            }
+            p = UInt32ToDecChars(p, d.Low, 0);
+
+            int i = (int)(buffer + DecimalPrecision - p);
+            number.scale = i - d.Scale;
+
+            char* dst = number.digits;
+            while (--i >= 0)
+            {
+                *dst++ = *p++;
+            }
+            *dst = '\0';
+        }
+
+        public static string FormatDouble(double value, string format, NumberFormatInfo info)
+        {
+            Span<char> stackBuffer = stackalloc char[CharStackBufferSize];
+            var sb = new ValueStringBuilder(stackBuffer);
+            return FormatDouble(ref sb, value, format, info) ?? sb.ToString();
+        }
+
+        public static bool TryFormatDouble(double value, ReadOnlySpan<char> format, NumberFormatInfo info, Span<char> destination, out int charsWritten)
+        {
+            Span<char> stackBuffer = stackalloc char[CharStackBufferSize];
+            var sb = new ValueStringBuilder(stackBuffer);
+            string s = FormatDouble(ref sb, value, format, info);
+            return s != null ?
+                TryCopyTo(s, destination, out charsWritten) :
+                sb.TryCopyTo(destination, out charsWritten);
+        }
+
+        /// <summary>Formats the specified value according to the specified format and info.</summary>
+        /// <returns>
+        /// Non-null if an existing string can be returned, in which case the builder will be unmodified.
+        /// Null if no existing string was returned, in which case the formatted output is in the builder.
+        /// </returns>
+        private static string FormatDouble(ref ValueStringBuilder sb, double value, ReadOnlySpan<char> format, NumberFormatInfo info)
+        {
+            char fmt = ParseFormatSpecifier(format, out int digits);
+            int precision = DoublePrecision;
+            NumberBuffer number = default;
+
+            switch (fmt)
+            {
+                case 'R':
+                case 'r':
+                    {
+                        // In order to give numbers that are both friendly to display and round-trippable, we parse the
+                        // number using 15 digits and then determine if it round trips to the same value. If it does, we
+                        // convert that NUMBER to a string, otherwise we reparse using 17 digits and display that.
+                        DoubleToNumber(value, DoublePrecision, ref number);
+                        if (number.scale == ScaleNAN)
+                        {
+                            return info.NaNSymbol;
+                        }
+                        else if (number.scale == ScaleINF)
+                        {
+                            return number.sign ? info.NegativeInfinitySymbol : info.PositiveInfinitySymbol;
+                        }
+
+                        if (NumberToDouble(ref number) == value)
+                        {
+                            NumberToString(ref sb, ref number, 'G', DoublePrecision, info, isDecimal: false);
+                        }
+                        else
+                        {
+                            DoubleToNumber(value, 17, ref number);
+                            NumberToString(ref sb, ref number, 'G', 17, info, isDecimal: false);
+                        }
+
+                        return null;
+                    }
+
+                case 'E':
+                case 'e':
+                    // Round values less than E14 to 15 digits
+                    if (digits > 14)
+                    {
+                        precision = 17;
+                    }
+                    break;
+
+                case 'G':
+                case 'g':
+                    // Round values less than G15 to 15 digits. G16 and G17 will not be touched.
+                    if (digits > 15)
+                    {
+                        precision = 17;
+                    }
+                    break;
+            }
+
+            DoubleToNumber(value, precision, ref number);
+            if (number.scale == ScaleNAN)
+            {
+                return info.NaNSymbol;
+            }
+            else if (number.scale == ScaleINF)
+            {
+                return number.sign ? info.NegativeInfinitySymbol : info.PositiveInfinitySymbol;
+            }
+
+            if (fmt != 0)
+            {
+                NumberToString(ref sb, ref number, fmt, digits, info, isDecimal: false);
+            }
+            else
+            {
+                NumberToStringFormat(ref sb, ref number, format, info);
+            }
+
+            return null;
+        }
+
+        public static string FormatSingle(float value, string format, NumberFormatInfo info)
+        {
+            Span<char> stackBuffer = stackalloc char[CharStackBufferSize];
+            var sb = new ValueStringBuilder(stackBuffer);
+            return FormatSingle(ref sb, value, format, info) ?? sb.ToString();
+        }
+
+        public static bool TryFormatSingle(float value, ReadOnlySpan<char> format, NumberFormatInfo info, Span<char> destination, out int charsWritten)
+        {
+            Span<char> stackBuffer = stackalloc char[CharStackBufferSize];
+            var sb = new ValueStringBuilder(stackBuffer);
+            string s = FormatSingle(ref sb, value, format, info);
+            return s != null ?
+                TryCopyTo(s, destination, out charsWritten) :
+                sb.TryCopyTo(destination, out charsWritten);
+        }
+
+        /// <summary>Formats the specified value according to the specified format and info.</summary>
+        /// <returns>
+        /// Non-null if an existing string can be returned, in which case the builder will be unmodified.
+        /// Null if no existing string was returned, in which case the formatted output is in the builder.
+        /// </returns>
+        private static string FormatSingle(ref ValueStringBuilder sb, float value, ReadOnlySpan<char> format, NumberFormatInfo info)
+        {
+            char fmt = ParseFormatSpecifier(format, out int digits);
+            int precision = FloatPrecision;
+            NumberBuffer number = default;
+
+            switch (fmt)
+            {
+                case 'R':
+                case 'r':
+                    {
+                        // In order to give numbers that are both friendly to display and round-trippable, we parse the
+                        // number using 7 digits and then determine if it round trips to the same value. If it does, we
+                        // convert that NUMBER to a string, otherwise we reparse using 9 digits and display that.
+                        DoubleToNumber(value, FloatPrecision, ref number);
+                        if (number.scale == ScaleNAN)
+                        {
+                            return info.NaNSymbol;
+                        }
+                        else if (number.scale == ScaleINF)
+                        {
+                            return number.sign ? info.NegativeInfinitySymbol : info.PositiveInfinitySymbol;
+                        }
+
+                        if ((float)NumberToDouble(ref number) == value)
+                        {
+                            NumberToString(ref sb, ref number, 'G', FloatPrecision, info, isDecimal: false);
+                        }
+                        else
+                        {
+                            DoubleToNumber(value, 9, ref number);
+                            NumberToString(ref sb, ref number, 'G', 9, info, isDecimal: false);
+                        }
+                        return null;
+                    }
+
+                case 'E':
+                case 'e':
+                    // Round values less than E14 to 15 digits.
+                    if (digits > 6)
+                    {
+                        precision = 9;
+                    }
+                    break;
+
+                case 'G':
+                case 'g':
+                    // Round values less than G15 to 15 digits. G16 and G17 will not be touched.
+                    if (digits > 7)
+                    {
+                        precision = 9;
+                    }
+                    break;
+            }
+
+            DoubleToNumber(value, precision, ref number);
+            if (number.scale == ScaleNAN)
+            {
+                return info.NaNSymbol;
+            }
+            else if (number.scale == ScaleINF)
+            {
+                return number.sign ? info.NegativeInfinitySymbol : info.PositiveInfinitySymbol;
+            }
+
+            if (fmt != 0)
+            {
+                NumberToString(ref sb, ref number, fmt, digits, info, false);
+            }
+            else
+            {
+                NumberToStringFormat(ref sb, ref number, format, info);
+            }
+            return null;
+        }
+
+        private static bool TryCopyTo(string source, Span<char> destination, out int charsWritten)
+        {
+            Debug.Assert(source != null);
+
+            if (source.AsSpan().TryCopyTo(destination))
+            {
+                charsWritten = source.Length;
+                return true;
+            }
+
+            charsWritten = 0;
+            return false;
+        }
+
+        public static string FormatInt32(int value, ReadOnlySpan<char> format, IFormatProvider provider)
+        {
+            // Fast path for default format with a non-negative value
+            if (value >= 0 && format.Length == 0)
+            {
+                return UInt32ToDecStr((uint)value, digits: -1);
+            }
+
+            char fmt = ParseFormatSpecifier(format, out int digits);
+            NumberFormatInfo info = NumberFormatInfo.GetInstance(provider);
+
+            char fmtUpper = (char)(fmt & 0xFFDF); // ensure fmt is upper-cased for purposes of comparison
+            if ((fmtUpper == 'G' && digits < 1) || fmtUpper == 'D')
+            {
+                return value >= 0 ?
+                    UInt32ToDecStr((uint)value, digits) :
+                    NegativeInt32ToDecStr(value, digits, info.NegativeSign);
+            }
+            else if (fmtUpper == 'X')
+            {
+                // The fmt-(X-A+10) hack has the effect of dictating whether we produce uppercase or lowercase
+                // hex numbers for a-f. 'X' as the fmt code produces uppercase. 'x' as the format code produces lowercase.
+                return Int32ToHexStr(value, (char)(fmt - ('X' - 'A' + 10)), digits);
+            }
+            else
+            {
+                NumberBuffer number = default;
+                Int32ToNumber(value, ref number);
+                ValueStringBuilder sb;
+                unsafe
+                {
+                    char* stackPtr = stackalloc char[CharStackBufferSize];
+                    sb = new ValueStringBuilder(new Span<char>(stackPtr, CharStackBufferSize));
+                }
+                if (fmt != 0)
+                {
+                    NumberToString(ref sb, ref number, fmt, digits, info, false);
+                }
+                else
+                {
+                    NumberToStringFormat(ref sb, ref number, format, info);
+                }
+                return sb.ToString();
+            }
+        }
+
+        public static bool TryFormatInt32(int value, ReadOnlySpan<char> format, IFormatProvider provider, Span<char> destination, out int charsWritten)
+        {
+            // Fast path for default format with a non-negative value
+            if (value >= 0 && format.Length == 0)
+            {
+                return TryUInt32ToDecStr((uint)value, digits: -1, destination, out charsWritten);
+            }
+
+            char fmt = ParseFormatSpecifier(format, out int digits);
+            NumberFormatInfo info = NumberFormatInfo.GetInstance(provider);
+
+            char fmtUpper = (char)(fmt & 0xFFDF); // ensure fmt is upper-cased for purposes of comparison
+            if ((fmtUpper == 'G' && digits < 1) || fmtUpper == 'D')
+            {
+                return value >= 0 ?
+                    TryUInt32ToDecStr((uint)value, digits, destination, out charsWritten) :
+                    TryNegativeInt32ToDecStr(value, digits, info.NegativeSign, destination, out charsWritten);
+            }
+            else if (fmtUpper == 'X')
+            {
+                // The fmt-(X-A+10) hack has the effect of dictating whether we produce uppercase or lowercase
+                // hex numbers for a-f. 'X' as the fmt code produces uppercase. 'x' as the format code produces lowercase.
+                return TryInt32ToHexStr(value, (char)(fmt - ('X' - 'A' + 10)), digits, destination, out charsWritten);
+            }
+            else
+            {
+                NumberBuffer number = default;
+                Int32ToNumber(value, ref number);
+                ValueStringBuilder sb;
+                unsafe
+                {
+                    char* stackPtr = stackalloc char[CharStackBufferSize];
+                    sb = new ValueStringBuilder(new Span<char>(stackPtr, CharStackBufferSize));
+                }
+                if (fmt != 0)
+                {
+                    NumberToString(ref sb, ref number, fmt, digits, info, false);
+                }
+                else
+                {
+                    NumberToStringFormat(ref sb, ref number, format, info);
+                }
+                return sb.TryCopyTo(destination, out charsWritten);
+            }
+        }
+
+        public static string FormatUInt32(uint value, ReadOnlySpan<char> format, IFormatProvider provider)
+        {
+            // Fast path for default format
+            if (format.Length == 0)
+            {
+                return UInt32ToDecStr(value, digits: -1);
+            }
+
+            char fmt = ParseFormatSpecifier(format, out int digits);
+            NumberFormatInfo info = NumberFormatInfo.GetInstance(provider);
+
+            char fmtUpper = (char)(fmt & 0xFFDF); // ensure fmt is upper-cased for purposes of comparison
+            if ((fmtUpper == 'G' && digits < 1) || fmtUpper == 'D')
+            {
+                return UInt32ToDecStr(value, digits);
+            }
+            else if (fmtUpper == 'X')
+            {
+                // The fmt-(X-A+10) hack has the effect of dictating whether we produce uppercase or lowercase
+                // hex numbers for a-f. 'X' as the fmt code produces uppercase. 'x' as the format code produces lowercase.
+                return Int32ToHexStr((int)value, (char)(fmt - ('X' - 'A' + 10)), digits);
+            }
+            else
+            {
+                NumberBuffer number = default;
+                UInt32ToNumber(value, ref number);
+                ValueStringBuilder sb;
+                unsafe
+                {
+                    char* stackPtr = stackalloc char[CharStackBufferSize];
+                    sb = new ValueStringBuilder(new Span<char>(stackPtr, CharStackBufferSize));
+                }
+                if (fmt != 0)
+                {
+                    NumberToString(ref sb, ref number, fmt, digits, info, false);
+                }
+                else
+                {
+                    NumberToStringFormat(ref sb, ref number, format, info);
+                }
+                return sb.ToString();
+            }
+        }
+
+        public static bool TryFormatUInt32(uint value, ReadOnlySpan<char> format, IFormatProvider provider, Span<char> destination, out int charsWritten)
+        {
+            // Fast path for default format
+            if (format.Length == 0)
+            {
+                return TryUInt32ToDecStr(value, digits: -1, destination, out charsWritten);
+            }
+
+            char fmt = ParseFormatSpecifier(format, out int digits);
+            NumberFormatInfo info = NumberFormatInfo.GetInstance(provider);
+
+            char fmtUpper = (char)(fmt & 0xFFDF); // ensure fmt is upper-cased for purposes of comparison
+            if ((fmtUpper == 'G' && digits < 1) || fmtUpper == 'D')
+            {
+                return TryUInt32ToDecStr(value, digits, destination, out charsWritten);
+            }
+            else if (fmtUpper == 'X')
+            {
+                // The fmt-(X-A+10) hack has the effect of dictating whether we produce uppercase or lowercase
+                // hex numbers for a-f. 'X' as the fmt code produces uppercase. 'x' as the format code produces lowercase.
+                return TryInt32ToHexStr((int)value, (char)(fmt - ('X' - 'A' + 10)), digits, destination, out charsWritten);
+            }
+            else
+            {
+                NumberBuffer number = default;
+                UInt32ToNumber(value, ref number);
+                ValueStringBuilder sb;
+                unsafe
+                {
+                    char* stackPtr = stackalloc char[CharStackBufferSize];
+                    sb = new ValueStringBuilder(new Span<char>(stackPtr, CharStackBufferSize));
+                }
+                if (fmt != 0)
+                {
+                    NumberToString(ref sb, ref number, fmt, digits, info, false);
+                }
+                else
+                {
+                    NumberToStringFormat(ref sb, ref number, format, info);
+                }
+                return sb.TryCopyTo(destination, out charsWritten);
+            }
+        }
+
+        public static string FormatInt64(long value, ReadOnlySpan<char> format, IFormatProvider provider)
+        {
+            // Fast path for default format with a non-negative value
+            if (value >= 0 && format.Length == 0)
+            {
+                return UInt64ToDecStr((ulong)value, digits: -1);
+            }
+
+            char fmt = ParseFormatSpecifier(format, out int digits);
+            NumberFormatInfo info = NumberFormatInfo.GetInstance(provider);
+
+            char fmtUpper = (char)(fmt & 0xFFDF); // ensure fmt is upper-cased for purposes of comparison
+            if ((fmtUpper == 'G' && digits < 1) || fmtUpper == 'D')
+            {
+                return value >= 0 ?
+                    UInt64ToDecStr((ulong)value, digits) :
+                    NegativeInt64ToDecStr(value, digits, info.NegativeSign);
+            }
+            else if (fmtUpper == 'X')
+            {
+                // The fmt-(X-A+10) hack has the effect of dictating whether we produce uppercase or lowercase
+                // hex numbers for a-f. 'X' as the fmt code produces uppercase. 'x' as the format code
+                // produces lowercase.
+                return Int64ToHexStr(value, (char)(fmt - ('X' - 'A' + 10)), digits);
+            }
+            else
+            {
+                NumberBuffer number = default;
+                Int64ToNumber(value, ref number);
+                ValueStringBuilder sb;
+                unsafe
+                {
+                    char* stackPtr = stackalloc char[CharStackBufferSize];
+                    sb = new ValueStringBuilder(new Span<char>(stackPtr, CharStackBufferSize));
+                }
+                if (fmt != 0)
+                {
+                    NumberToString(ref sb, ref number, fmt, digits, info, false);
+                }
+                else
+                {
+                    NumberToStringFormat(ref sb, ref number, format, info);
+                }
+                return sb.ToString();
+            }
+        }
+
+        public static bool TryFormatInt64(long value, ReadOnlySpan<char> format, IFormatProvider provider, Span<char> destination, out int charsWritten)
+        {
+            // Fast path for default format with a non-negative value
+            if (value >= 0 && format.Length == 0)
+            {
+                return TryUInt64ToDecStr((ulong)value, digits: -1, destination, out charsWritten);
+            }
+
+            char fmt = ParseFormatSpecifier(format, out int digits);
+            NumberFormatInfo info = NumberFormatInfo.GetInstance(provider);
+
+            char fmtUpper = (char)(fmt & 0xFFDF); // ensure fmt is upper-cased for purposes of comparison
+            if ((fmtUpper == 'G' && digits < 1) || fmtUpper == 'D')
+            {
+                return value >= 0 ?
+                    TryUInt64ToDecStr((ulong)value, digits, destination, out charsWritten) :
+                    TryNegativeInt64ToDecStr(value, digits, info.NegativeSign, destination, out charsWritten);
+            }
+            else if (fmtUpper == 'X')
+            {
+                // The fmt-(X-A+10) hack has the effect of dictating whether we produce uppercase or lowercase
+                // hex numbers for a-f. 'X' as the fmt code produces uppercase. 'x' as the format code
+                // produces lowercase.
+                return TryInt64ToHexStr(value, (char)(fmt - ('X' - 'A' + 10)), digits, destination, out charsWritten);
+            }
+            else
+            {
+                NumberBuffer number = default;
+                Int64ToNumber(value, ref number);
+                ValueStringBuilder sb;
+                unsafe
+                {
+                    char* stackPtr = stackalloc char[CharStackBufferSize];
+                    sb = new ValueStringBuilder(new Span<char>(stackPtr, CharStackBufferSize));
+                }
+                if (fmt != 0)
+                {
+                    NumberToString(ref sb, ref number, fmt, digits, info, false);
+                }
+                else
+                {
+                    NumberToStringFormat(ref sb, ref number, format, info);
+                }
+                return sb.TryCopyTo(destination, out charsWritten);
+            }
+        }
+
+        public static string FormatUInt64(ulong value, ReadOnlySpan<char> format, IFormatProvider provider)
+        {
+            // Fast path for default format
+            if (format.Length == 0)
+            {
+                return UInt64ToDecStr(value, digits: -1);
+            }
+
+            char fmt = ParseFormatSpecifier(format, out int digits);
+            NumberFormatInfo info = NumberFormatInfo.GetInstance(provider);
+
+            char fmtUpper = (char)(fmt & 0xFFDF); // ensure fmt is upper-cased for purposes of comparison
+            if ((fmtUpper == 'G' && digits < 1) || fmtUpper == 'D')
+            {
+                return UInt64ToDecStr(value, digits);
+            }
+            else if (fmtUpper == 'X')
+            {
+                // The fmt-(X-A+10) hack has the effect of dictating whether we produce uppercase or lowercase
+                // hex numbers for a-f. 'X' as the fmt code produces uppercase. 'x' as the format code
+                // produces lowercase.
+                return Int64ToHexStr((long)value, (char)(fmt - ('X' - 'A' + 10)), digits);
+            }
+            else
+            {
+                NumberBuffer number = default;
+                UInt64ToNumber(value, ref number);
+                ValueStringBuilder sb;
+                unsafe
+                {
+                    char* stackPtr = stackalloc char[CharStackBufferSize];
+                    sb = new ValueStringBuilder(new Span<char>(stackPtr, CharStackBufferSize));
+                }
+                if (fmt != 0)
+                {
+                    NumberToString(ref sb, ref number, fmt, digits, info, false);
+                }
+                else
+                {
+                    NumberToStringFormat(ref sb, ref number, format, info);
+                }
+                return sb.ToString();
+            }
+        }
+
+        public static bool TryFormatUInt64(ulong value, ReadOnlySpan<char> format, IFormatProvider provider, Span<char> destination, out int charsWritten)
+        {
+            // Fast path for default format
+            if (format.Length == 0)
+            {
+                return TryUInt64ToDecStr(value, digits: -1, destination, out charsWritten);
+            }
+
+            char fmt = ParseFormatSpecifier(format, out int digits);
+            NumberFormatInfo info = NumberFormatInfo.GetInstance(provider);
+
+            char fmtUpper = (char)(fmt & 0xFFDF); // ensure fmt is upper-cased for purposes of comparison
+            if ((fmtUpper == 'G' && digits < 1) || fmtUpper == 'D')
+            {
+                return TryUInt64ToDecStr(value, digits, destination, out charsWritten);
+            }
+            else if (fmtUpper == 'X')
+            {
+                // The fmt-(X-A+10) hack has the effect of dictating whether we produce uppercase or lowercase
+                // hex numbers for a-f. 'X' as the fmt code produces uppercase. 'x' as the format code
+                // produces lowercase.
+                return TryInt64ToHexStr((long)value, (char)(fmt - ('X' - 'A' + 10)), digits, destination, out charsWritten);
+            }
+            else
+            {
+                NumberBuffer number = default;
+                UInt64ToNumber(value, ref number);
+                ValueStringBuilder sb;
+                unsafe
+                {
+                    char* stackPtr = stackalloc char[CharStackBufferSize];
+                    sb = new ValueStringBuilder(new Span<char>(stackPtr, CharStackBufferSize));
+                }
+                if (fmt != 0)
+                {
+                    NumberToString(ref sb, ref number, fmt, digits, info, false);
+                }
+                else
+                {
+                    NumberToStringFormat(ref sb, ref number, format, info);
+                }
+                return sb.TryCopyTo(destination, out charsWritten);
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)] // called from only one location
+        private static unsafe void Int32ToNumber(int value, ref NumberBuffer number)
+        {
+            number.precision = Int32Precision;
+
+            if (value >= 0)
+            {
+                number.sign = false;
+            }
+            else
+            {
+                number.sign = true;
+                value = -value;
+            }
+
+            char* buffer = number.digits;
+            char* p = UInt32ToDecChars(buffer + Int32Precision, (uint)value, 0);
+            int i = (int)(buffer + Int32Precision - p);
+
+            number.scale = i;
+
+            char* dst = number.digits;
+            while (--i >= 0)
+                *dst++ = *p++;
+            *dst = '\0';
+        }
+
+        private static unsafe string NegativeInt32ToDecStr(int value, int digits, string sNegative)
+        {
+            Debug.Assert(value < 0);
+
+            if (digits < 1)
+                digits = 1;
+
+            int bufferLength = Math.Max(digits, FormattingHelpers.CountDigits((uint)(-value))) + sNegative.Length;
+            string result = string.FastAllocateString(bufferLength);
+            fixed (char* buffer = result)
+            {
+                char* p = UInt32ToDecChars(buffer + bufferLength, (uint)(-value), digits);
+                Debug.Assert(p == buffer + sNegative.Length);
+
+                for (int i = sNegative.Length - 1; i >= 0; i--)
+                {
+                    *(--p) = sNegative[i];
+                }
+                Debug.Assert(p == buffer);
+            }
+            return result;
+        }
+
+        private static unsafe bool TryNegativeInt32ToDecStr(int value, int digits, string sNegative, Span<char> destination, out int charsWritten)
+        {
+            Debug.Assert(value < 0);
+
+            if (digits < 1)
+                digits = 1;
+
+            int bufferLength = Math.Max(digits, FormattingHelpers.CountDigits((uint)(-value))) + sNegative.Length;
+            if (bufferLength > destination.Length)
+            {
+                charsWritten = 0;
+                return false;
+            }
+
+            charsWritten = bufferLength;
+            fixed (char* buffer = &MemoryMarshal.GetReference(destination))
+            {
+                char* p = UInt32ToDecChars(buffer + bufferLength, (uint)(-value), digits);
+                Debug.Assert(p == buffer + sNegative.Length);
+
+                for (int i = sNegative.Length - 1; i >= 0; i--)
+                {
+                    *(--p) = sNegative[i];
+                }
+                Debug.Assert(p == buffer);
+            }
+            return true;
+        }
+
+        private static unsafe string Int32ToHexStr(int value, char hexBase, int digits)
+        {
+            if (digits < 1)
+                digits = 1;
+
+            int bufferLength = Math.Max(digits, FormattingHelpers.CountHexDigits((uint)value));
+            string result = string.FastAllocateString(bufferLength);
+            fixed (char* buffer = result)
+            {
+                char* p = Int32ToHexChars(buffer + bufferLength, (uint)value, hexBase, digits);
+                Debug.Assert(p == buffer);
+            }
+            return result;
+        }
+
+        private static unsafe bool TryInt32ToHexStr(int value, char hexBase, int digits, Span<char> destination, out int charsWritten)
+        {
+            if (digits < 1)
+                digits = 1;
+
+            int bufferLength = Math.Max(digits, FormattingHelpers.CountHexDigits((uint)value));
+            if (bufferLength > destination.Length)
+            {
+                charsWritten = 0;
+                return false;
+            }
+
+            charsWritten = bufferLength;
+            fixed (char* buffer = &MemoryMarshal.GetReference(destination))
+            {
+                char* p = Int32ToHexChars(buffer + bufferLength, (uint)value, hexBase, digits);
+                Debug.Assert(p == buffer);
+            }
+            return true;
+        }
+
+        private static unsafe char* Int32ToHexChars(char* buffer, uint value, int hexBase, int digits)
+        {
+            while (--digits >= 0 || value != 0)
+            {
+                byte digit = (byte)(value & 0xF);
+                *(--buffer) = (char)(digit + (digit < 10 ? (byte)'0' : hexBase));
+                value >>= 4;
+            }
+            return buffer;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)] // called from only one location
+        private static unsafe void UInt32ToNumber(uint value, ref NumberBuffer number)
+        {
+            number.precision = UInt32Precision;
+            number.sign = false;
+
+            char* buffer = number.digits;
+            char* p = UInt32ToDecChars(buffer + UInt32Precision, value, 0);
+            int i = (int)(buffer + UInt32Precision - p);
+            number.scale = i;
+
+            char* dst = number.digits;
+            while (--i >= 0)
+                *dst++ = *p++;
+            *dst = '\0';
+        }
+
+        internal static unsafe char* UInt32ToDecChars(char* bufferEnd, uint value, int digits)
+        {
+            while (--digits >= 0 || value != 0)
+            {
+                // TODO https://github.com/dotnet/coreclr/issues/3439
+                uint newValue = value / 10;
+                *(--bufferEnd) = (char)(value - (newValue * 10) + '0');
+                value = newValue;
+            }
+            return bufferEnd;
+        }
+
+        private static unsafe string UInt32ToDecStr(uint value, int digits)
+        {
+            int bufferLength = Math.Max(digits, FormattingHelpers.CountDigits(value));
+            string result = string.FastAllocateString(bufferLength);
+            fixed (char* buffer = result)
+            {
+                char* p = buffer + bufferLength;
+                if (digits <= 1)
+                {
+                    do
+                    {
+                        // TODO https://github.com/dotnet/coreclr/issues/3439
+                        uint div = value / 10;
+                        *(--p) = (char)('0' + value - (div * 10));
+                        value = div;
+                    }
+                    while (value != 0);
+                }
+                else
+                {
+                    p = UInt32ToDecChars(p, value, digits);
+                }
+                Debug.Assert(p == buffer);
+            }
+            return result;
+        }
+
+        private static unsafe bool TryUInt32ToDecStr(uint value, int digits, Span<char> destination, out int charsWritten)
+        {
+            int bufferLength = Math.Max(digits, FormattingHelpers.CountDigits(value));
+            if (bufferLength > destination.Length)
+            {
+                charsWritten = 0;
+                return false;
+            }
+
+            charsWritten = bufferLength;
+            fixed (char* buffer = &MemoryMarshal.GetReference(destination))
+            {
+                char* p = buffer + bufferLength;
+                if (digits <= 1)
+                {
+                    do
+                    {
+                        // TODO https://github.com/dotnet/coreclr/issues/3439
+                        uint div = value / 10;
+                        *(--p) = (char)('0' + value - (div * 10));
+                        value = div;
+                    }
+                    while (value != 0);
+                }
+                else
+                {
+                    p = UInt32ToDecChars(p, value, digits);
+                }
+                Debug.Assert(p == buffer);
+            }
+            return true;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static unsafe bool TryCopyTo(char* src, int length, Span<char> destination, out int charsWritten)
+        {
+            if (new ReadOnlySpan<char>(src, length).TryCopyTo(destination))
+            {
+                charsWritten = length;
+                return true;
+            }
+            else
+            {
+                charsWritten = 0;
+                return false;
+            }
+        }
+
+        private static unsafe void Int64ToNumber(long input, ref NumberBuffer number)
+        {
+            ulong value = (ulong)input;
+            number.sign = input < 0;
+            number.precision = Int64Precision;
+            if (number.sign)
+            {
+                value = (ulong)(-input);
+            }
+
+            char* buffer = number.digits;
+            char* p = buffer + Int64Precision;
+            while (High32(value) != 0)
+                p = UInt32ToDecChars(p, Int64DivMod1E9(ref value), 9);
+            p = UInt32ToDecChars(p, Low32(value), 0);
+            int i = (int)(buffer + Int64Precision - p);
+
+            number.scale = i;
+
+            char* dst = number.digits;
+            while (--i >= 0)
+                *dst++ = *p++;
+            *dst = '\0';
+        }
+
+        private static unsafe string NegativeInt64ToDecStr(long input, int digits, string sNegative)
+        {
+            Debug.Assert(input < 0);
+
+            if (digits < 1)
+            {
+                digits = 1;
+            }
+
+            ulong value = (ulong)(-input);
+
+            int bufferLength = Math.Max(digits, FormattingHelpers.CountDigits(value)) + sNegative.Length;
+            string result = string.FastAllocateString(bufferLength);
+            fixed (char* buffer = result)
+            {
+                char* p = buffer + bufferLength;
+                while (High32(value) != 0)
+                {
+                    p = UInt32ToDecChars(p, Int64DivMod1E9(ref value), 9);
+                    digits -= 9;
+                }
+                p = UInt32ToDecChars(p, Low32(value), digits);
+                Debug.Assert(p == buffer + sNegative.Length);
+
+                for (int i = sNegative.Length - 1; i >= 0; i--)
+                {
+                    *(--p) = sNegative[i];
+                }
+                Debug.Assert(p == buffer);
+            }
+            return result;
+        }
+
+        private static unsafe bool TryNegativeInt64ToDecStr(long input, int digits, string sNegative, Span<char> destination, out int charsWritten)
+        {
+            Debug.Assert(input < 0);
+
+            if (digits < 1)
+            {
+                digits = 1;
+            }
+
+            ulong value = (ulong)(-input);
+
+            int bufferLength = Math.Max(digits, FormattingHelpers.CountDigits((ulong)(-input))) + sNegative.Length;
+            if (bufferLength > destination.Length)
+            {
+                charsWritten = 0;
+                return false;
+            }
+
+            charsWritten = bufferLength;
+            fixed (char* buffer = &MemoryMarshal.GetReference(destination))
+            {
+                char* p = buffer + bufferLength;
+                while (High32(value) != 0)
+                {
+                    p = UInt32ToDecChars(p, Int64DivMod1E9(ref value), 9);
+                    digits -= 9;
+                }
+                p = UInt32ToDecChars(p, Low32(value), digits);
+                Debug.Assert(p == buffer + sNegative.Length);
+
+                for (int i = sNegative.Length - 1; i >= 0; i--)
+                {
+                    *(--p) = sNegative[i];
+                }
+                Debug.Assert(p == buffer);
+            }
+            return true;
+        }
+
+        private static unsafe string Int64ToHexStr(long value, char hexBase, int digits)
+        {
+            int bufferLength = Math.Max(digits, FormattingHelpers.CountHexDigits((ulong)value));
+            string result = string.FastAllocateString(bufferLength);
+            fixed (char* buffer = result)
+            {
+                char* p = buffer + bufferLength;
+                if (High32((ulong)value) != 0)
+                {
+                    p = Int32ToHexChars(p, Low32((ulong)value), hexBase, 8);
+                    p = Int32ToHexChars(p, High32((ulong)value), hexBase, digits - 8);
+                }
+                else
+                {
+                    p = Int32ToHexChars(p, Low32((ulong)value), hexBase, Math.Max(digits, 1));
+                }
+                Debug.Assert(p == buffer);
+            }
+            return result;
+        }
+
+        private static unsafe bool TryInt64ToHexStr(long value, char hexBase, int digits, Span<char> destination, out int charsWritten)
+        {
+            int bufferLength = Math.Max(digits, FormattingHelpers.CountHexDigits((ulong)value));
+            if (bufferLength > destination.Length)
+            {
+                charsWritten = 0;
+                return false;
+            }
+
+            charsWritten = bufferLength;
+            fixed (char* buffer = &MemoryMarshal.GetReference(destination))
+            {
+                char* p = buffer + bufferLength;
+                if (High32((ulong)value) != 0)
+                {
+                    p = Int32ToHexChars(p, Low32((ulong)value), hexBase, 8);
+                    p = Int32ToHexChars(p, High32((ulong)value), hexBase, digits - 8);
+                }
+                else
+                {
+                    p = Int32ToHexChars(p, Low32((ulong)value), hexBase, Math.Max(digits, 1));
+                }
+                Debug.Assert(p == buffer);
+            }
+            return true;
+        }
+
+        private static unsafe void UInt64ToNumber(ulong value, ref NumberBuffer number)
+        {
+            number.precision = UInt64Precision;
+            number.sign = false;
+
+            char* buffer = number.digits;
+            char* p = buffer + UInt64Precision;
+
+            while (High32(value) != 0)
+                p = UInt32ToDecChars(p, Int64DivMod1E9(ref value), 9);
+            p = UInt32ToDecChars(p, Low32(value), 0);
+            int i = (int)(buffer + UInt64Precision - p);
+
+            number.scale = i;
+
+            char* dst = number.digits;
+            while (--i >= 0)
+                *dst++ = *p++;
+            *dst = '\0';
+        }
+
+        private static unsafe string UInt64ToDecStr(ulong value, int digits)
+        {
+            if (digits < 1)
+                digits = 1;
+
+            int bufferLength = Math.Max(digits, FormattingHelpers.CountDigits(value));
+            string result = string.FastAllocateString(bufferLength);
+            fixed (char* buffer = result)
+            {
+                char* p = buffer + bufferLength;
+                while (High32(value) != 0)
+                {
+                    p = UInt32ToDecChars(p, Int64DivMod1E9(ref value), 9);
+                    digits -= 9;
+                }
+                p = UInt32ToDecChars(p, Low32(value), digits);
+                Debug.Assert(p == buffer);
+            }
+            return result;
+        }
+
+        private static unsafe bool TryUInt64ToDecStr(ulong value, int digits, Span<char> destination, out int charsWritten)
+        {
+            if (digits < 1)
+                digits = 1;
+
+            int bufferLength = Math.Max(digits, FormattingHelpers.CountDigits(value));
+            if (bufferLength > destination.Length)
+            {
+                charsWritten = 0;
+                return false;
+            }
+
+            charsWritten = bufferLength;
+            fixed (char* buffer = &MemoryMarshal.GetReference(destination))
+            {
+                char* p = buffer + bufferLength;
+                while (High32(value) != 0)
+                {
+                    p = UInt32ToDecChars(p, Int64DivMod1E9(ref value), 9);
+                    digits -= 9;
+                }
+                p = UInt32ToDecChars(p, Low32(value), digits);
+                Debug.Assert(p == buffer);
+            }
+            return true;
+        }
+
+        internal static unsafe char ParseFormatSpecifier(ReadOnlySpan<char> format, out int digits)
+        {
+            char c = default;
+            if (format.Length > 0)
+            {
+                // If the format begins with a symbol, see if it's a standard format
+                // with or without a specified number of digits.
+                c = format[0];
+                if ((uint)(c - 'A') <= 'Z' - 'A' ||
+                    (uint)(c - 'a') <= 'z' - 'a')
+                {
+                    // Fast path for sole symbol, e.g. "D"
+                    if (format.Length == 1)
+                    {
+                        digits = -1;
+                        return c;
+                    }
+
+                    if (format.Length == 2)
+                    {
+                        // Fast path for symbol and single digit, e.g. "X4"
+                        int d = format[1] - '0';
+                        if ((uint)d < 10)
+                        {
+                            digits = d;
+                            return c;
+                        }
+                    }
+                    else if (format.Length == 3)
+                    {
+                        // Fast path for symbol and double digit, e.g. "F12"
+                        int d1 = format[1] - '0', d2 = format[2] - '0';
+                        if ((uint)d1 < 10 && (uint)d2 < 10)
+                        {
+                            digits = d1 * 10 + d2;
+                            return c;
+                        }
+                    }
+
+                    // Fallback for symbol and any length digits.  The digits value must be >= 0 && <= 99,
+                    // but it can begin with any number of 0s, and thus we may need to check more than two
+                    // digits.  Further, for compat, we need to stop when we hit a null char.
+                    int n = 0;
+                    int i = 1;
+                    while (i < format.Length && (((uint)format[i] - '0') < 10) && n < 10)
+                    {
+                        n = (n * 10) + format[i++] - '0';
+                    }
+
+                    // If we're at the end of the digits rather than having stopped because we hit something
+                    // other than a digit or overflowed, return the standard format info.
+                    if (i == format.Length || format[i] == '\0')
+                    {
+                        digits = n;
+                        return c;
+                    }
+                }
+            }
+
+            // Default empty format to be "G"; custom format is signified with '\0'.
+            digits = -1;
+            return format.Length == 0 || c == '\0' ? // For compat, treat '\0' as the end of the specifier, even if the specifier extends beyond it.
+                'G' : 
+                '\0';
+        }
+
+        internal static unsafe void NumberToString(ref ValueStringBuilder sb, ref NumberBuffer number, char format, int nMaxDigits, NumberFormatInfo info, bool isDecimal)
+        {
+            int nMinDigits = -1;
+
+            switch (format)
+            {
+                case 'C':
+                case 'c':
+                    {
+                        nMinDigits = nMaxDigits >= 0 ? nMaxDigits : info.CurrencyDecimalDigits;
+                        if (nMaxDigits < 0)
+                            nMaxDigits = info.CurrencyDecimalDigits;
+
+                        RoundNumber(ref number, number.scale + nMaxDigits); // Don't change this line to use digPos since digCount could have its sign changed.
+
+                        FormatCurrency(ref sb, ref number, nMinDigits, nMaxDigits, info);
+
+                        break;
+                    }
+
+                case 'F':
+                case 'f':
+                    {
+                        if (nMaxDigits < 0)
+                            nMaxDigits = nMinDigits = info.NumberDecimalDigits;
+                        else
+                            nMinDigits = nMaxDigits;
+
+                        RoundNumber(ref number, number.scale + nMaxDigits);
+
+                        if (number.sign)
+                            sb.Append(info.NegativeSign);
+
+                        FormatFixed(ref sb, ref number, nMinDigits, nMaxDigits, info, null, info.NumberDecimalSeparator, null);
+
+                        break;
+                    }
+
+                case 'N':
+                case 'n':
+                    {
+                        if (nMaxDigits < 0)
+                            nMaxDigits = nMinDigits = info.NumberDecimalDigits; // Since we are using digits in our calculation
+                        else
+                            nMinDigits = nMaxDigits;
+
+                        RoundNumber(ref number, number.scale + nMaxDigits);
+
+                        FormatNumber(ref sb, ref number, nMinDigits, nMaxDigits, info);
+
+                        break;
+                    }
+
+                case 'E':
+                case 'e':
+                    {
+                        if (nMaxDigits < 0)
+                            nMaxDigits = nMinDigits = 6;
+                        else
+                            nMinDigits = nMaxDigits;
+                        nMaxDigits++;
+
+                        RoundNumber(ref number, nMaxDigits);
+
+                        if (number.sign)
+                            sb.Append(info.NegativeSign);
+
+                        FormatScientific(ref sb, ref number, nMinDigits, nMaxDigits, info, format);
+
+                        break;
+                    }
+
+                case 'G':
+                case 'g':
+                    {
+                        bool enableRounding = true;
+                        if (nMaxDigits < 1)
+                        {
+                            if (isDecimal && (nMaxDigits == -1))
+                            {
+                                // Default to 29 digits precision only for G formatting without a precision specifier
+                                // This ensures that the PAL code pads out to the correct place even when we use the default precision
+                                nMaxDigits = nMinDigits = DecimalPrecision;
+                                enableRounding = false;  // Turn off rounding for ECMA compliance to output trailing 0's after decimal as significant
+                            }
+                            else
+                            {
+                                // This ensures that the PAL code pads out to the correct place even when we use the default precision
+                                nMaxDigits = nMinDigits = number.precision;
+                            }
+                        }
+                        else
+                            nMinDigits = nMaxDigits;
+
+                        if (enableRounding) // Don't round for G formatting without precision
+                            RoundNumber(ref number, nMaxDigits); // This also fixes up the minus zero case
+                        else
+                        {
+                            if (isDecimal && (number.digits[0] == 0))
+                            {
+                                // Minus zero should be formatted as 0
+                                number.sign = false;
+                            }
+                        }
+
+                        if (number.sign)
+                            sb.Append(info.NegativeSign);
+
+                        FormatGeneral(ref sb, ref number, nMinDigits, nMaxDigits, info, (char)(format - ('G' - 'E')), !enableRounding);
+
+                        break;
+                    }
+
+                case 'P':
+                case 'p':
+                    {
+                        if (nMaxDigits < 0)
+                            nMaxDigits = nMinDigits = info.PercentDecimalDigits;
+                        else
+                            nMinDigits = nMaxDigits;
+                        number.scale += 2;
+
+                        RoundNumber(ref number, number.scale + nMaxDigits);
+
+                        FormatPercent(ref sb, ref number, nMinDigits, nMaxDigits, info);
+
+                        break;
+                    }
+
+                default:
+                    throw new FormatException(SR.Argument_BadFormatSpecifier);
+            }
+        }
+
+        internal static unsafe void NumberToStringFormat(ref ValueStringBuilder sb, ref NumberBuffer number, ReadOnlySpan<char> format, NumberFormatInfo info)
+        {
+            int digitCount;
+            int decimalPos;
+            int firstDigit;
+            int lastDigit;
+            int digPos;
+            bool scientific;
+            int thousandPos;
+            int thousandCount = 0;
+            bool thousandSeps;
+            int scaleAdjust;
+            int adjust;
+
+            int section;
+            int src;
+            char* dig = number.digits;
+            char ch;
+
+            section = FindSection(format, dig[0] == 0 ? 2 : number.sign ? 1 : 0);
+
+            while (true)
+            {
+                digitCount = 0;
+                decimalPos = -1;
+                firstDigit = 0x7FFFFFFF;
+                lastDigit = 0;
+                scientific = false;
+                thousandPos = -1;
+                thousandSeps = false;
+                scaleAdjust = 0;
+                src = section;
+
+                fixed (char* pFormat = &MemoryMarshal.GetReference(format))
+                {
+                    while (src < format.Length && (ch = pFormat[src++]) != 0 && ch != ';')
+                    {
+                        switch (ch)
+                        {
+                            case '#':
+                                digitCount++;
+                                break;
+                            case '0':
+                                if (firstDigit == 0x7FFFFFFF)
+                                    firstDigit = digitCount;
+                                digitCount++;
+                                lastDigit = digitCount;
+                                break;
+                            case '.':
+                                if (decimalPos < 0)
+                                    decimalPos = digitCount;
+                                break;
+                            case ',':
+                                if (digitCount > 0 && decimalPos < 0)
+                                {
+                                    if (thousandPos >= 0)
+                                    {
+                                        if (thousandPos == digitCount)
+                                        {
+                                            thousandCount++;
+                                            break;
+                                        }
+                                        thousandSeps = true;
+                                    }
+                                    thousandPos = digitCount;
+                                    thousandCount = 1;
+                                }
+                                break;
+                            case '%':
+                                scaleAdjust += 2;
+                                break;
+                            case '\x2030':
+                                scaleAdjust += 3;
+                                break;
+                            case '\'':
+                            case '"':
+                                while (src < format.Length && pFormat[src] != 0 && pFormat[src++] != ch)
+                                    ;
+                                break;
+                            case '\\':
+                                if (src < format.Length && pFormat[src] != 0)
+                                    src++;
+                                break;
+                            case 'E':
+                            case 'e':
+                                if ((src < format.Length && pFormat[src] == '0') ||
+                                    (src + 1 < format.Length && (pFormat[src] == '+' || pFormat[src] == '-') && pFormat[src + 1] == '0'))
+                                {
+                                    while (++src < format.Length && pFormat[src] == '0');
+                                    scientific = true;
+                                }
+                                break;
+                        }
+                    }
+                }
+
+                if (decimalPos < 0)
+                    decimalPos = digitCount;
+
+                if (thousandPos >= 0)
+                {
+                    if (thousandPos == decimalPos)
+                        scaleAdjust -= thousandCount * 3;
+                    else
+                        thousandSeps = true;
+                }
+
+                if (dig[0] != 0)
+                {
+                    number.scale += scaleAdjust;
+                    int pos = scientific ? digitCount : number.scale + digitCount - decimalPos;
+                    RoundNumber(ref number, pos);
+                    if (dig[0] == 0)
+                    {
+                        src = FindSection(format, 2);
+                        if (src != section)
+                        {
+                            section = src;
+                            continue;
+                        }
+                    }
+                }
+                else
+                {
+                    number.sign = false;   // We need to format -0 without the sign set.
+                    number.scale = 0;      // Decimals with scale ('0.00') should be rounded.
+                }
+
+                break;
+            }
+
+            firstDigit = firstDigit < decimalPos ? decimalPos - firstDigit : 0;
+            lastDigit = lastDigit > decimalPos ? decimalPos - lastDigit : 0;
+            if (scientific)
+            {
+                digPos = decimalPos;
+                adjust = 0;
+            }
+            else
+            {
+                digPos = number.scale > decimalPos ? number.scale : decimalPos;
+                adjust = number.scale - decimalPos;
+            }
+            src = section;
+
+            // Adjust can be negative, so we make this an int instead of an unsigned int.
+            // Adjust represents the number of characters over the formatting e.g. format string is "0000" and you are trying to
+            // format 100000 (6 digits). Means adjust will be 2. On the other hand if you are trying to format 10 adjust will be
+            // -2 and we'll need to fixup these digits with 0 padding if we have 0 formatting as in this example.
+            Span<int> thousandsSepPos = stackalloc int[4];
+            int thousandsSepCtr = -1;
+
+            if (thousandSeps)
+            {
+                // We need to precompute this outside the number formatting loop
+                if (info.NumberGroupSeparator.Length > 0)
+                {
+                    // We need this array to figure out where to insert the thousands separator. We would have to traverse the string
+                    // backwards. PIC formatting always traverses forwards. These indices are precomputed to tell us where to insert
+                    // the thousands separator so we can get away with traversing forwards. Note we only have to compute up to digPos.
+                    // The max is not bound since you can have formatting strings of the form "000,000..", and this
+                    // should handle that case too.
+
+                    int[] groupDigits = info.numberGroupSizes;
+
+                    int groupSizeIndex = 0;     // Index into the groupDigits array.
+                    int groupTotalSizeCount = 0;
+                    int groupSizeLen = groupDigits.Length;    // The length of groupDigits array.
+                    if (groupSizeLen != 0)
+                        groupTotalSizeCount = groupDigits[groupSizeIndex];   // The current running total of group size.
+                    int groupSize = groupTotalSizeCount;
+
+                    int totalDigits = digPos + ((adjust < 0) ? adjust : 0); // Actual number of digits in o/p
+                    int numDigits = (firstDigit > totalDigits) ? firstDigit : totalDigits;
+                    while (numDigits > groupTotalSizeCount)
+                    {
+                        if (groupSize == 0)
+                            break;
+                        ++thousandsSepCtr;
+                        if (thousandsSepCtr >= thousandsSepPos.Length)
+                        {
+                            var newThousandsSepPos = new int[thousandsSepPos.Length * 2];
+                            thousandsSepPos.CopyTo(newThousandsSepPos);
+                            thousandsSepPos = newThousandsSepPos;
+                        }
+
+                        thousandsSepPos[thousandsSepCtr] = groupTotalSizeCount;
+                        if (groupSizeIndex < groupSizeLen - 1)
+                        {
+                            groupSizeIndex++;
+                            groupSize = groupDigits[groupSizeIndex];
+                        }
+                        groupTotalSizeCount += groupSize;
+                    }
+                }
+            }
+            
+            if (number.sign && section == 0)
+                sb.Append(info.NegativeSign);
+
+            bool decimalWritten = false;
+
+            fixed (char* pFormat = &MemoryMarshal.GetReference(format))
+            {
+                char* cur = dig;
+
+                while (src < format.Length && (ch = pFormat[src++]) != 0 && ch != ';')
+                {
+                    if (adjust > 0)
+                    {
+                        switch (ch)
+                        {
+                            case '#':
+                            case '0':
+                            case '.':
+                                while (adjust > 0)
+                                {
+                                    // digPos will be one greater than thousandsSepPos[thousandsSepCtr] since we are at
+                                    // the character after which the groupSeparator needs to be appended.
+                                    sb.Append(*cur != 0 ? *cur++ : '0');
+                                    if (thousandSeps && digPos > 1 && thousandsSepCtr >= 0)
+                                    {
+                                        if (digPos == thousandsSepPos[thousandsSepCtr] + 1)
+                                        {
+                                            sb.Append(info.NumberGroupSeparator);
+                                            thousandsSepCtr--;
+                                        }
+                                    }
+                                    digPos--;
+                                    adjust--;
+                                }
+                                break;
+                        }
+                    }
+
+                    switch (ch)
+                    {
+                        case '#':
+                        case '0':
+                            {
+                                if (adjust < 0)
+                                {
+                                    adjust++;
+                                    ch = digPos <= firstDigit ? '0' : '\0';
+                                }
+                                else
+                                {
+                                    ch = *cur != 0 ? *cur++ : digPos > lastDigit ? '0' : '\0';
+                                }
+                                if (ch != 0)
+                                {
+                                    sb.Append(ch);
+                                    if (thousandSeps && digPos > 1 && thousandsSepCtr >= 0)
+                                    {
+                                        if (digPos == thousandsSepPos[thousandsSepCtr] + 1)
+                                        {
+                                            sb.Append(info.NumberGroupSeparator);
+                                            thousandsSepCtr--;
+                                        }
+                                    }
+                                }
+
+                                digPos--;
+                                break;
+                            }
+                        case '.':
+                            {
+                                if (digPos != 0 || decimalWritten)
+                                {
+                                    // For compatibility, don't echo repeated decimals
+                                    break;
+                                }
+                                // If the format has trailing zeros or the format has a decimal and digits remain
+                                if (lastDigit < 0 || (decimalPos < digitCount && *cur != 0))
+                                {
+                                    sb.Append(info.NumberDecimalSeparator);
+                                    decimalWritten = true;
+                                }
+                                break;
+                            }
+                        case '\x2030':
+                            sb.Append(info.PerMilleSymbol);
+                            break;
+                        case '%':
+                            sb.Append(info.PercentSymbol);
+                            break;
+                        case ',':
+                            break;
+                        case '\'':
+                        case '"':
+                            while (src < format.Length && pFormat[src] != 0 && pFormat[src] != ch)
+                                sb.Append(pFormat[src++]);
+                            if (src < format.Length && pFormat[src] != 0)
+                                src++;
+                            break;
+                        case '\\':
+                            if (src < format.Length && pFormat[src] != 0)
+                                sb.Append(pFormat[src++]);
+                            break;
+                        case 'E':
+                        case 'e':
+                            {
+                                bool positiveSign = false;
+                                int i = 0;
+                                if (scientific)
+                                {
+                                    if (src < format.Length && pFormat[src] == '0')
+                                    {
+                                        // Handles E0, which should format the same as E-0
+                                        i++;
+                                    }
+                                    else if (src+1 < format.Length && pFormat[src] == '+' && pFormat[src + 1] == '0')
+                                    {
+                                        // Handles E+0
+                                        positiveSign = true;
+                                    }
+                                    else if (src+1 < format.Length && pFormat[src] == '-' && pFormat[src + 1] == '0')
+                                    {
+                                        // Handles E-0
+                                        // Do nothing, this is just a place holder s.t. we don't break out of the loop.
+                                    }
+                                    else
+                                    {
+                                        sb.Append(ch);
+                                        break;
+                                    }
+
+                                    while (++src < format.Length && pFormat[src] == '0')
+                                        i++;
+                                    if (i > 10)
+                                        i = 10;
+
+                                    int exp = dig[0] == 0 ? 0 : number.scale - decimalPos;
+                                    FormatExponent(ref sb, info, exp, ch, i, positiveSign);
+                                    scientific = false;
+                                }
+                                else
+                                {
+                                    sb.Append(ch); // Copy E or e to output
+                                    if (src < format.Length)
+                                    {
+                                        if (pFormat[src] == '+' || pFormat[src] == '-')
+                                            sb.Append(pFormat[src++]);
+                                        while (src < format.Length && pFormat[src] == '0')
+                                            sb.Append(pFormat[src++]);
+                                    }
+                                }
+                                break;
+                            }
+                        default:
+                            sb.Append(ch);
+                            break;
+                    }
+                }
+            }
+        }
+
+        private static void FormatCurrency(ref ValueStringBuilder sb, ref NumberBuffer number, int nMinDigits, int nMaxDigits, NumberFormatInfo info)
+        {
+            string fmt = number.sign ?
+                s_negCurrencyFormats[info.CurrencyNegativePattern] :
+                s_posCurrencyFormats[info.CurrencyPositivePattern];
+
+            foreach (char ch in fmt)
+            {
+                switch (ch)
+                {
+                    case '#':
+                        FormatFixed(ref sb, ref number, nMinDigits, nMaxDigits, info, info.currencyGroupSizes, info.CurrencyDecimalSeparator, info.CurrencyGroupSeparator);
+                        break;
+                    case '-':
+                        sb.Append(info.NegativeSign);
+                        break;
+                    case '$':
+                        sb.Append(info.CurrencySymbol);
+                        break;
+                    default:
+                        sb.Append(ch);
+                        break;
+                }
+            }
+        }
+
+        private static unsafe void FormatFixed(ref ValueStringBuilder sb, ref NumberBuffer number, int nMinDigits, int nMaxDigits, NumberFormatInfo info, int[] groupDigits, string sDecimal, string sGroup)
+        {
+            int digPos = number.scale;
+            char* dig = number.digits;
+
+            if (digPos > 0)
+            {
+                if (groupDigits != null)
+                {
+                    int groupSizeIndex = 0;                             // Index into the groupDigits array.
+                    int groupSizeCount = groupDigits[groupSizeIndex];   // The current total of group size.
+                    int bufferSize = digPos;                            // The length of the result buffer string.
+                    int groupSize = 0;                                  // The current group size.
+
+                    // Find out the size of the string buffer for the result.
+                    if (groupDigits.Length != 0) // You can pass in 0 length arrays
+                    {
+                        while (digPos > groupSizeCount)
+                        {
+                            groupSize = groupDigits[groupSizeIndex];
+                            if (groupSize == 0)
+                                break;
+
+                            bufferSize += sGroup.Length;
+                            if (groupSizeIndex < groupDigits.Length - 1)
+                                groupSizeIndex++;
+
+                            groupSizeCount += groupDigits[groupSizeIndex];
+                            if (groupSizeCount < 0 || bufferSize < 0)
+                                throw new ArgumentOutOfRangeException(); // If we overflow
+                        }
+
+                        groupSize = groupSizeCount == 0 ? 0 : groupDigits[0]; // If you passed in an array with one entry as 0, groupSizeCount == 0
+                    }
+
+                    groupSizeIndex = 0;
+                    int digitCount = 0;
+                    int digLength = string.wcslen(dig);
+                    int digStart = (digPos < digLength) ? digPos : digLength;
+                    fixed (char* spanPtr = &MemoryMarshal.GetReference(sb.AppendSpan(bufferSize)))
+                    {
+                        char* p = spanPtr + bufferSize - 1;
+                        for (int i = digPos - 1; i >= 0; i--)
+                        {
+                            *(p--) = (i < digStart) ? dig[i] : '0';
+
+                            if (groupSize > 0)
+                            {
+                                digitCount++;
+                                if ((digitCount == groupSize) && (i != 0))
+                                {
+                                    for (int j = sGroup.Length - 1; j >= 0; j--)
+                                        *(p--) = sGroup[j];
+
+                                    if (groupSizeIndex < groupDigits.Length - 1)
+                                    {
+                                        groupSizeIndex++;
+                                        groupSize = groupDigits[groupSizeIndex];
+                                    }
+                                    digitCount = 0;
+                                }
+                            }
+                        }
+
+                        Debug.Assert(p >= spanPtr - 1, "Underflow");
+                        dig += digStart;
+                    }
+                }
+                else
+                {
+                    do
+                    {
+                        sb.Append(*dig != 0 ? *dig++ : '0');
+                    }
+                    while (--digPos > 0);
+                }
+            }
+            else
+            {
+                sb.Append('0');
+            }
+
+            if (nMaxDigits > 0)
+            {
+                sb.Append(sDecimal);
+                if ((digPos < 0) && (nMaxDigits > 0))
+                {
+                    int zeroes = Math.Min(-digPos, nMaxDigits);
+                    sb.Append('0', zeroes);
+                    digPos += zeroes;
+                    nMaxDigits -= zeroes;
+                }
+
+                while (nMaxDigits > 0)
+                {
+                    sb.Append((*dig != 0) ? *dig++ : '0');
+                    nMaxDigits--;
+                }
+            }
+        }
+
+        private static void FormatNumber(ref ValueStringBuilder sb, ref NumberBuffer number, int nMinDigits, int nMaxDigits, NumberFormatInfo info)
+        {
+            string fmt = number.sign ?
+                s_negNumberFormats[info.NumberNegativePattern] :
+                PosNumberFormat;
+
+            foreach (char ch in fmt)
+            {
+                switch (ch)
+                {
+                    case '#':
+                        FormatFixed(ref sb, ref number, nMinDigits, nMaxDigits, info, info.numberGroupSizes, info.NumberDecimalSeparator, info.NumberGroupSeparator);
+                        break;
+                    case '-':
+                        sb.Append(info.NegativeSign);
+                        break;
+                    default:
+                        sb.Append(ch);
+                        break;
+                }
+            }
+        }
+
+        private static unsafe void FormatScientific(ref ValueStringBuilder sb, ref NumberBuffer number, int nMinDigits, int nMaxDigits, NumberFormatInfo info, char expChar)
+        {
+            char* dig = number.digits;
+
+            sb.Append((*dig != 0) ? *dig++ : '0');
+
+            if (nMaxDigits != 1) // For E0 we would like to suppress the decimal point
+                sb.Append(info.NumberDecimalSeparator);
+
+            while (--nMaxDigits > 0)
+                sb.Append((*dig != 0) ? *dig++ : '0');
+
+            int e = number.digits[0] == 0 ? 0 : number.scale - 1;
+            FormatExponent(ref sb, info, e, expChar, 3, true);
+        }
+
+        private static unsafe void FormatExponent(ref ValueStringBuilder sb, NumberFormatInfo info, int value, char expChar, int minDigits, bool positiveSign)
+        {
+            sb.Append(expChar);
+
+            if (value < 0)
+            {
+                sb.Append(info.NegativeSign);
+                value = -value;
+            }
+            else
+            {
+                if (positiveSign)
+                    sb.Append(info.PositiveSign);
+            }
+
+            char* digits = stackalloc char[MaxUInt32DecDigits];
+            char* p = UInt32ToDecChars(digits + MaxUInt32DecDigits, (uint)value, minDigits);
+            int i = (int)(digits + MaxUInt32DecDigits - p);
+            sb.Append(p, (int)(digits + MaxUInt32DecDigits - p));
+        }
+
+        private static unsafe void FormatGeneral(ref ValueStringBuilder sb, ref NumberBuffer number, int nMinDigits, int nMaxDigits, NumberFormatInfo info, char expChar, bool bSuppressScientific)
+        {
+            int digPos = number.scale;
+            bool scientific = false;
+
+            if (!bSuppressScientific)
+            {
+                // Don't switch to scientific notation
+                if (digPos > nMaxDigits || digPos < -3)
+                {
+                    digPos = 1;
+                    scientific = true;
+                }
+            }
+
+            char* dig = number.digits;
+
+            if (digPos > 0)
+            {
+                do
+                {
+                    sb.Append((*dig != 0) ? *dig++ : '0');
+                } while (--digPos > 0);
+            }
+            else
+            {
+                sb.Append('0');
+            }
+
+            if (*dig != 0 || digPos < 0)
+            {
+                sb.Append(info.NumberDecimalSeparator);
+
+                while (digPos < 0)
+                {
+                    sb.Append('0');
+                    digPos++;
+                }
+
+                while (*dig != 0)
+                    sb.Append(*dig++);
+            }
+
+            if (scientific)
+                FormatExponent(ref sb, info, number.scale - 1, expChar, 2, true);
+        }
+
+        private static void FormatPercent(ref ValueStringBuilder sb, ref NumberBuffer number, int nMinDigits, int nMaxDigits, NumberFormatInfo info)
+        {
+            string fmt = number.sign ?
+                s_negPercentFormats[info.PercentNegativePattern] :
+                s_posPercentFormats[info.PercentPositivePattern];
+
+            foreach (char ch in fmt)
+            {
+                switch (ch)
+                {
+                    case '#':
+                        FormatFixed(ref sb, ref number, nMinDigits, nMaxDigits, info, info.percentGroupSizes, info.PercentDecimalSeparator, info.PercentGroupSeparator);
+                        break;
+                    case '-':
+                        sb.Append(info.NegativeSign);
+                        break;
+                    case '%':
+                        sb.Append(info.PercentSymbol);
+                        break;
+                    default:
+                        sb.Append(ch);
+                        break;
+                }
+            }
+        }
+
+        private static unsafe void RoundNumber(ref NumberBuffer number, int pos)
+        {
+            char* dig = number.digits;
+
+            int i = 0;
+            while (i < pos && dig[i] != 0)
+                i++;
+
+            if (i == pos && dig[i] >= '5')
+            {
+                while (i > 0 && dig[i - 1] == '9')
+                    i--;
+
+                if (i > 0)
+                {
+                    dig[i - 1]++;
+                }
+                else
+                {
+                    number.scale++;
+                    dig[0] = '1';
+                    i = 1;
+                }
+            }
+            else
+            {
+                while (i > 0 && dig[i - 1] == '0')
+                    i--;
+            }
+            if (i == 0)
+            {
+                number.scale = 0;
+                number.sign = false;
+            }
+            dig[i] = '\0';
+        }
+
+        private static unsafe int FindSection(ReadOnlySpan<char> format, int section)
+        {
+            int src;
+            char ch;
+
+            if (section == 0)
+                return 0;
+
+            fixed (char* pFormat = &MemoryMarshal.GetReference(format))
+            {
+                src = 0;
+                for (;;)
+                {
+                    if (src >= format.Length)
+                    {
+                        return 0;
+                    }
+
+                    switch (ch = pFormat[src++])
+                    {
+                        case '\'':
+                        case '"':
+                            while (src < format.Length && pFormat[src] != 0 && pFormat[src++] != ch)
+                                ;
+                            break;
+                        case '\\':
+                            if (src < format.Length && pFormat[src] != 0)
+                                src++;
+                            break;
+                        case ';':
+                            if (--section != 0)
+                                break;
+                            if (src < format.Length && pFormat[src] != 0 && pFormat[src] != ';')
+                                return src;
+                            goto case '\0';
+                        case '\0':
+                            return 0;
+                    }
+                }
+            }
+        }
+
+        private static uint Low32(ulong value) => (uint)value;
+
+        private static uint High32(ulong value) => (uint)((value & 0xFFFFFFFF00000000) >> 32);
+
+        private static uint Int64DivMod1E9(ref ulong value)
+        {
+            uint rem = (uint)(value % 1000000000);
+            value /= 1000000000;
+            return rem;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Number.NumberBuffer.cs b/src/System.Private.CoreLib/shared/System/Number.NumberBuffer.cs
new file mode 100644
index 0000000000..2316f99bd3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Number.NumberBuffer.cs
@@ -0,0 +1,31 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System
+{
+    internal static partial class Number
+    {
+        private const int NumberMaxDigits = 50; // needs to == NUMBER_MAXDIGITS in coreclr's src/classlibnative/bcltype/number.h.
+
+        [StructLayout(LayoutKind.Sequential, Pack = 1)]
+        internal unsafe ref struct NumberBuffer // needs to match layout of NUMBER in coreclr's src/classlibnative/bcltype/number.h
+        {
+            public int precision;
+            public int scale;
+            private int _sign;
+            private DigitsAndNullTerminator _digits;
+            private char* _allDigits;
+
+            public bool sign { get => _sign != 0; set => _sign = value ? 1 : 0; }
+            public char* digits => (char*)Unsafe.AsPointer(ref _digits);
+
+            [StructLayout(LayoutKind.Sequential, Size = (NumberMaxDigits + 1) * sizeof(char))]
+            private struct DigitsAndNullTerminator { }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Number.Parsing.cs b/src/System.Private.CoreLib/shared/System/Number.Parsing.cs
new file mode 100644
index 0000000000..936a826c93
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Number.Parsing.cs
@@ -0,0 +1,973 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.InteropServices;
+
+namespace System
+{
+    // The Parse methods provided by the numeric classes convert a
+    // string to a numeric value. The optional style parameter specifies the
+    // permitted style of the numeric string. It must be a combination of bit flags
+    // from the NumberStyles enumeration. The optional info parameter
+    // specifies the NumberFormatInfo instance to use when parsing the
+    // string. If the info parameter is null or omitted, the numeric
+    // formatting information is obtained from the current culture.
+    //
+    // Numeric strings produced by the Format methods using the Currency,
+    // Decimal, Engineering, Fixed point, General, or Number standard formats
+    // (the C, D, E, F, G, and N format specifiers) are guaranteed to be parseable
+    // by the Parse methods if the NumberStyles.Any style is
+    // specified. Note, however, that the Parse methods do not accept
+    // NaNs or Infinities.
+
+    internal partial class Number
+    {
+        private const int Int32Precision = 10;
+        private const int UInt32Precision = Int32Precision;
+        private const int Int64Precision = 19;
+        private const int UInt64Precision = 20;
+
+        private static bool HexNumberToInt32(ref NumberBuffer number, ref int value)
+        {
+            uint passedValue = 0;
+            bool returnValue = HexNumberToUInt32(ref number, ref passedValue);
+            value = (int)passedValue;
+            return returnValue;
+        }
+
+        private static bool HexNumberToInt64(ref NumberBuffer number, ref long value)
+        {
+            ulong passedValue = 0;
+            bool returnValue = HexNumberToUInt64(ref number, ref passedValue);
+            value = (long)passedValue;
+            return returnValue;
+        }
+
+        private static unsafe bool HexNumberToUInt32(ref NumberBuffer number, ref uint value)
+        {
+            int i = number.scale;
+            if (i > UInt32Precision || i < number.precision)
+            {
+                return false;
+            }
+            char* p = number.digits;
+            Debug.Assert(p != null);
+
+            uint n = 0;
+            while (--i >= 0)
+            {
+                if (n > ((uint)0xFFFFFFFF / 16))
+                {
+                    return false;
+                }
+                n *= 16;
+                if (*p != '\0')
+                {
+                    uint newN = n;
+                    if (*p != '\0')
+                    {
+                        if (*p >= '0' && *p <= '9')
+                        {
+                            newN += (uint)(*p - '0');
+                        }
+                        else
+                        {
+                            if (*p >= 'A' && *p <= 'F')
+                            {
+                                newN += (uint)((*p - 'A') + 10);
+                            }
+                            else
+                            {
+                                Debug.Assert(*p >= 'a' && *p <= 'f');
+                                newN += (uint)((*p - 'a') + 10);
+                            }
+                        }
+                        p++;
+                    }
+
+                    // Detect an overflow here...
+                    if (newN < n)
+                    {
+                        return false;
+                    }
+                    n = newN;
+                }
+            }
+            value = n;
+            return true;
+        }
+
+        private static unsafe bool HexNumberToUInt64(ref NumberBuffer number, ref ulong value)
+        {
+            int i = number.scale;
+            if (i > UInt64Precision || i < number.precision)
+            {
+                return false;
+            }
+            char* p = number.digits;
+            Debug.Assert(p != null);
+
+            ulong n = 0;
+            while (--i >= 0)
+            {
+                if (n > (0xFFFFFFFFFFFFFFFF / 16))
+                {
+                    return false;
+                }
+                n *= 16;
+                if (*p != '\0')
+                {
+                    ulong newN = n;
+                    if (*p != '\0')
+                    {
+                        if (*p >= '0' && *p <= '9')
+                        {
+                            newN += (ulong)(*p - '0');
+                        }
+                        else
+                        {
+                            if (*p >= 'A' && *p <= 'F')
+                            {
+                                newN += (ulong)((*p - 'A') + 10);
+                            }
+                            else
+                            {
+                                Debug.Assert(*p >= 'a' && *p <= 'f');
+                                newN += (ulong)((*p - 'a') + 10);
+                            }
+                        }
+                        p++;
+                    }
+
+                    // Detect an overflow here...
+                    if (newN < n)
+                    {
+                        return false;
+                    }
+                    n = newN;
+                }
+            }
+            value = n;
+            return true;
+        }
+
+        private static unsafe bool NumberToInt32(ref NumberBuffer number, ref int value)
+        {
+            int i = number.scale;
+            if (i > Int32Precision || i < number.precision)
+            {
+                return false;
+            }
+            char* p = number.digits;
+            Debug.Assert(p != null);
+            int n = 0;
+            while (--i >= 0)
+            {
+                if ((uint)n > (0x7FFFFFFF / 10))
+                {
+                    return false;
+                }
+                n *= 10;
+                if (*p != '\0')
+                {
+                    n += (int)(*p++ - '0');
+                }
+            }
+            if (number.sign)
+            {
+                n = -n;
+                if (n > 0)
+                {
+                    return false;
+                }
+            }
+            else
+            {
+                if (n < 0)
+                {
+                    return false;
+                }
+            }
+            value = n;
+            return true;
+        }
+
+        private static unsafe bool NumberToInt64(ref NumberBuffer number, ref long value)
+        {
+            int i = number.scale;
+            if (i > Int64Precision || i < number.precision)
+            {
+                return false;
+            }
+            char* p = number.digits;
+            Debug.Assert(p != null);
+            long n = 0;
+            while (--i >= 0)
+            {
+                if ((ulong)n > (0x7FFFFFFFFFFFFFFF / 10))
+                {
+                    return false;
+                }
+                n *= 10;
+                if (*p != '\0')
+                {
+                    n += (int)(*p++ - '0');
+                }
+            }
+            if (number.sign)
+            {
+                n = -n;
+                if (n > 0)
+                {
+                    return false;
+                }
+            }
+            else
+            {
+                if (n < 0)
+                {
+                    return false;
+                }
+            }
+            value = n;
+            return true;
+        }
+
+        private static unsafe bool NumberToUInt32(ref NumberBuffer number, ref uint value)
+        {
+            int i = number.scale;
+            if (i > UInt32Precision || i < number.precision || number.sign)
+            {
+                return false;
+            }
+            char* p = number.digits;
+            Debug.Assert(p != null);
+            uint n = 0;
+            while (--i >= 0)
+            {
+                if (n > (0xFFFFFFFF / 10))
+                {
+                    return false;
+                }
+                n *= 10;
+                if (*p != '\0')
+                {
+                    uint newN = n + (uint)(*p++ - '0');
+                    // Detect an overflow here...
+                    if (newN < n)
+                    {
+                        return false;
+                    }
+                    n = newN;
+                }
+            }
+            value = n;
+            return true;
+        }
+
+        private static unsafe bool NumberToUInt64(ref NumberBuffer number, ref ulong value)
+        {
+            int i = number.scale;
+            if (i > UInt64Precision || i < number.precision || number.sign)
+            {
+                return false;
+            }
+            char* p = number.digits;
+            Debug.Assert(p != null);
+            ulong n = 0;
+            while (--i >= 0)
+            {
+                if (n > (0xFFFFFFFFFFFFFFFF / 10))
+                {
+                    return false;
+                }
+                n *= 10;
+                if (*p != '\0')
+                {
+                    ulong newN = n + (ulong)(*p++ - '0');
+                    // Detect an overflow here...
+                    if (newN < n)
+                    {
+                        return false;
+                    }
+                    n = newN;
+                }
+            }
+            value = n;
+            return true;
+        }
+
+        internal static unsafe int ParseInt32(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info)
+        {
+            NumberBuffer number = default;
+            int i = 0;
+
+            StringToNumber(s, style, ref number, info, false);
+
+            if ((style & NumberStyles.AllowHexSpecifier) != 0)
+            {
+                if (!HexNumberToInt32(ref number, ref i))
+                {
+                    throw new OverflowException(SR.Overflow_Int32);
+                }
+            }
+            else
+            {
+                if (!NumberToInt32(ref number, ref i))
+                {
+                    throw new OverflowException(SR.Overflow_Int32);
+                }
+            }
+            return i;
+        }
+
+        internal static unsafe long ParseInt64(ReadOnlySpan<char> value, NumberStyles options, NumberFormatInfo numfmt)
+        {
+            NumberBuffer number = default;
+            long i = 0;
+
+            StringToNumber(value, options, ref number, numfmt, false);
+
+            if ((options & NumberStyles.AllowHexSpecifier) != 0)
+            {
+                if (!HexNumberToInt64(ref number, ref i))
+                {
+                    throw new OverflowException(SR.Overflow_Int64);
+                }
+            }
+            else
+            {
+                if (!NumberToInt64(ref number, ref i))
+                {
+                    throw new OverflowException(SR.Overflow_Int64);
+                }
+            }
+            return i;
+        }
+
+        internal static unsafe uint ParseUInt32(ReadOnlySpan<char> value, NumberStyles options, NumberFormatInfo numfmt)
+        {
+            NumberBuffer number = default;
+            uint i = 0;
+
+            StringToNumber(value, options, ref number, numfmt, false);
+
+            if ((options & NumberStyles.AllowHexSpecifier) != 0)
+            {
+                if (!HexNumberToUInt32(ref number, ref i))
+                {
+                    throw new OverflowException(SR.Overflow_UInt32);
+                }
+            }
+            else
+            {
+                if (!NumberToUInt32(ref number, ref i))
+                {
+                    throw new OverflowException(SR.Overflow_UInt32);
+                }
+            }
+
+            return i;
+        }
+
+        internal static unsafe ulong ParseUInt64(ReadOnlySpan<char> value, NumberStyles options, NumberFormatInfo numfmt)
+        {
+            NumberBuffer number = default;
+            ulong i = 0;
+
+            StringToNumber(value, options, ref number, numfmt, false);
+            if ((options & NumberStyles.AllowHexSpecifier) != 0)
+            {
+                if (!HexNumberToUInt64(ref number, ref i))
+                {
+                    throw new OverflowException(SR.Overflow_UInt64);
+                }
+            }
+            else
+            {
+                if (!NumberToUInt64(ref number, ref i))
+                {
+                    throw new OverflowException(SR.Overflow_UInt64);
+                }
+            }
+            return i;
+        }
+
+        private static unsafe bool ParseNumber(ref char* str, char* strEnd, NumberStyles options, ref NumberBuffer number, NumberFormatInfo numfmt, bool parseDecimal)
+        {
+            Debug.Assert(str != null);
+            Debug.Assert(strEnd != null);
+            Debug.Assert(str <= strEnd);
+
+            const int StateSign = 0x0001;
+            const int StateParens = 0x0002;
+            const int StateDigits = 0x0004;
+            const int StateNonZero = 0x0008;
+            const int StateDecimal = 0x0010;
+            const int StateCurrency = 0x0020;
+
+            number.scale = 0;
+            number.sign = false;
+            string decSep;                  // decimal separator from NumberFormatInfo.
+            string groupSep;                // group separator from NumberFormatInfo.
+            string currSymbol = null;       // currency symbol from NumberFormatInfo.
+
+            bool parsingCurrency = false;
+            if ((options & NumberStyles.AllowCurrencySymbol) != 0)
+            {
+                currSymbol = numfmt.CurrencySymbol;
+
+                // The idea here is to match the currency separators and on failure match the number separators to keep the perf of VB's IsNumeric fast.
+                // The values of decSep are setup to use the correct relevant separator (currency in the if part and decimal in the else part).
+                decSep = numfmt.CurrencyDecimalSeparator;
+                groupSep = numfmt.CurrencyGroupSeparator;
+                parsingCurrency = true;
+            }
+            else
+            {
+                decSep = numfmt.NumberDecimalSeparator;
+                groupSep = numfmt.NumberGroupSeparator;
+            }
+
+            int state = 0;
+            char* p = str;
+            char ch = p < strEnd ? *p : '\0';
+            char* next;
+
+            while (true)
+            {
+                // Eat whitespace unless we've found a sign which isn't followed by a currency symbol.
+                // "-Kr 1231.47" is legal but "- 1231.47" is not.
+                if (!IsWhite(ch) || (options & NumberStyles.AllowLeadingWhite) == 0 || ((state & StateSign) != 0 && ((state & StateCurrency) == 0 && numfmt.NumberNegativePattern != 2)))
+                {
+                    if ((((options & NumberStyles.AllowLeadingSign) != 0) && (state & StateSign) == 0) && ((next = MatchChars(p, strEnd, numfmt.PositiveSign)) != null || ((next = MatchChars(p, strEnd, numfmt.NegativeSign)) != null && (number.sign = true))))
+                    {
+                        state |= StateSign;
+                        p = next - 1;
+                    }
+                    else if (ch == '(' && ((options & NumberStyles.AllowParentheses) != 0) && ((state & StateSign) == 0))
+                    {
+                        state |= StateSign | StateParens;
+                        number.sign = true;
+                    }
+                    else if (currSymbol != null && (next = MatchChars(p, strEnd, currSymbol)) != null)
+                    {
+                        state |= StateCurrency;
+                        currSymbol = null;
+                        // We already found the currency symbol. There should not be more currency symbols. Set
+                        // currSymbol to NULL so that we won't search it again in the later code path.
+                        p = next - 1;
+                    }
+                    else
+                    {
+                        break;
+                    }
+                }
+                ch = ++p < strEnd ? *p : '\0';
+            }
+            int digCount = 0;
+            int digEnd = 0;
+            while (true)
+            {
+                if ((ch >= '0' && ch <= '9') || (((options & NumberStyles.AllowHexSpecifier) != 0) && ((ch >= 'a' && ch <= 'f') || (ch >= 'A' && ch <= 'F'))))
+                {
+                    state |= StateDigits;
+
+                    if (ch != '0' || (state & StateNonZero) != 0)
+                    {
+                        if (digCount < NumberMaxDigits)
+                        {
+                            number.digits[digCount++] = ch;
+                            if (ch != '0' || parseDecimal)
+                            {
+                                digEnd = digCount;
+                            }
+                        }
+                        if ((state & StateDecimal) == 0)
+                        {
+                            number.scale++;
+                        }
+                        state |= StateNonZero;
+                    }
+                    else if ((state & StateDecimal) != 0)
+                    {
+                        number.scale--;
+                    }
+                }
+                else if (((options & NumberStyles.AllowDecimalPoint) != 0) && ((state & StateDecimal) == 0) && ((next = MatchChars(p, strEnd, decSep)) != null || ((parsingCurrency) && (state & StateCurrency) == 0) && (next = MatchChars(p, strEnd, numfmt.NumberDecimalSeparator)) != null))
+                {
+                    state |= StateDecimal;
+                    p = next - 1;
+                }
+                else if (((options & NumberStyles.AllowThousands) != 0) && ((state & StateDigits) != 0) && ((state & StateDecimal) == 0) && ((next = MatchChars(p, strEnd, groupSep)) != null || ((parsingCurrency) && (state & StateCurrency) == 0) && (next = MatchChars(p, strEnd, numfmt.NumberGroupSeparator)) != null))
+                {
+                    p = next - 1;
+                }
+                else
+                {
+                    break;
+                }
+                ch = ++p < strEnd ? *p : '\0';
+            }
+
+            bool negExp = false;
+            number.precision = digEnd;
+            number.digits[digEnd] = '\0';
+            if ((state & StateDigits) != 0)
+            {
+                if ((ch == 'E' || ch == 'e') && ((options & NumberStyles.AllowExponent) != 0))
+                {
+                    char* temp = p;
+                    ch = ++p < strEnd ? *p : '\0';
+                    if ((next = MatchChars(p, strEnd, numfmt.positiveSign)) != null)
+                    {
+                        ch = (p = next) < strEnd ? *p : '\0';
+                    }
+                    else if ((next = MatchChars(p, strEnd, numfmt.negativeSign)) != null)
+                    {
+                        ch = (p = next) < strEnd ? *p : '\0';
+                        negExp = true;
+                    }
+                    if (ch >= '0' && ch <= '9')
+                    {
+                        int exp = 0;
+                        do
+                        {
+                            exp = exp * 10 + (ch - '0');
+                            ch = ++p < strEnd ? *p : '\0';
+                            if (exp > 1000)
+                            {
+                                exp = 9999;
+                                while (ch >= '0' && ch <= '9')
+                                {
+                                    ch = ++p < strEnd ? *p : '\0';
+                                }
+                            }
+                        } while (ch >= '0' && ch <= '9');
+                        if (negExp)
+                        {
+                            exp = -exp;
+                        }
+                        number.scale += exp;
+                    }
+                    else
+                    {
+                        p = temp;
+                        ch = p < strEnd ? *p : '\0';
+                    }
+                }
+                while (true)
+                {
+                    if (!IsWhite(ch) || (options & NumberStyles.AllowTrailingWhite) == 0)
+                    {
+                        if (((options & NumberStyles.AllowTrailingSign) != 0 && ((state & StateSign) == 0)) && ((next = MatchChars(p, strEnd, numfmt.PositiveSign)) != null || (((next = MatchChars(p, strEnd, numfmt.NegativeSign)) != null) && (number.sign = true))))
+                        {
+                            state |= StateSign;
+                            p = next - 1;
+                        }
+                        else if (ch == ')' && ((state & StateParens) != 0))
+                        {
+                            state &= ~StateParens;
+                        }
+                        else if (currSymbol != null && (next = MatchChars(p, strEnd, currSymbol)) != null)
+                        {
+                            currSymbol = null;
+                            p = next - 1;
+                        }
+                        else
+                        {
+                            break;
+                        }
+                    }
+                    ch = ++p < strEnd ? *p : '\0';
+                }
+                if ((state & StateParens) == 0)
+                {
+                    if ((state & StateNonZero) == 0)
+                    {
+                        if (!parseDecimal)
+                        {
+                            number.scale = 0;
+                        }
+                        if ((state & StateDecimal) == 0)
+                        {
+                            number.sign = false;
+                        }
+                    }
+                    str = p;
+                    return true;
+                }
+            }
+            str = p;
+            return false;
+        }
+
+        internal static unsafe bool TryParseInt32(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info, out int result)
+        {
+            NumberBuffer number = default;
+            result = 0;
+
+            if (!TryStringToNumber(s, style, ref number, info, false))
+            {
+                return false;
+            }
+
+            if ((style & NumberStyles.AllowHexSpecifier) != 0)
+            {
+                if (!HexNumberToInt32(ref number, ref result))
+                {
+                    return false;
+                }
+            }
+            else
+            {
+                if (!NumberToInt32(ref number, ref result))
+                {
+                    return false;
+                }
+            }
+            return true;
+        }
+
+        internal static unsafe bool TryParseInt64(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info, out long result)
+        {
+            NumberBuffer number = default;
+            result = 0;
+
+            if (!TryStringToNumber(s, style, ref number, info, false))
+            {
+                return false;
+            }
+
+            if ((style & NumberStyles.AllowHexSpecifier) != 0)
+            {
+                if (!HexNumberToInt64(ref number, ref result))
+                {
+                    return false;
+                }
+            }
+            else
+            {
+                if (!NumberToInt64(ref number, ref result))
+                {
+                    return false;
+                }
+            }
+            return true;
+        }
+
+        internal static unsafe bool TryParseUInt32(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info, out uint result)
+        {
+            NumberBuffer number = default;
+            result = 0;
+
+            if (!TryStringToNumber(s, style, ref number, info, false))
+            {
+                return false;
+            }
+
+            if ((style & NumberStyles.AllowHexSpecifier) != 0)
+            {
+                if (!HexNumberToUInt32(ref number, ref result))
+                {
+                    return false;
+                }
+            }
+            else
+            {
+                if (!NumberToUInt32(ref number, ref result))
+                {
+                    return false;
+                }
+            }
+            return true;
+        }
+
+        internal static unsafe bool TryParseUInt64(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info, out ulong result)
+        {
+            NumberBuffer number = default;
+            result = 0;
+
+            if (!TryStringToNumber(s, style, ref number, info, false))
+            {
+                return false;
+            }
+
+            if ((style & NumberStyles.AllowHexSpecifier) != 0)
+            {
+                if (!HexNumberToUInt64(ref number, ref result))
+                {
+                    return false;
+                }
+            }
+            else
+            {
+                if (!NumberToUInt64(ref number, ref result))
+                {
+                    return false;
+                }
+            }
+            return true;
+        }
+
+        internal static unsafe decimal ParseDecimal(ReadOnlySpan<char> value, NumberStyles options, NumberFormatInfo numfmt)
+        {
+            NumberBuffer number = default;
+            decimal result = 0;
+
+            StringToNumber(value, options, ref number, numfmt, true);
+
+            if (!NumberBufferToDecimal(ref number, ref result))
+            {
+                throw new OverflowException(SR.Overflow_Decimal);
+            }
+            return result;
+        }
+
+        internal static unsafe double ParseDouble(ReadOnlySpan<char> value, NumberStyles options, NumberFormatInfo numfmt)
+        {
+            NumberBuffer number = default;
+            double d = 0;
+
+            if (!TryStringToNumber(value, options, ref number, numfmt, false))
+            {
+                //If we failed TryStringToNumber, it may be from one of our special strings.
+                //Check the three with which we're concerned and rethrow if it's not one of
+                //those strings.
+                ReadOnlySpan<char> sTrim = value.Trim();
+                if (sTrim.EqualsOrdinal(numfmt.PositiveInfinitySymbol))
+                {
+                    return double.PositiveInfinity;
+                }
+                if (sTrim.EqualsOrdinal(numfmt.NegativeInfinitySymbol))
+                {
+                    return double.NegativeInfinity;
+                }
+                if (sTrim.EqualsOrdinal(numfmt.NaNSymbol))
+                {
+                    return double.NaN;
+                }
+                throw new FormatException(SR.Format_InvalidString);
+            }
+
+            if (!NumberBufferToDouble(ref number, ref d))
+            {
+                throw new OverflowException(SR.Overflow_Double);
+            }
+
+            return d;
+        }
+
+        internal static unsafe float ParseSingle(ReadOnlySpan<char> value, NumberStyles options, NumberFormatInfo numfmt)
+        {
+            NumberBuffer number = default;
+            double d = 0;
+
+            if (!TryStringToNumber(value, options, ref number, numfmt, false))
+            {
+                //If we failed TryStringToNumber, it may be from one of our special strings.
+                //Check the three with which we're concerned and rethrow if it's not one of
+                //those strings.
+                ReadOnlySpan<char> sTrim = value.Trim();
+                if (sTrim.EqualsOrdinal(numfmt.PositiveInfinitySymbol))
+                {
+                    return float.PositiveInfinity;
+                }
+                if (sTrim.EqualsOrdinal(numfmt.NegativeInfinitySymbol))
+                {
+                    return float.NegativeInfinity;
+                }
+                if (sTrim.EqualsOrdinal(numfmt.NaNSymbol))
+                {
+                    return float.NaN;
+                }
+                throw new FormatException(SR.Format_InvalidString);
+            }
+
+            if (!NumberBufferToDouble(ref number, ref d))
+            {
+                throw new OverflowException(SR.Overflow_Single);
+            }
+            float castSingle = (float)d;
+            if (float.IsInfinity(castSingle))
+            {
+                throw new OverflowException(SR.Overflow_Single);
+            }
+            return castSingle;
+        }
+
+        internal static unsafe bool TryParseDecimal(ReadOnlySpan<char> value, NumberStyles options, NumberFormatInfo numfmt, out decimal result)
+        {
+            NumberBuffer number = default;
+            result = 0;
+
+            if (!TryStringToNumber(value, options, ref number, numfmt, true))
+            {
+                return false;
+            }
+
+            if (!NumberBufferToDecimal(ref number, ref result))
+            {
+                return false;
+            }
+            return true;
+        }
+
+        internal static unsafe bool TryParseDouble(ReadOnlySpan<char> value, NumberStyles options, NumberFormatInfo numfmt, out double result)
+        {
+            NumberBuffer number = default;
+            result = 0;
+
+
+            if (!TryStringToNumber(value, options, ref number, numfmt, false))
+            {
+                return false;
+            }
+            if (!NumberBufferToDouble(ref number, ref result))
+            {
+                return false;
+            }
+            return true;
+        }
+
+        internal static unsafe bool TryParseSingle(ReadOnlySpan<char> value, NumberStyles options, NumberFormatInfo numfmt, out float result)
+        {
+            NumberBuffer number = default;
+            result = 0;
+            double d = 0;
+
+            if (!TryStringToNumber(value, options, ref number, numfmt, false))
+            {
+                return false;
+            }
+            if (!NumberBufferToDouble(ref number, ref d))
+            {
+                return false;
+            }
+            float castSingle = (float)d;
+            if (float.IsInfinity(castSingle))
+            {
+                return false;
+            }
+
+            result = castSingle;
+            return true;
+        }
+
+        private static unsafe void StringToNumber(ReadOnlySpan<char> str, NumberStyles options, ref NumberBuffer number, NumberFormatInfo info, bool parseDecimal)
+        {
+            Debug.Assert(info != null);
+            fixed (char* stringPointer = &MemoryMarshal.GetReference(str))
+            {
+                char* p = stringPointer;
+                if (!ParseNumber(ref p, p + str.Length, options, ref number, info, parseDecimal)
+                    || (p - stringPointer < str.Length && !TrailingZeros(str, (int)(p - stringPointer))))
+                {
+                    throw new FormatException(SR.Format_InvalidString);
+                }
+            }
+        }
+
+        internal static unsafe bool TryStringToNumber(ReadOnlySpan<char> str, NumberStyles options, ref NumberBuffer number, NumberFormatInfo numfmt, bool parseDecimal)
+        {
+            Debug.Assert(numfmt != null);
+            fixed (char* stringPointer = &MemoryMarshal.GetReference(str))
+            {
+                char* p = stringPointer;
+                if (!ParseNumber(ref p, p + str.Length, options, ref number, numfmt, parseDecimal)
+                    || (p - stringPointer < str.Length && !TrailingZeros(str, (int)(p - stringPointer))))
+                {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
+        private static bool TrailingZeros(ReadOnlySpan<char> s, int index)
+        {
+            // For compatibility, we need to allow trailing zeros at the end of a number string
+            for (int i = index; i < s.Length; i++)
+            {
+                if (s[i] != '\0')
+                {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
+        private static unsafe char* MatchChars(char* p, char* pEnd, string str)
+        {
+            fixed (char* stringPointer = str)
+            {
+                return MatchChars(p, pEnd, stringPointer);
+            }
+        }
+
+        private static unsafe char* MatchChars(char* p, char* pEnd, char* str)
+        {
+            Debug.Assert(p != null && pEnd != null && p <= pEnd && str != null);
+
+            if (*str == '\0')
+            {
+                return null;
+            }
+            
+            // We only hurt the failure case
+            // This fix is for French or Kazakh cultures. Since a user cannot type 0xA0 as a
+            // space character we use 0x20 space character instead to mean the same.
+            while (true)
+            {
+                char cp = p < pEnd ? *p : '\0';
+                if (cp != *str && !(*str == '\u00a0' && cp == '\u0020'))
+                {
+                    break;
+                }
+                p++;
+                str++;
+                if (*str == '\0') return p;
+            }
+
+            return null;
+        }
+
+        private static bool IsWhite(char ch) => ch == 0x20 || (ch >= 0x09 && ch <= 0x0D);
+
+        private static bool NumberBufferToDouble(ref NumberBuffer number, ref double value)
+        {
+            double d = NumberToDouble(ref number);
+            uint e = DoubleHelper.Exponent(d);
+            ulong m = DoubleHelper.Mantissa(d);
+
+            if (e == 0x7FF)
+            {
+                return false;
+            }
+
+            if (e == 0 && m == 0)
+            {
+                d = 0;
+            }
+
+            value = d;
+            return true;
+        }
+
+        private static class DoubleHelper
+        {
+            public static unsafe uint Exponent(double d) =>
+                (*((uint*)&d + 1) >> 20) & 0x000007ff;
+
+            public static unsafe ulong Mantissa(double d) =>
+                *((ulong*)&d) & 0x000fffffffffffff;
+
+            public static unsafe bool Sign(double d) =>
+                (*((uint*)&d + 1) >> 31) != 0;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Numerics/ConstantHelper.cs b/src/System.Private.CoreLib/shared/System/Numerics/ConstantHelper.cs
new file mode 100644
index 0000000000..ea32ed3803
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Numerics/ConstantHelper.cs
@@ -0,0 +1,142 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System.Numerics
+{
+    internal class ConstantHelper
+    {
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Byte GetByteWithAllBitsSet()
+        {
+            Byte value = 0;
+            unsafe
+            {
+                unchecked
+                {
+                    *((Byte*)&value) = (Byte)0xff;
+                }
+            }
+            return value;
+        }
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static SByte GetSByteWithAllBitsSet()
+        {
+            SByte value = 0;
+            unsafe
+            {
+                unchecked
+                {
+                    *((SByte*)&value) = (SByte)0xff;
+                }
+            }
+            return value;
+        }
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static UInt16 GetUInt16WithAllBitsSet()
+        {
+            UInt16 value = 0;
+            unsafe
+            {
+                unchecked
+                {
+                    *((UInt16*)&value) = (UInt16)0xffff;
+                }
+            }
+            return value;
+        }
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Int16 GetInt16WithAllBitsSet()
+        {
+            Int16 value = 0;
+            unsafe
+            {
+                unchecked
+                {
+                    *((Int16*)&value) = (Int16)0xffff;
+                }
+            }
+            return value;
+        }
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static UInt32 GetUInt32WithAllBitsSet()
+        {
+            UInt32 value = 0;
+            unsafe
+            {
+                unchecked
+                {
+                    *((UInt32*)&value) = (UInt32)0xffffffff;
+                }
+            }
+            return value;
+        }
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Int32 GetInt32WithAllBitsSet()
+        {
+            Int32 value = 0;
+            unsafe
+            {
+                unchecked
+                {
+                    *((Int32*)&value) = (Int32)0xffffffff;
+                }
+            }
+            return value;
+        }
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static UInt64 GetUInt64WithAllBitsSet()
+        {
+            UInt64 value = 0;
+            unsafe
+            {
+                unchecked
+                {
+                    *((UInt64*)&value) = (UInt64)0xffffffffffffffff;
+                }
+            }
+            return value;
+        }
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Int64 GetInt64WithAllBitsSet()
+        {
+            Int64 value = 0;
+            unsafe
+            {
+                unchecked
+                {
+                    *((Int64*)&value) = (Int64)0xffffffffffffffff;
+                }
+            }
+            return value;
+        }
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Single GetSingleWithAllBitsSet()
+        {
+            Single value = 0;
+            unsafe
+            {
+                unchecked
+                {
+                    *((Int32*)&value) = (Int32)0xffffffff;
+                }
+            }
+            return value;
+        }
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Double GetDoubleWithAllBitsSet()
+        {
+            Double value = 0;
+            unsafe
+            {
+                unchecked
+                {
+                    *((Int64*)&value) = (Int64)0xffffffffffffffff;
+                }
+            }
+            return value;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Numerics/ConstantHelper.tt b/src/System.Private.CoreLib/shared/System/Numerics/ConstantHelper.tt
new file mode 100644
index 0000000000..4b1c677574
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Numerics/ConstantHelper.tt
@@ -0,0 +1,60 @@
+<#@ template debug="true" hostSpecific="true" #>
+<#@ output extension=".cs" #>
+<#@ Assembly Name="System.Core.dll" #>
+<#@ Assembly Name="System.Xml.dll" #>
+<#@ Assembly Name="System.Xml.Linq.dll" #>
+<#@ Assembly Name="System.Windows.Forms.dll" #>
+<#@ import namespace="System" #>
+<#@ import namespace="System.IO" #>
+<#@ import namespace="System.Diagnostics" #>
+<#@ import namespace="System.Linq" #>
+<#@ import namespace="System.Xml.Linq" #>
+<#@ import namespace="System.Collections" #>
+<#@ import namespace="System.Collections.Generic" #>
+<#@ import namespace="System.Runtime.InteropServices" #>
+<#@ include file="GenerationConfig.ttinclude" #><# GenerateCopyrightHeader(); #>
+
+using System.Runtime.CompilerServices;
+
+namespace System.Numerics
+{
+    internal class ConstantHelper
+    {
+<#    foreach (var type in supportedTypes)
+    {
+        string hexValue = "0x" + new string('f', Marshal.SizeOf(type) * 2);
+#>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static <#= type.Name #> Get<#= type.Name #>WithAllBitsSet()
+        {
+            <#= type.Name #> value = 0;
+            unsafe
+            {
+                unchecked
+                {
+                    *((<#= GetIntegralEquivalent(type).Name #>*)&value) = (<#=GetIntegralEquivalent(type).Name#>)<#= hexValue #>;
+                }
+            }
+            return value;
+        }
+<#
+    }
+#>
+    }
+}<#+
+    public Type GetIntegralEquivalent(Type type)
+    {
+        if (type == typeof(Single))
+        {
+            return typeof(Int32);
+        }
+        else if (type == typeof(double))
+        {
+            return typeof(Int64);
+        }
+        else 
+        {
+            return type;
+        }
+    }
+#>
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/shared/System/Numerics/GenerationConfig.ttinclude b/src/System.Private.CoreLib/shared/System/Numerics/GenerationConfig.ttinclude
new file mode 100644
index 0000000000..a21188e51b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Numerics/GenerationConfig.ttinclude
@@ -0,0 +1,173 @@
+<#@ import namespace="System.Linq" #>
+<#@ import namespace="System.Collections.Generic" #>
+<#@ import namespace="System.Text" #>
+<#+ 
+    /*    This file includes static data used as compilation configuration for the rest of the code generation. 
+        It is shared here to ensure that all generated code compiles with the same constants and configurations.    */
+
+    // The set of supported numeric types to compile
+    public static Type[] supportedTypes = new[] 
+    { 
+        typeof(Byte), typeof(SByte), typeof(UInt16), typeof(Int16),
+        typeof(UInt32), typeof(Int32), typeof(UInt64), typeof(Int64),
+        typeof(Single), typeof(Double)
+    };
+
+    // The set of unsigned types, a subset of the above. Used for excluding from certain methods, i.e. Abs and Negate
+    public static Type[] unsignedTypes = new[]
+    {
+        typeof(Byte), typeof(UInt16), typeof(UInt32), typeof(UInt64)
+    };
+
+    public static Type[] integralTypes = new[]
+    {
+        typeof(Byte), typeof(SByte), typeof(UInt16), typeof(Int16),
+        typeof(UInt32), typeof(Int32), typeof(UInt64), typeof(Int64)
+    };
+
+    public static Type[] nonClsCompliantTypes = new[]
+    {
+        typeof(SByte), typeof(UInt16), 
+        typeof(UInt32), typeof(UInt64)
+    };
+
+    // The total register size, in bytes. 16 for SSE2, 32 for AVX, 64 for AVX512
+    public static int totalSize = 16;
+
+    /* General template helper procedures */
+
+    // Returns the constructed register field name for the given type and index.
+    public string GetRegisterFieldName(Type t, int index)
+    {
+        return "register." + t.Name.ToLowerInvariant() + "_" + index;
+    }
+
+    // Returns the number of fields for a given type, based on the current configuration's register size
+    public int GetNumFields(Type t, int totalSize)
+    {
+        return totalSize / Marshal.SizeOf(t);
+    }
+
+    public static HashSet<Type> WidenableTypes { get; private set; } = new HashSet<Type>()
+    {
+        typeof(byte),
+        typeof(ushort),
+        typeof(uint),
+        typeof(sbyte),
+        typeof(short),
+        typeof(int),
+        typeof(float),
+    };
+
+    private static Dictionary<Type, Type> s_widenTargets = new Dictionary<Type, Type>()
+    {
+        { typeof(byte), typeof(ushort) },
+        { typeof(ushort), typeof(uint) },
+        { typeof(uint), typeof(ulong) },
+        { typeof(sbyte), typeof(short) },
+        { typeof(short), typeof(int) },
+        { typeof(int), typeof(long) },
+        { typeof(float), typeof(double) },
+    };
+
+    public Type GetWidenTarget(Type t)
+    {
+        Type target;
+        if (!s_widenTargets.TryGetValue(t, out target))
+        {
+            throw new InvalidOperationException("No widen target for " + t.Name);
+        }
+
+        return target;
+    }
+
+    public static HashSet<Type> NarrowableTypes { get; private set; } = new HashSet<Type>()
+    {
+        typeof(ushort),
+        typeof(uint),
+        typeof(ulong),
+        typeof(short),
+        typeof(int),
+        typeof(long),
+        typeof(double),
+    };
+
+    private static Dictionary<Type, Type> s_narrowTargets = new Dictionary<Type, Type>()
+    {
+        { typeof(ulong), typeof(uint) },
+        { typeof(uint), typeof(ushort) },
+        { typeof(ushort), typeof(byte) },
+        { typeof(long), typeof(int) },
+        { typeof(int), typeof(short) },
+        { typeof(short), typeof(sbyte) },
+        { typeof(double), typeof(float) },
+    };
+
+    public Type GetNarrowTarget(Type t)
+    {
+        Type target;
+        if (!s_narrowTargets.TryGetValue(t, out target))
+        {
+            throw new InvalidOperationException("No narrow target for " + t.Name);
+        }
+
+        return target;
+    }
+
+    public static List<KeyValuePair<Type, Type>> SameSizeConversionPairs = new List<KeyValuePair<Type, Type>>()
+    {
+        new KeyValuePair<Type, Type>(typeof(int), typeof(float)),
+        new KeyValuePair<Type, Type>(typeof(uint), typeof(float)),
+        new KeyValuePair<Type, Type>(typeof(long), typeof(double)),
+        new KeyValuePair<Type, Type>(typeof(ulong), typeof(double)),
+        new KeyValuePair<Type, Type>(typeof(float), typeof(int)),
+        new KeyValuePair<Type, Type>(typeof(float), typeof(uint)),
+        new KeyValuePair<Type, Type>(typeof(double), typeof(long)),
+        new KeyValuePair<Type, Type>(typeof(double), typeof(ulong)),
+    };
+
+    public void GenerateCopyrightHeader()
+    {
+#>// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+<#+
+    }
+
+    public string GenerateIfStatementHeader(Type type)
+    {
+        string keyword = (type == supportedTypes[0]) ? "if" : "else if";
+        return string.Format("{0} (typeof(T) == typeof({1}))", keyword, type.Name);
+    }
+
+    public string GenerateIfStatementHeader(Type type, IEnumerable<Type> allTypes)
+    {
+        string keyword = (type == allTypes.ToArray()[0]) ? "if" : "else if";
+        return string.Format("{0} (typeof(T) == typeof({1}))", keyword, type.Name);
+    }
+
+    public string MakeTypeComparisonCondition(Type type)
+    {
+        return string.Format("(typeof(T) == typeof({0}))", type.Name);
+    }
+
+    public string GenerateIfConditionAllTypes(IEnumerable<Type> allTypes)
+    {
+        StringBuilder sbuilder = new StringBuilder();
+        bool firstTime = true;
+        foreach (var type in allTypes)
+        {
+            if (firstTime)
+            {
+                sbuilder.Append("if (").Append(MakeTypeComparisonCondition(type));
+                firstTime = false;
+            }
+            else
+            {
+                sbuilder.AppendLine().Append("                || ").Append(MakeTypeComparisonCondition(type));
+            }
+        }
+        sbuilder.Append(")");
+        return sbuilder.ToString();
+    }
+#>
diff --git a/src/System.Private.CoreLib/shared/System/Numerics/Register.cs b/src/System.Private.CoreLib/shared/System/Numerics/Register.cs
new file mode 100644
index 0000000000..a27e922b9d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Numerics/Register.cs
@@ -0,0 +1,172 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+
+namespace System.Numerics
+{
+    /// <summary>
+    /// A structure describing the layout of an SSE2-sized register.
+    /// Contains overlapping fields representing the set of valid numeric types.
+    /// Allows the generic Vector'T struct to contain an explicit field layout.
+    /// </summary>
+    [StructLayout(LayoutKind.Explicit)]
+    internal struct Register
+    {
+        #region Internal Storage Fields
+        // Internal System.Byte Fields
+        [FieldOffset(0)]
+        internal Byte byte_0;
+        [FieldOffset(1)]
+        internal Byte byte_1;
+        [FieldOffset(2)]
+        internal Byte byte_2;
+        [FieldOffset(3)]
+        internal Byte byte_3;
+        [FieldOffset(4)]
+        internal Byte byte_4;
+        [FieldOffset(5)]
+        internal Byte byte_5;
+        [FieldOffset(6)]
+        internal Byte byte_6;
+        [FieldOffset(7)]
+        internal Byte byte_7;
+        [FieldOffset(8)]
+        internal Byte byte_8;
+        [FieldOffset(9)]
+        internal Byte byte_9;
+        [FieldOffset(10)]
+        internal Byte byte_10;
+        [FieldOffset(11)]
+        internal Byte byte_11;
+        [FieldOffset(12)]
+        internal Byte byte_12;
+        [FieldOffset(13)]
+        internal Byte byte_13;
+        [FieldOffset(14)]
+        internal Byte byte_14;
+        [FieldOffset(15)]
+        internal Byte byte_15;
+
+        // Internal System.SByte Fields
+        [FieldOffset(0)]
+        internal SByte sbyte_0;
+        [FieldOffset(1)]
+        internal SByte sbyte_1;
+        [FieldOffset(2)]
+        internal SByte sbyte_2;
+        [FieldOffset(3)]
+        internal SByte sbyte_3;
+        [FieldOffset(4)]
+        internal SByte sbyte_4;
+        [FieldOffset(5)]
+        internal SByte sbyte_5;
+        [FieldOffset(6)]
+        internal SByte sbyte_6;
+        [FieldOffset(7)]
+        internal SByte sbyte_7;
+        [FieldOffset(8)]
+        internal SByte sbyte_8;
+        [FieldOffset(9)]
+        internal SByte sbyte_9;
+        [FieldOffset(10)]
+        internal SByte sbyte_10;
+        [FieldOffset(11)]
+        internal SByte sbyte_11;
+        [FieldOffset(12)]
+        internal SByte sbyte_12;
+        [FieldOffset(13)]
+        internal SByte sbyte_13;
+        [FieldOffset(14)]
+        internal SByte sbyte_14;
+        [FieldOffset(15)]
+        internal SByte sbyte_15;
+
+        // Internal System.UInt16 Fields
+        [FieldOffset(0)]
+        internal UInt16 uint16_0;
+        [FieldOffset(2)]
+        internal UInt16 uint16_1;
+        [FieldOffset(4)]
+        internal UInt16 uint16_2;
+        [FieldOffset(6)]
+        internal UInt16 uint16_3;
+        [FieldOffset(8)]
+        internal UInt16 uint16_4;
+        [FieldOffset(10)]
+        internal UInt16 uint16_5;
+        [FieldOffset(12)]
+        internal UInt16 uint16_6;
+        [FieldOffset(14)]
+        internal UInt16 uint16_7;
+
+        // Internal System.Int16 Fields
+        [FieldOffset(0)]
+        internal Int16 int16_0;
+        [FieldOffset(2)]
+        internal Int16 int16_1;
+        [FieldOffset(4)]
+        internal Int16 int16_2;
+        [FieldOffset(6)]
+        internal Int16 int16_3;
+        [FieldOffset(8)]
+        internal Int16 int16_4;
+        [FieldOffset(10)]
+        internal Int16 int16_5;
+        [FieldOffset(12)]
+        internal Int16 int16_6;
+        [FieldOffset(14)]
+        internal Int16 int16_7;
+
+        // Internal System.UInt32 Fields
+        [FieldOffset(0)]
+        internal UInt32 uint32_0;
+        [FieldOffset(4)]
+        internal UInt32 uint32_1;
+        [FieldOffset(8)]
+        internal UInt32 uint32_2;
+        [FieldOffset(12)]
+        internal UInt32 uint32_3;
+
+        // Internal System.Int32 Fields
+        [FieldOffset(0)]
+        internal Int32 int32_0;
+        [FieldOffset(4)]
+        internal Int32 int32_1;
+        [FieldOffset(8)]
+        internal Int32 int32_2;
+        [FieldOffset(12)]
+        internal Int32 int32_3;
+
+        // Internal System.UInt64 Fields
+        [FieldOffset(0)]
+        internal UInt64 uint64_0;
+        [FieldOffset(8)]
+        internal UInt64 uint64_1;
+
+        // Internal System.Int64 Fields
+        [FieldOffset(0)]
+        internal Int64 int64_0;
+        [FieldOffset(8)]
+        internal Int64 int64_1;
+
+        // Internal System.Single Fields
+        [FieldOffset(0)]
+        internal Single single_0;
+        [FieldOffset(4)]
+        internal Single single_1;
+        [FieldOffset(8)]
+        internal Single single_2;
+        [FieldOffset(12)]
+        internal Single single_3;
+
+        // Internal System.Double Fields
+        [FieldOffset(0)]
+        internal Double double_0;
+        [FieldOffset(8)]
+        internal Double double_1;
+
+        #endregion Internal Storage Fields
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Numerics/Register.tt b/src/System.Private.CoreLib/shared/System/Numerics/Register.tt
new file mode 100644
index 0000000000..a9de3b9748
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Numerics/Register.tt
@@ -0,0 +1,46 @@
+<#@ template debug="true" hostSpecific="true" #>
+<#@ output extension=".cs" #>
+<#@ Assembly Name="System.Core.dll" #>
+<#@ Assembly Name="System.Xml.dll" #>
+<#@ import namespace="System" #>
+<#@ import namespace="System.Linq" #>
+<#@ import namespace="System.Runtime.InteropServices" #>
+<#@ import namespace="System.Diagnostics" #>
+<#@ include file="GenerationConfig.ttinclude" #><# GenerateCopyrightHeader(); #>
+
+using System.Runtime.InteropServices;
+
+namespace System.Numerics
+{
+    /// <summary>
+    /// A structure describing the layout of an SSE2-sized register.
+    /// Contains overlapping fields representing the set of valid numeric types.
+    /// Allows the generic Vector'T struct to contain an explicit field layout.
+    /// </summary>
+    [StructLayout(LayoutKind.Explicit)]
+    internal struct Register
+    {
+        #region Internal Storage Fields
+<#
+    foreach (var type in supportedTypes)
+    {
+        Debug.Assert(
+            totalSize % Marshal.SizeOf(type) == 0,
+            "The size of supported structs must be a factor of the supported register size.");    
+#>
+        // Internal <#= type.FullName #> Fields
+<#
+        for (int g = 0; g < totalSize / Marshal.SizeOf(type); g++)
+        {
+#>
+        [FieldOffset(<#=Marshal.SizeOf(type) * g#>)]
+        internal <#=type.Name#> <#= type.Name.ToLowerInvariant() + "_" + g #>;
+<#
+        }
+#>
+
+<#
+    }
+#>        #endregion Internal Storage Fields
+    }
+}
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/shared/System/Numerics/Vector.cs b/src/System.Private.CoreLib/shared/System/Numerics/Vector.cs
new file mode 100644
index 0000000000..42f86d9297
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Numerics/Vector.cs
@@ -0,0 +1,5538 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#if netcoreapp
+using Internal.Runtime.CompilerServices;
+#endif
+using System.Globalization;
+using System.Numerics.Hashing;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace System.Numerics
+{
+    /* Note: The following patterns are used throughout the code here and are described here
+    *
+    * PATTERN:
+    *    if (typeof(T) == typeof(Int32)) { ... }
+    *    else if (typeof(T) == typeof(Single)) { ... }
+    * EXPLANATION:
+    *    At runtime, each instantiation of Vector<T> will be type-specific, and each of these typeof blocks will be eliminated,
+    *    as typeof(T) is a (JIT) compile-time constant for each instantiation. This design was chosen to eliminate any overhead from
+    *    delegates and other patterns.
+    *
+    * PATTERN:
+    *    if (Vector.IsHardwareAccelerated) { ... }
+    *    else { ... }
+    * EXPLANATION
+    *    This pattern solves two problems:
+    *        1. Allows us to unroll loops when we know the size (when no hardware acceleration is present)
+    *        2. Allows reflection to work:
+    *            - If a method is called via reflection, it will not be "intrinsified", which would cause issues if we did
+    *              not provide an implementation for that case (i.e. if it only included a case which assumed 16-byte registers)
+    *    (NOTE: It is assumed that Vector.IsHardwareAccelerated will be a compile-time constant, eliminating these checks
+    *        from the JIT'd code.)
+    *
+    * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+    /// <summary>
+    /// A structure that represents a single Vector. The count of this Vector is fixed but CPU register dependent.
+    /// This struct only supports numerical types. This type is intended to be used as a building block for vectorizing
+    /// large algorithms. This type is immutable, individual elements cannot be modified.
+    /// </summary>
+    [Intrinsic]
+    public struct Vector<T> : IEquatable<Vector<T>>, IFormattable where T : struct
+    {
+        #region Fields
+        private Register register;
+        #endregion Fields
+
+        #region Static Members
+        /// <summary>
+        /// Returns the number of elements stored in the vector. This value is hardware dependent.
+        /// </summary>
+        public static int Count
+        {
+            [Intrinsic]
+            get
+            {
+                return s_count;
+            }
+        }
+        private static readonly int s_count = InitializeCount();
+
+        /// <summary>
+        /// Returns a vector containing all zeroes.
+        /// </summary>
+        public static Vector<T> Zero
+        {
+            [Intrinsic]
+            get
+            {
+                return s_zero;
+            }
+        }
+        private static readonly Vector<T> s_zero = new Vector<T>();
+
+        /// <summary>
+        /// Returns a vector containing all ones.
+        /// </summary>
+        public static Vector<T> One
+        {
+            [Intrinsic]
+            get
+            {
+                return s_one;
+            }
+        }
+        private static readonly Vector<T> s_one = new Vector<T>(GetOneValue());
+
+        internal static Vector<T> AllOnes { get { return s_allOnes; } }
+        private static readonly Vector<T> s_allOnes = new Vector<T>(GetAllBitsSetValue());
+        #endregion Static Members
+
+        #region Static Initialization
+        private struct VectorSizeHelper
+        {
+            internal Vector<T> _placeholder;
+            internal byte _byte;
+        }
+
+		// Calculates the size of this struct in bytes, by computing the offset of a field in a structure
+        private static unsafe int InitializeCount()
+        {
+            VectorSizeHelper vsh;
+            byte* vectorBase = &vsh._placeholder.register.byte_0;
+            byte* byteBase = &vsh._byte;
+            int vectorSizeInBytes = (int)(byteBase - vectorBase);
+
+            int typeSizeInBytes = -1;
+            if (typeof(T) == typeof(Byte))
+            {
+                typeSizeInBytes = sizeof(Byte);
+            }
+            else if (typeof(T) == typeof(SByte))
+            {
+                typeSizeInBytes = sizeof(SByte);
+            }
+            else if (typeof(T) == typeof(UInt16))
+            {
+                typeSizeInBytes = sizeof(UInt16);
+            }
+            else if (typeof(T) == typeof(Int16))
+            {
+                typeSizeInBytes = sizeof(Int16);
+            }
+            else if (typeof(T) == typeof(UInt32))
+            {
+                typeSizeInBytes = sizeof(UInt32);
+            }
+            else if (typeof(T) == typeof(Int32))
+            {
+                typeSizeInBytes = sizeof(Int32);
+            }
+            else if (typeof(T) == typeof(UInt64))
+            {
+                typeSizeInBytes = sizeof(UInt64);
+            }
+            else if (typeof(T) == typeof(Int64))
+            {
+                typeSizeInBytes = sizeof(Int64);
+            }
+            else if (typeof(T) == typeof(Single))
+            {
+                typeSizeInBytes = sizeof(Single);
+            }
+            else if (typeof(T) == typeof(Double))
+            {
+                typeSizeInBytes = sizeof(Double);
+            }
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+
+            return vectorSizeInBytes / typeSizeInBytes;
+        }
+        #endregion Static Initialization
+
+        #region Constructors
+        /// <summary>
+        /// Constructs a vector whose components are all <code>value</code>
+        /// </summary>
+        [Intrinsic]
+        public unsafe Vector(T value)
+            : this()
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    fixed (Byte* basePtr = &this.register.byte_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (Byte)(object)value;
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    fixed (SByte* basePtr = &this.register.sbyte_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (SByte)(object)value;
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    fixed (UInt16* basePtr = &this.register.uint16_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (UInt16)(object)value;
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    fixed (Int16* basePtr = &this.register.int16_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (Int16)(object)value;
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    fixed (UInt32* basePtr = &this.register.uint32_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (UInt32)(object)value;
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    fixed (Int32* basePtr = &this.register.int32_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (Int32)(object)value;
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    fixed (UInt64* basePtr = &this.register.uint64_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (UInt64)(object)value;
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    fixed (Int64* basePtr = &this.register.int64_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (Int64)(object)value;
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    fixed (Single* basePtr = &this.register.single_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (Single)(object)value;
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    fixed (Double* basePtr = &this.register.double_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (Double)(object)value;
+                        }
+                    }
+                }
+            }
+            else
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    register.byte_0 = (Byte)(object)value;
+                    register.byte_1 = (Byte)(object)value;
+                    register.byte_2 = (Byte)(object)value;
+                    register.byte_3 = (Byte)(object)value;
+                    register.byte_4 = (Byte)(object)value;
+                    register.byte_5 = (Byte)(object)value;
+                    register.byte_6 = (Byte)(object)value;
+                    register.byte_7 = (Byte)(object)value;
+                    register.byte_8 = (Byte)(object)value;
+                    register.byte_9 = (Byte)(object)value;
+                    register.byte_10 = (Byte)(object)value;
+                    register.byte_11 = (Byte)(object)value;
+                    register.byte_12 = (Byte)(object)value;
+                    register.byte_13 = (Byte)(object)value;
+                    register.byte_14 = (Byte)(object)value;
+                    register.byte_15 = (Byte)(object)value;
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    register.sbyte_0 = (SByte)(object)value;
+                    register.sbyte_1 = (SByte)(object)value;
+                    register.sbyte_2 = (SByte)(object)value;
+                    register.sbyte_3 = (SByte)(object)value;
+                    register.sbyte_4 = (SByte)(object)value;
+                    register.sbyte_5 = (SByte)(object)value;
+                    register.sbyte_6 = (SByte)(object)value;
+                    register.sbyte_7 = (SByte)(object)value;
+                    register.sbyte_8 = (SByte)(object)value;
+                    register.sbyte_9 = (SByte)(object)value;
+                    register.sbyte_10 = (SByte)(object)value;
+                    register.sbyte_11 = (SByte)(object)value;
+                    register.sbyte_12 = (SByte)(object)value;
+                    register.sbyte_13 = (SByte)(object)value;
+                    register.sbyte_14 = (SByte)(object)value;
+                    register.sbyte_15 = (SByte)(object)value;
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    register.uint16_0 = (UInt16)(object)value;
+                    register.uint16_1 = (UInt16)(object)value;
+                    register.uint16_2 = (UInt16)(object)value;
+                    register.uint16_3 = (UInt16)(object)value;
+                    register.uint16_4 = (UInt16)(object)value;
+                    register.uint16_5 = (UInt16)(object)value;
+                    register.uint16_6 = (UInt16)(object)value;
+                    register.uint16_7 = (UInt16)(object)value;
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    register.int16_0 = (Int16)(object)value;
+                    register.int16_1 = (Int16)(object)value;
+                    register.int16_2 = (Int16)(object)value;
+                    register.int16_3 = (Int16)(object)value;
+                    register.int16_4 = (Int16)(object)value;
+                    register.int16_5 = (Int16)(object)value;
+                    register.int16_6 = (Int16)(object)value;
+                    register.int16_7 = (Int16)(object)value;
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    register.uint32_0 = (UInt32)(object)value;
+                    register.uint32_1 = (UInt32)(object)value;
+                    register.uint32_2 = (UInt32)(object)value;
+                    register.uint32_3 = (UInt32)(object)value;
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    register.int32_0 = (Int32)(object)value;
+                    register.int32_1 = (Int32)(object)value;
+                    register.int32_2 = (Int32)(object)value;
+                    register.int32_3 = (Int32)(object)value;
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    register.uint64_0 = (UInt64)(object)value;
+                    register.uint64_1 = (UInt64)(object)value;
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    register.int64_0 = (Int64)(object)value;
+                    register.int64_1 = (Int64)(object)value;
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    register.single_0 = (Single)(object)value;
+                    register.single_1 = (Single)(object)value;
+                    register.single_2 = (Single)(object)value;
+                    register.single_3 = (Single)(object)value;
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    register.double_0 = (Double)(object)value;
+                    register.double_1 = (Double)(object)value;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Constructs a vector from the given array. The size of the given array must be at least Vector'T.Count.
+        /// </summary>
+        [Intrinsic]
+        public unsafe Vector(T[] values) : this(values, 0) { }
+
+        /// <summary>
+        /// Constructs a vector from the given array, starting from the given index.
+        /// The array must contain at least Vector'T.Count from the given index.
+        /// </summary>
+        public unsafe Vector(T[] values, int index)
+            : this()
+        {
+            if (values == null)
+            {
+                // Match the JIT's exception type here. For perf, a NullReference is thrown instead of an ArgumentNull.
+                throw new NullReferenceException(SR.Arg_NullArgumentNullRef);
+            }
+            if (index < 0 || (values.Length - index) < Count)
+            {
+                throw new IndexOutOfRangeException(SR.Format(SR.Arg_InsufficientNumberOfElements, Vector<T>.Count, nameof(values)));
+            }
+
+            if (Vector.IsHardwareAccelerated)
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    fixed (Byte* basePtr = &this.register.byte_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (Byte)(object)values[g + index];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    fixed (SByte* basePtr = &this.register.sbyte_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (SByte)(object)values[g + index];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    fixed (UInt16* basePtr = &this.register.uint16_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (UInt16)(object)values[g + index];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    fixed (Int16* basePtr = &this.register.int16_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (Int16)(object)values[g + index];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    fixed (UInt32* basePtr = &this.register.uint32_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (UInt32)(object)values[g + index];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    fixed (Int32* basePtr = &this.register.int32_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (Int32)(object)values[g + index];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    fixed (UInt64* basePtr = &this.register.uint64_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (UInt64)(object)values[g + index];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    fixed (Int64* basePtr = &this.register.int64_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (Int64)(object)values[g + index];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    fixed (Single* basePtr = &this.register.single_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (Single)(object)values[g + index];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    fixed (Double* basePtr = &this.register.double_0)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (Double)(object)values[g + index];
+                        }
+                    }
+                }
+            }
+            else
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    fixed (Byte* basePtr = &this.register.byte_0)
+                    {
+                        *(basePtr + 0) = (Byte)(object)values[0 + index];
+                        *(basePtr + 1) = (Byte)(object)values[1 + index];
+                        *(basePtr + 2) = (Byte)(object)values[2 + index];
+                        *(basePtr + 3) = (Byte)(object)values[3 + index];
+                        *(basePtr + 4) = (Byte)(object)values[4 + index];
+                        *(basePtr + 5) = (Byte)(object)values[5 + index];
+                        *(basePtr + 6) = (Byte)(object)values[6 + index];
+                        *(basePtr + 7) = (Byte)(object)values[7 + index];
+                        *(basePtr + 8) = (Byte)(object)values[8 + index];
+                        *(basePtr + 9) = (Byte)(object)values[9 + index];
+                        *(basePtr + 10) = (Byte)(object)values[10 + index];
+                        *(basePtr + 11) = (Byte)(object)values[11 + index];
+                        *(basePtr + 12) = (Byte)(object)values[12 + index];
+                        *(basePtr + 13) = (Byte)(object)values[13 + index];
+                        *(basePtr + 14) = (Byte)(object)values[14 + index];
+                        *(basePtr + 15) = (Byte)(object)values[15 + index];
+                    }
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    fixed (SByte* basePtr = &this.register.sbyte_0)
+                    {
+                        *(basePtr + 0) = (SByte)(object)values[0 + index];
+                        *(basePtr + 1) = (SByte)(object)values[1 + index];
+                        *(basePtr + 2) = (SByte)(object)values[2 + index];
+                        *(basePtr + 3) = (SByte)(object)values[3 + index];
+                        *(basePtr + 4) = (SByte)(object)values[4 + index];
+                        *(basePtr + 5) = (SByte)(object)values[5 + index];
+                        *(basePtr + 6) = (SByte)(object)values[6 + index];
+                        *(basePtr + 7) = (SByte)(object)values[7 + index];
+                        *(basePtr + 8) = (SByte)(object)values[8 + index];
+                        *(basePtr + 9) = (SByte)(object)values[9 + index];
+                        *(basePtr + 10) = (SByte)(object)values[10 + index];
+                        *(basePtr + 11) = (SByte)(object)values[11 + index];
+                        *(basePtr + 12) = (SByte)(object)values[12 + index];
+                        *(basePtr + 13) = (SByte)(object)values[13 + index];
+                        *(basePtr + 14) = (SByte)(object)values[14 + index];
+                        *(basePtr + 15) = (SByte)(object)values[15 + index];
+                    }
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    fixed (UInt16* basePtr = &this.register.uint16_0)
+                    {
+                        *(basePtr + 0) = (UInt16)(object)values[0 + index];
+                        *(basePtr + 1) = (UInt16)(object)values[1 + index];
+                        *(basePtr + 2) = (UInt16)(object)values[2 + index];
+                        *(basePtr + 3) = (UInt16)(object)values[3 + index];
+                        *(basePtr + 4) = (UInt16)(object)values[4 + index];
+                        *(basePtr + 5) = (UInt16)(object)values[5 + index];
+                        *(basePtr + 6) = (UInt16)(object)values[6 + index];
+                        *(basePtr + 7) = (UInt16)(object)values[7 + index];
+                    }
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    fixed (Int16* basePtr = &this.register.int16_0)
+                    {
+                        *(basePtr + 0) = (Int16)(object)values[0 + index];
+                        *(basePtr + 1) = (Int16)(object)values[1 + index];
+                        *(basePtr + 2) = (Int16)(object)values[2 + index];
+                        *(basePtr + 3) = (Int16)(object)values[3 + index];
+                        *(basePtr + 4) = (Int16)(object)values[4 + index];
+                        *(basePtr + 5) = (Int16)(object)values[5 + index];
+                        *(basePtr + 6) = (Int16)(object)values[6 + index];
+                        *(basePtr + 7) = (Int16)(object)values[7 + index];
+                    }
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    fixed (UInt32* basePtr = &this.register.uint32_0)
+                    {
+                        *(basePtr + 0) = (UInt32)(object)values[0 + index];
+                        *(basePtr + 1) = (UInt32)(object)values[1 + index];
+                        *(basePtr + 2) = (UInt32)(object)values[2 + index];
+                        *(basePtr + 3) = (UInt32)(object)values[3 + index];
+                    }
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    fixed (Int32* basePtr = &this.register.int32_0)
+                    {
+                        *(basePtr + 0) = (Int32)(object)values[0 + index];
+                        *(basePtr + 1) = (Int32)(object)values[1 + index];
+                        *(basePtr + 2) = (Int32)(object)values[2 + index];
+                        *(basePtr + 3) = (Int32)(object)values[3 + index];
+                    }
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    fixed (UInt64* basePtr = &this.register.uint64_0)
+                    {
+                        *(basePtr + 0) = (UInt64)(object)values[0 + index];
+                        *(basePtr + 1) = (UInt64)(object)values[1 + index];
+                    }
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    fixed (Int64* basePtr = &this.register.int64_0)
+                    {
+                        *(basePtr + 0) = (Int64)(object)values[0 + index];
+                        *(basePtr + 1) = (Int64)(object)values[1 + index];
+                    }
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    fixed (Single* basePtr = &this.register.single_0)
+                    {
+                        *(basePtr + 0) = (Single)(object)values[0 + index];
+                        *(basePtr + 1) = (Single)(object)values[1 + index];
+                        *(basePtr + 2) = (Single)(object)values[2 + index];
+                        *(basePtr + 3) = (Single)(object)values[3 + index];
+                    }
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    fixed (Double* basePtr = &this.register.double_0)
+                    {
+                        *(basePtr + 0) = (Double)(object)values[0 + index];
+                        *(basePtr + 1) = (Double)(object)values[1 + index];
+                    }
+                }
+            }
+        }
+
+#pragma warning disable 3001 // void* is not a CLS-Compliant argument type
+        internal unsafe Vector(void* dataPointer) : this(dataPointer, 0) { }
+#pragma warning restore 3001 // void* is not a CLS-Compliant argument type
+
+#pragma warning disable 3001 // void* is not a CLS-Compliant argument type
+        // Implemented with offset if this API ever becomes public; an offset of 0 is used internally.
+        internal unsafe Vector(void* dataPointer, int offset)
+            : this()
+        {
+            if (typeof(T) == typeof(Byte))
+            {
+                Byte* castedPtr = (Byte*)dataPointer;
+                castedPtr += offset;
+                fixed (Byte* registerBase = &this.register.byte_0)
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        registerBase[g] = castedPtr[g];
+                    }
+                }
+            }
+            else if (typeof(T) == typeof(SByte))
+            {
+                SByte* castedPtr = (SByte*)dataPointer;
+                castedPtr += offset;
+                fixed (SByte* registerBase = &this.register.sbyte_0)
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        registerBase[g] = castedPtr[g];
+                    }
+                }
+            }
+            else if (typeof(T) == typeof(UInt16))
+            {
+                UInt16* castedPtr = (UInt16*)dataPointer;
+                castedPtr += offset;
+                fixed (UInt16* registerBase = &this.register.uint16_0)
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        registerBase[g] = castedPtr[g];
+                    }
+                }
+            }
+            else if (typeof(T) == typeof(Int16))
+            {
+                Int16* castedPtr = (Int16*)dataPointer;
+                castedPtr += offset;
+                fixed (Int16* registerBase = &this.register.int16_0)
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        registerBase[g] = castedPtr[g];
+                    }
+                }
+            }
+            else if (typeof(T) == typeof(UInt32))
+            {
+                UInt32* castedPtr = (UInt32*)dataPointer;
+                castedPtr += offset;
+                fixed (UInt32* registerBase = &this.register.uint32_0)
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        registerBase[g] = castedPtr[g];
+                    }
+                }
+            }
+            else if (typeof(T) == typeof(Int32))
+            {
+                Int32* castedPtr = (Int32*)dataPointer;
+                castedPtr += offset;
+                fixed (Int32* registerBase = &this.register.int32_0)
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        registerBase[g] = castedPtr[g];
+                    }
+                }
+            }
+            else if (typeof(T) == typeof(UInt64))
+            {
+                UInt64* castedPtr = (UInt64*)dataPointer;
+                castedPtr += offset;
+                fixed (UInt64* registerBase = &this.register.uint64_0)
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        registerBase[g] = castedPtr[g];
+                    }
+                }
+            }
+            else if (typeof(T) == typeof(Int64))
+            {
+                Int64* castedPtr = (Int64*)dataPointer;
+                castedPtr += offset;
+                fixed (Int64* registerBase = &this.register.int64_0)
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        registerBase[g] = castedPtr[g];
+                    }
+                }
+            }
+            else if (typeof(T) == typeof(Single))
+            {
+                Single* castedPtr = (Single*)dataPointer;
+                castedPtr += offset;
+                fixed (Single* registerBase = &this.register.single_0)
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        registerBase[g] = castedPtr[g];
+                    }
+                }
+            }
+            else if (typeof(T) == typeof(Double))
+            {
+                Double* castedPtr = (Double*)dataPointer;
+                castedPtr += offset;
+                fixed (Double* registerBase = &this.register.double_0)
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        registerBase[g] = castedPtr[g];
+                    }
+                }
+            }
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+#pragma warning restore 3001 // void* is not a CLS-Compliant argument type
+
+        private Vector(ref Register existingRegister)
+        {
+            this.register = existingRegister;
+        }
+
+#if netcoreapp
+        /// <summary>
+        /// Constructs a vector from the given span. The span must contain at least Vector'T.Count elements.
+        /// </summary>
+        public Vector(Span<T> values)
+            : this()
+        {
+            if ((typeof(T) == typeof(Byte))
+                || (typeof(T) == typeof(SByte))
+                || (typeof(T) == typeof(UInt16))
+                || (typeof(T) == typeof(Int16))
+                || (typeof(T) == typeof(UInt32))
+                || (typeof(T) == typeof(Int32))
+                || (typeof(T) == typeof(UInt64))
+                || (typeof(T) == typeof(Int64))
+                || (typeof(T) == typeof(Single))
+                || (typeof(T) == typeof(Double)))
+            {
+                if (values.Length < Count)
+                {
+                    throw new IndexOutOfRangeException(SR.Format(SR.Arg_InsufficientNumberOfElements, Vector<T>.Count, nameof(values)));
+                }
+                this = Unsafe.ReadUnaligned<Vector<T>>(ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(values)));
+            }
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+#endif
+        #endregion Constructors
+
+        #region Public Instance Methods
+        /// <summary>
+        /// Copies the vector to the given destination array. The destination array must be at least size Vector'T.Count.
+        /// </summary>
+        /// <param name="destination">The destination array which the values are copied into</param>
+        /// <exception cref="ArgumentNullException">If the destination array is null</exception>
+        /// <exception cref="ArgumentException">If number of elements in source vector is greater than those available in destination array</exception>
+        [Intrinsic]
+        public unsafe void CopyTo(T[] destination)
+        {
+            CopyTo(destination, 0);
+        }
+
+        /// <summary>
+        /// Copies the vector to the given destination array. The destination array must be at least size Vector'T.Count.
+        /// </summary>
+        /// <param name="destination">The destination array which the values are copied into</param>
+        /// <param name="startIndex">The index to start copying to</param>
+        /// <exception cref="ArgumentNullException">If the destination array is null</exception>
+        /// <exception cref="ArgumentOutOfRangeException">If index is greater than end of the array or index is less than zero</exception>
+        /// <exception cref="ArgumentException">If number of elements in source vector is greater than those available in destination array</exception>
+        [Intrinsic]
+        public unsafe void CopyTo(T[] destination, int startIndex)
+        {
+            if (destination == null)
+            {
+                // Match the JIT's exception type here. For perf, a NullReference is thrown instead of an ArgumentNull.
+                throw new NullReferenceException(SR.Arg_NullArgumentNullRef);
+            }
+            if (startIndex < 0 || startIndex >= destination.Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.Format(SR.Arg_ArgumentOutOfRangeException, startIndex));
+            }
+            if ((destination.Length - startIndex) < Count)
+            {
+                throw new ArgumentException(SR.Format(SR.Arg_ElementsInSourceIsGreaterThanDestination, startIndex));
+            }
+
+            if (Vector.IsHardwareAccelerated)
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    Byte[] byteArray = (Byte[])(object)destination;
+                    fixed (Byte* destinationBase = byteArray)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            destinationBase[startIndex + g] = (Byte)(object)this[g];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    SByte[] sbyteArray = (SByte[])(object)destination;
+                    fixed (SByte* destinationBase = sbyteArray)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            destinationBase[startIndex + g] = (SByte)(object)this[g];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    UInt16[] uint16Array = (UInt16[])(object)destination;
+                    fixed (UInt16* destinationBase = uint16Array)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            destinationBase[startIndex + g] = (UInt16)(object)this[g];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    Int16[] int16Array = (Int16[])(object)destination;
+                    fixed (Int16* destinationBase = int16Array)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            destinationBase[startIndex + g] = (Int16)(object)this[g];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    UInt32[] uint32Array = (UInt32[])(object)destination;
+                    fixed (UInt32* destinationBase = uint32Array)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            destinationBase[startIndex + g] = (UInt32)(object)this[g];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    Int32[] int32Array = (Int32[])(object)destination;
+                    fixed (Int32* destinationBase = int32Array)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            destinationBase[startIndex + g] = (Int32)(object)this[g];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    UInt64[] uint64Array = (UInt64[])(object)destination;
+                    fixed (UInt64* destinationBase = uint64Array)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            destinationBase[startIndex + g] = (UInt64)(object)this[g];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    Int64[] int64Array = (Int64[])(object)destination;
+                    fixed (Int64* destinationBase = int64Array)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            destinationBase[startIndex + g] = (Int64)(object)this[g];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    Single[] singleArray = (Single[])(object)destination;
+                    fixed (Single* destinationBase = singleArray)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            destinationBase[startIndex + g] = (Single)(object)this[g];
+                        }
+                    }
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    Double[] doubleArray = (Double[])(object)destination;
+                    fixed (Double* destinationBase = doubleArray)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            destinationBase[startIndex + g] = (Double)(object)this[g];
+                        }
+                    }
+                }
+            }
+            else
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    Byte[] byteArray = (Byte[])(object)destination;
+                    fixed (Byte* destinationBase = byteArray)
+                    {
+                        destinationBase[startIndex + 0] = this.register.byte_0;
+                        destinationBase[startIndex + 1] = this.register.byte_1;
+                        destinationBase[startIndex + 2] = this.register.byte_2;
+                        destinationBase[startIndex + 3] = this.register.byte_3;
+                        destinationBase[startIndex + 4] = this.register.byte_4;
+                        destinationBase[startIndex + 5] = this.register.byte_5;
+                        destinationBase[startIndex + 6] = this.register.byte_6;
+                        destinationBase[startIndex + 7] = this.register.byte_7;
+                        destinationBase[startIndex + 8] = this.register.byte_8;
+                        destinationBase[startIndex + 9] = this.register.byte_9;
+                        destinationBase[startIndex + 10] = this.register.byte_10;
+                        destinationBase[startIndex + 11] = this.register.byte_11;
+                        destinationBase[startIndex + 12] = this.register.byte_12;
+                        destinationBase[startIndex + 13] = this.register.byte_13;
+                        destinationBase[startIndex + 14] = this.register.byte_14;
+                        destinationBase[startIndex + 15] = this.register.byte_15;
+                    }
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    SByte[] sbyteArray = (SByte[])(object)destination;
+                    fixed (SByte* destinationBase = sbyteArray)
+                    {
+                        destinationBase[startIndex + 0] = this.register.sbyte_0;
+                        destinationBase[startIndex + 1] = this.register.sbyte_1;
+                        destinationBase[startIndex + 2] = this.register.sbyte_2;
+                        destinationBase[startIndex + 3] = this.register.sbyte_3;
+                        destinationBase[startIndex + 4] = this.register.sbyte_4;
+                        destinationBase[startIndex + 5] = this.register.sbyte_5;
+                        destinationBase[startIndex + 6] = this.register.sbyte_6;
+                        destinationBase[startIndex + 7] = this.register.sbyte_7;
+                        destinationBase[startIndex + 8] = this.register.sbyte_8;
+                        destinationBase[startIndex + 9] = this.register.sbyte_9;
+                        destinationBase[startIndex + 10] = this.register.sbyte_10;
+                        destinationBase[startIndex + 11] = this.register.sbyte_11;
+                        destinationBase[startIndex + 12] = this.register.sbyte_12;
+                        destinationBase[startIndex + 13] = this.register.sbyte_13;
+                        destinationBase[startIndex + 14] = this.register.sbyte_14;
+                        destinationBase[startIndex + 15] = this.register.sbyte_15;
+                    }
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    UInt16[] uint16Array = (UInt16[])(object)destination;
+                    fixed (UInt16* destinationBase = uint16Array)
+                    {
+                        destinationBase[startIndex + 0] = this.register.uint16_0;
+                        destinationBase[startIndex + 1] = this.register.uint16_1;
+                        destinationBase[startIndex + 2] = this.register.uint16_2;
+                        destinationBase[startIndex + 3] = this.register.uint16_3;
+                        destinationBase[startIndex + 4] = this.register.uint16_4;
+                        destinationBase[startIndex + 5] = this.register.uint16_5;
+                        destinationBase[startIndex + 6] = this.register.uint16_6;
+                        destinationBase[startIndex + 7] = this.register.uint16_7;
+                    }
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    Int16[] int16Array = (Int16[])(object)destination;
+                    fixed (Int16* destinationBase = int16Array)
+                    {
+                        destinationBase[startIndex + 0] = this.register.int16_0;
+                        destinationBase[startIndex + 1] = this.register.int16_1;
+                        destinationBase[startIndex + 2] = this.register.int16_2;
+                        destinationBase[startIndex + 3] = this.register.int16_3;
+                        destinationBase[startIndex + 4] = this.register.int16_4;
+                        destinationBase[startIndex + 5] = this.register.int16_5;
+                        destinationBase[startIndex + 6] = this.register.int16_6;
+                        destinationBase[startIndex + 7] = this.register.int16_7;
+                    }
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    UInt32[] uint32Array = (UInt32[])(object)destination;
+                    fixed (UInt32* destinationBase = uint32Array)
+                    {
+                        destinationBase[startIndex + 0] = this.register.uint32_0;
+                        destinationBase[startIndex + 1] = this.register.uint32_1;
+                        destinationBase[startIndex + 2] = this.register.uint32_2;
+                        destinationBase[startIndex + 3] = this.register.uint32_3;
+                    }
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    Int32[] int32Array = (Int32[])(object)destination;
+                    fixed (Int32* destinationBase = int32Array)
+                    {
+                        destinationBase[startIndex + 0] = this.register.int32_0;
+                        destinationBase[startIndex + 1] = this.register.int32_1;
+                        destinationBase[startIndex + 2] = this.register.int32_2;
+                        destinationBase[startIndex + 3] = this.register.int32_3;
+                    }
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    UInt64[] uint64Array = (UInt64[])(object)destination;
+                    fixed (UInt64* destinationBase = uint64Array)
+                    {
+                        destinationBase[startIndex + 0] = this.register.uint64_0;
+                        destinationBase[startIndex + 1] = this.register.uint64_1;
+                    }
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    Int64[] int64Array = (Int64[])(object)destination;
+                    fixed (Int64* destinationBase = int64Array)
+                    {
+                        destinationBase[startIndex + 0] = this.register.int64_0;
+                        destinationBase[startIndex + 1] = this.register.int64_1;
+                    }
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    Single[] singleArray = (Single[])(object)destination;
+                    fixed (Single* destinationBase = singleArray)
+                    {
+                        destinationBase[startIndex + 0] = this.register.single_0;
+                        destinationBase[startIndex + 1] = this.register.single_1;
+                        destinationBase[startIndex + 2] = this.register.single_2;
+                        destinationBase[startIndex + 3] = this.register.single_3;
+                    }
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    Double[] doubleArray = (Double[])(object)destination;
+                    fixed (Double* destinationBase = doubleArray)
+                    {
+                        destinationBase[startIndex + 0] = this.register.double_0;
+                        destinationBase[startIndex + 1] = this.register.double_1;
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Returns the element at the given index.
+        /// </summary>
+        public unsafe T this[int index]
+        {
+            [Intrinsic]
+            get
+            {
+                if (index >= Count || index < 0)
+                {
+                    throw new IndexOutOfRangeException(SR.Format(SR.Arg_ArgumentOutOfRangeException, index));
+                }
+                if (typeof(T) == typeof(Byte))
+                {
+                    fixed (Byte* basePtr = &this.register.byte_0)
+                    {
+                        return (T)(object)*(basePtr + index);
+                    }
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    fixed (SByte* basePtr = &this.register.sbyte_0)
+                    {
+                        return (T)(object)*(basePtr + index);
+                    }
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    fixed (UInt16* basePtr = &this.register.uint16_0)
+                    {
+                        return (T)(object)*(basePtr + index);
+                    }
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    fixed (Int16* basePtr = &this.register.int16_0)
+                    {
+                        return (T)(object)*(basePtr + index);
+                    }
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    fixed (UInt32* basePtr = &this.register.uint32_0)
+                    {
+                        return (T)(object)*(basePtr + index);
+                    }
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    fixed (Int32* basePtr = &this.register.int32_0)
+                    {
+                        return (T)(object)*(basePtr + index);
+                    }
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    fixed (UInt64* basePtr = &this.register.uint64_0)
+                    {
+                        return (T)(object)*(basePtr + index);
+                    }
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    fixed (Int64* basePtr = &this.register.int64_0)
+                    {
+                        return (T)(object)*(basePtr + index);
+                    }
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    fixed (Single* basePtr = &this.register.single_0)
+                    {
+                        return (T)(object)*(basePtr + index);
+                    }
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    fixed (Double* basePtr = &this.register.double_0)
+                    {
+                        return (T)(object)*(basePtr + index);
+                    }
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether the given Object is equal to this vector instance.
+        /// </summary>
+        /// <param name="obj">The Object to compare against.</param>
+        /// <returns>True if the Object is equal to this vector; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public override bool Equals(object obj)
+        {
+            if (!(obj is Vector<T>))
+            {
+                return false;
+            }
+            return Equals((Vector<T>)obj);
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether the given vector is equal to this vector instance.
+        /// </summary>
+        /// <param name="other">The vector to compare this instance to.</param>
+        /// <returns>True if the other vector is equal to this instance; False otherwise.</returns>
+        [Intrinsic]
+        public bool Equals(Vector<T> other)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+                for (int g = 0; g < Count; g++)
+                {
+                    if (!ScalarEquals(this[g], other[g]))
+                    {
+                        return false;
+                    }
+                }
+                return true;
+            }
+            else
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    return
+                        this.register.byte_0 == other.register.byte_0
+                        && this.register.byte_1 == other.register.byte_1
+                        && this.register.byte_2 == other.register.byte_2
+                        && this.register.byte_3 == other.register.byte_3
+                        && this.register.byte_4 == other.register.byte_4
+                        && this.register.byte_5 == other.register.byte_5
+                        && this.register.byte_6 == other.register.byte_6
+                        && this.register.byte_7 == other.register.byte_7
+                        && this.register.byte_8 == other.register.byte_8
+                        && this.register.byte_9 == other.register.byte_9
+                        && this.register.byte_10 == other.register.byte_10
+                        && this.register.byte_11 == other.register.byte_11
+                        && this.register.byte_12 == other.register.byte_12
+                        && this.register.byte_13 == other.register.byte_13
+                        && this.register.byte_14 == other.register.byte_14
+                        && this.register.byte_15 == other.register.byte_15;
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    return
+                        this.register.sbyte_0 == other.register.sbyte_0
+                        && this.register.sbyte_1 == other.register.sbyte_1
+                        && this.register.sbyte_2 == other.register.sbyte_2
+                        && this.register.sbyte_3 == other.register.sbyte_3
+                        && this.register.sbyte_4 == other.register.sbyte_4
+                        && this.register.sbyte_5 == other.register.sbyte_5
+                        && this.register.sbyte_6 == other.register.sbyte_6
+                        && this.register.sbyte_7 == other.register.sbyte_7
+                        && this.register.sbyte_8 == other.register.sbyte_8
+                        && this.register.sbyte_9 == other.register.sbyte_9
+                        && this.register.sbyte_10 == other.register.sbyte_10
+                        && this.register.sbyte_11 == other.register.sbyte_11
+                        && this.register.sbyte_12 == other.register.sbyte_12
+                        && this.register.sbyte_13 == other.register.sbyte_13
+                        && this.register.sbyte_14 == other.register.sbyte_14
+                        && this.register.sbyte_15 == other.register.sbyte_15;
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    return
+                        this.register.uint16_0 == other.register.uint16_0
+                        && this.register.uint16_1 == other.register.uint16_1
+                        && this.register.uint16_2 == other.register.uint16_2
+                        && this.register.uint16_3 == other.register.uint16_3
+                        && this.register.uint16_4 == other.register.uint16_4
+                        && this.register.uint16_5 == other.register.uint16_5
+                        && this.register.uint16_6 == other.register.uint16_6
+                        && this.register.uint16_7 == other.register.uint16_7;
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    return
+                        this.register.int16_0 == other.register.int16_0
+                        && this.register.int16_1 == other.register.int16_1
+                        && this.register.int16_2 == other.register.int16_2
+                        && this.register.int16_3 == other.register.int16_3
+                        && this.register.int16_4 == other.register.int16_4
+                        && this.register.int16_5 == other.register.int16_5
+                        && this.register.int16_6 == other.register.int16_6
+                        && this.register.int16_7 == other.register.int16_7;
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    return
+                        this.register.uint32_0 == other.register.uint32_0
+                        && this.register.uint32_1 == other.register.uint32_1
+                        && this.register.uint32_2 == other.register.uint32_2
+                        && this.register.uint32_3 == other.register.uint32_3;
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    return
+                        this.register.int32_0 == other.register.int32_0
+                        && this.register.int32_1 == other.register.int32_1
+                        && this.register.int32_2 == other.register.int32_2
+                        && this.register.int32_3 == other.register.int32_3;
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    return
+                        this.register.uint64_0 == other.register.uint64_0
+                        && this.register.uint64_1 == other.register.uint64_1;
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    return
+                        this.register.int64_0 == other.register.int64_0
+                        && this.register.int64_1 == other.register.int64_1;
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    return
+                        this.register.single_0 == other.register.single_0
+                        && this.register.single_1 == other.register.single_1
+                        && this.register.single_2 == other.register.single_2
+                        && this.register.single_3 == other.register.single_3;
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    return
+                        this.register.double_0 == other.register.double_0
+                        && this.register.double_1 == other.register.double_1;
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Returns the hash code for this instance.
+        /// </summary>
+        /// <returns>The hash code.</returns>
+        public override int GetHashCode()
+        {
+            int hash = 0;
+
+            if (Vector.IsHardwareAccelerated)
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        hash = HashHelpers.Combine(hash, ((Byte)(object)this[g]).GetHashCode());
+                    }
+                    return hash;
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        hash = HashHelpers.Combine(hash, ((SByte)(object)this[g]).GetHashCode());
+                    }
+                    return hash;
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        hash = HashHelpers.Combine(hash, ((UInt16)(object)this[g]).GetHashCode());
+                    }
+                    return hash;
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        hash = HashHelpers.Combine(hash, ((Int16)(object)this[g]).GetHashCode());
+                    }
+                    return hash;
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        hash = HashHelpers.Combine(hash, ((UInt32)(object)this[g]).GetHashCode());
+                    }
+                    return hash;
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        hash = HashHelpers.Combine(hash, ((Int32)(object)this[g]).GetHashCode());
+                    }
+                    return hash;
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        hash = HashHelpers.Combine(hash, ((UInt64)(object)this[g]).GetHashCode());
+                    }
+                    return hash;
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        hash = HashHelpers.Combine(hash, ((Int64)(object)this[g]).GetHashCode());
+                    }
+                    return hash;
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        hash = HashHelpers.Combine(hash, ((Single)(object)this[g]).GetHashCode());
+                    }
+                    return hash;
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        hash = HashHelpers.Combine(hash, ((Double)(object)this[g]).GetHashCode());
+                    }
+                    return hash;
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    hash = HashHelpers.Combine(hash, this.register.byte_0.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_1.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_2.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_3.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_4.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_5.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_6.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_7.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_8.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_9.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_10.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_11.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_12.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_13.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_14.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.byte_15.GetHashCode());
+                    return hash;
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_0.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_1.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_2.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_3.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_4.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_5.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_6.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_7.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_8.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_9.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_10.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_11.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_12.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_13.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_14.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.sbyte_15.GetHashCode());
+                    return hash;
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    hash = HashHelpers.Combine(hash, this.register.uint16_0.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.uint16_1.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.uint16_2.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.uint16_3.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.uint16_4.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.uint16_5.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.uint16_6.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.uint16_7.GetHashCode());
+                    return hash;
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    hash = HashHelpers.Combine(hash, this.register.int16_0.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.int16_1.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.int16_2.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.int16_3.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.int16_4.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.int16_5.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.int16_6.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.int16_7.GetHashCode());
+                    return hash;
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    hash = HashHelpers.Combine(hash, this.register.uint32_0.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.uint32_1.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.uint32_2.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.uint32_3.GetHashCode());
+                    return hash;
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    hash = HashHelpers.Combine(hash, this.register.int32_0.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.int32_1.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.int32_2.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.int32_3.GetHashCode());
+                    return hash;
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    hash = HashHelpers.Combine(hash, this.register.uint64_0.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.uint64_1.GetHashCode());
+                    return hash;
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    hash = HashHelpers.Combine(hash, this.register.int64_0.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.int64_1.GetHashCode());
+                    return hash;
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    hash = HashHelpers.Combine(hash, this.register.single_0.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.single_1.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.single_2.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.single_3.GetHashCode());
+                    return hash;
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    hash = HashHelpers.Combine(hash, this.register.double_0.GetHashCode());
+                    hash = HashHelpers.Combine(hash, this.register.double_1.GetHashCode());
+                    return hash;
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Returns a String representing this vector.
+        /// </summary>
+        /// <returns>The string representation.</returns>
+        public override string ToString()
+        {
+            return ToString("G", CultureInfo.CurrentCulture);
+        }
+
+        /// <summary>
+        /// Returns a String representing this vector, using the specified format string to format individual elements.
+        /// </summary>
+        /// <param name="format">The format of individual elements.</param>
+        /// <returns>The string representation.</returns>
+        public string ToString(string format)
+        {
+            return ToString(format, CultureInfo.CurrentCulture);
+        }
+
+        /// <summary>
+        /// Returns a String representing this vector, using the specified format string to format individual elements
+        /// and the given IFormatProvider.
+        /// </summary>
+        /// <param name="format">The format of individual elements.</param>
+        /// <param name="formatProvider">The format provider to use when formatting elements.</param>
+        /// <returns>The string representation.</returns>
+        public string ToString(string format, IFormatProvider formatProvider)
+        {
+            StringBuilder sb = new StringBuilder();
+            string separator = NumberFormatInfo.GetInstance(formatProvider).NumberGroupSeparator;
+            sb.Append('<');
+            for (int g = 0; g < Count - 1; g++)
+            {
+                sb.Append(((IFormattable)this[g]).ToString(format, formatProvider));
+                sb.Append(separator);
+                sb.Append(' ');
+            }
+            // Append last element w/out separator
+            sb.Append(((IFormattable)this[Count - 1]).ToString(format, formatProvider));
+            sb.Append('>');
+            return sb.ToString();
+        }
+        #endregion Public Instance Methods
+
+        #region Arithmetic Operators
+        /// <summary>
+        /// Adds two vectors together.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The summed vector.</returns>
+        public static unsafe Vector<T> operator +(Vector<T> left, Vector<T> right)
+        {
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+                    if (typeof(T) == typeof(Byte))
+                    {
+                        Byte* dataPtr = stackalloc Byte[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Byte)(object)ScalarAdd(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(SByte))
+                    {
+                        SByte* dataPtr = stackalloc SByte[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (SByte)(object)ScalarAdd(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(UInt16))
+                    {
+                        UInt16* dataPtr = stackalloc UInt16[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (UInt16)(object)ScalarAdd(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Int16))
+                    {
+                        Int16* dataPtr = stackalloc Int16[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Int16)(object)ScalarAdd(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(UInt32))
+                    {
+                        UInt32* dataPtr = stackalloc UInt32[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (UInt32)(object)ScalarAdd(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Int32))
+                    {
+                        Int32* dataPtr = stackalloc Int32[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Int32)(object)ScalarAdd(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(UInt64))
+                    {
+                        UInt64* dataPtr = stackalloc UInt64[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (UInt64)(object)ScalarAdd(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Int64))
+                    {
+                        Int64* dataPtr = stackalloc Int64[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Int64)(object)ScalarAdd(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Single))
+                    {
+                        Single* dataPtr = stackalloc Single[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Single)(object)ScalarAdd(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Double))
+                    {
+                        Double* dataPtr = stackalloc Double[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Double)(object)ScalarAdd(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else
+                    {
+                        throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                    }
+                }
+                else
+                {
+                    Vector<T> sum = new Vector<T>();
+                    if (typeof(T) == typeof(Byte))
+                    {
+                        sum.register.byte_0 = (Byte)(left.register.byte_0 + right.register.byte_0);
+                        sum.register.byte_1 = (Byte)(left.register.byte_1 + right.register.byte_1);
+                        sum.register.byte_2 = (Byte)(left.register.byte_2 + right.register.byte_2);
+                        sum.register.byte_3 = (Byte)(left.register.byte_3 + right.register.byte_3);
+                        sum.register.byte_4 = (Byte)(left.register.byte_4 + right.register.byte_4);
+                        sum.register.byte_5 = (Byte)(left.register.byte_5 + right.register.byte_5);
+                        sum.register.byte_6 = (Byte)(left.register.byte_6 + right.register.byte_6);
+                        sum.register.byte_7 = (Byte)(left.register.byte_7 + right.register.byte_7);
+                        sum.register.byte_8 = (Byte)(left.register.byte_8 + right.register.byte_8);
+                        sum.register.byte_9 = (Byte)(left.register.byte_9 + right.register.byte_9);
+                        sum.register.byte_10 = (Byte)(left.register.byte_10 + right.register.byte_10);
+                        sum.register.byte_11 = (Byte)(left.register.byte_11 + right.register.byte_11);
+                        sum.register.byte_12 = (Byte)(left.register.byte_12 + right.register.byte_12);
+                        sum.register.byte_13 = (Byte)(left.register.byte_13 + right.register.byte_13);
+                        sum.register.byte_14 = (Byte)(left.register.byte_14 + right.register.byte_14);
+                        sum.register.byte_15 = (Byte)(left.register.byte_15 + right.register.byte_15);
+                    }
+                    else if (typeof(T) == typeof(SByte))
+                    {
+                        sum.register.sbyte_0 = (SByte)(left.register.sbyte_0 + right.register.sbyte_0);
+                        sum.register.sbyte_1 = (SByte)(left.register.sbyte_1 + right.register.sbyte_1);
+                        sum.register.sbyte_2 = (SByte)(left.register.sbyte_2 + right.register.sbyte_2);
+                        sum.register.sbyte_3 = (SByte)(left.register.sbyte_3 + right.register.sbyte_3);
+                        sum.register.sbyte_4 = (SByte)(left.register.sbyte_4 + right.register.sbyte_4);
+                        sum.register.sbyte_5 = (SByte)(left.register.sbyte_5 + right.register.sbyte_5);
+                        sum.register.sbyte_6 = (SByte)(left.register.sbyte_6 + right.register.sbyte_6);
+                        sum.register.sbyte_7 = (SByte)(left.register.sbyte_7 + right.register.sbyte_7);
+                        sum.register.sbyte_8 = (SByte)(left.register.sbyte_8 + right.register.sbyte_8);
+                        sum.register.sbyte_9 = (SByte)(left.register.sbyte_9 + right.register.sbyte_9);
+                        sum.register.sbyte_10 = (SByte)(left.register.sbyte_10 + right.register.sbyte_10);
+                        sum.register.sbyte_11 = (SByte)(left.register.sbyte_11 + right.register.sbyte_11);
+                        sum.register.sbyte_12 = (SByte)(left.register.sbyte_12 + right.register.sbyte_12);
+                        sum.register.sbyte_13 = (SByte)(left.register.sbyte_13 + right.register.sbyte_13);
+                        sum.register.sbyte_14 = (SByte)(left.register.sbyte_14 + right.register.sbyte_14);
+                        sum.register.sbyte_15 = (SByte)(left.register.sbyte_15 + right.register.sbyte_15);
+                    }
+                    else if (typeof(T) == typeof(UInt16))
+                    {
+                        sum.register.uint16_0 = (UInt16)(left.register.uint16_0 + right.register.uint16_0);
+                        sum.register.uint16_1 = (UInt16)(left.register.uint16_1 + right.register.uint16_1);
+                        sum.register.uint16_2 = (UInt16)(left.register.uint16_2 + right.register.uint16_2);
+                        sum.register.uint16_3 = (UInt16)(left.register.uint16_3 + right.register.uint16_3);
+                        sum.register.uint16_4 = (UInt16)(left.register.uint16_4 + right.register.uint16_4);
+                        sum.register.uint16_5 = (UInt16)(left.register.uint16_5 + right.register.uint16_5);
+                        sum.register.uint16_6 = (UInt16)(left.register.uint16_6 + right.register.uint16_6);
+                        sum.register.uint16_7 = (UInt16)(left.register.uint16_7 + right.register.uint16_7);
+                    }
+                    else if (typeof(T) == typeof(Int16))
+                    {
+                        sum.register.int16_0 = (Int16)(left.register.int16_0 + right.register.int16_0);
+                        sum.register.int16_1 = (Int16)(left.register.int16_1 + right.register.int16_1);
+                        sum.register.int16_2 = (Int16)(left.register.int16_2 + right.register.int16_2);
+                        sum.register.int16_3 = (Int16)(left.register.int16_3 + right.register.int16_3);
+                        sum.register.int16_4 = (Int16)(left.register.int16_4 + right.register.int16_4);
+                        sum.register.int16_5 = (Int16)(left.register.int16_5 + right.register.int16_5);
+                        sum.register.int16_6 = (Int16)(left.register.int16_6 + right.register.int16_6);
+                        sum.register.int16_7 = (Int16)(left.register.int16_7 + right.register.int16_7);
+                    }
+                    else if (typeof(T) == typeof(UInt32))
+                    {
+                        sum.register.uint32_0 = (UInt32)(left.register.uint32_0 + right.register.uint32_0);
+                        sum.register.uint32_1 = (UInt32)(left.register.uint32_1 + right.register.uint32_1);
+                        sum.register.uint32_2 = (UInt32)(left.register.uint32_2 + right.register.uint32_2);
+                        sum.register.uint32_3 = (UInt32)(left.register.uint32_3 + right.register.uint32_3);
+                    }
+                    else if (typeof(T) == typeof(Int32))
+                    {
+                        sum.register.int32_0 = (Int32)(left.register.int32_0 + right.register.int32_0);
+                        sum.register.int32_1 = (Int32)(left.register.int32_1 + right.register.int32_1);
+                        sum.register.int32_2 = (Int32)(left.register.int32_2 + right.register.int32_2);
+                        sum.register.int32_3 = (Int32)(left.register.int32_3 + right.register.int32_3);
+                    }
+                    else if (typeof(T) == typeof(UInt64))
+                    {
+                        sum.register.uint64_0 = (UInt64)(left.register.uint64_0 + right.register.uint64_0);
+                        sum.register.uint64_1 = (UInt64)(left.register.uint64_1 + right.register.uint64_1);
+                    }
+                    else if (typeof(T) == typeof(Int64))
+                    {
+                        sum.register.int64_0 = (Int64)(left.register.int64_0 + right.register.int64_0);
+                        sum.register.int64_1 = (Int64)(left.register.int64_1 + right.register.int64_1);
+                    }
+                    else if (typeof(T) == typeof(Single))
+                    {
+                        sum.register.single_0 = (Single)(left.register.single_0 + right.register.single_0);
+                        sum.register.single_1 = (Single)(left.register.single_1 + right.register.single_1);
+                        sum.register.single_2 = (Single)(left.register.single_2 + right.register.single_2);
+                        sum.register.single_3 = (Single)(left.register.single_3 + right.register.single_3);
+                    }
+                    else if (typeof(T) == typeof(Double))
+                    {
+                        sum.register.double_0 = (Double)(left.register.double_0 + right.register.double_0);
+                        sum.register.double_1 = (Double)(left.register.double_1 + right.register.double_1);
+                    }
+                    return sum;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Subtracts the second vector from the first.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The difference vector.</returns>
+        public static unsafe Vector<T> operator -(Vector<T> left, Vector<T> right)
+        {
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+                    if (typeof(T) == typeof(Byte))
+                    {
+                        Byte* dataPtr = stackalloc Byte[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Byte)(object)ScalarSubtract(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(SByte))
+                    {
+                        SByte* dataPtr = stackalloc SByte[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (SByte)(object)ScalarSubtract(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(UInt16))
+                    {
+                        UInt16* dataPtr = stackalloc UInt16[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (UInt16)(object)ScalarSubtract(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Int16))
+                    {
+                        Int16* dataPtr = stackalloc Int16[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Int16)(object)ScalarSubtract(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(UInt32))
+                    {
+                        UInt32* dataPtr = stackalloc UInt32[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (UInt32)(object)ScalarSubtract(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Int32))
+                    {
+                        Int32* dataPtr = stackalloc Int32[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Int32)(object)ScalarSubtract(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(UInt64))
+                    {
+                        UInt64* dataPtr = stackalloc UInt64[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (UInt64)(object)ScalarSubtract(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Int64))
+                    {
+                        Int64* dataPtr = stackalloc Int64[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Int64)(object)ScalarSubtract(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Single))
+                    {
+                        Single* dataPtr = stackalloc Single[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Single)(object)ScalarSubtract(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Double))
+                    {
+                        Double* dataPtr = stackalloc Double[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Double)(object)ScalarSubtract(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else
+                    {
+                        throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                    }
+                }
+                else
+                {
+                    Vector<T> difference = new Vector<T>();
+                    if (typeof(T) == typeof(Byte))
+                    {
+                        difference.register.byte_0 = (Byte)(left.register.byte_0 - right.register.byte_0);
+                        difference.register.byte_1 = (Byte)(left.register.byte_1 - right.register.byte_1);
+                        difference.register.byte_2 = (Byte)(left.register.byte_2 - right.register.byte_2);
+                        difference.register.byte_3 = (Byte)(left.register.byte_3 - right.register.byte_3);
+                        difference.register.byte_4 = (Byte)(left.register.byte_4 - right.register.byte_4);
+                        difference.register.byte_5 = (Byte)(left.register.byte_5 - right.register.byte_5);
+                        difference.register.byte_6 = (Byte)(left.register.byte_6 - right.register.byte_6);
+                        difference.register.byte_7 = (Byte)(left.register.byte_7 - right.register.byte_7);
+                        difference.register.byte_8 = (Byte)(left.register.byte_8 - right.register.byte_8);
+                        difference.register.byte_9 = (Byte)(left.register.byte_9 - right.register.byte_9);
+                        difference.register.byte_10 = (Byte)(left.register.byte_10 - right.register.byte_10);
+                        difference.register.byte_11 = (Byte)(left.register.byte_11 - right.register.byte_11);
+                        difference.register.byte_12 = (Byte)(left.register.byte_12 - right.register.byte_12);
+                        difference.register.byte_13 = (Byte)(left.register.byte_13 - right.register.byte_13);
+                        difference.register.byte_14 = (Byte)(left.register.byte_14 - right.register.byte_14);
+                        difference.register.byte_15 = (Byte)(left.register.byte_15 - right.register.byte_15);
+                    }
+                    else if (typeof(T) == typeof(SByte))
+                    {
+                        difference.register.sbyte_0 = (SByte)(left.register.sbyte_0 - right.register.sbyte_0);
+                        difference.register.sbyte_1 = (SByte)(left.register.sbyte_1 - right.register.sbyte_1);
+                        difference.register.sbyte_2 = (SByte)(left.register.sbyte_2 - right.register.sbyte_2);
+                        difference.register.sbyte_3 = (SByte)(left.register.sbyte_3 - right.register.sbyte_3);
+                        difference.register.sbyte_4 = (SByte)(left.register.sbyte_4 - right.register.sbyte_4);
+                        difference.register.sbyte_5 = (SByte)(left.register.sbyte_5 - right.register.sbyte_5);
+                        difference.register.sbyte_6 = (SByte)(left.register.sbyte_6 - right.register.sbyte_6);
+                        difference.register.sbyte_7 = (SByte)(left.register.sbyte_7 - right.register.sbyte_7);
+                        difference.register.sbyte_8 = (SByte)(left.register.sbyte_8 - right.register.sbyte_8);
+                        difference.register.sbyte_9 = (SByte)(left.register.sbyte_9 - right.register.sbyte_9);
+                        difference.register.sbyte_10 = (SByte)(left.register.sbyte_10 - right.register.sbyte_10);
+                        difference.register.sbyte_11 = (SByte)(left.register.sbyte_11 - right.register.sbyte_11);
+                        difference.register.sbyte_12 = (SByte)(left.register.sbyte_12 - right.register.sbyte_12);
+                        difference.register.sbyte_13 = (SByte)(left.register.sbyte_13 - right.register.sbyte_13);
+                        difference.register.sbyte_14 = (SByte)(left.register.sbyte_14 - right.register.sbyte_14);
+                        difference.register.sbyte_15 = (SByte)(left.register.sbyte_15 - right.register.sbyte_15);
+                    }
+                    else if (typeof(T) == typeof(UInt16))
+                    {
+                        difference.register.uint16_0 = (UInt16)(left.register.uint16_0 - right.register.uint16_0);
+                        difference.register.uint16_1 = (UInt16)(left.register.uint16_1 - right.register.uint16_1);
+                        difference.register.uint16_2 = (UInt16)(left.register.uint16_2 - right.register.uint16_2);
+                        difference.register.uint16_3 = (UInt16)(left.register.uint16_3 - right.register.uint16_3);
+                        difference.register.uint16_4 = (UInt16)(left.register.uint16_4 - right.register.uint16_4);
+                        difference.register.uint16_5 = (UInt16)(left.register.uint16_5 - right.register.uint16_5);
+                        difference.register.uint16_6 = (UInt16)(left.register.uint16_6 - right.register.uint16_6);
+                        difference.register.uint16_7 = (UInt16)(left.register.uint16_7 - right.register.uint16_7);
+                    }
+                    else if (typeof(T) == typeof(Int16))
+                    {
+                        difference.register.int16_0 = (Int16)(left.register.int16_0 - right.register.int16_0);
+                        difference.register.int16_1 = (Int16)(left.register.int16_1 - right.register.int16_1);
+                        difference.register.int16_2 = (Int16)(left.register.int16_2 - right.register.int16_2);
+                        difference.register.int16_3 = (Int16)(left.register.int16_3 - right.register.int16_3);
+                        difference.register.int16_4 = (Int16)(left.register.int16_4 - right.register.int16_4);
+                        difference.register.int16_5 = (Int16)(left.register.int16_5 - right.register.int16_5);
+                        difference.register.int16_6 = (Int16)(left.register.int16_6 - right.register.int16_6);
+                        difference.register.int16_7 = (Int16)(left.register.int16_7 - right.register.int16_7);
+                    }
+                    else if (typeof(T) == typeof(UInt32))
+                    {
+                        difference.register.uint32_0 = (UInt32)(left.register.uint32_0 - right.register.uint32_0);
+                        difference.register.uint32_1 = (UInt32)(left.register.uint32_1 - right.register.uint32_1);
+                        difference.register.uint32_2 = (UInt32)(left.register.uint32_2 - right.register.uint32_2);
+                        difference.register.uint32_3 = (UInt32)(left.register.uint32_3 - right.register.uint32_3);
+                    }
+                    else if (typeof(T) == typeof(Int32))
+                    {
+                        difference.register.int32_0 = (Int32)(left.register.int32_0 - right.register.int32_0);
+                        difference.register.int32_1 = (Int32)(left.register.int32_1 - right.register.int32_1);
+                        difference.register.int32_2 = (Int32)(left.register.int32_2 - right.register.int32_2);
+                        difference.register.int32_3 = (Int32)(left.register.int32_3 - right.register.int32_3);
+                    }
+                    else if (typeof(T) == typeof(UInt64))
+                    {
+                        difference.register.uint64_0 = (UInt64)(left.register.uint64_0 - right.register.uint64_0);
+                        difference.register.uint64_1 = (UInt64)(left.register.uint64_1 - right.register.uint64_1);
+                    }
+                    else if (typeof(T) == typeof(Int64))
+                    {
+                        difference.register.int64_0 = (Int64)(left.register.int64_0 - right.register.int64_0);
+                        difference.register.int64_1 = (Int64)(left.register.int64_1 - right.register.int64_1);
+                    }
+                    else if (typeof(T) == typeof(Single))
+                    {
+                        difference.register.single_0 = (Single)(left.register.single_0 - right.register.single_0);
+                        difference.register.single_1 = (Single)(left.register.single_1 - right.register.single_1);
+                        difference.register.single_2 = (Single)(left.register.single_2 - right.register.single_2);
+                        difference.register.single_3 = (Single)(left.register.single_3 - right.register.single_3);
+                    }
+                    else if (typeof(T) == typeof(Double))
+                    {
+                        difference.register.double_0 = (Double)(left.register.double_0 - right.register.double_0);
+                        difference.register.double_1 = (Double)(left.register.double_1 - right.register.double_1);
+                    }
+                    return difference;
+                }
+            }
+        }
+
+        // This method is intrinsic only for certain types. It cannot access fields directly unless we are sure the context is unaccelerated.
+        /// <summary>
+        /// Multiplies two vectors together.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The product vector.</returns>
+        public static unsafe Vector<T> operator *(Vector<T> left, Vector<T> right)
+        {
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+                    if (typeof(T) == typeof(Byte))
+                    {
+                        Byte* dataPtr = stackalloc Byte[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Byte)(object)ScalarMultiply(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(SByte))
+                    {
+                        SByte* dataPtr = stackalloc SByte[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (SByte)(object)ScalarMultiply(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(UInt16))
+                    {
+                        UInt16* dataPtr = stackalloc UInt16[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (UInt16)(object)ScalarMultiply(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Int16))
+                    {
+                        Int16* dataPtr = stackalloc Int16[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Int16)(object)ScalarMultiply(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(UInt32))
+                    {
+                        UInt32* dataPtr = stackalloc UInt32[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (UInt32)(object)ScalarMultiply(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Int32))
+                    {
+                        Int32* dataPtr = stackalloc Int32[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Int32)(object)ScalarMultiply(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(UInt64))
+                    {
+                        UInt64* dataPtr = stackalloc UInt64[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (UInt64)(object)ScalarMultiply(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Int64))
+                    {
+                        Int64* dataPtr = stackalloc Int64[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Int64)(object)ScalarMultiply(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Single))
+                    {
+                        Single* dataPtr = stackalloc Single[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Single)(object)ScalarMultiply(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Double))
+                    {
+                        Double* dataPtr = stackalloc Double[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Double)(object)ScalarMultiply(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else
+                    {
+                        throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                    }
+                }
+                else
+                {
+                    Vector<T> product = new Vector<T>();
+                    if (typeof(T) == typeof(Byte))
+                    {
+                        product.register.byte_0 = (Byte)(left.register.byte_0 * right.register.byte_0);
+                        product.register.byte_1 = (Byte)(left.register.byte_1 * right.register.byte_1);
+                        product.register.byte_2 = (Byte)(left.register.byte_2 * right.register.byte_2);
+                        product.register.byte_3 = (Byte)(left.register.byte_3 * right.register.byte_3);
+                        product.register.byte_4 = (Byte)(left.register.byte_4 * right.register.byte_4);
+                        product.register.byte_5 = (Byte)(left.register.byte_5 * right.register.byte_5);
+                        product.register.byte_6 = (Byte)(left.register.byte_6 * right.register.byte_6);
+                        product.register.byte_7 = (Byte)(left.register.byte_7 * right.register.byte_7);
+                        product.register.byte_8 = (Byte)(left.register.byte_8 * right.register.byte_8);
+                        product.register.byte_9 = (Byte)(left.register.byte_9 * right.register.byte_9);
+                        product.register.byte_10 = (Byte)(left.register.byte_10 * right.register.byte_10);
+                        product.register.byte_11 = (Byte)(left.register.byte_11 * right.register.byte_11);
+                        product.register.byte_12 = (Byte)(left.register.byte_12 * right.register.byte_12);
+                        product.register.byte_13 = (Byte)(left.register.byte_13 * right.register.byte_13);
+                        product.register.byte_14 = (Byte)(left.register.byte_14 * right.register.byte_14);
+                        product.register.byte_15 = (Byte)(left.register.byte_15 * right.register.byte_15);
+                    }
+                    else if (typeof(T) == typeof(SByte))
+                    {
+                        product.register.sbyte_0 = (SByte)(left.register.sbyte_0 * right.register.sbyte_0);
+                        product.register.sbyte_1 = (SByte)(left.register.sbyte_1 * right.register.sbyte_1);
+                        product.register.sbyte_2 = (SByte)(left.register.sbyte_2 * right.register.sbyte_2);
+                        product.register.sbyte_3 = (SByte)(left.register.sbyte_3 * right.register.sbyte_3);
+                        product.register.sbyte_4 = (SByte)(left.register.sbyte_4 * right.register.sbyte_4);
+                        product.register.sbyte_5 = (SByte)(left.register.sbyte_5 * right.register.sbyte_5);
+                        product.register.sbyte_6 = (SByte)(left.register.sbyte_6 * right.register.sbyte_6);
+                        product.register.sbyte_7 = (SByte)(left.register.sbyte_7 * right.register.sbyte_7);
+                        product.register.sbyte_8 = (SByte)(left.register.sbyte_8 * right.register.sbyte_8);
+                        product.register.sbyte_9 = (SByte)(left.register.sbyte_9 * right.register.sbyte_9);
+                        product.register.sbyte_10 = (SByte)(left.register.sbyte_10 * right.register.sbyte_10);
+                        product.register.sbyte_11 = (SByte)(left.register.sbyte_11 * right.register.sbyte_11);
+                        product.register.sbyte_12 = (SByte)(left.register.sbyte_12 * right.register.sbyte_12);
+                        product.register.sbyte_13 = (SByte)(left.register.sbyte_13 * right.register.sbyte_13);
+                        product.register.sbyte_14 = (SByte)(left.register.sbyte_14 * right.register.sbyte_14);
+                        product.register.sbyte_15 = (SByte)(left.register.sbyte_15 * right.register.sbyte_15);
+                    }
+                    else if (typeof(T) == typeof(UInt16))
+                    {
+                        product.register.uint16_0 = (UInt16)(left.register.uint16_0 * right.register.uint16_0);
+                        product.register.uint16_1 = (UInt16)(left.register.uint16_1 * right.register.uint16_1);
+                        product.register.uint16_2 = (UInt16)(left.register.uint16_2 * right.register.uint16_2);
+                        product.register.uint16_3 = (UInt16)(left.register.uint16_3 * right.register.uint16_3);
+                        product.register.uint16_4 = (UInt16)(left.register.uint16_4 * right.register.uint16_4);
+                        product.register.uint16_5 = (UInt16)(left.register.uint16_5 * right.register.uint16_5);
+                        product.register.uint16_6 = (UInt16)(left.register.uint16_6 * right.register.uint16_6);
+                        product.register.uint16_7 = (UInt16)(left.register.uint16_7 * right.register.uint16_7);
+                    }
+                    else if (typeof(T) == typeof(Int16))
+                    {
+                        product.register.int16_0 = (Int16)(left.register.int16_0 * right.register.int16_0);
+                        product.register.int16_1 = (Int16)(left.register.int16_1 * right.register.int16_1);
+                        product.register.int16_2 = (Int16)(left.register.int16_2 * right.register.int16_2);
+                        product.register.int16_3 = (Int16)(left.register.int16_3 * right.register.int16_3);
+                        product.register.int16_4 = (Int16)(left.register.int16_4 * right.register.int16_4);
+                        product.register.int16_5 = (Int16)(left.register.int16_5 * right.register.int16_5);
+                        product.register.int16_6 = (Int16)(left.register.int16_6 * right.register.int16_6);
+                        product.register.int16_7 = (Int16)(left.register.int16_7 * right.register.int16_7);
+                    }
+                    else if (typeof(T) == typeof(UInt32))
+                    {
+                        product.register.uint32_0 = (UInt32)(left.register.uint32_0 * right.register.uint32_0);
+                        product.register.uint32_1 = (UInt32)(left.register.uint32_1 * right.register.uint32_1);
+                        product.register.uint32_2 = (UInt32)(left.register.uint32_2 * right.register.uint32_2);
+                        product.register.uint32_3 = (UInt32)(left.register.uint32_3 * right.register.uint32_3);
+                    }
+                    else if (typeof(T) == typeof(Int32))
+                    {
+                        product.register.int32_0 = (Int32)(left.register.int32_0 * right.register.int32_0);
+                        product.register.int32_1 = (Int32)(left.register.int32_1 * right.register.int32_1);
+                        product.register.int32_2 = (Int32)(left.register.int32_2 * right.register.int32_2);
+                        product.register.int32_3 = (Int32)(left.register.int32_3 * right.register.int32_3);
+                    }
+                    else if (typeof(T) == typeof(UInt64))
+                    {
+                        product.register.uint64_0 = (UInt64)(left.register.uint64_0 * right.register.uint64_0);
+                        product.register.uint64_1 = (UInt64)(left.register.uint64_1 * right.register.uint64_1);
+                    }
+                    else if (typeof(T) == typeof(Int64))
+                    {
+                        product.register.int64_0 = (Int64)(left.register.int64_0 * right.register.int64_0);
+                        product.register.int64_1 = (Int64)(left.register.int64_1 * right.register.int64_1);
+                    }
+                    else if (typeof(T) == typeof(Single))
+                    {
+                        product.register.single_0 = (Single)(left.register.single_0 * right.register.single_0);
+                        product.register.single_1 = (Single)(left.register.single_1 * right.register.single_1);
+                        product.register.single_2 = (Single)(left.register.single_2 * right.register.single_2);
+                        product.register.single_3 = (Single)(left.register.single_3 * right.register.single_3);
+                    }
+                    else if (typeof(T) == typeof(Double))
+                    {
+                        product.register.double_0 = (Double)(left.register.double_0 * right.register.double_0);
+                        product.register.double_1 = (Double)(left.register.double_1 * right.register.double_1);
+                    }
+                    return product;
+                }
+            }
+        }
+
+        // This method is intrinsic only for certain types. It cannot access fields directly unless we are sure the context is unaccelerated.
+        /// <summary>
+        /// Multiplies a vector by the given scalar.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <param name="factor">The scalar value.</param>
+        /// <returns>The scaled vector.</returns>
+        public static Vector<T> operator *(Vector<T> value, T factor)
+        {
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+                    return new Vector<T>(factor) * value;
+                }
+                else
+                {
+                    Vector<T> product = new Vector<T>();
+                    if (typeof(T) == typeof(Byte))
+                    {
+                        product.register.byte_0 = (Byte)(value.register.byte_0 * (Byte)(object)factor);
+                        product.register.byte_1 = (Byte)(value.register.byte_1 * (Byte)(object)factor);
+                        product.register.byte_2 = (Byte)(value.register.byte_2 * (Byte)(object)factor);
+                        product.register.byte_3 = (Byte)(value.register.byte_3 * (Byte)(object)factor);
+                        product.register.byte_4 = (Byte)(value.register.byte_4 * (Byte)(object)factor);
+                        product.register.byte_5 = (Byte)(value.register.byte_5 * (Byte)(object)factor);
+                        product.register.byte_6 = (Byte)(value.register.byte_6 * (Byte)(object)factor);
+                        product.register.byte_7 = (Byte)(value.register.byte_7 * (Byte)(object)factor);
+                        product.register.byte_8 = (Byte)(value.register.byte_8 * (Byte)(object)factor);
+                        product.register.byte_9 = (Byte)(value.register.byte_9 * (Byte)(object)factor);
+                        product.register.byte_10 = (Byte)(value.register.byte_10 * (Byte)(object)factor);
+                        product.register.byte_11 = (Byte)(value.register.byte_11 * (Byte)(object)factor);
+                        product.register.byte_12 = (Byte)(value.register.byte_12 * (Byte)(object)factor);
+                        product.register.byte_13 = (Byte)(value.register.byte_13 * (Byte)(object)factor);
+                        product.register.byte_14 = (Byte)(value.register.byte_14 * (Byte)(object)factor);
+                        product.register.byte_15 = (Byte)(value.register.byte_15 * (Byte)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(SByte))
+                    {
+                        product.register.sbyte_0 = (SByte)(value.register.sbyte_0 * (SByte)(object)factor);
+                        product.register.sbyte_1 = (SByte)(value.register.sbyte_1 * (SByte)(object)factor);
+                        product.register.sbyte_2 = (SByte)(value.register.sbyte_2 * (SByte)(object)factor);
+                        product.register.sbyte_3 = (SByte)(value.register.sbyte_3 * (SByte)(object)factor);
+                        product.register.sbyte_4 = (SByte)(value.register.sbyte_4 * (SByte)(object)factor);
+                        product.register.sbyte_5 = (SByte)(value.register.sbyte_5 * (SByte)(object)factor);
+                        product.register.sbyte_6 = (SByte)(value.register.sbyte_6 * (SByte)(object)factor);
+                        product.register.sbyte_7 = (SByte)(value.register.sbyte_7 * (SByte)(object)factor);
+                        product.register.sbyte_8 = (SByte)(value.register.sbyte_8 * (SByte)(object)factor);
+                        product.register.sbyte_9 = (SByte)(value.register.sbyte_9 * (SByte)(object)factor);
+                        product.register.sbyte_10 = (SByte)(value.register.sbyte_10 * (SByte)(object)factor);
+                        product.register.sbyte_11 = (SByte)(value.register.sbyte_11 * (SByte)(object)factor);
+                        product.register.sbyte_12 = (SByte)(value.register.sbyte_12 * (SByte)(object)factor);
+                        product.register.sbyte_13 = (SByte)(value.register.sbyte_13 * (SByte)(object)factor);
+                        product.register.sbyte_14 = (SByte)(value.register.sbyte_14 * (SByte)(object)factor);
+                        product.register.sbyte_15 = (SByte)(value.register.sbyte_15 * (SByte)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(UInt16))
+                    {
+                        product.register.uint16_0 = (UInt16)(value.register.uint16_0 * (UInt16)(object)factor);
+                        product.register.uint16_1 = (UInt16)(value.register.uint16_1 * (UInt16)(object)factor);
+                        product.register.uint16_2 = (UInt16)(value.register.uint16_2 * (UInt16)(object)factor);
+                        product.register.uint16_3 = (UInt16)(value.register.uint16_3 * (UInt16)(object)factor);
+                        product.register.uint16_4 = (UInt16)(value.register.uint16_4 * (UInt16)(object)factor);
+                        product.register.uint16_5 = (UInt16)(value.register.uint16_5 * (UInt16)(object)factor);
+                        product.register.uint16_6 = (UInt16)(value.register.uint16_6 * (UInt16)(object)factor);
+                        product.register.uint16_7 = (UInt16)(value.register.uint16_7 * (UInt16)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(Int16))
+                    {
+                        product.register.int16_0 = (Int16)(value.register.int16_0 * (Int16)(object)factor);
+                        product.register.int16_1 = (Int16)(value.register.int16_1 * (Int16)(object)factor);
+                        product.register.int16_2 = (Int16)(value.register.int16_2 * (Int16)(object)factor);
+                        product.register.int16_3 = (Int16)(value.register.int16_3 * (Int16)(object)factor);
+                        product.register.int16_4 = (Int16)(value.register.int16_4 * (Int16)(object)factor);
+                        product.register.int16_5 = (Int16)(value.register.int16_5 * (Int16)(object)factor);
+                        product.register.int16_6 = (Int16)(value.register.int16_6 * (Int16)(object)factor);
+                        product.register.int16_7 = (Int16)(value.register.int16_7 * (Int16)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(UInt32))
+                    {
+                        product.register.uint32_0 = (UInt32)(value.register.uint32_0 * (UInt32)(object)factor);
+                        product.register.uint32_1 = (UInt32)(value.register.uint32_1 * (UInt32)(object)factor);
+                        product.register.uint32_2 = (UInt32)(value.register.uint32_2 * (UInt32)(object)factor);
+                        product.register.uint32_3 = (UInt32)(value.register.uint32_3 * (UInt32)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(Int32))
+                    {
+                        product.register.int32_0 = (Int32)(value.register.int32_0 * (Int32)(object)factor);
+                        product.register.int32_1 = (Int32)(value.register.int32_1 * (Int32)(object)factor);
+                        product.register.int32_2 = (Int32)(value.register.int32_2 * (Int32)(object)factor);
+                        product.register.int32_3 = (Int32)(value.register.int32_3 * (Int32)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(UInt64))
+                    {
+                        product.register.uint64_0 = (UInt64)(value.register.uint64_0 * (UInt64)(object)factor);
+                        product.register.uint64_1 = (UInt64)(value.register.uint64_1 * (UInt64)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(Int64))
+                    {
+                        product.register.int64_0 = (Int64)(value.register.int64_0 * (Int64)(object)factor);
+                        product.register.int64_1 = (Int64)(value.register.int64_1 * (Int64)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(Single))
+                    {
+                        product.register.single_0 = (Single)(value.register.single_0 * (Single)(object)factor);
+                        product.register.single_1 = (Single)(value.register.single_1 * (Single)(object)factor);
+                        product.register.single_2 = (Single)(value.register.single_2 * (Single)(object)factor);
+                        product.register.single_3 = (Single)(value.register.single_3 * (Single)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(Double))
+                    {
+                        product.register.double_0 = (Double)(value.register.double_0 * (Double)(object)factor);
+                        product.register.double_1 = (Double)(value.register.double_1 * (Double)(object)factor);
+                    }
+                    return product;
+                }
+            }
+        }
+
+        // This method is intrinsic only for certain types. It cannot access fields directly unless we are sure the context is unaccelerated.
+        /// <summary>
+        /// Multiplies a vector by the given scalar.
+        /// </summary>
+        /// <param name="factor">The scalar value.</param>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The scaled vector.</returns>
+        public static Vector<T> operator *(T factor, Vector<T> value)
+        {
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+                    return new Vector<T>(factor) * value;
+                }
+                else
+                {
+                    Vector<T> product = new Vector<T>();
+                    if (typeof(T) == typeof(Byte))
+                    {
+                        product.register.byte_0 = (Byte)(value.register.byte_0 * (Byte)(object)factor);
+                        product.register.byte_1 = (Byte)(value.register.byte_1 * (Byte)(object)factor);
+                        product.register.byte_2 = (Byte)(value.register.byte_2 * (Byte)(object)factor);
+                        product.register.byte_3 = (Byte)(value.register.byte_3 * (Byte)(object)factor);
+                        product.register.byte_4 = (Byte)(value.register.byte_4 * (Byte)(object)factor);
+                        product.register.byte_5 = (Byte)(value.register.byte_5 * (Byte)(object)factor);
+                        product.register.byte_6 = (Byte)(value.register.byte_6 * (Byte)(object)factor);
+                        product.register.byte_7 = (Byte)(value.register.byte_7 * (Byte)(object)factor);
+                        product.register.byte_8 = (Byte)(value.register.byte_8 * (Byte)(object)factor);
+                        product.register.byte_9 = (Byte)(value.register.byte_9 * (Byte)(object)factor);
+                        product.register.byte_10 = (Byte)(value.register.byte_10 * (Byte)(object)factor);
+                        product.register.byte_11 = (Byte)(value.register.byte_11 * (Byte)(object)factor);
+                        product.register.byte_12 = (Byte)(value.register.byte_12 * (Byte)(object)factor);
+                        product.register.byte_13 = (Byte)(value.register.byte_13 * (Byte)(object)factor);
+                        product.register.byte_14 = (Byte)(value.register.byte_14 * (Byte)(object)factor);
+                        product.register.byte_15 = (Byte)(value.register.byte_15 * (Byte)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(SByte))
+                    {
+                        product.register.sbyte_0 = (SByte)(value.register.sbyte_0 * (SByte)(object)factor);
+                        product.register.sbyte_1 = (SByte)(value.register.sbyte_1 * (SByte)(object)factor);
+                        product.register.sbyte_2 = (SByte)(value.register.sbyte_2 * (SByte)(object)factor);
+                        product.register.sbyte_3 = (SByte)(value.register.sbyte_3 * (SByte)(object)factor);
+                        product.register.sbyte_4 = (SByte)(value.register.sbyte_4 * (SByte)(object)factor);
+                        product.register.sbyte_5 = (SByte)(value.register.sbyte_5 * (SByte)(object)factor);
+                        product.register.sbyte_6 = (SByte)(value.register.sbyte_6 * (SByte)(object)factor);
+                        product.register.sbyte_7 = (SByte)(value.register.sbyte_7 * (SByte)(object)factor);
+                        product.register.sbyte_8 = (SByte)(value.register.sbyte_8 * (SByte)(object)factor);
+                        product.register.sbyte_9 = (SByte)(value.register.sbyte_9 * (SByte)(object)factor);
+                        product.register.sbyte_10 = (SByte)(value.register.sbyte_10 * (SByte)(object)factor);
+                        product.register.sbyte_11 = (SByte)(value.register.sbyte_11 * (SByte)(object)factor);
+                        product.register.sbyte_12 = (SByte)(value.register.sbyte_12 * (SByte)(object)factor);
+                        product.register.sbyte_13 = (SByte)(value.register.sbyte_13 * (SByte)(object)factor);
+                        product.register.sbyte_14 = (SByte)(value.register.sbyte_14 * (SByte)(object)factor);
+                        product.register.sbyte_15 = (SByte)(value.register.sbyte_15 * (SByte)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(UInt16))
+                    {
+                        product.register.uint16_0 = (UInt16)(value.register.uint16_0 * (UInt16)(object)factor);
+                        product.register.uint16_1 = (UInt16)(value.register.uint16_1 * (UInt16)(object)factor);
+                        product.register.uint16_2 = (UInt16)(value.register.uint16_2 * (UInt16)(object)factor);
+                        product.register.uint16_3 = (UInt16)(value.register.uint16_3 * (UInt16)(object)factor);
+                        product.register.uint16_4 = (UInt16)(value.register.uint16_4 * (UInt16)(object)factor);
+                        product.register.uint16_5 = (UInt16)(value.register.uint16_5 * (UInt16)(object)factor);
+                        product.register.uint16_6 = (UInt16)(value.register.uint16_6 * (UInt16)(object)factor);
+                        product.register.uint16_7 = (UInt16)(value.register.uint16_7 * (UInt16)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(Int16))
+                    {
+                        product.register.int16_0 = (Int16)(value.register.int16_0 * (Int16)(object)factor);
+                        product.register.int16_1 = (Int16)(value.register.int16_1 * (Int16)(object)factor);
+                        product.register.int16_2 = (Int16)(value.register.int16_2 * (Int16)(object)factor);
+                        product.register.int16_3 = (Int16)(value.register.int16_3 * (Int16)(object)factor);
+                        product.register.int16_4 = (Int16)(value.register.int16_4 * (Int16)(object)factor);
+                        product.register.int16_5 = (Int16)(value.register.int16_5 * (Int16)(object)factor);
+                        product.register.int16_6 = (Int16)(value.register.int16_6 * (Int16)(object)factor);
+                        product.register.int16_7 = (Int16)(value.register.int16_7 * (Int16)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(UInt32))
+                    {
+                        product.register.uint32_0 = (UInt32)(value.register.uint32_0 * (UInt32)(object)factor);
+                        product.register.uint32_1 = (UInt32)(value.register.uint32_1 * (UInt32)(object)factor);
+                        product.register.uint32_2 = (UInt32)(value.register.uint32_2 * (UInt32)(object)factor);
+                        product.register.uint32_3 = (UInt32)(value.register.uint32_3 * (UInt32)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(Int32))
+                    {
+                        product.register.int32_0 = (Int32)(value.register.int32_0 * (Int32)(object)factor);
+                        product.register.int32_1 = (Int32)(value.register.int32_1 * (Int32)(object)factor);
+                        product.register.int32_2 = (Int32)(value.register.int32_2 * (Int32)(object)factor);
+                        product.register.int32_3 = (Int32)(value.register.int32_3 * (Int32)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(UInt64))
+                    {
+                        product.register.uint64_0 = (UInt64)(value.register.uint64_0 * (UInt64)(object)factor);
+                        product.register.uint64_1 = (UInt64)(value.register.uint64_1 * (UInt64)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(Int64))
+                    {
+                        product.register.int64_0 = (Int64)(value.register.int64_0 * (Int64)(object)factor);
+                        product.register.int64_1 = (Int64)(value.register.int64_1 * (Int64)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(Single))
+                    {
+                        product.register.single_0 = (Single)(value.register.single_0 * (Single)(object)factor);
+                        product.register.single_1 = (Single)(value.register.single_1 * (Single)(object)factor);
+                        product.register.single_2 = (Single)(value.register.single_2 * (Single)(object)factor);
+                        product.register.single_3 = (Single)(value.register.single_3 * (Single)(object)factor);
+                    }
+                    else if (typeof(T) == typeof(Double))
+                    {
+                        product.register.double_0 = (Double)(value.register.double_0 * (Double)(object)factor);
+                        product.register.double_1 = (Double)(value.register.double_1 * (Double)(object)factor);
+                    }
+                    return product;
+                }
+            }
+        }
+
+        // This method is intrinsic only for certain types. It cannot access fields directly unless we are sure the context is unaccelerated.
+        /// <summary>
+        /// Divides the first vector by the second.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The vector resulting from the division.</returns>
+        public static unsafe Vector<T> operator /(Vector<T> left, Vector<T> right)
+        {
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+                    if (typeof(T) == typeof(Byte))
+                    {
+                        Byte* dataPtr = stackalloc Byte[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Byte)(object)ScalarDivide(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(SByte))
+                    {
+                        SByte* dataPtr = stackalloc SByte[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (SByte)(object)ScalarDivide(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(UInt16))
+                    {
+                        UInt16* dataPtr = stackalloc UInt16[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (UInt16)(object)ScalarDivide(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Int16))
+                    {
+                        Int16* dataPtr = stackalloc Int16[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Int16)(object)ScalarDivide(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(UInt32))
+                    {
+                        UInt32* dataPtr = stackalloc UInt32[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (UInt32)(object)ScalarDivide(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Int32))
+                    {
+                        Int32* dataPtr = stackalloc Int32[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Int32)(object)ScalarDivide(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(UInt64))
+                    {
+                        UInt64* dataPtr = stackalloc UInt64[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (UInt64)(object)ScalarDivide(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Int64))
+                    {
+                        Int64* dataPtr = stackalloc Int64[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Int64)(object)ScalarDivide(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Single))
+                    {
+                        Single* dataPtr = stackalloc Single[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Single)(object)ScalarDivide(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else if (typeof(T) == typeof(Double))
+                    {
+                        Double* dataPtr = stackalloc Double[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (Double)(object)ScalarDivide(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+                    else
+                    {
+                        throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                    }
+                }
+                else
+                {
+                    Vector<T> quotient = new Vector<T>();
+                    if (typeof(T) == typeof(Byte))
+                    {
+                        quotient.register.byte_0 = (Byte)(left.register.byte_0 / right.register.byte_0);
+                        quotient.register.byte_1 = (Byte)(left.register.byte_1 / right.register.byte_1);
+                        quotient.register.byte_2 = (Byte)(left.register.byte_2 / right.register.byte_2);
+                        quotient.register.byte_3 = (Byte)(left.register.byte_3 / right.register.byte_3);
+                        quotient.register.byte_4 = (Byte)(left.register.byte_4 / right.register.byte_4);
+                        quotient.register.byte_5 = (Byte)(left.register.byte_5 / right.register.byte_5);
+                        quotient.register.byte_6 = (Byte)(left.register.byte_6 / right.register.byte_6);
+                        quotient.register.byte_7 = (Byte)(left.register.byte_7 / right.register.byte_7);
+                        quotient.register.byte_8 = (Byte)(left.register.byte_8 / right.register.byte_8);
+                        quotient.register.byte_9 = (Byte)(left.register.byte_9 / right.register.byte_9);
+                        quotient.register.byte_10 = (Byte)(left.register.byte_10 / right.register.byte_10);
+                        quotient.register.byte_11 = (Byte)(left.register.byte_11 / right.register.byte_11);
+                        quotient.register.byte_12 = (Byte)(left.register.byte_12 / right.register.byte_12);
+                        quotient.register.byte_13 = (Byte)(left.register.byte_13 / right.register.byte_13);
+                        quotient.register.byte_14 = (Byte)(left.register.byte_14 / right.register.byte_14);
+                        quotient.register.byte_15 = (Byte)(left.register.byte_15 / right.register.byte_15);
+                    }
+                    else if (typeof(T) == typeof(SByte))
+                    {
+                        quotient.register.sbyte_0 = (SByte)(left.register.sbyte_0 / right.register.sbyte_0);
+                        quotient.register.sbyte_1 = (SByte)(left.register.sbyte_1 / right.register.sbyte_1);
+                        quotient.register.sbyte_2 = (SByte)(left.register.sbyte_2 / right.register.sbyte_2);
+                        quotient.register.sbyte_3 = (SByte)(left.register.sbyte_3 / right.register.sbyte_3);
+                        quotient.register.sbyte_4 = (SByte)(left.register.sbyte_4 / right.register.sbyte_4);
+                        quotient.register.sbyte_5 = (SByte)(left.register.sbyte_5 / right.register.sbyte_5);
+                        quotient.register.sbyte_6 = (SByte)(left.register.sbyte_6 / right.register.sbyte_6);
+                        quotient.register.sbyte_7 = (SByte)(left.register.sbyte_7 / right.register.sbyte_7);
+                        quotient.register.sbyte_8 = (SByte)(left.register.sbyte_8 / right.register.sbyte_8);
+                        quotient.register.sbyte_9 = (SByte)(left.register.sbyte_9 / right.register.sbyte_9);
+                        quotient.register.sbyte_10 = (SByte)(left.register.sbyte_10 / right.register.sbyte_10);
+                        quotient.register.sbyte_11 = (SByte)(left.register.sbyte_11 / right.register.sbyte_11);
+                        quotient.register.sbyte_12 = (SByte)(left.register.sbyte_12 / right.register.sbyte_12);
+                        quotient.register.sbyte_13 = (SByte)(left.register.sbyte_13 / right.register.sbyte_13);
+                        quotient.register.sbyte_14 = (SByte)(left.register.sbyte_14 / right.register.sbyte_14);
+                        quotient.register.sbyte_15 = (SByte)(left.register.sbyte_15 / right.register.sbyte_15);
+                    }
+                    else if (typeof(T) == typeof(UInt16))
+                    {
+                        quotient.register.uint16_0 = (UInt16)(left.register.uint16_0 / right.register.uint16_0);
+                        quotient.register.uint16_1 = (UInt16)(left.register.uint16_1 / right.register.uint16_1);
+                        quotient.register.uint16_2 = (UInt16)(left.register.uint16_2 / right.register.uint16_2);
+                        quotient.register.uint16_3 = (UInt16)(left.register.uint16_3 / right.register.uint16_3);
+                        quotient.register.uint16_4 = (UInt16)(left.register.uint16_4 / right.register.uint16_4);
+                        quotient.register.uint16_5 = (UInt16)(left.register.uint16_5 / right.register.uint16_5);
+                        quotient.register.uint16_6 = (UInt16)(left.register.uint16_6 / right.register.uint16_6);
+                        quotient.register.uint16_7 = (UInt16)(left.register.uint16_7 / right.register.uint16_7);
+                    }
+                    else if (typeof(T) == typeof(Int16))
+                    {
+                        quotient.register.int16_0 = (Int16)(left.register.int16_0 / right.register.int16_0);
+                        quotient.register.int16_1 = (Int16)(left.register.int16_1 / right.register.int16_1);
+                        quotient.register.int16_2 = (Int16)(left.register.int16_2 / right.register.int16_2);
+                        quotient.register.int16_3 = (Int16)(left.register.int16_3 / right.register.int16_3);
+                        quotient.register.int16_4 = (Int16)(left.register.int16_4 / right.register.int16_4);
+                        quotient.register.int16_5 = (Int16)(left.register.int16_5 / right.register.int16_5);
+                        quotient.register.int16_6 = (Int16)(left.register.int16_6 / right.register.int16_6);
+                        quotient.register.int16_7 = (Int16)(left.register.int16_7 / right.register.int16_7);
+                    }
+                    else if (typeof(T) == typeof(UInt32))
+                    {
+                        quotient.register.uint32_0 = (UInt32)(left.register.uint32_0 / right.register.uint32_0);
+                        quotient.register.uint32_1 = (UInt32)(left.register.uint32_1 / right.register.uint32_1);
+                        quotient.register.uint32_2 = (UInt32)(left.register.uint32_2 / right.register.uint32_2);
+                        quotient.register.uint32_3 = (UInt32)(left.register.uint32_3 / right.register.uint32_3);
+                    }
+                    else if (typeof(T) == typeof(Int32))
+                    {
+                        quotient.register.int32_0 = (Int32)(left.register.int32_0 / right.register.int32_0);
+                        quotient.register.int32_1 = (Int32)(left.register.int32_1 / right.register.int32_1);
+                        quotient.register.int32_2 = (Int32)(left.register.int32_2 / right.register.int32_2);
+                        quotient.register.int32_3 = (Int32)(left.register.int32_3 / right.register.int32_3);
+                    }
+                    else if (typeof(T) == typeof(UInt64))
+                    {
+                        quotient.register.uint64_0 = (UInt64)(left.register.uint64_0 / right.register.uint64_0);
+                        quotient.register.uint64_1 = (UInt64)(left.register.uint64_1 / right.register.uint64_1);
+                    }
+                    else if (typeof(T) == typeof(Int64))
+                    {
+                        quotient.register.int64_0 = (Int64)(left.register.int64_0 / right.register.int64_0);
+                        quotient.register.int64_1 = (Int64)(left.register.int64_1 / right.register.int64_1);
+                    }
+                    else if (typeof(T) == typeof(Single))
+                    {
+                        quotient.register.single_0 = (Single)(left.register.single_0 / right.register.single_0);
+                        quotient.register.single_1 = (Single)(left.register.single_1 / right.register.single_1);
+                        quotient.register.single_2 = (Single)(left.register.single_2 / right.register.single_2);
+                        quotient.register.single_3 = (Single)(left.register.single_3 / right.register.single_3);
+                    }
+                    else if (typeof(T) == typeof(Double))
+                    {
+                        quotient.register.double_0 = (Double)(left.register.double_0 / right.register.double_0);
+                        quotient.register.double_1 = (Double)(left.register.double_1 / right.register.double_1);
+                    }
+                    return quotient;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Negates a given vector.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The negated vector.</returns>
+        public static Vector<T> operator -(Vector<T> value)
+        {
+            return Zero - value;
+        }
+        #endregion Arithmetic Operators
+
+        #region Bitwise Operators
+        /// <summary>
+        /// Returns a new vector by performing a bitwise-and operation on each of the elements in the given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The resultant vector.</returns>
+        [Intrinsic]
+        public static unsafe Vector<T> operator &(Vector<T> left, Vector<T> right)
+        {
+            Vector<T> result = new Vector<T>();
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+                    Int64* resultBase = &result.register.int64_0;
+                    Int64* leftBase = &left.register.int64_0;
+                    Int64* rightBase = &right.register.int64_0;
+                    for (int g = 0; g < Vector<Int64>.Count; g++)
+                    {
+                        resultBase[g] = leftBase[g] & rightBase[g];
+                    }
+                }
+                else
+                {
+                    result.register.int64_0 = left.register.int64_0 & right.register.int64_0;
+                    result.register.int64_1 = left.register.int64_1 & right.register.int64_1;
+                }
+            }
+            return result;
+        }
+
+        /// <summary>
+        /// Returns a new vector by performing a bitwise-or operation on each of the elements in the given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The resultant vector.</returns>
+        [Intrinsic]
+        public static unsafe Vector<T> operator |(Vector<T> left, Vector<T> right)
+        {
+            Vector<T> result = new Vector<T>();
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+                    Int64* resultBase = &result.register.int64_0;
+                    Int64* leftBase = &left.register.int64_0;
+                    Int64* rightBase = &right.register.int64_0;
+                    for (int g = 0; g < Vector<Int64>.Count; g++)
+                    {
+                        resultBase[g] = leftBase[g] | rightBase[g];
+                    }
+                }
+                else
+                {
+                    result.register.int64_0 = left.register.int64_0 | right.register.int64_0;
+                    result.register.int64_1 = left.register.int64_1 | right.register.int64_1;
+                }
+            }
+            return result;
+        }
+
+        /// <summary>
+        /// Returns a new vector by performing a bitwise-exclusive-or operation on each of the elements in the given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The resultant vector.</returns>
+        [Intrinsic]
+        public static unsafe Vector<T> operator ^(Vector<T> left, Vector<T> right)
+        {
+            Vector<T> result = new Vector<T>();
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+                    Int64* resultBase = &result.register.int64_0;
+                    Int64* leftBase = &left.register.int64_0;
+                    Int64* rightBase = &right.register.int64_0;
+                    for (int g = 0; g < Vector<Int64>.Count; g++)
+                    {
+                        resultBase[g] = leftBase[g] ^ rightBase[g];
+                    }
+                }
+                else
+                {
+                    result.register.int64_0 = left.register.int64_0 ^ right.register.int64_0;
+                    result.register.int64_1 = left.register.int64_1 ^ right.register.int64_1;
+                }
+            }
+            return result;
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements are obtained by taking the one's complement of the given vector's elements.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The one's complement vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> operator ~(Vector<T> value)
+        {
+            return s_allOnes ^ value;
+        }
+        #endregion Bitwise Operators
+
+        #region Logical Operators
+        /// <summary>
+        /// Returns a boolean indicating whether each pair of elements in the given vectors are equal.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The first vector to compare.</param>
+        /// <returns>True if all elements are equal; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static bool operator ==(Vector<T> left, Vector<T> right)
+        {
+            return left.Equals(right);
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether any single pair of elements in the given vectors are not equal.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>True if left and right are not equal; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static bool operator !=(Vector<T> left, Vector<T> right)
+        {
+            return !(left == right);
+        }
+        #endregion Logical Operators
+
+        #region Conversions
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of another type.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [Intrinsic]
+        public static explicit operator Vector<Byte>(Vector<T> value)
+        {
+            return new Vector<Byte>(ref value.register);
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of another type.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static explicit operator Vector<SByte>(Vector<T> value)
+        {
+            return new Vector<SByte>(ref value.register);
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of another type.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static explicit operator Vector<UInt16>(Vector<T> value)
+        {
+            return new Vector<UInt16>(ref value.register);
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of another type.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [Intrinsic]
+        public static explicit operator Vector<Int16>(Vector<T> value)
+        {
+            return new Vector<Int16>(ref value.register);
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of another type.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static explicit operator Vector<UInt32>(Vector<T> value)
+        {
+            return new Vector<UInt32>(ref value.register);
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of another type.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [Intrinsic]
+        public static explicit operator Vector<Int32>(Vector<T> value)
+        {
+            return new Vector<Int32>(ref value.register);
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of another type.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static explicit operator Vector<UInt64>(Vector<T> value)
+        {
+            return new Vector<UInt64>(ref value.register);
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of another type.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [Intrinsic]
+        public static explicit operator Vector<Int64>(Vector<T> value)
+        {
+            return new Vector<Int64>(ref value.register);
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of another type.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [Intrinsic]
+        public static explicit operator Vector<Single>(Vector<T> value)
+        {
+            return new Vector<Single>(ref value.register);
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of another type.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [Intrinsic]
+        public static explicit operator Vector<Double>(Vector<T> value)
+        {
+            return new Vector<Double>(ref value.register);
+        }
+
+        #endregion Conversions
+
+        #region Internal Comparison Methods
+        [Intrinsic]
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        internal static unsafe Vector<T> Equals(Vector<T> left, Vector<T> right)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    Byte* dataPtr = stackalloc Byte[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarEquals(left[g], right[g]) ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    SByte* dataPtr = stackalloc SByte[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarEquals(left[g], right[g]) ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    UInt16* dataPtr = stackalloc UInt16[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarEquals(left[g], right[g]) ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    Int16* dataPtr = stackalloc Int16[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarEquals(left[g], right[g]) ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    UInt32* dataPtr = stackalloc UInt32[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarEquals(left[g], right[g]) ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    Int32* dataPtr = stackalloc Int32[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarEquals(left[g], right[g]) ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    UInt64* dataPtr = stackalloc UInt64[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarEquals(left[g], right[g]) ? ConstantHelper.GetUInt64WithAllBitsSet() : (UInt64)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    Int64* dataPtr = stackalloc Int64[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarEquals(left[g], right[g]) ? ConstantHelper.GetInt64WithAllBitsSet() : (Int64)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    Single* dataPtr = stackalloc Single[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarEquals(left[g], right[g]) ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    Double* dataPtr = stackalloc Double[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarEquals(left[g], right[g]) ? ConstantHelper.GetDoubleWithAllBitsSet() : (Double)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+                Register register = new Register();
+                if (typeof(T) == typeof(Byte))
+                {
+                    register.byte_0 = left.register.byte_0 == right.register.byte_0 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_1 = left.register.byte_1 == right.register.byte_1 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_2 = left.register.byte_2 == right.register.byte_2 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_3 = left.register.byte_3 == right.register.byte_3 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_4 = left.register.byte_4 == right.register.byte_4 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_5 = left.register.byte_5 == right.register.byte_5 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_6 = left.register.byte_6 == right.register.byte_6 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_7 = left.register.byte_7 == right.register.byte_7 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_8 = left.register.byte_8 == right.register.byte_8 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_9 = left.register.byte_9 == right.register.byte_9 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_10 = left.register.byte_10 == right.register.byte_10 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_11 = left.register.byte_11 == right.register.byte_11 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_12 = left.register.byte_12 == right.register.byte_12 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_13 = left.register.byte_13 == right.register.byte_13 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_14 = left.register.byte_14 == right.register.byte_14 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_15 = left.register.byte_15 == right.register.byte_15 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    register.sbyte_0 = left.register.sbyte_0 == right.register.sbyte_0 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_1 = left.register.sbyte_1 == right.register.sbyte_1 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_2 = left.register.sbyte_2 == right.register.sbyte_2 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_3 = left.register.sbyte_3 == right.register.sbyte_3 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_4 = left.register.sbyte_4 == right.register.sbyte_4 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_5 = left.register.sbyte_5 == right.register.sbyte_5 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_6 = left.register.sbyte_6 == right.register.sbyte_6 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_7 = left.register.sbyte_7 == right.register.sbyte_7 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_8 = left.register.sbyte_8 == right.register.sbyte_8 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_9 = left.register.sbyte_9 == right.register.sbyte_9 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_10 = left.register.sbyte_10 == right.register.sbyte_10 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_11 = left.register.sbyte_11 == right.register.sbyte_11 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_12 = left.register.sbyte_12 == right.register.sbyte_12 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_13 = left.register.sbyte_13 == right.register.sbyte_13 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_14 = left.register.sbyte_14 == right.register.sbyte_14 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_15 = left.register.sbyte_15 == right.register.sbyte_15 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    register.uint16_0 = left.register.uint16_0 == right.register.uint16_0 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_1 = left.register.uint16_1 == right.register.uint16_1 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_2 = left.register.uint16_2 == right.register.uint16_2 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_3 = left.register.uint16_3 == right.register.uint16_3 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_4 = left.register.uint16_4 == right.register.uint16_4 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_5 = left.register.uint16_5 == right.register.uint16_5 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_6 = left.register.uint16_6 == right.register.uint16_6 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_7 = left.register.uint16_7 == right.register.uint16_7 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    register.int16_0 = left.register.int16_0 == right.register.int16_0 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_1 = left.register.int16_1 == right.register.int16_1 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_2 = left.register.int16_2 == right.register.int16_2 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_3 = left.register.int16_3 == right.register.int16_3 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_4 = left.register.int16_4 == right.register.int16_4 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_5 = left.register.int16_5 == right.register.int16_5 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_6 = left.register.int16_6 == right.register.int16_6 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_7 = left.register.int16_7 == right.register.int16_7 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    register.uint32_0 = left.register.uint32_0 == right.register.uint32_0 ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    register.uint32_1 = left.register.uint32_1 == right.register.uint32_1 ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    register.uint32_2 = left.register.uint32_2 == right.register.uint32_2 ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    register.uint32_3 = left.register.uint32_3 == right.register.uint32_3 ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    register.int32_0 = left.register.int32_0 == right.register.int32_0 ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    register.int32_1 = left.register.int32_1 == right.register.int32_1 ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    register.int32_2 = left.register.int32_2 == right.register.int32_2 ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    register.int32_3 = left.register.int32_3 == right.register.int32_3 ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    register.uint64_0 = left.register.uint64_0 == right.register.uint64_0 ? ConstantHelper.GetUInt64WithAllBitsSet() : (UInt64)0;
+                    register.uint64_1 = left.register.uint64_1 == right.register.uint64_1 ? ConstantHelper.GetUInt64WithAllBitsSet() : (UInt64)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    register.int64_0 = left.register.int64_0 == right.register.int64_0 ? ConstantHelper.GetInt64WithAllBitsSet() : (Int64)0;
+                    register.int64_1 = left.register.int64_1 == right.register.int64_1 ? ConstantHelper.GetInt64WithAllBitsSet() : (Int64)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    register.single_0 = left.register.single_0 == right.register.single_0 ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    register.single_1 = left.register.single_1 == right.register.single_1 ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    register.single_2 = left.register.single_2 == right.register.single_2 ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    register.single_3 = left.register.single_3 == right.register.single_3 ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    register.double_0 = left.register.double_0 == right.register.double_0 ? ConstantHelper.GetDoubleWithAllBitsSet() : (Double)0;
+                    register.double_1 = left.register.double_1 == right.register.double_1 ? ConstantHelper.GetDoubleWithAllBitsSet() : (Double)0;
+                    return new Vector<T>(ref register);
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        [Intrinsic]
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        internal static unsafe Vector<T> LessThan(Vector<T> left, Vector<T> right)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    Byte* dataPtr = stackalloc Byte[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    SByte* dataPtr = stackalloc SByte[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    UInt16* dataPtr = stackalloc UInt16[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    Int16* dataPtr = stackalloc Int16[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    UInt32* dataPtr = stackalloc UInt32[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    Int32* dataPtr = stackalloc Int32[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    UInt64* dataPtr = stackalloc UInt64[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? ConstantHelper.GetUInt64WithAllBitsSet() : (UInt64)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    Int64* dataPtr = stackalloc Int64[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? ConstantHelper.GetInt64WithAllBitsSet() : (Int64)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    Single* dataPtr = stackalloc Single[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    Double* dataPtr = stackalloc Double[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? ConstantHelper.GetDoubleWithAllBitsSet() : (Double)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+                Register register = new Register();
+                if (typeof(T) == typeof(Byte))
+                {
+                    register.byte_0 = left.register.byte_0 < right.register.byte_0 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_1 = left.register.byte_1 < right.register.byte_1 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_2 = left.register.byte_2 < right.register.byte_2 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_3 = left.register.byte_3 < right.register.byte_3 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_4 = left.register.byte_4 < right.register.byte_4 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_5 = left.register.byte_5 < right.register.byte_5 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_6 = left.register.byte_6 < right.register.byte_6 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_7 = left.register.byte_7 < right.register.byte_7 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_8 = left.register.byte_8 < right.register.byte_8 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_9 = left.register.byte_9 < right.register.byte_9 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_10 = left.register.byte_10 < right.register.byte_10 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_11 = left.register.byte_11 < right.register.byte_11 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_12 = left.register.byte_12 < right.register.byte_12 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_13 = left.register.byte_13 < right.register.byte_13 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_14 = left.register.byte_14 < right.register.byte_14 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_15 = left.register.byte_15 < right.register.byte_15 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    register.sbyte_0 = left.register.sbyte_0 < right.register.sbyte_0 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_1 = left.register.sbyte_1 < right.register.sbyte_1 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_2 = left.register.sbyte_2 < right.register.sbyte_2 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_3 = left.register.sbyte_3 < right.register.sbyte_3 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_4 = left.register.sbyte_4 < right.register.sbyte_4 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_5 = left.register.sbyte_5 < right.register.sbyte_5 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_6 = left.register.sbyte_6 < right.register.sbyte_6 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_7 = left.register.sbyte_7 < right.register.sbyte_7 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_8 = left.register.sbyte_8 < right.register.sbyte_8 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_9 = left.register.sbyte_9 < right.register.sbyte_9 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_10 = left.register.sbyte_10 < right.register.sbyte_10 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_11 = left.register.sbyte_11 < right.register.sbyte_11 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_12 = left.register.sbyte_12 < right.register.sbyte_12 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_13 = left.register.sbyte_13 < right.register.sbyte_13 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_14 = left.register.sbyte_14 < right.register.sbyte_14 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_15 = left.register.sbyte_15 < right.register.sbyte_15 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    register.uint16_0 = left.register.uint16_0 < right.register.uint16_0 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_1 = left.register.uint16_1 < right.register.uint16_1 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_2 = left.register.uint16_2 < right.register.uint16_2 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_3 = left.register.uint16_3 < right.register.uint16_3 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_4 = left.register.uint16_4 < right.register.uint16_4 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_5 = left.register.uint16_5 < right.register.uint16_5 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_6 = left.register.uint16_6 < right.register.uint16_6 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_7 = left.register.uint16_7 < right.register.uint16_7 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    register.int16_0 = left.register.int16_0 < right.register.int16_0 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_1 = left.register.int16_1 < right.register.int16_1 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_2 = left.register.int16_2 < right.register.int16_2 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_3 = left.register.int16_3 < right.register.int16_3 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_4 = left.register.int16_4 < right.register.int16_4 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_5 = left.register.int16_5 < right.register.int16_5 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_6 = left.register.int16_6 < right.register.int16_6 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_7 = left.register.int16_7 < right.register.int16_7 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    register.uint32_0 = left.register.uint32_0 < right.register.uint32_0 ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    register.uint32_1 = left.register.uint32_1 < right.register.uint32_1 ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    register.uint32_2 = left.register.uint32_2 < right.register.uint32_2 ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    register.uint32_3 = left.register.uint32_3 < right.register.uint32_3 ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    register.int32_0 = left.register.int32_0 < right.register.int32_0 ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    register.int32_1 = left.register.int32_1 < right.register.int32_1 ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    register.int32_2 = left.register.int32_2 < right.register.int32_2 ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    register.int32_3 = left.register.int32_3 < right.register.int32_3 ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    register.uint64_0 = left.register.uint64_0 < right.register.uint64_0 ? ConstantHelper.GetUInt64WithAllBitsSet() : (UInt64)0;
+                    register.uint64_1 = left.register.uint64_1 < right.register.uint64_1 ? ConstantHelper.GetUInt64WithAllBitsSet() : (UInt64)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    register.int64_0 = left.register.int64_0 < right.register.int64_0 ? ConstantHelper.GetInt64WithAllBitsSet() : (Int64)0;
+                    register.int64_1 = left.register.int64_1 < right.register.int64_1 ? ConstantHelper.GetInt64WithAllBitsSet() : (Int64)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    register.single_0 = left.register.single_0 < right.register.single_0 ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    register.single_1 = left.register.single_1 < right.register.single_1 ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    register.single_2 = left.register.single_2 < right.register.single_2 ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    register.single_3 = left.register.single_3 < right.register.single_3 ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    register.double_0 = left.register.double_0 < right.register.double_0 ? ConstantHelper.GetDoubleWithAllBitsSet() : (Double)0;
+                    register.double_1 = left.register.double_1 < right.register.double_1 ? ConstantHelper.GetDoubleWithAllBitsSet() : (Double)0;
+                    return new Vector<T>(ref register);
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        [Intrinsic]
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        internal static unsafe Vector<T> GreaterThan(Vector<T> left, Vector<T> right)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    Byte* dataPtr = stackalloc Byte[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    SByte* dataPtr = stackalloc SByte[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    UInt16* dataPtr = stackalloc UInt16[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    Int16* dataPtr = stackalloc Int16[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    UInt32* dataPtr = stackalloc UInt32[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    Int32* dataPtr = stackalloc Int32[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    UInt64* dataPtr = stackalloc UInt64[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? ConstantHelper.GetUInt64WithAllBitsSet() : (UInt64)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    Int64* dataPtr = stackalloc Int64[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? ConstantHelper.GetInt64WithAllBitsSet() : (Int64)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    Single* dataPtr = stackalloc Single[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    Double* dataPtr = stackalloc Double[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? ConstantHelper.GetDoubleWithAllBitsSet() : (Double)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+                Register register = new Register();
+                if (typeof(T) == typeof(Byte))
+                {
+                    register.byte_0 = left.register.byte_0 > right.register.byte_0 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_1 = left.register.byte_1 > right.register.byte_1 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_2 = left.register.byte_2 > right.register.byte_2 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_3 = left.register.byte_3 > right.register.byte_3 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_4 = left.register.byte_4 > right.register.byte_4 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_5 = left.register.byte_5 > right.register.byte_5 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_6 = left.register.byte_6 > right.register.byte_6 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_7 = left.register.byte_7 > right.register.byte_7 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_8 = left.register.byte_8 > right.register.byte_8 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_9 = left.register.byte_9 > right.register.byte_9 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_10 = left.register.byte_10 > right.register.byte_10 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_11 = left.register.byte_11 > right.register.byte_11 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_12 = left.register.byte_12 > right.register.byte_12 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_13 = left.register.byte_13 > right.register.byte_13 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_14 = left.register.byte_14 > right.register.byte_14 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    register.byte_15 = left.register.byte_15 > right.register.byte_15 ? ConstantHelper.GetByteWithAllBitsSet() : (Byte)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    register.sbyte_0 = left.register.sbyte_0 > right.register.sbyte_0 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_1 = left.register.sbyte_1 > right.register.sbyte_1 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_2 = left.register.sbyte_2 > right.register.sbyte_2 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_3 = left.register.sbyte_3 > right.register.sbyte_3 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_4 = left.register.sbyte_4 > right.register.sbyte_4 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_5 = left.register.sbyte_5 > right.register.sbyte_5 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_6 = left.register.sbyte_6 > right.register.sbyte_6 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_7 = left.register.sbyte_7 > right.register.sbyte_7 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_8 = left.register.sbyte_8 > right.register.sbyte_8 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_9 = left.register.sbyte_9 > right.register.sbyte_9 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_10 = left.register.sbyte_10 > right.register.sbyte_10 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_11 = left.register.sbyte_11 > right.register.sbyte_11 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_12 = left.register.sbyte_12 > right.register.sbyte_12 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_13 = left.register.sbyte_13 > right.register.sbyte_13 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_14 = left.register.sbyte_14 > right.register.sbyte_14 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    register.sbyte_15 = left.register.sbyte_15 > right.register.sbyte_15 ? ConstantHelper.GetSByteWithAllBitsSet() : (SByte)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    register.uint16_0 = left.register.uint16_0 > right.register.uint16_0 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_1 = left.register.uint16_1 > right.register.uint16_1 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_2 = left.register.uint16_2 > right.register.uint16_2 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_3 = left.register.uint16_3 > right.register.uint16_3 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_4 = left.register.uint16_4 > right.register.uint16_4 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_5 = left.register.uint16_5 > right.register.uint16_5 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_6 = left.register.uint16_6 > right.register.uint16_6 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    register.uint16_7 = left.register.uint16_7 > right.register.uint16_7 ? ConstantHelper.GetUInt16WithAllBitsSet() : (UInt16)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    register.int16_0 = left.register.int16_0 > right.register.int16_0 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_1 = left.register.int16_1 > right.register.int16_1 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_2 = left.register.int16_2 > right.register.int16_2 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_3 = left.register.int16_3 > right.register.int16_3 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_4 = left.register.int16_4 > right.register.int16_4 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_5 = left.register.int16_5 > right.register.int16_5 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_6 = left.register.int16_6 > right.register.int16_6 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    register.int16_7 = left.register.int16_7 > right.register.int16_7 ? ConstantHelper.GetInt16WithAllBitsSet() : (Int16)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    register.uint32_0 = left.register.uint32_0 > right.register.uint32_0 ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    register.uint32_1 = left.register.uint32_1 > right.register.uint32_1 ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    register.uint32_2 = left.register.uint32_2 > right.register.uint32_2 ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    register.uint32_3 = left.register.uint32_3 > right.register.uint32_3 ? ConstantHelper.GetUInt32WithAllBitsSet() : (UInt32)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    register.int32_0 = left.register.int32_0 > right.register.int32_0 ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    register.int32_1 = left.register.int32_1 > right.register.int32_1 ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    register.int32_2 = left.register.int32_2 > right.register.int32_2 ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    register.int32_3 = left.register.int32_3 > right.register.int32_3 ? ConstantHelper.GetInt32WithAllBitsSet() : (Int32)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    register.uint64_0 = left.register.uint64_0 > right.register.uint64_0 ? ConstantHelper.GetUInt64WithAllBitsSet() : (UInt64)0;
+                    register.uint64_1 = left.register.uint64_1 > right.register.uint64_1 ? ConstantHelper.GetUInt64WithAllBitsSet() : (UInt64)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    register.int64_0 = left.register.int64_0 > right.register.int64_0 ? ConstantHelper.GetInt64WithAllBitsSet() : (Int64)0;
+                    register.int64_1 = left.register.int64_1 > right.register.int64_1 ? ConstantHelper.GetInt64WithAllBitsSet() : (Int64)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    register.single_0 = left.register.single_0 > right.register.single_0 ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    register.single_1 = left.register.single_1 > right.register.single_1 ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    register.single_2 = left.register.single_2 > right.register.single_2 ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    register.single_3 = left.register.single_3 > right.register.single_3 ? ConstantHelper.GetSingleWithAllBitsSet() : (Single)0;
+                    return new Vector<T>(ref register);
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    register.double_0 = left.register.double_0 > right.register.double_0 ? ConstantHelper.GetDoubleWithAllBitsSet() : (Double)0;
+                    register.double_1 = left.register.double_1 > right.register.double_1 ? ConstantHelper.GetDoubleWithAllBitsSet() : (Double)0;
+                    return new Vector<T>(ref register);
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        [Intrinsic]
+        internal static Vector<T> GreaterThanOrEqual(Vector<T> left, Vector<T> right)
+        {
+            return Equals(left, right) | GreaterThan(left, right);
+        }
+
+        [Intrinsic]
+        internal static Vector<T> LessThanOrEqual(Vector<T> left, Vector<T> right)
+        {
+            return Equals(left, right) | LessThan(left, right);
+        }
+
+        [Intrinsic]
+        internal static Vector<T> ConditionalSelect(Vector<T> condition, Vector<T> left, Vector<T> right)
+        {
+            return (left & condition) | (Vector.AndNot(right, condition));
+        }
+        #endregion Comparison Methods
+
+        #region Internal Math Methods
+        [Intrinsic]
+        internal static unsafe Vector<T> Abs(Vector<T> value)
+        {
+            if (typeof(T) == typeof(Byte))
+            {
+                return value;
+            }
+            else if (typeof(T) == typeof(UInt16))
+            {
+                return value;
+            }
+            else if (typeof(T) == typeof(UInt32))
+            {
+                return value;
+            }
+            else if (typeof(T) == typeof(UInt64))
+            {
+                return value;
+            }
+            if (Vector.IsHardwareAccelerated)
+            {
+                if (typeof(T) == typeof(SByte))
+                {
+                    SByte* dataPtr = stackalloc SByte[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = (SByte)(object)(Math.Abs((SByte)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    Int16* dataPtr = stackalloc Int16[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = (Int16)(object)(Math.Abs((Int16)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    Int32* dataPtr = stackalloc Int32[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = (Int32)(object)(Math.Abs((Int32)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    Int64* dataPtr = stackalloc Int64[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = (Int64)(object)(Math.Abs((Int64)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    Single* dataPtr = stackalloc Single[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = (Single)(object)(Math.Abs((Single)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    Double* dataPtr = stackalloc Double[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = (Double)(object)(Math.Abs((Double)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+                if (typeof(T) == typeof(SByte))
+                {
+                    value.register.sbyte_0 = (SByte)(Math.Abs(value.register.sbyte_0));
+                    value.register.sbyte_1 = (SByte)(Math.Abs(value.register.sbyte_1));
+                    value.register.sbyte_2 = (SByte)(Math.Abs(value.register.sbyte_2));
+                    value.register.sbyte_3 = (SByte)(Math.Abs(value.register.sbyte_3));
+                    value.register.sbyte_4 = (SByte)(Math.Abs(value.register.sbyte_4));
+                    value.register.sbyte_5 = (SByte)(Math.Abs(value.register.sbyte_5));
+                    value.register.sbyte_6 = (SByte)(Math.Abs(value.register.sbyte_6));
+                    value.register.sbyte_7 = (SByte)(Math.Abs(value.register.sbyte_7));
+                    value.register.sbyte_8 = (SByte)(Math.Abs(value.register.sbyte_8));
+                    value.register.sbyte_9 = (SByte)(Math.Abs(value.register.sbyte_9));
+                    value.register.sbyte_10 = (SByte)(Math.Abs(value.register.sbyte_10));
+                    value.register.sbyte_11 = (SByte)(Math.Abs(value.register.sbyte_11));
+                    value.register.sbyte_12 = (SByte)(Math.Abs(value.register.sbyte_12));
+                    value.register.sbyte_13 = (SByte)(Math.Abs(value.register.sbyte_13));
+                    value.register.sbyte_14 = (SByte)(Math.Abs(value.register.sbyte_14));
+                    value.register.sbyte_15 = (SByte)(Math.Abs(value.register.sbyte_15));
+                    return value;
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    value.register.int16_0 = (Int16)(Math.Abs(value.register.int16_0));
+                    value.register.int16_1 = (Int16)(Math.Abs(value.register.int16_1));
+                    value.register.int16_2 = (Int16)(Math.Abs(value.register.int16_2));
+                    value.register.int16_3 = (Int16)(Math.Abs(value.register.int16_3));
+                    value.register.int16_4 = (Int16)(Math.Abs(value.register.int16_4));
+                    value.register.int16_5 = (Int16)(Math.Abs(value.register.int16_5));
+                    value.register.int16_6 = (Int16)(Math.Abs(value.register.int16_6));
+                    value.register.int16_7 = (Int16)(Math.Abs(value.register.int16_7));
+                    return value;
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    value.register.int32_0 = (Int32)(Math.Abs(value.register.int32_0));
+                    value.register.int32_1 = (Int32)(Math.Abs(value.register.int32_1));
+                    value.register.int32_2 = (Int32)(Math.Abs(value.register.int32_2));
+                    value.register.int32_3 = (Int32)(Math.Abs(value.register.int32_3));
+                    return value;
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    value.register.int64_0 = (Int64)(Math.Abs(value.register.int64_0));
+                    value.register.int64_1 = (Int64)(Math.Abs(value.register.int64_1));
+                    return value;
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    value.register.single_0 = (Single)(Math.Abs(value.register.single_0));
+                    value.register.single_1 = (Single)(Math.Abs(value.register.single_1));
+                    value.register.single_2 = (Single)(Math.Abs(value.register.single_2));
+                    value.register.single_3 = (Single)(Math.Abs(value.register.single_3));
+                    return value;
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    value.register.double_0 = (Double)(Math.Abs(value.register.double_0));
+                    value.register.double_1 = (Double)(Math.Abs(value.register.double_1));
+                    return value;
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        [Intrinsic]
+        internal static unsafe Vector<T> Min(Vector<T> left, Vector<T> right)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    Byte* dataPtr = stackalloc Byte[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? (Byte)(object)left[g] : (Byte)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    SByte* dataPtr = stackalloc SByte[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? (SByte)(object)left[g] : (SByte)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    UInt16* dataPtr = stackalloc UInt16[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? (UInt16)(object)left[g] : (UInt16)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    Int16* dataPtr = stackalloc Int16[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? (Int16)(object)left[g] : (Int16)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    UInt32* dataPtr = stackalloc UInt32[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? (UInt32)(object)left[g] : (UInt32)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    Int32* dataPtr = stackalloc Int32[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? (Int32)(object)left[g] : (Int32)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    UInt64* dataPtr = stackalloc UInt64[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? (UInt64)(object)left[g] : (UInt64)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    Int64* dataPtr = stackalloc Int64[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? (Int64)(object)left[g] : (Int64)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    Single* dataPtr = stackalloc Single[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? (Single)(object)left[g] : (Single)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    Double* dataPtr = stackalloc Double[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? (Double)(object)left[g] : (Double)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+                Vector<T> vec = new Vector<T>();
+                if (typeof(T) == typeof(Byte))
+                {
+                    vec.register.byte_0 = left.register.byte_0 < right.register.byte_0 ? left.register.byte_0 : right.register.byte_0;
+                    vec.register.byte_1 = left.register.byte_1 < right.register.byte_1 ? left.register.byte_1 : right.register.byte_1;
+                    vec.register.byte_2 = left.register.byte_2 < right.register.byte_2 ? left.register.byte_2 : right.register.byte_2;
+                    vec.register.byte_3 = left.register.byte_3 < right.register.byte_3 ? left.register.byte_3 : right.register.byte_3;
+                    vec.register.byte_4 = left.register.byte_4 < right.register.byte_4 ? left.register.byte_4 : right.register.byte_4;
+                    vec.register.byte_5 = left.register.byte_5 < right.register.byte_5 ? left.register.byte_5 : right.register.byte_5;
+                    vec.register.byte_6 = left.register.byte_6 < right.register.byte_6 ? left.register.byte_6 : right.register.byte_6;
+                    vec.register.byte_7 = left.register.byte_7 < right.register.byte_7 ? left.register.byte_7 : right.register.byte_7;
+                    vec.register.byte_8 = left.register.byte_8 < right.register.byte_8 ? left.register.byte_8 : right.register.byte_8;
+                    vec.register.byte_9 = left.register.byte_9 < right.register.byte_9 ? left.register.byte_9 : right.register.byte_9;
+                    vec.register.byte_10 = left.register.byte_10 < right.register.byte_10 ? left.register.byte_10 : right.register.byte_10;
+                    vec.register.byte_11 = left.register.byte_11 < right.register.byte_11 ? left.register.byte_11 : right.register.byte_11;
+                    vec.register.byte_12 = left.register.byte_12 < right.register.byte_12 ? left.register.byte_12 : right.register.byte_12;
+                    vec.register.byte_13 = left.register.byte_13 < right.register.byte_13 ? left.register.byte_13 : right.register.byte_13;
+                    vec.register.byte_14 = left.register.byte_14 < right.register.byte_14 ? left.register.byte_14 : right.register.byte_14;
+                    vec.register.byte_15 = left.register.byte_15 < right.register.byte_15 ? left.register.byte_15 : right.register.byte_15;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    vec.register.sbyte_0 = left.register.sbyte_0 < right.register.sbyte_0 ? left.register.sbyte_0 : right.register.sbyte_0;
+                    vec.register.sbyte_1 = left.register.sbyte_1 < right.register.sbyte_1 ? left.register.sbyte_1 : right.register.sbyte_1;
+                    vec.register.sbyte_2 = left.register.sbyte_2 < right.register.sbyte_2 ? left.register.sbyte_2 : right.register.sbyte_2;
+                    vec.register.sbyte_3 = left.register.sbyte_3 < right.register.sbyte_3 ? left.register.sbyte_3 : right.register.sbyte_3;
+                    vec.register.sbyte_4 = left.register.sbyte_4 < right.register.sbyte_4 ? left.register.sbyte_4 : right.register.sbyte_4;
+                    vec.register.sbyte_5 = left.register.sbyte_5 < right.register.sbyte_5 ? left.register.sbyte_5 : right.register.sbyte_5;
+                    vec.register.sbyte_6 = left.register.sbyte_6 < right.register.sbyte_6 ? left.register.sbyte_6 : right.register.sbyte_6;
+                    vec.register.sbyte_7 = left.register.sbyte_7 < right.register.sbyte_7 ? left.register.sbyte_7 : right.register.sbyte_7;
+                    vec.register.sbyte_8 = left.register.sbyte_8 < right.register.sbyte_8 ? left.register.sbyte_8 : right.register.sbyte_8;
+                    vec.register.sbyte_9 = left.register.sbyte_9 < right.register.sbyte_9 ? left.register.sbyte_9 : right.register.sbyte_9;
+                    vec.register.sbyte_10 = left.register.sbyte_10 < right.register.sbyte_10 ? left.register.sbyte_10 : right.register.sbyte_10;
+                    vec.register.sbyte_11 = left.register.sbyte_11 < right.register.sbyte_11 ? left.register.sbyte_11 : right.register.sbyte_11;
+                    vec.register.sbyte_12 = left.register.sbyte_12 < right.register.sbyte_12 ? left.register.sbyte_12 : right.register.sbyte_12;
+                    vec.register.sbyte_13 = left.register.sbyte_13 < right.register.sbyte_13 ? left.register.sbyte_13 : right.register.sbyte_13;
+                    vec.register.sbyte_14 = left.register.sbyte_14 < right.register.sbyte_14 ? left.register.sbyte_14 : right.register.sbyte_14;
+                    vec.register.sbyte_15 = left.register.sbyte_15 < right.register.sbyte_15 ? left.register.sbyte_15 : right.register.sbyte_15;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    vec.register.uint16_0 = left.register.uint16_0 < right.register.uint16_0 ? left.register.uint16_0 : right.register.uint16_0;
+                    vec.register.uint16_1 = left.register.uint16_1 < right.register.uint16_1 ? left.register.uint16_1 : right.register.uint16_1;
+                    vec.register.uint16_2 = left.register.uint16_2 < right.register.uint16_2 ? left.register.uint16_2 : right.register.uint16_2;
+                    vec.register.uint16_3 = left.register.uint16_3 < right.register.uint16_3 ? left.register.uint16_3 : right.register.uint16_3;
+                    vec.register.uint16_4 = left.register.uint16_4 < right.register.uint16_4 ? left.register.uint16_4 : right.register.uint16_4;
+                    vec.register.uint16_5 = left.register.uint16_5 < right.register.uint16_5 ? left.register.uint16_5 : right.register.uint16_5;
+                    vec.register.uint16_6 = left.register.uint16_6 < right.register.uint16_6 ? left.register.uint16_6 : right.register.uint16_6;
+                    vec.register.uint16_7 = left.register.uint16_7 < right.register.uint16_7 ? left.register.uint16_7 : right.register.uint16_7;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    vec.register.int16_0 = left.register.int16_0 < right.register.int16_0 ? left.register.int16_0 : right.register.int16_0;
+                    vec.register.int16_1 = left.register.int16_1 < right.register.int16_1 ? left.register.int16_1 : right.register.int16_1;
+                    vec.register.int16_2 = left.register.int16_2 < right.register.int16_2 ? left.register.int16_2 : right.register.int16_2;
+                    vec.register.int16_3 = left.register.int16_3 < right.register.int16_3 ? left.register.int16_3 : right.register.int16_3;
+                    vec.register.int16_4 = left.register.int16_4 < right.register.int16_4 ? left.register.int16_4 : right.register.int16_4;
+                    vec.register.int16_5 = left.register.int16_5 < right.register.int16_5 ? left.register.int16_5 : right.register.int16_5;
+                    vec.register.int16_6 = left.register.int16_6 < right.register.int16_6 ? left.register.int16_6 : right.register.int16_6;
+                    vec.register.int16_7 = left.register.int16_7 < right.register.int16_7 ? left.register.int16_7 : right.register.int16_7;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    vec.register.uint32_0 = left.register.uint32_0 < right.register.uint32_0 ? left.register.uint32_0 : right.register.uint32_0;
+                    vec.register.uint32_1 = left.register.uint32_1 < right.register.uint32_1 ? left.register.uint32_1 : right.register.uint32_1;
+                    vec.register.uint32_2 = left.register.uint32_2 < right.register.uint32_2 ? left.register.uint32_2 : right.register.uint32_2;
+                    vec.register.uint32_3 = left.register.uint32_3 < right.register.uint32_3 ? left.register.uint32_3 : right.register.uint32_3;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    vec.register.int32_0 = left.register.int32_0 < right.register.int32_0 ? left.register.int32_0 : right.register.int32_0;
+                    vec.register.int32_1 = left.register.int32_1 < right.register.int32_1 ? left.register.int32_1 : right.register.int32_1;
+                    vec.register.int32_2 = left.register.int32_2 < right.register.int32_2 ? left.register.int32_2 : right.register.int32_2;
+                    vec.register.int32_3 = left.register.int32_3 < right.register.int32_3 ? left.register.int32_3 : right.register.int32_3;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    vec.register.uint64_0 = left.register.uint64_0 < right.register.uint64_0 ? left.register.uint64_0 : right.register.uint64_0;
+                    vec.register.uint64_1 = left.register.uint64_1 < right.register.uint64_1 ? left.register.uint64_1 : right.register.uint64_1;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    vec.register.int64_0 = left.register.int64_0 < right.register.int64_0 ? left.register.int64_0 : right.register.int64_0;
+                    vec.register.int64_1 = left.register.int64_1 < right.register.int64_1 ? left.register.int64_1 : right.register.int64_1;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    vec.register.single_0 = left.register.single_0 < right.register.single_0 ? left.register.single_0 : right.register.single_0;
+                    vec.register.single_1 = left.register.single_1 < right.register.single_1 ? left.register.single_1 : right.register.single_1;
+                    vec.register.single_2 = left.register.single_2 < right.register.single_2 ? left.register.single_2 : right.register.single_2;
+                    vec.register.single_3 = left.register.single_3 < right.register.single_3 ? left.register.single_3 : right.register.single_3;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    vec.register.double_0 = left.register.double_0 < right.register.double_0 ? left.register.double_0 : right.register.double_0;
+                    vec.register.double_1 = left.register.double_1 < right.register.double_1 ? left.register.double_1 : right.register.double_1;
+                    return vec;
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        [Intrinsic]
+        internal static unsafe Vector<T> Max(Vector<T> left, Vector<T> right)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    Byte* dataPtr = stackalloc Byte[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? (Byte)(object)left[g] : (Byte)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    SByte* dataPtr = stackalloc SByte[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? (SByte)(object)left[g] : (SByte)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    UInt16* dataPtr = stackalloc UInt16[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? (UInt16)(object)left[g] : (UInt16)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    Int16* dataPtr = stackalloc Int16[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? (Int16)(object)left[g] : (Int16)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    UInt32* dataPtr = stackalloc UInt32[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? (UInt32)(object)left[g] : (UInt32)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    Int32* dataPtr = stackalloc Int32[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? (Int32)(object)left[g] : (Int32)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    UInt64* dataPtr = stackalloc UInt64[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? (UInt64)(object)left[g] : (UInt64)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    Int64* dataPtr = stackalloc Int64[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? (Int64)(object)left[g] : (Int64)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    Single* dataPtr = stackalloc Single[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? (Single)(object)left[g] : (Single)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    Double* dataPtr = stackalloc Double[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? (Double)(object)left[g] : (Double)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+                Vector<T> vec = new Vector<T>();
+                if (typeof(T) == typeof(Byte))
+                {
+                    vec.register.byte_0 = left.register.byte_0 > right.register.byte_0 ? left.register.byte_0 : right.register.byte_0;
+                    vec.register.byte_1 = left.register.byte_1 > right.register.byte_1 ? left.register.byte_1 : right.register.byte_1;
+                    vec.register.byte_2 = left.register.byte_2 > right.register.byte_2 ? left.register.byte_2 : right.register.byte_2;
+                    vec.register.byte_3 = left.register.byte_3 > right.register.byte_3 ? left.register.byte_3 : right.register.byte_3;
+                    vec.register.byte_4 = left.register.byte_4 > right.register.byte_4 ? left.register.byte_4 : right.register.byte_4;
+                    vec.register.byte_5 = left.register.byte_5 > right.register.byte_5 ? left.register.byte_5 : right.register.byte_5;
+                    vec.register.byte_6 = left.register.byte_6 > right.register.byte_6 ? left.register.byte_6 : right.register.byte_6;
+                    vec.register.byte_7 = left.register.byte_7 > right.register.byte_7 ? left.register.byte_7 : right.register.byte_7;
+                    vec.register.byte_8 = left.register.byte_8 > right.register.byte_8 ? left.register.byte_8 : right.register.byte_8;
+                    vec.register.byte_9 = left.register.byte_9 > right.register.byte_9 ? left.register.byte_9 : right.register.byte_9;
+                    vec.register.byte_10 = left.register.byte_10 > right.register.byte_10 ? left.register.byte_10 : right.register.byte_10;
+                    vec.register.byte_11 = left.register.byte_11 > right.register.byte_11 ? left.register.byte_11 : right.register.byte_11;
+                    vec.register.byte_12 = left.register.byte_12 > right.register.byte_12 ? left.register.byte_12 : right.register.byte_12;
+                    vec.register.byte_13 = left.register.byte_13 > right.register.byte_13 ? left.register.byte_13 : right.register.byte_13;
+                    vec.register.byte_14 = left.register.byte_14 > right.register.byte_14 ? left.register.byte_14 : right.register.byte_14;
+                    vec.register.byte_15 = left.register.byte_15 > right.register.byte_15 ? left.register.byte_15 : right.register.byte_15;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    vec.register.sbyte_0 = left.register.sbyte_0 > right.register.sbyte_0 ? left.register.sbyte_0 : right.register.sbyte_0;
+                    vec.register.sbyte_1 = left.register.sbyte_1 > right.register.sbyte_1 ? left.register.sbyte_1 : right.register.sbyte_1;
+                    vec.register.sbyte_2 = left.register.sbyte_2 > right.register.sbyte_2 ? left.register.sbyte_2 : right.register.sbyte_2;
+                    vec.register.sbyte_3 = left.register.sbyte_3 > right.register.sbyte_3 ? left.register.sbyte_3 : right.register.sbyte_3;
+                    vec.register.sbyte_4 = left.register.sbyte_4 > right.register.sbyte_4 ? left.register.sbyte_4 : right.register.sbyte_4;
+                    vec.register.sbyte_5 = left.register.sbyte_5 > right.register.sbyte_5 ? left.register.sbyte_5 : right.register.sbyte_5;
+                    vec.register.sbyte_6 = left.register.sbyte_6 > right.register.sbyte_6 ? left.register.sbyte_6 : right.register.sbyte_6;
+                    vec.register.sbyte_7 = left.register.sbyte_7 > right.register.sbyte_7 ? left.register.sbyte_7 : right.register.sbyte_7;
+                    vec.register.sbyte_8 = left.register.sbyte_8 > right.register.sbyte_8 ? left.register.sbyte_8 : right.register.sbyte_8;
+                    vec.register.sbyte_9 = left.register.sbyte_9 > right.register.sbyte_9 ? left.register.sbyte_9 : right.register.sbyte_9;
+                    vec.register.sbyte_10 = left.register.sbyte_10 > right.register.sbyte_10 ? left.register.sbyte_10 : right.register.sbyte_10;
+                    vec.register.sbyte_11 = left.register.sbyte_11 > right.register.sbyte_11 ? left.register.sbyte_11 : right.register.sbyte_11;
+                    vec.register.sbyte_12 = left.register.sbyte_12 > right.register.sbyte_12 ? left.register.sbyte_12 : right.register.sbyte_12;
+                    vec.register.sbyte_13 = left.register.sbyte_13 > right.register.sbyte_13 ? left.register.sbyte_13 : right.register.sbyte_13;
+                    vec.register.sbyte_14 = left.register.sbyte_14 > right.register.sbyte_14 ? left.register.sbyte_14 : right.register.sbyte_14;
+                    vec.register.sbyte_15 = left.register.sbyte_15 > right.register.sbyte_15 ? left.register.sbyte_15 : right.register.sbyte_15;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    vec.register.uint16_0 = left.register.uint16_0 > right.register.uint16_0 ? left.register.uint16_0 : right.register.uint16_0;
+                    vec.register.uint16_1 = left.register.uint16_1 > right.register.uint16_1 ? left.register.uint16_1 : right.register.uint16_1;
+                    vec.register.uint16_2 = left.register.uint16_2 > right.register.uint16_2 ? left.register.uint16_2 : right.register.uint16_2;
+                    vec.register.uint16_3 = left.register.uint16_3 > right.register.uint16_3 ? left.register.uint16_3 : right.register.uint16_3;
+                    vec.register.uint16_4 = left.register.uint16_4 > right.register.uint16_4 ? left.register.uint16_4 : right.register.uint16_4;
+                    vec.register.uint16_5 = left.register.uint16_5 > right.register.uint16_5 ? left.register.uint16_5 : right.register.uint16_5;
+                    vec.register.uint16_6 = left.register.uint16_6 > right.register.uint16_6 ? left.register.uint16_6 : right.register.uint16_6;
+                    vec.register.uint16_7 = left.register.uint16_7 > right.register.uint16_7 ? left.register.uint16_7 : right.register.uint16_7;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    vec.register.int16_0 = left.register.int16_0 > right.register.int16_0 ? left.register.int16_0 : right.register.int16_0;
+                    vec.register.int16_1 = left.register.int16_1 > right.register.int16_1 ? left.register.int16_1 : right.register.int16_1;
+                    vec.register.int16_2 = left.register.int16_2 > right.register.int16_2 ? left.register.int16_2 : right.register.int16_2;
+                    vec.register.int16_3 = left.register.int16_3 > right.register.int16_3 ? left.register.int16_3 : right.register.int16_3;
+                    vec.register.int16_4 = left.register.int16_4 > right.register.int16_4 ? left.register.int16_4 : right.register.int16_4;
+                    vec.register.int16_5 = left.register.int16_5 > right.register.int16_5 ? left.register.int16_5 : right.register.int16_5;
+                    vec.register.int16_6 = left.register.int16_6 > right.register.int16_6 ? left.register.int16_6 : right.register.int16_6;
+                    vec.register.int16_7 = left.register.int16_7 > right.register.int16_7 ? left.register.int16_7 : right.register.int16_7;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    vec.register.uint32_0 = left.register.uint32_0 > right.register.uint32_0 ? left.register.uint32_0 : right.register.uint32_0;
+                    vec.register.uint32_1 = left.register.uint32_1 > right.register.uint32_1 ? left.register.uint32_1 : right.register.uint32_1;
+                    vec.register.uint32_2 = left.register.uint32_2 > right.register.uint32_2 ? left.register.uint32_2 : right.register.uint32_2;
+                    vec.register.uint32_3 = left.register.uint32_3 > right.register.uint32_3 ? left.register.uint32_3 : right.register.uint32_3;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    vec.register.int32_0 = left.register.int32_0 > right.register.int32_0 ? left.register.int32_0 : right.register.int32_0;
+                    vec.register.int32_1 = left.register.int32_1 > right.register.int32_1 ? left.register.int32_1 : right.register.int32_1;
+                    vec.register.int32_2 = left.register.int32_2 > right.register.int32_2 ? left.register.int32_2 : right.register.int32_2;
+                    vec.register.int32_3 = left.register.int32_3 > right.register.int32_3 ? left.register.int32_3 : right.register.int32_3;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    vec.register.uint64_0 = left.register.uint64_0 > right.register.uint64_0 ? left.register.uint64_0 : right.register.uint64_0;
+                    vec.register.uint64_1 = left.register.uint64_1 > right.register.uint64_1 ? left.register.uint64_1 : right.register.uint64_1;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    vec.register.int64_0 = left.register.int64_0 > right.register.int64_0 ? left.register.int64_0 : right.register.int64_0;
+                    vec.register.int64_1 = left.register.int64_1 > right.register.int64_1 ? left.register.int64_1 : right.register.int64_1;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    vec.register.single_0 = left.register.single_0 > right.register.single_0 ? left.register.single_0 : right.register.single_0;
+                    vec.register.single_1 = left.register.single_1 > right.register.single_1 ? left.register.single_1 : right.register.single_1;
+                    vec.register.single_2 = left.register.single_2 > right.register.single_2 ? left.register.single_2 : right.register.single_2;
+                    vec.register.single_3 = left.register.single_3 > right.register.single_3 ? left.register.single_3 : right.register.single_3;
+                    return vec;
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    vec.register.double_0 = left.register.double_0 > right.register.double_0 ? left.register.double_0 : right.register.double_0;
+                    vec.register.double_1 = left.register.double_1 > right.register.double_1 ? left.register.double_1 : right.register.double_1;
+                    return vec;
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        [Intrinsic]
+        internal static T DotProduct(Vector<T> left, Vector<T> right)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+                T product = default;
+                for (int g = 0; g < Count; g++)
+                {
+                    product = ScalarAdd(product, ScalarMultiply(left[g], right[g]));
+                }
+                return product;
+            }
+            else
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    Byte product = 0;
+                    product += (Byte)(left.register.byte_0 * right.register.byte_0);
+                    product += (Byte)(left.register.byte_1 * right.register.byte_1);
+                    product += (Byte)(left.register.byte_2 * right.register.byte_2);
+                    product += (Byte)(left.register.byte_3 * right.register.byte_3);
+                    product += (Byte)(left.register.byte_4 * right.register.byte_4);
+                    product += (Byte)(left.register.byte_5 * right.register.byte_5);
+                    product += (Byte)(left.register.byte_6 * right.register.byte_6);
+                    product += (Byte)(left.register.byte_7 * right.register.byte_7);
+                    product += (Byte)(left.register.byte_8 * right.register.byte_8);
+                    product += (Byte)(left.register.byte_9 * right.register.byte_9);
+                    product += (Byte)(left.register.byte_10 * right.register.byte_10);
+                    product += (Byte)(left.register.byte_11 * right.register.byte_11);
+                    product += (Byte)(left.register.byte_12 * right.register.byte_12);
+                    product += (Byte)(left.register.byte_13 * right.register.byte_13);
+                    product += (Byte)(left.register.byte_14 * right.register.byte_14);
+                    product += (Byte)(left.register.byte_15 * right.register.byte_15);
+                    return (T)(object)product;
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    SByte product = 0;
+                    product += (SByte)(left.register.sbyte_0 * right.register.sbyte_0);
+                    product += (SByte)(left.register.sbyte_1 * right.register.sbyte_1);
+                    product += (SByte)(left.register.sbyte_2 * right.register.sbyte_2);
+                    product += (SByte)(left.register.sbyte_3 * right.register.sbyte_3);
+                    product += (SByte)(left.register.sbyte_4 * right.register.sbyte_4);
+                    product += (SByte)(left.register.sbyte_5 * right.register.sbyte_5);
+                    product += (SByte)(left.register.sbyte_6 * right.register.sbyte_6);
+                    product += (SByte)(left.register.sbyte_7 * right.register.sbyte_7);
+                    product += (SByte)(left.register.sbyte_8 * right.register.sbyte_8);
+                    product += (SByte)(left.register.sbyte_9 * right.register.sbyte_9);
+                    product += (SByte)(left.register.sbyte_10 * right.register.sbyte_10);
+                    product += (SByte)(left.register.sbyte_11 * right.register.sbyte_11);
+                    product += (SByte)(left.register.sbyte_12 * right.register.sbyte_12);
+                    product += (SByte)(left.register.sbyte_13 * right.register.sbyte_13);
+                    product += (SByte)(left.register.sbyte_14 * right.register.sbyte_14);
+                    product += (SByte)(left.register.sbyte_15 * right.register.sbyte_15);
+                    return (T)(object)product;
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    UInt16 product = 0;
+                    product += (UInt16)(left.register.uint16_0 * right.register.uint16_0);
+                    product += (UInt16)(left.register.uint16_1 * right.register.uint16_1);
+                    product += (UInt16)(left.register.uint16_2 * right.register.uint16_2);
+                    product += (UInt16)(left.register.uint16_3 * right.register.uint16_3);
+                    product += (UInt16)(left.register.uint16_4 * right.register.uint16_4);
+                    product += (UInt16)(left.register.uint16_5 * right.register.uint16_5);
+                    product += (UInt16)(left.register.uint16_6 * right.register.uint16_6);
+                    product += (UInt16)(left.register.uint16_7 * right.register.uint16_7);
+                    return (T)(object)product;
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    Int16 product = 0;
+                    product += (Int16)(left.register.int16_0 * right.register.int16_0);
+                    product += (Int16)(left.register.int16_1 * right.register.int16_1);
+                    product += (Int16)(left.register.int16_2 * right.register.int16_2);
+                    product += (Int16)(left.register.int16_3 * right.register.int16_3);
+                    product += (Int16)(left.register.int16_4 * right.register.int16_4);
+                    product += (Int16)(left.register.int16_5 * right.register.int16_5);
+                    product += (Int16)(left.register.int16_6 * right.register.int16_6);
+                    product += (Int16)(left.register.int16_7 * right.register.int16_7);
+                    return (T)(object)product;
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    UInt32 product = 0;
+                    product += (UInt32)(left.register.uint32_0 * right.register.uint32_0);
+                    product += (UInt32)(left.register.uint32_1 * right.register.uint32_1);
+                    product += (UInt32)(left.register.uint32_2 * right.register.uint32_2);
+                    product += (UInt32)(left.register.uint32_3 * right.register.uint32_3);
+                    return (T)(object)product;
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    Int32 product = 0;
+                    product += (Int32)(left.register.int32_0 * right.register.int32_0);
+                    product += (Int32)(left.register.int32_1 * right.register.int32_1);
+                    product += (Int32)(left.register.int32_2 * right.register.int32_2);
+                    product += (Int32)(left.register.int32_3 * right.register.int32_3);
+                    return (T)(object)product;
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    UInt64 product = 0;
+                    product += (UInt64)(left.register.uint64_0 * right.register.uint64_0);
+                    product += (UInt64)(left.register.uint64_1 * right.register.uint64_1);
+                    return (T)(object)product;
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    Int64 product = 0;
+                    product += (Int64)(left.register.int64_0 * right.register.int64_0);
+                    product += (Int64)(left.register.int64_1 * right.register.int64_1);
+                    return (T)(object)product;
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    Single product = 0;
+                    product += (Single)(left.register.single_0 * right.register.single_0);
+                    product += (Single)(left.register.single_1 * right.register.single_1);
+                    product += (Single)(left.register.single_2 * right.register.single_2);
+                    product += (Single)(left.register.single_3 * right.register.single_3);
+                    return (T)(object)product;
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    Double product = 0;
+                    product += (Double)(left.register.double_0 * right.register.double_0);
+                    product += (Double)(left.register.double_1 * right.register.double_1);
+                    return (T)(object)product;
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        [Intrinsic]
+        internal static unsafe Vector<T> SquareRoot(Vector<T> value)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    Byte* dataPtr = stackalloc Byte[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = unchecked((Byte)Math.Sqrt((Byte)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    SByte* dataPtr = stackalloc SByte[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = unchecked((SByte)Math.Sqrt((SByte)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    UInt16* dataPtr = stackalloc UInt16[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = unchecked((UInt16)Math.Sqrt((UInt16)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    Int16* dataPtr = stackalloc Int16[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = unchecked((Int16)Math.Sqrt((Int16)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    UInt32* dataPtr = stackalloc UInt32[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = unchecked((UInt32)Math.Sqrt((UInt32)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    Int32* dataPtr = stackalloc Int32[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = unchecked((Int32)Math.Sqrt((Int32)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    UInt64* dataPtr = stackalloc UInt64[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = unchecked((UInt64)Math.Sqrt((UInt64)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    Int64* dataPtr = stackalloc Int64[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = unchecked((Int64)Math.Sqrt((Int64)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    Single* dataPtr = stackalloc Single[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = unchecked((Single)Math.Sqrt((Single)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    Double* dataPtr = stackalloc Double[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = unchecked((Double)Math.Sqrt((Double)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    value.register.byte_0 = (Byte)Math.Sqrt(value.register.byte_0);
+                    value.register.byte_1 = (Byte)Math.Sqrt(value.register.byte_1);
+                    value.register.byte_2 = (Byte)Math.Sqrt(value.register.byte_2);
+                    value.register.byte_3 = (Byte)Math.Sqrt(value.register.byte_3);
+                    value.register.byte_4 = (Byte)Math.Sqrt(value.register.byte_4);
+                    value.register.byte_5 = (Byte)Math.Sqrt(value.register.byte_5);
+                    value.register.byte_6 = (Byte)Math.Sqrt(value.register.byte_6);
+                    value.register.byte_7 = (Byte)Math.Sqrt(value.register.byte_7);
+                    value.register.byte_8 = (Byte)Math.Sqrt(value.register.byte_8);
+                    value.register.byte_9 = (Byte)Math.Sqrt(value.register.byte_9);
+                    value.register.byte_10 = (Byte)Math.Sqrt(value.register.byte_10);
+                    value.register.byte_11 = (Byte)Math.Sqrt(value.register.byte_11);
+                    value.register.byte_12 = (Byte)Math.Sqrt(value.register.byte_12);
+                    value.register.byte_13 = (Byte)Math.Sqrt(value.register.byte_13);
+                    value.register.byte_14 = (Byte)Math.Sqrt(value.register.byte_14);
+                    value.register.byte_15 = (Byte)Math.Sqrt(value.register.byte_15);
+                    return value;
+                }
+                else if (typeof(T) == typeof(SByte))
+                {
+                    value.register.sbyte_0 = (SByte)Math.Sqrt(value.register.sbyte_0);
+                    value.register.sbyte_1 = (SByte)Math.Sqrt(value.register.sbyte_1);
+                    value.register.sbyte_2 = (SByte)Math.Sqrt(value.register.sbyte_2);
+                    value.register.sbyte_3 = (SByte)Math.Sqrt(value.register.sbyte_3);
+                    value.register.sbyte_4 = (SByte)Math.Sqrt(value.register.sbyte_4);
+                    value.register.sbyte_5 = (SByte)Math.Sqrt(value.register.sbyte_5);
+                    value.register.sbyte_6 = (SByte)Math.Sqrt(value.register.sbyte_6);
+                    value.register.sbyte_7 = (SByte)Math.Sqrt(value.register.sbyte_7);
+                    value.register.sbyte_8 = (SByte)Math.Sqrt(value.register.sbyte_8);
+                    value.register.sbyte_9 = (SByte)Math.Sqrt(value.register.sbyte_9);
+                    value.register.sbyte_10 = (SByte)Math.Sqrt(value.register.sbyte_10);
+                    value.register.sbyte_11 = (SByte)Math.Sqrt(value.register.sbyte_11);
+                    value.register.sbyte_12 = (SByte)Math.Sqrt(value.register.sbyte_12);
+                    value.register.sbyte_13 = (SByte)Math.Sqrt(value.register.sbyte_13);
+                    value.register.sbyte_14 = (SByte)Math.Sqrt(value.register.sbyte_14);
+                    value.register.sbyte_15 = (SByte)Math.Sqrt(value.register.sbyte_15);
+                    return value;
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    value.register.uint16_0 = (UInt16)Math.Sqrt(value.register.uint16_0);
+                    value.register.uint16_1 = (UInt16)Math.Sqrt(value.register.uint16_1);
+                    value.register.uint16_2 = (UInt16)Math.Sqrt(value.register.uint16_2);
+                    value.register.uint16_3 = (UInt16)Math.Sqrt(value.register.uint16_3);
+                    value.register.uint16_4 = (UInt16)Math.Sqrt(value.register.uint16_4);
+                    value.register.uint16_5 = (UInt16)Math.Sqrt(value.register.uint16_5);
+                    value.register.uint16_6 = (UInt16)Math.Sqrt(value.register.uint16_6);
+                    value.register.uint16_7 = (UInt16)Math.Sqrt(value.register.uint16_7);
+                    return value;
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    value.register.int16_0 = (Int16)Math.Sqrt(value.register.int16_0);
+                    value.register.int16_1 = (Int16)Math.Sqrt(value.register.int16_1);
+                    value.register.int16_2 = (Int16)Math.Sqrt(value.register.int16_2);
+                    value.register.int16_3 = (Int16)Math.Sqrt(value.register.int16_3);
+                    value.register.int16_4 = (Int16)Math.Sqrt(value.register.int16_4);
+                    value.register.int16_5 = (Int16)Math.Sqrt(value.register.int16_5);
+                    value.register.int16_6 = (Int16)Math.Sqrt(value.register.int16_6);
+                    value.register.int16_7 = (Int16)Math.Sqrt(value.register.int16_7);
+                    return value;
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    value.register.uint32_0 = (UInt32)Math.Sqrt(value.register.uint32_0);
+                    value.register.uint32_1 = (UInt32)Math.Sqrt(value.register.uint32_1);
+                    value.register.uint32_2 = (UInt32)Math.Sqrt(value.register.uint32_2);
+                    value.register.uint32_3 = (UInt32)Math.Sqrt(value.register.uint32_3);
+                    return value;
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    value.register.int32_0 = (Int32)Math.Sqrt(value.register.int32_0);
+                    value.register.int32_1 = (Int32)Math.Sqrt(value.register.int32_1);
+                    value.register.int32_2 = (Int32)Math.Sqrt(value.register.int32_2);
+                    value.register.int32_3 = (Int32)Math.Sqrt(value.register.int32_3);
+                    return value;
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    value.register.uint64_0 = (UInt64)Math.Sqrt(value.register.uint64_0);
+                    value.register.uint64_1 = (UInt64)Math.Sqrt(value.register.uint64_1);
+                    return value;
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    value.register.int64_0 = (Int64)Math.Sqrt(value.register.int64_0);
+                    value.register.int64_1 = (Int64)Math.Sqrt(value.register.int64_1);
+                    return value;
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    value.register.single_0 = (Single)Math.Sqrt(value.register.single_0);
+                    value.register.single_1 = (Single)Math.Sqrt(value.register.single_1);
+                    value.register.single_2 = (Single)Math.Sqrt(value.register.single_2);
+                    value.register.single_3 = (Single)Math.Sqrt(value.register.single_3);
+                    return value;
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    value.register.double_0 = (Double)Math.Sqrt(value.register.double_0);
+                    value.register.double_1 = (Double)Math.Sqrt(value.register.double_1);
+                    return value;
+                }
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+        #endregion Internal Math Methods
+
+        #region Helper Methods
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static bool ScalarEquals(T left, T right)
+        {
+            if (typeof(T) == typeof(Byte))
+            {
+                return (Byte)(object)left == (Byte)(object)right;
+            }
+            else if (typeof(T) == typeof(SByte))
+            {
+                return (SByte)(object)left == (SByte)(object)right;
+            }
+            else if (typeof(T) == typeof(UInt16))
+            {
+                return (UInt16)(object)left == (UInt16)(object)right;
+            }
+            else if (typeof(T) == typeof(Int16))
+            {
+                return (Int16)(object)left == (Int16)(object)right;
+            }
+            else if (typeof(T) == typeof(UInt32))
+            {
+                return (UInt32)(object)left == (UInt32)(object)right;
+            }
+            else if (typeof(T) == typeof(Int32))
+            {
+                return (Int32)(object)left == (Int32)(object)right;
+            }
+            else if (typeof(T) == typeof(UInt64))
+            {
+                return (UInt64)(object)left == (UInt64)(object)right;
+            }
+            else if (typeof(T) == typeof(Int64))
+            {
+                return (Int64)(object)left == (Int64)(object)right;
+            }
+            else if (typeof(T) == typeof(Single))
+            {
+                return (Single)(object)left == (Single)(object)right;
+            }
+            else if (typeof(T) == typeof(Double))
+            {
+                return (Double)(object)left == (Double)(object)right;
+            }
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static bool ScalarLessThan(T left, T right)
+        {
+            if (typeof(T) == typeof(Byte))
+            {
+                return (Byte)(object)left < (Byte)(object)right;
+            }
+            else if (typeof(T) == typeof(SByte))
+            {
+                return (SByte)(object)left < (SByte)(object)right;
+            }
+            else if (typeof(T) == typeof(UInt16))
+            {
+                return (UInt16)(object)left < (UInt16)(object)right;
+            }
+            else if (typeof(T) == typeof(Int16))
+            {
+                return (Int16)(object)left < (Int16)(object)right;
+            }
+            else if (typeof(T) == typeof(UInt32))
+            {
+                return (UInt32)(object)left < (UInt32)(object)right;
+            }
+            else if (typeof(T) == typeof(Int32))
+            {
+                return (Int32)(object)left < (Int32)(object)right;
+            }
+            else if (typeof(T) == typeof(UInt64))
+            {
+                return (UInt64)(object)left < (UInt64)(object)right;
+            }
+            else if (typeof(T) == typeof(Int64))
+            {
+                return (Int64)(object)left < (Int64)(object)right;
+            }
+            else if (typeof(T) == typeof(Single))
+            {
+                return (Single)(object)left < (Single)(object)right;
+            }
+            else if (typeof(T) == typeof(Double))
+            {
+                return (Double)(object)left < (Double)(object)right;
+            }
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static bool ScalarGreaterThan(T left, T right)
+        {
+            if (typeof(T) == typeof(Byte))
+            {
+                return (Byte)(object)left > (Byte)(object)right;
+            }
+            else if (typeof(T) == typeof(SByte))
+            {
+                return (SByte)(object)left > (SByte)(object)right;
+            }
+            else if (typeof(T) == typeof(UInt16))
+            {
+                return (UInt16)(object)left > (UInt16)(object)right;
+            }
+            else if (typeof(T) == typeof(Int16))
+            {
+                return (Int16)(object)left > (Int16)(object)right;
+            }
+            else if (typeof(T) == typeof(UInt32))
+            {
+                return (UInt32)(object)left > (UInt32)(object)right;
+            }
+            else if (typeof(T) == typeof(Int32))
+            {
+                return (Int32)(object)left > (Int32)(object)right;
+            }
+            else if (typeof(T) == typeof(UInt64))
+            {
+                return (UInt64)(object)left > (UInt64)(object)right;
+            }
+            else if (typeof(T) == typeof(Int64))
+            {
+                return (Int64)(object)left > (Int64)(object)right;
+            }
+            else if (typeof(T) == typeof(Single))
+            {
+                return (Single)(object)left > (Single)(object)right;
+            }
+            else if (typeof(T) == typeof(Double))
+            {
+                return (Double)(object)left > (Double)(object)right;
+            }
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static T ScalarAdd(T left, T right)
+        {
+            if (typeof(T) == typeof(Byte))
+            {
+                return (T)(object)unchecked((Byte)((Byte)(object)left + (Byte)(object)right));
+            }
+            else if (typeof(T) == typeof(SByte))
+            {
+                return (T)(object)unchecked((SByte)((SByte)(object)left + (SByte)(object)right));
+            }
+            else if (typeof(T) == typeof(UInt16))
+            {
+                return (T)(object)unchecked((UInt16)((UInt16)(object)left + (UInt16)(object)right));
+            }
+            else if (typeof(T) == typeof(Int16))
+            {
+                return (T)(object)unchecked((Int16)((Int16)(object)left + (Int16)(object)right));
+            }
+            else if (typeof(T) == typeof(UInt32))
+            {
+                return (T)(object)unchecked((UInt32)((UInt32)(object)left + (UInt32)(object)right));
+            }
+            else if (typeof(T) == typeof(Int32))
+            {
+                return (T)(object)unchecked((Int32)((Int32)(object)left + (Int32)(object)right));
+            }
+            else if (typeof(T) == typeof(UInt64))
+            {
+                return (T)(object)unchecked((UInt64)((UInt64)(object)left + (UInt64)(object)right));
+            }
+            else if (typeof(T) == typeof(Int64))
+            {
+                return (T)(object)unchecked((Int64)((Int64)(object)left + (Int64)(object)right));
+            }
+            else if (typeof(T) == typeof(Single))
+            {
+                return (T)(object)unchecked((Single)((Single)(object)left + (Single)(object)right));
+            }
+            else if (typeof(T) == typeof(Double))
+            {
+                return (T)(object)unchecked((Double)((Double)(object)left + (Double)(object)right));
+            }
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static T ScalarSubtract(T left, T right)
+        {
+            if (typeof(T) == typeof(Byte))
+            {
+                return (T)(object)(Byte)((Byte)(object)left - (Byte)(object)right);
+            }
+            else if (typeof(T) == typeof(SByte))
+            {
+                return (T)(object)(SByte)((SByte)(object)left - (SByte)(object)right);
+            }
+            else if (typeof(T) == typeof(UInt16))
+            {
+                return (T)(object)(UInt16)((UInt16)(object)left - (UInt16)(object)right);
+            }
+            else if (typeof(T) == typeof(Int16))
+            {
+                return (T)(object)(Int16)((Int16)(object)left - (Int16)(object)right);
+            }
+            else if (typeof(T) == typeof(UInt32))
+            {
+                return (T)(object)(UInt32)((UInt32)(object)left - (UInt32)(object)right);
+            }
+            else if (typeof(T) == typeof(Int32))
+            {
+                return (T)(object)(Int32)((Int32)(object)left - (Int32)(object)right);
+            }
+            else if (typeof(T) == typeof(UInt64))
+            {
+                return (T)(object)(UInt64)((UInt64)(object)left - (UInt64)(object)right);
+            }
+            else if (typeof(T) == typeof(Int64))
+            {
+                return (T)(object)(Int64)((Int64)(object)left - (Int64)(object)right);
+            }
+            else if (typeof(T) == typeof(Single))
+            {
+                return (T)(object)(Single)((Single)(object)left - (Single)(object)right);
+            }
+            else if (typeof(T) == typeof(Double))
+            {
+                return (T)(object)(Double)((Double)(object)left - (Double)(object)right);
+            }
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static T ScalarMultiply(T left, T right)
+        {
+            if (typeof(T) == typeof(Byte))
+            {
+                return (T)(object)unchecked((Byte)((Byte)(object)left * (Byte)(object)right));
+            }
+            else if (typeof(T) == typeof(SByte))
+            {
+                return (T)(object)unchecked((SByte)((SByte)(object)left * (SByte)(object)right));
+            }
+            else if (typeof(T) == typeof(UInt16))
+            {
+                return (T)(object)unchecked((UInt16)((UInt16)(object)left * (UInt16)(object)right));
+            }
+            else if (typeof(T) == typeof(Int16))
+            {
+                return (T)(object)unchecked((Int16)((Int16)(object)left * (Int16)(object)right));
+            }
+            else if (typeof(T) == typeof(UInt32))
+            {
+                return (T)(object)unchecked((UInt32)((UInt32)(object)left * (UInt32)(object)right));
+            }
+            else if (typeof(T) == typeof(Int32))
+            {
+                return (T)(object)unchecked((Int32)((Int32)(object)left * (Int32)(object)right));
+            }
+            else if (typeof(T) == typeof(UInt64))
+            {
+                return (T)(object)unchecked((UInt64)((UInt64)(object)left * (UInt64)(object)right));
+            }
+            else if (typeof(T) == typeof(Int64))
+            {
+                return (T)(object)unchecked((Int64)((Int64)(object)left * (Int64)(object)right));
+            }
+            else if (typeof(T) == typeof(Single))
+            {
+                return (T)(object)unchecked((Single)((Single)(object)left * (Single)(object)right));
+            }
+            else if (typeof(T) == typeof(Double))
+            {
+                return (T)(object)unchecked((Double)((Double)(object)left * (Double)(object)right));
+            }
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static T ScalarDivide(T left, T right)
+        {
+            if (typeof(T) == typeof(Byte))
+            {
+                return (T)(object)(Byte)((Byte)(object)left / (Byte)(object)right);
+            }
+            else if (typeof(T) == typeof(SByte))
+            {
+                return (T)(object)(SByte)((SByte)(object)left / (SByte)(object)right);
+            }
+            else if (typeof(T) == typeof(UInt16))
+            {
+                return (T)(object)(UInt16)((UInt16)(object)left / (UInt16)(object)right);
+            }
+            else if (typeof(T) == typeof(Int16))
+            {
+                return (T)(object)(Int16)((Int16)(object)left / (Int16)(object)right);
+            }
+            else if (typeof(T) == typeof(UInt32))
+            {
+                return (T)(object)(UInt32)((UInt32)(object)left / (UInt32)(object)right);
+            }
+            else if (typeof(T) == typeof(Int32))
+            {
+                return (T)(object)(Int32)((Int32)(object)left / (Int32)(object)right);
+            }
+            else if (typeof(T) == typeof(UInt64))
+            {
+                return (T)(object)(UInt64)((UInt64)(object)left / (UInt64)(object)right);
+            }
+            else if (typeof(T) == typeof(Int64))
+            {
+                return (T)(object)(Int64)((Int64)(object)left / (Int64)(object)right);
+            }
+            else if (typeof(T) == typeof(Single))
+            {
+                return (T)(object)(Single)((Single)(object)left / (Single)(object)right);
+            }
+            else if (typeof(T) == typeof(Double))
+            {
+                return (T)(object)(Double)((Double)(object)left / (Double)(object)right);
+            }
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static T GetOneValue()
+        {
+            if (typeof(T) == typeof(Byte))
+            {
+                Byte value = 1;
+                return (T)(object)value;
+            }
+            else if (typeof(T) == typeof(SByte))
+            {
+                SByte value = 1;
+                return (T)(object)value;
+            }
+            else if (typeof(T) == typeof(UInt16))
+            {
+                UInt16 value = 1;
+                return (T)(object)value;
+            }
+            else if (typeof(T) == typeof(Int16))
+            {
+                Int16 value = 1;
+                return (T)(object)value;
+            }
+            else if (typeof(T) == typeof(UInt32))
+            {
+                UInt32 value = 1;
+                return (T)(object)value;
+            }
+            else if (typeof(T) == typeof(Int32))
+            {
+                Int32 value = 1;
+                return (T)(object)value;
+            }
+            else if (typeof(T) == typeof(UInt64))
+            {
+                UInt64 value = 1;
+                return (T)(object)value;
+            }
+            else if (typeof(T) == typeof(Int64))
+            {
+                Int64 value = 1;
+                return (T)(object)value;
+            }
+            else if (typeof(T) == typeof(Single))
+            {
+                Single value = 1;
+                return (T)(object)value;
+            }
+            else if (typeof(T) == typeof(Double))
+            {
+                Double value = 1;
+                return (T)(object)value;
+            }
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static T GetAllBitsSetValue()
+        {
+            if (typeof(T) == typeof(Byte))
+            {
+                return (T)(object)ConstantHelper.GetByteWithAllBitsSet();
+            }
+            else if (typeof(T) == typeof(SByte))
+            {
+                return (T)(object)ConstantHelper.GetSByteWithAllBitsSet();
+            }
+            else if (typeof(T) == typeof(UInt16))
+            {
+                return (T)(object)ConstantHelper.GetUInt16WithAllBitsSet();
+            }
+            else if (typeof(T) == typeof(Int16))
+            {
+                return (T)(object)ConstantHelper.GetInt16WithAllBitsSet();
+            }
+            else if (typeof(T) == typeof(UInt32))
+            {
+                return (T)(object)ConstantHelper.GetUInt32WithAllBitsSet();
+            }
+            else if (typeof(T) == typeof(Int32))
+            {
+                return (T)(object)ConstantHelper.GetInt32WithAllBitsSet();
+            }
+            else if (typeof(T) == typeof(UInt64))
+            {
+                return (T)(object)ConstantHelper.GetUInt64WithAllBitsSet();
+            }
+            else if (typeof(T) == typeof(Int64))
+            {
+                return (T)(object)ConstantHelper.GetInt64WithAllBitsSet();
+            }
+            else if (typeof(T) == typeof(Single))
+            {
+                return (T)(object)ConstantHelper.GetSingleWithAllBitsSet();
+            }
+            else if (typeof(T) == typeof(Double))
+            {
+                return (T)(object)ConstantHelper.GetDoubleWithAllBitsSet();
+            }
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+        #endregion
+    }
+
+    [Intrinsic]
+    public static partial class Vector
+    {
+        #region Widen/Narrow
+        /// <summary>
+        /// Widens a Vector{Byte} into two Vector{UInt16}'s.
+        /// <param name="source">The source vector whose elements are widened into the outputs.</param>
+        /// <param name="low">The first output vector, whose elements will contain the widened elements from lower indices in the source vector.</param>
+        /// <param name="high">The second output vector, whose elements will contain the widened elements from higher indices in the source vector.</param>
+        /// </summary>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static unsafe void Widen(Vector<Byte> source, out Vector<UInt16> low, out Vector<UInt16> high)
+        {
+            int elements = Vector<Byte>.Count;
+            UInt16* lowPtr = stackalloc UInt16[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                lowPtr[i] = (UInt16)source[i];
+            }
+            UInt16* highPtr = stackalloc UInt16[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                highPtr[i] = (UInt16)source[i + (elements / 2)];
+            }
+
+            low = new Vector<UInt16>(lowPtr);
+            high = new Vector<UInt16>(highPtr);
+        }
+
+        /// <summary>
+        /// Widens a Vector{UInt16} into two Vector{UInt32}'s.
+        /// <param name="source">The source vector whose elements are widened into the outputs.</param>
+        /// <param name="low">The first output vector, whose elements will contain the widened elements from lower indices in the source vector.</param>
+        /// <param name="high">The second output vector, whose elements will contain the widened elements from higher indices in the source vector.</param>
+        /// </summary>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static unsafe void Widen(Vector<UInt16> source, out Vector<UInt32> low, out Vector<UInt32> high)
+        {
+            int elements = Vector<UInt16>.Count;
+            UInt32* lowPtr = stackalloc UInt32[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                lowPtr[i] = (UInt32)source[i];
+            }
+            UInt32* highPtr = stackalloc UInt32[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                highPtr[i] = (UInt32)source[i + (elements / 2)];
+            }
+
+            low = new Vector<UInt32>(lowPtr);
+            high = new Vector<UInt32>(highPtr);
+        }
+
+        /// <summary>
+        /// Widens a Vector{UInt32} into two Vector{UInt64}'s.
+        /// <param name="source">The source vector whose elements are widened into the outputs.</param>
+        /// <param name="low">The first output vector, whose elements will contain the widened elements from lower indices in the source vector.</param>
+        /// <param name="high">The second output vector, whose elements will contain the widened elements from higher indices in the source vector.</param>
+        /// </summary>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static unsafe void Widen(Vector<UInt32> source, out Vector<UInt64> low, out Vector<UInt64> high)
+        {
+            int elements = Vector<UInt32>.Count;
+            UInt64* lowPtr = stackalloc UInt64[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                lowPtr[i] = (UInt64)source[i];
+            }
+            UInt64* highPtr = stackalloc UInt64[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                highPtr[i] = (UInt64)source[i + (elements / 2)];
+            }
+
+            low = new Vector<UInt64>(lowPtr);
+            high = new Vector<UInt64>(highPtr);
+        }
+
+        /// <summary>
+        /// Widens a Vector{SByte} into two Vector{Int16}'s.
+        /// <param name="source">The source vector whose elements are widened into the outputs.</param>
+        /// <param name="low">The first output vector, whose elements will contain the widened elements from lower indices in the source vector.</param>
+        /// <param name="high">The second output vector, whose elements will contain the widened elements from higher indices in the source vector.</param>
+        /// </summary>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static unsafe void Widen(Vector<SByte> source, out Vector<Int16> low, out Vector<Int16> high)
+        {
+            int elements = Vector<SByte>.Count;
+            Int16* lowPtr = stackalloc Int16[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                lowPtr[i] = (Int16)source[i];
+            }
+            Int16* highPtr = stackalloc Int16[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                highPtr[i] = (Int16)source[i + (elements / 2)];
+            }
+
+            low = new Vector<Int16>(lowPtr);
+            high = new Vector<Int16>(highPtr);
+        }
+
+        /// <summary>
+        /// Widens a Vector{Int16} into two Vector{Int32}'s.
+        /// <param name="source">The source vector whose elements are widened into the outputs.</param>
+        /// <param name="low">The first output vector, whose elements will contain the widened elements from lower indices in the source vector.</param>
+        /// <param name="high">The second output vector, whose elements will contain the widened elements from higher indices in the source vector.</param>
+        /// </summary>
+        [Intrinsic]
+        public static unsafe void Widen(Vector<Int16> source, out Vector<Int32> low, out Vector<Int32> high)
+        {
+            int elements = Vector<Int16>.Count;
+            Int32* lowPtr = stackalloc Int32[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                lowPtr[i] = (Int32)source[i];
+            }
+            Int32* highPtr = stackalloc Int32[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                highPtr[i] = (Int32)source[i + (elements / 2)];
+            }
+
+            low = new Vector<Int32>(lowPtr);
+            high = new Vector<Int32>(highPtr);
+        }
+
+        /// <summary>
+        /// Widens a Vector{Int32} into two Vector{Int64}'s.
+        /// <param name="source">The source vector whose elements are widened into the outputs.</param>
+        /// <param name="low">The first output vector, whose elements will contain the widened elements from lower indices in the source vector.</param>
+        /// <param name="high">The second output vector, whose elements will contain the widened elements from higher indices in the source vector.</param>
+        /// </summary>
+        [Intrinsic]
+        public static unsafe void Widen(Vector<Int32> source, out Vector<Int64> low, out Vector<Int64> high)
+        {
+            int elements = Vector<Int32>.Count;
+            Int64* lowPtr = stackalloc Int64[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                lowPtr[i] = (Int64)source[i];
+            }
+            Int64* highPtr = stackalloc Int64[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                highPtr[i] = (Int64)source[i + (elements / 2)];
+            }
+
+            low = new Vector<Int64>(lowPtr);
+            high = new Vector<Int64>(highPtr);
+        }
+
+        /// <summary>
+        /// Widens a Vector{Single} into two Vector{Double}'s.
+        /// <param name="source">The source vector whose elements are widened into the outputs.</param>
+        /// <param name="low">The first output vector, whose elements will contain the widened elements from lower indices in the source vector.</param>
+        /// <param name="high">The second output vector, whose elements will contain the widened elements from higher indices in the source vector.</param>
+        /// </summary>
+        [Intrinsic]
+        public static unsafe void Widen(Vector<Single> source, out Vector<Double> low, out Vector<Double> high)
+        {
+            int elements = Vector<Single>.Count;
+            Double* lowPtr = stackalloc Double[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                lowPtr[i] = (Double)source[i];
+            }
+            Double* highPtr = stackalloc Double[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                highPtr[i] = (Double)source[i + (elements / 2)];
+            }
+
+            low = new Vector<Double>(lowPtr);
+            high = new Vector<Double>(highPtr);
+        }
+
+        /// <summary>
+        /// Narrows two Vector{UInt16}'s into one Vector{Byte}.
+        /// <param name="low">The first source vector, whose elements become the lower-index elements of the return value.</param>
+        /// <param name="high">The second source vector, whose elements become the higher-index elements of the return value.</param>
+        /// <returns>A Vector{Byte} containing elements narrowed from the source vectors.</returns>
+        /// </summary>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static unsafe Vector<Byte> Narrow(Vector<UInt16> low, Vector<UInt16> high)
+        {
+		    unchecked
+		    {
+				int elements = Vector<Byte>.Count;
+				Byte* retPtr = stackalloc Byte[elements];
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i] = (Byte)low[i];
+				}
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i + (elements / 2)] = (Byte)high[i];
+				}
+
+				return new Vector<Byte>(retPtr);
+		    }
+        }
+
+        /// <summary>
+        /// Narrows two Vector{UInt32}'s into one Vector{UInt16}.
+        /// <param name="low">The first source vector, whose elements become the lower-index elements of the return value.</param>
+        /// <param name="high">The second source vector, whose elements become the higher-index elements of the return value.</param>
+        /// <returns>A Vector{UInt16} containing elements narrowed from the source vectors.</returns>
+        /// </summary>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static unsafe Vector<UInt16> Narrow(Vector<UInt32> low, Vector<UInt32> high)
+        {
+		    unchecked
+		    {
+				int elements = Vector<UInt16>.Count;
+				UInt16* retPtr = stackalloc UInt16[elements];
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i] = (UInt16)low[i];
+				}
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i + (elements / 2)] = (UInt16)high[i];
+				}
+
+				return new Vector<UInt16>(retPtr);
+		    }
+        }
+
+        /// <summary>
+        /// Narrows two Vector{UInt64}'s into one Vector{UInt32}.
+        /// <param name="low">The first source vector, whose elements become the lower-index elements of the return value.</param>
+        /// <param name="high">The second source vector, whose elements become the higher-index elements of the return value.</param>
+        /// <returns>A Vector{UInt32} containing elements narrowed from the source vectors.</returns>
+        /// </summary>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static unsafe Vector<UInt32> Narrow(Vector<UInt64> low, Vector<UInt64> high)
+        {
+		    unchecked
+		    {
+				int elements = Vector<UInt32>.Count;
+				UInt32* retPtr = stackalloc UInt32[elements];
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i] = (UInt32)low[i];
+				}
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i + (elements / 2)] = (UInt32)high[i];
+				}
+
+				return new Vector<UInt32>(retPtr);
+		    }
+        }
+
+        /// <summary>
+        /// Narrows two Vector{Int16}'s into one Vector{SByte}.
+        /// <param name="low">The first source vector, whose elements become the lower-index elements of the return value.</param>
+        /// <param name="high">The second source vector, whose elements become the higher-index elements of the return value.</param>
+        /// <returns>A Vector{SByte} containing elements narrowed from the source vectors.</returns>
+        /// </summary>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static unsafe Vector<SByte> Narrow(Vector<Int16> low, Vector<Int16> high)
+        {
+		    unchecked
+		    {
+				int elements = Vector<SByte>.Count;
+				SByte* retPtr = stackalloc SByte[elements];
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i] = (SByte)low[i];
+				}
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i + (elements / 2)] = (SByte)high[i];
+				}
+
+				return new Vector<SByte>(retPtr);
+		    }
+        }
+
+        /// <summary>
+        /// Narrows two Vector{Int32}'s into one Vector{Int16}.
+        /// <param name="low">The first source vector, whose elements become the lower-index elements of the return value.</param>
+        /// <param name="high">The second source vector, whose elements become the higher-index elements of the return value.</param>
+        /// <returns>A Vector{Int16} containing elements narrowed from the source vectors.</returns>
+        /// </summary>
+        [Intrinsic]
+        public static unsafe Vector<Int16> Narrow(Vector<Int32> low, Vector<Int32> high)
+        {
+		    unchecked
+		    {
+				int elements = Vector<Int16>.Count;
+				Int16* retPtr = stackalloc Int16[elements];
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i] = (Int16)low[i];
+				}
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i + (elements / 2)] = (Int16)high[i];
+				}
+
+				return new Vector<Int16>(retPtr);
+		    }
+        }
+
+        /// <summary>
+        /// Narrows two Vector{Int64}'s into one Vector{Int32}.
+        /// <param name="low">The first source vector, whose elements become the lower-index elements of the return value.</param>
+        /// <param name="high">The second source vector, whose elements become the higher-index elements of the return value.</param>
+        /// <returns>A Vector{Int32} containing elements narrowed from the source vectors.</returns>
+        /// </summary>
+        [Intrinsic]
+        public static unsafe Vector<Int32> Narrow(Vector<Int64> low, Vector<Int64> high)
+        {
+		    unchecked
+		    {
+				int elements = Vector<Int32>.Count;
+				Int32* retPtr = stackalloc Int32[elements];
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i] = (Int32)low[i];
+				}
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i + (elements / 2)] = (Int32)high[i];
+				}
+
+				return new Vector<Int32>(retPtr);
+		    }
+        }
+
+        /// <summary>
+        /// Narrows two Vector{Double}'s into one Vector{Single}.
+        /// <param name="low">The first source vector, whose elements become the lower-index elements of the return value.</param>
+        /// <param name="high">The second source vector, whose elements become the higher-index elements of the return value.</param>
+        /// <returns>A Vector{Single} containing elements narrowed from the source vectors.</returns>
+        /// </summary>
+        [Intrinsic]
+        public static unsafe Vector<Single> Narrow(Vector<Double> low, Vector<Double> high)
+        {
+		    unchecked
+		    {
+				int elements = Vector<Single>.Count;
+				Single* retPtr = stackalloc Single[elements];
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i] = (Single)low[i];
+				}
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i + (elements / 2)] = (Single)high[i];
+				}
+
+				return new Vector<Single>(retPtr);
+		    }
+        }
+
+        #endregion Widen/Narrow
+
+        #region Same-Size Conversion
+        /// <summary>
+        /// Converts a Vector{Int32} to a Vector{Single}.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The converted vector.</returns>
+        [Intrinsic]
+        public static unsafe Vector<Single> ConvertToSingle(Vector<Int32> value)
+        {
+			unchecked
+			{
+				int elements = Vector<Single>.Count;
+				Single* retPtr = stackalloc Single[elements];
+				for (int i = 0; i < elements; i++)
+				{
+					retPtr[i] = (Single)value[i];
+				}
+
+				return new Vector<Single>(retPtr);
+			}
+        }
+
+        /// <summary>
+        /// Converts a Vector{UInt32} to a Vector{Single}.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The converted vector.</returns>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static unsafe Vector<Single> ConvertToSingle(Vector<UInt32> value)
+        {
+			unchecked
+			{
+				int elements = Vector<Single>.Count;
+				Single* retPtr = stackalloc Single[elements];
+				for (int i = 0; i < elements; i++)
+				{
+					retPtr[i] = (Single)value[i];
+				}
+
+				return new Vector<Single>(retPtr);
+			}
+        }
+
+        /// <summary>
+        /// Converts a Vector{Int64} to a Vector{Double}.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The converted vector.</returns>
+        [Intrinsic]
+        public static unsafe Vector<Double> ConvertToDouble(Vector<Int64> value)
+        {
+			unchecked
+			{
+				int elements = Vector<Double>.Count;
+				Double* retPtr = stackalloc Double[elements];
+				for (int i = 0; i < elements; i++)
+				{
+					retPtr[i] = (Double)value[i];
+				}
+
+				return new Vector<Double>(retPtr);
+			}
+        }
+
+        /// <summary>
+        /// Converts a Vector{UInt64} to a Vector{Double}.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The converted vector.</returns>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static unsafe Vector<Double> ConvertToDouble(Vector<UInt64> value)
+        {
+			unchecked
+			{
+				int elements = Vector<Double>.Count;
+				Double* retPtr = stackalloc Double[elements];
+				for (int i = 0; i < elements; i++)
+				{
+					retPtr[i] = (Double)value[i];
+				}
+
+				return new Vector<Double>(retPtr);
+			}
+        }
+
+        /// <summary>
+        /// Converts a Vector{Single} to a Vector{Int32}.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The converted vector.</returns>
+        [Intrinsic]
+        public static unsafe Vector<Int32> ConvertToInt32(Vector<Single> value)
+        {
+			unchecked
+			{
+				int elements = Vector<Int32>.Count;
+				Int32* retPtr = stackalloc Int32[elements];
+				for (int i = 0; i < elements; i++)
+				{
+					retPtr[i] = (Int32)value[i];
+				}
+
+				return new Vector<Int32>(retPtr);
+			}
+        }
+
+        /// <summary>
+        /// Converts a Vector{Single} to a Vector{UInt32}.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The converted vector.</returns>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static unsafe Vector<UInt32> ConvertToUInt32(Vector<Single> value)
+        {
+			unchecked
+			{
+				int elements = Vector<UInt32>.Count;
+				UInt32* retPtr = stackalloc UInt32[elements];
+				for (int i = 0; i < elements; i++)
+				{
+					retPtr[i] = (UInt32)value[i];
+				}
+
+				return new Vector<UInt32>(retPtr);
+			}
+        }
+
+        /// <summary>
+        /// Converts a Vector{Double} to a Vector{Int64}.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The converted vector.</returns>
+        [Intrinsic]
+        public static unsafe Vector<Int64> ConvertToInt64(Vector<Double> value)
+        {
+			unchecked
+			{
+				int elements = Vector<Int64>.Count;
+				Int64* retPtr = stackalloc Int64[elements];
+				for (int i = 0; i < elements; i++)
+				{
+					retPtr[i] = (Int64)value[i];
+				}
+
+				return new Vector<Int64>(retPtr);
+			}
+        }
+
+        /// <summary>
+        /// Converts a Vector{Double} to a Vector{UInt64}.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The converted vector.</returns>
+        [CLSCompliant(false)]
+        [Intrinsic]
+        public static unsafe Vector<UInt64> ConvertToUInt64(Vector<Double> value)
+        {
+			unchecked
+			{
+				int elements = Vector<UInt64>.Count;
+				UInt64* retPtr = stackalloc UInt64[elements];
+				for (int i = 0; i < elements; i++)
+				{
+					retPtr[i] = (UInt64)value[i];
+				}
+
+				return new Vector<UInt64>(retPtr);
+			}
+        }
+
+        #endregion Same-Size Conversion
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Numerics/Vector.tt b/src/System.Private.CoreLib/shared/System/Numerics/Vector.tt
new file mode 100644
index 0000000000..d7622466b7
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Numerics/Vector.tt
@@ -0,0 +1,1834 @@
+<#@ template debug="true" hostSpecific="true" #>
+<#@ output extension=".cs" #>
+<#@ Assembly Name="System.Core.dll" #>
+<#@ Assembly Name="System.Xml.dll" #>
+<#@ import namespace="System" #>
+<#@ import namespace="System.Linq" #>
+<#@ import namespace="System.Runtime.InteropServices" #>
+<#@ include file="GenerationConfig.ttinclude" #><# GenerateCopyrightHeader(); #>
+
+#if netcoreapp
+using Internal.Runtime.CompilerServices;
+#endif
+using System.Globalization;
+using System.Numerics.Hashing;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace System.Numerics
+{
+    /* Note: The following patterns are used throughout the code here and are described here
+    *
+    * PATTERN:
+    *    if (typeof(T) == typeof(Int32)) { ... }
+    *    else if (typeof(T) == typeof(Single)) { ... }
+    * EXPLANATION:
+    *    At runtime, each instantiation of Vector<T> will be type-specific, and each of these typeof blocks will be eliminated,
+    *    as typeof(T) is a (JIT) compile-time constant for each instantiation. This design was chosen to eliminate any overhead from
+    *    delegates and other patterns.
+    *
+    * PATTERN:
+    *    if (Vector.IsHardwareAccelerated) { ... }
+    *    else { ... }
+    * EXPLANATION
+    *    This pattern solves two problems:
+    *        1. Allows us to unroll loops when we know the size (when no hardware acceleration is present)
+    *        2. Allows reflection to work:
+    *            - If a method is called via reflection, it will not be "intrinsified", which would cause issues if we did
+    *              not provide an implementation for that case (i.e. if it only included a case which assumed 16-byte registers)
+    *    (NOTE: It is assumed that Vector.IsHardwareAccelerated will be a compile-time constant, eliminating these checks
+    *        from the JIT'd code.)
+    *
+    * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+    /// <summary>
+    /// A structure that represents a single Vector. The count of this Vector is fixed but CPU register dependent.
+    /// This struct only supports numerical types. This type is intended to be used as a building block for vectorizing
+    /// large algorithms. This type is immutable, individual elements cannot be modified.
+    /// </summary>
+    [Intrinsic]
+    public struct Vector<T> : IEquatable<Vector<T>>, IFormattable where T : struct
+    {
+        #region Fields
+        private Register register;
+        #endregion Fields
+
+        #region Static Members
+        /// <summary>
+        /// Returns the number of elements stored in the vector. This value is hardware dependent.
+        /// </summary>
+        public static int Count
+        {
+            [Intrinsic]
+            get
+            {
+                return s_count;
+            }
+        }
+        private static readonly int s_count = InitializeCount();
+
+        /// <summary>
+        /// Returns a vector containing all zeroes.
+        /// </summary>
+        public static Vector<T> Zero
+        {
+            [Intrinsic]
+            get
+            {
+                return s_zero;
+            }
+        }
+        private static readonly Vector<T> s_zero = new Vector<T>();
+
+        /// <summary>
+        /// Returns a vector containing all ones.
+        /// </summary>
+        public static Vector<T> One
+        {
+            [Intrinsic]
+            get
+            {
+                return s_one;
+            }
+        }
+        private static readonly Vector<T> s_one = new Vector<T>(GetOneValue());
+
+        internal static Vector<T> AllOnes { get { return s_allOnes; } }
+        private static readonly Vector<T> s_allOnes = new Vector<T>(GetAllBitsSetValue());
+        #endregion Static Members
+
+        #region Static Initialization
+        private struct VectorSizeHelper
+        {
+            internal Vector<T> _placeholder;
+            internal byte _byte;
+        }
+
+		// Calculates the size of this struct in bytes, by computing the offset of a field in a structure
+        private static unsafe int InitializeCount()
+        {
+            VectorSizeHelper vsh;
+            byte* vectorBase = &vsh._placeholder.register.byte_0;
+            byte* byteBase = &vsh._byte;
+            int vectorSizeInBytes = (int)(byteBase - vectorBase);
+
+            int typeSizeInBytes = -1;
+<#    foreach (Type type in supportedTypes)
+      {
+#>
+            <#=GenerateIfStatementHeader(type)#>
+            {
+                typeSizeInBytes = sizeof(<#=type.Name#>);
+            }
+<#
+      }
+#>
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+
+            return vectorSizeInBytes / typeSizeInBytes;
+        }
+        #endregion Static Initialization
+
+        #region Constructors
+        /// <summary>
+        /// Constructs a vector whose components are all <code>value</code>
+        /// </summary>
+        [Intrinsic]
+        public unsafe Vector(T value)
+            : this()
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    fixed (<#=type.Name#>* basePtr = &this.<#=GetRegisterFieldName(type, 0)#>)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (<#=type.Name#>)(object)value;
+                        }
+                    }
+                }
+<#
+        }
+#>
+            }
+            else
+            {
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+<#
+            for (int g = 0; g < totalSize / Marshal.SizeOf(type); g++)
+            {
+#>
+                    <#=GetRegisterFieldName(type, g)#> = (<#=type.Name#>)(object)value;
+<#
+            }
+#>
+                }
+<#
+        }
+#>
+            }
+        }
+
+        /// <summary>
+        /// Constructs a vector from the given array. The size of the given array must be at least Vector'T.Count.
+        /// </summary>
+        [Intrinsic]
+        public unsafe Vector(T[] values) : this(values, 0) { }
+
+        /// <summary>
+        /// Constructs a vector from the given array, starting from the given index.
+        /// The array must contain at least Vector'T.Count from the given index.
+        /// </summary>
+        public unsafe Vector(T[] values, int index)
+            : this()
+        {
+            if (values == null)
+            {
+                // Match the JIT's exception type here. For perf, a NullReference is thrown instead of an ArgumentNull.
+                throw new NullReferenceException(SR.Arg_NullArgumentNullRef);
+            }
+            if (index < 0 || (values.Length - index) < Count)
+            {
+                throw new IndexOutOfRangeException(SR.Format(SR.Arg_InsufficientNumberOfElements, Vector<T>.Count, nameof(values)));
+            }
+
+            if (Vector.IsHardwareAccelerated)
+            {
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    fixed (<#=type.Name#>* basePtr = &this.<#=GetRegisterFieldName(type, 0)#>)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            *(basePtr + g) = (<#=type.Name#>)(object)values[g + index];
+                        }
+                    }
+                }
+<#
+        }
+#>
+            }
+            else
+            {
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    fixed (<#=type.Name#>* basePtr = &this.<#=GetRegisterFieldName(type, 0)#>)
+                    {
+<#
+            for (int g = 0; g < GetNumFields(type, totalSize); g++)
+            {
+#>
+                        *(basePtr + <#=g#>) = (<#=type.Name#>)(object)values[<#=g#> + index];
+<#
+            }
+#>
+                    }
+                }
+<#
+        }
+#>
+            }
+        }
+
+#pragma warning disable 3001 // void* is not a CLS-Compliant argument type
+        internal unsafe Vector(void* dataPointer) : this(dataPointer, 0) { }
+#pragma warning restore 3001 // void* is not a CLS-Compliant argument type
+
+#pragma warning disable 3001 // void* is not a CLS-Compliant argument type
+        // Implemented with offset if this API ever becomes public; an offset of 0 is used internally.
+        internal unsafe Vector(void* dataPointer, int offset)
+            : this()
+        {
+<# foreach (Type type in supportedTypes)
+ {
+#>
+            <#=GenerateIfStatementHeader(type)#>
+            {
+                <#=type.Name#>* castedPtr = (<#=type.Name#>*)dataPointer;
+                castedPtr += offset;
+                fixed (<#=type.Name#>* registerBase = &this.<#=GetRegisterFieldName(type, 0)#>)
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        registerBase[g] = castedPtr[g];
+                    }
+                }
+            }
+<#
+ }
+#>
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+#pragma warning restore 3001 // void* is not a CLS-Compliant argument type
+
+        private Vector(ref Register existingRegister)
+        {
+            this.register = existingRegister;
+        }
+
+#if netcoreapp
+        /// <summary>
+        /// Constructs a vector from the given span. The span must contain at least Vector'T.Count elements.
+        /// </summary>
+        public Vector(Span<T> values)
+            : this()
+        {
+            <#=GenerateIfConditionAllTypes(supportedTypes)#>
+            {
+                if (values.Length < Count)
+                {
+                    throw new IndexOutOfRangeException(SR.Format(SR.Arg_InsufficientNumberOfElements, Vector<T>.Count, nameof(values)));
+                }
+                this = Unsafe.ReadUnaligned<Vector<T>>(ref Unsafe.As<T, byte>(ref MemoryMarshal.GetReference(values)));
+            }
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+#endif
+        #endregion Constructors
+
+        #region Public Instance Methods
+        /// <summary>
+        /// Copies the vector to the given destination array. The destination array must be at least size Vector'T.Count.
+        /// </summary>
+        /// <param name="destination">The destination array which the values are copied into</param>
+        /// <exception cref="ArgumentNullException">If the destination array is null</exception>
+        /// <exception cref="ArgumentException">If number of elements in source vector is greater than those available in destination array</exception>
+        [Intrinsic]
+        public unsafe void CopyTo(T[] destination)
+        {
+            CopyTo(destination, 0);
+        }
+
+        /// <summary>
+        /// Copies the vector to the given destination array. The destination array must be at least size Vector'T.Count.
+        /// </summary>
+        /// <param name="destination">The destination array which the values are copied into</param>
+        /// <param name="startIndex">The index to start copying to</param>
+        /// <exception cref="ArgumentNullException">If the destination array is null</exception>
+        /// <exception cref="ArgumentOutOfRangeException">If index is greater than end of the array or index is less than zero</exception>
+        /// <exception cref="ArgumentException">If number of elements in source vector is greater than those available in destination array</exception>
+        [Intrinsic]
+        public unsafe void CopyTo(T[] destination, int startIndex)
+        {
+            if (destination == null)
+            {
+                // Match the JIT's exception type here. For perf, a NullReference is thrown instead of an ArgumentNull.
+                throw new NullReferenceException(SR.Arg_NullArgumentNullRef);
+            }
+            if (startIndex < 0 || startIndex >= destination.Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.Format(SR.Arg_ArgumentOutOfRangeException, startIndex));
+            }
+            if ((destination.Length - startIndex) < Count)
+            {
+                throw new ArgumentException(SR.Format(SR.Arg_ElementsInSourceIsGreaterThanDestination, startIndex));
+            }
+
+            if (Vector.IsHardwareAccelerated)
+            {
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    <#=type.Name#>[] <#=type.Name.ToLowerInvariant()#>Array = (<#=type.Name#>[])(object)destination;
+                    fixed (<#=type.Name#>* destinationBase = <#=type.Name.ToLowerInvariant()#>Array)
+                    {
+                        for (int g = 0; g < Count; g++)
+                        {
+                            destinationBase[startIndex + g] = (<#=type.Name#>)(object)this[g];
+                        }
+                    }
+                }
+<#
+        }
+#>
+            }
+            else
+            {
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    <#=type.Name#>[] <#=type.Name.ToLowerInvariant()#>Array = (<#=type.Name#>[])(object)destination;
+                    fixed (<#=type.Name#>* destinationBase = <#=type.Name.ToLowerInvariant()#>Array)
+                    {
+<#
+            for (int g = 0; g < GetNumFields(type, totalSize); g++)
+            {
+#>
+                        destinationBase[startIndex + <#=g#>] = this.<#=GetRegisterFieldName(type, g)#>;
+<#
+            }
+#>
+                    }
+                }
+<#
+        }
+#>
+            }
+        }
+
+        /// <summary>
+        /// Returns the element at the given index.
+        /// </summary>
+        public unsafe T this[int index]
+        {
+            [Intrinsic]
+            get
+            {
+                if (index >= Count || index < 0)
+                {
+                    throw new IndexOutOfRangeException(SR.Format(SR.Arg_ArgumentOutOfRangeException, index));
+                }
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    fixed (<#=type.Name#>* basePtr = &this.<#=GetRegisterFieldName(type, 0)#>)
+                    {
+                        return (T)(object)*(basePtr + index);
+                    }
+                }
+<#
+    }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether the given Object is equal to this vector instance.
+        /// </summary>
+        /// <param name="obj">The Object to compare against.</param>
+        /// <returns>True if the Object is equal to this vector; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public override bool Equals(object obj)
+        {
+            if (!(obj is Vector<T>))
+            {
+                return false;
+            }
+            return Equals((Vector<T>)obj);
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether the given vector is equal to this vector instance.
+        /// </summary>
+        /// <param name="other">The vector to compare this instance to.</param>
+        /// <returns>True if the other vector is equal to this instance; False otherwise.</returns>
+        [Intrinsic]
+        public bool Equals(Vector<T> other)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+                for (int g = 0; g < Count; g++)
+                {
+                    if (!ScalarEquals(this[g], other[g]))
+                    {
+                        return false;
+                    }
+                }
+                return true;
+            }
+            else
+            {
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    return
+<#
+            for (int g = 0; g < GetNumFields(type, totalSize); g++)
+            {
+#>
+<#
+                if (g == 0)
+                {
+#>
+                        this.<#=GetRegisterFieldName(type, g)#> == other.<#=GetRegisterFieldName(type, g)#>
+<#
+                }
+                else
+                {
+#>
+                        && this.<#=GetRegisterFieldName(type, g)#> == other.<#=GetRegisterFieldName(type, g)#><#=(g == (GetNumFields(type, totalSize) -1)) ? ";" : ""#>
+<#
+                }
+#>
+<#
+            }
+#>
+                }
+<#
+        }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Returns the hash code for this instance.
+        /// </summary>
+        /// <returns>The hash code.</returns>
+        public override int GetHashCode()
+        {
+            int hash = 0;
+
+            if (Vector.IsHardwareAccelerated)
+            {
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    for (int g = 0; g < Count; g++)
+                    {
+                        hash = HashHelpers.Combine(hash, ((<#=type.Name#>)(object)this[g]).GetHashCode());
+                    }
+                    return hash;
+                }
+<#
+        }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+<#
+            for (int g = 0; g < GetNumFields(type, totalSize); g++)
+            {
+#>
+                    hash = HashHelpers.Combine(hash, this.<#=GetRegisterFieldName(type, g)#>.GetHashCode());
+<#
+            }
+#>
+                    return hash;
+                }
+<#
+        }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Returns a String representing this vector.
+        /// </summary>
+        /// <returns>The string representation.</returns>
+        public override string ToString()
+        {
+            return ToString("G", CultureInfo.CurrentCulture);
+        }
+
+        /// <summary>
+        /// Returns a String representing this vector, using the specified format string to format individual elements.
+        /// </summary>
+        /// <param name="format">The format of individual elements.</param>
+        /// <returns>The string representation.</returns>
+        public string ToString(string format)
+        {
+            return ToString(format, CultureInfo.CurrentCulture);
+        }
+
+        /// <summary>
+        /// Returns a String representing this vector, using the specified format string to format individual elements
+        /// and the given IFormatProvider.
+        /// </summary>
+        /// <param name="format">The format of individual elements.</param>
+        /// <param name="formatProvider">The format provider to use when formatting elements.</param>
+        /// <returns>The string representation.</returns>
+        public string ToString(string format, IFormatProvider formatProvider)
+        {
+            StringBuilder sb = new StringBuilder();
+            string separator = NumberFormatInfo.GetInstance(formatProvider).NumberGroupSeparator;
+            sb.Append('<');
+            for (int g = 0; g < Count - 1; g++)
+            {
+                sb.Append(((IFormattable)this[g]).ToString(format, formatProvider));
+                sb.Append(separator);
+                sb.Append(' ');
+            }
+            // Append last element w/out separator
+            sb.Append(((IFormattable)this[Count - 1]).ToString(format, formatProvider));
+            sb.Append('>');
+            return sb.ToString();
+        }
+        #endregion Public Instance Methods
+
+        #region Arithmetic Operators
+        /// <summary>
+        /// Adds two vectors together.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The summed vector.</returns>
+        public static unsafe Vector<T> operator +(Vector<T> left, Vector<T> right)
+        {
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                    <#=GenerateIfStatementHeader(type)#>
+                    {
+                        <#=type.Name#>* dataPtr = stackalloc <#=type.Name#>[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (<#=type.Name#>)(object)ScalarAdd(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+<#
+        }
+#>
+                    else
+                    {
+                        throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                    }
+                }
+                else
+                {
+                    Vector<T> sum = new Vector<T>();
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                    <#=GenerateIfStatementHeader(type)#>
+                    {
+<#
+                for (int g = 0; g < GetNumFields(type, totalSize); g++)
+                {
+#>
+                        sum.<#= GetRegisterFieldName(type, g) #> = (<#=type.Name#>)(left.<#= GetRegisterFieldName(type, g) #> + right.<#= GetRegisterFieldName(type, g) #>);
+<#
+                }
+#>
+                    }
+<#
+        }
+#>
+                    return sum;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Subtracts the second vector from the first.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The difference vector.</returns>
+        public static unsafe Vector<T> operator -(Vector<T> left, Vector<T> right)
+        {
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                    <#=GenerateIfStatementHeader(type)#>
+                    {
+                        <#=type.Name#>* dataPtr = stackalloc <#=type.Name#>[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (<#=type.Name#>)(object)ScalarSubtract(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+<#
+        }
+#>
+                    else
+                    {
+                        throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                    }
+                }
+                else
+                {
+                    Vector<T> difference = new Vector<T>();
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                    <#=GenerateIfStatementHeader(type)#>
+                    {
+<#
+                for (int g = 0; g < GetNumFields(type, totalSize); g++)
+                {
+#>
+                        difference.<#= GetRegisterFieldName(type, g) #> = (<#=type.Name#>)(left.<#= GetRegisterFieldName(type, g) #> - right.<#= GetRegisterFieldName(type, g) #>);
+<#
+                }
+#>
+                    }
+<#
+        }
+#>
+                    return difference;
+                }
+            }
+        }
+
+        // This method is intrinsic only for certain types. It cannot access fields directly unless we are sure the context is unaccelerated.
+        /// <summary>
+        /// Multiplies two vectors together.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The product vector.</returns>
+        public static unsafe Vector<T> operator *(Vector<T> left, Vector<T> right)
+        {
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                    <#=GenerateIfStatementHeader(type)#>
+                    {
+                        <#=type.Name#>* dataPtr = stackalloc <#=type.Name#>[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (<#=type.Name#>)(object)ScalarMultiply(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+<#
+        }
+#>
+                    else
+                    {
+                        throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                    }
+                }
+                else
+                {
+                    Vector<T> product = new Vector<T>();
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                    <#=GenerateIfStatementHeader(type)#>
+                    {
+<#
+                for (int g = 0; g < GetNumFields(type, totalSize); g++)
+                {
+#>
+                        product.<#= GetRegisterFieldName(type, g) #> = (<#=type.Name#>)(left.<#= GetRegisterFieldName(type, g) #> * right.<#= GetRegisterFieldName(type, g) #>);
+<#
+                }
+#>
+                    }
+<#
+    }
+#>
+                    return product;
+                }
+            }
+        }
+
+        // This method is intrinsic only for certain types. It cannot access fields directly unless we are sure the context is unaccelerated.
+        /// <summary>
+        /// Multiplies a vector by the given scalar.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <param name="factor">The scalar value.</param>
+        /// <returns>The scaled vector.</returns>
+        public static Vector<T> operator *(Vector<T> value, T factor)
+        {
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+                    return new Vector<T>(factor) * value;
+                }
+                else
+                {
+                    Vector<T> product = new Vector<T>();
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                    <#=GenerateIfStatementHeader(type)#>
+                    {
+<#
+                for (int g = 0; g < GetNumFields(type, totalSize); g++)
+                {
+#>
+                        product.<#= GetRegisterFieldName(type, g) #> = (<#=type.Name#>)(value.<#= GetRegisterFieldName(type, g) #> * (<#=type.Name#>)(object)factor);
+<#
+                }
+#>
+                    }
+<#
+    }
+#>
+                    return product;
+                }
+            }
+        }
+
+        // This method is intrinsic only for certain types. It cannot access fields directly unless we are sure the context is unaccelerated.
+        /// <summary>
+        /// Multiplies a vector by the given scalar.
+        /// </summary>
+        /// <param name="factor">The scalar value.</param>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The scaled vector.</returns>
+        public static Vector<T> operator *(T factor, Vector<T> value)
+        {
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+                    return new Vector<T>(factor) * value;
+                }
+                else
+                {
+                    Vector<T> product = new Vector<T>();
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                    <#=GenerateIfStatementHeader(type)#>
+                    {
+<#
+                for (int g = 0; g < GetNumFields(type, totalSize); g++)
+                {
+#>
+                        product.<#= GetRegisterFieldName(type, g) #> = (<#=type.Name#>)(value.<#= GetRegisterFieldName(type, g) #> * (<#=type.Name#>)(object)factor);
+<#
+                }
+#>
+                    }
+<#
+    }
+#>
+                    return product;
+                }
+            }
+        }
+
+        // This method is intrinsic only for certain types. It cannot access fields directly unless we are sure the context is unaccelerated.
+        /// <summary>
+        /// Divides the first vector by the second.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The vector resulting from the division.</returns>
+        public static unsafe Vector<T> operator /(Vector<T> left, Vector<T> right)
+        {
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                    <#=GenerateIfStatementHeader(type)#>
+                    {
+                        <#=type.Name#>* dataPtr = stackalloc <#=type.Name#>[Count];
+                        for (int g = 0; g < Count; g++)
+                        {
+                            dataPtr[g] = (<#=type.Name#>)(object)ScalarDivide(left[g], right[g]);
+                        }
+                        return new Vector<T>(dataPtr);
+                    }
+<#
+        }
+#>
+                    else
+                    {
+                        throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                    }
+                }
+                else
+                {
+                    Vector<T> quotient = new Vector<T>();
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                    <#=GenerateIfStatementHeader(type)#>
+                    {
+<#
+                for (int g = 0; g < GetNumFields(type, totalSize); g++)
+                {
+#>
+                        quotient.<#= GetRegisterFieldName(type, g) #> = (<#=type.Name#>)(left.<#= GetRegisterFieldName(type, g) #> / right.<#= GetRegisterFieldName(type, g) #>);
+<#
+                }
+#>
+                    }
+<#
+    }
+#>
+                    return quotient;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Negates a given vector.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The negated vector.</returns>
+        public static Vector<T> operator -(Vector<T> value)
+        {
+            return Zero - value;
+        }
+        #endregion Arithmetic Operators
+
+        #region Bitwise Operators
+        /// <summary>
+        /// Returns a new vector by performing a bitwise-and operation on each of the elements in the given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The resultant vector.</returns>
+        [Intrinsic]
+        public static unsafe Vector<T> operator &(Vector<T> left, Vector<T> right)
+        {
+            Vector<T> result = new Vector<T>();
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+                    Int64* resultBase = &result.register.int64_0;
+                    Int64* leftBase = &left.register.int64_0;
+                    Int64* rightBase = &right.register.int64_0;
+                    for (int g = 0; g < Vector<Int64>.Count; g++)
+                    {
+                        resultBase[g] = leftBase[g] & rightBase[g];
+                    }
+                }
+                else
+                {
+                    result.<#=GetRegisterFieldName(typeof(Int64), 0)#> = left.<#=GetRegisterFieldName(typeof(Int64), 0)#> & right.<#=GetRegisterFieldName(typeof(Int64), 0)#>;
+                    result.<#=GetRegisterFieldName(typeof(Int64), 1)#> = left.<#=GetRegisterFieldName(typeof(Int64), 1)#> & right.<#=GetRegisterFieldName(typeof(Int64), 1)#>;
+                }
+            }
+            return result;
+        }
+
+        /// <summary>
+        /// Returns a new vector by performing a bitwise-or operation on each of the elements in the given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The resultant vector.</returns>
+        [Intrinsic]
+        public static unsafe Vector<T> operator |(Vector<T> left, Vector<T> right)
+        {
+            Vector<T> result = new Vector<T>();
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+                    Int64* resultBase = &result.register.int64_0;
+                    Int64* leftBase = &left.register.int64_0;
+                    Int64* rightBase = &right.register.int64_0;
+                    for (int g = 0; g < Vector<Int64>.Count; g++)
+                    {
+                        resultBase[g] = leftBase[g] | rightBase[g];
+                    }
+                }
+                else
+                {
+                    result.<#=GetRegisterFieldName(typeof(Int64), 0)#> = left.<#=GetRegisterFieldName(typeof(Int64), 0)#> | right.<#=GetRegisterFieldName(typeof(Int64), 0)#>;
+                    result.<#=GetRegisterFieldName(typeof(Int64), 1)#> = left.<#=GetRegisterFieldName(typeof(Int64), 1)#> | right.<#=GetRegisterFieldName(typeof(Int64), 1)#>;
+                }
+            }
+            return result;
+        }
+
+        /// <summary>
+        /// Returns a new vector by performing a bitwise-exclusive-or operation on each of the elements in the given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The resultant vector.</returns>
+        [Intrinsic]
+        public static unsafe Vector<T> operator ^(Vector<T> left, Vector<T> right)
+        {
+            Vector<T> result = new Vector<T>();
+            unchecked
+            {
+                if (Vector.IsHardwareAccelerated)
+                {
+                    Int64* resultBase = &result.register.int64_0;
+                    Int64* leftBase = &left.register.int64_0;
+                    Int64* rightBase = &right.register.int64_0;
+                    for (int g = 0; g < Vector<Int64>.Count; g++)
+                    {
+                        resultBase[g] = leftBase[g] ^ rightBase[g];
+                    }
+                }
+                else
+                {
+                    result.<#=GetRegisterFieldName(typeof(Int64), 0)#> = left.<#=GetRegisterFieldName(typeof(Int64), 0)#> ^ right.<#=GetRegisterFieldName(typeof(Int64), 0)#>;
+                    result.<#=GetRegisterFieldName(typeof(Int64), 1)#> = left.<#=GetRegisterFieldName(typeof(Int64), 1)#> ^ right.<#=GetRegisterFieldName(typeof(Int64), 1)#>;
+                }
+            }
+            return result;
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements are obtained by taking the one's complement of the given vector's elements.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The one's complement vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> operator ~(Vector<T> value)
+        {
+            return s_allOnes ^ value;
+        }
+        #endregion Bitwise Operators
+
+        #region Logical Operators
+        /// <summary>
+        /// Returns a boolean indicating whether each pair of elements in the given vectors are equal.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The first vector to compare.</param>
+        /// <returns>True if all elements are equal; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static bool operator ==(Vector<T> left, Vector<T> right)
+        {
+            return left.Equals(right);
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether any single pair of elements in the given vectors are not equal.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>True if left and right are not equal; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static bool operator !=(Vector<T> left, Vector<T> right)
+        {
+            return !(left == right);
+        }
+        #endregion Logical Operators
+
+        #region Conversions
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of another type.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+<#
+        if (nonClsCompliantTypes.Contains(type))
+        {
+#>
+        [CLSCompliant(false)]
+<#
+        }
+#>
+        [Intrinsic]
+        public static explicit operator Vector<<#=type.Name#>>(Vector<T> value)
+        {
+            return new Vector<<#=type.Name#>>(ref value.register);
+        }
+
+<#
+    }
+#>
+        #endregion Conversions
+
+        #region Internal Comparison Methods
+        [Intrinsic]
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        internal static unsafe Vector<T> Equals(Vector<T> left, Vector<T> right)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    <#=type.Name#>* dataPtr = stackalloc <#=type.Name#>[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarEquals(left[g], right[g]) ? ConstantHelper.Get<#=type.Name#>WithAllBitsSet() : (<#=type.Name#>)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+<#
+    }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+                Register register = new Register();
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+<#
+                for (int g = 0; g < GetNumFields(type, totalSize); g++)
+                {
+#>
+                    <#= GetRegisterFieldName(type, g) #> = left.<#= GetRegisterFieldName(type, g) #> == right.<#= GetRegisterFieldName(type, g) #> ? ConstantHelper.Get<#=type.Name#>WithAllBitsSet() : (<#=type.Name#>)0;
+<#
+                }
+#>
+                    return new Vector<T>(ref register);
+                }
+<#
+        }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        [Intrinsic]
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        internal static unsafe Vector<T> LessThan(Vector<T> left, Vector<T> right)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    <#=type.Name#>* dataPtr = stackalloc <#=type.Name#>[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? ConstantHelper.Get<#=type.Name#>WithAllBitsSet() : (<#=type.Name#>)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+<#
+    }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+                Register register = new Register();
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+<#
+                for (int g = 0; g < GetNumFields(type, totalSize); g++)
+                {
+#>
+                    <#= GetRegisterFieldName(type, g) #> = left.<#= GetRegisterFieldName(type, g) #> < right.<#= GetRegisterFieldName(type, g) #> ? ConstantHelper.Get<#=type.Name#>WithAllBitsSet() : (<#=type.Name#>)0;
+<#
+                }
+#>
+                    return new Vector<T>(ref register);
+                }
+<#
+        }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        [Intrinsic]
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        internal static unsafe Vector<T> GreaterThan(Vector<T> left, Vector<T> right)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    <#=type.Name#>* dataPtr = stackalloc <#=type.Name#>[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? ConstantHelper.Get<#=type.Name#>WithAllBitsSet() : (<#=type.Name#>)0;
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+<#
+    }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+                Register register = new Register();
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+<#
+                for (int g = 0; g < GetNumFields(type, totalSize); g++)
+                {
+#>
+                    <#= GetRegisterFieldName(type, g) #> = left.<#= GetRegisterFieldName(type, g) #> > right.<#= GetRegisterFieldName(type, g) #> ? ConstantHelper.Get<#=type.Name#>WithAllBitsSet() : (<#=type.Name#>)0;
+<#
+                }
+#>
+                    return new Vector<T>(ref register);
+                }
+<#
+        }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        [Intrinsic]
+        internal static Vector<T> GreaterThanOrEqual(Vector<T> left, Vector<T> right)
+        {
+            return Equals(left, right) | GreaterThan(left, right);
+        }
+
+        [Intrinsic]
+        internal static Vector<T> LessThanOrEqual(Vector<T> left, Vector<T> right)
+        {
+            return Equals(left, right) | LessThan(left, right);
+        }
+
+        [Intrinsic]
+        internal static Vector<T> ConditionalSelect(Vector<T> condition, Vector<T> left, Vector<T> right)
+        {
+            return (left & condition) | (Vector.AndNot(right, condition));
+        }
+        #endregion Comparison Methods
+
+        #region Internal Math Methods
+        [Intrinsic]
+        internal static unsafe Vector<T> Abs(Vector<T> value)
+        {
+<#
+    foreach (Type type in supportedTypes)
+    {
+        if (unsignedTypes.Contains(type))
+        {
+#>
+            <#=GenerateIfStatementHeader(type, unsignedTypes)#>
+            {
+                return value;
+            }
+<#
+        }
+    }
+#>
+            if (Vector.IsHardwareAccelerated)
+            {
+<#
+    foreach (Type type in supportedTypes.Except(unsignedTypes))
+    {
+#>
+                <#=GenerateIfStatementHeader(type, supportedTypes.Except(unsignedTypes))#>
+                {
+                    <#=type.Name#>* dataPtr = stackalloc <#=type.Name#>[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = (<#=type.Name#>)(object)(Math.Abs((<#=type.Name#>)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+<#
+    }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+<#
+    foreach (Type type in supportedTypes.Except(unsignedTypes))
+    {
+#>
+                <#=GenerateIfStatementHeader(type, supportedTypes.Except(unsignedTypes))#>
+                {
+<#
+        for (int g = 0; g < GetNumFields(type, totalSize); g++)
+        {
+#>
+                    value.<#=GetRegisterFieldName(type, g)#> = (<#=type.Name#>)(Math.Abs(value.<#=GetRegisterFieldName(type, g)#>));
+<#
+        }
+#>
+                    return value;
+                }
+<#
+    }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        [Intrinsic]
+        internal static unsafe Vector<T> Min(Vector<T> left, Vector<T> right)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    <#=type.Name#>* dataPtr = stackalloc <#=type.Name#>[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarLessThan(left[g], right[g]) ? (<#=type.Name#>)(object)left[g] : (<#=type.Name#>)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+<#
+    }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+                Vector<T> vec = new Vector<T>();
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+<#
+                for (int g = 0; g < GetNumFields(type, totalSize); g++)
+                {
+#>
+                    vec.<#=GetRegisterFieldName(type, g)#> = left.<#=GetRegisterFieldName(type, g)#> < right.<#=GetRegisterFieldName(type, g)#> ? left.<#=GetRegisterFieldName(type, g)#> : right.<#=GetRegisterFieldName(type, g)#>;
+<#
+                }
+#>
+                    return vec;
+                }
+<#
+        }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        [Intrinsic]
+        internal static unsafe Vector<T> Max(Vector<T> left, Vector<T> right)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+<#    foreach (Type type in supportedTypes)
+    {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    <#=type.Name#>* dataPtr = stackalloc <#=type.Name#>[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = ScalarGreaterThan(left[g], right[g]) ? (<#=type.Name#>)(object)left[g] : (<#=type.Name#>)(object)right[g];
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+<#
+    }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+                Vector<T> vec = new Vector<T>();
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+<#
+                for (int g = 0; g < GetNumFields(type, totalSize); g++)
+                {
+#>
+                    vec.<#=GetRegisterFieldName(type, g)#> = left.<#=GetRegisterFieldName(type, g)#> > right.<#=GetRegisterFieldName(type, g)#> ? left.<#=GetRegisterFieldName(type, g)#> : right.<#=GetRegisterFieldName(type, g)#>;
+<#
+                }
+#>
+                    return vec;
+                }
+<#
+        }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        [Intrinsic]
+        internal static T DotProduct(Vector<T> left, Vector<T> right)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+                T product = default;
+                for (int g = 0; g < Count; g++)
+                {
+                    product = ScalarAdd(product, ScalarMultiply(left[g], right[g]));
+                }
+                return product;
+            }
+            else
+            {
+<#    foreach (Type type in supportedTypes)
+        {
+    #>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    <#=type.Name#> product = 0;
+<#
+                for (int g = 0; g < GetNumFields(type, totalSize); g++)
+                {
+#>
+                    product += (<#=type.Name#>)(left.<#=GetRegisterFieldName(type, g)#> * right.<#=GetRegisterFieldName(type, g)#>);
+<#
+                }
+#>
+                    return (T)(object)product;
+                }
+<#
+        }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+
+        [Intrinsic]
+        internal static unsafe Vector<T> SquareRoot(Vector<T> value)
+        {
+            if (Vector.IsHardwareAccelerated)
+            {
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+                    <#=type.Name#>* dataPtr = stackalloc <#=type.Name#>[Count];
+                    for (int g = 0; g < Count; g++)
+                    {
+                        dataPtr[g] = unchecked((<#=type.Name#>)Math.Sqrt((<#=type.Name#>)(object)value[g]));
+                    }
+                    return new Vector<T>(dataPtr);
+                }
+<#
+        }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+            else
+            {
+<#    foreach (Type type in supportedTypes)
+        {
+#>
+                <#=GenerateIfStatementHeader(type)#>
+                {
+<#
+                for (int g = 0; g < GetNumFields(type, totalSize); g++)
+                {
+#>
+                    value.<#=GetRegisterFieldName(type, g)#> = (<#=type.Name#>)Math.Sqrt(value.<#=GetRegisterFieldName(type, g)#>);
+<#
+                }
+#>
+                    return value;
+                }
+<#
+        }
+#>
+                else
+                {
+                    throw new NotSupportedException(SR.Arg_TypeNotSupported);
+                }
+            }
+        }
+        #endregion Internal Math Methods
+
+        #region Helper Methods
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static bool ScalarEquals(T left, T right)
+        {
+<# foreach (Type type in supportedTypes)
+   {
+#>
+            <#=GenerateIfStatementHeader(type)#>
+            {
+                return (<#=type.Name#>)(object)left == (<#=type.Name#>)(object)right;
+            }
+<#
+   }
+#>
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static bool ScalarLessThan(T left, T right)
+        {
+<# foreach (Type type in supportedTypes)
+   {
+#>
+            <#=GenerateIfStatementHeader(type)#>
+            {
+                return (<#=type.Name#>)(object)left < (<#=type.Name#>)(object)right;
+            }
+<#
+   }
+#>
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static bool ScalarGreaterThan(T left, T right)
+        {
+<# foreach (Type type in supportedTypes)
+   {
+#>
+            <#=GenerateIfStatementHeader(type)#>
+            {
+                return (<#=type.Name#>)(object)left > (<#=type.Name#>)(object)right;
+            }
+<#
+   }
+#>
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static T ScalarAdd(T left, T right)
+        {
+<# foreach (Type type in supportedTypes)
+   {
+#>
+            <#=GenerateIfStatementHeader(type)#>
+            {
+                return (T)(object)unchecked((<#=type.Name#>)((<#=type.Name#>)(object)left + (<#=type.Name#>)(object)right));
+            }
+<#
+   }
+#>
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static T ScalarSubtract(T left, T right)
+        {
+<# foreach (Type type in supportedTypes)
+   {
+#>
+            <#=GenerateIfStatementHeader(type)#>
+            {
+                return (T)(object)(<#=type.Name#>)((<#=type.Name#>)(object)left - (<#=type.Name#>)(object)right);
+            }
+<#
+   }
+#>
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static T ScalarMultiply(T left, T right)
+        {
+<# foreach (Type type in supportedTypes)
+   {
+#>
+            <#=GenerateIfStatementHeader(type)#>
+            {
+                return (T)(object)unchecked((<#=type.Name#>)((<#=type.Name#>)(object)left * (<#=type.Name#>)(object)right));
+            }
+<#
+   }
+#>
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static T ScalarDivide(T left, T right)
+        {
+<# foreach (Type type in supportedTypes)
+   {
+#>
+            <#=GenerateIfStatementHeader(type)#>
+            {
+                return (T)(object)(<#=type.Name#>)((<#=type.Name#>)(object)left / (<#=type.Name#>)(object)right);
+            }
+<#
+   }
+#>
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static T GetOneValue()
+        {
+<# foreach (Type type in supportedTypes)
+   {
+#>
+            <#=GenerateIfStatementHeader(type)#>
+            {
+                <#=type.Name#> value = 1;
+                return (T)(object)value;
+            }
+<#
+   }
+#>
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        private static T GetAllBitsSetValue()
+        {
+<# foreach (Type type in supportedTypes)
+   {
+#>
+            <#=GenerateIfStatementHeader(type)#>
+            {
+                return (T)(object)ConstantHelper.Get<#=type.Name#>WithAllBitsSet();
+            }
+<#
+   }
+#>
+            else
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+        #endregion
+    }
+
+    [Intrinsic]
+    public static partial class Vector
+    {
+        #region Widen/Narrow
+<#    foreach (Type type in WidenableTypes)
+    {
+        Type widenTarget = GetWidenTarget(type);
+#>
+        /// <summary>
+        /// Widens a Vector{<#=type.Name#>} into two Vector{<#=widenTarget.Name#>}'s.
+        /// <param name="source">The source vector whose elements are widened into the outputs.</param>
+        /// <param name="low">The first output vector, whose elements will contain the widened elements from lower indices in the source vector.</param>
+        /// <param name="high">The second output vector, whose elements will contain the widened elements from higher indices in the source vector.</param>
+        /// </summary>
+<#
+        if (nonClsCompliantTypes.Contains(type) || nonClsCompliantTypes.Contains(widenTarget))
+        {
+#>
+        [CLSCompliant(false)]
+<#
+        }
+#>
+        [Intrinsic]
+        public static unsafe void Widen(Vector<<#=type.Name#>> source, out Vector<<#=widenTarget.Name#>> low, out Vector<<#=widenTarget.Name#>> high)
+        {
+            int elements = Vector<<#=type.Name#>>.Count;
+            <#=widenTarget.Name#>* lowPtr = stackalloc <#=widenTarget.Name#>[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                lowPtr[i] = (<#=widenTarget.Name#>)source[i];
+            }
+            <#=widenTarget.Name#>* highPtr = stackalloc <#=widenTarget.Name#>[elements / 2];
+            for (int i = 0; i < elements / 2; i++)
+            {
+                highPtr[i] = (<#=widenTarget.Name#>)source[i + (elements / 2)];
+            }
+
+            low = new Vector<<#=widenTarget.Name#>>(lowPtr);
+            high = new Vector<<#=widenTarget.Name#>>(highPtr);
+        }
+
+<#
+    }
+#>
+<#    foreach (Type narrowSource in NarrowableTypes)
+    {
+        Type narrowTarget = GetNarrowTarget(narrowSource);
+#>
+        /// <summary>
+        /// Narrows two Vector{<#=narrowSource.Name#>}'s into one Vector{<#=narrowTarget.Name#>}.
+        /// <param name="low">The first source vector, whose elements become the lower-index elements of the return value.</param>
+        /// <param name="high">The second source vector, whose elements become the higher-index elements of the return value.</param>
+        /// <returns>A Vector{<#=narrowTarget.Name#>} containing elements narrowed from the source vectors.</returns>
+        /// </summary>
+<#
+        if (nonClsCompliantTypes.Contains(narrowSource) || nonClsCompliantTypes.Contains(narrowTarget))
+        {
+#>
+        [CLSCompliant(false)]
+<#
+        }
+#>
+        [Intrinsic]
+        public static unsafe Vector<<#=narrowTarget.Name#>> Narrow(Vector<<#=narrowSource.Name#>> low, Vector<<#=narrowSource.Name#>> high)
+        {
+		    unchecked
+		    {
+				int elements = Vector<<#=narrowTarget.Name#>>.Count;
+				<#=narrowTarget.Name#>* retPtr = stackalloc <#=narrowTarget.Name#>[elements];
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i] = (<#=narrowTarget.Name#>)low[i];
+				}
+				for (int i = 0; i < elements / 2; i++)
+				{
+					retPtr[i + (elements / 2)] = (<#=narrowTarget.Name#>)high[i];
+				}
+
+				return new Vector<<#=narrowTarget.Name#>>(retPtr);
+		    }
+        }
+
+<#
+    }
+#>
+        #endregion Widen/Narrow
+
+        #region Same-Size Conversion
+<#    foreach (var pair in SameSizeConversionPairs)
+    {
+#>
+        /// <summary>
+        /// Converts a Vector{<#=pair.Key.Name#>} to a Vector{<#=pair.Value.Name#>}.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The converted vector.</returns>
+<#
+        if (nonClsCompliantTypes.Contains(pair.Key) || nonClsCompliantTypes.Contains(pair.Value))
+        {
+#>
+        [CLSCompliant(false)]
+<#
+        }
+#>
+        [Intrinsic]
+        public static unsafe Vector<<#=pair.Value.Name#>> ConvertTo<#=pair.Value.Name#>(Vector<<#=pair.Key.Name#>> value)
+        {
+			unchecked
+			{
+				int elements = Vector<<#=pair.Value.Name#>>.Count;
+				<#=pair.Value.Name#>* retPtr = stackalloc <#=pair.Value.Name#>[elements];
+				for (int i = 0; i < elements; i++)
+				{
+					retPtr[i] = (<#=pair.Value.Name#>)value[i];
+				}
+
+				return new Vector<<#=pair.Value.Name#>>(retPtr);
+			}
+        }
+
+<# } #>
+        #endregion Same-Size Conversion
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Numerics/Vector_Operations.cs b/src/System.Private.CoreLib/shared/System/Numerics/Vector_Operations.cs
new file mode 100644
index 0000000000..b69b058be9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Numerics/Vector_Operations.cs
@@ -0,0 +1,865 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System.Numerics
+{
+    /// <summary>
+    /// Contains various methods useful for creating, manipulating, combining, and converting generic vectors with one another.
+    /// </summary>
+    public static partial class Vector
+    {
+        // JIT is not looking at the Vector class methods
+        // all methods here should be inlined and they must be implemented in terms of Vector<T> intrinsics
+        #region Select Methods
+        /// <summary>
+        /// Creates a new vector with elements selected between the two given source vectors, and based on a mask vector.
+        /// </summary>
+        /// <param name="condition">The integral mask vector used to drive selection.</param>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The new vector with elements selected based on the mask.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<Single> ConditionalSelect(Vector<int> condition, Vector<Single> left, Vector<Single> right)
+        {
+            return (Vector<Single>)Vector<Single>.ConditionalSelect((Vector<Single>)condition, left, right);
+        }
+
+        /// <summary>
+        /// Creates a new vector with elements selected between the two given source vectors, and based on a mask vector.
+        /// </summary>
+        /// <param name="condition">The integral mask vector used to drive selection.</param>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The new vector with elements selected based on the mask.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<double> ConditionalSelect(Vector<long> condition, Vector<double> left, Vector<double> right)
+        {
+            return (Vector<double>)Vector<double>.ConditionalSelect((Vector<double>)condition, left, right);
+        }
+
+        /// <summary>
+        /// Creates a new vector with elements selected between the two given source vectors, and based on a mask vector.
+        /// </summary>
+        /// <param name="condition">The mask vector used to drive selection.</param>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The new vector with elements selected based on the mask.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> ConditionalSelect<T>(Vector<T> condition, Vector<T> left, Vector<T> right) where T : struct
+        {
+            return Vector<T>.ConditionalSelect(condition, left, right);
+        }
+        #endregion Select Methods
+
+        #region Comparison methods
+        #region Equals methods
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left and right were equal.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> Equals<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return Vector<T>.Equals(left, right);
+        }
+
+        /// <summary>
+        /// Returns an integral vector whose elements signal whether elements in the left and right floating point vectors were equal.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<int> Equals(Vector<Single> left, Vector<Single> right)
+        {
+            return (Vector<int>)Vector<Single>.Equals(left, right);
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left and right were equal.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<int> Equals(Vector<int> left, Vector<int> right)
+        {
+            return Vector<int>.Equals(left, right);
+        }
+
+        /// <summary>
+        /// Returns an integral vector whose elements signal whether elements in the left and right floating point vectors were equal.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<long> Equals(Vector<double> left, Vector<double> right)
+        {
+            return (Vector<long>)Vector<double>.Equals(left, right);
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left and right were equal.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<long> Equals(Vector<long> left, Vector<long> right)
+        {
+            return Vector<long>.Equals(left, right);
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether each pair of elements in the given vectors are equal.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The first vector to compare.</param>
+        /// <returns>True if all elements are equal; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static bool EqualsAll<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return left == right;
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether any single pair of elements in the given vectors are equal.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>True if any element pairs are equal; False if no element pairs are equal.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static bool EqualsAny<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return !Vector<T>.Equals(left, right).Equals(Vector<T>.Zero);
+        }
+        #endregion Equals methods
+
+        #region Lessthan Methods
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left were less than their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> LessThan<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return Vector<T>.LessThan(left, right);
+        }
+
+        /// <summary>
+        /// Returns an integral vector whose elements signal whether the elements in left were less than their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant integral vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<int> LessThan(Vector<Single> left, Vector<Single> right)
+        {
+            return (Vector<int>)Vector<Single>.LessThan(left, right);
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left were less than their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<int> LessThan(Vector<int> left, Vector<int> right)
+        {
+            return Vector<int>.LessThan(left, right);
+        }
+
+        /// <summary>
+        /// Returns an integral vector whose elements signal whether the elements in left were less than their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant integral vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<long> LessThan(Vector<double> left, Vector<double> right)
+        {
+            return (Vector<long>)Vector<double>.LessThan(left, right);
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left were less than their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<long> LessThan(Vector<long> left, Vector<long> right)
+        {
+            return Vector<long>.LessThan(left, right);
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether all of the elements in left are less than their corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>True if all elements in left are less than their corresponding elements in right; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static bool LessThanAll<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            Vector<int> cond = (Vector<int>)Vector<T>.LessThan(left, right);
+            return cond.Equals(Vector<int>.AllOnes);
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether any element in left is less than its corresponding element in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>True if any elements in left are less than their corresponding elements in right; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static bool LessThanAny<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            Vector<int> cond = (Vector<int>)Vector<T>.LessThan(left, right);
+            return !cond.Equals(Vector<int>.Zero);
+        }
+        #endregion LessthanMethods
+
+        #region Lessthanorequal methods
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left were less than or equal to their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> LessThanOrEqual<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return Vector<T>.LessThanOrEqual(left, right);
+        }
+
+        /// <summary>
+        /// Returns an integral vector whose elements signal whether the elements in left were less than or equal to their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant integral vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<int> LessThanOrEqual(Vector<Single> left, Vector<Single> right)
+        {
+            return (Vector<int>)Vector<Single>.LessThanOrEqual(left, right);
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left were less than or equal to their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<int> LessThanOrEqual(Vector<int> left, Vector<int> right)
+        {
+            return Vector<int>.LessThanOrEqual(left, right);
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left were less than or equal to their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<long> LessThanOrEqual(Vector<long> left, Vector<long> right)
+        {
+            return Vector<long>.LessThanOrEqual(left, right);
+        }
+
+        /// <summary>
+        /// Returns an integral vector whose elements signal whether the elements in left were less than or equal to their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant integral vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<long> LessThanOrEqual(Vector<double> left, Vector<double> right)
+        {
+            return (Vector<long>)Vector<double>.LessThanOrEqual(left, right);
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether all elements in left are less than or equal to their corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>True if all elements in left are less than or equal to their corresponding elements in right; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static bool LessThanOrEqualAll<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            Vector<int> cond = (Vector<int>)Vector<T>.LessThanOrEqual(left, right);
+            return cond.Equals(Vector<int>.AllOnes);
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether any element in left is less than or equal to its corresponding element in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>True if any elements in left are less than their corresponding elements in right; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static bool LessThanOrEqualAny<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            Vector<int> cond = (Vector<int>)Vector<T>.LessThanOrEqual(left, right);
+            return !cond.Equals(Vector<int>.Zero);
+        }
+        #endregion Lessthanorequal methods
+
+        #region Greaterthan methods
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left were greater than their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> GreaterThan<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return Vector<T>.GreaterThan(left, right);
+        }
+
+        /// <summary>
+        /// Returns an integral vector whose elements signal whether the elements in left were greater than their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant integral vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<int> GreaterThan(Vector<Single> left, Vector<Single> right)
+        {
+            return (Vector<int>)Vector<Single>.GreaterThan(left, right);
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left were greater than their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<int> GreaterThan(Vector<int> left, Vector<int> right)
+        {
+            return Vector<int>.GreaterThan(left, right);
+        }
+
+        /// <summary>
+        /// Returns an integral vector whose elements signal whether the elements in left were greater than their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant integral vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<long> GreaterThan(Vector<double> left, Vector<double> right)
+        {
+            return (Vector<long>)Vector<double>.GreaterThan(left, right);
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left were greater than their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<long> GreaterThan(Vector<long> left, Vector<long> right)
+        {
+            return Vector<long>.GreaterThan(left, right);
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether all elements in left are greater than the corresponding elements in right.
+        /// elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>True if all elements in left are greater than their corresponding elements in right; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static bool GreaterThanAll<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            Vector<int> cond = (Vector<int>)Vector<T>.GreaterThan(left, right);
+            return cond.Equals(Vector<int>.AllOnes);
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether any element in left is greater than its corresponding element in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>True if any elements in left are greater than their corresponding elements in right; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static bool GreaterThanAny<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            Vector<int> cond = (Vector<int>)Vector<T>.GreaterThan(left, right);
+            return !cond.Equals(Vector<int>.Zero);
+        }
+        #endregion Greaterthan methods
+
+        #region Greaterthanorequal methods
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left were greater than or equal to their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> GreaterThanOrEqual<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return Vector<T>.GreaterThanOrEqual(left, right);
+        }
+
+        /// <summary>
+        /// Returns an integral vector whose elements signal whether the elements in left were greater than or equal to their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant integral vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<int> GreaterThanOrEqual(Vector<Single> left, Vector<Single> right)
+        {
+            return (Vector<int>)Vector<Single>.GreaterThanOrEqual(left, right);
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left were greater than or equal to their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<int> GreaterThanOrEqual(Vector<int> left, Vector<int> right)
+        {
+            return Vector<int>.GreaterThanOrEqual(left, right);
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements signal whether the elements in left were greater than or equal to their
+        /// corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<long> GreaterThanOrEqual(Vector<long> left, Vector<long> right)
+        {
+            return Vector<long>.GreaterThanOrEqual(left, right);
+        }
+
+        /// <summary>
+        /// Returns an integral vector whose elements signal whether the elements in left were greater than or equal to 
+        /// their corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>The resultant integral vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<long> GreaterThanOrEqual(Vector<double> left, Vector<double> right)
+        {
+            return (Vector<long>)Vector<double>.GreaterThanOrEqual(left, right);
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether all of the elements in left are greater than or equal to 
+        /// their corresponding elements in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>True if all elements in left are greater than or equal to their corresponding elements in right; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static bool GreaterThanOrEqualAll<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            Vector<int> cond = (Vector<int>)Vector<T>.GreaterThanOrEqual(left, right);
+            return cond.Equals(Vector<int>.AllOnes);
+        }
+
+        /// <summary>
+        /// Returns a boolean indicating whether any element in left is greater than or equal to its corresponding element in right.
+        /// </summary>
+        /// <param name="left">The first vector to compare.</param>
+        /// <param name="right">The second vector to compare.</param>
+        /// <returns>True if any elements in left are greater than or equal to their corresponding elements in right; False otherwise.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static bool GreaterThanOrEqualAny<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            Vector<int> cond = (Vector<int>)Vector<T>.GreaterThanOrEqual(left, right);
+            return !cond.Equals(Vector<int>.Zero);
+        }
+        #endregion Greaterthanorequal methods
+        #endregion Comparison methods
+
+        #region Vector Math Methods
+        // Every operation must either be a JIT intrinsic or implemented over a JIT intrinsic
+        // as a thin wrapper
+        // Operations implemented over a JIT intrinsic should be inlined
+        // Methods that do not have a <T> type parameter are recognized as intrinsics
+        /// <summary>
+        /// Returns whether or not vector operations are subject to hardware acceleration through JIT intrinsic support.
+        /// </summary>
+        public static bool IsHardwareAccelerated
+        {
+            [Intrinsic]
+            get
+            {
+                return false;
+            }
+        }
+
+        // Vector<T>
+        // Basic Math
+        // All Math operations for Vector<T> are aggressively inlined here
+
+        /// <summary>
+        /// Returns a new vector whose elements are the absolute values of the given vector's elements.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The absolute value vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> Abs<T>(Vector<T> value) where T : struct
+        {
+            return Vector<T>.Abs(value);
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements are the minimum of each pair of elements in the two given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The minimum vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> Min<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return Vector<T>.Min(left, right);
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements are the maximum of each pair of elements in the two given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The maximum vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> Max<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return Vector<T>.Max(left, right);
+        }
+
+        // Specialized vector operations
+
+        /// <summary>
+        /// Returns the dot product of two vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The dot product.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static T Dot<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return Vector<T>.DotProduct(left, right);
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements are the square roots of the given vector's elements.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The square root vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> SquareRoot<T>(Vector<T> value) where T : struct
+        {
+            return Vector<T>.SquareRoot(value);
+        }
+        #endregion Vector Math Methods
+
+        #region Named Arithmetic Operators
+        /// <summary>
+        /// Creates a new vector whose values are the sum of each pair of elements from the two given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The summed vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> Add<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return left + right;
+        }
+
+        /// <summary>
+        /// Creates a new vector whose values are the difference between each pairs of elements in the given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The difference vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> Subtract<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return left - right;
+        }
+
+        /// <summary>
+        /// Creates a new vector whose values are the product of each pair of elements from the two given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The summed vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> Multiply<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return left * right;
+        }
+
+        /// <summary>
+        /// Returns a new vector whose values are the values of the given vector each multiplied by a scalar value.
+        /// </summary>
+        /// <param name="left">The source vector.</param>
+        /// <param name="right">The scalar factor.</param>
+        /// <returns>The scaled vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> Multiply<T>(Vector<T> left, T right) where T : struct
+        {
+            return left * right;
+        }
+
+        /// <summary>
+        /// Returns a new vector whose values are the values of the given vector each multiplied by a scalar value.
+        /// </summary>
+        /// <param name="left">The scalar factor.</param>
+        /// <param name="right">The source vector.</param>
+        /// <returns>The scaled vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> Multiply<T>(T left, Vector<T> right) where T : struct
+        {
+            return left * right;
+        }
+
+        /// <summary>
+        /// Returns a new vector whose values are the result of dividing the first vector's elements 
+        /// by the corresponding elements in the second vector.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The divided vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> Divide<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return left / right;
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements are the given vector's elements negated.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The negated vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> Negate<T>(Vector<T> value) where T : struct
+        {
+            return -value;
+        }
+        #endregion Named Arithmetic Operators
+
+        #region Named Bitwise Operators
+        /// <summary>
+        /// Returns a new vector by performing a bitwise-and operation on each of the elements in the given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> BitwiseAnd<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return left & right;
+        }
+
+        /// <summary>
+        /// Returns a new vector by performing a bitwise-or operation on each of the elements in the given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> BitwiseOr<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return left | right;
+        }
+
+        /// <summary>
+        /// Returns a new vector whose elements are obtained by taking the one's complement of the given vector's elements.
+        /// </summary>
+        /// <param name="value">The source vector.</param>
+        /// <returns>The one's complement vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> OnesComplement<T>(Vector<T> value) where T : struct
+        {
+            return ~value;
+        }
+
+        /// <summary>
+        /// Returns a new vector by performing a bitwise-exclusive-or operation on each of the elements in the given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> Xor<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return left ^ right;
+        }
+
+        /// <summary>
+        /// Returns a new vector by performing a bitwise-and-not operation on each of the elements in the given vectors.
+        /// </summary>
+        /// <param name="left">The first source vector.</param>
+        /// <param name="right">The second source vector.</param>
+        /// <returns>The resultant vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<T> AndNot<T>(Vector<T> left, Vector<T> right) where T : struct
+        {
+            return left & ~right;
+        }
+        #endregion Named Bitwise Operators
+
+        #region Conversion Methods
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of a vector of unsigned bytes.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<Byte> AsVectorByte<T>(Vector<T> value) where T : struct
+        {
+            return (Vector<Byte>)value;
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of a vector of signed bytes.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [CLSCompliant(false)]
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<SByte> AsVectorSByte<T>(Vector<T> value) where T : struct
+        {
+            return (Vector<SByte>)value;
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of a vector of 16-bit integers.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [CLSCompliant(false)]
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<UInt16> AsVectorUInt16<T>(Vector<T> value) where T : struct
+        {
+            return (Vector<UInt16>)value;
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of a vector of signed 16-bit integers.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<Int16> AsVectorInt16<T>(Vector<T> value) where T : struct
+        {
+            return (Vector<Int16>)value;
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of a vector of unsigned 32-bit integers.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [CLSCompliant(false)]
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<UInt32> AsVectorUInt32<T>(Vector<T> value) where T : struct
+        {
+            return (Vector<UInt32>)value;
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of a vector of signed 32-bit integers.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<Int32> AsVectorInt32<T>(Vector<T> value) where T : struct
+        {
+            return (Vector<Int32>)value;
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of a vector of unsigned 64-bit integers.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [CLSCompliant(false)]
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<UInt64> AsVectorUInt64<T>(Vector<T> value) where T : struct
+        {
+            return (Vector<UInt64>)value;
+        }
+
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of a vector of signed 64-bit integers.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<Int64> AsVectorInt64<T>(Vector<T> value) where T : struct
+        {
+            return (Vector<Int64>)value;
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of a vector of 32-bit floating point numbers.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<Single> AsVectorSingle<T>(Vector<T> value) where T : struct
+        {
+            return (Vector<Single>)value;
+        }
+
+        /// <summary>
+        /// Reinterprets the bits of the given vector into those of a vector of 64-bit floating point numbers.
+        /// </summary>
+        /// <param name="value">The source vector</param>
+        /// <returns>The reinterpreted vector.</returns>
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public static Vector<Double> AsVectorDouble<T>(Vector<T> value) where T : struct
+        {
+            return (Vector<Double>)value;
+        }
+        #endregion Conversion Methods
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ObjectDisposedException.cs b/src/System.Private.CoreLib/shared/System/ObjectDisposedException.cs
new file mode 100644
index 0000000000..3daed13bb6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ObjectDisposedException.cs
@@ -0,0 +1,83 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Runtime.Serialization;
+
+namespace System
+{
+    /// <devdoc>
+    ///    <para> The exception that is thrown when accessing an object that was
+    ///       disposed.</para>
+    /// </devdoc>
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class ObjectDisposedException : InvalidOperationException
+    {
+        private String _objectName;
+
+        // This constructor should only be called by the EE (COMPlusThrow)
+        private ObjectDisposedException() :
+            this(null, SR.ObjectDisposed_Generic)
+        {
+        }
+
+        public ObjectDisposedException(String objectName) :
+            this(objectName, SR.ObjectDisposed_Generic)
+        {
+        }
+
+        public ObjectDisposedException(String objectName, String message) : base(message)
+        {
+            HResult = HResults.COR_E_OBJECTDISPOSED;
+            _objectName = objectName;
+        }
+
+        public ObjectDisposedException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_OBJECTDISPOSED;
+        }
+
+        protected ObjectDisposedException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            _objectName = info.GetString("ObjectName");
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("ObjectName", ObjectName, typeof(string));
+        }
+
+        /// <devdoc>
+        ///    <para>Gets the text for the message for this exception.</para>
+        /// </devdoc>
+        public override String Message
+        {
+            get
+            {
+                String name = ObjectName;
+                if (name == null || name.Length == 0)
+                    return base.Message;
+
+                String objectDisposed = SR.Format(SR.ObjectDisposed_ObjectName_Name, name);
+                return base.Message + Environment.NewLine + objectDisposed;
+            }
+        }
+
+        public String ObjectName
+        {
+            get
+            {
+                if (_objectName == null)
+                {
+                    return String.Empty;
+                }
+                return _objectName;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ObsoleteAttribute.cs b/src/System.Private.CoreLib/shared/System/ObsoleteAttribute.cs
new file mode 100644
index 0000000000..a63db137f8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ObsoleteAttribute.cs
@@ -0,0 +1,60 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Attribute for functions, etc that will be removed.
+**
+** 
+===========================================================*/
+
+using System;
+
+namespace System
+{
+    // This attribute is attached to members that are not to be used any longer.
+    // Message is some human readable explanation of what to use
+    // Error indicates if the compiler should treat usage of such a method as an
+    //   error. (this would be used if the actual implementation of the obsolete 
+    //   method's implementation had changed).
+    // 
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Enum |
+        AttributeTargets.Interface | AttributeTargets.Constructor | AttributeTargets.Method | AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Event | AttributeTargets.Delegate
+        , Inherited = false)]
+    public sealed class ObsoleteAttribute : Attribute
+    {
+        private String _message;
+        private bool _error;
+
+        public ObsoleteAttribute()
+        {
+            _message = null;
+            _error = false;
+        }
+
+        public ObsoleteAttribute(String message)
+        {
+            _message = message;
+            _error = false;
+        }
+
+        public ObsoleteAttribute(String message, bool error)
+        {
+            _message = message;
+            _error = error;
+        }
+
+        public String Message
+        {
+            get { return _message; }
+        }
+
+        public bool IsError
+        {
+            get { return _error; }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/OperationCanceledException.cs b/src/System.Private.CoreLib/shared/System/OperationCanceledException.cs
new file mode 100644
index 0000000000..8a472c9ff0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/OperationCanceledException.cs
@@ -0,0 +1,74 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Exception for cancelled IO requests.
+**
+**
+===========================================================*/
+
+using System;
+using System.Runtime.Serialization;
+using System.Threading;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class OperationCanceledException : SystemException
+    {
+        [NonSerialized]
+        private CancellationToken _cancellationToken;
+
+        public CancellationToken CancellationToken
+        {
+            get { return _cancellationToken; }
+            private set { _cancellationToken = value; }
+        }
+
+        public OperationCanceledException()
+            : base(SR.OperationCanceled)
+        {
+            HResult = HResults.COR_E_OPERATIONCANCELED;
+        }
+
+        public OperationCanceledException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_OPERATIONCANCELED;
+        }
+
+        public OperationCanceledException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_OPERATIONCANCELED;
+        }
+
+
+        public OperationCanceledException(CancellationToken token)
+            : this()
+        {
+            CancellationToken = token;
+        }
+
+        public OperationCanceledException(String message, CancellationToken token)
+            : this(message)
+        {
+            CancellationToken = token;
+        }
+
+        public OperationCanceledException(String message, Exception innerException, CancellationToken token)
+            : this(message, innerException)
+        {
+            CancellationToken = token;
+        }
+
+        protected OperationCanceledException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/OverflowException.cs b/src/System.Private.CoreLib/shared/System/OverflowException.cs
new file mode 100644
index 0000000000..e28dcb87ed
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/OverflowException.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception class for Arithmetic Overflows.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class OverflowException : ArithmeticException
+    {
+        public OverflowException()
+            : base(SR.Arg_OverflowException)
+        {
+            HResult = HResults.COR_E_OVERFLOW;
+        }
+
+        public OverflowException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_OVERFLOW;
+        }
+
+        public OverflowException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_OVERFLOW;
+        }
+
+        protected OverflowException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ParamArrayAttribute.cs b/src/System.Private.CoreLib/shared/System/ParamArrayAttribute.cs
new file mode 100644
index 0000000000..d3c3d46d56
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ParamArrayAttribute.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Attribute for multiple parameters.
+**
+**
+=============================================================================*/
+
+namespace System
+{
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = true, AllowMultiple = false)]
+    public sealed class ParamArrayAttribute : Attribute
+    {
+        public ParamArrayAttribute() { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ParamsArray.cs b/src/System.Private.CoreLib/shared/System/ParamsArray.cs
new file mode 100644
index 0000000000..043ee679ee
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ParamsArray.cs
@@ -0,0 +1,82 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    internal readonly struct ParamsArray
+    {
+        // Sentinel fixed-length arrays eliminate the need for a "count" field keeping this
+        // struct down to just 4 fields. These are only used for their "Length" property,
+        // that is, their elements are never set or referenced.
+        private static readonly object[] s_oneArgArray = new object[1];
+        private static readonly object[] s_twoArgArray = new object[2];
+        private static readonly object[] s_threeArgArray = new object[3];
+
+        private readonly object _arg0;
+        private readonly object _arg1;
+        private readonly object _arg2;
+
+        // After construction, the first three elements of this array will never be accessed
+        // because the indexer will retrieve those values from arg0, arg1, and arg2.
+        private readonly object[] _args;
+
+        public ParamsArray(object arg0)
+        {
+            _arg0 = arg0;
+            _arg1 = null;
+            _arg2 = null;
+
+            // Always assign this.args to make use of its "Length" property
+            _args = s_oneArgArray;
+        }
+
+        public ParamsArray(object arg0, object arg1)
+        {
+            _arg0 = arg0;
+            _arg1 = arg1;
+            _arg2 = null;
+
+            // Always assign this.args to make use of its "Length" property
+            _args = s_twoArgArray;
+        }
+
+        public ParamsArray(object arg0, object arg1, object arg2)
+        {
+            _arg0 = arg0;
+            _arg1 = arg1;
+            _arg2 = arg2;
+
+            // Always assign this.args to make use of its "Length" property
+            _args = s_threeArgArray;
+        }
+
+        public ParamsArray(object[] args)
+        {
+            int len = args.Length;
+            _arg0 = len > 0 ? args[0] : null;
+            _arg1 = len > 1 ? args[1] : null;
+            _arg2 = len > 2 ? args[2] : null;
+            _args = args;
+        }
+
+        public int Length
+        {
+            get { return _args.Length; }
+        }
+
+        public object this[int index]
+        {
+            get { return index == 0 ? _arg0 : GetAtSlow(index); }
+        }
+
+        private object GetAtSlow(int index)
+        {
+            if (index == 1)
+                return _arg1;
+            if (index == 2)
+                return _arg2;
+            return _args[index];
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ParseNumbers.cs b/src/System.Private.CoreLib/shared/System/ParseNumbers.cs
new file mode 100644
index 0000000000..dab4cb2190
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ParseNumbers.cs
@@ -0,0 +1,664 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    /// <summary>Methods for parsing numbers and strings.</summary>
+    internal static class ParseNumbers
+    {
+        internal const int LeftAlign = 0x0001;
+        internal const int RightAlign = 0x0004;
+        internal const int PrefixSpace = 0x0008;
+        internal const int PrintSign = 0x0010;
+        internal const int PrintBase = 0x0020;
+        internal const int PrintAsI1 = 0x0040;
+        internal const int PrintAsI2 = 0x0080;
+        internal const int PrintAsI4 = 0x0100;
+        internal const int TreatAsUnsigned = 0x0200;
+        internal const int TreatAsI1 = 0x0400;
+        internal const int TreatAsI2 = 0x0800;
+        internal const int IsTight = 0x1000;
+        internal const int NoSpace = 0x2000;
+        internal const int PrintRadixBase = 0x4000;
+
+        private const int MinRadix = 2;
+        private const int MaxRadix = 36;
+
+        public static unsafe long StringToLong(ReadOnlySpan<char> s, int radix, int flags)
+        {
+            int pos = 0;
+            return StringToLong(s, radix, flags, ref pos);
+        }
+
+        public static long StringToLong(ReadOnlySpan<char> s, int radix, int flags, ref int currPos)
+        {
+            int i = currPos;
+
+            // Do some radix checking.
+            // A radix of -1 says to use whatever base is spec'd on the number.
+            // Parse in Base10 until we figure out what the base actually is.
+            int r = (-1 == radix) ? 10 : radix;
+
+            if (r != 2 && r != 10 && r != 8 && r != 16)
+                throw new ArgumentException(SR.Arg_InvalidBase, nameof(radix));
+
+            int length = s.Length;
+
+            if (i < 0 || i >= length)
+                throw new ArgumentOutOfRangeException(SR.ArgumentOutOfRange_Index);
+
+            // Get rid of the whitespace and then check that we've still got some digits to parse.
+            if (((flags & IsTight) == 0) && ((flags & NoSpace) == 0))
+            {
+                EatWhiteSpace(s, ref i);
+                if (i == length)
+                    throw new FormatException(SR.Format_EmptyInputString);
+            }
+
+            // Check for a sign
+            int sign = 1;
+            if (s[i] == '-')
+            {
+                if (r != 10)
+                    throw new ArgumentException(SR.Arg_CannotHaveNegativeValue);
+
+                if ((flags & TreatAsUnsigned) != 0)
+                    throw new OverflowException(SR.Overflow_NegativeUnsigned);
+
+                sign = -1;
+                i++;
+            }
+            else if (s[i] == '+')
+            {
+                i++;
+            }
+
+            if ((radix == -1 || radix == 16) && (i + 1 < length) && s[i] == '0')
+            {
+                if (s[i + 1] == 'x' || s[i + 1] == 'X')
+                {
+                    r = 16;
+                    i += 2;
+                }
+            }
+
+            int grabNumbersStart = i;
+            long result = GrabLongs(r, s, ref i, (flags & TreatAsUnsigned) != 0);
+
+            // Check if they passed us a string with no parsable digits.
+            if (i == grabNumbersStart)
+                throw new FormatException(SR.Format_NoParsibleDigits);
+
+            if ((flags & IsTight) != 0)
+            {
+                //If we've got effluvia left at the end of the string, complain.
+                if (i < length)
+                    throw new FormatException(SR.Format_ExtraJunkAtEnd);
+            }
+
+            // Put the current index back into the correct place.
+            currPos = i;
+
+            // Return the value properly signed.
+            if ((ulong)result == 0x8000000000000000 && sign == 1 && r == 10 && ((flags & TreatAsUnsigned) == 0))
+                throw new OverflowException(SR.Overflow_Int64);
+
+            if (r == 10)
+            {
+                result *= sign;
+            }
+
+            return result;
+        }
+
+        public static int StringToInt(ReadOnlySpan<char> s, int radix, int flags)
+        {
+            int pos = 0;
+            return StringToInt(s, radix, flags, ref pos);
+        }
+
+        public static int StringToInt(ReadOnlySpan<char> s, int radix, int flags, ref int currPos)
+        {
+            // They're requied to tell me where to start parsing.
+            int i = currPos;
+
+            // Do some radix checking.
+            // A radix of -1 says to use whatever base is spec'd on the number.
+            // Parse in Base10 until we figure out what the base actually is.
+            int r = (-1 == radix) ? 10 : radix;
+
+            if (r != 2 && r != 10 && r != 8 && r != 16)
+                throw new ArgumentException(SR.Arg_InvalidBase, nameof(radix));
+
+            int length = s.Length;
+
+            if (i < 0 || i >= length)
+                throw new ArgumentOutOfRangeException(SR.ArgumentOutOfRange_Index);
+
+            // Get rid of the whitespace and then check that we've still got some digits to parse.
+            if (((flags & IsTight) == 0) && ((flags & NoSpace) == 0))
+            {
+                EatWhiteSpace(s, ref i);
+                if (i == length)
+                    throw new FormatException(SR.Format_EmptyInputString);
+            }
+
+            // Check for a sign
+            int sign = 1;
+            if (s[i] == '-')
+            {
+                if (r != 10)
+                    throw new ArgumentException(SR.Arg_CannotHaveNegativeValue);
+
+                if ((flags & TreatAsUnsigned) != 0)
+                    throw new OverflowException(SR.Overflow_NegativeUnsigned);
+
+                sign = -1;
+                i++;
+            }
+            else if (s[i] == '+')
+            {
+                i++;
+            }
+
+            // Consume the 0x if we're in an unknown base or in base-16.
+            if ((radix == -1 || radix == 16) && (i + 1 < length) && s[i] == '0')
+            {
+                if (s[i + 1] == 'x' || s[i + 1] == 'X')
+                {
+                    r = 16;
+                    i += 2;
+                }
+            }
+
+            int grabNumbersStart = i;
+            int result = GrabInts(r, s, ref i, ((flags & TreatAsUnsigned) != 0));
+
+            // Check if they passed us a string with no parsable digits.
+            if (i == grabNumbersStart)
+                throw new FormatException(SR.Format_NoParsibleDigits);
+
+            if ((flags & IsTight) != 0)
+            {
+                // If we've got effluvia left at the end of the string, complain.
+                if (i < length)
+                    throw new FormatException(SR.Format_ExtraJunkAtEnd);
+            }
+
+            // Put the current index back into the correct place.
+            currPos = i;
+
+            // Return the value properly signed.
+            if ((flags & TreatAsI1) != 0)
+            {
+                if ((uint)result > 0xFF)
+                    throw new OverflowException(SR.Overflow_SByte);
+            }
+            else if ((flags & TreatAsI2) != 0)
+            {
+                if ((uint)result > 0xFFFF)
+                    throw new OverflowException(SR.Overflow_Int16);
+            }
+            else if ((uint)result == 0x80000000 && sign == 1 && r == 10 && ((flags & TreatAsUnsigned) == 0))
+            {
+                throw new OverflowException(SR.Overflow_Int32);
+            }
+
+            if (r == 10)
+            {
+                result *= sign;
+            }
+
+            return result;
+        }
+
+        public static string IntToString(int n, int radix, int width, char paddingChar, int flags)
+        {
+            Span<char> buffer = stackalloc char[66]; // Longest possible string length for an integer in binary notation with prefix
+
+            if (radix < MinRadix || radix > MaxRadix)
+                throw new ArgumentException(SR.Arg_InvalidBase, nameof(radix));
+
+            // If the number is negative, make it positive and remember the sign.
+            // If the number is MIN_VALUE, this will still be negative, so we'll have to
+            // special case this later.
+            bool isNegative = false;
+            uint l;
+            if (n < 0)
+            {
+                isNegative = true;
+
+                // For base 10, write out -num, but other bases write out the
+                // 2's complement bit pattern
+                l = (10 == radix) ? (uint)-n : (uint)n;
+            }
+            else
+            {
+                l = (uint)n;
+            }
+
+            // The conversion to a uint will sign extend the number.  In order to ensure
+            // that we only get as many bits as we expect, we chop the number.
+            if ((flags & PrintAsI1) != 0)
+            {
+                l &= 0xFF;
+            }
+            else if ((flags & PrintAsI2) != 0)
+            {
+                l &= 0xFFFF;
+            }
+
+            // Special case the 0.
+            int index;
+            if (0 == l)
+            {
+                buffer[0] = '0';
+                index = 1;
+            }
+            else
+            {
+                index = 0;
+                for (int i = 0; i < buffer.Length; i++) // for(...;i<buffer.Length;...) loop instead of do{...}while(l!=0) to help JIT eliminate span bounds checks
+                {
+                    uint div = l / (uint)radix; // TODO https://github.com/dotnet/coreclr/issues/3439
+                    uint charVal = l - (div * (uint)radix);
+                    l = div;
+
+                    buffer[i] = (charVal < 10) ?
+                        (char)(charVal + '0') :
+                        (char)(charVal + 'a' - 10);
+
+                    if (l == 0)
+                    {
+                        index = i + 1;
+                        break;
+                    }
+                }
+
+                Debug.Assert(l == 0, $"Expected {l} == 0");
+            }
+
+            // If they want the base, append that to the string (in reverse order)
+            if (radix != 10 && ((flags & PrintBase) != 0))
+            {
+                if (16 == radix)
+                {
+                    buffer[index++] = 'x';
+                    buffer[index++] = '0';
+                }
+                else if (8 == radix)
+                {
+                    buffer[index++] = '0';
+                }
+            }
+
+            if (10 == radix)
+            {
+                // If it was negative, append the sign, else if they requested, add the '+'.
+                // If they requested a leading space, put it on.
+                if (isNegative)
+                {
+                    buffer[index++] = '-';
+                }
+                else if ((flags & PrintSign) != 0)
+                {
+                    buffer[index++] = '+';
+                }
+                else if ((flags & PrefixSpace) != 0)
+                {
+                    buffer[index++] = ' ';
+                }
+            }
+
+            // Figure out the size of and allocate the resulting string
+            string result = string.FastAllocateString(Math.Max(width, index));
+            unsafe
+            {
+                // Put the characters into the string in reverse order.
+                // Fill the remaining space, if there is any, with the correct padding character.
+                fixed (char* resultPtr = result)
+                {
+                    char* p = resultPtr;
+                    int padding = result.Length - index;
+
+                    if ((flags & LeftAlign) != 0)
+                    {
+                        for (int i = 0; i < padding; i++)
+                        {
+                            *p++ = paddingChar;
+                        }
+
+                        for (int i = 0; i < index; i++)
+                        {
+                            *p++ = buffer[index - i - 1];
+                        }
+                    }
+                    else
+                    {
+                        for (int i = 0; i < index; i++)
+                        {
+                            *p++ = buffer[index - i - 1];
+                        }
+
+                        for (int i = 0; i < padding; i++)
+                        {
+                            *p++ = paddingChar;
+                        }
+                    }
+
+                    Debug.Assert((p - resultPtr) == result.Length, $"Expected {p - resultPtr} == {result.Length}");
+                }
+            }
+            return result;
+        }
+
+        public static string LongToString(long n, int radix, int width, char paddingChar, int flags)
+        {
+            Span<char> buffer = stackalloc char[67]; // Longest possible string length for an integer in binary notation with prefix
+
+            if (radix < MinRadix || radix > MaxRadix)
+                throw new ArgumentException(SR.Arg_InvalidBase, nameof(radix));
+
+            //If the number is negative, make it positive and remember the sign.
+            ulong ul;
+            bool isNegative = false;
+            if (n < 0)
+            {
+                isNegative = true;
+
+                // For base 10, write out -num, but other bases write out the
+                // 2's complement bit pattern
+                ul = (10 == radix) ? (ulong)(-n) : (ulong)n;
+            }
+            else
+            {
+                ul = (ulong)n;
+            }
+
+            if ((flags & PrintAsI1) != 0)
+            {
+                ul = ul & 0xFF;
+            }
+            else if ((flags & PrintAsI2) != 0)
+            {
+                ul = ul & 0xFFFF;
+            }
+            else if ((flags & PrintAsI4) != 0)
+            {
+                ul = ul & 0xFFFFFFFF;
+            }
+
+            //Special case the 0.
+            int index;
+            if (0 == ul)
+            {
+                buffer[0] = '0';
+                index = 1;
+            }
+            else
+            {
+                index = 0;
+                for (int i = 0; i < buffer.Length; i++) // for loop instead of do{...}while(l!=0) to help JIT eliminate span bounds checks
+                {
+                    ulong div = ul / (ulong)radix; // TODO https://github.com/dotnet/coreclr/issues/3439
+                    int charVal = (int)(ul - (div * (ulong)radix));
+                    ul = div;
+
+                    buffer[i] = (charVal < 10) ?
+                        (char)(charVal + '0') :
+                        (char)(charVal + 'a' - 10);
+
+                    if (ul == 0)
+                    {
+                        index = i + 1;
+                        break;
+                    }
+                }
+                Debug.Assert(ul == 0, $"Expected {ul} == 0");
+            }
+
+            //If they want the base, append that to the string (in reverse order)
+            if (radix != 10 && ((flags & PrintBase) != 0))
+            {
+                if (16 == radix)
+                {
+                    buffer[index++] = 'x';
+                    buffer[index++] = '0';
+                }
+                else if (8 == radix)
+                {
+                    buffer[index++] = '0';
+                }
+                else if ((flags & PrintRadixBase) != 0)
+                {
+                    buffer[index++] = '#';
+                    buffer[index++] = (char)((radix % 10) + '0');
+                    buffer[index++] = (char)((radix / 10) + '0');
+                }
+            }
+
+            if (10 == radix)
+            {
+                //If it was negative, append the sign.
+                if (isNegative)
+                {
+                    buffer[index++] = '-';
+                }
+
+                //else if they requested, add the '+';
+                else if ((flags & PrintSign) != 0)
+                {
+                    buffer[index++] = '+';
+                }
+
+                //If they requested a leading space, put it on.
+                else if ((flags & PrefixSpace) != 0)
+                {
+                    buffer[index++] = ' ';
+                }
+            }
+
+            // Figure out the size of and allocate the resulting string
+            string result = string.FastAllocateString(Math.Max(width, index));
+            unsafe
+            {
+                // Put the characters into the string in reverse order.
+                // Fill the remaining space, if there is any, with the correct padding character.
+                fixed (char* resultPtr = result)
+                {
+                    char* p = resultPtr;
+                    int padding = result.Length - index;
+
+                    if ((flags & LeftAlign) != 0)
+                    {
+                        for (int i = 0; i < padding; i++)
+                        {
+                            *p++ = paddingChar;
+                        }
+
+                        for (int i = 0; i < index; i++)
+                        {
+                            *p++ = buffer[index - i - 1];
+                        }
+                    }
+                    else
+                    {
+                        for (int i = 0; i < index; i++)
+                        {
+                            *p++ = buffer[index - i - 1];
+                        }
+
+                        for (int i = 0; i < padding; i++)
+                        {
+                            *p++ = paddingChar;
+                        }
+                    }
+
+                    Debug.Assert((p - resultPtr) == result.Length, $"Expected {p - resultPtr} == {result.Length}");
+                }
+            }
+            return result;
+        }
+
+        private static void EatWhiteSpace(ReadOnlySpan<char> s, ref int i)
+        {
+            int localIndex = i;
+            for (; localIndex < s.Length && char.IsWhiteSpace(s[localIndex]); localIndex++);
+            i = localIndex;
+        }
+
+        private static long GrabLongs(int radix, ReadOnlySpan<char> s, ref int i, bool isUnsigned)
+        {
+            ulong result = 0;
+            ulong maxVal;
+
+            // Allow all non-decimal numbers to set the sign bit.
+            if (radix == 10 && !isUnsigned)
+            {
+                maxVal = 0x7FFFFFFFFFFFFFFF / 10;
+
+                // Read all of the digits and convert to a number
+                while (i < s.Length && IsDigit(s[i], radix, out int value))
+                {
+                    // Check for overflows - this is sufficient & correct.
+                    if (result > maxVal || ((long)result) < 0)
+                    {
+                        ThrowOverflowInt64Exception();
+                    }
+
+                    result = result * (ulong)radix + (ulong)value;
+                    i++;
+                }
+
+                if ((long)result < 0 && result != 0x8000000000000000)
+                {
+                    ThrowOverflowInt64Exception();
+                }
+            }
+            else
+            {
+                Debug.Assert(radix == 2 || radix == 8 || radix == 10 || radix == 16);
+                maxVal =
+                    radix == 10 ? 0xffffffffffffffff / 10 :
+                    radix == 16 ? 0xffffffffffffffff / 16 :
+                    radix == 8 ? 0xffffffffffffffff / 8 :
+                    0xffffffffffffffff / 2;
+
+                // Read all of the digits and convert to a number
+                while (i < s.Length && IsDigit(s[i], radix, out int value))
+                {
+                    // Check for overflows - this is sufficient & correct.
+                    if (result > maxVal)
+                    {
+                        ThrowOverflowUInt64Exception();
+                    }
+
+                    ulong temp = result * (ulong)radix + (ulong)value;
+
+                    if (temp < result) // this means overflow as well
+                    {
+                        ThrowOverflowUInt64Exception();
+                    }
+
+                    result = temp;
+                    i++;
+                }
+            }
+
+            return (long)result;
+        }
+
+        private static int GrabInts(int radix, ReadOnlySpan<char> s, ref int i, bool isUnsigned)
+        {
+            uint result = 0;
+            uint maxVal;
+
+            // Allow all non-decimal numbers to set the sign bit.
+            if (radix == 10 && !isUnsigned)
+            {
+                maxVal = (0x7FFFFFFF / 10);
+
+                // Read all of the digits and convert to a number
+                while (i < s.Length && IsDigit(s[i], radix, out int value))
+                {
+                    // Check for overflows - this is sufficient & correct.
+                    if (result > maxVal || (int)result < 0)
+                    {
+                        ThrowOverflowInt32Exception();
+                    }
+                    result = result * (uint)radix + (uint)value;
+                    i++;
+                }
+                if ((int)result < 0 && result != 0x80000000)
+                {
+                    ThrowOverflowInt32Exception();
+                }
+            }
+            else
+            {
+                Debug.Assert(radix == 2 || radix == 8 || radix == 10 || radix == 16);
+                maxVal =
+                    radix == 10 ? 0xffffffff / 10 :
+                    radix == 16 ? 0xffffffff / 16 :
+                    radix == 8 ? 0xffffffff / 8 :
+                    0xffffffff / 2;
+
+                // Read all of the digits and convert to a number
+                while (i < s.Length && IsDigit(s[i], radix, out int value))
+                {
+                    // Check for overflows - this is sufficient & correct.
+                    if (result > maxVal)
+                    {
+                        throw new OverflowException(SR.Overflow_UInt32);
+                    }
+
+                    uint temp = result * (uint)radix + (uint)value;
+
+                    if (temp < result) // this means overflow as well
+                    {
+                        ThrowOverflowUInt32Exception();
+                    }
+
+                    result = temp;
+                    i++;
+                }
+            }
+
+            return (int)result;
+        }
+
+        private static void ThrowOverflowInt32Exception() => throw new OverflowException(SR.Overflow_Int32);
+        private static void ThrowOverflowInt64Exception() => throw new OverflowException(SR.Overflow_Int64);
+        private static void ThrowOverflowUInt32Exception() => throw new OverflowException(SR.Overflow_UInt32);
+        private static void ThrowOverflowUInt64Exception() => throw new OverflowException(SR.Overflow_UInt64);
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static bool IsDigit(char c, int radix, out int result)
+        {
+            int tmp;
+            if ((uint)(c - '0') <= 9)
+            {
+                result = tmp = c - '0';
+            }
+            else if ((uint)(c - 'A') <= 'Z' - 'A')
+            {
+                result = tmp = c - 'A' + 10;
+            }
+            else if ((uint)(c - 'a') <= 'z' - 'a')
+            {
+                result = tmp = c - 'a' + 10;
+            }
+            else
+            {
+                result = -1;
+                return false;
+            }
+
+            return tmp < radix;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/PlatformNotSupportedException.cs b/src/System.Private.CoreLib/shared/System/PlatformNotSupportedException.cs
new file mode 100644
index 0000000000..5039f3f441
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/PlatformNotSupportedException.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: To handle features that don't run on particular platforms
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class PlatformNotSupportedException : NotSupportedException
+    {
+        public PlatformNotSupportedException()
+            : base(SR.Arg_PlatformNotSupported)
+        {
+            HResult = HResults.COR_E_PLATFORMNOTSUPPORTED;
+        }
+
+        public PlatformNotSupportedException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_PLATFORMNOTSUPPORTED;
+        }
+
+        public PlatformNotSupportedException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_PLATFORMNOTSUPPORTED;
+        }
+
+        protected PlatformNotSupportedException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Progress.cs b/src/System.Private.CoreLib/shared/System/Progress.cs
new file mode 100644
index 0000000000..755e7719fe
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Progress.cs
@@ -0,0 +1,105 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading;
+using System.Diagnostics;
+
+namespace System
+{
+    /// <summary>
+    /// Provides an IProgress{T} that invokes callbacks for each reported progress value.
+    /// </summary>
+    /// <typeparam name="T">Specifies the type of the progress report value.</typeparam>
+    /// <remarks>
+    /// Any handler provided to the constructor or event handlers registered with
+    /// the <see cref="ProgressChanged"/> event are invoked through a 
+    /// <see cref="System.Threading.SynchronizationContext"/> instance captured
+    /// when the instance is constructed.  If there is no current SynchronizationContext
+    /// at the time of construction, the callbacks will be invoked on the ThreadPool.
+    /// </remarks>
+    public class Progress<T> : IProgress<T>
+    {
+        /// <summary>The synchronization context captured upon construction.  This will never be null.</summary>
+        private readonly SynchronizationContext _synchronizationContext;
+        /// <summary>The handler specified to the constructor.  This may be null.</summary>
+        private readonly Action<T> _handler;
+        /// <summary>A cached delegate used to post invocation to the synchronization context.</summary>
+        private readonly SendOrPostCallback _invokeHandlers;
+
+        /// <summary>Initializes the <see cref="Progress{T}"/>.</summary>
+        public Progress()
+        {
+            // Capture the current synchronization context.
+            // If there is no current context, we use a default instance targeting the ThreadPool.
+            _synchronizationContext = SynchronizationContext.Current ?? ProgressStatics.DefaultContext;
+            Debug.Assert(_synchronizationContext != null);
+            _invokeHandlers = new SendOrPostCallback(InvokeHandlers);
+        }
+
+        /// <summary>Initializes the <see cref="Progress{T}"/> with the specified callback.</summary>
+        /// <param name="handler">
+        /// A handler to invoke for each reported progress value.  This handler will be invoked
+        /// in addition to any delegates registered with the <see cref="ProgressChanged"/> event.
+        /// Depending on the <see cref="System.Threading.SynchronizationContext"/> instance captured by 
+        /// the <see cref="Progress"/> at construction, it's possible that this handler instance
+        /// could be invoked concurrently with itself.
+        /// </param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="handler"/> is null (Nothing in Visual Basic).</exception>
+        public Progress(Action<T> handler) : this()
+        {
+            if (handler == null) throw new ArgumentNullException(nameof(handler));
+            _handler = handler;
+        }
+
+        /// <summary>Raised for each reported progress value.</summary>
+        /// <remarks>
+        /// Handlers registered with this event will be invoked on the 
+        /// <see cref="System.Threading.SynchronizationContext"/> captured when the instance was constructed.
+        /// </remarks>
+        public event EventHandler<T> ProgressChanged;
+
+        /// <summary>Reports a progress change.</summary>
+        /// <param name="value">The value of the updated progress.</param>
+        protected virtual void OnReport(T value)
+        {
+            // If there's no handler, don't bother going through the sync context.
+            // Inside the callback, we'll need to check again, in case 
+            // an event handler is removed between now and then.
+            Action<T> handler = _handler;
+            EventHandler<T> changedEvent = ProgressChanged;
+            if (handler != null || changedEvent != null)
+            {
+                // Post the processing to the sync context.
+                // (If T is a value type, it will get boxed here.)
+                _synchronizationContext.Post(_invokeHandlers, value);
+            }
+        }
+
+        /// <summary>Reports a progress change.</summary>
+        /// <param name="value">The value of the updated progress.</param>
+        void IProgress<T>.Report(T value) { OnReport(value); }
+
+        /// <summary>Invokes the action and event callbacks.</summary>
+        /// <param name="state">The progress value.</param>
+        private void InvokeHandlers(object state)
+        {
+            T value = (T)state;
+
+            Action<T> handler = _handler;
+            EventHandler<T> changedEvent = ProgressChanged;
+
+            if (handler != null) handler(value);
+            if (changedEvent != null) changedEvent(this, value);
+        }
+    }
+
+    /// <summary>Holds static values for <see cref="Progress{T}"/>.</summary>
+    /// <remarks>This avoids one static instance per type T.</remarks>
+    internal static class ProgressStatics
+    {
+        /// <summary>A default synchronization context that targets the ThreadPool.</summary>
+        internal static readonly SynchronizationContext DefaultContext = new SynchronizationContext();
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Random.cs b/src/System.Private.CoreLib/shared/System/Random.cs
new file mode 100644
index 0000000000..20f035e2e8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Random.cs
@@ -0,0 +1,263 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    public class Random
+    {
+        //
+        // Private Constants 
+        //
+        private const int MBIG = int.MaxValue;
+        private const int MSEED = 161803398;
+        private const int MZ = 0;
+
+        //
+        // Member Variables
+        //
+        private int _inext;
+        private int _inextp;
+        private int[] _seedArray = new int[56];
+
+        //
+        // Public Constants
+        //
+
+        //
+        // Native Declarations
+        //
+
+        //
+        // Constructors
+        //
+
+        /*=========================================================================================
+        **Action: Initializes a new instance of the Random class, using a default seed value
+        ===========================================================================================*/
+        public Random()
+          : this(GenerateSeed())
+        {
+        }
+
+        /*=========================================================================================
+        **Action: Initializes a new instance of the Random class, using a specified seed value
+        ===========================================================================================*/
+        public Random(int Seed)
+        {
+            int ii = 0;
+            int mj, mk;
+
+            //Initialize our Seed array.
+            int subtraction = (Seed == int.MinValue) ? int.MaxValue : Math.Abs(Seed);
+            mj = MSEED - subtraction;
+            _seedArray[55] = mj;
+            mk = 1;
+            for (int i = 1; i < 55; i++)
+            {  //Apparently the range [1..55] is special (Knuth) and so we're wasting the 0'th position.
+                if ((ii += 21) >= 55) ii -= 55;
+                _seedArray[ii] = mk;
+                mk = mj - mk;
+                if (mk < 0) mk += MBIG;
+                mj = _seedArray[ii];
+            }
+            for (int k = 1; k < 5; k++)
+            {
+                for (int i = 1; i < 56; i++)
+                {
+                    int n = i + 30;
+                    if (n >= 55) n -= 55;
+                    _seedArray[i] -= _seedArray[1 + n];
+                    if (_seedArray[i] < 0) _seedArray[i] += MBIG;
+                }
+            }
+            _inext = 0;
+            _inextp = 21;
+            Seed = 1;
+        }
+
+        //
+        // Package Private Methods
+        //
+
+        /*====================================Sample====================================
+        **Action: Return a new random number [0..1) and reSeed the Seed array.
+        **Returns: A double [0..1)
+        **Arguments: None
+        **Exceptions: None
+        ==============================================================================*/
+        protected virtual double Sample()
+        {
+            //Including this division at the end gives us significantly improved
+            //random number distribution.
+            return (InternalSample() * (1.0 / MBIG));
+        }
+
+        private int InternalSample()
+        {
+            int retVal;
+            int locINext = _inext;
+            int locINextp = _inextp;
+
+            if (++locINext >= 56) locINext = 1;
+            if (++locINextp >= 56) locINextp = 1;
+
+            retVal = _seedArray[locINext] - _seedArray[locINextp];
+
+            if (retVal == MBIG) retVal--;
+            if (retVal < 0) retVal += MBIG;
+
+            _seedArray[locINext] = retVal;
+
+            _inext = locINext;
+            _inextp = locINextp;
+
+            return retVal;
+        }
+
+        [ThreadStatic]
+        private static Random t_threadRandom;
+        private static readonly Random s_globalRandom = new Random(GenerateGlobalSeed());
+
+        /*=====================================GenerateSeed=====================================
+        **Returns: An integer that can be used as seed values for consecutively
+                   creating lots of instances on the same thread within a short period of time.
+        ========================================================================================*/
+        private static int GenerateSeed()
+        {
+            Random rnd = t_threadRandom;
+            if (rnd == null)
+            {
+                int seed;
+                lock (s_globalRandom)
+                {
+                    seed = s_globalRandom.Next();
+                }
+                rnd = new Random(seed);
+                t_threadRandom = rnd;
+            }
+            return rnd.Next();
+        }
+
+        /*==================================GenerateGlobalSeed====================================
+        **Action:  Creates a number to use as global seed.
+        **Returns: An integer that is safe to use as seed values for thread-local seed generators.
+        ==========================================================================================*/
+        private static unsafe int GenerateGlobalSeed()
+        {
+            int result;
+            Interop.GetRandomBytes((byte*)&result, sizeof(int));
+            return result;
+        }
+
+        //
+        // Public Instance Methods
+        // 
+
+
+        /*=====================================Next=====================================
+        **Returns: An int [0..Int32.MaxValue)
+        **Arguments: None
+        **Exceptions: None.
+        ==============================================================================*/
+        public virtual int Next()
+        {
+            return InternalSample();
+        }
+
+        private double GetSampleForLargeRange()
+        {
+            // The distribution of double value returned by Sample 
+            // is not distributed well enough for a large range.
+            // If we use Sample for a range [Int32.MinValue..Int32.MaxValue)
+            // We will end up getting even numbers only.
+
+            int result = InternalSample();
+            // Note we can't use addition here. The distribution will be bad if we do that.
+            bool negative = (InternalSample() % 2 == 0) ? true : false;  // decide the sign based on second sample
+            if (negative)
+            {
+                result = -result;
+            }
+            double d = result;
+            d += (int.MaxValue - 1); // get a number in range [0 .. 2 * Int32MaxValue - 1)
+            d /= 2 * (uint)int.MaxValue - 1;
+            return d;
+        }
+
+
+        /*=====================================Next=====================================
+        **Returns: An int [minvalue..maxvalue)
+        **Arguments: minValue -- the least legal value for the Random number.
+        **           maxValue -- One greater than the greatest legal return value.
+        **Exceptions: None.
+        ==============================================================================*/
+        public virtual int Next(int minValue, int maxValue)
+        {
+            if (minValue > maxValue)
+            {
+                throw new ArgumentOutOfRangeException(nameof(minValue), SR.Format(SR.Argument_MinMaxValue, nameof(minValue), nameof(maxValue)));
+            }
+
+            long range = (long)maxValue - minValue;
+            if (range <= int.MaxValue)
+            {
+                return ((int)(Sample() * range) + minValue);
+            }
+            else
+            {
+                return (int)((long)(GetSampleForLargeRange() * range) + minValue);
+            }
+        }
+
+
+        /*=====================================Next=====================================
+        **Returns: An int [0..maxValue)
+        **Arguments: maxValue -- One more than the greatest legal return value.
+        **Exceptions: None.
+        ==============================================================================*/
+        public virtual int Next(int maxValue)
+        {
+            if (maxValue < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(maxValue), SR.Format(SR.ArgumentOutOfRange_MustBePositive, nameof(maxValue)));
+            }
+            return (int)(Sample() * maxValue);
+        }
+
+
+        /*=====================================Next=====================================
+        **Returns: A double [0..1)
+        **Arguments: None
+        **Exceptions: None
+        ==============================================================================*/
+        public virtual double NextDouble()
+        {
+            return Sample();
+        }
+
+
+        /*==================================NextBytes===================================
+        **Action:  Fills the byte array with random bytes [0..0x7f].  The entire array is filled.
+        **Returns:Void
+        **Arguments:  buffer -- the array to be filled.
+        **Exceptions: None
+        ==============================================================================*/
+        public virtual void NextBytes(byte[] buffer)
+        {
+            if (buffer == null) throw new ArgumentNullException(nameof(buffer));
+            for (int i = 0; i < buffer.Length; i++)
+            {
+                buffer[i] = (byte)InternalSample();
+            }
+        }
+
+        public virtual void NextBytes(Span<byte> buffer)
+        {
+            for (int i = 0; i < buffer.Length; i++)
+            {
+                buffer[i] = (byte)Next();
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/RankException.cs b/src/System.Private.CoreLib/shared/System/RankException.cs
new file mode 100644
index 0000000000..bdd2cd51f1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/RankException.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: For methods that are passed arrays with the wrong number of
+**          dimensions.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class RankException : SystemException
+    {
+        public RankException()
+            : base(SR.Arg_RankException)
+        {
+            HResult = HResults.COR_E_RANK;
+        }
+
+        public RankException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_RANK;
+        }
+
+        public RankException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_RANK;
+        }
+
+        protected RankException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ReadOnlyMemory.cs b/src/System.Private.CoreLib/shared/System/ReadOnlyMemory.cs
new file mode 100644
index 0000000000..78f328a880
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ReadOnlyMemory.cs
@@ -0,0 +1,359 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Buffers;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using EditorBrowsableAttribute = System.ComponentModel.EditorBrowsableAttribute;
+using EditorBrowsableState = System.ComponentModel.EditorBrowsableState;
+#if !FEATURE_PORTABLE_SPAN
+using Internal.Runtime.CompilerServices;
+#endif // FEATURE_PORTABLE_SPAN
+
+namespace System
+{
+    /// <summary>
+    /// Represents a contiguous region of memory, similar to <see cref="ReadOnlySpan{T}"/>.
+    /// Unlike <see cref="ReadOnlySpan{T}"/>, it is not a byref-like type.
+    /// </summary>
+    [DebuggerTypeProxy(typeof(MemoryDebugView<>))]
+    [DebuggerDisplay("{ToString(),raw}")]
+    public readonly struct ReadOnlyMemory<T>
+    {
+        // NOTE: With the current implementation, Memory<T> and ReadOnlyMemory<T> must have the same layout,
+        // as code uses Unsafe.As to cast between them.
+
+        // The highest order bit of _index is used to discern whether _object is an array/string or an owned memory
+        // if (_index >> 31) == 1, _object is an MemoryManager<T>
+        // else, _object is a T[] or string.
+        //     if (_length >> 31) == 1, _object is a pre-pinned array, so Pin() will not allocate a new GCHandle
+        //     else, Pin() needs to allocate a new GCHandle to pin the object.
+        private readonly object _object;
+        private readonly int _index;
+        private readonly int _length;
+
+        internal const int RemoveFlagsBitMask = 0x7FFFFFFF;
+
+        /// <summary>
+        /// Creates a new memory over the entirety of the target array.
+        /// </summary>
+        /// <param name="array">The target array.</param>
+        /// <remarks>Returns default when <paramref name="array"/> is null.</remarks>
+        /// <exception cref="System.ArrayTypeMismatchException">Thrown when <paramref name="array"/> is covariant and array's type is not exactly T[].</exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ReadOnlyMemory(T[] array)
+        {
+            if (array == null)
+            {
+                this = default;
+                return; // returns default
+            }
+
+            _object = array;
+            _index = 0;
+            _length = array.Length;
+        }
+
+        /// <summary>
+        /// Creates a new memory over the portion of the target array beginning
+        /// at 'start' index and ending at 'end' index (exclusive).
+        /// </summary>
+        /// <param name="array">The target array.</param>
+        /// <param name="start">The index at which to begin the memory.</param>
+        /// <param name="length">The number of items in the memory.</param>
+        /// <remarks>Returns default when <paramref name="array"/> is null.</remarks>
+        /// <exception cref="System.ArrayTypeMismatchException">Thrown when <paramref name="array"/> is covariant and array's type is not exactly T[].</exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in the range (&lt;0 or &gt;=Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ReadOnlyMemory(T[] array, int start, int length)
+        {
+            if (array == null)
+            {
+                if (start != 0 || length != 0)
+                    ThrowHelper.ThrowArgumentOutOfRangeException();
+                this = default;
+                return; // returns default
+            }
+            if ((uint)start > (uint)array.Length || (uint)length > (uint)(array.Length - start))
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            _object = array;
+            _index = start;
+            _length = length;
+        }
+
+        /// <summary>Creates a new memory over the existing object, start, and length. No validation is performed.</summary>
+        /// <param name="obj">The target object.</param>
+        /// <param name="start">The index at which to begin the memory.</param>
+        /// <param name="length">The number of items in the memory.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal ReadOnlyMemory(object obj, int start, int length)
+        {
+            // No validation performed; caller must provide any necessary validation.
+            _object = obj;
+            _index = start;
+            _length = length;
+        }
+
+        /// <summary>
+        /// Defines an implicit conversion of an array to a <see cref="ReadOnlyMemory{T}"/>
+        /// </summary>
+        public static implicit operator ReadOnlyMemory<T>(T[] array) => new ReadOnlyMemory<T>(array);
+
+        /// <summary>
+        /// Defines an implicit conversion of a <see cref="ArraySegment{T}"/> to a <see cref="ReadOnlyMemory{T}"/>
+        /// </summary>
+        public static implicit operator ReadOnlyMemory<T>(ArraySegment<T> segment) => new ReadOnlyMemory<T>(segment.Array, segment.Offset, segment.Count);
+
+        /// <summary>
+        /// Returns an empty <see cref="ReadOnlyMemory{T}"/>
+        /// </summary>
+        public static ReadOnlyMemory<T> Empty => default;
+
+        /// <summary>
+        /// The number of items in the memory.
+        /// </summary>
+        public int Length => _length & RemoveFlagsBitMask;
+
+        /// <summary>
+        /// Returns true if Length is 0.
+        /// </summary>
+        public bool IsEmpty => (_length & RemoveFlagsBitMask) == 0;
+
+        /// <summary>
+        /// For <see cref="ReadOnlyMemory{Char}"/>, returns a new instance of string that represents the characters pointed to by the memory.
+        /// Otherwise, returns a <see cref="string"/> with the name of the type and the number of elements.
+        /// </summary>
+        public override string ToString()
+        {
+            if (typeof(T) == typeof(char))
+            {
+                return (_object is string str) ? str.Substring(_index, _length & RemoveFlagsBitMask) : Span.ToString();
+            }
+            return string.Format("System.ReadOnlyMemory<{0}>[{1}]", typeof(T).Name, _length & RemoveFlagsBitMask);
+        }
+
+        /// <summary>
+        /// Forms a slice out of the given memory, beginning at 'start'.
+        /// </summary>
+        /// <param name="start">The index at which to begin this slice.</param>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> index is not in range (&lt;0 or &gt;=Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ReadOnlyMemory<T> Slice(int start)
+        {
+            // Used to maintain the high-bit which indicates whether the Memory has been pre-pinned or not.
+            int capturedLength = _length;
+            int actualLength = capturedLength & RemoveFlagsBitMask;
+            if ((uint)start > (uint)actualLength)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+            }
+
+            // It is expected for (capturedLength - start) to be negative if the memory is already pre-pinned.
+            return new ReadOnlyMemory<T>(_object, _index + start, capturedLength - start);
+        }
+
+        /// <summary>
+        /// Forms a slice out of the given memory, beginning at 'start', of given length
+        /// </summary>
+        /// <param name="start">The index at which to begin this slice.</param>
+        /// <param name="length">The desired length for the slice (exclusive).</param>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in range (&lt;0 or &gt;=Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ReadOnlyMemory<T> Slice(int start, int length)
+        {
+            // Used to maintain the high-bit which indicates whether the Memory has been pre-pinned or not.
+            int capturedLength = _length;
+            int actualLength = _length & RemoveFlagsBitMask;
+            if ((uint)start > (uint)actualLength || (uint)length > (uint)(actualLength - start))
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
+            }
+
+            // Set the high-bit to match the this._length high bit (1 for pre-pinned, 0 for unpinned).
+            return new ReadOnlyMemory<T>(_object, _index + start, length | (capturedLength & ~RemoveFlagsBitMask));
+        }
+
+        /// <summary>
+        /// Returns a span from the memory.
+        /// </summary>
+        public ReadOnlySpan<T> Span
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                if (_index < 0)
+                {
+                    Debug.Assert(_length >= 0);
+                    Debug.Assert(_object != null);
+                    return ((MemoryManager<T>)_object).GetSpan().Slice(_index & RemoveFlagsBitMask, _length);
+                }
+                else if (typeof(T) == typeof(char) && _object is string s)
+                {
+                    Debug.Assert(_length >= 0);
+#if FEATURE_PORTABLE_SPAN
+                    return new ReadOnlySpan<T>(Unsafe.As<Pinnable<T>>(s), MemoryExtensions.StringAdjustment, s.Length).Slice(_index, _length);
+#else
+                    return new ReadOnlySpan<T>(ref Unsafe.As<char, T>(ref s.GetRawStringData()), s.Length).Slice(_index, _length);
+#endif // FEATURE_PORTABLE_SPAN
+                }
+                else if (_object != null)
+                {
+                    return new ReadOnlySpan<T>((T[])_object, _index, _length & RemoveFlagsBitMask);
+                }
+                else
+                {
+                    return default;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Copies the contents of the read-only memory into the destination. If the source
+        /// and destination overlap, this method behaves as if the original values are in
+        /// a temporary location before the destination is overwritten.
+        ///
+        /// <param name="destination">The Memory to copy items into.</param>
+        /// <exception cref="System.ArgumentException">
+        /// Thrown when the destination is shorter than the source.
+        /// </exception>
+        /// </summary>
+        public void CopyTo(Memory<T> destination) => Span.CopyTo(destination.Span);
+
+        /// <summary>
+        /// Copies the contents of the readonly-only memory into the destination. If the source
+        /// and destination overlap, this method behaves as if the original values are in
+        /// a temporary location before the destination is overwritten.
+        ///
+        /// <returns>If the destination is shorter than the source, this method
+        /// return false and no data is written to the destination.</returns>
+        /// </summary>
+        /// <param name="destination">The span to copy items into.</param>
+        public bool TryCopyTo(Memory<T> destination) => Span.TryCopyTo(destination.Span);
+
+        /// <summary>
+        /// Creates a handle for the memory.
+        /// The GC will not move the memory until the returned <see cref="MemoryHandle"/>
+        /// is disposed, enabling taking and using the memory's address.
+        /// <exception cref="System.ArgumentException">
+        /// An instance with nonprimitive (non-blittable) members cannot be pinned.
+        /// </exception>
+        /// </summary>
+        public unsafe MemoryHandle Pin()
+        {
+            if (_index < 0)
+            {
+                Debug.Assert(_object != null);
+                return ((MemoryManager<T>)_object).Pin((_index & RemoveFlagsBitMask));
+            }
+            else if (typeof(T) == typeof(char) && _object is string s)
+            {
+                GCHandle handle = GCHandle.Alloc(s, GCHandleType.Pinned);
+#if FEATURE_PORTABLE_SPAN
+                void* pointer = Unsafe.Add<T>((void*)handle.AddrOfPinnedObject(), _index);
+#else
+                void* pointer = Unsafe.Add<T>(Unsafe.AsPointer(ref s.GetRawStringData()), _index);
+#endif // FEATURE_PORTABLE_SPAN
+                return new MemoryHandle(pointer, handle);
+            }
+            else if (_object is T[] array)
+            {
+                // Array is already pre-pinned
+                if (_length < 0)
+                {
+#if FEATURE_PORTABLE_SPAN
+                    void* pointer = Unsafe.Add<T>(Unsafe.AsPointer(ref MemoryMarshal.GetReference<T>(array)), _index);
+#else
+                    void* pointer = Unsafe.Add<T>(Unsafe.AsPointer(ref array.GetRawSzArrayData()), _index);
+#endif // FEATURE_PORTABLE_SPAN
+                    return new MemoryHandle(pointer);
+                }
+                else
+                {
+                    GCHandle handle = GCHandle.Alloc(array, GCHandleType.Pinned);
+#if FEATURE_PORTABLE_SPAN
+                    void* pointer = Unsafe.Add<T>((void*)handle.AddrOfPinnedObject(), _index);
+#else
+                    void* pointer = Unsafe.Add<T>(Unsafe.AsPointer(ref array.GetRawSzArrayData()), _index);
+#endif // FEATURE_PORTABLE_SPAN
+                    return new MemoryHandle(pointer, handle);
+                }
+            }
+            return default;
+        }
+
+        /// <summary>
+        /// Copies the contents from the memory into a new array.  This heap
+        /// allocates, so should generally be avoided, however it is sometimes
+        /// necessary to bridge the gap with APIs written in terms of arrays.
+        /// </summary>
+        public T[] ToArray() => Span.ToArray();
+
+        /// <summary>Determines whether the specified object is equal to the current object.</summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public override bool Equals(object obj)
+        {
+            if (obj is ReadOnlyMemory<T> readOnlyMemory)
+            {
+                return Equals(readOnlyMemory);
+            }
+            else if (obj is Memory<T> memory)
+            {
+                return Equals(memory);
+            }
+            else
+            {
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// Returns true if the memory points to the same array and has the same length.  Note that
+        /// this does *not* check to see if the *contents* are equal.
+        /// </summary>
+        public bool Equals(ReadOnlyMemory<T> other)
+        {
+            return
+                _object == other._object &&
+                _index == other._index &&
+                _length == other._length;
+        }
+
+        /// <summary>Returns the hash code for this <see cref="ReadOnlyMemory{T}"/></summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public override int GetHashCode()
+        {
+            return _object != null ? CombineHashCodes(_object.GetHashCode(), _index.GetHashCode(), _length.GetHashCode()) : 0;
+        }
+
+        private static int CombineHashCodes(int left, int right)
+        {
+            return ((left << 5) + left) ^ right;
+        }
+
+        private static int CombineHashCodes(int h1, int h2, int h3)
+        {
+            return CombineHashCodes(CombineHashCodes(h1, h2), h3);
+        }
+
+        /// <summary>Gets the state of the memory as individual fields.</summary>
+        /// <param name="start">The offset.</param>
+        /// <param name="length">The count.</param>
+        /// <returns>The object.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal object GetObjectStartLength(out int start, out int length)
+        {
+            start = _index;
+            length = _length;
+            return _object;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ReadOnlySpan.Fast.cs b/src/System.Private.CoreLib/shared/System/ReadOnlySpan.Fast.cs
new file mode 100644
index 0000000000..38d62dcfa8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ReadOnlySpan.Fast.cs
@@ -0,0 +1,277 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+using Internal.Runtime.CompilerServices;
+
+#pragma warning disable 0809  //warning CS0809: Obsolete member 'Span<T>.Equals(object)' overrides non-obsolete member 'object.Equals(object)'
+
+#if BIT64
+using nuint = System.UInt64;
+#else
+using nuint = System.UInt32;
+#endif
+
+namespace System
+{
+    /// <summary>
+    /// ReadOnlySpan represents a contiguous region of arbitrary memory. Unlike arrays, it can point to either managed
+    /// or native memory, or to memory allocated on the stack. It is type- and memory-safe.
+    /// </summary>
+    [DebuggerTypeProxy(typeof(SpanDebugView<>))]
+    [DebuggerDisplay("{ToString(),raw}")]
+    [NonVersionable]
+    public readonly ref partial struct ReadOnlySpan<T>
+    {
+        /// <summary>A byref or a native ptr.</summary>
+        internal readonly ByReference<T> _pointer;
+        /// <summary>The number of elements this ReadOnlySpan contains.</summary>
+#if PROJECTN
+        [Bound]
+#endif
+        private readonly int _length;
+
+        /// <summary>
+        /// Creates a new read-only span over the entirety of the target array.
+        /// </summary>
+        /// <param name="array">The target array.</param>
+        /// <remarks>Returns default when <paramref name="array"/> is null.</remarks>
+        /// reference (Nothing in Visual Basic).</exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ReadOnlySpan(T[] array)
+        {
+            if (array == null)
+            {
+                this = default;
+                return; // returns default
+            }
+
+            _pointer = new ByReference<T>(ref Unsafe.As<byte, T>(ref array.GetRawSzArrayData()));
+            _length = array.Length;
+        }
+
+        /// <summary>
+        /// Creates a new read-only span over the portion of the target array beginning
+        /// at 'start' index and ending at 'end' index (exclusive).
+        /// </summary>
+        /// <param name="array">The target array.</param>
+        /// <param name="start">The index at which to begin the read-only span.</param>
+        /// <param name="length">The number of items in the read-only span.</param>
+        /// <remarks>Returns default when <paramref name="array"/> is null.</remarks>
+        /// reference (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in the range (&lt;0 or &gt;=Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ReadOnlySpan(T[] array, int start, int length)
+        {
+            if (array == null)
+            {
+                if (start != 0 || length != 0)
+                    ThrowHelper.ThrowArgumentOutOfRangeException();
+                this = default;
+                return; // returns default
+            }
+            if ((uint)start > (uint)array.Length || (uint)length > (uint)(array.Length - start))
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            _pointer = new ByReference<T>(ref Unsafe.Add(ref Unsafe.As<byte, T>(ref array.GetRawSzArrayData()), start));
+            _length = length;
+        }
+
+        /// <summary>
+        /// Creates a new read-only span over the target unmanaged buffer.  Clearly this
+        /// is quite dangerous, because we are creating arbitrarily typed T's
+        /// out of a void*-typed block of memory.  And the length is not checked.
+        /// But if this creation is correct, then all subsequent uses are correct.
+        /// </summary>
+        /// <param name="pointer">An unmanaged pointer to memory.</param>
+        /// <param name="length">The number of <typeparamref name="T"/> elements the memory contains.</param>
+        /// <exception cref="System.ArgumentException">
+        /// Thrown when <typeparamref name="T"/> is reference type or contains pointers and hence cannot be stored in unmanaged memory.
+        /// </exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="length"/> is negative.
+        /// </exception>
+        [CLSCompliant(false)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public unsafe ReadOnlySpan(void* pointer, int length)
+        {
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+                ThrowHelper.ThrowInvalidTypeWithPointersNotSupported(typeof(T));
+            if (length < 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            _pointer = new ByReference<T>(ref Unsafe.As<byte, T>(ref *(byte*)pointer));
+            _length = length;
+        }
+
+        // Constructor for internal use only.
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal ReadOnlySpan(ref T ptr, int length)
+        {
+            Debug.Assert(length >= 0);
+
+            _pointer = new ByReference<T>(ref ptr);
+            _length = length;
+        }
+
+        /// <summary>
+        /// Returns the specified element of the read-only span.
+        /// </summary>
+        /// <param name="index"></param>
+        /// <returns></returns>
+        /// <exception cref="System.IndexOutOfRangeException">
+        /// Thrown when index less than 0 or index greater than or equal to Length
+        /// </exception>
+        public ref readonly T this[int index]
+        {
+#if PROJECTN
+            [BoundsChecking]
+            get
+            {
+                return ref Unsafe.Add(ref _pointer.Value, index);
+            }
+#else
+            [Intrinsic]
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            [NonVersionable]
+            get
+            {
+                if ((uint)index >= (uint)_length)
+                    ThrowHelper.ThrowIndexOutOfRangeException();
+                return ref Unsafe.Add(ref _pointer.Value, index);
+            }
+#endif
+        }
+
+        /// <summary>
+        /// Returns a reference to the 0th element of the Span. If the Span is empty, returns null reference.
+        /// It can be used for pinning and is required to support the use of span within a fixed statement.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public unsafe ref readonly T GetPinnableReference() => ref (_length != 0) ? ref _pointer.Value : ref Unsafe.AsRef<T>(null);
+
+        /// <summary>
+        /// Copies the contents of this read-only span into destination span. If the source
+        /// and destinations overlap, this method behaves as if the original values in
+        /// a temporary location before the destination is overwritten.
+        ///
+        /// <param name="destination">The span to copy items into.</param>
+        /// <exception cref="System.ArgumentException">
+        /// Thrown when the destination Span is shorter than the source Span.
+        /// </exception>
+        /// </summary>
+        public void CopyTo(Span<T> destination)
+        {
+            // Using "if (!TryCopyTo(...))" results in two branches: one for the length
+            // check, and one for the result of TryCopyTo. Since these checks are equivalent,
+            // we can optimize by performing the check once ourselves then calling Memmove directly.
+
+            if ((uint)_length <= (uint)destination.Length)
+            {
+                Buffer.Memmove(ref destination._pointer.Value, ref _pointer.Value, (nuint)_length);
+            }
+            else
+            {
+                ThrowHelper.ThrowArgumentException_DestinationTooShort();
+            }
+        }
+
+        /// Copies the contents of this read-only span into destination span. If the source
+        /// and destinations overlap, this method behaves as if the original values in
+        /// a temporary location before the destination is overwritten.
+        /// </summary>
+        /// <returns>If the destination span is shorter than the source span, this method
+        /// return false and no data is written to the destination.</returns>
+        /// <param name="destination">The span to copy items into.</param>
+        public bool TryCopyTo(Span<T> destination)
+        {
+            bool retVal = false;
+            if ((uint)_length <= (uint)destination.Length)
+            {
+                Buffer.Memmove(ref destination._pointer.Value, ref _pointer.Value, (nuint)_length);
+                retVal = true;
+            }
+            return retVal;
+        }
+
+        /// <summary>
+        /// Returns true if left and right point at the same memory and have the same length.  Note that
+        /// this does *not* check to see if the *contents* are equal.
+        /// </summary>
+        public static bool operator ==(ReadOnlySpan<T> left, ReadOnlySpan<T> right)
+        {
+            return left._length == right._length && Unsafe.AreSame<T>(ref left._pointer.Value, ref right._pointer.Value);
+        }
+
+        /// <summary>
+        /// For <see cref="ReadOnlySpan{Char}"/>, returns a new instance of string that represents the characters pointed to by the span.
+        /// Otherwise, returns a <see cref="String"/> with the name of the type and the number of elements.
+        /// </summary>
+        public override string ToString()
+        {
+            if (typeof(T) == typeof(char))
+            {
+                unsafe
+                {
+                    fixed (char* src = &Unsafe.As<T, char>(ref _pointer.Value))
+                        return new string(src, 0, _length);
+                }
+            }
+            return string.Format("System.ReadOnlySpan<{0}>[{1}]", typeof(T).Name, _length);
+        }
+
+        /// <summary>
+        /// Forms a slice out of the given read-only span, beginning at 'start'.
+        /// </summary>
+        /// <param name="start">The index at which to begin this slice.</param>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> index is not in range (&lt;0 or &gt;=Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ReadOnlySpan<T> Slice(int start)
+        {
+            if ((uint)start > (uint)_length)
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            return new ReadOnlySpan<T>(ref Unsafe.Add(ref _pointer.Value, start), _length - start);
+        }
+
+        /// <summary>
+        /// Forms a slice out of the given read-only span, beginning at 'start', of given length
+        /// </summary>
+        /// <param name="start">The index at which to begin this slice.</param>
+        /// <param name="length">The desired length for the slice (exclusive).</param>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in range (&lt;0 or &gt;=Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ReadOnlySpan<T> Slice(int start, int length)
+        {
+            if ((uint)start > (uint)_length || (uint)length > (uint)(_length - start))
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            return new ReadOnlySpan<T>(ref Unsafe.Add(ref _pointer.Value, start), length);
+        }
+
+        /// <summary>
+        /// Copies the contents of this read-only span into a new array.  This heap
+        /// allocates, so should generally be avoided, however it is sometimes
+        /// necessary to bridge the gap with APIs written in terms of arrays.
+        /// </summary>
+        public T[] ToArray()
+        {
+            if (_length == 0)
+                return Array.Empty<T>();
+
+            var destination = new T[_length];
+            Buffer.Memmove(ref Unsafe.As<byte, T>(ref destination.GetRawSzArrayData()), ref _pointer.Value, (nuint)_length);
+            return destination;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ReadOnlySpan.cs b/src/System.Private.CoreLib/shared/System/ReadOnlySpan.cs
new file mode 100644
index 0000000000..14b33e23f2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ReadOnlySpan.cs
@@ -0,0 +1,141 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+#if !FEATURE_PORTABLE_SPAN
+using System.Runtime.Versioning;
+#endif // !FEATURE_PORTABLE_SPAN
+
+#pragma warning disable 0809  //warning CS0809: Obsolete member 'Span<T>.Equals(object)' overrides non-obsolete member 'object.Equals(object)'
+
+namespace System
+{
+    /// <summary>
+    /// ReadOnlySpan represents a contiguous region of arbitrary memory. Unlike arrays, it can point to either managed
+    /// or native memory, or to memory allocated on the stack. It is type- and memory-safe.
+    /// </summary>
+    [DebuggerTypeProxy(typeof(SpanDebugView<>))]
+    [DebuggerDisplay("{ToString(),raw}")]
+    public readonly ref partial struct ReadOnlySpan<T>
+    {
+        /// <summary>
+        /// The number of items in the read-only span.
+        /// </summary>
+        public int Length
+        {
+#if !FEATURE_PORTABLE_SPAN
+            [NonVersionable]
+#endif // !FEATURE_PORTABLE_SPAN
+            get
+            {
+                return _length;
+            }
+        }
+
+        /// <summary>
+        /// Returns true if Length is 0.
+        /// </summary>
+        public bool IsEmpty
+        {
+#if !FEATURE_PORTABLE_SPAN
+            [NonVersionable]
+#endif // !FEATURE_PORTABLE_SPAN
+            get
+            {
+                return _length == 0;
+            }
+        }
+        /// <summary>
+        /// Returns false if left and right point at the same memory and have the same length.  Note that
+        /// this does *not* check to see if the *contents* are equal.
+        /// </summary>
+        public static bool operator !=(ReadOnlySpan<T> left, ReadOnlySpan<T> right) => !(left == right);
+
+        /// <summary>
+        /// This method is not supported as spans cannot be boxed. To compare two spans, use operator==.
+        /// <exception cref="System.NotSupportedException">
+        /// Always thrown by this method.
+        /// </exception>
+        /// </summary>
+        [Obsolete("Equals() on ReadOnlySpan will always throw an exception. Use == instead.")]
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public override bool Equals(object obj)
+        {
+            throw new NotSupportedException(SR.NotSupported_CannotCallEqualsOnSpan);
+        }
+
+        /// <summary>
+        /// This method is not supported as spans cannot be boxed.
+        /// <exception cref="System.NotSupportedException">
+        /// Always thrown by this method.
+        /// </exception>
+        /// </summary>
+        [Obsolete("GetHashCode() on ReadOnlySpan will always throw an exception.")]
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public override int GetHashCode()
+        {
+            throw new NotSupportedException(SR.NotSupported_CannotCallGetHashCodeOnSpan);
+        }
+
+        /// <summary>
+        /// Defines an implicit conversion of an array to a <see cref="ReadOnlySpan{T}"/>
+        /// </summary>
+        public static implicit operator ReadOnlySpan<T>(T[] array) => new ReadOnlySpan<T>(array);
+
+        /// <summary>
+        /// Defines an implicit conversion of a <see cref="ArraySegment{T}"/> to a <see cref="ReadOnlySpan{T}"/>
+        /// </summary>
+        public static implicit operator ReadOnlySpan<T>(ArraySegment<T> segment)
+            => new ReadOnlySpan<T>(segment.Array, segment.Offset, segment.Count);
+
+        /// <summary>
+        /// Returns a 0-length read-only span whose base is the null pointer.
+        /// </summary>
+        public static ReadOnlySpan<T> Empty => default(ReadOnlySpan<T>);
+
+        /// <summary>Gets an enumerator for this span.</summary>
+        public Enumerator GetEnumerator() => new Enumerator(this);
+
+        /// <summary>Enumerates the elements of a <see cref="ReadOnlySpan{T}"/>.</summary>
+        public ref struct Enumerator
+        {
+            /// <summary>The span being enumerated.</summary>
+            private readonly ReadOnlySpan<T> _span;
+            /// <summary>The next index to yield.</summary>
+            private int _index;
+
+            /// <summary>Initialize the enumerator.</summary>
+            /// <param name="span">The span to enumerate.</param>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            internal Enumerator(ReadOnlySpan<T> span)
+            {
+                _span = span;
+                _index = -1;
+            }
+
+            /// <summary>Advances the enumerator to the next element of the span.</summary>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            public bool MoveNext()
+            {
+                int index = _index + 1;
+                if (index < _span.Length)
+                {
+                    _index = index;
+                    return true;
+                }
+
+                return false;
+            }
+
+            /// <summary>Gets the element at the current position of the enumerator.</summary>
+            public ref readonly T Current
+            {
+                [MethodImpl(MethodImplOptions.AggressiveInlining)]
+                get => ref _span[_index];
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AmbiguousMatchException.cs b/src/System.Private.CoreLib/shared/System/Reflection/AmbiguousMatchException.cs
new file mode 100644
index 0000000000..643a127c49
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AmbiguousMatchException.cs
@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Reflection
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class AmbiguousMatchException : SystemException
+    {
+        public AmbiguousMatchException()
+            : base(SR.RFLCT_Ambiguous)
+        {
+            HResult = HResults.COR_E_AMBIGUOUSMATCH;
+        }
+
+        public AmbiguousMatchException(string message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_AMBIGUOUSMATCH;
+        }
+
+        public AmbiguousMatchException(string message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_AMBIGUOUSMATCH;
+        }
+
+        internal AmbiguousMatchException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/Assembly.cs b/src/System.Private.CoreLib/shared/System/Reflection/Assembly.cs
new file mode 100644
index 0000000000..7280869c02
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/Assembly.cs
@@ -0,0 +1,201 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.IO;
+using System.Globalization;
+using System.Collections.Generic;
+using System.Configuration.Assemblies;
+using System.Runtime.Serialization;
+using System.Security;
+
+namespace System.Reflection
+{
+    public abstract partial class Assembly : ICustomAttributeProvider, ISerializable
+    {
+        protected Assembly() { }
+
+        public virtual IEnumerable<TypeInfo> DefinedTypes
+        {
+            get
+            {
+                Type[] types = GetTypes();
+                TypeInfo[] typeinfos = new TypeInfo[types.Length];
+                for (int i = 0; i < types.Length; i++)
+                {
+                    TypeInfo typeinfo = types[i].GetTypeInfo();
+                    if (typeinfo == null)
+                        throw new NotSupportedException(SR.Format(SR.NotSupported_NoTypeInfo, types[i].FullName));
+
+                    typeinfos[i] = typeinfo;
+                }
+                return typeinfos;
+            }
+        }
+
+        public virtual Type[] GetTypes()
+        {
+            Module[] m = GetModules(false);
+
+            int finalLength = 0;
+            Type[][] moduleTypes = new Type[m.Length][];
+
+            for (int i = 0; i < moduleTypes.Length; i++)
+            {
+                moduleTypes[i] = m[i].GetTypes();
+                finalLength += moduleTypes[i].Length;
+            }
+
+            int current = 0;
+            Type[] ret = new Type[finalLength];
+            for (int i = 0; i < moduleTypes.Length; i++)
+            {
+                int length = moduleTypes[i].Length;
+                Array.Copy(moduleTypes[i], 0, ret, current, length);
+                current += length;
+            }
+
+            return ret;
+        }
+
+        public virtual IEnumerable<Type> ExportedTypes => GetExportedTypes();
+        public virtual Type[] GetExportedTypes() { throw NotImplemented.ByDesign; }
+        public virtual Type[] GetForwardedTypes() { throw NotImplemented.ByDesign; }
+
+        public virtual string CodeBase { get { throw NotImplemented.ByDesign; } }
+        public virtual MethodInfo EntryPoint { get { throw NotImplemented.ByDesign; } }
+        public virtual string FullName { get { throw NotImplemented.ByDesign; } }
+        public virtual string ImageRuntimeVersion { get { throw NotImplemented.ByDesign; } }
+        public virtual bool IsDynamic => false;
+        public virtual string Location { get { throw NotImplemented.ByDesign; } }
+        public virtual bool ReflectionOnly { get { throw NotImplemented.ByDesign; } }
+
+        public virtual ManifestResourceInfo GetManifestResourceInfo(string resourceName) { throw NotImplemented.ByDesign; }
+        public virtual string[] GetManifestResourceNames() { throw NotImplemented.ByDesign; }
+        public virtual Stream GetManifestResourceStream(string name) { throw NotImplemented.ByDesign; }
+        public virtual Stream GetManifestResourceStream(Type type, string name) { throw NotImplemented.ByDesign; }
+
+        public bool IsFullyTrusted => true;
+
+        public virtual AssemblyName GetName() => GetName(copiedName: false);
+        public virtual AssemblyName GetName(bool copiedName) { throw NotImplemented.ByDesign; }
+
+        public virtual Type GetType(string name) => GetType(name, throwOnError: false, ignoreCase: false);
+        public virtual Type GetType(string name, bool throwOnError) => GetType(name, throwOnError: throwOnError, ignoreCase: false);
+        public virtual Type GetType(string name, bool throwOnError, bool ignoreCase) { throw NotImplemented.ByDesign; }
+
+        public virtual bool IsDefined(Type attributeType, bool inherit) { throw NotImplemented.ByDesign; }
+
+        public virtual IEnumerable<CustomAttributeData> CustomAttributes => GetCustomAttributesData();
+        public virtual IList<CustomAttributeData> GetCustomAttributesData() { throw NotImplemented.ByDesign; }
+
+        public virtual object[] GetCustomAttributes(bool inherit) { throw NotImplemented.ByDesign; }
+        public virtual object[] GetCustomAttributes(Type attributeType, bool inherit) { throw NotImplemented.ByDesign; }
+
+        public virtual string EscapedCodeBase => AssemblyName.EscapeCodeBase(CodeBase);
+
+        public object CreateInstance(string typeName) => CreateInstance(typeName, false, BindingFlags.Public | BindingFlags.Instance, binder: null, args: null, culture: null, activationAttributes: null);
+        public object CreateInstance(string typeName, bool ignoreCase) => CreateInstance(typeName, ignoreCase, BindingFlags.Public | BindingFlags.Instance, binder: null, args: null, culture: null, activationAttributes: null);
+        public virtual object CreateInstance(string typeName, bool ignoreCase, BindingFlags bindingAttr, Binder binder, object[] args, CultureInfo culture, object[] activationAttributes)
+        {
+            Type t = GetType(typeName, throwOnError: false, ignoreCase: ignoreCase);
+            if (t == null)
+                return null;
+
+            return Activator.CreateInstance(t, bindingAttr, binder, args, culture, activationAttributes);
+        }
+
+        public virtual event ModuleResolveEventHandler ModuleResolve { add { throw NotImplemented.ByDesign; } remove { throw NotImplemented.ByDesign; } }
+
+        public virtual Module ManifestModule { get { throw NotImplemented.ByDesign; } }
+        public virtual Module GetModule(string name) { throw NotImplemented.ByDesign; }
+
+        public Module[] GetModules() => GetModules(getResourceModules: false);
+        public virtual Module[] GetModules(bool getResourceModules) { throw NotImplemented.ByDesign; }
+
+        public virtual IEnumerable<Module> Modules => GetLoadedModules(getResourceModules: true);
+        public Module[] GetLoadedModules() => GetLoadedModules(getResourceModules: false);
+        public virtual Module[] GetLoadedModules(bool getResourceModules) { throw NotImplemented.ByDesign; }
+
+        public virtual AssemblyName[] GetReferencedAssemblies() { throw NotImplemented.ByDesign; }
+
+        public virtual Assembly GetSatelliteAssembly(CultureInfo culture) { throw NotImplemented.ByDesign; }
+        public virtual Assembly GetSatelliteAssembly(CultureInfo culture, Version version) { throw NotImplemented.ByDesign; }
+
+        public virtual FileStream GetFile(string name) { throw NotImplemented.ByDesign; }
+        public virtual FileStream[] GetFiles() => GetFiles(getResourceModules: false);
+        public virtual FileStream[] GetFiles(bool getResourceModules) { throw NotImplemented.ByDesign; }
+
+        public virtual void GetObjectData(SerializationInfo info, StreamingContext context) { throw NotImplemented.ByDesign; }
+
+        public override string ToString()
+        {
+            string displayName = FullName;
+            if (displayName == null)
+                return base.ToString();
+            else
+                return displayName;
+        }
+
+        /*
+          Returns true if the assembly was loaded from the global assembly cache.
+        */
+        public virtual bool GlobalAssemblyCache { get { throw NotImplemented.ByDesign; } }
+        public virtual Int64 HostContext { get { throw NotImplemented.ByDesign; } }
+
+        public override bool Equals(object o) => base.Equals(o);
+        public override int GetHashCode() => base.GetHashCode();
+
+        public static bool operator ==(Assembly left, Assembly right)
+        {
+            if (object.ReferenceEquals(left, right))
+                return true;
+
+            if ((object)left == null || (object)right == null)
+                return false;
+
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(Assembly left, Assembly right)
+        {
+            return !(left == right);
+        }
+
+        public static string CreateQualifiedName(string assemblyName, string typeName) => typeName + ", " + assemblyName;
+
+        public static Assembly GetAssembly(Type type)
+        {
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+
+            Module m = type.Module;
+            if (m == null)
+                return null;
+            else
+                return m.Assembly;
+        }
+
+        public static Assembly Load(byte[] rawAssembly) => Load(rawAssembly, rawSymbolStore: null);
+
+        [Obsolete("This method has been deprecated. Please use Assembly.Load() instead. http://go.microsoft.com/fwlink/?linkid=14202")]
+        public static Assembly LoadWithPartialName(string partialName)
+        {
+            if (partialName == null)
+                throw new ArgumentNullException(nameof(partialName));
+
+            return Load(partialName);
+        }
+
+        public static Assembly UnsafeLoadFrom(string assemblyFile) => LoadFrom(assemblyFile);
+
+        public Module LoadModule(string moduleName, byte[] rawModule) => LoadModule(moduleName, rawModule, null);
+        public virtual Module LoadModule(string moduleName, byte[] rawModule, byte[] rawSymbolStore) { throw NotImplemented.ByDesign; }
+
+        public static Assembly ReflectionOnlyLoad(byte[] rawAssembly) { throw new PlatformNotSupportedException(SR.PlatformNotSupported_ReflectionOnly); }
+        public static Assembly ReflectionOnlyLoad(string assemblyString) { throw new PlatformNotSupportedException(SR.PlatformNotSupported_ReflectionOnly); }
+        public static Assembly ReflectionOnlyLoadFrom(string assemblyFile) { throw new PlatformNotSupportedException(SR.PlatformNotSupported_ReflectionOnly); }
+
+        public virtual SecurityRuleSet SecurityRuleSet => SecurityRuleSet.None;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyAlgorithmIdAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyAlgorithmIdAttribute.cs
new file mode 100644
index 0000000000..fe24f353be
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyAlgorithmIdAttribute.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Configuration.Assemblies;
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyAlgorithmIdAttribute : Attribute
+    {
+        public AssemblyAlgorithmIdAttribute(AssemblyHashAlgorithm algorithmId)
+        {
+            AlgorithmId = (uint)algorithmId;
+        }
+
+        [CLSCompliant(false)]
+        public AssemblyAlgorithmIdAttribute(uint algorithmId)
+        {
+            AlgorithmId = algorithmId;
+        }
+
+        [CLSCompliant(false)]
+        public uint AlgorithmId { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyCompanyAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyCompanyAttribute.cs
new file mode 100644
index 0000000000..d986db60a3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyCompanyAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyCompanyAttribute : Attribute
+    {
+        public AssemblyCompanyAttribute(string company)
+        {
+            Company = company;
+        }
+
+        public string Company { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyConfigurationAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyConfigurationAttribute.cs
new file mode 100644
index 0000000000..195c4d0ca6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyConfigurationAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyConfigurationAttribute : Attribute
+    {
+        public AssemblyConfigurationAttribute(string configuration)
+        {
+            Configuration = configuration;
+        }
+
+        public string Configuration { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyContentType.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyContentType.cs
new file mode 100644
index 0000000000..2ee1a00818
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyContentType.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public enum AssemblyContentType
+    {
+        Default = 0,
+        WindowsRuntime = 1,
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyCopyrightAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyCopyrightAttribute.cs
new file mode 100644
index 0000000000..e50e19932b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyCopyrightAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyCopyrightAttribute : Attribute
+    {
+        public AssemblyCopyrightAttribute(string copyright)
+        {
+            Copyright = copyright;
+        }
+
+        public string Copyright { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyCultureAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyCultureAttribute.cs
new file mode 100644
index 0000000000..e31c6f9c1c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyCultureAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyCultureAttribute : Attribute
+    {
+        public AssemblyCultureAttribute(string culture)
+        {
+            Culture = culture;
+        }
+
+        public string Culture { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyDefaultAliasAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyDefaultAliasAttribute.cs
new file mode 100644
index 0000000000..ced35ed3fd
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyDefaultAliasAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyDefaultAliasAttribute : Attribute
+    {
+        public AssemblyDefaultAliasAttribute(string defaultAlias)
+        {
+            DefaultAlias = defaultAlias;
+        }
+
+        public string DefaultAlias { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyDelaySignAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyDelaySignAttribute.cs
new file mode 100644
index 0000000000..eae2cf613c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyDelaySignAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyDelaySignAttribute : Attribute
+    {
+        public AssemblyDelaySignAttribute(bool delaySign)
+        {
+            DelaySign = delaySign;
+        }
+
+        public bool DelaySign { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyDescriptionAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyDescriptionAttribute.cs
new file mode 100644
index 0000000000..50f57c96a6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyDescriptionAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyDescriptionAttribute : Attribute
+    {
+        public AssemblyDescriptionAttribute(string description)
+        {
+            Description = description;
+        }
+
+        public string Description { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyFileVersionAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyFileVersionAttribute.cs
new file mode 100644
index 0000000000..b5face65bc
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyFileVersionAttribute.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyFileVersionAttribute : Attribute
+    {
+        public AssemblyFileVersionAttribute(string version)
+        {
+            if (version == null)
+                throw new ArgumentNullException(nameof(version));
+            Version = version;
+        }
+
+        public string Version { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyFlagsAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyFlagsAttribute.cs
new file mode 100644
index 0000000000..103413340c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyFlagsAttribute.cs
@@ -0,0 +1,43 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyFlagsAttribute : Attribute
+    {
+        private AssemblyNameFlags _flags;
+
+        [Obsolete("This constructor has been deprecated. Please use AssemblyFlagsAttribute(AssemblyNameFlags) instead. http://go.microsoft.com/fwlink/?linkid=14202")]
+        [CLSCompliant(false)]
+        public AssemblyFlagsAttribute(uint flags)
+        {
+            _flags = (AssemblyNameFlags)flags;
+        }
+
+        [Obsolete("This property has been deprecated. Please use AssemblyFlags instead. http://go.microsoft.com/fwlink/?linkid=14202")]
+        [CLSCompliant(false)]
+        public uint Flags
+        {
+            get { return (uint)_flags; }
+        }
+
+        public int AssemblyFlags
+        {
+            get { return (int)_flags; }
+        }
+
+        [Obsolete("This constructor has been deprecated. Please use AssemblyFlagsAttribute(AssemblyNameFlags) instead. http://go.microsoft.com/fwlink/?linkid=14202")]
+        public AssemblyFlagsAttribute(int assemblyFlags)
+        {
+            _flags = (AssemblyNameFlags)assemblyFlags;
+        }
+
+        public AssemblyFlagsAttribute(AssemblyNameFlags assemblyFlags)
+        {
+            _flags = assemblyFlags;
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyInformationalVersionAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyInformationalVersionAttribute.cs
new file mode 100644
index 0000000000..915b973ab9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyInformationalVersionAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyInformationalVersionAttribute : Attribute
+    {
+        public AssemblyInformationalVersionAttribute(string informationalVersion)
+        {
+            InformationalVersion = informationalVersion;
+        }
+
+        public string InformationalVersion { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyKeyFileAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyKeyFileAttribute.cs
new file mode 100644
index 0000000000..9f7387d8af
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyKeyFileAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyKeyFileAttribute : Attribute
+    {
+        public AssemblyKeyFileAttribute(string keyFile)
+        {
+            KeyFile = keyFile;
+        }
+
+        public string KeyFile { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyKeyNameAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyKeyNameAttribute.cs
new file mode 100644
index 0000000000..4cf51754ea
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyKeyNameAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyKeyNameAttribute : Attribute
+    {
+        public AssemblyKeyNameAttribute(string keyName)
+        {
+            KeyName = keyName;
+        }
+
+        public string KeyName { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyMetadataAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyMetadataAttribute.cs
new file mode 100644
index 0000000000..de9f6351ec
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyMetadataAttribute.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true, Inherited = false)]
+    public sealed class AssemblyMetadataAttribute : Attribute
+    {
+        public AssemblyMetadataAttribute(string key, string value)
+        {
+            Key = key;
+            Value = value;
+        }
+
+        public string Key { get; }
+
+        public string Value { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyNameFlags.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyNameFlags.cs
new file mode 100644
index 0000000000..d321032031
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyNameFlags.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [Flags]
+    public enum AssemblyNameFlags
+    {
+        None = 0x0000,
+        // Flag used to indicate that an assembly ref contains the full public key, not the compressed token.
+        // Must match afPublicKey in CorHdr.h.
+        PublicKey = 0x0001,
+        //ProcArchMask              = 0x00F0,     // Bits describing the processor architecture
+        // Accessible via AssemblyName.ProcessorArchitecture
+        EnableJITcompileOptimizer = 0x4000,
+        EnableJITcompileTracking = 0x8000,
+        Retargetable = 0x0100,
+        //ContentType             = 0x0E00, // Bits describing the ContentType are accessible via AssemblyName.ContentType
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyNameFormatter.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyNameFormatter.cs
new file mode 100644
index 0000000000..716afb045c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyNameFormatter.cs
@@ -0,0 +1,156 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.IO;
+using System.Text;
+using System.Globalization;
+using System.Collections.Generic;
+
+namespace System.Reflection
+{
+    internal static class AssemblyNameFormatter
+    {
+        public static string ComputeDisplayName(string name, Version version, string cultureName, byte[] pkt, AssemblyNameFlags flags, AssemblyContentType contentType)
+        {
+            const int PUBLIC_KEY_TOKEN_LEN = 8;
+
+            if (name == string.Empty)
+                throw new FileLoadException();
+
+            StringBuilder sb = new StringBuilder();
+            if (name != null)
+            {
+                sb.AppendQuoted(name);
+            }
+
+            if (version != null)
+            {
+                Version canonicalizedVersion = version.CanonicalizeVersion();
+                if (canonicalizedVersion.Major != ushort.MaxValue)
+                {
+                    sb.Append(", Version=");
+                    sb.Append(canonicalizedVersion.Major);
+
+                    if (canonicalizedVersion.Minor != ushort.MaxValue)
+                    {
+                        sb.Append('.');
+                        sb.Append(canonicalizedVersion.Minor);
+
+                        if (canonicalizedVersion.Build != ushort.MaxValue)
+                        {
+                            sb.Append('.');
+                            sb.Append(canonicalizedVersion.Build);
+
+                            if (canonicalizedVersion.Revision != ushort.MaxValue)
+                            {
+                                sb.Append('.');
+                                sb.Append(canonicalizedVersion.Revision);
+                            }
+                        }
+                    }
+                }
+            }
+
+            if (cultureName != null)
+            {
+                if (cultureName == string.Empty)
+                    cultureName = "neutral";
+                sb.Append(", Culture=");
+                sb.AppendQuoted(cultureName);
+            }
+
+            if (pkt != null)
+            {
+                if (pkt.Length > PUBLIC_KEY_TOKEN_LEN)
+                    throw new ArgumentException();
+
+                sb.Append(", PublicKeyToken=");
+                if (pkt.Length == 0)
+                    sb.Append("null");
+                else
+                {
+                    foreach (byte b in pkt)
+                    {
+                        sb.Append(b.ToString("x2", CultureInfo.InvariantCulture));
+                    }
+                }
+            }
+
+            if (0 != (flags & AssemblyNameFlags.Retargetable))
+                sb.Append(", Retargetable=Yes");
+
+            if (contentType == AssemblyContentType.WindowsRuntime)
+                sb.Append(", ContentType=WindowsRuntime");
+
+            // NOTE: By design (desktop compat) AssemblyName.FullName and ToString() do not include ProcessorArchitecture.
+
+            return sb.ToString();
+        }
+
+        private static void AppendQuoted(this StringBuilder sb, string s)
+        {
+            bool needsQuoting = false;
+            const char quoteChar = '\"';
+
+            //@todo: App-compat: You can use double or single quotes to quote a name, and Fusion (or rather the IdentityAuthority) picks one
+            // by some algorithm. Rather than guess at it, I'll just use double-quote consistently.
+            if (s != s.Trim() || s.Contains('\"') || s.Contains('\''))
+                needsQuoting = true;
+
+            if (needsQuoting)
+                sb.Append(quoteChar);
+
+            for (int i = 0; i < s.Length; i++)
+            {
+                bool addedEscape = false;
+                foreach (KeyValuePair<char, string> kv in EscapeSequences)
+                {
+                    string escapeReplacement = kv.Value;
+                    if (!(s[i] == escapeReplacement[0]))
+                        continue;
+                    if ((s.Length - i) < escapeReplacement.Length)
+                        continue;
+                    string prefix = s.Substring(i, escapeReplacement.Length);
+                    if (prefix == escapeReplacement)
+                    {
+                        sb.Append('\\');
+                        sb.Append(kv.Key);
+                        addedEscape = true;
+                    }
+                }
+
+                if (!addedEscape)
+                    sb.Append(s[i]);
+            }
+
+            if (needsQuoting)
+                sb.Append(quoteChar);
+        }
+
+        private static Version CanonicalizeVersion(this Version version)
+        {
+            ushort major = (ushort)version.Major;
+            ushort minor = (ushort)version.Minor;
+            ushort build = (ushort)version.Build;
+            ushort revision = (ushort)version.Revision;
+
+            if (major == version.Major && minor == version.Minor && build == version.Build && revision == version.Revision)
+                return version;
+
+            return new Version(major, minor, build, revision);
+        }
+
+        public static KeyValuePair<char, string>[] EscapeSequences =
+        {
+            new KeyValuePair<char, string>('\\', "\\"),
+            new KeyValuePair<char, string>(',', ","),
+            new KeyValuePair<char, string>('=', "="),
+            new KeyValuePair<char, string>('\'', "'"),
+            new KeyValuePair<char, string>('\"', "\""),
+            new KeyValuePair<char, string>('n', Environment.NewLine),
+            new KeyValuePair<char, string>('t', "\t"),
+        };
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyProductAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyProductAttribute.cs
new file mode 100644
index 0000000000..43cb62df99
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyProductAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyProductAttribute : Attribute
+    {
+        public AssemblyProductAttribute(string product)
+        {
+            Product = product;
+        }
+
+        public string Product { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblySignatureKeyAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblySignatureKeyAttribute.cs
new file mode 100644
index 0000000000..e6ec8af1b3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblySignatureKeyAttribute.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false, AllowMultiple = false)]
+    public sealed class AssemblySignatureKeyAttribute : Attribute
+    {
+        public AssemblySignatureKeyAttribute(string publicKey, string countersignature)
+        {
+            PublicKey = publicKey;
+            Countersignature = countersignature;
+        }
+
+        public string PublicKey { get; }
+
+        public string Countersignature { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyTitleAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyTitleAttribute.cs
new file mode 100644
index 0000000000..26d7a2e66c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyTitleAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyTitleAttribute : Attribute
+    {
+        public AssemblyTitleAttribute(string title)
+        {
+            Title = title;
+        }
+
+        public string Title { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyTrademarkAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyTrademarkAttribute.cs
new file mode 100644
index 0000000000..1d3edf51d5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyTrademarkAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyTrademarkAttribute : Attribute
+    {
+        public AssemblyTrademarkAttribute(string trademark)
+        {
+            Trademark = trademark;
+        }
+
+        public string Trademark { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/AssemblyVersionAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyVersionAttribute.cs
new file mode 100644
index 0000000000..b3557bac97
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/AssemblyVersionAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class AssemblyVersionAttribute : Attribute
+    {
+        public AssemblyVersionAttribute(string version)
+        {
+            Version = version;
+        }
+
+        public string Version { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/Binder.cs b/src/System.Private.CoreLib/shared/System/Reflection/Binder.cs
new file mode 100644
index 0000000000..3dc5665d52
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/Binder.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+
+namespace System.Reflection
+{
+    public abstract class Binder
+    {
+        protected Binder() { }
+        public abstract FieldInfo BindToField(BindingFlags bindingAttr, FieldInfo[] match, object value, CultureInfo culture);
+        public abstract MethodBase BindToMethod(BindingFlags bindingAttr, MethodBase[] match, ref object[] args, ParameterModifier[] modifiers, CultureInfo culture, string[] names, out object state);
+        public abstract object ChangeType(object value, Type type, CultureInfo culture);
+        public abstract void ReorderArgumentArray(ref object[] args, object state);
+        public abstract MethodBase SelectMethod(BindingFlags bindingAttr, MethodBase[] match, Type[] types, ParameterModifier[] modifiers);
+        public abstract PropertyInfo SelectProperty(BindingFlags bindingAttr, PropertyInfo[] match, Type returnType, Type[] indexes, ParameterModifier[] modifiers);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/BindingFlags.cs b/src/System.Private.CoreLib/shared/System/Reflection/BindingFlags.cs
new file mode 100644
index 0000000000..7ba83e20da
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/BindingFlags.cs
@@ -0,0 +1,51 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [Flags]
+    public enum BindingFlags
+    {
+        // NOTES: We have lookup masks defined in RuntimeType and Activator.  If we
+        //    change the lookup values then these masks may need to change also.
+
+        // a place holder for no flag specifed
+        Default = 0x00,
+
+        // These flags indicate what to search for when binding
+        IgnoreCase = 0x01,          // Ignore the case of Names while searching
+        DeclaredOnly = 0x02,        // Only look at the members declared on the Type
+        Instance = 0x04,            // Include Instance members in search
+        Static = 0x08,              // Include Static members in search
+        Public = 0x10,              // Include Public members in search
+        NonPublic = 0x20,           // Include Non-Public members in search
+        FlattenHierarchy = 0x40,    // Rollup the statics into the class.
+
+        // These flags are used by InvokeMember to determine
+        // what type of member we are trying to Invoke.
+        // BindingAccess = 0xFF00;
+        InvokeMethod = 0x0100,
+        CreateInstance = 0x0200,
+        GetField = 0x0400,
+        SetField = 0x0800,
+        GetProperty = 0x1000,
+        SetProperty = 0x2000,
+
+        // These flags are also used by InvokeMember but they should only
+        // be used when calling InvokeMember on a COM object.
+        PutDispProperty = 0x4000,
+        PutRefDispProperty = 0x8000,
+
+        ExactBinding = 0x010000,    // Bind with Exact Type matching, No Change type
+        SuppressChangeType = 0x020000,
+
+        // DefaultValueBinding will return the set of methods having ArgCount or 
+        //    more parameters.  This is used for default values, etc.
+        OptionalParamBinding = 0x040000,
+
+        // These are a couple of misc attributes used
+        IgnoreReturn = 0x01000000,  // This is used in COM Interop
+        DoNotWrapExceptions = 0x02000000, // Disables wrapping exceptions in TargetInvocationException
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/CallingConventions.cs b/src/System.Private.CoreLib/shared/System/Reflection/CallingConventions.cs
new file mode 100644
index 0000000000..bb6d6cd809
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/CallingConventions.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// CallingConventions is a set of Bits representing the calling conventions in the system.
+
+namespace System.Reflection
+{
+    [Flags]
+    public enum CallingConventions
+    {
+        //NOTE: If you change this please update COMMember.cpp.  These
+        //    are defined there.
+        Standard = 0x0001,
+        VarArgs = 0x0002,
+        Any = Standard | VarArgs,
+        HasThis = 0x0020,
+        ExplicitThis = 0x0040,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ConstructorInfo.cs b/src/System.Private.CoreLib/shared/System/Reflection/ConstructorInfo.cs
new file mode 100644
index 0000000000..3ee1dbf855
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ConstructorInfo.cs
@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Globalization;
+
+namespace System.Reflection
+{
+    public abstract partial class ConstructorInfo : MethodBase
+    {
+        protected ConstructorInfo() { }
+
+        public override MemberTypes MemberType => MemberTypes.Constructor;
+
+        [DebuggerHidden]
+        [DebuggerStepThrough]
+        public object Invoke(object[] parameters) => Invoke(BindingFlags.Default, binder: null, parameters: parameters, culture: null);
+        public abstract object Invoke(BindingFlags invokeAttr, Binder binder, object[] parameters, CultureInfo culture);
+
+        public override bool Equals(object obj) => base.Equals(obj);
+        public override int GetHashCode() => base.GetHashCode();
+
+        public static bool operator ==(ConstructorInfo left, ConstructorInfo right)
+        {
+            if (object.ReferenceEquals(left, right))
+                return true;
+
+            if ((object)left == null || (object)right == null)
+                return false;
+
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(ConstructorInfo left, ConstructorInfo right) => !(left == right);
+
+        public static readonly string ConstructorName = ".ctor";
+        public static readonly string TypeConstructorName = ".cctor";
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/CustomAttributeFormatException.cs b/src/System.Private.CoreLib/shared/System/Reflection/CustomAttributeFormatException.cs
new file mode 100644
index 0000000000..1d7d4a7671
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/CustomAttributeFormatException.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Reflection
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class CustomAttributeFormatException : FormatException
+    {
+        public CustomAttributeFormatException()
+            : this(SR.Arg_CustomAttributeFormatException)
+        {
+        }
+
+        public CustomAttributeFormatException(string message)
+            : this(message, null)
+        {
+        }
+
+        public CustomAttributeFormatException(string message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_CUSTOMATTRIBUTEFORMAT;
+        }
+
+        protected CustomAttributeFormatException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/DefaultMemberAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/DefaultMemberAttribute.cs
new file mode 100644
index 0000000000..585fdb07cd
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/DefaultMemberAttribute.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Interface)]
+    public sealed class DefaultMemberAttribute : Attribute
+    {
+        // You must provide the name of the member, this is required
+        public DefaultMemberAttribute(string memberName)
+        {
+            MemberName = memberName;
+        }
+
+        // A get accessor to return the name from the attribute.
+        // NOTE: There is no setter because the name must be provided
+        //    to the constructor.  The name is not optional.
+        public string MemberName { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/EventAttributes.cs b/src/System.Private.CoreLib/shared/System/Reflection/EventAttributes.cs
new file mode 100644
index 0000000000..fbc2972f69
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/EventAttributes.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// EventAttributes are an enum defining the attributes associated with and Event.
+// These are defined in CorHdr.h and are a combination of bits and enums.
+
+namespace System.Reflection
+{
+    [Flags]
+    public enum EventAttributes
+    {
+        None = 0x0000,
+
+        // This Enum matchs the CorEventAttr defined in CorHdr.h
+        SpecialName = 0x0200,     // event is special.  Name describes how.
+
+        RTSpecialName = 0x0400,     // Runtime(metadata internal APIs) should check name encoding.
+
+        ReservedMask = 0x0400,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/EventInfo.cs b/src/System.Private.CoreLib/shared/System/Reflection/EventInfo.cs
new file mode 100644
index 0000000000..ccd9acf648
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/EventInfo.cs
@@ -0,0 +1,115 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+#if FEATURE_COMINTEROP
+using EventRegistrationToken = System.Runtime.InteropServices.WindowsRuntime.EventRegistrationToken;
+#endif //#if FEATURE_COMINTEROP
+
+namespace System.Reflection
+{
+    public abstract class EventInfo : MemberInfo
+    {
+        protected EventInfo() { }
+
+        public override MemberTypes MemberType => MemberTypes.Event;
+
+        public abstract EventAttributes Attributes { get; }
+        public bool IsSpecialName => (Attributes & EventAttributes.SpecialName) != 0;
+
+        public MethodInfo[] GetOtherMethods() => GetOtherMethods(nonPublic: false);
+        public virtual MethodInfo[] GetOtherMethods(bool nonPublic) { throw NotImplemented.ByDesign; }
+
+        public virtual MethodInfo AddMethod => GetAddMethod(nonPublic: true);
+        public virtual MethodInfo RemoveMethod => GetRemoveMethod(nonPublic: true);
+        public virtual MethodInfo RaiseMethod => GetRaiseMethod(nonPublic: true);
+
+        public MethodInfo GetAddMethod() => GetAddMethod(nonPublic: false);
+        public MethodInfo GetRemoveMethod() => GetRemoveMethod(nonPublic: false);
+        public MethodInfo GetRaiseMethod() => GetRaiseMethod(nonPublic: false);
+
+        public abstract MethodInfo GetAddMethod(bool nonPublic);
+        public abstract MethodInfo GetRemoveMethod(bool nonPublic);
+        public abstract MethodInfo GetRaiseMethod(bool nonPublic);
+
+        public virtual bool IsMulticast
+        {
+            get
+            {
+                Type cl = EventHandlerType;
+                Type mc = typeof(MulticastDelegate);
+                return mc.IsAssignableFrom(cl);
+            }
+        }
+
+        public virtual Type EventHandlerType
+        {
+            get
+            {
+                MethodInfo m = GetAddMethod(true);
+                ParameterInfo[] p = m.GetParametersNoCopy();
+                Type del = typeof(Delegate);
+                for (int i = 0; i < p.Length; i++)
+                {
+                    Type c = p[i].ParameterType;
+                    if (c.IsSubclassOf(del))
+                        return c;
+                }
+                return null;
+            }
+        }
+
+        [DebuggerHidden]
+        [DebuggerStepThrough]
+        public virtual void AddEventHandler(object target, Delegate handler)
+        {
+            MethodInfo addMethod = GetAddMethod(nonPublic: false);
+
+            if (addMethod == null)
+                throw new InvalidOperationException(SR.InvalidOperation_NoPublicAddMethod);
+
+#if FEATURE_COMINTEROP
+            if (addMethod.ReturnType == typeof(EventRegistrationToken))
+                throw new InvalidOperationException(SR.InvalidOperation_NotSupportedOnWinRTEvent);
+#endif //#if FEATURE_COMINTEROP
+
+            addMethod.Invoke(target, new object[] { handler });
+        }
+
+        [DebuggerHidden]
+        [DebuggerStepThrough]
+        public virtual void RemoveEventHandler(object target, Delegate handler)
+        {
+            MethodInfo removeMethod = GetRemoveMethod(nonPublic: false);
+
+            if (removeMethod == null)
+                throw new InvalidOperationException(SR.InvalidOperation_NoPublicRemoveMethod);
+
+#if FEATURE_COMINTEROP
+            ParameterInfo[] parameters = removeMethod.GetParametersNoCopy();
+            if (parameters[0].ParameterType == typeof(EventRegistrationToken))
+                throw new InvalidOperationException(SR.InvalidOperation_NotSupportedOnWinRTEvent);
+#endif //#if FEATURE_COMINTEROP
+
+            removeMethod.Invoke(target, new object[] { handler });
+        }
+
+        public override bool Equals(object obj) => base.Equals(obj);
+        public override int GetHashCode() => base.GetHashCode();
+
+        public static bool operator ==(EventInfo left, EventInfo right)
+        {
+            if (object.ReferenceEquals(left, right))
+                return true;
+
+            if ((object)left == null || (object)right == null)
+                return false;
+
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(EventInfo left, EventInfo right) => !(left == right);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ExceptionHandlingClauseOptions.cs b/src/System.Private.CoreLib/shared/System/Reflection/ExceptionHandlingClauseOptions.cs
new file mode 100644
index 0000000000..46285f7c82
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ExceptionHandlingClauseOptions.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [Flags]
+    public enum ExceptionHandlingClauseOptions : int
+    {
+        Clause = 0x0,
+        Filter = 0x1,
+        Finally = 0x2,
+        Fault = 0x4,
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/FieldAttributes.cs b/src/System.Private.CoreLib/shared/System/Reflection/FieldAttributes.cs
new file mode 100644
index 0000000000..048d0e7031
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/FieldAttributes.cs
@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    // This Enum matchs the CorFieldAttr defined in CorHdr.h
+    [Flags]
+    public enum FieldAttributes
+    {
+        // member access mask - Use this mask to retrieve accessibility information.
+        FieldAccessMask = 0x0007,
+        PrivateScope = 0x0000,    // Member not referenceable.
+        Private = 0x0001,    // Accessible only by the parent type.  
+        FamANDAssem = 0x0002,    // Accessible by sub-types only in this Assembly.
+        Assembly = 0x0003,    // Accessibly by anyone in the Assembly.
+        Family = 0x0004,    // Accessible only by type and sub-types.    
+        FamORAssem = 0x0005,    // Accessibly by sub-types anywhere, plus anyone in assembly.
+        Public = 0x0006,    // Accessibly by anyone who has visibility to this scope.    
+                            // end member access mask
+
+        // field contract attributes.
+        Static = 0x0010,        // Defined on type, else per instance.
+        InitOnly = 0x0020,     // Field may only be initialized, not written to after init.
+        Literal = 0x0040,        // Value is compile time constant.
+        NotSerialized = 0x0080,        // Field does not have to be serialized when type is remoted.
+
+        SpecialName = 0x0200,     // field is special.  Name describes how.
+
+        // interop attributes
+        PinvokeImpl = 0x2000,        // Implementation is forwarded through pinvoke.
+
+        RTSpecialName = 0x0400,     // Runtime(metadata internal APIs) should check name encoding.
+        HasFieldMarshal = 0x1000,     // Field has marshalling information.
+        HasDefault = 0x8000,     // Field has default.
+        HasFieldRVA = 0x0100,     // Field has RVA.
+
+        ReservedMask = 0x9500,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/FieldInfo.cs b/src/System.Private.CoreLib/shared/System/Reflection/FieldInfo.cs
new file mode 100644
index 0000000000..0863c2b019
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/FieldInfo.cs
@@ -0,0 +1,72 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Globalization;
+
+namespace System.Reflection
+{
+    public abstract partial class FieldInfo : MemberInfo
+    {
+        protected FieldInfo() { }
+
+        public override MemberTypes MemberType => MemberTypes.Field;
+
+        public abstract FieldAttributes Attributes { get; }
+        public abstract Type FieldType { get; }
+
+        public bool IsInitOnly => (Attributes & FieldAttributes.InitOnly) != 0;
+        public bool IsLiteral => (Attributes & FieldAttributes.Literal) != 0;
+        public bool IsNotSerialized => (Attributes & FieldAttributes.NotSerialized) != 0;
+        public bool IsPinvokeImpl => (Attributes & FieldAttributes.PinvokeImpl) != 0;
+        public bool IsSpecialName => (Attributes & FieldAttributes.SpecialName) != 0;
+        public bool IsStatic => (Attributes & FieldAttributes.Static) != 0;
+
+        public bool IsAssembly => (Attributes & FieldAttributes.FieldAccessMask) == FieldAttributes.Assembly;
+        public bool IsFamily => (Attributes & FieldAttributes.FieldAccessMask) == FieldAttributes.Family;
+        public bool IsFamilyAndAssembly => (Attributes & FieldAttributes.FieldAccessMask) == FieldAttributes.FamANDAssem;
+        public bool IsFamilyOrAssembly => (Attributes & FieldAttributes.FieldAccessMask) == FieldAttributes.FamORAssem;
+        public bool IsPrivate => (Attributes & FieldAttributes.FieldAccessMask) == FieldAttributes.Private;
+        public bool IsPublic => (Attributes & FieldAttributes.FieldAccessMask) == FieldAttributes.Public;
+
+        public virtual bool IsSecurityCritical => true;
+        public virtual bool IsSecuritySafeCritical => false;
+        public virtual bool IsSecurityTransparent => false;
+
+        public abstract RuntimeFieldHandle FieldHandle { get; }
+
+        public override bool Equals(object obj) => base.Equals(obj);
+        public override int GetHashCode() => base.GetHashCode();
+
+        public static bool operator ==(FieldInfo left, FieldInfo right)
+        {
+            if (object.ReferenceEquals(left, right))
+                return true;
+
+            if ((object)left == null || (object)right == null)
+                return false;
+
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(FieldInfo left, FieldInfo right) => !(left == right);
+
+        public abstract object GetValue(object obj);
+
+        [DebuggerHidden]
+        [DebuggerStepThrough]
+        public void SetValue(object obj, object value) => SetValue(obj, value, BindingFlags.Default, Type.DefaultBinder, null);
+        public abstract void SetValue(object obj, object value, BindingFlags invokeAttr, Binder binder, CultureInfo culture);
+
+        [CLSCompliant(false)]
+        public virtual void SetValueDirect(TypedReference obj, object value) { throw new NotSupportedException(SR.NotSupported_AbstractNonCLS); }
+        [CLSCompliant(false)]
+        public virtual object GetValueDirect(TypedReference obj) { throw new NotSupportedException(SR.NotSupported_AbstractNonCLS); }
+
+        public virtual object GetRawConstantValue() { throw new NotSupportedException(SR.NotSupported_AbstractNonCLS); }
+
+        public virtual Type[] GetOptionalCustomModifiers() { throw NotImplemented.ByDesign; }
+        public virtual Type[] GetRequiredCustomModifiers() { throw NotImplemented.ByDesign; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/GenericParameterAttributes.cs b/src/System.Private.CoreLib/shared/System/Reflection/GenericParameterAttributes.cs
new file mode 100644
index 0000000000..4b579d273e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/GenericParameterAttributes.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [Flags]
+    public enum GenericParameterAttributes
+    {
+        None = 0x0000,
+        VarianceMask = 0x0003,
+        Covariant = 0x0001,
+        Contravariant = 0x0002,
+        SpecialConstraintMask = 0x001C,
+        ReferenceTypeConstraint = 0x0004,
+        NotNullableValueTypeConstraint = 0x0008,
+        DefaultConstructorConstraint = 0x0010,
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ICustomAttributeProvider.cs b/src/System.Private.CoreLib/shared/System/Reflection/ICustomAttributeProvider.cs
new file mode 100644
index 0000000000..3cae295bc4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ICustomAttributeProvider.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public interface ICustomAttributeProvider
+    {
+        object[] GetCustomAttributes(bool inherit);
+        object[] GetCustomAttributes(Type attributeType, bool inherit);
+        bool IsDefined(Type attributeType, bool inherit);
+    }
+}
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/IReflect.cs b/src/System.Private.CoreLib/shared/System/Reflection/IReflect.cs
new file mode 100644
index 0000000000..a7e84b6168
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/IReflect.cs
@@ -0,0 +1,76 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+
+namespace System.Reflection
+{
+    public interface IReflect
+    {
+        // Return the requested method if it is implemented by the Reflection object.  The
+        // match is based upon the name and DescriptorInfo which describes the signature
+        // of the method. 
+        MethodInfo GetMethod(string name, BindingFlags bindingAttr, Binder binder, Type[] types, ParameterModifier[] modifiers);
+
+        // Return the requested method if it is implemented by the Reflection object.  The
+        // match is based upon the name of the method.  If the object implementes multiple methods
+        // with the same name an AmbiguousMatchException is thrown.
+        MethodInfo GetMethod(string name, BindingFlags bindingAttr);
+
+        MethodInfo[] GetMethods(BindingFlags bindingAttr);
+
+        // Return the requestion field if it is implemented by the Reflection object.  The
+        // match is based upon a name.  There cannot be more than a single field with
+        // a name.
+        FieldInfo GetField(string name, BindingFlags bindingAttr);
+
+        FieldInfo[] GetFields(BindingFlags bindingAttr);
+
+        // Return the property based upon name.  If more than one property has the given
+        // name an AmbiguousMatchException will be thrown.  Returns null if no property
+        // is found.
+        PropertyInfo GetProperty(string name, BindingFlags bindingAttr);
+
+        // Return the property based upon the name and Descriptor info describing the property
+        // indexing.  Return null if no property is found.
+        PropertyInfo GetProperty(string name, BindingFlags bindingAttr, Binder binder, Type returnType, Type[] types, ParameterModifier[] modifiers);
+
+        // Returns an array of PropertyInfos for all the properties defined on 
+        // the Reflection object.
+        PropertyInfo[] GetProperties(BindingFlags bindingAttr);
+
+        // Return an array of members which match the passed in name.
+        MemberInfo[] GetMember(string name, BindingFlags bindingAttr);
+
+        // Return an array of all of the members defined for this object.
+        MemberInfo[] GetMembers(BindingFlags bindingAttr);
+
+        // Description of the Binding Process.
+        // We must invoke a method that is accessible and for which the provided
+        // parameters have the most specific match.  A method may be called if
+        // 1. The number of parameters in the method declaration equals the number of 
+        //    arguments provided to the invocation
+        // 2. The type of each argument can be converted by the binder to the
+        //    type of the type of the parameter.
+        // 
+        // The binder will find all of the matching methods.  These method are found based
+        // upon the type of binding requested (MethodInvoke, Get/Set Properties).  The set
+        // of methods is filtered by the name, number of arguments and a set of search modifiers
+        // defined in the Binder.
+        // 
+        // After the method is selected, it will be invoked.  Accessibility is checked
+        // at that point.  The search may be control which set of methods are searched based
+        // upon the accessibility attribute associated with the method.
+        // 
+        // The BindToMethod method is responsible for selecting the method to be invoked.
+        // For the default binder, the most specific method will be selected.
+        // 
+        // This will invoke a specific member...
+        object InvokeMember(string name, BindingFlags invokeAttr, Binder binder, object target, object[] args, ParameterModifier[] modifiers, CultureInfo culture, string[] namedParameters);
+
+        // Return the underlying Type that represents the IReflect Object.  For expando object,
+        // this is the (Object) IReflectInstance.GetType().  For Type object it is this.
+        Type UnderlyingSystemType { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/IReflectableType.cs b/src/System.Private.CoreLib/shared/System/Reflection/IReflectableType.cs
new file mode 100644
index 0000000000..5e2c0edab4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/IReflectableType.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public interface IReflectableType
+    {
+        TypeInfo GetTypeInfo();
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ImageFileMachine.cs b/src/System.Private.CoreLib/shared/System/Reflection/ImageFileMachine.cs
new file mode 100644
index 0000000000..230bc952e5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ImageFileMachine.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public enum ImageFileMachine
+    {
+        I386 = 0x014c,
+        IA64 = 0x0200,
+        AMD64 = 0x8664,
+        ARM = 0x01c4,
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/InterfaceMapping.cs b/src/System.Private.CoreLib/shared/System/Reflection/InterfaceMapping.cs
new file mode 100644
index 0000000000..2e0c0d8a28
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/InterfaceMapping.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public struct InterfaceMapping
+    {
+        public Type TargetType;               // The type implementing the interface
+        public Type InterfaceType;            // The type representing the interface
+        public MethodInfo[] TargetMethods;    // The methods implementing the interface
+        public MethodInfo[] InterfaceMethods; // The methods defined on the interface
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/IntrospectionExtensions.cs b/src/System.Private.CoreLib/shared/System/Reflection/IntrospectionExtensions.cs
new file mode 100644
index 0000000000..acf5987d44
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/IntrospectionExtensions.cs
@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Reflection
+{
+    public static class IntrospectionExtensions
+    {
+        public static TypeInfo GetTypeInfo(this Type type)
+        {
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+
+            if (type is IReflectableType reflectableType)
+                return reflectableType.GetTypeInfo();
+
+            return new TypeDelegator(type);
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/InvalidFilterCriteriaException.cs b/src/System.Private.CoreLib/shared/System/Reflection/InvalidFilterCriteriaException.cs
new file mode 100644
index 0000000000..dedcc54f4c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/InvalidFilterCriteriaException.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Reflection
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class InvalidFilterCriteriaException : ApplicationException
+    {
+        public InvalidFilterCriteriaException()
+            : this(SR.Arg_InvalidFilterCriteriaException)
+        {
+        }
+
+        public InvalidFilterCriteriaException(string message)
+            : this(message, null)
+        {
+        }
+
+        public InvalidFilterCriteriaException(string message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_INVALIDFILTERCRITERIA;
+        }
+
+        protected InvalidFilterCriteriaException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ManifestResourceInfo.cs b/src/System.Private.CoreLib/shared/System/Reflection/ManifestResourceInfo.cs
new file mode 100644
index 0000000000..b9c56ab857
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ManifestResourceInfo.cs
@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public class ManifestResourceInfo
+    {
+        public ManifestResourceInfo(Assembly containingAssembly,
+                                      string containingFileName,
+                                      ResourceLocation resourceLocation)
+        {
+            ReferencedAssembly = containingAssembly;
+            FileName = containingFileName;
+            ResourceLocation = resourceLocation;
+        }
+
+        public virtual Assembly ReferencedAssembly { get; }
+        public virtual string FileName { get; }
+        public virtual ResourceLocation ResourceLocation { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/MemberFilter.cs b/src/System.Private.CoreLib/shared/System/Reflection/MemberFilter.cs
new file mode 100644
index 0000000000..bb1b15796a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/MemberFilter.cs
@@ -0,0 +1,8 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public delegate bool MemberFilter(MemberInfo m, object filterCriteria);
+}
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/MemberInfo.cs b/src/System.Private.CoreLib/shared/System/Reflection/MemberInfo.cs
new file mode 100644
index 0000000000..d8a7458632
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/MemberInfo.cs
@@ -0,0 +1,77 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+
+namespace System.Reflection
+{
+    public abstract partial class MemberInfo : ICustomAttributeProvider
+    {
+        protected MemberInfo() { }
+
+        public abstract MemberTypes MemberType { get; }
+        public abstract string Name { get; }
+        public abstract Type DeclaringType { get; }
+        public abstract Type ReflectedType { get; }
+
+        public virtual Module Module
+        {
+            get
+            {
+                // This check is necessary because for some reason, Type adds a new "Module" property that hides the inherited one instead 
+                // of overriding.
+
+                Type type = this as Type;
+                if (type != null)
+                    return type.Module;
+
+                throw NotImplemented.ByDesign;
+            }
+        }
+
+        public virtual bool HasSameMetadataDefinitionAs(MemberInfo other) { throw NotImplemented.ByDesign; }
+
+        public abstract bool IsDefined(Type attributeType, bool inherit);
+        public abstract object[] GetCustomAttributes(bool inherit);
+        public abstract object[] GetCustomAttributes(Type attributeType, bool inherit);
+
+        public virtual IEnumerable<CustomAttributeData> CustomAttributes => GetCustomAttributesData();
+        public virtual IList<CustomAttributeData> GetCustomAttributesData() { throw NotImplemented.ByDesign; }
+
+        public virtual int MetadataToken { get { throw new InvalidOperationException(); } }
+
+        public override bool Equals(object obj) => base.Equals(obj);
+        public override int GetHashCode() => base.GetHashCode();
+
+        public static bool operator ==(MemberInfo left, MemberInfo right)
+        {
+            if (object.ReferenceEquals(left, right))
+                return true;
+
+            if ((object)left == null || (object)right == null)
+                return false;
+
+            Type type1, type2;
+            MethodBase method1, method2;
+            FieldInfo field1, field2;
+            EventInfo event1, event2;
+            PropertyInfo property1, property2;
+
+            if ((type1 = left as Type) != null && (type2 = right as Type) != null)
+                return type1 == type2;
+            else if ((method1 = left as MethodBase) != null && (method2 = right as MethodBase) != null)
+                return method1 == method2;
+            else if ((field1 = left as FieldInfo) != null && (field2 = right as FieldInfo) != null)
+                return field1 == field2;
+            else if ((event1 = left as EventInfo) != null && (event2 = right as EventInfo) != null)
+                return event1 == event2;
+            else if ((property1 = left as PropertyInfo) != null && (property2 = right as PropertyInfo) != null)
+                return property1 == property2;
+
+            return false;
+        }
+
+        public static bool operator !=(MemberInfo left, MemberInfo right) => !(left == right);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/MemberTypes.cs b/src/System.Private.CoreLib/shared/System/Reflection/MemberTypes.cs
new file mode 100644
index 0000000000..57072dcfbe
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/MemberTypes.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [Flags]
+    public enum MemberTypes
+    {
+        Constructor = 0x01,
+        Event = 0x02,
+        Field = 0x04,
+        Method = 0x08,
+        Property = 0x10,
+        TypeInfo = 0x20,
+        Custom = 0x40,
+        NestedType = 0x80,
+        All = Constructor | Event | Field | Method | Property | TypeInfo | NestedType,
+    }
+}
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/MethodAttributes.cs b/src/System.Private.CoreLib/shared/System/Reflection/MethodAttributes.cs
new file mode 100644
index 0000000000..1a7c7bf154
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/MethodAttributes.cs
@@ -0,0 +1,50 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [Flags]
+    public enum MethodAttributes
+    {
+        // NOTE: This Enum matchs the CorMethodAttr defined in CorHdr.h
+
+        // member access mask - Use this mask to retrieve accessibility information.
+        MemberAccessMask = 0x0007,
+        PrivateScope = 0x0000,     // Member not referenceable.
+        Private = 0x0001,     // Accessible only by the parent type.  
+        FamANDAssem = 0x0002,     // Accessible by sub-types only in this Assembly.
+        Assembly = 0x0003,     // Accessibly by anyone in the Assembly.
+        Family = 0x0004,     // Accessible only by type and sub-types.    
+        FamORAssem = 0x0005,     // Accessibly by sub-types anywhere, plus anyone in assembly.
+        Public = 0x0006,     // Accessibly by anyone who has visibility to this scope.    
+                             // end member access mask
+
+        // method contract attributes.
+        Static = 0x0010,     // Defined on type, else per instance.
+        Final = 0x0020,     // Method may not be overridden.
+        Virtual = 0x0040,     // Method virtual.
+        HideBySig = 0x0080,     // Method hides by name+sig, else just by name.
+        CheckAccessOnOverride = 0x0200,
+
+        // vtable layout mask - Use this mask to retrieve vtable attributes.
+        VtableLayoutMask = 0x0100,
+        ReuseSlot = 0x0000,     // The default.
+        NewSlot = 0x0100,     // Method always gets a new slot in the vtable.
+                              // end vtable layout mask
+
+        // method implementation attributes.
+        Abstract = 0x0400,     // Method does not provide an implementation.
+        SpecialName = 0x0800,     // Method is special.  Name describes how.
+
+        // interop attributes
+        PinvokeImpl = 0x2000,     // Implementation is forwarded through pinvoke.
+        UnmanagedExport = 0x0008,     // Managed method exported via thunk to unmanaged code.
+        RTSpecialName = 0x1000,     // Runtime should check name encoding.
+
+        HasSecurity = 0x4000,     // Method has security associate with it.
+        RequireSecObject = 0x8000,     // Method calls another method containing security code.
+
+        ReservedMask = 0xd000,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/MethodBase.cs b/src/System.Private.CoreLib/shared/System/Reflection/MethodBase.cs
new file mode 100644
index 0000000000..0037c74f4c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/MethodBase.cs
@@ -0,0 +1,86 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Diagnostics;
+
+namespace System.Reflection
+{
+    public abstract partial class MethodBase : MemberInfo
+    {
+        protected MethodBase() { }
+
+        public abstract ParameterInfo[] GetParameters();
+        public abstract MethodAttributes Attributes { get; }
+        public virtual MethodImplAttributes MethodImplementationFlags => GetMethodImplementationFlags();
+        public abstract MethodImplAttributes GetMethodImplementationFlags();
+        public virtual MethodBody GetMethodBody() { throw new InvalidOperationException(); }
+        public virtual CallingConventions CallingConvention => CallingConventions.Standard;
+
+        public bool IsAbstract => (Attributes & MethodAttributes.Abstract) != 0;
+        public bool IsConstructor
+        {
+            get
+            {
+                // To be backward compatible we only return true for instance RTSpecialName ctors.
+                return (this is ConstructorInfo &&
+                        !IsStatic &&
+                        ((Attributes & MethodAttributes.RTSpecialName) == MethodAttributes.RTSpecialName));
+            }
+        }
+        public bool IsFinal => (Attributes & MethodAttributes.Final) != 0;
+        public bool IsHideBySig => (Attributes & MethodAttributes.HideBySig) != 0;
+        public bool IsSpecialName => (Attributes & MethodAttributes.SpecialName) != 0;
+        public bool IsStatic => (Attributes & MethodAttributes.Static) != 0;
+        public bool IsVirtual => (Attributes & MethodAttributes.Virtual) != 0;
+
+        public bool IsAssembly => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Assembly;
+        public bool IsFamily => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Family;
+        public bool IsFamilyAndAssembly => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.FamANDAssem;
+        public bool IsFamilyOrAssembly => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.FamORAssem;
+        public bool IsPrivate => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Private;
+        public bool IsPublic => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Public;
+
+        public virtual bool IsConstructedGenericMethod => IsGenericMethod && !IsGenericMethodDefinition;
+        public virtual bool IsGenericMethod => false;
+        public virtual bool IsGenericMethodDefinition => false;
+        public virtual Type[] GetGenericArguments() { throw new NotSupportedException(SR.NotSupported_SubclassOverride); }
+        public virtual bool ContainsGenericParameters => false;
+
+        [DebuggerHidden]
+        [DebuggerStepThrough]
+        public object Invoke(object obj, object[] parameters) => Invoke(obj, BindingFlags.Default, binder: null, parameters: parameters, culture: null);
+        public abstract object Invoke(object obj, BindingFlags invokeAttr, Binder binder, object[] parameters, CultureInfo culture);
+
+        public abstract RuntimeMethodHandle MethodHandle { get; }
+
+        public virtual bool IsSecurityCritical { get { throw NotImplemented.ByDesign; } }
+        public virtual bool IsSecuritySafeCritical { get { throw NotImplemented.ByDesign; } }
+        public virtual bool IsSecurityTransparent { get { throw NotImplemented.ByDesign; } }
+
+        public override bool Equals(object obj) => base.Equals(obj);
+        public override int GetHashCode() => base.GetHashCode();
+
+        public static bool operator ==(MethodBase left, MethodBase right)
+        {
+            if (object.ReferenceEquals(left, right))
+                return true;
+
+            if ((object)left == null || (object)right == null)
+                return false;
+
+            MethodInfo method1, method2;
+            ConstructorInfo constructor1, constructor2;
+
+            if ((method1 = left as MethodInfo) != null && (method2 = right as MethodInfo) != null)
+                return method1 == method2;
+            else if ((constructor1 = left as ConstructorInfo) != null && (constructor2 = right as ConstructorInfo) != null)
+                return constructor1 == constructor2;
+
+            return false;
+        }
+
+        public static bool operator !=(MethodBase left, MethodBase right) => !(left == right);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/MethodImplAttributes.cs b/src/System.Private.CoreLib/shared/System/Reflection/MethodImplAttributes.cs
new file mode 100644
index 0000000000..a1ed326002
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/MethodImplAttributes.cs
@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    // This Enum matchs the CorMethodImpl defined in CorHdr.h
+    public enum MethodImplAttributes
+    {
+        // code impl mask
+        CodeTypeMask = 0x0003,   // Flags about code type.   
+        IL = 0x0000,   // Method impl is IL.
+        Native = 0x0001,   // Method impl is native.     
+        OPTIL = 0x0002,   // Method impl is OPTIL 
+        Runtime = 0x0003,   // Method impl is provided by the runtime.
+                            // end code impl mask
+
+        // managed mask
+        ManagedMask = 0x0004,   // Flags specifying whether the code is managed or unmanaged.
+        Unmanaged = 0x0004,   // Method impl is unmanaged, otherwise managed.
+        Managed = 0x0000,   // Method impl is managed.
+                            // end managed mask
+
+        // implementation info and interop
+        ForwardRef = 0x0010,   // Indicates method is not defined; used primarily in merge scenarios.
+        PreserveSig = 0x0080,   // Indicates method sig is exported exactly as declared.
+
+        InternalCall = 0x1000,   // Internal Call...
+
+        Synchronized = 0x0020,   // Method is single threaded through the body.
+        NoInlining = 0x0008,   // Method may not be inlined.
+        AggressiveInlining = 0x0100,   // Method should be inlined if possible.
+        NoOptimization = 0x0040,   // Method may not be optimized.
+
+        MaxMethodImplVal = 0xffff,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/MethodInfo.Internal.cs b/src/System.Private.CoreLib/shared/System/Reflection/MethodInfo.Internal.cs
new file mode 100644
index 0000000000..2806be639e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/MethodInfo.Internal.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public abstract partial class MethodInfo : MethodBase
+    {
+#if CORERT        
+        public // Needs to be public so that Reflection.Core can see it.
+#else
+        internal
+#endif
+        virtual int GenericParameterCount => GetGenericArguments().Length;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/MethodInfo.cs b/src/System.Private.CoreLib/shared/System/Reflection/MethodInfo.cs
new file mode 100644
index 0000000000..95c62ba7f0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/MethodInfo.cs
@@ -0,0 +1,43 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public abstract partial class MethodInfo : MethodBase
+    {
+        protected MethodInfo() { }
+
+        public override MemberTypes MemberType => MemberTypes.Method;
+
+        public virtual ParameterInfo ReturnParameter { get { throw NotImplemented.ByDesign; } }
+        public virtual Type ReturnType { get { throw NotImplemented.ByDesign; } }
+
+        public override Type[] GetGenericArguments() { throw new NotSupportedException(SR.NotSupported_SubclassOverride); }
+        public virtual MethodInfo GetGenericMethodDefinition() { throw new NotSupportedException(SR.NotSupported_SubclassOverride); }
+        public virtual MethodInfo MakeGenericMethod(params Type[] typeArguments) { throw new NotSupportedException(SR.NotSupported_SubclassOverride); }
+
+        public abstract MethodInfo GetBaseDefinition();
+
+        public abstract ICustomAttributeProvider ReturnTypeCustomAttributes { get; }
+
+        public virtual Delegate CreateDelegate(Type delegateType) { throw new NotSupportedException(SR.NotSupported_SubclassOverride); }
+        public virtual Delegate CreateDelegate(Type delegateType, object target) { throw new NotSupportedException(SR.NotSupported_SubclassOverride); }
+
+        public override bool Equals(object obj) => base.Equals(obj);
+        public override int GetHashCode() => base.GetHashCode();
+
+        public static bool operator ==(MethodInfo left, MethodInfo right)
+        {
+            if (object.ReferenceEquals(left, right))
+                return true;
+
+            if ((object)left == null || (object)right == null)
+                return false;
+
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(MethodInfo left, MethodInfo right) => !(left == right);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/Missing.cs b/src/System.Private.CoreLib/shared/System/Reflection/Missing.cs
new file mode 100644
index 0000000000..46ab32fccf
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/Missing.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Reflection
+{
+    public sealed class Missing : ISerializable
+    {
+        public static readonly Missing Value = new Missing();
+
+        private Missing() { }
+
+        void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            throw new PlatformNotSupportedException();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/Module.cs b/src/System.Private.CoreLib/shared/System/Reflection/Module.cs
new file mode 100644
index 0000000000..56f83c40d9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/Module.cs
@@ -0,0 +1,182 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Runtime.Serialization;
+
+namespace System.Reflection
+{
+    public abstract class Module : ICustomAttributeProvider, ISerializable
+    {
+        protected Module() { }
+
+        public virtual Assembly Assembly { get { throw NotImplemented.ByDesign; } }
+        public virtual string FullyQualifiedName { get { throw NotImplemented.ByDesign; } }
+        public virtual string Name { get { throw NotImplemented.ByDesign; } }
+
+        public virtual int MDStreamVersion { get { throw NotImplemented.ByDesign; } }
+        public virtual Guid ModuleVersionId { get { throw NotImplemented.ByDesign; } }
+        public virtual string ScopeName { get { throw NotImplemented.ByDesign; } }
+        public ModuleHandle ModuleHandle => GetModuleHandleImpl();
+        protected virtual ModuleHandle GetModuleHandleImpl() => ModuleHandle.EmptyHandle; // Not an api but declared protected because of Reflection.Core/Corelib divide (when built by CoreRt)
+        public virtual void GetPEKind(out PortableExecutableKinds peKind, out ImageFileMachine machine) { throw NotImplemented.ByDesign; }
+        public virtual bool IsResource() { throw NotImplemented.ByDesign; }
+
+        public virtual bool IsDefined(Type attributeType, bool inherit) { throw NotImplemented.ByDesign; }
+        public virtual IEnumerable<CustomAttributeData> CustomAttributes => GetCustomAttributesData();
+        public virtual IList<CustomAttributeData> GetCustomAttributesData() { throw NotImplemented.ByDesign; }
+        public virtual object[] GetCustomAttributes(bool inherit) { throw NotImplemented.ByDesign; }
+        public virtual object[] GetCustomAttributes(Type attributeType, bool inherit) { throw NotImplemented.ByDesign; }
+
+        public MethodInfo GetMethod(string name)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            return GetMethodImpl(name, Module.DefaultLookup, null, CallingConventions.Any, null, null);
+        }
+
+        public MethodInfo GetMethod(string name, Type[] types) => GetMethod(name, Module.DefaultLookup, null, CallingConventions.Any, types, null);
+        public MethodInfo GetMethod(string name, BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+            if (types == null)
+                throw new ArgumentNullException(nameof(types));
+            for (int i = 0; i < types.Length; i++)
+            {
+                if (types[i] == null)
+                    throw new ArgumentNullException(nameof(types));
+            }
+            return GetMethodImpl(name, bindingAttr, binder, callConvention, types, modifiers);
+        }
+
+        protected virtual MethodInfo GetMethodImpl(string name, BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers) { throw NotImplemented.ByDesign; }
+
+        public MethodInfo[] GetMethods() => GetMethods(Module.DefaultLookup);
+        public virtual MethodInfo[] GetMethods(BindingFlags bindingFlags) { throw NotImplemented.ByDesign; }
+
+        public FieldInfo GetField(string name) => GetField(name, Module.DefaultLookup);
+        public virtual FieldInfo GetField(string name, BindingFlags bindingAttr) { throw NotImplemented.ByDesign; }
+
+        public FieldInfo[] GetFields() => GetFields(Module.DefaultLookup);
+        public virtual FieldInfo[] GetFields(BindingFlags bindingFlags) { throw NotImplemented.ByDesign; }
+
+        public virtual Type[] GetTypes() { throw NotImplemented.ByDesign; }
+
+        public virtual Type GetType(string className) => GetType(className, throwOnError: false, ignoreCase: false);
+        public virtual Type GetType(string className, bool ignoreCase) => GetType(className, throwOnError: false, ignoreCase: ignoreCase);
+        public virtual Type GetType(string className, bool throwOnError, bool ignoreCase) { throw NotImplemented.ByDesign; }
+
+        public virtual Type[] FindTypes(TypeFilter filter, object filterCriteria)
+        {
+            Type[] c = GetTypes();
+            int cnt = 0;
+            for (int i = 0; i < c.Length; i++)
+            {
+                if (filter != null && !filter(c[i], filterCriteria))
+                    c[i] = null;
+                else
+                    cnt++;
+            }
+            if (cnt == c.Length)
+                return c;
+
+            Type[] ret = new Type[cnt];
+            cnt = 0;
+            for (int i = 0; i < c.Length; i++)
+            {
+                if (c[i] != null)
+                    ret[cnt++] = c[i];
+            }
+            return ret;
+        }
+
+        public virtual int MetadataToken { get { throw NotImplemented.ByDesign; } }
+
+        public FieldInfo ResolveField(int metadataToken) => ResolveField(metadataToken, null, null);
+        public virtual FieldInfo ResolveField(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments) { throw NotImplemented.ByDesign; }
+
+        public MemberInfo ResolveMember(int metadataToken) => ResolveMember(metadataToken, null, null);
+        public virtual MemberInfo ResolveMember(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments) { throw NotImplemented.ByDesign; }
+
+        public MethodBase ResolveMethod(int metadataToken) => ResolveMethod(metadataToken, null, null);
+        public virtual MethodBase ResolveMethod(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments) { throw NotImplemented.ByDesign; }
+
+        public virtual byte[] ResolveSignature(int metadataToken) { throw NotImplemented.ByDesign; }
+        public virtual string ResolveString(int metadataToken) { throw NotImplemented.ByDesign; }
+
+        public Type ResolveType(int metadataToken) => ResolveType(metadataToken, null, null);
+        public virtual Type ResolveType(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments) { throw NotImplemented.ByDesign; }
+
+        public virtual void GetObjectData(SerializationInfo info, StreamingContext context) { throw NotImplemented.ByDesign; }
+
+        public override bool Equals(object o) => base.Equals(o);
+        public override int GetHashCode() => base.GetHashCode();
+
+        public static bool operator ==(Module left, Module right)
+        {
+            if (object.ReferenceEquals(left, right))
+                return true;
+
+            if ((object)left == null || (object)right == null)
+                return false;
+
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(Module left, Module right) => !(left == right);
+
+        public override string ToString() => ScopeName;
+
+        public static readonly TypeFilter FilterTypeName = FilterTypeNameImpl;
+        public static readonly TypeFilter FilterTypeNameIgnoreCase = FilterTypeNameIgnoreCaseImpl;
+
+        private const BindingFlags DefaultLookup = BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public;
+
+        // FilterTypeName 
+        // This method will filter the class based upon the name.  It supports
+        //    a trailing wild card.
+        private static bool FilterTypeNameImpl(Type cls, object filterCriteria)
+        {
+            // Check that the criteria object is a String object
+            if (filterCriteria == null || !(filterCriteria is string))
+                throw new InvalidFilterCriteriaException(SR.InvalidFilterCriteriaException_CritString);
+
+            string str = (string)filterCriteria;
+
+            // Check to see if this is a prefix or exact match requirement
+            if (str.Length > 0 && str[str.Length - 1] == '*')
+            {
+                str = str.Substring(0, str.Length - 1);
+                return cls.Name.StartsWith(str, StringComparison.Ordinal);
+            }
+
+            return cls.Name.Equals(str);
+        }
+
+        // FilterFieldNameIgnoreCase
+        // This method filter the Type based upon name, it ignores case.
+        private static bool FilterTypeNameIgnoreCaseImpl(Type cls, object filterCriteria)
+        {
+            // Check that the criteria object is a String object
+            if (filterCriteria == null || !(filterCriteria is string))
+                throw new InvalidFilterCriteriaException(SR.InvalidFilterCriteriaException_CritString);
+
+            string str = (string)filterCriteria;
+
+            // Check to see if this is a prefix or exact match requirement
+            if (str.Length > 0 && str[str.Length - 1] == '*')
+            {
+                str = str.Substring(0, str.Length - 1);
+                string name = cls.Name;
+                if (name.Length >= str.Length)
+                    return (string.Compare(name, 0, str, 0, str.Length, StringComparison.OrdinalIgnoreCase) == 0);
+                else
+                    return false;
+            }
+            return (string.Compare(str, cls.Name, StringComparison.OrdinalIgnoreCase) == 0);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ModuleResolveEventHandler.cs b/src/System.Private.CoreLib/shared/System/Reflection/ModuleResolveEventHandler.cs
new file mode 100644
index 0000000000..eb8926b5db
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ModuleResolveEventHandler.cs
@@ -0,0 +1,9 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public delegate Module ModuleResolveEventHandler(object sender, ResolveEventArgs e);
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ObfuscateAssemblyAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/ObfuscateAssemblyAttribute.cs
new file mode 100644
index 0000000000..f8f765ced2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ObfuscateAssemblyAttribute.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = false, Inherited = false)]
+    public sealed class ObfuscateAssemblyAttribute : Attribute
+    {
+        public ObfuscateAssemblyAttribute(bool assemblyIsPrivate)
+        {
+            AssemblyIsPrivate = assemblyIsPrivate;
+        }
+
+        public bool AssemblyIsPrivate { get; }
+        public bool StripAfterObfuscation { get; set; } = true;
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ObfuscationAttribute.cs b/src/System.Private.CoreLib/shared/System/Reflection/ObfuscationAttribute.cs
new file mode 100644
index 0000000000..11d93b6313
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ObfuscationAttribute.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Method | AttributeTargets.Parameter | AttributeTargets.Field | AttributeTargets.Property | AttributeTargets.Event | AttributeTargets.Interface | AttributeTargets.Enum | AttributeTargets.Delegate,
+        AllowMultiple = true, Inherited = false)]
+    public sealed class ObfuscationAttribute : Attribute
+    {
+        public ObfuscationAttribute()
+        {
+        }
+
+        public bool StripAfterObfuscation { get; set; } = true;
+        public bool Exclude { get; set; } = true;
+        public bool ApplyToMembers { get; set; } = true;
+        public string Feature { get; set; } = "all";
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ParameterAttributes.cs b/src/System.Private.CoreLib/shared/System/Reflection/ParameterAttributes.cs
new file mode 100644
index 0000000000..ce195897c2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ParameterAttributes.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// ParameterAttributes is an enum defining the attributes that may be 
+// associated with a Parameter.  These are defined in CorHdr.h.
+
+namespace System.Reflection
+{
+    // This Enum matchs the CorParamAttr defined in CorHdr.h
+    [Flags]
+    public enum ParameterAttributes
+    {
+        None = 0x0000,      // no flag is specified
+        In = 0x0001,     // Param is [In]    
+        Out = 0x0002,     // Param is [Out]   
+        Lcid = 0x0004,     // Param is [lcid]  
+
+        Retval = 0x0008,     // Param is [Retval]
+        Optional = 0x0010,     // Param is optional 
+
+        HasDefault = 0x1000,     // Param has default value.
+        HasFieldMarshal = 0x2000,     // Param has FieldMarshal.
+
+        Reserved3 = 0x4000,
+        Reserved4 = 0x8000,
+        ReservedMask = 0xf000,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ParameterInfo.cs b/src/System.Private.CoreLib/shared/System/Reflection/ParameterInfo.cs
new file mode 100644
index 0000000000..94bfffaa53
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ParameterInfo.cs
@@ -0,0 +1,110 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Runtime.Serialization;
+
+namespace System.Reflection
+{
+    public class ParameterInfo : ICustomAttributeProvider, IObjectReference
+    {
+        protected ParameterInfo() { }
+
+        public virtual ParameterAttributes Attributes => AttrsImpl;
+        public virtual MemberInfo Member => MemberImpl;
+        public virtual string Name => NameImpl;
+        public virtual Type ParameterType => ClassImpl;
+        public virtual int Position => PositionImpl;
+
+        public bool IsIn => (Attributes & ParameterAttributes.In) != 0;
+        public bool IsLcid => (Attributes & ParameterAttributes.Lcid) != 0;
+        public bool IsOptional => (Attributes & ParameterAttributes.Optional) != 0;
+        public bool IsOut => (Attributes & ParameterAttributes.Out) != 0;
+        public bool IsRetval => (Attributes & ParameterAttributes.Retval) != 0;
+
+        public virtual object DefaultValue { get { throw NotImplemented.ByDesign; } }
+        public virtual object RawDefaultValue { get { throw NotImplemented.ByDesign; } }
+        public virtual bool HasDefaultValue { get { throw NotImplemented.ByDesign; } }
+
+        public virtual bool IsDefined(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            return false;
+        }
+
+        public virtual IEnumerable<CustomAttributeData> CustomAttributes => GetCustomAttributesData();
+        public virtual IList<CustomAttributeData> GetCustomAttributesData() { throw NotImplemented.ByDesign; }
+
+        public virtual object[] GetCustomAttributes(bool inherit) => Array.Empty<object>();
+        public virtual object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            return Array.Empty<object>();
+        }
+
+        public virtual Type[] GetOptionalCustomModifiers() => Array.Empty<Type>();
+        public virtual Type[] GetRequiredCustomModifiers() => Array.Empty<Type>();
+
+        public virtual int MetadataToken => MetadataToken_ParamDef;
+
+        public object GetRealObject(StreamingContext context)
+        {
+            // Once all the serializable fields have come in we can set up the real
+            // instance based on just two of them (MemberImpl and PositionImpl).
+
+            if (MemberImpl == null)
+                throw new SerializationException(SR.Serialization_InsufficientState);
+
+            ParameterInfo[] args = null;
+
+            switch (MemberImpl.MemberType)
+            {
+                case MemberTypes.Constructor:
+                case MemberTypes.Method:
+                    if (PositionImpl == -1)
+                    {
+                        if (MemberImpl.MemberType == MemberTypes.Method)
+                            return ((MethodInfo)MemberImpl).ReturnParameter;
+                        else
+                            throw new SerializationException(SR.Serialization_BadParameterInfo);
+                    }
+                    else
+                    {
+                        args = ((MethodBase)MemberImpl).GetParametersNoCopy();
+
+                        if (args != null && PositionImpl < args.Length)
+                            return args[PositionImpl];
+                        else
+                            throw new SerializationException(SR.Serialization_BadParameterInfo);
+                    }
+
+                case MemberTypes.Property:
+                    args = ((PropertyInfo)MemberImpl).GetIndexParameters();
+
+                    if (args != null && PositionImpl > -1 && PositionImpl < args.Length)
+                        return args[PositionImpl];
+                    else
+                        throw new SerializationException(SR.Serialization_BadParameterInfo);
+
+                default:
+                    throw new SerializationException(SR.Serialization_NoParameterInfo);
+            }
+        }
+
+        public override string ToString() => ParameterType.FormatTypeName() + " " + Name;
+
+        protected ParameterAttributes AttrsImpl;
+        protected Type ClassImpl;
+        protected object DefaultValueImpl;
+        protected MemberInfo MemberImpl;
+        protected string NameImpl;
+        protected int PositionImpl;
+
+        private const int MetadataToken_ParamDef = 0x08000000;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ParameterModifier.cs b/src/System.Private.CoreLib/shared/System/Reflection/ParameterModifier.cs
new file mode 100644
index 0000000000..0fb75ffbd8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ParameterModifier.cs
@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public readonly struct ParameterModifier
+    {
+        private readonly bool[] _byRef;
+
+        public ParameterModifier(int parameterCount)
+        {
+            if (parameterCount <= 0)
+                throw new ArgumentException(SR.Arg_ParmArraySize);
+
+            _byRef = new bool[parameterCount];
+        }
+
+        public bool this[int index]
+        {
+            get
+            {
+                return _byRef[index];
+            }
+            set
+            {
+                _byRef[index] = value;
+            }
+        }
+
+#if CORECLR
+        internal bool[] IsByRefArray => _byRef;
+#endif
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/Pointer.cs b/src/System.Private.CoreLib/shared/System/Reflection/Pointer.cs
new file mode 100644
index 0000000000..e1a9990cf0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/Pointer.cs
@@ -0,0 +1,51 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.Serialization;
+
+namespace System.Reflection
+{
+    [CLSCompliant(false)]
+    public sealed unsafe class Pointer : ISerializable
+    {
+        // CoreCLR: Do not add or remove fields without updating the ReflectionPointer class in runtimehandles.h
+        private readonly void* _ptr;
+        private readonly Type _ptrType;
+
+        private Pointer(void* ptr, Type ptrType)
+        {
+            Debug.Assert(ptrType.IsRuntimeImplemented()); // CoreCLR: For CoreRT's sake, _ptrType has to be declared as "Type", but in fact, it is always a RuntimeType. Code on CoreCLR expects this.
+            _ptr = ptr;
+            _ptrType = ptrType;
+        }
+
+        public static object Box(void* ptr, Type type)
+        {
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+            if (!type.IsPointer)
+                throw new ArgumentException(SR.Arg_MustBePointer, nameof(ptr));
+            if (!type.IsRuntimeImplemented())
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(ptr));
+
+            return new Pointer(ptr, type);
+        }
+
+        public static void* Unbox(object ptr)
+        {
+            if (!(ptr is Pointer))
+                throw new ArgumentException(SR.Arg_MustBePointer, nameof(ptr));
+            return ((Pointer)ptr)._ptr;
+        }
+
+        void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            throw new PlatformNotSupportedException();
+        }
+
+        internal Type GetPointerType() => _ptrType;
+        internal IntPtr GetPointerValue() => (IntPtr)_ptr;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/PortableExecutableKinds.cs b/src/System.Private.CoreLib/shared/System/Reflection/PortableExecutableKinds.cs
new file mode 100644
index 0000000000..79be338685
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/PortableExecutableKinds.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [Flags]
+    public enum PortableExecutableKinds
+    {
+        NotAPortableExecutableImage = 0x0,
+        ILOnly = 0x1,
+        Required32Bit = 0x2,
+        PE32Plus = 0x4,
+        Unmanaged32Bit = 0x8,
+        Preferred32Bit = 0x10,
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ProcessorArchitecture.cs b/src/System.Private.CoreLib/shared/System/Reflection/ProcessorArchitecture.cs
new file mode 100644
index 0000000000..becb346c4f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ProcessorArchitecture.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public enum ProcessorArchitecture
+    {
+        None = 0x0000,
+        MSIL = 0x0001,
+        X86 = 0x0002,
+        IA64 = 0x0003,
+        Amd64 = 0x0004,
+        Arm = 0x0005
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/PropertyAttributes.cs b/src/System.Private.CoreLib/shared/System/Reflection/PropertyAttributes.cs
new file mode 100644
index 0000000000..31e7a653bb
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/PropertyAttributes.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// PropertyAttributes is an enum which defines the attributes that may be associated
+// with a property.  The values here are defined in Corhdr.h.
+
+namespace System.Reflection
+{
+    // This Enum matchs the CorPropertyAttr defined in CorHdr.h
+    [Flags]
+    public enum PropertyAttributes
+    {
+        None = 0x0000,
+        SpecialName = 0x0200,     // property is special.  Name describes how.
+
+        RTSpecialName = 0x0400,     // Runtime(metadata internal APIs) should check name encoding.
+        HasDefault = 0x1000,     // Property has default 
+
+        Reserved2 = 0x2000,
+        Reserved3 = 0x4000,
+        Reserved4 = 0x8000,
+        ReservedMask = 0xf400,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/PropertyInfo.cs b/src/System.Private.CoreLib/shared/System/Reflection/PropertyInfo.cs
new file mode 100644
index 0000000000..ff8a02e96d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/PropertyInfo.cs
@@ -0,0 +1,74 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Globalization;
+
+namespace System.Reflection
+{
+    public abstract class PropertyInfo : MemberInfo
+    {
+        protected PropertyInfo() { }
+
+        public override MemberTypes MemberType => MemberTypes.Property;
+
+        public abstract Type PropertyType { get; }
+        public abstract ParameterInfo[] GetIndexParameters();
+
+        public abstract PropertyAttributes Attributes { get; }
+        public bool IsSpecialName => (Attributes & PropertyAttributes.SpecialName) != 0;
+
+        public abstract bool CanRead { get; }
+        public abstract bool CanWrite { get; }
+
+        public MethodInfo[] GetAccessors() => GetAccessors(nonPublic: false);
+        public abstract MethodInfo[] GetAccessors(bool nonPublic);
+
+        public virtual MethodInfo GetMethod => GetGetMethod(nonPublic: true);
+        public MethodInfo GetGetMethod() => GetGetMethod(nonPublic: false);
+        public abstract MethodInfo GetGetMethod(bool nonPublic);
+
+        public virtual MethodInfo SetMethod => GetSetMethod(nonPublic: true);
+        public MethodInfo GetSetMethod() => GetSetMethod(nonPublic: false);
+        public abstract MethodInfo GetSetMethod(bool nonPublic);
+
+        public virtual Type[] GetOptionalCustomModifiers() => Array.Empty<Type>();
+        public virtual Type[] GetRequiredCustomModifiers() => Array.Empty<Type>();
+
+        [DebuggerHidden]
+        [DebuggerStepThrough]
+        public object GetValue(object obj) => GetValue(obj, index: null);
+        [DebuggerHidden]
+        [DebuggerStepThrough]
+        public virtual object GetValue(object obj, object[] index) => GetValue(obj, BindingFlags.Default, binder: null, index: index, culture: null);
+        public abstract object GetValue(object obj, BindingFlags invokeAttr, Binder binder, object[] index, CultureInfo culture);
+
+        public virtual object GetConstantValue() { throw NotImplemented.ByDesign; }
+        public virtual object GetRawConstantValue() { throw NotImplemented.ByDesign; }
+
+        [DebuggerHidden]
+        [DebuggerStepThrough]
+        public void SetValue(object obj, object value) => SetValue(obj, value, index: null);
+        [DebuggerHidden]
+        [DebuggerStepThrough]
+        public virtual void SetValue(object obj, object value, object[] index) => SetValue(obj, value, BindingFlags.Default, binder: null, index: index, culture: null);
+        public abstract void SetValue(object obj, object value, BindingFlags invokeAttr, Binder binder, object[] index, CultureInfo culture);
+
+        public override bool Equals(object obj) => base.Equals(obj);
+        public override int GetHashCode() => base.GetHashCode();
+
+        public static bool operator ==(PropertyInfo left, PropertyInfo right)
+        {
+            if (object.ReferenceEquals(left, right))
+                return true;
+
+            if ((object)left == null || (object)right == null)
+                return false;
+
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(PropertyInfo left, PropertyInfo right) => !(left == right);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ReflectionContext.cs b/src/System.Private.CoreLib/shared/System/Reflection/ReflectionContext.cs
new file mode 100644
index 0000000000..e9e93dab81
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ReflectionContext.cs
@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public abstract class ReflectionContext
+    {
+        protected ReflectionContext() { }
+
+        public abstract Assembly MapAssembly(Assembly assembly);
+
+        public abstract TypeInfo MapType(TypeInfo type);
+
+        public virtual TypeInfo GetTypeForObject(object value)
+        {
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            return MapType(value.GetType().GetTypeInfo());
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ReflectionTypeLoadException.cs b/src/System.Private.CoreLib/shared/System/Reflection/ReflectionTypeLoadException.cs
new file mode 100644
index 0000000000..5011c50053
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ReflectionTypeLoadException.cs
@@ -0,0 +1,73 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+using System.Text;
+
+namespace System.Reflection
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class ReflectionTypeLoadException : SystemException, ISerializable
+    {
+        public ReflectionTypeLoadException(Type[] classes, Exception[] exceptions)
+            : base(null)
+        {
+            Types = classes;
+            LoaderExceptions = exceptions;
+            HResult = HResults.COR_E_REFLECTIONTYPELOAD;
+        }
+
+        public ReflectionTypeLoadException(Type[] classes, Exception[] exceptions, string message)
+            : base(message)
+        {
+            Types = classes;
+            LoaderExceptions = exceptions;
+            HResult = HResults.COR_E_REFLECTIONTYPELOAD;
+        }
+
+        private ReflectionTypeLoadException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            LoaderExceptions = (Exception[])(info.GetValue("Exceptions", typeof(Exception[])));
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("Types", null, typeof(Type[]));
+            info.AddValue("Exceptions", LoaderExceptions, typeof(Exception[]));
+        }
+
+        public Type[] Types { get; }
+
+        public Exception[] LoaderExceptions { get; }
+
+        public override string Message => CreateString(isMessage: true);
+
+        public override string ToString() => CreateString(isMessage: false);
+
+        private string CreateString(bool isMessage)
+        {
+            string baseValue = isMessage ? base.Message : base.ToString();
+
+            Exception[] exceptions = LoaderExceptions;
+            if (exceptions == null || exceptions.Length == 0)
+            {
+                return baseValue;
+            }
+
+            var text = new StringBuilder(baseValue);
+            foreach (Exception e in exceptions)
+            {
+                if (e != null)
+                {
+                    text.AppendLine();
+                    text.Append(isMessage ? e.Message : e.ToString());
+                }
+            }
+            return text.ToString();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ResourceAttributes.cs b/src/System.Private.CoreLib/shared/System/Reflection/ResourceAttributes.cs
new file mode 100644
index 0000000000..2d03f42ba0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ResourceAttributes.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [Flags]
+    public enum ResourceAttributes
+    {
+        Public = 0x0001,
+        Private = 0x0002,
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/ResourceLocation.cs b/src/System.Private.CoreLib/shared/System/Reflection/ResourceLocation.cs
new file mode 100644
index 0000000000..4902333ac0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/ResourceLocation.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    [Flags]
+    public enum ResourceLocation
+    {
+        ContainedInAnotherAssembly = 2,
+        ContainedInManifestFile = 4,
+        Embedded = 1,
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/SignatureArrayType.cs b/src/System.Private.CoreLib/shared/System/Reflection/SignatureArrayType.cs
new file mode 100644
index 0000000000..52011b8a9d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/SignatureArrayType.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Reflection
+{
+    internal sealed class SignatureArrayType : SignatureHasElementType
+    {
+        internal SignatureArrayType(SignatureType elementType, int rank, bool isMultiDim)
+            : base(elementType)
+        {
+            Debug.Assert(rank > 0);
+            Debug.Assert(rank == 1 || isMultiDim);
+    
+            _rank = rank;
+            _isMultiDim = isMultiDim;
+        }
+    
+        protected sealed override bool IsArrayImpl() => true;
+        protected sealed override bool IsByRefImpl() => false;
+        protected sealed override bool IsPointerImpl() => false;
+    
+        public sealed override bool IsSZArray => !_isMultiDim;
+        public sealed override bool IsVariableBoundArray => _isMultiDim;
+    
+        public sealed override int GetArrayRank() => _rank;
+    
+        protected sealed override string Suffix
+        {
+            get
+            {
+                if (!_isMultiDim)
+                    return "[]";
+                else if (_rank == 1)
+                    return "[*]";
+                else
+                    return "[" + new string(',', _rank - 1) + "]";
+            }
+        }
+    
+        private readonly int _rank;
+        private readonly bool _isMultiDim;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/SignatureByRefType.cs b/src/System.Private.CoreLib/shared/System/Reflection/SignatureByRefType.cs
new file mode 100644
index 0000000000..eb5f6de42e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/SignatureByRefType.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Reflection
+{
+    internal sealed class SignatureByRefType : SignatureHasElementType
+    {
+        internal SignatureByRefType(SignatureType elementType)
+            : base(elementType)
+        {
+        }
+    
+        protected sealed override bool IsArrayImpl() => false;
+        protected sealed override bool IsByRefImpl() => true;
+        protected sealed override bool IsPointerImpl() => false;
+    
+        public sealed override bool IsSZArray => false;
+        public sealed override bool IsVariableBoundArray => false;
+    
+        public sealed override int GetArrayRank() => throw new ArgumentException(SR.Argument_HasToBeArrayClass);
+    
+        protected sealed override string Suffix => "&";
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/SignatureConstructedGenericType.cs b/src/System.Private.CoreLib/shared/System/Reflection/SignatureConstructedGenericType.cs
new file mode 100644
index 0000000000..cd97ffa21b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/SignatureConstructedGenericType.cs
@@ -0,0 +1,74 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Text;
+using System.Diagnostics;
+
+namespace System.Reflection
+{
+    internal sealed class SignatureConstructedGenericType : SignatureType
+    {
+        internal SignatureConstructedGenericType(Type genericTypeDefinition, Type[] genericTypeArguments)
+        {
+            Debug.Assert(genericTypeDefinition != null && genericTypeArguments != null);
+            _genericTypeDefinition = genericTypeDefinition;
+            _genericTypeArguments = (Type[])(genericTypeArguments.Clone());
+        }
+    
+        public sealed override bool IsTypeDefinition => false;
+        public sealed override bool IsGenericTypeDefinition => false;
+        protected sealed override bool HasElementTypeImpl() => false;
+        protected sealed override bool IsArrayImpl() => false;
+        protected sealed override bool IsByRefImpl() => false;
+        public sealed override bool IsByRefLike => _genericTypeDefinition.IsByRefLike;
+        protected sealed override bool IsPointerImpl() => false;
+        public sealed override bool IsSZArray => false;
+        public sealed override bool IsVariableBoundArray => false;
+        public sealed override bool IsConstructedGenericType => true;
+        public sealed override bool IsGenericParameter => false;
+        public sealed override bool IsGenericTypeParameter => false;
+        public sealed override bool IsGenericMethodParameter => false;
+        public sealed override bool ContainsGenericParameters
+        {
+            get
+            {
+                for (int i = 0; i < _genericTypeArguments.Length; i++)
+                {
+                    if (_genericTypeArguments[i].ContainsGenericParameters)
+                        return true;
+                }
+                return false;
+            }
+        }
+    
+        internal sealed override SignatureType ElementType => null;
+        public sealed override int GetArrayRank() => throw new ArgumentException(SR.Argument_HasToBeArrayClass);
+        public sealed override Type GetGenericTypeDefinition() => _genericTypeDefinition;
+        public sealed override Type[] GetGenericArguments() => GenericTypeArguments;
+        public sealed override Type[] GenericTypeArguments => (Type[])(_genericTypeArguments.Clone());
+        public sealed override int GenericParameterPosition => throw new InvalidOperationException(SR.Arg_NotGenericParameter);
+    
+        public sealed override string Name => _genericTypeDefinition.Name;
+        public sealed override string Namespace => _genericTypeDefinition.Namespace;
+    
+        public sealed override string ToString()
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append(_genericTypeDefinition.ToString());
+            sb.Append('[');
+            for (int i = 0; i < _genericTypeArguments.Length; i++)
+            {
+                if (i != 0)
+                    sb.Append(',');
+                sb.Append(_genericTypeArguments[i].ToString());
+            }
+            sb.Append(']');
+            return sb.ToString();
+        }
+    
+        private readonly Type _genericTypeDefinition;
+        private readonly Type[] _genericTypeArguments;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/SignatureGenericMethodParameterType.cs b/src/System.Private.CoreLib/shared/System/Reflection/SignatureGenericMethodParameterType.cs
new file mode 100644
index 0000000000..d0790283fb
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/SignatureGenericMethodParameterType.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    internal sealed class SignatureGenericMethodParameterType : SignatureGenericParameterType
+    {
+        internal SignatureGenericMethodParameterType(int position)
+            : base(position)
+        {
+        }
+
+        public sealed override bool IsGenericTypeParameter => false;
+        public sealed override bool IsGenericMethodParameter => true;
+    
+        public sealed override string Name => "!!" + GenericParameterPosition;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/SignatureGenericParameterType.cs b/src/System.Private.CoreLib/shared/System/Reflection/SignatureGenericParameterType.cs
new file mode 100644
index 0000000000..fee7bce353
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/SignatureGenericParameterType.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+
+namespace System.Reflection
+{
+    internal abstract class SignatureGenericParameterType : SignatureType
+    {
+        protected SignatureGenericParameterType(int position)
+        {
+            Debug.Assert(position >= 0);
+            _position = position;
+        }
+    
+        public sealed override bool IsTypeDefinition => false;
+        public sealed override bool IsGenericTypeDefinition => false;
+        protected sealed override bool HasElementTypeImpl() => false;
+        protected sealed override bool IsArrayImpl() => false;
+        protected sealed override bool IsByRefImpl() => false;
+        public sealed override bool IsByRefLike => false;
+        protected sealed override bool IsPointerImpl() => false;
+        public sealed override bool IsSZArray => false;
+        public sealed override bool IsVariableBoundArray => false;
+        public sealed override bool IsConstructedGenericType => false;
+        public sealed override bool IsGenericParameter => true;
+        public abstract override bool IsGenericMethodParameter { get; }
+        public sealed override bool ContainsGenericParameters => true;
+    
+        internal sealed override SignatureType ElementType => null;
+        public sealed override int GetArrayRank() => throw new ArgumentException(SR.Argument_HasToBeArrayClass);
+        public sealed override Type GetGenericTypeDefinition() => throw new InvalidOperationException(SR.InvalidOperation_NotGenericType);
+        public sealed override Type[] GetGenericArguments() => Array.Empty<Type>();
+        public sealed override Type[] GenericTypeArguments => Array.Empty<Type>();
+        public sealed override int GenericParameterPosition => _position;
+    
+        public abstract override string Name { get; }
+        public sealed override string Namespace => null;
+    
+        public sealed override string ToString() => Name;
+    
+        private readonly int _position;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/SignatureHasElementType.cs b/src/System.Private.CoreLib/shared/System/Reflection/SignatureHasElementType.cs
new file mode 100644
index 0000000000..e74e5f5aa2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/SignatureHasElementType.cs
@@ -0,0 +1,49 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+
+namespace System.Reflection
+{
+    internal abstract class SignatureHasElementType : SignatureType
+    {
+        protected SignatureHasElementType(SignatureType elementType)
+        {
+            Debug.Assert(elementType != null);  
+            _elementType = elementType;
+        }
+    
+        public sealed override bool IsTypeDefinition => false;
+        public sealed override bool IsGenericTypeDefinition => false;
+        protected sealed override bool HasElementTypeImpl() => true;
+        protected abstract override bool IsArrayImpl();
+        protected abstract override bool IsByRefImpl();
+        public sealed override bool IsByRefLike => false;
+        protected abstract override bool IsPointerImpl();
+        public abstract override bool IsSZArray { get; }
+        public abstract override bool IsVariableBoundArray { get; }
+        public sealed override bool IsConstructedGenericType => false;
+        public sealed override bool IsGenericParameter => false;
+        public sealed override bool IsGenericTypeParameter => false;
+        public sealed override bool IsGenericMethodParameter => false;
+        public sealed override bool ContainsGenericParameters => _elementType.ContainsGenericParameters;
+    
+        internal sealed override SignatureType ElementType => _elementType;
+        public abstract override int GetArrayRank();
+        public sealed override Type GetGenericTypeDefinition() => throw new InvalidOperationException(SR.InvalidOperation_NotGenericType);
+        public sealed override Type[] GetGenericArguments() => Array.Empty<Type>();
+        public sealed override Type[] GenericTypeArguments => Array.Empty<Type>();
+        public sealed override int GenericParameterPosition => throw new InvalidOperationException(SR.Arg_NotGenericParameter);
+    
+        public sealed override string Name => _elementType.Name + Suffix;
+        public sealed override string Namespace => _elementType.Namespace;
+    
+        public sealed override string ToString() => _elementType.ToString() + Suffix;
+    
+        protected abstract string Suffix { get; } 
+    
+        private readonly SignatureType _elementType;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/SignaturePointerType.cs b/src/System.Private.CoreLib/shared/System/Reflection/SignaturePointerType.cs
new file mode 100644
index 0000000000..a75a208165
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/SignaturePointerType.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Reflection
+{
+    internal sealed class SignaturePointerType : SignatureHasElementType
+    {
+        internal SignaturePointerType(SignatureType elementType)
+            : base(elementType)
+        {
+        }
+    
+        protected sealed override bool IsArrayImpl() => false;
+        protected sealed override bool IsByRefImpl() => false;
+        protected sealed override bool IsPointerImpl() => true;
+    
+        public sealed override bool IsSZArray => false;
+        public sealed override bool IsVariableBoundArray => false;
+    
+        public sealed override int GetArrayRank() => throw new ArgumentException(SR.Argument_HasToBeArrayClass);
+    
+        protected sealed override string Suffix => "*";
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/SignatureType.cs b/src/System.Private.CoreLib/shared/System/Reflection/SignatureType.cs
new file mode 100644
index 0000000000..40a0590448
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/SignatureType.cs
@@ -0,0 +1,140 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+
+namespace System.Reflection
+{
+    //
+    // Signature Types are highly restricted Type objects that can be passed in the Type[] parameter to Type.GetMethod(). Their primary
+    // use is to pass types representing generic parameters defined by the method, or types composed from them. Passing in the normal
+    // generic parameter Type obtained from MethodInfo.GetGenericArguments() is usually impractical (if you had the method, you wouldn't
+    // be looking for it!)
+    //
+    internal abstract class SignatureType : Type
+    {
+        public sealed override bool IsSignatureType => true;
+
+        // Type flavor predicates
+        public abstract override bool IsTypeDefinition { get; }
+        protected abstract override bool HasElementTypeImpl();
+        protected abstract override bool IsArrayImpl();
+        public abstract override bool IsSZArray { get; }
+        public abstract override bool IsVariableBoundArray { get; }
+        protected abstract override bool IsByRefImpl();
+        public abstract override bool IsByRefLike { get; }
+        protected abstract override bool IsPointerImpl();
+        public sealed override bool IsGenericType => IsGenericTypeDefinition || IsConstructedGenericType;
+        public abstract override bool IsGenericTypeDefinition { get; }
+        public abstract override bool IsConstructedGenericType { get; }
+        public abstract override bool IsGenericParameter { get; }
+        public abstract override bool IsGenericTypeParameter { get; }
+        public abstract override bool IsGenericMethodParameter { get; }
+        public abstract override bool ContainsGenericParameters { get; }
+        public sealed override MemberTypes MemberType => MemberTypes.TypeInfo;
+
+        // Compositors
+        public sealed override Type MakeArrayType() => new SignatureArrayType(this, rank: 1, isMultiDim: false);
+        public sealed override Type MakeArrayType(int rank)
+        {
+            if (rank <= 0)
+                throw new IndexOutOfRangeException();
+            return new SignatureArrayType(this, rank: rank, isMultiDim: true);
+        }
+        public sealed override Type MakeByRefType() => new SignatureByRefType(this);
+        public sealed override Type MakePointerType() => new SignaturePointerType(this);
+        public sealed override Type MakeGenericType(params Type[] typeArguments) => throw new NotSupportedException(SR.NotSupported_SignatureType); // There is no SignatureType for type definition types so it would never be legal to call this.
+
+        // Dissectors
+        public sealed override Type GetElementType() => ElementType;
+        public abstract override int GetArrayRank();
+        public abstract override Type GetGenericTypeDefinition();
+        public abstract override Type[] GenericTypeArguments { get; }
+        public abstract override Type[] GetGenericArguments();
+        public abstract override int GenericParameterPosition { get; }
+        internal abstract SignatureType ElementType { get; }
+
+        // Identity
+#if DEBUG
+        public sealed override bool Equals(object o) => base.Equals(o);
+        public sealed override bool Equals(Type o) => base.Equals(o);
+        public sealed override int GetHashCode() => base.GetHashCode();
+#endif
+        public sealed override Type UnderlyingSystemType => this;  // Equals(Type) depends on this.
+    
+        // Naming and diagnostics
+        public abstract override string Name { get; }
+        public abstract override string Namespace { get; }
+        public sealed override string FullName => null;
+        public sealed override string AssemblyQualifiedName => null;
+        public abstract override string ToString();
+
+        // Not supported on Signature Types
+        public sealed override Assembly Assembly => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override Module Module => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override Type ReflectedType => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override Type BaseType => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override Type[] GetInterfaces() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override bool IsAssignableFrom(Type c) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override int MetadataToken => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override bool HasSameMetadataDefinitionAs(MemberInfo other) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override Type DeclaringType => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override MethodBase DeclaringMethod => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override Type[] GetGenericParameterConstraints() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override GenericParameterAttributes GenericParameterAttributes => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override bool IsEnumDefined(object value) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override string GetEnumName(object value) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override string[] GetEnumNames() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override Type GetEnumUnderlyingType() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override Array GetEnumValues() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override Guid GUID => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        protected sealed override TypeCode GetTypeCodeImpl() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        protected sealed override TypeAttributes GetAttributeFlagsImpl() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override ConstructorInfo[] GetConstructors(BindingFlags bindingAttr) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override EventInfo GetEvent(string name, BindingFlags bindingAttr) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override EventInfo[] GetEvents(BindingFlags bindingAttr) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override FieldInfo GetField(string name, BindingFlags bindingAttr) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override FieldInfo[] GetFields(BindingFlags bindingAttr) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override MemberInfo[] GetMembers(BindingFlags bindingAttr) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override MethodInfo[] GetMethods(BindingFlags bindingAttr) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override Type GetNestedType(string name, BindingFlags bindingAttr) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override Type[] GetNestedTypes(BindingFlags bindingAttr) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override PropertyInfo[] GetProperties(BindingFlags bindingAttr) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override object InvokeMember(string name, BindingFlags invokeAttr, Binder binder, object target, object[] args, ParameterModifier[] modifiers, CultureInfo culture, string[] namedParameters) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        protected sealed override MethodInfo GetMethodImpl(string name, BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        protected sealed override MethodInfo GetMethodImpl(string name, int genericParameterCount, BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        protected sealed override PropertyInfo GetPropertyImpl(string name, BindingFlags bindingAttr, Binder binder, Type returnType, Type[] types, ParameterModifier[] modifiers) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override MemberInfo[] FindMembers(MemberTypes memberType, BindingFlags bindingAttr, MemberFilter filter, object filterCriteria) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override MemberInfo[] GetMember(string name, BindingFlags bindingAttr) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override MemberInfo[] GetMember(string name, MemberTypes type, BindingFlags bindingAttr) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override MemberInfo[] GetDefaultMembers() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override EventInfo[] GetEvents() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override object[] GetCustomAttributes(bool inherit) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override object[] GetCustomAttributes(Type attributeType, bool inherit) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override bool IsDefined(Type attributeType, bool inherit) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override IList<CustomAttributeData> GetCustomAttributesData() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override Type GetInterface(string name, bool ignoreCase) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        protected sealed override ConstructorInfo GetConstructorImpl(BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        protected sealed override bool IsCOMObjectImpl() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        protected sealed override bool IsPrimitiveImpl() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override IEnumerable<CustomAttributeData> CustomAttributes => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override Type[] FindInterfaces(TypeFilter filter, object filterCriteria) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override InterfaceMapping GetInterfaceMap(Type interfaceType) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        protected sealed override bool IsContextfulImpl() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override bool IsEnum => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override bool IsEquivalentTo(Type other) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override bool IsInstanceOfType(object o) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        protected sealed override bool IsMarshalByRefImpl() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override bool IsSecurityCritical => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override bool IsSecuritySafeCritical => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override bool IsSecurityTransparent => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override bool IsSerializable => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override bool IsSubclassOf(Type c) => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        protected sealed override bool IsValueTypeImpl() => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override StructLayoutAttribute StructLayoutAttribute => throw new NotSupportedException(SR.NotSupported_SignatureType);
+        public sealed override RuntimeTypeHandle TypeHandle => throw new NotSupportedException(SR.NotSupported_SignatureType);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/SignatureTypeExtensions.cs b/src/System.Private.CoreLib/shared/System/Reflection/SignatureTypeExtensions.cs
new file mode 100644
index 0000000000..9247132546
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/SignatureTypeExtensions.cs
@@ -0,0 +1,228 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Reflection;
+using System.Diagnostics;
+
+namespace System.Reflection
+{
+#if CORERT
+    [System.Runtime.CompilerServices.ReflectionBlocked]
+    public // Needs to be public so that Reflection.Core can see it.
+#else
+    internal
+#endif
+    static class SignatureTypeExtensions
+    {
+        /// <summary>
+        /// This is semantically identical to 
+        /// 
+        ///      parameter.ParameterType == pattern.TryResolveAgainstGenericMethod(parameter.Member)
+        ///      
+        /// but without the allocation overhead of TryResolve.
+        /// </summary>
+        public static bool MatchesParameterTypeExactly(this Type pattern, ParameterInfo parameter)
+        {
+            if (pattern is SignatureType signatureType)
+                return signatureType.MatchesExactly(parameter.ParameterType);
+            else
+                return pattern == (object)(parameter.ParameterType);
+        }
+
+        /// <summary>
+        /// This is semantically identical to 
+        /// 
+        ///      actual == pattern.TryResolveAgainstGenericMethod(parameterMember)
+        ///      
+        /// but without the allocation overhead of TryResolve.
+        /// </summary>
+        internal static bool MatchesExactly(this SignatureType pattern, Type actual)
+        {
+            if (pattern.IsSZArray)
+            {
+                return actual.IsSZArray && pattern.ElementType.MatchesExactly(actual.GetElementType());
+            }
+            else if (pattern.IsVariableBoundArray)
+            {
+                return actual.IsVariableBoundArray && pattern.GetArrayRank() == actual.GetArrayRank() && pattern.ElementType.MatchesExactly(actual.GetElementType());
+            }
+            else if (pattern.IsByRef)
+            {
+                return actual.IsByRef && pattern.ElementType.MatchesExactly(actual.GetElementType());
+            }
+            else if (pattern.IsPointer)
+            {
+                return actual.IsPointer && pattern.ElementType.MatchesExactly(actual.GetElementType());
+            }
+            else if (pattern.IsConstructedGenericType)
+            {
+                if (!actual.IsConstructedGenericType)
+                    return false;
+                if (!(pattern.GetGenericTypeDefinition() == actual.GetGenericTypeDefinition()))
+                    return false;
+                Type[] patternGenericTypeArguments = pattern.GenericTypeArguments;
+                Type[] actualGenericTypeArguments = actual.GenericTypeArguments;
+                int count = patternGenericTypeArguments.Length;
+                if (count != actualGenericTypeArguments.Length)
+                    return false;
+                for (int i = 0; i < count; i++)
+                {
+                    Type patternGenericTypeArgument = patternGenericTypeArguments[i];
+                    if (patternGenericTypeArgument is SignatureType signatureType)
+                    {
+                        if (!signatureType.MatchesExactly(actualGenericTypeArguments[i]))
+                            return false;
+                    }
+                    else
+                    {
+                        if (patternGenericTypeArgument != actualGenericTypeArguments[i])
+                            return false;
+                    }
+                }
+                return true;
+            }
+            else if (pattern.IsGenericMethodParameter)
+            {
+                if (!actual.IsGenericMethodParameter)
+                    return false;
+                if (pattern.GenericParameterPosition != actual.GenericParameterPosition)
+                    return false;
+                return true;
+            }
+            else
+            {
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// Translates a SignatureType into its equivalent resolved Type by recursively substituting all generic parameter references
+        /// with its corresponding generic parameter definition. This is slow so MatchesExactly or MatchesParameterTypeExactly should be
+        /// substituted instead whenever possible. This is only used by the DefaultBinder when its fast-path checks have been exhausted and
+        /// it needs to call non-trivial methods like IsAssignableFrom which SignatureTypes will never support.
+        /// 
+        /// Because this method is used to eliminate method candidates in a GetMethod() lookup, it is entirely possible that the Type
+        /// might not be creatable due to conflicting generic constraints. Since this merely implies that this candidate is not
+        /// the method we're looking for, we return null rather than let the TypeLoadException bubble up. The DefaultBinder will catch
+        /// the null and continue its search for a better candidate.
+        /// </summary>
+        internal static Type TryResolveAgainstGenericMethod(this SignatureType signatureType, MethodInfo genericMethod)
+        {
+            return signatureType.TryResolve(genericMethod.GetGenericArguments());
+        }
+    
+        private static Type TryResolve(this SignatureType signatureType, Type[] genericMethodParameters)
+        {
+            if (signatureType.IsSZArray)
+            {
+                return signatureType.ElementType.TryResolve(genericMethodParameters)?.TryMakeArrayType();
+            }
+            else if (signatureType.IsVariableBoundArray)
+            {
+                return signatureType.ElementType.TryResolve(genericMethodParameters)?.TryMakeArrayType(signatureType.GetArrayRank());
+            }
+            else if (signatureType.IsByRef)
+            {
+                return signatureType.ElementType.TryResolve(genericMethodParameters)?.TryMakeByRefType();
+            }
+            else if (signatureType.IsPointer)
+            {
+                return signatureType.ElementType.TryResolve(genericMethodParameters)?.TryMakePointerType();
+            }
+            else if (signatureType.IsConstructedGenericType)
+            {
+                Type[] genericTypeArguments = signatureType.GenericTypeArguments;
+                int count = genericTypeArguments.Length;
+                Type[] newGenericTypeArguments = new Type[count];
+                for (int i = 0; i < count; i++)
+                {
+                    Type genericTypeArgument = genericTypeArguments[i];
+                    if (genericTypeArgument is SignatureType signatureGenericTypeArgument)
+                    {
+                        newGenericTypeArguments[i] = signatureGenericTypeArgument.TryResolve(genericMethodParameters);
+                        if (newGenericTypeArguments[i] == null)
+                            return null;
+                    }
+                    else
+                    {
+                        newGenericTypeArguments[i] = genericTypeArgument;
+                    }
+                }
+                return signatureType.GetGenericTypeDefinition().TryMakeGenericType(newGenericTypeArguments);
+            }
+            else if (signatureType.IsGenericMethodParameter)
+            {
+                int position = signatureType.GenericParameterPosition;
+                if (position >= genericMethodParameters.Length)
+                    return null;
+                return genericMethodParameters[position];
+            }
+            else
+            {
+                return null;
+            }
+        }
+    
+        private static Type TryMakeArrayType(this Type type)
+        {
+            try
+            {
+                return type.MakeArrayType();
+            }
+            catch
+            {
+                return null;
+            }
+        }
+    
+        private static Type TryMakeArrayType(this Type type, int rank)
+        {
+            try
+            {
+                return type.MakeArrayType(rank);
+            }
+            catch
+            {
+                return null;
+            }
+        }
+    
+        private static Type TryMakeByRefType(this Type type)
+        {
+            try
+            {
+                return type.MakeByRefType();
+            }
+            catch
+            {
+                return null;
+            }
+        }
+    
+        private static Type TryMakePointerType(this Type type)
+        {
+            try
+            {
+                return type.MakePointerType();
+            }
+            catch
+            {
+                return null;
+            }
+        }
+    
+        private static Type TryMakeGenericType(this Type type, Type[] instantiation)
+        {
+            try
+            {
+                return type.MakeGenericType(instantiation);
+            }
+            catch
+            {
+                return null;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/StrongNameKeyPair.cs b/src/System.Private.CoreLib/shared/System/Reflection/StrongNameKeyPair.cs
new file mode 100644
index 0000000000..a0ba97f835
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/StrongNameKeyPair.cs
@@ -0,0 +1,58 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.IO;
+using System.Runtime.Serialization;
+
+namespace System.Reflection
+{
+    public class StrongNameKeyPair : IDeserializationCallback, ISerializable
+    {
+        // Build key pair from file.
+        public StrongNameKeyPair(FileStream keyPairFile)
+        {
+            if (keyPairFile == null)
+                throw new ArgumentNullException(nameof(keyPairFile));
+
+            int length = (int)keyPairFile.Length;
+            byte[] keyPairArray = new byte[length];
+            keyPairFile.Read(keyPairArray, 0, length);
+        }
+
+        // Build key pair from byte array in memory.
+        public StrongNameKeyPair(byte[] keyPairArray)
+        {
+            if (keyPairArray == null)
+                throw new ArgumentNullException(nameof(keyPairArray));
+        }
+
+        protected StrongNameKeyPair(SerializationInfo info, StreamingContext context)
+        {
+            throw new PlatformNotSupportedException();
+        }
+
+        public StrongNameKeyPair(string keyPairContainer)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_StrongNameSigning);
+        }
+
+        public byte[] PublicKey
+        {
+            get
+            {
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_StrongNameSigning);
+            }
+        }
+
+        void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            throw new PlatformNotSupportedException();
+        }
+
+        void IDeserializationCallback.OnDeserialization(object sender)
+        {
+            throw new PlatformNotSupportedException();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/TargetException.cs b/src/System.Private.CoreLib/shared/System/Reflection/TargetException.cs
new file mode 100644
index 0000000000..c200000738
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/TargetException.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Reflection
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class TargetException : ApplicationException
+    {
+        public TargetException()
+            : this(null)
+        {
+        }
+
+        public TargetException(string message)
+            : this(message, null)
+        {
+        }
+
+        public TargetException(string message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_TARGET;
+        }
+
+        protected TargetException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/TargetInvocationException.cs b/src/System.Private.CoreLib/shared/System/Reflection/TargetInvocationException.cs
new file mode 100644
index 0000000000..822ddfdfb2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/TargetInvocationException.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Reflection
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class TargetInvocationException : ApplicationException
+    {
+        public TargetInvocationException(Exception inner)
+            : base(SR.Arg_TargetInvocationException, inner)
+        {
+            HResult = HResults.COR_E_TARGETINVOCATION;
+        }
+
+        public TargetInvocationException(string message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_TARGETINVOCATION;
+        }
+
+        internal TargetInvocationException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/TargetParameterCountException.cs b/src/System.Private.CoreLib/shared/System/Reflection/TargetParameterCountException.cs
new file mode 100644
index 0000000000..c68c467290
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/TargetParameterCountException.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Reflection
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class TargetParameterCountException : ApplicationException
+    {
+        public TargetParameterCountException()
+            : base(SR.Arg_TargetParameterCountException)
+        {
+            HResult = HResults.COR_E_TARGETPARAMCOUNT;
+        }
+
+        public TargetParameterCountException(string message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_TARGETPARAMCOUNT;
+        }
+
+        public TargetParameterCountException(string message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_TARGETPARAMCOUNT;
+        }
+
+        internal TargetParameterCountException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/TypeAttributes.cs b/src/System.Private.CoreLib/shared/System/Reflection/TypeAttributes.cs
new file mode 100644
index 0000000000..aa30331856
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/TypeAttributes.cs
@@ -0,0 +1,63 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+
+namespace System.Reflection
+{
+    // This Enum matchs the CorTypeAttr defined in CorHdr.h
+    [Flags]
+    public enum TypeAttributes
+    {
+        VisibilityMask = 0x00000007,
+        NotPublic = 0x00000000,     // Class is not public scope.
+        Public = 0x00000001,     // Class is public scope.
+        NestedPublic = 0x00000002,     // Class is nested with public visibility.
+        NestedPrivate = 0x00000003,     // Class is nested with private visibility.
+        NestedFamily = 0x00000004,     // Class is nested with family visibility.
+        NestedAssembly = 0x00000005,     // Class is nested with assembly visibility.
+        NestedFamANDAssem = 0x00000006,     // Class is nested with family and assembly visibility.
+        NestedFamORAssem = 0x00000007,     // Class is nested with family or assembly visibility.
+
+        // Use this mask to retrieve class layout informaiton
+        // 0 is AutoLayout, 0x2 is SequentialLayout, 4 is ExplicitLayout
+        LayoutMask = 0x00000018,
+        AutoLayout = 0x00000000,     // Class fields are auto-laid out
+        SequentialLayout = 0x00000008,     // Class fields are laid out sequentially
+        ExplicitLayout = 0x00000010,     // Layout is supplied explicitly
+                                         // end layout mask
+
+        // Use this mask to distinguish whether a type declaration is an interface.  (Class vs. ValueType done based on whether it subclasses S.ValueType)
+        ClassSemanticsMask = 0x00000020,
+        Class = 0x00000000,     // Type is a class (or a value type).
+        Interface = 0x00000020,     // Type is an interface.
+
+        // Special semantics in addition to class semantics.
+        Abstract = 0x00000080,     // Class is abstract
+        Sealed = 0x00000100,     // Class is concrete and may not be extended
+        SpecialName = 0x00000400,     // Class name is special.  Name describes how.
+
+        // Implementation attributes.
+        Import = 0x00001000,     // Class / interface is imported
+        Serializable = 0x00002000,     // The class is Serializable.
+        WindowsRuntime = 0x00004000,     // Type is a Windows Runtime type.
+
+        // Use tdStringFormatMask to retrieve string information for native interop
+        StringFormatMask = 0x00030000,
+        AnsiClass = 0x00000000,     // LPTSTR is interpreted as ANSI in this class
+        UnicodeClass = 0x00010000,     // LPTSTR is interpreted as UNICODE
+        AutoClass = 0x00020000,     // LPTSTR is interpreted automatically
+        CustomFormatClass = 0x00030000,     // A non-standard encoding specified by CustomFormatMask
+        CustomFormatMask = 0x00C00000,     // Use this mask to retrieve non-standard encoding information for native interop. The meaning of the values of these 2 bits is unspecified.
+
+        // end string format mask
+
+        BeforeFieldInit = 0x00100000,     // Initialize the class any time before first static field access.
+
+        RTSpecialName = 0x00000800,     // Runtime should check name encoding.
+        HasSecurity = 0x00040000,     // Class has security associate with it.
+
+        ReservedMask = 0x00040800,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/TypeDelegator.cs b/src/System.Private.CoreLib/shared/System/Reflection/TypeDelegator.cs
new file mode 100644
index 0000000000..e0be6e87b6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/TypeDelegator.cs
@@ -0,0 +1,130 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// TypeDelegator
+// 
+// This class wraps a Type object and delegates all methods to that Type.
+
+using CultureInfo = System.Globalization.CultureInfo;
+
+namespace System.Reflection
+{
+    public class TypeDelegator : TypeInfo
+    {
+        public override bool IsAssignableFrom(TypeInfo typeInfo)
+        {
+            if (typeInfo == null)
+                return false;
+            return IsAssignableFrom(typeInfo.AsType());
+        }
+
+        protected Type typeImpl;
+
+        protected TypeDelegator() { }
+
+        public TypeDelegator(Type delegatingType)
+        {
+            if (delegatingType == null)
+                throw new ArgumentNullException(nameof(delegatingType));
+
+            typeImpl = delegatingType;
+        }
+
+        public override Guid GUID => typeImpl.GUID;
+        public override int MetadataToken => typeImpl.MetadataToken;
+
+        public override object InvokeMember(string name, BindingFlags invokeAttr, Binder binder, object target,
+            object[] args, ParameterModifier[] modifiers, CultureInfo culture, string[] namedParameters)
+        {
+            return typeImpl.InvokeMember(name, invokeAttr, binder, target, args, modifiers, culture, namedParameters);
+        }
+
+        public override Module Module => typeImpl.Module;
+        public override Assembly Assembly => typeImpl.Assembly;
+        public override RuntimeTypeHandle TypeHandle => typeImpl.TypeHandle;
+        public override string Name => typeImpl.Name;
+        public override string FullName => typeImpl.FullName;
+        public override string Namespace => typeImpl.Namespace;
+        public override string AssemblyQualifiedName => typeImpl.AssemblyQualifiedName;
+        public override Type BaseType => typeImpl.BaseType;
+
+        protected override ConstructorInfo GetConstructorImpl(BindingFlags bindingAttr, Binder binder,
+                CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            return typeImpl.GetConstructor(bindingAttr, binder, callConvention, types, modifiers);
+        }
+
+        public override ConstructorInfo[] GetConstructors(BindingFlags bindingAttr) => typeImpl.GetConstructors(bindingAttr);
+
+        protected override MethodInfo GetMethodImpl(string name, BindingFlags bindingAttr, Binder binder,
+                CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            // This is interesting there are two paths into the impl.  One that validates
+            //  type as non-null and one where type may be null.
+            if (types == null)
+                return typeImpl.GetMethod(name, bindingAttr);
+            else
+                return typeImpl.GetMethod(name, bindingAttr, binder, callConvention, types, modifiers);
+        }
+
+        public override MethodInfo[] GetMethods(BindingFlags bindingAttr) => typeImpl.GetMethods(bindingAttr);
+
+        public override FieldInfo GetField(string name, BindingFlags bindingAttr) => typeImpl.GetField(name, bindingAttr);
+        public override FieldInfo[] GetFields(BindingFlags bindingAttr) => typeImpl.GetFields(bindingAttr);
+
+        public override Type GetInterface(string name, bool ignoreCase) => typeImpl.GetInterface(name, ignoreCase);
+
+        public override Type[] GetInterfaces() => typeImpl.GetInterfaces();
+
+        public override EventInfo GetEvent(string name, BindingFlags bindingAttr) => typeImpl.GetEvent(name, bindingAttr);
+
+        public override EventInfo[] GetEvents() => typeImpl.GetEvents();
+
+        protected override PropertyInfo GetPropertyImpl(string name, BindingFlags bindingAttr, Binder binder,
+                        Type returnType, Type[] types, ParameterModifier[] modifiers)
+        {
+            if (returnType == null && types == null)
+                return typeImpl.GetProperty(name, bindingAttr);
+            else
+                return typeImpl.GetProperty(name, bindingAttr, binder, returnType, types, modifiers);
+        }
+
+        public override PropertyInfo[] GetProperties(BindingFlags bindingAttr) => typeImpl.GetProperties(bindingAttr);
+        public override EventInfo[] GetEvents(BindingFlags bindingAttr) => typeImpl.GetEvents(bindingAttr);
+        public override Type[] GetNestedTypes(BindingFlags bindingAttr) => typeImpl.GetNestedTypes(bindingAttr);
+        public override Type GetNestedType(string name, BindingFlags bindingAttr) => typeImpl.GetNestedType(name, bindingAttr);
+        public override MemberInfo[] GetMember(string name, MemberTypes type, BindingFlags bindingAttr) => typeImpl.GetMember(name, type, bindingAttr);
+        public override MemberInfo[] GetMembers(BindingFlags bindingAttr) => typeImpl.GetMembers(bindingAttr);
+
+        protected override TypeAttributes GetAttributeFlagsImpl() => typeImpl.Attributes;
+
+        public override bool IsTypeDefinition => typeImpl.IsTypeDefinition;
+        public override bool IsSZArray => typeImpl.IsSZArray;
+
+        protected override bool IsArrayImpl() => typeImpl.IsArray;
+        protected override bool IsPrimitiveImpl() => typeImpl.IsPrimitive;
+        protected override bool IsByRefImpl() => typeImpl.IsByRef;
+        public override bool IsGenericTypeParameter => typeImpl.IsGenericTypeParameter;
+        public override bool IsGenericMethodParameter => typeImpl.IsGenericMethodParameter;
+        protected override bool IsPointerImpl() => typeImpl.IsPointer;
+        protected override bool IsValueTypeImpl() => typeImpl.IsValueType;
+        protected override bool IsCOMObjectImpl() => typeImpl.IsCOMObject;
+        public override bool IsByRefLike => typeImpl.IsByRefLike;
+        public override bool IsConstructedGenericType => typeImpl.IsConstructedGenericType;
+
+        public override bool IsCollectible => typeImpl.IsCollectible;
+
+        public override Type GetElementType() => typeImpl.GetElementType();
+        protected override bool HasElementTypeImpl() => typeImpl.HasElementType;
+
+        public override Type UnderlyingSystemType => typeImpl.UnderlyingSystemType;
+
+        // ICustomAttributeProvider
+        public override object[] GetCustomAttributes(bool inherit) => typeImpl.GetCustomAttributes(inherit);
+        public override object[] GetCustomAttributes(Type attributeType, bool inherit) => typeImpl.GetCustomAttributes(attributeType, inherit);
+
+        public override bool IsDefined(Type attributeType, bool inherit) => typeImpl.IsDefined(attributeType, inherit);
+        public override InterfaceMapping GetInterfaceMap(Type interfaceType) => typeImpl.GetInterfaceMap(interfaceType);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/TypeFilter.cs b/src/System.Private.CoreLib/shared/System/Reflection/TypeFilter.cs
new file mode 100644
index 0000000000..eb049f81f9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/TypeFilter.cs
@@ -0,0 +1,8 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public delegate bool TypeFilter(Type m, object filterCriteria);
+}
diff --git a/src/System.Private.CoreLib/shared/System/Reflection/TypeInfo.cs b/src/System.Private.CoreLib/shared/System/Reflection/TypeInfo.cs
new file mode 100644
index 0000000000..f4add736f4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Reflection/TypeInfo.cs
@@ -0,0 +1,84 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+
+namespace System.Reflection
+{
+    public abstract partial class TypeInfo : Type, IReflectableType
+    {
+        protected TypeInfo() { }
+
+        TypeInfo IReflectableType.GetTypeInfo() => this;
+        public virtual Type AsType() => this;
+
+        public virtual Type[] GenericTypeParameters => IsGenericTypeDefinition ? GetGenericArguments() : Type.EmptyTypes;
+
+        public virtual EventInfo GetDeclaredEvent(string name) => GetEvent(name, TypeInfo.DeclaredOnlyLookup);
+        public virtual FieldInfo GetDeclaredField(string name) => GetField(name, TypeInfo.DeclaredOnlyLookup);
+        public virtual MethodInfo GetDeclaredMethod(string name) => GetMethod(name, TypeInfo.DeclaredOnlyLookup);
+        public virtual TypeInfo GetDeclaredNestedType(string name) => GetNestedType(name, TypeInfo.DeclaredOnlyLookup)?.GetTypeInfo();
+        public virtual PropertyInfo GetDeclaredProperty(string name) => GetProperty(name, TypeInfo.DeclaredOnlyLookup);
+
+        public virtual IEnumerable<MethodInfo> GetDeclaredMethods(string name)
+        {
+            foreach (MethodInfo method in GetMethods(TypeInfo.DeclaredOnlyLookup))
+            {
+                if (method.Name == name)
+                    yield return method;
+            }
+        }
+
+        public virtual IEnumerable<ConstructorInfo> DeclaredConstructors => GetConstructors(TypeInfo.DeclaredOnlyLookup);
+        public virtual IEnumerable<EventInfo> DeclaredEvents => GetEvents(TypeInfo.DeclaredOnlyLookup);
+        public virtual IEnumerable<FieldInfo> DeclaredFields => GetFields(TypeInfo.DeclaredOnlyLookup);
+        public virtual IEnumerable<MemberInfo> DeclaredMembers => GetMembers(TypeInfo.DeclaredOnlyLookup);
+        public virtual IEnumerable<MethodInfo> DeclaredMethods => GetMethods(TypeInfo.DeclaredOnlyLookup);
+        public virtual IEnumerable<System.Reflection.TypeInfo> DeclaredNestedTypes
+        {
+            get
+            {
+                foreach (Type t in GetNestedTypes(TypeInfo.DeclaredOnlyLookup))
+                {
+                    yield return t.GetTypeInfo();
+                }
+            }
+        }
+        public virtual IEnumerable<PropertyInfo> DeclaredProperties => GetProperties(TypeInfo.DeclaredOnlyLookup);
+
+        public virtual IEnumerable<Type> ImplementedInterfaces => GetInterfaces();
+
+        //a re-implementation of ISAF from Type, skipping the use of UnderlyingType
+        public virtual bool IsAssignableFrom(TypeInfo typeInfo)
+        {
+            if (typeInfo == null)
+                return false;
+
+            if (this == typeInfo)
+                return true;
+
+            // If c is a subclass of this class, then c can be cast to this type.
+            if (typeInfo.IsSubclassOf(this))
+                return true;
+
+            if (this.IsInterface)
+            {
+                return typeInfo.ImplementInterface(this);
+            }
+            else if (IsGenericParameter)
+            {
+                Type[] constraints = GetGenericParameterConstraints();
+                for (int i = 0; i < constraints.Length; i++)
+                    if (!constraints[i].IsAssignableFrom(typeInfo))
+                        return false;
+
+                return true;
+            }
+
+            return false;
+        }
+
+        private const BindingFlags DeclaredOnlyLookup = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Static | BindingFlags.DeclaredOnly;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ResolveEventArgs.cs b/src/System.Private.CoreLib/shared/System/ResolveEventArgs.cs
new file mode 100644
index 0000000000..6196947bb5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ResolveEventArgs.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+
+namespace System
+{
+    public class ResolveEventArgs : EventArgs
+    {
+        public ResolveEventArgs(string name)
+        {
+            Name = name;
+        }
+
+        public ResolveEventArgs(string name, Assembly requestingAssembly)
+        {
+            Name = name;
+            RequestingAssembly = requestingAssembly;
+        }
+
+        public string Name { get; }
+        public Assembly RequestingAssembly { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ResolveEventHandler.cs b/src/System.Private.CoreLib/shared/System/ResolveEventHandler.cs
new file mode 100644
index 0000000000..cb9af5de66
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ResolveEventHandler.cs
@@ -0,0 +1,10 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+
+namespace System
+{
+    public delegate Assembly ResolveEventHandler(object sender, ResolveEventArgs args);
+}
diff --git a/src/System.Private.CoreLib/shared/System/Resources/IResourceReader.cs b/src/System.Private.CoreLib/shared/System/Resources/IResourceReader.cs
new file mode 100644
index 0000000000..543a5a67de
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Resources/IResourceReader.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Abstraction to read streams of resources.
+**
+** 
+===========================================================*/
+
+using System;
+using System.Collections;
+
+namespace System.Resources
+{
+    public interface IResourceReader : IEnumerable, IDisposable
+    {
+        // Interface does not need to be marked with the serializable attribute
+        // Closes the ResourceReader, releasing any resources associated with it.
+        // This could close a network connection, a file, or do nothing.
+        void Close();
+
+        new IDictionaryEnumerator GetEnumerator();
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Resources/MissingManifestResourceException.cs b/src/System.Private.CoreLib/shared/System/Resources/MissingManifestResourceException.cs
new file mode 100644
index 0000000000..20914ac7e1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Resources/MissingManifestResourceException.cs
@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System.Resources
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class MissingManifestResourceException : SystemException
+    {
+        public MissingManifestResourceException()
+            : base(SR.Arg_MissingManifestResourceException)
+        {
+            HResult = System.HResults.COR_E_MISSINGMANIFESTRESOURCE;
+        }
+
+        public MissingManifestResourceException(string message)
+            : base(message)
+        {
+            HResult = System.HResults.COR_E_MISSINGMANIFESTRESOURCE;
+        }
+
+        public MissingManifestResourceException(string message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = System.HResults.COR_E_MISSINGMANIFESTRESOURCE;
+        }
+
+        protected MissingManifestResourceException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Resources/MissingSatelliteAssemblyException.cs b/src/System.Private.CoreLib/shared/System/Resources/MissingSatelliteAssemblyException.cs
new file mode 100644
index 0000000000..af547b21f1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Resources/MissingSatelliteAssemblyException.cs
@@ -0,0 +1,64 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Exception for a missing satellite assembly needed
+**          for ultimate resource fallback.  This usually
+**          indicates a setup and/or deployment problem.
+**
+**
+===========================================================*/
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System.Resources
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class MissingSatelliteAssemblyException : SystemException
+    {
+        private String _cultureName;
+
+        public MissingSatelliteAssemblyException()
+            : base(SR.MissingSatelliteAssembly_Default)
+        {
+            HResult = System.HResults.COR_E_MISSINGSATELLITEASSEMBLY;
+        }
+
+        public MissingSatelliteAssemblyException(string message)
+            : base(message)
+        {
+            HResult = System.HResults.COR_E_MISSINGSATELLITEASSEMBLY;
+        }
+
+        public MissingSatelliteAssemblyException(string message, String cultureName)
+            : base(message)
+        {
+            HResult = System.HResults.COR_E_MISSINGSATELLITEASSEMBLY;
+            _cultureName = cultureName;
+        }
+
+        public MissingSatelliteAssemblyException(string message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = System.HResults.COR_E_MISSINGSATELLITEASSEMBLY;
+        }
+
+        protected MissingSatelliteAssemblyException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+
+        public String CultureName
+        {
+            get { return _cultureName; }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Resources/NeutralResourcesLanguageAttribute.cs b/src/System.Private.CoreLib/shared/System/Resources/NeutralResourcesLanguageAttribute.cs
new file mode 100644
index 0000000000..495c5205b2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Resources/NeutralResourcesLanguageAttribute.cs
@@ -0,0 +1,33 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Resources
+{
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = false)]
+    public sealed class NeutralResourcesLanguageAttribute : Attribute
+    {
+        public NeutralResourcesLanguageAttribute(string cultureName)
+        {
+            if (cultureName == null)
+                throw new ArgumentNullException(nameof(cultureName));
+
+            CultureName = cultureName;
+            Location = UltimateResourceFallbackLocation.MainAssembly;
+        }
+
+        public NeutralResourcesLanguageAttribute(string cultureName, UltimateResourceFallbackLocation location)
+        {
+            if (cultureName == null)
+                throw new ArgumentNullException(nameof(cultureName));
+            if (!Enum.IsDefined(typeof(UltimateResourceFallbackLocation), location))
+                throw new ArgumentException(SR.Format(SR.Arg_InvalidNeutralResourcesLanguage_FallbackLoc, location));
+
+            CultureName = cultureName;
+            Location = location;
+        }
+
+        public string CultureName { get; }
+        public UltimateResourceFallbackLocation Location { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Resources/ResourceFallbackManager.cs b/src/System.Private.CoreLib/shared/System/Resources/ResourceFallbackManager.cs
new file mode 100644
index 0000000000..8268f3208d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Resources/ResourceFallbackManager.cs
@@ -0,0 +1,87 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Encapsulates CultureInfo fallback for resource 
+** lookup
+**
+** 
+===========================================================*/
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace System.Resources
+{
+    internal class ResourceFallbackManager : IEnumerable<CultureInfo>
+    {
+        private CultureInfo m_startingCulture;
+        private CultureInfo m_neutralResourcesCulture;
+        private bool m_useParents;
+
+        internal ResourceFallbackManager(CultureInfo startingCulture, CultureInfo neutralResourcesCulture, bool useParents)
+        {
+            if (startingCulture != null)
+            {
+                m_startingCulture = startingCulture;
+            }
+            else
+            {
+                m_startingCulture = CultureInfo.CurrentUICulture;
+            }
+
+            m_neutralResourcesCulture = neutralResourcesCulture;
+            m_useParents = useParents;
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+
+        // WARING: This function must be kept in sync with ResourceManager.GetFirstResourceSet()
+        public IEnumerator<CultureInfo> GetEnumerator()
+        {
+            bool reachedNeutralResourcesCulture = false;
+
+            // 1. starting culture chain, up to neutral
+            CultureInfo currentCulture = m_startingCulture;
+            do
+            {
+                if (m_neutralResourcesCulture != null && currentCulture.Name == m_neutralResourcesCulture.Name)
+                {
+                    // Return the invariant culture all the time, even if the UltimateResourceFallbackLocation
+                    // is a satellite assembly.  This is fixed up later in ManifestBasedResourceGroveler::UltimateFallbackFixup.
+                    yield return CultureInfo.InvariantCulture;
+                    reachedNeutralResourcesCulture = true;
+                    break;
+                }
+                yield return currentCulture;
+                currentCulture = currentCulture.Parent;
+            } while (m_useParents && !currentCulture.HasInvariantCultureName);
+
+            if (!m_useParents || m_startingCulture.HasInvariantCultureName)
+            {
+                yield break;
+            }
+
+            // 2. invariant
+            //    Don't return invariant twice though.
+            if (reachedNeutralResourcesCulture)
+                yield break;
+
+            yield return CultureInfo.InvariantCulture;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Resources/ResourceTypeCode.cs b/src/System.Private.CoreLib/shared/System/Resources/ResourceTypeCode.cs
new file mode 100644
index 0000000000..b0ceb61df4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Resources/ResourceTypeCode.cs
@@ -0,0 +1,58 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Marker for types in .resources files
+**
+** 
+===========================================================*/
+
+namespace System.Resources
+{
+    /* An internal implementation detail for .resources files, describing
+       what type an object is.  
+       Ranges:
+       0 - 0x1F     Primitives and reserved values
+       0x20 - 0x3F  Specially recognized types, like byte[] and Streams
+
+       Note this data must be included in any documentation describing the
+       internals of .resources files.
+    */
+    internal enum ResourceTypeCode
+    {
+        // Primitives
+        Null = 0,
+        String = 1,
+        Boolean = 2,
+        Char = 3,
+        Byte = 4,
+        SByte = 5,
+        Int16 = 6,
+        UInt16 = 7,
+        Int32 = 8,
+        UInt32 = 9,
+        Int64 = 0xa,
+        UInt64 = 0xb,
+        Single = 0xc,
+        Double = 0xd,
+        Decimal = 0xe,
+        DateTime = 0xf,
+        TimeSpan = 0x10,
+
+        // A meta-value - change this if you add new primitives
+        LastPrimitive = TimeSpan,
+
+        // Types with a special representation, like byte[] and Stream
+        ByteArray = 0x20,
+        Stream = 0x21,
+
+        // User types - serialized using the binary formatter.
+        StartOfUserTypes = 0x40
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Resources/RuntimeResourceSet.cs b/src/System.Private.CoreLib/shared/System/Resources/RuntimeResourceSet.cs
new file mode 100644
index 0000000000..a63e68c19d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Resources/RuntimeResourceSet.cs
@@ -0,0 +1,434 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: CultureInfo-specific collection of resources.
+**
+** 
+===========================================================*/
+
+using System;
+using System.IO;
+using System.Collections;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Reflection;
+using System.Runtime.Versioning;
+using System.Diagnostics;
+
+namespace System.Resources
+{
+    // A RuntimeResourceSet stores all the resources defined in one 
+    // particular CultureInfo, with some loading optimizations.
+    //
+    // It is expected that nearly all the runtime's users will be satisfied with the
+    // default resource file format, and it will be more efficient than most simple
+    // implementations.  Users who would consider creating their own ResourceSets and/or
+    // ResourceReaders and ResourceWriters are people who have to interop with a 
+    // legacy resource file format, are creating their own resource file format 
+    // (using XML, for instance), or require doing resource lookups at runtime over 
+    // the network.  This group will hopefully be small, but all the infrastructure 
+    // should be in place to let these users write & plug in their own tools.
+    //
+    // The Default Resource File Format
+    //
+    // The fundamental problems addressed by the resource file format are:
+    //
+    // * Versioning - A ResourceReader could in theory support many different 
+    // file format revisions.
+    // * Storing intrinsic datatypes (ie, ints, Strings, DateTimes, etc) in a compact
+    // format
+    // * Support for user-defined classes - Accomplished using Serialization
+    // * Resource lookups should not require loading an entire resource file - If you 
+    // look up a resource, we only load the value for that resource, minimizing working set.
+    // 
+    // 
+    // There are four sections to the default file format.  The first
+    // is the Resource Manager header, which consists of a magic number
+    // that identifies this as a Resource file, and a ResourceSet class name.
+    // The class name is written here to allow users to provide their own 
+    // implementation of a ResourceSet (and a matching ResourceReader) to 
+    // control policy.  If objects greater than a certain size or matching a
+    // certain naming scheme shouldn't be stored in memory, users can tweak that
+    // with their own subclass of ResourceSet.
+    // 
+    // The second section in the system default file format is the 
+    // RuntimeResourceSet specific header.  This contains a version number for
+    // the .resources file, the number of resources in this file, the number of 
+    // different types contained in the file, followed by a list of fully 
+    // qualified type names.  After this, we include an array of hash values for
+    // each resource name, then an array of virtual offsets into the name section
+    // of the file.  The hashes allow us to do a binary search on an array of 
+    // integers to find a resource name very quickly without doing many string
+    // compares (except for once we find the real type, of course).  If a hash
+    // matches, the index into the array of hash values is used as the index
+    // into the name position array to find the name of the resource.  The type
+    // table allows us to read multiple different classes from the same file, 
+    // including user-defined types, in a more efficient way than using 
+    // Serialization, at least when your .resources file contains a reasonable 
+    // proportion of base data types such as Strings or ints.  We use 
+    // Serialization for all the non-instrinsic types.
+    // 
+    // The third section of the file is the name section.  It contains a 
+    // series of resource names, written out as byte-length prefixed little
+    // endian Unicode strings (UTF-16).  After each name is a four byte virtual
+    // offset into the data section of the file, pointing to the relevant 
+    // string or serialized blob for this resource name.
+    //
+    // The fourth section in the file is the data section, which consists
+    // of a type and a blob of bytes for each item in the file.  The type is 
+    // an integer index into the type table.  The data is specific to that type,
+    // but may be a number written in binary format, a String, or a serialized 
+    // Object.
+    // 
+    // The system default file format (V1) is as follows:
+    // 
+    //     What                                               Type of Data
+    // ====================================================   ===========
+    //
+    //                        Resource Manager header
+    // Magic Number (0xBEEFCACE)                              Int32
+    // Resource Manager header version                        Int32
+    // Num bytes to skip from here to get past this header    Int32
+    // Class name of IResourceReader to parse this file       String
+    // Class name of ResourceSet to parse this file           String
+    //
+    //                       RuntimeResourceReader header
+    // ResourceReader version number                          Int32
+    // [Only in debug V2 builds - "***DEBUG***"]              String
+    // Number of resources in the file                        Int32
+    // Number of types in the type table                      Int32
+    // Name of each type                                      Set of Strings
+    // Padding bytes for 8-byte alignment (use PAD)           Bytes (0-7)
+    // Hash values for each resource name                     Int32 array, sorted
+    // Virtual offset of each resource name                   Int32 array, coupled with hash values
+    // Absolute location of Data section                      Int32
+    //
+    //                     RuntimeResourceReader Name Section
+    // Name & virtual offset of each resource                 Set of (UTF-16 String, Int32) pairs
+    //
+    //                     RuntimeResourceReader Data Section
+    // Type and Value of each resource                Set of (Int32, blob of bytes) pairs
+    // 
+    // This implementation, when used with the default ResourceReader class,
+    // loads only the strings that you look up for.  It can do string comparisons
+    // without having to create a new String instance due to some memory mapped 
+    // file optimizations in the ResourceReader and FastResourceComparer 
+    // classes.  This keeps the memory we touch to a minimum when loading 
+    // resources. 
+    //
+    // If you use a different IResourceReader class to read a file, or if you
+    // do case-insensitive lookups (and the case-sensitive lookup fails) then
+    // we will load all the names of each resource and each resource value.
+    // This could probably use some optimization.
+    // 
+    // In addition, this supports object serialization in a similar fashion.
+    // We build an array of class types contained in this file, and write it
+    // to RuntimeResourceReader header section of the file.  Every resource
+    // will contain its type (as an index into the array of classes) with the data
+    // for that resource.  We will use the Runtime's serialization support for this.
+    // 
+    // All strings in the file format are written with BinaryReader and
+    // BinaryWriter, which writes out the length of the String in bytes as an 
+    // Int32 then the contents as Unicode chars encoded in UTF-8.  In the name
+    // table though, each resource name is written in UTF-16 so we can do a
+    // string compare byte by byte against the contents of the file, without
+    // allocating objects.  Ideally we'd have a way of comparing UTF-8 bytes 
+    // directly against a String object, but that may be a lot of work.
+    // 
+    // The offsets of each resource string are relative to the beginning 
+    // of the Data section of the file.  This way, if a tool decided to add 
+    // one resource to a file, it would only need to increment the number of 
+    // resources, add the hash &amp; location of last byte in the name section
+    // to the array of resource hashes and resource name positions (carefully
+    // keeping these arrays sorted), add the name to the end of the name &amp; 
+    // offset list, possibly add the type list of types types (and increase 
+    // the number of items in the type table), and add the resource value at 
+    // the end of the file.  The other offsets wouldn't need to be updated to 
+    // reflect the longer header section.
+    // 
+    // Resource files are currently limited to 2 gigabytes due to these 
+    // design parameters.  A future version may raise the limit to 4 gigabytes
+    // by using unsigned integers, or may use negative numbers to load items 
+    // out of an assembly manifest.  Also, we may try sectioning the resource names
+    // into smaller chunks, each of size sqrt(n), would be substantially better for
+    // resource files containing thousands of resources.
+    // 
+#if CORERT
+    public  // On CoreRT, this must be public because of need to whitelist past the ReflectionBlock.
+#else
+    internal
+#endif
+    sealed class RuntimeResourceSet : ResourceSet, IEnumerable
+    {
+        internal const int Version = 2;            // File format version number
+
+        // Cache for resources.  Key is the resource name, which can be cached
+        // for arbitrarily long times, since the object is usually a string
+        // literal that will live for the lifetime of the appdomain.  The
+        // value is a ResourceLocator instance, which might cache the object.
+        private Dictionary<String, ResourceLocator> _resCache;
+
+
+        // For our special load-on-demand reader, cache the cast.  The 
+        // RuntimeResourceSet's implementation knows how to treat this reader specially.
+        private ResourceReader _defaultReader;
+
+        // This is a lookup table for case-insensitive lookups, and may be null.
+        // Consider always using a case-insensitive resource cache, as we don't
+        // want to fill this out if we can avoid it.  The problem is resource
+        // fallback will somewhat regularly cause us to look up resources that 
+        // don't exist.
+        private Dictionary<String, ResourceLocator> _caseInsensitiveTable;
+
+        // If we're not using our custom reader, then enumerate through all
+        // the resources once, adding them into the table.
+        private bool _haveReadFromReader;
+
+        internal RuntimeResourceSet(String fileName) : base(false)
+        {
+            _resCache = new Dictionary<String, ResourceLocator>(FastResourceComparer.Default);
+            Stream stream = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read);
+            _defaultReader = new ResourceReader(stream, _resCache);
+            Reader = _defaultReader;
+        }
+
+        internal RuntimeResourceSet(Stream stream) : base(false)
+        {
+            _resCache = new Dictionary<String, ResourceLocator>(FastResourceComparer.Default);
+            _defaultReader = new ResourceReader(stream, _resCache);
+            Reader = _defaultReader;
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            if (Reader == null)
+                return;
+
+            if (disposing)
+            {
+                lock (Reader)
+                {
+                    _resCache = null;
+                    if (_defaultReader != null)
+                    {
+                        _defaultReader.Close();
+                        _defaultReader = null;
+                    }
+                    _caseInsensitiveTable = null;
+                    // Set Reader to null to avoid a race in GetObject.
+                    base.Dispose(disposing);
+                }
+            }
+            else
+            {
+                // Just to make sure we always clear these fields in the future...
+                _resCache = null;
+                _caseInsensitiveTable = null;
+                _defaultReader = null;
+                base.Dispose(disposing);
+            }
+        }
+
+        public override IDictionaryEnumerator GetEnumerator()
+        {
+            return GetEnumeratorHelper();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumeratorHelper();
+        }
+
+        private IDictionaryEnumerator GetEnumeratorHelper()
+        {
+            IResourceReader copyOfReader = Reader;
+            if (copyOfReader == null || _resCache == null)
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ResourceSet);
+
+            return copyOfReader.GetEnumerator();
+        }
+
+
+        public override String GetString(String key)
+        {
+            Object o = GetObject(key, false, true);
+            return (String)o;
+        }
+
+        public override String GetString(String key, bool ignoreCase)
+        {
+            Object o = GetObject(key, ignoreCase, true);
+            return (String)o;
+        }
+
+        public override Object GetObject(String key)
+        {
+            return GetObject(key, false, false);
+        }
+
+        public override Object GetObject(String key, bool ignoreCase)
+        {
+            return GetObject(key, ignoreCase, false);
+        }
+
+        private Object GetObject(String key, bool ignoreCase, bool isString)
+        {
+            if (key == null)
+                throw new ArgumentNullException(nameof(key));
+            if (Reader == null || _resCache == null)
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ResourceSet);
+
+            Object value = null;
+            ResourceLocator resLocation;
+
+            lock (Reader)
+            {
+                if (Reader == null)
+                    throw new ObjectDisposedException(null, SR.ObjectDisposed_ResourceSet);
+
+                if (_defaultReader != null)
+                {
+                    // Find the offset within the data section
+                    int dataPos = -1;
+                    if (_resCache.TryGetValue(key, out resLocation))
+                    {
+                        value = resLocation.Value;
+                        dataPos = resLocation.DataPosition;
+                    }
+
+                    if (dataPos == -1 && value == null)
+                    {
+                        dataPos = _defaultReader.FindPosForResource(key);
+                    }
+
+                    if (dataPos != -1 && value == null)
+                    {
+                        Debug.Assert(dataPos >= 0, "data section offset cannot be negative!");
+                        // Normally calling LoadString or LoadObject requires
+                        // taking a lock.  Note that in this case, we took a
+                        // lock on the entire RuntimeResourceSet, which is 
+                        // sufficient since we never pass this ResourceReader
+                        // to anyone else.
+                        ResourceTypeCode typeCode;
+                        if (isString)
+                        {
+                            value = _defaultReader.LoadString(dataPos);
+                            typeCode = ResourceTypeCode.String;
+                        }
+                        else
+                        {
+                            value = _defaultReader.LoadObject(dataPos, out typeCode);
+                        }
+
+                        resLocation = new ResourceLocator(dataPos, (ResourceLocator.CanCache(typeCode)) ? value : null);
+                        lock (_resCache)
+                        {
+                            _resCache[key] = resLocation;
+                        }
+                    }
+
+                    if (value != null || !ignoreCase)
+                    {
+                        return value;  // may be null
+                    }
+                }  // if (_defaultReader != null)
+
+                // At this point, we either don't have our default resource reader
+                // or we haven't found the particular resource we're looking for
+                // and may have to search for it in a case-insensitive way.
+                if (!_haveReadFromReader)
+                {
+                    // If necessary, init our case insensitive hash table.
+                    if (ignoreCase && _caseInsensitiveTable == null)
+                    {
+                        _caseInsensitiveTable = new Dictionary<String, ResourceLocator>(StringComparer.OrdinalIgnoreCase);
+                    }
+
+                    if (_defaultReader == null)
+                    {
+                        IDictionaryEnumerator en = Reader.GetEnumerator();
+                        while (en.MoveNext())
+                        {
+                            DictionaryEntry entry = en.Entry;
+                            String readKey = (String)entry.Key;
+                            ResourceLocator resLoc = new ResourceLocator(-1, entry.Value);
+                            _resCache.Add(readKey, resLoc);
+                            if (ignoreCase)
+                                _caseInsensitiveTable.Add(readKey, resLoc);
+                        }
+                        // Only close the reader if it is NOT our default one,
+                        // since we need it around to resolve ResourceLocators.
+                        if (!ignoreCase)
+                            Reader.Close();
+                    }
+                    else
+                    {
+                        Debug.Assert(ignoreCase, "This should only happen for case-insensitive lookups");
+                        ResourceReader.ResourceEnumerator en = _defaultReader.GetEnumeratorInternal();
+                        while (en.MoveNext())
+                        {
+                            // Note: Always ask for the resource key before the data position.
+                            String currentKey = (String)en.Key;
+                            int dataPos = en.DataPosition;
+                            ResourceLocator resLoc = new ResourceLocator(dataPos, null);
+                            _caseInsensitiveTable.Add(currentKey, resLoc);
+                        }
+                    }
+                    _haveReadFromReader = true;
+                }
+                Object obj = null;
+                bool found = false;
+                bool keyInWrongCase = false;
+                if (_defaultReader != null)
+                {
+                    if (_resCache.TryGetValue(key, out resLocation))
+                    {
+                        found = true;
+                        obj = ResolveResourceLocator(resLocation, key, _resCache, keyInWrongCase);
+                    }
+                }
+                if (!found && ignoreCase)
+                {
+                    if (_caseInsensitiveTable.TryGetValue(key, out resLocation))
+                    {
+                        found = true;
+                        keyInWrongCase = true;
+                        obj = ResolveResourceLocator(resLocation, key, _resCache, keyInWrongCase);
+                    }
+                }
+                return obj;
+            } // lock(Reader)
+        }
+
+        // The last parameter indicates whether the lookup required a 
+        // case-insensitive lookup to succeed, indicating we shouldn't add 
+        // the ResourceLocation to our case-sensitive cache.
+        private Object ResolveResourceLocator(ResourceLocator resLocation, String key, Dictionary<String, ResourceLocator> copyOfCache, bool keyInWrongCase)
+        {
+            // We need to explicitly resolve loosely linked manifest
+            // resources, and we need to resolve ResourceLocators with null objects.
+            Object value = resLocation.Value;
+            if (value == null)
+            {
+                ResourceTypeCode typeCode;
+                lock (Reader)
+                {
+                    value = _defaultReader.LoadObject(resLocation.DataPosition, out typeCode);
+                }
+                if (!keyInWrongCase && ResourceLocator.CanCache(typeCode))
+                {
+                    resLocation.Value = value;
+                    copyOfCache[key] = resLocation;
+                }
+            }
+            return value;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Resources/SatelliteContractVersionAttribute.cs b/src/System.Private.CoreLib/shared/System/Resources/SatelliteContractVersionAttribute.cs
new file mode 100644
index 0000000000..0707447677
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Resources/SatelliteContractVersionAttribute.cs
@@ -0,0 +1,31 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Specifies which version of a satellite assembly 
+**          the ResourceManager should ask for.
+**
+**
+===========================================================*/
+
+namespace System.Resources
+{
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = false)]
+    public sealed class SatelliteContractVersionAttribute : Attribute
+    {
+        public SatelliteContractVersionAttribute(String version)
+        {
+            if (version == null)
+                throw new ArgumentNullException(nameof(version));
+            Version = version;
+        }
+
+        public String Version { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Resources/UltimateResourceFallbackLocation.cs b/src/System.Private.CoreLib/shared/System/Resources/UltimateResourceFallbackLocation.cs
new file mode 100644
index 0000000000..83640ec9fe
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Resources/UltimateResourceFallbackLocation.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+**
+** Purpose: Tells the ResourceManager where to find the
+**          ultimate fallback resources for your assembly.
+**
+**
+===========================================================*/
+
+using System;
+
+namespace System.Resources
+{
+    public enum UltimateResourceFallbackLocation
+    {
+        MainAssembly,
+        Satellite
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AccessedThroughPropertyAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AccessedThroughPropertyAttribute.cs
new file mode 100644
index 0000000000..25efcafa3f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AccessedThroughPropertyAttribute.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Field)]
+    public sealed class AccessedThroughPropertyAttribute : Attribute
+    {
+        public AccessedThroughPropertyAttribute(string propertyName)
+        {
+            PropertyName = propertyName;
+        }
+
+        public string PropertyName { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AsyncMethodBuilderAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AsyncMethodBuilderAttribute.cs
new file mode 100644
index 0000000000..688a3a01ba
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AsyncMethodBuilderAttribute.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Indicates the type of the async method builder that should be used by a language compiler to
+    /// build the attributed type when used as the return type of an async method.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Interface | AttributeTargets.Delegate | AttributeTargets.Enum, Inherited = false, AllowMultiple = false)]
+    public sealed class AsyncMethodBuilderAttribute : Attribute
+    {
+        /// <summary>Initializes the <see cref="AsyncMethodBuilderAttribute"/>.</summary>
+        /// <param name="builderType">The <see cref="Type"/> of the associated builder.</param>
+        public AsyncMethodBuilderAttribute(Type builderType) => BuilderType = builderType;
+
+        /// <summary>Gets the <see cref="Type"/> of the associated builder.</summary>
+        public Type BuilderType { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AsyncStateMachineAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AsyncStateMachineAttribute.cs
new file mode 100644
index 0000000000..66c9175ee7
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AsyncStateMachineAttribute.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Method, Inherited = false, AllowMultiple = false)]
+    public sealed class AsyncStateMachineAttribute : StateMachineAttribute
+    {
+        public AsyncStateMachineAttribute(Type stateMachineType)
+            : base(stateMachineType)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AsyncValueTaskMethodBuilder.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AsyncValueTaskMethodBuilder.cs
new file mode 100644
index 0000000000..0e1220d119
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/AsyncValueTaskMethodBuilder.cs
@@ -0,0 +1,219 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using System.Security;
+using System.Threading.Tasks;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>Represents a builder for asynchronous methods that return a <see cref="ValueTask"/>.</summary>
+    [StructLayout(LayoutKind.Auto)]
+    public struct AsyncValueTaskMethodBuilder
+    {
+        /// <summary>The <see cref="AsyncTaskMethodBuilder"/> to which most operations are delegated.</summary>
+        private AsyncTaskMethodBuilder _methodBuilder; // mutable struct; do not make it readonly
+        /// <summary>true if completed synchronously and successfully; otherwise, false.</summary>
+        private bool _haveResult;
+        /// <summary>true if the builder should be used for setting/getting the result; otherwise, false.</summary>
+        private bool _useBuilder;
+
+        /// <summary>Creates an instance of the <see cref="AsyncValueTaskMethodBuilder"/> struct.</summary>
+        /// <returns>The initialized instance.</returns>
+        public static AsyncValueTaskMethodBuilder Create() =>
+#if CORERT
+            // corert's AsyncTaskMethodBuilder.Create() currently does additional debugger-related
+            // work, so we need to delegate to it.
+            new AsyncValueTaskMethodBuilder() { _methodBuilder = AsyncTaskMethodBuilder.Create() };
+#else
+            // _methodBuilder should be initialized to AsyncTaskMethodBuilder.Create(), but on coreclr
+            // that Create() is a nop, so we can just return the default here.
+            default;
+#endif
+
+        /// <summary>Begins running the builder with the associated state machine.</summary>
+        /// <typeparam name="TStateMachine">The type of the state machine.</typeparam>
+        /// <param name="stateMachine">The state machine instance, passed by reference.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Start<TStateMachine>(ref TStateMachine stateMachine) where TStateMachine : IAsyncStateMachine =>
+            // will provide the right ExecutionContext semantics
+#if netstandard
+            _methodBuilder.Start(ref stateMachine);
+#else
+            AsyncMethodBuilderCore.Start(ref stateMachine);
+#endif
+
+        /// <summary>Associates the builder with the specified state machine.</summary>
+        /// <param name="stateMachine">The state machine instance to associate with the builder.</param>
+        public void SetStateMachine(IAsyncStateMachine stateMachine) => _methodBuilder.SetStateMachine(stateMachine);
+
+        /// <summary>Marks the task as successfully completed.</summary>
+        public void SetResult()
+        {
+            if (_useBuilder)
+            {
+                _methodBuilder.SetResult();
+            }
+            else
+            {
+                _haveResult = true;
+            }
+        }
+
+        /// <summary>Marks the task as failed and binds the specified exception to the task.</summary>
+        /// <param name="exception">The exception to bind to the task.</param>
+        public void SetException(Exception exception) => _methodBuilder.SetException(exception);
+
+        /// <summary>Gets the task for this builder.</summary>
+        public ValueTask Task
+        {
+            get
+            {
+                if (_haveResult)
+                {
+                    return default;
+                }
+                else
+                {
+                    _useBuilder = true;
+                    return new ValueTask(_methodBuilder.Task);
+                }
+            }
+        }
+
+        /// <summary>Schedules the state machine to proceed to the next action when the specified awaiter completes.</summary>
+        /// <typeparam name="TAwaiter">The type of the awaiter.</typeparam>
+        /// <typeparam name="TStateMachine">The type of the state machine.</typeparam>
+        /// <param name="awaiter">The awaiter.</param>
+        /// <param name="stateMachine">The state machine.</param>
+        public void AwaitOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)
+            where TAwaiter : INotifyCompletion
+            where TStateMachine : IAsyncStateMachine
+        {
+            _useBuilder = true;
+            _methodBuilder.AwaitOnCompleted(ref awaiter, ref stateMachine);
+        }
+
+        /// <summary>Schedules the state machine to proceed to the next action when the specified awaiter completes.</summary>
+        /// <typeparam name="TAwaiter">The type of the awaiter.</typeparam>
+        /// <typeparam name="TStateMachine">The type of the state machine.</typeparam>
+        /// <param name="awaiter">The awaiter.</param>
+        /// <param name="stateMachine">The state machine.</param>
+        [SecuritySafeCritical]
+        public void AwaitUnsafeOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)
+            where TAwaiter : ICriticalNotifyCompletion
+            where TStateMachine : IAsyncStateMachine
+        {
+            _useBuilder = true;
+            _methodBuilder.AwaitUnsafeOnCompleted(ref awaiter, ref stateMachine);
+        }
+    }
+
+    /// <summary>Represents a builder for asynchronous methods that returns a <see cref="ValueTask{TResult}"/>.</summary>
+    /// <typeparam name="TResult">The type of the result.</typeparam>
+    [StructLayout(LayoutKind.Auto)]
+    public struct AsyncValueTaskMethodBuilder<TResult>
+    {
+        /// <summary>The <see cref="AsyncTaskMethodBuilder{TResult}"/> to which most operations are delegated.</summary>
+        private AsyncTaskMethodBuilder<TResult> _methodBuilder; // mutable struct; do not make it readonly
+        /// <summary>The result for this builder, if it's completed before any awaits occur.</summary>
+        private TResult _result;
+        /// <summary>true if <see cref="_result"/> contains the synchronous result for the async method; otherwise, false.</summary>
+        private bool _haveResult;
+        /// <summary>true if the builder should be used for setting/getting the result; otherwise, false.</summary>
+        private bool _useBuilder;
+
+        /// <summary>Creates an instance of the <see cref="AsyncValueTaskMethodBuilder{TResult}"/> struct.</summary>
+        /// <returns>The initialized instance.</returns>
+        public static AsyncValueTaskMethodBuilder<TResult> Create() =>
+#if CORERT
+            // corert's AsyncTaskMethodBuilder<TResult>.Create() currently does additional debugger-related
+            // work, so we need to delegate to it.
+            new AsyncValueTaskMethodBuilder<TResult>() { _methodBuilder = AsyncTaskMethodBuilder<TResult>.Create() };
+#else
+            // _methodBuilder should be initialized to AsyncTaskMethodBuilder<TResult>.Create(), but on coreclr
+            // that Create() is a nop, so we can just return the default here.
+            default;
+#endif
+
+        /// <summary>Begins running the builder with the associated state machine.</summary>
+        /// <typeparam name="TStateMachine">The type of the state machine.</typeparam>
+        /// <param name="stateMachine">The state machine instance, passed by reference.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Start<TStateMachine>(ref TStateMachine stateMachine) where TStateMachine : IAsyncStateMachine =>
+            // will provide the right ExecutionContext semantics
+#if netstandard
+            _methodBuilder.Start(ref stateMachine);
+#else
+            AsyncMethodBuilderCore.Start(ref stateMachine);
+#endif
+
+        /// <summary>Associates the builder with the specified state machine.</summary>
+        /// <param name="stateMachine">The state machine instance to associate with the builder.</param>
+        public void SetStateMachine(IAsyncStateMachine stateMachine) => _methodBuilder.SetStateMachine(stateMachine);
+
+        /// <summary>Marks the task as successfully completed.</summary>
+        /// <param name="result">The result to use to complete the task.</param>
+        public void SetResult(TResult result)
+        {
+            if (_useBuilder)
+            {
+                _methodBuilder.SetResult(result);
+            }
+            else
+            {
+                _result = result;
+                _haveResult = true;
+            }
+        }
+
+        /// <summary>Marks the task as failed and binds the specified exception to the task.</summary>
+        /// <param name="exception">The exception to bind to the task.</param>
+        public void SetException(Exception exception) => _methodBuilder.SetException(exception);
+
+        /// <summary>Gets the task for this builder.</summary>
+        public ValueTask<TResult> Task
+        {
+            get
+            {
+                if (_haveResult)
+                {
+                    return new ValueTask<TResult>(_result);
+                }
+                else
+                {
+                    _useBuilder = true;
+                    return new ValueTask<TResult>(_methodBuilder.Task);
+                }
+            }
+        }
+
+        /// <summary>Schedules the state machine to proceed to the next action when the specified awaiter completes.</summary>
+        /// <typeparam name="TAwaiter">The type of the awaiter.</typeparam>
+        /// <typeparam name="TStateMachine">The type of the state machine.</typeparam>
+        /// <param name="awaiter">the awaiter</param>
+        /// <param name="stateMachine">The state machine.</param>
+        public void AwaitOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)
+            where TAwaiter : INotifyCompletion
+            where TStateMachine : IAsyncStateMachine
+        {
+            _useBuilder = true;
+            _methodBuilder.AwaitOnCompleted(ref awaiter, ref stateMachine);
+        }
+
+        /// <summary>Schedules the state machine to proceed to the next action when the specified awaiter completes.</summary>
+        /// <typeparam name="TAwaiter">The type of the awaiter.</typeparam>
+        /// <typeparam name="TStateMachine">The type of the state machine.</typeparam>
+        /// <param name="awaiter">the awaiter</param>
+        /// <param name="stateMachine">The state machine.</param>
+        [SecuritySafeCritical]
+        public void AwaitUnsafeOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)
+            where TAwaiter : ICriticalNotifyCompletion 
+            where TStateMachine : IAsyncStateMachine
+        {
+            _useBuilder = true;
+            _methodBuilder.AwaitUnsafeOnCompleted(ref awaiter, ref stateMachine);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CallerFilePathAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CallerFilePathAttribute.cs
new file mode 100644
index 0000000000..5858634b42
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CallerFilePathAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+    public sealed class CallerFilePathAttribute : Attribute
+    {
+        public CallerFilePathAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CallerLineNumberAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CallerLineNumberAttribute.cs
new file mode 100644
index 0000000000..5bd2fcb91b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CallerLineNumberAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+    public sealed class CallerLineNumberAttribute : Attribute
+    {
+        public CallerLineNumberAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CallerMemberNameAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CallerMemberNameAttribute.cs
new file mode 100644
index 0000000000..8b046335b5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CallerMemberNameAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+    public sealed class CallerMemberNameAttribute : Attribute
+    {
+        public CallerMemberNameAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CompilationRelaxations.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CompilationRelaxations.cs
new file mode 100644
index 0000000000..88e2657a6a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CompilationRelaxations.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    /// IMPORTANT: Keep this in sync with corhdr.h
+    [Flags]
+    public enum CompilationRelaxations : int
+    {
+        NoStringInterning = 0x0008  // Start in 0x0008, we had other non public flags in this enum before,
+                                    // so we'll start here just in case somebody used them. This flag is only
+                                    // valid when set for Assemblies.
+    }
+}
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CompilationRelaxationsAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CompilationRelaxationsAttribute.cs
new file mode 100644
index 0000000000..d6da23fdf2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CompilationRelaxationsAttribute.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Module | AttributeTargets.Class | AttributeTargets.Method)]
+    public class CompilationRelaxationsAttribute : Attribute
+    {
+        public CompilationRelaxationsAttribute(int relaxations)
+        {
+            CompilationRelaxations = relaxations;
+        }
+
+        public CompilationRelaxationsAttribute(CompilationRelaxations relaxations)
+        {
+            CompilationRelaxations = (int)relaxations;
+        }
+
+        public int CompilationRelaxations { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CompilerGeneratedAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CompilerGeneratedAttribute.cs
new file mode 100644
index 0000000000..1c05abd1fe
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CompilerGeneratedAttribute.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.All, Inherited = true)]
+    public sealed class CompilerGeneratedAttribute : Attribute
+    {
+        public CompilerGeneratedAttribute() { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CompilerGlobalScopeAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CompilerGlobalScopeAttribute.cs
new file mode 100644
index 0000000000..752295e876
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CompilerGlobalScopeAttribute.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    // Attribute used to communicate to the VS7 debugger that a class should be treated as if it has global scope.
+    
+    [AttributeUsage(AttributeTargets.Class)]
+    public class CompilerGlobalScopeAttribute : Attribute
+    {
+        public CompilerGlobalScopeAttribute() { }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ConfiguredValueTaskAwaitable.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ConfiguredValueTaskAwaitable.cs
new file mode 100644
index 0000000000..8f7b0c809c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ConfiguredValueTaskAwaitable.cs
@@ -0,0 +1,236 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
+using System.Threading.Tasks.Sources;
+
+#if !netstandard
+using Internal.Runtime.CompilerServices;
+#endif
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>Provides an awaitable type that enables configured awaits on a <see cref="ValueTask"/>.</summary>
+    [StructLayout(LayoutKind.Auto)]
+    public readonly struct ConfiguredValueTaskAwaitable
+    {
+        /// <summary>The wrapped <see cref="Task"/>.</summary>
+        private readonly ValueTask _value;
+
+        /// <summary>Initializes the awaitable.</summary>
+        /// <param name="value">The wrapped <see cref="ValueTask"/>.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal ConfiguredValueTaskAwaitable(ValueTask value) => _value = value;
+
+        /// <summary>Returns an awaiter for this <see cref="ConfiguredValueTaskAwaitable"/> instance.</summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ConfiguredValueTaskAwaiter GetAwaiter() => new ConfiguredValueTaskAwaiter(_value);
+
+        /// <summary>Provides an awaiter for a <see cref="ConfiguredValueTaskAwaitable"/>.</summary>
+        [StructLayout(LayoutKind.Auto)]
+        public readonly struct ConfiguredValueTaskAwaiter : ICriticalNotifyCompletion
+#if CORECLR
+            , IStateMachineBoxAwareAwaiter
+#endif
+        {
+            /// <summary>The value being awaited.</summary>
+            private readonly ValueTask _value;
+
+            /// <summary>Initializes the awaiter.</summary>
+            /// <param name="value">The value to be awaited.</param>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            internal ConfiguredValueTaskAwaiter(ValueTask value) => _value = value;
+
+            /// <summary>Gets whether the <see cref="ConfiguredValueTaskAwaitable"/> has completed.</summary>
+            public bool IsCompleted
+            {
+                [MethodImpl(MethodImplOptions.AggressiveInlining)]
+                get => _value.IsCompleted;
+            }
+
+            /// <summary>Gets the result of the ValueTask.</summary>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            [StackTraceHidden]
+            public void GetResult() => _value.ThrowIfCompletedUnsuccessfully();
+
+            /// <summary>Schedules the continuation action for the <see cref="ConfiguredValueTaskAwaitable"/>.</summary>
+            public void OnCompleted(Action continuation)
+            {
+                object obj = _value._obj;
+                Debug.Assert(obj == null || obj is Task || obj is IValueTaskSource);
+
+                if (obj is Task t)
+                {
+                    t.ConfigureAwait(_value._continueOnCapturedContext).GetAwaiter().OnCompleted(continuation);
+                }
+                else if (obj != null)
+                {
+                    Unsafe.As<IValueTaskSource>(obj).OnCompleted(ValueTaskAwaiter.s_invokeActionDelegate, continuation, _value._token,
+                        ValueTaskSourceOnCompletedFlags.FlowExecutionContext |
+                            (_value._continueOnCapturedContext ? ValueTaskSourceOnCompletedFlags.UseSchedulingContext : ValueTaskSourceOnCompletedFlags.None));
+                }
+                else
+                {
+                    ValueTask.CompletedTask.ConfigureAwait(_value._continueOnCapturedContext).GetAwaiter().OnCompleted(continuation);
+                }
+            }
+
+            /// <summary>Schedules the continuation action for the <see cref="ConfiguredValueTaskAwaitable"/>.</summary>
+            public void UnsafeOnCompleted(Action continuation)
+            {
+                object obj = _value._obj;
+                Debug.Assert(obj == null || obj is Task || obj is IValueTaskSource);
+
+                if (obj is Task t)
+                {
+                    t.ConfigureAwait(_value._continueOnCapturedContext).GetAwaiter().UnsafeOnCompleted(continuation);
+                }
+                else if (obj != null)
+                {
+                    Unsafe.As<IValueTaskSource>(obj).OnCompleted(ValueTaskAwaiter.s_invokeActionDelegate, continuation, _value._token,
+                        _value._continueOnCapturedContext ? ValueTaskSourceOnCompletedFlags.UseSchedulingContext : ValueTaskSourceOnCompletedFlags.None);
+                }
+                else
+                {
+                    ValueTask.CompletedTask.ConfigureAwait(_value._continueOnCapturedContext).GetAwaiter().UnsafeOnCompleted(continuation);
+                }
+            }
+
+#if CORECLR
+            void IStateMachineBoxAwareAwaiter.AwaitUnsafeOnCompleted(IAsyncStateMachineBox box)
+            {
+                object obj = _value._obj;
+                Debug.Assert(obj == null || obj is Task || obj is IValueTaskSource);
+
+                if (obj is Task t)
+                {
+                    TaskAwaiter.UnsafeOnCompletedInternal(t, box, _value._continueOnCapturedContext);
+                }
+                else if (obj != null)
+                {
+                    Unsafe.As<IValueTaskSource>(obj).OnCompleted(ValueTaskAwaiter.s_invokeAsyncStateMachineBox, box, _value._token,
+                        _value._continueOnCapturedContext ? ValueTaskSourceOnCompletedFlags.UseSchedulingContext : ValueTaskSourceOnCompletedFlags.None);
+                }
+                else
+                {
+                    TaskAwaiter.UnsafeOnCompletedInternal(Task.CompletedTask, box, _value._continueOnCapturedContext);
+                }
+            }
+#endif
+        }
+    }
+
+    /// <summary>Provides an awaitable type that enables configured awaits on a <see cref="ValueTask{TResult}"/>.</summary>
+    /// <typeparam name="TResult">The type of the result produced.</typeparam>
+    [StructLayout(LayoutKind.Auto)]
+    public readonly struct ConfiguredValueTaskAwaitable<TResult>
+    {
+        /// <summary>The wrapped <see cref="ValueTask{TResult}"/>.</summary>
+        private readonly ValueTask<TResult> _value;
+
+        /// <summary>Initializes the awaitable.</summary>
+        /// <param name="value">The wrapped <see cref="ValueTask{TResult}"/>.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal ConfiguredValueTaskAwaitable(ValueTask<TResult> value) => _value = value;
+
+        /// <summary>Returns an awaiter for this <see cref="ConfiguredValueTaskAwaitable{TResult}"/> instance.</summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ConfiguredValueTaskAwaiter GetAwaiter() => new ConfiguredValueTaskAwaiter(_value);
+
+        /// <summary>Provides an awaiter for a <see cref="ConfiguredValueTaskAwaitable{TResult}"/>.</summary>
+        [StructLayout(LayoutKind.Auto)]
+        public readonly struct ConfiguredValueTaskAwaiter : ICriticalNotifyCompletion
+#if CORECLR
+            , IStateMachineBoxAwareAwaiter
+#endif
+        {
+            /// <summary>The value being awaited.</summary>
+            private readonly ValueTask<TResult> _value;
+
+            /// <summary>Initializes the awaiter.</summary>
+            /// <param name="value">The value to be awaited.</param>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            internal ConfiguredValueTaskAwaiter(ValueTask<TResult> value) => _value = value;
+
+            /// <summary>Gets whether the <see cref="ConfiguredValueTaskAwaitable{TResult}"/> has completed.</summary>
+            public bool IsCompleted
+            {
+                [MethodImpl(MethodImplOptions.AggressiveInlining)]
+                get => _value.IsCompleted;
+            }
+
+            /// <summary>Gets the result of the ValueTask.</summary>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            [StackTraceHidden]
+            public TResult GetResult() => _value.Result;
+
+            /// <summary>Schedules the continuation action for the <see cref="ConfiguredValueTaskAwaitable{TResult}"/>.</summary>
+            public void OnCompleted(Action continuation)
+            {
+                object obj = _value._obj;
+                Debug.Assert(obj == null || obj is Task<TResult> || obj is IValueTaskSource<TResult>);
+
+                if (obj is Task<TResult> t)
+                {
+                    t.ConfigureAwait(_value._continueOnCapturedContext).GetAwaiter().OnCompleted(continuation);
+                }
+                else if (obj != null)
+                {
+                    Unsafe.As<IValueTaskSource<TResult>>(obj).OnCompleted(ValueTaskAwaiter.s_invokeActionDelegate, continuation, _value._token,
+                        ValueTaskSourceOnCompletedFlags.FlowExecutionContext |
+                            (_value._continueOnCapturedContext ? ValueTaskSourceOnCompletedFlags.UseSchedulingContext : ValueTaskSourceOnCompletedFlags.None));
+                }
+                else
+                {
+                    ValueTask.CompletedTask.ConfigureAwait(_value._continueOnCapturedContext).GetAwaiter().OnCompleted(continuation);
+                }
+            }
+
+            /// <summary>Schedules the continuation action for the <see cref="ConfiguredValueTaskAwaitable{TResult}"/>.</summary>
+            public void UnsafeOnCompleted(Action continuation)
+            {
+                object obj = _value._obj;
+                Debug.Assert(obj == null || obj is Task<TResult> || obj is IValueTaskSource<TResult>);
+
+                if (obj is Task<TResult> t)
+                {
+                    t.ConfigureAwait(_value._continueOnCapturedContext).GetAwaiter().UnsafeOnCompleted(continuation);
+                }
+                else if (obj != null)
+                {
+                    Unsafe.As<IValueTaskSource<TResult>>(obj).OnCompleted(ValueTaskAwaiter.s_invokeActionDelegate, continuation, _value._token,
+                        _value._continueOnCapturedContext ? ValueTaskSourceOnCompletedFlags.UseSchedulingContext : ValueTaskSourceOnCompletedFlags.None);
+                }
+                else
+                {
+                    ValueTask.CompletedTask.ConfigureAwait(_value._continueOnCapturedContext).GetAwaiter().UnsafeOnCompleted(continuation);
+                }
+            }
+
+#if CORECLR
+            void IStateMachineBoxAwareAwaiter.AwaitUnsafeOnCompleted(IAsyncStateMachineBox box)
+            {
+                object obj = _value._obj;
+                Debug.Assert(obj == null || obj is Task<TResult> || obj is IValueTaskSource<TResult>);
+
+                if (obj is Task<TResult> t)
+                {
+                    TaskAwaiter.UnsafeOnCompletedInternal(t, box, _value._continueOnCapturedContext);
+                }
+                else if (obj != null)
+                {
+                    Unsafe.As<IValueTaskSource<TResult>>(obj).OnCompleted(ValueTaskAwaiter.s_invokeAsyncStateMachineBox, box, _value._token,
+                        _value._continueOnCapturedContext ? ValueTaskSourceOnCompletedFlags.UseSchedulingContext : ValueTaskSourceOnCompletedFlags.None);
+                }
+                else
+                {
+                    TaskAwaiter.UnsafeOnCompletedInternal(Task.CompletedTask, box, _value._continueOnCapturedContext);
+                }
+            }
+#endif
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CustomConstantAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CustomConstantAttribute.cs
new file mode 100644
index 0000000000..f75693eb40
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/CustomConstantAttribute.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter, Inherited = false)]
+    public abstract class CustomConstantAttribute : Attribute
+    {
+        public abstract Object Value { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DateTimeConstantAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DateTimeConstantAttribute.cs
new file mode 100644
index 0000000000..813e6803bf
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DateTimeConstantAttribute.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter, Inherited = false)]
+    public sealed class DateTimeConstantAttribute : CustomConstantAttribute
+    {
+        private DateTime _date;
+
+        public DateTimeConstantAttribute(long ticks)
+        {
+            _date = new DateTime(ticks);
+        }
+
+        public override Object Value => _date;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DecimalConstantAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DecimalConstantAttribute.cs
new file mode 100644
index 0000000000..19db84eb43
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DecimalConstantAttribute.cs
@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// Note: If you add a new ctor overloads you need to update ParameterInfo.RawDefaultValue
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter, Inherited = false)]
+    public sealed class DecimalConstantAttribute : Attribute
+    {
+        private Decimal _dec;
+
+        [CLSCompliant(false)]
+        public DecimalConstantAttribute(
+            byte scale,
+            byte sign,
+            uint hi,
+            uint mid,
+            uint low
+        )
+        {
+            _dec = new Decimal((int)low, (int)mid, (int)hi, (sign != 0), scale);
+        }
+
+        public DecimalConstantAttribute(
+            byte scale,
+            byte sign,
+            int hi,
+            int mid,
+            int low
+        )
+        {
+            _dec = new Decimal(low, mid, hi, (sign != 0), scale);
+        }
+
+        public Decimal Value => _dec;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DefaultDependencyAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DefaultDependencyAttribute.cs
new file mode 100644
index 0000000000..4c1f489215
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DefaultDependencyAttribute.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Assembly)]
+    public sealed class DefaultDependencyAttribute : Attribute
+    {
+        public DefaultDependencyAttribute(LoadHint loadHintArgument)
+        {
+            LoadHint = loadHintArgument;
+        }
+
+        public LoadHint LoadHint { get; }
+    }
+}
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DependencyAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DependencyAttribute.cs
new file mode 100644
index 0000000000..0fe07edc9e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DependencyAttribute.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]
+    public sealed class DependencyAttribute : Attribute
+    {
+        public DependencyAttribute(String dependentAssemblyArgument, LoadHint loadHintArgument)
+        {
+            DependentAssembly = dependentAssemblyArgument;
+            LoadHint = loadHintArgument;
+        }
+
+        public String DependentAssembly { get; }
+        public LoadHint LoadHint { get; }
+    }
+}
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DisablePrivateReflectionAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DisablePrivateReflectionAttribute.cs
new file mode 100644
index 0000000000..4fc00e10ed
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DisablePrivateReflectionAttribute.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = false, Inherited = false)]
+    public sealed class DisablePrivateReflectionAttribute : Attribute
+    {
+        public DisablePrivateReflectionAttribute() { }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DiscardableAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DiscardableAttribute.cs
new file mode 100644
index 0000000000..c88b3a7599
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/DiscardableAttribute.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    // Custom attribute to indicating a TypeDef is a discardable attribute.
+    
+    public class DiscardableAttribute : Attribute
+    {
+        public DiscardableAttribute() { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ExtensionAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ExtensionAttribute.cs
new file mode 100644
index 0000000000..92170880f1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ExtensionAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Indicates that a method is an extension method, or that a class or assembly contains extension methods.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Class | AttributeTargets.Assembly)]
+    public sealed class ExtensionAttribute : Attribute { }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/FixedAddressValueTypeAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/FixedAddressValueTypeAttribute.cs
new file mode 100644
index 0000000000..8dc6c43126
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/FixedAddressValueTypeAttribute.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Field)]
+    public sealed class FixedAddressValueTypeAttribute : Attribute
+    {
+        public FixedAddressValueTypeAttribute() { }
+    }
+}
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/FixedBufferAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/FixedBufferAttribute.cs
new file mode 100644
index 0000000000..bb8f00f686
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/FixedBufferAttribute.cs
@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+** Purpose: Used by a compiler for generating value types
+**   in-place within other value types containing a certain
+**   number of elements of the given (primitive) type.  Somewhat
+**   similar to P/Invoke's ByValTStr attribute.
+**   Used by C# with this syntax: "fixed int buffer[10];"
+**
+===========================================================*/
+
+using System;
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Field, Inherited = false)]
+    public sealed class FixedBufferAttribute : Attribute
+    {
+        public FixedBufferAttribute(Type elementType, int length)
+        {
+            ElementType = elementType;
+            Length = length;
+        }
+
+        public Type ElementType { get; }
+        public int Length { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/FormattableStringFactory.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/FormattableStringFactory.cs
new file mode 100644
index 0000000000..23d03860ed
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/FormattableStringFactory.cs
@@ -0,0 +1,58 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: implementation of the FormattableStringFactory
+** class.
+**
+===========================================================*/
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// A factory type used by compilers to create instances of the type <see cref="FormattableString"/>.
+    /// </summary>
+    public static class FormattableStringFactory
+    {
+        /// <summary>
+        /// Create a <see cref="FormattableString"/> from a composite format string and object
+        /// array containing zero or more objects to format.
+        /// </summary>
+        public static FormattableString Create(string format, params object[] arguments)
+        {
+            if (format == null)
+            {
+                throw new ArgumentNullException(nameof(format));
+            }
+
+            if (arguments == null)
+            {
+                throw new ArgumentNullException(nameof(arguments));
+            }
+
+            return new ConcreteFormattableString(format, arguments);
+        }
+
+        private sealed class ConcreteFormattableString : FormattableString
+        {
+            private readonly string _format;
+            private readonly object[] _arguments;
+
+            internal ConcreteFormattableString(string format, object[] arguments)
+            {
+                _format = format;
+                _arguments = arguments;
+            }
+
+            public override string Format { get { return _format; } }
+            public override object[] GetArguments() { return _arguments; }
+            public override int ArgumentCount { get { return _arguments.Length; } }
+            public override object GetArgument(int index) { return _arguments[index]; }
+            public override string ToString(IFormatProvider formatProvider) { return string.Format(formatProvider, _format, _arguments); }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IAsyncStateMachine.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IAsyncStateMachine.cs
new file mode 100644
index 0000000000..7fb7ea5395
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IAsyncStateMachine.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// Represents state machines generated for asynchronous methods.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Represents state machines generated for asynchronous methods.
+    /// This type is intended for compiler use only.
+    /// </summary>
+    public interface IAsyncStateMachine
+    {
+        /// <summary>Moves the state machine to its next state.</summary>
+        void MoveNext();
+        /// <summary>Configures the state machine with a heap-allocated replica.</summary>
+        /// <param name="stateMachine">The heap-allocated replica.</param>
+        void SetStateMachine(IAsyncStateMachine stateMachine);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/INotifyCompletion.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/INotifyCompletion.cs
new file mode 100644
index 0000000000..aba0a0691f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/INotifyCompletion.cs
@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=
+//
+//
+//
+// Interfaces used to represent instances that notify listeners of their completion via continuations.
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
+
+using System;
+using System.Security;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Represents an operation that will schedule continuations when the operation completes.
+    /// </summary>
+    public interface INotifyCompletion
+    {
+        /// <summary>Schedules the continuation action to be invoked when the instance completes.</summary>
+        /// <param name="continuation">The action to invoke when the operation completes.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+        void OnCompleted(Action continuation);
+    }
+
+    /// <summary>
+    /// Represents an awaiter used to schedule continuations when an await operation completes.
+    /// </summary>
+    public interface ICriticalNotifyCompletion : INotifyCompletion
+    {
+        /// <summary>Schedules the continuation action to be invoked when the instance completes.</summary>
+        /// <param name="continuation">The action to invoke when the operation completes.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+        /// <remarks>Unlike OnCompleted, UnsafeOnCompleted need not propagate ExecutionContext information.</remarks>
+        void UnsafeOnCompleted(Action continuation);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ITuple.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ITuple.cs
new file mode 100644
index 0000000000..cafee11f8a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ITuple.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// This interface is required for types that want to be indexed into by dynamic patterns.
+    /// </summary>
+    public interface ITuple
+    {
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int Length { get; }
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object this[int index] { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IndexerNameAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IndexerNameAttribute.cs
new file mode 100644
index 0000000000..ea843b3daa
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IndexerNameAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Property, Inherited = true)]
+    public sealed class IndexerNameAttribute : Attribute
+    {
+        public IndexerNameAttribute(String indexerName)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/InternalsVisibleToAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/InternalsVisibleToAttribute.cs
new file mode 100644
index 0000000000..f754694815
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/InternalsVisibleToAttribute.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true, Inherited = false)]
+    public sealed class InternalsVisibleToAttribute : Attribute
+    {
+        public InternalsVisibleToAttribute(string assemblyName)
+        {
+            AssemblyName = assemblyName;
+        }
+
+        public string AssemblyName { get; }
+        public bool AllInternalsVisible { get; set; } = true;
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IntrinsicAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IntrinsicAttribute.cs
new file mode 100644
index 0000000000..6bdd91d844
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IntrinsicAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    // Calls to methods or references to fields marked with this attribute may be replaced at
+    // some call sites with jit intrinsic expansions.
+    // Types marked with this attribute may be specially treated by the runtime/compiler.
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Field, Inherited = false)]
+    internal sealed class IntrinsicAttribute : Attribute
+    {
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IsByRefLikeAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IsByRefLikeAttribute.cs
new file mode 100644
index 0000000000..90e49d2a42
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IsByRefLikeAttribute.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Reserved to be used by the compiler for tracking metadata.
+    /// This attribute should not be used by developers in source code.
+    /// </summary>
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    [AttributeUsage(AttributeTargets.Struct)]
+    public sealed class IsByRefLikeAttribute : Attribute
+    {
+        public IsByRefLikeAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IsConst.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IsConst.cs
new file mode 100644
index 0000000000..7f948b608a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IsConst.cs
@@ -0,0 +1,10 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    public static partial class IsConst
+    {
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IsReadOnlyAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IsReadOnlyAttribute.cs
new file mode 100644
index 0000000000..657df43957
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IsReadOnlyAttribute.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Reserved to be used by the compiler for tracking metadata.
+    /// This attribute should not be used by developers in source code.
+    /// </summary>
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    [AttributeUsage(AttributeTargets.All, Inherited = false)]
+    public sealed class IsReadOnlyAttribute : Attribute
+    {
+        public IsReadOnlyAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IsVolatile.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IsVolatile.cs
new file mode 100644
index 0000000000..fd1c6a1b12
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IsVolatile.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    public static class IsVolatile
+    {
+        // no instantiation, please!
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IteratorStateMachineAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IteratorStateMachineAttribute.cs
new file mode 100644
index 0000000000..53afc95664
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/IteratorStateMachineAttribute.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Method, Inherited = false, AllowMultiple = false)]
+    public sealed class IteratorStateMachineAttribute : StateMachineAttribute
+    {
+        public IteratorStateMachineAttribute(Type stateMachineType)
+            : base(stateMachineType)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/LoadHint.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/LoadHint.cs
new file mode 100644
index 0000000000..3820f8544b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/LoadHint.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    public enum LoadHint
+    {
+        Default = 0x0000,           // No preference specified
+        Always = 0x0001,            // Dependency is always loaded
+        Sometimes = 0x0002,         // Dependency is sometimes loaded
+    }
+}
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/MethodCodeType.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/MethodCodeType.cs
new file mode 100644
index 0000000000..841b666198
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/MethodCodeType.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+
+namespace System.Runtime.CompilerServices
+{
+    public enum MethodCodeType
+    {
+        IL = MethodImplAttributes.IL,
+        Native = MethodImplAttributes.Native,
+        OPTIL = MethodImplAttributes.OPTIL,
+        Runtime = MethodImplAttributes.Runtime
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/MethodImplAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/MethodImplAttribute.cs
new file mode 100644
index 0000000000..8e8f93c268
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/MethodImplAttribute.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    // Custom attribute to specify additional method properties.
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor, Inherited = false)]
+    sealed public class MethodImplAttribute : Attribute
+    {
+        public MethodCodeType MethodCodeType;
+
+        public MethodImplAttribute(MethodImplOptions methodImplOptions)
+        {
+            Value = methodImplOptions;
+        }
+
+        public MethodImplAttribute(short value)
+        {
+            Value = (MethodImplOptions)value;
+        }
+
+        public MethodImplAttribute()
+        {
+        }
+
+        public MethodImplOptions Value { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/MethodImplOptions.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/MethodImplOptions.cs
new file mode 100644
index 0000000000..2b5affc699
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/MethodImplOptions.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    // This Enum matchs the miImpl flags defined in corhdr.h. It is used to specify 
+    // certain method properties.
+    [Flags]
+    public enum MethodImplOptions
+    {
+        Unmanaged = 0x0004,
+        NoInlining = 0x0008,
+        ForwardRef = 0x0010,
+        Synchronized = 0x0020,
+        NoOptimization = 0x0040,
+        PreserveSig = 0x0080,
+        AggressiveInlining = 0x0100,
+        InternalCall = 0x1000
+    }
+}
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ReferenceAssemblyAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ReferenceAssemblyAttribute.cs
new file mode 100644
index 0000000000..f3842ec562
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ReferenceAssemblyAttribute.cs
@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Attribute: ReferenceAssemblyAttribute
+**
+** Purpose: Identifies an assembly as being a "reference 
+**    assembly", meaning it contains public surface area but
+**    no usable implementation.  Reference assemblies 
+**    should be loadable for introspection, but not execution.
+**
+============================================================*/
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = false)]
+    public sealed class ReferenceAssemblyAttribute : Attribute
+    {
+        public ReferenceAssemblyAttribute()
+        {
+        }
+
+        public ReferenceAssemblyAttribute(String description)
+        {
+            Description = description;
+        }
+
+        public String Description { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/RuntimeCompatibilityAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/RuntimeCompatibilityAttribute.cs
new file mode 100644
index 0000000000..609c560330
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/RuntimeCompatibilityAttribute.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Mark up the program to indicate various legacy or new opt-in behaviors.
+**
+**
+=============================================================================*/
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false, AllowMultiple = false)]
+    public sealed class RuntimeCompatibilityAttribute : Attribute
+    {
+        public RuntimeCompatibilityAttribute()
+        {
+            // legacy behavior is the default, and WrapNonExceptionThrows is implicitly
+            // false thanks to the CLR's guarantee of zeroed memory.
+        }
+
+        // If a non-CLSCompliant exception (i.e. one that doesn't derive from System.Exception) is
+        // thrown, should it be wrapped up in a System.Runtime.CompilerServices.RuntimeWrappedException
+        // instance when presented to catch handlers?
+        public bool WrapNonExceptionThrows { get; set; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/RuntimeFeature.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/RuntimeFeature.cs
new file mode 100644
index 0000000000..c6a97eca20
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/RuntimeFeature.cs
@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    public static class RuntimeFeature
+    {
+        /// <summary>
+        /// Name of the Portable PDB feature.
+        /// </summary>
+        public const string PortablePdb = nameof(PortablePdb);
+
+#if FEATURE_DEFAULT_INTERFACES
+        /// <summary>
+        /// Indicates that this version of runtime supports default interface method implementations.
+        /// </summary>
+        public const string DefaultImplementationsOfInterfaces = nameof(DefaultImplementationsOfInterfaces);
+#endif
+
+        /// <summary>
+        /// Checks whether a certain feature is supported by the Runtime.
+        /// </summary>
+        public static bool IsSupported(string feature)
+        {
+            switch (feature)
+            {
+                case PortablePdb:
+#if FEATURE_DEFAULT_INTERFACES
+                case DefaultImplementationsOfInterfaces:
+#endif
+                    return true;
+            }
+
+            return false;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/RuntimeWrappedException.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/RuntimeWrappedException.cs
new file mode 100644
index 0000000000..72996c6dfc
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/RuntimeWrappedException.cs
@@ -0,0 +1,41 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Exception used to wrap all non-CLS compliant exceptions.
+    /// </summary>
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class RuntimeWrappedException : Exception
+    {
+        private object _wrappedException; // EE expects this name
+
+        // Not an api but has to be public as System.Linq.Expression invokes this through Reflection when an expression
+        // throws an object that doesn't derive from Exception.
+        public RuntimeWrappedException(object thrownObject)
+            : base(SR.RuntimeWrappedException)
+        {
+            HResult = HResults.COR_E_RUNTIMEWRAPPED;
+            _wrappedException = thrownObject;
+        }
+
+        private RuntimeWrappedException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            _wrappedException = info.GetValue("WrappedException", typeof(object));
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("WrappedException", _wrappedException, typeof(object));
+        }
+
+        public object WrappedException => _wrappedException;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/SpecialNameAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/SpecialNameAttribute.cs
new file mode 100644
index 0000000000..b18e62895f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/SpecialNameAttribute.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices 
+{
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method | AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Event | AttributeTargets.Struct)]
+    public sealed class SpecialNameAttribute : Attribute
+    {
+        public SpecialNameAttribute() { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/StateMachineAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/StateMachineAttribute.cs
new file mode 100644
index 0000000000..e081d63e71
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/StateMachineAttribute.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Method, Inherited = false, AllowMultiple = false)]
+    public class StateMachineAttribute : Attribute
+    {
+        public StateMachineAttribute(Type stateMachineType)
+        {
+            StateMachineType = stateMachineType;
+        }
+
+        public Type StateMachineType { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/StringFreezingAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/StringFreezingAttribute.cs
new file mode 100644
index 0000000000..25a8bfbc26
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/StringFreezingAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    // Custom attribute to indicate that strings should be frozen.
+    
+    [AttributeUsage(AttributeTargets.Assembly, Inherited = false)]
+    public sealed class StringFreezingAttribute : Attribute
+    {
+        public StringFreezingAttribute() { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/StrongBox.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/StrongBox.cs
new file mode 100644
index 0000000000..0a1a565f54
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/StrongBox.cs
@@ -0,0 +1,59 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Holds a reference to a value.
+    /// </summary>
+    /// <typeparam name="T">The type of the value that the <see cref = "StrongBox{T}"></see> references.</typeparam>
+    public class StrongBox<T> : IStrongBox
+    {
+        /// <summary>
+        /// Gets the strongly typed value associated with the <see cref = "StrongBox{T}"></see>
+        /// <remarks>This is explicitly exposed as a field instead of a property to enable loading the address of the field.</remarks>
+        /// </summary>
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1051:DoNotDeclareVisibleInstanceFields")]
+        public T Value;
+
+        /// <summary>
+        /// Initializes a new StrongBox which can receive a value when used in a reference call.
+        /// </summary>
+        public StrongBox()
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref = "StrongBox{T}"></see> with the specified value.
+        /// </summary>
+        /// <param name="value">A value that the <see cref = "StrongBox{T}"></see> will reference.</param>
+        public StrongBox(T value)
+        {
+            Value = value;
+        }
+
+        object IStrongBox.Value
+        {
+            get
+            {
+                return Value;
+            }
+            set
+            {
+                Value = (T)value;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Defines a property for accessing the value that an object references.
+    /// </summary>
+    public interface IStrongBox
+    {
+        /// <summary>
+        /// Gets or sets the value the object references.
+        /// </summary>
+        object Value { get; set; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/SuppressIldasmAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/SuppressIldasmAttribute.cs
new file mode 100644
index 0000000000..b4224b1c89
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/SuppressIldasmAttribute.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Module)]
+    public sealed class SuppressIldasmAttribute : Attribute
+    {
+        public SuppressIldasmAttribute() { }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/TupleElementNamesAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/TupleElementNamesAttribute.cs
new file mode 100644
index 0000000000..ad923dfae5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/TupleElementNamesAttribute.cs
@@ -0,0 +1,57 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Indicates that the use of <see cref="System.ValueTuple"/> on a member is meant to be treated as a tuple with element names.
+    /// </summary>
+    [CLSCompliant(false)]
+    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Event)]
+    public sealed class TupleElementNamesAttribute : Attribute
+    {
+        private readonly string[] _transformNames;
+
+        /// <summary>
+        /// Initializes a new instance of the <see
+        /// cref="TupleElementNamesAttribute"/> class.
+        /// </summary>
+        /// <param name="transformNames">
+        /// Specifies, in a pre-order depth-first traversal of a type's
+        /// construction, which <see cref="System.ValueType"/> occurrences are
+        /// meant to carry element names.
+        /// </param>
+        /// <remarks>
+        /// This constructor is meant to be used on types that contain an
+        /// instantiation of <see cref="System.ValueType"/> that contains
+        /// element names.  For instance, if <c>C</c> is a generic type with
+        /// two type parameters, then a use of the constructed type <c>C{<see
+        /// cref="System.ValueTuple{T1, T2}"/>, <see
+        /// cref="System.ValueTuple{T1, T2, T3}"/></c> might be intended to
+        /// treat the first type argument as a tuple with element names and the
+        /// second as a tuple without element names. In which case, the
+        /// appropriate attribute specification should use a
+        /// <c>transformNames</c> value of <c>{ "name1", "name2", null, null,
+        /// null }</c>.
+        /// </remarks>
+        public TupleElementNamesAttribute(string[] transformNames)
+        {
+            if (transformNames == null)
+            {
+                throw new ArgumentNullException(nameof(transformNames));
+            }
+
+            _transformNames = transformNames;
+        }
+
+        /// <summary>
+        /// Specifies, in a pre-order depth-first traversal of a type's
+        /// construction, which <see cref="System.ValueTuple"/> elements are
+        /// meant to carry element names.
+        /// </summary>
+        public IList<string> TransformNames => _transformNames;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/TypeForwardedFromAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/TypeForwardedFromAttribute.cs
new file mode 100644
index 0000000000..27dd645755
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/TypeForwardedFromAttribute.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Enum | AttributeTargets.Interface | AttributeTargets.Delegate, Inherited = false, AllowMultiple = false)]
+    public sealed class TypeForwardedFromAttribute : Attribute
+    {
+        public TypeForwardedFromAttribute(string assemblyFullName)
+        {
+            if (string.IsNullOrEmpty(assemblyFullName))
+                throw new ArgumentNullException(nameof(assemblyFullName));
+
+            AssemblyFullName = assemblyFullName;
+        }
+
+        public string AssemblyFullName { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/TypeForwardedToAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/TypeForwardedToAttribute.cs
new file mode 100644
index 0000000000..85d5c030c1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/TypeForwardedToAttribute.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true, Inherited = false)]
+    public sealed class TypeForwardedToAttribute : Attribute
+    {
+        public TypeForwardedToAttribute(Type destination)
+        {
+            Destination = destination;
+        }
+
+        public Type Destination { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/UnsafeValueTypeAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/UnsafeValueTypeAttribute.cs
new file mode 100644
index 0000000000..f049c89b3f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/UnsafeValueTypeAttribute.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.CompilerServices
+{
+    [AttributeUsage(AttributeTargets.Struct)]
+    sealed public class UnsafeValueTypeAttribute : Attribute
+    {
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ValueTaskAwaiter.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ValueTaskAwaiter.cs
new file mode 100644
index 0000000000..02b5910b77
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/ValueTaskAwaiter.cs
@@ -0,0 +1,223 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Threading.Tasks;
+using System.Threading.Tasks.Sources;
+
+#if !netstandard
+using Internal.Runtime.CompilerServices;
+#endif
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>Provides an awaiter for a <see cref="ValueTask"/>.</summary>
+    public readonly struct ValueTaskAwaiter : ICriticalNotifyCompletion
+#if CORECLR
+            , IStateMachineBoxAwareAwaiter
+#endif
+    {
+        /// <summary>Shim used to invoke an <see cref="Action"/> passed as the state argument to a <see cref="Action{Object}"/>.</summary>
+        internal static readonly Action<object> s_invokeActionDelegate = state =>
+        {
+            if (!(state is Action action))
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.state);
+                return;
+            }
+
+            action();
+        };
+        /// <summary>The value being awaited.</summary>
+        private readonly ValueTask _value;
+
+        /// <summary>Initializes the awaiter.</summary>
+        /// <param name="value">The value to be awaited.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal ValueTaskAwaiter(ValueTask value) => _value = value;
+
+        /// <summary>Gets whether the <see cref="ValueTask"/> has completed.</summary>
+        public bool IsCompleted
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => _value.IsCompleted;
+        }
+
+        /// <summary>Gets the result of the ValueTask.</summary>
+        [StackTraceHidden]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void GetResult() => _value.ThrowIfCompletedUnsuccessfully();
+
+        /// <summary>Schedules the continuation action for this ValueTask.</summary>
+        public void OnCompleted(Action continuation)
+        {
+            object obj = _value._obj;
+            Debug.Assert(obj == null || obj is Task || obj is IValueTaskSource);
+
+            if (obj is Task t)
+            {
+                t.GetAwaiter().OnCompleted(continuation);
+            }
+            else if (obj != null)
+            {
+                Unsafe.As<IValueTaskSource>(obj).OnCompleted(s_invokeActionDelegate, continuation, _value._token, ValueTaskSourceOnCompletedFlags.UseSchedulingContext | ValueTaskSourceOnCompletedFlags.FlowExecutionContext);
+            }
+            else
+            {
+                ValueTask.CompletedTask.GetAwaiter().OnCompleted(continuation);
+            }
+        }
+
+        /// <summary>Schedules the continuation action for this ValueTask.</summary>
+        public void UnsafeOnCompleted(Action continuation)
+        {
+            object obj = _value._obj;
+            Debug.Assert(obj == null || obj is Task || obj is IValueTaskSource);
+
+            if (obj is Task t)
+            {
+                t.GetAwaiter().UnsafeOnCompleted(continuation);
+            }
+            else if (obj != null)
+            {
+                Unsafe.As<IValueTaskSource>(obj).OnCompleted(s_invokeActionDelegate, continuation, _value._token, ValueTaskSourceOnCompletedFlags.UseSchedulingContext);
+            }
+            else
+            {
+                ValueTask.CompletedTask.GetAwaiter().UnsafeOnCompleted(continuation);
+            }
+        }
+
+#if CORECLR
+        void IStateMachineBoxAwareAwaiter.AwaitUnsafeOnCompleted(IAsyncStateMachineBox box)
+        {
+            object obj = _value._obj;
+            Debug.Assert(obj == null || obj is Task || obj is IValueTaskSource);
+
+            if (obj is Task t)
+            {
+                TaskAwaiter.UnsafeOnCompletedInternal(t, box, continueOnCapturedContext: true);
+            }
+            else if (obj != null)
+            {
+                Unsafe.As<IValueTaskSource>(obj).OnCompleted(s_invokeAsyncStateMachineBox, box, _value._token, ValueTaskSourceOnCompletedFlags.UseSchedulingContext);
+            }
+            else
+            {
+                TaskAwaiter.UnsafeOnCompletedInternal(Task.CompletedTask, box, continueOnCapturedContext: true);
+            }
+        }
+
+        /// <summary>Shim used to invoke <see cref="ITaskCompletionAction.Invoke"/> of the supplied <see cref="IAsyncStateMachineBox"/>.</summary>
+        internal static readonly Action<object> s_invokeAsyncStateMachineBox = state =>
+        {
+            if (!(state is IAsyncStateMachineBox box))
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.state);
+                return;
+            }
+
+            box.MoveNext();
+        };
+#endif
+    }
+
+    /// <summary>Provides an awaiter for a <see cref="ValueTask{TResult}"/>.</summary>
+    public readonly struct ValueTaskAwaiter<TResult> : ICriticalNotifyCompletion
+#if CORECLR
+            , IStateMachineBoxAwareAwaiter
+#endif
+    {
+        /// <summary>The value being awaited.</summary>
+        private readonly ValueTask<TResult> _value;
+
+        /// <summary>Initializes the awaiter.</summary>
+        /// <param name="value">The value to be awaited.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal ValueTaskAwaiter(ValueTask<TResult> value) => _value = value;
+
+        /// <summary>Gets whether the <see cref="ValueTask{TResult}"/> has completed.</summary>
+        public bool IsCompleted
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => _value.IsCompleted;
+        }
+
+        /// <summary>Gets the result of the ValueTask.</summary>
+        [StackTraceHidden]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public TResult GetResult() => _value.Result;
+
+        /// <summary>Schedules the continuation action for this ValueTask.</summary>
+        public void OnCompleted(Action continuation)
+        {
+            object obj = _value._obj;
+            Debug.Assert(obj == null || obj is Task<TResult> || obj is IValueTaskSource<TResult>);
+
+            if (obj is Task<TResult> t)
+            {
+                t.GetAwaiter().OnCompleted(continuation);
+            }
+            else if (obj != null)
+            {
+                Unsafe.As<IValueTaskSource<TResult>>(obj).OnCompleted(ValueTaskAwaiter.s_invokeActionDelegate, continuation, _value._token, ValueTaskSourceOnCompletedFlags.UseSchedulingContext | ValueTaskSourceOnCompletedFlags.FlowExecutionContext);
+            }
+            else
+            {
+                ValueTask.CompletedTask.GetAwaiter().OnCompleted(continuation);
+            }
+        }
+
+        /// <summary>Schedules the continuation action for this ValueTask.</summary>
+        public void UnsafeOnCompleted(Action continuation)
+        {
+            object obj = _value._obj;
+            Debug.Assert(obj == null || obj is Task<TResult> || obj is IValueTaskSource<TResult>);
+
+            if (obj is Task<TResult> t)
+            {
+                t.GetAwaiter().UnsafeOnCompleted(continuation);
+            }
+            else if (obj != null)
+            {
+                Unsafe.As<IValueTaskSource<TResult>>(obj).OnCompleted(ValueTaskAwaiter.s_invokeActionDelegate, continuation, _value._token, ValueTaskSourceOnCompletedFlags.UseSchedulingContext);
+            }
+            else
+            {
+                ValueTask.CompletedTask.GetAwaiter().UnsafeOnCompleted(continuation);
+            }
+        }
+
+#if CORECLR
+        void IStateMachineBoxAwareAwaiter.AwaitUnsafeOnCompleted(IAsyncStateMachineBox box)
+        {
+            object obj = _value._obj;
+            Debug.Assert(obj == null || obj is Task<TResult> || obj is IValueTaskSource<TResult>);
+
+            if (obj is Task<TResult> t)
+            {
+                TaskAwaiter.UnsafeOnCompletedInternal(t, box, continueOnCapturedContext: true);
+            }
+            else if (obj != null)
+            {
+                Unsafe.As<IValueTaskSource<TResult>>(obj).OnCompleted(ValueTaskAwaiter.s_invokeAsyncStateMachineBox, box, _value._token, ValueTaskSourceOnCompletedFlags.UseSchedulingContext);
+            }
+            else
+            {
+                TaskAwaiter.UnsafeOnCompletedInternal(Task.CompletedTask, box, continueOnCapturedContext: true);
+            }
+        }
+#endif
+    }
+
+#if CORECLR
+    /// <summary>Internal interface used to enable optimizations from <see cref="AsyncTaskMethodBuilder"/>.</summary>>
+    internal interface IStateMachineBoxAwareAwaiter
+    {
+        /// <summary>Invoked to set <see cref="ITaskCompletionAction.Invoke"/> of the <paramref name="box"/> as the awaiter's continuation.</summary>
+        /// <param name="box">The box object.</param>
+        void AwaitUnsafeOnCompleted(IAsyncStateMachineBox box);
+    }
+#endif
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/YieldAwaitable.cs b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/YieldAwaitable.cs
new file mode 100644
index 0000000000..8aed0fcd5a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/CompilerServices/YieldAwaitable.cs
@@ -0,0 +1,202 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// Compiler-targeted type for switching back into the current execution context, e.g.
+// 
+//   await Task.Yield();
+//   =====================
+//   var $awaiter = Task.Yield().GetAwaiter();
+//   if (!$awaiter.IsCompleted)
+//   {
+//       $builder.AwaitUnsafeOnCompleted(ref $awaiter, ref this);
+//       return;
+//       Label:
+//   }
+//   $awaiter.GetResult();
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System;
+using System.Security;
+using System.Diagnostics;
+using System.Diagnostics.Tracing;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.Runtime.CompilerServices
+{
+    // NOTE: YieldAwaitable currently has no state; while developers are encouraged to use Task.Yield() to produce one,
+    // no validation is performed to ensure that the developer isn't doing "await new YieldAwaitable()".  Such validation
+    // would require additional, useless state to be stored, and as this is a type in the CompilerServices namespace, and
+    // as the above example isn't harmful, we take the cheaper approach of not validating anything.
+
+    /// <summary>Provides an awaitable context for switching into a target environment.</summary>
+    /// <remarks>This type is intended for compiler use only.</remarks>
+    public readonly struct YieldAwaitable
+    {
+        /// <summary>Gets an awaiter for this <see cref="YieldAwaitable"/>.</summary>
+        /// <returns>An awaiter for this awaitable.</returns>
+        /// <remarks>This method is intended for compiler user rather than use directly in code.</remarks>
+        public YieldAwaiter GetAwaiter() { return new YieldAwaiter(); }
+
+        /// <summary>Provides an awaiter that switches into a target environment.</summary>
+        /// <remarks>This type is intended for compiler use only.</remarks>
+        public readonly struct YieldAwaiter : ICriticalNotifyCompletion
+#if CORECLR
+            , IStateMachineBoxAwareAwaiter
+#endif
+        {
+            /// <summary>Gets whether a yield is not required.</summary>
+            /// <remarks>This property is intended for compiler user rather than use directly in code.</remarks>
+            public bool IsCompleted { get { return false; } } // yielding is always required for YieldAwaiter, hence false
+
+            /// <summary>Posts the <paramref name="continuation"/> back to the current context.</summary>
+            /// <param name="continuation">The action to invoke asynchronously.</param>
+            /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+            public void OnCompleted(Action continuation)
+            {
+                QueueContinuation(continuation, flowContext: true);
+            }
+
+            /// <summary>Posts the <paramref name="continuation"/> back to the current context.</summary>
+            /// <param name="continuation">The action to invoke asynchronously.</param>
+            /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+            public void UnsafeOnCompleted(Action continuation)
+            {
+                QueueContinuation(continuation, flowContext: false);
+            }
+
+            /// <summary>Posts the <paramref name="continuation"/> back to the current context.</summary>
+            /// <param name="continuation">The action to invoke asynchronously.</param>
+            /// <param name="flowContext">true to flow ExecutionContext; false if flowing is not required.</param>
+            /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+            private static void QueueContinuation(Action continuation, bool flowContext)
+            {
+                // Validate arguments
+                if (continuation == null) throw new ArgumentNullException(nameof(continuation));
+
+                if (TplEtwProvider.Log.IsEnabled())
+                {
+                    continuation = OutputCorrelationEtwEvent(continuation);
+                }
+                // Get the current SynchronizationContext, and if there is one,
+                // post the continuation to it.  However, treat the base type
+                // as if there wasn't a SynchronizationContext, since that's what it
+                // logically represents.
+                var syncCtx = SynchronizationContext.Current;
+                if (syncCtx != null && syncCtx.GetType() != typeof(SynchronizationContext))
+                {
+                    syncCtx.Post(s_sendOrPostCallbackRunAction, continuation);
+                }
+                else
+                {
+                    // If we're targeting the default scheduler, queue to the thread pool, so that we go into the global
+                    // queue.  As we're going into the global queue, we might as well use QUWI, which for the global queue is
+                    // just a tad faster than task, due to a smaller object getting allocated and less work on the execution path.
+                    TaskScheduler scheduler = TaskScheduler.Current;
+                    if (scheduler == TaskScheduler.Default)
+                    {
+                        if (flowContext)
+                        {
+                            ThreadPool.QueueUserWorkItem(s_waitCallbackRunAction, continuation);
+                        }
+                        else
+                        {
+                            ThreadPool.UnsafeQueueUserWorkItem(s_waitCallbackRunAction, continuation);
+                        }
+                    }
+                    // We're targeting a custom scheduler, so queue a task.
+                    else
+                    {
+                        Task.Factory.StartNew(continuation, default(CancellationToken), TaskCreationOptions.PreferFairness, scheduler);
+                    }
+                }
+            }
+
+#if CORECLR
+            void IStateMachineBoxAwareAwaiter.AwaitUnsafeOnCompleted(IAsyncStateMachineBox box)
+            {
+                Debug.Assert(box != null);
+
+                // If tracing is enabled, delegate the Action-based implementation.
+                if (TplEtwProvider.Log.IsEnabled())
+                {
+                    QueueContinuation(box.MoveNextAction, flowContext: false);
+                    return;
+                }
+
+                // Otherwise, this is the same logic as in QueueContinuation, except using
+                // an IAsyncStateMachineBox instead of an Action, and only for flowContext:false.
+
+                SynchronizationContext syncCtx = SynchronizationContext.Current;
+                if (syncCtx != null && syncCtx.GetType() != typeof(SynchronizationContext))
+                {
+                    syncCtx.Post(s => ((IAsyncStateMachineBox)s).MoveNext(), box);
+                }
+                else
+                {
+                    TaskScheduler scheduler = TaskScheduler.Current;
+                    if (scheduler == TaskScheduler.Default)
+                    {
+                        ThreadPool.UnsafeQueueUserWorkItem(s => ((IAsyncStateMachineBox)s).MoveNext(), box);
+                    }
+                    else
+                    {
+                        Task.Factory.StartNew(s => ((IAsyncStateMachineBox)s).MoveNext(), box, default, TaskCreationOptions.PreferFairness, scheduler);
+                    }
+                }
+            }
+#endif
+
+            private static Action OutputCorrelationEtwEvent(Action continuation)
+            {
+#if CORERT
+                // TODO
+                return continuation;
+#else
+                int continuationId = Task.NewId();
+                Task currentTask = Task.InternalCurrent;
+                // fire the correlation ETW event
+                TplEtwProvider.Log.AwaitTaskContinuationScheduled(TaskScheduler.Current.Id, (currentTask != null) ? currentTask.Id : 0, continuationId);
+
+                return AsyncMethodBuilderCore.CreateContinuationWrapper(continuation, (innerContinuation,continuationIdTask) =>
+                {
+                    var etwLog = TplEtwProvider.Log;
+                    etwLog.TaskWaitContinuationStarted(((Task<int>)continuationIdTask).Result);
+
+                    // ETW event for Task Wait End.
+                    Guid prevActivityId = new Guid();
+                    // Ensure the continuation runs under the correlated activity ID generated above
+                    if (etwLog.TasksSetActivityIds)
+                        EventSource.SetCurrentThreadActivityId(TplEtwProvider.CreateGuidForTaskID(((Task<int>)continuationIdTask).Result), out prevActivityId);
+
+                    // Invoke the original continuation provided to OnCompleted.
+                    innerContinuation();
+                    // Restore activity ID
+
+                    if (etwLog.TasksSetActivityIds)
+                        EventSource.SetCurrentThreadActivityId(prevActivityId);
+
+                    etwLog.TaskWaitContinuationComplete(((Task<int>)continuationIdTask).Result);
+                }, Task.FromResult(continuationId)); // pass the ID in a task to avoid a closure\
+#endif
+            }
+
+            /// <summary>WaitCallback that invokes the Action supplied as object state.</summary>
+            private static readonly WaitCallback s_waitCallbackRunAction = RunAction;
+            /// <summary>SendOrPostCallback that invokes the Action supplied as object state.</summary>
+            private static readonly SendOrPostCallback s_sendOrPostCallbackRunAction = RunAction;
+            /// <summary>Runs an Action delegate provided as state.</summary>
+            /// <param name="state">The Action delegate to invoke.</param>
+            private static void RunAction(object state) { ((Action)state)(); }
+
+            /// <summary>Ends the await operation.</summary>
+            public void GetResult() { } // Nop. It exists purely because the compiler pattern demands it.
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/ConstrainedExecution/Cer.cs b/src/System.Private.CoreLib/shared/System/Runtime/ConstrainedExecution/Cer.cs
new file mode 100644
index 0000000000..77ab3ea770
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/ConstrainedExecution/Cer.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.ConstrainedExecution
+{
+    public enum Cer : int
+    {
+        None = 0,
+        MayFail = 1,  // Might fail, but the method will say it failed
+        Success = 2,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/ConstrainedExecution/Consistency.cs b/src/System.Private.CoreLib/shared/System/Runtime/ConstrainedExecution/Consistency.cs
new file mode 100644
index 0000000000..e2cc79ec35
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/ConstrainedExecution/Consistency.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.ConstrainedExecution
+{
+    public enum Consistency : int
+    {
+        MayCorruptProcess = 0,
+        MayCorruptAppDomain = 1,
+        MayCorruptInstance = 2,
+        WillNotCorruptState = 3,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/ConstrainedExecution/CriticalFinalizerObject.cs b/src/System.Private.CoreLib/shared/System/Runtime/ConstrainedExecution/CriticalFinalizerObject.cs
new file mode 100644
index 0000000000..3f35f816a3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/ConstrainedExecution/CriticalFinalizerObject.cs
@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+** Deriving from this class will cause any finalizer you define to be critical
+** (i.e. the finalizer is guaranteed to run, won't be aborted by the host and is
+** run after the finalizers of other objects collected at the same time).
+**
+** 
+===========================================================*/
+
+namespace System.Runtime.ConstrainedExecution
+{
+    public abstract class CriticalFinalizerObject
+    {
+        protected CriticalFinalizerObject()
+        {
+        }
+
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1821:RemoveEmptyFinalizers")]
+        ~CriticalFinalizerObject()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/ConstrainedExecution/ReliabilityContractAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/ConstrainedExecution/ReliabilityContractAttribute.cs
new file mode 100644
index 0000000000..b3cb0143fa
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/ConstrainedExecution/ReliabilityContractAttribute.cs
@@ -0,0 +1,33 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+/*============================================================
+**
+**
+**
+** Purpose: Defines a publically documentable contract for 
+** reliability between a method and its callers, expressing
+** what state will remain consistent in the presence of 
+** failures (ie async exceptions like thread abort) and whether
+** the method needs to be called from within a CER.
+**
+**
+===========================================================*/
+
+namespace System.Runtime.ConstrainedExecution
+{
+    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Constructor | AttributeTargets.Method | AttributeTargets.Interface /* | AttributeTargets.Delegate*/, Inherited = false)]
+    public sealed class ReliabilityContractAttribute : Attribute
+    {
+        public ReliabilityContractAttribute(Consistency consistencyGuarantee, Cer cer)
+        {
+            ConsistencyGuarantee = consistencyGuarantee;
+            Cer = cer;
+        }
+
+        public Consistency ConsistencyGuarantee { get; }
+        public Cer Cer { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/ExceptionServices/ExceptionNotification.cs b/src/System.Private.CoreLib/shared/System/Runtime/ExceptionServices/ExceptionNotification.cs
new file mode 100644
index 0000000000..605588d657
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/ExceptionServices/ExceptionNotification.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.ExceptionServices
+{
+    // Definition of the argument-type passed to the FirstChanceException event handler
+    public class FirstChanceExceptionEventArgs : EventArgs
+    {
+        public FirstChanceExceptionEventArgs(Exception exception)
+        {
+            Exception = exception;
+        }
+
+        // Returns the exception object pertaining to the first chance exception
+        public Exception Exception { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/ExceptionServices/HandleProcessCorruptedStateExceptionsAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/ExceptionServices/HandleProcessCorruptedStateExceptionsAttribute.cs
new file mode 100644
index 0000000000..cc1bc81e5a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/ExceptionServices/HandleProcessCorruptedStateExceptionsAttribute.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.ExceptionServices
+{
+    // This attribute can be applied to methods to indicate that ProcessCorruptedState
+    // Exceptions should be delivered to them.
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = false)]
+    public sealed class HandleProcessCorruptedStateExceptionsAttribute : Attribute
+    {
+        public HandleProcessCorruptedStateExceptionsAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/BestFitMappingAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/BestFitMappingAttribute.cs
new file mode 100644
index 0000000000..4ebee1538c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/BestFitMappingAttribute.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Interface | AttributeTargets.Class | AttributeTargets.Struct, Inherited = false)]
+    public sealed class BestFitMappingAttribute : Attribute
+    {
+        public BestFitMappingAttribute(bool BestFitMapping)
+        {
+            this.BestFitMapping = BestFitMapping;
+        }
+
+        public bool BestFitMapping { get; }
+
+        public bool ThrowOnUnmappableChar;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/CallingConvention.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/CallingConvention.cs
new file mode 100644
index 0000000000..3b18fdee3a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/CallingConvention.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    // Used for the CallingConvention named argument to the DllImport and NativeCallable attribute
+    public enum CallingConvention
+    {
+        Winapi = 1,
+        Cdecl = 2,
+        StdCall = 3,
+        ThisCall = 4,
+        FastCall = 5,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/CharSet.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/CharSet.cs
new file mode 100644
index 0000000000..d587ec006b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/CharSet.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    // Use this in P/Invoke function prototypes to specify 
+    // which character set to use when marshalling Strings.
+    // Using Ansi will marshal the strings as 1 byte char*'s.
+    // Using Unicode will marshal the strings as 2 byte wchar*'s.
+    // Generally you probably want to use Auto, which does the
+    // right thing 99% of the time.
+
+    public enum CharSet
+    {
+        None = 1,        // User didn't specify how to marshal strings.
+        Ansi = 2,        // Strings should be marshalled as ANSI 1 byte chars. 
+        Unicode = 3,     // Strings should be marshalled as Unicode 2 byte chars.
+        Auto = 4,        // Marshal Strings in the right way for the target system. 
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/ComVisibleAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/ComVisibleAttribute.cs
new file mode 100644
index 0000000000..84b9505a5a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/ComVisibleAttribute.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Interface | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Delegate | AttributeTargets.Enum | AttributeTargets.Field | AttributeTargets.Method | AttributeTargets.Property, Inherited = false)]
+    public sealed class ComVisibleAttribute : Attribute
+    {
+        public ComVisibleAttribute(bool visibility)
+        {
+            Value = visibility;
+        }
+
+        public bool Value { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/DefaultCharSetAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/DefaultCharSetAttribute.cs
new file mode 100644
index 0000000000..7a486f7017
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/DefaultCharSetAttribute.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Module, Inherited = false)]
+    public sealed class DefaultCharSetAttribute : Attribute
+    {
+        public DefaultCharSetAttribute(CharSet charSet)
+        {
+            CharSet = charSet;
+        }
+
+        public CharSet CharSet { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/DefaultDllImportSearchPathsAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/DefaultDllImportSearchPathsAttribute.cs
new file mode 100644
index 0000000000..1ff27fbbd5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/DefaultDllImportSearchPathsAttribute.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Method, AllowMultiple = false)]
+    public sealed class DefaultDllImportSearchPathsAttribute : Attribute
+    {
+        public DefaultDllImportSearchPathsAttribute(DllImportSearchPath paths)
+        {
+            Paths = paths;
+        }
+
+        public DllImportSearchPath Paths { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/DllImportAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/DllImportAttribute.cs
new file mode 100644
index 0000000000..97f870d49c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/DllImportAttribute.cs
@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Method, Inherited = false)]
+    public sealed class DllImportAttribute : Attribute
+    {
+        public DllImportAttribute(string dllName)
+        {
+            Value = dllName;
+        }
+
+        public string Value { get; }
+
+        public string EntryPoint;
+        public CharSet CharSet;
+        public bool SetLastError;
+        public bool ExactSpelling;
+        public CallingConvention CallingConvention;
+        public bool BestFitMapping;
+        public bool PreserveSig;
+        public bool ThrowOnUnmappableChar;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/DllImportSearchPath.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/DllImportSearchPath.cs
new file mode 100644
index 0000000000..8dbdb40be9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/DllImportSearchPath.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [Flags]
+    public enum DllImportSearchPath
+    {
+        UseDllDirectoryForDependencies = 0x100,
+        ApplicationDirectory = 0x200,
+        UserDirectories = 0x400,
+        System32 = 0x800,
+        SafeDirectories = 0x1000,
+        AssemblyDirectory = 0x2,
+        LegacyBehavior = 0x0
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/ExternalException.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/ExternalException.cs
new file mode 100644
index 0000000000..160fe301e8
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/ExternalException.cs
@@ -0,0 +1,89 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception base class for all errors from Interop or Structured 
+**          Exception Handling code.
+**
+**
+=============================================================================*/
+
+using System;
+using System.Globalization;
+using System.Runtime.Serialization;
+
+namespace System.Runtime.InteropServices
+{
+    // Base exception for COM Interop errors &; Structured Exception Handler
+    // exceptions.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class ExternalException : SystemException
+    {
+        public ExternalException()
+            : base(SR.Arg_ExternalException)
+        {
+            HResult = HResults.E_FAIL;
+        }
+
+        public ExternalException(string message)
+            : base(message)
+        {
+            HResult = HResults.E_FAIL;
+        }
+
+        public ExternalException(string message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.E_FAIL;
+        }
+
+        public ExternalException(string message, int errorCode)
+            : base(message)
+        {
+            HResult = errorCode;
+        }
+
+        protected ExternalException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+
+        public virtual int ErrorCode
+        {
+            get
+            {
+                return HResult;
+            }
+        }
+
+        public override string ToString()
+        {
+            string message = Message;
+            string className = GetType().ToString();
+
+            string s = className + " (0x" + HResult.ToString("X8", CultureInfo.InvariantCulture) + ")";
+
+            if (!(String.IsNullOrEmpty(message)))
+            {
+                s = s + ": " + message;
+            }
+
+            Exception innerException = InnerException;
+
+            if (innerException != null)
+            {
+                s = s + " ---> " + innerException.ToString();
+            }
+
+            if (StackTrace != null)
+                s += Environment.NewLine + StackTrace;
+
+            return s;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/FieldOffsetAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/FieldOffsetAttribute.cs
new file mode 100644
index 0000000000..27e1097749
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/FieldOffsetAttribute.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Field, Inherited = false)]
+    public sealed class FieldOffsetAttribute : Attribute
+    {
+        public FieldOffsetAttribute(int offset)
+        {
+            Value = offset;
+        }
+
+        public int Value { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/GuidAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/GuidAttribute.cs
new file mode 100644
index 0000000000..cf60b9bf70
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/GuidAttribute.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Interface | AttributeTargets.Class | AttributeTargets.Enum | AttributeTargets.Struct | AttributeTargets.Delegate, Inherited = false)]
+    public sealed class GuidAttribute : Attribute
+    {
+        public GuidAttribute(string guid)
+        {
+            Value = guid;
+        }
+
+        public string Value { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/HandleRef.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/HandleRef.cs
new file mode 100644
index 0000000000..64d0553130
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/HandleRef.cs
@@ -0,0 +1,47 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    public struct HandleRef
+    {
+        // ! Do not add or rearrange fields as the EE depends on this layout.
+        //------------------------------------------------------------------
+        private object _wrapper;
+        private IntPtr _handle;
+        //------------------------------------------------------------------
+
+        public HandleRef(object wrapper, IntPtr handle)
+        {
+            _wrapper = wrapper;
+            _handle = handle;
+        }
+
+        public object Wrapper
+        {
+            get
+            {
+                return _wrapper;
+            }
+        }
+
+        public IntPtr Handle
+        {
+            get
+            {
+                return _handle;
+            }
+        }
+
+        public static explicit operator IntPtr(HandleRef value)
+        {
+            return value._handle;
+        }
+
+        public static IntPtr ToIntPtr(HandleRef value)
+        {
+            return value._handle;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/InAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/InAttribute.cs
new file mode 100644
index 0000000000..39f5a958bc
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/InAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+    public sealed class InAttribute : Attribute
+    {
+        public InAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/LayoutKind.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/LayoutKind.cs
new file mode 100644
index 0000000000..dbd7ec62d5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/LayoutKind.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    // Used in the StructLayoutAttribute class
+    public enum LayoutKind
+    {
+        Sequential = 0,
+        Explicit = 2,
+        Auto = 3,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/MarshalAsAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/MarshalAsAttribute.cs
new file mode 100644
index 0000000000..4a64050ed1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/MarshalAsAttribute.cs
@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Parameter | AttributeTargets.Field | AttributeTargets.ReturnValue, Inherited = false)]
+    public sealed class MarshalAsAttribute : Attribute
+    {
+        public MarshalAsAttribute(UnmanagedType unmanagedType)
+        {
+            Value = unmanagedType;
+        }
+        public MarshalAsAttribute(short unmanagedType)
+        {
+            Value = (UnmanagedType)unmanagedType;
+        }
+
+        public UnmanagedType Value { get; }
+
+        // Fields used with SubType = SafeArray.
+        public VarEnum SafeArraySubType;
+        public Type SafeArrayUserDefinedSubType;
+
+        // Field used with iid_is attribute (interface pointers).
+        public int IidParameterIndex;
+
+        // Fields used with SubType = ByValArray and LPArray.
+        // Array size =  parameter(PI) * PM + C
+        public UnmanagedType ArraySubType;
+        public short SizeParamIndex;           // param index PI
+        public int SizeConst;                // constant C
+
+        // Fields used with SubType = CustomMarshaler
+        public string MarshalType;              // Name of marshaler class
+        public Type MarshalTypeRef;           // Type of marshaler class
+        public string MarshalCookie;            // cookie to pass to marshaler
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/MarshalDirectiveException.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/MarshalDirectiveException.cs
new file mode 100644
index 0000000000..1d0d59fab6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/MarshalDirectiveException.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+** Purpose: This exception is thrown when the marshaller encounters a signature
+**          that has an invalid MarshalAs CA for a given argument or is not
+**          supported.
+**
+=============================================================================*/
+
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System.Runtime.InteropServices
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class MarshalDirectiveException : SystemException
+    {
+        public MarshalDirectiveException()
+            : base(SR.Arg_MarshalDirectiveException)
+        {
+            HResult = HResults.COR_E_MARSHALDIRECTIVE;
+        }
+
+        public MarshalDirectiveException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_MARSHALDIRECTIVE;
+        }
+
+        public MarshalDirectiveException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_MARSHALDIRECTIVE;
+        }
+
+        protected MarshalDirectiveException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/MemoryMarshal.Fast.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/MemoryMarshal.Fast.cs
new file mode 100644
index 0000000000..80ae450b51
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/MemoryMarshal.Fast.cs
@@ -0,0 +1,232 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Buffers;
+using System.Runtime.CompilerServices;
+using System.Collections.Generic;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices
+{
+    /// <summary>
+    /// Provides a collection of methods for interoperating with <see cref="Memory{T}"/>, <see cref="ReadOnlyMemory{T}"/>,
+    /// <see cref="Span{T}"/>, and <see cref="ReadOnlySpan{T}"/>.
+    /// </summary>
+    public static partial class MemoryMarshal
+    {
+        /// <summary>
+        /// Casts a Span of one primitive type <typeparamref name="T"/> to Span of bytes.
+        /// That type may not contain pointers or references. This is checked at runtime in order to preserve type safety.
+        /// </summary>
+        /// <param name="span">The source slice, of type <typeparamref name="T"/>.</param>
+        /// <exception cref="System.ArgumentException">
+        /// Thrown when <typeparamref name="T"/> contains pointers.
+        /// </exception>
+        /// <exception cref="System.OverflowException">
+        /// Thrown if the Length property of the new Span would exceed Int32.MaxValue.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Span<byte> AsBytes<T>(Span<T> span)
+            where T : struct
+        {
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+                ThrowHelper.ThrowInvalidTypeWithPointersNotSupported(typeof(T));
+
+            return new Span<byte>(
+                ref Unsafe.As<T, byte>(ref GetReference(span)),
+                checked(span.Length * Unsafe.SizeOf<T>()));
+        }
+
+        /// <summary>
+        /// Casts a ReadOnlySpan of one primitive type <typeparamref name="T"/> to ReadOnlySpan of bytes.
+        /// That type may not contain pointers or references. This is checked at runtime in order to preserve type safety.
+        /// </summary>
+        /// <param name="span">The source slice, of type <typeparamref name="T"/>.</param>
+        /// <exception cref="System.ArgumentException">
+        /// Thrown when <typeparamref name="T"/> contains pointers.
+        /// </exception>
+        /// <exception cref="System.OverflowException">
+        /// Thrown if the Length property of the new Span would exceed Int32.MaxValue.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ReadOnlySpan<byte> AsBytes<T>(ReadOnlySpan<T> span)
+            where T : struct
+        {
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+                ThrowHelper.ThrowInvalidTypeWithPointersNotSupported(typeof(T));
+
+            return new ReadOnlySpan<byte>(
+                ref Unsafe.As<T, byte>(ref GetReference(span)),
+                checked(span.Length * Unsafe.SizeOf<T>()));
+        }
+
+        /// <summary>Creates a <see cref="Memory{T}"/> from a <see cref="ReadOnlyMemory{T}"/>.</summary>
+        /// <param name="memory">The <see cref="ReadOnlyMemory{T}"/>.</param>
+        /// <returns>A <see cref="Memory{T}"/> representing the same memory as the <see cref="ReadOnlyMemory{T}"/>, but writable.</returns>
+        /// <remarks>
+        /// <see cref="AsMemory{T}(ReadOnlyMemory{T})"/> must be used with extreme caution.  <see cref="ReadOnlyMemory{T}"/> is used
+        /// to represent immutable data and other memory that is not meant to be written to; <see cref="Memory{T}"/> instances created
+        /// by <see cref="AsMemory{T}(ReadOnlyMemory{T})"/> should not be written to.  The method exists to enable variables typed
+        /// as <see cref="Memory{T}"/> but only used for reading to store a <see cref="ReadOnlyMemory{T}"/>.
+        /// </remarks>
+        public static Memory<T> AsMemory<T>(ReadOnlyMemory<T> memory) =>
+            Unsafe.As<ReadOnlyMemory<T>, Memory<T>>(ref memory);
+
+        /// <summary>
+        /// Returns a reference to the 0th element of the Span. If the Span is empty, returns a reference to the location where the 0th element
+        /// would have been stored. Such a reference may or may not be null. It can be used for pinning but must never be dereferenced.
+        /// </summary>
+        public static ref T GetReference<T>(Span<T> span) => ref span._pointer.Value;
+
+        /// <summary>
+        /// Returns a reference to the 0th element of the ReadOnlySpan. If the ReadOnlySpan is empty, returns a reference to the location where the 0th element
+        /// would have been stored. Such a reference may or may not be null. It can be used for pinning but must never be dereferenced.
+        /// </summary>
+        public static ref T GetReference<T>(ReadOnlySpan<T> span) => ref span._pointer.Value;
+
+        /// <summary>
+        /// Returns a reference to the 0th element of the Span. If the Span is empty, returns a reference to fake non-null pointer. Such a reference can be used
+        /// for pinning but must never be dereferenced. This is useful for interop with methods that do not accept null pointers for zero-sized buffers.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static unsafe ref T GetNonNullPinnableReference<T>(Span<T> span) => ref (span.Length != 0) ? ref span._pointer.Value : ref Unsafe.AsRef<T>((void*)1);
+
+        /// <summary>
+        /// Returns a reference to the 0th element of the ReadOnlySpan. If the ReadOnlySpan is empty, returns a reference to fake non-null pointer. Such a reference
+        /// can be used for pinning but must never be dereferenced. This is useful for interop with methods that do not accept null pointers for zero-sized buffers.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static unsafe ref T GetNonNullPinnableReference<T>(ReadOnlySpan<T> span) => ref (span.Length != 0) ? ref span._pointer.Value : ref Unsafe.AsRef<T>((void*)1);
+
+        /// <summary>
+        /// Casts a Span of one primitive type <typeparamref name="TFrom"/> to another primitive type <typeparamref name="TTo"/>.
+        /// These types may not contain pointers or references. This is checked at runtime in order to preserve type safety.
+        /// </summary>
+        /// <remarks>
+        /// Supported only for platforms that support misaligned memory access.
+        /// </remarks>
+        /// <param name="span">The source slice, of type <typeparamref name="TFrom"/>.</param>
+        /// <exception cref="System.ArgumentException">
+        /// Thrown when <typeparamref name="TFrom"/> or <typeparamref name="TTo"/> contains pointers.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Span<TTo> Cast<TFrom, TTo>(Span<TFrom> span)
+            where TFrom : struct
+            where TTo : struct
+        {
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<TFrom>())
+                ThrowHelper.ThrowInvalidTypeWithPointersNotSupported(typeof(TFrom));
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<TTo>())
+                ThrowHelper.ThrowInvalidTypeWithPointersNotSupported(typeof(TTo));
+
+            // Use unsigned integers - unsigned division by constant (especially by power of 2)
+            // and checked casts are faster and smaller.
+            uint fromSize = (uint)Unsafe.SizeOf<TFrom>();
+            uint toSize = (uint)Unsafe.SizeOf<TTo>();
+            uint fromLength = (uint)span.Length;
+            int toLength;
+            if (fromSize == toSize)
+            {
+                // Special case for same size types - `(ulong)fromLength * (ulong)fromSize / (ulong)toSize`
+                // should be optimized to just `length` but the JIT doesn't do that today.
+                toLength = (int)fromLength;
+            }
+            else if (fromSize == 1)
+            {
+                // Special case for byte sized TFrom - `(ulong)fromLength * (ulong)fromSize / (ulong)toSize`
+                // becomes `(ulong)fromLength / (ulong)toSize` but the JIT can't narrow it down to `int`
+                // and can't eliminate the checked cast. This also avoids a 32 bit specific issue,
+                // the JIT can't eliminate long multiply by 1.
+                toLength = (int)(fromLength / toSize);
+            }
+            else
+            {
+                // Ensure that casts are done in such a way that the JIT is able to "see"
+                // the uint->ulong casts and the multiply together so that on 32 bit targets
+                // 32x32to64 multiplication is used.
+                ulong toLengthUInt64 = (ulong)fromLength * (ulong)fromSize / (ulong)toSize;
+                toLength = checked((int)toLengthUInt64);
+            }
+
+            return new Span<TTo>(
+                ref Unsafe.As<TFrom, TTo>(ref span._pointer.Value),
+                toLength);
+        }
+
+        /// <summary>
+        /// Casts a ReadOnlySpan of one primitive type <typeparamref name="TFrom"/> to another primitive type <typeparamref name="TTo"/>.
+        /// These types may not contain pointers or references. This is checked at runtime in order to preserve type safety.
+        /// </summary>
+        /// <remarks>
+        /// Supported only for platforms that support misaligned memory access.
+        /// </remarks>
+        /// <param name="span">The source slice, of type <typeparamref name="TFrom"/>.</param>
+        /// <exception cref="System.ArgumentException">
+        /// Thrown when <typeparamref name="TFrom"/> or <typeparamref name="TTo"/> contains pointers.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ReadOnlySpan<TTo> Cast<TFrom, TTo>(ReadOnlySpan<TFrom> span)
+            where TFrom : struct
+            where TTo : struct
+        {
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<TFrom>())
+                ThrowHelper.ThrowInvalidTypeWithPointersNotSupported(typeof(TFrom));
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<TTo>())
+                ThrowHelper.ThrowInvalidTypeWithPointersNotSupported(typeof(TTo));
+
+            // Use unsigned integers - unsigned division by constant (especially by power of 2)
+            // and checked casts are faster and smaller.
+            uint fromSize = (uint)Unsafe.SizeOf<TFrom>();
+            uint toSize = (uint)Unsafe.SizeOf<TTo>();
+            uint fromLength = (uint)span.Length;
+            int toLength;
+            if (fromSize == toSize)
+            {
+                // Special case for same size types - `(ulong)fromLength * (ulong)fromSize / (ulong)toSize`
+                // should be optimized to just `length` but the JIT doesn't do that today.
+                toLength = (int)fromLength;
+            }
+            else if (fromSize == 1)
+            {
+                // Special case for byte sized TFrom - `(ulong)fromLength * (ulong)fromSize / (ulong)toSize`
+                // becomes `(ulong)fromLength / (ulong)toSize` but the JIT can't narrow it down to `int`
+                // and can't eliminate the checked cast. This also avoids a 32 bit specific issue,
+                // the JIT can't eliminate long multiply by 1.
+                toLength = (int)(fromLength / toSize);
+            }
+            else
+            {
+                // Ensure that casts are done in such a way that the JIT is able to "see"
+                // the uint->ulong casts and the multiply together so that on 32 bit targets
+                // 32x32to64 multiplication is used.
+                ulong toLengthUInt64 = (ulong)fromLength * (ulong)fromSize / (ulong)toSize;
+                toLength = checked((int)toLengthUInt64);
+            }
+
+            return new ReadOnlySpan<TTo>(
+                ref Unsafe.As<TFrom, TTo>(ref MemoryMarshal.GetReference(span)),
+                toLength);
+        }
+
+        /// <summary>
+        /// Create a new span over a portion of a regular managed object. This can be useful
+        /// if part of a managed object represents a "fixed array." This is dangerous because the
+        /// <paramref name="length"/> is not checked.
+        /// </summary>
+        /// <param name="reference">A reference to data.</param>
+        /// <param name="length">The number of <typeparamref name="T"/> elements the memory contains.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Span<T> CreateSpan<T>(ref T reference, int length) => new Span<T>(ref reference, length);
+
+        /// <summary>
+        /// Create a new read-only span over a portion of a regular managed object. This can be useful
+        /// if part of a managed object represents a "fixed array." This is dangerous because the
+        /// <paramref name="length"/> is not checked.
+        /// </summary>
+        /// <param name="reference">A reference to data.</param>
+        /// <param name="length">The number of <typeparamref name="T"/> elements the memory contains.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ReadOnlySpan<T> CreateReadOnlySpan<T>(ref T reference, int length) => new ReadOnlySpan<T>(ref reference, length);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/MemoryMarshal.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/MemoryMarshal.cs
new file mode 100644
index 0000000000..8eec0fd07c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/MemoryMarshal.cs
@@ -0,0 +1,281 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Buffers;
+using System.Runtime.CompilerServices;
+using System.Collections.Generic;
+using System.Diagnostics;
+
+#if !netstandard
+using Internal.Runtime.CompilerServices;
+#endif
+
+namespace System.Runtime.InteropServices
+{
+    /// <summary>
+    /// Provides a collection of methods for interoperating with <see cref="Memory{T}"/>, <see cref="ReadOnlyMemory{T}"/>,
+    /// <see cref="Span{T}"/>, and <see cref="ReadOnlySpan{T}"/>.
+    /// </summary>
+    public static partial class MemoryMarshal
+    {
+        /// <summary>
+        /// Get an array segment from the underlying memory.
+        /// If unable to get the array segment, return false with a default array segment.
+        /// </summary>
+        public static bool TryGetArray<T>(ReadOnlyMemory<T> memory, out ArraySegment<T> segment)
+        {
+            object obj = memory.GetObjectStartLength(out int index, out int length);
+            if (index < 0)
+            {
+                Debug.Assert(length >= 0);
+                if (((MemoryManager<T>)obj).TryGetArray(out ArraySegment<T> arraySegment))
+                {
+                    segment = new ArraySegment<T>(arraySegment.Array, arraySegment.Offset + (index & ReadOnlyMemory<T>.RemoveFlagsBitMask), length);
+                    return true;
+                }
+            }
+            else if (obj is T[] arr)
+            {
+                segment = new ArraySegment<T>(arr, index, length & ReadOnlyMemory<T>.RemoveFlagsBitMask);
+                return true;
+            }
+
+            if ((length & ReadOnlyMemory<T>.RemoveFlagsBitMask) == 0)
+            {
+#if FEATURE_PORTABLE_SPAN
+                segment = new ArraySegment<T>(SpanHelpers.PerTypeValues<T>.EmptyArray);
+#else
+                segment = ArraySegment<T>.Empty;
+#endif // FEATURE_PORTABLE_SPAN
+                return true;
+            }
+
+            segment = default;
+            return false;
+        }
+
+        /// <summary>
+        /// Gets an <see cref="MemoryManager{T}"/> from the underlying read-only memory.
+        /// If unable to get the <typeparamref name="TManager"/> type, returns false.
+        /// </summary>
+        /// <typeparam name="T">The element type of the <paramref name="memory" />.</typeparam>
+        /// <typeparam name="TManager">The type of <see cref="MemoryManager{T}"/> to try and retrive.</typeparam>
+        /// <param name="memory">The memory to get the manager for.</param>
+        /// <param name="manager">The returned manager of the <see cref="ReadOnlyMemory{T}"/>.</param>
+        /// <returns>A <see cref="bool"/> indicating if it was successful.</returns>
+        public static bool TryGetMemoryManager<T, TManager>(ReadOnlyMemory<T> memory, out TManager manager)
+            where TManager : MemoryManager<T>
+        {
+            TManager localManager; // Use register for null comparison rather than byref
+            manager = localManager = memory.GetObjectStartLength(out _, out _) as TManager;
+            return !ReferenceEquals(manager, null);
+        }
+
+        /// <summary>
+        /// Gets an <see cref="MemoryManager{T}"/> and <paramref name="start" />, <paramref name="length" /> from the underlying read-only memory.
+        /// If unable to get the <typeparamref name="TManager"/> type, returns false.
+        /// </summary>
+        /// <typeparam name="T">The element type of the <paramref name="memory" />.</typeparam>
+        /// <typeparam name="TManager">The type of <see cref="MemoryManager{T}"/> to try and retrive.</typeparam>
+        /// <param name="memory">The memory to get the manager for.</param>
+        /// <param name="manager">The returned manager of the <see cref="ReadOnlyMemory{T}"/>.</param>
+        /// <param name="start">The offset from the start of the <paramref name="manager" /> that the <paramref name="memory" /> represents.</param>
+        /// <param name="length">The length of the <paramref name="manager" /> that the <paramref name="memory" /> represents.</param>
+        /// <returns>A <see cref="bool"/> indicating if it was successful.</returns>
+        public static bool TryGetMemoryManager<T, TManager>(ReadOnlyMemory<T> memory, out TManager manager, out int start, out int length)
+           where TManager : MemoryManager<T>
+        {
+            TManager localManager; // Use register for null comparison rather than byref
+            manager = localManager = memory.GetObjectStartLength(out start, out length) as TManager;
+            start &= ReadOnlyMemory<T>.RemoveFlagsBitMask;
+
+            Debug.Assert(length >= 0);
+
+            if (ReferenceEquals(manager, null))
+            {
+                start = default;
+                length = default;
+                return false;
+            }
+            return true;
+        }
+
+        /// <summary>
+        /// Creates an <see cref="IEnumerable{T}"/> view of the given <paramref name="memory" /> to allow
+        /// the <paramref name="memory" /> to be used in existing APIs that take an <see cref="IEnumerable{T}"/>.
+        /// </summary>
+        /// <typeparam name="T">The element type of the <paramref name="memory" />.</typeparam>
+        /// <param name="memory">The ReadOnlyMemory to view as an <see cref="IEnumerable{T}"/></param>
+        /// <returns>An <see cref="IEnumerable{T}"/> view of the given <paramref name="memory" /></returns>
+        public static IEnumerable<T> ToEnumerable<T>(ReadOnlyMemory<T> memory)
+        {
+            for (int i = 0; i < memory.Length; i++)
+                yield return memory.Span[i];
+        }
+
+        /// <summary>Attempts to get the underlying <see cref="string"/> from a <see cref="ReadOnlyMemory{T}"/>.</summary>
+        /// <param name="memory">The memory that may be wrapping a <see cref="string"/> object.</param>
+        /// <param name="text">The string.</param>
+        /// <param name="start">The starting location in <paramref name="text"/>.</param>
+        /// <param name="length">The number of items in <paramref name="text"/>.</param>
+        /// <returns></returns>
+        public static bool TryGetString(ReadOnlyMemory<char> memory, out string text, out int start, out int length)
+        {
+            if (memory.GetObjectStartLength(out int offset, out int count) is string s)
+            {
+                Debug.Assert(offset >= 0);
+                Debug.Assert(count >= 0);
+                text = s;
+                start = offset;
+                length = count;
+                return true;
+            }
+            else
+            {
+                text = null;
+                start = 0;
+                length = 0;
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// Reads a structure of type T out of a read-only span of bytes.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static T Read<T>(ReadOnlySpan<byte> source)
+            where T : struct
+        {
+#if netstandard
+            if (SpanHelpers.IsReferenceOrContainsReferences<T>())
+            {
+                ThrowHelper.ThrowArgumentException_InvalidTypeWithPointersNotSupported(typeof(T));
+            }
+#else
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+            {
+                ThrowHelper.ThrowInvalidTypeWithPointersNotSupported(typeof(T));
+            }
+#endif
+            if (Unsafe.SizeOf<T>() > source.Length)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.length);
+            }
+            return Unsafe.ReadUnaligned<T>(ref GetReference(source));
+        }
+
+        /// <summary>
+        /// Reads a structure of type T out of a span of bytes.
+        /// <returns>If the span is too small to contain the type T, return false.</returns>
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool TryRead<T>(ReadOnlySpan<byte> source, out T value)
+            where T : struct
+        {
+#if netstandard
+            if (SpanHelpers.IsReferenceOrContainsReferences<T>())
+            {
+                ThrowHelper.ThrowArgumentException_InvalidTypeWithPointersNotSupported(typeof(T));
+            }
+#else
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+            {
+                ThrowHelper.ThrowInvalidTypeWithPointersNotSupported(typeof(T));
+            }
+#endif
+            if (Unsafe.SizeOf<T>() > (uint)source.Length)
+            {
+                value = default;
+                return false;
+            }
+            value = Unsafe.ReadUnaligned<T>(ref GetReference(source));
+            return true;
+        }
+
+        /// <summary>
+        /// Writes a structure of type T into a span of bytes.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void Write<T>(Span<byte> destination, ref T value)
+            where T : struct
+        {
+#if netstandard
+            if (SpanHelpers.IsReferenceOrContainsReferences<T>())
+            {
+                ThrowHelper.ThrowArgumentException_InvalidTypeWithPointersNotSupported(typeof(T));
+            }
+#else
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+            {
+                ThrowHelper.ThrowInvalidTypeWithPointersNotSupported(typeof(T));
+            }
+#endif
+            if ((uint)Unsafe.SizeOf<T>() > (uint)destination.Length)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.length);
+            }
+            Unsafe.WriteUnaligned<T>(ref GetReference(destination), value);
+        }
+
+        /// <summary>
+        /// Writes a structure of type T into a span of bytes.
+        /// <returns>If the span is too small to contain the type T, return false.</returns>
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool TryWrite<T>(Span<byte> destination, ref T value)
+            where T : struct
+        {
+#if netstandard
+            if (SpanHelpers.IsReferenceOrContainsReferences<T>())
+            {
+                ThrowHelper.ThrowArgumentException_InvalidTypeWithPointersNotSupported(typeof(T));
+            }
+#else
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+            {
+                ThrowHelper.ThrowInvalidTypeWithPointersNotSupported(typeof(T));
+            }
+#endif
+            if (Unsafe.SizeOf<T>() > (uint)destination.Length)
+            {
+                return false;
+            }
+            Unsafe.WriteUnaligned<T>(ref GetReference(destination), value);
+            return true;
+        }
+
+        /// <summary>
+        /// Creates a new memory over the portion of the pre-pinned target array beginning
+        /// at 'start' index and ending at 'end' index (exclusive).
+        /// </summary>
+        /// <param name="array">The pre-pinned target array.</param>
+        /// <param name="start">The index at which to begin the memory.</param>
+        /// <param name="length">The number of items in the memory.</param>
+        /// <remarks>This method should only be called on an array that is already pinned and 
+        /// that array should not be unpinned while the returned Memory<typeparamref name="T"/> is still in use.
+        /// Calling this method on an unpinned array could result in memory corruption.</remarks>
+        /// <remarks>Returns default when <paramref name="array"/> is null.</remarks>
+        /// <exception cref="System.ArrayTypeMismatchException">Thrown when <paramref name="array"/> is covariant and array's type is not exactly T[].</exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in the range (&lt;0 or &gt;=Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Memory<T> CreateFromPinnedArray<T>(T[] array, int start, int length)
+        {
+            if (array == null)
+            {
+                if (start != 0 || length != 0)
+                    ThrowHelper.ThrowArgumentOutOfRangeException();
+                return default;
+            }
+            if (default(T) == null && array.GetType() != typeof(T[]))
+                ThrowHelper.ThrowArrayTypeMismatchException();
+            if ((uint)start > (uint)array.Length || (uint)length > (uint)(array.Length - start))
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            // Before using _length, check if _length < 0, then 'and' it with RemoveFlagsBitMask
+            return new Memory<T>((object)array, start, length | (1 << 31));
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/OptionalAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/OptionalAttribute.cs
new file mode 100644
index 0000000000..5ac75d7b3e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/OptionalAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+    public sealed class OptionalAttribute : Attribute
+    {
+        public OptionalAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/OutAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/OutAttribute.cs
new file mode 100644
index 0000000000..338ceac91e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/OutAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+    public sealed class OutAttribute : Attribute
+    {
+        public OutAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/PreserveSigAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/PreserveSigAttribute.cs
new file mode 100644
index 0000000000..464e1abcbe
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/PreserveSigAttribute.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Method, Inherited = false)]
+    public sealed class PreserveSigAttribute : Attribute
+    {
+        public PreserveSigAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/SafeBuffer.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/SafeBuffer.cs
new file mode 100644
index 0000000000..455e413928
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/SafeBuffer.cs
@@ -0,0 +1,405 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Purpose: Unsafe code that uses pointers should use
+** SafePointer to fix subtle lifetime problems with the
+** underlying resource.
+**
+===========================================================*/
+
+// Design points:
+// *) Avoid handle-recycling problems (including ones triggered via
+// resurrection attacks) for all accesses via pointers.  This requires tying
+// together the lifetime of the unmanaged resource with the code that reads
+// from that resource, in a package that uses synchronization to enforce
+// the correct semantics during finalization.  We're using SafeHandle's
+// ref count as a gate on whether the pointer can be dereferenced because that
+// controls the lifetime of the resource.
+//
+// *) Keep the penalties for using this class small, both in terms of space
+// and time.  Having multiple threads reading from a memory mapped file
+// will already require 2 additional interlocked operations.  If we add in
+// a "current position" concept, that requires additional space in memory and
+// synchronization.  Since the position in memory is often (but not always)
+// something that can be stored on the stack, we can save some memory by
+// excluding it from this object.  However, avoiding the need for
+// synchronization is a more significant win.  This design allows multiple
+// threads to read and write memory simultaneously without locks (as long as
+// you don't write to a region of memory that overlaps with what another
+// thread is accessing).
+//
+// *) Space-wise, we use the following memory, including SafeHandle's fields:
+// Object Header  MT*  handle  int bool bool <2 pad bytes> length
+// On 32 bit platforms: 24 bytes.  On 64 bit platforms: 40 bytes.
+// (We can safe 4 bytes on x86 only by shrinking SafeHandle)
+//
+// *) Wrapping a SafeHandle would have been a nice solution, but without an
+// ordering between critical finalizable objects, it would have required
+// changes to each SafeHandle subclass to opt in to being usable from a
+// SafeBuffer (or some clever exposure of SafeHandle's state fields and a
+// way of forcing ReleaseHandle to run even after the SafeHandle has been
+// finalized with a ref count > 1).  We can use less memory and create fewer
+// objects by simply inserting a SafeBuffer into the class hierarchy.
+//
+// *) In an ideal world, we could get marshaling support for SafeBuffer that
+// would allow us to annotate a P/Invoke declaration, saying this parameter
+// specifies the length of the buffer, and the units of that length are X.
+// P/Invoke would then pass that size parameter to SafeBuffer.
+//     [DllImport(...)]
+//     static extern SafeMemoryHandle AllocCharBuffer(int numChars);
+// If we could put an attribute on the SafeMemoryHandle saying numChars is
+// the element length, and it must be multiplied by 2 to get to the byte
+// length, we can simplify the usage model for SafeBuffer.
+//
+// *) This class could benefit from a constraint saying T is a value type
+// containing no GC references.
+
+// Implementation notes:
+// *) The Initialize method must be called before you use any instance of
+// a SafeBuffer.  To avoid race conditions when storing SafeBuffers in statics,
+// you either need to take a lock when publishing the SafeBuffer, or you
+// need to create a local, initialize the SafeBuffer, then assign to the
+// static variable (perhaps using Interlocked.CompareExchange).  Of course,
+// assignments in a static class constructor are under a lock implicitly.
+
+using System;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+using Microsoft.Win32.SafeHandles;
+
+namespace System.Runtime.InteropServices
+{
+    public abstract unsafe class SafeBuffer : SafeHandleZeroOrMinusOneIsInvalid
+    {
+        // Steal UIntPtr.MaxValue as our uninitialized value.
+        private static readonly UIntPtr Uninitialized = (UIntPtr.Size == 4) ?
+            ((UIntPtr)UInt32.MaxValue) : ((UIntPtr)UInt64.MaxValue);
+
+        private UIntPtr _numBytes;
+
+        protected SafeBuffer(bool ownsHandle) : base(ownsHandle)
+        {
+            _numBytes = Uninitialized;
+        }
+
+        /// <summary>
+        /// Specifies the size of the region of memory, in bytes.  Must be
+        /// called before using the SafeBuffer.
+        /// </summary>
+        /// <param name="numBytes">Number of valid bytes in memory.</param>
+        [CLSCompliant(false)]
+        public void Initialize(ulong numBytes)
+        {
+            if (IntPtr.Size == 4 && numBytes > UInt32.MaxValue)
+                throw new ArgumentOutOfRangeException(nameof(numBytes), SR.ArgumentOutOfRange_AddressSpace);
+
+            if (numBytes >= (ulong)Uninitialized)
+                throw new ArgumentOutOfRangeException(nameof(numBytes), SR.ArgumentOutOfRange_UIntPtrMax);
+
+            _numBytes = (UIntPtr)numBytes;
+        }
+
+        /// <summary>
+        /// Specifies the size of the region in memory, as the number of
+        /// elements in an array.  Must be called before using the SafeBuffer.
+        /// </summary>
+        [CLSCompliant(false)]
+        public void Initialize(uint numElements, uint sizeOfEachElement)
+        {
+            if (IntPtr.Size == 4 && numElements * sizeOfEachElement > UInt32.MaxValue)
+                throw new ArgumentOutOfRangeException("numBytes", SR.ArgumentOutOfRange_AddressSpace);
+
+            if (numElements * sizeOfEachElement >= (ulong)Uninitialized)
+                throw new ArgumentOutOfRangeException(nameof(numElements), SR.ArgumentOutOfRange_UIntPtrMax);
+
+            _numBytes = checked((UIntPtr)(numElements * sizeOfEachElement));
+        }
+
+        /// <summary>
+        /// Specifies the size of the region in memory, as the number of
+        /// elements in an array.  Must be called before using the SafeBuffer.
+        /// </summary>
+        [CLSCompliant(false)]
+        public void Initialize<T>(uint numElements) where T : struct
+        {
+            Initialize(numElements, AlignedSizeOf<T>());
+        }
+
+        // Callers should ensure that they check whether the pointer ref param
+        // is null when AcquirePointer returns.  If it is not null, they must
+        // call ReleasePointer.  This method calls DangerousAddRef
+        // & exposes the pointer. Unlike Read, it does not alter the "current
+        // position" of the pointer.  Here's how to use it:
+        //
+        // byte* pointer = null;
+        // try {
+        //     safeBuffer.AcquirePointer(ref pointer);
+        //     // Use pointer here, with your own bounds checking
+        // }
+        // finally {
+        //     if (pointer != null)
+        //         safeBuffer.ReleasePointer();
+        // }
+        //
+        // Note: If you cast this byte* to a T*, you have to worry about
+        // whether your pointer is aligned.  Additionally, you must take
+        // responsibility for all bounds checking with this pointer.
+        /// <summary>
+        /// Obtain the pointer from a SafeBuffer for a block of code,
+        /// with the express responsibility for bounds checking and calling
+        /// ReleasePointer later to ensure the pointer can be freed later.
+        /// This method either completes successfully or throws an exception 
+        /// and returns with pointer set to null.
+        /// </summary>
+        /// <param name="pointer">A byte*, passed by reference, to receive
+        /// the pointer from within the SafeBuffer.  You must set
+        /// pointer to null before calling this method.</param>
+        [CLSCompliant(false)]
+        public void AcquirePointer(ref byte* pointer)
+        {
+            if (_numBytes == Uninitialized)
+                throw NotInitialized();
+
+            pointer = null;
+
+            bool junk = false;
+            DangerousAddRef(ref junk);
+            pointer = (byte*)handle;
+        }
+
+        public void ReleasePointer()
+        {
+            if (_numBytes == Uninitialized)
+                throw NotInitialized();
+
+            DangerousRelease();
+        }
+
+        /// <summary>
+        /// Read a value type from memory at the given offset.  This is
+        /// equivalent to:  return *(T*)(bytePtr + byteOffset);
+        /// </summary>
+        /// <typeparam name="T">The value type to read</typeparam>
+        /// <param name="byteOffset">Where to start reading from memory.  You
+        /// may have to consider alignment.</param>
+        /// <returns>An instance of T read from memory.</returns>
+        [CLSCompliant(false)]
+        public T Read<T>(ulong byteOffset) where T : struct
+        {
+            if (_numBytes == Uninitialized)
+                throw NotInitialized();
+
+            uint sizeofT = SizeOf<T>();
+            byte* ptr = (byte*)handle + byteOffset;
+            SpaceCheck(ptr, sizeofT);
+
+            // return *(T*) (_ptr + byteOffset);
+            T value = default(T);
+            bool mustCallRelease = false;
+            try
+            {
+                DangerousAddRef(ref mustCallRelease);
+
+                fixed (byte* pStructure = &Unsafe.As<T, byte>(ref value))
+                    Buffer.Memmove(pStructure, ptr, sizeofT);
+            }
+            finally
+            {
+                if (mustCallRelease)
+                    DangerousRelease();
+            }
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        public void ReadArray<T>(ulong byteOffset, T[] array, int index, int count)
+            where T : struct
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array), SR.ArgumentNull_Buffer);
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (array.Length - index < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+            if (_numBytes == Uninitialized)
+                throw NotInitialized();
+
+            uint sizeofT = SizeOf<T>();
+            uint alignedSizeofT = AlignedSizeOf<T>();
+            byte* ptr = (byte*)handle + byteOffset;
+            SpaceCheck(ptr, checked((ulong)(alignedSizeofT * count)));
+
+            bool mustCallRelease = false;
+            try
+            {
+                DangerousAddRef(ref mustCallRelease);
+
+                if (count > 0)
+                {
+                    unsafe
+                    {
+                        fixed (byte* pStructure = &Unsafe.As<T, byte>(ref array[index]))
+                        {
+                            for (int i = 0; i < count; i++)
+                                Buffer.Memmove(pStructure + sizeofT * i, ptr + alignedSizeofT * i, sizeofT);
+                        }
+                    }
+                }
+            }
+            finally
+            {
+                if (mustCallRelease)
+                    DangerousRelease();
+            }
+        }
+
+        /// <summary>
+        /// Write a value type to memory at the given offset.  This is
+        /// equivalent to:  *(T*)(bytePtr + byteOffset) = value;
+        /// </summary>
+        /// <typeparam name="T">The type of the value type to write to memory.</typeparam>
+        /// <param name="byteOffset">The location in memory to write to.  You
+        /// may have to consider alignment.</param>
+        /// <param name="value">The value type to write to memory.</param>
+        [CLSCompliant(false)]
+        public void Write<T>(ulong byteOffset, T value) where T : struct
+        {
+            if (_numBytes == Uninitialized)
+                throw NotInitialized();
+
+            uint sizeofT = SizeOf<T>();
+            byte* ptr = (byte*)handle + byteOffset;
+            SpaceCheck(ptr, sizeofT);
+
+            // *((T*) (_ptr + byteOffset)) = value;
+            bool mustCallRelease = false;
+            try
+            {
+                DangerousAddRef(ref mustCallRelease);
+
+                fixed (byte* pStructure = &Unsafe.As<T, byte>(ref value))
+                    Buffer.Memmove(ptr, pStructure, sizeofT);
+            }
+            finally
+            {
+                if (mustCallRelease)
+                    DangerousRelease();
+            }
+        }
+
+        [CLSCompliant(false)]
+        public void WriteArray<T>(ulong byteOffset, T[] array, int index, int count)
+            where T : struct
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array), SR.ArgumentNull_Buffer);
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (array.Length - index < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+            if (_numBytes == Uninitialized)
+                throw NotInitialized();
+
+            uint sizeofT = SizeOf<T>();
+            uint alignedSizeofT = AlignedSizeOf<T>();
+            byte* ptr = (byte*)handle + byteOffset;
+            SpaceCheck(ptr, checked((ulong)(alignedSizeofT * count)));
+
+            bool mustCallRelease = false;
+            try
+            {
+                DangerousAddRef(ref mustCallRelease);
+
+                if (count > 0)
+                {
+                    unsafe
+                    {
+                        fixed (byte* pStructure = &Unsafe.As<T, byte>(ref array[index]))
+                        {
+                            for (int i = 0; i < count; i++)
+                                Buffer.Memmove(ptr + alignedSizeofT * i, pStructure + sizeofT * i, sizeofT);
+                        }
+                    }
+                }
+            }
+            finally
+            {
+                if (mustCallRelease)
+                    DangerousRelease();
+            }
+        }
+
+        /// <summary>
+        /// Returns the number of bytes in the memory region.
+        /// </summary>
+        [CLSCompliant(false)]
+        public ulong ByteLength
+        {
+            get
+            {
+                if (_numBytes == Uninitialized)
+                    throw NotInitialized();
+
+                return (ulong)_numBytes;
+            }
+        }
+
+        /* No indexer.  The perf would be misleadingly bad.  People should use
+         * AcquirePointer and ReleasePointer instead.  */
+
+        private void SpaceCheck(byte* ptr, ulong sizeInBytes)
+        {
+            if ((ulong)_numBytes < sizeInBytes)
+                NotEnoughRoom();
+            if ((ulong)(ptr - (byte*)handle) > ((ulong)_numBytes) - sizeInBytes)
+                NotEnoughRoom();
+        }
+
+        private static void NotEnoughRoom()
+        {
+            throw new ArgumentException(SR.Arg_BufferTooSmall);
+        }
+
+        private static InvalidOperationException NotInitialized()
+        {
+            return new InvalidOperationException(SR.InvalidOperation_MustCallInitialize);
+        }
+
+        /// <summary>
+        /// Returns the size that SafeBuffer (and hence, UnmanagedMemoryAccessor) reserves in the unmanaged buffer for each element of an array of T. This is not the same
+        /// value that sizeof(T) returns! Since the primary use case is to parse memory mapped files, we cannot change this algorithm as this defines a de-facto serialization format.
+        /// Throws if T contains GC references.
+        /// </summary>
+        internal static uint AlignedSizeOf<T>() where T : struct
+        {
+            uint size = SizeOf<T>();
+            if (size == 1 || size == 2)
+            {
+                return size;
+            }
+
+            return (uint)(((size + 3) & (~3)));
+        }
+
+        /// <summary>
+        /// Returns same value as sizeof(T) but throws if T contains GC references.
+        /// </summary>
+        internal static uint SizeOf<T>() where T : struct
+        {
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+                throw new ArgumentException(SR.Argument_NeedStructWithNoRefs);
+
+            return (uint)Unsafe.SizeOf<T>();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/StructLayoutAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/StructLayoutAttribute.cs
new file mode 100644
index 0000000000..c4cce9956e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/StructLayoutAttribute.cs
@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct, Inherited = false)]
+    public sealed class StructLayoutAttribute : Attribute
+    {
+        public StructLayoutAttribute(LayoutKind layoutKind)
+        {
+            Value = layoutKind;
+        }
+
+        public StructLayoutAttribute(short layoutKind)
+        {
+            Value = (LayoutKind)layoutKind;
+        }
+
+        public LayoutKind Value { get; }
+
+        public int Pack;
+        public int Size;
+        public CharSet CharSet;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/UnmanagedFunctionPointerAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/UnmanagedFunctionPointerAttribute.cs
new file mode 100644
index 0000000000..c4f96903ee
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/UnmanagedFunctionPointerAttribute.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Delegate, AllowMultiple = false, Inherited = false)]
+    public sealed class UnmanagedFunctionPointerAttribute : Attribute
+    {
+        public UnmanagedFunctionPointerAttribute()
+        {
+            CallingConvention = CallingConvention.Winapi;
+        }
+
+        public UnmanagedFunctionPointerAttribute(CallingConvention callingConvention)
+        {
+            CallingConvention = callingConvention;
+        }
+
+        public CallingConvention CallingConvention { get; }
+
+        public bool BestFitMapping;
+        public bool SetLastError;
+        public bool ThrowOnUnmappableChar;
+        public CharSet CharSet;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/UnmanagedType.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/UnmanagedType.cs
new file mode 100644
index 0000000000..4deca7fe0c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/UnmanagedType.cs
@@ -0,0 +1,48 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    public enum UnmanagedType
+    {
+        Bool = 0x2,         // 4 byte boolean value (true != 0, false == 0)
+        I1 = 0x3,           // 1 byte signed value
+        U1 = 0x4,           // 1 byte unsigned value
+        I2 = 0x5,           // 2 byte signed value
+        U2 = 0x6,           // 2 byte unsigned value
+        I4 = 0x7,           // 4 byte signed value
+        U4 = 0x8,           // 4 byte unsigned value
+        I8 = 0x9,           // 8 byte signed value
+        U8 = 0xa,           // 8 byte unsigned value
+        R4 = 0xb,           // 4 byte floating point
+        R8 = 0xc,           // 8 byte floating point
+        Currency = 0xf,     // A currency
+        BStr = 0x13,        // OLE Unicode BSTR
+        LPStr = 0x14,       // Ptr to SBCS string
+        LPWStr = 0x15,      // Ptr to Unicode string
+        LPTStr = 0x16,      // Ptr to OS preferred (SBCS/Unicode) string
+        ByValTStr = 0x17,   // OS preferred (SBCS/Unicode) inline string (only valid in structs)
+        IUnknown = 0x19,    // COM IUnknown pointer.
+        IDispatch = 0x1a,   // COM IDispatch pointer
+        Struct = 0x1b,      // Structure
+        Interface = 0x1c,   // COM interface
+        SafeArray = 0x1d,   // OLE SafeArray
+        ByValArray = 0x1e,  // Array of fixed size (only valid in structs)
+        SysInt = 0x1f,      // Hardware natural sized signed integer
+        SysUInt = 0x20,
+        VBByRefStr = 0x22,
+        AnsiBStr = 0x23,    // OLE BSTR containing SBCS characters
+        TBStr = 0x24,       // Ptr to OS preferred (SBCS/Unicode) BSTR
+        VariantBool = 0x25, // OLE defined BOOLEAN (2 bytes, true == -1, false == 0)
+        FunctionPtr = 0x26, // Function pointer
+        AsAny = 0x28,       // Paired with Object type and does runtime marshalling determination
+        LPArray = 0x2a,     // C style array
+        LPStruct = 0x2b,    // Pointer to a structure
+        CustomMarshaler = 0x2c,
+        Error = 0x2d,
+        IInspectable = 0x2e,
+        HString = 0x2f,     // Windows Runtime HSTRING
+        LPUTF8Str = 0x30,   // UTF8 string
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/VarEnum.cs b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/VarEnum.cs
new file mode 100644
index 0000000000..495aeca6d1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/InteropServices/VarEnum.cs
@@ -0,0 +1,54 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    public enum VarEnum
+    {
+        VT_EMPTY = 0,
+        VT_NULL = 1,
+        VT_I2 = 2,
+        VT_I4 = 3,
+        VT_R4 = 4,
+        VT_R8 = 5,
+        VT_CY = 6,
+        VT_DATE = 7,
+        VT_BSTR = 8,
+        VT_DISPATCH = 9,
+        VT_ERROR = 10,
+        VT_BOOL = 11,
+        VT_VARIANT = 12,
+        VT_UNKNOWN = 13,
+        VT_DECIMAL = 14,
+        VT_I1 = 16,
+        VT_UI1 = 17,
+        VT_UI2 = 18,
+        VT_UI4 = 19,
+        VT_I8 = 20,
+        VT_UI8 = 21,
+        VT_INT = 22,
+        VT_UINT = 23,
+        VT_VOID = 24,
+        VT_HRESULT = 25,
+        VT_PTR = 26,
+        VT_SAFEARRAY = 27,
+        VT_CARRAY = 28,
+        VT_USERDEFINED = 29,
+        VT_LPSTR = 30,
+        VT_LPWSTR = 31,
+        VT_RECORD = 36,
+        VT_FILETIME = 64,
+        VT_BLOB = 65,
+        VT_STREAM = 66,
+        VT_STORAGE = 67,
+        VT_STREAMED_OBJECT = 68,
+        VT_STORED_OBJECT = 69,
+        VT_BLOB_OBJECT = 70,
+        VT_CF = 71,
+        VT_CLSID = 72,
+        VT_VECTOR = 0x1000,
+        VT_ARRAY = 0x2000,
+        VT_BYREF = 0x4000
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Serialization/IDeserializationCallback.cs b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/IDeserializationCallback.cs
new file mode 100644
index 0000000000..a1c1671a8b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/IDeserializationCallback.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.Serialization
+{
+    public interface IDeserializationCallback
+    {
+        void OnDeserialization(object sender);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Serialization/IFormatterConverter.cs b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/IFormatterConverter.cs
new file mode 100644
index 0000000000..c173144854
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/IFormatterConverter.cs
@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.Serialization
+{
+    [CLSCompliant(false)]
+    public interface IFormatterConverter
+    {
+        object Convert(object value, Type type);
+        object Convert(object value, TypeCode typeCode);
+        bool ToBoolean(object value);
+        char ToChar(object value);
+        sbyte ToSByte(object value);
+        byte ToByte(object value);
+        short ToInt16(object value);
+        ushort ToUInt16(object value);
+        int ToInt32(object value);
+        uint ToUInt32(object value);
+        long ToInt64(object value);
+        ulong ToUInt64(object value);
+        float ToSingle(object value);
+        double ToDouble(object value);
+        decimal ToDecimal(object value);
+        DateTime ToDateTime(object value);
+        string ToString(object value);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Serialization/IObjectReference.cs b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/IObjectReference.cs
new file mode 100644
index 0000000000..d41bc50dde
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/IObjectReference.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.Serialization
+{
+    public interface IObjectReference
+    {
+        object GetRealObject(StreamingContext context);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Serialization/ISafeSerializationData.cs b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/ISafeSerializationData.cs
new file mode 100644
index 0000000000..5089d134c3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/ISafeSerializationData.cs
@@ -0,0 +1,207 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.Serialization
+{
+    //
+    // #SafeSerialization
+    // 
+    // Types which are serializable via the ISerializable interface have a problem when it comes to allowing
+    // transparent subtypes which can allow themselves to serialize since the GetObjectData method is
+    // SecurityCritical.
+    // 
+    // For instance, System.Exception implements ISerializable, however it is also desirable to have
+    // transparent exceptions with their own fields that need to be serialized.  (For instance, in transparent
+    // assemblies such as the DLR and F#, or even in partial trust application code).  Since overriding
+    // GetObjectData requires that the overriding method be security critical, this won't work directly.
+    //
+    // SafeSerializationManager solves this problem by allowing any partial trust code to contribute
+    // individual chunks of serializable data to be included in the serialized version of the derived class. 
+    // These chunks are then deserialized back out of the serialized type and notified that they should
+    // populate the fields of the deserialized object when serialization is complete.  This allows partial
+    // trust or transparent code to participate in serialization of an ISerializable type without having to
+    // override GetObjectData or implement the ISerializable constructor.
+    //
+    // On the serialization side, SafeSerializationManager has an event SerializeObjectState which it will
+    // fire in response to serialization in order to gather the units of serializable data that should be
+    // stored with the rest of the object during serialization.  Methods which respond to these events
+    // create serializable objects which implement the ISafeSerializationData interface and add them to the
+    // collection of other serialized data by calling AddSerializedState on the SafeSerializationEventArgs
+    // passed into the event.
+    // 
+    // By using an event rather than a virtual method on the base ISerializable object, we allow multiple
+    // potentially untrusted subclasses to participate in serialization, without each one having to ensure
+    // that it calls up to the base type in order for the whole system to work.  (For instance Exception :
+    // TrustedException : UntrustedException, in this scenario UntrustedException would be able to override
+    // the virtual method an prevent TrustedException from ever seeing the method call, either accidentally
+    // or maliciously).
+    // 
+    // Further, by only allowing additions of new chunks of serialization state rather than exposing the
+    // whole underlying list, we avoid exposing potentially sensitive serialized state to any of the
+    // potentially untrusted subclasses.
+    // 
+    // At deserialization time, SafeSerializationManager performs the reverse operation.  It deserializes the
+    // chunks of serialized state, and then notifies them that the object they belong to is deserialized by
+    // calling their CompleteSerialization method. In repsonse to this call, the state objects populate the
+    // fields of the object being deserialized with the state that they held.
+    // 
+    // From a security perspective, the chunks of serialized state can only contain data that the specific
+    // subclass itself had access to read (otherwise it wouldn't be able to populate the type with that
+    // data), as opposed to having access to far more data in the SerializationInfo that GetObjectData uses.
+    // Similarly, at deserialization time, the serialized state can only modify fields that the type itself
+    // has access to (again, as opposed to the full SerializationInfo which could be modified).
+    // 
+    // Individual types which wish to participate in safe serialization do so by containing an instance of a
+    // SafeSerializationManager and exposing its serialization event.  During GetObjectData, the
+    // SafeSerializationManager is serialized just like any other field of the containing type.  However, at
+    // the end of serialization it is called back one last time to CompleteSerialization.
+    // 
+    // In CompleteSerialization, if the SafeSerializationManager detects that it has extra chunks of
+    // data to handle, it substitutes the root type being serialized (formerly the real type hosting the
+    // SafeSerializationManager) with itself.  This allows it to gain more control over the deserialization
+    // process.  It also saves away an extra bit of state in the serialization info indicating the real type
+    // of object that should be recreated during deserialization.
+    //
+    // At this point the serialized state looks like this:
+    //   Data:
+    //     realSerializedData1
+    //       ...
+    //     realSerializedDataN
+    //     safeSerializationData     -> this is the serialization data member of the parent type
+    //       _serializedState        -> list of saved serialized states from subclasses responding to the safe
+    //                                  serialization event
+    //     RealTypeSerializationName -> type which is using safe serialization
+    //   Type:
+    //     SafeSerializationManager
+    //
+    //  That is, the serialized data claims to be of type SafeSerializationManager, however contains only the
+    //  data from the real object being serialized along with one bit of safe serialization metadata.
+    //  
+    //  At deserialization time, since the serialized data claims to be of type SafeSerializationManager, the
+    //  root object being created is an instance of the SafeSerializationManager class.  However, it detects
+    //  that this isn't a real SafeSerializationManager (by looking for the real type field in the metadata),
+    //  and simply saves away the SerializationInfo and the real type being deserialized.
+    //  
+    //  Since SafeSerializationManager implements IObjectReference, the next step of deserialization is the
+    //  GetRealObject callback.  This callback is the one responsible for getting the
+    //  SafeSerializationManager out of the way and instead creating an instance of the actual type which was
+    //  serialized.
+    //  
+    //  It does this by first creating an instance of the real type being deserialzed (saved away in the
+    //  deserialzation constructor), but not running any of its constructors.  Instead, it walks the
+    //  inheritance hierarchy (moving toward the most derived type) looking for the last full trust type to
+    //  implement the standard ISerializable constructor before any type does not implement the constructor. 
+    //  It is this last type's deserialization constructor which is then invoked, passing in the saved
+    //  SerializationInfo.  Once the constructors are run, we return this object as the real deserialized
+    //  object.
+    //  
+    //  The reason that we do this walk is so that ISerializable types can protect themselves from malicious
+    //  input during deserialization by making their deserialization constructors unavailable to partial
+    //  trust code.  By not requiring every type have a copy of this constructor, partial trust code can
+    //  participate in safe serialization and not be required to have access to the parent's constructor. 
+    //  
+    //  It should be noted however, that this heuristic means that if a full trust type does derive from
+    //  a transparent or partial trust type using this safe serialization mechanism, that full trust type
+    //  will not have its constructor called. Further, the protection of not invoking partial trust
+    //  deserialization constructors only comes into play if SafeSerializationManager is in control of
+    //  deserialization, which means there must be at least one (even empty) safe serialization event
+    //  handler registered.
+    //  
+    //  Another interesting note is that at this point there are now two SafeSerializationManagers alive for
+    //  this deserialization.  The first object is the one which is controlling the deserialization and was
+    //  created as the root object of the deserialization.  The second one is the object which contains the
+    //  serialized data chunks and is a data member of the real object being deserialized.  For this reason,
+    //  the data objects cannot be notified that the deserialization is complete during GetRealObject since
+    //  the ISafeSerializationData objects are not members of the active SafeSerializationManager instance.
+    //  
+    //  The next step is the OnDeserialized callback, which comes to SafeSerializableObject since it was
+    //  pretending to be the root object of the deserialization.  It responds to this callback by calling
+    //  any existing OnDeserialized callback on the real type that was deserialized.
+    //  
+    //  The real type needs to call its data member SafeSerializationData object's CompleteDeserialization
+    //  method in response to the OnDeserialized call.  This CompleteDeserialization call will then iterate
+    //  through the ISafeSerializationData objects calling each of their CompleteDeserialization methods so
+    //  that they can plug the nearly-complete object with their saved data.
+    //  
+    //  The reason for having a new ISafeSerializationData interface which is basically identical to
+    //  IDeserializationCallback is that IDeserializationCallback will be called on the stored data chunks
+    //  by the serialization code when they are deserialized, and that's not a desirable behavior. 
+    //  Essentially, we need to change the meaning of the object parameter to mean "parent object which
+    //  participated in safe serialization", rather than "this object".
+    //  
+    //  Implementing safe serialization on an ISerialiable type is relatively straight forward.  (For an
+    //  example, see System.Exception):
+    //  
+    //    1. Include a data member of type SafeSerializationManager:
+    //  
+    //       private SafeSerializationManager _safeSerializationManager;
+    //     
+    //    2. Add a protected SerializeObjectState event, which passes through to the SafeSerializationManager:
+    //  
+    //       protected event EventHandler<SafeSerializationEventArgs> SerializeObjectState
+    //       {
+    //           add { _safeSerializationManager.SerializeObjectState += value; }
+    //           remove { _safeSerializationManager.SerializeObjectState -= value; }
+    //       }
+    //
+    //    3. Serialize the safe serialization object in GetObjectData, and call its CompleteSerialization method:
+    //  
+    //       {
+    //           info.AddValue("_safeSerializationManager", _safeSerializationManager, typeof(SafeSerializationManager));
+    //           _safeSerializationManager.CompleteSerialization(this, info, context);
+    //       }
+    //
+    //    4. Add an OnDeserialized handler if one doesn't already exist, and call CompleteDeserialization in it:
+    //  
+    //       [OnDeserialized]
+    //       private void OnDeserialized(StreamingContext context)
+    //       {
+    //           _safeSerializationManager.CompleteDeserialization(this);
+    //       }
+    //
+    // On the client side, using safe serialization is also pretty easy.  For example:
+    // 
+    //   [Serializable]
+    //   public class TransparentException : Exception
+    //   {
+    //       [Serializable]
+    //       private struct TransparentExceptionState : ISafeSerializationData
+    //       {
+    //           public string _extraData;
+    //
+    //           void ISafeSerializationData.CompleteDeserialization(object obj)
+    //           {
+    //               TransparentException exception = obj as TransparentException;
+    //               exception._state = this;
+    //           }
+    //       }
+    //
+    //       [NonSerialized]
+    //       private TransparentExceptionState _state = new TransparentExceptionState();
+    //
+    //       public TransparentException()
+    //       {
+    //           SerializeObjectState += delegate(object exception, SafeSerializationEventArgs eventArgs)
+    //           {
+    //               eventArgs.AddSerializedState(_state);
+    //           };
+    //       }
+    //
+    //       public string ExtraData
+    //       {
+    //           get { return _state._extraData; }
+    //           set { _state._extraData = value; }
+    //       }
+    //   }
+    // 
+
+    // Interface to be supported by objects which are stored in safe serialization stores
+    public interface ISafeSerializationData
+    {
+        // CompleteDeserialization is called when the object to which the extra serialized data was attached
+        // has completed its deserialization, and now needs to be populated with the extra data stored in
+        // this object.
+        void CompleteDeserialization(object deserialized);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Serialization/ISerializable.cs b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/ISerializable.cs
new file mode 100644
index 0000000000..383b3f07af
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/ISerializable.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.Serialization
+{
+    public interface ISerializable
+    {
+        void GetObjectData(SerializationInfo info, StreamingContext context);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OnDeserializedAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OnDeserializedAttribute.cs
new file mode 100644
index 0000000000..408a55ccf9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OnDeserializedAttribute.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.Serialization
+{
+    [AttributeUsage(AttributeTargets.Method, Inherited = false)]
+    public sealed class OnDeserializedAttribute : Attribute
+    {
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OnDeserializingAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OnDeserializingAttribute.cs
new file mode 100644
index 0000000000..162857e8d3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OnDeserializingAttribute.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.Serialization
+{
+    [AttributeUsage(AttributeTargets.Method, Inherited = false)]
+    public sealed class OnDeserializingAttribute : Attribute
+    {
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OnSerializedAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OnSerializedAttribute.cs
new file mode 100644
index 0000000000..020dd0257c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OnSerializedAttribute.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.Serialization
+{
+    [AttributeUsage(AttributeTargets.Method, Inherited = false)]
+    public sealed class OnSerializedAttribute : Attribute
+    {
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OnSerializingAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OnSerializingAttribute.cs
new file mode 100644
index 0000000000..8dc8af3f23
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OnSerializingAttribute.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.Serialization
+{
+    [AttributeUsage(AttributeTargets.Method, Inherited = false)]
+    public sealed class OnSerializingAttribute : Attribute
+    {
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OptionalFieldAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OptionalFieldAttribute.cs
new file mode 100644
index 0000000000..84daa539be
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/OptionalFieldAttribute.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.Serialization
+{
+    [AttributeUsage(AttributeTargets.Field, Inherited = false)]
+    public sealed class OptionalFieldAttribute : Attribute
+    {
+        private int _versionAdded = 1;
+
+        public int VersionAdded
+        {
+            get { return _versionAdded; }
+            set
+            {
+                if (value < 1)
+                {
+                    throw new ArgumentException(SR.Serialization_OptionalFieldVersionValue);
+                }
+                _versionAdded = value;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Serialization/SafeSerializationEventArgs.cs b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/SafeSerializationEventArgs.cs
new file mode 100644
index 0000000000..896b91fca0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/SafeSerializationEventArgs.cs
@@ -0,0 +1,31 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+
+namespace System.Runtime.Serialization
+{
+    // SafeSerializationEventArgs are provided to the delegates which do safe serialization.  Each delegate
+    // serializes its own state into an IDeserializationCallback instance which must, itself, be serializable.
+    // These indivdiual states are then added to the SafeSerializationEventArgs in order to be saved away when
+    // the original ISerializable type is serialized.
+    public sealed class SafeSerializationEventArgs : EventArgs
+    {
+        private readonly List<object> _serializedStates = new List<object>();
+
+        internal SafeSerializationEventArgs() { }
+
+        public void AddSerializedState(ISafeSerializationData serializedState)
+        {
+            if (serializedState == null)
+                throw new ArgumentNullException(nameof(serializedState));
+            if (!serializedState.GetType().IsSerializable)
+                throw new ArgumentException(SR.Format(SR.Serialization_NonSerType, serializedState.GetType(), serializedState.GetType().Assembly.FullName));
+
+            _serializedStates.Add(serializedState);
+        }
+
+        public StreamingContext StreamingContext { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Serialization/SerializationException.cs b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/SerializationException.cs
new file mode 100644
index 0000000000..1c9c21eabb
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/SerializationException.cs
@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Runtime.Serialization
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class SerializationException : SystemException
+    {
+        private static String s_nullMessage = SR.SerializationException;
+
+        // Creates a new SerializationException with its message 
+        // string set to a default message.
+        public SerializationException()
+            : base(s_nullMessage)
+        {
+            HResult = HResults.COR_E_SERIALIZATION;
+        }
+
+        public SerializationException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_SERIALIZATION;
+        }
+
+        public SerializationException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_SERIALIZATION;
+        }
+
+        protected SerializationException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Serialization/SerializationInfoEnumerator.cs b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/SerializationInfoEnumerator.cs
new file mode 100644
index 0000000000..6399510736
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/SerializationInfoEnumerator.cs
@@ -0,0 +1,127 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.Diagnostics;
+
+namespace System.Runtime.Serialization
+{
+    public struct SerializationEntry
+    {
+        private string _name;
+        private object _value;
+        private Type _type;
+
+        internal SerializationEntry(string entryName, object entryValue, Type entryType)
+        {
+            _name = entryName;
+            _value = entryValue;
+            _type = entryType;
+        }
+
+        public object Value => _value;
+        public string Name => _name;
+        public Type ObjectType => _type;
+    }
+
+    public sealed class SerializationInfoEnumerator : IEnumerator
+    {
+        private readonly string[] _members;
+        private readonly object[] _data;
+        private readonly Type[] _types;
+        private readonly int _numItems;
+        private int _currItem;
+        private bool _current;
+
+        internal SerializationInfoEnumerator(string[] members, object[] info, Type[] types, int numItems)
+        {
+            Debug.Assert(members != null, "[SerializationInfoEnumerator.ctor]members!=null");
+            Debug.Assert(info != null, "[SerializationInfoEnumerator.ctor]info!=null");
+            Debug.Assert(types != null, "[SerializationInfoEnumerator.ctor]types!=null");
+            Debug.Assert(numItems >= 0, "[SerializationInfoEnumerator.ctor]numItems>=0");
+            Debug.Assert(members.Length >= numItems, "[SerializationInfoEnumerator.ctor]members.Length>=numItems");
+            Debug.Assert(info.Length >= numItems, "[SerializationInfoEnumerator.ctor]info.Length>=numItems");
+            Debug.Assert(types.Length >= numItems, "[SerializationInfoEnumerator.ctor]types.Length>=numItems");
+
+            _members = members;
+            _data = info;
+            _types = types;
+
+            //The MoveNext semantic is much easier if we enforce that [0..m_numItems] are valid entries
+            //in the enumerator, hence we subtract 1.
+            _numItems = numItems - 1;
+            _currItem = -1;
+            _current = false;
+        }
+
+        public bool MoveNext()
+        {
+            if (_currItem < _numItems)
+            {
+                _currItem++;
+                _current = true;
+            }
+            else
+            {
+                _current = false;
+            }
+
+            return _current;
+        }
+
+        object IEnumerator.Current => Current;
+
+        public SerializationEntry Current
+        {
+            get
+            {
+                if (_current == false)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+                }
+                return new SerializationEntry(_members[_currItem], _data[_currItem], _types[_currItem]);
+            }
+        }
+
+        public void Reset()
+        {
+            _currItem = -1;
+            _current = false;
+        }
+
+        public string Name
+        {
+            get
+            {
+                if (_current == false)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+                }
+                return _members[_currItem];
+            }
+        }
+        public object Value
+        {
+            get
+            {
+                if (_current == false)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+                }
+                return _data[_currItem];
+            }
+        }
+        public Type ObjectType
+        {
+            get
+            {
+                if (_current == false)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+                }
+                return _types[_currItem];
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Serialization/StreamingContext.cs b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/StreamingContext.cs
new file mode 100644
index 0000000000..cdcb1c335b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Serialization/StreamingContext.cs
@@ -0,0 +1,52 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.Serialization
+{
+    public readonly struct StreamingContext
+    {
+        private readonly object _additionalContext;
+        private readonly StreamingContextStates _state;
+
+        public StreamingContext(StreamingContextStates state) : this(state, null)
+        {
+        }
+
+        public StreamingContext(StreamingContextStates state, object additional)
+        {
+            _state = state;
+            _additionalContext = additional;
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (!(obj is StreamingContext))
+            {
+                return false;
+            }
+            StreamingContext ctx = (StreamingContext)obj;
+            return ctx._additionalContext == _additionalContext && ctx._state == _state;
+        }
+
+        public override int GetHashCode() => (int)_state;
+
+        public StreamingContextStates State => _state;
+
+        public object Context => _additionalContext;
+    }
+
+    [Flags]
+    public enum StreamingContextStates
+    {
+        CrossProcess = 0x01,
+        CrossMachine = 0x02,
+        File = 0x04,
+        Persistence = 0x08,
+        Remoting = 0x10,
+        Other = 0x20,
+        Clone = 0x40,
+        CrossAppDomain = 0x80,
+        All = 0xFF,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Versioning/NonVersionableAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/Versioning/NonVersionableAttribute.cs
new file mode 100644
index 0000000000..e4809953bc
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Versioning/NonVersionableAttribute.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** The [NonVersionable] attribute is applied to indicate that the implementation 
+** of a particular member or layout of a struct cannot be changed for given platform in incompatible way.
+** This allows cross-module inlining of methods and data structures whose implementation 
+** is never changed in ReadyToRun native images. Any changes to such members or types would be 
+** breaking changes for ReadyToRun.
+**
+** Applying this type also has the side effect that the inlining tables in R2R images will not
+** report that inlining of NonVersionable attributed methods occured. These inlining tables are used
+** by profilers to figure out the set of methods that need to be rejited when one method is instrumented,
+** so in effect NonVersionable methods are also non-instrumentable. Generally this is OK for
+** extremely trivial low level methods where NonVersionable gets used, but if there is any plan to 
+** significantly extend its usage or allow 3rd parties to use it please discuss with the diagnostics team.
+===========================================================*/
+
+using System;
+using System.Diagnostics;
+
+namespace System.Runtime.Versioning
+{
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Method | AttributeTargets.Constructor,
+                    AllowMultiple = false, Inherited = false)]
+    internal sealed class NonVersionableAttribute : Attribute
+    {
+        public NonVersionableAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Runtime/Versioning/TargetFrameworkAttribute.cs b/src/System.Private.CoreLib/shared/System/Runtime/Versioning/TargetFrameworkAttribute.cs
new file mode 100644
index 0000000000..a819066382
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Runtime/Versioning/TargetFrameworkAttribute.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Identifies which SKU and version of the .NET
+**   Framework that a particular library was compiled against.
+**   Emitted by VS, and can help catch deployment problems.
+**
+===========================================================*/
+
+using System;
+
+namespace System.Runtime.Versioning
+{
+    [AttributeUsageAttribute(AttributeTargets.Assembly, AllowMultiple = false, Inherited = false)]
+    public sealed class TargetFrameworkAttribute : Attribute
+    {
+        private String _frameworkName;  // A target framework moniker
+        private String _frameworkDisplayName;
+
+        // The frameworkName parameter is intended to be the string form of a FrameworkName instance.
+        public TargetFrameworkAttribute(String frameworkName)
+        {
+            if (frameworkName == null)
+                throw new ArgumentNullException(nameof(frameworkName));
+            _frameworkName = frameworkName;
+        }
+
+        // The target framework moniker that this assembly was compiled against.
+        // Use the FrameworkName class to interpret target framework monikers.
+        public String FrameworkName
+        {
+            get { return _frameworkName; }
+        }
+
+        public String FrameworkDisplayName
+        {
+            get { return _frameworkDisplayName; }
+            set { _frameworkDisplayName = value; }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/SByte.cs b/src/System.Private.CoreLib/shared/System/SByte.cs
new file mode 100644
index 0000000000..c7cee2adc2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/SByte.cs
@@ -0,0 +1,332 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    [Serializable]
+    [CLSCompliant(false)]    [StructLayout(LayoutKind.Sequential)]
+    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct SByte : IComparable, IConvertible, IFormattable, IComparable<SByte>, IEquatable<SByte>, ISpanFormattable
+    {
+        private sbyte m_value; // Do not rename (binary serialization)
+
+        // The maximum value that a Byte may represent: 127.
+        public const sbyte MaxValue = (sbyte)0x7F;
+
+        // The minimum value that a Byte may represent: -128.
+        public const sbyte MinValue = unchecked((sbyte)0x80);
+
+
+        // Compares this object to another object, returning an integer that
+        // indicates the relationship. 
+        // Returns a value less than zero if this  object
+        // null is considered to be less than any instance.
+        // If object is not of type SByte, this method throws an ArgumentException.
+        // 
+        public int CompareTo(Object obj)
+        {
+            if (obj == null)
+            {
+                return 1;
+            }
+            if (!(obj is SByte))
+            {
+                throw new ArgumentException(SR.Arg_MustBeSByte);
+            }
+            return m_value - ((SByte)obj).m_value;
+        }
+
+        public int CompareTo(SByte value)
+        {
+            return m_value - value;
+        }
+
+        // Determines whether two Byte objects are equal.
+        public override bool Equals(Object obj)
+        {
+            if (!(obj is SByte))
+            {
+                return false;
+            }
+            return m_value == ((SByte)obj).m_value;
+        }
+
+        [NonVersionable]
+        public bool Equals(SByte obj)
+        {
+            return m_value == obj;
+        }
+
+        // Gets a hash code for this instance.
+        public override int GetHashCode()
+        {
+            return ((int)m_value ^ (int)m_value << 8);
+        }
+
+
+        // Provides a string representation of a byte.
+        public override String ToString()
+        {
+            return Number.FormatInt32(m_value, null, null);
+        }
+
+        public String ToString(IFormatProvider provider)
+        {
+            return Number.FormatInt32(m_value, null, provider);
+        }
+
+        public String ToString(String format)
+        {
+            return ToString(format, null);
+        }
+
+        public String ToString(String format, IFormatProvider provider)
+        {
+            if (m_value < 0 && format != null && format.Length > 0 && (format[0] == 'X' || format[0] == 'x'))
+            {
+                uint temp = (uint)(m_value & 0x000000FF);
+                return Number.FormatUInt32(temp, format, provider);
+            }
+            return Number.FormatInt32(m_value, format, provider);
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider provider = null)
+        {
+            if (m_value < 0 && format.Length > 0 && (format[0] == 'X' || format[0] == 'x'))
+            {
+                uint temp = (uint)(m_value & 0x000000FF);
+                return Number.TryFormatUInt32(temp, format, provider, destination, out charsWritten);
+            }
+            return Number.TryFormatInt32(m_value, format, provider, destination, out charsWritten);
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte Parse(String s)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo);
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte Parse(String s, NumberStyles style)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, style, NumberFormatInfo.CurrentInfo);
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte Parse(String s, IFormatProvider provider)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.GetInstance(provider));
+        }
+
+        // Parses a signed byte from a String in the given style.  If
+        // a NumberFormatInfo isn't specified, the current culture's 
+        // NumberFormatInfo is assumed.
+        // 
+        [CLSCompliant(false)]
+        public static sbyte Parse(String s, NumberStyles style, IFormatProvider provider)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        [CLSCompliant(false)]
+        public static sbyte Parse(ReadOnlySpan<char> s, NumberStyles style = NumberStyles.Integer, IFormatProvider provider = null)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return Parse(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        private static sbyte Parse(String s, NumberStyles style, NumberFormatInfo info)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, style, info);
+        }
+
+        private static sbyte Parse(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info)
+        {
+            int i = 0;
+            try
+            {
+                i = Number.ParseInt32(s, style, info);
+            }
+            catch (OverflowException e)
+            {
+                throw new OverflowException(SR.Overflow_SByte, e);
+            }
+
+            if ((style & NumberStyles.AllowHexSpecifier) != 0)
+            { // We are parsing a hexadecimal number
+                if ((i < 0) || i > Byte.MaxValue)
+                {
+                    throw new OverflowException(SR.Overflow_SByte);
+                }
+                return (sbyte)i;
+            }
+
+            if (i < MinValue || i > MaxValue) throw new OverflowException(SR.Overflow_SByte);
+            return (sbyte)i;
+        }
+
+        [CLSCompliant(false)]
+        public static bool TryParse(String s, out SByte result)
+        {
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return TryParse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        [CLSCompliant(false)]
+        public static bool TryParse(ReadOnlySpan<char> s, out sbyte result)
+        {
+            return TryParse(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        [CLSCompliant(false)]
+        public static bool TryParse(String s, NumberStyles style, IFormatProvider provider, out SByte result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return TryParse((ReadOnlySpan<char>)s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        [CLSCompliant(false)]
+        public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider provider, out sbyte result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return TryParse(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        private static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info, out SByte result)
+        {
+            result = 0;
+            int i;
+            if (!Number.TryParseInt32(s, style, info, out i))
+            {
+                return false;
+            }
+
+            if ((style & NumberStyles.AllowHexSpecifier) != 0)
+            { // We are parsing a hexadecimal number
+                if ((i < 0) || i > Byte.MaxValue)
+                {
+                    return false;
+                }
+                result = (sbyte)i;
+                return true;
+            }
+
+            if (i < MinValue || i > MaxValue)
+            {
+                return false;
+            }
+            result = (sbyte)i;
+            return true;
+        }
+
+        //
+        // IConvertible implementation
+        // 
+
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.SByte;
+        }
+
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            return Convert.ToBoolean(m_value);
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            return Convert.ToChar(m_value);
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return m_value;
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return Convert.ToByte(m_value);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return Convert.ToInt16(m_value);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return Convert.ToUInt16(m_value);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return m_value;
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return Convert.ToUInt32(m_value);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return Convert.ToInt64(m_value);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return Convert.ToUInt64(m_value);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            return Convert.ToSingle(m_value);
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            return Convert.ToDouble(m_value);
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            return Convert.ToDecimal(m_value);
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "SByte", "DateTime"));
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Security/AllowPartiallyTrustedCallersAttribute.cs b/src/System.Private.CoreLib/shared/System/Security/AllowPartiallyTrustedCallersAttribute.cs
new file mode 100644
index 0000000000..84ad65c4c0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/AllowPartiallyTrustedCallersAttribute.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security
+{
+    // AllowPartiallyTrustedCallersAttribute:
+    //  Indicates that the Assembly is secure and can be used by untrusted
+    //  and semitrusted clients
+    //  For v.1, this is valid only on Assemblies, but could be expanded to 
+    //  include Module, Method, class
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = false, Inherited = false)]
+    public sealed class AllowPartiallyTrustedCallersAttribute : Attribute
+    {
+        public AllowPartiallyTrustedCallersAttribute() { }
+        public PartialTrustVisibilityLevel PartialTrustVisibilityLevel { get; set; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Security/CryptographicException.cs b/src/System.Private.CoreLib/shared/System/Security/CryptographicException.cs
new file mode 100644
index 0000000000..78ee290693
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/CryptographicException.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Runtime.Serialization;
+
+namespace System.Security.Cryptography
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class CryptographicException : SystemException
+    {
+        public CryptographicException()
+            : base(SR.Arg_CryptographyException)
+        {
+        }
+
+        public CryptographicException(int hr)
+            : base(SR.Arg_CryptographyException)
+        {
+            HResult = hr;
+        }
+
+        public CryptographicException(string message)
+            : base(message)
+        {
+        }
+
+        public CryptographicException(string message, Exception inner)
+            : base(message, inner)
+        {
+        }
+
+        public CryptographicException(string format, string insert)
+            : base(string.Format(CultureInfo.CurrentCulture, format, insert))
+        {
+        }
+
+        protected CryptographicException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Security/PartialTrustVisibilityLevel.cs b/src/System.Private.CoreLib/shared/System/Security/PartialTrustVisibilityLevel.cs
new file mode 100644
index 0000000000..a0cb5789ac
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/PartialTrustVisibilityLevel.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security
+{
+    public enum PartialTrustVisibilityLevel
+    {
+        VisibleToAllHosts = 0,
+        NotVisibleByDefault = 1
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Security/SafeBSTRHandle.cs b/src/System.Private.CoreLib/shared/System/Security/SafeBSTRHandle.cs
new file mode 100644
index 0000000000..bc93fecef1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/SafeBSTRHandle.cs
@@ -0,0 +1,82 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System.Security
+{
+    internal sealed class SafeBSTRHandle : SafeBuffer
+    {
+        internal SafeBSTRHandle() : base(true) { }
+
+        internal static SafeBSTRHandle Allocate(uint lenInChars)
+        {
+            ulong lenInBytes = (ulong)lenInChars * sizeof(char);
+            SafeBSTRHandle bstr = Interop.OleAut32.SysAllocStringLen(IntPtr.Zero, lenInChars);
+            if (bstr.IsInvalid) // SysAllocStringLen returns a NULL ptr when there's insufficient memory
+            {
+                throw new OutOfMemoryException();
+            }
+            bstr.Initialize(lenInBytes);
+            return bstr;
+        }
+
+        override protected bool ReleaseHandle()
+        {
+            RuntimeImports.RhZeroMemory(handle, (UIntPtr)(Interop.OleAut32.SysStringLen(handle) * sizeof(char)));
+            Interop.OleAut32.SysFreeString(handle);
+            return true;
+        }
+
+        internal unsafe void ClearBuffer()
+        {
+            byte* bufferPtr = null;
+            try
+            {
+                AcquirePointer(ref bufferPtr);
+                RuntimeImports.RhZeroMemory((IntPtr)bufferPtr, (UIntPtr)(Interop.OleAut32.SysStringLen((IntPtr)bufferPtr) * sizeof(char)));
+            }
+            finally
+            {
+                if (bufferPtr != null)
+                {
+                    ReleasePointer();
+                }
+            }
+        }
+
+        internal unsafe uint Length => Interop.OleAut32.SysStringLen(this);
+
+        internal static unsafe void Copy(SafeBSTRHandle source, SafeBSTRHandle target, uint bytesToCopy)
+        {
+            if (bytesToCopy == 0)
+            {
+                return;
+            }
+
+            byte* sourcePtr = null, targetPtr = null;
+            try
+            {
+                source.AcquirePointer(ref sourcePtr);
+                target.AcquirePointer(ref targetPtr);
+
+                Debug.Assert(source.ByteLength >= bytesToCopy, "Source buffer is too small.");
+                Buffer.MemoryCopy(sourcePtr, targetPtr, target.ByteLength, bytesToCopy);
+            }
+            finally
+            {
+                if (targetPtr != null)
+                {
+                    target.ReleasePointer();
+                }
+                if (sourcePtr != null)
+                {
+                    source.ReleasePointer();
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Security/SecureString.Unix.cs b/src/System.Private.CoreLib/shared/System/Security/SecureString.Unix.cs
new file mode 100644
index 0000000000..cfeebc1daf
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/SecureString.Unix.cs
@@ -0,0 +1,325 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace System.Security
+{
+    // SecureString attempts to provide a defense-in-depth solution.
+    // 
+    // On Windows, this is done with several mechanisms:
+    // 1. keeping the data in unmanaged memory so that copies of it aren't implicitly made by the GC moving it around
+    // 2. zero'ing out that unmanaged memory so that the string is reliably removed from memory when done with it
+    // 3. encrypting the data while it's not being used (it's unencrypted to manipulate and use it)
+    // 
+    // On Unix, we do 1 and 2, but we don't do 3 as there's no CryptProtectData equivalent.
+
+    public sealed partial class SecureString
+    {
+        private UnmanagedBuffer _buffer;
+
+        internal SecureString(SecureString str)
+        {
+            // Allocate enough space to store the provided string
+            EnsureCapacity(str._decryptedLength);
+            _decryptedLength = str._decryptedLength;
+
+            // Copy the string into the newly allocated space
+            if (_decryptedLength > 0)
+            {
+                UnmanagedBuffer.Copy(str._buffer, _buffer, (ulong)(str._decryptedLength * sizeof(char)));
+            }
+        }
+
+        private unsafe void InitializeSecureString(char* value, int length)
+        {
+            // Allocate enough space to store the provided string
+            EnsureCapacity(length);
+            _decryptedLength = length;
+            if (length == 0)
+            {
+                return;
+            }
+
+            // Copy the string into the newly allocated space
+            byte* ptr = null;
+            try
+            {
+                _buffer.AcquirePointer(ref ptr);
+                Buffer.MemoryCopy(value, ptr, _buffer.ByteLength, (ulong)(length * sizeof(char)));
+            }
+            finally
+            {
+                if (ptr != null)
+                {
+                    _buffer.ReleasePointer();
+                }
+            }
+        }
+
+        private void DisposeCore()
+        {
+            if (_buffer != null && !_buffer.IsInvalid)
+            {
+                _buffer.Dispose();
+                _buffer = null;
+            }
+        }
+
+        private void EnsureNotDisposed()
+        {
+            if (_buffer == null)
+            {
+                throw new ObjectDisposedException(GetType().Name);
+            }
+        }
+
+        private void ClearCore()
+        {
+            _decryptedLength = 0;
+            _buffer.Clear();
+        }
+
+        private unsafe void AppendCharCore(char c)
+        {
+            // Make sure we have enough space for the new character, then write it at the end.
+            EnsureCapacity(_decryptedLength + 1);
+            _buffer.Write((ulong)(_decryptedLength * sizeof(char)), c);
+            _decryptedLength++;
+        }
+
+        private unsafe void InsertAtCore(int index, char c)
+        {
+            // Make sure we have enough space for the new character, then shift all of the characters above it and insert it.
+            EnsureCapacity(_decryptedLength + 1);
+            byte* ptr = null;
+            try
+            {
+                _buffer.AcquirePointer(ref ptr);
+                ptr += index * sizeof(char);
+                long bytesToShift = (_decryptedLength - index) * sizeof(char);
+                Buffer.MemoryCopy(ptr, ptr + sizeof(char), bytesToShift, bytesToShift);
+                *((char*)ptr) = c;
+                ++_decryptedLength;
+            }
+            finally
+            {
+                if (ptr != null)
+                {
+                    _buffer.ReleasePointer();
+                }
+            }
+        }
+
+        private unsafe void RemoveAtCore(int index)
+        {
+            // Shift down all values above the specified index, then null out the empty space at the end.
+            byte* ptr = null;
+            try
+            {
+                _buffer.AcquirePointer(ref ptr);
+                ptr += index * sizeof(char);
+                long bytesToShift = (_decryptedLength - index - 1) * sizeof(char);
+                Buffer.MemoryCopy(ptr + sizeof(char), ptr, bytesToShift, bytesToShift);
+                *((char*)(ptr + bytesToShift)) = (char)0;
+                --_decryptedLength;
+            }
+            finally
+            {
+                if (ptr != null)
+                {
+                    _buffer.ReleasePointer();
+                }
+            }
+        }
+
+        private void SetAtCore(int index, char c)
+        {
+            // Overwrite the character at the specified index
+            _buffer.Write((ulong)(index * sizeof(char)), c);
+        }
+
+        internal unsafe IntPtr MarshalToBSTR()
+        {
+            int length = _decryptedLength;
+            IntPtr ptr = IntPtr.Zero;
+            IntPtr result = IntPtr.Zero;
+            byte* bufferPtr = null;
+            
+            try
+            {
+                _buffer.AcquirePointer(ref bufferPtr);
+                int resultByteLength = (length + 1) * sizeof(char);
+
+                ptr = PInvokeMarshal.AllocBSTR(length);
+
+                Buffer.MemoryCopy(bufferPtr, (byte*)ptr, resultByteLength, length * sizeof(char));
+
+                result = ptr;
+            }
+            finally
+            {
+                // If we failed for any reason, free the new buffer
+                if (result == IntPtr.Zero && ptr != IntPtr.Zero)
+                {
+                    RuntimeImports.RhZeroMemory(ptr, (UIntPtr)(length * sizeof(char)));
+                    PInvokeMarshal.FreeBSTR(ptr);
+                }
+
+                if (bufferPtr != null)
+                {
+                    _buffer.ReleasePointer();
+                }
+            }
+            return result;
+        }
+
+        internal unsafe IntPtr MarshalToStringCore(bool globalAlloc, bool unicode)
+        {
+            int length = _decryptedLength;
+
+            byte* bufferPtr = null;
+            IntPtr stringPtr = IntPtr.Zero, result = IntPtr.Zero;
+            try
+            {
+                _buffer.AcquirePointer(ref bufferPtr);
+                if (unicode)
+                {
+                    int resultLength = (length + 1) * sizeof(char);
+                    stringPtr = globalAlloc ? Marshal.AllocHGlobal(resultLength) : Marshal.AllocCoTaskMem(resultLength);
+                    Buffer.MemoryCopy(
+                        source: bufferPtr,
+                        destination: (byte*)stringPtr.ToPointer(),
+                        destinationSizeInBytes: resultLength,
+                        sourceBytesToCopy: length * sizeof(char));
+                    *(length + (char*)stringPtr) = '\0';
+                }
+                else
+                {
+                    int resultLength = Encoding.UTF8.GetByteCount((char*)bufferPtr, length) + 1;
+                    stringPtr = globalAlloc ? Marshal.AllocHGlobal(resultLength) : Marshal.AllocCoTaskMem(resultLength);
+                    int encodedLength = Encoding.UTF8.GetBytes((char*)bufferPtr, length, (byte*)stringPtr, resultLength);
+                    Debug.Assert(encodedLength + 1 == resultLength, $"Expected encoded length to match result, got {encodedLength} != {resultLength}");
+                    *(resultLength - 1 + (byte*)stringPtr) = 0;
+                }
+
+                result = stringPtr;
+            }
+            finally
+            {
+                // If there was a failure, such that result isn't initialized, 
+                // release the string if we had one.
+                if (stringPtr != IntPtr.Zero && result == IntPtr.Zero)
+                {
+                    RuntimeImports.RhZeroMemory(stringPtr, (UIntPtr)(length * sizeof(char)));
+                    MarshalFree(stringPtr, globalAlloc);
+                }
+
+                if (bufferPtr != null)
+                {
+                    _buffer.ReleasePointer();
+                }
+            }
+
+            return result;
+        }
+
+        // -----------------------------
+        // ---- PAL layer ends here ----
+        // -----------------------------
+
+        private void EnsureCapacity(int capacity)
+        {
+            // Make sure the requested capacity doesn't exceed SecureString's defined limit
+            if (capacity > MaxLength)
+            {
+                throw new ArgumentOutOfRangeException(nameof(capacity), SR.ArgumentOutOfRange_Capacity);
+            }
+
+            // If we already have enough space allocated, we're done
+            if (_buffer != null && (capacity * sizeof(char)) <= (int)_buffer.ByteLength)
+            {
+                return;
+            }
+
+            // We need more space, so allocate a new buffer, copy all our data into it,
+            // and then swap the new for the old.
+            UnmanagedBuffer newBuffer = UnmanagedBuffer.Allocate(capacity * sizeof(char));
+            if (_buffer != null)
+            {
+                UnmanagedBuffer.Copy(_buffer, newBuffer, _buffer.ByteLength);
+                _buffer.Dispose();
+            }
+            _buffer = newBuffer;
+        }
+
+        /// <summary>SafeBuffer for managing memory meant to be kept confidential.</summary>
+        private sealed class UnmanagedBuffer : SafeBuffer
+        {
+            internal UnmanagedBuffer() : base(true) { }
+
+            internal static UnmanagedBuffer Allocate(int bytes)
+            {
+                Debug.Assert(bytes >= 0);
+                UnmanagedBuffer buffer = new UnmanagedBuffer();
+                buffer.SetHandle(Marshal.AllocHGlobal(bytes));
+                buffer.Initialize((ulong)bytes);
+                return buffer;
+            }
+
+            internal unsafe void Clear()
+            {
+                byte* ptr = null;
+                try
+                {
+                    AcquirePointer(ref ptr);
+                    RuntimeImports.RhZeroMemory((IntPtr)ptr, (UIntPtr)ByteLength);
+                }
+                finally
+                {
+                    if (ptr != null)
+                    {
+                        ReleasePointer();
+                    }
+                }
+            }
+
+            internal static unsafe void Copy(UnmanagedBuffer source, UnmanagedBuffer destination, ulong bytesLength)
+            {
+                if (bytesLength == 0)
+                {
+                    return;
+                }
+
+                byte* srcPtr = null, dstPtr = null;
+                try
+                {
+                    source.AcquirePointer(ref srcPtr);
+                    destination.AcquirePointer(ref dstPtr);
+                    Buffer.MemoryCopy(srcPtr, dstPtr, destination.ByteLength, bytesLength);
+                }
+                finally
+                {
+                    if (dstPtr != null)
+                    {
+                        destination.ReleasePointer();
+                    }
+                    if (srcPtr != null)
+                    {
+                        source.ReleasePointer();
+                    }
+                }
+            }
+
+            protected override unsafe bool ReleaseHandle()
+            {
+                Marshal.FreeHGlobal(handle);
+                return true;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Security/SecureString.Windows.cs b/src/System.Private.CoreLib/shared/System/Security/SecureString.Windows.cs
new file mode 100644
index 0000000000..2a80081912
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/SecureString.Windows.cs
@@ -0,0 +1,308 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime;
+using System.Runtime.InteropServices;
+using System.Security.Cryptography;
+using Microsoft.Win32;
+
+namespace System.Security
+{
+    public sealed partial class SecureString
+    {
+        internal SecureString(SecureString str)
+        {
+            Debug.Assert(str != null, "Expected non-null SecureString");
+            Debug.Assert(str._buffer != null, "Expected other SecureString's buffer to be non-null");
+            Debug.Assert(str._encrypted, "Expected to be used only on encrypted SecureStrings");
+
+            AllocateBuffer(str._buffer.Length);
+            SafeBSTRHandle.Copy(str._buffer, _buffer, str._buffer.Length * sizeof(char));
+
+            _decryptedLength = str._decryptedLength;
+            _encrypted = str._encrypted;
+        }
+
+        private unsafe void InitializeSecureString(char* value, int length)
+        {
+            Debug.Assert(length >= 0, $"Expected non-negative length, got {length}");
+
+            AllocateBuffer((uint)length);
+            _decryptedLength = length;
+
+            byte* bufferPtr = null;
+            try
+            {
+                _buffer.AcquirePointer(ref bufferPtr);
+                Buffer.MemoryCopy((byte*)value, bufferPtr, (long)_buffer.ByteLength, length * sizeof(char));
+            }
+            finally
+            {
+                if (bufferPtr != null)
+                {
+                    _buffer.ReleasePointer();
+                }
+            }
+
+            ProtectMemory();
+        }
+
+        private void AppendCharCore(char c)
+        {
+            UnprotectMemory();
+            try
+            {
+                EnsureCapacity(_decryptedLength + 1);
+                _buffer.Write<char>((uint)_decryptedLength * sizeof(char), c);
+                _decryptedLength++;
+            }
+            finally
+            {
+                ProtectMemory();
+            }
+        }
+
+        private void ClearCore()
+        {
+            _decryptedLength = 0;
+            _buffer.ClearBuffer();
+        }
+
+        private void DisposeCore()
+        {
+            if (_buffer != null)
+            {
+                _buffer.Dispose();
+                _buffer = null;
+            }
+        }
+
+        private unsafe void InsertAtCore(int index, char c)
+        {
+            byte* bufferPtr = null;
+            UnprotectMemory();
+            try
+            {
+                EnsureCapacity(_decryptedLength + 1);
+
+                _buffer.AcquirePointer(ref bufferPtr);
+                char* pBuffer = (char*)bufferPtr;
+
+                for (int i = _decryptedLength; i > index; i--)
+                {
+                    pBuffer[i] = pBuffer[i - 1];
+                }
+                pBuffer[index] = c;
+                ++_decryptedLength;
+            }
+            finally
+            {
+                ProtectMemory();
+                if (bufferPtr != null)
+                {
+                    _buffer.ReleasePointer();
+                }
+            }
+        }
+
+        private unsafe void RemoveAtCore(int index)
+        {
+            byte* bufferPtr = null;
+            UnprotectMemory();
+            try
+            {
+                _buffer.AcquirePointer(ref bufferPtr);
+                char* pBuffer = (char*)bufferPtr;
+
+                for (int i = index; i < _decryptedLength - 1; i++)
+                {
+                    pBuffer[i] = pBuffer[i + 1];
+                }
+                pBuffer[--_decryptedLength] = (char)0;
+            }
+            finally
+            {
+                ProtectMemory();
+                if (bufferPtr != null)
+                {
+                    _buffer.ReleasePointer();
+                }
+            }
+        }
+
+        private void SetAtCore(int index, char c)
+        {
+            UnprotectMemory();
+            try
+            {
+                _buffer.Write<char>((uint)index * sizeof(char), c);
+            }
+            finally
+            {
+                ProtectMemory();
+            }
+        }
+
+        internal unsafe IntPtr MarshalToBSTR()
+        {
+            int length = _decryptedLength;
+            IntPtr ptr = IntPtr.Zero;
+            IntPtr result = IntPtr.Zero;
+            byte* bufferPtr = null;
+
+            UnprotectMemory();
+            try
+            {
+                _buffer.AcquirePointer(ref bufferPtr);
+                int resultByteLength = (length + 1) * sizeof(char);
+
+                ptr = PInvokeMarshal.AllocBSTR(length);
+
+                Buffer.MemoryCopy(bufferPtr, (byte*)ptr, resultByteLength, length * sizeof(char));
+
+                result = ptr;
+            }
+            finally
+            {
+                ProtectMemory();
+
+                // If we failed for any reason, free the new buffer
+                if (result == IntPtr.Zero && ptr != IntPtr.Zero)
+                {
+                    RuntimeImports.RhZeroMemory(ptr, (UIntPtr)(length * sizeof(char)));
+                    PInvokeMarshal.FreeBSTR(ptr);
+                }
+
+                if (bufferPtr != null)
+                {
+                    _buffer.ReleasePointer();
+                }
+            }
+            return result;
+        }
+
+        internal unsafe IntPtr MarshalToStringCore(bool globalAlloc, bool unicode)
+        {
+            int length = _decryptedLength;
+            IntPtr ptr = IntPtr.Zero;
+            IntPtr result = IntPtr.Zero;
+            byte* bufferPtr = null;
+
+            UnprotectMemory();
+            try
+            {
+                _buffer.AcquirePointer(ref bufferPtr);
+                if (unicode)
+                {
+                    int resultByteLength = (length + 1) * sizeof(char);
+                    ptr = globalAlloc ? Marshal.AllocHGlobal(resultByteLength) : Marshal.AllocCoTaskMem(resultByteLength);
+                    Buffer.MemoryCopy(bufferPtr, (byte*)ptr, resultByteLength, length * sizeof(char));
+                    *(length + (char*)ptr) = '\0';
+                }
+                else
+                {
+                    uint defaultChar = '?';
+                    int resultByteLength = 1 + Interop.Kernel32.WideCharToMultiByte(
+                        Interop.Kernel32.CP_ACP, Interop.Kernel32.WC_NO_BEST_FIT_CHARS, (char*)bufferPtr, length, null, 0, (IntPtr)(&defaultChar), IntPtr.Zero);
+                    ptr = globalAlloc ? Marshal.AllocHGlobal(resultByteLength) : Marshal.AllocCoTaskMem(resultByteLength);
+                    Interop.Kernel32.WideCharToMultiByte(
+                        Interop.Kernel32.CP_ACP, Interop.Kernel32.WC_NO_BEST_FIT_CHARS, (char*)bufferPtr, length, (byte*)ptr, resultByteLength - 1, (IntPtr)(&defaultChar), IntPtr.Zero);
+                    *(resultByteLength - 1 + (byte*)ptr) = 0;
+                }
+                result = ptr;
+            }
+            finally
+            {
+                ProtectMemory();
+
+                // If we failed for any reason, free the new buffer
+                if (result == IntPtr.Zero && ptr != IntPtr.Zero)
+                {
+                    RuntimeImports.RhZeroMemory(ptr, (UIntPtr)(length * sizeof(char)));
+                    MarshalFree(ptr, globalAlloc);
+                }
+
+                if (bufferPtr != null)
+                {
+                    _buffer.ReleasePointer();
+                }
+            }
+            return result;
+        }
+
+        private void EnsureNotDisposed()
+        {
+            if (_buffer == null)
+            {
+                throw new ObjectDisposedException(GetType().Name);
+            }
+        }
+
+        // -----------------------------
+        // ---- PAL layer ends here ----
+        // -----------------------------
+
+        private const int BlockSize = (int)Interop.Crypt32.CRYPTPROTECTMEMORY_BLOCK_SIZE / sizeof(char);
+        private SafeBSTRHandle _buffer;
+        private bool _encrypted;
+
+        private void AllocateBuffer(uint size)
+        {
+            _buffer = SafeBSTRHandle.Allocate(GetAlignedSize(size));
+        }
+
+        private static uint GetAlignedSize(uint size) =>
+            size == 0 || size % BlockSize != 0 ?
+                BlockSize + ((size / BlockSize) * BlockSize) :
+                size;
+
+        private void EnsureCapacity(int capacity)
+        {
+            if (capacity > MaxLength)
+            {
+                throw new ArgumentOutOfRangeException(nameof(capacity), SR.ArgumentOutOfRange_Capacity);
+            }
+
+            if (((uint)capacity * sizeof(char)) <= _buffer.ByteLength)
+            {
+                return;
+            }
+
+            var oldBuffer = _buffer;
+            SafeBSTRHandle newBuffer = SafeBSTRHandle.Allocate(GetAlignedSize((uint)capacity));
+            SafeBSTRHandle.Copy(oldBuffer, newBuffer, (uint)_decryptedLength * sizeof(char));
+            _buffer = newBuffer;
+            oldBuffer.Dispose();
+        }
+
+        private void ProtectMemory()
+        {
+            Debug.Assert(!_buffer.IsInvalid, "Invalid buffer!");
+
+            if (_decryptedLength != 0 &&
+                !_encrypted &&
+                !Interop.Crypt32.CryptProtectMemory(_buffer, _buffer.Length * sizeof(char), Interop.Crypt32.CRYPTPROTECTMEMORY_SAME_PROCESS))
+            {
+                throw new CryptographicException(Marshal.GetLastWin32Error());
+            }
+
+            _encrypted = true;
+        }
+
+        private void UnprotectMemory()
+        {
+            Debug.Assert(!_buffer.IsInvalid, "Invalid buffer!");
+
+            if (_decryptedLength != 0 &&
+                _encrypted &&
+                !Interop.Crypt32.CryptUnprotectMemory(_buffer, _buffer.Length * sizeof(char), Interop.Crypt32.CRYPTPROTECTMEMORY_SAME_PROCESS))
+            {
+                throw new CryptographicException(Marshal.GetLastWin32Error());
+            }
+
+            _encrypted = false;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Security/SecureString.cs b/src/System.Private.CoreLib/shared/System/Security/SecureString.cs
new file mode 100644
index 0000000000..22f15accaa
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/SecureString.cs
@@ -0,0 +1,180 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Threading;
+
+namespace System.Security
+{
+    public sealed partial class SecureString : IDisposable
+    {
+        private const int MaxLength = 65536;
+        private readonly object _methodLock = new object();
+        private bool _readOnly;
+        private int _decryptedLength;
+
+        public unsafe SecureString()
+        {
+            InitializeSecureString(null, 0);
+        }
+
+        [CLSCompliant(false)]
+        public unsafe SecureString(char* value, int length)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            if (length < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (length > MaxLength)
+            {
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_Length);
+            }
+
+            InitializeSecureString(value, length);
+        }
+
+        public int Length
+        {
+            get
+            {
+                EnsureNotDisposed();
+                return Volatile.Read(ref _decryptedLength);
+            }
+        }
+
+        public void AppendChar(char c)
+        {
+            lock (_methodLock)
+            {
+                EnsureNotDisposed();
+                EnsureNotReadOnly();
+                AppendCharCore(c);
+            }
+        }
+
+        // clears the current contents. Only available if writable
+        public void Clear()
+        {
+            lock (_methodLock)
+            {
+                EnsureNotDisposed();
+                EnsureNotReadOnly();
+                ClearCore();
+            }
+        }
+
+        // Do a deep-copy of the SecureString 
+        public SecureString Copy()
+        {
+            lock (_methodLock)
+            {
+                EnsureNotDisposed();
+                return new SecureString(this);
+            }
+        }
+
+        public void Dispose()
+        {
+            lock (_methodLock)
+            {
+                DisposeCore();
+            }
+        }
+
+        public void InsertAt(int index, char c)
+        {
+            lock (_methodLock)
+            {
+                if (index < 0 || index > _decryptedLength)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_IndexString);
+                }
+
+                EnsureNotDisposed();
+                EnsureNotReadOnly();
+
+                InsertAtCore(index, c);
+            }
+        }
+
+        public bool IsReadOnly()
+        {
+            EnsureNotDisposed();
+            return Volatile.Read(ref _readOnly);
+        }
+
+        public void MakeReadOnly()
+        {
+            EnsureNotDisposed();
+            Volatile.Write(ref _readOnly, true);
+        }
+
+        public void RemoveAt(int index)
+        {
+            lock (_methodLock)
+            {
+                EnsureNotDisposed();
+                EnsureNotReadOnly();
+
+                if (index < 0 || index >= _decryptedLength)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_IndexString);
+                }
+
+                RemoveAtCore(index);
+            }
+        }
+
+        public void SetAt(int index, char c)
+        {
+            lock (_methodLock)
+            {
+                if (index < 0 || index >= _decryptedLength)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_IndexString);
+                }
+                Debug.Assert(index <= Int32.MaxValue / sizeof(char));
+
+                EnsureNotDisposed();
+                EnsureNotReadOnly();
+
+                SetAtCore(index, c);
+            }
+        }
+
+        private void EnsureNotReadOnly()
+        {
+            if (_readOnly)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+            }
+        }
+
+        internal unsafe IntPtr MarshalToString(bool globalAlloc, bool unicode)
+        {
+            lock (_methodLock)
+            {
+                EnsureNotDisposed();
+                return MarshalToStringCore(globalAlloc, unicode);
+            }
+        }
+
+        private static void MarshalFree(IntPtr ptr, bool globalAlloc)
+        {
+            if (globalAlloc)
+            {
+                Marshal.FreeHGlobal(ptr);
+            }
+            else
+            {
+                Marshal.FreeCoTaskMem(ptr);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Security/SecurityCriticalAttribute.cs b/src/System.Private.CoreLib/shared/System/Security/SecurityCriticalAttribute.cs
new file mode 100644
index 0000000000..2bf1700afb
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/SecurityCriticalAttribute.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security
+{
+    // SecurityCriticalAttribute
+    //  Indicates that the decorated code or assembly performs security critical operations (e.g. Assert, "unsafe", LinkDemand, etc.)
+    //  The attribute can be placed on most targets, except on arguments/return values.
+    [AttributeUsage(AttributeTargets.Assembly |
+                    AttributeTargets.Class |
+                    AttributeTargets.Struct |
+                    AttributeTargets.Enum |
+                    AttributeTargets.Constructor |
+                    AttributeTargets.Method |
+                    AttributeTargets.Field |
+                    AttributeTargets.Interface |
+                    AttributeTargets.Delegate,
+        AllowMultiple = false,
+        Inherited = false)]
+    public sealed class SecurityCriticalAttribute : Attribute
+    {
+#pragma warning disable 618    // We still use SecurityCriticalScope for v2 compat
+        public SecurityCriticalAttribute() { }
+
+        public SecurityCriticalAttribute(SecurityCriticalScope scope)
+        {
+            Scope = scope;
+        }
+
+        [Obsolete("SecurityCriticalScope is only used for .NET 2.0 transparency compatibility.")]
+        public SecurityCriticalScope Scope { get; }
+#pragma warning restore 618
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Security/SecurityCriticalScope.cs b/src/System.Private.CoreLib/shared/System/Security/SecurityCriticalScope.cs
new file mode 100644
index 0000000000..e0f5a8e2cd
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/SecurityCriticalScope.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security
+{
+    [Obsolete("SecurityCriticalScope is only used for .NET 2.0 transparency compatibility.")]
+    public enum SecurityCriticalScope
+    {
+        Explicit = 0,
+        Everything = 0x1
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Security/SecurityException.cs b/src/System.Private.CoreLib/shared/System/Security/SecurityException.cs
new file mode 100644
index 0000000000..61504c3ba1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/SecurityException.cs
@@ -0,0 +1,89 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+using System.Runtime.Serialization;
+
+namespace System.Security
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class SecurityException : SystemException
+    {
+        private const string DemandedName = "Demanded";
+        private const string GrantedSetName = "GrantedSet";
+        private const string RefusedSetName = "RefusedSet";
+        private const string DeniedName = "Denied";
+        private const string PermitOnlyName = "PermitOnly";
+        private const string UrlName = "Url";
+
+        public SecurityException()
+            : base(SR.Arg_SecurityException)
+        {
+            HResult = HResults.COR_E_SECURITY;
+        }
+
+        public SecurityException(string message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_SECURITY;
+        }
+
+        public SecurityException(string message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_SECURITY;
+        }
+
+        public SecurityException(string message, Type type)
+            : base(message)
+        {
+            HResult = HResults.COR_E_SECURITY;
+            PermissionType = type;
+        }
+
+        public SecurityException(string message, Type type, string state)
+            : base(message)
+        {
+            HResult = HResults.COR_E_SECURITY;
+            PermissionType = type;
+            PermissionState = state;
+        }
+
+        protected SecurityException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            Demanded = (string)info.GetValueNoThrow(DemandedName, typeof(string));
+            GrantedSet = (string)info.GetValueNoThrow(GrantedSetName, typeof(string));
+            RefusedSet = (string)info.GetValueNoThrow(RefusedSetName, typeof(string));
+            DenySetInstance = (string)info.GetValueNoThrow(DeniedName, typeof(string));
+            PermitOnlySetInstance = (string)info.GetValueNoThrow(PermitOnlyName, typeof(string));
+            Url = (string)info.GetValueNoThrow(UrlName, typeof(string));
+        }
+
+        public override string ToString() => base.ToString();
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context); 
+            info.AddValue(DemandedName, Demanded, typeof(string));
+            info.AddValue(GrantedSetName, GrantedSet, typeof(string));
+            info.AddValue(RefusedSetName, RefusedSet, typeof(string));
+            info.AddValue(DeniedName, DenySetInstance, typeof(string));
+            info.AddValue(PermitOnlyName, PermitOnlySetInstance, typeof(string));
+            info.AddValue(UrlName, Url, typeof(string));
+        }
+
+        public object Demanded { get; set; }
+        public object DenySetInstance { get; set; }
+        public AssemblyName FailedAssemblyInfo { get; set; }
+        public string GrantedSet { get; set; }
+        public MethodInfo Method { get; set; }
+        public string PermissionState { get; set; }
+        public Type PermissionType { get; set; }
+        public object PermitOnlySetInstance { get; set; }
+        public string RefusedSet { get; set; }
+        public string Url { get; set; }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Security/SecurityRuleSet.cs b/src/System.Private.CoreLib/shared/System/Security/SecurityRuleSet.cs
new file mode 100644
index 0000000000..1b62fd4e7d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/SecurityRuleSet.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security
+{
+    public enum SecurityRuleSet : byte
+    {
+        None = 0,
+        Level1 = 1,    // v2.0 transparency model
+        Level2 = 2,    // v4.0 transparency model
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Security/SecurityRulesAttribute.cs b/src/System.Private.CoreLib/shared/System/Security/SecurityRulesAttribute.cs
new file mode 100644
index 0000000000..ad17087f8b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/SecurityRulesAttribute.cs
@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security
+{
+    // SecurityRulesAttribute
+    //
+    // Indicates which set of security rules an assembly was authored against, and therefore which set of
+    // rules the runtime should enforce on the assembly.  For instance, an assembly marked with
+    // [SecurityRules(SecurityRuleSet.Level1)] will follow the v2.0 transparency rules, where transparent code
+    // can call a LinkDemand by converting it to a full demand, public critical methods are implicitly
+    // treat as safe, and the remainder of the v2.0 rules apply.
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = false)]
+    public sealed class SecurityRulesAttribute : Attribute
+    {
+        public SecurityRulesAttribute(SecurityRuleSet ruleSet)
+        {
+            RuleSet = ruleSet;
+        }
+
+        // Should fully trusted transparent code skip IL verification
+        public bool SkipVerificationInFullTrust { get; set; }
+
+        public SecurityRuleSet RuleSet { get; }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Security/SecuritySafeCriticalAttribute.cs b/src/System.Private.CoreLib/shared/System/Security/SecuritySafeCriticalAttribute.cs
new file mode 100644
index 0000000000..ee2e4b0499
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/SecuritySafeCriticalAttribute.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security
+{
+    // SecuritySafeCriticalAttribute: 
+    // Indicates that the code may contain violations to the security critical rules (e.g. transitions from
+    //      critical to non-public transparent, transparent to non-public critical, etc.), has been audited for
+    //      security concerns and is considered security clean. Also indicates that the code is considered SecurityCritical.
+    // The effect of this attribute is as if the code was marked [SecurityCritical][SecurityTreatAsSafe].
+    // At assembly-scope, all rule checks will be suppressed within the assembly and for calls made against the assembly.
+    // At type-scope, all rule checks will be suppressed for members within the type and for calls made against the type.
+    // At member level (e.g. field and method) the code will be treated as public - i.e. no rule checks for the members.
+
+    [AttributeUsage(AttributeTargets.Class |
+                    AttributeTargets.Struct |
+                    AttributeTargets.Enum |
+                    AttributeTargets.Constructor |
+                    AttributeTargets.Method |
+                    AttributeTargets.Field |
+                    AttributeTargets.Interface |
+                    AttributeTargets.Delegate,
+        AllowMultiple = false,
+        Inherited = false)]
+    public sealed class SecuritySafeCriticalAttribute : Attribute
+    {
+        public SecuritySafeCriticalAttribute() { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Security/SecurityTransparentAttribute.cs b/src/System.Private.CoreLib/shared/System/Security/SecurityTransparentAttribute.cs
new file mode 100644
index 0000000000..03f41387ae
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/SecurityTransparentAttribute.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security
+{
+    // SecurityTransparentAttribute:
+    // Indicates the assembly contains only transparent code.
+    // Security critical actions will be restricted or converted into less critical actions. For example,
+    // Assert will be restricted, SuppressUnmanagedCode, LinkDemand, unsafe, and unverifiable code will be converted
+    // into Full-Demands.
+
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = false, Inherited = false)]
+    public sealed class SecurityTransparentAttribute : Attribute
+    {
+        public SecurityTransparentAttribute() { }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Security/SecurityTreatAsSafeAttribute.cs b/src/System.Private.CoreLib/shared/System/Security/SecurityTreatAsSafeAttribute.cs
new file mode 100644
index 0000000000..7a95122bf0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/SecurityTreatAsSafeAttribute.cs
@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security
+{
+    // SecurityTreatAsSafeAttribute:
+    // Indicates that the code may contain violations to the security critical rules (e.g. transitions from
+    //      critical to non-public transparent, transparent to non-public critical, etc.), has been audited for
+    //      security concerns and is considered security clean.
+    // At assembly-scope, all rule checks will be suppressed within the assembly and for calls made against the assembly.
+    // At type-scope, all rule checks will be suppressed for members within the type and for calls made against the type.
+    // At member level (e.g. field and method) the code will be treated as public - i.e. no rule checks for the members.
+
+    [AttributeUsage(AttributeTargets.Assembly |
+                    AttributeTargets.Class |
+                    AttributeTargets.Struct |
+                    AttributeTargets.Enum |
+                    AttributeTargets.Constructor |
+                    AttributeTargets.Method |
+                    AttributeTargets.Field |
+                    AttributeTargets.Interface |
+                    AttributeTargets.Delegate,
+        AllowMultiple = false,
+        Inherited = false)]
+    [Obsolete("SecurityTreatAsSafe is only used for .NET 2.0 transparency compatibility.  Please use the SecuritySafeCriticalAttribute instead.")]
+    public sealed class SecurityTreatAsSafeAttribute : Attribute
+    {
+        public SecurityTreatAsSafeAttribute() { }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Security/SuppressUnmanagedCodeSecurityAttribute.cs b/src/System.Private.CoreLib/shared/System/Security/SuppressUnmanagedCodeSecurityAttribute.cs
new file mode 100644
index 0000000000..a60b8d3668
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/SuppressUnmanagedCodeSecurityAttribute.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security
+{
+    // SuppressUnmanagedCodeSecurityAttribute:
+    //  Indicates that the target P/Invoke method(s) should skip the per-call
+    //  security checked for unmanaged code permission.
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Class | AttributeTargets.Interface | AttributeTargets.Delegate, AllowMultiple = true, Inherited = false)]
+    public sealed class SuppressUnmanagedCodeSecurityAttribute : Attribute
+    {
+        public SuppressUnmanagedCodeSecurityAttribute() { }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Security/UnverifiableCodeAttribute.cs b/src/System.Private.CoreLib/shared/System/Security/UnverifiableCodeAttribute.cs
new file mode 100644
index 0000000000..1560b6617b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/UnverifiableCodeAttribute.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Security
+{
+    // UnverifiableCodeAttribute:
+    //  Indicates that the target module contains unverifiable code.
+    [AttributeUsage(AttributeTargets.Module, AllowMultiple = true, Inherited = false)]
+    public sealed class UnverifiableCodeAttribute : Attribute
+    {
+        public UnverifiableCodeAttribute() { }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Security/VerificationException.cs b/src/System.Private.CoreLib/shared/System/Security/VerificationException.cs
new file mode 100644
index 0000000000..e2afd4cabe
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Security/VerificationException.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Security
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class VerificationException : SystemException
+    {
+        public VerificationException()
+            : base(SR.Verification_Exception)
+        {
+            HResult = HResults.COR_E_VERIFICATION;
+        }
+
+        public VerificationException(string message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_VERIFICATION;
+        }
+
+        public VerificationException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_VERIFICATION;
+        }
+
+        protected VerificationException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/SerializableAttribute.cs b/src/System.Private.CoreLib/shared/System/SerializableAttribute.cs
new file mode 100644
index 0000000000..c256931373
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/SerializableAttribute.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Enum | AttributeTargets.Delegate, Inherited = false)]
+    public sealed class SerializableAttribute : Attribute
+    {
+        public SerializableAttribute() { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Single.cs b/src/System.Private.CoreLib/shared/System/Single.cs
new file mode 100644
index 0000000000..a74d3770fa
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Single.cs
@@ -0,0 +1,443 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: A wrapper class for the primitive type float.
+**
+**
+===========================================================*/
+
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+using Internal.Runtime.CompilerServices;
+
+namespace System
+{
+    [Serializable]
+    [StructLayout(LayoutKind.Sequential)]
+    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct Single : IComparable, IConvertible, IFormattable, IComparable<Single>, IEquatable<Single>, ISpanFormattable
+    {
+        private float m_value; // Do not rename (binary serialization)
+
+        //
+        // Public constants
+        //
+        public const float MinValue = (float)-3.40282346638528859e+38;
+        public const float Epsilon = (float)1.4e-45;
+        public const float MaxValue = (float)3.40282346638528859e+38;
+        public const float PositiveInfinity = (float)1.0 / (float)0.0;
+        public const float NegativeInfinity = (float)-1.0 / (float)0.0;
+        public const float NaN = (float)0.0 / (float)0.0;
+
+        // We use this explicit definition to avoid the confusion between 0.0 and -0.0.
+        internal const float NegativeZero = (float)-0.0;
+
+        /// <summary>Determines whether the specified value is finite (zero, subnormal, or normal).</summary>
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool IsFinite(float f)
+        {
+            var bits = BitConverter.SingleToInt32Bits(f);
+            return (bits & 0x7FFFFFFF) < 0x7F800000;
+        }
+
+        /// <summary>Determines whether the specified value is infinite.</summary>
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe bool IsInfinity(float f)
+        {
+            var bits = BitConverter.SingleToInt32Bits(f);
+            return (bits & 0x7FFFFFFF) == 0x7F800000;
+        }
+
+        /// <summary>Determines whether the specified value is NaN.</summary>
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe bool IsNaN(float f)
+        {
+            var bits = BitConverter.SingleToInt32Bits(f);
+            return (bits & 0x7FFFFFFF) > 0x7F800000;
+        }
+
+        /// <summary>Determines whether the specified value is negative.</summary>
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe bool IsNegative(float f)
+        {
+            var bits = unchecked((uint)BitConverter.SingleToInt32Bits(f));
+            return (bits & 0x80000000) == 0x80000000;
+        }
+
+        /// <summary>Determines whether the specified value is negative infinity.</summary>
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe bool IsNegativeInfinity(float f)
+        {
+            return (f == float.NegativeInfinity);
+        }
+
+        /// <summary>Determines whether the specified value is normal.</summary>
+        [NonVersionable]
+        // This is probably not worth inlining, it has branches and should be rarely called
+        public static unsafe bool IsNormal(float f)
+        {
+            var bits = BitConverter.SingleToInt32Bits(f);
+            bits &= 0x7FFFFFFF;
+            return (bits < 0x7F800000) && (bits != 0) && ((bits & 0x7F800000) != 0);
+        }
+
+        /// <summary>Determines whether the specified value is positive infinity.</summary>
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe bool IsPositiveInfinity(float f)
+        {
+            return (f == float.PositiveInfinity);
+        }
+
+        /// <summary>Determines whether the specified value is subnormal.</summary>
+        [NonVersionable]
+        // This is probably not worth inlining, it has branches and should be rarely called
+        public static unsafe bool IsSubnormal(float f)
+        {
+            var bits = BitConverter.SingleToInt32Bits(f);
+            bits &= 0x7FFFFFFF;
+            return (bits < 0x7F800000) && (bits != 0) && ((bits & 0x7F800000) == 0);
+        }
+
+        // Compares this object to another object, returning an integer that
+        // indicates the relationship.
+        // Returns a value less than zero if this  object
+        // null is considered to be less than any instance.
+        // If object is not of type Single, this method throws an ArgumentException.
+        //
+        public int CompareTo(Object value)
+        {
+            if (value == null)
+            {
+                return 1;
+            }
+            if (value is Single)
+            {
+                float f = (float)value;
+                if (m_value < f) return -1;
+                if (m_value > f) return 1;
+                if (m_value == f) return 0;
+
+                // At least one of the values is NaN.
+                if (IsNaN(m_value))
+                    return (IsNaN(f) ? 0 : -1);
+                else // f is NaN.
+                    return 1;
+            }
+            throw new ArgumentException(SR.Arg_MustBeSingle);
+        }
+
+
+        public int CompareTo(Single value)
+        {
+            if (m_value < value) return -1;
+            if (m_value > value) return 1;
+            if (m_value == value) return 0;
+
+            // At least one of the values is NaN.
+            if (IsNaN(m_value))
+                return (IsNaN(value) ? 0 : -1);
+            else // f is NaN.
+                return 1;
+        }
+
+        [NonVersionable]
+        public static bool operator ==(Single left, Single right)
+        {
+            return left == right;
+        }
+
+        [NonVersionable]
+        public static bool operator !=(Single left, Single right)
+        {
+            return left != right;
+        }
+
+        [NonVersionable]
+        public static bool operator <(Single left, Single right)
+        {
+            return left < right;
+        }
+
+        [NonVersionable]
+        public static bool operator >(Single left, Single right)
+        {
+            return left > right;
+        }
+
+        [NonVersionable]
+        public static bool operator <=(Single left, Single right)
+        {
+            return left <= right;
+        }
+
+        [NonVersionable]
+        public static bool operator >=(Single left, Single right)
+        {
+            return left >= right;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (!(obj is Single))
+            {
+                return false;
+            }
+            float temp = ((Single)obj).m_value;
+            if (temp == m_value)
+            {
+                return true;
+            }
+
+            return IsNaN(temp) && IsNaN(m_value);
+        }
+
+        public bool Equals(Single obj)
+        {
+            if (obj == m_value)
+            {
+                return true;
+            }
+
+            return IsNaN(obj) && IsNaN(m_value);
+        }
+
+        public override int GetHashCode()
+        {
+            var bits = Unsafe.As<float, int>(ref m_value);
+
+            // Optimized check for IsNan() || IsZero()
+            if (((bits - 1) & 0x7FFFFFFF) >= 0x7F800000)
+            {
+                // Ensure that all NaNs and both zeros have the same hash code
+                bits &= 0x7F800000;
+            }
+
+            return bits;
+        }
+
+        public override String ToString()
+        {
+            return Number.FormatSingle(m_value, null, NumberFormatInfo.CurrentInfo);
+        }
+
+        public String ToString(IFormatProvider provider)
+        {
+            return Number.FormatSingle(m_value, null, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public String ToString(String format)
+        {
+            return Number.FormatSingle(m_value, format, NumberFormatInfo.CurrentInfo);
+        }
+
+        public String ToString(String format, IFormatProvider provider)
+        {
+            return Number.FormatSingle(m_value, format, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider provider = null)
+        {
+            return Number.TryFormatSingle(m_value, format, NumberFormatInfo.GetInstance(provider), destination, out charsWritten);
+        }
+
+        // Parses a float from a String in the given style.  If
+        // a NumberFormatInfo isn't specified, the current culture's
+        // NumberFormatInfo is assumed.
+        //
+        // This method will not throw an OverflowException, but will return
+        // PositiveInfinity or NegativeInfinity for a number that is too
+        // large or too small.
+        //
+        public static float Parse(String s)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseSingle(s, NumberStyles.Float | NumberStyles.AllowThousands, NumberFormatInfo.CurrentInfo);
+        }
+
+        public static float Parse(String s, NumberStyles style)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseSingle(s, style, NumberFormatInfo.CurrentInfo);
+        }
+
+        public static float Parse(String s, IFormatProvider provider)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseSingle(s, NumberStyles.Float | NumberStyles.AllowThousands, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public static float Parse(String s, NumberStyles style, IFormatProvider provider)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseSingle(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public static float Parse(ReadOnlySpan<char> s, NumberStyles style = NumberStyles.Float | NumberStyles.AllowThousands, IFormatProvider provider = null)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            return Number.ParseSingle(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public static Boolean TryParse(String s, out Single result)
+        {
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return TryParse((ReadOnlySpan<char>)s, NumberStyles.Float | NumberStyles.AllowThousands, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, out float result)
+        {
+            return TryParse(s, NumberStyles.Float | NumberStyles.AllowThousands, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        public static Boolean TryParse(String s, NumberStyles style, IFormatProvider provider, out Single result)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return TryParse((ReadOnlySpan<char>)s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider provider, out float result)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            return TryParse(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        private static Boolean TryParse(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info, out Single result)
+        {
+            bool success = Number.TryParseSingle(s, style, info, out result);
+            if (!success)
+            {
+                ReadOnlySpan<char> sTrim = s.Trim();
+                if (sTrim.EqualsOrdinal(info.PositiveInfinitySymbol))
+                {
+                    result = PositiveInfinity;
+                }
+                else if (sTrim.EqualsOrdinal(info.NegativeInfinitySymbol))
+                {
+                    result = NegativeInfinity;
+                }
+                else if (sTrim.EqualsOrdinal(info.NaNSymbol))
+                {
+                    result = NaN;
+                }
+                else
+                {
+                    return false; // We really failed
+                }
+            }
+            return true;
+        }
+
+        //
+        // IConvertible implementation
+        //
+
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.Single;
+        }
+
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            return Convert.ToBoolean(m_value);
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Single", "Char"));
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return Convert.ToSByte(m_value);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return Convert.ToByte(m_value);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return Convert.ToInt16(m_value);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return Convert.ToUInt16(m_value);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return Convert.ToInt32(m_value);
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return Convert.ToUInt32(m_value);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return Convert.ToInt64(m_value);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return Convert.ToUInt64(m_value);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            return m_value;
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            return Convert.ToDouble(m_value);
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            return Convert.ToDecimal(m_value);
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Single", "DateTime"));
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Span.Fast.cs b/src/System.Private.CoreLib/shared/System/Span.Fast.cs
new file mode 100644
index 0000000000..131694bc0c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Span.Fast.cs
@@ -0,0 +1,357 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+using Internal.Runtime.CompilerServices;
+
+#pragma warning disable 0809  //warning CS0809: Obsolete member 'Span<T>.Equals(object)' overrides non-obsolete member 'object.Equals(object)'
+
+#if BIT64
+using nuint = System.UInt64;
+#else
+using nuint = System.UInt32;
+#endif
+
+namespace System
+{
+    /// <summary>
+    /// Span represents a contiguous region of arbitrary memory. Unlike arrays, it can point to either managed
+    /// or native memory, or to memory allocated on the stack. It is type- and memory-safe.
+    /// </summary>
+    [DebuggerTypeProxy(typeof(SpanDebugView<>))]
+    [DebuggerDisplay("{ToString(),raw}")]
+    [NonVersionable]
+    public readonly ref partial struct Span<T>
+    {
+        /// <summary>A byref or a native ptr.</summary>
+        internal readonly ByReference<T> _pointer;
+        /// <summary>The number of elements this Span contains.</summary>
+#if PROJECTN
+        [Bound]
+#endif
+        private readonly int _length;
+
+        /// <summary>
+        /// Creates a new span over the entirety of the target array.
+        /// </summary>
+        /// <param name="array">The target array.</param>
+        /// <remarks>Returns default when <paramref name="array"/> is null.</remarks>
+        /// reference (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.ArrayTypeMismatchException">Thrown when <paramref name="array"/> is covariant and array's type is not exactly T[].</exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public Span(T[] array)
+        {
+            if (array == null)
+            {
+                this = default;
+                return; // returns default
+            }
+            if (default(T) == null && array.GetType() != typeof(T[]))
+                ThrowHelper.ThrowArrayTypeMismatchException();
+
+            _pointer = new ByReference<T>(ref Unsafe.As<byte, T>(ref array.GetRawSzArrayData()));
+            _length = array.Length;
+        }
+
+        /// <summary>
+        /// Creates a new span over the portion of the target array beginning
+        /// at 'start' index and ending at 'end' index (exclusive).
+        /// </summary>
+        /// <param name="array">The target array.</param>
+        /// <param name="start">The index at which to begin the span.</param>
+        /// <param name="length">The number of items in the span.</param>
+        /// <remarks>Returns default when <paramref name="array"/> is null.</remarks>
+        /// reference (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.ArrayTypeMismatchException">Thrown when <paramref name="array"/> is covariant and array's type is not exactly T[].</exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in the range (&lt;0 or &gt;=Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public Span(T[] array, int start, int length)
+        {
+            if (array == null)
+            {
+                if (start != 0 || length != 0)
+                    ThrowHelper.ThrowArgumentOutOfRangeException();
+                this = default;
+                return; // returns default
+            }
+            if (default(T) == null && array.GetType() != typeof(T[]))
+                ThrowHelper.ThrowArrayTypeMismatchException();
+            if ((uint)start > (uint)array.Length || (uint)length > (uint)(array.Length - start))
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            _pointer = new ByReference<T>(ref Unsafe.Add(ref Unsafe.As<byte, T>(ref array.GetRawSzArrayData()), start));
+            _length = length;
+        }
+
+        /// <summary>
+        /// Creates a new span over the target unmanaged buffer.  Clearly this
+        /// is quite dangerous, because we are creating arbitrarily typed T's
+        /// out of a void*-typed block of memory.  And the length is not checked.
+        /// But if this creation is correct, then all subsequent uses are correct.
+        /// </summary>
+        /// <param name="pointer">An unmanaged pointer to memory.</param>
+        /// <param name="length">The number of <typeparamref name="T"/> elements the memory contains.</param>
+        /// <exception cref="System.ArgumentException">
+        /// Thrown when <typeparamref name="T"/> is reference type or contains pointers and hence cannot be stored in unmanaged memory.
+        /// </exception>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="length"/> is negative.
+        /// </exception>
+        [CLSCompliant(false)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public unsafe Span(void* pointer, int length)
+        {
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+                ThrowHelper.ThrowInvalidTypeWithPointersNotSupported(typeof(T));
+            if (length < 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            _pointer = new ByReference<T>(ref Unsafe.As<byte, T>(ref *(byte*)pointer));
+            _length = length;
+        }
+
+        // Constructor for internal use only.
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal Span(ref T ptr, int length)
+        {
+            Debug.Assert(length >= 0);
+
+            _pointer = new ByReference<T>(ref ptr);
+            _length = length;
+        }
+
+        /// Returns a reference to specified element of the Span.
+        /// </summary>
+        /// <param name="index"></param>
+        /// <returns></returns>
+        /// <exception cref="System.IndexOutOfRangeException">
+        /// Thrown when index less than 0 or index greater than or equal to Length
+        /// </exception>
+        public ref T this[int index]
+        {
+#if PROJECTN
+            [BoundsChecking]
+            get
+            {
+                return ref Unsafe.Add(ref _pointer.Value, index);
+            }
+#else
+            [Intrinsic]
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            [NonVersionable]
+            get
+            {
+                if ((uint)index >= (uint)_length)
+                    ThrowHelper.ThrowIndexOutOfRangeException();
+                return ref Unsafe.Add(ref _pointer.Value, index);
+            }
+#endif
+        }
+
+        /// <summary>
+        /// Returns a reference to the 0th element of the Span. If the Span is empty, returns null reference.
+        /// It can be used for pinning and is required to support the use of span within a fixed statement.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public unsafe ref T GetPinnableReference() => ref (_length != 0) ? ref _pointer.Value : ref Unsafe.AsRef<T>(null);
+
+        /// <summary>
+        /// Clears the contents of this span.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Clear()
+        {
+            if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+            {
+                SpanHelpers.ClearWithReferences(ref Unsafe.As<T, IntPtr>(ref _pointer.Value), (nuint)_length * (nuint)(Unsafe.SizeOf<T>() / sizeof(nuint)));
+            }
+            else
+            {
+                SpanHelpers.ClearWithoutReferences(ref Unsafe.As<T, byte>(ref _pointer.Value), (nuint)_length * (nuint)Unsafe.SizeOf<T>());
+            }
+        }
+
+        /// <summary>
+        /// Fills the contents of this span with the given value.
+        /// </summary>
+        public void Fill(T value)
+        {
+            if (Unsafe.SizeOf<T>() == 1)
+            {
+                uint length = (uint)_length;
+                if (length == 0)
+                    return;
+
+                T tmp = value; // Avoid taking address of the "value" argument. It would regress performance of the loop below.
+                Unsafe.InitBlockUnaligned(ref Unsafe.As<T, byte>(ref _pointer.Value), Unsafe.As<T, byte>(ref tmp), length);
+            }
+            else
+            {
+                // Do all math as nuint to avoid unnecessary 64->32->64 bit integer truncations
+                nuint length = (uint)_length;
+                if (length == 0)
+                    return;
+
+                ref T r = ref _pointer.Value;
+
+                // TODO: Create block fill for value types of power of two sizes e.g. 2,4,8,16
+
+                nuint elementSize = (uint)Unsafe.SizeOf<T>();
+                nuint i = 0;
+                for (; i < (length & ~(nuint)7); i += 8)
+                {
+                    Unsafe.AddByteOffset<T>(ref r, (i + 0) * elementSize) = value;
+                    Unsafe.AddByteOffset<T>(ref r, (i + 1) * elementSize) = value;
+                    Unsafe.AddByteOffset<T>(ref r, (i + 2) * elementSize) = value;
+                    Unsafe.AddByteOffset<T>(ref r, (i + 3) * elementSize) = value;
+                    Unsafe.AddByteOffset<T>(ref r, (i + 4) * elementSize) = value;
+                    Unsafe.AddByteOffset<T>(ref r, (i + 5) * elementSize) = value;
+                    Unsafe.AddByteOffset<T>(ref r, (i + 6) * elementSize) = value;
+                    Unsafe.AddByteOffset<T>(ref r, (i + 7) * elementSize) = value;
+                }
+                if (i < (length & ~(nuint)3))
+                {
+                    Unsafe.AddByteOffset<T>(ref r, (i + 0) * elementSize) = value;
+                    Unsafe.AddByteOffset<T>(ref r, (i + 1) * elementSize) = value;
+                    Unsafe.AddByteOffset<T>(ref r, (i + 2) * elementSize) = value;
+                    Unsafe.AddByteOffset<T>(ref r, (i + 3) * elementSize) = value;
+                    i += 4;
+                }
+                for (; i < length; i++)
+                {
+                    Unsafe.AddByteOffset<T>(ref r, i * elementSize) = value;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Copies the contents of this span into destination span. If the source
+        /// and destinations overlap, this method behaves as if the original values in
+        /// a temporary location before the destination is overwritten.
+        /// </summary>
+        /// <param name="destination">The span to copy items into.</param>
+        /// <exception cref="System.ArgumentException">
+        /// Thrown when the destination Span is shorter than the source Span.
+        /// </exception>
+        public void CopyTo(Span<T> destination)
+        {
+            // Using "if (!TryCopyTo(...))" results in two branches: one for the length
+            // check, and one for the result of TryCopyTo. Since these checks are equivalent,
+            // we can optimize by performing the check once ourselves then calling Memmove directly.
+
+            if ((uint)_length <= (uint)destination.Length)
+            {
+                Buffer.Memmove(ref destination._pointer.Value, ref _pointer.Value, (nuint)_length);
+            }
+            else
+            {
+                ThrowHelper.ThrowArgumentException_DestinationTooShort();
+            }
+        }
+
+        /// <summary>
+        /// Copies the contents of this span into destination span. If the source
+        /// and destinations overlap, this method behaves as if the original values in
+        /// a temporary location before the destination is overwritten.
+        /// </summary>
+        /// <param name="destination">The span to copy items into.</param>
+        /// <returns>If the destination span is shorter than the source span, this method
+        /// return false and no data is written to the destination.</returns>
+        public bool TryCopyTo(Span<T> destination)
+        {
+            bool retVal = false;
+            if ((uint)_length <= (uint)destination.Length)
+            {
+                Buffer.Memmove(ref destination._pointer.Value, ref _pointer.Value, (nuint)_length);
+                retVal = true;
+            }
+            return retVal;
+        }
+
+        /// <summary>
+        /// Returns true if left and right point at the same memory and have the same length.  Note that
+        /// this does *not* check to see if the *contents* are equal.
+        /// </summary>
+        public static bool operator ==(Span<T> left, Span<T> right)
+        {
+            return left._length == right._length && Unsafe.AreSame<T>(ref left._pointer.Value, ref right._pointer.Value);
+        }
+
+        /// <summary>
+        /// Defines an implicit conversion of a <see cref="Span{T}"/> to a <see cref="ReadOnlySpan{T}"/>
+        /// </summary>
+        public static implicit operator ReadOnlySpan<T>(Span<T> span) => new ReadOnlySpan<T>(ref span._pointer.Value, span._length);
+
+        /// <summary>
+        /// For <see cref="Span{Char}"/>, returns a new instance of string that represents the characters pointed to by the span.
+        /// Otherwise, returns a <see cref="String"/> with the name of the type and the number of elements.
+        /// </summary>
+        public override string ToString()
+        {
+            if (typeof(T) == typeof(char))
+            {
+                unsafe
+                {
+                    fixed (char* src = &Unsafe.As<T, char>(ref _pointer.Value))
+                        return new string(src, 0, _length);
+                }
+            }
+            return string.Format("System.Span<{0}>[{1}]", typeof(T).Name, _length);
+        }
+
+        /// <summary>
+        /// Forms a slice out of the given span, beginning at 'start'.
+        /// </summary>
+        /// <param name="start">The index at which to begin this slice.</param>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> index is not in range (&lt;0 or &gt;=Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public Span<T> Slice(int start)
+        {
+            if ((uint)start > (uint)_length)
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            return new Span<T>(ref Unsafe.Add(ref _pointer.Value, start), _length - start);
+        }
+
+        /// <summary>
+        /// Forms a slice out of the given span, beginning at 'start', of given length
+        /// </summary>
+        /// <param name="start">The index at which to begin this slice.</param>
+        /// <param name="length">The desired length for the slice (exclusive).</param>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the specified <paramref name="start"/> or end index is not in range (&lt;0 or &gt;=Length).
+        /// </exception>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public Span<T> Slice(int start, int length)
+        {
+            if ((uint)start > (uint)_length || (uint)length > (uint)(_length - start))
+                ThrowHelper.ThrowArgumentOutOfRangeException();
+
+            return new Span<T>(ref Unsafe.Add(ref _pointer.Value, start), length);
+        }
+
+        /// <summary>
+        /// Copies the contents of this span into a new array.  This heap
+        /// allocates, so should generally be avoided, however it is sometimes
+        /// necessary to bridge the gap with APIs written in terms of arrays.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public T[] ToArray()
+        {
+            if (_length == 0)
+                return Array.Empty<T>();
+
+            var destination = new T[_length];
+            Buffer.Memmove(ref Unsafe.As<byte, T>(ref destination.GetRawSzArrayData()), ref _pointer.Value, (nuint)_length);
+            return destination;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Span.cs b/src/System.Private.CoreLib/shared/System/Span.cs
new file mode 100644
index 0000000000..81288a7627
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Span.cs
@@ -0,0 +1,142 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+#if !FEATURE_PORTABLE_SPAN
+using System.Runtime.Versioning;
+#endif // !FEATURE_PORTABLE_SPAN
+
+#pragma warning disable 0809  //warning CS0809: Obsolete member 'Span<T>.Equals(object)' overrides non-obsolete member 'object.Equals(object)'
+
+namespace System
+{
+    /// <summary>
+    /// Span represents a contiguous region of arbitrary memory. Unlike arrays, it can point to either managed
+    /// or native memory, or to memory allocated on the stack. It is type- and memory-safe.
+    /// </summary>
+    [DebuggerTypeProxy(typeof(SpanDebugView<>))]
+    [DebuggerDisplay("{ToString(),raw}")]
+    public readonly ref partial struct Span<T>
+    {
+        /// <summary>
+        /// The number of items in the span.
+        /// </summary>
+        public int Length
+        {
+#if !FEATURE_PORTABLE_SPAN
+            [NonVersionable]
+#endif // !FEATURE_PORTABLE_SPAN
+            get
+            {
+                return _length;
+            }
+        }
+
+        /// <summary>
+        /// Returns true if Length is 0.
+        /// </summary>
+        public bool IsEmpty
+        {
+#if !FEATURE_PORTABLE_SPAN
+            [NonVersionable]
+#endif // !FEATURE_PORTABLE_SPAN
+            get
+            {
+                return _length == 0;
+            }
+        }
+
+        /// <summary>
+        /// Returns false if left and right point at the same memory and have the same length.  Note that
+        /// this does *not* check to see if the *contents* are equal.
+        /// </summary>
+        public static bool operator !=(Span<T> left, Span<T> right) => !(left == right);
+
+        /// <summary>
+        /// This method is not supported as spans cannot be boxed. To compare two spans, use operator==.
+        /// <exception cref="System.NotSupportedException">
+        /// Always thrown by this method.
+        /// </exception>
+        /// </summary>
+        [Obsolete("Equals() on Span will always throw an exception. Use == instead.")]
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public override bool Equals(object obj)
+        {
+            throw new NotSupportedException(SR.NotSupported_CannotCallEqualsOnSpan);
+        }
+
+        /// <summary>
+        /// This method is not supported as spans cannot be boxed.
+        /// <exception cref="System.NotSupportedException">
+        /// Always thrown by this method.
+        /// </exception>
+        /// </summary>
+        [Obsolete("GetHashCode() on Span will always throw an exception.")]
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public override int GetHashCode()
+        {
+            throw new NotSupportedException(SR.NotSupported_CannotCallGetHashCodeOnSpan);
+        }
+
+        /// <summary>
+        /// Defines an implicit conversion of an array to a <see cref="Span{T}"/>
+        /// </summary>
+        public static implicit operator Span<T>(T[] array) => new Span<T>(array);
+
+        /// <summary>
+        /// Defines an implicit conversion of a <see cref="ArraySegment{T}"/> to a <see cref="Span{T}"/>
+        /// </summary>
+        public static implicit operator Span<T>(ArraySegment<T> segment)
+            => new Span<T>(segment.Array, segment.Offset, segment.Count);
+
+        /// <summary>
+        /// Returns an empty <see cref="Span{T}"/>
+        /// </summary>
+        public static Span<T> Empty => default(Span<T>);
+
+        /// <summary>Gets an enumerator for this span.</summary>
+        public Enumerator GetEnumerator() => new Enumerator(this);
+
+        /// <summary>Enumerates the elements of a <see cref="Span{T}"/>.</summary>
+        public ref struct Enumerator
+        {
+            /// <summary>The span being enumerated.</summary>
+            private readonly Span<T> _span;
+            /// <summary>The next index to yield.</summary>
+            private int _index;
+
+            /// <summary>Initialize the enumerator.</summary>
+            /// <param name="span">The span to enumerate.</param>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            internal Enumerator(Span<T> span)
+            {
+                _span = span;
+                _index = -1;
+            }
+
+            /// <summary>Advances the enumerator to the next element of the span.</summary>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            public bool MoveNext()
+            {
+                int index = _index + 1;
+                if (index < _span.Length)
+                {
+                    _index = index;
+                    return true;
+                }
+
+                return false;
+            }
+
+            /// <summary>Gets the element at the current position of the enumerator.</summary>
+            public ref T Current
+            {
+                [MethodImpl(MethodImplOptions.AggressiveInlining)]
+                get => ref _span[_index];
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/SpanDebugView.cs b/src/System.Private.CoreLib/shared/System/SpanDebugView.cs
new file mode 100644
index 0000000000..caa12ef9ed
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/SpanDebugView.cs
@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    internal sealed class SpanDebugView<T>
+    {
+        private readonly T[] _array;
+
+        public SpanDebugView(Span<T> span)
+        {
+           _array = span.ToArray();
+        }
+
+        public SpanDebugView(ReadOnlySpan<T> span)
+        {
+            _array = span.ToArray();
+        }
+
+        [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+        public T[] Items => _array;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/SpanHelpers.BinarySearch.cs b/src/System.Private.CoreLib/shared/System/SpanHelpers.BinarySearch.cs
new file mode 100644
index 0000000000..656b864e22
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/SpanHelpers.BinarySearch.cs
@@ -0,0 +1,83 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+#if !netstandard
+using Internal.Runtime.CompilerServices;
+#endif
+
+namespace System
+{
+    internal static partial class SpanHelpers
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int BinarySearch<T, TComparable>(
+            this ReadOnlySpan<T> span, TComparable comparable)
+            where TComparable : IComparable<T>
+        {
+            if (comparable == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.comparable);
+
+            return BinarySearch(ref MemoryMarshal.GetReference(span), span.Length, comparable);
+        }
+
+        public static int BinarySearch<T, TComparable>(
+            ref T spanStart, int length, TComparable comparable) 
+            where TComparable : IComparable<T>
+        {
+            int lo = 0;
+            int hi = length - 1;
+            // If length == 0, hi == -1, and loop will not be entered
+            while (lo <= hi)
+            {
+                // PERF: `lo` or `hi` will never be negative inside the loop,
+                //       so computing median using uints is safe since we know 
+                //       `length <= int.MaxValue`, and indices are >= 0
+                //       and thus cannot overflow an uint. 
+                //       Saves one subtraction per loop compared to 
+                //       `int i = lo + ((hi - lo) >> 1);`
+                int i = (int)(((uint)hi + (uint)lo) >> 1);
+
+                int c = comparable.CompareTo(Unsafe.Add(ref spanStart, i));
+                if (c == 0)
+                {
+                    return i;
+                }
+                else if (c > 0)
+                {
+                    lo = i + 1;
+                }
+                else
+                {
+                    hi = i - 1;
+                }
+            }
+            // If none found, then a negative number that is the bitwise complement
+            // of the index of the next element that is larger than or, if there is
+            // no larger element, the bitwise complement of `length`, which
+            // is `lo` at this point.
+            return ~lo;
+        }
+
+        // Helper to allow sharing all code via IComparable<T> inlineable
+        internal struct ComparerComparable<T, TComparer> : IComparable<T>
+            where TComparer : IComparer<T>
+        {
+            readonly T _value;
+            readonly TComparer _comparer;
+
+            public ComparerComparable(T value, TComparer comparer)
+            {
+                _value = value;
+                _comparer = comparer;
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            public int CompareTo(T other) => _comparer.Compare(_value, other);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/SpanHelpers.Byte.cs b/src/System.Private.CoreLib/shared/System/SpanHelpers.Byte.cs
new file mode 100644
index 0000000000..2b91b640e2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/SpanHelpers.Byte.cs
@@ -0,0 +1,1092 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+
+#if !netstandard
+using Internal.Runtime.CompilerServices;
+#endif
+
+#if !netstandard11
+using System.Numerics;
+#endif
+
+#if netstandard
+using nuint = System.NUInt;
+#else
+#if BIT64
+using nuint = System.UInt64;
+#else
+using nuint = System.UInt32;
+#endif // BIT64
+#endif // netstandard
+
+namespace System
+{
+    internal static partial class SpanHelpers
+    {
+        public static int IndexOf(ref byte searchSpace, int searchSpaceLength, ref byte value, int valueLength)
+        {
+            Debug.Assert(searchSpaceLength >= 0);
+            Debug.Assert(valueLength >= 0);
+
+            if (valueLength == 0)
+                return 0;  // A zero-length sequence is always treated as "found" at the start of the search space.
+
+            byte valueHead = value;
+            ref byte valueTail = ref Unsafe.Add(ref value, 1);
+            int valueTailLength = valueLength - 1;
+
+            int index = 0;
+            for (; ; )
+            {
+                Debug.Assert(0 <= index && index <= searchSpaceLength); // Ensures no deceptive underflows in the computation of "remainingSearchSpaceLength".
+                int remainingSearchSpaceLength = searchSpaceLength - index - valueTailLength;
+                if (remainingSearchSpaceLength <= 0)
+                    break;  // The unsearched portion is now shorter than the sequence we're looking for. So it can't be there.
+
+                // Do a quick search for the first element of "value".
+                int relativeIndex = IndexOf(ref Unsafe.Add(ref searchSpace, index), valueHead, remainingSearchSpaceLength);
+                if (relativeIndex == -1)
+                    break;
+                index += relativeIndex;
+
+                // Found the first element of "value". See if the tail matches.
+                if (SequenceEqual(ref Unsafe.Add(ref searchSpace, index + 1), ref valueTail, valueTailLength))
+                    return index;  // The tail matched. Return a successful find.
+
+                index++;
+            }
+            return -1;
+        }
+
+        public static int IndexOfAny(ref byte searchSpace, int searchSpaceLength, ref byte value, int valueLength)
+        {
+            Debug.Assert(searchSpaceLength >= 0);
+            Debug.Assert(valueLength >= 0);
+
+            if (valueLength == 0)
+                return 0;  // A zero-length sequence is always treated as "found" at the start of the search space.
+
+            int index = -1;
+            for (int i = 0; i < valueLength; i++)
+            {
+                var tempIndex = IndexOf(ref searchSpace, Unsafe.Add(ref value, i), searchSpaceLength);
+                if ((uint)tempIndex < (uint)index)
+                {
+                    index = tempIndex;
+                    // Reduce space for search, cause we don't care if we find the search value after the index of a previously found value
+                    searchSpaceLength = tempIndex;
+
+                    if (index == 0) break;
+                }
+            }
+            return index;
+        }
+
+        public static int LastIndexOfAny(ref byte searchSpace, int searchSpaceLength, ref byte value, int valueLength)
+        {
+            Debug.Assert(searchSpaceLength >= 0);
+            Debug.Assert(valueLength >= 0);
+
+            if (valueLength == 0)
+                return 0;  // A zero-length sequence is always treated as "found" at the start of the search space.
+
+            int index = -1;
+            for (int i = 0; i < valueLength; i++)
+            {
+                var tempIndex = LastIndexOf(ref searchSpace, Unsafe.Add(ref value, i), searchSpaceLength);
+                if (tempIndex > index) index = tempIndex;
+            }
+            return index;
+        }
+
+        public static unsafe int IndexOf(ref byte searchSpace, byte value, int length)
+        {
+            Debug.Assert(length >= 0);
+
+            uint uValue = value; // Use uint for comparisons to avoid unnecessary 8->32 extensions
+            IntPtr index = (IntPtr)0; // Use IntPtr for arithmetic to avoid unnecessary 64->32->64 truncations
+            IntPtr nLength = (IntPtr)length;
+#if !netstandard11
+            if (Vector.IsHardwareAccelerated && length >= Vector<byte>.Count * 2)
+            {
+                int unaligned = (int)Unsafe.AsPointer(ref searchSpace) & (Vector<byte>.Count - 1);
+                nLength = (IntPtr)((Vector<byte>.Count - unaligned) & (Vector<byte>.Count - 1));
+            }
+        SequentialScan:
+#endif
+            while ((byte*)nLength >= (byte*)8)
+            {
+                nLength -= 8;
+
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index))
+                    goto Found;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 1))
+                    goto Found1;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 2))
+                    goto Found2;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 3))
+                    goto Found3;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 4))
+                    goto Found4;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 5))
+                    goto Found5;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 6))
+                    goto Found6;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 7))
+                    goto Found7;
+
+                index += 8;
+            }
+
+            if ((byte*)nLength >= (byte*)4)
+            {
+                nLength -= 4;
+
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index))
+                    goto Found;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 1))
+                    goto Found1;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 2))
+                    goto Found2;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 3))
+                    goto Found3;
+
+                index += 4;
+            }
+
+            while ((byte*)nLength > (byte*)0)
+            {
+                nLength -= 1;
+
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index))
+                    goto Found;
+
+                index += 1;
+            }
+#if !netstandard11
+            if (Vector.IsHardwareAccelerated && ((int)(byte*)index < length))
+            {
+                nLength = (IntPtr)((length - (int)(byte*)index) & ~(Vector<byte>.Count - 1));
+
+                // Get comparison Vector
+                Vector<byte> vComparison = GetVector(value);
+
+                while ((byte*)nLength > (byte*)index)
+                {
+                    var vMatches = Vector.Equals(vComparison, Unsafe.ReadUnaligned<Vector<byte>>(ref Unsafe.AddByteOffset(ref searchSpace, index)));
+                    if (Vector<byte>.Zero.Equals(vMatches))
+                    {
+                        index += Vector<byte>.Count;
+                        continue;
+                    }
+                    // Find offset of first match
+                    return (int)(byte*)index + LocateFirstFoundByte(vMatches);
+                }
+
+                if ((int)(byte*)index < length)
+                {
+                    nLength = (IntPtr)(length - (int)(byte*)index);
+                    goto SequentialScan;
+                }
+            }
+#endif
+            return -1;
+        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            return (int)(byte*)index;
+        Found1:
+            return (int)(byte*)(index + 1);
+        Found2:
+            return (int)(byte*)(index + 2);
+        Found3:
+            return (int)(byte*)(index + 3);
+        Found4:
+            return (int)(byte*)(index + 4);
+        Found5:
+            return (int)(byte*)(index + 5);
+        Found6:
+            return (int)(byte*)(index + 6);
+        Found7:
+            return (int)(byte*)(index + 7);
+        }
+
+        public static int LastIndexOf(ref byte searchSpace, int searchSpaceLength, ref byte value, int valueLength)
+        {
+            Debug.Assert(searchSpaceLength >= 0);
+            Debug.Assert(valueLength >= 0);
+
+            if (valueLength == 0)
+                return 0;  // A zero-length sequence is always treated as "found" at the start of the search space.
+
+            byte valueHead = value;
+            ref byte valueTail = ref Unsafe.Add(ref value, 1);
+            int valueTailLength = valueLength - 1;
+
+            int index = 0;
+            for (; ; )
+            {
+                Debug.Assert(0 <= index && index <= searchSpaceLength); // Ensures no deceptive underflows in the computation of "remainingSearchSpaceLength".
+                int remainingSearchSpaceLength = searchSpaceLength - index - valueTailLength;
+                if (remainingSearchSpaceLength <= 0)
+                    break;  // The unsearched portion is now shorter than the sequence we're looking for. So it can't be there.
+
+                // Do a quick search for the first element of "value".
+                int relativeIndex = LastIndexOf(ref searchSpace, valueHead, remainingSearchSpaceLength);
+                if (relativeIndex == -1)
+                    break;
+
+                // Found the first element of "value". See if the tail matches.
+                if (SequenceEqual(ref Unsafe.Add(ref searchSpace, relativeIndex + 1), ref valueTail, valueTailLength))
+                    return relativeIndex;  // The tail matched. Return a successful find.
+
+                index += remainingSearchSpaceLength - relativeIndex;
+            }
+            return -1;
+        }
+
+        public static unsafe int LastIndexOf(ref byte searchSpace, byte value, int length)
+        {
+            Debug.Assert(length >= 0);
+
+            uint uValue = value; // Use uint for comparisons to avoid unnecessary 8->32 extensions
+            IntPtr index = (IntPtr)length; // Use IntPtr for arithmetic to avoid unnecessary 64->32->64 truncations
+            IntPtr nLength = (IntPtr)length;
+#if !netstandard11
+            if (Vector.IsHardwareAccelerated && length >= Vector<byte>.Count * 2)
+            {
+                int unaligned = (int)Unsafe.AsPointer(ref searchSpace) & (Vector<byte>.Count - 1);
+                nLength = (IntPtr)(((length & (Vector<byte>.Count - 1)) + unaligned) & (Vector<byte>.Count - 1));
+            }
+        SequentialScan:
+#endif
+            while ((byte*)nLength >= (byte*)8)
+            {
+                nLength -= 8;
+                index -= 8;
+
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 7))
+                    goto Found7;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 6))
+                    goto Found6;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 5))
+                    goto Found5;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 4))
+                    goto Found4;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 3))
+                    goto Found3;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 2))
+                    goto Found2;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 1))
+                    goto Found1;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index))
+                    goto Found;
+            }
+
+            if ((byte*)nLength >= (byte*)4)
+            {
+                nLength -= 4;
+                index -= 4;
+
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 3))
+                    goto Found3;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 2))
+                    goto Found2;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index + 1))
+                    goto Found1;
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index))
+                    goto Found;
+            }
+
+            while ((byte*)nLength > (byte*)0)
+            {
+                nLength -= 1;
+                index -= 1;
+
+                if (uValue == Unsafe.AddByteOffset(ref searchSpace, index))
+                    goto Found;
+            }
+#if !netstandard11
+            if (Vector.IsHardwareAccelerated && ((byte*)index > (byte*)0))
+            {
+                nLength = (IntPtr)((int)(byte*)index & ~(Vector<byte>.Count - 1));
+
+                // Get comparison Vector
+                Vector<byte> vComparison = GetVector(value);
+
+                while ((byte*)nLength > (byte*)(Vector<byte>.Count - 1))
+                {
+                    var vMatches = Vector.Equals(vComparison, Unsafe.ReadUnaligned<Vector<byte>>(ref Unsafe.AddByteOffset(ref searchSpace, index - Vector<byte>.Count)));
+                    if (Vector<byte>.Zero.Equals(vMatches))
+                    {
+                        index -= Vector<byte>.Count;
+                        nLength -= Vector<byte>.Count;
+                        continue;
+                    }
+                    // Find offset of first match
+                    return (int)(index) - Vector<byte>.Count + LocateLastFoundByte(vMatches);
+                }
+                if ((byte*)index > (byte*)0)
+                {
+                    nLength = index;
+                    goto SequentialScan;
+                }
+            }
+#endif
+            return -1;
+        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            return (int)(byte*)index;
+        Found1:
+            return (int)(byte*)(index + 1);
+        Found2:
+            return (int)(byte*)(index + 2);
+        Found3:
+            return (int)(byte*)(index + 3);
+        Found4:
+            return (int)(byte*)(index + 4);
+        Found5:
+            return (int)(byte*)(index + 5);
+        Found6:
+            return (int)(byte*)(index + 6);
+        Found7:
+            return (int)(byte*)(index + 7);
+        }
+
+        public static unsafe int IndexOfAny(ref byte searchSpace, byte value0, byte value1, int length)
+        {
+            Debug.Assert(length >= 0);
+
+            uint uValue0 = value0; // Use uint for comparisons to avoid unnecessary 8->32 extensions
+            uint uValue1 = value1; // Use uint for comparisons to avoid unnecessary 8->32 extensions
+            IntPtr index = (IntPtr)0; // Use IntPtr for arithmetic to avoid unnecessary 64->32->64 truncations
+            IntPtr nLength = (IntPtr)length;
+#if !netstandard11
+            if (Vector.IsHardwareAccelerated && length >= Vector<byte>.Count * 2)
+            {
+                int unaligned = (int)Unsafe.AsPointer(ref searchSpace) & (Vector<byte>.Count - 1);
+                nLength = (IntPtr)((Vector<byte>.Count - unaligned) & (Vector<byte>.Count - 1));
+            }
+        SequentialScan:
+#endif
+            uint lookUp;
+            while ((byte*)nLength >= (byte*)8)
+            {
+                nLength -= 8;
+
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 1);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found1;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 2);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found2;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 3);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found3;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 4);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found4;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 5);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found5;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 6);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found6;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 7);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found7;
+
+                index += 8;
+            }
+
+            if ((byte*)nLength >= (byte*)4)
+            {
+                nLength -= 4;
+
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 1);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found1;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 2);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found2;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 3);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found3;
+
+                index += 4;
+            }
+
+            while ((byte*)nLength > (byte*)0)
+            {
+                nLength -= 1;
+
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found;
+
+                index += 1;
+            }
+#if !netstandard11
+            if (Vector.IsHardwareAccelerated && ((int)(byte*)index < length))
+            {
+                nLength = (IntPtr)((length - (int)(byte*)index) & ~(Vector<byte>.Count - 1));
+
+                // Get comparison Vector
+                Vector<byte> values0 = GetVector(value0);
+                Vector<byte> values1 = GetVector(value1);
+
+                while ((byte*)nLength > (byte*)index)
+                {
+                    Vector<byte> vData = Unsafe.ReadUnaligned<Vector<byte>>(ref Unsafe.AddByteOffset(ref searchSpace, index));
+                    var vMatches = Vector.BitwiseOr(
+                                    Vector.Equals(vData, values0),
+                                    Vector.Equals(vData, values1));
+                    if (Vector<byte>.Zero.Equals(vMatches))
+                    {
+                        index += Vector<byte>.Count;
+                        continue;
+                    }
+                    // Find offset of first match
+                    return (int)(byte*)index + LocateFirstFoundByte(vMatches);
+                }
+
+                if ((int)(byte*)index < length)
+                {
+                    nLength = (IntPtr)(length - (int)(byte*)index);
+                    goto SequentialScan;
+                }
+            }
+#endif
+            return -1;
+        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            return (int)(byte*)index;
+        Found1:
+            return (int)(byte*)(index + 1);
+        Found2:
+            return (int)(byte*)(index + 2);
+        Found3:
+            return (int)(byte*)(index + 3);
+        Found4:
+            return (int)(byte*)(index + 4);
+        Found5:
+            return (int)(byte*)(index + 5);
+        Found6:
+            return (int)(byte*)(index + 6);
+        Found7:
+            return (int)(byte*)(index + 7);
+        }
+
+        public static unsafe int IndexOfAny(ref byte searchSpace, byte value0, byte value1, byte value2, int length)
+        {
+            Debug.Assert(length >= 0);
+
+            uint uValue0 = value0; // Use uint for comparisons to avoid unnecessary 8->32 extensions
+            uint uValue1 = value1; // Use uint for comparisons to avoid unnecessary 8->32 extensions
+            uint uValue2 = value2; // Use uint for comparisons to avoid unnecessary 8->32 extensions
+            IntPtr index = (IntPtr)0; // Use IntPtr for arithmetic to avoid unnecessary 64->32->64 truncations
+            IntPtr nLength = (IntPtr)length;
+#if !netstandard11
+            if (Vector.IsHardwareAccelerated && length >= Vector<byte>.Count * 2)
+            {
+                int unaligned = (int)Unsafe.AsPointer(ref searchSpace) & (Vector<byte>.Count - 1);
+                nLength = (IntPtr)((Vector<byte>.Count - unaligned) & (Vector<byte>.Count - 1));
+            }
+        SequentialScan:
+#endif
+            uint lookUp;
+            while ((byte*)nLength >= (byte*)8)
+            {
+                nLength -= 8;
+
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 1);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found1;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 2);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found2;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 3);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found3;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 4);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found4;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 5);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found5;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 6);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found6;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 7);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found7;
+
+                index += 8;
+            }
+
+            if ((byte*)nLength >= (byte*)4)
+            {
+                nLength -= 4;
+
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 1);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found1;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 2);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found2;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 3);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found3;
+
+                index += 4;
+            }
+
+            while ((byte*)nLength > (byte*)0)
+            {
+                nLength -= 1;
+
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found;
+
+                index += 1;
+            }
+#if !netstandard11
+            if (Vector.IsHardwareAccelerated && ((int)(byte*)index < length))
+            {
+                nLength = (IntPtr)((length - (int)(byte*)index) & ~(Vector<byte>.Count - 1));
+
+                // Get comparison Vector
+                Vector<byte> values0 = GetVector(value0);
+                Vector<byte> values1 = GetVector(value1);
+                Vector<byte> values2 = GetVector(value2);
+
+                while ((byte*)nLength > (byte*)index)
+                {
+                    Vector<byte> vData = Unsafe.ReadUnaligned<Vector<byte>>(ref Unsafe.AddByteOffset(ref searchSpace, index));
+
+                    var vMatches = Vector.BitwiseOr(
+                                    Vector.BitwiseOr(
+                                        Vector.Equals(vData, values0),
+                                        Vector.Equals(vData, values1)),
+                                    Vector.Equals(vData, values2));
+
+                    if (Vector<byte>.Zero.Equals(vMatches))
+                    {
+                        index += Vector<byte>.Count;
+                        continue;
+                    }
+                    // Find offset of first match
+                    return (int)(byte*)index + LocateFirstFoundByte(vMatches);
+                }
+
+                if ((int)(byte*)index < length)
+                {
+                    nLength = (IntPtr)(length - (int)(byte*)index);
+                    goto SequentialScan;
+                }
+            }
+#endif
+            return -1;
+        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            return (int)(byte*)index;
+        Found1:
+            return (int)(byte*)(index + 1);
+        Found2:
+            return (int)(byte*)(index + 2);
+        Found3:
+            return (int)(byte*)(index + 3);
+        Found4:
+            return (int)(byte*)(index + 4);
+        Found5:
+            return (int)(byte*)(index + 5);
+        Found6:
+            return (int)(byte*)(index + 6);
+        Found7:
+            return (int)(byte*)(index + 7);
+        }
+
+        public static unsafe int LastIndexOfAny(ref byte searchSpace, byte value0, byte value1, int length)
+        {
+            Debug.Assert(length >= 0);
+
+            uint uValue0 = value0; // Use uint for comparisons to avoid unnecessary 8->32 extensions
+            uint uValue1 = value1; // Use uint for comparisons to avoid unnecessary 8->32 extensions
+            IntPtr index = (IntPtr)length; // Use IntPtr for arithmetic to avoid unnecessary 64->32->64 truncations
+            IntPtr nLength = (IntPtr)length;
+#if !netstandard11
+            if (Vector.IsHardwareAccelerated && length >= Vector<byte>.Count * 2)
+            {
+                int unaligned = (int)Unsafe.AsPointer(ref searchSpace) & (Vector<byte>.Count - 1);
+                nLength = (IntPtr)(((length & (Vector<byte>.Count - 1)) + unaligned) & (Vector<byte>.Count - 1));
+            }
+        SequentialScan:
+#endif
+            uint lookUp;
+            while ((byte*)nLength >= (byte*)8)
+            {
+                nLength -= 8;
+                index -= 8;
+
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 7);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found7;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 6);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found6;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 5);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found5;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 4);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found4;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 3);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found3;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 2);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found2;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 1);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found1;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found;
+            }
+
+            if ((byte*)nLength >= (byte*)4)
+            {
+                nLength -= 4;
+                index -= 4;
+
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 3);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found3;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 2);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found2;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 1);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found1;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found;
+            }
+
+            while ((byte*)nLength > (byte*)0)
+            {
+                nLength -= 1;
+                index -= 1;
+
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index);
+                if (uValue0 == lookUp || uValue1 == lookUp)
+                    goto Found;
+            }
+#if !netstandard11
+            if (Vector.IsHardwareAccelerated && ((byte*)index > (byte*)0))
+            {
+                nLength = (IntPtr)((int)(byte*)index & ~(Vector<byte>.Count - 1));
+
+                // Get comparison Vector
+                Vector<byte> values0 = GetVector(value0);
+                Vector<byte> values1 = GetVector(value1);
+
+                while ((byte*)nLength > (byte*)(Vector<byte>.Count - 1))
+                {
+                    Vector<byte> vData = Unsafe.ReadUnaligned<Vector<byte>>(ref Unsafe.AddByteOffset(ref searchSpace, index - Vector<byte>.Count));
+                    var vMatches = Vector.BitwiseOr(
+                                    Vector.Equals(vData, values0),
+                                    Vector.Equals(vData, values1));
+                    if (Vector<byte>.Zero.Equals(vMatches))
+                    {
+                        index -= Vector<byte>.Count;
+                        nLength -= Vector<byte>.Count;
+                        continue;
+                    }
+                    // Find offset of first match
+                    return (int)(index) - Vector<byte>.Count + LocateLastFoundByte(vMatches);
+                }
+
+                if ((byte*)index > (byte*)0)
+                {
+                    nLength = index;
+                    goto SequentialScan;
+                }
+            }
+#endif
+            return -1;
+        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            return (int)(byte*)index;
+        Found1:
+            return (int)(byte*)(index + 1);
+        Found2:
+            return (int)(byte*)(index + 2);
+        Found3:
+            return (int)(byte*)(index + 3);
+        Found4:
+            return (int)(byte*)(index + 4);
+        Found5:
+            return (int)(byte*)(index + 5);
+        Found6:
+            return (int)(byte*)(index + 6);
+        Found7:
+            return (int)(byte*)(index + 7);
+        }
+
+        public static unsafe int LastIndexOfAny(ref byte searchSpace, byte value0, byte value1, byte value2, int length)
+        {
+            Debug.Assert(length >= 0);
+
+            uint uValue0 = value0; // Use uint for comparisons to avoid unnecessary 8->32 extensions
+            uint uValue1 = value1; // Use uint for comparisons to avoid unnecessary 8->32 extensions
+            uint uValue2 = value2; // Use uint for comparisons to avoid unnecessary 8->32 extensions
+            IntPtr index = (IntPtr)length; // Use IntPtr for arithmetic to avoid unnecessary 64->32->64 truncations
+            IntPtr nLength = (IntPtr)length;
+#if !netstandard11
+            if (Vector.IsHardwareAccelerated && length >= Vector<byte>.Count * 2)
+            {
+                int unaligned = (int)Unsafe.AsPointer(ref searchSpace) & (Vector<byte>.Count - 1);
+                nLength = (IntPtr)(((length & (Vector<byte>.Count - 1)) + unaligned) & (Vector<byte>.Count - 1));
+            }
+        SequentialScan:
+#endif
+            uint lookUp;
+            while ((byte*)nLength >= (byte*)8)
+            {
+                nLength -= 8;
+                index -= 8;
+
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 7);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found7;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 6);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found6;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 5);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found5;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 4);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found4;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 3);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found3;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 2);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found2;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 1);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found1;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found;
+            }
+
+            if ((byte*)nLength >= (byte*)4)
+            {
+                nLength -= 4;
+                index -= 4;
+
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 3);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found3;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 2);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found2;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index + 1);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found1;
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found;
+            }
+
+            while ((byte*)nLength > (byte*)0)
+            {
+                nLength -= 1;
+                index -= 1;
+
+                lookUp = Unsafe.AddByteOffset(ref searchSpace, index);
+                if (uValue0 == lookUp || uValue1 == lookUp || uValue2 == lookUp)
+                    goto Found;
+            }
+#if !netstandard11
+            if (Vector.IsHardwareAccelerated && ((byte*)index > (byte*)0))
+            {
+                nLength = (IntPtr)((int)(byte*)index & ~(Vector<byte>.Count - 1));
+
+                // Get comparison Vector
+                Vector<byte> values0 = GetVector(value0);
+                Vector<byte> values1 = GetVector(value1);
+                Vector<byte> values2 = GetVector(value2);
+
+                while ((byte*)nLength > (byte*)(Vector<byte>.Count - 1))
+                {
+                    Vector<byte> vData = Unsafe.ReadUnaligned<Vector<byte>>(ref Unsafe.AddByteOffset(ref searchSpace, index - Vector<byte>.Count));
+
+                    var vMatches = Vector.BitwiseOr(
+                                    Vector.BitwiseOr(
+                                        Vector.Equals(vData, values0),
+                                        Vector.Equals(vData, values1)),
+                                    Vector.Equals(vData, values2));
+
+                    if (Vector<byte>.Zero.Equals(vMatches))
+                    {
+                        index -= Vector<byte>.Count;
+                        nLength -= Vector<byte>.Count;
+                        continue;
+                    }
+                    // Find offset of first match
+                    return (int)(index) - Vector<byte>.Count + LocateLastFoundByte(vMatches);
+                }
+
+                if ((byte*)index > (byte*)0)
+                {
+                    nLength = index;
+                    goto SequentialScan;
+                }
+            }
+#endif
+            return -1;
+        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            return (int)(byte*)index;
+        Found1:
+            return (int)(byte*)(index + 1);
+        Found2:
+            return (int)(byte*)(index + 2);
+        Found3:
+            return (int)(byte*)(index + 3);
+        Found4:
+            return (int)(byte*)(index + 4);
+        Found5:
+            return (int)(byte*)(index + 5);
+        Found6:
+            return (int)(byte*)(index + 6);
+        Found7:
+            return (int)(byte*)(index + 7);
+        }
+
+        // Optimized byte-based SequenceEquals. The "length" parameter for this one is declared a nuint rather than int as we also use it for types other than byte
+        // where the length can exceed 2Gb once scaled by sizeof(T).
+        public static unsafe bool SequenceEqual(ref byte first, ref byte second, nuint length)
+        {
+            if (Unsafe.AreSame(ref first, ref second))
+                goto Equal;
+
+            IntPtr i = (IntPtr)0; // Use IntPtr for arithmetic to avoid unnecessary 64->32->64 truncations
+            IntPtr n = (IntPtr)(void*)length;
+
+#if !netstandard11
+            if (Vector.IsHardwareAccelerated && (byte*)n >= (byte*)Vector<byte>.Count)
+            {
+                n -= Vector<byte>.Count;
+                while ((byte*)n > (byte*)i)
+                {
+                    if (Unsafe.ReadUnaligned<Vector<byte>>(ref Unsafe.AddByteOffset(ref first, i)) !=
+                        Unsafe.ReadUnaligned<Vector<byte>>(ref Unsafe.AddByteOffset(ref second, i)))
+                    {
+                        goto NotEqual;
+                    }
+                    i += Vector<byte>.Count;
+                }
+                return Unsafe.ReadUnaligned<Vector<byte>>(ref Unsafe.AddByteOffset(ref first, n)) ==
+                       Unsafe.ReadUnaligned<Vector<byte>>(ref Unsafe.AddByteOffset(ref second, n));
+            }
+#endif
+
+            if ((byte*)n >= (byte*)sizeof(UIntPtr))
+            {
+                n -= sizeof(UIntPtr);
+                while ((byte*)n > (byte*)i)
+                {
+                    if (Unsafe.ReadUnaligned<UIntPtr>(ref Unsafe.AddByteOffset(ref first, i)) !=
+                        Unsafe.ReadUnaligned<UIntPtr>(ref Unsafe.AddByteOffset(ref second, i)))
+                    {
+                        goto NotEqual;
+                    }
+                    i += sizeof(UIntPtr);
+                }
+                return Unsafe.ReadUnaligned<UIntPtr>(ref Unsafe.AddByteOffset(ref first, n)) ==
+                       Unsafe.ReadUnaligned<UIntPtr>(ref Unsafe.AddByteOffset(ref second, n));
+            }
+
+            while ((byte*)n > (byte*)i)
+            {
+                if (Unsafe.AddByteOffset(ref first, i) != Unsafe.AddByteOffset(ref second, i))
+                    goto NotEqual;
+                i += 1;
+            }
+
+        Equal:
+            return true;
+
+        NotEqual: // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            return false;
+        }
+
+#if !netstandard11
+        // Vector sub-search adapted from https://github.com/aspnet/KestrelHttpServer/pull/1138
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int LocateFirstFoundByte(Vector<byte> match)
+        {
+            var vector64 = Vector.AsVectorUInt64(match);
+            ulong candidate = 0;
+            int i = 0;
+            // Pattern unrolled by jit https://github.com/dotnet/coreclr/pull/8001
+            for (; i < Vector<ulong>.Count; i++)
+            {
+                candidate = vector64[i];
+                if (candidate != 0)
+                {
+                    break;
+                }
+            }
+
+            // Single LEA instruction with jitted const (using function result)
+            return i * 8 + LocateFirstFoundByte(candidate);
+        }
+#endif
+
+        public static unsafe int SequenceCompareTo(ref byte first, int firstLength, ref byte second, int secondLength)
+        {
+            Debug.Assert(firstLength >= 0);
+            Debug.Assert(secondLength >= 0);
+
+            if (Unsafe.AreSame(ref first, ref second))
+                goto Equal;
+
+            IntPtr minLength = (IntPtr)((firstLength < secondLength) ? firstLength : secondLength);
+
+            IntPtr i = (IntPtr)0; // Use IntPtr for arithmetic to avoid unnecessary 64->32->64 truncations
+            IntPtr n = (IntPtr)(void*)minLength;
+
+#if !netstandard11
+            if (Vector.IsHardwareAccelerated && (byte*)n > (byte*)Vector<byte>.Count)
+            {
+                n -= Vector<byte>.Count;
+                while ((byte*)n > (byte*)i)
+                {
+                    if (Unsafe.ReadUnaligned<Vector<byte>>(ref Unsafe.AddByteOffset(ref first, i)) !=
+                        Unsafe.ReadUnaligned<Vector<byte>>(ref Unsafe.AddByteOffset(ref second, i)))
+                    {
+                        goto NotEqual;
+                    }
+                    i += Vector<byte>.Count;
+                }
+                goto NotEqual;
+            }
+#endif
+
+            if ((byte*)n > (byte*)sizeof(UIntPtr))
+            {
+                n -= sizeof(UIntPtr);
+                while ((byte*)n > (byte*)i)
+                {
+                    if (Unsafe.ReadUnaligned<UIntPtr>(ref Unsafe.AddByteOffset(ref first, i)) !=
+                        Unsafe.ReadUnaligned<UIntPtr>(ref Unsafe.AddByteOffset(ref second, i)))
+                    {
+                        goto NotEqual;
+                    }
+                    i += sizeof(UIntPtr);
+                }
+            }
+
+        NotEqual:  // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            while ((byte*)minLength > (byte*)i)
+            {
+                int result = Unsafe.AddByteOffset(ref first, i).CompareTo(Unsafe.AddByteOffset(ref second, i));
+                if (result != 0) return result;
+                i += 1;
+            }
+
+        Equal:
+            return firstLength - secondLength;
+        }
+
+#if !netstandard11
+        // Vector sub-search adapted from https://github.com/aspnet/KestrelHttpServer/pull/1138
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int LocateLastFoundByte(Vector<byte> match)
+        {
+            var vector64 = Vector.AsVectorUInt64(match);
+            ulong candidate = 0;
+            int i = Vector<ulong>.Count - 1;
+            // Pattern unrolled by jit https://github.com/dotnet/coreclr/pull/8001
+            for (; i >= 0; i--)
+            {
+                candidate = vector64[i];
+                if (candidate != 0)
+                {
+                    break;
+                }
+            }
+
+            // Single LEA instruction with jitted const (using function result)
+            return i * 8 + LocateLastFoundByte(candidate);
+        }
+#endif
+
+#if !netstandard11
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int LocateFirstFoundByte(ulong match)
+        {
+            // Flag least significant power of two bit
+            var powerOfTwoFlag = match ^ (match - 1);
+            // Shift all powers of two into the high byte and extract
+            return (int)((powerOfTwoFlag * XorPowerOfTwoToHighByte) >> 57);
+        }
+#endif
+
+#if !netstandard11
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int LocateLastFoundByte(ulong match)
+        {
+            // Find the most significant byte that has its highest bit set
+            int index = 7;
+            while ((long)match > 0)
+            {
+                match = match << 8;
+                index--;
+            }
+            return index;
+        }
+#endif
+
+#if !netstandard11
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector<byte> GetVector(byte vectorByte)
+        {
+#if !netcoreapp
+            // Vector<byte> .ctor doesn't become an intrinsic due to detection issue
+            // However this does cause it to become an intrinsic (with additional multiply and reg->reg copy)
+            // https://github.com/dotnet/coreclr/issues/7459#issuecomment-253965670
+            return Vector.AsVectorByte(new Vector<uint>(vectorByte * 0x01010101u));
+#else
+            return new Vector<byte>(vectorByte);
+#endif
+        }
+#endif
+
+#if !netstandard11
+        private const ulong XorPowerOfTwoToHighByte = (0x07ul |
+                                                       0x06ul << 8 |
+                                                       0x05ul << 16 |
+                                                       0x04ul << 24 |
+                                                       0x03ul << 32 |
+                                                       0x02ul << 40 |
+                                                       0x01ul << 48) + 1;
+#endif
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/SpanHelpers.Char.cs b/src/System.Private.CoreLib/shared/System/SpanHelpers.Char.cs
new file mode 100644
index 0000000000..51ace58a39
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/SpanHelpers.Char.cs
@@ -0,0 +1,341 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+
+#if !netstandard
+using Internal.Runtime.CompilerServices;
+#endif
+
+#if !netstandard11
+using System.Numerics;
+#endif
+
+namespace System
+{
+    internal static partial class SpanHelpers
+    {
+        public static unsafe int SequenceCompareTo(ref char first, int firstLength, ref char second, int secondLength)
+        {
+            Debug.Assert(firstLength >= 0);
+            Debug.Assert(secondLength >= 0);
+
+            int lengthDelta = firstLength - secondLength;
+
+            if (Unsafe.AreSame(ref first, ref second))
+                goto Equal;
+
+            IntPtr minLength = (IntPtr)((firstLength < secondLength) ? firstLength : secondLength);
+            IntPtr i = (IntPtr)0; // Use IntPtr for arithmetic to avoid unnecessary 64->32->64 truncations
+
+            if ((byte*)minLength >= (byte*)(sizeof(UIntPtr) / sizeof(char)))
+            {
+#if !netstandard11
+                if (Vector.IsHardwareAccelerated && (byte*)minLength >= (byte*)Vector<ushort>.Count)
+                {
+                    IntPtr nLength = minLength - Vector<ushort>.Count;
+                    do
+                    {
+                        if (Unsafe.ReadUnaligned<Vector<ushort>>(ref Unsafe.As<char, byte>(ref Unsafe.Add(ref first, i))) !=
+                            Unsafe.ReadUnaligned<Vector<ushort>>(ref Unsafe.As<char, byte>(ref Unsafe.Add(ref second, i))))
+                        {
+                            break;
+                        }
+                        i += Vector<ushort>.Count;
+                    }
+                    while ((byte*)nLength >= (byte*)i);
+                }
+#endif
+
+                while ((byte*)minLength >= (byte*)(i + sizeof(UIntPtr) / sizeof(char)))
+                {
+                    if (Unsafe.ReadUnaligned<UIntPtr>(ref Unsafe.As<char, byte>(ref Unsafe.Add(ref first, i))) !=
+                        Unsafe.ReadUnaligned<UIntPtr>(ref Unsafe.As<char, byte>(ref Unsafe.Add(ref second, i))))
+                    {
+                        break;
+                    }
+                    i += sizeof(UIntPtr) / sizeof(char);
+                }
+            }
+
+            if (sizeof(UIntPtr) > sizeof(int) && (byte*)minLength >= (byte*)(i + sizeof(int) / sizeof(char)))
+            {
+                if (Unsafe.ReadUnaligned<int>(ref Unsafe.As<char, byte>(ref Unsafe.Add(ref first, i))) ==
+                    Unsafe.ReadUnaligned<int>(ref Unsafe.As<char, byte>(ref Unsafe.Add(ref second, i))))
+                {
+                    i += sizeof(int) / sizeof(char);
+                }
+            }
+
+            while ((byte*)i < (byte*)minLength)
+            {
+                int result = Unsafe.Add(ref first, i).CompareTo(Unsafe.Add(ref second, i));
+                if (result != 0)
+                    return result;
+                i += 1;
+            }
+
+        Equal:
+            return lengthDelta;
+        }
+
+        public static unsafe int IndexOf(ref char searchSpace, char value, int length)
+        {
+            Debug.Assert(length >= 0);
+
+            fixed (char* pChars = &searchSpace)
+            {
+                char* pCh = pChars;
+                char* pEndCh = pCh + length;
+
+#if !netstandard11
+                if (Vector.IsHardwareAccelerated && length >= Vector<ushort>.Count * 2)
+                {
+                    // Figure out how many characters to read sequentially until we are vector aligned
+                    // This is equivalent to:
+                    //         unaligned = ((int)pCh % Unsafe.SizeOf<Vector<ushort>>()) / elementsPerByte
+                    //         length = (Vector<ushort>.Count - unaligned) % Vector<ushort>.Count
+                    const int elementsPerByte = sizeof(ushort) / sizeof(byte);
+                    int unaligned = ((int)pCh & (Unsafe.SizeOf<Vector<ushort>>() - 1)) / elementsPerByte;
+                    length = (Vector<ushort>.Count - unaligned) & (Vector<ushort>.Count - 1);
+                }
+            SequentialScan:
+#endif
+                while (length >= 4)
+                {
+                    length -= 4;
+
+                    if (*pCh == value)
+                        goto Found;
+                    if (*(pCh + 1) == value)
+                        goto Found1;
+                    if (*(pCh + 2) == value)
+                        goto Found2;
+                    if (*(pCh + 3) == value)
+                        goto Found3;
+
+                    pCh += 4;
+                }
+
+                while (length > 0)
+                {
+                    length -= 1;
+
+                    if (*pCh == value)
+                        goto Found;
+
+                    pCh += 1;
+                }
+#if !netstandard11
+                // We get past SequentialScan only if IsHardwareAccelerated is true. However, we still have the redundant check to allow
+                // the JIT to see that the code is unreachable and eliminate it when the platform does not have hardware accelerated.
+                if (Vector.IsHardwareAccelerated && pCh < pEndCh)
+                {
+                    // Get the highest multiple of Vector<ushort>.Count that is within the search space.
+                    // That will be how many times we iterate in the loop below.
+                    // This is equivalent to: length = Vector<ushort>.Count * ((int)(pEndCh - pCh) / Vector<ushort>.Count)
+                    length = (int)((pEndCh - pCh) & ~(Vector<ushort>.Count - 1));
+
+                    // Get comparison Vector
+                    Vector<ushort> vComparison = new Vector<ushort>(value);
+
+                    while (length > 0)
+                    {
+                        // Using Unsafe.Read instead of ReadUnaligned since the search space is pinned and pCh is always vector aligned
+                        Debug.Assert(((int)pCh & (Unsafe.SizeOf<Vector<ushort>>() - 1)) == 0);
+                        Vector<ushort> vMatches = Vector.Equals(vComparison, Unsafe.Read<Vector<ushort>>(pCh));
+                        if (Vector<ushort>.Zero.Equals(vMatches))
+                        {
+                            pCh += Vector<ushort>.Count;
+                            length -= Vector<ushort>.Count;
+                            continue;
+                        }
+                        // Find offset of first match
+                        return (int)(pCh - pChars) + LocateFirstFoundChar(vMatches);
+                    }
+
+                    if (pCh < pEndCh)
+                    {
+                        length = (int)(pEndCh - pCh);
+                        goto SequentialScan;
+                    }
+                }
+#endif
+                return -1;
+            Found3:
+                pCh++;
+            Found2:
+                pCh++;
+            Found1:
+                pCh++;
+            Found:
+                return (int)(pCh - pChars);
+            }
+        }
+
+        public static unsafe int LastIndexOf(ref char searchSpace, char value, int length)
+        {
+            Debug.Assert(length >= 0);
+
+            fixed (char* pChars = &searchSpace)
+            {
+                char* pCh = pChars + length;
+                char* pEndCh = pChars;
+
+#if !netstandard11
+                if (Vector.IsHardwareAccelerated && length >= Vector<ushort>.Count * 2)
+                {
+                    // Figure out how many characters to read sequentially from the end until we are vector aligned
+                    // This is equivalent to: length = ((int)pCh % Unsafe.SizeOf<Vector<ushort>>()) / elementsPerByte
+                    const int elementsPerByte = sizeof(ushort) / sizeof(byte);
+                    length = ((int)pCh & (Unsafe.SizeOf<Vector<ushort>>() - 1)) / elementsPerByte;
+                }
+            SequentialScan:
+#endif
+                while (length >= 4)
+                {
+                    length -= 4;
+                    pCh -= 4;
+
+                    if (*(pCh + 3) == value)
+                        goto Found3;
+                    if (*(pCh + 2) == value)
+                        goto Found2;
+                    if (*(pCh + 1) == value)
+                        goto Found1;
+                    if (*pCh == value)
+                        goto Found;
+                }
+
+                while (length > 0)
+                {
+                    length -= 1;
+                    pCh -= 1;
+
+                    if (*pCh == value)
+                        goto Found;
+                }
+#if !netstandard11
+                // We get past SequentialScan only if IsHardwareAccelerated is true. However, we still have the redundant check to allow
+                // the JIT to see that the code is unreachable and eliminate it when the platform does not have hardware accelerated.
+                if (Vector.IsHardwareAccelerated && pCh > pEndCh)
+                {
+                    // Get the highest multiple of Vector<ushort>.Count that is within the search space.
+                    // That will be how many times we iterate in the loop below.
+                    // This is equivalent to: length = Vector<ushort>.Count * ((int)(pCh - pEndCh) / Vector<ushort>.Count)
+                    length = (int)((pCh - pEndCh) & ~(Vector<ushort>.Count - 1));
+
+                    // Get comparison Vector
+                    Vector<ushort> vComparison = new Vector<ushort>(value);
+
+                    while (length > 0)
+                    {
+                        char* pStart = pCh - Vector<ushort>.Count;
+                        // Using Unsafe.Read instead of ReadUnaligned since the search space is pinned and pCh (and hence pSart) is always vector aligned
+                        Debug.Assert(((int)pStart & (Unsafe.SizeOf<Vector<ushort>>() - 1)) == 0);
+                        Vector<ushort> vMatches = Vector.Equals(vComparison, Unsafe.Read<Vector<ushort>>(pStart));
+                        if (Vector<ushort>.Zero.Equals(vMatches))
+                        {
+                            pCh -= Vector<ushort>.Count;
+                            length -= Vector<ushort>.Count;
+                            continue;
+                        }
+                        // Find offset of last match
+                        return (int)(pStart - pEndCh) + LocateLastFoundChar(vMatches);
+                    }
+
+                    if (pCh > pEndCh)
+                    {
+                        length = (int)(pCh - pEndCh);
+                        goto SequentialScan;
+                    }
+                }
+#endif
+                return -1;
+            Found:
+                return (int)(pCh - pEndCh);
+            Found1:
+                return (int)(pCh - pEndCh) + 1;
+            Found2:
+                return (int)(pCh - pEndCh) + 2;
+            Found3:
+                return (int)(pCh - pEndCh) + 3;
+            }
+        }
+
+#if !netstandard11
+        // Vector sub-search adapted from https://github.com/aspnet/KestrelHttpServer/pull/1138
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int LocateFirstFoundChar(Vector<ushort> match)
+        {
+            var vector64 = Vector.AsVectorUInt64(match);
+            ulong candidate = 0;
+            int i = 0;
+            // Pattern unrolled by jit https://github.com/dotnet/coreclr/pull/8001
+            for (; i < Vector<ulong>.Count; i++)
+            {
+                candidate = vector64[i];
+                if (candidate != 0)
+                {
+                    break;
+                }
+            }
+
+            // Single LEA instruction with jitted const (using function result)
+            return i * 4 + LocateFirstFoundChar(candidate);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int LocateFirstFoundChar(ulong match)
+        {
+            unchecked
+            {
+                // Flag least significant power of two bit
+                var powerOfTwoFlag = match ^ (match - 1);
+                // Shift all powers of two into the high byte and extract
+                return (int)((powerOfTwoFlag * XorPowerOfTwoToHighChar) >> 49);
+            }
+        }
+
+        private const ulong XorPowerOfTwoToHighChar = (0x03ul |
+                                                       0x02ul << 16 |
+                                                       0x01ul << 32) + 1;
+
+        // Vector sub-search adapted from https://github.com/aspnet/KestrelHttpServer/pull/1138
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int LocateLastFoundChar(Vector<ushort> match)
+        {
+            var vector64 = Vector.AsVectorUInt64(match);
+            ulong candidate = 0;
+            int i = Vector<ulong>.Count - 1;
+            // Pattern unrolled by jit https://github.com/dotnet/coreclr/pull/8001
+            for (; i >= 0; i--)
+            {
+                candidate = vector64[i];
+                if (candidate != 0)
+                {
+                    break;
+                }
+            }
+
+            // Single LEA instruction with jitted const (using function result)
+            return i * 4 + LocateLastFoundChar(candidate);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int LocateLastFoundChar(ulong match)
+        {
+            // Find the most significant char that has its highest bit set
+            int index = 3;
+            while ((long)match > 0)
+            {
+                match = match << 16;
+                index--;
+            }
+            return index;
+        }
+#endif
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/SpanHelpers.T.cs b/src/System.Private.CoreLib/shared/System/SpanHelpers.T.cs
new file mode 100644
index 0000000000..4567deddb9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/SpanHelpers.T.cs
@@ -0,0 +1,686 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+
+#if !netstandard
+using Internal.Runtime.CompilerServices;
+#endif
+
+#if !netstandard11
+using System.Numerics;
+#endif
+
+namespace System
+{
+    internal static partial class SpanHelpers
+    {
+        public static int IndexOf<T>(ref T searchSpace, int searchSpaceLength, ref T value, int valueLength)
+            where T : IEquatable<T>
+        {
+            Debug.Assert(searchSpaceLength >= 0);
+            Debug.Assert(valueLength >= 0);
+
+            if (valueLength == 0)
+                return 0;  // A zero-length sequence is always treated as "found" at the start of the search space.
+
+            T valueHead = value;
+            ref T valueTail = ref Unsafe.Add(ref value, 1);
+            int valueTailLength = valueLength - 1;
+
+            int index = 0;
+            for (; ; )
+            {
+                Debug.Assert(0 <= index && index <= searchSpaceLength); // Ensures no deceptive underflows in the computation of "remainingSearchSpaceLength".
+                int remainingSearchSpaceLength = searchSpaceLength - index - valueTailLength;
+                if (remainingSearchSpaceLength <= 0)
+                    break;  // The unsearched portion is now shorter than the sequence we're looking for. So it can't be there.
+
+                // Do a quick search for the first element of "value".
+                int relativeIndex = IndexOf(ref Unsafe.Add(ref searchSpace, index), valueHead, remainingSearchSpaceLength);
+                if (relativeIndex == -1)
+                    break;
+                index += relativeIndex;
+
+                // Found the first element of "value". See if the tail matches.
+                if (SequenceEqual(ref Unsafe.Add(ref searchSpace, index + 1), ref valueTail, valueTailLength))
+                    return index;  // The tail matched. Return a successful find.
+
+                index++;
+            }
+            return -1;
+        }
+
+        public static unsafe int IndexOf<T>(ref T searchSpace, T value, int length)
+            where T : IEquatable<T>
+        {
+            Debug.Assert(length >= 0);
+
+            IntPtr index = (IntPtr)0; // Use IntPtr for arithmetic to avoid unnecessary 64->32->64 truncations
+            while (length >= 8)
+            {
+                length -= 8;
+
+                if (value.Equals(Unsafe.Add(ref searchSpace, index)))
+                    goto Found;
+                if (value.Equals(Unsafe.Add(ref searchSpace, index + 1)))
+                    goto Found1;
+                if (value.Equals(Unsafe.Add(ref searchSpace, index + 2)))
+                    goto Found2;
+                if (value.Equals(Unsafe.Add(ref searchSpace, index + 3)))
+                    goto Found3;
+                if (value.Equals(Unsafe.Add(ref searchSpace, index + 4)))
+                    goto Found4;
+                if (value.Equals(Unsafe.Add(ref searchSpace, index + 5)))
+                    goto Found5;
+                if (value.Equals(Unsafe.Add(ref searchSpace, index + 6)))
+                    goto Found6;
+                if (value.Equals(Unsafe.Add(ref searchSpace, index + 7)))
+                    goto Found7;
+
+                index += 8;
+            }
+
+            if (length >= 4)
+            {
+                length -= 4;
+
+                if (value.Equals(Unsafe.Add(ref searchSpace, index)))
+                    goto Found;
+                if (value.Equals(Unsafe.Add(ref searchSpace, index + 1)))
+                    goto Found1;
+                if (value.Equals(Unsafe.Add(ref searchSpace, index + 2)))
+                    goto Found2;
+                if (value.Equals(Unsafe.Add(ref searchSpace, index + 3)))
+                    goto Found3;
+
+                index += 4;
+            }
+
+            while (length > 0)
+            {
+                if (value.Equals(Unsafe.Add(ref searchSpace, index)))
+                    goto Found;
+
+                index += 1;
+                length--;
+            }
+            return -1;
+
+        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            return (int)(byte*)index;
+        Found1:
+            return (int)(byte*)(index + 1);
+        Found2:
+            return (int)(byte*)(index + 2);
+        Found3:
+            return (int)(byte*)(index + 3);
+        Found4:
+            return (int)(byte*)(index + 4);
+        Found5:
+            return (int)(byte*)(index + 5);
+        Found6:
+            return (int)(byte*)(index + 6);
+        Found7:
+            return (int)(byte*)(index + 7);
+        }
+
+        public static int IndexOfAny<T>(ref T searchSpace, T value0, T value1, int length)
+            where T : IEquatable<T>
+        {
+            Debug.Assert(length >= 0);
+
+            T lookUp;
+            int index = 0;
+            while ((length - index) >= 8)
+            {
+                lookUp = Unsafe.Add(ref searchSpace, index);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found;
+                lookUp = Unsafe.Add(ref searchSpace, index + 1);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found1;
+                lookUp = Unsafe.Add(ref searchSpace, index + 2);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found2;
+                lookUp = Unsafe.Add(ref searchSpace, index + 3);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found3;
+                lookUp = Unsafe.Add(ref searchSpace, index + 4);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found4;
+                lookUp = Unsafe.Add(ref searchSpace, index + 5);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found5;
+                lookUp = Unsafe.Add(ref searchSpace, index + 6);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found6;
+                lookUp = Unsafe.Add(ref searchSpace, index + 7);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found7;
+
+                index += 8;
+            }
+
+            if ((length - index) >= 4)
+            {
+                lookUp = Unsafe.Add(ref searchSpace, index);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found;
+                lookUp = Unsafe.Add(ref searchSpace, index + 1);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found1;
+                lookUp = Unsafe.Add(ref searchSpace, index + 2);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found2;
+                lookUp = Unsafe.Add(ref searchSpace, index + 3);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found3;
+
+                index += 4;
+            }
+
+            while (index < length)
+            {
+                lookUp = Unsafe.Add(ref searchSpace, index);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found;
+
+                index++;
+            }
+            return -1;
+
+        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            return index;
+        Found1:
+            return index + 1;
+        Found2:
+            return index + 2;
+        Found3:
+            return index + 3;
+        Found4:
+            return index + 4;
+        Found5:
+            return index + 5;
+        Found6:
+            return index + 6;
+        Found7:
+            return index + 7;
+        }
+
+        public static int IndexOfAny<T>(ref T searchSpace, T value0, T value1, T value2, int length)
+            where T : IEquatable<T>
+        {
+            Debug.Assert(length >= 0);
+
+            T lookUp;
+            int index = 0;
+            while ((length - index) >= 8)
+            {
+                lookUp = Unsafe.Add(ref searchSpace, index);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found;
+                lookUp = Unsafe.Add(ref searchSpace, index + 1);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found1;
+                lookUp = Unsafe.Add(ref searchSpace, index + 2);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found2;
+                lookUp = Unsafe.Add(ref searchSpace, index + 3);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found3;
+                lookUp = Unsafe.Add(ref searchSpace, index + 4);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found4;
+                lookUp = Unsafe.Add(ref searchSpace, index + 5);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found5;
+                lookUp = Unsafe.Add(ref searchSpace, index + 6);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found6;
+                lookUp = Unsafe.Add(ref searchSpace, index + 7);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found7;
+
+                index += 8;
+            }
+
+            if ((length - index) >= 4)
+            {
+                lookUp = Unsafe.Add(ref searchSpace, index);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found;
+                lookUp = Unsafe.Add(ref searchSpace, index + 1);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found1;
+                lookUp = Unsafe.Add(ref searchSpace, index + 2);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found2;
+                lookUp = Unsafe.Add(ref searchSpace, index + 3);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found3;
+
+                index += 4;
+            }
+
+            while (index < length)
+            {
+                lookUp = Unsafe.Add(ref searchSpace, index);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found;
+
+                index++;
+            }
+            return -1;
+
+        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            return index;
+        Found1:
+            return index + 1;
+        Found2:
+            return index + 2;
+        Found3:
+            return index + 3;
+        Found4:
+            return index + 4;
+        Found5:
+            return index + 5;
+        Found6:
+            return index + 6;
+        Found7:
+            return index + 7;
+        }
+
+        public static int IndexOfAny<T>(ref T searchSpace, int searchSpaceLength, ref T value, int valueLength)
+            where T : IEquatable<T>
+        {
+            Debug.Assert(searchSpaceLength >= 0);
+            Debug.Assert(valueLength >= 0);
+
+            if (valueLength == 0)
+                return 0;  // A zero-length sequence is always treated as "found" at the start of the search space.
+
+            int index = -1;
+            for (int i = 0; i < valueLength; i++)
+            {
+                var tempIndex = IndexOf(ref searchSpace, Unsafe.Add(ref value, i), searchSpaceLength);
+                if ((uint)tempIndex < (uint)index)
+                {
+                    index = tempIndex;
+                    // Reduce space for search, cause we don't care if we find the search value after the index of a previously found value
+                    searchSpaceLength = tempIndex;
+
+                    if (index == 0) break;
+                }
+            }
+            return index;
+        }
+
+        public static int LastIndexOf<T>(ref T searchSpace, int searchSpaceLength, ref T value, int valueLength)
+            where T : IEquatable<T>
+        {
+            Debug.Assert(searchSpaceLength >= 0);
+            Debug.Assert(valueLength >= 0);
+
+            if (valueLength == 0)
+                return 0;  // A zero-length sequence is always treated as "found" at the start of the search space.
+
+            T valueHead = value;
+            ref T valueTail = ref Unsafe.Add(ref value, 1);
+            int valueTailLength = valueLength - 1;
+
+            int index = 0;
+            for (; ; )
+            {
+                Debug.Assert(0 <= index && index <= searchSpaceLength); // Ensures no deceptive underflows in the computation of "remainingSearchSpaceLength".
+                int remainingSearchSpaceLength = searchSpaceLength - index - valueTailLength;
+                if (remainingSearchSpaceLength <= 0)
+                    break;  // The unsearched portion is now shorter than the sequence we're looking for. So it can't be there.
+
+                // Do a quick search for the first element of "value".
+                int relativeIndex = LastIndexOf(ref searchSpace, valueHead, remainingSearchSpaceLength);
+                if (relativeIndex == -1)
+                    break;
+
+                // Found the first element of "value". See if the tail matches.
+                if (SequenceEqual(ref Unsafe.Add(ref searchSpace, relativeIndex + 1), ref valueTail, valueTailLength))
+                    return relativeIndex;  // The tail matched. Return a successful find.
+
+                index += remainingSearchSpaceLength - relativeIndex;
+            }
+            return -1;
+        }
+
+        public static int LastIndexOf<T>(ref T searchSpace, T value, int length)
+            where T : IEquatable<T>
+        {
+            Debug.Assert(length >= 0);
+
+            while (length >= 8)
+            {
+                length -= 8;
+
+                if (value.Equals(Unsafe.Add(ref searchSpace, length + 7)))
+                    goto Found7;
+                if (value.Equals(Unsafe.Add(ref searchSpace, length + 6)))
+                    goto Found6;
+                if (value.Equals(Unsafe.Add(ref searchSpace, length + 5)))
+                    goto Found5;
+                if (value.Equals(Unsafe.Add(ref searchSpace, length + 4)))
+                    goto Found4;
+                if (value.Equals(Unsafe.Add(ref searchSpace, length + 3)))
+                    goto Found3;
+                if (value.Equals(Unsafe.Add(ref searchSpace, length + 2)))
+                    goto Found2;
+                if (value.Equals(Unsafe.Add(ref searchSpace, length + 1)))
+                    goto Found1;
+                if (value.Equals(Unsafe.Add(ref searchSpace, length)))
+                    goto Found;
+            }
+
+            if (length >= 4)
+            {
+                length -= 4;
+
+                if (value.Equals(Unsafe.Add(ref searchSpace, length + 3)))
+                    goto Found3;
+                if (value.Equals(Unsafe.Add(ref searchSpace, length + 2)))
+                    goto Found2;
+                if (value.Equals(Unsafe.Add(ref searchSpace, length + 1)))
+                    goto Found1;
+                if (value.Equals(Unsafe.Add(ref searchSpace, length)))
+                    goto Found;
+            }
+
+            while (length > 0)
+            {
+                length--;
+
+                if (value.Equals(Unsafe.Add(ref searchSpace, length)))
+                    goto Found;
+            }
+            return -1;
+
+        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            return length;
+        Found1:
+            return length + 1;
+        Found2:
+            return length + 2;
+        Found3:
+            return length + 3;
+        Found4:
+            return length + 4;
+        Found5:
+            return length + 5;
+        Found6:
+            return length + 6;
+        Found7:
+            return length + 7;
+        }
+
+        public static int LastIndexOfAny<T>(ref T searchSpace, T value0, T value1, int length)
+            where T : IEquatable<T>
+        {
+            Debug.Assert(length >= 0);
+
+            T lookUp;
+            while (length >= 8)
+            {
+                length -= 8;
+
+                lookUp = Unsafe.Add(ref searchSpace, length + 7);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found7;
+                lookUp = Unsafe.Add(ref searchSpace, length + 6);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found6;
+                lookUp = Unsafe.Add(ref searchSpace, length + 5);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found5;
+                lookUp = Unsafe.Add(ref searchSpace, length + 4);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found4;
+                lookUp = Unsafe.Add(ref searchSpace, length + 3);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found3;
+                lookUp = Unsafe.Add(ref searchSpace, length + 2);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found2;
+                lookUp = Unsafe.Add(ref searchSpace, length + 1);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found1;
+                lookUp = Unsafe.Add(ref searchSpace, length);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found;
+            }
+
+            if (length >= 4)
+            {
+                length -= 4;
+
+                lookUp = Unsafe.Add(ref searchSpace, length + 3);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found3;
+                lookUp = Unsafe.Add(ref searchSpace, length + 2);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found2;
+                lookUp = Unsafe.Add(ref searchSpace, length + 1);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found1;
+                lookUp = Unsafe.Add(ref searchSpace, length);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found;
+            }
+
+            while (length > 0)
+            {
+                length--;
+
+                lookUp = Unsafe.Add(ref searchSpace, length);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp))
+                    goto Found;
+            }
+            return -1;
+
+        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            return length;
+        Found1:
+            return length + 1;
+        Found2:
+            return length + 2;
+        Found3:
+            return length + 3;
+        Found4:
+            return length + 4;
+        Found5:
+            return length + 5;
+        Found6:
+            return length + 6;
+        Found7:
+            return length + 7;
+        }
+
+        public static int LastIndexOfAny<T>(ref T searchSpace, T value0, T value1, T value2, int length)
+            where T : IEquatable<T>
+        {
+            Debug.Assert(length >= 0);
+
+            T lookUp;
+            while (length >= 8)
+            {
+                length -= 8;
+
+                lookUp = Unsafe.Add(ref searchSpace, length + 7);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found7;
+                lookUp = Unsafe.Add(ref searchSpace, length + 6);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found6;
+                lookUp = Unsafe.Add(ref searchSpace, length + 5);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found5;
+                lookUp = Unsafe.Add(ref searchSpace, length + 4);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found4;
+                lookUp = Unsafe.Add(ref searchSpace, length + 3);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found3;
+                lookUp = Unsafe.Add(ref searchSpace, length + 2);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found2;
+                lookUp = Unsafe.Add(ref searchSpace, length + 1);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found1;
+                lookUp = Unsafe.Add(ref searchSpace, length);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found;
+            }
+
+            if (length >= 4)
+            {
+                length -= 4;
+
+                lookUp = Unsafe.Add(ref searchSpace, length + 3);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found3;
+                lookUp = Unsafe.Add(ref searchSpace, length + 2);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found2;
+                lookUp = Unsafe.Add(ref searchSpace, length + 1);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found1;
+                lookUp = Unsafe.Add(ref searchSpace, length);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found;
+            }
+
+            while (length > 0)
+            {
+                length--;
+
+                lookUp = Unsafe.Add(ref searchSpace, length);
+                if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
+                    goto Found;
+            }
+            return -1;
+
+        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            return length;
+        Found1:
+            return length + 1;
+        Found2:
+            return length + 2;
+        Found3:
+            return length + 3;
+        Found4:
+            return length + 4;
+        Found5:
+            return length + 5;
+        Found6:
+            return length + 6;
+        Found7:
+            return length + 7;
+        }
+
+        public static int LastIndexOfAny<T>(ref T searchSpace, int searchSpaceLength, ref T value, int valueLength)
+            where T : IEquatable<T>
+        {
+            Debug.Assert(searchSpaceLength >= 0);
+            Debug.Assert(valueLength >= 0);
+
+            if (valueLength == 0)
+                return 0;  // A zero-length sequence is always treated as "found" at the start of the search space.
+
+            int index = -1;
+            for (int i = 0; i < valueLength; i++)
+            {
+                var tempIndex = LastIndexOf(ref searchSpace, Unsafe.Add(ref value, i), searchSpaceLength);
+                if (tempIndex > index) index = tempIndex;
+            }
+            return index;
+        }
+
+        public static bool SequenceEqual<T>(ref T first, ref T second, int length)
+            where T : IEquatable<T>
+        {
+            Debug.Assert(length >= 0);
+
+            if (Unsafe.AreSame(ref first, ref second))
+                goto Equal;
+
+            IntPtr index = (IntPtr)0; // Use IntPtr for arithmetic to avoid unnecessary 64->32->64 truncations
+            while (length >= 8)
+            {
+                length -= 8;
+
+                if (!Unsafe.Add(ref first, index).Equals(Unsafe.Add(ref second, index)))
+                    goto NotEqual;
+                if (!Unsafe.Add(ref first, index + 1).Equals(Unsafe.Add(ref second, index + 1)))
+                    goto NotEqual;
+                if (!Unsafe.Add(ref first, index + 2).Equals(Unsafe.Add(ref second, index + 2)))
+                    goto NotEqual;
+                if (!Unsafe.Add(ref first, index + 3).Equals(Unsafe.Add(ref second, index + 3)))
+                    goto NotEqual;
+                if (!Unsafe.Add(ref first, index + 4).Equals(Unsafe.Add(ref second, index + 4)))
+                    goto NotEqual;
+                if (!Unsafe.Add(ref first, index + 5).Equals(Unsafe.Add(ref second, index + 5)))
+                    goto NotEqual;
+                if (!Unsafe.Add(ref first, index + 6).Equals(Unsafe.Add(ref second, index + 6)))
+                    goto NotEqual;
+                if (!Unsafe.Add(ref first, index + 7).Equals(Unsafe.Add(ref second, index + 7)))
+                    goto NotEqual;
+
+                index += 8;
+            }
+
+            if (length >= 4)
+            {
+                length -= 4;
+
+                if (!Unsafe.Add(ref first, index).Equals(Unsafe.Add(ref second, index)))
+                    goto NotEqual;
+                if (!Unsafe.Add(ref first, index + 1).Equals(Unsafe.Add(ref second, index + 1)))
+                    goto NotEqual;
+                if (!Unsafe.Add(ref first, index + 2).Equals(Unsafe.Add(ref second, index + 2)))
+                    goto NotEqual;
+                if (!Unsafe.Add(ref first, index + 3).Equals(Unsafe.Add(ref second, index + 3)))
+                    goto NotEqual;
+
+                index += 4;
+            }
+
+            while (length > 0)
+            {
+                if (!Unsafe.Add(ref first, index).Equals(Unsafe.Add(ref second, index)))
+                    goto NotEqual;
+                index += 1;
+                length--;
+            }
+
+        Equal:
+            return true;
+
+        NotEqual: // Workaround for https://github.com/dotnet/coreclr/issues/13549
+            return false;
+        }
+
+        public static int SequenceCompareTo<T>(ref T first, int firstLength, ref T second, int secondLength)
+            where T : IComparable<T>
+        {
+            Debug.Assert(firstLength >= 0);
+            Debug.Assert(secondLength >= 0);
+
+            var minLength = firstLength;
+            if (minLength > secondLength) minLength = secondLength;
+            for (int i = 0; i < minLength; i++)
+            {
+                int result = Unsafe.Add(ref first, i).CompareTo(Unsafe.Add(ref second, i));
+                if (result != 0) return result;
+            }
+            return firstLength.CompareTo(secondLength);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/SpanHelpers.cs b/src/System.Private.CoreLib/shared/System/SpanHelpers.cs
new file mode 100644
index 0000000000..83cdfce71a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/SpanHelpers.cs
@@ -0,0 +1,416 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime;
+using System.Runtime.InteropServices;
+
+using Internal.Runtime.CompilerServices;
+
+#if BIT64
+using nuint = System.UInt64;
+#else
+using nuint = System.UInt32;
+#endif
+
+namespace System
+{
+    internal static partial class SpanHelpers
+    {
+        public static unsafe void ClearWithoutReferences(ref byte b, nuint byteLength)
+        {
+            if (byteLength == 0)
+                return;
+
+#if CORECLR && (AMD64 || ARM64)
+            if (byteLength > 4096)
+                goto PInvoke;
+            Unsafe.InitBlockUnaligned(ref b, 0, (uint)byteLength);
+            return;
+#else
+            // TODO: Optimize other platforms to be on par with AMD64 CoreCLR
+            // Note: It's important that this switch handles lengths at least up to 22.
+            // See notes below near the main loop for why.
+
+            // The switch will be very fast since it can be implemented using a jump
+            // table in assembly. See http://stackoverflow.com/a/449297/4077294 for more info.
+
+            switch (byteLength)
+            {
+                case 1:
+                    b = 0;
+                    return;
+                case 2:
+                    Unsafe.As<byte, short>(ref b) = 0;
+                    return;
+                case 3:
+                    Unsafe.As<byte, short>(ref b) = 0;
+                    Unsafe.Add<byte>(ref b, 2) = 0;
+                    return;
+                case 4:
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    return;
+                case 5:
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.Add<byte>(ref b, 4) = 0;
+                    return;
+                case 6:
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, short>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+                    return;
+                case 7:
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, short>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+                    Unsafe.Add<byte>(ref b, 6) = 0;
+                    return;
+                case 8:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+#endif
+                    return;
+                case 9:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+#endif
+                    Unsafe.Add<byte>(ref b, 8) = 0;
+                    return;
+                case 10:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+#endif
+                    Unsafe.As<byte, short>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+                    return;
+                case 11:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+#endif
+                    Unsafe.As<byte, short>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+                    Unsafe.Add<byte>(ref b, 10) = 0;
+                    return;
+                case 12:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+#endif
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+                    return;
+                case 13:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+#endif
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+                    Unsafe.Add<byte>(ref b, 12) = 0;
+                    return;
+                case 14:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+#endif
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+                    Unsafe.As<byte, short>(ref Unsafe.Add<byte>(ref b, 12)) = 0;
+                    return;
+                case 15:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+#endif
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+                    Unsafe.As<byte, short>(ref Unsafe.Add<byte>(ref b, 12)) = 0;
+                    Unsafe.Add<byte>(ref b, 14) = 0;
+                    return;
+                case 16:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+                    Unsafe.As<byte, long>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 12)) = 0;
+#endif
+                    return;
+                case 17:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+                    Unsafe.As<byte, long>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 12)) = 0;
+#endif
+                    Unsafe.Add<byte>(ref b, 16) = 0;
+                    return;
+                case 18:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+                    Unsafe.As<byte, long>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 12)) = 0;
+#endif
+                    Unsafe.As<byte, short>(ref Unsafe.Add<byte>(ref b, 16)) = 0;
+                    return;
+                case 19:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+                    Unsafe.As<byte, long>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 12)) = 0;
+#endif
+                    Unsafe.As<byte, short>(ref Unsafe.Add<byte>(ref b, 16)) = 0;
+                    Unsafe.Add<byte>(ref b, 18) = 0;
+                    return;
+                case 20:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+                    Unsafe.As<byte, long>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 12)) = 0;
+#endif
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 16)) = 0;
+                    return;
+                case 21:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+                    Unsafe.As<byte, long>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 12)) = 0;
+#endif
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 16)) = 0;
+                    Unsafe.Add<byte>(ref b, 20) = 0;
+                    return;
+                case 22:
+#if BIT64
+                    Unsafe.As<byte, long>(ref b) = 0;
+                    Unsafe.As<byte, long>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+#else
+                    Unsafe.As<byte, int>(ref b) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 4)) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 8)) = 0;
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 12)) = 0;
+#endif
+                    Unsafe.As<byte, int>(ref Unsafe.Add<byte>(ref b, 16)) = 0;
+                    Unsafe.As<byte, short>(ref Unsafe.Add<byte>(ref b, 20)) = 0;
+                    return;
+            }
+
+            // P/Invoke into the native version for large lengths
+            if (byteLength >= 512) goto PInvoke;
+
+            nuint i = 0; // byte offset at which we're copying
+
+            if ((Unsafe.As<byte, int>(ref b) & 3) != 0)
+            {
+                if ((Unsafe.As<byte, int>(ref b) & 1) != 0)
+                {
+                    Unsafe.AddByteOffset<byte>(ref b, i) = 0;
+                    i += 1;
+                    if ((Unsafe.As<byte, int>(ref b) & 2) != 0)
+                        goto IntAligned;
+                }
+                Unsafe.As<byte, short>(ref Unsafe.AddByteOffset<byte>(ref b, i)) = 0;
+                i += 2;
+            }
+
+            IntAligned:
+
+            // On 64-bit IntPtr.Size == 8, so we want to advance to the next 8-aligned address. If
+            // (int)b % 8 is 0, 5, 6, or 7, we will already have advanced by 0, 3, 2, or 1
+            // bytes to the next aligned address (respectively), so do nothing. On the other hand,
+            // if it is 1, 2, 3, or 4 we will want to copy-and-advance another 4 bytes until
+            // we're aligned.
+            // The thing 1, 2, 3, and 4 have in common that the others don't is that if you
+            // subtract one from them, their 3rd lsb will not be set. Hence, the below check.
+
+            if (((Unsafe.As<byte, int>(ref b) - 1) & 4) == 0)
+            {
+                Unsafe.As<byte, int>(ref Unsafe.AddByteOffset<byte>(ref b, i)) = 0;
+                i += 4;
+            }
+
+            nuint end = byteLength - 16;
+            byteLength -= i; // lower 4 bits of byteLength represent how many bytes are left *after* the unrolled loop
+
+            // We know due to the above switch-case that this loop will always run 1 iteration; max
+            // bytes we clear before checking is 23 (7 to align the pointers, 16 for 1 iteration) so
+            // the switch handles lengths 0-22.
+            Debug.Assert(end >= 7 && i <= end);
+
+            // This is separated out into a different variable, so the i + 16 addition can be
+            // performed at the start of the pipeline and the loop condition does not have
+            // a dependency on the writes.
+            nuint counter;
+
+            do
+            {
+                counter = i + 16;
+
+                // This loop looks very costly since there appear to be a bunch of temporary values
+                // being created with the adds, but the jit (for x86 anyways) will convert each of
+                // these to use memory addressing operands.
+
+                // So the only cost is a bit of code size, which is made up for by the fact that
+                // we save on writes to b.
+
+#if BIT64
+                Unsafe.As<byte, long>(ref Unsafe.AddByteOffset<byte>(ref b, i)) = 0;
+                Unsafe.As<byte, long>(ref Unsafe.AddByteOffset<byte>(ref b, i + 8)) = 0;
+#else
+                Unsafe.As<byte, int>(ref Unsafe.AddByteOffset<byte>(ref b, i)) = 0;
+                Unsafe.As<byte, int>(ref Unsafe.AddByteOffset<byte>(ref b, i + 4)) = 0;
+                Unsafe.As<byte, int>(ref Unsafe.AddByteOffset<byte>(ref b, i + 8)) = 0;
+                Unsafe.As<byte, int>(ref Unsafe.AddByteOffset<byte>(ref b, i + 12)) = 0;
+#endif
+
+                i = counter;
+
+                // See notes above for why this wasn't used instead
+                // i += 16;
+            }
+            while (counter <= end);
+
+            if ((byteLength & 8) != 0)
+            {
+#if BIT64
+                Unsafe.As<byte, long>(ref Unsafe.AddByteOffset<byte>(ref b, i)) = 0;
+#else
+                Unsafe.As<byte, int>(ref Unsafe.AddByteOffset<byte>(ref b, i)) = 0;
+                Unsafe.As<byte, int>(ref Unsafe.AddByteOffset<byte>(ref b, i + 4)) = 0;
+#endif
+                i += 8;
+            }
+            if ((byteLength & 4) != 0)
+            {
+                Unsafe.As<byte, int>(ref Unsafe.AddByteOffset<byte>(ref b, i)) = 0;
+                i += 4;
+            }
+            if ((byteLength & 2) != 0)
+            {
+                Unsafe.As<byte, short>(ref Unsafe.AddByteOffset<byte>(ref b, i)) = 0;
+                i += 2;
+            }
+            if ((byteLength & 1) != 0)
+            {
+                Unsafe.AddByteOffset<byte>(ref b, i) = 0;
+                // We're not using i after this, so not needed
+                // i += 1;
+            }
+
+            return;
+#endif
+
+        PInvoke:
+            RuntimeImports.RhZeroMemory(ref b, byteLength);
+        }
+
+        public static unsafe void ClearWithReferences(ref IntPtr ip, nuint pointerSizeLength)
+        {
+            Debug.Assert((int)Unsafe.AsPointer(ref ip) % sizeof(IntPtr) == 0, "Should've been aligned on natural word boundary.");
+
+            // First write backward 8 natural words at a time.
+            // Writing backward allows us to get away with only simple modifications to the
+            // mov instruction's base and index registers between loop iterations.
+
+            for (; pointerSizeLength >= 8; pointerSizeLength -= 8)
+            {
+                Unsafe.Add(ref Unsafe.Add(ref ip, (IntPtr)pointerSizeLength), -1) = default(IntPtr);
+                Unsafe.Add(ref Unsafe.Add(ref ip, (IntPtr)pointerSizeLength), -2) = default(IntPtr);
+                Unsafe.Add(ref Unsafe.Add(ref ip, (IntPtr)pointerSizeLength), -3) = default(IntPtr);
+                Unsafe.Add(ref Unsafe.Add(ref ip, (IntPtr)pointerSizeLength), -4) = default(IntPtr);
+                Unsafe.Add(ref Unsafe.Add(ref ip, (IntPtr)pointerSizeLength), -5) = default(IntPtr);
+                Unsafe.Add(ref Unsafe.Add(ref ip, (IntPtr)pointerSizeLength), -6) = default(IntPtr);
+                Unsafe.Add(ref Unsafe.Add(ref ip, (IntPtr)pointerSizeLength), -7) = default(IntPtr);
+                Unsafe.Add(ref Unsafe.Add(ref ip, (IntPtr)pointerSizeLength), -8) = default(IntPtr);
+            }
+
+            Debug.Assert(pointerSizeLength <= 7);
+
+            // The logic below works by trying to minimize the number of branches taken for any
+            // given range of lengths. For example, the lengths [ 4 .. 7 ] are handled by a single
+            // branch, [ 2 .. 3 ] are handled by a single branch, and [ 1 ] is handled by a single
+            // branch.
+            // 
+            // We can write both forward and backward as a perf improvement. For example,
+            // the lengths [ 4 .. 7 ] can be handled by zeroing out the first four natural
+            // words and the last 3 natural words. In the best case (length = 7), there are
+            // no overlapping writes. In the worst case (length = 4), there are three
+            // overlapping writes near the middle of the buffer. In perf testing, the
+            // penalty for performing duplicate writes is less expensive than the penalty
+            // for complex branching.
+
+            if (pointerSizeLength >= 4)
+            {
+                goto Write4To7;
+            }
+            else if (pointerSizeLength >= 2)
+            {
+                goto Write2To3;
+            }
+            else if (pointerSizeLength > 0)
+            {
+                goto Write1;
+            }
+            else
+            {
+                return; // nothing to write
+            }
+
+        Write4To7:
+            Debug.Assert(pointerSizeLength >= 4);
+
+            // Write first four and last three.
+            Unsafe.Add(ref ip, 2) = default(IntPtr);
+            Unsafe.Add(ref ip, 3) = default(IntPtr);
+            Unsafe.Add(ref Unsafe.Add(ref ip, (IntPtr)pointerSizeLength), -3) = default(IntPtr);
+            Unsafe.Add(ref Unsafe.Add(ref ip, (IntPtr)pointerSizeLength), -2) = default(IntPtr);
+
+        Write2To3:
+            Debug.Assert(pointerSizeLength >= 2);
+
+            // Write first two and last one.
+            Unsafe.Add(ref ip, 1) = default(IntPtr);
+            Unsafe.Add(ref Unsafe.Add(ref ip, (IntPtr)pointerSizeLength), -1) = default(IntPtr);
+
+        Write1:
+            Debug.Assert(pointerSizeLength >= 1);
+
+            // Write only element.
+            ip = default(IntPtr);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/StackOverflowException.cs b/src/System.Private.CoreLib/shared/System/StackOverflowException.cs
new file mode 100644
index 0000000000..6f954cc75a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/StackOverflowException.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: The exception class for stack overflow.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class StackOverflowException : SystemException
+    {
+        public StackOverflowException()
+            : base(SR.Arg_StackOverflowException)
+        {
+            HResult = HResults.COR_E_STACKOVERFLOW;
+        }
+
+        public StackOverflowException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_STACKOVERFLOW;
+        }
+
+        public StackOverflowException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_STACKOVERFLOW;
+        }
+
+        internal StackOverflowException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/String.Comparison.cs b/src/System.Private.CoreLib/shared/System/String.Comparison.cs
new file mode 100644
index 0000000000..03c7cf6f3c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/String.Comparison.cs
@@ -0,0 +1,1007 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+using Internal.Runtime.CompilerServices;
+
+#if BIT64
+using nuint = System.UInt64;
+#else
+using nuint = System.UInt32;
+#endif
+
+namespace System
+{
+    public partial class String
+    {
+        private static unsafe int CompareOrdinalIgnoreCaseHelper(string strA, string strB)
+        {
+            Debug.Assert(strA != null);
+            Debug.Assert(strB != null);
+            int length = Math.Min(strA.Length, strB.Length);
+
+            fixed (char* ap = &strA._firstChar) fixed (char* bp = &strB._firstChar)
+            {
+                char* a = ap;
+                char* b = bp;
+                int charA = 0, charB = 0;
+
+                while (length != 0)
+                {
+                    charA = *a;
+                    charB = *b;
+
+                    Debug.Assert((charA | charB) <= 0x7F, "strings have to be ASCII");
+
+                    // uppercase both chars - notice that we need just one compare per char
+                    if ((uint)(charA - 'a') <= (uint)('z' - 'a')) charA -= 0x20;
+                    if ((uint)(charB - 'a') <= (uint)('z' - 'a')) charB -= 0x20;
+
+                    //Return the (case-insensitive) difference between them.
+                    if (charA != charB)
+                        return charA - charB;
+
+                    // Next char
+                    a++; b++;
+                    length--;
+                }
+
+                return strA.Length - strB.Length;
+            }
+        }
+
+        //
+        // Search/Query methods
+        //
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static bool EqualsHelper(string strA, string strB)
+        {
+            Debug.Assert(strA != null);
+            Debug.Assert(strB != null);
+            Debug.Assert(strA.Length == strB.Length);
+
+            return SpanHelpers.SequenceEqual(
+                    ref Unsafe.As<char, byte>(ref strA.GetRawStringData()),
+                    ref Unsafe.As<char, byte>(ref strB.GetRawStringData()),
+                    ((nuint)strA.Length) * 2);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int CompareOrdinalHelper(string strA, int indexA, int countA, string strB, int indexB, int countB)
+        {
+            Debug.Assert(strA != null);
+            Debug.Assert(strB != null);
+            Debug.Assert(indexA >= 0 && indexB >= 0);
+            Debug.Assert(countA >= 0 && countB >= 0);
+            Debug.Assert(indexA + countA <= strA.Length && indexB + countB <= strB.Length);
+
+            return SpanHelpers.SequenceCompareTo(ref Unsafe.Add(ref strA.GetRawStringData(), indexA), countA, ref Unsafe.Add(ref strB.GetRawStringData(), indexB), countB);
+        }
+
+        private static unsafe bool EqualsIgnoreCaseAsciiHelper(string strA, string strB)
+        {
+            Debug.Assert(strA != null);
+            Debug.Assert(strB != null);
+            Debug.Assert(strA.Length == strB.Length);
+            int length = strA.Length;
+
+            fixed (char* ap = &strA._firstChar) fixed (char* bp = &strB._firstChar)
+            {
+                char* a = ap;
+                char* b = bp;
+
+                while (length != 0)
+                {
+                    int charA = *a;
+                    int charB = *b;
+
+                    Debug.Assert((charA | charB) <= 0x7F, "strings have to be ASCII");
+
+                    // Ordinal equals or lowercase equals if the result ends up in the a-z range 
+                    if (charA == charB ||
+                       ((charA | 0x20) == (charB | 0x20) &&
+                          (uint)((charA | 0x20) - 'a') <= (uint)('z' - 'a')))
+                    {
+                        a++;
+                        b++;
+                        length--;
+                    }
+                    else
+                    {
+                        return false;
+                    }
+                }
+
+                return true;
+            }
+        }
+
+        private static unsafe int CompareOrdinalHelper(string strA, string strB)
+        {
+            Debug.Assert(strA != null);
+            Debug.Assert(strB != null);
+
+            // NOTE: This may be subject to change if eliminating the check
+            // in the callers makes them small enough to be inlined
+            Debug.Assert(strA._firstChar == strB._firstChar,
+                "For performance reasons, callers of this method should " +
+                "check/short-circuit beforehand if the first char is the same.");
+
+            int length = Math.Min(strA.Length, strB.Length);
+
+            fixed (char* ap = &strA._firstChar) fixed (char* bp = &strB._firstChar)
+            {
+                char* a = ap;
+                char* b = bp;
+
+                // Check if the second chars are different here
+                // The reason we check if _firstChar is different is because
+                // it's the most common case and allows us to avoid a method call
+                // to here.
+                // The reason we check if the second char is different is because
+                // if the first two chars the same we can increment by 4 bytes,
+                // leaving us word-aligned on both 32-bit (12 bytes into the string)
+                // and 64-bit (16 bytes) platforms.
+
+                // For empty strings, the second char will be null due to padding.
+                // The start of the string is the type pointer + string length, which
+                // takes up 8 bytes on 32-bit, 12 on x64. For empty strings the null
+                // terminator immediately follows, leaving us with an object
+                // 10/14 bytes in size. Since everything needs to be a multiple
+                // of 4/8, this will get padded and zeroed out.
+
+                // For one-char strings the second char will be the null terminator.
+
+                // NOTE: If in the future there is a way to read the second char
+                // without pinning the string (e.g. System.Runtime.CompilerServices.Unsafe
+                // is exposed to mscorlib, or a future version of C# allows inline IL),
+                // then do that and short-circuit before the fixed.
+
+                if (*(a + 1) != *(b + 1)) goto DiffOffset1;
+
+                // Since we know that the first two chars are the same,
+                // we can increment by 2 here and skip 4 bytes.
+                // This leaves us 8-byte aligned, which results
+                // on better perf for 64-bit platforms.
+                length -= 2; a += 2; b += 2;
+
+                // unroll the loop
+#if BIT64
+                while (length >= 12)
+                {
+                    if (*(long*)a != *(long*)b) goto DiffOffset0;
+                    if (*(long*)(a + 4) != *(long*)(b + 4)) goto DiffOffset4;
+                    if (*(long*)(a + 8) != *(long*)(b + 8)) goto DiffOffset8;
+                    length -= 12; a += 12; b += 12;
+                }
+#else // BIT64
+                while (length >= 10)
+                {
+                    if (*(int*)a != *(int*)b) goto DiffOffset0;
+                    if (*(int*)(a + 2) != *(int*)(b + 2)) goto DiffOffset2;
+                    if (*(int*)(a + 4) != *(int*)(b + 4)) goto DiffOffset4;
+                    if (*(int*)(a + 6) != *(int*)(b + 6)) goto DiffOffset6;
+                    if (*(int*)(a + 8) != *(int*)(b + 8)) goto DiffOffset8;
+                    length -= 10; a += 10; b += 10; 
+                }
+#endif // BIT64
+
+                // Fallback loop:
+                // go back to slower code path and do comparison on 4 bytes at a time.
+                // This depends on the fact that the String objects are
+                // always zero terminated and that the terminating zero is not included
+                // in the length. For odd string sizes, the last compare will include
+                // the zero terminator.
+                while (length > 0)
+                {
+                    if (*(int*)a != *(int*)b) goto DiffNextInt;
+                    length -= 2;
+                    a += 2;
+                    b += 2;
+                }
+
+                // At this point, we have compared all the characters in at least one string.
+                // The longer string will be larger.
+                return strA.Length - strB.Length;
+
+#if BIT64
+            DiffOffset8: a += 4; b += 4;
+            DiffOffset4: a += 4; b += 4;
+#else // BIT64
+                // Use jumps instead of falling through, since
+                // otherwise going to DiffOffset8 will involve
+                // 8 add instructions before getting to DiffNextInt
+                DiffOffset8: a += 8; b += 8; goto DiffOffset0;
+                DiffOffset6: a += 6; b += 6; goto DiffOffset0;
+                DiffOffset4: a += 2; b += 2;
+                DiffOffset2: a += 2; b += 2;
+#endif // BIT64
+
+            DiffOffset0:
+                // If we reached here, we already see a difference in the unrolled loop above
+#if BIT64
+                if (*(int*)a == *(int*)b)
+                {
+                    a += 2; b += 2;
+                }
+#endif // BIT64
+
+            DiffNextInt:
+                if (*a != *b) return *a - *b;
+
+                DiffOffset1:
+                Debug.Assert(*(a + 1) != *(b + 1), "This char must be different if we reach here!");
+                return *(a + 1) - *(b + 1);
+            }
+        }
+
+        // Provides a culture-correct string comparison. StrA is compared to StrB
+        // to determine whether it is lexicographically less, equal, or greater, and then returns
+        // either a negative integer, 0, or a positive integer; respectively.
+        //
+        public static int Compare(string strA, string strB)
+        {
+            return Compare(strA, strB, StringComparison.CurrentCulture);
+        }
+
+
+        // Provides a culture-correct string comparison. strA is compared to strB
+        // to determine whether it is lexicographically less, equal, or greater, and then a
+        // negative integer, 0, or a positive integer is returned; respectively.
+        // The case-sensitive option is set by ignoreCase
+        //
+        public static int Compare(string strA, string strB, bool ignoreCase)
+        {
+            var comparisonType = ignoreCase ? StringComparison.CurrentCultureIgnoreCase : StringComparison.CurrentCulture;
+            return Compare(strA, strB, comparisonType);
+        }
+
+
+        // Provides a more flexible function for string comparison. See StringComparison 
+        // for meaning of different comparisonType.
+        public static int Compare(string strA, string strB, StringComparison comparisonType)
+        {
+            if (object.ReferenceEquals(strA, strB))
+            {
+                CheckStringComparison(comparisonType);
+                return 0;
+            }
+
+            // They can't both be null at this point.
+            if (strA == null)
+            {
+                CheckStringComparison(comparisonType);
+                return -1;
+            }
+            if (strB == null)
+            {
+                CheckStringComparison(comparisonType);
+                return 1;
+            }
+
+            switch (comparisonType)
+            {
+                case StringComparison.CurrentCulture:
+                case StringComparison.CurrentCultureIgnoreCase:
+                    return CultureInfo.CurrentCulture.CompareInfo.Compare(strA, strB, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.InvariantCulture:
+                case StringComparison.InvariantCultureIgnoreCase:
+                    return CompareInfo.Invariant.Compare(strA, strB, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.Ordinal:
+                    // Most common case: first character is different.
+                    // Returns false for empty strings.
+                    if (strA._firstChar != strB._firstChar)
+                    {
+                        return strA._firstChar - strB._firstChar;
+                    }
+
+                    return CompareOrdinalHelper(strA, strB);
+
+                case StringComparison.OrdinalIgnoreCase:
+#if CORECLR
+                    // If both strings are ASCII strings, we can take the fast path.
+                    if (strA.IsAscii() && strB.IsAscii())
+                    {
+                        return CompareOrdinalIgnoreCaseHelper(strA, strB);
+                    }
+#endif
+                    return CompareInfo.CompareOrdinalIgnoreCase(strA, 0, strA.Length, strB, 0, strB.Length);
+
+                default:
+                    throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType));
+            }
+        }
+
+
+        // Provides a culture-correct string comparison. strA is compared to strB
+        // to determine whether it is lexicographically less, equal, or greater, and then a
+        // negative integer, 0, or a positive integer is returned; respectively.
+        //
+        public static int Compare(string strA, string strB, CultureInfo culture, CompareOptions options)
+        {
+            if (culture == null)
+            {
+                throw new ArgumentNullException(nameof(culture));
+            }
+
+            return culture.CompareInfo.Compare(strA, strB, options);
+        }
+
+
+
+        // Provides a culture-correct string comparison. strA is compared to strB
+        // to determine whether it is lexicographically less, equal, or greater, and then a
+        // negative integer, 0, or a positive integer is returned; respectively.
+        // The case-sensitive option is set by ignoreCase, and the culture is set
+        // by culture
+        //
+        public static int Compare(string strA, string strB, bool ignoreCase, CultureInfo culture)
+        {
+            var options = ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None;
+            return Compare(strA, strB, culture, options);
+        }
+
+        // Determines whether two string regions match.  The substring of strA beginning
+        // at indexA of given length is compared with the substring of strB
+        // beginning at indexB of the same length.
+        //
+        public static int Compare(string strA, int indexA, string strB, int indexB, int length)
+        {
+            // NOTE: It's important we call the boolean overload, and not the StringComparison
+            // one. The two have some subtly different behavior (see notes in the former).
+            return Compare(strA, indexA, strB, indexB, length, ignoreCase: false);
+        }
+
+        // Determines whether two string regions match.  The substring of strA beginning
+        // at indexA of given length is compared with the substring of strB
+        // beginning at indexB of the same length.  Case sensitivity is determined by the ignoreCase boolean.
+        //
+        public static int Compare(string strA, int indexA, string strB, int indexB, int length, bool ignoreCase)
+        {
+            // Ideally we would just forward to the string.Compare overload that takes
+            // a StringComparison parameter, and just pass in CurrentCulture/CurrentCultureIgnoreCase.
+            // That function will return early if an optimization can be applied, e.g. if
+            // (object)strA == strB && indexA == indexB then it will return 0 straightaway.
+            // There are a couple of subtle behavior differences that prevent us from doing so
+            // however:
+            // - string.Compare(null, -1, null, -1, -1, StringComparison.CurrentCulture) works
+            //   since that method also returns early for nulls before validation. It shouldn't
+            //   for this overload.
+            // - Since we originally forwarded to CompareInfo.Compare for all of the argument
+            //   validation logic, the ArgumentOutOfRangeExceptions thrown will contain different
+            //   parameter names.
+            // Therefore, we have to duplicate some of the logic here.
+
+            int lengthA = length;
+            int lengthB = length;
+
+            if (strA != null)
+            {
+                lengthA = Math.Min(lengthA, strA.Length - indexA);
+            }
+
+            if (strB != null)
+            {
+                lengthB = Math.Min(lengthB, strB.Length - indexB);
+            }
+
+            var options = ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None;
+            return CultureInfo.CurrentCulture.CompareInfo.Compare(strA, indexA, lengthA, strB, indexB, lengthB, options);
+        }
+
+        // Determines whether two string regions match.  The substring of strA beginning
+        // at indexA of length length is compared with the substring of strB
+        // beginning at indexB of the same length.  Case sensitivity is determined by the ignoreCase boolean,
+        // and the culture is set by culture.
+        //
+        public static int Compare(string strA, int indexA, string strB, int indexB, int length, bool ignoreCase, CultureInfo culture)
+        {
+            var options = ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None;
+            return Compare(strA, indexA, strB, indexB, length, culture, options);
+        }
+
+
+        // Determines whether two string regions match.  The substring of strA beginning
+        // at indexA of length length is compared with the substring of strB
+        // beginning at indexB of the same length.
+        //
+        public static int Compare(string strA, int indexA, string strB, int indexB, int length, CultureInfo culture, CompareOptions options)
+        {
+            if (culture == null)
+            {
+                throw new ArgumentNullException(nameof(culture));
+            }
+
+            int lengthA = length;
+            int lengthB = length;
+
+            if (strA != null)
+            {
+                lengthA = Math.Min(lengthA, strA.Length - indexA);
+            }
+
+            if (strB != null)
+            {
+                lengthB = Math.Min(lengthB, strB.Length - indexB);
+            }
+
+            return culture.CompareInfo.Compare(strA, indexA, lengthA, strB, indexB, lengthB, options);
+        }
+
+        public static int Compare(string strA, int indexA, string strB, int indexB, int length, StringComparison comparisonType)
+        {
+            CheckStringComparison(comparisonType);
+
+            if (strA == null || strB == null)
+            {
+
+                if (object.ReferenceEquals(strA, strB))
+                {
+                    // They're both null
+                    return 0;
+                }
+
+                return strA == null ? -1 : 1;
+            }
+
+            if (length < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_NegativeLength);
+            }
+
+            if (indexA < 0 || indexB < 0)
+            {
+                string paramName = indexA < 0 ? nameof(indexA) : nameof(indexB);
+                throw new ArgumentOutOfRangeException(paramName, SR.ArgumentOutOfRange_Index);
+            }
+
+            if (strA.Length - indexA < 0 || strB.Length - indexB < 0)
+            {
+                string paramName = strA.Length - indexA < 0 ? nameof(indexA) : nameof(indexB);
+                throw new ArgumentOutOfRangeException(paramName, SR.ArgumentOutOfRange_Index);
+            }
+
+            if (length == 0 || (object.ReferenceEquals(strA, strB) && indexA == indexB))
+            {
+                return 0;
+            }
+
+            int lengthA = Math.Min(length, strA.Length - indexA);
+            int lengthB = Math.Min(length, strB.Length - indexB);
+
+            switch (comparisonType)
+            {
+                case StringComparison.CurrentCulture:
+                case StringComparison.CurrentCultureIgnoreCase:
+                    return CultureInfo.CurrentCulture.CompareInfo.Compare(strA, indexA, lengthA, strB, indexB, lengthB, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.InvariantCulture:
+                case StringComparison.InvariantCultureIgnoreCase:
+                    return CompareInfo.Invariant.Compare(strA, indexA, lengthA, strB, indexB, lengthB, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.Ordinal:
+                    return CompareOrdinalHelper(strA, indexA, lengthA, strB, indexB, lengthB);
+
+                case StringComparison.OrdinalIgnoreCase:
+                    return CompareInfo.CompareOrdinalIgnoreCase(strA, indexA, lengthA, strB, indexB, lengthB);
+
+                default:
+                    throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType));
+            }
+        }
+
+        // Compares strA and strB using an ordinal (code-point) comparison.
+        //
+        public static int CompareOrdinal(string strA, string strB)
+        {
+            if (object.ReferenceEquals(strA, strB))
+            {
+                return 0;
+            }
+
+            // They can't both be null at this point.
+            if (strA == null)
+            {
+                return -1;
+            }
+            if (strB == null)
+            {
+                return 1;
+            }
+
+            // Most common case, first character is different.
+            // This will return false for empty strings.
+            if (strA._firstChar != strB._firstChar)
+            {
+                return strA._firstChar - strB._firstChar;
+            }
+
+            return CompareOrdinalHelper(strA, strB);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static int CompareOrdinal(ReadOnlySpan<char> strA, ReadOnlySpan<char> strB)
+            => SpanHelpers.SequenceCompareTo(ref MemoryMarshal.GetReference(strA), strA.Length, ref MemoryMarshal.GetReference(strB), strB.Length);
+
+        // Compares strA and strB using an ordinal (code-point) comparison.
+        //
+        public static int CompareOrdinal(string strA, int indexA, string strB, int indexB, int length)
+        {
+            if (strA == null || strB == null)
+            {
+                if (object.ReferenceEquals(strA, strB))
+                {
+                    // They're both null
+                    return 0;
+                }
+
+                return strA == null ? -1 : 1;
+            }
+
+            // COMPAT: Checking for nulls should become before the arguments are validated,
+            // but other optimizations which allow us to return early should come after.
+
+            if (length < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_NegativeCount);
+            }
+
+            if (indexA < 0 || indexB < 0)
+            {
+                string paramName = indexA < 0 ? nameof(indexA) : nameof(indexB);
+                throw new ArgumentOutOfRangeException(paramName, SR.ArgumentOutOfRange_Index);
+            }
+
+            int lengthA = Math.Min(length, strA.Length - indexA);
+            int lengthB = Math.Min(length, strB.Length - indexB);
+
+            if (lengthA < 0 || lengthB < 0)
+            {
+                string paramName = lengthA < 0 ? nameof(indexA) : nameof(indexB);
+                throw new ArgumentOutOfRangeException(paramName, SR.ArgumentOutOfRange_Index);
+            }
+
+            if (length == 0 || (object.ReferenceEquals(strA, strB) && indexA == indexB))
+            {
+                return 0;
+            }
+
+            return CompareOrdinalHelper(strA, indexA, lengthA, strB, indexB, lengthB);
+        }
+
+        // Compares this String to another String (cast as object), returning an integer that
+        // indicates the relationship. This method returns a value less than 0 if this is less than value, 0
+        // if this is equal to value, or a value greater than 0 if this is greater than value.
+        //
+        public int CompareTo(object value)
+        {
+            if (value == null)
+            {
+                return 1;
+            }
+
+            string other = value as string;
+
+            if (other == null)
+            {
+                throw new ArgumentException(SR.Arg_MustBeString);
+            }
+
+            return CompareTo(other); // will call the string-based overload
+        }
+
+        // Determines the sorting relation of StrB to the current instance.
+        //
+        public int CompareTo(string strB)
+        {
+            return string.Compare(this, strB, StringComparison.CurrentCulture);
+        }
+
+        // Determines whether a specified string is a suffix of the current instance.
+        //
+        // The case-sensitive and culture-sensitive option is set by options,
+        // and the default culture is used.
+        //        
+        public bool EndsWith(string value)
+        {
+            return EndsWith(value, StringComparison.CurrentCulture);
+        }
+
+        public bool EndsWith(string value, StringComparison comparisonType)
+        {
+            if ((object)value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            
+            if ((object)this == (object)value)
+            {
+                CheckStringComparison(comparisonType);
+                return true;
+            }
+
+            if (value.Length == 0)
+            {
+                CheckStringComparison(comparisonType);
+                return true;
+            }
+
+            switch (comparisonType)
+            {
+                case StringComparison.CurrentCulture:
+                case StringComparison.CurrentCultureIgnoreCase:
+                    return CultureInfo.CurrentCulture.CompareInfo.IsSuffix(this, value, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.InvariantCulture:
+                case StringComparison.InvariantCultureIgnoreCase:
+                    return CompareInfo.Invariant.IsSuffix(this, value, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.Ordinal:
+                    return this.Length < value.Length ? false : (CompareOrdinalHelper(this, this.Length - value.Length, value.Length, value, 0, value.Length) == 0);
+
+                case StringComparison.OrdinalIgnoreCase:
+                    return this.Length < value.Length ? false : (CompareInfo.CompareOrdinalIgnoreCase(this, this.Length - value.Length, value.Length, value, 0, value.Length) == 0);
+
+                default:
+                    throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType));
+            }
+        }
+
+        public bool EndsWith(string value, bool ignoreCase, CultureInfo culture)
+        {
+            if (null == value)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+
+            if ((object)this == (object)value)
+            {
+                return true;
+            }
+
+            CultureInfo referenceCulture = culture ?? CultureInfo.CurrentCulture;
+            return referenceCulture.CompareInfo.IsSuffix(this, value, ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None);
+        }
+
+        public bool EndsWith(char value)
+        {
+            int thisLen = Length;
+            return thisLen != 0 && this[thisLen - 1] == value;
+        }
+
+        // Determines whether two strings match.
+        public override bool Equals(object obj)
+        {
+            if (object.ReferenceEquals(this, obj))
+                return true;
+
+            string str = obj as string;
+            if (str == null)
+                return false;
+
+            if (this.Length != str.Length)
+                return false;
+
+            return EqualsHelper(this, str);
+        }
+
+        // Determines whether two strings match.
+        public bool Equals(string value)
+        {
+            if (object.ReferenceEquals(this, value))
+                return true;
+
+            // NOTE: No need to worry about casting to object here.
+            // If either side of an == comparison between strings
+            // is null, Roslyn generates a simple ceq instruction
+            // instead of calling string.op_Equality.
+            if (value == null)
+                return false;
+
+            if (this.Length != value.Length)
+                return false;
+
+            return EqualsHelper(this, value);
+        }
+
+        public bool Equals(string value, StringComparison comparisonType)
+        {
+            if ((object)this == (object)value)
+            {
+                CheckStringComparison(comparisonType);
+                return true;
+            }
+
+            if ((object)value == null)
+            {
+                CheckStringComparison(comparisonType);
+                return false;
+            }
+
+            switch (comparisonType)
+            {
+                case StringComparison.CurrentCulture:
+                case StringComparison.CurrentCultureIgnoreCase:
+                    return (CultureInfo.CurrentCulture.CompareInfo.Compare(this, value, GetCaseCompareOfComparisonCulture(comparisonType)) == 0);
+
+                case StringComparison.InvariantCulture:
+                case StringComparison.InvariantCultureIgnoreCase:
+                    return (CompareInfo.Invariant.Compare(this, value, GetCaseCompareOfComparisonCulture(comparisonType)) == 0);
+
+                case StringComparison.Ordinal:
+                    if (this.Length != value.Length)
+                        return false;
+                    return EqualsHelper(this, value);
+
+                case StringComparison.OrdinalIgnoreCase:
+                    if (this.Length != value.Length)
+                        return false;
+#if CORECLR
+                    // If both strings are ASCII strings, we can take the fast path.
+                    if (this.IsAscii() && value.IsAscii())
+                    {
+                        return EqualsIgnoreCaseAsciiHelper(this, value);
+                    }
+#endif
+                    return (CompareInfo.CompareOrdinalIgnoreCase(this, 0, this.Length, value, 0, value.Length) == 0);
+
+                default:
+                    throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType));
+            }
+        }
+
+
+        // Determines whether two Strings match.
+        public static bool Equals(string a, string b)
+        {
+            if ((object)a == (object)b)
+            {
+                return true;
+            }
+
+            if ((object)a == null || (object)b == null || a.Length != b.Length)
+            {
+                return false;
+            }
+
+            return EqualsHelper(a, b);
+        }
+
+        public static bool Equals(string a, string b, StringComparison comparisonType)
+        {
+            if ((object)a == (object)b)
+            {
+                CheckStringComparison(comparisonType);
+                return true;
+            }
+
+            if ((object)a == null || (object)b == null)
+            {
+                CheckStringComparison(comparisonType);
+                return false;
+            }
+
+            switch (comparisonType)
+            {
+                case StringComparison.CurrentCulture:
+                case StringComparison.CurrentCultureIgnoreCase:
+                    return (CultureInfo.CurrentCulture.CompareInfo.Compare(a, b, GetCaseCompareOfComparisonCulture(comparisonType)) == 0);
+
+                case StringComparison.InvariantCulture:
+                case StringComparison.InvariantCultureIgnoreCase:
+                    return (CompareInfo.Invariant.Compare(a, b, GetCaseCompareOfComparisonCulture(comparisonType)) == 0);
+
+                case StringComparison.Ordinal:
+                    if (a.Length != b.Length)
+                        return false;
+                    return EqualsHelper(a, b);
+
+                case StringComparison.OrdinalIgnoreCase:
+                    if (a.Length != b.Length)
+                        return false;
+#if CORECLR
+                    // If both strings are ASCII strings, we can take the fast path.
+                    if (a.IsAscii() && b.IsAscii())
+                    {
+                        return EqualsIgnoreCaseAsciiHelper(a, b);
+                    }
+#endif
+                    return (CompareInfo.CompareOrdinalIgnoreCase(a, 0, a.Length, b, 0, b.Length) == 0);
+
+                default:
+                    throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType));
+            }
+        }
+
+        public static bool operator ==(string a, string b)
+        {
+            return string.Equals(a, b);
+        }
+
+        public static bool operator !=(string a, string b)
+        {
+            return !string.Equals(a, b);
+        }
+
+        // Gets a hash code for this string.  If strings A and B are such that A.Equals(B), then
+        // they will return the same hash code.
+        public override int GetHashCode()
+        {
+            return Marvin.ComputeHash32(ref Unsafe.As<char, byte>(ref _firstChar), _stringLength * 2, Marvin.DefaultSeed);
+        }
+
+        // Gets a hash code for this string and this comparison. If strings A and B and comparison C are such
+        // that string.Equals(A, B, C), then they will return the same hash code with this comparison C.
+        public int GetHashCode(StringComparison comparisonType) => StringComparer.FromComparison(comparisonType).GetHashCode(this);
+
+        // Use this if and only if you need the hashcode to not change across app domains (e.g. you have an app domain agile
+        // hash table).
+        internal int GetLegacyNonRandomizedHashCode()
+        {
+            unsafe
+            {
+                fixed (char* src = &_firstChar)
+                {
+                    Debug.Assert(src[this.Length] == '\0', "src[this.Length] == '\\0'");
+                    Debug.Assert(((int)src) % 4 == 0, "Managed string should start at 4 bytes boundary");
+#if BIT64
+                    int hash1 = 5381;
+#else // !BIT64 (32)
+                    int hash1 = (5381<<16) + 5381;
+#endif
+                    int hash2 = hash1;
+
+#if BIT64
+                    int c;
+                    char* s = src;
+                    while ((c = s[0]) != 0)
+                    {
+                        hash1 = ((hash1 << 5) + hash1) ^ c;
+                        c = s[1];
+                        if (c == 0)
+                            break;
+                        hash2 = ((hash2 << 5) + hash2) ^ c;
+                        s += 2;
+                    }
+#else // !BIT64 (32)
+                    // 32 bit machines.
+                    int* pint = (int *)src;
+                    int len = this.Length;
+                    while (len > 2)
+                    {
+                        hash1 = ((hash1 << 5) + hash1 + (hash1 >> 27)) ^ pint[0];
+                        hash2 = ((hash2 << 5) + hash2 + (hash2 >> 27)) ^ pint[1];
+                        pint += 2;
+                        len  -= 4;
+                    }
+
+                    if (len > 0)
+                    {
+                        hash1 = ((hash1 << 5) + hash1 + (hash1 >> 27)) ^ pint[0];
+                    }
+#endif
+                    return hash1 + (hash2 * 1566083941);
+                }
+            }
+        }
+
+        // Determines whether a specified string is a prefix of the current instance
+        //
+        public bool StartsWith(string value)
+        {
+            if ((object)value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return StartsWith(value, StringComparison.CurrentCulture);
+        }
+
+        public bool StartsWith(string value, StringComparison comparisonType)
+        {
+            if ((object)value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+
+            if ((object)this == (object)value)
+            {
+                CheckStringComparison(comparisonType);
+                return true;
+            }
+
+            if (value.Length == 0)
+            {
+                CheckStringComparison(comparisonType);
+                return true;
+            }
+
+            switch (comparisonType)
+            {
+                case StringComparison.CurrentCulture:
+                case StringComparison.CurrentCultureIgnoreCase:
+                    return CultureInfo.CurrentCulture.CompareInfo.IsPrefix(this, value, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.InvariantCulture:
+                case StringComparison.InvariantCultureIgnoreCase:
+                    return CompareInfo.Invariant.IsPrefix(this, value, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.Ordinal:
+                    if (this.Length < value.Length || _firstChar != value._firstChar)
+                    {
+                        return false;
+                    }
+                    return (value.Length == 1) ?
+                            true :                 // First char is the same and thats all there is to compare
+                            SpanHelpers.SequenceEqual(
+                                ref Unsafe.As<char, byte>(ref this.GetRawStringData()),
+                                ref Unsafe.As<char, byte>(ref value.GetRawStringData()),
+                                ((nuint)value.Length) * 2);
+
+                case StringComparison.OrdinalIgnoreCase:
+                    if (this.Length < value.Length)
+                    {
+                        return false;
+                    }
+                    return (CompareInfo.CompareOrdinalIgnoreCase(this, 0, value.Length, value, 0, value.Length) == 0);
+
+                default:
+                    throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType));
+            }
+        }
+
+        public bool StartsWith(string value, bool ignoreCase, CultureInfo culture)
+        {
+            if (null == value)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+
+            if ((object)this == (object)value)
+            {
+                return true;
+            }
+
+            CultureInfo referenceCulture = culture ?? CultureInfo.CurrentCulture;
+            return referenceCulture.CompareInfo.IsPrefix(this, value, ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None);
+        }
+
+        public bool StartsWith(char value) => Length != 0 && _firstChar == value;
+
+        internal static void CheckStringComparison(StringComparison comparisonType)
+        {
+            // Single comparison to check if comparisonType is within [CurrentCulture .. OrdinalIgnoreCase]
+            if ((uint)comparisonType > (uint)StringComparison.OrdinalIgnoreCase)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.NotSupported_StringComparison, ExceptionArgument.comparisonType);
+            }
+        }
+
+        internal static CompareOptions GetCaseCompareOfComparisonCulture(StringComparison comparisonType)
+        {
+            Debug.Assert((uint)comparisonType <= (uint)StringComparison.OrdinalIgnoreCase);
+
+            // Culture enums can be & with CompareOptions.IgnoreCase 0x01 to extract if IgnoreCase or CompareOptions.None 0x00
+            //
+            // CompareOptions.None                          0x00
+            // CompareOptions.IgnoreCase                    0x01
+            //
+            // StringComparison.CurrentCulture:             0x00
+            // StringComparison.InvariantCulture:           0x02
+            // StringComparison.Ordinal                     0x04
+            //
+            // StringComparison.CurrentCultureIgnoreCase:   0x01
+            // StringComparison.InvariantCultureIgnoreCase: 0x03
+            // StringComparison.OrdinalIgnoreCase           0x05
+
+            return (CompareOptions)((int)comparisonType & (int)CompareOptions.IgnoreCase);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/String.Manipulation.cs b/src/System.Private.CoreLib/shared/System/String.Manipulation.cs
new file mode 100644
index 0000000000..5face0764a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/String.Manipulation.cs
@@ -0,0 +1,1848 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Buffers;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Text;
+using Internal.Runtime.CompilerServices;
+
+namespace System
+{
+    public partial class String
+    {
+        private const int StackallocIntBufferSizeLimit = 128;
+
+        private static unsafe void FillStringChecked(string dest, int destPos, string src)
+        {
+            Debug.Assert(dest != null);
+            Debug.Assert(src != null);
+            if (src.Length > dest.Length - destPos)
+            {
+                throw new IndexOutOfRangeException();
+            }
+
+            fixed (char* pDest = &dest._firstChar)
+            fixed (char* pSrc = &src._firstChar)
+            {
+                wstrcpy(pDest + destPos, pSrc, src.Length);
+            }
+        }
+
+        public static string Concat(object arg0)
+        {
+            if (arg0 == null)
+            {
+                return string.Empty;
+            }
+            return arg0.ToString();
+        }
+
+        public static string Concat(object arg0, object arg1)
+        {
+            if (arg0 == null)
+            {
+                arg0 = string.Empty;
+            }
+
+            if (arg1 == null)
+            {
+                arg1 = string.Empty;
+            }
+            return Concat(arg0.ToString(), arg1.ToString());
+        }
+
+        public static string Concat(object arg0, object arg1, object arg2)
+        {
+            if (arg0 == null)
+            {
+                arg0 = string.Empty;
+            }
+
+            if (arg1 == null)
+            {
+                arg1 = string.Empty;
+            }
+
+            if (arg2 == null)
+            {
+                arg2 = string.Empty;
+            }
+
+            return Concat(arg0.ToString(), arg1.ToString(), arg2.ToString());
+        }
+
+        public static string Concat(params object[] args)
+        {
+            if (args == null)
+            {
+                throw new ArgumentNullException(nameof(args));
+            }
+
+            if (args.Length <= 1)
+            {
+                return args.Length == 0 ?
+                    string.Empty :
+                    args[0]?.ToString() ?? string.Empty;
+            }
+
+            // We need to get an intermediary string array
+            // to fill with each of the args' ToString(),
+            // and then just concat that in one operation.
+
+            // This way we avoid any intermediary string representations,
+            // or buffer resizing if we use StringBuilder (although the
+            // latter case is partially alleviated due to StringBuilder's
+            // linked-list style implementation)
+
+            var strings = new string[args.Length];
+
+            int totalLength = 0;
+
+            for (int i = 0; i < args.Length; i++)
+            {
+                object value = args[i];
+
+                string toString = value?.ToString() ?? string.Empty; // We need to handle both the cases when value or value.ToString() is null
+                strings[i] = toString;
+
+                totalLength += toString.Length;
+
+                if (totalLength < 0) // Check for a positive overflow
+                {
+                    throw new OutOfMemoryException();
+                }
+            }
+
+            // If all of the ToStrings are null/empty, just return string.Empty
+            if (totalLength == 0)
+            {
+                return string.Empty;
+            }
+
+            string result = FastAllocateString(totalLength);
+            int position = 0; // How many characters we've copied so far
+
+            for (int i = 0; i < strings.Length; i++)
+            {
+                string s = strings[i];
+
+                Debug.Assert(s != null);
+                Debug.Assert(position <= totalLength - s.Length, "We didn't allocate enough space for the result string!");
+
+                FillStringChecked(result, position, s);
+                position += s.Length;
+            }
+
+            return result;
+        }
+
+        public static string Concat<T>(IEnumerable<T> values)
+        {
+            if (values == null)
+                throw new ArgumentNullException(nameof(values));
+
+            if (typeof(T) == typeof(char))
+            {
+                // Special-case T==char, as we can handle that case much more efficiently,
+                // and string.Concat(IEnumerable<char>) can be used as an efficient
+                // enumerable-based equivalent of new string(char[]).
+                using (IEnumerator<char> en = Unsafe.As<IEnumerable<char>>(values).GetEnumerator())
+                {
+                    if (!en.MoveNext())
+                    {
+                        // There weren't any chars.  Return the empty string.
+                        return Empty;
+                    }
+
+                    char c = en.Current; // save the first char
+
+                    if (!en.MoveNext())
+                    {
+                        // There was only one char.  Return a string from it directly.
+                        return CreateFromChar(c);
+                    }
+
+                    // Create the StringBuilder, add the chars we've already enumerated,
+                    // add the rest, and then get the resulting string.
+                    StringBuilder result = StringBuilderCache.Acquire();
+                    result.Append(c); // first value
+                    do
+                    {
+                        c = en.Current;
+                        result.Append(c);
+                    }
+                    while (en.MoveNext());
+                    return StringBuilderCache.GetStringAndRelease(result);
+                }
+            }
+            else
+            {
+                using (IEnumerator<T> en = values.GetEnumerator())
+                {
+                    if (!en.MoveNext())
+                        return string.Empty;
+
+                    // We called MoveNext once, so this will be the first item
+                    T currentValue = en.Current;
+
+                    // Call ToString before calling MoveNext again, since
+                    // we want to stay consistent with the below loop
+                    // Everything should be called in the order
+                    // MoveNext-Current-ToString, unless further optimizations
+                    // can be made, to avoid breaking changes
+                    string firstString = currentValue?.ToString();
+
+                    // If there's only 1 item, simply call ToString on that
+                    if (!en.MoveNext())
+                    {
+                        // We have to handle the case of either currentValue
+                        // or its ToString being null
+                        return firstString ?? string.Empty;
+                    }
+
+                    StringBuilder result = StringBuilderCache.Acquire();
+
+                    result.Append(firstString);
+
+                    do
+                    {
+                        currentValue = en.Current;
+
+                        if (currentValue != null)
+                        {
+                            result.Append(currentValue.ToString());
+                        }
+                    }
+                    while (en.MoveNext());
+
+                    return StringBuilderCache.GetStringAndRelease(result);
+                }
+            }
+        }
+
+        public static string Concat(IEnumerable<string> values)
+        {
+            if (values == null)
+                throw new ArgumentNullException(nameof(values));
+
+            using (IEnumerator<string> en = values.GetEnumerator())
+            {
+                if (!en.MoveNext())
+                    return string.Empty;
+
+                string firstValue = en.Current;
+
+                if (!en.MoveNext())
+                {
+                    return firstValue ?? string.Empty;
+                }
+
+                StringBuilder result = StringBuilderCache.Acquire();
+                result.Append(firstValue);
+
+                do
+                {
+                    result.Append(en.Current);
+                }
+                while (en.MoveNext());
+
+                return StringBuilderCache.GetStringAndRelease(result);
+            }
+        }
+
+        public static string Concat(string str0, string str1)
+        {
+            if (IsNullOrEmpty(str0))
+            {
+                if (IsNullOrEmpty(str1))
+                {
+                    return string.Empty;
+                }
+                return str1;
+            }
+
+            if (IsNullOrEmpty(str1))
+            {
+                return str0;
+            }
+
+            int str0Length = str0.Length;
+
+            string result = FastAllocateString(str0Length + str1.Length);
+
+            FillStringChecked(result, 0, str0);
+            FillStringChecked(result, str0Length, str1);
+
+            return result;
+        }
+
+        public static string Concat(string str0, string str1, string str2)
+        {
+            if (IsNullOrEmpty(str0))
+            {
+                return Concat(str1, str2);
+            }
+
+            if (IsNullOrEmpty(str1))
+            {
+                return Concat(str0, str2);
+            }
+
+            if (IsNullOrEmpty(str2))
+            {
+                return Concat(str0, str1);
+            }
+
+            int totalLength = str0.Length + str1.Length + str2.Length;
+
+            string result = FastAllocateString(totalLength);
+            FillStringChecked(result, 0, str0);
+            FillStringChecked(result, str0.Length, str1);
+            FillStringChecked(result, str0.Length + str1.Length, str2);
+
+            return result;
+        }
+
+        public static string Concat(string str0, string str1, string str2, string str3)
+        {
+            if (IsNullOrEmpty(str0))
+            {
+                return Concat(str1, str2, str3);
+            }
+
+            if (IsNullOrEmpty(str1))
+            {
+                return Concat(str0, str2, str3);
+            }
+
+            if (IsNullOrEmpty(str2))
+            {
+                return Concat(str0, str1, str3);
+            }
+
+            if (IsNullOrEmpty(str3))
+            {
+                return Concat(str0, str1, str2);
+            }
+
+            int totalLength = str0.Length + str1.Length + str2.Length + str3.Length;
+
+            string result = FastAllocateString(totalLength);
+            FillStringChecked(result, 0, str0);
+            FillStringChecked(result, str0.Length, str1);
+            FillStringChecked(result, str0.Length + str1.Length, str2);
+            FillStringChecked(result, str0.Length + str1.Length + str2.Length, str3);
+
+            return result;
+        }
+
+        public static string Concat(params string[] values)
+        {
+            if (values == null)
+                throw new ArgumentNullException(nameof(values));
+
+            if (values.Length <= 1)
+            {
+                return values.Length == 0 ?
+                    string.Empty :
+                    values[0] ?? string.Empty;
+            }
+
+            // It's possible that the input values array could be changed concurrently on another
+            // thread, such that we can't trust that each read of values[i] will be equivalent.
+            // Worst case, we can make a defensive copy of the array and use that, but we first
+            // optimistically try the allocation and copies assuming that the array isn't changing,
+            // which represents the 99.999% case, in particular since string.Concat is used for
+            // string concatenation by the languages, with the input array being a params array.
+
+            // Sum the lengths of all input strings
+            long totalLengthLong = 0;
+            for (int i = 0; i < values.Length; i++)
+            {
+                string value = values[i];
+                if (value != null)
+                {
+                    totalLengthLong += value.Length;
+                }
+            }
+
+            // If it's too long, fail, or if it's empty, return an empty string.
+            if (totalLengthLong > int.MaxValue)
+            {
+                throw new OutOfMemoryException();
+            }
+            int totalLength = (int)totalLengthLong;
+            if (totalLength == 0)
+            {
+                return string.Empty;
+            }
+
+            // Allocate a new string and copy each input string into it
+            string result = FastAllocateString(totalLength);
+            int copiedLength = 0;
+            for (int i = 0; i < values.Length; i++)
+            {
+                string value = values[i];
+                if (!string.IsNullOrEmpty(value))
+                {
+                    int valueLen = value.Length;
+                    if (valueLen > totalLength - copiedLength)
+                    {
+                        copiedLength = -1;
+                        break;
+                    }
+
+                    FillStringChecked(result, copiedLength, value);
+                    copiedLength += valueLen;
+                }
+            }
+
+            // If we copied exactly the right amount, return the new string.  Otherwise,
+            // something changed concurrently to mutate the input array: fall back to
+            // doing the concatenation again, but this time with a defensive copy. This
+            // fall back should be extremely rare.
+            return copiedLength == totalLength ? result : Concat((string[])values.Clone());
+        }
+
+        public static string Format(string format, object arg0)
+        {
+            return FormatHelper(null, format, new ParamsArray(arg0));
+        }
+
+        public static string Format(string format, object arg0, object arg1)
+        {
+            return FormatHelper(null, format, new ParamsArray(arg0, arg1));
+        }
+
+        public static string Format(string format, object arg0, object arg1, object arg2)
+        {
+            return FormatHelper(null, format, new ParamsArray(arg0, arg1, arg2));
+        }
+
+        public static string Format(string format, params object[] args)
+        {
+            if (args == null)
+            {
+                // To preserve the original exception behavior, throw an exception about format if both
+                // args and format are null. The actual null check for format is in FormatHelper.
+                throw new ArgumentNullException((format == null) ? nameof(format) : nameof(args));
+            }
+
+            return FormatHelper(null, format, new ParamsArray(args));
+        }
+
+        public static string Format(IFormatProvider provider, string format, object arg0)
+        {
+            return FormatHelper(provider, format, new ParamsArray(arg0));
+        }
+
+        public static string Format(IFormatProvider provider, string format, object arg0, object arg1)
+        {
+            return FormatHelper(provider, format, new ParamsArray(arg0, arg1));
+        }
+
+        public static string Format(IFormatProvider provider, string format, object arg0, object arg1, object arg2)
+        {
+            return FormatHelper(provider, format, new ParamsArray(arg0, arg1, arg2));
+        }
+
+        public static string Format(IFormatProvider provider, string format, params object[] args)
+        {
+            if (args == null)
+            {
+                // To preserve the original exception behavior, throw an exception about format if both
+                // args and format are null. The actual null check for format is in FormatHelper.
+                throw new ArgumentNullException((format == null) ? nameof(format) : nameof(args));
+            }
+
+            return FormatHelper(provider, format, new ParamsArray(args));
+        }
+
+        private static string FormatHelper(IFormatProvider provider, string format, ParamsArray args)
+        {
+            if (format == null)
+                throw new ArgumentNullException(nameof(format));
+
+            return StringBuilderCache.GetStringAndRelease(
+                StringBuilderCache
+                    .Acquire(format.Length + args.Length * 8)
+                    .AppendFormatHelper(provider, format, args));
+        }
+
+        public string Insert(int startIndex, string value)
+        {
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+            if (startIndex < 0 || startIndex > this.Length)
+                throw new ArgumentOutOfRangeException(nameof(startIndex));
+
+            int oldLength = Length;
+            int insertLength = value.Length;
+
+            if (oldLength == 0)
+                return value;
+            if (insertLength == 0)
+                return this;
+
+            // In case this computation overflows, newLength will be negative and FastAllocateString throws OutOfMemoryException
+            int newLength = oldLength + insertLength;
+            string result = FastAllocateString(newLength);
+            unsafe
+            {
+                fixed (char* srcThis = &_firstChar)
+                {
+                    fixed (char* srcInsert = &value._firstChar)
+                    {
+                        fixed (char* dst = &result._firstChar)
+                        {
+                            wstrcpy(dst, srcThis, startIndex);
+                            wstrcpy(dst + startIndex, srcInsert, insertLength);
+                            wstrcpy(dst + startIndex + insertLength, srcThis + startIndex, oldLength - startIndex);
+                        }
+                    }
+                }
+            }
+            return result;
+        }
+
+        public static string Join(char separator, params string[] value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+
+            return Join(separator, value, 0, value.Length);
+        }
+
+        public static unsafe string Join(char separator, params object[] values)
+        {
+            // Defer argument validation to the internal function
+            return JoinCore(&separator, 1, values);
+        }
+
+        public static unsafe string Join<T>(char separator, IEnumerable<T> values)
+        {
+            // Defer argument validation to the internal function
+            return JoinCore(&separator, 1, values);
+        }
+
+        public static unsafe string Join(char separator, string[] value, int startIndex, int count)
+        {
+            // Defer argument validation to the internal function
+            return JoinCore(&separator, 1, value, startIndex, count);
+        }
+
+        // Joins an array of strings together as one string with a separator between each original string.
+        //
+        public static string Join(string separator, params string[] value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return Join(separator, value, 0, value.Length);
+        }
+
+        public static unsafe string Join(string separator, params object[] values)
+        {
+            separator = separator ?? string.Empty;
+            fixed (char* pSeparator = &separator._firstChar)
+            {
+                // Defer argument validation to the internal function
+                return JoinCore(pSeparator, separator.Length, values);
+            }
+        }
+
+        public static unsafe string Join<T>(string separator, IEnumerable<T> values)
+        {
+            separator = separator ?? string.Empty;
+            fixed (char* pSeparator = &separator._firstChar)
+            {
+                // Defer argument validation to the internal function
+                return JoinCore(pSeparator, separator.Length, values);
+            }
+        }
+
+        public static string Join(string separator, IEnumerable<string> values)
+        {
+            if (values == null)
+            {
+                throw new ArgumentNullException(nameof(values));
+            }
+
+            using (IEnumerator<string> en = values.GetEnumerator())
+            {
+                if (!en.MoveNext())
+                {
+                    return string.Empty;
+                }
+
+                string firstValue = en.Current;
+
+                if (!en.MoveNext())
+                {
+                    // Only one value available
+                    return firstValue ?? string.Empty;
+                }
+
+                // Null separator and values are handled by the StringBuilder
+                StringBuilder result = StringBuilderCache.Acquire();
+                result.Append(firstValue);
+
+                do
+                {
+                    result.Append(separator);
+                    result.Append(en.Current);
+                }
+                while (en.MoveNext());
+
+                return StringBuilderCache.GetStringAndRelease(result);
+            }
+        }
+
+        // Joins an array of strings together as one string with a separator between each original string.
+        //
+        public static unsafe string Join(string separator, string[] value, int startIndex, int count)
+        {
+            separator = separator ?? string.Empty;
+            fixed (char* pSeparator = &separator._firstChar)
+            {
+                // Defer argument validation to the internal function
+                return JoinCore(pSeparator, separator.Length, value, startIndex, count);
+            }
+        }
+
+        private static unsafe string JoinCore(char* separator, int separatorLength, object[] values)
+        {
+            if (values == null)
+            {
+                throw new ArgumentNullException(nameof(values));
+            }
+
+            if (values.Length == 0)
+            {
+                return string.Empty;
+            }
+
+            string firstString = values[0]?.ToString();
+
+            if (values.Length == 1)
+            {
+                return firstString ?? string.Empty;
+            }
+
+            StringBuilder result = StringBuilderCache.Acquire();
+            result.Append(firstString);
+
+            for (int i = 1; i < values.Length; i++)
+            {
+                result.Append(separator, separatorLength);
+                object value = values[i];
+                if (value != null)
+                {
+                    result.Append(value.ToString());
+                }
+            }
+
+            return StringBuilderCache.GetStringAndRelease(result);
+        }
+
+        private static unsafe string JoinCore<T>(char* separator, int separatorLength, IEnumerable<T> values)
+        {
+            if (values == null)
+            {
+                throw new ArgumentNullException(nameof(values));
+            }
+
+            using (IEnumerator<T> en = values.GetEnumerator())
+            {
+                if (!en.MoveNext())
+                {
+                    return string.Empty;
+                }
+
+                // We called MoveNext once, so this will be the first item
+                T currentValue = en.Current;
+
+                // Call ToString before calling MoveNext again, since
+                // we want to stay consistent with the below loop
+                // Everything should be called in the order
+                // MoveNext-Current-ToString, unless further optimizations
+                // can be made, to avoid breaking changes
+                string firstString = currentValue?.ToString();
+
+                // If there's only 1 item, simply call ToString on that
+                if (!en.MoveNext())
+                {
+                    // We have to handle the case of either currentValue
+                    // or its ToString being null
+                    return firstString ?? string.Empty;
+                }
+
+                StringBuilder result = StringBuilderCache.Acquire();
+
+                result.Append(firstString);
+
+                do
+                {
+                    currentValue = en.Current;
+
+                    result.Append(separator, separatorLength);
+                    if (currentValue != null)
+                    {
+                        result.Append(currentValue.ToString());
+                    }
+                }
+                while (en.MoveNext());
+
+                return StringBuilderCache.GetStringAndRelease(result);
+            }
+        }
+
+        private static unsafe string JoinCore(char* separator, int separatorLength, string[] value, int startIndex, int count)
+        {
+            // If the separator is null, it is converted to an empty string before entering this function.
+            // Even for empty strings, fixed should never return null (it should return a pointer to a null char).
+            Debug.Assert(separator != null);
+            Debug.Assert(separatorLength >= 0);
+
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            if (startIndex < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndex);
+            }
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NegativeCount);
+            }
+            if (startIndex > value.Length - count)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_IndexCountBuffer);
+            }
+
+            if (count <= 1)
+            {
+                return count == 0 ?
+                    string.Empty :
+                    value[startIndex] ?? string.Empty;
+            }
+
+            long totalSeparatorsLength = (long)(count - 1) * separatorLength;
+            if (totalSeparatorsLength > int.MaxValue)
+            {
+                throw new OutOfMemoryException();
+            }
+            int totalLength = (int)totalSeparatorsLength;
+
+            // Calculate the length of the resultant string so we know how much space to allocate.
+            for (int i = startIndex, end = startIndex + count; i < end; i++)
+            {
+                string currentValue = value[i];
+                if (currentValue != null)
+                {
+                    totalLength += currentValue.Length;
+                    if (totalLength < 0) // Check for overflow
+                    {
+                        throw new OutOfMemoryException();
+                    }
+                }
+            }
+
+            // Copy each of the strings into the resultant buffer, interleaving with the separator.
+            string result = FastAllocateString(totalLength);
+            int copiedLength = 0;
+
+            for (int i = startIndex, end = startIndex + count; i < end; i++)
+            {
+                // It's possible that another thread may have mutated the input array
+                // such that our second read of an index will not be the same string
+                // we got during the first read.
+
+                // We range check again to avoid buffer overflows if this happens.
+
+                string currentValue = value[i];
+                if (currentValue != null)
+                {
+                    int valueLen = currentValue.Length;
+                    if (valueLen > totalLength - copiedLength)
+                    {
+                        copiedLength = -1;
+                        break;
+                    }
+
+                    // Fill in the value.
+                    FillStringChecked(result, copiedLength, currentValue);
+                    copiedLength += valueLen;
+                }
+
+                if (i < end - 1)
+                {
+                    // Fill in the separator.
+                    fixed (char* pResult = &result._firstChar)
+                    {
+                        // If we are called from the char-based overload, we will not
+                        // want to call MemoryCopy each time we fill in the separator. So
+                        // specialize for 1-length separators.
+                        if (separatorLength == 1)
+                        {
+                            pResult[copiedLength] = *separator;
+                        }
+                        else
+                        {
+                            wstrcpy(pResult + copiedLength, separator, separatorLength);
+                        }
+                    }
+                    copiedLength += separatorLength;
+                }
+            }
+
+            // If we copied exactly the right amount, return the new string.  Otherwise,
+            // something changed concurrently to mutate the input array: fall back to
+            // doing the concatenation again, but this time with a defensive copy. This
+            // fall back should be extremely rare.
+            return copiedLength == totalLength ?
+                result :
+                JoinCore(separator, separatorLength, (string[])value.Clone(), startIndex, count);
+        }
+
+        public string PadLeft(int totalWidth) => PadLeft(totalWidth, ' ');
+
+        public string PadLeft(int totalWidth, char paddingChar)
+        {
+            if (totalWidth < 0)
+                throw new ArgumentOutOfRangeException(nameof(totalWidth), SR.ArgumentOutOfRange_NeedNonNegNum);
+            int oldLength = Length;
+            int count = totalWidth - oldLength;
+            if (count <= 0)
+                return this;
+            string result = FastAllocateString(totalWidth);
+            unsafe
+            {
+                fixed (char* dst = &result._firstChar)
+                {
+                    for (int i = 0; i < count; i++)
+                        dst[i] = paddingChar;
+                    fixed (char* src = &_firstChar)
+                    {
+                        wstrcpy(dst + count, src, oldLength);
+                    }
+                }
+            }
+            return result;
+        }
+
+        public string PadRight(int totalWidth) => PadRight(totalWidth, ' ');
+
+        public string PadRight(int totalWidth, char paddingChar)
+        {
+            if (totalWidth < 0)
+                throw new ArgumentOutOfRangeException(nameof(totalWidth), SR.ArgumentOutOfRange_NeedNonNegNum);
+            int oldLength = Length;
+            int count = totalWidth - oldLength;
+            if (count <= 0)
+                return this;
+            string result = FastAllocateString(totalWidth);
+            unsafe
+            {
+                fixed (char* dst = &result._firstChar)
+                {
+                    fixed (char* src = &_firstChar)
+                    {
+                        wstrcpy(dst, src, oldLength);
+                    }
+                    for (int i = 0; i < count; i++)
+                        dst[oldLength + i] = paddingChar;
+                }
+            }
+            return result;
+        }
+
+        public string Remove(int startIndex, int count)
+        {
+            if (startIndex < 0)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndex);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NegativeCount);
+            int oldLength = this.Length;
+            if (count > oldLength - startIndex)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_IndexCount);
+
+            if (count == 0)
+                return this;
+            int newLength = oldLength - count;
+            if (newLength == 0)
+                return string.Empty;
+
+            string result = FastAllocateString(newLength);
+            unsafe
+            {
+                fixed (char* src = &_firstChar)
+                {
+                    fixed (char* dst = &result._firstChar)
+                    {
+                        wstrcpy(dst, src, startIndex);
+                        wstrcpy(dst + startIndex, src + startIndex + count, newLength - startIndex);
+                    }
+                }
+            }
+            return result;
+        }
+
+        // a remove that just takes a startindex.
+        public string Remove(int startIndex)
+        {
+            if (startIndex < 0)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndex);
+
+            if (startIndex >= Length)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndexLessThanLength);
+
+            return Substring(0, startIndex);
+        }
+
+        public string Replace(string oldValue, string newValue, bool ignoreCase, CultureInfo culture)
+        {
+            return ReplaceCore(oldValue, newValue, culture, ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None);
+        }
+
+        public string Replace(string oldValue, string newValue, StringComparison comparisonType)
+        {
+            switch (comparisonType)
+            {
+                case StringComparison.CurrentCulture:
+                case StringComparison.CurrentCultureIgnoreCase:
+                    return ReplaceCore(oldValue, newValue, CultureInfo.CurrentCulture, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.InvariantCulture:
+                case StringComparison.InvariantCultureIgnoreCase:
+                    return ReplaceCore(oldValue, newValue, CultureInfo.InvariantCulture, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.Ordinal:
+                    return Replace(oldValue, newValue);
+
+                case StringComparison.OrdinalIgnoreCase:
+                    return ReplaceCore(oldValue, newValue, CultureInfo.InvariantCulture, CompareOptions.OrdinalIgnoreCase);
+
+                default:
+                    throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType));
+            }
+        }
+
+        private unsafe string ReplaceCore(string oldValue, string newValue, CultureInfo culture, CompareOptions options)
+        {
+            if (oldValue == null)
+                throw new ArgumentNullException(nameof(oldValue));
+            if (oldValue.Length == 0)
+                throw new ArgumentException(SR.Argument_StringZeroLength, nameof(oldValue));
+
+            // If they asked to replace oldValue with a null, replace all occurrences
+            // with the empty string.
+            if (newValue == null)
+                newValue = string.Empty;
+
+            CultureInfo referenceCulture = culture ?? CultureInfo.CurrentCulture;
+            StringBuilder result = StringBuilderCache.Acquire();
+
+            int startIndex = 0;
+            int index = 0;
+
+            int matchLength = 0;
+
+            bool hasDoneAnyReplacements = false;
+            CompareInfo ci = referenceCulture.CompareInfo;
+
+            do
+            {
+                index = ci.IndexOf(this, oldValue, startIndex, this.Length - startIndex, options, &matchLength);
+                if (index >= 0)
+                {
+                    // append the unmodified portion of string
+                    result.Append(this, startIndex, index - startIndex);
+
+                    // append the replacement
+                    result.Append(newValue);
+
+                    startIndex = index + matchLength;
+                    hasDoneAnyReplacements = true;
+                }
+                else if (!hasDoneAnyReplacements)
+                {
+                    // small optimization,
+                    // if we have not done any replacements,
+                    // we will return the original string
+                    StringBuilderCache.Release(result);
+                    return this;
+                }
+                else
+                {
+                    result.Append(this, startIndex, this.Length - startIndex);
+                }
+            } while (index >= 0);
+
+            return StringBuilderCache.GetStringAndRelease(result);
+        }
+
+        // Replaces all instances of oldChar with newChar.
+        //
+        public string Replace(char oldChar, char newChar)
+        {
+            if (oldChar == newChar)
+                return this;
+
+            unsafe
+            {
+                int remainingLength = Length;
+
+                fixed (char* pChars = &_firstChar)
+                {
+                    char* pSrc = pChars;
+
+                    while (remainingLength > 0)
+                    {
+                        if (*pSrc == oldChar)
+                        {
+                            break;
+                        }
+
+                        remainingLength--;
+                        pSrc++;
+                    }
+                }
+
+                if (remainingLength == 0)
+                    return this;
+
+                string result = FastAllocateString(Length);
+
+                fixed (char* pChars = &_firstChar)
+                {
+                    fixed (char* pResult = &result._firstChar)
+                    {
+                        int copyLength = Length - remainingLength;
+
+                        //Copy the characters already proven not to match.
+                        if (copyLength > 0)
+                        {
+                            wstrcpy(pResult, pChars, copyLength);
+                        }
+
+                        //Copy the remaining characters, doing the replacement as we go.
+                        char* pSrc = pChars + copyLength;
+                        char* pDst = pResult + copyLength;
+
+                        do
+                        {
+                            char currentChar = *pSrc;
+                            if (currentChar == oldChar)
+                                currentChar = newChar;
+                            *pDst = currentChar;
+
+                            remainingLength--;
+                            pSrc++;
+                            pDst++;
+                        } while (remainingLength > 0);
+                    }
+                }
+
+                return result;
+            }
+        }
+
+        public string Replace(string oldValue, string newValue)
+        {
+            if (oldValue == null)
+                throw new ArgumentNullException(nameof(oldValue));
+            if (oldValue.Length == 0)
+                throw new ArgumentException(SR.Argument_StringZeroLength, nameof(oldValue));
+
+            // Api behavior: if newValue is null, instances of oldValue are to be removed.
+            if (newValue == null)
+                newValue = string.Empty;
+
+            Span<int> initialSpan = stackalloc int[StackallocIntBufferSizeLimit];
+            var replacementIndices = new ValueListBuilder<int>(initialSpan);
+
+            unsafe
+            {
+                fixed (char* pThis = &_firstChar)
+                {
+                    int matchIdx = 0;
+                    int lastPossibleMatchIdx = this.Length - oldValue.Length;
+                    while (matchIdx <= lastPossibleMatchIdx)
+                    {
+                        char* pMatch = pThis + matchIdx;
+                        for (int probeIdx = 0; probeIdx < oldValue.Length; probeIdx++)
+                        {
+                            if (pMatch[probeIdx] != oldValue[probeIdx])
+                            {
+                                goto Next;
+                            }
+                        }
+                        // Found a match for the string. Record the location of the match and skip over the "oldValue."
+                        replacementIndices.Append(matchIdx);
+                        matchIdx += oldValue.Length;
+                        continue;
+
+                    Next:
+                        matchIdx++;
+                    }
+                }
+            }
+
+            if (replacementIndices.Length == 0)
+                return this;
+
+            // String allocation and copying is in separate method to make this method faster for the case where
+            // nothing needs replacing.
+            string dst = ReplaceHelper(oldValue.Length, newValue, replacementIndices.AsSpan());
+
+            replacementIndices.Dispose();
+
+            return dst;
+        }
+
+        private string ReplaceHelper(int oldValueLength, string newValue, ReadOnlySpan<int> indices)
+        {
+            Debug.Assert(indices.Length > 0);
+
+            long dstLength = this.Length + ((long)(newValue.Length - oldValueLength)) * indices.Length;
+            if (dstLength > int.MaxValue)
+                throw new OutOfMemoryException();
+            string dst = FastAllocateString((int)dstLength);
+
+            Span<char> dstSpan = new Span<char>(ref dst.GetRawStringData(), dst.Length);
+
+            int thisIdx = 0;
+            int dstIdx = 0;
+
+            for (int r = 0; r < indices.Length; r++)
+            {
+                int replacementIdx = indices[r];
+
+                // Copy over the non-matching portion of the original that precedes this occurrence of oldValue.
+                int count = replacementIdx - thisIdx;
+                if (count != 0)
+                {
+                    this.AsSpan(thisIdx, count).CopyTo(dstSpan.Slice(dstIdx));
+                    dstIdx += count;
+                }
+                thisIdx = replacementIdx + oldValueLength;
+
+                // Copy over newValue to replace the oldValue.
+                newValue.AsSpan().CopyTo(dstSpan.Slice(dstIdx));
+                dstIdx += newValue.Length;
+            }
+
+            // Copy over the final non-matching portion at the end of the string.
+            Debug.Assert(this.Length - thisIdx == dstSpan.Length - dstIdx);
+            this.AsSpan(thisIdx).CopyTo(dstSpan.Slice(dstIdx));
+
+            return dst;
+        }
+
+        public string[] Split(char separator, StringSplitOptions options = StringSplitOptions.None)
+        {
+            return SplitInternal(new ReadOnlySpan<char>(ref separator, 1), int.MaxValue, options);
+        }
+
+        public string[] Split(char separator, int count, StringSplitOptions options = StringSplitOptions.None)
+        {
+            return SplitInternal(new ReadOnlySpan<char>(ref separator, 1), count, options);
+        }
+
+        // Creates an array of strings by splitting this string at each
+        // occurrence of a separator.  The separator is searched for, and if found,
+        // the substring preceding the occurrence is stored as the first element in
+        // the array of strings.  We then continue in this manner by searching
+        // the substring that follows the occurrence.  On the other hand, if the separator
+        // is not found, the array of strings will contain this instance as its only element.
+        // If the separator is null
+        // whitespace (i.e., Character.IsWhitespace) is used as the separator.
+        //
+        public string[] Split(params char[] separator)
+        {
+            return SplitInternal(separator, int.MaxValue, StringSplitOptions.None);
+        }
+
+        // Creates an array of strings by splitting this string at each
+        // occurrence of a separator.  The separator is searched for, and if found,
+        // the substring preceding the occurrence is stored as the first element in
+        // the array of strings.  We then continue in this manner by searching
+        // the substring that follows the occurrence.  On the other hand, if the separator
+        // is not found, the array of strings will contain this instance as its only element.
+        // If the separator is the empty string (i.e., string.Empty), then
+        // whitespace (i.e., Character.IsWhitespace) is used as the separator.
+        // If there are more than count different strings, the last n-(count-1)
+        // elements are concatenated and added as the last string.
+        //
+        public string[] Split(char[] separator, int count)
+        {
+            return SplitInternal(separator, count, StringSplitOptions.None);
+        }
+
+        public string[] Split(char[] separator, StringSplitOptions options)
+        {
+            return SplitInternal(separator, int.MaxValue, options);
+        }
+
+        public string[] Split(char[] separator, int count, StringSplitOptions options)
+        {
+            return SplitInternal(separator, count, options);
+        }
+
+        private string[] SplitInternal(ReadOnlySpan<char> separators, int count, StringSplitOptions options)
+        {
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count),
+                    SR.ArgumentOutOfRange_NegativeCount);
+
+            if (options < StringSplitOptions.None || options > StringSplitOptions.RemoveEmptyEntries)
+                throw new ArgumentException(SR.Format(SR.Arg_EnumIllegalVal, options));
+
+            bool omitEmptyEntries = (options == StringSplitOptions.RemoveEmptyEntries);
+
+            if ((count == 0) || (omitEmptyEntries && Length == 0))
+            {
+                return Array.Empty<string>();
+            }
+
+            if (count == 1)
+            {
+                return new string[] { this };
+            }
+
+            Span<int> initialSpan = stackalloc int[StackallocIntBufferSizeLimit];
+            var sepListBuilder = new ValueListBuilder<int>(initialSpan);
+
+            MakeSeparatorList(separators, ref sepListBuilder);
+            ReadOnlySpan<int> sepList = sepListBuilder.AsSpan();
+
+            // Handle the special case of no replaces.
+            if (sepList.Length == 0)
+            {
+                return new string[] { this };
+            }
+
+            string[] result = omitEmptyEntries
+                ? SplitOmitEmptyEntries(sepList, default, 1, count)
+                : SplitKeepEmptyEntries(sepList, default, 1, count);
+
+            sepListBuilder.Dispose();
+
+            return result;
+        }
+
+        public string[] Split(string separator, StringSplitOptions options = StringSplitOptions.None)
+        {
+            return SplitInternal(separator ?? string.Empty, null, int.MaxValue, options);
+        }
+
+        public string[] Split(string separator, Int32 count, StringSplitOptions options = StringSplitOptions.None)
+        {
+            return SplitInternal(separator ?? string.Empty, null, count, options);
+        }
+
+        public string[] Split(string[] separator, StringSplitOptions options)
+        {
+            return SplitInternal(null, separator, int.MaxValue, options);
+        }
+
+        public string[] Split(string[] separator, Int32 count, StringSplitOptions options)
+        {
+            return SplitInternal(null, separator, count, options);
+        }
+
+        private string[] SplitInternal(string separator, string[] separators, int count, StringSplitOptions options)
+        {
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count),
+                    SR.ArgumentOutOfRange_NegativeCount);
+            }
+
+            if (options < StringSplitOptions.None || options > StringSplitOptions.RemoveEmptyEntries)
+            {
+                throw new ArgumentException(SR.Format(SR.Arg_EnumIllegalVal, (int)options));
+            }
+
+            bool omitEmptyEntries = (options == StringSplitOptions.RemoveEmptyEntries);
+
+            bool singleSeparator = separator != null;
+
+            if (!singleSeparator && (separators == null || separators.Length == 0))
+            {
+                return SplitInternal((char[])null, count, options);
+            }
+
+            if ((count == 0) || (omitEmptyEntries && Length == 0))
+            {
+                return Array.Empty<string>();
+            }
+
+            if (count == 1 || (singleSeparator && separator.Length == 0))
+            {
+                return new string[] { this };
+            }
+
+            if (singleSeparator)
+            {
+                return SplitInternal(separator, count, options);
+            }
+
+            Span<int> sepListInitialSpan = stackalloc int[StackallocIntBufferSizeLimit];
+            var sepListBuilder = new ValueListBuilder<int>(sepListInitialSpan);
+
+            Span<int> lengthListInitialSpan = stackalloc int[StackallocIntBufferSizeLimit];
+            var lengthListBuilder = new ValueListBuilder<int>(lengthListInitialSpan);
+
+            MakeSeparatorList(separators, ref sepListBuilder, ref lengthListBuilder);
+            ReadOnlySpan<int> sepList = sepListBuilder.AsSpan();
+            ReadOnlySpan<int> lengthList = lengthListBuilder.AsSpan();
+
+            // Handle the special case of no replaces.
+            if (sepList.Length == 0)
+            {
+                return new string[] { this };
+            }
+
+            string[] result = omitEmptyEntries
+                ? SplitOmitEmptyEntries(sepList, lengthList, 0, count)
+                : SplitKeepEmptyEntries(sepList, lengthList, 0, count);
+
+            sepListBuilder.Dispose();
+            lengthListBuilder.Dispose();
+
+            return result;
+        }
+
+        private string[] SplitInternal(string separator, int count, StringSplitOptions options)
+        {
+            Span<int> sepListInitialSpan = stackalloc int[StackallocIntBufferSizeLimit];
+            var sepListBuilder = new ValueListBuilder<int>(sepListInitialSpan);
+
+            MakeSeparatorList(separator, ref sepListBuilder);
+            ReadOnlySpan<int> sepList = sepListBuilder.AsSpan();
+            if (sepList.Length == 0)
+            {
+                // there are no separators so sepListBuilder did not rent an array from pool and there is no need to dispose it
+                return new string[] { this };
+            }
+
+            string[] result = options == StringSplitOptions.RemoveEmptyEntries
+                ? SplitOmitEmptyEntries(sepList, default, separator.Length, count)
+                : SplitKeepEmptyEntries(sepList, default, separator.Length, count);
+
+            sepListBuilder.Dispose();
+
+            return result;
+        }
+
+        private string[] SplitKeepEmptyEntries(ReadOnlySpan<int> sepList, ReadOnlySpan<int> lengthList, int defaultLength, int count)
+        {
+            Debug.Assert(count >= 2);
+
+            int currIndex = 0;
+            int arrIndex = 0;
+
+            count--;
+            int numActualReplaces = (sepList.Length < count) ? sepList.Length : count;
+
+            //Allocate space for the new array.
+            //+1 for the string from the end of the last replace to the end of the string.
+            string[] splitStrings = new string[numActualReplaces + 1];
+
+            for (int i = 0; i < numActualReplaces && currIndex < Length; i++)
+            {
+                splitStrings[arrIndex++] = Substring(currIndex, sepList[i] - currIndex);
+                currIndex = sepList[i] + (lengthList.IsEmpty ? defaultLength : lengthList[i]);
+            }
+
+            //Handle the last string at the end of the array if there is one.
+            if (currIndex < Length && numActualReplaces >= 0)
+            {
+                splitStrings[arrIndex] = Substring(currIndex);
+            }
+            else if (arrIndex == numActualReplaces)
+            {
+                //We had a separator character at the end of a string.  Rather than just allowing
+                //a null character, we'll replace the last element in the array with an empty string.
+                splitStrings[arrIndex] = string.Empty;
+            }
+
+            return splitStrings;
+        }
+
+
+        // This function will not keep the Empty string
+        private string[] SplitOmitEmptyEntries(ReadOnlySpan<int> sepList, ReadOnlySpan<int> lengthList, int defaultLength, int count)
+        {
+            Debug.Assert(count >= 2);
+
+            int numReplaces = sepList.Length;
+
+            // Allocate array to hold items. This array may not be
+            // filled completely in this function, we will create a
+            // new array and copy string references to that new array.
+            int maxItems = (numReplaces < count) ? (numReplaces + 1) : count;
+            string[] splitStrings = new string[maxItems];
+
+            int currIndex = 0;
+            int arrIndex = 0;
+
+            for (int i = 0; i < numReplaces && currIndex < Length; i++)
+            {
+                if (sepList[i] - currIndex > 0)
+                {
+                    splitStrings[arrIndex++] = Substring(currIndex, sepList[i] - currIndex);
+                }
+                currIndex = sepList[i] + (lengthList.IsEmpty ? defaultLength : lengthList[i]);
+                if (arrIndex == count - 1)
+                {
+                    // If all the remaining entries at the end are empty, skip them
+                    while (i < numReplaces - 1 && currIndex == sepList[++i])
+                    {
+                        currIndex += (lengthList.IsEmpty ? defaultLength : lengthList[i]);
+                    }
+                    break;
+                }
+            }
+
+            // we must have at least one slot left to fill in the last string.
+            Debug.Assert(arrIndex < maxItems);
+
+            //Handle the last string at the end of the array if there is one.
+            if (currIndex < Length)
+            {
+                splitStrings[arrIndex++] = Substring(currIndex);
+            }
+
+            string[] stringArray = splitStrings;
+            if (arrIndex != maxItems)
+            {
+                stringArray = new string[arrIndex];
+                for (int j = 0; j < arrIndex; j++)
+                {
+                    stringArray[j] = splitStrings[j];
+                }
+            }
+            return stringArray;
+        }
+
+        /// <summary>
+        /// Uses ValueListBuilder to create list that holds indexes of separators in string.
+        /// </summary>
+        /// <param name="separators"><see cref="ReadOnlySpan{T}"/> of separator chars</param>
+        /// <param name="sepListBuilder"><see cref="ValueListBuilder{T}"/> to store indexes</param>
+        /// <returns></returns>
+        private void MakeSeparatorList(ReadOnlySpan<char> separators, ref ValueListBuilder<int> sepListBuilder)
+        {
+            char sep0, sep1, sep2;
+
+            switch (separators.Length)
+            {
+                // Special-case no separators to mean any whitespace is a separator.
+                case 0:
+                    for (int i = 0; i < Length; i++)
+                    {
+                        if (char.IsWhiteSpace(this[i]))
+                        {
+                            sepListBuilder.Append(i);
+                        }
+                    }
+                    break;
+
+                // Special-case the common cases of 1, 2, and 3 separators, with manual comparisons against each separator.
+                case 1:
+                    sep0 = separators[0];
+                    for (int i = 0; i < Length; i++)
+                    {
+                        if (this[i] == sep0)
+                        {
+                            sepListBuilder.Append(i);
+                        }
+                    }
+                    break;
+                case 2:
+                    sep0 = separators[0];
+                    sep1 = separators[1];
+                    for (int i = 0; i < Length; i++)
+                    {
+                        char c = this[i];
+                        if (c == sep0 || c == sep1)
+                        {
+                            sepListBuilder.Append(i);
+                        }
+                    }
+                    break;
+                case 3:
+                    sep0 = separators[0];
+                    sep1 = separators[1];
+                    sep2 = separators[2];
+                    for (int i = 0; i < Length; i++)
+                    {
+                        char c = this[i];
+                        if (c == sep0 || c == sep1 || c == sep2)
+                        {
+                            sepListBuilder.Append(i);
+                        }
+                    }
+                    break;
+
+                // Handle > 3 separators with a probabilistic map, ala IndexOfAny.
+                // This optimizes for chars being unlikely to match a separator.
+                default:
+                    unsafe
+                    {
+                        ProbabilisticMap map = default;
+                        uint* charMap = (uint*)&map;
+                        InitializeProbabilisticMap(charMap, separators);
+
+                        for (int i = 0; i < Length; i++)
+                        {
+                            char c = this[i];
+                            if (IsCharBitSet(charMap, (byte)c) && IsCharBitSet(charMap, (byte)(c >> 8)) &&
+                                separators.Contains(c))
+                            {
+                                sepListBuilder.Append(i);
+                            }
+                        }
+                    }
+                    break;
+            }
+        }
+
+        /// <summary>
+        /// Uses ValueListBuilder to create list that holds indexes of separators in string.
+        /// </summary>
+        /// <param name="separator">separator string</param>
+        /// <param name="sepListBuilder"><see cref="ValueListBuilder{T}"/> to store indexes</param>
+        /// <returns></returns>
+        private void MakeSeparatorList(string separator, ref ValueListBuilder<int> sepListBuilder)
+        {
+            Debug.Assert(!IsNullOrEmpty(separator), "!string.IsNullOrEmpty(separator)");
+
+            int currentSepLength = separator.Length;
+
+            for (int i = 0; i < Length; i++)
+            {
+                if (this[i] == separator[0] && currentSepLength <= Length - i)
+                {
+                    if (currentSepLength == 1
+                        || this.AsSpan(i, currentSepLength).SequenceEqual(separator))
+                    {
+                        sepListBuilder.Append(i);
+                        i += currentSepLength - 1;
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Uses ValueListBuilder to create list that holds indexes of separators in string and list that holds length of separator strings.
+        /// </summary>
+        /// <param name="separators">separator strngs</param>
+        /// <param name="sepListBuilder"><see cref="ValueListBuilder{T}"/> for separator indexes</param>
+        /// <param name="lengthListBuilder"><see cref="ValueListBuilder{T}"/> for separator length values</param>
+        private void MakeSeparatorList(string[] separators, ref ValueListBuilder<int> sepListBuilder, ref ValueListBuilder<int> lengthListBuilder)
+        {
+            Debug.Assert(separators != null && separators.Length > 0, "separators != null && separators.Length > 0");
+
+            int sepCount = separators.Length;
+
+            for (int i = 0; i < Length; i++)
+            {
+                for (int j = 0; j < separators.Length; j++)
+                {
+                    string separator = separators[j];
+                    if (IsNullOrEmpty(separator))
+                    {
+                        continue;
+                    }
+                    int currentSepLength = separator.Length;
+                    if (this[i] == separator[0] && currentSepLength <= Length - i)
+                    {
+                        if (currentSepLength == 1
+                            || this.AsSpan(i, currentSepLength).SequenceEqual(separator))
+                        {
+                            sepListBuilder.Append(i);
+                            lengthListBuilder.Append(currentSepLength);
+                            i += currentSepLength - 1;
+                            break;
+                        }
+                    }
+                }
+            }
+        }
+
+        // Returns a substring of this string.
+        //
+        public string Substring(int startIndex) => Substring(startIndex, Length - startIndex);
+
+        public string Substring(int startIndex, int length)
+        {
+            if (startIndex < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndex);
+            }
+
+            if (startIndex > Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndexLargerThanLength);
+            }
+
+            if (length < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_NegativeLength);
+            }
+
+            if (startIndex > Length - length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_IndexLength);
+            }
+
+            if (length == 0)
+            {
+                return string.Empty;
+            }
+
+            if (startIndex == 0 && length == this.Length)
+            {
+                return this;
+            }
+
+            return InternalSubString(startIndex, length);
+        }
+
+        private unsafe string InternalSubString(int startIndex, int length)
+        {
+            Debug.Assert(startIndex >= 0 && startIndex <= this.Length, "StartIndex is out of range!");
+            Debug.Assert(length >= 0 && startIndex <= this.Length - length, "length is out of range!");
+
+            string result = FastAllocateString(length);
+
+            fixed (char* dest = &result._firstChar)
+            fixed (char* src = &_firstChar)
+            {
+                wstrcpy(dest, src + startIndex, length);
+            }
+
+            return result;
+        }
+
+        // Creates a copy of this string in lower case.  The culture is set by culture.
+        public string ToLower()
+        {
+            return CultureInfo.CurrentCulture.TextInfo.ToLower(this);
+        }
+
+        // Creates a copy of this string in lower case.  The culture is set by culture.
+        public string ToLower(CultureInfo culture)
+        {
+            if (culture == null)
+            {
+                throw new ArgumentNullException(nameof(culture));
+            }
+            return culture.TextInfo.ToLower(this);
+        }
+
+        // Creates a copy of this string in lower case based on invariant culture.
+        public string ToLowerInvariant()
+        {
+            return CultureInfo.InvariantCulture.TextInfo.ToLower(this);
+        }
+
+        public string ToUpper()
+        {
+            return CultureInfo.CurrentCulture.TextInfo.ToUpper(this);
+        }
+
+        // Creates a copy of this string in upper case.  The culture is set by culture.
+        public string ToUpper(CultureInfo culture)
+        {
+            if (culture == null)
+            {
+                throw new ArgumentNullException(nameof(culture));
+            }
+            return culture.TextInfo.ToUpper(this);
+        }
+
+        //Creates a copy of this string in upper case based on invariant culture.
+        public string ToUpperInvariant()
+        {
+            return CultureInfo.InvariantCulture.TextInfo.ToUpper(this);
+        }
+
+        // Trims the whitespace from both ends of the string.  Whitespace is defined by
+        // Char.IsWhiteSpace.
+        //
+        public string Trim() => TrimWhiteSpaceHelper(TrimType.Both);
+
+        // Removes a set of characters from the beginning and end of this string.
+        public unsafe string Trim(char trimChar) => TrimHelper(&trimChar, 1, TrimType.Both);
+
+        // Removes a set of characters from the beginning and end of this string.
+        public unsafe string Trim(params char[] trimChars)
+        {
+            if (trimChars == null || trimChars.Length == 0)
+            {
+                return TrimWhiteSpaceHelper(TrimType.Both);
+            }
+            fixed (char* pTrimChars = &trimChars[0])
+            {
+                return TrimHelper(pTrimChars, trimChars.Length, TrimType.Both);
+            }
+        }
+
+        // Removes a set of characters from the beginning of this string.
+        public string TrimStart() => TrimWhiteSpaceHelper(TrimType.Head);
+
+        // Removes a set of characters from the beginning of this string.
+        public unsafe string TrimStart(char trimChar) => TrimHelper(&trimChar, 1, TrimType.Head);
+
+        // Removes a set of characters from the beginning of this string.
+        public unsafe string TrimStart(params char[] trimChars)
+        {
+            if (trimChars == null || trimChars.Length == 0)
+            {
+                return TrimWhiteSpaceHelper(TrimType.Head);
+            }
+            fixed (char* pTrimChars = &trimChars[0])
+            {
+                return TrimHelper(pTrimChars, trimChars.Length, TrimType.Head);
+            }
+        }
+
+        // Removes a set of characters from the end of this string.
+        public string TrimEnd() => TrimWhiteSpaceHelper(TrimType.Tail);
+
+        // Removes a set of characters from the end of this string.
+        public unsafe string TrimEnd(char trimChar) => TrimHelper(&trimChar, 1, TrimType.Tail);
+
+        // Removes a set of characters from the end of this string.
+        public unsafe string TrimEnd(params char[] trimChars)
+        {
+            if (trimChars == null || trimChars.Length == 0)
+            {
+                return TrimWhiteSpaceHelper(TrimType.Tail);
+            }
+            fixed (char* pTrimChars = &trimChars[0])
+            {
+                return TrimHelper(pTrimChars, trimChars.Length, TrimType.Tail);
+            }
+        }
+
+        private string TrimWhiteSpaceHelper(TrimType trimType)
+        {
+            // end will point to the first non-trimmed character on the right.
+            // start will point to the first non-trimmed character on the left.
+            int end = Length - 1;
+            int start = 0;
+
+            // Trim specified characters.
+            if (trimType != TrimType.Tail)
+            {
+                for (start = 0; start < Length; start++)
+                {
+                    if (!char.IsWhiteSpace(this[start]))
+                    {
+                        break;
+                    }
+                }
+            }
+
+            if (trimType != TrimType.Head)
+            {
+                for (end = Length - 1; end >= start; end--)
+                {
+                    if (!char.IsWhiteSpace(this[end]))
+                    {
+                        break;
+                    }
+                }
+            }
+
+            return CreateTrimmedString(start, end);
+        }
+
+        private unsafe string TrimHelper(char* trimChars, int trimCharsLength, TrimType trimType)
+        {
+            Debug.Assert(trimChars != null);
+            Debug.Assert(trimCharsLength > 0);
+
+            // end will point to the first non-trimmed character on the right.
+            // start will point to the first non-trimmed character on the left.
+            int end = Length - 1;
+            int start = 0;
+
+            // Trim specified characters.
+            if (trimType != TrimType.Tail)
+            {
+                for (start = 0; start < Length; start++)
+                {
+                    int i = 0;
+                    char ch = this[start];
+                    for (i = 0; i < trimCharsLength; i++)
+                    {
+                        if (trimChars[i] == ch)
+                        {
+                            break;
+                        }
+                    }
+                    if (i == trimCharsLength)
+                    {
+                        // The character is not in trimChars, so stop trimming.
+                        break;
+                    }
+                }
+            }
+
+            if (trimType != TrimType.Head)
+            {
+                for (end = Length - 1; end >= start; end--)
+                {
+                    int i = 0;
+                    char ch = this[end];
+                    for (i = 0; i < trimCharsLength; i++)
+                    {
+                        if (trimChars[i] == ch)
+                        {
+                            break;
+                        }
+                    }
+                    if (i == trimCharsLength)
+                    {
+                        // The character is not in trimChars, so stop trimming.
+                        break;
+                    }
+                }
+            }
+
+            return CreateTrimmedString(start, end);
+        }
+
+        private string CreateTrimmedString(int start, int end)
+        {
+            int len = end - start + 1;
+            return
+                len == Length ? this :
+                len == 0 ? string.Empty :
+                InternalSubString(start, len);
+        }
+
+        private enum TrimType
+        {
+            Head = 0,
+            Tail = 1,
+            Both = 2
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/String.Searching.cs b/src/System.Private.CoreLib/shared/System/String.Searching.cs
new file mode 100644
index 0000000000..3a6ffc3093
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/String.Searching.cs
@@ -0,0 +1,534 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Numerics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System
+{
+    public partial class String
+    {
+        public bool Contains(string value)
+        {
+            return (IndexOf(value, StringComparison.Ordinal) >= 0);
+        }
+
+        public bool Contains(string value, StringComparison comparisonType)
+        {
+            return (IndexOf(value, comparisonType) >= 0);
+        }
+
+        public bool Contains(char value)
+        {
+            return IndexOf(value) != -1;
+        }
+
+        public bool Contains(char value, StringComparison comparisonType)
+        {
+            return IndexOf(value, comparisonType) != -1;
+        }
+
+        // Returns the index of the first occurrence of a specified character in the current instance.
+        // The search starts at startIndex and runs thorough the next count characters.
+        //
+        public int IndexOf(char value) => SpanHelpers.IndexOf(ref _firstChar, value, Length);
+
+        public int IndexOf(char value, int startIndex)
+        {
+            return IndexOf(value, startIndex, this.Length - startIndex);
+        }
+
+        public int IndexOf(char value, StringComparison comparisonType)
+        {
+            switch (comparisonType)
+            {
+                case StringComparison.CurrentCulture:
+                case StringComparison.CurrentCultureIgnoreCase:
+                    return CultureInfo.CurrentCulture.CompareInfo.IndexOf(this, value, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.InvariantCulture:
+                case StringComparison.InvariantCultureIgnoreCase:
+                    return CompareInfo.Invariant.IndexOf(this, value, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.Ordinal:
+                    return CompareInfo.Invariant.IndexOf(this, value, CompareOptions.Ordinal);
+
+                case StringComparison.OrdinalIgnoreCase:
+                    return CompareInfo.Invariant.IndexOf(this, value, CompareOptions.OrdinalIgnoreCase);
+
+                default:
+                    throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType));
+            }
+        }
+
+        public unsafe int IndexOf(char value, int startIndex, int count)
+        {
+            if ((uint)startIndex > (uint)Length)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+
+            if ((uint)count > (uint)(Length - startIndex))
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Count);
+
+            int result = SpanHelpers.IndexOf(ref Unsafe.Add(ref _firstChar, startIndex), value, count);
+
+            return result == -1 ? result : result + startIndex;
+        }
+
+        // Returns the index of the first occurrence of any specified character in the current instance.
+        // The search starts at startIndex and runs to startIndex + count - 1.
+        //
+        public int IndexOfAny(char[] anyOf)
+        {
+            return IndexOfAny(anyOf, 0, this.Length);
+        }
+
+        public int IndexOfAny(char[] anyOf, int startIndex)
+        {
+            return IndexOfAny(anyOf, startIndex, this.Length - startIndex);
+        }
+
+        public int IndexOfAny(char[] anyOf, int startIndex, int count)
+        {
+            if (anyOf == null)
+                throw new ArgumentNullException(nameof(anyOf));
+
+            if ((uint)startIndex > (uint)Length)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+
+            if ((uint)count > (uint)(Length - startIndex))
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Count);
+
+            if (anyOf.Length == 2)
+            {
+                // Very common optimization for directory separators (/, \), quotes (", '), brackets, etc
+                return IndexOfAny(anyOf[0], anyOf[1], startIndex, count);
+            }
+            else if (anyOf.Length == 3)
+            {
+                return IndexOfAny(anyOf[0], anyOf[1], anyOf[2], startIndex, count);
+            }
+            else if (anyOf.Length > 3)
+            {
+                return IndexOfCharArray(anyOf, startIndex, count);
+            }
+            else if (anyOf.Length == 1)
+            {
+                return IndexOf(anyOf[0], startIndex, count);
+            }
+            else // anyOf.Length == 0
+            {
+                return -1;
+            }
+        }
+
+        private unsafe int IndexOfAny(char value1, char value2, int startIndex, int count)
+        {
+            fixed (char* pChars = &_firstChar)
+            {
+                char* pCh = pChars + startIndex;
+
+                while (count > 0)
+                {
+                    char c = *pCh;
+
+                    if (c == value1 || c == value2)
+                        return (int)(pCh - pChars);
+
+                    // Possibly reads outside of count and can include null terminator
+                    // Handled in the return logic
+                    c = *(pCh + 1);
+
+                    if (c == value1 || c == value2)
+                        return (count == 1 ? -1 : (int)(pCh - pChars) + 1);
+
+                    pCh += 2;
+                    count -= 2;
+                }
+
+                return -1;
+            }
+        }
+
+        private unsafe int IndexOfAny(char value1, char value2, char value3, int startIndex, int count)
+        {
+            fixed (char* pChars = &_firstChar)
+            {
+                char* pCh = pChars + startIndex;
+
+                while (count > 0)
+                {
+                    char c = *pCh;
+
+                    if (c == value1 || c == value2 || c == value3)
+                        return (int)(pCh - pChars);
+
+                    pCh++;
+                    count--;
+                }
+
+                return -1;
+            }
+        }
+
+        private unsafe int IndexOfCharArray(char[] anyOf, int startIndex, int count)
+        {
+            // use probabilistic map, see InitializeProbabilisticMap
+            ProbabilisticMap map = default(ProbabilisticMap);
+            uint* charMap = (uint*)&map;
+
+            InitializeProbabilisticMap(charMap, anyOf);
+
+            fixed (char* pChars = &_firstChar)
+            {
+                char* pCh = pChars + startIndex;
+
+                while (count > 0)
+                {
+                    int thisChar = *pCh;
+
+                    if (IsCharBitSet(charMap, (byte)thisChar) &&
+                        IsCharBitSet(charMap, (byte)(thisChar >> 8)) &&
+                        ArrayContains((char)thisChar, anyOf))
+                    {
+                        return (int)(pCh - pChars);
+                    }
+
+                    count--;
+                    pCh++;
+                }
+
+                return -1;
+            }
+        }
+
+        private const int PROBABILISTICMAP_BLOCK_INDEX_MASK = 0x7;
+        private const int PROBABILISTICMAP_BLOCK_INDEX_SHIFT = 0x3;
+        private const int PROBABILISTICMAP_SIZE = 0x8;
+
+        // A probabilistic map is an optimization that is used in IndexOfAny/
+        // LastIndexOfAny methods. The idea is to create a bit map of the characters we
+        // are searching for and use this map as a "cheap" check to decide if the
+        // current character in the string exists in the array of input characters.
+        // There are 256 bits in the map, with each character mapped to 2 bits. Every
+        // character is divided into 2 bytes, and then every byte is mapped to 1 bit.
+        // The character map is an array of 8 integers acting as map blocks. The 3 lsb
+        // in each byte in the character is used to index into this map to get the
+        // right block, the value of the remaining 5 msb are used as the bit position
+        // inside this block. 
+        private static unsafe void InitializeProbabilisticMap(uint* charMap, ReadOnlySpan<char> anyOf)
+        {
+            bool hasAscii = false;
+            uint* charMapLocal = charMap; // https://github.com/dotnet/coreclr/issues/14264
+
+            for (int i = 0; i < anyOf.Length; ++i)
+            {
+                int c = anyOf[i];
+
+                // Map low bit
+                SetCharBit(charMapLocal, (byte)c);
+
+                // Map high bit
+                c >>= 8;
+
+                if (c == 0)
+                {
+                    hasAscii = true;
+                }
+                else
+                {
+                    SetCharBit(charMapLocal, (byte)c);
+                }
+            }
+
+            if (hasAscii)
+            {
+                // Common to search for ASCII symbols. Just set the high value once.
+                charMapLocal[0] |= 1u;
+            }
+        }
+
+        private static bool ArrayContains(char searchChar, char[] anyOf)
+        {
+            for (int i = 0; i < anyOf.Length; i++)
+            {
+                if (anyOf[i] == searchChar)
+                    return true;
+            }
+
+            return false;
+        }
+
+        private static unsafe bool IsCharBitSet(uint* charMap, byte value)
+        {
+            return (charMap[value & PROBABILISTICMAP_BLOCK_INDEX_MASK] & (1u << (value >> PROBABILISTICMAP_BLOCK_INDEX_SHIFT))) != 0;
+        }
+
+        private static unsafe void SetCharBit(uint* charMap, byte value)
+        {
+            charMap[value & PROBABILISTICMAP_BLOCK_INDEX_MASK] |= 1u << (value >> PROBABILISTICMAP_BLOCK_INDEX_SHIFT);
+        }
+
+        public int IndexOf(string value)
+        {
+            return IndexOf(value, StringComparison.CurrentCulture);
+        }
+
+        public int IndexOf(string value, int startIndex)
+        {
+            return IndexOf(value, startIndex, StringComparison.CurrentCulture);
+        }
+
+        public int IndexOf(string value, int startIndex, int count)
+        {
+            if (startIndex < 0 || startIndex > this.Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+            }
+
+            if (count < 0 || count > this.Length - startIndex)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Count);
+            }
+
+            return IndexOf(value, startIndex, count, StringComparison.CurrentCulture);
+        }
+
+        public int IndexOf(string value, StringComparison comparisonType)
+        {
+            return IndexOf(value, 0, this.Length, comparisonType);
+        }
+
+        public int IndexOf(string value, int startIndex, StringComparison comparisonType)
+        {
+            return IndexOf(value, startIndex, this.Length - startIndex, comparisonType);
+        }
+
+        public int IndexOf(string value, int startIndex, int count, StringComparison comparisonType)
+        {
+            // Validate inputs
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            if (startIndex < 0 || startIndex > this.Length)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+
+            if (count < 0 || startIndex > this.Length - count)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Count);
+
+            switch (comparisonType)
+            {
+                case StringComparison.CurrentCulture:
+                case StringComparison.CurrentCultureIgnoreCase:
+                    return CultureInfo.CurrentCulture.CompareInfo.IndexOf(this, value, startIndex, count, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.InvariantCulture:
+                case StringComparison.InvariantCultureIgnoreCase:
+                    return CompareInfo.Invariant.IndexOf(this, value, startIndex, count, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.Ordinal:
+                case StringComparison.OrdinalIgnoreCase:
+                    return CompareInfo.Invariant.IndexOfOrdinal(this, value, startIndex, count, GetCaseCompareOfComparisonCulture(comparisonType) != CompareOptions.None);
+
+                default:
+                    throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType));
+            }
+        }
+
+        // Returns the index of the last occurrence of a specified character in the current instance.
+        // The search starts at startIndex and runs backwards to startIndex - count + 1.
+        // The character at position startIndex is included in the search.  startIndex is the larger
+        // index within the string.
+        //
+        public int LastIndexOf(char value) => SpanHelpers.LastIndexOf(ref _firstChar, value, Length);
+
+        public int LastIndexOf(char value, int startIndex)
+        {
+            return LastIndexOf(value, startIndex, startIndex + 1);
+        }
+
+        public unsafe int LastIndexOf(char value, int startIndex, int count)
+        {
+            if (Length == 0)
+                return -1;
+
+            if ((uint)startIndex >= (uint)Length)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+
+            if ((uint)count > (uint)startIndex + 1)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Count);
+
+            int startSearchAt = startIndex + 1 - count;
+            int result = SpanHelpers.LastIndexOf(ref Unsafe.Add(ref _firstChar, startSearchAt), value, count);
+
+            return result == -1 ? result : result + startSearchAt;
+        }
+
+        // Returns the index of the last occurrence of any specified character in the current instance.
+        // The search starts at startIndex and runs backwards to startIndex - count + 1.
+        // The character at position startIndex is included in the search.  startIndex is the larger
+        // index within the string.
+        //
+        public int LastIndexOfAny(char[] anyOf)
+        {
+            return LastIndexOfAny(anyOf, this.Length - 1, this.Length);
+        }
+
+        public int LastIndexOfAny(char[] anyOf, int startIndex)
+        {
+            return LastIndexOfAny(anyOf, startIndex, startIndex + 1);
+        }
+
+        public unsafe int LastIndexOfAny(char[] anyOf, int startIndex, int count)
+        {
+            if (anyOf == null)
+                throw new ArgumentNullException(nameof(anyOf));
+
+            if (Length == 0)
+                return -1;
+
+            if ((uint)startIndex >= (uint)Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+            }
+
+            if ((count < 0) || ((count - 1) > startIndex))
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Count);
+            }
+
+            if (anyOf.Length > 1)
+            {
+                return LastIndexOfCharArray(anyOf, startIndex, count);
+            }
+            else if (anyOf.Length == 1)
+            {
+                return LastIndexOf(anyOf[0], startIndex, count);
+            }
+            else // anyOf.Length == 0
+            {
+                return -1;
+            }
+        }
+
+        private unsafe int LastIndexOfCharArray(char[] anyOf, int startIndex, int count)
+        {
+            // use probabilistic map, see InitializeProbabilisticMap
+            ProbabilisticMap map = default(ProbabilisticMap);
+            uint* charMap = (uint*)&map;
+
+            InitializeProbabilisticMap(charMap, anyOf);
+
+            fixed (char* pChars = &_firstChar)
+            {
+                char* pCh = pChars + startIndex;
+
+                while (count > 0)
+                {
+                    int thisChar = *pCh;
+
+                    if (IsCharBitSet(charMap, (byte)thisChar) &&
+                        IsCharBitSet(charMap, (byte)(thisChar >> 8)) &&
+                        ArrayContains((char)thisChar, anyOf))
+                    {
+                        return (int)(pCh - pChars);
+                    }
+
+                    count--;
+                    pCh--;
+                }
+
+                return -1;
+            }
+        }
+
+        // Returns the index of the last occurrence of any character in value in the current instance.
+        // The search starts at startIndex and runs backwards to startIndex - count + 1.
+        // The character at position startIndex is included in the search.  startIndex is the larger
+        // index within the string.
+        //
+        public int LastIndexOf(string value)
+        {
+            return LastIndexOf(value, this.Length - 1, this.Length, StringComparison.CurrentCulture);
+        }
+
+        public int LastIndexOf(string value, int startIndex)
+        {
+            return LastIndexOf(value, startIndex, startIndex + 1, StringComparison.CurrentCulture);
+        }
+
+        public int LastIndexOf(string value, int startIndex, int count)
+        {
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Count);
+            }
+
+            return LastIndexOf(value, startIndex, count, StringComparison.CurrentCulture);
+        }
+
+        public int LastIndexOf(string value, StringComparison comparisonType)
+        {
+            return LastIndexOf(value, this.Length - 1, this.Length, comparisonType);
+        }
+
+        public int LastIndexOf(string value, int startIndex, StringComparison comparisonType)
+        {
+            return LastIndexOf(value, startIndex, startIndex + 1, comparisonType);
+        }
+
+        public int LastIndexOf(string value, int startIndex, int count, StringComparison comparisonType)
+        {
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            // Special case for 0 length input strings
+            if (this.Length == 0 && (startIndex == -1 || startIndex == 0))
+                return (value.Length == 0) ? 0 : -1;
+
+            // Now after handling empty strings, make sure we're not out of range
+            if (startIndex < 0 || startIndex > this.Length)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+
+            // Make sure that we allow startIndex == this.Length
+            if (startIndex == this.Length)
+            {
+                startIndex--;
+                if (count > 0)
+                    count--;
+            }
+
+            // 2nd half of this also catches when startIndex == MAXINT, so MAXINT - 0 + 1 == -1, which is < 0.
+            if (count < 0 || startIndex - count + 1 < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Count);
+
+            // If we are looking for nothing, just return startIndex
+            if (value.Length == 0)
+                return startIndex;
+
+            switch (comparisonType)
+            {
+                case StringComparison.CurrentCulture:
+                case StringComparison.CurrentCultureIgnoreCase:
+                    return CultureInfo.CurrentCulture.CompareInfo.LastIndexOf(this, value, startIndex, count, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.InvariantCulture:
+                case StringComparison.InvariantCultureIgnoreCase:
+                    return CompareInfo.Invariant.LastIndexOf(this, value, startIndex, count, GetCaseCompareOfComparisonCulture(comparisonType));
+
+                case StringComparison.Ordinal:
+                case StringComparison.OrdinalIgnoreCase:
+                    return CompareInfo.Invariant.LastIndexOfOrdinal(this, value, startIndex, count, GetCaseCompareOfComparisonCulture(comparisonType) != CompareOptions.None);
+
+                default:
+                    throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType));
+            }
+        }
+
+        [StructLayout(LayoutKind.Explicit, Size = PROBABILISTICMAP_SIZE * sizeof(uint))]
+        private struct ProbabilisticMap { }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/String.cs b/src/System.Private.CoreLib/shared/System/String.cs
new file mode 100644
index 0000000000..8c095ab899
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/String.cs
@@ -0,0 +1,766 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Buffers;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+using System.Text;
+
+namespace System
+{
+    // The String class represents a static string of characters.  Many of
+    // the String methods perform some type of transformation on the current
+    // instance and return the result as a new String.  As with arrays, character
+    // positions (indices) are zero-based.
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed partial class String : IComparable, IEnumerable, IConvertible, IEnumerable<char>, IComparable<String>, IEquatable<String>, ICloneable
+    {
+        // String constructors
+        // These are special. The implementation methods for these have a different signature from the
+        // declared constructors.
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern String(char[] value);
+
+#if PROJECTN
+        [DependencyReductionRoot]
+#endif
+#if !CORECLR
+        static
+#endif
+        private string Ctor(char[] value)
+        {
+            if (value == null || value.Length == 0)
+                return Empty;
+
+            string result = FastAllocateString(value.Length);
+            unsafe
+            {
+                fixed (char* dest = &result._firstChar, source = value)
+                    wstrcpy(dest, source, value.Length);
+            }
+            return result;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern String(char[] value, int startIndex, int length);
+
+#if PROJECTN
+        [DependencyReductionRoot]
+#endif
+#if !CORECLR
+        static
+#endif
+        private string Ctor(char[] value, int startIndex, int length)
+        {
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            if (startIndex < 0)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndex);
+
+            if (length < 0)
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_NegativeLength);
+
+            if (startIndex > value.Length - length)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+
+            if (length == 0)
+                return Empty;
+
+            string result = FastAllocateString(length);
+            unsafe
+            {
+                fixed (char* dest = &result._firstChar, source = value)
+                    wstrcpy(dest, source + startIndex, length);
+            }
+            return result;
+        }
+
+        [CLSCompliant(false)]
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern unsafe String(char* value);
+
+#if PROJECTN
+        [DependencyReductionRoot]
+#endif
+#if !CORECLR
+        static
+#endif
+        private unsafe string Ctor(char* ptr)
+        {
+            if (ptr == null)
+                return Empty;
+
+            int count = wcslen(ptr);
+            if (count == 0)
+                return Empty;
+
+            string result = FastAllocateString(count);
+            fixed (char* dest = &result._firstChar)
+                wstrcpy(dest, ptr, count);
+            return result;
+        }
+
+        [CLSCompliant(false)]
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern unsafe String(char* value, int startIndex, int length);
+
+#if PROJECTN
+        [DependencyReductionRoot]
+#endif
+#if !CORECLR
+        static
+#endif
+        private unsafe string Ctor(char* ptr, int startIndex, int length)
+        {
+            if (length < 0)
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_NegativeLength);
+
+            if (startIndex < 0)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndex);
+
+            char* pStart = ptr + startIndex;
+
+            // overflow check
+            if (pStart < ptr)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_PartialWCHAR);
+
+            if (length == 0)
+                return Empty;
+
+            if (ptr == null)
+                throw new ArgumentOutOfRangeException(nameof(ptr), SR.ArgumentOutOfRange_PartialWCHAR);
+
+            string result = FastAllocateString(length);
+            fixed (char* dest = &result._firstChar)
+                wstrcpy(dest, pStart, length);
+            return result;
+        }
+
+        [CLSCompliant(false)]
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public extern unsafe String(sbyte* value);
+
+#if PROJECTN
+        [DependencyReductionRoot]
+#endif
+#if !CORECLR
+        static
+#endif
+        private unsafe string Ctor(sbyte* value)
+        {
+            byte* pb = (byte*)value;
+            if (pb == null)
+                return Empty;
+
+            int numBytes = new ReadOnlySpan<byte>((byte*)value, int.MaxValue).IndexOf<byte>(0);
+
+            // Check for overflow
+            if (numBytes < 0)
+                throw new ArgumentException(SR.Arg_MustBeNullTerminatedString);
+
+            return CreateStringForSByteConstructor(pb, numBytes);
+        }
+
+        [CLSCompliant(false)]
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public extern unsafe String(sbyte* value, int startIndex, int length);
+
+#if PROJECTN
+        [DependencyReductionRoot]
+#endif
+#if !CORECLR
+        static
+#endif
+        private unsafe string Ctor(sbyte* value, int startIndex, int length)
+        {
+            if (startIndex < 0)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndex);
+
+            if (length < 0)
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_NegativeLength);
+
+            if (value == null)
+            {
+                if (length == 0)
+                    return Empty;
+
+                throw new ArgumentNullException(nameof(value));
+            }
+
+            byte* pStart = (byte*)(value + startIndex);
+
+            // overflow check
+            if (pStart < value)
+                throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_PartialWCHAR);
+
+            return CreateStringForSByteConstructor(pStart, length);
+        }
+
+        // Encoder for String..ctor(sbyte*) and String..ctor(sbyte*, int, int)
+        private static unsafe string CreateStringForSByteConstructor(byte *pb, int numBytes)
+        {
+            Debug.Assert(numBytes >= 0);
+            Debug.Assert(pb <= (pb + numBytes));
+
+            if (numBytes == 0)
+                return Empty;
+
+#if PLATFORM_UNIX
+            return Encoding.UTF8.GetString(pb, numBytes);
+#else
+            int numCharsRequired = Interop.Kernel32.MultiByteToWideChar(Interop.Kernel32.CP_ACP, Interop.Kernel32.MB_PRECOMPOSED, pb, numBytes, (char*)null, 0);
+            if (numCharsRequired == 0)
+                throw new ArgumentException(SR.Arg_InvalidANSIString);
+
+            string newString = FastAllocateString(numCharsRequired);
+            fixed (char *pFirstChar = &newString._firstChar)
+            {
+                numCharsRequired = Interop.Kernel32.MultiByteToWideChar(Interop.Kernel32.CP_ACP, Interop.Kernel32.MB_PRECOMPOSED, pb, numBytes, pFirstChar, numCharsRequired);
+            }
+            if (numCharsRequired == 0)
+                throw new ArgumentException(SR.Arg_InvalidANSIString);
+            return newString;
+#endif
+        }
+
+        [CLSCompliant(false)]
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public extern unsafe String(sbyte* value, int startIndex, int length, Encoding enc);
+
+#if PROJECTN
+        [DependencyReductionRoot]
+#endif
+#if !CORECLR
+        static
+#endif
+        private unsafe string Ctor(sbyte* value, int startIndex, int length, Encoding enc)
+        {
+            if (enc == null)
+                return new string(value, startIndex, length);
+
+            if (length < 0)
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (startIndex < 0)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndex);
+
+            if (value == null)
+            {
+                if (length == 0)
+                    return Empty;
+
+                throw new ArgumentNullException(nameof(value));
+            }
+
+            byte* pStart = (byte*)(value + startIndex);
+
+            // overflow check
+            if (pStart < value)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_PartialWCHAR);
+
+            return enc.GetString(new ReadOnlySpan<byte>(pStart, length));
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern String(char c, int count);
+
+#if PROJECTN
+        [DependencyReductionRoot]
+#endif
+#if !CORECLR
+        static
+#endif
+        private string Ctor(char c, int count)
+        {
+            if (count <= 0)
+            {
+                if (count == 0)
+                    return Empty;
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NegativeCount);
+            }
+
+            string result = FastAllocateString(count);
+
+            if (c != '\0') // Fast path null char string
+            {
+                unsafe
+                {
+                    fixed (char* dest = &result._firstChar)
+                    {
+                        uint cc = (uint)((c << 16) | c);
+                        uint* dmem = (uint*)dest;
+                        if (count >= 4)
+                        {
+                            count -= 4;
+                            do
+                            {
+                                dmem[0] = cc;
+                                dmem[1] = cc;
+                                dmem += 2;
+                                count -= 4;
+                            } while (count >= 0);
+                        }
+                        if ((count & 2) != 0)
+                        {
+                            *dmem = cc;
+                            dmem++;
+                        }
+                        if ((count & 1) != 0)
+                            ((char*)dmem)[0] = c;
+                    }
+                }
+            }
+            return result;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern String(ReadOnlySpan<char> value);
+
+#if PROJECTN
+        [DependencyReductionRoot]
+#endif
+#if !CORECLR
+        static
+#endif
+        private unsafe string Ctor(ReadOnlySpan<char> value)
+        {
+            if (value.Length == 0)
+                return Empty;
+
+            string result = FastAllocateString(value.Length);
+            fixed (char* dest = &result._firstChar, src = &MemoryMarshal.GetReference(value))
+                wstrcpy(dest, src, value.Length);
+            return result;
+        }
+
+        public static string Create<TState>(int length, TState state, SpanAction<char, TState> action)
+        {
+            if (action == null)
+                throw new ArgumentNullException(nameof(action));
+
+            if (length <= 0)
+            {
+                if (length == 0)
+                    return Empty;
+                throw new ArgumentOutOfRangeException(nameof(length));
+            }
+
+            string result = FastAllocateString(length);
+            action(new Span<char>(ref result.GetRawStringData(), length), state);
+            return result;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static implicit operator ReadOnlySpan<char>(string value) =>
+            value != null ? new ReadOnlySpan<char>(ref value.GetRawStringData(), value.Length) : default;
+
+        public object Clone()
+        {
+            return this;
+        }
+
+        public static unsafe string Copy(string str)
+        {
+            if (str == null)
+                throw new ArgumentNullException(nameof(str));
+
+            string result = FastAllocateString(str.Length);
+            fixed (char* dest = &result._firstChar, src = &str._firstChar)
+                wstrcpy(dest, src, str.Length);
+            return result;
+        }
+
+        // Converts a substring of this string to an array of characters.  Copies the
+        // characters of this string beginning at position sourceIndex and ending at
+        // sourceIndex + count - 1 to the character array buffer, beginning
+        // at destinationIndex.
+        //
+        public unsafe void CopyTo(int sourceIndex, char[] destination, int destinationIndex, int count)
+        {
+            if (destination == null)
+                throw new ArgumentNullException(nameof(destination));
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NegativeCount);
+            if (sourceIndex < 0)
+                throw new ArgumentOutOfRangeException(nameof(sourceIndex), SR.ArgumentOutOfRange_Index);
+            if (count > Length - sourceIndex)
+                throw new ArgumentOutOfRangeException(nameof(sourceIndex), SR.ArgumentOutOfRange_IndexCount);
+            if (destinationIndex > destination.Length - count || destinationIndex < 0)
+                throw new ArgumentOutOfRangeException(nameof(destinationIndex), SR.ArgumentOutOfRange_IndexCount);
+
+            fixed (char* src = &_firstChar, dest = destination)
+                wstrcpy(dest + destinationIndex, src + sourceIndex, count);
+        }
+
+        // Returns the entire string as an array of characters.
+        public unsafe char[] ToCharArray()
+        {
+            if (Length == 0)
+                return Array.Empty<char>();
+
+            char[] chars = new char[Length];
+            fixed (char* src = &_firstChar, dest = &chars[0])
+                wstrcpy(dest, src, Length);
+            return chars;
+        }
+
+        // Returns a substring of this string as an array of characters.
+        //
+        public unsafe char[] ToCharArray(int startIndex, int length)
+        {
+            // Range check everything.
+            if (startIndex < 0 || startIndex > Length || startIndex > Length - length)
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+
+            if (length <= 0)
+            {
+                if (length == 0)
+                    return Array.Empty<char>();
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_Index);
+            }
+
+            char[] chars = new char[length];
+            fixed (char* src = &_firstChar, dest = &chars[0])
+                wstrcpy(dest, src + startIndex, length);
+            return chars;
+        }
+
+        [NonVersionable]
+        public static bool IsNullOrEmpty(string value)
+        {
+            // Using 0u >= (uint)value.Length rather than
+            // value.Length == 0 as it will elide the bounds check to
+            // the first char: value[0] if that is performed following the test
+            // for the same test cost.
+            // Ternary operator returning true/false prevents redundant asm generation:
+            // https://github.com/dotnet/coreclr/issues/914
+            return (value == null || 0u >= (uint)value.Length) ? true : false;
+        }
+
+        public static bool IsNullOrWhiteSpace(string value)
+        {
+            if (value == null) return true;
+
+            for (int i = 0; i < value.Length; i++)
+            {
+                if (!Char.IsWhiteSpace(value[i])) return false;
+            }
+
+            return true;
+        }
+
+        internal ref char GetRawStringData() => ref _firstChar;
+
+        // Helper for encodings so they can talk to our buffer directly
+        // stringLength must be the exact size we'll expect
+        internal static unsafe string CreateStringFromEncoding(
+            byte* bytes, int byteLength, Encoding encoding)
+        {
+            Debug.Assert(bytes != null);
+            Debug.Assert(byteLength >= 0);
+
+            // Get our string length
+            int stringLength = encoding.GetCharCount(bytes, byteLength, null);
+            Debug.Assert(stringLength >= 0, "stringLength >= 0");
+
+            // They gave us an empty string if they needed one
+            // 0 bytelength might be possible if there's something in an encoder
+            if (stringLength == 0)
+                return Empty;
+
+            string s = FastAllocateString(stringLength);
+            fixed (char* pTempChars = &s._firstChar)
+            {
+                int doubleCheck = encoding.GetChars(bytes, byteLength, pTempChars, stringLength, null);
+                Debug.Assert(stringLength == doubleCheck,
+                    "Expected encoding.GetChars to return same length as encoding.GetCharCount");
+            }
+
+            return s;
+        }
+
+        // This is only intended to be used by char.ToString.
+        // It is necessary to put the code in this class instead of Char, since _firstChar is a private member.
+        // Making _firstChar internal would be dangerous since it would make it much easier to break String's immutability.
+        internal static string CreateFromChar(char c)
+        {
+            string result = FastAllocateString(1);
+            result._firstChar = c;
+            return result;
+        }
+
+        internal static unsafe void wstrcpy(char* dmem, char* smem, int charCount)
+        {
+            Buffer.Memmove((byte*)dmem, (byte*)smem, ((uint)charCount) * 2);
+        }
+
+
+        // Returns this string.
+        public override string ToString()
+        {
+            return this;
+        }
+
+        // Returns this string.
+        public string ToString(IFormatProvider provider)
+        {
+            return this;
+        }
+
+        public CharEnumerator GetEnumerator()
+        {
+            return new CharEnumerator(this);
+        }
+
+        IEnumerator<char> IEnumerable<char>.GetEnumerator()
+        {
+            return new CharEnumerator(this);
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return new CharEnumerator(this);
+        }
+
+        internal static unsafe int wcslen(char* ptr)
+        {
+            char* end = ptr;
+
+            // First make sure our pointer is aligned on a word boundary
+            int alignment = IntPtr.Size - 1;
+
+            // If ptr is at an odd address (e.g. 0x5), this loop will simply iterate all the way
+            while (((uint)end & (uint)alignment) != 0)
+            {
+                if (*end == 0) goto FoundZero;
+                end++;
+            }
+
+#if !BIT64
+            // The following code is (somewhat surprisingly!) significantly faster than a naive loop,
+            // at least on x86 and the current jit.
+
+            // The loop condition below works because if "end[0] & end[1]" is non-zero, that means
+            // neither operand can have been zero. If is zero, we have to look at the operands individually,
+            // but we hope this going to fairly rare.
+
+            // In general, it would be incorrect to access end[1] if we haven't made sure
+            // end[0] is non-zero. However, we know the ptr has been aligned by the loop above
+            // so end[0] and end[1] must be in the same word (and therefore page), so they're either both accessible, or both not.
+
+            while ((end[0] & end[1]) != 0 || (end[0] != 0 && end[1] != 0))
+            {
+                end += 2;
+            }
+
+            Debug.Assert(end[0] == 0 || end[1] == 0);
+            if (end[0] != 0) end++;
+#else // !BIT64
+            // Based on https://graphics.stanford.edu/~seander/bithacks.html#ZeroInWord
+
+            // 64-bit implementation: process 1 ulong (word) at a time
+
+            // What we do here is add 0x7fff from each of the
+            // 4 individual chars within the ulong, using MagicMask.
+            // If the char > 0 and < 0x8001, it will have its high bit set.
+            // We then OR with MagicMask, to set all the other bits.
+            // This will result in all bits set (ulong.MaxValue) for any
+            // char that fits the above criteria, and something else otherwise.
+
+            // Note that for any char > 0x8000, this will be a false
+            // positive and we will fallback to the slow path and
+            // check each char individually. This is OK though, since
+            // we optimize for the common case (ASCII chars, which are < 0x80).
+
+            // NOTE: We can access a ulong a time since the ptr is aligned,
+            // and therefore we're only accessing the same word/page. (See notes
+            // for the 32-bit version above.)
+
+            const ulong MagicMask = 0x7fff7fff7fff7fff;
+
+            while (true)
+            {
+                ulong word = *(ulong*)end;
+                word += MagicMask; // cause high bit to be set if not zero, and <= 0x8000
+                word |= MagicMask; // set everything besides the high bits
+
+                if (word == ulong.MaxValue) // 0xffff...
+                {
+                    // all of the chars have their bits set (and therefore none can be 0)
+                    end += 4;
+                    continue;
+                }
+
+                // at least one of them didn't have their high bit set!
+                // go through each char and check for 0.
+
+                if (end[0] == 0) goto EndAt0;
+                if (end[1] == 0) goto EndAt1;
+                if (end[2] == 0) goto EndAt2;
+                if (end[3] == 0) goto EndAt3;
+
+                // if we reached here, it was a false positive-- just continue
+                end += 4;
+            }
+
+            EndAt3: end++;
+            EndAt2: end++;
+            EndAt1: end++;
+            EndAt0:
+#endif // !BIT64
+
+            FoundZero:
+            Debug.Assert(*end == 0);
+
+            int count = (int)(end - ptr);
+
+#if BIT64
+            // Check for overflow
+            if (ptr + count != end)
+                throw new ArgumentException(SR.Arg_MustBeNullTerminatedString);
+#else
+            Debug.Assert(ptr + count == end);
+#endif
+
+            return count;
+        }
+
+        //
+        // IConvertible implementation
+        // 
+
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.String;
+        }
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            return Convert.ToBoolean(this, provider);
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            return Convert.ToChar(this, provider);
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return Convert.ToSByte(this, provider);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return Convert.ToByte(this, provider);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return Convert.ToInt16(this, provider);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return Convert.ToUInt16(this, provider);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return Convert.ToInt32(this, provider);
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return Convert.ToUInt32(this, provider);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return Convert.ToInt64(this, provider);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return Convert.ToUInt64(this, provider);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            return Convert.ToSingle(this, provider);
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            return Convert.ToDouble(this, provider);
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            return Convert.ToDecimal(this, provider);
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            return Convert.ToDateTime(this, provider);
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+
+        // Normalization Methods
+        // These just wrap calls to Normalization class
+        public bool IsNormalized()
+        {
+            return IsNormalized(NormalizationForm.FormC);
+        }
+
+        public bool IsNormalized(NormalizationForm normalizationForm)
+        {
+#if CORECLR
+            if (this.IsFastSort())
+            {
+                // If its FastSort && one of the 4 main forms, then its already normalized
+                if (normalizationForm == NormalizationForm.FormC ||
+                    normalizationForm == NormalizationForm.FormKC ||
+                    normalizationForm == NormalizationForm.FormD ||
+                    normalizationForm == NormalizationForm.FormKD)
+                    return true;
+            }
+#endif
+            return Normalization.IsNormalized(this, normalizationForm);
+        }
+
+        public string Normalize()
+        {
+            return Normalize(NormalizationForm.FormC);
+        }
+
+        public string Normalize(NormalizationForm normalizationForm)
+        {
+#if CORECLR
+            if (this.IsAscii())
+            {
+                // If its FastSort && one of the 4 main forms, then its already normalized
+                if (normalizationForm == NormalizationForm.FormC ||
+                    normalizationForm == NormalizationForm.FormKC ||
+                    normalizationForm == NormalizationForm.FormD ||
+                    normalizationForm == NormalizationForm.FormKD)
+                    return this;
+            }
+#endif
+            return Normalization.Normalize(this, normalizationForm);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/StringComparer.cs b/src/System.Private.CoreLib/shared/System/StringComparer.cs
new file mode 100644
index 0000000000..cb2d32fccb
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/StringComparer.cs
@@ -0,0 +1,387 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public abstract class StringComparer : IComparer, IEqualityComparer, IComparer<string>, IEqualityComparer<string>
+    {
+        private static readonly CultureAwareComparer s_invariantCulture = new CultureAwareComparer(CultureInfo.InvariantCulture, CompareOptions.None);
+        private static readonly CultureAwareComparer s_invariantCultureIgnoreCase = new CultureAwareComparer(CultureInfo.InvariantCulture, CompareOptions.IgnoreCase);
+        private static readonly OrdinalCaseSensitiveComparer s_ordinal = new OrdinalCaseSensitiveComparer();
+        private static readonly OrdinalIgnoreCaseComparer s_ordinalIgnoreCase = new OrdinalIgnoreCaseComparer();        
+
+        public static StringComparer InvariantCulture
+        {
+            get
+            {
+                return s_invariantCulture;
+            }
+        }
+
+        public static StringComparer InvariantCultureIgnoreCase
+        {
+            get
+            {
+                return s_invariantCultureIgnoreCase;
+            }
+        }
+
+        public static StringComparer CurrentCulture
+        {
+            get
+            {
+                return new CultureAwareComparer(CultureInfo.CurrentCulture, CompareOptions.None);
+            }
+        }
+
+        public static StringComparer CurrentCultureIgnoreCase
+        {
+            get
+            {
+                return new CultureAwareComparer(CultureInfo.CurrentCulture, CompareOptions.IgnoreCase);
+            }
+        }
+
+        public static StringComparer Ordinal
+        {
+            get
+            {
+                return s_ordinal;
+            }
+        }
+
+        public static StringComparer OrdinalIgnoreCase
+        {
+            get
+            {
+                return s_ordinalIgnoreCase;
+            }
+        }
+
+        // Convert a StringComparison to a StringComparer
+        public static StringComparer FromComparison(StringComparison comparisonType)
+        {
+            switch (comparisonType)
+            {
+                case StringComparison.CurrentCulture:
+                    return CurrentCulture;
+                case StringComparison.CurrentCultureIgnoreCase:
+                    return CurrentCultureIgnoreCase;
+                case StringComparison.InvariantCulture:
+                    return InvariantCulture;
+                case StringComparison.InvariantCultureIgnoreCase:
+                    return InvariantCultureIgnoreCase;
+                case StringComparison.Ordinal:
+                    return Ordinal;
+                case StringComparison.OrdinalIgnoreCase:
+                    return OrdinalIgnoreCase;
+                default:
+                    throw new ArgumentException(SR.NotSupported_StringComparison, nameof(comparisonType));
+            }
+        }
+
+        public static StringComparer Create(CultureInfo culture, bool ignoreCase)
+        {
+            if (culture == null)
+            {
+                throw new ArgumentNullException(nameof(culture));
+            }
+            
+            return new CultureAwareComparer(culture, ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None);
+        }
+
+        public static StringComparer Create(CultureInfo culture, CompareOptions options)
+        {
+            if (culture == null)
+            {
+                throw new ArgumentException(nameof(culture));
+            }
+
+            return new CultureAwareComparer(culture, options);
+        }
+
+        public int Compare(object x, object y)
+        {
+            if (x == y) return 0;
+            if (x == null) return -1;
+            if (y == null) return 1;
+
+            String sa = x as String;
+            if (sa != null)
+            {
+                String sb = y as String;
+                if (sb != null)
+                {
+                    return Compare(sa, sb);
+                }
+            }
+
+            IComparable ia = x as IComparable;
+            if (ia != null)
+            {
+                return ia.CompareTo(y);
+            }
+
+            throw new ArgumentException(SR.Argument_ImplementIComparable);
+        }
+
+        public new bool Equals(Object x, Object y)
+        {
+            if (x == y) return true;
+            if (x == null || y == null) return false;
+
+            String sa = x as String;
+            if (sa != null)
+            {
+                String sb = y as String;
+                if (sb != null)
+                {
+                    return Equals(sa, sb);
+                }
+            }
+            return x.Equals(y);
+        }
+
+        public int GetHashCode(object obj)
+        {
+            if (obj == null)
+            {
+                throw new ArgumentNullException(nameof(obj));
+            }
+
+            string s = obj as string;
+            if (s != null)
+            {
+                return GetHashCode(s);
+            }
+            return obj.GetHashCode();
+        }
+
+        public abstract int Compare(String x, String y);
+        public abstract bool Equals(String x, String y);
+        public abstract int GetHashCode(string obj);
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class CultureAwareComparer : StringComparer, ISerializable
+    {
+        private const CompareOptions ValidCompareMaskOffFlags = ~(CompareOptions.IgnoreCase | CompareOptions.IgnoreSymbols | CompareOptions.IgnoreNonSpace | CompareOptions.IgnoreWidth | CompareOptions.IgnoreKanaType | CompareOptions.StringSort);
+
+        private readonly CompareInfo _compareInfo; // Do not rename (binary serialization)
+        private CompareOptions _options;
+
+        internal CultureAwareComparer(CultureInfo culture, CompareOptions options) : this(culture.CompareInfo, options) { }
+
+        internal CultureAwareComparer(CompareInfo compareInfo, CompareOptions options)
+        {
+            _compareInfo = compareInfo;
+
+            if ((options & ValidCompareMaskOffFlags) != 0)
+            {
+                throw new ArgumentException(SR.Argument_InvalidFlag, nameof(options));
+            }
+            _options = options;
+        }
+
+        private CultureAwareComparer(SerializationInfo info, StreamingContext context)
+        {
+            _compareInfo = (CompareInfo)info.GetValue("_compareInfo", typeof(CompareInfo));
+            bool ignoreCase = info.GetBoolean("_ignoreCase");
+
+            var obj = info.GetValueNoThrow("_options", typeof(CompareOptions));
+            if (obj != null)
+                _options = (CompareOptions)obj;
+
+            // fix up the _options value in case we are getting old serialized object not having _options
+            _options |= ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None;
+        }
+
+        public override int Compare(string x, string y)
+        {
+            if (object.ReferenceEquals(x, y)) return 0;
+            if (x == null) return -1;
+            if (y == null) return 1;
+            return _compareInfo.Compare(x, y, _options);
+        }
+
+        public override bool Equals(string x, string y)
+        {
+            if (object.ReferenceEquals(x, y)) return true;
+            if (x == null || y == null) return false;
+            return _compareInfo.Compare(x, y, _options) == 0;
+        }
+
+        public override int GetHashCode(string obj)
+        {
+            if (obj == null)
+            {
+                throw new ArgumentNullException(nameof(obj));
+            }
+            return _compareInfo.GetHashCodeOfString(obj, _options);
+        }
+
+        // Equals method for the comparer itself.
+        public override bool Equals(object obj)
+        {
+            CultureAwareComparer comparer = obj as CultureAwareComparer;
+            return
+                comparer != null &&
+                _options == comparer._options &&
+                _compareInfo.Equals(comparer._compareInfo);
+        }
+
+        public override int GetHashCode()
+        {
+            return _compareInfo.GetHashCode() ^ ((int)_options & 0x7FFFFFFF);
+        }
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            info.AddValue("_compareInfo", _compareInfo);
+            info.AddValue("_options", _options);
+            info.AddValue("_ignoreCase", (_options & CompareOptions.IgnoreCase) != 0);
+        }
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class OrdinalComparer : StringComparer 
+    {
+        private readonly bool _ignoreCase; // Do not rename (binary serialization)
+
+        internal OrdinalComparer(bool ignoreCase)
+        {
+            _ignoreCase = ignoreCase;
+        }
+
+        public override int Compare(string x, string y)
+        {
+            if (ReferenceEquals(x, y))
+                return 0;
+            if (x == null)
+                return -1;
+            if (y == null)
+                return 1;
+
+            if (_ignoreCase)
+            {
+                return string.Compare(x, y, StringComparison.OrdinalIgnoreCase);
+            }
+
+            return string.CompareOrdinal(x, y);
+        }
+
+        public override bool Equals(string x, string y)
+        {
+            if (ReferenceEquals(x, y))
+                return true;
+            if (x == null || y == null)
+                return false;
+
+            if (_ignoreCase)
+            {
+                if (x.Length != y.Length)
+                {
+                    return false;
+                }
+                return (string.Compare(x, y, StringComparison.OrdinalIgnoreCase) == 0);
+            }
+            return x.Equals(y);
+        }
+
+        public override int GetHashCode(string obj)
+        {
+            if (obj == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.obj);
+            }
+
+            if (_ignoreCase)
+            {
+                return CompareInfo.GetIgnoreCaseHash(obj);
+            }
+
+            return obj.GetHashCode();
+        }
+
+        // Equals method for the comparer itself. 
+        public override bool Equals(object obj)
+        {
+            OrdinalComparer comparer = obj as OrdinalComparer;
+            if (comparer == null)
+            {
+                return false;
+            }
+            return (this._ignoreCase == comparer._ignoreCase);
+        }
+
+        public override int GetHashCode()
+        {
+            int hashCode = nameof(OrdinalComparer).GetHashCode();
+            return _ignoreCase ? (~hashCode) : hashCode;
+        }
+    }
+
+    [Serializable]
+    internal sealed class OrdinalCaseSensitiveComparer : OrdinalComparer, ISerializable
+    {
+        public OrdinalCaseSensitiveComparer() : base(false)
+        {
+        }
+
+        public override int Compare(string x, string y) => string.CompareOrdinal(x, y);
+
+        public override bool Equals(string x, string y) => string.Equals(x, y);
+
+        public override int GetHashCode(string obj)
+        {
+            if (obj == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.obj);
+            }
+            return obj.GetHashCode();
+        }
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            info.SetType(typeof(OrdinalComparer));
+            info.AddValue("_ignoreCase", false);
+        }
+    }
+
+    [Serializable]
+    internal sealed class OrdinalIgnoreCaseComparer : OrdinalComparer, ISerializable
+    {
+        public OrdinalIgnoreCaseComparer() : base(true)
+        {
+        }
+
+        public override int Compare(string x, string y) => string.Compare(x, y, StringComparison.OrdinalIgnoreCase);
+
+        public override bool Equals(string x, string y) => string.Equals(x, y, StringComparison.OrdinalIgnoreCase);
+
+        public override int GetHashCode(string obj)
+        {
+            if (obj == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.obj);
+            }
+            return CompareInfo.GetIgnoreCaseHash(obj);
+        }
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            info.SetType(typeof(OrdinalComparer));
+            info.AddValue("_ignoreCase", true);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/StringComparison.cs b/src/System.Private.CoreLib/shared/System/StringComparison.cs
new file mode 100644
index 0000000000..d5c18c8021
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/StringComparison.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    public enum StringComparison
+    {
+        CurrentCulture = 0,
+        CurrentCultureIgnoreCase = 1,
+        InvariantCulture = 2,
+        InvariantCultureIgnoreCase = 3,
+        Ordinal = 4,
+        OrdinalIgnoreCase = 5,
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/StringSplitOptions.cs b/src/System.Private.CoreLib/shared/System/StringSplitOptions.cs
new file mode 100644
index 0000000000..d7020559a1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/StringSplitOptions.cs
@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    [Flags]
+    public enum StringSplitOptions
+    {
+        None = 0,
+        RemoveEmptyEntries = 1
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/SystemException.cs b/src/System.Private.CoreLib/shared/System/SystemException.cs
new file mode 100644
index 0000000000..b7e8e42175
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/SystemException.cs
@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class SystemException : Exception
+    {
+        public SystemException()
+            : base(SR.Arg_SystemException)
+        {
+            HResult = HResults.COR_E_SYSTEM;
+        }
+
+        public SystemException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_SYSTEM;
+        }
+
+        public SystemException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_SYSTEM;
+        }
+
+        protected SystemException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/ASCIIEncoding.cs b/src/System.Private.CoreLib/shared/System/Text/ASCIIEncoding.cs
new file mode 100644
index 0000000000..e89943a192
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/ASCIIEncoding.cs
@@ -0,0 +1,945 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System.Text
+{
+    // ASCIIEncoding
+    //
+    // Note that ASCIIEncoding is optimized with no best fit and ? for fallback.
+    // It doesn't come in other flavors.
+    //
+    // Note: ASCIIEncoding is the only encoding that doesn't do best fit (windows has best fit).
+    //
+    // Note: IsAlwaysNormalized remains false because 1/2 the code points are unassigned, so they'd
+    //       use fallbacks, and we cannot guarantee that fallbacks are normalized.
+
+    public class ASCIIEncoding : Encoding
+    {
+        // Allow for devirtualization (see https://github.com/dotnet/coreclr/pull/9230)
+        internal sealed class ASCIIEncodingSealed : ASCIIEncoding { }
+
+        // Used by Encoding.ASCII for lazy initialization
+        // The initialization code will not be run until a static member of the class is referenced
+        internal static readonly ASCIIEncodingSealed s_default = new ASCIIEncodingSealed();
+
+        public ASCIIEncoding() : base(Encoding.CodePageASCII)
+        {
+        }
+
+        internal override void SetDefaultFallbacks()
+        {
+            // For ASCIIEncoding we just use default replacement fallback
+            this.encoderFallback = EncoderFallback.ReplacementFallback;
+            this.decoderFallback = DecoderFallback.ReplacementFallback;
+        }
+
+        // WARNING: GetByteCount(string chars), GetBytes(string chars,...), and GetString(byte[] byteIndex...)
+        // WARNING: have different variable names than EncodingNLS.cs, so this can't just be cut & pasted,
+        // WARNING: or it'll break VB's way of calling these.
+        //
+        // The following methods are copied from EncodingNLS.cs.
+        // Unfortunately EncodingNLS.cs is internal and we're public, so we have to re-implement them here.
+        // These should be kept in sync for the following classes:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        // Returns the number of bytes required to encode a range of characters in
+        // a character array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetByteCount(char[] chars, int index, int count)
+        {
+            // Validate input parameters
+            if (chars == null)
+                throw new ArgumentNullException("chars", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - index < count)
+                throw new ArgumentOutOfRangeException("chars", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // If no input, return 0, avoid fixed empty array problem
+            if (count == 0)
+                return 0;
+
+            // Just call the pointer version
+            fixed (char* pChars = chars)
+                return GetByteCount(pChars + index, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetByteCount(String chars)
+        {
+            // Validate input
+            if (chars==null)
+                throw new ArgumentNullException("chars");
+
+            fixed (char* pChars = chars)
+                return GetByteCount(pChars, chars.Length, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetByteCount(char* chars, int count)
+        {
+            // Validate Parameters
+            if (chars == null)
+                throw new ArgumentNullException("chars", SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException("count", SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Call it with empty encoder
+            return GetByteCount(chars, count, null);
+        }
+
+        // Parent method is safe.
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        public override unsafe int GetBytes(String chars, int charIndex, int charCount,
+                                              byte[] bytes, int byteIndex)
+        {
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException((chars == null ? "chars" : "bytes"), SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? "charIndex" : "charCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException("chars", SR.ArgumentOutOfRange_IndexCount);
+
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+                throw new ArgumentOutOfRangeException("byteIndex", SR.ArgumentOutOfRange_Index);
+
+            int byteCount = bytes.Length - byteIndex;
+
+            fixed (char* pChars = chars) fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+                return GetBytes(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, null);
+        }
+
+        // Encodes a range of characters in a character array into a range of bytes
+        // in a byte array. An exception occurs if the byte array is not large
+        // enough to hold the complete encoding of the characters. The
+        // GetByteCount method can be used to determine the exact number of
+        // bytes that will be produced for a given range of characters.
+        // Alternatively, the GetMaxByteCount method can be used to
+        // determine the maximum number of bytes that will be produced for a given
+        // number of characters, regardless of the actual character values.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetBytes(char[] chars, int charIndex, int charCount,
+                                               byte[] bytes, int byteIndex)
+        {
+            // Validate parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException((chars == null ? "chars" : "bytes"), SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? "charIndex" : "charCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException("chars", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+                throw new ArgumentOutOfRangeException("byteIndex", SR.ArgumentOutOfRange_Index);
+
+            // If nothing to encode return 0
+            if (charCount == 0)
+                return 0;
+
+            // Just call pointer version
+            int byteCount = bytes.Length - byteIndex;
+
+            fixed (char* pChars = chars)  fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+                // Remember that byteCount is # to decode, not size of array.
+                return GetBytes(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetBytes(char* chars, int charCount, byte* bytes, int byteCount)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? "charCount" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetBytes(chars, charCount, bytes, byteCount, null);
+        }
+
+        // Returns the number of characters produced by decoding a range of bytes
+        // in a byte array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetCharCount(byte[] bytes, int index, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (bytes.Length - index < count)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // If no input just return 0, fixed doesn't like 0 length arrays
+            if (count == 0)
+                return 0;
+
+            // Just call pointer version
+            fixed (byte* pBytes = bytes)
+                return GetCharCount(pBytes + index, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetCharCount(byte* bytes, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException("count", SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetCharCount(bytes, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetChars(byte[] bytes, int byteIndex, int byteCount,
+                                              char[] chars, int charIndex)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (byteIndex < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((byteIndex < 0 ? "byteIndex" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if ( bytes.Length - byteIndex < byteCount)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (charIndex < 0 || charIndex > chars.Length)
+                throw new ArgumentOutOfRangeException("charIndex", SR.ArgumentOutOfRange_Index);
+
+            // If no input, return 0 & avoid fixed problem
+            if (byteCount == 0)
+                return 0;
+
+            // Just call pointer version
+            int charCount = chars.Length - charIndex;
+
+            fixed (byte* pBytes = bytes) fixed (char* pChars = &MemoryMarshal.GetReference((Span<char>)chars))
+                // Remember that charCount is # to decode, not size of array
+                return GetChars(pBytes + byteIndex, byteCount, pChars + charIndex, charCount, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public unsafe override int GetChars(byte* bytes, int byteCount, char* chars, int charCount)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? "charCount" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetChars(bytes, byteCount, chars, charCount, null);
+        }
+
+        // Returns a string containing the decoded representation of a range of
+        // bytes in a byte array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe String GetString(byte[] bytes, int byteIndex, int byteCount)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (byteIndex < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((byteIndex < 0 ? "byteIndex" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+
+            if (bytes.Length - byteIndex < byteCount)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // Avoid problems with empty input buffer
+            if (byteCount == 0) return String.Empty;
+
+            fixed (byte* pBytes = bytes)
+                return String.CreateStringFromEncoding(
+                    pBytes + byteIndex, byteCount, this);
+        }
+
+        //
+        // End of standard methods copied from EncodingNLS.cs
+        //
+
+        // GetByteCount
+        // Note: We start by assuming that the output will be the same as count.  Having
+        // an encoder or fallback may change that assumption
+        internal override unsafe int GetByteCount(char* chars, int charCount, EncoderNLS encoder)
+        {
+            // Just need to ASSERT, this is called by something else internal that checked parameters already
+            Debug.Assert(charCount >= 0, "[ASCIIEncoding.GetByteCount]count is negative");
+            Debug.Assert(chars != null, "[ASCIIEncoding.GetByteCount]chars is null");
+
+            // Assert because we shouldn't be able to have a null encoder.
+            Debug.Assert(encoderFallback != null, "[ASCIIEncoding.GetByteCount]Attempting to use null fallback encoder");
+
+            char charLeftOver = (char)0;
+            EncoderReplacementFallback fallback = null;
+
+            // Start by assuming default count, then +/- for fallback characters
+            char* charEnd = chars + charCount;
+
+            // For fallback we may need a fallback buffer, we know we aren't default fallback.
+            EncoderFallbackBuffer fallbackBuffer = null;
+            char* charsForFallback;
+
+            if (encoder != null)
+            {
+                charLeftOver = encoder._charLeftOver;
+                Debug.Assert(charLeftOver == 0 || Char.IsHighSurrogate(charLeftOver),
+                    "[ASCIIEncoding.GetByteCount]leftover character should be high surrogate");
+
+                fallback = encoder.Fallback as EncoderReplacementFallback;
+
+                // We mustn't have left over fallback data when counting
+                if (encoder.InternalHasFallbackBuffer)
+                {
+                    // We always need the fallback buffer in get bytes so we can flush any remaining ones if necessary
+                    fallbackBuffer = encoder.FallbackBuffer;
+                    if (fallbackBuffer.Remaining > 0 && encoder._throwOnOverflow)
+                        throw new ArgumentException(SR.Format(SR.Argument_EncoderFallbackNotEmpty, this.EncodingName, encoder.Fallback.GetType()));
+
+                    // Set our internal fallback interesting things.
+                    fallbackBuffer.InternalInitialize(chars, charEnd, encoder, false);
+                }
+
+                // Verify that we have no fallbackbuffer, for ASCII its always empty, so just assert
+                Debug.Assert(!encoder._throwOnOverflow || !encoder.InternalHasFallbackBuffer ||
+                    encoder.FallbackBuffer.Remaining == 0,
+                    "[ASCIICodePageEncoding.GetByteCount]Expected empty fallback buffer");
+            }
+            else
+            {
+                fallback = this.EncoderFallback as EncoderReplacementFallback;
+            }
+
+            // If we have an encoder AND we aren't using default fallback,
+            // then we may have a complicated count.
+            if (fallback != null && fallback.MaxCharCount == 1)
+            {
+                // Replacement fallback encodes surrogate pairs as two ?? (or two whatever), so return size is always
+                // same as input size.
+                // Note that no existing SBCS code pages map code points to supplimentary characters, so this is easy.
+
+                // We could however have 1 extra byte if the last call had an encoder and a funky fallback and
+                // if we don't use the funky fallback this time.
+
+                // Do we have an extra char left over from last time?
+                if (charLeftOver > 0)
+                    charCount++;
+
+                return (charCount);
+            }
+
+            // Count is more complicated if you have a funky fallback
+            // For fallback we may need a fallback buffer, we know we're not default fallback
+            int byteCount = 0;
+
+            // We may have a left over character from last time, try and process it.
+            if (charLeftOver > 0)
+            {
+                Debug.Assert(Char.IsHighSurrogate(charLeftOver), "[ASCIIEncoding.GetByteCount]leftover character should be high surrogate");
+                Debug.Assert(encoder != null, "[ASCIIEncoding.GetByteCount]Expected encoder");
+
+                // Since left over char was a surrogate, it'll have to be fallen back.
+                // Get Fallback
+                fallbackBuffer = encoder.FallbackBuffer;
+                fallbackBuffer.InternalInitialize(chars, charEnd, encoder, false);
+
+                // This will fallback a pair if *chars is a low surrogate
+                charsForFallback = chars; // Avoid passing chars by reference to allow it to be enregistered
+                fallbackBuffer.InternalFallback(charLeftOver, ref charsForFallback);
+                chars = charsForFallback;
+            }
+
+            // Now we may have fallback char[] already from the encoder
+
+            // Go ahead and do it, including the fallback.
+            char ch;
+            while ((ch = (fallbackBuffer == null) ? '\0' : fallbackBuffer.InternalGetNextChar()) != 0 ||
+                    chars < charEnd)
+            {
+                // First unwind any fallback
+                if (ch == 0)
+                {
+                    // No fallback, just get next char
+                    ch = *chars;
+                    chars++;
+                }
+
+                // Check for fallback, this'll catch surrogate pairs too.
+                // no chars >= 0x80 are allowed.
+                if (ch > 0x7f)
+                {
+                    if (fallbackBuffer == null)
+                    {
+                        // Initialize the buffer
+                        if (encoder == null)
+                            fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = encoder.FallbackBuffer;
+                        fallbackBuffer.InternalInitialize(charEnd - charCount, charEnd, encoder, false);
+                    }
+
+                    // Get Fallback
+                    charsForFallback = chars; // Avoid passing chars by reference to allow it to be enregistered
+                    fallbackBuffer.InternalFallback(ch, ref charsForFallback);
+                    chars = charsForFallback;
+                    continue;
+                }
+
+                // We'll use this one
+                byteCount++;
+            }
+
+            Debug.Assert(fallbackBuffer == null || fallbackBuffer.Remaining == 0,
+                "[ASCIIEncoding.GetByteCount]Expected Empty fallback buffer");
+
+            return byteCount;
+        }
+
+        internal override unsafe int GetBytes(char* chars, int charCount,
+                                                byte* bytes, int byteCount, EncoderNLS encoder)
+        {
+            // Just need to ASSERT, this is called by something else internal that checked parameters already
+            Debug.Assert(bytes != null, "[ASCIIEncoding.GetBytes]bytes is null");
+            Debug.Assert(byteCount >= 0, "[ASCIIEncoding.GetBytes]byteCount is negative");
+            Debug.Assert(chars != null, "[ASCIIEncoding.GetBytes]chars is null");
+            Debug.Assert(charCount >= 0, "[ASCIIEncoding.GetBytes]charCount is negative");
+
+            // Assert because we shouldn't be able to have a null encoder.
+            Debug.Assert(encoderFallback != null, "[ASCIIEncoding.GetBytes]Attempting to use null encoder fallback");
+
+            // Get any left over characters
+            char charLeftOver = (char)0;
+            EncoderReplacementFallback fallback = null;
+
+            // For fallback we may need a fallback buffer, we know we aren't default fallback.
+            EncoderFallbackBuffer fallbackBuffer = null;
+            char* charsForFallback;
+
+            // prepare our end
+            char* charEnd = chars + charCount;
+            byte* byteStart = bytes;
+            char* charStart = chars;
+
+            if (encoder != null)
+            {
+                charLeftOver = encoder._charLeftOver;
+                fallback = encoder.Fallback as EncoderReplacementFallback;
+
+                // We mustn't have left over fallback data when counting
+                if (encoder.InternalHasFallbackBuffer)
+                {
+                    // We always need the fallback buffer in get bytes so we can flush any remaining ones if necessary
+                    fallbackBuffer = encoder.FallbackBuffer;
+                    if (fallbackBuffer.Remaining > 0 && encoder._throwOnOverflow)
+                        throw new ArgumentException(SR.Format(SR.Argument_EncoderFallbackNotEmpty, this.EncodingName, encoder.Fallback.GetType()));
+
+                    // Set our internal fallback interesting things.
+                    fallbackBuffer.InternalInitialize(charStart, charEnd, encoder, true);
+                }
+
+                Debug.Assert(charLeftOver == 0 || Char.IsHighSurrogate(charLeftOver),
+                    "[ASCIIEncoding.GetBytes]leftover character should be high surrogate");
+
+                // Verify that we have no fallbackbuffer, for ASCII its always empty, so just assert
+                Debug.Assert(!encoder._throwOnOverflow || !encoder.InternalHasFallbackBuffer ||
+                    encoder.FallbackBuffer.Remaining == 0,
+                    "[ASCIICodePageEncoding.GetBytes]Expected empty fallback buffer");
+            }
+            else
+            {
+                fallback = this.EncoderFallback as EncoderReplacementFallback;
+            }
+
+
+            // See if we do the fast default or slightly slower fallback
+            if (fallback != null && fallback.MaxCharCount == 1)
+            {
+                // Fast version
+                char cReplacement = fallback.DefaultString[0];
+
+                // Check for replacements in range, otherwise fall back to slow version.
+                if (cReplacement <= (char)0x7f)
+                {
+                    // We should have exactly as many output bytes as input bytes, unless there's a left
+                    // over character, in which case we may need one more.
+                    // If we had a left over character will have to add a ?  (This happens if they had a funky
+                    // fallback last time, but not this time.) (We can't spit any out though
+                    // because with fallback encoder each surrogate is treated as a seperate code point)
+                    if (charLeftOver > 0)
+                    {
+                        // Have to have room
+                        // Throw even if doing no throw version because this is just 1 char,
+                        // so buffer will never be big enough
+                        if (byteCount == 0)
+                            ThrowBytesOverflow(encoder, true);
+
+                        // This'll make sure we still have more room and also make sure our return value is correct.
+                        *(bytes++) = (byte)cReplacement;
+                        byteCount--;                // We used one of the ones we were counting.
+                    }
+
+                    // This keeps us from overrunning our output buffer
+                    if (byteCount < charCount)
+                    {
+                        // Throw or make buffer smaller?
+                        ThrowBytesOverflow(encoder, byteCount < 1);
+
+                        // Just use what we can
+                        charEnd = chars + byteCount;
+                    }
+
+                    // We just do a quick copy
+                    while (chars < charEnd)
+                    {
+                        char ch2 = *(chars++);
+                        if (ch2 >= 0x0080) *(bytes++) = (byte)cReplacement;
+                        else *(bytes++) = unchecked((byte)(ch2));
+                    }
+
+                    // Clear encoder
+                    if (encoder != null)
+                    {
+                        encoder._charLeftOver = (char)0;
+                        encoder._charsUsed = (int)(chars - charStart);
+                    }
+
+                    return (int)(bytes - byteStart);
+                }
+            }
+
+            // Slower version, have to do real fallback.
+
+            // prepare our end
+            byte* byteEnd = bytes + byteCount;
+
+            // We may have a left over character from last time, try and process it.
+            if (charLeftOver > 0)
+            {
+                // Initialize the buffer
+                Debug.Assert(encoder != null,
+                    "[ASCIIEncoding.GetBytes]Expected non null encoder if we have surrogate left over");
+                fallbackBuffer = encoder.FallbackBuffer;
+                fallbackBuffer.InternalInitialize(chars, charEnd, encoder, true);
+
+                // Since left over char was a surrogate, it'll have to be fallen back.
+                // Get Fallback
+                // This will fallback a pair if *chars is a low surrogate
+                charsForFallback = chars; // Avoid passing chars by reference to allow it to be enregistered
+                fallbackBuffer.InternalFallback(charLeftOver, ref charsForFallback);
+                chars = charsForFallback;
+            }
+
+            // Now we may have fallback char[] already from the encoder
+
+            // Go ahead and do it, including the fallback.
+            char ch;
+            while ((ch = (fallbackBuffer == null) ? '\0' : fallbackBuffer.InternalGetNextChar()) != 0 ||
+                    chars < charEnd)
+            {
+                // First unwind any fallback
+                if (ch == 0)
+                {
+                    // No fallback, just get next char
+                    ch = *chars;
+                    chars++;
+                }
+
+                // Check for fallback, this'll catch surrogate pairs too.
+                // All characters >= 0x80 must fall back.
+                if (ch > 0x7f)
+                {
+                    // Initialize the buffer
+                    if (fallbackBuffer == null)
+                    {
+                        if (encoder == null)
+                            fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = encoder.FallbackBuffer;
+                        fallbackBuffer.InternalInitialize(charEnd - charCount, charEnd, encoder, true);
+                    }
+
+                    // Get Fallback
+                    charsForFallback = chars; // Avoid passing chars by reference to allow it to be enregistered
+                    fallbackBuffer.InternalFallback(ch, ref charsForFallback);
+                    chars = charsForFallback;
+
+                    // Go ahead & continue (& do the fallback)
+                    continue;
+                }
+
+                // We'll use this one
+                // Bounds check
+                if (bytes >= byteEnd)
+                {
+                    // didn't use this char, we'll throw or use buffer
+                    if (fallbackBuffer == null || fallbackBuffer.bFallingBack == false)
+                    {
+                        Debug.Assert(chars > charStart || bytes == byteStart,
+                            "[ASCIIEncoding.GetBytes]Expected chars to have advanced already.");
+                        chars--;                                        // don't use last char
+                    }
+                    else
+                        fallbackBuffer.MovePrevious();
+
+                    // Are we throwing or using buffer?
+                    ThrowBytesOverflow(encoder, bytes == byteStart);    // throw?
+                    break;                                              // don't throw, stop
+                }
+
+                // Go ahead and add it
+                *bytes = unchecked((byte)ch);
+                bytes++;
+            }
+
+            // Need to do encoder stuff
+            if (encoder != null)
+            {
+                // Fallback stuck it in encoder if necessary, but we have to clear MustFlush cases
+                if (fallbackBuffer != null && !fallbackBuffer.bUsedEncoder)
+                    // Clear it in case of MustFlush
+                    encoder._charLeftOver = (char)0;
+
+                // Set our chars used count
+                encoder._charsUsed = (int)(chars - charStart);
+            }
+
+            Debug.Assert(fallbackBuffer == null || fallbackBuffer.Remaining == 0 ||
+                (encoder != null && !encoder._throwOnOverflow),
+                "[ASCIIEncoding.GetBytes]Expected Empty fallback buffer at end");
+
+            return (int)(bytes - byteStart);
+        }
+
+        // This is internal and called by something else,
+        internal override unsafe int GetCharCount(byte* bytes, int count, DecoderNLS decoder)
+        {
+            // Just assert, we're called internally so these should be safe, checked already
+            Debug.Assert(bytes != null, "[ASCIIEncoding.GetCharCount]bytes is null");
+            Debug.Assert(count >= 0, "[ASCIIEncoding.GetCharCount]byteCount is negative");
+
+            // ASCII doesn't do best fit, so don't have to check for it, find out which decoder fallback we're using
+            DecoderReplacementFallback fallback = null;
+
+            if (decoder == null)
+                fallback = this.DecoderFallback as DecoderReplacementFallback;
+            else
+            {
+                fallback = decoder.Fallback as DecoderReplacementFallback;
+                Debug.Assert(!decoder._throwOnOverflow || !decoder.InternalHasFallbackBuffer ||
+                    decoder.FallbackBuffer.Remaining == 0,
+                    "[ASCIICodePageEncoding.GetCharCount]Expected empty fallback buffer");
+            }
+
+            if (fallback != null && fallback.MaxCharCount == 1)
+            {
+                // Just return length, SBCS stay the same length because they don't map to surrogate
+                // pairs and we don't have a decoder fallback.
+
+                return count;
+            }
+
+            // Only need decoder fallback buffer if not using default replacement fallback, no best fit for ASCII
+            DecoderFallbackBuffer fallbackBuffer = null;
+
+            // Have to do it the hard way.
+            // Assume charCount will be == count
+            int charCount = count;
+            byte[] byteBuffer = new byte[1];
+
+            // Do it our fast way
+            byte* byteEnd = bytes + count;
+
+            // Quick loop
+            while (bytes < byteEnd)
+            {
+                // Faster if don't use *bytes++;
+                byte b = *bytes;
+                bytes++;
+
+                // If unknown we have to do fallback count
+                if (b >= 0x80)
+                {
+                    if (fallbackBuffer == null)
+                    {
+                        if (decoder == null)
+                            fallbackBuffer = this.DecoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = decoder.FallbackBuffer;
+                        fallbackBuffer.InternalInitialize(byteEnd - count, null);
+                    }
+
+                    // Use fallback buffer
+                    byteBuffer[0] = b;
+                    charCount--;            // Have to unreserve the one we already allocated for b
+                    charCount += fallbackBuffer.InternalFallback(byteBuffer, bytes);
+                }
+            }
+
+            // Fallback buffer must be empty
+            Debug.Assert(fallbackBuffer == null || fallbackBuffer.Remaining == 0,
+                "[ASCIIEncoding.GetCharCount]Expected Empty fallback buffer");
+
+            // Converted sequence is same length as input
+            return charCount;
+        }
+
+        internal override unsafe int GetChars(byte* bytes, int byteCount,
+                                                char* chars, int charCount, DecoderNLS decoder)
+        {
+            // Just need to ASSERT, this is called by something else internal that checked parameters already
+            Debug.Assert(bytes != null, "[ASCIIEncoding.GetChars]bytes is null");
+            Debug.Assert(byteCount >= 0, "[ASCIIEncoding.GetChars]byteCount is negative");
+            Debug.Assert(chars != null, "[ASCIIEncoding.GetChars]chars is null");
+            Debug.Assert(charCount >= 0, "[ASCIIEncoding.GetChars]charCount is negative");
+
+            // Do it fast way if using ? replacement fallback
+            byte* byteEnd = bytes + byteCount;
+            byte* byteStart = bytes;
+            char* charStart = chars;
+
+            // Note: ASCII doesn't do best fit, but we have to fallback if they use something > 0x7f
+            // Only need decoder fallback buffer if not using ? fallback.
+            // ASCII doesn't do best fit, so don't have to check for it, find out which decoder fallback we're using
+            DecoderReplacementFallback fallback = null;
+            char* charsForFallback;
+
+            if (decoder == null)
+                fallback = this.DecoderFallback as DecoderReplacementFallback;
+            else
+            {
+                fallback = decoder.Fallback as DecoderReplacementFallback;
+                Debug.Assert(!decoder._throwOnOverflow || !decoder.InternalHasFallbackBuffer ||
+                    decoder.FallbackBuffer.Remaining == 0,
+                    "[ASCIICodePageEncoding.GetChars]Expected empty fallback buffer");
+            }
+
+            if (fallback != null && fallback.MaxCharCount == 1)
+            {
+                // Try it the fast way
+                char replacementChar = fallback.DefaultString[0];
+
+                // Need byteCount chars, otherwise too small buffer
+                if (charCount < byteCount)
+                {
+                    // Need at least 1 output byte, throw if must throw
+                    ThrowCharsOverflow(decoder, charCount < 1);
+
+                    // Not throwing, use what we can
+                    byteEnd = bytes + charCount;
+                }
+
+                // Quick loop, just do '?' replacement because we don't have fallbacks for decodings.
+                while (bytes < byteEnd)
+                {
+                    byte b = *(bytes++);
+                    if (b >= 0x80)
+                        // This is an invalid byte in the ASCII encoding.
+                        *(chars++) = replacementChar;
+                    else
+                        *(chars++) = unchecked((char)b);
+                }
+
+                // bytes & chars used are the same
+                if (decoder != null)
+                    decoder._bytesUsed = (int)(bytes - byteStart);
+                return (int)(chars - charStart);
+            }
+
+            // Slower way's going to need a fallback buffer
+            DecoderFallbackBuffer fallbackBuffer = null;
+            byte[] byteBuffer = new byte[1];
+            char* charEnd = chars + charCount;
+
+            // Not quite so fast loop
+            while (bytes < byteEnd)
+            {
+                // Faster if don't use *bytes++;
+                byte b = *(bytes);
+                bytes++;
+
+                if (b >= 0x80)
+                {
+                    // This is an invalid byte in the ASCII encoding.
+                    if (fallbackBuffer == null)
+                    {
+                        if (decoder == null)
+                            fallbackBuffer = this.DecoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = decoder.FallbackBuffer;
+                        fallbackBuffer.InternalInitialize(byteEnd - byteCount, charEnd);
+                    }
+
+                    // Use fallback buffer
+                    byteBuffer[0] = b;
+
+                    // Note that chars won't get updated unless this succeeds
+                    charsForFallback = chars; // Avoid passing chars by reference to allow it to be enregistered
+                    bool fallbackResult = fallbackBuffer.InternalFallback(byteBuffer, bytes, ref charsForFallback);
+                    chars = charsForFallback;
+
+                    if (!fallbackResult)
+                    {
+                        // May or may not throw, but we didn't get this byte
+                        Debug.Assert(bytes > byteStart || chars == charStart,
+                            "[ASCIIEncoding.GetChars]Expected bytes to have advanced already (fallback case)");
+                        bytes--;                                            // unused byte
+                        fallbackBuffer.InternalReset();                     // Didn't fall this back
+                        ThrowCharsOverflow(decoder, chars == charStart);    // throw?
+                        break;                                              // don't throw, but stop loop
+                    }
+                }
+                else
+                {
+                    // Make sure we have buffer space
+                    if (chars >= charEnd)
+                    {
+                        Debug.Assert(bytes > byteStart || chars == charStart,
+                            "[ASCIIEncoding.GetChars]Expected bytes to have advanced already (normal case)");
+                        bytes--;                                            // unused byte
+                        ThrowCharsOverflow(decoder, chars == charStart);    // throw?
+                        break;                                              // don't throw, but stop loop
+                    }
+
+                    *(chars) = unchecked((char)b);
+                    chars++;
+                }
+            }
+
+            // Might have had decoder fallback stuff.
+            if (decoder != null)
+                decoder._bytesUsed = (int)(bytes - byteStart);
+
+            // Expect Empty fallback buffer for GetChars
+            Debug.Assert(fallbackBuffer == null || fallbackBuffer.Remaining == 0,
+                "[ASCIIEncoding.GetChars]Expected Empty fallback buffer");
+
+            return (int)(chars - charStart);
+        }
+
+
+        public override int GetMaxByteCount(int charCount)
+        {
+            if (charCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(charCount),
+                     SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Characters would be # of characters + 1 in case high surrogate is ? * max fallback
+            long byteCount = (long)charCount + 1;
+
+            if (EncoderFallback.MaxCharCount > 1)
+                byteCount *= EncoderFallback.MaxCharCount;
+
+            // 1 to 1 for most characters.  Only surrogates with fallbacks have less.
+
+            if (byteCount > 0x7fffffff)
+                throw new ArgumentOutOfRangeException(nameof(charCount), SR.ArgumentOutOfRange_GetByteCountOverflow);
+            return (int)byteCount;
+        }
+
+
+        public override int GetMaxCharCount(int byteCount)
+        {
+            if (byteCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(byteCount),
+                     SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Just return length, SBCS stay the same length because they don't map to surrogate
+            long charCount = (long)byteCount;
+
+            // 1 to 1 for most characters.  Only surrogates with fallbacks have less, unknown fallbacks could be longer.
+            if (DecoderFallback.MaxCharCount > 1)
+                charCount *= DecoderFallback.MaxCharCount;
+
+            if (charCount > 0x7fffffff)
+                throw new ArgumentOutOfRangeException(nameof(byteCount), SR.ArgumentOutOfRange_GetCharCountOverflow);
+
+            return (int)charCount;
+        }
+
+        // True if and only if the encoding only uses single byte code points.  (Ie, ASCII, 1252, etc)
+
+        public override bool IsSingleByte
+        {
+            get
+            {
+                return true;
+            }
+        }
+
+        public override Decoder GetDecoder()
+        {
+            return new DecoderNLS(this);
+        }
+
+
+        public override Encoder GetEncoder()
+        {
+            return new EncoderNLS(this);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/Decoder.cs b/src/System.Private.CoreLib/shared/System/Text/Decoder.cs
new file mode 100644
index 0000000000..b4a7575ba6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/Decoder.cs
@@ -0,0 +1,351 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text;
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System.Text
+{
+    // A Decoder is used to decode a sequence of blocks of bytes into a
+    // sequence of blocks of characters. Following instantiation of a decoder,
+    // sequential blocks of bytes are converted into blocks of characters through
+    // calls to the GetChars method. The decoder maintains state between the
+    // conversions, allowing it to correctly decode byte sequences that span
+    // adjacent blocks.
+    //
+    // Instances of specific implementations of the Decoder abstract base
+    // class are typically obtained through calls to the GetDecoder method
+    // of Encoding objects.
+    //
+    public abstract class Decoder
+    {
+        internal DecoderFallback _fallback = null;
+
+        internal DecoderFallbackBuffer _fallbackBuffer = null;
+
+        protected Decoder()
+        {
+            // We don't call default reset because default reset probably isn't good if we aren't initialized.
+        }
+
+        public DecoderFallback Fallback
+        {
+            get
+            {
+                return _fallback;
+            }
+
+            set
+            {
+                if (value == null)
+                    throw new ArgumentNullException(nameof(value));
+
+                // Can't change fallback if buffer is wrong
+                if (_fallbackBuffer != null && _fallbackBuffer.Remaining > 0)
+                    throw new ArgumentException(
+                      SR.Argument_FallbackBufferNotEmpty, nameof(value));
+
+                _fallback = value;
+                _fallbackBuffer = null;
+            }
+        }
+
+        // Note: we don't test for threading here because async access to Encoders and Decoders
+        // doesn't work anyway.
+        public DecoderFallbackBuffer FallbackBuffer
+        {
+            get
+            {
+                if (_fallbackBuffer == null)
+                {
+                    if (_fallback != null)
+                        _fallbackBuffer = _fallback.CreateFallbackBuffer();
+                    else
+                        _fallbackBuffer = DecoderFallback.ReplacementFallback.CreateFallbackBuffer();
+                }
+
+                return _fallbackBuffer;
+            }
+        }
+
+        internal bool InternalHasFallbackBuffer
+        {
+            get
+            {
+                return _fallbackBuffer != null;
+            }
+        }
+
+        // Reset the Decoder
+        //
+        // Normally if we call GetChars() and an error is thrown we don't change the state of the Decoder.  This
+        // would allow the caller to correct the error condition and try again (such as if they need a bigger buffer.)
+        //
+        // If the caller doesn't want to try again after GetChars() throws an error, then they need to call Reset().
+        //
+        // Virtual implementation has to call GetChars with flush and a big enough buffer to clear a 0 byte string
+        // We avoid GetMaxCharCount() because a) we can't call the base encoder and b) it might be really big.
+        public virtual void Reset()
+        {
+            byte[] byteTemp = Array.Empty<byte>();
+            char[] charTemp = new char[GetCharCount(byteTemp, 0, 0, true)];
+            GetChars(byteTemp, 0, 0, charTemp, 0, true);
+            _fallbackBuffer?.Reset();
+        }
+
+        // Returns the number of characters the next call to GetChars will
+        // produce if presented with the given range of bytes. The returned value
+        // takes into account the state in which the decoder was left following the
+        // last call to GetChars. The state of the decoder is not affected
+        // by a call to this method.
+        //
+        public abstract int GetCharCount(byte[] bytes, int index, int count);
+
+        public virtual int GetCharCount(byte[] bytes, int index, int count, bool flush)
+        {
+            return GetCharCount(bytes, index, count);
+        }
+
+        // We expect this to be the workhorse for NLS Encodings, but for existing
+        // ones we need a working (if slow) default implementation)
+        [CLSCompliant(false)]
+        public virtual unsafe int GetCharCount(byte* bytes, int count, bool flush)
+        {
+            // Validate input parameters
+            if (bytes == null)
+                throw new ArgumentNullException(nameof(bytes),
+                      SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            byte[] arrbyte = new byte[count];
+            int index;
+
+            for (index = 0; index < count; index++)
+                arrbyte[index] = bytes[index];
+
+            return GetCharCount(arrbyte, 0, count);
+        }
+
+        public virtual unsafe int GetCharCount(ReadOnlySpan<byte> bytes, bool flush)
+        {
+            fixed (byte* bytesPtr = &MemoryMarshal.GetNonNullPinnableReference(bytes))
+            {
+                return GetCharCount(bytesPtr, bytes.Length, flush);
+            }
+        }
+
+        // Decodes a range of bytes in a byte array into a range of characters
+        // in a character array. The method decodes byteCount bytes from
+        // bytes starting at index byteIndex, storing the resulting
+        // characters in chars starting at index charIndex. The
+        // decoding takes into account the state in which the decoder was left
+        // following the last call to this method.
+        //
+        // An exception occurs if the character array is not large enough to
+        // hold the complete decoding of the bytes. The GetCharCount method
+        // can be used to determine the exact number of characters that will be
+        // produced for a given range of bytes. Alternatively, the
+        // GetMaxCharCount method of the Encoding that produced this
+        // decoder can be used to determine the maximum number of characters that
+        // will be produced for a given number of bytes, regardless of the actual
+        // byte values.
+        //
+        public abstract int GetChars(byte[] bytes, int byteIndex, int byteCount,
+                                        char[] chars, int charIndex);
+
+        public virtual int GetChars(byte[] bytes, int byteIndex, int byteCount,
+                                       char[] chars, int charIndex, bool flush)
+        {
+            return GetChars(bytes, byteIndex, byteCount, chars, charIndex);
+        }
+
+        // We expect this to be the workhorse for NLS Encodings, but for existing
+        // ones we need a working (if slow) default implementation)
+        //
+        // WARNING WARNING WARNING
+        //
+        // WARNING: If this breaks it could be a security threat.  Obviously we
+        // call this internally, so you need to make sure that your pointers, counts
+        // and indexes are correct when you call this method.
+        //
+        // In addition, we have internal code, which will be marked as "safe" calling
+        // this code.  However this code is dependent upon the implementation of an
+        // external GetChars() method, which could be overridden by a third party and
+        // the results of which cannot be guaranteed.  We use that result to copy
+        // the char[] to our char* output buffer.  If the result count was wrong, we
+        // could easily overflow our output buffer.  Therefore we do an extra test
+        // when we copy the buffer so that we don't overflow charCount either.
+        [CLSCompliant(false)]
+        public virtual unsafe int GetChars(byte* bytes, int byteCount,
+                                              char* chars, int charCount, bool flush)
+        {
+            // Validate input parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException(chars == null ? nameof(chars) : nameof(bytes),
+                    SR.ArgumentNull_Array);
+
+            if (byteCount < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((byteCount < 0 ? nameof(byteCount) : nameof(charCount)),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Get the byte array to convert
+            byte[] arrByte = new byte[byteCount];
+
+            int index;
+            for (index = 0; index < byteCount; index++)
+                arrByte[index] = bytes[index];
+
+            // Get the char array to fill
+            char[] arrChar = new char[charCount];
+
+            // Do the work
+            int result = GetChars(arrByte, 0, byteCount, arrChar, 0, flush);
+
+            Debug.Assert(result <= charCount, "Returned more chars than we have space for");
+
+            // Copy the char array
+            // WARNING: We MUST make sure that we don't copy too many chars.  We can't
+            // rely on result because it could be a 3rd party implementation.  We need
+            // to make sure we never copy more than charCount chars no matter the value
+            // of result
+            if (result < charCount)
+                charCount = result;
+
+            // We check both result and charCount so that we don't accidentally overrun
+            // our pointer buffer just because of an issue in GetChars
+            for (index = 0; index < charCount; index++)
+                chars[index] = arrChar[index];
+
+            return charCount;
+        }
+
+        public virtual unsafe int GetChars(ReadOnlySpan<byte> bytes, Span<char> chars, bool flush)
+        {
+            fixed (byte* bytesPtr = &MemoryMarshal.GetNonNullPinnableReference(bytes))
+            fixed (char* charsPtr = &MemoryMarshal.GetNonNullPinnableReference(chars))
+            {
+                return GetChars(bytesPtr, bytes.Length, charsPtr, chars.Length, flush);
+            }
+        }
+
+        // This method is used when the output buffer might not be large enough.
+        // It will decode until it runs out of bytes, and then it will return
+        // true if it the entire input was converted.  In either case it
+        // will also return the number of converted bytes and output characters used.
+        // It will only throw a buffer overflow exception if the entire lenght of chars[] is
+        // too small to store the next char. (like 0 or maybe 1 or 4 for some encodings)
+        // We're done processing this buffer only if completed returns true.
+        //
+        // Might consider checking Max...Count to avoid the extra counting step.
+        //
+        // Note that if all of the input bytes are not consumed, then we'll do a /2, which means
+        // that its likely that we didn't consume as many bytes as we could have.  For some
+        // applications this could be slow.  (Like trying to exactly fill an output buffer from a bigger stream)
+        public virtual void Convert(byte[] bytes, int byteIndex, int byteCount,
+                                      char[] chars, int charIndex, int charCount, bool flush,
+                                      out int bytesUsed, out int charsUsed, out bool completed)
+        {
+            // Validate parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException((bytes == null ? nameof(bytes) : nameof(chars)),
+                      SR.ArgumentNull_Array);
+
+            if (byteIndex < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((byteIndex < 0 ? nameof(byteIndex) : nameof(byteCount)),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? nameof(charIndex) : nameof(charCount)),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (bytes.Length - byteIndex < byteCount)
+                throw new ArgumentOutOfRangeException(nameof(bytes),
+                      SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (chars.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException(nameof(chars),
+                      SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            bytesUsed = byteCount;
+
+            // Its easy to do if it won't overrun our buffer.
+            while (bytesUsed > 0)
+            {
+                if (GetCharCount(bytes, byteIndex, bytesUsed, flush) <= charCount)
+                {
+                    charsUsed = GetChars(bytes, byteIndex, bytesUsed, chars, charIndex, flush);
+                    completed = (bytesUsed == byteCount &&
+                        (_fallbackBuffer == null || _fallbackBuffer.Remaining == 0));
+                    return;
+                }
+
+                // Try again with 1/2 the count, won't flush then 'cause won't read it all
+                flush = false;
+                bytesUsed /= 2;
+            }
+
+            // Oops, we didn't have anything, we'll have to throw an overflow
+            throw new ArgumentException(SR.Argument_ConversionOverflow);
+        }
+
+        // This is the version that uses *.
+        // We're done processing this buffer only if completed returns true.
+        //
+        // Might consider checking Max...Count to avoid the extra counting step.
+        //
+        // Note that if all of the input bytes are not consumed, then we'll do a /2, which means
+        // that its likely that we didn't consume as many bytes as we could have.  For some
+        // applications this could be slow.  (Like trying to exactly fill an output buffer from a bigger stream)
+        [CLSCompliant(false)]
+        public virtual unsafe void Convert(byte* bytes, int byteCount,
+                                             char* chars, int charCount, bool flush,
+                                             out int bytesUsed, out int charsUsed, out bool completed)
+        {
+            // Validate input parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException(chars == null ? nameof(chars) : nameof(bytes),
+                    SR.ArgumentNull_Array);
+
+            if (byteCount < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((byteCount < 0 ? nameof(byteCount) : nameof(charCount)),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Get ready to do it
+            bytesUsed = byteCount;
+
+            // Its easy to do if it won't overrun our buffer.
+            while (bytesUsed > 0)
+            {
+                if (GetCharCount(bytes, bytesUsed, flush) <= charCount)
+                {
+                    charsUsed = GetChars(bytes, bytesUsed, chars, charCount, flush);
+                    completed = (bytesUsed == byteCount &&
+                        (_fallbackBuffer == null || _fallbackBuffer.Remaining == 0));
+                    return;
+                }
+
+                // Try again with 1/2 the count, won't flush then 'cause won't read it all
+                flush = false;
+                bytesUsed /= 2;
+            }
+
+            // Oops, we didn't have anything, we'll have to throw an overflow
+            throw new ArgumentException(SR.Argument_ConversionOverflow);
+        }
+
+        public virtual unsafe void Convert(ReadOnlySpan<byte> bytes, Span<char> chars, bool flush, out int bytesUsed, out int charsUsed, out bool completed)
+        {
+            fixed (byte* bytesPtr = &MemoryMarshal.GetNonNullPinnableReference(bytes))
+            fixed (char* charsPtr = &MemoryMarshal.GetNonNullPinnableReference(chars))
+            {
+                Convert(bytesPtr, bytes.Length, charsPtr, chars.Length, flush, out bytesUsed, out charsUsed, out completed);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/DecoderBestFitFallback.cs b/src/System.Private.CoreLib/shared/System/Text/DecoderBestFitFallback.cs
new file mode 100644
index 0000000000..30c817c91a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/DecoderBestFitFallback.cs
@@ -0,0 +1,242 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+// This is used internally to create best fit behavior as per the original windows best fit behavior.
+//
+
+using System.Diagnostics;
+using System.Threading;
+
+namespace System.Text
+{
+    internal sealed class InternalDecoderBestFitFallback : DecoderFallback
+    {
+        // Our variables
+        internal Encoding _encoding = null;
+        internal char[] _arrayBestFit = null;
+        internal char _cReplacement = '?';
+
+        internal InternalDecoderBestFitFallback(Encoding encoding)
+        {
+            // Need to load our replacement characters table.
+            _encoding = encoding;
+        }
+
+        public override DecoderFallbackBuffer CreateFallbackBuffer()
+        {
+            return new InternalDecoderBestFitFallbackBuffer(this);
+        }
+
+        // Maximum number of characters that this instance of this fallback could return
+        public override int MaxCharCount
+        {
+            get
+            {
+                return 1;
+            }
+        }
+
+        public override bool Equals(Object value)
+        {
+            InternalDecoderBestFitFallback that = value as InternalDecoderBestFitFallback;
+            if (that != null)
+            {
+                return (_encoding.CodePage == that._encoding.CodePage);
+            }
+            return (false);
+        }
+
+        public override int GetHashCode()
+        {
+            return _encoding.CodePage;
+        }
+    }
+
+    internal sealed class InternalDecoderBestFitFallbackBuffer : DecoderFallbackBuffer
+    {
+        // Our variables
+        private char _cBestFit = '\0';
+        private int _iCount = -1;
+        private int _iSize;
+        private InternalDecoderBestFitFallback _oFallback;
+
+        // Private object for locking instead of locking on a public type for SQL reliability work.
+        private static Object s_InternalSyncObject;
+        private static Object InternalSyncObject
+        {
+            get
+            {
+                if (s_InternalSyncObject == null)
+                {
+                    Object o = new Object();
+                    Interlocked.CompareExchange<Object>(ref s_InternalSyncObject, o, null);
+                }
+                return s_InternalSyncObject;
+            }
+        }
+
+        // Constructor
+        public InternalDecoderBestFitFallbackBuffer(InternalDecoderBestFitFallback fallback)
+        {
+            _oFallback = fallback;
+
+            if (_oFallback._arrayBestFit == null)
+            {
+                // Lock so we don't confuse ourselves.
+                lock (InternalSyncObject)
+                {
+                    // Double check before we do it again.
+                    if (_oFallback._arrayBestFit == null)
+                        _oFallback._arrayBestFit = fallback._encoding.GetBestFitBytesToUnicodeData();
+                }
+            }
+        }
+
+        // Fallback methods
+        public override bool Fallback(byte[] bytesUnknown, int index)
+        {
+            // We expect no previous fallback in our buffer
+            Debug.Assert(_iCount < 1, "[DecoderReplacementFallbackBuffer.Fallback] Calling fallback without a previously empty buffer");
+
+            _cBestFit = TryBestFit(bytesUnknown);
+            if (_cBestFit == '\0')
+                _cBestFit = _oFallback._cReplacement;
+
+            _iCount = _iSize = 1;
+
+            return true;
+        }
+
+        // Default version is overridden in DecoderReplacementFallback.cs
+        public override char GetNextChar()
+        {
+            // We want it to get < 0 because == 0 means that the current/last character is a fallback
+            // and we need to detect recursion.  We could have a flag but we already have this counter.
+            _iCount--;
+
+            // Do we have anything left? 0 is now last fallback char, negative is nothing left
+            if (_iCount < 0)
+                return '\0';
+
+            // Need to get it out of the buffer.
+            // Make sure it didn't wrap from the fast count-- path
+            if (_iCount == int.MaxValue)
+            {
+                _iCount = -1;
+                return '\0';
+            }
+
+            // Return the best fit character
+            return _cBestFit;
+        }
+
+        public override bool MovePrevious()
+        {
+            // Exception fallback doesn't have anywhere to back up to.
+            if (_iCount >= 0)
+                _iCount++;
+
+            // Return true if we could do it.
+            return (_iCount >= 0 && _iCount <= _iSize);
+        }
+
+        // How many characters left to output?
+        public override int Remaining
+        {
+            get
+            {
+                return (_iCount > 0) ? _iCount : 0;
+            }
+        }
+
+        // Clear the buffer
+        public override unsafe void Reset()
+        {
+            _iCount = -1;
+            byteStart = null;
+        }
+
+        // This version just counts the fallback and doesn't actually copy anything.
+        internal unsafe override int InternalFallback(byte[] bytes, byte* pBytes)
+        // Right now this has both bytes and bytes[], since we might have extra bytes, hence the
+        // array, and we might need the index, hence the byte*
+        {
+            // return our replacement string Length (always 1 for InternalDecoderBestFitFallback, either
+            // a best fit char or ?
+            return 1;
+        }
+
+        // private helper methods
+        private char TryBestFit(byte[] bytesCheck)
+        {
+            // Need to figure out our best fit character, low is beginning of array, high is 1 AFTER end of array
+            int lowBound = 0;
+            int highBound = _oFallback._arrayBestFit.Length;
+            int index;
+            char cCheck;
+
+            // Check trivial case first (no best fit)
+            if (highBound == 0)
+                return '\0';
+
+            // If our array is too small or too big we can't check
+            if (bytesCheck.Length == 0 || bytesCheck.Length > 2)
+                return '\0';
+
+            if (bytesCheck.Length == 1)
+                cCheck = unchecked((char)bytesCheck[0]);
+            else
+                cCheck = unchecked((char)((bytesCheck[0] << 8) + bytesCheck[1]));
+
+            // Check trivial out of range case
+            if (cCheck < _oFallback._arrayBestFit[0] || cCheck > _oFallback._arrayBestFit[highBound - 2])
+                return '\0';
+
+            // Binary search the array
+            int iDiff;
+            while ((iDiff = (highBound - lowBound)) > 6)
+            {
+                // Look in the middle, which is complicated by the fact that we have 2 #s for each pair,
+                // so we don't want index to be odd because it must be word aligned.
+                // Also note that index can never == highBound (because diff is rounded down)
+                index = ((iDiff / 2) + lowBound) & 0xFFFE;
+
+                char cTest = _oFallback._arrayBestFit[index];
+                if (cTest == cCheck)
+                {
+                    // We found it
+                    Debug.Assert(index + 1 < _oFallback._arrayBestFit.Length,
+                        "[InternalDecoderBestFitFallbackBuffer.TryBestFit]Expected replacement character at end of array");
+                    return _oFallback._arrayBestFit[index + 1];
+                }
+                else if (cTest < cCheck)
+                {
+                    // We weren't high enough
+                    lowBound = index;
+                }
+                else
+                {
+                    // We weren't low enough
+                    highBound = index;
+                }
+            }
+
+            for (index = lowBound; index < highBound; index += 2)
+            {
+                if (_oFallback._arrayBestFit[index] == cCheck)
+                {
+                    // We found it
+                    Debug.Assert(index + 1 < _oFallback._arrayBestFit.Length,
+                        "[InternalDecoderBestFitFallbackBuffer.TryBestFit]Expected replacement character at end of array");
+                    return _oFallback._arrayBestFit[index + 1];
+                }
+            }
+
+            // Char wasn't in our table            
+            return '\0';
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Text/DecoderExceptionFallback.cs b/src/System.Private.CoreLib/shared/System/Text/DecoderExceptionFallback.cs
new file mode 100644
index 0000000000..8bfc1f32d3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/DecoderExceptionFallback.cs
@@ -0,0 +1,155 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Globalization;
+using System.Runtime.Serialization;
+
+namespace System.Text
+{
+    public sealed class DecoderExceptionFallback : DecoderFallback
+    {
+        // Construction
+        public DecoderExceptionFallback()
+        {
+        }
+
+        public override DecoderFallbackBuffer CreateFallbackBuffer()
+        {
+            return new DecoderExceptionFallbackBuffer();
+        }
+
+        // Maximum number of characters that this instance of this fallback could return
+        public override int MaxCharCount
+        {
+            get
+            {
+                return 0;
+            }
+        }
+
+        public override bool Equals(Object value)
+        {
+            DecoderExceptionFallback that = value as DecoderExceptionFallback;
+            if (that != null)
+            {
+                return (true);
+            }
+            return (false);
+        }
+
+        public override int GetHashCode()
+        {
+            return 879;
+        }
+    }
+
+
+    public sealed class DecoderExceptionFallbackBuffer : DecoderFallbackBuffer
+    {
+        public override bool Fallback(byte[] bytesUnknown, int index)
+        {
+            Throw(bytesUnknown, index);
+            return true;
+        }
+
+        public override char GetNextChar()
+        {
+            return (char)0;
+        }
+
+        public override bool MovePrevious()
+        {
+            // Exception fallback doesn't have anywhere to back up to.
+            return false;
+        }
+
+        // Exceptions are always empty
+        public override int Remaining
+        {
+            get
+            {
+                return 0;
+            }
+        }
+
+        private void Throw(byte[] bytesUnknown, int index)
+        {
+            // Create a string representation of our bytes.            
+            StringBuilder strBytes = new StringBuilder(bytesUnknown.Length * 3);
+
+            int i;
+            for (i = 0; i < bytesUnknown.Length && i < 20; i++)
+            {
+                strBytes.Append('[');
+                strBytes.Append(bytesUnknown[i].ToString("X2", CultureInfo.InvariantCulture));
+                strBytes.Append(']');
+            }
+
+            // In case the string's really long
+            if (i == 20)
+                strBytes.Append(" ...");
+
+            // Known index
+            throw new DecoderFallbackException(
+                SR.Format(SR.Argument_InvalidCodePageBytesIndex,
+                   strBytes, index), bytesUnknown, index);
+        }
+    }
+
+    // Exception for decoding unknown byte sequences.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class DecoderFallbackException : ArgumentException
+    {
+        private byte[] _bytesUnknown = null;
+        private int _index = 0;
+
+        public DecoderFallbackException()
+            : base(SR.Arg_ArgumentException)
+        {
+            HResult = HResults.COR_E_ARGUMENT;
+        }
+
+        public DecoderFallbackException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_ARGUMENT;
+        }
+
+        public DecoderFallbackException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_ARGUMENT;
+        }
+
+        public DecoderFallbackException(String message, byte[] bytesUnknown, int index)
+            : base(message)
+        {
+            _bytesUnknown = bytesUnknown;
+            _index = index;
+        }
+
+        private DecoderFallbackException(SerializationInfo serializationInfo, StreamingContext streamingContext)
+            : base(serializationInfo, streamingContext)
+        {
+        }
+
+        public byte[] BytesUnknown
+        {
+            get
+            {
+                return (_bytesUnknown);
+            }
+        }
+
+        public int Index
+        {
+            get
+            {
+                return _index;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/DecoderFallback.cs b/src/System.Private.CoreLib/shared/System/Text/DecoderFallback.cs
new file mode 100644
index 0000000000..11b9539b5c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/DecoderFallback.cs
@@ -0,0 +1,216 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Globalization;
+using System.Threading;
+
+namespace System.Text
+{
+    public abstract class DecoderFallback
+    {
+        private static DecoderFallback s_replacementFallback; // Default fallback, uses no best fit & "?"
+        private static DecoderFallback s_exceptionFallback;
+
+        public static DecoderFallback ReplacementFallback =>
+            s_replacementFallback ?? Interlocked.CompareExchange(ref s_replacementFallback, new DecoderReplacementFallback(), null) ?? s_replacementFallback;        
+
+
+        public static DecoderFallback ExceptionFallback =>
+            s_exceptionFallback ?? Interlocked.CompareExchange<DecoderFallback>(ref s_exceptionFallback, new DecoderExceptionFallback(), null) ?? s_exceptionFallback;
+
+        // Fallback
+        //
+        // Return the appropriate unicode string alternative to the character that need to fall back.
+        // Most implementations will be:
+        //      return new MyCustomDecoderFallbackBuffer(this);
+
+        public abstract DecoderFallbackBuffer CreateFallbackBuffer();
+
+        // Maximum number of characters that this instance of this fallback could return
+
+        public abstract int MaxCharCount { get; }
+    }
+
+
+    public abstract class DecoderFallbackBuffer
+    {
+        // Most implementations will probably need an implementation-specific constructor
+
+        // internal methods that cannot be overridden that let us do our fallback thing
+        // These wrap the internal methods so that we can check for people doing stuff that's incorrect
+
+        public abstract bool Fallback(byte[] bytesUnknown, int index);
+
+        // Get next character
+
+        public abstract char GetNextChar();
+
+        // Back up a character
+
+        public abstract bool MovePrevious();
+
+        // How many chars left in this fallback?
+
+        public abstract int Remaining { get; }
+
+        // Clear the buffer
+
+        public virtual void Reset()
+        {
+            while (GetNextChar() != (char)0) ;
+        }
+
+        // Internal items to help us figure out what we're doing as far as error messages, etc.
+        // These help us with our performance and messages internally
+        internal unsafe byte* byteStart;
+        internal unsafe char* charEnd;
+
+        // Internal Reset
+        internal unsafe void InternalReset()
+        {
+            byteStart = null;
+            Reset();
+        }
+
+        // Set the above values
+        // This can't be part of the constructor because DecoderFallbacks would have to know how to implement these.
+        internal unsafe void InternalInitialize(byte* byteStart, char* charEnd)
+        {
+            this.byteStart = byteStart;
+            this.charEnd = charEnd;
+        }
+
+        // Fallback the current byte by sticking it into the remaining char buffer.
+        // This can only be called by our encodings (other have to use the public fallback methods), so
+        // we can use our DecoderNLS here too (except we don't).
+        // Returns true if we are successful, false if we can't fallback the character (no buffer space)
+        // So caller needs to throw buffer space if return false.
+        // Right now this has both bytes and bytes[], since we might have extra bytes, hence the
+        // array, and we might need the index, hence the byte*
+        // Don't touch ref chars unless we succeed
+        internal unsafe virtual bool InternalFallback(byte[] bytes, byte* pBytes, ref char* chars)
+        {
+            Debug.Assert(byteStart != null, "[DecoderFallback.InternalFallback]Used InternalFallback without calling InternalInitialize");
+
+            // See if there's a fallback character and we have an output buffer then copy our string.
+            if (this.Fallback(bytes, (int)(pBytes - byteStart - bytes.Length)))
+            {
+                // Copy the chars to our output
+                char ch;
+                char* charTemp = chars;
+                bool bHighSurrogate = false;
+                while ((ch = GetNextChar()) != 0)
+                {
+                    // Make sure no mixed up surrogates
+                    if (Char.IsSurrogate(ch))
+                    {
+                        if (Char.IsHighSurrogate(ch))
+                        {
+                            // High Surrogate
+                            if (bHighSurrogate)
+                                throw new ArgumentException(SR.Argument_InvalidCharSequenceNoIndex);
+                            bHighSurrogate = true;
+                        }
+                        else
+                        {
+                            // Low surrogate
+                            if (bHighSurrogate == false)
+                                throw new ArgumentException(SR.Argument_InvalidCharSequenceNoIndex);
+                            bHighSurrogate = false;
+                        }
+                    }
+
+                    if (charTemp >= charEnd)
+                    {
+                        // No buffer space
+                        return false;
+                    }
+
+                    *(charTemp++) = ch;
+                }
+
+                // Need to make sure that bHighSurrogate isn't true
+                if (bHighSurrogate)
+                    throw new ArgumentException(SR.Argument_InvalidCharSequenceNoIndex);
+
+                // Now we aren't going to be false, so its OK to update chars
+                chars = charTemp;
+            }
+
+            return true;
+        }
+
+        // This version just counts the fallback and doesn't actually copy anything.
+        internal unsafe virtual int InternalFallback(byte[] bytes, byte* pBytes)
+        // Right now this has both bytes and bytes[], since we might have extra bytes, hence the
+        // array, and we might need the index, hence the byte*
+        {
+            Debug.Assert(byteStart != null, "[DecoderFallback.InternalFallback]Used InternalFallback without calling InternalInitialize");
+
+            // See if there's a fallback character and we have an output buffer then copy our string.
+            if (this.Fallback(bytes, (int)(pBytes - byteStart - bytes.Length)))
+            {
+                int count = 0;
+
+                char ch;
+                bool bHighSurrogate = false;
+                while ((ch = GetNextChar()) != 0)
+                {
+                    // Make sure no mixed up surrogates
+                    if (Char.IsSurrogate(ch))
+                    {
+                        if (Char.IsHighSurrogate(ch))
+                        {
+                            // High Surrogate
+                            if (bHighSurrogate)
+                                throw new ArgumentException(SR.Argument_InvalidCharSequenceNoIndex);
+                            bHighSurrogate = true;
+                        }
+                        else
+                        {
+                            // Low surrogate
+                            if (bHighSurrogate == false)
+                                throw new ArgumentException(SR.Argument_InvalidCharSequenceNoIndex);
+                            bHighSurrogate = false;
+                        }
+                    }
+
+                    count++;
+                }
+
+                // Need to make sure that bHighSurrogate isn't true
+                if (bHighSurrogate)
+                    throw new ArgumentException(SR.Argument_InvalidCharSequenceNoIndex);
+
+                return count;
+            }
+
+            // If no fallback return 0
+            return 0;
+        }
+
+        // private helper methods
+        internal void ThrowLastBytesRecursive(byte[] bytesUnknown)
+        {
+            // Create a string representation of our bytes.
+            StringBuilder strBytes = new StringBuilder(bytesUnknown.Length * 3);
+            int i;
+            for (i = 0; i < bytesUnknown.Length && i < 20; i++)
+            {
+                if (strBytes.Length > 0)
+                    strBytes.Append(' ');
+                strBytes.AppendFormat(CultureInfo.InvariantCulture, "\\x{0:X2}", bytesUnknown[i]);
+            }
+            // In case the string's really long
+            if (i == 20)
+                strBytes.Append(" ...");
+
+            // Throw it, using our complete bytes
+            throw new ArgumentException(
+                SR.Format(SR.Argument_RecursiveFallbackBytes,
+                    strBytes.ToString()), nameof(bytesUnknown));
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/DecoderNLS.cs b/src/System.Private.CoreLib/shared/System/Text/DecoderNLS.cs
new file mode 100644
index 0000000000..ee88c22f9d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/DecoderNLS.cs
@@ -0,0 +1,242 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+using System.Text;
+using System;
+using System.Runtime.InteropServices;
+
+namespace System.Text
+{
+    // A Decoder is used to decode a sequence of blocks of bytes into a
+    // sequence of blocks of characters. Following instantiation of a decoder,
+    // sequential blocks of bytes are converted into blocks of characters through
+    // calls to the GetChars method. The decoder maintains state between the
+    // conversions, allowing it to correctly decode byte sequences that span
+    // adjacent blocks.
+    //
+    // Instances of specific implementations of the Decoder abstract base
+    // class are typically obtained through calls to the GetDecoder method
+    // of Encoding objects.
+
+    internal class DecoderNLS : Decoder
+    {
+        // Remember our encoding
+        private Encoding _encoding;
+        private bool _mustFlush;
+        internal bool _throwOnOverflow;
+        internal int _bytesUsed;
+
+        internal DecoderNLS(Encoding encoding)
+        {
+            _encoding = encoding;
+            _fallback = this._encoding.DecoderFallback;
+            this.Reset();
+        }
+
+        // This is used by our child deserializers
+        internal DecoderNLS()
+        {
+            _encoding = null;
+            this.Reset();
+        }
+
+        public override void Reset()
+        {
+            _fallbackBuffer?.Reset();
+        }
+
+        public override unsafe int GetCharCount(byte[] bytes, int index, int count)
+        {
+            return GetCharCount(bytes, index, count, false);
+        }
+
+        public override unsafe int GetCharCount(byte[] bytes, int index, int count, bool flush)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException(nameof(bytes),
+                    SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? nameof(index) : nameof(count)),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (bytes.Length - index < count)
+                throw new ArgumentOutOfRangeException(nameof(bytes),
+                    SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // Just call pointer version
+            fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+                return GetCharCount(pBytes + index, count, flush);
+        }
+
+        public unsafe override int GetCharCount(byte* bytes, int count, bool flush)
+        {
+            // Validate parameters
+            if (bytes == null)
+                throw new ArgumentNullException(nameof(bytes),
+                      SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Remember the flush
+            _mustFlush = flush;
+            _throwOnOverflow = true;
+
+            // By default just call the encoding version, no flush by default
+            return _encoding.GetCharCount(bytes, count, this);
+        }
+
+        public override unsafe int GetChars(byte[] bytes, int byteIndex, int byteCount,
+                                             char[] chars, int charIndex)
+        {
+            return GetChars(bytes, byteIndex, byteCount, chars, charIndex, false);
+        }
+
+        public override unsafe int GetChars(byte[] bytes, int byteIndex, int byteCount,
+                                             char[] chars, int charIndex, bool flush)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? nameof(bytes) : nameof(chars),
+                    SR.ArgumentNull_Array);
+
+            if (byteIndex < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((byteIndex < 0 ? nameof(byteIndex) : nameof(byteCount)),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (bytes.Length - byteIndex < byteCount)
+                throw new ArgumentOutOfRangeException(nameof(bytes),
+                    SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (charIndex < 0 || charIndex > chars.Length)
+                throw new ArgumentOutOfRangeException(nameof(charIndex),
+                    SR.ArgumentOutOfRange_Index);
+
+            int charCount = chars.Length - charIndex;
+
+            // Just call pointer version
+            fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+            fixed (char* pChars = &MemoryMarshal.GetReference((Span<char>)chars))
+                // Remember that charCount is # to decode, not size of array
+                return GetChars(pBytes + byteIndex, byteCount,
+                                pChars + charIndex, charCount, flush);
+        }
+
+        public unsafe override int GetChars(byte* bytes, int byteCount,
+                                              char* chars, int charCount, bool flush)
+        {
+            // Validate parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException((chars == null ? nameof(chars) : nameof(bytes)),
+                      SR.ArgumentNull_Array);
+
+            if (byteCount < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((byteCount < 0 ? nameof(byteCount) : nameof(charCount)),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Remember our flush
+            _mustFlush = flush;
+            _throwOnOverflow = true;
+
+            // By default just call the encodings version
+            return _encoding.GetChars(bytes, byteCount, chars, charCount, this);
+        }
+
+        // This method is used when the output buffer might not be big enough.
+        // Just call the pointer version.  (This gets chars)
+        public override unsafe void Convert(byte[] bytes, int byteIndex, int byteCount,
+                                              char[] chars, int charIndex, int charCount, bool flush,
+                                              out int bytesUsed, out int charsUsed, out bool completed)
+        {
+            // Validate parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException((bytes == null ? nameof(bytes) : nameof(chars)),
+                      SR.ArgumentNull_Array);
+
+            if (byteIndex < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((byteIndex < 0 ? nameof(byteIndex) : nameof(byteCount)),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? nameof(charIndex) : nameof(charCount)),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (bytes.Length - byteIndex < byteCount)
+                throw new ArgumentOutOfRangeException(nameof(bytes),
+                      SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (chars.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException(nameof(chars),
+                      SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // Just call the pointer version (public overrides can't do this)
+            fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+            {
+                fixed (char* pChars = &MemoryMarshal.GetReference((Span<char>)chars))
+                {
+                    Convert(pBytes + byteIndex, byteCount, pChars + charIndex, charCount, flush,
+                        out bytesUsed, out charsUsed, out completed);
+                }
+            }
+        }
+
+        // This is the version that used pointers.  We call the base encoding worker function
+        // after setting our appropriate internal variables.  This is getting chars
+        public unsafe override void Convert(byte* bytes, int byteCount,
+                                              char* chars, int charCount, bool flush,
+                                              out int bytesUsed, out int charsUsed, out bool completed)
+        {
+            // Validate input parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException(chars == null ? nameof(chars) : nameof(bytes),
+                    SR.ArgumentNull_Array);
+
+            if (byteCount < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((byteCount < 0 ? nameof(byteCount) : nameof(charCount)),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // We don't want to throw
+            _mustFlush = flush;
+            _throwOnOverflow = false;
+            _bytesUsed = 0;
+
+            // Do conversion
+            charsUsed = _encoding.GetChars(bytes, byteCount, chars, charCount, this);
+            bytesUsed = _bytesUsed;
+
+            // Its completed if they've used what they wanted AND if they didn't want flush or if we are flushed
+            completed = (bytesUsed == byteCount) && (!flush || !this.HasState) &&
+                               (_fallbackBuffer == null || _fallbackBuffer.Remaining == 0);
+
+            // Our data thingy are now full, we can return
+        }
+
+        public bool MustFlush
+        {
+            get
+            {
+                return _mustFlush;
+            }
+        }
+
+        // Anything left in our decoder?
+        internal virtual bool HasState
+        {
+            get
+            {
+                return false;
+            }
+        }
+
+        // Allow encoding to clear our must flush instead of throwing (in ThrowCharsOverflow)
+        internal void ClearMustFlush()
+        {
+            _mustFlush = false;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/DecoderReplacementFallback.cs b/src/System.Private.CoreLib/shared/System/Text/DecoderReplacementFallback.cs
new file mode 100644
index 0000000000..422b80bb2f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/DecoderReplacementFallback.cs
@@ -0,0 +1,204 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Text
+{
+    public sealed class DecoderReplacementFallback : DecoderFallback
+    {
+        // Our variables
+        private String _strDefault;
+
+        // Construction.  Default replacement fallback uses no best fit and ? replacement string
+        public DecoderReplacementFallback() : this("?")
+        {
+        }
+
+        public DecoderReplacementFallback(String replacement)
+        {
+            if (replacement == null)
+                throw new ArgumentNullException(nameof(replacement));
+
+            // Make sure it doesn't have bad surrogate pairs
+            bool bFoundHigh = false;
+            for (int i = 0; i < replacement.Length; i++)
+            {
+                // Found a surrogate?
+                if (Char.IsSurrogate(replacement, i))
+                {
+                    // High or Low?
+                    if (Char.IsHighSurrogate(replacement, i))
+                    {
+                        // if already had a high one, stop
+                        if (bFoundHigh)
+                            break;  // break & throw at the bFoundHIgh below
+                        bFoundHigh = true;
+                    }
+                    else
+                    {
+                        // Low, did we have a high?
+                        if (!bFoundHigh)
+                        {
+                            // Didn't have one, make if fail when we stop
+                            bFoundHigh = true;
+                            break;
+                        }
+
+                        // Clear flag
+                        bFoundHigh = false;
+                    }
+                }
+                // If last was high we're in trouble (not surrogate so not low surrogate, so break)
+                else if (bFoundHigh)
+                    break;
+            }
+            if (bFoundHigh)
+                throw new ArgumentException(SR.Format(SR.Argument_InvalidCharSequenceNoIndex, nameof(replacement)));
+
+            _strDefault = replacement;
+        }
+
+        public String DefaultString
+        {
+            get
+            {
+                return _strDefault;
+            }
+        }
+
+        public override DecoderFallbackBuffer CreateFallbackBuffer()
+        {
+            return new DecoderReplacementFallbackBuffer(this);
+        }
+
+        // Maximum number of characters that this instance of this fallback could return
+        public override int MaxCharCount
+        {
+            get
+            {
+                return _strDefault.Length;
+            }
+        }
+
+        public override bool Equals(Object value)
+        {
+            DecoderReplacementFallback that = value as DecoderReplacementFallback;
+            if (that != null)
+            {
+                return (_strDefault == that._strDefault);
+            }
+            return (false);
+        }
+
+        public override int GetHashCode()
+        {
+            return _strDefault.GetHashCode();
+        }
+    }
+
+
+
+    public sealed class DecoderReplacementFallbackBuffer : DecoderFallbackBuffer
+    {
+        // Store our default string
+        private String _strDefault;
+        private int _fallbackCount = -1;
+        private int _fallbackIndex = -1;
+
+        // Construction
+        public DecoderReplacementFallbackBuffer(DecoderReplacementFallback fallback)
+        {
+            _strDefault = fallback.DefaultString;
+        }
+
+        // Fallback Methods
+        public override bool Fallback(byte[] bytesUnknown, int index)
+        {
+            // We expect no previous fallback in our buffer
+            // We can't call recursively but others might (note, we don't test on last char!!!)
+            if (_fallbackCount >= 1)
+            {
+                ThrowLastBytesRecursive(bytesUnknown);
+            }
+
+            // Go ahead and get our fallback
+            if (_strDefault.Length == 0)
+                return false;
+
+            _fallbackCount = _strDefault.Length;
+            _fallbackIndex = -1;
+
+            return true;
+        }
+
+        public override char GetNextChar()
+        {
+            // We want it to get < 0 because == 0 means that the current/last character is a fallback
+            // and we need to detect recursion.  We could have a flag but we already have this counter.
+            _fallbackCount--;
+            _fallbackIndex++;
+
+            // Do we have anything left? 0 is now last fallback char, negative is nothing left
+            if (_fallbackCount < 0)
+                return '\0';
+
+            // Need to get it out of the buffer.
+            // Make sure it didn't wrap from the fast count-- path
+            if (_fallbackCount == int.MaxValue)
+            {
+                _fallbackCount = -1;
+                return '\0';
+            }
+
+            // Now make sure its in the expected range
+            Debug.Assert(_fallbackIndex < _strDefault.Length && _fallbackIndex >= 0,
+                            "Index exceeds buffer range");
+
+            return _strDefault[_fallbackIndex];
+        }
+
+        public override bool MovePrevious()
+        {
+            // Back up one, only if we just processed the last character (or earlier)
+            if (_fallbackCount >= -1 && _fallbackIndex >= 0)
+            {
+                _fallbackIndex--;
+                _fallbackCount++;
+                return true;
+            }
+
+            // Return false 'cause we couldn't do it.
+            return false;
+        }
+
+        // How many characters left to output?
+        public override int Remaining
+        {
+            get
+            {
+                // Our count is 0 for 1 character left.
+                return (_fallbackCount < 0) ? 0 : _fallbackCount;
+            }
+        }
+
+        // Clear the buffer
+        public override unsafe void Reset()
+        {
+            _fallbackCount = -1;
+            _fallbackIndex = -1;
+            byteStart = null;
+        }
+
+        // This version just counts the fallback and doesn't actually copy anything.
+        internal unsafe override int InternalFallback(byte[] bytes, byte* pBytes)
+        // Right now this has both bytes and bytes[], since we might have extra bytes, hence the
+        // array, and we might need the index, hence the byte*
+        {
+            // return our replacement string Length
+            return _strDefault.Length;
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Text/Encoder.cs b/src/System.Private.CoreLib/shared/System/Text/Encoder.cs
new file mode 100644
index 0000000000..df7d51203f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/Encoder.cs
@@ -0,0 +1,346 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text;
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System.Text
+{
+    // An Encoder is used to encode a sequence of blocks of characters into
+    // a sequence of blocks of bytes. Following instantiation of an encoder,
+    // sequential blocks of characters are converted into blocks of bytes through
+    // calls to the GetBytes method. The encoder maintains state between the
+    // conversions, allowing it to correctly encode character sequences that span
+    // adjacent blocks.
+    //
+    // Instances of specific implementations of the Encoder abstract base
+    // class are typically obtained through calls to the GetEncoder method
+    // of Encoding objects.
+    //
+    public abstract class Encoder
+    {
+        internal EncoderFallback _fallback = null;
+
+        internal EncoderFallbackBuffer _fallbackBuffer = null;
+
+        protected Encoder()
+        {
+            // We don't call default reset because default reset probably isn't good if we aren't initialized.
+        }
+
+        public EncoderFallback Fallback
+        {
+            get
+            {
+                return _fallback;
+            }
+
+            set
+            {
+                if (value == null)
+                    throw new ArgumentNullException(nameof(value));
+
+                // Can't change fallback if buffer is wrong
+                if (_fallbackBuffer != null && _fallbackBuffer.Remaining > 0)
+                    throw new ArgumentException(
+                      SR.Argument_FallbackBufferNotEmpty, nameof(value));
+
+                _fallback = value;
+                _fallbackBuffer = null;
+            }
+        }
+
+        // Note: we don't test for threading here because async access to Encoders and Decoders
+        // doesn't work anyway.
+        public EncoderFallbackBuffer FallbackBuffer
+        {
+            get
+            {
+                if (_fallbackBuffer == null)
+                {
+                    if (_fallback != null)
+                        _fallbackBuffer = _fallback.CreateFallbackBuffer();
+                    else
+                        _fallbackBuffer = EncoderFallback.ReplacementFallback.CreateFallbackBuffer();
+                }
+
+                return _fallbackBuffer;
+            }
+        }
+
+        internal bool InternalHasFallbackBuffer
+        {
+            get
+            {
+                return _fallbackBuffer != null;
+            }
+        }
+
+        // Reset the Encoder
+        //
+        // Normally if we call GetBytes() and an error is thrown we don't change the state of the encoder.  This
+        // would allow the caller to correct the error condition and try again (such as if they need a bigger buffer.)
+        //
+        // If the caller doesn't want to try again after GetBytes() throws an error, then they need to call Reset().
+        //
+        // Virtual implementation has to call GetBytes with flush and a big enough buffer to clear a 0 char string
+        // We avoid GetMaxByteCount() because a) we can't call the base encoder and b) it might be really big.
+        public virtual void Reset()
+        {
+            char[] charTemp = { };
+            byte[] byteTemp = new byte[GetByteCount(charTemp, 0, 0, true)];
+            GetBytes(charTemp, 0, 0, byteTemp, 0, true);
+            if (_fallbackBuffer != null)
+                _fallbackBuffer.Reset();
+        }
+
+        // Returns the number of bytes the next call to GetBytes will
+        // produce if presented with the given range of characters and the given
+        // value of the flush parameter. The returned value takes into
+        // account the state in which the encoder was left following the last call
+        // to GetBytes. The state of the encoder is not affected by a call
+        // to this method.
+        //
+        public abstract int GetByteCount(char[] chars, int index, int count, bool flush);
+
+        // We expect this to be the workhorse for NLS encodings
+        // unfortunately for existing overrides, it has to call the [] version,
+        // which is really slow, so avoid this method if you might be calling external encodings.
+        [CLSCompliant(false)]
+        public virtual unsafe int GetByteCount(char* chars, int count, bool flush)
+        {
+            // Validate input parameters
+            if (chars == null)
+                throw new ArgumentNullException(nameof(chars),
+                      SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            char[] arrChar = new char[count];
+            int index;
+
+            for (index = 0; index < count; index++)
+                arrChar[index] = chars[index];
+
+            return GetByteCount(arrChar, 0, count, flush);
+        }
+
+        public virtual unsafe int GetByteCount(ReadOnlySpan<char> chars, bool flush)
+        {
+            fixed (char* charsPtr = &MemoryMarshal.GetNonNullPinnableReference(chars))
+            {
+                return GetByteCount(charsPtr, chars.Length, flush);
+            }
+        }
+
+        // Encodes a range of characters in a character array into a range of bytes
+        // in a byte array. The method encodes charCount characters from
+        // chars starting at index charIndex, storing the resulting
+        // bytes in bytes starting at index byteIndex. The encoding
+        // takes into account the state in which the encoder was left following the
+        // last call to this method. The flush parameter indicates whether
+        // the encoder should flush any shift-states and partial characters at the
+        // end of the conversion. To ensure correct termination of a sequence of
+        // blocks of encoded bytes, the last call to GetBytes should specify
+        // a value of true for the flush parameter.
+        //
+        // An exception occurs if the byte array is not large enough to hold the
+        // complete encoding of the characters. The GetByteCount method can
+        // be used to determine the exact number of bytes that will be produced for
+        // a given range of characters. Alternatively, the GetMaxByteCount
+        // method of the Encoding that produced this encoder can be used to
+        // determine the maximum number of bytes that will be produced for a given
+        // number of characters, regardless of the actual character values.
+        //
+        public abstract int GetBytes(char[] chars, int charIndex, int charCount,
+                                        byte[] bytes, int byteIndex, bool flush);
+
+        // We expect this to be the workhorse for NLS Encodings, but for existing
+        // ones we need a working (if slow) default implementation)
+        //
+        // WARNING WARNING WARNING
+        //
+        // WARNING: If this breaks it could be a security threat.  Obviously we
+        // call this internally, so you need to make sure that your pointers, counts
+        // and indexes are correct when you call this method.
+        //
+        // In addition, we have internal code, which will be marked as "safe" calling
+        // this code.  However this code is dependent upon the implementation of an
+        // external GetBytes() method, which could be overridden by a third party and
+        // the results of which cannot be guaranteed.  We use that result to copy
+        // the byte[] to our byte* output buffer.  If the result count was wrong, we
+        // could easily overflow our output buffer.  Therefore we do an extra test
+        // when we copy the buffer so that we don't overflow byteCount either.
+        [CLSCompliant(false)]
+        public virtual unsafe int GetBytes(char* chars, int charCount,
+                                              byte* bytes, int byteCount, bool flush)
+        {
+            // Validate input parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? nameof(bytes) : nameof(chars),
+                    SR.ArgumentNull_Array);
+
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? nameof(charCount) : nameof(byteCount)),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Get the char array to convert
+            char[] arrChar = new char[charCount];
+
+            int index;
+            for (index = 0; index < charCount; index++)
+                arrChar[index] = chars[index];
+
+            // Get the byte array to fill
+            byte[] arrByte = new byte[byteCount];
+
+            // Do the work
+            int result = GetBytes(arrChar, 0, charCount, arrByte, 0, flush);
+
+            Debug.Assert(result <= byteCount, "Returned more bytes than we have space for");
+
+            // Copy the byte array
+            // WARNING: We MUST make sure that we don't copy too many bytes.  We can't
+            // rely on result because it could be a 3rd party implementation.  We need
+            // to make sure we never copy more than byteCount bytes no matter the value
+            // of result
+            if (result < byteCount)
+                byteCount = result;
+
+            // Don't copy too many bytes!
+            for (index = 0; index < byteCount; index++)
+                bytes[index] = arrByte[index];
+
+            return byteCount;
+        }
+
+        public virtual unsafe int GetBytes(ReadOnlySpan<char> chars, Span<byte> bytes, bool flush)
+        {
+            fixed (char* charsPtr = &MemoryMarshal.GetNonNullPinnableReference(chars))
+            fixed (byte* bytesPtr = &MemoryMarshal.GetNonNullPinnableReference(bytes))
+            {
+                return GetBytes(charsPtr, chars.Length, bytesPtr, bytes.Length, flush);
+            }
+        }
+
+        // This method is used to avoid running out of output buffer space.
+        // It will encode until it runs out of chars, and then it will return
+        // true if it the entire input was converted.  In either case it
+        // will also return the number of converted chars and output bytes used.
+        // It will only throw a buffer overflow exception if the entire lenght of bytes[] is
+        // too small to store the next byte. (like 0 or maybe 1 or 4 for some encodings)
+        // We're done processing this buffer only if completed returns true.
+        //
+        // Might consider checking Max...Count to avoid the extra counting step.
+        //
+        // Note that if all of the input chars are not consumed, then we'll do a /2, which means
+        // that its likely that we didn't consume as many chars as we could have.  For some
+        // applications this could be slow.  (Like trying to exactly fill an output buffer from a bigger stream)
+        public virtual void Convert(char[] chars, int charIndex, int charCount,
+                                      byte[] bytes, int byteIndex, int byteCount, bool flush,
+                                      out int charsUsed, out int bytesUsed, out bool completed)
+        {
+            // Validate parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException((chars == null ? nameof(chars) : nameof(bytes)),
+                      SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? nameof(charIndex) : nameof(charCount)),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (byteIndex < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((byteIndex < 0 ? nameof(byteIndex) : nameof(byteCount)),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException(nameof(chars),
+                      SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (bytes.Length - byteIndex < byteCount)
+                throw new ArgumentOutOfRangeException(nameof(bytes),
+                      SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            charsUsed = charCount;
+
+            // Its easy to do if it won't overrun our buffer.
+            // Note: We don't want to call unsafe version because that might be an untrusted version
+            // which could be really unsafe and we don't want to mix it up.
+            while (charsUsed > 0)
+            {
+                if (GetByteCount(chars, charIndex, charsUsed, flush) <= byteCount)
+                {
+                    bytesUsed = GetBytes(chars, charIndex, charsUsed, bytes, byteIndex, flush);
+                    completed = (charsUsed == charCount &&
+                        (_fallbackBuffer == null || _fallbackBuffer.Remaining == 0));
+                    return;
+                }
+
+                // Try again with 1/2 the count, won't flush then 'cause won't read it all
+                flush = false;
+                charsUsed /= 2;
+            }
+
+            // Oops, we didn't have anything, we'll have to throw an overflow
+            throw new ArgumentException(SR.Argument_ConversionOverflow);
+        }
+
+        // Same thing, but using pointers
+        //
+        // Might consider checking Max...Count to avoid the extra counting step.
+        //
+        // Note that if all of the input chars are not consumed, then we'll do a /2, which means
+        // that its likely that we didn't consume as many chars as we could have.  For some
+        // applications this could be slow.  (Like trying to exactly fill an output buffer from a bigger stream)
+        [CLSCompliant(false)]
+        public virtual unsafe void Convert(char* chars, int charCount,
+                                             byte* bytes, int byteCount, bool flush,
+                                             out int charsUsed, out int bytesUsed, out bool completed)
+        {
+            // Validate input parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? nameof(bytes) : nameof(chars),
+                    SR.ArgumentNull_Array);
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? nameof(charCount) : nameof(byteCount)),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Get ready to do it
+            charsUsed = charCount;
+
+            // Its easy to do if it won't overrun our buffer.
+            while (charsUsed > 0)
+            {
+                if (GetByteCount(chars, charsUsed, flush) <= byteCount)
+                {
+                    bytesUsed = GetBytes(chars, charsUsed, bytes, byteCount, flush);
+                    completed = (charsUsed == charCount &&
+                        (_fallbackBuffer == null || _fallbackBuffer.Remaining == 0));
+                    return;
+                }
+
+                // Try again with 1/2 the count, won't flush then 'cause won't read it all
+                flush = false;
+                charsUsed /= 2;
+            }
+
+            // Oops, we didn't have anything, we'll have to throw an overflow
+            throw new ArgumentException(SR.Argument_ConversionOverflow);
+        }
+
+        public virtual unsafe void Convert(ReadOnlySpan<char> chars, Span<byte> bytes, bool flush, out int charsUsed, out int bytesUsed, out bool completed)
+        {
+            fixed (char* charsPtr = &MemoryMarshal.GetNonNullPinnableReference(chars))
+            fixed (byte* bytesPtr = &MemoryMarshal.GetNonNullPinnableReference(bytes))
+            {
+                Convert(charsPtr, chars.Length, bytesPtr, bytes.Length, flush, out charsUsed, out bytesUsed, out completed);
+            }
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Text/EncoderBestFitFallback.cs b/src/System.Private.CoreLib/shared/System/Text/EncoderBestFitFallback.cs
new file mode 100644
index 0000000000..7f3be2a7a6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/EncoderBestFitFallback.cs
@@ -0,0 +1,242 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+// This is used internally to create best fit behavior as per the original windows best fit behavior.
+//
+
+using System.Diagnostics;
+using System.Globalization;
+using System.Threading;
+
+namespace System.Text
+{
+    internal class InternalEncoderBestFitFallback : EncoderFallback
+    {
+        // Our variables
+        internal Encoding _encoding = null;
+        internal char[] _arrayBestFit = null;
+
+        internal InternalEncoderBestFitFallback(Encoding encoding)
+        {
+            // Need to load our replacement characters table.
+            _encoding = encoding;
+        }
+
+        public override EncoderFallbackBuffer CreateFallbackBuffer()
+        {
+            return new InternalEncoderBestFitFallbackBuffer(this);
+        }
+
+        // Maximum number of characters that this instance of this fallback could return
+        public override int MaxCharCount
+        {
+            get
+            {
+                return 1;
+            }
+        }
+
+        public override bool Equals(Object value)
+        {
+            InternalEncoderBestFitFallback that = value as InternalEncoderBestFitFallback;
+            if (that != null)
+            {
+                return (_encoding.CodePage == that._encoding.CodePage);
+            }
+            return (false);
+        }
+
+        public override int GetHashCode()
+        {
+            return _encoding.CodePage;
+        }
+    }
+
+    internal sealed class InternalEncoderBestFitFallbackBuffer : EncoderFallbackBuffer
+    {
+        // Our variables
+        private char _cBestFit = '\0';
+        private InternalEncoderBestFitFallback _oFallback;
+        private int _iCount = -1;
+        private int _iSize;
+
+        // Private object for locking instead of locking on a public type for SQL reliability work.
+        private static Object s_InternalSyncObject;
+        private static Object InternalSyncObject
+        {
+            get
+            {
+                if (s_InternalSyncObject == null)
+                {
+                    Object o = new Object();
+                    Interlocked.CompareExchange<Object>(ref s_InternalSyncObject, o, null);
+                }
+                return s_InternalSyncObject;
+            }
+        }
+
+        // Constructor
+        public InternalEncoderBestFitFallbackBuffer(InternalEncoderBestFitFallback fallback)
+        {
+            _oFallback = fallback;
+
+            if (_oFallback._arrayBestFit == null)
+            {
+                // Lock so we don't confuse ourselves.
+                lock (InternalSyncObject)
+                {
+                    // Double check before we do it again.
+                    if (_oFallback._arrayBestFit == null)
+                        _oFallback._arrayBestFit = fallback._encoding.GetBestFitUnicodeToBytesData();
+                }
+            }
+        }
+
+        // Fallback methods
+        public override bool Fallback(char charUnknown, int index)
+        {
+            // If we had a buffer already we're being recursive, throw, it's probably at the suspect
+            // character in our array.
+            // Shouldn't be able to get here for all of our code pages, table would have to be messed up.
+            Debug.Assert(_iCount < 1, "[InternalEncoderBestFitFallbackBuffer.Fallback(non surrogate)] Fallback char " + ((int)_cBestFit).ToString("X4", CultureInfo.InvariantCulture) + " caused recursive fallback");
+
+            _iCount = _iSize = 1;
+            _cBestFit = TryBestFit(charUnknown);
+            if (_cBestFit == '\0')
+                _cBestFit = '?';
+
+            return true;
+        }
+
+        public override bool Fallback(char charUnknownHigh, char charUnknownLow, int index)
+        {
+            // Double check input surrogate pair
+            if (!Char.IsHighSurrogate(charUnknownHigh))
+                throw new ArgumentOutOfRangeException(nameof(charUnknownHigh),
+                    SR.Format(SR.ArgumentOutOfRange_Range,
+                    0xD800, 0xDBFF));
+
+            if (!Char.IsLowSurrogate(charUnknownLow))
+                throw new ArgumentOutOfRangeException(nameof(charUnknownLow),
+                    SR.Format(SR.ArgumentOutOfRange_Range,
+                    0xDC00, 0xDFFF));
+
+            // If we had a buffer already we're being recursive, throw, it's probably at the suspect
+            // character in our array.  0 is processing last character, < 0 is not falling back
+            // Shouldn't be able to get here, table would have to be messed up.
+            Debug.Assert(_iCount < 1, "[InternalEncoderBestFitFallbackBuffer.Fallback(surrogate)] Fallback char " + ((int)_cBestFit).ToString("X4", CultureInfo.InvariantCulture) + " caused recursive fallback");
+
+            // Go ahead and get our fallback, surrogates don't have best fit
+            _cBestFit = '?';
+            _iCount = _iSize = 2;
+
+            return true;
+        }
+
+        // Default version is overridden in EncoderReplacementFallback.cs
+        public override char GetNextChar()
+        {
+            // We want it to get < 0 because == 0 means that the current/last character is a fallback
+            // and we need to detect recursion.  We could have a flag but we already have this counter.
+            _iCount--;
+
+            // Do we have anything left? 0 is now last fallback char, negative is nothing left
+            if (_iCount < 0)
+                return '\0';
+
+            // Need to get it out of the buffer.
+            // Make sure it didn't wrap from the fast count-- path
+            if (_iCount == int.MaxValue)
+            {
+                _iCount = -1;
+                return '\0';
+            }
+
+            // Return the best fit character
+            return _cBestFit;
+        }
+
+        public override bool MovePrevious()
+        {
+            // Exception fallback doesn't have anywhere to back up to.
+            if (_iCount >= 0)
+                _iCount++;
+
+            // Return true if we could do it.
+            return (_iCount >= 0 && _iCount <= _iSize);
+        }
+
+
+        // How many characters left to output?
+        public override int Remaining
+        {
+            get
+            {
+                return (_iCount > 0) ? _iCount : 0;
+            }
+        }
+
+        // Clear the buffer
+        public override unsafe void Reset()
+        {
+            _iCount = -1;
+            charStart = null;
+            bFallingBack = false;
+        }
+
+        // private helper methods
+        private char TryBestFit(char cUnknown)
+        {
+            // Need to figure out our best fit character, low is beginning of array, high is 1 AFTER end of array
+            int lowBound = 0;
+            int highBound = _oFallback._arrayBestFit.Length;
+            int index;
+
+            // Binary search the array
+            int iDiff;
+            while ((iDiff = (highBound - lowBound)) > 6)
+            {
+                // Look in the middle, which is complicated by the fact that we have 2 #s for each pair,
+                // so we don't want index to be odd because we want to be on word boundaries.
+                // Also note that index can never == highBound (because diff is rounded down)
+                index = ((iDiff / 2) + lowBound) & 0xFFFE;
+
+                char cTest = _oFallback._arrayBestFit[index];
+                if (cTest == cUnknown)
+                {
+                    // We found it
+                    Debug.Assert(index + 1 < _oFallback._arrayBestFit.Length,
+                        "[InternalEncoderBestFitFallbackBuffer.TryBestFit]Expected replacement character at end of array");
+                    return _oFallback._arrayBestFit[index + 1];
+                }
+                else if (cTest < cUnknown)
+                {
+                    // We weren't high enough
+                    lowBound = index;
+                }
+                else
+                {
+                    // We weren't low enough
+                    highBound = index;
+                }
+            }
+
+            for (index = lowBound; index < highBound; index += 2)
+            {
+                if (_oFallback._arrayBestFit[index] == cUnknown)
+                {
+                    // We found it
+                    Debug.Assert(index + 1 < _oFallback._arrayBestFit.Length,
+                        "[InternalEncoderBestFitFallbackBuffer.TryBestFit]Expected replacement character at end of array");
+                    return _oFallback._arrayBestFit[index + 1];
+                }
+            }
+
+            // Char wasn't in our table
+            return '\0';
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Text/EncoderExceptionFallback.cs b/src/System.Private.CoreLib/shared/System/Text/EncoderExceptionFallback.cs
new file mode 100644
index 0000000000..66de1940f6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/EncoderExceptionFallback.cs
@@ -0,0 +1,195 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System.Text
+{
+    public sealed class EncoderExceptionFallback : EncoderFallback
+    {
+        // Construction
+        public EncoderExceptionFallback()
+        {
+        }
+
+        public override EncoderFallbackBuffer CreateFallbackBuffer()
+        {
+            return new EncoderExceptionFallbackBuffer();
+        }
+
+        // Maximum number of characters that this instance of this fallback could return
+        public override int MaxCharCount
+        {
+            get
+            {
+                return 0;
+            }
+        }
+
+        public override bool Equals(Object value)
+        {
+            EncoderExceptionFallback that = value as EncoderExceptionFallback;
+            if (that != null)
+            {
+                return (true);
+            }
+            return (false);
+        }
+
+        public override int GetHashCode()
+        {
+            return 654;
+        }
+    }
+
+
+    public sealed class EncoderExceptionFallbackBuffer : EncoderFallbackBuffer
+    {
+        public EncoderExceptionFallbackBuffer() { }
+        public override bool Fallback(char charUnknown, int index)
+        {
+            // Fall back our char
+            throw new EncoderFallbackException(
+                SR.Format(SR.Argument_InvalidCodePageConversionIndex, (int)charUnknown, index), charUnknown, index);
+        }
+
+        public override bool Fallback(char charUnknownHigh, char charUnknownLow, int index)
+        {
+            if (!Char.IsHighSurrogate(charUnknownHigh))
+            {
+                throw new ArgumentOutOfRangeException(nameof(charUnknownHigh),
+                    SR.Format(SR.ArgumentOutOfRange_Range, 0xD800, 0xDBFF));
+            }
+            if (!Char.IsLowSurrogate(charUnknownLow))
+            {
+                throw new ArgumentOutOfRangeException(nameof(charUnknownLow),
+                    SR.Format(SR.ArgumentOutOfRange_Range, 0xDC00, 0xDFFF));
+            }
+
+            int iTemp = Char.ConvertToUtf32(charUnknownHigh, charUnknownLow);
+
+            // Fall back our char
+            throw new EncoderFallbackException(
+                SR.Format(SR.Argument_InvalidCodePageConversionIndex, iTemp, index), charUnknownHigh, charUnknownLow, index);
+        }
+
+        public override char GetNextChar()
+        {
+            return (char)0;
+        }
+
+        public override bool MovePrevious()
+        {
+            // Exception fallback doesn't have anywhere to back up to.
+            return false;
+        }
+
+        // Exceptions are always empty
+        public override int Remaining
+        {
+            get
+            {
+                return 0;
+            }
+        }
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class EncoderFallbackException : ArgumentException
+    {
+        private char _charUnknown;
+        private char _charUnknownHigh;
+        private char _charUnknownLow;
+        private int _index;
+
+        public EncoderFallbackException()
+            : base(SR.Arg_ArgumentException)
+        {
+            HResult = HResults.COR_E_ARGUMENT;
+        }
+
+        public EncoderFallbackException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_ARGUMENT;
+        }
+
+        public EncoderFallbackException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_ARGUMENT;
+        }
+
+        internal EncoderFallbackException(
+            String message, char charUnknown, int index) : base(message)
+        {
+            _charUnknown = charUnknown;
+            _index = index;
+        }
+
+        internal EncoderFallbackException(
+            String message, char charUnknownHigh, char charUnknownLow, int index) : base(message)
+        {
+            if (!Char.IsHighSurrogate(charUnknownHigh))
+            {
+                throw new ArgumentOutOfRangeException(nameof(charUnknownHigh),
+                    SR.Format(SR.ArgumentOutOfRange_Range, 0xD800, 0xDBFF));
+            }
+            if (!Char.IsLowSurrogate(charUnknownLow))
+            {
+                throw new ArgumentOutOfRangeException(nameof(CharUnknownLow),
+                    SR.Format(SR.ArgumentOutOfRange_Range, 0xDC00, 0xDFFF));
+            }
+
+            _charUnknownHigh = charUnknownHigh;
+            _charUnknownLow = charUnknownLow;
+            _index = index;
+        }
+
+        private EncoderFallbackException(SerializationInfo serializationInfo, StreamingContext streamingContext)
+            : base(serializationInfo, streamingContext)
+        {
+        }
+
+        public char CharUnknown
+        {
+            get
+            {
+                return (_charUnknown);
+            }
+        }
+
+        public char CharUnknownHigh
+        {
+            get
+            {
+                return (_charUnknownHigh);
+            }
+        }
+
+        public char CharUnknownLow
+        {
+            get
+            {
+                return (_charUnknownLow);
+            }
+        }
+
+        public int Index
+        {
+            get
+            {
+                return _index;
+            }
+        }
+
+        // Return true if the unknown character is a surrogate pair.
+        public bool IsUnknownSurrogate()
+        {
+            return (_charUnknownHigh != '\0');
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/EncoderFallback.cs b/src/System.Private.CoreLib/shared/System/Text/EncoderFallback.cs
new file mode 100644
index 0000000000..d860a02a76
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/EncoderFallback.cs
@@ -0,0 +1,202 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Threading;
+
+namespace System.Text
+{
+    public abstract class EncoderFallback
+    {
+        private static EncoderFallback s_replacementFallback; // Default fallback, uses no best fit & "?"
+        private static EncoderFallback s_exceptionFallback;
+
+        // Get each of our generic fallbacks.
+
+        public static EncoderFallback ReplacementFallback
+        {
+            get
+            {
+                if (s_replacementFallback == null)
+                    Interlocked.CompareExchange<EncoderFallback>(ref s_replacementFallback, new EncoderReplacementFallback(), null);
+
+                return s_replacementFallback;
+            }
+        }
+
+
+        public static EncoderFallback ExceptionFallback
+        {
+            get
+            {
+                if (s_exceptionFallback == null)
+                    Interlocked.CompareExchange<EncoderFallback>(ref s_exceptionFallback, new EncoderExceptionFallback(), null);
+
+                return s_exceptionFallback;
+            }
+        }
+
+        // Fallback
+        //
+        // Return the appropriate unicode string alternative to the character that need to fall back.
+        // Most implementations will be:
+        //      return new MyCustomEncoderFallbackBuffer(this);
+
+        public abstract EncoderFallbackBuffer CreateFallbackBuffer();
+
+        // Maximum number of characters that this instance of this fallback could return
+
+        public abstract int MaxCharCount { get; }
+    }
+
+
+    public abstract class EncoderFallbackBuffer
+    {
+        // Most implementations will probably need an implementation-specific constructor
+
+        // Public methods that cannot be overridden that let us do our fallback thing
+        // These wrap the internal methods so that we can check for people doing stuff that is incorrect
+
+        public abstract bool Fallback(char charUnknown, int index);
+
+        public abstract bool Fallback(char charUnknownHigh, char charUnknownLow, int index);
+
+        // Get next character
+
+        public abstract char GetNextChar();
+
+        // Back up a character
+
+        public abstract bool MovePrevious();
+
+        // How many chars left in this fallback?
+
+        public abstract int Remaining { get; }
+
+        // Not sure if this should be public or not.
+        // Clear the buffer
+
+        public virtual void Reset()
+        {
+            while (GetNextChar() != (char)0) ;
+        }
+
+        // Internal items to help us figure out what we're doing as far as error messages, etc.
+        // These help us with our performance and messages internally
+        internal unsafe char* charStart;
+        internal unsafe char* charEnd;
+        internal EncoderNLS encoder;
+        internal bool setEncoder;
+        internal bool bUsedEncoder;
+        internal bool bFallingBack = false;
+        internal int iRecursionCount = 0;
+        private const int iMaxRecursion = 250;
+
+        // Internal Reset
+        // For example, what if someone fails a conversion and wants to reset one of our fallback buffers?
+        internal unsafe void InternalReset()
+        {
+            charStart = null;
+            bFallingBack = false;
+            iRecursionCount = 0;
+            Reset();
+        }
+
+        // Set the above values
+        // This can't be part of the constructor because EncoderFallbacks would have to know how to implement these.
+        internal unsafe void InternalInitialize(char* charStart, char* charEnd, EncoderNLS encoder, bool setEncoder)
+        {
+            this.charStart = charStart;
+            this.charEnd = charEnd;
+            this.encoder = encoder;
+            this.setEncoder = setEncoder;
+            this.bUsedEncoder = false;
+            this.bFallingBack = false;
+            this.iRecursionCount = 0;
+        }
+
+        internal char InternalGetNextChar()
+        {
+            char ch = GetNextChar();
+            bFallingBack = (ch != 0);
+            if (ch == 0) iRecursionCount = 0;
+            return ch;
+        }
+
+        // Fallback the current character using the remaining buffer and encoder if necessary
+        // This can only be called by our encodings (other have to use the public fallback methods), so
+        // we can use our EncoderNLS here too.
+        // setEncoder is true if we're calling from a GetBytes method, false if we're calling from a GetByteCount
+        //
+        // Note that this could also change the contents of this.encoder, which is the same
+        // object that the caller is using, so the caller could mess up the encoder for us
+        // if they aren't careful.
+        internal unsafe virtual bool InternalFallback(char ch, ref char* chars)
+        {
+            // Shouldn't have null charStart
+            Debug.Assert(charStart != null,
+                "[EncoderFallback.InternalFallbackBuffer]Fallback buffer is not initialized");
+
+            // Get our index, remember chars was preincremented to point at next char, so have to -1
+            int index = (int)(chars - charStart) - 1;
+
+            // See if it was a high surrogate
+            if (Char.IsHighSurrogate(ch))
+            {
+                // See if there's a low surrogate to go with it
+                if (chars >= this.charEnd)
+                {
+                    // Nothing left in input buffer
+                    // No input, return 0 if mustflush is false
+                    if (this.encoder != null && !this.encoder.MustFlush)
+                    {
+                        // Done, nothing to fallback
+                        if (this.setEncoder)
+                        {
+                            bUsedEncoder = true;
+                            this.encoder._charLeftOver = ch;
+                        }
+                        bFallingBack = false;
+                        return false;
+                    }
+                }
+                else
+                {
+                    // Might have a low surrogate
+                    char cNext = *chars;
+                    if (Char.IsLowSurrogate(cNext))
+                    {
+                        // If already falling back then fail
+                        if (bFallingBack && iRecursionCount++ > iMaxRecursion)
+                            ThrowLastCharRecursive(Char.ConvertToUtf32(ch, cNext));
+
+                        // Next is a surrogate, add it as surrogate pair, and increment chars
+                        chars++;
+                        bFallingBack = Fallback(ch, cNext, index);
+                        return bFallingBack;
+                    }
+                    // Next isn't a low surrogate, just fallback the high surrogate
+                }
+            }
+
+            // If already falling back then fail
+            if (bFallingBack && iRecursionCount++ > iMaxRecursion)
+                ThrowLastCharRecursive((int)ch);
+
+            // Fall back our char
+            bFallingBack = Fallback(ch, index);
+
+            return bFallingBack;
+        }
+
+        // private helper methods
+        internal void ThrowLastCharRecursive(int charRecursive)
+        {
+            // Throw it, using our complete character
+            throw new ArgumentException(
+                SR.Format(SR.Argument_RecursiveFallback,
+                    charRecursive), "chars");
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/EncoderNLS.cs b/src/System.Private.CoreLib/shared/System/Text/EncoderNLS.cs
new file mode 100644
index 0000000000..e83666f7a3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/EncoderNLS.cs
@@ -0,0 +1,239 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text;
+using System;
+using System.Runtime.InteropServices;
+
+namespace System.Text
+{
+    // An Encoder is used to encode a sequence of blocks of characters into
+    // a sequence of blocks of bytes. Following instantiation of an encoder,
+    // sequential blocks of characters are converted into blocks of bytes through
+    // calls to the GetBytes method. The encoder maintains state between the
+    // conversions, allowing it to correctly encode character sequences that span
+    // adjacent blocks.
+    //
+    // Instances of specific implementations of the Encoder abstract base
+    // class are typically obtained through calls to the GetEncoder method
+    // of Encoding objects.
+    //
+
+    internal class EncoderNLS : Encoder
+    {
+        // Need a place for the last left over character, most of our encodings use this
+        internal char _charLeftOver;
+        private Encoding _encoding;
+        private bool _mustFlush;
+        internal bool _throwOnOverflow;
+        internal int _charsUsed;
+
+        internal EncoderNLS(Encoding encoding)
+        {
+            _encoding = encoding;
+            _fallback = _encoding.EncoderFallback;
+            this.Reset();
+        }
+
+        internal EncoderNLS()
+        {
+            _encoding = null;
+            this.Reset();
+        }
+
+        public override void Reset()
+        {
+            _charLeftOver = (char)0;
+            if (_fallbackBuffer != null)
+                _fallbackBuffer.Reset();
+        }
+
+        public override unsafe int GetByteCount(char[] chars, int index, int count, bool flush)
+        {
+            // Validate input parameters
+            if (chars == null)
+                throw new ArgumentNullException(nameof(chars),
+                      SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? nameof(index) : nameof(count)),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - index < count)
+                throw new ArgumentOutOfRangeException(nameof(chars),
+                      SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // Just call the pointer version
+            int result = -1;
+            fixed (char* pChars = &MemoryMarshal.GetReference((Span<char>)chars))
+            {
+                result = GetByteCount(pChars + index, count, flush);
+            }
+            return result;
+        }
+
+        public unsafe override int GetByteCount(char* chars, int count, bool flush)
+        {
+            // Validate input parameters
+            if (chars == null)
+                throw new ArgumentNullException(nameof(chars),
+                      SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            _mustFlush = flush;
+            _throwOnOverflow = true;
+            return _encoding.GetByteCount(chars, count, this);
+        }
+
+        public override unsafe int GetBytes(char[] chars, int charIndex, int charCount,
+                                              byte[] bytes, int byteIndex, bool flush)
+        {
+            // Validate parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException((chars == null ? nameof(chars) : nameof(bytes)),
+                      SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? nameof(charIndex) : nameof(charCount)),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException(nameof(chars),
+                      SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+                throw new ArgumentOutOfRangeException(nameof(byteIndex),
+                     SR.ArgumentOutOfRange_Index);
+
+            int byteCount = bytes.Length - byteIndex;
+
+            // Just call pointer version
+            fixed (char* pChars = &MemoryMarshal.GetReference((Span<char>)chars))
+            fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+
+                // Remember that charCount is # to decode, not size of array.
+                return GetBytes(pChars + charIndex, charCount,
+                                pBytes + byteIndex, byteCount, flush);
+        }
+
+        public unsafe override int GetBytes(char* chars, int charCount, byte* bytes, int byteCount, bool flush)
+        {
+            // Validate parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException((chars == null ? nameof(chars) : nameof(bytes)),
+                      SR.ArgumentNull_Array);
+
+            if (byteCount < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((byteCount < 0 ? nameof(byteCount) : nameof(charCount)),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            _mustFlush = flush;
+            _throwOnOverflow = true;
+            return _encoding.GetBytes(chars, charCount, bytes, byteCount, this);
+        }
+
+        // This method is used when your output buffer might not be large enough for the entire result.
+        // Just call the pointer version.  (This gets bytes)
+        public override unsafe void Convert(char[] chars, int charIndex, int charCount,
+                                              byte[] bytes, int byteIndex, int byteCount, bool flush,
+                                              out int charsUsed, out int bytesUsed, out bool completed)
+        {
+            // Validate parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException((chars == null ? nameof(chars) : nameof(bytes)),
+                      SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? nameof(charIndex) : nameof(charCount)),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (byteIndex < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((byteIndex < 0 ? nameof(byteIndex) : nameof(byteCount)),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException(nameof(chars),
+                      SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (bytes.Length - byteIndex < byteCount)
+                throw new ArgumentOutOfRangeException(nameof(bytes),
+                      SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // Just call the pointer version (can't do this for non-msft encoders)
+            fixed (char* pChars = &MemoryMarshal.GetReference((Span<char>)chars))
+            {
+                fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+                {
+                    Convert(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, flush,
+                        out charsUsed, out bytesUsed, out completed);
+                }
+            }
+        }
+
+        // This is the version that uses pointers.  We call the base encoding worker function
+        // after setting our appropriate internal variables.  This is getting bytes
+        public override unsafe void Convert(char* chars, int charCount,
+                                              byte* bytes, int byteCount, bool flush,
+                                              out int charsUsed, out int bytesUsed, out bool completed)
+        {
+            // Validate input parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? nameof(bytes) : nameof(chars),
+                    SR.ArgumentNull_Array);
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? nameof(charCount) : nameof(byteCount)),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // We don't want to throw
+            _mustFlush = flush;
+            _throwOnOverflow = false;
+            _charsUsed = 0;
+
+            // Do conversion
+            bytesUsed = _encoding.GetBytes(chars, charCount, bytes, byteCount, this);
+            charsUsed = _charsUsed;
+
+            // Its completed if they've used what they wanted AND if they didn't want flush or if we are flushed
+            completed = (charsUsed == charCount) && (!flush || !this.HasState) &&
+                (_fallbackBuffer == null || _fallbackBuffer.Remaining == 0);
+
+            // Our data thingys are now full, we can return
+        }
+
+        public Encoding Encoding
+        {
+            get
+            {
+                return _encoding;
+            }
+        }
+
+        public bool MustFlush
+        {
+            get
+            {
+                return _mustFlush;
+            }
+        }
+
+
+        // Anything left in our encoder?
+        internal virtual bool HasState
+        {
+            get
+            {
+                return (_charLeftOver != (char)0);
+            }
+        }
+
+        // Allow encoding to clear our must flush instead of throwing (in ThrowBytesOverflow)
+        internal void ClearMustFlush()
+        {
+            _mustFlush = false;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/EncoderReplacementFallback.cs b/src/System.Private.CoreLib/shared/System/Text/EncoderReplacementFallback.cs
new file mode 100644
index 0000000000..a1d0bbcd95
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/EncoderReplacementFallback.cs
@@ -0,0 +1,227 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime;
+using System.Diagnostics;
+
+namespace System.Text
+{
+    public sealed class EncoderReplacementFallback : EncoderFallback
+    {
+        // Our variables
+        private String _strDefault;
+
+        // Construction.  Default replacement fallback uses no best fit and ? replacement string
+        public EncoderReplacementFallback() : this("?")
+        {
+        }
+
+        public EncoderReplacementFallback(String replacement)
+        {
+            // Must not be null
+            if (replacement == null)
+                throw new ArgumentNullException(nameof(replacement));
+
+            // Make sure it doesn't have bad surrogate pairs
+            bool bFoundHigh = false;
+            for (int i = 0; i < replacement.Length; i++)
+            {
+                // Found a surrogate?
+                if (Char.IsSurrogate(replacement, i))
+                {
+                    // High or Low?
+                    if (Char.IsHighSurrogate(replacement, i))
+                    {
+                        // if already had a high one, stop
+                        if (bFoundHigh)
+                            break;  // break & throw at the bFoundHIgh below
+                        bFoundHigh = true;
+                    }
+                    else
+                    {
+                        // Low, did we have a high?
+                        if (!bFoundHigh)
+                        {
+                            // Didn't have one, make if fail when we stop
+                            bFoundHigh = true;
+                            break;
+                        }
+
+                        // Clear flag
+                        bFoundHigh = false;
+                    }
+                }
+                // If last was high we're in trouble (not surrogate so not low surrogate, so break)
+                else if (bFoundHigh)
+                    break;
+            }
+            if (bFoundHigh)
+                throw new ArgumentException(SR.Format(SR.Argument_InvalidCharSequenceNoIndex, nameof(replacement)));
+
+            _strDefault = replacement;
+        }
+
+        public String DefaultString
+        {
+            get
+            {
+                return _strDefault;
+            }
+        }
+
+        public override EncoderFallbackBuffer CreateFallbackBuffer()
+        {
+            return new EncoderReplacementFallbackBuffer(this);
+        }
+
+        // Maximum number of characters that this instance of this fallback could return
+        public override int MaxCharCount
+        {
+            get
+            {
+                return _strDefault.Length;
+            }
+        }
+
+        public override bool Equals(Object value)
+        {
+            EncoderReplacementFallback that = value as EncoderReplacementFallback;
+            if (that != null)
+            {
+                return (_strDefault == that._strDefault);
+            }
+            return (false);
+        }
+
+        public override int GetHashCode()
+        {
+            return _strDefault.GetHashCode();
+        }
+    }
+
+
+
+    public sealed class EncoderReplacementFallbackBuffer : EncoderFallbackBuffer
+    {
+        // Store our default string
+        private String _strDefault;
+        private int _fallbackCount = -1;
+        private int _fallbackIndex = -1;
+
+        // Construction
+        public EncoderReplacementFallbackBuffer(EncoderReplacementFallback fallback)
+        {
+            // 2X in case we're a surrogate pair
+            _strDefault = fallback.DefaultString + fallback.DefaultString;
+        }
+
+        // Fallback Methods
+        public override bool Fallback(char charUnknown, int index)
+        {
+            // If we had a buffer already we're being recursive, throw, it's probably at the suspect
+            // character in our array.
+            if (_fallbackCount >= 1)
+            {
+                // If we're recursive we may still have something in our buffer that makes this a surrogate
+                if (char.IsHighSurrogate(charUnknown) && _fallbackCount >= 0 &&
+                    char.IsLowSurrogate(_strDefault[_fallbackIndex + 1]))
+                    ThrowLastCharRecursive(Char.ConvertToUtf32(charUnknown, _strDefault[_fallbackIndex + 1]));
+
+                // Nope, just one character
+                ThrowLastCharRecursive(unchecked((int)charUnknown));
+            }
+
+            // Go ahead and get our fallback
+            // Divide by 2 because we aren't a surrogate pair
+            _fallbackCount = _strDefault.Length / 2;
+            _fallbackIndex = -1;
+
+            return _fallbackCount != 0;
+        }
+
+        public override bool Fallback(char charUnknownHigh, char charUnknownLow, int index)
+        {
+            // Double check input surrogate pair
+            if (!Char.IsHighSurrogate(charUnknownHigh))
+                throw new ArgumentOutOfRangeException(nameof(charUnknownHigh),
+                    SR.Format(SR.ArgumentOutOfRange_Range, 0xD800, 0xDBFF));
+
+            if (!Char.IsLowSurrogate(charUnknownLow))
+                throw new ArgumentOutOfRangeException(nameof(charUnknownLow),
+                    SR.Format(SR.ArgumentOutOfRange_Range, 0xDC00, 0xDFFF));
+
+            // If we had a buffer already we're being recursive, throw, it's probably at the suspect
+            // character in our array.
+            if (_fallbackCount >= 1)
+                ThrowLastCharRecursive(Char.ConvertToUtf32(charUnknownHigh, charUnknownLow));
+
+            // Go ahead and get our fallback
+            _fallbackCount = _strDefault.Length;
+            _fallbackIndex = -1;
+
+            return _fallbackCount != 0;
+        }
+
+        public override char GetNextChar()
+        {
+            // We want it to get < 0 because == 0 means that the current/last character is a fallback
+            // and we need to detect recursion.  We could have a flag but we already have this counter.
+            _fallbackCount--;
+            _fallbackIndex++;
+
+            // Do we have anything left? 0 is now last fallback char, negative is nothing left
+            if (_fallbackCount < 0)
+                return '\0';
+
+            // Need to get it out of the buffer.
+            // Make sure it didn't wrap from the fast count-- path
+            if (_fallbackCount == int.MaxValue)
+            {
+                _fallbackCount = -1;
+                return '\0';
+            }
+
+            // Now make sure its in the expected range
+            Debug.Assert(_fallbackIndex < _strDefault.Length && _fallbackIndex >= 0,
+                            "Index exceeds buffer range");
+
+            return _strDefault[_fallbackIndex];
+        }
+
+        public override bool MovePrevious()
+        {
+            // Back up one, only if we just processed the last character (or earlier)
+            if (_fallbackCount >= -1 && _fallbackIndex >= 0)
+            {
+                _fallbackIndex--;
+                _fallbackCount++;
+                return true;
+            }
+
+            // Return false 'cause we couldn't do it.
+            return false;
+        }
+
+        // How many characters left to output?
+        public override int Remaining
+        {
+            get
+            {
+                // Our count is 0 for 1 character left.
+                return (_fallbackCount < 0) ? 0 : _fallbackCount;
+            }
+        }
+
+        // Clear the buffer
+        public override unsafe void Reset()
+        {
+            _fallbackCount = -1;
+            _fallbackIndex = 0;
+            charStart = null;
+            bFallingBack = false;
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Text/Encoding.cs b/src/System.Private.CoreLib/shared/System/Text/Encoding.cs
new file mode 100644
index 0000000000..e191ce14fd
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/Encoding.cs
@@ -0,0 +1,1789 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Globalization;
+using System.Threading;
+using System.Runtime.InteropServices;
+using System.Runtime.Serialization;
+using System.Diagnostics.CodeAnalysis;
+
+namespace System.Text
+{
+    // This abstract base class represents a character encoding. The class provides
+    // methods to convert arrays and strings of Unicode characters to and from
+    // arrays of bytes. A number of Encoding implementations are provided in
+    // the System.Text package, including:
+    //
+    // ASCIIEncoding, which encodes Unicode characters as single 7-bit
+    // ASCII characters. This encoding only supports character values between 0x00
+    //     and 0x7F.
+    // BaseCodePageEncoding, which encapsulates a Windows code page. Any
+    //     installed code page can be accessed through this encoding, and conversions
+    //     are performed using the WideCharToMultiByte and
+    //     MultiByteToWideChar Windows API functions.
+    // UnicodeEncoding, which encodes each Unicode character as two
+    //    consecutive bytes. Both little-endian (code page 1200) and big-endian (code
+    //    page 1201) encodings are recognized.
+    // UTF7Encoding, which encodes Unicode characters using the UTF-7
+    //     encoding (UTF-7 stands for UCS Transformation Format, 7-bit form). This
+    //     encoding supports all Unicode character values, and can also be accessed
+    //     as code page 65000.
+    // UTF8Encoding, which encodes Unicode characters using the UTF-8
+    //     encoding (UTF-8 stands for UCS Transformation Format, 8-bit form). This
+    //     encoding supports all Unicode character values, and can also be accessed
+    //     as code page 65001.
+    // UTF32Encoding, both 12000 (little endian) & 12001 (big endian)
+    //
+    // In addition to directly instantiating Encoding objects, an
+    // application can use the ForCodePage, GetASCII,
+    // GetDefault, GetUnicode, GetUTF7, and GetUTF8
+    // methods in this class to obtain encodings.
+    //
+    // Through an encoding, the GetBytes method is used to convert arrays
+    // of characters to arrays of bytes, and the GetChars method is used to
+    // convert arrays of bytes to arrays of characters. The GetBytes and
+    // GetChars methods maintain no state between conversions, and are
+    // generally intended for conversions of complete blocks of bytes and
+    // characters in one operation. When the data to be converted is only available
+    // in sequential blocks (such as data read from a stream) or when the amount of
+    // data is so large that it needs to be divided into smaller blocks, an
+    // application may choose to use a Decoder or an Encoder to
+    // perform the conversion. Decoders and encoders allow sequential blocks of
+    // data to be converted and they maintain the state required to support
+    // conversions of data that spans adjacent blocks. Decoders and encoders are
+    // obtained using the GetDecoder and GetEncoder methods.
+    //
+    // The core GetBytes and GetChars methods require the caller
+    // to provide the destination buffer and ensure that the buffer is large enough
+    // to hold the entire result of the conversion. When using these methods,
+    // either directly on an Encoding object or on an associated
+    // Decoder or Encoder, an application can use one of two methods
+    // to allocate destination buffers.
+    //
+    // The GetByteCount and GetCharCount methods can be used to
+    // compute the exact size of the result of a particular conversion, and an
+    // appropriately sized buffer for that conversion can then be allocated.
+    // The GetMaxByteCount and GetMaxCharCount methods can be
+    // be used to compute the maximum possible size of a conversion of a given
+    // number of bytes or characters, and a buffer of that size can then be reused
+    // for multiple conversions.
+    //
+    // The first method generally uses less memory, whereas the second method
+    // generally executes faster.
+    //
+
+    public abstract class Encoding : ICloneable
+    {
+        // For netcore we use UTF8 as default encoding since ANSI isn't available
+        private static readonly UTF8Encoding.UTF8EncodingSealed s_defaultEncoding  = new UTF8Encoding.UTF8EncodingSealed(encoderShouldEmitUTF8Identifier: false);
+
+        // Returns an encoding for the system's current ANSI code page.
+        public static Encoding Default => s_defaultEncoding;
+
+        //
+        // The following values are from mlang.idl.  These values
+        // should be in sync with those in mlang.idl.
+        //
+        internal const int MIMECONTF_MAILNEWS = 0x00000001;
+        internal const int MIMECONTF_BROWSER = 0x00000002;
+        internal const int MIMECONTF_SAVABLE_MAILNEWS = 0x00000100;
+        internal const int MIMECONTF_SAVABLE_BROWSER = 0x00000200;
+
+        // Special Case Code Pages
+        private const int CodePageDefault = 0;
+        private const int CodePageNoOEM = 1;        // OEM Code page not supported
+        private const int CodePageNoMac = 2;        // MAC code page not supported
+        private const int CodePageNoThread = 3;        // Thread code page not supported
+        private const int CodePageNoSymbol = 42;       // Symbol code page not supported
+        private const int CodePageUnicode = 1200;     // Unicode
+        private const int CodePageBigEndian = 1201;     // Big Endian Unicode
+        private const int CodePageWindows1252 = 1252;     // Windows 1252 code page
+
+        // 20936 has same code page as 10008, so we'll special case it
+        private const int CodePageMacGB2312 = 10008;
+        private const int CodePageGB2312 = 20936;
+        private const int CodePageMacKorean = 10003;
+        private const int CodePageDLLKorean = 20949;
+
+        // ISO 2022 Code Pages
+        private const int ISO2022JP = 50220;
+        private const int ISO2022JPESC = 50221;
+        private const int ISO2022JPSISO = 50222;
+        private const int ISOKorean = 50225;
+        private const int ISOSimplifiedCN = 50227;
+        private const int EUCJP = 51932;
+        private const int ChineseHZ = 52936;    // HZ has ~}~{~~ sequences
+
+        // 51936 is the same as 936
+        private const int DuplicateEUCCN = 51936;
+        private const int EUCCN = 936;
+
+        private const int EUCKR = 51949;
+
+        // Latin 1 & ASCII Code Pages
+        internal const int CodePageASCII = 20127;    // ASCII
+        internal const int ISO_8859_1 = 28591;    // Latin1
+
+        // ISCII
+        private const int ISCIIAssemese = 57006;
+        private const int ISCIIBengali = 57003;
+        private const int ISCIIDevanagari = 57002;
+        private const int ISCIIGujarathi = 57010;
+        private const int ISCIIKannada = 57008;
+        private const int ISCIIMalayalam = 57009;
+        private const int ISCIIOriya = 57007;
+        private const int ISCIIPanjabi = 57011;
+        private const int ISCIITamil = 57004;
+        private const int ISCIITelugu = 57005;
+
+        // GB18030
+        private const int GB18030 = 54936;
+
+        // Other
+        private const int ISO_8859_8I = 38598;
+        private const int ISO_8859_8_Visual = 28598;
+
+        // 50229 is currently unsupported // "Chinese Traditional (ISO-2022)"
+        private const int ENC50229 = 50229;
+
+        // Special code pages
+        private const int CodePageUTF7 = 65000;
+        private const int CodePageUTF8 = 65001;
+        private const int CodePageUTF32 = 12000;
+        private const int CodePageUTF32BE = 12001;
+
+        internal int _codePage = 0;
+
+        internal CodePageDataItem _dataItem = null;
+
+        // Because of encoders we may be read only
+        [OptionalField(VersionAdded = 2)]
+        private bool _isReadOnly = true;
+
+        // Encoding (encoder) fallback
+        internal EncoderFallback encoderFallback = null;
+        internal DecoderFallback decoderFallback = null;
+
+        protected Encoding() : this(0)
+        {
+        }
+
+
+        protected Encoding(int codePage)
+        {
+            // Validate code page
+            if (codePage < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(codePage));
+            }
+
+            // Remember code page
+            _codePage = codePage;
+
+            // Use default encoder/decoder fallbacks
+            this.SetDefaultFallbacks();
+        }
+
+        // This constructor is needed to allow any sub-classing implementation to provide encoder/decoder fallback objects 
+        // because the encoding object is always created as read-only object and don't allow setting encoder/decoder fallback 
+        // after the creation is done. 
+        protected Encoding(int codePage, EncoderFallback encoderFallback, DecoderFallback decoderFallback)
+        {
+            // Validate code page
+            if (codePage < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(codePage));
+            }
+
+            // Remember code page
+            _codePage = codePage;
+
+            this.encoderFallback = encoderFallback ?? new InternalEncoderBestFitFallback(this);
+            this.decoderFallback = decoderFallback ?? new InternalDecoderBestFitFallback(this);
+        }
+
+        // Default fallback that we'll use.
+        internal virtual void SetDefaultFallbacks()
+        {
+            // For UTF-X encodings, we use a replacement fallback with an "\xFFFD" string,
+            // For ASCII we use "?" replacement fallback, etc.
+            encoderFallback = new InternalEncoderBestFitFallback(this);
+            decoderFallback = new InternalDecoderBestFitFallback(this);
+        }
+
+        // Converts a byte array from one encoding to another. The bytes in the
+        // bytes array are converted from srcEncoding to
+        // dstEncoding, and the returned value is a new byte array
+        // containing the result of the conversion.
+        //
+        public static byte[] Convert(Encoding srcEncoding, Encoding dstEncoding,
+            byte[] bytes)
+        {
+            if (bytes == null)
+                throw new ArgumentNullException(nameof(bytes));
+
+            return Convert(srcEncoding, dstEncoding, bytes, 0, bytes.Length);
+        }
+
+        // Converts a range of bytes in a byte array from one encoding to another.
+        // This method converts count bytes from bytes starting at
+        // index index from srcEncoding to dstEncoding, and
+        // returns a new byte array containing the result of the conversion.
+        //
+        public static byte[] Convert(Encoding srcEncoding, Encoding dstEncoding,
+            byte[] bytes, int index, int count)
+        {
+            if (srcEncoding == null || dstEncoding == null)
+            {
+                throw new ArgumentNullException((srcEncoding == null ? nameof(srcEncoding) : nameof(dstEncoding)),
+                    SR.ArgumentNull_Array);
+            }
+            if (bytes == null)
+            {
+                throw new ArgumentNullException(nameof(bytes),
+                    SR.ArgumentNull_Array);
+            }
+
+            return dstEncoding.GetBytes(srcEncoding.GetChars(bytes, index, count));
+        }
+
+        public static void RegisterProvider(EncodingProvider provider)
+        {
+            // Parameters validated inside EncodingProvider
+            EncodingProvider.AddProvider(provider);
+        }
+
+        public static Encoding GetEncoding(int codepage)
+        {
+            Encoding result = EncodingProvider.GetEncodingFromProvider(codepage);
+            if (result != null)
+                return result;
+
+            //
+            // NOTE: If you add a new encoding that can be retrieved by codepage, be sure to
+            // add the corresponding item in EncodingTable.
+            // Otherwise, the code below will throw exception when trying to call
+            // EncodingTable.GetDataItem().
+            //
+            if (codepage < 0 || codepage > 65535)
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(codepage), SR.Format(SR.ArgumentOutOfRange_Range, 0, 65535));
+            }
+
+
+            switch (codepage)
+            {
+                case CodePageDefault: return Default;            // 0
+                case CodePageUnicode: return Unicode;            // 1200
+                case CodePageBigEndian: return BigEndianUnicode; // 1201
+                case CodePageUTF32: return UTF32;                // 12000
+                case CodePageUTF32BE: return BigEndianUTF32;     // 12001
+                case CodePageUTF7: return UTF7;                  // 65000
+                case CodePageUTF8: return UTF8;                  // 65001
+                case CodePageASCII: return ASCII;                // 20127
+                case ISO_8859_1: return Latin1;                  // 28591
+
+                // We don't allow the following special code page values that Win32 allows.
+                case CodePageNoOEM:                              // 1 CP_OEMCP
+                case CodePageNoMac:                              // 2 CP_MACCP
+                case CodePageNoThread:                           // 3 CP_THREAD_ACP
+                case CodePageNoSymbol:                           // 42 CP_SYMBOL
+                    throw new ArgumentException(SR.Format(SR.Argument_CodepageNotSupported, codepage), nameof(codepage));
+            }
+
+            // Is it a valid code page?
+            if (EncodingTable.GetCodePageDataItem(codepage) == null)
+            {
+                throw new NotSupportedException(
+                    SR.Format(SR.NotSupported_NoCodepageData, codepage));
+            }
+
+            return UTF8;
+        }
+
+        public static Encoding GetEncoding(int codepage,
+            EncoderFallback encoderFallback, DecoderFallback decoderFallback)
+        {
+            Encoding baseEncoding = EncodingProvider.GetEncodingFromProvider(codepage, encoderFallback, decoderFallback);
+
+            if (baseEncoding != null)
+                return baseEncoding;
+
+            // Get the default encoding (which is cached and read only)
+            baseEncoding = GetEncoding(codepage);
+
+            // Clone it and set the fallback
+            Encoding fallbackEncoding = (Encoding)baseEncoding.Clone();
+            fallbackEncoding.EncoderFallback = encoderFallback;
+            fallbackEncoding.DecoderFallback = decoderFallback;
+
+            return fallbackEncoding;
+        }
+
+        // Returns an Encoding object for a given name or a given code page value.
+        //
+        public static Encoding GetEncoding(String name)
+        {
+            Encoding baseEncoding = EncodingProvider.GetEncodingFromProvider(name);
+            if (baseEncoding != null)
+                return baseEncoding;
+
+            //
+            // NOTE: If you add a new encoding that can be requested by name, be sure to
+            // add the corresponding item in EncodingTable.
+            // Otherwise, the code below will throw exception when trying to call
+            // EncodingTable.GetCodePageFromName().
+            //
+            return GetEncoding(EncodingTable.GetCodePageFromName(name));
+        }
+
+        // Returns an Encoding object for a given name or a given code page value.
+        //
+        public static Encoding GetEncoding(String name,
+            EncoderFallback encoderFallback, DecoderFallback decoderFallback)
+        {
+            Encoding baseEncoding = EncodingProvider.GetEncodingFromProvider(name, encoderFallback, decoderFallback);
+            if (baseEncoding != null)
+                return baseEncoding;
+
+            //
+            // NOTE: If you add a new encoding that can be requested by name, be sure to
+            // add the corresponding item in EncodingTable.
+            // Otherwise, the code below will throw exception when trying to call
+            // EncodingTable.GetCodePageFromName().
+            //
+            return (GetEncoding(EncodingTable.GetCodePageFromName(name), encoderFallback, decoderFallback));
+        }
+
+        // Return a list of all EncodingInfo objects describing all of our encodings
+        public static EncodingInfo[] GetEncodings()
+        {
+            return EncodingTable.GetEncodings();
+        }
+
+        public virtual byte[] GetPreamble()
+        {
+            return Array.Empty<byte>();
+        }
+
+        public virtual ReadOnlySpan<byte> Preamble => GetPreamble();
+
+        private void GetDataItem()
+        {
+            if (_dataItem == null)
+            {
+                _dataItem = EncodingTable.GetCodePageDataItem(_codePage);
+                if (_dataItem == null)
+                {
+                    throw new NotSupportedException(SR.Format(SR.NotSupported_NoCodepageData, _codePage));
+                }
+            }
+        }
+
+        // Returns the name for this encoding that can be used with mail agent body tags.
+        // If the encoding may not be used, the string is empty.
+
+        public virtual String BodyName
+        {
+            get
+            {
+                if (_dataItem == null)
+                {
+                    GetDataItem();
+                }
+                return (_dataItem.BodyName);
+            }
+        }
+
+        // Returns the human-readable description of the encoding ( e.g. Hebrew (DOS)).
+#if PROJECTN
+        public virtual String EncodingName
+        {
+            get
+            {
+                string encodingName = GetLocalizedEncodingNameResource(this.CodePage);
+                if (encodingName == null)
+                {
+                    throw new NotSupportedException(SR.Format(SR.MissingEncodingNameResource, this.CodePage));
+                }
+
+                if (encodingName.StartsWith("Globalization_cp_", StringComparison.Ordinal))
+                {
+                    // On ProjectN, resource strings are stripped from retail builds and replaced by
+                    // their identifier names. Since this property is meant to be a localized string,
+                    // but we don't localize ProjectN, we specifically need to do something reasonable
+                    // in this case. This currently returns the English name of the encoding from a
+                    // static data table.
+                    encodingName = EncodingTable.GetCodePageDataItem(this.CodePage).EnglishName;
+                    if (encodingName == null)
+                    {
+                        throw new NotSupportedException(SR.Format(SR.MissingEncodingNameResource, this.WebName, this.CodePage));
+                    }
+                }
+                return encodingName;
+            }
+        }
+
+        private static string GetLocalizedEncodingNameResource(int codePage)
+        {
+            switch (codePage)
+            {
+                case 1200: return SR.Globalization_cp_1200;
+                case 1201: return SR.Globalization_cp_1201;
+                case 12000: return SR.Globalization_cp_12000;
+                case 12001: return SR.Globalization_cp_12001;
+                case 20127: return SR.Globalization_cp_20127;
+                case 28591: return SR.Globalization_cp_28591;
+                case 65000: return SR.Globalization_cp_65000;
+                case 65001: return SR.Globalization_cp_65001;
+                default: return null;
+            }
+        }
+#else
+        public virtual String EncodingName
+        {
+            get
+            {
+                return SR.GetResourceString("Globalization_cp_" + _codePage.ToString());
+            }
+        }
+#endif
+        // Returns the name for this encoding that can be used with mail agent header
+        // tags.  If the encoding may not be used, the string is empty.
+
+        public virtual String HeaderName
+        {
+            get
+            {
+                if (_dataItem == null)
+                {
+                    GetDataItem();
+                }
+                return (_dataItem.HeaderName);
+            }
+        }
+
+        // Returns the IANA preferred name for this encoding.
+        public virtual String WebName
+        {
+            get
+            {
+                if (_dataItem == null)
+                {
+                    GetDataItem();
+                }
+                return (_dataItem.WebName);
+            }
+        }
+
+        // Returns the windows code page that most closely corresponds to this encoding.
+
+        public virtual int WindowsCodePage
+        {
+            get
+            {
+                if (_dataItem == null)
+                {
+                    GetDataItem();
+                }
+                return (_dataItem.UIFamilyCodePage);
+            }
+        }
+
+
+        // True if and only if the encoding is used for display by browsers clients.
+
+        public virtual bool IsBrowserDisplay
+        {
+            get
+            {
+                if (_dataItem == null)
+                {
+                    GetDataItem();
+                }
+                return ((_dataItem.Flags & MIMECONTF_BROWSER) != 0);
+            }
+        }
+
+        // True if and only if the encoding is used for saving by browsers clients.
+
+        public virtual bool IsBrowserSave
+        {
+            get
+            {
+                if (_dataItem == null)
+                {
+                    GetDataItem();
+                }
+                return ((_dataItem.Flags & MIMECONTF_SAVABLE_BROWSER) != 0);
+            }
+        }
+
+        // True if and only if the encoding is used for display by mail and news clients.
+
+        public virtual bool IsMailNewsDisplay
+        {
+            get
+            {
+                if (_dataItem == null)
+                {
+                    GetDataItem();
+                }
+                return ((_dataItem.Flags & MIMECONTF_MAILNEWS) != 0);
+            }
+        }
+
+
+        // True if and only if the encoding is used for saving documents by mail and
+        // news clients
+
+        public virtual bool IsMailNewsSave
+        {
+            get
+            {
+                if (_dataItem == null)
+                {
+                    GetDataItem();
+                }
+                return ((_dataItem.Flags & MIMECONTF_SAVABLE_MAILNEWS) != 0);
+            }
+        }
+
+        // True if and only if the encoding only uses single byte code points.  (Ie, ASCII, 1252, etc)
+
+        public virtual bool IsSingleByte
+        {
+            get
+            {
+                return false;
+            }
+        }
+
+
+        public EncoderFallback EncoderFallback
+        {
+            get
+            {
+                return encoderFallback;
+            }
+
+            set
+            {
+                if (this.IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+
+                if (value == null)
+                    throw new ArgumentNullException(nameof(value));
+
+                encoderFallback = value;
+            }
+        }
+
+
+        public DecoderFallback DecoderFallback
+        {
+            get
+            {
+                return decoderFallback;
+            }
+
+            set
+            {
+                if (this.IsReadOnly)
+                    throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+
+                if (value == null)
+                    throw new ArgumentNullException(nameof(value));
+
+                decoderFallback = value;
+            }
+        }
+
+
+        public virtual Object Clone()
+        {
+            Encoding newEncoding = (Encoding)this.MemberwiseClone();
+
+            // New one should be readable
+            newEncoding._isReadOnly = false;
+            return newEncoding;
+        }
+
+
+        public bool IsReadOnly
+        {
+            get
+            {
+                return (_isReadOnly);
+            }
+        }
+
+        // Returns an encoding for the ASCII character set. The returned encoding
+        // will be an instance of the ASCIIEncoding class.
+
+        public static Encoding ASCII => ASCIIEncoding.s_default;
+
+        // Returns an encoding for the Latin1 character set. The returned encoding
+        // will be an instance of the Latin1Encoding class.
+        //
+        // This is for our optimizations
+        private static Encoding Latin1 => Latin1Encoding.s_default;
+
+        // Returns the number of bytes required to encode the given character
+        // array.
+        //
+        public virtual int GetByteCount(char[] chars)
+        {
+            if (chars == null)
+            {
+                throw new ArgumentNullException(nameof(chars),
+                    SR.ArgumentNull_Array);
+            }
+
+            return GetByteCount(chars, 0, chars.Length);
+        }
+
+        public virtual int GetByteCount(String s)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+
+            char[] chars = s.ToCharArray();
+            return GetByteCount(chars, 0, chars.Length);
+        }
+
+        // Returns the number of bytes required to encode a range of characters in
+        // a character array.
+        //
+        public abstract int GetByteCount(char[] chars, int index, int count);
+
+        // Returns the number of bytes required to encode a string range.
+        //
+        public int GetByteCount(string s, int index, int count)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s),
+                    SR.ArgumentNull_String);
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (index > s.Length - count)
+                throw new ArgumentOutOfRangeException(nameof(index),
+                      SR.ArgumentOutOfRange_IndexCount);
+
+            unsafe
+            {
+                fixed (char* pChar = s)
+                {
+                    return GetByteCount(pChar + index, count);
+                }
+            }
+        }
+
+        // We expect this to be the workhorse for NLS encodings
+        // unfortunately for existing overrides, it has to call the [] version,
+        // which is really slow, so this method should be avoided if you're calling
+        // a 3rd party encoding.
+        [CLSCompliant(false)]
+        public virtual unsafe int GetByteCount(char* chars, int count)
+        {
+            // Validate input parameters
+            if (chars == null)
+                throw new ArgumentNullException(nameof(chars),
+                      SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            char[] arrChar = new char[count];
+            int index;
+
+            for (index = 0; index < count; index++)
+                arrChar[index] = chars[index];
+
+            return GetByteCount(arrChar, 0, count);
+        }
+
+        public virtual unsafe int GetByteCount(ReadOnlySpan<char> chars)
+        {
+            fixed (char* charsPtr = &MemoryMarshal.GetNonNullPinnableReference(chars))
+            {
+                return GetByteCount(charsPtr, chars.Length);
+            }
+        }
+
+        // For NLS Encodings, workhorse takes an encoder (may be null)
+        // Always validate parameters before calling internal version, which will only assert.
+        internal virtual unsafe int GetByteCount(char* chars, int count, EncoderNLS encoder)
+        {
+            Debug.Assert(chars != null);
+            Debug.Assert(count >= 0);
+
+            return GetByteCount(chars, count);
+        }
+
+        // Returns a byte array containing the encoded representation of the given
+        // character array.
+        //
+        public virtual byte[] GetBytes(char[] chars)
+        {
+            if (chars == null)
+            {
+                throw new ArgumentNullException(nameof(chars),
+                    SR.ArgumentNull_Array);
+            }
+            return GetBytes(chars, 0, chars.Length);
+        }
+
+        // Returns a byte array containing the encoded representation of a range
+        // of characters in a character array.
+        //
+        public virtual byte[] GetBytes(char[] chars, int index, int count)
+        {
+            byte[] result = new byte[GetByteCount(chars, index, count)];
+            GetBytes(chars, index, count, result, 0);
+            return result;
+        }
+
+        // Encodes a range of characters in a character array into a range of bytes
+        // in a byte array. An exception occurs if the byte array is not large
+        // enough to hold the complete encoding of the characters. The
+        // GetByteCount method can be used to determine the exact number of
+        // bytes that will be produced for a given range of characters.
+        // Alternatively, the GetMaxByteCount method can be used to
+        // determine the maximum number of bytes that will be produced for a given
+        // number of characters, regardless of the actual character values.
+        //
+        public abstract int GetBytes(char[] chars, int charIndex, int charCount,
+            byte[] bytes, int byteIndex);
+
+        // Returns a byte array containing the encoded representation of the given
+        // string.
+        //
+        public virtual byte[] GetBytes(String s)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s),
+                    SR.ArgumentNull_String);
+
+            int byteCount = GetByteCount(s);
+            byte[] bytes = new byte[byteCount];
+            int bytesReceived = GetBytes(s, 0, s.Length, bytes, 0);
+            Debug.Assert(byteCount == bytesReceived);
+            return bytes;
+        }
+
+        // Returns a byte array containing the encoded representation of the given
+        // string range.
+        //
+        public byte[] GetBytes(string s, int index, int count)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s),
+                    SR.ArgumentNull_String);
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (index > s.Length - count)
+                throw new ArgumentOutOfRangeException(nameof(index),
+                      SR.ArgumentOutOfRange_IndexCount);
+
+            unsafe
+            {
+                fixed (char* pChar = s)
+                {
+                    int byteCount = GetByteCount(pChar + index, count);
+                    if (byteCount == 0)
+                        return Array.Empty<byte>();
+
+                    byte[] bytes = new byte[byteCount];
+                    fixed (byte* pBytes = &bytes[0])
+                    {
+                        int bytesReceived = GetBytes(pChar + index, count, pBytes, byteCount);
+                        Debug.Assert(byteCount == bytesReceived);
+                    }
+                    return bytes;
+                }
+            }
+        }
+
+        public virtual int GetBytes(String s, int charIndex, int charCount,
+                                       byte[] bytes, int byteIndex)
+        {
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+            return GetBytes(s.ToCharArray(), charIndex, charCount, bytes, byteIndex);
+        }
+
+        // This is our internal workhorse
+        // Always validate parameters before calling internal version, which will only assert.
+        internal virtual unsafe int GetBytes(char* chars, int charCount,
+                                                byte* bytes, int byteCount, EncoderNLS encoder)
+        {
+            return GetBytes(chars, charCount, bytes, byteCount);
+        }
+
+        // We expect this to be the workhorse for NLS Encodings, but for existing
+        // ones we need a working (if slow) default implementation)
+        //
+        // WARNING WARNING WARNING
+        //
+        // WARNING: If this breaks it could be a security threat.  Obviously we
+        // call this internally, so you need to make sure that your pointers, counts
+        // and indexes are correct when you call this method.
+        //
+        // In addition, we have internal code, which will be marked as "safe" calling
+        // this code.  However this code is dependent upon the implementation of an
+        // external GetBytes() method, which could be overridden by a third party and
+        // the results of which cannot be guaranteed.  We use that result to copy
+        // the byte[] to our byte* output buffer.  If the result count was wrong, we
+        // could easily overflow our output buffer.  Therefore we do an extra test
+        // when we copy the buffer so that we don't overflow byteCount either.
+
+        [CLSCompliant(false)]
+        public virtual unsafe int GetBytes(char* chars, int charCount,
+                                              byte* bytes, int byteCount)
+        {
+            // Validate input parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? nameof(bytes) : nameof(chars),
+                    SR.ArgumentNull_Array);
+
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? nameof(charCount) : nameof(byteCount)),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Get the char array to convert
+            char[] arrChar = new char[charCount];
+
+            int index;
+            for (index = 0; index < charCount; index++)
+                arrChar[index] = chars[index];
+
+            // Get the byte array to fill
+            byte[] arrByte = new byte[byteCount];
+
+            // Do the work
+            int result = GetBytes(arrChar, 0, charCount, arrByte, 0);
+
+            Debug.Assert(result <= byteCount, "[Encoding.GetBytes]Returned more bytes than we have space for");
+
+            // Copy the byte array
+            // WARNING: We MUST make sure that we don't copy too many bytes.  We can't
+            // rely on result because it could be a 3rd party implementation.  We need
+            // to make sure we never copy more than byteCount bytes no matter the value
+            // of result
+            if (result < byteCount)
+                byteCount = result;
+
+            // Copy the data, don't overrun our array!
+            for (index = 0; index < byteCount; index++)
+                bytes[index] = arrByte[index];
+
+            return byteCount;
+        }
+
+        public virtual unsafe int GetBytes(ReadOnlySpan<char> chars, Span<byte> bytes)
+        {
+            fixed (char* charsPtr = &MemoryMarshal.GetNonNullPinnableReference(chars))
+            fixed (byte* bytesPtr = &MemoryMarshal.GetNonNullPinnableReference(bytes))
+            {
+                return GetBytes(charsPtr, chars.Length, bytesPtr, bytes.Length);
+            }
+        }
+
+        // Returns the number of characters produced by decoding the given byte
+        // array.
+        //
+        public virtual int GetCharCount(byte[] bytes)
+        {
+            if (bytes == null)
+            {
+                throw new ArgumentNullException(nameof(bytes),
+                    SR.ArgumentNull_Array);
+            }
+            return GetCharCount(bytes, 0, bytes.Length);
+        }
+
+        // Returns the number of characters produced by decoding a range of bytes
+        // in a byte array.
+        //
+        public abstract int GetCharCount(byte[] bytes, int index, int count);
+
+        // We expect this to be the workhorse for NLS Encodings, but for existing
+        // ones we need a working (if slow) default implementation)
+        [CLSCompliant(false)]
+        public virtual unsafe int GetCharCount(byte* bytes, int count)
+        {
+            // Validate input parameters
+            if (bytes == null)
+                throw new ArgumentNullException(nameof(bytes),
+                      SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count),
+                      SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            byte[] arrbyte = new byte[count];
+            int index;
+
+            for (index = 0; index < count; index++)
+                arrbyte[index] = bytes[index];
+
+            return GetCharCount(arrbyte, 0, count);
+        }
+
+        public virtual unsafe int GetCharCount(ReadOnlySpan<byte> bytes)
+        {
+            fixed (byte* bytesPtr = &MemoryMarshal.GetNonNullPinnableReference(bytes))
+            {
+                return GetCharCount(bytesPtr, bytes.Length);
+            }
+        }
+
+        // This is our internal workhorse
+        // Always validate parameters before calling internal version, which will only assert.
+        internal virtual unsafe int GetCharCount(byte* bytes, int count, DecoderNLS decoder)
+        {
+            return GetCharCount(bytes, count);
+        }
+
+        // Returns a character array containing the decoded representation of a
+        // given byte array.
+        //
+        public virtual char[] GetChars(byte[] bytes)
+        {
+            if (bytes == null)
+            {
+                throw new ArgumentNullException(nameof(bytes),
+                    SR.ArgumentNull_Array);
+            }
+            return GetChars(bytes, 0, bytes.Length);
+        }
+
+        // Returns a character array containing the decoded representation of a
+        // range of bytes in a byte array.
+        //
+        public virtual char[] GetChars(byte[] bytes, int index, int count)
+        {
+            char[] result = new char[GetCharCount(bytes, index, count)];
+            GetChars(bytes, index, count, result, 0);
+            return result;
+        }
+
+        // Decodes a range of bytes in a byte array into a range of characters in a
+        // character array. An exception occurs if the character array is not large
+        // enough to hold the complete decoding of the bytes. The
+        // GetCharCount method can be used to determine the exact number of
+        // characters that will be produced for a given range of bytes.
+        // Alternatively, the GetMaxCharCount method can be used to
+        // determine the maximum number of characters that will be produced for a
+        // given number of bytes, regardless of the actual byte values.
+        //
+
+        public abstract int GetChars(byte[] bytes, int byteIndex, int byteCount,
+                                       char[] chars, int charIndex);
+
+
+        // We expect this to be the workhorse for NLS Encodings, but for existing
+        // ones we need a working (if slow) default implementation)
+        //
+        // WARNING WARNING WARNING
+        //
+        // WARNING: If this breaks it could be a security threat.  Obviously we
+        // call this internally, so you need to make sure that your pointers, counts
+        // and indexes are correct when you call this method.
+        //
+        // In addition, we have internal code, which will be marked as "safe" calling
+        // this code.  However this code is dependent upon the implementation of an
+        // external GetChars() method, which could be overridden by a third party and
+        // the results of which cannot be guaranteed.  We use that result to copy
+        // the char[] to our char* output buffer.  If the result count was wrong, we
+        // could easily overflow our output buffer.  Therefore we do an extra test
+        // when we copy the buffer so that we don't overflow charCount either.
+
+        [CLSCompliant(false)]
+        public virtual unsafe int GetChars(byte* bytes, int byteCount,
+                                              char* chars, int charCount)
+        {
+            // Validate input parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException(chars == null ? nameof(chars) : nameof(bytes),
+                    SR.ArgumentNull_Array);
+
+            if (byteCount < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((byteCount < 0 ? nameof(byteCount) : nameof(charCount)),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Get the byte array to convert
+            byte[] arrByte = new byte[byteCount];
+
+            int index;
+            for (index = 0; index < byteCount; index++)
+                arrByte[index] = bytes[index];
+
+            // Get the char array to fill
+            char[] arrChar = new char[charCount];
+
+            // Do the work
+            int result = GetChars(arrByte, 0, byteCount, arrChar, 0);
+
+            Debug.Assert(result <= charCount, "[Encoding.GetChars]Returned more chars than we have space for");
+
+            // Copy the char array
+            // WARNING: We MUST make sure that we don't copy too many chars.  We can't
+            // rely on result because it could be a 3rd party implementation.  We need
+            // to make sure we never copy more than charCount chars no matter the value
+            // of result
+            if (result < charCount)
+                charCount = result;
+
+            // Copy the data, don't overrun our array!
+            for (index = 0; index < charCount; index++)
+                chars[index] = arrChar[index];
+
+            return charCount;
+        }
+
+        public virtual unsafe int GetChars(ReadOnlySpan<byte> bytes, Span<char> chars)
+        {
+            fixed (byte* bytesPtr = &MemoryMarshal.GetNonNullPinnableReference(bytes))
+            fixed (char* charsPtr = &MemoryMarshal.GetNonNullPinnableReference(chars))
+            {
+                return GetChars(bytesPtr, bytes.Length, charsPtr, chars.Length);
+            }
+        }
+
+        // This is our internal workhorse
+        // Always validate parameters before calling internal version, which will only assert.
+        internal virtual unsafe int GetChars(byte* bytes, int byteCount,
+                                                char* chars, int charCount, DecoderNLS decoder)
+        {
+            return GetChars(bytes, byteCount, chars, charCount);
+        }
+
+
+        [CLSCompliant(false)]
+        public unsafe string GetString(byte* bytes, int byteCount)
+        {
+            if (bytes == null)
+                throw new ArgumentNullException(nameof(bytes), SR.ArgumentNull_Array);
+
+            if (byteCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(byteCount), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return String.CreateStringFromEncoding(bytes, byteCount, this);
+        }
+
+        public unsafe string GetString(ReadOnlySpan<byte> bytes)
+        {
+            fixed (byte* bytesPtr = &MemoryMarshal.GetNonNullPinnableReference(bytes))
+            {
+                return GetString(bytesPtr, bytes.Length);
+            }
+        }
+
+
+        // Returns the code page identifier of this encoding. The returned value is
+        // an integer between 0 and 65535 if the encoding has a code page
+        // identifier, or -1 if the encoding does not represent a code page.
+        //
+
+        public virtual int CodePage
+        {
+            get
+            {
+                return _codePage;
+            }
+        }
+
+        // IsAlwaysNormalized
+        // Returns true if the encoding is always normalized for the specified encoding form
+        public bool IsAlwaysNormalized()
+        {
+            return this.IsAlwaysNormalized(NormalizationForm.FormC);
+        }
+
+        public virtual bool IsAlwaysNormalized(NormalizationForm form)
+        {
+            // Assume false unless the encoding knows otherwise
+            return false;
+        }
+
+        // Returns a Decoder object for this encoding. The returned object
+        // can be used to decode a sequence of bytes into a sequence of characters.
+        // Contrary to the GetChars family of methods, a Decoder can
+        // convert partial sequences of bytes into partial sequences of characters
+        // by maintaining the appropriate state between the conversions.
+        //
+        // This default implementation returns a Decoder that simply
+        // forwards calls to the GetCharCount and GetChars methods to
+        // the corresponding methods of this encoding. Encodings that require state
+        // to be maintained between successive conversions should override this
+        // method and return an instance of an appropriate Decoder
+        // implementation.
+        //
+
+        public virtual Decoder GetDecoder()
+        {
+            return new DefaultDecoder(this);
+        }
+
+        // Returns an Encoder object for this encoding. The returned object
+        // can be used to encode a sequence of characters into a sequence of bytes.
+        // Contrary to the GetBytes family of methods, an Encoder can
+        // convert partial sequences of characters into partial sequences of bytes
+        // by maintaining the appropriate state between the conversions.
+        //
+        // This default implementation returns an Encoder that simply
+        // forwards calls to the GetByteCount and GetBytes methods to
+        // the corresponding methods of this encoding. Encodings that require state
+        // to be maintained between successive conversions should override this
+        // method and return an instance of an appropriate Encoder
+        // implementation.
+        //
+
+        public virtual Encoder GetEncoder()
+        {
+            return new DefaultEncoder(this);
+        }
+
+        // Returns the maximum number of bytes required to encode a given number of
+        // characters. This method can be used to determine an appropriate buffer
+        // size for byte arrays passed to the GetBytes method of this
+        // encoding or the GetBytes method of an Encoder for this
+        // encoding. All encodings must guarantee that no buffer overflow
+        // exceptions will occur if buffers are sized according to the results of
+        // this method.
+        //
+        // WARNING: If you're using something besides the default replacement encoder fallback,
+        // then you could have more bytes than this returned from an actual call to GetBytes().
+        //
+        public abstract int GetMaxByteCount(int charCount);
+
+        // Returns the maximum number of characters produced by decoding a given
+        // number of bytes. This method can be used to determine an appropriate
+        // buffer size for character arrays passed to the GetChars method of
+        // this encoding or the GetChars method of a Decoder for this
+        // encoding. All encodings must guarantee that no buffer overflow
+        // exceptions will occur if buffers are sized according to the results of
+        // this method.
+        //
+        public abstract int GetMaxCharCount(int byteCount);
+
+        // Returns a string containing the decoded representation of a given byte
+        // array.
+        //
+        public virtual String GetString(byte[] bytes)
+        {
+            if (bytes == null)
+                throw new ArgumentNullException(nameof(bytes),
+                    SR.ArgumentNull_Array);
+
+            return GetString(bytes, 0, bytes.Length);
+        }
+
+        // Returns a string containing the decoded representation of a range of
+        // bytes in a byte array.
+        //
+        // Internally we override this for performance
+        //
+        public virtual String GetString(byte[] bytes, int index, int count)
+        {
+            return new String(GetChars(bytes, index, count));
+        }
+
+        // Returns an encoding for Unicode format. The returned encoding will be
+        // an instance of the UnicodeEncoding class.
+        //
+        // It will use little endian byte order, but will detect
+        // input in big endian if it finds a byte order mark per Unicode 2.0.
+
+        public static Encoding Unicode => UnicodeEncoding.s_littleEndianDefault;
+
+        // Returns an encoding for Unicode format. The returned encoding will be
+        // an instance of the UnicodeEncoding class.
+        //
+        // It will use big endian byte order, but will detect
+        // input in little endian if it finds a byte order mark per Unicode 2.0.
+
+        public static Encoding BigEndianUnicode => UnicodeEncoding.s_bigEndianDefault;
+
+        // Returns an encoding for the UTF-7 format. The returned encoding will be
+        // an instance of the UTF7Encoding class.
+
+        public static Encoding UTF7 => UTF7Encoding.s_default;
+
+        // Returns an encoding for the UTF-8 format. The returned encoding will be
+        // an instance of the UTF8Encoding class.
+
+        public static Encoding UTF8 => UTF8Encoding.s_default;
+
+        // Returns an encoding for the UTF-32 format. The returned encoding will be
+        // an instance of the UTF32Encoding class.
+
+        public static Encoding UTF32 => UTF32Encoding.s_default;
+
+        // Returns an encoding for the UTF-32 format. The returned encoding will be
+        // an instance of the UTF32Encoding class.
+        //
+        // It will use big endian byte order.
+
+        private static Encoding BigEndianUTF32 => UTF32Encoding.s_bigEndianDefault;
+
+        public override bool Equals(Object value)
+        {
+            Encoding that = value as Encoding;
+            if (that != null)
+                return (_codePage == that._codePage) &&
+                       (EncoderFallback.Equals(that.EncoderFallback)) &&
+                       (DecoderFallback.Equals(that.DecoderFallback));
+            return (false);
+        }
+
+
+        public override int GetHashCode()
+        {
+            return _codePage + this.EncoderFallback.GetHashCode() + this.DecoderFallback.GetHashCode();
+        }
+
+        internal virtual char[] GetBestFitUnicodeToBytesData()
+        {
+            // Normally we don't have any best fit data.
+            return Array.Empty<char>();
+        }
+
+        internal virtual char[] GetBestFitBytesToUnicodeData()
+        {
+            // Normally we don't have any best fit data.
+            return Array.Empty<char>();
+        }
+
+        internal void ThrowBytesOverflow()
+        {
+            // Special message to include fallback type in case fallback's GetMaxCharCount is broken
+            // This happens if user has implemented an encoder fallback with a broken GetMaxCharCount
+            throw new ArgumentException(
+                SR.Format(SR.Argument_EncodingConversionOverflowBytes, EncodingName, EncoderFallback.GetType()), "bytes");
+        }
+
+        internal void ThrowBytesOverflow(EncoderNLS encoder, bool nothingEncoded)
+        {
+            if (encoder == null || encoder._throwOnOverflow || nothingEncoded)
+            {
+                if (encoder != null && encoder.InternalHasFallbackBuffer)
+                    encoder.FallbackBuffer.InternalReset();
+                // Special message to include fallback type in case fallback's GetMaxCharCount is broken
+                // This happens if user has implemented an encoder fallback with a broken GetMaxCharCount
+                ThrowBytesOverflow();
+            }
+
+            // If we didn't throw, we are in convert and have to remember our flushing
+            encoder.ClearMustFlush();
+        }
+
+        internal void ThrowCharsOverflow()
+        {
+            // Special message to include fallback type in case fallback's GetMaxCharCount is broken
+            // This happens if user has implemented a decoder fallback with a broken GetMaxCharCount
+            throw new ArgumentException(
+                SR.Format(SR.Argument_EncodingConversionOverflowChars, EncodingName, DecoderFallback.GetType()), "chars");
+        }
+
+        internal void ThrowCharsOverflow(DecoderNLS decoder, bool nothingDecoded)
+        {
+            if (decoder == null || decoder._throwOnOverflow || nothingDecoded)
+            {
+                if (decoder != null && decoder.InternalHasFallbackBuffer)
+                    decoder.FallbackBuffer.InternalReset();
+
+                // Special message to include fallback type in case fallback's GetMaxCharCount is broken
+                // This happens if user has implemented a decoder fallback with a broken GetMaxCharCount
+                ThrowCharsOverflow();
+            }
+
+            // If we didn't throw, we are in convert and have to remember our flushing
+            decoder.ClearMustFlush();
+        }
+
+        internal sealed class DefaultEncoder : Encoder, IObjectReference
+        {
+            private Encoding _encoding;
+
+            public DefaultEncoder(Encoding encoding)
+            {
+                _encoding = encoding;
+            }
+            
+            public Object GetRealObject(StreamingContext context)
+            {
+                throw new PlatformNotSupportedException();
+            }
+
+            // Returns the number of bytes the next call to GetBytes will
+            // produce if presented with the given range of characters and the given
+            // value of the flush parameter. The returned value takes into
+            // account the state in which the encoder was left following the last call
+            // to GetBytes. The state of the encoder is not affected by a call
+            // to this method.
+            //
+
+            public override int GetByteCount(char[] chars, int index, int count, bool flush)
+            {
+                return _encoding.GetByteCount(chars, index, count);
+            }
+
+            public unsafe override int GetByteCount(char* chars, int count, bool flush)
+            {
+                return _encoding.GetByteCount(chars, count);
+            }
+
+            // Encodes a range of characters in a character array into a range of bytes
+            // in a byte array. The method encodes charCount characters from
+            // chars starting at index charIndex, storing the resulting
+            // bytes in bytes starting at index byteIndex. The encoding
+            // takes into account the state in which the encoder was left following the
+            // last call to this method. The flush parameter indicates whether
+            // the encoder should flush any shift-states and partial characters at the
+            // end of the conversion. To ensure correct termination of a sequence of
+            // blocks of encoded bytes, the last call to GetBytes should specify
+            // a value of true for the flush parameter.
+            //
+            // An exception occurs if the byte array is not large enough to hold the
+            // complete encoding of the characters. The GetByteCount method can
+            // be used to determine the exact number of bytes that will be produced for
+            // a given range of characters. Alternatively, the GetMaxByteCount
+            // method of the Encoding that produced this encoder can be used to
+            // determine the maximum number of bytes that will be produced for a given
+            // number of characters, regardless of the actual character values.
+            //
+
+            public override int GetBytes(char[] chars, int charIndex, int charCount,
+                                          byte[] bytes, int byteIndex, bool flush)
+            {
+                return _encoding.GetBytes(chars, charIndex, charCount, bytes, byteIndex);
+            }
+
+            public unsafe override int GetBytes(char* chars, int charCount,
+                                                 byte* bytes, int byteCount, bool flush)
+            {
+                return _encoding.GetBytes(chars, charCount, bytes, byteCount);
+            }
+        }
+
+        internal sealed class DefaultDecoder : Decoder, IObjectReference
+        {
+            private Encoding _encoding;
+
+            public DefaultDecoder(Encoding encoding)
+            {
+                _encoding = encoding;
+            }
+
+            public Object GetRealObject(StreamingContext context)
+            {
+                throw new PlatformNotSupportedException();
+            }
+
+            // Returns the number of characters the next call to GetChars will
+            // produce if presented with the given range of bytes. The returned value
+            // takes into account the state in which the decoder was left following the
+            // last call to GetChars. The state of the decoder is not affected
+            // by a call to this method.
+            //
+
+            public override int GetCharCount(byte[] bytes, int index, int count)
+            {
+                return GetCharCount(bytes, index, count, false);
+            }
+
+            public override int GetCharCount(byte[] bytes, int index, int count, bool flush)
+            {
+                return _encoding.GetCharCount(bytes, index, count);
+            }
+
+            public unsafe override int GetCharCount(byte* bytes, int count, bool flush)
+            {
+                // By default just call the encoding version, no flush by default
+                return _encoding.GetCharCount(bytes, count);
+            }
+
+            // Decodes a range of bytes in a byte array into a range of characters
+            // in a character array. The method decodes byteCount bytes from
+            // bytes starting at index byteIndex, storing the resulting
+            // characters in chars starting at index charIndex. The
+            // decoding takes into account the state in which the decoder was left
+            // following the last call to this method.
+            //
+            // An exception occurs if the character array is not large enough to
+            // hold the complete decoding of the bytes. The GetCharCount method
+            // can be used to determine the exact number of characters that will be
+            // produced for a given range of bytes. Alternatively, the
+            // GetMaxCharCount method of the Encoding that produced this
+            // decoder can be used to determine the maximum number of characters that
+            // will be produced for a given number of bytes, regardless of the actual
+            // byte values.
+            //
+
+            public override int GetChars(byte[] bytes, int byteIndex, int byteCount,
+                                           char[] chars, int charIndex)
+            {
+                return GetChars(bytes, byteIndex, byteCount, chars, charIndex, false);
+            }
+
+            public override int GetChars(byte[] bytes, int byteIndex, int byteCount,
+                                           char[] chars, int charIndex, bool flush)
+            {
+                return _encoding.GetChars(bytes, byteIndex, byteCount, chars, charIndex);
+            }
+
+            public unsafe override int GetChars(byte* bytes, int byteCount,
+                                                  char* chars, int charCount, bool flush)
+            {
+                // By default just call the encoding's version
+                return _encoding.GetChars(bytes, byteCount, chars, charCount);
+            }
+        }
+
+        internal class EncodingCharBuffer
+        {
+            private unsafe char* _chars;
+            private unsafe char* _charStart;
+            private unsafe char* _charEnd;
+            private int _charCountResult = 0;
+            private Encoding _enc;
+            private DecoderNLS _decoder;
+            private unsafe byte* _byteStart;
+            private unsafe byte* _byteEnd;
+            private unsafe byte* _bytes;
+            private DecoderFallbackBuffer _fallbackBuffer;
+
+            internal unsafe EncodingCharBuffer(Encoding enc, DecoderNLS decoder, char* charStart, int charCount,
+                                                    byte* byteStart, int byteCount)
+            {
+                _enc = enc;
+                _decoder = decoder;
+
+                _chars = charStart;
+                _charStart = charStart;
+                _charEnd = charStart + charCount;
+
+                _byteStart = byteStart;
+                _bytes = byteStart;
+                _byteEnd = byteStart + byteCount;
+
+                if (_decoder == null)
+                    _fallbackBuffer = enc.DecoderFallback.CreateFallbackBuffer();
+                else
+                    _fallbackBuffer = _decoder.FallbackBuffer;
+
+                // If we're getting chars or getting char count we don't expect to have
+                // to remember fallbacks between calls (so it should be empty)
+                Debug.Assert(_fallbackBuffer.Remaining == 0,
+                    "[Encoding.EncodingCharBuffer.EncodingCharBuffer]Expected empty fallback buffer for getchars/charcount");
+                _fallbackBuffer.InternalInitialize(_bytes, _charEnd);
+            }
+
+            internal unsafe bool AddChar(char ch, int numBytes)
+            {
+                if (_chars != null)
+                {
+                    if (_chars >= _charEnd)
+                    {
+                        // Throw maybe
+                        _bytes -= numBytes;                                        // Didn't encode these bytes
+                        _enc.ThrowCharsOverflow(_decoder, _bytes <= _byteStart);    // Throw?
+                        return false;                                           // No throw, but no store either
+                    }
+
+                    *(_chars++) = ch;
+                }
+                _charCountResult++;
+                return true;
+            }
+
+            internal unsafe bool AddChar(char ch)
+            {
+                return AddChar(ch, 1);
+            }
+
+
+            internal unsafe bool AddChar(char ch1, char ch2, int numBytes)
+            {
+                // Need room for 2 chars
+                if (_chars >= _charEnd - 1)
+                {
+                    // Throw maybe
+                    _bytes -= numBytes;                                        // Didn't encode these bytes
+                    _enc.ThrowCharsOverflow(_decoder, _bytes <= _byteStart);    // Throw?
+                    return false;                                           // No throw, but no store either
+                }
+                return AddChar(ch1, numBytes) && AddChar(ch2, numBytes);
+            }
+
+            internal unsafe void AdjustBytes(int count)
+            {
+                _bytes += count;
+            }
+
+            internal unsafe bool MoreData
+            {
+                get
+                {
+                    return _bytes < _byteEnd;
+                }
+            }
+
+            // Do we have count more bytes?
+            internal unsafe bool EvenMoreData(int count)
+            {
+                return (_bytes <= _byteEnd - count);
+            }
+
+            // GetNextByte shouldn't be called unless the caller's already checked more data or even more data,
+            // but we'll double check just to make sure.
+            internal unsafe byte GetNextByte()
+            {
+                Debug.Assert(_bytes < _byteEnd, "[EncodingCharBuffer.GetNextByte]Expected more date");
+                if (_bytes >= _byteEnd)
+                    return 0;
+                return *(_bytes++);
+            }
+
+            internal unsafe int BytesUsed
+            {
+                get
+                {
+                    return (int)(_bytes - _byteStart);
+                }
+            }
+
+            internal unsafe bool Fallback(byte fallbackByte)
+            {
+                // Build our buffer
+                byte[] byteBuffer = new byte[] { fallbackByte };
+
+                // Do the fallback and add the data.
+                return Fallback(byteBuffer);
+            }
+
+            internal unsafe bool Fallback(byte byte1, byte byte2)
+            {
+                // Build our buffer
+                byte[] byteBuffer = new byte[] { byte1, byte2 };
+
+                // Do the fallback and add the data.
+                return Fallback(byteBuffer);
+            }
+
+            internal unsafe bool Fallback(byte byte1, byte byte2, byte byte3, byte byte4)
+            {
+                // Build our buffer
+                byte[] byteBuffer = new byte[] { byte1, byte2, byte3, byte4 };
+
+                // Do the fallback and add the data.
+                return Fallback(byteBuffer);
+            }
+
+            internal unsafe bool Fallback(byte[] byteBuffer)
+            {
+                // Do the fallback and add the data.
+                if (_chars != null)
+                {
+                    char* pTemp = _chars;
+                    if (_fallbackBuffer.InternalFallback(byteBuffer, _bytes, ref _chars) == false)
+                    {
+                        // Throw maybe
+                        _bytes -= byteBuffer.Length;                             // Didn't use how many ever bytes we're falling back
+                        _fallbackBuffer.InternalReset();                         // We didn't use this fallback.
+                        _enc.ThrowCharsOverflow(_decoder, _chars == _charStart);    // Throw?
+                        return false;                                           // No throw, but no store either
+                    }
+                    _charCountResult += unchecked((int)(_chars - pTemp));
+                }
+                else
+                {
+                    _charCountResult += _fallbackBuffer.InternalFallback(byteBuffer, _bytes);
+                }
+
+                return true;
+            }
+
+            internal unsafe int Count
+            {
+                get
+                {
+                    return _charCountResult;
+                }
+            }
+        }
+
+        internal class EncodingByteBuffer
+        {
+            private unsafe byte* _bytes;
+            private unsafe byte* _byteStart;
+            private unsafe byte* _byteEnd;
+            private unsafe char* _chars;
+            private unsafe char* _charStart;
+            private unsafe char* _charEnd;
+            private int _byteCountResult = 0;
+            private Encoding _enc;
+            private EncoderNLS _encoder;
+            internal EncoderFallbackBuffer fallbackBuffer;
+
+            internal unsafe EncodingByteBuffer(Encoding inEncoding, EncoderNLS inEncoder,
+                        byte* inByteStart, int inByteCount, char* inCharStart, int inCharCount)
+            {
+                _enc = inEncoding;
+                _encoder = inEncoder;
+
+                _charStart = inCharStart;
+                _chars = inCharStart;
+                _charEnd = inCharStart + inCharCount;
+
+                _bytes = inByteStart;
+                _byteStart = inByteStart;
+                _byteEnd = inByteStart + inByteCount;
+
+                if (_encoder == null)
+                    this.fallbackBuffer = _enc.EncoderFallback.CreateFallbackBuffer();
+                else
+                {
+                    this.fallbackBuffer = _encoder.FallbackBuffer;
+                    // If we're not converting we must not have data in our fallback buffer
+                    if (_encoder._throwOnOverflow && _encoder.InternalHasFallbackBuffer &&
+                        this.fallbackBuffer.Remaining > 0)
+                        throw new ArgumentException(SR.Format(SR.Argument_EncoderFallbackNotEmpty,
+                            _encoder.Encoding.EncodingName, _encoder.Fallback.GetType()));
+                }
+                fallbackBuffer.InternalInitialize(_chars, _charEnd, _encoder, _bytes != null);
+            }
+
+            internal unsafe bool AddByte(byte b, int moreBytesExpected)
+            {
+                Debug.Assert(moreBytesExpected >= 0, "[EncodingByteBuffer.AddByte]expected non-negative moreBytesExpected");
+                if (_bytes != null)
+                {
+                    if (_bytes >= _byteEnd - moreBytesExpected)
+                    {
+                        // Throw maybe.  Check which buffer to back up (only matters if Converting)
+                        this.MovePrevious(true);            // Throw if necessary
+                        return false;                       // No throw, but no store either
+                    }
+
+                    *(_bytes++) = b;
+                }
+                _byteCountResult++;
+                return true;
+            }
+
+            internal unsafe bool AddByte(byte b1)
+            {
+                return (AddByte(b1, 0));
+            }
+
+            internal unsafe bool AddByte(byte b1, byte b2)
+            {
+                return (AddByte(b1, b2, 0));
+            }
+
+            internal unsafe bool AddByte(byte b1, byte b2, int moreBytesExpected)
+            {
+                return (AddByte(b1, 1 + moreBytesExpected) && AddByte(b2, moreBytesExpected));
+            }
+
+            internal unsafe bool AddByte(byte b1, byte b2, byte b3)
+            {
+                return AddByte(b1, b2, b3, (int)0);
+            }
+
+            internal unsafe bool AddByte(byte b1, byte b2, byte b3, int moreBytesExpected)
+            {
+                return (AddByte(b1, 2 + moreBytesExpected) &&
+                        AddByte(b2, 1 + moreBytesExpected) &&
+                        AddByte(b3, moreBytesExpected));
+            }
+
+            internal unsafe bool AddByte(byte b1, byte b2, byte b3, byte b4)
+            {
+                return (AddByte(b1, 3) &&
+                        AddByte(b2, 2) &&
+                        AddByte(b3, 1) &&
+                        AddByte(b4, 0));
+            }
+
+            internal unsafe void MovePrevious(bool bThrow)
+            {
+                if (fallbackBuffer.bFallingBack)
+                    fallbackBuffer.MovePrevious();                      // don't use last fallback
+                else
+                {
+                    Debug.Assert(_chars > _charStart ||
+                        ((bThrow == true) && (_bytes == _byteStart)),
+                        "[EncodingByteBuffer.MovePrevious]expected previous data or throw");
+                    if (_chars > _charStart)
+                        _chars--;                                        // don't use last char
+                }
+
+                if (bThrow)
+                    _enc.ThrowBytesOverflow(_encoder, _bytes == _byteStart);    // Throw? (and reset fallback if not converting)
+            }
+
+            internal unsafe bool Fallback(char charFallback)
+            {
+                // Do the fallback
+                return fallbackBuffer.InternalFallback(charFallback, ref _chars);
+            }
+
+            internal unsafe bool MoreData
+            {
+                get
+                {
+                    // See if fallbackBuffer is not empty or if there's data left in chars buffer.
+                    return ((fallbackBuffer.Remaining > 0) || (_chars < _charEnd));
+                }
+            }
+
+            internal unsafe char GetNextChar()
+            {
+                // See if there's something in our fallback buffer
+                char cReturn = fallbackBuffer.InternalGetNextChar();
+
+                // Nothing in the fallback buffer, return our normal data.
+                if (cReturn == 0)
+                {
+                    if (_chars < _charEnd)
+                        cReturn = *(_chars++);
+                }
+
+                return cReturn;
+            }
+
+            internal unsafe int CharsUsed
+            {
+                get
+                {
+                    return (int)(_chars - _charStart);
+                }
+            }
+
+            internal unsafe int Count
+            {
+                get
+                {
+                    return _byteCountResult;
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/EncodingInfo.cs b/src/System.Private.CoreLib/shared/System/Text/EncodingInfo.cs
new file mode 100644
index 0000000000..99995f759b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/EncodingInfo.cs
@@ -0,0 +1,71 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Text;
+
+namespace System.Text
+{
+    public sealed class EncodingInfo
+    {
+        private int iCodePage;          // Code Page #
+        private string strEncodingName;    // Short name (web name)
+        private string strDisplayName;     // Full localized name
+
+        internal EncodingInfo(int codePage, string name, string displayName)
+        {
+            iCodePage = codePage;
+            strEncodingName = name;
+            strDisplayName = displayName;
+        }
+
+
+        public int CodePage
+        {
+            get
+            {
+                return iCodePage;
+            }
+        }
+
+
+        public string Name
+        {
+            get
+            {
+                return strEncodingName;
+            }
+        }
+
+
+        public string DisplayName
+        {
+            get
+            {
+                return strDisplayName;
+            }
+        }
+
+
+        public Encoding GetEncoding()
+        {
+            return Encoding.GetEncoding(iCodePage);
+        }
+
+        public override bool Equals(Object value)
+        {
+            EncodingInfo that = value as EncodingInfo;
+            if (that != null)
+            {
+                return (this.CodePage == that.CodePage);
+            }
+            return (false);
+        }
+
+        public override int GetHashCode()
+        {
+            return this.CodePage;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/EncodingNLS.cs b/src/System.Private.CoreLib/shared/System/Text/EncodingNLS.cs
new file mode 100644
index 0000000000..d5de9e553a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/EncodingNLS.cs
@@ -0,0 +1,298 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections;
+using System.Globalization;
+using System.Runtime.InteropServices;
+using System.Threading;
+
+namespace System.Text
+{
+    // This class overrides Encoding with the things we need for our NLS Encodings
+    //
+    // All of the GetBytes/Chars GetByte/CharCount methods are just wrappers for the pointer
+    // plus decoder/encoder method that is our real workhorse.  Note that this is an internal
+    // class, so our public classes cannot derive from this class.  Because of this, all of the
+    // GetBytes/Chars GetByte/CharCount wrapper methods are duplicated in all of our public
+    // encodings, which currently include:
+    //
+    //      EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, & UnicodeEncoding
+    //
+    // So if you change the wrappers in this class, you must change the wrappers in the other classes
+    // as well because they should have the same behavior.
+
+    internal abstract class EncodingNLS : Encoding
+    {
+        protected EncodingNLS(int codePage) : base(codePage)
+        {
+        }
+
+        // Returns the number of bytes required to encode a range of characters in
+        // a character array.
+        // 
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+        public override unsafe int GetByteCount(char[] chars, int index, int count)
+        {
+            // Validate input parameters
+            if (chars == null)
+                throw new ArgumentNullException("chars", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - index < count)
+                throw new ArgumentOutOfRangeException("chars", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // If no input, return 0, avoid fixed empty array problem
+            if (count == 0)
+                return 0;
+
+            // Just call the pointer version
+            fixed (char* pChars = chars)
+                return GetByteCount(pChars + index, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+        public override unsafe int GetByteCount(String s)
+        {
+            // Validate input
+            if (s==null)
+                throw new ArgumentNullException("s");
+
+            fixed (char* pChars = s)
+                return GetByteCount(pChars, s.Length, null);
+        }       
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        public override unsafe int GetByteCount(char* chars, int count)
+        {
+            // Validate Parameters
+            if (chars == null)
+                throw new ArgumentNullException("chars", SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException("count", SR.ArgumentOutOfRange_NeedNonNegNum);
+            
+            // Call it with empty encoder
+            return GetByteCount(chars, count, null);
+        }
+
+        // Parent method is safe.
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        public override unsafe int GetBytes(String s, int charIndex, int charCount,
+                                              byte[] bytes, int byteIndex)
+        {
+            if (s == null || bytes == null)
+                throw new ArgumentNullException((s == null ? "s" : "bytes"), SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? "charIndex" : "charCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (s.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException("s", SR.ArgumentOutOfRange_IndexCount);
+
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+                throw new ArgumentOutOfRangeException("byteIndex", SR.ArgumentOutOfRange_Index);
+
+            int byteCount = bytes.Length - byteIndex;
+
+            fixed (char* pChars = s) fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+                return GetBytes(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, null);
+        }
+
+        // Encodes a range of characters in a character array into a range of bytes
+        // in a byte array. An exception occurs if the byte array is not large
+        // enough to hold the complete encoding of the characters. The
+        // GetByteCount method can be used to determine the exact number of
+        // bytes that will be produced for a given range of characters.
+        // Alternatively, the GetMaxByteCount method can be used to
+        // determine the maximum number of bytes that will be produced for a given
+        // number of characters, regardless of the actual character values.
+        // 
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+        public override unsafe int GetBytes(char[] chars, int charIndex, int charCount,
+                                               byte[] bytes, int byteIndex)
+        {
+            // Validate parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException((chars == null ? "chars" : "bytes"), SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? "charIndex" : "charCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException("chars", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+                throw new ArgumentOutOfRangeException("byteIndex", SR.ArgumentOutOfRange_Index);
+
+            // If nothing to encode return 0, avoid fixed problem
+            if (charCount == 0)
+                return 0;
+
+            // Just call pointer version
+            int byteCount = bytes.Length - byteIndex;
+
+            fixed (char* pChars = chars) fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+                // Remember that byteCount is # to decode, not size of array.
+                return GetBytes(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        public override unsafe int GetBytes(char* chars, int charCount, byte* bytes, int byteCount)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? "charCount" : "byteCount"),  SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetBytes(chars, charCount, bytes, byteCount, null);
+        }
+
+        // Returns the number of characters produced by decoding a range of bytes
+        // in a byte array.
+        // 
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+        public override unsafe int GetCharCount(byte[] bytes, int index, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+                                   
+            if (bytes.Length - index < count)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // If no input just return 0, fixed doesn't like 0 length arrays
+            if (count == 0)
+                return 0;
+
+            // Just call pointer version
+            fixed (byte* pBytes = bytes)
+                return GetCharCount(pBytes + index, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        public override unsafe int GetCharCount(byte* bytes, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException("count", SR.ArgumentOutOfRange_NeedNonNegNum);
+            
+            return GetCharCount(bytes, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+        public override unsafe int GetChars(byte[] bytes, int byteIndex, int byteCount,
+                                              char[] chars, int charIndex)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (byteIndex < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((byteIndex < 0 ? "byteIndex" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if ( bytes.Length - byteIndex < byteCount)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (charIndex < 0 || charIndex > chars.Length)
+                throw new ArgumentOutOfRangeException("charIndex", SR.ArgumentOutOfRange_Index);
+
+            // If no input, return 0 & avoid fixed problem
+            if (byteCount == 0)
+                return 0;
+
+            // Just call pointer version
+            int charCount = chars.Length - charIndex;
+
+            fixed (byte* pBytes = bytes) fixed (char* pChars = &MemoryMarshal.GetReference((Span<char>)chars))
+                // Remember that charCount is # to decode, not size of array
+                return GetChars(pBytes + byteIndex, byteCount, pChars + charIndex, charCount, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        public unsafe override int GetChars(byte* bytes, int byteCount, char* chars, int charCount)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? "charCount" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+            
+            return GetChars(bytes, byteCount, chars, charCount, null);
+        }
+
+        // Returns a string containing the decoded representation of a range of
+        // bytes in a byte array.
+        // 
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+        public override unsafe String GetString(byte[] bytes, int index, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (bytes.Length - index < count)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // Avoid problems with empty input buffer
+            if (count == 0) return String.Empty;
+            
+            fixed (byte* pBytes = bytes)
+                return String.CreateStringFromEncoding(
+                    pBytes + index, count, this);
+        }
+
+        public override Decoder GetDecoder()
+        {
+            return new DecoderNLS(this);
+        }
+
+        public override Encoder GetEncoder()
+        {
+            return new EncoderNLS(this);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/EncodingProvider.cs b/src/System.Private.CoreLib/shared/System/Text/EncodingProvider.cs
new file mode 100644
index 0000000000..ce8c3e0208
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/EncodingProvider.cs
@@ -0,0 +1,136 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+
+namespace System.Text
+{
+    public abstract class EncodingProvider
+    {
+        public EncodingProvider() { }
+        public abstract Encoding GetEncoding(string name);
+        public abstract Encoding GetEncoding(int codepage);
+
+        // GetEncoding should return either valid encoding or null. shouldn't throw any exception except on null name
+        public virtual Encoding GetEncoding(string name, EncoderFallback encoderFallback, DecoderFallback decoderFallback)
+        {
+            Encoding enc = GetEncoding(name);
+            if (enc != null)
+            {
+                enc = (Encoding)GetEncoding(name).Clone();
+                enc.EncoderFallback = encoderFallback;
+                enc.DecoderFallback = decoderFallback;
+            }
+
+            return enc;
+        }
+
+        public virtual Encoding GetEncoding(int codepage, EncoderFallback encoderFallback, DecoderFallback decoderFallback)
+        {
+            Encoding enc = GetEncoding(codepage);
+            if (enc != null)
+            {
+                enc = (Encoding)GetEncoding(codepage).Clone();
+                enc.EncoderFallback = encoderFallback;
+                enc.DecoderFallback = decoderFallback;
+            }
+
+            return enc;
+        }
+
+        internal static void AddProvider(EncodingProvider provider)
+        {
+            if (provider == null)
+                throw new ArgumentNullException(nameof(provider));
+
+            lock (s_InternalSyncObject)
+            {
+                if (s_providers == null)
+                {
+                    s_providers = new EncodingProvider[1] { provider };
+                    return;
+                }
+
+                if (Array.IndexOf(s_providers, provider) >= 0)
+                {
+                    return;
+                }
+
+                EncodingProvider[] providers = new EncodingProvider[s_providers.Length + 1];
+                Array.Copy(s_providers, providers, s_providers.Length);
+                providers[providers.Length - 1] = provider;
+                s_providers = providers;
+            }
+        }
+
+        internal static Encoding GetEncodingFromProvider(int codepage)
+        {
+            if (s_providers == null)
+                return null;
+
+            EncodingProvider[] providers = s_providers;
+            foreach (EncodingProvider provider in providers)
+            {
+                Encoding enc = provider.GetEncoding(codepage);
+                if (enc != null)
+                    return enc;
+            }
+
+            return null;
+        }
+
+        internal static Encoding GetEncodingFromProvider(string encodingName)
+        {
+            if (s_providers == null)
+                return null;
+
+            EncodingProvider[] providers = s_providers;
+            foreach (EncodingProvider provider in providers)
+            {
+                Encoding enc = provider.GetEncoding(encodingName);
+                if (enc != null)
+                    return enc;
+            }
+
+            return null;
+        }
+
+        internal static Encoding GetEncodingFromProvider(int codepage, EncoderFallback enc, DecoderFallback dec)
+        {
+            if (s_providers == null)
+                return null;
+
+            EncodingProvider[] providers = s_providers;
+            foreach (EncodingProvider provider in providers)
+            {
+                Encoding encing = provider.GetEncoding(codepage, enc, dec);
+                if (encing != null)
+                    return encing;
+            }
+
+            return null;
+        }
+
+        internal static Encoding GetEncodingFromProvider(string encodingName, EncoderFallback enc, DecoderFallback dec)
+        {
+            if (s_providers == null)
+                return null;
+
+            EncodingProvider[] providers = s_providers;
+            foreach (EncodingProvider provider in providers)
+            {
+                Encoding encoding = provider.GetEncoding(encodingName, enc, dec);
+                if (encoding != null)
+                    return encoding;
+            }
+
+            return null;
+        }
+
+        private static Object s_InternalSyncObject = new Object();
+        private static volatile EncodingProvider[] s_providers;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/Latin1Encoding.cs b/src/System.Private.CoreLib/shared/System/Text/Latin1Encoding.cs
new file mode 100644
index 0000000000..335eb76e3c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/Latin1Encoding.cs
@@ -0,0 +1,884 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+
+namespace System.Text
+{
+    //
+    // Latin1Encoding is a simple override to optimize the GetString version of Latin1Encoding.
+    // because of the best fit cases we can't do this when encoding the string, only when decoding
+    //
+    internal class Latin1Encoding : EncodingNLS
+    {
+        // Used by Encoding.Latin1 for lazy initialization
+        // The initialization code will not be run until a static member of the class is referenced
+        internal static readonly Latin1Encoding s_default = new Latin1Encoding();
+
+        // We only use the best-fit table, of which ASCII is a superset for us.
+        public Latin1Encoding() : base(Encoding.ISO_8859_1)
+        {
+        }
+
+        // GetByteCount
+        // Note: We start by assuming that the output will be the same as count.  Having
+        // an encoder or fallback may change that assumption
+        internal override unsafe int GetByteCount(char* chars, int charCount, EncoderNLS encoder)
+        {
+            // Just need to ASSERT, this is called by something else internal that checked parameters already
+            Debug.Assert(charCount >= 0, "[Latin1Encoding.GetByteCount]count is negative");
+            Debug.Assert(chars != null, "[Latin1Encoding.GetByteCount]chars is null");
+
+            // Assert because we shouldn't be able to have a null encoder.
+            Debug.Assert(encoderFallback != null, "[Latin1Encoding.GetByteCount]Attempting to use null fallback encoder");
+
+            char charLeftOver = (char)0;
+
+            // If we have an encoder AND we aren't using default fallback,
+            // then we may have a complicated count.
+            EncoderReplacementFallback fallback;
+            if (encoder != null)
+            {
+                charLeftOver = encoder._charLeftOver;
+                Debug.Assert(charLeftOver == 0 || Char.IsHighSurrogate(charLeftOver),
+                    "[Latin1Encoding.GetByteCount]leftover character should be high surrogate");
+
+                fallback = encoder.Fallback as EncoderReplacementFallback;
+
+                // Verify that we have no fallbackbuffer, for Latin1 its always empty, so just assert
+                Debug.Assert(!encoder._throwOnOverflow || !encoder.InternalHasFallbackBuffer ||
+                    encoder.FallbackBuffer.Remaining == 0,
+                    "[Latin1CodePageEncoding.GetByteCount]Expected empty fallback buffer");
+            }
+            else
+                fallback = this.EncoderFallback as EncoderReplacementFallback;
+
+            if ((fallback != null && fallback.MaxCharCount == 1)/* || bIsBestFit*/)
+            {
+                // Replacement fallback encodes surrogate pairs as two ?? (or two whatever), so return size is always
+                // same as input size.
+                // Note that no existing SBCS code pages map code points to supplimentary characters, so this is easy.
+
+                // We could however have 1 extra byte if the last call had an encoder and a funky fallback and
+                // if we don't use the funky fallback this time.
+
+                // Do we have an extra char left over from last time?
+                if (charLeftOver > 0)
+                    charCount++;
+
+                return (charCount);
+            }
+
+            // Count is more complicated if you have a funky fallback
+            // For fallback we may need a fallback buffer, we know we're not default fallback
+            int byteCount = 0;
+
+            // Start by assuming default count, then +/- for fallback characters
+            char* charEnd = chars + charCount;
+
+            // For fallback we may need a fallback buffer, we know we aren't default fallback.
+            EncoderFallbackBuffer fallbackBuffer = null;
+            char* charsForFallback;
+
+            // We may have a left over character from last time, try and process it.
+            if (charLeftOver > 0)
+            {
+                // Initialize the buffer
+                Debug.Assert(encoder != null,
+                    "[Latin1Encoding.GetByteCount]Expected encoder if we have charLeftOver");
+                fallbackBuffer = encoder.FallbackBuffer;
+                fallbackBuffer.InternalInitialize(chars, charEnd, encoder, false);
+
+                // Since left over char was a surrogate, it'll have to be fallen back.
+                // Get Fallback
+                // This will fallback a pair if *chars is a low surrogate
+                charsForFallback = chars;
+                fallbackBuffer.InternalFallback(charLeftOver, ref charsForFallback);
+                chars = charsForFallback;
+            }
+
+            // Now we may have fallback char[] already from the encoder
+
+            // Go ahead and do it, including the fallback.
+            char ch;
+            while ((ch = (fallbackBuffer == null) ? '\0' : fallbackBuffer.InternalGetNextChar()) != 0 ||
+                    chars < charEnd)
+            {
+                // First unwind any fallback
+                if (ch == 0)
+                {
+                    // No fallback, just get next char
+                    ch = *chars;
+                    chars++;
+                }
+
+                // Check for fallback, this'll catch surrogate pairs too.
+                // no chars >= 0x100 are allowed.
+                if (ch > 0xff)
+                {
+                    // Initialize the buffer
+                    if (fallbackBuffer == null)
+                    {
+                        if (encoder == null)
+                            fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = encoder.FallbackBuffer;
+                        fallbackBuffer.InternalInitialize(charEnd - charCount, charEnd, encoder, false);
+                    }
+
+                    // Get Fallback
+                    charsForFallback = chars;
+                    fallbackBuffer.InternalFallback(ch, ref charsForFallback);
+                    chars = charsForFallback;
+                    continue;
+                }
+
+                // We'll use this one
+                byteCount++;
+            }
+
+            Debug.Assert(fallbackBuffer == null || fallbackBuffer.Remaining == 0,
+                "[Latin1Encoding.GetByteCount]Expected Empty fallback buffer");
+
+            return byteCount;
+        }
+
+        internal override unsafe int GetBytes(char* chars, int charCount,
+                                                byte* bytes, int byteCount, EncoderNLS encoder)
+        {
+            // Just need to ASSERT, this is called by something else internal that checked parameters already
+            Debug.Assert(bytes != null, "[Latin1Encoding.GetBytes]bytes is null");
+            Debug.Assert(byteCount >= 0, "[Latin1Encoding.GetBytes]byteCount is negative");
+            Debug.Assert(chars != null, "[Latin1Encoding.GetBytes]chars is null");
+            Debug.Assert(charCount >= 0, "[Latin1Encoding.GetBytes]charCount is negative");
+
+            // Assert because we shouldn't be able to have a null encoder.
+            Debug.Assert(encoderFallback != null, "[Latin1Encoding.GetBytes]Attempting to use null encoder fallback");
+
+            // Get any left over characters & check fast or slower fallback type
+            char charLeftOver = (char)0;
+            EncoderReplacementFallback fallback = null;
+            if (encoder != null)
+            {
+                charLeftOver = encoder._charLeftOver;
+                fallback = encoder.Fallback as EncoderReplacementFallback;
+                Debug.Assert(charLeftOver == 0 || Char.IsHighSurrogate(charLeftOver),
+                    "[Latin1Encoding.GetBytes]leftover character should be high surrogate");
+
+                // Verify that we have no fallbackbuffer, for ASCII its always empty, so just assert
+                Debug.Assert(!encoder._throwOnOverflow || !encoder.InternalHasFallbackBuffer ||
+                    encoder.FallbackBuffer.Remaining == 0,
+                    "[Latin1CodePageEncoding.GetBytes]Expected empty fallback buffer");
+            }
+            else
+            {
+                fallback = this.EncoderFallback as EncoderReplacementFallback;
+            }
+
+            // prepare our end
+            char* charEnd = chars + charCount;
+            byte* byteStart = bytes;
+            char* charStart = chars;
+
+            // See if we do the fast default or slightly slower fallback
+            if (fallback != null && fallback.MaxCharCount == 1)
+            {
+                // Fast version
+                char cReplacement = fallback.DefaultString[0];
+
+                // Check for replacements in range, otherwise fall back to slow version.
+                if (cReplacement <= (char)0xff)
+                {
+                    // We should have exactly as many output bytes as input bytes, unless there's a left
+                    // over character, in which case we may need one more.
+
+                    // If we had a left over character will have to add a ?  (This happens if they had a funky
+                    // fallback last time, but not this time.) (We can't spit any out though
+                    // because with fallback encoder each surrogate is treated as a seperate code point)
+                    if (charLeftOver > 0)
+                    {
+                        // Have to have room
+                        // Throw even if doing no throw version because this is just 1 char,
+                        // so buffer will never be big enough
+                        if (byteCount == 0)
+                            ThrowBytesOverflow(encoder, true);
+
+                        // This'll make sure we still have more room and also make sure our return value is correct.
+                        *(bytes++) = (byte)cReplacement;
+                        byteCount--;                // We used one of the ones we were counting.
+                    }
+
+                    // This keeps us from overrunning our output buffer
+                    if (byteCount < charCount)
+                    {
+                        // Throw or make buffer smaller?
+                        ThrowBytesOverflow(encoder, byteCount < 1);
+
+                        // Just use what we can
+                        charEnd = chars + byteCount;
+                    }
+
+                    // We just do a quick copy
+                    while (chars < charEnd)
+                    {
+                        char ch2 = *(chars++);
+                        if (ch2 > 0x00ff) *(bytes++) = (byte)cReplacement;
+                        else *(bytes++) = (byte)ch2;
+                    }
+
+                    // Clear encoder
+                    if (encoder != null)
+                    {
+                        encoder._charLeftOver = (char)0;
+                        encoder._charsUsed = (int)(chars - charStart);
+                    }
+                    return (int)(bytes - byteStart);
+                }
+            }
+
+            // Slower version, have to do real fallback.
+
+            // prepare our end
+            byte* byteEnd = bytes + byteCount;
+
+            // For fallback we may need a fallback buffer, we know we aren't default fallback, create & init it
+            EncoderFallbackBuffer fallbackBuffer = null;
+            char* charsForFallback;
+
+            // We may have a left over character from last time, try and process it.
+            if (charLeftOver > 0)
+            {
+                // Since left over char was a surrogate, it'll have to be fallen back.
+                // Get Fallback
+                Debug.Assert(encoder != null,
+                    "[Latin1Encoding.GetBytes]Expected encoder if we have charLeftOver");
+                fallbackBuffer = encoder.FallbackBuffer;
+                fallbackBuffer.InternalInitialize(chars, charEnd, encoder, true);
+
+                // Since left over char was a surrogate, it'll have to be fallen back.
+                // Get Fallback
+                // This will fallback a pair if *chars is a low surrogate
+                charsForFallback = chars;
+                fallbackBuffer.InternalFallback(charLeftOver, ref charsForFallback);
+                chars = charsForFallback;
+
+                if (fallbackBuffer.Remaining > byteEnd - bytes)
+                {
+                    // Throw it, if we don't have enough for this we never will
+                    ThrowBytesOverflow(encoder, true);
+                }
+            }
+
+            // Now we may have fallback char[] already from the encoder fallback above
+
+            // Go ahead and do it, including the fallback.
+            char ch;
+            while ((ch = (fallbackBuffer == null) ? '\0' : fallbackBuffer.InternalGetNextChar()) != 0 ||
+                    chars < charEnd)
+            {
+                // First unwind any fallback
+                if (ch == 0)
+                {
+                    // No fallback, just get next char
+                    ch = *chars;
+                    chars++;
+                }
+
+                // Check for fallback, this'll catch surrogate pairs too.
+                // All characters >= 0x100 must fall back.
+                if (ch > 0xff)
+                {
+                    // Initialize the buffer
+                    if (fallbackBuffer == null)
+                    {
+                        if (encoder == null)
+                            fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = encoder.FallbackBuffer;
+                        fallbackBuffer.InternalInitialize(charEnd - charCount, charEnd, encoder, true);
+                    }
+
+                    // Get Fallback
+                    charsForFallback = chars;
+                    fallbackBuffer.InternalFallback(ch, ref charsForFallback);
+                    chars = charsForFallback;
+
+                    // Make sure we have enough room.  Each fallback char will be 1 output char
+                    // (or else cause a recursion exception)
+                    if (fallbackBuffer.Remaining > byteEnd - bytes)
+                    {
+                        // Didn't use this char, throw it.  Chars should've advanced by now
+                        // If we had encoder fallback data it would've thrown before the loop
+                        Debug.Assert(chars > charStart,
+                            "[Latin1Encoding.GetBytes]Expected chars to have advanced (fallback case)");
+                        chars--;
+                        fallbackBuffer.InternalReset();
+
+                        // Throw it
+                        ThrowBytesOverflow(encoder, chars == charStart);
+                        break;
+                    }
+
+                    continue;
+                }
+
+                // We'll use this one
+                // Bounds check
+                if (bytes >= byteEnd)
+                {
+                    // didn't use this char, we'll throw or use buffer
+                    Debug.Assert(fallbackBuffer == null || fallbackBuffer.bFallingBack == false,
+                        "[Latin1Encoding.GetBytes]Expected fallback to have throw initially if insufficient space");
+                    if (fallbackBuffer == null || fallbackBuffer.bFallingBack == false)
+                    {
+                        Debug.Assert(chars > charStart,
+                            "[Latin1Encoding.GetBytes]Expected chars to have advanced (fallback case)");
+                        chars--;                                        // don't use last char
+                    }
+                    ThrowBytesOverflow(encoder, chars == charStart);    // throw ?
+                    break;                                              // don't throw, stop
+                }
+
+                // Go ahead and add it
+                *bytes = unchecked((byte)ch);
+                bytes++;
+            }
+
+            // Need to do encoder stuff
+            if (encoder != null)
+            {
+                // Fallback stuck it in encoder if necessary, but we have to clear MustFlush cases
+                if (fallbackBuffer != null && !fallbackBuffer.bUsedEncoder)
+                    // Clear it in case of MustFlush
+                    encoder._charLeftOver = (char)0;
+
+                // Set our chars used count
+                encoder._charsUsed = (int)(chars - charStart);
+            }
+
+            Debug.Assert(fallbackBuffer == null || fallbackBuffer.Remaining == 0,
+                "[Latin1Encoding.GetBytes]Expected Empty fallback buffer");
+
+            return (int)(bytes - byteStart);
+        }
+
+        // This is internal and called by something else,
+        internal override unsafe int GetCharCount(byte* bytes, int count, DecoderNLS decoder)
+        {
+            // Just assert, we're called internally so these should be safe, checked already
+            Debug.Assert(bytes != null, "[Latin1Encoding.GetCharCount]bytes is null");
+            Debug.Assert(count >= 0, "[Latin1Encoding.GetCharCount]byteCount is negative");
+
+            // Just return length, SBCS stay the same length because they don't map to surrogate
+            // pairs and we don't have to fallback because all latin1Encoding code points are unicode
+            return count;
+        }
+
+        internal override unsafe int GetChars(byte* bytes, int byteCount,
+                                                char* chars, int charCount, DecoderNLS decoder)
+        {
+            // Just need to ASSERT, this is called by something else internal that checked parameters already
+            Debug.Assert(bytes != null, "[Latin1Encoding.GetChars]bytes is null");
+            Debug.Assert(byteCount >= 0, "[Latin1Encoding.GetChars]byteCount is negative");
+            Debug.Assert(chars != null, "[Latin1Encoding.GetChars]chars is null");
+            Debug.Assert(charCount >= 0, "[Latin1Encoding.GetChars]charCount is negative");
+
+            // Need byteCount chars, otherwise too small buffer
+            if (charCount < byteCount)
+            {
+                // Buffer too small.  Do we throw?
+                ThrowCharsOverflow(decoder, charCount < 1);
+
+                // Don't throw, correct buffer size
+                byteCount = charCount;
+            }
+
+            // Do it our fast way
+            byte* byteEnd = bytes + byteCount;
+
+            // Quick loop, all bytes are the same as chars, so no fallbacks for latin1
+            while (bytes < byteEnd)
+            {
+                *(chars) = unchecked((char)*(bytes));
+                chars++;
+                bytes++;
+            }
+
+            // Might need to know input bytes used
+            if (decoder != null)
+                decoder._bytesUsed = byteCount;
+
+            // Converted sequence is same length as input, so output charsUsed is same as byteCount;
+            return byteCount;
+        }
+
+        public override int GetMaxByteCount(int charCount)
+        {
+            if (charCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(charCount),
+                     SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Characters would be # of characters + 1 in case high surrogate is ? * max fallback
+            long byteCount = (long)charCount + 1;
+
+            if (EncoderFallback.MaxCharCount > 1)
+                byteCount *= EncoderFallback.MaxCharCount;
+
+            // 1 to 1 for most characters.  Only surrogates with fallbacks have less.
+
+            if (byteCount > 0x7fffffff)
+                throw new ArgumentOutOfRangeException(nameof(charCount), SR.ArgumentOutOfRange_GetByteCountOverflow);
+            return (int)byteCount;
+        }
+
+        public override int GetMaxCharCount(int byteCount)
+        {
+            if (byteCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(byteCount),
+                     SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Just return length, SBCS stay the same length because they don't map to surrogate
+            long charCount = (long)byteCount;
+
+            // 1 to 1 for most characters.  Only surrogates with fallbacks have less, unknown fallbacks could be longer.
+            if (DecoderFallback.MaxCharCount > 1)
+                charCount *= DecoderFallback.MaxCharCount;
+
+            if (charCount > 0x7fffffff)
+                throw new ArgumentOutOfRangeException(nameof(byteCount), SR.ArgumentOutOfRange_GetCharCountOverflow);
+
+            return (int)charCount;
+        }
+
+        // True if and only if the encoding only uses single byte code points.  (Ie, ASCII, 1252, etc)
+        public override bool IsSingleByte
+        {
+            get
+            {
+                return true;
+            }
+        }
+
+        public override bool IsAlwaysNormalized(NormalizationForm form)
+        {
+            // Latin-1 contains precomposed characters, so normal for Form C.
+            // Since some are composed, not normal for D & KD.
+            // Also some letters like 0x00A8 (spacing diarisis) have compatibility decompositions, so false for KD & KC.
+
+            // Only true for form C.
+            return (form == NormalizationForm.FormC);
+        }
+        // Since our best fit table is small we'll hard code it
+        internal override char[] GetBestFitUnicodeToBytesData()
+        {
+            // Get our best fit data
+            return Latin1Encoding.arrayCharBestFit;
+        }
+
+        // Best fit for ASCII, and since it works for ASCII, we use it for latin1 as well.
+        private static readonly char[] arrayCharBestFit =
+        {
+// The first many are in case you wanted to use this for ASCIIEncoding, which we don't need to do any more.
+//          (char)0x00a0, (char)0x0020,    // No-Break Space -> Space
+//          (char)0x00a1, (char)0x0021,    // Inverted Exclamation Mark -> !
+//          (char)0x00a2, (char)0x0063,    // Cent Sign -> c
+//          (char)0x00a3, (char)0x003f,    // Pound Sign
+//          (char)0x00a4, (char)0x0024,    // Currency Sign -> $
+//          (char)0x00a5, (char)0x0059,    // Yen Sign -> Y
+//          (char)0x00a6, (char)0x007c,    // Broken Bar -> |
+//          (char)0x00a7, (char)0x003f,    // Section Sign
+//          (char)0x00a8, (char)0x003f,    // Diaeresis
+//          (char)0x00a9, (char)0x0043,    // Copyright Sign -> C
+//          (char)0x00aa, (char)0x0061,    // Feminine Ordinal Indicator -> a
+//          (char)0x00ab, (char)0x003c,    // Left-Pointing Double Angle Quotation Mark -> <
+//          (char)0x00ac, (char)0x003f,    // Not Sign
+//          (char)0x00ad, (char)0x002d,    // Soft Hyphen -> -
+//          (char)0x00ae, (char)0x0052,    // Registered Sign -> R
+//          (char)0x00af, (char)0x003f,    // Macron
+//          (char)0x00b0, (char)0x003f,    // Degree Sign
+//          (char)0x00b1, (char)0x003f,    // Plus-Minus Sign
+//          (char)0x00b2, (char)0x0032,    // Superscript Two -> 2
+//          (char)0x00b3, (char)0x0033,    // Superscript Three -> 3
+//          (char)0x00b4, (char)0x003f,    // Acute Accent
+//          (char)0x00b5, (char)0x003f,    // Micro Sign
+//          (char)0x00b6, (char)0x003f,    // Pilcrow Sign
+//          (char)0x00b7, (char)0x002e,    // Middle Dot -> .
+//          (char)0x00b8, (char)0x002c,    // Cedilla -> ,
+//          (char)0x00b9, (char)0x0031,    // Superscript One -> 1
+//          (char)0x00ba, (char)0x006f,    // Masculine Ordinal Indicator -> o
+//          (char)0x00bb, (char)0x003e,    // Right-Pointing Double Angle Quotation Mark -> >
+//          (char)0x00bc, (char)0x003f,    // Vulgar Fraction One Quarter
+//          (char)0x00bd, (char)0x003f,    // Vulgar Fraction One Half
+//          (char)0x00be, (char)0x003f,    // Vulgar Fraction Three Quarters
+//          (char)0x00bf, (char)0x003f,    // Inverted Question Mark
+//          (char)0x00c0, (char)0x0041,    // Latin Capital Letter A With Grave -> A
+//          (char)0x00c1, (char)0x0041,    // Latin Capital Letter A With Acute -> A
+//          (char)0x00c2, (char)0x0041,    // Latin Capital Letter A With Circumflex -> A
+//          (char)0x00c3, (char)0x0041,    // Latin Capital Letter A With Tilde -> A
+//          (char)0x00c4, (char)0x0041,    // Latin Capital Letter A With Diaeresis -> A
+//          (char)0x00c5, (char)0x0041,    // Latin Capital Letter A With Ring Above -> A
+//          (char)0x00c6, (char)0x0041,    // Latin Capital Ligature Ae -> A
+//          (char)0x00c7, (char)0x0043,    // Latin Capital Letter C With Cedilla -> C
+//          (char)0x00c8, (char)0x0045,    // Latin Capital Letter E With Grave -> E
+//          (char)0x00c9, (char)0x0045,    // Latin Capital Letter E With Acute -> E
+//          (char)0x00ca, (char)0x0045,    // Latin Capital Letter E With Circumflex -> E
+//          (char)0x00cb, (char)0x0045,    // Latin Capital Letter E With Diaeresis -> E
+//          (char)0x00cc, (char)0x0049,    // Latin Capital Letter I With Grave -> I
+//          (char)0x00cd, (char)0x0049,    // Latin Capital Letter I With Acute -> I
+//          (char)0x00ce, (char)0x0049,    // Latin Capital Letter I With Circumflex -> I
+//          (char)0x00cf, (char)0x0049,    // Latin Capital Letter I With Diaeresis -> I
+//          (char)0x00d0, (char)0x0044,    // Latin Capital Letter Eth -> D
+//          (char)0x00d1, (char)0x004e,    // Latin Capital Letter N With Tilde -> N
+//          (char)0x00d2, (char)0x004f,    // Latin Capital Letter O With Grave -> O
+//          (char)0x00d3, (char)0x004f,    // Latin Capital Letter O With Acute -> O
+//          (char)0x00d4, (char)0x004f,    // Latin Capital Letter O With Circumflex -> O
+//          (char)0x00d5, (char)0x004f,    // Latin Capital Letter O With Tilde -> O
+//          (char)0x00d6, (char)0x004f,    // Latin Capital Letter O With Diaeresis -> O
+//          (char)0x00d7, (char)0x003f,    // Multiplication Sign
+//          (char)0x00d8, (char)0x004f,    // Latin Capital Letter O With Stroke -> O
+//          (char)0x00d9, (char)0x0055,    // Latin Capital Letter U With Grave -> U
+//          (char)0x00da, (char)0x0055,    // Latin Capital Letter U With Acute -> U
+//          (char)0x00db, (char)0x0055,    // Latin Capital Letter U With Circumflex -> U
+//          (char)0x00dc, (char)0x0055,    // Latin Capital Letter U With Diaeresis -> U
+//          (char)0x00dd, (char)0x0059,    // Latin Capital Letter Y With Acute -> Y
+//          (char)0x00de, (char)0x003f,    // Latin Capital Letter Thorn
+//          (char)0x00df, (char)0x003f,    // Latin Small Letter Sharp S
+//          (char)0x00e0, (char)0x0061,    // Latin Small Letter A With Grave -> a
+//          (char)0x00e1, (char)0x0061,    // Latin Small Letter A With Acute -> a
+//          (char)0x00e2, (char)0x0061,    // Latin Small Letter A With Circumflex -> a
+//          (char)0x00e3, (char)0x0061,    // Latin Small Letter A With Tilde -> a
+//          (char)0x00e4, (char)0x0061,    // Latin Small Letter A With Diaeresis -> a
+//          (char)0x00e5, (char)0x0061,    // Latin Small Letter A With Ring Above -> a
+//          (char)0x00e6, (char)0x0061,    // Latin Small Ligature Ae -> a
+//          (char)0x00e7, (char)0x0063,    // Latin Small Letter C With Cedilla -> c
+//          (char)0x00e8, (char)0x0065,    // Latin Small Letter E With Grave -> e
+//          (char)0x00e9, (char)0x0065,    // Latin Small Letter E With Acute -> e
+//          (char)0x00ea, (char)0x0065,    // Latin Small Letter E With Circumflex -> e
+//          (char)0x00eb, (char)0x0065,    // Latin Small Letter E With Diaeresis -> e
+//          (char)0x00ec, (char)0x0069,    // Latin Small Letter I With Grave -> i
+//          (char)0x00ed, (char)0x0069,    // Latin Small Letter I With Acute -> i
+//          (char)0x00ee, (char)0x0069,    // Latin Small Letter I With Circumflex -> i
+//          (char)0x00ef, (char)0x0069,    // Latin Small Letter I With Diaeresis -> i
+//          (char)0x00f0, (char)0x003f,    // Latin Small Letter Eth
+//          (char)0x00f1, (char)0x006e,    // Latin Small Letter N With Tilde -> n
+//          (char)0x00f2, (char)0x006f,    // Latin Small Letter O With Grave -> o
+//          (char)0x00f3, (char)0x006f,    // Latin Small Letter O With Acute -> o
+//          (char)0x00f4, (char)0x006f,    // Latin Small Letter O With Circumflex -> o
+//          (char)0x00f5, (char)0x006f,    // Latin Small Letter O With Tilde -> o
+//          (char)0x00f6, (char)0x006f,    // Latin Small Letter O With Diaeresis -> o
+//          (char)0x00f7, (char)0x003f,    // Division Sign
+//          (char)0x00f8, (char)0x006f,    // Latin Small Letter O With Stroke -> o
+//          (char)0x00f9, (char)0x0075,    // Latin Small Letter U With Grave -> u
+//          (char)0x00fa, (char)0x0075,    // Latin Small Letter U With Acute -> u
+//          (char)0x00fb, (char)0x0075,    // Latin Small Letter U With Circumflex -> u
+//          (char)0x00fc, (char)0x0075,    // Latin Small Letter U With Diaeresis -> u
+//          (char)0x00fd, (char)0x0079,    // Latin Small Letter Y With Acute -> y
+//          (char)0x00fe, (char)0x003f,    // Latin Small Letter Thorn
+//          (char)0x00ff, (char)0x0079,    // Latin Small Letter Y With Diaeresis -> y
+            (char)0x0100, (char)0x0041,    // Latin Capital Letter A With Macron -> A
+            (char)0x0101, (char)0x0061,    // Latin Small Letter A With Macron -> a
+            (char)0x0102, (char)0x0041,    // Latin Capital Letter A With Breve -> A
+            (char)0x0103, (char)0x0061,    // Latin Small Letter A With Breve -> a
+            (char)0x0104, (char)0x0041,    // Latin Capital Letter A With Ogonek -> A
+            (char)0x0105, (char)0x0061,    // Latin Small Letter A With Ogonek -> a
+            (char)0x0106, (char)0x0043,    // Latin Capital Letter C With Acute -> C
+            (char)0x0107, (char)0x0063,    // Latin Small Letter C With Acute -> c
+            (char)0x0108, (char)0x0043,    // Latin Capital Letter C With Circumflex -> C
+            (char)0x0109, (char)0x0063,    // Latin Small Letter C With Circumflex -> c
+            (char)0x010a, (char)0x0043,    // Latin Capital Letter C With Dot Above -> C
+            (char)0x010b, (char)0x0063,    // Latin Small Letter C With Dot Above -> c
+            (char)0x010c, (char)0x0043,    // Latin Capital Letter C With Caron -> C
+            (char)0x010d, (char)0x0063,    // Latin Small Letter C With Caron -> c
+            (char)0x010e, (char)0x0044,    // Latin Capital Letter D With Caron -> D
+            (char)0x010f, (char)0x0064,    // Latin Small Letter D With Caron -> d
+            (char)0x0110, (char)0x0044,    // Latin Capital Letter D With Stroke -> D
+            (char)0x0111, (char)0x0064,    // Latin Small Letter D With Stroke -> d
+            (char)0x0112, (char)0x0045,    // Latin Capital Letter E With Macron -> E
+            (char)0x0113, (char)0x0065,    // Latin Small Letter E With Macron -> e
+            (char)0x0114, (char)0x0045,    // Latin Capital Letter E With Breve -> E
+            (char)0x0115, (char)0x0065,    // Latin Small Letter E With Breve -> e
+            (char)0x0116, (char)0x0045,    // Latin Capital Letter E With Dot Above -> E
+            (char)0x0117, (char)0x0065,    // Latin Small Letter E With Dot Above -> e
+            (char)0x0118, (char)0x0045,    // Latin Capital Letter E With Ogonek -> E
+            (char)0x0119, (char)0x0065,    // Latin Small Letter E With Ogonek -> e
+            (char)0x011a, (char)0x0045,    // Latin Capital Letter E With Caron -> E
+            (char)0x011b, (char)0x0065,    // Latin Small Letter E With Caron -> e
+            (char)0x011c, (char)0x0047,    // Latin Capital Letter G With Circumflex -> G
+            (char)0x011d, (char)0x0067,    // Latin Small Letter G With Circumflex -> g
+            (char)0x011e, (char)0x0047,    // Latin Capital Letter G With Breve -> G
+            (char)0x011f, (char)0x0067,    // Latin Small Letter G With Breve -> g
+            (char)0x0120, (char)0x0047,    // Latin Capital Letter G With Dot Above -> G
+            (char)0x0121, (char)0x0067,    // Latin Small Letter G With Dot Above -> g
+            (char)0x0122, (char)0x0047,    // Latin Capital Letter G With Cedilla -> G
+            (char)0x0123, (char)0x0067,    // Latin Small Letter G With Cedilla -> g
+            (char)0x0124, (char)0x0048,    // Latin Capital Letter H With Circumflex -> H
+            (char)0x0125, (char)0x0068,    // Latin Small Letter H With Circumflex -> h
+            (char)0x0126, (char)0x0048,    // Latin Capital Letter H With Stroke -> H
+            (char)0x0127, (char)0x0068,    // Latin Small Letter H With Stroke -> h
+            (char)0x0128, (char)0x0049,    // Latin Capital Letter I With Tilde -> I
+            (char)0x0129, (char)0x0069,    // Latin Small Letter I With Tilde -> i
+            (char)0x012a, (char)0x0049,    // Latin Capital Letter I With Macron -> I
+            (char)0x012b, (char)0x0069,    // Latin Small Letter I With Macron -> i
+            (char)0x012c, (char)0x0049,    // Latin Capital Letter I With Breve -> I
+            (char)0x012d, (char)0x0069,    // Latin Small Letter I With Breve -> i
+            (char)0x012e, (char)0x0049,    // Latin Capital Letter I With Ogonek -> I
+            (char)0x012f, (char)0x0069,    // Latin Small Letter I With Ogonek -> i
+            (char)0x0130, (char)0x0049,    // Latin Capital Letter I With Dot Above -> I
+            (char)0x0131, (char)0x0069,    // Latin Small Letter Dotless I -> i
+            (char)0x0134, (char)0x004a,    // Latin Capital Letter J With Circumflex -> J
+            (char)0x0135, (char)0x006a,    // Latin Small Letter J With Circumflex -> j
+            (char)0x0136, (char)0x004b,    // Latin Capital Letter K With Cedilla -> K
+            (char)0x0137, (char)0x006b,    // Latin Small Letter K With Cedilla -> k
+            (char)0x0139, (char)0x004c,    // Latin Capital Letter L With Acute -> L
+            (char)0x013a, (char)0x006c,    // Latin Small Letter L With Acute -> l
+            (char)0x013b, (char)0x004c,    // Latin Capital Letter L With Cedilla -> L
+            (char)0x013c, (char)0x006c,    // Latin Small Letter L With Cedilla -> l
+            (char)0x013d, (char)0x004c,    // Latin Capital Letter L With Caron -> L
+            (char)0x013e, (char)0x006c,    // Latin Small Letter L With Caron -> l
+            (char)0x0141, (char)0x004c,    // Latin Capital Letter L With Stroke -> L
+            (char)0x0142, (char)0x006c,    // Latin Small Letter L With Stroke -> l
+            (char)0x0143, (char)0x004e,    // Latin Capital Letter N With Acute -> N
+            (char)0x0144, (char)0x006e,    // Latin Small Letter N With Acute -> n
+            (char)0x0145, (char)0x004e,    // Latin Capital Letter N With Cedilla -> N
+            (char)0x0146, (char)0x006e,    // Latin Small Letter N With Cedilla -> n
+            (char)0x0147, (char)0x004e,    // Latin Capital Letter N With Caron -> N
+            (char)0x0148, (char)0x006e,    // Latin Small Letter N With Caron -> n
+            (char)0x014c, (char)0x004f,    // Latin Capital Letter O With Macron -> O
+            (char)0x014d, (char)0x006f,    // Latin Small Letter O With Macron -> o
+            (char)0x014e, (char)0x004f,    // Latin Capital Letter O With Breve -> O
+            (char)0x014f, (char)0x006f,    // Latin Small Letter O With Breve -> o
+            (char)0x0150, (char)0x004f,    // Latin Capital Letter O With Double Acute -> O
+            (char)0x0151, (char)0x006f,    // Latin Small Letter O With Double Acute -> o
+            (char)0x0152, (char)0x004f,    // Latin Capital Ligature Oe -> O
+            (char)0x0153, (char)0x006f,    // Latin Small Ligature Oe -> o
+            (char)0x0154, (char)0x0052,    // Latin Capital Letter R With Acute -> R
+            (char)0x0155, (char)0x0072,    // Latin Small Letter R With Acute -> r
+            (char)0x0156, (char)0x0052,    // Latin Capital Letter R With Cedilla -> R
+            (char)0x0157, (char)0x0072,    // Latin Small Letter R With Cedilla -> r
+            (char)0x0158, (char)0x0052,    // Latin Capital Letter R With Caron -> R
+            (char)0x0159, (char)0x0072,    // Latin Small Letter R With Caron -> r
+            (char)0x015a, (char)0x0053,    // Latin Capital Letter S With Acute -> S
+            (char)0x015b, (char)0x0073,    // Latin Small Letter S With Acute -> s
+            (char)0x015c, (char)0x0053,    // Latin Capital Letter S With Circumflex -> S
+            (char)0x015d, (char)0x0073,    // Latin Small Letter S With Circumflex -> s
+            (char)0x015e, (char)0x0053,    // Latin Capital Letter S With Cedilla -> S
+            (char)0x015f, (char)0x0073,    // Latin Small Letter S With Cedilla -> s
+            (char)0x0160, (char)0x0053,    // Latin Capital Letter S With Caron -> S
+            (char)0x0161, (char)0x0073,    // Latin Small Letter S With Caron -> s
+            (char)0x0162, (char)0x0054,    // Latin Capital Letter T With Cedilla -> T
+            (char)0x0163, (char)0x0074,    // Latin Small Letter T With Cedilla -> t
+            (char)0x0164, (char)0x0054,    // Latin Capital Letter T With Caron -> T
+            (char)0x0165, (char)0x0074,    // Latin Small Letter T With Caron -> t
+            (char)0x0166, (char)0x0054,    // Latin Capital Letter T With Stroke -> T
+            (char)0x0167, (char)0x0074,    // Latin Small Letter T With Stroke -> t
+            (char)0x0168, (char)0x0055,    // Latin Capital Letter U With Tilde -> U
+            (char)0x0169, (char)0x0075,    // Latin Small Letter U With Tilde -> u
+            (char)0x016a, (char)0x0055,    // Latin Capital Letter U With Macron -> U
+            (char)0x016b, (char)0x0075,    // Latin Small Letter U With Macron -> u
+            (char)0x016c, (char)0x0055,    // Latin Capital Letter U With Breve -> U
+            (char)0x016d, (char)0x0075,    // Latin Small Letter U With Breve -> u
+            (char)0x016e, (char)0x0055,    // Latin Capital Letter U With Ring Above -> U
+            (char)0x016f, (char)0x0075,    // Latin Small Letter U With Ring Above -> u
+            (char)0x0170, (char)0x0055,    // Latin Capital Letter U With Double Acute -> U
+            (char)0x0171, (char)0x0075,    // Latin Small Letter U With Double Acute -> u
+            (char)0x0172, (char)0x0055,    // Latin Capital Letter U With Ogonek -> U
+            (char)0x0173, (char)0x0075,    // Latin Small Letter U With Ogonek -> u
+            (char)0x0174, (char)0x0057,    // Latin Capital Letter W With Circumflex -> W
+            (char)0x0175, (char)0x0077,    // Latin Small Letter W With Circumflex -> w
+            (char)0x0176, (char)0x0059,    // Latin Capital Letter Y With Circumflex -> Y
+            (char)0x0177, (char)0x0079,    // Latin Small Letter Y With Circumflex -> y
+            (char)0x0178, (char)0x0059,    // Latin Capital Letter Y With Diaeresis -> Y
+            (char)0x0179, (char)0x005a,    // Latin Capital Letter Z With Acute -> Z
+            (char)0x017a, (char)0x007a,    // Latin Small Letter Z With Acute -> z
+            (char)0x017b, (char)0x005a,    // Latin Capital Letter Z With Dot Above -> Z
+            (char)0x017c, (char)0x007a,    // Latin Small Letter Z With Dot Above -> z
+            (char)0x017d, (char)0x005a,    // Latin Capital Letter Z With Caron -> Z
+            (char)0x017e, (char)0x007a,    // Latin Small Letter Z With Caron -> z
+            (char)0x0180, (char)0x0062,    // Latin Small Letter B With Stroke -> b
+            (char)0x0189, (char)0x0044,    // Latin Capital Letter African D -> D
+            (char)0x0191, (char)0x0046,    // Latin Capital Letter F With Hook -> F
+            (char)0x0192, (char)0x0066,    // Latin Small Letter F With Hook -> f
+            (char)0x0197, (char)0x0049,    // Latin Capital Letter I With Stroke -> I
+            (char)0x019a, (char)0x006c,    // Latin Small Letter L With Bar -> l
+            (char)0x019f, (char)0x004f,    // Latin Capital Letter O With Middle Tilde -> O
+            (char)0x01a0, (char)0x004f,    // Latin Capital Letter O With Horn -> O
+            (char)0x01a1, (char)0x006f,    // Latin Small Letter O With Horn -> o
+            (char)0x01ab, (char)0x0074,    // Latin Small Letter T With Palatal Hook -> t
+            (char)0x01ae, (char)0x0054,    // Latin Capital Letter T With Retroflex Hook -> T
+            (char)0x01af, (char)0x0055,    // Latin Capital Letter U With Horn -> U
+            (char)0x01b0, (char)0x0075,    // Latin Small Letter U With Horn -> u
+            (char)0x01b6, (char)0x007a,    // Latin Small Letter Z With Stroke -> z
+            (char)0x01cd, (char)0x0041,    // Latin Capital Letter A With Caron -> A
+            (char)0x01ce, (char)0x0061,    // Latin Small Letter A With Caron -> a
+            (char)0x01cf, (char)0x0049,    // Latin Capital Letter I With Caron -> I
+            (char)0x01d0, (char)0x0069,    // Latin Small Letter I With Caron -> i
+            (char)0x01d1, (char)0x004f,    // Latin Capital Letter O With Caron -> O
+            (char)0x01d2, (char)0x006f,    // Latin Small Letter O With Caron -> o
+            (char)0x01d3, (char)0x0055,    // Latin Capital Letter U With Caron -> U
+            (char)0x01d4, (char)0x0075,    // Latin Small Letter U With Caron -> u
+            (char)0x01d5, (char)0x0055,    // Latin Capital Letter U With Diaeresis And Macron -> U
+            (char)0x01d6, (char)0x0075,    // Latin Small Letter U With Diaeresis And Macron -> u
+            (char)0x01d7, (char)0x0055,    // Latin Capital Letter U With Diaeresis And Acute -> U
+            (char)0x01d8, (char)0x0075,    // Latin Small Letter U With Diaeresis And Acute -> u
+            (char)0x01d9, (char)0x0055,    // Latin Capital Letter U With Diaeresis And Caron -> U
+            (char)0x01da, (char)0x0075,    // Latin Small Letter U With Diaeresis And Caron -> u
+            (char)0x01db, (char)0x0055,    // Latin Capital Letter U With Diaeresis And Grave -> U
+            (char)0x01dc, (char)0x0075,    // Latin Small Letter U With Diaeresis And Grave -> u
+            (char)0x01de, (char)0x0041,    // Latin Capital Letter A With Diaeresis And Macron -> A
+            (char)0x01df, (char)0x0061,    // Latin Small Letter A With Diaeresis And Macron -> a
+            (char)0x01e4, (char)0x0047,    // Latin Capital Letter G With Stroke -> G
+            (char)0x01e5, (char)0x0067,    // Latin Small Letter G With Stroke -> g
+            (char)0x01e6, (char)0x0047,    // Latin Capital Letter G With Caron -> G
+            (char)0x01e7, (char)0x0067,    // Latin Small Letter G With Caron -> g
+            (char)0x01e8, (char)0x004b,    // Latin Capital Letter K With Caron -> K
+            (char)0x01e9, (char)0x006b,    // Latin Small Letter K With Caron -> k
+            (char)0x01ea, (char)0x004f,    // Latin Capital Letter O With Ogonek -> O
+            (char)0x01eb, (char)0x006f,    // Latin Small Letter O With Ogonek -> o
+            (char)0x01ec, (char)0x004f,    // Latin Capital Letter O With Ogonek And Macron -> O
+            (char)0x01ed, (char)0x006f,    // Latin Small Letter O With Ogonek And Macron -> o
+            (char)0x01f0, (char)0x006a,    // Latin Small Letter J With Caron -> j
+            (char)0x0261, (char)0x0067,    // Latin Small Letter Script G -> g
+            (char)0x02b9, (char)0x0027,    // Modifier Letter Prime -> '
+            (char)0x02ba, (char)0x0022,    // Modifier Letter Double Prime -> "
+            (char)0x02bc, (char)0x0027,    // Modifier Letter Apostrophe -> '
+            (char)0x02c4, (char)0x005e,    // Modifier Letter Up Arrowhead -> ^
+            (char)0x02c6, (char)0x005e,    // Modifier Letter Circumflex Accent -> ^
+            (char)0x02c8, (char)0x0027,    // Modifier Letter Vertical Line -> '
+            (char)0x02c9, (char)0x003f,    // Modifier Letter Macron
+            (char)0x02ca, (char)0x003f,    // Modifier Letter Acute Accent
+            (char)0x02cb, (char)0x0060,    // Modifier Letter Grave Accent -> `
+            (char)0x02cd, (char)0x005f,    // Modifier Letter Low Macron -> _
+            (char)0x02da, (char)0x003f,    // Ring Above
+            (char)0x02dc, (char)0x007e,    // Small Tilde -> ~
+            (char)0x0300, (char)0x0060,    // Combining Grave Accent -> `
+            (char)0x0302, (char)0x005e,    // Combining Circumflex Accent -> ^
+            (char)0x0303, (char)0x007e,    // Combining Tilde -> ~
+            (char)0x030e, (char)0x0022,    // Combining Double Vertical Line Above -> "
+            (char)0x0331, (char)0x005f,    // Combining Macron Below -> _
+            (char)0x0332, (char)0x005f,    // Combining Low Line -> _
+            (char)0x2000, (char)0x0020,    // En Quad
+            (char)0x2001, (char)0x0020,    // Em Quad
+            (char)0x2002, (char)0x0020,    // En Space
+            (char)0x2003, (char)0x0020,    // Em Space
+            (char)0x2004, (char)0x0020,    // Three-Per-Em Space
+            (char)0x2005, (char)0x0020,    // Four-Per-Em Space
+            (char)0x2006, (char)0x0020,    // Six-Per-Em Space
+            (char)0x2010, (char)0x002d,    // Hyphen -> -
+            (char)0x2011, (char)0x002d,    // Non-Breaking Hyphen -> -
+            (char)0x2013, (char)0x002d,    // En Dash -> -
+            (char)0x2014, (char)0x002d,    // Em Dash -> -
+            (char)0x2018, (char)0x0027,    // Left Single Quotation Mark -> '
+            (char)0x2019, (char)0x0027,    // Right Single Quotation Mark -> '
+            (char)0x201a, (char)0x002c,    // Single Low-9 Quotation Mark -> ,
+            (char)0x201c, (char)0x0022,    // Left Double Quotation Mark -> "
+            (char)0x201d, (char)0x0022,    // Right Double Quotation Mark -> "
+            (char)0x201e, (char)0x0022,    // Double Low-9 Quotation Mark -> "
+            (char)0x2020, (char)0x003f,    // Dagger
+            (char)0x2021, (char)0x003f,    // Double Dagger
+            (char)0x2022, (char)0x002e,    // Bullet -> .
+            (char)0x2026, (char)0x002e,    // Horizontal Ellipsis -> .
+            (char)0x2030, (char)0x003f,    // Per Mille Sign
+            (char)0x2032, (char)0x0027,    // Prime -> '
+            (char)0x2035, (char)0x0060,    // Reversed Prime -> `
+            (char)0x2039, (char)0x003c,    // Single Left-Pointing Angle Quotation Mark -> <
+            (char)0x203a, (char)0x003e,    // Single Right-Pointing Angle Quotation Mark -> >
+            (char)0x2122, (char)0x0054,    // Trade Mark Sign -> T
+            (char)0xff01, (char)0x0021,    // Fullwidth Exclamation Mark -> !
+            (char)0xff02, (char)0x0022,    // Fullwidth Quotation Mark -> "
+            (char)0xff03, (char)0x0023,    // Fullwidth Number Sign -> #
+            (char)0xff04, (char)0x0024,    // Fullwidth Dollar Sign -> $
+            (char)0xff05, (char)0x0025,    // Fullwidth Percent Sign -> %
+            (char)0xff06, (char)0x0026,    // Fullwidth Ampersand -> &
+            (char)0xff07, (char)0x0027,    // Fullwidth Apostrophe -> '
+            (char)0xff08, (char)0x0028,    // Fullwidth Left Parenthesis -> (
+            (char)0xff09, (char)0x0029,    // Fullwidth Right Parenthesis -> )
+            (char)0xff0a, (char)0x002a,    // Fullwidth Asterisk -> *
+            (char)0xff0b, (char)0x002b,    // Fullwidth Plus Sign -> +
+            (char)0xff0c, (char)0x002c,    // Fullwidth Comma -> ,
+            (char)0xff0d, (char)0x002d,    // Fullwidth Hyphen-Minus -> -
+            (char)0xff0e, (char)0x002e,    // Fullwidth Full Stop -> .
+            (char)0xff0f, (char)0x002f,    // Fullwidth Solidus -> /
+            (char)0xff10, (char)0x0030,    // Fullwidth Digit Zero -> 0
+            (char)0xff11, (char)0x0031,    // Fullwidth Digit One -> 1
+            (char)0xff12, (char)0x0032,    // Fullwidth Digit Two -> 2
+            (char)0xff13, (char)0x0033,    // Fullwidth Digit Three -> 3
+            (char)0xff14, (char)0x0034,    // Fullwidth Digit Four -> 4
+            (char)0xff15, (char)0x0035,    // Fullwidth Digit Five -> 5
+            (char)0xff16, (char)0x0036,    // Fullwidth Digit Six -> 6
+            (char)0xff17, (char)0x0037,    // Fullwidth Digit Seven -> 7
+            (char)0xff18, (char)0x0038,    // Fullwidth Digit Eight -> 8
+            (char)0xff19, (char)0x0039,    // Fullwidth Digit Nine -> 9
+            (char)0xff1a, (char)0x003a,    // Fullwidth Colon -> :
+            (char)0xff1b, (char)0x003b,    // Fullwidth Semicolon -> ;
+            (char)0xff1c, (char)0x003c,    // Fullwidth Less-Than Sign -> <
+            (char)0xff1d, (char)0x003d,    // Fullwidth Equals Sign -> =
+            (char)0xff1e, (char)0x003e,    // Fullwidth Greater-Than Sign -> >
+            (char)0xff1f, (char)0x003f,    // Fullwidth Question Mark
+            (char)0xff20, (char)0x0040,    // Fullwidth Commercial At -> @
+            (char)0xff21, (char)0x0041,    // Fullwidth Latin Capital Letter A -> A
+            (char)0xff22, (char)0x0042,    // Fullwidth Latin Capital Letter B -> B
+            (char)0xff23, (char)0x0043,    // Fullwidth Latin Capital Letter C -> C
+            (char)0xff24, (char)0x0044,    // Fullwidth Latin Capital Letter D -> D
+            (char)0xff25, (char)0x0045,    // Fullwidth Latin Capital Letter E -> E
+            (char)0xff26, (char)0x0046,    // Fullwidth Latin Capital Letter F -> F
+            (char)0xff27, (char)0x0047,    // Fullwidth Latin Capital Letter G -> G
+            (char)0xff28, (char)0x0048,    // Fullwidth Latin Capital Letter H -> H
+            (char)0xff29, (char)0x0049,    // Fullwidth Latin Capital Letter I -> I
+            (char)0xff2a, (char)0x004a,    // Fullwidth Latin Capital Letter J -> J
+            (char)0xff2b, (char)0x004b,    // Fullwidth Latin Capital Letter K -> K
+            (char)0xff2c, (char)0x004c,    // Fullwidth Latin Capital Letter L -> L
+            (char)0xff2d, (char)0x004d,    // Fullwidth Latin Capital Letter M -> M
+            (char)0xff2e, (char)0x004e,    // Fullwidth Latin Capital Letter N -> N
+            (char)0xff2f, (char)0x004f,    // Fullwidth Latin Capital Letter O -> O
+            (char)0xff30, (char)0x0050,    // Fullwidth Latin Capital Letter P -> P
+            (char)0xff31, (char)0x0051,    // Fullwidth Latin Capital Letter Q -> Q
+            (char)0xff32, (char)0x0052,    // Fullwidth Latin Capital Letter R -> R
+            (char)0xff33, (char)0x0053,    // Fullwidth Latin Capital Letter S -> S
+            (char)0xff34, (char)0x0054,    // Fullwidth Latin Capital Letter T -> T
+            (char)0xff35, (char)0x0055,    // Fullwidth Latin Capital Letter U -> U
+            (char)0xff36, (char)0x0056,    // Fullwidth Latin Capital Letter V -> V
+            (char)0xff37, (char)0x0057,    // Fullwidth Latin Capital Letter W -> W
+            (char)0xff38, (char)0x0058,    // Fullwidth Latin Capital Letter X -> X
+            (char)0xff39, (char)0x0059,    // Fullwidth Latin Capital Letter Y -> Y
+            (char)0xff3a, (char)0x005a,    // Fullwidth Latin Capital Letter Z -> Z
+            (char)0xff3b, (char)0x005b,    // Fullwidth Left Square Bracket -> [
+            (char)0xff3c, (char)0x005c,    // Fullwidth Reverse Solidus -> \
+            (char)0xff3d, (char)0x005d,    // Fullwidth Right Square Bracket -> ]
+            (char)0xff3e, (char)0x005e,    // Fullwidth Circumflex Accent -> ^
+            (char)0xff3f, (char)0x005f,    // Fullwidth Low Line -> _
+            (char)0xff40, (char)0x0060,    // Fullwidth Grave Accent -> `
+            (char)0xff41, (char)0x0061,    // Fullwidth Latin Small Letter A -> a
+            (char)0xff42, (char)0x0062,    // Fullwidth Latin Small Letter B -> b
+            (char)0xff43, (char)0x0063,    // Fullwidth Latin Small Letter C -> c
+            (char)0xff44, (char)0x0064,    // Fullwidth Latin Small Letter D -> d
+            (char)0xff45, (char)0x0065,    // Fullwidth Latin Small Letter E -> e
+            (char)0xff46, (char)0x0066,    // Fullwidth Latin Small Letter F -> f
+            (char)0xff47, (char)0x0067,    // Fullwidth Latin Small Letter G -> g
+            (char)0xff48, (char)0x0068,    // Fullwidth Latin Small Letter H -> h
+            (char)0xff49, (char)0x0069,    // Fullwidth Latin Small Letter I -> i
+            (char)0xff4a, (char)0x006a,    // Fullwidth Latin Small Letter J -> j
+            (char)0xff4b, (char)0x006b,    // Fullwidth Latin Small Letter K -> k
+            (char)0xff4c, (char)0x006c,    // Fullwidth Latin Small Letter L -> l
+            (char)0xff4d, (char)0x006d,    // Fullwidth Latin Small Letter M -> m
+            (char)0xff4e, (char)0x006e,    // Fullwidth Latin Small Letter N -> n
+            (char)0xff4f, (char)0x006f,    // Fullwidth Latin Small Letter O -> o
+            (char)0xff50, (char)0x0070,    // Fullwidth Latin Small Letter P -> p
+            (char)0xff51, (char)0x0071,    // Fullwidth Latin Small Letter Q -> q
+            (char)0xff52, (char)0x0072,    // Fullwidth Latin Small Letter R -> r
+            (char)0xff53, (char)0x0073,    // Fullwidth Latin Small Letter S -> s
+            (char)0xff54, (char)0x0074,    // Fullwidth Latin Small Letter T -> t
+            (char)0xff55, (char)0x0075,    // Fullwidth Latin Small Letter U -> u
+            (char)0xff56, (char)0x0076,    // Fullwidth Latin Small Letter V -> v
+            (char)0xff57, (char)0x0077,    // Fullwidth Latin Small Letter W -> w
+            (char)0xff58, (char)0x0078,    // Fullwidth Latin Small Letter X -> x
+            (char)0xff59, (char)0x0079,    // Fullwidth Latin Small Letter Y -> y
+            (char)0xff5a, (char)0x007a,    // Fullwidth Latin Small Letter Z -> z
+            (char)0xff5b, (char)0x007b,    // Fullwidth Left Curly Bracket -> {
+            (char)0xff5c, (char)0x007c,    // Fullwidth Vertical Line -> |
+            (char)0xff5d, (char)0x007d,    // Fullwidth Right Curly Bracket -> }
+            (char)0xff5e, (char)0x007e     // Fullwidth Tilde -> ~
+        };
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/NormalizationForm.cs b/src/System.Private.CoreLib/shared/System/Text/NormalizationForm.cs
new file mode 100644
index 0000000000..976756251a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/NormalizationForm.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Text
+{
+    public enum NormalizationForm
+    {
+        FormC = 1,
+        FormD = 2,
+        FormKC = 5,
+        FormKD = 6
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/StringBuilder.Debug.cs b/src/System.Private.CoreLib/shared/System/Text/StringBuilder.Debug.cs
new file mode 100644
index 0000000000..a62c4777ad
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/StringBuilder.Debug.cs
@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Text
+{
+    public sealed partial class StringBuilder
+    {
+        private void ShowChunks(int maxChunksToShow = 10)
+        {
+            int count = 0;
+            StringBuilder head = this, current = this;
+            while (current != null)
+            {
+                if (count < maxChunksToShow)
+                {
+                    count++;
+                }
+                else
+                {
+                    head = head.m_ChunkPrevious;
+                }
+                current = current.m_ChunkPrevious;
+            }
+            current = head;
+            string[] chunks = new string[count];
+            for (int i = count; i > 0; i--)
+            {
+                chunks[i - 1] = new string(current.m_ChunkChars).Replace('\0', '.');
+                current = current.m_ChunkPrevious;
+            }
+            Debug.WriteLine('|' + string.Join('|', chunks) + '|');
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/StringBuilder.cs b/src/System.Private.CoreLib/shared/System/Text/StringBuilder.cs
new file mode 100644
index 0000000000..8c1e045216
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/StringBuilder.cs
@@ -0,0 +1,2445 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text;
+using System.Runtime;
+using System.Runtime.Serialization;
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+using System.Security;
+using System.Threading;
+using System.Globalization;
+using System.Diagnostics;
+using System.Collections.Generic;
+
+namespace System.Text
+{
+    // This class represents a mutable string.  It is convenient for situations in
+    // which it is desirable to modify a string, perhaps by removing, replacing, or
+    // inserting characters, without creating a new String subsequent to
+    // each modification.
+    //
+    // The methods contained within this class do not return a new StringBuilder
+    // object unless specified otherwise.  This class may be used in conjunction with the String
+    // class to carry out modifications upon strings.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed partial class StringBuilder : ISerializable
+    {
+        // A StringBuilder is internally represented as a linked list of blocks each of which holds
+        // a chunk of the string.  It turns out string as a whole can also be represented as just a chunk,
+        // so that is what we do.
+
+        /// <summary>
+        /// The character buffer for this chunk.
+        /// </summary>
+        internal char[] m_ChunkChars;
+
+        /// <summary>
+        /// The chunk that logically precedes this chunk.
+        /// </summary>
+        internal StringBuilder m_ChunkPrevious;
+
+        /// <summary>
+        /// The number of characters in this chunk.
+        /// This is the number of elements in <see cref="m_ChunkChars"/> that are in use, from the start of the buffer.
+        /// </summary>
+        internal int m_ChunkLength;
+
+        /// <summary>
+        /// The logical offset of this chunk's characters in the string it is a part of.
+        /// This is the sum of the number of characters in preceding blocks.
+        /// </summary>
+        internal int m_ChunkOffset;
+
+        /// <summary>
+        /// The maximum capacity this builder is allowed to have.
+        /// </summary>
+        internal int m_MaxCapacity;
+
+        /// <summary>
+        /// The default capacity of a <see cref="StringBuilder"/>.
+        /// </summary>
+        internal const int DefaultCapacity = 16;
+
+        private const string CapacityField = "Capacity"; // Do not rename (binary serialization)
+        private const string MaxCapacityField = "m_MaxCapacity"; // Do not rename (binary serialization)
+        private const string StringValueField = "m_StringValue"; // Do not rename (binary serialization)
+        private const string ThreadIDField = "m_currentThread"; // Do not rename (binary serialization)
+
+        // We want to keep chunk arrays out of large object heap (< 85K bytes ~ 40K chars) to be sure.
+        // Making the maximum chunk size big means less allocation code called, but also more waste
+        // in unused characters and slower inserts / replaces (since you do need to slide characters over
+        // within a buffer).
+        internal const int MaxChunkSize = 8000;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="StringBuilder"/> class.
+        /// </summary>
+        public StringBuilder()
+        {
+            m_MaxCapacity = int.MaxValue;
+            m_ChunkChars = new char[DefaultCapacity];
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="StringBuilder"/> class.
+        /// </summary>
+        /// <param name="capacity">The initial capacity of this builder.</param>
+        public StringBuilder(int capacity)
+            : this(capacity, int.MaxValue)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="StringBuilder"/> class.
+        /// </summary>
+        /// <param name="value">The initial contents of this builder.</param>
+        public StringBuilder(string value)
+            : this(value, DefaultCapacity)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="StringBuilder"/> class.
+        /// </summary>
+        /// <param name="value">The initial contents of this builder.</param>
+        /// <param name="capacity">The initial capacity of this builder.</param>
+        public StringBuilder(string value, int capacity)
+            : this(value, 0, value?.Length ?? 0, capacity)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="StringBuilder"/> class.
+        /// </summary>
+        /// <param name="value">The initial contents of this builder.</param>
+        /// <param name="startIndex">The index to start in <paramref name="value"/>.</param>
+        /// <param name="length">The number of characters to read in <paramref name="value"/>.</param>
+        /// <param name="capacity">The initial capacity of this builder.</param>
+        public StringBuilder(string value, int startIndex, int length, int capacity)
+        {
+            if (capacity < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(capacity), SR.Format(SR.ArgumentOutOfRange_MustBePositive, nameof(capacity)));
+            }
+            if (length < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(length), SR.Format(SR.ArgumentOutOfRange_MustBeNonNegNum, nameof(length)));
+            }
+            if (startIndex < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndex);
+            }
+
+            if (value == null)
+            {
+                value = string.Empty;
+            }
+            if (startIndex > value.Length - length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_IndexLength);
+            }
+
+            m_MaxCapacity = int.MaxValue;
+            if (capacity == 0)
+            {
+                capacity = DefaultCapacity;
+            }
+            capacity = Math.Max(capacity, length);
+
+            m_ChunkChars = new char[capacity];
+            m_ChunkLength = length;
+
+            unsafe
+            {
+                fixed (char* sourcePtr = value)
+                {
+                    ThreadSafeCopy(sourcePtr + startIndex, m_ChunkChars, 0, length);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="StringBuilder"/> class.
+        /// </summary>
+        /// <param name="capacity">The initial capacity of this builder.</param>
+        /// <param name="maxCapacity">The maximum capacity of this builder.</param>
+        public StringBuilder(int capacity, int maxCapacity)
+        {
+            if (capacity > maxCapacity)
+            {
+                throw new ArgumentOutOfRangeException(nameof(capacity), SR.ArgumentOutOfRange_Capacity);
+            }
+            if (maxCapacity < 1)
+            {
+                throw new ArgumentOutOfRangeException(nameof(maxCapacity), SR.ArgumentOutOfRange_SmallMaxCapacity);
+            }
+            if (capacity < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(capacity), SR.Format(SR.ArgumentOutOfRange_MustBePositive, nameof(capacity)));
+            }
+
+            if (capacity == 0)
+            {
+                capacity = Math.Min(DefaultCapacity, maxCapacity);
+            }
+
+            m_MaxCapacity = maxCapacity;
+            m_ChunkChars = new char[capacity];
+        }
+
+        private StringBuilder(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+
+            int persistedCapacity = 0;
+            string persistedString = null;
+            int persistedMaxCapacity = Int32.MaxValue;
+            bool capacityPresent = false;
+
+            // Get the data
+            SerializationInfoEnumerator enumerator = info.GetEnumerator();
+            while (enumerator.MoveNext())
+            {
+                switch (enumerator.Name)
+                {
+                    case MaxCapacityField:
+                        persistedMaxCapacity = info.GetInt32(MaxCapacityField);
+                        break;
+                    case StringValueField:
+                        persistedString = info.GetString(StringValueField);
+                        break;
+                    case CapacityField:
+                        persistedCapacity = info.GetInt32(CapacityField);
+                        capacityPresent = true;
+                        break;
+                    default:
+                        // Ignore other fields for forwards-compatibility.
+                        break;
+                }
+            }
+
+            // Check values and set defaults
+            if (persistedString == null)
+            {
+                persistedString = string.Empty;
+            }
+            if (persistedMaxCapacity < 1 || persistedString.Length > persistedMaxCapacity)
+            {
+                throw new SerializationException(SR.Serialization_StringBuilderMaxCapacity);
+            }
+
+            if (!capacityPresent)
+            {
+                // StringBuilder in V1.X did not persist the Capacity, so this is a valid legacy code path.
+                persistedCapacity = Math.Min(Math.Max(DefaultCapacity, persistedString.Length), persistedMaxCapacity);
+            }
+
+            if (persistedCapacity < 0 || persistedCapacity < persistedString.Length || persistedCapacity > persistedMaxCapacity)
+            {
+                throw new SerializationException(SR.Serialization_StringBuilderCapacity);
+            }
+
+            // Assign
+            m_MaxCapacity = persistedMaxCapacity;
+            m_ChunkChars = new char[persistedCapacity];
+            persistedString.CopyTo(0, m_ChunkChars, 0, persistedString.Length);
+            m_ChunkLength = persistedString.Length;
+            m_ChunkPrevious = null;
+            AssertInvariants();
+        }
+
+        void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+
+            AssertInvariants();
+            info.AddValue(MaxCapacityField, m_MaxCapacity);
+            info.AddValue(CapacityField, Capacity);
+            info.AddValue(StringValueField, ToString());
+            // Note: persist "m_currentThread" to be compatible with old versions
+            info.AddValue(ThreadIDField, 0);
+        }
+
+        [System.Diagnostics.Conditional("DEBUG")]
+        private void AssertInvariants()
+        {
+            Debug.Assert(m_ChunkOffset + m_ChunkChars.Length >= m_ChunkOffset, "The length of the string is greater than int.MaxValue.");
+
+            StringBuilder currentBlock = this;
+            int maxCapacity = this.m_MaxCapacity;
+            for (;;)
+            {
+                // All blocks have the same max capacity.
+                Debug.Assert(currentBlock.m_MaxCapacity == maxCapacity);
+                Debug.Assert(currentBlock.m_ChunkChars != null);
+
+                Debug.Assert(currentBlock.m_ChunkLength <= currentBlock.m_ChunkChars.Length);
+                Debug.Assert(currentBlock.m_ChunkLength >= 0);
+                Debug.Assert(currentBlock.m_ChunkOffset >= 0);
+
+                StringBuilder prevBlock = currentBlock.m_ChunkPrevious;
+                if (prevBlock == null)
+                {
+                    Debug.Assert(currentBlock.m_ChunkOffset == 0);
+                    break;
+                }
+                // There are no gaps in the blocks.
+                Debug.Assert(currentBlock.m_ChunkOffset == prevBlock.m_ChunkOffset + prevBlock.m_ChunkLength);
+                currentBlock = prevBlock;
+            }
+        }
+
+        public int Capacity
+        {
+            get { return m_ChunkChars.Length + m_ChunkOffset; }
+            set
+            {
+                if (value < 0)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_NegativeCapacity);
+                }
+                if (value > MaxCapacity)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_Capacity);
+                }
+                if (value < Length)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_SmallCapacity);
+                }
+
+                if (Capacity != value)
+                {
+                    int newLen = value - m_ChunkOffset;
+                    char[] newArray = new char[newLen];
+                    Array.Copy(m_ChunkChars, 0, newArray, 0, m_ChunkLength);
+                    m_ChunkChars = newArray;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets the maximum capacity this builder is allowed to have.
+        /// </summary>
+        public int MaxCapacity => m_MaxCapacity;
+
+        /// <summary>
+        /// Ensures that the capacity of this builder is at least the specified value.
+        /// </summary>
+        /// <param name="capacity">The new capacity for this builder.</param>
+        /// <remarks>
+        /// If <paramref name="capacity"/> is less than or equal to the current capacity of
+        /// this builder, the capacity remains unchanged.
+        /// </remarks>
+        public int EnsureCapacity(int capacity)
+        {
+            if (capacity < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(capacity), SR.ArgumentOutOfRange_NegativeCapacity);
+            }
+
+            if (Capacity < capacity)
+                Capacity = capacity;
+            return Capacity;
+        }
+
+        public override String ToString()
+        {
+            AssertInvariants();
+
+            if (Length == 0)
+            {
+                return string.Empty;
+            }
+
+            string result = string.FastAllocateString(Length);
+            StringBuilder chunk = this;
+            unsafe
+            {
+                fixed (char* destinationPtr = result)
+                {
+                    do
+                    {
+                        if (chunk.m_ChunkLength > 0)
+                        {
+                            // Copy these into local variables so that they are stable even in the presence of race conditions
+                            char[] sourceArray = chunk.m_ChunkChars;
+                            int chunkOffset = chunk.m_ChunkOffset;
+                            int chunkLength = chunk.m_ChunkLength;
+
+                            // Check that we will not overrun our boundaries.
+                            if ((uint)(chunkLength + chunkOffset) <= (uint)result.Length && (uint)chunkLength <= (uint)sourceArray.Length)
+                            {
+                                fixed (char* sourcePtr = &sourceArray[0])
+                                    string.wstrcpy(destinationPtr + chunkOffset, sourcePtr, chunkLength);
+                            }
+                            else
+                            {
+                                throw new ArgumentOutOfRangeException(nameof(chunkLength), SR.ArgumentOutOfRange_Index);
+                            }
+                        }
+                        chunk = chunk.m_ChunkPrevious;
+                    }
+                    while (chunk != null);
+
+                    return result;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Creates a string from a substring of this builder.
+        /// </summary>
+        /// <param name="startIndex">The index to start in this builder.</param>
+        /// <param name="length">The number of characters to read in this builder.</param>
+        public string ToString(int startIndex, int length)
+        {
+            int currentLength = this.Length;
+            if (startIndex < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndex);
+            }
+            if (startIndex > currentLength)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndexLargerThanLength);
+            }
+            if (length < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_NegativeLength);
+            }
+            if (startIndex > currentLength - length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_IndexLength);
+            }
+
+            AssertInvariants();
+            string result = string.FastAllocateString(length);
+            unsafe
+            {
+                fixed (char* destinationPtr = result)
+                {
+                    this.CopyTo(startIndex, new Span<char>(destinationPtr, length), length);
+                    return result;
+                }
+            }
+        }
+
+        public StringBuilder Clear()
+        {
+            this.Length = 0;
+            return this;
+        }
+
+        /// <summary>
+        /// Gets or sets the length of this builder.
+        /// </summary>
+        public int Length
+        {
+            get
+            {
+                return m_ChunkOffset + m_ChunkLength;
+            }
+            set
+            {
+                //If the new length is less than 0 or greater than our Maximum capacity, bail.
+                if (value < 0)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_NegativeLength);
+                }
+
+                if (value > MaxCapacity)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_SmallCapacity);
+                }
+
+                if (value == 0 && m_ChunkPrevious == null)
+                {
+                    m_ChunkLength = 0;
+                    m_ChunkOffset = 0;
+                    return;
+                }
+
+                int delta = value - Length;
+                if (delta > 0)
+                {
+                    // Pad ourselves with null characters.
+                    Append('\0', delta);
+                }
+                else
+                {
+                    StringBuilder chunk = FindChunkForIndex(value);
+                    if (chunk != this)
+                    {
+                        // Avoid possible infinite capacity growth.  See https://github.com/dotnet/coreclr/pull/16926
+                        int capacityToPreserve = Math.Min(Capacity, Math.Max(Length * 6 / 5, m_ChunkChars.Length));
+                        int newLen = capacityToPreserve - chunk.m_ChunkOffset;
+                        if (newLen > chunk.m_ChunkChars.Length)
+                        {
+                            // We crossed a chunk boundary when reducing the Length. We must replace this middle-chunk with a new larger chunk,
+                            // to ensure the capacity we want is preserved.
+                            char[] newArray = new char[newLen];
+                            Array.Copy(chunk.m_ChunkChars, 0, newArray, 0, chunk.m_ChunkLength);
+                            m_ChunkChars = newArray;
+                        }
+                        else
+                        {
+                            // Special case where the capacity we want to keep corresponds exactly to the size of the content.
+                            // Just take ownership of the array.
+                            Debug.Assert(newLen == chunk.m_ChunkChars.Length, "The new chunk should be larger or equal to the one it is replacing.");
+                            m_ChunkChars = chunk.m_ChunkChars;
+                        }
+
+                        m_ChunkPrevious = chunk.m_ChunkPrevious;
+                        m_ChunkOffset = chunk.m_ChunkOffset;
+                    }
+                    m_ChunkLength = value - chunk.m_ChunkOffset;
+                    AssertInvariants();
+                }
+                Debug.Assert(Length == value, "Something went wrong setting Length.");
+            }
+        }
+
+        [IndexerName("Chars")]
+        public char this[int index]
+        {
+            get
+            {
+                StringBuilder chunk = this;
+                for (;;)
+                {
+                    int indexInBlock = index - chunk.m_ChunkOffset;
+                    if (indexInBlock >= 0)
+                    {
+                        if (indexInBlock >= chunk.m_ChunkLength)
+                        {
+                            throw new IndexOutOfRangeException();
+                        }
+                        return chunk.m_ChunkChars[indexInBlock];
+                    }
+                    chunk = chunk.m_ChunkPrevious;
+                    if (chunk == null)
+                    {
+                        throw new IndexOutOfRangeException();
+                    }
+                }
+            }
+            set
+            {
+                StringBuilder chunk = this;
+                for (;;)
+                {
+                    int indexInBlock = index - chunk.m_ChunkOffset;
+                    if (indexInBlock >= 0)
+                    {
+                        if (indexInBlock >= chunk.m_ChunkLength)
+                        {
+                            throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+                        }
+                        chunk.m_ChunkChars[indexInBlock] = value;
+                        return;
+                    }
+                    chunk = chunk.m_ChunkPrevious;
+                    if (chunk == null)
+                    {
+                        throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Appends a character 0 or more times to the end of this builder.
+        /// </summary>
+        /// <param name="value">The character to append.</param>
+        /// <param name="repeatCount">The number of times to append <paramref name="value"/>.</param>
+        public StringBuilder Append(char value, int repeatCount)
+        {
+            if (repeatCount < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(repeatCount), SR.ArgumentOutOfRange_NegativeCount);
+            }
+
+            if (repeatCount == 0)
+            {
+                return this;
+            }
+
+            // this is where we can check if the repeatCount will put us over m_MaxCapacity
+            // We are doing the check here to prevent the corruption of the StringBuilder.
+            int newLength = Length + repeatCount;
+            if (newLength > m_MaxCapacity || newLength < repeatCount)
+            {
+                throw new ArgumentOutOfRangeException(nameof(repeatCount), SR.ArgumentOutOfRange_LengthGreaterThanCapacity);
+            }
+
+            int index = m_ChunkLength;
+            while (repeatCount > 0)
+            {
+                if (index < m_ChunkChars.Length)
+                {
+                    m_ChunkChars[index++] = value;
+                    --repeatCount;
+                }
+                else
+                {
+                    m_ChunkLength = index;
+                    ExpandByABlock(repeatCount);
+                    Debug.Assert(m_ChunkLength == 0);
+                    index = 0;
+                }
+            }
+
+            m_ChunkLength = index;
+            AssertInvariants();
+            return this;
+        }
+
+        /// <summary>
+        /// Appends a range of characters to the end of this builder.
+        /// </summary>
+        /// <param name="value">The characters to append.</param>
+        /// <param name="startIndex">The index to start in <paramref name="value"/>.</param>
+        /// <param name="charCount">The number of characters to read in <paramref name="value"/>.</param>
+        public StringBuilder Append(char[] value, int startIndex, int charCount)
+        {
+            if (startIndex < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_GenericPositive);
+            }
+            if (charCount < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(charCount), SR.ArgumentOutOfRange_GenericPositive);
+            }
+
+            if (value == null)
+            {
+                if (startIndex == 0 && charCount == 0)
+                {
+                    return this;
+                }
+
+                throw new ArgumentNullException(nameof(value));
+            }
+            if (charCount > value.Length - startIndex)
+            {
+                throw new ArgumentOutOfRangeException(nameof(charCount), SR.ArgumentOutOfRange_Index);
+            }
+
+            if (charCount == 0)
+            {
+                return this;
+            }
+
+            unsafe
+            {
+                fixed (char* valueChars = &value[startIndex])
+                {
+                    Append(valueChars, charCount);
+                    return this;
+                }
+            }
+        }
+
+
+        /// <summary>
+        /// Appends a string to the end of this builder.
+        /// </summary>
+        /// <param name="value">The string to append.</param>
+        public StringBuilder Append(String value)
+        {
+            if (value != null)
+            {
+                // We could have just called AppendHelper here; this is a hand-specialization of that code.
+                char[] chunkChars = m_ChunkChars;
+                int chunkLength = m_ChunkLength;
+                int valueLen = value.Length;
+                int newCurrentIndex = chunkLength + valueLen;
+
+                if (newCurrentIndex < chunkChars.Length) // Use strictly < to avoid issues if count == 0, newIndex == length
+                {
+                    if (valueLen <= 2)
+                    {
+                        if (valueLen > 0)
+                            chunkChars[chunkLength] = value[0];
+                        if (valueLen > 1)
+                            chunkChars[chunkLength + 1] = value[1];
+                    }
+                    else
+                    {
+                        unsafe
+                        {
+                            fixed (char* valuePtr = value)
+                            fixed (char* destPtr = &chunkChars[chunkLength])
+                            {
+                                string.wstrcpy(destPtr, valuePtr, valueLen);
+                            }
+                        }
+                    }
+
+                    m_ChunkLength = newCurrentIndex;
+                }
+                else
+                {
+                    AppendHelper(value);
+                }
+            }
+
+            return this;
+        }
+
+        // We put this fixed in its own helper to avoid the cost of zero-initing `valueChars` in the
+        // case we don't actually use it.
+        private void AppendHelper(string value)
+        {
+            unsafe
+            {
+                fixed (char* valueChars = value)
+                {
+                    Append(valueChars, value.Length);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Appends part of a string to the end of this builder.
+        /// </summary>
+        /// <param name="value">The string to append.</param>
+        /// <param name="startIndex">The index to start in <paramref name="value"/>.</param>
+        /// <param name="count">The number of characters to read in <paramref name="value"/>.</param>
+        public StringBuilder Append(string value, int startIndex, int count)
+        {
+            if (startIndex < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+            }
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_GenericPositive);
+            }
+
+            if (value == null)
+            {
+                if (startIndex == 0 && count == 0)
+                {
+                    return this;
+                }
+                throw new ArgumentNullException(nameof(value));
+            }
+
+            if (count == 0)
+            {
+                return this;
+            }
+
+            if (startIndex > value.Length - count)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+            }
+
+            unsafe
+            {
+                fixed (char* valueChars = value)
+                {
+                    Append(valueChars + startIndex, count);
+                    return this;
+                }
+            }
+        }
+
+        public StringBuilder Append(StringBuilder value)
+        {
+            if (value != null && value.Length != 0)
+            {
+                return AppendCore(value, 0, value.Length);
+            }
+            return this;
+        }
+
+        public StringBuilder Append(StringBuilder value, int startIndex, int count)
+        {
+            if (startIndex < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+            }
+
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_GenericPositive);
+            }
+
+            if (value == null)
+            {
+                if (startIndex == 0 && count == 0)
+                {
+                    return this;
+                }
+                throw new ArgumentNullException(nameof(value));
+            }
+
+            if (count == 0)
+            {
+                return this;
+            }
+
+            if (count > value.Length - startIndex)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+            }
+
+            return AppendCore(value, startIndex, count);
+        }
+
+        private StringBuilder AppendCore(StringBuilder value, int startIndex, int count)
+        {
+            if (value == this)
+                return Append(value.ToString(startIndex, count));
+
+            int newLength = Length + count;
+
+            if ((uint)newLength > (uint)m_MaxCapacity)
+            {
+                throw new ArgumentOutOfRangeException(nameof(Capacity), SR.ArgumentOutOfRange_Capacity);
+            }
+
+            while (count > 0)
+            {
+                int length = Math.Min(m_ChunkChars.Length - m_ChunkLength, count);
+                if (length == 0)
+                {
+                    ExpandByABlock(count);
+                    length = Math.Min(m_ChunkChars.Length - m_ChunkLength, count);
+                }
+                value.CopyTo(startIndex, new Span<char>(m_ChunkChars, m_ChunkLength, length), length);
+
+                m_ChunkLength += length;
+                startIndex += length;
+                count -= length;
+            }
+
+            return this;
+        }
+
+        public StringBuilder AppendLine() => Append(Environment.NewLine);
+
+        public StringBuilder AppendLine(string value)
+        {
+            Append(value);
+            return Append(Environment.NewLine);
+        }
+
+        public void CopyTo(int sourceIndex, char[] destination, int destinationIndex, int count)
+        {
+            if (destination == null)
+            {
+                throw new ArgumentNullException(nameof(destination));
+            }
+
+            if (destinationIndex < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(destinationIndex), SR.Format(SR.ArgumentOutOfRange_MustBeNonNegNum, nameof(destinationIndex)));
+            }
+
+            if (destinationIndex > destination.Length - count)
+            {
+                throw new ArgumentException(SR.ArgumentOutOfRange_OffsetOut);
+            }
+
+            CopyTo(sourceIndex, new Span<char>(destination).Slice(destinationIndex), count);
+        }
+
+        public void CopyTo(int sourceIndex, Span<char> destination, int count)
+        {
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.Arg_NegativeArgCount);
+            }
+
+            if ((uint)sourceIndex > (uint)Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(sourceIndex), SR.ArgumentOutOfRange_Index);
+            }
+
+            if (sourceIndex > Length - count)
+            {
+                throw new ArgumentException(SR.Arg_LongerThanSrcString);
+            }
+
+            AssertInvariants();
+
+            StringBuilder chunk = this;
+            int sourceEndIndex = sourceIndex + count;
+            int curDestIndex = count;
+            while (count > 0)
+            {
+                int chunkEndIndex = sourceEndIndex - chunk.m_ChunkOffset;
+                if (chunkEndIndex >= 0)
+                {
+                    chunkEndIndex = Math.Min(chunkEndIndex, chunk.m_ChunkLength);
+
+                    int chunkCount = count;
+                    int chunkStartIndex = chunkEndIndex - count;
+                    if (chunkStartIndex < 0)
+                    {
+                        chunkCount += chunkStartIndex;
+                        chunkStartIndex = 0;
+                    }
+                    curDestIndex -= chunkCount;
+                    count -= chunkCount;
+
+                    // We ensure that chunkStartIndex + chunkCount are within range of m_chunkChars as well as
+                    // ensuring that curDestIndex + chunkCount are within range of destination
+                    ThreadSafeCopy(chunk.m_ChunkChars, chunkStartIndex, destination, curDestIndex, chunkCount);
+                }
+                chunk = chunk.m_ChunkPrevious;
+            }
+        }
+
+        /// <summary>
+        /// Inserts a string 0 or more times into this builder at the specified position.
+        /// </summary>
+        /// <param name="index">The index to insert in this builder.</param>
+        /// <param name="value">The string to insert.</param>
+        /// <param name="count">The number of times to insert the string.</param>
+        public StringBuilder Insert(int index, String value, int count)
+        {
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            int currentLength = Length;
+            if ((uint)index > (uint)currentLength)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+            }
+
+            if (string.IsNullOrEmpty(value) || count == 0)
+            {
+                return this;
+            }
+
+            // Ensure we don't insert more chars than we can hold, and we don't
+            // have any integer overflow in our new length.
+            long insertingChars = (long)value.Length * count;
+            if (insertingChars > MaxCapacity - this.Length)
+            {
+                throw new OutOfMemoryException();
+            }
+            Debug.Assert(insertingChars + this.Length < int.MaxValue);
+
+            StringBuilder chunk;
+            int indexInChunk;
+            MakeRoom(index, (int)insertingChars, out chunk, out indexInChunk, false);
+            unsafe
+            {
+                fixed (char* valuePtr = value)
+                {
+                    while (count > 0)
+                    {
+                        ReplaceInPlaceAtChunk(ref chunk, ref indexInChunk, valuePtr, value.Length);
+                        --count;
+                    }
+
+                    return this;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Removes a range of characters from this builder.
+        /// </summary>
+        /// <remarks>
+        /// This method does not reduce the capacity of this builder.
+        /// </remarks>
+        public StringBuilder Remove(int startIndex, int length)
+        {
+            if (length < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_NegativeLength);
+            }
+
+            if (startIndex < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndex);
+            }
+
+            if (length > Length - startIndex)
+            {
+                throw new ArgumentOutOfRangeException(nameof(length), SR.ArgumentOutOfRange_Index);
+            }
+
+            if (Length == length && startIndex == 0)
+            {
+                Length = 0;
+                return this;
+            }
+
+            if (length > 0)
+            {
+                StringBuilder chunk;
+                int indexInChunk;
+                Remove(startIndex, length, out chunk, out indexInChunk);
+            }
+
+            return this;
+        }
+
+        public StringBuilder Append(bool value) => Append(value.ToString());
+
+        public StringBuilder Append(char value)
+        {
+            if (m_ChunkLength < m_ChunkChars.Length)
+            {
+                m_ChunkChars[m_ChunkLength++] = value;
+            }
+            else
+            {
+                Append(value, 1);
+            }
+
+            return this;
+        }
+
+        [CLSCompliant(false)]
+        public StringBuilder Append(sbyte value) => AppendSpanFormattable(value);
+
+        public StringBuilder Append(byte value) => AppendSpanFormattable(value);
+
+        public StringBuilder Append(short value) => AppendSpanFormattable(value);
+
+        public StringBuilder Append(int value) => AppendSpanFormattable(value);
+
+        public StringBuilder Append(long value) => AppendSpanFormattable(value);
+
+        public StringBuilder Append(float value) => AppendSpanFormattable(value);
+
+        public StringBuilder Append(double value) => AppendSpanFormattable(value);
+
+        public StringBuilder Append(decimal value) => AppendSpanFormattable(value);
+
+        [CLSCompliant(false)]
+        public StringBuilder Append(ushort value) => AppendSpanFormattable(value);
+
+        [CLSCompliant(false)]
+        public StringBuilder Append(uint value) => AppendSpanFormattable(value);
+
+        [CLSCompliant(false)]
+        public StringBuilder Append(ulong value) => AppendSpanFormattable(value);
+
+        private StringBuilder AppendSpanFormattable<T>(T value) where T : ISpanFormattable
+        {
+            if (value.TryFormat(RemainingCurrentChunk, out int charsWritten, format: default, provider: null))
+            {
+                m_ChunkLength += charsWritten;
+                return this;
+            }
+
+            return Append(value.ToString());
+        }
+
+        public StringBuilder Append(object value) => (value == null) ? this : Append(value.ToString());
+
+        public StringBuilder Append(char[] value)
+        {
+            if (value?.Length > 0)
+            {
+                unsafe
+                {
+                    fixed (char* valueChars = &value[0])
+                    {
+                        Append(valueChars, value.Length);
+                    }
+                }
+            }
+            return this;
+        }
+
+        public StringBuilder Append(ReadOnlySpan<char> value)
+        {
+            if (value.Length > 0)
+            {
+                unsafe
+                {
+                    fixed (char* valueChars = &MemoryMarshal.GetReference(value))
+                    {
+                        Append(valueChars, value.Length);
+                    }
+                }
+            }
+            return this;
+        }
+
+        #region AppendJoin
+
+        public unsafe StringBuilder AppendJoin(string separator, params object[] values)
+        {
+            separator = separator ?? string.Empty;
+            fixed (char* pSeparator = separator)
+            {
+                return AppendJoinCore(pSeparator, separator.Length, values);
+            }
+        }
+
+        public unsafe StringBuilder AppendJoin<T>(string separator, IEnumerable<T> values)
+        {
+            separator = separator ?? string.Empty;
+            fixed (char* pSeparator = separator)
+            {
+                return AppendJoinCore(pSeparator, separator.Length, values);
+            }
+        }
+
+        public unsafe StringBuilder AppendJoin(string separator, params string[] values)
+        {
+            separator = separator ?? string.Empty;
+            fixed (char* pSeparator = separator)
+            {
+                return AppendJoinCore(pSeparator, separator.Length, values);
+            }
+        }
+
+        public unsafe StringBuilder AppendJoin(char separator, params object[] values)
+        {
+            return AppendJoinCore(&separator, 1, values);
+        }
+
+        public unsafe StringBuilder AppendJoin<T>(char separator, IEnumerable<T> values)
+        {
+            return AppendJoinCore(&separator, 1, values);
+        }
+
+        public unsafe StringBuilder AppendJoin(char separator, params string[] values)
+        {
+            return AppendJoinCore(&separator, 1, values);
+        }
+
+        private unsafe StringBuilder AppendJoinCore<T>(char* separator, int separatorLength, IEnumerable<T> values)
+        {
+            Debug.Assert(separator != null);
+            Debug.Assert(separatorLength >= 0);
+
+            if (values == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.values);
+            }
+
+            using (IEnumerator<T> en = values.GetEnumerator())
+            {
+                if (!en.MoveNext())
+                {
+                    return this;
+                }
+
+                var value = en.Current;
+                if (value != null)
+                {
+                    Append(value.ToString());
+                }
+
+                while (en.MoveNext())
+                {
+                    Append(separator, separatorLength);
+                    value = en.Current;
+                    if (value != null)
+                    {
+                        Append(value.ToString());
+                    }
+                }
+            }
+            return this;
+        }
+
+        private unsafe StringBuilder AppendJoinCore<T>(char* separator, int separatorLength, T[] values)
+        {
+            if (values == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.values);
+            }
+
+            if (values.Length == 0)
+            {
+                return this;
+            }
+
+            if (values[0] != null)
+            {
+                Append(values[0].ToString());
+            }
+
+            for (int i = 1; i < values.Length; i++)
+            {
+                Append(separator, separatorLength);
+                if (values[i] != null)
+                {
+                    Append(values[i].ToString());
+                }
+            }
+            return this;
+        }
+
+        #endregion
+
+        public StringBuilder Insert(int index, String value)
+        {
+            if ((uint)index > (uint)Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+            }
+
+            if (value != null)
+            {
+                unsafe
+                {
+                    fixed (char* sourcePtr = value)
+                        Insert(index, sourcePtr, value.Length);
+                }
+            }
+            return this;
+        }
+
+        public StringBuilder Insert(int index, bool value) => Insert(index, value.ToString(), 1);
+
+        [CLSCompliant(false)]
+        public StringBuilder Insert(int index, sbyte value) => Insert(index, value.ToString(), 1);
+
+        public StringBuilder Insert(int index, byte value) => Insert(index, value.ToString(), 1);
+
+        public StringBuilder Insert(int index, short value) => Insert(index, value.ToString(), 1);
+
+        public StringBuilder Insert(int index, char value)
+        {
+            unsafe
+            {
+                Insert(index, &value, 1);
+            }
+            return this;
+        }
+
+        public StringBuilder Insert(int index, char[] value)
+        {
+            if ((uint)index > (uint)Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+            }
+
+            if (value != null)
+                Insert(index, value, 0, value.Length);
+            return this;
+        }
+
+        public StringBuilder Insert(int index, char[] value, int startIndex, int charCount)
+        {
+            int currentLength = Length;
+            if ((uint)index > (uint)currentLength)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+            }
+
+            if (value == null)
+            {
+                if (startIndex == 0 && charCount == 0)
+                {
+                    return this;
+                }
+                throw new ArgumentNullException(nameof(value), SR.ArgumentNull_String);
+            }
+
+            if (startIndex < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_StartIndex);
+            }
+
+            if (charCount < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(charCount), SR.ArgumentOutOfRange_GenericPositive);
+            }
+
+            if (startIndex > value.Length - charCount)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+            }
+
+            if (charCount > 0)
+            {
+                unsafe
+                {
+                    fixed (char* sourcePtr = &value[startIndex])
+                        Insert(index, sourcePtr, charCount);
+                }
+            }
+            return this;
+        }
+
+        public StringBuilder Insert(int index, int value) => Insert(index, value.ToString(), 1);
+
+        public StringBuilder Insert(int index, long value) => Insert(index, value.ToString(), 1);
+
+        public StringBuilder Insert(int index, float value) => Insert(index, value.ToString(), 1);
+
+        public StringBuilder Insert(int index, double value) => Insert(index, value.ToString(), 1);
+
+        public StringBuilder Insert(int index, decimal value) => Insert(index, value.ToString(), 1);
+
+        [CLSCompliant(false)]
+        public StringBuilder Insert(int index, ushort value) => Insert(index, value.ToString(), 1);
+
+        [CLSCompliant(false)]
+        public StringBuilder Insert(int index, uint value) => Insert(index, value.ToString(), 1);
+
+        [CLSCompliant(false)]
+        public StringBuilder Insert(int index, ulong value) => Insert(index, value.ToString(), 1);
+
+        public StringBuilder Insert(int index, Object value) => (value == null) ? this : Insert(index, value.ToString(), 1);
+
+        public StringBuilder Insert(int index, ReadOnlySpan<char> value)
+        {
+            if ((uint)index > (uint)Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+            }
+
+            if (value.Length > 0)
+            {
+                unsafe
+                {
+                    fixed (char* sourcePtr = &MemoryMarshal.GetReference(value))
+                        Insert(index, sourcePtr, value.Length);
+                }
+            }
+            return this;
+        }
+
+        public StringBuilder AppendFormat(String format, Object arg0) => AppendFormatHelper(null, format, new ParamsArray(arg0));
+
+        public StringBuilder AppendFormat(String format, Object arg0, Object arg1) => AppendFormatHelper(null, format, new ParamsArray(arg0, arg1));
+
+        public StringBuilder AppendFormat(String format, Object arg0, Object arg1, Object arg2) => AppendFormatHelper(null, format, new ParamsArray(arg0, arg1, arg2));
+
+        public StringBuilder AppendFormat(String format, params Object[] args)
+        {
+            if (args == null)
+            {
+                // To preserve the original exception behavior, throw an exception about format if both
+                // args and format are null. The actual null check for format is in AppendFormatHelper.
+                string paramName = (format == null) ? nameof(format) : nameof(args);
+                throw new ArgumentNullException(paramName);
+            }
+
+            return AppendFormatHelper(null, format, new ParamsArray(args));
+        }
+
+        public StringBuilder AppendFormat(IFormatProvider provider, String format, Object arg0) => AppendFormatHelper(provider, format, new ParamsArray(arg0));
+
+        public StringBuilder AppendFormat(IFormatProvider provider, String format, Object arg0, Object arg1) => AppendFormatHelper(provider, format, new ParamsArray(arg0, arg1));
+
+        public StringBuilder AppendFormat(IFormatProvider provider, String format, Object arg0, Object arg1, Object arg2) => AppendFormatHelper(provider, format, new ParamsArray(arg0, arg1, arg2));
+
+        public StringBuilder AppendFormat(IFormatProvider provider, String format, params Object[] args)
+        {
+            if (args == null)
+            {
+                // To preserve the original exception behavior, throw an exception about format if both
+                // args and format are null. The actual null check for format is in AppendFormatHelper.
+                string paramName = (format == null) ? nameof(format) : nameof(args);
+                throw new ArgumentNullException(paramName);
+            }
+
+            return AppendFormatHelper(provider, format, new ParamsArray(args));
+        }
+
+        private static void FormatError()
+        {
+            throw new FormatException(SR.Format_InvalidString);
+        }
+
+        // Undocumented exclusive limits on the range for Argument Hole Index and Argument Hole Alignment.
+        private const int IndexLimit = 1000000; // Note:            0 <= ArgIndex < IndexLimit
+        private const int WidthLimit = 1000000; // Note:  -WidthLimit <  ArgAlign < WidthLimit
+
+        internal StringBuilder AppendFormatHelper(IFormatProvider provider, String format, ParamsArray args)
+        {
+            if (format == null)
+            {
+                throw new ArgumentNullException(nameof(format));
+            }
+
+            int pos = 0;
+            int len = format.Length;
+            char ch = '\x0';
+            StringBuilder unescapedItemFormat = null;
+
+            ICustomFormatter cf = null;
+            if (provider != null)
+            {
+                cf = (ICustomFormatter)provider.GetFormat(typeof(ICustomFormatter));
+            }
+
+            while (true)
+            {
+                while (pos < len)
+                {
+                    ch = format[pos];
+
+                    pos++;
+                    // Is it a closing brace?
+                    if (ch == '}')
+                    {
+                        // Check next character (if there is one) to see if it is escaped. eg }}
+                        if (pos < len && format[pos] == '}')
+                            pos++;
+                        else
+                            // Otherwise treat it as an error (Mismatched closing brace)
+                            FormatError();
+                    }
+                    // Is it a opening brace?
+                    if (ch == '{')
+                    {
+                        // Check next character (if there is one) to see if it is escaped. eg {{
+                        if (pos < len && format[pos] == '{')
+                            pos++;
+                        else
+                        {
+                            // Otherwise treat it as the opening brace of an Argument Hole.
+                            pos--;
+                            break;
+                        }
+                    }
+                    // If it neither then treat the character as just text.
+                    Append(ch);
+                }
+
+                //
+                // Start of parsing of Argument Hole.
+                // Argument Hole ::= { Index (, WS* Alignment WS*)? (: Formatting)? }
+                //
+                if (pos == len) break;
+
+                //
+                //  Start of parsing required Index parameter.
+                //  Index ::= ('0'-'9')+ WS*
+                //
+                pos++;
+                // If reached end of text then error (Unexpected end of text)
+                // or character is not a digit then error (Unexpected Character)
+                if (pos == len || (ch = format[pos]) < '0' || ch > '9') FormatError();
+                int index = 0;
+                do
+                {
+                    index = index * 10 + ch - '0';
+                    pos++;
+                    // If reached end of text then error (Unexpected end of text)
+                    if (pos == len) FormatError();
+                    ch = format[pos];
+                    // so long as character is digit and value of the index is less than 1000000 ( index limit )
+                }
+                while (ch >= '0' && ch <= '9' && index < IndexLimit);
+
+                // If value of index is not within the range of the arguments passed in then error (Index out of range)
+                if (index >= args.Length) throw new FormatException(SR.Format_IndexOutOfRange);
+
+                // Consume optional whitespace.
+                while (pos < len && (ch = format[pos]) == ' ') pos++;
+                // End of parsing index parameter.
+
+                //
+                //  Start of parsing of optional Alignment
+                //  Alignment ::= comma WS* minus? ('0'-'9')+ WS*
+                //
+                bool leftJustify = false;
+                int width = 0;
+                // Is the character a comma, which indicates the start of alignment parameter.
+                if (ch == ',')
+                {
+                    pos++;
+
+                    // Consume Optional whitespace
+                    while (pos < len && format[pos] == ' ') pos++;
+
+                    // If reached the end of the text then error (Unexpected end of text)
+                    if (pos == len) FormatError();
+
+                    // Is there a minus sign?
+                    ch = format[pos];
+                    if (ch == '-')
+                    {
+                        // Yes, then alignment is left justified.
+                        leftJustify = true;
+                        pos++;
+                        // If reached end of text then error (Unexpected end of text)
+                        if (pos == len) FormatError();
+                        ch = format[pos];
+                    }
+
+                    // If current character is not a digit then error (Unexpected character)
+                    if (ch < '0' || ch > '9') FormatError();
+                    // Parse alignment digits.
+                    do
+                    {
+                        width = width * 10 + ch - '0';
+                        pos++;
+                        // If reached end of text then error. (Unexpected end of text)
+                        if (pos == len) FormatError();
+                        ch = format[pos];
+                        // So long a current character is a digit and the value of width is less than 100000 ( width limit )
+                    }
+                    while (ch >= '0' && ch <= '9' && width < WidthLimit);
+                    // end of parsing Argument Alignment
+                }
+
+                // Consume optional whitespace
+                while (pos < len && (ch = format[pos]) == ' ') pos++;
+
+                //
+                // Start of parsing of optional formatting parameter.
+                //
+                Object arg = args[index];
+                String itemFormat = null;
+                ReadOnlySpan<char> itemFormatSpan = default; // used if itemFormat is null
+                // Is current character a colon? which indicates start of formatting parameter.
+                if (ch == ':')
+                {
+                    pos++;
+                    int startPos = pos;
+
+                    while (true)
+                    {
+                        // If reached end of text then error. (Unexpected end of text)
+                        if (pos == len) FormatError();
+                        ch = format[pos];
+                        pos++;
+
+                        // Is character a opening or closing brace?
+                        if (ch == '}' || ch == '{')
+                        {
+                            if (ch == '{')
+                            {
+                                // Yes, is next character also a opening brace, then treat as escaped. eg {{
+                                if (pos < len && format[pos] == '{')
+                                    pos++;
+                                else
+                                    // Error Argument Holes can not be nested.
+                                    FormatError();
+                            }
+                            else
+                            {
+                                // Yes, is next character also a closing brace, then treat as escaped. eg }}
+                                if (pos < len && format[pos] == '}')
+                                    pos++;
+                                else
+                                {
+                                    // No, then treat it as the closing brace of an Arg Hole.
+                                    pos--;
+                                    break;
+                                }
+                            }
+
+                            // Reaching here means the brace has been escaped
+                            // so we need to build up the format string in segments
+                            if (unescapedItemFormat == null)
+                            {
+                                unescapedItemFormat = new StringBuilder();
+                            }
+                            unescapedItemFormat.Append(format, startPos, pos - startPos - 1);
+                            startPos = pos;
+                        }
+                    }
+
+                    if (unescapedItemFormat == null || unescapedItemFormat.Length == 0)
+                    {
+                        if (startPos != pos)
+                        {
+                            // There was no brace escaping, extract the item format as a single string
+                            itemFormatSpan = format.AsSpan(startPos, pos - startPos);
+                        }
+                    }
+                    else
+                    {
+                        unescapedItemFormat.Append(format, startPos, pos - startPos);
+                        itemFormatSpan = itemFormat = unescapedItemFormat.ToString();
+                        unescapedItemFormat.Clear();
+                    }
+                }
+                // If current character is not a closing brace then error. (Unexpected Character)
+                if (ch != '}') FormatError();
+                // Construct the output for this arg hole.
+                pos++;
+                String s = null;
+                if (cf != null)
+                {
+                    if (itemFormatSpan.Length != 0 && itemFormat == null)
+                    {
+                        itemFormat = new string(itemFormatSpan);
+                    }
+                    s = cf.Format(itemFormat, arg, provider);
+                }
+
+                if (s == null)
+                {
+                    // If arg is ISpanFormattable and the beginning doesn't need padding,
+                    // try formatting it into the remaining current chunk.
+                    if (arg is ISpanFormattable spanFormattableArg &&
+                        (leftJustify || width == 0) &&
+                        spanFormattableArg.TryFormat(RemainingCurrentChunk, out int charsWritten, itemFormatSpan, provider))
+                    {
+                        m_ChunkLength += charsWritten;
+
+                        // Pad the end, if needed.
+                        int padding = width - charsWritten;
+                        if (leftJustify && padding > 0) Append(' ', padding);
+
+                        // Continue to parse other characters.
+                        continue;
+                    }
+
+                    // Otherwise, fallback to trying IFormattable or calling ToString.
+                    if (arg is IFormattable formattableArg)
+                    {
+                        if (itemFormatSpan.Length != 0 && itemFormat == null)
+                        {
+                            itemFormat = new string(itemFormatSpan);
+                        }
+                        s = formattableArg.ToString(itemFormat, provider);
+                    }
+                    else if (arg != null)
+                    {
+                        s = arg.ToString();
+                    }
+                }
+                // Append it to the final output of the Format String.
+                if (s == null) s = String.Empty;
+                int pad = width - s.Length;
+                if (!leftJustify && pad > 0) Append(' ', pad);
+                Append(s);
+                if (leftJustify && pad > 0) Append(' ', pad);
+                // Continue to parse other characters.
+            }
+            return this;
+        }
+
+        /// <summary>
+        /// Replaces all instances of one string with another in this builder.
+        /// </summary>
+        /// <param name="oldValue">The string to replace.</param>
+        /// <param name="newValue">The string to replace <paramref name="oldValue"/> with.</param>
+        /// <remarks>
+        /// If <paramref name="newValue"/> is <c>null</c>, instances of <paramref name="oldValue"/>
+        /// are removed from this builder.
+        /// </remarks>
+        public StringBuilder Replace(String oldValue, String newValue) => Replace(oldValue, newValue, 0, Length);
+
+        /// <summary>
+        /// Determines if the contents of this builder are equal to the contents of another builder.
+        /// </summary>
+        /// <param name="sb">The other builder.</param>
+        public bool Equals(StringBuilder sb)
+        {
+            if (sb == null)
+                return false;
+            if (Capacity != sb.Capacity || MaxCapacity != sb.MaxCapacity || Length != sb.Length)
+                return false;
+            if (sb == this)
+                return true;
+
+            StringBuilder thisChunk = this;
+            int thisChunkIndex = thisChunk.m_ChunkLength;
+            StringBuilder sbChunk = sb;
+            int sbChunkIndex = sbChunk.m_ChunkLength;
+            for (;;)
+            {
+                --thisChunkIndex;
+                --sbChunkIndex;
+
+                while (thisChunkIndex < 0)
+                {
+                    thisChunk = thisChunk.m_ChunkPrevious;
+                    if (thisChunk == null)
+                        break;
+                    thisChunkIndex = thisChunk.m_ChunkLength + thisChunkIndex;
+                }
+
+                while (sbChunkIndex < 0)
+                {
+                    sbChunk = sbChunk.m_ChunkPrevious;
+                    if (sbChunk == null)
+                        break;
+                    sbChunkIndex = sbChunk.m_ChunkLength + sbChunkIndex;
+                }
+
+                if (thisChunkIndex < 0)
+                    return sbChunkIndex < 0;
+                if (sbChunkIndex < 0)
+                    return false;
+                if (thisChunk.m_ChunkChars[thisChunkIndex] != sbChunk.m_ChunkChars[sbChunkIndex])
+                    return false;
+            }
+        }
+
+        /// <summary>
+        /// Determines if the contents of this builder are equal to the contents of ReadOnlySpan<char>.
+        /// </summary>
+        /// <param name="span">The ReadOnlySpan{char}.</param>
+        public bool Equals(ReadOnlySpan<char> span)
+        {
+            if (span.Length != Length)
+                return false;
+
+            StringBuilder sbChunk = this;
+            int offset = 0;
+
+            do
+            {
+                int chunk_length = sbChunk.m_ChunkLength;
+                offset += chunk_length;
+
+                ReadOnlySpan<char> chunk = new ReadOnlySpan<char>(sbChunk.m_ChunkChars, 0, chunk_length);
+
+                if (!chunk.EqualsOrdinal(span.Slice(span.Length - offset, chunk_length)))
+                    return false;
+
+                sbChunk = sbChunk.m_ChunkPrevious;
+            } while (sbChunk != null);
+
+            Debug.Assert(offset == Length);
+            return true;
+        }
+
+        /// <summary>
+        /// Replaces all instances of one string with another in part of this builder.
+        /// </summary>
+        /// <param name="oldValue">The string to replace.</param>
+        /// <param name="newValue">The string to replace <paramref name="oldValue"/> with.</param>
+        /// <param name="startIndex">The index to start in this builder.</param>
+        /// <param name="count">The number of characters to read in this builder.</param>
+        /// <remarks>
+        /// If <paramref name="newValue"/> is <c>null</c>, instances of <paramref name="oldValue"/>
+        /// are removed from this builder.
+        /// </remarks>
+        public StringBuilder Replace(String oldValue, String newValue, int startIndex, int count)
+        {
+            int currentLength = Length;
+            if ((uint)startIndex > (uint)currentLength)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+            }
+            if (count < 0 || startIndex > currentLength - count)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Index);
+            }
+            if (oldValue == null)
+            {
+                throw new ArgumentNullException(nameof(oldValue));
+            }
+            if (oldValue.Length == 0)
+            {
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(oldValue));
+            }
+
+            newValue = newValue ?? string.Empty;
+
+            int deltaLength = newValue.Length - oldValue.Length;
+
+            int[] replacements = null; // A list of replacement positions in a chunk to apply
+            int replacementsCount = 0;
+
+            // Find the chunk, indexInChunk for the starting point
+            StringBuilder chunk = FindChunkForIndex(startIndex);
+            int indexInChunk = startIndex - chunk.m_ChunkOffset;
+            while (count > 0)
+            {
+                // Look for a match in the chunk,indexInChunk pointer
+                if (StartsWith(chunk, indexInChunk, count, oldValue))
+                {
+                    // Push it on the replacements array (with growth), we will do all replacements in a
+                    // given chunk in one operation below (see ReplaceAllInChunk) so we don't have to slide
+                    // many times.
+                    if (replacements == null)
+                    {
+                        replacements = new int[5];
+                    }
+                    else if (replacementsCount >= replacements.Length)
+                    {
+                        Array.Resize(ref replacements, replacements.Length * 3 / 2 + 4); // Grow by ~1.5x, but more in the begining
+                    }
+                    replacements[replacementsCount++] = indexInChunk;
+                    indexInChunk += oldValue.Length;
+                    count -= oldValue.Length;
+                }
+                else
+                {
+                    indexInChunk++;
+                    --count;
+                }
+
+                if (indexInChunk >= chunk.m_ChunkLength || count == 0) // Have we moved out of the current chunk?
+                {
+                    // Replacing mutates the blocks, so we need to convert to a logical index and back afterwards.
+                    int index = indexInChunk + chunk.m_ChunkOffset;
+                    int indexBeforeAdjustment = index;
+
+                    // See if we accumulated any replacements, if so apply them.
+                    ReplaceAllInChunk(replacements, replacementsCount, chunk, oldValue.Length, newValue);
+                    // The replacement has affected the logical index.  Adjust it.
+                    index += ((newValue.Length - oldValue.Length) * replacementsCount);
+                    replacementsCount = 0;
+
+                    chunk = FindChunkForIndex(index);
+                    indexInChunk = index - chunk.m_ChunkOffset;
+                    Debug.Assert(chunk != null || count == 0, "Chunks ended prematurely!");
+                }
+            }
+
+            AssertInvariants();
+            return this;
+        }
+
+        /// <summary>
+        /// Replaces all instances of one character with another in this builder.
+        /// </summary>
+        /// <param name="oldChar">The character to replace.</param>
+        /// <param name="newChar">The character to replace <paramref name="oldChar"/> with.</param>
+        public StringBuilder Replace(char oldChar, char newChar)
+        {
+            return Replace(oldChar, newChar, 0, Length);
+        }
+
+        /// <summary>
+        /// Replaces all instances of one character with another in this builder.
+        /// </summary>
+        /// <param name="oldChar">The character to replace.</param>
+        /// <param name="newChar">The character to replace <paramref name="oldChar"/> with.</param>
+        /// <param name="startIndex">The index to start in this builder.</param>
+        /// <param name="count">The number of characters to read in this builder.</param>
+        public StringBuilder Replace(char oldChar, char newChar, int startIndex, int count)
+        {
+            int currentLength = Length;
+            if ((uint)startIndex > (uint)currentLength)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startIndex), SR.ArgumentOutOfRange_Index);
+            }
+
+            if (count < 0 || startIndex > currentLength - count)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_Index);
+            }
+
+            int endIndex = startIndex + count;
+            StringBuilder chunk = this;
+
+            for (;;)
+            {
+                int endIndexInChunk = endIndex - chunk.m_ChunkOffset;
+                int startIndexInChunk = startIndex - chunk.m_ChunkOffset;
+                if (endIndexInChunk >= 0)
+                {
+                    int curInChunk = Math.Max(startIndexInChunk, 0);
+                    int endInChunk = Math.Min(chunk.m_ChunkLength, endIndexInChunk);
+                    while (curInChunk < endInChunk)
+                    {
+                        if (chunk.m_ChunkChars[curInChunk] == oldChar)
+                            chunk.m_ChunkChars[curInChunk] = newChar;
+                        curInChunk++;
+                    }
+                }
+                if (startIndexInChunk >= 0)
+                    break;
+                chunk = chunk.m_ChunkPrevious;
+            }
+
+            AssertInvariants();
+            return this;
+        }
+
+        /// <summary>
+        /// Appends a character buffer to this builder.
+        /// </summary>
+        /// <param name="value">The pointer to the start of the buffer.</param>
+        /// <param name="valueCount">The number of characters in the buffer.</param>
+        [CLSCompliant(false)]
+        public unsafe StringBuilder Append(char* value, int valueCount)
+        {
+            // We don't check null value as this case will throw null reference exception anyway
+            if (valueCount < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(valueCount), SR.ArgumentOutOfRange_NegativeCount);
+            }
+
+            // this is where we can check if the valueCount will put us over m_MaxCapacity
+            // We are doing the check here to prevent the corruption of the StringBuilder.
+            int newLength = Length + valueCount;
+            if (newLength > m_MaxCapacity || newLength < valueCount)
+            {
+                throw new ArgumentOutOfRangeException(nameof(valueCount), SR.ArgumentOutOfRange_LengthGreaterThanCapacity);
+            }
+
+            // This case is so common we want to optimize for it heavily.
+            int newIndex = valueCount + m_ChunkLength;
+            if (newIndex <= m_ChunkChars.Length)
+            {
+                ThreadSafeCopy(value, m_ChunkChars, m_ChunkLength, valueCount);
+                m_ChunkLength = newIndex;
+            }
+            else
+            {
+                // Copy the first chunk
+                int firstLength = m_ChunkChars.Length - m_ChunkLength;
+                if (firstLength > 0)
+                {
+                    ThreadSafeCopy(value, m_ChunkChars, m_ChunkLength, firstLength);
+                    m_ChunkLength = m_ChunkChars.Length;
+                }
+
+                // Expand the builder to add another chunk.
+                int restLength = valueCount - firstLength;
+                ExpandByABlock(restLength);
+                Debug.Assert(m_ChunkLength == 0, "A new block was not created.");
+
+                // Copy the second chunk
+                ThreadSafeCopy(value + firstLength, m_ChunkChars, 0, restLength);
+                m_ChunkLength = restLength;
+            }
+            AssertInvariants();
+            return this;
+        }
+
+        /// <summary>
+        /// Inserts a character buffer into this builder at the specified position.
+        /// </summary>
+        /// <param name="index">The index to insert in this builder.</param>
+        /// <param name="value">The pointer to the start of the buffer.</param>
+        /// <param name="valueCount">The number of characters in the buffer.</param>
+        private unsafe void Insert(int index, char* value, int valueCount)
+        {
+            if ((uint)index > (uint)Length)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_Index);
+            }
+
+            if (valueCount > 0)
+            {
+                StringBuilder chunk;
+                int indexInChunk;
+                MakeRoom(index, valueCount, out chunk, out indexInChunk, false);
+                ReplaceInPlaceAtChunk(ref chunk, ref indexInChunk, value, valueCount);
+            }
+        }
+
+        /// <summary>
+        /// Replaces strings at specified indices with a new string in a chunk.
+        /// </summary>
+        /// <param name="replacements">The list of indices, relative to the beginning of the chunk, to remove at.</param>
+        /// <param name="replacementsCount">The number of replacements to make.</param>
+        /// <param name="sourceChunk">The source chunk.</param>
+        /// <param name="removeCount">The number of characters to remove at each replacement.</param>
+        /// <param name="value">The string to insert at each replacement.</param>
+        /// <remarks>
+        /// This routine is very efficient because it does replacements in bulk.
+        /// </remarks>
+        private void ReplaceAllInChunk(int[] replacements, int replacementsCount, StringBuilder sourceChunk, int removeCount, string value)
+        {
+            if (replacementsCount <= 0)
+            {
+                return;
+            }
+
+            unsafe
+            {
+                fixed (char* valuePtr = value)
+                {
+                    // calculate the total amount of extra space or space needed for all the replacements.
+                    int delta = (value.Length - removeCount) * replacementsCount;
+
+                    StringBuilder targetChunk = sourceChunk;        // the target as we copy chars down
+                    int targetIndexInChunk = replacements[0];
+
+                    // Make the room needed for all the new characters if needed.
+                    if (delta > 0)
+                        MakeRoom(targetChunk.m_ChunkOffset + targetIndexInChunk, delta, out targetChunk, out targetIndexInChunk, true);
+                    // We made certain that characters after the insertion point are not moved,
+                    int i = 0;
+                    for (;;)
+                    {
+                        // Copy in the new string for the ith replacement
+                        ReplaceInPlaceAtChunk(ref targetChunk, ref targetIndexInChunk, valuePtr, value.Length);
+                        int gapStart = replacements[i] + removeCount;
+                        i++;
+                        if (i >= replacementsCount)
+                        {
+                            break;
+                        }
+
+                        int gapEnd = replacements[i];
+                        Debug.Assert(gapStart < sourceChunk.m_ChunkChars.Length, "gap starts at end of buffer.  Should not happen");
+                        Debug.Assert(gapStart <= gapEnd, "negative gap size");
+                        Debug.Assert(gapEnd <= sourceChunk.m_ChunkLength, "gap too big");
+                        if (delta != 0)     // can skip the sliding of gaps if source an target string are the same size.
+                        {
+                            // Copy the gap data between the current replacement and the next replacement
+                            fixed (char* sourcePtr = &sourceChunk.m_ChunkChars[gapStart])
+                                ReplaceInPlaceAtChunk(ref targetChunk, ref targetIndexInChunk, sourcePtr, gapEnd - gapStart);
+                        }
+                        else
+                        {
+                            targetIndexInChunk += gapEnd - gapStart;
+                            Debug.Assert(targetIndexInChunk <= targetChunk.m_ChunkLength, "gap not in chunk");
+                        }
+                    }
+
+                    // Remove extra space if necessary.
+                    if (delta < 0)
+                        Remove(targetChunk.m_ChunkOffset + targetIndexInChunk, -delta, out targetChunk, out targetIndexInChunk);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Returns a value indicating whether a substring of a builder starts with a specified prefix.
+        /// </summary>
+        /// <param name="chunk">The chunk in which the substring starts.</param>
+        /// <param name="indexInChunk">The index in <paramref name="chunk"/> at which the substring starts.</param>
+        /// <param name="count">The logical count of the substring.</param>
+        /// <param name="value">The prefix.</param>
+        private bool StartsWith(StringBuilder chunk, int indexInChunk, int count, string value)
+        {
+            for (int i = 0; i < value.Length; i++)
+            {
+                if (count == 0)
+                {
+                    return false;
+                }
+
+                if (indexInChunk >= chunk.m_ChunkLength)
+                {
+                    chunk = Next(chunk);
+                    if (chunk == null)
+                        return false;
+                    indexInChunk = 0;
+                }
+
+                if (value[i] != chunk.m_ChunkChars[indexInChunk])
+                {
+                    return false;
+                }
+
+                indexInChunk++;
+                --count;
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// Replaces characters at a specified location with the contents of a character buffer.
+        /// This function is the logical equivalent of memcpy.
+        /// </summary>
+        /// <param name="chunk">
+        /// The chunk in which to start replacing characters.
+        /// Receives the chunk in which character replacement ends.
+        /// </param>
+        /// <param name="indexInChunk">
+        /// The index in <paramref name="chunk"/> to start replacing characters at.
+        /// Receives the index at which character replacement ends.
+        /// </param>
+        /// <param name="value">The pointer to the start of the character buffer.</param>
+        /// <param name="count">The number of characters in the buffer.</param>
+        private unsafe void ReplaceInPlaceAtChunk(ref StringBuilder chunk, ref int indexInChunk, char* value, int count)
+        {
+            if (count != 0)
+            {
+                for (;;)
+                {
+                    int lengthInChunk = chunk.m_ChunkLength - indexInChunk;
+                    Debug.Assert(lengthInChunk >= 0, "Index isn't in the chunk.");
+
+                    int lengthToCopy = Math.Min(lengthInChunk, count);
+                    ThreadSafeCopy(value, chunk.m_ChunkChars, indexInChunk, lengthToCopy);
+
+                    // Advance the index.
+                    indexInChunk += lengthToCopy;
+                    if (indexInChunk >= chunk.m_ChunkLength)
+                    {
+                        chunk = Next(chunk);
+                        indexInChunk = 0;
+                    }
+                    count -= lengthToCopy;
+                    if (count == 0)
+                    {
+                        break;
+                    }
+                    value += lengthToCopy;
+                }
+            }
+        }
+
+        /// <remarks>
+        /// This method prevents out-of-bounds writes in the case a different thread updates a field in the builder just before a copy begins.
+        /// All interesting variables are copied out of the heap into the parameters of this method, and then bounds checks are run.
+        /// </remarks>
+        private static unsafe void ThreadSafeCopy(char* sourcePtr, char[] destination, int destinationIndex, int count)
+        {
+            if (count > 0)
+            {
+                if ((uint)destinationIndex <= (uint)destination.Length && (destinationIndex + count) <= destination.Length)
+                {
+                    fixed (char* destinationPtr = &destination[destinationIndex])
+                        string.wstrcpy(destinationPtr, sourcePtr, count);
+                }
+                else
+                {
+                    throw new ArgumentOutOfRangeException(nameof(destinationIndex), SR.ArgumentOutOfRange_Index);
+                }
+            }
+        }
+
+        private static unsafe void ThreadSafeCopy(char[] source, int sourceIndex, Span<char> destination, int destinationIndex, int count)
+        {
+            if (count > 0)
+            {
+                if ((uint)sourceIndex > (uint)source.Length || count > source.Length - sourceIndex)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(sourceIndex), SR.ArgumentOutOfRange_Index);
+                }
+
+                if ((uint)destinationIndex > (uint)destination.Length || count > destination.Length - destinationIndex)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(destinationIndex), SR.ArgumentOutOfRange_Index);
+                }
+
+                fixed (char* sourcePtr = &source[sourceIndex])
+                    fixed (char* destinationPtr = &MemoryMarshal.GetReference(destination))
+                        string.wstrcpy(destinationPtr + destinationIndex, sourcePtr, count);
+            }
+        }
+
+        /// <summary>
+        /// Gets the chunk corresponding to the logical index in this builder.
+        /// </summary>
+        /// <param name="index">The logical index in this builder.</param>
+        /// <remarks>
+        /// After calling this method, you can obtain the actual index within the chunk by
+        /// subtracting <see cref="m_ChunkOffset"/> from <paramref name="index"/>.
+        /// </remarks>
+        private StringBuilder FindChunkForIndex(int index)
+        {
+            Debug.Assert(0 <= index && index <= Length);
+
+            StringBuilder result = this;
+            while (result.m_ChunkOffset > index)
+            {
+                result = result.m_ChunkPrevious;
+            }
+
+            Debug.Assert(result != null);
+            return result;
+        }
+
+        /// <summary>
+        /// Gets the chunk corresponding to the logical byte index in this builder.
+        /// </summary>
+        /// <param name="byteIndex">The logical byte index in this builder.</param>
+        private StringBuilder FindChunkForByte(int byteIndex)
+        {
+            Debug.Assert(0 <= byteIndex && byteIndex <= Length * sizeof(char));
+
+            StringBuilder result = this;
+            while (result.m_ChunkOffset * sizeof(char) > byteIndex)
+            {
+                result = result.m_ChunkPrevious;
+            }
+
+            Debug.Assert(result != null);
+            return result;
+        }
+
+        /// <summary>Gets a span representing the remaining space available in the current chunk.</summary>
+        private Span<char> RemainingCurrentChunk
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => new Span<char>(m_ChunkChars, m_ChunkLength, m_ChunkChars.Length - m_ChunkLength);
+        }
+
+        /// <summary>
+        /// Finds the chunk that logically succeeds the specified chunk.
+        /// </summary>
+        /// <param name="chunk">The chunk whose successor should be found.</param>
+        /// <remarks>
+        /// Each chunk only stores the pointer to its logical predecessor, so this routine has to start
+        /// from the 'this' pointer (which is assumed to represent the whole StringBuilder) and work its
+        /// way down until it finds the specified chunk (which is O(n)). Thus, it is more expensive than
+        /// a field fetch.
+        /// </remarks>
+        private StringBuilder Next(StringBuilder chunk) => chunk == this ? null : FindChunkForIndex(chunk.m_ChunkOffset + chunk.m_ChunkLength);
+
+        /// <summary>
+        /// Transfers the character buffer from this chunk to a new chunk, and allocates a new buffer with a minimum size for this chunk.
+        /// </summary>
+        /// <param name="minBlockCharCount">The minimum size of the new buffer to be allocated for this chunk.</param>
+        /// <remarks>
+        /// This method requires that the current chunk is full. Otherwise, there's no point in shifting the characters over.
+        /// It also assumes that 'this' is the last chunk in the linked list.
+        /// </remarks>
+        private void ExpandByABlock(int minBlockCharCount)
+        {
+            Debug.Assert(Capacity == Length, nameof(ExpandByABlock) + " should only be called when there is no space left.");
+            Debug.Assert(minBlockCharCount > 0);
+
+            AssertInvariants();
+
+            if ((minBlockCharCount + Length) > m_MaxCapacity || minBlockCharCount + Length < minBlockCharCount)
+            {
+                throw new ArgumentOutOfRangeException("requiredLength", SR.ArgumentOutOfRange_SmallCapacity);
+            }
+
+            // - We always need to make the new chunk at least as big as was requested (`minBlockCharCount`).
+            // - We'd also prefer to make it at least at big as the current length (thus doubling capacity).
+            //   - But this is only up to a maximum, so we stay in the small object heap, and never allocate
+            //     really big chunks even if the string gets really big.
+            int newBlockLength = Math.Max(minBlockCharCount, Math.Min(Length, MaxChunkSize));
+
+            // Move all of the data from this chunk to a new one, via a few O(1) pointer adjustments.
+            // Then, have this chunk point to the new one as its predecessor.
+            m_ChunkPrevious = new StringBuilder(this);
+            m_ChunkOffset += m_ChunkLength;
+            m_ChunkLength = 0;
+
+            // Check for integer overflow (logical buffer size > int.MaxValue)
+            if (m_ChunkOffset + newBlockLength < newBlockLength)
+            {
+                m_ChunkChars = null;
+                throw new OutOfMemoryException();
+            }
+            m_ChunkChars = new char[newBlockLength];
+
+            AssertInvariants();
+        }
+
+        /// <summary>
+        /// Creates a new chunk with fields copied from an existing chunk.
+        /// </summary>
+        /// <param name="from">The chunk from which to copy fields.</param>
+        /// <remarks>
+        /// <para>
+        /// This method runs in O(1) time. It does not copy data within the character buffer
+        /// <paramref name="from"/> holds, but copies the reference to the character buffer itself
+        /// (plus a few other fields).
+        /// </para>
+        /// <para>
+        /// Callers are expected to update <paramref name="from"/> subsequently to point to this
+        /// chunk as its predecessor.
+        /// </para>
+        /// </remarks>
+        private StringBuilder(StringBuilder from)
+        {
+            m_ChunkLength = from.m_ChunkLength;
+            m_ChunkOffset = from.m_ChunkOffset;
+            m_ChunkChars = from.m_ChunkChars;
+            m_ChunkPrevious = from.m_ChunkPrevious;
+            m_MaxCapacity = from.m_MaxCapacity;
+
+            AssertInvariants();
+        }
+
+        /// <summary>
+        /// Creates a gap at a logical index with the specified count.
+        /// </summary>
+        /// <param name="index">The logical index in this builder.</param>
+        /// <param name="count">The number of characters in the gap.</param>
+        /// <param name="chunk">Receives the chunk containing the gap.</param>
+        /// <param name="indexInChunk">The index in <paramref name="chunk"/> that points to the gap.</param>
+        /// <param name="doNotMoveFollowingChars">
+        /// - If <c>true</c>, then room must be made by inserting a chunk before the current chunk.
+        /// - If <c>false</c>, then room can be made by shifting characters ahead of <paramref name="index"/>
+        ///   in this block forward by <paramref name="count"/> provided the characters will still fit in
+        ///   the current chunk after being shifted.
+        ///   - Providing <c>false</c> does not make a difference most of the time, but it can matter when someone
+        ///     inserts lots of small strings at a position in the buffer.
+        /// </param>
+        /// <remarks>
+        /// <para>
+        /// Since chunks do not contain references to their successors, it is not always possible for us to make room
+        /// by inserting space after <paramref name="index"/> in case this chunk runs out of space. Thus, we make room
+        /// by inserting space before the specified index, and having logical indices refer to new locations by the end
+        /// of this method.
+        /// </para>
+        /// <para>
+        /// <see cref="ReplaceInPlaceAtChunk"/> can be used in conjunction with this method to fill in the newly created gap.
+        /// </para>
+        /// </remarks>
+        private void MakeRoom(int index, int count, out StringBuilder chunk, out int indexInChunk, bool doNotMoveFollowingChars)
+        {
+            AssertInvariants();
+            Debug.Assert(count > 0);
+            Debug.Assert(index >= 0);
+
+            if (count + Length > m_MaxCapacity || count + Length < count)
+            {
+                throw new ArgumentOutOfRangeException("requiredLength", SR.ArgumentOutOfRange_SmallCapacity);
+            }
+
+            chunk = this;
+            while (chunk.m_ChunkOffset > index)
+            {
+                chunk.m_ChunkOffset += count;
+                chunk = chunk.m_ChunkPrevious;
+            }
+            indexInChunk = index - chunk.m_ChunkOffset;
+
+            // Cool, we have some space in this block, and we don't have to copy much to get at it, so go ahead and use it.
+            // This typically happens when someone repeatedly inserts small strings at a spot (usually the absolute front) of the buffer.
+            if (!doNotMoveFollowingChars && chunk.m_ChunkLength <= DefaultCapacity * 2 && chunk.m_ChunkChars.Length - chunk.m_ChunkLength >= count)
+            {
+                for (int i = chunk.m_ChunkLength; i > indexInChunk; )
+                {
+                    --i;
+                    chunk.m_ChunkChars[i + count] = chunk.m_ChunkChars[i];
+                }
+                chunk.m_ChunkLength += count;
+                return;
+            }
+
+            // Allocate space for the new chunk, which will go before the current one.
+            StringBuilder newChunk = new StringBuilder(Math.Max(count, DefaultCapacity), chunk.m_MaxCapacity, chunk.m_ChunkPrevious);
+            newChunk.m_ChunkLength = count;
+
+            // Copy the head of the current buffer to the new buffer.
+            int copyCount1 = Math.Min(count, indexInChunk);
+            if (copyCount1 > 0)
+            {
+                unsafe
+                {
+                    fixed (char* chunkCharsPtr = &chunk.m_ChunkChars[0])
+                    {
+                        ThreadSafeCopy(chunkCharsPtr, newChunk.m_ChunkChars, 0, copyCount1);
+
+                        // Slide characters over in the current buffer to make room.
+                        int copyCount2 = indexInChunk - copyCount1;
+                        if (copyCount2 >= 0)
+                        {
+                            ThreadSafeCopy(chunkCharsPtr + copyCount1, chunk.m_ChunkChars, 0, copyCount2);
+                            indexInChunk = copyCount2;
+                        }
+                    }
+                }
+            }
+
+            // Wire in the new chunk.
+            chunk.m_ChunkPrevious = newChunk;
+            chunk.m_ChunkOffset += count;
+            if (copyCount1 < count)
+            {
+                chunk = newChunk;
+                indexInChunk = copyCount1;
+            }
+
+            AssertInvariants();
+        }
+
+        /// <summary>
+        /// Used by <see cref="MakeRoom"/> to allocate another chunk.
+        /// </summary>
+        /// <param name="size">The size of the character buffer for this chunk.</param>
+        /// <param name="maxCapacity">The maximum capacity, to be stored in this chunk.</param>
+        /// <param name="previousBlock">The predecessor of this chunk.</param>
+        private StringBuilder(int size, int maxCapacity, StringBuilder previousBlock)
+        {
+            Debug.Assert(size > 0);
+            Debug.Assert(maxCapacity > 0);
+
+            m_ChunkChars = new char[size];
+            m_MaxCapacity = maxCapacity;
+            m_ChunkPrevious = previousBlock;
+            if (previousBlock != null)
+            {
+                m_ChunkOffset = previousBlock.m_ChunkOffset + previousBlock.m_ChunkLength;
+            }
+
+            AssertInvariants();
+        }
+
+        /// <summary>
+        /// Removes a specified number of characters beginning at a logical index in this builder.
+        /// </summary>
+        /// <param name="startIndex">The logical index in this builder to start removing characters.</param>
+        /// <param name="count">The number of characters to remove.</param>
+        /// <param name="chunk">Receives the new chunk containing the logical index.</param>
+        /// <param name="indexInChunk">
+        /// Receives the new index in <paramref name="chunk"/> that is associated with the logical index.
+        /// </param>
+        private void Remove(int startIndex, int count, out StringBuilder chunk, out int indexInChunk)
+        {
+            AssertInvariants();
+            Debug.Assert(startIndex >= 0 && startIndex < Length);
+
+            int endIndex = startIndex + count;
+
+            // Find the chunks for the start and end of the block to delete.
+            chunk = this;
+            StringBuilder endChunk = null;
+            int endIndexInChunk = 0;
+            for (;;)
+            {
+                if (endIndex - chunk.m_ChunkOffset >= 0)
+                {
+                    if (endChunk == null)
+                    {
+                        endChunk = chunk;
+                        endIndexInChunk = endIndex - endChunk.m_ChunkOffset;
+                    }
+                    if (startIndex - chunk.m_ChunkOffset >= 0)
+                    {
+                        indexInChunk = startIndex - chunk.m_ChunkOffset;
+                        break;
+                    }
+                }
+                else
+                {
+                    chunk.m_ChunkOffset -= count;
+                }
+                chunk = chunk.m_ChunkPrevious;
+            }
+            Debug.Assert(chunk != null, "We fell off the beginning of the string!");
+
+            int copyTargetIndexInChunk = indexInChunk;
+            int copyCount = endChunk.m_ChunkLength - endIndexInChunk;
+            if (endChunk != chunk)
+            {
+                copyTargetIndexInChunk = 0;
+                // Remove the characters after `startIndex` to the end of the chunk.
+                chunk.m_ChunkLength = indexInChunk;
+
+                // Remove the characters in chunks between the start and the end chunk.
+                endChunk.m_ChunkPrevious = chunk;
+                endChunk.m_ChunkOffset = chunk.m_ChunkOffset + chunk.m_ChunkLength;
+
+                // If the start is 0, then we can throw away the whole start chunk.
+                if (indexInChunk == 0)
+                {
+                    endChunk.m_ChunkPrevious = chunk.m_ChunkPrevious;
+                    chunk = endChunk;
+                }
+            }
+            endChunk.m_ChunkLength -= (endIndexInChunk - copyTargetIndexInChunk);
+
+            // SafeCritical: We ensure that `endIndexInChunk + copyCount` is within range of `m_ChunkChars`, and
+            // also ensure that `copyTargetIndexInChunk + copyCount` is within the chunk.
+
+            // Remove any characters in the end chunk, by sliding the characters down.
+            if (copyTargetIndexInChunk != endIndexInChunk) // Sometimes no move is necessary
+            {
+                ThreadSafeCopy(endChunk.m_ChunkChars, endIndexInChunk, endChunk.m_ChunkChars, copyTargetIndexInChunk, copyCount);
+            }
+
+            Debug.Assert(chunk != null, "We fell off the beginning of the string!");
+            AssertInvariants();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/UTF32Encoding.cs b/src/System.Private.CoreLib/shared/System/Text/UTF32Encoding.cs
new file mode 100644
index 0000000000..7828775ea0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/UTF32Encoding.cs
@@ -0,0 +1,1213 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+// Don't override IsAlwaysNormalized because it is just a Unicode Transformation and could be confused.
+//
+
+using System;
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.InteropServices;
+
+namespace System.Text
+{
+    // Encodes text into and out of UTF-32.  UTF-32 is a way of writing
+    // Unicode characters with a single storage unit (32 bits) per character,
+    //
+    // The UTF-32 byte order mark is simply the Unicode byte order mark
+    // (0x00FEFF) written in UTF-32 (0x0000FEFF or 0xFFFE0000).  The byte order
+    // mark is used mostly to distinguish UTF-32 text from other encodings, and doesn't
+    // switch the byte orderings.
+
+    public sealed class UTF32Encoding : Encoding
+    {
+        /*
+            words   bits    UTF-32 representation
+            -----   ----    -----------------------------------
+            1       16      00000000 00000000 xxxxxxxx xxxxxxxx
+            2       21      00000000 000xxxxx hhhhhhll llllllll
+            -----   ----    -----------------------------------
+
+            Surrogate:
+            Real Unicode value = (HighSurrogate - 0xD800) * 0x400 + (LowSurrogate - 0xDC00) + 0x10000
+        */
+
+        // Used by Encoding.UTF32/BigEndianUTF32 for lazy initialization
+        // The initialization code will not be run until a static member of the class is referenced
+        internal static readonly UTF32Encoding s_default = new UTF32Encoding(bigEndian: false, byteOrderMark: true);
+        internal static readonly UTF32Encoding s_bigEndianDefault = new UTF32Encoding(bigEndian: true, byteOrderMark: true);
+
+        private static readonly byte[] s_bigEndianPreamble = new byte[4] { 0x00, 0x00, 0xFE, 0xFF };
+        private static readonly byte[] s_littleEndianPreamble = new byte[4] { 0xFF, 0xFE, 0x00, 0x00 };
+
+        private bool _emitUTF32ByteOrderMark = false;
+        private bool _isThrowException = false;
+        private bool _bigEndian = false;
+
+
+        public UTF32Encoding() : this(false, true, false)
+        {
+        }
+
+
+        public UTF32Encoding(bool bigEndian, bool byteOrderMark) :
+            this(bigEndian, byteOrderMark, false)
+        {
+        }
+
+
+        public UTF32Encoding(bool bigEndian, bool byteOrderMark, bool throwOnInvalidCharacters) :
+            base(bigEndian ? 12001 : 12000)
+        {
+            _bigEndian = bigEndian;
+            _emitUTF32ByteOrderMark = byteOrderMark;
+            _isThrowException = throwOnInvalidCharacters;
+
+            // Encoding constructor already did this, but it'll be wrong if we're throwing exceptions
+            if (_isThrowException)
+                SetDefaultFallbacks();
+        }
+
+        internal override void SetDefaultFallbacks()
+        {
+            // For UTF-X encodings, we use a replacement fallback with an empty string
+            if (_isThrowException)
+            {
+                this.encoderFallback = EncoderFallback.ExceptionFallback;
+                this.decoderFallback = DecoderFallback.ExceptionFallback;
+            }
+            else
+            {
+                this.encoderFallback = new EncoderReplacementFallback("\xFFFD");
+                this.decoderFallback = new DecoderReplacementFallback("\xFFFD");
+            }
+        }
+
+
+        // The following methods are copied from EncodingNLS.cs.
+        // Unfortunately EncodingNLS.cs is internal and we're public, so we have to re-implement them here.
+        // These should be kept in sync for the following classes:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        // Returns the number of bytes required to encode a range of characters in
+        // a character array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetByteCount(char[] chars, int index, int count)
+        {
+            // Validate input parameters
+            if (chars == null)
+                throw new ArgumentNullException("chars", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - index < count)
+                throw new ArgumentOutOfRangeException("chars", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // If no input, return 0, avoid fixed empty array problem
+            if (count == 0)
+                return 0;
+
+            // Just call the pointer version
+            fixed (char* pChars = chars)
+                return GetByteCount(pChars + index, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetByteCount(String s)
+        {
+            // Validate input
+            if (s==null)
+                throw new ArgumentNullException("s");
+
+            fixed (char* pChars = s)
+                return GetByteCount(pChars, s.Length, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetByteCount(char* chars, int count)
+        {
+            // Validate Parameters
+            if (chars == null)
+                throw new ArgumentNullException("chars", SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException("count", SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Call it with empty encoder
+            return GetByteCount(chars, count, null);
+        }
+
+        // Parent method is safe.
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        public override unsafe int GetBytes(String s, int charIndex, int charCount,
+                                              byte[] bytes, int byteIndex)
+        {
+            if (s == null || bytes == null)
+                throw new ArgumentNullException((s == null ? "s" : "bytes"), SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? "charIndex" : "charCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (s.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException("s", SR.ArgumentOutOfRange_IndexCount);
+
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+                throw new ArgumentOutOfRangeException("byteIndex", SR.ArgumentOutOfRange_Index);
+
+            int byteCount = bytes.Length - byteIndex;
+
+            fixed (char* pChars = s) fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+                return GetBytes(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, null);
+        }
+
+        // Encodes a range of characters in a character array into a range of bytes
+        // in a byte array. An exception occurs if the byte array is not large
+        // enough to hold the complete encoding of the characters. The
+        // GetByteCount method can be used to determine the exact number of
+        // bytes that will be produced for a given range of characters.
+        // Alternatively, the GetMaxByteCount method can be used to
+        // determine the maximum number of bytes that will be produced for a given
+        // number of characters, regardless of the actual character values.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetBytes(char[] chars, int charIndex, int charCount,
+                                               byte[] bytes, int byteIndex)
+        {
+            // Validate parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException((chars == null ? "chars" : "bytes"), SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? "charIndex" : "charCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException("chars", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+                throw new ArgumentOutOfRangeException("byteIndex", SR.ArgumentOutOfRange_Index);
+
+            // If nothing to encode return 0, avoid fixed problem
+            if (charCount == 0)
+                return 0;
+
+            // Just call pointer version
+            int byteCount = bytes.Length - byteIndex;
+
+            fixed (char* pChars = chars) fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+                // Remember that byteCount is # to decode, not size of array.
+                return GetBytes(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetBytes(char* chars, int charCount, byte* bytes, int byteCount)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? "charCount" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetBytes(chars, charCount, bytes, byteCount, null);
+        }
+
+        // Returns the number of characters produced by decoding a range of bytes
+        // in a byte array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetCharCount(byte[] bytes, int index, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (bytes.Length - index < count)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // If no input just return 0, fixed doesn't like 0 length arrays.
+            if (count == 0)
+                return 0;
+
+            // Just call pointer version
+            fixed (byte* pBytes = bytes)
+                return GetCharCount(pBytes + index, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetCharCount(byte* bytes, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException("count", SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetCharCount(bytes, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetChars(byte[] bytes, int byteIndex, int byteCount,
+                                              char[] chars, int charIndex)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (byteIndex < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((byteIndex < 0 ? "byteIndex" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if ( bytes.Length - byteIndex < byteCount)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (charIndex < 0 || charIndex > chars.Length)
+                throw new ArgumentOutOfRangeException("charIndex", SR.ArgumentOutOfRange_Index);
+
+            // If no input, return 0 & avoid fixed problem
+            if (byteCount == 0)
+                return 0;
+
+            // Just call pointer version
+            int charCount = chars.Length - charIndex;
+
+            fixed (byte* pBytes = bytes) fixed (char* pChars = &MemoryMarshal.GetReference((Span<char>)chars))
+                // Remember that charCount is # to decode, not size of array
+                return GetChars(pBytes + byteIndex, byteCount, pChars + charIndex, charCount, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public unsafe override int GetChars(byte* bytes, int byteCount, char* chars, int charCount)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? "charCount" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetChars(bytes, byteCount, chars, charCount, null);
+        }
+
+        // Returns a string containing the decoded representation of a range of
+        // bytes in a byte array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe String GetString(byte[] bytes, int index, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (bytes.Length - index < count)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // Avoid problems with empty input buffer
+            if (count == 0) return String.Empty;
+
+            fixed (byte* pBytes = bytes)
+                return String.CreateStringFromEncoding(
+                    pBytes + index, count, this);
+        }
+
+        //
+        // End of standard methods copied from EncodingNLS.cs
+        //
+
+        internal override unsafe int GetByteCount(char* chars, int count, EncoderNLS encoder)
+        {
+            Debug.Assert(chars != null, "[UTF32Encoding.GetByteCount]chars!=null");
+            Debug.Assert(count >= 0, "[UTF32Encoding.GetByteCount]count >=0");
+
+            char* end = chars + count;
+            char* charStart = chars;
+            int byteCount = 0;
+
+            char highSurrogate = '\0';
+
+            // For fallback we may need a fallback buffer
+            EncoderFallbackBuffer fallbackBuffer = null;
+            char* charsForFallback;
+
+            if (encoder != null)
+            {
+                highSurrogate = encoder._charLeftOver;
+                fallbackBuffer = encoder.FallbackBuffer;
+
+                // We mustn't have left over fallback data when counting
+                if (fallbackBuffer.Remaining > 0)
+                    throw new ArgumentException(SR.Format(SR.Argument_EncoderFallbackNotEmpty, this.EncodingName, encoder.Fallback.GetType()));
+            }
+            else
+            {
+                fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+            }
+
+            // Set our internal fallback interesting things.
+            fallbackBuffer.InternalInitialize(charStart, end, encoder, false);
+
+            char ch;
+        TryAgain:
+
+            while (((ch = fallbackBuffer.InternalGetNextChar()) != 0) || chars < end)
+            {
+                // First unwind any fallback
+                if (ch == 0)
+                {
+                    // No fallback, just get next char
+                    ch = *chars;
+                    chars++;
+                }
+
+                // Do we need a low surrogate?
+                if (highSurrogate != '\0')
+                {
+                    //
+                    // In previous char, we encounter a high surrogate, so we are expecting a low surrogate here.
+                    //
+                    if (Char.IsLowSurrogate(ch))
+                    {
+                        // They're all legal
+                        highSurrogate = '\0';
+
+                        //
+                        // One surrogate pair will be translated into 4 bytes UTF32.
+                        //
+
+                        byteCount += 4;
+                        continue;
+                    }
+
+                    // We are missing our low surrogate, decrement chars and fallback the high surrogate
+                    // The high surrogate may have come from the encoder, but nothing else did.
+                    Debug.Assert(chars > charStart,
+                        "[UTF32Encoding.GetByteCount]Expected chars to have advanced if no low surrogate");
+                    chars--;
+
+                    // Do the fallback
+                    charsForFallback = chars;
+                    fallbackBuffer.InternalFallback(highSurrogate, ref charsForFallback);
+                    chars = charsForFallback;
+
+                    // We're going to fallback the old high surrogate.
+                    highSurrogate = '\0';
+                    continue;
+                }
+
+                // Do we have another high surrogate?
+                if (Char.IsHighSurrogate(ch))
+                {
+                    //
+                    // We'll have a high surrogate to check next time.
+                    //
+                    highSurrogate = ch;
+                    continue;
+                }
+
+                // Check for illegal characters
+                if (Char.IsLowSurrogate(ch))
+                {
+                    // We have a leading low surrogate, do the fallback
+                    charsForFallback = chars;
+                    fallbackBuffer.InternalFallback(ch, ref charsForFallback);
+                    chars = charsForFallback;
+
+                    // Try again with fallback buffer
+                    continue;
+                }
+
+                // We get to add the character (4 bytes UTF32)
+                byteCount += 4;
+            }
+
+            // May have to do our last surrogate
+            if ((encoder == null || encoder.MustFlush) && highSurrogate > 0)
+            {
+                // We have to do the fallback for the lonely high surrogate
+                charsForFallback = chars;
+                fallbackBuffer.InternalFallback(highSurrogate, ref charsForFallback);
+                chars = charsForFallback;
+
+                highSurrogate = (char)0;
+                goto TryAgain;
+            }
+
+            // Check for overflows.
+            if (byteCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_GetByteCountOverflow);
+
+            // Shouldn't have anything in fallback buffer for GetByteCount
+            // (don't have to check _throwOnOverflow for count)
+            Debug.Assert(fallbackBuffer.Remaining == 0,
+                "[UTF32Encoding.GetByteCount]Expected empty fallback buffer at end");
+
+            // Return our count
+            return byteCount;
+        }
+
+        internal override unsafe int GetBytes(char* chars, int charCount,
+                                                 byte* bytes, int byteCount, EncoderNLS encoder)
+        {
+            Debug.Assert(chars != null, "[UTF32Encoding.GetBytes]chars!=null");
+            Debug.Assert(bytes != null, "[UTF32Encoding.GetBytes]bytes!=null");
+            Debug.Assert(byteCount >= 0, "[UTF32Encoding.GetBytes]byteCount >=0");
+            Debug.Assert(charCount >= 0, "[UTF32Encoding.GetBytes]charCount >=0");
+
+            char* charStart = chars;
+            char* charEnd = chars + charCount;
+            byte* byteStart = bytes;
+            byte* byteEnd = bytes + byteCount;
+
+            char highSurrogate = '\0';
+
+            // For fallback we may need a fallback buffer
+            EncoderFallbackBuffer fallbackBuffer = null;
+            char* charsForFallback;
+
+            if (encoder != null)
+            {
+                highSurrogate = encoder._charLeftOver;
+                fallbackBuffer = encoder.FallbackBuffer;
+
+                // We mustn't have left over fallback data when not converting
+                if (encoder._throwOnOverflow && fallbackBuffer.Remaining > 0)
+                    throw new ArgumentException(SR.Format(SR.Argument_EncoderFallbackNotEmpty, this.EncodingName, encoder.Fallback.GetType()));
+            }
+            else
+            {
+                fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+            }
+
+            // Set our internal fallback interesting things.
+            fallbackBuffer.InternalInitialize(charStart, charEnd, encoder, true);
+
+            char ch;
+        TryAgain:
+
+            while (((ch = fallbackBuffer.InternalGetNextChar()) != 0) || chars < charEnd)
+            {
+                // First unwind any fallback
+                if (ch == 0)
+                {
+                    // No fallback, just get next char
+                    ch = *chars;
+                    chars++;
+                }
+
+                // Do we need a low surrogate?
+                if (highSurrogate != '\0')
+                {
+                    //
+                    // In previous char, we encountered a high surrogate, so we are expecting a low surrogate here.
+                    //
+                    if (Char.IsLowSurrogate(ch))
+                    {
+                        // Is it a legal one?
+                        uint iTemp = GetSurrogate(highSurrogate, ch);
+                        highSurrogate = '\0';
+
+                        //
+                        // One surrogate pair will be translated into 4 bytes UTF32.
+                        //
+                        if (bytes + 3 >= byteEnd)
+                        {
+                            // Don't have 4 bytes
+                            if (fallbackBuffer.bFallingBack)
+                            {
+                                fallbackBuffer.MovePrevious();                  // Aren't using these 2 fallback chars
+                                fallbackBuffer.MovePrevious();
+                            }
+                            else
+                            {
+                                // If we don't have enough room, then either we should've advanced a while
+                                // or we should have bytes==byteStart and throw below
+                                Debug.Assert(chars > charStart + 1 || bytes == byteStart,
+                                    "[UnicodeEncoding.GetBytes]Expected chars to have when no room to add surrogate pair");
+                                chars -= 2;                                       // Aren't using those 2 chars
+                            }
+                            ThrowBytesOverflow(encoder, bytes == byteStart);    // Throw maybe (if no bytes written)
+                            highSurrogate = (char)0;                            // Nothing left over (we backed up to start of pair if supplimentary)
+                            break;
+                        }
+
+                        if (_bigEndian)
+                        {
+                            *(bytes++) = (byte)(0x00);
+                            *(bytes++) = (byte)(iTemp >> 16);       // Implies & 0xFF, which isn't needed cause high are all 0
+                            *(bytes++) = (byte)(iTemp >> 8);        // Implies & 0xFF
+                            *(bytes++) = (byte)(iTemp);             // Implies & 0xFF
+                        }
+                        else
+                        {
+                            *(bytes++) = (byte)(iTemp);             // Implies & 0xFF
+                            *(bytes++) = (byte)(iTemp >> 8);        // Implies & 0xFF
+                            *(bytes++) = (byte)(iTemp >> 16);       // Implies & 0xFF, which isn't needed cause high are all 0
+                            *(bytes++) = (byte)(0x00);
+                        }
+                        continue;
+                    }
+
+                    // We are missing our low surrogate, decrement chars and fallback the high surrogate
+                    // The high surrogate may have come from the encoder, but nothing else did.
+                    Debug.Assert(chars > charStart,
+                        "[UTF32Encoding.GetBytes]Expected chars to have advanced if no low surrogate");
+                    chars--;
+
+                    // Do the fallback
+                    charsForFallback = chars;
+                    fallbackBuffer.InternalFallback(highSurrogate, ref charsForFallback);
+                    chars = charsForFallback;
+
+                    // We're going to fallback the old high surrogate.
+                    highSurrogate = '\0';
+                    continue;
+                }
+
+                // Do we have another high surrogate?, if so remember it
+                if (Char.IsHighSurrogate(ch))
+                {
+                    //
+                    // We'll have a high surrogate to check next time.
+                    //
+                    highSurrogate = ch;
+                    continue;
+                }
+
+                // Check for illegal characters (low surrogate)
+                if (Char.IsLowSurrogate(ch))
+                {
+                    // We have a leading low surrogate, do the fallback
+                    charsForFallback = chars;
+                    fallbackBuffer.InternalFallback(ch, ref charsForFallback);
+                    chars = charsForFallback;
+
+                    // Try again with fallback buffer
+                    continue;
+                }
+
+                // We get to add the character, yippee.
+                if (bytes + 3 >= byteEnd)
+                {
+                    // Don't have 4 bytes
+                    if (fallbackBuffer.bFallingBack)
+                        fallbackBuffer.MovePrevious();                  // Aren't using this fallback char
+                    else
+                    {
+                        // Must've advanced already
+                        Debug.Assert(chars > charStart,
+                            "[UTF32Encoding.GetBytes]Expected chars to have advanced if normal character");
+                        chars--;                                        // Aren't using this char
+                    }
+                    ThrowBytesOverflow(encoder, bytes == byteStart);    // Throw maybe (if no bytes written)
+                    break;                                              // Didn't throw, stop
+                }
+
+                if (_bigEndian)
+                {
+                    *(bytes++) = (byte)(0x00);
+                    *(bytes++) = (byte)(0x00);
+                    *(bytes++) = (byte)((uint)ch >> 8); // Implies & 0xFF
+                    *(bytes++) = (byte)(ch);            // Implies & 0xFF
+                }
+                else
+                {
+                    *(bytes++) = (byte)(ch);            // Implies & 0xFF
+                    *(bytes++) = (byte)((uint)ch >> 8); // Implies & 0xFF
+                    *(bytes++) = (byte)(0x00);
+                    *(bytes++) = (byte)(0x00);
+                }
+            }
+
+            // May have to do our last surrogate
+            if ((encoder == null || encoder.MustFlush) && highSurrogate > 0)
+            {
+                // We have to do the fallback for the lonely high surrogate
+                charsForFallback = chars;
+                fallbackBuffer.InternalFallback(highSurrogate, ref charsForFallback);
+                chars = charsForFallback;
+
+                highSurrogate = (char)0;
+                goto TryAgain;
+            }
+
+            // Fix our encoder if we have one
+            Debug.Assert(highSurrogate == 0 || (encoder != null && !encoder.MustFlush),
+                "[UTF32Encoding.GetBytes]Expected encoder to be flushed.");
+
+            if (encoder != null)
+            {
+                // Remember our left over surrogate (or 0 if flushing)
+                encoder._charLeftOver = highSurrogate;
+
+                // Need # chars used
+                encoder._charsUsed = (int)(chars - charStart);
+            }
+
+            // return the new length
+            return (int)(bytes - byteStart);
+        }
+
+        internal override unsafe int GetCharCount(byte* bytes, int count, DecoderNLS baseDecoder)
+        {
+            Debug.Assert(bytes != null, "[UTF32Encoding.GetCharCount]bytes!=null");
+            Debug.Assert(count >= 0, "[UTF32Encoding.GetCharCount]count >=0");
+
+            UTF32Decoder decoder = (UTF32Decoder)baseDecoder;
+
+            // None so far!
+            int charCount = 0;
+            byte* end = bytes + count;
+            byte* byteStart = bytes;
+
+            // Set up decoder
+            int readCount = 0;
+            uint iChar = 0;
+
+            // For fallback we may need a fallback buffer
+            DecoderFallbackBuffer fallbackBuffer = null;
+
+            // See if there's anything in our decoder
+            if (decoder != null)
+            {
+                readCount = decoder.readByteCount;
+                iChar = (uint)decoder.iChar;
+                fallbackBuffer = decoder.FallbackBuffer;
+
+                // Shouldn't have anything in fallback buffer for GetCharCount
+                // (don't have to check _throwOnOverflow for chars or count)
+                Debug.Assert(fallbackBuffer.Remaining == 0,
+                    "[UTF32Encoding.GetCharCount]Expected empty fallback buffer at start");
+            }
+            else
+            {
+                fallbackBuffer = this.decoderFallback.CreateFallbackBuffer();
+            }
+
+            // Set our internal fallback interesting things.
+            fallbackBuffer.InternalInitialize(byteStart, null);
+
+            // Loop through our input, 4 characters at a time!
+            while (bytes < end && charCount >= 0)
+            {
+                // Get our next character
+                if (_bigEndian)
+                {
+                    // Scoot left and add it to the bottom
+                    iChar <<= 8;
+                    iChar += *(bytes++);
+                }
+                else
+                {
+                    // Scoot right and add it to the top
+                    iChar >>= 8;
+                    iChar += (uint)(*(bytes++)) << 24;
+                }
+
+                readCount++;
+
+                // See if we have all the bytes yet
+                if (readCount < 4)
+                    continue;
+
+                // Have the bytes
+                readCount = 0;
+
+                // See if its valid to encode
+                if (iChar > 0x10FFFF || (iChar >= 0xD800 && iChar <= 0xDFFF))
+                {
+                    // Need to fall back these 4 bytes
+                    byte[] fallbackBytes;
+                    if (_bigEndian)
+                    {
+                        fallbackBytes = new byte[] {
+                            unchecked((byte)(iChar>>24)), unchecked((byte)(iChar>>16)),
+                            unchecked((byte)(iChar>>8)), unchecked((byte)(iChar)) };
+                    }
+                    else
+                    {
+                        fallbackBytes = new byte[] {
+                            unchecked((byte)(iChar)), unchecked((byte)(iChar>>8)),
+                            unchecked((byte)(iChar>>16)), unchecked((byte)(iChar>>24)) };
+                    }
+
+                    charCount += fallbackBuffer.InternalFallback(fallbackBytes, bytes);
+
+                    // Ignore the illegal character
+                    iChar = 0;
+                    continue;
+                }
+
+                // Ok, we have something we can add to our output
+                if (iChar >= 0x10000)
+                {
+                    // Surrogates take 2
+                    charCount++;
+                }
+
+                // Add the rest of the surrogate or our normal character
+                charCount++;
+
+                // iChar is back to 0
+                iChar = 0;
+            }
+
+            // See if we have something left over that has to be decoded
+            if (readCount > 0 && (decoder == null || decoder.MustFlush))
+            {
+                // Oops, there's something left over with no place to go.
+                byte[] fallbackBytes = new byte[readCount];
+                if (_bigEndian)
+                {
+                    while (readCount > 0)
+                    {
+                        fallbackBytes[--readCount] = unchecked((byte)iChar);
+                        iChar >>= 8;
+                    }
+                }
+                else
+                {
+                    while (readCount > 0)
+                    {
+                        fallbackBytes[--readCount] = unchecked((byte)(iChar >> 24));
+                        iChar <<= 8;
+                    }
+                }
+
+                charCount += fallbackBuffer.InternalFallback(fallbackBytes, bytes);
+            }
+
+            // Check for overflows.
+            if (charCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_GetByteCountOverflow);
+
+            // Shouldn't have anything in fallback buffer for GetCharCount
+            // (don't have to check _throwOnOverflow for chars or count)
+            Debug.Assert(fallbackBuffer.Remaining == 0,
+                "[UTF32Encoding.GetCharCount]Expected empty fallback buffer at end");
+
+            // Return our count
+            return charCount;
+        }
+
+        internal override unsafe int GetChars(byte* bytes, int byteCount,
+                                                char* chars, int charCount, DecoderNLS baseDecoder)
+        {
+            Debug.Assert(chars != null, "[UTF32Encoding.GetChars]chars!=null");
+            Debug.Assert(bytes != null, "[UTF32Encoding.GetChars]bytes!=null");
+            Debug.Assert(byteCount >= 0, "[UTF32Encoding.GetChars]byteCount >=0");
+            Debug.Assert(charCount >= 0, "[UTF32Encoding.GetChars]charCount >=0");
+
+            UTF32Decoder decoder = (UTF32Decoder)baseDecoder;
+
+            // None so far!
+            char* charStart = chars;
+            char* charEnd = chars + charCount;
+
+            byte* byteStart = bytes;
+            byte* byteEnd = bytes + byteCount;
+
+            // See if there's anything in our decoder (but don't clear it yet)
+            int readCount = 0;
+            uint iChar = 0;
+
+            // For fallback we may need a fallback buffer
+            DecoderFallbackBuffer fallbackBuffer = null;
+            char* charsForFallback;
+
+            // See if there's anything in our decoder
+            if (decoder != null)
+            {
+                readCount = decoder.readByteCount;
+                iChar = (uint)decoder.iChar;
+                fallbackBuffer = baseDecoder.FallbackBuffer;
+
+                // Shouldn't have anything in fallback buffer for GetChars
+                // (don't have to check _throwOnOverflow for chars)
+                Debug.Assert(fallbackBuffer.Remaining == 0,
+                    "[UTF32Encoding.GetChars]Expected empty fallback buffer at start");
+            }
+            else
+            {
+                fallbackBuffer = this.decoderFallback.CreateFallbackBuffer();
+            }
+
+            // Set our internal fallback interesting things.
+            fallbackBuffer.InternalInitialize(bytes, chars + charCount);
+
+            // Loop through our input, 4 characters at a time!
+            while (bytes < byteEnd)
+            {
+                // Get our next character
+                if (_bigEndian)
+                {
+                    // Scoot left and add it to the bottom
+                    iChar <<= 8;
+                    iChar += *(bytes++);
+                }
+                else
+                {
+                    // Scoot right and add it to the top
+                    iChar >>= 8;
+                    iChar += (uint)(*(bytes++)) << 24;
+                }
+
+                readCount++;
+
+                // See if we have all the bytes yet
+                if (readCount < 4)
+                    continue;
+
+                // Have the bytes
+                readCount = 0;
+
+                // See if its valid to encode
+                if (iChar > 0x10FFFF || (iChar >= 0xD800 && iChar <= 0xDFFF))
+                {
+                    // Need to fall back these 4 bytes
+                    byte[] fallbackBytes;
+                    if (_bigEndian)
+                    {
+                        fallbackBytes = new byte[] {
+                            unchecked((byte)(iChar>>24)), unchecked((byte)(iChar>>16)),
+                            unchecked((byte)(iChar>>8)), unchecked((byte)(iChar)) };
+                    }
+                    else
+                    {
+                        fallbackBytes = new byte[] {
+                            unchecked((byte)(iChar)), unchecked((byte)(iChar>>8)),
+                            unchecked((byte)(iChar>>16)), unchecked((byte)(iChar>>24)) };
+                    }
+
+                    // Chars won't be updated unless this works.
+                    charsForFallback = chars;
+                    bool fallbackResult = fallbackBuffer.InternalFallback(fallbackBytes, bytes, ref charsForFallback);
+                    chars = charsForFallback;
+
+                    if (!fallbackResult)
+                    {
+                        // Couldn't fallback, throw or wait til next time
+                        // We either read enough bytes for bytes-=4 to work, or we're
+                        // going to throw in ThrowCharsOverflow because chars == charStart
+                        Debug.Assert(bytes >= byteStart + 4 || chars == charStart,
+                            "[UTF32Encoding.GetChars]Expected to have consumed bytes or throw (bad surrogate)");
+                        bytes -= 4;                                       // get back to where we were
+                        iChar = 0;                                        // Remembering nothing
+                        fallbackBuffer.InternalReset();
+                        ThrowCharsOverflow(decoder, chars == charStart);// Might throw, if no chars output
+                        break;                                          // Stop here, didn't throw
+                    }
+
+                    // Ignore the illegal character
+                    iChar = 0;
+                    continue;
+                }
+
+
+                // Ok, we have something we can add to our output
+                if (iChar >= 0x10000)
+                {
+                    // Surrogates take 2
+                    if (chars >= charEnd - 1)
+                    {
+                        // Throwing or stopping
+                        // We either read enough bytes for bytes-=4 to work, or we're
+                        // going to throw in ThrowCharsOverflow because chars == charStart
+                        Debug.Assert(bytes >= byteStart + 4 || chars == charStart,
+                            "[UTF32Encoding.GetChars]Expected to have consumed bytes or throw (surrogate)");
+                        bytes -= 4;                                       // get back to where we were
+                        iChar = 0;                                        // Remembering nothing
+                        ThrowCharsOverflow(decoder, chars == charStart);// Might throw, if no chars output
+                        break;                                          // Stop here, didn't throw
+                    }
+
+                    *(chars++) = GetHighSurrogate(iChar);
+                    iChar = GetLowSurrogate(iChar);
+                }
+                // Bounds check for normal character
+                else if (chars >= charEnd)
+                {
+                    // Throwing or stopping
+                    // We either read enough bytes for bytes-=4 to work, or we're
+                    // going to throw in ThrowCharsOverflow because chars == charStart
+                    Debug.Assert(bytes >= byteStart + 4 || chars == charStart,
+                        "[UTF32Encoding.GetChars]Expected to have consumed bytes or throw (normal char)");
+                    bytes -= 4;                                       // get back to where we were
+                    iChar = 0;                                        // Remembering nothing                    
+                    ThrowCharsOverflow(decoder, chars == charStart);// Might throw, if no chars output
+                    break;                                          // Stop here, didn't throw
+                }
+
+                // Add the rest of the surrogate or our normal character
+                *(chars++) = (char)iChar;
+
+                // iChar is back to 0
+                iChar = 0;
+            }
+
+            // See if we have something left over that has to be decoded
+            if (readCount > 0 && (decoder == null || decoder.MustFlush))
+            {
+                // Oops, there's something left over with no place to go.
+                byte[] fallbackBytes = new byte[readCount];
+                int tempCount = readCount;
+                if (_bigEndian)
+                {
+                    while (tempCount > 0)
+                    {
+                        fallbackBytes[--tempCount] = unchecked((byte)iChar);
+                        iChar >>= 8;
+                    }
+                }
+                else
+                {
+                    while (tempCount > 0)
+                    {
+                        fallbackBytes[--tempCount] = unchecked((byte)(iChar >> 24));
+                        iChar <<= 8;
+                    }
+                }
+
+                charsForFallback = chars;
+                bool fallbackResult = fallbackBuffer.InternalFallback(fallbackBytes, bytes, ref charsForFallback);
+                chars = charsForFallback;
+
+                if (!fallbackResult)
+                {
+                    // Couldn't fallback.
+                    fallbackBuffer.InternalReset();
+                    ThrowCharsOverflow(decoder, chars == charStart);// Might throw, if no chars output
+                    // Stop here, didn't throw, backed up, so still nothing in buffer
+                }
+                else
+                {
+                    // Don't clear our decoder unless we could fall it back.
+                    // If we caught the if above, then we're a convert() and will catch this next time.
+                    readCount = 0;
+                    iChar = 0;
+                }
+            }
+
+            // Remember any left over stuff, clearing buffer as well for MustFlush
+            if (decoder != null)
+            {
+                decoder.iChar = (int)iChar;
+                decoder.readByteCount = readCount;
+                decoder._bytesUsed = (int)(bytes - byteStart);
+            }
+
+            // Shouldn't have anything in fallback buffer for GetChars
+            // (don't have to check _throwOnOverflow for chars)
+            Debug.Assert(fallbackBuffer.Remaining == 0,
+                "[UTF32Encoding.GetChars]Expected empty fallback buffer at end");
+
+            // Return our count
+            return (int)(chars - charStart);
+        }
+
+
+        private uint GetSurrogate(char cHigh, char cLow)
+        {
+            return (((uint)cHigh - 0xD800) * 0x400) + ((uint)cLow - 0xDC00) + 0x10000;
+        }
+
+        private char GetHighSurrogate(uint iChar)
+        {
+            return (char)((iChar - 0x10000) / 0x400 + 0xD800);
+        }
+
+        private char GetLowSurrogate(uint iChar)
+        {
+            return (char)((iChar - 0x10000) % 0x400 + 0xDC00);
+        }
+
+
+        public override Decoder GetDecoder()
+        {
+            return new UTF32Decoder(this);
+        }
+
+
+        public override Encoder GetEncoder()
+        {
+            return new EncoderNLS(this);
+        }
+
+
+        public override int GetMaxByteCount(int charCount)
+        {
+            if (charCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(charCount),
+                     SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Characters would be # of characters + 1 in case left over high surrogate is ? * max fallback
+            long byteCount = (long)charCount + 1;
+
+            if (EncoderFallback.MaxCharCount > 1)
+                byteCount *= EncoderFallback.MaxCharCount;
+
+            // 4 bytes per char
+            byteCount *= 4;
+
+            if (byteCount > 0x7fffffff)
+                throw new ArgumentOutOfRangeException(nameof(charCount), SR.ArgumentOutOfRange_GetByteCountOverflow);
+
+            return (int)byteCount;
+        }
+
+
+        public override int GetMaxCharCount(int byteCount)
+        {
+            if (byteCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(byteCount),
+                     SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // A supplementary character becomes 2 surrogate characters, so 4 input bytes becomes 2 chars,
+            // plus we may have 1 surrogate char left over if the decoder has 3 bytes in it already for a non-bmp char.
+            // Have to add another one because 1/2 == 0, but 3 bytes left over could be 2 char surrogate pair
+            int charCount = (byteCount / 2) + 2;
+
+            // Also consider fallback because our input bytes could be out of range of unicode.
+            // Since fallback would fallback 4 bytes at a time, we'll only fall back 1/2 of MaxCharCount.
+            if (DecoderFallback.MaxCharCount > 2)
+            {
+                // Multiply time fallback size
+                charCount *= DecoderFallback.MaxCharCount;
+
+                // We were already figuring 2 chars per 4 bytes, but fallback will be different #
+                charCount /= 2;
+            }
+
+            if (charCount > 0x7fffffff)
+                throw new ArgumentOutOfRangeException(nameof(byteCount), SR.ArgumentOutOfRange_GetCharCountOverflow);
+
+            return (int)charCount;
+        }
+
+
+        public override byte[] GetPreamble()
+        {
+            if (_emitUTF32ByteOrderMark)
+            {
+                // Allocate new array to prevent users from modifying it.
+                if (_bigEndian)
+                {
+                    return new byte[4] { 0x00, 0x00, 0xFE, 0xFF };
+                }
+                else
+                {
+                    return new byte[4] { 0xFF, 0xFE, 0x00, 0x00 }; // 00 00 FE FF
+                }
+            }
+            else
+                return Array.Empty<byte>();
+        }
+
+        public override ReadOnlySpan<byte> Preamble =>
+            GetType() != typeof(UTF32Encoding) ? GetPreamble() : // in case a derived UTF32Encoding overrode GetPreamble
+            _emitUTF32ByteOrderMark ? (_bigEndian ? s_bigEndianPreamble : s_littleEndianPreamble) :
+            Array.Empty<byte>();
+
+        public override bool Equals(Object value)
+        {
+            UTF32Encoding that = value as UTF32Encoding;
+            if (that != null)
+            {
+                return (_emitUTF32ByteOrderMark == that._emitUTF32ByteOrderMark) &&
+                       (_bigEndian == that._bigEndian) &&
+                       (EncoderFallback.Equals(that.EncoderFallback)) &&
+                       (DecoderFallback.Equals(that.DecoderFallback));
+            }
+            return (false);
+        }
+
+
+        public override int GetHashCode()
+        {
+            //Not great distribution, but this is relatively unlikely to be used as the key in a hashtable.
+            return this.EncoderFallback.GetHashCode() + this.DecoderFallback.GetHashCode() +
+                   CodePage + (_emitUTF32ByteOrderMark ? 4 : 0) + (_bigEndian ? 8 : 0);
+        }
+
+        private sealed class UTF32Decoder : DecoderNLS
+        {
+            // Need a place to store any extra bytes we may have picked up
+            internal int iChar = 0;
+            internal int readByteCount = 0;
+
+            public UTF32Decoder(UTF32Encoding encoding) : base(encoding)
+            {
+                // base calls reset
+            }
+
+            public override void Reset()
+            {
+                this.iChar = 0;
+                this.readByteCount = 0;
+                if (_fallbackBuffer != null)
+                    _fallbackBuffer.Reset();
+            }
+
+            // Anything left in our decoder?
+            internal override bool HasState
+            {
+                get
+                {
+                    // ReadByteCount is our flag.  (iChar==0 doesn't mean much).
+                    return (this.readByteCount != 0);
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/UTF7Encoding.cs b/src/System.Private.CoreLib/shared/System/Text/UTF7Encoding.cs
new file mode 100644
index 0000000000..0246c28915
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/UTF7Encoding.cs
@@ -0,0 +1,978 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+// Don't override IsAlwaysNormalized because it is just a Unicode Transformation and could be confused.
+//
+
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System.Text
+{
+    public class UTF7Encoding : Encoding
+    {
+        private const String base64Chars =
+            "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+        //   0123456789111111111122222222223333333333444444444455555555556666
+        //             012345678901234567890123456789012345678901234567890123
+
+        // These are the characters that can be directly encoded in UTF7.
+        private const String directChars =
+            "\t\n\r '(),-./0123456789:?ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+
+        // These are the characters that can be optionally directly encoded in UTF7.
+        private const String optionalChars =
+            "!\"#$%&*;<=>@[]^_`{|}";
+
+        // Used by Encoding.UTF7 for lazy initialization
+        // The initialization code will not be run until a static member of the class is referenced
+        internal static readonly UTF7Encoding s_default = new UTF7Encoding();
+
+        // The set of base 64 characters.
+        private byte[] _base64Bytes;
+        // The decoded bits for every base64 values. This array has a size of 128 elements.
+        // The index is the code point value of the base 64 characters.  The value is -1 if
+        // the code point is not a valid base 64 character.  Otherwise, the value is a value
+        // from 0 ~ 63.
+        private sbyte[] _base64Values;
+        // The array to decide if a Unicode code point below 0x80 can be directly encoded in UTF7.
+        // This array has a size of 128.
+        private bool[] _directEncode;
+
+        private bool _allowOptionals;
+
+        private const int UTF7_CODEPAGE = 65000;
+
+
+        public UTF7Encoding()
+            : this(false)
+        {
+        }
+
+        public UTF7Encoding(bool allowOptionals)
+            : base(UTF7_CODEPAGE) //Set the data item.
+        {
+            // Allowing optionals?
+            _allowOptionals = allowOptionals;
+
+            // Make our tables
+            MakeTables();
+        }
+
+        private void MakeTables()
+        {
+            // Build our tables
+            _base64Bytes = new byte[64];
+            for (int i = 0; i < 64; i++) _base64Bytes[i] = (byte)base64Chars[i];
+            _base64Values = new sbyte[128];
+            for (int i = 0; i < 128; i++) _base64Values[i] = -1;
+            for (int i = 0; i < 64; i++) _base64Values[_base64Bytes[i]] = (sbyte)i;
+            _directEncode = new bool[128];
+            int count = directChars.Length;
+            for (int i = 0; i < count; i++)
+            {
+                _directEncode[directChars[i]] = true;
+            }
+
+            if (_allowOptionals)
+            {
+                count = optionalChars.Length;
+                for (int i = 0; i < count; i++)
+                {
+                    _directEncode[optionalChars[i]] = true;
+                }
+            }
+        }
+
+        // We go ahead and set this because Encoding expects it, however nothing can fall back in UTF7.
+        internal override void SetDefaultFallbacks()
+        {
+            // UTF7 had an odd decoderFallback behavior, and the Encoder fallback
+            // is irrelevant because we encode surrogates individually and never check for unmatched ones
+            // (so nothing can fallback during encoding)
+            this.encoderFallback = new EncoderReplacementFallback(String.Empty);
+            this.decoderFallback = new DecoderUTF7Fallback();
+        }
+
+        public override bool Equals(Object value)
+        {
+            UTF7Encoding that = value as UTF7Encoding;
+            if (that != null)
+            {
+                return (_allowOptionals == that._allowOptionals) &&
+                       (EncoderFallback.Equals(that.EncoderFallback)) &&
+                       (DecoderFallback.Equals(that.DecoderFallback));
+            }
+            return (false);
+        }
+
+        // Compared to all the other encodings, variations of UTF7 are unlikely
+
+        public override int GetHashCode()
+        {
+            return this.CodePage + this.EncoderFallback.GetHashCode() + this.DecoderFallback.GetHashCode();
+        }
+
+        // The following methods are copied from EncodingNLS.cs.
+        // Unfortunately EncodingNLS.cs is internal and we're public, so we have to re-implement them here.
+        // These should be kept in sync for the following classes:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        // Returns the number of bytes required to encode a range of characters in
+        // a character array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetByteCount(char[] chars, int index, int count)
+        {
+            // Validate input parameters
+            if (chars == null)
+                throw new ArgumentNullException("chars", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - index < count)
+                throw new ArgumentOutOfRangeException("chars", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // If no input, return 0, avoid fixed empty array problem
+            if (count == 0)
+                return 0;
+
+            // Just call the pointer version
+            fixed (char* pChars = chars)
+                return GetByteCount(pChars + index, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetByteCount(string s)
+        {
+            // Validate input
+            if (s==null)
+                throw new ArgumentNullException("s");
+
+            fixed (char* pChars = s)
+                return GetByteCount(pChars, s.Length, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetByteCount(char* chars, int count)
+        {
+            // Validate Parameters
+            if (chars == null)
+                throw new ArgumentNullException("chars", SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException("count", SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Call it with empty encoder
+            return GetByteCount(chars, count, null);
+        }
+
+        // Parent method is safe.
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        public override unsafe int GetBytes(string s, int charIndex, int charCount,
+                                              byte[] bytes, int byteIndex)
+        {
+            if (s == null || bytes == null)
+                throw new ArgumentNullException((s == null ? "s" : "bytes"), SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? "charIndex" : "charCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (s.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException("s", SR.ArgumentOutOfRange_IndexCount);
+
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+                throw new ArgumentOutOfRangeException("byteIndex", SR.ArgumentOutOfRange_Index);
+
+            int byteCount = bytes.Length - byteIndex;
+
+            fixed (char* pChars = s) fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+                return GetBytes(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, null);
+        }
+
+        // Encodes a range of characters in a character array into a range of bytes
+        // in a byte array. An exception occurs if the byte array is not large
+        // enough to hold the complete encoding of the characters. The
+        // GetByteCount method can be used to determine the exact number of
+        // bytes that will be produced for a given range of characters.
+        // Alternatively, the GetMaxByteCount method can be used to
+        // determine the maximum number of bytes that will be produced for a given
+        // number of characters, regardless of the actual character values.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetBytes(char[] chars, int charIndex, int charCount,
+                                               byte[] bytes, int byteIndex)
+        {
+            // Validate parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException((chars == null ? "chars" : "bytes"), SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? "charIndex" : "charCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException("chars", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+                throw new ArgumentOutOfRangeException("byteIndex", SR.ArgumentOutOfRange_Index);
+
+            // If nothing to encode return 0, avoid fixed problem
+            if (charCount == 0)
+                return 0;
+
+            // Just call pointer version
+            int byteCount = bytes.Length - byteIndex;
+
+            fixed (char* pChars = chars) fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+                // Remember that byteCount is # to decode, not size of array.
+                return GetBytes(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetBytes(char* chars, int charCount, byte* bytes, int byteCount)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? "charCount" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetBytes(chars, charCount, bytes, byteCount, null);
+        }
+
+        // Returns the number of characters produced by decoding a range of bytes
+        // in a byte array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetCharCount(byte[] bytes, int index, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (bytes.Length - index < count)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // If no input just return 0, fixed doesn't like 0 length arrays.
+            if (count == 0)
+                return 0;
+
+            // Just call pointer version
+            fixed (byte* pBytes = bytes)
+                return GetCharCount(pBytes + index, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetCharCount(byte* bytes, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException("count", SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetCharCount(bytes, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetChars(byte[] bytes, int byteIndex, int byteCount,
+                                              char[] chars, int charIndex)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (byteIndex < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((byteIndex < 0 ? "byteIndex" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if ( bytes.Length - byteIndex < byteCount)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (charIndex < 0 || charIndex > chars.Length)
+                throw new ArgumentOutOfRangeException("charIndex", SR.ArgumentOutOfRange_Index);
+
+            // If no input, return 0 & avoid fixed problem
+            if (byteCount == 0)
+                return 0;
+
+            // Just call pointer version
+            int charCount = chars.Length - charIndex;
+
+            fixed (byte* pBytes = bytes) fixed (char* pChars = &MemoryMarshal.GetReference((Span<char>)chars))
+                // Remember that charCount is # to decode, not size of array
+                return GetChars(pBytes + byteIndex, byteCount, pChars + charIndex, charCount, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public unsafe override int GetChars(byte* bytes, int byteCount, char* chars, int charCount)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? "charCount" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetChars(bytes, byteCount, chars, charCount, null);
+        }
+
+        // Returns a string containing the decoded representation of a range of
+        // bytes in a byte array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe String GetString(byte[] bytes, int index, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (bytes.Length - index < count)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // Avoid problems with empty input buffer
+            if (count == 0) return String.Empty;
+
+            fixed (byte* pBytes = bytes)
+                return String.CreateStringFromEncoding(
+                    pBytes + index, count, this);
+        }
+
+        //
+        // End of standard methods copied from EncodingNLS.cs
+        //
+
+        internal override unsafe int GetByteCount(char* chars, int count, EncoderNLS baseEncoder)
+        {
+            Debug.Assert(chars != null, "[UTF7Encoding.GetByteCount]chars!=null");
+            Debug.Assert(count >= 0, "[UTF7Encoding.GetByteCount]count >=0");
+
+            // Just call GetBytes with bytes == null
+            return GetBytes(chars, count, null, 0, baseEncoder);
+        }
+
+        internal override unsafe int GetBytes(char* chars, int charCount,
+                                                byte* bytes, int byteCount, EncoderNLS baseEncoder)
+        {
+            Debug.Assert(byteCount >= 0, "[UTF7Encoding.GetBytes]byteCount >=0");
+            Debug.Assert(chars != null, "[UTF7Encoding.GetBytes]chars!=null");
+            Debug.Assert(charCount >= 0, "[UTF7Encoding.GetBytes]charCount >=0");
+
+            // Get encoder info
+            UTF7Encoding.Encoder encoder = (UTF7Encoding.Encoder)baseEncoder;
+
+            // Default bits & count
+            int bits = 0;
+            int bitCount = -1;
+
+            // prepare our helpers
+            Encoding.EncodingByteBuffer buffer = new Encoding.EncodingByteBuffer(
+                this, encoder, bytes, byteCount, chars, charCount);
+
+            if (encoder != null)
+            {
+                bits = encoder.bits;
+                bitCount = encoder.bitCount;
+
+                // May have had too many left over
+                while (bitCount >= 6)
+                {
+                    bitCount -= 6;
+                    // If we fail we'll never really have enough room
+                    if (!buffer.AddByte(_base64Bytes[(bits >> bitCount) & 0x3F]))
+                        ThrowBytesOverflow(encoder, buffer.Count == 0);
+                }
+            }
+
+            while (buffer.MoreData)
+            {
+                char currentChar = buffer.GetNextChar();
+
+                if (currentChar < 0x80 && _directEncode[currentChar])
+                {
+                    if (bitCount >= 0)
+                    {
+                        if (bitCount > 0)
+                        {
+                            // Try to add the next byte
+                            if (!buffer.AddByte(_base64Bytes[bits << 6 - bitCount & 0x3F]))
+                                break;                                          // Stop here, didn't throw
+
+                            bitCount = 0;
+                        }
+
+                        // Need to get emit '-' and our char, 2 bytes total
+                        if (!buffer.AddByte((byte)'-'))
+                            break;                                          // Stop here, didn't throw
+
+                        bitCount = -1;
+                    }
+
+                    // Need to emit our char
+                    if (!buffer.AddByte((byte)currentChar))
+                        break;                                          // Stop here, didn't throw
+                }
+                else if (bitCount < 0 && currentChar == '+')
+                {
+                    if (!buffer.AddByte((byte)'+', (byte)'-'))
+                        break;                                          // Stop here, didn't throw
+                }
+                else
+                {
+                    if (bitCount < 0)
+                    {
+                        // Need to emit a + and 12 bits (3 bytes)
+                        // Only 12 of the 16 bits will be emitted this time, the other 4 wait 'til next time
+                        if (!buffer.AddByte((byte)'+'))
+                            break;                                          // Stop here, didn't throw
+
+                        // We're now in bit mode, but haven't stored data yet
+                        bitCount = 0;
+                    }
+
+                    // Add our bits
+                    bits = bits << 16 | currentChar;
+                    bitCount += 16;
+
+                    while (bitCount >= 6)
+                    {
+                        bitCount -= 6;
+                        if (!buffer.AddByte(_base64Bytes[(bits >> bitCount) & 0x3F]))
+                        {
+                            bitCount += 6;                              // We didn't use these bits
+                            currentChar = buffer.GetNextChar();              // We're processing this char still, but AddByte
+                                                                             // --'d it when we ran out of space
+                            break;                                      // Stop here, not enough room for bytes
+                        }
+                    }
+
+                    if (bitCount >= 6)
+                        break;                  // Didn't have room to encode enough bits
+                }
+            }
+
+            // Now if we have bits left over we have to encode them.
+            // MustFlush may have been cleared by encoding.ThrowBytesOverflow earlier if converting
+            if (bitCount >= 0 && (encoder == null || encoder.MustFlush))
+            {
+                // Do we have bits we have to stick in?
+                if (bitCount > 0)
+                {
+                    if (buffer.AddByte(_base64Bytes[(bits << (6 - bitCount)) & 0x3F]))
+                    {
+                        // Emitted spare bits, 0 bits left
+                        bitCount = 0;
+                    }
+                }
+
+                // If converting and failed bitCount above, then we'll fail this too
+                if (buffer.AddByte((byte)'-'))
+                {
+                    // turned off bit mode';
+                    bits = 0;
+                    bitCount = -1;
+                }
+                else
+                    // If not successful, convert will maintain state for next time, also
+                    // AddByte will have decremented our char count, however we need it to remain the same
+                    buffer.GetNextChar();
+            }
+
+            // Do we have an encoder we're allowed to use?
+            // bytes == null if counting, so don't use encoder then
+            if (bytes != null && encoder != null)
+            {
+                // We already cleared bits & bitcount for mustflush case
+                encoder.bits = bits;
+                encoder.bitCount = bitCount;
+                encoder._charsUsed = buffer.CharsUsed;
+            }
+
+            return buffer.Count;
+        }
+
+        internal override unsafe int GetCharCount(byte* bytes, int count, DecoderNLS baseDecoder)
+        {
+            Debug.Assert(count >= 0, "[UTF7Encoding.GetCharCount]count >=0");
+            Debug.Assert(bytes != null, "[UTF7Encoding.GetCharCount]bytes!=null");
+
+            // Just call GetChars with null char* to do counting
+            return GetChars(bytes, count, null, 0, baseDecoder);
+        }
+
+        internal override unsafe int GetChars(byte* bytes, int byteCount,
+                                                char* chars, int charCount, DecoderNLS baseDecoder)
+        {
+            Debug.Assert(byteCount >= 0, "[UTF7Encoding.GetChars]byteCount >=0");
+            Debug.Assert(bytes != null, "[UTF7Encoding.GetChars]bytes!=null");
+            Debug.Assert(charCount >= 0, "[UTF7Encoding.GetChars]charCount >=0");
+
+            // Might use a decoder
+            UTF7Encoding.Decoder decoder = (UTF7Encoding.Decoder)baseDecoder;
+
+            // Get our output buffer info.
+            Encoding.EncodingCharBuffer buffer = new Encoding.EncodingCharBuffer(
+                this, decoder, chars, charCount, bytes, byteCount);
+
+            // Get decoder info
+            int bits = 0;
+            int bitCount = -1;
+            bool firstByte = false;
+            if (decoder != null)
+            {
+                bits = decoder.bits;
+                bitCount = decoder.bitCount;
+                firstByte = decoder.firstByte;
+
+                Debug.Assert(firstByte == false || decoder.bitCount <= 0,
+                    "[UTF7Encoding.GetChars]If remembered bits, then first byte flag shouldn't be set");
+            }
+
+            // We may have had bits in the decoder that we couldn't output last time, so do so now
+            if (bitCount >= 16)
+            {
+                // Check our decoder buffer
+                if (!buffer.AddChar((char)((bits >> (bitCount - 16)) & 0xFFFF)))
+                    ThrowCharsOverflow(decoder, true);  // Always throw, they need at least 1 char even in Convert
+
+                // Used this one, clean up extra bits
+                bitCount -= 16;
+            }
+
+            // Loop through the input
+            while (buffer.MoreData)
+            {
+                byte currentByte = buffer.GetNextByte();
+                int c;
+
+                if (bitCount >= 0)
+                {
+                    //
+                    // Modified base 64 encoding.
+                    //
+                    sbyte v;
+                    if (currentByte < 0x80 && ((v = _base64Values[currentByte]) >= 0))
+                    {
+                        firstByte = false;
+                        bits = (bits << 6) | ((byte)v);
+                        bitCount += 6;
+                        if (bitCount >= 16)
+                        {
+                            c = (bits >> (bitCount - 16)) & 0xFFFF;
+                            bitCount -= 16;
+                        }
+                        // If not enough bits just continue
+                        else continue;
+                    }
+                    else
+                    {
+                        // If it wasn't a base 64 byte, everything's going to turn off base 64 mode
+                        bitCount = -1;
+
+                        if (currentByte != '-')
+                        {
+                            // >= 0x80 (because of 1st if statemtn)
+                            // We need this check since the _base64Values[b] check below need b <= 0x7f.
+                            // This is not a valid base 64 byte.  Terminate the shifted-sequence and
+                            // emit this byte.
+
+                            // not in base 64 table
+                            // According to the RFC 1642 and the example code of UTF-7
+                            // in Unicode 2.0, we should just zero-extend the invalid UTF7 byte
+
+                            // Chars won't be updated unless this works, try to fallback
+                            if (!buffer.Fallback(currentByte))
+                                break;                                          // Stop here, didn't throw
+
+                            // Used that byte, we're done with it
+                            continue;
+                        }
+
+                        //
+                        // The encoding for '+' is "+-".
+                        //
+                        if (firstByte) c = '+';
+                        // We just turn it off if not emitting a +, so we're done.
+                        else continue;
+                    }
+                    //
+                    // End of modified base 64 encoding block.
+                    //
+                }
+                else if (currentByte == '+')
+                {
+                    //
+                    // Found the start of a modified base 64 encoding block or a plus sign.
+                    //
+                    bitCount = 0;
+                    firstByte = true;
+                    continue;
+                }
+                else
+                {
+                    // Normal character
+                    if (currentByte >= 0x80)
+                    {
+                        // Try to fallback
+                        if (!buffer.Fallback(currentByte))
+                            break;                                          // Stop here, didn't throw
+
+                        // Done falling back
+                        continue;
+                    }
+
+                    // Use the normal character
+                    c = currentByte;
+                }
+
+                if (c >= 0)
+                {
+                    // Check our buffer
+                    if (!buffer.AddChar((char)c))
+                    {
+                        // No room.  If it was a plain char we'll try again later.
+                        // Note, we'll consume this byte and stick it in decoder, even if we can't output it
+                        if (bitCount >= 0)                                  // Can we rememmber this byte (char)
+                        {
+                            buffer.AdjustBytes(+1);                         // Need to readd the byte that AddChar subtracted when it failed
+                            bitCount += 16;                                 // We'll still need that char we have in our bits
+                        }
+                        break;                                              // didn't throw, stop
+                    }
+                }
+            }
+
+            // Stick stuff in the decoder if we can (chars == null if counting, so don't store decoder)
+            if (chars != null && decoder != null)
+            {
+                // MustFlush?  (Could've been cleared by ThrowCharsOverflow if Convert & didn't reach end of buffer)
+                if (decoder.MustFlush)
+                {
+                    // RFC doesn't specify what would happen if we have non-0 leftover bits, we just drop them
+                    decoder.bits = 0;
+                    decoder.bitCount = -1;
+                    decoder.firstByte = false;
+                }
+                else
+                {
+                    decoder.bits = bits;
+                    decoder.bitCount = bitCount;
+                    decoder.firstByte = firstByte;
+                }
+                decoder._bytesUsed = buffer.BytesUsed;
+            }
+            // else ignore any hanging bits.
+
+            // Return our count
+            return buffer.Count;
+        }
+
+
+        public override System.Text.Decoder GetDecoder()
+        {
+            return new UTF7Encoding.Decoder(this);
+        }
+
+
+        public override System.Text.Encoder GetEncoder()
+        {
+            return new UTF7Encoding.Encoder(this);
+        }
+
+
+        public override int GetMaxByteCount(int charCount)
+        {
+            if (charCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(charCount),
+                     SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Suppose that every char can not be direct-encoded, we know that
+            // a byte can encode 6 bits of the Unicode character.  And we will
+            // also need two extra bytes for the shift-in ('+') and shift-out ('-') mark.
+            // Therefore, the max byte should be:
+            // byteCount = 2 + Math.Ceiling((double)charCount * 16 / 6);
+            // That is always <= 2 + 3 * charCount;
+            // Longest case is alternating encoded, direct, encoded data for 5 + 1 + 5... bytes per char.
+            // UTF7 doesn't have left over surrogates, but if no input we may need an output - to turn off
+            // encoding if MustFlush is true.
+
+            // Its easiest to think of this as 2 bytes to turn on/off the base64 mode, then 3 bytes per char.
+            // 3 bytes is 18 bits of encoding, which is more than we need, but if its direct encoded then 3
+            // bytes allows us to turn off and then back on base64 mode if necessary.
+
+            // Note that UTF7 encoded surrogates individually and isn't worried about mismatches, so all
+            // code points are encodable int UTF7.
+            long byteCount = (long)charCount * 3 + 2;
+
+            // check for overflow
+            if (byteCount > 0x7fffffff)
+                throw new ArgumentOutOfRangeException(nameof(charCount), SR.ArgumentOutOfRange_GetByteCountOverflow);
+
+            return (int)byteCount;
+        }
+
+
+        public override int GetMaxCharCount(int byteCount)
+        {
+            if (byteCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(byteCount),
+                     SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Worst case is 1 char per byte.  Minimum 1 for left over bits in case decoder is being flushed
+            // Also note that we ignore extra bits (per spec), so UTF7 doesn't have unknown in this direction.
+            int charCount = byteCount;
+            if (charCount == 0) charCount = 1;
+
+            return charCount;
+        }
+
+        // Of all the amazing things... This MUST be Decoder so that our com name
+        // for System.Text.Decoder doesn't change
+        private sealed class Decoder : DecoderNLS
+        {
+            /*private*/
+            internal int bits;
+            /*private*/
+            internal int bitCount;
+            /*private*/
+            internal bool firstByte;
+
+            public Decoder(UTF7Encoding encoding) : base(encoding)
+            {
+                // base calls reset
+            }
+
+            public override void Reset()
+            {
+                this.bits = 0;
+                this.bitCount = -1;
+                this.firstByte = false;
+                if (_fallbackBuffer != null)
+                    _fallbackBuffer.Reset();
+            }
+
+            // Anything left in our encoder?
+            internal override bool HasState
+            {
+                get
+                {
+                    // NOTE: This forces the last -, which some encoder might not encode.  If we
+                    // don't see it we don't think we're done reading.
+                    return (this.bitCount != -1);
+                }
+            }
+        }
+
+        // Of all the amazing things... This MUST be Encoder so that our com name
+        // for System.Text.Encoder doesn't change
+        private sealed class Encoder : EncoderNLS
+        {
+            /*private*/
+            internal int bits;
+            /*private*/
+            internal int bitCount;
+
+            public Encoder(UTF7Encoding encoding) : base(encoding)
+            {
+                // base calls reset
+            }
+
+            public override void Reset()
+            {
+                this.bitCount = -1;
+                this.bits = 0;
+                if (_fallbackBuffer != null)
+                    _fallbackBuffer.Reset();
+            }
+
+            // Anything left in our encoder?
+            internal override bool HasState
+            {
+                get
+                {
+                    return (this.bits != 0 || this.bitCount != -1);
+                }
+            }
+        }
+
+        // Preexisting UTF7 behavior for bad bytes was just to spit out the byte as the next char
+        // and turn off base64 mode if it was in that mode.  We still exit the mode, but now we fallback.
+        private sealed class DecoderUTF7Fallback : DecoderFallback
+        {
+            // Construction.  Default replacement fallback uses no best fit and ? replacement string
+            public DecoderUTF7Fallback()
+            {
+            }
+
+            public override DecoderFallbackBuffer CreateFallbackBuffer()
+            {
+                return new DecoderUTF7FallbackBuffer(this);
+            }
+
+            // Maximum number of characters that this instance of this fallback could return
+            public override int MaxCharCount
+            {
+                get
+                {
+                    // returns 1 char per bad byte
+                    return 1;
+                }
+            }
+
+            public override bool Equals(Object value)
+            {
+                DecoderUTF7Fallback that = value as DecoderUTF7Fallback;
+                if (that != null)
+                {
+                    return true;
+                }
+                return (false);
+            }
+
+            public override int GetHashCode()
+            {
+                return 984;
+            }
+        }
+
+        private sealed class DecoderUTF7FallbackBuffer : DecoderFallbackBuffer
+        {
+            // Store our default string
+            private char cFallback = (char)0;
+            private int iCount = -1;
+            private int iSize;
+
+            // Construction
+            public DecoderUTF7FallbackBuffer(DecoderUTF7Fallback fallback)
+            {
+            }
+
+            // Fallback Methods
+            public override bool Fallback(byte[] bytesUnknown, int index)
+            {
+                // We expect no previous fallback in our buffer
+                Debug.Assert(iCount < 0, "[DecoderUTF7FallbackBuffer.Fallback] Can't have recursive fallbacks");
+                Debug.Assert(bytesUnknown.Length == 1, "[DecoderUTF7FallbackBuffer.Fallback] Only possible fallback case should be 1 unknown byte");
+
+                // Go ahead and get our fallback
+                cFallback = (char)bytesUnknown[0];
+
+                // Any of the fallback characters can be handled except for 0
+                if (cFallback == 0)
+                {
+                    return false;
+                }
+
+                iCount = iSize = 1;
+
+                return true;
+            }
+
+            public override char GetNextChar()
+            {
+                if (iCount-- > 0)
+                    return cFallback;
+
+                // Note: this means that 0 in UTF7 stream will never be emitted.
+                return (char)0;
+            }
+
+            public override bool MovePrevious()
+            {
+                if (iCount >= 0)
+                {
+                    iCount++;
+                }
+
+                // return true if we were allowed to do this
+                return (iCount >= 0 && iCount <= iSize);
+            }
+
+            // Return # of chars left in this fallback
+            public override int Remaining
+            {
+                get
+                {
+                    return (iCount > 0) ? iCount : 0;
+                }
+            }
+
+            // Clear the buffer
+            public override unsafe void Reset()
+            {
+                iCount = -1;
+                byteStart = null;
+            }
+
+            // This version just counts the fallback and doesn't actually copy anything.
+            internal unsafe override int InternalFallback(byte[] bytes, byte* pBytes)
+            // Right now this has both bytes and bytes[], since we might have extra bytes, hence the
+            // array, and we might need the index, hence the byte*
+            {
+                // We expect no previous fallback in our buffer
+                Debug.Assert(iCount < 0, "[DecoderUTF7FallbackBuffer.InternalFallback] Can't have recursive fallbacks");
+                if (bytes.Length != 1)
+                {
+                    throw new ArgumentException(SR.Argument_InvalidCharSequenceNoIndex);
+                }
+
+                // Can't fallback a byte 0, so return for that case, 1 otherwise.
+                return bytes[0] == 0 ? 0 : 1;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/UTF8Encoding.cs b/src/System.Private.CoreLib/shared/System/Text/UTF8Encoding.cs
new file mode 100644
index 0000000000..2ea5096243
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/UTF8Encoding.cs
@@ -0,0 +1,2561 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// The worker functions in this file was optimized for performance. If you make changes
+// you should use care to consider all of the interesting cases.
+
+// The code of all worker functions in this file is written twice: Once as as a slow loop, and the
+// second time as a fast loop. The slow loops handles all special cases, throws exceptions, etc.
+// The fast loops attempts to blaze through as fast as possible with optimistic range checks,
+// processing multiple characters at a time, and falling back to the slow loop for all special cases.
+
+// This define can be used to turn off the fast loops. Useful for finding whether
+// the problem is fastloop-specific.
+#define FASTLOOP
+
+using System;
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.InteropServices;
+
+namespace System.Text
+{
+    // Encodes text into and out of UTF-8.  UTF-8 is a way of writing
+    // Unicode characters with variable numbers of bytes per character,
+    // optimized for the lower 127 ASCII characters.  It's an efficient way
+    // of encoding US English in an internationalizable way.
+    //
+    // Don't override IsAlwaysNormalized because it is just a Unicode Transformation and could be confused.
+    //
+    // The UTF-8 byte order mark is simply the Unicode byte order mark
+    // (0xFEFF) written in UTF-8 (0xEF 0xBB 0xBF).  The byte order mark is
+    // used mostly to distinguish UTF-8 text from other encodings, and doesn't
+    // switch the byte orderings.
+
+    public class UTF8Encoding : Encoding
+    {
+        /*
+            bytes   bits    UTF-8 representation
+            -----   ----    -----------------------------------
+            1        7      0vvvvvvv
+            2       11      110vvvvv 10vvvvvv
+            3       16      1110vvvv 10vvvvvv 10vvvvvv
+            4       21      11110vvv 10vvvvvv 10vvvvvv 10vvvvvv
+            -----   ----    -----------------------------------
+
+            Surrogate:
+            Real Unicode value = (HighSurrogate - 0xD800) * 0x400 + (LowSurrogate - 0xDC00) + 0x10000
+        */
+
+        private const int UTF8_CODEPAGE = 65001;
+
+        // Allow for de-virtualization (see https://github.com/dotnet/coreclr/pull/9230)
+        internal sealed class UTF8EncodingSealed : UTF8Encoding
+        {
+            public UTF8EncodingSealed(bool encoderShouldEmitUTF8Identifier) : base(encoderShouldEmitUTF8Identifier) { }
+
+            public override ReadOnlySpan<byte> Preamble => _emitUTF8Identifier ? s_preamble : Array.Empty<byte>();
+        }
+
+        // Used by Encoding.UTF8 for lazy initialization
+        // The initialization code will not be run until a static member of the class is referenced
+        internal static readonly UTF8EncodingSealed s_default = new UTF8EncodingSealed(encoderShouldEmitUTF8Identifier: true);
+
+        internal static readonly byte[] s_preamble = new byte[3] { 0xEF, 0xBB, 0xBF };
+
+        // Yes, the idea of emitting U+FEFF as a UTF-8 identifier has made it into
+        // the standard.
+        internal readonly bool _emitUTF8Identifier = false;
+
+        private bool _isThrowException = false;
+
+
+        public UTF8Encoding() : this(false)
+        {
+        }
+
+
+        public UTF8Encoding(bool encoderShouldEmitUTF8Identifier) :
+            this(encoderShouldEmitUTF8Identifier, false)
+        {
+        }
+
+
+        public UTF8Encoding(bool encoderShouldEmitUTF8Identifier, bool throwOnInvalidBytes) :
+            base(UTF8_CODEPAGE)
+        {
+            _emitUTF8Identifier = encoderShouldEmitUTF8Identifier;
+            _isThrowException = throwOnInvalidBytes;
+
+            // Encoding's constructor already did this, but it'll be wrong if we're throwing exceptions
+            if (_isThrowException)
+                SetDefaultFallbacks();
+        }
+
+        internal override void SetDefaultFallbacks()
+        {
+            // For UTF-X encodings, we use a replacement fallback with an empty string
+            if (_isThrowException)
+            {
+                this.encoderFallback = EncoderFallback.ExceptionFallback;
+                this.decoderFallback = DecoderFallback.ExceptionFallback;
+            }
+            else
+            {
+                this.encoderFallback = new EncoderReplacementFallback("\xFFFD");
+                this.decoderFallback = new DecoderReplacementFallback("\xFFFD");
+            }
+        }
+
+
+        // WARNING: GetByteCount(string chars)
+        // WARNING: has different variable names than EncodingNLS.cs, so this can't just be cut & pasted,
+        // WARNING: otherwise it'll break VB's way of declaring these.
+        //
+        // The following methods are copied from EncodingNLS.cs.
+        // Unfortunately EncodingNLS.cs is internal and we're public, so we have to re-implement them here.
+        // These should be kept in sync for the following classes:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        // Returns the number of bytes required to encode a range of characters in
+        // a character array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetByteCount(char[] chars, int index, int count)
+        {
+            // Validate input parameters
+            if (chars == null)
+                throw new ArgumentNullException("chars", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - index < count)
+                throw new ArgumentOutOfRangeException("chars", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // If no input, return 0, avoid fixed empty array problem
+            if (count == 0)
+                return 0;
+
+            // Just call the pointer version
+            fixed (char* pChars = chars)
+                return GetByteCount(pChars + index, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetByteCount(String chars)
+        {
+            // Validate input
+            if (chars==null)
+                throw new ArgumentNullException("s");
+
+            fixed (char* pChars = chars)
+                return GetByteCount(pChars, chars.Length, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetByteCount(char* chars, int count)
+        {
+            // Validate Parameters
+            if (chars == null)
+                throw new ArgumentNullException("chars", SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException("count", SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Call it with empty encoder
+            return GetByteCount(chars, count, null);
+        }
+
+        // Parent method is safe.
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        public override unsafe int GetBytes(String s, int charIndex, int charCount,
+                                              byte[] bytes, int byteIndex)
+        {
+            if (s == null || bytes == null)
+                throw new ArgumentNullException((s == null ? "s" : "bytes"), SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? "charIndex" : "charCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (s.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException("s", SR.ArgumentOutOfRange_IndexCount);
+
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+                throw new ArgumentOutOfRangeException("byteIndex", SR.ArgumentOutOfRange_Index);
+
+            int byteCount = bytes.Length - byteIndex;
+
+            fixed (char* pChars = s) fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+                return GetBytes(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, null);
+        }
+
+        // Encodes a range of characters in a character array into a range of bytes
+        // in a byte array. An exception occurs if the byte array is not large
+        // enough to hold the complete encoding of the characters. The
+        // GetByteCount method can be used to determine the exact number of
+        // bytes that will be produced for a given range of characters.
+        // Alternatively, the GetMaxByteCount method can be used to
+        // determine the maximum number of bytes that will be produced for a given
+        // number of characters, regardless of the actual character values.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetBytes(char[] chars, int charIndex, int charCount,
+                                               byte[] bytes, int byteIndex)
+        {
+            // Validate parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException((chars == null ? "chars" : "bytes"), SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? "charIndex" : "charCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException("chars", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+                throw new ArgumentOutOfRangeException("byteIndex", SR.ArgumentOutOfRange_Index);
+
+            // If nothing to encode return 0, avoid fixed problem
+            if (charCount == 0)
+                return 0;
+
+            // Just call pointer version
+            int byteCount = bytes.Length - byteIndex;
+
+            fixed (char* pChars = chars) fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+                // Remember that byteCount is # to decode, not size of array.
+                return GetBytes(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetBytes(char* chars, int charCount, byte* bytes, int byteCount)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? "charCount" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetBytes(chars, charCount, bytes, byteCount, null);
+        }
+
+        // Returns the number of characters produced by decoding a range of bytes
+        // in a byte array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetCharCount(byte[] bytes, int index, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (bytes.Length - index < count)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // If no input just return 0, fixed doesn't like 0 length arrays.
+            if (count == 0)
+                return 0;
+
+            // Just call pointer version
+            fixed (byte* pBytes = bytes)
+                return GetCharCount(pBytes + index, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetCharCount(byte* bytes, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException("count", SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetCharCount(bytes, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetChars(byte[] bytes, int byteIndex, int byteCount,
+                                              char[] chars, int charIndex)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (byteIndex < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((byteIndex < 0 ? "byteIndex" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if ( bytes.Length - byteIndex < byteCount)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (charIndex < 0 || charIndex > chars.Length)
+                throw new ArgumentOutOfRangeException("charIndex", SR.ArgumentOutOfRange_Index);
+
+            // If no input, return 0 & avoid fixed problem
+            if (byteCount == 0)
+                return 0;
+
+            // Just call pointer version
+            int charCount = chars.Length - charIndex;
+
+            fixed (byte* pBytes = bytes) fixed (char* pChars = &MemoryMarshal.GetReference((Span<char>)chars))
+                // Remember that charCount is # to decode, not size of array
+                return GetChars(pBytes + byteIndex, byteCount, pChars + charIndex, charCount, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public unsafe override int GetChars(byte* bytes, int byteCount, char* chars, int charCount)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? "charCount" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetChars(bytes, byteCount, chars, charCount, null);
+        }
+
+        // Returns a string containing the decoded representation of a range of
+        // bytes in a byte array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe String GetString(byte[] bytes, int index, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (bytes.Length - index < count)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // Avoid problems with empty input buffer
+            if (count == 0) return String.Empty;
+
+            fixed (byte* pBytes = bytes)
+                return String.CreateStringFromEncoding(
+                    pBytes + index, count, this);
+        }
+
+        //
+        // End of standard methods copied from EncodingNLS.cs
+        //
+
+        // To simplify maintenance, the structure of GetByteCount and GetBytes should be
+        // kept the same as much as possible
+        internal override unsafe int GetByteCount(char* chars, int count, EncoderNLS baseEncoder)
+        {
+            // For fallback we may need a fallback buffer.
+            // We wait to initialize it though in case we don't have any broken input unicode
+            EncoderFallbackBuffer fallbackBuffer = null;
+            char* pSrcForFallback;
+
+            char* pSrc = chars;
+            char* pEnd = pSrc + count;
+
+            // Start by assuming we have as many as count
+            int byteCount = count;
+
+            int ch = 0;
+
+            if (baseEncoder != null)
+            {
+                UTF8Encoder encoder = (UTF8Encoder)baseEncoder;
+                ch = encoder.surrogateChar;
+
+                // We mustn't have left over fallback data when counting
+                if (encoder.InternalHasFallbackBuffer)
+                {
+                    fallbackBuffer = encoder.FallbackBuffer;
+                    if (fallbackBuffer.Remaining > 0)
+                        throw new ArgumentException(SR.Format(SR.Argument_EncoderFallbackNotEmpty, this.EncodingName, encoder.Fallback.GetType()));
+
+                    // Set our internal fallback interesting things.
+                    fallbackBuffer.InternalInitialize(chars, pEnd, encoder, false);
+                }
+            }
+
+            for (;;)
+            {
+                // SLOWLOOP: does all range checks, handles all special cases, but it is slow
+                if (pSrc >= pEnd)
+                {
+                    if (ch == 0)
+                    {
+                        // Unroll any fallback that happens at the end
+                        ch = fallbackBuffer != null ? fallbackBuffer.InternalGetNextChar() : 0;
+                        if (ch > 0)
+                        {
+                            byteCount++;
+                            goto ProcessChar;
+                        }
+                    }
+                    else
+                    {
+                        // Case of surrogates in the fallback.
+                        if (fallbackBuffer != null && fallbackBuffer.bFallingBack)
+                        {
+                            Debug.Assert(ch >= 0xD800 && ch <= 0xDBFF,
+                                "[UTF8Encoding.GetBytes]expected high surrogate, not 0x" + ((int)ch).ToString("X4", CultureInfo.InvariantCulture));
+
+                            ch = fallbackBuffer.InternalGetNextChar();
+                            byteCount++;
+
+                            if (InRange(ch, CharUnicodeInfo.LOW_SURROGATE_START, CharUnicodeInfo.LOW_SURROGATE_END))
+                            {
+                                ch = 0xfffd;
+                                byteCount++;
+                                goto EncodeChar;
+                            }
+                            else if (ch > 0)
+                            {
+                                goto ProcessChar;
+                            }
+                            else
+                            {
+                                byteCount--; // ignore last one.
+                                break;
+                            }
+                        }
+                    }
+
+                    if (ch <= 0)
+                    {
+                        break;
+                    }
+                    if (baseEncoder != null && !baseEncoder.MustFlush)
+                    {
+                        break;
+                    }
+
+                    // attempt to encode the partial surrogate (will fallback or ignore it), it'll also subtract 1.
+                    byteCount++;
+                    goto EncodeChar;
+                }
+
+                if (ch > 0)
+                {
+                    Debug.Assert(ch >= 0xD800 && ch <= 0xDBFF,
+                        "[UTF8Encoding.GetBytes]expected high surrogate, not 0x" + ((int)ch).ToString("X4", CultureInfo.InvariantCulture));
+
+                    // use separate helper variables for local contexts so that the jit optimizations
+                    // won't get confused about the variable lifetimes
+                    int cha = *pSrc;
+
+                    // count the pending surrogate
+                    byteCount++;
+
+                    // In previous byte, we encountered a high surrogate, so we are expecting a low surrogate here.
+                    // if (IsLowSurrogate(cha)) {
+                    if (InRange(cha, CharUnicodeInfo.LOW_SURROGATE_START, CharUnicodeInfo.LOW_SURROGATE_END))
+                    {
+                        // Don't need a real # because we're just counting, anything > 0x7ff ('cept surrogate) will do.
+                        ch = 0xfffd;
+                        //                        ch = cha + (ch << 10) +
+                        //                            (0x10000
+                        //                            - CharUnicodeInfo.LOW_SURROGATE_START
+                        //                            - (CharUnicodeInfo.HIGH_SURROGATE_START << 10) );
+
+                        // Use this next char
+                        pSrc++;
+                    }
+                    // else ch is still high surrogate and encoding will fail (so don't add count)
+
+                    // attempt to encode the surrogate or partial surrogate
+                    goto EncodeChar;
+                }
+
+                // If we've used a fallback, then we have to check for it
+                if (fallbackBuffer != null)
+                {
+                    ch = fallbackBuffer.InternalGetNextChar();
+                    if (ch > 0)
+                    {
+                        // We have an extra byte we weren't expecting.
+                        byteCount++;
+                        goto ProcessChar;
+                    }
+                }
+
+                // read next char. The JIT optimization seems to be getting confused when
+                // compiling "ch = *pSrc++;", so rather use "ch = *pSrc; pSrc++;" instead
+                ch = *pSrc;
+                pSrc++;
+
+            ProcessChar:
+                // if (IsHighSurrogate(ch)) {
+                if (InRange(ch, CharUnicodeInfo.HIGH_SURROGATE_START, CharUnicodeInfo.HIGH_SURROGATE_END))
+                {
+                    // we will count this surrogate next time around
+                    byteCount--;
+                    continue;
+                }
+            // either good char or partial surrogate
+
+            EncodeChar:
+                // throw exception on partial surrogate if necessary
+                // if (IsLowSurrogate(ch) || IsHighSurrogate(ch))
+                if (InRange(ch, CharUnicodeInfo.HIGH_SURROGATE_START, CharUnicodeInfo.LOW_SURROGATE_END))
+                {
+                    // Lone surrogates aren't allowed
+                    // Have to make a fallback buffer if we don't have one
+                    if (fallbackBuffer == null)
+                    {
+                        // wait on fallbacks if we can
+                        // For fallback we may need a fallback buffer
+                        if (baseEncoder == null)
+                            fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = baseEncoder.FallbackBuffer;
+
+                        // Set our internal fallback interesting things.
+                        fallbackBuffer.InternalInitialize(chars, chars + count, baseEncoder, false);
+                    }
+
+                    // Do our fallback.  Actually we already know its a mixed up surrogate,
+                    // so the ref pSrc isn't gonna do anything.
+                    pSrcForFallback = pSrc; // Avoid passing pSrc by reference to allow it to be en-registered
+                    fallbackBuffer.InternalFallback(unchecked((char)ch), ref pSrcForFallback);
+                    pSrc = pSrcForFallback;
+
+                    // Ignore it if we don't throw (we had preallocated this ch)
+                    byteCount--;
+                    ch = 0;
+                    continue;
+                }
+
+                // Count them
+                if (ch > 0x7F)
+                {
+                    if (ch > 0x7FF)
+                    {
+                        // the extra surrogate byte was compensated by the second surrogate character
+                        // (2 surrogates make 4 bytes.  We've already counted 2 bytes, 1 per char)
+                        byteCount++;
+                    }
+                    byteCount++;
+                }
+
+#if BIT64
+                // check for overflow
+                if (byteCount < 0)
+                {
+                    break;
+                }
+#endif
+
+#if FASTLOOP
+                // If still have fallback don't do fast loop
+                if (fallbackBuffer != null && (ch = fallbackBuffer.InternalGetNextChar()) != 0)
+                {
+                    // We're reserving 1 byte for each char by default
+                    byteCount++;
+                    goto ProcessChar;
+                }
+
+                int availableChars = PtrDiff(pEnd, pSrc);
+
+                // don't fall into the fast decoding loop if we don't have enough characters
+                if (availableChars <= 13)
+                {
+                    // try to get over the remainder of the ascii characters fast though
+                    char* pLocalEnd = pEnd; // hint to get pLocalEnd en-registered
+                    while (pSrc < pLocalEnd)
+                    {
+                        ch = *pSrc;
+                        pSrc++;
+                        if (ch > 0x7F)
+                            goto ProcessChar;
+                    }
+
+                    // we are done
+                    break;
+                }
+
+#if BIT64
+                // make sure that we won't get a silent overflow inside the fast loop
+                // (Fall out to slow loop if we have this many characters)
+                availableChars &= 0x0FFFFFFF;
+#endif
+
+                // To compute the upper bound, assume that all characters are ASCII characters at this point,
+                //  the boundary will be decreased for every non-ASCII character we encounter
+                // Also, we need 3 + 4 chars reserve for the unrolled ansi decoding loop and for decoding of surrogates
+                char* pStop = pSrc + availableChars - (3 + 4);
+
+                while (pSrc < pStop)
+                {
+                    ch = *pSrc;
+                    pSrc++;
+
+                    if (ch > 0x7F)                                                  // Not ASCII
+                    {
+                        if (ch > 0x7FF)                                             // Not 2 Byte
+                        {
+                            if ((ch & 0xF800) == 0xD800)                            // See if its a Surrogate
+                                goto LongCode;
+                            byteCount++;
+                        }
+                        byteCount++;
+                    }
+
+                    // get pSrc aligned
+                    if ((unchecked((int)pSrc) & 0x2) != 0)
+                    {
+                        ch = *pSrc;
+                        pSrc++;
+                        if (ch > 0x7F)                                              // Not ASCII
+                        {
+                            if (ch > 0x7FF)                                         // Not 2 Byte
+                            {
+                                if ((ch & 0xF800) == 0xD800)                        // See if its a Surrogate
+                                    goto LongCode;
+                                byteCount++;
+                            }
+                            byteCount++;
+                        }
+                    }
+
+                    // Run 2 * 4 characters at a time!
+                    while (pSrc < pStop)
+                    {
+                        ch = *(int*)pSrc;
+                        int chc = *(int*)(pSrc + 2);
+                        if (((ch | chc) & unchecked((int)0xFF80FF80)) != 0)         // See if not ASCII
+                        {
+                            if (((ch | chc) & unchecked((int)0xF800F800)) != 0)     // See if not 2 Byte
+                            {
+                                goto LongCodeWithMask;
+                            }
+
+
+                            if ((ch & unchecked((int)0xFF800000)) != 0)             // Actually 0x07800780 is all we care about (4 bits)
+                                byteCount++;
+                            if ((ch & unchecked((int)0xFF80)) != 0)
+                                byteCount++;
+                            if ((chc & unchecked((int)0xFF800000)) != 0)
+                                byteCount++;
+                            if ((chc & unchecked((int)0xFF80)) != 0)
+                                byteCount++;
+                        }
+                        pSrc += 4;
+
+                        ch = *(int*)pSrc;
+                        chc = *(int*)(pSrc + 2);
+                        if (((ch | chc) & unchecked((int)0xFF80FF80)) != 0)         // See if not ASCII
+                        {
+                            if (((ch | chc) & unchecked((int)0xF800F800)) != 0)     // See if not 2 Byte
+                            {
+                                goto LongCodeWithMask;
+                            }
+
+                            if ((ch & unchecked((int)0xFF800000)) != 0)
+                                byteCount++;
+                            if ((ch & unchecked((int)0xFF80)) != 0)
+                                byteCount++;
+                            if ((chc & unchecked((int)0xFF800000)) != 0)
+                                byteCount++;
+                            if ((chc & unchecked((int)0xFF80)) != 0)
+                                byteCount++;
+                        }
+                        pSrc += 4;
+                    }
+                    break;
+
+                LongCodeWithMask:
+#if BIGENDIAN
+                    // be careful about the sign extension
+                    ch = (int)(((uint)ch) >> 16);
+#else // BIGENDIAN
+                    ch = (char)ch;
+#endif // BIGENDIAN
+                    pSrc++;
+
+                    if (ch <= 0x7F)
+                    {
+                        continue;
+                    }
+
+                LongCode:
+                    // use separate helper variables for slow and fast loop so that the jit optimizations
+                    // won't get confused about the variable lifetimes
+                    if (ch > 0x7FF)
+                    {
+                        // if (IsLowSurrogate(ch) || IsHighSurrogate(ch))
+                        if (InRange(ch, CharUnicodeInfo.HIGH_SURROGATE_START, CharUnicodeInfo.LOW_SURROGATE_END))
+                        {
+                            // 4 byte encoding - high surrogate + low surrogate
+
+                            int chd = *pSrc;
+                            if (
+                                // !IsHighSurrogate(ch) // low without high -> bad
+                                ch > CharUnicodeInfo.HIGH_SURROGATE_END ||
+                                // !IsLowSurrogate(chd) // high not followed by low -> bad
+                                !InRange(chd, CharUnicodeInfo.LOW_SURROGATE_START, CharUnicodeInfo.LOW_SURROGATE_END))
+                            {
+                                // Back up and drop out to slow loop to figure out error
+                                pSrc--;
+                                break;
+                            }
+                            pSrc++;
+
+                            // byteCount - this byte is compensated by the second surrogate character
+                        }
+                        byteCount++;
+                    }
+                    byteCount++;
+
+                    // byteCount - the last byte is already included
+                }
+#endif // FASTLOOP
+
+                // no pending char at this point
+                ch = 0;
+            }
+
+#if BIT64
+            // check for overflow
+            if (byteCount < 0)
+            {
+                throw new ArgumentException(
+                        SR.Argument_ConversionOverflow);
+            }
+#endif
+
+            Debug.Assert(fallbackBuffer == null || fallbackBuffer.Remaining == 0,
+                "[UTF8Encoding.GetByteCount]Expected Empty fallback buffer");
+
+            return byteCount;
+        }
+
+        // diffs two char pointers using unsigned arithmetic. The unsigned arithmetic
+        // is good enough for us, and it tends to generate better code than the signed
+        // arithmetic generated by default
+        private static unsafe int PtrDiff(char* a, char* b)
+        {
+            return (int)(((uint)((byte*)a - (byte*)b)) >> 1);
+        }
+
+        // byte* flavor just for parity
+        private static unsafe int PtrDiff(byte* a, byte* b)
+        {
+            return (int)(a - b);
+        }
+
+        private static bool InRange(int ch, int start, int end)
+        {
+            return (uint)(ch - start) <= (uint)(end - start);
+        }
+
+        // Our workhorse
+        // Note:  We ignore mismatched surrogates, unless the exception flag is set in which case we throw
+        internal override unsafe int GetBytes(char* chars, int charCount,
+                                                byte* bytes, int byteCount, EncoderNLS baseEncoder)
+        {
+            Debug.Assert(chars != null, "[UTF8Encoding.GetBytes]chars!=null");
+            Debug.Assert(byteCount >= 0, "[UTF8Encoding.GetBytes]byteCount >=0");
+            Debug.Assert(charCount >= 0, "[UTF8Encoding.GetBytes]charCount >=0");
+            Debug.Assert(bytes != null, "[UTF8Encoding.GetBytes]bytes!=null");
+
+            UTF8Encoder encoder = null;
+
+            // For fallback we may need a fallback buffer.
+            // We wait to initialize it though in case we don't have any broken input unicode
+            EncoderFallbackBuffer fallbackBuffer = null;
+            char* pSrcForFallback;
+
+            char* pSrc = chars;
+            byte* pTarget = bytes;
+
+            char* pEnd = pSrc + charCount;
+            byte* pAllocatedBufferEnd = pTarget + byteCount;
+
+            int ch = 0;
+
+            // assume that JIT will en-register pSrc, pTarget and ch
+
+            if (baseEncoder != null)
+            {
+                encoder = (UTF8Encoder)baseEncoder;
+                ch = encoder.surrogateChar;
+
+                // We mustn't have left over fallback data when counting
+                if (encoder.InternalHasFallbackBuffer)
+                {
+                    // We always need the fallback buffer in get bytes so we can flush any remaining ones if necessary
+                    fallbackBuffer = encoder.FallbackBuffer;
+                    if (fallbackBuffer.Remaining > 0 && encoder._throwOnOverflow)
+                        throw new ArgumentException(SR.Format(SR.Argument_EncoderFallbackNotEmpty, this.EncodingName, encoder.Fallback.GetType()));
+
+                    // Set our internal fallback interesting things.
+                    fallbackBuffer.InternalInitialize(chars, pEnd, encoder, true);
+                }
+            }
+
+            for (;;)
+            {
+                // SLOWLOOP: does all range checks, handles all special cases, but it is slow
+
+                if (pSrc >= pEnd)
+                {
+                    if (ch == 0)
+                    {
+                        // Check if there's anything left to get out of the fallback buffer
+                        ch = fallbackBuffer != null ? fallbackBuffer.InternalGetNextChar() : 0;
+                        if (ch > 0)
+                        {
+                            goto ProcessChar;
+                        }
+                    }
+                    else
+                    {
+                        // Case of leftover surrogates in the fallback buffer
+                        if (fallbackBuffer != null && fallbackBuffer.bFallingBack)
+                        {
+                            Debug.Assert(ch >= 0xD800 && ch <= 0xDBFF,
+                                "[UTF8Encoding.GetBytes]expected high surrogate, not 0x" + ((int)ch).ToString("X4", CultureInfo.InvariantCulture));
+
+                            int cha = ch;
+
+                            ch = fallbackBuffer.InternalGetNextChar();
+
+                            if (InRange(ch, CharUnicodeInfo.LOW_SURROGATE_START, CharUnicodeInfo.LOW_SURROGATE_END))
+                            {
+                                ch = ch + (cha << 10) + (0x10000 - CharUnicodeInfo.LOW_SURROGATE_START - (CharUnicodeInfo.HIGH_SURROGATE_START << 10));
+                                goto EncodeChar;
+                            }
+                            else if (ch > 0)
+                            {
+                                goto ProcessChar;
+                            }
+                            else
+                            {
+                                break;
+                            }
+                        }
+                    }
+
+                    // attempt to encode the partial surrogate (will fail or ignore)
+                    if (ch > 0 && (encoder == null || encoder.MustFlush))
+                        goto EncodeChar;
+
+                    // We're done
+                    break;
+                }
+
+                if (ch > 0)
+                {
+                    // We have a high surrogate left over from a previous loop.
+                    Debug.Assert(ch >= 0xD800 && ch <= 0xDBFF,
+                        "[UTF8Encoding.GetBytes]expected high surrogate, not 0x" + ((int)ch).ToString("X4", CultureInfo.InvariantCulture));
+
+                    // use separate helper variables for local contexts so that the jit optimizations
+                    // won't get confused about the variable lifetimes
+                    int cha = *pSrc;
+
+                    // In previous byte, we encountered a high surrogate, so we are expecting a low surrogate here.
+                    // if (IsLowSurrogate(cha)) {
+                    if (InRange(cha, CharUnicodeInfo.LOW_SURROGATE_START, CharUnicodeInfo.LOW_SURROGATE_END))
+                    {
+                        ch = cha + (ch << 10) +
+                            (0x10000
+                            - CharUnicodeInfo.LOW_SURROGATE_START
+                            - (CharUnicodeInfo.HIGH_SURROGATE_START << 10));
+
+                        pSrc++;
+                    }
+                    // else ch is still high surrogate and encoding will fail
+
+                    // attempt to encode the surrogate or partial surrogate
+                    goto EncodeChar;
+                }
+
+                // If we've used a fallback, then we have to check for it
+                if (fallbackBuffer != null)
+                {
+                    ch = fallbackBuffer.InternalGetNextChar();
+                    if (ch > 0) goto ProcessChar;
+                }
+
+                // read next char. The JIT optimization seems to be getting confused when
+                // compiling "ch = *pSrc++;", so rather use "ch = *pSrc; pSrc++;" instead
+                ch = *pSrc;
+                pSrc++;
+
+            ProcessChar:
+                // if (IsHighSurrogate(ch)) {
+                if (InRange(ch, CharUnicodeInfo.HIGH_SURROGATE_START, CharUnicodeInfo.HIGH_SURROGATE_END))
+                {
+                    continue;
+                }
+            // either good char or partial surrogate
+
+            EncodeChar:
+                // throw exception on partial surrogate if necessary
+                // if (IsLowSurrogate(ch) || IsHighSurrogate(ch))
+                if (InRange(ch, CharUnicodeInfo.HIGH_SURROGATE_START, CharUnicodeInfo.LOW_SURROGATE_END))
+                {
+                    // Lone surrogates aren't allowed, we have to do fallback for them
+                    // Have to make a fallback buffer if we don't have one
+                    if (fallbackBuffer == null)
+                    {
+                        // wait on fallbacks if we can
+                        // For fallback we may need a fallback buffer
+                        if (baseEncoder == null)
+                            fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = baseEncoder.FallbackBuffer;
+
+                        // Set our internal fallback interesting things.
+                        fallbackBuffer.InternalInitialize(chars, pEnd, baseEncoder, true);
+                    }
+
+                    // Do our fallback.  Actually we already know its a mixed up surrogate,
+                    // so the ref pSrc isn't gonna do anything.
+                    pSrcForFallback = pSrc; // Avoid passing pSrc by reference to allow it to be en-registered
+                    fallbackBuffer.InternalFallback(unchecked((char)ch), ref pSrcForFallback);
+                    pSrc = pSrcForFallback;
+
+                    // Ignore it if we don't throw
+                    ch = 0;
+                    continue;
+                }
+
+                // Count bytes needed
+                int bytesNeeded = 1;
+                if (ch > 0x7F)
+                {
+                    if (ch > 0x7FF)
+                    {
+                        if (ch > 0xFFFF)
+                        {
+                            bytesNeeded++;  // 4 bytes (surrogate pair)
+                        }
+                        bytesNeeded++;      // 3 bytes (800-FFFF)
+                    }
+                    bytesNeeded++;          // 2 bytes (80-7FF)
+                }
+
+                if (pTarget > pAllocatedBufferEnd - bytesNeeded)
+                {
+                    // Left over surrogate from last time will cause pSrc == chars, so we'll throw
+                    if (fallbackBuffer != null && fallbackBuffer.bFallingBack)
+                    {
+                        fallbackBuffer.MovePrevious();              // Didn't use this fallback char
+                        if (ch > 0xFFFF)
+                            fallbackBuffer.MovePrevious();          // Was surrogate, didn't use 2nd part either
+                    }
+                    else
+                    {
+                        pSrc--;                                     // Didn't use this char
+                        if (ch > 0xFFFF)
+                            pSrc--;                                 // Was surrogate, didn't use 2nd part either
+                    }
+                    Debug.Assert(pSrc >= chars || pTarget == bytes,
+                        "[UTF8Encoding.GetBytes]Expected pSrc to be within buffer or to throw with insufficient room.");
+                    ThrowBytesOverflow(encoder, pTarget == bytes);  // Throw if we must
+                    ch = 0;                                         // Nothing left over (we backed up to start of pair if supplementary)
+                    break;
+                }
+
+                if (ch <= 0x7F)
+                {
+                    *pTarget = (byte)ch;
+                }
+                else
+                {
+                    // use separate helper variables for local contexts so that the jit optimizations
+                    // won't get confused about the variable lifetimes
+                    int chb;
+                    if (ch <= 0x7FF)
+                    {
+                        // 2 byte encoding
+                        chb = (byte)(unchecked((sbyte)0xC0) | (ch >> 6));
+                    }
+                    else
+                    {
+                        if (ch <= 0xFFFF)
+                        {
+                            chb = (byte)(unchecked((sbyte)0xE0) | (ch >> 12));
+                        }
+                        else
+                        {
+                            *pTarget = (byte)(unchecked((sbyte)0xF0) | (ch >> 18));
+                            pTarget++;
+
+                            chb = unchecked((sbyte)0x80) | (ch >> 12) & 0x3F;
+                        }
+                        *pTarget = (byte)chb;
+                        pTarget++;
+
+                        chb = unchecked((sbyte)0x80) | (ch >> 6) & 0x3F;
+                    }
+                    *pTarget = (byte)chb;
+                    pTarget++;
+
+                    *pTarget = (byte)(unchecked((sbyte)0x80) | ch & 0x3F);
+                }
+                pTarget++;
+
+
+#if FASTLOOP
+                // If still have fallback don't do fast loop
+                if (fallbackBuffer != null && (ch = fallbackBuffer.InternalGetNextChar()) != 0)
+                    goto ProcessChar;
+
+                int availableChars = PtrDiff(pEnd, pSrc);
+                int availableBytes = PtrDiff(pAllocatedBufferEnd, pTarget);
+
+                // don't fall into the fast decoding loop if we don't have enough characters
+                // Note that if we don't have enough bytes, pStop will prevent us from entering the fast loop.
+                if (availableChars <= 13)
+                {
+                    // we are hoping for 1 byte per char
+                    if (availableBytes < availableChars)
+                    {
+                        // not enough output room.  no pending bits at this point
+                        ch = 0;
+                        continue;
+                    }
+
+                    // try to get over the remainder of the ascii characters fast though
+                    char* pLocalEnd = pEnd; // hint to get pLocalEnd en-registered
+                    while (pSrc < pLocalEnd)
+                    {
+                        ch = *pSrc;
+                        pSrc++;
+
+                        // Not ASCII, need more than 1 byte per char
+                        if (ch > 0x7F)
+                            goto ProcessChar;
+
+                        *pTarget = (byte)ch;
+                        pTarget++;
+                    }
+                    // we are done, let ch be 0 to clear encoder
+                    ch = 0;
+                    break;
+                }
+
+                // we need at least 1 byte per character, but Convert might allow us to convert
+                // only part of the input, so try as much as we can.  Reduce charCount if necessary
+                if (availableBytes < availableChars)
+                {
+                    availableChars = availableBytes;
+                }
+
+                // FASTLOOP:
+                // - optimistic range checks
+                // - fallbacks to the slow loop for all special cases, exception throwing, etc.
+
+                // To compute the upper bound, assume that all characters are ASCII characters at this point,
+                //  the boundary will be decreased for every non-ASCII character we encounter
+                // Also, we need 5 chars reserve for the unrolled ansi decoding loop and for decoding of surrogates
+                // If there aren't enough bytes for the output, then pStop will be <= pSrc and will bypass the loop.
+                char* pStop = pSrc + availableChars - 5;
+
+                while (pSrc < pStop)
+                {
+                    ch = *pSrc;
+                    pSrc++;
+
+                    if (ch > 0x7F)
+                    {
+                        goto LongCode;
+                    }
+                    *pTarget = (byte)ch;
+                    pTarget++;
+
+                    // get pSrc aligned
+                    if ((unchecked((int)pSrc) & 0x2) != 0)
+                    {
+                        ch = *pSrc;
+                        pSrc++;
+                        if (ch > 0x7F)
+                        {
+                            goto LongCode;
+                        }
+                        *pTarget = (byte)ch;
+                        pTarget++;
+                    }
+
+                    // Run 4 characters at a time!
+                    while (pSrc < pStop)
+                    {
+                        ch = *(int*)pSrc;
+                        int chc = *(int*)(pSrc + 2);
+                        if (((ch | chc) & unchecked((int)0xFF80FF80)) != 0)
+                        {
+                            goto LongCodeWithMask;
+                        }
+
+                        // Unfortunately, this is endianess sensitive
+#if BIGENDIAN
+                        *pTarget = (byte)(ch>>16);
+                        *(pTarget+1) = (byte)ch;
+                        pSrc += 4;
+                        *(pTarget+2) = (byte)(chc>>16);
+                        *(pTarget+3) = (byte)chc;
+                        pTarget += 4;
+#else // BIGENDIAN
+                        *pTarget = (byte)ch;
+                        *(pTarget + 1) = (byte)(ch >> 16);
+                        pSrc += 4;
+                        *(pTarget + 2) = (byte)chc;
+                        *(pTarget + 3) = (byte)(chc >> 16);
+                        pTarget += 4;
+#endif // BIGENDIAN
+                    }
+                    continue;
+
+                LongCodeWithMask:
+#if BIGENDIAN
+                    // be careful about the sign extension
+                    ch = (int)(((uint)ch) >> 16);
+#else // BIGENDIAN
+                    ch = (char)ch;
+#endif // BIGENDIAN
+                    pSrc++;
+
+                    if (ch > 0x7F)
+                    {
+                        goto LongCode;
+                    }
+                    *pTarget = (byte)ch;
+                    pTarget++;
+                    continue;
+
+                LongCode:
+                    // use separate helper variables for slow and fast loop so that the jit optimizations
+                    // won't get confused about the variable lifetimes
+                    int chd;
+                    if (ch <= 0x7FF)
+                    {
+                        // 2 byte encoding
+                        chd = unchecked((sbyte)0xC0) | (ch >> 6);
+                    }
+                    else
+                    {
+                        // if (!IsLowSurrogate(ch) && !IsHighSurrogate(ch))
+                        if (!InRange(ch, CharUnicodeInfo.HIGH_SURROGATE_START, CharUnicodeInfo.LOW_SURROGATE_END))
+                        {
+                            // 3 byte encoding
+                            chd = unchecked((sbyte)0xE0) | (ch >> 12);
+                        }
+                        else
+                        {
+                            // 4 byte encoding - high surrogate + low surrogate
+                            // if (!IsHighSurrogate(ch))
+                            if (ch > CharUnicodeInfo.HIGH_SURROGATE_END)
+                            {
+                                // low without high -> bad, try again in slow loop
+                                pSrc -= 1;
+                                break;
+                            }
+
+                            chd = *pSrc;
+                            pSrc++;
+
+                            // if (!IsLowSurrogate(chd)) {
+                            if (!InRange(chd, CharUnicodeInfo.LOW_SURROGATE_START, CharUnicodeInfo.LOW_SURROGATE_END))
+                            {
+                                // high not followed by low -> bad, try again in slow loop
+                                pSrc -= 2;
+                                break;
+                            }
+
+                            ch = chd + (ch << 10) +
+                                (0x10000
+                                - CharUnicodeInfo.LOW_SURROGATE_START
+                                - (CharUnicodeInfo.HIGH_SURROGATE_START << 10));
+
+                            *pTarget = (byte)(unchecked((sbyte)0xF0) | (ch >> 18));
+                            // pStop - this byte is compensated by the second surrogate character
+                            // 2 input chars require 4 output bytes.  2 have been anticipated already
+                            // and 2 more will be accounted for by the 2 pStop-- calls below.
+                            pTarget++;
+
+                            chd = unchecked((sbyte)0x80) | (ch >> 12) & 0x3F;
+                        }
+                        *pTarget = (byte)chd;
+                        pStop--;                    // 3 byte sequence for 1 char, so need pStop-- and the one below too.
+                        pTarget++;
+
+                        chd = unchecked((sbyte)0x80) | (ch >> 6) & 0x3F;
+                    }
+                    *pTarget = (byte)chd;
+                    pStop--;                        // 2 byte sequence for 1 char so need pStop--.
+                    pTarget++;
+
+                    *pTarget = (byte)(unchecked((sbyte)0x80) | ch & 0x3F);
+                    // pStop - this byte is already included
+                    pTarget++;
+                }
+
+                Debug.Assert(pTarget <= pAllocatedBufferEnd, "[UTF8Encoding.GetBytes]pTarget <= pAllocatedBufferEnd");
+
+#endif // FASTLOOP
+
+                // no pending char at this point
+                ch = 0;
+            }
+
+            // Do we have to set the encoder bytes?
+            if (encoder != null)
+            {
+                Debug.Assert(!encoder.MustFlush || ch == 0,
+                    "[UTF8Encoding.GetBytes] Expected no mustflush or 0 leftover ch " + ch.ToString("X2", CultureInfo.InvariantCulture));
+
+                encoder.surrogateChar = ch;
+                encoder._charsUsed = (int)(pSrc - chars);
+            }
+
+            Debug.Assert(fallbackBuffer == null || fallbackBuffer.Remaining == 0 ||
+                baseEncoder == null || !baseEncoder._throwOnOverflow,
+                "[UTF8Encoding.GetBytes]Expected empty fallback buffer if not converting");
+
+            return (int)(pTarget - bytes);
+        }
+
+
+        // These are bitmasks used to maintain the state in the decoder. They occupy the higher bits
+        // while the actual character is being built in the lower bits. They are shifted together
+        // with the actual bits of the character.
+
+        // bits 30 & 31 are used for pending bits fixup
+        private const int FinalByte = 1 << 29;
+        private const int SupplimentarySeq = 1 << 28;
+        private const int ThreeByteSeq = 1 << 27;
+
+        // Note:  We throw exceptions on individually encoded surrogates and other non-shortest forms.
+        //        If exceptions aren't turned on, then we drop all non-shortest &individual surrogates.
+        //
+        // To simplify maintenance, the structure of GetCharCount and GetChars should be
+        // kept the same as much as possible
+        internal override unsafe int GetCharCount(byte* bytes, int count, DecoderNLS baseDecoder)
+        {
+            Debug.Assert(count >= 0, "[UTF8Encoding.GetCharCount]count >=0");
+            Debug.Assert(bytes != null, "[UTF8Encoding.GetCharCount]bytes!=null");
+
+            // Initialize stuff
+            byte* pSrc = bytes;
+            byte* pEnd = pSrc + count;
+
+            // Start by assuming we have as many as count, charCount always includes the adjustment
+            // for the character being decoded
+            int charCount = count;
+            int ch = 0;
+            DecoderFallbackBuffer fallback = null;
+
+            if (baseDecoder != null)
+            {
+                UTF8Decoder decoder = (UTF8Decoder)baseDecoder;
+                ch = decoder.bits;
+                charCount -= (ch >> 30);        // Adjust char count for # of expected bytes and expected output chars.
+
+                // Shouldn't have anything in fallback buffer for GetCharCount
+                // (don't have to check _throwOnOverflow for count)
+                Debug.Assert(!decoder.InternalHasFallbackBuffer || decoder.FallbackBuffer.Remaining == 0,
+                    "[UTF8Encoding.GetCharCount]Expected empty fallback buffer at start");
+            }
+
+            for (;;)
+            {
+                // SLOWLOOP: does all range checks, handles all special cases, but it is slow
+
+                if (pSrc >= pEnd)
+                {
+                    break;
+                }
+
+                if (ch == 0)
+                {
+                    // no pending bits
+                    goto ReadChar;
+                }
+
+                // read next byte. The JIT optimization seems to be getting confused when
+                // compiling "ch = *pSrc++;", so rather use "ch = *pSrc; pSrc++;" instead
+                int cha = *pSrc;
+                pSrc++;
+
+                // we are expecting to see trailing bytes like 10vvvvvv
+                if ((cha & unchecked((sbyte)0xC0)) != 0x80)
+                {
+                    // This can be a valid starting byte for another UTF8 byte sequence, so let's put
+                    // the current byte back, and try to see if this is a valid byte for another UTF8 byte sequence
+                    pSrc--;
+                    charCount += (ch >> 30);
+                    goto InvalidByteSequence;
+                }
+
+                // fold in the new byte
+                ch = (ch << 6) | (cha & 0x3F);
+
+                if ((ch & FinalByte) == 0)
+                {
+                    Debug.Assert((ch & (SupplimentarySeq | ThreeByteSeq)) != 0,
+                        "[UTF8Encoding.GetChars]Invariant volation");
+
+                    if ((ch & SupplimentarySeq) != 0)
+                    {
+                        if ((ch & (FinalByte >> 6)) != 0)
+                        {
+                            // this is 3rd byte (of 4 byte supplementary) - nothing to do
+                            continue;
+                        }
+
+                        // 2nd byte, check for non-shortest form of supplementary char and the valid
+                        // supplementary characters in range 0x010000 - 0x10FFFF at the same time
+                        if (!InRange(ch & 0x1F0, 0x10, 0x100))
+                        {
+                            goto InvalidByteSequence;
+                        }
+                    }
+                    else
+                    {
+                        // Must be 2nd byte of a 3-byte sequence
+                        // check for non-shortest form of 3 byte seq
+                        if ((ch & (0x1F << 5)) == 0 ||                  // non-shortest form
+                            (ch & (0xF800 >> 6)) == (0xD800 >> 6))     // illegal individually encoded surrogate
+                        {
+                            goto InvalidByteSequence;
+                        }
+                    }
+                    continue;
+                }
+
+                // ready to punch
+
+                // adjust for surrogates in non-shortest form
+                if ((ch & (SupplimentarySeq | 0x1F0000)) == SupplimentarySeq)
+                {
+                    charCount--;
+                }
+                goto EncodeChar;
+
+            InvalidByteSequence:
+                // this code fragment should be close to the goto referencing it
+                // Have to do fallback for invalid bytes
+                if (fallback == null)
+                {
+                    if (baseDecoder == null)
+                        fallback = this.decoderFallback.CreateFallbackBuffer();
+                    else
+                        fallback = baseDecoder.FallbackBuffer;
+                    fallback.InternalInitialize(bytes, null);
+                }
+                charCount += FallbackInvalidByteSequence(pSrc, ch, fallback);
+
+                ch = 0;
+                continue;
+
+            ReadChar:
+                ch = *pSrc;
+                pSrc++;
+
+            ProcessChar:
+                if (ch > 0x7F)
+                {
+                    // If its > 0x7F, its start of a new multi-byte sequence
+
+                    // Long sequence, so unreserve our char.
+                    charCount--;
+
+                    // bit 6 has to be non-zero for start of multibyte chars.
+                    if ((ch & 0x40) == 0)
+                    {
+                        // Unexpected trail byte
+                        goto InvalidByteSequence;
+                    }
+
+                    // start a new long code
+                    if ((ch & 0x20) != 0)
+                    {
+                        if ((ch & 0x10) != 0)
+                        {
+                            // 4 byte encoding - supplimentary character (2 surrogates)
+
+                            ch &= 0x0F;
+
+                            // check that bit 4 is zero and the valid supplimentary character
+                            // range 0x000000 - 0x10FFFF at the same time
+                            if (ch > 0x04)
+                            {
+                                ch |= 0xf0;
+                                goto InvalidByteSequence;
+                            }
+
+                            // Add bit flags so that when we check new characters & rotate we'll be flagged correctly.
+                            // Final byte flag, count fix if we don't make final byte & supplimentary sequence flag.
+                            ch |= (FinalByte >> 3 * 6) |  // Final byte is 3 more bytes from now
+                                  (1 << 30) |           // If it dies on next byte we'll need an extra char
+                                  (3 << (30 - 2 * 6)) |     // If it dies on last byte we'll need to subtract a char
+                                (SupplimentarySeq) | (SupplimentarySeq >> 6) |
+                                (SupplimentarySeq >> 2 * 6) | (SupplimentarySeq >> 3 * 6);
+
+                            // Our character count will be 2 characters for these 4 bytes, so subtract another char
+                            charCount--;
+                        }
+                        else
+                        {
+                            // 3 byte encoding
+                            // Add bit flags so that when we check new characters & rotate we'll be flagged correctly.
+                            ch = (ch & 0x0F) | ((FinalByte >> 2 * 6) | (1 << 30) |
+                                (ThreeByteSeq) | (ThreeByteSeq >> 6) | (ThreeByteSeq >> 2 * 6));
+
+                            // We'll expect 1 character for these 3 bytes, so subtract another char.
+                            charCount--;
+                        }
+                    }
+                    else
+                    {
+                        // 2 byte encoding
+
+                        ch &= 0x1F;
+
+                        // check for non-shortest form
+                        if (ch <= 1)
+                        {
+                            ch |= 0xc0;
+                            goto InvalidByteSequence;
+                        }
+
+                        // Add bit flags so we'll be flagged correctly
+                        ch |= (FinalByte >> 6);
+                    }
+                    continue;
+                }
+
+            EncodeChar:
+
+#if FASTLOOP
+                int availableBytes = PtrDiff(pEnd, pSrc);
+
+                // don't fall into the fast decoding loop if we don't have enough bytes
+                if (availableBytes <= 13)
+                {
+                    // try to get over the remainder of the ascii characters fast though
+                    byte* pLocalEnd = pEnd; // hint to get pLocalEnd en-registered
+                    while (pSrc < pLocalEnd)
+                    {
+                        ch = *pSrc;
+                        pSrc++;
+
+                        if (ch > 0x7F)
+                            goto ProcessChar;
+                    }
+                    // we are done
+                    ch = 0;
+                    break;
+                }
+
+                // To compute the upper bound, assume that all characters are ASCII characters at this point,
+                //  the boundary will be decreased for every non-ASCII character we encounter
+                // Also, we need 7 chars reserve for the unrolled ansi decoding loop and for decoding of multibyte sequences
+                byte* pStop = pSrc + availableBytes - 7;
+
+                while (pSrc < pStop)
+                {
+                    ch = *pSrc;
+                    pSrc++;
+
+                    if (ch > 0x7F)
+                    {
+                        goto LongCode;
+                    }
+
+                    // get pSrc 2-byte aligned
+                    if ((unchecked((int)pSrc) & 0x1) != 0)
+                    {
+                        ch = *pSrc;
+                        pSrc++;
+                        if (ch > 0x7F)
+                        {
+                            goto LongCode;
+                        }
+                    }
+
+                    // get pSrc 4-byte aligned
+                    if ((unchecked((int)pSrc) & 0x2) != 0)
+                    {
+                        ch = *(ushort*)pSrc;
+                        if ((ch & 0x8080) != 0)
+                        {
+                            goto LongCodeWithMask16;
+                        }
+                        pSrc += 2;
+                    }
+
+                    // Run 8 + 8 characters at a time!
+                    while (pSrc < pStop)
+                    {
+                        ch = *(int*)pSrc;
+                        int chb = *(int*)(pSrc + 4);
+                        if (((ch | chb) & unchecked((int)0x80808080)) != 0)
+                        {
+                            goto LongCodeWithMask32;
+                        }
+                        pSrc += 8;
+
+                        // This is a really small loop - unroll it
+                        if (pSrc >= pStop)
+                            break;
+
+                        ch = *(int*)pSrc;
+                        chb = *(int*)(pSrc + 4);
+                        if (((ch | chb) & unchecked((int)0x80808080)) != 0)
+                        {
+                            goto LongCodeWithMask32;
+                        }
+                        pSrc += 8;
+                    }
+                    break;
+
+#if BIGENDIAN
+                LongCodeWithMask32:
+                    // be careful about the sign extension
+                    ch = (int)(((uint)ch) >> 16);
+                LongCodeWithMask16:
+                    ch = (int)(((uint)ch) >> 8);
+#else // BIGENDIAN
+                LongCodeWithMask32:
+                LongCodeWithMask16:
+                    ch &= 0xFF;
+#endif // BIGENDIAN
+                    pSrc++;
+                    if (ch <= 0x7F)
+                    {
+                        continue;
+                    }
+
+                LongCode:
+                    int chc = *pSrc;
+                    pSrc++;
+
+                    if (
+                        // bit 6 has to be zero
+                        (ch & 0x40) == 0 ||
+                        // we are expecting to see trailing bytes like 10vvvvvv
+                        (chc & unchecked((sbyte)0xC0)) != 0x80)
+                    {
+                        goto BadLongCode;
+                    }
+
+                    chc &= 0x3F;
+
+                    // start a new long code
+                    if ((ch & 0x20) != 0)
+                    {
+                        // fold the first two bytes together
+                        chc |= (ch & 0x0F) << 6;
+
+                        if ((ch & 0x10) != 0)
+                        {
+                            // 4 byte encoding - surrogate
+                            ch = *pSrc;
+                            if (
+                                // check that bit 4 is zero, the non-shortest form of surrogate
+                                // and the valid surrogate range 0x000000 - 0x10FFFF at the same time
+                                !InRange(chc >> 4, 0x01, 0x10) ||
+                                // we are expecting to see trailing bytes like 10vvvvvv
+                                (ch & unchecked((sbyte)0xC0)) != 0x80)
+                            {
+                                goto BadLongCode;
+                            }
+
+                            chc = (chc << 6) | (ch & 0x3F);
+
+                            ch = *(pSrc + 1);
+                            // we are expecting to see trailing bytes like 10vvvvvv
+                            if ((ch & unchecked((sbyte)0xC0)) != 0x80)
+                            {
+                                goto BadLongCode;
+                            }
+                            pSrc += 2;
+
+                            // extra byte
+                            charCount--;
+                        }
+                        else
+                        {
+                            // 3 byte encoding
+                            ch = *pSrc;
+                            if (
+                                // check for non-shortest form of 3 byte seq
+                                (chc & (0x1F << 5)) == 0 ||
+                                // Can't have surrogates here.
+                                (chc & (0xF800 >> 6)) == (0xD800 >> 6) ||
+                                // we are expecting to see trailing bytes like 10vvvvvv
+                                (ch & unchecked((sbyte)0xC0)) != 0x80)
+                            {
+                                goto BadLongCode;
+                            }
+                            pSrc++;
+
+                            // extra byte
+                            charCount--;
+                        }
+                    }
+                    else
+                    {
+                        // 2 byte encoding
+
+                        // check for non-shortest form
+                        if ((ch & 0x1E) == 0)
+                        {
+                            goto BadLongCode;
+                        }
+                    }
+
+                    // extra byte
+                    charCount--;
+                }
+#endif // FASTLOOP
+
+                // no pending bits at this point
+                ch = 0;
+                continue;
+
+            BadLongCode:
+                pSrc -= 2;
+                ch = 0;
+                continue;
+            }
+
+            // May have a problem if we have to flush
+            if (ch != 0)
+            {
+                // We were already adjusting for these, so need to un-adjust
+                charCount += (ch >> 30);
+                if (baseDecoder == null || baseDecoder.MustFlush)
+                {
+                    // Have to do fallback for invalid bytes
+                    if (fallback == null)
+                    {
+                        if (baseDecoder == null)
+                            fallback = this.decoderFallback.CreateFallbackBuffer();
+                        else
+                            fallback = baseDecoder.FallbackBuffer;
+                        fallback.InternalInitialize(bytes, null);
+                    }
+                    charCount += FallbackInvalidByteSequence(pSrc, ch, fallback);
+                }
+            }
+
+            // Shouldn't have anything in fallback buffer for GetCharCount
+            // (don't have to check _throwOnOverflow for count)
+            Debug.Assert(fallback == null || fallback.Remaining == 0,
+                "[UTF8Encoding.GetCharCount]Expected empty fallback buffer at end");
+
+            return charCount;
+        }
+
+        // WARNING:  If we throw an error, then System.Resources.ResourceReader calls this method.
+        //           So if we're really broken, then that could also throw an error... recursively.
+        //           So try to make sure GetChars can at least process all uses by
+        //           System.Resources.ResourceReader!
+        //
+        // Note:  We throw exceptions on individually encoded surrogates and other non-shortest forms.
+        //        If exceptions aren't turned on, then we drop all non-shortest &individual surrogates.
+        //
+        // To simplify maintenance, the structure of GetCharCount and GetChars should be
+        // kept the same as much as possible
+        internal override unsafe int GetChars(byte* bytes, int byteCount,
+                                                char* chars, int charCount, DecoderNLS baseDecoder)
+        {
+            Debug.Assert(chars != null, "[UTF8Encoding.GetChars]chars!=null");
+            Debug.Assert(byteCount >= 0, "[UTF8Encoding.GetChars]count >=0");
+            Debug.Assert(charCount >= 0, "[UTF8Encoding.GetChars]charCount >=0");
+            Debug.Assert(bytes != null, "[UTF8Encoding.GetChars]bytes!=null");
+
+            byte* pSrc = bytes;
+            char* pTarget = chars;
+
+            byte* pEnd = pSrc + byteCount;
+            char* pAllocatedBufferEnd = pTarget + charCount;
+
+            int ch = 0;
+
+            DecoderFallbackBuffer fallback = null;
+            byte* pSrcForFallback;
+            char* pTargetForFallback;
+            if (baseDecoder != null)
+            {
+                UTF8Decoder decoder = (UTF8Decoder)baseDecoder;
+                ch = decoder.bits;
+
+                // Shouldn't have anything in fallback buffer for GetChars
+                // (don't have to check _throwOnOverflow for chars, we always use all or none so always should be empty)
+                Debug.Assert(!decoder.InternalHasFallbackBuffer || decoder.FallbackBuffer.Remaining == 0,
+                    "[UTF8Encoding.GetChars]Expected empty fallback buffer at start");
+            }
+
+            for (;;)
+            {
+                // SLOWLOOP: does all range checks, handles all special cases, but it is slow
+
+                if (pSrc >= pEnd)
+                {
+                    break;
+                }
+
+                if (ch == 0)
+                {
+                    // no pending bits
+                    goto ReadChar;
+                }
+
+                // read next byte. The JIT optimization seems to be getting confused when
+                // compiling "ch = *pSrc++;", so rather use "ch = *pSrc; pSrc++;" instead
+                int cha = *pSrc;
+                pSrc++;
+
+                // we are expecting to see trailing bytes like 10vvvvvv
+                if ((cha & unchecked((sbyte)0xC0)) != 0x80)
+                {
+                    // This can be a valid starting byte for another UTF8 byte sequence, so let's put
+                    // the current byte back, and try to see if this is a valid byte for another UTF8 byte sequence
+                    pSrc--;
+                    goto InvalidByteSequence;
+                }
+
+                // fold in the new byte
+                ch = (ch << 6) | (cha & 0x3F);
+
+                if ((ch & FinalByte) == 0)
+                {
+                    // Not at last byte yet
+                    Debug.Assert((ch & (SupplimentarySeq | ThreeByteSeq)) != 0,
+                        "[UTF8Encoding.GetChars]Invariant volation");
+
+                    if ((ch & SupplimentarySeq) != 0)
+                    {
+                        // Its a 4-byte supplimentary sequence
+                        if ((ch & (FinalByte >> 6)) != 0)
+                        {
+                            // this is 3rd byte of 4 byte sequence - nothing to do
+                            continue;
+                        }
+
+                        // 2nd byte of 4 bytes
+                        // check for non-shortest form of surrogate and the valid surrogate
+                        // range 0x000000 - 0x10FFFF at the same time
+                        if (!InRange(ch & 0x1F0, 0x10, 0x100))
+                        {
+                            goto InvalidByteSequence;
+                        }
+                    }
+                    else
+                    {
+                        // Must be 2nd byte of a 3-byte sequence
+                        // check for non-shortest form of 3 byte seq
+                        if ((ch & (0x1F << 5)) == 0 ||                  // non-shortest form
+                            (ch & (0xF800 >> 6)) == (0xD800 >> 6))     // illegal individually encoded surrogate
+                        {
+                            goto InvalidByteSequence;
+                        }
+                    }
+                    continue;
+                }
+
+                // ready to punch
+
+                // surrogate in shortest form?
+                // Might be possible to get rid of this?  Already did non-shortest check for 4-byte sequence when reading 2nd byte?
+                if ((ch & (SupplimentarySeq | 0x1F0000)) > SupplimentarySeq)
+                {
+                    // let the range check for the second char throw the exception
+                    if (pTarget < pAllocatedBufferEnd)
+                    {
+                        *pTarget = (char)(((ch >> 10) & 0x7FF) +
+                            unchecked((short)((CharUnicodeInfo.HIGH_SURROGATE_START - (0x10000 >> 10)))));
+                        pTarget++;
+
+                        ch = (ch & 0x3FF) +
+                            unchecked((int)(CharUnicodeInfo.LOW_SURROGATE_START));
+                    }
+                }
+
+                goto EncodeChar;
+
+            InvalidByteSequence:
+                // this code fragment should be close to the gotos referencing it
+                // Have to do fallback for invalid bytes
+                if (fallback == null)
+                {
+                    if (baseDecoder == null)
+                        fallback = this.decoderFallback.CreateFallbackBuffer();
+                    else
+                        fallback = baseDecoder.FallbackBuffer;
+                    fallback.InternalInitialize(bytes, pAllocatedBufferEnd);
+                }
+                // That'll back us up the appropriate # of bytes if we didn't get anywhere
+                pSrcForFallback = pSrc; // Avoid passing pSrc by reference to allow it to be en-registered
+                pTargetForFallback = pTarget; // Avoid passing pTarget by reference to allow it to be en-registered
+                bool fallbackResult = FallbackInvalidByteSequence(ref pSrcForFallback, ch, fallback, ref pTargetForFallback);
+                pSrc = pSrcForFallback;
+                pTarget = pTargetForFallback;
+
+                if (!fallbackResult)
+                {
+                    // Ran out of buffer space
+                    // Need to throw an exception?
+                    Debug.Assert(pSrc >= bytes || pTarget == chars,
+                        "[UTF8Encoding.GetChars]Expected to throw or remain in byte buffer after fallback");
+                    fallback.InternalReset();
+                    ThrowCharsOverflow(baseDecoder, pTarget == chars);
+                    ch = 0;
+                    break;
+                }
+                Debug.Assert(pSrc >= bytes,
+                    "[UTF8Encoding.GetChars]Expected invalid byte sequence to have remained within the byte array");
+                ch = 0;
+                continue;
+
+            ReadChar:
+                ch = *pSrc;
+                pSrc++;
+
+            ProcessChar:
+                if (ch > 0x7F)
+                {
+                    // If its > 0x7F, its start of a new multi-byte sequence
+
+                    // bit 6 has to be non-zero
+                    if ((ch & 0x40) == 0)
+                    {
+                        goto InvalidByteSequence;
+                    }
+
+                    // start a new long code
+                    if ((ch & 0x20) != 0)
+                    {
+                        if ((ch & 0x10) != 0)
+                        {
+                            // 4 byte encoding - supplimentary character (2 surrogates)
+
+                            ch &= 0x0F;
+
+                            // check that bit 4 is zero and the valid supplimentary character
+                            // range 0x000000 - 0x10FFFF at the same time
+                            if (ch > 0x04)
+                            {
+                                ch |= 0xf0;
+                                goto InvalidByteSequence;
+                            }
+
+                            ch |= (FinalByte >> 3 * 6) | (1 << 30) | (3 << (30 - 2 * 6)) |
+                                (SupplimentarySeq) | (SupplimentarySeq >> 6) |
+                                (SupplimentarySeq >> 2 * 6) | (SupplimentarySeq >> 3 * 6);
+                        }
+                        else
+                        {
+                            // 3 byte encoding
+                            ch = (ch & 0x0F) | ((FinalByte >> 2 * 6) | (1 << 30) |
+                                (ThreeByteSeq) | (ThreeByteSeq >> 6) | (ThreeByteSeq >> 2 * 6));
+                        }
+                    }
+                    else
+                    {
+                        // 2 byte encoding
+
+                        ch &= 0x1F;
+
+                        // check for non-shortest form
+                        if (ch <= 1)
+                        {
+                            ch |= 0xc0;
+                            goto InvalidByteSequence;
+                        }
+
+                        ch |= (FinalByte >> 6);
+                    }
+                    continue;
+                }
+
+            EncodeChar:
+                // write the pending character
+                if (pTarget >= pAllocatedBufferEnd)
+                {
+                    // Fix chars so we make sure to throw if we didn't output anything
+                    ch &= 0x1fffff;
+                    if (ch > 0x7f)
+                    {
+                        if (ch > 0x7ff)
+                        {
+                            if (ch >= CharUnicodeInfo.LOW_SURROGATE_START &&
+                                ch <= CharUnicodeInfo.LOW_SURROGATE_END)
+                            {
+                                pSrc--;     // It was 4 bytes
+                                pTarget--;  // 1 was stored already, but we can't remember 1/2, so back up
+                            }
+                            else if (ch > 0xffff)
+                            {
+                                pSrc--;     // It was 4 bytes, nothing was stored
+                            }
+                            pSrc--;         // It was at least 3 bytes
+                        }
+                        pSrc--;             // It was at least 2 bytes
+                    }
+                    pSrc--;
+
+                    // Throw that we don't have enough room (pSrc could be < chars if we had started to process
+                    // a 4 byte sequence already)
+                    Debug.Assert(pSrc >= bytes || pTarget == chars,
+                        "[UTF8Encoding.GetChars]Expected pSrc to be within input buffer or throw due to no output]");
+                    ThrowCharsOverflow(baseDecoder, pTarget == chars);
+
+                    // Don't store ch in decoder, we already backed up to its start
+                    ch = 0;
+
+                    // Didn't throw, just use this buffer size.
+                    break;
+                }
+                *pTarget = (char)ch;
+                pTarget++;
+
+#if FASTLOOP
+                int availableChars = PtrDiff(pAllocatedBufferEnd, pTarget);
+                int availableBytes = PtrDiff(pEnd, pSrc);
+
+                // don't fall into the fast decoding loop if we don't have enough bytes
+                // Test for availableChars is done because pStop would be <= pTarget.
+                if (availableBytes <= 13)
+                {
+                    // we may need as many as 1 character per byte
+                    if (availableChars < availableBytes)
+                    {
+                        // not enough output room.  no pending bits at this point
+                        ch = 0;
+                        continue;
+                    }
+
+                    // try to get over the remainder of the ascii characters fast though
+                    byte* pLocalEnd = pEnd; // hint to get pLocalEnd enregistered
+                    while (pSrc < pLocalEnd)
+                    {
+                        ch = *pSrc;
+                        pSrc++;
+
+                        if (ch > 0x7F)
+                            goto ProcessChar;
+
+                        *pTarget = (char)ch;
+                        pTarget++;
+                    }
+                    // we are done
+                    ch = 0;
+                    break;
+                }
+
+                // we may need as many as 1 character per byte, so reduce the byte count if necessary.
+                // If availableChars is too small, pStop will be before pTarget and we won't do fast loop.
+                if (availableChars < availableBytes)
+                {
+                    availableBytes = availableChars;
+                }
+
+                // To compute the upper bound, assume that all characters are ASCII characters at this point,
+                //  the boundary will be decreased for every non-ASCII character we encounter
+                // Also, we need 7 chars reserve for the unrolled ansi decoding loop and for decoding of multibyte sequences
+                char* pStop = pTarget + availableBytes - 7;
+
+                while (pTarget < pStop)
+                {
+                    ch = *pSrc;
+                    pSrc++;
+
+                    if (ch > 0x7F)
+                    {
+                        goto LongCode;
+                    }
+                    *pTarget = (char)ch;
+                    pTarget++;
+
+                    // get pSrc to be 2-byte aligned
+                    if ((unchecked((int)pSrc) & 0x1) != 0)
+                    {
+                        ch = *pSrc;
+                        pSrc++;
+                        if (ch > 0x7F)
+                        {
+                            goto LongCode;
+                        }
+                        *pTarget = (char)ch;
+                        pTarget++;
+                    }
+
+                    // get pSrc to be 4-byte aligned
+                    if ((unchecked((int)pSrc) & 0x2) != 0)
+                    {
+                        ch = *(ushort*)pSrc;
+                        if ((ch & 0x8080) != 0)
+                        {
+                            goto LongCodeWithMask16;
+                        }
+
+                        // Unfortunately, this is endianess sensitive
+#if BIGENDIAN
+                        *pTarget = (char)((ch >> 8) & 0x7F);
+                        pSrc += 2;
+                        *(pTarget+1) = (char)(ch & 0x7F);
+                        pTarget += 2;
+#else // BIGENDIAN
+                        *pTarget = (char)(ch & 0x7F);
+                        pSrc += 2;
+                        *(pTarget + 1) = (char)((ch >> 8) & 0x7F);
+                        pTarget += 2;
+#endif // BIGENDIAN
+                    }
+
+                    // Run 8 characters at a time!
+                    while (pTarget < pStop)
+                    {
+                        ch = *(int*)pSrc;
+                        int chb = *(int*)(pSrc + 4);
+                        if (((ch | chb) & unchecked((int)0x80808080)) != 0)
+                        {
+                            goto LongCodeWithMask32;
+                        }
+
+                        // Unfortunately, this is endianess sensitive
+#if BIGENDIAN
+                        *pTarget = (char)((ch >> 24) & 0x7F);
+                        *(pTarget+1) = (char)((ch >> 16) & 0x7F);
+                        *(pTarget+2) = (char)((ch >> 8) & 0x7F);
+                        *(pTarget+3) = (char)(ch & 0x7F);
+                        pSrc += 8;
+                        *(pTarget+4) = (char)((chb >> 24) & 0x7F);
+                        *(pTarget+5) = (char)((chb >> 16) & 0x7F);
+                        *(pTarget+6) = (char)((chb >> 8) & 0x7F);
+                        *(pTarget+7) = (char)(chb & 0x7F);
+                        pTarget += 8;
+#else // BIGENDIAN
+                        *pTarget = (char)(ch & 0x7F);
+                        *(pTarget + 1) = (char)((ch >> 8) & 0x7F);
+                        *(pTarget + 2) = (char)((ch >> 16) & 0x7F);
+                        *(pTarget + 3) = (char)((ch >> 24) & 0x7F);
+                        pSrc += 8;
+                        *(pTarget + 4) = (char)(chb & 0x7F);
+                        *(pTarget + 5) = (char)((chb >> 8) & 0x7F);
+                        *(pTarget + 6) = (char)((chb >> 16) & 0x7F);
+                        *(pTarget + 7) = (char)((chb >> 24) & 0x7F);
+                        pTarget += 8;
+#endif // BIGENDIAN
+                    }
+                    break;
+
+#if BIGENDIAN
+                LongCodeWithMask32:
+                    // be careful about the sign extension
+                    ch = (int)(((uint)ch) >> 16);
+                LongCodeWithMask16:
+                    ch = (int)(((uint)ch) >> 8);
+#else // BIGENDIAN
+                LongCodeWithMask32:
+                LongCodeWithMask16:
+                    ch &= 0xFF;
+#endif // BIGENDIAN
+                    pSrc++;
+                    if (ch <= 0x7F)
+                    {
+                        *pTarget = (char)ch;
+                        pTarget++;
+                        continue;
+                    }
+
+                LongCode:
+                    int chc = *pSrc;
+                    pSrc++;
+
+                    if (
+                        // bit 6 has to be zero
+                        (ch & 0x40) == 0 ||
+                        // we are expecting to see trailing bytes like 10vvvvvv
+                        (chc & unchecked((sbyte)0xC0)) != 0x80)
+                    {
+                        goto BadLongCode;
+                    }
+
+                    chc &= 0x3F;
+
+                    // start a new long code
+                    if ((ch & 0x20) != 0)
+                    {
+                        // fold the first two bytes together
+                        chc |= (ch & 0x0F) << 6;
+
+                        if ((ch & 0x10) != 0)
+                        {
+                            // 4 byte encoding - surrogate
+                            ch = *pSrc;
+                            if (
+                                // check that bit 4 is zero, the non-shortest form of surrogate
+                                // and the valid surrogate range 0x000000 - 0x10FFFF at the same time
+                                !InRange(chc >> 4, 0x01, 0x10) ||
+                                // we are expecting to see trailing bytes like 10vvvvvv
+                                (ch & unchecked((sbyte)0xC0)) != 0x80)
+                            {
+                                goto BadLongCode;
+                            }
+
+                            chc = (chc << 6) | (ch & 0x3F);
+
+                            ch = *(pSrc + 1);
+                            // we are expecting to see trailing bytes like 10vvvvvv
+                            if ((ch & unchecked((sbyte)0xC0)) != 0x80)
+                            {
+                                goto BadLongCode;
+                            }
+                            pSrc += 2;
+
+                            ch = (chc << 6) | (ch & 0x3F);
+
+                            *pTarget = (char)(((ch >> 10) & 0x7FF) +
+                                unchecked((short)(CharUnicodeInfo.HIGH_SURROGATE_START - (0x10000 >> 10))));
+                            pTarget++;
+
+                            ch = (ch & 0x3FF) +
+                                unchecked((short)(CharUnicodeInfo.LOW_SURROGATE_START));
+
+                            // extra byte, we're already planning 2 chars for 2 of these bytes,
+                            // but the big loop is testing the target against pStop, so we need
+                            // to subtract 2 more or we risk overrunning the input.  Subtract 
+                            // one here and one below.
+                            pStop--;
+                        }
+                        else
+                        {
+                            // 3 byte encoding
+                            ch = *pSrc;
+                            if (
+                                // check for non-shortest form of 3 byte seq
+                                (chc & (0x1F << 5)) == 0 ||
+                                // Can't have surrogates here.
+                                (chc & (0xF800 >> 6)) == (0xD800 >> 6) ||
+                                // we are expecting to see trailing bytes like 10vvvvvv
+                                (ch & unchecked((sbyte)0xC0)) != 0x80)
+                            {
+                                goto BadLongCode;
+                            }
+                            pSrc++;
+
+                            ch = (chc << 6) | (ch & 0x3F);
+
+                            // extra byte, we're only expecting 1 char for each of these 3 bytes,
+                            // but the loop is testing the target (not source) against pStop, so
+                            // we need to subtract 2 more or we risk overrunning the input.
+                            // Subtract 1 here and one more below
+                            pStop--;
+                        }
+                    }
+                    else
+                    {
+                        // 2 byte encoding
+
+                        ch &= 0x1F;
+
+                        // check for non-shortest form
+                        if (ch <= 1)
+                        {
+                            goto BadLongCode;
+                        }
+                        ch = (ch << 6) | chc;
+                    }
+
+                    *pTarget = (char)ch;
+                    pTarget++;
+
+                    // extra byte, we're only expecting 1 char for each of these 2 bytes,
+                    // but the loop is testing the target (not source) against pStop.
+                    // subtract an extra count from pStop so that we don't overrun the input.
+                    pStop--;
+                }
+#endif // FASTLOOP
+
+                Debug.Assert(pTarget <= pAllocatedBufferEnd, "[UTF8Encoding.GetChars]pTarget <= pAllocatedBufferEnd");
+
+                // no pending bits at this point
+                ch = 0;
+                continue;
+
+            BadLongCode:
+                pSrc -= 2;
+                ch = 0;
+                continue;
+            }
+
+            if (ch != 0 && (baseDecoder == null || baseDecoder.MustFlush))
+            {
+                // Have to do fallback for invalid bytes
+                if (fallback == null)
+                {
+                    if (baseDecoder == null)
+                        fallback = this.decoderFallback.CreateFallbackBuffer();
+                    else
+                        fallback = baseDecoder.FallbackBuffer;
+                    fallback.InternalInitialize(bytes, pAllocatedBufferEnd);
+                }
+
+                // That'll back us up the appropriate # of bytes if we didn't get anywhere
+                pSrcForFallback = pSrc; // Avoid passing pSrc by reference to allow it to be en-registered
+                pTargetForFallback = pTarget; // Avoid passing pTarget by reference to allow it to be en-registered
+                bool fallbackResult = FallbackInvalidByteSequence(ref pSrcForFallback, ch, fallback, ref pTargetForFallback);
+                pSrc = pSrcForFallback;
+                pTarget = pTargetForFallback;
+
+                if (!fallbackResult)
+                {
+                    Debug.Assert(pSrc >= bytes || pTarget == chars,
+                        "[UTF8Encoding.GetChars]Expected to throw or remain in byte buffer while flushing");
+
+                    // Ran out of buffer space
+                    // Need to throw an exception?
+                    fallback.InternalReset();
+                    ThrowCharsOverflow(baseDecoder, pTarget == chars);
+                }
+                Debug.Assert(pSrc >= bytes,
+                    "[UTF8Encoding.GetChars]Expected flushing invalid byte sequence to have remained within the byte array");
+                ch = 0;
+            }
+
+            if (baseDecoder != null)
+            {
+                UTF8Decoder decoder = (UTF8Decoder)baseDecoder;
+
+                // If we're storing flush data we expect all bits to be used or else
+                // we're stuck in the middle of a conversion
+                Debug.Assert(!baseDecoder.MustFlush || ch == 0 || !baseDecoder._throwOnOverflow,
+                    "[UTF8Encoding.GetChars]Expected no must flush or no left over bits or no throw on overflow.");
+
+                // Remember our leftover bits.
+                decoder.bits = ch;
+
+                baseDecoder._bytesUsed = (int)(pSrc - bytes);
+            }
+
+            // Shouldn't have anything in fallback buffer for GetChars
+            // (don't have to check _throwOnOverflow for chars)
+            Debug.Assert(fallback == null || fallback.Remaining == 0,
+                "[UTF8Encoding.GetChars]Expected empty fallback buffer at end");
+
+            return PtrDiff(pTarget, chars);
+        }
+
+        // During GetChars we had an invalid byte sequence
+        // pSrc is backed up to the start of the bad sequence if we didn't have room to
+        // fall it back.  Otherwise pSrc remains where it is.
+        private unsafe bool FallbackInvalidByteSequence(
+            ref byte* pSrc, int ch, DecoderFallbackBuffer fallback, ref char* pTarget)
+        {
+            // Get our byte[]
+            byte* pStart = pSrc;
+            byte[] bytesUnknown = GetBytesUnknown(ref pStart, ch);
+
+            // Do the actual fallback
+            if (!fallback.InternalFallback(bytesUnknown, pSrc, ref pTarget))
+            {
+                // Oops, it failed, back up to pStart
+                pSrc = pStart;
+                return false;
+            }
+
+            // It worked
+            return true;
+        }
+
+        // During GetCharCount we had an invalid byte sequence
+        // pSrc is used to find the index that points to the invalid bytes,
+        // however the byte[] contains the fallback bytes (in case the index is -1)
+        private unsafe int FallbackInvalidByteSequence(
+            byte* pSrc, int ch, DecoderFallbackBuffer fallback)
+        {
+            // Get our byte[]
+            byte[] bytesUnknown = GetBytesUnknown(ref pSrc, ch);
+
+            // Do the actual fallback
+            int count = fallback.InternalFallback(bytesUnknown, pSrc);
+
+            // # of fallback chars expected.
+            // Note that we only get here for "long" sequences, and have already unreserved
+            // the count that we prereserved for the input bytes
+            return count;
+        }
+
+        // Note that some of these bytes may have come from a previous fallback, so we cannot
+        // just decrement the pointer and use the values we read.  In those cases we have 
+        // to regenerate the original values.
+        private unsafe byte[] GetBytesUnknown(ref byte* pSrc, int ch)
+        {
+            // Get our byte[]
+            byte[] bytesUnknown = null;
+
+            // See if it was a plain char
+            // (have to check >= 0 because we have all sorts of wierd bit flags)
+            if (ch < 0x100 && ch >= 0)
+            {
+                pSrc--;
+                bytesUnknown = new byte[] { unchecked((byte)ch) };
+            }
+            // See if its an unfinished 2 byte sequence
+            else if ((ch & (SupplimentarySeq | ThreeByteSeq)) == 0)
+            {
+                pSrc--;
+                bytesUnknown = new byte[] { unchecked((byte)((ch & 0x1F) | 0xc0)) };
+            }
+            // So now we're either 2nd byte of 3 or 4 byte sequence or
+            // we hit a non-trail byte or we ran out of space for 3rd byte of 4 byte sequence
+            // 1st check if its a 4 byte sequence
+            else if ((ch & SupplimentarySeq) != 0)
+            {
+                //  3rd byte of 4 byte sequence?
+                if ((ch & (FinalByte >> 6)) != 0)
+                {
+                    // 3rd byte of 4 byte sequence
+                    pSrc -= 3;
+                    bytesUnknown = new byte[] {
+                        unchecked((byte)(((ch >> 12) & 0x07) | 0xF0)),
+                        unchecked((byte)(((ch >> 6) & 0x3F) | 0x80)),
+                        unchecked((byte)(((ch) & 0x3F) | 0x80)) };
+                }
+                else if ((ch & (FinalByte >> 12)) != 0)
+                {
+                    // 2nd byte of a 4 byte sequence
+                    pSrc -= 2;
+                    bytesUnknown = new byte[] {
+                        unchecked((byte)(((ch >> 6) & 0x07) | 0xF0)),
+                        unchecked((byte)(((ch) & 0x3F) | 0x80)) };
+                }
+                else
+                {
+                    // 4th byte of a 4 byte sequence
+                    pSrc--;
+                    bytesUnknown = new byte[] { unchecked((byte)(((ch) & 0x07) | 0xF0)) };
+                }
+            }
+            else
+            {
+                // 2nd byte of 3 byte sequence?
+                if ((ch & (FinalByte >> 6)) != 0)
+                {
+                    // So its 2nd byte of a 3 byte sequence
+                    pSrc -= 2;
+                    bytesUnknown = new byte[] {
+                        unchecked((byte)(((ch >> 6) & 0x0F) | 0xE0)), unchecked ((byte)(((ch) & 0x3F) | 0x80)) };
+                }
+                else
+                {
+                    // 1st byte of a 3 byte sequence
+                    pSrc--;
+                    bytesUnknown = new byte[] { unchecked((byte)(((ch) & 0x0F) | 0xE0)) };
+                }
+            }
+
+            return bytesUnknown;
+        }
+
+
+        public override Decoder GetDecoder()
+        {
+            return new UTF8Decoder(this);
+        }
+
+
+        public override Encoder GetEncoder()
+        {
+            return new UTF8Encoder(this);
+        }
+
+
+        public override int GetMaxByteCount(int charCount)
+        {
+            if (charCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(charCount),
+                     SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Characters would be # of characters + 1 in case left over high surrogate is ? * max fallback
+            long byteCount = (long)charCount + 1;
+
+            if (EncoderFallback.MaxCharCount > 1)
+                byteCount *= EncoderFallback.MaxCharCount;
+
+            // Max 3 bytes per char.  (4 bytes per 2 chars for surrogates)
+            byteCount *= 3;
+
+            if (byteCount > 0x7fffffff)
+                throw new ArgumentOutOfRangeException(nameof(charCount), SR.ArgumentOutOfRange_GetByteCountOverflow);
+
+            return (int)byteCount;
+        }
+
+
+        public override int GetMaxCharCount(int byteCount)
+        {
+            if (byteCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(byteCount),
+                     SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Figure out our length, 1 char per input byte + 1 char if 1st byte is last byte of 4 byte surrogate pair
+            long charCount = ((long)byteCount + 1);
+
+            // Non-shortest form would fall back, so get max count from fallback.
+            // So would 11... followed by 11..., so you could fall back every byte
+            if (DecoderFallback.MaxCharCount > 1)
+            {
+                charCount *= DecoderFallback.MaxCharCount;
+            }
+
+            if (charCount > 0x7fffffff)
+                throw new ArgumentOutOfRangeException(nameof(byteCount), SR.ArgumentOutOfRange_GetCharCountOverflow);
+
+            return (int)charCount;
+        }
+
+
+        public override byte[] GetPreamble()
+        {
+            if (_emitUTF8Identifier)
+            {
+                // Allocate new array to prevent users from modifying it.
+                return new byte[3] { 0xEF, 0xBB, 0xBF };
+            }
+            else
+                return Array.Empty<byte>();
+        }
+
+        public override ReadOnlySpan<byte> Preamble =>
+            GetType() != typeof(UTF8Encoding) ? GetPreamble() : // in case a derived UTF8Encoding overrode GetPreamble
+            _emitUTF8Identifier ? s_preamble :
+            Array.Empty<byte>();
+
+        public override bool Equals(Object value)
+        {
+            UTF8Encoding that = value as UTF8Encoding;
+            if (that != null)
+            {
+                return (_emitUTF8Identifier == that._emitUTF8Identifier) &&
+                       (EncoderFallback.Equals(that.EncoderFallback)) &&
+                       (DecoderFallback.Equals(that.DecoderFallback));
+            }
+            return (false);
+        }
+
+
+        public override int GetHashCode()
+        {
+            //Not great distribution, but this is relatively unlikely to be used as the key in a hashtable.
+            return this.EncoderFallback.GetHashCode() + this.DecoderFallback.GetHashCode() +
+                   UTF8_CODEPAGE + (_emitUTF8Identifier ? 1 : 0);
+        }
+
+        private sealed class UTF8Encoder : EncoderNLS
+        {
+            // We must save a high surrogate value until the next call, looking
+            // for a low surrogate value.
+            internal int surrogateChar;
+
+            public UTF8Encoder(UTF8Encoding encoding) : base(encoding)
+            {
+                // base calls reset
+            }
+
+            public override void Reset()
+
+            {
+                this.surrogateChar = 0;
+                if (_fallbackBuffer != null)
+                    _fallbackBuffer.Reset();
+            }
+
+            // Anything left in our encoder?
+            internal override bool HasState
+            {
+                get
+                {
+                    return (this.surrogateChar != 0);
+                }
+            }
+        }
+
+        private sealed class UTF8Decoder : DecoderNLS
+        {
+            // We'll need to remember the previous information. See the comments around definition
+            // of FinalByte for details.
+            internal int bits;
+
+            public UTF8Decoder(UTF8Encoding encoding) : base(encoding)
+            {
+                // base calls reset
+            }
+
+            public override void Reset()
+            {
+                this.bits = 0;
+                if (_fallbackBuffer != null)
+                    _fallbackBuffer.Reset();
+            }
+
+            // Anything left in our decoder?
+            internal override bool HasState
+            {
+                get
+                {
+                    return (this.bits != 0);
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Text/UnicodeEncoding.cs b/src/System.Private.CoreLib/shared/System/Text/UnicodeEncoding.cs
new file mode 100644
index 0000000000..342bf53d62
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/UnicodeEncoding.cs
@@ -0,0 +1,1985 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+// Don't override IsAlwaysNormalized because it is just a Unicode Transformation and could be confused.
+//
+
+using System;
+using System.Globalization;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System.Text
+{
+    public class UnicodeEncoding : Encoding
+    {
+        // Used by Encoding.BigEndianUnicode/Unicode for lazy initialization
+        // The initialization code will not be run until a static member of the class is referenced
+        internal static readonly UnicodeEncoding s_bigEndianDefault = new UnicodeEncoding(bigEndian: true, byteOrderMark: true);
+        internal static readonly UnicodeEncoding s_littleEndianDefault = new UnicodeEncoding(bigEndian: false, byteOrderMark: true);
+
+        private static readonly byte[] s_bigEndianPreamble = new byte[2] { 0xfe, 0xff };
+        private static readonly byte[] s_littleEndianPreamble = new byte[2] { 0xff, 0xfe };
+
+        internal bool isThrowException = false;
+
+        internal bool bigEndian = false;
+        internal bool byteOrderMark = true;
+
+        // Unicode version 2.0 character size in bytes
+        public const int CharSize = 2;
+
+
+        public UnicodeEncoding()
+            : this(false, true)
+        {
+        }
+
+
+        public UnicodeEncoding(bool bigEndian, bool byteOrderMark)
+            : this(bigEndian, byteOrderMark, false)
+        {
+        }
+
+
+        public UnicodeEncoding(bool bigEndian, bool byteOrderMark, bool throwOnInvalidBytes)
+            : base(bigEndian ? 1201 : 1200)  //Set the data item.
+        {
+            this.isThrowException = throwOnInvalidBytes;
+            this.bigEndian = bigEndian;
+            this.byteOrderMark = byteOrderMark;
+
+            // Encoding constructor already did this, but it'll be wrong if we're throwing exceptions
+            if (this.isThrowException)
+                SetDefaultFallbacks();
+        }
+
+        internal override void SetDefaultFallbacks()
+        {
+            // For UTF-X encodings, we use a replacement fallback with an empty string
+            if (this.isThrowException)
+            {
+                this.encoderFallback = EncoderFallback.ExceptionFallback;
+                this.decoderFallback = DecoderFallback.ExceptionFallback;
+            }
+            else
+            {
+                this.encoderFallback = new EncoderReplacementFallback("\xFFFD");
+                this.decoderFallback = new DecoderReplacementFallback("\xFFFD");
+            }
+        }
+
+        // The following methods are copied from EncodingNLS.cs.
+        // Unfortunately EncodingNLS.cs is internal and we're public, so we have to re-implement them here.
+        // These should be kept in sync for the following classes:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        //
+
+        // Returns the number of bytes required to encode a range of characters in
+        // a character array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetByteCount(char[] chars, int index, int count)
+        {
+            // Validate input parameters
+            if (chars == null)
+                throw new ArgumentNullException("chars", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - index < count)
+                throw new ArgumentOutOfRangeException("chars", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // If no input, return 0, avoid fixed empty array problem
+            if (count == 0)
+                return 0;
+
+            // Just call the pointer version
+            fixed (char* pChars = chars)
+                return GetByteCount(pChars + index, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetByteCount(String s)
+        {
+            // Validate input
+            if (s==null)
+                throw new ArgumentNullException("s");
+
+            fixed (char* pChars = s)
+                return GetByteCount(pChars, s.Length, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetByteCount(char* chars, int count)
+        {
+            // Validate Parameters
+            if (chars == null)
+                throw new ArgumentNullException("chars", SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException("count", SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Call it with empty encoder
+            return GetByteCount(chars, count, null);
+        }
+
+        // Parent method is safe.
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        public override unsafe int GetBytes(String s, int charIndex, int charCount,
+                                              byte[] bytes, int byteIndex)
+        {
+            if (s == null || bytes == null)
+                throw new ArgumentNullException((s == null ? "s" : "bytes"), SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? "charIndex" : "charCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (s.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException("s", SR.ArgumentOutOfRange_IndexCount);
+
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+                throw new ArgumentOutOfRangeException("byteIndex", SR.ArgumentOutOfRange_Index);
+
+            int byteCount = bytes.Length - byteIndex;
+
+            fixed (char* pChars = s) fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+                return GetBytes(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, null);
+        }
+
+        // Encodes a range of characters in a character array into a range of bytes
+        // in a byte array. An exception occurs if the byte array is not large
+        // enough to hold the complete encoding of the characters. The
+        // GetByteCount method can be used to determine the exact number of
+        // bytes that will be produced for a given range of characters.
+        // Alternatively, the GetMaxByteCount method can be used to
+        // determine the maximum number of bytes that will be produced for a given
+        // number of characters, regardless of the actual character values.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetBytes(char[] chars, int charIndex, int charCount,
+                                               byte[] bytes, int byteIndex)
+        {
+            // Validate parameters
+            if (chars == null || bytes == null)
+                throw new ArgumentNullException((chars == null ? "chars" : "bytes"), SR.ArgumentNull_Array);
+
+            if (charIndex < 0 || charCount < 0)
+                throw new ArgumentOutOfRangeException((charIndex < 0 ? "charIndex" : "charCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (chars.Length - charIndex < charCount)
+                throw new ArgumentOutOfRangeException("chars", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (byteIndex < 0 || byteIndex > bytes.Length)
+                throw new ArgumentOutOfRangeException("byteIndex", SR.ArgumentOutOfRange_Index);
+
+            // If nothing to encode return 0, avoid fixed problem
+            if (charCount == 0)
+                return 0;
+
+            // Just call pointer version
+            int byteCount = bytes.Length - byteIndex;
+
+            fixed (char* pChars = chars) fixed (byte* pBytes = &MemoryMarshal.GetReference((Span<byte>)bytes))
+                // Remember that byteCount is # to decode, not size of array.
+                return GetBytes(pChars + charIndex, charCount, pBytes + byteIndex, byteCount, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetBytes(char* chars, int charCount, byte* bytes, int byteCount)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? "charCount" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetBytes(chars, charCount, bytes, byteCount, null);
+        }
+
+        // Returns the number of characters produced by decoding a range of bytes
+        // in a byte array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetCharCount(byte[] bytes, int index, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (bytes.Length - index < count)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // If no input just return 0, fixed doesn't like 0 length arrays
+            if (count == 0)
+                return 0;
+
+            // Just call pointer version
+            fixed (byte* pBytes = bytes)
+                return GetCharCount(pBytes + index, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public override unsafe int GetCharCount(byte* bytes, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (count < 0)
+                throw new ArgumentOutOfRangeException("count", SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetCharCount(bytes, count, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe int GetChars(byte[] bytes, int byteIndex, int byteCount,
+                                              char[] chars, int charIndex)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (byteIndex < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((byteIndex < 0 ? "byteIndex" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if ( bytes.Length - byteIndex < byteCount)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            if (charIndex < 0 || charIndex > chars.Length)
+                throw new ArgumentOutOfRangeException("charIndex", SR.ArgumentOutOfRange_Index);
+
+            // If no input, return 0 & avoid fixed problem
+            if (byteCount == 0)
+                return 0;
+
+            // Just call pointer version
+            int charCount = chars.Length - charIndex;
+
+            fixed (byte* pBytes = bytes) fixed (char* pChars = &MemoryMarshal.GetReference((Span<char>)chars))
+                // Remember that charCount is # to decode, not size of array
+                return GetChars(pBytes + byteIndex, byteCount, pChars + charIndex, charCount, null);
+        }
+
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+
+        [CLSCompliant(false)]
+        public unsafe override int GetChars(byte* bytes, int byteCount, char* chars, int charCount)
+        {
+            // Validate Parameters
+            if (bytes == null || chars == null)
+                throw new ArgumentNullException(bytes == null ? "bytes" : "chars", SR.ArgumentNull_Array);
+
+            if (charCount < 0 || byteCount < 0)
+                throw new ArgumentOutOfRangeException((charCount < 0 ? "charCount" : "byteCount"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return GetChars(bytes, byteCount, chars, charCount, null);
+        }
+
+        // Returns a string containing the decoded representation of a range of
+        // bytes in a byte array.
+        //
+        // All of our public Encodings that don't use EncodingNLS must have this (including EncodingNLS)
+        // So if you fix this, fix the others.  Currently those include:
+        // EncodingNLS, UTF7Encoding, UTF8Encoding, UTF32Encoding, ASCIIEncoding, UnicodeEncoding
+        // parent method is safe
+
+        public override unsafe string GetString(byte[] bytes, int index, int count)
+        {
+            // Validate Parameters
+            if (bytes == null)
+                throw new ArgumentNullException("bytes", SR.ArgumentNull_Array);
+
+            if (index < 0 || count < 0)
+                throw new ArgumentOutOfRangeException((index < 0 ? "index" : "count"), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (bytes.Length - index < count)
+                throw new ArgumentOutOfRangeException("bytes", SR.ArgumentOutOfRange_IndexCountBuffer);
+
+            // Avoid problems with empty input buffer
+            if (count == 0) return String.Empty;
+
+            fixed (byte* pBytes = bytes)
+                return String.CreateStringFromEncoding(
+                    pBytes + index, count, this);
+        }
+
+        //
+        // End of standard methods copied from EncodingNLS.cs
+        //
+
+        internal override unsafe int GetByteCount(char* chars, int count, EncoderNLS encoder)
+        {
+            Debug.Assert(chars != null, "[UnicodeEncoding.GetByteCount]chars!=null");
+            Debug.Assert(count >= 0, "[UnicodeEncoding.GetByteCount]count >=0");
+
+            // Start by assuming each char gets 2 bytes
+            int byteCount = count << 1;
+
+            // Check for overflow in byteCount
+            // (If they were all invalid chars, this would actually be wrong,
+            // but that's a ridiculously large # so we're not concerned about that case)
+            if (byteCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_GetByteCountOverflow);
+
+            char* charStart = chars;
+            char* charEnd = chars + count;
+            char charLeftOver = (char)0;
+
+            bool wasHereBefore = false;
+
+            // Need -1 to check 2 at a time.  If we have an even #, longChars will go
+            // from longEnd - 1/2 long to longEnd + 1/2 long.  If we're odd, longChars
+            // will go from longEnd - 1 long to longEnd. (Might not get to use this)
+            ulong* longEnd = (ulong*)(charEnd - 3);
+
+            // For fallback we may need a fallback buffer
+            EncoderFallbackBuffer fallbackBuffer = null;
+            char* charsForFallback;
+
+            if (encoder != null)
+            {
+                charLeftOver = encoder._charLeftOver;
+
+                // Assume extra bytes to encode charLeftOver if it existed
+                if (charLeftOver > 0)
+                    byteCount += 2;
+
+                // We mustn't have left over fallback data when counting
+                if (encoder.InternalHasFallbackBuffer)
+                {
+                    fallbackBuffer = encoder.FallbackBuffer;
+                    if (fallbackBuffer.Remaining > 0)
+                        throw new ArgumentException(SR.Format(SR.Argument_EncoderFallbackNotEmpty, this.EncodingName, encoder.Fallback.GetType()));
+
+                    // Set our internal fallback interesting things.
+                    fallbackBuffer.InternalInitialize(charStart, charEnd, encoder, false);
+                }
+            }
+
+            char ch;
+        TryAgain:
+
+            while (((ch = (fallbackBuffer == null) ? (char)0 : fallbackBuffer.InternalGetNextChar()) != 0) || chars < charEnd)
+            {
+                // First unwind any fallback
+                if (ch == 0)
+                {
+                    // No fallback, maybe we can do it fast
+#if !NO_FAST_UNICODE_LOOP
+#if BIGENDIAN       // If endianess is backwards then each pair of bytes would be backwards.
+                    if ( bigEndian &&
+#else
+                    if (!bigEndian &&
+#endif // BIGENDIAN
+
+#if BIT64           // 64 bit CPU needs to be long aligned for this to work.
+                          charLeftOver == 0 && (unchecked((long)chars) & 7) == 0)
+#else
+                          charLeftOver == 0 && (unchecked((int)chars) & 3) == 0)
+#endif
+                    {
+                        // Need new char* so we can check 4 at a time
+                        ulong* longChars = (ulong*)chars;
+
+                        while (longChars < longEnd)
+                        {
+                            // See if we potentially have surrogates (0x8000 bit set)
+                            // (We're either big endian on a big endian machine or little endian on 
+                            // a little endian machine so that'll work)                            
+                            if ((0x8000800080008000 & *longChars) != 0)
+                            {
+                                // See if any of these are high or low surrogates (0xd800 - 0xdfff).  If the high
+                                // 5 bits looks like 11011, then its a high or low surrogate.
+                                // We do the & f800 to filter the 5 bits, then ^ d800 to ensure the 0 isn't set.
+                                // Note that we expect BMP characters to be more common than surrogates
+                                // & each char with 11111... then ^ with 11011.  Zeroes then indicate surrogates
+                                ulong uTemp = (0xf800f800f800f800 & *longChars) ^ 0xd800d800d800d800;
+
+                                // Check each of the 4 chars.  0 for those 16 bits means it was a surrogate
+                                // but no clue if they're high or low.
+                                // If each of the 4 characters are non-zero, then none are surrogates.
+                                if ((uTemp & 0xFFFF000000000000) == 0 ||
+                                    (uTemp & 0x0000FFFF00000000) == 0 ||
+                                    (uTemp & 0x00000000FFFF0000) == 0 ||
+                                    (uTemp & 0x000000000000FFFF) == 0)
+                                {
+                                    // It has at least 1 surrogate, but we don't know if they're high or low surrogates,
+                                    // or if there's 1 or 4 surrogates
+
+                                    // If they happen to be high/low/high/low, we may as well continue.  Check the next
+                                    // bit to see if its set (low) or not (high) in the right pattern
+#if BIGENDIAN
+                                    if (((0xfc00fc00fc00fc00 & *longChars) ^ 0xd800dc00d800dc00) != 0)
+#else
+                                    if (((0xfc00fc00fc00fc00 & *longChars) ^ 0xdc00d800dc00d800) != 0)
+#endif
+                                    {
+                                        // Either there weren't 4 surrogates, or the 0x0400 bit was set when a high
+                                        // was hoped for or the 0x0400 bit wasn't set where a low was hoped for.
+
+                                        // Drop out to the slow loop to resolve the surrogates
+                                        break;
+                                    }
+                                    // else they are all surrogates in High/Low/High/Low order, so we can use them.
+                                }
+                                // else none are surrogates, so we can use them.
+                            }
+                            // else all < 0x8000 so we can use them                            
+
+                            // We already counted these four chars, go to next long.
+                            longChars++;
+                        }
+
+                        chars = (char*)longChars;
+
+                        if (chars >= charEnd)
+                            break;
+                    }
+#endif // !NO_FAST_UNICODE_LOOP
+
+                    // No fallback, just get next char
+                    ch = *chars;
+                    chars++;
+                }
+                else
+                {
+                    // We weren't preallocating fallback space.
+                    byteCount += 2;
+                }
+
+                // Check for high or low surrogates
+                if (ch >= 0xd800 && ch <= 0xdfff)
+                {
+                    // Was it a high surrogate?
+                    if (ch <= 0xdbff)
+                    {
+                        // Its a high surrogate, if we already had a high surrogate do its fallback
+                        if (charLeftOver > 0)
+                        {
+                            // Unwind the current character, this should be safe because we
+                            // don't have leftover data in the fallback, so chars must have
+                            // advanced already.
+                            Debug.Assert(chars > charStart,
+                                "[UnicodeEncoding.GetByteCount]Expected chars to have advanced in unexpected high surrogate");
+                            chars--;
+
+                            // If previous high surrogate deallocate 2 bytes
+                            byteCount -= 2;
+
+                            // Fallback the previous surrogate
+                            // Need to initialize fallback buffer?
+                            if (fallbackBuffer == null)
+                            {
+                                if (encoder == null)
+                                    fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+                                else
+                                    fallbackBuffer = encoder.FallbackBuffer;
+
+                                // Set our internal fallback interesting things.
+                                fallbackBuffer.InternalInitialize(charStart, charEnd, encoder, false);
+                            }
+
+                            charsForFallback = chars; // Avoid passing chars by reference to allow it to be enregistered
+                            fallbackBuffer.InternalFallback(charLeftOver, ref charsForFallback);
+                            chars = charsForFallback;
+
+                            // Now no high surrogate left over
+                            charLeftOver = (char)0;
+                            continue;
+                        }
+
+                        // Remember this high surrogate
+                        charLeftOver = ch;
+                        continue;
+                    }
+
+
+                    // Its a low surrogate
+                    if (charLeftOver == 0)
+                    {
+                        // Expected a previous high surrogate.
+                        // Don't count this one (we'll count its fallback if necessary)
+                        byteCount -= 2;
+
+                        // fallback this one
+                        // Need to initialize fallback buffer?
+                        if (fallbackBuffer == null)
+                        {
+                            if (encoder == null)
+                                fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+                            else
+                                fallbackBuffer = encoder.FallbackBuffer;
+
+                            // Set our internal fallback interesting things.
+                            fallbackBuffer.InternalInitialize(charStart, charEnd, encoder, false);
+                        }
+                        charsForFallback = chars; // Avoid passing chars by reference to allow it to be en-registered
+                        fallbackBuffer.InternalFallback(ch, ref charsForFallback);
+                        chars = charsForFallback;
+                        continue;
+                    }
+
+                    // Valid surrogate pair, add our charLeftOver
+                    charLeftOver = (char)0;
+                    continue;
+                }
+                else if (charLeftOver > 0)
+                {
+                    // Expected a low surrogate, but this char is normal
+
+                    // Rewind the current character, fallback previous character.
+                    // this should be safe because we don't have leftover data in the
+                    // fallback, so chars must have advanced already.
+                    Debug.Assert(chars > charStart,
+                        "[UnicodeEncoding.GetByteCount]Expected chars to have advanced when expected low surrogate");
+                    chars--;
+
+                    // fallback previous chars
+                    // Need to initialize fallback buffer?
+                    if (fallbackBuffer == null)
+                    {
+                        if (encoder == null)
+                            fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = encoder.FallbackBuffer;
+
+                        // Set our internal fallback interesting things.
+                        fallbackBuffer.InternalInitialize(charStart, charEnd, encoder, false);
+                    }
+                    charsForFallback = chars; // Avoid passing chars by reference to allow it to be en-registered
+                    fallbackBuffer.InternalFallback(charLeftOver, ref charsForFallback);
+                    chars = charsForFallback;
+
+                    // Ignore charLeftOver or throw
+                    byteCount -= 2;
+                    charLeftOver = (char)0;
+
+                    continue;
+                }
+
+                // Ok we had something to add (already counted)
+            }
+
+            // Don't allocate space for left over char
+            if (charLeftOver > 0)
+            {
+                byteCount -= 2;
+
+                // If we have to flush, stick it in fallback and try again
+                if (encoder == null || encoder.MustFlush)
+                {
+                    if (wasHereBefore)
+                    {
+                        // Throw it, using our complete character
+                        throw new ArgumentException(
+                            SR.Format(SR.Argument_RecursiveFallback, charLeftOver), nameof(chars));
+                    }
+                    else
+                    {
+                        // Need to initialize fallback buffer?
+                        if (fallbackBuffer == null)
+                        {
+                            if (encoder == null)
+                                fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+                            else
+                                fallbackBuffer = encoder.FallbackBuffer;
+
+                            // Set our internal fallback interesting things.
+                            fallbackBuffer.InternalInitialize(charStart, charEnd, encoder, false);
+                        }
+                        charsForFallback = chars; // Avoid passing chars by reference to allow it to be en-registered
+                        fallbackBuffer.InternalFallback(charLeftOver, ref charsForFallback);
+                        chars = charsForFallback;
+                        charLeftOver = (char)0;
+                        wasHereBefore = true;
+                        goto TryAgain;
+                    }
+                }
+            }
+
+            // Shouldn't have anything in fallback buffer for GetByteCount
+            // (don't have to check _throwOnOverflow for count)
+            Debug.Assert(fallbackBuffer == null || fallbackBuffer.Remaining == 0,
+                "[UnicodeEncoding.GetByteCount]Expected empty fallback buffer at end");
+
+            // Don't remember fallbackBuffer.encoder for counting
+            return byteCount;
+        }
+
+        internal override unsafe int GetBytes(char* chars, int charCount,
+                                                byte* bytes, int byteCount, EncoderNLS encoder)
+        {
+            Debug.Assert(chars != null, "[UnicodeEncoding.GetBytes]chars!=null");
+            Debug.Assert(byteCount >= 0, "[UnicodeEncoding.GetBytes]byteCount >=0");
+            Debug.Assert(charCount >= 0, "[UnicodeEncoding.GetBytes]charCount >=0");
+            Debug.Assert(bytes != null, "[UnicodeEncoding.GetBytes]bytes!=null");
+
+            char charLeftOver = (char)0;
+            char ch;
+            bool wasHereBefore = false;
+
+
+            byte* byteEnd = bytes + byteCount;
+            char* charEnd = chars + charCount;
+            byte* byteStart = bytes;
+            char* charStart = chars;
+
+            // For fallback we may need a fallback buffer
+            EncoderFallbackBuffer fallbackBuffer = null;
+            char* charsForFallback;
+
+            // Get our encoder, but don't clear it yet.
+            if (encoder != null)
+            {
+                charLeftOver = encoder._charLeftOver;
+
+                // We mustn't have left over fallback data when counting
+                if (encoder.InternalHasFallbackBuffer)
+                {
+                    // We always need the fallback buffer in get bytes so we can flush any remaining ones if necessary
+                    fallbackBuffer = encoder.FallbackBuffer;
+                    if (fallbackBuffer.Remaining > 0 && encoder._throwOnOverflow)
+                        throw new ArgumentException(SR.Format(SR.Argument_EncoderFallbackNotEmpty, this.EncodingName, encoder.Fallback.GetType()));
+
+                    // Set our internal fallback interesting things.
+                    fallbackBuffer.InternalInitialize(charStart, charEnd, encoder, false);
+                }
+            }
+
+        TryAgain:
+            while (((ch = (fallbackBuffer == null) ?
+                        (char)0 : fallbackBuffer.InternalGetNextChar()) != 0) ||
+                    chars < charEnd)
+            {
+                // First unwind any fallback
+                if (ch == 0)
+                {
+                    // No fallback, maybe we can do it fast
+#if !NO_FAST_UNICODE_LOOP
+#if BIGENDIAN           // If endianess is backwards then each pair of bytes would be backwards.
+                    if ( bigEndian &&
+#else
+                    if (!bigEndian &&
+#endif // BIGENDIAN
+#if BIT64           // 64 bit CPU needs to be long aligned for this to work, 32 bit CPU needs to be 32 bit aligned
+                        (unchecked((long)chars) & 7) == 0 && (unchecked((long)bytes) & 7) == 0 &&
+#else
+                        (unchecked((int)chars) & 3) == 0 && (unchecked((int)bytes) & 3) == 0 &&
+#endif // BIT64
+                        charLeftOver == 0)
+                    {
+                        // Need -1 to check 2 at a time.  If we have an even #, longChars will go
+                        // from longEnd - 1/2 long to longEnd + 1/2 long.  If we're odd, longChars
+                        // will go from longEnd - 1 long to longEnd. (Might not get to use this)
+                        // We can only go iCount units (limited by shorter of char or byte buffers.
+                        ulong* longEnd = (ulong*)(chars - 3 +
+                                                  (((byteEnd - bytes) >> 1 < charEnd - chars) ?
+                                                    (byteEnd - bytes) >> 1 : charEnd - chars));
+
+                        // Need new char* so we can check 4 at a time
+                        ulong* longChars = (ulong*)chars;
+                        ulong* longBytes = (ulong*)bytes;
+
+                        while (longChars < longEnd)
+                        {
+                            // See if we potentially have surrogates (0x8000 bit set)
+                            // (We're either big endian on a big endian machine or little endian on 
+                            // a little endian machine so that'll work)                            
+                            if ((0x8000800080008000 & *longChars) != 0)
+                            {
+                                // See if any of these are high or low surrogates (0xd800 - 0xdfff).  If the high
+                                // 5 bits looks like 11011, then its a high or low surrogate.
+                                // We do the & f800 to filter the 5 bits, then ^ d800 to ensure the 0 isn't set.
+                                // Note that we expect BMP characters to be more common than surrogates
+                                // & each char with 11111... then ^ with 11011.  Zeroes then indicate surrogates
+                                ulong uTemp = (0xf800f800f800f800 & *longChars) ^ 0xd800d800d800d800;
+
+                                // Check each of the 4 chars.  0 for those 16 bits means it was a surrogate
+                                // but no clue if they're high or low.
+                                // If each of the 4 characters are non-zero, then none are surrogates.
+                                if ((uTemp & 0xFFFF000000000000) == 0 ||
+                                    (uTemp & 0x0000FFFF00000000) == 0 ||
+                                    (uTemp & 0x00000000FFFF0000) == 0 ||
+                                    (uTemp & 0x000000000000FFFF) == 0)
+                                {
+                                    // It has at least 1 surrogate, but we don't know if they're high or low surrogates,
+                                    // or if there's 1 or 4 surrogates
+
+                                    // If they happen to be high/low/high/low, we may as well continue.  Check the next
+                                    // bit to see if its set (low) or not (high) in the right pattern
+#if BIGENDIAN
+                                    if (((0xfc00fc00fc00fc00 & *longChars) ^ 0xd800dc00d800dc00) != 0)
+#else
+                                    if (((0xfc00fc00fc00fc00 & *longChars) ^ 0xdc00d800dc00d800) != 0)
+#endif
+                                    {
+                                        // Either there weren't 4 surrogates, or the 0x0400 bit was set when a high
+                                        // was hoped for or the 0x0400 bit wasn't set where a low was hoped for.
+
+                                        // Drop out to the slow loop to resolve the surrogates
+                                        break;
+                                    }
+                                    // else they are all surrogates in High/Low/High/Low order, so we can use them.
+                                }
+                                // else none are surrogates, so we can use them.
+                            }
+                            // else all < 0x8000 so we can use them
+
+                            // We can use these 4 chars.
+                            *longBytes = *longChars;
+                            longChars++;
+                            longBytes++;
+                        }
+
+                        chars = (char*)longChars;
+                        bytes = (byte*)longBytes;
+
+                        if (chars >= charEnd)
+                            break;
+                    }
+                    // Not aligned, but maybe we can still be somewhat faster
+                    // Also somehow this optimizes the above loop?  It seems to cause something above
+                    // to get enregistered, but I haven't figured out how to make that happen without this loop.
+                    else if ((charLeftOver == 0) &&
+#if BIGENDIAN
+                        bigEndian &&
+#else
+                        !bigEndian &&
+#endif // BIGENDIAN
+
+#if BIT64
+                        (unchecked((long)chars) & 7) != (unchecked((long)bytes) & 7) &&  // Only do this if chars & bytes are out of line, otherwise faster loop will be faster next time
+#else
+                        (unchecked((int)chars) & 3) != (unchecked((int)bytes) & 3) &&  // Only do this if chars & bytes are out of line, otherwise faster loop will be faster next time
+#endif // BIT64
+                        (unchecked((int)(bytes)) & 1) == 0)
+                    {
+                        // # to use
+                        long iCount = ((byteEnd - bytes) >> 1 < charEnd - chars) ?
+                                       (byteEnd - bytes) >> 1 : charEnd - chars;
+
+                        // Need new char*
+                        char* charOut = ((char*)bytes);     // a char* for our output
+                        char* tempEnd = chars + iCount - 1; // Our end pointer
+
+                        while (chars < tempEnd)
+                        {
+                            if (*chars >= (char)0xd800 && *chars <= (char)0xdfff)
+                            {
+                                // break for fallback for low surrogate
+                                if (*chars >= 0xdc00)
+                                    break;
+
+                                // break if next one's not a low surrogate (will do fallback)
+                                if (*(chars + 1) < 0xdc00 || *(chars + 1) > 0xdfff)
+                                    break;
+
+                                // They both exist, use them
+                            }
+                            // If 2nd char is surrogate & this one isn't then only add one
+                            else if (*(chars + 1) >= (char)0xd800 && *(chars + 1) <= 0xdfff)
+                            {
+                                *charOut = *chars;
+                                charOut++;
+                                chars++;
+                                continue;
+                            }
+
+                            *charOut = *chars;
+                            *(charOut + 1) = *(chars + 1);
+                            charOut += 2;
+                            chars += 2;
+                        }
+
+                        bytes = (byte*)charOut;
+
+                        if (chars >= charEnd)
+                            break;
+                    }
+#endif // !NO_FAST_UNICODE_LOOP
+
+                    // No fallback, just get next char
+                    ch = *chars;
+                    chars++;
+                }
+
+                // Check for high or low surrogates
+                if (ch >= 0xd800 && ch <= 0xdfff)
+                {
+                    // Was it a high surrogate?
+                    if (ch <= 0xdbff)
+                    {
+                        // Its a high surrogate, see if we already had a high surrogate
+                        if (charLeftOver > 0)
+                        {
+                            // Unwind the current character, this should be safe because we
+                            // don't have leftover data in the fallback, so chars must have
+                            // advanced already.
+                            Debug.Assert(chars > charStart,
+                                "[UnicodeEncoding.GetBytes]Expected chars to have advanced in unexpected high surrogate");
+                            chars--;
+
+                            // Fallback the previous surrogate
+                            // Might need to create our fallback buffer
+                            if (fallbackBuffer == null)
+                            {
+                                if (encoder == null)
+                                    fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+                                else
+                                    fallbackBuffer = encoder.FallbackBuffer;
+
+                                // Set our internal fallback interesting things.
+                                fallbackBuffer.InternalInitialize(charStart, charEnd, encoder, true);
+                            }
+
+                            charsForFallback = chars; // Avoid passing chars by reference to allow it to be en-registered
+                            fallbackBuffer.InternalFallback(charLeftOver, ref charsForFallback);
+                            chars = charsForFallback;
+
+                            charLeftOver = (char)0;
+                            continue;
+                        }
+
+                        // Remember this high surrogate
+                        charLeftOver = ch;
+                        continue;
+                    }
+
+                    // Its a low surrogate
+                    if (charLeftOver == 0)
+                    {
+                        // We'll fall back this one
+                        // Might need to create our fallback buffer
+                        if (fallbackBuffer == null)
+                        {
+                            if (encoder == null)
+                                fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+                            else
+                                fallbackBuffer = encoder.FallbackBuffer;
+
+                            // Set our internal fallback interesting things.
+                            fallbackBuffer.InternalInitialize(charStart, charEnd, encoder, true);
+                        }
+
+                        charsForFallback = chars; // Avoid passing chars by reference to allow it to be en-registered
+                        fallbackBuffer.InternalFallback(ch, ref charsForFallback);
+                        chars = charsForFallback;
+                        continue;
+                    }
+
+                    // Valid surrogate pair, add our charLeftOver
+                    if (bytes + 3 >= byteEnd)
+                    {
+                        // Not enough room to add this surrogate pair
+                        if (fallbackBuffer != null && fallbackBuffer.bFallingBack)
+                        {
+                            // These must have both been from the fallbacks.
+                            // Both of these MUST have been from a fallback because if the 1st wasn't
+                            // from a fallback, then a high surrogate followed by an illegal char 
+                            // would've caused the high surrogate to fall back.  If a high surrogate
+                            // fell back, then it was consumed and both chars came from the fallback.
+                            fallbackBuffer.MovePrevious();                     // Didn't use either fallback surrogate
+                            fallbackBuffer.MovePrevious();
+                        }
+                        else
+                        {
+                            // If we don't have enough room, then either we should've advanced a while
+                            // or we should have bytes==byteStart and throw below
+                            Debug.Assert(chars > charStart + 1 || bytes == byteStart,
+                                "[UnicodeEncoding.GetBytes]Expected chars to have when no room to add surrogate pair");
+                            chars -= 2;                                        // Didn't use either surrogate
+                        }
+                        ThrowBytesOverflow(encoder, bytes == byteStart);    // Throw maybe (if no bytes written)
+                        charLeftOver = (char)0;                             // we'll retry it later
+                        break;                                               // Didn't throw, but stop 'til next time.
+                    }
+
+                    if (bigEndian)
+                    {
+                        *(bytes++) = (byte)(charLeftOver >> 8);
+                        *(bytes++) = (byte)charLeftOver;
+                    }
+                    else
+                    {
+                        *(bytes++) = (byte)charLeftOver;
+                        *(bytes++) = (byte)(charLeftOver >> 8);
+                    }
+
+                    charLeftOver = (char)0;
+                }
+                else if (charLeftOver > 0)
+                {
+                    // Expected a low surrogate, but this char is normal
+
+                    // Rewind the current character, fallback previous character.
+                    // this should be safe because we don't have leftover data in the
+                    // fallback, so chars must have advanced already.
+                    Debug.Assert(chars > charStart,
+                        "[UnicodeEncoding.GetBytes]Expected chars to have advanced after expecting low surrogate");
+                    chars--;
+
+                    // fallback previous chars
+                    // Might need to create our fallback buffer
+                    if (fallbackBuffer == null)
+                    {
+                        if (encoder == null)
+                            fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = encoder.FallbackBuffer;
+
+                        // Set our internal fallback interesting things.
+                        fallbackBuffer.InternalInitialize(charStart, charEnd, encoder, true);
+                    }
+
+                    charsForFallback = chars; // Avoid passing chars by reference to allow it to be en-registered
+                    fallbackBuffer.InternalFallback(charLeftOver, ref charsForFallback);
+                    chars = charsForFallback;
+
+                    // Ignore charLeftOver or throw
+                    charLeftOver = (char)0;
+                    continue;
+                }
+
+                // Ok, we have a char to add
+                if (bytes + 1 >= byteEnd)
+                {
+                    // Couldn't add this char
+                    if (fallbackBuffer != null && fallbackBuffer.bFallingBack)
+                        fallbackBuffer.MovePrevious();                     // Not using this fallback char
+                    else
+                    {
+                        // Lonely charLeftOver (from previous call) would've been caught up above,
+                        // so this must be a case where we've already read an input char.
+                        Debug.Assert(chars > charStart,
+                            "[UnicodeEncoding.GetBytes]Expected chars to have advanced for failed fallback");
+                        chars--;                                         // Not using this char
+                    }
+                    ThrowBytesOverflow(encoder, bytes == byteStart);    // Throw maybe (if no bytes written)
+                    break;                                               // didn't throw, just stop
+                }
+
+                if (bigEndian)
+                {
+                    *(bytes++) = (byte)(ch >> 8);
+                    *(bytes++) = (byte)ch;
+                }
+                else
+                {
+                    *(bytes++) = (byte)ch;
+                    *(bytes++) = (byte)(ch >> 8);
+                }
+            }
+
+            // Don't allocate space for left over char
+            if (charLeftOver > 0)
+            {
+                // If we aren't flushing we need to fall this back
+                if (encoder == null || encoder.MustFlush)
+                {
+                    if (wasHereBefore)
+                    {
+                        // Throw it, using our complete character
+                        throw new ArgumentException(
+                            SR.Format(SR.Argument_RecursiveFallback, charLeftOver), nameof(chars));
+                    }
+                    else
+                    {
+                        // If we have to flush, stick it in fallback and try again
+                        // Might need to create our fallback buffer
+                        if (fallbackBuffer == null)
+                        {
+                            if (encoder == null)
+                                fallbackBuffer = this.encoderFallback.CreateFallbackBuffer();
+                            else
+                                fallbackBuffer = encoder.FallbackBuffer;
+
+                            // Set our internal fallback interesting things.
+                            fallbackBuffer.InternalInitialize(charStart, charEnd, encoder, true);
+                        }
+
+                        // If we're not flushing, that'll remember the left over character.
+                        charsForFallback = chars; // Avoid passing chars by reference to allow it to be en-registered
+                        fallbackBuffer.InternalFallback(charLeftOver, ref charsForFallback);
+                        chars = charsForFallback;
+
+                        charLeftOver = (char)0;
+                        wasHereBefore = true;
+                        goto TryAgain;
+                    }
+                }
+            }
+
+            // Not flushing, remember it in the encoder
+            if (encoder != null)
+            {
+                encoder._charLeftOver = charLeftOver;
+                encoder._charsUsed = (int)(chars - charStart);
+            }
+
+            // Remember charLeftOver if we must, or clear it if we're flushing
+            // (charLeftOver should be 0 if we're flushing)
+            Debug.Assert((encoder != null && !encoder.MustFlush) || charLeftOver == (char)0,
+                "[UnicodeEncoding.GetBytes] Expected no left over characters if flushing");
+
+            Debug.Assert(fallbackBuffer == null || fallbackBuffer.Remaining == 0 ||
+                encoder == null || !encoder._throwOnOverflow,
+                "[UnicodeEncoding.GetBytes]Expected empty fallback buffer if not converting");
+
+            // We used to copy it fast, but this doesn't check for surrogates
+            // System.IO.__UnmanagedMemoryStream.memcpyimpl(bytes, (byte*)chars, usedByteCount);
+
+            return (int)(bytes - byteStart);
+        }
+
+        internal override unsafe int GetCharCount(byte* bytes, int count, DecoderNLS baseDecoder)
+        {
+            Debug.Assert(bytes != null, "[UnicodeEncoding.GetCharCount]bytes!=null");
+            Debug.Assert(count >= 0, "[UnicodeEncoding.GetCharCount]count >=0");
+
+            UnicodeEncoding.Decoder decoder = (UnicodeEncoding.Decoder)baseDecoder;
+
+            byte* byteEnd = bytes + count;
+            byte* byteStart = bytes;
+
+            // Need last vars
+            int lastByte = -1;
+            char lastChar = (char)0;
+
+            // Start by assuming same # of chars as bytes
+            int charCount = count >> 1;
+
+            // Need -1 to check 2 at a time.  If we have an even #, longBytes will go
+            // from longEnd - 1/2 long to longEnd + 1/2 long.  If we're odd, longBytes
+            // will go from longEnd - 1 long to longEnd. (Might not get to use this)
+            ulong* longEnd = (ulong*)(byteEnd - 7);
+
+            // For fallback we may need a fallback buffer
+            DecoderFallbackBuffer fallbackBuffer = null;
+
+            if (decoder != null)
+            {
+                lastByte = decoder.lastByte;
+                lastChar = decoder.lastChar;
+
+                // Assume extra char if last char was around
+                if (lastChar > 0)
+                    charCount++;
+
+                // Assume extra char if extra last byte makes up odd # of input bytes
+                if (lastByte >= 0 && (count & 1) == 1)
+                {
+                    charCount++;
+                }
+
+                // Shouldn't have anything in fallback buffer for GetCharCount
+                // (don't have to check _throwOnOverflow for count)
+                Debug.Assert(!decoder.InternalHasFallbackBuffer || decoder.FallbackBuffer.Remaining == 0,
+                    "[UnicodeEncoding.GetCharCount]Expected empty fallback buffer at start");
+            }
+
+            while (bytes < byteEnd)
+            {
+                // If we're aligned then maybe we can do it fast
+                // That'll hurt if we're unaligned because we'll always test but never be aligned
+#if !NO_FAST_UNICODE_LOOP
+#if BIGENDIAN
+                if (bigEndian &&
+#else // BIGENDIAN
+                if (!bigEndian &&
+#endif // BIGENDIAN
+#if BIT64 // win64 has to be long aligned
+                    (unchecked((long)bytes) & 7) == 0 &&
+#else
+                    (unchecked((int)bytes) & 3) == 0 &&
+#endif // BIT64
+                    lastByte == -1 && lastChar == 0)
+                {
+                    // Need new char* so we can check 4 at a time
+                    ulong* longBytes = (ulong*)bytes;
+
+                    while (longBytes < longEnd)
+                    {
+                        // See if we potentially have surrogates (0x8000 bit set)
+                        // (We're either big endian on a big endian machine or little endian on 
+                        // a little endian machine so that'll work)
+                        if ((0x8000800080008000 & *longBytes) != 0)
+                        {
+                            // See if any of these are high or low surrogates (0xd800 - 0xdfff).  If the high
+                            // 5 bits looks like 11011, then its a high or low surrogate.
+                            // We do the & f800 to filter the 5 bits, then ^ d800 to ensure the 0 isn't set.
+                            // Note that we expect BMP characters to be more common than surrogates
+                            // & each char with 11111... then ^ with 11011.  Zeroes then indicate surrogates
+                            ulong uTemp = (0xf800f800f800f800 & *longBytes) ^ 0xd800d800d800d800;
+
+                            // Check each of the 4 chars.  0 for those 16 bits means it was a surrogate
+                            // but no clue if they're high or low.
+                            // If each of the 4 characters are non-zero, then none are surrogates.
+                            if ((uTemp & 0xFFFF000000000000) == 0 ||
+                                (uTemp & 0x0000FFFF00000000) == 0 ||
+                                (uTemp & 0x00000000FFFF0000) == 0 ||
+                                (uTemp & 0x000000000000FFFF) == 0)
+                            {
+                                // It has at least 1 surrogate, but we don't know if they're high or low surrogates,
+                                // or if there's 1 or 4 surrogates
+
+                                // If they happen to be high/low/high/low, we may as well continue.  Check the next
+                                // bit to see if its set (low) or not (high) in the right pattern
+#if BIGENDIAN
+                                if (((0xfc00fc00fc00fc00 & *longBytes) ^ 0xd800dc00d800dc00) != 0)
+#else
+                                if (((0xfc00fc00fc00fc00 & *longBytes) ^ 0xdc00d800dc00d800) != 0)
+#endif
+                                {
+                                    // Either there weren't 4 surrogates, or the 0x0400 bit was set when a high
+                                    // was hoped for or the 0x0400 bit wasn't set where a low was hoped for.
+
+                                    // Drop out to the slow loop to resolve the surrogates
+                                    break;
+                                }
+                                // else they are all surrogates in High/Low/High/Low order, so we can use them.
+                            }
+                            // else none are surrogates, so we can use them.
+                        }
+                        // else all < 0x8000 so we can use them
+
+                        // We can use these 4 chars.
+                        longBytes++;
+                    }
+
+                    bytes = (byte*)longBytes;
+
+                    if (bytes >= byteEnd)
+                        break;
+                }
+#endif // !NO_FAST_UNICODE_LOOP
+
+                // Get 1st byte
+                if (lastByte < 0)
+                {
+                    lastByte = *bytes++;
+                    if (bytes >= byteEnd) break;
+                }
+
+                // Get full char
+                char ch;
+                if (bigEndian)
+                {
+                    ch = (char)(lastByte << 8 | *(bytes++));
+                }
+                else
+                {
+                    ch = (char)(*(bytes++) << 8 | lastByte);
+                }
+                lastByte = -1;
+
+                // See if the char's valid
+                if (ch >= 0xd800 && ch <= 0xdfff)
+                {
+                    // Was it a high surrogate?
+                    if (ch <= 0xdbff)
+                    {
+                        // Its a high surrogate, if we had one then do fallback for previous one
+                        if (lastChar > 0)
+                        {
+                            // Ignore previous bad high surrogate
+                            charCount--;
+
+                            // Get fallback for previous high surrogate
+                            // Note we have to reconstruct bytes because some may have been in decoder
+                            byte[] byteBuffer = null;
+                            if (bigEndian)
+                            {
+                                byteBuffer = new byte[]
+                                    { unchecked((byte)(lastChar >> 8)), unchecked((byte)lastChar) };
+                            }
+                            else
+                            {
+                                byteBuffer = new byte[]
+                                    { unchecked((byte)lastChar), unchecked((byte)(lastChar >> 8)) };
+                            }
+
+                            if (fallbackBuffer == null)
+                            {
+                                if (decoder == null)
+                                    fallbackBuffer = this.decoderFallback.CreateFallbackBuffer();
+                                else
+                                    fallbackBuffer = decoder.FallbackBuffer;
+
+                                // Set our internal fallback interesting things.
+                                fallbackBuffer.InternalInitialize(byteStart, null);
+                            }
+
+                            // Get fallback.
+                            charCount += fallbackBuffer.InternalFallback(byteBuffer, bytes);
+                        }
+
+                        // Ignore the last one which fell back already,
+                        // and remember the new high surrogate
+                        lastChar = ch;
+                        continue;
+                    }
+
+                    // Its a low surrogate
+                    if (lastChar == 0)
+                    {
+                        // Expected a previous high surrogate
+                        charCount--;
+
+                        // Get fallback for this low surrogate
+                        // Note we have to reconstruct bytes because some may have been in decoder
+                        byte[] byteBuffer = null;
+                        if (bigEndian)
+                        {
+                            byteBuffer = new byte[]
+                                { unchecked((byte)(ch >> 8)), unchecked((byte)ch) };
+                        }
+                        else
+                        {
+                            byteBuffer = new byte[]
+                                { unchecked((byte)ch), unchecked((byte)(ch >> 8)) };
+                        }
+
+                        if (fallbackBuffer == null)
+                        {
+                            if (decoder == null)
+                                fallbackBuffer = this.decoderFallback.CreateFallbackBuffer();
+                            else
+                                fallbackBuffer = decoder.FallbackBuffer;
+
+                            // Set our internal fallback interesting things.
+                            fallbackBuffer.InternalInitialize(byteStart, null);
+                        }
+
+                        charCount += fallbackBuffer.InternalFallback(byteBuffer, bytes);
+
+                        // Ignore this one (we already did its fallback)
+                        continue;
+                    }
+
+                    // Valid surrogate pair, already counted.
+                    lastChar = (char)0;
+                }
+                else if (lastChar > 0)
+                {
+                    // Had a high surrogate, expected a low surrogate
+                    // Un-count the last high surrogate
+                    charCount--;
+
+                    // fall back the high surrogate.
+                    byte[] byteBuffer = null;
+                    if (bigEndian)
+                    {
+                        byteBuffer = new byte[]
+                            { unchecked((byte)(lastChar >> 8)), unchecked((byte)lastChar) };
+                    }
+                    else
+                    {
+                        byteBuffer = new byte[]
+                            { unchecked((byte)lastChar), unchecked((byte)(lastChar >> 8)) };
+                    }
+
+                    if (fallbackBuffer == null)
+                    {
+                        if (decoder == null)
+                            fallbackBuffer = this.decoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = decoder.FallbackBuffer;
+
+                        // Set our internal fallback interesting things.
+                        fallbackBuffer.InternalInitialize(byteStart, null);
+                    }
+
+                    // Already subtracted high surrogate
+                    charCount += fallbackBuffer.InternalFallback(byteBuffer, bytes);
+
+                    // Not left over now, clear previous high surrogate and continue to add current char
+                    lastChar = (char)0;
+                }
+
+                // Valid char, already counted
+            }
+
+            // Extra space if we can't use decoder
+            if (decoder == null || decoder.MustFlush)
+            {
+                if (lastChar > 0)
+                {
+                    // No hanging high surrogates allowed, do fallback and remove count for it
+                    charCount--;
+                    byte[] byteBuffer = null;
+                    if (bigEndian)
+                    {
+                        byteBuffer = new byte[]
+                            { unchecked((byte)(lastChar >> 8)), unchecked((byte)lastChar) };
+                    }
+                    else
+                    {
+                        byteBuffer = new byte[]
+                            { unchecked((byte)lastChar), unchecked((byte)(lastChar >> 8)) };
+                    }
+
+                    if (fallbackBuffer == null)
+                    {
+                        if (decoder == null)
+                            fallbackBuffer = this.decoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = decoder.FallbackBuffer;
+
+                        // Set our internal fallback interesting things.
+                        fallbackBuffer.InternalInitialize(byteStart, null);
+                    }
+
+                    charCount += fallbackBuffer.InternalFallback(byteBuffer, bytes);
+
+                    lastChar = (char)0;
+                }
+
+                if (lastByte >= 0)
+                {
+                    if (fallbackBuffer == null)
+                    {
+                        if (decoder == null)
+                            fallbackBuffer = this.decoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = decoder.FallbackBuffer;
+
+                        // Set our internal fallback interesting things.
+                        fallbackBuffer.InternalInitialize(byteStart, null);
+                    }
+
+                    // No hanging odd bytes allowed if must flush
+                    charCount += fallbackBuffer.InternalFallback(new byte[] { unchecked((byte)lastByte) }, bytes);
+                    lastByte = -1;
+                }
+            }
+
+            // If we had a high surrogate left over, we can't count it
+            if (lastChar > 0)
+                charCount--;
+
+            // Shouldn't have anything in fallback buffer for GetCharCount
+            // (don't have to check _throwOnOverflow for count)
+            Debug.Assert(fallbackBuffer == null || fallbackBuffer.Remaining == 0,
+                "[UnicodeEncoding.GetCharCount]Expected empty fallback buffer at end");
+
+            return charCount;
+        }
+
+        internal override unsafe int GetChars(byte* bytes, int byteCount,
+                                                char* chars, int charCount, DecoderNLS baseDecoder)
+        {
+            Debug.Assert(chars != null, "[UnicodeEncoding.GetChars]chars!=null");
+            Debug.Assert(byteCount >= 0, "[UnicodeEncoding.GetChars]byteCount >=0");
+            Debug.Assert(charCount >= 0, "[UnicodeEncoding.GetChars]charCount >=0");
+            Debug.Assert(bytes != null, "[UnicodeEncoding.GetChars]bytes!=null");
+
+            UnicodeEncoding.Decoder decoder = (UnicodeEncoding.Decoder)baseDecoder;
+
+            // Need last vars
+            int lastByte = -1;
+            char lastChar = (char)0;
+
+            // Get our decoder (but don't clear it yet)
+            if (decoder != null)
+            {
+                lastByte = decoder.lastByte;
+                lastChar = decoder.lastChar;
+
+                // Shouldn't have anything in fallback buffer for GetChars
+                // (don't have to check _throwOnOverflow for chars)
+                Debug.Assert(!decoder.InternalHasFallbackBuffer || decoder.FallbackBuffer.Remaining == 0,
+                    "[UnicodeEncoding.GetChars]Expected empty fallback buffer at start");
+            }
+
+            // For fallback we may need a fallback buffer
+            DecoderFallbackBuffer fallbackBuffer = null;
+            char* charsForFallback;
+
+            byte* byteEnd = bytes + byteCount;
+            char* charEnd = chars + charCount;
+            byte* byteStart = bytes;
+            char* charStart = chars;
+
+            while (bytes < byteEnd)
+            {
+                // If we're aligned then maybe we can do it fast
+                // That'll hurt if we're unaligned because we'll always test but never be aligned
+#if !NO_FAST_UNICODE_LOOP
+#if BIGENDIAN
+                if (bigEndian &&
+#else // BIGENDIAN
+                if (!bigEndian &&
+#endif // BIGENDIAN
+#if BIT64 // win64 has to be long aligned
+                    (unchecked((long)chars) & 7) == 0 && (unchecked((long)bytes) & 7) == 0 &&
+#else
+                    (unchecked((int)chars) & 3) == 0 && (unchecked((int)bytes) & 3) == 0 &&
+#endif // BIT64
+                    lastByte == -1 && lastChar == 0)
+                {
+                    // Need -1 to check 2 at a time.  If we have an even #, longChars will go
+                    // from longEnd - 1/2 long to longEnd + 1/2 long.  If we're odd, longChars
+                    // will go from longEnd - 1 long to longEnd. (Might not get to use this)
+                    // We can only go iCount units (limited by shorter of char or byte buffers.
+                    ulong* longEnd = (ulong*)(bytes - 7 +
+                                                (((byteEnd - bytes) >> 1 < charEnd - chars) ?
+                                                  (byteEnd - bytes) : (charEnd - chars) << 1));
+
+                    // Need new char* so we can check 4 at a time
+                    ulong* longBytes = (ulong*)bytes;
+                    ulong* longChars = (ulong*)chars;
+
+                    while (longBytes < longEnd)
+                    {
+                        // See if we potentially have surrogates (0x8000 bit set)
+                        // (We're either big endian on a big endian machine or little endian on 
+                        // a little endian machine so that'll work)
+                        if ((0x8000800080008000 & *longBytes) != 0)
+                        {
+                            // See if any of these are high or low surrogates (0xd800 - 0xdfff).  If the high
+                            // 5 bits looks like 11011, then its a high or low surrogate.
+                            // We do the & f800 to filter the 5 bits, then ^ d800 to ensure the 0 isn't set.
+                            // Note that we expect BMP characters to be more common than surrogates
+                            // & each char with 11111... then ^ with 11011.  Zeroes then indicate surrogates
+                            ulong uTemp = (0xf800f800f800f800 & *longBytes) ^ 0xd800d800d800d800;
+
+                            // Check each of the 4 chars.  0 for those 16 bits means it was a surrogate
+                            // but no clue if they're high or low.
+                            // If each of the 4 characters are non-zero, then none are surrogates.
+                            if ((uTemp & 0xFFFF000000000000) == 0 ||
+                                (uTemp & 0x0000FFFF00000000) == 0 ||
+                                (uTemp & 0x00000000FFFF0000) == 0 ||
+                                (uTemp & 0x000000000000FFFF) == 0)
+                            {
+                                // It has at least 1 surrogate, but we don't know if they're high or low surrogates,
+                                // or if there's 1 or 4 surrogates
+
+                                // If they happen to be high/low/high/low, we may as well continue.  Check the next
+                                // bit to see if its set (low) or not (high) in the right pattern
+#if BIGENDIAN
+                                if (((0xfc00fc00fc00fc00 & *longBytes) ^ 0xd800dc00d800dc00) != 0)
+#else
+                                if (((0xfc00fc00fc00fc00 & *longBytes) ^ 0xdc00d800dc00d800) != 0)
+#endif
+                                {
+                                    // Either there weren't 4 surrogates, or the 0x0400 bit was set when a high
+                                    // was hoped for or the 0x0400 bit wasn't set where a low was hoped for.
+
+                                    // Drop out to the slow loop to resolve the surrogates
+                                    break;
+                                }
+                                // else they are all surrogates in High/Low/High/Low order, so we can use them.
+                            }
+                            // else none are surrogates, so we can use them.
+                        }
+                        // else all < 0x8000 so we can use them
+
+                        // We can use these 4 chars.
+                        *longChars = *longBytes;
+                        longBytes++;
+                        longChars++;
+                    }
+
+                    chars = (char*)longChars;
+                    bytes = (byte*)longBytes;
+
+                    if (bytes >= byteEnd)
+                        break;
+                }
+#endif // !NO_FAST_UNICODE_LOOP
+
+                // Get 1st byte
+                if (lastByte < 0)
+                {
+                    lastByte = *bytes++;
+                    continue;
+                }
+
+                // Get full char
+                char ch;
+                if (bigEndian)
+                {
+                    ch = (char)(lastByte << 8 | *(bytes++));
+                }
+                else
+                {
+                    ch = (char)(*(bytes++) << 8 | lastByte);
+                }
+                lastByte = -1;
+
+                // See if the char's valid
+                if (ch >= 0xd800 && ch <= 0xdfff)
+                {
+                    // Was it a high surrogate?
+                    if (ch <= 0xdbff)
+                    {
+                        // Its a high surrogate, if we had one then do fallback for previous one
+                        if (lastChar > 0)
+                        {
+                            // Get fallback for previous high surrogate
+                            // Note we have to reconstruct bytes because some may have been in decoder
+                            byte[] byteBuffer = null;
+                            if (bigEndian)
+                            {
+                                byteBuffer = new byte[]
+                                    { unchecked((byte)(lastChar >> 8)), unchecked((byte)lastChar) };
+                            }
+                            else
+                            {
+                                byteBuffer = new byte[]
+                                    { unchecked((byte)lastChar), unchecked((byte)(lastChar >> 8)) };
+                            }
+
+                            if (fallbackBuffer == null)
+                            {
+                                if (decoder == null)
+                                    fallbackBuffer = this.decoderFallback.CreateFallbackBuffer();
+                                else
+                                    fallbackBuffer = decoder.FallbackBuffer;
+
+                                // Set our internal fallback interesting things.
+                                fallbackBuffer.InternalInitialize(byteStart, charEnd);
+                            }
+
+                            charsForFallback = chars; // Avoid passing chars by reference to allow it to be en-registered
+                            bool fallbackResult = fallbackBuffer.InternalFallback(byteBuffer, bytes, ref charsForFallback);
+                            chars = charsForFallback;
+
+                            if (!fallbackResult)
+                            {
+                                // couldn't fall back lonely surrogate
+                                // We either advanced bytes or chars should == charStart and throw below
+                                Debug.Assert(bytes >= byteStart + 2 || chars == charStart,
+                                    "[UnicodeEncoding.GetChars]Expected bytes to have advanced or no output (bad surrogate)");
+                                bytes -= 2;                                       // didn't use these 2 bytes
+                                fallbackBuffer.InternalReset();
+                                ThrowCharsOverflow(decoder, chars == charStart);// Might throw, if no chars output
+                                break;                                          // couldn't fallback but didn't throw
+                            }
+                        }
+
+                        // Ignore the previous high surrogate which fell back already,
+                        // yet remember the current high surrogate for next time.
+                        lastChar = ch;
+                        continue;
+                    }
+
+                    // Its a low surrogate
+                    if (lastChar == 0)
+                    {
+                        // Expected a previous high surrogate
+                        // Get fallback for this low surrogate
+                        // Note we have to reconstruct bytes because some may have been in decoder
+                        byte[] byteBuffer = null;
+                        if (bigEndian)
+                        {
+                            byteBuffer = new byte[]
+                                { unchecked((byte)(ch >> 8)), unchecked((byte)ch) };
+                        }
+                        else
+                        {
+                            byteBuffer = new byte[]
+                                { unchecked((byte)ch), unchecked((byte)(ch >> 8)) };
+                        }
+
+                        if (fallbackBuffer == null)
+                        {
+                            if (decoder == null)
+                                fallbackBuffer = this.decoderFallback.CreateFallbackBuffer();
+                            else
+                                fallbackBuffer = decoder.FallbackBuffer;
+
+                            // Set our internal fallback interesting things.
+                            fallbackBuffer.InternalInitialize(byteStart, charEnd);
+                        }
+
+                        charsForFallback = chars; // Avoid passing chars by reference to allow it to be en-registered
+                        bool fallbackResult = fallbackBuffer.InternalFallback(byteBuffer, bytes, ref charsForFallback);
+                        chars = charsForFallback;
+
+                        if (!fallbackResult)
+                        {
+                            // couldn't fall back lonely surrogate
+                            // We either advanced bytes or chars should == charStart and throw below
+                            Debug.Assert(bytes >= byteStart + 2 || chars == charStart,
+                                "[UnicodeEncoding.GetChars]Expected bytes to have advanced or no output (lonely surrogate)");
+                            bytes -= 2;                                       // didn't use these 2 bytes
+                            fallbackBuffer.InternalReset();
+                            ThrowCharsOverflow(decoder, chars == charStart);// Might throw, if no chars output
+                            break;                                          // couldn't fallback but didn't throw
+                        }
+
+                        // Didn't throw, ignore this one (we already did its fallback)
+                        continue;
+                    }
+
+                    // Valid surrogate pair, add our lastChar (will need 2 chars)
+                    if (chars >= charEnd - 1)
+                    {
+                        // couldn't find room for this surrogate pair
+                        // We either advanced bytes or chars should == charStart and throw below
+                        Debug.Assert(bytes >= byteStart + 2 || chars == charStart,
+                            "[UnicodeEncoding.GetChars]Expected bytes to have advanced or no output (surrogate pair)");
+                        bytes -= 2;                                       // didn't use these 2 bytes
+                        ThrowCharsOverflow(decoder, chars == charStart);// Might throw, if no chars output
+                        // Leave lastChar for next call to Convert()
+                        break;                                          // couldn't fallback but didn't throw
+                    }
+
+                    *chars++ = lastChar;
+                    lastChar = (char)0;
+                }
+                else if (lastChar > 0)
+                {
+                    // Had a high surrogate, expected a low surrogate, fall back the high surrogate.
+                    byte[] byteBuffer = null;
+                    if (bigEndian)
+                    {
+                        byteBuffer = new byte[]
+                            { unchecked((byte)(lastChar >> 8)), unchecked((byte)lastChar) };
+                    }
+                    else
+                    {
+                        byteBuffer = new byte[]
+                            { unchecked((byte)lastChar), unchecked((byte)(lastChar >> 8)) };
+                    }
+
+                    if (fallbackBuffer == null)
+                    {
+                        if (decoder == null)
+                            fallbackBuffer = this.decoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = decoder.FallbackBuffer;
+
+                        // Set our internal fallback interesting things.
+                        fallbackBuffer.InternalInitialize(byteStart, charEnd);
+                    }
+
+                    charsForFallback = chars; // Avoid passing chars by reference to allow it to be en-registered
+                    bool fallbackResult = fallbackBuffer.InternalFallback(byteBuffer, bytes, ref charsForFallback);
+                    chars = charsForFallback;
+
+                    if (!fallbackResult)
+                    {
+                        // couldn't fall back high surrogate, or char that would be next
+                        // We either advanced bytes or chars should == charStart and throw below
+                        Debug.Assert(bytes >= byteStart + 2 || chars == charStart,
+                            "[UnicodeEncoding.GetChars]Expected bytes to have advanced or no output (no low surrogate)");
+                        bytes -= 2;                                       // didn't use these 2 bytes
+                        fallbackBuffer.InternalReset();
+                        ThrowCharsOverflow(decoder, chars == charStart);// Might throw, if no chars output
+                        break;                                          // couldn't fallback but didn't throw
+                    }
+
+                    // Not left over now, clear previous high surrogate and continue to add current char
+                    lastChar = (char)0;
+                }
+
+                // Valid char, room for it?
+                if (chars >= charEnd)
+                {
+                    // 2 bytes couldn't fall back
+                    // We either advanced bytes or chars should == charStart and throw below
+                    Debug.Assert(bytes >= byteStart + 2 || chars == charStart,
+                        "[UnicodeEncoding.GetChars]Expected bytes to have advanced or no output (normal)");
+                    bytes -= 2;                                       // didn't use these bytes
+                    ThrowCharsOverflow(decoder, chars == charStart);// Might throw, if no chars output
+                    break;                                          // couldn't fallback but didn't throw
+                }
+
+                // add it
+                *chars++ = ch;
+            }
+
+            // Remember our decoder if we must
+            if (decoder == null || decoder.MustFlush)
+            {
+                if (lastChar > 0)
+                {
+                    // No hanging high surrogates allowed, do fallback and remove count for it
+                    byte[] byteBuffer = null;
+                    if (bigEndian)
+                    {
+                        byteBuffer = new byte[]
+                            { unchecked((byte)(lastChar >> 8)), unchecked((byte)lastChar) };
+                    }
+                    else
+                    {
+                        byteBuffer = new byte[]
+                            { unchecked((byte)lastChar), unchecked((byte)(lastChar >> 8)) };
+                    }
+
+                    if (fallbackBuffer == null)
+                    {
+                        if (decoder == null)
+                            fallbackBuffer = this.decoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = decoder.FallbackBuffer;
+
+                        // Set our internal fallback interesting things.
+                        fallbackBuffer.InternalInitialize(byteStart, charEnd);
+                    }
+
+                    charsForFallback = chars; // Avoid passing chars by reference to allow it to be en-registered
+                    bool fallbackResult = fallbackBuffer.InternalFallback(byteBuffer, bytes, ref charsForFallback);
+                    chars = charsForFallback;
+
+                    if (!fallbackResult)
+                    {
+                        // 2 bytes couldn't fall back
+                        // We either advanced bytes or chars should == charStart and throw below
+                        Debug.Assert(bytes >= byteStart + 2 || chars == charStart,
+                            "[UnicodeEncoding.GetChars]Expected bytes to have advanced or no output (decoder)");
+                        bytes -= 2;                                       // didn't use these bytes
+                        if (lastByte >= 0)
+                            bytes--;                                    // had an extra last byte hanging around
+                        fallbackBuffer.InternalReset();
+                        ThrowCharsOverflow(decoder, chars == charStart);// Might throw, if no chars output
+                        // We'll remember these in our decoder though
+                        bytes += 2;
+                        if (lastByte >= 0)
+                            bytes++;
+                        goto End;
+                    }
+
+                    // done with this one
+                    lastChar = (char)0;
+                }
+
+                if (lastByte >= 0)
+                {
+                    if (fallbackBuffer == null)
+                    {
+                        if (decoder == null)
+                            fallbackBuffer = this.decoderFallback.CreateFallbackBuffer();
+                        else
+                            fallbackBuffer = decoder.FallbackBuffer;
+
+                        // Set our internal fallback interesting things.
+                        fallbackBuffer.InternalInitialize(byteStart, charEnd);
+                    }
+
+                    // No hanging odd bytes allowed if must flush
+                    charsForFallback = chars; // Avoid passing chars by reference to allow it to be en-registered
+                    bool fallbackResult = fallbackBuffer.InternalFallback(new byte[] { unchecked((byte)lastByte) }, bytes, ref charsForFallback);
+                    chars = charsForFallback;
+
+                    if (!fallbackResult)
+                    {
+                        // odd byte couldn't fall back
+                        bytes--;                                        // didn't use this byte
+                        fallbackBuffer.InternalReset();
+                        ThrowCharsOverflow(decoder, chars == charStart);// Might throw, if no chars output
+                        // didn't throw, but we'll remember it in the decoder
+                        bytes++;
+                        goto End;
+                    }
+
+                    // Didn't fail, clear buffer
+                    lastByte = -1;
+                }
+            }
+
+        End:
+
+            // Remember our decoder if we must
+            if (decoder != null)
+            {
+                Debug.Assert((decoder.MustFlush == false) || ((lastChar == (char)0) && (lastByte == -1)),
+                    "[UnicodeEncoding.GetChars] Expected no left over chars or bytes if flushing"
+                    //                    + " " + ((int)lastChar).ToString("X4") + " " + lastByte.ToString("X2")
+                    );
+
+                decoder._bytesUsed = (int)(bytes - byteStart);
+                decoder.lastChar = lastChar;
+                decoder.lastByte = lastByte;
+            }
+
+            // Used to do this the old way
+            // System.IO.__UnmanagedMemoryStream.memcpyimpl((byte*)chars, bytes, byteCount);
+
+            // Shouldn't have anything in fallback buffer for GetChars
+            // (don't have to check _throwOnOverflow for count or chars)
+            Debug.Assert(fallbackBuffer == null || fallbackBuffer.Remaining == 0,
+                "[UnicodeEncoding.GetChars]Expected empty fallback buffer at end");
+
+            return (int)(chars - charStart);
+        }
+
+
+        public override System.Text.Encoder GetEncoder()
+        {
+            return new EncoderNLS(this);
+        }
+
+
+        public override System.Text.Decoder GetDecoder()
+        {
+            return new UnicodeEncoding.Decoder(this);
+        }
+
+
+        public override byte[] GetPreamble()
+        {
+            if (byteOrderMark)
+            {
+                // Note - we must allocate new byte[]'s here to prevent someone
+                // from modifying a cached byte[].
+                if (bigEndian)
+                    return new byte[2] { 0xfe, 0xff };
+                else
+                    return new byte[2] { 0xff, 0xfe };
+            }
+            return Array.Empty<Byte>();
+        }
+
+        public override ReadOnlySpan<byte> Preamble =>
+            GetType() != typeof(UnicodeEncoding) ? GetPreamble() : // in case a derived UnicodeEncoding overrode GetPreamble
+            byteOrderMark ? (bigEndian ? s_bigEndianPreamble : s_littleEndianPreamble) :
+            Array.Empty<byte>();
+
+        public override int GetMaxByteCount(int charCount)
+        {
+            if (charCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(charCount),
+                     SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // Characters would be # of characters + 1 in case left over high surrogate is ? * max fallback
+            long byteCount = (long)charCount + 1;
+
+            if (EncoderFallback.MaxCharCount > 1)
+                byteCount *= EncoderFallback.MaxCharCount;
+
+            // 2 bytes per char
+            byteCount <<= 1;
+
+            if (byteCount > 0x7fffffff)
+                throw new ArgumentOutOfRangeException(nameof(charCount), SR.ArgumentOutOfRange_GetByteCountOverflow);
+
+            return (int)byteCount;
+        }
+
+
+        public override int GetMaxCharCount(int byteCount)
+        {
+            if (byteCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(byteCount),
+                     SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            // long because byteCount could be biggest int.
+            // 1 char per 2 bytes.  Round up in case 1 left over in decoder.
+            // Round up using &1 in case byteCount is max size
+            // Might also need an extra 1 if there's a left over high surrogate in the decoder.
+            long charCount = (long)(byteCount >> 1) + (byteCount & 1) + 1;
+
+            // Don't forget fallback (in case they have a bunch of lonely surrogates or something bizarre like that)
+            if (DecoderFallback.MaxCharCount > 1)
+                charCount *= DecoderFallback.MaxCharCount;
+
+            if (charCount > 0x7fffffff)
+                throw new ArgumentOutOfRangeException(nameof(byteCount), SR.ArgumentOutOfRange_GetCharCountOverflow);
+
+            return (int)charCount;
+        }
+
+
+        public override bool Equals(Object value)
+        {
+            UnicodeEncoding that = value as UnicodeEncoding;
+            if (that != null)
+            {
+                //
+                // Big Endian Unicode has different code page (1201) than small Endian one (1200),
+                // so we still have to check _codePage here.
+                //
+                return (CodePage == that.CodePage) &&
+                        byteOrderMark == that.byteOrderMark &&
+                        //                        isThrowException == that.isThrowException &&  // Same as Encoder/Decoder being exception fallbacks
+                        bigEndian == that.bigEndian &&
+                       (EncoderFallback.Equals(that.EncoderFallback)) &&
+                       (DecoderFallback.Equals(that.DecoderFallback));
+            }
+            return (false);
+        }
+
+        public override int GetHashCode()
+        {
+            return CodePage + this.EncoderFallback.GetHashCode() + this.DecoderFallback.GetHashCode() +
+                   (byteOrderMark ? 4 : 0) + (bigEndian ? 8 : 0);
+        }
+
+        private sealed class Decoder : System.Text.DecoderNLS
+        {
+            internal int lastByte = -1;
+            internal char lastChar = '\0';
+
+            public Decoder(UnicodeEncoding encoding) : base(encoding)
+            {
+                // base calls reset
+            }
+            
+            public override void Reset()
+            {
+                lastByte = -1;
+                lastChar = '\0';
+                if (_fallbackBuffer != null)
+                    _fallbackBuffer.Reset();
+            }
+
+            // Anything left in our decoder?
+            internal override bool HasState
+            {
+                get
+                {
+                    return (this.lastByte != -1 || this.lastChar != '\0');
+                }
+            }
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Text/ValueStringBuilder.cs b/src/System.Private.CoreLib/shared/System/Text/ValueStringBuilder.cs
new file mode 100644
index 0000000000..d41bea0be9
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Text/ValueStringBuilder.cs
@@ -0,0 +1,257 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Buffers;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace System.Text
+{
+    internal ref struct ValueStringBuilder
+    {
+        private char[] _arrayToReturnToPool;
+        private Span<char> _chars;
+        private int _pos;
+
+        public ValueStringBuilder(Span<char> initialBuffer)
+        {
+            _arrayToReturnToPool = null;
+            _chars = initialBuffer;
+            _pos = 0;
+        }
+
+        public int Length
+        {
+            get => _pos;
+            set
+            {
+                Debug.Assert(value >= 0);
+                Debug.Assert(value <= _chars.Length);
+                _pos = value;
+            }
+        }
+
+        public int Capacity => _chars.Length;
+
+        public void EnsureCapacity(int capacity)
+        {
+            if (capacity > _chars.Length)
+                Grow(capacity - _chars.Length);
+        }
+
+        /// <summary>
+        /// Get a pinnable reference to the builder.
+        /// </summary>
+        /// <param name="terminate">Ensures that the builder has a null char after <see cref="Length"/></param>
+        public ref char GetPinnableReference(bool terminate = false)
+        {
+            if (terminate)
+            {
+                EnsureCapacity(Length + 1);
+                _chars[Length] = '\0';
+            }
+            return ref MemoryMarshal.GetReference(_chars);
+        }
+
+        public ref char this[int index]
+        {
+            get
+            {
+                Debug.Assert(index < _pos);
+                return ref _chars[index];
+            }
+        }
+
+        public override string ToString()
+        {
+            var s = new string(_chars.Slice(0, _pos));
+            Dispose();
+            return s;
+        }
+
+        /// <summary>Returns the underlying storage of the builder.</summary>
+        public Span<char> RawChars => _chars;
+
+        /// <summary>
+        /// Returns a span around the contents of the builder.
+        /// </summary>
+        /// <param name="terminate">Ensures that the builder has a null char after <see cref="Length"/></param>
+        public ReadOnlySpan<char> AsSpan(bool terminate)
+        {
+            if (terminate)
+            {
+                EnsureCapacity(Length + 1);
+                _chars[Length] = '\0';
+            }
+            return _chars.Slice(0, _pos);
+        }
+
+        public ReadOnlySpan<char> AsSpan() => _chars.Slice(0, _pos);
+        public ReadOnlySpan<char> AsSpan(int start) => _chars.Slice(start, _pos - start);
+        public ReadOnlySpan<char> AsSpan(int start, int length) => _chars.Slice(start, length);
+
+        public bool TryCopyTo(Span<char> destination, out int charsWritten)
+        {
+            if (_chars.Slice(0, _pos).TryCopyTo(destination))
+            {
+                charsWritten = _pos;
+                Dispose();
+                return true;
+            }
+            else
+            {
+                charsWritten = 0;
+                Dispose();
+                return false;
+            }
+        }
+
+        public void Insert(int index, char value, int count)
+        {
+            if (_pos > _chars.Length - count)
+            {
+                Grow(count);
+            }
+
+            int remaining = _pos - index;
+            _chars.Slice(index, remaining).CopyTo(_chars.Slice(index + count));
+            _chars.Slice(index, count).Fill(value);
+            _pos += count;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Append(char c)
+        {
+            int pos = _pos;
+            if (pos < _chars.Length)
+            {
+                _chars[pos] = c;
+                _pos = pos + 1;
+            }
+            else
+            {
+                GrowAndAppend(c);
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Append(string s)
+        {
+            int pos = _pos;
+            if (s.Length == 1 && pos < _chars.Length) // very common case, e.g. appending strings from NumberFormatInfo like separators, percent symbols, etc.
+            {
+                _chars[pos] = s[0];
+                _pos = pos + 1;
+            }
+            else
+            {
+                AppendSlow(s);
+            }
+        }
+
+        private void AppendSlow(string s)
+        {
+            int pos = _pos;
+            if (pos > _chars.Length - s.Length)
+            {
+                Grow(s.Length);
+            }
+
+            s.AsSpan().CopyTo(_chars.Slice(pos));
+            _pos += s.Length;
+        }
+
+        public void Append(char c, int count)
+        {
+            if (_pos > _chars.Length - count)
+            {
+                Grow(count);
+            }
+
+            Span<char> dst = _chars.Slice(_pos, count);
+            for (int i = 0; i < dst.Length; i++)
+            {
+                dst[i] = c;
+            }
+            _pos += count;
+        }
+
+        public unsafe void Append(char* value, int length)
+        {
+            int pos = _pos;
+            if (pos > _chars.Length - length)
+            {
+                Grow(length);
+            }
+
+            Span<char> dst = _chars.Slice(_pos, length);
+            for (int i = 0; i < dst.Length; i++)
+            {
+                dst[i] = *value++;
+            }
+            _pos += length;
+        }
+
+        public unsafe void Append(ReadOnlySpan<char> value)
+        {
+            int pos = _pos;
+            if (pos > _chars.Length - value.Length)
+            {
+                Grow(value.Length);
+            }
+
+            value.CopyTo(_chars.Slice(_pos));
+            _pos += value.Length;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public Span<char> AppendSpan(int length)
+        {
+            int origPos = _pos;
+            if (origPos > _chars.Length - length)
+            {
+                Grow(length);
+            }
+
+            _pos = origPos + length;
+            return _chars.Slice(origPos, length);
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private void GrowAndAppend(char c)
+        {
+            Grow(1);
+            Append(c);
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private void Grow(int requiredAdditionalCapacity)
+        {
+            Debug.Assert(requiredAdditionalCapacity > 0);
+
+            char[] poolArray = ArrayPool<char>.Shared.Rent(Math.Max(_pos + requiredAdditionalCapacity, _chars.Length * 2));
+
+            _chars.CopyTo(poolArray);
+
+            char[] toReturn = _arrayToReturnToPool;
+            _chars = _arrayToReturnToPool = poolArray;
+            if (toReturn != null)
+            {
+                ArrayPool<char>.Shared.Return(toReturn);
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Dispose()
+        {
+            char[] toReturn = _arrayToReturnToPool;
+            this = default; // for safety, to avoid using pooled array if this instance is erroneously appended to again
+            if (toReturn != null)
+            {
+                ArrayPool<char>.Shared.Return(toReturn);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ThreadAttributes.cs b/src/System.Private.CoreLib/shared/System/ThreadAttributes.cs
new file mode 100644
index 0000000000..6248736107
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ThreadAttributes.cs
@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+** Purpose: For Threads-related custom attributes.
+**
+=============================================================================*/
+
+namespace System
+{
+    [AttributeUsage(AttributeTargets.Method)]
+    public sealed class STAThreadAttribute : Attribute
+    {
+        public STAThreadAttribute()
+        {
+        }
+    }
+
+    [AttributeUsage(AttributeTargets.Method)]
+    public sealed class MTAThreadAttribute : Attribute
+    {
+        public MTAThreadAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ThreadStaticAttribute.cs b/src/System.Private.CoreLib/shared/System/ThreadStaticAttribute.cs
new file mode 100644
index 0000000000..c12ac1c18d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ThreadStaticAttribute.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose:     Custom attribute to indicate that the field should be treated 
+**              as a static relative to a thread.
+**          
+**
+**
+===========================================================*/
+
+using System;
+
+namespace System
+{
+    [AttributeUsage(AttributeTargets.Field, Inherited = false)]
+    public class ThreadStaticAttribute : Attribute
+    {
+        public ThreadStaticAttribute()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/AbandonedMutexException.cs b/src/System.Private.CoreLib/shared/System/Threading/AbandonedMutexException.cs
new file mode 100644
index 0000000000..c7e604f33d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/AbandonedMutexException.cs
@@ -0,0 +1,78 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+//
+// AbandonedMutexException
+// Thrown when a wait completes because one or more mutexes was abandoned.
+// AbandonedMutexs indicate serious error in user code or machine state.
+////////////////////////////////////////////////////////////////////////////////
+
+using System;
+using System.Threading;
+using System.Runtime.InteropServices;
+using System.Runtime.Serialization;
+
+namespace System.Threading
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class AbandonedMutexException : SystemException
+    {
+        private int _mutexIndex = -1;
+        private Mutex _mutex = null;
+
+        public AbandonedMutexException()
+            : base(SR.Threading_AbandonedMutexException)
+        {
+            HResult = HResults.COR_E_ABANDONEDMUTEX;
+        }
+
+        public AbandonedMutexException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_ABANDONEDMUTEX;
+        }
+
+        public AbandonedMutexException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_ABANDONEDMUTEX;
+        }
+
+        public AbandonedMutexException(int location, WaitHandle handle)
+            : base(SR.Threading_AbandonedMutexException)
+        {
+            HResult = HResults.COR_E_ABANDONEDMUTEX;
+            SetupException(location, handle);
+        }
+
+        public AbandonedMutexException(String message, int location, WaitHandle handle)
+            : base(message)
+        {
+            HResult = HResults.COR_E_ABANDONEDMUTEX;
+            SetupException(location, handle);
+        }
+
+        public AbandonedMutexException(String message, Exception inner, int location, WaitHandle handle)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_ABANDONEDMUTEX;
+            SetupException(location, handle);
+        }
+
+        protected AbandonedMutexException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+
+        private void SetupException(int location, WaitHandle handle)
+        {
+            _mutexIndex = location;
+            if (handle != null)
+                _mutex = handle as Mutex;
+        }
+
+        public Mutex Mutex => _mutex;
+        public int MutexIndex => _mutexIndex;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/ApartmentState.cs b/src/System.Private.CoreLib/shared/System/Threading/ApartmentState.cs
new file mode 100644
index 0000000000..47c1677cb5
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/ApartmentState.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Threading
+{
+    public enum ApartmentState
+    {
+        /*=========================================================================
+        ** Constants for thread apartment states.
+        =========================================================================*/
+        STA = 0,
+        MTA = 1,
+        Unknown = 2
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/AsyncLocal.cs b/src/System.Private.CoreLib/shared/System/Threading/AsyncLocal.cs
new file mode 100644
index 0000000000..2bf8a046b7
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/AsyncLocal.cs
@@ -0,0 +1,499 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System.Threading
+{
+    //
+    // AsyncLocal<T> represents "ambient" data that is local to a given asynchronous control flow, such as an
+    // async method.  For example, say you want to associate a culture with a given async flow:
+    //
+    // static AsyncLocal<Culture> s_currentCulture = new AsyncLocal<Culture>();
+    //
+    // static async Task SomeOperationAsync(Culture culture)
+    // {
+    //    s_currentCulture.Value = culture;
+    //
+    //    await FooAsync();
+    // }
+    //
+    // static async Task FooAsync()
+    // {
+    //    PrintStringWithCulture(s_currentCulture.Value);
+    // }
+    //
+    // AsyncLocal<T> also provides optional notifications when the value associated with the current thread
+    // changes, either because it was explicitly changed by setting the Value property, or implicitly changed
+    // when the thread encountered an "await" or other context transition.  For example, we might want our
+    // current culture to be communicated to the OS as well:
+    //
+    // static AsyncLocal<Culture> s_currentCulture = new AsyncLocal<Culture>(
+    //   args =>
+    //   {
+    //      NativeMethods.SetThreadCulture(args.CurrentValue.LCID);
+    //   });
+    //
+    public sealed class AsyncLocal<T> : IAsyncLocal
+    {
+        private readonly Action<AsyncLocalValueChangedArgs<T>> m_valueChangedHandler;
+
+        //
+        // Constructs an AsyncLocal<T> that does not receive change notifications.
+        //
+        public AsyncLocal()
+        {
+        }
+
+        //
+        // Constructs an AsyncLocal<T> with a delegate that is called whenever the current value changes
+        // on any thread.
+        //
+        public AsyncLocal(Action<AsyncLocalValueChangedArgs<T>> valueChangedHandler)
+        {
+            m_valueChangedHandler = valueChangedHandler;
+        }
+
+        public T Value
+        {
+            get
+            {
+                object obj = ExecutionContext.GetLocalValue(this);
+                return (obj == null) ? default(T) : (T)obj;
+            }
+            set
+            {
+                ExecutionContext.SetLocalValue(this, value, m_valueChangedHandler != null);
+            }
+        }
+
+        void IAsyncLocal.OnValueChanged(object previousValueObj, object currentValueObj, bool contextChanged)
+        {
+            Debug.Assert(m_valueChangedHandler != null);
+            T previousValue = previousValueObj == null ? default(T) : (T)previousValueObj;
+            T currentValue = currentValueObj == null ? default(T) : (T)currentValueObj;
+            m_valueChangedHandler(new AsyncLocalValueChangedArgs<T>(previousValue, currentValue, contextChanged));
+        }
+    }
+
+    //
+    // Interface to allow non-generic code in ExecutionContext to call into the generic AsyncLocal<T> type.
+    //
+    internal interface IAsyncLocal
+    {
+        void OnValueChanged(object previousValue, object currentValue, bool contextChanged);
+    }
+
+    public struct AsyncLocalValueChangedArgs<T>
+    {
+        public T PreviousValue { get; private set; }
+        public T CurrentValue { get; private set; }
+
+        //
+        // If the value changed because we changed to a different ExecutionContext, this is true.  If it changed
+        // because someone set the Value property, this is false.
+        //
+        public bool ThreadContextChanged { get; private set; }
+
+        internal AsyncLocalValueChangedArgs(T previousValue, T currentValue, bool contextChanged)
+            : this()
+        {
+            PreviousValue = previousValue;
+            CurrentValue = currentValue;
+            ThreadContextChanged = contextChanged;
+        }
+    }
+
+    //
+    // Interface used to store an IAsyncLocal => object mapping in ExecutionContext.
+    // Implementations are specialized based on the number of elements in the immutable
+    // map in order to minimize memory consumption and look-up times.
+    //
+    internal interface IAsyncLocalValueMap
+    {
+        bool TryGetValue(IAsyncLocal key, out object value);
+        IAsyncLocalValueMap Set(IAsyncLocal key, object value, bool treatNullValueAsNonexistent);
+    }
+
+    //
+    // Utility functions for getting/creating instances of IAsyncLocalValueMap
+    //
+    internal static class AsyncLocalValueMap
+    {
+        public static IAsyncLocalValueMap Empty { get; } = new EmptyAsyncLocalValueMap();
+
+        public static bool IsEmpty(IAsyncLocalValueMap asyncLocalValueMap)
+        {
+            Debug.Assert(asyncLocalValueMap != null);
+            Debug.Assert(asyncLocalValueMap == Empty || asyncLocalValueMap.GetType() != typeof(EmptyAsyncLocalValueMap));
+
+            return asyncLocalValueMap == Empty;
+        }
+
+        public static IAsyncLocalValueMap Create(IAsyncLocal key, object value, bool treatNullValueAsNonexistent)
+        {
+            // If the value isn't null or a null value may not be treated as nonexistent, then create a new one-element map
+            // to store the key/value pair.  Otherwise, use the empty map.
+            return value != null || !treatNullValueAsNonexistent ?
+                new OneElementAsyncLocalValueMap(key, value) :
+                Empty;
+        }
+
+        // Instance without any key/value pairs.  Used as a singleton/
+        private sealed class EmptyAsyncLocalValueMap : IAsyncLocalValueMap
+        {
+            public IAsyncLocalValueMap Set(IAsyncLocal key, object value, bool treatNullValueAsNonexistent)
+            {
+                // If the value isn't null or a null value may not be treated as nonexistent, then create a new one-element map
+                // to store the key/value pair.  Otherwise, use the empty map.
+                return value != null || !treatNullValueAsNonexistent ?
+                    new OneElementAsyncLocalValueMap(key, value) :
+                    (IAsyncLocalValueMap)this;
+            }
+
+            public bool TryGetValue(IAsyncLocal key, out object value)
+            {
+                value = null;
+                return false;
+            }
+        }
+
+        // Instance with one key/value pair.
+        private sealed class OneElementAsyncLocalValueMap : IAsyncLocalValueMap
+        {
+            private readonly IAsyncLocal _key1;
+            private readonly object _value1;
+
+            public OneElementAsyncLocalValueMap(IAsyncLocal key, object value)
+            {
+                _key1 = key; _value1 = value;
+            }
+
+            public IAsyncLocalValueMap Set(IAsyncLocal key, object value, bool treatNullValueAsNonexistent)
+            {
+                if (value != null || !treatNullValueAsNonexistent)
+                {
+                    // If the key matches one already contained in this map, then create a new one-element map with the updated
+                    // value, otherwise create a two-element map with the additional key/value.
+                    return ReferenceEquals(key, _key1) ?
+                        new OneElementAsyncLocalValueMap(key, value) :
+                        (IAsyncLocalValueMap)new TwoElementAsyncLocalValueMap(_key1, _value1, key, value);
+                }
+                else
+                {
+                    // If the key exists in this map, remove it by downgrading to an empty map.  Otherwise, there's nothing to
+                    // add or remove, so just return this map.
+                    return ReferenceEquals(key, _key1) ?
+                        Empty :
+                        (IAsyncLocalValueMap)this;
+                }
+            }
+
+            public bool TryGetValue(IAsyncLocal key, out object value)
+            {
+                if (ReferenceEquals(key, _key1))
+                {
+                    value = _value1;
+                    return true;
+                }
+                else
+                {
+                    value = null;
+                    return false;
+                }
+            }
+        }
+
+        // Instance with two key/value pairs.
+        private sealed class TwoElementAsyncLocalValueMap : IAsyncLocalValueMap
+        {
+            private readonly IAsyncLocal _key1, _key2;
+            private readonly object _value1, _value2;
+
+            public TwoElementAsyncLocalValueMap(IAsyncLocal key1, object value1, IAsyncLocal key2, object value2)
+            {
+                _key1 = key1; _value1 = value1;
+                _key2 = key2; _value2 = value2;
+            }
+
+            public IAsyncLocalValueMap Set(IAsyncLocal key, object value, bool treatNullValueAsNonexistent)
+            {
+                if (value != null || !treatNullValueAsNonexistent)
+                {
+                    // If the key matches one already contained in this map, then create a new two-element map with the updated
+                    // value, otherwise create a three-element map with the additional key/value.
+                    return
+                        ReferenceEquals(key, _key1) ? new TwoElementAsyncLocalValueMap(key, value, _key2, _value2) :
+                        ReferenceEquals(key, _key2) ? new TwoElementAsyncLocalValueMap(_key1, _value1, key, value) :
+                        (IAsyncLocalValueMap)new ThreeElementAsyncLocalValueMap(_key1, _value1, _key2, _value2, key, value);
+                }
+                else
+                {
+                    // If the key exists in this map, remove it by downgrading to a one-element map without the key.  Otherwise,
+                    // there's nothing to add or remove, so just return this map.
+                    return
+                        ReferenceEquals(key, _key1) ? new OneElementAsyncLocalValueMap(_key2, _value2) :
+                        ReferenceEquals(key, _key2) ? new OneElementAsyncLocalValueMap(_key1, _value1) :
+                        (IAsyncLocalValueMap)this;
+                }
+            }
+
+            public bool TryGetValue(IAsyncLocal key, out object value)
+            {
+                if (ReferenceEquals(key, _key1))
+                {
+                    value = _value1;
+                    return true;
+                }
+                else if (ReferenceEquals(key, _key2))
+                {
+                    value = _value2;
+                    return true;
+                }
+                else
+                {
+                    value = null;
+                    return false;
+                }
+            }
+        }
+
+        // Instance with three key/value pairs.
+        private sealed class ThreeElementAsyncLocalValueMap : IAsyncLocalValueMap
+        {
+            private readonly IAsyncLocal _key1, _key2, _key3;
+            private readonly object _value1, _value2, _value3;
+
+            public ThreeElementAsyncLocalValueMap(IAsyncLocal key1, object value1, IAsyncLocal key2, object value2, IAsyncLocal key3, object value3)
+            {
+                _key1 = key1; _value1 = value1;
+                _key2 = key2; _value2 = value2;
+                _key3 = key3; _value3 = value3;
+            }
+
+            public IAsyncLocalValueMap Set(IAsyncLocal key, object value, bool treatNullValueAsNonexistent)
+            {
+                if (value != null || !treatNullValueAsNonexistent)
+                {
+                    // If the key matches one already contained in this map, then create a new three-element map with the
+                    // updated value.
+                    if (ReferenceEquals(key, _key1)) return new ThreeElementAsyncLocalValueMap(key, value, _key2, _value2, _key3, _value3);
+                    if (ReferenceEquals(key, _key2)) return new ThreeElementAsyncLocalValueMap(_key1, _value1, key, value, _key3, _value3);
+                    if (ReferenceEquals(key, _key3)) return new ThreeElementAsyncLocalValueMap(_key1, _value1, _key2, _value2, key, value);
+
+                    // The key doesn't exist in this map, so upgrade to a multi map that contains
+                    // the additional key/value pair.
+                    var multi = new MultiElementAsyncLocalValueMap(4);
+                    multi.UnsafeStore(0, _key1, _value1);
+                    multi.UnsafeStore(1, _key2, _value2);
+                    multi.UnsafeStore(2, _key3, _value3);
+                    multi.UnsafeStore(3, key, value);
+                    return multi;
+                }
+                else
+                {
+                    // If the key exists in this map, remove it by downgrading to a two-element map without the key.  Otherwise,
+                    // there's nothing to add or remove, so just return this map.
+                    return
+                        ReferenceEquals(key, _key1) ? new TwoElementAsyncLocalValueMap(_key2, _value2, _key3, _value3) :
+                        ReferenceEquals(key, _key2) ? new TwoElementAsyncLocalValueMap(_key1, _value1, _key3, _value3) :
+                        ReferenceEquals(key, _key3) ? new TwoElementAsyncLocalValueMap(_key1, _value1, _key2, _value2) :
+                        (IAsyncLocalValueMap)this;
+                }
+            }
+
+            public bool TryGetValue(IAsyncLocal key, out object value)
+            {
+                if (ReferenceEquals(key, _key1))
+                {
+                    value = _value1;
+                    return true;
+                }
+                else if (ReferenceEquals(key, _key2))
+                {
+                    value = _value2;
+                    return true;
+                }
+                else if (ReferenceEquals(key, _key3))
+                {
+                    value = _value3;
+                    return true;
+                }
+                else
+                {
+                    value = null;
+                    return false;
+                }
+            }
+        }
+
+        // Instance with up to 16 key/value pairs.
+        private sealed class MultiElementAsyncLocalValueMap : IAsyncLocalValueMap
+        {
+            internal const int MaxMultiElements = 16;
+            private readonly KeyValuePair<IAsyncLocal, object>[] _keyValues;
+
+            internal MultiElementAsyncLocalValueMap(int count)
+            {
+                Debug.Assert(count <= MaxMultiElements);
+                _keyValues = new KeyValuePair<IAsyncLocal, object>[count];
+            }
+
+            internal void UnsafeStore(int index, IAsyncLocal key, object value)
+            {
+                Debug.Assert(index < _keyValues.Length);
+                _keyValues[index] = new KeyValuePair<IAsyncLocal, object>(key, value);
+            }
+
+            public IAsyncLocalValueMap Set(IAsyncLocal key, object value, bool treatNullValueAsNonexistent)
+            {
+                // Find the key in this map.
+                for (int i = 0; i < _keyValues.Length; i++)
+                {
+                    if (ReferenceEquals(key, _keyValues[i].Key))
+                    {
+                        // The key is in the map.
+                        if (value != null || !treatNullValueAsNonexistent)
+                        {
+                            // Create a new map of the same size that has all of the same pairs, with this new key/value pair
+                            // overwriting the old.
+                            var multi = new MultiElementAsyncLocalValueMap(_keyValues.Length);
+                            Array.Copy(_keyValues, 0, multi._keyValues, 0, _keyValues.Length);
+                            multi._keyValues[i] = new KeyValuePair<IAsyncLocal, object>(key, value);
+                            return multi;
+                        }
+                        else if (_keyValues.Length == 4)
+                        {
+                            // We only have four elements, one of which we're removing, so downgrade to a three-element map,
+                            // without the matching element.
+                            return
+                                i == 0 ? new ThreeElementAsyncLocalValueMap(_keyValues[1].Key, _keyValues[1].Value, _keyValues[2].Key, _keyValues[2].Value, _keyValues[3].Key, _keyValues[3].Value) :
+                                i == 1 ? new ThreeElementAsyncLocalValueMap(_keyValues[0].Key, _keyValues[0].Value, _keyValues[2].Key, _keyValues[2].Value, _keyValues[3].Key, _keyValues[3].Value) :
+                                i == 2 ? new ThreeElementAsyncLocalValueMap(_keyValues[0].Key, _keyValues[0].Value, _keyValues[1].Key, _keyValues[1].Value, _keyValues[3].Key, _keyValues[3].Value) :
+                                (IAsyncLocalValueMap)new ThreeElementAsyncLocalValueMap(_keyValues[0].Key, _keyValues[0].Value, _keyValues[1].Key, _keyValues[1].Value, _keyValues[2].Key, _keyValues[2].Value);
+                        }
+                        else
+                        {
+                            // We have enough elements remaining to warrant a multi map.  Create a new one and copy all of the
+                            // elements from this one, except the one to be removed.
+                            var multi = new MultiElementAsyncLocalValueMap(_keyValues.Length - 1);
+                            if (i != 0) Array.Copy(_keyValues, 0, multi._keyValues, 0, i);
+                            if (i != _keyValues.Length - 1) Array.Copy(_keyValues, i + 1, multi._keyValues, i, _keyValues.Length - i - 1);
+                            return multi;
+                        }
+                    }
+                }
+
+                // The key does not already exist in this map.
+
+                if (value == null && treatNullValueAsNonexistent)
+                {
+                    // We can simply return this same map, as there's nothing to add or remove.
+                    return this;
+                }
+
+                // We need to create a new map that has the additional key/value pair.
+                // If with the addition we can still fit in a multi map, create one.
+                if (_keyValues.Length < MaxMultiElements)
+                {
+                    var multi = new MultiElementAsyncLocalValueMap(_keyValues.Length + 1);
+                    Array.Copy(_keyValues, 0, multi._keyValues, 0, _keyValues.Length);
+                    multi._keyValues[_keyValues.Length] = new KeyValuePair<IAsyncLocal, object>(key, value);
+                    return multi;
+                }
+
+                // Otherwise, upgrade to a many map.
+                var many = new ManyElementAsyncLocalValueMap(MaxMultiElements + 1);
+                foreach (KeyValuePair<IAsyncLocal, object> pair in _keyValues)
+                {
+                    many[pair.Key] = pair.Value;
+                }
+                many[key] = value;
+                return many;
+            }
+
+            public bool TryGetValue(IAsyncLocal key, out object value)
+            {
+                foreach (KeyValuePair<IAsyncLocal, object> pair in _keyValues)
+                {
+                    if (ReferenceEquals(key, pair.Key))
+                    {
+                        value = pair.Value;
+                        return true;
+                    }
+                }
+                value = null;
+                return false;
+            }
+        }
+
+        // Instance with any number of key/value pairs.
+        private sealed class ManyElementAsyncLocalValueMap : Dictionary<IAsyncLocal, object>, IAsyncLocalValueMap
+        {
+            public ManyElementAsyncLocalValueMap(int capacity) : base(capacity) { }
+
+            public IAsyncLocalValueMap Set(IAsyncLocal key, object value, bool treatNullValueAsNonexistent)
+            {
+                int count = Count;
+                bool containsKey = ContainsKey(key);
+
+                // If the value being set exists, create a new many map, copy all of the elements from this one,
+                // and then store the new key/value pair into it.  This is the most common case.
+                if (value != null || !treatNullValueAsNonexistent)
+                {
+                    var map = new ManyElementAsyncLocalValueMap(count + (containsKey ? 0 : 1));
+                    foreach (KeyValuePair<IAsyncLocal, object> pair in this)
+                    {
+                        map[pair.Key] = pair.Value;
+                    }
+                    map[key] = value;
+                    return map;
+                }
+
+                // Otherwise, the value is null and a null value may be treated as nonexistent. We can downgrade to a smaller
+                // map rather than storing null.
+
+                // If the key is contained in this map, we're going to create a new map that's one pair smaller.
+                if (containsKey)
+                {
+                    // If the new count would be within range of a multi map instead of a many map,
+                    // downgrade to the multi map, which uses less memory and is faster to access.
+                    // Otherwise, just create a new many map that's missing this key.
+                    if (count == MultiElementAsyncLocalValueMap.MaxMultiElements + 1)
+                    {
+                        var multi = new MultiElementAsyncLocalValueMap(MultiElementAsyncLocalValueMap.MaxMultiElements);
+                        int index = 0;
+                        foreach (KeyValuePair<IAsyncLocal, object> pair in this)
+                        {
+                            if (!ReferenceEquals(key, pair.Key))
+                            {
+                                multi.UnsafeStore(index++, pair.Key, pair.Value);
+                            }
+                        }
+                        Debug.Assert(index == MultiElementAsyncLocalValueMap.MaxMultiElements);
+                        return multi;
+                    }
+                    else
+                    {
+                        var map = new ManyElementAsyncLocalValueMap(count - 1);
+                        foreach (KeyValuePair<IAsyncLocal, object> pair in this)
+                        {
+                            if (!ReferenceEquals(key, pair.Key))
+                            {
+                                map[pair.Key] = pair.Value;
+                            }
+                        }
+                        Debug.Assert(map.Count == count - 1);
+                        return map;
+                    }
+                }
+
+                // We were storing null and a null value may be treated as nonexistent, but the key wasn't in the map, so
+                // there's nothing to change.  Just return this instance.
+                return this;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/AutoResetEvent.cs b/src/System.Private.CoreLib/shared/System/Threading/AutoResetEvent.cs
new file mode 100644
index 0000000000..8320d7ad5a
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/AutoResetEvent.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Threading
+{
+    public sealed class AutoResetEvent : EventWaitHandle
+    {
+        public AutoResetEvent(bool initialState) : base(initialState, EventResetMode.AutoReset) { }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Threading/DeferredDisposableLifetime.cs b/src/System.Private.CoreLib/shared/System/Threading/DeferredDisposableLifetime.cs
new file mode 100644
index 0000000000..e2b1eb983b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/DeferredDisposableLifetime.cs
@@ -0,0 +1,116 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Threading
+{
+    /// <summary>
+    /// Provides callbacks to objects whose lifetime is managed by <see cref="DeferredDisposableLifetime{T}"/>.
+    /// </summary>
+    internal interface IDeferredDisposable
+    {
+        /// <summary>
+        /// Called when the object's refcount reaches zero.
+        /// </summary>
+        /// <param name="disposed">
+        /// Indicates whether the object has been disposed.
+        /// </param>
+        /// <remarks>
+        /// If the refcount reaches zero before the object is disposed, this method will be called with
+        /// <paramref name="disposed"/> set to false.  If the object is then disposed, this method will be
+        /// called again, with <paramref name="disposed"/> set to true.  If the refcount reaches zero
+        /// after the object has already been disposed, this will be called a single time, with 
+        /// <paramref name="disposed"/> set to true.
+        /// </remarks>
+        void OnFinalRelease(bool disposed);
+    }
+
+    /// <summary>
+    /// Manages the lifetime of an object which implements IDisposable, but which must defer the actual
+    /// cleanup of state until all existing uses of the object are complete.
+    /// </summary>
+    /// <typeparam name="T">The type of object whose lifetime will be managed.</typeparam>
+    /// <remarks>
+    /// This type maintains a reference count, and tracks whether the object has been disposed.  When
+    /// Callbacks are made to <see cref="IDeferredDisposable.OnFinalRelease(bool)"/> when the refcount
+    /// reaches zero.  Objects that need to defer cleanup until they have been disposed *and* they have
+    /// no more references can do so in <see cref="IDeferredDisposable.OnFinalRelease(bool)"/> when
+    /// 'disposed' is true.
+    /// </remarks>
+    internal struct DeferredDisposableLifetime<T> where T : class, IDeferredDisposable
+    {
+        //
+        // _count is positive until Dispose is called, after which it's (-1 - refcount).
+        //
+        private int _count;
+
+        public bool AddRef(T obj)
+        {
+            while (true)
+            {
+                int oldCount = Volatile.Read(ref _count);
+
+                // Have we been disposed?
+                if (oldCount < 0)
+                    throw new ObjectDisposedException(typeof(T).ToString());
+
+                int newCount = checked(oldCount + 1);
+
+                if (Interlocked.CompareExchange(ref _count, newCount, oldCount) == oldCount)
+                    return true;
+            }
+        }
+
+        public void Release(T obj)
+        {
+            while (true)
+            {
+                int oldCount = Volatile.Read(ref _count);
+                if (oldCount > 0)
+                {
+                    // We haven't been disposed.  Decrement _count.
+                    int newCount = oldCount - 1;
+                    if (Interlocked.CompareExchange(ref _count, newCount, oldCount) == oldCount)
+                    {
+                        if (newCount == 0)
+                            obj.OnFinalRelease(disposed: false);
+                        return;
+                    }
+                }
+                else
+                {
+                    Debug.Assert(oldCount != 0 && oldCount != -1);
+
+                    // We've been disposed.  Increment _count.
+                    int newCount = oldCount + 1;
+                    if (Interlocked.CompareExchange(ref _count, newCount, oldCount) == oldCount)
+                    {
+                        if (newCount == -1)
+                            obj.OnFinalRelease(disposed: true);
+                        return;
+                    }
+                }
+            }
+        }
+
+        public void Dispose(T obj)
+        {
+            while (true)
+            {
+                int oldCount = Volatile.Read(ref _count);
+                if (oldCount < 0)
+                    return; // already disposed
+
+                int newCount = -1 - oldCount;
+                if (Interlocked.CompareExchange(ref _count, newCount, oldCount) == oldCount)
+                {
+                    if (newCount == -1)
+                        obj.OnFinalRelease(disposed: true);
+                    return;
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/EventResetMode.cs b/src/System.Private.CoreLib/shared/System/Threading/EventResetMode.cs
new file mode 100644
index 0000000000..7aac0f51eb
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/EventResetMode.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+** Enum: EventResetMode
+**
+**
+** Purpose: Enum to determine the Event type to create
+**
+**
+=============================================================================*/
+
+namespace System.Threading
+{
+    public enum EventResetMode
+    {
+        AutoReset = 0,
+        ManualReset = 1
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/ExecutionContext.cs b/src/System.Private.CoreLib/shared/System/Threading/ExecutionContext.cs
new file mode 100644
index 0000000000..975ed02d42
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/ExecutionContext.cs
@@ -0,0 +1,460 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Capture execution  context for a thread
+**
+**
+===========================================================*/
+
+using System.Diagnostics;
+using System.Runtime.ExceptionServices;
+using System.Runtime.Serialization;
+
+using Thread = Internal.Runtime.Augments.RuntimeThread;
+
+namespace System.Threading
+{
+    public delegate void ContextCallback(Object state);
+
+    public sealed class ExecutionContext : IDisposable, ISerializable
+    {
+        internal static readonly ExecutionContext Default = new ExecutionContext(isDefault: true);
+        internal static readonly ExecutionContext DefaultFlowSuppressed = new ExecutionContext(AsyncLocalValueMap.Empty, Array.Empty<IAsyncLocal>(), isFlowSuppressed: true);
+
+        private readonly IAsyncLocalValueMap m_localValues;
+        private readonly IAsyncLocal[] m_localChangeNotifications;
+        private readonly bool m_isFlowSuppressed;
+        private readonly bool m_isDefault;
+
+        private ExecutionContext(bool isDefault)
+        {
+            m_isDefault = isDefault;
+        }
+
+        private ExecutionContext(
+            IAsyncLocalValueMap localValues,
+            IAsyncLocal[] localChangeNotifications,
+            bool isFlowSuppressed)
+        {
+            m_localValues = localValues;
+            m_localChangeNotifications = localChangeNotifications;
+            m_isFlowSuppressed = isFlowSuppressed;
+        }
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            throw new PlatformNotSupportedException();
+        }
+
+        public static ExecutionContext Capture()
+        {
+            ExecutionContext executionContext = Thread.CurrentThread.ExecutionContext;
+            return
+                executionContext == null ? Default :
+                executionContext.m_isFlowSuppressed ? null :
+                executionContext;
+        }
+
+        private ExecutionContext ShallowClone(bool isFlowSuppressed)
+        {
+            Debug.Assert(isFlowSuppressed != m_isFlowSuppressed);
+
+            if (m_localValues == null || AsyncLocalValueMap.IsEmpty(m_localValues))
+            {
+                return isFlowSuppressed ?
+                    DefaultFlowSuppressed :
+                    null; // implies the default context
+            }
+
+            return new ExecutionContext(m_localValues, m_localChangeNotifications, isFlowSuppressed);
+        }
+
+        public static AsyncFlowControl SuppressFlow()
+        {
+            Thread currentThread = Thread.CurrentThread;
+            ExecutionContext executionContext = currentThread.ExecutionContext ?? Default;
+            if (executionContext.m_isFlowSuppressed)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_CannotSupressFlowMultipleTimes);
+            }
+
+            executionContext = executionContext.ShallowClone(isFlowSuppressed: true);
+            var asyncFlowControl = new AsyncFlowControl();
+            currentThread.ExecutionContext = executionContext;
+            asyncFlowControl.Initialize(currentThread);
+            return asyncFlowControl;
+        }
+
+        public static void RestoreFlow()
+        {
+            Thread currentThread = Thread.CurrentThread;
+            ExecutionContext executionContext = currentThread.ExecutionContext;
+            if (executionContext == null || !executionContext.m_isFlowSuppressed)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_CannotRestoreUnsupressedFlow);
+            }
+
+            currentThread.ExecutionContext = executionContext.ShallowClone(isFlowSuppressed: false);
+        }
+
+        public static bool IsFlowSuppressed()
+        {
+            ExecutionContext executionContext = Thread.CurrentThread.ExecutionContext;
+            return executionContext != null && executionContext.m_isFlowSuppressed;
+        }
+
+        internal bool HasChangeNotifications => m_localChangeNotifications != null;
+
+        internal bool IsDefault => m_isDefault;
+
+        public static void Run(ExecutionContext executionContext, ContextCallback callback, Object state)
+        {
+            // Note: ExecutionContext.Run is an extremely hot function and used by every await, ThreadPool execution, etc.
+            if (executionContext == null)
+            {
+                ThrowNullContext();
+            }
+
+            RunInternal(executionContext, callback, state);
+        }
+
+        internal static void RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
+        {
+            // Note: ExecutionContext.RunInternal is an extremely hot function and used by every await, ThreadPool execution, etc.
+            // Note: Manual enregistering may be addressed by "Exception Handling Write Through Optimization"
+            //       https://github.com/dotnet/coreclr/blob/master/Documentation/design-docs/eh-writethru.md
+
+            // Enregister variables with 0 post-fix so they can be used in registers without EH forcing them to stack
+            // Capture references to Thread Contexts
+            Thread currentThread0 = Thread.CurrentThread;
+            Thread currentThread = currentThread0;
+            ExecutionContext previousExecutionCtx0 = currentThread0.ExecutionContext;
+
+            // Store current ExecutionContext and SynchronizationContext as "previousXxx".
+            // This allows us to restore them and undo any Context changes made in callback.Invoke
+            // so that they won't "leak" back into caller.
+            // These variables will cross EH so be forced to stack
+            ExecutionContext previousExecutionCtx = previousExecutionCtx0;
+            SynchronizationContext previousSyncCtx = currentThread0.SynchronizationContext;
+
+            if (executionContext != null && executionContext.m_isDefault)
+            {
+                // Default is a null ExecutionContext internally
+                executionContext = null;
+            }
+
+            if (previousExecutionCtx0 != executionContext)
+            {
+                // Restore changed ExecutionContext
+                currentThread0.ExecutionContext = executionContext;
+                if ((executionContext != null && executionContext.HasChangeNotifications) ||
+                    (previousExecutionCtx0 != null && previousExecutionCtx0.HasChangeNotifications))
+                {
+                    // There are change notifications; trigger any affected
+                    OnValuesChanged(previousExecutionCtx0, executionContext);
+                }
+            }
+
+            ExceptionDispatchInfo edi = null;
+            try
+            {
+                callback.Invoke(state);
+            }
+            catch (Exception ex)
+            {
+                // Note: we have a "catch" rather than a "finally" because we want
+                // to stop the first pass of EH here.  That way we can restore the previous
+                // context before any of our callers' EH filters run.
+                edi = ExceptionDispatchInfo.Capture(ex);
+            }
+
+            // Re-enregistrer variables post EH with 1 post-fix so they can be used in registers rather than from stack
+            SynchronizationContext previousSyncCtx1 = previousSyncCtx;
+            Thread currentThread1 = currentThread;
+            // The common case is that these have not changed, so avoid the cost of a write barrier if not needed.
+            if (currentThread1.SynchronizationContext != previousSyncCtx1)
+            {
+                // Restore changed SynchronizationContext back to previous
+                currentThread1.SynchronizationContext = previousSyncCtx1;
+            }
+
+            ExecutionContext previousExecutionCtx1 = previousExecutionCtx;
+            ExecutionContext currentExecutionCtx1 = currentThread1.ExecutionContext;
+            if (currentExecutionCtx1 != previousExecutionCtx1)
+            {
+                // Restore changed ExecutionContext back to previous
+                currentThread1.ExecutionContext = previousExecutionCtx1;
+                if ((currentExecutionCtx1 != null && currentExecutionCtx1.HasChangeNotifications) ||
+                    (previousExecutionCtx1 != null && previousExecutionCtx1.HasChangeNotifications))
+                {
+                    // There are change notifications; trigger any affected
+                    OnValuesChanged(currentExecutionCtx1, previousExecutionCtx1);
+                }
+            }
+
+            // If exception was thrown by callback, rethrow it now original contexts are restored
+            edi?.Throw();
+        }
+
+        internal static void OnValuesChanged(ExecutionContext previousExecutionCtx, ExecutionContext nextExecutionCtx)
+        {
+            Debug.Assert(previousExecutionCtx != nextExecutionCtx);
+
+            // Collect Change Notifications 
+            IAsyncLocal[] previousChangeNotifications = previousExecutionCtx?.m_localChangeNotifications;
+            IAsyncLocal[] nextChangeNotifications = nextExecutionCtx?.m_localChangeNotifications;
+
+            // At least one side must have notifications
+            Debug.Assert(previousChangeNotifications != null || nextChangeNotifications != null);
+
+            // Fire Change Notifications
+            try
+            {
+                if (previousChangeNotifications != null && nextChangeNotifications != null)
+                {
+                    // Notifications can't exist without values
+                    Debug.Assert(previousExecutionCtx.m_localValues != null);
+                    Debug.Assert(nextExecutionCtx.m_localValues != null);
+                    // Both contexts have change notifications, check previousExecutionCtx first
+                    foreach (IAsyncLocal local in previousChangeNotifications)
+                    {
+                        previousExecutionCtx.m_localValues.TryGetValue(local, out object previousValue);
+                        nextExecutionCtx.m_localValues.TryGetValue(local, out object currentValue);
+
+                        if (previousValue != currentValue)
+                        {
+                            local.OnValueChanged(previousValue, currentValue, contextChanged: true);
+                        }
+                    }
+
+                    if (nextChangeNotifications != previousChangeNotifications)
+                    {
+                        // Check for additional notifications in nextExecutionCtx
+                        foreach (IAsyncLocal local in nextChangeNotifications)
+                        {
+                            // If the local has a value in the previous context, we already fired the event 
+                            // for that local in the code above.
+                            if (!previousExecutionCtx.m_localValues.TryGetValue(local, out object previousValue))
+                            {
+                                nextExecutionCtx.m_localValues.TryGetValue(local, out object currentValue);
+                                if (previousValue != currentValue)
+                                {
+                                    local.OnValueChanged(previousValue, currentValue, contextChanged: true);
+                                }
+                            }
+                        }
+                    }
+                }
+                else if (previousChangeNotifications != null)
+                {
+                    // Notifications can't exist without values
+                    Debug.Assert(previousExecutionCtx.m_localValues != null);
+                    // No current values, so just check previous against null
+                    foreach (IAsyncLocal local in previousChangeNotifications)
+                    {
+                        previousExecutionCtx.m_localValues.TryGetValue(local, out object previousValue);
+                        if (previousValue != null)
+                        {
+                            local.OnValueChanged(previousValue, null, contextChanged: true);
+                        }
+                    }
+                }
+                else // Implied: nextChangeNotifications != null
+                {
+                    // Notifications can't exist without values
+                    Debug.Assert(nextExecutionCtx.m_localValues != null);
+                    // No previous values, so just check current against null
+                    foreach (IAsyncLocal local in nextChangeNotifications)
+                    {
+                        nextExecutionCtx.m_localValues.TryGetValue(local, out object currentValue);
+                        if (currentValue != null)
+                        {
+                            local.OnValueChanged(null, currentValue, contextChanged: true);
+                        }
+                    }
+                }
+            }
+            catch (Exception ex)
+            {
+                Environment.FailFast(
+                    SR.ExecutionContext_ExceptionInAsyncLocalNotification,
+                    ex);
+            }
+        }
+
+        [StackTraceHidden]
+        private static void ThrowNullContext()
+        {
+            throw new InvalidOperationException(SR.InvalidOperation_NullContext);
+        }
+
+        internal static object GetLocalValue(IAsyncLocal local)
+        {
+            ExecutionContext current = Thread.CurrentThread.ExecutionContext;
+            if (current == null)
+            {
+                return null;
+            }
+
+            current.m_localValues.TryGetValue(local, out object value);
+            return value;
+        }
+
+        internal static void SetLocalValue(IAsyncLocal local, object newValue, bool needChangeNotifications)
+        {
+            ExecutionContext current = Thread.CurrentThread.ExecutionContext;
+
+            object previousValue = null;
+            bool hadPreviousValue = false;
+            if (current != null)
+            {
+                hadPreviousValue = current.m_localValues.TryGetValue(local, out previousValue);
+            }
+
+            if (previousValue == newValue)
+            {
+                return;
+            }
+
+            // Regarding 'treatNullValueAsNonexistent: !needChangeNotifications' below:
+            // - When change notifications are not necessary for this IAsyncLocal, there is no observable difference between
+            //   storing a null value and removing the IAsyncLocal from 'm_localValues'
+            // - When change notifications are necessary for this IAsyncLocal, the IAsyncLocal's absence in 'm_localValues'
+            //   indicates that this is the first value change for the IAsyncLocal and it needs to be registered for change
+            //   notifications. So in this case, a null value must be stored in 'm_localValues' to indicate that the IAsyncLocal
+            //   is already registered for change notifications.
+            IAsyncLocal[] newChangeNotifications = null;
+            IAsyncLocalValueMap newValues;
+            bool isFlowSuppressed = false;
+            if (current != null)
+            {
+                isFlowSuppressed = current.m_isFlowSuppressed;
+                newValues = current.m_localValues.Set(local, newValue, treatNullValueAsNonexistent: !needChangeNotifications);
+                newChangeNotifications = current.m_localChangeNotifications;
+            }
+            else
+            {
+                // First AsyncLocal
+                newValues = AsyncLocalValueMap.Create(local, newValue, treatNullValueAsNonexistent: !needChangeNotifications);
+            }
+
+            //
+            // Either copy the change notification array, or create a new one, depending on whether we need to add a new item.
+            //
+            if (needChangeNotifications)
+            {
+                if (hadPreviousValue)
+                {
+                    Debug.Assert(newChangeNotifications != null);
+                    Debug.Assert(Array.IndexOf(newChangeNotifications, local) >= 0);
+                }
+                else if (newChangeNotifications == null)
+                {
+                    newChangeNotifications = new IAsyncLocal[1] { local };
+                }
+                else
+                {
+                    int newNotificationIndex = newChangeNotifications.Length;
+                    Array.Resize(ref newChangeNotifications, newNotificationIndex + 1);
+                    newChangeNotifications[newNotificationIndex] = local;
+                }
+            }
+
+            Thread.CurrentThread.ExecutionContext = 
+                (!isFlowSuppressed && AsyncLocalValueMap.IsEmpty(newValues)) ?
+                null : // No values, return to Default context
+                new ExecutionContext(newValues, newChangeNotifications, isFlowSuppressed);
+
+            if (needChangeNotifications)
+            {
+                local.OnValueChanged(previousValue, newValue, contextChanged: false);
+            }
+        }
+
+        public ExecutionContext CreateCopy()
+        {
+            return this; // since CoreCLR's ExecutionContext is immutable, we don't need to create copies.
+        }
+
+        public void Dispose()
+        {
+            // For CLR compat only
+        }
+    }
+
+    public struct AsyncFlowControl : IDisposable
+    {
+        private Thread _thread;
+
+        internal void Initialize(Thread currentThread)
+        {
+            Debug.Assert(currentThread == Thread.CurrentThread);
+            _thread = currentThread;
+        }
+
+        public void Undo()
+        {
+            if (_thread == null)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_CannotUseAFCMultiple);
+            }
+            if (Thread.CurrentThread != _thread)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_CannotUseAFCOtherThread);
+            }
+
+            // An async flow control cannot be undone when a different execution context is applied. The desktop framework
+            // mutates the execution context when its state changes, and only changes the instance when an execution context
+            // is applied (for instance, through ExecutionContext.Run). The framework prevents a suppressed-flow execution
+            // context from being applied by returning null from ExecutionContext.Capture, so the only type of execution
+            // context that can be applied is one whose flow is not suppressed. After suppressing flow and changing an async
+            // local's value, the desktop framework verifies that a different execution context has not been applied by
+            // checking the execution context instance against the one saved from when flow was suppressed. In .NET Core,
+            // since the execution context instance will change after changing the async local's value, it verifies that a
+            // different execution context has not been applied, by instead ensuring that the current execution context's
+            // flow is suppressed.
+            if (!ExecutionContext.IsFlowSuppressed())
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_AsyncFlowCtrlCtxMismatch);
+            }
+
+            _thread = null;
+            ExecutionContext.RestoreFlow();
+        }
+
+        public void Dispose()
+        {
+            Undo();
+        }
+
+        public override bool Equals(object obj)
+        {
+            return obj is AsyncFlowControl && Equals((AsyncFlowControl)obj);
+        }
+
+        public bool Equals(AsyncFlowControl obj)
+        {
+            return _thread == obj._thread;
+        }
+
+        public override int GetHashCode()
+        {
+            return _thread?.GetHashCode() ?? 0;
+        }
+
+        public static bool operator ==(AsyncFlowControl a, AsyncFlowControl b)
+        {
+            return a.Equals(b);
+        }
+
+        public static bool operator !=(AsyncFlowControl a, AsyncFlowControl b)
+        {
+            return !(a == b);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/LazyInitializer.cs b/src/System.Private.CoreLib/shared/System/Threading/LazyInitializer.cs
new file mode 100644
index 0000000000..f422ab9172
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/LazyInitializer.cs
@@ -0,0 +1,288 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+// a set of lightweight static helpers for lazy initialization.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Diagnostics;
+
+namespace System.Threading
+{
+    /// <summary>
+    /// Provides lazy initialization routines.
+    /// </summary>
+    /// <remarks>
+    /// These routines avoid needing to allocate a dedicated, lazy-initialization instance, instead using
+    /// references to ensure targets have been initialized as they are accessed.
+    /// </remarks>
+    public static class LazyInitializer
+    {
+        /// <summary>
+        /// Initializes a target reference type with the type's default constructor if the target has not
+        /// already been initialized.
+        /// </summary>
+        /// <typeparam name="T">The reference type of the reference to be initialized.</typeparam>
+        /// <param name="target">A reference of type <typeparamref name="T"/> to initialize if it has not
+        /// already been initialized.</param>
+        /// <returns>The initialized reference of type <typeparamref name="T"/>.</returns>
+        /// <exception cref="T:System.MissingMemberException">Type <typeparamref name="T"/> does not have a default
+        /// constructor.</exception>
+        /// <exception cref="T:System.MemberAccessException">
+        /// Permissions to access the constructor of type <typeparamref name="T"/> were missing.
+        /// </exception>
+        /// <remarks>
+        /// <para>
+        /// This method may only be used on reference types. To ensure initialization of value
+        /// types, see other overloads of EnsureInitialized.
+        /// </para>
+        /// <para>
+        /// This method may be used concurrently by multiple threads to initialize <paramref name="target"/>.  
+        /// In the event that multiple threads access this method concurrently, multiple instances of <typeparamref name="T"/>
+        /// may be created, but only one will be stored into <paramref name="target"/>. In such an occurrence, this method will not dispose of the
+        /// objects that were not stored.  If such objects must be disposed, it is up to the caller to determine 
+        /// if an object was not used and to then dispose of the object appropriately.
+        /// </para>
+        /// </remarks>
+        public static T EnsureInitialized<T>(ref T target) where T : class =>
+            Volatile.Read(ref target) ?? EnsureInitializedCore(ref target);
+
+        /// <summary>
+        /// Initializes a target reference type with the type's default constructor (slow path)
+        /// </summary>
+        /// <typeparam name="T">The reference type of the reference to be initialized.</typeparam>
+        /// <param name="target">The variable that need to be initialized</param>
+        /// <returns>The initialized variable</returns>
+        private static T EnsureInitializedCore<T>(ref T target) where T : class
+        {
+            try
+            {
+                Interlocked.CompareExchange(ref target, Activator.CreateInstance<T>(), null);
+            }
+            catch (MissingMethodException)
+            {
+                throw new MissingMemberException(SR.Lazy_CreateValue_NoParameterlessCtorForT);
+            }
+
+            Debug.Assert(target != null);
+            return target;
+        }
+
+        /// <summary>
+        /// Initializes a target reference type using the specified function if it has not already been
+        /// initialized.
+        /// </summary>
+        /// <typeparam name="T">The reference type of the reference to be initialized.</typeparam>
+        /// <param name="target">The reference of type <typeparamref name="T"/> to initialize if it has not
+        /// already been initialized.</param>
+        /// <param name="valueFactory">The <see cref="T:System.Func{T}"/> invoked to initialize the
+        /// reference.</param>
+        /// <returns>The initialized reference of type <typeparamref name="T"/>.</returns>
+        /// <exception cref="T:System.MissingMemberException">Type <typeparamref name="T"/> does not have a
+        /// default constructor.</exception>
+        /// <exception cref="T:System.InvalidOperationException"><paramref name="valueFactory"/> returned
+        /// null.</exception>
+        /// <remarks>
+        /// <para>
+        /// This method may only be used on reference types, and <paramref name="valueFactory"/> may
+        /// not return a null reference (Nothing in Visual Basic). To ensure initialization of value types or
+        /// to allow null reference types, see other overloads of EnsureInitialized.
+        /// </para>
+        /// <para>
+        /// This method may be used concurrently by multiple threads to initialize <paramref name="target"/>.  
+        /// In the event that multiple threads access this method concurrently, multiple instances of <typeparamref name="T"/>
+        /// may be created, but only one will be stored into <paramref name="target"/>. In such an occurrence, this method will not dispose of the
+        /// objects that were not stored.  If such objects must be disposed, it is up to the caller to determine 
+        /// if an object was not used and to then dispose of the object appropriately.
+        /// </para>
+        /// </remarks>
+        public static T EnsureInitialized<T>(ref T target, Func<T> valueFactory) where T : class =>
+            Volatile.Read(ref target) ?? EnsureInitializedCore(ref target, valueFactory);
+
+        /// <summary>
+        /// Initialize the target using the given delegate (slow path).
+        /// </summary>
+        /// <typeparam name="T">The reference type of the reference to be initialized.</typeparam>
+        /// <param name="target">The variable that need to be initialized</param>
+        /// <param name="valueFactory">The delegate that will be executed to initialize the target</param>
+        /// <returns>The initialized variable</returns>
+        private static T EnsureInitializedCore<T>(ref T target, Func<T> valueFactory) where T : class
+        {
+            T value = valueFactory();
+            if (value == null)
+            {
+                throw new InvalidOperationException(SR.Lazy_StaticInit_InvalidOperation);
+            }
+
+            Interlocked.CompareExchange(ref target, value, null);
+            Debug.Assert(target != null);
+            return target;
+        }
+
+        /// <summary>
+        /// Initializes a target reference or value type with its default constructor if it has not already
+        /// been initialized.
+        /// </summary>
+        /// <typeparam name="T">The type of the reference to be initialized.</typeparam>
+        /// <param name="target">A reference or value of type <typeparamref name="T"/> to initialize if it
+        /// has not already been initialized.</param>
+        /// <param name="initialized">A reference to a boolean that determines whether the target has already
+        /// been initialized.</param>
+        /// <param name="syncLock">A reference to an object used as the mutually exclusive lock for initializing
+        /// <paramref name="target"/>. If <paramref name="syncLock"/> is null, a new object will be instantiated.</param>
+        /// <returns>The initialized value of type <typeparamref name="T"/>.</returns>
+        public static T EnsureInitialized<T>(ref T target, ref bool initialized, ref object syncLock)
+        {
+            // Fast path.
+            if (Volatile.Read(ref initialized))
+            {
+                return target;
+            }
+
+            return EnsureInitializedCore(ref target, ref initialized, ref syncLock);
+        }
+
+        /// <summary>
+        /// Ensure the target is initialized and return the value (slow path). This overload permits nulls
+        /// and also works for value type targets. Uses the type's default constructor to create the value.
+        /// </summary>
+        /// <typeparam name="T">The type of target.</typeparam>
+        /// <param name="target">A reference to the target to be initialized.</param>
+        /// <param name="initialized">A reference to a location tracking whether the target has been initialized.</param>
+        /// <param name="syncLock">A reference to a location containing a mutual exclusive lock. If <paramref name="syncLock"/> is null, 
+        /// a new object will be instantiated.</param>
+        /// </param>
+        /// <returns>The initialized object.</returns>
+        private static T EnsureInitializedCore<T>(ref T target, ref bool initialized, ref object syncLock)
+        {
+            // Lazily initialize the lock if necessary and then double check if initialization is still required.
+            lock (EnsureLockInitialized(ref syncLock))
+            {
+                if (!Volatile.Read(ref initialized))
+                {
+                    try
+                    {
+                        target = Activator.CreateInstance<T>();
+                    }
+                    catch (MissingMethodException)
+                    {
+                        throw new MissingMemberException(SR.Lazy_CreateValue_NoParameterlessCtorForT);
+                    }
+
+                    Volatile.Write(ref initialized, true);
+                }
+            }
+
+            return target;
+        }
+
+        /// <summary>
+        /// Initializes a target reference or value type with a specified function if it has not already been
+        /// initialized.
+        /// </summary>
+        /// <typeparam name="T">The type of the reference to be initialized.</typeparam>
+        /// <param name="target">A reference or value of type <typeparamref name="T"/> to initialize if it
+        /// has not already been initialized.</param>
+        /// <param name="initialized">A reference to a boolean that determines whether the target has already
+        /// been initialized.</param>
+        /// <param name="syncLock">A reference to an object used as the mutually exclusive lock for initializing
+        /// <paramref name="target"/>. If <paramref name="syncLock"/> is null, a new object will be instantiated.</param>
+        /// <param name="valueFactory">The <see cref="T:System.Func{T}"/> invoked to initialize the
+        /// reference or value.</param>
+        /// <returns>The initialized value of type <typeparamref name="T"/>.</returns>
+        public static T EnsureInitialized<T>(ref T target, ref bool initialized, ref object syncLock, Func<T> valueFactory)
+        {
+            // Fast path.
+            if (Volatile.Read(ref initialized))
+            {
+                return target;
+            }
+
+            return EnsureInitializedCore(ref target, ref initialized, ref syncLock, valueFactory);
+        }
+
+        /// <summary>
+        /// Ensure the target is initialized and return the value (slow path). This overload permits nulls
+        /// and also works for value type targets. Uses the supplied function to create the value.
+        /// </summary>
+        /// <typeparam name="T">The type of target.</typeparam>
+        /// <param name="target">A reference to the target to be initialized.</param>
+        /// <param name="initialized">A reference to a location tracking whether the target has been initialized.</param>
+        /// <param name="syncLock">A reference to a location containing a mutual exclusive lock. If <paramref name="syncLock"/> is null, 
+        /// a new object will be instantiated.</param>
+        /// <param name="valueFactory">
+        /// The <see cref="T:System.Func{T}"/> to invoke in order to produce the lazily-initialized value.
+        /// </param>
+        /// <returns>The initialized object.</returns>
+        private static T EnsureInitializedCore<T>(ref T target, ref bool initialized, ref object syncLock, Func<T> valueFactory)
+        {
+            // Lazily initialize the lock if necessary and then double check if initialization is still required.
+            lock (EnsureLockInitialized(ref syncLock))
+            {
+                if (!Volatile.Read(ref initialized))
+                {
+                    target = valueFactory();
+                    Volatile.Write(ref initialized, true);
+                }
+            }
+
+            return target;
+        }
+
+        /// <summary>
+        /// Initializes a target reference type with a specified function if it has not already been initialized.
+        /// </summary>
+        /// <typeparam name="T">The type of the reference to be initialized. Has to be reference type.</typeparam>
+        /// <param name="target">A reference of type <typeparamref name="T"/> to initialize if it has not already been initialized.</param>
+        /// <param name="syncLock">A reference to an object used as the mutually exclusive lock for initializing
+        /// <paramref name="target"/>. If <paramref name="syncLock"/> is null, a new object will be instantiated.</param>
+        /// <param name="valueFactory">The <see cref="T:System.Func{T}"/> invoked to initialize the reference.</param>
+        /// <returns>The initialized value of type <typeparamref name="T"/>.</returns>
+        public static T EnsureInitialized<T>(ref T target, ref object syncLock, Func<T> valueFactory) where T : class =>
+            Volatile.Read(ref target) ?? EnsureInitializedCore(ref target, ref syncLock, valueFactory);
+
+        /// <summary>
+        /// Ensure the target is initialized and return the value (slow path). This overload works only for reference type targets.
+        /// Uses the supplied function to create the value.
+        /// </summary>
+        /// <typeparam name="T">The type of target. Has to be reference type.</typeparam>
+        /// <param name="target">A reference to the target to be initialized.</param>
+        /// <param name="syncLock">A reference to a location containing a mutual exclusive lock. If <paramref name="syncLock"/> is null, 
+        /// a new object will be instantiated.</param>
+        /// <param name="valueFactory">
+        /// The <see cref="T:System.Func{T}"/> to invoke in order to produce the lazily-initialized value.
+        /// </param>
+        /// <returns>The initialized object.</returns>
+        private static T EnsureInitializedCore<T>(ref T target, ref object syncLock, Func<T> valueFactory) where T : class
+        {
+            // Lazily initialize the lock if necessary and then double check if initialization is still required.
+            lock (EnsureLockInitialized(ref syncLock))
+            {
+                if (Volatile.Read(ref target) == null)
+                {
+                    Volatile.Write(ref target, valueFactory());
+                    if (target == null)
+                    {
+                        throw new InvalidOperationException(SR.Lazy_StaticInit_InvalidOperation);
+                    }
+                }
+            }
+
+            return target;
+        }
+
+        /// <summary>
+        /// Ensure the lock object is initialized.
+        /// </summary>
+        /// <param name="syncLock">A reference to a location containing a mutual exclusive lock. If <paramref name="syncLock"/> is null,
+        /// a new object will be instantiated.</param>
+        /// <returns>Initialized lock object.</returns>
+        private static object EnsureLockInitialized(ref object syncLock) =>
+            syncLock ??
+            Interlocked.CompareExchange(ref syncLock, new object(), null) ??
+            syncLock;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/LazyThreadSafetyMode.cs b/src/System.Private.CoreLib/shared/System/Threading/LazyThreadSafetyMode.cs
new file mode 100644
index 0000000000..2d13f23762
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/LazyThreadSafetyMode.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+// a set of lightweight static helpers for lazy initialization.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+namespace System.Threading
+{
+    /// <summary>
+    /// Specifies how a <see cref="T:System.Threading.Lazy{T}"/> instance should synchronize access among multiple threads.
+    /// </summary>
+    public enum LazyThreadSafetyMode
+    {
+        /// <summary>
+        /// This mode makes no guarantees around the thread-safety of the <see cref="T:System.Threading.Lazy{T}"/> instance.  If used from multiple threads, the behavior of the <see cref="T:System.Threading.Lazy{T}"/> is undefined.
+        /// This mode should be used when a <see cref="T:System.Threading.Lazy{T}"/> is guaranteed to never be initialized from more than one thread simultaneously and high performance is crucial. 
+        /// If valueFactory throws an exception when the <see cref="T:System.Threading.Lazy{T}"/> is initialized, the exception will be cached and returned on subsequent accesses to Value. Also, if valueFactory recursively
+        /// accesses Value on this <see cref="T:System.Threading.Lazy{T}"/> instance, a <see cref="T:System.InvalidOperationException"/> will be thrown.
+        /// </summary>
+        None,
+
+        /// <summary>
+        /// When multiple threads attempt to simultaneously initialize a <see cref="T:System.Threading.Lazy{T}"/> instance, this mode allows each thread to execute the
+        /// valueFactory but only the first thread to complete initialization will be allowed to set the final value of the  <see cref="T:System.Threading.Lazy{T}"/>.
+        /// Once initialized successfully, any future calls to Value will return the cached result.  If valueFactory throws an exception on any thread, that exception will be
+        /// propagated out of Value. If any thread executes valueFactory without throwing an exception and, therefore, successfully sets the value, that value will be returned on
+        /// subsequent accesses to Value from any thread.  If no thread succeeds in setting the value, IsValueCreated will remain false and subsequent accesses to Value will result in
+        /// the valueFactory delegate re-executing.  Also, if valueFactory recursively accesses Value on this  <see cref="T:System.Threading.Lazy{T}"/> instance, an exception will NOT be thrown.
+        /// </summary>
+        PublicationOnly,
+
+        /// <summary>
+        /// This mode uses locks to ensure that only a single thread can initialize a <see cref="T:System.Threading.Lazy{T}"/> instance in a thread-safe manner.  In general,
+        /// taken if this mode is used in conjunction with a <see cref="T:System.Threading.Lazy{T}"/> valueFactory delegate that uses locks internally, a deadlock can occur if not
+        /// handled carefully.  If valueFactory throws an exception when the<see cref="T:System.Threading.Lazy{T}"/> is initialized, the exception will be cached and returned on
+        /// subsequent accesses to Value. Also, if valueFactory recursively accesses Value on this <see cref="T:System.Threading.Lazy{T}"/> instance, a  <see cref="T:System.InvalidOperationException"/> will be thrown.
+        /// </summary>
+        ExecutionAndPublication
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/LockRecursionException.cs b/src/System.Private.CoreLib/shared/System/Threading/LockRecursionException.cs
new file mode 100644
index 0000000000..c76c7a5040
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/LockRecursionException.cs
@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System.Threading
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class LockRecursionException : System.Exception
+    {
+        public LockRecursionException()
+        {
+        }
+
+        public LockRecursionException(string message)
+            : base(message)
+        {
+        }
+
+        public LockRecursionException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
+
+        protected LockRecursionException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/ManualResetEvent.cs b/src/System.Private.CoreLib/shared/System/Threading/ManualResetEvent.cs
new file mode 100644
index 0000000000..4b8d61f960
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/ManualResetEvent.cs
@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Threading
+{
+    public sealed class ManualResetEvent : EventWaitHandle
+    {
+        public ManualResetEvent(bool initialState) : base(initialState, EventResetMode.ManualReset) { }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Threading/ParameterizedThreadStart.cs b/src/System.Private.CoreLib/shared/System/Threading/ParameterizedThreadStart.cs
new file mode 100644
index 0000000000..c0f29e8e80
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/ParameterizedThreadStart.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: This class is a Delegate which defines the start method
+**  for starting a thread.  That method must match this delegate.
+**
+**
+=============================================================================*/
+
+namespace System.Threading
+{
+    public delegate void ParameterizedThreadStart(object obj);
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/ReaderWriterLockSlim.cs b/src/System.Private.CoreLib/shared/System/Threading/ReaderWriterLockSlim.cs
new file mode 100644
index 0000000000..45175488e7
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/ReaderWriterLockSlim.cs
@@ -0,0 +1,1682 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Internal.Runtime.Augments;
+using System.Diagnostics; // for TraceInformation
+using System.Runtime.CompilerServices;
+
+namespace System.Threading
+{
+    public enum LockRecursionPolicy
+    {
+        NoRecursion = 0,
+        SupportsRecursion = 1,
+    }
+
+    //
+    // ReaderWriterCount tracks how many of each kind of lock is held by each thread.
+    // We keep a linked list for each thread, attached to a ThreadStatic field.
+    // These are reused wherever possible, so that a given thread will only
+    // allocate N of these, where N is the maximum number of locks held simultaneously
+    // by that thread.
+    // 
+    internal class ReaderWriterCount
+    {
+        // Which lock does this object belong to?  This is a numeric ID for two reasons:
+        // 1) We don't want this field to keep the lock object alive, and a WeakReference would
+        //    be too expensive.
+        // 2) Setting the value of a long is faster than setting the value of a reference.
+        //    The "hot" paths in ReaderWriterLockSlim are short enough that this actually
+        //    matters.
+        public long lockID;
+
+        // How many reader locks does this thread hold on this ReaderWriterLockSlim instance?
+        public int readercount;
+
+        // Ditto for writer/upgrader counts.  These are only used if the lock allows recursion.
+        // But we have to have the fields on every ReaderWriterCount instance, because 
+        // we reuse it for different locks.
+        public int writercount;
+        public int upgradecount;
+
+        // Next RWC in this thread's list.
+        public ReaderWriterCount next;
+    }
+
+    /// <summary>
+    /// A reader-writer lock implementation that is intended to be simple, yet very
+    /// efficient.  In particular only 1 interlocked operation is taken for any lock 
+    /// operation (we use spin locks to achieve this).  The spin lock is never held
+    /// for more than a few instructions (in particular, we never call event APIs
+    /// or in fact any non-trivial API while holding the spin lock).   
+    /// </summary>
+    public class ReaderWriterLockSlim : IDisposable
+    {
+        private static readonly int ProcessorCount = Environment.ProcessorCount;
+
+        //Specifying if the lock can be reacquired recursively.
+        private readonly bool _fIsReentrant;
+
+        // Lock specification for _spinLock:  This lock protects exactly the local fields associated with this
+        // instance of ReaderWriterLockSlim.  It does NOT protect the memory associated with 
+        // the events that hang off this lock (eg writeEvent, readEvent upgradeEvent).
+        SpinLock _spinLock;
+
+        // These variables allow use to avoid Setting events (which is expensive) if we don't have to. 
+        private uint _numWriteWaiters;        // maximum number of threads that can be doing a WaitOne on the writeEvent 
+        private uint _numReadWaiters;         // maximum number of threads that can be doing a WaitOne on the readEvent
+        private uint _numWriteUpgradeWaiters;      // maximum number of threads that can be doing a WaitOne on the upgradeEvent (at most 1). 
+        private uint _numUpgradeWaiters;
+
+        private WaiterStates _waiterStates;
+
+        private int _upgradeLockOwnerId;
+        private int _writeLockOwnerId;
+
+        // conditions we wait on. 
+        private EventWaitHandle _writeEvent;    // threads waiting to acquire a write lock go here.
+        private EventWaitHandle _readEvent;     // threads waiting to acquire a read lock go here (will be released in bulk)
+        private EventWaitHandle _upgradeEvent;  // thread waiting to acquire the upgrade lock
+        private EventWaitHandle _waitUpgradeEvent;  // thread waiting to upgrade from the upgrade lock to a write lock go here (at most one)
+
+        // Every lock instance has a unique ID, which is used by ReaderWriterCount to associate itself with the lock
+        // without holding a reference to it.
+        private static long s_nextLockID;
+        private long _lockID;
+
+        // See comments on ReaderWriterCount.
+        [ThreadStatic]
+        private static ReaderWriterCount t_rwc;
+
+        private bool _fUpgradeThreadHoldingRead;
+
+        private const int MaxSpinCount = 20;
+
+        //The uint, that contains info like if the writer lock is held, num of 
+        //readers etc.
+        private uint _owners;
+
+        //Various R/W masks
+        //Note:
+        //The Uint is divided as follows:
+        //
+        //Writer-Owned  Waiting-Writers   Waiting Upgraders     Num-Readers
+        //    31          30                 29                 28.......0
+        //
+        //Dividing the uint, allows to vastly simplify logic for checking if a 
+        //reader should go in etc. Setting the writer bit will automatically
+        //make the value of the uint much larger than the max num of readers 
+        //allowed, thus causing the check for max_readers to fail. 
+
+        private const uint WRITER_HELD = 0x80000000;
+        private const uint WAITING_WRITERS = 0x40000000;
+        private const uint WAITING_UPGRADER = 0x20000000;
+
+        //The max readers is actually one less then its theoretical max.
+        //This is done in order to prevent reader count overflows. If the reader
+        //count reaches max, other readers will wait.
+        private const uint MAX_READER = 0x10000000 - 2;
+
+        private const uint READER_MASK = 0x10000000 - 1;
+
+        private bool _fDisposed;
+
+        private void InitializeThreadCounts()
+        {
+            _upgradeLockOwnerId = -1;
+            _writeLockOwnerId = -1;
+        }
+
+        public ReaderWriterLockSlim()
+            : this(LockRecursionPolicy.NoRecursion)
+        {
+        }
+
+        public ReaderWriterLockSlim(LockRecursionPolicy recursionPolicy)
+        {
+            if (recursionPolicy == LockRecursionPolicy.SupportsRecursion)
+            {
+                _fIsReentrant = true;
+            }
+            InitializeThreadCounts();
+            _waiterStates = WaiterStates.NoWaiters;
+            _lockID = Interlocked.Increment(ref s_nextLockID);
+        }
+
+        private bool HasNoWaiters
+        {
+            get
+            {
+#if DEBUG
+                Debug.Assert(_spinLock.IsHeld);
+#endif
+
+                return (_waiterStates & WaiterStates.NoWaiters) != WaiterStates.None;
+            }
+            set
+            {
+#if DEBUG
+                Debug.Assert(_spinLock.IsHeld);
+#endif
+
+                if (value)
+                {
+                    _waiterStates |= WaiterStates.NoWaiters;
+                }
+                else
+                {
+                    _waiterStates &= ~WaiterStates.NoWaiters;
+                }
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static bool IsRWEntryEmpty(ReaderWriterCount rwc)
+        {
+            if (rwc.lockID == 0)
+                return true;
+            else if (rwc.readercount == 0 && rwc.writercount == 0 && rwc.upgradecount == 0)
+                return true;
+            else
+                return false;
+        }
+
+        private bool IsRwHashEntryChanged(ReaderWriterCount lrwc)
+        {
+            return lrwc.lockID != _lockID;
+        }
+
+        /// <summary>
+        /// This routine retrieves/sets the per-thread counts needed to enforce the
+        /// various rules related to acquiring the lock. 
+        /// 
+        /// DontAllocate is set to true if the caller just wants to get an existing
+        /// entry for this thread, but doesn't want to add one if an existing one
+        /// could not be found.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private ReaderWriterCount GetThreadRWCount(bool dontAllocate)
+        {
+            ReaderWriterCount rwc = t_rwc;
+            ReaderWriterCount empty = null;
+            while (rwc != null)
+            {
+                if (rwc.lockID == _lockID)
+                    return rwc;
+
+                if (!dontAllocate && empty == null && IsRWEntryEmpty(rwc))
+                    empty = rwc;
+
+                rwc = rwc.next;
+            }
+
+            if (dontAllocate)
+                return null;
+
+            if (empty == null)
+            {
+                empty = new ReaderWriterCount();
+                empty.next = t_rwc;
+                t_rwc = empty;
+            }
+
+            empty.lockID = _lockID;
+            return empty;
+        }
+
+        public void EnterReadLock()
+        {
+            TryEnterReadLock(-1);
+        }
+
+        //
+        // Common timeout support
+        //
+        private struct TimeoutTracker
+        {
+            private int _total;
+            private int _start;
+
+            public TimeoutTracker(TimeSpan timeout)
+            {
+                long ltm = (long)timeout.TotalMilliseconds;
+                if (ltm < -1 || ltm > (long)Int32.MaxValue)
+                    throw new ArgumentOutOfRangeException(nameof(timeout));
+                _total = (int)ltm;
+                if (_total != -1 && _total != 0)
+                    _start = Environment.TickCount;
+                else
+                    _start = 0;
+            }
+
+            public TimeoutTracker(int millisecondsTimeout)
+            {
+                if (millisecondsTimeout < -1)
+                    throw new ArgumentOutOfRangeException(nameof(millisecondsTimeout));
+                _total = millisecondsTimeout;
+                if (_total != -1 && _total != 0)
+                    _start = Environment.TickCount;
+                else
+                    _start = 0;
+            }
+
+            public int RemainingMilliseconds
+            {
+                get
+                {
+                    if (_total == -1 || _total == 0)
+                        return _total;
+
+                    int elapsed = Environment.TickCount - _start;
+                    // elapsed may be negative if TickCount has overflowed by 2^31 milliseconds.
+                    if (elapsed < 0 || elapsed >= _total)
+                        return 0;
+
+                    return _total - elapsed;
+                }
+            }
+
+            public bool IsExpired
+            {
+                get
+                {
+                    return RemainingMilliseconds == 0;
+                }
+            }
+        }
+
+        public bool TryEnterReadLock(TimeSpan timeout)
+        {
+            return TryEnterReadLock(new TimeoutTracker(timeout));
+        }
+
+        public bool TryEnterReadLock(int millisecondsTimeout)
+        {
+            return TryEnterReadLock(new TimeoutTracker(millisecondsTimeout));
+        }
+
+        private bool TryEnterReadLock(TimeoutTracker timeout)
+        {
+            return TryEnterReadLockCore(timeout);
+        }
+
+        private bool TryEnterReadLockCore(TimeoutTracker timeout)
+        {
+            if (_fDisposed)
+                throw new ObjectDisposedException(null);
+
+            ReaderWriterCount lrwc = null;
+            int id = Environment.CurrentManagedThreadId;
+
+            if (!_fIsReentrant)
+            {
+                if (id == _writeLockOwnerId)
+                {
+                    //Check for AW->AR
+                    throw new LockRecursionException(SR.LockRecursionException_ReadAfterWriteNotAllowed);
+                }
+
+                _spinLock.Enter(EnterSpinLockReason.EnterAnyRead);
+
+                lrwc = GetThreadRWCount(false);
+
+                //Check if the reader lock is already acquired. Note, we could
+                //check the presence of a reader by not allocating rwc (But that 
+                //would lead to two lookups in the common case. It's better to keep
+                //a count in the structure).
+                if (lrwc.readercount > 0)
+                {
+                    _spinLock.Exit();
+                    throw new LockRecursionException(SR.LockRecursionException_RecursiveReadNotAllowed);
+                }
+                else if (id == _upgradeLockOwnerId)
+                {
+                    //The upgrade lock is already held.
+                    //Update the global read counts and exit.
+
+                    lrwc.readercount++;
+                    _owners++;
+                    _spinLock.Exit();
+                    return true;
+                }
+            }
+            else
+            {
+                _spinLock.Enter(EnterSpinLockReason.EnterAnyRead);
+                lrwc = GetThreadRWCount(false);
+                if (lrwc.readercount > 0)
+                {
+                    lrwc.readercount++;
+                    _spinLock.Exit();
+                    return true;
+                }
+                else if (id == _upgradeLockOwnerId)
+                {
+                    //The upgrade lock is already held.
+                    //Update the global read counts and exit.
+                    lrwc.readercount++;
+                    _owners++;
+                    _spinLock.Exit();
+                    _fUpgradeThreadHoldingRead = true;
+                    return true;
+                }
+                else if (id == _writeLockOwnerId)
+                {
+                    //The write lock is already held.
+                    //Update global read counts here,
+                    lrwc.readercount++;
+                    _owners++;
+                    _spinLock.Exit();
+                    return true;
+                }
+            }
+
+            bool retVal = true;
+            int spinCount = 0;
+
+            for (; ;)
+            {
+                // We can enter a read lock if there are only read-locks have been given out
+                // and a writer is not trying to get in.  
+
+                if (_owners < MAX_READER)
+                {
+                    // Good case, there is no contention, we are basically done
+                    _owners++;       // Indicate we have another reader
+                    lrwc.readercount++;
+                    break;
+                }
+
+                if (timeout.IsExpired)
+                {
+                    _spinLock.Exit();
+                    return false;
+                }
+
+                if (spinCount < MaxSpinCount && ShouldSpinForEnterAnyRead())
+                {
+                    _spinLock.Exit();
+                    spinCount++;
+                    SpinWait(spinCount);
+                    _spinLock.Enter(EnterSpinLockReason.EnterAnyRead);
+                    //The per-thread structure may have been recycled as the lock is acquired (due to message pumping), load again.
+                    if (IsRwHashEntryChanged(lrwc))
+                        lrwc = GetThreadRWCount(false);
+                    continue;
+                }
+
+                // Drat, we need to wait.  Mark that we have waiters and wait.  
+                if (_readEvent == null)      // Create the needed event 
+                {
+                    LazyCreateEvent(ref _readEvent, EnterLockType.Read);
+                    if (IsRwHashEntryChanged(lrwc))
+                        lrwc = GetThreadRWCount(false);
+                    continue;   // since we left the lock, start over. 
+                }
+
+                retVal = WaitOnEvent(_readEvent, ref _numReadWaiters, timeout, EnterLockType.Read);
+                if (!retVal)
+                {
+                    return false;
+                }
+                if (IsRwHashEntryChanged(lrwc))
+                    lrwc = GetThreadRWCount(false);
+            }
+
+            _spinLock.Exit();
+            return retVal;
+        }
+
+        public void EnterWriteLock()
+        {
+            TryEnterWriteLock(-1);
+        }
+
+        public bool TryEnterWriteLock(TimeSpan timeout)
+        {
+            return TryEnterWriteLock(new TimeoutTracker(timeout));
+        }
+
+        public bool TryEnterWriteLock(int millisecondsTimeout)
+        {
+            return TryEnterWriteLock(new TimeoutTracker(millisecondsTimeout));
+        }
+
+        private bool TryEnterWriteLock(TimeoutTracker timeout)
+        {
+            return TryEnterWriteLockCore(timeout);
+        }
+
+        private bool TryEnterWriteLockCore(TimeoutTracker timeout)
+        {
+            if (_fDisposed)
+                throw new ObjectDisposedException(null);
+
+            int id = Environment.CurrentManagedThreadId;
+            ReaderWriterCount lrwc;
+            bool upgradingToWrite = false;
+
+            if (!_fIsReentrant)
+            {
+                EnterSpinLockReason enterMyLockReason;
+                if (id == _writeLockOwnerId)
+                {
+                    //Check for AW->AW
+                    throw new LockRecursionException(SR.LockRecursionException_RecursiveWriteNotAllowed);
+                }
+                else if (id == _upgradeLockOwnerId)
+                {
+                    //AU->AW case is allowed once.
+                    upgradingToWrite = true;
+                    enterMyLockReason = EnterSpinLockReason.UpgradeToWrite;
+                }
+                else
+                {
+                    enterMyLockReason = EnterSpinLockReason.EnterWrite;
+                }
+                _spinLock.Enter(enterMyLockReason);
+
+                lrwc = GetThreadRWCount(true);
+
+                //Can't acquire write lock with reader lock held. 
+                if (lrwc != null && lrwc.readercount > 0)
+                {
+                    _spinLock.Exit();
+                    throw new LockRecursionException(SR.LockRecursionException_WriteAfterReadNotAllowed);
+                }
+            }
+            else
+            {
+                EnterSpinLockReason enterMyLockReason;
+                if (id == _writeLockOwnerId)
+                {
+                    enterMyLockReason = EnterSpinLockReason.EnterRecursiveWrite;
+                }
+                else if (id == _upgradeLockOwnerId)
+                {
+                    enterMyLockReason = EnterSpinLockReason.UpgradeToWrite;
+                }
+                else
+                {
+                    enterMyLockReason = EnterSpinLockReason.EnterWrite;
+                }
+                _spinLock.Enter(enterMyLockReason);
+
+                lrwc = GetThreadRWCount(false);
+
+                if (id == _writeLockOwnerId)
+                {
+                    lrwc.writercount++;
+                    _spinLock.Exit();
+                    return true;
+                }
+                else if (id == _upgradeLockOwnerId)
+                {
+                    upgradingToWrite = true;
+                }
+                else if (lrwc.readercount > 0)
+                {
+                    //Write locks may not be acquired if only read locks have been
+                    //acquired.
+                    _spinLock.Exit();
+                    throw new LockRecursionException(SR.LockRecursionException_WriteAfterReadNotAllowed);
+                }
+            }
+
+            bool retVal = true;
+            int spinCount = 0;
+
+            for (; ;)
+            {
+                if (IsWriterAcquired())
+                {
+                    // Good case, there is no contention, we are basically done
+                    SetWriterAcquired();
+                    break;
+                }
+
+                //Check if there is just one upgrader, and no readers.
+                //Assumption: Only one thread can have the upgrade lock, so the 
+                //following check will fail for all other threads that may sneak in 
+                //when the upgrading thread is waiting.
+
+                if (upgradingToWrite)
+                {
+                    uint readercount = GetNumReaders();
+
+                    if (readercount == 1)
+                    {
+                        //Good case again, there is just one upgrader, and no readers.
+                        SetWriterAcquired();    // indicate we have a writer.
+                        break;
+                    }
+                    else if (readercount == 2)
+                    {
+                        if (lrwc != null)
+                        {
+                            if (IsRwHashEntryChanged(lrwc))
+                                lrwc = GetThreadRWCount(false);
+
+                            if (lrwc.readercount > 0)
+                            {
+                                //This check is needed for EU->ER->EW case, as the owner count will be two.
+                                Debug.Assert(_fIsReentrant);
+                                Debug.Assert(_fUpgradeThreadHoldingRead);
+
+                                //Good case again, there is just one upgrader, and no readers.
+                                SetWriterAcquired();   // indicate we have a writer.
+                                break;
+                            }
+                        }
+                    }
+                }
+
+                if (timeout.IsExpired)
+                {
+                    _spinLock.Exit();
+                    return false;
+                }
+
+                if (spinCount < MaxSpinCount && ShouldSpinForEnterAnyWrite(upgradingToWrite))
+                {
+                    _spinLock.Exit();
+                    spinCount++;
+                    SpinWait(spinCount);
+                    _spinLock.Enter(upgradingToWrite ? EnterSpinLockReason.UpgradeToWrite : EnterSpinLockReason.EnterWrite);
+                    continue;
+                }
+
+                if (upgradingToWrite)
+                {
+                    if (_waitUpgradeEvent == null)   // Create the needed event
+                    {
+                        LazyCreateEvent(ref _waitUpgradeEvent, EnterLockType.UpgradeToWrite);
+                        continue;   // since we left the lock, start over. 
+                    }
+
+                    Debug.Assert(_numWriteUpgradeWaiters == 0, "There can be at most one thread with the upgrade lock held.");
+
+                    retVal = WaitOnEvent(_waitUpgradeEvent, ref _numWriteUpgradeWaiters, timeout, EnterLockType.UpgradeToWrite);
+
+                    //The lock is not held in case of failure.
+                    if (!retVal)
+                        return false;
+                }
+                else
+                {
+                    // Drat, we need to wait.  Mark that we have waiters and wait.
+                    if (_writeEvent == null)     // create the needed event.
+                    {
+                        LazyCreateEvent(ref _writeEvent, EnterLockType.Write);
+                        continue;   // since we left the lock, start over. 
+                    }
+
+                    retVal = WaitOnEvent(_writeEvent, ref _numWriteWaiters, timeout, EnterLockType.Write);
+                    //The lock is not held in case of failure.
+                    if (!retVal)
+                        return false;
+                }
+            }
+
+            Debug.Assert((_owners & WRITER_HELD) > 0);
+
+            if (_fIsReentrant)
+            {
+                if (IsRwHashEntryChanged(lrwc))
+                    lrwc = GetThreadRWCount(false);
+                lrwc.writercount++;
+            }
+
+            _spinLock.Exit();
+
+            _writeLockOwnerId = id;
+
+            return true;
+        }
+
+        public void EnterUpgradeableReadLock()
+        {
+            TryEnterUpgradeableReadLock(-1);
+        }
+
+        public bool TryEnterUpgradeableReadLock(TimeSpan timeout)
+        {
+            return TryEnterUpgradeableReadLock(new TimeoutTracker(timeout));
+        }
+
+        public bool TryEnterUpgradeableReadLock(int millisecondsTimeout)
+        {
+            return TryEnterUpgradeableReadLock(new TimeoutTracker(millisecondsTimeout));
+        }
+
+        private bool TryEnterUpgradeableReadLock(TimeoutTracker timeout)
+        {
+            return TryEnterUpgradeableReadLockCore(timeout);
+        }
+
+        private bool TryEnterUpgradeableReadLockCore(TimeoutTracker timeout)
+        {
+            if (_fDisposed)
+                throw new ObjectDisposedException(null);
+
+            int id = Environment.CurrentManagedThreadId;
+            ReaderWriterCount lrwc;
+
+            if (!_fIsReentrant)
+            {
+                if (id == _upgradeLockOwnerId)
+                {
+                    //Check for AU->AU
+                    throw new LockRecursionException(SR.LockRecursionException_RecursiveUpgradeNotAllowed);
+                }
+                else if (id == _writeLockOwnerId)
+                {
+                    //Check for AU->AW
+                    throw new LockRecursionException(SR.LockRecursionException_UpgradeAfterWriteNotAllowed);
+                }
+
+                _spinLock.Enter(EnterSpinLockReason.EnterAnyRead);
+                lrwc = GetThreadRWCount(true);
+                //Can't acquire upgrade lock with reader lock held. 
+                if (lrwc != null && lrwc.readercount > 0)
+                {
+                    _spinLock.Exit();
+                    throw new LockRecursionException(SR.LockRecursionException_UpgradeAfterReadNotAllowed);
+                }
+            }
+            else
+            {
+                _spinLock.Enter(EnterSpinLockReason.EnterAnyRead);
+                lrwc = GetThreadRWCount(false);
+
+                if (id == _upgradeLockOwnerId)
+                {
+                    lrwc.upgradecount++;
+                    _spinLock.Exit();
+                    return true;
+                }
+                else if (id == _writeLockOwnerId)
+                {
+                    //Write lock is already held, Just update the global state 
+                    //to show presence of upgrader.
+                    Debug.Assert((_owners & WRITER_HELD) > 0);
+                    _owners++;
+                    _upgradeLockOwnerId = id;
+                    lrwc.upgradecount++;
+                    if (lrwc.readercount > 0)
+                        _fUpgradeThreadHoldingRead = true;
+                    _spinLock.Exit();
+                    return true;
+                }
+                else if (lrwc.readercount > 0)
+                {
+                    //Upgrade locks may not be acquired if only read locks have been
+                    //acquired.                
+                    _spinLock.Exit();
+                    throw new LockRecursionException(SR.LockRecursionException_UpgradeAfterReadNotAllowed);
+                }
+            }
+
+            bool retVal = true;
+            int spinCount = 0;
+
+            for (; ;)
+            {
+                //Once an upgrade lock is taken, it's like having a reader lock held
+                //until upgrade or downgrade operations are performed.              
+
+                if ((_upgradeLockOwnerId == -1) && (_owners < MAX_READER))
+                {
+                    _owners++;
+                    _upgradeLockOwnerId = id;
+                    break;
+                }
+
+                if (timeout.IsExpired)
+                {
+                    _spinLock.Exit();
+                    return false;
+                }
+
+                if (spinCount < MaxSpinCount && ShouldSpinForEnterAnyRead())
+                {
+                    _spinLock.Exit();
+                    spinCount++;
+                    SpinWait(spinCount);
+                    _spinLock.Enter(EnterSpinLockReason.EnterAnyRead);
+                    continue;
+                }
+
+                // Drat, we need to wait.  Mark that we have waiters and wait. 
+                if (_upgradeEvent == null)   // Create the needed event
+                {
+                    LazyCreateEvent(ref _upgradeEvent, EnterLockType.UpgradeableRead);
+                    continue;   // since we left the lock, start over. 
+                }
+
+                //Only one thread with the upgrade lock held can proceed.
+                retVal = WaitOnEvent(_upgradeEvent, ref _numUpgradeWaiters, timeout, EnterLockType.UpgradeableRead);
+                if (!retVal)
+                    return false;
+            }
+
+            if (_fIsReentrant)
+            {
+                //The lock may have been dropped getting here, so make a quick check to see whether some other
+                //thread did not grab the entry.
+                if (IsRwHashEntryChanged(lrwc))
+                    lrwc = GetThreadRWCount(false);
+                lrwc.upgradecount++;
+            }
+
+            _spinLock.Exit();
+
+            return true;
+        }
+
+        public void ExitReadLock()
+        {
+            ReaderWriterCount lrwc = null;
+
+            _spinLock.Enter(EnterSpinLockReason.ExitAnyRead);
+
+            lrwc = GetThreadRWCount(true);
+
+            if (lrwc == null || lrwc.readercount < 1)
+            {
+                //You have to be holding the read lock to make this call.
+                _spinLock.Exit();
+                throw new SynchronizationLockException(SR.SynchronizationLockException_MisMatchedRead);
+            }
+
+            if (_fIsReentrant)
+            {
+                if (lrwc.readercount > 1)
+                {
+                    lrwc.readercount--;
+                    _spinLock.Exit();
+                    return;
+                }
+
+                if (Environment.CurrentManagedThreadId == _upgradeLockOwnerId)
+                {
+                    _fUpgradeThreadHoldingRead = false;
+                }
+            }
+
+            Debug.Assert(_owners > 0, "ReleasingReaderLock: releasing lock and no read lock taken");
+
+            --_owners;
+
+            Debug.Assert(lrwc.readercount == 1);
+            lrwc.readercount--;
+
+            ExitAndWakeUpAppropriateWaiters();
+        }
+
+        public void ExitWriteLock()
+        {
+            ReaderWriterCount lrwc;
+            if (!_fIsReentrant)
+            {
+                if (Environment.CurrentManagedThreadId != _writeLockOwnerId)
+                {
+                    //You have to be holding the write lock to make this call.
+                    throw new SynchronizationLockException(SR.SynchronizationLockException_MisMatchedWrite);
+                }
+                _spinLock.Enter(EnterSpinLockReason.ExitAnyWrite);
+            }
+            else
+            {
+                _spinLock.Enter(EnterSpinLockReason.ExitAnyWrite);
+                lrwc = GetThreadRWCount(false);
+
+                if (lrwc == null)
+                {
+                    _spinLock.Exit();
+                    throw new SynchronizationLockException(SR.SynchronizationLockException_MisMatchedWrite);
+                }
+
+                if (lrwc.writercount < 1)
+                {
+                    _spinLock.Exit();
+                    throw new SynchronizationLockException(SR.SynchronizationLockException_MisMatchedWrite);
+                }
+
+                lrwc.writercount--;
+
+                if (lrwc.writercount > 0)
+                {
+                    _spinLock.Exit();
+                    return;
+                }
+            }
+
+            Debug.Assert((_owners & WRITER_HELD) > 0, "Calling ReleaseWriterLock when no write lock is held");
+
+            ClearWriterAcquired();
+
+            _writeLockOwnerId = -1;
+
+            ExitAndWakeUpAppropriateWaiters();
+        }
+
+        public void ExitUpgradeableReadLock()
+        {
+            ReaderWriterCount lrwc;
+            if (!_fIsReentrant)
+            {
+                if (Environment.CurrentManagedThreadId != _upgradeLockOwnerId)
+                {
+                    //You have to be holding the upgrade lock to make this call.
+                    throw new SynchronizationLockException(SR.SynchronizationLockException_MisMatchedUpgrade);
+                }
+                _spinLock.Enter(EnterSpinLockReason.ExitAnyRead);
+            }
+            else
+            {
+                _spinLock.Enter(EnterSpinLockReason.ExitAnyRead);
+                lrwc = GetThreadRWCount(true);
+
+                if (lrwc == null)
+                {
+                    _spinLock.Exit();
+                    throw new SynchronizationLockException(SR.SynchronizationLockException_MisMatchedUpgrade);
+                }
+
+                if (lrwc.upgradecount < 1)
+                {
+                    _spinLock.Exit();
+                    throw new SynchronizationLockException(SR.SynchronizationLockException_MisMatchedUpgrade);
+                }
+
+                lrwc.upgradecount--;
+
+                if (lrwc.upgradecount > 0)
+                {
+                    _spinLock.Exit();
+                    return;
+                }
+
+                _fUpgradeThreadHoldingRead = false;
+            }
+
+            _owners--;
+            _upgradeLockOwnerId = -1;
+
+            ExitAndWakeUpAppropriateWaiters();
+        }
+
+        /// <summary>
+        /// A routine for lazily creating a event outside the lock (so if errors
+        /// happen they are outside the lock and that we don't do much work
+        /// while holding a spin lock).  If all goes well, reenter the lock and
+        /// set 'waitEvent' 
+        /// </summary>
+        private void LazyCreateEvent(ref EventWaitHandle waitEvent, EnterLockType enterLockType)
+        {
+#if DEBUG
+            Debug.Assert(_spinLock.IsHeld);
+            Debug.Assert(waitEvent == null);
+#endif
+
+            _spinLock.Exit();
+
+            var newEvent =
+                new EventWaitHandle(
+                    false,
+                    enterLockType == EnterLockType.Read ? EventResetMode.ManualReset : EventResetMode.AutoReset);
+
+            EnterSpinLockReason enterMyLockReason;
+            switch (enterLockType)
+            {
+                case EnterLockType.Read:
+                case EnterLockType.UpgradeableRead:
+                    enterMyLockReason = EnterSpinLockReason.EnterAnyRead | EnterSpinLockReason.Wait;
+                    break;
+
+                case EnterLockType.Write:
+                    enterMyLockReason = EnterSpinLockReason.EnterWrite | EnterSpinLockReason.Wait;
+                    break;
+
+                default:
+                    Debug.Assert(enterLockType == EnterLockType.UpgradeToWrite);
+                    enterMyLockReason = EnterSpinLockReason.UpgradeToWrite | EnterSpinLockReason.Wait;
+                    break;
+            }
+            _spinLock.Enter(enterMyLockReason);
+
+            if (waitEvent == null)          // maybe someone snuck in. 
+                waitEvent = newEvent;
+            else
+                newEvent.Dispose();
+        }
+
+        /// <summary>
+        /// Waits on 'waitEvent' with a timeout  
+        /// Before the wait 'numWaiters' is incremented and is restored before leaving this routine.
+        /// </summary>
+        private bool WaitOnEvent(
+            EventWaitHandle waitEvent,
+            ref uint numWaiters,
+            TimeoutTracker timeout,
+            EnterLockType enterLockType)
+        {
+#if DEBUG
+            Debug.Assert(_spinLock.IsHeld);
+#endif
+
+            WaiterStates waiterSignaledState = WaiterStates.None;
+            EnterSpinLockReason enterMyLockReason;
+            switch (enterLockType)
+            {
+                case EnterLockType.UpgradeableRead:
+                    waiterSignaledState = WaiterStates.UpgradeableReadWaiterSignaled;
+                    goto case EnterLockType.Read;
+
+                case EnterLockType.Read:
+                    enterMyLockReason = EnterSpinLockReason.EnterAnyRead;
+                    break;
+
+                case EnterLockType.Write:
+                    waiterSignaledState = WaiterStates.WriteWaiterSignaled;
+                    enterMyLockReason = EnterSpinLockReason.EnterWrite;
+                    break;
+
+                default:
+                    Debug.Assert(enterLockType == EnterLockType.UpgradeToWrite);
+                    enterMyLockReason = EnterSpinLockReason.UpgradeToWrite;
+                    break;
+            }
+
+            // It was not possible to acquire the RW lock because some other thread was holding some type of lock. The other
+            // thread, when it releases its lock, will wake appropriate waiters. Along with resetting the wait event, clear the
+            // waiter signaled bit for this type of waiter if applicable, to indicate that a waiter of this type is no longer
+            // signaled.
+            //
+            // If the waiter signaled bit is not updated upon event reset, the following scenario would lead to deadlock:
+            //   - Thread T0 signals the write waiter event or the upgradeable read waiter event to wake a waiter
+            //   - There are no threads waiting on the event, but T1 is in WaitOnEvent() after exiting the spin lock and before
+            //     actually waiting on the event (that is, it's recorded that there is one waiter for the event). It remains in
+            //     this region for a while, in the repro case it typically gets context-switched out.
+            //   - T2 acquires the RW lock in some fashion that blocks T0 or T3 from acquiring the RW lock
+            //   - T0 or T3 fails to acquire the RW lock enough times for it to enter WaitOnEvent for the same event as T1
+            //   - T0 or T3 resets the event
+            //   - T2 releases the RW lock and does not wake a waiter because the reset at the previous step lost a signal but
+            //     _waiterStates was not updated to reflect that
+            //   - T1 and other threads begin waiting on the event, but there's no longer any thread that would wake them
+            if (waiterSignaledState != WaiterStates.None && (_waiterStates & waiterSignaledState) != WaiterStates.None)
+            {
+                _waiterStates &= ~waiterSignaledState;
+            }
+            waitEvent.Reset();
+
+            numWaiters++;
+            HasNoWaiters = false;
+
+            //Setting these bits will prevent new readers from getting in.
+            if (_numWriteWaiters == 1)
+                SetWritersWaiting();
+            if (_numWriteUpgradeWaiters == 1)
+                SetUpgraderWaiting();
+
+            bool waitSuccessful = false;
+            _spinLock.Exit();      // Do the wait outside of any lock
+
+            try
+            {
+                waitSuccessful = waitEvent.WaitOne(timeout.RemainingMilliseconds);
+            }
+            finally
+            {
+                _spinLock.Enter(enterMyLockReason);
+
+                --numWaiters;
+
+                if (waitSuccessful &&
+                    waiterSignaledState != WaiterStates.None &&
+                    (_waiterStates & waiterSignaledState) != WaiterStates.None)
+                {
+                    // Indicate that a signaled waiter of this type has woken. Since non-read waiters are signaled to wake one
+                    // at a time, we avoid waking up more than one waiter of that type upon successive enter/exit loops until
+                    // the signaled thread actually wakes up. For example, if there are multiple write waiters and one thread is
+                    // repeatedly entering and exiting a write lock, every exit would otherwise signal a different write waiter
+                    // to wake up unnecessarily when only one woken waiter may actually succeed in entering the write lock.
+                    _waiterStates &= ~waiterSignaledState;
+                }
+
+                if (_numWriteWaiters == 0 && _numWriteUpgradeWaiters == 0 && _numUpgradeWaiters == 0 && _numReadWaiters == 0)
+                    HasNoWaiters = true;
+
+                if (_numWriteWaiters == 0)
+                    ClearWritersWaiting();
+                if (_numWriteUpgradeWaiters == 0)
+                    ClearUpgraderWaiting();
+
+                if (!waitSuccessful)        // We may also be about to throw for some reason.  Exit myLock.
+                {
+                    if (enterLockType >= EnterLockType.Write)
+                    {
+                        // Write waiters block read waiters from acquiring the lock. Since this was the last write waiter, try
+                        // to wake up the appropriate read waiters.
+                        ExitAndWakeUpAppropriateReadWaiters();
+                    }
+                    else
+                    {
+                        _spinLock.Exit();
+                    }
+                }
+            }
+            return waitSuccessful;
+        }
+
+        /// <summary>
+        /// Determines the appropriate events to set, leaves the locks, and sets the events. 
+        /// </summary>
+        private void ExitAndWakeUpAppropriateWaiters()
+        {
+#if DEBUG
+            Debug.Assert(_spinLock.IsHeld);
+#endif
+            if (HasNoWaiters)
+            {
+                _spinLock.Exit();
+                return;
+            }
+
+            ExitAndWakeUpAppropriateWaitersPreferringWriters();
+        }
+
+        private void ExitAndWakeUpAppropriateWaitersPreferringWriters()
+        {
+            uint readercount = GetNumReaders();
+
+            //We need this case for EU->ER->EW case, as the read count will be 2 in
+            //that scenario.
+            if (_fIsReentrant)
+            {
+                if (_numWriteUpgradeWaiters > 0 && _fUpgradeThreadHoldingRead && readercount == 2)
+                {
+                    _spinLock.Exit();      // Exit before signaling to improve efficiency (wakee will need the lock)
+                    _waitUpgradeEvent.Set();     // release all upgraders (however there can be at most one). 
+                    return;
+                }
+            }
+
+            if (readercount == 1 && _numWriteUpgradeWaiters > 0)
+            {
+                //We have to be careful now, as we are dropping the lock. 
+                //No new writes should be allowed to sneak in if an upgrade
+                //was pending. 
+
+                _spinLock.Exit();      // Exit before signaling to improve efficiency (wakee will need the lock)
+                _waitUpgradeEvent.Set();     // release all upgraders (however there can be at most one).            
+            }
+            else if (readercount == 0 && _numWriteWaiters > 0)
+            {
+                // Check if a waiter of the same type has already been signaled but hasn't woken yet. If so, avoid signaling
+                // and waking another waiter unnecessarily.
+                WaiterStates signaled = _waiterStates & WaiterStates.WriteWaiterSignaled;
+                if (signaled == WaiterStates.None)
+                {
+                    _waiterStates |= WaiterStates.WriteWaiterSignaled;
+                }
+
+                _spinLock.Exit();      // Exit before signaling to improve efficiency (wakee will need the lock)
+
+                if (signaled == WaiterStates.None)
+                {
+                    _writeEvent.Set();   // release one writer. 
+                }
+            }
+            else
+            {
+                ExitAndWakeUpAppropriateReadWaiters();
+            }
+        }
+
+        private void ExitAndWakeUpAppropriateReadWaiters()
+        {
+#if DEBUG
+            Debug.Assert(_spinLock.IsHeld);
+#endif
+
+            if (_numWriteWaiters != 0 || _numWriteUpgradeWaiters != 0 || HasNoWaiters)
+            {
+                _spinLock.Exit();
+                return;
+            }
+
+            Debug.Assert(_numReadWaiters != 0 || _numUpgradeWaiters != 0);
+
+            bool setReadEvent = _numReadWaiters != 0;
+            bool setUpgradeEvent = _numUpgradeWaiters != 0 && _upgradeLockOwnerId == -1;
+            if (setUpgradeEvent)
+            {
+                // Check if a waiter of the same type has already been signaled but hasn't woken yet. If so, avoid signaling
+                // and waking another waiter unnecessarily.
+                if ((_waiterStates & WaiterStates.UpgradeableReadWaiterSignaled) == WaiterStates.None)
+                {
+                    _waiterStates |= WaiterStates.UpgradeableReadWaiterSignaled;
+                }
+                else
+                {
+                    setUpgradeEvent = false;
+                }
+            }
+
+            _spinLock.Exit();    // Exit before signaling to improve efficiency (wakee will need the lock)
+
+            if (setReadEvent)
+                _readEvent.Set();  // release all readers. 
+
+            if (setUpgradeEvent)
+                _upgradeEvent.Set(); //release one upgrader.
+        }
+
+        private bool IsWriterAcquired()
+        {
+            return (_owners & ~WAITING_WRITERS) == 0;
+        }
+
+        private void SetWriterAcquired()
+        {
+            _owners |= WRITER_HELD;    // indicate we have a writer.
+        }
+
+        private void ClearWriterAcquired()
+        {
+            _owners &= ~WRITER_HELD;
+        }
+
+        private void SetWritersWaiting()
+        {
+            _owners |= WAITING_WRITERS;
+        }
+
+        private void ClearWritersWaiting()
+        {
+            _owners &= ~WAITING_WRITERS;
+        }
+
+        private void SetUpgraderWaiting()
+        {
+            _owners |= WAITING_UPGRADER;
+        }
+
+        private void ClearUpgraderWaiting()
+        {
+            _owners &= ~WAITING_UPGRADER;
+        }
+
+        private uint GetNumReaders()
+        {
+            return _owners & READER_MASK;
+        }
+
+        private bool ShouldSpinForEnterAnyRead()
+        {
+            // If there is a write waiter or write upgrade waiter, the waiter would block a reader from acquiring the RW lock
+            // because the waiter takes precedence. In that case, the reader is not likely to make progress by spinning.
+            // Although another thread holding a write lock would prevent this thread from acquiring a read lock, it is by
+            // itself not a good enough reason to skip spinning.
+            return HasNoWaiters || (_numWriteWaiters == 0 && _numWriteUpgradeWaiters == 0);
+        }
+
+        private bool ShouldSpinForEnterAnyWrite(bool isUpgradeToWrite)
+        {
+            // If there is a write upgrade waiter, the waiter would block a writer from acquiring the RW lock because the waiter
+            // holds a read lock. In that case, the writer is not likely to make progress by spinning. Regarding upgrading to a
+            // write lock, there is no type of waiter that would block the upgrade from happening. Although another thread
+            // holding a read or write lock would prevent this thread from acquiring the write lock, it is by itself not a good
+            // enough reason to skip spinning.
+            return isUpgradeToWrite || _numWriteUpgradeWaiters == 0;
+        }
+
+        private static void SpinWait(int spinCount)
+        {
+            const int LockSpinCycles = 20;
+
+            //Exponential back-off
+            if ((spinCount < 5) && (ProcessorCount > 1))
+            {
+                RuntimeThread.SpinWait(LockSpinCycles * spinCount);
+            }
+            else
+            {
+                RuntimeThread.Sleep(0);
+            }
+
+            // Don't want to Sleep(1) in this spin wait:
+            //   - Don't want to spin for that long, since a proper wait will follow when the spin wait fails. The artificial
+            //     delay introduced by Sleep(1) will in some cases be much longer than desired.
+            //   - Sleep(1) would put the thread into a wait state, and a proper wait will follow when the spin wait fails
+            //     anyway, so it's preferable to put the thread into the proper wait state
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+        }
+
+        private void Dispose(bool disposing)
+        {
+            if (disposing && !_fDisposed)
+            {
+                if (WaitingReadCount > 0 || WaitingUpgradeCount > 0 || WaitingWriteCount > 0)
+                    throw new SynchronizationLockException(SR.SynchronizationLockException_IncorrectDispose);
+
+                if (IsReadLockHeld || IsUpgradeableReadLockHeld || IsWriteLockHeld)
+                    throw new SynchronizationLockException(SR.SynchronizationLockException_IncorrectDispose);
+
+                if (_writeEvent != null)
+                {
+                    _writeEvent.Dispose();
+                    _writeEvent = null;
+                }
+
+                if (_readEvent != null)
+                {
+                    _readEvent.Dispose();
+                    _readEvent = null;
+                }
+
+                if (_upgradeEvent != null)
+                {
+                    _upgradeEvent.Dispose();
+                    _upgradeEvent = null;
+                }
+
+                if (_waitUpgradeEvent != null)
+                {
+                    _waitUpgradeEvent.Dispose();
+                    _waitUpgradeEvent = null;
+                }
+
+                _fDisposed = true;
+            }
+        }
+
+        public bool IsReadLockHeld
+        {
+            get
+            {
+                if (RecursiveReadCount > 0)
+                    return true;
+                else
+                    return false;
+            }
+        }
+
+        public bool IsUpgradeableReadLockHeld
+        {
+            get
+            {
+                if (RecursiveUpgradeCount > 0)
+                    return true;
+                else
+                    return false;
+            }
+        }
+
+        public bool IsWriteLockHeld
+        {
+            get
+            {
+                if (RecursiveWriteCount > 0)
+                    return true;
+                else
+                    return false;
+            }
+        }
+
+        public LockRecursionPolicy RecursionPolicy
+        {
+            get
+            {
+                if (_fIsReentrant)
+                {
+                    return LockRecursionPolicy.SupportsRecursion;
+                }
+                else
+                {
+                    return LockRecursionPolicy.NoRecursion;
+                }
+            }
+        }
+
+        public int CurrentReadCount
+        {
+            get
+            {
+                int numreaders = (int)GetNumReaders();
+
+                if (_upgradeLockOwnerId != -1)
+                    return numreaders - 1;
+                else
+                    return numreaders;
+            }
+        }
+
+
+        public int RecursiveReadCount
+        {
+            get
+            {
+                int count = 0;
+                ReaderWriterCount lrwc = GetThreadRWCount(true);
+                if (lrwc != null)
+                    count = lrwc.readercount;
+
+                return count;
+            }
+        }
+
+        public int RecursiveUpgradeCount
+        {
+            get
+            {
+                if (_fIsReentrant)
+                {
+                    int count = 0;
+
+                    ReaderWriterCount lrwc = GetThreadRWCount(true);
+                    if (lrwc != null)
+                        count = lrwc.upgradecount;
+
+                    return count;
+                }
+                else
+                {
+                    if (Environment.CurrentManagedThreadId == _upgradeLockOwnerId)
+                        return 1;
+                    else
+                        return 0;
+                }
+            }
+        }
+
+        public int RecursiveWriteCount
+        {
+            get
+            {
+                if (_fIsReentrant)
+                {
+                    int count = 0;
+
+                    ReaderWriterCount lrwc = GetThreadRWCount(true);
+                    if (lrwc != null)
+                        count = lrwc.writercount;
+
+                    return count;
+                }
+                else
+                {
+                    if (Environment.CurrentManagedThreadId == _writeLockOwnerId)
+                        return 1;
+                    else
+                        return 0;
+                }
+            }
+        }
+
+        public int WaitingReadCount
+        {
+            get
+            {
+                return (int)_numReadWaiters;
+            }
+        }
+
+        public int WaitingUpgradeCount
+        {
+            get
+            {
+                return (int)_numUpgradeWaiters;
+            }
+        }
+
+        public int WaitingWriteCount
+        {
+            get
+            {
+                return (int)_numWriteWaiters;
+            }
+        }
+
+        private struct SpinLock
+        {
+            private int _isLocked;
+
+            /// <summary>
+            /// Used to deprioritize threads attempting to enter the lock when they would not make progress after doing so.
+            /// <see cref="EnterSpin(EnterSpinLockReason)"/> avoids acquiring the lock as long as the operation for which it
+            /// was called is deprioritized.
+            /// 
+            /// Layout:
+            /// - Low 16 bits: Number of threads that have deprioritized an enter-any-write operation
+            /// - High 16 bits: Number of threads that have deprioritized an enter-any-read operation
+            /// </summary>
+            private int _enterDeprioritizationState;
+
+            // Layout-specific constants for _enterDeprioritizationState
+            private const int DeprioritizeEnterAnyReadIncrement = 1 << 16;
+            private const int DeprioritizeEnterAnyWriteIncrement = 1;
+
+            // The variables controlling spinning behavior of this spin lock
+            private const int LockSpinCycles = 20;
+            private const int LockSpinCount = 10;
+            private const int LockSleep0Count = 5;
+            private const int DeprioritizedLockSleep1Count = 5;
+
+            private static int GetEnterDeprioritizationStateChange(EnterSpinLockReason reason)
+            {
+                EnterSpinLockReason operation = reason & EnterSpinLockReason.OperationMask;
+                switch (operation)
+                {
+                    case EnterSpinLockReason.EnterAnyRead:
+                        return 0;
+
+                    case EnterSpinLockReason.ExitAnyRead:
+                        // A read lock is held until this thread is able to exit it, so deprioritize enter-write threads as they
+                        // will not be able to make progress
+                        return DeprioritizeEnterAnyWriteIncrement;
+
+                    case EnterSpinLockReason.EnterWrite:
+                        // Writers are typically much less frequent and much less in number than readers. Waiting writers take
+                        // precedence over new read attempts in order to let current readers release their lock and allow a
+                        // writer to obtain the lock. Before a writer can register as a waiter though, the presence of just
+                        // relatively few enter-read spins can easily starve the enter-write from even entering this lock,
+                        // delaying its spin loop for an unreasonable duration.
+                        //
+                        // Deprioritize enter-read to preference enter-write. This makes it easier for enter-write threads to
+                        // starve enter-read threads. However, writers can already by design starve readers. A waiting writer
+                        // blocks enter-read threads and a new enter-write that needs to wait will be given precedence over
+                        // previously waiting enter-read threads. So this is not a new problem, and the RW lock is designed for
+                        // scenarios where writers are rare compared to readers.
+                        return DeprioritizeEnterAnyReadIncrement;
+
+                    default:
+                        Debug.Assert(
+                            operation == EnterSpinLockReason.UpgradeToWrite ||
+                            operation == EnterSpinLockReason.EnterRecursiveWrite ||
+                            operation == EnterSpinLockReason.ExitAnyWrite);
+
+                        // UpgradeToWrite:
+                        // - A read lock is held and an exit-read is not nearby, so deprioritize enter-write threads as they
+                        //   will not be able to make progress. This thread also intends to enter a write lock, so deprioritize
+                        //   enter -read threads as well, see case EnterSpinLockReason.EnterWrite for the rationale.
+                        // EnterRecursiveWrite, ExitAnyWrite:
+                        // - In both cases, a write lock is held until this thread is able to exit it, so deprioritize
+                        //   enter -read and enter-write threads as they will not be able to make progress
+                        return DeprioritizeEnterAnyReadIncrement + DeprioritizeEnterAnyWriteIncrement;
+                }
+            }
+
+            private ushort EnterForEnterAnyReadDeprioritizedCount
+            {
+                get
+                {
+                    Debug.Assert(DeprioritizeEnterAnyReadIncrement == (1 << 16));
+                    return (ushort)((uint)_enterDeprioritizationState >> 16);
+                }
+            }
+
+            private ushort EnterForEnterAnyWriteDeprioritizedCount
+            {
+                get
+                {
+                    Debug.Assert(DeprioritizeEnterAnyWriteIncrement == 1);
+                    return (ushort)_enterDeprioritizationState;
+                }
+            }
+
+            private bool IsEnterDeprioritized(EnterSpinLockReason reason)
+            {
+                Debug.Assert((reason & EnterSpinLockReason.Wait) != 0 || reason == (reason & EnterSpinLockReason.OperationMask));
+                Debug.Assert(
+                    (reason & EnterSpinLockReason.Wait) == 0 ||
+                    (reason & EnterSpinLockReason.OperationMask) == EnterSpinLockReason.EnterAnyRead ||
+                    (reason & EnterSpinLockReason.OperationMask) == EnterSpinLockReason.EnterWrite ||
+                    (reason & EnterSpinLockReason.OperationMask) == EnterSpinLockReason.UpgradeToWrite);
+
+                switch (reason)
+                {
+                    default:
+                        Debug.Assert(
+                            (reason & EnterSpinLockReason.Wait) != 0 ||
+                            reason == EnterSpinLockReason.ExitAnyRead ||
+                            reason == EnterSpinLockReason.EnterRecursiveWrite ||
+                            reason == EnterSpinLockReason.ExitAnyWrite);
+                        return false;
+
+                    case EnterSpinLockReason.EnterAnyRead:
+                        return EnterForEnterAnyReadDeprioritizedCount != 0;
+
+                    case EnterSpinLockReason.EnterWrite:
+                        Debug.Assert((GetEnterDeprioritizationStateChange(reason) & DeprioritizeEnterAnyWriteIncrement) == 0);
+                        return EnterForEnterAnyWriteDeprioritizedCount != 0;
+
+                    case EnterSpinLockReason.UpgradeToWrite:
+                        Debug.Assert((GetEnterDeprioritizationStateChange(reason) & DeprioritizeEnterAnyWriteIncrement) != 0);
+                        return EnterForEnterAnyWriteDeprioritizedCount > 1;
+                }
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            private bool TryEnter()
+            {
+                return Interlocked.CompareExchange(ref _isLocked, 1, 0) == 0;
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            public void Enter(EnterSpinLockReason reason)
+            {
+                if (!TryEnter())
+                {
+                    EnterSpin(reason);
+                }
+            }
+
+            private void EnterSpin(EnterSpinLockReason reason)
+            {
+                int deprioritizationStateChange = GetEnterDeprioritizationStateChange(reason);
+                if (deprioritizationStateChange != 0)
+                {
+                    Interlocked.Add(ref _enterDeprioritizationState, deprioritizationStateChange);
+                }
+
+                int processorCount = ProcessorCount;
+                for (int spinIndex = 0; ; spinIndex++)
+                {
+                    if (spinIndex < LockSpinCount && processorCount > 1)
+                    {
+                        RuntimeThread.SpinWait(LockSpinCycles * (spinIndex + 1)); // Wait a few dozen instructions to let another processor release lock.
+                    }
+                    else if (spinIndex < (LockSpinCount + LockSleep0Count))
+                    {
+                        RuntimeThread.Sleep(0);   // Give up my quantum.
+                    }
+                    else
+                    {
+                        RuntimeThread.Sleep(1);   // Give up my quantum.
+                    }
+
+                    if (!IsEnterDeprioritized(reason))
+                    {
+                        if (_isLocked == 0 && TryEnter())
+                        {
+                            if (deprioritizationStateChange != 0)
+                            {
+                                Interlocked.Add(ref _enterDeprioritizationState, -deprioritizationStateChange);
+                            }
+                            return;
+                        }
+                        continue;
+                    }
+
+                    // It's possible for an Enter thread to be deprioritized for an extended duration. It's undesirable for a
+                    // deprioritized thread to keep waking up to spin despite a Sleep(1) when a large number of such threads are
+                    // involved. After a threshold of Sleep(1)s, ignore the deprioritization and enter this lock to allow this
+                    // thread to stop spinning and hopefully enter a proper wait state.
+                    Debug.Assert(
+                        reason == EnterSpinLockReason.EnterAnyRead ||
+                        reason == EnterSpinLockReason.EnterWrite ||
+                        reason == EnterSpinLockReason.UpgradeToWrite);
+                    if (spinIndex >= (LockSpinCount + LockSleep0Count + DeprioritizedLockSleep1Count))
+                    {
+                        reason |= EnterSpinLockReason.Wait;
+                        spinIndex = -1;
+                    }
+                }
+            }
+
+            public void Exit()
+            {
+                Debug.Assert(_isLocked != 0, "Exiting spin lock that is not held");
+                Volatile.Write(ref _isLocked, 0);
+            }
+
+#if DEBUG
+            public bool IsHeld => _isLocked != 0;
+#endif
+        }
+
+        [Flags]
+        private enum WaiterStates : byte
+        {
+            None = 0x0,
+
+            // Used for quick check when there are no waiters
+            NoWaiters = 0x1,
+
+            // Used to avoid signaling more than one waiter to wake up when only one can make progress, see WaitOnEvent
+            WriteWaiterSignaled = 0x2,
+            UpgradeableReadWaiterSignaled = 0x4
+            // Write upgrade waiters are excluded because there can only be one at any given time
+        }
+
+        private enum EnterSpinLockReason
+        {
+            EnterAnyRead = 0,
+            ExitAnyRead = 1,
+            EnterWrite = 2,
+            UpgradeToWrite = 3,
+            EnterRecursiveWrite = 4,
+            ExitAnyWrite = 5,
+
+            OperationMask = 0x7,
+
+            Wait = 0x8
+        }
+
+        private enum EnterLockType
+        {
+            Read,
+            UpgradeableRead,
+            Write,
+            UpgradeToWrite
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/SemaphoreFullException.cs b/src/System.Private.CoreLib/shared/System/Threading/SemaphoreFullException.cs
new file mode 100644
index 0000000000..18558b19e0
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/SemaphoreFullException.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System.Threading
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class SemaphoreFullException : SystemException
+    {
+        public SemaphoreFullException() : base(SR.Threading_SemaphoreFullException)
+        {
+        }
+
+        public SemaphoreFullException(String message) : base(message)
+        {
+        }
+
+        public SemaphoreFullException(String message, Exception innerException) : base(message, innerException)
+        {
+        }
+
+        protected SemaphoreFullException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/SendOrPostCallback.cs b/src/System.Private.CoreLib/shared/System/Threading/SendOrPostCallback.cs
new file mode 100644
index 0000000000..6692d35ab2
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/SendOrPostCallback.cs
@@ -0,0 +1,8 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Threading
+{
+    public delegate void SendOrPostCallback(Object state);
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/SpinWait.cs b/src/System.Private.CoreLib/shared/System/Threading/SpinWait.cs
new file mode 100644
index 0000000000..414ad1852f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/SpinWait.cs
@@ -0,0 +1,359 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+// Central spin logic used across the entire code-base.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Diagnostics;
+using Internal.Runtime.Augments;
+
+namespace System.Threading
+{
+    // SpinWait is just a little value type that encapsulates some common spinning
+    // logic. It ensures we always yield on single-proc machines (instead of using busy
+    // waits), and that we work well on HT. It encapsulates a good mixture of spinning
+    // and real yielding. It's a value type so that various areas of the engine can use
+    // one by allocating it on the stack w/out unnecessary GC allocation overhead, e.g.:
+    //
+    //     void f() {
+    //         SpinWait wait = new SpinWait();
+    //         while (!p) { wait.SpinOnce(); }
+    //         ...
+    //     }
+    //
+    // Internally it just maintains a counter that is used to decide when to yield, etc.
+    // 
+    // A common usage is to spin before blocking. In those cases, the NextSpinWillYield
+    // property allows a user to decide to fall back to waiting once it returns true:
+    // 
+    //     void f() {
+    //         SpinWait wait = new SpinWait();
+    //         while (!p) {
+    //             if (wait.NextSpinWillYield) { /* block! */ }
+    //             else { wait.SpinOnce(); }
+    //         }
+    //         ...
+    //     }
+
+    /// <summary>
+    /// Provides support for spin-based waiting.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// <see cref="SpinWait"/> encapsulates common spinning logic. On single-processor machines, yields are
+    /// always used instead of busy waits, and on computers with Intel(R) processors employing Hyper-Threading
+    /// technology, it helps to prevent hardware thread starvation. SpinWait encapsulates a good mixture of
+    /// spinning and true yielding.
+    /// </para>
+    /// <para>
+    /// <see cref="SpinWait"/> is a value type, which means that low-level code can utilize SpinWait without
+    /// fear of unnecessary allocation overheads. SpinWait is not generally useful for ordinary applications.
+    /// In most cases, you should use the synchronization classes provided by the .NET Framework, such as
+    /// <see cref="System.Threading.Monitor"/>. For most purposes where spin waiting is required, however,
+    /// the <see cref="SpinWait"/> type should be preferred over the <see
+    /// cref="System.Threading.Thread.SpinWait"/> method.
+    /// </para>
+    /// <para>
+    /// While SpinWait is designed to be used in concurrent applications, it is not designed to be
+    /// used from multiple threads concurrently.  SpinWait's members are not thread-safe.  If multiple
+    /// threads must spin, each should use its own instance of SpinWait.
+    /// </para>
+    /// </remarks>
+    public struct SpinWait
+    {
+        // These constants determine the frequency of yields versus spinning. The
+        // numbers may seem fairly arbitrary, but were derived with at least some
+        // thought in the design document.  I fully expect they will need to change
+        // over time as we gain more experience with performance.
+        internal const int YieldThreshold = 10; // When to switch over to a true yield.
+        private const int Sleep0EveryHowManyYields = 5; // After how many yields should we Sleep(0)?
+        internal const int DefaultSleep1Threshold = 20; // After how many yields should we Sleep(1) frequently?
+
+        /// <summary>
+        /// A suggested number of spin iterations before doing a proper wait, such as waiting on an event that becomes signaled
+        /// when the resource becomes available.
+        /// </summary>
+        /// <remarks>
+        /// These numbers were arrived at by experimenting with different numbers in various cases that currently use it. It's
+        /// only a suggested value and typically works well when the proper wait is something like an event.
+        /// 
+        /// Spinning less can lead to early waiting and more context switching, spinning more can decrease latency but may use
+        /// up some CPU time unnecessarily. Depends on the situation too, for instance SemaphoreSlim uses more iterations
+        /// because the waiting there is currently a lot more expensive (involves more spinning, taking a lock, etc.). It also
+        /// depends on the likelihood of the spin being successful and how long the wait would be but those are not accounted
+        /// for here.
+        /// </remarks>
+        internal static readonly int SpinCountforSpinBeforeWait = PlatformHelper.IsSingleProcessor ? 1 : 35;
+        internal const int Sleep1ThresholdForSpinBeforeWait = 40; // should be greater than SpinCountforSpinBeforeWait
+
+        // The number of times we've spun already.
+        private int _count;
+
+        /// <summary>
+        /// Gets the number of times <see cref="SpinOnce"/> has been called on this instance.
+        /// </summary>
+        public int Count
+        {
+            get => _count;
+            internal set
+            {
+                Debug.Assert(value >= 0);
+                _count = value;
+            }
+        }
+
+        /// <summary>
+        /// Gets whether the next call to <see cref="SpinOnce"/> will yield the processor, triggering a
+        /// forced context switch.
+        /// </summary>
+        /// <value>Whether the next call to <see cref="SpinOnce"/> will yield the processor, triggering a
+        /// forced context switch.</value>
+        /// <remarks>
+        /// On a single-CPU machine, <see cref="SpinOnce"/> always yields the processor. On machines with
+        /// multiple CPUs, <see cref="SpinOnce"/> may yield after an unspecified number of calls.
+        /// </remarks>
+        public bool NextSpinWillYield => _count >= YieldThreshold || PlatformHelper.IsSingleProcessor;
+
+        /// <summary>
+        /// Performs a single spin.
+        /// </summary>
+        /// <remarks>
+        /// This is typically called in a loop, and may change in behavior based on the number of times a
+        /// <see cref="SpinOnce"/> has been called thus far on this instance.
+        /// </remarks>
+        public void SpinOnce()
+        {
+            SpinOnce(DefaultSleep1Threshold);
+        }
+
+        internal void SpinOnce(int sleep1Threshold)
+        {
+            Debug.Assert(sleep1Threshold >= YieldThreshold || PlatformHelper.IsSingleProcessor); // so that NextSpinWillYield behaves as requested
+
+            // (_count - YieldThreshold) % 2 == 0: The purpose of this check is to interleave Thread.Yield/Sleep(0) with
+            // Thread.SpinWait. Otherwise, the following issues occur:
+            //   - When there are no threads to switch to, Yield and Sleep(0) become no-op and it turns the spin loop into a
+            //     busy-spin that may quickly reach the max spin count and cause the thread to enter a wait state, or may
+            //     just busy-spin for longer than desired before a Sleep(1). Completing the spin loop too early can cause
+            //     excessive context switcing if a wait follows, and entering the Sleep(1) stage too early can cause
+            //     excessive delays.
+            //   - If there are multiple threads doing Yield and Sleep(0) (typically from the same spin loop due to
+            //     contention), they may switch between one another, delaying work that can make progress.
+            if ((
+                    _count >= YieldThreshold &&
+                    (_count >= sleep1Threshold || (_count - YieldThreshold) % 2 == 0)
+                ) ||
+                PlatformHelper.IsSingleProcessor)
+            {
+                //
+                // We must yield.
+                //
+                // We prefer to call Thread.Yield first, triggering a SwitchToThread. This
+                // unfortunately doesn't consider all runnable threads on all OS SKUs. In
+                // some cases, it may only consult the runnable threads whose ideal processor
+                // is the one currently executing code. Thus we occasionally issue a call to
+                // Sleep(0), which considers all runnable threads at equal priority. Even this
+                // is insufficient since we may be spin waiting for lower priority threads to
+                // execute; we therefore must call Sleep(1) once in a while too, which considers
+                // all runnable threads, regardless of ideal processor and priority, but may
+                // remove the thread from the scheduler's queue for 10+ms, if the system is
+                // configured to use the (default) coarse-grained system timer.
+                //
+
+                if (_count >= sleep1Threshold)
+                {
+                    RuntimeThread.Sleep(1);
+                }
+                else
+                {
+                    int yieldsSoFar = _count >= YieldThreshold ? (_count - YieldThreshold) / 2 : _count;
+                    if ((yieldsSoFar % Sleep0EveryHowManyYields) == (Sleep0EveryHowManyYields - 1))
+                    {
+                        RuntimeThread.Sleep(0);
+                    }
+                    else
+                    {
+                        RuntimeThread.Yield();
+                    }
+                }
+            }
+            else
+            {
+                //
+                // Otherwise, we will spin.
+                //
+                // We do this using the CLR's SpinWait API, which is just a busy loop that
+                // issues YIELD/PAUSE instructions to ensure multi-threaded CPUs can react
+                // intelligently to avoid starving. (These are NOOPs on other CPUs.) We
+                // choose a number for the loop iteration count such that each successive
+                // call spins for longer, to reduce cache contention.  We cap the total
+                // number of spins we are willing to tolerate to reduce delay to the caller,
+                // since we expect most callers will eventually block anyway.
+                //
+                // Also, cap the maximum spin count to a value such that many thousands of CPU cycles would not be wasted doing
+                // the equivalent of YieldProcessor(), as that that point SwitchToThread/Sleep(0) are more likely to be able to
+                // allow other useful work to run. Long YieldProcessor() loops can help to reduce contention, but Sleep(1) is
+                // usually better for that.
+                //
+                // RuntimeThread.OptimalMaxSpinWaitsPerSpinIteration:
+                //   - See Thread::InitializeYieldProcessorNormalized(), which describes and calculates this value.
+                //
+                int n = RuntimeThread.OptimalMaxSpinWaitsPerSpinIteration;
+                if (_count <= 30 && (1 << _count) < n)
+                {
+                    n = 1 << _count;
+                }
+                RuntimeThread.SpinWait(n);
+            }
+
+            // Finally, increment our spin counter.
+            _count = (_count == int.MaxValue ? YieldThreshold : _count + 1);
+        }
+
+        /// <summary>
+        /// Resets the spin counter.
+        /// </summary>
+        /// <remarks>
+        /// This makes <see cref="SpinOnce"/> and <see cref="NextSpinWillYield"/> behave as though no calls
+        /// to <see cref="SpinOnce"/> had been issued on this instance. If a <see cref="SpinWait"/> instance
+        /// is reused many times, it may be useful to reset it to avoid yielding too soon.
+        /// </remarks>
+        public void Reset()
+        {
+            _count = 0;
+        }
+
+        #region Static Methods
+        /// <summary>
+        /// Spins until the specified condition is satisfied.
+        /// </summary>
+        /// <param name="condition">A delegate to be executed over and over until it returns true.</param>
+        /// <exception cref="ArgumentNullException">The <paramref name="condition"/> argument is null.</exception>
+        public static void SpinUntil(Func<bool> condition)
+        {
+#if DEBUG
+            bool result =
+#endif
+            SpinUntil(condition, Timeout.Infinite);
+#if DEBUG
+            Debug.Assert(result);
+#endif
+        }
+
+        /// <summary>
+        /// Spins until the specified condition is satisfied or until the specified timeout is expired.
+        /// </summary>
+        /// <param name="condition">A delegate to be executed over and over until it returns true.</param>
+        /// <param name="timeout">
+        /// A <see cref="TimeSpan"/> that represents the number of milliseconds to wait, 
+        /// or a TimeSpan that represents -1 milliseconds to wait indefinitely.</param>
+        /// <returns>True if the condition is satisfied within the timeout; otherwise, false</returns>
+        /// <exception cref="ArgumentNullException">The <paramref name="condition"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="timeout"/> is a negative number
+        /// other than -1 milliseconds, which represents an infinite time-out -or- timeout is greater than
+        /// <see cref="System.Int32.MaxValue"/>.</exception>
+        public static bool SpinUntil(Func<bool> condition, TimeSpan timeout)
+        {
+            // Validate the timeout
+            long totalMilliseconds = (long)timeout.TotalMilliseconds;
+            if (totalMilliseconds < -1 || totalMilliseconds > int.MaxValue)
+            {
+                throw new System.ArgumentOutOfRangeException(
+                    nameof(timeout), timeout, SR.SpinWait_SpinUntil_TimeoutWrong);
+            }
+
+            // Call wait with the timeout milliseconds
+            return SpinUntil(condition, (int)totalMilliseconds);
+        }
+
+        /// <summary>
+        /// Spins until the specified condition is satisfied or until the specified timeout is expired.
+        /// </summary>
+        /// <param name="condition">A delegate to be executed over and over until it returns true.</param>
+        /// <param name="millisecondsTimeout">The number of milliseconds to wait, or <see
+        /// cref="System.Threading.Timeout.Infinite"/> (-1) to wait indefinitely.</param>
+        /// <returns>True if the condition is satisfied within the timeout; otherwise, false</returns>
+        /// <exception cref="ArgumentNullException">The <paramref name="condition"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="millisecondsTimeout"/> is a
+        /// negative number other than -1, which represents an infinite time-out.</exception>
+        public static bool SpinUntil(Func<bool> condition, int millisecondsTimeout)
+        {
+            if (millisecondsTimeout < Timeout.Infinite)
+            {
+                throw new ArgumentOutOfRangeException(
+                   nameof(millisecondsTimeout), millisecondsTimeout, SR.SpinWait_SpinUntil_TimeoutWrong);
+            }
+            if (condition == null)
+            {
+                throw new ArgumentNullException(nameof(condition), SR.SpinWait_SpinUntil_ArgumentNull);
+            }
+            uint startTime = 0;
+            if (millisecondsTimeout != 0 && millisecondsTimeout != Timeout.Infinite)
+            {
+                startTime = TimeoutHelper.GetTime();
+            }
+            SpinWait spinner = new SpinWait();
+            while (!condition())
+            {
+                if (millisecondsTimeout == 0)
+                {
+                    return false;
+                }
+
+                spinner.SpinOnce();
+
+                if (millisecondsTimeout != Timeout.Infinite && spinner.NextSpinWillYield)
+                {
+                    if (millisecondsTimeout <= (TimeoutHelper.GetTime() - startTime))
+                    {
+                        return false;
+                    }
+                }
+            }
+            return true;
+        }
+        #endregion
+    }
+
+    /// <summary>
+    /// A helper class to get the number of processors, it updates the numbers of processors every sampling interval.
+    /// </summary>
+    internal static class PlatformHelper
+    {
+        private const int PROCESSOR_COUNT_REFRESH_INTERVAL_MS = 30000; // How often to refresh the count, in milliseconds.
+        private static volatile int s_processorCount; // The last count seen.
+        private static volatile int s_lastProcessorCountRefreshTicks; // The last time we refreshed.
+
+        /// <summary>
+        /// Gets the number of available processors
+        /// </summary>
+        internal static int ProcessorCount
+        {
+            get
+            {
+                int now = Environment.TickCount;
+                int procCount = s_processorCount;
+                if (procCount == 0 || (now - s_lastProcessorCountRefreshTicks) >= PROCESSOR_COUNT_REFRESH_INTERVAL_MS)
+                {
+                    s_processorCount = procCount = Environment.ProcessorCount;
+                    s_lastProcessorCountRefreshTicks = now;
+                }
+
+                Debug.Assert(procCount > 0,
+                    "Processor count should be greater than 0.");
+
+                return procCount;
+            }
+        }
+
+        /// <summary>
+        /// Gets whether the current machine has only a single processor.
+        /// </summary>
+        /// <remarks>This typically does not change on a machine, so it's checked only once.</remarks>
+        internal static readonly bool IsSingleProcessor = ProcessorCount == 1;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/SynchronizationLockException.cs b/src/System.Private.CoreLib/shared/System/Threading/SynchronizationLockException.cs
new file mode 100644
index 0000000000..e050e1539d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/SynchronizationLockException.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Wait(), Notify() or NotifyAll() was called from an unsynchronized
+**          block of code.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System.Threading
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class SynchronizationLockException : SystemException
+    {
+        public SynchronizationLockException()
+            : base(SR.Arg_SynchronizationLockException)
+        {
+            HResult = HResults.COR_E_SYNCHRONIZATIONLOCK;
+        }
+
+        public SynchronizationLockException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_SYNCHRONIZATIONLOCK;
+        }
+
+        public SynchronizationLockException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_SYNCHRONIZATIONLOCK;
+        }
+
+        protected SynchronizationLockException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Tasks/ConcurrentExclusiveSchedulerPair.cs b/src/System.Private.CoreLib/shared/System/Threading/Tasks/ConcurrentExclusiveSchedulerPair.cs
new file mode 100644
index 0000000000..6a6483f9af
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/Tasks/ConcurrentExclusiveSchedulerPair.cs
@@ -0,0 +1,750 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// A pair of schedulers that together support concurrent (reader) / exclusive (writer) 
+// task scheduling.  Using just the exclusive scheduler can be used to simulate a serial
+// processing queue, and using just the concurrent scheduler with a specified 
+// MaximumConcurrentlyLevel can be used to achieve a MaxDegreeOfParallelism across
+// a bunch of tasks, parallel loops, dataflow blocks, etc.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+
+namespace System.Threading.Tasks
+{
+    /// <summary>
+    /// Provides concurrent and exclusive task schedulers that coordinate to execute
+    /// tasks while ensuring that concurrent tasks may run concurrently and exclusive tasks never do.
+    /// </summary>
+    [DebuggerDisplay("Concurrent={ConcurrentTaskCountForDebugger}, Exclusive={ExclusiveTaskCountForDebugger}, Mode={ModeForDebugger}")]
+    [DebuggerTypeProxy(typeof(ConcurrentExclusiveSchedulerPair.DebugView))]
+    public class ConcurrentExclusiveSchedulerPair
+    {
+        /// <summary>A processing mode to denote what kinds of tasks are currently being processed on this thread.</summary>
+        private readonly ThreadLocal<ProcessingMode> m_threadProcessingMode = new ThreadLocal<ProcessingMode>();
+        /// <summary>The scheduler used to queue and execute "concurrent" tasks that may run concurrently with other concurrent tasks.</summary>
+        private readonly ConcurrentExclusiveTaskScheduler m_concurrentTaskScheduler;
+        /// <summary>The scheduler used to queue and execute "exclusive" tasks that must run exclusively while no other tasks for this pair are running.</summary>
+        private readonly ConcurrentExclusiveTaskScheduler m_exclusiveTaskScheduler;
+        /// <summary>The underlying task scheduler to which all work should be scheduled.</summary>
+        private readonly TaskScheduler m_underlyingTaskScheduler;
+        /// <summary>
+        /// The maximum number of tasks allowed to run concurrently.  This only applies to concurrent tasks, 
+        /// since exclusive tasks are inherently limited to 1.
+        /// </summary>
+        private readonly int m_maxConcurrencyLevel;
+        /// <summary>The maximum number of tasks we can process before recycling our runner tasks.</summary>
+        private readonly int m_maxItemsPerTask;
+        /// <summary>
+        /// If positive, it represents the number of concurrently running concurrent tasks.
+        /// If negative, it means an exclusive task has been scheduled.
+        /// If 0, nothing has been scheduled.
+        /// </summary>
+        private int m_processingCount;
+        /// <summary>Completion state for a task representing the completion of this pair.</summary>
+        /// <remarks>Lazily-initialized only if the scheduler pair is shutting down or if the Completion is requested.</remarks>
+        private CompletionState m_completionState;
+
+        /// <summary>A constant value used to signal unlimited processing.</summary>
+        private const int UNLIMITED_PROCESSING = -1;
+        /// <summary>Constant used for m_processingCount to indicate that an exclusive task is being processed.</summary>
+        private const int EXCLUSIVE_PROCESSING_SENTINEL = -1;
+        /// <summary>Default MaxItemsPerTask to use for processing if none is specified.</summary>
+        private const int DEFAULT_MAXITEMSPERTASK = UNLIMITED_PROCESSING;
+        /// <summary>Default MaxConcurrencyLevel is the processor count if not otherwise specified.</summary>
+        private static Int32 DefaultMaxConcurrencyLevel { get { return Environment.ProcessorCount; } }
+
+        /// <summary>Gets the sync obj used to protect all state on this instance.</summary>
+        private object ValueLock { get { return m_threadProcessingMode; } }
+
+        /// <summary>
+        /// Initializes the ConcurrentExclusiveSchedulerPair.
+        /// </summary>
+        public ConcurrentExclusiveSchedulerPair() :
+            this(TaskScheduler.Default, DefaultMaxConcurrencyLevel, DEFAULT_MAXITEMSPERTASK)
+        { }
+
+        /// <summary>
+        /// Initializes the ConcurrentExclusiveSchedulerPair to target the specified scheduler.
+        /// </summary>
+        /// <param name="taskScheduler">The target scheduler on which this pair should execute.</param>
+        public ConcurrentExclusiveSchedulerPair(TaskScheduler taskScheduler) :
+            this(taskScheduler, DefaultMaxConcurrencyLevel, DEFAULT_MAXITEMSPERTASK)
+        { }
+
+        /// <summary>
+        /// Initializes the ConcurrentExclusiveSchedulerPair to target the specified scheduler with a maximum concurrency level.
+        /// </summary>
+        /// <param name="taskScheduler">The target scheduler on which this pair should execute.</param>
+        /// <param name="maxConcurrencyLevel">The maximum number of tasks to run concurrently.</param>
+        public ConcurrentExclusiveSchedulerPair(TaskScheduler taskScheduler, int maxConcurrencyLevel) :
+            this(taskScheduler, maxConcurrencyLevel, DEFAULT_MAXITEMSPERTASK)
+        { }
+
+        /// <summary>
+        /// Initializes the ConcurrentExclusiveSchedulerPair to target the specified scheduler with a maximum 
+        /// concurrency level and a maximum number of scheduled tasks that may be processed as a unit.
+        /// </summary>
+        /// <param name="taskScheduler">The target scheduler on which this pair should execute.</param>
+        /// <param name="maxConcurrencyLevel">The maximum number of tasks to run concurrently.</param>
+        /// <param name="maxItemsPerTask">The maximum number of tasks to process for each underlying scheduled task used by the pair.</param>
+        public ConcurrentExclusiveSchedulerPair(TaskScheduler taskScheduler, int maxConcurrencyLevel, int maxItemsPerTask)
+        {
+            // Validate arguments
+            if (taskScheduler == null) throw new ArgumentNullException(nameof(taskScheduler));
+            if (maxConcurrencyLevel == 0 || maxConcurrencyLevel < -1) throw new ArgumentOutOfRangeException(nameof(maxConcurrencyLevel));
+            if (maxItemsPerTask == 0 || maxItemsPerTask < -1) throw new ArgumentOutOfRangeException(nameof(maxItemsPerTask));
+
+            // Store configuration
+            m_underlyingTaskScheduler = taskScheduler;
+            m_maxConcurrencyLevel = maxConcurrencyLevel;
+            m_maxItemsPerTask = maxItemsPerTask;
+
+            // Downgrade to the underlying scheduler's max degree of parallelism if it's lower than the user-supplied level
+            int mcl = taskScheduler.MaximumConcurrencyLevel;
+            if (mcl > 0 && mcl < m_maxConcurrencyLevel) m_maxConcurrencyLevel = mcl;
+
+            // Treat UNLIMITED_PROCESSING/-1 for both MCL and MIPT as the biggest possible value so that we don't
+            // have to special case UNLIMITED_PROCESSING later on in processing.
+            if (m_maxConcurrencyLevel == UNLIMITED_PROCESSING) m_maxConcurrencyLevel = Int32.MaxValue;
+            if (m_maxItemsPerTask == UNLIMITED_PROCESSING) m_maxItemsPerTask = Int32.MaxValue;
+
+            // Create the concurrent/exclusive schedulers for this pair
+            m_exclusiveTaskScheduler = new ConcurrentExclusiveTaskScheduler(this, 1, ProcessingMode.ProcessingExclusiveTask);
+            m_concurrentTaskScheduler = new ConcurrentExclusiveTaskScheduler(this, m_maxConcurrencyLevel, ProcessingMode.ProcessingConcurrentTasks);
+        }
+
+        /// <summary>Informs the scheduler pair that it should not accept any more tasks.</summary>
+        /// <remarks>
+        /// Calling <see cref="Complete"/> is optional, and it's only necessary if the <see cref="Completion"/>
+        /// will be relied on for notification of all processing being completed.
+        /// </remarks>
+        public void Complete()
+        {
+            lock (ValueLock)
+            {
+                if (!CompletionRequested)
+                {
+                    RequestCompletion();
+                    CleanupStateIfCompletingAndQuiesced();
+                }
+            }
+        }
+
+        /// <summary>Gets a <see cref="System.Threading.Tasks.Task"/> that will complete when the scheduler has completed processing.</summary>
+        public Task Completion
+        {
+            // ValueLock not needed, but it's ok if it's held
+            get { return EnsureCompletionStateInitialized().Task; }
+        }
+
+        /// <summary>Gets the lazily-initialized completion state.</summary>
+        private CompletionState EnsureCompletionStateInitialized()
+        {
+            // ValueLock not needed, but it's ok if it's held
+            return LazyInitializer.EnsureInitialized(ref m_completionState, () => new CompletionState());
+        }
+
+        /// <summary>Gets whether completion has been requested.</summary>
+        private bool CompletionRequested
+        {
+            // ValueLock not needed, but it's ok if it's held
+            get { return m_completionState != null && Volatile.Read(ref m_completionState.m_completionRequested); }
+        }
+
+        /// <summary>Sets that completion has been requested.</summary>
+        private void RequestCompletion()
+        {
+            ContractAssertMonitorStatus(ValueLock, held: true);
+            EnsureCompletionStateInitialized().m_completionRequested = true;
+        }
+
+        /// <summary>
+        /// Cleans up state if and only if there's no processing currently happening
+        /// and no more to be done later.
+        /// </summary>
+        private void CleanupStateIfCompletingAndQuiesced()
+        {
+            ContractAssertMonitorStatus(ValueLock, held: true);
+            if (ReadyToComplete) CompleteTaskAsync();
+        }
+
+        /// <summary>Gets whether the pair is ready to complete.</summary>
+        private bool ReadyToComplete
+        {
+            get
+            {
+                ContractAssertMonitorStatus(ValueLock, held: true);
+
+                // We can only complete if completion has been requested and no processing is currently happening.
+                if (!CompletionRequested || m_processingCount != 0) return false;
+
+                // Now, only allow shutdown if an exception occurred or if there are no more tasks to process.
+                var cs = EnsureCompletionStateInitialized();
+                return
+                    (cs.m_exceptions != null && cs.m_exceptions.Count > 0) ||
+                    (m_concurrentTaskScheduler.m_tasks.IsEmpty && m_exclusiveTaskScheduler.m_tasks.IsEmpty);
+            }
+        }
+
+        /// <summary>Completes the completion task asynchronously.</summary>
+        private void CompleteTaskAsync()
+        {
+            Debug.Assert(ReadyToComplete, "The block must be ready to complete to be here.");
+            ContractAssertMonitorStatus(ValueLock, held: true);
+
+            // Ensure we only try to complete once, then schedule completion
+            // in order to escape held locks and the caller's context
+            var cs = EnsureCompletionStateInitialized();
+            if (!cs.m_completionQueued)
+            {
+                cs.m_completionQueued = true;
+                ThreadPool.QueueUserWorkItem(state =>
+                {
+                    var localThis = (ConcurrentExclusiveSchedulerPair)state;
+                    Debug.Assert(!localThis.m_completionState.Task.IsCompleted, "Completion should only happen once.");
+
+                    List<Exception> exceptions = localThis.m_completionState.m_exceptions;
+                    bool success = (exceptions != null && exceptions.Count > 0) ?
+                        localThis.m_completionState.TrySetException(exceptions) :
+                        localThis.m_completionState.TrySetResult(default);
+                    Debug.Assert(success, "Expected to complete completion task.");
+
+                    localThis.m_threadProcessingMode.Dispose();
+                }, this);
+            }
+        }
+
+        /// <summary>Initiates scheduler shutdown due to a worker task faulting.</summary>
+        /// <param name="faultedTask">The faulted worker task that's initiating the shutdown.</param>
+        private void FaultWithTask(Task faultedTask)
+        {
+            Debug.Assert(faultedTask != null && faultedTask.IsFaulted && faultedTask.Exception.InnerExceptions.Count > 0,
+                "Needs a task in the faulted state and thus with exceptions.");
+            ContractAssertMonitorStatus(ValueLock, held: true);
+
+            // Store the faulted task's exceptions
+            var cs = EnsureCompletionStateInitialized();
+            if (cs.m_exceptions == null) cs.m_exceptions = new List<Exception>();
+            cs.m_exceptions.AddRange(faultedTask.Exception.InnerExceptions);
+
+            // Now that we're doomed, request completion
+            RequestCompletion();
+        }
+
+        /// <summary>
+        /// Gets a TaskScheduler that can be used to schedule tasks to this pair
+        /// that may run concurrently with other tasks on this pair.
+        /// </summary>
+        public TaskScheduler ConcurrentScheduler { get { return m_concurrentTaskScheduler; } }
+        /// <summary>
+        /// Gets a TaskScheduler that can be used to schedule tasks to this pair
+        /// that must run exclusively with regards to other tasks on this pair.
+        /// </summary>
+        public TaskScheduler ExclusiveScheduler { get { return m_exclusiveTaskScheduler; } }
+
+        /// <summary>Gets the number of tasks waiting to run concurrently.</summary>
+        /// <remarks>This does not take the necessary lock, as it's only called from under the debugger.</remarks>
+        [SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
+        private int ConcurrentTaskCountForDebugger { get { return m_concurrentTaskScheduler.m_tasks.Count; } }
+
+        /// <summary>Gets the number of tasks waiting to run exclusively.</summary>
+        /// <remarks>This does not take the necessary lock, as it's only called from under the debugger.</remarks>
+        [SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
+        private int ExclusiveTaskCountForDebugger { get { return m_exclusiveTaskScheduler.m_tasks.Count; } }
+
+        /// <summary>Notifies the pair that new work has arrived to be processed.</summary>
+        /// <param name="fairly">Whether tasks should be scheduled fairly with regards to other tasks.</param>
+        /// <remarks>Must only be called while holding the lock.</remarks>
+        [SuppressMessage("Microsoft.Design", "CA1031:DoNotCatchGeneralExceptionTypes")]
+        [SuppressMessage("Microsoft.Performance", "CA1804:RemoveUnusedLocals")]
+        [SuppressMessage("Microsoft.Reliability", "CA2000:Dispose objects before losing scope")]
+        private void ProcessAsyncIfNecessary(bool fairly = false)
+        {
+            ContractAssertMonitorStatus(ValueLock, held: true);
+
+            // If the current processing count is >= 0, we can potentially launch further processing.
+            if (m_processingCount >= 0)
+            {
+                // We snap whether there are any exclusive tasks or concurrent tasks waiting.
+                // (We grab the concurrent count below only once we know we need it.)
+                // With processing happening concurrent to this operation, this data may 
+                // immediately be out of date, but it can only go from non-empty
+                // to empty and not the other way around.  As such, this is safe, 
+                // as worst case is we'll schedule an extra  task when we didn't
+                // otherwise need to, and we'll just eat its overhead.
+                bool exclusiveTasksAreWaiting = !m_exclusiveTaskScheduler.m_tasks.IsEmpty;
+
+                // If there's no processing currently happening but there are waiting exclusive tasks,
+                // let's start processing those exclusive tasks.
+                Task processingTask = null;
+                if (m_processingCount == 0 && exclusiveTasksAreWaiting)
+                {
+                    // Launch exclusive task processing
+                    m_processingCount = EXCLUSIVE_PROCESSING_SENTINEL; // -1
+                    try
+                    {
+                        processingTask = new Task(thisPair => ((ConcurrentExclusiveSchedulerPair)thisPair).ProcessExclusiveTasks(), this,
+                            default(CancellationToken), GetCreationOptionsForTask(fairly));
+                        processingTask.Start(m_underlyingTaskScheduler);
+                        // When we call Start, if the underlying scheduler throws in QueueTask, TPL will fault the task and rethrow
+                        // the exception.  To deal with that, we need a reference to the task object, so that we can observe its exception.
+                        // Hence, we separate creation and starting, so that we can store a reference to the task before we attempt QueueTask.
+                    }
+                    catch
+                    {
+                        m_processingCount = 0;
+                        FaultWithTask(processingTask);
+                    }
+                }
+                // If there are no waiting exclusive tasks, there are concurrent tasks, and we haven't reached our maximum
+                // concurrency level for processing, let's start processing more concurrent tasks.
+                else
+                {
+                    int concurrentTasksWaitingCount = m_concurrentTaskScheduler.m_tasks.Count;
+
+                    if (concurrentTasksWaitingCount > 0 && !exclusiveTasksAreWaiting && m_processingCount < m_maxConcurrencyLevel)
+                    {
+                        // Launch concurrent task processing, up to the allowed limit
+                        for (int i = 0; i < concurrentTasksWaitingCount && m_processingCount < m_maxConcurrencyLevel; ++i)
+                        {
+                            ++m_processingCount;
+                            try
+                            {
+                                processingTask = new Task(thisPair => ((ConcurrentExclusiveSchedulerPair)thisPair).ProcessConcurrentTasks(), this,
+                                    default(CancellationToken), GetCreationOptionsForTask(fairly));
+                                processingTask.Start(m_underlyingTaskScheduler); // See above logic for why we use new + Start rather than StartNew
+                            }
+                            catch
+                            {
+                                --m_processingCount;
+                                FaultWithTask(processingTask);
+                            }
+                        }
+                    }
+                }
+
+                // Check to see if all tasks have completed and if completion has been requested.
+                CleanupStateIfCompletingAndQuiesced();
+            }
+            else Debug.Assert(m_processingCount == EXCLUSIVE_PROCESSING_SENTINEL, "The processing count must be the sentinel if it's not >= 0.");
+        }
+
+        /// <summary>
+        /// Processes exclusive tasks serially until either there are no more to process
+        /// or we've reached our user-specified maximum limit.
+        /// </summary>
+        private void ProcessExclusiveTasks()
+        {
+            Debug.Assert(m_processingCount == EXCLUSIVE_PROCESSING_SENTINEL, "Processing exclusive tasks requires being in exclusive mode.");
+            Debug.Assert(!m_exclusiveTaskScheduler.m_tasks.IsEmpty, "Processing exclusive tasks requires tasks to be processed.");
+            ContractAssertMonitorStatus(ValueLock, held: false);
+            try
+            {
+                // Note that we're processing exclusive tasks on the current thread
+                Debug.Assert(m_threadProcessingMode.Value == ProcessingMode.NotCurrentlyProcessing,
+                    "This thread should not yet be involved in this pair's processing.");
+                m_threadProcessingMode.Value = ProcessingMode.ProcessingExclusiveTask;
+
+                // Process up to the maximum number of items per task allowed
+                for (int i = 0; i < m_maxItemsPerTask; i++)
+                {
+                    // Get the next available exclusive task.  If we can't find one, bail.
+                    Task exclusiveTask;
+                    if (!m_exclusiveTaskScheduler.m_tasks.TryDequeue(out exclusiveTask)) break;
+
+                    // Execute the task.  If the scheduler was previously faulted,
+                    // this task could have been faulted when it was queued; ignore such tasks.
+                    if (!exclusiveTask.IsFaulted) m_exclusiveTaskScheduler.ExecuteTask(exclusiveTask);
+                }
+            }
+            finally
+            {
+                // We're no longer processing exclusive tasks on the current thread
+                Debug.Assert(m_threadProcessingMode.Value == ProcessingMode.ProcessingExclusiveTask,
+                    "Somehow we ended up escaping exclusive mode.");
+                m_threadProcessingMode.Value = ProcessingMode.NotCurrentlyProcessing;
+
+                lock (ValueLock)
+                {
+                    // When this task was launched, we tracked it by setting m_processingCount to WRITER_IN_PROGRESS.
+                    // now reset it to 0.  Then check to see whether there's more processing to be done.
+                    // There might be more concurrent tasks available, for example, if concurrent tasks arrived
+                    // after we exited the loop, or if we exited the loop while concurrent tasks were still
+                    // available but we hit our maxItemsPerTask limit.
+                    Debug.Assert(m_processingCount == EXCLUSIVE_PROCESSING_SENTINEL, "The processing mode should not have deviated from exclusive.");
+                    m_processingCount = 0;
+                    ProcessAsyncIfNecessary(true);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Processes concurrent tasks serially until either there are no more to process,
+        /// we've reached our user-specified maximum limit, or exclusive tasks have arrived.
+        /// </summary>
+        private void ProcessConcurrentTasks()
+        {
+            Debug.Assert(m_processingCount > 0, "Processing concurrent tasks requires us to be in concurrent mode.");
+            ContractAssertMonitorStatus(ValueLock, held: false);
+            try
+            {
+                // Note that we're processing concurrent tasks on the current thread
+                Debug.Assert(m_threadProcessingMode.Value == ProcessingMode.NotCurrentlyProcessing,
+                    "This thread should not yet be involved in this pair's processing.");
+                m_threadProcessingMode.Value = ProcessingMode.ProcessingConcurrentTasks;
+
+                // Process up to the maximum number of items per task allowed
+                for (int i = 0; i < m_maxItemsPerTask; i++)
+                {
+                    // Get the next available concurrent task.  If we can't find one, bail.
+                    Task concurrentTask;
+                    if (!m_concurrentTaskScheduler.m_tasks.TryDequeue(out concurrentTask)) break;
+
+                    // Execute the task.  If the scheduler was previously faulted,
+                    // this task could have been faulted when it was queued; ignore such tasks.
+                    if (!concurrentTask.IsFaulted) m_concurrentTaskScheduler.ExecuteTask(concurrentTask);
+
+                    // Now check to see if exclusive tasks have arrived; if any have, they take priority
+                    // so we'll bail out here.  Note that we could have checked this condition
+                    // in the for loop's condition, but that could lead to extra overhead
+                    // in the case where a concurrent task arrives, this task is launched, and then
+                    // before entering the loop an exclusive task arrives.  If we didn't execute at
+                    // least one task, we would have spent all of the overhead to launch a
+                    // task but with none of the benefit.  There's of course also an inherent
+                    // race condition here with regards to exclusive tasks arriving, and we're ok with
+                    // executing one more concurrent task than we should before giving priority to exclusive tasks.
+                    if (!m_exclusiveTaskScheduler.m_tasks.IsEmpty) break;
+                }
+            }
+            finally
+            {
+                // We're no longer processing concurrent tasks on the current thread
+                Debug.Assert(m_threadProcessingMode.Value == ProcessingMode.ProcessingConcurrentTasks,
+                    "Somehow we ended up escaping concurrent mode.");
+                m_threadProcessingMode.Value = ProcessingMode.NotCurrentlyProcessing;
+
+                lock (ValueLock)
+                {
+                    // When this task was launched, we tracked it with a positive processing count;
+                    // decrement that count.  Then check to see whether there's more processing to be done.
+                    // There might be more concurrent tasks available, for example, if concurrent tasks arrived
+                    // after we exited the loop, or if we exited the loop while concurrent tasks were still
+                    // available but we hit our maxItemsPerTask limit.
+                    Debug.Assert(m_processingCount > 0, "The procesing mode should not have deviated from concurrent.");
+                    if (m_processingCount > 0) --m_processingCount;
+                    ProcessAsyncIfNecessary(true);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Holder for lazily-initialized state about the completion of a scheduler pair.
+        /// Completion is only triggered either by rare exceptional conditions or by
+        /// the user calling Complete, and as such we only lazily initialize this
+        /// state in one of those conditions or if the user explicitly asks for
+        /// the Completion.
+        /// </summary>
+        [SuppressMessage("Microsoft.Performance", "CA1812:AvoidUninstantiatedInternalClasses")]
+        private sealed class CompletionState : TaskCompletionSource<VoidTaskResult>
+        {
+            /// <summary>Whether the scheduler has had completion requested.</summary>
+            /// <remarks>This variable is not volatile, so to gurantee safe reading reads, Volatile.Read is used in TryExecuteTaskInline.</remarks>
+            internal bool m_completionRequested;
+            /// <summary>Whether completion processing has been queued.</summary>
+            internal bool m_completionQueued;
+            /// <summary>Unrecoverable exceptions incurred while processing.</summary>
+            internal List<Exception> m_exceptions;
+        }
+
+        /// <summary>
+        /// A scheduler shim used to queue tasks to the pair and execute those tasks on request of the pair.
+        /// </summary>
+        [DebuggerDisplay("Count={CountForDebugger}, MaxConcurrencyLevel={m_maxConcurrencyLevel}, Id={Id}")]
+        [DebuggerTypeProxy(typeof(ConcurrentExclusiveTaskScheduler.DebugView))]
+        private sealed class ConcurrentExclusiveTaskScheduler : TaskScheduler
+        {
+            /// <summary>Cached delegate for invoking TryExecuteTaskShim.</summary>
+            private static readonly Func<object, bool> s_tryExecuteTaskShim = new Func<object, bool>(TryExecuteTaskShim);
+            /// <summary>The parent pair.</summary>
+            private readonly ConcurrentExclusiveSchedulerPair m_pair;
+            /// <summary>The maximum concurrency level for the scheduler.</summary>
+            private readonly int m_maxConcurrencyLevel;
+            /// <summary>The processing mode of this scheduler, exclusive or concurrent.</summary>
+            private readonly ProcessingMode m_processingMode;
+            /// <summary>Gets the queue of tasks for this scheduler.</summary>
+            internal readonly IProducerConsumerQueue<Task> m_tasks;
+
+            /// <summary>Initializes the scheduler.</summary>
+            /// <param name="pair">The parent pair.</param>
+            /// <param name="maxConcurrencyLevel">The maximum degree of concurrency this scheduler may use.</param>
+            /// <param name="processingMode">The processing mode of this scheduler.</param>
+            internal ConcurrentExclusiveTaskScheduler(ConcurrentExclusiveSchedulerPair pair, int maxConcurrencyLevel, ProcessingMode processingMode)
+            {
+                Debug.Assert(pair != null, "Scheduler must be associated with a valid pair.");
+                Debug.Assert(processingMode == ProcessingMode.ProcessingConcurrentTasks || processingMode == ProcessingMode.ProcessingExclusiveTask,
+                    "Scheduler must be for concurrent or exclusive processing.");
+                Debug.Assert(
+                    (processingMode == ProcessingMode.ProcessingConcurrentTasks && (maxConcurrencyLevel >= 1 || maxConcurrencyLevel == UNLIMITED_PROCESSING)) ||
+                    (processingMode == ProcessingMode.ProcessingExclusiveTask && maxConcurrencyLevel == 1),
+                    "If we're in concurrent mode, our concurrency level should be positive or unlimited.  If exclusive, it should be 1.");
+
+                m_pair = pair;
+                m_maxConcurrencyLevel = maxConcurrencyLevel;
+                m_processingMode = processingMode;
+                m_tasks = (processingMode == ProcessingMode.ProcessingExclusiveTask) ?
+                    (IProducerConsumerQueue<Task>)new SingleProducerSingleConsumerQueue<Task>() :
+                    (IProducerConsumerQueue<Task>)new MultiProducerMultiConsumerQueue<Task>();
+            }
+
+            /// <summary>Gets the maximum concurrency level this scheduler is able to support.</summary>
+            public override int MaximumConcurrencyLevel { get { return m_maxConcurrencyLevel; } }
+
+            /// <summary>Queues a task to the scheduler.</summary>
+            /// <param name="task">The task to be queued.</param>
+            protected internal override void QueueTask(Task task)
+            {
+                Debug.Assert(task != null, "Infrastructure should have provided a non-null task.");
+                lock (m_pair.ValueLock)
+                {
+                    // If the scheduler has already had completion requested, no new work is allowed to be scheduled
+                    if (m_pair.CompletionRequested) throw new InvalidOperationException(GetType().ToString());
+
+                    // Queue the task, and then let the pair know that more work is now available to be scheduled
+                    m_tasks.Enqueue(task);
+                    m_pair.ProcessAsyncIfNecessary();
+                }
+            }
+
+            /// <summary>Executes a task on this scheduler.</summary>
+            /// <param name="task">The task to be executed.</param>
+            internal void ExecuteTask(Task task)
+            {
+                Debug.Assert(task != null, "Infrastructure should have provided a non-null task.");
+                base.TryExecuteTask(task);
+            }
+
+            /// <summary>Tries to execute the task synchronously on this scheduler.</summary>
+            /// <param name="task">The task to execute.</param>
+            /// <param name="taskWasPreviouslyQueued">Whether the task was previously queued to the scheduler.</param>
+            /// <returns>true if the task could be executed; otherwise, false.</returns>
+            protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
+            {
+                Debug.Assert(task != null, "Infrastructure should have provided a non-null task.");
+
+                // If the scheduler has had completion requested, no new work is allowed to be scheduled.
+                // A non-locked read on m_completionRequested (in CompletionRequested) is acceptable here because:
+                // a) we don't need to be exact... a Complete call could come in later in the function anyway
+                // b) this is only a fast path escape hatch.  To actually inline the task,
+                //    we need to be inside of an already executing task, and in such a case,
+                //    while completion may have been requested, we can't have shutdown yet.
+                if (!taskWasPreviouslyQueued && m_pair.CompletionRequested) return false;
+
+                // We know the implementation of the default scheduler and how it will behave. 
+                // As it's the most common underlying scheduler, we optimize for it.
+                bool isDefaultScheduler = m_pair.m_underlyingTaskScheduler == TaskScheduler.Default;
+
+                // If we're targeting the default scheduler and taskWasPreviouslyQueued is true,
+                // we know that the default scheduler will only allow it to be inlined
+                // if we're on a thread pool thread (but it won't always allow it in that case,
+                // since it'll only allow inlining if it can find the task in the local queue).
+                // As such, if we're not on a thread pool thread, we know for sure the
+                // task won't be inlined, so let's not even try.
+                if (isDefaultScheduler && taskWasPreviouslyQueued && !Thread.CurrentThread.IsThreadPoolThread)
+                {
+                    return false;
+                }
+                else
+                {
+                    // If a task is already running on this thread, allow inline execution to proceed.
+                    // If there's already a task from this scheduler running on the current thread, we know it's safe
+                    // to run this task, in effect temporarily taking that task's count allocation.
+                    if (m_pair.m_threadProcessingMode.Value == m_processingMode)
+                    {
+                        // If we're targeting the default scheduler and taskWasPreviouslyQueued is false,
+                        // we know the default scheduler will allow it, so we can just execute it here.
+                        // Otherwise, delegate to the target scheduler's inlining.
+                        return (isDefaultScheduler && !taskWasPreviouslyQueued) ?
+                            TryExecuteTask(task) :
+                            TryExecuteTaskInlineOnTargetScheduler(task);
+                    }
+                }
+
+                // We're not in the context of a task already executing on this scheduler.  Bail.
+                return false;
+            }
+
+            /// <summary>
+            /// Implements a reasonable approximation for TryExecuteTaskInline on the underlying scheduler, 
+            /// which we can't call directly on the underlying scheduler.
+            /// </summary>
+            /// <param name="task">The task to execute inline if possible.</param>
+            /// <returns>true if the task was inlined successfully; otherwise, false.</returns>
+            [SuppressMessage("Microsoft.Performance", "CA1804:RemoveUnusedLocals", MessageId = "ignored")]
+            private bool TryExecuteTaskInlineOnTargetScheduler(Task task)
+            {
+                // We'd like to simply call TryExecuteTaskInline here, but we can't.
+                // As there's no built-in API for this, a workaround is to create a new task that,
+                // when executed, will simply call TryExecuteTask to run the real task, and then
+                // we run our new shim task synchronously on the target scheduler.  If all goes well,
+                // our synchronous invocation will succeed in running the shim task on the current thread,
+                // which will in turn run the real task on the current thread.  If the scheduler
+                // doesn't allow that execution, RunSynchronously will block until the underlying scheduler
+                // is able to invoke the task, which might account for an additional but unavoidable delay.
+                // Once it's done, we can return whether the task executed by returning the
+                // shim task's Result, which is in turn the result of TryExecuteTask.
+                var t = new Task<bool>(s_tryExecuteTaskShim, Tuple.Create(this, task));
+                try
+                {
+                    t.RunSynchronously(m_pair.m_underlyingTaskScheduler);
+                    return t.Result;
+                }
+                catch
+                {
+                    Debug.Assert(t.IsFaulted, "Task should be faulted due to the scheduler faulting it and throwing the exception.");
+                    var ignored = t.Exception;
+                    throw;
+                }
+                finally { t.Dispose(); }
+            }
+
+            /// <summary>Shim used to invoke this.TryExecuteTask(task).</summary>
+            /// <param name="state">A tuple of the ConcurrentExclusiveTaskScheduler and the task to execute.</param>
+            /// <returns>true if the task was successfully inlined; otherwise, false.</returns>
+            /// <remarks>
+            /// This method is separated out not because of performance reasons but so that
+            /// the SecuritySafeCritical attribute may be employed.
+            /// </remarks>
+            private static bool TryExecuteTaskShim(object state)
+            {
+                var tuple = (Tuple<ConcurrentExclusiveTaskScheduler, Task>)state;
+                return tuple.Item1.TryExecuteTask(tuple.Item2);
+            }
+
+            /// <summary>Gets for debugging purposes the tasks scheduled to this scheduler.</summary>
+            /// <returns>An enumerable of the tasks queued.</returns>
+            protected override IEnumerable<Task> GetScheduledTasks() { return m_tasks; }
+
+            /// <summary>Gets the number of tasks queued to this scheduler.</summary>
+            [SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
+            private int CountForDebugger { get { return m_tasks.Count; } }
+
+            /// <summary>Provides a debug view for ConcurrentExclusiveTaskScheduler.</summary>
+            private sealed class DebugView
+            {
+                /// <summary>The scheduler being debugged.</summary>
+                private readonly ConcurrentExclusiveTaskScheduler m_taskScheduler;
+
+                /// <summary>Initializes the debug view.</summary>
+                /// <param name="scheduler">The scheduler being debugged.</param>
+                public DebugView(ConcurrentExclusiveTaskScheduler scheduler)
+                {
+                    Debug.Assert(scheduler != null, "Need a scheduler with which to construct the debug view.");
+                    m_taskScheduler = scheduler;
+                }
+
+                /// <summary>Gets this pair's maximum allowed concurrency level.</summary>
+                public int MaximumConcurrencyLevel { get { return m_taskScheduler.m_maxConcurrencyLevel; } }
+                /// <summary>Gets the tasks scheduled to this scheduler.</summary>
+                public IEnumerable<Task> ScheduledTasks { get { return m_taskScheduler.m_tasks; } }
+                /// <summary>Gets the scheduler pair with which this scheduler is associated.</summary>
+                public ConcurrentExclusiveSchedulerPair SchedulerPair { get { return m_taskScheduler.m_pair; } }
+            }
+        }
+
+        /// <summary>Provides a debug view for ConcurrentExclusiveSchedulerPair.</summary>
+        private sealed class DebugView
+        {
+            /// <summary>The pair being debugged.</summary>
+            private readonly ConcurrentExclusiveSchedulerPair m_pair;
+
+            /// <summary>Initializes the debug view.</summary>
+            /// <param name="pair">The pair being debugged.</param>
+            public DebugView(ConcurrentExclusiveSchedulerPair pair)
+            {
+                Debug.Assert(pair != null, "Need a pair with which to construct the debug view.");
+                m_pair = pair;
+            }
+
+            /// <summary>Gets a representation of the execution state of the pair.</summary>
+            public ProcessingMode Mode { get { return m_pair.ModeForDebugger; } }
+            /// <summary>Gets the number of tasks waiting to run exclusively.</summary>
+            public IEnumerable<Task> ScheduledExclusive { get { return m_pair.m_exclusiveTaskScheduler.m_tasks; } }
+            /// <summary>Gets the number of tasks waiting to run concurrently.</summary>
+            public IEnumerable<Task> ScheduledConcurrent { get { return m_pair.m_concurrentTaskScheduler.m_tasks; } }
+            /// <summary>Gets the number of tasks currently being executed.</summary>
+            public int CurrentlyExecutingTaskCount
+            {
+                get { return (m_pair.m_processingCount == EXCLUSIVE_PROCESSING_SENTINEL) ? 1 : m_pair.m_processingCount; }
+            }
+            /// <summary>Gets the underlying task scheduler that actually executes the tasks.</summary>
+            public TaskScheduler TargetScheduler { get { return m_pair.m_underlyingTaskScheduler; } }
+        }
+
+        /// <summary>Gets an enumeration for debugging that represents the current state of the scheduler pair.</summary>
+        /// <remarks>This is only for debugging.  It does not take the necessary locks to be useful for runtime usage.</remarks>
+        private ProcessingMode ModeForDebugger
+        {
+            get
+            {
+                // If our completion task is done, so are we.
+                if (m_completionState != null && m_completionState.Task.IsCompleted) return ProcessingMode.Completed;
+
+                // Otherwise, summarize our current state.
+                var mode = ProcessingMode.NotCurrentlyProcessing;
+                if (m_processingCount == EXCLUSIVE_PROCESSING_SENTINEL) mode |= ProcessingMode.ProcessingExclusiveTask;
+                if (m_processingCount >= 1) mode |= ProcessingMode.ProcessingConcurrentTasks;
+                if (CompletionRequested) mode |= ProcessingMode.Completing;
+                return mode;
+            }
+        }
+
+        /// <summary>Asserts that a given synchronization object is either held or not held.</summary>
+        /// <param name="syncObj">The monitor to check.</param>
+        /// <param name="held">Whether we want to assert that it's currently held or not held.</param>
+        [Conditional("DEBUG")]
+        private static void ContractAssertMonitorStatus(object syncObj, bool held)
+        {
+            Debug.Assert(syncObj != null, "The monitor object to check must be provided.");
+            Debug.Assert(Monitor.IsEntered(syncObj) == held, "The locking scheme was not correctly followed.");
+        }
+
+        /// <summary>Gets the options to use for tasks.</summary>
+        /// <param name="isReplacementReplica">If this task is being created to replace another.</param>
+        /// <remarks>
+        /// These options should be used for all tasks that have the potential to run user code or
+        /// that are repeatedly spawned and thus need a modicum of fair treatment.
+        /// </remarks>
+        /// <returns>The options to use.</returns>
+        internal static TaskCreationOptions GetCreationOptionsForTask(bool isReplacementReplica = false)
+        {
+            TaskCreationOptions options = TaskCreationOptions.DenyChildAttach;
+            if (isReplacementReplica) options |= TaskCreationOptions.PreferFairness;
+            return options;
+        }
+
+        /// <summary>Provides an enumeration that represents the current state of the scheduler pair.</summary>
+        [Flags]
+        private enum ProcessingMode : byte
+        {
+            /// <summary>The scheduler pair is currently dormant, with no work scheduled.</summary>
+            NotCurrentlyProcessing = 0x0,
+            /// <summary>The scheduler pair has queued processing for exclusive tasks.</summary>
+            ProcessingExclusiveTask = 0x1,
+            /// <summary>The scheduler pair has queued processing for concurrent tasks.</summary>
+            ProcessingConcurrentTasks = 0x2,
+            /// <summary>Completion has been requested.</summary>
+            Completing = 0x4,
+            /// <summary>The scheduler pair is finished processing.</summary>
+            Completed = 0x8
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Tasks/Sources/IValueTaskSource.cs b/src/System.Private.CoreLib/shared/System/Threading/Tasks/Sources/IValueTaskSource.cs
new file mode 100644
index 0000000000..e411146a1d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/Tasks/Sources/IValueTaskSource.cs
@@ -0,0 +1,82 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Threading.Tasks.Sources
+{
+    /// <summary>
+    /// Flags passed from <see cref="ValueTask"/> and <see cref="ValueTask{TResult}"/> to
+    /// <see cref="IValueTaskSource.OnCompleted"/> and <see cref="IValueTaskSource{TResult}.OnCompleted"/>
+    /// to control behavior.
+    /// </summary>
+    [Flags]
+    public enum ValueTaskSourceOnCompletedFlags
+    {
+        /// <summary>
+        /// No requirements are placed on how the continuation is invoked.
+        /// </summary>
+        None,
+        /// <summary>
+        /// Set if OnCompleted should capture the current scheduling context (e.g. SynchronizationContext)
+        /// and use it when queueing the continuation for execution.  If this is not set, the implementation
+        /// may choose to execute the continuation in an arbitrary location.
+        /// </summary>
+        UseSchedulingContext = 0x1,
+        /// <summary>
+        /// Set if OnCompleted should capture the current ExecutionContext and use it to run the continuation.
+        /// </summary>
+        FlowExecutionContext = 0x2,
+    }
+
+    /// <summary>Indicates the status of an <see cref="IValueTaskSource"/> or <see cref="IValueTaskSource{TResult}"/>.</summary>
+    public enum ValueTaskSourceStatus
+    {
+        /// <summary>The operation has not yet completed.</summary>
+        Pending = 0,
+        /// <summary>The operation completed successfully.</summary>
+        Succeeded = 1,
+        /// <summary>The operation completed with an error.</summary>
+        Faulted = 2,
+        /// <summary>The operation completed due to cancellation.</summary>
+        Canceled = 3
+    }
+
+    /// <summary>Represents an object that can be wrapped by a <see cref="ValueTask"/>.</summary>
+    public interface IValueTaskSource
+    {
+        /// <summary>Gets the status of the current operation.</summary>
+        /// <param name="token">Opaque value that was provided to the <see cref="ValueTask"/>'s constructor.</param>
+        ValueTaskSourceStatus GetStatus(short token);
+
+        /// <summary>Schedules the continuation action for this <see cref="IValueTaskSource"/>.</summary>
+        /// <param name="continuation">The continuation to invoke when the operation has completed.</param>
+        /// <param name="state">The state object to pass to <paramref name="continuation"/> when it's invoked.</param>
+        /// <param name="token">Opaque value that was provided to the <see cref="ValueTask"/>'s constructor.</param>
+        /// <param name="flags">The flags describing the behavior of the continuation.</param>
+        void OnCompleted(Action<object> continuation, object state, short token, ValueTaskSourceOnCompletedFlags flags);
+
+        /// <summary>Gets the result of the <see cref="IValueTaskSource"/>.</summary>
+        /// <param name="token">Opaque value that was provided to the <see cref="ValueTask"/>'s constructor.</param>
+        void GetResult(short token);
+    }
+
+    /// <summary>Represents an object that can be wrapped by a <see cref="ValueTask{TResult}"/>.</summary>
+    /// <typeparam name="TResult">Specifies the type of data returned from the object.</typeparam>
+    public interface IValueTaskSource<out TResult>
+    {
+        /// <summary>Gets the status of the current operation.</summary>
+        /// <param name="token">Opaque value that was provided to the <see cref="ValueTask"/>'s constructor.</param>
+        ValueTaskSourceStatus GetStatus(short token);
+
+        /// <summary>Schedules the continuation action for this <see cref="IValueTaskSource{TResult}"/>.</summary>
+        /// <param name="continuation">The continuation to invoke when the operation has completed.</param>
+        /// <param name="state">The state object to pass to <paramref name="continuation"/> when it's invoked.</param>
+        /// <param name="token">Opaque value that was provided to the <see cref="ValueTask"/>'s constructor.</param>
+        /// <param name="flags">The flags describing the behavior of the continuation.</param>
+        void OnCompleted(Action<object> continuation, object state, short token, ValueTaskSourceOnCompletedFlags flags);
+
+        /// <summary>Gets the result of the <see cref="IValueTaskSource{TResult}"/>.</summary>
+        /// <param name="token">Opaque value that was provided to the <see cref="ValueTask"/>'s constructor.</param>
+        TResult GetResult(short token);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskCanceledException.cs b/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskCanceledException.cs
new file mode 100644
index 0000000000..c3ee31a53c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskCanceledException.cs
@@ -0,0 +1,99 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// An exception for task cancellations.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System;
+using System.Runtime.InteropServices;
+using System.Runtime.Serialization;
+
+namespace System.Threading.Tasks
+{
+    /// <summary>
+    /// Represents an exception used to communicate task cancellation.
+    /// </summary>
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class TaskCanceledException : OperationCanceledException
+    {
+        [NonSerialized]
+        private readonly Task _canceledTask; // The task which has been canceled.
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Tasks.TaskCanceledException"/> class.
+        /// </summary>
+        public TaskCanceledException() : base(SR.TaskCanceledException_ctor_DefaultMessage)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Tasks.TaskCanceledException"/>
+        /// class with a specified error message.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        public TaskCanceledException(string message) : base(message)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Tasks.TaskCanceledException"/>
+        /// class with a specified error message and a reference to the inner exception that is the cause of
+        /// this exception.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        /// <param name="innerException">The exception that is the cause of the current exception.</param>
+        public TaskCanceledException(string message, Exception innerException) : base(message, innerException)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Tasks.TaskCanceledException"/>
+        /// class with a specified error message, a reference to the inner exception that is the cause of
+        /// this exception, and the <see cref="CancellationToken"/> that triggered the cancellation.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        /// <param name="innerException">The exception that is the cause of the current exception.</param>
+        /// <param name="token">The <see cref="CancellationToken"/> that triggered the cancellation.</param>
+        public TaskCanceledException(string message, Exception innerException, CancellationToken token) : base(message, innerException, token)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Tasks.TaskCanceledException"/> class
+        /// with a reference to the <see cref="T:System.Threading.Tasks.Task"/> that has been canceled.
+        /// </summary>
+        /// <param name="task">A task that has been canceled.</param>
+        public TaskCanceledException(Task task) :
+            base(SR.TaskCanceledException_ctor_DefaultMessage, task != null ? task.CancellationToken : new CancellationToken())
+        {
+            _canceledTask = task;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Tasks.TaskCanceledException"/>
+        /// class with serialized data.
+        /// </summary>
+        /// <param name="info">The <see cref="T:System.Runtime.Serialization.SerializationInfo"/> that holds the serialized object data about the exception being thrown.</param>
+        /// <param name="context">The <see cref="T:System.Runtime.Serialization.StreamingContext"/> that contains contextual information about the source or destination. </param>
+        protected TaskCanceledException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+
+        /// <summary>
+        /// Gets the task associated with this exception.
+        /// </summary>
+        /// <remarks>
+        /// It is permissible for no Task to be associated with a 
+        /// <see cref="T:System.Threading.Tasks.TaskCanceledException"/>, in which case
+        /// this property will return null.
+        /// </remarks>
+        public Task Task => _canceledTask;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskCompletionSource.cs b/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskCompletionSource.cs
new file mode 100644
index 0000000000..992e9db767
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskCompletionSource.cs
@@ -0,0 +1,349 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// TaskCompletionSource<TResult> is the producer end of an unbound future.  Its
+// Task member may be distributed as the consumer end of the future.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System;
+using System.Diagnostics;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Runtime.ExceptionServices;
+using System.Threading;
+
+// Disable the "reference to volatile field not treated as volatile" error.
+#pragma warning disable 0420
+
+namespace System.Threading.Tasks
+{
+    /// <summary>
+    /// Represents the producer side of a <see cref="T:System.Threading.Tasks.Task{TResult}"/> unbound to a
+    /// delegate, providing access to the consumer side through the <see cref="Task"/> property.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// It is often the case that a <see cref="T:System.Threading.Tasks.Task{TResult}"/> is desired to
+    /// represent another asynchronous operation.
+    /// <see cref="TaskCompletionSource{TResult}">TaskCompletionSource</see> is provided for this purpose. It enables
+    /// the creation of a task that can be handed out to consumers, and those consumers can use the members
+    /// of the task as they would any other. However, unlike most tasks, the state of a task created by a
+    /// TaskCompletionSource is controlled explicitly by the methods on TaskCompletionSource. This enables the
+    /// completion of the external asynchronous operation to be propagated to the underlying Task. The
+    /// separation also ensures that consumers are not able to transition the state without access to the
+    /// corresponding TaskCompletionSource.
+    /// </para>
+    /// <para>
+    /// All members of <see cref="TaskCompletionSource{TResult}"/> are thread-safe
+    /// and may be used from multiple threads concurrently.
+    /// </para>
+    /// </remarks>
+    /// <typeparam name="TResult">The type of the result value associated with this <see
+    /// cref="TaskCompletionSource{TResult}"/>.</typeparam>
+    public class TaskCompletionSource<TResult>
+    {
+        private readonly Task<TResult> _task;
+
+        /// <summary>
+        /// Creates a <see cref="TaskCompletionSource{TResult}"/>.
+        /// </summary>
+        public TaskCompletionSource()
+        {
+            _task = new Task<TResult>();
+        }
+
+        /// <summary>
+        /// Creates a <see cref="TaskCompletionSource{TResult}"/>
+        /// with the specified options.
+        /// </summary>
+        /// <remarks>
+        /// The <see cref="T:System.Threading.Tasks.Task{TResult}"/> created
+        /// by this instance and accessible through its <see cref="Task"/> property
+        /// will be instantiated using the specified <paramref name="creationOptions"/>.
+        /// </remarks>
+        /// <param name="creationOptions">The options to use when creating the underlying
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="creationOptions"/> represent options invalid for use
+        /// with a <see cref="TaskCompletionSource{TResult}"/>.
+        /// </exception>
+        public TaskCompletionSource(TaskCreationOptions creationOptions)
+            : this(null, creationOptions)
+        {
+        }
+
+        /// <summary>
+        /// Creates a <see cref="TaskCompletionSource{TResult}"/>
+        /// with the specified state.
+        /// </summary>
+        /// <param name="state">The state to use as the underlying 
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/>'s AsyncState.</param>
+        public TaskCompletionSource(object state)
+            : this(state, TaskCreationOptions.None)
+        {
+        }
+
+        /// <summary>
+        /// Creates a <see cref="TaskCompletionSource{TResult}"/> with
+        /// the specified state and options.
+        /// </summary>
+        /// <param name="creationOptions">The options to use when creating the underlying
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="state">The state to use as the underlying 
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/>'s AsyncState.</param>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="creationOptions"/> represent options invalid for use
+        /// with a <see cref="TaskCompletionSource{TResult}"/>.
+        /// </exception>
+        public TaskCompletionSource(object state, TaskCreationOptions creationOptions)
+        {
+            _task = new Task<TResult>(state, creationOptions);
+        }
+
+
+        /// <summary>
+        /// Gets the <see cref="T:System.Threading.Tasks.Task{TResult}"/> created
+        /// by this <see cref="TaskCompletionSource{TResult}"/>.
+        /// </summary>
+        /// <remarks>
+        /// This property enables a consumer access to the <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/> that is controlled by this instance.
+        /// The <see cref="SetResult"/>, <see cref="SetException(System.Exception)"/>,
+        /// <see cref="SetException(System.Collections.Generic.IEnumerable{System.Exception})"/>, and <see cref="SetCanceled"/>
+        /// methods (and their "Try" variants) on this instance all result in the relevant state
+        /// transitions on this underlying Task.
+        /// </remarks>
+        public Task<TResult> Task => _task;
+
+        /// <summary>Spins until the underlying task is completed.</summary>
+        /// <remarks>This should only be called if the task is in the process of being completed by another thread.</remarks>
+        private void SpinUntilCompleted()
+        {
+            // Spin wait until the completion is finalized by another thread.
+            var sw = new SpinWait();
+            while (!_task.IsCompleted)
+                sw.SpinOnce();
+        }
+
+        /// <summary>
+        /// Attempts to transition the underlying
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/> into the 
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>
+        /// state.
+        /// </summary>
+        /// <param name="exception">The exception to bind to this <see 
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>True if the operation was successful; otherwise, false.</returns>
+        /// <remarks>This operation will return false if the 
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/> is already in one
+        /// of the three final states:
+        /// <see cref="System.Threading.Tasks.TaskStatus.RanToCompletion">RanToCompletion</see>, 
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>, or
+        /// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="exception"/> argument is null.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The <see cref="Task"/> was disposed.</exception>
+        public bool TrySetException(Exception exception)
+        {
+            if (exception == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.exception);
+
+            bool rval = _task.TrySetException(exception);
+            if (!rval && !_task.IsCompleted) SpinUntilCompleted();
+            return rval;
+        }
+
+        /// <summary>
+        /// Attempts to transition the underlying
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/> into the 
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>
+        /// state.
+        /// </summary>
+        /// <param name="exceptions">The collection of exceptions to bind to this <see 
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>True if the operation was successful; otherwise, false.</returns>
+        /// <remarks>This operation will return false if the 
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/> is already in one
+        /// of the three final states:
+        /// <see cref="System.Threading.Tasks.TaskStatus.RanToCompletion">RanToCompletion</see>, 
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>, or
+        /// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="exceptions"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">There are one or more null elements in <paramref name="exceptions"/>.</exception>
+        /// <exception cref="T:System.ArgumentException">The <paramref name="exceptions"/> collection is empty.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The <see cref="Task"/> was disposed.</exception>
+        public bool TrySetException(IEnumerable<Exception> exceptions)
+        {
+            if (exceptions == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.exceptions);
+
+            List<Exception> defensiveCopy = new List<Exception>();
+            foreach (Exception e in exceptions)
+            {
+                if (e == null)
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.TaskCompletionSourceT_TrySetException_NullException, ExceptionArgument.exceptions);
+                defensiveCopy.Add(e);
+            }
+
+            if (defensiveCopy.Count == 0)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.TaskCompletionSourceT_TrySetException_NoExceptions, ExceptionArgument.exceptions);
+
+            bool rval = _task.TrySetException(defensiveCopy);
+            if (!rval && !_task.IsCompleted) SpinUntilCompleted();
+            return rval;
+        }
+
+        /// <summary>
+        /// Transitions the underlying
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/> into the 
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>
+        /// state.
+        /// </summary>
+        /// <param name="exception">The exception to bind to this <see 
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="exception"/> argument is null.</exception>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The underlying <see cref="T:System.Threading.Tasks.Task{TResult}"/> is already in one
+        /// of the three final states:
+        /// <see cref="System.Threading.Tasks.TaskStatus.RanToCompletion">RanToCompletion</see>, 
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>, or
+        /// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The <see cref="Task"/> was disposed.</exception>
+        public void SetException(Exception exception)
+        {
+            if (exception == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.exception);
+
+            if (!TrySetException(exception))
+            {
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.TaskT_TransitionToFinal_AlreadyCompleted);
+            }
+        }
+
+        /// <summary>
+        /// Transitions the underlying
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/> into the 
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>
+        /// state.
+        /// </summary>
+        /// <param name="exceptions">The collection of exceptions to bind to this <see 
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="exceptions"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">There are one or more null elements in <paramref name="exceptions"/>.</exception>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The underlying <see cref="T:System.Threading.Tasks.Task{TResult}"/> is already in one
+        /// of the three final states:
+        /// <see cref="System.Threading.Tasks.TaskStatus.RanToCompletion">RanToCompletion</see>, 
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>, or
+        /// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The <see cref="Task"/> was disposed.</exception>
+        public void SetException(IEnumerable<Exception> exceptions)
+        {
+            if (!TrySetException(exceptions))
+            {
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.TaskT_TransitionToFinal_AlreadyCompleted);
+            }
+        }
+
+
+        /// <summary>
+        /// Attempts to transition the underlying
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/> into the 
+        /// <see cref="System.Threading.Tasks.TaskStatus.RanToCompletion">RanToCompletion</see>
+        /// state.
+        /// </summary>
+        /// <param name="result">The result value to bind to this <see 
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>True if the operation was successful; otherwise, false.</returns>
+        /// <remarks>This operation will return false if the 
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/> is already in one
+        /// of the three final states:
+        /// <see cref="System.Threading.Tasks.TaskStatus.RanToCompletion">RanToCompletion</see>, 
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>, or
+        /// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>.
+        /// </remarks>
+        /// <exception cref="T:System.ObjectDisposedException">The <see cref="Task"/> was disposed.</exception>
+        public bool TrySetResult(TResult result)
+        {
+            bool rval = _task.TrySetResult(result);
+            if (!rval) SpinUntilCompleted();
+            return rval;
+        }
+
+        /// <summary>
+        /// Transitions the underlying
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/> into the 
+        /// <see cref="System.Threading.Tasks.TaskStatus.RanToCompletion">RanToCompletion</see>
+        /// state.
+        /// </summary>
+        /// <param name="result">The result value to bind to this <see 
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The underlying <see cref="T:System.Threading.Tasks.Task{TResult}"/> is already in one
+        /// of the three final states:
+        /// <see cref="System.Threading.Tasks.TaskStatus.RanToCompletion">RanToCompletion</see>, 
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>, or
+        /// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The <see cref="Task"/> was disposed.</exception>
+        public void SetResult(TResult result)
+        {
+            if (!TrySetResult(result))
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.TaskT_TransitionToFinal_AlreadyCompleted);
+        }
+
+        /// <summary>
+        /// Attempts to transition the underlying
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/> into the 
+        /// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>
+        /// state.
+        /// </summary>
+        /// <returns>True if the operation was successful; otherwise, false.</returns>
+        /// <remarks>This operation will return false if the 
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/> is already in one
+        /// of the three final states:
+        /// <see cref="System.Threading.Tasks.TaskStatus.RanToCompletion">RanToCompletion</see>, 
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>, or
+        /// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>.
+        /// </remarks>
+        /// <exception cref="T:System.ObjectDisposedException">The <see cref="Task"/> was disposed.</exception>
+        public bool TrySetCanceled()
+        {
+            return TrySetCanceled(default(CancellationToken));
+        }
+
+        // Enables a token to be stored into the canceled task
+        public bool TrySetCanceled(CancellationToken cancellationToken)
+        {
+            bool rval = _task.TrySetCanceled(cancellationToken);
+            if (!rval && !_task.IsCompleted) SpinUntilCompleted();
+            return rval;
+        }
+
+        /// <summary>
+        /// Transitions the underlying
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/> into the 
+        /// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>
+        /// state.
+        /// </summary>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The underlying <see cref="T:System.Threading.Tasks.Task{TResult}"/> is already in one
+        /// of the three final states:
+        /// <see cref="System.Threading.Tasks.TaskStatus.RanToCompletion">RanToCompletion</see>, 
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>, or
+        /// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The <see cref="Task"/> was disposed.</exception>
+        public void SetCanceled()
+        {
+            if (!TrySetCanceled())
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.TaskT_TransitionToFinal_AlreadyCompleted);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskExtensions.cs b/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskExtensions.cs
new file mode 100644
index 0000000000..97f2013d79
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskExtensions.cs
@@ -0,0 +1,48 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Threading.Tasks
+{
+    /// <summary>Provides a set of static methods for working with specific kinds of <see cref="Task"/> instances.</summary>
+    public static class TaskExtensions
+    {
+        /// <summary>Creates a proxy <see cref="Task"/> that represents the asynchronous operation of a <see cref="Task{Task}"/>.</summary>
+        /// <param name="task">The <see cref="Task{Task}"/> to unwrap.</param>
+        /// <returns>A <see cref="Task"/> that represents the asynchronous operation of the provided <see cref="Task{Task}"/>.</returns>
+        public static Task Unwrap(this Task<Task> task)
+        {
+            if (task == null)
+            {
+                throw new ArgumentNullException(nameof(task));
+            }
+
+            // If the task hasn't completed or was faulted/canceled, wrap it in an unwrap promise. Otherwise,
+            // it completed successfully.  Return its inner task to avoid unnecessary wrapping, or if the inner
+            // task is null, return a canceled task to match the same semantics as CreateUnwrapPromise.
+            return
+                !task.IsCompletedSuccessfully ? Task.CreateUnwrapPromise<VoidTaskResult>(task, lookForOce: false) :
+                task.Result ??
+                Task.FromCanceled(new CancellationToken(true));
+        }
+
+        /// <summary>Creates a proxy <see cref="Task{TResult}"/> that represents the asynchronous operation of a <see cref="Task{Task{TResult}}"/>.</summary>
+        /// <param name="task">The <see cref="Task{Task{TResult}}"/> to unwrap.</param>
+        /// <returns>A <see cref="Task{TResult}"/> that represents the asynchronous operation of the provided <see cref="Task{Task{TResult}}"/>.</returns>
+        public static Task<TResult> Unwrap<TResult>(this Task<Task<TResult>> task)
+        {
+            if (task == null)
+            {
+                throw new ArgumentNullException(nameof(task));
+            }
+
+            // If the task hasn't completed or was faulted/canceled, wrap it in an unwrap promise. Otherwise,
+            // it completed successfully.  Return its inner task to avoid unnecessary wrapping, or if the inner
+            // task is null, return a canceled task to match the same semantics as CreateUnwrapPromise.
+            return
+                !task.IsCompletedSuccessfully ? Task.CreateUnwrapPromise<TResult>(task, lookForOce: false) :
+                task.Result ??
+                Task.FromCanceled<TResult>(new CancellationToken(true));
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskSchedulerException.cs b/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskSchedulerException.cs
new file mode 100644
index 0000000000..85ec497219
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskSchedulerException.cs
@@ -0,0 +1,78 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// An exception for task schedulers.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System;
+using System.Runtime.InteropServices;
+using System.Runtime.Serialization;
+
+namespace System.Threading.Tasks
+{
+    /// <summary>
+    /// Represents an exception used to communicate an invalid operation by a
+    /// <see cref="T:System.Threading.Tasks.TaskScheduler"/>.
+    /// </summary>
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class TaskSchedulerException : Exception
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Tasks.TaskSchedulerException"/> class.
+        /// </summary>
+        public TaskSchedulerException() : base(SR.TaskSchedulerException_ctor_DefaultMessage) // 
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Tasks.TaskSchedulerException"/>
+        /// class with a specified error message.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        public TaskSchedulerException(string message) : base(message)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Tasks.TaskSchedulerException"/>
+        /// class using the default error message and a reference to the inner exception that is the cause of
+        /// this exception.
+        /// </summary>
+        /// <param name="innerException">The exception that is the cause of the current exception.</param>
+        public TaskSchedulerException(Exception innerException)
+            : base(SR.TaskSchedulerException_ctor_DefaultMessage, innerException)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Tasks.TaskSchedulerException"/>
+        /// class with a specified error message and a reference to the inner exception that is the cause of
+        /// this exception.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        /// <param name="innerException">The exception that is the cause of the current exception.</param>
+        public TaskSchedulerException(string message, Exception innerException) : base(message, innerException)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.Tasks.TaskSchedulerException"/>
+        /// class with serialized data.
+        /// </summary>
+        /// <param name="info">The <see cref="T:System.Runtime.Serialization.SerializationInfo"/> that holds
+        /// the serialized object data about the exception being thrown.</param>
+        /// <param name="context">The <see cref="T:System.Runtime.Serialization.StreamingContext"/> that
+        /// contains contextual information about the source or destination. </param>
+        protected TaskSchedulerException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskToApm.cs b/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskToApm.cs
new file mode 100644
index 0000000000..add41f588e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/Tasks/TaskToApm.cs
@@ -0,0 +1,189 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// Helper methods for using Tasks to implement the APM pattern.
+//
+// Example usage, wrapping a Task<int>-returning FooAsync method with Begin/EndFoo methods:
+//
+//     public IAsyncResult BeginFoo(..., AsyncCallback callback, object state)
+//     {
+//         Task<int> t = FooAsync(...);
+//         return TaskToApm.Begin(t, callback, state);
+//     }
+//     public int EndFoo(IAsyncResult asyncResult)
+//     {
+//         return TaskToApm.End<int>(asyncResult);
+//     }
+
+using System.Diagnostics;
+
+namespace System.Threading.Tasks
+{
+    /// <summary>
+    /// Provides support for efficiently using Tasks to implement the APM (Begin/End) pattern.
+    /// </summary>
+    internal static class TaskToApm
+    {
+        /// <summary>
+        /// Marshals the Task as an IAsyncResult, using the supplied callback and state
+        /// to implement the APM pattern.
+        /// </summary>
+        /// <param name="task">The Task to be marshaled.</param>
+        /// <param name="callback">The callback to be invoked upon completion.</param>
+        /// <param name="state">The state to be stored in the IAsyncResult.</param>
+        /// <returns>An IAsyncResult to represent the task's asynchronous operation.</returns>
+        public static IAsyncResult Begin(Task task, AsyncCallback callback, object state)
+        {
+            Debug.Assert(task != null);
+
+            // If the task has already completed, then since the Task's CompletedSynchronously==false
+            // and we want it to be true, we need to create a new IAsyncResult. (We also need the AsyncState to match.)
+            IAsyncResult asyncResult;
+            if (task.IsCompleted)
+            {
+                // Synchronous completion.
+                asyncResult = new TaskWrapperAsyncResult(task, state, completedSynchronously: true);
+                callback?.Invoke(asyncResult);
+            }
+            else
+            {
+                // For asynchronous completion we need to schedule a callback.  Whether we can use the Task as the IAsyncResult
+                // depends on whether the Task's AsyncState has reference equality with the requested state.
+                asyncResult = task.AsyncState == state ? (IAsyncResult)task : new TaskWrapperAsyncResult(task, state, completedSynchronously: false);
+                if (callback != null)
+                {
+                    InvokeCallbackWhenTaskCompletes(task, callback, asyncResult);
+                }
+            }
+            return asyncResult;
+        }
+
+        /// <summary>Processes an IAsyncResult returned by Begin.</summary>
+        /// <param name="asyncResult">The IAsyncResult to unwrap.</param>
+        public static void End(IAsyncResult asyncResult)
+        {
+            Task task;
+
+            // If the IAsyncResult is our task-wrapping IAsyncResult, extract the Task.
+            var twar = asyncResult as TaskWrapperAsyncResult;
+            if (twar != null)
+            {
+                task = twar.Task;
+                Debug.Assert(task != null, "TaskWrapperAsyncResult should never wrap a null Task.");
+            }
+            else
+            {
+                // Otherwise, the IAsyncResult should be a Task.
+                task = asyncResult as Task;
+            }
+
+            // Make sure we actually got a task, then complete the operation by waiting on it.
+            if (task == null)
+            {
+                throw new ArgumentNullException();
+            }
+
+            task.GetAwaiter().GetResult();
+        }
+
+        /// <summary>Processes an IAsyncResult returned by Begin.</summary>
+        /// <param name="asyncResult">The IAsyncResult to unwrap.</param>
+        public static TResult End<TResult>(IAsyncResult asyncResult)
+        {
+            Task<TResult> task;
+
+            // If the IAsyncResult is our task-wrapping IAsyncResult, extract the Task.
+            var twar = asyncResult as TaskWrapperAsyncResult;
+            if (twar != null)
+            {
+                task = twar.Task as Task<TResult>;
+                Debug.Assert(twar.Task != null, "TaskWrapperAsyncResult should never wrap a null Task.");
+            }
+            else
+            {
+                // Otherwise, the IAsyncResult should be a Task<TResult>.
+                task = asyncResult as Task<TResult>;
+            }
+
+            // Make sure we actually got a task, then complete the operation by waiting on it.
+            if (task == null)
+            {
+                throw new ArgumentNullException();
+            }
+
+            return task.GetAwaiter().GetResult();
+        }
+
+        /// <summary>Invokes the callback asynchronously when the task has completed.</summary>
+        /// <param name="antecedent">The Task to await.</param>
+        /// <param name="callback">The callback to invoke when the Task completes.</param>
+        /// <param name="asyncResult">The Task used as the IAsyncResult.</param>
+        private static void InvokeCallbackWhenTaskCompletes(Task antecedent, AsyncCallback callback, IAsyncResult asyncResult)
+        {
+            Debug.Assert(antecedent != null);
+            Debug.Assert(callback != null);
+            Debug.Assert(asyncResult != null);
+
+            // We use OnCompleted rather than ContinueWith in order to avoid running synchronously
+            // if the task has already completed by the time we get here.  This is separated out into
+            // its own method currently so that we only pay for the closure if necessary.
+            antecedent.ConfigureAwait(continueOnCapturedContext: false)
+                      .GetAwaiter()
+                      .OnCompleted(() => callback(asyncResult));
+
+            // PERFORMANCE NOTE:
+            // Assuming we're in the default ExecutionContext, the "slow path" of an incomplete
+            // task will result in four allocations: the new IAsyncResult,  the delegate+closure
+            // in this method, and the continuation object inside of OnCompleted (necessary
+            // to capture both the Action delegate and the ExecutionContext in a single object).  
+            // In the future, if performance requirements drove a need, those four 
+            // allocations could be reduced to one.  This would be achieved by having TaskWrapperAsyncResult
+            // also implement ITaskCompletionAction (and optionally IThreadPoolWorkItem).  It would need
+            // additional fields to store the AsyncCallback and an ExecutionContext.  Once configured, 
+            // it would be set into the Task as a continuation.  Its Invoke method would then be run when 
+            // the antecedent completed, and, doing all of the necessary work to flow ExecutionContext, 
+            // it would invoke the AsyncCallback.  It could also have a field on it for the antecedent, 
+            // so that the End method would have access to the completed antecedent. For related examples, 
+            // see other implementations of ITaskCompletionAction, and in particular ReadWriteTask 
+            // used in Stream.Begin/EndXx's implementation.
+        }
+
+        /// <summary>
+        /// Provides a simple IAsyncResult that wraps a Task.  This, in effect, allows
+        /// for overriding what's seen for the CompletedSynchronously and AsyncState values.
+        /// </summary>
+        private sealed class TaskWrapperAsyncResult : IAsyncResult
+        {
+            /// <summary>The wrapped Task.</summary>
+            internal readonly Task Task;
+            /// <summary>The new AsyncState value.</summary>
+            private readonly object _state;
+            /// <summary>The new CompletedSynchronously value.</summary>
+            private readonly bool _completedSynchronously;
+
+            /// <summary>Initializes the IAsyncResult with the Task to wrap and the overriding AsyncState and CompletedSynchronously values.</summary>
+            /// <param name="task">The Task to wrap.</param>
+            /// <param name="state">The new AsyncState value</param>
+            /// <param name="completedSynchronously">The new CompletedSynchronously value.</param>
+            internal TaskWrapperAsyncResult(Task task, object state, bool completedSynchronously)
+            {
+                Debug.Assert(task != null);
+                Debug.Assert(!completedSynchronously || task.IsCompleted, "If completedSynchronously is true, the task must be completed.");
+
+                this.Task = task;
+                _state = state;
+                _completedSynchronously = completedSynchronously;
+            }
+
+            // The IAsyncResult implementation.  
+            // - IsCompleted and AsyncWaitHandle just pass through to the Task.
+            // - AsyncState and CompletedSynchronously return the corresponding values stored in this object.
+
+            object IAsyncResult.AsyncState { get { return _state; } }
+            bool IAsyncResult.CompletedSynchronously { get { return _completedSynchronously; } }
+            bool IAsyncResult.IsCompleted { get { return this.Task.IsCompleted; } }
+            WaitHandle IAsyncResult.AsyncWaitHandle { get { return ((IAsyncResult)this.Task).AsyncWaitHandle; } }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Tasks/ValueTask.cs b/src/System.Private.CoreLib/shared/System/Threading/Tasks/ValueTask.cs
new file mode 100644
index 0000000000..8ee1a2026e
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/Tasks/ValueTask.cs
@@ -0,0 +1,849 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Threading.Tasks.Sources;
+
+#if !netstandard
+using Internal.Runtime.CompilerServices;
+#endif
+
+namespace System.Threading.Tasks
+{
+    // TYPE SAFETY WARNING:
+    // This code uses Unsafe.As to cast _obj.  This is done in order to minimize the costs associated with
+    // casting _obj to a variety of different types that can be stored in a ValueTask, e.g. Task<TResult>
+    // vs IValueTaskSource<TResult>.  Previous attempts at this were faulty due to using a separate field
+    // to store information about the type of the object in _obj; this is faulty because if the ValueTask
+    // is stored into a field, concurrent read/writes can result in tearing the _obj from the type information
+    // stored in a separate field.  This means we can rely only on the _obj field to determine how to handle
+    // it.  As such, the pattern employed is to copy _obj into a local obj, and then check it for null and
+    // type test against Task/Task<TResult>.  Since the ValueTask can only be constructed with null, Task,
+    // or IValueTaskSource, we can then be confident in knowing that if it doesn't match one of those values,
+    // it must be an IValueTaskSource, and we can use Unsafe.As.  This could be defeated by other unsafe means,
+    // like private reflection or using Unsafe.As manually, but at that point you're already doing things
+    // that can violate type safety; we only care about getting correct behaviors when using "safe" code.
+    // There are still other race conditions in user's code that can result in errors, but such errors don't
+    // cause ValueTask to violate type safety.
+
+    /// <summary>Provides an awaitable result of an asynchronous operation.</summary>
+    /// <remarks>
+    /// <see cref="ValueTask"/>s are meant to be directly awaited.  To do more complicated operations with them, a <see cref="Task"/>
+    /// should be extracted using <see cref="AsTask"/>.  Such operations might include caching an instance to be awaited later,
+    /// registering multiple continuations with a single operation, awaiting the same task multiple times, and using combinators over
+    /// multiple operations.
+    /// </remarks>
+    [AsyncMethodBuilder(typeof(AsyncValueTaskMethodBuilder))]
+    [StructLayout(LayoutKind.Auto)]
+    public readonly struct ValueTask : IEquatable<ValueTask>
+    {
+        /// <summary>A task canceled using `new CancellationToken(true)`.</summary>
+        private static readonly Task s_canceledTask =
+#if netstandard
+            Task.Delay(Timeout.Infinite, new CancellationToken(canceled: true));
+#else
+            Task.FromCanceled(new CancellationToken(canceled: true));
+#endif
+        /// <summary>A successfully completed task.</summary>
+        internal static Task CompletedTask
+#if netstandard
+            { get; } = Task.Delay(0);
+#else
+            => Task.CompletedTask;
+#endif
+
+        /// <summary>null if representing a successful synchronous completion, otherwise a <see cref="Task"/> or a <see cref="IValueTaskSource"/>.</summary>
+        internal readonly object _obj;
+        /// <summary>Opaque value passed through to the <see cref="IValueTaskSource"/>.</summary>
+        internal readonly short _token;
+        /// <summary>true to continue on the capture context; otherwise, true.</summary>
+        /// <remarks>Stored in the <see cref="ValueTask"/> rather than in the configured awaiter to utilize otherwise padding space.</remarks>
+        internal readonly bool _continueOnCapturedContext;
+
+        // An instance created with the default ctor (a zero init'd struct) represents a synchronously, successfully completed operation.
+
+        /// <summary>Initialize the <see cref="ValueTask"/> with a <see cref="Task"/> that represents the operation.</summary>
+        /// <param name="task">The task.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ValueTask(Task task)
+        {
+            if (task == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.task);
+            }
+
+            _obj = task;
+
+            _continueOnCapturedContext = true;
+            _token = 0;
+        }
+
+        /// <summary>Initialize the <see cref="ValueTask"/> with a <see cref="IValueTaskSource"/> object that represents the operation.</summary>
+        /// <param name="source">The source.</param>
+        /// <param name="token">Opaque value passed through to the <see cref="IValueTaskSource"/>.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ValueTask(IValueTaskSource source, short token)
+        {
+            if (source == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
+            }
+
+            _obj = source;
+            _token = token;
+
+            _continueOnCapturedContext = true;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private ValueTask(object obj, short token, bool continueOnCapturedContext)
+        {
+            _obj = obj;
+            _token = token;
+            _continueOnCapturedContext = continueOnCapturedContext;
+        }
+
+        /// <summary>Returns the hash code for this instance.</summary>
+        public override int GetHashCode() => _obj?.GetHashCode() ?? 0;
+
+        /// <summary>Returns a value indicating whether this value is equal to a specified <see cref="object"/>.</summary>
+        public override bool Equals(object obj) =>
+            obj is ValueTask &&
+            Equals((ValueTask)obj);
+
+        /// <summary>Returns a value indicating whether this value is equal to a specified <see cref="ValueTask"/> value.</summary>
+        public bool Equals(ValueTask other) => _obj == other._obj && _token == other._token;
+
+        /// <summary>Returns a value indicating whether two <see cref="ValueTask"/> values are equal.</summary>
+        public static bool operator ==(ValueTask left, ValueTask right) =>
+            left.Equals(right);
+
+        /// <summary>Returns a value indicating whether two <see cref="ValueTask"/> values are not equal.</summary>
+        public static bool operator !=(ValueTask left, ValueTask right) =>
+            !left.Equals(right);
+
+        /// <summary>
+        /// Gets a <see cref="Task"/> object to represent this ValueTask.
+        /// </summary>
+        /// <remarks>
+        /// It will either return the wrapped task object if one exists, or it'll
+        /// manufacture a new task object to represent the result.
+        /// </remarks>
+        public Task AsTask()
+        {
+            object obj = _obj;
+            Debug.Assert(obj == null || obj is Task || obj is IValueTaskSource);
+            return 
+                obj == null ? CompletedTask :
+                obj as Task ??
+                GetTaskForValueTaskSource(Unsafe.As<IValueTaskSource>(obj));
+        }
+
+        /// <summary>Gets a <see cref="ValueTask"/> that may be used at any point in the future.</summary>
+        public ValueTask Preserve() => _obj == null ? this : new ValueTask(AsTask());
+
+        /// <summary>Creates a <see cref="Task"/> to represent the <see cref="IValueTaskSource"/>.</summary>
+        /// <remarks>
+        /// The <see cref="IValueTaskSource"/> is passed in rather than reading and casting <see cref="_obj"/>
+        /// so that the caller can pass in an object it's already validated.
+        /// </remarks>
+        private Task GetTaskForValueTaskSource(IValueTaskSource t)
+        {
+            ValueTaskSourceStatus status = t.GetStatus(_token);
+            if (status != ValueTaskSourceStatus.Pending)
+            {
+                try
+                {
+                    // Propagate any exceptions that may have occurred, then return
+                    // an already successfully completed task.
+                    t.GetResult(_token);
+                    return CompletedTask;
+
+                    // If status is Faulted or Canceled, GetResult should throw.  But
+                    // we can't guarantee every implementation will do the "right thing".
+                    // If it doesn't throw, we just treat that as success and ignore
+                    // the status.
+                }
+                catch (Exception exc)
+                {
+                    if (status == ValueTaskSourceStatus.Canceled)
+                    {
+#if !netstandard
+                        if (exc is OperationCanceledException oce)
+                        {
+                            var task = new Task<VoidTaskResult>();
+                            task.TrySetCanceled(oce.CancellationToken, oce);
+                            return task;
+                        }
+#endif
+                        return s_canceledTask;
+                    }
+                    else
+                    {
+#if netstandard
+                        var tcs = new TaskCompletionSource<bool>();
+                        tcs.TrySetException(exc);
+                        return tcs.Task;
+#else
+                        return Task.FromException(exc);
+#endif
+                    }
+                }
+            }
+
+            var m = new ValueTaskSourceAsTask(t, _token);
+            return
+#if netstandard
+                m.Task;
+#else
+                m;
+#endif
+        }
+
+        /// <summary>Type used to create a <see cref="Task"/> to represent a <see cref="IValueTaskSource"/>.</summary>
+        private sealed class ValueTaskSourceAsTask :
+#if netstandard
+            TaskCompletionSource<bool>
+#else
+            Task<VoidTaskResult>
+#endif
+        {
+            private static readonly Action<object> s_completionAction = state =>
+            {
+                if (!(state is ValueTaskSourceAsTask vtst) ||
+                    !(vtst._source is IValueTaskSource source))
+                {
+                    // This could only happen if the IValueTaskSource passed the wrong state
+                    // or if this callback were invoked multiple times such that the state
+                    // was previously nulled out.
+                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.state);
+                    return;
+                }
+
+                vtst._source = null;
+                ValueTaskSourceStatus status = source.GetStatus(vtst._token);
+                try
+                {
+                    source.GetResult(vtst._token);
+                    vtst.TrySetResult(default);
+                }
+                catch (Exception exc)
+                {
+                    if (status == ValueTaskSourceStatus.Canceled)
+                    {
+#if netstandard
+                        vtst.TrySetCanceled();
+#else
+                        if (exc is OperationCanceledException oce)
+                        {
+                            vtst.TrySetCanceled(oce.CancellationToken, oce);
+                        }
+                        else
+                        {
+                            vtst.TrySetCanceled(new CancellationToken(true));
+                        }
+#endif
+                    }
+                    else
+                    {
+                        vtst.TrySetException(exc);
+                    }
+                }
+            };
+
+            /// <summary>The associated <see cref="IValueTaskSource"/>.</summary>
+            private IValueTaskSource _source;
+            /// <summary>The token to pass through to operations on <see cref="_source"/></summary>
+            private readonly short _token;
+
+            public ValueTaskSourceAsTask(IValueTaskSource source, short token)
+            {
+                _token = token;
+                _source = source;
+                source.OnCompleted(s_completionAction, this, token, ValueTaskSourceOnCompletedFlags.None);
+            }
+        }
+
+        /// <summary>Gets whether the <see cref="ValueTask"/> represents a completed operation.</summary>
+        public bool IsCompleted
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                object obj = _obj;
+                Debug.Assert(obj == null || obj is Task || obj is IValueTaskSource);
+
+                if (obj == null)
+                {
+                    return true;
+                }
+
+                if (obj is Task t)
+                {
+                    return t.IsCompleted;
+                }
+
+                return Unsafe.As<IValueTaskSource>(obj).GetStatus(_token) != ValueTaskSourceStatus.Pending;
+            }
+        }
+
+        /// <summary>Gets whether the <see cref="ValueTask"/> represents a successfully completed operation.</summary>
+        public bool IsCompletedSuccessfully
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                object obj = _obj;
+                Debug.Assert(obj == null || obj is Task || obj is IValueTaskSource);
+
+                if (obj == null)
+                {
+                    return true;
+                }
+
+                if (obj is Task t)
+                {
+                    return
+#if netstandard
+                        t.Status == TaskStatus.RanToCompletion;
+#else
+                        t.IsCompletedSuccessfully;
+#endif
+                }
+
+                return Unsafe.As<IValueTaskSource>(obj).GetStatus(_token) == ValueTaskSourceStatus.Succeeded;
+            }
+        }
+
+        /// <summary>Gets whether the <see cref="ValueTask"/> represents a failed operation.</summary>
+        public bool IsFaulted
+        {
+            get
+            {
+                object obj = _obj;
+                Debug.Assert(obj == null || obj is Task || obj is IValueTaskSource);
+
+                if (obj == null)
+                {
+                    return false;
+                }
+
+                if (obj is Task t)
+                {
+                    return t.IsFaulted;
+                }
+
+                return Unsafe.As<IValueTaskSource>(obj).GetStatus(_token) == ValueTaskSourceStatus.Faulted;
+            }
+        }
+
+        /// <summary>Gets whether the <see cref="ValueTask"/> represents a canceled operation.</summary>
+        /// <remarks>
+        /// If the <see cref="ValueTask"/> is backed by a result or by a <see cref="IValueTaskSource"/>,
+        /// this will always return false.  If it's backed by a <see cref="Task"/>, it'll return the
+        /// value of the task's <see cref="Task.IsCanceled"/> property.
+        /// </remarks>
+        public bool IsCanceled
+        {
+            get
+            {
+                object obj = _obj;
+                Debug.Assert(obj == null || obj is Task || obj is IValueTaskSource);
+
+                if (obj == null)
+                {
+                    return false;
+                }
+
+                if (obj is Task t)
+                {
+                    return t.IsCanceled;
+                }
+
+                return Unsafe.As<IValueTaskSource>(obj).GetStatus(_token) == ValueTaskSourceStatus.Canceled;
+            }
+        }
+
+        /// <summary>Throws the exception that caused the <see cref="ValueTask"/> to fail.  If it completed successfully, nothing is thrown.</summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        [StackTraceHidden]
+        internal void ThrowIfCompletedUnsuccessfully()
+        {
+            object obj = _obj;
+            Debug.Assert(obj == null || obj is Task || obj is IValueTaskSource);
+
+            if (obj != null)
+            {
+                if (obj is Task t)
+                {
+#if netstandard
+                    t.GetAwaiter().GetResult();
+#else
+                    TaskAwaiter.ValidateEnd(t);
+#endif
+                }
+                else
+                {
+                    Unsafe.As<IValueTaskSource>(obj).GetResult(_token);
+                }
+            }
+        }
+
+        /// <summary>Gets an awaiter for this <see cref="ValueTask"/>.</summary>
+        public ValueTaskAwaiter GetAwaiter() => new ValueTaskAwaiter(this);
+
+        /// <summary>Configures an awaiter for this <see cref="ValueTask"/>.</summary>
+        /// <param name="continueOnCapturedContext">
+        /// true to attempt to marshal the continuation back to the captured context; otherwise, false.
+        /// </param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ConfiguredValueTaskAwaitable ConfigureAwait(bool continueOnCapturedContext) =>
+            new ConfiguredValueTaskAwaitable(new ValueTask(_obj, _token, continueOnCapturedContext));
+    }
+
+    /// <summary>Provides a value type that can represent a synchronously available value or a task object.</summary>
+    /// <typeparam name="TResult">Specifies the type of the result.</typeparam>
+    /// <remarks>
+    /// <see cref="ValueTask{TResult}"/>s are meant to be directly awaited.  To do more complicated operations with them, a <see cref="Task"/>
+    /// should be extracted using <see cref="AsTask"/> or <see cref="Preserve"/>.  Such operations might include caching an instance to
+    /// be awaited later, registering multiple continuations with a single operation, awaiting the same task multiple times, and using
+    /// combinators over multiple operations.
+    /// </remarks>
+    [AsyncMethodBuilder(typeof(AsyncValueTaskMethodBuilder<>))]
+    [StructLayout(LayoutKind.Auto)]
+    public readonly struct ValueTask<TResult> : IEquatable<ValueTask<TResult>>
+    {
+        /// <summary>A task canceled using `new CancellationToken(true)`. Lazily created only when first needed.</summary>
+        private static Task<TResult> s_canceledTask;
+        /// <summary>null if <see cref="_result"/> has the result, otherwise a <see cref="Task{TResult}"/> or a <see cref="IValueTaskSource{TResult}"/>.</summary>
+        internal readonly object _obj;
+        /// <summary>The result to be used if the operation completed successfully synchronously.</summary>
+        internal readonly TResult _result;
+        /// <summary>Opaque value passed through to the <see cref="IValueTaskSource{TResult}"/>.</summary>
+        internal readonly short _token;
+        /// <summary>true to continue on the captured context; otherwise, false.</summary>
+        /// <remarks>Stored in the <see cref="ValueTask{TResult}"/> rather than in the configured awaiter to utilize otherwise padding space.</remarks>
+        internal readonly bool _continueOnCapturedContext;
+
+        // An instance created with the default ctor (a zero init'd struct) represents a synchronously, successfully completed operation
+        // with a result of default(TResult).
+
+        /// <summary>Initialize the <see cref="ValueTask{TResult}"/> with a <typeparamref name="TResult"/> result value.</summary>
+        /// <param name="result">The result.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ValueTask(TResult result)
+        {
+            _result = result;
+
+            _obj = null;
+            _continueOnCapturedContext = true;
+            _token = 0;
+        }
+
+        /// <summary>Initialize the <see cref="ValueTask{TResult}"/> with a <see cref="Task{TResult}"/> that represents the operation.</summary>
+        /// <param name="task">The task.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ValueTask(Task<TResult> task)
+        {
+            if (task == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.task);
+            }
+
+            _obj = task;
+
+            _result = default;
+            _continueOnCapturedContext = true;
+            _token = 0;
+        }
+
+        /// <summary>Initialize the <see cref="ValueTask{TResult}"/> with a <see cref="IValueTaskSource{TResult}"/> object that represents the operation.</summary>
+        /// <param name="source">The source.</param>
+        /// <param name="token">Opaque value passed through to the <see cref="IValueTaskSource"/>.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ValueTask(IValueTaskSource<TResult> source, short token)
+        {
+            if (source == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.source);
+            }
+
+            _obj = source;
+            _token = token;
+
+            _result = default;
+            _continueOnCapturedContext = true;
+        }
+
+        /// <summary>Non-verified initialization of the struct to the specified values.</summary>
+        /// <param name="obj">The object.</param>
+        /// <param name="result">The result.</param>
+        /// <param name="token">The token.</param>
+        /// <param name="continueOnCapturedContext">true to continue on captured context; otherwise, false.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private ValueTask(object obj, TResult result, short token, bool continueOnCapturedContext)
+        {
+            _obj = obj;
+            _result = result;
+            _token = token;
+            _continueOnCapturedContext = continueOnCapturedContext;
+        }
+
+
+        /// <summary>Returns the hash code for this instance.</summary>
+        public override int GetHashCode() =>
+            _obj != null ? _obj.GetHashCode() :
+            _result != null ? _result.GetHashCode() :
+            0;
+
+        /// <summary>Returns a value indicating whether this value is equal to a specified <see cref="object"/>.</summary>
+        public override bool Equals(object obj) =>
+            obj is ValueTask<TResult> &&
+            Equals((ValueTask<TResult>)obj);
+
+        /// <summary>Returns a value indicating whether this value is equal to a specified <see cref="ValueTask{TResult}"/> value.</summary>
+        public bool Equals(ValueTask<TResult> other) =>
+            _obj != null || other._obj != null ?
+                _obj == other._obj && _token == other._token :
+                EqualityComparer<TResult>.Default.Equals(_result, other._result);
+
+        /// <summary>Returns a value indicating whether two <see cref="ValueTask{TResult}"/> values are equal.</summary>
+        public static bool operator ==(ValueTask<TResult> left, ValueTask<TResult> right) =>
+            left.Equals(right);
+
+        /// <summary>Returns a value indicating whether two <see cref="ValueTask{TResult}"/> values are not equal.</summary>
+        public static bool operator !=(ValueTask<TResult> left, ValueTask<TResult> right) =>
+            !left.Equals(right);
+
+        /// <summary>
+        /// Gets a <see cref="Task{TResult}"/> object to represent this ValueTask.
+        /// </summary>
+        /// <remarks>
+        /// It will either return the wrapped task object if one exists, or it'll
+        /// manufacture a new task object to represent the result.
+        /// </remarks>
+        public Task<TResult> AsTask()
+        {
+            object obj = _obj;
+            Debug.Assert(obj == null || obj is Task<TResult> || obj is IValueTaskSource<TResult>);
+
+            if (obj == null)
+            {
+                return
+#if netstandard
+                    Task.FromResult(_result);
+#else
+                    AsyncTaskMethodBuilder<TResult>.GetTaskForResult(_result);
+#endif
+            }
+
+            if (obj is Task<TResult> t)
+            {
+                return t;
+            }
+
+            return GetTaskForValueTaskSource(Unsafe.As<IValueTaskSource<TResult>>(obj));
+        }
+
+        /// <summary>Gets a <see cref="ValueTask{TResult}"/> that may be used at any point in the future.</summary>
+        public ValueTask<TResult> Preserve() => _obj == null ? this : new ValueTask<TResult>(AsTask());
+
+        /// <summary>Creates a <see cref="Task{TResult}"/> to represent the <see cref="IValueTaskSource{TResult}"/>.</summary>
+        /// <remarks>
+        /// The <see cref="IValueTaskSource{TResult}"/> is passed in rather than reading and casting <see cref="_obj"/>
+        /// so that the caller can pass in an object it's already validated.
+        /// </remarks>
+        private Task<TResult> GetTaskForValueTaskSource(IValueTaskSource<TResult> t)
+        {
+            ValueTaskSourceStatus status = t.GetStatus(_token);
+            if (status != ValueTaskSourceStatus.Pending)
+            {
+                try
+                {
+                    // Get the result of the operation and return a task for it.
+                    // If any exception occurred, propagate it
+                    return
+#if netstandard
+                        Task.FromResult(t.GetResult(_token));
+#else
+                        AsyncTaskMethodBuilder<TResult>.GetTaskForResult(t.GetResult(_token));
+#endif
+
+                    // If status is Faulted or Canceled, GetResult should throw.  But
+                    // we can't guarantee every implementation will do the "right thing".
+                    // If it doesn't throw, we just treat that as success and ignore
+                    // the status.
+                }
+                catch (Exception exc)
+                {
+                    if (status == ValueTaskSourceStatus.Canceled)
+                    {
+#if !netstandard
+                        if (exc is OperationCanceledException oce)
+                        {
+                            var task = new Task<TResult>();
+                            task.TrySetCanceled(oce.CancellationToken, oce);
+                            return task;
+                        }
+#endif
+
+                        Task<TResult> canceledTask = s_canceledTask;
+                        if (canceledTask == null)
+                        {
+#if netstandard
+                            var tcs = new TaskCompletionSource<TResult>();
+                            tcs.TrySetCanceled();
+                            canceledTask = tcs.Task;
+#else
+                            canceledTask = Task.FromCanceled<TResult>(new CancellationToken(true));
+#endif
+                            // Benign race condition to initialize cached task, as identity doesn't matter.
+                            s_canceledTask = canceledTask;
+                        }
+                        return canceledTask;
+                    }
+                    else
+                    {
+#if netstandard
+                        var tcs = new TaskCompletionSource<TResult>();
+                        tcs.TrySetException(exc);
+                        return tcs.Task;
+#else
+                        return Task.FromException<TResult>(exc);
+#endif
+                    }
+                }
+            }
+
+            var m = new ValueTaskSourceAsTask(t, _token);
+            return
+#if netstandard
+                m.Task;
+#else
+                m;
+#endif
+        }
+
+        /// <summary>Type used to create a <see cref="Task{TResult}"/> to represent a <see cref="IValueTaskSource{TResult}"/>.</summary>
+        private sealed class ValueTaskSourceAsTask :
+#if netstandard
+            TaskCompletionSource<TResult>
+#else
+            Task<TResult>
+#endif
+        {
+            private static readonly Action<object> s_completionAction = state =>
+            {
+                if (!(state is ValueTaskSourceAsTask vtst) ||
+                    !(vtst._source is IValueTaskSource<TResult> source))
+                {
+                    // This could only happen if the IValueTaskSource<TResult> passed the wrong state
+                    // or if this callback were invoked multiple times such that the state
+                    // was previously nulled out.
+                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.state);
+                    return;
+                }
+
+                vtst._source = null;
+                ValueTaskSourceStatus status = source.GetStatus(vtst._token);
+                try
+                {
+                    vtst.TrySetResult(source.GetResult(vtst._token));
+                }
+                catch (Exception exc)
+                {
+                    if (status == ValueTaskSourceStatus.Canceled)
+                    {
+#if netstandard
+                        vtst.TrySetCanceled();
+#else
+                        if (exc is OperationCanceledException oce)
+                        {
+                            vtst.TrySetCanceled(oce.CancellationToken, oce);
+                        }
+                        else
+                        {
+                            vtst.TrySetCanceled(new CancellationToken(true));
+                        }
+#endif
+                    }
+                    else
+                    {
+                        vtst.TrySetException(exc);
+                    }
+                }
+            };
+
+            /// <summary>The associated <see cref="IValueTaskSource"/>.</summary>
+            private IValueTaskSource<TResult> _source;
+            /// <summary>The token to pass through to operations on <see cref="_source"/></summary>
+            private readonly short _token;
+
+            public ValueTaskSourceAsTask(IValueTaskSource<TResult> source, short token)
+            {
+                _source = source;
+                _token = token;
+                source.OnCompleted(s_completionAction, this, token, ValueTaskSourceOnCompletedFlags.None);
+            }
+        }
+
+        /// <summary>Gets whether the <see cref="ValueTask{TResult}"/> represents a completed operation.</summary>
+        public bool IsCompleted
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                object obj = _obj;
+                Debug.Assert(obj == null || obj is Task<TResult> || obj is IValueTaskSource<TResult>);
+
+                if (obj == null)
+                {
+                    return true;
+                }
+
+                if (obj is Task<TResult> t)
+                {
+                    return t.IsCompleted;
+                }
+
+                return Unsafe.As<IValueTaskSource<TResult>>(obj).GetStatus(_token) != ValueTaskSourceStatus.Pending;
+            }
+        }
+
+        /// <summary>Gets whether the <see cref="ValueTask{TResult}"/> represents a successfully completed operation.</summary>
+        public bool IsCompletedSuccessfully
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                object obj = _obj;
+                Debug.Assert(obj == null || obj is Task<TResult> || obj is IValueTaskSource<TResult>);
+
+                if (obj == null)
+                {
+                    return true;
+                }
+
+                if (obj is Task<TResult> t)
+                {
+                    return
+#if netstandard
+                        t.Status == TaskStatus.RanToCompletion;
+#else
+                        t.IsCompletedSuccessfully;
+#endif
+                }
+
+                return Unsafe.As<IValueTaskSource<TResult>>(obj).GetStatus(_token) == ValueTaskSourceStatus.Succeeded;
+            }
+        }
+
+        /// <summary>Gets whether the <see cref="ValueTask{TResult}"/> represents a failed operation.</summary>
+        public bool IsFaulted
+        {
+            get
+            {
+                object obj = _obj;
+                Debug.Assert(obj == null || obj is Task<TResult> || obj is IValueTaskSource<TResult>);
+
+                if (obj == null)
+                {
+                    return false;
+                }
+
+                if (obj is Task<TResult> t)
+                {
+                    return t.IsFaulted;
+                }
+
+                return Unsafe.As<IValueTaskSource<TResult>>(obj).GetStatus(_token) == ValueTaskSourceStatus.Faulted;
+            }
+        }
+
+        /// <summary>Gets whether the <see cref="ValueTask{TResult}"/> represents a canceled operation.</summary>
+        /// <remarks>
+        /// If the <see cref="ValueTask{TResult}"/> is backed by a result or by a <see cref="IValueTaskSource{TResult}"/>,
+        /// this will always return false.  If it's backed by a <see cref="Task"/>, it'll return the
+        /// value of the task's <see cref="Task.IsCanceled"/> property.
+        /// </remarks>
+        public bool IsCanceled
+        {
+            get
+            {
+                object obj = _obj;
+                Debug.Assert(obj == null || obj is Task<TResult> || obj is IValueTaskSource<TResult>);
+
+                if (obj == null)
+                {
+                    return false;
+                }
+
+                if (obj is Task<TResult> t)
+                {
+                    return t.IsCanceled;
+                }
+
+                return Unsafe.As<IValueTaskSource<TResult>>(obj).GetStatus(_token) == ValueTaskSourceStatus.Canceled;
+            }
+        }
+
+        /// <summary>Gets the result.</summary>
+        public TResult Result
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                object obj = _obj;
+                Debug.Assert(obj == null || obj is Task<TResult> || obj is IValueTaskSource<TResult>);
+
+                if (obj == null)
+                {
+                    return _result;
+                }
+
+                if (obj is Task<TResult> t)
+                {
+#if netstandard
+                    return t.GetAwaiter().GetResult();
+#else
+                    TaskAwaiter.ValidateEnd(t);
+                    return t.ResultOnSuccess;
+#endif
+                }
+
+                return Unsafe.As<IValueTaskSource<TResult>>(obj).GetResult(_token);
+            }
+        }
+
+        /// <summary>Gets an awaiter for this <see cref="ValueTask{TResult}"/>.</summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ValueTaskAwaiter<TResult> GetAwaiter() => new ValueTaskAwaiter<TResult>(this);
+
+        /// <summary>Configures an awaiter for this <see cref="ValueTask{TResult}"/>.</summary>
+        /// <param name="continueOnCapturedContext">
+        /// true to attempt to marshal the continuation back to the captured context; otherwise, false.
+        /// </param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ConfiguredValueTaskAwaitable<TResult> ConfigureAwait(bool continueOnCapturedContext) =>
+            new ConfiguredValueTaskAwaitable<TResult>(new ValueTask<TResult>(_obj, _result, _token, continueOnCapturedContext));
+
+        /// <summary>Gets a string-representation of this <see cref="ValueTask{TResult}"/>.</summary>
+        public override string ToString()
+        {
+            if (IsCompletedSuccessfully)
+            {
+                TResult result = Result;
+                if (result != null)
+                {
+                    return result.ToString();
+                }
+            }
+
+            return string.Empty;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/ThreadAbortException.cs b/src/System.Private.CoreLib/shared/System/Threading/ThreadAbortException.cs
new file mode 100644
index 0000000000..360e84d256
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/ThreadAbortException.cs
@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: An exception class which is thrown into a thread to cause it to
+**          abort. This is a special non-catchable exception and results in
+**            the thread's death.  This is thrown by the VM only and can NOT be
+**          thrown by any user thread, and subclassing this is useless.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System.Threading
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class ThreadAbortException : SystemException
+    {
+        internal ThreadAbortException()
+        {
+            HResult = HResults.COR_E_THREADABORTED;
+        }
+
+        public object ExceptionState => null;
+
+        internal ThreadAbortException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/ThreadPriority.cs b/src/System.Private.CoreLib/shared/System/Threading/ThreadPriority.cs
new file mode 100644
index 0000000000..3b34bd5eac
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/ThreadPriority.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Threading
+{
+    public enum ThreadPriority
+    {
+        /*=========================================================================
+        ** Constants for thread priorities.
+        =========================================================================*/
+        Lowest = 0,
+        BelowNormal = 1,
+        Normal = 2,
+        AboveNormal = 3,
+        Highest = 4
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/ThreadStart.cs b/src/System.Private.CoreLib/shared/System/Threading/ThreadStart.cs
new file mode 100644
index 0000000000..5532539fc7
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/ThreadStart.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: This class is a Delegate which defines the start method
+**  for starting a thread.  That method must match this delegate.
+**
+**
+=============================================================================*/
+
+namespace System.Threading
+{
+    public delegate void ThreadStart();
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/ThreadStartException.cs b/src/System.Private.CoreLib/shared/System/Threading/ThreadStartException.cs
new file mode 100644
index 0000000000..5172555418
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/ThreadStartException.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Threading
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class ThreadStartException : SystemException
+    {
+        internal ThreadStartException()
+            : base(SR.Arg_ThreadStartException)
+        {
+            HResult = HResults.COR_E_THREADSTART;
+        }
+
+        internal ThreadStartException(Exception reason)
+            : base(SR.Arg_ThreadStartException, reason)
+        {
+            HResult = HResults.COR_E_THREADSTART;
+        }
+
+        private ThreadStartException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/ThreadState.cs b/src/System.Private.CoreLib/shared/System/Threading/ThreadState.cs
new file mode 100644
index 0000000000..4bf3b5184d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/ThreadState.cs
@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Threading
+{
+    [Flags]
+    public enum ThreadState
+    {
+        /*=========================================================================
+        ** Constants for thread states.
+        =========================================================================*/
+        Running = 0,
+        StopRequested = 1,
+        SuspendRequested = 2,
+        Background = 4,
+        Unstarted = 8,
+        Stopped = 16,
+        WaitSleepJoin = 32,
+        Suspended = 64,
+        AbortRequested = 128,
+        Aborted = 256
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/ThreadStateException.cs b/src/System.Private.CoreLib/shared/System/Threading/ThreadStateException.cs
new file mode 100644
index 0000000000..6fc06a8516
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/ThreadStateException.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: An exception class to indicate that the Thread class is in an
+**          invalid state for the method.
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System.Threading
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class ThreadStateException : SystemException
+    {
+        public ThreadStateException()
+            : base(SR.Arg_ThreadStateException)
+        {
+            HResult = HResults.COR_E_THREADSTATE;
+        }
+
+        public ThreadStateException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_THREADSTATE;
+        }
+
+        public ThreadStateException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_THREADSTATE;
+        }
+
+        protected ThreadStateException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Timeout.cs b/src/System.Private.CoreLib/shared/System/Threading/Timeout.cs
new file mode 100644
index 0000000000..df1ea5f2bc
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/Timeout.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading;
+using System;
+
+namespace System.Threading
+{
+    // A constant used by methods that take a timeout (Object.Wait, Thread.Sleep
+    // etc) to indicate that no timeout should occur.
+    //
+    public static class Timeout
+    {
+        public static readonly TimeSpan InfiniteTimeSpan = new TimeSpan(0, 0, 0, 0, Timeout.Infinite);
+
+        public const int Infinite = -1;
+        internal const uint UnsignedInfinite = unchecked((uint)-1);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/TimeoutHelper.cs b/src/System.Private.CoreLib/shared/System/Threading/TimeoutHelper.cs
new file mode 100644
index 0000000000..c96a4d00d6
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/TimeoutHelper.cs
@@ -0,0 +1,54 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Threading
+{
+    /// <summary>
+    /// A helper class to capture a start time using Environment.TickCout as a time in milliseconds, also updates a given timeout bu subtracting the current time from
+    /// the start time
+    /// </summary>
+    internal static class TimeoutHelper
+    {
+        /// <summary>
+        /// Returns the Environment.TickCount as a start time in milliseconds as a uint, TickCount tools over from positive to negative every ~ 25 days
+        /// then ~25 days to back to positive again, uint is sued to ignore the sign and double the range to 50 days
+        /// </summary>
+        /// <returns></returns>
+        public static uint GetTime()
+        {
+            return (uint)Environment.TickCount;
+        }
+
+        /// <summary>
+        /// Helper function to measure and update the elapsed time
+        /// </summary>
+        /// <param name="startTime"> The first time (in milliseconds) observed when the wait started</param>
+        /// <param name="originalWaitMillisecondsTimeout">The original wait timeout in milliseconds</param>
+        /// <returns>The new wait time in milliseconds, -1 if the time expired</returns>
+        public static int UpdateTimeOut(uint startTime, int originalWaitMillisecondsTimeout)
+        {
+            // The function must be called in case the time out is not infinite
+            Debug.Assert(originalWaitMillisecondsTimeout != Timeout.Infinite);
+
+            uint elapsedMilliseconds = (GetTime() - startTime);
+
+            // Check the elapsed milliseconds is greater than max int because this property is uint
+            if (elapsedMilliseconds > int.MaxValue)
+            {
+                return 0;
+            }
+
+            // Subtract the elapsed time from the current wait time
+            int currentWaitTimeout = originalWaitMillisecondsTimeout - (int)elapsedMilliseconds; ;
+            if (currentWaitTimeout <= 0)
+            {
+                return 0;
+            }
+
+            return currentWaitTimeout;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Threading/WaitHandleCannotBeOpenedException.cs b/src/System.Private.CoreLib/shared/System/Threading/WaitHandleCannotBeOpenedException.cs
new file mode 100644
index 0000000000..e60e46d2be
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/WaitHandleCannotBeOpenedException.cs
@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System.Threading
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class WaitHandleCannotBeOpenedException : ApplicationException
+    {
+        public WaitHandleCannotBeOpenedException() : base(SR.Threading_WaitHandleCannotBeOpenedException)
+        {
+            HResult = HResults.COR_E_WAITHANDLECANNOTBEOPENED;
+        }
+
+        public WaitHandleCannotBeOpenedException(String message) : base(message)
+        {
+            HResult = HResults.COR_E_WAITHANDLECANNOTBEOPENED;
+        }
+
+        public WaitHandleCannotBeOpenedException(String message, Exception innerException) : base(message, innerException)
+        {
+            HResult = HResults.COR_E_WAITHANDLECANNOTBEOPENED;
+        }
+
+        protected WaitHandleCannotBeOpenedException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TimeSpan.cs b/src/System.Private.CoreLib/shared/System/TimeSpan.cs
new file mode 100644
index 0000000000..4293ed505b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TimeSpan.cs
@@ -0,0 +1,564 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text;
+using System;
+using System.Runtime;
+using System.Runtime.CompilerServices;
+using System.Globalization;
+
+namespace System
+{
+    // TimeSpan represents a duration of time.  A TimeSpan can be negative
+    // or positive.
+    //
+    // TimeSpan is internally represented as a number of milliseconds.  While
+    // this maps well into units of time such as hours and days, any
+    // periods longer than that aren't representable in a nice fashion.
+    // For instance, a month can be between 28 and 31 days, while a year
+    // can contain 365 or 364 days.  A decade can have between 1 and 3 leapyears,
+    // depending on when you map the TimeSpan into the calendar.  This is why
+    // we do not provide Years() or Months().
+    //
+    // Note: System.TimeSpan needs to interop with the WinRT structure
+    // type Windows::Foundation:TimeSpan. These types are currently binary-compatible in
+    // memory so no custom marshalling is required. If at any point the implementation
+    // details of this type should change, or new fields added, we need to remember to add
+    // an appropriate custom ILMarshaler to keep WInRT interop scenarios enabled.
+    //
+    [Serializable]
+    public struct TimeSpan : IComparable, IComparable<TimeSpan>, IEquatable<TimeSpan>, IFormattable, ISpanFormattable
+    {
+        public const long TicksPerMillisecond = 10000;
+        private const double MillisecondsPerTick = 1.0 / TicksPerMillisecond;
+
+        public const long TicksPerSecond = TicksPerMillisecond * 1000;   // 10,000,000
+        private const double SecondsPerTick = 1.0 / TicksPerSecond;         // 0.0001
+
+        public const long TicksPerMinute = TicksPerSecond * 60;         // 600,000,000
+        private const double MinutesPerTick = 1.0 / TicksPerMinute; // 1.6666666666667e-9
+
+        public const long TicksPerHour = TicksPerMinute * 60;        // 36,000,000,000
+        private const double HoursPerTick = 1.0 / TicksPerHour; // 2.77777777777777778e-11
+
+        public const long TicksPerDay = TicksPerHour * 24;          // 864,000,000,000
+        private const double DaysPerTick = 1.0 / TicksPerDay; // 1.1574074074074074074e-12
+
+        private const int MillisPerSecond = 1000;
+        private const int MillisPerMinute = MillisPerSecond * 60; //     60,000
+        private const int MillisPerHour = MillisPerMinute * 60;   //  3,600,000
+        private const int MillisPerDay = MillisPerHour * 24;      // 86,400,000
+
+        internal const long MaxSeconds = Int64.MaxValue / TicksPerSecond;
+        internal const long MinSeconds = Int64.MinValue / TicksPerSecond;
+
+        internal const long MaxMilliSeconds = Int64.MaxValue / TicksPerMillisecond;
+        internal const long MinMilliSeconds = Int64.MinValue / TicksPerMillisecond;
+
+        internal const long TicksPerTenthSecond = TicksPerMillisecond * 100;
+
+        public static readonly TimeSpan Zero = new TimeSpan(0);
+
+        public static readonly TimeSpan MaxValue = new TimeSpan(Int64.MaxValue);
+        public static readonly TimeSpan MinValue = new TimeSpan(Int64.MinValue);
+
+        // internal so that DateTime doesn't have to call an extra get
+        // method for some arithmetic operations.
+        internal long _ticks; // Do not rename (binary serialization)
+
+        public TimeSpan(long ticks)
+        {
+            this._ticks = ticks;
+        }
+
+        public TimeSpan(int hours, int minutes, int seconds)
+        {
+            _ticks = TimeToTicks(hours, minutes, seconds);
+        }
+
+        public TimeSpan(int days, int hours, int minutes, int seconds)
+            : this(days, hours, minutes, seconds, 0)
+        {
+        }
+
+        public TimeSpan(int days, int hours, int minutes, int seconds, int milliseconds)
+        {
+            Int64 totalMilliSeconds = ((Int64)days * 3600 * 24 + (Int64)hours * 3600 + (Int64)minutes * 60 + seconds) * 1000 + milliseconds;
+            if (totalMilliSeconds > MaxMilliSeconds || totalMilliSeconds < MinMilliSeconds)
+                throw new ArgumentOutOfRangeException(null, SR.Overflow_TimeSpanTooLong);
+            _ticks = (long)totalMilliSeconds * TicksPerMillisecond;
+        }
+
+        public long Ticks
+        {
+            get { return _ticks; }
+        }
+
+        public int Days
+        {
+            get { return (int)(_ticks / TicksPerDay); }
+        }
+
+        public int Hours
+        {
+            get { return (int)((_ticks / TicksPerHour) % 24); }
+        }
+
+        public int Milliseconds
+        {
+            get { return (int)((_ticks / TicksPerMillisecond) % 1000); }
+        }
+
+        public int Minutes
+        {
+            get { return (int)((_ticks / TicksPerMinute) % 60); }
+        }
+
+        public int Seconds
+        {
+            get { return (int)((_ticks / TicksPerSecond) % 60); }
+        }
+
+        public double TotalDays
+        {
+            get { return ((double)_ticks) * DaysPerTick; }
+        }
+
+        public double TotalHours
+        {
+            get { return (double)_ticks * HoursPerTick; }
+        }
+
+        public double TotalMilliseconds
+        {
+            get
+            {
+                double temp = (double)_ticks * MillisecondsPerTick;
+                if (temp > MaxMilliSeconds)
+                    return (double)MaxMilliSeconds;
+
+                if (temp < MinMilliSeconds)
+                    return (double)MinMilliSeconds;
+
+                return temp;
+            }
+        }
+
+        public double TotalMinutes
+        {
+            get { return (double)_ticks * MinutesPerTick; }
+        }
+
+        public double TotalSeconds
+        {
+            get { return (double)_ticks * SecondsPerTick; }
+        }
+
+        public TimeSpan Add(TimeSpan ts)
+        {
+            long result = _ticks + ts._ticks;
+            // Overflow if signs of operands was identical and result's
+            // sign was opposite.
+            // >> 63 gives the sign bit (either 64 1's or 64 0's).
+            if ((_ticks >> 63 == ts._ticks >> 63) && (_ticks >> 63 != result >> 63))
+                throw new OverflowException(SR.Overflow_TimeSpanTooLong);
+            return new TimeSpan(result);
+        }
+
+
+        // Compares two TimeSpan values, returning an integer that indicates their
+        // relationship.
+        //
+        public static int Compare(TimeSpan t1, TimeSpan t2)
+        {
+            if (t1._ticks > t2._ticks) return 1;
+            if (t1._ticks < t2._ticks) return -1;
+            return 0;
+        }
+
+        // Returns a value less than zero if this  object
+        public int CompareTo(Object value)
+        {
+            if (value == null) return 1;
+            if (!(value is TimeSpan))
+                throw new ArgumentException(SR.Arg_MustBeTimeSpan);
+            long t = ((TimeSpan)value)._ticks;
+            if (_ticks > t) return 1;
+            if (_ticks < t) return -1;
+            return 0;
+        }
+
+        public int CompareTo(TimeSpan value)
+        {
+            long t = value._ticks;
+            if (_ticks > t) return 1;
+            if (_ticks < t) return -1;
+            return 0;
+        }
+
+        public static TimeSpan FromDays(double value)
+        {
+            return Interval(value, MillisPerDay);
+        }
+
+        public TimeSpan Duration()
+        {
+            if (Ticks == TimeSpan.MinValue.Ticks)
+                throw new OverflowException(SR.Overflow_Duration);
+            return new TimeSpan(_ticks >= 0 ? _ticks : -_ticks);
+        }
+
+        public override bool Equals(Object value)
+        {
+            if (value is TimeSpan)
+            {
+                return _ticks == ((TimeSpan)value)._ticks;
+            }
+            return false;
+        }
+
+        public bool Equals(TimeSpan obj)
+        {
+            return _ticks == obj._ticks;
+        }
+
+        public static bool Equals(TimeSpan t1, TimeSpan t2)
+        {
+            return t1._ticks == t2._ticks;
+        }
+
+        public override int GetHashCode()
+        {
+            return (int)_ticks ^ (int)(_ticks >> 32);
+        }
+
+        public static TimeSpan FromHours(double value)
+        {
+            return Interval(value, MillisPerHour);
+        }
+
+        private static TimeSpan Interval(double value, int scale)
+        {
+            if (Double.IsNaN(value))
+                throw new ArgumentException(SR.Arg_CannotBeNaN);
+            double tmp = value * scale;
+            double millis = tmp + (value >= 0 ? 0.5 : -0.5);
+            if ((millis > Int64.MaxValue / TicksPerMillisecond) || (millis < Int64.MinValue / TicksPerMillisecond))
+                throw new OverflowException(SR.Overflow_TimeSpanTooLong);
+            return new TimeSpan((long)millis * TicksPerMillisecond);
+        }
+
+        public static TimeSpan FromMilliseconds(double value)
+        {
+            return Interval(value, 1);
+        }
+
+        public static TimeSpan FromMinutes(double value)
+        {
+            return Interval(value, MillisPerMinute);
+        }
+
+        public TimeSpan Negate()
+        {
+            if (Ticks == TimeSpan.MinValue.Ticks)
+                throw new OverflowException(SR.Overflow_NegateTwosCompNum);
+            return new TimeSpan(-_ticks);
+        }
+
+        public static TimeSpan FromSeconds(double value)
+        {
+            return Interval(value, MillisPerSecond);
+        }
+
+        public TimeSpan Subtract(TimeSpan ts)
+        {
+            long result = _ticks - ts._ticks;
+            // Overflow if signs of operands was different and result's
+            // sign was opposite from the first argument's sign.
+            // >> 63 gives the sign bit (either 64 1's or 64 0's).
+            if ((_ticks >> 63 != ts._ticks >> 63) && (_ticks >> 63 != result >> 63))
+                throw new OverflowException(SR.Overflow_TimeSpanTooLong);
+            return new TimeSpan(result);
+        }
+
+        public TimeSpan Multiply(double factor) => this * factor;
+
+        public TimeSpan Divide(double divisor) => this / divisor;
+
+        public double Divide(TimeSpan ts) => this / ts;
+
+        public static TimeSpan FromTicks(long value)
+        {
+            return new TimeSpan(value);
+        }
+
+        internal static long TimeToTicks(int hour, int minute, int second)
+        {
+            // totalSeconds is bounded by 2^31 * 2^12 + 2^31 * 2^8 + 2^31,
+            // which is less than 2^44, meaning we won't overflow totalSeconds.
+            long totalSeconds = (long)hour * 3600 + (long)minute * 60 + (long)second;
+            if (totalSeconds > MaxSeconds || totalSeconds < MinSeconds)
+                throw new ArgumentOutOfRangeException(null, SR.Overflow_TimeSpanTooLong);
+            return totalSeconds * TicksPerSecond;
+        }
+
+        // See System.Globalization.TimeSpanParse and System.Globalization.TimeSpanFormat 
+        #region ParseAndFormat
+        private static void ValidateStyles(TimeSpanStyles style, String parameterName)
+        {
+            if (style != TimeSpanStyles.None && style != TimeSpanStyles.AssumeNegative)
+                throw new ArgumentException(SR.Argument_InvalidTimeSpanStyles, parameterName);
+        }
+        public static TimeSpan Parse(String s)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.input);
+            /* Constructs a TimeSpan from a string.  Leading and trailing white space characters are allowed. */
+            return TimeSpanParse.Parse(s, null);
+        }
+        public static TimeSpan Parse(String input, IFormatProvider formatProvider)
+        {
+            if (input == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.input);
+            return TimeSpanParse.Parse(input, formatProvider);
+        }
+        public static TimeSpan Parse(ReadOnlySpan<char> input, IFormatProvider formatProvider = null)
+        {
+            return TimeSpanParse.Parse(input, formatProvider);
+        }
+        public static TimeSpan ParseExact(String input, String format, IFormatProvider formatProvider)
+        {
+            if (input == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.input);
+            if (format == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.format);
+            return TimeSpanParse.ParseExact(input, format, formatProvider, TimeSpanStyles.None);
+        }
+        public static TimeSpan ParseExact(String input, String[] formats, IFormatProvider formatProvider)
+        {
+            if (input == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.input);
+            return TimeSpanParse.ParseExactMultiple(input, formats, formatProvider, TimeSpanStyles.None);
+        }
+        public static TimeSpan ParseExact(String input, String format, IFormatProvider formatProvider, TimeSpanStyles styles)
+        {
+            ValidateStyles(styles, nameof(styles));
+            if (input == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.input);
+            if (format == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.format);
+            return TimeSpanParse.ParseExact(input, format, formatProvider, styles);
+        }
+
+        public static TimeSpan ParseExact(ReadOnlySpan<char> input, ReadOnlySpan<char> format, IFormatProvider formatProvider, TimeSpanStyles styles = TimeSpanStyles.None)
+        {
+            ValidateStyles(styles, nameof(styles));
+            return TimeSpanParse.ParseExact(input, format, formatProvider, styles);
+        }
+        public static TimeSpan ParseExact(String input, String[] formats, IFormatProvider formatProvider, TimeSpanStyles styles)
+        {
+            ValidateStyles(styles, nameof(styles));
+            if (input == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.input);
+            return TimeSpanParse.ParseExactMultiple(input, formats, formatProvider, styles);
+        }
+        public static TimeSpan ParseExact(ReadOnlySpan<char> input, string[] formats, IFormatProvider formatProvider, TimeSpanStyles styles = TimeSpanStyles.None)
+        {
+            ValidateStyles(styles, nameof(styles));
+            return TimeSpanParse.ParseExactMultiple(input, formats, formatProvider, styles);
+        }
+        public static Boolean TryParse(String s, out TimeSpan result)
+        {
+            if (s == null)
+            {
+                result = default(TimeSpan);
+                return false;
+            }
+            return TimeSpanParse.TryParse(s, null, out result);
+        }
+        public static bool TryParse(ReadOnlySpan<char> s, out TimeSpan result)
+        {
+            return TimeSpanParse.TryParse(s, null, out result);
+        }
+
+        public static Boolean TryParse(String input, IFormatProvider formatProvider, out TimeSpan result)
+        {
+            if (input == null)
+            {
+                result = default(TimeSpan);
+                return false;
+            }
+            return TimeSpanParse.TryParse(input, formatProvider, out result);
+        }
+        public static bool TryParse(ReadOnlySpan<char> input, IFormatProvider formatProvider, out TimeSpan result)
+        {
+            return TimeSpanParse.TryParse(input, formatProvider, out result);
+        }
+        public static Boolean TryParseExact(String input, String format, IFormatProvider formatProvider, out TimeSpan result)
+        {
+            if (input == null || format == null)
+            {
+                result = default;
+                return false;
+            }
+            return TimeSpanParse.TryParseExact(input, format, formatProvider, TimeSpanStyles.None, out result);
+        }
+
+        public static bool TryParseExact(ReadOnlySpan<char> input, ReadOnlySpan<char> format, IFormatProvider formatProvider, out TimeSpan result)
+        {
+            return TimeSpanParse.TryParseExact(input, format, formatProvider, TimeSpanStyles.None, out result);
+        }
+        public static Boolean TryParseExact(String input, String[] formats, IFormatProvider formatProvider, out TimeSpan result)
+        {
+            if (input == null)
+            {
+                result = default(TimeSpan);
+                return false;
+            }
+            return TimeSpanParse.TryParseExactMultiple(input, formats, formatProvider, TimeSpanStyles.None, out result);
+        }
+        public static bool TryParseExact(ReadOnlySpan<char> input, string[] formats, IFormatProvider formatProvider, out TimeSpan result)
+        {
+            return TimeSpanParse.TryParseExactMultiple(input, formats, formatProvider, TimeSpanStyles.None, out result);
+        }
+
+        public static Boolean TryParseExact(String input, String format, IFormatProvider formatProvider, TimeSpanStyles styles, out TimeSpan result)
+        {
+            ValidateStyles(styles, nameof(styles));
+            if (input == null || format == null)
+            {
+                result = default;
+                return false;
+            }
+
+            return TimeSpanParse.TryParseExact(input, format, formatProvider, styles, out result);
+        }
+
+        public static bool TryParseExact(ReadOnlySpan<char> input, ReadOnlySpan<char> format, IFormatProvider formatProvider, TimeSpanStyles styles, out TimeSpan result)
+        {
+            ValidateStyles(styles, nameof(styles));
+            return TimeSpanParse.TryParseExact(input, format, formatProvider, styles, out result);
+        }
+        public static Boolean TryParseExact(String input, String[] formats, IFormatProvider formatProvider, TimeSpanStyles styles, out TimeSpan result)
+        {
+            ValidateStyles(styles, nameof(styles));
+            if (input == null)
+            {
+                result = default(TimeSpan);
+                return false;
+            }
+            return TimeSpanParse.TryParseExactMultiple(input, formats, formatProvider, styles, out result);
+        }
+
+        public static bool TryParseExact(ReadOnlySpan<char> input, string[] formats, IFormatProvider formatProvider, TimeSpanStyles styles, out TimeSpan result)
+        {
+            ValidateStyles(styles, nameof(styles));
+            return TimeSpanParse.TryParseExactMultiple(input, formats, formatProvider, styles, out result);
+        }
+        public override String ToString()
+        {
+            return TimeSpanFormat.Format(this, null, null);
+        }
+        public String ToString(String format)
+        {
+            return TimeSpanFormat.Format(this, format, null);
+        }
+        public String ToString(String format, IFormatProvider formatProvider)
+        {
+            return TimeSpanFormat.Format(this, format, formatProvider);
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider formatProvider = null)
+        {
+            return TimeSpanFormat.TryFormat(this, destination, out charsWritten, format, formatProvider);
+        }
+        #endregion
+
+        public static TimeSpan operator -(TimeSpan t)
+        {
+            if (t._ticks == TimeSpan.MinValue._ticks)
+                throw new OverflowException(SR.Overflow_NegateTwosCompNum);
+            return new TimeSpan(-t._ticks);
+        }
+
+        public static TimeSpan operator -(TimeSpan t1, TimeSpan t2)
+        {
+            return t1.Subtract(t2);
+        }
+
+        public static TimeSpan operator +(TimeSpan t)
+        {
+            return t;
+        }
+
+        public static TimeSpan operator +(TimeSpan t1, TimeSpan t2)
+        {
+            return t1.Add(t2);
+        }
+
+        public static TimeSpan operator *(TimeSpan timeSpan, double factor)
+        {
+            if (double.IsNaN(factor))
+            {
+                throw new ArgumentException(SR.Arg_CannotBeNaN, nameof(factor));
+            }
+
+            // Rounding to the nearest tick is as close to the result we would have with unlimited
+            // precision as possible, and so likely to have the least potential to surprise.
+            double ticks = Math.Round(timeSpan.Ticks * factor);
+            if (ticks > long.MaxValue | ticks < long.MinValue)
+            {
+                throw new OverflowException(SR.Overflow_TimeSpanTooLong);
+            }
+
+            return FromTicks((long)ticks);
+        }
+
+        public static TimeSpan operator *(double factor, TimeSpan timeSpan) => timeSpan * factor;
+
+        public static TimeSpan operator /(TimeSpan timeSpan, double divisor)
+        {
+            if (double.IsNaN(divisor))
+            {
+                throw new ArgumentException(SR.Arg_CannotBeNaN, nameof(divisor));
+            }
+
+            double ticks = Math.Round(timeSpan.Ticks / divisor);
+            if (ticks > long.MaxValue | ticks < long.MinValue || double.IsNaN(ticks))
+            {
+                throw new OverflowException(SR.Overflow_TimeSpanTooLong);
+            }
+
+            return FromTicks((long)ticks);
+        }
+
+        // Using floating-point arithmetic directly means that infinities can be returned, which is reasonable
+        // if we consider TimeSpan.FromHours(1) / TimeSpan.Zero asks how many zero-second intervals there are in
+        // an hour for which infinity is the mathematic correct answer. Having TimeSpan.Zero / TimeSpan.Zero return NaN
+        // is perhaps less useful, but no less useful than an exception.
+        public static double operator /(TimeSpan t1, TimeSpan t2) => t1.Ticks / (double)t2.Ticks;
+
+        public static bool operator ==(TimeSpan t1, TimeSpan t2)
+        {
+            return t1._ticks == t2._ticks;
+        }
+
+        public static bool operator !=(TimeSpan t1, TimeSpan t2)
+        {
+            return t1._ticks != t2._ticks;
+        }
+
+        public static bool operator <(TimeSpan t1, TimeSpan t2)
+        {
+            return t1._ticks < t2._ticks;
+        }
+
+        public static bool operator <=(TimeSpan t1, TimeSpan t2)
+        {
+            return t1._ticks <= t2._ticks;
+        }
+
+        public static bool operator >(TimeSpan t1, TimeSpan t2)
+        {
+            return t1._ticks > t2._ticks;
+        }
+
+        public static bool operator >=(TimeSpan t1, TimeSpan t2)
+        {
+            return t1._ticks >= t2._ticks;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TimeZone.cs b/src/System.Private.CoreLib/shared/System/TimeZone.cs
new file mode 100644
index 0000000000..d4059babfc
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TimeZone.cs
@@ -0,0 +1,280 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: 
+** This class is used to represent a TimeZone.  It
+** has methods for converting a DateTime to UTC from local time
+** and to local time from UTC and methods for getting the 
+** standard name and daylight name of the time zone.  
+**
+** The only TimeZone that we support in version 1 is the 
+** CurrentTimeZone as determined by the system timezone.
+**
+**
+============================================================*/
+
+using System;
+using System.Text;
+using System.Threading;
+using System.Collections;
+using System.Globalization;
+
+namespace System
+{
+    [Obsolete("System.TimeZone has been deprecated.  Please investigate the use of System.TimeZoneInfo instead.")]
+    public abstract class TimeZone
+    {
+        private static volatile TimeZone currentTimeZone = null;
+
+        // Private object for locking instead of locking on a public type for SQL reliability work.
+        private static Object s_InternalSyncObject;
+        private static Object InternalSyncObject
+        {
+            get
+            {
+                if (s_InternalSyncObject == null)
+                {
+                    Object o = new Object();
+                    Interlocked.CompareExchange<Object>(ref s_InternalSyncObject, o, null);
+                }
+                return s_InternalSyncObject;
+            }
+        }
+
+
+        protected TimeZone()
+        {
+        }
+
+        public static TimeZone CurrentTimeZone
+        {
+            get
+            {
+                //Grabbing the cached value is required at the top of this function so that
+                //we don't incur a race condition with the ResetTimeZone method below.
+                TimeZone tz = currentTimeZone;
+                if (tz == null)
+                {
+                    lock (InternalSyncObject)
+                    {
+                        if (currentTimeZone == null)
+                        {
+                            currentTimeZone = new CurrentSystemTimeZone();
+                        }
+                        tz = currentTimeZone;
+                    }
+                }
+                return (tz);
+            }
+        }
+
+        //This method is called by CultureInfo.ClearCachedData in response to control panel
+        //change events.  It must be synchronized because otherwise there is a race condition 
+        //with the CurrentTimeZone property above.
+        internal static void ResetTimeZone()
+        {
+            if (currentTimeZone != null)
+            {
+                lock (InternalSyncObject)
+                {
+                    currentTimeZone = null;
+                }
+            }
+        }
+
+        public abstract String StandardName
+        {
+            get;
+        }
+
+        public abstract String DaylightName
+        {
+            get;
+        }
+
+        public abstract TimeSpan GetUtcOffset(DateTime time);
+
+        //
+        // Converts the specified datatime to the Universal time base on the current timezone 
+        //
+        public virtual DateTime ToUniversalTime(DateTime time)
+        {
+            if (time.Kind == DateTimeKind.Utc)
+            {
+                return time;
+            }
+            long tickCount = time.Ticks - GetUtcOffset(time).Ticks;
+            if (tickCount > DateTime.MaxTicks)
+            {
+                return new DateTime(DateTime.MaxTicks, DateTimeKind.Utc);
+            }
+            if (tickCount < DateTime.MinTicks)
+            {
+                return new DateTime(DateTime.MinTicks, DateTimeKind.Utc);
+            }
+            return new DateTime(tickCount, DateTimeKind.Utc);
+        }
+
+        //
+        // Convert the specified datetime value from UTC to the local time based on the time zone.
+        //
+        public virtual DateTime ToLocalTime(DateTime time)
+        {
+            if (time.Kind == DateTimeKind.Local)
+            {
+                return time;
+            }
+            Boolean isAmbiguousLocalDst = false;
+            Int64 offset = ((CurrentSystemTimeZone)(TimeZone.CurrentTimeZone)).GetUtcOffsetFromUniversalTime(time, ref isAmbiguousLocalDst);
+            return new DateTime(time.Ticks + offset, DateTimeKind.Local, isAmbiguousLocalDst);
+        }
+
+        // Return an array of DaylightTime which reflects the daylight saving periods in a particular year.
+        // We currently only support having one DaylightSavingTime per year.
+        // If daylight saving time is not used in this timezone, null will be returned.
+        public abstract DaylightTime GetDaylightChanges(int year);
+
+        public virtual bool IsDaylightSavingTime(DateTime time)
+        {
+            return (IsDaylightSavingTime(time, GetDaylightChanges(time.Year)));
+        }
+
+        // Check if the specified time is in a daylight saving time.  Allows the user to
+        // specify the array of Daylight Saving Times.
+        public static bool IsDaylightSavingTime(DateTime time, DaylightTime daylightTimes)
+        {
+            return CalculateUtcOffset(time, daylightTimes) != TimeSpan.Zero;
+        }
+
+        //
+        // NOTENOTE: Implementation detail
+        // In the transition from standard time to daylight saving time, 
+        // if we convert local time to Universal time, we can have the
+        // following (take PST as an example):
+        //      Local               Universal       UTC Offset
+        //      -----               ---------       ----------
+        //      01:00AM             09:00           -8:00
+        //      02:00 (=> 03:00)    10:00           -8:00   [This time doesn't actually exist, but it can be created from DateTime]
+        //      03:00               10:00           -7:00
+        //      04:00               11:00           -7:00
+        //      05:00               12:00           -7:00
+        //      
+        //      So from 02:00 - 02:59:59, we should return the standard offset, instead of the daylight saving offset.
+        //
+        // In the transition from daylight saving time to standard time,
+        // if we convert local time to Universal time, we can have the
+        // following (take PST as an example):
+        //      Local               Universal       UTC Offset
+        //      -----               ---------       ----------
+        //      01:00AM             08:00           -7:00
+        //      02:00 (=> 01:00)    09:00           -8:00   
+        //      02:00               10:00           -8:00
+        //      03:00               11:00           -8:00
+        //      04:00               12:00           -8:00
+        //      
+        //      So in this case, the 02:00 does exist after the first 2:00 rolls back to 01:00. We don't need to special case this.
+        //      But note that there are two 01:00 in the local time.
+
+        //
+        // And imagine if the daylight saving offset is negative (although this does not exist in real life)
+        // In the transition from standard time to daylight saving time, 
+        // if we convert local time to Universal time, we can have the
+        // following (take PST as an example, but the daylight saving offset is -01:00):
+        //      Local               Universal       UTC Offset
+        //      -----               ---------       ----------
+        //      01:00AM             09:00           -8:00
+        //      02:00 (=> 01:00)    10:00           -9:00
+        //      02:00               11:00           -9:00
+        //      03:00               12:00           -9:00
+        //      04:00               13:00           -9:00
+        //      05:00               14:00           -9:00
+        //      
+        //      So in this case, the 02:00 does exist after the first 2:00 rolls back to 01:00. We don't need to special case this.
+        //
+        // In the transition from daylight saving time to standard time,
+        // if we convert local time to Universal time, we can have the
+        // following (take PST as an example, daylight saving offset is -01:00):
+        //
+        //      Local               Universal       UTC Offset
+        //      -----               ---------       ----------
+        //      01:00AM             10:00           -9:00
+        //      02:00 (=> 03:00)    11:00           -9:00
+        //      03:00               11:00           -8:00
+        //      04:00               12:00           -8:00
+        //      05:00               13:00           -8:00
+        //      06:00               14:00           -8:00
+        //      
+        //      So from 02:00 - 02:59:59, we should return the daylight saving offset, instead of the standard offset.
+        //
+        internal static TimeSpan CalculateUtcOffset(DateTime time, DaylightTime daylightTimes)
+        {
+            if (daylightTimes == null)
+            {
+                return TimeSpan.Zero;
+            }
+            DateTimeKind kind = time.Kind;
+            if (kind == DateTimeKind.Utc)
+            {
+                return TimeSpan.Zero;
+            }
+
+            DateTime startTime;
+            DateTime endTime;
+
+            // startTime and endTime represent the period from either the start of DST to the end and includes the 
+            // potentially overlapped times
+            startTime = daylightTimes.Start + daylightTimes.Delta;
+            endTime = daylightTimes.End;
+
+            // For normal time zones, the ambiguous hour is the last hour of daylight saving when you wind the 
+            // clock back. It is theoretically possible to have a positive delta, (which would really be daylight
+            // reduction time), where you would have to wind the clock back in the begnning.
+            DateTime ambiguousStart;
+            DateTime ambiguousEnd;
+            if (daylightTimes.Delta.Ticks > 0)
+            {
+                ambiguousStart = endTime - daylightTimes.Delta;
+                ambiguousEnd = endTime;
+            }
+            else
+            {
+                ambiguousStart = startTime;
+                ambiguousEnd = startTime - daylightTimes.Delta;
+            }
+
+            Boolean isDst = false;
+            if (startTime > endTime)
+            {
+                // In southern hemisphere, the daylight saving time starts later in the year, and ends in the beginning of next year.
+                // Note, the summer in the southern hemisphere begins late in the year.
+                if (time >= startTime || time < endTime)
+                {
+                    isDst = true;
+                }
+            }
+            else if (time >= startTime && time < endTime)
+            {
+                // In northern hemisphere, the daylight saving time starts in the middle of the year.
+                isDst = true;
+            }
+
+            // If this date was previously converted from a UTC date and we were able to detect that the local
+            // DateTime would be ambiguous, this data is stored in the DateTime to resolve this ambiguity. 
+            if (isDst && time >= ambiguousStart && time < ambiguousEnd)
+            {
+                isDst = time.IsAmbiguousDaylightSavingTime();
+            }
+
+            if (isDst)
+            {
+                return daylightTimes.Delta;
+            }
+            return TimeSpan.Zero;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TimeZoneInfo.AdjustmentRule.cs b/src/System.Private.CoreLib/shared/System/TimeZoneInfo.AdjustmentRule.cs
new file mode 100644
index 0000000000..0e949a30ec
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TimeZoneInfo.AdjustmentRule.cs
@@ -0,0 +1,248 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    public sealed partial class TimeZoneInfo
+    {
+        [Serializable]
+        public sealed class AdjustmentRule : IEquatable<AdjustmentRule>, ISerializable, IDeserializationCallback
+        {
+            private readonly DateTime _dateStart;
+            private readonly DateTime _dateEnd;
+            private readonly TimeSpan _daylightDelta;
+            private readonly TransitionTime _daylightTransitionStart;
+            private readonly TransitionTime _daylightTransitionEnd;
+            private readonly TimeSpan _baseUtcOffsetDelta;   // delta from the default Utc offset (utcOffset = defaultUtcOffset + _baseUtcOffsetDelta)
+            private readonly bool _noDaylightTransitions;
+
+            public DateTime DateStart => _dateStart;
+
+            public DateTime DateEnd => _dateEnd;
+
+            public TimeSpan DaylightDelta => _daylightDelta;
+
+            public TransitionTime DaylightTransitionStart => _daylightTransitionStart;
+
+            public TransitionTime DaylightTransitionEnd => _daylightTransitionEnd;
+
+            internal TimeSpan BaseUtcOffsetDelta => _baseUtcOffsetDelta;
+
+            /// <summary>
+            /// Gets a value indicating that this AdjustmentRule fixes the time zone offset
+            /// from DateStart to DateEnd without any daylight transitions in between.
+            /// </summary>
+            internal bool NoDaylightTransitions => _noDaylightTransitions;
+
+            internal bool HasDaylightSaving =>
+                DaylightDelta != TimeSpan.Zero ||
+                (DaylightTransitionStart != default(TransitionTime) && DaylightTransitionStart.TimeOfDay != DateTime.MinValue) ||
+                (DaylightTransitionEnd != default(TransitionTime) && DaylightTransitionEnd.TimeOfDay != DateTime.MinValue.AddMilliseconds(1));
+
+            public bool Equals(AdjustmentRule other) =>
+                other != null &&
+                _dateStart == other._dateStart &&
+                _dateEnd == other._dateEnd &&
+                _daylightDelta == other._daylightDelta &&
+                _baseUtcOffsetDelta == other._baseUtcOffsetDelta &&
+                _daylightTransitionEnd.Equals(other._daylightTransitionEnd) &&
+                _daylightTransitionStart.Equals(other._daylightTransitionStart);
+
+            public override int GetHashCode() => _dateStart.GetHashCode();
+
+            private AdjustmentRule(
+                DateTime dateStart,
+                DateTime dateEnd,
+                TimeSpan daylightDelta,
+                TransitionTime daylightTransitionStart,
+                TransitionTime daylightTransitionEnd,
+                TimeSpan baseUtcOffsetDelta,
+                bool noDaylightTransitions)
+            {
+                ValidateAdjustmentRule(dateStart, dateEnd, daylightDelta,
+                       daylightTransitionStart, daylightTransitionEnd, noDaylightTransitions);
+
+                _dateStart = dateStart;
+                _dateEnd = dateEnd;
+                _daylightDelta = daylightDelta;
+                _daylightTransitionStart = daylightTransitionStart;
+                _daylightTransitionEnd = daylightTransitionEnd;
+                _baseUtcOffsetDelta = baseUtcOffsetDelta;
+                _noDaylightTransitions = noDaylightTransitions;
+            }
+
+            public static AdjustmentRule CreateAdjustmentRule(
+                DateTime dateStart,
+                DateTime dateEnd,
+                TimeSpan daylightDelta,
+                TransitionTime daylightTransitionStart,
+                TransitionTime daylightTransitionEnd)
+            {
+                return new AdjustmentRule(
+                    dateStart,
+                    dateEnd,
+                    daylightDelta,
+                    daylightTransitionStart,
+                    daylightTransitionEnd,
+                    baseUtcOffsetDelta: TimeSpan.Zero,
+                    noDaylightTransitions: false);
+            }
+
+            internal static AdjustmentRule CreateAdjustmentRule(
+                DateTime dateStart,
+                DateTime dateEnd,
+                TimeSpan daylightDelta,
+                TransitionTime daylightTransitionStart,
+                TransitionTime daylightTransitionEnd,
+                TimeSpan baseUtcOffsetDelta,
+                bool noDaylightTransitions)
+            {
+                return new AdjustmentRule(
+                    dateStart,
+                    dateEnd,
+                    daylightDelta,
+                    daylightTransitionStart,
+                    daylightTransitionEnd,
+                    baseUtcOffsetDelta,
+                    noDaylightTransitions);
+            }
+
+            //
+            // When Windows sets the daylight transition start Jan 1st at 12:00 AM, it means the year starts with the daylight saving on.
+            // We have to special case this value and not adjust it when checking if any date is in the daylight saving period.
+            //
+            internal bool IsStartDateMarkerForBeginningOfYear() =>
+                !NoDaylightTransitions &&
+                DaylightTransitionStart.Month == 1 && DaylightTransitionStart.Day == 1 && DaylightTransitionStart.TimeOfDay.Hour == 0 &&
+                DaylightTransitionStart.TimeOfDay.Minute == 0 && DaylightTransitionStart.TimeOfDay.Second == 0 &&
+                _dateStart.Year == _dateEnd.Year;
+
+            //
+            // When Windows sets the daylight transition end Jan 1st at 12:00 AM, it means the year ends with the daylight saving on.
+            // We have to special case this value and not adjust it when checking if any date is in the daylight saving period.
+            //
+            internal bool IsEndDateMarkerForEndOfYear() =>
+                !NoDaylightTransitions &&
+                DaylightTransitionEnd.Month == 1 && DaylightTransitionEnd.Day == 1 && DaylightTransitionEnd.TimeOfDay.Hour == 0 &&
+                DaylightTransitionEnd.TimeOfDay.Minute == 0 && DaylightTransitionEnd.TimeOfDay.Second == 0 &&
+                _dateStart.Year == _dateEnd.Year;
+
+            /// <summary>
+            /// Helper function that performs all of the validation checks for the factory methods and deserialization callback.
+            /// </summary>
+            private static void ValidateAdjustmentRule(
+                DateTime dateStart,
+                DateTime dateEnd,
+                TimeSpan daylightDelta,
+                TransitionTime daylightTransitionStart,
+                TransitionTime daylightTransitionEnd,
+                bool noDaylightTransitions)
+            {
+                if (dateStart.Kind != DateTimeKind.Unspecified && dateStart.Kind != DateTimeKind.Utc)
+                {
+                    throw new ArgumentException(SR.Argument_DateTimeKindMustBeUnspecifiedOrUtc, nameof(dateStart));
+                }
+
+                if (dateEnd.Kind != DateTimeKind.Unspecified && dateEnd.Kind != DateTimeKind.Utc)
+                {
+                    throw new ArgumentException(SR.Argument_DateTimeKindMustBeUnspecifiedOrUtc, nameof(dateEnd));
+                }
+
+                if (daylightTransitionStart.Equals(daylightTransitionEnd) && !noDaylightTransitions)
+                {
+                    throw new ArgumentException(SR.Argument_TransitionTimesAreIdentical, nameof(daylightTransitionEnd));
+                }
+
+                if (dateStart > dateEnd)
+                {
+                    throw new ArgumentException(SR.Argument_OutOfOrderDateTimes, nameof(dateStart));
+                }
+
+                // This cannot use UtcOffsetOutOfRange to account for the scenario where Samoa moved across the International Date Line,
+                // which caused their current BaseUtcOffset to be +13. But on the other side of the line it was UTC-11 (+1 for daylight).
+                // So when trying to describe DaylightDeltas for those times, the DaylightDelta needs
+                // to be -23 (what it takes to go from UTC+13 to UTC-10)
+                if (daylightDelta.TotalHours < -23.0 || daylightDelta.TotalHours > 14.0)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(daylightDelta), daylightDelta, SR.ArgumentOutOfRange_UtcOffset);
+                }
+
+                if (daylightDelta.Ticks % TimeSpan.TicksPerMinute != 0)
+                {
+                    throw new ArgumentException(SR.Argument_TimeSpanHasSeconds, nameof(daylightDelta));
+                }
+
+                if (dateStart != DateTime.MinValue && dateStart.Kind == DateTimeKind.Unspecified && dateStart.TimeOfDay != TimeSpan.Zero)
+                {
+                    throw new ArgumentException(SR.Argument_DateTimeHasTimeOfDay, nameof(dateStart));
+                }
+
+                if (dateEnd != DateTime.MaxValue && dateEnd.Kind == DateTimeKind.Unspecified && dateEnd.TimeOfDay != TimeSpan.Zero)
+                {
+                    throw new ArgumentException(SR.Argument_DateTimeHasTimeOfDay, nameof(dateEnd));
+                }
+            }
+
+            void IDeserializationCallback.OnDeserialization(object sender)
+            {
+                // OnDeserialization is called after each instance of this class is deserialized.
+                // This callback method performs AdjustmentRule validation after being deserialized.
+
+                try
+                {
+                    ValidateAdjustmentRule(_dateStart, _dateEnd, _daylightDelta,
+                                           _daylightTransitionStart, _daylightTransitionEnd, _noDaylightTransitions);
+                }
+                catch (ArgumentException e)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData, e);
+                }
+            }
+
+            void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
+            {
+                if (info == null)
+                {
+                    throw new ArgumentNullException(nameof(info));
+                }
+
+                info.AddValue("DateStart", _dateStart); // Do not rename (binary serialization)
+                info.AddValue("DateEnd", _dateEnd); // Do not rename (binary serialization)
+                info.AddValue("DaylightDelta", _daylightDelta); // Do not rename (binary serialization)
+                info.AddValue("DaylightTransitionStart", _daylightTransitionStart); // Do not rename (binary serialization)
+                info.AddValue("DaylightTransitionEnd", _daylightTransitionEnd); // Do not rename (binary serialization)
+                info.AddValue("BaseUtcOffsetDelta", _baseUtcOffsetDelta); // Do not rename (binary serialization)
+                info.AddValue("NoDaylightTransitions", _noDaylightTransitions); // Do not rename (binary serialization)
+            }
+
+            private AdjustmentRule(SerializationInfo info, StreamingContext context)
+            {
+                if (info == null)
+                {
+                    throw new ArgumentNullException(nameof(info));
+                }
+
+                _dateStart = (DateTime)info.GetValue("DateStart", typeof(DateTime)); // Do not rename (binary serialization)
+                _dateEnd = (DateTime)info.GetValue("DateEnd", typeof(DateTime)); // Do not rename (binary serialization)
+                _daylightDelta = (TimeSpan)info.GetValue("DaylightDelta", typeof(TimeSpan)); // Do not rename (binary serialization)
+                _daylightTransitionStart = (TransitionTime)info.GetValue("DaylightTransitionStart", typeof(TransitionTime)); // Do not rename (binary serialization)
+                _daylightTransitionEnd = (TransitionTime)info.GetValue("DaylightTransitionEnd", typeof(TransitionTime)); // Do not rename (binary serialization)
+
+                object o = info.GetValueNoThrow("BaseUtcOffsetDelta", typeof(TimeSpan)); // Do not rename (binary serialization)
+                if (o != null)
+                {
+                    _baseUtcOffsetDelta = (TimeSpan)o;
+                }
+
+                o = info.GetValueNoThrow("NoDaylightTransitions", typeof(bool)); // Do not rename (binary serialization)
+                if (o != null)
+                {
+                    _noDaylightTransitions = (bool)o;
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TimeZoneInfo.StringSerializer.cs b/src/System.Private.CoreLib/shared/System/TimeZoneInfo.StringSerializer.cs
new file mode 100644
index 0000000000..e3e9ddbf58
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TimeZoneInfo.StringSerializer.cs
@@ -0,0 +1,625 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Globalization;
+using System.Runtime.Serialization;
+using System.Text;
+
+namespace System
+{
+    public sealed partial class TimeZoneInfo
+    {
+        /// <summary>
+        /// Used to serialize and deserialize TimeZoneInfo objects based on the custom string serialization format.
+        /// </summary>
+        private struct StringSerializer
+        {
+            private enum State
+            {
+                Escaped = 0,
+                NotEscaped = 1,
+                StartOfToken = 2,
+                EndOfLine = 3
+            }
+
+            private readonly string _serializedText;
+            private int _currentTokenStartIndex;
+            private State _state;
+
+            // the majority of the strings contained in the OS time zones fit in 64 chars
+            private const int InitialCapacityForString = 64;
+            private const char Esc = '\\';
+            private const char Sep = ';';
+            private const char Lhs = '[';
+            private const char Rhs = ']';
+            private const string DateTimeFormat = "MM:dd:yyyy";
+            private const string TimeOfDayFormat = "HH:mm:ss.FFF";
+
+            /// <summary>
+            /// Creates the custom serialized string representation of a TimeZoneInfo instance.
+            /// </summary>
+            public static string GetSerializedString(TimeZoneInfo zone)
+            {
+                StringBuilder serializedText = StringBuilderCache.Acquire();
+
+                //
+                // <_id>;<_baseUtcOffset>;<_displayName>;<_standardDisplayName>;<_daylightDispayName>
+                //
+                SerializeSubstitute(zone.Id, serializedText);
+                serializedText.Append(Sep);
+                serializedText.Append(zone.BaseUtcOffset.TotalMinutes.ToString(CultureInfo.InvariantCulture));
+                serializedText.Append(Sep);
+                SerializeSubstitute(zone.DisplayName, serializedText);
+                serializedText.Append(Sep);
+                SerializeSubstitute(zone.StandardName, serializedText);
+                serializedText.Append(Sep);
+                SerializeSubstitute(zone.DaylightName, serializedText);
+                serializedText.Append(Sep);
+
+                AdjustmentRule[] rules = zone.GetAdjustmentRules();
+                foreach (AdjustmentRule rule in rules)
+                {
+                    serializedText.Append(Lhs);
+                    serializedText.Append(rule.DateStart.ToString(DateTimeFormat, DateTimeFormatInfo.InvariantInfo));
+                    serializedText.Append(Sep);
+                    serializedText.Append(rule.DateEnd.ToString(DateTimeFormat, DateTimeFormatInfo.InvariantInfo));
+                    serializedText.Append(Sep);
+                    serializedText.Append(rule.DaylightDelta.TotalMinutes.ToString(CultureInfo.InvariantCulture));
+                    serializedText.Append(Sep);
+                    // serialize the TransitionTime's
+                    SerializeTransitionTime(rule.DaylightTransitionStart, serializedText);
+                    serializedText.Append(Sep);
+                    SerializeTransitionTime(rule.DaylightTransitionEnd, serializedText);
+                    serializedText.Append(Sep);
+                    if (rule.BaseUtcOffsetDelta != TimeSpan.Zero)
+                    {
+                        // Serialize it only when BaseUtcOffsetDelta has a value to reduce the impact of adding rule.BaseUtcOffsetDelta
+                        serializedText.Append(rule.BaseUtcOffsetDelta.TotalMinutes.ToString(CultureInfo.InvariantCulture));
+                        serializedText.Append(Sep);
+                    }
+                    if (rule.NoDaylightTransitions)
+                    {
+                        // Serialize it only when NoDaylightTransitions is true to reduce the impact of adding rule.NoDaylightTransitions
+                        serializedText.Append('1');
+                        serializedText.Append(Sep);
+                    }
+                    serializedText.Append(Rhs);
+                }
+                serializedText.Append(Sep);
+
+                return StringBuilderCache.GetStringAndRelease(serializedText);
+            }
+
+            /// <summary>
+            /// Instantiates a TimeZoneInfo from a custom serialized string.
+            /// </summary>
+            public static TimeZoneInfo GetDeserializedTimeZoneInfo(string source)
+            {
+                StringSerializer s = new StringSerializer(source);
+
+                string id = s.GetNextStringValue();
+                TimeSpan baseUtcOffset = s.GetNextTimeSpanValue();
+                string displayName = s.GetNextStringValue();
+                string standardName = s.GetNextStringValue();
+                string daylightName = s.GetNextStringValue();
+                AdjustmentRule[] rules = s.GetNextAdjustmentRuleArrayValue();
+
+                try
+                {
+                    return new TimeZoneInfo(id, baseUtcOffset, displayName, standardName, daylightName, rules, disableDaylightSavingTime: false);
+                }
+                catch (ArgumentException ex)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData, ex);
+                }
+                catch (InvalidTimeZoneException ex)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData, ex);
+                }
+            }
+
+            private StringSerializer(string str)
+            {
+                _serializedText = str;
+                _currentTokenStartIndex = 0;
+                _state = State.StartOfToken;
+            }
+
+            /// <summary>
+            /// Appends the String to the StringBuilder with all of the reserved chars escaped.
+            ///
+            /// ";" -> "\;"
+            /// "[" -> "\["
+            /// "]" -> "\]"
+            /// "\" -> "\\"
+            /// </summary>
+            private static void SerializeSubstitute(string text, StringBuilder serializedText)
+            {
+                foreach (char c in text)
+                {
+                    if (c == Esc || c == Lhs || c == Rhs || c == Sep)
+                    {
+                        serializedText.Append('\\');
+                    }
+                    serializedText.Append(c);
+                }
+            }
+
+            /// <summary>
+            /// Helper method to serialize a TimeZoneInfo.TransitionTime object.
+            /// </summary>
+            private static void SerializeTransitionTime(TransitionTime time, StringBuilder serializedText)
+            {
+                serializedText.Append(Lhs);
+                serializedText.Append(time.IsFixedDateRule ? '1' : '0');
+                serializedText.Append(Sep);
+                serializedText.Append(time.TimeOfDay.ToString(TimeOfDayFormat, DateTimeFormatInfo.InvariantInfo));
+                serializedText.Append(Sep);
+                serializedText.Append(time.Month.ToString(CultureInfo.InvariantCulture));
+                serializedText.Append(Sep);
+                if (time.IsFixedDateRule)
+                {
+                    serializedText.Append(time.Day.ToString(CultureInfo.InvariantCulture));
+                    serializedText.Append(Sep);
+                }
+                else
+                {
+                    serializedText.Append(time.Week.ToString(CultureInfo.InvariantCulture));
+                    serializedText.Append(Sep);
+                    serializedText.Append(((int)time.DayOfWeek).ToString(CultureInfo.InvariantCulture));
+                    serializedText.Append(Sep);
+                }
+                serializedText.Append(Rhs);
+            }
+
+            /// <summary>
+            /// Helper function to determine if the passed in string token is allowed to be preceded by an escape sequence token.
+            /// </summary>
+            private static void VerifyIsEscapableCharacter(char c)
+            {
+                if (c != Esc && c != Sep && c != Lhs && c != Rhs)
+                {
+                    throw new SerializationException(SR.Format(SR.Serialization_InvalidEscapeSequence, c));
+                }
+            }
+
+            /// <summary>
+            /// Helper function that reads past "v.Next" data fields. Receives a "depth" parameter indicating the
+            /// current relative nested bracket depth that _currentTokenStartIndex is at. The function ends
+            /// successfully when "depth" returns to zero (0).
+            /// </summary>
+            private void SkipVersionNextDataFields(int depth /* starting depth in the nested brackets ('[', ']')*/)
+            {
+                if (_currentTokenStartIndex < 0 || _currentTokenStartIndex >= _serializedText.Length)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+                State tokenState = State.NotEscaped;
+
+                // walk the serialized text, building up the token as we go...
+                for (int i = _currentTokenStartIndex; i < _serializedText.Length; i++)
+                {
+                    if (tokenState == State.Escaped)
+                    {
+                        VerifyIsEscapableCharacter(_serializedText[i]);
+                        tokenState = State.NotEscaped;
+                    }
+                    else if (tokenState == State.NotEscaped)
+                    {
+                        switch (_serializedText[i])
+                        {
+                            case Esc:
+                                tokenState = State.Escaped;
+                                break;
+
+                            case Lhs:
+                                depth++;
+                                break;
+                            case Rhs:
+                                depth--;
+                                if (depth == 0)
+                                {
+                                    _currentTokenStartIndex = i + 1;
+                                    if (_currentTokenStartIndex >= _serializedText.Length)
+                                    {
+                                        _state = State.EndOfLine;
+                                    }
+                                    else
+                                    {
+                                        _state = State.StartOfToken;
+                                    }
+                                    return;
+                                }
+                                break;
+
+                            case '\0':
+                                // invalid character
+                                throw new SerializationException(SR.Serialization_InvalidData);
+
+                            default:
+                                break;
+                        }
+                    }
+                }
+
+                throw new SerializationException(SR.Serialization_InvalidData);
+            }
+
+            /// <summary>
+            /// Helper function that reads a string token from the serialized text. The function
+            /// updates <see cref="_currentTokenStartIndex"/> to point to the next token on exit.
+            /// Also <see cref="_state"/> is set to either <see cref="State.StartOfToken"/> or
+            /// <see cref="State.EndOfLine"/> on exit.
+            /// </summary>
+            private string GetNextStringValue()
+            {
+                // first verify the internal state of the object
+                if (_state == State.EndOfLine)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+                if (_currentTokenStartIndex < 0 || _currentTokenStartIndex >= _serializedText.Length)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+                State tokenState = State.NotEscaped;
+                StringBuilder token = StringBuilderCache.Acquire(InitialCapacityForString);
+
+                // walk the serialized text, building up the token as we go...
+                for (int i = _currentTokenStartIndex; i < _serializedText.Length; i++)
+                {
+                    if (tokenState == State.Escaped)
+                    {
+                        VerifyIsEscapableCharacter(_serializedText[i]);
+                        token.Append(_serializedText[i]);
+                        tokenState = State.NotEscaped;
+                    }
+                    else if (tokenState == State.NotEscaped)
+                    {
+                        switch (_serializedText[i])
+                        {
+                            case Esc:
+                                tokenState = State.Escaped;
+                                break;
+
+                            case Lhs:
+                                // '[' is an unexpected character
+                                throw new SerializationException(SR.Serialization_InvalidData);
+
+                            case Rhs:
+                                // ']' is an unexpected character
+                                throw new SerializationException(SR.Serialization_InvalidData);
+
+                            case Sep:
+                                _currentTokenStartIndex = i + 1;
+                                if (_currentTokenStartIndex >= _serializedText.Length)
+                                {
+                                    _state = State.EndOfLine;
+                                }
+                                else
+                                {
+                                    _state = State.StartOfToken;
+                                }
+                                return StringBuilderCache.GetStringAndRelease(token);
+
+                            case '\0':
+                                // invalid character
+                                throw new SerializationException(SR.Serialization_InvalidData);
+
+                            default:
+                                token.Append(_serializedText[i]);
+                                break;
+                        }
+                    }
+                }
+                //
+                // we are at the end of the line
+                //
+                if (tokenState == State.Escaped)
+                {
+                    // we are at the end of the serialized text but we are in an escaped state
+                    throw new SerializationException(SR.Format(SR.Serialization_InvalidEscapeSequence, string.Empty));
+                }
+
+                throw new SerializationException(SR.Serialization_InvalidData);
+            }
+
+            /// <summary>
+            /// Helper function to read a DateTime token.
+            /// </summary>
+            private DateTime GetNextDateTimeValue(string format)
+            {
+                string token = GetNextStringValue();
+                DateTime time;
+                if (!DateTime.TryParseExact(token, format, DateTimeFormatInfo.InvariantInfo, DateTimeStyles.None, out time))
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+                return time;
+            }
+
+            /// <summary>
+            /// Helper function to read a TimeSpan token.
+            /// </summary>
+            private TimeSpan GetNextTimeSpanValue()
+            {
+                int token = GetNextInt32Value();
+                try
+                {
+                    return new TimeSpan(hours: 0, minutes: token, seconds: 0);
+                }
+                catch (ArgumentOutOfRangeException e)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData, e);
+                }
+            }
+
+            /// <summary>
+            /// Helper function to read an Int32 token.
+            /// </summary>
+            private int GetNextInt32Value()
+            {
+                string token = GetNextStringValue();
+                int value;
+                if (!int.TryParse(token, NumberStyles.AllowLeadingSign /* "[sign]digits" */, CultureInfo.InvariantCulture, out value))
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+                return value;
+            }
+
+            /// <summary>
+            /// Helper function to read an AdjustmentRule[] token.
+            /// </summary>
+            private AdjustmentRule[] GetNextAdjustmentRuleArrayValue()
+            {
+                List<AdjustmentRule> rules = new List<AdjustmentRule>(1);
+                int count = 0;
+
+                // individual AdjustmentRule array elements do not require semicolons
+                AdjustmentRule rule = GetNextAdjustmentRuleValue();
+                while (rule != null)
+                {
+                    rules.Add(rule);
+                    count++;
+
+                    rule = GetNextAdjustmentRuleValue();
+                }
+
+                // the AdjustmentRule array must end with a separator
+                if (_state == State.EndOfLine)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+                if (_currentTokenStartIndex < 0 || _currentTokenStartIndex >= _serializedText.Length)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+
+                return count != 0 ? rules.ToArray() : null;
+            }
+
+            /// <summary>
+            /// Helper function to read an AdjustmentRule token.
+            /// </summary>
+            private AdjustmentRule GetNextAdjustmentRuleValue()
+            {
+                // first verify the internal state of the object
+                if (_state == State.EndOfLine)
+                {
+                    return null;
+                }
+
+                if (_currentTokenStartIndex < 0 || _currentTokenStartIndex >= _serializedText.Length)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+
+                // check to see if the very first token we see is the separator
+                if (_serializedText[_currentTokenStartIndex] == Sep)
+                {
+                    return null;
+                }
+
+                // verify the current token is a left-hand-side marker ("[")
+                if (_serializedText[_currentTokenStartIndex] != Lhs)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+                _currentTokenStartIndex++;
+
+                DateTime dateStart = GetNextDateTimeValue(DateTimeFormat);
+                DateTime dateEnd = GetNextDateTimeValue(DateTimeFormat);
+                TimeSpan daylightDelta = GetNextTimeSpanValue();
+                TransitionTime daylightStart = GetNextTransitionTimeValue();
+                TransitionTime daylightEnd = GetNextTransitionTimeValue();
+                TimeSpan baseUtcOffsetDelta = TimeSpan.Zero;
+                int noDaylightTransitions = 0;
+
+                // verify that the string is now at the right-hand-side marker ("]") ...
+
+                if (_state == State.EndOfLine || _currentTokenStartIndex >= _serializedText.Length)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+
+                // Check if we have baseUtcOffsetDelta in the serialized string and then deserialize it
+                if ((_serializedText[_currentTokenStartIndex] >= '0' && _serializedText[_currentTokenStartIndex] <= '9') ||
+                    _serializedText[_currentTokenStartIndex] == '-' || _serializedText[_currentTokenStartIndex] == '+')
+                {
+                    baseUtcOffsetDelta = GetNextTimeSpanValue();
+                }
+
+                // Check if we have NoDaylightTransitions in the serialized string and then deserialize it
+                if ((_serializedText[_currentTokenStartIndex] >= '0' && _serializedText[_currentTokenStartIndex] <= '1'))
+                {
+                    noDaylightTransitions = GetNextInt32Value();
+                }
+
+                if (_state == State.EndOfLine || _currentTokenStartIndex >= _serializedText.Length)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+
+                if (_serializedText[_currentTokenStartIndex] != Rhs)
+                {
+                    // skip ahead of any "v.Next" data at the end of the AdjustmentRule
+                    //
+                    // FUTURE: if the serialization format is extended in the future then this
+                    // code section will need to be changed to read the new fields rather
+                    // than just skipping the data at the end of the [AdjustmentRule].
+                    SkipVersionNextDataFields(1);
+                }
+                else
+                {
+                    _currentTokenStartIndex++;
+                }
+
+                // create the AdjustmentRule from the deserialized fields ...
+
+                AdjustmentRule rule;
+                try
+                {
+                    rule = AdjustmentRule.CreateAdjustmentRule(dateStart, dateEnd, daylightDelta, daylightStart, daylightEnd, baseUtcOffsetDelta, noDaylightTransitions > 0);
+                }
+                catch (ArgumentException e)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData, e);
+                }
+
+                // finally set the state to either EndOfLine or StartOfToken for the next caller
+                if (_currentTokenStartIndex >= _serializedText.Length)
+                {
+                    _state = State.EndOfLine;
+                }
+                else
+                {
+                    _state = State.StartOfToken;
+                }
+                return rule;
+            }
+
+            /// <summary>
+            /// Helper function to read a TransitionTime token.
+            /// </summary>
+            private TransitionTime GetNextTransitionTimeValue()
+            {
+                // first verify the internal state of the object
+
+                if (_state == State.EndOfLine ||
+                    (_currentTokenStartIndex < _serializedText.Length && _serializedText[_currentTokenStartIndex] == Rhs))
+                {
+                    //
+                    // we are at the end of the line or we are starting at a "]" character
+                    //
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+
+                if (_currentTokenStartIndex < 0 || _currentTokenStartIndex >= _serializedText.Length)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+
+                // verify the current token is a left-hand-side marker ("[")
+
+                if (_serializedText[_currentTokenStartIndex] != Lhs)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+                _currentTokenStartIndex++;
+
+                int isFixedDate = GetNextInt32Value();
+
+                if (isFixedDate != 0 && isFixedDate != 1)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+
+                TransitionTime transition;
+
+                DateTime timeOfDay = GetNextDateTimeValue(TimeOfDayFormat);
+                timeOfDay = new DateTime(1, 1, 1, timeOfDay.Hour, timeOfDay.Minute, timeOfDay.Second, timeOfDay.Millisecond);
+
+                int month = GetNextInt32Value();
+
+                if (isFixedDate == 1)
+                {
+                    int day = GetNextInt32Value();
+
+                    try
+                    {
+                        transition = TransitionTime.CreateFixedDateRule(timeOfDay, month, day);
+                    }
+                    catch (ArgumentException e)
+                    {
+                        throw new SerializationException(SR.Serialization_InvalidData, e);
+                    }
+                }
+                else
+                {
+                    int week = GetNextInt32Value();
+                    int dayOfWeek = GetNextInt32Value();
+
+                    try
+                    {
+                        transition = TransitionTime.CreateFloatingDateRule(timeOfDay, month, week, (DayOfWeek)dayOfWeek);
+                    }
+                    catch (ArgumentException e)
+                    {
+                        throw new SerializationException(SR.Serialization_InvalidData, e);
+                    }
+                }
+
+                // verify that the string is now at the right-hand-side marker ("]") ...
+
+                if (_state == State.EndOfLine || _currentTokenStartIndex >= _serializedText.Length)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+
+                if (_serializedText[_currentTokenStartIndex] != Rhs)
+                {
+                    // skip ahead of any "v.Next" data at the end of the AdjustmentRule
+                    //
+                    // FUTURE: if the serialization format is extended in the future then this
+                    // code section will need to be changed to read the new fields rather
+                    // than just skipping the data at the end of the [TransitionTime].
+                    SkipVersionNextDataFields(1);
+                }
+                else
+                {
+                    _currentTokenStartIndex++;
+                }
+
+                // check to see if the string is now at the separator (";") ...
+                bool sepFound = false;
+                if (_currentTokenStartIndex < _serializedText.Length &&
+                    _serializedText[_currentTokenStartIndex] == Sep)
+                {
+                    // handle the case where we ended on a ";"
+                    _currentTokenStartIndex++;
+                    sepFound = true;
+                }
+
+                if (!sepFound)
+                {
+                    // we MUST end on a separator
+                    throw new SerializationException(SR.Serialization_InvalidData);
+                }
+
+                // finally set the state to either EndOfLine or StartOfToken for the next caller
+                if (_currentTokenStartIndex >= _serializedText.Length)
+                {
+                    _state = State.EndOfLine;
+                }
+                else
+                {
+                    _state = State.StartOfToken;
+                }
+                return transition;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TimeZoneInfo.TransitionTime.cs b/src/System.Private.CoreLib/shared/System/TimeZoneInfo.TransitionTime.cs
new file mode 100644
index 0000000000..b93794262c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TimeZoneInfo.TransitionTime.cs
@@ -0,0 +1,155 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    public sealed partial class TimeZoneInfo
+    {
+        [Serializable]
+        public readonly struct TransitionTime : IEquatable<TransitionTime>, ISerializable, IDeserializationCallback
+        {
+            private readonly DateTime _timeOfDay;
+            private readonly byte _month;
+            private readonly byte _week;
+            private readonly byte _day;
+            private readonly DayOfWeek _dayOfWeek;
+            private readonly bool _isFixedDateRule;
+
+            public DateTime TimeOfDay => _timeOfDay;
+
+            public int Month => _month;
+
+            public int Week => _week;
+
+            public int Day => _day;
+
+            public DayOfWeek DayOfWeek => _dayOfWeek;
+
+            public bool IsFixedDateRule => _isFixedDateRule;
+
+            public override bool Equals(object obj) =>
+                obj is TransitionTime && Equals((TransitionTime)obj);
+
+            public static bool operator ==(TransitionTime t1, TransitionTime t2) => t1.Equals(t2);
+
+            public static bool operator !=(TransitionTime t1, TransitionTime t2) => !t1.Equals(t2);
+
+            public bool Equals(TransitionTime other) =>
+                _isFixedDateRule == other._isFixedDateRule &&
+                _timeOfDay == other._timeOfDay &&
+                _month == other._month &&
+                (other._isFixedDateRule ?
+                    _day == other._day :
+                    _week == other._week && _dayOfWeek == other._dayOfWeek);
+
+            public override int GetHashCode() => (int)_month ^ (int)_week << 8;
+
+            private TransitionTime(DateTime timeOfDay, int month, int week, int day, DayOfWeek dayOfWeek, bool isFixedDateRule)
+            {
+                ValidateTransitionTime(timeOfDay, month, week, day, dayOfWeek);
+
+                _timeOfDay = timeOfDay;
+                _month = (byte)month;
+                _week = (byte)week;
+                _day = (byte)day;
+                _dayOfWeek = dayOfWeek;
+                _isFixedDateRule = isFixedDateRule;
+            }
+
+            public static TransitionTime CreateFixedDateRule(DateTime timeOfDay, int month, int day) =>
+                new TransitionTime(timeOfDay, month, 1, day, DayOfWeek.Sunday, isFixedDateRule: true);
+
+            public static TransitionTime CreateFloatingDateRule(DateTime timeOfDay, int month, int week, DayOfWeek dayOfWeek) =>
+                new TransitionTime(timeOfDay, month, week, 1, dayOfWeek, isFixedDateRule: false);
+
+            /// <summary>
+            /// Helper function that validates a TransitionTime instance.
+            /// </summary>
+            private static void ValidateTransitionTime(DateTime timeOfDay, int month, int week, int day, DayOfWeek dayOfWeek)
+            {
+                if (timeOfDay.Kind != DateTimeKind.Unspecified)
+                {
+                    throw new ArgumentException(SR.Argument_DateTimeKindMustBeUnspecified, nameof(timeOfDay));
+                }
+
+                // Month range 1-12
+                if (month < 1 || month > 12)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(month), SR.ArgumentOutOfRange_MonthParam);
+                }
+
+                // Day range 1-31
+                if (day < 1 || day > 31)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(day), SR.ArgumentOutOfRange_DayParam);
+                }
+
+                // Week range 1-5
+                if (week < 1 || week > 5)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(week), SR.ArgumentOutOfRange_Week);
+                }
+
+                // DayOfWeek range 0-6
+                if ((int)dayOfWeek < 0 || (int)dayOfWeek > 6)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(dayOfWeek), SR.ArgumentOutOfRange_DayOfWeek);
+                }
+
+                timeOfDay.GetDatePart(out int timeOfDayYear, out int timeOfDayMonth, out int timeOfDayDay);
+                if (timeOfDayYear != 1 || timeOfDayMonth != 1 || timeOfDayDay != 1 || (timeOfDay.Ticks % TimeSpan.TicksPerMillisecond != 0))
+                {
+                    throw new ArgumentException(SR.Argument_DateTimeHasTicks, nameof(timeOfDay));
+                }
+            }
+
+            void IDeserializationCallback.OnDeserialization(object sender)
+            {
+                // OnDeserialization is called after each instance of this class is deserialized.
+                // This callback method performs TransitionTime validation after being deserialized.
+
+                try
+                {
+                    ValidateTransitionTime(_timeOfDay, _month, _week, _day, _dayOfWeek);
+                }
+                catch (ArgumentException e)
+                {
+                    throw new SerializationException(SR.Serialization_InvalidData, e);
+                }
+            }
+
+            void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
+            {
+                if (info == null)
+                {
+                    throw new ArgumentNullException(nameof(info));
+                }
+
+                info.AddValue("TimeOfDay", _timeOfDay); // Do not rename (binary serialization)
+                info.AddValue("Month", _month); // Do not rename (binary serialization)
+                info.AddValue("Week", _week); // Do not rename (binary serialization)
+                info.AddValue("Day", _day); // Do not rename (binary serialization)
+                info.AddValue("DayOfWeek", _dayOfWeek); // Do not rename (binary serialization)
+                info.AddValue("IsFixedDateRule", _isFixedDateRule); // Do not rename (binary serialization)
+            }
+
+            private TransitionTime(SerializationInfo info, StreamingContext context)
+            {
+                if (info == null)
+                {
+                    throw new ArgumentNullException(nameof(info));
+                }
+
+                _timeOfDay = (DateTime)info.GetValue("TimeOfDay", typeof(DateTime)); // Do not rename (binary serialization)
+                _month = (byte)info.GetValue("Month", typeof(byte)); // Do not rename (binary serialization)
+                _week = (byte)info.GetValue("Week", typeof(byte)); // Do not rename (binary serialization)
+                _day = (byte)info.GetValue("Day", typeof(byte)); // Do not rename (binary serialization)
+                _dayOfWeek = (DayOfWeek)info.GetValue("DayOfWeek", typeof(DayOfWeek)); // Do not rename (binary serialization)
+                _isFixedDateRule = (bool)info.GetValue("IsFixedDateRule", typeof(bool)); // Do not rename (binary serialization)
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TimeZoneInfo.Unix.cs b/src/System.Private.CoreLib/shared/System/TimeZoneInfo.Unix.cs
new file mode 100644
index 0000000000..920131d898
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TimeZoneInfo.Unix.cs
@@ -0,0 +1,1633 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using System.IO;
+using System.Text;
+using System.Threading;
+using System.Security;
+
+using Internal.IO;
+
+namespace System
+{
+    public sealed partial class TimeZoneInfo
+    {
+        private const string DefaultTimeZoneDirectory = "/usr/share/zoneinfo/";
+        private const string ZoneTabFileName = "zone.tab";
+        private const string TimeZoneEnvironmentVariable = "TZ";
+        private const string TimeZoneDirectoryEnvironmentVariable = "TZDIR";
+
+        private TimeZoneInfo(byte[] data, string id, bool dstDisabled)
+        {
+            TZifHead t;
+            DateTime[] dts;
+            byte[] typeOfLocalTime;
+            TZifType[] transitionType;
+            string zoneAbbreviations;
+            bool[] StandardTime;
+            bool[] GmtTime;
+            string futureTransitionsPosixFormat;
+
+            // parse the raw TZif bytes; this method can throw ArgumentException when the data is malformed.
+            TZif_ParseRaw(data, out t, out dts, out typeOfLocalTime, out transitionType, out zoneAbbreviations, out StandardTime, out GmtTime, out futureTransitionsPosixFormat);
+
+            _id = id;
+            _displayName = LocalId;
+            _baseUtcOffset = TimeSpan.Zero;
+
+            // find the best matching baseUtcOffset and display strings based on the current utcNow value.
+            // NOTE: read the display strings from the tzfile now in case they can't be loaded later
+            // from the globalization data.
+            DateTime utcNow = DateTime.UtcNow;
+            for (int i = 0; i < dts.Length && dts[i] <= utcNow; i++)
+            {
+                int type = typeOfLocalTime[i];
+                if (!transitionType[type].IsDst)
+                {
+                    _baseUtcOffset = transitionType[type].UtcOffset;
+                    _standardDisplayName = TZif_GetZoneAbbreviation(zoneAbbreviations, transitionType[type].AbbreviationIndex);
+                }
+                else
+                {
+                    _daylightDisplayName = TZif_GetZoneAbbreviation(zoneAbbreviations, transitionType[type].AbbreviationIndex);
+                }
+            }
+
+            if (dts.Length == 0)
+            {
+                // time zones like Africa/Bujumbura and Etc/GMT* have no transition times but still contain
+                // TZifType entries that may contain a baseUtcOffset and display strings
+                for (int i = 0; i < transitionType.Length; i++)
+                {
+                    if (!transitionType[i].IsDst)
+                    {
+                        _baseUtcOffset = transitionType[i].UtcOffset;
+                        _standardDisplayName = TZif_GetZoneAbbreviation(zoneAbbreviations, transitionType[i].AbbreviationIndex);
+                    }
+                    else
+                    {
+                        _daylightDisplayName = TZif_GetZoneAbbreviation(zoneAbbreviations, transitionType[i].AbbreviationIndex);
+                    }
+                }
+            }
+            _displayName = _standardDisplayName;
+
+            GetDisplayName(Interop.Globalization.TimeZoneDisplayNameType.Generic, ref _displayName);
+            GetDisplayName(Interop.Globalization.TimeZoneDisplayNameType.Standard, ref _standardDisplayName);
+            GetDisplayName(Interop.Globalization.TimeZoneDisplayNameType.DaylightSavings, ref _daylightDisplayName);
+
+            // TZif supports seconds-level granularity with offsets but TimeZoneInfo only supports minutes since it aligns
+            // with DateTimeOffset, SQL Server, and the W3C XML Specification
+            if (_baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
+            {
+                _baseUtcOffset = new TimeSpan(_baseUtcOffset.Hours, _baseUtcOffset.Minutes, 0);
+            }
+
+            if (!dstDisabled)
+            {
+                // only create the adjustment rule if DST is enabled
+                TZif_GenerateAdjustmentRules(out _adjustmentRules, _baseUtcOffset, dts, typeOfLocalTime, transitionType, StandardTime, GmtTime, futureTransitionsPosixFormat);
+            }
+
+            ValidateTimeZoneInfo(_id, _baseUtcOffset, _adjustmentRules, out _supportsDaylightSavingTime);
+        }
+
+        private void GetDisplayName(Interop.Globalization.TimeZoneDisplayNameType nameType, ref string displayName)
+        {
+            if (GlobalizationMode.Invariant)
+            {
+                displayName = _standardDisplayName;
+                return;
+            }
+
+            string timeZoneDisplayName;
+            bool result = Interop.CallStringMethod(
+                (locale, id, type, stringBuilder) => Interop.Globalization.GetTimeZoneDisplayName(
+                    locale,
+                    id,
+                    type,
+                    stringBuilder,
+                    stringBuilder.Capacity),
+                CultureInfo.CurrentUICulture.Name,
+                _id,
+                nameType,
+                out timeZoneDisplayName);
+
+            // If there is an unknown error, don't set the displayName field.
+            // It will be set to the abbreviation that was read out of the tzfile.
+            if (result)
+            {
+                displayName = timeZoneDisplayName;
+            }
+        }
+
+        /// <summary>
+        /// Returns a cloned array of AdjustmentRule objects
+        /// </summary>
+        public AdjustmentRule[] GetAdjustmentRules()
+        {
+            if (_adjustmentRules == null)
+            {
+                return Array.Empty<AdjustmentRule>();
+            }
+
+            // The rules we use in Unix care mostly about the start and end dates but don't fill the transition start and end info.
+            // as the rules now is public, we should fill it properly so the caller doesn't have to know how we use it internally
+            // and can use it as it is used in Windows
+
+            AdjustmentRule[] rules = new AdjustmentRule[_adjustmentRules.Length];
+
+            for (int i = 0; i < _adjustmentRules.Length; i++)
+            {
+                var rule = _adjustmentRules[i];
+                var start = rule.DateStart.Kind == DateTimeKind.Utc ?
+                            // At the daylight start we didn't start the daylight saving yet then we convert to Local time
+                            // by adding the _baseUtcOffset to the UTC time
+                            new DateTime(rule.DateStart.Ticks + _baseUtcOffset.Ticks, DateTimeKind.Unspecified) :
+                            rule.DateStart;
+                var end = rule.DateEnd.Kind == DateTimeKind.Utc ?
+                            // At the daylight saving end, the UTC time is mapped to local time which is already shifted by the daylight delta
+                            // we calculate the local time by adding _baseUtcOffset + DaylightDelta to the UTC time
+                            new DateTime(rule.DateEnd.Ticks + _baseUtcOffset.Ticks + rule.DaylightDelta.Ticks, DateTimeKind.Unspecified) :
+                            rule.DateEnd;
+
+                var startTransition = TimeZoneInfo.TransitionTime.CreateFixedDateRule(new DateTime(1, 1, 1, start.Hour, start.Minute, start.Second), start.Month, start.Day);
+                var endTransition = TimeZoneInfo.TransitionTime.CreateFixedDateRule(new DateTime(1, 1, 1, end.Hour, end.Minute, end.Second), end.Month, end.Day);
+
+                rules[i] = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(start.Date, end.Date, rule.DaylightDelta, startTransition, endTransition);
+            }
+
+            return rules;
+        }
+
+        private static void PopulateAllSystemTimeZones(CachedData cachedData)
+        {
+            Debug.Assert(Monitor.IsEntered(cachedData));
+
+            string timeZoneDirectory = GetTimeZoneDirectory();
+            foreach (string timeZoneId in GetTimeZoneIds(timeZoneDirectory))
+            {
+                TimeZoneInfo value;
+                Exception ex;
+                TryGetTimeZone(timeZoneId, false, out value, out ex, cachedData, alwaysFallbackToLocalMachine: true);  // populate the cache
+            }
+        }
+
+        /// <summary>
+        /// Helper function for retrieving the local system time zone.
+        /// May throw COMException, TimeZoneNotFoundException, InvalidTimeZoneException.
+        /// Assumes cachedData lock is taken.
+        /// </summary>
+        /// <returns>A new TimeZoneInfo instance.</returns>
+        private static TimeZoneInfo GetLocalTimeZone(CachedData cachedData)
+        {
+            Debug.Assert(Monitor.IsEntered(cachedData));
+
+            // Without Registry support, create the TimeZoneInfo from a TZ file
+            return GetLocalTimeZoneFromTzFile();
+        }
+
+        private static TimeZoneInfoResult TryGetTimeZoneFromLocalMachine(string id, out TimeZoneInfo value, out Exception e)
+        {
+            value = null;
+            e = null;
+
+            string timeZoneDirectory = GetTimeZoneDirectory();
+            string timeZoneFilePath = Path.Combine(timeZoneDirectory, id);
+            byte[] rawData;
+            try
+            {
+                rawData = File.ReadAllBytes(timeZoneFilePath);
+            }
+            catch (UnauthorizedAccessException ex)
+            {
+                e = ex;
+                return TimeZoneInfoResult.SecurityException;
+            }
+            catch (FileNotFoundException ex)
+            {
+                e = ex;
+                return TimeZoneInfoResult.TimeZoneNotFoundException;
+            }
+            catch (DirectoryNotFoundException ex)
+            {
+                e = ex;
+                return TimeZoneInfoResult.TimeZoneNotFoundException;
+            }
+            catch (IOException ex)
+            {
+                e = new InvalidTimeZoneException(SR.Format(SR.InvalidTimeZone_InvalidFileData, id, timeZoneFilePath), ex);
+                return TimeZoneInfoResult.InvalidTimeZoneException;
+            }
+
+            value = GetTimeZoneFromTzData(rawData, id);
+
+            if (value == null)
+            {
+                e = new InvalidTimeZoneException(SR.Format(SR.InvalidTimeZone_InvalidFileData, id, timeZoneFilePath));
+                return TimeZoneInfoResult.InvalidTimeZoneException;
+            }
+
+            return TimeZoneInfoResult.Success;
+        }
+
+        /// <summary>
+        /// Returns a collection of TimeZone Id values from the zone.tab file in the timeZoneDirectory.
+        /// </summary>
+        /// <remarks>
+        /// Lines that start with # are comments and are skipped.
+        /// </remarks>
+        private static List<string> GetTimeZoneIds(string timeZoneDirectory)
+        {
+            List<string> timeZoneIds = new List<string>();
+
+            try
+            {
+                using (StreamReader sr = new StreamReader(Path.Combine(timeZoneDirectory, ZoneTabFileName), Encoding.UTF8))
+                {
+                    string zoneTabFileLine;
+                    while ((zoneTabFileLine = sr.ReadLine()) != null)
+                    {
+                        if (!string.IsNullOrEmpty(zoneTabFileLine) && zoneTabFileLine[0] != '#')
+                        {
+                            // the format of the line is "country-code \t coordinates \t TimeZone Id \t comments"
+
+                            int firstTabIndex = zoneTabFileLine.IndexOf('\t');
+                            if (firstTabIndex != -1)
+                            {
+                                int secondTabIndex = zoneTabFileLine.IndexOf('\t', firstTabIndex + 1);
+                                if (secondTabIndex != -1)
+                                {
+                                    string timeZoneId;
+                                    int startIndex = secondTabIndex + 1;
+                                    int thirdTabIndex = zoneTabFileLine.IndexOf('\t', startIndex);
+                                    if (thirdTabIndex != -1)
+                                    {
+                                        int length = thirdTabIndex - startIndex;
+                                        timeZoneId = zoneTabFileLine.Substring(startIndex, length);
+                                    }
+                                    else
+                                    {
+                                        timeZoneId = zoneTabFileLine.Substring(startIndex);
+                                    }
+
+                                    if (!string.IsNullOrEmpty(timeZoneId))
+                                    {
+                                        timeZoneIds.Add(timeZoneId);
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+            catch (IOException) { }
+            catch (UnauthorizedAccessException) { }
+
+            return timeZoneIds;
+        }
+
+        /// <summary>
+        /// Gets the tzfile raw data for the current 'local' time zone using the following rules.
+        /// 1. Read the TZ environment variable.  If it is set, use it.
+        /// 2. Look for the data in /etc/localtime.
+        /// 3. Look for the data in GetTimeZoneDirectory()/localtime.
+        /// 4. Use UTC if all else fails.
+        /// </summary>
+        private static bool TryGetLocalTzFile(out byte[] rawData, out string id)
+        {
+            rawData = null;
+            id = null;
+            string tzVariable = GetTzEnvironmentVariable();
+
+            // If the env var is null, use the localtime file
+            if (tzVariable == null)
+            {
+                return
+                    TryLoadTzFile("/etc/localtime", ref rawData, ref id) ||
+                    TryLoadTzFile(Path.Combine(GetTimeZoneDirectory(), "localtime"), ref rawData, ref id);
+            }
+
+            // If it's empty, use UTC (TryGetLocalTzFile() should return false).
+            if (tzVariable.Length == 0)
+            {
+                return false;
+            }
+
+            // Otherwise, use the path from the env var.  If it's not absolute, make it relative
+            // to the system timezone directory
+            string tzFilePath;
+            if (tzVariable[0] != '/')
+            {
+                id = tzVariable;
+                tzFilePath = Path.Combine(GetTimeZoneDirectory(), tzVariable);
+            }
+            else
+            {
+                tzFilePath = tzVariable;
+            }
+            return TryLoadTzFile(tzFilePath, ref rawData, ref id);
+        }
+
+        private static string GetTzEnvironmentVariable()
+        {
+            string result = Environment.GetEnvironmentVariable(TimeZoneEnvironmentVariable);
+            if (!string.IsNullOrEmpty(result))
+            {
+                if (result[0] == ':')
+                {
+                    // strip off the ':' prefix
+                    result = result.Substring(1);
+                }
+            }
+
+            return result;
+        }
+
+        private static bool TryLoadTzFile(string tzFilePath, ref byte[] rawData, ref string id)
+        {
+            if (File.Exists(tzFilePath))
+            {
+                try
+                {
+                    rawData = File.ReadAllBytes(tzFilePath);
+                    if (string.IsNullOrEmpty(id))
+                    {
+                        id = FindTimeZoneIdUsingReadLink(tzFilePath);
+
+                        if (string.IsNullOrEmpty(id))
+                        {
+                            id = FindTimeZoneId(rawData);
+                        }
+                    }
+                    return true;
+                }
+                catch (IOException) { }
+                catch (SecurityException) { }
+                catch (UnauthorizedAccessException) { }
+            }
+            return false;
+        }
+
+        /// <summary>
+        /// Finds the time zone id by using 'readlink' on the path to see if tzFilePath is
+        /// a symlink to a file.
+        /// </summary>
+        private static string FindTimeZoneIdUsingReadLink(string tzFilePath)
+        {
+            string id = null;
+
+            string symlinkPath = Interop.Sys.ReadLink(tzFilePath);
+            if (symlinkPath != null)
+            {
+                // symlinkPath can be relative path, use Path to get the full absolute path.
+                symlinkPath = Path.GetFullPath(symlinkPath, Path.GetDirectoryName(tzFilePath));
+
+                string timeZoneDirectory = GetTimeZoneDirectory();
+                if (symlinkPath.StartsWith(timeZoneDirectory, StringComparison.Ordinal))
+                {
+                    id = symlinkPath.Substring(timeZoneDirectory.Length);
+                }
+            }
+
+            return id;
+        }
+
+        /// <summary>
+        /// Enumerate files
+        /// </summary>
+        private static IEnumerable<string> EnumerateFilesRecursively(string path)
+        {
+            List<string> toExplore = null; // List used as a stack
+
+            string currentPath = path;
+            for(;;)
+            {
+                using (Microsoft.Win32.SafeHandles.SafeDirectoryHandle dirHandle = Interop.Sys.OpenDir(currentPath))
+                {
+                    if (dirHandle.IsInvalid)
+                    {
+                        throw Interop.GetExceptionForIoErrno(Interop.Sys.GetLastErrorInfo(), currentPath, isDirectory: true);
+                    }
+
+                    // Read each entry from the enumerator
+                    Interop.Sys.DirectoryEntry dirent;
+                    while (Interop.Sys.ReadDir(dirHandle, out dirent) == 0)
+                    {
+                        if (dirent.InodeName == "." || dirent.InodeName == "..")
+                            continue;
+
+                        string fullPath = Path.Combine(currentPath, dirent.InodeName);
+
+                        // Get from the dir entry whether the entry is a file or directory.
+                        // We classify everything as a file unless we know it to be a directory.
+                        bool isDir;
+                        if (dirent.InodeType == Interop.Sys.NodeType.DT_DIR)
+                        {
+                            // We know it's a directory.
+                            isDir = true;
+                        }
+                        else if (dirent.InodeType == Interop.Sys.NodeType.DT_LNK || dirent.InodeType == Interop.Sys.NodeType.DT_UNKNOWN)
+                        {
+                            // It's a symlink or unknown: stat to it to see if we can resolve it to a directory.
+                            // If we can't (e.g. symlink to a file, broken symlink, etc.), we'll just treat it as a file.
+
+                            Interop.Sys.FileStatus fileinfo;
+                            if (Interop.Sys.Stat(fullPath, out fileinfo) >= 0)
+                            {
+                                isDir = (fileinfo.Mode & Interop.Sys.FileTypes.S_IFMT) == Interop.Sys.FileTypes.S_IFDIR;
+                            }
+                            else
+                            {
+                                isDir = false;
+                            }
+                        }
+                        else
+                        {
+                            // Otherwise, treat it as a file.  This includes regular files, FIFOs, etc.
+                            isDir = false;
+                        }
+
+                        // Yield the result if the user has asked for it.  In the case of directories,
+                        // always explore it by pushing it onto the stack, regardless of whether
+                        // we're returning directories.
+                        if (isDir)
+                        {
+                            if (toExplore == null)
+                            {
+                                toExplore = new List<string>();
+                            }
+                            toExplore.Add(fullPath);
+                        }
+                        else
+                        {
+                            yield return fullPath;
+                        }
+                    }
+                }
+
+                if (toExplore == null || toExplore.Count == 0)
+                    break;
+
+                currentPath = toExplore[toExplore.Count - 1];
+                toExplore.RemoveAt(toExplore.Count - 1);
+            }
+        }
+
+        /// <summary>
+        /// Find the time zone id by searching all the tzfiles for the one that matches rawData
+        /// and return its file name.
+        /// </summary>
+        private static string FindTimeZoneId(byte[] rawData)
+        {
+            // default to "Local" if we can't find the right tzfile
+            string id = LocalId;
+            string timeZoneDirectory = GetTimeZoneDirectory();
+            string localtimeFilePath = Path.Combine(timeZoneDirectory, "localtime");
+            string posixrulesFilePath = Path.Combine(timeZoneDirectory, "posixrules");
+            byte[] buffer = new byte[rawData.Length];
+
+            try
+            {
+                foreach (string filePath in EnumerateFilesRecursively(timeZoneDirectory))
+                {
+                    // skip the localtime and posixrules file, since they won't give us the correct id
+                    if (!string.Equals(filePath, localtimeFilePath, StringComparison.OrdinalIgnoreCase)
+                        && !string.Equals(filePath, posixrulesFilePath, StringComparison.OrdinalIgnoreCase))
+                    {
+                        if (CompareTimeZoneFile(filePath, buffer, rawData))
+                        {
+                            // if all bytes are the same, this must be the right tz file
+                            id = filePath;
+
+                            // strip off the root time zone directory
+                            if (id.StartsWith(timeZoneDirectory, StringComparison.Ordinal))
+                            {
+                                id = id.Substring(timeZoneDirectory.Length);
+                            }
+                            break;
+                        }
+                    }
+                }
+            }
+            catch (IOException) { }
+            catch (SecurityException) { }
+            catch (UnauthorizedAccessException) { }
+
+            return id;
+        }
+
+        private static bool CompareTimeZoneFile(string filePath, byte[] buffer, byte[] rawData)
+        {
+            try
+            {
+                // bufferSize == 1 used to avoid unnecessary buffer in FileStream
+                using (FileStream stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize: 1))
+                {
+                    if (stream.Length == rawData.Length)
+                    {
+                        int index = 0;
+                        int count = rawData.Length;
+
+                        while (count > 0)
+                        {
+                            int n = stream.Read(buffer, index, count);
+                            if (n == 0)
+                                throw Error.GetEndOfFile();
+
+                            int end = index + n;
+                            for (; index < end; index++)
+                            {
+                                if (buffer[index] != rawData[index])
+                                {
+                                    return false;
+                                }
+                            }
+
+                            count -= n;
+                        }
+
+                        return true;
+                    }
+                }
+            }
+            catch (IOException) { }
+            catch (SecurityException) { }
+            catch (UnauthorizedAccessException) { }
+
+            return false;
+        }
+
+        /// <summary>
+        /// Helper function used by 'GetLocalTimeZone()' - this function wraps the call
+        /// for loading time zone data from computers without Registry support.
+        ///
+        /// The TryGetLocalTzFile() call returns a Byte[] containing the compiled tzfile.
+        /// </summary>
+        private static TimeZoneInfo GetLocalTimeZoneFromTzFile()
+        {
+            byte[] rawData;
+            string id;
+            if (TryGetLocalTzFile(out rawData, out id))
+            {
+                TimeZoneInfo result = GetTimeZoneFromTzData(rawData, id);
+                if (result != null)
+                {
+                    return result;
+                }
+            }
+
+            // if we can't find a local time zone, return UTC
+            return Utc;
+        }
+
+        private static TimeZoneInfo GetTimeZoneFromTzData(byte[] rawData, string id)
+        {
+            if (rawData != null)
+            {
+                try
+                {
+                    return new TimeZoneInfo(rawData, id, dstDisabled: false); // create a TimeZoneInfo instance from the TZif data w/ DST support
+                }
+                catch (ArgumentException) { }
+                catch (InvalidTimeZoneException) { }
+                try
+                {
+                    return new TimeZoneInfo(rawData, id, dstDisabled: true); // create a TimeZoneInfo instance from the TZif data w/o DST support
+                }
+                catch (ArgumentException) { }
+                catch (InvalidTimeZoneException) { }
+            }
+
+            return null;
+        }
+
+        private static string GetTimeZoneDirectory()
+        {
+            string tzDirectory = Environment.GetEnvironmentVariable(TimeZoneDirectoryEnvironmentVariable);
+
+            if (tzDirectory == null)
+            {
+                tzDirectory = DefaultTimeZoneDirectory;
+            }
+            else if (!tzDirectory.EndsWith(Path.DirectorySeparatorChar))
+            {
+                tzDirectory += Path.DirectorySeparatorChar;
+            }
+
+            return tzDirectory;
+        }
+
+        /// <summary>
+        /// Helper function for retrieving a TimeZoneInfo object by <time_zone_name>.
+        /// This function wraps the logic necessary to keep the private
+        /// SystemTimeZones cache in working order
+        ///
+        /// This function will either return a valid TimeZoneInfo instance or
+        /// it will throw 'InvalidTimeZoneException' / 'TimeZoneNotFoundException'.
+        /// </summary>
+        public static TimeZoneInfo FindSystemTimeZoneById(string id)
+        {
+            // Special case for Utc as it will not exist in the dictionary with the rest
+            // of the system time zones.  There is no need to do this check for Local.Id
+            // since Local is a real time zone that exists in the dictionary cache
+            if (string.Equals(id, UtcId, StringComparison.OrdinalIgnoreCase))
+            {
+                return Utc;
+            }
+
+            if (id == null)
+            {
+                throw new ArgumentNullException(nameof(id));
+            }
+            else if (id.Length == 0 || id.Contains('\0'))
+            {
+                throw new TimeZoneNotFoundException(SR.Format(SR.TimeZoneNotFound_MissingData, id));
+            }
+
+            TimeZoneInfo value;
+            Exception e;
+
+            TimeZoneInfoResult result;
+
+            CachedData cachedData = s_cachedData;
+
+            lock (cachedData)
+            {
+                result = TryGetTimeZone(id, false, out value, out e, cachedData, alwaysFallbackToLocalMachine: true);
+            }
+
+            if (result == TimeZoneInfoResult.Success)
+            {
+                return value;
+            }
+            else if (result == TimeZoneInfoResult.InvalidTimeZoneException)
+            {
+                Debug.Assert(e is InvalidTimeZoneException,
+                    "TryGetTimeZone must create an InvalidTimeZoneException when it returns TimeZoneInfoResult.InvalidTimeZoneException");
+                throw e;
+            }
+            else if (result == TimeZoneInfoResult.SecurityException)
+            {
+                throw new SecurityException(SR.Format(SR.Security_CannotReadFileData, id), e);
+            }
+            else
+            {
+                throw new TimeZoneNotFoundException(SR.Format(SR.TimeZoneNotFound_MissingData, id), e);
+            }
+        }
+
+        // DateTime.Now fast path that avoids allocating an historically accurate TimeZoneInfo.Local and just creates a 1-year (current year) accurate time zone
+        internal static TimeSpan GetDateTimeNowUtcOffsetFromUtc(DateTime time, out bool isAmbiguousLocalDst)
+        {
+            bool isDaylightSavings;
+            // Use the standard code path for Unix since there isn't a faster way of handling current-year-only time zones
+            return GetUtcOffsetFromUtc(time, Local, out isDaylightSavings, out isAmbiguousLocalDst);
+        }
+
+        // TZFILE(5)                   BSD File Formats Manual                  TZFILE(5)
+        //
+        // NAME
+        //      tzfile -- timezone information
+        //
+        // SYNOPSIS
+        //      #include "/usr/src/lib/libc/stdtime/tzfile.h"
+        //
+        // DESCRIPTION
+        //      The time zone information files used by tzset(3) begin with the magic
+        //      characters ``TZif'' to identify them as time zone information files, fol-
+        //      lowed by sixteen bytes reserved for future use, followed by four four-
+        //      byte values written in a ``standard'' byte order (the high-order byte of
+        //      the value is written first).  These values are, in order:
+        //
+        //      tzh_ttisgmtcnt  The number of UTC/local indicators stored in the file.
+        //      tzh_ttisstdcnt  The number of standard/wall indicators stored in the
+        //                      file.
+        //      tzh_leapcnt     The number of leap seconds for which data is stored in
+        //                      the file.
+        //      tzh_timecnt     The number of ``transition times'' for which data is
+        //                      stored in the file.
+        //      tzh_typecnt     The number of ``local time types'' for which data is
+        //                      stored in the file (must not be zero).
+        //      tzh_charcnt     The number of characters of ``time zone abbreviation
+        //                      strings'' stored in the file.
+        //
+        //      The above header is followed by tzh_timecnt four-byte values of type
+        //      long, sorted in ascending order.  These values are written in ``stan-
+        //      dard'' byte order.  Each is used as a transition time (as returned by
+        //      time(3)) at which the rules for computing local time change.  Next come
+        //      tzh_timecnt one-byte values of type unsigned char; each one tells which
+        //      of the different types of ``local time'' types described in the file is
+        //      associated with the same-indexed transition time.  These values serve as
+        //      indices into an array of ttinfo structures that appears next in the file;
+        //      these structures are defined as follows:
+        //
+        //            struct ttinfo {
+        //                    long    tt_gmtoff;
+        //                    int     tt_isdst;
+        //                    unsigned int    tt_abbrind;
+        //            };
+        //
+        //      Each structure is written as a four-byte value for tt_gmtoff of type
+        //      long, in a standard byte order, followed by a one-byte value for tt_isdst
+        //      and a one-byte value for tt_abbrind.  In each structure, tt_gmtoff gives
+        //      the number of seconds to be added to UTC, tt_isdst tells whether tm_isdst
+        //      should be set by localtime(3) and tt_abbrind serves as an index into the
+        //      array of time zone abbreviation characters that follow the ttinfo struc-
+        //      ture(s) in the file.
+        //
+        //      Then there are tzh_leapcnt pairs of four-byte values, written in standard
+        //      byte order; the first value of each pair gives the time (as returned by
+        //      time(3)) at which a leap second occurs; the second gives the total number
+        //      of leap seconds to be applied after the given time.  The pairs of values
+        //      are sorted in ascending order by time.b
+        //
+        //      Then there are tzh_ttisstdcnt standard/wall indicators, each stored as a
+        //      one-byte value; they tell whether the transition times associated with
+        //      local time types were specified as standard time or wall clock time, and
+        //      are used when a time zone file is used in handling POSIX-style time zone
+        //      environment variables.
+        //
+        //      Finally there are tzh_ttisgmtcnt UTC/local indicators, each stored as a
+        //      one-byte value; they tell whether the transition times associated with
+        //      local time types were specified as UTC or local time, and are used when a
+        //      time zone file is used in handling POSIX-style time zone environment
+        //      variables.
+        //
+        //      localtime uses the first standard-time ttinfo structure in the file (or
+        //      simply the first ttinfo structure in the absence of a standard-time
+        //      structure) if either tzh_timecnt is zero or the time argument is less
+        //      than the first transition time recorded in the file.
+        //
+        // SEE ALSO
+        //      ctime(3), time2posix(3), zic(8)
+        //
+        // BSD                           September 13, 1994                           BSD
+        //
+        //
+        //
+        // TIME(3)                  BSD Library Functions Manual                  TIME(3)
+        //
+        // NAME
+        //      time -- get time of day
+        //
+        // LIBRARY
+        //      Standard C Library (libc, -lc)
+        //
+        // SYNOPSIS
+        //      #include <time.h>
+        //
+        //      time_t
+        //      time(time_t *tloc);
+        //
+        // DESCRIPTION
+        //      The time() function returns the value of time in seconds since 0 hours, 0
+        //      minutes, 0 seconds, January 1, 1970, Coordinated Universal Time, without
+        //      including leap seconds.  If an error occurs, time() returns the value
+        //      (time_t)-1.
+        //
+        //      The return value is also stored in *tloc, provided that tloc is non-null.
+        //
+        // ERRORS
+        //      The time() function may fail for any of the reasons described in
+        //      gettimeofday(2).
+        //
+        // SEE ALSO
+        //      gettimeofday(2), ctime(3)
+        //
+        // STANDARDS
+        //      The time function conforms to IEEE Std 1003.1-2001 (``POSIX.1'').
+        //
+        // BUGS
+        //      Neither ISO/IEC 9899:1999 (``ISO C99'') nor IEEE Std 1003.1-2001
+        //      (``POSIX.1'') requires time() to set errno on failure; thus, it is impos-
+        //      sible for an application to distinguish the valid time value -1 (repre-
+        //      senting the last UTC second of 1969) from the error return value.
+        //
+        //      Systems conforming to earlier versions of the C and POSIX standards
+        //      (including older versions of FreeBSD) did not set *tloc in the error
+        //      case.
+        //
+        // HISTORY
+        //      A time() function appeared in Version 6 AT&T UNIX.
+        //
+        // BSD                              July 18, 2003                             BSD
+        //
+        //
+        private static void TZif_GenerateAdjustmentRules(out AdjustmentRule[] rules, TimeSpan baseUtcOffset, DateTime[] dts, byte[] typeOfLocalTime,
+            TZifType[] transitionType, bool[] StandardTime, bool[] GmtTime, string futureTransitionsPosixFormat)
+        {
+            rules = null;
+
+            if (dts.Length > 0)
+            {
+                int index = 0;
+                List<AdjustmentRule> rulesList = new List<AdjustmentRule>();
+
+                while (index <= dts.Length)
+                {
+                    TZif_GenerateAdjustmentRule(ref index, baseUtcOffset, rulesList, dts, typeOfLocalTime, transitionType, StandardTime, GmtTime, futureTransitionsPosixFormat);
+                }
+
+                rules = rulesList.ToArray();
+                if (rules != null && rules.Length == 0)
+                {
+                    rules = null;
+                }
+            }
+        }
+
+        private static void TZif_GenerateAdjustmentRule(ref int index, TimeSpan timeZoneBaseUtcOffset, List<AdjustmentRule> rulesList, DateTime[] dts,
+            byte[] typeOfLocalTime, TZifType[] transitionTypes, bool[] StandardTime, bool[] GmtTime, string futureTransitionsPosixFormat)
+        {
+            // To generate AdjustmentRules, use the following approach:
+            // The first AdjustmentRule will go from DateTime.MinValue to the first transition time greater than DateTime.MinValue.
+            // Each middle AdjustmentRule wil go from dts[index-1] to dts[index].
+            // The last AdjustmentRule will go from dts[dts.Length-1] to Datetime.MaxValue.
+
+            // 0. Skip any DateTime.MinValue transition times. In newer versions of the tzfile, there
+            // is a "big bang" transition time, which is before the year 0001. Since any times before year 0001
+            // cannot be represented by DateTime, there is no reason to make AdjustmentRules for these unrepresentable time periods.
+            // 1. If there are no DateTime.MinValue times, the first AdjustmentRule goes from DateTime.MinValue
+            // to the first transition and uses the first standard transitionType (or the first transitionType if none of them are standard)
+            // 2. Create an AdjustmentRule for each transition, i.e. from dts[index - 1] to dts[index].
+            // This rule uses the transitionType[index - 1] and the whole AdjustmentRule only describes a single offset - either
+            // all daylight savings, or all stanard time.
+            // 3. After all the transitions are filled out, the last AdjustmentRule is created from either:
+            //   a. a POSIX-style timezone description ("futureTransitionsPosixFormat"), if there is one or
+            //   b. continue the last transition offset until DateTime.Max
+
+            while (index < dts.Length && dts[index] == DateTime.MinValue)
+            {
+                index++;
+            }
+
+            if (index == 0)
+            {
+                TZifType transitionType = TZif_GetEarlyDateTransitionType(transitionTypes);
+                DateTime endTransitionDate = dts[index];
+
+                TimeSpan transitionOffset = TZif_CalculateTransitionOffsetFromBase(transitionType.UtcOffset, timeZoneBaseUtcOffset);
+                TimeSpan daylightDelta = transitionType.IsDst ? transitionOffset : TimeSpan.Zero;
+                TimeSpan baseUtcDelta = transitionType.IsDst ? TimeSpan.Zero : transitionOffset;
+
+                AdjustmentRule r = AdjustmentRule.CreateAdjustmentRule(
+                        DateTime.MinValue,
+                        endTransitionDate.AddTicks(-1),
+                        daylightDelta,
+                        default(TransitionTime),
+                        default(TransitionTime),
+                        baseUtcDelta,
+                        noDaylightTransitions: true);
+                rulesList.Add(r);
+            }
+            else if (index < dts.Length)
+            {
+                DateTime startTransitionDate = dts[index - 1];
+                TZifType startTransitionType = transitionTypes[typeOfLocalTime[index - 1]];
+
+                DateTime endTransitionDate = dts[index];
+
+                TimeSpan transitionOffset = TZif_CalculateTransitionOffsetFromBase(startTransitionType.UtcOffset, timeZoneBaseUtcOffset);
+                TimeSpan daylightDelta = startTransitionType.IsDst ? transitionOffset : TimeSpan.Zero;
+                TimeSpan baseUtcDelta = startTransitionType.IsDst ? TimeSpan.Zero : transitionOffset;
+
+                TransitionTime dstStart;
+                if (startTransitionType.IsDst)
+                {
+                    // the TransitionTime fields are not used when AdjustmentRule.NoDaylightTransitions == true.
+                    // However, there are some cases in the past where DST = true, and the daylight savings offset
+                    // now equals what the current BaseUtcOffset is.  In that case, the AdjustmentRule.DaylightOffset
+                    // is going to be TimeSpan.Zero.  But we still need to return 'true' from AdjustmentRule.HasDaylightSaving.
+                    // To ensure we always return true from HasDaylightSaving, make a "special" dstStart that will make the logic
+                    // in HasDaylightSaving return true.
+                    dstStart = TransitionTime.CreateFixedDateRule(DateTime.MinValue.AddMilliseconds(2), 1, 1);
+                }
+                else
+                {
+                    dstStart = default(TransitionTime);
+                }
+
+                AdjustmentRule r = AdjustmentRule.CreateAdjustmentRule(
+                        startTransitionDate,
+                        endTransitionDate.AddTicks(-1),
+                        daylightDelta,
+                        dstStart,
+                        default(TransitionTime),
+                        baseUtcDelta,
+                        noDaylightTransitions: true);
+                rulesList.Add(r);
+            }
+            else
+            {
+                // create the AdjustmentRule that will be used for all DateTimes after the last transition
+
+                // NOTE: index == dts.Length
+                DateTime startTransitionDate = dts[index - 1];
+
+                if (!string.IsNullOrEmpty(futureTransitionsPosixFormat))
+                {
+                    AdjustmentRule r = TZif_CreateAdjustmentRuleForPosixFormat(futureTransitionsPosixFormat, startTransitionDate, timeZoneBaseUtcOffset);
+                    if (r != null)
+                    {
+                        rulesList.Add(r);
+                    }
+                }
+                else
+                {
+                    // just use the last transition as the rule which will be used until the end of time
+
+                    TZifType transitionType = transitionTypes[typeOfLocalTime[index - 1]];
+                    TimeSpan transitionOffset = TZif_CalculateTransitionOffsetFromBase(transitionType.UtcOffset, timeZoneBaseUtcOffset);
+                    TimeSpan daylightDelta = transitionType.IsDst ? transitionOffset : TimeSpan.Zero;
+                    TimeSpan baseUtcDelta = transitionType.IsDst ? TimeSpan.Zero : transitionOffset;
+
+                    AdjustmentRule r = AdjustmentRule.CreateAdjustmentRule(
+                        startTransitionDate,
+                        DateTime.MaxValue,
+                        daylightDelta,
+                        default(TransitionTime),
+                        default(TransitionTime),
+                        baseUtcDelta,
+                        noDaylightTransitions: true);
+                    rulesList.Add(r);
+                }
+            }
+
+            index++;
+        }
+
+        private static TimeSpan TZif_CalculateTransitionOffsetFromBase(TimeSpan transitionOffset, TimeSpan timeZoneBaseUtcOffset)
+        {
+            TimeSpan result = transitionOffset - timeZoneBaseUtcOffset;
+
+            // TZif supports seconds-level granularity with offsets but TimeZoneInfo only supports minutes since it aligns
+            // with DateTimeOffset, SQL Server, and the W3C XML Specification
+            if (result.Ticks % TimeSpan.TicksPerMinute != 0)
+            {
+                result = new TimeSpan(result.Hours, result.Minutes, 0);
+            }
+
+            return result;
+        }
+
+        /// <summary>
+        /// Gets the first standard-time transition type, or simply the first transition type
+        /// if there are no standard transition types.
+        /// </summary>>
+        /// <remarks>
+        /// from 'man tzfile':
+        /// localtime(3)  uses the first standard-time ttinfo structure in the file
+        /// (or simply the first ttinfo structure in the absence of a standard-time
+        /// structure)  if  either tzh_timecnt is zero or the time argument is less
+        /// than the first transition time recorded in the file.
+        /// </remarks>
+        private static TZifType TZif_GetEarlyDateTransitionType(TZifType[] transitionTypes)
+        {
+            foreach (TZifType transitionType in transitionTypes)
+            {
+                if (!transitionType.IsDst)
+                {
+                    return transitionType;
+                }
+            }
+
+            if (transitionTypes.Length > 0)
+            {
+                return transitionTypes[0];
+            }
+
+            throw new InvalidTimeZoneException(SR.InvalidTimeZone_NoTTInfoStructures);
+        }
+
+        /// <summary>
+        /// Creates an AdjustmentRule given the POSIX TZ environment variable string.
+        /// </summary>
+        /// <remarks>
+        /// See http://man7.org/linux/man-pages/man3/tzset.3.html for the format and semantics of this POSX string.
+        /// </remarks>
+        private static AdjustmentRule TZif_CreateAdjustmentRuleForPosixFormat(string posixFormat, DateTime startTransitionDate, TimeSpan timeZoneBaseUtcOffset)
+        {
+            string standardName;
+            string standardOffset;
+            string daylightSavingsName;
+            string daylightSavingsOffset;
+            string start;
+            string startTime;
+            string end;
+            string endTime;
+
+            if (TZif_ParsePosixFormat(posixFormat, out standardName, out standardOffset, out daylightSavingsName,
+                out daylightSavingsOffset, out start, out startTime, out end, out endTime))
+            {
+                // a valid posixFormat has at least standardName and standardOffset
+
+                TimeSpan? parsedBaseOffset = TZif_ParseOffsetString(standardOffset);
+                if (parsedBaseOffset.HasValue)
+                {
+                    TimeSpan baseOffset = parsedBaseOffset.Value.Negate(); // offsets are backwards in POSIX notation
+                    baseOffset = TZif_CalculateTransitionOffsetFromBase(baseOffset, timeZoneBaseUtcOffset);
+
+                    // having a daylightSavingsName means there is a DST rule
+                    if (!string.IsNullOrEmpty(daylightSavingsName))
+                    {
+                        TimeSpan? parsedDaylightSavings = TZif_ParseOffsetString(daylightSavingsOffset);
+                        TimeSpan daylightSavingsTimeSpan;
+                        if (!parsedDaylightSavings.HasValue)
+                        {
+                            // default DST to 1 hour if it isn't specified
+                            daylightSavingsTimeSpan = new TimeSpan(1, 0, 0);
+                        }
+                        else
+                        {
+                            daylightSavingsTimeSpan = parsedDaylightSavings.Value.Negate(); // offsets are backwards in POSIX notation
+                            daylightSavingsTimeSpan = TZif_CalculateTransitionOffsetFromBase(daylightSavingsTimeSpan, timeZoneBaseUtcOffset);
+                            daylightSavingsTimeSpan = TZif_CalculateTransitionOffsetFromBase(daylightSavingsTimeSpan, baseOffset);
+                        }
+
+                        TransitionTime dstStart = TZif_CreateTransitionTimeFromPosixRule(start, startTime);
+                        TransitionTime dstEnd = TZif_CreateTransitionTimeFromPosixRule(end, endTime);
+
+                        return AdjustmentRule.CreateAdjustmentRule(
+                            startTransitionDate,
+                            DateTime.MaxValue,
+                            daylightSavingsTimeSpan,
+                            dstStart,
+                            dstEnd,
+                            baseOffset,
+                            noDaylightTransitions: false);
+                    }
+                    else
+                    {
+                        // if there is no daylightSavingsName, the whole AdjustmentRule should be with no transitions - just the baseOffset
+                        return AdjustmentRule.CreateAdjustmentRule(
+                               startTransitionDate,
+                               DateTime.MaxValue,
+                               TimeSpan.Zero,
+                               default(TransitionTime),
+                               default(TransitionTime),
+                               baseOffset,
+                               noDaylightTransitions: true);
+                    }
+                }
+            }
+
+            return null;
+        }
+
+        private static TimeSpan? TZif_ParseOffsetString(string offset)
+        {
+            TimeSpan? result = null;
+
+            if (!string.IsNullOrEmpty(offset))
+            {
+                bool negative = offset[0] == '-';
+                if (negative || offset[0] == '+')
+                {
+                    offset = offset.Substring(1);
+                }
+
+                // Try parsing just hours first.
+                // Note, TimeSpan.TryParseExact "%h" can't be used here because some time zones using values
+                // like "26" or "144" and TimeSpan parsing would turn that into 26 or 144 *days* instead of hours.
+                int hours;
+                if (int.TryParse(offset, out hours))
+                {
+                    result = new TimeSpan(hours, 0, 0);
+                }
+                else
+                {
+                    TimeSpan parsedTimeSpan;
+                    if (TimeSpan.TryParseExact(offset, "g", CultureInfo.InvariantCulture, out parsedTimeSpan))
+                    {
+                        result = parsedTimeSpan;
+                    }
+                }
+
+                if (result.HasValue && negative)
+                {
+                    result = result.Value.Negate();
+                }
+            }
+
+            return result;
+        }
+
+        private static DateTime ParseTimeOfDay(string time)
+        {
+            DateTime timeOfDay;
+            TimeSpan? timeOffset = TZif_ParseOffsetString(time);
+            if (timeOffset.HasValue)
+            {
+                // This logic isn't correct and can't be corrected until https://github.com/dotnet/corefx/issues/2618 is fixed.
+                // Some time zones use time values like, "26", "144", or "-2".
+                // This allows the week to sometimes be week 4 and sometimes week 5 in the month.
+                // For now, strip off any 'days' in the offset, and just get the time of day correct
+                timeOffset = new TimeSpan(timeOffset.Value.Hours, timeOffset.Value.Minutes, timeOffset.Value.Seconds);
+                if (timeOffset.Value < TimeSpan.Zero)
+                {
+                    timeOfDay = new DateTime(1, 1, 2, 0, 0, 0);
+                }
+                else
+                {
+                    timeOfDay = new DateTime(1, 1, 1, 0, 0, 0);
+                }
+
+                timeOfDay += timeOffset.Value;
+            }
+            else
+            {
+                // default to 2AM.
+                timeOfDay = new DateTime(1, 1, 1, 2, 0, 0);
+            }
+
+            return timeOfDay;
+        }
+
+        private static TransitionTime TZif_CreateTransitionTimeFromPosixRule(string date, string time)
+        {
+            if (string.IsNullOrEmpty(date))
+            {
+                return default(TransitionTime);
+            }
+
+            if (date[0] == 'M')
+            {
+                // Mm.w.d
+                // This specifies day d of week w of month m. The day d must be between 0(Sunday) and 6.The week w must be between 1 and 5;
+                // week 1 is the first week in which day d occurs, and week 5 specifies the last d day in the month. The month m should be between 1 and 12.
+
+                int month;
+                int week;
+                DayOfWeek day;
+                if (!TZif_ParseMDateRule(date, out month, out week, out day))
+                {
+                    throw new InvalidTimeZoneException(SR.Format(SR.InvalidTimeZone_UnparseablePosixMDateString, date));
+                }
+
+                return TransitionTime.CreateFloatingDateRule(ParseTimeOfDay(time), month, week, day);
+            }
+            else
+            {
+                if (date[0] != 'J')
+                {
+                    // should be n Julian day format which we don't support. 
+                    // 
+                    // This specifies the Julian day, with n between 0 and 365. February 29 is counted in leap years.
+                    //
+                    // n would be a relative number from the begining of the year. which should handle if the 
+                    // the year is a leap year or not.
+                    // 
+                    // In leap year, n would be counted as:
+                    // 
+                    // 0                30 31              59 60              90      335            365
+                    // |-------Jan--------|-------Feb--------|-------Mar--------|....|-------Dec--------|
+                    //
+                    // while in non leap year we'll have 
+                    // 
+                    // 0                30 31              58 59              89      334            364
+                    // |-------Jan--------|-------Feb--------|-------Mar--------|....|-------Dec--------|
+                    //
+                    // 
+                    // For example if n is specified as 60, this means in leap year the rule will start at Mar 1,
+                    // while in non leap year the rule will start at Mar 2.
+                    // 
+                    // If we need to support n format, we'll have to have a floating adjustment rule support this case.
+                    
+                    throw new InvalidTimeZoneException(SR.InvalidTimeZone_NJulianDayNotSupported);
+                }
+                
+                // Julian day
+                TZif_ParseJulianDay(date, out int month, out int day);
+                return TransitionTime.CreateFixedDateRule(ParseTimeOfDay(time), month, day);
+            }
+        }
+
+        /// <summary>
+        /// Parses a string like Jn or n into month and day values.
+        /// </summary>
+        /// <returns>
+        /// true if the parsing succeeded; otherwise, false.
+        /// </returns>
+        private static void TZif_ParseJulianDay(string date, out int month, out int day)
+        {
+            // Jn
+            // This specifies the Julian day, with n between 1 and 365.February 29 is never counted, even in leap years.
+            Debug.Assert(date[0] == 'J');
+            Debug.Assert(!String.IsNullOrEmpty(date));
+            month = day = 0;
+
+            int index = 1;
+
+            if (index >= date.Length || ((uint)(date[index] - '0') > '9'-'0'))
+            {
+                throw new InvalidTimeZoneException(SR.InvalidTimeZone_InvalidJulianDay);
+            }
+
+            int julianDay = 0;
+
+            do
+            {
+                julianDay = julianDay * 10 + (int) (date[index] - '0');
+                index++;
+            } while (index < date.Length && ((uint)(date[index] - '0') <= '9'-'0'));
+
+            int[] days = GregorianCalendarHelper.DaysToMonth365;
+
+            if (julianDay == 0 || julianDay > days[days.Length - 1])
+            {
+                throw new InvalidTimeZoneException(SR.InvalidTimeZone_InvalidJulianDay);
+            }
+
+            int i = 1;
+            while (i < days.Length && julianDay > days[i])
+            {
+                i++;
+            }
+            
+            Debug.Assert(i > 0 && i < days.Length);
+
+            month = i;
+            day = julianDay - days[i - 1];
+        }
+
+        /// <summary>
+        /// Parses a string like Mm.w.d into month, week and DayOfWeek values.
+        /// </summary>
+        /// <returns>
+        /// true if the parsing succeeded; otherwise, false.
+        /// </returns>
+        private static bool TZif_ParseMDateRule(string dateRule, out int month, out int week, out DayOfWeek dayOfWeek)
+        {
+            if (dateRule[0] == 'M')
+            {
+                int firstDotIndex = dateRule.IndexOf('.');
+                if (firstDotIndex > 0)
+                {
+                    int secondDotIndex = dateRule.IndexOf('.', firstDotIndex + 1);
+                    if (secondDotIndex > 0)
+                    {
+                        if (int.TryParse(dateRule.AsSpan(1, firstDotIndex - 1), out month) &&
+                            int.TryParse(dateRule.AsSpan(firstDotIndex + 1, secondDotIndex - firstDotIndex - 1), out week) &&
+                            int.TryParse(dateRule.AsSpan(secondDotIndex + 1), out int day))
+                        {
+                            dayOfWeek = (DayOfWeek)day;
+                            return true;
+                        }
+                    }
+                }
+            }
+
+            month = 0;
+            week = 0;
+            dayOfWeek = default(DayOfWeek);
+            return false;
+        }
+
+        private static bool TZif_ParsePosixFormat(
+            string posixFormat,
+            out string standardName,
+            out string standardOffset,
+            out string daylightSavingsName,
+            out string daylightSavingsOffset,
+            out string start,
+            out string startTime,
+            out string end,
+            out string endTime)
+        {
+            standardName = null;
+            standardOffset = null;
+            daylightSavingsName = null;
+            daylightSavingsOffset = null;
+            start = null;
+            startTime = null;
+            end = null;
+            endTime = null;
+
+            int index = 0;
+            standardName = TZif_ParsePosixName(posixFormat, ref index);
+            standardOffset = TZif_ParsePosixOffset(posixFormat, ref index);
+
+            daylightSavingsName = TZif_ParsePosixName(posixFormat, ref index);
+            if (!string.IsNullOrEmpty(daylightSavingsName))
+            {
+                daylightSavingsOffset = TZif_ParsePosixOffset(posixFormat, ref index);
+
+                if (index < posixFormat.Length && posixFormat[index] == ',')
+                {
+                    index++;
+                    TZif_ParsePosixDateTime(posixFormat, ref index, out start, out startTime);
+
+                    if (index < posixFormat.Length && posixFormat[index] == ',')
+                    {
+                        index++;
+                        TZif_ParsePosixDateTime(posixFormat, ref index, out end, out endTime);
+                    }
+                }
+            }
+
+            return !string.IsNullOrEmpty(standardName) && !string.IsNullOrEmpty(standardOffset);
+        }
+
+        private static string TZif_ParsePosixName(string posixFormat, ref int index)
+        {
+            bool isBracketEnclosed = index < posixFormat.Length && posixFormat[index] == '<';
+            if (isBracketEnclosed)
+            {
+                // move past the opening bracket
+                index++;
+
+                string result = TZif_ParsePosixString(posixFormat, ref index, c => c == '>');
+
+                // move past the closing bracket
+                if (index < posixFormat.Length && posixFormat[index] == '>')
+                {
+                    index++;
+                }
+
+                return result;
+            }
+            else
+            {
+                return TZif_ParsePosixString(
+                    posixFormat,
+                    ref index,
+                    c => char.IsDigit(c) || c == '+' || c == '-' || c == ',');
+            }
+        }
+
+        private static string TZif_ParsePosixOffset(string posixFormat, ref int index) =>
+            TZif_ParsePosixString(posixFormat, ref index, c => !char.IsDigit(c) && c != '+' && c != '-' && c != ':');
+
+        private static void TZif_ParsePosixDateTime(string posixFormat, ref int index, out string date, out string time)
+        {
+            time = null;
+
+            date = TZif_ParsePosixDate(posixFormat, ref index);
+            if (index < posixFormat.Length && posixFormat[index] == '/')
+            {
+                index++;
+                time = TZif_ParsePosixTime(posixFormat, ref index);
+            }
+        }
+
+        private static string TZif_ParsePosixDate(string posixFormat, ref int index) =>
+            TZif_ParsePosixString(posixFormat, ref index, c => c == '/' || c == ',');
+
+        private static string TZif_ParsePosixTime(string posixFormat, ref int index) =>
+            TZif_ParsePosixString(posixFormat, ref index, c => c == ',');
+
+        private static string TZif_ParsePosixString(string posixFormat, ref int index, Func<char, bool> breakCondition)
+        {
+            int startIndex = index;
+            for (; index < posixFormat.Length; index++)
+            {
+                char current = posixFormat[index];
+                if (breakCondition(current))
+                {
+                    break;
+                }
+            }
+
+            return posixFormat.Substring(startIndex, index - startIndex);
+        }
+
+        // Returns the Substring from zoneAbbreviations starting at index and ending at '\0'
+        // zoneAbbreviations is expected to be in the form: "PST\0PDT\0PWT\0\PPT"
+        private static string TZif_GetZoneAbbreviation(string zoneAbbreviations, int index)
+        {
+            int lastIndex = zoneAbbreviations.IndexOf('\0', index);
+            return lastIndex > 0 ?
+                zoneAbbreviations.Substring(index, lastIndex - index) :
+                zoneAbbreviations.Substring(index);
+        }
+
+        // Converts an array of bytes into an int - always using standard byte order (Big Endian)
+        // per TZif file standard
+        private static unsafe int TZif_ToInt32(byte[] value, int startIndex)
+        {
+            fixed (byte* pbyte = &value[startIndex])
+            {
+                return (*pbyte << 24) | (*(pbyte + 1) << 16) | (*(pbyte + 2) << 8) | (*(pbyte + 3));
+            }
+        }
+
+        // Converts an array of bytes into a long - always using standard byte order (Big Endian)
+        // per TZif file standard
+        private static unsafe long TZif_ToInt64(byte[] value, int startIndex)
+        {
+            fixed (byte* pbyte = &value[startIndex])
+            {
+                int i1 = (*pbyte << 24) | (*(pbyte + 1) << 16) | (*(pbyte + 2) << 8) | (*(pbyte + 3));
+                int i2 = (*(pbyte + 4) << 24) | (*(pbyte + 5) << 16) | (*(pbyte + 6) << 8) | (*(pbyte + 7));
+                return (uint)i2 | ((long)i1 << 32);
+            }
+        }
+
+        private static long TZif_ToUnixTime(byte[] value, int startIndex, TZVersion version) =>
+            version != TZVersion.V1 ?
+                TZif_ToInt64(value, startIndex) :
+                TZif_ToInt32(value, startIndex);
+
+        private static DateTime TZif_UnixTimeToDateTime(long unixTime) =>
+            unixTime < DateTimeOffset.UnixMinSeconds ? DateTime.MinValue :
+            unixTime > DateTimeOffset.UnixMaxSeconds ? DateTime.MaxValue :
+            DateTimeOffset.FromUnixTimeSeconds(unixTime).UtcDateTime;
+
+        private static void TZif_ParseRaw(byte[] data, out TZifHead t, out DateTime[] dts, out byte[] typeOfLocalTime, out TZifType[] transitionType,
+                                          out string zoneAbbreviations, out bool[] StandardTime, out bool[] GmtTime, out string futureTransitionsPosixFormat)
+        {
+            // initialize the out parameters in case the TZifHead ctor throws
+            dts = null;
+            typeOfLocalTime = null;
+            transitionType = null;
+            zoneAbbreviations = string.Empty;
+            StandardTime = null;
+            GmtTime = null;
+            futureTransitionsPosixFormat = null;
+
+            // read in the 44-byte TZ header containing the count/length fields
+            //
+            int index = 0;
+            t = new TZifHead(data, index);
+            index += TZifHead.Length;
+
+            int timeValuesLength = 4; // the first version uses 4-bytes to specify times
+            if (t.Version != TZVersion.V1)
+            {
+                // move index past the V1 information to read the V2 information
+                index += (int)((timeValuesLength * t.TimeCount) + t.TimeCount + (6 * t.TypeCount) + ((timeValuesLength + 4) * t.LeapCount) + t.IsStdCount + t.IsGmtCount + t.CharCount);
+
+                // read the V2 header
+                t = new TZifHead(data, index);
+                index += TZifHead.Length;
+                timeValuesLength = 8; // the second version uses 8-bytes
+            }
+
+            // initialize the containers for the rest of the TZ data
+            dts = new DateTime[t.TimeCount];
+            typeOfLocalTime = new byte[t.TimeCount];
+            transitionType = new TZifType[t.TypeCount];
+            zoneAbbreviations = string.Empty;
+            StandardTime = new bool[t.TypeCount];
+            GmtTime = new bool[t.TypeCount];
+
+            // read in the UTC transition points and convert them to Windows
+            //
+            for (int i = 0; i < t.TimeCount; i++)
+            {
+                long unixTime = TZif_ToUnixTime(data, index, t.Version);
+                dts[i] = TZif_UnixTimeToDateTime(unixTime);
+                index += timeValuesLength;
+            }
+
+            // read in the Type Indices; there is a 1:1 mapping of UTC transition points to Type Indices
+            // these indices directly map to the array index in the transitionType array below
+            //
+            for (int i = 0; i < t.TimeCount; i++)
+            {
+                typeOfLocalTime[i] = data[index];
+                index += 1;
+            }
+
+            // read in the Type table.  Each 6-byte entry represents
+            // {UtcOffset, IsDst, AbbreviationIndex}
+            //
+            // each AbbreviationIndex is a character index into the zoneAbbreviations string below
+            //
+            for (int i = 0; i < t.TypeCount; i++)
+            {
+                transitionType[i] = new TZifType(data, index);
+                index += 6;
+            }
+
+            // read in the Abbreviation ASCII string.  This string will be in the form:
+            // "PST\0PDT\0PWT\0\PPT"
+            //
+            Encoding enc = Encoding.UTF8;
+            zoneAbbreviations = enc.GetString(data, index, (int)t.CharCount);
+            index += (int)t.CharCount;
+
+            // skip ahead of the Leap-Seconds Adjustment data.  In a future release, consider adding
+            // support for Leap-Seconds
+            //
+            index += (int)(t.LeapCount * (timeValuesLength + 4)); // skip the leap second transition times
+
+            // read in the Standard Time table.  There should be a 1:1 mapping between Type-Index and Standard
+            // Time table entries.
+            //
+            // TRUE     =     transition time is standard time
+            // FALSE    =     transition time is wall clock time
+            // ABSENT   =     transition time is wall clock time
+            //
+            for (int i = 0; i < t.IsStdCount && i < t.TypeCount && index < data.Length; i++)
+            {
+                StandardTime[i] = (data[index++] != 0);
+            }
+
+            // read in the GMT Time table.  There should be a 1:1 mapping between Type-Index and GMT Time table
+            // entries.
+            //
+            // TRUE     =     transition time is UTC
+            // FALSE    =     transition time is local time
+            // ABSENT   =     transition time is local time
+            //
+            for (int i = 0; i < t.IsGmtCount && i < t.TypeCount && index < data.Length; i++)
+            {
+                GmtTime[i] = (data[index++] != 0);
+            }
+
+            if (t.Version != TZVersion.V1)
+            {
+                // read the POSIX-style format, which should be wrapped in newlines with the last newline at the end of the file
+                if (data[index++] == '\n' && data[data.Length - 1] == '\n')
+                {
+                    futureTransitionsPosixFormat = enc.GetString(data, index, data.Length - index - 1);
+                }
+            }
+        }
+
+        private struct TZifType
+        {
+            public const int Length = 6;
+
+            public readonly TimeSpan UtcOffset;
+            public readonly bool IsDst;
+            public readonly byte AbbreviationIndex;
+
+            public TZifType(byte[] data, int index)
+            {
+                if (data == null || data.Length < index + Length)
+                {
+                    throw new ArgumentException(SR.Argument_TimeZoneInfoInvalidTZif, nameof(data));
+                }
+                UtcOffset = new TimeSpan(0, 0, TZif_ToInt32(data, index + 00));
+                IsDst = (data[index + 4] != 0);
+                AbbreviationIndex = data[index + 5];
+            }
+        }
+
+        private struct TZifHead
+        {
+            public const int Length = 44;
+
+            public readonly uint Magic; // TZ_MAGIC "TZif"
+            public readonly TZVersion Version; // 1 byte for a \0 or 2 or 3
+            // public byte[15] Reserved; // reserved for future use
+            public readonly uint IsGmtCount; // number of transition time flags
+            public readonly uint IsStdCount; // number of transition time flags
+            public readonly uint LeapCount; // number of leap seconds
+            public readonly uint TimeCount; // number of transition times
+            public readonly uint TypeCount; // number of local time types
+            public readonly uint CharCount; // number of abbreviated characters
+
+            public TZifHead(byte[] data, int index)
+            {
+                if (data == null || data.Length < Length)
+                {
+                    throw new ArgumentException("bad data", nameof(data));
+                }
+
+                Magic = (uint)TZif_ToInt32(data, index + 00);
+
+                if (Magic != 0x545A6966)
+                {
+                    // 0x545A6966 = {0x54, 0x5A, 0x69, 0x66} = "TZif"
+                    throw new ArgumentException(SR.Argument_TimeZoneInfoBadTZif, nameof(data));
+                }
+
+                byte version = data[index + 04];
+                Version =
+                    version == '2' ? TZVersion.V2 :
+                    version == '3' ? TZVersion.V3 :
+                    TZVersion.V1;  // default/fallback to V1 to guard against future, unsupported version numbers
+
+                // skip the 15 byte reserved field
+
+                // don't use the BitConverter class which parses data
+                // based on the Endianess of the machine architecture.
+                // this data is expected to always be in "standard byte order",
+                // regardless of the machine it is being processed on.
+
+                IsGmtCount = (uint)TZif_ToInt32(data, index + 20);
+                IsStdCount = (uint)TZif_ToInt32(data, index + 24);
+                LeapCount = (uint)TZif_ToInt32(data, index + 28);
+                TimeCount = (uint)TZif_ToInt32(data, index + 32);
+                TypeCount = (uint)TZif_ToInt32(data, index + 36);
+                CharCount = (uint)TZif_ToInt32(data, index + 40);
+            }
+        }
+
+        private enum TZVersion : byte
+        {
+            V1 = 0,
+            V2,
+            V3,
+            // when adding more versions, ensure all the logic using TZVersion is still correct
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TimeZoneInfo.Win32.cs b/src/System.Private.CoreLib/shared/System/TimeZoneInfo.Win32.cs
new file mode 100644
index 0000000000..03f54a5432
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TimeZoneInfo.Win32.cs
@@ -0,0 +1,999 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using System.IO;
+using System.Security;
+using System.Text;
+using System.Threading;
+
+using Microsoft.Win32;
+using Microsoft.Win32.SafeHandles;
+
+using Internal.Runtime.CompilerServices;
+
+using REG_TZI_FORMAT = Interop.Kernel32.REG_TZI_FORMAT;
+using TIME_ZONE_INFORMATION = Interop.Kernel32.TIME_ZONE_INFORMATION;
+using TIME_DYNAMIC_ZONE_INFORMATION = Interop.Kernel32.TIME_DYNAMIC_ZONE_INFORMATION;
+
+namespace System
+{
+    public sealed partial class TimeZoneInfo
+    {
+        // registry constants for the 'Time Zones' hive
+        //
+        private const string TimeZonesRegistryHive = @"SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones";
+        private const string DisplayValue = "Display";
+        private const string DaylightValue = "Dlt";
+        private const string StandardValue = "Std";
+        private const string MuiDisplayValue = "MUI_Display";
+        private const string MuiDaylightValue = "MUI_Dlt";
+        private const string MuiStandardValue = "MUI_Std";
+        private const string TimeZoneInfoValue = "TZI";
+        private const string FirstEntryValue = "FirstEntry";
+        private const string LastEntryValue = "LastEntry";
+
+        private const int MaxKeyLength = 255;
+
+#pragma warning disable 0420
+        private sealed partial class CachedData
+        {
+            private static TimeZoneInfo GetCurrentOneYearLocal()
+            {
+                // load the data from the OS
+                TIME_ZONE_INFORMATION timeZoneInformation;
+                uint result = Interop.Kernel32.GetTimeZoneInformation(out timeZoneInformation);
+                return result == Interop.Kernel32.TIME_ZONE_ID_INVALID ?
+                    CreateCustomTimeZone(LocalId, TimeSpan.Zero, LocalId, LocalId) :
+                    GetLocalTimeZoneFromWin32Data(timeZoneInformation, dstDisabled: false);
+            }
+
+            private volatile OffsetAndRule _oneYearLocalFromUtc;
+
+            public OffsetAndRule GetOneYearLocalFromUtc(int year)
+            {
+                OffsetAndRule oneYearLocFromUtc = _oneYearLocalFromUtc;
+                if (oneYearLocFromUtc == null || oneYearLocFromUtc.Year != year)
+                {
+                    TimeZoneInfo currentYear = GetCurrentOneYearLocal();
+                    AdjustmentRule rule = currentYear._adjustmentRules == null ? null : currentYear._adjustmentRules[0];
+                    oneYearLocFromUtc = new OffsetAndRule(year, currentYear.BaseUtcOffset, rule);
+                    _oneYearLocalFromUtc = oneYearLocFromUtc;
+                }
+                return oneYearLocFromUtc;
+            }
+        }
+#pragma warning restore 0420
+
+        private sealed class OffsetAndRule
+        {
+            public readonly int Year;
+            public readonly TimeSpan Offset;
+            public readonly AdjustmentRule Rule;
+
+            public OffsetAndRule(int year, TimeSpan offset, AdjustmentRule rule)
+            {
+                Year = year;
+                Offset = offset;
+                Rule = rule;
+            }
+        }
+
+        /// <summary>
+        /// Returns a cloned array of AdjustmentRule objects
+        /// </summary>
+        public AdjustmentRule[] GetAdjustmentRules()
+        {
+            if (_adjustmentRules == null)
+            {
+                return Array.Empty<AdjustmentRule>();
+            }
+
+            return (AdjustmentRule[])_adjustmentRules.Clone();
+        }
+
+        private static void PopulateAllSystemTimeZones(CachedData cachedData)
+        {
+            Debug.Assert(Monitor.IsEntered(cachedData));
+
+            using (RegistryKey reg = Registry.LocalMachine.OpenSubKey(TimeZonesRegistryHive, writable: false))
+            {
+                if (reg != null)
+                {
+                    foreach (string keyName in reg.GetSubKeyNames())
+                    {
+                        TimeZoneInfo value;
+                        Exception ex;
+                        TryGetTimeZone(keyName, false, out value, out ex, cachedData);  // populate the cache
+                    }
+                }
+            }
+        }
+
+        private TimeZoneInfo(in TIME_ZONE_INFORMATION zone, bool dstDisabled)
+        {
+            string standardName = zone.GetStandardName();
+            if (standardName.Length == 0)
+            {
+                _id = LocalId;  // the ID must contain at least 1 character - initialize _id to "Local"
+            }
+            else
+            {
+                _id = standardName;
+            }
+            _baseUtcOffset = new TimeSpan(0, -(zone.Bias), 0);
+
+            if (!dstDisabled)
+            {
+                // only create the adjustment rule if DST is enabled
+                REG_TZI_FORMAT regZone = new REG_TZI_FORMAT(zone);
+                AdjustmentRule rule = CreateAdjustmentRuleFromTimeZoneInformation(regZone, DateTime.MinValue.Date, DateTime.MaxValue.Date, zone.Bias);
+                if (rule != null)
+                {
+                    _adjustmentRules = new[] { rule };
+                }
+            }
+
+            ValidateTimeZoneInfo(_id, _baseUtcOffset, _adjustmentRules, out _supportsDaylightSavingTime);
+            _displayName = standardName;
+            _standardDisplayName = standardName;
+            _daylightDisplayName = zone.GetDaylightName();
+        }
+
+        /// <summary>
+        /// Helper function to check if the current TimeZoneInformation struct does not support DST.
+        /// This check returns true when the DaylightDate == StandardDate.
+        /// This check is only meant to be used for "Local".
+        /// </summary>
+        private static bool CheckDaylightSavingTimeNotSupported(in TIME_ZONE_INFORMATION timeZone) =>
+            timeZone.DaylightDate.Equals(timeZone.StandardDate);
+
+        /// <summary>
+        /// Converts a REG_TZI_FORMAT struct to an AdjustmentRule.
+        /// </summary>
+        private static AdjustmentRule CreateAdjustmentRuleFromTimeZoneInformation(in REG_TZI_FORMAT timeZoneInformation, DateTime startDate, DateTime endDate, int defaultBaseUtcOffset)
+        {
+            bool supportsDst = timeZoneInformation.StandardDate.Month != 0;
+
+            if (!supportsDst)
+            {
+                if (timeZoneInformation.Bias == defaultBaseUtcOffset)
+                {
+                    // this rule will not contain any information to be used to adjust dates. just ignore it
+                    return null;
+                }
+
+                return AdjustmentRule.CreateAdjustmentRule(
+                    startDate,
+                    endDate,
+                    TimeSpan.Zero, // no daylight saving transition
+                    TransitionTime.CreateFixedDateRule(DateTime.MinValue, 1, 1),
+                    TransitionTime.CreateFixedDateRule(DateTime.MinValue.AddMilliseconds(1), 1, 1),
+                    new TimeSpan(0, defaultBaseUtcOffset - timeZoneInformation.Bias, 0),  // Bias delta is all what we need from this rule
+                    noDaylightTransitions: false);
+            }
+
+            //
+            // Create an AdjustmentRule with TransitionTime objects
+            //
+            TransitionTime daylightTransitionStart;
+            if (!TransitionTimeFromTimeZoneInformation(timeZoneInformation, out daylightTransitionStart, readStartDate: true))
+            {
+                return null;
+            }
+
+            TransitionTime daylightTransitionEnd;
+            if (!TransitionTimeFromTimeZoneInformation(timeZoneInformation, out daylightTransitionEnd, readStartDate: false))
+            {
+                return null;
+            }
+
+            if (daylightTransitionStart.Equals(daylightTransitionEnd))
+            {
+                // this happens when the time zone does support DST but the OS has DST disabled
+                return null;
+            }
+
+            return AdjustmentRule.CreateAdjustmentRule(
+                startDate,
+                endDate,
+                new TimeSpan(0, -timeZoneInformation.DaylightBias, 0),
+                daylightTransitionStart,
+                daylightTransitionEnd,
+                new TimeSpan(0, defaultBaseUtcOffset - timeZoneInformation.Bias, 0),
+                noDaylightTransitions: false);
+        }
+
+        /// <summary>
+        /// Helper function that searches the registry for a time zone entry
+        /// that matches the TimeZoneInformation struct.
+        /// </summary>
+        private static string FindIdFromTimeZoneInformation(in TIME_ZONE_INFORMATION timeZone, out bool dstDisabled)
+        {
+            dstDisabled = false;
+
+            using (RegistryKey key = Registry.LocalMachine.OpenSubKey(TimeZonesRegistryHive, writable: false))
+            {
+                if (key == null)
+                {
+                    return null;
+                }
+
+                foreach (string keyName in key.GetSubKeyNames())
+                {
+                    if (TryCompareTimeZoneInformationToRegistry(timeZone, keyName, out dstDisabled))
+                    {
+                        return keyName;
+                    }
+                }
+            }
+
+            return null;
+        }
+
+        /// <summary>
+        /// Helper function for retrieving the local system time zone.
+        /// May throw COMException, TimeZoneNotFoundException, InvalidTimeZoneException.
+        /// Assumes cachedData lock is taken.
+        /// </summary>
+        /// <returns>A new TimeZoneInfo instance.</returns>
+        private static TimeZoneInfo GetLocalTimeZone(CachedData cachedData)
+        {
+            Debug.Assert(Monitor.IsEntered(cachedData));
+
+            //
+            // Try using the "kernel32!GetDynamicTimeZoneInformation" API to get the "id"
+            //
+            var dynamicTimeZoneInformation = new TIME_DYNAMIC_ZONE_INFORMATION();
+
+            // call kernel32!GetDynamicTimeZoneInformation...
+            uint result = Interop.Kernel32.GetDynamicTimeZoneInformation(out dynamicTimeZoneInformation);
+            if (result == Interop.Kernel32.TIME_ZONE_ID_INVALID)
+            {
+                // return a dummy entry
+                return CreateCustomTimeZone(LocalId, TimeSpan.Zero, LocalId, LocalId);
+            }
+
+            // check to see if we can use the key name returned from the API call
+            string dynamicTimeZoneKeyName = dynamicTimeZoneInformation.GetTimeZoneKeyName();
+            if (dynamicTimeZoneKeyName.Length != 0)
+            {
+                TimeZoneInfo zone;
+                Exception ex;
+
+                if (TryGetTimeZone(dynamicTimeZoneKeyName, dynamicTimeZoneInformation.DynamicDaylightTimeDisabled != 0, out zone, out ex, cachedData) == TimeZoneInfoResult.Success)
+                {
+                    // successfully loaded the time zone from the registry
+                    return zone;
+                }
+            }
+
+            var timeZoneInformation = new TIME_ZONE_INFORMATION(dynamicTimeZoneInformation);
+
+            // the key name was not returned or it pointed to a bogus entry - search for the entry ourselves
+            string id = FindIdFromTimeZoneInformation(timeZoneInformation, out bool dstDisabled);
+
+            if (id != null)
+            {
+                TimeZoneInfo zone;
+                Exception ex;
+                if (TryGetTimeZone(id, dstDisabled, out zone, out ex, cachedData) == TimeZoneInfoResult.Success)
+                {
+                    // successfully loaded the time zone from the registry
+                    return zone;
+                }
+            }
+
+            // We could not find the data in the registry.  Fall back to using
+            // the data from the Win32 API
+            return GetLocalTimeZoneFromWin32Data(timeZoneInformation, dstDisabled);
+        }
+
+        /// <summary>
+        /// Helper function used by 'GetLocalTimeZone()' - this function wraps a bunch of
+        /// try/catch logic for handling the TimeZoneInfo private constructor that takes
+        /// a TIME_ZONE_INFORMATION structure.
+        /// </summary>
+        private static TimeZoneInfo GetLocalTimeZoneFromWin32Data(in TIME_ZONE_INFORMATION timeZoneInformation, bool dstDisabled)
+        {
+            // first try to create the TimeZoneInfo with the original 'dstDisabled' flag
+            try
+            {
+                return new TimeZoneInfo(timeZoneInformation, dstDisabled);
+            }
+            catch (ArgumentException) { }
+            catch (InvalidTimeZoneException) { }
+
+            // if 'dstDisabled' was false then try passing in 'true' as a last ditch effort
+            if (!dstDisabled)
+            {
+                try
+                {
+                    return new TimeZoneInfo(timeZoneInformation, dstDisabled: true);
+                }
+                catch (ArgumentException) { }
+                catch (InvalidTimeZoneException) { }
+            }
+
+            // the data returned from Windows is completely bogus; return a dummy entry
+            return CreateCustomTimeZone(LocalId, TimeSpan.Zero, LocalId, LocalId);
+        }
+
+        /// <summary>
+        /// Helper function for retrieving a TimeZoneInfo object by <time_zone_name>.
+        /// This function wraps the logic necessary to keep the private
+        /// SystemTimeZones cache in working order
+        ///
+        /// This function will either return a valid TimeZoneInfo instance or
+        /// it will throw 'InvalidTimeZoneException' / 'TimeZoneNotFoundException'.
+        /// </summary>
+        public static TimeZoneInfo FindSystemTimeZoneById(string id)
+        {
+            // Special case for Utc as it will not exist in the dictionary with the rest
+            // of the system time zones.  There is no need to do this check for Local.Id
+            // since Local is a real time zone that exists in the dictionary cache
+            if (string.Equals(id, UtcId, StringComparison.OrdinalIgnoreCase))
+            {
+                return Utc;
+            }
+
+            if (id == null)
+            {
+                throw new ArgumentNullException(nameof(id));
+            }
+            if (id.Length == 0 || id.Length > MaxKeyLength || id.Contains('\0'))
+            {
+                throw new TimeZoneNotFoundException(SR.Format(SR.TimeZoneNotFound_MissingData, id));
+            }
+
+            TimeZoneInfo value;
+            Exception e;
+
+            TimeZoneInfoResult result;
+
+            CachedData cachedData = s_cachedData;
+
+            lock (cachedData)
+            {
+                result = TryGetTimeZone(id, false, out value, out e, cachedData);
+            }
+
+            if (result == TimeZoneInfoResult.Success)
+            {
+                return value;
+            }
+            else if (result == TimeZoneInfoResult.InvalidTimeZoneException)
+            {
+                throw new InvalidTimeZoneException(SR.Format(SR.InvalidTimeZone_InvalidRegistryData, id), e);
+            }
+            else if (result == TimeZoneInfoResult.SecurityException)
+            {
+                throw new SecurityException(SR.Format(SR.Security_CannotReadRegistryData, id), e);
+            }
+            else
+            {
+                throw new TimeZoneNotFoundException(SR.Format(SR.TimeZoneNotFound_MissingData, id), e);
+            }
+        }
+
+        // DateTime.Now fast path that avoids allocating an historically accurate TimeZoneInfo.Local and just creates a 1-year (current year) accurate time zone
+        internal static TimeSpan GetDateTimeNowUtcOffsetFromUtc(DateTime time, out bool isAmbiguousLocalDst)
+        {
+            bool isDaylightSavings = false;
+            isAmbiguousLocalDst = false;
+            TimeSpan baseOffset;
+            int timeYear = time.Year;
+
+            OffsetAndRule match = s_cachedData.GetOneYearLocalFromUtc(timeYear);
+            baseOffset = match.Offset;
+
+            if (match.Rule != null)
+            {
+                baseOffset = baseOffset + match.Rule.BaseUtcOffsetDelta;
+                if (match.Rule.HasDaylightSaving)
+                {
+                    isDaylightSavings = GetIsDaylightSavingsFromUtc(time, timeYear, match.Offset, match.Rule, null, out isAmbiguousLocalDst, Local);
+                    baseOffset += (isDaylightSavings ? match.Rule.DaylightDelta : TimeSpan.Zero /* FUTURE: rule.StandardDelta */);
+                }
+            }
+            return baseOffset;
+        }
+
+        /// <summary>
+        /// Converts a REG_TZI_FORMAT struct to a TransitionTime
+        /// - When the argument 'readStart' is true the corresponding daylightTransitionTimeStart field is read
+        /// - When the argument 'readStart' is false the corresponding dayightTransitionTimeEnd field is read
+        /// </summary>
+        private static bool TransitionTimeFromTimeZoneInformation(in REG_TZI_FORMAT timeZoneInformation, out TransitionTime transitionTime, bool readStartDate)
+        {
+            //
+            // SYSTEMTIME -
+            //
+            // If the time zone does not support daylight saving time or if the caller needs
+            // to disable daylight saving time, the wMonth member in the SYSTEMTIME structure
+            // must be zero. If this date is specified, the DaylightDate value in the
+            // TIME_ZONE_INFORMATION structure must also be specified. Otherwise, the system
+            // assumes the time zone data is invalid and no changes will be applied.
+            //
+            bool supportsDst = (timeZoneInformation.StandardDate.Month != 0);
+
+            if (!supportsDst)
+            {
+                transitionTime = default(TransitionTime);
+                return false;
+            }
+
+            //
+            // SYSTEMTIME -
+            //
+            // * FixedDateRule -
+            //   If the Year member is not zero, the transition date is absolute; it will only occur one time
+            //
+            // * FloatingDateRule -
+            //   To select the correct day in the month, set the Year member to zero, the Hour and Minute
+            //   members to the transition time, the DayOfWeek member to the appropriate weekday, and the
+            //   Day member to indicate the occurence of the day of the week within the month (first through fifth).
+            //
+            //   Using this notation, specify the 2:00a.m. on the first Sunday in April as follows:
+            //   Hour      = 2,
+            //   Month     = 4,
+            //   DayOfWeek = 0,
+            //   Day       = 1.
+            //
+            //   Specify 2:00a.m. on the last Thursday in October as follows:
+            //   Hour      = 2,
+            //   Month     = 10,
+            //   DayOfWeek = 4,
+            //   Day       = 5.
+            //
+            if (readStartDate)
+            {
+                //
+                // read the "daylightTransitionStart"
+                //
+                if (timeZoneInformation.DaylightDate.Year == 0)
+                {
+                    transitionTime = TransitionTime.CreateFloatingDateRule(
+                                     new DateTime(1,    /* year  */
+                                                  1,    /* month */
+                                                  1,    /* day   */
+                                                  timeZoneInformation.DaylightDate.Hour,
+                                                  timeZoneInformation.DaylightDate.Minute,
+                                                  timeZoneInformation.DaylightDate.Second,
+                                                  timeZoneInformation.DaylightDate.Milliseconds),
+                                     timeZoneInformation.DaylightDate.Month,
+                                     timeZoneInformation.DaylightDate.Day,   /* Week 1-5 */
+                                     (DayOfWeek)timeZoneInformation.DaylightDate.DayOfWeek);
+                }
+                else
+                {
+                    transitionTime = TransitionTime.CreateFixedDateRule(
+                                     new DateTime(1,    /* year  */
+                                                  1,    /* month */
+                                                  1,    /* day   */
+                                                  timeZoneInformation.DaylightDate.Hour,
+                                                  timeZoneInformation.DaylightDate.Minute,
+                                                  timeZoneInformation.DaylightDate.Second,
+                                                  timeZoneInformation.DaylightDate.Milliseconds),
+                                     timeZoneInformation.DaylightDate.Month,
+                                     timeZoneInformation.DaylightDate.Day);
+                }
+            }
+            else
+            {
+                //
+                // read the "daylightTransitionEnd"
+                //
+                if (timeZoneInformation.StandardDate.Year == 0)
+                {
+                    transitionTime = TransitionTime.CreateFloatingDateRule(
+                                     new DateTime(1,    /* year  */
+                                                  1,    /* month */
+                                                  1,    /* day   */
+                                                  timeZoneInformation.StandardDate.Hour,
+                                                  timeZoneInformation.StandardDate.Minute,
+                                                  timeZoneInformation.StandardDate.Second,
+                                                  timeZoneInformation.StandardDate.Milliseconds),
+                                     timeZoneInformation.StandardDate.Month,
+                                     timeZoneInformation.StandardDate.Day,   /* Week 1-5 */
+                                     (DayOfWeek)timeZoneInformation.StandardDate.DayOfWeek);
+                }
+                else
+                {
+                    transitionTime = TransitionTime.CreateFixedDateRule(
+                                     new DateTime(1,    /* year  */
+                                                  1,    /* month */
+                                                  1,    /* day   */
+                                                  timeZoneInformation.StandardDate.Hour,
+                                                  timeZoneInformation.StandardDate.Minute,
+                                                  timeZoneInformation.StandardDate.Second,
+                                                  timeZoneInformation.StandardDate.Milliseconds),
+                                     timeZoneInformation.StandardDate.Month,
+                                     timeZoneInformation.StandardDate.Day);
+                }
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// Helper function that takes:
+        ///  1. A string representing a <time_zone_name> registry key name.
+        ///  2. A REG_TZI_FORMAT struct containing the default rule.
+        ///  3. An AdjustmentRule[] out-parameter.
+        /// </summary>
+        private static bool TryCreateAdjustmentRules(string id, in REG_TZI_FORMAT defaultTimeZoneInformation, out AdjustmentRule[] rules, out Exception e, int defaultBaseUtcOffset)
+        {
+            rules = null;
+            e = null;
+
+            try
+            {
+                // Optional, Dynamic Time Zone Registry Data
+                // -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+                //
+                // HKLM
+                //     Software
+                //         Microsoft
+                //             Windows NT
+                //                 CurrentVersion
+                //                     Time Zones
+                //                         <time_zone_name>
+                //                             Dynamic DST
+                // * "FirstEntry" REG_DWORD "1980"
+                //                           First year in the table. If the current year is less than this value,
+                //                           this entry will be used for DST boundaries
+                // * "LastEntry"  REG_DWORD "2038"
+                //                           Last year in the table. If the current year is greater than this value,
+                //                           this entry will be used for DST boundaries"
+                // * "<year1>"    REG_BINARY REG_TZI_FORMAT
+                // * "<year2>"    REG_BINARY REG_TZI_FORMAT
+                // * "<year3>"    REG_BINARY REG_TZI_FORMAT
+                //
+                using (RegistryKey dynamicKey = Registry.LocalMachine.OpenSubKey(TimeZonesRegistryHive + "\\" + id + "\\Dynamic DST", writable: false))
+                {
+                    if (dynamicKey == null)
+                    {
+                        AdjustmentRule rule = CreateAdjustmentRuleFromTimeZoneInformation(
+                            defaultTimeZoneInformation, DateTime.MinValue.Date, DateTime.MaxValue.Date, defaultBaseUtcOffset);
+                        if (rule != null)
+                        {
+                            rules = new[] { rule };
+                        }
+                        return true;
+                    }
+
+                    //
+                    // loop over all of the "<time_zone_name>\Dynamic DST" hive entries
+                    //
+                    // read FirstEntry  {MinValue      - (year1, 12, 31)}
+                    // read MiddleEntry {(yearN, 1, 1) - (yearN, 12, 31)}
+                    // read LastEntry   {(yearN, 1, 1) - MaxValue       }
+
+                    // read the FirstEntry and LastEntry key values (ex: "1980", "2038")
+                    int first = (int)dynamicKey.GetValue(FirstEntryValue, -1, RegistryValueOptions.None);
+                    int last = (int)dynamicKey.GetValue(LastEntryValue, -1, RegistryValueOptions.None);
+
+                    if (first == -1 || last == -1 || first > last)
+                    {
+                        return false;
+                    }
+
+                    // read the first year entry
+                    REG_TZI_FORMAT dtzi;
+
+                    if (!TryGetTimeZoneEntryFromRegistry(dynamicKey, first.ToString(CultureInfo.InvariantCulture), out dtzi))
+                    {
+                        return false;
+                    }
+
+                    if (first == last)
+                    {
+                        // there is just 1 dynamic rule for this time zone.
+                        AdjustmentRule rule = CreateAdjustmentRuleFromTimeZoneInformation(dtzi, DateTime.MinValue.Date, DateTime.MaxValue.Date, defaultBaseUtcOffset);
+                        if (rule != null)
+                        {
+                            rules = new[] { rule };
+                        }
+                        return true;
+                    }
+
+                    List<AdjustmentRule> rulesList = new List<AdjustmentRule>(1);
+
+                    // there are more than 1 dynamic rules for this time zone.
+                    AdjustmentRule firstRule = CreateAdjustmentRuleFromTimeZoneInformation(
+                        dtzi,
+                        DateTime.MinValue.Date,        // MinValue
+                        new DateTime(first, 12, 31),   // December 31, <FirstYear>
+                        defaultBaseUtcOffset);
+
+                    if (firstRule != null)
+                    {
+                        rulesList.Add(firstRule);
+                    }
+
+                    // read the middle year entries
+                    for (int i = first + 1; i < last; i++)
+                    {
+                        if (!TryGetTimeZoneEntryFromRegistry(dynamicKey, i.ToString(CultureInfo.InvariantCulture), out dtzi))
+                        {
+                            return false;
+                        }
+                        AdjustmentRule middleRule = CreateAdjustmentRuleFromTimeZoneInformation(
+                            dtzi,
+                            new DateTime(i, 1, 1),    // January  01, <Year>
+                            new DateTime(i, 12, 31),  // December 31, <Year>
+                            defaultBaseUtcOffset);
+
+                        if (middleRule != null)
+                        {
+                            rulesList.Add(middleRule);
+                        }
+                    }
+
+                    // read the last year entry
+                    if (!TryGetTimeZoneEntryFromRegistry(dynamicKey, last.ToString(CultureInfo.InvariantCulture), out dtzi))
+                    {
+                        return false;
+                    }
+                    AdjustmentRule lastRule = CreateAdjustmentRuleFromTimeZoneInformation(
+                        dtzi,
+                        new DateTime(last, 1, 1),    // January  01, <LastYear>
+                        DateTime.MaxValue.Date,      // MaxValue
+                        defaultBaseUtcOffset);
+
+                    if (lastRule != null)
+                    {
+                        rulesList.Add(lastRule);
+                    }
+
+                    // convert the List to an AdjustmentRule array
+                    if (rulesList.Count != 0)
+                    {
+                        rules = rulesList.ToArray();
+                    }
+                } // end of: using (RegistryKey dynamicKey...
+            }
+            catch (InvalidCastException ex)
+            {
+                // one of the RegistryKey.GetValue calls could not be cast to an expected value type
+                e = ex;
+                return false;
+            }
+            catch (ArgumentOutOfRangeException ex)
+            {
+                e = ex;
+                return false;
+            }
+            catch (ArgumentException ex)
+            {
+                e = ex;
+                return false;
+            }
+            return true;
+        }
+
+        private static unsafe bool TryGetTimeZoneEntryFromRegistry(RegistryKey key, string name, out REG_TZI_FORMAT dtzi)
+        {
+            byte[] regValue = key.GetValue(name, null, RegistryValueOptions.None) as byte[];
+            if (regValue == null || regValue.Length != sizeof(REG_TZI_FORMAT))
+            {
+                dtzi = default;
+                return false;
+            }
+            fixed (byte * pBytes = &regValue[0])
+                dtzi = *(REG_TZI_FORMAT *)pBytes;
+            return true;
+        }
+
+        /// <summary>
+        /// Helper function that compares the StandardBias and StandardDate portion a
+        /// TimeZoneInformation struct to a time zone registry entry.
+        /// </summary>
+        private static bool TryCompareStandardDate(in TIME_ZONE_INFORMATION timeZone, in REG_TZI_FORMAT registryTimeZoneInfo) =>
+            timeZone.Bias == registryTimeZoneInfo.Bias &&
+            timeZone.StandardBias == registryTimeZoneInfo.StandardBias &&
+            timeZone.StandardDate.Equals(registryTimeZoneInfo.StandardDate);
+
+        /// <summary>
+        /// Helper function that compares a TimeZoneInformation struct to a time zone registry entry.
+        /// </summary>
+        private static bool TryCompareTimeZoneInformationToRegistry(in TIME_ZONE_INFORMATION timeZone, string id, out bool dstDisabled)
+        {
+            dstDisabled = false;
+
+            using (RegistryKey key = Registry.LocalMachine.OpenSubKey(TimeZonesRegistryHive + "\\" + id, writable: false))
+            {
+                if (key == null)
+                {
+                    return false;
+                }
+
+                REG_TZI_FORMAT registryTimeZoneInfo;
+                if (!TryGetTimeZoneEntryFromRegistry(key, TimeZoneInfoValue, out registryTimeZoneInfo))
+                {
+                    return false;
+                }
+
+                //
+                // first compare the bias and standard date information between the data from the Win32 API
+                // and the data from the registry...
+                //
+                bool result = TryCompareStandardDate(timeZone, registryTimeZoneInfo);
+
+                if (!result)
+                {
+                    return false;
+                }
+
+                result = dstDisabled || CheckDaylightSavingTimeNotSupported(timeZone) ||
+                    //
+                    // since Daylight Saving Time is not "disabled", do a straight comparision between
+                    // the Win32 API data and the registry data ...
+                    //
+                    (timeZone.DaylightBias == registryTimeZoneInfo.DaylightBias &&
+                    timeZone.DaylightDate.Equals(registryTimeZoneInfo.DaylightDate));
+
+                // Finally compare the "StandardName" string value...
+                //
+                // we do not compare "DaylightName" as this TimeZoneInformation field may contain
+                // either "StandardName" or "DaylightName" depending on the time of year and current machine settings
+                //
+                if (result)
+                {
+                    string registryStandardName = key.GetValue(StandardValue, string.Empty, RegistryValueOptions.None) as string;
+                    result = string.Equals(registryStandardName, timeZone.GetStandardName(), StringComparison.Ordinal);
+                }
+                return result;
+            }
+        }
+
+        /// <summary>
+        /// Helper function for retrieving a localized string resource via MUI.
+        /// The function expects a string in the form: "@resource.dll, -123"
+        ///
+        /// "resource.dll" is a language-neutral portable executable (LNPE) file in
+        /// the %windir%\system32 directory.  The OS is queried to find the best-fit
+        /// localized resource file for this LNPE (ex: %windir%\system32\en-us\resource.dll.mui).
+        /// If a localized resource file exists, we LoadString resource ID "123" and
+        /// return it to our caller.
+        /// </summary>
+        private static string TryGetLocalizedNameByMuiNativeResource(string resource)
+        {
+            if (string.IsNullOrEmpty(resource))
+            {
+                return string.Empty;
+            }
+
+            // parse "@tzres.dll, -100"
+            //
+            // filePath   = "C:\Windows\System32\tzres.dll"
+            // resourceId = -100
+            //
+            string[] resources = resource.Split(',');
+            if (resources.Length != 2)
+            {
+                return string.Empty;
+            }
+
+            string filePath;
+            int resourceId;
+
+            // get the path to Windows\System32
+            string system32 = Environment.SystemDirectory;
+
+            // trim the string "@tzres.dll" => "tzres.dll"
+            string tzresDll = resources[0].TrimStart('@');
+
+            try
+            {
+                filePath = Path.Combine(system32, tzresDll);
+            }
+            catch (ArgumentException)
+            {
+                // there were probably illegal characters in the path
+                return string.Empty;
+            }
+
+            if (!int.TryParse(resources[1], NumberStyles.Integer, CultureInfo.InvariantCulture, out resourceId))
+            {
+                return string.Empty;
+            }
+            resourceId = -resourceId;
+
+            try
+            {
+                StringBuilder fileMuiPath = StringBuilderCache.Acquire(Interop.Kernel32.MAX_PATH);
+                fileMuiPath.Length = Interop.Kernel32.MAX_PATH;
+                int fileMuiPathLength = Interop.Kernel32.MAX_PATH;
+                int languageLength = 0;
+                long enumerator = 0;
+
+                bool succeeded = Interop.Kernel32.GetFileMUIPath(
+                                        Interop.Kernel32.MUI_PREFERRED_UI_LANGUAGES,
+                                        filePath, null /* language */, ref languageLength,
+                                        fileMuiPath, ref fileMuiPathLength, ref enumerator);
+                if (!succeeded)
+                {
+                    StringBuilderCache.Release(fileMuiPath);
+                    return string.Empty;
+                }
+                return TryGetLocalizedNameByNativeResource(StringBuilderCache.GetStringAndRelease(fileMuiPath), resourceId);
+            }
+            catch (EntryPointNotFoundException)
+            {
+                return string.Empty;
+            }
+        }
+
+        /// <summary>
+        /// Helper function for retrieving a localized string resource via a native resource DLL.
+        /// The function expects a string in the form: "C:\Windows\System32\en-us\resource.dll"
+        ///
+        /// "resource.dll" is a language-specific resource DLL.
+        /// If the localized resource DLL exists, LoadString(resource) is returned.
+        /// </summary>
+        private static string TryGetLocalizedNameByNativeResource(string filePath, int resource)
+        {
+            using (SafeLibraryHandle handle =
+                       Interop.Kernel32.LoadLibraryEx(filePath, IntPtr.Zero, Interop.Kernel32.LOAD_LIBRARY_AS_DATAFILE))
+            {
+                if (!handle.IsInvalid)
+                {
+                    const int LoadStringMaxLength = 500;
+
+                    StringBuilder localizedResource = StringBuilderCache.Acquire(LoadStringMaxLength);
+
+                    int result = Interop.User32.LoadString(handle, resource,
+                                     localizedResource, LoadStringMaxLength);
+
+                    if (result != 0)
+                    {
+                        return StringBuilderCache.GetStringAndRelease(localizedResource);
+                    }
+                }
+            }
+            return string.Empty;
+        }
+
+        /// <summary>
+        /// Helper function for retrieving the DisplayName, StandardName, and DaylightName from the registry
+        ///
+        /// The function first checks the MUI_ key-values, and if they exist, it loads the strings from the MUI
+        /// resource dll(s).  When the keys do not exist, the function falls back to reading from the standard
+        /// key-values
+        /// </summary>
+        private static void GetLocalizedNamesByRegistryKey(RegistryKey key, out string displayName, out string standardName, out string daylightName)
+        {
+            displayName = string.Empty;
+            standardName = string.Empty;
+            daylightName = string.Empty;
+
+            // read the MUI_ registry keys
+            string displayNameMuiResource = key.GetValue(MuiDisplayValue, string.Empty, RegistryValueOptions.None) as string;
+            string standardNameMuiResource = key.GetValue(MuiStandardValue, string.Empty, RegistryValueOptions.None) as string;
+            string daylightNameMuiResource = key.GetValue(MuiDaylightValue, string.Empty, RegistryValueOptions.None) as string;
+
+            // try to load the strings from the native resource DLL(s)
+            if (!string.IsNullOrEmpty(displayNameMuiResource))
+            {
+                displayName = TryGetLocalizedNameByMuiNativeResource(displayNameMuiResource);
+            }
+
+            if (!string.IsNullOrEmpty(standardNameMuiResource))
+            {
+                standardName = TryGetLocalizedNameByMuiNativeResource(standardNameMuiResource);
+            }
+
+            if (!string.IsNullOrEmpty(daylightNameMuiResource))
+            {
+                daylightName = TryGetLocalizedNameByMuiNativeResource(daylightNameMuiResource);
+            }
+
+            // fallback to using the standard registry keys
+            if (string.IsNullOrEmpty(displayName))
+            {
+                displayName = key.GetValue(DisplayValue, string.Empty, RegistryValueOptions.None) as string;
+            }
+            if (string.IsNullOrEmpty(standardName))
+            {
+                standardName = key.GetValue(StandardValue, string.Empty, RegistryValueOptions.None) as string;
+            }
+            if (string.IsNullOrEmpty(daylightName))
+            {
+                daylightName = key.GetValue(DaylightValue, string.Empty, RegistryValueOptions.None) as string;
+            }
+        }
+
+        /// <summary>
+        /// Helper function that takes a string representing a <time_zone_name> registry key name
+        /// and returns a TimeZoneInfo instance.
+        /// </summary>
+        private static TimeZoneInfoResult TryGetTimeZoneFromLocalMachine(string id, out TimeZoneInfo value, out Exception e)
+        {
+            e = null;
+
+            // Standard Time Zone Registry Data
+            // -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
+            // HKLM
+            //     Software
+            //         Microsoft
+            //             Windows NT
+            //                 CurrentVersion
+            //                     Time Zones
+            //                         <time_zone_name>
+            // * STD,         REG_SZ "Standard Time Name"
+            //                       (For OS installed zones, this will always be English)
+            // * MUI_STD,     REG_SZ "@tzres.dll,-1234"
+            //                       Indirect string to localized resource for Standard Time,
+            //                       add "%windir%\system32\" after "@"
+            // * DLT,         REG_SZ "Daylight Time Name"
+            //                       (For OS installed zones, this will always be English)
+            // * MUI_DLT,     REG_SZ "@tzres.dll,-1234"
+            //                       Indirect string to localized resource for Daylight Time,
+            //                       add "%windir%\system32\" after "@"
+            // * Display,     REG_SZ "Display Name like (GMT-8:00) Pacific Time..."
+            // * MUI_Display, REG_SZ "@tzres.dll,-1234"
+            //                       Indirect string to localized resource for the Display,
+            //                       add "%windir%\system32\" after "@"
+            // * TZI,         REG_BINARY REG_TZI_FORMAT
+            //
+            using (RegistryKey key = Registry.LocalMachine.OpenSubKey(TimeZonesRegistryHive + "\\" + id, writable: false))
+            {
+                if (key == null)
+                {
+                    value = null;
+                    return TimeZoneInfoResult.TimeZoneNotFoundException;
+                }
+
+                REG_TZI_FORMAT defaultTimeZoneInformation;
+                if (!TryGetTimeZoneEntryFromRegistry(key, TimeZoneInfoValue, out defaultTimeZoneInformation))
+                {
+                    // the registry value could not be cast to a byte array
+                    value = null;
+                    return TimeZoneInfoResult.InvalidTimeZoneException;
+                }
+
+                AdjustmentRule[] adjustmentRules;
+                if (!TryCreateAdjustmentRules(id, defaultTimeZoneInformation, out adjustmentRules, out e, defaultTimeZoneInformation.Bias))
+                {
+                    value = null;
+                    return TimeZoneInfoResult.InvalidTimeZoneException;
+                }
+
+                GetLocalizedNamesByRegistryKey(key, out string displayName, out string standardName, out string daylightName);
+
+                try
+                {
+                    value = new TimeZoneInfo(
+                        id,
+                        new TimeSpan(0, -(defaultTimeZoneInformation.Bias), 0),
+                        displayName,
+                        standardName,
+                        daylightName,
+                        adjustmentRules,
+                        disableDaylightSavingTime: false);
+
+                    return TimeZoneInfoResult.Success;
+                }
+                catch (ArgumentException ex)
+                {
+                    // TimeZoneInfo constructor can throw ArgumentException and InvalidTimeZoneException
+                    value = null;
+                    e = ex;
+                    return TimeZoneInfoResult.InvalidTimeZoneException;
+                }
+                catch (InvalidTimeZoneException ex)
+                {
+                    // TimeZoneInfo constructor can throw ArgumentException and InvalidTimeZoneException
+                    value = null;
+                    e = ex;
+                    return TimeZoneInfoResult.InvalidTimeZoneException;
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TimeZoneInfo.cs b/src/System.Private.CoreLib/shared/System/TimeZoneInfo.cs
new file mode 100644
index 0000000000..6e27376b68
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TimeZoneInfo.cs
@@ -0,0 +1,1993 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.Serialization;
+using System.Threading;
+
+namespace System
+{
+    //
+    // DateTime uses TimeZoneInfo under the hood for IsDaylightSavingTime, IsAmbiguousTime, and GetUtcOffset.
+    // These TimeZoneInfo APIs can throw ArgumentException when an Invalid-Time is passed in.  To avoid this
+    // unwanted behavior in DateTime public APIs, DateTime internally passes the
+    // TimeZoneInfoOptions.NoThrowOnInvalidTime flag to internal TimeZoneInfo APIs.
+    //
+    // In the future we can consider exposing similar options on the public TimeZoneInfo APIs if there is enough
+    // demand for this alternate behavior.
+    //
+    [Flags]
+    internal enum TimeZoneInfoOptions
+    {
+        None = 1,
+        NoThrowOnInvalidTime = 2
+    };
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed partial class TimeZoneInfo : IEquatable<TimeZoneInfo>, ISerializable, IDeserializationCallback
+    {
+        private enum TimeZoneInfoResult
+        {
+            Success = 0,
+            TimeZoneNotFoundException = 1,
+            InvalidTimeZoneException = 2,
+            SecurityException = 3
+        };
+
+        private readonly string _id;
+        private readonly string _displayName;
+        private readonly string _standardDisplayName;
+        private readonly string _daylightDisplayName;
+        private readonly TimeSpan _baseUtcOffset;
+        private readonly bool _supportsDaylightSavingTime;
+        private readonly AdjustmentRule[] _adjustmentRules;
+
+        // constants for TimeZoneInfo.Local and TimeZoneInfo.Utc
+        private const string UtcId = "UTC";
+        private const string LocalId = "Local";
+
+        private static readonly TimeZoneInfo s_utcTimeZone = CreateCustomTimeZone(UtcId, TimeSpan.Zero, UtcId, UtcId);
+
+        private static CachedData s_cachedData = new CachedData();
+
+        //
+        // All cached data are encapsulated in a helper class to allow consistent view even when the data are refreshed using ClearCachedData()
+        //
+        // For example, TimeZoneInfo.Local can be cleared by another thread calling TimeZoneInfo.ClearCachedData. Without the consistent snapshot,
+        // there is a chance that the internal ConvertTime calls will throw since 'source' won't be reference equal to the new TimeZoneInfo.Local.
+        //
+#pragma warning disable 0420
+        private sealed partial class CachedData
+        {
+            private volatile TimeZoneInfo _localTimeZone;
+
+            private TimeZoneInfo CreateLocal()
+            {
+                lock (this)
+                {
+                    TimeZoneInfo timeZone = _localTimeZone;
+                    if (timeZone == null)
+                    {
+                        timeZone = GetLocalTimeZone(this);
+
+                        // this step is to break the reference equality
+                        // between TimeZoneInfo.Local and a second time zone
+                        // such as "Pacific Standard Time"
+                        timeZone = new TimeZoneInfo(
+                                            timeZone._id,
+                                            timeZone._baseUtcOffset,
+                                            timeZone._displayName,
+                                            timeZone._standardDisplayName,
+                                            timeZone._daylightDisplayName,
+                                            timeZone._adjustmentRules,
+                                            disableDaylightSavingTime: false);
+
+                        _localTimeZone = timeZone;
+                    }
+                    return timeZone;
+                }
+            }
+
+            public TimeZoneInfo Local
+            {
+                get
+                {
+                    TimeZoneInfo timeZone = _localTimeZone;
+                    if (timeZone == null)
+                    {
+                        timeZone = CreateLocal();
+                    }
+                    return timeZone;
+                }
+            }
+
+            /// <summary>
+            /// Helper function that returns the corresponding DateTimeKind for this TimeZoneInfo.
+            /// </summary>
+            public DateTimeKind GetCorrespondingKind(TimeZoneInfo timeZone)
+            {
+                // We check reference equality to see if 'this' is the same as
+                // TimeZoneInfo.Local or TimeZoneInfo.Utc.  This check is needed to
+                // support setting the DateTime Kind property to 'Local' or
+                // 'Utc' on the ConverTime(...) return value.
+                //
+                // Using reference equality instead of value equality was a
+                // performance based design compromise.  The reference equality
+                // has much greater performance, but it reduces the number of
+                // returned DateTime's that can be properly set as 'Local' or 'Utc'.
+                //
+                // For example, the user could be converting to the TimeZoneInfo returned
+                // by FindSystemTimeZoneById("Pacific Standard Time") and their local
+                // machine may be in Pacific time.  If we used value equality to determine
+                // the corresponding Kind then this conversion would be tagged as 'Local';
+                // where as we are currently tagging the returned DateTime as 'Unspecified'
+                // in this example.  Only when the user passes in TimeZoneInfo.Local or
+                // TimeZoneInfo.Utc to the ConvertTime(...) methods will this check succeed.
+                //
+                return
+                    ReferenceEquals(timeZone, s_utcTimeZone) ? DateTimeKind.Utc :
+                    ReferenceEquals(timeZone, _localTimeZone) ? DateTimeKind.Local :
+                    DateTimeKind.Unspecified;
+            }
+
+            public Dictionary<string, TimeZoneInfo> _systemTimeZones;
+            public ReadOnlyCollection<TimeZoneInfo> _readOnlySystemTimeZones;
+            public bool _allSystemTimeZonesRead;
+        };
+#pragma warning restore 0420
+
+        // used by GetUtcOffsetFromUtc (DateTime.Now, DateTime.ToLocalTime) for max/min whole-day range checks
+        private static readonly DateTime s_maxDateOnly = new DateTime(9999, 12, 31);
+        private static readonly DateTime s_minDateOnly = new DateTime(1, 1, 2);
+
+        public string Id => _id;
+
+        public string DisplayName => _displayName ?? string.Empty;
+
+        public string StandardName => _standardDisplayName ?? string.Empty;
+
+        public string DaylightName => _daylightDisplayName ?? string.Empty;
+
+        public TimeSpan BaseUtcOffset => _baseUtcOffset;
+
+        public bool SupportsDaylightSavingTime => _supportsDaylightSavingTime;
+
+        /// <summary>
+        /// Returns an array of TimeSpan objects representing all of
+        /// possible UTC offset values for this ambiguous time.
+        /// </summary>
+        public TimeSpan[] GetAmbiguousTimeOffsets(DateTimeOffset dateTimeOffset)
+        {
+            if (!SupportsDaylightSavingTime)
+            {
+                throw new ArgumentException(SR.Argument_DateTimeOffsetIsNotAmbiguous, nameof(dateTimeOffset));
+            }
+
+            DateTime adjustedTime = ConvertTime(dateTimeOffset, this).DateTime;
+
+            bool isAmbiguous = false;
+            int? ruleIndex;
+            AdjustmentRule rule = GetAdjustmentRuleForAmbiguousOffsets(adjustedTime, out ruleIndex);
+            if (rule != null && rule.HasDaylightSaving)
+            {
+                DaylightTimeStruct daylightTime = GetDaylightTime(adjustedTime.Year, rule, ruleIndex);
+                isAmbiguous = GetIsAmbiguousTime(adjustedTime, rule, daylightTime);
+            }
+
+            if (!isAmbiguous)
+            {
+                throw new ArgumentException(SR.Argument_DateTimeOffsetIsNotAmbiguous, nameof(dateTimeOffset));
+            }
+
+            // the passed in dateTime is ambiguous in this TimeZoneInfo instance
+            TimeSpan[] timeSpans = new TimeSpan[2];
+
+            TimeSpan actualUtcOffset = _baseUtcOffset + rule.BaseUtcOffsetDelta;
+
+            // the TimeSpan array must be sorted from least to greatest
+            if (rule.DaylightDelta > TimeSpan.Zero)
+            {
+                timeSpans[0] = actualUtcOffset; // FUTURE:  + rule.StandardDelta;
+                timeSpans[1] = actualUtcOffset + rule.DaylightDelta;
+            }
+            else
+            {
+                timeSpans[0] = actualUtcOffset + rule.DaylightDelta;
+                timeSpans[1] = actualUtcOffset; // FUTURE: + rule.StandardDelta;
+            }
+            return timeSpans;
+        }
+
+        /// <summary>
+        /// Returns an array of TimeSpan objects representing all of
+        /// possible UTC offset values for this ambiguous time.
+        /// </summary>
+        public TimeSpan[] GetAmbiguousTimeOffsets(DateTime dateTime)
+        {
+            if (!SupportsDaylightSavingTime)
+            {
+                throw new ArgumentException(SR.Argument_DateTimeIsNotAmbiguous, nameof(dateTime));
+            }
+
+            DateTime adjustedTime;
+            if (dateTime.Kind == DateTimeKind.Local)
+            {
+                CachedData cachedData = s_cachedData;
+                adjustedTime = ConvertTime(dateTime, cachedData.Local, this, TimeZoneInfoOptions.None, cachedData);
+            }
+            else if (dateTime.Kind == DateTimeKind.Utc)
+            {
+                CachedData cachedData = s_cachedData;
+                adjustedTime = ConvertTime(dateTime, s_utcTimeZone, this, TimeZoneInfoOptions.None, cachedData);
+            }
+            else
+            {
+                adjustedTime = dateTime;
+            }
+
+            bool isAmbiguous = false;
+            int? ruleIndex;
+            AdjustmentRule rule = GetAdjustmentRuleForAmbiguousOffsets(adjustedTime, out ruleIndex);
+            if (rule != null && rule.HasDaylightSaving)
+            {
+                DaylightTimeStruct daylightTime = GetDaylightTime(adjustedTime.Year, rule, ruleIndex);
+                isAmbiguous = GetIsAmbiguousTime(adjustedTime, rule, daylightTime);
+            }
+
+            if (!isAmbiguous)
+            {
+                throw new ArgumentException(SR.Argument_DateTimeIsNotAmbiguous, nameof(dateTime));
+            }
+
+            // the passed in dateTime is ambiguous in this TimeZoneInfo instance
+            TimeSpan[] timeSpans = new TimeSpan[2];
+            TimeSpan actualUtcOffset = _baseUtcOffset + rule.BaseUtcOffsetDelta;
+
+            // the TimeSpan array must be sorted from least to greatest
+            if (rule.DaylightDelta > TimeSpan.Zero)
+            {
+                timeSpans[0] = actualUtcOffset; // FUTURE:  + rule.StandardDelta;
+                timeSpans[1] = actualUtcOffset + rule.DaylightDelta;
+            }
+            else
+            {
+                timeSpans[0] = actualUtcOffset + rule.DaylightDelta;
+                timeSpans[1] = actualUtcOffset; // FUTURE: + rule.StandardDelta;
+            }
+            return timeSpans;
+        }
+
+        // note the time is already adjusted
+        private AdjustmentRule GetAdjustmentRuleForAmbiguousOffsets(DateTime adjustedTime, out int? ruleIndex)
+        {
+            AdjustmentRule rule = GetAdjustmentRuleForTime(adjustedTime, out ruleIndex);
+            if (rule != null && rule.NoDaylightTransitions && !rule.HasDaylightSaving)
+            {
+                // When using NoDaylightTransitions rules, each rule is only for one offset.
+                // When looking for the Daylight savings rules, and we found the non-DST rule,
+                // then we get the rule right before this rule.
+                return GetPreviousAdjustmentRule(rule, ruleIndex);
+            }
+
+            return rule;
+        }
+
+        /// <summary>
+        /// Gets the AdjustmentRule that is immediately preceding the specified rule.
+        /// If the specified rule is the first AdjustmentRule, or it isn't in _adjustmentRules,
+        /// then the specified rule is returned.
+        /// </summary>
+        private AdjustmentRule GetPreviousAdjustmentRule(AdjustmentRule rule, int? ruleIndex)
+        {
+            Debug.Assert(rule.NoDaylightTransitions, "GetPreviousAdjustmentRule should only be used with NoDaylightTransitions rules.");
+
+            if (ruleIndex.HasValue && 0 < ruleIndex.Value && ruleIndex.Value < _adjustmentRules.Length)
+            {
+                return _adjustmentRules[ruleIndex.Value - 1];
+            }
+
+            AdjustmentRule result = rule;
+            for (int i = 1; i < _adjustmentRules.Length; i++)
+            {
+                // use ReferenceEquals here instead of AdjustmentRule.Equals because 
+                // ReferenceEquals is much faster. This is safe because all the callers
+                // of GetPreviousAdjustmentRule pass in a rule that was retrieved from
+                // _adjustmentRules.  A different approach will be needed if this ever changes.
+                if (ReferenceEquals(rule, _adjustmentRules[i]))
+                {
+                    result = _adjustmentRules[i - 1];
+                    break;
+                }
+            }
+            return result;
+        }
+
+        /// <summary>
+        /// Returns the Universal Coordinated Time (UTC) Offset for the current TimeZoneInfo instance.
+        /// </summary>
+        public TimeSpan GetUtcOffset(DateTimeOffset dateTimeOffset) =>
+            GetUtcOffsetFromUtc(dateTimeOffset.UtcDateTime, this);
+
+        /// <summary>
+        /// Returns the Universal Coordinated Time (UTC) Offset for the current TimeZoneInfo instance.
+        /// </summary>
+        public TimeSpan GetUtcOffset(DateTime dateTime) =>
+            GetUtcOffset(dateTime, TimeZoneInfoOptions.NoThrowOnInvalidTime, s_cachedData);
+
+        // Shortcut for TimeZoneInfo.Local.GetUtcOffset
+        internal static TimeSpan GetLocalUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags)
+        {
+            CachedData cachedData = s_cachedData;
+            return cachedData.Local.GetUtcOffset(dateTime, flags, cachedData);
+        }
+
+        /// <summary>
+        /// Returns the Universal Coordinated Time (UTC) Offset for the current TimeZoneInfo instance.
+        /// </summary>
+        internal TimeSpan GetUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags) =>
+            GetUtcOffset(dateTime, flags, s_cachedData);
+
+        private TimeSpan GetUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags, CachedData cachedData)
+        {
+            if (dateTime.Kind == DateTimeKind.Local)
+            {
+                if (cachedData.GetCorrespondingKind(this) != DateTimeKind.Local)
+                {
+                    //
+                    // normal case of converting from Local to Utc and then getting the offset from the UTC DateTime
+                    //
+                    DateTime adjustedTime = ConvertTime(dateTime, cachedData.Local, s_utcTimeZone, flags);
+                    return GetUtcOffsetFromUtc(adjustedTime, this);
+                }
+
+                //
+                // Fall through for TimeZoneInfo.Local.GetUtcOffset(date)
+                // to handle an edge case with Invalid-Times for DateTime formatting:
+                //
+                // Consider the invalid PST time "2007-03-11T02:00:00.0000000-08:00"
+                //
+                // By directly calling GetUtcOffset instead of converting to UTC and then calling GetUtcOffsetFromUtc
+                // the correct invalid offset of "-08:00" is returned.  In the normal case of converting to UTC as an
+                // interim-step, the invalid time is adjusted into a *valid* UTC time which causes a change in output:
+                //
+                // 1) invalid PST time "2007-03-11T02:00:00.0000000-08:00"
+                // 2) converted to UTC "2007-03-11T10:00:00.0000000Z"
+                // 3) offset returned  "2007-03-11T03:00:00.0000000-07:00"
+                //
+            }
+            else if (dateTime.Kind == DateTimeKind.Utc)
+            {
+                if (cachedData.GetCorrespondingKind(this) == DateTimeKind.Utc)
+                {
+                    return _baseUtcOffset;
+                }
+                else
+                {
+                    //
+                    // passing in a UTC dateTime to a non-UTC TimeZoneInfo instance is a
+                    // special Loss-Less case.
+                    //
+                    return GetUtcOffsetFromUtc(dateTime, this);
+                }
+            }
+
+            return GetUtcOffset(dateTime, this, flags);
+        }
+
+        /// <summary>
+        /// Returns true if the time is during the ambiguous time period
+        /// for the current TimeZoneInfo instance.
+        /// </summary>
+        public bool IsAmbiguousTime(DateTimeOffset dateTimeOffset)
+        {
+            if (!_supportsDaylightSavingTime)
+            {
+                return false;
+            }
+
+            DateTimeOffset adjustedTime = ConvertTime(dateTimeOffset, this);
+            return IsAmbiguousTime(adjustedTime.DateTime);
+        }
+
+        /// <summary>
+        /// Returns true if the time is during the ambiguous time period
+        /// for the current TimeZoneInfo instance.
+        /// </summary>
+        public bool IsAmbiguousTime(DateTime dateTime) =>
+            IsAmbiguousTime(dateTime, TimeZoneInfoOptions.NoThrowOnInvalidTime);
+
+        /// <summary>
+        /// Returns true if the time is during the ambiguous time period
+        /// for the current TimeZoneInfo instance.
+        /// </summary>
+        internal bool IsAmbiguousTime(DateTime dateTime, TimeZoneInfoOptions flags)
+        {
+            if (!_supportsDaylightSavingTime)
+            {
+                return false;
+            }
+
+            CachedData cachedData = s_cachedData;
+            DateTime adjustedTime =
+                dateTime.Kind == DateTimeKind.Local ? ConvertTime(dateTime, cachedData.Local, this, flags, cachedData) :
+                dateTime.Kind == DateTimeKind.Utc ? ConvertTime(dateTime, s_utcTimeZone, this, flags, cachedData) :
+                dateTime;
+
+            int? ruleIndex;
+            AdjustmentRule rule = GetAdjustmentRuleForTime(adjustedTime, out ruleIndex);
+            if (rule != null && rule.HasDaylightSaving)
+            {
+                DaylightTimeStruct daylightTime = GetDaylightTime(adjustedTime.Year, rule, ruleIndex);
+                return GetIsAmbiguousTime(adjustedTime, rule, daylightTime);
+            }
+            return false;
+        }
+
+        /// <summary>
+        /// Returns true if the time is during Daylight Saving time for the current TimeZoneInfo instance.
+        /// </summary>
+        public bool IsDaylightSavingTime(DateTimeOffset dateTimeOffset)
+        {
+            bool isDaylightSavingTime;
+            GetUtcOffsetFromUtc(dateTimeOffset.UtcDateTime, this, out isDaylightSavingTime);
+            return isDaylightSavingTime;
+        }
+
+        /// <summary>
+        /// Returns true if the time is during Daylight Saving time for the current TimeZoneInfo instance.
+        /// </summary>
+        public bool IsDaylightSavingTime(DateTime dateTime) =>
+            IsDaylightSavingTime(dateTime, TimeZoneInfoOptions.NoThrowOnInvalidTime, s_cachedData);
+
+        /// <summary>
+        /// Returns true if the time is during Daylight Saving time for the current TimeZoneInfo instance.
+        /// </summary>
+        internal bool IsDaylightSavingTime(DateTime dateTime, TimeZoneInfoOptions flags) =>
+            IsDaylightSavingTime(dateTime, flags, s_cachedData);
+
+        private bool IsDaylightSavingTime(DateTime dateTime, TimeZoneInfoOptions flags, CachedData cachedData)
+        {
+            //
+            //    dateTime.Kind is UTC, then time will be converted from UTC
+            //        into current instance's timezone
+            //    dateTime.Kind is Local, then time will be converted from Local
+            //        into current instance's timezone
+            //    dateTime.Kind is UnSpecified, then time is already in
+            //        current instance's timezone
+            //
+            // Our DateTime handles ambiguous times, (one is in the daylight and
+            // one is in standard.) If a new DateTime is constructed during ambiguous
+            // time, it is defaulted to "Standard" (i.e. this will return false).
+            // For Invalid times, we will return false
+
+            if (!_supportsDaylightSavingTime || _adjustmentRules == null)
+            {
+                return false;
+            }
+
+            DateTime adjustedTime;
+            //
+            // handle any Local/Utc special cases...
+            //
+            if (dateTime.Kind == DateTimeKind.Local)
+            {
+                adjustedTime = ConvertTime(dateTime, cachedData.Local, this, flags, cachedData);
+            }
+            else if (dateTime.Kind == DateTimeKind.Utc)
+            {
+                if (cachedData.GetCorrespondingKind(this) == DateTimeKind.Utc)
+                {
+                    // simple always false case: TimeZoneInfo.Utc.IsDaylightSavingTime(dateTime, flags);
+                    return false;
+                }
+                else
+                {
+                    //
+                    // passing in a UTC dateTime to a non-UTC TimeZoneInfo instance is a
+                    // special Loss-Less case.
+                    //
+                    bool isDaylightSavings;
+                    GetUtcOffsetFromUtc(dateTime, this, out isDaylightSavings);
+                    return isDaylightSavings;
+                }
+            }
+            else
+            {
+                adjustedTime = dateTime;
+            }
+
+            //
+            // handle the normal cases...
+            //
+            int? ruleIndex;
+            AdjustmentRule rule = GetAdjustmentRuleForTime(adjustedTime, out ruleIndex);
+            if (rule != null && rule.HasDaylightSaving)
+            {
+                DaylightTimeStruct daylightTime = GetDaylightTime(adjustedTime.Year, rule, ruleIndex);
+                return GetIsDaylightSavings(adjustedTime, rule, daylightTime, flags);
+            }
+            else
+            {
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// Returns true when dateTime falls into a "hole in time".
+        /// </summary>
+        public bool IsInvalidTime(DateTime dateTime)
+        {
+            bool isInvalid = false;
+
+            if ((dateTime.Kind == DateTimeKind.Unspecified) ||
+                (dateTime.Kind == DateTimeKind.Local && s_cachedData.GetCorrespondingKind(this) == DateTimeKind.Local))
+            {
+                // only check Unspecified and (Local when this TimeZoneInfo instance is Local)
+                int? ruleIndex;
+                AdjustmentRule rule = GetAdjustmentRuleForTime(dateTime, out ruleIndex);
+
+                if (rule != null && rule.HasDaylightSaving)
+                {
+                    DaylightTimeStruct daylightTime = GetDaylightTime(dateTime.Year, rule, ruleIndex);
+                    isInvalid = GetIsInvalidTime(dateTime, rule, daylightTime);
+                }
+                else
+                {
+                    isInvalid = false;
+                }
+            }
+
+            return isInvalid;
+        }
+
+        /// <summary>
+        /// Clears data from static members.
+        /// </summary>
+        public static void ClearCachedData()
+        {
+            // Clear a fresh instance of cached data
+            s_cachedData = new CachedData();
+        }
+
+        /// <summary>
+        /// Converts the value of a DateTime object from sourceTimeZone to destinationTimeZone.
+        /// </summary>
+        public static DateTimeOffset ConvertTimeBySystemTimeZoneId(DateTimeOffset dateTimeOffset, string destinationTimeZoneId) =>
+            ConvertTime(dateTimeOffset, FindSystemTimeZoneById(destinationTimeZoneId));
+
+        /// <summary>
+        /// Converts the value of a DateTime object from sourceTimeZone to destinationTimeZone.
+        /// </summary>
+        public static DateTime ConvertTimeBySystemTimeZoneId(DateTime dateTime, string destinationTimeZoneId) =>
+            ConvertTime(dateTime, FindSystemTimeZoneById(destinationTimeZoneId));
+
+        /// <summary>
+        /// Converts the value of a DateTime object from sourceTimeZone to destinationTimeZone.
+        /// </summary>
+        public static DateTime ConvertTimeBySystemTimeZoneId(DateTime dateTime, string sourceTimeZoneId, string destinationTimeZoneId)
+        {
+            if (dateTime.Kind == DateTimeKind.Local && string.Equals(sourceTimeZoneId, Local.Id, StringComparison.OrdinalIgnoreCase))
+            {
+                // TimeZoneInfo.Local can be cleared by another thread calling TimeZoneInfo.ClearCachedData.
+                // Take snapshot of cached data to guarantee this method will not be impacted by the ClearCachedData call.
+                // Without the snapshot, there is a chance that ConvertTime will throw since 'source' won't
+                // be reference equal to the new TimeZoneInfo.Local
+                //
+                CachedData cachedData = s_cachedData;
+                return ConvertTime(dateTime, cachedData.Local, FindSystemTimeZoneById(destinationTimeZoneId), TimeZoneInfoOptions.None, cachedData);
+            }
+            else if (dateTime.Kind == DateTimeKind.Utc && string.Equals(sourceTimeZoneId, Utc.Id, StringComparison.OrdinalIgnoreCase))
+            {
+                return ConvertTime(dateTime, s_utcTimeZone, FindSystemTimeZoneById(destinationTimeZoneId), TimeZoneInfoOptions.None, s_cachedData);
+            }
+            else
+            {
+                return ConvertTime(dateTime, FindSystemTimeZoneById(sourceTimeZoneId), FindSystemTimeZoneById(destinationTimeZoneId));
+            }
+        }
+
+        /// <summary>
+        /// Converts the value of the dateTime object from sourceTimeZone to destinationTimeZone
+        /// </summary>
+        public static DateTimeOffset ConvertTime(DateTimeOffset dateTimeOffset, TimeZoneInfo destinationTimeZone)
+        {
+            if (destinationTimeZone == null)
+            {
+                throw new ArgumentNullException(nameof(destinationTimeZone));
+            }
+
+            // calculate the destination time zone offset
+            DateTime utcDateTime = dateTimeOffset.UtcDateTime;
+            TimeSpan destinationOffset = GetUtcOffsetFromUtc(utcDateTime, destinationTimeZone);
+
+            // check for overflow
+            long ticks = utcDateTime.Ticks + destinationOffset.Ticks;
+
+            return
+                ticks > DateTimeOffset.MaxValue.Ticks ? DateTimeOffset.MaxValue :
+                ticks < DateTimeOffset.MinValue.Ticks ? DateTimeOffset.MinValue :
+                new DateTimeOffset(ticks, destinationOffset);
+        }
+
+        /// <summary>
+        /// Converts the value of the dateTime object from sourceTimeZone to destinationTimeZone
+        /// </summary>
+        public static DateTime ConvertTime(DateTime dateTime, TimeZoneInfo destinationTimeZone)
+        {
+            if (destinationTimeZone == null)
+            {
+                throw new ArgumentNullException(nameof(destinationTimeZone));
+            }
+
+            // Special case to give a way clearing the cache without exposing ClearCachedData()
+            if (dateTime.Ticks == 0)
+            {
+                ClearCachedData();
+            }
+            CachedData cachedData = s_cachedData;
+            TimeZoneInfo sourceTimeZone = dateTime.Kind == DateTimeKind.Utc ? s_utcTimeZone : cachedData.Local;
+            return ConvertTime(dateTime, sourceTimeZone, destinationTimeZone, TimeZoneInfoOptions.None, cachedData);
+        }
+
+        /// <summary>
+        /// Converts the value of the dateTime object from sourceTimeZone to destinationTimeZone
+        /// </summary>
+        public static DateTime ConvertTime(DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone) =>
+            ConvertTime(dateTime, sourceTimeZone, destinationTimeZone, TimeZoneInfoOptions.None, s_cachedData);
+
+        /// <summary>
+        /// Converts the value of the dateTime object from sourceTimeZone to destinationTimeZone
+        /// </summary>
+        internal static DateTime ConvertTime(DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone, TimeZoneInfoOptions flags) =>
+            ConvertTime(dateTime, sourceTimeZone, destinationTimeZone, flags, s_cachedData);
+
+        private static DateTime ConvertTime(DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone, TimeZoneInfoOptions flags, CachedData cachedData)
+        {
+            if (sourceTimeZone == null)
+            {
+                throw new ArgumentNullException(nameof(sourceTimeZone));
+            }
+
+            if (destinationTimeZone == null)
+            {
+                throw new ArgumentNullException(nameof(destinationTimeZone));
+            }
+
+            DateTimeKind sourceKind = cachedData.GetCorrespondingKind(sourceTimeZone);
+            if (((flags & TimeZoneInfoOptions.NoThrowOnInvalidTime) == 0) && (dateTime.Kind != DateTimeKind.Unspecified) && (dateTime.Kind != sourceKind))
+            {
+                throw new ArgumentException(SR.Argument_ConvertMismatch, nameof(sourceTimeZone));
+            }
+
+            //
+            // check to see if the DateTime is in an invalid time range.  This check
+            // requires the current AdjustmentRule and DaylightTime - which are also
+            // needed to calculate 'sourceOffset' in the normal conversion case.
+            // By calculating the 'sourceOffset' here we improve the
+            // performance for the normal case at the expense of the 'ArgumentException'
+            // case and Loss-less Local special cases.
+            //
+            int? sourceRuleIndex;
+            AdjustmentRule sourceRule = sourceTimeZone.GetAdjustmentRuleForTime(dateTime, out sourceRuleIndex);
+            TimeSpan sourceOffset = sourceTimeZone.BaseUtcOffset;
+
+            if (sourceRule != null)
+            {
+                sourceOffset = sourceOffset + sourceRule.BaseUtcOffsetDelta;
+                if (sourceRule.HasDaylightSaving)
+                {
+                    bool sourceIsDaylightSavings = false;
+                    DaylightTimeStruct sourceDaylightTime = sourceTimeZone.GetDaylightTime(dateTime.Year, sourceRule, sourceRuleIndex);
+
+                    // 'dateTime' might be in an invalid time range since it is in an AdjustmentRule
+                    // period that supports DST
+                    if (((flags & TimeZoneInfoOptions.NoThrowOnInvalidTime) == 0) && GetIsInvalidTime(dateTime, sourceRule, sourceDaylightTime))
+                    {
+                        throw new ArgumentException(SR.Argument_DateTimeIsInvalid, nameof(dateTime));
+                    }
+                    sourceIsDaylightSavings = GetIsDaylightSavings(dateTime, sourceRule, sourceDaylightTime, flags);
+
+                    // adjust the sourceOffset according to the Adjustment Rule / Daylight Saving Rule
+                    sourceOffset += (sourceIsDaylightSavings ? sourceRule.DaylightDelta : TimeSpan.Zero /*FUTURE: sourceRule.StandardDelta*/);
+                }
+            }
+
+            DateTimeKind targetKind = cachedData.GetCorrespondingKind(destinationTimeZone);
+
+            // handle the special case of Loss-less Local->Local and UTC->UTC)
+            if (dateTime.Kind != DateTimeKind.Unspecified && sourceKind != DateTimeKind.Unspecified && sourceKind == targetKind)
+            {
+                return dateTime;
+            }
+
+            long utcTicks = dateTime.Ticks - sourceOffset.Ticks;
+
+            // handle the normal case by converting from 'source' to UTC and then to 'target'
+            bool isAmbiguousLocalDst;
+            DateTime targetConverted = ConvertUtcToTimeZone(utcTicks, destinationTimeZone, out isAmbiguousLocalDst);
+
+            if (targetKind == DateTimeKind.Local)
+            {
+                // Because the ticks conversion between UTC and local is lossy, we need to capture whether the
+                // time is in a repeated hour so that it can be passed to the DateTime constructor.
+                return new DateTime(targetConverted.Ticks, DateTimeKind.Local, isAmbiguousLocalDst);
+            }
+            else
+            {
+                return new DateTime(targetConverted.Ticks, targetKind);
+            }
+        }
+
+        /// <summary>
+        /// Converts the value of a DateTime object from Coordinated Universal Time (UTC) to the destinationTimeZone.
+        /// </summary>
+        public static DateTime ConvertTimeFromUtc(DateTime dateTime, TimeZoneInfo destinationTimeZone) =>
+            ConvertTime(dateTime, s_utcTimeZone, destinationTimeZone, TimeZoneInfoOptions.None, s_cachedData);
+
+        /// <summary>
+        /// Converts the value of a DateTime object to Coordinated Universal Time (UTC).
+        /// </summary>
+        public static DateTime ConvertTimeToUtc(DateTime dateTime)
+        {
+            if (dateTime.Kind == DateTimeKind.Utc)
+            {
+                return dateTime;
+            }
+            CachedData cachedData = s_cachedData;
+            return ConvertTime(dateTime, cachedData.Local, s_utcTimeZone, TimeZoneInfoOptions.None, cachedData);
+        }
+
+        /// <summary>
+        /// Converts the value of a DateTime object to Coordinated Universal Time (UTC).
+        /// </summary>
+        internal static DateTime ConvertTimeToUtc(DateTime dateTime, TimeZoneInfoOptions flags)
+        {
+            if (dateTime.Kind == DateTimeKind.Utc)
+            {
+                return dateTime;
+            }
+            CachedData cachedData = s_cachedData;
+            return ConvertTime(dateTime, cachedData.Local, s_utcTimeZone, flags, cachedData);
+        }
+
+        /// <summary>
+        /// Converts the value of a DateTime object to Coordinated Universal Time (UTC).
+        /// </summary>
+        public static DateTime ConvertTimeToUtc(DateTime dateTime, TimeZoneInfo sourceTimeZone) =>
+            ConvertTime(dateTime, sourceTimeZone, s_utcTimeZone, TimeZoneInfoOptions.None, s_cachedData);
+
+        /// <summary>
+        /// Returns value equality. Equals does not compare any localizable
+        /// String objects (DisplayName, StandardName, DaylightName).
+        /// </summary>
+        public bool Equals(TimeZoneInfo other) =>
+            other != null &&
+            string.Equals(_id, other._id, StringComparison.OrdinalIgnoreCase) &&
+            HasSameRules(other);
+
+        public override bool Equals(object obj) => Equals(obj as TimeZoneInfo);
+
+        public static TimeZoneInfo FromSerializedString(string source)
+        {
+            if (source == null)
+            {
+                throw new ArgumentNullException(nameof(source));
+            }
+            if (source.Length == 0)
+            {
+                throw new ArgumentException(SR.Format(SR.Argument_InvalidSerializedString, source), nameof(source));
+            }
+
+            return StringSerializer.GetDeserializedTimeZoneInfo(source);
+        }
+
+        public override int GetHashCode() => StringComparer.OrdinalIgnoreCase.GetHashCode(_id);
+
+        /// <summary>
+        /// Returns a ReadOnlyCollection<TimeZoneInfo> containing all valid TimeZone's
+        /// from the local machine. The entries in the collection are sorted by
+        /// <see cref="DisplayName"/>.
+        /// This method does *not* throw TimeZoneNotFoundException or InvalidTimeZoneException.
+        /// </summary>
+        public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones()
+        {
+            CachedData cachedData = s_cachedData;
+
+            lock (cachedData)
+            {
+                if (cachedData._readOnlySystemTimeZones == null)
+                {
+                    PopulateAllSystemTimeZones(cachedData);
+                    cachedData._allSystemTimeZonesRead = true;
+
+                    List<TimeZoneInfo> list;
+                    if (cachedData._systemTimeZones != null)
+                    {
+                        // return a collection of the cached system time zones
+                        list = new List<TimeZoneInfo>(cachedData._systemTimeZones.Values);
+                    }
+                    else
+                    {
+                        // return an empty collection
+                        list = new List<TimeZoneInfo>();
+                    }
+
+                    // sort and copy the TimeZoneInfo's into a ReadOnlyCollection for the user
+                    list.Sort((x, y) =>
+                    {
+                        // sort by BaseUtcOffset first and by DisplayName second - this is similar to the Windows Date/Time control panel
+                        int comparison = x.BaseUtcOffset.CompareTo(y.BaseUtcOffset);
+                        return comparison == 0 ? string.CompareOrdinal(x.DisplayName, y.DisplayName) : comparison;
+                    });
+
+                    cachedData._readOnlySystemTimeZones = new ReadOnlyCollection<TimeZoneInfo>(list);
+                }
+            }
+            return cachedData._readOnlySystemTimeZones;
+        }
+
+        /// <summary>
+        /// Value equality on the "adjustmentRules" array
+        /// </summary>
+        public bool HasSameRules(TimeZoneInfo other)
+        {
+            if (other == null)
+            {
+                throw new ArgumentNullException(nameof(other));
+            }
+
+            // check the utcOffset and supportsDaylightSavingTime members
+            if (_baseUtcOffset != other._baseUtcOffset ||
+                _supportsDaylightSavingTime != other._supportsDaylightSavingTime)
+            {
+                return false;
+            }
+
+            bool sameRules;
+            AdjustmentRule[] currentRules = _adjustmentRules;
+            AdjustmentRule[] otherRules = other._adjustmentRules;
+
+            sameRules =
+                (currentRules == null && otherRules == null) ||
+                (currentRules != null && otherRules != null);
+
+            if (!sameRules)
+            {
+                // AdjustmentRule array mismatch
+                return false;
+            }
+
+            if (currentRules != null)
+            {
+                if (currentRules.Length != otherRules.Length)
+                {
+                    // AdjustmentRule array length mismatch
+                    return false;
+                }
+
+                for (int i = 0; i < currentRules.Length; i++)
+                {
+                    if (!(currentRules[i]).Equals(otherRules[i]))
+                    {
+                        // AdjustmentRule value-equality mismatch
+                        return false;
+                    }
+                }
+            }
+            return sameRules;
+        }
+
+        /// <summary>
+        /// Returns a TimeZoneInfo instance that represents the local time on the machine.
+        /// Accessing this property may throw InvalidTimeZoneException or COMException
+        /// if the machine is in an unstable or corrupt state.
+        /// </summary>
+        public static TimeZoneInfo Local => s_cachedData.Local;
+
+        //
+        // ToSerializedString -
+        //
+        // "TimeZoneInfo"           := TimeZoneInfo Data;[AdjustmentRule Data 1];...;[AdjustmentRule Data N]
+        //
+        // "TimeZoneInfo Data"      := <_id>;<_baseUtcOffset>;<_displayName>;
+        //                          <_standardDisplayName>;<_daylightDispayName>;
+        //
+        // "AdjustmentRule Data" := <DateStart>;<DateEnd>;<DaylightDelta>;
+        //                          [TransitionTime Data DST Start]
+        //                          [TransitionTime Data DST End]
+        //
+        // "TransitionTime Data" += <DaylightStartTimeOfDat>;<Month>;<Week>;<DayOfWeek>;<Day>
+        //
+        public string ToSerializedString() => StringSerializer.GetSerializedString(this);
+
+        /// <summary>
+        /// Returns the <see cref="DisplayName"/>: "(GMT-08:00) Pacific Time (US &amp; Canada); Tijuana"
+        /// </summary>
+        public override string ToString() => DisplayName;
+
+        /// <summary>
+        /// Returns a TimeZoneInfo instance that represents Universal Coordinated Time (UTC)
+        /// </summary>
+        public static TimeZoneInfo Utc => s_utcTimeZone;
+
+        private TimeZoneInfo(
+                string id,
+                TimeSpan baseUtcOffset,
+                string displayName,
+                string standardDisplayName,
+                string daylightDisplayName,
+                AdjustmentRule[] adjustmentRules,
+                bool disableDaylightSavingTime)
+        {
+            bool adjustmentRulesSupportDst;
+            ValidateTimeZoneInfo(id, baseUtcOffset, adjustmentRules, out adjustmentRulesSupportDst);
+
+            _id = id;
+            _baseUtcOffset = baseUtcOffset;
+            _displayName = displayName;
+            _standardDisplayName = standardDisplayName;
+            _daylightDisplayName = disableDaylightSavingTime ? null : daylightDisplayName;
+            _supportsDaylightSavingTime = adjustmentRulesSupportDst && !disableDaylightSavingTime;
+            _adjustmentRules = adjustmentRules;
+        }
+
+        /// <summary>
+        /// Returns a simple TimeZoneInfo instance that does not support Daylight Saving Time.
+        /// </summary>
+        public static TimeZoneInfo CreateCustomTimeZone(
+            string id,
+            TimeSpan baseUtcOffset,
+            string displayName,
+            string standardDisplayName)
+        {
+            return new TimeZoneInfo(
+                id,
+                baseUtcOffset,
+                displayName,
+                standardDisplayName,
+                standardDisplayName,
+                adjustmentRules: null,
+                disableDaylightSavingTime: false);
+        }
+
+        /// <summary>
+        /// Returns a TimeZoneInfo instance that may support Daylight Saving Time.
+        /// </summary>
+        public static TimeZoneInfo CreateCustomTimeZone(
+            string id,
+            TimeSpan baseUtcOffset,
+            string displayName,
+            string standardDisplayName,
+            string daylightDisplayName,
+            AdjustmentRule[] adjustmentRules)
+        {
+            return CreateCustomTimeZone(
+                id,
+                baseUtcOffset,
+                displayName,
+                standardDisplayName,
+                daylightDisplayName,
+                adjustmentRules,
+                disableDaylightSavingTime: false);
+        }
+
+        /// <summary>
+        /// Returns a TimeZoneInfo instance that may support Daylight Saving Time.
+        /// </summary>
+        public static TimeZoneInfo CreateCustomTimeZone(
+            string id,
+            TimeSpan baseUtcOffset,
+            string displayName,
+            string standardDisplayName,
+            string daylightDisplayName,
+            AdjustmentRule[] adjustmentRules,
+            bool disableDaylightSavingTime)
+        {
+            if (!disableDaylightSavingTime && adjustmentRules?.Length > 0)
+            {
+                adjustmentRules = (AdjustmentRule[])adjustmentRules.Clone();
+            }
+
+            return new TimeZoneInfo(
+                id,
+                baseUtcOffset,
+                displayName,
+                standardDisplayName,
+                daylightDisplayName,
+                adjustmentRules,
+                disableDaylightSavingTime);
+        }
+
+        void IDeserializationCallback.OnDeserialization(object sender)
+        {
+            try
+            {
+                bool adjustmentRulesSupportDst;
+                ValidateTimeZoneInfo(_id, _baseUtcOffset, _adjustmentRules, out adjustmentRulesSupportDst);
+
+                if (adjustmentRulesSupportDst != _supportsDaylightSavingTime)
+                {
+                    throw new SerializationException(SR.Format(SR.Serialization_CorruptField, "SupportsDaylightSavingTime"));
+                }
+            }
+            catch (ArgumentException e)
+            {
+                throw new SerializationException(SR.Serialization_InvalidData, e);
+            }
+            catch (InvalidTimeZoneException e)
+            {
+                throw new SerializationException(SR.Serialization_InvalidData, e);
+            }
+        }
+
+        void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+
+            info.AddValue("Id", _id); // Do not rename (binary serialization)
+            info.AddValue("DisplayName", _displayName); // Do not rename (binary serialization)
+            info.AddValue("StandardName", _standardDisplayName); // Do not rename (binary serialization)
+            info.AddValue("DaylightName", _daylightDisplayName); // Do not rename (binary serialization)
+            info.AddValue("BaseUtcOffset", _baseUtcOffset); // Do not rename (binary serialization)
+            info.AddValue("AdjustmentRules", _adjustmentRules); // Do not rename (binary serialization)
+            info.AddValue("SupportsDaylightSavingTime", _supportsDaylightSavingTime); // Do not rename (binary serialization)
+        }
+
+        private TimeZoneInfo(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+
+            _id = (string)info.GetValue("Id", typeof(string)); // Do not rename (binary serialization)
+            _displayName = (string)info.GetValue("DisplayName", typeof(string)); // Do not rename (binary serialization)
+            _standardDisplayName = (string)info.GetValue("StandardName", typeof(string)); // Do not rename (binary serialization)
+            _daylightDisplayName = (string)info.GetValue("DaylightName", typeof(string)); // Do not rename (binary serialization)
+            _baseUtcOffset = (TimeSpan)info.GetValue("BaseUtcOffset", typeof(TimeSpan)); // Do not rename (binary serialization)
+            _adjustmentRules = (AdjustmentRule[])info.GetValue("AdjustmentRules", typeof(AdjustmentRule[])); // Do not rename (binary serialization)
+            _supportsDaylightSavingTime = (bool)info.GetValue("SupportsDaylightSavingTime", typeof(bool)); // Do not rename (binary serialization)
+        }
+
+        private AdjustmentRule GetAdjustmentRuleForTime(DateTime dateTime, out int? ruleIndex)
+        {
+            AdjustmentRule result = GetAdjustmentRuleForTime(dateTime, dateTimeisUtc: false, ruleIndex: out ruleIndex);
+            Debug.Assert(result == null || ruleIndex.HasValue, "If an AdjustmentRule was found, ruleIndex should also be set.");
+
+            return result;
+        }
+        
+        private AdjustmentRule GetAdjustmentRuleForTime(DateTime dateTime, bool dateTimeisUtc, out int? ruleIndex)
+        {
+            if (_adjustmentRules == null || _adjustmentRules.Length == 0)
+            {
+                ruleIndex = null;
+                return null;
+            }
+
+            // Only check the whole-date portion of the dateTime for DateTimeKind.Unspecified rules -
+            // This is because the AdjustmentRule DateStart & DateEnd are stored as
+            // Date-only values {4/2/2006 - 10/28/2006} but actually represent the
+            // time span {4/2/2006@00:00:00.00000 - 10/28/2006@23:59:59.99999}
+            DateTime date = dateTimeisUtc ?
+                (dateTime + BaseUtcOffset).Date :
+                dateTime.Date;
+
+            int low = 0;
+            int high = _adjustmentRules.Length - 1;
+
+            while (low <= high)
+            {
+                int median = low + ((high - low) >> 1);
+
+                AdjustmentRule rule = _adjustmentRules[median];
+                AdjustmentRule previousRule = median > 0 ? _adjustmentRules[median - 1] : rule;
+
+                int compareResult = CompareAdjustmentRuleToDateTime(rule, previousRule, dateTime, date, dateTimeisUtc);
+                if (compareResult == 0)
+                {
+                    ruleIndex = median;
+                    return rule;
+                }
+                else if (compareResult < 0)
+                {
+                    low = median + 1;
+                }
+                else
+                {
+                    high = median - 1;
+                }
+            }
+
+            ruleIndex = null;
+            return null;
+        }
+
+        /// <summary>
+        /// Determines if 'rule' is the correct AdjustmentRule for the given dateTime.
+        /// </summary>
+        /// <returns>
+        /// A value less than zero if rule is for times before dateTime.
+        /// Zero if rule is correct for dateTime.
+        /// A value greater than zero if rule is for times after dateTime.
+        /// </returns>
+        private int CompareAdjustmentRuleToDateTime(AdjustmentRule rule, AdjustmentRule previousRule,
+            DateTime dateTime, DateTime dateOnly, bool dateTimeisUtc)
+        {
+            bool isAfterStart;
+            if (rule.DateStart.Kind == DateTimeKind.Utc)
+            {
+                DateTime dateTimeToCompare = dateTimeisUtc ?
+                    dateTime :
+                    // use the previous rule to compute the dateTimeToCompare, since the time daylight savings "switches"
+                    // is based on the previous rule's offset
+                    ConvertToUtc(dateTime, previousRule.DaylightDelta, previousRule.BaseUtcOffsetDelta);
+
+                isAfterStart = dateTimeToCompare >= rule.DateStart;
+            }
+            else
+            {
+                // if the rule's DateStart is Unspecified, then use the whole-date portion
+                isAfterStart = dateOnly >= rule.DateStart;
+            }
+
+            if (!isAfterStart)
+            {
+                return 1;
+            }
+
+            bool isBeforeEnd;
+            if (rule.DateEnd.Kind == DateTimeKind.Utc)
+            {
+                DateTime dateTimeToCompare = dateTimeisUtc ?
+                    dateTime :
+                    ConvertToUtc(dateTime, rule.DaylightDelta, rule.BaseUtcOffsetDelta);
+
+                isBeforeEnd = dateTimeToCompare <= rule.DateEnd;
+            }
+            else
+            {
+                // if the rule's DateEnd is Unspecified, then use the whole-date portion
+                isBeforeEnd = dateOnly <= rule.DateEnd;
+            }
+
+            return isBeforeEnd ? 0 : -1;
+        }
+
+        /// <summary>
+        /// Converts the dateTime to UTC using the specified deltas.
+        /// </summary>
+        private DateTime ConvertToUtc(DateTime dateTime, TimeSpan daylightDelta, TimeSpan baseUtcOffsetDelta) =>
+            ConvertToFromUtc(dateTime, daylightDelta, baseUtcOffsetDelta, convertToUtc: true);
+
+        /// <summary>
+        /// Converts the dateTime from UTC using the specified deltas.
+        /// </summary>
+        private DateTime ConvertFromUtc(DateTime dateTime, TimeSpan daylightDelta, TimeSpan baseUtcOffsetDelta) =>
+            ConvertToFromUtc(dateTime, daylightDelta, baseUtcOffsetDelta, convertToUtc: false);
+
+        /// <summary>
+        /// Converts the dateTime to or from UTC using the specified deltas.
+        /// </summary>
+        private DateTime ConvertToFromUtc(DateTime dateTime, TimeSpan daylightDelta, TimeSpan baseUtcOffsetDelta, bool convertToUtc)
+        {
+            TimeSpan offset = BaseUtcOffset + daylightDelta + baseUtcOffsetDelta;
+            if (convertToUtc)
+            {
+                offset = offset.Negate();
+            }
+
+            long ticks = dateTime.Ticks + offset.Ticks;
+
+            return
+                ticks > DateTime.MaxValue.Ticks ? DateTime.MaxValue :
+                ticks < DateTime.MinValue.Ticks ? DateTime.MinValue :
+                new DateTime(ticks);
+        }
+
+        /// <summary>
+        /// Helper function that converts a dateTime from UTC into the destinationTimeZone
+        /// - Returns DateTime.MaxValue when the converted value is too large.
+        /// - Returns DateTime.MinValue when the converted value is too small.
+        /// </summary>
+        private static DateTime ConvertUtcToTimeZone(long ticks, TimeZoneInfo destinationTimeZone, out bool isAmbiguousLocalDst)
+        {
+            // used to calculate the UTC offset in the destinationTimeZone
+            DateTime utcConverted =
+                ticks > DateTime.MaxValue.Ticks ? DateTime.MaxValue :
+                ticks < DateTime.MinValue.Ticks ? DateTime.MinValue :
+                new DateTime(ticks);
+
+            // verify the time is between MinValue and MaxValue in the new time zone
+            TimeSpan offset = GetUtcOffsetFromUtc(utcConverted, destinationTimeZone, out isAmbiguousLocalDst);
+            ticks += offset.Ticks;
+
+            return
+                ticks > DateTime.MaxValue.Ticks ? DateTime.MaxValue :
+                ticks < DateTime.MinValue.Ticks ? DateTime.MinValue :
+                new DateTime(ticks);
+        }
+
+        /// <summary>
+        /// Helper function that returns a DaylightTime from a year and AdjustmentRule.
+        /// </summary>
+        private DaylightTimeStruct GetDaylightTime(int year, AdjustmentRule rule, int? ruleIndex)
+        {
+            TimeSpan delta = rule.DaylightDelta;
+            DateTime startTime;
+            DateTime endTime;
+            if (rule.NoDaylightTransitions)
+            {
+                // NoDaylightTransitions rules don't use DaylightTransition Start and End, instead
+                // the DateStart and DateEnd are UTC times that represent when daylight savings time changes.
+                // Convert the UTC times into adjusted time zone times.
+
+                // use the previous rule to calculate the startTime, since the DST change happens w.r.t. the previous rule
+                AdjustmentRule previousRule = GetPreviousAdjustmentRule(rule, ruleIndex);
+                startTime = ConvertFromUtc(rule.DateStart, previousRule.DaylightDelta, previousRule.BaseUtcOffsetDelta);
+
+                endTime = ConvertFromUtc(rule.DateEnd, rule.DaylightDelta, rule.BaseUtcOffsetDelta);
+            }
+            else
+            {
+                startTime = TransitionTimeToDateTime(year, rule.DaylightTransitionStart);
+                endTime = TransitionTimeToDateTime(year, rule.DaylightTransitionEnd);
+            }
+            return new DaylightTimeStruct(startTime, endTime, delta);
+        }
+
+        /// <summary>
+        /// Helper function that checks if a given dateTime is in Daylight Saving Time (DST).
+        /// This function assumes the dateTime and AdjustmentRule are both in the same time zone.
+        /// </summary>
+        private static bool GetIsDaylightSavings(DateTime time, AdjustmentRule rule, DaylightTimeStruct daylightTime, TimeZoneInfoOptions flags)
+        {
+            if (rule == null)
+            {
+                return false;
+            }
+
+            DateTime startTime;
+            DateTime endTime;
+
+            if (time.Kind == DateTimeKind.Local)
+            {
+                // startTime and endTime represent the period from either the start of
+                // DST to the end and ***includes*** the potentially overlapped times
+                startTime = rule.IsStartDateMarkerForBeginningOfYear() ?
+                    new DateTime(daylightTime.Start.Year, 1, 1, 0, 0, 0) :
+                    daylightTime.Start + daylightTime.Delta;
+
+                endTime = rule.IsEndDateMarkerForEndOfYear() ?
+                    new DateTime(daylightTime.End.Year + 1, 1, 1, 0, 0, 0).AddTicks(-1) :
+                    daylightTime.End;
+            }
+            else
+            {
+                // startTime and endTime represent the period from either the start of DST to the end and
+                // ***does not include*** the potentially overlapped times
+                //
+                //         -=-=-=-=-=- Pacific Standard Time -=-=-=-=-=-=-
+                //    April 2, 2006                            October 29, 2006
+                // 2AM            3AM                        1AM              2AM
+                // |      +1 hr     |                        |       -1 hr      |
+                // | <invalid time> |                        | <ambiguous time> |
+                //                  [========== DST ========>)
+                //
+                //        -=-=-=-=-=- Some Weird Time Zone -=-=-=-=-=-=-
+                //    April 2, 2006                          October 29, 2006
+                // 1AM              2AM                    2AM              3AM
+                // |      -1 hr       |                      |       +1 hr      |
+                // | <ambiguous time> |                      |  <invalid time>  |
+                //                    [======== DST ========>)
+                //
+                bool invalidAtStart = rule.DaylightDelta > TimeSpan.Zero;
+
+                startTime = rule.IsStartDateMarkerForBeginningOfYear() ?
+                    new DateTime(daylightTime.Start.Year, 1, 1, 0, 0, 0) :
+                    daylightTime.Start + (invalidAtStart ? rule.DaylightDelta : TimeSpan.Zero); /* FUTURE: - rule.StandardDelta; */
+
+                endTime = rule.IsEndDateMarkerForEndOfYear() ?
+                    new DateTime(daylightTime.End.Year + 1, 1, 1, 0, 0, 0).AddTicks(-1) :
+                    daylightTime.End + (invalidAtStart ? -rule.DaylightDelta : TimeSpan.Zero);
+            }
+
+            bool isDst = CheckIsDst(startTime, time, endTime, false, rule);
+
+            // If this date was previously converted from a UTC date and we were able to detect that the local
+            // DateTime would be ambiguous, this data is stored in the DateTime to resolve this ambiguity.
+            if (isDst && time.Kind == DateTimeKind.Local)
+            {
+                // For normal time zones, the ambiguous hour is the last hour of daylight saving when you wind the
+                // clock back. It is theoretically possible to have a positive delta, (which would really be daylight
+                // reduction time), where you would have to wind the clock back in the begnning.
+                if (GetIsAmbiguousTime(time, rule, daylightTime))
+                {
+                    isDst = time.IsAmbiguousDaylightSavingTime();
+                }
+            }
+
+            return isDst;
+        }
+
+        /// <summary>
+        /// Gets the offset that should be used to calculate DST start times from a UTC time.
+        /// </summary>
+        private TimeSpan GetDaylightSavingsStartOffsetFromUtc(TimeSpan baseUtcOffset, AdjustmentRule rule, int? ruleIndex)
+        {
+            if (rule.NoDaylightTransitions)
+            {
+                // use the previous rule to calculate the startTime, since the DST change happens w.r.t. the previous rule
+                AdjustmentRule previousRule = GetPreviousAdjustmentRule(rule, ruleIndex);
+                return baseUtcOffset + previousRule.BaseUtcOffsetDelta + previousRule.DaylightDelta;
+            }
+            else
+            {
+                return baseUtcOffset + rule.BaseUtcOffsetDelta; /* FUTURE: + rule.StandardDelta; */
+            }
+        }
+
+        /// <summary>
+        /// Gets the offset that should be used to calculate DST end times from a UTC time.
+        /// </summary>
+        private TimeSpan GetDaylightSavingsEndOffsetFromUtc(TimeSpan baseUtcOffset, AdjustmentRule rule)
+        {
+            // NOTE: even NoDaylightTransitions rules use this logic since DST ends w.r.t. the current rule
+            return baseUtcOffset + rule.BaseUtcOffsetDelta + rule.DaylightDelta; /* FUTURE: + rule.StandardDelta; */
+        }
+
+        /// <summary>
+        /// Helper function that checks if a given dateTime is in Daylight Saving Time (DST).
+        /// This function assumes the dateTime is in UTC and AdjustmentRule is in a different time zone.
+        /// </summary>
+        private static bool GetIsDaylightSavingsFromUtc(DateTime time, int year, TimeSpan utc, AdjustmentRule rule, int? ruleIndex, out bool isAmbiguousLocalDst, TimeZoneInfo zone)
+        {
+            isAmbiguousLocalDst = false;
+
+            if (rule == null)
+            {
+                return false;
+            }
+
+            // Get the daylight changes for the year of the specified time.
+            DaylightTimeStruct daylightTime = zone.GetDaylightTime(year, rule, ruleIndex);
+
+            // The start and end times represent the range of universal times that are in DST for that year.
+            // Within that there is an ambiguous hour, usually right at the end, but at the beginning in
+            // the unusual case of a negative daylight savings delta.
+            // We need to handle the case if the current rule has daylight saving end by the end of year. If so, we need to check if next year starts with daylight saving on
+            // and get the actual daylight saving end time. Here is example for such case:
+            //      Converting the UTC datetime "12/31/2011 8:00:00 PM" to "(UTC+03:00) Moscow, St. Petersburg, Volgograd (RTZ 2)" zone.
+            //      In 2011 the daylight saving will go through the end of the year. If we use the end of 2011 as the daylight saving end,
+            //      that will fail the conversion because the UTC time +4 hours (3 hours for the zone UTC offset and 1 hour for daylight saving) will move us to the next year "1/1/2012 12:00 AM",
+            //      checking against the end of 2011 will tell we are not in daylight saving which is wrong and the conversion will be off by one hour.
+            // Note we handle the similar case when rule year start with daylight saving and previous year end with daylight saving.
+
+            bool ignoreYearAdjustment = false;
+            TimeSpan dstStartOffset = zone.GetDaylightSavingsStartOffsetFromUtc(utc, rule, ruleIndex);
+            DateTime startTime;
+            if (rule.IsStartDateMarkerForBeginningOfYear() && daylightTime.Start.Year > DateTime.MinValue.Year)
+            {
+                int? previousYearRuleIndex;
+                AdjustmentRule previousYearRule = zone.GetAdjustmentRuleForTime(
+                    new DateTime(daylightTime.Start.Year - 1, 12, 31),
+                    out previousYearRuleIndex);
+                if (previousYearRule != null && previousYearRule.IsEndDateMarkerForEndOfYear())
+                {
+                    DaylightTimeStruct previousDaylightTime = zone.GetDaylightTime(
+                        daylightTime.Start.Year - 1, 
+                        previousYearRule, 
+                        previousYearRuleIndex);
+                    startTime = previousDaylightTime.Start - utc - previousYearRule.BaseUtcOffsetDelta;
+                    ignoreYearAdjustment = true;
+                }
+                else
+                {
+                    startTime = new DateTime(daylightTime.Start.Year, 1, 1, 0, 0, 0) - dstStartOffset;
+                }
+            }
+            else
+            {
+                startTime = daylightTime.Start - dstStartOffset;
+            }
+
+            TimeSpan dstEndOffset = zone.GetDaylightSavingsEndOffsetFromUtc(utc, rule);
+            DateTime endTime;
+            if (rule.IsEndDateMarkerForEndOfYear() && daylightTime.End.Year < DateTime.MaxValue.Year)
+            {
+                int? nextYearRuleIndex;
+                AdjustmentRule nextYearRule = zone.GetAdjustmentRuleForTime(
+                    new DateTime(daylightTime.End.Year + 1, 1, 1),
+                    out nextYearRuleIndex);
+                if (nextYearRule != null && nextYearRule.IsStartDateMarkerForBeginningOfYear())
+                {
+                    if (nextYearRule.IsEndDateMarkerForEndOfYear())
+                    {
+                        // next year end with daylight saving on too
+                        endTime = new DateTime(daylightTime.End.Year + 1, 12, 31) - utc - nextYearRule.BaseUtcOffsetDelta - nextYearRule.DaylightDelta;
+                    }
+                    else
+                    {
+                        DaylightTimeStruct nextdaylightTime = zone.GetDaylightTime(
+                            daylightTime.End.Year + 1, 
+                            nextYearRule,
+                            nextYearRuleIndex);
+                        endTime = nextdaylightTime.End - utc - nextYearRule.BaseUtcOffsetDelta - nextYearRule.DaylightDelta;
+                    }
+                    ignoreYearAdjustment = true;
+                }
+                else
+                {
+                    endTime = new DateTime(daylightTime.End.Year + 1, 1, 1, 0, 0, 0).AddTicks(-1) - dstEndOffset;
+                }
+            }
+            else
+            {
+                endTime = daylightTime.End - dstEndOffset;
+            }
+
+            DateTime ambiguousStart;
+            DateTime ambiguousEnd;
+            if (daylightTime.Delta.Ticks > 0)
+            {
+                ambiguousStart = endTime - daylightTime.Delta;
+                ambiguousEnd = endTime;
+            }
+            else
+            {
+                ambiguousStart = startTime;
+                ambiguousEnd = startTime - daylightTime.Delta;
+            }
+
+            bool isDst = CheckIsDst(startTime, time, endTime, ignoreYearAdjustment, rule);
+
+            // See if the resulting local time becomes ambiguous. This must be captured here or the
+            // DateTime will not be able to round-trip back to UTC accurately.
+            if (isDst)
+            {
+                isAmbiguousLocalDst = (time >= ambiguousStart && time < ambiguousEnd);
+
+                if (!isAmbiguousLocalDst && ambiguousStart.Year != ambiguousEnd.Year)
+                {
+                    // there exists an extreme corner case where the start or end period is on a year boundary and
+                    // because of this the comparison above might have been performed for a year-early or a year-later
+                    // than it should have been.
+                    DateTime ambiguousStartModified;
+                    DateTime ambiguousEndModified;
+                    try
+                    {
+                        ambiguousStartModified = ambiguousStart.AddYears(1);
+                        ambiguousEndModified = ambiguousEnd.AddYears(1);
+                        isAmbiguousLocalDst = (time >= ambiguousStart && time < ambiguousEnd);
+                    }
+                    catch (ArgumentOutOfRangeException) { }
+
+                    if (!isAmbiguousLocalDst)
+                    {
+                        try
+                        {
+                            ambiguousStartModified = ambiguousStart.AddYears(-1);
+                            ambiguousEndModified = ambiguousEnd.AddYears(-1);
+                            isAmbiguousLocalDst = (time >= ambiguousStart && time < ambiguousEnd);
+                        }
+                        catch (ArgumentOutOfRangeException) { }
+                    }
+                }
+            }
+
+            return isDst;
+        }
+
+        private static bool CheckIsDst(DateTime startTime, DateTime time, DateTime endTime, bool ignoreYearAdjustment, AdjustmentRule rule)
+        {
+            // NoDaylightTransitions AdjustmentRules should never get their year adjusted since they adjust the offset for the
+            // entire time period - which may be for multiple years
+            if (!ignoreYearAdjustment && !rule.NoDaylightTransitions)
+            {
+                int startTimeYear = startTime.Year;
+                int endTimeYear = endTime.Year;
+
+                if (startTimeYear != endTimeYear)
+                {
+                    endTime = endTime.AddYears(startTimeYear - endTimeYear);
+                }
+
+                int timeYear = time.Year;
+
+                if (startTimeYear != timeYear)
+                {
+                    time = time.AddYears(startTimeYear - timeYear);
+                }
+            }
+
+            if (startTime > endTime)
+            {
+                // In southern hemisphere, the daylight saving time starts later in the year, and ends in the beginning of next year.
+                // Note, the summer in the southern hemisphere begins late in the year.
+                return (time < endTime || time >= startTime);
+            }
+            else if (rule.NoDaylightTransitions)
+            {
+                // In NoDaylightTransitions AdjustmentRules, the startTime is always before the endTime,
+                // and both the start and end times are inclusive
+                return time >= startTime && time <= endTime;
+            }
+            else
+            {
+                // In northern hemisphere, the daylight saving time starts in the middle of the year.
+                return time >= startTime && time < endTime;
+            }
+        }
+
+        /// <summary>
+        /// Returns true when the dateTime falls into an ambiguous time range.
+        ///
+        /// For example, in Pacific Standard Time on Sunday, October 29, 2006 time jumps from
+        /// 2AM to 1AM.  This means the timeline on Sunday proceeds as follows:
+        /// 12AM ... [1AM ... 1:59:59AM -> 1AM ... 1:59:59AM] 2AM ... 3AM ...
+        ///
+        /// In this example, any DateTime values that fall into the [1AM - 1:59:59AM] range
+        /// are ambiguous; as it is unclear if these times are in Daylight Saving Time.
+        /// </summary>
+        private static bool GetIsAmbiguousTime(DateTime time, AdjustmentRule rule, DaylightTimeStruct daylightTime)
+        {
+            bool isAmbiguous = false;
+            if (rule == null || rule.DaylightDelta == TimeSpan.Zero)
+            {
+                return isAmbiguous;
+            }
+
+            DateTime startAmbiguousTime;
+            DateTime endAmbiguousTime;
+
+            // if at DST start we transition forward in time then there is an ambiguous time range at the DST end
+            if (rule.DaylightDelta > TimeSpan.Zero)
+            {
+                if (rule.IsEndDateMarkerForEndOfYear())
+                { // year end with daylight on so there is no ambiguous time
+                    return false;
+                }
+                startAmbiguousTime = daylightTime.End;
+                endAmbiguousTime = daylightTime.End - rule.DaylightDelta; /* FUTURE: + rule.StandardDelta; */
+            }
+            else
+            {
+                if (rule.IsStartDateMarkerForBeginningOfYear())
+                { // year start with daylight on so there is no ambiguous time
+                    return false;
+                }
+                startAmbiguousTime = daylightTime.Start;
+                endAmbiguousTime = daylightTime.Start + rule.DaylightDelta; /* FUTURE: - rule.StandardDelta; */
+            }
+
+            isAmbiguous = (time >= endAmbiguousTime && time < startAmbiguousTime);
+
+            if (!isAmbiguous && startAmbiguousTime.Year != endAmbiguousTime.Year)
+            {
+                // there exists an extreme corner case where the start or end period is on a year boundary and
+                // because of this the comparison above might have been performed for a year-early or a year-later
+                // than it should have been.
+                DateTime startModifiedAmbiguousTime;
+                DateTime endModifiedAmbiguousTime;
+                try
+                {
+                    startModifiedAmbiguousTime = startAmbiguousTime.AddYears(1);
+                    endModifiedAmbiguousTime = endAmbiguousTime.AddYears(1);
+                    isAmbiguous = (time >= endModifiedAmbiguousTime && time < startModifiedAmbiguousTime);
+                }
+                catch (ArgumentOutOfRangeException) { }
+
+                if (!isAmbiguous)
+                {
+                    try
+                    {
+                        startModifiedAmbiguousTime = startAmbiguousTime.AddYears(-1);
+                        endModifiedAmbiguousTime = endAmbiguousTime.AddYears(-1);
+                        isAmbiguous = (time >= endModifiedAmbiguousTime && time < startModifiedAmbiguousTime);
+                    }
+                    catch (ArgumentOutOfRangeException) { }
+                }
+            }
+            return isAmbiguous;
+        }
+
+        /// <summary>
+        /// Helper function that checks if a given DateTime is in an invalid time ("time hole")
+        /// A "time hole" occurs at a DST transition point when time jumps forward;
+        /// For example, in Pacific Standard Time on Sunday, April 2, 2006 time jumps from
+        /// 1:59:59.9999999 to 3AM.  The time range 2AM to 2:59:59.9999999AM is the "time hole".
+        /// A "time hole" is not limited to only occurring at the start of DST, and may occur at
+        /// the end of DST as well.
+        /// </summary>
+        private static bool GetIsInvalidTime(DateTime time, AdjustmentRule rule, DaylightTimeStruct daylightTime)
+        {
+            bool isInvalid = false;
+            if (rule == null || rule.DaylightDelta == TimeSpan.Zero)
+            {
+                return isInvalid;
+            }
+
+            DateTime startInvalidTime;
+            DateTime endInvalidTime;
+
+            // if at DST start we transition forward in time then there is an ambiguous time range at the DST end
+            if (rule.DaylightDelta < TimeSpan.Zero)
+            {
+                // if the year ends with daylight saving on then there cannot be any time-hole's in that year.
+                if (rule.IsEndDateMarkerForEndOfYear())
+                    return false;
+
+                startInvalidTime = daylightTime.End;
+                endInvalidTime = daylightTime.End - rule.DaylightDelta; /* FUTURE: + rule.StandardDelta; */
+            }
+            else
+            {
+                // if the year starts with daylight saving on then there cannot be any time-hole's in that year.
+                if (rule.IsStartDateMarkerForBeginningOfYear())
+                    return false;
+
+                startInvalidTime = daylightTime.Start;
+                endInvalidTime = daylightTime.Start + rule.DaylightDelta; /* FUTURE: - rule.StandardDelta; */
+            }
+
+            isInvalid = (time >= startInvalidTime && time < endInvalidTime);
+
+            if (!isInvalid && startInvalidTime.Year != endInvalidTime.Year)
+            {
+                // there exists an extreme corner case where the start or end period is on a year boundary and
+                // because of this the comparison above might have been performed for a year-early or a year-later
+                // than it should have been.
+                DateTime startModifiedInvalidTime;
+                DateTime endModifiedInvalidTime;
+                try
+                {
+                    startModifiedInvalidTime = startInvalidTime.AddYears(1);
+                    endModifiedInvalidTime = endInvalidTime.AddYears(1);
+                    isInvalid = (time >= startModifiedInvalidTime && time < endModifiedInvalidTime);
+                }
+                catch (ArgumentOutOfRangeException) { }
+
+                if (!isInvalid)
+                {
+                    try
+                    {
+                        startModifiedInvalidTime = startInvalidTime.AddYears(-1);
+                        endModifiedInvalidTime = endInvalidTime.AddYears(-1);
+                        isInvalid = (time >= startModifiedInvalidTime && time < endModifiedInvalidTime);
+                    }
+                    catch (ArgumentOutOfRangeException) { }
+                }
+            }
+            return isInvalid;
+        }
+
+        /// <summary>
+        /// Helper function that calculates the UTC offset for a dateTime in a timeZone.
+        /// This function assumes that the dateTime is already converted into the timeZone.
+        /// </summary>
+        private static TimeSpan GetUtcOffset(DateTime time, TimeZoneInfo zone, TimeZoneInfoOptions flags)
+        {
+            TimeSpan baseOffset = zone.BaseUtcOffset;
+            int? ruleIndex;
+            AdjustmentRule rule = zone.GetAdjustmentRuleForTime(time, out ruleIndex);
+
+            if (rule != null)
+            {
+                baseOffset = baseOffset + rule.BaseUtcOffsetDelta;
+                if (rule.HasDaylightSaving)
+                {
+                    DaylightTimeStruct daylightTime = zone.GetDaylightTime(time.Year, rule, ruleIndex);
+                    bool isDaylightSavings = GetIsDaylightSavings(time, rule, daylightTime, flags);
+                    baseOffset += (isDaylightSavings ? rule.DaylightDelta : TimeSpan.Zero /* FUTURE: rule.StandardDelta */);
+                }
+            }
+
+            return baseOffset;
+        }
+
+        /// <summary>
+        /// Helper function that calculates the UTC offset for a UTC-dateTime in a timeZone.
+        /// This function assumes that the dateTime is represented in UTC and has *not* already been converted into the timeZone.
+        /// </summary>
+        private static TimeSpan GetUtcOffsetFromUtc(DateTime time, TimeZoneInfo zone)
+        {
+            bool isDaylightSavings;
+            return GetUtcOffsetFromUtc(time, zone, out isDaylightSavings);
+        }
+
+        /// <summary>
+        /// Helper function that calculates the UTC offset for a UTC-dateTime in a timeZone.
+        /// This function assumes that the dateTime is represented in UTC and has *not* already been converted into the timeZone.
+        /// </summary>
+        private static TimeSpan GetUtcOffsetFromUtc(DateTime time, TimeZoneInfo zone, out bool isDaylightSavings)
+        {
+            bool isAmbiguousLocalDst;
+            return GetUtcOffsetFromUtc(time, zone, out isDaylightSavings, out isAmbiguousLocalDst);
+        }
+
+        /// <summary>
+        /// Helper function that calculates the UTC offset for a UTC-dateTime in a timeZone.
+        /// This function assumes that the dateTime is represented in UTC and has *not* already been converted into the timeZone.
+        /// </summary>
+        internal static TimeSpan GetUtcOffsetFromUtc(DateTime time, TimeZoneInfo zone, out bool isDaylightSavings, out bool isAmbiguousLocalDst)
+        {
+            isDaylightSavings = false;
+            isAmbiguousLocalDst = false;
+            TimeSpan baseOffset = zone.BaseUtcOffset;
+            int year;
+            int? ruleIndex;
+            AdjustmentRule rule;
+
+            if (time > s_maxDateOnly)
+            {
+                rule = zone.GetAdjustmentRuleForTime(DateTime.MaxValue, out ruleIndex);
+                year = 9999;
+            }
+            else if (time < s_minDateOnly)
+            {
+                rule = zone.GetAdjustmentRuleForTime(DateTime.MinValue, out ruleIndex);
+                year = 1;
+            }
+            else
+            {
+                rule = zone.GetAdjustmentRuleForTime(time, dateTimeisUtc: true, ruleIndex: out ruleIndex);
+                Debug.Assert(rule == null || ruleIndex.HasValue, 
+                    "If GetAdjustmentRuleForTime returned an AdjustmentRule, ruleIndex should also be set.");
+
+                // As we get the associated rule using the adjusted targetTime, we should use the adjusted year (targetTime.Year) too as after adding the baseOffset,
+                // sometimes the year value can change if the input datetime was very close to the beginning or the end of the year. Examples of such cases:
+                //      Libya Standard Time when used with the date 2011-12-31T23:59:59.9999999Z
+                //      "W. Australia Standard Time" used with date 2005-12-31T23:59:00.0000000Z
+                DateTime targetTime = time + baseOffset;
+                year = targetTime.Year;
+            }
+
+            if (rule != null)
+            {
+                baseOffset = baseOffset + rule.BaseUtcOffsetDelta;
+                if (rule.HasDaylightSaving)
+                {
+                    isDaylightSavings = GetIsDaylightSavingsFromUtc(time, year, zone._baseUtcOffset, rule, ruleIndex, out isAmbiguousLocalDst, zone);
+                    baseOffset += (isDaylightSavings ? rule.DaylightDelta : TimeSpan.Zero /* FUTURE: rule.StandardDelta */);
+                }
+            }
+
+            return baseOffset;
+        }
+
+        /// <summary>
+        /// Helper function that converts a year and TransitionTime into a DateTime.
+        /// </summary>
+        internal static DateTime TransitionTimeToDateTime(int year, TransitionTime transitionTime)
+        {
+            DateTime value;
+            DateTime timeOfDay = transitionTime.TimeOfDay;
+
+            if (transitionTime.IsFixedDateRule)
+            {
+                // create a DateTime from the passed in year and the properties on the transitionTime
+
+                // if the day is out of range for the month then use the last day of the month
+                int day = DateTime.DaysInMonth(year, transitionTime.Month);
+
+                value = new DateTime(year, transitionTime.Month, (day < transitionTime.Day) ? day : transitionTime.Day,
+                            timeOfDay.Hour, timeOfDay.Minute, timeOfDay.Second, timeOfDay.Millisecond);
+            }
+            else
+            {
+                if (transitionTime.Week <= 4)
+                {
+                    //
+                    // Get the (transitionTime.Week)th Sunday.
+                    //
+                    value = new DateTime(year, transitionTime.Month, 1,
+                            timeOfDay.Hour, timeOfDay.Minute, timeOfDay.Second, timeOfDay.Millisecond);
+
+                    int dayOfWeek = (int)value.DayOfWeek;
+                    int delta = (int)transitionTime.DayOfWeek - dayOfWeek;
+                    if (delta < 0)
+                    {
+                        delta += 7;
+                    }
+                    delta += 7 * (transitionTime.Week - 1);
+
+                    if (delta > 0)
+                    {
+                        value = value.AddDays(delta);
+                    }
+                }
+                else
+                {
+                    //
+                    // If TransitionWeek is greater than 4, we will get the last week.
+                    //
+                    int daysInMonth = DateTime.DaysInMonth(year, transitionTime.Month);
+                    value = new DateTime(year, transitionTime.Month, daysInMonth,
+                            timeOfDay.Hour, timeOfDay.Minute, timeOfDay.Second, timeOfDay.Millisecond);
+
+                    // This is the day of week for the last day of the month.
+                    int dayOfWeek = (int)value.DayOfWeek;
+                    int delta = dayOfWeek - (int)transitionTime.DayOfWeek;
+                    if (delta < 0)
+                    {
+                        delta += 7;
+                    }
+
+                    if (delta > 0)
+                    {
+                        value = value.AddDays(-delta);
+                    }
+                }
+            }
+            return value;
+        }
+
+        /// <summary>
+        /// Helper function for retrieving a TimeZoneInfo object by <time_zone_name>.
+        ///
+        /// This function may return null.
+        ///
+        /// assumes cachedData lock is taken
+        /// </summary>
+        private static TimeZoneInfoResult TryGetTimeZone(string id, bool dstDisabled, out TimeZoneInfo value, out Exception e, CachedData cachedData, bool alwaysFallbackToLocalMachine = false)
+        {
+            Debug.Assert(Monitor.IsEntered(cachedData));
+
+            TimeZoneInfoResult result = TimeZoneInfoResult.Success;
+            e = null;
+            TimeZoneInfo match = null;
+
+            // check the cache
+            if (cachedData._systemTimeZones != null)
+            {
+                if (cachedData._systemTimeZones.TryGetValue(id, out match))
+                {
+                    if (dstDisabled && match._supportsDaylightSavingTime)
+                    {
+                        // we found a cache hit but we want a time zone without DST and this one has DST data
+                        value = CreateCustomTimeZone(match._id, match._baseUtcOffset, match._displayName, match._standardDisplayName);
+                    }
+                    else
+                    {
+                        value = new TimeZoneInfo(match._id, match._baseUtcOffset, match._displayName, match._standardDisplayName,
+                                              match._daylightDisplayName, match._adjustmentRules, disableDaylightSavingTime: false);
+                    }
+                    return result;
+                }
+            }
+
+            // Fall back to reading from the local machine when the cache is not fully populated.
+            // On UNIX, there may be some tzfiles that aren't in the zones.tab file, and thus aren't returned from GetSystemTimeZones().
+            // If a caller asks for one of these zones before calling GetSystemTimeZones(), the time zone is returned successfully. But if
+            // GetSystemTimeZones() is called first, FindSystemTimeZoneById will throw TimeZoneNotFoundException, which is inconsistent.
+            // To fix this, when 'alwaysFallbackToLocalMachine' is true, even if _allSystemTimeZonesRead is true, try reading the tzfile
+            // from disk, but don't add the time zone to the list returned from GetSystemTimeZones(). These time zones will only be
+            // available if asked for directly.
+            if (!cachedData._allSystemTimeZonesRead || alwaysFallbackToLocalMachine)
+            {
+                result = TryGetTimeZoneFromLocalMachine(id, dstDisabled, out value, out e, cachedData);
+            }
+            else
+            {
+                result = TimeZoneInfoResult.TimeZoneNotFoundException;
+                value = null;
+            }
+
+            return result;
+        }
+
+        private static TimeZoneInfoResult TryGetTimeZoneFromLocalMachine(string id, bool dstDisabled, out TimeZoneInfo value, out Exception e, CachedData cachedData)
+        {
+            TimeZoneInfoResult result;
+            TimeZoneInfo match;
+
+            result = TryGetTimeZoneFromLocalMachine(id, out match, out e);
+
+            if (result == TimeZoneInfoResult.Success)
+            {
+                if (cachedData._systemTimeZones == null)
+                    cachedData._systemTimeZones = new Dictionary<string, TimeZoneInfo>(StringComparer.OrdinalIgnoreCase);
+
+                cachedData._systemTimeZones.Add(id, match);
+
+                if (dstDisabled && match._supportsDaylightSavingTime)
+                {
+                    // we found a cache hit but we want a time zone without DST and this one has DST data
+                    value = CreateCustomTimeZone(match._id, match._baseUtcOffset, match._displayName, match._standardDisplayName);
+                }
+                else
+                {
+                    value = new TimeZoneInfo(match._id, match._baseUtcOffset, match._displayName, match._standardDisplayName,
+                                          match._daylightDisplayName, match._adjustmentRules, disableDaylightSavingTime: false);
+                }
+            }
+            else
+            {
+                value = null;
+            }
+
+            return result;
+        }
+
+        /// <summary>
+        /// Helper function that validates the TimeSpan is within +/- 14.0 hours
+        /// </summary>
+        internal static bool UtcOffsetOutOfRange(TimeSpan offset) =>
+            offset.TotalHours < -14.0 || offset.TotalHours > 14.0;
+
+        /// <summary>
+        /// Helper function that performs all of the validation checks for the
+        /// factory methods and deserialization callback.
+        /// </summary>
+        private static void ValidateTimeZoneInfo(string id, TimeSpan baseUtcOffset, AdjustmentRule[] adjustmentRules, out bool adjustmentRulesSupportDst)
+        {
+            if (id == null)
+            {
+                throw new ArgumentNullException(nameof(id));
+            }
+
+            if (id.Length == 0)
+            {
+                throw new ArgumentException(SR.Format(SR.Argument_InvalidId, id), nameof(id));
+            }
+
+            if (UtcOffsetOutOfRange(baseUtcOffset))
+            {
+                throw new ArgumentOutOfRangeException(nameof(baseUtcOffset), SR.ArgumentOutOfRange_UtcOffset);
+            }
+
+            if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
+            {
+                throw new ArgumentException(SR.Argument_TimeSpanHasSeconds, nameof(baseUtcOffset));
+            }
+
+            adjustmentRulesSupportDst = false;
+
+            //
+            // "adjustmentRules" can either be null or a valid array of AdjustmentRule objects.
+            // A valid array is one that does not contain any null elements and all elements
+            // are sorted in chronological order
+            //
+
+            if (adjustmentRules != null && adjustmentRules.Length != 0)
+            {
+                adjustmentRulesSupportDst = true;
+                AdjustmentRule prev = null;
+                AdjustmentRule current = null;
+                for (int i = 0; i < adjustmentRules.Length; i++)
+                {
+                    prev = current;
+                    current = adjustmentRules[i];
+
+                    if (current == null)
+                    {
+                        throw new InvalidTimeZoneException(SR.Argument_AdjustmentRulesNoNulls);
+                    }
+
+                    // FUTURE: check to see if this rule supports Daylight Saving Time
+                    // adjustmentRulesSupportDst = adjustmentRulesSupportDst || current.SupportsDaylightSavingTime;
+                    // FUTURE: test baseUtcOffset + current.StandardDelta
+
+                    if (UtcOffsetOutOfRange(baseUtcOffset + current.DaylightDelta))
+                    {
+                        throw new InvalidTimeZoneException(SR.ArgumentOutOfRange_UtcOffsetAndDaylightDelta);
+                    }
+
+                    if (prev != null && current.DateStart <= prev.DateEnd)
+                    {
+                        // verify the rules are in chronological order and the DateStart/DateEnd do not overlap
+                        throw new InvalidTimeZoneException(SR.Argument_AdjustmentRulesOutOfOrder);
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TimeZoneNotFoundException.cs b/src/System.Private.CoreLib/shared/System/TimeZoneNotFoundException.cs
new file mode 100644
index 0000000000..f83c6443c3
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TimeZoneNotFoundException.cs
@@ -0,0 +1,31 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class TimeZoneNotFoundException : Exception
+    {
+        public TimeZoneNotFoundException()
+        {
+        }
+
+        public TimeZoneNotFoundException(String message)
+            : base(message)
+        {
+        }
+
+        public TimeZoneNotFoundException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
+
+        protected TimeZoneNotFoundException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TimeoutException.cs b/src/System.Private.CoreLib/shared/System/TimeoutException.cs
new file mode 100644
index 0000000000..ddaa47747d
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TimeoutException.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception class for Timeout
+**
+**
+=============================================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class TimeoutException : SystemException
+    {
+        public TimeoutException()
+            : base(SR.Arg_TimeoutException)
+        {
+            HResult = HResults.COR_E_TIMEOUT;
+        }
+
+        public TimeoutException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_TIMEOUT;
+        }
+
+        public TimeoutException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_TIMEOUT;
+        }
+
+        protected TimeoutException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Tuple.cs b/src/System.Private.CoreLib/shared/System/Tuple.cs
new file mode 100644
index 0000000000..2d027cd40c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Tuple.cs
@@ -0,0 +1,1271 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Text;
+
+//
+// Note: F# compiler depends on the exact tuple hashing algorithm. Do not ever change it.
+//
+
+namespace System
+{
+    /// <summary>
+    /// Helper so we can call some tuple methods recursively without knowing the underlying types.
+    /// </summary>
+    internal interface ITupleInternal : ITuple
+    {
+        string ToString(StringBuilder sb);
+        int GetHashCode(IEqualityComparer comparer);
+    }
+
+    public static class Tuple
+    {
+        public static Tuple<T1> Create<T1>(T1 item1)
+        {
+            return new Tuple<T1>(item1);
+        }
+
+        public static Tuple<T1, T2> Create<T1, T2>(T1 item1, T2 item2)
+        {
+            return new Tuple<T1, T2>(item1, item2);
+        }
+
+        public static Tuple<T1, T2, T3> Create<T1, T2, T3>(T1 item1, T2 item2, T3 item3)
+        {
+            return new Tuple<T1, T2, T3>(item1, item2, item3);
+        }
+
+        public static Tuple<T1, T2, T3, T4> Create<T1, T2, T3, T4>(T1 item1, T2 item2, T3 item3, T4 item4)
+        {
+            return new Tuple<T1, T2, T3, T4>(item1, item2, item3, item4);
+        }
+
+        public static Tuple<T1, T2, T3, T4, T5> Create<T1, T2, T3, T4, T5>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5)
+        {
+            return new Tuple<T1, T2, T3, T4, T5>(item1, item2, item3, item4, item5);
+        }
+
+        public static Tuple<T1, T2, T3, T4, T5, T6> Create<T1, T2, T3, T4, T5, T6>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6)
+        {
+            return new Tuple<T1, T2, T3, T4, T5, T6>(item1, item2, item3, item4, item5, item6);
+        }
+
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7> Create<T1, T2, T3, T4, T5, T6, T7>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7)
+        {
+            return new Tuple<T1, T2, T3, T4, T5, T6, T7>(item1, item2, item3, item4, item5, item6, item7);
+        }
+
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8>> Create<T1, T2, T3, T4, T5, T6, T7, T8>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7, T8 item8)
+        {
+            return new Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8>>(item1, item2, item3, item4, item5, item6, item7, new Tuple<T8>(item8));
+        }
+
+        // From System.Web.Util.HashCodeCombiner
+        internal static int CombineHashCodes(int h1, int h2)
+        {
+            return (((h1 << 5) + h1) ^ h2);
+        }
+
+        internal static int CombineHashCodes(int h1, int h2, int h3)
+        {
+            return CombineHashCodes(CombineHashCodes(h1, h2), h3);
+        }
+
+        internal static int CombineHashCodes(int h1, int h2, int h3, int h4)
+        {
+            return CombineHashCodes(CombineHashCodes(h1, h2), CombineHashCodes(h3, h4));
+        }
+
+        internal static int CombineHashCodes(int h1, int h2, int h3, int h4, int h5)
+        {
+            return CombineHashCodes(CombineHashCodes(h1, h2, h3, h4), h5);
+        }
+
+        internal static int CombineHashCodes(int h1, int h2, int h3, int h4, int h5, int h6)
+        {
+            return CombineHashCodes(CombineHashCodes(h1, h2, h3, h4), CombineHashCodes(h5, h6));
+        }
+
+        internal static int CombineHashCodes(int h1, int h2, int h3, int h4, int h5, int h6, int h7)
+        {
+            return CombineHashCodes(CombineHashCodes(h1, h2, h3, h4), CombineHashCodes(h5, h6, h7));
+        }
+
+        internal static int CombineHashCodes(int h1, int h2, int h3, int h4, int h5, int h6, int h7, int h8)
+        {
+            return CombineHashCodes(CombineHashCodes(h1, h2, h3, h4), CombineHashCodes(h5, h6, h7, h8));
+        }
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class Tuple<T1> : IStructuralEquatable, IStructuralComparable, IComparable, ITupleInternal, ITuple
+    {
+        private readonly T1 m_Item1; // Do not rename (binary serialization)
+
+        public T1 Item1 { get { return m_Item1; } }
+
+        public Tuple(T1 item1)
+        {
+            m_Item1 = item1;
+        }
+
+        public override Boolean Equals(Object obj)
+        {
+            return ((IStructuralEquatable)this).Equals(obj, EqualityComparer<Object>.Default);
+        }
+
+        Boolean IStructuralEquatable.Equals(Object other, IEqualityComparer comparer)
+        {
+            if (other == null) return false;
+
+            Tuple<T1> objTuple = other as Tuple<T1>;
+
+            if (objTuple == null)
+            {
+                return false;
+            }
+
+            return comparer.Equals(m_Item1, objTuple.m_Item1);
+        }
+
+        Int32 IComparable.CompareTo(Object obj)
+        {
+            return ((IStructuralComparable)this).CompareTo(obj, Comparer<Object>.Default);
+        }
+
+        Int32 IStructuralComparable.CompareTo(Object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            Tuple<T1> objTuple = other as Tuple<T1>;
+
+            if (objTuple == null)
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_TupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            return comparer.Compare(m_Item1, objTuple.m_Item1);
+        }
+
+        public override int GetHashCode()
+        {
+            return ((IStructuralEquatable)this).GetHashCode(EqualityComparer<Object>.Default);
+        }
+
+        Int32 IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return comparer.GetHashCode(m_Item1);
+        }
+
+        Int32 ITupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return ((IStructuralEquatable)this).GetHashCode(comparer);
+        }
+        public override string ToString()
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append('(');
+            return ((ITupleInternal)this).ToString(sb);
+        }
+
+        string ITupleInternal.ToString(StringBuilder sb)
+        {
+            sb.Append(m_Item1);
+            sb.Append(')');
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 1;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                if (index != 0)
+                {
+                    throw new IndexOutOfRangeException();
+                }
+                return Item1;
+            }
+        }
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class Tuple<T1, T2> : IStructuralEquatable, IStructuralComparable, IComparable, ITupleInternal, ITuple
+    {
+        private readonly T1 m_Item1; // Do not rename (binary serialization)
+        private readonly T2 m_Item2; // Do not rename (binary serialization)
+
+        public T1 Item1 { get { return m_Item1; } }
+        public T2 Item2 { get { return m_Item2; } }
+
+        public Tuple(T1 item1, T2 item2)
+        {
+            m_Item1 = item1;
+            m_Item2 = item2;
+        }
+
+        public override Boolean Equals(Object obj)
+        {
+            return ((IStructuralEquatable)this).Equals(obj, EqualityComparer<Object>.Default); ;
+        }
+
+        Boolean IStructuralEquatable.Equals(Object other, IEqualityComparer comparer)
+        {
+            if (other == null) return false;
+
+            Tuple<T1, T2> objTuple = other as Tuple<T1, T2>;
+
+            if (objTuple == null)
+            {
+                return false;
+            }
+
+            return comparer.Equals(m_Item1, objTuple.m_Item1) && comparer.Equals(m_Item2, objTuple.m_Item2);
+        }
+
+        Int32 IComparable.CompareTo(Object obj)
+        {
+            return ((IStructuralComparable)this).CompareTo(obj, Comparer<Object>.Default);
+        }
+
+        Int32 IStructuralComparable.CompareTo(Object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            Tuple<T1, T2> objTuple = other as Tuple<T1, T2>;
+
+            if (objTuple == null)
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_TupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            int c = 0;
+
+            c = comparer.Compare(m_Item1, objTuple.m_Item1);
+
+            if (c != 0) return c;
+
+            return comparer.Compare(m_Item2, objTuple.m_Item2);
+        }
+
+        public override int GetHashCode()
+        {
+            return ((IStructuralEquatable)this).GetHashCode(EqualityComparer<Object>.Default);
+        }
+
+        Int32 IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return Tuple.CombineHashCodes(comparer.GetHashCode(m_Item1), comparer.GetHashCode(m_Item2));
+        }
+
+        Int32 ITupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return ((IStructuralEquatable)this).GetHashCode(comparer);
+        }
+        public override string ToString()
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append('(');
+            return ((ITupleInternal)this).ToString(sb);
+        }
+
+        string ITupleInternal.ToString(StringBuilder sb)
+        {
+            sb.Append(m_Item1);
+            sb.Append(", ");
+            sb.Append(m_Item2);
+            sb.Append(')');
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 2;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class Tuple<T1, T2, T3> : IStructuralEquatable, IStructuralComparable, IComparable, ITupleInternal, ITuple
+    {
+        private readonly T1 m_Item1; // Do not rename (binary serialization)
+        private readonly T2 m_Item2; // Do not rename (binary serialization)
+        private readonly T3 m_Item3; // Do not rename (binary serialization)
+
+        public T1 Item1 { get { return m_Item1; } }
+        public T2 Item2 { get { return m_Item2; } }
+        public T3 Item3 { get { return m_Item3; } }
+
+        public Tuple(T1 item1, T2 item2, T3 item3)
+        {
+            m_Item1 = item1;
+            m_Item2 = item2;
+            m_Item3 = item3;
+        }
+
+        public override Boolean Equals(Object obj)
+        {
+            return ((IStructuralEquatable)this).Equals(obj, EqualityComparer<Object>.Default); ;
+        }
+
+        Boolean IStructuralEquatable.Equals(Object other, IEqualityComparer comparer)
+        {
+            if (other == null) return false;
+
+            Tuple<T1, T2, T3> objTuple = other as Tuple<T1, T2, T3>;
+
+            if (objTuple == null)
+            {
+                return false;
+            }
+
+            return comparer.Equals(m_Item1, objTuple.m_Item1) && comparer.Equals(m_Item2, objTuple.m_Item2) && comparer.Equals(m_Item3, objTuple.m_Item3);
+        }
+
+        Int32 IComparable.CompareTo(Object obj)
+        {
+            return ((IStructuralComparable)this).CompareTo(obj, Comparer<Object>.Default);
+        }
+
+        Int32 IStructuralComparable.CompareTo(Object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            Tuple<T1, T2, T3> objTuple = other as Tuple<T1, T2, T3>;
+
+            if (objTuple == null)
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_TupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            int c = 0;
+
+            c = comparer.Compare(m_Item1, objTuple.m_Item1);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item2, objTuple.m_Item2);
+
+            if (c != 0) return c;
+
+            return comparer.Compare(m_Item3, objTuple.m_Item3);
+        }
+
+        public override int GetHashCode()
+        {
+            return ((IStructuralEquatable)this).GetHashCode(EqualityComparer<Object>.Default);
+        }
+
+        Int32 IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return Tuple.CombineHashCodes(comparer.GetHashCode(m_Item1), comparer.GetHashCode(m_Item2), comparer.GetHashCode(m_Item3));
+        }
+
+        Int32 ITupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return ((IStructuralEquatable)this).GetHashCode(comparer);
+        }
+        public override string ToString()
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append('(');
+            return ((ITupleInternal)this).ToString(sb);
+        }
+
+        string ITupleInternal.ToString(StringBuilder sb)
+        {
+            sb.Append(m_Item1);
+            sb.Append(", ");
+            sb.Append(m_Item2);
+            sb.Append(", ");
+            sb.Append(m_Item3);
+            sb.Append(')');
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 3;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class Tuple<T1, T2, T3, T4> : IStructuralEquatable, IStructuralComparable, IComparable, ITupleInternal, ITuple
+    {
+        private readonly T1 m_Item1; // Do not rename (binary serialization)
+        private readonly T2 m_Item2; // Do not rename (binary serialization)
+        private readonly T3 m_Item3; // Do not rename (binary serialization)
+        private readonly T4 m_Item4; // Do not rename (binary serialization)
+
+        public T1 Item1 { get { return m_Item1; } }
+        public T2 Item2 { get { return m_Item2; } }
+        public T3 Item3 { get { return m_Item3; } }
+        public T4 Item4 { get { return m_Item4; } }
+
+        public Tuple(T1 item1, T2 item2, T3 item3, T4 item4)
+        {
+            m_Item1 = item1;
+            m_Item2 = item2;
+            m_Item3 = item3;
+            m_Item4 = item4;
+        }
+
+        public override Boolean Equals(Object obj)
+        {
+            return ((IStructuralEquatable)this).Equals(obj, EqualityComparer<Object>.Default); ;
+        }
+
+        Boolean IStructuralEquatable.Equals(Object other, IEqualityComparer comparer)
+        {
+            if (other == null) return false;
+
+            Tuple<T1, T2, T3, T4> objTuple = other as Tuple<T1, T2, T3, T4>;
+
+            if (objTuple == null)
+            {
+                return false;
+            }
+
+            return comparer.Equals(m_Item1, objTuple.m_Item1) && comparer.Equals(m_Item2, objTuple.m_Item2) && comparer.Equals(m_Item3, objTuple.m_Item3) && comparer.Equals(m_Item4, objTuple.m_Item4);
+        }
+
+        Int32 IComparable.CompareTo(Object obj)
+        {
+            return ((IStructuralComparable)this).CompareTo(obj, Comparer<Object>.Default);
+        }
+
+        Int32 IStructuralComparable.CompareTo(Object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            Tuple<T1, T2, T3, T4> objTuple = other as Tuple<T1, T2, T3, T4>;
+
+            if (objTuple == null)
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_TupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            int c = 0;
+
+            c = comparer.Compare(m_Item1, objTuple.m_Item1);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item2, objTuple.m_Item2);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item3, objTuple.m_Item3);
+
+            if (c != 0) return c;
+
+            return comparer.Compare(m_Item4, objTuple.m_Item4);
+        }
+
+        public override int GetHashCode()
+        {
+            return ((IStructuralEquatable)this).GetHashCode(EqualityComparer<Object>.Default);
+        }
+
+        Int32 IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return Tuple.CombineHashCodes(comparer.GetHashCode(m_Item1), comparer.GetHashCode(m_Item2), comparer.GetHashCode(m_Item3), comparer.GetHashCode(m_Item4));
+        }
+
+        Int32 ITupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return ((IStructuralEquatable)this).GetHashCode(comparer);
+        }
+        public override string ToString()
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append('(');
+            return ((ITupleInternal)this).ToString(sb);
+        }
+
+        string ITupleInternal.ToString(StringBuilder sb)
+        {
+            sb.Append(m_Item1);
+            sb.Append(", ");
+            sb.Append(m_Item2);
+            sb.Append(", ");
+            sb.Append(m_Item3);
+            sb.Append(", ");
+            sb.Append(m_Item4);
+            sb.Append(')');
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 4;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class Tuple<T1, T2, T3, T4, T5> : IStructuralEquatable, IStructuralComparable, IComparable, ITupleInternal, ITuple
+    {
+        private readonly T1 m_Item1; // Do not rename (binary serialization)
+        private readonly T2 m_Item2; // Do not rename (binary serialization)
+        private readonly T3 m_Item3; // Do not rename (binary serialization)
+        private readonly T4 m_Item4; // Do not rename (binary serialization)
+        private readonly T5 m_Item5; // Do not rename (binary serialization)
+
+        public T1 Item1 { get { return m_Item1; } }
+        public T2 Item2 { get { return m_Item2; } }
+        public T3 Item3 { get { return m_Item3; } }
+        public T4 Item4 { get { return m_Item4; } }
+        public T5 Item5 { get { return m_Item5; } }
+
+        public Tuple(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5)
+        {
+            m_Item1 = item1;
+            m_Item2 = item2;
+            m_Item3 = item3;
+            m_Item4 = item4;
+            m_Item5 = item5;
+        }
+
+        public override Boolean Equals(Object obj)
+        {
+            return ((IStructuralEquatable)this).Equals(obj, EqualityComparer<Object>.Default); ;
+        }
+
+        Boolean IStructuralEquatable.Equals(Object other, IEqualityComparer comparer)
+        {
+            if (other == null) return false;
+
+            Tuple<T1, T2, T3, T4, T5> objTuple = other as Tuple<T1, T2, T3, T4, T5>;
+
+            if (objTuple == null)
+            {
+                return false;
+            }
+
+            return comparer.Equals(m_Item1, objTuple.m_Item1) && comparer.Equals(m_Item2, objTuple.m_Item2) && comparer.Equals(m_Item3, objTuple.m_Item3) && comparer.Equals(m_Item4, objTuple.m_Item4) && comparer.Equals(m_Item5, objTuple.m_Item5);
+        }
+
+        Int32 IComparable.CompareTo(Object obj)
+        {
+            return ((IStructuralComparable)this).CompareTo(obj, Comparer<Object>.Default);
+        }
+
+        Int32 IStructuralComparable.CompareTo(Object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            Tuple<T1, T2, T3, T4, T5> objTuple = other as Tuple<T1, T2, T3, T4, T5>;
+
+            if (objTuple == null)
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_TupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            int c = 0;
+
+            c = comparer.Compare(m_Item1, objTuple.m_Item1);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item2, objTuple.m_Item2);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item3, objTuple.m_Item3);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item4, objTuple.m_Item4);
+
+            if (c != 0) return c;
+
+            return comparer.Compare(m_Item5, objTuple.m_Item5);
+        }
+
+        public override int GetHashCode()
+        {
+            return ((IStructuralEquatable)this).GetHashCode(EqualityComparer<Object>.Default);
+        }
+
+        Int32 IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return Tuple.CombineHashCodes(comparer.GetHashCode(m_Item1), comparer.GetHashCode(m_Item2), comparer.GetHashCode(m_Item3), comparer.GetHashCode(m_Item4), comparer.GetHashCode(m_Item5));
+        }
+
+        Int32 ITupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return ((IStructuralEquatable)this).GetHashCode(comparer);
+        }
+        public override string ToString()
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append('(');
+            return ((ITupleInternal)this).ToString(sb);
+        }
+
+        string ITupleInternal.ToString(StringBuilder sb)
+        {
+            sb.Append(m_Item1);
+            sb.Append(", ");
+            sb.Append(m_Item2);
+            sb.Append(", ");
+            sb.Append(m_Item3);
+            sb.Append(", ");
+            sb.Append(m_Item4);
+            sb.Append(", ");
+            sb.Append(m_Item5);
+            sb.Append(')');
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 5;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    case 4:
+                        return Item5;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class Tuple<T1, T2, T3, T4, T5, T6> : IStructuralEquatable, IStructuralComparable, IComparable, ITupleInternal, ITuple
+    {
+        private readonly T1 m_Item1; // Do not rename (binary serialization)
+        private readonly T2 m_Item2; // Do not rename (binary serialization)
+        private readonly T3 m_Item3; // Do not rename (binary serialization)
+        private readonly T4 m_Item4; // Do not rename (binary serialization)
+        private readonly T5 m_Item5; // Do not rename (binary serialization)
+        private readonly T6 m_Item6; // Do not rename (binary serialization)
+
+        public T1 Item1 { get { return m_Item1; } }
+        public T2 Item2 { get { return m_Item2; } }
+        public T3 Item3 { get { return m_Item3; } }
+        public T4 Item4 { get { return m_Item4; } }
+        public T5 Item5 { get { return m_Item5; } }
+        public T6 Item6 { get { return m_Item6; } }
+
+        public Tuple(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6)
+        {
+            m_Item1 = item1;
+            m_Item2 = item2;
+            m_Item3 = item3;
+            m_Item4 = item4;
+            m_Item5 = item5;
+            m_Item6 = item6;
+        }
+
+        public override Boolean Equals(Object obj)
+        {
+            return ((IStructuralEquatable)this).Equals(obj, EqualityComparer<Object>.Default); ;
+        }
+
+        Boolean IStructuralEquatable.Equals(Object other, IEqualityComparer comparer)
+        {
+            if (other == null) return false;
+
+            Tuple<T1, T2, T3, T4, T5, T6> objTuple = other as Tuple<T1, T2, T3, T4, T5, T6>;
+
+            if (objTuple == null)
+            {
+                return false;
+            }
+
+            return comparer.Equals(m_Item1, objTuple.m_Item1) && comparer.Equals(m_Item2, objTuple.m_Item2) && comparer.Equals(m_Item3, objTuple.m_Item3) && comparer.Equals(m_Item4, objTuple.m_Item4) && comparer.Equals(m_Item5, objTuple.m_Item5) && comparer.Equals(m_Item6, objTuple.m_Item6);
+        }
+
+        Int32 IComparable.CompareTo(Object obj)
+        {
+            return ((IStructuralComparable)this).CompareTo(obj, Comparer<Object>.Default);
+        }
+
+        Int32 IStructuralComparable.CompareTo(Object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            Tuple<T1, T2, T3, T4, T5, T6> objTuple = other as Tuple<T1, T2, T3, T4, T5, T6>;
+
+            if (objTuple == null)
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_TupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            int c = 0;
+
+            c = comparer.Compare(m_Item1, objTuple.m_Item1);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item2, objTuple.m_Item2);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item3, objTuple.m_Item3);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item4, objTuple.m_Item4);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item5, objTuple.m_Item5);
+
+            if (c != 0) return c;
+
+            return comparer.Compare(m_Item6, objTuple.m_Item6);
+        }
+
+        public override int GetHashCode()
+        {
+            return ((IStructuralEquatable)this).GetHashCode(EqualityComparer<Object>.Default);
+        }
+
+        Int32 IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return Tuple.CombineHashCodes(comparer.GetHashCode(m_Item1), comparer.GetHashCode(m_Item2), comparer.GetHashCode(m_Item3), comparer.GetHashCode(m_Item4), comparer.GetHashCode(m_Item5), comparer.GetHashCode(m_Item6));
+        }
+
+        Int32 ITupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return ((IStructuralEquatable)this).GetHashCode(comparer);
+        }
+        public override string ToString()
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append('(');
+            return ((ITupleInternal)this).ToString(sb);
+        }
+
+        string ITupleInternal.ToString(StringBuilder sb)
+        {
+            sb.Append(m_Item1);
+            sb.Append(", ");
+            sb.Append(m_Item2);
+            sb.Append(", ");
+            sb.Append(m_Item3);
+            sb.Append(", ");
+            sb.Append(m_Item4);
+            sb.Append(", ");
+            sb.Append(m_Item5);
+            sb.Append(", ");
+            sb.Append(m_Item6);
+            sb.Append(')');
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 6;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    case 4:
+                        return Item5;
+                    case 5:
+                        return Item6;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class Tuple<T1, T2, T3, T4, T5, T6, T7> : IStructuralEquatable, IStructuralComparable, IComparable, ITupleInternal, ITuple
+    {
+        private readonly T1 m_Item1; // Do not rename (binary serialization)
+        private readonly T2 m_Item2; // Do not rename (binary serialization)
+        private readonly T3 m_Item3; // Do not rename (binary serialization)
+        private readonly T4 m_Item4; // Do not rename (binary serialization)
+        private readonly T5 m_Item5; // Do not rename (binary serialization)
+        private readonly T6 m_Item6; // Do not rename (binary serialization)
+        private readonly T7 m_Item7; // Do not rename (binary serialization)
+
+        public T1 Item1 { get { return m_Item1; } }
+        public T2 Item2 { get { return m_Item2; } }
+        public T3 Item3 { get { return m_Item3; } }
+        public T4 Item4 { get { return m_Item4; } }
+        public T5 Item5 { get { return m_Item5; } }
+        public T6 Item6 { get { return m_Item6; } }
+        public T7 Item7 { get { return m_Item7; } }
+
+        public Tuple(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7)
+        {
+            m_Item1 = item1;
+            m_Item2 = item2;
+            m_Item3 = item3;
+            m_Item4 = item4;
+            m_Item5 = item5;
+            m_Item6 = item6;
+            m_Item7 = item7;
+        }
+
+        public override Boolean Equals(Object obj)
+        {
+            return ((IStructuralEquatable)this).Equals(obj, EqualityComparer<Object>.Default); ;
+        }
+
+        Boolean IStructuralEquatable.Equals(Object other, IEqualityComparer comparer)
+        {
+            if (other == null) return false;
+
+            Tuple<T1, T2, T3, T4, T5, T6, T7> objTuple = other as Tuple<T1, T2, T3, T4, T5, T6, T7>;
+
+            if (objTuple == null)
+            {
+                return false;
+            }
+
+            return comparer.Equals(m_Item1, objTuple.m_Item1) && comparer.Equals(m_Item2, objTuple.m_Item2) && comparer.Equals(m_Item3, objTuple.m_Item3) && comparer.Equals(m_Item4, objTuple.m_Item4) && comparer.Equals(m_Item5, objTuple.m_Item5) && comparer.Equals(m_Item6, objTuple.m_Item6) && comparer.Equals(m_Item7, objTuple.m_Item7);
+        }
+
+        Int32 IComparable.CompareTo(Object obj)
+        {
+            return ((IStructuralComparable)this).CompareTo(obj, Comparer<Object>.Default);
+        }
+
+        Int32 IStructuralComparable.CompareTo(Object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            Tuple<T1, T2, T3, T4, T5, T6, T7> objTuple = other as Tuple<T1, T2, T3, T4, T5, T6, T7>;
+
+            if (objTuple == null)
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_TupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            int c = 0;
+
+            c = comparer.Compare(m_Item1, objTuple.m_Item1);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item2, objTuple.m_Item2);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item3, objTuple.m_Item3);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item4, objTuple.m_Item4);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item5, objTuple.m_Item5);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item6, objTuple.m_Item6);
+
+            if (c != 0) return c;
+
+            return comparer.Compare(m_Item7, objTuple.m_Item7);
+        }
+
+        public override int GetHashCode()
+        {
+            return ((IStructuralEquatable)this).GetHashCode(EqualityComparer<Object>.Default);
+        }
+
+        Int32 IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return Tuple.CombineHashCodes(comparer.GetHashCode(m_Item1), comparer.GetHashCode(m_Item2), comparer.GetHashCode(m_Item3), comparer.GetHashCode(m_Item4), comparer.GetHashCode(m_Item5), comparer.GetHashCode(m_Item6), comparer.GetHashCode(m_Item7));
+        }
+
+        Int32 ITupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return ((IStructuralEquatable)this).GetHashCode(comparer);
+        }
+        public override string ToString()
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append('(');
+            return ((ITupleInternal)this).ToString(sb);
+        }
+
+        string ITupleInternal.ToString(StringBuilder sb)
+        {
+            sb.Append(m_Item1);
+            sb.Append(", ");
+            sb.Append(m_Item2);
+            sb.Append(", ");
+            sb.Append(m_Item3);
+            sb.Append(", ");
+            sb.Append(m_Item4);
+            sb.Append(", ");
+            sb.Append(m_Item5);
+            sb.Append(", ");
+            sb.Append(m_Item6);
+            sb.Append(", ");
+            sb.Append(m_Item7);
+            sb.Append(')');
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 7;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    case 4:
+                        return Item5;
+                    case 5:
+                        return Item6;
+                    case 6:
+                        return Item7;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class Tuple<T1, T2, T3, T4, T5, T6, T7, TRest> : IStructuralEquatable, IStructuralComparable, IComparable, ITupleInternal, ITuple
+    {
+        private readonly T1 m_Item1; // Do not rename (binary serialization)
+        private readonly T2 m_Item2; // Do not rename (binary serialization)
+        private readonly T3 m_Item3; // Do not rename (binary serialization)
+        private readonly T4 m_Item4; // Do not rename (binary serialization)
+        private readonly T5 m_Item5; // Do not rename (binary serialization)
+        private readonly T6 m_Item6; // Do not rename (binary serialization)
+        private readonly T7 m_Item7; // Do not rename (binary serialization)
+        private readonly TRest m_Rest; // Do not rename (binary serialization)
+
+        public T1 Item1 { get { return m_Item1; } }
+        public T2 Item2 { get { return m_Item2; } }
+        public T3 Item3 { get { return m_Item3; } }
+        public T4 Item4 { get { return m_Item4; } }
+        public T5 Item5 { get { return m_Item5; } }
+        public T6 Item6 { get { return m_Item6; } }
+        public T7 Item7 { get { return m_Item7; } }
+        public TRest Rest { get { return m_Rest; } }
+
+        public Tuple(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7, TRest rest)
+        {
+            if (!(rest is ITupleInternal))
+            {
+                throw new ArgumentException(SR.ArgumentException_TupleLastArgumentNotATuple);
+            }
+
+            m_Item1 = item1;
+            m_Item2 = item2;
+            m_Item3 = item3;
+            m_Item4 = item4;
+            m_Item5 = item5;
+            m_Item6 = item6;
+            m_Item7 = item7;
+            m_Rest = rest;
+        }
+
+        public override Boolean Equals(Object obj)
+        {
+            return ((IStructuralEquatable)this).Equals(obj, EqualityComparer<Object>.Default); ;
+        }
+
+        Boolean IStructuralEquatable.Equals(Object other, IEqualityComparer comparer)
+        {
+            if (other == null) return false;
+
+            Tuple<T1, T2, T3, T4, T5, T6, T7, TRest> objTuple = other as Tuple<T1, T2, T3, T4, T5, T6, T7, TRest>;
+
+            if (objTuple == null)
+            {
+                return false;
+            }
+
+            return comparer.Equals(m_Item1, objTuple.m_Item1) && comparer.Equals(m_Item2, objTuple.m_Item2) && comparer.Equals(m_Item3, objTuple.m_Item3) && comparer.Equals(m_Item4, objTuple.m_Item4) && comparer.Equals(m_Item5, objTuple.m_Item5) && comparer.Equals(m_Item6, objTuple.m_Item6) && comparer.Equals(m_Item7, objTuple.m_Item7) && comparer.Equals(m_Rest, objTuple.m_Rest);
+        }
+
+        Int32 IComparable.CompareTo(Object obj)
+        {
+            return ((IStructuralComparable)this).CompareTo(obj, Comparer<Object>.Default);
+        }
+
+        Int32 IStructuralComparable.CompareTo(Object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            Tuple<T1, T2, T3, T4, T5, T6, T7, TRest> objTuple = other as Tuple<T1, T2, T3, T4, T5, T6, T7, TRest>;
+
+            if (objTuple == null)
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_TupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            int c = 0;
+
+            c = comparer.Compare(m_Item1, objTuple.m_Item1);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item2, objTuple.m_Item2);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item3, objTuple.m_Item3);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item4, objTuple.m_Item4);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item5, objTuple.m_Item5);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item6, objTuple.m_Item6);
+
+            if (c != 0) return c;
+
+            c = comparer.Compare(m_Item7, objTuple.m_Item7);
+
+            if (c != 0) return c;
+
+            return comparer.Compare(m_Rest, objTuple.m_Rest);
+        }
+
+        public override int GetHashCode()
+        {
+            return ((IStructuralEquatable)this).GetHashCode(EqualityComparer<Object>.Default);
+        }
+
+        Int32 IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            // We want to have a limited hash in this case.  We'll use the last 8 elements of the tuple
+            ITupleInternal t = (ITupleInternal)m_Rest;
+            if (t.Length >= 8) { return t.GetHashCode(comparer); }
+
+            // In this case, the rest memeber has less than 8 elements so we need to combine some our elements with the elements in rest
+            int k = 8 - t.Length;
+            switch (k)
+            {
+                case 1:
+                    return Tuple.CombineHashCodes(comparer.GetHashCode(m_Item7), t.GetHashCode(comparer));
+                case 2:
+                    return Tuple.CombineHashCodes(comparer.GetHashCode(m_Item6), comparer.GetHashCode(m_Item7), t.GetHashCode(comparer));
+                case 3:
+                    return Tuple.CombineHashCodes(comparer.GetHashCode(m_Item5), comparer.GetHashCode(m_Item6), comparer.GetHashCode(m_Item7), t.GetHashCode(comparer));
+                case 4:
+                    return Tuple.CombineHashCodes(comparer.GetHashCode(m_Item4), comparer.GetHashCode(m_Item5), comparer.GetHashCode(m_Item6), comparer.GetHashCode(m_Item7), t.GetHashCode(comparer));
+                case 5:
+                    return Tuple.CombineHashCodes(comparer.GetHashCode(m_Item3), comparer.GetHashCode(m_Item4), comparer.GetHashCode(m_Item5), comparer.GetHashCode(m_Item6), comparer.GetHashCode(m_Item7), t.GetHashCode(comparer));
+                case 6:
+                    return Tuple.CombineHashCodes(comparer.GetHashCode(m_Item2), comparer.GetHashCode(m_Item3), comparer.GetHashCode(m_Item4), comparer.GetHashCode(m_Item5), comparer.GetHashCode(m_Item6), comparer.GetHashCode(m_Item7), t.GetHashCode(comparer));
+                case 7:
+                    return Tuple.CombineHashCodes(comparer.GetHashCode(m_Item1), comparer.GetHashCode(m_Item2), comparer.GetHashCode(m_Item3), comparer.GetHashCode(m_Item4), comparer.GetHashCode(m_Item5), comparer.GetHashCode(m_Item6), comparer.GetHashCode(m_Item7), t.GetHashCode(comparer));
+            }
+            Debug.Fail("Missed all cases for computing Tuple hash code");
+            return -1;
+        }
+
+        Int32 ITupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return ((IStructuralEquatable)this).GetHashCode(comparer);
+        }
+        public override string ToString()
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append('(');
+            return ((ITupleInternal)this).ToString(sb);
+        }
+
+        string ITupleInternal.ToString(StringBuilder sb)
+        {
+            sb.Append(m_Item1);
+            sb.Append(", ");
+            sb.Append(m_Item2);
+            sb.Append(", ");
+            sb.Append(m_Item3);
+            sb.Append(", ");
+            sb.Append(m_Item4);
+            sb.Append(", ");
+            sb.Append(m_Item5);
+            sb.Append(", ");
+            sb.Append(m_Item6);
+            sb.Append(", ");
+            sb.Append(m_Item7);
+            sb.Append(", ");
+            return ((ITupleInternal)m_Rest).ToString(sb);
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length
+        {
+            get
+            {
+                return 7 + ((ITupleInternal)Rest).Length;
+            }
+        }
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    case 4:
+                        return Item5;
+                    case 5:
+                        return Item6;
+                    case 6:
+                        return Item7;
+                }
+
+                return ((ITupleInternal)Rest)[index - 7];
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TupleExtensions.cs b/src/System.Private.CoreLib/shared/System/TupleExtensions.cs
new file mode 100644
index 0000000000..106a88a08b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TupleExtensions.cs
@@ -0,0 +1,930 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    /// <summary>
+    /// Provides extension methods for <see cref="Tuple"/> instances to interop with C# tuples features (deconstruction syntax, converting from and to <see cref="ValueTuple"/>).
+    /// </summary>
+    public static class TupleExtensions
+    {
+        #region Deconstruct
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 1 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1>(
+            this Tuple<T1> value,
+            out T1 item1)
+        {
+            item1 = value.Item1;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 2 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2>(
+            this Tuple<T1, T2> value,
+            out T1 item1, out T2 item2)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 3 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3>(
+            this Tuple<T1, T2, T3> value,
+            out T1 item1, out T2 item2, out T3 item3)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 4 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4>(
+            this Tuple<T1, T2, T3, T4> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 5 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5>(
+            this Tuple<T1, T2, T3, T4, T5> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 6 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6>(
+            this Tuple<T1, T2, T3, T4, T5, T6> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 7 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 8 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7, T8>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8>> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7, out T8 item8)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+            item8 = value.Rest.Item1;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 9 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7, T8, T9>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9>> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7, out T8 item8, out T9 item9)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+            item8 = value.Rest.Item1;
+            item9 = value.Rest.Item2;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 10 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10>> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7, out T8 item8, out T9 item9, out T10 item10)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+            item8 = value.Rest.Item1;
+            item9 = value.Rest.Item2;
+            item10 = value.Rest.Item3;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 11 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11>> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7, out T8 item8, out T9 item9, out T10 item10, out T11 item11)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+            item8 = value.Rest.Item1;
+            item9 = value.Rest.Item2;
+            item10 = value.Rest.Item3;
+            item11 = value.Rest.Item4;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 12 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12>> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7, out T8 item8, out T9 item9, out T10 item10, out T11 item11, out T12 item12)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+            item8 = value.Rest.Item1;
+            item9 = value.Rest.Item2;
+            item10 = value.Rest.Item3;
+            item11 = value.Rest.Item4;
+            item12 = value.Rest.Item5;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 13 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13>> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7, out T8 item8, out T9 item9, out T10 item10, out T11 item11, out T12 item12, out T13 item13)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+            item8 = value.Rest.Item1;
+            item9 = value.Rest.Item2;
+            item10 = value.Rest.Item3;
+            item11 = value.Rest.Item4;
+            item12 = value.Rest.Item5;
+            item13 = value.Rest.Item6;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 14 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14>> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7, out T8 item8, out T9 item9, out T10 item10, out T11 item11, out T12 item12, out T13 item13, out T14 item14)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+            item8 = value.Rest.Item1;
+            item9 = value.Rest.Item2;
+            item10 = value.Rest.Item3;
+            item11 = value.Rest.Item4;
+            item12 = value.Rest.Item5;
+            item13 = value.Rest.Item6;
+            item14 = value.Rest.Item7;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 15 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15>>> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7, out T8 item8, out T9 item9, out T10 item10, out T11 item11, out T12 item12, out T13 item13, out T14 item14, out T15 item15)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+            item8 = value.Rest.Item1;
+            item9 = value.Rest.Item2;
+            item10 = value.Rest.Item3;
+            item11 = value.Rest.Item4;
+            item12 = value.Rest.Item5;
+            item13 = value.Rest.Item6;
+            item14 = value.Rest.Item7;
+            item15 = value.Rest.Rest.Item1;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 16 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16>>> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7, out T8 item8, out T9 item9, out T10 item10, out T11 item11, out T12 item12, out T13 item13, out T14 item14, out T15 item15, out T16 item16)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+            item8 = value.Rest.Item1;
+            item9 = value.Rest.Item2;
+            item10 = value.Rest.Item3;
+            item11 = value.Rest.Item4;
+            item12 = value.Rest.Item5;
+            item13 = value.Rest.Item6;
+            item14 = value.Rest.Item7;
+            item15 = value.Rest.Rest.Item1;
+            item16 = value.Rest.Rest.Item2;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 17 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17>>> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7, out T8 item8, out T9 item9, out T10 item10, out T11 item11, out T12 item12, out T13 item13, out T14 item14, out T15 item15, out T16 item16, out T17 item17)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+            item8 = value.Rest.Item1;
+            item9 = value.Rest.Item2;
+            item10 = value.Rest.Item3;
+            item11 = value.Rest.Item4;
+            item12 = value.Rest.Item5;
+            item13 = value.Rest.Item6;
+            item14 = value.Rest.Item7;
+            item15 = value.Rest.Rest.Item1;
+            item16 = value.Rest.Rest.Item2;
+            item17 = value.Rest.Rest.Item3;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 18 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17, T18>>> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7, out T8 item8, out T9 item9, out T10 item10, out T11 item11, out T12 item12, out T13 item13, out T14 item14, out T15 item15, out T16 item16, out T17 item17, out T18 item18)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+            item8 = value.Rest.Item1;
+            item9 = value.Rest.Item2;
+            item10 = value.Rest.Item3;
+            item11 = value.Rest.Item4;
+            item12 = value.Rest.Item5;
+            item13 = value.Rest.Item6;
+            item14 = value.Rest.Item7;
+            item15 = value.Rest.Rest.Item1;
+            item16 = value.Rest.Rest.Item2;
+            item17 = value.Rest.Rest.Item3;
+            item18 = value.Rest.Rest.Item4;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 19 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17, T18, T19>>> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7, out T8 item8, out T9 item9, out T10 item10, out T11 item11, out T12 item12, out T13 item13, out T14 item14, out T15 item15, out T16 item16, out T17 item17, out T18 item18, out T19 item19)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+            item8 = value.Rest.Item1;
+            item9 = value.Rest.Item2;
+            item10 = value.Rest.Item3;
+            item11 = value.Rest.Item4;
+            item12 = value.Rest.Item5;
+            item13 = value.Rest.Item6;
+            item14 = value.Rest.Item7;
+            item15 = value.Rest.Rest.Item1;
+            item16 = value.Rest.Rest.Item2;
+            item17 = value.Rest.Rest.Item3;
+            item18 = value.Rest.Rest.Item4;
+            item19 = value.Rest.Rest.Item5;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 20 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17, T18, T19, T20>>> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7, out T8 item8, out T9 item9, out T10 item10, out T11 item11, out T12 item12, out T13 item13, out T14 item14, out T15 item15, out T16 item16, out T17 item17, out T18 item18, out T19 item19, out T20 item20)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+            item8 = value.Rest.Item1;
+            item9 = value.Rest.Item2;
+            item10 = value.Rest.Item3;
+            item11 = value.Rest.Item4;
+            item12 = value.Rest.Item5;
+            item13 = value.Rest.Item6;
+            item14 = value.Rest.Item7;
+            item15 = value.Rest.Rest.Item1;
+            item16 = value.Rest.Rest.Item2;
+            item17 = value.Rest.Rest.Item3;
+            item18 = value.Rest.Rest.Item4;
+            item19 = value.Rest.Rest.Item5;
+            item20 = value.Rest.Rest.Item6;
+        }
+
+        /// <summary>
+        /// Deconstruct a properly nested <see cref="Tuple"/> with 21 elements.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public static void Deconstruct<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21>(
+            this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17, T18, T19, T20, T21>>> value,
+            out T1 item1, out T2 item2, out T3 item3, out T4 item4, out T5 item5, out T6 item6, out T7 item7, out T8 item8, out T9 item9, out T10 item10, out T11 item11, out T12 item12, out T13 item13, out T14 item14, out T15 item15, out T16 item16, out T17 item17, out T18 item18, out T19 item19, out T20 item20, out T21 item21)
+        {
+            item1 = value.Item1;
+            item2 = value.Item2;
+            item3 = value.Item3;
+            item4 = value.Item4;
+            item5 = value.Item5;
+            item6 = value.Item6;
+            item7 = value.Item7;
+            item8 = value.Rest.Item1;
+            item9 = value.Rest.Item2;
+            item10 = value.Rest.Item3;
+            item11 = value.Rest.Item4;
+            item12 = value.Rest.Item5;
+            item13 = value.Rest.Item6;
+            item14 = value.Rest.Item7;
+            item15 = value.Rest.Rest.Item1;
+            item16 = value.Rest.Rest.Item2;
+            item17 = value.Rest.Rest.Item3;
+            item18 = value.Rest.Rest.Item4;
+            item19 = value.Rest.Rest.Item5;
+            item20 = value.Rest.Rest.Item6;
+            item21 = value.Rest.Rest.Item7;
+        }
+        #endregion
+
+        #region ToValueTuple
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 1 element.
+        /// </summary>
+        public static ValueTuple<T1>
+            ToValueTuple<T1>(
+                this Tuple<T1> value)
+        {
+            return ValueTuple.Create(value.Item1);
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 2 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2>
+            ToValueTuple<T1, T2>(
+                this Tuple<T1, T2> value)
+        {
+            return ValueTuple.Create(value.Item1, value.Item2);
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 3 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3>
+            ToValueTuple<T1, T2, T3>(
+                this Tuple<T1, T2, T3> value)
+        {
+            return ValueTuple.Create(value.Item1, value.Item2, value.Item3);
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 4 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4>
+            ToValueTuple<T1, T2, T3, T4>(
+                this Tuple<T1, T2, T3, T4> value)
+        {
+            return ValueTuple.Create(value.Item1, value.Item2, value.Item3, value.Item4);
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 5 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5>
+            ToValueTuple<T1, T2, T3, T4, T5>(
+                this Tuple<T1, T2, T3, T4, T5> value)
+        {
+            return ValueTuple.Create(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5);
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 6 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6>
+            ToValueTuple<T1, T2, T3, T4, T5, T6>(
+                this Tuple<T1, T2, T3, T4, T5, T6> value)
+        {
+            return ValueTuple.Create(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6);
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 7 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7> value)
+        {
+            return ValueTuple.Create(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7);
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 8 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8>>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7, T8>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8>> value)
+        {
+            return CreateLong(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        ValueTuple.Create(value.Rest.Item1));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 9 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9>>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9>> value)
+        {
+            return CreateLong(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        ValueTuple.Create(value.Rest.Item1, value.Rest.Item2));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 10 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10>>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10>> value)
+        {
+            return CreateLong(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        ValueTuple.Create(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 11 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11>>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11>> value)
+        {
+            return CreateLong(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        ValueTuple.Create(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 12 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12>>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12>> value)
+        {
+            return CreateLong(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        ValueTuple.Create(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 13 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13>>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13>> value)
+        {
+            return CreateLong(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        ValueTuple.Create(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 14 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14>>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14>> value)
+        {
+            return CreateLong(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        ValueTuple.Create(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 15 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14, ValueTuple<T15>>>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15>>> value)
+        {
+            return CreateLong(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        CreateLong(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7,
+                            ValueTuple.Create(value.Rest.Rest.Item1)));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 16 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14, ValueTuple<T15, T16>>>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16>>> value)
+        {
+            return CreateLong(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        CreateLong(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7,
+                            ValueTuple.Create(value.Rest.Rest.Item1, value.Rest.Rest.Item2)));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 17 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14, ValueTuple<T15, T16, T17>>>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17>>> value)
+        {
+            return CreateLong(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        CreateLong(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7,
+                            ValueTuple.Create(value.Rest.Rest.Item1, value.Rest.Rest.Item2, value.Rest.Rest.Item3)));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 18 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14, ValueTuple<T15, T16, T17, T18>>>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17, T18>>> value)
+        {
+            return CreateLong(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        CreateLong(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7,
+                            ValueTuple.Create(value.Rest.Rest.Item1, value.Rest.Rest.Item2, value.Rest.Rest.Item3, value.Rest.Rest.Item4)));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 19 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14, ValueTuple<T15, T16, T17, T18, T19>>>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17, T18, T19>>> value)
+        {
+            return CreateLong(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        CreateLong(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7,
+                            ValueTuple.Create(value.Rest.Rest.Item1, value.Rest.Rest.Item2, value.Rest.Rest.Item3, value.Rest.Rest.Item4, value.Rest.Rest.Item5)));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 20 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14, ValueTuple<T15, T16, T17, T18, T19, T20>>>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17, T18, T19, T20>>> value)
+        {
+            return CreateLong(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        CreateLong(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7,
+                            ValueTuple.Create(value.Rest.Rest.Item1, value.Rest.Rest.Item2, value.Rest.Rest.Item3, value.Rest.Rest.Item4, value.Rest.Rest.Item5, value.Rest.Rest.Item6)));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="ValueTuple"/> from a properly nested <see cref="Tuple"/> with 21 elements.
+        /// </summary>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14, ValueTuple<T15, T16, T17, T18, T19, T20, T21>>>
+            ToValueTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21>(
+                this Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17, T18, T19, T20, T21>>> value)
+        {
+            return CreateLong(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        CreateLong(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7,
+                            ValueTuple.Create(value.Rest.Rest.Item1, value.Rest.Rest.Item2, value.Rest.Rest.Item3, value.Rest.Rest.Item4, value.Rest.Rest.Item5, value.Rest.Rest.Item6, value.Rest.Rest.Item7)));
+        }
+        #endregion
+
+        #region ToTuple
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 1 element.
+        /// </summary>
+        public static Tuple<T1>
+            ToTuple<T1>(
+                this ValueTuple<T1> value)
+        {
+            return Tuple.Create(value.Item1);
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 2 elements.
+        /// </summary>
+        public static Tuple<T1, T2>
+            ToTuple<T1, T2>(
+                this ValueTuple<T1, T2> value)
+        {
+            return Tuple.Create(value.Item1, value.Item2);
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 3 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3>
+            ToTuple<T1, T2, T3>(
+                this ValueTuple<T1, T2, T3> value)
+        {
+            return Tuple.Create(value.Item1, value.Item2, value.Item3);
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 4 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4>
+            ToTuple<T1, T2, T3, T4>(
+                this ValueTuple<T1, T2, T3, T4> value)
+        {
+            return Tuple.Create(value.Item1, value.Item2, value.Item3, value.Item4);
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 5 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5>
+            ToTuple<T1, T2, T3, T4, T5>(
+                this ValueTuple<T1, T2, T3, T4, T5> value)
+        {
+            return Tuple.Create(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5);
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 6 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6>
+            ToTuple<T1, T2, T3, T4, T5, T6>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6> value)
+        {
+            return Tuple.Create(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6);
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 7 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7> value)
+        {
+            return Tuple.Create(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7);
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 8 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8>>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7, T8>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8>> value)
+        {
+            return CreateLongRef(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        Tuple.Create(value.Rest.Item1));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 9 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9>>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9>> value)
+        {
+            return CreateLongRef(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        Tuple.Create(value.Rest.Item1, value.Rest.Item2));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 10 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10>>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10>> value)
+        {
+            return CreateLongRef(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        Tuple.Create(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 11 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11>>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11>> value)
+        {
+            return CreateLongRef(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        Tuple.Create(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 12 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12>>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12>> value)
+        {
+            return CreateLongRef(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        Tuple.Create(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 13 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13>>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13>> value)
+        {
+            return CreateLongRef(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        Tuple.Create(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 14 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14>>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14>> value)
+        {
+            return CreateLongRef(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        Tuple.Create(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 15 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15>>>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14, ValueTuple<T15>>> value)
+        {
+            return CreateLongRef(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        CreateLongRef(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7,
+                            Tuple.Create(value.Rest.Rest.Item1)));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 16 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16>>>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14, ValueTuple<T15, T16>>> value)
+        {
+            return CreateLongRef(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        CreateLongRef(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7,
+                            Tuple.Create(value.Rest.Rest.Item1, value.Rest.Rest.Item2)));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 17 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17>>>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14, ValueTuple<T15, T16, T17>>> value)
+        {
+            return CreateLongRef(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        CreateLongRef(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7,
+                            Tuple.Create(value.Rest.Rest.Item1, value.Rest.Rest.Item2, value.Rest.Rest.Item3)));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 18 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17, T18>>>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14, ValueTuple<T15, T16, T17, T18>>> value)
+        {
+            return CreateLongRef(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        CreateLongRef(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7,
+                            Tuple.Create(value.Rest.Rest.Item1, value.Rest.Rest.Item2, value.Rest.Rest.Item3, value.Rest.Rest.Item4)));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 19 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17, T18, T19>>>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14, ValueTuple<T15, T16, T17, T18, T19>>> value)
+        {
+            return CreateLongRef(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        CreateLongRef(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7,
+                            Tuple.Create(value.Rest.Rest.Item1, value.Rest.Rest.Item2, value.Rest.Rest.Item3, value.Rest.Rest.Item4, value.Rest.Rest.Item5)));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 20 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17, T18, T19, T20>>>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14, ValueTuple<T15, T16, T17, T18, T19, T20>>> value)
+        {
+            return CreateLongRef(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        CreateLongRef(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7,
+                            Tuple.Create(value.Rest.Rest.Item1, value.Rest.Rest.Item2, value.Rest.Rest.Item3, value.Rest.Rest.Item4, value.Rest.Rest.Item5, value.Rest.Rest.Item6)));
+        }
+
+        /// <summary>
+        /// Make a properly nested <see cref="Tuple"/> from a properly nested <see cref="ValueTuple"/> with 21 elements.
+        /// </summary>
+        public static Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8, T9, T10, T11, T12, T13, T14, Tuple<T15, T16, T17, T18, T19, T20, T21>>>
+            ToTuple<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21>(
+                this ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8, T9, T10, T11, T12, T13, T14, ValueTuple<T15, T16, T17, T18, T19, T20, T21>>> value)
+        {
+            return CreateLongRef(value.Item1, value.Item2, value.Item3, value.Item4, value.Item5, value.Item6, value.Item7,
+                        CreateLongRef(value.Rest.Item1, value.Rest.Item2, value.Rest.Item3, value.Rest.Item4, value.Rest.Item5, value.Rest.Item6, value.Rest.Item7,
+                            Tuple.Create(value.Rest.Rest.Item1, value.Rest.Rest.Item2, value.Rest.Rest.Item3, value.Rest.Rest.Item4, value.Rest.Rest.Item5, value.Rest.Rest.Item6, value.Rest.Rest.Item7)));
+        }
+        #endregion
+
+        private static ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest> CreateLong<T1, T2, T3, T4, T5, T6, T7, TRest>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7, TRest rest) where TRest : struct, ITuple =>
+            new ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>(item1, item2, item3, item4, item5, item6, item7, rest);
+
+        private static Tuple<T1, T2, T3, T4, T5, T6, T7, TRest> CreateLongRef<T1, T2, T3, T4, T5, T6, T7, TRest>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7, TRest rest) where TRest : ITuple =>
+            new Tuple<T1, T2, T3, T4, T5, T6, T7, TRest>(item1, item2, item3, item4, item5, item6, item7, rest);
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Type.Enum.cs b/src/System.Private.CoreLib/shared/System/Type.Enum.cs
new file mode 100644
index 0000000000..4d82410383
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Type.Enum.cs
@@ -0,0 +1,186 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+using System.Collections;
+using System.Collections.Generic;
+
+namespace System
+{
+    //
+    // This file collects a set of Enum-related apis that run when the Type is subclassed by an application.
+    // None of it runs on normal Type objects supplied by the runtime (as those types override these methods.)
+    //
+    // Since app-subclassed Types are "untrusted classes" that may or may not implement the complete surface area correctly,
+    // this code should be considered brittle and not changed lightly.
+    //
+    public abstract partial class Type
+    {
+        public virtual bool IsEnumDefined(object value)
+        {
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            if (!IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
+
+            // Check if both of them are of the same type
+            Type valueType = value.GetType();
+
+            // If the value is an Enum then we need to extract the underlying value from it
+            if (valueType.IsEnum)
+            {
+                if (!valueType.IsEquivalentTo(this))
+                    throw new ArgumentException(SR.Format(SR.Arg_EnumAndObjectMustBeSameType, valueType.ToString(), this.ToString()));
+
+                valueType = valueType.GetEnumUnderlyingType();
+            }
+
+            // If a string is passed in
+            if (valueType == typeof(string))
+            {
+                string[] names = GetEnumNames();
+                if (Array.IndexOf(names, value) >= 0)
+                    return true;
+                else
+                    return false;
+            }
+
+            // If an enum or integer value is passed in
+            if (Type.IsIntegerType(valueType))
+            {
+                Type underlyingType = GetEnumUnderlyingType();
+                // We cannot compare the types directly because valueType is always a runtime type but underlyingType might not be.
+                if (underlyingType.GetTypeCodeImpl() != valueType.GetTypeCodeImpl())
+                    throw new ArgumentException(SR.Format(SR.Arg_EnumUnderlyingTypeAndObjectMustBeSameType, valueType.ToString(), underlyingType.ToString()));
+
+                Array values = GetEnumRawConstantValues();
+                return (BinarySearch(values, value) >= 0);
+            }
+            else
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_UnknownEnumType);
+            }
+        }
+
+        public virtual string GetEnumName(object value)
+        {
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            if (!IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
+
+            Type valueType = value.GetType();
+
+            if (!(valueType.IsEnum || Type.IsIntegerType(valueType)))
+                throw new ArgumentException(SR.Arg_MustBeEnumBaseTypeOrEnum, nameof(value));
+
+            Array values = GetEnumRawConstantValues();
+            int index = BinarySearch(values, value);
+
+            if (index >= 0)
+            {
+                string[] names = GetEnumNames();
+                return names[index];
+            }
+
+            return null;
+        }
+
+        public virtual string[] GetEnumNames()
+        {
+            if (!IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
+
+            string[] names;
+            Array values;
+            GetEnumData(out names, out values);
+            return names;
+        }
+
+
+        // Returns the enum values as an object array.
+        private Array GetEnumRawConstantValues()
+        {
+            string[] names;
+            Array values;
+            GetEnumData(out names, out values);
+            return values;
+        }
+
+        // This will return enumValues and enumNames sorted by the values.
+        private void GetEnumData(out string[] enumNames, out Array enumValues)
+        {
+            FieldInfo[] flds = GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static);
+
+            object[] values = new object[flds.Length];
+            string[] names = new string[flds.Length];
+
+            for (int i = 0; i < flds.Length; i++)
+            {
+                names[i] = flds[i].Name;
+                values[i] = flds[i].GetRawConstantValue();
+            }
+
+            // Insertion Sort these values in ascending order.
+            // We use this O(n^2) algorithm, but it turns out that most of the time the elements are already in sorted order and
+            // the common case performance will be faster than quick sorting this.
+            IComparer comparer = Comparer<object>.Default;
+            for (int i = 1; i < values.Length; i++)
+            {
+                int j = i;
+                string tempStr = names[i];
+                object val = values[i];
+                bool exchanged = false;
+
+                // Since the elements are sorted we only need to do one comparision, we keep the check for j inside the loop.
+                while (comparer.Compare(values[j - 1], val) > 0)
+                {
+                    names[j] = names[j - 1];
+                    values[j] = values[j - 1];
+                    j--;
+                    exchanged = true;
+                    if (j == 0)
+                        break;
+                }
+
+                if (exchanged)
+                {
+                    names[j] = tempStr;
+                    values[j] = val;
+                }
+            }
+
+            enumNames = names;
+            enumValues = values;
+        }
+
+        // Convert everything to ulong then perform a binary search.
+        private static int BinarySearch(Array array, object value)
+        {
+            ulong[] ulArray = new ulong[array.Length];
+            for (int i = 0; i < array.Length; ++i)
+                ulArray[i] = Enum.ToUInt64(array.GetValue(i));
+
+            ulong ulValue = Enum.ToUInt64(value);
+
+            return Array.BinarySearch(ulArray, ulValue);
+        }
+
+        internal static bool IsIntegerType(Type t)
+        {
+            return (t == typeof(int) ||
+                    t == typeof(short) ||
+                    t == typeof(ushort) ||
+                    t == typeof(byte) ||
+                    t == typeof(sbyte) ||
+                    t == typeof(uint) ||
+                    t == typeof(long) ||
+                    t == typeof(ulong) ||
+                    t == typeof(char) ||
+                    t == typeof(bool));
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Type.Helpers.cs b/src/System.Private.CoreLib/shared/System/Type.Helpers.cs
new file mode 100644
index 0000000000..db8df231e4
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Type.Helpers.cs
@@ -0,0 +1,527 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+
+namespace System
+{
+    // This file collects the longer methods of Type to make the main Type class more readable.
+    public abstract partial class Type : MemberInfo, IReflect
+    {
+        public virtual bool IsSerializable
+        {
+            get
+            {
+                if ((GetAttributeFlagsImpl() & TypeAttributes.Serializable) != 0)
+                    return true;
+
+                Type underlyingType = UnderlyingSystemType;
+                if (underlyingType.IsRuntimeImplemented())
+                {
+                    do
+                    {
+                        // In all sane cases we only need to compare the direct level base type with
+                        // System.Enum and System.MulticastDelegate. However, a generic parameter can
+                        // have a base type constraint that is Delegate or even a real delegate type.
+                        // Let's maintain compatibility and return true for them.
+                        if (underlyingType == typeof(Delegate) || underlyingType == typeof(Enum))
+                            return true;
+
+                        underlyingType = underlyingType.BaseType;
+                    }
+                    while (underlyingType != null);
+                }
+
+                return false;
+            }
+        }
+
+        public virtual bool ContainsGenericParameters
+        {
+            get
+            {
+                if (HasElementType)
+                    return GetRootElementType().ContainsGenericParameters;
+
+                if (IsGenericParameter)
+                    return true;
+
+                if (!IsGenericType)
+                    return false;
+
+                Type[] genericArguments = GetGenericArguments();
+                for (int i = 0; i < genericArguments.Length; i++)
+                {
+                    if (genericArguments[i].ContainsGenericParameters)
+                        return true;
+                }
+
+                return false;
+            }
+        }
+
+        internal Type GetRootElementType()
+        {
+            Type rootElementType = this;
+
+            while (rootElementType.HasElementType)
+                rootElementType = rootElementType.GetElementType();
+
+            return rootElementType;
+        }
+
+        public bool IsVisible
+        {
+            get
+            {
+#if CORECLR
+                RuntimeType rt = this as RuntimeType;
+                if (rt != null)
+                    return RuntimeTypeHandle.IsVisible(rt);
+#endif //CORECLR
+
+                if (IsGenericParameter)
+                    return true;
+
+                if (HasElementType)
+                    return GetElementType().IsVisible;
+
+                Type type = this;
+                while (type.IsNested)
+                {
+                    if (!type.IsNestedPublic)
+                        return false;
+
+                    // this should be null for non-nested types.
+                    type = type.DeclaringType;
+                }
+
+                // Now "type" should be a top level type
+                if (!type.IsPublic)
+                    return false;
+
+                if (IsGenericType && !IsGenericTypeDefinition)
+                {
+                    foreach (Type t in GetGenericArguments())
+                    {
+                        if (!t.IsVisible)
+                            return false;
+                    }
+                }
+
+                return true;
+            }
+        }
+
+        public virtual Type[] FindInterfaces(TypeFilter filter, object filterCriteria)
+        {
+            if (filter == null)
+                throw new ArgumentNullException(nameof(filter));
+
+            Type[] c = GetInterfaces();
+            int cnt = 0;
+            for (int i = 0; i < c.Length; i++)
+            {
+                if (!filter(c[i], filterCriteria))
+                    c[i] = null;
+                else
+                    cnt++;
+            }
+            if (cnt == c.Length)
+                return c;
+
+            Type[] ret = new Type[cnt];
+            cnt = 0;
+            for (int i = 0; i < c.Length; i++)
+            {
+                if (c[i] != null)
+                    ret[cnt++] = c[i];
+            }
+            return ret;
+        }
+
+        public virtual MemberInfo[] FindMembers(MemberTypes memberType, BindingFlags bindingAttr, MemberFilter filter, object filterCriteria)
+        {
+            // Define the work arrays
+            MethodInfo[] m = null;
+            ConstructorInfo[] c = null;
+            FieldInfo[] f = null;
+            PropertyInfo[] p = null;
+            EventInfo[] e = null;
+            Type[] t = null;
+
+            int i = 0;
+            int cnt = 0;            // Total Matchs
+
+            // Check the methods
+            if ((memberType & MemberTypes.Method) != 0)
+            {
+                m = GetMethods(bindingAttr);
+                if (filter != null)
+                {
+                    for (i = 0; i < m.Length; i++)
+                        if (!filter(m[i], filterCriteria))
+                            m[i] = null;
+                        else
+                            cnt++;
+                }
+                else
+                {
+                    cnt += m.Length;
+                }
+            }
+
+            // Check the constructors
+            if ((memberType & MemberTypes.Constructor) != 0)
+            {
+                c = GetConstructors(bindingAttr);
+                if (filter != null)
+                {
+                    for (i = 0; i < c.Length; i++)
+                        if (!filter(c[i], filterCriteria))
+                            c[i] = null;
+                        else
+                            cnt++;
+                }
+                else
+                {
+                    cnt += c.Length;
+                }
+            }
+
+            // Check the fields
+            if ((memberType & MemberTypes.Field) != 0)
+            {
+                f = GetFields(bindingAttr);
+                if (filter != null)
+                {
+                    for (i = 0; i < f.Length; i++)
+                        if (!filter(f[i], filterCriteria))
+                            f[i] = null;
+                        else
+                            cnt++;
+                }
+                else
+                {
+                    cnt += f.Length;
+                }
+            }
+
+            // Check the Properties
+            if ((memberType & MemberTypes.Property) != 0)
+            {
+                p = GetProperties(bindingAttr);
+                if (filter != null)
+                {
+                    for (i = 0; i < p.Length; i++)
+                        if (!filter(p[i], filterCriteria))
+                            p[i] = null;
+                        else
+                            cnt++;
+                }
+                else
+                {
+                    cnt += p.Length;
+                }
+            }
+
+            // Check the Events
+            if ((memberType & MemberTypes.Event) != 0)
+            {
+                e = GetEvents(bindingAttr);
+                if (filter != null)
+                {
+                    for (i = 0; i < e.Length; i++)
+                        if (!filter(e[i], filterCriteria))
+                            e[i] = null;
+                        else
+                            cnt++;
+                }
+                else
+                {
+                    cnt += e.Length;
+                }
+            }
+
+            // Check the Types
+            if ((memberType & MemberTypes.NestedType) != 0)
+            {
+                t = GetNestedTypes(bindingAttr);
+                if (filter != null)
+                {
+                    for (i = 0; i < t.Length; i++)
+                        if (!filter(t[i], filterCriteria))
+                            t[i] = null;
+                        else
+                            cnt++;
+                }
+                else
+                {
+                    cnt += t.Length;
+                }
+            }
+
+            // Allocate the Member Info
+            MemberInfo[] ret = new MemberInfo[cnt];
+
+            // Copy the Methods
+            cnt = 0;
+            if (m != null)
+            {
+                for (i = 0; i < m.Length; i++)
+                    if (m[i] != null)
+                        ret[cnt++] = m[i];
+            }
+
+            // Copy the Constructors
+            if (c != null)
+            {
+                for (i = 0; i < c.Length; i++)
+                    if (c[i] != null)
+                        ret[cnt++] = c[i];
+            }
+
+            // Copy the Fields
+            if (f != null)
+            {
+                for (i = 0; i < f.Length; i++)
+                    if (f[i] != null)
+                        ret[cnt++] = f[i];
+            }
+
+            // Copy the Properties
+            if (p != null)
+            {
+                for (i = 0; i < p.Length; i++)
+                    if (p[i] != null)
+                        ret[cnt++] = p[i];
+            }
+
+            // Copy the Events
+            if (e != null)
+            {
+                for (i = 0; i < e.Length; i++)
+                    if (e[i] != null)
+                        ret[cnt++] = e[i];
+            }
+
+            // Copy the Types
+            if (t != null)
+            {
+                for (i = 0; i < t.Length; i++)
+                    if (t[i] != null)
+                        ret[cnt++] = t[i];
+            }
+
+            return ret;
+        }
+
+        public virtual bool IsSubclassOf(Type c)
+        {
+            Type p = this;
+            if (p == c)
+                return false;
+            while (p != null)
+            {
+                if (p == c)
+                    return true;
+                p = p.BaseType;
+            }
+            return false;
+        }
+
+        public virtual bool IsAssignableFrom(Type c)
+        {
+            if (c == null)
+                return false;
+
+            if (this == c)
+                return true;
+
+            // For backward-compatibility, we need to special case for the types
+            // whose UnderlyingSystemType are runtime implemented. 
+            Type toType = this.UnderlyingSystemType;
+            if (toType.IsRuntimeImplemented())
+                return toType.IsAssignableFrom(c);
+
+            // If c is a subclass of this class, then c can be cast to this type.
+            if (c.IsSubclassOf(this))
+                return true;
+
+            if (this.IsInterface)
+            {
+                return c.ImplementInterface(this);
+            }
+            else if (IsGenericParameter)
+            {
+                Type[] constraints = GetGenericParameterConstraints();
+                for (int i = 0; i < constraints.Length; i++)
+                    if (!constraints[i].IsAssignableFrom(c))
+                        return false;
+
+                return true;
+            }
+
+            return false;
+        }
+
+        internal bool ImplementInterface(Type ifaceType)
+        {
+            Type t = this;
+            while (t != null)
+            {
+                Type[] interfaces = t.GetInterfaces();
+                if (interfaces != null)
+                {
+                    for (int i = 0; i < interfaces.Length; i++)
+                    {
+                        // Interfaces don't derive from other interfaces, they implement them.
+                        // So instead of IsSubclassOf, we should use ImplementInterface instead.
+                        if (interfaces[i] == ifaceType ||
+                            (interfaces[i] != null && interfaces[i].ImplementInterface(ifaceType)))
+                            return true;
+                    }
+                }
+
+                t = t.BaseType;
+            }
+
+            return false;
+        }
+
+        // FilterAttribute
+        //  This method will search for a member based upon the attribute passed in.
+        //  filterCriteria -- an Int32 representing the attribute
+        private static bool FilterAttributeImpl(MemberInfo m, object filterCriteria)
+        {
+            // Check that the criteria object is an Integer object
+            if (filterCriteria == null)
+                throw new InvalidFilterCriteriaException(SR.InvalidFilterCriteriaException_CritInt);
+
+            switch (m.MemberType)
+            {
+                case MemberTypes.Constructor:
+                case MemberTypes.Method:
+                    {
+                        MethodAttributes criteria = 0;
+                        try
+                        {
+                            int i = (int)filterCriteria;
+                            criteria = (MethodAttributes)i;
+                        }
+                        catch
+                        {
+                            throw new InvalidFilterCriteriaException(SR.InvalidFilterCriteriaException_CritInt);
+                        }
+
+
+                        MethodAttributes attr;
+                        if (m.MemberType == MemberTypes.Method)
+                            attr = ((MethodInfo)m).Attributes;
+                        else
+                            attr = ((ConstructorInfo)m).Attributes;
+
+                        if (((criteria & MethodAttributes.MemberAccessMask) != 0) && (attr & MethodAttributes.MemberAccessMask) != (criteria & MethodAttributes.MemberAccessMask))
+                            return false;
+                        if (((criteria & MethodAttributes.Static) != 0) && (attr & MethodAttributes.Static) == 0)
+                            return false;
+                        if (((criteria & MethodAttributes.Final) != 0) && (attr & MethodAttributes.Final) == 0)
+                            return false;
+                        if (((criteria & MethodAttributes.Virtual) != 0) && (attr & MethodAttributes.Virtual) == 0)
+                            return false;
+                        if (((criteria & MethodAttributes.Abstract) != 0) && (attr & MethodAttributes.Abstract) == 0)
+                            return false;
+                        if (((criteria & MethodAttributes.SpecialName) != 0) && (attr & MethodAttributes.SpecialName) == 0)
+                            return false;
+                        return true;
+                    }
+                case MemberTypes.Field:
+                    {
+                        FieldAttributes criteria = 0;
+                        try
+                        {
+                            int i = (int)filterCriteria;
+                            criteria = (FieldAttributes)i;
+                        }
+                        catch
+                        {
+                            throw new InvalidFilterCriteriaException(SR.InvalidFilterCriteriaException_CritInt);
+                        }
+
+                        FieldAttributes attr = ((FieldInfo)m).Attributes;
+                        if (((criteria & FieldAttributes.FieldAccessMask) != 0) && (attr & FieldAttributes.FieldAccessMask) != (criteria & FieldAttributes.FieldAccessMask))
+                            return false;
+                        if (((criteria & FieldAttributes.Static) != 0) && (attr & FieldAttributes.Static) == 0)
+                            return false;
+                        if (((criteria & FieldAttributes.InitOnly) != 0) && (attr & FieldAttributes.InitOnly) == 0)
+                            return false;
+                        if (((criteria & FieldAttributes.Literal) != 0) && (attr & FieldAttributes.Literal) == 0)
+                            return false;
+                        if (((criteria & FieldAttributes.NotSerialized) != 0) && (attr & FieldAttributes.NotSerialized) == 0)
+                            return false;
+                        if (((criteria & FieldAttributes.PinvokeImpl) != 0) && (attr & FieldAttributes.PinvokeImpl) == 0)
+                            return false;
+                        return true;
+                    }
+            }
+
+            return false;
+        }
+
+        // FilterName
+        // This method will filter based upon the name.  A partial wildcard
+        //  at the end of the string is supported.
+        //  filterCriteria -- This is the string name
+        private static bool FilterNameImpl(MemberInfo m, object filterCriteria)
+        {
+            // Check that the criteria object is a String object
+            if (filterCriteria == null || !(filterCriteria is string))
+                throw new InvalidFilterCriteriaException(SR.InvalidFilterCriteriaException_CritString);
+
+            // At the moment this fails if its done on a single line....
+            string str = ((string)filterCriteria);
+            str = str.Trim();
+
+            string name = m.Name;
+            // Get the nested class name only, as opposed to the mangled one
+            if (m.MemberType == MemberTypes.NestedType)
+                name = name.Substring(name.LastIndexOf('+') + 1);
+            // Check to see if this is a prefix or exact match requirement
+            if (str.Length > 0 && str[str.Length - 1] == '*')
+            {
+                str = str.Substring(0, str.Length - 1);
+                return (name.StartsWith(str, StringComparison.Ordinal));
+            }
+
+            return (name.Equals(str));
+        }
+
+        // FilterIgnoreCase
+        // This delegate will do a name search but does it with the
+        //  ignore case specified.
+        private static bool FilterNameIgnoreCaseImpl(MemberInfo m, object filterCriteria)
+        {
+            // Check that the criteria object is a String object
+            if (filterCriteria == null || !(filterCriteria is string))
+                throw new InvalidFilterCriteriaException(SR.InvalidFilterCriteriaException_CritString);
+
+            string str = (string)filterCriteria;
+            str = str.Trim();
+
+            string name = m.Name;
+            // Get the nested class name only, as opposed to the mangled one
+            if (m.MemberType == MemberTypes.NestedType)
+                name = name.Substring(name.LastIndexOf('+') + 1);
+            // Check to see if this is a prefix or exact match requirement
+            if (str.Length > 0 && str[str.Length - 1] == '*')
+            {
+                str = str.Substring(0, str.Length - 1);
+                return (string.Compare(name, 0, str, 0, str.Length, StringComparison.OrdinalIgnoreCase) == 0);
+            }
+
+            return (string.Compare(str, name, StringComparison.OrdinalIgnoreCase) == 0);
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/Type.cs b/src/System.Private.CoreLib/shared/System/Type.cs
new file mode 100644
index 0000000000..b57baa869f
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Type.cs
@@ -0,0 +1,395 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading;
+using System.Reflection;
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.InteropServices;
+
+namespace System
+{
+    public abstract partial class Type : MemberInfo, IReflect
+    {
+        protected Type() { }
+
+        public override MemberTypes MemberType => MemberTypes.TypeInfo;
+
+        public new Type GetType() => base.GetType();
+
+        public abstract string Namespace { get; }
+        public abstract string AssemblyQualifiedName { get; }
+        public abstract string FullName { get; }
+
+        public abstract Assembly Assembly { get; }
+        public abstract new Module Module { get; }
+
+        public bool IsNested => DeclaringType != null;
+        public override Type DeclaringType => null;
+        public virtual MethodBase DeclaringMethod => null;
+
+        public override Type ReflectedType => null;
+        public abstract Type UnderlyingSystemType { get; }
+
+        public virtual bool IsTypeDefinition { get { throw NotImplemented.ByDesign; } }
+        public bool IsArray => IsArrayImpl();
+        protected abstract bool IsArrayImpl();
+        public bool IsByRef => IsByRefImpl();
+        protected abstract bool IsByRefImpl();
+        public bool IsPointer => IsPointerImpl();
+        protected abstract bool IsPointerImpl();
+        public virtual bool IsConstructedGenericType { get { throw NotImplemented.ByDesign; } }
+        public virtual bool IsGenericParameter => false;
+        public virtual bool IsGenericTypeParameter => IsGenericParameter && DeclaringMethod == null;
+        public virtual bool IsGenericMethodParameter => IsGenericParameter && DeclaringMethod != null;
+        public virtual bool IsGenericType => false;
+        public virtual bool IsGenericTypeDefinition => false;
+
+        public virtual bool IsSZArray { get { throw NotImplemented.ByDesign; } }
+        public virtual bool IsVariableBoundArray => IsArray && !IsSZArray;
+
+        public virtual bool IsByRefLike => throw new NotSupportedException(SR.NotSupported_SubclassOverride);
+
+        public bool HasElementType => HasElementTypeImpl();
+        protected abstract bool HasElementTypeImpl();
+        public abstract Type GetElementType();
+
+        public virtual int GetArrayRank() { throw new NotSupportedException(SR.NotSupported_SubclassOverride); }
+
+        public virtual Type GetGenericTypeDefinition() { throw new NotSupportedException(SR.NotSupported_SubclassOverride); }
+        public virtual Type[] GenericTypeArguments => (IsGenericType && !IsGenericTypeDefinition) ? GetGenericArguments() : Array.Empty<Type>();
+        public virtual Type[] GetGenericArguments() { throw new NotSupportedException(SR.NotSupported_SubclassOverride); }
+
+        public virtual int GenericParameterPosition { get { throw new InvalidOperationException(SR.Arg_NotGenericParameter); } }
+        public virtual GenericParameterAttributes GenericParameterAttributes { get { throw new NotSupportedException(); } }
+        public virtual Type[] GetGenericParameterConstraints()
+        {
+            if (!IsGenericParameter)
+                throw new InvalidOperationException(SR.Arg_NotGenericParameter);
+            throw new InvalidOperationException();
+        }
+
+        public TypeAttributes Attributes => GetAttributeFlagsImpl();
+        protected abstract TypeAttributes GetAttributeFlagsImpl();
+
+        public bool IsAbstract => (GetAttributeFlagsImpl() & TypeAttributes.Abstract) != 0;
+        public bool IsImport => (GetAttributeFlagsImpl() & TypeAttributes.Import) != 0;
+        public bool IsSealed => (GetAttributeFlagsImpl() & TypeAttributes.Sealed) != 0;
+        public bool IsSpecialName => (GetAttributeFlagsImpl() & TypeAttributes.SpecialName) != 0;
+
+        public bool IsClass => (GetAttributeFlagsImpl() & TypeAttributes.ClassSemanticsMask) == TypeAttributes.Class && !IsValueType;
+
+        public bool IsNestedAssembly => (GetAttributeFlagsImpl() & TypeAttributes.VisibilityMask) == TypeAttributes.NestedAssembly;
+        public bool IsNestedFamANDAssem => (GetAttributeFlagsImpl() & TypeAttributes.VisibilityMask) == TypeAttributes.NestedFamANDAssem;
+        public bool IsNestedFamily => (GetAttributeFlagsImpl() & TypeAttributes.VisibilityMask) == TypeAttributes.NestedFamily;
+        public bool IsNestedFamORAssem => (GetAttributeFlagsImpl() & TypeAttributes.VisibilityMask) == TypeAttributes.NestedFamORAssem;
+        public bool IsNestedPrivate => (GetAttributeFlagsImpl() & TypeAttributes.VisibilityMask) == TypeAttributes.NestedPrivate;
+        public bool IsNestedPublic => (GetAttributeFlagsImpl() & TypeAttributes.VisibilityMask) == TypeAttributes.NestedPublic;
+        public bool IsNotPublic => (GetAttributeFlagsImpl() & TypeAttributes.VisibilityMask) == TypeAttributes.NotPublic;
+        public bool IsPublic => (GetAttributeFlagsImpl() & TypeAttributes.VisibilityMask) == TypeAttributes.Public;
+
+        public bool IsAutoLayout => (GetAttributeFlagsImpl() & TypeAttributes.LayoutMask) == TypeAttributes.AutoLayout;
+        public bool IsExplicitLayout => (GetAttributeFlagsImpl() & TypeAttributes.LayoutMask) == TypeAttributes.ExplicitLayout;
+        public bool IsLayoutSequential => (GetAttributeFlagsImpl() & TypeAttributes.LayoutMask) == TypeAttributes.SequentialLayout;
+
+        public bool IsAnsiClass => (GetAttributeFlagsImpl() & TypeAttributes.StringFormatMask) == TypeAttributes.AnsiClass;
+        public bool IsAutoClass => (GetAttributeFlagsImpl() & TypeAttributes.StringFormatMask) == TypeAttributes.AutoClass;
+        public bool IsUnicodeClass => (GetAttributeFlagsImpl() & TypeAttributes.StringFormatMask) == TypeAttributes.UnicodeClass;
+
+        public bool IsCOMObject => IsCOMObjectImpl();
+        protected abstract bool IsCOMObjectImpl();
+        public bool IsContextful => IsContextfulImpl();
+        protected virtual bool IsContextfulImpl() => false;
+
+        public virtual bool IsCollectible => true;
+
+        public virtual bool IsEnum => IsSubclassOf(typeof(Enum));
+        public bool IsMarshalByRef => IsMarshalByRefImpl();
+        protected virtual bool IsMarshalByRefImpl() => false;
+        public bool IsPrimitive => IsPrimitiveImpl();
+        protected abstract bool IsPrimitiveImpl();
+        public bool IsValueType => IsValueTypeImpl();
+        protected virtual bool IsValueTypeImpl() => IsSubclassOf(typeof(ValueType));
+
+        public virtual bool IsSignatureType => false;
+
+        public virtual bool IsSecurityCritical { get { throw NotImplemented.ByDesign; } }
+        public virtual bool IsSecuritySafeCritical { get { throw NotImplemented.ByDesign; } }
+        public virtual bool IsSecurityTransparent { get { throw NotImplemented.ByDesign; } }
+
+        public virtual StructLayoutAttribute StructLayoutAttribute { get { throw new NotSupportedException(); } }
+        public ConstructorInfo TypeInitializer => GetConstructorImpl(BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic, null, CallingConventions.Any, Type.EmptyTypes, null);
+
+        public ConstructorInfo GetConstructor(Type[] types) => GetConstructor(BindingFlags.Public | BindingFlags.Instance, null, types, null);
+        public ConstructorInfo GetConstructor(BindingFlags bindingAttr, Binder binder, Type[] types, ParameterModifier[] modifiers) => GetConstructor(bindingAttr, binder, CallingConventions.Any, types, modifiers);
+        public ConstructorInfo GetConstructor(BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            if (types == null)
+                throw new ArgumentNullException(nameof(types));
+            for (int i = 0; i < types.Length; i++)
+            {
+                if (types[i] == null)
+                    throw new ArgumentNullException(nameof(types));
+            }
+            return GetConstructorImpl(bindingAttr, binder, callConvention, types, modifiers);
+        }
+        protected abstract ConstructorInfo GetConstructorImpl(BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers);
+
+        public ConstructorInfo[] GetConstructors() => GetConstructors(BindingFlags.Public | BindingFlags.Instance);
+        public abstract ConstructorInfo[] GetConstructors(BindingFlags bindingAttr);
+
+        public EventInfo GetEvent(string name) => GetEvent(name, Type.DefaultLookup);
+        public abstract EventInfo GetEvent(string name, BindingFlags bindingAttr);
+
+        public virtual EventInfo[] GetEvents() => GetEvents(Type.DefaultLookup);
+        public abstract EventInfo[] GetEvents(BindingFlags bindingAttr);
+
+        public FieldInfo GetField(string name) => GetField(name, Type.DefaultLookup);
+        public abstract FieldInfo GetField(string name, BindingFlags bindingAttr);
+
+        public FieldInfo[] GetFields() => GetFields(Type.DefaultLookup);
+        public abstract FieldInfo[] GetFields(BindingFlags bindingAttr);
+
+        public MemberInfo[] GetMember(string name) => GetMember(name, Type.DefaultLookup);
+        public virtual MemberInfo[] GetMember(string name, BindingFlags bindingAttr) => GetMember(name, MemberTypes.All, bindingAttr);
+        public virtual MemberInfo[] GetMember(string name, MemberTypes type, BindingFlags bindingAttr) { throw new NotSupportedException(SR.NotSupported_SubclassOverride); }
+
+        public MemberInfo[] GetMembers() => GetMembers(Type.DefaultLookup);
+        public abstract MemberInfo[] GetMembers(BindingFlags bindingAttr);
+
+        public MethodInfo GetMethod(string name) => GetMethod(name, Type.DefaultLookup);
+        public MethodInfo GetMethod(string name, BindingFlags bindingAttr)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+            return GetMethodImpl(name, bindingAttr, null, CallingConventions.Any, null, null);
+        }
+
+        public MethodInfo GetMethod(string name, Type[] types) => GetMethod(name, types, null);
+        public MethodInfo GetMethod(string name, Type[] types, ParameterModifier[] modifiers) => GetMethod(name, Type.DefaultLookup, null, types, modifiers);
+        public MethodInfo GetMethod(string name, BindingFlags bindingAttr, Binder binder, Type[] types, ParameterModifier[] modifiers) => GetMethod(name, bindingAttr, binder, CallingConventions.Any, types, modifiers);
+        public MethodInfo GetMethod(string name, BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+            if (types == null)
+                throw new ArgumentNullException(nameof(types));
+            for (int i = 0; i < types.Length; i++)
+            {
+                if (types[i] == null)
+                    throw new ArgumentNullException(nameof(types));
+            }
+            return GetMethodImpl(name, bindingAttr, binder, callConvention, types, modifiers);
+        }
+
+        protected abstract MethodInfo GetMethodImpl(string name, BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers);
+
+        public MethodInfo GetMethod(string name, int genericParameterCount, Type[] types) => GetMethod(name, genericParameterCount, types, null);
+        public MethodInfo GetMethod(string name, int genericParameterCount, Type[] types, ParameterModifier[] modifiers) => GetMethod(name, genericParameterCount, Type.DefaultLookup, null, types, modifiers);
+        public MethodInfo GetMethod(string name, int genericParameterCount, BindingFlags bindingAttr, Binder binder, Type[] types, ParameterModifier[] modifiers) => GetMethod(name, genericParameterCount, bindingAttr, binder, CallingConventions.Any, types, modifiers);
+        public MethodInfo GetMethod(string name, int genericParameterCount, BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+            if (genericParameterCount < 0)
+                throw new ArgumentException(SR.ArgumentOutOfRange_NeedNonNegNum, nameof(genericParameterCount));
+            if (types == null)
+                throw new ArgumentNullException(nameof(types));
+            for (int i = 0; i < types.Length; i++)
+            {
+                if (types[i] == null)
+                    throw new ArgumentNullException(nameof(types));
+            }
+            return GetMethodImpl(name, genericParameterCount, bindingAttr, binder, callConvention, types, modifiers);
+        }
+
+        protected virtual MethodInfo GetMethodImpl(string name, int genericParameterCount, BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers) => throw new NotSupportedException();
+
+        public MethodInfo[] GetMethods() => GetMethods(Type.DefaultLookup);
+        public abstract MethodInfo[] GetMethods(BindingFlags bindingAttr);
+
+        public Type GetNestedType(string name) => GetNestedType(name, Type.DefaultLookup);
+        public abstract Type GetNestedType(string name, BindingFlags bindingAttr);
+
+        public Type[] GetNestedTypes() => GetNestedTypes(Type.DefaultLookup);
+        public abstract Type[] GetNestedTypes(BindingFlags bindingAttr);
+
+        public PropertyInfo GetProperty(string name) => GetProperty(name, Type.DefaultLookup);
+        public PropertyInfo GetProperty(string name, BindingFlags bindingAttr)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+            return GetPropertyImpl(name, bindingAttr, null, null, null, null);
+        }
+
+        public PropertyInfo GetProperty(string name, Type returnType)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+            if (returnType == null)
+                throw new ArgumentNullException(nameof(returnType));
+            return GetPropertyImpl(name, Type.DefaultLookup, null, returnType, null, null);
+        }
+
+        public PropertyInfo GetProperty(string name, Type[] types) => GetProperty(name, null, types);
+        public PropertyInfo GetProperty(string name, Type returnType, Type[] types) => GetProperty(name, returnType, types, null);
+        public PropertyInfo GetProperty(string name, Type returnType, Type[] types, ParameterModifier[] modifiers) => GetProperty(name, Type.DefaultLookup, null, returnType, types, modifiers);
+        public PropertyInfo GetProperty(string name, BindingFlags bindingAttr, Binder binder, Type returnType, Type[] types, ParameterModifier[] modifiers)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+            if (types == null)
+                throw new ArgumentNullException(nameof(types));
+            return GetPropertyImpl(name, bindingAttr, binder, returnType, types, modifiers);
+        }
+
+        protected abstract PropertyInfo GetPropertyImpl(string name, BindingFlags bindingAttr, Binder binder, Type returnType, Type[] types, ParameterModifier[] modifiers);
+
+        public PropertyInfo[] GetProperties() => GetProperties(Type.DefaultLookup);
+        public abstract PropertyInfo[] GetProperties(BindingFlags bindingAttr);
+
+        public virtual MemberInfo[] GetDefaultMembers() { throw NotImplemented.ByDesign; }
+
+        public virtual RuntimeTypeHandle TypeHandle { get { throw new NotSupportedException(); } }
+        public static RuntimeTypeHandle GetTypeHandle(object o)
+        {
+            if (o == null)
+                throw new ArgumentNullException(null, SR.Arg_InvalidHandle);
+            Type type = o.GetType();
+            return type.TypeHandle;
+        }
+
+        public static Type[] GetTypeArray(object[] args)
+        {
+            if (args == null)
+                throw new ArgumentNullException(nameof(args));
+
+            Type[] cls = new Type[args.Length];
+            for (int i = 0; i < cls.Length; i++)
+            {
+                if (args[i] == null)
+                    throw new ArgumentNullException();
+                cls[i] = args[i].GetType();
+            }
+            return cls;
+        }
+
+        public static TypeCode GetTypeCode(Type type)
+        {
+            if (type == null)
+                return TypeCode.Empty;
+            return type.GetTypeCodeImpl();
+        }
+        protected virtual TypeCode GetTypeCodeImpl()
+        {
+            if (this != UnderlyingSystemType && UnderlyingSystemType != null)
+                return Type.GetTypeCode(UnderlyingSystemType);
+
+            return TypeCode.Object;
+        }
+
+        public abstract Guid GUID { get; }
+
+        public static Type GetTypeFromCLSID(Guid clsid) => GetTypeFromCLSID(clsid, null, throwOnError: false);
+        public static Type GetTypeFromCLSID(Guid clsid, bool throwOnError) => GetTypeFromCLSID(clsid, null, throwOnError: throwOnError);
+        public static Type GetTypeFromCLSID(Guid clsid, string server) => GetTypeFromCLSID(clsid, server, throwOnError: false);
+
+        public static Type GetTypeFromProgID(string progID) => GetTypeFromProgID(progID, null, throwOnError: false);
+        public static Type GetTypeFromProgID(string progID, bool throwOnError) => GetTypeFromProgID(progID, null, throwOnError: throwOnError);
+        public static Type GetTypeFromProgID(string progID, string server) => GetTypeFromProgID(progID, server, throwOnError: false);
+
+        public abstract Type BaseType { get; }
+
+        [DebuggerHidden]
+        [DebuggerStepThrough]
+        public object InvokeMember(string name, BindingFlags invokeAttr, Binder binder, object target, object[] args) => InvokeMember(name, invokeAttr, binder, target, args, null, null, null);
+
+        [DebuggerHidden]
+        [DebuggerStepThrough]
+        public object InvokeMember(string name, BindingFlags invokeAttr, Binder binder, object target, object[] args, CultureInfo culture) => InvokeMember(name, invokeAttr, binder, target, args, null, culture, null);
+        public abstract object InvokeMember(string name, BindingFlags invokeAttr, Binder binder, object target, object[] args, ParameterModifier[] modifiers, CultureInfo culture, string[] namedParameters);
+
+        public Type GetInterface(string name) => GetInterface(name, ignoreCase: false);
+        public abstract Type GetInterface(string name, bool ignoreCase);
+        public abstract Type[] GetInterfaces();
+
+        public virtual InterfaceMapping GetInterfaceMap(Type interfaceType) { throw new NotSupportedException(SR.NotSupported_SubclassOverride); }
+
+        public virtual bool IsInstanceOfType(object o) => o == null ? false : IsAssignableFrom(o.GetType());
+        public virtual bool IsEquivalentTo(Type other) => this == other;
+
+        public virtual Type GetEnumUnderlyingType()
+        {
+            if (!IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
+
+            FieldInfo[] fields = GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
+            if (fields == null || fields.Length != 1)
+                throw new ArgumentException(SR.Argument_InvalidEnum, "enumType");
+
+            return fields[0].FieldType;
+        }
+        public virtual Array GetEnumValues()
+        {
+            if (!IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
+
+            // We don't support GetEnumValues in the default implementation because we cannot create an array of
+            // a non-runtime type. If there is strong need we can consider returning an object or int64 array.
+            throw NotImplemented.ByDesign;
+        }
+
+        public virtual Type MakeArrayType() { throw new NotSupportedException(); }
+        public virtual Type MakeArrayType(int rank) { throw new NotSupportedException(); }
+        public virtual Type MakeByRefType() { throw new NotSupportedException(); }
+        public virtual Type MakeGenericType(params Type[] typeArguments) { throw new NotSupportedException(SR.NotSupported_SubclassOverride); }
+        public virtual Type MakePointerType() { throw new NotSupportedException(); }
+
+        public static Type MakeGenericMethodParameter(int position)
+        {
+            if (position < 0)
+                throw new ArgumentException(SR.ArgumentOutOfRange_NeedNonNegNum, nameof(position));
+            return new SignatureGenericMethodParameterType(position);
+        }
+
+        public override string ToString() => "Type: " + Name;  // Why do we add the "Type: " prefix?
+
+        public override bool Equals(object o) => o == null ? false : Equals(o as Type);
+        public override int GetHashCode()
+        {
+            Type systemType = UnderlyingSystemType;
+            if (!object.ReferenceEquals(systemType, this))
+                return systemType.GetHashCode();
+            return base.GetHashCode();
+        }
+        public virtual bool Equals(Type o) => o == null ? false : object.ReferenceEquals(this.UnderlyingSystemType, o.UnderlyingSystemType);
+
+        public static Type ReflectionOnlyGetType(string typeName, bool throwIfNotFound, bool ignoreCase) { throw new PlatformNotSupportedException(SR.PlatformNotSupported_ReflectionOnly); }
+
+        public static Binder DefaultBinder
+        {
+            get
+            {
+                if (s_defaultBinder == null)
+                {
+                    DefaultBinder binder = new DefaultBinder();
+                    Interlocked.CompareExchange<Binder>(ref s_defaultBinder, binder, null);
+                }
+                return s_defaultBinder;
+            }
+        }
+
+        private static volatile Binder s_defaultBinder;
+
+        public static readonly char Delimiter = '.';
+        public static readonly Type[] EmptyTypes = Array.Empty<Type>();
+        public static readonly object Missing = System.Reflection.Missing.Value;
+
+        public static readonly MemberFilter FilterAttribute = FilterAttributeImpl;
+        public static readonly MemberFilter FilterName = FilterNameImpl;
+        public static readonly MemberFilter FilterNameIgnoreCase = FilterNameIgnoreCaseImpl;
+
+        private const BindingFlags DefaultLookup = BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public;
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TypeAccessException.cs b/src/System.Private.CoreLib/shared/System/TypeAccessException.cs
new file mode 100644
index 0000000000..e12a8b08dd
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TypeAccessException.cs
@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    // TypeAccessException derives from TypeLoadException rather than MemberAccessException because in
+    // pre-v4 releases of the runtime TypeLoadException was used in lieu of a TypeAccessException.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class TypeAccessException : TypeLoadException
+    {
+        public TypeAccessException()
+            : base(SR.Arg_TypeAccessException)
+        {
+            HResult = HResults.COR_E_TYPEACCESS;
+        }
+
+        public TypeAccessException(string message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_TYPEACCESS;
+        }
+
+        public TypeAccessException(string message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_TYPEACCESS;
+        }
+
+        protected TypeAccessException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TypeCode.cs b/src/System.Private.CoreLib/shared/System/TypeCode.cs
new file mode 100644
index 0000000000..296198656b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TypeCode.cs
@@ -0,0 +1,47 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// The TypeCode enum represents the type code of an object. To obtain the
+// TypeCode for a given object, use the Value.GetTypeCode() method. The
+// TypeCode.Empty value represents a null object reference. The TypeCode.Object
+// value represents an object that doesn't implement the IConvertible interface. The
+// TypeCode.DBNull value represents the database null, which is distinct and
+// different from a null reference. The other type codes represent values that
+// use the given simple type encoding.
+//
+// Note that when an object has a given TypeCode, there is no guarantee that
+// the object is an instance of the corresponding System.XXX value class. For
+// example, an object with the type code TypeCode.Int32 might actually be an
+// instance of a nullable 32-bit integer type (with a value that isn't the
+// database null).
+//
+// There are no type codes for "Missing", "Error", "IDispatch", and "IUnknown".
+// These types of values are instead represented as classes. When the type code
+// of an object is TypeCode.Object, a further instance-of check can be used to
+// determine if the object is one of these values.
+
+namespace System
+{
+    public enum TypeCode
+    {
+        Empty = 0,          // Null reference
+        Object = 1,         // Instance that isn't a value
+        DBNull = 2,         // Database null value
+        Boolean = 3,        // Boolean
+        Char = 4,           // Unicode character
+        SByte = 5,          // Signed 8-bit integer
+        Byte = 6,           // Unsigned 8-bit integer
+        Int16 = 7,          // Signed 16-bit integer
+        UInt16 = 8,         // Unsigned 16-bit integer
+        Int32 = 9,          // Signed 32-bit integer
+        UInt32 = 10,        // Unsigned 32-bit integer
+        Int64 = 11,         // Signed 64-bit integer
+        UInt64 = 12,        // Unsigned 64-bit integer
+        Single = 13,        // IEEE 32-bit float
+        Double = 14,        // IEEE 64-bit double
+        Decimal = 15,       // Decimal
+        DateTime = 16,      // DateTime
+        String = 18,        // Unicode character string
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TypeInitializationException.cs b/src/System.Private.CoreLib/shared/System/TypeInitializationException.cs
new file mode 100644
index 0000000000..4bf2906217
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TypeInitializationException.cs
@@ -0,0 +1,80 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: The exception class to wrap exceptions thrown by
+**          a type's class initializer (.cctor).  This is sufficiently
+**          distinct from a TypeLoadException, which means we couldn't
+**          find the type.
+**
+**
+=============================================================================*/
+
+using System.Globalization;
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class TypeInitializationException : SystemException
+    {
+        private String _typeName;
+
+        // This exception is not creatable without specifying the
+        //    inner exception.
+        private TypeInitializationException()
+            : base(SR.TypeInitialization_Default)
+        {
+            HResult = HResults.COR_E_TYPEINITIALIZATION;
+        }
+
+
+        public TypeInitializationException(String fullTypeName, Exception innerException)
+            : this(fullTypeName, SR.Format(SR.TypeInitialization_Type, fullTypeName), innerException)
+        {
+        }
+
+        // This is called from within the runtime.  I believe this is necessary
+        // for Interop only, though it's not particularly useful.
+        internal TypeInitializationException(String message) : base(message)
+        {
+            HResult = HResults.COR_E_TYPEINITIALIZATION;
+        }
+
+        internal TypeInitializationException(String fullTypeName, String message, Exception innerException)
+            : base(message, innerException)
+        {
+            _typeName = fullTypeName;
+            HResult = HResults.COR_E_TYPEINITIALIZATION;
+        }
+
+        internal TypeInitializationException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            _typeName = info.GetString("TypeName");
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("TypeName", TypeName, typeof(string));
+        }
+
+        public String TypeName
+        {
+            get
+            {
+                if (_typeName == null)
+                {
+                    return String.Empty;
+                }
+                return _typeName;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/TypeUnloadedException.cs b/src/System.Private.CoreLib/shared/System/TypeUnloadedException.cs
new file mode 100644
index 0000000000..a01ef37a8b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/TypeUnloadedException.cs
@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class TypeUnloadedException : SystemException
+    {
+        public TypeUnloadedException()
+            : base(SR.Arg_TypeUnloadedException)
+        {
+            HResult = HResults.COR_E_TYPEUNLOADED;
+        }
+
+        public TypeUnloadedException(string message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_TYPEUNLOADED;
+        }
+
+        public TypeUnloadedException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_TYPEUNLOADED;
+        }
+        
+        protected TypeUnloadedException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/shared/System/UInt16.cs b/src/System.Private.CoreLib/shared/System/UInt16.cs
new file mode 100644
index 0000000000..3047d18198
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/UInt16.cs
@@ -0,0 +1,289 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    [Serializable]
+    [CLSCompliant(false)]
+    [StructLayout(LayoutKind.Sequential)]
+    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct UInt16 : IComparable, IConvertible, IFormattable, IComparable<UInt16>, IEquatable<UInt16>, ISpanFormattable
+    {
+        private ushort m_value; // Do not rename (binary serialization)
+
+        public const ushort MaxValue = (ushort)0xFFFF;
+        public const ushort MinValue = 0;
+
+
+        // Compares this object to another object, returning an integer that
+        // indicates the relationship. 
+        // Returns a value less than zero if this  object
+        // null is considered to be less than any instance.
+        // If object is not of type UInt16, this method throws an ArgumentException.
+        // 
+        public int CompareTo(Object value)
+        {
+            if (value == null)
+            {
+                return 1;
+            }
+            if (value is UInt16)
+            {
+                return ((int)m_value - (int)(((UInt16)value).m_value));
+            }
+            throw new ArgumentException(SR.Arg_MustBeUInt16);
+        }
+
+        public int CompareTo(UInt16 value)
+        {
+            return ((int)m_value - (int)value);
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (!(obj is UInt16))
+            {
+                return false;
+            }
+            return m_value == ((UInt16)obj).m_value;
+        }
+
+        [NonVersionable]
+        public bool Equals(UInt16 obj)
+        {
+            return m_value == obj;
+        }
+
+        // Returns a HashCode for the UInt16
+        public override int GetHashCode()
+        {
+            return (int)m_value;
+        }
+
+        // Converts the current value to a String in base-10 with no extra padding.
+        public override String ToString()
+        {
+            return Number.FormatUInt32(m_value, null, null);
+        }
+
+        public String ToString(IFormatProvider provider)
+        {
+            return Number.FormatUInt32(m_value, null, provider);
+        }
+
+
+        public String ToString(String format)
+        {
+            return Number.FormatUInt32(m_value, format, null);
+        }
+
+        public String ToString(String format, IFormatProvider provider)
+        {
+            return Number.FormatUInt32(m_value, format, provider);
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider provider = null)
+        {
+            return Number.TryFormatUInt32(m_value, format, provider, destination, out charsWritten);
+        }
+
+        [CLSCompliant(false)]
+        public static ushort Parse(String s)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo);
+        }
+
+        [CLSCompliant(false)]
+        public static ushort Parse(String s, NumberStyles style)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, style, NumberFormatInfo.CurrentInfo);
+        }
+
+
+        [CLSCompliant(false)]
+        public static ushort Parse(String s, IFormatProvider provider)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.GetInstance(provider));
+        }
+
+        [CLSCompliant(false)]
+        public static ushort Parse(String s, NumberStyles style, IFormatProvider provider)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Parse((ReadOnlySpan<char>)s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        [CLSCompliant(false)]
+        public static ushort Parse(ReadOnlySpan<char> s, NumberStyles style = NumberStyles.Integer, IFormatProvider provider = null)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return Parse(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        private static ushort Parse(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info)
+        {
+            uint i = 0;
+            try
+            {
+                i = Number.ParseUInt32(s, style, info);
+            }
+            catch (OverflowException e)
+            {
+                throw new OverflowException(SR.Overflow_UInt16, e);
+            }
+
+            if (i > MaxValue) throw new OverflowException(SR.Overflow_UInt16);
+            return (ushort)i;
+        }
+
+        [CLSCompliant(false)]
+        public static bool TryParse(String s, out UInt16 result)
+        {
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return TryParse((ReadOnlySpan<char>)s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        [CLSCompliant(false)]
+        public static bool TryParse(ReadOnlySpan<char> s, out ushort result)
+        {
+            return TryParse(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        [CLSCompliant(false)]
+        public static bool TryParse(String s, NumberStyles style, IFormatProvider provider, out UInt16 result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return TryParse((ReadOnlySpan<char>)s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        [CLSCompliant(false)]
+        public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider provider, out ushort result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return TryParse(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        private static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info, out UInt16 result)
+        {
+            result = 0;
+            UInt32 i;
+            if (!Number.TryParseUInt32(s, style, info, out i))
+            {
+                return false;
+            }
+            if (i > MaxValue)
+            {
+                return false;
+            }
+            result = (UInt16)i;
+            return true;
+        }
+
+        //
+        // IConvertible implementation
+        // 
+
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.UInt16;
+        }
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            return Convert.ToBoolean(m_value);
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            return Convert.ToChar(m_value);
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return Convert.ToSByte(m_value);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return Convert.ToByte(m_value);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return Convert.ToInt16(m_value);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return m_value;
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return Convert.ToInt32(m_value);
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return Convert.ToUInt32(m_value);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return Convert.ToInt64(m_value);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return Convert.ToUInt64(m_value);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            return Convert.ToSingle(m_value);
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            return Convert.ToDouble(m_value);
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            return Convert.ToDecimal(m_value);
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "UInt16", "DateTime"));
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/UInt32.cs b/src/System.Private.CoreLib/shared/System/UInt32.cs
new file mode 100644
index 0000000000..1e33dcf17b
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/UInt32.cs
@@ -0,0 +1,265 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    [Serializable]
+    [CLSCompliant(false)]
+    [StructLayout(LayoutKind.Sequential)]
+    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct UInt32 : IComparable, IConvertible, IFormattable, IComparable<UInt32>, IEquatable<UInt32>, ISpanFormattable
+    {
+        private uint m_value; // Do not rename (binary serialization)
+
+        public const uint MaxValue = (uint)0xffffffff;
+        public const uint MinValue = 0U;
+
+
+        // Compares this object to another object, returning an integer that
+        // indicates the relationship. 
+        // Returns a value less than zero if this  object
+        // null is considered to be less than any instance.
+        // If object is not of type UInt32, this method throws an ArgumentException.
+        // 
+        public int CompareTo(Object value)
+        {
+            if (value == null)
+            {
+                return 1;
+            }
+            if (value is UInt32)
+            {
+                // Need to use compare because subtraction will wrap
+                // to positive for very large neg numbers, etc.
+                uint i = (uint)value;
+                if (m_value < i) return -1;
+                if (m_value > i) return 1;
+                return 0;
+            }
+            throw new ArgumentException(SR.Arg_MustBeUInt32);
+        }
+
+        public int CompareTo(UInt32 value)
+        {
+            // Need to use compare because subtraction will wrap
+            // to positive for very large neg numbers, etc.
+            if (m_value < value) return -1;
+            if (m_value > value) return 1;
+            return 0;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (!(obj is UInt32))
+            {
+                return false;
+            }
+            return m_value == ((UInt32)obj).m_value;
+        }
+
+        [NonVersionable]
+        public bool Equals(UInt32 obj)
+        {
+            return m_value == obj;
+        }
+
+        // The absolute value of the int contained.
+        public override int GetHashCode()
+        {
+            return ((int)m_value);
+        }
+
+        // The base 10 representation of the number with no extra padding.
+        public override String ToString()
+        {
+            return Number.FormatUInt32(m_value, null, null);
+        }
+
+        public String ToString(IFormatProvider provider)
+        {
+            return Number.FormatUInt32(m_value, null, provider);
+        }
+
+        public String ToString(String format)
+        {
+            return Number.FormatUInt32(m_value, format, null);
+        }
+
+        public String ToString(String format, IFormatProvider provider)
+        {
+            return Number.FormatUInt32(m_value, format, provider);
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider provider = null)
+        {
+            return Number.TryFormatUInt32(m_value, format, provider, destination, out charsWritten);
+        }
+
+        [CLSCompliant(false)]
+        public static uint Parse(String s)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseUInt32(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo);
+        }
+
+        [CLSCompliant(false)]
+        public static uint Parse(String s, NumberStyles style)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseUInt32(s, style, NumberFormatInfo.CurrentInfo);
+        }
+
+
+        [CLSCompliant(false)]
+        public static uint Parse(String s, IFormatProvider provider)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseUInt32(s, NumberStyles.Integer, NumberFormatInfo.GetInstance(provider));
+        }
+
+        [CLSCompliant(false)]
+        public static uint Parse(String s, NumberStyles style, IFormatProvider provider)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseUInt32(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        [CLSCompliant(false)]
+        public static uint Parse(ReadOnlySpan<char> s, NumberStyles style = NumberStyles.Integer, IFormatProvider provider = null)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return Number.ParseUInt32(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        [CLSCompliant(false)]
+        public static bool TryParse(String s, out UInt32 result)
+        {
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return Number.TryParseUInt32(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        [CLSCompliant(false)]
+        public static bool TryParse(ReadOnlySpan<char> s, out uint result)
+        {
+            return Number.TryParseUInt32(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        [CLSCompliant(false)]
+        public static bool TryParse(String s, NumberStyles style, IFormatProvider provider, out UInt32 result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return Number.TryParseUInt32(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        [CLSCompliant(false)]
+        public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider provider, out uint result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return Number.TryParseUInt32(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        //
+        // IConvertible implementation
+        // 
+
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.UInt32;
+        }
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            return Convert.ToBoolean(m_value);
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            return Convert.ToChar(m_value);
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return Convert.ToSByte(m_value);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return Convert.ToByte(m_value);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return Convert.ToInt16(m_value);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return Convert.ToUInt16(m_value);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return Convert.ToInt32(m_value);
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return m_value;
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return Convert.ToInt64(m_value);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return Convert.ToUInt64(m_value);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            return Convert.ToSingle(m_value);
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            return Convert.ToDouble(m_value);
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            return Convert.ToDecimal(m_value);
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "UInt32", "DateTime"));
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/UInt64.cs b/src/System.Private.CoreLib/shared/System/UInt64.cs
new file mode 100644
index 0000000000..d30fbe1e42
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/UInt64.cs
@@ -0,0 +1,262 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    [Serializable]
+    [CLSCompliant(false)]
+    [StructLayout(LayoutKind.Sequential)]
+    [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct UInt64 : IComparable, IConvertible, IFormattable, IComparable<UInt64>, IEquatable<UInt64>, ISpanFormattable
+    {
+        private ulong m_value; // Do not rename (binary serialization)
+
+        public const ulong MaxValue = (ulong)0xffffffffffffffffL;
+        public const ulong MinValue = 0x0;
+
+        // Compares this object to another object, returning an integer that
+        // indicates the relationship. 
+        // Returns a value less than zero if this  object
+        // null is considered to be less than any instance.
+        // If object is not of type UInt64, this method throws an ArgumentException.
+        // 
+        public int CompareTo(Object value)
+        {
+            if (value == null)
+            {
+                return 1;
+            }
+            if (value is UInt64)
+            {
+                // Need to use compare because subtraction will wrap
+                // to positive for very large neg numbers, etc.
+                ulong i = (ulong)value;
+                if (m_value < i) return -1;
+                if (m_value > i) return 1;
+                return 0;
+            }
+            throw new ArgumentException(SR.Arg_MustBeUInt64);
+        }
+
+        public int CompareTo(UInt64 value)
+        {
+            // Need to use compare because subtraction will wrap
+            // to positive for very large neg numbers, etc.
+            if (m_value < value) return -1;
+            if (m_value > value) return 1;
+            return 0;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (!(obj is UInt64))
+            {
+                return false;
+            }
+            return m_value == ((UInt64)obj).m_value;
+        }
+
+        [NonVersionable]
+        public bool Equals(UInt64 obj)
+        {
+            return m_value == obj;
+        }
+
+        // The value of the lower 32 bits XORed with the uppper 32 bits.
+        public override int GetHashCode()
+        {
+            return ((int)m_value) ^ (int)(m_value >> 32);
+        }
+
+        public override String ToString()
+        {
+            return Number.FormatUInt64(m_value, null, null);
+        }
+
+        public String ToString(IFormatProvider provider)
+        {
+            return Number.FormatUInt64(m_value, null, provider);
+        }
+
+        public String ToString(String format)
+        {
+            return Number.FormatUInt64(m_value, format, null);
+        }
+
+        public String ToString(String format, IFormatProvider provider)
+        {
+            return Number.FormatUInt64(m_value, format, provider);
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider provider = null)
+        {
+            return Number.TryFormatUInt64(m_value, format, provider, destination, out charsWritten);
+        }
+
+        [CLSCompliant(false)]
+        public static ulong Parse(String s)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseUInt64(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo);
+        }
+
+        [CLSCompliant(false)]
+        public static ulong Parse(String s, NumberStyles style)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseUInt64(s, style, NumberFormatInfo.CurrentInfo);
+        }
+
+        [CLSCompliant(false)]
+        public static ulong Parse(string s, IFormatProvider provider)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseUInt64(s, NumberStyles.Integer, NumberFormatInfo.GetInstance(provider));
+        }
+
+        [CLSCompliant(false)]
+        public static ulong Parse(String s, NumberStyles style, IFormatProvider provider)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseUInt64(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        [CLSCompliant(false)]
+        public static ulong Parse(ReadOnlySpan<char> s, NumberStyles style = NumberStyles.Integer, IFormatProvider provider = null)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return Number.ParseUInt64(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        [CLSCompliant(false)]
+        public static Boolean TryParse(String s, out UInt64 result)
+        {
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return Number.TryParseUInt64(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        [CLSCompliant(false)]
+        public static bool TryParse(ReadOnlySpan<char> s, out ulong result)
+        {
+            return Number.TryParseUInt64(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        [CLSCompliant(false)]
+        public static Boolean TryParse(String s, NumberStyles style, IFormatProvider provider, out UInt64 result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return Number.TryParseUInt64(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        [CLSCompliant(false)]
+        public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider provider, out ulong result)
+        {
+            NumberFormatInfo.ValidateParseStyleInteger(style);
+            return Number.TryParseUInt64(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        //
+        // IConvertible implementation
+        // 
+
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.UInt64;
+        }
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            return Convert.ToBoolean(m_value);
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            return Convert.ToChar(m_value);
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return Convert.ToSByte(m_value);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return Convert.ToByte(m_value);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return Convert.ToInt16(m_value);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return Convert.ToUInt16(m_value);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return Convert.ToInt32(m_value);
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return Convert.ToUInt32(m_value);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return Convert.ToInt64(m_value);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return m_value;
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            return Convert.ToSingle(m_value);
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            return Convert.ToDouble(m_value);
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            return Convert.ToDecimal(m_value);
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "UInt64", "DateTime"));
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/UIntPtr.cs b/src/System.Private.CoreLib/shared/System/UIntPtr.cs
new file mode 100644
index 0000000000..8b2568fde1
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/UIntPtr.cs
@@ -0,0 +1,221 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.Serialization;
+using System.Runtime.Versioning;
+
+#if BIT64
+using nuint = System.UInt64;
+#else
+using nuint = System.UInt32;
+#endif
+
+namespace System
+{
+    [Serializable]
+    [CLSCompliant(false)]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public struct UIntPtr : IEquatable<UIntPtr>, ISerializable
+    {
+        private unsafe void* _value; // Do not rename (binary serialization)
+
+        [Intrinsic]
+        public static readonly UIntPtr Zero;
+
+        [Intrinsic]
+        [NonVersionable]
+        public unsafe UIntPtr(uint value)
+        {
+            _value = (void*)value;
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public unsafe UIntPtr(ulong value)
+        {
+#if BIT64
+            _value = (void*)value;
+#else
+            _value = (void*)checked((uint)value);
+#endif
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public unsafe UIntPtr(void* value)
+        {
+            _value = value;
+        }
+
+        private unsafe UIntPtr(SerializationInfo info, StreamingContext context)
+        {
+            ulong l = info.GetUInt64("value");
+
+            if (Size == 4 && l > uint.MaxValue)
+                throw new ArgumentException(SR.Serialization_InvalidPtrValue);
+
+            _value = (void*)l;
+        }
+
+        unsafe void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+                throw new ArgumentNullException(nameof(info));
+
+            info.AddValue("value", ToUInt64());
+        }
+
+        public unsafe override bool Equals(Object obj)
+        {
+            if (obj is UIntPtr)
+            {
+                return (_value == ((UIntPtr)obj)._value);
+            }
+            return false;
+        }
+
+        unsafe bool IEquatable<UIntPtr>.Equals(UIntPtr other)
+        {
+            return _value == other._value;
+        }
+
+        public unsafe override int GetHashCode()
+        {
+#if BIT64
+            ulong l = (ulong)_value;
+            return (unchecked((int)l) ^ (int)(l >> 32));
+#else
+            return unchecked((int)_value);
+#endif
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public unsafe uint ToUInt32()
+        {
+#if BIT64
+            return checked((uint)_value);
+#else
+            return (uint)_value;
+#endif
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public unsafe ulong ToUInt64()
+        {
+            return (ulong)_value;
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static explicit operator UIntPtr(uint value)
+        {
+            return new UIntPtr(value);
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static explicit operator UIntPtr(ulong value)
+        {
+            return new UIntPtr(value);
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe explicit operator UIntPtr(void* value)
+        {
+            return new UIntPtr(value);
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe explicit operator void* (UIntPtr value)
+        {
+            return value._value;
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe explicit operator uint(UIntPtr value)
+        {
+#if BIT64
+            return checked((uint)value._value);
+#else
+            return (uint)value._value;
+#endif
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe explicit operator ulong(UIntPtr value)
+        {
+            return (ulong)value._value;
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe bool operator ==(UIntPtr value1, UIntPtr value2)
+        {
+            return value1._value == value2._value;
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe bool operator !=(UIntPtr value1, UIntPtr value2)
+        {
+            return value1._value != value2._value;
+        }
+
+        [NonVersionable]
+        public static UIntPtr Add(UIntPtr pointer, int offset)
+        {
+            return pointer + offset;
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe UIntPtr operator +(UIntPtr pointer, int offset)
+        {
+            return new UIntPtr((nuint)pointer._value + (nuint)offset);
+        }
+
+        [NonVersionable]
+        public static UIntPtr Subtract(UIntPtr pointer, int offset)
+        {
+            return pointer - offset;
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public static unsafe UIntPtr operator -(UIntPtr pointer, int offset)
+        {
+            return new UIntPtr((nuint)pointer._value - (nuint)offset);
+        }
+
+        public static unsafe int Size
+        {
+            [Intrinsic]
+            [NonVersionable]
+            get
+            {
+                return sizeof(nuint);
+            }
+        }
+
+        [Intrinsic]
+        [NonVersionable]
+        public unsafe void* ToPointer()
+        {
+            return _value;
+        }
+
+        public unsafe override string ToString()
+        {
+            return ((nuint)_value).ToString(CultureInfo.InvariantCulture);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/UnauthorizedAccessException.cs b/src/System.Private.CoreLib/shared/System/UnauthorizedAccessException.cs
new file mode 100644
index 0000000000..a28f6dd73c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/UnauthorizedAccessException.cs
@@ -0,0 +1,48 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: An exception for OS 'access denied' types of 
+**          errors, including IO and limited security types 
+**          of errors.
+**
+** 
+===========================================================*/
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    // The UnauthorizedAccessException is thrown when access errors 
+    // occur from IO or other OS methods.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class UnauthorizedAccessException : SystemException
+    {
+        public UnauthorizedAccessException()
+            : base(SR.Arg_UnauthorizedAccessException)
+        {
+            HResult = HResults.COR_E_UNAUTHORIZEDACCESS;
+        }
+
+        public UnauthorizedAccessException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_UNAUTHORIZEDACCESS;
+        }
+
+        public UnauthorizedAccessException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_UNAUTHORIZEDACCESS;
+        }
+
+        protected UnauthorizedAccessException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/UnhandledExceptionEventArgs.cs b/src/System.Private.CoreLib/shared/System/UnhandledExceptionEventArgs.cs
new file mode 100644
index 0000000000..5cde572161
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/UnhandledExceptionEventArgs.cs
@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    public class UnhandledExceptionEventArgs : EventArgs
+    {
+        private Object _exception;
+        private bool _isTerminating;
+
+        public UnhandledExceptionEventArgs(Object exception, bool isTerminating)
+        {
+            _exception = exception;
+            _isTerminating = isTerminating;
+        }
+
+        public Object ExceptionObject
+        {
+            get { return _exception; }
+        }
+
+        public bool IsTerminating
+        {
+            get { return _isTerminating; }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/UnhandledExceptionEventHandler.cs b/src/System.Private.CoreLib/shared/System/UnhandledExceptionEventHandler.cs
new file mode 100644
index 0000000000..14e31c7bbd
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/UnhandledExceptionEventHandler.cs
@@ -0,0 +1,8 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    public delegate void UnhandledExceptionEventHandler(Object sender, UnhandledExceptionEventArgs e);
+}
diff --git a/src/System.Private.CoreLib/shared/System/UnitySerializationHolder.cs b/src/System.Private.CoreLib/shared/System/UnitySerializationHolder.cs
new file mode 100644
index 0000000000..53323c32bc
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/UnitySerializationHolder.cs
@@ -0,0 +1,62 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    /// <summary>
+    /// Holds Null class for which we guarantee that there is only ever one instance of.
+    /// This only exists for compatibility with .NET Framework.
+    /// </summary>
+    [Serializable]
+    // Needs to be public to support binary serialization compatibility
+    public sealed class UnitySerializationHolder : ISerializable, IObjectReference
+    {
+        internal const int NullUnity = 0x0002;
+        private readonly int _unityType;
+        private readonly string _data;
+
+        /// <summary>
+        /// A helper method that returns the SerializationInfo that a class utilizing 
+        /// UnitySerializationHelper should return from a call to GetObjectData. It contains
+        /// the unityType (defined above) and any optional data (used only for the reflection types).
+        /// </summary>
+        internal static void GetUnitySerializationInfo(SerializationInfo info, int unityType)
+        {
+            info.SetType(typeof(UnitySerializationHolder));
+            info.AddValue("Data", null, typeof(string));
+            info.AddValue("UnityType", unityType);
+            info.AddValue("AssemblyName", string.Empty);
+        }
+
+        public UnitySerializationHolder(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+
+            // We are ignoring any other serialization input as we are only concerned about DBNull.
+            // We also store data and use it for erorr logging.
+            _unityType = info.GetInt32("UnityType");
+            _data = info.GetString("Data");
+        }
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context) =>
+            throw new NotSupportedException(SR.NotSupported_UnitySerHolder);
+
+        public object GetRealObject(StreamingContext context)
+        {
+            // We are only support deserializing DBNull and throwing for everything else.
+            if (_unityType != NullUnity)
+            {
+                throw new ArgumentException(SR.Format(SR.Argument_InvalidUnity, _data ?? "UnityType"));
+            }
+
+            // We are always returning the same DBNull instance.
+            return DBNull.Value;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/ValueTuple.cs b/src/System.Private.CoreLib/shared/System/ValueTuple.cs
new file mode 100644
index 0000000000..d3ae20f416
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/ValueTuple.cs
@@ -0,0 +1,2333 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using HashHelpers = System.Numerics.Hashing.HashHelpers;
+
+namespace System
+{
+    /// <summary>
+    /// Helper so we can call some tuple methods recursively without knowing the underlying types.
+    /// </summary>
+    internal interface IValueTupleInternal : ITuple
+    {
+        int GetHashCode(IEqualityComparer comparer);
+        string ToStringEnd();
+    }
+
+    /// <summary>
+    /// The ValueTuple types (from arity 0 to 8) comprise the runtime implementation that underlies tuples in C# and struct tuples in F#.
+    /// Aside from created via language syntax, they are most easily created via the ValueTuple.Create factory methods.
+    /// The System.ValueTuple types differ from the System.Tuple types in that:
+    /// - they are structs rather than classes,
+    /// - they are mutable rather than readonly, and
+    /// - their members (such as Item1, Item2, etc) are fields rather than properties.
+    /// </summary>
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]  
+    public struct ValueTuple
+        : IEquatable<ValueTuple>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple>, IValueTupleInternal, ITuple
+    {
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple"/> instance is equal to a specified object.
+        /// </summary>
+        /// <param name="obj">The object to compare with this instance.</param>
+        /// <returns><see langword="true"/> if <paramref name="obj"/> is a <see cref="ValueTuple"/>.</returns>
+        public override bool Equals(object obj)
+        {
+            return obj is ValueTuple;
+        }
+
+        /// <summary>Returns a value indicating whether this instance is equal to a specified value.</summary>
+        /// <param name="other">An instance to compare to this instance.</param>
+        /// <returns>true if <paramref name="other"/> has the same value as this instance; otherwise, false.</returns>
+        public bool Equals(ValueTuple other)
+        {
+            return true;
+        }
+
+        bool IStructuralEquatable.Equals(object other, IEqualityComparer comparer)
+        {
+            return other is ValueTuple;
+        }
+
+        int IComparable.CompareTo(object other)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            return 0;
+        }
+
+        /// <summary>Compares this instance to a specified instance and returns an indication of their relative values.</summary>
+        /// <param name="other">An instance to compare.</param>
+        /// <returns>
+        /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
+        /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// than <paramref name="other"/>.
+        /// </returns>
+        public int CompareTo(ValueTuple other)
+        {
+            return 0;
+        }
+
+        int IStructuralComparable.CompareTo(object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            return 0;
+        }
+
+        /// <summary>Returns the hash code for this instance.</summary>
+        /// <returns>A 32-bit signed integer hash code.</returns>
+        public override int GetHashCode()
+        {
+            return 0;
+        }
+
+        int IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return 0;
+        }
+
+        int IValueTupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return 0;
+        }
+
+        /// <summary>
+        /// Returns a string that represents the value of this <see cref="ValueTuple"/> instance.
+        /// </summary>
+        /// <returns>The string representation of this <see cref="ValueTuple"/> instance.</returns>
+        /// <remarks>
+        /// The string returned by this method takes the form <c>()</c>.
+        /// </remarks>
+        public override string ToString()
+        {
+            return "()";
+        }
+
+        string IValueTupleInternal.ToStringEnd()
+        {
+            return ")";
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 0;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                throw new IndexOutOfRangeException();
+            }
+        }
+
+        /// <summary>Creates a new struct 0-tuple.</summary>
+        /// <returns>A 0-tuple.</returns>
+        public static ValueTuple Create() =>
+            new ValueTuple();
+
+        /// <summary>Creates a new struct 1-tuple, or singleton.</summary>
+        /// <typeparam name="T1">The type of the first component of the tuple.</typeparam>
+        /// <param name="item1">The value of the first component of the tuple.</param>
+        /// <returns>A 1-tuple (singleton) whose value is (item1).</returns>
+        public static ValueTuple<T1> Create<T1>(T1 item1) =>
+            new ValueTuple<T1>(item1);
+
+        /// <summary>Creates a new struct 2-tuple, or pair.</summary>
+        /// <typeparam name="T1">The type of the first component of the tuple.</typeparam>
+        /// <typeparam name="T2">The type of the second component of the tuple.</typeparam>
+        /// <param name="item1">The value of the first component of the tuple.</param>
+        /// <param name="item2">The value of the second component of the tuple.</param>
+        /// <returns>A 2-tuple (pair) whose value is (item1, item2).</returns>
+        public static ValueTuple<T1, T2> Create<T1, T2>(T1 item1, T2 item2) =>
+            new ValueTuple<T1, T2>(item1, item2);
+
+        /// <summary>Creates a new struct 3-tuple, or triple.</summary>
+        /// <typeparam name="T1">The type of the first component of the tuple.</typeparam>
+        /// <typeparam name="T2">The type of the second component of the tuple.</typeparam>
+        /// <typeparam name="T3">The type of the third component of the tuple.</typeparam>
+        /// <param name="item1">The value of the first component of the tuple.</param>
+        /// <param name="item2">The value of the second component of the tuple.</param>
+        /// <param name="item3">The value of the third component of the tuple.</param>
+        /// <returns>A 3-tuple (triple) whose value is (item1, item2, item3).</returns>
+        public static ValueTuple<T1, T2, T3> Create<T1, T2, T3>(T1 item1, T2 item2, T3 item3) =>
+            new ValueTuple<T1, T2, T3>(item1, item2, item3);
+
+        /// <summary>Creates a new struct 4-tuple, or quadruple.</summary>
+        /// <typeparam name="T1">The type of the first component of the tuple.</typeparam>
+        /// <typeparam name="T2">The type of the second component of the tuple.</typeparam>
+        /// <typeparam name="T3">The type of the third component of the tuple.</typeparam>
+        /// <typeparam name="T4">The type of the fourth component of the tuple.</typeparam>
+        /// <param name="item1">The value of the first component of the tuple.</param>
+        /// <param name="item2">The value of the second component of the tuple.</param>
+        /// <param name="item3">The value of the third component of the tuple.</param>
+        /// <param name="item4">The value of the fourth component of the tuple.</param>
+        /// <returns>A 4-tuple (quadruple) whose value is (item1, item2, item3, item4).</returns>
+        public static ValueTuple<T1, T2, T3, T4> Create<T1, T2, T3, T4>(T1 item1, T2 item2, T3 item3, T4 item4) =>
+            new ValueTuple<T1, T2, T3, T4>(item1, item2, item3, item4);
+
+        /// <summary>Creates a new struct 5-tuple, or quintuple.</summary>
+        /// <typeparam name="T1">The type of the first component of the tuple.</typeparam>
+        /// <typeparam name="T2">The type of the second component of the tuple.</typeparam>
+        /// <typeparam name="T3">The type of the third component of the tuple.</typeparam>
+        /// <typeparam name="T4">The type of the fourth component of the tuple.</typeparam>
+        /// <typeparam name="T5">The type of the fifth component of the tuple.</typeparam>
+        /// <param name="item1">The value of the first component of the tuple.</param>
+        /// <param name="item2">The value of the second component of the tuple.</param>
+        /// <param name="item3">The value of the third component of the tuple.</param>
+        /// <param name="item4">The value of the fourth component of the tuple.</param>
+        /// <param name="item5">The value of the fifth component of the tuple.</param>
+        /// <returns>A 5-tuple (quintuple) whose value is (item1, item2, item3, item4, item5).</returns>
+        public static ValueTuple<T1, T2, T3, T4, T5> Create<T1, T2, T3, T4, T5>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5) =>
+            new ValueTuple<T1, T2, T3, T4, T5>(item1, item2, item3, item4, item5);
+
+        /// <summary>Creates a new struct 6-tuple, or sextuple.</summary>
+        /// <typeparam name="T1">The type of the first component of the tuple.</typeparam>
+        /// <typeparam name="T2">The type of the second component of the tuple.</typeparam>
+        /// <typeparam name="T3">The type of the third component of the tuple.</typeparam>
+        /// <typeparam name="T4">The type of the fourth component of the tuple.</typeparam>
+        /// <typeparam name="T5">The type of the fifth component of the tuple.</typeparam>
+        /// <typeparam name="T6">The type of the sixth component of the tuple.</typeparam>
+        /// <param name="item1">The value of the first component of the tuple.</param>
+        /// <param name="item2">The value of the second component of the tuple.</param>
+        /// <param name="item3">The value of the third component of the tuple.</param>
+        /// <param name="item4">The value of the fourth component of the tuple.</param>
+        /// <param name="item5">The value of the fifth component of the tuple.</param>
+        /// <param name="item6">The value of the sixth component of the tuple.</param>
+        /// <returns>A 6-tuple (sextuple) whose value is (item1, item2, item3, item4, item5, item6).</returns>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6> Create<T1, T2, T3, T4, T5, T6>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6) =>
+            new ValueTuple<T1, T2, T3, T4, T5, T6>(item1, item2, item3, item4, item5, item6);
+
+        /// <summary>Creates a new struct 7-tuple, or septuple.</summary>
+        /// <typeparam name="T1">The type of the first component of the tuple.</typeparam>
+        /// <typeparam name="T2">The type of the second component of the tuple.</typeparam>
+        /// <typeparam name="T3">The type of the third component of the tuple.</typeparam>
+        /// <typeparam name="T4">The type of the fourth component of the tuple.</typeparam>
+        /// <typeparam name="T5">The type of the fifth component of the tuple.</typeparam>
+        /// <typeparam name="T6">The type of the sixth component of the tuple.</typeparam>
+        /// <typeparam name="T7">The type of the seventh component of the tuple.</typeparam>
+        /// <param name="item1">The value of the first component of the tuple.</param>
+        /// <param name="item2">The value of the second component of the tuple.</param>
+        /// <param name="item3">The value of the third component of the tuple.</param>
+        /// <param name="item4">The value of the fourth component of the tuple.</param>
+        /// <param name="item5">The value of the fifth component of the tuple.</param>
+        /// <param name="item6">The value of the sixth component of the tuple.</param>
+        /// <param name="item7">The value of the seventh component of the tuple.</param>
+        /// <returns>A 7-tuple (septuple) whose value is (item1, item2, item3, item4, item5, item6, item7).</returns>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7> Create<T1, T2, T3, T4, T5, T6, T7>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7) =>
+            new ValueTuple<T1, T2, T3, T4, T5, T6, T7>(item1, item2, item3, item4, item5, item6, item7);
+
+        /// <summary>Creates a new struct 8-tuple, or octuple.</summary>
+        /// <typeparam name="T1">The type of the first component of the tuple.</typeparam>
+        /// <typeparam name="T2">The type of the second component of the tuple.</typeparam>
+        /// <typeparam name="T3">The type of the third component of the tuple.</typeparam>
+        /// <typeparam name="T4">The type of the fourth component of the tuple.</typeparam>
+        /// <typeparam name="T5">The type of the fifth component of the tuple.</typeparam>
+        /// <typeparam name="T6">The type of the sixth component of the tuple.</typeparam>
+        /// <typeparam name="T7">The type of the seventh component of the tuple.</typeparam>
+        /// <typeparam name="T8">The type of the eighth component of the tuple.</typeparam>
+        /// <param name="item1">The value of the first component of the tuple.</param>
+        /// <param name="item2">The value of the second component of the tuple.</param>
+        /// <param name="item3">The value of the third component of the tuple.</param>
+        /// <param name="item4">The value of the fourth component of the tuple.</param>
+        /// <param name="item5">The value of the fifth component of the tuple.</param>
+        /// <param name="item6">The value of the sixth component of the tuple.</param>
+        /// <param name="item7">The value of the seventh component of the tuple.</param>
+        /// <param name="item8">The value of the eighth component of the tuple.</param>
+        /// <returns>An 8-tuple (octuple) whose value is (item1, item2, item3, item4, item5, item6, item7, item8).</returns>
+        public static ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8>> Create<T1, T2, T3, T4, T5, T6, T7, T8>(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7, T8 item8) =>
+            new ValueTuple<T1, T2, T3, T4, T5, T6, T7, ValueTuple<T8>>(item1, item2, item3, item4, item5, item6, item7, ValueTuple.Create(item8));
+
+        internal static int CombineHashCodes(int h1, int h2)
+        {
+            return HashHelpers.Combine(HashHelpers.Combine(HashHelpers.RandomSeed, h1), h2);
+        }
+
+        internal static int CombineHashCodes(int h1, int h2, int h3)
+        {
+            return HashHelpers.Combine(CombineHashCodes(h1, h2), h3);
+        }
+
+        internal static int CombineHashCodes(int h1, int h2, int h3, int h4)
+        {
+            return HashHelpers.Combine(CombineHashCodes(h1, h2, h3), h4);
+        }
+
+        internal static int CombineHashCodes(int h1, int h2, int h3, int h4, int h5)
+        {
+            return HashHelpers.Combine(CombineHashCodes(h1, h2, h3, h4), h5);
+        }
+
+        internal static int CombineHashCodes(int h1, int h2, int h3, int h4, int h5, int h6)
+        {
+            return HashHelpers.Combine(CombineHashCodes(h1, h2, h3, h4, h5), h6);
+        }
+
+        internal static int CombineHashCodes(int h1, int h2, int h3, int h4, int h5, int h6, int h7)
+        {
+            return HashHelpers.Combine(CombineHashCodes(h1, h2, h3, h4, h5, h6), h7);
+        }
+
+        internal static int CombineHashCodes(int h1, int h2, int h3, int h4, int h5, int h6, int h7, int h8)
+        {
+            return HashHelpers.Combine(CombineHashCodes(h1, h2, h3, h4, h5, h6, h7), h8);
+        }
+    }
+
+    /// <summary>Represents a 1-tuple, or singleton, as a value type.</summary>
+    /// <typeparam name="T1">The type of the tuple's only component.</typeparam>
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]  
+    public struct ValueTuple<T1>
+        : IEquatable<ValueTuple<T1>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1>>, IValueTupleInternal, ITuple
+    {
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1}"/> instance's first component.
+        /// </summary>
+        public T1 Item1;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ValueTuple{T1}"/> value type.
+        /// </summary>
+        /// <param name="item1">The value of the tuple's first component.</param>
+        public ValueTuple(T1 item1)
+        {
+            Item1 = item1;
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1}"/> instance is equal to a specified object.
+        /// </summary>
+        /// <param name="obj">The object to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified object; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="obj"/> parameter is considered to be equal to the current instance under the following conditions:
+        /// <list type="bullet">
+        ///     <item><description>It is a <see cref="ValueTuple{T1}"/> value type.</description></item>
+        ///     <item><description>Its components are of the same types as those of the current instance.</description></item>
+        ///     <item><description>Its components are equal to those of the current instance. Equality is determined by the default object equality comparer for each component.</description></item>
+        /// </list>
+        /// </remarks>
+        public override bool Equals(object obj)
+        {
+            return obj is ValueTuple<T1> && Equals((ValueTuple<T1>)obj);
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1}"/>
+        /// instance is equal to a specified <see cref="ValueTuple{T1}"/>.
+        /// </summary>
+        /// <param name="other">The tuple to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified tuple; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="other"/> parameter is considered to be equal to the current instance if each of its field
+        /// is equal to that of the current instance, using the default comparer for that field's type.
+        /// </remarks>
+        public bool Equals(ValueTuple<T1> other)
+        {
+            return EqualityComparer<T1>.Default.Equals(Item1, other.Item1);
+        }
+
+        bool IStructuralEquatable.Equals(object other, IEqualityComparer comparer)
+        {
+            if (other == null || !(other is ValueTuple<T1>)) return false;
+
+            var objTuple = (ValueTuple<T1>)other;
+
+            return comparer.Equals(Item1, objTuple.Item1);
+        }
+
+        int IComparable.CompareTo(object other)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            var objTuple = (ValueTuple<T1>)other;
+
+            return Comparer<T1>.Default.Compare(Item1, objTuple.Item1);
+        }
+
+        /// <summary>Compares this instance to a specified instance and returns an indication of their relative values.</summary>
+        /// <param name="other">An instance to compare.</param>
+        /// <returns>
+        /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
+        /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// than <paramref name="other"/>.
+        /// </returns>
+        public int CompareTo(ValueTuple<T1> other)
+        {
+            return Comparer<T1>.Default.Compare(Item1, other.Item1);
+        }
+
+        int IStructuralComparable.CompareTo(object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            var objTuple = (ValueTuple<T1>)other;
+
+            return comparer.Compare(Item1, objTuple.Item1);
+        }
+
+        /// <summary>
+        /// Returns the hash code for the current <see cref="ValueTuple{T1}"/> instance.
+        /// </summary>
+        /// <returns>A 32-bit signed integer hash code.</returns>
+        public override int GetHashCode()
+        {
+            return Item1?.GetHashCode() ?? 0;
+        }
+
+        int IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return comparer.GetHashCode(Item1);
+        }
+
+        int IValueTupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return comparer.GetHashCode(Item1);
+        }
+
+        /// <summary>
+        /// Returns a string that represents the value of this <see cref="ValueTuple{T1}"/> instance.
+        /// </summary>
+        /// <returns>The string representation of this <see cref="ValueTuple{T1}"/> instance.</returns>
+        /// <remarks>
+        /// The string returned by this method takes the form <c>(Item1)</c>,
+        /// where <c>Item1</c> represents the value of <see cref="Item1"/>. If the field is <see langword="null"/>,
+        /// it is represented as <see cref="string.Empty"/>.
+        /// </remarks>
+        public override string ToString()
+        {
+            return "(" + Item1?.ToString() + ")";
+        }
+
+        string IValueTupleInternal.ToStringEnd()
+        {
+            return Item1?.ToString() + ")";
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 1;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                if (index != 0)
+                {
+                    throw new IndexOutOfRangeException();
+                }
+                return Item1;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Represents a 2-tuple, or pair, as a value type.
+    /// </summary>
+    /// <typeparam name="T1">The type of the tuple's first component.</typeparam>
+    /// <typeparam name="T2">The type of the tuple's second component.</typeparam>
+    [Serializable]
+    [StructLayout(LayoutKind.Auto)]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]  
+    public struct ValueTuple<T1, T2>
+        : IEquatable<ValueTuple<T1, T2>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2>>, IValueTupleInternal, ITuple
+    {
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2}"/> instance's first component.
+        /// </summary>
+        public T1 Item1;
+
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2}"/> instance's first component.
+        /// </summary>
+        public T2 Item2;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ValueTuple{T1, T2}"/> value type.
+        /// </summary>
+        /// <param name="item1">The value of the tuple's first component.</param>
+        /// <param name="item2">The value of the tuple's second component.</param>
+        public ValueTuple(T1 item1, T2 item2)
+        {
+            Item1 = item1;
+            Item2 = item2;
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2}"/> instance is equal to a specified object.
+        /// </summary>
+        /// <param name="obj">The object to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified object; otherwise, <see langword="false"/>.</returns>
+        ///
+        /// <remarks>
+        /// The <paramref name="obj"/> parameter is considered to be equal to the current instance under the following conditions:
+        /// <list type="bullet">
+        ///     <item><description>It is a <see cref="ValueTuple{T1, T2}"/> value type.</description></item>
+        ///     <item><description>Its components are of the same types as those of the current instance.</description></item>
+        ///     <item><description>Its components are equal to those of the current instance. Equality is determined by the default object equality comparer for each component.</description></item>
+        /// </list>
+        /// </remarks>
+        public override bool Equals(object obj)
+        {
+            return obj is ValueTuple<T1, T2> && Equals((ValueTuple<T1, T2>)obj);
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2}"/> instance is equal to a specified <see cref="ValueTuple{T1, T2}"/>.
+        /// </summary>
+        /// <param name="other">The tuple to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified tuple; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="other"/> parameter is considered to be equal to the current instance if each of its fields
+        /// are equal to that of the current instance, using the default comparer for that field's type.
+        /// </remarks>
+        public bool Equals(ValueTuple<T1, T2> other)
+        {
+            return EqualityComparer<T1>.Default.Equals(Item1, other.Item1)
+                && EqualityComparer<T2>.Default.Equals(Item2, other.Item2);
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2}"/> instance is equal to a specified object based on a specified comparison method.
+        /// </summary>
+        /// <param name="other">The object to compare with this instance.</param>
+        /// <param name="comparer">An object that defines the method to use to evaluate whether the two objects are equal.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified object; otherwise, <see langword="false"/>.</returns>
+        ///
+        /// <remarks>
+        /// This member is an explicit interface member implementation. It can be used only when the
+        ///  <see cref="ValueTuple{T1, T2}"/> instance is cast to an <see cref="IStructuralEquatable"/> interface.
+        ///
+        /// The <see cref="IEqualityComparer.Equals"/> implementation is called only if <c>other</c> is not <see langword="null"/>,
+        ///  and if it can be successfully cast (in C#) or converted (in Visual Basic) to a <see cref="ValueTuple{T1, T2}"/>
+        ///  whose components are of the same types as those of the current instance. The IStructuralEquatable.Equals(Object, IEqualityComparer) method
+        ///  first passes the <see cref="Item1"/> values of the <see cref="ValueTuple{T1, T2}"/> objects to be compared to the
+        ///  <see cref="IEqualityComparer.Equals"/> implementation. If this method call returns <see langword="true"/>, the method is
+        ///  called again and passed the <see cref="Item2"/> values of the two <see cref="ValueTuple{T1, T2}"/> instances.
+        /// </remarks>
+        bool IStructuralEquatable.Equals(object other, IEqualityComparer comparer)
+        {
+            if (other == null || !(other is ValueTuple<T1, T2>)) return false;
+
+            var objTuple = (ValueTuple<T1, T2>)other;
+
+            return comparer.Equals(Item1, objTuple.Item1)
+                && comparer.Equals(Item2, objTuple.Item2);
+        }
+
+        int IComparable.CompareTo(object other)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1, T2>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            return CompareTo((ValueTuple<T1, T2>)other);
+        }
+
+        /// <summary>Compares this instance to a specified instance and returns an indication of their relative values.</summary>
+        /// <param name="other">An instance to compare.</param>
+        /// <returns>
+        /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
+        /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// than <paramref name="other"/>.
+        /// </returns>
+        public int CompareTo(ValueTuple<T1, T2> other)
+        {
+            int c = Comparer<T1>.Default.Compare(Item1, other.Item1);
+            if (c != 0) return c;
+
+            return Comparer<T2>.Default.Compare(Item2, other.Item2);
+        }
+
+        int IStructuralComparable.CompareTo(object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1, T2>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            var objTuple = (ValueTuple<T1, T2>)other;
+
+            int c = comparer.Compare(Item1, objTuple.Item1);
+            if (c != 0) return c;
+
+            return comparer.Compare(Item2, objTuple.Item2);
+        }
+
+        /// <summary>
+        /// Returns the hash code for the current <see cref="ValueTuple{T1, T2}"/> instance.
+        /// </summary>
+        /// <returns>A 32-bit signed integer hash code.</returns>
+        public override int GetHashCode()
+        {
+            return ValueTuple.CombineHashCodes(Item1?.GetHashCode() ?? 0,
+                                               Item2?.GetHashCode() ?? 0);
+        }
+
+        int IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return GetHashCodeCore(comparer);
+        }
+
+        private int GetHashCodeCore(IEqualityComparer comparer)
+        {
+            return ValueTuple.CombineHashCodes(comparer.GetHashCode(Item1),
+                                               comparer.GetHashCode(Item2));
+        }
+
+        int IValueTupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return GetHashCodeCore(comparer);
+        }
+
+        /// <summary>
+        /// Returns a string that represents the value of this <see cref="ValueTuple{T1, T2}"/> instance.
+        /// </summary>
+        /// <returns>The string representation of this <see cref="ValueTuple{T1, T2}"/> instance.</returns>
+        /// <remarks>
+        /// The string returned by this method takes the form <c>(Item1, Item2)</c>,
+        /// where <c>Item1</c> and <c>Item2</c> represent the values of the <see cref="Item1"/>
+        /// and <see cref="Item2"/> fields. If either field value is <see langword="null"/>,
+        /// it is represented as <see cref="String.Empty"/>.
+        /// </remarks>
+        public override string ToString()
+        {
+            return "(" + Item1?.ToString() + ", " + Item2?.ToString() + ")";
+        }
+
+        string IValueTupleInternal.ToStringEnd()
+        {
+            return Item1?.ToString() + ", " + Item2?.ToString() + ")";
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 2;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
+    }
+
+    /// <summary>
+    /// Represents a 3-tuple, or triple, as a value type.
+    /// </summary>
+    /// <typeparam name="T1">The type of the tuple's first component.</typeparam>
+    /// <typeparam name="T2">The type of the tuple's second component.</typeparam>
+    /// <typeparam name="T3">The type of the tuple's third component.</typeparam>
+    [Serializable]
+    [StructLayout(LayoutKind.Auto)]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]  
+    public struct ValueTuple<T1, T2, T3>
+        : IEquatable<ValueTuple<T1, T2, T3>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3>>, IValueTupleInternal, ITuple
+    {
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3}"/> instance's first component.
+        /// </summary>
+        public T1 Item1;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3}"/> instance's second component.
+        /// </summary>
+        public T2 Item2;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3}"/> instance's third component.
+        /// </summary>
+        public T3 Item3;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ValueTuple{T1, T2, T3}"/> value type.
+        /// </summary>
+        /// <param name="item1">The value of the tuple's first component.</param>
+        /// <param name="item2">The value of the tuple's second component.</param>
+        /// <param name="item3">The value of the tuple's third component.</param>
+        public ValueTuple(T1 item1, T2 item2, T3 item3)
+        {
+            Item1 = item1;
+            Item2 = item2;
+            Item3 = item3;
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2, T3}"/> instance is equal to a specified object.
+        /// </summary>
+        /// <param name="obj">The object to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified object; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="obj"/> parameter is considered to be equal to the current instance under the following conditions:
+        /// <list type="bullet">
+        ///     <item><description>It is a <see cref="ValueTuple{T1, T2, T3}"/> value type.</description></item>
+        ///     <item><description>Its components are of the same types as those of the current instance.</description></item>
+        ///     <item><description>Its components are equal to those of the current instance. Equality is determined by the default object equality comparer for each component.</description></item>
+        /// </list>
+        /// </remarks>
+        public override bool Equals(object obj)
+        {
+            return obj is ValueTuple<T1, T2, T3> && Equals((ValueTuple<T1, T2, T3>)obj);
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2, T3}"/>
+        /// instance is equal to a specified <see cref="ValueTuple{T1, T2, T3}"/>.
+        /// </summary>
+        /// <param name="other">The tuple to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified tuple; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="other"/> parameter is considered to be equal to the current instance if each of its fields
+        /// are equal to that of the current instance, using the default comparer for that field's type.
+        /// </remarks>
+        public bool Equals(ValueTuple<T1, T2, T3> other)
+        {
+            return EqualityComparer<T1>.Default.Equals(Item1, other.Item1)
+                && EqualityComparer<T2>.Default.Equals(Item2, other.Item2)
+                && EqualityComparer<T3>.Default.Equals(Item3, other.Item3);
+        }
+
+        bool IStructuralEquatable.Equals(object other, IEqualityComparer comparer)
+        {
+            if (other == null || !(other is ValueTuple<T1, T2, T3>)) return false;
+
+            var objTuple = (ValueTuple<T1, T2, T3>)other;
+
+            return comparer.Equals(Item1, objTuple.Item1)
+                && comparer.Equals(Item2, objTuple.Item2)
+                && comparer.Equals(Item3, objTuple.Item3);
+        }
+
+        int IComparable.CompareTo(object other)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1, T2, T3>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            return CompareTo((ValueTuple<T1, T2, T3>)other);
+        }
+
+        /// <summary>Compares this instance to a specified instance and returns an indication of their relative values.</summary>
+        /// <param name="other">An instance to compare.</param>
+        /// <returns>
+        /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
+        /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// than <paramref name="other"/>.
+        /// </returns>
+        public int CompareTo(ValueTuple<T1, T2, T3> other)
+        {
+            int c = Comparer<T1>.Default.Compare(Item1, other.Item1);
+            if (c != 0) return c;
+
+            c = Comparer<T2>.Default.Compare(Item2, other.Item2);
+            if (c != 0) return c;
+
+            return Comparer<T3>.Default.Compare(Item3, other.Item3);
+        }
+
+        int IStructuralComparable.CompareTo(object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1, T2, T3>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            var objTuple = (ValueTuple<T1, T2, T3>)other;
+
+            int c = comparer.Compare(Item1, objTuple.Item1);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item2, objTuple.Item2);
+            if (c != 0) return c;
+
+            return comparer.Compare(Item3, objTuple.Item3);
+        }
+
+        /// <summary>
+        /// Returns the hash code for the current <see cref="ValueTuple{T1, T2, T3}"/> instance.
+        /// </summary>
+        /// <returns>A 32-bit signed integer hash code.</returns>
+        public override int GetHashCode()
+        {
+            return ValueTuple.CombineHashCodes(Item1?.GetHashCode() ?? 0,
+                                               Item2?.GetHashCode() ?? 0,
+                                               Item3?.GetHashCode() ?? 0);
+        }
+
+        int IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return GetHashCodeCore(comparer);
+        }
+
+        private int GetHashCodeCore(IEqualityComparer comparer)
+        {
+            return ValueTuple.CombineHashCodes(comparer.GetHashCode(Item1),
+                                               comparer.GetHashCode(Item2),
+                                               comparer.GetHashCode(Item3));
+        }
+
+        int IValueTupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return GetHashCodeCore(comparer);
+        }
+
+        /// <summary>
+        /// Returns a string that represents the value of this <see cref="ValueTuple{T1, T2, T3}"/> instance.
+        /// </summary>
+        /// <returns>The string representation of this <see cref="ValueTuple{T1, T2, T3}"/> instance.</returns>
+        /// <remarks>
+        /// The string returned by this method takes the form <c>(Item1, Item2, Item3)</c>.
+        /// If any field value is <see langword="null"/>, it is represented as <see cref="String.Empty"/>.
+        /// </remarks>
+        public override string ToString()
+        {
+            return "(" + Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ")";
+        }
+
+        string IValueTupleInternal.ToStringEnd()
+        {
+            return Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ")";
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 3;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
+    }
+
+    /// <summary>
+    /// Represents a 4-tuple, or quadruple, as a value type.
+    /// </summary>
+    /// <typeparam name="T1">The type of the tuple's first component.</typeparam>
+    /// <typeparam name="T2">The type of the tuple's second component.</typeparam>
+    /// <typeparam name="T3">The type of the tuple's third component.</typeparam>
+    /// <typeparam name="T4">The type of the tuple's fourth component.</typeparam>
+    [Serializable]
+    [StructLayout(LayoutKind.Auto)]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]  
+    public struct ValueTuple<T1, T2, T3, T4>
+        : IEquatable<ValueTuple<T1, T2, T3, T4>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4>>, IValueTupleInternal, ITuple
+    {
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4}"/> instance's first component.
+        /// </summary>
+        public T1 Item1;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4}"/> instance's second component.
+        /// </summary>
+        public T2 Item2;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4}"/> instance's third component.
+        /// </summary>
+        public T3 Item3;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4}"/> instance's fourth component.
+        /// </summary>
+        public T4 Item4;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ValueTuple{T1, T2, T3, T4}"/> value type.
+        /// </summary>
+        /// <param name="item1">The value of the tuple's first component.</param>
+        /// <param name="item2">The value of the tuple's second component.</param>
+        /// <param name="item3">The value of the tuple's third component.</param>
+        /// <param name="item4">The value of the tuple's fourth component.</param>
+        public ValueTuple(T1 item1, T2 item2, T3 item3, T4 item4)
+        {
+            Item1 = item1;
+            Item2 = item2;
+            Item3 = item3;
+            Item4 = item4;
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2, T3, T4}"/> instance is equal to a specified object.
+        /// </summary>
+        /// <param name="obj">The object to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified object; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="obj"/> parameter is considered to be equal to the current instance under the following conditions:
+        /// <list type="bullet">
+        ///     <item><description>It is a <see cref="ValueTuple{T1, T2, T3, T4}"/> value type.</description></item>
+        ///     <item><description>Its components are of the same types as those of the current instance.</description></item>
+        ///     <item><description>Its components are equal to those of the current instance. Equality is determined by the default object equality comparer for each component.</description></item>
+        /// </list>
+        /// </remarks>
+        public override bool Equals(object obj)
+        {
+            return obj is ValueTuple<T1, T2, T3, T4> && Equals((ValueTuple<T1, T2, T3, T4>)obj);
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2, T3, T4}"/>
+        /// instance is equal to a specified <see cref="ValueTuple{T1, T2, T3, T4}"/>.
+        /// </summary>
+        /// <param name="other">The tuple to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified tuple; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="other"/> parameter is considered to be equal to the current instance if each of its fields
+        /// are equal to that of the current instance, using the default comparer for that field's type.
+        /// </remarks>
+        public bool Equals(ValueTuple<T1, T2, T3, T4> other)
+        {
+            return EqualityComparer<T1>.Default.Equals(Item1, other.Item1)
+                && EqualityComparer<T2>.Default.Equals(Item2, other.Item2)
+                && EqualityComparer<T3>.Default.Equals(Item3, other.Item3)
+                && EqualityComparer<T4>.Default.Equals(Item4, other.Item4);
+        }
+
+        bool IStructuralEquatable.Equals(object other, IEqualityComparer comparer)
+        {
+            if (other == null || !(other is ValueTuple<T1, T2, T3, T4>)) return false;
+
+            var objTuple = (ValueTuple<T1, T2, T3, T4>)other;
+
+            return comparer.Equals(Item1, objTuple.Item1)
+                && comparer.Equals(Item2, objTuple.Item2)
+                && comparer.Equals(Item3, objTuple.Item3)
+                && comparer.Equals(Item4, objTuple.Item4);
+        }
+
+        int IComparable.CompareTo(object other)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1, T2, T3, T4>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            return CompareTo((ValueTuple<T1, T2, T3, T4>)other);
+        }
+
+        /// <summary>Compares this instance to a specified instance and returns an indication of their relative values.</summary>
+        /// <param name="other">An instance to compare.</param>
+        /// <returns>
+        /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
+        /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// than <paramref name="other"/>.
+        /// </returns>
+        public int CompareTo(ValueTuple<T1, T2, T3, T4> other)
+        {
+            int c = Comparer<T1>.Default.Compare(Item1, other.Item1);
+            if (c != 0) return c;
+
+            c = Comparer<T2>.Default.Compare(Item2, other.Item2);
+            if (c != 0) return c;
+
+            c = Comparer<T3>.Default.Compare(Item3, other.Item3);
+            if (c != 0) return c;
+
+            return Comparer<T4>.Default.Compare(Item4, other.Item4);
+        }
+
+        int IStructuralComparable.CompareTo(object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1, T2, T3, T4>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            var objTuple = (ValueTuple<T1, T2, T3, T4>)other;
+
+            int c = comparer.Compare(Item1, objTuple.Item1);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item2, objTuple.Item2);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item3, objTuple.Item3);
+            if (c != 0) return c;
+
+            return comparer.Compare(Item4, objTuple.Item4);
+        }
+
+        /// <summary>
+        /// Returns the hash code for the current <see cref="ValueTuple{T1, T2, T3, T4}"/> instance.
+        /// </summary>
+        /// <returns>A 32-bit signed integer hash code.</returns>
+        public override int GetHashCode()
+        {
+            return ValueTuple.CombineHashCodes(Item1?.GetHashCode() ?? 0,
+                                               Item2?.GetHashCode() ?? 0,
+                                               Item3?.GetHashCode() ?? 0,
+                                               Item4?.GetHashCode() ?? 0);
+        }
+
+        int IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return GetHashCodeCore(comparer);
+        }
+
+        private int GetHashCodeCore(IEqualityComparer comparer)
+        {
+            return ValueTuple.CombineHashCodes(comparer.GetHashCode(Item1),
+                                               comparer.GetHashCode(Item2),
+                                               comparer.GetHashCode(Item3),
+                                               comparer.GetHashCode(Item4));
+        }
+
+        int IValueTupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return GetHashCodeCore(comparer);
+        }
+
+        /// <summary>
+        /// Returns a string that represents the value of this <see cref="ValueTuple{T1, T2, T3, T4}"/> instance.
+        /// </summary>
+        /// <returns>The string representation of this <see cref="ValueTuple{T1, T2, T3, T4}"/> instance.</returns>
+        /// <remarks>
+        /// The string returned by this method takes the form <c>(Item1, Item2, Item3, Item4)</c>.
+        /// If any field value is <see langword="null"/>, it is represented as <see cref="String.Empty"/>.
+        /// </remarks>
+        public override string ToString()
+        {
+            return "(" + Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ")";
+        }
+
+        string IValueTupleInternal.ToStringEnd()
+        {
+            return Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ")";
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 4;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
+    }
+
+    /// <summary>
+    /// Represents a 5-tuple, or quintuple, as a value type.
+    /// </summary>
+    /// <typeparam name="T1">The type of the tuple's first component.</typeparam>
+    /// <typeparam name="T2">The type of the tuple's second component.</typeparam>
+    /// <typeparam name="T3">The type of the tuple's third component.</typeparam>
+    /// <typeparam name="T4">The type of the tuple's fourth component.</typeparam>
+    /// <typeparam name="T5">The type of the tuple's fifth component.</typeparam>
+    [Serializable]
+    [StructLayout(LayoutKind.Auto)]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]  
+    public struct ValueTuple<T1, T2, T3, T4, T5>
+        : IEquatable<ValueTuple<T1, T2, T3, T4, T5>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4, T5>>, IValueTupleInternal, ITuple
+    {
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5}"/> instance's first component.
+        /// </summary>
+        public T1 Item1;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5}"/> instance's second component.
+        /// </summary>
+        public T2 Item2;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5}"/> instance's third component.
+        /// </summary>
+        public T3 Item3;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5}"/> instance's fourth component.
+        /// </summary>
+        public T4 Item4;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5}"/> instance's fifth component.
+        /// </summary>
+        public T5 Item5;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ValueTuple{T1, T2, T3, T4, T5}"/> value type.
+        /// </summary>
+        /// <param name="item1">The value of the tuple's first component.</param>
+        /// <param name="item2">The value of the tuple's second component.</param>
+        /// <param name="item3">The value of the tuple's third component.</param>
+        /// <param name="item4">The value of the tuple's fourth component.</param>
+        /// <param name="item5">The value of the tuple's fifth component.</param>
+        public ValueTuple(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5)
+        {
+            Item1 = item1;
+            Item2 = item2;
+            Item3 = item3;
+            Item4 = item4;
+            Item5 = item5;
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2, T3, T4, T5}"/> instance is equal to a specified object.
+        /// </summary>
+        /// <param name="obj">The object to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified object; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="obj"/> parameter is considered to be equal to the current instance under the following conditions:
+        /// <list type="bullet">
+        ///     <item><description>It is a <see cref="ValueTuple{T1, T2, T3, T4, T5}"/> value type.</description></item>
+        ///     <item><description>Its components are of the same types as those of the current instance.</description></item>
+        ///     <item><description>Its components are equal to those of the current instance. Equality is determined by the default object equality comparer for each component.</description></item>
+        /// </list>
+        /// </remarks>
+        public override bool Equals(object obj)
+        {
+            return obj is ValueTuple<T1, T2, T3, T4, T5> && Equals((ValueTuple<T1, T2, T3, T4, T5>)obj);
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2, T3, T4, T5}"/>
+        /// instance is equal to a specified <see cref="ValueTuple{T1, T2, T3, T4, T5}"/>.
+        /// </summary>
+        /// <param name="other">The tuple to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified tuple; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="other"/> parameter is considered to be equal to the current instance if each of its fields
+        /// are equal to that of the current instance, using the default comparer for that field's type.
+        /// </remarks>
+        public bool Equals(ValueTuple<T1, T2, T3, T4, T5> other)
+        {
+            return EqualityComparer<T1>.Default.Equals(Item1, other.Item1)
+                && EqualityComparer<T2>.Default.Equals(Item2, other.Item2)
+                && EqualityComparer<T3>.Default.Equals(Item3, other.Item3)
+                && EqualityComparer<T4>.Default.Equals(Item4, other.Item4)
+                && EqualityComparer<T5>.Default.Equals(Item5, other.Item5);
+        }
+
+        bool IStructuralEquatable.Equals(object other, IEqualityComparer comparer)
+        {
+            if (other == null || !(other is ValueTuple<T1, T2, T3, T4, T5>)) return false;
+
+            var objTuple = (ValueTuple<T1, T2, T3, T4, T5>)other;
+
+            return comparer.Equals(Item1, objTuple.Item1)
+                && comparer.Equals(Item2, objTuple.Item2)
+                && comparer.Equals(Item3, objTuple.Item3)
+                && comparer.Equals(Item4, objTuple.Item4)
+                && comparer.Equals(Item5, objTuple.Item5);
+        }
+
+        int IComparable.CompareTo(object other)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1, T2, T3, T4, T5>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            return CompareTo((ValueTuple<T1, T2, T3, T4, T5>)other);
+        }
+
+        /// <summary>Compares this instance to a specified instance and returns an indication of their relative values.</summary>
+        /// <param name="other">An instance to compare.</param>
+        /// <returns>
+        /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
+        /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// than <paramref name="other"/>.
+        /// </returns>
+        public int CompareTo(ValueTuple<T1, T2, T3, T4, T5> other)
+        {
+            int c = Comparer<T1>.Default.Compare(Item1, other.Item1);
+            if (c != 0) return c;
+
+            c = Comparer<T2>.Default.Compare(Item2, other.Item2);
+            if (c != 0) return c;
+
+            c = Comparer<T3>.Default.Compare(Item3, other.Item3);
+            if (c != 0) return c;
+
+            c = Comparer<T4>.Default.Compare(Item4, other.Item4);
+            if (c != 0) return c;
+
+            return Comparer<T5>.Default.Compare(Item5, other.Item5);
+        }
+
+        int IStructuralComparable.CompareTo(object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1, T2, T3, T4, T5>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            var objTuple = (ValueTuple<T1, T2, T3, T4, T5>)other;
+
+            int c = comparer.Compare(Item1, objTuple.Item1);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item2, objTuple.Item2);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item3, objTuple.Item3);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item4, objTuple.Item4);
+            if (c != 0) return c;
+
+            return comparer.Compare(Item5, objTuple.Item5);
+        }
+
+        /// <summary>
+        /// Returns the hash code for the current <see cref="ValueTuple{T1, T2, T3, T4, T5}"/> instance.
+        /// </summary>
+        /// <returns>A 32-bit signed integer hash code.</returns>
+        public override int GetHashCode()
+        {
+            return ValueTuple.CombineHashCodes(Item1?.GetHashCode() ?? 0,
+                                               Item2?.GetHashCode() ?? 0,
+                                               Item3?.GetHashCode() ?? 0,
+                                               Item4?.GetHashCode() ?? 0,
+                                               Item5?.GetHashCode() ?? 0);
+        }
+
+        int IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return GetHashCodeCore(comparer);
+        }
+
+        private int GetHashCodeCore(IEqualityComparer comparer)
+        {
+            return ValueTuple.CombineHashCodes(comparer.GetHashCode(Item1),
+                                               comparer.GetHashCode(Item2),
+                                               comparer.GetHashCode(Item3),
+                                               comparer.GetHashCode(Item4),
+                                               comparer.GetHashCode(Item5));
+        }
+
+        int IValueTupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return GetHashCodeCore(comparer);
+        }
+
+        /// <summary>
+        /// Returns a string that represents the value of this <see cref="ValueTuple{T1, T2, T3, T4, T5}"/> instance.
+        /// </summary>
+        /// <returns>The string representation of this <see cref="ValueTuple{T1, T2, T3, T4, T5}"/> instance.</returns>
+        /// <remarks>
+        /// The string returned by this method takes the form <c>(Item1, Item2, Item3, Item4, Item5)</c>.
+        /// If any field value is <see langword="null"/>, it is represented as <see cref="String.Empty"/>.
+        /// </remarks>
+        public override string ToString()
+        {
+            return "(" + Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ", " + Item5?.ToString() + ")";
+        }
+
+        string IValueTupleInternal.ToStringEnd()
+        {
+            return Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ", " + Item5?.ToString() + ")";
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 5;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    case 4:
+                        return Item5;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
+    }
+
+    /// <summary>
+    /// Represents a 6-tuple, or sixtuple, as a value type.
+    /// </summary>
+    /// <typeparam name="T1">The type of the tuple's first component.</typeparam>
+    /// <typeparam name="T2">The type of the tuple's second component.</typeparam>
+    /// <typeparam name="T3">The type of the tuple's third component.</typeparam>
+    /// <typeparam name="T4">The type of the tuple's fourth component.</typeparam>
+    /// <typeparam name="T5">The type of the tuple's fifth component.</typeparam>
+    /// <typeparam name="T6">The type of the tuple's sixth component.</typeparam>
+    [Serializable]
+    [StructLayout(LayoutKind.Auto)]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]  
+    public struct ValueTuple<T1, T2, T3, T4, T5, T6>
+        : IEquatable<ValueTuple<T1, T2, T3, T4, T5, T6>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4, T5, T6>>, IValueTupleInternal, ITuple
+    {
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/> instance's first component.
+        /// </summary>
+        public T1 Item1;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/> instance's second component.
+        /// </summary>
+        public T2 Item2;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/> instance's third component.
+        /// </summary>
+        public T3 Item3;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/> instance's fourth component.
+        /// </summary>
+        public T4 Item4;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/> instance's fifth component.
+        /// </summary>
+        public T5 Item5;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/> instance's sixth component.
+        /// </summary>
+        public T6 Item6;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/> value type.
+        /// </summary>
+        /// <param name="item1">The value of the tuple's first component.</param>
+        /// <param name="item2">The value of the tuple's second component.</param>
+        /// <param name="item3">The value of the tuple's third component.</param>
+        /// <param name="item4">The value of the tuple's fourth component.</param>
+        /// <param name="item5">The value of the tuple's fifth component.</param>
+        /// <param name="item6">The value of the tuple's sixth component.</param>
+        public ValueTuple(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6)
+        {
+            Item1 = item1;
+            Item2 = item2;
+            Item3 = item3;
+            Item4 = item4;
+            Item5 = item5;
+            Item6 = item6;
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/> instance is equal to a specified object.
+        /// </summary>
+        /// <param name="obj">The object to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified object; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="obj"/> parameter is considered to be equal to the current instance under the following conditions:
+        /// <list type="bullet">
+        ///     <item><description>It is a <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/> value type.</description></item>
+        ///     <item><description>Its components are of the same types as those of the current instance.</description></item>
+        ///     <item><description>Its components are equal to those of the current instance. Equality is determined by the default object equality comparer for each component.</description></item>
+        /// </list>
+        /// </remarks>
+        public override bool Equals(object obj)
+        {
+            return obj is ValueTuple<T1, T2, T3, T4, T5, T6> && Equals((ValueTuple<T1, T2, T3, T4, T5, T6>)obj);
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/>
+        /// instance is equal to a specified <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/>.
+        /// </summary>
+        /// <param name="other">The tuple to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified tuple; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="other"/> parameter is considered to be equal to the current instance if each of its fields
+        /// are equal to that of the current instance, using the default comparer for that field's type.
+        /// </remarks>
+        public bool Equals(ValueTuple<T1, T2, T3, T4, T5, T6> other)
+        {
+            return EqualityComparer<T1>.Default.Equals(Item1, other.Item1)
+                && EqualityComparer<T2>.Default.Equals(Item2, other.Item2)
+                && EqualityComparer<T3>.Default.Equals(Item3, other.Item3)
+                && EqualityComparer<T4>.Default.Equals(Item4, other.Item4)
+                && EqualityComparer<T5>.Default.Equals(Item5, other.Item5)
+                && EqualityComparer<T6>.Default.Equals(Item6, other.Item6);
+        }
+
+        bool IStructuralEquatable.Equals(object other, IEqualityComparer comparer)
+        {
+            if (other == null || !(other is ValueTuple<T1, T2, T3, T4, T5, T6>)) return false;
+
+            var objTuple = (ValueTuple<T1, T2, T3, T4, T5, T6>)other;
+
+            return comparer.Equals(Item1, objTuple.Item1)
+                && comparer.Equals(Item2, objTuple.Item2)
+                && comparer.Equals(Item3, objTuple.Item3)
+                && comparer.Equals(Item4, objTuple.Item4)
+                && comparer.Equals(Item5, objTuple.Item5)
+                && comparer.Equals(Item6, objTuple.Item6);
+        }
+
+        int IComparable.CompareTo(object other)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1, T2, T3, T4, T5, T6>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            return CompareTo((ValueTuple<T1, T2, T3, T4, T5, T6>)other);
+        }
+
+        /// <summary>Compares this instance to a specified instance and returns an indication of their relative values.</summary>
+        /// <param name="other">An instance to compare.</param>
+        /// <returns>
+        /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
+        /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// than <paramref name="other"/>.
+        /// </returns>
+        public int CompareTo(ValueTuple<T1, T2, T3, T4, T5, T6> other)
+        {
+            int c = Comparer<T1>.Default.Compare(Item1, other.Item1);
+            if (c != 0) return c;
+
+            c = Comparer<T2>.Default.Compare(Item2, other.Item2);
+            if (c != 0) return c;
+
+            c = Comparer<T3>.Default.Compare(Item3, other.Item3);
+            if (c != 0) return c;
+
+            c = Comparer<T4>.Default.Compare(Item4, other.Item4);
+            if (c != 0) return c;
+
+            c = Comparer<T5>.Default.Compare(Item5, other.Item5);
+            if (c != 0) return c;
+
+            return Comparer<T6>.Default.Compare(Item6, other.Item6);
+        }
+
+        int IStructuralComparable.CompareTo(object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1, T2, T3, T4, T5, T6>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            var objTuple = (ValueTuple<T1, T2, T3, T4, T5, T6>)other;
+
+            int c = comparer.Compare(Item1, objTuple.Item1);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item2, objTuple.Item2);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item3, objTuple.Item3);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item4, objTuple.Item4);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item5, objTuple.Item5);
+            if (c != 0) return c;
+
+            return comparer.Compare(Item6, objTuple.Item6);
+        }
+
+        /// <summary>
+        /// Returns the hash code for the current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/> instance.
+        /// </summary>
+        /// <returns>A 32-bit signed integer hash code.</returns>
+        public override int GetHashCode()
+        {
+            return ValueTuple.CombineHashCodes(Item1?.GetHashCode() ?? 0,
+                                               Item2?.GetHashCode() ?? 0,
+                                               Item3?.GetHashCode() ?? 0,
+                                               Item4?.GetHashCode() ?? 0,
+                                               Item5?.GetHashCode() ?? 0,
+                                               Item6?.GetHashCode() ?? 0);
+        }
+
+        int IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return GetHashCodeCore(comparer);
+        }
+
+        private int GetHashCodeCore(IEqualityComparer comparer)
+        {
+            return ValueTuple.CombineHashCodes(comparer.GetHashCode(Item1),
+                                               comparer.GetHashCode(Item2),
+                                               comparer.GetHashCode(Item3),
+                                               comparer.GetHashCode(Item4),
+                                               comparer.GetHashCode(Item5),
+                                               comparer.GetHashCode(Item6));
+        }
+
+        int IValueTupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return GetHashCodeCore(comparer);
+        }
+
+        /// <summary>
+        /// Returns a string that represents the value of this <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/> instance.
+        /// </summary>
+        /// <returns>The string representation of this <see cref="ValueTuple{T1, T2, T3, T4, T5, T6}"/> instance.</returns>
+        /// <remarks>
+        /// The string returned by this method takes the form <c>(Item1, Item2, Item3, Item4, Item5, Item6)</c>.
+        /// If any field value is <see langword="null"/>, it is represented as <see cref="String.Empty"/>.
+        /// </remarks>
+        public override string ToString()
+        {
+            return "(" + Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ", " + Item5?.ToString() + ", " + Item6?.ToString() + ")";
+        }
+
+        string IValueTupleInternal.ToStringEnd()
+        {
+            return Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ", " + Item5?.ToString() + ", " + Item6?.ToString() + ")";
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 6;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    case 4:
+                        return Item5;
+                    case 5:
+                        return Item6;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
+    }
+
+    /// <summary>
+    /// Represents a 7-tuple, or sentuple, as a value type.
+    /// </summary>
+    /// <typeparam name="T1">The type of the tuple's first component.</typeparam>
+    /// <typeparam name="T2">The type of the tuple's second component.</typeparam>
+    /// <typeparam name="T3">The type of the tuple's third component.</typeparam>
+    /// <typeparam name="T4">The type of the tuple's fourth component.</typeparam>
+    /// <typeparam name="T5">The type of the tuple's fifth component.</typeparam>
+    /// <typeparam name="T6">The type of the tuple's sixth component.</typeparam>
+    /// <typeparam name="T7">The type of the tuple's seventh component.</typeparam>
+    [Serializable]
+    [StructLayout(LayoutKind.Auto)]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]  
+    public struct ValueTuple<T1, T2, T3, T4, T5, T6, T7>
+        : IEquatable<ValueTuple<T1, T2, T3, T4, T5, T6, T7>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4, T5, T6, T7>>, IValueTupleInternal, ITuple
+    {
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/> instance's first component.
+        /// </summary>
+        public T1 Item1;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/> instance's second component.
+        /// </summary>
+        public T2 Item2;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/> instance's third component.
+        /// </summary>
+        public T3 Item3;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/> instance's fourth component.
+        /// </summary>
+        public T4 Item4;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/> instance's fifth component.
+        /// </summary>
+        public T5 Item5;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/> instance's sixth component.
+        /// </summary>
+        public T6 Item6;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/> instance's seventh component.
+        /// </summary>
+        public T7 Item7;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/> value type.
+        /// </summary>
+        /// <param name="item1">The value of the tuple's first component.</param>
+        /// <param name="item2">The value of the tuple's second component.</param>
+        /// <param name="item3">The value of the tuple's third component.</param>
+        /// <param name="item4">The value of the tuple's fourth component.</param>
+        /// <param name="item5">The value of the tuple's fifth component.</param>
+        /// <param name="item6">The value of the tuple's sixth component.</param>
+        /// <param name="item7">The value of the tuple's seventh component.</param>
+        public ValueTuple(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7)
+        {
+            Item1 = item1;
+            Item2 = item2;
+            Item3 = item3;
+            Item4 = item4;
+            Item5 = item5;
+            Item6 = item6;
+            Item7 = item7;
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/> instance is equal to a specified object.
+        /// </summary>
+        /// <param name="obj">The object to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified object; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="obj"/> parameter is considered to be equal to the current instance under the following conditions:
+        /// <list type="bullet">
+        ///     <item><description>It is a <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/> value type.</description></item>
+        ///     <item><description>Its components are of the same types as those of the current instance.</description></item>
+        ///     <item><description>Its components are equal to those of the current instance. Equality is determined by the default object equality comparer for each component.</description></item>
+        /// </list>
+        /// </remarks>
+        public override bool Equals(object obj)
+        {
+            return obj is ValueTuple<T1, T2, T3, T4, T5, T6, T7> && Equals((ValueTuple<T1, T2, T3, T4, T5, T6, T7>)obj);
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/>
+        /// instance is equal to a specified <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/>.
+        /// </summary>
+        /// <param name="other">The tuple to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified tuple; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="other"/> parameter is considered to be equal to the current instance if each of its fields
+        /// are equal to that of the current instance, using the default comparer for that field's type.
+        /// </remarks>
+        public bool Equals(ValueTuple<T1, T2, T3, T4, T5, T6, T7> other)
+        {
+            return EqualityComparer<T1>.Default.Equals(Item1, other.Item1)
+                && EqualityComparer<T2>.Default.Equals(Item2, other.Item2)
+                && EqualityComparer<T3>.Default.Equals(Item3, other.Item3)
+                && EqualityComparer<T4>.Default.Equals(Item4, other.Item4)
+                && EqualityComparer<T5>.Default.Equals(Item5, other.Item5)
+                && EqualityComparer<T6>.Default.Equals(Item6, other.Item6)
+                && EqualityComparer<T7>.Default.Equals(Item7, other.Item7);
+        }
+
+        bool IStructuralEquatable.Equals(object other, IEqualityComparer comparer)
+        {
+            if (other == null || !(other is ValueTuple<T1, T2, T3, T4, T5, T6, T7>)) return false;
+
+            var objTuple = (ValueTuple<T1, T2, T3, T4, T5, T6, T7>)other;
+
+            return comparer.Equals(Item1, objTuple.Item1)
+                && comparer.Equals(Item2, objTuple.Item2)
+                && comparer.Equals(Item3, objTuple.Item3)
+                && comparer.Equals(Item4, objTuple.Item4)
+                && comparer.Equals(Item5, objTuple.Item5)
+                && comparer.Equals(Item6, objTuple.Item6)
+                && comparer.Equals(Item7, objTuple.Item7);
+        }
+
+        int IComparable.CompareTo(object other)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1, T2, T3, T4, T5, T6, T7>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            return CompareTo((ValueTuple<T1, T2, T3, T4, T5, T6, T7>)other);
+        }
+
+        /// <summary>Compares this instance to a specified instance and returns an indication of their relative values.</summary>
+        /// <param name="other">An instance to compare.</param>
+        /// <returns>
+        /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
+        /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// than <paramref name="other"/>.
+        /// </returns>
+        public int CompareTo(ValueTuple<T1, T2, T3, T4, T5, T6, T7> other)
+        {
+            int c = Comparer<T1>.Default.Compare(Item1, other.Item1);
+            if (c != 0) return c;
+
+            c = Comparer<T2>.Default.Compare(Item2, other.Item2);
+            if (c != 0) return c;
+
+            c = Comparer<T3>.Default.Compare(Item3, other.Item3);
+            if (c != 0) return c;
+
+            c = Comparer<T4>.Default.Compare(Item4, other.Item4);
+            if (c != 0) return c;
+
+            c = Comparer<T5>.Default.Compare(Item5, other.Item5);
+            if (c != 0) return c;
+
+            c = Comparer<T6>.Default.Compare(Item6, other.Item6);
+            if (c != 0) return c;
+
+            return Comparer<T7>.Default.Compare(Item7, other.Item7);
+        }
+
+        int IStructuralComparable.CompareTo(object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1, T2, T3, T4, T5, T6, T7>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            var objTuple = (ValueTuple<T1, T2, T3, T4, T5, T6, T7>)other;
+
+            int c = comparer.Compare(Item1, objTuple.Item1);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item2, objTuple.Item2);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item3, objTuple.Item3);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item4, objTuple.Item4);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item5, objTuple.Item5);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item6, objTuple.Item6);
+            if (c != 0) return c;
+
+            return comparer.Compare(Item7, objTuple.Item7);
+        }
+
+        /// <summary>
+        /// Returns the hash code for the current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/> instance.
+        /// </summary>
+        /// <returns>A 32-bit signed integer hash code.</returns>
+        public override int GetHashCode()
+        {
+            return ValueTuple.CombineHashCodes(Item1?.GetHashCode() ?? 0,
+                                                Item2?.GetHashCode() ?? 0,
+                                                Item3?.GetHashCode() ?? 0,
+                                                Item4?.GetHashCode() ?? 0,
+                                                Item5?.GetHashCode() ?? 0,
+                                                Item6?.GetHashCode() ?? 0,
+                                                Item7?.GetHashCode() ?? 0);
+        }
+
+        int IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return GetHashCodeCore(comparer);
+        }
+
+        private int GetHashCodeCore(IEqualityComparer comparer)
+        {
+            return ValueTuple.CombineHashCodes(comparer.GetHashCode(Item1),
+                                               comparer.GetHashCode(Item2),
+                                               comparer.GetHashCode(Item3),
+                                               comparer.GetHashCode(Item4),
+                                               comparer.GetHashCode(Item5),
+                                               comparer.GetHashCode(Item6),
+                                               comparer.GetHashCode(Item7));
+        }
+
+        int IValueTupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return GetHashCodeCore(comparer);
+        }
+
+        /// <summary>
+        /// Returns a string that represents the value of this <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/> instance.
+        /// </summary>
+        /// <returns>The string representation of this <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7}"/> instance.</returns>
+        /// <remarks>
+        /// The string returned by this method takes the form <c>(Item1, Item2, Item3, Item4, Item5, Item6, Item7)</c>.
+        /// If any field value is <see langword="null"/>, it is represented as <see cref="String.Empty"/>.
+        /// </remarks>
+        public override string ToString()
+        {
+            return "(" + Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ", " + Item5?.ToString() + ", " + Item6?.ToString() + ", " + Item7?.ToString() + ")";
+        }
+
+        string IValueTupleInternal.ToStringEnd()
+        {
+            return Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ", " + Item5?.ToString() + ", " + Item6?.ToString() + ", " + Item7?.ToString() + ")";
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length => 7;
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    case 4:
+                        return Item5;
+                    case 5:
+                        return Item6;
+                    case 6:
+                        return Item7;
+                    default:
+                        throw new IndexOutOfRangeException();
+                }
+            }
+        }
+    }
+
+    /// <summary>
+    /// Represents an 8-tuple, or octuple, as a value type.
+    /// </summary>
+    /// <typeparam name="T1">The type of the tuple's first component.</typeparam>
+    /// <typeparam name="T2">The type of the tuple's second component.</typeparam>
+    /// <typeparam name="T3">The type of the tuple's third component.</typeparam>
+    /// <typeparam name="T4">The type of the tuple's fourth component.</typeparam>
+    /// <typeparam name="T5">The type of the tuple's fifth component.</typeparam>
+    /// <typeparam name="T6">The type of the tuple's sixth component.</typeparam>
+    /// <typeparam name="T7">The type of the tuple's seventh component.</typeparam>
+    /// <typeparam name="TRest">The type of the tuple's eighth component.</typeparam>
+    [Serializable]
+    [StructLayout(LayoutKind.Auto)]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]  
+    public struct ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>
+    : IEquatable<ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>>, IStructuralEquatable, IStructuralComparable, IComparable, IComparable<ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>>, IValueTupleInternal, ITuple
+    where TRest : struct
+    {
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> instance's first component.
+        /// </summary>
+        public T1 Item1;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> instance's second component.
+        /// </summary>
+        public T2 Item2;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> instance's third component.
+        /// </summary>
+        public T3 Item3;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> instance's fourth component.
+        /// </summary>
+        public T4 Item4;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> instance's fifth component.
+        /// </summary>
+        public T5 Item5;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> instance's sixth component.
+        /// </summary>
+        public T6 Item6;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> instance's seventh component.
+        /// </summary>
+        public T7 Item7;
+        /// <summary>
+        /// The current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> instance's eighth component.
+        /// </summary>
+        public TRest Rest;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> value type.
+        /// </summary>
+        /// <param name="item1">The value of the tuple's first component.</param>
+        /// <param name="item2">The value of the tuple's second component.</param>
+        /// <param name="item3">The value of the tuple's third component.</param>
+        /// <param name="item4">The value of the tuple's fourth component.</param>
+        /// <param name="item5">The value of the tuple's fifth component.</param>
+        /// <param name="item6">The value of the tuple's sixth component.</param>
+        /// <param name="item7">The value of the tuple's seventh component.</param>
+        /// <param name="rest">The value of the tuple's eight component.</param>
+        public ValueTuple(T1 item1, T2 item2, T3 item3, T4 item4, T5 item5, T6 item6, T7 item7, TRest rest)
+        {
+            if (!(rest is IValueTupleInternal))
+            {
+                throw new ArgumentException(SR.ArgumentException_ValueTupleLastArgumentNotAValueTuple);
+            }
+
+            Item1 = item1;
+            Item2 = item2;
+            Item3 = item3;
+            Item4 = item4;
+            Item5 = item5;
+            Item6 = item6;
+            Item7 = item7;
+            Rest = rest;
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> instance is equal to a specified object.
+        /// </summary>
+        /// <param name="obj">The object to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified object; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="obj"/> parameter is considered to be equal to the current instance under the following conditions:
+        /// <list type="bullet">
+        ///     <item><description>It is a <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> value type.</description></item>
+        ///     <item><description>Its components are of the same types as those of the current instance.</description></item>
+        ///     <item><description>Its components are equal to those of the current instance. Equality is determined by the default object equality comparer for each component.</description></item>
+        /// </list>
+        /// </remarks>
+        public override bool Equals(object obj)
+        {
+            return obj is ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest> && Equals((ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>)obj);
+        }
+
+        /// <summary>
+        /// Returns a value that indicates whether the current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/>
+        /// instance is equal to a specified <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/>.
+        /// </summary>
+        /// <param name="other">The tuple to compare with this instance.</param>
+        /// <returns><see langword="true"/> if the current instance is equal to the specified tuple; otherwise, <see langword="false"/>.</returns>
+        /// <remarks>
+        /// The <paramref name="other"/> parameter is considered to be equal to the current instance if each of its fields
+        /// are equal to that of the current instance, using the default comparer for that field's type.
+        /// </remarks>
+        public bool Equals(ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest> other)
+        {
+            return EqualityComparer<T1>.Default.Equals(Item1, other.Item1)
+                && EqualityComparer<T2>.Default.Equals(Item2, other.Item2)
+                && EqualityComparer<T3>.Default.Equals(Item3, other.Item3)
+                && EqualityComparer<T4>.Default.Equals(Item4, other.Item4)
+                && EqualityComparer<T5>.Default.Equals(Item5, other.Item5)
+                && EqualityComparer<T6>.Default.Equals(Item6, other.Item6)
+                && EqualityComparer<T7>.Default.Equals(Item7, other.Item7)
+                && EqualityComparer<TRest>.Default.Equals(Rest, other.Rest);
+        }
+
+        bool IStructuralEquatable.Equals(object other, IEqualityComparer comparer)
+        {
+            if (other == null || !(other is ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>)) return false;
+
+            var objTuple = (ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>)other;
+
+            return comparer.Equals(Item1, objTuple.Item1)
+                && comparer.Equals(Item2, objTuple.Item2)
+                && comparer.Equals(Item3, objTuple.Item3)
+                && comparer.Equals(Item4, objTuple.Item4)
+                && comparer.Equals(Item5, objTuple.Item5)
+                && comparer.Equals(Item6, objTuple.Item6)
+                && comparer.Equals(Item7, objTuple.Item7)
+                && comparer.Equals(Rest, objTuple.Rest);
+        }
+
+        int IComparable.CompareTo(object other)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            return CompareTo((ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>)other);
+        }
+
+        /// <summary>Compares this instance to a specified instance and returns an indication of their relative values.</summary>
+        /// <param name="other">An instance to compare.</param>
+        /// <returns>
+        /// A signed number indicating the relative values of this instance and <paramref name="other"/>.
+        /// Returns less than zero if this instance is less than <paramref name="other"/>, zero if this
+        /// instance is equal to <paramref name="other"/>, and greater than zero if this instance is greater 
+        /// than <paramref name="other"/>.
+        /// </returns>
+        public int CompareTo(ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest> other)
+        {
+            int c = Comparer<T1>.Default.Compare(Item1, other.Item1);
+            if (c != 0) return c;
+
+            c = Comparer<T2>.Default.Compare(Item2, other.Item2);
+            if (c != 0) return c;
+
+            c = Comparer<T3>.Default.Compare(Item3, other.Item3);
+            if (c != 0) return c;
+
+            c = Comparer<T4>.Default.Compare(Item4, other.Item4);
+            if (c != 0) return c;
+
+            c = Comparer<T5>.Default.Compare(Item5, other.Item5);
+            if (c != 0) return c;
+
+            c = Comparer<T6>.Default.Compare(Item6, other.Item6);
+            if (c != 0) return c;
+
+            c = Comparer<T7>.Default.Compare(Item7, other.Item7);
+            if (c != 0) return c;
+
+            return Comparer<TRest>.Default.Compare(Rest, other.Rest);
+        }
+
+        int IStructuralComparable.CompareTo(object other, IComparer comparer)
+        {
+            if (other == null) return 1;
+
+            if (!(other is ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>))
+            {
+                throw new ArgumentException(SR.Format(SR.ArgumentException_ValueTupleIncorrectType, this.GetType().ToString()), nameof(other));
+            }
+
+            var objTuple = (ValueTuple<T1, T2, T3, T4, T5, T6, T7, TRest>)other;
+
+            int c = comparer.Compare(Item1, objTuple.Item1);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item2, objTuple.Item2);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item3, objTuple.Item3);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item4, objTuple.Item4);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item5, objTuple.Item5);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item6, objTuple.Item6);
+            if (c != 0) return c;
+
+            c = comparer.Compare(Item7, objTuple.Item7);
+            if (c != 0) return c;
+
+            return comparer.Compare(Rest, objTuple.Rest);
+        }
+
+        /// <summary>
+        /// Returns the hash code for the current <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> instance.
+        /// </summary>
+        /// <returns>A 32-bit signed integer hash code.</returns>
+        public override int GetHashCode()
+        {
+            // We want to have a limited hash in this case.  We'll use the last 8 elements of the tuple
+            IValueTupleInternal rest = Rest as IValueTupleInternal;
+            if (rest == null)
+            {
+                return ValueTuple.CombineHashCodes(Item1?.GetHashCode() ?? 0,
+                                                   Item2?.GetHashCode() ?? 0,
+                                                   Item3?.GetHashCode() ?? 0,
+                                                   Item4?.GetHashCode() ?? 0,
+                                                   Item5?.GetHashCode() ?? 0,
+                                                   Item6?.GetHashCode() ?? 0,
+                                                   Item7?.GetHashCode() ?? 0);
+            }
+
+            int size = rest.Length;
+            if (size >= 8) { return rest.GetHashCode(); }
+
+            // In this case, the rest member has less than 8 elements so we need to combine some our elements with the elements in rest
+            int k = 8 - size;
+            switch (k)
+            {
+                case 1:
+                    return ValueTuple.CombineHashCodes(Item7?.GetHashCode() ?? 0,
+                                                       rest.GetHashCode());
+                case 2:
+                    return ValueTuple.CombineHashCodes(Item6?.GetHashCode() ?? 0,
+                                                       Item7?.GetHashCode() ?? 0,
+                                                       rest.GetHashCode());
+                case 3:
+                    return ValueTuple.CombineHashCodes(Item5?.GetHashCode() ?? 0,
+                                                       Item6?.GetHashCode() ?? 0,
+                                                       Item7?.GetHashCode() ?? 0,
+                                                       rest.GetHashCode());
+                case 4:
+                    return ValueTuple.CombineHashCodes(Item4?.GetHashCode() ?? 0,
+                                                       Item5?.GetHashCode() ?? 0,
+                                                       Item6?.GetHashCode() ?? 0,
+                                                       Item7?.GetHashCode() ?? 0,
+                                                       rest.GetHashCode());
+                case 5:
+                    return ValueTuple.CombineHashCodes(Item3?.GetHashCode() ?? 0,
+                                                       Item4?.GetHashCode() ?? 0,
+                                                       Item5?.GetHashCode() ?? 0,
+                                                       Item6?.GetHashCode() ?? 0,
+                                                       Item7?.GetHashCode() ?? 0,
+                                                       rest.GetHashCode());
+                case 6:
+                    return ValueTuple.CombineHashCodes(Item2?.GetHashCode() ?? 0,
+                                                       Item3?.GetHashCode() ?? 0,
+                                                       Item4?.GetHashCode() ?? 0,
+                                                       Item5?.GetHashCode() ?? 0,
+                                                       Item6?.GetHashCode() ?? 0,
+                                                       Item7?.GetHashCode() ?? 0,
+                                                       rest.GetHashCode());
+                case 7:
+                case 8:
+                    return ValueTuple.CombineHashCodes(Item1?.GetHashCode() ?? 0,
+                                                       Item2?.GetHashCode() ?? 0,
+                                                       Item3?.GetHashCode() ?? 0,
+                                                       Item4?.GetHashCode() ?? 0,
+                                                       Item5?.GetHashCode() ?? 0,
+                                                       Item6?.GetHashCode() ?? 0,
+                                                       Item7?.GetHashCode() ?? 0,
+                                                       rest.GetHashCode());
+            }
+
+            Debug.Fail("Missed all cases for computing ValueTuple hash code");
+            return -1;
+        }
+
+        int IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            return GetHashCodeCore(comparer);
+        }
+
+        private int GetHashCodeCore(IEqualityComparer comparer)
+        {
+            // We want to have a limited hash in this case.  We'll use the last 8 elements of the tuple
+            IValueTupleInternal rest = Rest as IValueTupleInternal;
+            if (rest == null)
+            {
+                return ValueTuple.CombineHashCodes(comparer.GetHashCode(Item1), comparer.GetHashCode(Item2), comparer.GetHashCode(Item3),
+                                                   comparer.GetHashCode(Item4), comparer.GetHashCode(Item5), comparer.GetHashCode(Item6),
+                                                   comparer.GetHashCode(Item7));
+            }
+
+            int size = rest.Length;
+            if (size >= 8) { return rest.GetHashCode(comparer); }
+
+            // In this case, the rest member has less than 8 elements so we need to combine some our elements with the elements in rest
+            int k = 8 - size;
+            switch (k)
+            {
+                case 1:
+                    return ValueTuple.CombineHashCodes(comparer.GetHashCode(Item7), rest.GetHashCode(comparer));
+                case 2:
+                    return ValueTuple.CombineHashCodes(comparer.GetHashCode(Item6), comparer.GetHashCode(Item7), rest.GetHashCode(comparer));
+                case 3:
+                    return ValueTuple.CombineHashCodes(comparer.GetHashCode(Item5), comparer.GetHashCode(Item6), comparer.GetHashCode(Item7),
+                                                       rest.GetHashCode(comparer));
+                case 4:
+                    return ValueTuple.CombineHashCodes(comparer.GetHashCode(Item4), comparer.GetHashCode(Item5), comparer.GetHashCode(Item6),
+                                                       comparer.GetHashCode(Item7), rest.GetHashCode(comparer));
+                case 5:
+                    return ValueTuple.CombineHashCodes(comparer.GetHashCode(Item3), comparer.GetHashCode(Item4), comparer.GetHashCode(Item5),
+                                                       comparer.GetHashCode(Item6), comparer.GetHashCode(Item7), rest.GetHashCode(comparer));
+                case 6:
+                    return ValueTuple.CombineHashCodes(comparer.GetHashCode(Item2), comparer.GetHashCode(Item3), comparer.GetHashCode(Item4),
+                                                       comparer.GetHashCode(Item5), comparer.GetHashCode(Item6), comparer.GetHashCode(Item7),
+                                                       rest.GetHashCode(comparer));
+                case 7:
+                case 8:
+                    return ValueTuple.CombineHashCodes(comparer.GetHashCode(Item1), comparer.GetHashCode(Item2), comparer.GetHashCode(Item3),
+                                                       comparer.GetHashCode(Item4), comparer.GetHashCode(Item5), comparer.GetHashCode(Item6),
+                                                       comparer.GetHashCode(Item7), rest.GetHashCode(comparer));
+            }
+
+            Debug.Fail("Missed all cases for computing ValueTuple hash code");
+            return -1;
+        }
+
+        int IValueTupleInternal.GetHashCode(IEqualityComparer comparer)
+        {
+            return GetHashCodeCore(comparer);
+        }
+
+        /// <summary>
+        /// Returns a string that represents the value of this <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> instance.
+        /// </summary>
+        /// <returns>The string representation of this <see cref="ValueTuple{T1, T2, T3, T4, T5, T6, T7, TRest}"/> instance.</returns>
+        /// <remarks>
+        /// The string returned by this method takes the form <c>(Item1, Item2, Item3, Item4, Item5, Item6, Item7, Rest)</c>.
+        /// If any field value is <see langword="null"/>, it is represented as <see cref="String.Empty"/>.
+        /// </remarks>
+        public override string ToString()
+        {
+            IValueTupleInternal rest = Rest as IValueTupleInternal;
+            if (rest == null)
+            {
+                return "(" + Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ", " + Item5?.ToString() + ", " + Item6?.ToString() + ", " + Item7?.ToString() + ", " + Rest.ToString() + ")";
+            }
+            else
+            {
+                return "(" + Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ", " + Item5?.ToString() + ", " + Item6?.ToString() + ", " + Item7?.ToString() + ", " + rest.ToStringEnd();
+            }
+        }
+
+        string IValueTupleInternal.ToStringEnd()
+        {
+            IValueTupleInternal rest = Rest as IValueTupleInternal;
+            if (rest == null)
+            {
+                return Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ", " + Item5?.ToString() + ", " + Item6?.ToString() + ", " + Item7?.ToString() + ", " + Rest.ToString() + ")";
+            }
+            else
+            {
+                return Item1?.ToString() + ", " + Item2?.ToString() + ", " + Item3?.ToString() + ", " + Item4?.ToString() + ", " + Item5?.ToString() + ", " + Item6?.ToString() + ", " + Item7?.ToString() + ", " + rest.ToStringEnd();
+            }
+        }
+
+        /// <summary>
+        /// The number of positions in this data structure.
+        /// </summary>
+        int ITuple.Length
+        {
+            get
+            {
+                IValueTupleInternal rest = Rest as IValueTupleInternal;
+                return rest == null ? 8 : 7 + rest.Length;
+            }
+        }
+
+        /// <summary>
+        /// Get the element at position <param name="index"/>.
+        /// </summary>
+        object ITuple.this[int index]
+        {
+            get
+            {
+                switch (index)
+                {
+                    case 0:
+                        return Item1;
+                    case 1:
+                        return Item2;
+                    case 2:
+                        return Item3;
+                    case 3:
+                        return Item4;
+                    case 4:
+                        return Item5;
+                    case 5:
+                        return Item6;
+                    case 6:
+                        return Item7;
+                }
+
+                IValueTupleInternal rest = Rest as IValueTupleInternal;
+                if (rest == null)
+                {
+                    if (index == 7)
+                    {
+                        return Rest;
+                    }
+                    throw new IndexOutOfRangeException();
+                }
+                return rest[index - 7];
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Version.cs b/src/System.Private.CoreLib/shared/System/Version.cs
new file mode 100644
index 0000000000..fe086be512
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Version.cs
@@ -0,0 +1,447 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Diagnostics;
+using System.Text;
+
+namespace System
+{
+    // A Version object contains four hierarchical numeric components: major, minor,
+    // build and revision.  Build and revision may be unspecified, which is represented 
+    // internally as a -1.  By definition, an unspecified component matches anything 
+    // (both unspecified and specified), and an unspecified component is "less than" any
+    // specified component.
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class Version : ICloneable, IComparable, IComparable<Version>, IEquatable<Version>, ISpanFormattable
+    {
+        // AssemblyName depends on the order staying the same
+        private readonly int _Major; // Do not rename (binary serialization)
+        private readonly int _Minor; // Do not rename (binary serialization)
+        private readonly int _Build = -1; // Do not rename (binary serialization)
+        private readonly int _Revision = -1; // Do not rename (binary serialization)
+
+        public Version(int major, int minor, int build, int revision)
+        {
+            if (major < 0)
+                throw new ArgumentOutOfRangeException(nameof(major), SR.ArgumentOutOfRange_Version);
+
+            if (minor < 0)
+                throw new ArgumentOutOfRangeException(nameof(minor), SR.ArgumentOutOfRange_Version);
+
+            if (build < 0)
+                throw new ArgumentOutOfRangeException(nameof(build), SR.ArgumentOutOfRange_Version);
+
+            if (revision < 0)
+                throw new ArgumentOutOfRangeException(nameof(revision), SR.ArgumentOutOfRange_Version);
+
+            _Major = major;
+            _Minor = minor;
+            _Build = build;
+            _Revision = revision;
+        }
+
+        public Version(int major, int minor, int build)
+        {
+            if (major < 0)
+                throw new ArgumentOutOfRangeException(nameof(major), SR.ArgumentOutOfRange_Version);
+
+            if (minor < 0)
+                throw new ArgumentOutOfRangeException(nameof(minor), SR.ArgumentOutOfRange_Version);
+
+            if (build < 0)
+                throw new ArgumentOutOfRangeException(nameof(build), SR.ArgumentOutOfRange_Version);
+
+
+            _Major = major;
+            _Minor = minor;
+            _Build = build;
+        }
+
+        public Version(int major, int minor)
+        {
+            if (major < 0)
+                throw new ArgumentOutOfRangeException(nameof(major), SR.ArgumentOutOfRange_Version);
+
+            if (minor < 0)
+                throw new ArgumentOutOfRangeException(nameof(minor), SR.ArgumentOutOfRange_Version);
+
+            _Major = major;
+            _Minor = minor;
+        }
+
+        public Version(String version)
+        {
+            Version v = Version.Parse(version);
+            _Major = v.Major;
+            _Minor = v.Minor;
+            _Build = v.Build;
+            _Revision = v.Revision;
+        }
+
+        public Version()
+        {
+            _Major = 0;
+            _Minor = 0;
+        }
+
+        private Version(Version version)
+        {
+            Debug.Assert(version != null);
+
+            _Major = version._Major;
+            _Minor = version._Minor;
+            _Build = version._Build;
+            _Revision = version._Revision;
+        }
+
+        public object Clone()
+        {
+            return new Version(this);
+        }
+
+        // Properties for setting and getting version numbers
+        public int Major
+        {
+            get { return _Major; }
+        }
+
+        public int Minor
+        {
+            get { return _Minor; }
+        }
+
+        public int Build
+        {
+            get { return _Build; }
+        }
+
+        public int Revision
+        {
+            get { return _Revision; }
+        }
+
+        public short MajorRevision
+        {
+            get { return (short)(_Revision >> 16); }
+        }
+
+        public short MinorRevision
+        {
+            get { return (short)(_Revision & 0xFFFF); }
+        }
+
+        public int CompareTo(Object version)
+        {
+            if (version == null)
+            {
+                return 1;
+            }
+
+            Version v = version as Version;
+            if (v == null)
+            {
+                throw new ArgumentException(SR.Arg_MustBeVersion);
+            }
+
+            return CompareTo(v);
+        }
+
+        public int CompareTo(Version value)
+        {
+            return
+                object.ReferenceEquals(value, this) ? 0 :
+                object.ReferenceEquals(value, null) ? 1 :
+                _Major != value._Major ? (_Major > value._Major ? 1 : -1) :
+                _Minor != value._Minor ? (_Minor > value._Minor ? 1 : -1) :
+                _Build != value._Build ? (_Build > value._Build ? 1 : -1) :
+                _Revision != value._Revision ? (_Revision > value._Revision ? 1 : -1) :
+                0;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            return Equals(obj as Version);
+        }
+
+        public bool Equals(Version obj)
+        {
+            return object.ReferenceEquals(obj, this) ||
+                (!object.ReferenceEquals(obj, null) &&
+                _Major == obj._Major &&
+                _Minor == obj._Minor &&
+                _Build == obj._Build &&
+                _Revision == obj._Revision);
+        }
+
+        public override int GetHashCode()
+        {
+            // Let's assume that most version numbers will be pretty small and just
+            // OR some lower order bits together.
+
+            int accumulator = 0;
+
+            accumulator |= (_Major & 0x0000000F) << 28;
+            accumulator |= (_Minor & 0x000000FF) << 20;
+            accumulator |= (_Build & 0x000000FF) << 12;
+            accumulator |= (_Revision & 0x00000FFF);
+
+            return accumulator;
+        }
+
+        public override string ToString() =>
+            ToString(DefaultFormatFieldCount);
+
+        public string ToString(int fieldCount) =>
+            fieldCount == 0 ? string.Empty :
+            fieldCount == 1 ? _Major.ToString() :
+            StringBuilderCache.GetStringAndRelease(ToCachedStringBuilder(fieldCount));
+
+        public bool TryFormat(Span<char> destination, out int charsWritten) =>
+            TryFormat(destination, DefaultFormatFieldCount, out charsWritten);
+
+        public bool TryFormat(Span<char> destination, int fieldCount, out int charsWritten)
+        {
+            if (fieldCount == 0)
+            {
+                charsWritten = 0;
+                return true;
+            }
+            else if (fieldCount == 1)
+            {
+                return _Major.TryFormat(destination, out charsWritten);
+            }
+
+            StringBuilder sb = ToCachedStringBuilder(fieldCount);
+            if (sb.Length <= destination.Length)
+            {
+                sb.CopyTo(0, destination, sb.Length);
+                StringBuilderCache.Release(sb);
+                charsWritten = sb.Length;
+                return true;
+            }
+
+            StringBuilderCache.Release(sb);
+            charsWritten = 0;
+            return false;
+        }
+
+        bool ISpanFormattable.TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format, IFormatProvider provider)
+        {
+            // format and provider are ignored.
+            return TryFormat(destination, out charsWritten);
+        }
+
+        private int DefaultFormatFieldCount =>
+            _Build == -1 ? 2 :
+            _Revision == -1 ? 3 :
+            4;
+
+        private StringBuilder ToCachedStringBuilder(int fieldCount)
+        {
+            // Note: As we always have positive numbers then it is safe to convert the number to string
+            // regardless of the current culture as we'll not have any punctuation marks in the number.
+
+            if (fieldCount == 2)
+            {
+                StringBuilder sb = StringBuilderCache.Acquire();
+                sb.Append(_Major);
+                sb.Append('.');
+                sb.Append(_Minor);
+                return sb;
+            }
+            else
+            {
+                if (_Build == -1)
+                {
+                    throw new ArgumentException(SR.Format(SR.ArgumentOutOfRange_Bounds_Lower_Upper, "0", "2"), nameof(fieldCount));
+                }
+
+                if (fieldCount == 3)
+                {
+                    StringBuilder sb = StringBuilderCache.Acquire();
+                    sb.Append(_Major);
+                    sb.Append('.');
+                    sb.Append(_Minor);
+                    sb.Append('.');
+                    sb.Append(_Build);
+                    return sb;
+                }
+
+                if (_Revision == -1)
+                {
+                    throw new ArgumentException(SR.Format(SR.ArgumentOutOfRange_Bounds_Lower_Upper, "0", "3"), nameof(fieldCount));
+                }
+
+                if (fieldCount == 4)
+                {
+                    StringBuilder sb = StringBuilderCache.Acquire();
+                    sb.Append(_Major);
+                    sb.Append('.');
+                    sb.Append(_Minor);
+                    sb.Append('.');
+                    sb.Append(_Build);
+                    sb.Append('.');
+                    sb.Append(_Revision);
+                    return sb;
+                }
+
+                throw new ArgumentException(SR.Format(SR.ArgumentOutOfRange_Bounds_Lower_Upper, "0", "4"), nameof(fieldCount));
+            }
+        }
+
+        public static Version Parse(string input)
+        {
+            if (input == null)
+            {
+                throw new ArgumentNullException(nameof(input));
+            }
+
+            return ParseVersion(input.AsSpan(), throwOnFailure: true);
+        }
+
+        public static Version Parse(ReadOnlySpan<char> input) =>
+            ParseVersion(input, throwOnFailure: true);
+
+        public static bool TryParse(string input, out Version result)
+        {
+            if (input == null)
+            {
+                result = null;
+                return false;
+            }
+
+            return (result = ParseVersion(input.AsSpan(), throwOnFailure: false)) != null;
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> input, out Version result) =>
+            (result = ParseVersion(input, throwOnFailure: false)) != null;
+
+        private static Version ParseVersion(ReadOnlySpan<char> input, bool throwOnFailure)
+        {
+            // Find the separator between major and minor.  It must exist.
+            int majorEnd = input.IndexOf('.');
+            if (majorEnd < 0)
+            {
+                if (throwOnFailure) throw new ArgumentException(SR.Arg_VersionString, nameof(input));
+                return null;
+            }
+
+            // Find the ends of the optional minor and build portions.
+            // We musn't have any separators after build.
+            int buildEnd = -1;
+            int minorEnd = input.Slice(majorEnd + 1).IndexOf('.');
+            if (minorEnd != -1)
+            {
+                minorEnd += (majorEnd + 1);
+                buildEnd = input.Slice(minorEnd + 1).IndexOf('.');
+                if (buildEnd != -1)
+                {
+                    buildEnd += (minorEnd + 1);
+                    if (input.Slice(buildEnd + 1).IndexOf('.') != -1)
+                    {
+                        if (throwOnFailure) throw new ArgumentException(SR.Arg_VersionString, nameof(input));
+                        return null;
+                    }
+                }
+            }
+
+            int minor, build, revision;
+
+            // Parse the major version
+            if (!TryParseComponent(input.Slice(0, majorEnd), nameof(input), throwOnFailure, out int major))
+            {
+                return null;
+            }
+
+            if (minorEnd != -1)
+            {
+                // If there's more than a major and minor, parse the minor, too.
+                if (!TryParseComponent(input.Slice(majorEnd + 1, minorEnd - majorEnd - 1), nameof(input), throwOnFailure, out minor))
+                {
+                    return null;
+                }
+
+                if (buildEnd != -1)
+                {
+                    // major.minor.build.revision
+                    return
+                        TryParseComponent(input.Slice(minorEnd + 1, buildEnd - minorEnd - 1), nameof(build), throwOnFailure, out build) &&
+                        TryParseComponent(input.Slice(buildEnd + 1), nameof(revision), throwOnFailure, out revision) ?
+                            new Version(major, minor, build, revision) :
+                            null;
+                }
+                else
+                {
+                    // major.minor.build
+                    return TryParseComponent(input.Slice(minorEnd + 1), nameof(build), throwOnFailure, out build) ?
+                        new Version(major, minor, build) :
+                        null;
+                }
+            }
+            else
+            {
+                // major.minor
+                return TryParseComponent(input.Slice(majorEnd + 1), nameof(input), throwOnFailure, out minor) ?
+                    new Version(major, minor) :
+                    null;
+            }
+        }
+
+        private static bool TryParseComponent(ReadOnlySpan<char> component, string componentName, bool throwOnFailure, out int parsedComponent)
+        {
+            if (throwOnFailure)
+            {
+                if ((parsedComponent = int.Parse(component, NumberStyles.Integer, CultureInfo.InvariantCulture)) < 0)
+                {
+                    throw new ArgumentOutOfRangeException(componentName, SR.ArgumentOutOfRange_Version);
+                }
+                return true;
+            }
+
+            return int.TryParse(component, NumberStyles.Integer, CultureInfo.InvariantCulture, out parsedComponent) && parsedComponent >= 0;
+        }
+
+        public static bool operator ==(Version v1, Version v2)
+        {
+            if (Object.ReferenceEquals(v1, null))
+            {
+                return Object.ReferenceEquals(v2, null);
+            }
+
+            return v1.Equals(v2);
+        }
+
+        public static bool operator !=(Version v1, Version v2)
+        {
+            return !(v1 == v2);
+        }
+
+        public static bool operator <(Version v1, Version v2)
+        {
+            if ((Object)v1 == null)
+                throw new ArgumentNullException(nameof(v1));
+            return (v1.CompareTo(v2) < 0);
+        }
+
+        public static bool operator <=(Version v1, Version v2)
+        {
+            if ((Object)v1 == null)
+                throw new ArgumentNullException(nameof(v1));
+            return (v1.CompareTo(v2) <= 0);
+        }
+
+        public static bool operator >(Version v1, Version v2)
+        {
+            return (v2 < v1);
+        }
+
+        public static bool operator >=(Version v1, Version v2)
+        {
+            return (v2 <= v1);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/shared/System/Void.cs b/src/System.Private.CoreLib/shared/System/Void.cs
new file mode 100644
index 0000000000..5162e6ad02
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Void.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////////
+// Void
+//    This class represents the void return type
+////////////////////////////////////////////////////////////////////////////////
+
+namespace System
+{
+    // This class represents the void return type
+    public struct Void
+    {
+    }
+}
diff --git a/src/System.Private.CoreLib/src/Internal/Console.cs b/src/System.Private.CoreLib/src/Internal/Console.cs
new file mode 100644
index 0000000000..a2a323fa13
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Internal/Console.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Text;
+using System.Security;
+using Microsoft.Win32;
+using Microsoft.Win32.SafeHandles;
+
+namespace Internal
+{
+    //
+    // Simple limited console class for internal printf-style debugging in System.Private.CoreLib
+    // and low-level tests that want to call System.Private.CoreLib directly
+    //
+
+    public static class Console
+    {
+        private static readonly SafeFileHandle _outputHandle =
+            new SafeFileHandle(Win32Native.GetStdHandle(Win32Native.STD_OUTPUT_HANDLE), false);
+
+        public static unsafe void Write(string s)
+        {
+            byte[] bytes = Encoding.UTF8.GetBytes(s);
+
+            fixed (byte* pBytes = bytes)
+            {
+                int bytesWritten;
+                Win32Native.WriteFile(_outputHandle, pBytes, bytes.Length, out bytesWritten, IntPtr.Zero);
+            }
+        }
+
+        public static void WriteLine(string s)
+        {
+            Write(s + Environment.NewLine);
+        }
+
+        public static void WriteLine()
+        {
+            Write(Environment.NewLine);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/Internal/Padding.cs b/src/System.Private.CoreLib/src/Internal/Padding.cs
new file mode 100644
index 0000000000..14bf998bab
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Internal/Padding.cs
@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+
+namespace Internal
+{
+    /// <summary>A class for common padding constants and eventually routines.</summary>
+    internal static class PaddingHelpers
+    {
+        /// <summary>A size greater than or equal to the size of the most common CPU cache lines.</summary>
+#if ARM64
+        internal const int CACHE_LINE_SIZE = 128;
+#else
+        internal const int CACHE_LINE_SIZE = 64;
+#endif
+    }
+
+    /// <summary>Padding structure used to minimize false sharing</summary>
+    [StructLayout(LayoutKind.Explicit, Size = PaddingHelpers.CACHE_LINE_SIZE - sizeof(int))]
+    internal struct PaddingFor32
+    {
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/Internal/Runtime/Augments/EnvironmentAugments.cs b/src/System.Private.CoreLib/src/Internal/Runtime/Augments/EnvironmentAugments.cs
new file mode 100644
index 0000000000..8bed354ac1
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Internal/Runtime/Augments/EnvironmentAugments.cs
@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+
+namespace Internal.Runtime.Augments
+{
+    /// <summary>For internal use only.  Exposes runtime functionality to the Environments implementation in corefx.</summary>
+    public static class EnvironmentAugments
+    {
+        public static int CurrentManagedThreadId => Environment.CurrentManagedThreadId;
+        public static void Exit(int exitCode) => Environment.Exit(exitCode);
+        public static int ExitCode { get { return Environment.ExitCode; } set { Environment.ExitCode = value; } }
+        public static void FailFast(string message, Exception error) => Environment.FailFast(message, error);
+        public static string[] GetCommandLineArgs() => Environment.GetCommandLineArgs();
+        public static bool HasShutdownStarted => Environment.HasShutdownStarted;
+        public static int TickCount => Environment.TickCount;
+        public static string GetEnvironmentVariable(string variable) => Environment.GetEnvironmentVariable(variable);
+        public static string GetEnvironmentVariable(string variable, EnvironmentVariableTarget target) => Environment.GetEnvironmentVariable(variable, target);
+        public static IEnumerable<KeyValuePair<string, string>> EnumerateEnvironmentVariables() => Environment.EnumerateEnvironmentVariables();
+        public static IEnumerable<KeyValuePair<string, string>> EnumerateEnvironmentVariables(EnvironmentVariableTarget target) => Environment.EnumerateEnvironmentVariables(target);
+        public static int ProcessorCount => Environment.ProcessorCount;
+
+        public static void SetEnvironmentVariable(string variable, string value) => Environment.SetEnvironmentVariable(variable, value);
+        public static void SetEnvironmentVariable(string variable, string value, EnvironmentVariableTarget target) => Environment.SetEnvironmentVariable(variable, value, target);
+
+        public static string StackTrace
+        {
+            [MethodImpl(MethodImplOptions.NoInlining)] // Prevent inlining from affecting where the stacktrace starts
+            get
+            {
+                return new StackTrace(1 /* skip this one frame */, true).ToString(System.Diagnostics.StackTrace.TraceFormat.Normal);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/Internal/Runtime/Augments/RuntimeThread.cs b/src/System.Private.CoreLib/src/Internal/Runtime/Augments/RuntimeThread.cs
new file mode 100644
index 0000000000..4678be6c8b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Internal/Runtime/Augments/RuntimeThread.cs
@@ -0,0 +1,268 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.ConstrainedExecution;
+using System.Runtime.InteropServices;
+using System.Security;
+using System.Threading;
+
+namespace Internal.Runtime.Augments
+{
+    public class RuntimeThread : CriticalFinalizerObject
+    {
+        private static int s_optimalMaxSpinWaitsPerSpinIteration;
+
+        internal RuntimeThread() { }
+
+        public static RuntimeThread Create(ThreadStart start) => new Thread(start);
+        public static RuntimeThread Create(ThreadStart start, int maxStackSize) => new Thread(start, maxStackSize);
+        public static RuntimeThread Create(ParameterizedThreadStart start) => new Thread(start);
+        public static RuntimeThread Create(ParameterizedThreadStart start, int maxStackSize) => new Thread(start, maxStackSize);
+
+        private Thread AsThread()
+        {
+            Debug.Assert(this is Thread);
+            return (Thread)this;
+        }
+
+        public static RuntimeThread CurrentThread => Thread.CurrentThread;
+
+        /*=========================================================================
+        ** Returns true if the thread has been started and is not dead.
+        =========================================================================*/
+        public extern bool IsAlive
+        {
+            [MethodImpl(MethodImplOptions.InternalCall)]
+            get;
+        }
+
+        /*=========================================================================
+        ** Return whether or not this thread is a background thread.  Background
+        ** threads do not affect when the Execution Engine shuts down.
+        **
+        ** Exceptions: ThreadStateException if the thread is dead.
+        =========================================================================*/
+        public bool IsBackground
+        {
+            get { return IsBackgroundNative(); }
+            set { SetBackgroundNative(value); }
+        }
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private extern bool IsBackgroundNative();
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private extern void SetBackgroundNative(bool isBackground);
+
+        /*=========================================================================
+        ** Returns true if the thread is a threadpool thread.
+        =========================================================================*/
+        public extern bool IsThreadPoolThread
+        {
+            [MethodImpl(MethodImplOptions.InternalCall)]
+            get;
+        }
+
+        public int ManagedThreadId => AsThread().ManagedThreadId;
+        public string Name { get { return AsThread().Name; } set { AsThread().Name = value; } }
+
+        /*=========================================================================
+        ** Returns the priority of the thread.
+        **
+        ** Exceptions: ThreadStateException if the thread is dead.
+        =========================================================================*/
+        public ThreadPriority Priority
+        {
+            get { return (ThreadPriority)GetPriorityNative(); }
+            set { SetPriorityNative((int)value); }
+        }
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private extern int GetPriorityNative();
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private extern void SetPriorityNative(int priority);
+
+        /*=========================================================================
+        ** Return the thread state as a consistent set of bits.  This is more
+        ** general then IsAlive or IsBackground.
+        =========================================================================*/
+        public ThreadState ThreadState
+        {
+            get { return (ThreadState)GetThreadStateNative(); }
+        }
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private extern int GetThreadStateNative();
+
+        public ApartmentState GetApartmentState()
+        {
+#if FEATURE_COMINTEROP_APARTMENT_SUPPORT
+            return (ApartmentState)GetApartmentStateNative();
+#else // !FEATURE_COMINTEROP_APARTMENT_SUPPORT
+            Debug.Assert(false); // the Thread class in CoreFX should have handled this case
+            return ApartmentState.MTA;
+#endif // FEATURE_COMINTEROP_APARTMENT_SUPPORT
+        }
+
+        /*=========================================================================
+        ** An unstarted thread can be marked to indicate that it will host a
+        ** single-threaded or multi-threaded apartment.
+        =========================================================================*/
+        public bool TrySetApartmentState(ApartmentState state)
+        {
+#if FEATURE_COMINTEROP_APARTMENT_SUPPORT
+            return SetApartmentStateHelper(state, false);
+#else // !FEATURE_COMINTEROP_APARTMENT_SUPPORT
+            Debug.Assert(false); // the Thread class in CoreFX should have handled this case
+            return false;
+#endif // FEATURE_COMINTEROP_APARTMENT_SUPPORT
+        }
+
+#if FEATURE_COMINTEROP_APARTMENT_SUPPORT
+        internal bool SetApartmentStateHelper(ApartmentState state, bool fireMDAOnMismatch)
+        {
+            ApartmentState retState = (ApartmentState)SetApartmentStateNative((int)state, fireMDAOnMismatch);
+
+            // Special case where we pass in Unknown and get back MTA.
+            //  Once we CoUninitialize the thread, the OS will still
+            //  report the thread as implicitly in the MTA if any
+            //  other thread in the process is CoInitialized.
+            if ((state == System.Threading.ApartmentState.Unknown) && (retState == System.Threading.ApartmentState.MTA))
+                return true;
+
+            if (retState != state)
+                return false;
+
+            return true;
+        }
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal extern int GetApartmentStateNative();
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal extern int SetApartmentStateNative(int state, bool fireMDAOnMismatch);
+#endif // FEATURE_COMINTEROP_APARTMENT_SUPPORT
+
+#if FEATURE_COMINTEROP
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public extern void DisableComObjectEagerCleanup();
+#else // !FEATURE_COMINTEROP
+        public void DisableComObjectEagerCleanup()
+        {
+            Debug.Assert(false); // the Thread class in CoreFX should have handled this case
+        }
+#endif // FEATURE_COMINTEROP
+
+        /*=========================================================================
+        ** Interrupts a thread that is inside a Wait(), Sleep() or Join().  If that
+        ** thread is not currently blocked in that manner, it will be interrupted
+        ** when it next begins to block.
+        =========================================================================*/
+        public void Interrupt() => InterruptInternal();
+
+        // Internal helper (since we can't place security demands on
+        // ecalls/fcalls).
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private extern void InterruptInternal();
+
+        /*=========================================================================
+        ** Waits for the thread to die or for timeout milliseconds to elapse.
+        ** Returns true if the thread died, or false if the wait timed out. If
+        ** Timeout.Infinite is given as the parameter, no timeout will occur.
+        **
+        ** Exceptions: ArgumentException if timeout < 0.
+        **             ThreadInterruptedException if the thread is interrupted while waiting.
+        **             ThreadStateException if the thread has not been started yet.
+        =========================================================================*/
+        public void Join() => JoinInternal(Timeout.Infinite);
+
+        public bool Join(int millisecondsTimeout) => JoinInternal(millisecondsTimeout);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private extern bool JoinInternal(int millisecondsTimeout);
+
+        public static void Sleep(int millisecondsTimeout) => Thread.Sleep(millisecondsTimeout);
+
+        [DllImport(JitHelpers.QCall)]
+        private static extern int GetOptimalMaxSpinWaitsPerSpinIterationInternal();
+
+        /// <summary>
+        /// Max value to be passed into <see cref="SpinWait(int)"/> for optimal delaying. This value is normalized to be
+        /// appropriate for the processor.
+        /// </summary>
+        internal static int OptimalMaxSpinWaitsPerSpinIteration
+        {
+            get
+            {
+                if (s_optimalMaxSpinWaitsPerSpinIteration != 0)
+                {
+                    return s_optimalMaxSpinWaitsPerSpinIteration;
+                }
+
+                // This is done lazily because the first call to the function below in the process triggers a measurement that
+                // takes a nontrivial amount of time if the measurement has not already been done in the backgorund.
+                // See Thread::InitializeYieldProcessorNormalized(), which describes and calculates this value.
+                s_optimalMaxSpinWaitsPerSpinIteration = GetOptimalMaxSpinWaitsPerSpinIterationInternal();
+                Debug.Assert(s_optimalMaxSpinWaitsPerSpinIteration > 0);
+                return s_optimalMaxSpinWaitsPerSpinIteration;
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int GetCurrentProcessorNumber();
+
+        // The upper bits of t_currentProcessorIdCache are the currentProcessorId. The lower bits of
+        // the t_currentProcessorIdCache are counting down to get it periodically refreshed.
+        // TODO: Consider flushing the currentProcessorIdCache on Wait operations or similar 
+        // actions that are likely to result in changing the executing core
+        [ThreadStatic]
+        private static int t_currentProcessorIdCache;
+
+        private const int ProcessorIdCacheShift = 16;
+        private const int ProcessorIdCacheCountDownMask = (1 << ProcessorIdCacheShift) - 1;
+        private const int ProcessorIdRefreshRate = 5000;
+
+        private static int RefreshCurrentProcessorId()
+        {
+            int currentProcessorId = GetCurrentProcessorNumber();
+
+            // On Unix, GetCurrentProcessorNumber() is implemented in terms of sched_getcpu, which
+            // doesn't exist on all platforms.  On those it doesn't exist on, GetCurrentProcessorNumber()
+            // returns -1.  As a fallback in that case and to spread the threads across the buckets
+            // by default, we use the current managed thread ID as a proxy.
+            if (currentProcessorId < 0) currentProcessorId = Environment.CurrentManagedThreadId;
+
+            // Add offset to make it clear that it is not guaranteed to be 0-based processor number
+            currentProcessorId += 100;
+
+            Debug.Assert(ProcessorIdRefreshRate <= ProcessorIdCacheCountDownMask);
+
+            // Mask with Int32.MaxValue to ensure the execution Id is not negative
+            t_currentProcessorIdCache = ((currentProcessorId << ProcessorIdCacheShift) & Int32.MaxValue) | ProcessorIdRefreshRate;
+
+            return currentProcessorId;
+        }
+
+        // Cached processor id used as a hint for which per-core stack to access. It is periodically
+        // refreshed to trail the actual thread core affinity.
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int GetCurrentProcessorId()
+        {
+            int currentProcessorIdCache = t_currentProcessorIdCache--;
+            if ((currentProcessorIdCache & ProcessorIdCacheCountDownMask) == 0)
+                return RefreshCurrentProcessorId();
+            return (currentProcessorIdCache >> ProcessorIdCacheShift);
+        }
+
+        public static void SpinWait(int iterations) => Thread.SpinWait(iterations);
+        public static bool Yield() => Thread.Yield();
+
+        public void Start() => AsThread().Start();
+        public void Start(object parameter) => AsThread().Start(parameter);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/Interop/Unix/Interop.Libraries.cs b/src/System.Private.CoreLib/src/Interop/Unix/Interop.Libraries.cs
new file mode 100644
index 0000000000..31df8c75de
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Interop/Unix/Interop.Libraries.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+internal static partial class Interop
+{
+    internal static partial class Libraries
+    {
+        internal const string Kernel32 = "libcoreclr";
+        internal const string User32   = "libcoreclr";
+        internal const string Ole32    = "libcoreclr";
+        internal const string OleAut32 = "libcoreclr";
+    }
+}
diff --git a/src/System.Private.CoreLib/src/Interop/Windows/Kernel32/Interop.GetSystemDirectoryW.cs b/src/System.Private.CoreLib/src/Interop/Windows/Kernel32/Interop.GetSystemDirectoryW.cs
new file mode 100644
index 0000000000..cf1b31d62c
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Interop/Windows/Kernel32/Interop.GetSystemDirectoryW.cs
@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Kernel32
+    {
+        [DllImport(Libraries.Kernel32, CharSet = CharSet.Unicode, SetLastError = true)]
+        private static extern unsafe int GetSystemDirectoryW(char* lpBuffer, int uSize);
+
+        internal static unsafe int GetSystemDirectoryW(Span<char> buffer)
+        {
+            fixed (char* bufferPtr = &MemoryMarshal.GetReference(buffer))
+            {
+                return GetSystemDirectoryW(bufferPtr, buffer.Length);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/Microsoft/Win32/OAVariantLib.cs b/src/System.Private.CoreLib/src/Microsoft/Win32/OAVariantLib.cs
new file mode 100644
index 0000000000..053507b2d4
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Microsoft/Win32/OAVariantLib.cs
@@ -0,0 +1,133 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: This class only exists to provide support for 
+**          implenting IDispatch on managed objects. It is 
+**          used to provide OleAut style coercion rules.
+**
+** 
+===========================================================*/
+
+namespace Microsoft.Win32
+{
+    using System;
+    using System.Diagnostics;
+    using System.Reflection;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.Versioning;
+    using CultureInfo = System.Globalization.CultureInfo;
+
+    internal static class OAVariantLib
+    {
+        #region Constants
+
+        // Constants for VariantChangeType from OleAuto.h
+        public const int NoValueProp = 0x01;
+        public const int AlphaBool = 0x02;
+        public const int NoUserOverride = 0x04;
+        public const int CalendarHijri = 0x08;
+        public const int LocalBool = 0x10;
+
+        internal static readonly Type[] ClassTypes = {
+            typeof(Empty),
+            typeof(void),
+            typeof(Boolean),
+            typeof(Char),
+            typeof(SByte),
+            typeof(Byte),
+            typeof(Int16),
+            typeof(UInt16),
+            typeof(Int32),
+            typeof(UInt32),
+            typeof(Int64),
+            typeof(UInt64),
+            typeof(Single),
+            typeof(Double),
+            typeof(String),
+            typeof(void),
+            typeof(DateTime),
+            typeof(TimeSpan),
+            typeof(Object),
+            typeof(Decimal),
+            null,  // Enums - what do we do here?
+            typeof(Missing),
+            typeof(DBNull),
+        };
+
+        // Keep these numbers in sync w/ the above array.
+        private const int CV_OBJECT = 0x12;
+
+        #endregion
+
+
+        #region Internal Methods
+
+        /**
+         * Changes a Variant from one type to another, calling the OLE
+         * Automation VariantChangeTypeEx routine.  Note the legal types here are
+         * restricted to the subset of what can be legally found in a VB
+         * Variant and the types that CLR supports explicitly in the 
+         * CLR Variant class.  
+         */
+        internal static Variant ChangeType(Variant source, Type targetClass, short options, CultureInfo culture)
+        {
+            if (targetClass == null)
+                throw new ArgumentNullException(nameof(targetClass));
+            if (culture == null)
+                throw new ArgumentNullException(nameof(culture));
+            Variant result = new Variant();
+            ChangeTypeEx(ref result, ref source,
+#if FEATURE_USE_LCID
+                         culture.LCID,
+#else
+        // @CORESYSTODO: what does CoreSystem expect for this argument?
+                        0,
+#endif
+                         targetClass.TypeHandle.Value, GetCVTypeFromClass(targetClass), options);
+            return result;
+        }
+
+        #endregion
+
+
+        #region Private Helpers
+
+        private static int GetCVTypeFromClass(Type ctype)
+        {
+            Debug.Assert(ctype != null);
+            Debug.Assert(ClassTypes[CV_OBJECT] == typeof(Object), "OAVariantLib::ClassTypes[CV_OBJECT] == Object.class");
+
+            int cvtype = -1;
+            for (int i = 0; i < ClassTypes.Length; i++)
+            {
+                if (ctype.Equals(ClassTypes[i]))
+                {
+                    cvtype = i;
+                    break;
+                }
+            }
+
+            // OleAut Binder works better if unrecognized
+            // types were changed to Object.  So don't throw here.
+            if (cvtype == -1)
+                cvtype = CV_OBJECT;
+
+            return cvtype;
+        }
+
+        #endregion
+
+
+        #region Private FCalls
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void ChangeTypeEx(ref Variant result, ref Variant source, int lcid, IntPtr typeHandle, int cvType, short flags);
+
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/Microsoft/Win32/Registry.cs b/src/System.Private.CoreLib/src/Microsoft/Win32/Registry.cs
new file mode 100644
index 0000000000..11f95903af
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Microsoft/Win32/Registry.cs
@@ -0,0 +1,145 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace Microsoft.Win32
+{
+    /**
+     * Registry encapsulation. Contains members representing all top level system
+     * keys.
+     *
+     * @security(checkClassLinking=on)
+     */
+    //This class contains only static members and does not need to be serializable.
+    internal static class Registry
+    {
+        /**
+         * Current User Key.
+         * 
+         * This key should be used as the root for all user specific settings.
+         */
+        public static readonly RegistryKey CurrentUser = RegistryKey.GetBaseKey(RegistryKey.HKEY_CURRENT_USER);
+
+        /**
+         * Local Machine Key.
+         * 
+         * This key should be used as the root for all machine specific settings.
+         */
+        public static readonly RegistryKey LocalMachine = RegistryKey.GetBaseKey(RegistryKey.HKEY_LOCAL_MACHINE);
+
+        /**
+         * Classes Root Key.
+         * 
+         * This is the root key of class information.
+         */
+        public static readonly RegistryKey ClassesRoot = RegistryKey.GetBaseKey(RegistryKey.HKEY_CLASSES_ROOT);
+
+        /**
+         * Users Root Key.
+         * 
+         * This is the root of users.
+         */
+        public static readonly RegistryKey Users = RegistryKey.GetBaseKey(RegistryKey.HKEY_USERS);
+
+        /**
+         * Performance Root Key.
+         * 
+         * This is where dynamic performance data is stored on NT.
+         */
+        public static readonly RegistryKey PerformanceData = RegistryKey.GetBaseKey(RegistryKey.HKEY_PERFORMANCE_DATA);
+
+        /**
+         * Current Config Root Key.
+         * 
+         * This is where current configuration information is stored.
+         */
+        public static readonly RegistryKey CurrentConfig = RegistryKey.GetBaseKey(RegistryKey.HKEY_CURRENT_CONFIG);
+
+        //
+        // Following function will parse a keyName and returns the basekey for it.
+        // It will also store the subkey name in the out parameter.
+        // If the keyName is not valid, we will throw ArgumentException.
+        // The return value shouldn't be null. 
+        //
+        private static RegistryKey GetBaseKeyFromKeyName(string keyName, out string subKeyName)
+        {
+            if (keyName == null)
+            {
+                throw new ArgumentNullException(nameof(keyName));
+            }
+
+            string basekeyName;
+            int i = keyName.IndexOf('\\');
+            if (i != -1)
+            {
+                basekeyName = keyName.Substring(0, i).ToUpper(System.Globalization.CultureInfo.InvariantCulture);
+            }
+            else
+            {
+                basekeyName = keyName.ToUpper(System.Globalization.CultureInfo.InvariantCulture);
+            }
+            RegistryKey basekey = null;
+
+            switch (basekeyName)
+            {
+                case "HKEY_CURRENT_USER":
+                    basekey = Registry.CurrentUser;
+                    break;
+                case "HKEY_LOCAL_MACHINE":
+                    basekey = Registry.LocalMachine;
+                    break;
+                case "HKEY_CLASSES_ROOT":
+                    basekey = Registry.ClassesRoot;
+                    break;
+                case "HKEY_USERS":
+                    basekey = Registry.Users;
+                    break;
+                case "HKEY_PERFORMANCE_DATA":
+                    basekey = Registry.PerformanceData;
+                    break;
+                case "HKEY_CURRENT_CONFIG":
+                    basekey = Registry.CurrentConfig;
+                    break;
+                default:
+                    throw new ArgumentException(SR.Format(SR.Arg_RegInvalidKeyName, nameof(keyName)));
+            }
+            if (i == -1 || i == keyName.Length)
+            {
+                subKeyName = string.Empty;
+            }
+            else
+            {
+                subKeyName = keyName.Substring(i + 1, keyName.Length - i - 1);
+            }
+            return basekey;
+        }
+
+        public static object GetValue(string keyName, string valueName, object defaultValue)
+        {
+            string subKeyName;
+            RegistryKey basekey = GetBaseKeyFromKeyName(keyName, out subKeyName);
+            Debug.Assert(basekey != null, "basekey can't be null.");
+            RegistryKey key = basekey.OpenSubKey(subKeyName);
+            if (key == null)
+            { // if the key doesn't exist, do nothing
+                return null;
+            }
+            try
+            {
+                return key.GetValue(valueName, defaultValue);
+            }
+            finally
+            {
+                key.Close();
+            }
+        }
+    }
+}
+
+
diff --git a/src/System.Private.CoreLib/src/Microsoft/Win32/RegistryKey.cs b/src/System.Private.CoreLib/src/Microsoft/Win32/RegistryKey.cs
new file mode 100644
index 0000000000..f9b4af8d10
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Microsoft/Win32/RegistryKey.cs
@@ -0,0 +1,1159 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+/*
+  Note on transaction support:
+  Eventually we will want to add support for NT's transactions to our
+  RegistryKey API's (possibly Whidbey M3?).  When we do this, here's
+  the list of API's we need to make transaction-aware:
+
+  RegCreateKeyEx
+  RegDeleteKey
+  RegDeleteValue
+  RegEnumKeyEx
+  RegEnumValue
+  RegOpenKeyEx
+  RegQueryInfoKey
+  RegQueryValueEx
+  RegSetValueEx
+
+  We can ignore RegConnectRegistry (remote registry access doesn't yet have
+  transaction support) and RegFlushKey.  RegCloseKey doesn't require any
+  additional work.  .
+ */
+
+/*
+  Note on ACL support:
+  The key thing to note about ACL's is you set them on a kernel object like a
+  registry key, then the ACL only gets checked when you construct handles to 
+  them.  So if you set an ACL to deny read access to yourself, you'll still be
+  able to read with that handle, but not with new handles.
+
+  Another peculiarity is a Terminal Server app compatibility workaround.  The OS
+  will second guess your attempt to open a handle sometimes.  If a certain
+  combination of Terminal Server app compat registry keys are set, then the
+  OS will try to reopen your handle with lesser permissions if you couldn't
+  open it in the specified mode.  So on some machines, we will see handles that
+  may not be able to read or write to a registry key.  It's very strange.  But
+  the real test of these handles is attempting to read or set a value in an
+  affected registry key.
+  
+  For reference, at least two registry keys must be set to particular values 
+  for this behavior:
+  HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Terminal Server\RegistryExtensionFlags, the least significant bit must be 1.
+  HKLM\SYSTEM\CurrentControlSet\Control\TerminalServer\TSAppCompat must be 1
+  There might possibly be an interaction with yet a third registry key as well.
+
+*/
+
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.Buffers;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Text;
+
+namespace Microsoft.Win32
+{
+    /**
+     * Registry encapsulation. To get an instance of a RegistryKey use the
+     * Registry class's static members then call OpenSubKey.
+     *
+     * @see Registry
+     * @security(checkDllCalls=off)
+     * @security(checkClassLinking=on)
+     */
+    internal sealed class RegistryKey : MarshalByRefObject, IDisposable
+    {
+        // We could use const here, if C# supported ELEMENT_TYPE_I fully.
+        internal static readonly IntPtr HKEY_CLASSES_ROOT = new IntPtr(unchecked((int)0x80000000));
+        internal static readonly IntPtr HKEY_CURRENT_USER = new IntPtr(unchecked((int)0x80000001));
+        internal static readonly IntPtr HKEY_LOCAL_MACHINE = new IntPtr(unchecked((int)0x80000002));
+        internal static readonly IntPtr HKEY_USERS = new IntPtr(unchecked((int)0x80000003));
+        internal static readonly IntPtr HKEY_PERFORMANCE_DATA = new IntPtr(unchecked((int)0x80000004));
+        internal static readonly IntPtr HKEY_CURRENT_CONFIG = new IntPtr(unchecked((int)0x80000005));
+
+        // Dirty indicates that we have munged data that should be potentially
+        // written to disk.
+        //
+        private const int STATE_DIRTY = 0x0001;
+
+        // SystemKey indicates that this is a "SYSTEMKEY" and shouldn't be "opened"
+        // or "closed".
+        //
+        private const int STATE_SYSTEMKEY = 0x0002;
+
+        // Access
+        //
+        private const int STATE_WRITEACCESS = 0x0004;
+
+        // Indicates if this key is for HKEY_PERFORMANCE_DATA
+        private const int STATE_PERF_DATA = 0x0008;
+
+        // Names of keys.  This array must be in the same order as the HKEY values listed above.
+        //
+        private static readonly String[] hkeyNames = new String[] {
+                "HKEY_CLASSES_ROOT",
+                "HKEY_CURRENT_USER",
+                "HKEY_LOCAL_MACHINE",
+                "HKEY_USERS",
+                "HKEY_PERFORMANCE_DATA",
+                "HKEY_CURRENT_CONFIG",
+                };
+
+        // MSDN defines the following limits for registry key names & values:
+        // Key Name: 255 characters
+        // Value name:  16,383 Unicode characters
+        // Value: either 1 MB or current available memory, depending on registry format.
+        private const int MaxKeyLength = 255;
+        private const int MaxValueLength = 16383;
+
+        private volatile SafeRegistryHandle hkey = null;
+        private volatile int state = 0;
+        private volatile String keyName;
+        private volatile bool remoteKey = false;
+        private volatile RegistryKeyPermissionCheck checkMode;
+        private volatile RegistryView regView = RegistryView.Default;
+
+        /**
+         * Creates a RegistryKey.
+         *
+         * This key is bound to hkey, if writable is <b>false</b> then no write operations
+         * will be allowed. If systemkey is set then the hkey won't be released
+         * when the object is GC'ed.
+         * The remoteKey flag when set to true indicates that we are dealing with registry entries
+         * on a remote machine and requires the program making these calls to have full trust.
+         */
+        private RegistryKey(SafeRegistryHandle hkey, bool writable, bool systemkey, bool remoteKey, bool isPerfData, RegistryView view)
+        {
+            this.hkey = hkey;
+            keyName = "";
+            this.remoteKey = remoteKey;
+            regView = view;
+            if (systemkey)
+            {
+                state |= STATE_SYSTEMKEY;
+            }
+            if (writable)
+            {
+                state |= STATE_WRITEACCESS;
+            }
+            if (isPerfData)
+                state |= STATE_PERF_DATA;
+            ValidateKeyView(view);
+        }
+
+        /**
+         * Closes this key, flushes it to disk if the contents have been modified.
+         */
+        public void Close()
+        {
+            Dispose(true);
+        }
+
+        private void Dispose(bool disposing)
+        {
+            if (hkey != null)
+            {
+                if (!IsSystemKey())
+                {
+                    try
+                    {
+                        hkey.Dispose();
+                    }
+                    catch (IOException)
+                    {
+                        // we don't really care if the handle is invalid at this point
+                    }
+                    finally
+                    {
+                        hkey = null;
+                    }
+                }
+                else if (disposing && IsPerfDataKey())
+                {
+                    // System keys should never be closed.  However, we want to call RegCloseKey
+                    // on HKEY_PERFORMANCE_DATA when called from PerformanceCounter.CloseSharedResources
+                    // (i.e. when disposing is true) so that we release the PERFLIB cache and cause it
+                    // to be refreshed (by re-reading the registry) when accessed subsequently. 
+                    // This is the only way we can see the just installed perf counter.  
+                    // NOTE: since HKEY_PERFORMANCE_DATA is process wide, there is inherent race condition in closing
+                    // the key asynchronously. While Vista is smart enough to rebuild the PERFLIB resources
+                    // in this situation the down level OSes are not. We have a small window between  
+                    // the dispose below and usage elsewhere (other threads). This is By Design. 
+                    // This is less of an issue when OS > NT5 (i.e Vista & higher), we can close the perfkey  
+                    // (to release & refresh PERFLIB resources) and the OS will rebuild PERFLIB as necessary. 
+                    SafeRegistryHandle.RegCloseKey(RegistryKey.HKEY_PERFORMANCE_DATA);
+                }
+            }
+        }
+
+        void IDisposable.Dispose()
+        {
+            Dispose(true);
+        }
+
+        public void DeleteValue(String name, bool throwOnMissingValue)
+        {
+            EnsureWriteable();
+            int errorCode = Win32Native.RegDeleteValue(hkey, name);
+
+            //
+            // From windows 2003 server, if the name is too long we will get error code ERROR_FILENAME_EXCED_RANGE  
+            // This still means the name doesn't exist. We need to be consistent with previous OS.
+            //
+            if (errorCode == Interop.Errors.ERROR_FILE_NOT_FOUND || errorCode == Interop.Errors.ERROR_FILENAME_EXCED_RANGE)
+            {
+                if (throwOnMissingValue)
+                {
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RegSubKeyValueAbsent);
+                }
+                // Otherwise, just return giving no indication to the user.
+                // (For compatibility)
+            }
+            // We really should throw an exception here if errorCode was bad,
+            // but we can't for compatibility reasons.
+            Debug.Assert(errorCode == 0, "RegDeleteValue failed.  Here's your error code: " + errorCode);
+        }
+
+        /**
+         * Retrieves a new RegistryKey that represents the requested key. Valid
+         * values are:
+         *
+         * HKEY_CLASSES_ROOT,
+         * HKEY_CURRENT_USER,
+         * HKEY_LOCAL_MACHINE,
+         * HKEY_USERS,
+         * HKEY_PERFORMANCE_DATA,
+         * HKEY_CURRENT_CONFIG,
+         * HKEY_DYN_DATA.
+         *
+         * @param hKey HKEY_* to open.
+         *
+         * @return the RegistryKey requested.
+         */
+        internal static RegistryKey GetBaseKey(IntPtr hKey)
+        {
+            return GetBaseKey(hKey, RegistryView.Default);
+        }
+
+        internal static RegistryKey GetBaseKey(IntPtr hKey, RegistryView view)
+        {
+            int index = ((int)hKey) & 0x0FFFFFFF;
+            Debug.Assert(index >= 0 && index < hkeyNames.Length, "index is out of range!");
+            Debug.Assert((((int)hKey) & 0xFFFFFFF0) == 0x80000000, "Invalid hkey value!");
+
+            bool isPerf = hKey == HKEY_PERFORMANCE_DATA;
+            // only mark the SafeHandle as ownsHandle if the key is HKEY_PERFORMANCE_DATA.
+            SafeRegistryHandle srh = new SafeRegistryHandle(hKey, isPerf);
+
+            RegistryKey key = new RegistryKey(srh, true, true, false, isPerf, view);
+            key.checkMode = RegistryKeyPermissionCheck.Default;
+            key.keyName = hkeyNames[index];
+            return key;
+        }
+
+        /**
+         * Retrieves a subkey. If readonly is <b>true</b>, then the subkey is opened with
+         * read-only access.
+         *
+         * @param name Name or path of subkey to open.
+         * @param readonly Set to <b>true</b> if you only need readonly access.
+         *
+         * @return the Subkey requested, or <b>null</b> if the operation failed.
+         */
+        public RegistryKey OpenSubKey(string name, bool writable)
+        {
+            ValidateKeyName(name);
+            EnsureNotDisposed();
+            name = FixupName(name); // Fixup multiple slashes to a single slash
+
+            SafeRegistryHandle result = null;
+            int ret = Win32Native.RegOpenKeyEx(hkey,
+                name,
+                0,
+                GetRegistryKeyAccess(writable) | (int)regView,
+                out result);
+
+            if (ret == 0 && !result.IsInvalid)
+            {
+                RegistryKey key = new RegistryKey(result, writable, false, remoteKey, false, regView);
+                key.checkMode = GetSubKeyPermissonCheck(writable);
+                key.keyName = keyName + "\\" + name;
+                return key;
+            }
+
+            // Return null if we didn't find the key.
+            if (ret == Interop.Errors.ERROR_ACCESS_DENIED || ret == Interop.Errors.ERROR_BAD_IMPERSONATION_LEVEL)
+            {
+                // We need to throw SecurityException here for compatibility reasons,
+                // although UnauthorizedAccessException will make more sense.
+                ThrowHelper.ThrowSecurityException(ExceptionResource.Security_RegistryPermission);
+            }
+
+            return null;
+        }
+
+        /**
+         * Returns a subkey with read only permissions.
+         *
+         * @param name Name or path of subkey to open.
+         *
+         * @return the Subkey requested, or <b>null</b> if the operation failed.
+         */
+        public RegistryKey OpenSubKey(String name)
+        {
+            return OpenSubKey(name, false);
+        }
+
+        /// <summary>
+        /// Retrieves an array of strings containing all the subkey names.
+        /// </summary>
+        public string[] GetSubKeyNames()
+        {
+            EnsureNotDisposed();
+
+            var names = new List<string>();
+            char[] name = ArrayPool<char>.Shared.Rent(MaxKeyLength + 1);
+
+            try
+            {
+                int result;
+                int nameLength = name.Length;
+
+                while ((result = Win32Native.RegEnumKeyEx(
+                    hkey,
+                    names.Count,
+                    name,
+                    ref nameLength,
+                    null,
+                    null,
+                    null,
+                    null)) != Interop.Errors.ERROR_NO_MORE_ITEMS)
+                {
+                    switch (result)
+                    {
+                        case Interop.Errors.ERROR_SUCCESS:
+                            names.Add(new string(name, 0, nameLength));
+                            nameLength = name.Length;
+                            break;
+                        default:
+                            // Throw the error
+                            Win32Error(result, null);
+                            break;
+                    }
+                }
+            }
+            finally
+            {
+                ArrayPool<char>.Shared.Return(name);
+            }
+
+            return names.ToArray();
+        }
+
+        /// <summary>
+        /// Retrieves an array of strings containing all the value names.
+        /// </summary>
+        public unsafe string[] GetValueNames()
+        {
+            EnsureNotDisposed();
+            var names = new List<string>();
+
+            // Names in the registry aren't usually very long, although they can go to as large
+            // as 16383 characters (MaxValueLength).
+            //
+            // Every call to RegEnumValue will allocate another buffer to get the data from
+            // NtEnumerateValueKey before copying it back out to our passed in buffer. This can
+            // add up quickly- we'll try to keep the memory pressure low and grow the buffer
+            // only if needed.
+
+            char[] name = ArrayPool<char>.Shared.Rent(100);
+
+            try
+            {
+                int result;
+                int nameLength = name.Length;
+
+                while ((result = Win32Native.RegEnumValue(
+                    hkey,
+                    names.Count,
+                    name,
+                    ref nameLength,
+                    IntPtr.Zero,
+                    null,
+                    null,
+                    null)) != Interop.Errors.ERROR_NO_MORE_ITEMS)
+                {
+                    switch (result)
+                    {
+                        // The size is only ever reported back correctly in the case
+                        // of ERROR_SUCCESS. It will almost always be changed, however.
+                        case Interop.Errors.ERROR_SUCCESS:
+                            names.Add(new string(name, 0, nameLength));
+                            break;
+                        case Interop.Errors.ERROR_MORE_DATA:
+                            if (IsPerfDataKey())
+                            {
+                                // Enumerating the values for Perf keys always returns
+                                // ERROR_MORE_DATA, but has a valid name. Buffer does need
+                                // to be big enough however. 8 characters is the largest
+                                // known name. The size isn't returned, but the string is
+                                // null terminated.
+                                fixed (char* c = &name[0])
+                                {
+                                    names.Add(new string(c));
+                                }
+                            }
+                            else
+                            {
+                                char[] oldName = name;
+                                int oldLength = oldName.Length;
+                                name = null;
+                                ArrayPool<char>.Shared.Return(oldName);
+                                name = ArrayPool<char>.Shared.Rent(checked(oldLength * 2));
+                            }
+                            break;
+                        default:
+                            // Throw the error
+                            Win32Error(result, null);
+                            break;
+                    }
+
+                    // Always set the name length back to the buffer size
+                    nameLength = name.Length;
+                }
+            }
+            finally
+            {
+                if (name != null)
+                    ArrayPool<char>.Shared.Return(name);
+            }
+
+            return names.ToArray();
+        }
+
+        /**
+         * Retrieves the specified value. <b>null</b> is returned if the value
+         * doesn't exist.
+         *
+         * Note that <var>name</var> can be null or "", at which point the
+         * unnamed or default value of this Registry key is returned, if any.
+         *
+         * @param name Name of value to retrieve.
+         *
+         * @return the data associated with the value.
+         */
+        public Object GetValue(String name)
+        {
+            return InternalGetValue(name, null, false, true);
+        }
+
+        /**
+         * Retrieves the specified value. <i>defaultValue</i> is returned if the value doesn't exist.
+         *
+         * Note that <var>name</var> can be null or "", at which point the
+         * unnamed or default value of this Registry key is returned, if any.
+         * The default values for RegistryKeys are OS-dependent.  NT doesn't
+         * have them by default, but they can exist and be of any type. 
+         *
+         * @param name Name of value to retrieve.
+         * @param defaultValue Value to return if <i>name</i> doesn't exist.
+         *
+         * @return the data associated with the value.
+         */
+        public Object GetValue(String name, Object defaultValue)
+        {
+            return InternalGetValue(name, defaultValue, false, true);
+        }
+
+        public Object GetValue(String name, Object defaultValue, RegistryValueOptions options)
+        {
+            if (options < RegistryValueOptions.None || options > RegistryValueOptions.DoNotExpandEnvironmentNames)
+            {
+                throw new ArgumentException(SR.Format(SR.Arg_EnumIllegalVal, (int)options), nameof(options));
+            }
+            bool doNotExpand = (options == RegistryValueOptions.DoNotExpandEnvironmentNames);
+            return InternalGetValue(name, defaultValue, doNotExpand, true);
+        }
+
+        internal Object InternalGetValue(String name, Object defaultValue, bool doNotExpand, bool checkSecurity)
+        {
+            if (checkSecurity)
+            {
+                // Name can be null!  It's the most common use of RegQueryValueEx
+                EnsureNotDisposed();
+            }
+
+            Object data = defaultValue;
+            int type = 0;
+            int datasize = 0;
+
+            int ret = Win32Native.RegQueryValueEx(hkey, name, null, ref type, (byte[])null, ref datasize);
+
+            if (ret != 0)
+            {
+                if (IsPerfDataKey())
+                {
+                    int size = 65000;
+                    int sizeInput = size;
+
+                    int r;
+                    byte[] blob = new byte[size];
+                    while (Interop.Errors.ERROR_MORE_DATA == (r = Win32Native.RegQueryValueEx(hkey, name, null, ref type, blob, ref sizeInput)))
+                    {
+                        if (size == Int32.MaxValue)
+                        {
+                            // ERROR_MORE_DATA was returned however we cannot increase the buffer size beyond Int32.MaxValue
+                            Win32Error(r, name);
+                        }
+                        else if (size > (Int32.MaxValue / 2))
+                        {
+                            // at this point in the loop "size * 2" would cause an overflow
+                            size = Int32.MaxValue;
+                        }
+                        else
+                        {
+                            size *= 2;
+                        }
+                        sizeInput = size;
+                        blob = new byte[size];
+                    }
+                    if (r != 0)
+                        Win32Error(r, name);
+                    return blob;
+                }
+                else
+                {
+                    // For stuff like ERROR_FILE_NOT_FOUND, we want to return null (data).
+                    // Some OS's returned ERROR_MORE_DATA even in success cases, so we 
+                    // want to continue on through the function. 
+                    if (ret != Interop.Errors.ERROR_MORE_DATA)
+                        return data;
+                }
+            }
+
+            if (datasize < 0)
+            {
+                // unexpected code path
+                Debug.Fail("[InternalGetValue] RegQueryValue returned ERROR_SUCCESS but gave a negative datasize");
+                datasize = 0;
+            }
+
+
+            switch (type)
+            {
+                case Win32Native.REG_NONE:
+                case Win32Native.REG_DWORD_BIG_ENDIAN:
+                case Win32Native.REG_BINARY:
+                    {
+                        byte[] blob = new byte[datasize];
+                        ret = Win32Native.RegQueryValueEx(hkey, name, null, ref type, blob, ref datasize);
+                        data = blob;
+                    }
+                    break;
+                case Win32Native.REG_QWORD:
+                    {    // also REG_QWORD_LITTLE_ENDIAN
+                        if (datasize > 8)
+                        {
+                            // prevent an AV in the edge case that datasize is larger than sizeof(long)
+                            goto case Win32Native.REG_BINARY;
+                        }
+                        long blob = 0;
+                        Debug.Assert(datasize == 8, "datasize==8");
+                        // Here, datasize must be 8 when calling this
+                        ret = Win32Native.RegQueryValueEx(hkey, name, null, ref type, ref blob, ref datasize);
+
+                        data = blob;
+                    }
+                    break;
+                case Win32Native.REG_DWORD:
+                    {    // also REG_DWORD_LITTLE_ENDIAN
+                        if (datasize > 4)
+                        {
+                            // prevent an AV in the edge case that datasize is larger than sizeof(int)
+                            goto case Win32Native.REG_QWORD;
+                        }
+                        int blob = 0;
+                        Debug.Assert(datasize == 4, "datasize==4");
+                        // Here, datasize must be four when calling this
+                        ret = Win32Native.RegQueryValueEx(hkey, name, null, ref type, ref blob, ref datasize);
+
+                        data = blob;
+                    }
+                    break;
+
+                case Win32Native.REG_SZ:
+                    {
+                        if (datasize % 2 == 1)
+                        {
+                            // handle the case where the registry contains an odd-byte length (corrupt data?)
+                            try
+                            {
+                                datasize = checked(datasize + 1);
+                            }
+                            catch (OverflowException e)
+                            {
+                                throw new IOException(SR.Arg_RegGetOverflowBug, e);
+                            }
+                        }
+                        char[] blob = new char[datasize / 2];
+
+                        ret = Win32Native.RegQueryValueEx(hkey, name, null, ref type, blob, ref datasize);
+                        if (blob.Length > 0 && blob[blob.Length - 1] == (char)0)
+                        {
+                            data = new String(blob, 0, blob.Length - 1);
+                        }
+                        else
+                        {
+                            // in the very unlikely case the data is missing null termination, 
+                            // pass in the whole char[] to prevent truncating a character
+                            data = new String(blob);
+                        }
+                    }
+                    break;
+
+                case Win32Native.REG_EXPAND_SZ:
+                    {
+                        if (datasize % 2 == 1)
+                        {
+                            // handle the case where the registry contains an odd-byte length (corrupt data?)
+                            try
+                            {
+                                datasize = checked(datasize + 1);
+                            }
+                            catch (OverflowException e)
+                            {
+                                throw new IOException(SR.Arg_RegGetOverflowBug, e);
+                            }
+                        }
+                        char[] blob = new char[datasize / 2];
+
+                        ret = Win32Native.RegQueryValueEx(hkey, name, null, ref type, blob, ref datasize);
+
+                        if (blob.Length > 0 && blob[blob.Length - 1] == (char)0)
+                        {
+                            data = new String(blob, 0, blob.Length - 1);
+                        }
+                        else
+                        {
+                            // in the very unlikely case the data is missing null termination, 
+                            // pass in the whole char[] to prevent truncating a character
+                            data = new String(blob);
+                        }
+
+                        if (!doNotExpand)
+                            data = Environment.ExpandEnvironmentVariables((String)data);
+                    }
+                    break;
+                case Win32Native.REG_MULTI_SZ:
+                    {
+                        if (datasize % 2 == 1)
+                        {
+                            // handle the case where the registry contains an odd-byte length (corrupt data?)
+                            try
+                            {
+                                datasize = checked(datasize + 1);
+                            }
+                            catch (OverflowException e)
+                            {
+                                throw new IOException(SR.Arg_RegGetOverflowBug, e);
+                            }
+                        }
+                        char[] blob = new char[datasize / 2];
+
+                        ret = Win32Native.RegQueryValueEx(hkey, name, null, ref type, blob, ref datasize);
+
+                        // make sure the string is null terminated before processing the data
+                        if (blob.Length > 0 && blob[blob.Length - 1] != (char)0)
+                        {
+                            try
+                            {
+                                char[] newBlob = new char[checked(blob.Length + 1)];
+                                for (int i = 0; i < blob.Length; i++)
+                                {
+                                    newBlob[i] = blob[i];
+                                }
+                                newBlob[newBlob.Length - 1] = (char)0;
+                                blob = newBlob;
+                            }
+                            catch (OverflowException e)
+                            {
+                                throw new IOException(SR.Arg_RegGetOverflowBug, e);
+                            }
+                            blob[blob.Length - 1] = (char)0;
+                        }
+
+
+                        IList<String> strings = new List<String>();
+                        int cur = 0;
+                        int len = blob.Length;
+
+                        while (ret == 0 && cur < len)
+                        {
+                            int nextNull = cur;
+                            while (nextNull < len && blob[nextNull] != (char)0)
+                            {
+                                nextNull++;
+                            }
+
+                            if (nextNull < len)
+                            {
+                                Debug.Assert(blob[nextNull] == (char)0, "blob[nextNull] should be 0");
+                                if (nextNull - cur > 0)
+                                {
+                                    strings.Add(new String(blob, cur, nextNull - cur));
+                                }
+                                else
+                                {
+                                    // we found an empty string.  But if we're at the end of the data, 
+                                    // it's just the extra null terminator. 
+                                    if (nextNull != len - 1)
+                                        strings.Add(String.Empty);
+                                }
+                            }
+                            else
+                            {
+                                strings.Add(new String(blob, cur, len - cur));
+                            }
+                            cur = nextNull + 1;
+                        }
+
+                        data = new String[strings.Count];
+                        strings.CopyTo((String[])data, 0);
+                    }
+                    break;
+                case Win32Native.REG_LINK:
+                default:
+                    break;
+            }
+
+            return data;
+        }
+
+        private bool IsSystemKey()
+        {
+            return (state & STATE_SYSTEMKEY) != 0;
+        }
+
+        private bool IsWritable()
+        {
+            return (state & STATE_WRITEACCESS) != 0;
+        }
+
+        private bool IsPerfDataKey()
+        {
+            return (state & STATE_PERF_DATA) != 0;
+        }
+
+        private void SetDirty()
+        {
+            state |= STATE_DIRTY;
+        }
+
+        /**
+         * Sets the specified value.
+         *
+         * @param name Name of value to store data in.
+         * @param value Data to store.
+         */
+        public void SetValue(String name, Object value)
+        {
+            SetValue(name, value, RegistryValueKind.Unknown);
+        }
+
+        public unsafe void SetValue(String name, Object value, RegistryValueKind valueKind)
+        {
+            if (value == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.value);
+
+            if (name != null && name.Length > MaxValueLength)
+            {
+                throw new ArgumentException(SR.Arg_RegValStrLenBug);
+            }
+
+            if (!Enum.IsDefined(typeof(RegistryValueKind), valueKind))
+                throw new ArgumentException(SR.Arg_RegBadKeyKind, nameof(valueKind));
+
+            EnsureWriteable();
+
+            if (valueKind == RegistryValueKind.Unknown)
+            {
+                // this is to maintain compatibility with the old way of autodetecting the type.
+                // SetValue(string, object) will come through this codepath.
+                valueKind = CalculateValueKind(value);
+            }
+
+            int ret = 0;
+            try
+            {
+                switch (valueKind)
+                {
+                    case RegistryValueKind.ExpandString:
+                    case RegistryValueKind.String:
+                        {
+                            String data = value.ToString();
+                            ret = Win32Native.RegSetValueEx(hkey,
+                                name,
+                                0,
+                                valueKind,
+                                data,
+                                checked(data.Length * 2 + 2));
+                            break;
+                        }
+
+                    case RegistryValueKind.MultiString:
+                        {
+                            // Other thread might modify the input array after we calculate the buffer length.                            
+                            // Make a copy of the input array to be safe.
+                            string[] dataStrings = (string[])(((string[])value).Clone());
+                            int sizeInBytes = 0;
+
+                            // First determine the size of the array
+                            //
+                            for (int i = 0; i < dataStrings.Length; i++)
+                            {
+                                if (dataStrings[i] == null)
+                                {
+                                    ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RegSetStrArrNull);
+                                }
+                                sizeInBytes = checked(sizeInBytes + (dataStrings[i].Length + 1) * 2);
+                            }
+                            sizeInBytes = checked(sizeInBytes + 2);
+
+                            byte[] basePtr = new byte[sizeInBytes];
+                            fixed (byte* b = basePtr)
+                            {
+                                IntPtr currentPtr = new IntPtr((void*)b);
+
+                                // Write out the strings...
+                                //
+                                for (int i = 0; i < dataStrings.Length; i++)
+                                {
+                                    // Assumes that the Strings are always null terminated.
+                                    String.InternalCopy(dataStrings[i], currentPtr, (checked(dataStrings[i].Length * 2)));
+                                    currentPtr = new IntPtr((long)currentPtr + (checked(dataStrings[i].Length * 2)));
+                                    *(char*)(currentPtr.ToPointer()) = '\0';
+                                    currentPtr = new IntPtr((long)currentPtr + 2);
+                                }
+
+                                *(char*)(currentPtr.ToPointer()) = '\0';
+                                currentPtr = new IntPtr((long)currentPtr + 2);
+
+                                ret = Win32Native.RegSetValueEx(hkey,
+                                    name,
+                                    0,
+                                    RegistryValueKind.MultiString,
+                                    basePtr,
+                                    sizeInBytes);
+                            }
+                            break;
+                        }
+
+                    case RegistryValueKind.None:
+                    case RegistryValueKind.Binary:
+                        byte[] dataBytes = (byte[])value;
+                        ret = Win32Native.RegSetValueEx(hkey,
+                            name,
+                            0,
+                            (valueKind == RegistryValueKind.None ? Win32Native.REG_NONE : RegistryValueKind.Binary),
+                            dataBytes,
+                            dataBytes.Length);
+                        break;
+
+                    case RegistryValueKind.DWord:
+                        {
+                            // We need to use Convert here because we could have a boxed type cannot be
+                            // unboxed and cast at the same time.  I.e. ((int)(object)(short) 5) will fail.
+                            int data = Convert.ToInt32(value, System.Globalization.CultureInfo.InvariantCulture);
+
+                            ret = Win32Native.RegSetValueEx(hkey,
+                                name,
+                                0,
+                                RegistryValueKind.DWord,
+                                ref data,
+                                4);
+                            break;
+                        }
+
+                    case RegistryValueKind.QWord:
+                        {
+                            long data = Convert.ToInt64(value, System.Globalization.CultureInfo.InvariantCulture);
+
+                            ret = Win32Native.RegSetValueEx(hkey,
+                                name,
+                                0,
+                                RegistryValueKind.QWord,
+                                ref data,
+                                8);
+                            break;
+                        }
+                }
+            }
+            catch (OverflowException)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RegSetMismatchedKind);
+            }
+            catch (InvalidOperationException)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RegSetMismatchedKind);
+            }
+            catch (FormatException)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RegSetMismatchedKind);
+            }
+            catch (InvalidCastException)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RegSetMismatchedKind);
+            }
+
+            if (ret == 0)
+            {
+                SetDirty();
+            }
+            else
+                Win32Error(ret, null);
+        }
+
+        private RegistryValueKind CalculateValueKind(Object value)
+        {
+            // This logic matches what used to be in SetValue(string name, object value) in the v1.0 and v1.1 days.
+            // Even though we could add detection for an int64 in here, we want to maintain compatibility with the
+            // old behavior.
+            if (value is Int32)
+                return RegistryValueKind.DWord;
+            else if (value is Array)
+            {
+                if (value is byte[])
+                    return RegistryValueKind.Binary;
+                else if (value is String[])
+                    return RegistryValueKind.MultiString;
+                else
+                    throw new ArgumentException(SR.Format(SR.Arg_RegSetBadArrType, value.GetType().Name));
+            }
+            else
+                return RegistryValueKind.String;
+        }
+
+        /**
+         * Retrieves a string representation of this key.
+         *
+         * @return a string representing the key.
+         */
+        public override String ToString()
+        {
+            EnsureNotDisposed();
+            return keyName;
+        }
+
+        /**
+         * After calling GetLastWin32Error(), it clears the last error field,
+         * so you must save the HResult and pass it to this method.  This method
+         * will determine the appropriate exception to throw dependent on your
+         * error, and depending on the error, insert a string into the message
+         * gotten from the ResourceManager.
+         */
+        internal void Win32Error(int errorCode, String str)
+        {
+            switch (errorCode)
+            {
+                case Interop.Errors.ERROR_ACCESS_DENIED:
+                    if (str != null)
+                        throw new UnauthorizedAccessException(SR.Format(SR.UnauthorizedAccess_RegistryKeyGeneric_Key, str));
+                    else
+                        throw new UnauthorizedAccessException();
+
+                case Interop.Errors.ERROR_INVALID_HANDLE:
+                    /**
+                     * For normal RegistryKey instances we dispose the SafeRegHandle and throw IOException.
+                     * However, for HKEY_PERFORMANCE_DATA (on a local or remote machine) we avoid disposing the
+                     * SafeRegHandle and only throw the IOException.  This is to workaround reentrancy issues
+                     * in PerformanceCounter.NextValue() where the API could throw {NullReference, ObjectDisposed, ArgumentNull}Exception
+                     * on reentrant calls because of this error code path in RegistryKey
+                     *
+                     * Normally we'd make our caller synchronize access to a shared RegistryKey instead of doing something like this,
+                     * however we shipped PerformanceCounter.NextValue() un-synchronized in v2.0RTM and customers have taken a dependency on 
+                     * this behavior (being able to simultaneously query multiple remote-machine counters on multiple threads, instead of 
+                     * having serialized access).
+                     */
+                    if (!IsPerfDataKey())
+                    {
+                        hkey.SetHandleAsInvalid();
+                        hkey = null;
+                    }
+                    goto default;
+
+                case Interop.Errors.ERROR_FILE_NOT_FOUND:
+                    throw new IOException(SR.Arg_RegKeyNotFound, errorCode);
+
+                default:
+                    throw new IOException(Interop.Kernel32.GetMessage(errorCode), errorCode);
+            }
+        }
+
+        internal static String FixupName(String name)
+        {
+            Debug.Assert(name != null, "[FixupName]name!=null");
+            if (name.IndexOf('\\') == -1)
+                return name;
+
+            StringBuilder sb = new StringBuilder(name);
+            FixupPath(sb);
+            int temp = sb.Length - 1;
+            if (temp >= 0 && sb[temp] == '\\') // Remove trailing slash
+                sb.Length = temp;
+            return sb.ToString();
+        }
+
+
+        private static void FixupPath(StringBuilder path)
+        {
+            Debug.Assert(path != null);
+            int length = path.Length;
+            bool fixup = false;
+            char markerChar = (char)0xFFFF;
+
+            int i = 1;
+            while (i < length - 1)
+            {
+                if (path[i] == '\\')
+                {
+                    i++;
+                    while (i < length)
+                    {
+                        if (path[i] == '\\')
+                        {
+                            path[i] = markerChar;
+                            i++;
+                            fixup = true;
+                        }
+                        else
+                            break;
+                    }
+                }
+                i++;
+            }
+
+            if (fixup)
+            {
+                i = 0;
+                int j = 0;
+                while (i < length)
+                {
+                    if (path[i] == markerChar)
+                    {
+                        i++;
+                        continue;
+                    }
+                    path[j] = path[i];
+                    i++;
+                    j++;
+                }
+                path.Length += j - i;
+            }
+        }
+
+        private void EnsureNotDisposed()
+        {
+            if (hkey == null)
+            {
+                ThrowHelper.ThrowObjectDisposedException(keyName, ExceptionResource.ObjectDisposed_RegKeyClosed);
+            }
+        }
+
+        private void EnsureWriteable()
+        {
+            EnsureNotDisposed();
+            if (!IsWritable())
+            {
+                ThrowHelper.ThrowUnauthorizedAccessException(ExceptionResource.UnauthorizedAccess_RegistryNoWrite);
+            }
+        }
+
+        private static int GetRegistryKeyAccess(bool isWritable)
+        {
+            int winAccess;
+            if (!isWritable)
+            {
+                winAccess = Win32Native.KEY_READ;
+            }
+            else
+            {
+                winAccess = Win32Native.KEY_READ | Win32Native.KEY_WRITE;
+            }
+
+            return winAccess;
+        }
+
+        private RegistryKeyPermissionCheck GetSubKeyPermissonCheck(bool subkeyWritable)
+        {
+            if (checkMode == RegistryKeyPermissionCheck.Default)
+            {
+                return checkMode;
+            }
+
+            if (subkeyWritable)
+            {
+                return RegistryKeyPermissionCheck.ReadWriteSubTree;
+            }
+            else
+            {
+                return RegistryKeyPermissionCheck.ReadSubTree;
+            }
+        }
+
+        private static void ValidateKeyName(string name)
+        {
+            if (name == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.name);
+            }
+
+            int nextSlash = name.IndexOf("\\", StringComparison.OrdinalIgnoreCase);
+            int current = 0;
+            while (nextSlash != -1)
+            {
+                if ((nextSlash - current) > MaxKeyLength)
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RegKeyStrLenBug);
+
+                current = nextSlash + 1;
+                nextSlash = name.IndexOf("\\", current, StringComparison.OrdinalIgnoreCase);
+            }
+
+            if ((name.Length - current) > MaxKeyLength)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RegKeyStrLenBug);
+        }
+
+        private static void ValidateKeyView(RegistryView view)
+        {
+            if (view != RegistryView.Default && view != RegistryView.Registry32 && view != RegistryView.Registry64)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidRegistryViewCheck, ExceptionArgument.view);
+            }
+        }
+
+        // Win32 constants for error handling
+        private const int FORMAT_MESSAGE_IGNORE_INSERTS = 0x00000200;
+        private const int FORMAT_MESSAGE_FROM_SYSTEM = 0x00001000;
+        private const int FORMAT_MESSAGE_ARGUMENT_ARRAY = 0x00002000;
+    }
+
+    [Flags]
+    internal enum RegistryValueOptions
+    {
+        None = 0,
+        DoNotExpandEnvironmentNames = 1
+    }
+
+    // the name for this API is meant to mimic FileMode, which has similar values
+
+    internal enum RegistryKeyPermissionCheck
+    {
+        Default = 0,
+        ReadSubTree = 1,
+        ReadWriteSubTree = 2
+    }
+}
diff --git a/src/System.Private.CoreLib/src/Microsoft/Win32/RegistryValueKind.cs b/src/System.Private.CoreLib/src/Microsoft/Win32/RegistryValueKind.cs
new file mode 100644
index 0000000000..6e2a4f3b6e
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Microsoft/Win32/RegistryValueKind.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+namespace Microsoft.Win32
+{
+    internal enum RegistryValueKind
+    {
+        String = Win32Native.REG_SZ,
+        ExpandString = Win32Native.REG_EXPAND_SZ,
+        Binary = Win32Native.REG_BINARY,
+        DWord = Win32Native.REG_DWORD,
+        MultiString = Win32Native.REG_MULTI_SZ,
+        QWord = Win32Native.REG_QWORD,
+        Unknown = 0,                          // REG_NONE is defined as zero but BCL
+        None = unchecked((int)0xFFFFFFFF), //  mistakingly overrode this value.  
+    }   // Now instead of using Win32Native.REG_NONE we use "-1" and play games internally.
+}
+
diff --git a/src/System.Private.CoreLib/src/Microsoft/Win32/RegistryView.cs b/src/System.Private.CoreLib/src/Microsoft/Win32/RegistryView.cs
new file mode 100644
index 0000000000..e4158656a8
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Microsoft/Win32/RegistryView.cs
@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+//
+//
+// Implements Microsoft.Win32.RegistryView
+//
+// ======================================================================================
+
+using System;
+
+namespace Microsoft.Win32
+{
+    internal enum RegistryView
+    {
+        Default = 0,                           // 0x0000 operate on the default registry view
+        Registry64 = Win32Native.KEY_WOW64_64KEY, // 0x0100 operate on the 64-bit registry view
+        Registry32 = Win32Native.KEY_WOW64_32KEY, // 0x0200 operate on the 32-bit registry view
+    };
+}
diff --git a/src/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeRegistryHandle.cs b/src/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeRegistryHandle.cs
new file mode 100644
index 0000000000..b69bc42e64
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeRegistryHandle.cs
@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+//
+//
+// Implements Microsoft.Win32.SafeHandles.SafeRegistryHandle
+//
+// ======================================================================================
+
+using System;
+using System.Security;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Runtime.ConstrainedExecution;
+using System.Runtime.Versioning;
+
+namespace Microsoft.Win32.SafeHandles
+{
+    internal sealed class SafeRegistryHandle : SafeHandleZeroOrMinusOneIsInvalid
+    {
+        internal SafeRegistryHandle() : base(true) { }
+
+        public SafeRegistryHandle(IntPtr preexistingHandle, bool ownsHandle) : base(ownsHandle)
+        {
+            SetHandle(preexistingHandle);
+        }
+
+        override protected bool ReleaseHandle()
+        {
+            return (RegCloseKey(handle) == Interop.Errors.ERROR_SUCCESS);
+        }
+
+        [DllImport(Win32Native.ADVAPI32)]
+        internal static extern int RegCloseKey(IntPtr hKey);
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeWaitHandle.cs b/src/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeWaitHandle.cs
new file mode 100644
index 0000000000..1141e6d027
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeWaitHandle.cs
@@ -0,0 +1,43 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** A wrapper for Win32 events (mutexes, auto reset events, and
+** manual reset events).  Used by WaitHandle.
+**
+** 
+===========================================================*/
+
+using System;
+using System.Security;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Runtime.ConstrainedExecution;
+using System.Runtime.Versioning;
+using Microsoft.Win32;
+using System.Threading;
+
+namespace Microsoft.Win32.SafeHandles
+{
+    public sealed class SafeWaitHandle : SafeHandleZeroOrMinusOneIsInvalid
+    {
+        // Called by P/Invoke marshaler
+        private SafeWaitHandle() : base(true)
+        {
+        }
+
+        public SafeWaitHandle(IntPtr existingHandle, bool ownsHandle) : base(ownsHandle)
+        {
+            SetHandle(existingHandle);
+        }
+
+        override protected bool ReleaseHandle()
+        {
+            return Win32Native.CloseHandle(handle);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/Microsoft/Win32/UnsafeNativeMethods.cs b/src/System.Private.CoreLib/src/Microsoft/Win32/UnsafeNativeMethods.cs
new file mode 100644
index 0000000000..cc8887aed6
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Microsoft/Win32/UnsafeNativeMethods.cs
@@ -0,0 +1,199 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.Win32
+{
+    using Microsoft.Win32.SafeHandles;
+    using System;
+    using System.Diagnostics.Tracing;
+    using System.Runtime.InteropServices;
+    using System.Security;
+    using System.Text;
+
+    internal static class UnsafeNativeMethods
+    {
+        internal static unsafe class ManifestEtw
+        {
+            //
+            // Constants error coded returned by ETW APIs
+            //
+
+            // The event size is larger than the allowed maximum (64k - header).
+            internal const int ERROR_ARITHMETIC_OVERFLOW = 534;
+
+            // Occurs when filled buffers are trying to flush to disk, 
+            // but disk IOs are not happening fast enough. 
+            // This happens when the disk is slow and event traffic is heavy. 
+            // Eventually, there are no more free (empty) buffers and the event is dropped.
+            internal const int ERROR_NOT_ENOUGH_MEMORY = 8;
+
+            internal const int ERROR_MORE_DATA = 0xEA;
+            internal const int ERROR_NOT_SUPPORTED = 50;
+            internal const int ERROR_INVALID_PARAMETER = 0x57;
+
+            //
+            // ETW Methods
+            //
+
+            internal const int EVENT_CONTROL_CODE_DISABLE_PROVIDER = 0;
+            internal const int EVENT_CONTROL_CODE_ENABLE_PROVIDER = 1;
+            internal const int EVENT_CONTROL_CODE_CAPTURE_STATE = 2;
+
+            //
+            // Callback
+            //
+            internal unsafe delegate void EtwEnableCallback(
+                [In] ref Guid sourceId,
+                [In] int isEnabled,
+                [In] byte level,
+                [In] long matchAnyKeywords,
+                [In] long matchAllKeywords,
+                [In] EVENT_FILTER_DESCRIPTOR* filterData,
+                [In] void* callbackContext
+                );
+
+            //
+            // Registration APIs
+            //
+            [DllImport(Win32Native.ADVAPI32, ExactSpelling = true, EntryPoint = "EventRegister", CharSet = System.Runtime.InteropServices.CharSet.Unicode)]
+            internal static extern unsafe uint EventRegister(
+                        [In] ref Guid providerId,
+                        [In]EtwEnableCallback enableCallback,
+                        [In]void* callbackContext,
+                        [In][Out]ref long registrationHandle
+                        );
+
+            // 
+            [DllImport(Win32Native.ADVAPI32, ExactSpelling = true, EntryPoint = "EventUnregister", CharSet = System.Runtime.InteropServices.CharSet.Unicode)]
+            internal static extern uint EventUnregister([In] long registrationHandle);
+
+            [DllImport(Win32Native.ADVAPI32, ExactSpelling = true, EntryPoint = "EventWriteString", CharSet = System.Runtime.InteropServices.CharSet.Unicode)]
+            internal static extern unsafe int EventWriteString(
+                    [In] long registrationHandle,
+                    [In] byte level,
+                    [In] long keyword,
+                    [In] string msg
+                    );
+
+            [StructLayout(LayoutKind.Sequential)]
+            internal unsafe struct EVENT_FILTER_DESCRIPTOR
+            {
+                public long Ptr;
+                public int Size;
+                public int Type;
+            };
+
+            /// <summary>
+            ///  Call the ETW native API EventWriteTransfer and checks for invalid argument error. 
+            ///  The implementation of EventWriteTransfer on some older OSes (Windows 2008) does not accept null relatedActivityId.
+            ///  So, for these cases we will retry the call with an empty Guid.
+            /// </summary>
+            internal static int EventWriteTransferWrapper(long registrationHandle,
+                                                         ref EventDescriptor eventDescriptor,
+                                                         Guid* activityId,
+                                                         Guid* relatedActivityId,
+                                                         int userDataCount,
+                                                         EventProvider.EventData* userData)
+            {
+                int HResult = EventWriteTransfer(registrationHandle, ref eventDescriptor, activityId, relatedActivityId, userDataCount, userData);
+                if (HResult == ERROR_INVALID_PARAMETER && relatedActivityId == null)
+                {
+                    Guid emptyGuid = Guid.Empty;
+                    HResult = EventWriteTransfer(registrationHandle, ref eventDescriptor, activityId, &emptyGuid, userDataCount, userData);
+                }
+
+                return HResult;
+            }
+
+            [DllImport(Win32Native.ADVAPI32, ExactSpelling = true, EntryPoint = "EventWriteTransfer", CharSet = System.Runtime.InteropServices.CharSet.Unicode)]
+            private static extern int EventWriteTransfer(
+                    [In] long registrationHandle,
+                    [In] ref EventDescriptor eventDescriptor,
+                    [In] Guid* activityId,
+                    [In] Guid* relatedActivityId,
+                    [In] int userDataCount,
+                    [In] EventProvider.EventData* userData
+                    );
+
+            internal enum ActivityControl : uint
+            {
+                EVENT_ACTIVITY_CTRL_GET_ID = 1,
+                EVENT_ACTIVITY_CTRL_SET_ID = 2,
+                EVENT_ACTIVITY_CTRL_CREATE_ID = 3,
+                EVENT_ACTIVITY_CTRL_GET_SET_ID = 4,
+                EVENT_ACTIVITY_CTRL_CREATE_SET_ID = 5
+            };
+
+            [DllImport(Win32Native.ADVAPI32, ExactSpelling = true, EntryPoint = "EventActivityIdControl", CharSet = System.Runtime.InteropServices.CharSet.Unicode)]
+            internal static extern int EventActivityIdControl([In] ActivityControl ControlCode, [In][Out] ref Guid ActivityId);
+
+            internal enum EVENT_INFO_CLASS
+            {
+                BinaryTrackInfo,
+                SetEnableAllKeywords,
+                SetTraits,
+            }
+
+            [DllImport(Win32Native.ADVAPI32, ExactSpelling = true, EntryPoint = "EventSetInformation", CharSet = System.Runtime.InteropServices.CharSet.Unicode)]
+            internal static extern int EventSetInformation(
+                [In] long registrationHandle,
+                [In] EVENT_INFO_CLASS informationClass,
+                [In] void* eventInformation,
+                [In] int informationLength);
+
+            // Support for EnumerateTraceGuidsEx
+            internal enum TRACE_QUERY_INFO_CLASS
+            {
+                TraceGuidQueryList,
+                TraceGuidQueryInfo,
+                TraceGuidQueryProcess,
+                TraceStackTracingInfo,
+                MaxTraceSetInfoClass
+            };
+
+            internal struct TRACE_GUID_INFO
+            {
+                public int InstanceCount;
+                public int Reserved;
+            };
+
+            internal struct TRACE_PROVIDER_INSTANCE_INFO
+            {
+                public int NextOffset;
+                public int EnableCount;
+                public int Pid;
+                public int Flags;
+            };
+
+            internal struct TRACE_ENABLE_INFO
+            {
+                public int IsEnabled;
+                public byte Level;
+                public byte Reserved1;
+                public ushort LoggerId;
+                public int EnableProperty;
+                public int Reserved2;
+                public long MatchAnyKeyword;
+                public long MatchAllKeyword;
+            };
+
+            [DllImport(Win32Native.ADVAPI32, ExactSpelling = true, EntryPoint = "EnumerateTraceGuidsEx", CharSet = System.Runtime.InteropServices.CharSet.Unicode)]
+            internal static extern int EnumerateTraceGuidsEx(
+                TRACE_QUERY_INFO_CLASS TraceQueryInfoClass,
+                void* InBuffer,
+                int InBufferSize,
+                void* OutBuffer,
+                int OutBufferSize,
+                ref int ReturnLength);
+        }
+
+#if FEATURE_COMINTEROP
+        [DllImport("combase.dll", PreserveSig = true)]
+        internal static extern int RoGetActivationFactory(
+            [MarshalAs(UnmanagedType.HString)] string activatableClassId,
+            [In] ref Guid iid,
+            [Out, MarshalAs(UnmanagedType.IInspectable)] out Object factory);
+#endif
+    }
+}
diff --git a/src/System.Private.CoreLib/src/Microsoft/Win32/Win32Native.cs b/src/System.Private.CoreLib/src/Microsoft/Win32/Win32Native.cs
new file mode 100644
index 0000000000..3545328f8a
--- /dev/null
+++ b/src/System.Private.CoreLib/src/Microsoft/Win32/Win32Native.cs
@@ -0,0 +1,469 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: The CLR wrapper for all Win32 as well as 
+**          ROTOR-style Unix PAL, etc. native operations
+**
+**
+===========================================================*/
+/**
+ * Notes to PInvoke users:  Getting the syntax exactly correct is crucial, and
+ * more than a little confusing.  Here's some guidelines.
+ *
+ * For handles, you should use a SafeHandle subclass specific to your handle
+ * type.  For files, we have the following set of interesting definitions:
+ *
+ *  [DllImport(Interop.Libraries.Kernel32, SetLastError=true, CharSet=CharSet.Auto, BestFitMapping=false)]
+ *  private static extern SafeFileHandle CreateFile(...);
+ *
+ *  [DllImport(Interop.Libraries.Kernel32, SetLastError=true)]
+ *  internal static extern unsafe int ReadFile(SafeFileHandle handle, ...);
+ *
+ *  [DllImport(Interop.Libraries.Kernel32, SetLastError=true)]
+ *  internal static extern bool CloseHandle(IntPtr handle);
+ * 
+ * P/Invoke will create the SafeFileHandle instance for you and assign the 
+ * return value from CreateFile into the handle atomically.  When we call 
+ * ReadFile, P/Invoke will increment a ref count, make the call, then decrement
+ * it (preventing handle recycling vulnerabilities).  Then SafeFileHandle's
+ * ReleaseHandle method will call CloseHandle, passing in the handle field
+ * as an IntPtr.
+ *
+ * If for some reason you cannot use a SafeHandle subclass for your handles,
+ * then use IntPtr as the handle type (or possibly HandleRef - understand when
+ * to use GC.KeepAlive).  If your code will run in SQL Server (or any other
+ * long-running process that can't be recycled easily), use a constrained 
+ * execution region to prevent thread aborts while allocating your 
+ * handle, and consider making your handle wrapper subclass 
+ * CriticalFinalizerObject to ensure you can free the handle.  As you can 
+ * probably guess, SafeHandle  will save you a lot of headaches if your code 
+ * needs to be robust to thread aborts and OOM.
+ *
+ *
+ * If you have a method that takes a native struct, you have two options for
+ * declaring that struct.  You can make it a value type ('struct' in CSharp),
+ * or a reference type ('class').  This choice doesn't seem very interesting, 
+ * but your function prototype must use different syntax depending on your 
+ * choice.  For example, if your native method is prototyped as such:
+ *
+ *    bool GetVersionEx(OSVERSIONINFO & lposvi);
+ *
+ *
+ * you must use EITHER THIS OR THE NEXT syntax:
+ *
+ *    [StructLayout(LayoutKind.Sequential, CharSet=CharSet.Auto)]
+ *    internal struct OSVERSIONINFO {  ...  }
+ *
+ *    [DllImport(Interop.Libraries.Kernel32, CharSet=CharSet.Auto)]
+ *    internal static extern bool GetVersionEx(ref OSVERSIONINFO lposvi);
+ *
+ * OR:
+ *
+ *    [StructLayout(LayoutKind.Sequential, CharSet=CharSet.Auto)]
+ *    internal class OSVERSIONINFO {  ...  }
+ *
+ *    [DllImport(Interop.Libraries.Kernel32, CharSet=CharSet.Auto)]
+ *    internal static extern bool GetVersionEx([In, Out] OSVERSIONINFO lposvi);
+ *
+ * Note that classes require being marked as [In, Out] while value types must
+ * be passed as ref parameters.
+ *
+ * Also note the CharSet.Auto on GetVersionEx - while it does not take a String
+ * as a parameter, the OSVERSIONINFO contains an embedded array of TCHARs, so
+ * the size of the struct varies on different platforms, and there's a
+ * GetVersionExA & a GetVersionExW.  Also, the OSVERSIONINFO struct has a sizeof
+ * field so the OS can ensure you've passed in the correctly-sized copy of an
+ * OSVERSIONINFO.  You must explicitly set this using Marshal.SizeOf(Object);
+ *
+ * For security reasons, if you're making a P/Invoke method to a Win32 method
+ * that takes an ANSI String and that String is the name of some resource you've 
+ * done a security check on (such as a file name), you want to disable best fit 
+ * mapping in WideCharToMultiByte.  Do this by setting BestFitMapping=false 
+ * in your DllImportAttribute.
+ */
+
+namespace Microsoft.Win32
+{
+    using System;
+    using System.Security;
+    using System.Text;
+    using System.Configuration.Assemblies;
+    using System.Runtime.InteropServices;
+    using System.Threading;
+    using Microsoft.Win32.SafeHandles;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.ConstrainedExecution;
+    using System.Runtime.Versioning;
+
+    using BOOL = System.Int32;
+    using DWORD = System.UInt32;
+    using ULONG = System.UInt32;
+
+    /**
+     * Win32 encapsulation for MSCORLIB.
+     */
+    // Remove the default demands for all P/Invoke methods with this
+    // global declaration on the class.
+
+    internal static class Win32Native
+    {
+        internal const int KEY_QUERY_VALUE = 0x0001;
+        internal const int KEY_SET_VALUE = 0x0002;
+        internal const int KEY_CREATE_SUB_KEY = 0x0004;
+        internal const int KEY_ENUMERATE_SUB_KEYS = 0x0008;
+        internal const int KEY_NOTIFY = 0x0010;
+        internal const int KEY_CREATE_LINK = 0x0020;
+        internal const int KEY_READ = ((STANDARD_RIGHTS_READ |
+                                                           KEY_QUERY_VALUE |
+                                                           KEY_ENUMERATE_SUB_KEYS |
+                                                           KEY_NOTIFY)
+                                                          &
+                                                          (~SYNCHRONIZE));
+
+        internal const int KEY_WRITE = ((STANDARD_RIGHTS_WRITE |
+                                                           KEY_SET_VALUE |
+                                                           KEY_CREATE_SUB_KEY)
+                                                          &
+                                                          (~SYNCHRONIZE));
+        internal const int KEY_WOW64_64KEY = 0x0100;     //
+        internal const int KEY_WOW64_32KEY = 0x0200;     //
+        internal const int REG_OPTION_NON_VOLATILE = 0x0000;     // (default) keys are persisted beyond reboot/unload
+        internal const int REG_OPTION_VOLATILE = 0x0001;     // All keys created by the function are volatile
+        internal const int REG_OPTION_CREATE_LINK = 0x0002;     // They key is a symbolic link
+        internal const int REG_OPTION_BACKUP_RESTORE = 0x0004;  // Use SE_BACKUP_NAME process special privileges
+        internal const int REG_NONE = 0;     // No value type
+        internal const int REG_SZ = 1;     // Unicode nul terminated string
+        internal const int REG_EXPAND_SZ = 2;     // Unicode nul terminated string
+        // (with environment variable references)
+        internal const int REG_BINARY = 3;     // Free form binary
+        internal const int REG_DWORD = 4;     // 32-bit number
+        internal const int REG_DWORD_LITTLE_ENDIAN = 4;     // 32-bit number (same as REG_DWORD)
+        internal const int REG_DWORD_BIG_ENDIAN = 5;     // 32-bit number
+        internal const int REG_LINK = 6;     // Symbolic Link (unicode)
+        internal const int REG_MULTI_SZ = 7;     // Multiple Unicode strings
+        internal const int REG_RESOURCE_LIST = 8;     // Resource list in the resource map
+        internal const int REG_FULL_RESOURCE_DESCRIPTOR = 9;   // Resource list in the hardware description
+        internal const int REG_RESOURCE_REQUIREMENTS_LIST = 10;
+        internal const int REG_QWORD = 11;    // 64-bit number
+
+        // Win32 ACL-related constants:
+        internal const int READ_CONTROL = 0x00020000;
+        internal const int SYNCHRONIZE = 0x00100000;
+        internal const int MAXIMUM_ALLOWED = 0x02000000;
+
+        internal const int STANDARD_RIGHTS_READ = READ_CONTROL;
+        internal const int STANDARD_RIGHTS_WRITE = READ_CONTROL;
+
+        // STANDARD_RIGHTS_REQUIRED  (0x000F0000L)
+        // SEMAPHORE_ALL_ACCESS          (STANDARD_RIGHTS_REQUIRED|SYNCHRONIZE|0x3) 
+
+        // SEMAPHORE and Event both use 0x0002
+        // MUTEX uses 0x001 (MUTANT_QUERY_STATE)
+
+        // Note that you may need to specify the SYNCHRONIZE bit as well
+        // to be able to open a synchronization primitive.
+        internal const int SEMAPHORE_MODIFY_STATE = 0x00000002;
+        internal const int EVENT_MODIFY_STATE = 0x00000002;
+        internal const int MUTEX_MODIFY_STATE = 0x00000001;
+
+        // CreateEventEx: flags
+        internal const uint CREATE_EVENT_MANUAL_RESET = 0x1;
+        internal const uint CREATE_EVENT_INITIAL_SET = 0x2;
+
+        // CreateMutexEx: flags
+        internal const uint CREATE_MUTEX_INITIAL_OWNER = 0x1;
+
+        internal const int LMEM_FIXED = 0x0000;
+        internal const int LMEM_ZEROINIT = 0x0040;
+        internal const int LPTR = (LMEM_FIXED | LMEM_ZEROINIT);
+
+        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
+        internal class OSVERSIONINFOEX
+        {
+            public OSVERSIONINFOEX()
+            {
+                OSVersionInfoSize = (int)Marshal.SizeOf(this);
+            }
+
+            // The OSVersionInfoSize field must be set to Marshal.SizeOf(this)
+            internal int OSVersionInfoSize = 0;
+            internal int MajorVersion = 0;
+            internal int MinorVersion = 0;
+            internal int BuildNumber = 0;
+            internal int PlatformId = 0;
+            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
+            internal string CSDVersion = null;
+            internal ushort ServicePackMajor = 0;
+            internal ushort ServicePackMinor = 0;
+            internal short SuiteMask = 0;
+            internal byte ProductType = 0;
+            internal byte Reserved = 0;
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal class SECURITY_ATTRIBUTES
+        {
+            internal int nLength = 0;
+            // don't remove null, or this field will disappear in bcl.small
+            internal unsafe byte* pSecurityDescriptor = null;
+            internal int bInheritHandle = 0;
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal struct MEMORYSTATUSEX
+        {
+            // The length field must be set to the size of this data structure.
+            internal int length;
+            internal int memoryLoad;
+            internal ulong totalPhys;
+            internal ulong availPhys;
+            internal ulong totalPageFile;
+            internal ulong availPageFile;
+            internal ulong totalVirtual;
+            internal ulong availVirtual;
+            internal ulong availExtendedVirtual;
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal unsafe struct MEMORY_BASIC_INFORMATION
+        {
+            internal void* BaseAddress;
+            internal void* AllocationBase;
+            internal uint AllocationProtect;
+            internal UIntPtr RegionSize;
+            internal uint State;
+            internal uint Protect;
+            internal uint Type;
+        }
+
+        internal const String ADVAPI32 = "advapi32.dll";
+        internal const String SHELL32 = "shell32.dll";
+        internal const String SHIM = "mscoree.dll";
+        internal const String CRYPT32 = "crypt32.dll";
+        internal const String SECUR32 = "secur32.dll";
+        internal const String MSCORWKS = "coreclr.dll";
+
+        [DllImport(Interop.Libraries.Kernel32, EntryPoint = "LocalAlloc")]
+        internal static extern IntPtr LocalAlloc_NoSafeHandle(int uFlags, UIntPtr sizetdwBytes);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true)]
+        internal static extern IntPtr LocalFree(IntPtr handle);
+
+        internal static bool GlobalMemoryStatusEx(ref MEMORYSTATUSEX buffer)
+        {
+            buffer.length = Marshal.SizeOf(typeof(MEMORYSTATUSEX));
+            return GlobalMemoryStatusExNative(ref buffer);
+        }
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true, EntryPoint = "GlobalMemoryStatusEx")]
+        private static extern bool GlobalMemoryStatusExNative([In, Out] ref MEMORYSTATUSEX buffer);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true)]
+        internal static extern unsafe UIntPtr VirtualQuery(void* address, ref MEMORY_BASIC_INFORMATION buffer, UIntPtr sizeOfBuffer);
+
+        // VirtualAlloc should generally be avoided, but is needed in 
+        // the MemoryFailPoint implementation (within a CER) to increase the 
+        // size of the page file, ignoring any host memory allocators.
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true)]
+        internal static extern unsafe void* VirtualAlloc(void* address, UIntPtr numBytes, int commitOrReserve, int pageProtectionMode);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true)]
+        internal static extern unsafe bool VirtualFree(void* address, UIntPtr numBytes, int pageFreeMode);
+
+        [DllImport(Interop.Libraries.Kernel32, CharSet = CharSet.Ansi, ExactSpelling = true, EntryPoint = "lstrlenA")]
+        internal static extern int lstrlenA(IntPtr ptr);
+
+        [DllImport(Interop.Libraries.Kernel32, CharSet = CharSet.Unicode, ExactSpelling = true, EntryPoint = "lstrlenW")]
+        internal static extern int lstrlenW(IntPtr ptr);
+
+        [DllImport(Interop.Libraries.OleAut32, CharSet = CharSet.Unicode)]
+        internal static extern IntPtr SysAllocStringLen(String src, int len);  // BSTR
+
+        [DllImport(Interop.Libraries.OleAut32)]
+        internal static extern uint SysStringLen(IntPtr bstr);
+
+        [DllImport(Interop.Libraries.OleAut32)]
+        internal static extern void SysFreeString(IntPtr bstr);
+
+#if FEATURE_COMINTEROP
+        [DllImport(Interop.Libraries.OleAut32)]
+        internal static extern IntPtr SysAllocStringByteLen(byte[] str, uint len);  // BSTR
+
+        [DllImport(Interop.Libraries.OleAut32)]
+        internal static extern uint SysStringByteLen(IntPtr bstr);
+
+#endif
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true)]
+        internal static extern bool SetEvent(SafeWaitHandle handle);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true)]
+        internal static extern bool ResetEvent(SafeWaitHandle handle);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern SafeWaitHandle CreateEventEx(SECURITY_ATTRIBUTES lpSecurityAttributes, string name, uint flags, uint desiredAccess);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern SafeWaitHandle OpenEvent(uint desiredAccess, bool inheritHandle, string name);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern SafeWaitHandle CreateMutexEx(SECURITY_ATTRIBUTES lpSecurityAttributes, string name, uint flags, uint desiredAccess);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern SafeWaitHandle OpenMutex(uint desiredAccess, bool inheritHandle, string name);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true)]
+        internal static extern bool ReleaseMutex(SafeWaitHandle handle);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true)]
+        internal static extern bool CloseHandle(IntPtr handle);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true)]
+        internal static extern unsafe int WriteFile(SafeFileHandle handle, byte* bytes, int numBytesToWrite, out int numBytesWritten, IntPtr mustBeZero);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern SafeWaitHandle CreateSemaphoreEx(SECURITY_ATTRIBUTES lpSecurityAttributes, int initialCount, int maximumCount, string name, uint flags, uint desiredAccess);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern bool ReleaseSemaphore(SafeWaitHandle handle, int releaseCount, out int previousCount);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern SafeWaitHandle OpenSemaphore(uint desiredAccess, bool inheritHandle, string name);
+
+        internal static readonly IntPtr INVALID_HANDLE_VALUE = new IntPtr(-1);  // WinBase.h
+
+        // Note, these are #defines used to extract handles, and are NOT handles.
+        internal const int STD_INPUT_HANDLE = -10;
+        internal const int STD_OUTPUT_HANDLE = -11;
+        internal const int STD_ERROR_HANDLE = -12;
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true)]
+        internal static extern IntPtr GetStdHandle(int nStdHandle);  // param is NOT a handle, but it returns one!
+
+        internal const int PAGE_READWRITE = 0x04;
+
+        internal const int MEM_COMMIT = 0x1000;
+        internal const int MEM_RESERVE = 0x2000;
+        internal const int MEM_RELEASE = 0x8000;
+        internal const int MEM_FREE = 0x10000;
+
+        [DllImport(Interop.Libraries.Kernel32)]
+        internal static extern unsafe int WideCharToMultiByte(uint cp, uint flags, char* pwzSource, int cchSource, byte* pbDestBuffer, int cbDestBuffer, IntPtr null1, IntPtr null2);
+
+        [DllImport(Interop.Libraries.Kernel32, CharSet = CharSet.Auto, SetLastError = true, BestFitMapping = false)]
+        internal static extern bool SetEnvironmentVariable(string lpName, string lpValue);
+
+        [DllImport(Interop.Libraries.Kernel32, CharSet = CharSet.Auto, SetLastError = true, BestFitMapping = false)]
+        private static extern unsafe int GetEnvironmentVariable(string lpName, char* lpValue, int size);
+
+        internal static unsafe int GetEnvironmentVariable(string lpName, Span<char> lpValue)
+        {
+            fixed (char* lpValuePtr = &MemoryMarshal.GetReference(lpValue))
+            {
+                return GetEnvironmentVariable(lpName, lpValuePtr, lpValue.Length);
+            }
+        }
+
+        [DllImport(Interop.Libraries.Kernel32, CharSet = CharSet.Unicode)]
+        internal static extern unsafe char* GetEnvironmentStrings();
+
+        [DllImport(Interop.Libraries.Kernel32, CharSet = CharSet.Unicode)]
+        internal static extern unsafe bool FreeEnvironmentStrings(char* pStrings);
+
+        [DllImport(Interop.Libraries.Kernel32, CharSet = CharSet.Auto, SetLastError = true)]
+        internal static extern uint GetCurrentProcessId();
+
+        [DllImport(Interop.Libraries.Ole32)]
+        internal static extern IntPtr CoTaskMemAlloc(UIntPtr cb);
+
+        [DllImport(Interop.Libraries.Ole32)]
+        internal static extern void CoTaskMemFree(IntPtr ptr);
+
+        [DllImport(Interop.Libraries.Ole32)]
+        internal static extern IntPtr CoTaskMemRealloc(IntPtr pv, UIntPtr cb);
+
+#if FEATURE_WIN32_REGISTRY
+
+        [DllImport(ADVAPI32, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern int RegDeleteValue(SafeRegistryHandle hKey, String lpValueName);
+
+        [DllImport(ADVAPI32, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern unsafe int RegEnumKeyEx(SafeRegistryHandle hKey, int dwIndex,
+                    char[] lpName, ref int lpcbName, int[] lpReserved,
+                    [Out]StringBuilder lpClass, int[] lpcbClass,
+                    long[] lpftLastWriteTime);
+
+        [DllImport(ADVAPI32, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern unsafe int RegEnumValue(SafeRegistryHandle hKey, int dwIndex,
+                    char[] lpValueName, ref int lpcbValueName,
+                    IntPtr lpReserved_MustBeZero, int[] lpType, byte[] lpData,
+                    int[] lpcbData);
+
+        [DllImport(ADVAPI32, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern int RegOpenKeyEx(SafeRegistryHandle hKey, String lpSubKey,
+                    int ulOptions, int samDesired, out SafeRegistryHandle hkResult);
+
+        [DllImport(ADVAPI32, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern int RegQueryValueEx(SafeRegistryHandle hKey, String lpValueName,
+                    int[] lpReserved, ref int lpType, [Out] byte[] lpData,
+                    ref int lpcbData);
+
+        [DllImport(ADVAPI32, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern int RegQueryValueEx(SafeRegistryHandle hKey, String lpValueName,
+                    int[] lpReserved, ref int lpType, ref int lpData,
+                    ref int lpcbData);
+
+        [DllImport(ADVAPI32, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern int RegQueryValueEx(SafeRegistryHandle hKey, String lpValueName,
+                    int[] lpReserved, ref int lpType, ref long lpData,
+                    ref int lpcbData);
+
+        [DllImport(ADVAPI32, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern int RegQueryValueEx(SafeRegistryHandle hKey, String lpValueName,
+                     int[] lpReserved, ref int lpType, [Out] char[] lpData,
+                     ref int lpcbData);
+
+        [DllImport(ADVAPI32, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern int RegSetValueEx(SafeRegistryHandle hKey, String lpValueName,
+                    int Reserved, RegistryValueKind dwType, byte[] lpData, int cbData);
+
+        [DllImport(ADVAPI32, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern int RegSetValueEx(SafeRegistryHandle hKey, String lpValueName,
+                    int Reserved, RegistryValueKind dwType, ref int lpData, int cbData);
+
+        [DllImport(ADVAPI32, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern int RegSetValueEx(SafeRegistryHandle hKey, String lpValueName,
+                    int Reserved, RegistryValueKind dwType, ref long lpData, int cbData);
+
+        [DllImport(ADVAPI32, CharSet = CharSet.Auto, BestFitMapping = false)]
+        internal static extern int RegSetValueEx(SafeRegistryHandle hKey, String lpValueName,
+                    int Reserved, RegistryValueKind dwType, String lpData, int cbData);
+#endif // FEATURE_WIN32_REGISTRY
+
+        [DllImport(Interop.Libraries.Kernel32, CharSet = CharSet.Auto, SetLastError = true, BestFitMapping = false)]
+        internal static extern int ExpandEnvironmentStrings(String lpSrc, [Out]StringBuilder lpDst, int nSize);
+
+        [DllImport(Interop.Libraries.Kernel32)]
+        internal static extern IntPtr LocalReAlloc(IntPtr handle, IntPtr sizetcbBytes, int uFlags);
+
+        [DllImport(Interop.Libraries.Kernel32, SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern bool QueryUnbiasedInterruptTime(out ulong UnbiasedTime);
+
+        internal const byte VER_GREATER_EQUAL = 0x3;
+        internal const uint VER_MAJORVERSION = 0x0000002;
+        internal const uint VER_MINORVERSION = 0x0000001;
+        internal const uint VER_SERVICEPACKMAJOR = 0x0000020;
+        internal const uint VER_SERVICEPACKMINOR = 0x0000010;
+        [DllImport("kernel32.dll")]
+        internal static extern bool VerifyVersionInfoW([In, Out] OSVERSIONINFOEX lpVersionInfo, uint dwTypeMask, ulong dwlConditionMask);
+        [DllImport("kernel32.dll")]
+        internal static extern ulong VerSetConditionMask(ulong dwlConditionMask, uint dwTypeBitMask, byte dwConditionMask);        
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Activator.cs b/src/System.Private.CoreLib/src/System/Activator.cs
new file mode 100644
index 0000000000..05b8f3766e
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Activator.cs
@@ -0,0 +1,78 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+using System.Globalization;
+
+namespace System
+{
+    /// <summary>
+    /// Activator contains the Activation (CreateInstance/New) methods for late bound support.
+    /// </summary>
+    public static class Activator
+    {
+        internal const BindingFlags ConstructorDefault = BindingFlags.Instance | BindingFlags.Public | BindingFlags.CreateInstance;
+
+        public static object CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, object[] args, CultureInfo culture) =>
+            CreateInstance(type, bindingAttr, binder, args, culture, null);
+
+        public static object CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, object[] args, CultureInfo culture, object[] activationAttributes)
+        {
+            if (type is null)
+                throw new ArgumentNullException(nameof(type));
+
+            if (type is System.Reflection.Emit.TypeBuilder)
+                throw new NotSupportedException(SR.NotSupported_CreateInstanceWithTypeBuilder);
+
+            // If they didn't specify a lookup, then we will provide the default lookup.
+            const int LookupMask = 0x000000FF;
+            if ((bindingAttr & (BindingFlags)LookupMask) == 0)
+                bindingAttr |= ConstructorDefault;
+
+            if (activationAttributes?.Length > 0)
+                throw new PlatformNotSupportedException(SR.NotSupported_ActivAttr);
+
+            if (type.UnderlyingSystemType is RuntimeType rt)
+                return rt.CreateInstanceImpl(bindingAttr, binder, args, culture, activationAttributes);
+
+            throw new ArgumentException(SR.Arg_MustBeType, nameof(type));
+        }
+
+        public static object CreateInstance(Type type, params object[] args) =>
+            CreateInstance(type, ConstructorDefault, null, args, null, null);
+
+        public static object CreateInstance(Type type, object[] args, object[] activationAttributes) =>
+            CreateInstance(type, ConstructorDefault, null, args, null, activationAttributes);
+
+        public static object CreateInstance(Type type) =>
+            CreateInstance(type, nonPublic: false);
+
+        public static object CreateInstance(Type type, bool nonPublic) =>
+            CreateInstance(type, nonPublic, wrapExceptions: true);
+
+        internal static object CreateInstance(Type type, bool nonPublic, bool wrapExceptions)
+        {
+            if (type is null)
+                throw new ArgumentNullException(nameof(type));
+
+            if (type.UnderlyingSystemType is RuntimeType rt)
+                return rt.CreateInstanceDefaultCtor(!nonPublic, false, true, wrapExceptions);
+
+            throw new ArgumentException(SR.Arg_MustBeType, nameof(type));
+        }
+
+        public static T CreateInstance<T>()
+        {
+            var rt = (RuntimeType)typeof(T);
+
+            // This is a workaround to maintain compatibility with V2. Without this we would throw a NotSupportedException for void[].
+            // Array, Ref, and Pointer types don't have default constructors.
+            if (rt.HasElementType)
+                throw new MissingMethodException(SR.Arg_NoDefCTor);
+
+            // Skip the CreateInstanceCheckThis call to avoid perf cost and to maintain compatibility with V2 (throwing the same exceptions).
+            return (T)rt.CreateInstanceDefaultCtor(publicOnly: true, skipCheckThis: true, fillCache: true, wrapExceptions: true);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/AppContext/AppContext.cs b/src/System.Private.CoreLib/src/System/AppContext/AppContext.cs
new file mode 100644
index 0000000000..7c7e74f19b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/AppContext/AppContext.cs
@@ -0,0 +1,238 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System.Collections.Generic;
+
+namespace System
+{
+    public static class AppContext
+    {
+        [Flags]
+        private enum SwitchValueState
+        {
+            HasFalseValue = 0x1,
+            HasTrueValue = 0x2,
+            HasLookedForOverride = 0x4,
+            UnknownValue = 0x8 // Has no default and could not find an override
+        }
+        private static readonly Dictionary<string, SwitchValueState> s_switchMap = new Dictionary<string, SwitchValueState>();
+
+        static AppContext()
+        {
+            // Unloading event must happen before ProcessExit event
+            AppDomain.CurrentDomain.ProcessExit += OnUnloading;
+            AppDomain.CurrentDomain.ProcessExit += OnProcessExit;
+
+            // populate the AppContext with the default set of values
+            AppContextDefaultValues.PopulateDefaultValues();
+        }
+
+        public static string BaseDirectory
+        {
+            get
+            {
+                // The value of APP_CONTEXT_BASE_DIRECTORY key has to be a string and it is not allowed to be any other type. 
+                // Otherwise the caller will get invalid cast exception
+                return (string)AppDomain.CurrentDomain.GetData("APP_CONTEXT_BASE_DIRECTORY") ?? AppDomain.CurrentDomain.BaseDirectory;
+            }
+        }
+
+        public static string TargetFrameworkName
+        {
+            get
+            {
+                // Forward the value that is set on the current domain.
+                return AppDomain.CurrentDomain.SetupInformation.TargetFrameworkName;
+            }
+        }
+
+        public static object GetData(string name)
+        {
+            return AppDomain.CurrentDomain.GetData(name);
+        }
+
+        public static void SetData(string name, object data)
+        {
+            AppDomain.CurrentDomain.SetData(name, data);
+        }
+
+        public static event UnhandledExceptionEventHandler UnhandledException
+        {
+            add
+            {
+                AppDomain.CurrentDomain.UnhandledException += value;
+            }
+
+            remove
+            {
+                AppDomain.CurrentDomain.UnhandledException -= value;
+            }
+        }
+
+        public static event System.EventHandler<System.Runtime.ExceptionServices.FirstChanceExceptionEventArgs> FirstChanceException
+        {
+            add
+            {
+                AppDomain.CurrentDomain.FirstChanceException += value;
+            }
+            remove
+            {
+                AppDomain.CurrentDomain.FirstChanceException -= value;
+            }
+        }
+
+        public static event System.EventHandler ProcessExit;
+        internal static event System.EventHandler Unloading;
+
+        private static void OnProcessExit(object sender, EventArgs e)
+        {
+            var processExit = ProcessExit;
+            if (processExit != null)
+            {
+                processExit(null, EventArgs.Empty);
+            }
+        }
+
+        private static void OnUnloading(object sender, EventArgs e)
+        {
+            var unloading = Unloading;
+            if (unloading != null)
+            {
+                unloading(null, EventArgs.Empty);
+            }
+        }
+
+        #region Switch APIs
+        /// <summary>
+        /// Try to get the value of the switch.
+        /// </summary>
+        /// <param name="switchName">The name of the switch</param>
+        /// <param name="isEnabled">A variable where to place the value of the switch</param>
+        /// <returns>A return value of true represents that the switch was set and <paramref name="isEnabled"/> contains the value of the switch</returns>
+        public static bool TryGetSwitch(string switchName, out bool isEnabled)
+        {
+            if (switchName == null)
+                throw new ArgumentNullException(nameof(switchName));
+            if (switchName.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(switchName));
+
+            // By default, the switch is not enabled.
+            isEnabled = false;
+
+            SwitchValueState switchValue;
+            lock (s_switchMap)
+            {
+                if (s_switchMap.TryGetValue(switchName, out switchValue))
+                {
+                    // The value is in the dictionary. 
+                    // There are 3 cases here:
+                    // 1. The value of the switch is 'unknown'. This means that the switch name is not known to the system (either via defaults or checking overrides).
+                    //    Example: This is the case when, during a servicing event, a switch is added to System.Xml which ships before mscorlib. The value of the switch
+                    //             Will be unknown to mscorlib.dll and we want to prevent checking the overrides every time we check this switch
+                    // 2. The switch has a valid value AND we have read the overrides for it
+                    //    Example: TryGetSwitch is called for a switch set via SetSwitch
+                    // 3. The switch has the default value and we need to check for overrides
+                    //    Example: TryGetSwitch is called for the first time for a switch that has a default value 
+
+                    // 1. The value is unknown
+                    if (switchValue == SwitchValueState.UnknownValue)
+                    {
+                        isEnabled = false;
+                        return false;
+                    }
+
+                    // We get the value of isEnabled from the value that we stored in the dictionary
+                    isEnabled = (switchValue & SwitchValueState.HasTrueValue) == SwitchValueState.HasTrueValue;
+
+                    // 2. The switch has a valid value AND we have checked for overrides
+                    if ((switchValue & SwitchValueState.HasLookedForOverride) == SwitchValueState.HasLookedForOverride)
+                    {
+                        return true;
+                    }
+
+                    // 3. The switch has a valid value, but we need to check for overrides.
+                    // Regardless of whether or not the switch has an override, we need to update the value to reflect
+                    // the fact that we checked for overrides. 
+                    bool overrideValue;
+                    if (AppContextDefaultValues.TryGetSwitchOverride(switchName, out overrideValue))
+                    {
+                        // we found an override!
+                        isEnabled = overrideValue;
+                    }
+
+                    // Update the switch in the dictionary to mark it as 'checked for override'
+                    s_switchMap[switchName] = (isEnabled ? SwitchValueState.HasTrueValue : SwitchValueState.HasFalseValue)
+                                                | SwitchValueState.HasLookedForOverride;
+
+                    return true;
+                }
+                else
+                {
+                    // The value is NOT in the dictionary
+                    // In this case we need to see if we have an override defined for the value.
+                    // There are 2 cases:
+                    // 1. The value has an override specified. In this case we need to add the value to the dictionary 
+                    //    and mark it as checked for overrides
+                    //    Example: In a servicing event, System.Xml introduces a switch and an override is specified.
+                    //             The value is not found in mscorlib (as System.Xml ships independent of mscorlib)
+                    // 2. The value does not have an override specified
+                    //    In this case, we want to capture the fact that we looked for a value and found nothing by adding 
+                    //    an entry in the dictionary with the 'sentinel' value of 'SwitchValueState.UnknownValue'.
+                    //    Example: This will prevent us from trying to find overrides for values that we don't have in the dictionary
+
+                    // 1. The value has an override specified.
+                    bool overrideValue;
+                    if (AppContextDefaultValues.TryGetSwitchOverride(switchName, out overrideValue))
+                    {
+                        isEnabled = overrideValue;
+
+                        // Update the switch in the dictionary to mark it as 'checked for override'
+                        s_switchMap[switchName] = (isEnabled ? SwitchValueState.HasTrueValue : SwitchValueState.HasFalseValue)
+                                                    | SwitchValueState.HasLookedForOverride;
+
+                        return true;
+                    }
+
+                    // 2. The value does not have an override.
+                    s_switchMap[switchName] = SwitchValueState.UnknownValue;
+                }
+            }
+            return false; // we did not find a value for the switch
+        }
+
+        /// <summary>
+        /// Assign a switch a value
+        /// </summary>
+        /// <param name="switchName">The name of the switch</param>
+        /// <param name="isEnabled">The value to assign</param>
+        public static void SetSwitch(string switchName, bool isEnabled)
+        {
+            if (switchName == null)
+                throw new ArgumentNullException(nameof(switchName));
+            if (switchName.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(switchName));
+
+            SwitchValueState switchValue = (isEnabled ? SwitchValueState.HasTrueValue : SwitchValueState.HasFalseValue)
+                                            | SwitchValueState.HasLookedForOverride;
+
+            lock (s_switchMap)
+            {
+                // Store the new value and the fact that we checked in the dictionary
+                s_switchMap[switchName] = switchValue;
+            }
+        }
+
+        /// <summary>
+        /// This method is going to be called from the AppContextDefaultValues class when setting up the 
+        /// default values for the switches. !!!! This method is called during the static constructor so it does not
+        /// take a lock !!!! If you are planning to use this outside of that, please ensure proper locking.
+        /// </summary>
+        internal static void DefineSwitchDefault(string switchName, bool isEnabled)
+        {
+            s_switchMap[switchName] = isEnabled ? SwitchValueState.HasTrueValue : SwitchValueState.HasFalseValue;
+        }
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/AppContext/AppContextDefaultValues.CoreClrOverrides.cs b/src/System.Private.CoreLib/src/System/AppContext/AppContextDefaultValues.CoreClrOverrides.cs
new file mode 100644
index 0000000000..89893c6bee
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/AppContext/AppContextDefaultValues.CoreClrOverrides.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    internal static partial class AppContextDefaultValues
+    {
+        static partial void TryGetSwitchOverridePartial(string switchName, ref bool overrideFound, ref bool overrideValue)
+        {
+            overrideFound = false;
+            overrideValue = false;
+
+            string value = AppContext.GetData(switchName) as string;
+            if (value != null)
+            {
+                overrideFound = bool.TryParse(value, out overrideValue);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/AppContext/AppContextDefaultValues.Defaults.Central.cs b/src/System.Private.CoreLib/src/System/AppContext/AppContextDefaultValues.Defaults.Central.cs
new file mode 100644
index 0000000000..92c9917113
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/AppContext/AppContextDefaultValues.Defaults.Central.cs
@@ -0,0 +1,33 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+//
+// This file is used to provide an implementation for defining a default value
+// This should be compiled only in mscorlib where the AppContext class is available
+//
+
+namespace System
+{
+    internal static partial class AppContextDefaultValues
+    {
+        /// <summary>
+        /// This method allows reading the override for a switch. 
+        /// The implementation is platform specific
+        /// </summary>
+        public static bool TryGetSwitchOverride(string switchName, out bool overrideValue)
+        {
+            // The default value for a switch is 'false'
+            overrideValue = false;
+
+            // Read the override value
+            bool overrideFound = false;
+
+            // This partial method will be removed if there are no implementations of it.
+            TryGetSwitchOverridePartial(switchName, ref overrideFound, ref overrideValue);
+
+            return overrideFound;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/AppContext/AppContextDefaultValues.Defaults.cs b/src/System.Private.CoreLib/src/System/AppContext/AppContextDefaultValues.Defaults.cs
new file mode 100644
index 0000000000..a6243536d1
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/AppContext/AppContextDefaultValues.Defaults.cs
@@ -0,0 +1,57 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System
+{
+    internal static partial class AppContextDefaultValues
+    {
+        internal static readonly string SwitchNoAsyncCurrentCulture = "Switch.System.Globalization.NoAsyncCurrentCulture";
+        internal static readonly string SwitchPreserveEventListnerObjectIdentity = "Switch.System.Diagnostics.EventSource.PreserveEventListnerObjectIdentity";
+
+        // This is a partial method. Platforms can provide an implementation of it that will set override values
+        // from whatever mechanism is available on that platform. If no implementation is provided, the compiler is going to remove the calls
+        // to it from the code
+        // We are going to have an implementation of this method for the Desktop platform that will read the overrides from app.config, registry and
+        // the shim database. Additional implementation can be provided for other platforms.
+        static partial void PopulateOverrideValuesPartial();
+
+        static partial void PopulateDefaultValuesPartial(string platformIdentifier, string profile, int version)
+        {
+            // When defining a new switch  you should add it to the last known version.
+            // For instance, if you are adding a switch in .NET 4.6 (the release after 4.5.2) you should defined your switch
+            // like this:
+            //    if (version <= 40502) ...
+            // This ensures that all previous versions of that platform (up-to 4.5.2) will get the old behavior by default
+            // NOTE: When adding a default value for a switch please make sure that the default value is added to ALL of the existing platforms!
+            // NOTE: When adding a new if statement for the version please ensure that ALL previous switches are enabled (ie. don't use else if)
+            switch (platformIdentifier)
+            {
+                case ".NETCore":
+                case ".NETFramework":
+                    {
+                        if (version <= 40502)
+                        {
+                            AppContext.DefineSwitchDefault(SwitchNoAsyncCurrentCulture, true);
+                        }
+
+                        break;
+                    }
+                case "WindowsPhone":
+                case "WindowsPhoneApp":
+                    {
+                        if (version <= 80100)
+                        {
+                            AppContext.DefineSwitchDefault(SwitchNoAsyncCurrentCulture, true);
+                        }
+                        break;
+                    }
+            }
+
+            // At this point we should read the overrides if any are defined
+            PopulateOverrideValuesPartial();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/AppContext/AppContextDefaultValues.cs b/src/System.Private.CoreLib/src/System/AppContext/AppContextDefaultValues.cs
new file mode 100644
index 0000000000..320a14109b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/AppContext/AppContextDefaultValues.cs
@@ -0,0 +1,158 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+
+namespace System
+{
+    internal static partial class AppContextDefaultValues
+    {
+        public static void PopulateDefaultValues()
+        {
+            string platformIdentifier, profile;
+            int version;
+
+            ParseTargetFrameworkName(out platformIdentifier, out profile, out version);
+
+            // Call into each library to populate their default switches
+            PopulateDefaultValuesPartial(platformIdentifier, profile, version);
+        }
+
+        /// <summary>
+        /// We have this separate method for getting the parsed elements out of the TargetFrameworkName so we can
+        /// more easily support this on other platforms.
+        /// </summary>
+        private static void ParseTargetFrameworkName(out string identifier, out string profile, out int version)
+        {
+            string targetFrameworkMoniker = AppDomain.CurrentDomain.SetupInformation.TargetFrameworkName;
+
+            if (!TryParseFrameworkName(targetFrameworkMoniker, out identifier, out version, out profile))
+            {
+                // If we can't parse the TFM or we don't have a TFM, default to latest behavior for all 
+                // switches (ie. all of them false).
+                // If we want to use the latest behavior it is enough to set the value of the switch to string.Empty.
+                // When the get to the caller of this method (PopulateDefaultValuesPartial) we are going to use the 
+                // identifier we just set to decide which switches to turn on. By having an empty string as the 
+                // identifier we are simply saying -- don't turn on any switches, and we are going to get the latest
+                // behavior for all the switches
+                identifier = string.Empty;
+            }
+        }
+
+        // This code was a constructor copied from the FrameworkName class, which is located in System.dll.
+        // Parses strings in the following format: "<identifier>, Version=[v|V]<version>, Profile=<profile>"
+        //  - The identifier and version is required, profile is optional
+        //  - Only three components are allowed.
+        //  - The version string must be in the System.Version format; an optional "v" or "V" prefix is allowed
+        private static bool TryParseFrameworkName(String frameworkName, out String identifier, out int version, out String profile)
+        {
+            // For parsing a target Framework moniker, from the FrameworkName class
+            const char c_componentSeparator = ',';
+            const char c_keyValueSeparator = '=';
+            const char c_versionValuePrefix = 'v';
+            const String c_versionKey = "Version";
+            const String c_profileKey = "Profile";
+
+            identifier = profile = string.Empty;
+            version = 0;
+
+            if (frameworkName == null || frameworkName.Length == 0)
+            {
+                return false;
+            }
+
+            String[] components = frameworkName.Split(c_componentSeparator);
+            version = 0;
+
+            // Identifer and Version are required, Profile is optional.
+            if (components.Length < 2 || components.Length > 3)
+            {
+                return false;
+            }
+
+            //
+            // 1) Parse the "Identifier", which must come first. Trim any whitespace
+            //
+            identifier = components[0].Trim();
+
+            if (identifier.Length == 0)
+            {
+                return false;
+            }
+
+            bool versionFound = false;
+            profile = null;
+
+            // 
+            // The required "Version" and optional "Profile" component can be in any order
+            //
+            for (int i = 1; i < components.Length; i++)
+            {
+                // Get the key/value pair separated by '='
+                string[] keyValuePair = components[i].Split(c_keyValueSeparator);
+
+                if (keyValuePair.Length != 2)
+                {
+                    return false;
+                }
+
+                // Get the key and value, trimming any whitespace
+                string key = keyValuePair[0].Trim();
+                string value = keyValuePair[1].Trim();
+
+                //
+                // 2) Parse the required "Version" key value
+                //
+                if (key.Equals(c_versionKey, StringComparison.OrdinalIgnoreCase))
+                {
+                    versionFound = true;
+
+                    // Allow the version to include a 'v' or 'V' prefix...
+                    if (value.Length > 0 && (value[0] == c_versionValuePrefix || value[0] == 'V'))
+                    {
+                        value = value.Substring(1);
+                    }
+                    Version realVersion = Version.Parse(value);
+                    // The version class will represent some unset values as -1 internally (instead of 0).
+                    version = realVersion.Major * 10000;
+                    if (realVersion.Minor > 0)
+                        version += realVersion.Minor * 100;
+                    if (realVersion.Build > 0)
+                        version += realVersion.Build;
+                }
+                //
+                // 3) Parse the optional "Profile" key value
+                //
+                else if (key.Equals(c_profileKey, StringComparison.OrdinalIgnoreCase))
+                {
+                    if (!String.IsNullOrEmpty(value))
+                    {
+                        profile = value;
+                    }
+                }
+                else
+                {
+                    return false;
+                }
+            }
+
+            if (!versionFound)
+            {
+                return false;
+            }
+
+            return true;
+        }
+
+        // This is a partial method. Platforms (such as Desktop) can provide an implementation of it that will read override value
+        // from whatever mechanism is available on that platform. If no implementation is provided, the compiler is going to remove the calls
+        // to it from the code
+        static partial void TryGetSwitchOverridePartial(string switchName, ref bool overrideFound, ref bool overrideValue);
+
+        /// This is a partial method. This method is responsible for populating the default values based on a TFM.
+        /// It is partial because each library should define this method in their code to contain their defaults.
+        static partial void PopulateDefaultValuesPartial(string platformIdentifier, string profile, int version);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/AppContext/AppContextSwitches.cs b/src/System.Private.CoreLib/src/System/AppContext/AppContextSwitches.cs
new file mode 100644
index 0000000000..b62d253a64
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/AppContext/AppContextSwitches.cs
@@ -0,0 +1,70 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    internal static class AppContextSwitches
+    {
+        private static int _noAsyncCurrentCulture;
+        public static bool NoAsyncCurrentCulture
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                return GetCachedSwitchValue(AppContextDefaultValues.SwitchNoAsyncCurrentCulture, ref _noAsyncCurrentCulture);
+            }
+        }
+
+        private static int _preserveEventListnerObjectIdentity;
+        public static bool PreserveEventListnerObjectIdentity
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                return GetCachedSwitchValue(AppContextDefaultValues.SwitchPreserveEventListnerObjectIdentity, ref _preserveEventListnerObjectIdentity);
+            }
+        }
+
+        //
+        // Implementation details
+        //
+
+        private static bool DisableCaching { get; set; }
+
+        static AppContextSwitches()
+        {
+            bool isEnabled;
+            if (AppContext.TryGetSwitch(@"TestSwitch.LocalAppContext.DisableCaching", out isEnabled))
+            {
+                DisableCaching = isEnabled;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static bool GetCachedSwitchValue(string switchName, ref int switchValue)
+        {
+            if (switchValue < 0) return false;
+            if (switchValue > 0) return true;
+
+            return GetCachedSwitchValueInternal(switchName, ref switchValue);
+        }
+
+        private static bool GetCachedSwitchValueInternal(string switchName, ref int switchValue)
+        {
+            bool isSwitchEnabled;
+            AppContext.TryGetSwitch(switchName, out isSwitchEnabled);
+
+            if (DisableCaching)
+            {
+                return isSwitchEnabled;
+            }
+
+            switchValue = isSwitchEnabled ? 1 /*true*/ : -1 /*false*/;
+            return isSwitchEnabled;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/AppDomain.cs b/src/System.Private.CoreLib/src/System/AppDomain.cs
new file mode 100644
index 0000000000..292fa926cb
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/AppDomain.cs
@@ -0,0 +1,698 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Diagnostics.Contracts;
+using System.IO;
+using System.Reflection;
+using System.Reflection.Emit;
+using System.Runtime.CompilerServices;
+using System.Runtime.ExceptionServices;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading;
+
+namespace System
+{
+    /// <summary>
+    /// Domains represent an application within the runtime. Objects cannot be
+    /// shared between domains and each domain can be configured independently.
+    /// </summary>
+    internal sealed class AppDomain
+    {
+        // Domain security information
+        // These fields initialized from the other side only. (NOTE: order
+        // of these fields cannot be changed without changing the layout in
+        // the EE- AppDomainBaseObject in this case)
+
+        private AppDomainManager _domainManager;
+        private Dictionary<string, object> _LocalStore;
+        private AppDomainSetup _FusionStore;
+        public event AssemblyLoadEventHandler AssemblyLoad;
+
+        private ResolveEventHandler _TypeResolve;
+
+        public event ResolveEventHandler TypeResolve
+        {
+            add
+            {
+                lock (this)
+                {
+                    _TypeResolve += value;
+                }
+            }
+
+            remove
+            {
+                lock (this)
+                {
+                    _TypeResolve -= value;
+                }
+            }
+        }
+
+        private ResolveEventHandler _ResourceResolve;
+
+        public event ResolveEventHandler ResourceResolve
+        {
+            add
+            {
+                lock (this)
+                {
+                    _ResourceResolve += value;
+                }
+            }
+
+            remove
+            {
+                lock (this)
+                {
+                    _ResourceResolve -= value;
+                }
+            }
+        }
+
+        private ResolveEventHandler _AssemblyResolve;
+
+        public event ResolveEventHandler AssemblyResolve
+        {
+            add
+            {
+                lock (this)
+                {
+                    _AssemblyResolve += value;
+                }
+            }
+
+            remove
+            {
+                lock (this)
+                {
+                    _AssemblyResolve -= value;
+                }
+            }
+        }
+
+        private EventHandler _processExit;
+
+        private EventHandler _domainUnload;
+
+        private UnhandledExceptionEventHandler _unhandledException;
+
+        // The compat flags are set at domain creation time to indicate that the given breaking
+        // changes (named in the strings) should not be used in this domain. We only use the
+        // keys, the vhe values are ignored.
+        private Dictionary<string, object> _compatFlags;
+
+        // Delegate that will hold references to FirstChance exception notifications
+        private EventHandler<FirstChanceExceptionEventArgs> _firstChanceException;
+
+        private IntPtr _pDomain;                      // this is an unmanaged pointer (AppDomain * m_pDomain)` used from the VM.
+
+        private bool _compatFlagsInitialized;
+
+#if FEATURE_APPX
+        private static APPX_FLAGS s_flags;
+
+        //
+        // Keep in async with vm\appdomainnative.cpp
+        //
+        [Flags]
+        private enum APPX_FLAGS
+        {
+            APPX_FLAGS_INITIALIZED = 0x01,
+
+            APPX_FLAGS_APPX_MODEL = 0x02,
+            APPX_FLAGS_APPX_DESIGN_MODE = 0x04,
+            APPX_FLAGS_APPX_MASK = APPX_FLAGS_APPX_MODEL |
+                                            APPX_FLAGS_APPX_DESIGN_MODE,
+        }
+
+        private static APPX_FLAGS Flags
+        {
+            get
+            {
+                if (s_flags == 0)
+                    s_flags = nGetAppXFlags();
+
+                Debug.Assert(s_flags != 0);
+                return s_flags;
+            }
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        [return: MarshalAs(UnmanagedType.I4)]
+        private static extern APPX_FLAGS nGetAppXFlags();
+#endif
+
+        /// <summary>
+        ///     If this AppDomain is configured to have an AppDomain manager then create the instance of it.
+        ///     This method is also called from the VM to create the domain manager in the default domain.
+        /// </summary>
+        private void CreateAppDomainManager()
+        {
+            Debug.Assert(_domainManager == null, "_domainManager == null");
+
+            AppDomainSetup adSetup = FusionStore;
+            string trustedPlatformAssemblies = (string)GetData("TRUSTED_PLATFORM_ASSEMBLIES");
+            if (trustedPlatformAssemblies != null)
+            {
+                string platformResourceRoots = (string)GetData("PLATFORM_RESOURCE_ROOTS") ?? string.Empty;
+                string appPaths = (string)GetData("APP_PATHS") ?? string.Empty;
+                string appNiPaths = (string)GetData("APP_NI_PATHS") ?? string.Empty;
+                string appLocalWinMD = (string)GetData("APP_LOCAL_WINMETADATA") ?? string.Empty;
+                SetupBindingPaths(trustedPlatformAssemblies, platformResourceRoots, appPaths, appNiPaths, appLocalWinMD);
+            }
+
+            InitializeCompatibilityFlags();
+        }
+
+        /// <summary>
+        ///     Initialize the compatibility flags to non-NULL values.
+        ///     This method is also called from the VM when the default domain doesn't have a domain manager.
+        /// </summary>
+        private void InitializeCompatibilityFlags()
+        {
+            AppDomainSetup adSetup = FusionStore;
+
+            // set up shim flags regardless of whether we create a DomainManager in this method.
+            if (adSetup.GetCompatibilityFlags() != null)
+            {
+                _compatFlags = new Dictionary<string, object>(adSetup.GetCompatibilityFlags(), StringComparer.OrdinalIgnoreCase);
+            }
+
+            // for perf, we don't intialize the _compatFlags dictionary when we don't need to.  However, we do need to make a
+            // note that we've run this method, because IsCompatibilityFlagsSet needs to return different values for the
+            // case where the compat flags have been setup.
+            Debug.Assert(!_compatFlagsInitialized);
+            _compatFlagsInitialized = true;
+        }
+
+        /// <summary>
+        ///     Returns whether the current AppDomain follows the AppX rules.
+        /// </summary>
+        [Pure]
+        internal static bool IsAppXModel()
+        {
+#if FEATURE_APPX
+            return (Flags & APPX_FLAGS.APPX_FLAGS_APPX_MODEL) != 0;
+#else
+            return false;
+#endif
+        }
+
+        /// <summary>
+        ///     Returns the setting of the AppXDevMode config switch.
+        /// </summary>
+        [Pure]
+        internal static bool IsAppXDesignMode()
+        {
+#if FEATURE_APPX
+            return (Flags & APPX_FLAGS.APPX_FLAGS_APPX_MASK) == (APPX_FLAGS.APPX_FLAGS_APPX_MODEL | APPX_FLAGS.APPX_FLAGS_APPX_DESIGN_MODE);
+#else
+            return false;
+#endif
+        }
+
+        /// <summary>
+        ///     Checks (and throws on failure) if the domain supports Assembly.LoadFrom.
+        /// </summary>
+        [Pure]
+        internal static void CheckLoadFromSupported()
+        {
+#if FEATURE_APPX
+            if (IsAppXModel())
+                throw new NotSupportedException(SR.Format(SR.NotSupported_AppX, "Assembly.LoadFrom"));
+#endif
+        }
+
+        /// <summary>
+        ///     Checks (and throws on failure) if the domain supports Assembly.LoadFile.
+        /// </summary>
+        [Pure]
+        internal static void CheckLoadFileSupported()
+        {
+#if FEATURE_APPX
+            if (IsAppXModel())
+                throw new NotSupportedException(SR.Format(SR.NotSupported_AppX, "Assembly.LoadFile"));
+#endif
+        }
+
+        /// <summary>
+        ///     Checks (and throws on failure) if the domain supports Assembly.Load(byte[] ...).
+        /// </summary>
+        [Pure]
+        internal static void CheckLoadByteArraySupported()
+        {
+#if FEATURE_APPX
+            if (IsAppXModel())
+                throw new NotSupportedException(SR.Format(SR.NotSupported_AppX, "Assembly.Load(byte[], ...)"));
+#endif
+        }
+
+        public AppDomainManager DomainManager => _domainManager;
+
+        public static AppDomain CurrentDomain => Thread.GetDomain();
+
+        public string BaseDirectory => FusionStore.ApplicationBase;
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private extern Assembly[] nGetAssemblies(bool forIntrospection);
+
+        internal Assembly[] GetAssemblies(bool forIntrospection)
+        {
+            return nGetAssemblies(forIntrospection);
+        }
+
+        // this is true when we've just started going through the finalizers and are forcing objects to finalize
+        // so must be aware that certain infrastructure may have gone away
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public extern bool IsFinalizingForUnload();
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal static extern void PublishAnonymouslyHostedDynamicMethodsAssembly(RuntimeAssembly assemblyHandle);
+
+        public void SetData(string name, object data)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            lock (((ICollection)LocalStore).SyncRoot)
+            {
+                LocalStore[name] = data;
+            }
+        }
+
+        [Pure]
+        public object GetData(string name)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            object data;
+            lock (((ICollection)LocalStore).SyncRoot)
+            {
+                LocalStore.TryGetValue(name, out data);
+            }
+
+            return data;
+        }
+
+        [Obsolete("AppDomain.GetCurrentThreadId has been deprecated because it does not provide a stable Id when managed threads are running on fibers (aka lightweight threads). To get a stable identifier for a managed thread, use the ManagedThreadId property on Thread.  http://go.microsoft.com/fwlink/?linkid=14202", false)]
+        [DllImport(Interop.Libraries.Kernel32)]
+        public static extern int GetCurrentThreadId();
+
+        private AppDomain()
+        {
+            Debug.Fail("Object cannot be created through this constructor.");
+        }
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal extern void nCreateContext();
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void nSetupBindingPaths(string trustedPlatformAssemblies, string platformResourceRoots, string appPath, string appNiPaths, string appLocalWinMD);
+
+        internal void SetupBindingPaths(string trustedPlatformAssemblies, string platformResourceRoots, string appPath, string appNiPaths, string appLocalWinMD)
+        {
+            nSetupBindingPaths(trustedPlatformAssemblies, platformResourceRoots, appPath, appNiPaths, appLocalWinMD);
+        }
+
+        // support reliability for certain event handlers, if the target
+        // methods also participate in this discipline.  If caller passes
+        // an existing MulticastDelegate, then we could use a MDA to indicate
+        // that reliability is not guaranteed.  But if it is a single cast
+        // scenario, we can make it work.
+
+        public event EventHandler ProcessExit
+        {
+            add
+            {
+                if (value != null)
+                {
+                    RuntimeHelpers.PrepareContractedDelegate(value);
+                    lock (this)
+                        _processExit += value;
+                }
+            }
+            remove
+            {
+                lock (this)
+                    _processExit -= value;
+            }
+        }
+
+        public event EventHandler DomainUnload
+        {
+            add
+            {
+                if (value != null)
+                {
+                    RuntimeHelpers.PrepareContractedDelegate(value);
+                    lock (this)
+                        _domainUnload += value;
+                }
+            }
+            remove
+            {
+                lock (this)
+                    _domainUnload -= value;
+            }
+        }
+
+        public event UnhandledExceptionEventHandler UnhandledException
+        {
+            add
+            {
+                if (value != null)
+                {
+                    RuntimeHelpers.PrepareContractedDelegate(value);
+                    lock (this)
+                        _unhandledException += value;
+                }
+            }
+            remove
+            {
+                lock (this)
+                    _unhandledException -= value;
+            }
+        }
+
+        // This is the event managed code can wireup against to be notified
+        // about first chance exceptions.
+        //
+        // To register/unregister the callback, the code must be SecurityCritical.
+        public event EventHandler<FirstChanceExceptionEventArgs> FirstChanceException
+        {
+            add
+            {
+                if (value != null)
+                {
+                    RuntimeHelpers.PrepareContractedDelegate(value);
+                    lock (this)
+                        _firstChanceException += value;
+                }
+            }
+            remove
+            {
+                lock (this)
+                    _firstChanceException -= value;
+            }
+        }
+
+        // This method is called by the VM.
+        private void OnAssemblyLoadEvent(RuntimeAssembly LoadedAssembly)
+        {
+            AssemblyLoad?.Invoke(this, new AssemblyLoadEventArgs(LoadedAssembly));
+        }
+
+        // This method is called by the VM.
+        private RuntimeAssembly OnResourceResolveEvent(RuntimeAssembly assembly, string resourceName)
+        {
+            return InvokeResolveEvent(_ResourceResolve, assembly, resourceName);
+        }
+
+        // This method is called by the VM
+        private RuntimeAssembly OnTypeResolveEvent(RuntimeAssembly assembly, string typeName)
+        {
+            return InvokeResolveEvent(_TypeResolve, assembly, typeName);
+        }
+
+        // This method is called by the VM.
+        private RuntimeAssembly OnAssemblyResolveEvent(RuntimeAssembly assembly, string assemblyFullName)
+        {
+            return InvokeResolveEvent(_AssemblyResolve, assembly, assemblyFullName);
+        }
+
+        private RuntimeAssembly InvokeResolveEvent(ResolveEventHandler eventHandler, RuntimeAssembly assembly, string name)
+        {
+            if (eventHandler == null)
+                return null;
+
+            var args = new ResolveEventArgs(name, assembly);
+
+            foreach (ResolveEventHandler handler in eventHandler.GetInvocationList())
+            {
+                Assembly asm = handler(this, args);
+                RuntimeAssembly ret = GetRuntimeAssembly(asm);
+                if (ret != null)
+                    return ret;
+            }
+
+            return null;
+        }
+
+#if FEATURE_COMINTEROP
+        // Called by VM - code:CLRPrivTypeCacheWinRT::RaiseDesignerNamespaceResolveEvent
+        private string[] OnDesignerNamespaceResolveEvent(string namespaceName)
+        {
+            return System.Runtime.InteropServices.WindowsRuntime.WindowsRuntimeMetadata.OnDesignerNamespaceResolveEvent(this, namespaceName);
+        }
+#endif // FEATURE_COMINTEROP
+
+        internal AppDomainSetup FusionStore
+        {
+            get
+            {
+                Debug.Assert(_FusionStore != null, "Fusion store has not been correctly setup in this domain");
+                return _FusionStore;
+            }
+        }
+
+        private static RuntimeAssembly GetRuntimeAssembly(Assembly asm)
+        {
+            return
+                asm == null ? null :
+                asm is RuntimeAssembly rtAssembly ? rtAssembly :
+                asm is AssemblyBuilder ab ? ab.InternalAssembly :
+                null;
+        }
+
+        private Dictionary<string, object> LocalStore
+        {
+            get
+            {
+                return _LocalStore ?? (_LocalStore = new Dictionary<string, object>());
+            }
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void nSetNativeDllSearchDirectories(string paths);
+
+        private void SetupFusionStore(AppDomainSetup info, AppDomainSetup oldInfo)
+        {
+            Debug.Assert(info != null);
+
+            if (info.ApplicationBase == null)
+            {
+                info.SetupDefaults(RuntimeEnvironment.GetModuleFileName(), imageLocationAlreadyNormalized: true);
+            }
+
+            nCreateContext();
+
+            // This must be the last action taken
+            _FusionStore = info;
+        }
+
+        // Used to switch into other AppDomain and call SetupRemoteDomain.
+        //   We cannot simply call through the proxy, because if there
+        //   are any remoting sinks registered, they can add non-mscorlib
+        //   objects to the message (causing an assembly load exception when
+        //   we try to deserialize it on the other side)
+        private static object PrepareDataForSetup(string friendlyName,
+                                                        AppDomainSetup setup,
+                                                        string[] propertyNames,
+                                                        string[] propertyValues)
+        {
+            var newSetup = new AppDomainSetup(setup, copyDomainBoundData: false);
+
+            // Remove the special AppDomainCompatSwitch entries from the set of name value pairs
+            // And add them to the AppDomainSetup
+            //
+            // This is only supported on CoreCLR through ICLRRuntimeHost2.CreateAppDomainWithManager
+            // Desktop code should use System.AppDomain.CreateDomain() or
+            // System.AppDomainManager.CreateDomain() and add the flags to the AppDomainSetup
+            var compatList = new List<string>();
+
+            if (propertyNames != null && propertyValues != null)
+            {
+                for (int i = 0; i < propertyNames.Length; i++)
+                {
+                    if (string.Equals(propertyNames[i], "AppDomainCompatSwitch", StringComparison.OrdinalIgnoreCase))
+                    {
+                        compatList.Add(propertyValues[i]);
+                        propertyNames[i] = null;
+                        propertyValues[i] = null;
+                    }
+                }
+
+                if (compatList.Count > 0)
+                {
+                    newSetup.SetCompatibilitySwitches(compatList);
+                }
+            }
+
+            return new object[]
+            {
+                friendlyName,
+                newSetup,
+                propertyNames,
+                propertyValues
+            };
+        } // PrepareDataForSetup
+
+        private static object Setup(object arg)
+        {
+            var args = (object[])arg;
+            var friendlyName = (string)args[0];
+            var setup = (AppDomainSetup)args[1];
+            var propertyNames = (string[])args[2]; // can contain null elements
+            var propertyValues = (string[])args[3]; // can contain null elements
+
+            AppDomain ad = CurrentDomain;
+            var newSetup = new AppDomainSetup(setup, copyDomainBoundData: false);
+
+            if (propertyNames != null && propertyValues != null)
+            {
+                for (int i = 0; i < propertyNames.Length; i++)
+                {
+                    // We want to set native dll probing directories before any P/Invokes have a
+                    // chance to fire. The Path class, for one, has P/Invokes.
+                    if (propertyNames[i] == "NATIVE_DLL_SEARCH_DIRECTORIES")
+                    {
+                        if (propertyValues[i] == null)
+                            throw new ArgumentNullException("NATIVE_DLL_SEARCH_DIRECTORIES");
+
+                        string paths = propertyValues[i];
+                        if (paths.Length == 0)
+                            break;
+
+                        nSetNativeDllSearchDirectories(paths);
+                    }
+                }
+
+                for (int i = 0; i < propertyNames.Length; i++)
+                {
+                    if (propertyNames[i] == "APPBASE") // make sure in sync with Fusion
+                    {
+                        if (propertyValues[i] == null)
+                            throw new ArgumentNullException("APPBASE");
+
+                        if (PathInternal.IsPartiallyQualified(propertyValues[i]))
+                            throw new ArgumentException(SR.Argument_AbsolutePathRequired);
+
+                        newSetup.ApplicationBase = NormalizePath(propertyValues[i], fullCheck: true);
+                    }
+                    else if (propertyNames[i] == "TRUSTED_PLATFORM_ASSEMBLIES" ||
+                       propertyNames[i] == "PLATFORM_RESOURCE_ROOTS" ||
+                       propertyNames[i] == "APP_PATHS" ||
+                       propertyNames[i] == "APP_NI_PATHS")
+                    {
+                        string values = propertyValues[i];
+                        if (values == null)
+                            throw new ArgumentNullException(propertyNames[i]);
+
+                        ad.SetData(propertyNames[i], NormalizeAppPaths(values));
+                    }
+                    else if (propertyNames[i] != null)
+                    {
+                        ad.SetData(propertyNames[i], propertyValues[i]);     // just propagate
+                    }
+                }
+            }
+
+            ad.SetupFusionStore(newSetup, null); // makes FusionStore a ref to newSetup
+
+            // technically, we don't need this, newSetup refers to the same object as FusionStore
+            // but it's confusing since it isn't immediately obvious whether we have a ref or a copy
+            AppDomainSetup adSetup = ad.FusionStore;
+
+            // set up the friendly name
+            ad.nSetupFriendlyName(friendlyName);
+
+            ad.CreateAppDomainManager(); // could modify FusionStore's object
+
+            return null;
+        }
+
+        private static string NormalizeAppPaths(string values)
+        {
+            int estimatedLength = values.Length + 1; // +1 for extra separator temporarily added at end
+            StringBuilder sb = StringBuilderCache.Acquire(estimatedLength);
+
+            for (int pos = 0; pos < values.Length; pos++)
+            {
+                string path;
+
+                int nextPos = values.IndexOf(Path.PathSeparator, pos);
+                if (nextPos == -1)
+                {
+                    path = values.Substring(pos);
+                    pos = values.Length - 1;
+                }
+                else
+                {
+                    path = values.Substring(pos, nextPos - pos);
+                    pos = nextPos;
+                }
+
+                // Skip empty directories
+                if (path.Length == 0)
+                    continue;
+
+                if (PathInternal.IsPartiallyQualified(path))
+                    throw new ArgumentException(SR.Argument_AbsolutePathRequired);
+
+                string appPath = NormalizePath(path, fullCheck: true);
+                sb.Append(appPath);
+                sb.Append(Path.PathSeparator);
+            }
+
+            // Strip the last separator
+            if (sb.Length > 0)
+            {
+                sb.Remove(sb.Length - 1, 1);
+            }
+
+            return StringBuilderCache.GetStringAndRelease(sb);
+        }
+
+        internal static string NormalizePath(string path, bool fullCheck) => Path.GetFullPath(path);
+
+        // This routine is called from unmanaged code to
+        // set the default fusion context.
+        private void SetupDomain(bool allowRedirects, string path, string configFile, string[] propertyNames, string[] propertyValues)
+        {
+            // It is possible that we could have multiple threads initializing
+            // the default domain. We will just take the winner of these two.
+            // (eg. one thread doing a com call and another doing attach for IJW)
+            lock (this)
+            {
+                if (_FusionStore == null)
+                {
+                    // always use internet permission set
+                    SetupFusionStore(new AppDomainSetup(), null);
+                }
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private extern void nSetupFriendlyName(string friendlyName);
+
+        public AppDomainSetup SetupInformation => new AppDomainSetup(FusionStore, copyDomainBoundData: true);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal extern string IsStringInterned(string str);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal extern string GetOrInternString(string str);
+
+        public int Id => GetId();
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal extern int GetId();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/AppDomainManager.cs b/src/System.Private.CoreLib/src/System/AppDomainManager.cs
new file mode 100644
index 0000000000..f8ea51d536
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/AppDomainManager.cs
@@ -0,0 +1,59 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+//
+// An AppDomainManager gives a hosting application the chance to 
+// participate in the creation and control the settings of new AppDomains.
+//
+
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Security;
+using System.Runtime.InteropServices;
+
+namespace System
+{
+    internal class AppDomainManager : MarshalByRefObject
+    {
+        public AppDomainManager() { }
+
+        public virtual void InitializeNewDomain(AppDomainSetup appDomainInfo)
+        {
+            // By default, InitializeNewDomain does nothing. AppDomain.CreateAppDomainManager relies on this fact.
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetEntryAssembly(ObjectHandleOnStack retAssembly);
+
+        private Assembly m_entryAssembly = null;
+        public virtual Assembly EntryAssembly
+        {
+            get
+            {
+                // The default AppDomainManager sets the EntryAssembly depending on whether the
+                // AppDomain is a manifest application domain or not. In the first case, we parse
+                // the application manifest to find out the entry point assembly and return that assembly.
+                // In the second case, we maintain the old behavior by calling GetEntryAssembly().
+                if (m_entryAssembly == null)
+                {
+                    {
+                        RuntimeAssembly entryAssembly = null;
+                        GetEntryAssembly(JitHelpers.GetObjectHandleOnStack(ref entryAssembly));
+                        m_entryAssembly = entryAssembly;
+                    }
+                }
+                return m_entryAssembly;
+            }
+        }
+
+        internal static AppDomainManager CurrentAppDomainManager
+        {
+            get
+            {
+                return AppDomain.CurrentDomain.DomainManager;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/AppDomainSetup.cs b/src/System.Private.CoreLib/src/System/AppDomainSetup.cs
new file mode 100644
index 0000000000..f3b3d8c823
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/AppDomainSetup.cs
@@ -0,0 +1,185 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+** 
+** Purpose: Defines the settings that the loader uses to find assemblies in an
+**          AppDomain
+**
+**
+=============================================================================*/
+namespace System
+{
+    using System.Text;
+    using System.Runtime.InteropServices;
+    using System.Security;
+    using Path = System.IO.Path;
+    using System.Diagnostics;
+    using System.Collections.Generic;
+
+    internal sealed class AppDomainSetup
+    {
+        internal enum LoaderInformation
+        {
+            // If you add a new value, add the corresponding property
+            // to AppDomain.GetData() and SetData()'s switch statements,
+            // as well as fusionsetup.h.
+            ApplicationBaseValue = 0,  // LOADER_APPLICATION_BASE
+            ConfigurationFileValue = 1,  // LOADER_CONFIGURATION_BASE
+            DynamicBaseValue = 2,  // LOADER_DYNAMIC_BASE
+            DevPathValue = 3,  // LOADER_DEVPATH
+            ApplicationNameValue = 4,  // LOADER_APPLICATION_NAME
+            PrivateBinPathValue = 5,  // LOADER_PRIVATE_PATH
+            PrivateBinPathProbeValue = 6,  // LOADER_PRIVATE_BIN_PATH_PROBE
+            ShadowCopyDirectoriesValue = 7,  // LOADER_SHADOW_COPY_DIRECTORIES
+            ShadowCopyFilesValue = 8,  // LOADER_SHADOW_COPY_FILES
+            CachePathValue = 9,  // LOADER_CACHE_PATH
+            LicenseFileValue = 10, // LOADER_LICENSE_FILE
+            DisallowPublisherPolicyValue = 11, // LOADER_DISALLOW_PUBLISHER_POLICY
+            DisallowCodeDownloadValue = 12, // LOADER_DISALLOW_CODE_DOWNLOAD
+            DisallowBindingRedirectsValue = 13, // LOADER_DISALLOW_BINDING_REDIRECTS
+            DisallowAppBaseProbingValue = 14, // LOADER_DISALLOW_APPBASE_PROBING
+            ConfigurationBytesValue = 15, // LOADER_CONFIGURATION_BYTES
+            LoaderMaximum = 18  // LOADER_MAXIMUM
+        }
+
+        // Constants from fusionsetup.h.
+        private const string LOADER_OPTIMIZATION = "LOADER_OPTIMIZATION";
+
+        private const string ACTAG_APP_BASE_URL = "APPBASE";
+
+        // This class has an unmanaged representation so be aware you will need to make edits in vm\object.h if you change the order
+        // of these fields or add new ones.
+
+        private string[] _Entries;
+#pragma warning disable 169
+        private String _AppBase; // for compat with v1.1
+#pragma warning restore 169
+
+        // A collection of strings used to indicate which breaking changes shouldn't be applied
+        // to an AppDomain. We only use the keys, the values are ignored.
+        private Dictionary<string, object> _CompatFlags;
+
+        internal AppDomainSetup(AppDomainSetup copy, bool copyDomainBoundData)
+        {
+            string[] mine = Value;
+            if (copy != null)
+            {
+                string[] other = copy.Value;
+                int mineSize = _Entries.Length;
+                int otherSize = other.Length;
+                int size = (otherSize < mineSize) ? otherSize : mineSize;
+
+                for (int i = 0; i < size; i++)
+                    mine[i] = other[i];
+
+                if (size < mineSize)
+                {
+                    // This case can happen when the copy is a deserialized version of
+                    // an AppDomainSetup object serialized by Everett.
+                    for (int i = size; i < mineSize; i++)
+                        mine[i] = null;
+                }
+
+                if (copy._CompatFlags != null)
+                {
+                    SetCompatibilitySwitches(copy._CompatFlags.Keys);
+                }
+            }
+        }
+
+        public AppDomainSetup()
+        {
+        }
+
+        internal void SetupDefaults(string imageLocation, bool imageLocationAlreadyNormalized = false)
+        {
+            char[] sep = { '\\', '/' };
+            int i = imageLocation.LastIndexOfAny(sep);
+
+            if (i == -1)
+            {
+                ApplicationName = imageLocation;
+            }
+            else
+            {
+                ApplicationName = imageLocation.Substring(i + 1);
+                string appBase = imageLocation.Substring(0, i + 1);
+
+                if (imageLocationAlreadyNormalized)
+                    Value[(int)LoaderInformation.ApplicationBaseValue] = appBase;
+                else
+                    ApplicationBase = appBase;
+            }
+        }
+
+        internal string[] Value
+        {
+            get
+            {
+                if (_Entries == null)
+                    _Entries = new String[(int)LoaderInformation.LoaderMaximum];
+                return _Entries;
+            }
+        }
+
+        public String ApplicationBase
+        {
+            get
+            {
+                return Value[(int)LoaderInformation.ApplicationBaseValue];
+            }
+
+            set
+            {
+                Value[(int)LoaderInformation.ApplicationBaseValue] = (value == null || value.Length == 0)?null:Path.GetFullPath(value);
+            }
+        }
+        
+        // only needed by AppDomain.Setup(). Not really needed by users. 
+        internal Dictionary<string, object> GetCompatibilityFlags()
+        {
+            return _CompatFlags;
+        }
+
+        public void SetCompatibilitySwitches(IEnumerable<String> switches)
+        {
+            if (switches != null)
+            {
+                _CompatFlags = new Dictionary<string, object>();
+                foreach (String str in switches)
+                {
+                    _CompatFlags.Add(str, null);
+                }
+            }
+            else
+            {
+                _CompatFlags = null;
+            }
+        }
+
+        // A target Framework moniker, in a format parsible by the FrameworkName class.
+        public String TargetFrameworkName
+        {
+            get
+            {
+                return null;
+            }
+        }
+
+        public String ApplicationName
+        {
+            get
+            {
+                return Value[(int)LoaderInformation.ApplicationNameValue];
+            }
+
+            set
+            {
+                Value[(int)LoaderInformation.ApplicationNameValue] = value;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/AppDomainUnloadedException.cs b/src/System.Private.CoreLib/src/System/AppDomainUnloadedException.cs
new file mode 100644
index 0000000000..597a39c5a1
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/AppDomainUnloadedException.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+** 
+**
+** Purpose: Exception class for attempt to access an unloaded AppDomain
+**
+**
+=============================================================================*/
+
+
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    internal class AppDomainUnloadedException : SystemException
+    {
+        public AppDomainUnloadedException()
+            : base(SR.Arg_AppDomainUnloadedException)
+        {
+            HResult = HResults.COR_E_APPDOMAINUNLOADED;
+        }
+
+        protected AppDomainUnloadedException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/ArgIterator.cs b/src/System.Private.CoreLib/src/System/ArgIterator.cs
new file mode 100644
index 0000000000..67e549c9dc
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/ArgIterator.cs
@@ -0,0 +1,185 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    using System;
+    using System.Runtime.InteropServices;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.Versioning;
+
+    // This class will not be marked serializable
+    // Note: This type must have the same layout as the CLR's VARARGS type in CLRVarArgs.h.
+    // It also contains an inline SigPointer data structure - must keep those fields in sync.
+    [StructLayout(LayoutKind.Sequential)]
+    public ref struct ArgIterator
+    {
+        private IntPtr ArgCookie;               // Cookie from the EE.
+
+        // The SigPointer structure consists of the following members.  (Note: this is an inline native SigPointer data type)
+        private IntPtr sigPtr;                  // Pointer to remaining signature.
+        private IntPtr sigPtrLen;               // Remaining length of the pointer
+
+        // Note, sigPtrLen is actually a DWORD, but on 64bit systems this structure becomes
+        // 8-byte aligned, which requires us to pad it.
+
+        private IntPtr ArgPtr;                  // Pointer to remaining args.
+        private int RemainingArgs;           // # of remaining args.
+
+#if VARARGS_ENABLED //The JIT doesn't support Varargs calling convention.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern ArgIterator(IntPtr arglist);
+
+        // create an arg iterator that points at the first argument that
+        // is not statically declared (that is the first ... arg)
+        // 'arglist' is the value returned by the ARGLIST instruction
+        public ArgIterator(RuntimeArgumentHandle arglist) : this(arglist.Value)
+        {
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern unsafe ArgIterator(IntPtr arglist, void *ptr);
+        
+        // create an arg iterator that points just past 'firstArg'.  
+        // 'arglist' is the value returned by the ARGLIST instruction
+        // This is much like the C va_start macro
+
+        [CLSCompliant(false)]
+        public unsafe ArgIterator(RuntimeArgumentHandle arglist, void* ptr) : this(arglist.Value, ptr)
+        {
+        }
+
+        // Fetch an argument as a typed referece, advance the iterator.
+        // Throws an exception if past end of argument list
+        [CLSCompliant(false)]
+        public TypedReference GetNextArg()
+        {
+            TypedReference result = new TypedReference ();
+            // reference to TypedReference is banned, so have to pass result as pointer
+            unsafe
+            {
+                FCallGetNextArg (&result);
+            }
+            return result;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        // reference to TypedReference is banned, so have to pass result as void pointer
+        private extern unsafe void FCallGetNextArg(void * result);
+
+        // Alternate version of GetNextArg() intended primarily for IJW code
+        // generated by VC's "va_arg()" construct. 
+        [CLSCompliant(false)]
+        public TypedReference GetNextArg(RuntimeTypeHandle rth)
+        {
+            if (sigPtr != IntPtr.Zero)
+            {
+                // This is an ordinary ArgIterator capable of determining
+                // types from a signature. Just do a regular GetNextArg.
+                return GetNextArg();
+            }
+            else
+            {
+                // Prevent abuse of this API with a default ArgIterator (it
+                // doesn't require permission to create a zero-inited value
+                // type). Check that ArgPtr isn't zero or this API will allow a
+                // malicious caller to increment the pointer to an arbitrary
+                // location in memory and read the contents.
+                if (ArgPtr == IntPtr.Zero)
+                    throw new ArgumentNullException();
+
+                TypedReference result = new TypedReference ();
+                // reference to TypedReference is banned, so have to pass result as pointer
+                unsafe
+                {
+                    InternalGetNextArg(&result, rth.GetRuntimeType());
+                }
+                return result;
+            }
+        }
+
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        // reference to TypedReference is banned, so have to pass result as void pointer
+        private extern unsafe void InternalGetNextArg(void * result, RuntimeType rt);
+
+        // This method should invalidate the iterator (va_end). It is not supported yet.
+        public void End()
+        {
+        }
+    
+        // How many arguments are left in the list 
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern int GetRemainingCount();
+    
+        // Gets the type of the current arg, does NOT advance the iterator
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern unsafe void* _GetNextArgType();
+
+        public unsafe RuntimeTypeHandle GetNextArgType() 
+        {
+            return new RuntimeTypeHandle(Type.GetTypeFromHandleUnsafe((IntPtr)_GetNextArgType()));
+        }
+    
+        public override int GetHashCode()
+        {
+            return ValueType.GetHashCodeOfPtr(ArgCookie);
+        }
+    
+        // Inherited from object
+        public override bool Equals(Object o)
+        {
+            throw new NotSupportedException(SR.NotSupported_NYI);
+        }
+#else
+        public ArgIterator(RuntimeArgumentHandle arglist)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ArgIterator); // https://github.com/dotnet/coreclr/issues/9204
+        }
+
+        [CLSCompliant(false)]
+        public unsafe ArgIterator(RuntimeArgumentHandle arglist, void* ptr)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ArgIterator); // https://github.com/dotnet/coreclr/issues/9204
+        }
+
+        public void End()
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ArgIterator); // https://github.com/dotnet/coreclr/issues/9204
+        }
+
+        public override bool Equals(Object o)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ArgIterator); // https://github.com/dotnet/coreclr/issues/9204
+        }
+
+        public override int GetHashCode()
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ArgIterator); // https://github.com/dotnet/coreclr/issues/9204
+        }
+
+        [System.CLSCompliantAttribute(false)]
+        public System.TypedReference GetNextArg()
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ArgIterator); // https://github.com/dotnet/coreclr/issues/9204
+        }
+
+        [System.CLSCompliantAttribute(false)]
+        public System.TypedReference GetNextArg(System.RuntimeTypeHandle rth)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ArgIterator); // https://github.com/dotnet/coreclr/issues/9204
+        }
+
+        public unsafe System.RuntimeTypeHandle GetNextArgType()
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ArgIterator); // https://github.com/dotnet/coreclr/issues/9204
+        }
+
+        public int GetRemainingCount()
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ArgIterator); // https://github.com/dotnet/coreclr/issues/9204
+        }
+#endif //VARARGS_ENABLED
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Array.cs b/src/System.Private.CoreLib/src/System/Array.cs
new file mode 100644
index 0000000000..d8a958d6ab
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Array.cs
@@ -0,0 +1,2640 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+** Purpose: Base class which can be used to access any array
+**
+===========================================================*/
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Runtime.ConstrainedExecution;
+using System.Runtime.Versioning;
+using System.Security;
+using Internal.Runtime.CompilerServices;
+
+namespace System
+{
+    // Note that we make a T[] (single-dimensional w/ zero as the lower bound) implement both 
+    // IList<U> and IReadOnlyList<U>, where T : U dynamically.  See the SZArrayHelper class for details.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public abstract class Array : ICloneable, IList, IStructuralComparable, IStructuralEquatable
+    {
+        // This ctor exists solely to prevent C# from generating a protected .ctor that violates the surface area. I really want this to be a
+        // "protected-and-internal" rather than "internal" but C# has no keyword for the former.
+        internal Array() { }
+
+        public static ReadOnlyCollection<T> AsReadOnly<T>(T[] array)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            // T[] implements IList<T>.
+            return new ReadOnlyCollection<T>(array);
+        }
+
+        public static void Resize<T>(ref T[] array, int newSize)
+        {
+            if (newSize < 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.newSize, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+
+            T[] larray = array;
+            if (larray == null)
+            {
+                array = new T[newSize];
+                return;
+            }
+
+            if (larray.Length != newSize)
+            {
+                T[] newArray = new T[newSize];
+                Array.Copy(larray, 0, newArray, 0, larray.Length > newSize ? newSize : larray.Length);
+                array = newArray;
+            }
+        }
+
+        // Create instance will create an array
+        public static unsafe Array CreateInstance(Type elementType, int length)
+        {
+            if ((object)elementType == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.elementType);
+            if (length < 0)
+                ThrowHelper.ThrowLengthArgumentOutOfRange_ArgumentOutOfRange_NeedNonNegNum();
+
+            RuntimeType t = elementType.UnderlyingSystemType as RuntimeType;
+            if (t == null)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_MustBeType, ExceptionArgument.elementType);
+            return InternalCreate((void*)t.TypeHandle.Value, 1, &length, null);
+        }
+
+        public static unsafe Array CreateInstance(Type elementType, int length1, int length2)
+        {
+            if ((object)elementType == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.elementType);
+            if (length1 < 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.length1, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+            if (length2 < 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.length2, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+
+            RuntimeType t = elementType.UnderlyingSystemType as RuntimeType;
+            if (t == null)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_MustBeType, ExceptionArgument.elementType);
+            int* pLengths = stackalloc int[2];
+            pLengths[0] = length1;
+            pLengths[1] = length2;
+            return InternalCreate((void*)t.TypeHandle.Value, 2, pLengths, null);
+        }
+
+        public static unsafe Array CreateInstance(Type elementType, int length1, int length2, int length3)
+        {
+            if ((object)elementType == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.elementType);
+            if (length1 < 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.length1, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+            if (length2 < 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.length2, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+            if (length3 < 0)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.length3, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+
+            RuntimeType t = elementType.UnderlyingSystemType as RuntimeType;
+            if (t == null)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_MustBeType, ExceptionArgument.elementType);
+            int* pLengths = stackalloc int[3];
+            pLengths[0] = length1;
+            pLengths[1] = length2;
+            pLengths[2] = length3;
+            return InternalCreate((void*)t.TypeHandle.Value, 3, pLengths, null);
+        }
+
+        public static unsafe Array CreateInstance(Type elementType, params int[] lengths)
+        {
+            if ((object)elementType == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.elementType);
+            if (lengths == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.lengths);
+            if (lengths.Length == 0)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NeedAtLeast1Rank);
+
+            RuntimeType t = elementType.UnderlyingSystemType as RuntimeType;
+            if (t == null)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_MustBeType, ExceptionArgument.elementType);
+
+            // Check to make sure the lenghts are all positive. Note that we check this here to give
+            // a good exception message if they are not; however we check this again inside the execution 
+            // engine's low level allocation function after having made a copy of the array to prevent a 
+            // malicious caller from mutating the array after this check.           
+            for (int i = 0; i < lengths.Length; i++)
+                if (lengths[i] < 0)
+                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.lengths, i, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+
+            fixed (int* pLengths = &lengths[0])
+                return InternalCreate((void*)t.TypeHandle.Value, lengths.Length, pLengths, null);
+        }
+
+        public static Array CreateInstance(Type elementType, params long[] lengths)
+        {
+            if (lengths == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.lengths);
+            }
+            if (lengths.Length == 0)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NeedAtLeast1Rank);
+
+            int[] intLengths = new int[lengths.Length];
+
+            for (int i = 0; i < lengths.Length; ++i)
+            {
+                long len = lengths[i];
+                if (len > Int32.MaxValue || len < Int32.MinValue)
+                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.len, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+                intLengths[i] = (int)len;
+            }
+
+            return Array.CreateInstance(elementType, intLengths);
+        }
+
+
+        public static unsafe Array CreateInstance(Type elementType, int[] lengths, int[] lowerBounds)
+        {
+            if (elementType == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.elementType);
+            if (lengths == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.lengths);
+            if (lowerBounds == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.lowerBounds);
+            if (lengths.Length != lowerBounds.Length)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RanksAndBounds);
+            if (lengths.Length == 0)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NeedAtLeast1Rank);
+
+            RuntimeType t = elementType.UnderlyingSystemType as RuntimeType;
+            if (t == null)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_MustBeType, ExceptionArgument.elementType);
+
+            // Check to make sure the lenghts are all positive. Note that we check this here to give
+            // a good exception message if they are not; however we check this again inside the execution 
+            // engine's low level allocation function after having made a copy of the array to prevent a 
+            // malicious caller from mutating the array after this check.           
+            for (int i = 0; i < lengths.Length; i++)
+                if (lengths[i] < 0)
+                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.lengths, i, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+
+            fixed (int* pLengths = &lengths[0])
+            fixed (int* pLowerBounds = &lowerBounds[0])
+                return InternalCreate((void*)t.TypeHandle.Value, lengths.Length, pLengths, pLowerBounds);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe Array InternalCreate(void* elementType, int rank, int* pLengths, int* pLowerBounds);
+
+        internal static Array UnsafeCreateInstance(Type elementType, int length)
+        {
+            return CreateInstance(elementType, length);
+        }
+
+        // Copies length elements from sourceArray, starting at index 0, to
+        // destinationArray, starting at index 0.
+        //
+        public static void Copy(Array sourceArray, Array destinationArray, int length)
+        {
+            if (sourceArray == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.sourceArray);
+            if (destinationArray == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.destinationArray);
+
+            Copy(sourceArray, sourceArray.GetLowerBound(0), destinationArray, destinationArray.GetLowerBound(0), length, false);
+        }
+
+        // Copies length elements from sourceArray, starting at sourceIndex, to
+        // destinationArray, starting at destinationIndex.
+        //
+        public static void Copy(Array sourceArray, int sourceIndex, Array destinationArray, int destinationIndex, int length)
+        {
+            Copy(sourceArray, sourceIndex, destinationArray, destinationIndex, length, false);
+        }
+
+        // Reliability-wise, this method will either possibly corrupt your 
+        // instance & might fail when called from within a CER, or if the
+        // reliable flag is true, it will either always succeed or always
+        // throw an exception with no side effects.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void Copy(Array sourceArray, int sourceIndex, Array destinationArray, int destinationIndex, int length, bool reliable);
+
+        // Provides a strong exception guarantee - either it succeeds, or
+        // it throws an exception with no side effects.  The arrays must be
+        // compatible array types based on the array element type - this 
+        // method does not support casting, boxing, or primitive widening.
+        // It will up-cast, assuming the array types are correct.
+        public static void ConstrainedCopy(Array sourceArray, int sourceIndex, Array destinationArray, int destinationIndex, int length)
+        {
+            Copy(sourceArray, sourceIndex, destinationArray, destinationIndex, length, true);
+        }
+
+        public static void Copy(Array sourceArray, Array destinationArray, long length)
+        {
+            if (length > Int32.MaxValue || length < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.length, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+
+            Array.Copy(sourceArray, destinationArray, (int)length);
+        }
+
+        public static void Copy(Array sourceArray, long sourceIndex, Array destinationArray, long destinationIndex, long length)
+        {
+            if (sourceIndex > Int32.MaxValue || sourceIndex < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.sourceIndex, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+            if (destinationIndex > Int32.MaxValue || destinationIndex < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.destinationIndex, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+            if (length > Int32.MaxValue || length < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.length, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+
+            Array.Copy(sourceArray, (int)sourceIndex, destinationArray, (int)destinationIndex, (int)length);
+        }
+
+
+        // Sets length elements in array to 0 (or null for Object arrays), starting
+        // at index.
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void Clear(Array array, int index, int length);
+
+        // The various Get values...
+        public unsafe Object GetValue(params int[] indices)
+        {
+            if (indices == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.indices);
+            if (Rank != indices.Length)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankIndices);
+
+            TypedReference elemref = new TypedReference();
+            fixed (int* pIndices = &indices[0])
+                InternalGetReference(&elemref, indices.Length, pIndices);
+            return TypedReference.InternalToObject(&elemref);
+        }
+
+        public unsafe Object GetValue(int index)
+        {
+            if (Rank != 1)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_Need1DArray);
+
+            TypedReference elemref = new TypedReference();
+            InternalGetReference(&elemref, 1, &index);
+            return TypedReference.InternalToObject(&elemref);
+        }
+
+        public unsafe Object GetValue(int index1, int index2)
+        {
+            if (Rank != 2)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_Need2DArray);
+
+            int* pIndices = stackalloc int[2];
+            pIndices[0] = index1;
+            pIndices[1] = index2;
+
+            TypedReference elemref = new TypedReference();
+            InternalGetReference(&elemref, 2, pIndices);
+            return TypedReference.InternalToObject(&elemref);
+        }
+
+        public unsafe Object GetValue(int index1, int index2, int index3)
+        {
+            if (Rank != 3)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_Need3DArray);
+
+            int* pIndices = stackalloc int[3];
+            pIndices[0] = index1;
+            pIndices[1] = index2;
+            pIndices[2] = index3;
+
+            TypedReference elemref = new TypedReference();
+            InternalGetReference(&elemref, 3, pIndices);
+            return TypedReference.InternalToObject(&elemref);
+        }
+
+        public Object GetValue(long index)
+        {
+            if (index > Int32.MaxValue || index < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+
+            return this.GetValue((int)index);
+        }
+
+        public Object GetValue(long index1, long index2)
+        {
+            if (index1 > Int32.MaxValue || index1 < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index1, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+            if (index2 > Int32.MaxValue || index2 < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index2, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+
+            return this.GetValue((int)index1, (int)index2);
+        }
+
+        public Object GetValue(long index1, long index2, long index3)
+        {
+            if (index1 > Int32.MaxValue || index1 < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index1, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+            if (index2 > Int32.MaxValue || index2 < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index2, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+            if (index3 > Int32.MaxValue || index3 < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index3, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+
+            return this.GetValue((int)index1, (int)index2, (int)index3);
+        }
+
+        public Object GetValue(params long[] indices)
+        {
+            if (indices == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.indices);
+            if (Rank != indices.Length)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankIndices);
+
+            int[] intIndices = new int[indices.Length];
+
+            for (int i = 0; i < indices.Length; ++i)
+            {
+                long index = indices[i];
+                if (index > Int32.MaxValue || index < Int32.MinValue)
+                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+                intIndices[i] = (int)index;
+            }
+
+            return this.GetValue(intIndices);
+        }
+
+
+        public unsafe void SetValue(Object value, int index)
+        {
+            if (Rank != 1)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_Need1DArray);
+
+            TypedReference elemref = new TypedReference();
+            InternalGetReference(&elemref, 1, &index);
+            InternalSetValue(&elemref, value);
+        }
+
+        public unsafe void SetValue(Object value, int index1, int index2)
+        {
+            if (Rank != 2)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_Need2DArray);
+
+            int* pIndices = stackalloc int[2];
+            pIndices[0] = index1;
+            pIndices[1] = index2;
+
+            TypedReference elemref = new TypedReference();
+            InternalGetReference(&elemref, 2, pIndices);
+            InternalSetValue(&elemref, value);
+        }
+
+        public unsafe void SetValue(Object value, int index1, int index2, int index3)
+        {
+            if (Rank != 3)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_Need3DArray);
+
+            int* pIndices = stackalloc int[3];
+            pIndices[0] = index1;
+            pIndices[1] = index2;
+            pIndices[2] = index3;
+
+            TypedReference elemref = new TypedReference();
+            InternalGetReference(&elemref, 3, pIndices);
+            InternalSetValue(&elemref, value);
+        }
+
+        public unsafe void SetValue(Object value, params int[] indices)
+        {
+            if (indices == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.indices);
+            if (Rank != indices.Length)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankIndices);
+
+            TypedReference elemref = new TypedReference();
+            fixed (int* pIndices = &indices[0])
+                InternalGetReference(&elemref, indices.Length, pIndices);
+            InternalSetValue(&elemref, value);
+        }
+
+        public void SetValue(Object value, long index)
+        {
+            if (index > Int32.MaxValue || index < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+
+            this.SetValue(value, (int)index);
+        }
+
+        public void SetValue(Object value, long index1, long index2)
+        {
+            if (index1 > Int32.MaxValue || index1 < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index1, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+            if (index2 > Int32.MaxValue || index2 < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index2, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+
+            this.SetValue(value, (int)index1, (int)index2);
+        }
+
+        public void SetValue(Object value, long index1, long index2, long index3)
+        {
+            if (index1 > Int32.MaxValue || index1 < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index1, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+            if (index2 > Int32.MaxValue || index2 < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index2, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+            if (index3 > Int32.MaxValue || index3 < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index3, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+
+            this.SetValue(value, (int)index1, (int)index2, (int)index3);
+        }
+
+        public void SetValue(Object value, params long[] indices)
+        {
+            if (indices == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.indices);
+            if (Rank != indices.Length)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankIndices);
+
+            int[] intIndices = new int[indices.Length];
+
+            for (int i = 0; i < indices.Length; ++i)
+            {
+                long index = indices[i];
+                if (index > Int32.MaxValue || index < Int32.MinValue)
+                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+                intIndices[i] = (int)index;
+            }
+
+            this.SetValue(value, intIndices);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        // reference to TypedReference is banned, so have to pass result as pointer
+        private extern unsafe void InternalGetReference(void* elemRef, int rank, int* pIndices);
+
+        // Ideally, we would like to use TypedReference.SetValue instead. Unfortunately, TypedReference.SetValue
+        // always throws not-supported exception
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe void InternalSetValue(void* target, Object value);
+
+        public extern int Length
+        {
+            [MethodImpl(MethodImplOptions.InternalCall)]
+            get;
+        }
+
+        private static int GetMedian(int low, int hi)
+        {
+            // Note both may be negative, if we are dealing with arrays w/ negative lower bounds.
+            Debug.Assert(low <= hi);
+            Debug.Assert(hi - low >= 0, "Length overflow!");
+            return low + ((hi - low) >> 1);
+        }
+
+        // We impose limits on maximum array lenght in each dimension to allow efficient 
+        // implementation of advanced range check elimination in future.
+        // Keep in sync with vm\gcscan.cpp and HashHelpers.MaxPrimeArrayLength.
+        // The constants are defined in this method: inline SIZE_T MaxArrayLength(SIZE_T componentSize) from gcscan
+        // We have different max sizes for arrays with elements of size 1 for backwards compatibility
+        internal const int MaxArrayLength = 0X7FEFFFFF;
+        internal const int MaxByteArrayLength = 0x7FFFFFC7;
+
+        public extern long LongLength
+        {
+            [MethodImpl(MethodImplOptions.InternalCall)]
+            get;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern int GetLength(int dimension);
+
+        public long GetLongLength(int dimension)
+        {
+            //This method should throw an IndexOufOfRangeException for compat if dimension < 0 or >= Rank
+            return GetLength(dimension);
+        }
+
+        public extern int Rank
+        {
+            [MethodImplAttribute(MethodImplOptions.InternalCall)]
+            get;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern int GetUpperBound(int dimension);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern int GetLowerBound(int dimension);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern int GetDataPtrOffsetInternal();
+
+        // Number of elements in the Array.
+        int ICollection.Count
+        { get { return Length; } }
+
+
+        // Returns an object appropriate for synchronizing access to this 
+        // Array.
+        public Object SyncRoot
+        { get { return this; } }
+
+        // Is this Array read-only?
+        public bool IsReadOnly
+        { get { return false; } }
+
+        public bool IsFixedSize
+        {
+            get { return true; }
+        }
+
+        // Is this Array synchronized (i.e., thread-safe)?  If you want a synchronized
+        // collection, you can use SyncRoot as an object to synchronize your 
+        // collection with.  You could also call GetSynchronized() 
+        // to get a synchronized wrapper around the Array.
+        public bool IsSynchronized
+        { get { return false; } }
+
+
+        Object IList.this[int index]
+        {
+            get { return GetValue(index); }
+            set { SetValue(value, index); }
+        }
+
+        int IList.Add(Object value)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_FixedSizeCollection);
+            return default(int);
+        }
+
+        bool IList.Contains(Object value)
+        {
+            return Array.IndexOf(this, value) >= this.GetLowerBound(0);
+        }
+
+        void IList.Clear()
+        {
+            Array.Clear(this, this.GetLowerBound(0), this.Length);
+        }
+
+        int IList.IndexOf(Object value)
+        {
+            return Array.IndexOf(this, value);
+        }
+
+        void IList.Insert(int index, Object value)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_FixedSizeCollection);
+        }
+
+        void IList.Remove(Object value)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_FixedSizeCollection);
+        }
+
+        void IList.RemoveAt(int index)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_FixedSizeCollection);
+        }
+
+        // Make a new array which is a shallow copy of the original array.
+        // 
+        public Object Clone()
+        {
+            return MemberwiseClone();
+        }
+
+        Int32 IStructuralComparable.CompareTo(Object other, IComparer comparer)
+        {
+            if (other == null)
+            {
+                return 1;
+            }
+
+            Array o = other as Array;
+
+            if (o == null || this.Length != o.Length)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.ArgumentException_OtherNotArrayOfCorrectLength, ExceptionArgument.other);
+            }
+
+            int i = 0;
+            int c = 0;
+
+            while (i < o.Length && c == 0)
+            {
+                object left = GetValue(i);
+                object right = o.GetValue(i);
+
+                c = comparer.Compare(left, right);
+                i++;
+            }
+
+            return c;
+        }
+
+        Boolean IStructuralEquatable.Equals(Object other, IEqualityComparer comparer)
+        {
+            if (other == null)
+            {
+                return false;
+            }
+
+            if (Object.ReferenceEquals(this, other))
+            {
+                return true;
+            }
+
+            Array o = other as Array;
+
+            if (o == null || o.Length != this.Length)
+            {
+                return false;
+            }
+
+            int i = 0;
+            while (i < o.Length)
+            {
+                object left = GetValue(i);
+                object right = o.GetValue(i);
+
+                if (!comparer.Equals(left, right))
+                {
+                    return false;
+                }
+                i++;
+            }
+
+            return true;
+        }
+
+        // From System.Web.Util.HashCodeCombiner
+        internal static int CombineHashCodes(int h1, int h2)
+        {
+            return (((h1 << 5) + h1) ^ h2);
+        }
+
+        int IStructuralEquatable.GetHashCode(IEqualityComparer comparer)
+        {
+            if (comparer == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.comparer);
+
+            int ret = 0;
+
+            for (int i = (this.Length >= 8 ? this.Length - 8 : 0); i < this.Length; i++)
+            {
+                ret = CombineHashCodes(ret, comparer.GetHashCode(GetValue(i)));
+            }
+
+            return ret;
+        }
+
+        // Searches an array for a given element using a binary search algorithm.
+        // Elements of the array are compared to the search value using the
+        // IComparable interface, which must be implemented by all elements
+        // of the array and the given search value. This method assumes that the
+        // array is already sorted according to the IComparable interface;
+        // if this is not the case, the result will be incorrect.
+        //
+        // The method returns the index of the given value in the array. If the
+        // array does not contain the given value, the method returns a negative
+        // integer. The bitwise complement operator (~) can be applied to a
+        // negative result to produce the index of the first element (if any) that
+        // is larger than the given search value.
+        // 
+        public static int BinarySearch(Array array, Object value)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            int lb = array.GetLowerBound(0);
+            return BinarySearch(array, lb, array.Length, value, null);
+        }
+
+        // Searches a section of an array for a given element using a binary search
+        // algorithm. Elements of the array are compared to the search value using
+        // the IComparable interface, which must be implemented by all
+        // elements of the array and the given search value. This method assumes
+        // that the array is already sorted according to the IComparable
+        // interface; if this is not the case, the result will be incorrect.
+        //
+        // The method returns the index of the given value in the array. If the
+        // array does not contain the given value, the method returns a negative
+        // integer. The bitwise complement operator (~) can be applied to a
+        // negative result to produce the index of the first element (if any) that
+        // is larger than the given search value.
+        // 
+        public static int BinarySearch(Array array, int index, int length, Object value)
+        {
+            return BinarySearch(array, index, length, value, null);
+        }
+
+        // Searches an array for a given element using a binary search algorithm.
+        // Elements of the array are compared to the search value using the given
+        // IComparer interface. If comparer is null, elements of the
+        // array are compared to the search value using the IComparable
+        // interface, which in that case must be implemented by all elements of the
+        // array and the given search value. This method assumes that the array is
+        // already sorted; if this is not the case, the result will be incorrect.
+        // 
+        // The method returns the index of the given value in the array. If the
+        // array does not contain the given value, the method returns a negative
+        // integer. The bitwise complement operator (~) can be applied to a
+        // negative result to produce the index of the first element (if any) that
+        // is larger than the given search value.
+        // 
+        public static int BinarySearch(Array array, Object value, IComparer comparer)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            int lb = array.GetLowerBound(0);
+            return BinarySearch(array, lb, array.Length, value, comparer);
+        }
+
+        // Searches a section of an array for a given element using a binary search
+        // algorithm. Elements of the array are compared to the search value using
+        // the given IComparer interface. If comparer is null,
+        // elements of the array are compared to the search value using the
+        // IComparable interface, which in that case must be implemented by
+        // all elements of the array and the given search value. This method
+        // assumes that the array is already sorted; if this is not the case, the
+        // result will be incorrect.
+        // 
+        // The method returns the index of the given value in the array. If the
+        // array does not contain the given value, the method returns a negative
+        // integer. The bitwise complement operator (~) can be applied to a
+        // negative result to produce the index of the first element (if any) that
+        // is larger than the given search value.
+        // 
+        public static int BinarySearch(Array array, int index, int length, Object value, IComparer comparer)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            int lb = array.GetLowerBound(0);
+            if (index < lb)
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            if (length < 0)
+                ThrowHelper.ThrowLengthArgumentOutOfRange_ArgumentOutOfRange_NeedNonNegNum();
+            if (array.Length - (index - lb) < length)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
+            if (array.Rank != 1)
+                ThrowHelper.ThrowRankException(ExceptionResource.Rank_MultiDimNotSupported);
+
+            if (comparer == null) comparer = Comparer.Default;
+            if (comparer == Comparer.Default)
+            {
+                int retval;
+                bool r = TrySZBinarySearch(array, index, length, value, out retval);
+                if (r)
+                    return retval;
+            }
+
+            int lo = index;
+            int hi = index + length - 1;
+            Object[] objArray = array as Object[];
+            if (objArray != null)
+            {
+                while (lo <= hi)
+                {
+                    // i might overflow if lo and hi are both large positive numbers. 
+                    int i = GetMedian(lo, hi);
+
+                    int c = 0;
+                    try
+                    {
+                        c = comparer.Compare(objArray[i], value);
+                    }
+                    catch (Exception e)
+                    {
+                        ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_IComparerFailed, e);
+                    }
+                    if (c == 0) return i;
+                    if (c < 0)
+                    {
+                        lo = i + 1;
+                    }
+                    else
+                    {
+                        hi = i - 1;
+                    }
+                }
+            }
+            else
+            {
+                while (lo <= hi)
+                {
+                    int i = GetMedian(lo, hi);
+
+                    int c = 0;
+                    try
+                    {
+                        c = comparer.Compare(array.GetValue(i), value);
+                    }
+                    catch (Exception e)
+                    {
+                        ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_IComparerFailed, e);
+                    }
+                    if (c == 0) return i;
+                    if (c < 0)
+                    {
+                        lo = i + 1;
+                    }
+                    else
+                    {
+                        hi = i - 1;
+                    }
+                }
+            }
+            return ~lo;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool TrySZBinarySearch(Array sourceArray, int sourceIndex, int count, Object value, out int retVal);
+
+        public static int BinarySearch<T>(T[] array, T value)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            return BinarySearch<T>(array, 0, array.Length, value, null);
+        }
+
+        public static int BinarySearch<T>(T[] array, T value, System.Collections.Generic.IComparer<T> comparer)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            return BinarySearch<T>(array, 0, array.Length, value, comparer);
+        }
+
+        public static int BinarySearch<T>(T[] array, int index, int length, T value)
+        {
+            return BinarySearch<T>(array, index, length, value, null);
+        }
+
+        public static int BinarySearch<T>(T[] array, int index, int length, T value, System.Collections.Generic.IComparer<T> comparer)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            if (index < 0)
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            if (length < 0)
+                ThrowHelper.ThrowLengthArgumentOutOfRange_ArgumentOutOfRange_NeedNonNegNum();
+
+            if (array.Length - index < length)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
+
+            return ArraySortHelper<T>.Default.BinarySearch(array, index, length, value, comparer);
+        }
+
+        public static TOutput[] ConvertAll<TInput, TOutput>(TInput[] array, Converter<TInput, TOutput> converter)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (converter == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.converter);
+            }
+
+            TOutput[] newArray = new TOutput[array.Length];
+            for (int i = 0; i < array.Length; i++)
+            {
+                newArray[i] = converter(array[i]);
+            }
+            return newArray;
+        }
+
+        // CopyTo copies a collection into an Array, starting at a particular
+        // index into the array.
+        // 
+        // This method is to support the ICollection interface, and calls
+        // Array.Copy internally.  If you aren't using ICollection explicitly,
+        // call Array.Copy to avoid an extra indirection.
+        // 
+        public void CopyTo(Array array, int index)
+        {
+            if (array != null && array.Rank != 1)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
+            // Note: Array.Copy throws a RankException and we want a consistent ArgumentException for all the IList CopyTo methods.
+            Array.Copy(this, GetLowerBound(0), array, index, Length);
+        }
+
+        public void CopyTo(Array array, long index)
+        {
+            if (index > Int32.MaxValue || index < Int32.MinValue)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_HugeArrayNotSupported);
+
+            this.CopyTo(array, (int)index);
+        }
+
+        private static class EmptyArray<T>
+        {
+            internal static readonly T[] Value = new T[0];
+        }
+
+        public static T[] Empty<T>()
+        {
+            return EmptyArray<T>.Value;
+        }
+
+        public static bool Exists<T>(T[] array, Predicate<T> match)
+        {
+            return Array.FindIndex(array, match) != -1;
+        }
+
+        public static void Fill<T>(T[] array, T value)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            for (int i = 0; i < array.Length; i++)
+            {
+                array[i] = value;
+            }
+        }
+
+        public static void Fill<T>(T[] array, T value, int startIndex, int count)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (startIndex < 0 || startIndex > array.Length)
+            {
+                ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
+            }
+
+            if (count < 0 || startIndex > array.Length - count)
+            {
+                ThrowHelper.ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count();
+            }
+
+            for (int i = startIndex; i < startIndex + count; i++)
+            {
+                array[i] = value;
+            }
+        }
+
+        public static T Find<T>(T[] array, Predicate<T> match)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (match == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
+            }
+
+            for (int i = 0; i < array.Length; i++)
+            {
+                if (match(array[i]))
+                {
+                    return array[i];
+                }
+            }
+            return default(T);
+        }
+
+        public static T[] FindAll<T>(T[] array, Predicate<T> match)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (match == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
+            }
+
+            List<T> list = new List<T>();
+            for (int i = 0; i < array.Length; i++)
+            {
+                if (match(array[i]))
+                {
+                    list.Add(array[i]);
+                }
+            }
+            return list.ToArray();
+        }
+
+        public static int FindIndex<T>(T[] array, Predicate<T> match)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            return FindIndex(array, 0, array.Length, match);
+        }
+
+        public static int FindIndex<T>(T[] array, int startIndex, Predicate<T> match)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            return FindIndex(array, startIndex, array.Length - startIndex, match);
+        }
+
+        public static int FindIndex<T>(T[] array, int startIndex, int count, Predicate<T> match)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (startIndex < 0 || startIndex > array.Length)
+            {
+                ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
+            }
+
+            if (count < 0 || startIndex > array.Length - count)
+            {
+                ThrowHelper.ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count();
+            }
+
+            if (match == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
+            }
+
+            int endIndex = startIndex + count;
+            for (int i = startIndex; i < endIndex; i++)
+            {
+                if (match(array[i])) return i;
+            }
+            return -1;
+        }
+
+        public static T FindLast<T>(T[] array, Predicate<T> match)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (match == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
+            }
+
+            for (int i = array.Length - 1; i >= 0; i--)
+            {
+                if (match(array[i]))
+                {
+                    return array[i];
+                }
+            }
+            return default(T);
+        }
+
+        public static int FindLastIndex<T>(T[] array, Predicate<T> match)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            return FindLastIndex(array, array.Length - 1, array.Length, match);
+        }
+
+        public static int FindLastIndex<T>(T[] array, int startIndex, Predicate<T> match)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            return FindLastIndex(array, startIndex, startIndex + 1, match);
+        }
+
+        public static int FindLastIndex<T>(T[] array, int startIndex, int count, Predicate<T> match)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (match == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
+            }
+
+            if (array.Length == 0)
+            {
+                // Special case for 0 length List
+                if (startIndex != -1)
+                {
+                    ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
+                }
+            }
+            else
+            {
+                // Make sure we're not out of range            
+                if (startIndex < 0 || startIndex >= array.Length)
+                {
+                    ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
+                }
+            }
+
+            // 2nd have of this also catches when startIndex == MAXINT, so MAXINT - 0 + 1 == -1, which is < 0.
+            if (count < 0 || startIndex - count + 1 < 0)
+            {
+                ThrowHelper.ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count();
+            }
+
+            int endIndex = startIndex - count;
+            for (int i = startIndex; i > endIndex; i--)
+            {
+                if (match(array[i]))
+                {
+                    return i;
+                }
+            }
+            return -1;
+        }
+
+        public static void ForEach<T>(T[] array, Action<T> action)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (action == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.action);
+            }
+
+            for (int i = 0; i < array.Length; i++)
+            {
+                action(array[i]);
+            }
+        }
+
+        // GetEnumerator returns an IEnumerator over this Array.  
+        // 
+        // Currently, only one dimensional arrays are supported.
+        // 
+        public IEnumerator GetEnumerator()
+        {
+            int lowerBound = GetLowerBound(0);
+            if (Rank == 1 && lowerBound == 0)
+                return new SZArrayEnumerator(this);
+            else
+                return new ArrayEnumerator(this, lowerBound, Length);
+        }
+
+        // Returns the index of the first occurrence of a given value in an array.
+        // The array is searched forwards, and the elements of the array are
+        // compared to the given value using the Object.Equals method.
+        // 
+        public static int IndexOf(Array array, Object value)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            int lb = array.GetLowerBound(0);
+            return IndexOf(array, value, lb, array.Length);
+        }
+
+        // Returns the index of the first occurrence of a given value in a range of
+        // an array. The array is searched forwards, starting at index
+        // startIndex and ending at the last element of the array. The
+        // elements of the array are compared to the given value using the
+        // Object.Equals method.
+        // 
+        public static int IndexOf(Array array, Object value, int startIndex)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            int lb = array.GetLowerBound(0);
+            return IndexOf(array, value, startIndex, array.Length - startIndex + lb);
+        }
+
+        // Returns the index of the first occurrence of a given value in a range of
+        // an array. The array is searched forwards, starting at index
+        // startIndex and upto count elements. The
+        // elements of the array are compared to the given value using the
+        // Object.Equals method.
+        // 
+        public static int IndexOf(Array array, Object value, int startIndex, int count)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            if (array.Rank != 1)
+                ThrowHelper.ThrowRankException(ExceptionResource.Rank_MultiDimNotSupported);
+
+            int lb = array.GetLowerBound(0);
+            if (startIndex < lb || startIndex > array.Length + lb)
+                ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
+            if (count < 0 || count > array.Length - startIndex + lb)
+                ThrowHelper.ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count();
+
+            // Try calling a quick native method to handle primitive types.
+            int retVal;
+            bool r = TrySZIndexOf(array, startIndex, count, value, out retVal);
+            if (r)
+                return retVal;
+
+            Object[] objArray = array as Object[];
+            int endIndex = startIndex + count;
+            if (objArray != null)
+            {
+                if (value == null)
+                {
+                    for (int i = startIndex; i < endIndex; i++)
+                    {
+                        if (objArray[i] == null) return i;
+                    }
+                }
+                else
+                {
+                    for (int i = startIndex; i < endIndex; i++)
+                    {
+                        Object obj = objArray[i];
+                        if (obj != null && obj.Equals(value)) return i;
+                    }
+                }
+            }
+            else
+            {
+                for (int i = startIndex; i < endIndex; i++)
+                {
+                    Object obj = array.GetValue(i);
+                    if (obj == null)
+                    {
+                        if (value == null) return i;
+                    }
+                    else
+                    {
+                        if (obj.Equals(value)) return i;
+                    }
+                }
+            }
+            // Return one less than the lower bound of the array.  This way,
+            // for arrays with a lower bound of -1 we will not return -1 when the
+            // item was not found.  And for SZArrays (the vast majority), -1 still
+            // works for them.
+            return lb - 1;
+        }
+
+        public static int IndexOf<T>(T[] array, T value)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            return IndexOf(array, value, 0, array.Length);
+        }
+
+        public static int IndexOf<T>(T[] array, T value, int startIndex)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            return IndexOf(array, value, startIndex, array.Length - startIndex);
+        }
+
+        public static int IndexOf<T>(T[] array, T value, int startIndex, int count)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (startIndex < 0 || startIndex > array.Length)
+            {
+                ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
+            }
+
+            if (count < 0 || count > array.Length - startIndex)
+            {
+                ThrowHelper.ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count();
+            }
+
+            return EqualityComparer<T>.Default.IndexOf(array, value, startIndex, count);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool TrySZIndexOf(Array sourceArray, int sourceIndex, int count, Object value, out int retVal);
+
+
+        // Returns the index of the last occurrence of a given value in an array.
+        // The array is searched backwards, and the elements of the array are
+        // compared to the given value using the Object.Equals method.
+        // 
+        public static int LastIndexOf(Array array, Object value)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            int lb = array.GetLowerBound(0);
+            return LastIndexOf(array, value, array.Length - 1 + lb, array.Length);
+        }
+
+        // Returns the index of the last occurrence of a given value in a range of
+        // an array. The array is searched backwards, starting at index
+        // startIndex and ending at index 0. The elements of the array are
+        // compared to the given value using the Object.Equals method.
+        // 
+        public static int LastIndexOf(Array array, Object value, int startIndex)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            int lb = array.GetLowerBound(0);
+            return LastIndexOf(array, value, startIndex, startIndex + 1 - lb);
+        }
+
+        // Returns the index of the last occurrence of a given value in a range of
+        // an array. The array is searched backwards, starting at index
+        // startIndex and counting uptocount elements. The elements of
+        // the array are compared to the given value using the Object.Equals
+        // method.
+        // 
+        public static int LastIndexOf(Array array, Object value, int startIndex, int count)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            int lb = array.GetLowerBound(0);
+            if (array.Length == 0)
+            {
+                return lb - 1;
+            }
+
+            if (startIndex < lb || startIndex >= array.Length + lb)
+                ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
+            if (count < 0)
+                ThrowHelper.ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count();
+            if (count > startIndex - lb + 1)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.endIndex, ExceptionResource.ArgumentOutOfRange_EndIndexStartIndex);
+            if (array.Rank != 1)
+                ThrowHelper.ThrowRankException(ExceptionResource.Rank_MultiDimNotSupported);
+
+            // Try calling a quick native method to handle primitive types.
+            int retVal;
+            bool r = TrySZLastIndexOf(array, startIndex, count, value, out retVal);
+            if (r)
+                return retVal;
+
+            Object[] objArray = array as Object[];
+            int endIndex = startIndex - count + 1;
+            if (objArray != null)
+            {
+                if (value == null)
+                {
+                    for (int i = startIndex; i >= endIndex; i--)
+                    {
+                        if (objArray[i] == null) return i;
+                    }
+                }
+                else
+                {
+                    for (int i = startIndex; i >= endIndex; i--)
+                    {
+                        Object obj = objArray[i];
+                        if (obj != null && obj.Equals(value)) return i;
+                    }
+                }
+            }
+            else
+            {
+                for (int i = startIndex; i >= endIndex; i--)
+                {
+                    Object obj = array.GetValue(i);
+                    if (obj == null)
+                    {
+                        if (value == null) return i;
+                    }
+                    else
+                    {
+                        if (obj.Equals(value)) return i;
+                    }
+                }
+            }
+            return lb - 1;  // Return lb-1 for arrays with negative lower bounds.
+        }
+
+        public static int LastIndexOf<T>(T[] array, T value)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            return LastIndexOf(array, value, array.Length - 1, array.Length);
+        }
+
+        public static int LastIndexOf<T>(T[] array, T value, int startIndex)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+            // if array is empty and startIndex is 0, we need to pass 0 as count
+            return LastIndexOf(array, value, startIndex, (array.Length == 0) ? 0 : (startIndex + 1));
+        }
+
+        public static int LastIndexOf<T>(T[] array, T value, int startIndex, int count)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (array.Length == 0)
+            {
+                //
+                // Special case for 0 length List
+                // accept -1 and 0 as valid startIndex for compablility reason.
+                //
+                if (startIndex != -1 && startIndex != 0)
+                {
+                    ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
+                }
+
+                // only 0 is a valid value for count if array is empty
+                if (count != 0)
+                {
+                    ThrowHelper.ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count();
+                }
+                return -1;
+            }
+
+            // Make sure we're not out of range            
+            if (startIndex < 0 || startIndex >= array.Length)
+            {
+                ThrowHelper.ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index();
+            }
+
+            // 2nd have of this also catches when startIndex == MAXINT, so MAXINT - 0 + 1 == -1, which is < 0.
+            if (count < 0 || startIndex - count + 1 < 0)
+            {
+                ThrowHelper.ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count();
+            }
+
+            return EqualityComparer<T>.Default.LastIndexOf(array, value, startIndex, count);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool TrySZLastIndexOf(Array sourceArray, int sourceIndex, int count, Object value, out int retVal);
+
+
+        // Reverses all elements of the given array. Following a call to this
+        // method, an element previously located at index i will now be
+        // located at index length - i - 1, where length is the
+        // length of the array.
+        // 
+        public static void Reverse(Array array)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            Reverse(array, array.GetLowerBound(0), array.Length);
+        }
+
+        // Reverses the elements in a range of an array. Following a call to this
+        // method, an element in the range given by index and count
+        // which was previously located at index i will now be located at
+        // index index + (index + count - i - 1).
+        // Reliability note: This may fail because it may have to box objects.
+        // 
+        public static void Reverse(Array array, int index, int length)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            int lowerBound = array.GetLowerBound(0);
+            if (index < lowerBound)
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            if (length < 0)
+                ThrowHelper.ThrowLengthArgumentOutOfRange_ArgumentOutOfRange_NeedNonNegNum();
+
+            if (array.Length - (index - lowerBound) < length)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
+            if (array.Rank != 1)
+                ThrowHelper.ThrowRankException(ExceptionResource.Rank_MultiDimNotSupported);
+
+            if (length <= 1)
+                return;
+
+            bool r = TrySZReverse(array, index, length);
+            if (r)
+                return;
+
+            Object[] objArray = array as Object[];
+            if (objArray != null)
+            {
+                Array.Reverse<object>(objArray, index, length);
+            }
+            else
+            {
+                int i = index;
+                int j = index + length - 1;
+                while (i < j)
+                {
+                    Object temp = array.GetValue(i);
+                    array.SetValue(array.GetValue(j), i);
+                    array.SetValue(temp, j);
+                    i++;
+                    j--;
+                }
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool TrySZReverse(Array array, int index, int count);
+
+        public static void Reverse<T>(T[] array)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            Reverse(array, 0, array.Length);
+        }
+        
+        public static void Reverse<T>(T[] array, int index, int length)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            if (index < 0)
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            if (length < 0)
+                ThrowHelper.ThrowLengthArgumentOutOfRange_ArgumentOutOfRange_NeedNonNegNum();
+            if (array.Length - index < length)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
+
+            if (length <= 1)
+                return;
+
+            ref T first = ref Unsafe.Add(ref Unsafe.As<byte, T>(ref array.GetRawSzArrayData()), index);
+            ref T last = ref Unsafe.Add(ref Unsafe.Add(ref first, length), -1);
+            do
+            {
+                T temp = first;
+                first = last;
+                last = temp;
+                first = ref Unsafe.Add(ref first, 1);
+                last = ref Unsafe.Add(ref last, -1);
+            } while (Unsafe.IsAddressLessThan(ref first, ref last));
+        }
+
+        // Sorts the elements of an array. The sort compares the elements to each
+        // other using the IComparable interface, which must be implemented
+        // by all elements of the array.
+        // 
+        public static void Sort(Array array)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            Sort(array, null, array.GetLowerBound(0), array.Length, null);
+        }
+
+        // Sorts the elements of two arrays based on the keys in the first array.
+        // Elements in the keys array specify the sort keys for
+        // corresponding elements in the items array. The sort compares the
+        // keys to each other using the IComparable interface, which must be
+        // implemented by all elements of the keys array.
+        // 
+        public static void Sort(Array keys, Array items)
+        {
+            if (keys == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.keys);
+            Sort(keys, items, keys.GetLowerBound(0), keys.Length, null);
+        }
+
+        // Sorts the elements in a section of an array. The sort compares the
+        // elements to each other using the IComparable interface, which
+        // must be implemented by all elements in the given section of the array.
+        // 
+        public static void Sort(Array array, int index, int length)
+        {
+            Sort(array, null, index, length, null);
+        }
+
+        // Sorts the elements in a section of two arrays based on the keys in the
+        // first array. Elements in the keys array specify the sort keys for
+        // corresponding elements in the items array. The sort compares the
+        // keys to each other using the IComparable interface, which must be
+        // implemented by all elements of the keys array.
+        // 
+        public static void Sort(Array keys, Array items, int index, int length)
+        {
+            Sort(keys, items, index, length, null);
+        }
+
+        // Sorts the elements of an array. The sort compares the elements to each
+        // other using the given IComparer interface. If comparer is
+        // null, the elements are compared to each other using the
+        // IComparable interface, which in that case must be implemented by
+        // all elements of the array.
+        // 
+        public static void Sort(Array array, IComparer comparer)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            Sort(array, null, array.GetLowerBound(0), array.Length, comparer);
+        }
+
+        // Sorts the elements of two arrays based on the keys in the first array.
+        // Elements in the keys array specify the sort keys for
+        // corresponding elements in the items array. The sort compares the
+        // keys to each other using the given IComparer interface. If
+        // comparer is null, the elements are compared to each other using
+        // the IComparable interface, which in that case must be implemented
+        // by all elements of the keys array.
+        // 
+        public static void Sort(Array keys, Array items, IComparer comparer)
+        {
+            if (keys == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.keys);
+            Sort(keys, items, keys.GetLowerBound(0), keys.Length, comparer);
+        }
+
+        // Sorts the elements in a section of an array. The sort compares the
+        // elements to each other using the given IComparer interface. If
+        // comparer is null, the elements are compared to each other using
+        // the IComparable interface, which in that case must be implemented
+        // by all elements in the given section of the array.
+        // 
+        public static void Sort(Array array, int index, int length, IComparer comparer)
+        {
+            Sort(array, null, index, length, comparer);
+        }
+
+        // Sorts the elements in a section of two arrays based on the keys in the
+        // first array. Elements in the keys array specify the sort keys for
+        // corresponding elements in the items array. The sort compares the
+        // keys to each other using the given IComparer interface. If
+        // comparer is null, the elements are compared to each other using
+        // the IComparable interface, which in that case must be implemented
+        // by all elements of the given section of the keys array.
+        // 
+        public static void Sort(Array keys, Array items, int index, int length, IComparer comparer)
+        {
+            if (keys == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.keys);
+            if (keys.Rank != 1 || (items != null && items.Rank != 1))
+                ThrowHelper.ThrowRankException(ExceptionResource.Rank_MultiDimNotSupported);
+            int keysLowerBound = keys.GetLowerBound(0);
+            if (items != null && keysLowerBound != items.GetLowerBound(0))
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_LowerBoundsMustMatch);
+            if (index < keysLowerBound)
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            if (length < 0)
+                ThrowHelper.ThrowLengthArgumentOutOfRange_ArgumentOutOfRange_NeedNonNegNum();
+
+            if (keys.Length - (index - keysLowerBound) < length || (items != null && (index - keysLowerBound) > items.Length - length))
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
+
+
+            if (length > 1)
+            {
+                if (comparer == Comparer.Default || comparer == null)
+                {
+                    bool r = TrySZSort(keys, items, index, index + length - 1);
+                    if (r)
+                        return;
+                }
+
+                Object[] objKeys = keys as Object[];
+                Object[] objItems = null;
+                if (objKeys != null)
+                    objItems = items as Object[];
+                if (objKeys != null && (items == null || objItems != null))
+                {
+                    SorterObjectArray sorter = new SorterObjectArray(objKeys, objItems, comparer);
+                    sorter.Sort(index, length);
+                }
+                else
+                {
+                    SorterGenericArray sorter = new SorterGenericArray(keys, items, comparer);
+                    sorter.Sort(index, length);
+                }
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool TrySZSort(Array keys, Array items, int left, int right);
+
+        public static void Sort<T>(T[] array)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            Sort<T>(array, 0, array.Length, null);
+        }
+
+        public static void Sort<TKey, TValue>(TKey[] keys, TValue[] items)
+        {
+            if (keys == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.keys);
+            Sort<TKey, TValue>(keys, items, 0, keys.Length, null);
+        }
+
+        public static void Sort<T>(T[] array, int index, int length)
+        {
+            Sort<T>(array, index, length, null);
+        }
+
+        public static void Sort<TKey, TValue>(TKey[] keys, TValue[] items, int index, int length)
+        {
+            Sort<TKey, TValue>(keys, items, index, length, null);
+        }
+
+        public static void Sort<T>(T[] array, System.Collections.Generic.IComparer<T> comparer)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            Sort<T>(array, 0, array.Length, comparer);
+        }
+
+        public static void Sort<TKey, TValue>(TKey[] keys, TValue[] items, System.Collections.Generic.IComparer<TKey> comparer)
+        {
+            if (keys == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.keys);
+            Sort<TKey, TValue>(keys, items, 0, keys.Length, comparer);
+        }
+
+        public static void Sort<T>(T[] array, int index, int length, System.Collections.Generic.IComparer<T> comparer)
+        {
+            if (array == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            if (index < 0)
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            if (length < 0)
+                ThrowHelper.ThrowLengthArgumentOutOfRange_ArgumentOutOfRange_NeedNonNegNum();
+            if (array.Length - index < length)
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
+
+            if (length > 1)
+            {
+                if (comparer == null || comparer == Comparer<T>.Default)
+                {
+                    if (TrySZSort(array, null, index, index + length - 1))
+                    {
+                        return;
+                    }
+                }
+
+                ArraySortHelper<T>.Default.Sort(array, index, length, comparer);
+            }
+        }
+
+        public static void Sort<TKey, TValue>(TKey[] keys, TValue[] items, int index, int length, System.Collections.Generic.IComparer<TKey> comparer)
+        {
+            if (keys == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.keys);
+            if (index < 0)
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            if (length < 0)
+                ThrowHelper.ThrowLengthArgumentOutOfRange_ArgumentOutOfRange_NeedNonNegNum();
+            if (keys.Length - index < length || (items != null && index > items.Length - length))
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
+
+            if (length > 1)
+            {
+                if (comparer == null || comparer == Comparer<TKey>.Default)
+                {
+                    if (TrySZSort(keys, items, index, index + length - 1))
+                    {
+                        return;
+                    }
+                }
+
+                if (items == null)
+                {
+                    Sort<TKey>(keys, index, length, comparer);
+                    return;
+                }
+
+                ArraySortHelper<TKey, TValue>.Default.Sort(keys, items, index, length, comparer);
+            }
+        }
+
+        public static void Sort<T>(T[] array, Comparison<T> comparison)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (comparison == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.comparison);
+            }
+
+            ArraySortHelper<T>.Sort(array, 0, array.Length, comparison);
+        }
+
+        public static bool TrueForAll<T>(T[] array, Predicate<T> match)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (match == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
+            }
+
+            for (int i = 0; i < array.Length; i++)
+            {
+                if (!match(array[i]))
+                {
+                    return false;
+                }
+            }
+            return true;
+        }
+
+
+        // Private value type used by the Sort methods.
+        private struct SorterObjectArray
+        {
+            private Object[] keys;
+            private Object[] items;
+            private IComparer comparer;
+
+            internal SorterObjectArray(Object[] keys, Object[] items, IComparer comparer)
+            {
+                if (comparer == null) comparer = Comparer.Default;
+                this.keys = keys;
+                this.items = items;
+                this.comparer = comparer;
+            }
+
+            internal void SwapIfGreaterWithItems(int a, int b)
+            {
+                if (a != b)
+                {
+                    if (comparer.Compare(keys[a], keys[b]) > 0)
+                    {
+                        Object temp = keys[a];
+                        keys[a] = keys[b];
+                        keys[b] = temp;
+                        if (items != null)
+                        {
+                            Object item = items[a];
+                            items[a] = items[b];
+                            items[b] = item;
+                        }
+                    }
+                }
+            }
+
+            private void Swap(int i, int j)
+            {
+                Object t = keys[i];
+                keys[i] = keys[j];
+                keys[j] = t;
+
+                if (items != null)
+                {
+                    Object item = items[i];
+                    items[i] = items[j];
+                    items[j] = item;
+                }
+            }
+
+            internal void Sort(int left, int length)
+            {
+                IntrospectiveSort(left, length);
+            }
+
+            private void IntrospectiveSort(int left, int length)
+            {
+                if (length < 2)
+                    return;
+
+                try
+                {
+                    IntroSort(left, length + left - 1, 2 * IntrospectiveSortUtilities.FloorLog2PlusOne(length));
+                }
+                catch (IndexOutOfRangeException)
+                {
+                    IntrospectiveSortUtilities.ThrowOrIgnoreBadComparer(comparer);
+                }
+                catch (Exception e)
+                {
+                    ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_IComparerFailed, e);
+                }
+            }
+
+            private void IntroSort(int lo, int hi, int depthLimit)
+            {
+                while (hi > lo)
+                {
+                    int partitionSize = hi - lo + 1;
+                    if (partitionSize <= IntrospectiveSortUtilities.IntrosortSizeThreshold)
+                    {
+                        if (partitionSize == 1)
+                        {
+                            return;
+                        }
+                        if (partitionSize == 2)
+                        {
+                            SwapIfGreaterWithItems(lo, hi);
+                            return;
+                        }
+                        if (partitionSize == 3)
+                        {
+                            SwapIfGreaterWithItems(lo, hi - 1);
+                            SwapIfGreaterWithItems(lo, hi);
+                            SwapIfGreaterWithItems(hi - 1, hi);
+                            return;
+                        }
+
+                        InsertionSort(lo, hi);
+                        return;
+                    }
+
+                    if (depthLimit == 0)
+                    {
+                        Heapsort(lo, hi);
+                        return;
+                    }
+                    depthLimit--;
+
+                    int p = PickPivotAndPartition(lo, hi);
+                    IntroSort(p + 1, hi, depthLimit);
+                    hi = p - 1;
+                }
+            }
+
+            private int PickPivotAndPartition(int lo, int hi)
+            {
+                // Compute median-of-three.  But also partition them, since we've done the comparison.
+                int mid = lo + (hi - lo) / 2;
+                // Sort lo, mid and hi appropriately, then pick mid as the pivot.
+                SwapIfGreaterWithItems(lo, mid);
+                SwapIfGreaterWithItems(lo, hi);
+                SwapIfGreaterWithItems(mid, hi);
+
+                Object pivot = keys[mid];
+                Swap(mid, hi - 1);
+                int left = lo, right = hi - 1;  // We already partitioned lo and hi and put the pivot in hi - 1.  And we pre-increment & decrement below.
+
+                while (left < right)
+                {
+                    while (comparer.Compare(keys[++left], pivot) < 0) ;
+                    while (comparer.Compare(pivot, keys[--right]) < 0) ;
+
+                    if (left >= right)
+                        break;
+
+                    Swap(left, right);
+                }
+
+                // Put pivot in the right location.
+                Swap(left, (hi - 1));
+                return left;
+            }
+
+            private void Heapsort(int lo, int hi)
+            {
+                int n = hi - lo + 1;
+                for (int i = n / 2; i >= 1; i = i - 1)
+                {
+                    DownHeap(i, n, lo);
+                }
+                for (int i = n; i > 1; i = i - 1)
+                {
+                    Swap(lo, lo + i - 1);
+
+                    DownHeap(1, i - 1, lo);
+                }
+            }
+
+            private void DownHeap(int i, int n, int lo)
+            {
+                Object d = keys[lo + i - 1];
+                Object dt = (items != null) ? items[lo + i - 1] : null;
+                int child;
+                while (i <= n / 2)
+                {
+                    child = 2 * i;
+                    if (child < n && comparer.Compare(keys[lo + child - 1], keys[lo + child]) < 0)
+                    {
+                        child++;
+                    }
+                    if (!(comparer.Compare(d, keys[lo + child - 1]) < 0))
+                        break;
+                    keys[lo + i - 1] = keys[lo + child - 1];
+                    if (items != null)
+                        items[lo + i - 1] = items[lo + child - 1];
+                    i = child;
+                }
+                keys[lo + i - 1] = d;
+                if (items != null)
+                    items[lo + i - 1] = dt;
+            }
+
+            private void InsertionSort(int lo, int hi)
+            {
+                int i, j;
+                Object t, ti;
+                for (i = lo; i < hi; i++)
+                {
+                    j = i;
+                    t = keys[i + 1];
+                    ti = (items != null) ? items[i + 1] : null;
+                    while (j >= lo && comparer.Compare(t, keys[j]) < 0)
+                    {
+                        keys[j + 1] = keys[j];
+                        if (items != null)
+                            items[j + 1] = items[j];
+                        j--;
+                    }
+                    keys[j + 1] = t;
+                    if (items != null)
+                        items[j + 1] = ti;
+                }
+            }
+        }
+
+        // Private value used by the Sort methods for instances of Array.
+        // This is slower than the one for Object[], since we can't use the JIT helpers
+        // to access the elements.  We must use GetValue & SetValue.
+        private struct SorterGenericArray
+        {
+            private Array keys;
+            private Array items;
+            private IComparer comparer;
+
+            internal SorterGenericArray(Array keys, Array items, IComparer comparer)
+            {
+                if (comparer == null) comparer = Comparer.Default;
+                this.keys = keys;
+                this.items = items;
+                this.comparer = comparer;
+            }
+
+            internal void SwapIfGreaterWithItems(int a, int b)
+            {
+                if (a != b)
+                {
+                    if (comparer.Compare(keys.GetValue(a), keys.GetValue(b)) > 0)
+                    {
+                        Object key = keys.GetValue(a);
+                        keys.SetValue(keys.GetValue(b), a);
+                        keys.SetValue(key, b);
+                        if (items != null)
+                        {
+                            Object item = items.GetValue(a);
+                            items.SetValue(items.GetValue(b), a);
+                            items.SetValue(item, b);
+                        }
+                    }
+                }
+            }
+
+            private void Swap(int i, int j)
+            {
+                Object t1 = keys.GetValue(i);
+                keys.SetValue(keys.GetValue(j), i);
+                keys.SetValue(t1, j);
+
+                if (items != null)
+                {
+                    Object t2 = items.GetValue(i);
+                    items.SetValue(items.GetValue(j), i);
+                    items.SetValue(t2, j);
+                }
+            }
+
+            internal void Sort(int left, int length)
+            {
+                IntrospectiveSort(left, length);
+            }
+
+            private void IntrospectiveSort(int left, int length)
+            {
+                if (length < 2)
+                    return;
+
+                try
+                {
+                    IntroSort(left, length + left - 1, 2 * IntrospectiveSortUtilities.FloorLog2PlusOne(length));
+                }
+                catch (IndexOutOfRangeException)
+                {
+                    IntrospectiveSortUtilities.ThrowOrIgnoreBadComparer(comparer);
+                }
+                catch (Exception e)
+                {
+                    ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_IComparerFailed, e);
+                }
+            }
+
+            private void IntroSort(int lo, int hi, int depthLimit)
+            {
+                while (hi > lo)
+                {
+                    int partitionSize = hi - lo + 1;
+                    if (partitionSize <= IntrospectiveSortUtilities.IntrosortSizeThreshold)
+                    {
+                        if (partitionSize == 1)
+                        {
+                            return;
+                        }
+                        if (partitionSize == 2)
+                        {
+                            SwapIfGreaterWithItems(lo, hi);
+                            return;
+                        }
+                        if (partitionSize == 3)
+                        {
+                            SwapIfGreaterWithItems(lo, hi - 1);
+                            SwapIfGreaterWithItems(lo, hi);
+                            SwapIfGreaterWithItems(hi - 1, hi);
+                            return;
+                        }
+
+                        InsertionSort(lo, hi);
+                        return;
+                    }
+
+                    if (depthLimit == 0)
+                    {
+                        Heapsort(lo, hi);
+                        return;
+                    }
+                    depthLimit--;
+
+                    int p = PickPivotAndPartition(lo, hi);
+                    IntroSort(p + 1, hi, depthLimit);
+                    hi = p - 1;
+                }
+            }
+
+            private int PickPivotAndPartition(int lo, int hi)
+            {
+                // Compute median-of-three.  But also partition them, since we've done the comparison.
+                int mid = lo + (hi - lo) / 2;
+
+                SwapIfGreaterWithItems(lo, mid);
+                SwapIfGreaterWithItems(lo, hi);
+                SwapIfGreaterWithItems(mid, hi);
+
+                Object pivot = keys.GetValue(mid);
+                Swap(mid, hi - 1);
+                int left = lo, right = hi - 1;  // We already partitioned lo and hi and put the pivot in hi - 1.  And we pre-increment & decrement below.
+
+                while (left < right)
+                {
+                    while (comparer.Compare(keys.GetValue(++left), pivot) < 0) ;
+                    while (comparer.Compare(pivot, keys.GetValue(--right)) < 0) ;
+
+                    if (left >= right)
+                        break;
+
+                    Swap(left, right);
+                }
+
+                // Put pivot in the right location.
+                Swap(left, (hi - 1));
+                return left;
+            }
+
+            private void Heapsort(int lo, int hi)
+            {
+                int n = hi - lo + 1;
+                for (int i = n / 2; i >= 1; i = i - 1)
+                {
+                    DownHeap(i, n, lo);
+                }
+                for (int i = n; i > 1; i = i - 1)
+                {
+                    Swap(lo, lo + i - 1);
+
+                    DownHeap(1, i - 1, lo);
+                }
+            }
+
+            private void DownHeap(int i, int n, int lo)
+            {
+                Object d = keys.GetValue(lo + i - 1);
+                Object dt = (items != null) ? items.GetValue(lo + i - 1) : null;
+                int child;
+                while (i <= n / 2)
+                {
+                    child = 2 * i;
+                    if (child < n && comparer.Compare(keys.GetValue(lo + child - 1), keys.GetValue(lo + child)) < 0)
+                    {
+                        child++;
+                    }
+
+                    if (!(comparer.Compare(d, keys.GetValue(lo + child - 1)) < 0))
+                        break;
+
+                    keys.SetValue(keys.GetValue(lo + child - 1), lo + i - 1);
+                    if (items != null)
+                        items.SetValue(items.GetValue(lo + child - 1), lo + i - 1);
+                    i = child;
+                }
+                keys.SetValue(d, lo + i - 1);
+                if (items != null)
+                    items.SetValue(dt, lo + i - 1);
+            }
+
+            private void InsertionSort(int lo, int hi)
+            {
+                int i, j;
+                Object t, dt;
+                for (i = lo; i < hi; i++)
+                {
+                    j = i;
+                    t = keys.GetValue(i + 1);
+                    dt = (items != null) ? items.GetValue(i + 1) : null;
+
+                    while (j >= lo && comparer.Compare(t, keys.GetValue(j)) < 0)
+                    {
+                        keys.SetValue(keys.GetValue(j), j + 1);
+                        if (items != null)
+                            items.SetValue(items.GetValue(j), j + 1);
+                        j--;
+                    }
+
+                    keys.SetValue(t, j + 1);
+                    if (items != null)
+                        items.SetValue(dt, j + 1);
+                }
+            }
+        }
+
+        private sealed class SZArrayEnumerator : IEnumerator, ICloneable
+        {
+            private readonly Array _array;
+            private int _index;
+            private int _endIndex; // Cache Array.Length, since it's a little slow.
+
+            internal SZArrayEnumerator(Array array)
+            {
+                Debug.Assert(array.Rank == 1 && array.GetLowerBound(0) == 0, "SZArrayEnumerator only works on single dimension arrays w/ a lower bound of zero.");
+
+                _array = array;
+                _index = -1;
+                _endIndex = array.Length;
+            }
+
+            public Object Clone()
+            {
+                return MemberwiseClone();
+            }
+
+            public bool MoveNext()
+            {
+                if (_index < _endIndex)
+                {
+                    _index++;
+                    return (_index < _endIndex);
+                }
+                return false;
+            }
+
+            public Object Current
+            {
+                get
+                {
+                    if (_index < 0) ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumNotStarted();
+                    if (_index >= _endIndex) ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumEnded();
+                    return _array.GetValue(_index);
+                }
+            }
+
+            public void Reset()
+            {
+                _index = -1;
+            }
+        }
+
+        private sealed class ArrayEnumerator : IEnumerator, ICloneable
+        {
+            private Array array;
+            private int index;
+            private int endIndex;
+            private int startIndex;    // Save for Reset.
+            private int[] _indices;    // The current position in a multidim array
+            private bool _complete;
+
+            internal ArrayEnumerator(Array array, int index, int count)
+            {
+                this.array = array;
+                this.index = index - 1;
+                startIndex = index;
+                endIndex = index + count;
+                _indices = new int[array.Rank];
+                int checkForZero = 1;  // Check for dimensions of size 0.
+                for (int i = 0; i < array.Rank; i++)
+                {
+                    _indices[i] = array.GetLowerBound(i);
+                    checkForZero *= array.GetLength(i);
+                }
+                // To make MoveNext simpler, decrement least significant index.
+                _indices[_indices.Length - 1]--;
+                _complete = (checkForZero == 0);
+            }
+
+            private void IncArray()
+            {
+                // This method advances us to the next valid array index,
+                // handling all the multiple dimension & bounds correctly.
+                // Think of it like an odometer in your car - we start with
+                // the last digit, increment it, and check for rollover.  If
+                // it rolls over, we set all digits to the right and including 
+                // the current to the appropriate lower bound.  Do these overflow
+                // checks for each dimension, and if the most significant digit 
+                // has rolled over it's upper bound, we're done.
+                //
+                int rank = array.Rank;
+                _indices[rank - 1]++;
+                for (int dim = rank - 1; dim >= 0; dim--)
+                {
+                    if (_indices[dim] > array.GetUpperBound(dim))
+                    {
+                        if (dim == 0)
+                        {
+                            _complete = true;
+                            break;
+                        }
+                        for (int j = dim; j < rank; j++)
+                            _indices[j] = array.GetLowerBound(j);
+                        _indices[dim - 1]++;
+                    }
+                }
+            }
+
+            public Object Clone()
+            {
+                return MemberwiseClone();
+            }
+
+            public bool MoveNext()
+            {
+                if (_complete)
+                {
+                    index = endIndex;
+                    return false;
+                }
+                index++;
+                IncArray();
+                return !_complete;
+            }
+
+            public Object Current
+            {
+                get
+                {
+                    if (index < startIndex) ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumNotStarted();
+                    if (_complete) ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumEnded();
+                    return array.GetValue(_indices);
+                }
+            }
+
+            public void Reset()
+            {
+                index = startIndex - 1;
+                int checkForZero = 1;
+                for (int i = 0; i < array.Rank; i++)
+                {
+                    _indices[i] = array.GetLowerBound(i);
+                    checkForZero *= array.GetLength(i);
+                }
+                _complete = (checkForZero == 0);
+                // To make MoveNext simpler, decrement least significant index.
+                _indices[_indices.Length - 1]--;
+            }
+        }
+
+
+        // if this is an array of value classes and that value class has a default constructor 
+        // then this calls this default constructor on every element in the value class array.
+        // otherwise this is a no-op.  Generally this method is called automatically by the compiler
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern void Initialize();
+    }
+
+
+
+
+
+
+
+    //----------------------------------------------------------------------------------------
+    // ! READ THIS BEFORE YOU WORK ON THIS CLASS.
+    // 
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not SZArrayHelper objects. Rather, they are of type U[]
+    // where U[] is castable to T[]. No actual SZArrayHelper object is ever instantiated. Thus, you will
+    // see a lot of expressions that cast "this" "T[]". 
+    //
+    // This class is needed to allow an SZ array of type T[] to expose IList<T>,
+    // IList<T.BaseType>, etc., etc. all the way up to IList<Object>. When the following call is
+    // made:
+    //
+    //   ((IList<T>) (new U[n])).SomeIListMethod()
+    //
+    // the interface stub dispatcher treats this as a special case, loads up SZArrayHelper,
+    // finds the corresponding generic method (matched simply by method name), instantiates
+    // it for type <T> and executes it. 
+    //
+    // The "T" will reflect the interface used to invoke the method. The actual runtime "this" will be
+    // array that is castable to "T[]" (i.e. for primitivs and valuetypes, it will be exactly
+    // "T[]" - for orefs, it may be a "U[]" where U derives from T.)
+    //----------------------------------------------------------------------------------------
+    internal sealed class SZArrayHelper
+    {
+        // It is never legal to instantiate this class.
+        private SZArrayHelper()
+        {
+            Debug.Fail("Hey! How'd I get here?");
+        }
+
+        // -----------------------------------------------------------
+        // ------- Implement IEnumerable<T> interface methods --------
+        // -----------------------------------------------------------
+        internal IEnumerator<T> GetEnumerator<T>()
+        {
+            //! Warning: "this" is an array, not an SZArrayHelper. See comments above
+            //! or you may introduce a security hole!
+            T[] _this = Unsafe.As<T[]>(this);
+            return _this.Length == 0 ? SZGenericArrayEnumerator<T>.Empty : new SZGenericArrayEnumerator<T>(_this);
+        }
+
+        // -----------------------------------------------------------
+        // ------- Implement ICollection<T> interface methods --------
+        // -----------------------------------------------------------
+        private void CopyTo<T>(T[] array, int index)
+        {
+            //! Warning: "this" is an array, not an SZArrayHelper. See comments above
+            //! or you may introduce a security hole!
+
+            T[] _this = Unsafe.As<T[]>(this);
+            Array.Copy(_this, 0, array, index, _this.Length);
+        }
+
+        internal int get_Count<T>()
+        {
+            //! Warning: "this" is an array, not an SZArrayHelper. See comments above
+            //! or you may introduce a security hole!
+            T[] _this = Unsafe.As<T[]>(this);
+            return _this.Length;
+        }
+
+        // -----------------------------------------------------------
+        // ---------- Implement IList<T> interface methods -----------
+        // -----------------------------------------------------------
+        internal T get_Item<T>(int index)
+        {
+            //! Warning: "this" is an array, not an SZArrayHelper. See comments above
+            //! or you may introduce a security hole!
+            T[] _this = Unsafe.As<T[]>(this);
+            if ((uint)index >= (uint)_this.Length)
+            {
+                ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+            }
+
+            return _this[index];
+        }
+
+        internal void set_Item<T>(int index, T value)
+        {
+            //! Warning: "this" is an array, not an SZArrayHelper. See comments above
+            //! or you may introduce a security hole!
+            T[] _this = Unsafe.As<T[]>(this);
+            if ((uint)index >= (uint)_this.Length)
+            {
+                ThrowHelper.ThrowArgumentOutOfRange_IndexException();
+            }
+
+            _this[index] = value;
+        }
+
+        private void Add<T>(T value)
+        {
+            // Not meaningful for arrays.
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_FixedSizeCollection);
+        }
+
+        private bool Contains<T>(T value)
+        {
+            //! Warning: "this" is an array, not an SZArrayHelper. See comments above
+            //! or you may introduce a security hole!
+            T[] _this = Unsafe.As<T[]>(this);
+            return Array.IndexOf(_this, value, 0, _this.Length) >= 0;
+        }
+
+        private bool get_IsReadOnly<T>()
+        {
+            return true;
+        }
+
+        private void Clear<T>()
+        {
+            //! Warning: "this" is an array, not an SZArrayHelper. See comments above
+            //! or you may introduce a security hole!
+
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+
+        private int IndexOf<T>(T value)
+        {
+            //! Warning: "this" is an array, not an SZArrayHelper. See comments above
+            //! or you may introduce a security hole!
+            T[] _this = Unsafe.As<T[]>(this);
+            return Array.IndexOf(_this, value, 0, _this.Length);
+        }
+
+        private void Insert<T>(int index, T value)
+        {
+            // Not meaningful for arrays
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_FixedSizeCollection);
+        }
+
+        private bool Remove<T>(T value)
+        {
+            // Not meaningful for arrays
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_FixedSizeCollection);
+            return default(bool);
+        }
+
+        private void RemoveAt<T>(int index)
+        {
+            // Not meaningful for arrays
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_FixedSizeCollection);
+        }
+
+        // This is a normal generic Enumerator for SZ arrays. It doesn't have any of the "this" stuff
+        // that SZArrayHelper does.
+        //
+        private sealed class SZGenericArrayEnumerator<T> : IEnumerator<T>
+        {
+            private readonly T[] _array;
+            private int _index;
+
+            // Array.Empty is intentionally omitted here, since we don't want to pay for generic instantiations that
+            // wouldn't have otherwise been used.
+            internal static readonly SZGenericArrayEnumerator<T> Empty = new SZGenericArrayEnumerator<T>(new T[0]);
+
+            internal SZGenericArrayEnumerator(T[] array)
+            {
+                Debug.Assert(array != null);
+
+                _array = array;
+                _index = -1;
+            }
+
+            public bool MoveNext()
+            {
+                int index = _index + 1;
+                bool result = index < _array.Length;
+                
+                if (result)
+                {
+                    _index = index;
+                }
+
+                return result;
+            }
+    
+            public T Current
+            {
+                get
+                {
+                    int index = _index;
+                    T[] array = _array;
+
+                    if ((uint)index >= (uint)array.Length)
+                    {
+                        ThrowHelper.ThrowInvalidOperationException_EnumCurrent(index);
+                    }
+
+                    return array[index];
+                }
+            }
+    
+            object IEnumerator.Current => Current;
+
+            void IEnumerator.Reset() => _index = -1;
+
+            public void Dispose()
+            {
+            }
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Attribute.cs b/src/System.Private.CoreLib/src/System/Attribute.cs
new file mode 100644
index 0000000000..5934284c0f
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Attribute.cs
@@ -0,0 +1,944 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+
+using System;
+using System.Reflection;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using System.Globalization;
+using System.Diagnostics;
+using System.Security;
+
+namespace System
+{
+    [Serializable]
+    [AttributeUsageAttribute(AttributeTargets.All, Inherited = true, AllowMultiple = false)]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public abstract class Attribute
+    {
+        #region Private Statics
+
+        #region PropertyInfo
+        private static Attribute[] InternalGetCustomAttributes(PropertyInfo element, Type type, bool inherit)
+        {
+            Debug.Assert(element != null);
+            Debug.Assert(type != null);
+            Debug.Assert(type.IsSubclassOf(typeof(Attribute)) || type == typeof(Attribute));
+
+            // walk up the hierarchy chain
+            Attribute[] attributes = (Attribute[])element.GetCustomAttributes(type, inherit);
+
+            if (!inherit)
+                return attributes;
+
+            // create the hashtable that keeps track of inherited types
+            Dictionary<Type, AttributeUsageAttribute> types = new Dictionary<Type, AttributeUsageAttribute>(11);
+
+            // create an array list to collect all the requested attibutes
+            List<Attribute> attributeList = new List<Attribute>();
+            CopyToArrayList(attributeList, attributes, types);
+
+            //if this is an index we need to get the parameter types to help disambiguate
+            Type[] indexParamTypes = GetIndexParameterTypes(element);
+
+
+            PropertyInfo baseProp = GetParentDefinition(element, indexParamTypes);
+            while (baseProp != null)
+            {
+                attributes = GetCustomAttributes(baseProp, type, false);
+                AddAttributesToList(attributeList, attributes, types);
+                baseProp = GetParentDefinition(baseProp, indexParamTypes);
+            }
+            Array array = CreateAttributeArrayHelper(type, attributeList.Count);
+            Array.Copy(attributeList.ToArray(), 0, array, 0, attributeList.Count);
+            return (Attribute[])array;
+        }
+
+        private static bool InternalIsDefined(PropertyInfo element, Type attributeType, bool inherit)
+        {
+            // walk up the hierarchy chain
+            if (element.IsDefined(attributeType, inherit))
+                return true;
+
+            if (inherit)
+            {
+                AttributeUsageAttribute usage = InternalGetAttributeUsage(attributeType);
+
+                if (!usage.Inherited)
+                    return false;
+
+                //if this is an index we need to get the parameter types to help disambiguate
+                Type[] indexParamTypes = GetIndexParameterTypes(element);
+
+                PropertyInfo baseProp = GetParentDefinition(element, indexParamTypes);
+
+                while (baseProp != null)
+                {
+                    if (baseProp.IsDefined(attributeType, false))
+                        return true;
+
+                    baseProp = GetParentDefinition(baseProp, indexParamTypes);
+                }
+            }
+
+            return false;
+        }
+
+        private static PropertyInfo GetParentDefinition(PropertyInfo property, Type[] propertyParameters)
+        {
+            Debug.Assert(property != null);
+
+            // for the current property get the base class of the getter and the setter, they might be different
+            // note that this only works for RuntimeMethodInfo
+            MethodInfo propAccessor = property.GetGetMethod(true);
+
+            if (propAccessor == null)
+                propAccessor = property.GetSetMethod(true);
+
+            RuntimeMethodInfo rtPropAccessor = propAccessor as RuntimeMethodInfo;
+
+            if (rtPropAccessor != null)
+            {
+                rtPropAccessor = rtPropAccessor.GetParentDefinition();
+
+                if (rtPropAccessor != null)
+                {
+                    // There is a public overload of Type.GetProperty that takes both a BingingFlags enum and a return type.
+                    // However, we cannot use that because it doesn't accept null for "types".
+                    return rtPropAccessor.DeclaringType.GetProperty(
+                        property.Name,
+                        BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.DeclaredOnly,
+                        null, //will use default binder
+                        property.PropertyType,
+                        propertyParameters, //used for index properties
+                        null);
+                }
+            }
+
+            return null;
+        }
+
+        #endregion
+
+        #region EventInfo
+        private static Attribute[] InternalGetCustomAttributes(EventInfo element, Type type, bool inherit)
+        {
+            Debug.Assert(element != null);
+            Debug.Assert(type != null);
+            Debug.Assert(type.IsSubclassOf(typeof(Attribute)) || type == typeof(Attribute));
+
+            // walk up the hierarchy chain
+            Attribute[] attributes = (Attribute[])element.GetCustomAttributes(type, inherit);
+            if (inherit)
+            {
+                // create the hashtable that keeps track of inherited types
+                Dictionary<Type, AttributeUsageAttribute> types = new Dictionary<Type, AttributeUsageAttribute>(11);
+                // create an array list to collect all the requested attibutes
+                List<Attribute> attributeList = new List<Attribute>();
+                CopyToArrayList(attributeList, attributes, types);
+
+                EventInfo baseEvent = GetParentDefinition(element);
+                while (baseEvent != null)
+                {
+                    attributes = GetCustomAttributes(baseEvent, type, false);
+                    AddAttributesToList(attributeList, attributes, types);
+                    baseEvent = GetParentDefinition(baseEvent);
+                }
+                Array array = CreateAttributeArrayHelper(type, attributeList.Count);
+                Array.Copy(attributeList.ToArray(), 0, array, 0, attributeList.Count);
+                return (Attribute[])array;
+            }
+            else
+                return attributes;
+        }
+
+        private static EventInfo GetParentDefinition(EventInfo ev)
+        {
+            Debug.Assert(ev != null);
+
+            // note that this only works for RuntimeMethodInfo
+            MethodInfo add = ev.GetAddMethod(true);
+
+            RuntimeMethodInfo rtAdd = add as RuntimeMethodInfo;
+
+            if (rtAdd != null)
+            {
+                rtAdd = rtAdd.GetParentDefinition();
+                if (rtAdd != null)
+                    return rtAdd.DeclaringType.GetEvent(ev.Name);
+            }
+            return null;
+        }
+
+        private static bool InternalIsDefined(EventInfo element, Type attributeType, bool inherit)
+        {
+            Debug.Assert(element != null);
+
+            // walk up the hierarchy chain
+            if (element.IsDefined(attributeType, inherit))
+                return true;
+
+            if (inherit)
+            {
+                AttributeUsageAttribute usage = InternalGetAttributeUsage(attributeType);
+
+                if (!usage.Inherited)
+                    return false;
+
+                EventInfo baseEvent = GetParentDefinition(element);
+
+                while (baseEvent != null)
+                {
+                    if (baseEvent.IsDefined(attributeType, false))
+                        return true;
+                    baseEvent = GetParentDefinition(baseEvent);
+                }
+            }
+
+            return false;
+        }
+
+        #endregion
+
+        #region ParameterInfo
+        private static ParameterInfo GetParentDefinition(ParameterInfo param)
+        {
+            Debug.Assert(param != null);
+
+            // note that this only works for RuntimeMethodInfo
+            RuntimeMethodInfo rtMethod = param.Member as RuntimeMethodInfo;
+
+            if (rtMethod != null)
+            {
+                rtMethod = rtMethod.GetParentDefinition();
+
+                if (rtMethod != null)
+                {
+                    // Find the ParameterInfo on this method
+                    int position = param.Position;
+                    if (position == -1)
+                    {
+                        return rtMethod.ReturnParameter;
+                    }
+                    else
+                    {
+                        ParameterInfo[] parameters = rtMethod.GetParameters();
+                        return parameters[position]; // Point to the correct ParameterInfo of the method
+                    }
+                }
+            }
+            return null;
+        }
+
+        private static Attribute[] InternalParamGetCustomAttributes(ParameterInfo param, Type type, bool inherit)
+        {
+            Debug.Assert(param != null);
+
+            // For ParameterInfo's we need to make sure that we chain through all the MethodInfo's in the inheritance chain that
+            // have this ParameterInfo defined. .We pick up all the CustomAttributes for the starting ParameterInfo. We need to pick up only attributes 
+            // that are marked inherited from the remainder of the MethodInfo's in the inheritance chain.
+            // For MethodInfo's on an interface we do not do an inheritance walk so the default ParameterInfo attributes are returned.
+            // For MethodInfo's on a class we walk up the inheritance chain but do not look at the MethodInfo's on the interfaces that the
+            // class inherits from and return the respective ParameterInfo attributes
+
+            List<Type> disAllowMultiple = new List<Type>();
+            Object[] objAttr;
+
+            if (type == null)
+                type = typeof(Attribute);
+
+            objAttr = param.GetCustomAttributes(type, false);
+
+            for (int i = 0; i < objAttr.Length; i++)
+            {
+                Type objType = objAttr[i].GetType();
+                AttributeUsageAttribute attribUsage = InternalGetAttributeUsage(objType);
+                if (attribUsage.AllowMultiple == false)
+                    disAllowMultiple.Add(objType);
+            }
+
+            // Get all the attributes that have Attribute as the base class
+            Attribute[] ret = null;
+            if (objAttr.Length == 0)
+                ret = CreateAttributeArrayHelper(type, 0);
+            else
+                ret = (Attribute[])objAttr;
+
+            if (param.Member.DeclaringType == null) // This is an interface so we are done.
+                return ret;
+
+            if (!inherit)
+                return ret;
+
+            ParameterInfo baseParam = GetParentDefinition(param);
+
+            while (baseParam != null)
+            {
+                objAttr = baseParam.GetCustomAttributes(type, false);
+
+                int count = 0;
+                for (int i = 0; i < objAttr.Length; i++)
+                {
+                    Type objType = objAttr[i].GetType();
+                    AttributeUsageAttribute attribUsage = InternalGetAttributeUsage(objType);
+
+                    if ((attribUsage.Inherited) && (disAllowMultiple.Contains(objType) == false))
+                    {
+                        if (attribUsage.AllowMultiple == false)
+                            disAllowMultiple.Add(objType);
+                        count++;
+                    }
+                    else
+                        objAttr[i] = null;
+                }
+
+                // Get all the attributes that have Attribute as the base class
+                Attribute[] attributes = CreateAttributeArrayHelper(type, count);
+
+                count = 0;
+                for (int i = 0; i < objAttr.Length; i++)
+                {
+                    if (objAttr[i] != null)
+                    {
+                        attributes[count] = (Attribute)objAttr[i];
+                        count++;
+                    }
+                }
+
+                Attribute[] temp = ret;
+                ret = CreateAttributeArrayHelper(type, temp.Length + count);
+                Array.Copy(temp, ret, temp.Length);
+
+                int offset = temp.Length;
+
+                for (int i = 0; i < attributes.Length; i++)
+                    ret[offset + i] = attributes[i];
+
+                baseParam = GetParentDefinition(baseParam);
+            }
+
+            return ret;
+        }
+
+        private static bool InternalParamIsDefined(ParameterInfo param, Type type, bool inherit)
+        {
+            Debug.Assert(param != null);
+            Debug.Assert(type != null);
+
+            // For ParameterInfo's we need to make sure that we chain through all the MethodInfo's in the inheritance chain.
+            // We pick up all the CustomAttributes for the starting ParameterInfo. We need to pick up only attributes 
+            // that are marked inherited from the remainder of the ParameterInfo's in the inheritance chain.
+            // For MethodInfo's on an interface we do not do an inheritance walk. For ParameterInfo's on a
+            // Class we walk up the inheritance chain but do not look at the MethodInfo's on the interfaces that the class inherits from.
+
+            if (param.IsDefined(type, false))
+                return true;
+
+            if (param.Member.DeclaringType == null || !inherit) // This is an interface so we are done.
+                return false;
+
+            ParameterInfo baseParam = GetParentDefinition(param);
+
+            while (baseParam != null)
+            {
+                Object[] objAttr = baseParam.GetCustomAttributes(type, false);
+
+                for (int i = 0; i < objAttr.Length; i++)
+                {
+                    Type objType = objAttr[i].GetType();
+                    AttributeUsageAttribute attribUsage = InternalGetAttributeUsage(objType);
+
+                    if ((objAttr[i] is Attribute) && (attribUsage.Inherited))
+                        return true;
+                }
+
+                baseParam = GetParentDefinition(baseParam);
+            }
+
+            return false;
+        }
+
+        #endregion
+
+        #region Utility
+        private static void CopyToArrayList(List<Attribute> attributeList, Attribute[] attributes, Dictionary<Type, AttributeUsageAttribute> types)
+        {
+            for (int i = 0; i < attributes.Length; i++)
+            {
+                attributeList.Add(attributes[i]);
+
+                Type attrType = attributes[i].GetType();
+
+                if (!types.ContainsKey(attrType))
+                    types[attrType] = InternalGetAttributeUsage(attrType);
+            }
+        }
+
+        private static Type[] GetIndexParameterTypes(PropertyInfo element)
+        {
+            ParameterInfo[] indexParams = element.GetIndexParameters();
+
+            if (indexParams.Length > 0)
+            {
+                Type[] indexParamTypes = new Type[indexParams.Length];
+                for (int i = 0; i < indexParams.Length; i++)
+                {
+                    indexParamTypes[i] = indexParams[i].ParameterType;
+                }
+                return indexParamTypes;
+            }
+
+            return Array.Empty<Type>();
+        }
+
+        private static void AddAttributesToList(List<Attribute> attributeList, Attribute[] attributes, Dictionary<Type, AttributeUsageAttribute> types)
+        {
+            for (int i = 0; i < attributes.Length; i++)
+            {
+                Type attrType = attributes[i].GetType();
+                AttributeUsageAttribute usage = null;
+                types.TryGetValue(attrType, out usage);
+
+                if (usage == null)
+                {
+                    // the type has never been seen before if it's inheritable add it to the list
+                    usage = InternalGetAttributeUsage(attrType);
+                    types[attrType] = usage;
+
+                    if (usage.Inherited)
+                        attributeList.Add(attributes[i]);
+                }
+                else if (usage.Inherited && usage.AllowMultiple)
+                {
+                    // we saw this type already add it only if it is inheritable and it does allow multiple 
+                    attributeList.Add(attributes[i]);
+                }
+            }
+        }
+
+        private static AttributeUsageAttribute InternalGetAttributeUsage(Type type)
+        {
+            // Check if the custom attributes is Inheritable
+            Object[] obj = type.GetCustomAttributes(typeof(AttributeUsageAttribute), false);
+
+            if (obj.Length == 1)
+                return (AttributeUsageAttribute)obj[0];
+
+            if (obj.Length == 0)
+                return AttributeUsageAttribute.Default;
+
+            throw new FormatException(
+                SR.Format(SR.Format_AttributeUsage, type));
+        }
+
+        private static Attribute[] CreateAttributeArrayHelper(Type elementType, int elementCount)
+        {
+            return (Attribute[])Array.UnsafeCreateInstance(elementType, elementCount);
+        }
+        #endregion
+
+        #endregion
+
+        #region Public Statics
+
+        #region MemberInfo
+        public static Attribute[] GetCustomAttributes(MemberInfo element, Type type)
+        {
+            return GetCustomAttributes(element, type, true);
+        }
+
+        public static Attribute[] GetCustomAttributes(MemberInfo element, Type type, bool inherit)
+        {
+            if (element == null)
+                throw new ArgumentNullException(nameof(element));
+
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+
+            if (!type.IsSubclassOf(typeof(Attribute)) && type != typeof(Attribute))
+                throw new ArgumentException(SR.Argument_MustHaveAttributeBaseClass);
+
+            switch (element.MemberType)
+            {
+                case MemberTypes.Property:
+                    return InternalGetCustomAttributes((PropertyInfo)element, type, inherit);
+
+                case MemberTypes.Event:
+                    return InternalGetCustomAttributes((EventInfo)element, type, inherit);
+
+                default:
+                    return element.GetCustomAttributes(type, inherit) as Attribute[];
+            }
+        }
+
+        public static Attribute[] GetCustomAttributes(MemberInfo element)
+        {
+            return GetCustomAttributes(element, true);
+        }
+
+        public static Attribute[] GetCustomAttributes(MemberInfo element, bool inherit)
+        {
+            if (element == null)
+                throw new ArgumentNullException(nameof(element));
+
+            switch (element.MemberType)
+            {
+                case MemberTypes.Property:
+                    return InternalGetCustomAttributes((PropertyInfo)element, typeof(Attribute), inherit);
+
+                case MemberTypes.Event:
+                    return InternalGetCustomAttributes((EventInfo)element, typeof(Attribute), inherit);
+
+                default:
+                    return element.GetCustomAttributes(typeof(Attribute), inherit) as Attribute[];
+            }
+        }
+
+        public static bool IsDefined(MemberInfo element, Type attributeType)
+        {
+            return IsDefined(element, attributeType, true);
+        }
+
+        public static bool IsDefined(MemberInfo element, Type attributeType, bool inherit)
+        {
+            // Returns true if a custom attribute subclass of attributeType class/interface with inheritance walk
+            if (element == null)
+                throw new ArgumentNullException(nameof(element));
+
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            if (!attributeType.IsSubclassOf(typeof(Attribute)) && attributeType != typeof(Attribute))
+                throw new ArgumentException(SR.Argument_MustHaveAttributeBaseClass);
+
+            switch (element.MemberType)
+            {
+                case MemberTypes.Property:
+                    return InternalIsDefined((PropertyInfo)element, attributeType, inherit);
+
+                case MemberTypes.Event:
+                    return InternalIsDefined((EventInfo)element, attributeType, inherit);
+
+                default:
+                    return element.IsDefined(attributeType, inherit);
+            }
+        }
+
+        public static Attribute GetCustomAttribute(MemberInfo element, Type attributeType)
+        {
+            return GetCustomAttribute(element, attributeType, true);
+        }
+
+        public static Attribute GetCustomAttribute(MemberInfo element, Type attributeType, bool inherit)
+        {
+            Attribute[] attrib = GetCustomAttributes(element, attributeType, inherit);
+
+            if (attrib == null || attrib.Length == 0)
+                return null;
+
+            if (attrib.Length == 1)
+                return attrib[0];
+
+            throw new AmbiguousMatchException(SR.RFLCT_AmbigCust);
+        }
+
+        #endregion
+
+        #region ParameterInfo
+        public static Attribute[] GetCustomAttributes(ParameterInfo element)
+        {
+            return GetCustomAttributes(element, true);
+        }
+
+        public static Attribute[] GetCustomAttributes(ParameterInfo element, Type attributeType)
+        {
+            return (Attribute[])GetCustomAttributes(element, attributeType, true);
+        }
+
+        public static Attribute[] GetCustomAttributes(ParameterInfo element, Type attributeType, bool inherit)
+        {
+            if (element == null)
+                throw new ArgumentNullException(nameof(element));
+
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            if (!attributeType.IsSubclassOf(typeof(Attribute)) && attributeType != typeof(Attribute))
+                throw new ArgumentException(SR.Argument_MustHaveAttributeBaseClass);
+
+            if (element.Member == null)
+                throw new ArgumentException(SR.Argument_InvalidParameterInfo, nameof(element));
+
+
+            MemberInfo member = element.Member;
+            if (member.MemberType == MemberTypes.Method && inherit)
+                return InternalParamGetCustomAttributes(element, attributeType, inherit) as Attribute[];
+
+            return element.GetCustomAttributes(attributeType, inherit) as Attribute[];
+        }
+
+        public static Attribute[] GetCustomAttributes(ParameterInfo element, bool inherit)
+        {
+            if (element == null)
+                throw new ArgumentNullException(nameof(element));
+
+            if (element.Member == null)
+                throw new ArgumentException(SR.Argument_InvalidParameterInfo, nameof(element));
+
+
+            MemberInfo member = element.Member;
+            if (member.MemberType == MemberTypes.Method && inherit)
+                return InternalParamGetCustomAttributes(element, null, inherit) as Attribute[];
+
+            return element.GetCustomAttributes(typeof(Attribute), inherit) as Attribute[];
+        }
+
+        public static bool IsDefined(ParameterInfo element, Type attributeType)
+        {
+            return IsDefined(element, attributeType, true);
+        }
+
+        public static bool IsDefined(ParameterInfo element, Type attributeType, bool inherit)
+        {
+            // Returns true is a custom attribute subclass of attributeType class/interface with inheritance walk
+            if (element == null)
+                throw new ArgumentNullException(nameof(element));
+
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            if (!attributeType.IsSubclassOf(typeof(Attribute)) && attributeType != typeof(Attribute))
+                throw new ArgumentException(SR.Argument_MustHaveAttributeBaseClass);
+
+            MemberInfo member = element.Member;
+
+            switch (member.MemberType)
+            {
+                case MemberTypes.Method: // We need to climb up the member hierarchy            
+                    return InternalParamIsDefined(element, attributeType, inherit);
+
+                case MemberTypes.Constructor:
+                    return element.IsDefined(attributeType, false);
+
+                case MemberTypes.Property:
+                    return element.IsDefined(attributeType, false);
+
+                default:
+                    Debug.Fail("Invalid type for ParameterInfo member in Attribute class");
+                    throw new ArgumentException(SR.Argument_InvalidParamInfo);
+            }
+        }
+
+        public static Attribute GetCustomAttribute(ParameterInfo element, Type attributeType)
+        {
+            return GetCustomAttribute(element, attributeType, true);
+        }
+
+        public static Attribute GetCustomAttribute(ParameterInfo element, Type attributeType, bool inherit)
+        {
+            // Returns an Attribute of base class/inteface attributeType on the ParameterInfo or null if none exists.
+            // throws an AmbiguousMatchException if there are more than one defined.
+            Attribute[] attrib = GetCustomAttributes(element, attributeType, inherit);
+
+            if (attrib == null || attrib.Length == 0)
+                return null;
+
+            if (attrib.Length == 0)
+                return null;
+
+            if (attrib.Length == 1)
+                return attrib[0];
+
+            throw new AmbiguousMatchException(SR.RFLCT_AmbigCust);
+        }
+
+        #endregion
+
+        #region Module
+        public static Attribute[] GetCustomAttributes(Module element, Type attributeType)
+        {
+            return GetCustomAttributes(element, attributeType, true);
+        }
+
+        public static Attribute[] GetCustomAttributes(Module element)
+        {
+            return GetCustomAttributes(element, true);
+        }
+
+        public static Attribute[] GetCustomAttributes(Module element, bool inherit)
+        {
+            if (element == null)
+                throw new ArgumentNullException(nameof(element));
+
+            return (Attribute[])element.GetCustomAttributes(typeof(Attribute), inherit);
+        }
+
+        public static Attribute[] GetCustomAttributes(Module element, Type attributeType, bool inherit)
+        {
+            if (element == null)
+                throw new ArgumentNullException(nameof(element));
+
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            if (!attributeType.IsSubclassOf(typeof(Attribute)) && attributeType != typeof(Attribute))
+                throw new ArgumentException(SR.Argument_MustHaveAttributeBaseClass);
+
+            return (Attribute[])element.GetCustomAttributes(attributeType, inherit);
+        }
+
+        public static bool IsDefined(Module element, Type attributeType)
+        {
+            return IsDefined(element, attributeType, false);
+        }
+
+        public static bool IsDefined(Module element, Type attributeType, bool inherit)
+        {
+            // Returns true is a custom attribute subclass of attributeType class/interface with no inheritance walk
+            if (element == null)
+                throw new ArgumentNullException(nameof(element));
+
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            if (!attributeType.IsSubclassOf(typeof(Attribute)) && attributeType != typeof(Attribute))
+                throw new ArgumentException(SR.Argument_MustHaveAttributeBaseClass);
+
+            return element.IsDefined(attributeType, false);
+        }
+
+        public static Attribute GetCustomAttribute(Module element, Type attributeType)
+        {
+            return GetCustomAttribute(element, attributeType, true);
+        }
+
+        public static Attribute GetCustomAttribute(Module element, Type attributeType, bool inherit)
+        {
+            // Returns an Attribute of base class/inteface attributeType on the Module or null if none exists.
+            // throws an AmbiguousMatchException if there are more than one defined.
+            Attribute[] attrib = GetCustomAttributes(element, attributeType, inherit);
+
+            if (attrib == null || attrib.Length == 0)
+                return null;
+
+            if (attrib.Length == 1)
+                return attrib[0];
+
+            throw new AmbiguousMatchException(SR.RFLCT_AmbigCust);
+        }
+
+        #endregion
+
+        #region Assembly
+        public static Attribute[] GetCustomAttributes(Assembly element, Type attributeType)
+        {
+            return GetCustomAttributes(element, attributeType, true);
+        }
+
+        public static Attribute[] GetCustomAttributes(Assembly element, Type attributeType, bool inherit)
+        {
+            if (element == null)
+                throw new ArgumentNullException(nameof(element));
+
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            if (!attributeType.IsSubclassOf(typeof(Attribute)) && attributeType != typeof(Attribute))
+                throw new ArgumentException(SR.Argument_MustHaveAttributeBaseClass);
+
+            return (Attribute[])element.GetCustomAttributes(attributeType, inherit);
+        }
+
+        public static Attribute[] GetCustomAttributes(Assembly element)
+        {
+            return GetCustomAttributes(element, true);
+        }
+
+        public static Attribute[] GetCustomAttributes(Assembly element, bool inherit)
+        {
+            if (element == null)
+                throw new ArgumentNullException(nameof(element));
+
+            return (Attribute[])element.GetCustomAttributes(typeof(Attribute), inherit);
+        }
+
+        public static bool IsDefined(Assembly element, Type attributeType)
+        {
+            return IsDefined(element, attributeType, true);
+        }
+
+        public static bool IsDefined(Assembly element, Type attributeType, bool inherit)
+        {
+            // Returns true is a custom attribute subclass of attributeType class/interface with no inheritance walk
+            if (element == null)
+                throw new ArgumentNullException(nameof(element));
+
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            if (!attributeType.IsSubclassOf(typeof(Attribute)) && attributeType != typeof(Attribute))
+                throw new ArgumentException(SR.Argument_MustHaveAttributeBaseClass);
+
+            return element.IsDefined(attributeType, false);
+        }
+
+        public static Attribute GetCustomAttribute(Assembly element, Type attributeType)
+        {
+            return GetCustomAttribute(element, attributeType, true);
+        }
+
+        public static Attribute GetCustomAttribute(Assembly element, Type attributeType, bool inherit)
+        {
+            // Returns an Attribute of base class/inteface attributeType on the Assembly or null if none exists.
+            // throws an AmbiguousMatchException if there are more than one defined.
+            Attribute[] attrib = GetCustomAttributes(element, attributeType, inherit);
+
+            if (attrib == null || attrib.Length == 0)
+                return null;
+
+            if (attrib.Length == 1)
+                return attrib[0];
+
+            throw new AmbiguousMatchException(SR.RFLCT_AmbigCust);
+        }
+
+        #endregion
+
+        #endregion
+
+        #region Constructor
+        protected Attribute() { }
+        #endregion
+
+        #region Object Overrides
+        public override bool Equals(Object obj)
+        {
+            if (obj == null)
+                return false;
+
+            Type thisType = this.GetType();
+            Type thatType = obj.GetType();
+
+            if (thatType != thisType)
+                return false;
+
+            Object thisObj = this;
+            Object thisResult, thatResult;
+
+            while (thisType != typeof(Attribute))
+            {
+                FieldInfo[] thisFields = thisType.GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.DeclaredOnly);
+
+                for (int i = 0; i < thisFields.Length; i++)
+                {
+                    // Visibility check and consistency check are not necessary.
+                    thisResult = ((RtFieldInfo)thisFields[i]).UnsafeGetValue(thisObj);
+                    thatResult = ((RtFieldInfo)thisFields[i]).UnsafeGetValue(obj);
+
+                    if (!AreFieldValuesEqual(thisResult, thatResult))
+                    {
+                        return false;
+                    }
+                }
+                thisType = thisType.BaseType;
+            }
+
+            return true;
+        }
+
+        // Compares values of custom-attribute fields.    
+        private static bool AreFieldValuesEqual(Object thisValue, Object thatValue)
+        {
+            if (thisValue == null && thatValue == null)
+                return true;
+            if (thisValue == null || thatValue == null)
+                return false;
+
+            if (thisValue.GetType().IsArray)
+            {
+                // Ensure both are arrays of the same type.
+                if (!thisValue.GetType().Equals(thatValue.GetType()))
+                {
+                    return false;
+                }
+
+                Array thisValueArray = thisValue as Array;
+                Array thatValueArray = thatValue as Array;
+                if (thisValueArray.Length != thatValueArray.Length)
+                {
+                    return false;
+                }
+
+                // Attributes can only contain single-dimension arrays, so we don't need to worry about 
+                // multidimensional arrays.
+                Debug.Assert(thisValueArray.Rank == 1 && thatValueArray.Rank == 1);
+                for (int j = 0; j < thisValueArray.Length; j++)
+                {
+                    if (!AreFieldValuesEqual(thisValueArray.GetValue(j), thatValueArray.GetValue(j)))
+                    {
+                        return false;
+                    }
+                }
+            }
+            else
+            {
+                // An object of type Attribute will cause a stack overflow. 
+                // However, this should never happen because custom attributes cannot contain values other than
+                // constants, single-dimensional arrays and typeof expressions.
+                Debug.Assert(!(thisValue is Attribute));
+                if (!thisValue.Equals(thatValue))
+                    return false;
+            }
+
+            return true;
+        }
+
+        public override int GetHashCode()
+        {
+            Type type = GetType();
+
+            while (type != typeof(Attribute))
+            {
+                FieldInfo[] fields = type.GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.DeclaredOnly);
+                Object vThis = null;
+
+                for (int i = 0; i < fields.Length; i++)
+                {
+                    // Visibility check and consistency check are not necessary.
+                    Object fieldValue = ((RtFieldInfo)fields[i]).UnsafeGetValue(this);
+
+                    // The hashcode of an array ignores the contents of the array, so it can produce 
+                    // different hashcodes for arrays with the same contents.
+                    // Since we do deep comparisons of arrays in Equals(), this means Equals and GetHashCode will
+                    // be inconsistent for arrays. Therefore, we ignore hashes of arrays.
+                    if (fieldValue != null && !fieldValue.GetType().IsArray)
+                        vThis = fieldValue;
+
+                    if (vThis != null)
+                        break;
+                }
+
+                if (vThis != null)
+                    return vThis.GetHashCode();
+
+                type = type.BaseType;
+            }
+
+            return type.GetHashCode();
+        }
+        #endregion
+
+        #region Public Virtual Members
+        public virtual Object TypeId { get { return GetType(); } }
+
+        public virtual bool Match(Object obj) { return Equals(obj); }
+        #endregion
+
+        #region Public Members
+        public virtual bool IsDefaultAttribute() { return false; }
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/BadImageFormatException.CoreCLR.cs b/src/System.Private.CoreLib/src/System/BadImageFormatException.CoreCLR.cs
new file mode 100644
index 0000000000..094668bde0
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/BadImageFormatException.CoreCLR.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    public partial class BadImageFormatException
+    {
+        // Do not delete: this is invoked from native code.
+        private BadImageFormatException(string fileName, string fusionLog, int hResult)
+            : base(null)
+        {
+            HResult = hResult;
+            _fileName = fileName;
+            _fusionLog = fusionLog;
+            SetMessageField();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Buffer.cs b/src/System.Private.CoreLib/src/System/Buffer.cs
new file mode 100644
index 0000000000..43372ca673
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Buffer.cs
@@ -0,0 +1,652 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#if AMD64 || ARM64 || (BIT32 && !ARM)
+#define HAS_CUSTOM_BLOCKS
+#endif
+
+namespace System
+{
+    //Only contains static methods.  Does not require serialization
+
+    using System;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.ConstrainedExecution;
+    using System.Runtime.InteropServices;
+    using System.Runtime.Versioning;
+    using System.Diagnostics;
+    using System.Security;
+    using System.Runtime;
+    using Internal.Runtime.CompilerServices;
+
+#if BIT64
+    using nint = System.Int64;
+    using nuint = System.UInt64;
+#else // BIT64
+    using nint = System.Int32;
+    using nuint = System.UInt32;
+#endif // BIT64
+
+    public static class Buffer
+    {
+        // Copies from one primitive array to another primitive array without
+        // respecting types.  This calls memmove internally.  The count and 
+        // offset parameters here are in bytes.  If you want to use traditional
+        // array element indices and counts, use Array.Copy.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void BlockCopy(Array src, int srcOffset,
+            Array dst, int dstOffset, int count);
+
+        // Returns a bool to indicate if the array is of primitive data types
+        // or not.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool IsPrimitiveTypeArray(Array array);
+
+        // Gets a particular byte out of the array.  The array must be an
+        // array of primitives.  
+        //
+        // This essentially does the following: 
+        // return ((byte*)array) + index.
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern byte _GetByte(Array array, int index);
+
+        public static byte GetByte(Array array, int index)
+        {
+            // Is the array present?
+            if (array == null)
+                throw new ArgumentNullException(nameof(array));
+
+            // Is it of primitive types?
+            if (!IsPrimitiveTypeArray(array))
+                throw new ArgumentException(SR.Arg_MustBePrimArray, nameof(array));
+
+            // Is the index in valid range of the array?
+            if (index < 0 || index >= _ByteLength(array))
+                throw new ArgumentOutOfRangeException(nameof(index));
+
+            return _GetByte(array, index);
+        }
+
+        // Sets a particular byte in an the array.  The array must be an
+        // array of primitives.  
+        //
+        // This essentially does the following: 
+        // *(((byte*)array) + index) = value.
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _SetByte(Array array, int index, byte value);
+
+        public static void SetByte(Array array, int index, byte value)
+        {
+            // Is the array present?
+            if (array == null)
+                throw new ArgumentNullException(nameof(array));
+
+            // Is it of primitive types?
+            if (!IsPrimitiveTypeArray(array))
+                throw new ArgumentException(SR.Arg_MustBePrimArray, nameof(array));
+
+            // Is the index in valid range of the array?
+            if (index < 0 || index >= _ByteLength(array))
+                throw new ArgumentOutOfRangeException(nameof(index));
+
+            // Make the FCall to do the work
+            _SetByte(array, index, value);
+        }
+
+
+        // Gets a particular byte out of the array.  The array must be an
+        // array of primitives.  
+        //
+        // This essentially does the following: 
+        // return array.length * sizeof(array.UnderlyingElementType).
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int _ByteLength(Array array);
+
+        public static int ByteLength(Array array)
+        {
+            // Is the array present?
+            if (array == null)
+                throw new ArgumentNullException(nameof(array));
+
+            // Is it of primitive types?
+            if (!IsPrimitiveTypeArray(array))
+                throw new ArgumentException(SR.Arg_MustBePrimArray, nameof(array));
+
+            return _ByteLength(array);
+        }
+
+        internal static unsafe void ZeroMemory(byte* src, long len)
+        {
+            while (len-- > 0)
+                *(src + len) = 0;
+        }
+
+        internal static unsafe void Memcpy(byte[] dest, int destIndex, byte* src, int srcIndex, int len)
+        {
+            Debug.Assert((srcIndex >= 0) && (destIndex >= 0) && (len >= 0), "Index and length must be non-negative!");
+            Debug.Assert(dest.Length - destIndex >= len, "not enough bytes in dest");
+            // If dest has 0 elements, the fixed statement will throw an 
+            // IndexOutOfRangeException.  Special-case 0-byte copies.
+            if (len == 0)
+                return;
+            fixed (byte* pDest = dest)
+            {
+                Memcpy(pDest + destIndex, src + srcIndex, len);
+            }
+        }
+
+        internal static unsafe void Memcpy(byte* pDest, int destIndex, byte[] src, int srcIndex, int len)
+        {
+            Debug.Assert((srcIndex >= 0) && (destIndex >= 0) && (len >= 0), "Index and length must be non-negative!");
+            Debug.Assert(src.Length - srcIndex >= len, "not enough bytes in src");
+            // If dest has 0 elements, the fixed statement will throw an 
+            // IndexOutOfRangeException.  Special-case 0-byte copies.
+            if (len == 0)
+                return;
+            fixed (byte* pSrc = src)
+            {
+                Memcpy(pDest + destIndex, pSrc + srcIndex, len);
+            }
+        }
+
+        // This is tricky to get right AND fast, so lets make it useful for the whole Fx.
+        // E.g. System.Runtime.WindowsRuntime!WindowsRuntimeBufferExtensions.MemCopy uses it.
+
+        // This method has a slightly different behavior on arm and other platforms.
+        // On arm this method behaves like memcpy and does not handle overlapping buffers.
+        // While on other platforms it behaves like memmove and handles overlapping buffers.
+        // This behavioral difference is unfortunate but intentional because
+        // 1. This method is given access to other internal dlls and this close to release we do not want to change it.
+        // 2. It is difficult to get this right for arm and again due to release dates we would like to visit it later.
+#if ARM
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern unsafe void Memcpy(byte* dest, byte* src, int len);
+#else // ARM
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        internal static unsafe void Memcpy(byte* dest, byte* src, int len)
+        {
+            Debug.Assert(len >= 0, "Negative length in memcopy!");
+            Memmove(dest, src, (uint)len);
+        }
+#endif // ARM
+
+        // This method has different signature for x64 and other platforms and is done for performance reasons.
+        internal static unsafe void Memmove(byte* dest, byte* src, nuint len)
+        {
+#if AMD64 || (BIT32 && !ARM)
+            const nuint CopyThreshold = 2048;
+#elif ARM64
+#if PLATFORM_WINDOWS
+            // Determined optimal value for Windows.
+            // https://github.com/dotnet/coreclr/issues/13843
+            const nuint CopyThreshold = UInt64.MaxValue;
+#else // PLATFORM_WINDOWS
+            // Managed code is currently faster than glibc unoptimized memmove
+            // TODO-ARM64-UNIX-OPT revisit when glibc optimized memmove is in Linux distros
+            // https://github.com/dotnet/coreclr/issues/13844
+            const nuint CopyThreshold = UInt64.MaxValue;
+#endif // PLATFORM_WINDOWS
+#else
+            const nuint CopyThreshold = 512;
+#endif // AMD64 || (BIT32 && !ARM)
+
+            // P/Invoke into the native version when the buffers are overlapping.
+
+            if (((nuint)dest - (nuint)src < len) || ((nuint)src - (nuint)dest < len)) goto PInvoke;
+
+            byte* srcEnd = src + len;
+            byte* destEnd = dest + len;
+
+            if (len <= 16) goto MCPY02;
+            if (len > 64) goto MCPY05;
+
+            MCPY00:
+            // Copy bytes which are multiples of 16 and leave the remainder for MCPY01 to handle.
+            Debug.Assert(len > 16 && len <= 64);
+#if HAS_CUSTOM_BLOCKS
+            *(Block16*)dest = *(Block16*)src;                   // [0,16]
+#elif BIT64
+            *(long*)dest = *(long*)src;
+            *(long*)(dest + 8) = *(long*)(src + 8);             // [0,16]
+#else
+            *(int*)dest = *(int*)src;
+            *(int*)(dest + 4) = *(int*)(src + 4);
+            *(int*)(dest + 8) = *(int*)(src + 8);
+            *(int*)(dest + 12) = *(int*)(src + 12);             // [0,16]
+#endif
+            if (len <= 32) goto MCPY01;
+#if HAS_CUSTOM_BLOCKS
+            *(Block16*)(dest + 16) = *(Block16*)(src + 16);     // [0,32]
+#elif BIT64
+            *(long*)(dest + 16) = *(long*)(src + 16);
+            *(long*)(dest + 24) = *(long*)(src + 24);           // [0,32]
+#else
+            *(int*)(dest + 16) = *(int*)(src + 16);
+            *(int*)(dest + 20) = *(int*)(src + 20);
+            *(int*)(dest + 24) = *(int*)(src + 24);
+            *(int*)(dest + 28) = *(int*)(src + 28);             // [0,32]
+#endif
+            if (len <= 48) goto MCPY01;
+#if HAS_CUSTOM_BLOCKS
+            *(Block16*)(dest + 32) = *(Block16*)(src + 32);     // [0,48]
+#elif BIT64
+            *(long*)(dest + 32) = *(long*)(src + 32);
+            *(long*)(dest + 40) = *(long*)(src + 40);           // [0,48]
+#else
+            *(int*)(dest + 32) = *(int*)(src + 32);
+            *(int*)(dest + 36) = *(int*)(src + 36);
+            *(int*)(dest + 40) = *(int*)(src + 40);
+            *(int*)(dest + 44) = *(int*)(src + 44);             // [0,48]
+#endif
+
+            MCPY01:
+            // Unconditionally copy the last 16 bytes using destEnd and srcEnd and return.
+            Debug.Assert(len > 16 && len <= 64);
+#if HAS_CUSTOM_BLOCKS
+            *(Block16*)(destEnd - 16) = *(Block16*)(srcEnd - 16);
+#elif BIT64
+            *(long*)(destEnd - 16) = *(long*)(srcEnd - 16);
+            *(long*)(destEnd - 8) = *(long*)(srcEnd - 8);
+#else
+            *(int*)(destEnd - 16) = *(int*)(srcEnd - 16);
+            *(int*)(destEnd - 12) = *(int*)(srcEnd - 12);
+            *(int*)(destEnd - 8) = *(int*)(srcEnd - 8);
+            *(int*)(destEnd - 4) = *(int*)(srcEnd - 4);
+#endif
+            return;
+
+            MCPY02:
+            // Copy the first 8 bytes and then unconditionally copy the last 8 bytes and return.
+            if ((len & 24) == 0) goto MCPY03;
+            Debug.Assert(len >= 8 && len <= 16);
+#if BIT64
+            *(long*)dest = *(long*)src;
+            *(long*)(destEnd - 8) = *(long*)(srcEnd - 8);
+#else
+            *(int*)dest = *(int*)src;
+            *(int*)(dest + 4) = *(int*)(src + 4);
+            *(int*)(destEnd - 8) = *(int*)(srcEnd - 8);
+            *(int*)(destEnd - 4) = *(int*)(srcEnd - 4);
+#endif
+            return;
+
+            MCPY03:
+            // Copy the first 4 bytes and then unconditionally copy the last 4 bytes and return.
+            if ((len & 4) == 0) goto MCPY04;
+            Debug.Assert(len >= 4 && len < 8);
+            *(int*)dest = *(int*)src;
+            *(int*)(destEnd - 4) = *(int*)(srcEnd - 4);
+            return;
+
+            MCPY04:
+            // Copy the first byte. For pending bytes, do an unconditionally copy of the last 2 bytes and return.
+            Debug.Assert(len < 4);
+            if (len == 0) return;
+            *dest = *src;
+            if ((len & 2) == 0) return;
+            *(short*)(destEnd - 2) = *(short*)(srcEnd - 2);
+            return;
+
+            MCPY05:
+            // PInvoke to the native version when the copy length exceeds the threshold.
+            if (len > CopyThreshold)
+            {
+                goto PInvoke;
+            }
+            // Copy 64-bytes at a time until the remainder is less than 64.
+            // If remainder is greater than 16 bytes, then jump to MCPY00. Otherwise, unconditionally copy the last 16 bytes and return.
+            Debug.Assert(len > 64 && len <= CopyThreshold);
+            nuint n = len >> 6;
+
+            MCPY06:
+#if HAS_CUSTOM_BLOCKS
+            *(Block64*)dest = *(Block64*)src;
+#elif BIT64
+            *(long*)dest = *(long*)src;
+            *(long*)(dest + 8) = *(long*)(src + 8);
+            *(long*)(dest + 16) = *(long*)(src + 16);
+            *(long*)(dest + 24) = *(long*)(src + 24);
+            *(long*)(dest + 32) = *(long*)(src + 32);
+            *(long*)(dest + 40) = *(long*)(src + 40);
+            *(long*)(dest + 48) = *(long*)(src + 48);
+            *(long*)(dest + 56) = *(long*)(src + 56);
+#else
+            *(int*)dest = *(int*)src;
+            *(int*)(dest + 4) = *(int*)(src + 4);
+            *(int*)(dest + 8) = *(int*)(src + 8);
+            *(int*)(dest + 12) = *(int*)(src + 12);
+            *(int*)(dest + 16) = *(int*)(src + 16);
+            *(int*)(dest + 20) = *(int*)(src + 20);
+            *(int*)(dest + 24) = *(int*)(src + 24);
+            *(int*)(dest + 28) = *(int*)(src + 28);
+            *(int*)(dest + 32) = *(int*)(src + 32);
+            *(int*)(dest + 36) = *(int*)(src + 36);
+            *(int*)(dest + 40) = *(int*)(src + 40);
+            *(int*)(dest + 44) = *(int*)(src + 44);
+            *(int*)(dest + 48) = *(int*)(src + 48);
+            *(int*)(dest + 52) = *(int*)(src + 52);
+            *(int*)(dest + 56) = *(int*)(src + 56);
+            *(int*)(dest + 60) = *(int*)(src + 60);
+#endif
+            dest += 64;
+            src += 64;
+            n--;
+            if (n != 0) goto MCPY06;
+
+            len %= 64;
+            if (len > 16) goto MCPY00;
+#if HAS_CUSTOM_BLOCKS
+            *(Block16*)(destEnd - 16) = *(Block16*)(srcEnd - 16);
+#elif BIT64
+            *(long*)(destEnd - 16) = *(long*)(srcEnd - 16);
+            *(long*)(destEnd - 8) = *(long*)(srcEnd - 8);
+#else
+            *(int*)(destEnd - 16) = *(int*)(srcEnd - 16);
+            *(int*)(destEnd - 12) = *(int*)(srcEnd - 12);
+            *(int*)(destEnd - 8) = *(int*)(srcEnd - 8);
+            *(int*)(destEnd - 4) = *(int*)(srcEnd - 4);
+#endif
+            return;
+
+            PInvoke:
+            _Memmove(dest, src, len);
+        }
+        
+        // This method has different signature for x64 and other platforms and is done for performance reasons.
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static void Memmove<T>(ref T destination, ref T source, nuint elementCount)
+        {
+            if (!RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+            {
+                // Blittable memmove
+
+                Memmove(
+                    ref Unsafe.As<T, byte>(ref destination),
+                    ref Unsafe.As<T, byte>(ref source),
+                    elementCount * (nuint)Unsafe.SizeOf<T>());
+            }
+            else
+            {
+                // Non-blittable memmove
+
+                // Try to avoid calling RhBulkMoveWithWriteBarrier if we can get away
+                // with a no-op.
+                if (!Unsafe.AreSame(ref destination, ref source) && elementCount != 0)
+                {
+                    RuntimeImports.RhBulkMoveWithWriteBarrier(
+                        ref Unsafe.As<T, byte>(ref destination),
+                        ref Unsafe.As<T, byte>(ref source),
+                        elementCount * (nuint)Unsafe.SizeOf<T>());
+                }
+            }
+        }
+
+        // This method has different signature for x64 and other platforms and is done for performance reasons.
+        private static void Memmove(ref byte dest, ref byte src, nuint len)
+        {
+#if AMD64 || (BIT32 && !ARM)
+            const nuint CopyThreshold = 2048;
+#elif ARM64
+#if PLATFORM_WINDOWS
+            // Determined optimal value for Windows.
+            // https://github.com/dotnet/coreclr/issues/13843
+            const nuint CopyThreshold = UInt64.MaxValue;
+#else // PLATFORM_WINDOWS
+            // Managed code is currently faster than glibc unoptimized memmove
+            // TODO-ARM64-UNIX-OPT revisit when glibc optimized memmove is in Linux distros
+            // https://github.com/dotnet/coreclr/issues/13844
+            const nuint CopyThreshold = UInt64.MaxValue;
+#endif // PLATFORM_WINDOWS
+#else
+            const nuint CopyThreshold = 512;
+#endif // AMD64 || (BIT32 && !ARM)
+
+            // P/Invoke into the native version when the buffers are overlapping.            
+
+            if (((nuint)Unsafe.ByteOffset(ref src, ref dest) < len) || ((nuint)Unsafe.ByteOffset(ref dest, ref src) < len))
+            {
+                goto BuffersOverlap;
+            }
+
+            // Use "(IntPtr)(nint)len" to avoid overflow checking on the explicit cast to IntPtr
+
+            ref byte srcEnd = ref Unsafe.Add(ref src, (IntPtr)(nint)len);
+            ref byte destEnd = ref Unsafe.Add(ref dest, (IntPtr)(nint)len);
+
+            if (len <= 16)
+                goto MCPY02;
+            if (len > 64)
+                goto MCPY05;
+
+MCPY00:
+// Copy bytes which are multiples of 16 and leave the remainder for MCPY01 to handle.
+            Debug.Assert(len > 16 && len <= 64);
+#if HAS_CUSTOM_BLOCKS
+            Unsafe.As<byte, Block16>(ref dest) = Unsafe.As<byte, Block16>(ref src); // [0,16]
+#elif BIT64
+            Unsafe.As<byte, long>(ref dest) = Unsafe.As<byte, long>(ref src);
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref dest, 8)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref src, 8)); // [0,16]
+#else
+            Unsafe.As<byte, int>(ref dest) = Unsafe.As<byte, int>(ref src);
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 4)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 4));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 8)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 8));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 12)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 12)); // [0,16]
+#endif
+            if (len <= 32)
+                goto MCPY01;
+#if HAS_CUSTOM_BLOCKS
+            Unsafe.As<byte, Block16>(ref Unsafe.Add(ref dest, 16)) = Unsafe.As<byte, Block16>(ref Unsafe.Add(ref src, 16)); // [0,32]
+#elif BIT64
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref dest, 16)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref src, 16));
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref dest, 24)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref src, 24)); // [0,32]
+#else
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 16)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 16));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 20)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 20));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 24)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 24));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 28)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 28)); // [0,32]
+#endif
+            if (len <= 48)
+                goto MCPY01;
+#if HAS_CUSTOM_BLOCKS
+            Unsafe.As<byte, Block16>(ref Unsafe.Add(ref dest, 32)) = Unsafe.As<byte, Block16>(ref Unsafe.Add(ref src, 32)); // [0,48]
+#elif BIT64
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref dest, 32)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref src, 32));
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref dest, 40)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref src, 40)); // [0,48]
+#else
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 32)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 32));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 36)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 36));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 40)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 40));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 44)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 44)); // [0,48]
+#endif
+
+MCPY01:
+// Unconditionally copy the last 16 bytes using destEnd and srcEnd and return.
+            Debug.Assert(len > 16 && len <= 64);
+#if HAS_CUSTOM_BLOCKS
+            Unsafe.As<byte, Block16>(ref Unsafe.Add(ref destEnd, -16)) = Unsafe.As<byte, Block16>(ref Unsafe.Add(ref srcEnd, -16));
+#elif BIT64
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref destEnd, -16)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref srcEnd, -16));
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref destEnd, -8)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref srcEnd, -8));
+#else
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref destEnd, -16)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref srcEnd, -16));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref destEnd, -12)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref srcEnd, -12));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref destEnd, -8)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref srcEnd, -8));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref destEnd, -4)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref srcEnd, -4));
+#endif
+            return;
+
+MCPY02:
+// Copy the first 8 bytes and then unconditionally copy the last 8 bytes and return.
+            if ((len & 24) == 0)
+                goto MCPY03;
+            Debug.Assert(len >= 8 && len <= 16);
+#if BIT64
+            Unsafe.As<byte, long>(ref dest) = Unsafe.As<byte, long>(ref src);
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref destEnd, -8)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref srcEnd, -8));
+#else
+            Unsafe.As<byte, int>(ref dest) = Unsafe.As<byte, int>(ref src);
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 4)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 4));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref destEnd, -8)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref srcEnd, -8));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref destEnd, -4)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref srcEnd, -4));
+#endif
+            return;
+
+MCPY03:
+// Copy the first 4 bytes and then unconditionally copy the last 4 bytes and return.
+            if ((len & 4) == 0)
+                goto MCPY04;
+            Debug.Assert(len >= 4 && len < 8);
+            Unsafe.As<byte, int>(ref dest) = Unsafe.As<byte, int>(ref src);
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref destEnd, -4)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref srcEnd, -4));
+            return;
+
+MCPY04:
+// Copy the first byte. For pending bytes, do an unconditionally copy of the last 2 bytes and return.
+            Debug.Assert(len < 4);
+            if (len == 0)
+                return;
+            dest = src;
+            if ((len & 2) == 0)
+                return;
+            Unsafe.As<byte, short>(ref Unsafe.Add(ref destEnd, -2)) = Unsafe.As<byte, short>(ref Unsafe.Add(ref srcEnd, -2));
+            return;
+
+MCPY05:
+// PInvoke to the native version when the copy length exceeds the threshold.
+            if (len > CopyThreshold)
+            {
+                goto PInvoke;
+            }
+            // Copy 64-bytes at a time until the remainder is less than 64.
+            // If remainder is greater than 16 bytes, then jump to MCPY00. Otherwise, unconditionally copy the last 16 bytes and return.
+            Debug.Assert(len > 64 && len <= CopyThreshold);
+            nuint n = len >> 6;
+
+MCPY06:
+#if HAS_CUSTOM_BLOCKS
+            Unsafe.As<byte, Block64>(ref dest) = Unsafe.As<byte, Block64>(ref src);
+#elif BIT64
+            Unsafe.As<byte, long>(ref dest) = Unsafe.As<byte, long>(ref src);
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref dest, 8)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref src, 8));
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref dest, 16)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref src, 16));
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref dest, 24)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref src, 24));
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref dest, 32)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref src, 32));
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref dest, 40)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref src, 40));
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref dest, 48)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref src, 48));
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref dest, 56)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref src, 56));
+#else
+            Unsafe.As<byte, int>(ref dest) = Unsafe.As<byte, int>(ref src);
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 4)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 4));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 8)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 8));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 12)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 12));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 16)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 16));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 20)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 20));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 24)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 24));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 28)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 28));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 32)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 32));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 36)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 36));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 40)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 40));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 44)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 44));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 48)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 48));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 52)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 52));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 56)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 56));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref dest, 60)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref src, 60));
+#endif
+            dest = ref Unsafe.Add(ref dest, 64);
+            src = ref Unsafe.Add(ref src, 64);
+            n--;
+            if (n != 0)
+                goto MCPY06;
+
+            len %= 64;
+            if (len > 16)
+                goto MCPY00;
+#if HAS_CUSTOM_BLOCKS
+            Unsafe.As<byte, Block16>(ref Unsafe.Add(ref destEnd, -16)) = Unsafe.As<byte, Block16>(ref Unsafe.Add(ref srcEnd, -16));
+#elif BIT64
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref destEnd, -16)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref srcEnd, -16));
+            Unsafe.As<byte, long>(ref Unsafe.Add(ref destEnd, -8)) = Unsafe.As<byte, long>(ref Unsafe.Add(ref srcEnd, -8));
+#else
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref destEnd, -16)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref srcEnd, -16));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref destEnd, -12)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref srcEnd, -12));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref destEnd, -8)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref srcEnd, -8));
+            Unsafe.As<byte, int>(ref Unsafe.Add(ref destEnd, -4)) = Unsafe.As<byte, int>(ref Unsafe.Add(ref srcEnd, -4));
+#endif
+            return;
+
+BuffersOverlap:
+            // If the buffers overlap perfectly, there's no point to copying the data.
+            if (Unsafe.AreSame(ref dest, ref src))
+            {
+                return;
+            }
+
+PInvoke:
+            _Memmove(ref dest, ref src, len);
+        }
+
+        // Non-inlinable wrapper around the QCall that avoids polluting the fast path
+        // with P/Invoke prolog/epilog.
+        [MethodImplAttribute(MethodImplOptions.NoInlining)]
+        private static unsafe void _Memmove(byte* dest, byte* src, nuint len)
+        {
+            __Memmove(dest, src, len);
+        }
+
+        // Non-inlinable wrapper around the QCall that avoids polluting the fast path
+        // with P/Invoke prolog/epilog.
+        [MethodImplAttribute(MethodImplOptions.NoInlining)]
+        private static unsafe void _Memmove(ref byte dest, ref byte src, nuint len)
+        {
+            fixed (byte* pDest = &dest)
+            fixed (byte* pSrc = &src)
+                __Memmove(pDest, pSrc, len);
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern unsafe void __Memmove(byte* dest, byte* src, nuint len);
+
+        // The attributes on this method are chosen for best JIT performance. 
+        // Please do not edit unless intentional.
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        [CLSCompliant(false)]
+        public static unsafe void MemoryCopy(void* source, void* destination, long destinationSizeInBytes, long sourceBytesToCopy)
+        {
+            if (sourceBytesToCopy > destinationSizeInBytes)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.sourceBytesToCopy);
+            }
+            Memmove((byte*)destination, (byte*)source, checked((nuint)sourceBytesToCopy));
+        }
+
+
+        // The attributes on this method are chosen for best JIT performance. 
+        // Please do not edit unless intentional.
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        [CLSCompliant(false)]
+        public static unsafe void MemoryCopy(void* source, void* destination, ulong destinationSizeInBytes, ulong sourceBytesToCopy)
+        {
+            if (sourceBytesToCopy > destinationSizeInBytes)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.sourceBytesToCopy);
+            }
+#if BIT64
+            Memmove((byte*)destination, (byte*)source, sourceBytesToCopy);
+#else // BIT64
+            Memmove((byte*)destination, (byte*)source, checked((uint)sourceBytesToCopy));
+#endif // BIT64
+        }
+        
+#if HAS_CUSTOM_BLOCKS        
+        [StructLayout(LayoutKind.Sequential, Size = 16)]
+        private struct Block16 { }
+
+        [StructLayout(LayoutKind.Sequential, Size = 64)]
+        private struct Block64 { } 
+#endif // HAS_CUSTOM_BLOCKS         
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/ByReference.cs b/src/System.Private.CoreLib/src/System/ByReference.cs
new file mode 100644
index 0000000000..3e1fa8a7f3
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/ByReference.cs
@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    // ByReference<T> is meant to be used to represent "ref T" fields. It is working
+    // around lack of first class support for byref fields in C# and IL. The JIT and 
+    // type loader has special handling for it that turns it into a thin wrapper around ref T.
+    [NonVersionable]
+    internal ref struct ByReference<T>
+    {
+        private IntPtr _value;
+
+        public ByReference(ref T value)
+        {
+            // Implemented as a JIT intrinsic - This default implementation is for 
+            // completeness and to provide a concrete error if called via reflection
+            // or if intrinsic is missed.
+            throw new System.PlatformNotSupportedException();
+        }
+
+        public ref T Value
+        {
+            get
+            {
+                // Implemented as a JIT intrinsic - This default implementation is for 
+                // completeness and to provide a concrete error if called via reflection
+                // or if the intrinsic is missed.
+                throw new System.PlatformNotSupportedException();
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/CLRConfig.cs b/src/System.Private.CoreLib/src/System/CLRConfig.cs
new file mode 100644
index 0000000000..08bf95dc99
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/CLRConfig.cs
@@ -0,0 +1,59 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using Microsoft.Win32;
+
+namespace System
+{
+    // CLRConfig is mainly reading the config switch values. this is used when we cannot use the AppContext class
+    // one example, is using the context switch in the globalization code which require to read the switch very
+    // early even before the appdomain get initialized.
+    // In general AppContext should be used instead of CLRConfig if there is no reason prevent that.
+    internal class CLRConfig
+    {
+        internal static bool GetBoolValue(string switchName, out bool exist)
+        {
+            return GetConfigBoolValue(switchName, out exist);
+        }
+
+        internal static bool GetBoolValueWithFallbacks(string switchName, string environmentName, bool defaultValue)
+        {
+            bool value = GetBoolValue(switchName, out bool exists);
+
+            if (exists)
+                return value;
+
+            // Calls to this API can be very early- we want to avoid using higher-level
+            // abstractions where reasonably possible.
+
+            Span<char> buffer = stackalloc char[32];
+
+            int length = Win32Native.GetEnvironmentVariable(environmentName, buffer);
+            switch (length)
+            {
+                case 1:
+                    if (buffer[0] == '0')
+                        return false;
+                    if (buffer[0] == '1')
+                        return true;
+                    break;
+                case 4:
+                    if ("true".AsSpan().EqualsOrdinalIgnoreCase(buffer.Slice(0, 4)))
+                        return true;
+                    break;
+                case 5:
+                    if ("false".AsSpan().EqualsOrdinalIgnoreCase(buffer.Slice(0, 5)))
+                        return false;
+                    break;
+            }
+
+            return defaultValue;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern bool GetConfigBoolValue(string configSwitchName, out bool exist);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentDictionary.cs b/src/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentDictionary.cs
new file mode 100644
index 0000000000..1f4543e8e5
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentDictionary.cs
@@ -0,0 +1,1592 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Class:   ConcurrentDictionary
+**
+**
+** Purpose: A scalable dictionary for concurrent access
+**
+**
+===========================================================*/
+
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Threading;
+
+namespace System.Collections.Concurrent
+{
+    /// <summary>
+    /// Represents a thread-safe collection of keys and values.
+    /// </summary>
+    /// <typeparam name="TKey">The type of the keys in the dictionary.</typeparam>
+    /// <typeparam name="TValue">The type of the values in the dictionary.</typeparam>
+    /// <remarks>
+    /// All public and protected members of <see cref="ConcurrentDictionary{TKey,TValue}"/> are thread-safe and may be used
+    /// concurrently from multiple threads.
+    /// </remarks>
+    [DebuggerTypeProxy(typeof(IDictionaryDebugView<,>))]
+    [DebuggerDisplay("Count = {Count}")]
+    internal class ConcurrentDictionary<TKey, TValue> : IDictionary<TKey, TValue>, IDictionary, IReadOnlyDictionary<TKey, TValue>
+    {
+        /// <summary>
+        /// Tables that hold the internal state of the ConcurrentDictionary
+        ///
+        /// Wrapping the three tables in a single object allows us to atomically
+        /// replace all tables at once.
+        /// </summary>
+        private sealed class Tables
+        {
+            internal readonly Node[] _buckets; // A singly-linked list for each bucket.
+            internal readonly object[] _locks; // A set of locks, each guarding a section of the table.
+            internal volatile int[] _countPerLock; // The number of elements guarded by each lock.
+
+            internal Tables(Node[] buckets, object[] locks, int[] countPerLock)
+            {
+                _buckets = buckets;
+                _locks = locks;
+                _countPerLock = countPerLock;
+            }
+        }
+
+        private volatile Tables _tables; // Internal tables of the dictionary
+        private IEqualityComparer<TKey> _comparer; // Key equality comparer
+        private readonly bool _growLockArray; // Whether to dynamically increase the size of the striped lock
+        private int _budget; // The maximum number of elements per lock before a resize operation is triggered
+
+        // The default capacity, i.e. the initial # of buckets. When choosing this value, we are making
+        // a trade-off between the size of a very small dictionary, and the number of resizes when
+        // constructing a large dictionary. Also, the capacity should not be divisible by a small prime.
+        private const int DefaultCapacity = 31;
+
+        // The maximum size of the striped lock that will not be exceeded when locks are automatically
+        // added as the dictionary grows. However, the user is allowed to exceed this limit by passing
+        // a concurrency level larger than MaxLockNumber into the constructor.
+        private const int MaxLockNumber = 1024;
+
+        // Whether TValue is a type that can be written atomically (i.e., with no danger of torn reads)
+        private static readonly bool s_isValueWriteAtomic = IsValueWriteAtomic();
+
+        /// <summary>
+        /// Determines whether type TValue can be written atomically
+        /// </summary>
+        private static bool IsValueWriteAtomic()
+        {
+            //
+            // Section 12.6.6 of ECMA CLI explains which types can be read and written atomically without
+            // the risk of tearing.
+            //
+            // See http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-335.pdf
+            //
+            Type valueType = typeof(TValue);
+            if (!valueType.IsValueType)
+            {
+                return true;
+            }
+            if (valueType.IsEnum)
+            {
+                valueType = Enum.GetUnderlyingType(valueType);
+            }
+
+            switch (Type.GetTypeCode(valueType))
+            {
+                case TypeCode.Boolean:
+                case TypeCode.Byte:
+                case TypeCode.Char:
+                case TypeCode.Int16:
+                case TypeCode.Int32:
+                case TypeCode.SByte:
+                case TypeCode.Single:
+                case TypeCode.UInt16:
+                case TypeCode.UInt32:
+                    return true;
+                case TypeCode.Int64:
+                case TypeCode.Double:
+                case TypeCode.UInt64:
+                    return IntPtr.Size == 8;
+                default:
+                    return false;
+            }
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see
+        /// cref="ConcurrentDictionary{TKey,TValue}"/>
+        /// class that is empty, has the default concurrency level, has the default initial capacity, and
+        /// uses the default comparer for the key type.
+        /// </summary>
+        public ConcurrentDictionary() : this(DefaultConcurrencyLevel, DefaultCapacity, true, null) { }
+
+        internal ConcurrentDictionary(int concurrencyLevel, int capacity, bool growLockArray, IEqualityComparer<TKey> comparer)
+        {
+            if (concurrencyLevel < 1)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.concurrencyLevel, ExceptionResource.ConcurrentDictionary_ConcurrencyLevelMustBePositive);
+            }
+            if (capacity < 0)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.capacity, ExceptionResource.ConcurrentDictionary_CapacityMustNotBeNegative);
+            }
+
+            // The capacity should be at least as large as the concurrency level. Otherwise, we would have locks that don't guard
+            // any buckets.
+            if (capacity < concurrencyLevel)
+            {
+                capacity = concurrencyLevel;
+            }
+
+            object[] locks = new object[concurrencyLevel];
+            for (int i = 0; i < locks.Length; i++)
+            {
+                locks[i] = new object();
+            }
+
+            int[] countPerLock = new int[locks.Length];
+            Node[] buckets = new Node[capacity];
+            _tables = new Tables(buckets, locks, countPerLock);
+
+            _comparer = comparer ?? EqualityComparer<TKey>.Default;
+            _growLockArray = growLockArray;
+            _budget = buckets.Length / locks.Length;
+        }
+
+        /// <summary>
+        /// Attempts to add the specified key and value to the <see cref="ConcurrentDictionary{TKey,
+        /// TValue}"/>.
+        /// </summary>
+        /// <param name="key">The key of the element to add.</param>
+        /// <param name="value">The value of the element to add. The value can be a null reference (Nothing
+        /// in Visual Basic) for reference types.</param>
+        /// <returns>true if the key/value pair was added to the <see cref="ConcurrentDictionary{TKey,
+        /// TValue}"/>
+        /// successfully; otherwise, false.</returns>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="key"/> is null reference
+        /// (Nothing in Visual Basic).</exception>
+        /// <exception cref="T:System.OverflowException">The <see cref="ConcurrentDictionary{TKey, TValue}"/>
+        /// contains too many elements.</exception>
+        public bool TryAdd(TKey key, TValue value)
+        {
+            if (key == null) ThrowKeyNullException();
+            TValue dummy;
+            return TryAddInternal(key, _comparer.GetHashCode(key), value, false, true, out dummy);
+        }
+
+        /// <summary>
+        /// Determines whether the <see cref="ConcurrentDictionary{TKey, TValue}"/> contains the specified
+        /// key.
+        /// </summary>
+        /// <param name="key">The key to locate in the <see cref="ConcurrentDictionary{TKey,
+        /// TValue}"/>.</param>
+        /// <returns>true if the <see cref="ConcurrentDictionary{TKey, TValue}"/> contains an element with
+        /// the specified key; otherwise, false.</returns>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="key"/> is a null reference
+        /// (Nothing in Visual Basic).</exception>
+        public bool ContainsKey(TKey key)
+        {
+            if (key == null) ThrowKeyNullException();
+
+            TValue throwAwayValue;
+            return TryGetValue(key, out throwAwayValue);
+        }
+
+        /// <summary>
+        /// Attempts to remove and return the value with the specified key from the
+        /// <see cref="ConcurrentDictionary{TKey, TValue}"/>.
+        /// </summary>
+        /// <param name="key">The key of the element to remove and return.</param>
+        /// <param name="value">When this method returns, <paramref name="value"/> contains the object removed from the
+        /// <see cref="ConcurrentDictionary{TKey,TValue}"/> or the default value of <typeparamref
+        /// name="TValue"/>
+        /// if the operation failed.</param>
+        /// <returns>true if an object was removed successfully; otherwise, false.</returns>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="key"/> is a null reference
+        /// (Nothing in Visual Basic).</exception>
+        public bool TryRemove(TKey key, out TValue value)
+        {
+            if (key == null) ThrowKeyNullException();
+
+            return TryRemoveInternal(key, out value, false, default(TValue));
+        }
+
+        /// <summary>
+        /// Removes the specified key from the dictionary if it exists and returns its associated value.
+        /// If matchValue flag is set, the key will be removed only if is associated with a particular
+        /// value.
+        /// </summary>
+        /// <param name="key">The key to search for and remove if it exists.</param>
+        /// <param name="value">The variable into which the removed value, if found, is stored.</param>
+        /// <param name="matchValue">Whether removal of the key is conditional on its value.</param>
+        /// <param name="oldValue">The conditional value to compare against if <paramref name="matchValue"/> is true</param>
+        /// <returns></returns>
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "Reviewed for thread safety")]
+        private bool TryRemoveInternal(TKey key, out TValue value, bool matchValue, TValue oldValue)
+        {
+            int hashcode = _comparer.GetHashCode(key);
+            while (true)
+            {
+                Tables tables = _tables;
+
+                int bucketNo, lockNo;
+                GetBucketAndLockNo(hashcode, out bucketNo, out lockNo, tables._buckets.Length, tables._locks.Length);
+
+                lock (tables._locks[lockNo])
+                {
+                    // If the table just got resized, we may not be holding the right lock, and must retry.
+                    // This should be a rare occurrence.
+                    if (tables != _tables)
+                    {
+                        continue;
+                    }
+
+                    Node prev = null;
+                    for (Node curr = tables._buckets[bucketNo]; curr != null; curr = curr._next)
+                    {
+                        Debug.Assert((prev == null && curr == tables._buckets[bucketNo]) || prev._next == curr);
+
+                        if (hashcode == curr._hashcode && _comparer.Equals(curr._key, key))
+                        {
+                            if (matchValue)
+                            {
+                                bool valuesMatch = EqualityComparer<TValue>.Default.Equals(oldValue, curr._value);
+                                if (!valuesMatch)
+                                {
+                                    value = default(TValue);
+                                    return false;
+                                }
+                            }
+
+                            if (prev == null)
+                            {
+                                Volatile.Write<Node>(ref tables._buckets[bucketNo], curr._next);
+                            }
+                            else
+                            {
+                                prev._next = curr._next;
+                            }
+
+                            value = curr._value;
+                            tables._countPerLock[lockNo]--;
+                            return true;
+                        }
+                        prev = curr;
+                    }
+                }
+
+                value = default(TValue);
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// Attempts to get the value associated with the specified key from the <see
+        /// cref="ConcurrentDictionary{TKey,TValue}"/>.
+        /// </summary>
+        /// <param name="key">The key of the value to get.</param>
+        /// <param name="value">When this method returns, <paramref name="value"/> contains the object from
+        /// the
+        /// <see cref="ConcurrentDictionary{TKey,TValue}"/> with the specified key or the default value of
+        /// <typeparamref name="TValue"/>, if the operation failed.</param>
+        /// <returns>true if the key was found in the <see cref="ConcurrentDictionary{TKey,TValue}"/>;
+        /// otherwise, false.</returns>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="key"/> is a null reference
+        /// (Nothing in Visual Basic).</exception>
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "Reviewed for thread safety")]
+        public bool TryGetValue(TKey key, out TValue value)
+        {
+            if (key == null) ThrowKeyNullException();
+            return TryGetValueInternal(key, _comparer.GetHashCode(key), out value);
+        }
+
+        private bool TryGetValueInternal(TKey key, int hashcode, out TValue value)
+        {
+            Debug.Assert(_comparer.GetHashCode(key) == hashcode);
+            
+            // We must capture the _buckets field in a local variable. It is set to a new table on each table resize.
+            Tables tables = _tables;
+
+            int bucketNo = GetBucket(hashcode, tables._buckets.Length);
+
+            // We can get away w/out a lock here.
+            // The Volatile.Read ensures that we have a copy of the reference to tables._buckets[bucketNo].
+            // This protects us from reading fields ('_hashcode', '_key', '_value' and '_next') of different instances.
+            Node n = Volatile.Read<Node>(ref tables._buckets[bucketNo]);
+
+            while (n != null)
+            {
+                if (hashcode == n._hashcode && _comparer.Equals(n._key, key))
+                {
+                    value = n._value;
+                    return true;
+                }
+                n = n._next;
+            }
+
+            value = default(TValue);
+            return false;
+        }
+
+        /// <summary>
+        /// Removes all keys and values from the <see cref="ConcurrentDictionary{TKey,TValue}"/>.
+        /// </summary>
+        public void Clear()
+        {
+            int locksAcquired = 0;
+            try
+            {
+                AcquireAllLocks(ref locksAcquired);
+
+                Tables newTables = new Tables(new Node[DefaultCapacity], _tables._locks, new int[_tables._countPerLock.Length]);
+                _tables = newTables;
+                _budget = Math.Max(1, newTables._buckets.Length / newTables._locks.Length);
+            }
+            finally
+            {
+                ReleaseLocks(0, locksAcquired);
+            }
+        }
+
+        /// <summary>
+        /// Copies the elements of the <see cref="T:System.Collections.Generic.ICollection"/> to an array of
+        /// type <see cref="T:System.Collections.Generic.KeyValuePair{TKey,TValue}"/>, starting at the
+        /// specified array index.
+        /// </summary>
+        /// <param name="array">The one-dimensional array of type <see
+        /// cref="T:System.Collections.Generic.KeyValuePair{TKey,TValue}"/>
+        /// that is the destination of the <see
+        /// cref="T:System.Collections.Generic.KeyValuePair{TKey,TValue}"/> elements copied from the <see
+        /// cref="T:System.Collections.ICollection"/>. The array must have zero-based indexing.</param>
+        /// <param name="index">The zero-based index in <paramref name="array"/> at which copying
+        /// begins.</param>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="array"/> is a null reference
+        /// (Nothing in Visual Basic).</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="index"/> is less than
+        /// 0.</exception>
+        /// <exception cref="T:System.ArgumentException"><paramref name="index"/> is equal to or greater than
+        /// the length of the <paramref name="array"/>. -or- The number of elements in the source <see
+        /// cref="T:System.Collections.ICollection"/>
+        /// is greater than the available space from <paramref name="index"/> to the end of the destination
+        /// <paramref name="array"/>.</exception>
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "ConcurrencyCop just doesn't know about these locks")]
+        void ICollection<KeyValuePair<TKey, TValue>>.CopyTo(KeyValuePair<TKey, TValue>[] array, int index)
+        {
+            if (array == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            if (index < 0) ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ConcurrentDictionary_IndexIsNegative);
+
+            int locksAcquired = 0;
+            try
+            {
+                AcquireAllLocks(ref locksAcquired);
+
+                int count = 0;
+
+                for (int i = 0; i < _tables._locks.Length && count >= 0; i++)
+                {
+                    count += _tables._countPerLock[i];
+                }
+
+                if (array.Length - count < index || count < 0) //"count" itself or "count + index" can overflow
+                {
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.ConcurrentDictionary_ArrayNotLargeEnough);
+                }
+
+                CopyToPairs(array, index);
+            }
+            finally
+            {
+                ReleaseLocks(0, locksAcquired);
+            }
+        }
+
+        /// <summary>
+        /// Copies the key and value pairs stored in the <see cref="ConcurrentDictionary{TKey,TValue}"/> to a
+        /// new array.
+        /// </summary>
+        /// <returns>A new array containing a snapshot of key and value pairs copied from the <see
+        /// cref="ConcurrentDictionary{TKey,TValue}"/>.</returns>
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "ConcurrencyCop just doesn't know about these locks")]
+        public KeyValuePair<TKey, TValue>[] ToArray()
+        {
+            int locksAcquired = 0;
+            try
+            {
+                AcquireAllLocks(ref locksAcquired);
+                int count = 0;
+                checked
+                {
+                    for (int i = 0; i < _tables._locks.Length; i++)
+                    {
+                        count += _tables._countPerLock[i];
+                    }
+                }
+
+                if (count == 0)
+                {
+                    return Array.Empty<KeyValuePair<TKey, TValue>>();
+                }
+
+                KeyValuePair<TKey, TValue>[] array = new KeyValuePair<TKey, TValue>[count];
+                CopyToPairs(array, 0);
+                return array;
+            }
+            finally
+            {
+                ReleaseLocks(0, locksAcquired);
+            }
+        }
+
+        /// <summary>
+        /// Copy dictionary contents to an array - shared implementation between ToArray and CopyTo.
+        /// 
+        /// Important: the caller must hold all locks in _locks before calling CopyToPairs.
+        /// </summary>
+        private void CopyToPairs(KeyValuePair<TKey, TValue>[] array, int index)
+        {
+            Node[] buckets = _tables._buckets;
+            for (int i = 0; i < buckets.Length; i++)
+            {
+                for (Node current = buckets[i]; current != null; current = current._next)
+                {
+                    array[index] = new KeyValuePair<TKey, TValue>(current._key, current._value);
+                    index++; //this should never flow, CopyToPairs is only called when there's no overflow risk
+                }
+            }
+        }
+
+        /// <summary>
+        /// Copy dictionary contents to an array - shared implementation between ToArray and CopyTo.
+        /// 
+        /// Important: the caller must hold all locks in _locks before calling CopyToEntries.
+        /// </summary>
+        private void CopyToEntries(DictionaryEntry[] array, int index)
+        {
+            Node[] buckets = _tables._buckets;
+            for (int i = 0; i < buckets.Length; i++)
+            {
+                for (Node current = buckets[i]; current != null; current = current._next)
+                {
+                    array[index] = new DictionaryEntry(current._key, current._value);
+                    index++;  //this should never flow, CopyToEntries is only called when there's no overflow risk
+                }
+            }
+        }
+
+        /// <summary>
+        /// Copy dictionary contents to an array - shared implementation between ToArray and CopyTo.
+        /// 
+        /// Important: the caller must hold all locks in _locks before calling CopyToObjects.
+        /// </summary>
+        private void CopyToObjects(object[] array, int index)
+        {
+            Node[] buckets = _tables._buckets;
+            for (int i = 0; i < buckets.Length; i++)
+            {
+                for (Node current = buckets[i]; current != null; current = current._next)
+                {
+                    array[index] = new KeyValuePair<TKey, TValue>(current._key, current._value);
+                    index++; //this should never flow, CopyToObjects is only called when there's no overflow risk
+                }
+            }
+        }
+
+        /// <summary>Returns an enumerator that iterates through the <see
+        /// cref="ConcurrentDictionary{TKey,TValue}"/>.</summary>
+        /// <returns>An enumerator for the <see cref="ConcurrentDictionary{TKey,TValue}"/>.</returns>
+        /// <remarks>
+        /// The enumerator returned from the dictionary is safe to use concurrently with
+        /// reads and writes to the dictionary, however it does not represent a moment-in-time snapshot
+        /// of the dictionary.  The contents exposed through the enumerator may contain modifications
+        /// made to the dictionary after <see cref="GetEnumerator"/> was called.
+        /// </remarks>
+        public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
+        {
+            Node[] buckets = _tables._buckets;
+
+            for (int i = 0; i < buckets.Length; i++)
+            {
+                // The Volatile.Read ensures that we have a copy of the reference to buckets[i].
+                // This protects us from reading fields ('_key', '_value' and '_next') of different instances.
+                Node current = Volatile.Read<Node>(ref buckets[i]);
+
+                while (current != null)
+                {
+                    yield return new KeyValuePair<TKey, TValue>(current._key, current._value);
+                    current = current._next;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Shared internal implementation for inserts and updates.
+        /// If key exists, we always return false; and if updateIfExists == true we force update with value;
+        /// If key doesn't exist, we always add value and return true;
+        /// </summary>
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "Reviewed for thread safety")]
+        private bool TryAddInternal(TKey key, int hashcode, TValue value, bool updateIfExists, bool acquireLock, out TValue resultingValue)
+        {
+            Debug.Assert(_comparer.GetHashCode(key) == hashcode);
+
+            while (true)
+            {
+                int bucketNo, lockNo;
+
+                Tables tables = _tables;
+                GetBucketAndLockNo(hashcode, out bucketNo, out lockNo, tables._buckets.Length, tables._locks.Length);
+
+                bool resizeDesired = false;
+                bool lockTaken = false;
+                try
+                {
+                    if (acquireLock)
+                        Monitor.Enter(tables._locks[lockNo], ref lockTaken);
+
+                    // If the table just got resized, we may not be holding the right lock, and must retry.
+                    // This should be a rare occurrence.
+                    if (tables != _tables)
+                    {
+                        continue;
+                    }
+
+                    // Try to find this key in the bucket
+                    Node prev = null;
+                    for (Node node = tables._buckets[bucketNo]; node != null; node = node._next)
+                    {
+                        Debug.Assert((prev == null && node == tables._buckets[bucketNo]) || prev._next == node);
+                        if (hashcode == node._hashcode && _comparer.Equals(node._key, key))
+                        {
+                            // The key was found in the dictionary. If updates are allowed, update the value for that key.
+                            // We need to create a new node for the update, in order to support TValue types that cannot
+                            // be written atomically, since lock-free reads may be happening concurrently.
+                            if (updateIfExists)
+                            {
+                                if (s_isValueWriteAtomic)
+                                {
+                                    node._value = value;
+                                }
+                                else
+                                {
+                                    Node newNode = new Node(node._key, value, hashcode, node._next);
+                                    if (prev == null)
+                                    {
+                                        Volatile.Write(ref tables._buckets[bucketNo], newNode);
+                                    }
+                                    else
+                                    {
+                                        prev._next = newNode;
+                                    }
+                                }
+                                resultingValue = value;
+                            }
+                            else
+                            {
+                                resultingValue = node._value;
+                            }
+                            return false;
+                        }
+                        prev = node;
+                    }
+
+                    // The key was not found in the bucket. Insert the key-value pair.
+                    Volatile.Write<Node>(ref tables._buckets[bucketNo], new Node(key, value, hashcode, tables._buckets[bucketNo]));
+                    checked
+                    {
+                        tables._countPerLock[lockNo]++;
+                    }
+
+                    //
+                    // If the number of elements guarded by this lock has exceeded the budget, resize the bucket table.
+                    // It is also possible that GrowTable will increase the budget but won't resize the bucket table.
+                    // That happens if the bucket table is found to be poorly utilized due to a bad hash function.
+                    //
+                    if (tables._countPerLock[lockNo] > _budget)
+                    {
+                        resizeDesired = true;
+                    }
+                }
+                finally
+                {
+                    if (lockTaken)
+                        Monitor.Exit(tables._locks[lockNo]);
+                }
+
+                //
+                // The fact that we got here means that we just performed an insertion. If necessary, we will grow the table.
+                //
+                // Concurrency notes:
+                // - Notice that we are not holding any locks at when calling GrowTable. This is necessary to prevent deadlocks.
+                // - As a result, it is possible that GrowTable will be called unnecessarily. But, GrowTable will obtain lock 0
+                //   and then verify that the table we passed to it as the argument is still the current table.
+                //
+                if (resizeDesired)
+                {
+                    GrowTable(tables);
+                }
+
+                resultingValue = value;
+                return true;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the value associated with the specified key.
+        /// </summary>
+        /// <param name="key">The key of the value to get or set.</param>
+        /// <value>The value associated with the specified key. If the specified key is not found, a get
+        /// operation throws a
+        /// <see cref="T:System.Collections.Generic.KeyNotFoundException"/>, and a set operation creates a new
+        /// element with the specified key.</value>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="key"/> is a null reference
+        /// (Nothing in Visual Basic).</exception>
+        /// <exception cref="T:System.Collections.Generic.KeyNotFoundException">The property is retrieved and
+        /// <paramref name="key"/>
+        /// does not exist in the collection.</exception>
+        public TValue this[TKey key]
+        {
+            get
+            {
+                TValue value;
+                if (!TryGetValue(key, out value))
+                {
+                    ThrowKeyNotFoundException(key);
+                }
+                return value;
+            }
+            set
+            {
+                if (key == null) ThrowKeyNullException();
+                TValue dummy;
+                TryAddInternal(key, _comparer.GetHashCode(key), value, true, true, out dummy);
+            }
+        }
+
+        // These exception throwing sites have been extracted into their own NoInlining methods
+        // as these are uncommonly needed and when inlined are observed to prevent the inlining
+        // of important methods like TryGetValue and ContainsKey.
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void ThrowKeyNotFoundException(object key)
+        {
+            throw new KeyNotFoundException(SR.Format(SR.Arg_KeyNotFoundWithKey, key.ToString()));
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void ThrowKeyNullException()
+        {
+            throw new ArgumentNullException("key");
+        }
+
+        /// <summary>
+        /// Gets the number of key/value pairs contained in the <see
+        /// cref="ConcurrentDictionary{TKey,TValue}"/>.
+        /// </summary>
+        /// <exception cref="T:System.OverflowException">The dictionary contains too many
+        /// elements.</exception>
+        /// <value>The number of key/value pairs contained in the <see
+        /// cref="ConcurrentDictionary{TKey,TValue}"/>.</value>
+        /// <remarks>Count has snapshot semantics and represents the number of items in the <see
+        /// cref="ConcurrentDictionary{TKey,TValue}"/>
+        /// at the moment when Count was accessed.</remarks>
+        public int Count
+        {
+            [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "ConcurrencyCop just doesn't know about these locks")]
+            get
+            {
+                int acquiredLocks = 0;
+                try
+                {
+                    // Acquire all locks
+                    AcquireAllLocks(ref acquiredLocks);
+
+                    return GetCountInternal();
+                }
+                finally
+                {
+                    // Release locks that have been acquired earlier
+                    ReleaseLocks(0, acquiredLocks);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets the number of key/value pairs contained in the <see
+        /// cref="ConcurrentDictionary{TKey,TValue}"/>. Should only be used after all locks
+        /// have been acquired.
+        /// </summary>
+        /// <exception cref="T:System.OverflowException">The dictionary contains too many
+        /// elements.</exception>
+        /// <value>The number of key/value pairs contained in the <see
+        /// cref="ConcurrentDictionary{TKey,TValue}"/>.</value>
+        /// <remarks>Count has snapshot semantics and represents the number of items in the <see
+        /// cref="ConcurrentDictionary{TKey,TValue}"/>
+        /// at the moment when Count was accessed.</remarks>
+        private int GetCountInternal()
+        {
+            int count = 0;
+
+            // Compute the count, we allow overflow
+            for (int i = 0; i < _tables._countPerLock.Length; i++)
+            {
+                count += _tables._countPerLock[i];
+            }
+
+            return count;
+        }
+
+        /// <summary>
+        /// Gets a value that indicates whether the <see cref="ConcurrentDictionary{TKey,TValue}"/> is empty.
+        /// </summary>
+        /// <value>true if the <see cref="ConcurrentDictionary{TKey,TValue}"/> is empty; otherwise,
+        /// false.</value>
+        public bool IsEmpty
+        {
+            [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "ConcurrencyCop just doesn't know about these locks")]
+            get
+            {
+                int acquiredLocks = 0;
+                try
+                {
+                    // Acquire all locks
+                    AcquireAllLocks(ref acquiredLocks);
+
+                    for (int i = 0; i < _tables._countPerLock.Length; i++)
+                    {
+                        if (_tables._countPerLock[i] != 0)
+                        {
+                            return false;
+                        }
+                    }
+                }
+                finally
+                {
+                    // Release locks that have been acquired earlier
+                    ReleaseLocks(0, acquiredLocks);
+                }
+
+                return true;
+            }
+        }
+
+        #region IDictionary<TKey,TValue> members
+
+        /// <summary>
+        /// Adds the specified key and value to the <see
+        /// cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"/>.
+        /// </summary>
+        /// <param name="key">The object to use as the key of the element to add.</param>
+        /// <param name="value">The object to use as the value of the element to add.</param>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="key"/> is a null reference
+        /// (Nothing in Visual Basic).</exception>
+        /// <exception cref="T:System.OverflowException">The dictionary contains too many
+        /// elements.</exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// An element with the same key already exists in the <see
+        /// cref="ConcurrentDictionary{TKey,TValue}"/>.</exception>
+        void IDictionary<TKey, TValue>.Add(TKey key, TValue value)
+        {
+            if (!TryAdd(key, value))
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.ConcurrentDictionary_KeyAlreadyExisted, ExceptionArgument.key);
+            }
+        }
+
+        /// <summary>
+        /// Removes the element with the specified key from the <see
+        /// cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"/>.
+        /// </summary>
+        /// <param name="key">The key of the element to remove.</param>
+        /// <returns>true if the element is successfully remove; otherwise false. This method also returns
+        /// false if
+        /// <paramref name="key"/> was not found in the original <see
+        /// cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"/>.
+        /// </returns>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="key"/> is a null reference
+        /// (Nothing in Visual Basic).</exception>
+        bool IDictionary<TKey, TValue>.Remove(TKey key)
+        {
+            TValue throwAwayValue;
+            return TryRemove(key, out throwAwayValue);
+        }
+
+        /// <summary>
+        /// Gets a collection containing the keys in the <see
+        /// cref="T:System.Collections.Generic.Dictionary{TKey,TValue}"/>.
+        /// </summary>
+        /// <value>An <see cref="T:System.Collections.Generic.ICollection{TKey}"/> containing the keys in the
+        /// <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}"/>.</value>
+        public ICollection<TKey> Keys
+        {
+            get { return GetKeys(); }
+        }
+
+        /// <summary>
+        /// Gets an <see cref="T:System.Collections.Generic.IEnumerable{TKey}"/> containing the keys of
+        /// the <see cref="T:System.Collections.Generic.IReadOnlyDictionary{TKey,TValue}"/>.
+        /// </summary>
+        /// <value>An <see cref="T:System.Collections.Generic.IEnumerable{TKey}"/> containing the keys of
+        /// the <see cref="T:System.Collections.Generic.IReadOnlyDictionary{TKey,TValue}"/>.</value>
+        IEnumerable<TKey> IReadOnlyDictionary<TKey, TValue>.Keys
+        {
+            get { return GetKeys(); }
+        }
+
+        /// <summary>
+        /// Gets a collection containing the values in the <see
+        /// cref="T:System.Collections.Generic.Dictionary{TKey,TValue}"/>.
+        /// </summary>
+        /// <value>An <see cref="T:System.Collections.Generic.ICollection{TValue}"/> containing the values in
+        /// the
+        /// <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}"/>.</value>
+        public ICollection<TValue> Values
+        {
+            get { return GetValues(); }
+        }
+
+        /// <summary>
+        /// Gets an <see cref="T:System.Collections.Generic.IEnumerable{TValue}"/> containing the values
+        /// in the <see cref="T:System.Collections.Generic.IReadOnlyDictionary{TKey,TValue}"/>.
+        /// </summary>
+        /// <value>An <see cref="T:System.Collections.Generic.IEnumerable{TValue}"/> containing the
+        /// values in the <see cref="T:System.Collections.Generic.IReadOnlyDictionary{TKey,TValue}"/>.</value>
+        IEnumerable<TValue> IReadOnlyDictionary<TKey, TValue>.Values
+        {
+            get { return GetValues(); }
+        }
+        #endregion
+
+        #region ICollection<KeyValuePair<TKey,TValue>> Members
+
+        /// <summary>
+        /// Adds the specified value to the <see cref="T:System.Collections.Generic.ICollection{TValue}"/>
+        /// with the specified key.
+        /// </summary>
+        /// <param name="keyValuePair">The <see cref="T:System.Collections.Generic.KeyValuePair{TKey,TValue}"/>
+        /// structure representing the key and value to add to the <see
+        /// cref="T:System.Collections.Generic.Dictionary{TKey,TValue}"/>.</param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="keyValuePair"/> of <paramref
+        /// name="keyValuePair"/> is null.</exception>
+        /// <exception cref="T:System.OverflowException">The <see
+        /// cref="T:System.Collections.Generic.Dictionary{TKey,TValue}"/>
+        /// contains too many elements.</exception>
+        /// <exception cref="T:System.ArgumentException">An element with the same key already exists in the
+        /// <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}"/></exception>
+        void ICollection<KeyValuePair<TKey, TValue>>.Add(KeyValuePair<TKey, TValue> keyValuePair)
+        {
+            ((IDictionary<TKey, TValue>)this).Add(keyValuePair.Key, keyValuePair.Value);
+        }
+
+        /// <summary>
+        /// Determines whether the <see cref="T:System.Collections.Generic.ICollection{TKey,TValue}"/>
+        /// contains a specific key and value.
+        /// </summary>
+        /// <param name="keyValuePair">The <see cref="T:System.Collections.Generic.KeyValuePair{TKey,TValue}"/>
+        /// structure to locate in the <see
+        /// cref="T:System.Collections.Generic.ICollection{TValue}"/>.</param>
+        /// <returns>true if the <paramref name="keyValuePair"/> is found in the <see
+        /// cref="T:System.Collections.Generic.ICollection{TKey,TValue}"/>; otherwise, false.</returns>
+        bool ICollection<KeyValuePair<TKey, TValue>>.Contains(KeyValuePair<TKey, TValue> keyValuePair)
+        {
+            TValue value;
+            if (!TryGetValue(keyValuePair.Key, out value))
+            {
+                return false;
+            }
+            return EqualityComparer<TValue>.Default.Equals(value, keyValuePair.Value);
+        }
+
+        /// <summary>
+        /// Gets a value indicating whether the dictionary is read-only.
+        /// </summary>
+        /// <value>true if the <see cref="T:System.Collections.Generic.ICollection{TKey,TValue}"/> is
+        /// read-only; otherwise, false. For <see
+        /// cref="T:System.Collections.Generic.Dictionary{TKey,TValue}"/>, this property always returns
+        /// false.</value>
+        bool ICollection<KeyValuePair<TKey, TValue>>.IsReadOnly
+        {
+            get { return false; }
+        }
+
+        /// <summary>
+        /// Removes a key and value from the dictionary.
+        /// </summary>
+        /// <param name="keyValuePair">The <see
+        /// cref="T:System.Collections.Generic.KeyValuePair{TKey,TValue}"/>
+        /// structure representing the key and value to remove from the <see
+        /// cref="T:System.Collections.Generic.Dictionary{TKey,TValue}"/>.</param>
+        /// <returns>true if the key and value represented by <paramref name="keyValuePair"/> is successfully
+        /// found and removed; otherwise, false.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The Key property of <paramref
+        /// name="keyValuePair"/> is a null reference (Nothing in Visual Basic).</exception>
+        bool ICollection<KeyValuePair<TKey, TValue>>.Remove(KeyValuePair<TKey, TValue> keyValuePair)
+        {
+            if (keyValuePair.Key == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.keyValuePair, ExceptionResource.ConcurrentDictionary_ItemKeyIsNull);
+
+            TValue throwAwayValue;
+            return TryRemoveInternal(keyValuePair.Key, out throwAwayValue, true, keyValuePair.Value);
+        }
+
+        #endregion
+
+        #region IEnumerable Members
+
+        /// <summary>Returns an enumerator that iterates through the <see
+        /// cref="ConcurrentDictionary{TKey,TValue}"/>.</summary>
+        /// <returns>An enumerator for the <see cref="ConcurrentDictionary{TKey,TValue}"/>.</returns>
+        /// <remarks>
+        /// The enumerator returned from the dictionary is safe to use concurrently with
+        /// reads and writes to the dictionary, however it does not represent a moment-in-time snapshot
+        /// of the dictionary.  The contents exposed through the enumerator may contain modifications
+        /// made to the dictionary after <see cref="GetEnumerator"/> was called.
+        /// </remarks>
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return ((ConcurrentDictionary<TKey, TValue>)this).GetEnumerator();
+        }
+
+        #endregion
+
+        #region IDictionary Members
+
+        /// <summary>
+        /// Adds the specified key and value to the dictionary.
+        /// </summary>
+        /// <param name="key">The object to use as the key.</param>
+        /// <param name="value">The object to use as the value.</param>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="key"/> is a null reference
+        /// (Nothing in Visual Basic).</exception>
+        /// <exception cref="T:System.OverflowException">The dictionary contains too many
+        /// elements.</exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// <paramref name="key"/> is of a type that is not assignable to the key type <typeparamref
+        /// name="TKey"/> of the <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}"/>. -or-
+        /// <paramref name="value"/> is of a type that is not assignable to <typeparamref name="TValue"/>,
+        /// the type of values in the <see cref="T:System.Collections.Generic.Dictionary{TKey,TValue}"/>.
+        /// -or- A value with the same key already exists in the <see
+        /// cref="T:System.Collections.Generic.Dictionary{TKey,TValue}"/>.
+        /// </exception>
+        void IDictionary.Add(object key, object value)
+        {
+            if (key == null) ThrowKeyNullException();
+            if (!(key is TKey)) ThrowHelper.ThrowArgumentException(ExceptionResource.ConcurrentDictionary_TypeOfKeyIncorrect, ExceptionArgument.key);
+
+            TValue typedValue;
+            try
+            {
+                typedValue = (TValue)value;
+            }
+            catch (InvalidCastException)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.ConcurrentDictionary_TypeOfValueIncorrect, ExceptionArgument.value);
+                return;
+            }
+
+            ((IDictionary<TKey, TValue>)this).Add((TKey)key, typedValue);
+        }
+
+        /// <summary>
+        /// Gets whether the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"/> contains an
+        /// element with the specified key.
+        /// </summary>
+        /// <param name="key">The key to locate in the <see
+        /// cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"/>.</param>
+        /// <returns>true if the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"/> contains
+        /// an element with the specified key; otherwise, false.</returns>
+        /// <exception cref="T:System.ArgumentNullException"> <paramref name="key"/> is a null reference
+        /// (Nothing in Visual Basic).</exception>
+        bool IDictionary.Contains(object key)
+        {
+            if (key == null) ThrowKeyNullException();
+
+            return (key is TKey) && this.ContainsKey((TKey)key);
+        }
+
+        /// <summary>Provides an <see cref="T:System.Collections.Generics.IDictionaryEnumerator"/> for the
+        /// <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"/>.</summary>
+        /// <returns>An <see cref="T:System.Collections.Generics.IDictionaryEnumerator"/> for the <see
+        /// cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"/>.</returns>
+        IDictionaryEnumerator IDictionary.GetEnumerator()
+        {
+            return new DictionaryEnumerator(this);
+        }
+
+        /// <summary>
+        /// Gets a value indicating whether the <see
+        /// cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"/> has a fixed size.
+        /// </summary>
+        /// <value>true if the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"/> has a
+        /// fixed size; otherwise, false. For <see
+        /// cref="T:System.Collections.Generic.ConcurrentDictionary{TKey,TValue}"/>, this property always
+        /// returns false.</value>
+        bool IDictionary.IsFixedSize
+        {
+            get { return false; }
+        }
+
+        /// <summary>
+        /// Gets a value indicating whether the <see
+        /// cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"/> is read-only.
+        /// </summary>
+        /// <value>true if the <see cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"/> is
+        /// read-only; otherwise, false. For <see
+        /// cref="T:System.Collections.Generic.ConcurrentDictionary{TKey,TValue}"/>, this property always
+        /// returns false.</value>
+        bool IDictionary.IsReadOnly
+        {
+            get { return false; }
+        }
+
+        /// <summary>
+        /// Gets an <see cref="T:System.Collections.ICollection"/> containing the keys of the <see
+        /// cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"/>.
+        /// </summary>
+        /// <value>An <see cref="T:System.Collections.ICollection"/> containing the keys of the <see
+        /// cref="T:System.Collections.Generic.IDictionary{TKey,TValue}"/>.</value>
+        ICollection IDictionary.Keys
+        {
+            get { return GetKeys(); }
+        }
+
+        /// <summary>
+        /// Removes the element with the specified key from the <see
+        /// cref="T:System.Collections.IDictionary"/>.
+        /// </summary>
+        /// <param name="key">The key of the element to remove.</param>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="key"/> is a null reference
+        /// (Nothing in Visual Basic).</exception>
+        void IDictionary.Remove(object key)
+        {
+            if (key == null) ThrowKeyNullException();
+
+            TValue throwAwayValue;
+            if (key is TKey)
+            {
+                TryRemove((TKey)key, out throwAwayValue);
+            }
+        }
+
+        /// <summary>
+        /// Gets an <see cref="T:System.Collections.ICollection"/> containing the values in the <see
+        /// cref="T:System.Collections.IDictionary"/>.
+        /// </summary>
+        /// <value>An <see cref="T:System.Collections.ICollection"/> containing the values in the <see
+        /// cref="T:System.Collections.IDictionary"/>.</value>
+        ICollection IDictionary.Values
+        {
+            get { return GetValues(); }
+        }
+
+        /// <summary>
+        /// Gets or sets the value associated with the specified key.
+        /// </summary>
+        /// <param name="key">The key of the value to get or set.</param>
+        /// <value>The value associated with the specified key, or a null reference (Nothing in Visual Basic)
+        /// if <paramref name="key"/> is not in the dictionary or <paramref name="key"/> is of a type that is
+        /// not assignable to the key type <typeparamref name="TKey"/> of the <see
+        /// cref="T:System.Collections.Generic.ConcurrentDictionary{TKey,TValue}"/>.</value>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="key"/> is a null reference
+        /// (Nothing in Visual Basic).</exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// A value is being assigned, and <paramref name="key"/> is of a type that is not assignable to the
+        /// key type <typeparamref name="TKey"/> of the <see
+        /// cref="T:System.Collections.Generic.ConcurrentDictionary{TKey,TValue}"/>. -or- A value is being
+        /// assigned, and <paramref name="key"/> is of a type that is not assignable to the value type
+        /// <typeparamref name="TValue"/> of the <see
+        /// cref="T:System.Collections.Generic.ConcurrentDictionary{TKey,TValue}"/>
+        /// </exception>
+        object IDictionary.this[object key]
+        {
+            get
+            {
+                if (key == null) ThrowKeyNullException();
+
+                TValue value;
+                if (key is TKey && TryGetValue((TKey)key, out value))
+                {
+                    return value;
+                }
+
+                return null;
+            }
+            set
+            {
+                if (key == null) ThrowKeyNullException();
+
+                if (!(key is TKey)) ThrowHelper.ThrowArgumentException(ExceptionResource.ConcurrentDictionary_TypeOfKeyIncorrect, ExceptionArgument.key);
+                if (!(value is TValue)) ThrowHelper.ThrowArgumentException(ExceptionResource.ConcurrentDictionary_TypeOfValueIncorrect, ExceptionArgument.value);
+
+                ((ConcurrentDictionary<TKey, TValue>)this)[(TKey)key] = (TValue)value;
+            }
+        }
+
+        #endregion
+
+        #region ICollection Members
+
+        /// <summary>
+        /// Copies the elements of the <see cref="T:System.Collections.ICollection"/> to an array, starting
+        /// at the specified array index.
+        /// </summary>
+        /// <param name="array">The one-dimensional array that is the destination of the elements copied from
+        /// the <see cref="T:System.Collections.ICollection"/>. The array must have zero-based
+        /// indexing.</param>
+        /// <param name="index">The zero-based index in <paramref name="array"/> at which copying
+        /// begins.</param>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="array"/> is a null reference
+        /// (Nothing in Visual Basic).</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="index"/> is less than
+        /// 0.</exception>
+        /// <exception cref="T:System.ArgumentException"><paramref name="index"/> is equal to or greater than
+        /// the length of the <paramref name="array"/>. -or- The number of elements in the source <see
+        /// cref="T:System.Collections.ICollection"/>
+        /// is greater than the available space from <paramref name="index"/> to the end of the destination
+        /// <paramref name="array"/>.</exception>
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "ConcurrencyCop just doesn't know about these locks")]
+        void ICollection.CopyTo(Array array, int index)
+        {
+            if (array == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            if (index < 0) ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ConcurrentDictionary_IndexIsNegative);
+
+            int locksAcquired = 0;
+            try
+            {
+                AcquireAllLocks(ref locksAcquired);
+                Tables tables = _tables;
+
+                int count = 0;
+
+                for (int i = 0; i < tables._locks.Length && count >= 0; i++)
+                {
+                    count += tables._countPerLock[i];
+                }
+
+                if (array.Length - count < index || count < 0) //"count" itself or "count + index" can overflow
+                {
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.ConcurrentDictionary_ArrayNotLargeEnough);
+                }
+
+                // To be consistent with the behavior of ICollection.CopyTo() in Dictionary<TKey,TValue>,
+                // we recognize three types of target arrays:
+                //    - an array of KeyValuePair<TKey, TValue> structs
+                //    - an array of DictionaryEntry structs
+                //    - an array of objects
+
+                KeyValuePair<TKey, TValue>[] pairs = array as KeyValuePair<TKey, TValue>[];
+                if (pairs != null)
+                {
+                    CopyToPairs(pairs, index);
+                    return;
+                }
+
+                DictionaryEntry[] entries = array as DictionaryEntry[];
+                if (entries != null)
+                {
+                    CopyToEntries(entries, index);
+                    return;
+                }
+
+                object[] objects = array as object[];
+                if (objects != null)
+                {
+                    CopyToObjects(objects, index);
+                    return;
+                }
+
+                ThrowHelper.ThrowArgumentException(ExceptionResource.ConcurrentDictionary_ArrayIncorrectType, ExceptionArgument.array);
+            }
+            finally
+            {
+                ReleaseLocks(0, locksAcquired);
+            }
+        }
+
+        /// <summary>
+        /// Gets a value indicating whether access to the <see cref="T:System.Collections.ICollection"/> is
+        /// synchronized with the SyncRoot.
+        /// </summary>
+        /// <value>true if access to the <see cref="T:System.Collections.ICollection"/> is synchronized
+        /// (thread safe); otherwise, false. For <see
+        /// cref="T:System.Collections.Concurrent.ConcurrentDictionary{TKey,TValue}"/>, this property always
+        /// returns false.</value>
+        bool ICollection.IsSynchronized
+        {
+            get { return false; }
+        }
+
+        /// <summary>
+        /// Gets an object that can be used to synchronize access to the <see
+        /// cref="T:System.Collections.ICollection"/>. This property is not supported.
+        /// </summary>
+        /// <exception cref="T:System.NotSupportedException">The SyncRoot property is not supported.</exception>
+        object ICollection.SyncRoot
+        {
+            get
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.ConcurrentCollection_SyncRoot_NotSupported);
+                return default(object);
+            }
+        }
+
+        #endregion
+
+        /// <summary>
+        /// Replaces the bucket table with a larger one. To prevent multiple threads from resizing the
+        /// table as a result of races, the Tables instance that holds the table of buckets deemed too
+        /// small is passed in as an argument to GrowTable(). GrowTable() obtains a lock, and then checks
+        /// the Tables instance has been replaced in the meantime or not.
+        /// </summary>
+        private void GrowTable(Tables tables)
+        {
+            const int MaxArrayLength = 0X7FEFFFFF;
+            int locksAcquired = 0;
+            try
+            {
+                // The thread that first obtains _locks[0] will be the one doing the resize operation
+                AcquireLocks(0, 1, ref locksAcquired);
+
+                // Make sure nobody resized the table while we were waiting for lock 0:
+                if (tables != _tables)
+                {
+                    // We assume that since the table reference is different, it was already resized (or the budget
+                    // was adjusted). If we ever decide to do table shrinking, or replace the table for other reasons,
+                    // we will have to revisit this logic.
+                    return;
+                }
+
+                // Compute the (approx.) total size. Use an Int64 accumulation variable to avoid an overflow.
+                long approxCount = 0;
+                for (int i = 0; i < tables._countPerLock.Length; i++)
+                {
+                    approxCount += tables._countPerLock[i];
+                }
+
+                //
+                // If the bucket array is too empty, double the budget instead of resizing the table
+                //
+                if (approxCount < tables._buckets.Length / 4)
+                {
+                    _budget = 2 * _budget;
+                    if (_budget < 0)
+                    {
+                        _budget = int.MaxValue;
+                    }
+                    return;
+                }
+
+
+                // Compute the new table size. We find the smallest integer larger than twice the previous table size, and not divisible by
+                // 2,3,5 or 7. We can consider a different table-sizing policy in the future.
+                int newLength = 0;
+                bool maximizeTableSize = false;
+                try
+                {
+                    checked
+                    {
+                        // Double the size of the buckets table and add one, so that we have an odd integer.
+                        newLength = tables._buckets.Length * 2 + 1;
+
+                        // Now, we only need to check odd integers, and find the first that is not divisible
+                        // by 3, 5 or 7.
+                        while (newLength % 3 == 0 || newLength % 5 == 0 || newLength % 7 == 0)
+                        {
+                            newLength += 2;
+                        }
+
+                        Debug.Assert(newLength % 2 != 0);
+
+                        if (newLength > MaxArrayLength)
+                        {
+                            maximizeTableSize = true;
+                        }
+                    }
+                }
+                catch (OverflowException)
+                {
+                    maximizeTableSize = true;
+                }
+
+                if (maximizeTableSize)
+                {
+                    newLength = MaxArrayLength;
+
+                    // We want to make sure that GrowTable will not be called again, since table is at the maximum size.
+                    // To achieve that, we set the budget to int.MaxValue.
+                    //
+                    // (There is one special case that would allow GrowTable() to be called in the future: 
+                    // calling Clear() on the ConcurrentDictionary will shrink the table and lower the budget.)
+                    _budget = int.MaxValue;
+                }
+
+                // Now acquire all other locks for the table
+                AcquireLocks(1, tables._locks.Length, ref locksAcquired);
+
+                object[] newLocks = tables._locks;
+
+                // Add more locks
+                if (_growLockArray && tables._locks.Length < MaxLockNumber)
+                {
+                    newLocks = new object[tables._locks.Length * 2];
+                    Array.Copy(tables._locks, 0, newLocks, 0, tables._locks.Length);
+                    for (int i = tables._locks.Length; i < newLocks.Length; i++)
+                    {
+                        newLocks[i] = new object();
+                    }
+                }
+
+                Node[] newBuckets = new Node[newLength];
+                int[] newCountPerLock = new int[newLocks.Length];
+
+                // Copy all data into a new table, creating new nodes for all elements
+                for (int i = 0; i < tables._buckets.Length; i++)
+                {
+                    Node current = tables._buckets[i];
+                    while (current != null)
+                    {
+                        Node next = current._next;
+                        int newBucketNo, newLockNo;
+                        GetBucketAndLockNo(current._hashcode, out newBucketNo, out newLockNo, newBuckets.Length, newLocks.Length);
+
+                        newBuckets[newBucketNo] = new Node(current._key, current._value, current._hashcode, newBuckets[newBucketNo]);
+
+                        checked
+                        {
+                            newCountPerLock[newLockNo]++;
+                        }
+
+                        current = next;
+                    }
+                }
+
+                // Adjust the budget
+                _budget = Math.Max(1, newBuckets.Length / newLocks.Length);
+
+                // Replace tables with the new versions
+                _tables = new Tables(newBuckets, newLocks, newCountPerLock);
+            }
+            finally
+            {
+                // Release all locks that we took earlier
+                ReleaseLocks(0, locksAcquired);
+            }
+        }
+
+        /// <summary>
+        /// Computes the bucket for a particular key. 
+        /// </summary>
+        private static int GetBucket(int hashcode, int bucketCount)
+        {
+            int bucketNo = (hashcode & 0x7fffffff) % bucketCount;
+            Debug.Assert(bucketNo >= 0 && bucketNo < bucketCount);
+            return bucketNo;
+        }
+
+        /// <summary>
+        /// Computes the bucket and lock number for a particular key. 
+        /// </summary>
+        private static void GetBucketAndLockNo(int hashcode, out int bucketNo, out int lockNo, int bucketCount, int lockCount)
+        {
+            bucketNo = (hashcode & 0x7fffffff) % bucketCount;
+            lockNo = bucketNo % lockCount;
+
+            Debug.Assert(bucketNo >= 0 && bucketNo < bucketCount);
+            Debug.Assert(lockNo >= 0 && lockNo < lockCount);
+        }
+
+        /// <summary>
+        /// The number of concurrent writes for which to optimize by default.
+        /// </summary>
+        private static int DefaultConcurrencyLevel
+        {
+            get { return PlatformHelper.ProcessorCount; }
+        }
+
+        /// <summary>
+        /// Acquires all locks for this hash table, and increments locksAcquired by the number
+        /// of locks that were successfully acquired. The locks are acquired in an increasing
+        /// order.
+        /// </summary>
+        private void AcquireAllLocks(ref int locksAcquired)
+        {
+            // First, acquire lock 0
+            AcquireLocks(0, 1, ref locksAcquired);
+
+            // Now that we have lock 0, the _locks array will not change (i.e., grow),
+            // and so we can safely read _locks.Length.
+            AcquireLocks(1, _tables._locks.Length, ref locksAcquired);
+            Debug.Assert(locksAcquired == _tables._locks.Length);
+        }
+
+        /// <summary>
+        /// Acquires a contiguous range of locks for this hash table, and increments locksAcquired
+        /// by the number of locks that were successfully acquired. The locks are acquired in an
+        /// increasing order.
+        /// </summary>
+        private void AcquireLocks(int fromInclusive, int toExclusive, ref int locksAcquired)
+        {
+            Debug.Assert(fromInclusive <= toExclusive);
+            object[] locks = _tables._locks;
+
+            for (int i = fromInclusive; i < toExclusive; i++)
+            {
+                bool lockTaken = false;
+                try
+                {
+                    Monitor.Enter(locks[i], ref lockTaken);
+                }
+                finally
+                {
+                    if (lockTaken)
+                    {
+                        locksAcquired++;
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Releases a contiguous range of locks.
+        /// </summary>
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "Reviewed for thread safety")]
+        private void ReleaseLocks(int fromInclusive, int toExclusive)
+        {
+            Debug.Assert(fromInclusive <= toExclusive);
+
+            for (int i = fromInclusive; i < toExclusive; i++)
+            {
+                Monitor.Exit(_tables._locks[i]);
+            }
+        }
+
+        /// <summary>
+        /// Gets a collection containing the keys in the dictionary.
+        /// </summary>
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "ConcurrencyCop just doesn't know about these locks")]
+        private ReadOnlyCollection<TKey> GetKeys()
+        {
+            int locksAcquired = 0;
+            try
+            {
+                AcquireAllLocks(ref locksAcquired);
+
+                int count = GetCountInternal();
+                if (count < 0) ThrowHelper.ThrowOutOfMemoryException();
+
+                List<TKey> keys = new List<TKey>(count);
+                for (int i = 0; i < _tables._buckets.Length; i++)
+                {
+                    Node current = _tables._buckets[i];
+                    while (current != null)
+                    {
+                        keys.Add(current._key);
+                        current = current._next;
+                    }
+                }
+
+                return new ReadOnlyCollection<TKey>(keys);
+            }
+            finally
+            {
+                ReleaseLocks(0, locksAcquired);
+            }
+        }
+
+        /// <summary>
+        /// Gets a collection containing the values in the dictionary.
+        /// </summary>
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "ConcurrencyCop just doesn't know about these locks")]
+        private ReadOnlyCollection<TValue> GetValues()
+        {
+            int locksAcquired = 0;
+            try
+            {
+                AcquireAllLocks(ref locksAcquired);
+
+                int count = GetCountInternal();
+                if (count < 0) ThrowHelper.ThrowOutOfMemoryException();
+
+                List<TValue> values = new List<TValue>(count);
+                for (int i = 0; i < _tables._buckets.Length; i++)
+                {
+                    Node current = _tables._buckets[i];
+                    while (current != null)
+                    {
+                        values.Add(current._value);
+                        current = current._next;
+                    }
+                }
+
+                return new ReadOnlyCollection<TValue>(values);
+            }
+            finally
+            {
+                ReleaseLocks(0, locksAcquired);
+            }
+        }
+
+        /// <summary>
+        /// A node in a singly-linked list representing a particular hash table bucket.
+        /// </summary>
+        private sealed class Node
+        {
+            internal readonly TKey _key;
+            internal TValue _value;
+            internal volatile Node _next;
+            internal readonly int _hashcode;
+
+            internal Node(TKey key, TValue value, int hashcode, Node next)
+            {
+                _key = key;
+                _value = value;
+                _next = next;
+                _hashcode = hashcode;
+            }
+        }
+
+        /// <summary>
+        /// A private class to represent enumeration over the dictionary that implements the 
+        /// IDictionaryEnumerator interface.
+        /// </summary>
+        private sealed class DictionaryEnumerator : IDictionaryEnumerator
+        {
+            IEnumerator<KeyValuePair<TKey, TValue>> _enumerator; // Enumerator over the dictionary.
+
+            internal DictionaryEnumerator(ConcurrentDictionary<TKey, TValue> dictionary)
+            {
+                _enumerator = dictionary.GetEnumerator();
+            }
+
+            public DictionaryEntry Entry
+            {
+                get { return new DictionaryEntry(_enumerator.Current.Key, _enumerator.Current.Value); }
+            }
+
+            public object Key
+            {
+                get { return _enumerator.Current.Key; }
+            }
+
+            public object Value
+            {
+                get { return _enumerator.Current.Value; }
+            }
+
+            public object Current
+            {
+                get { return Entry; }
+            }
+
+            public bool MoveNext()
+            {
+                return _enumerator.MoveNext();
+            }
+
+            public void Reset()
+            {
+                _enumerator.Reset();
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueue.cs b/src/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueue.cs
new file mode 100644
index 0000000000..304bcd6b79
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentQueue.cs
@@ -0,0 +1,1091 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Threading;
+
+namespace System.Collections.Concurrent
+{
+    /// <summary>
+    /// Represents a thread-safe first-in, first-out collection of objects.
+    /// </summary>
+    /// <typeparam name="T">Specifies the type of elements in the queue.</typeparam>
+    /// <remarks>
+    /// All public and protected members of <see cref="ConcurrentQueue{T}"/> are thread-safe and may be used
+    /// concurrently from multiple threads.
+    /// </remarks>
+    [DebuggerDisplay("Count = {Count}")]
+    [DebuggerTypeProxy(typeof(SystemCollectionsConcurrent_ProducerConsumerCollectionDebugView<>))]
+    internal class ConcurrentQueue<T> : IProducerConsumerCollection<T>, IReadOnlyCollection<T>
+    {
+        // This implementation provides an unbounded, multi-producer multi-consumer queue
+        // that supports the standard Enqueue/TryDequeue operations, as well as support for
+        // snapshot enumeration (GetEnumerator, ToArray, CopyTo), peeking, and Count/IsEmpty.
+        // It is composed of a linked list of bounded ring buffers, each of which has a head
+        // and a tail index, isolated from each other to minimize false sharing.  As long as
+        // the number of elements in the queue remains less than the size of the current
+        // buffer (Segment), no additional allocations are required for enqueued items.  When
+        // the number of items exceeds the size of the current segment, the current segment is
+        // "frozen" to prevent further enqueues, and a new segment is linked from it and set
+        // as the new tail segment for subsequent enqueues.  As old segments are consumed by
+        // dequeues, the head reference is updated to point to the segment that dequeuers should
+        // try next.  To support snapshot enumeration, segments also support the notion of
+        // preserving for observation, whereby they avoid overwriting state as part of dequeues.
+        // Any operation that requires a snapshot results in all current segments being
+        // both frozen for enqueues and preserved for observation: any new enqueues will go
+        // to new segments, and dequeuers will consume from the existing segments but without
+        // overwriting the existing data.
+
+        /// <summary>Initial length of the segments used in the queue.</summary>
+        private const int InitialSegmentLength = 32;
+        /// <summary>
+        /// Maximum length of the segments used in the queue.  This is a somewhat arbitrary limit:
+        /// larger means that as long as we don't exceed the size, we avoid allocating more segments,
+        /// but if we do exceed it, then the segment becomes garbage.
+        /// </summary>
+        private const int MaxSegmentLength = 1024 * 1024;
+
+        /// <summary>
+        /// Lock used to protect cross-segment operations, including any updates to <see cref="_tail"/> or <see cref="_head"/>
+        /// and any operations that need to get a consistent view of them.
+        /// </summary>
+        private object _crossSegmentLock;
+        /// <summary>The current tail segment.</summary>
+        private volatile Segment _tail;
+        /// <summary>The current head segment.</summary>
+        private volatile Segment _head;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ConcurrentQueue{T}"/> class.
+        /// </summary>
+        public ConcurrentQueue()
+        {
+            _crossSegmentLock = new object();
+            _tail = _head = new Segment(InitialSegmentLength);
+        }
+
+        /// <summary>
+        /// Initializes the contents of the queue from an existing collection.
+        /// </summary>
+        /// <param name="collection">A collection from which to copy elements.</param>
+        private void InitializeFromCollection(IEnumerable<T> collection)
+        {
+            _crossSegmentLock = new object();
+
+            // Determine the initial segment size.  We'll use the default,
+            // unless the collection is known to be larger than than, in which
+            // case we round its length up to a power of 2, as all segments must
+            // be a power of 2 in length.
+            int length = InitialSegmentLength;
+            var c = collection as ICollection<T>;
+            if (c != null)
+            {
+                int count = c.Count;
+                if (count > length)
+                {
+                    length = Math.Min(RoundUpToPowerOf2(count), MaxSegmentLength);
+                }
+            }
+
+            // Initialize the segment and add all of the data to it.
+            _tail = _head = new Segment(length);
+            foreach (T item in collection)
+            {
+                Enqueue(item);
+            }
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ConcurrentQueue{T}"/> class that contains elements copied
+        /// from the specified collection.
+        /// </summary>
+        /// <param name="collection">
+        /// The collection whose elements are copied to the new <see cref="ConcurrentQueue{T}"/>.
+        /// </param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="collection"/> argument is null.</exception>
+        public ConcurrentQueue(IEnumerable<T> collection)
+        {
+            if (collection == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.collection);
+            }
+
+            InitializeFromCollection(collection);
+        }
+
+        /// <summary>
+        /// Copies the elements of the <see cref="ICollection"/> to an <see
+        /// cref="Array"/>, starting at a particular <see cref="Array"/> index.
+        /// </summary>
+        /// <param name="array">
+        /// The one-dimensional <see cref="Array">Array</see> that is the destination of the
+        /// elements copied from the <see cref="ConcurrentQueue{T}"/>. <paramref name="array"/> must have
+        /// zero-based indexing.
+        /// </param>
+        /// <param name="index">The zero-based index in <paramref name="array"/> at which copying begins.</param>
+        /// <exception cref="ArgumentNullException"><paramref name="array"/> is a null reference (Nothing in
+        /// Visual Basic).</exception>
+        /// <exception cref="ArgumentOutOfRangeException"><paramref name="index"/> is less than
+        /// zero.</exception>
+        /// <exception cref="ArgumentException">
+        /// <paramref name="array"/> is multidimensional. -or-
+        /// <paramref name="array"/> does not have zero-based indexing. -or-
+        /// <paramref name="index"/> is equal to or greater than the length of the <paramref name="array"/>
+        /// -or- The number of elements in the source <see cref="ICollection"/> is
+        /// greater than the available space from <paramref name="index"/> to the end of the destination
+        /// <paramref name="array"/>. -or- The type of the source <see
+        /// cref="ICollection"/> cannot be cast automatically to the type of the
+        /// destination <paramref name="array"/>.
+        /// </exception>
+        void ICollection.CopyTo(Array array, int index)
+        {
+            // Special-case when the Array is actually a T[], taking a faster path
+            T[] szArray = array as T[];
+            if (szArray != null)
+            {
+                CopyTo(szArray, index);
+                return;
+            }
+
+            // Validate arguments.
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            // Otherwise, fall back to the slower path that first copies the contents
+            // to an array, and then uses that array's non-generic CopyTo to do the copy.
+            ToArray().CopyTo(array, index);
+        }
+
+        /// <summary>
+        /// Gets a value indicating whether access to the <see cref="ICollection"/> is
+        /// synchronized with the SyncRoot.
+        /// </summary>
+        /// <value>true if access to the <see cref="ICollection"/> is synchronized
+        /// with the SyncRoot; otherwise, false. For <see cref="ConcurrentQueue{T}"/>, this property always
+        /// returns false.</value>
+        bool ICollection.IsSynchronized => false; // always false, as true implies synchronization via SyncRoot
+
+        /// <summary>
+        /// Gets an object that can be used to synchronize access to the <see
+        /// cref="ICollection"/>. This property is not supported.
+        /// </summary>
+        /// <exception cref="NotSupportedException">The SyncRoot property is not supported.</exception>
+        object ICollection.SyncRoot { get { ThrowHelper.ThrowNotSupportedException(ExceptionResource.ConcurrentCollection_SyncRoot_NotSupported); return default(object); } }
+
+        /// <summary>Returns an enumerator that iterates through a collection.</summary>
+        /// <returns>An <see cref="IEnumerator"/> that can be used to iterate through the collection.</returns>
+        IEnumerator IEnumerable.GetEnumerator() => ((IEnumerable<T>)this).GetEnumerator();
+
+        /// <summary>
+        /// Gets a value that indicates whether the <see cref="ConcurrentQueue{T}"/> is empty.
+        /// </summary>
+        /// <value>true if the <see cref="ConcurrentQueue{T}"/> is empty; otherwise, false.</value>
+        /// <remarks>
+        /// For determining whether the collection contains any items, use of this property is recommended
+        /// rather than retrieving the number of items from the <see cref="Count"/> property and comparing it
+        /// to 0.  However, as this collection is intended to be accessed concurrently, it may be the case
+        /// that another thread will modify the collection after <see cref="IsEmpty"/> returns, thus invalidating
+        /// the result.
+        /// </remarks>
+        public bool IsEmpty
+        {
+            get
+            {
+                // IsEmpty == !TryPeek. We use a "resultUsed:false" peek in order to avoid marking
+                // segments as preserved for observation, making IsEmpty a cheaper way than either
+                // TryPeek(out T) or Count == 0 to check whether any elements are in the queue.
+                T ignoredResult;
+                return !TryPeek(out ignoredResult, resultUsed: false);
+            }
+        }
+
+        /// <summary>Copies the elements stored in the <see cref="ConcurrentQueue{T}"/> to a new array.</summary>
+        /// <returns>A new array containing a snapshot of elements copied from the <see cref="ConcurrentQueue{T}"/>.</returns>
+        public T[] ToArray()
+        {
+            // Snap the current contents for enumeration.
+            Segment head, tail;
+            int headHead, tailTail;
+            SnapForObservation(out head, out headHead, out tail, out tailTail);
+
+            // Count the number of items in that snapped set, and use it to allocate an
+            // array of the right size.
+            long count = GetCount(head, headHead, tail, tailTail);
+            T[] arr = new T[count];
+
+            // Now enumerate the contents, copying each element into the array.
+            using (IEnumerator<T> e = Enumerate(head, headHead, tail, tailTail))
+            {
+                int i = 0;
+                while (e.MoveNext())
+                {
+                    arr[i++] = e.Current;
+                }
+                Debug.Assert(count == i);
+            }
+
+            // And return it.
+            return arr;
+        }
+
+        /// <summary>
+        /// Gets the number of elements contained in the <see cref="ConcurrentQueue{T}"/>.
+        /// </summary>
+        /// <value>The number of elements contained in the <see cref="ConcurrentQueue{T}"/>.</value>
+        /// <remarks>
+        /// For determining whether the collection contains any items, use of the <see cref="IsEmpty"/>
+        /// property is recommended rather than retrieving the number of items from the <see cref="Count"/>
+        /// property and comparing it to 0.
+        /// </remarks>
+        public int Count
+        {
+            get
+            {
+                Segment head, tail;
+                int headHead, headTail, tailHead, tailTail;
+                var spinner = new SpinWait();
+                while (true)
+                {
+                    // Capture the head and tail, as well as the head's head and tail.
+                    head = _head;
+                    tail = _tail;
+                    headHead = Volatile.Read(ref head._headAndTail.Head);
+                    headTail = Volatile.Read(ref head._headAndTail.Tail);
+
+                    if (head == tail)
+                    {
+                        // There was a single segment in the queue.  If the captured
+                        // values still (or again) represent reality, return the segment's
+                        // count. A single segment should be the most common case once the
+                        // queue's size has stabilized after segments have grown to
+                        // the point where growing is no longer needed.
+                        if (head == _head &&
+                            head == _tail &&
+                            headHead == Volatile.Read(ref head._headAndTail.Head) &&
+                            headTail == Volatile.Read(ref head._headAndTail.Tail))
+                        {
+                            return GetCount(head, headHead, headTail);
+                        }
+                    }
+                    else if (head._nextSegment == tail)
+                    {
+                        // There were two segments in the queue.  Get the positions
+                        // from the tail, and if the captured values still (or again) match
+                        // reality, return the sum of the counts from both segments.
+                        tailHead = Volatile.Read(ref tail._headAndTail.Head);
+                        tailTail = Volatile.Read(ref tail._headAndTail.Tail);
+                        if (head == _head &&
+                            tail == _tail &&
+                            headHead == Volatile.Read(ref head._headAndTail.Head) &&
+                            headTail == Volatile.Read(ref head._headAndTail.Tail) &&
+                            tailHead == Volatile.Read(ref tail._headAndTail.Head) &&
+                            tailTail == Volatile.Read(ref tail._headAndTail.Tail))
+                        {
+                            // We got stable values, so we can just compute the sizes based on those
+                            // values and return the sum of the counts of the segments.
+                            return GetCount(head, headHead, headTail) + GetCount(tail, tailHead, tailTail);
+                        }
+                    }
+                    else
+                    {
+                        // There were more than two segments.  Take the slower path, where we freeze the
+                        // queue and then count the now stable segments.
+                        SnapForObservation(out head, out headHead, out tail, out tailTail);
+                        return unchecked((int)GetCount(head, headHead, tail, tailTail));
+                    }
+
+                    // We raced with enqueues/dequeues and captured an inconsistent picture of the queue.
+                    // Spin and try again.
+                    spinner.SpinOnce();
+                }
+            }
+        }
+
+        /// <summary>Computes the number of items in a segment based on a fixed head and tail in that segment.</summary>
+        private static int GetCount(Segment s, int head, int tail)
+        {
+            if (head != tail && head != tail - s.FreezeOffset)
+            {
+                head &= s._slotsMask;
+                tail &= s._slotsMask;
+                return head < tail ? tail - head : s._slots.Length - head + tail;
+            }
+            return 0;
+        }
+
+        /// <summary>Gets the number of items in snapped region.</summary>
+        private static long GetCount(Segment head, int headHead, Segment tail, int tailTail)
+        {
+            // All of the segments should have been both frozen for enqueues and preserved for observation.
+            // Validate that here for head and tail; we'll validate it for intermediate segments later.
+            Debug.Assert(head._preservedForObservation);
+            Debug.Assert(head._frozenForEnqueues);
+            Debug.Assert(tail._preservedForObservation);
+            Debug.Assert(tail._frozenForEnqueues);
+
+            long count = 0;
+
+            // Head segment.  We've already marked it as frozen for enqueues, so its tail position is fixed,
+            // and we've already marked it as preserved for observation (before we grabbed the head), so we
+            // can safely enumerate from its head to its tail and access its elements.
+            int headTail = (head == tail ? tailTail : Volatile.Read(ref head._headAndTail.Tail)) - head.FreezeOffset;
+            if (headHead < headTail)
+            {
+                // Mask the head and tail for the head segment
+                headHead &= head._slotsMask;
+                headTail &= head._slotsMask;
+
+                // Increase the count by either the one or two regions, based on whether tail
+                // has wrapped to be less than head.
+                count += headHead < headTail ?
+                    headTail - headHead :
+                    head._slots.Length - headHead + headTail;
+            }
+
+            // We've enumerated the head.  If the tail is different from the head, we need to
+            // enumerate the remaining segments.
+            if (head != tail)
+            {
+                // Count the contents of each segment between head and tail, not including head and tail.
+                // Since there were segments before these, for our purposes we consider them to start at
+                // the 0th element, and since there is at least one segment after each, each was frozen
+                // by the time we snapped it, so we can iterate until each's frozen tail.
+                for (Segment s = head._nextSegment; s != tail; s = s._nextSegment)
+                {
+                    Debug.Assert(s._preservedForObservation);
+                    Debug.Assert(s._frozenForEnqueues);
+                    count += s._headAndTail.Tail - s.FreezeOffset;
+                }
+
+                // Finally, enumerate the tail.  As with the intermediate segments, there were segments
+                // before this in the snapped region, so we can start counting from the beginning. Unlike
+                // the intermediate segments, we can't just go until the Tail, as that could still be changing;
+                // instead we need to go until the tail we snapped for observation.
+                count += tailTail - tail.FreezeOffset;
+            }
+
+            // Return the computed count.
+            return count;
+        }
+
+        /// <summary>
+        /// Copies the <see cref="ConcurrentQueue{T}"/> elements to an existing one-dimensional <see
+        /// cref="Array">Array</see>, starting at the specified array index.
+        /// </summary>
+        /// <param name="array">The one-dimensional <see cref="Array">Array</see> that is the
+        /// destination of the elements copied from the
+        /// <see cref="ConcurrentQueue{T}"/>. The <see cref="Array">Array</see> must have zero-based
+        /// indexing.</param>
+        /// <param name="index">The zero-based index in <paramref name="array"/> at which copying
+        /// begins.</param>
+        /// <exception cref="ArgumentNullException"><paramref name="array"/> is a null reference (Nothing in
+        /// Visual Basic).</exception>
+        /// <exception cref="ArgumentOutOfRangeException"><paramref name="index"/> is less than
+        /// zero.</exception>
+        /// <exception cref="ArgumentException"><paramref name="index"/> is equal to or greater than the
+        /// length of the <paramref name="array"/>
+        /// -or- The number of elements in the source <see cref="ConcurrentQueue{T}"/> is greater than the
+        /// available space from <paramref name="index"/> to the end of the destination <paramref
+        /// name="array"/>.
+        /// </exception>
+        public void CopyTo(T[] array, int index)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+            if (index < 0)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index);
+            }
+
+            // Snap for enumeration
+            Segment head, tail;
+            int headHead, tailTail;
+            SnapForObservation(out head, out headHead, out tail, out tailTail);
+
+            // Get the number of items to be enumerated
+            long count = GetCount(head, headHead, tail, tailTail);
+            if (index > array.Length - count)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall);
+            }
+
+            // Copy the items to the target array
+            int i = index;
+            using (IEnumerator<T> e = Enumerate(head, headHead, tail, tailTail))
+            {
+                while (e.MoveNext())
+                {
+                    array[i++] = e.Current;
+                }
+            }
+            Debug.Assert(count == i - index);
+        }
+
+        /// <summary>Returns an enumerator that iterates through the <see cref="ConcurrentQueue{T}"/>.</summary>
+        /// <returns>An enumerator for the contents of the <see
+        /// cref="ConcurrentQueue{T}"/>.</returns>
+        /// <remarks>
+        /// The enumeration represents a moment-in-time snapshot of the contents
+        /// of the queue.  It does not reflect any updates to the collection after 
+        /// <see cref="GetEnumerator"/> was called.  The enumerator is safe to use
+        /// concurrently with reads from and writes to the queue.
+        /// </remarks>
+        public IEnumerator<T> GetEnumerator()
+        {
+            Segment head, tail;
+            int headHead, tailTail;
+            SnapForObservation(out head, out headHead, out tail, out tailTail);
+            return Enumerate(head, headHead, tail, tailTail);
+        }
+
+        /// <summary>
+        /// Gets the head and tail information of the current contents of the queue.
+        /// After this call returns, the specified region can be enumerated any number
+        /// of times and will not change.
+        /// </summary>
+        private void SnapForObservation(out Segment head, out int headHead, out Segment tail, out int tailTail)
+        {
+            lock (_crossSegmentLock) // _head and _tail may only change while the lock is held.
+            {
+                // Snap the head and tail
+                head = _head;
+                tail = _tail;
+                Debug.Assert(head != null);
+                Debug.Assert(tail != null);
+                Debug.Assert(tail._nextSegment == null);
+
+                // Mark them and all segments in between as preserving, and ensure no additional items
+                // can be added to the tail.
+                for (Segment s = head; ; s = s._nextSegment)
+                {
+                    s._preservedForObservation = true;
+                    if (s == tail) break;
+                    Debug.Assert(s._frozenForEnqueues); // any non-tail should already be marked
+                }
+                tail.EnsureFrozenForEnqueues(); // we want to prevent the tailTail from moving
+
+                // At this point, any dequeues from any segment won't overwrite the value, and
+                // none of the existing segments can have new items enqueued.
+
+                headHead = Volatile.Read(ref head._headAndTail.Head);
+                tailTail = Volatile.Read(ref tail._headAndTail.Tail);
+            }
+        }
+
+        /// <summary>Gets the item stored in the <paramref name="i"/>th entry in <paramref name="segment"/>.</summary>
+        private T GetItemWhenAvailable(Segment segment, int i)
+        {
+            Debug.Assert(segment._preservedForObservation);
+
+            // Get the expected value for the sequence number
+            int expectedSequenceNumberAndMask = (i + 1) & segment._slotsMask;
+
+            // If the expected sequence number is not yet written, we're still waiting for
+            // an enqueuer to finish storing it.  Spin until it's there.
+            if ((segment._slots[i].SequenceNumber & segment._slotsMask) != expectedSequenceNumberAndMask)
+            {
+                var spinner = new SpinWait();
+                while ((Volatile.Read(ref segment._slots[i].SequenceNumber) & segment._slotsMask) != expectedSequenceNumberAndMask)
+                {
+                    spinner.SpinOnce();
+                }
+            }
+
+            // Return the value from the slot.
+            return segment._slots[i].Item;
+        }
+
+        private IEnumerator<T> Enumerate(Segment head, int headHead, Segment tail, int tailTail)
+        {
+            Debug.Assert(head._preservedForObservation);
+            Debug.Assert(head._frozenForEnqueues);
+            Debug.Assert(tail._preservedForObservation);
+            Debug.Assert(tail._frozenForEnqueues);
+
+            // Head segment.  We've already marked it as not accepting any more enqueues,
+            // so its tail position is fixed, and we've already marked it as preserved for
+            // enumeration (before we grabbed its head), so we can safely enumerate from
+            // its head to its tail.
+            int headTail = (head == tail ? tailTail : Volatile.Read(ref head._headAndTail.Tail)) - head.FreezeOffset;
+            if (headHead < headTail)
+            {
+                headHead &= head._slotsMask;
+                headTail &= head._slotsMask;
+
+                if (headHead < headTail)
+                {
+                    for (int i = headHead; i < headTail; i++) yield return GetItemWhenAvailable(head, i);
+                }
+                else
+                {
+                    for (int i = headHead; i < head._slots.Length; i++) yield return GetItemWhenAvailable(head, i);
+                    for (int i = 0; i < headTail; i++) yield return GetItemWhenAvailable(head, i);
+                }
+            }
+
+            // We've enumerated the head.  If the tail is the same, we're done.
+            if (head != tail)
+            {
+                // Each segment between head and tail, not including head and tail.  Since there were
+                // segments before these, for our purposes we consider it to start at the 0th element.
+                for (Segment s = head._nextSegment; s != tail; s = s._nextSegment)
+                {
+                    Debug.Assert(s._preservedForObservation, "Would have had to been preserved as a segment part of enumeration");
+                    Debug.Assert(s._frozenForEnqueues, "Would have had to be frozen for enqueues as it's intermediate");
+
+                    int sTail = s._headAndTail.Tail - s.FreezeOffset;
+                    for (int i = 0; i < sTail; i++)
+                    {
+                        yield return GetItemWhenAvailable(s, i);
+                    }
+                }
+
+                // Enumerate the tail.  Since there were segments before this, we can just start at
+                // its beginning, and iterate until the tail we already grabbed.
+                tailTail -= tail.FreezeOffset;
+                for (int i = 0; i < tailTail; i++)
+                {
+                    yield return GetItemWhenAvailable(tail, i);
+                }
+            }
+        }
+
+        /// <summary>Round the specified value up to the next power of 2, if it isn't one already.</summary>
+        private static int RoundUpToPowerOf2(int i)
+        {
+            --i;
+            i |= i >> 1;
+            i |= i >> 2;
+            i |= i >> 4;
+            i |= i >> 8;
+            i |= i >> 16;
+            return i + 1;
+        }
+
+        /// <summary>Adds an object to the end of the <see cref="ConcurrentQueue{T}"/>.</summary>
+        /// <param name="item">
+        /// The object to add to the end of the <see cref="ConcurrentQueue{T}"/>.
+        /// The value can be a null reference (Nothing in Visual Basic) for reference types.
+        /// </param>
+        public void Enqueue(T item)
+        {
+            // Try to enqueue to the current tail.
+            if (!_tail.TryEnqueue(item))
+            {
+                // If we're unable to, we need to take a slow path that will
+                // try to add a new tail segment.
+                EnqueueSlow(item);
+            }
+        }
+
+        /// <summary>Adds to the end of the queue, adding a new segment if necessary.</summary>
+        private void EnqueueSlow(T item)
+        {
+            while (true)
+            {
+                Segment tail = _tail;
+
+                // Try to append to the existing tail.
+                if (tail.TryEnqueue(item))
+                {
+                    return;
+                }
+
+                // If we were unsuccessful, take the lock so that we can compare and manipulate
+                // the tail.  Assuming another enqueuer hasn't already added a new segment,
+                // do so, then loop around to try enqueueing again.
+                lock (_crossSegmentLock)
+                {
+                    if (tail == _tail)
+                    {
+                        // Make sure no one else can enqueue to this segment.
+                        tail.EnsureFrozenForEnqueues();
+
+                        // We determine the new segment's length based on the old length.
+                        // In general, we double the size of the segment, to make it less likely
+                        // that we'll need to grow again.  However, if the tail segment is marked
+                        // as preserved for observation, something caused us to avoid reusing this
+                        // segment, and if that happens a lot and we grow, we'll end up allocating
+                        // lots of wasted space.  As such, in such situations we reset back to the
+                        // initial segment length; if these observations are happening frequently,
+                        // this will help to avoid wasted memory, and if they're not, we'll
+                        // relatively quickly grow again to a larger size.
+                        int nextSize = tail._preservedForObservation ? InitialSegmentLength : Math.Min(tail.Capacity * 2, MaxSegmentLength);
+                        var newTail = new Segment(nextSize);
+
+                        // Hook up the new tail.
+                        tail._nextSegment = newTail;
+                        _tail = newTail;
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Attempts to remove and return the object at the beginning of the <see
+        /// cref="ConcurrentQueue{T}"/>.
+        /// </summary>
+        /// <param name="result">
+        /// When this method returns, if the operation was successful, <paramref name="result"/> contains the
+        /// object removed. If no object was available to be removed, the value is unspecified.
+        /// </param>
+        /// <returns>
+        /// true if an element was removed and returned from the beginning of the
+        /// <see cref="ConcurrentQueue{T}"/> successfully; otherwise, false.
+        /// </returns>
+        public bool TryDequeue(out T result) =>
+            _head.TryDequeue(out result) || // fast-path that operates just on the head segment
+            TryDequeueSlow(out result); // slow path that needs to fix up segments
+
+        /// <summary>Tries to dequeue an item, removing empty segments as needed.</summary>
+        private bool TryDequeueSlow(out T item)
+        {
+            while (true)
+            {
+                // Get the current head
+                Segment head = _head;
+
+                // Try to take.  If we're successful, we're done.
+                if (head.TryDequeue(out item))
+                {
+                    return true;
+                }
+
+                // Check to see whether this segment is the last. If it is, we can consider
+                // this to be a moment-in-time empty condition (even though between the TryDequeue
+                // check and this check, another item could have arrived).
+                if (head._nextSegment == null)
+                {
+                    item = default(T);
+                    return false;
+                }
+
+                // At this point we know that head.Next != null, which means
+                // this segment has been frozen for additional enqueues. But between
+                // the time that we ran TryDequeue and checked for a next segment,
+                // another item could have been added.  Try to dequeue one more time
+                // to confirm that the segment is indeed empty.
+                Debug.Assert(head._frozenForEnqueues);
+                if (head.TryDequeue(out item))
+                {
+                    return true;
+                }
+
+                // This segment is frozen (nothing more can be added) and empty (nothing is in it).
+                // Update head to point to the next segment in the list, assuming no one's beat us to it.
+                lock (_crossSegmentLock)
+                {
+                    if (head == _head)
+                    {
+                        _head = head._nextSegment;
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Attempts to return an object from the beginning of the <see cref="ConcurrentQueue{T}"/>
+        /// without removing it.
+        /// </summary>
+        /// <param name="result">
+        /// When this method returns, <paramref name="result"/> contains an object from
+        /// the beginning of the <see cref="Concurrent.ConcurrentQueue{T}"/> or default(T)
+        /// if the operation failed.
+        /// </param>
+        /// <returns>true if and object was returned successfully; otherwise, false.</returns>
+        /// <remarks>
+        /// For determining whether the collection contains any items, use of the <see cref="IsEmpty"/>
+        /// property is recommended rather than peeking.
+        /// </remarks>
+        public bool TryPeek(out T result) => TryPeek(out result, resultUsed: true);
+
+        /// <summary>Attempts to retrieve the value for the first element in the queue.</summary>
+        /// <param name="result">The value of the first element, if found.</param>
+        /// <param name="resultUsed">true if the result is needed; otherwise false if only the true/false outcome is needed.</param>
+        /// <returns>true if an element was found; otherwise, false.</returns>
+        private bool TryPeek(out T result, bool resultUsed)
+        {
+            // Starting with the head segment, look through all of the segments
+            // for the first one we can find that's not empty.
+            Segment s = _head;
+            while (true)
+            {
+                // Grab the next segment from this one, before we peek.
+                // This is to be able to see whether the value has changed
+                // during the peek operation.
+                Segment next = Volatile.Read(ref s._nextSegment);
+
+                // Peek at the segment.  If we find an element, we're done.
+                if (s.TryPeek(out result, resultUsed))
+                {
+                    return true;
+                }
+
+                // The current segment was empty at the moment we checked.
+
+                if (next != null)
+                {
+                    // If prior to the peek there was already a next segment, then
+                    // during the peek no additional items could have been enqueued
+                    // to it and we can just move on to check the next segment.
+                    Debug.Assert(next == s._nextSegment);
+                    s = next;
+                }
+                else if (Volatile.Read(ref s._nextSegment) == null)
+                {
+                    // The next segment is null.  Nothing more to peek at.
+                    break;
+                }
+
+                // The next segment was null before we peeked but non-null after.
+                // That means either when we peeked the first segment had
+                // already been frozen but the new segment not yet added,
+                // or that the first segment was empty and between the time
+                // that we peeked and then checked _nextSegment, so many items
+                // were enqueued that we filled the first segment and went
+                // into the next.  Since we need to peek in order, we simply
+                // loop around again to peek on the same segment.  The next
+                // time around on this segment we'll then either successfully
+                // peek or we'll find that next was non-null before peeking,
+                // and we'll traverse to that segment.
+            }
+
+            result = default(T);
+            return false;
+        }
+
+        /// <summary>
+        /// Removes all objects from the <see cref="ConcurrentQueue{T}"/>.
+        /// </summary>
+        public void Clear()
+        {
+            lock (_crossSegmentLock)
+            {
+                // Simply substitute a new segment for the existing head/tail,
+                // as is done in the constructor.  Operations currently in flight
+                // may still read from or write to an existing segment that's
+                // getting dropped, meaning that in flight operations may not be
+                // linear with regards to this clear operation.  To help mitigate
+                // in-flight operations enqueuing onto the tail that's about to
+                // be dropped, we first freeze it; that'll force enqueuers to take
+                // this lock to synchronize and see the new tail.
+                _tail.EnsureFrozenForEnqueues();
+                _tail = _head = new Segment(InitialSegmentLength);
+            }
+        }
+
+        /// <summary>
+        /// Provides a multi-producer, multi-consumer thread-safe bounded segment.  When the queue is full,
+        /// enqueues fail and return false.  When the queue is empty, dequeues fail and return null.
+        /// These segments are linked together to form the unbounded <see cref="ConcurrentQueue{T}"/>. 
+        /// </summary>
+        [DebuggerDisplay("Capacity = {Capacity}")]
+        private sealed class Segment
+        {
+            // Segment design is inspired by the algorithm outlined at:
+            // http://www.1024cores.net/home/lock-free-algorithms/queues/bounded-mpmc-queue
+
+            /// <summary>The array of items in this queue.  Each slot contains the item in that slot and its "sequence number".</summary>
+            internal readonly Slot[] _slots;
+            /// <summary>Mask for quickly accessing a position within the queue's array.</summary>
+            internal readonly int _slotsMask;
+            /// <summary>The head and tail positions, with padding to help avoid false sharing contention.</summary>
+            /// <remarks>Dequeuing happens from the head, enqueuing happens at the tail.</remarks>
+            internal PaddedHeadAndTail _headAndTail; // mutable struct: do not make this readonly
+
+            /// <summary>Indicates whether the segment has been marked such that dequeues don't overwrite the removed data.</summary>
+            internal bool _preservedForObservation;
+            /// <summary>Indicates whether the segment has been marked such that no additional items may be enqueued.</summary>
+            internal bool _frozenForEnqueues;
+            /// <summary>The segment following this one in the queue, or null if this segment is the last in the queue.</summary>
+            internal Segment _nextSegment;
+
+            /// <summary>Creates the segment.</summary>
+            /// <param name="boundedLength">
+            /// The maximum number of elements the segment can contain.  Must be a power of 2.
+            /// </param>
+            public Segment(int boundedLength)
+            {
+                // Validate the length
+                Debug.Assert(boundedLength >= 2, $"Must be >= 2, got {boundedLength}");
+                Debug.Assert((boundedLength & (boundedLength - 1)) == 0, $"Must be a power of 2, got {boundedLength}");
+
+                // Initialize the slots and the mask.  The mask is used as a way of quickly doing "% _slots.Length",
+                // instead letting us do "& _slotsMask".
+                _slots = new Slot[boundedLength];
+                _slotsMask = boundedLength - 1;
+
+                // Initialize the sequence number for each slot.  The sequence number provides a ticket that
+                // allows dequeuers to know whether they can dequeue and enqueuers to know whether they can
+                // enqueue.  An enqueuer at position N can enqueue when the sequence number is N, and a dequeuer
+                // for position N can dequeue when the sequence number is N + 1.  When an enqueuer is done writing
+                // at position N, it sets the sequence number to N + 1 so that a dequeuer will be able to dequeue,
+                // and when a dequeuer is done dequeueing at position N, it sets the sequence number to N + _slots.Length,
+                // so that when an enqueuer loops around the slots, it'll find that the sequence number at
+                // position N is N.  This also means that when an enqueuer finds that at position N the sequence
+                // number is < N, there is still a value in that slot, i.e. the segment is full, and when a
+                // dequeuer finds that the value in a slot is < N + 1, there is nothing currently available to
+                // dequeue. (It is possible for multiple enqueuers to enqueue concurrently, writing into
+                // subsequent slots, and to have the first enqueuer take longer, so that the slots for 1, 2, 3, etc.
+                // may have values, but the 0th slot may still be being filled... in that case, TryDequeue will
+                // return false.)
+                for (int i = 0; i < _slots.Length; i++)
+                {
+                    _slots[i].SequenceNumber = i;
+                }
+            }
+
+            /// <summary>Gets the number of elements this segment can store.</summary>
+            internal int Capacity => _slots.Length;
+
+            /// <summary>Gets the "freeze offset" for this segment.</summary>
+            internal int FreezeOffset => _slots.Length * 2;
+
+            /// <summary>
+            /// Ensures that the segment will not accept any subsequent enqueues that aren't already underway.
+            /// </summary>
+            /// <remarks>
+            /// When we mark a segment as being frozen for additional enqueues,
+            /// we set the <see cref="_frozenForEnqueues"/> bool, but that's mostly
+            /// as a small helper to avoid marking it twice.  The real marking comes
+            /// by modifying the Tail for the segment, increasing it by this
+            /// <see cref="FreezeOffset"/>.  This effectively knocks it off the
+            /// sequence expected by future enqueuers, such that any additional enqueuer
+            /// will be unable to enqueue due to it not lining up with the expected
+            /// sequence numbers.  This value is chosen specially so that Tail will grow
+            /// to a value that maps to the same slot but that won't be confused with
+            /// any other enqueue/dequeue sequence number.
+            /// </remarks>
+            internal void EnsureFrozenForEnqueues() // must only be called while queue's segment lock is held
+            {
+                if (!_frozenForEnqueues) // flag used to ensure we don't increase the Tail more than once if frozen more than once
+                {
+                    _frozenForEnqueues = true;
+
+                    // Increase the tail by FreezeOffset, spinning until we're successful in doing so.
+                    var spinner = new SpinWait();
+                    while (true)
+                    {
+                        int tail = Volatile.Read(ref _headAndTail.Tail);
+                        if (Interlocked.CompareExchange(ref _headAndTail.Tail, tail + FreezeOffset, tail) == tail)
+                        {
+                            break;
+                        }
+                        spinner.SpinOnce();
+                    }
+                }
+            }
+
+            /// <summary>Tries to dequeue an element from the queue.</summary>
+            public bool TryDequeue(out T item)
+            {
+                // Loop in case of contention...
+                var spinner = new SpinWait();
+                while (true)
+                {
+                    // Get the head at which to try to dequeue.
+                    int currentHead = Volatile.Read(ref _headAndTail.Head);
+                    int slotsIndex = currentHead & _slotsMask;
+
+                    // Read the sequence number for the head position.
+                    int sequenceNumber = Volatile.Read(ref _slots[slotsIndex].SequenceNumber);
+
+                    // We can dequeue from this slot if it's been filled by an enqueuer, which
+                    // would have left the sequence number at pos+1.
+                    int diff = sequenceNumber - (currentHead + 1);
+                    if (diff == 0)
+                    {
+                        // We may be racing with other dequeuers.  Try to reserve the slot by incrementing
+                        // the head.  Once we've done that, no one else will be able to read from this slot,
+                        // and no enqueuer will be able to read from this slot until we've written the new
+                        // sequence number. WARNING: The next few lines are not reliable on a runtime that
+                        // supports thread aborts. If a thread abort were to sneak in after the CompareExchange
+                        // but before the Volatile.Write, enqueuers trying to enqueue into this slot would
+                        // spin indefinitely.  If this implementation is ever used on such a platform, this
+                        // if block should be wrapped in a finally / prepared region.
+                        if (Interlocked.CompareExchange(ref _headAndTail.Head, currentHead + 1, currentHead) == currentHead)
+                        {
+                            // Successfully reserved the slot.  Note that after the above CompareExchange, other threads
+                            // trying to dequeue from this slot will end up spinning until we do the subsequent Write.
+                            item = _slots[slotsIndex].Item;
+                            if (!Volatile.Read(ref _preservedForObservation))
+                            {
+                                // If we're preserving, though, we don't zero out the slot, as we need it for
+                                // enumerations, peeking, ToArray, etc.  And we don't update the sequence number,
+                                // so that an enqueuer will see it as full and be forced to move to a new segment.
+                                _slots[slotsIndex].Item = default(T);
+                                Volatile.Write(ref _slots[slotsIndex].SequenceNumber, currentHead + _slots.Length);
+                            }
+                            return true;
+                        }
+                    }
+                    else if (diff < 0)
+                    {
+                        // The sequence number was less than what we needed, which means this slot doesn't
+                        // yet contain a value we can dequeue, i.e. the segment is empty.  Technically it's
+                        // possible that multiple enqueuers could have written concurrently, with those
+                        // getting later slots actually finishing first, so there could be elements after
+                        // this one that are available, but we need to dequeue in order.  So before declaring
+                        // failure and that the segment is empty, we check the tail to see if we're actually
+                        // empty or if we're just waiting for items in flight or after this one to become available.
+                        bool frozen = _frozenForEnqueues;
+                        int currentTail = Volatile.Read(ref _headAndTail.Tail);
+                        if (currentTail - currentHead <= 0 || (frozen && (currentTail - FreezeOffset - currentHead <= 0)))
+                        {
+                            item = default(T);
+                            return false;
+                        }
+
+                        // It's possible it could have become frozen after we checked _frozenForEnqueues
+                        // and before reading the tail.  That's ok: in that rare race condition, we just
+                        // loop around again.
+                    }
+
+                    // Lost a race. Spin a bit, then try again.
+                    spinner.SpinOnce();
+                }
+            }
+
+            /// <summary>Tries to peek at an element from the queue, without removing it.</summary>
+            public bool TryPeek(out T result, bool resultUsed)
+            {
+                if (resultUsed)
+                {
+                    // In order to ensure we don't get a torn read on the value, we mark the segment
+                    // as preserving for observation.  Additional items can still be enqueued to this
+                    // segment, but no space will be freed during dequeues, such that the segment will
+                    // no longer be reusable.
+                    _preservedForObservation = true;
+                    Interlocked.MemoryBarrier();
+                }
+
+                // Loop in case of contention...
+                var spinner = new SpinWait();
+                while (true)
+                {
+                    // Get the head at which to try to peek.
+                    int currentHead = Volatile.Read(ref _headAndTail.Head);
+                    int slotsIndex = currentHead & _slotsMask;
+
+                    // Read the sequence number for the head position.
+                    int sequenceNumber = Volatile.Read(ref _slots[slotsIndex].SequenceNumber);
+
+                    // We can peek from this slot if it's been filled by an enqueuer, which
+                    // would have left the sequence number at pos+1.
+                    int diff = sequenceNumber - (currentHead + 1);
+                    if (diff == 0)
+                    {
+                        result = resultUsed ? _slots[slotsIndex].Item : default(T);
+                        return true;
+                    }
+                    else if (diff < 0)
+                    {
+                        // The sequence number was less than what we needed, which means this slot doesn't
+                        // yet contain a value we can peek, i.e. the segment is empty.  Technically it's
+                        // possible that multiple enqueuers could have written concurrently, with those
+                        // getting later slots actually finishing first, so there could be elements after
+                        // this one that are available, but we need to peek in order.  So before declaring
+                        // failure and that the segment is empty, we check the tail to see if we're actually
+                        // empty or if we're just waiting for items in flight or after this one to become available.
+                        bool frozen = _frozenForEnqueues;
+                        int currentTail = Volatile.Read(ref _headAndTail.Tail);
+                        if (currentTail - currentHead <= 0 || (frozen && (currentTail - FreezeOffset - currentHead <= 0)))
+                        {
+                            result = default(T);
+                            return false;
+                        }
+
+                        // It's possible it could have become frozen after we checked _frozenForEnqueues
+                        // and before reading the tail.  That's ok: in that rare race condition, we just
+                        // loop around again.
+                    }
+
+                    // Lost a race. Spin a bit, then try again.
+                    spinner.SpinOnce();
+                }
+            }
+
+            /// <summary>
+            /// Attempts to enqueue the item.  If successful, the item will be stored
+            /// in the queue and true will be returned; otherwise, the item won't be stored, and false
+            /// will be returned.
+            /// </summary>
+            public bool TryEnqueue(T item)
+            {
+                // Loop in case of contention...
+                var spinner = new SpinWait();
+                while (true)
+                {
+                    // Get the tail at which to try to return.
+                    int currentTail = Volatile.Read(ref _headAndTail.Tail);
+                    int slotsIndex = currentTail & _slotsMask;
+
+                    // Read the sequence number for the tail position.
+                    int sequenceNumber = Volatile.Read(ref _slots[slotsIndex].SequenceNumber);
+
+                    // The slot is empty and ready for us to enqueue into it if its sequence
+                    // number matches the slot.
+                    int diff = sequenceNumber - currentTail;
+                    if (diff == 0)
+                    {
+                        // We may be racing with other enqueuers.  Try to reserve the slot by incrementing
+                        // the tail.  Once we've done that, no one else will be able to write to this slot,
+                        // and no dequeuer will be able to read from this slot until we've written the new
+                        // sequence number. WARNING: The next few lines are not reliable on a runtime that
+                        // supports thread aborts. If a thread abort were to sneak in after the CompareExchange
+                        // but before the Volatile.Write, other threads will spin trying to access this slot.
+                        // If this implementation is ever used on such a platform, this if block should be
+                        // wrapped in a finally / prepared region.
+                        if (Interlocked.CompareExchange(ref _headAndTail.Tail, currentTail + 1, currentTail) == currentTail)
+                        {
+                            // Successfully reserved the slot.  Note that after the above CompareExchange, other threads
+                            // trying to return will end up spinning until we do the subsequent Write.
+                            _slots[slotsIndex].Item = item;
+                            Volatile.Write(ref _slots[slotsIndex].SequenceNumber, currentTail + 1);
+                            return true;
+                        }
+                    }
+                    else if (diff < 0)
+                    {
+                        // The sequence number was less than what we needed, which means this slot still
+                        // contains a value, i.e. the segment is full.  Technically it's possible that multiple
+                        // dequeuers could have read concurrently, with those getting later slots actually
+                        // finishing first, so there could be spaces after this one that are available, but
+                        // we need to enqueue in order.
+                        return false;
+                    }
+
+                    // Lost a race. Spin a bit, then try again.
+                    spinner.SpinOnce();
+                }
+            }
+
+            /// <summary>Represents a slot in the queue.</summary>
+            [StructLayout(LayoutKind.Auto)]
+            [DebuggerDisplay("Item = {Item}, SequenceNumber = {SequenceNumber}")]
+            internal struct Slot
+            {
+                /// <summary>The item.</summary>
+                public T Item;
+                /// <summary>The sequence number for this slot, used to synchronize between enqueuers and dequeuers.</summary>
+                public int SequenceNumber;
+            }
+        }
+    }
+
+    /// <summary>Padded head and tail indices, to avoid false sharing between producers and consumers.</summary>
+    [DebuggerDisplay("Head = {Head}, Tail = {Tail}")]
+    [StructLayout(LayoutKind.Explicit, Size = 3*Internal.PaddingHelpers.CACHE_LINE_SIZE)] // padding before/between/after fields
+    internal struct PaddedHeadAndTail
+    {
+        [FieldOffset(1*Internal.PaddingHelpers.CACHE_LINE_SIZE)] public int Head;
+        [FieldOffset(2*Internal.PaddingHelpers.CACHE_LINE_SIZE)] public int Tail;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentStack.cs b/src/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentStack.cs
new file mode 100644
index 0000000000..d1c2d42dce
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Collections/Concurrent/ConcurrentStack.cs
@@ -0,0 +1,460 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+// ConcurrentStack.cs
+//
+// A lock-free, concurrent stack primitive, and its associated debugger view type.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Threading;
+
+namespace System.Collections.Concurrent
+{
+    // A stack that uses CAS operations internally to maintain thread-safety in a lock-free
+    // manner. Attempting to push or pop concurrently from the stack will not trigger waiting,
+    // although some optimistic concurrency and retry is used, possibly leading to lack of
+    // fairness and/or livelock. The stack uses spinning and backoff to add some randomization,
+    // in hopes of statistically decreasing the possibility of livelock.
+    // 
+    // Note that we currently allocate a new node on every push. This avoids having to worry
+    // about potential ABA issues, since the CLR GC ensures that a memory address cannot be
+    // reused before all references to it have died.
+
+    /// <summary>
+    /// Represents a thread-safe last-in, first-out collection of objects.
+    /// </summary>
+    /// <typeparam name="T">Specifies the type of elements in the stack.</typeparam>
+    /// <remarks>
+    /// All public and protected members of <see cref="ConcurrentStack{T}"/> are thread-safe and may be used
+    /// concurrently from multiple threads.
+    /// </remarks>
+    [DebuggerDisplay("Count = {Count}")]
+    [DebuggerTypeProxy(typeof(SystemCollectionsConcurrent_ProducerConsumerCollectionDebugView<>))]
+    internal class ConcurrentStack<T> : IProducerConsumerCollection<T>, IReadOnlyCollection<T>
+    {
+        /// <summary>
+        /// A simple (internal) node type used to store elements of concurrent stacks and queues.
+        /// </summary>
+        private class Node
+        {
+            internal readonly T _value; // Value of the node.
+            internal Node _next; // Next pointer.
+
+            /// <summary>
+            /// Constructs a new node with the specified value and no next node.
+            /// </summary>
+            /// <param name="value">The value of the node.</param>
+            internal Node(T value)
+            {
+                _value = value;
+                _next = null;
+            }
+        }
+
+        private volatile Node _head; // The stack is a singly linked list, and only remembers the head.
+        private const int BACKOFF_MAX_YIELDS = 8; // Arbitrary number to cap backoff.
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ConcurrentStack{T}"/>
+        /// class.
+        /// </summary>
+        public ConcurrentStack()
+        {
+        }
+
+        /// <summary>
+        /// Gets the number of elements contained in the <see cref="ConcurrentStack{T}"/>.
+        /// </summary>
+        /// <value>The number of elements contained in the <see cref="ConcurrentStack{T}"/>.</value>
+        /// <remarks>
+        /// For determining whether the collection contains any items, use of the <see cref="IsEmpty"/>
+        /// property is recommended rather than retrieving the number of items from the <see cref="Count"/>
+        /// property and comparing it to 0.
+        /// </remarks>
+        public int Count
+        {
+            // Counts the number of entries in the stack. This is an O(n) operation. The answer may be out
+            // of date before returning, but guarantees to return a count that was once valid. Conceptually,
+            // the implementation snaps a copy of the list and then counts the entries, though physically
+            // this is not what actually happens.
+            get
+            {
+                int count = 0;
+
+                // Just whip through the list and tally up the number of nodes. We rely on the fact that
+                // node next pointers are immutable after being enqueued for the first time, even as
+                // they are being dequeued. If we ever changed this (e.g. to pool nodes somehow),
+                // we'd need to revisit this implementation.
+
+                for (Node curr = _head; curr != null; curr = curr._next)
+                {
+                    count++; //we don't handle overflow, to be consistent with existing generic collection types in CLR
+                }
+
+                return count;
+            }
+        }
+
+
+        /// <summary>
+        /// Gets a value indicating whether access to the <see cref="T:System.Collections.ICollection"/> is
+        /// synchronized with the SyncRoot.
+        /// </summary>
+        /// <value>true if access to the <see cref="T:System.Collections.ICollection"/> is synchronized
+        /// with the SyncRoot; otherwise, false. For <see cref="ConcurrentStack{T}"/>, this property always
+        /// returns false.</value>
+        bool ICollection.IsSynchronized
+        {
+            // Gets a value indicating whether access to this collection is synchronized. Always returns
+            // false. The reason is subtle. While access is in face thread safe, it's not the case that
+            // locking on the SyncRoot would have prevented concurrent pushes and pops, as this property
+            // would typically indicate; that's because we internally use CAS operations vs. true locks.
+            get { return false; }
+        }
+
+        /// <summary>
+        /// Gets an object that can be used to synchronize access to the <see
+        /// cref="T:System.Collections.ICollection"/>. This property is not supported.
+        /// </summary>
+        /// <exception cref="T:System.NotSupportedException">The SyncRoot property is not supported</exception>
+        object ICollection.SyncRoot
+        {
+            get
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.ConcurrentCollection_SyncRoot_NotSupported);
+                return default(object);
+            }
+        }
+
+        /// <summary>
+        /// Copies the elements of the <see cref="T:System.Collections.ICollection"/> to an <see
+        /// cref="T:System.Array"/>, starting at a particular
+        /// <see cref="T:System.Array"/> index.
+        /// </summary>
+        /// <param name="array">The one-dimensional <see cref="T:System.Array"/> that is the destination of
+        /// the elements copied from the
+        /// <see cref="ConcurrentStack{T}"/>. The <see cref="T:System.Array"/> must
+        /// have zero-based indexing.</param>
+        /// <param name="index">The zero-based index in <paramref name="array"/> at which copying
+        /// begins.</param>
+        /// <exception cref="ArgumentNullException"><paramref name="array"/> is a null reference (Nothing in
+        /// Visual Basic).</exception>
+        /// <exception cref="ArgumentOutOfRangeException"><paramref name="index"/> is less than
+        /// zero.</exception>
+        /// <exception cref="ArgumentException">
+        /// <paramref name="array"/> is multidimensional. -or-
+        /// <paramref name="array"/> does not have zero-based indexing. -or-
+        /// <paramref name="index"/> is equal to or greater than the length of the <paramref name="array"/>
+        /// -or- The number of elements in the source <see cref="T:System.Collections.ICollection"/> is
+        /// greater than the available space from <paramref name="index"/> to the end of the destination
+        /// <paramref name="array"/>. -or- The type of the source <see
+        /// cref="T:System.Collections.ICollection"/> cannot be cast automatically to the type of the
+        /// destination <paramref name="array"/>.
+        /// </exception>
+        void ICollection.CopyTo(Array array, int index)
+        {
+            // Validate arguments.
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            // We must be careful not to corrupt the array, so we will first accumulate an
+            // internal list of elements that we will then copy to the array. This requires
+            // some extra allocation, but is necessary since we don't know up front whether
+            // the array is sufficiently large to hold the stack's contents.
+            ((ICollection)ToList()).CopyTo(array, index);
+        }
+
+        /// <summary>
+        /// Copies the <see cref="ConcurrentStack{T}"/> elements to an existing one-dimensional <see
+        /// cref="T:System.Array"/>, starting at the specified array index.
+        /// </summary>
+        /// <param name="array">The one-dimensional <see cref="T:System.Array"/> that is the destination of
+        /// the elements copied from the
+        /// <see cref="ConcurrentStack{T}"/>. The <see cref="T:System.Array"/> must have zero-based
+        /// indexing.</param>
+        /// <param name="index">The zero-based index in <paramref name="array"/> at which copying
+        /// begins.</param>
+        /// <exception cref="ArgumentNullException"><paramref name="array"/> is a null reference (Nothing in
+        /// Visual Basic).</exception>
+        /// <exception cref="ArgumentOutOfRangeException"><paramref name="index"/> is less than
+        /// zero.</exception>
+        /// <exception cref="ArgumentException"><paramref name="index"/> is equal to or greater than the
+        /// length of the <paramref name="array"/>
+        /// -or- The number of elements in the source <see cref="ConcurrentStack{T}"/> is greater than the
+        /// available space from <paramref name="index"/> to the end of the destination <paramref
+        /// name="array"/>.
+        /// </exception>
+        public void CopyTo(T[] array, int index)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            // We must be careful not to corrupt the array, so we will first accumulate an
+            // internal list of elements that we will then copy to the array. This requires
+            // some extra allocation, but is necessary since we don't know up front whether
+            // the array is sufficiently large to hold the stack's contents.
+            ToList().CopyTo(array, index);
+        }
+
+#pragma warning disable 0420 // No warning for Interlocked.xxx if compiled with new managed compiler (Roslyn)
+        /// <summary>
+        /// Inserts an object at the top of the <see cref="ConcurrentStack{T}"/>.
+        /// </summary>
+        /// <param name="item">The object to push onto the <see cref="ConcurrentStack{T}"/>. The value can be
+        /// a null reference (Nothing in Visual Basic) for reference types.
+        /// </param>
+        public void Push(T item)
+        {
+            // Pushes a node onto the front of the stack thread-safely. Internally, this simply
+            // swaps the current head pointer using a (thread safe) CAS operation to accomplish
+            // lock freedom. If the CAS fails, we add some back off to statistically decrease
+            // contention at the head, and then go back around and retry.
+
+            Node newNode = new Node(item);
+            newNode._next = _head;
+            if (Interlocked.CompareExchange(ref _head, newNode, newNode._next) == newNode._next)
+            {
+                return;
+            }
+
+            // If we failed, go to the slow path and loop around until we succeed.
+            PushCore(newNode, newNode);
+        }
+
+
+        /// <summary>
+        /// Push one or many nodes into the stack, if head and tails are equal then push one node to the stack other wise push the list between head
+        /// and tail to the stack
+        /// </summary>
+        /// <param name="head">The head pointer to the new list</param>
+        /// <param name="tail">The tail pointer to the new list</param>
+        private void PushCore(Node head, Node tail)
+        {
+            SpinWait spin = new SpinWait();
+
+            // Keep trying to CAS the existing head with the new node until we succeed.
+            do
+            {
+                spin.SpinOnce();
+                // Reread the head and link our new node.
+                tail._next = _head;
+            }
+            while (Interlocked.CompareExchange(
+                ref _head, head, tail._next) != tail._next);
+        }
+
+        /// <summary>
+        /// Attempts to pop and return the object at the top of the <see cref="ConcurrentStack{T}"/>.
+        /// </summary>
+        /// <param name="result">
+        /// When this method returns, if the operation was successful, <paramref name="result"/> contains the
+        /// object removed. If no object was available to be removed, the value is unspecified.
+        /// </param>
+        /// <returns>true if an element was removed and returned from the top of the <see
+        /// cref="ConcurrentStack{T}"/>
+        /// successfully; otherwise, false.</returns>
+        public bool TryPop(out T result)
+        {
+            Node head = _head;
+            //stack is empty
+            if (head == null)
+            {
+                result = default(T);
+                return false;
+            }
+            if (Interlocked.CompareExchange(ref _head, head._next, head) == head)
+            {
+                result = head._value;
+                return true;
+            }
+
+            // Fall through to the slow path.
+            return TryPopCore(out result);
+        }
+
+        /// <summary>
+        /// Local helper function to Pop an item from the stack, slow path
+        /// </summary>
+        /// <param name="result">The popped item</param>
+        /// <returns>True if succeeded, false otherwise</returns>
+        private bool TryPopCore(out T result)
+        {
+            Node poppedNode;
+
+            if (TryPopCore(1, out poppedNode) == 1)
+            {
+                result = poppedNode._value;
+                return true;
+            }
+
+            result = default(T);
+            return false;
+        }
+
+        /// <summary>
+        /// Slow path helper for TryPop. This method assumes an initial attempt to pop an element
+        /// has already occurred and failed, so it begins spinning right away.
+        /// </summary>
+        /// <param name="count">The number of items to pop.</param>
+        /// <param name="poppedHead">
+        /// When this method returns, if the pop succeeded, contains the removed object. If no object was
+        /// available to be removed, the value is unspecified. This parameter is passed uninitialized.
+        /// </param>
+        /// <returns>The number of objects successfully popped from the top of
+        /// the <see cref="ConcurrentStack{T}"/>.</returns>
+        private int TryPopCore(int count, out Node poppedHead)
+        {
+            SpinWait spin = new SpinWait();
+
+            // Try to CAS the head with its current next.  We stop when we succeed or
+            // when we notice that the stack is empty, whichever comes first.
+            Node head;
+            Node next;
+            int backoff = 1;
+            Random r = null;
+            while (true)
+            {
+                head = _head;
+                // Is the stack empty?
+                if (head == null)
+                {
+                    poppedHead = null;
+                    return 0;
+                }
+                next = head;
+                int nodesCount = 1;
+                for (; nodesCount < count && next._next != null; nodesCount++)
+                {
+                    next = next._next;
+                }
+
+                // Try to swap the new head.  If we succeed, break out of the loop.
+                if (Interlocked.CompareExchange(ref _head, next._next, head) == head)
+                {
+                    // Return the popped Node.
+                    poppedHead = head;
+                    return nodesCount;
+                }
+
+                // We failed to CAS the new head.  Spin briefly and retry.
+                for (int i = 0; i < backoff; i++)
+                {
+                    spin.SpinOnce();
+                }
+
+                if (spin.NextSpinWillYield)
+                {
+                    if (r == null)
+                    {
+                        r = new Random();
+                    }
+                    backoff = r.Next(1, BACKOFF_MAX_YIELDS);
+                }
+                else
+                {
+                    backoff *= 2;
+                }
+            }
+        }
+#pragma warning restore 0420
+
+        /// <summary>
+        /// Copies the items stored in the <see cref="ConcurrentStack{T}"/> to a new array.
+        /// </summary>
+        /// <returns>A new array containing a snapshot of elements copied from the <see
+        /// cref="ConcurrentStack{T}"/>.</returns>
+        public T[] ToArray()
+        {
+            Node curr = _head;
+            return curr == null ?
+                Array.Empty<T>() :
+                ToList(curr).ToArray();
+        }
+
+        /// <summary>
+        /// Returns an array containing a snapshot of the list's contents, using
+        /// the target list node as the head of a region in the list.
+        /// </summary>
+        /// <returns>A list of the stack's contents.</returns>
+        private List<T> ToList()
+        {
+            return ToList(_head);
+        }
+
+        /// <summary>
+        /// Returns an array containing a snapshot of the list's contents starting at the specified node.
+        /// </summary>
+        /// <returns>A list of the stack's contents starting at the specified node.</returns>
+        private List<T> ToList(Node curr)
+        {
+            List<T> list = new List<T>();
+
+            while (curr != null)
+            {
+                list.Add(curr._value);
+                curr = curr._next;
+            }
+
+            return list;
+        }
+
+        /// <summary>
+        /// Returns an enumerator that iterates through the <see cref="ConcurrentStack{T}"/>.
+        /// </summary>
+        /// <returns>An enumerator for the <see cref="ConcurrentStack{T}"/>.</returns>
+        /// <remarks>
+        /// The enumeration represents a moment-in-time snapshot of the contents
+        /// of the stack.  It does not reflect any updates to the collection after 
+        /// <see cref="GetEnumerator"/> was called.  The enumerator is safe to use
+        /// concurrently with reads from and writes to the stack.
+        /// </remarks>
+        public IEnumerator<T> GetEnumerator()
+        {
+            // Returns an enumerator for the stack. This effectively takes a snapshot
+            // of the stack's contents at the time of the call, i.e. subsequent modifications
+            // (pushes or pops) will not be reflected in the enumerator's contents.
+
+            //If we put yield-return here, the iterator will be lazily evaluated. As a result a snapshot of
+            //the stack is not taken when GetEnumerator is initialized but when MoveNext() is first called.
+            //This is inconsistent with existing generic collections. In order to prevent it, we capture the 
+            //value of _head in a buffer and call out to a helper method
+            return GetEnumerator(_head);
+        }
+
+        private IEnumerator<T> GetEnumerator(Node head)
+        {
+            Node current = head;
+            while (current != null)
+            {
+                yield return current._value;
+                current = current._next;
+            }
+        }
+
+        /// <summary>
+        /// Returns an enumerator that iterates through a collection.
+        /// </summary>
+        /// <returns>An <see cref="T:System.Collections.IEnumerator"/> that can be used to iterate through
+        /// the collection.</returns>
+        /// <remarks>
+        /// The enumeration represents a moment-in-time snapshot of the contents of the stack. It does not
+        /// reflect any updates to the collection after
+        /// <see cref="GetEnumerator"/> was called. The enumerator is safe to use concurrently with reads
+        /// from and writes to the stack.
+        /// </remarks>
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return ((IEnumerable<T>)this).GetEnumerator();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Collections/Concurrent/IProducerConsumerCollection.cs b/src/System.Private.CoreLib/src/System/Collections/Concurrent/IProducerConsumerCollection.cs
new file mode 100644
index 0000000000..7c585d8b98
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Collections/Concurrent/IProducerConsumerCollection.cs
@@ -0,0 +1,67 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// A common interface for all concurrent collections.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System.Collections.Concurrent
+{
+    /// <summary>
+    /// Defines methods to manipulate thread-safe collections intended for producer/consumer usage.
+    /// </summary>
+    /// <typeparam name="T">Specifies the type of elements in the collection.</typeparam>
+    /// <remarks>
+    /// All implementations of this interface must enable all members of this interface
+    /// to be used concurrently from multiple threads.
+    /// </remarks>
+    internal interface IProducerConsumerCollection<T> : IEnumerable<T>, ICollection
+    {
+        /// <summary>
+        /// Copies the elements of the <see cref="IProducerConsumerCollection{T}"/> to
+        /// an
+        /// <see cref="T:System.Array"/>, starting at a specified index.
+        /// </summary>
+        /// <param name="array">The one-dimensional <see cref="T:System.Array"/> that is the destination of
+        /// the elements copied from the <see cref="IProducerConsumerCollection{T}"/>.
+        /// The array must have zero-based indexing.</param>
+        /// <param name="index">The zero-based index in <paramref name="array"/> at which copying
+        /// begins.</param>
+        /// <exception cref="ArgumentNullException"><paramref name="array"/> is a null reference (Nothing in
+        /// Visual Basic).</exception>
+        /// <exception cref="ArgumentOutOfRangeException"><paramref name="index"/> is less than
+        /// zero.</exception>
+        /// <exception cref="ArgumentException"><paramref name="index"/> is equal to or greater than the
+        /// length of the <paramref name="array"/>
+        /// -or- The number of elements in the source <see cref="ConcurrentQueue{T}"/> is greater than the
+        /// available space from <paramref name="index"/> to the end of the destination <paramref
+        /// name="array"/>.
+        /// </exception>
+        void CopyTo(T[] array, int index);
+
+        /// <summary>
+        /// Copies the elements contained in the <see cref="IProducerConsumerCollection{T}"/> to a new array.
+        /// </summary>
+        /// <returns>A new array containing the elements copied from the <see cref="IProducerConsumerCollection{T}"/>.</returns>
+        T[] ToArray();
+    }
+
+    /// <summary>
+    /// A debugger view of the IProducerConsumerCollection that makes it simple to browse the
+    /// collection's contents at a point in time.
+    /// </summary>
+    /// <typeparam name="T">The type of elements stored within.</typeparam>
+    internal sealed class SystemCollectionsConcurrent_ProducerConsumerCollectionDebugView<T>
+    {
+        private IProducerConsumerCollection<T> m_collection; // The collection being viewed.
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Collections/EmptyReadOnlyDictionaryInternal.cs b/src/System.Private.CoreLib/src/System/Collections/EmptyReadOnlyDictionaryInternal.cs
new file mode 100644
index 0000000000..a6a04b4964
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Collections/EmptyReadOnlyDictionaryInternal.cs
@@ -0,0 +1,228 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+** 
+**
+**
+** Purpose: List for exceptions.
+**
+** 
+===========================================================*/
+
+
+namespace System.Collections
+{
+    ///    This is a simple implementation of IDictionary that is empty and readonly.
+    internal sealed class EmptyReadOnlyDictionaryInternal : IDictionary
+    {
+        // Note that this class must be agile with respect to AppDomains.  See its usage in
+        // System.Exception to understand why this is the case.
+
+        public EmptyReadOnlyDictionaryInternal()
+        {
+        }
+
+        // IEnumerable members
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return new NodeEnumerator();
+        }
+
+        // ICollection members
+
+        public void CopyTo(Array array, int index)
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array));
+
+            if (array.Rank != 1)
+                throw new ArgumentException(SR.Arg_RankMultiDimNotSupported);
+
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (array.Length - index < this.Count)
+                throw new ArgumentException(SR.ArgumentOutOfRange_Index, nameof(index));
+
+            // the actual copy is a NOP
+        }
+
+        public int Count
+        {
+            get
+            {
+                return 0;
+            }
+        }
+
+        public Object SyncRoot
+        {
+            get
+            {
+                return this;
+            }
+        }
+
+        public bool IsSynchronized
+        {
+            get
+            {
+                return false;
+            }
+        }
+
+        // IDictionary members
+
+        public Object this[Object key]
+        {
+            get
+            {
+                if (key == null)
+                {
+                    throw new ArgumentNullException(nameof(key), SR.ArgumentNull_Key);
+                }
+                return null;
+            }
+            set
+            {
+                if (key == null)
+                {
+                    throw new ArgumentNullException(nameof(key), SR.ArgumentNull_Key);
+                }
+
+                if (!key.GetType().IsSerializable)
+                    throw new ArgumentException(SR.Argument_NotSerializable, nameof(key));
+
+                if ((value != null) && (!value.GetType().IsSerializable))
+                    throw new ArgumentException(SR.Argument_NotSerializable, nameof(value));
+
+                throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+            }
+        }
+
+        public ICollection Keys
+        {
+            get
+            {
+                return Array.Empty<Object>();
+            }
+        }
+
+        public ICollection Values
+        {
+            get
+            {
+                return Array.Empty<Object>();
+            }
+        }
+
+        public bool Contains(Object key)
+        {
+            return false;
+        }
+
+        public void Add(Object key, Object value)
+        {
+            if (key == null)
+            {
+                throw new ArgumentNullException(nameof(key), SR.ArgumentNull_Key);
+            }
+
+            if (!key.GetType().IsSerializable)
+                throw new ArgumentException(SR.Argument_NotSerializable, nameof(key));
+
+            if ((value != null) && (!value.GetType().IsSerializable))
+                throw new ArgumentException(SR.Argument_NotSerializable, nameof(value));
+
+            throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+        }
+
+        public void Clear()
+        {
+            throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+        }
+
+        public bool IsReadOnly
+        {
+            get
+            {
+                return true;
+            }
+        }
+
+        public bool IsFixedSize
+        {
+            get
+            {
+                return true;
+            }
+        }
+
+        public IDictionaryEnumerator GetEnumerator()
+        {
+            return new NodeEnumerator();
+        }
+
+        public void Remove(Object key)
+        {
+            throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+        }
+
+        private sealed class NodeEnumerator : IDictionaryEnumerator
+        {
+            public NodeEnumerator()
+            {
+            }
+
+            // IEnumerator members
+
+            public bool MoveNext()
+            {
+                return false;
+            }
+
+            public Object Current
+            {
+                get
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+                }
+            }
+
+            public void Reset()
+            {
+            }
+
+            // IDictionaryEnumerator members
+
+            public Object Key
+            {
+                get
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+                }
+            }
+
+            public Object Value
+            {
+                get
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+                }
+            }
+
+            public DictionaryEntry Entry
+            {
+                get
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_EnumOpCantHappen);
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Collections/Generic/ArraySortHelper.cs b/src/System.Private.CoreLib/src/System/Collections/Generic/ArraySortHelper.cs
new file mode 100644
index 0000000000..103bb1b4f5
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Collections/Generic/ArraySortHelper.cs
@@ -0,0 +1,1189 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+** 
+**
+**
+** Purpose: class to sort arrays
+**
+** 
+===========================================================*/
+
+using System;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Diagnostics;
+using System.Runtime.Versioning;
+
+namespace System.Collections.Generic
+{
+    #region ArraySortHelper for single arrays
+
+    internal interface IArraySortHelper<TKey>
+    {
+        void Sort(TKey[] keys, int index, int length, IComparer<TKey> comparer);
+        int BinarySearch(TKey[] keys, int index, int length, TKey value, IComparer<TKey> comparer);
+    }
+
+    internal static class IntrospectiveSortUtilities
+    {
+        // This is the threshold where Introspective sort switches to Insertion sort.
+        // Empirically, 16 seems to speed up most cases without slowing down others, at least for integers.
+        // Large value types may benefit from a smaller number.
+        internal const int IntrosortSizeThreshold = 16;
+
+        internal static int FloorLog2PlusOne(int n)
+        {
+            int result = 0;
+            while (n >= 1)
+            {
+                result++;
+                n = n / 2;
+            }
+            return result;
+        }
+
+        internal static void ThrowOrIgnoreBadComparer(Object comparer)
+        {
+            throw new ArgumentException(SR.Format(SR.Arg_BogusIComparer, comparer));
+        }
+    }
+
+    [TypeDependencyAttribute("System.Collections.Generic.GenericArraySortHelper`1")]
+    internal class ArraySortHelper<T>
+        : IArraySortHelper<T>
+    {
+        private static volatile IArraySortHelper<T> defaultArraySortHelper;
+
+        public static IArraySortHelper<T> Default
+        {
+            get
+            {
+                IArraySortHelper<T> sorter = defaultArraySortHelper;
+                if (sorter == null)
+                    sorter = CreateArraySortHelper();
+
+                return sorter;
+            }
+        }
+
+        private static IArraySortHelper<T> CreateArraySortHelper()
+        {
+            if (typeof(IComparable<T>).IsAssignableFrom(typeof(T)))
+            {
+                defaultArraySortHelper = (IArraySortHelper<T>)RuntimeTypeHandle.Allocate(typeof(GenericArraySortHelper<string>).TypeHandle.Instantiate(new Type[] { typeof(T) }));
+            }
+            else
+            {
+                defaultArraySortHelper = new ArraySortHelper<T>();
+            }
+            return defaultArraySortHelper;
+        }
+
+        #region IArraySortHelper<T> Members
+
+        public void Sort(T[] keys, int index, int length, IComparer<T> comparer)
+        {
+            Debug.Assert(keys != null, "Check the arguments in the caller!");
+            Debug.Assert(index >= 0 && length >= 0 && (keys.Length - index >= length), "Check the arguments in the caller!");
+
+            // Add a try block here to detect IComparers (or their
+            // underlying IComparables, etc) that are bogus.
+            try
+            {
+                if (comparer == null)
+                {
+                    comparer = Comparer<T>.Default;
+                }
+
+                IntrospectiveSort(keys, index, length, comparer.Compare);
+            }
+            catch (IndexOutOfRangeException)
+            {
+                IntrospectiveSortUtilities.ThrowOrIgnoreBadComparer(comparer);
+            }
+            catch (Exception e)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_IComparerFailed, e);
+            }
+        }
+
+        public int BinarySearch(T[] array, int index, int length, T value, IComparer<T> comparer)
+        {
+            try
+            {
+                if (comparer == null)
+                {
+                    comparer = Comparer<T>.Default;
+                }
+
+                return InternalBinarySearch(array, index, length, value, comparer);
+            }
+            catch (Exception e)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_IComparerFailed, e);
+            }
+        }
+
+        #endregion
+
+        internal static void Sort(T[] keys, int index, int length, Comparison<T> comparer)
+        {
+            Debug.Assert(keys != null, "Check the arguments in the caller!");
+            Debug.Assert(index >= 0 && length >= 0 && (keys.Length - index >= length), "Check the arguments in the caller!");
+            Debug.Assert(comparer != null, "Check the arguments in the caller!");
+
+            // Add a try block here to detect bogus comparisons
+            try
+            {
+                IntrospectiveSort(keys, index, length, comparer);
+            }
+            catch (IndexOutOfRangeException)
+            {
+                IntrospectiveSortUtilities.ThrowOrIgnoreBadComparer(comparer);
+            }
+            catch (Exception e)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_IComparerFailed, e);
+            }
+        }
+
+        internal static int InternalBinarySearch(T[] array, int index, int length, T value, IComparer<T> comparer)
+        {
+            Debug.Assert(array != null, "Check the arguments in the caller!");
+            Debug.Assert(index >= 0 && length >= 0 && (array.Length - index >= length), "Check the arguments in the caller!");
+
+            int lo = index;
+            int hi = index + length - 1;
+            while (lo <= hi)
+            {
+                int i = lo + ((hi - lo) >> 1);
+                int order = comparer.Compare(array[i], value);
+
+                if (order == 0) return i;
+                if (order < 0)
+                {
+                    lo = i + 1;
+                }
+                else
+                {
+                    hi = i - 1;
+                }
+            }
+
+            return ~lo;
+        }
+
+        private static void SwapIfGreater(T[] keys, Comparison<T> comparer, int a, int b)
+        {
+            if (a != b)
+            {
+                if (comparer(keys[a], keys[b]) > 0)
+                {
+                    T key = keys[a];
+                    keys[a] = keys[b];
+                    keys[b] = key;
+                }
+            }
+        }
+
+        private static void Swap(T[] a, int i, int j)
+        {
+            if (i != j)
+            {
+                T t = a[i];
+                a[i] = a[j];
+                a[j] = t;
+            }
+        }
+
+        internal static void IntrospectiveSort(T[] keys, int left, int length, Comparison<T> comparer)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(comparer != null);
+            Debug.Assert(left >= 0);
+            Debug.Assert(length >= 0);
+            Debug.Assert(length <= keys.Length);
+            Debug.Assert(length + left <= keys.Length);
+
+            if (length < 2)
+                return;
+
+            IntroSort(keys, left, length + left - 1, 2 * IntrospectiveSortUtilities.FloorLog2PlusOne(length), comparer);
+        }
+
+        private static void IntroSort(T[] keys, int lo, int hi, int depthLimit, Comparison<T> comparer)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(comparer != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi < keys.Length);
+
+            while (hi > lo)
+            {
+                int partitionSize = hi - lo + 1;
+                if (partitionSize <= IntrospectiveSortUtilities.IntrosortSizeThreshold)
+                {
+                    if (partitionSize == 1)
+                    {
+                        return;
+                    }
+                    if (partitionSize == 2)
+                    {
+                        SwapIfGreater(keys, comparer, lo, hi);
+                        return;
+                    }
+                    if (partitionSize == 3)
+                    {
+                        SwapIfGreater(keys, comparer, lo, hi - 1);
+                        SwapIfGreater(keys, comparer, lo, hi);
+                        SwapIfGreater(keys, comparer, hi - 1, hi);
+                        return;
+                    }
+
+                    InsertionSort(keys, lo, hi, comparer);
+                    return;
+                }
+
+                if (depthLimit == 0)
+                {
+                    Heapsort(keys, lo, hi, comparer);
+                    return;
+                }
+                depthLimit--;
+
+                int p = PickPivotAndPartition(keys, lo, hi, comparer);
+                // Note we've already partitioned around the pivot and do not have to move the pivot again.
+                IntroSort(keys, p + 1, hi, depthLimit, comparer);
+                hi = p - 1;
+            }
+        }
+
+        private static int PickPivotAndPartition(T[] keys, int lo, int hi, Comparison<T> comparer)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(comparer != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi > lo);
+            Debug.Assert(hi < keys.Length);
+
+            // Compute median-of-three.  But also partition them, since we've done the comparison.
+            int middle = lo + ((hi - lo) / 2);
+
+            // Sort lo, mid and hi appropriately, then pick mid as the pivot.
+            SwapIfGreater(keys, comparer, lo, middle);  // swap the low with the mid point
+            SwapIfGreater(keys, comparer, lo, hi);   // swap the low with the high
+            SwapIfGreater(keys, comparer, middle, hi); // swap the middle with the high
+
+            T pivot = keys[middle];
+            Swap(keys, middle, hi - 1);
+            int left = lo, right = hi - 1;  // We already partitioned lo and hi and put the pivot in hi - 1.  And we pre-increment & decrement below.
+
+            while (left < right)
+            {
+                while (comparer(keys[++left], pivot) < 0) ;
+                while (comparer(pivot, keys[--right]) < 0) ;
+
+                if (left >= right)
+                    break;
+
+                Swap(keys, left, right);
+            }
+
+            // Put pivot in the right location.
+            Swap(keys, left, (hi - 1));
+            return left;
+        }
+
+        private static void Heapsort(T[] keys, int lo, int hi, Comparison<T> comparer)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(comparer != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi > lo);
+            Debug.Assert(hi < keys.Length);
+
+            int n = hi - lo + 1;
+            for (int i = n / 2; i >= 1; i = i - 1)
+            {
+                DownHeap(keys, i, n, lo, comparer);
+            }
+            for (int i = n; i > 1; i = i - 1)
+            {
+                Swap(keys, lo, lo + i - 1);
+                DownHeap(keys, 1, i - 1, lo, comparer);
+            }
+        }
+
+        private static void DownHeap(T[] keys, int i, int n, int lo, Comparison<T> comparer)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(comparer != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(lo < keys.Length);
+
+            T d = keys[lo + i - 1];
+            int child;
+            while (i <= n / 2)
+            {
+                child = 2 * i;
+                if (child < n && comparer(keys[lo + child - 1], keys[lo + child]) < 0)
+                {
+                    child++;
+                }
+                if (!(comparer(d, keys[lo + child - 1]) < 0))
+                    break;
+                keys[lo + i - 1] = keys[lo + child - 1];
+                i = child;
+            }
+            keys[lo + i - 1] = d;
+        }
+
+        private static void InsertionSort(T[] keys, int lo, int hi, Comparison<T> comparer)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi >= lo);
+            Debug.Assert(hi <= keys.Length);
+
+            int i, j;
+            T t;
+            for (i = lo; i < hi; i++)
+            {
+                j = i;
+                t = keys[i + 1];
+                while (j >= lo && comparer(t, keys[j]) < 0)
+                {
+                    keys[j + 1] = keys[j];
+                    j--;
+                }
+                keys[j + 1] = t;
+            }
+        }
+    }
+
+    internal class GenericArraySortHelper<T>
+        : IArraySortHelper<T>
+        where T : IComparable<T>
+    {
+        // Do not add a constructor to this class because ArraySortHelper<T>.CreateSortHelper will not execute it
+
+        #region IArraySortHelper<T> Members
+
+        public void Sort(T[] keys, int index, int length, IComparer<T> comparer)
+        {
+            Debug.Assert(keys != null, "Check the arguments in the caller!");
+            Debug.Assert(index >= 0 && length >= 0 && (keys.Length - index >= length), "Check the arguments in the caller!");
+
+            try
+            {
+                if (comparer == null || comparer == Comparer<T>.Default)
+                {
+                    IntrospectiveSort(keys, index, length);
+                }
+                else
+                {
+                    ArraySortHelper<T>.IntrospectiveSort(keys, index, length, comparer.Compare);
+                }
+            }
+            catch (IndexOutOfRangeException)
+            {
+                IntrospectiveSortUtilities.ThrowOrIgnoreBadComparer(comparer);
+            }
+            catch (Exception e)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_IComparerFailed, e);
+            }
+        }
+
+        public int BinarySearch(T[] array, int index, int length, T value, IComparer<T> comparer)
+        {
+            Debug.Assert(array != null, "Check the arguments in the caller!");
+            Debug.Assert(index >= 0 && length >= 0 && (array.Length - index >= length), "Check the arguments in the caller!");
+
+            try
+            {
+                if (comparer == null || comparer == Comparer<T>.Default)
+                {
+                    return BinarySearch(array, index, length, value);
+                }
+                else
+                {
+                    return ArraySortHelper<T>.InternalBinarySearch(array, index, length, value, comparer);
+                }
+            }
+            catch (Exception e)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_IComparerFailed, e);
+            }
+        }
+
+        #endregion
+
+        // This function is called when the user doesn't specify any comparer.
+        // Since T is constrained here, we can call IComparable<T>.CompareTo here.
+        // We can avoid boxing for value type and casting for reference types.
+        private static int BinarySearch(T[] array, int index, int length, T value)
+        {
+            int lo = index;
+            int hi = index + length - 1;
+            while (lo <= hi)
+            {
+                int i = lo + ((hi - lo) >> 1);
+                int order;
+                if (array[i] == null)
+                {
+                    order = (value == null) ? 0 : -1;
+                }
+                else
+                {
+                    order = array[i].CompareTo(value);
+                }
+
+                if (order == 0)
+                {
+                    return i;
+                }
+
+                if (order < 0)
+                {
+                    lo = i + 1;
+                }
+                else
+                {
+                    hi = i - 1;
+                }
+            }
+
+            return ~lo;
+        }
+
+        private static void SwapIfGreaterWithItems(T[] keys, int a, int b)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(0 <= a && a < keys.Length);
+            Debug.Assert(0 <= b && b < keys.Length);
+
+            if (a != b)
+            {
+                if (keys[a] != null && keys[a].CompareTo(keys[b]) > 0)
+                {
+                    T key = keys[a];
+                    keys[a] = keys[b];
+                    keys[b] = key;
+                }
+            }
+        }
+
+        private static void Swap(T[] a, int i, int j)
+        {
+            if (i != j)
+            {
+                T t = a[i];
+                a[i] = a[j];
+                a[j] = t;
+            }
+        }
+
+        internal static void IntrospectiveSort(T[] keys, int left, int length)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(left >= 0);
+            Debug.Assert(length >= 0);
+            Debug.Assert(length <= keys.Length);
+            Debug.Assert(length + left <= keys.Length);
+
+            if (length < 2)
+                return;
+
+            IntroSort(keys, left, length + left - 1, 2 * IntrospectiveSortUtilities.FloorLog2PlusOne(length));
+        }
+
+        private static void IntroSort(T[] keys, int lo, int hi, int depthLimit)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi < keys.Length);
+
+            while (hi > lo)
+            {
+                int partitionSize = hi - lo + 1;
+                if (partitionSize <= IntrospectiveSortUtilities.IntrosortSizeThreshold)
+                {
+                    if (partitionSize == 1)
+                    {
+                        return;
+                    }
+                    if (partitionSize == 2)
+                    {
+                        SwapIfGreaterWithItems(keys, lo, hi);
+                        return;
+                    }
+                    if (partitionSize == 3)
+                    {
+                        SwapIfGreaterWithItems(keys, lo, hi - 1);
+                        SwapIfGreaterWithItems(keys, lo, hi);
+                        SwapIfGreaterWithItems(keys, hi - 1, hi);
+                        return;
+                    }
+
+                    InsertionSort(keys, lo, hi);
+                    return;
+                }
+
+                if (depthLimit == 0)
+                {
+                    Heapsort(keys, lo, hi);
+                    return;
+                }
+                depthLimit--;
+
+                int p = PickPivotAndPartition(keys, lo, hi);
+                // Note we've already partitioned around the pivot and do not have to move the pivot again.
+                IntroSort(keys, p + 1, hi, depthLimit);
+                hi = p - 1;
+            }
+        }
+
+        private static int PickPivotAndPartition(T[] keys, int lo, int hi)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi > lo);
+            Debug.Assert(hi < keys.Length);
+
+            // Compute median-of-three.  But also partition them, since we've done the comparison.
+            int middle = lo + ((hi - lo) / 2);
+
+            // Sort lo, mid and hi appropriately, then pick mid as the pivot.
+            SwapIfGreaterWithItems(keys, lo, middle);  // swap the low with the mid point
+            SwapIfGreaterWithItems(keys, lo, hi);   // swap the low with the high
+            SwapIfGreaterWithItems(keys, middle, hi); // swap the middle with the high
+
+            T pivot = keys[middle];
+            Swap(keys, middle, hi - 1);
+            int left = lo, right = hi - 1;  // We already partitioned lo and hi and put the pivot in hi - 1.  And we pre-increment & decrement below.
+
+            while (left < right)
+            {
+                if (pivot == null)
+                {
+                    while (left < (hi - 1) && keys[++left] == null) ;
+                    while (right > lo && keys[--right] != null) ;
+                }
+                else
+                {
+                    while (pivot.CompareTo(keys[++left]) > 0) ;
+                    while (pivot.CompareTo(keys[--right]) < 0) ;
+                }
+
+                if (left >= right)
+                    break;
+
+                Swap(keys, left, right);
+            }
+
+            // Put pivot in the right location.
+            Swap(keys, left, (hi - 1));
+            return left;
+        }
+
+        private static void Heapsort(T[] keys, int lo, int hi)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi > lo);
+            Debug.Assert(hi < keys.Length);
+
+            int n = hi - lo + 1;
+            for (int i = n / 2; i >= 1; i = i - 1)
+            {
+                DownHeap(keys, i, n, lo);
+            }
+            for (int i = n; i > 1; i = i - 1)
+            {
+                Swap(keys, lo, lo + i - 1);
+                DownHeap(keys, 1, i - 1, lo);
+            }
+        }
+
+        private static void DownHeap(T[] keys, int i, int n, int lo)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(lo < keys.Length);
+
+            T d = keys[lo + i - 1];
+            int child;
+            while (i <= n / 2)
+            {
+                child = 2 * i;
+                if (child < n && (keys[lo + child - 1] == null || keys[lo + child - 1].CompareTo(keys[lo + child]) < 0))
+                {
+                    child++;
+                }
+                if (keys[lo + child - 1] == null || keys[lo + child - 1].CompareTo(d) < 0)
+                    break;
+                keys[lo + i - 1] = keys[lo + child - 1];
+                i = child;
+            }
+            keys[lo + i - 1] = d;
+        }
+
+        private static void InsertionSort(T[] keys, int lo, int hi)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi >= lo);
+            Debug.Assert(hi <= keys.Length);
+
+            int i, j;
+            T t;
+            for (i = lo; i < hi; i++)
+            {
+                j = i;
+                t = keys[i + 1];
+                while (j >= lo && (t == null || t.CompareTo(keys[j]) < 0))
+                {
+                    keys[j + 1] = keys[j];
+                    j--;
+                }
+                keys[j + 1] = t;
+            }
+        }
+    }
+
+    #endregion
+
+    #region ArraySortHelper for paired key and value arrays
+
+    internal interface IArraySortHelper<TKey, TValue>
+    {
+        void Sort(TKey[] keys, TValue[] values, int index, int length, IComparer<TKey> comparer);
+    }
+
+    [TypeDependencyAttribute("System.Collections.Generic.GenericArraySortHelper`2")]
+    internal class ArraySortHelper<TKey, TValue>
+        : IArraySortHelper<TKey, TValue>
+    {
+        private static volatile IArraySortHelper<TKey, TValue> defaultArraySortHelper;
+
+        public static IArraySortHelper<TKey, TValue> Default
+        {
+            get
+            {
+                IArraySortHelper<TKey, TValue> sorter = defaultArraySortHelper;
+                if (sorter == null)
+                    sorter = CreateArraySortHelper();
+
+                return sorter;
+            }
+        }
+
+        private static IArraySortHelper<TKey, TValue> CreateArraySortHelper()
+        {
+            if (typeof(IComparable<TKey>).IsAssignableFrom(typeof(TKey)))
+            {
+                defaultArraySortHelper = (IArraySortHelper<TKey, TValue>)RuntimeTypeHandle.Allocate(typeof(GenericArraySortHelper<string, string>).TypeHandle.Instantiate(new Type[] { typeof(TKey), typeof(TValue) }));
+            }
+            else
+            {
+                defaultArraySortHelper = new ArraySortHelper<TKey, TValue>();
+            }
+            return defaultArraySortHelper;
+        }
+
+        public void Sort(TKey[] keys, TValue[] values, int index, int length, IComparer<TKey> comparer)
+        {
+            Debug.Assert(keys != null, "Check the arguments in the caller!");  // Precondition on interface method
+            Debug.Assert(values != null, "Check the arguments in the caller!");
+            Debug.Assert(index >= 0 && length >= 0 && (keys.Length - index >= length), "Check the arguments in the caller!");
+
+            // Add a try block here to detect IComparers (or their
+            // underlying IComparables, etc) that are bogus.
+            try
+            {
+                if (comparer == null || comparer == Comparer<TKey>.Default)
+                {
+                    comparer = Comparer<TKey>.Default;
+                }
+
+                IntrospectiveSort(keys, values, index, length, comparer);
+            }
+            catch (IndexOutOfRangeException)
+            {
+                IntrospectiveSortUtilities.ThrowOrIgnoreBadComparer(comparer);
+            }
+            catch (Exception e)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_IComparerFailed, e);
+            }
+        }
+
+        private static void SwapIfGreaterWithItems(TKey[] keys, TValue[] values, IComparer<TKey> comparer, int a, int b)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(values != null && values.Length >= keys.Length);
+            Debug.Assert(comparer != null);
+            Debug.Assert(0 <= a && a < keys.Length);
+            Debug.Assert(0 <= b && b < keys.Length);
+
+            if (a != b)
+            {
+                if (comparer.Compare(keys[a], keys[b]) > 0)
+                {
+                    TKey key = keys[a];
+                    keys[a] = keys[b];
+                    keys[b] = key;
+
+                    TValue value = values[a];
+                    values[a] = values[b];
+                    values[b] = value;                    
+                }
+            }
+        }
+
+        private static void Swap(TKey[] keys, TValue[] values, int i, int j)
+        {
+            if (i != j)
+            {
+                TKey k = keys[i];
+                keys[i] = keys[j];
+                keys[j] = k;
+
+                TValue v = values[i];
+                values[i] = values[j];
+                values[j] = v;                
+            }
+        }
+
+        internal static void IntrospectiveSort(TKey[] keys, TValue[] values, int left, int length, IComparer<TKey> comparer)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(values != null);
+            Debug.Assert(comparer != null);
+            Debug.Assert(left >= 0);
+            Debug.Assert(length >= 0);
+            Debug.Assert(length <= keys.Length);
+            Debug.Assert(length + left <= keys.Length);
+            Debug.Assert(length + left <= values.Length);
+
+            if (length < 2)
+                return;
+
+            IntroSort(keys, values, left, length + left - 1, 2 * IntrospectiveSortUtilities.FloorLog2PlusOne(length), comparer);
+        }
+
+        private static void IntroSort(TKey[] keys, TValue[] values, int lo, int hi, int depthLimit, IComparer<TKey> comparer)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(values != null);
+            Debug.Assert(comparer != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi < keys.Length);
+
+            while (hi > lo)
+            {
+                int partitionSize = hi - lo + 1;
+                if (partitionSize <= IntrospectiveSortUtilities.IntrosortSizeThreshold)
+                {
+                    if (partitionSize == 1)
+                    {
+                        return;
+                    }
+                    if (partitionSize == 2)
+                    {
+                        SwapIfGreaterWithItems(keys, values, comparer, lo, hi);
+                        return;
+                    }
+                    if (partitionSize == 3)
+                    {
+                        SwapIfGreaterWithItems(keys, values, comparer, lo, hi - 1);
+                        SwapIfGreaterWithItems(keys, values, comparer, lo, hi);
+                        SwapIfGreaterWithItems(keys, values, comparer, hi - 1, hi);
+                        return;
+                    }
+
+                    InsertionSort(keys, values, lo, hi, comparer);
+                    return;
+                }
+
+                if (depthLimit == 0)
+                {
+                    Heapsort(keys, values, lo, hi, comparer);
+                    return;
+                }
+                depthLimit--;
+
+                int p = PickPivotAndPartition(keys, values, lo, hi, comparer);
+                // Note we've already partitioned around the pivot and do not have to move the pivot again.
+                IntroSort(keys, values, p + 1, hi, depthLimit, comparer);
+                hi = p - 1;
+            }
+        }
+
+        private static int PickPivotAndPartition(TKey[] keys, TValue[] values, int lo, int hi, IComparer<TKey> comparer)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(values != null);
+            Debug.Assert(comparer != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi > lo);
+            Debug.Assert(hi < keys.Length);
+
+            // Compute median-of-three.  But also partition them, since we've done the comparison.
+            int middle = lo + ((hi - lo) / 2);
+
+            // Sort lo, mid and hi appropriately, then pick mid as the pivot.
+            SwapIfGreaterWithItems(keys, values, comparer, lo, middle);  // swap the low with the mid point
+            SwapIfGreaterWithItems(keys, values, comparer, lo, hi);   // swap the low with the high
+            SwapIfGreaterWithItems(keys, values, comparer, middle, hi); // swap the middle with the high
+
+            TKey pivot = keys[middle];
+            Swap(keys, values, middle, hi - 1);
+            int left = lo, right = hi - 1;  // We already partitioned lo and hi and put the pivot in hi - 1.  And we pre-increment & decrement below.
+
+            while (left < right)
+            {
+                while (comparer.Compare(keys[++left], pivot) < 0) ;
+                while (comparer.Compare(pivot, keys[--right]) < 0) ;
+
+                if (left >= right)
+                    break;
+
+                Swap(keys, values, left, right);
+            }
+
+            // Put pivot in the right location.
+            Swap(keys, values, left, (hi - 1));
+            return left;
+        }
+
+        private static void Heapsort(TKey[] keys, TValue[] values, int lo, int hi, IComparer<TKey> comparer)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(values != null);
+            Debug.Assert(comparer != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi > lo);
+            Debug.Assert(hi < keys.Length);
+
+            int n = hi - lo + 1;
+            for (int i = n / 2; i >= 1; i = i - 1)
+            {
+                DownHeap(keys, values, i, n, lo, comparer);
+            }
+            for (int i = n; i > 1; i = i - 1)
+            {
+                Swap(keys, values, lo, lo + i - 1);
+                DownHeap(keys, values, 1, i - 1, lo, comparer);
+            }
+        }
+
+        private static void DownHeap(TKey[] keys, TValue[] values, int i, int n, int lo, IComparer<TKey> comparer)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(values != null);
+            Debug.Assert(comparer != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(lo < keys.Length);
+
+            TKey d = keys[lo + i - 1];
+            TValue dValue = values[lo + i - 1];
+            int child;
+            while (i <= n / 2)
+            {
+                child = 2 * i;
+                if (child < n && comparer.Compare(keys[lo + child - 1], keys[lo + child]) < 0)
+                {
+                    child++;
+                }
+                if (!(comparer.Compare(d, keys[lo + child - 1]) < 0))
+                    break;
+                keys[lo + i - 1] = keys[lo + child - 1];
+                values[lo + i - 1] = values[lo + child - 1];
+                i = child;
+            }
+            keys[lo + i - 1] = d;
+            values[lo + i - 1] = dValue;
+        }
+
+        private static void InsertionSort(TKey[] keys, TValue[] values, int lo, int hi, IComparer<TKey> comparer)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(values != null);
+            Debug.Assert(comparer != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi >= lo);
+            Debug.Assert(hi <= keys.Length);
+
+            int i, j;
+            TKey t;
+            TValue tValue;
+            for (i = lo; i < hi; i++)
+            {
+                j = i;
+                t = keys[i + 1];
+                tValue = values[i + 1];
+                while (j >= lo && comparer.Compare(t, keys[j]) < 0)
+                {
+                    keys[j + 1] = keys[j];
+                    values[j + 1] = values[j];
+                    j--;
+                }
+                keys[j + 1] = t;
+                values[j + 1] = tValue;
+            }
+        }
+    }
+
+    internal class GenericArraySortHelper<TKey, TValue>
+        : IArraySortHelper<TKey, TValue>
+        where TKey : IComparable<TKey>
+    {
+        public void Sort(TKey[] keys, TValue[] values, int index, int length, IComparer<TKey> comparer)
+        {
+            Debug.Assert(keys != null, "Check the arguments in the caller!");
+            Debug.Assert(index >= 0 && length >= 0 && (keys.Length - index >= length), "Check the arguments in the caller!");
+
+            // Add a try block here to detect IComparers (or their
+            // underlying IComparables, etc) that are bogus.
+            try
+            {
+                if (comparer == null || comparer == Comparer<TKey>.Default)
+                {
+                    IntrospectiveSort(keys, values, index, length);
+                }
+                else
+                {
+                    ArraySortHelper<TKey, TValue>.IntrospectiveSort(keys, values, index, length, comparer);
+                }
+            }
+            catch (IndexOutOfRangeException)
+            {
+                IntrospectiveSortUtilities.ThrowOrIgnoreBadComparer(comparer);
+            }
+            catch (Exception e)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_IComparerFailed, e);
+            }
+        }
+
+        private static void SwapIfGreaterWithItems(TKey[] keys, TValue[] values, int a, int b)
+        {
+            if (a != b)
+            {
+                if (keys[a] != null && keys[a].CompareTo(keys[b]) > 0)
+                {
+                    TKey key = keys[a];
+                    keys[a] = keys[b];
+                    keys[b] = key;
+
+                    TValue value = values[a];
+                    values[a] = values[b];
+                    values[b] = value;                    
+                }
+            }
+        }
+
+        private static void Swap(TKey[] keys, TValue[] values, int i, int j)
+        {
+            if (i != j)
+            {
+                TKey k = keys[i];
+                keys[i] = keys[j];
+                keys[j] = k;
+
+                TValue v = values[i];
+                values[i] = values[j];
+                values[j] = v;
+            }
+        }
+
+        internal static void IntrospectiveSort(TKey[] keys, TValue[] values, int left, int length)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(values != null);
+            Debug.Assert(left >= 0);
+            Debug.Assert(length >= 0);
+            Debug.Assert(length <= keys.Length);
+            Debug.Assert(length + left <= keys.Length);
+            Debug.Assert(length + left <= values.Length);
+
+            if (length < 2)
+                return;
+
+            IntroSort(keys, values, left, length + left - 1, 2 * IntrospectiveSortUtilities.FloorLog2PlusOne(length));
+        }
+
+        private static void IntroSort(TKey[] keys, TValue[] values, int lo, int hi, int depthLimit)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(values != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi < keys.Length);
+
+            while (hi > lo)
+            {
+                int partitionSize = hi - lo + 1;
+                if (partitionSize <= IntrospectiveSortUtilities.IntrosortSizeThreshold)
+                {
+                    if (partitionSize == 1)
+                    {
+                        return;
+                    }
+                    if (partitionSize == 2)
+                    {
+                        SwapIfGreaterWithItems(keys, values, lo, hi);
+                        return;
+                    }
+                    if (partitionSize == 3)
+                    {
+                        SwapIfGreaterWithItems(keys, values, lo, hi - 1);
+                        SwapIfGreaterWithItems(keys, values, lo, hi);
+                        SwapIfGreaterWithItems(keys, values, hi - 1, hi);
+                        return;
+                    }
+
+                    InsertionSort(keys, values, lo, hi);
+                    return;
+                }
+
+                if (depthLimit == 0)
+                {
+                    Heapsort(keys, values, lo, hi);
+                    return;
+                }
+                depthLimit--;
+
+                int p = PickPivotAndPartition(keys, values, lo, hi);
+                // Note we've already partitioned around the pivot and do not have to move the pivot again.
+                IntroSort(keys, values, p + 1, hi, depthLimit);
+                hi = p - 1;
+            }
+        }
+
+        private static int PickPivotAndPartition(TKey[] keys, TValue[] values, int lo, int hi)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(values != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi > lo);
+            Debug.Assert(hi < keys.Length);
+
+            // Compute median-of-three.  But also partition them, since we've done the comparison.
+            int middle = lo + ((hi - lo) / 2);
+
+            // Sort lo, mid and hi appropriately, then pick mid as the pivot.
+            SwapIfGreaterWithItems(keys, values, lo, middle);  // swap the low with the mid point
+            SwapIfGreaterWithItems(keys, values, lo, hi);   // swap the low with the high
+            SwapIfGreaterWithItems(keys, values, middle, hi); // swap the middle with the high
+
+            TKey pivot = keys[middle];
+            Swap(keys, values, middle, hi - 1);
+            int left = lo, right = hi - 1;  // We already partitioned lo and hi and put the pivot in hi - 1.  And we pre-increment & decrement below.
+
+            while (left < right)
+            {
+                if (pivot == null)
+                {
+                    while (left < (hi - 1) && keys[++left] == null) ;
+                    while (right > lo && keys[--right] != null) ;
+                }
+                else
+                {
+                    while (pivot.CompareTo(keys[++left]) > 0) ;
+                    while (pivot.CompareTo(keys[--right]) < 0) ;
+                }
+
+                if (left >= right)
+                    break;
+
+                Swap(keys, values, left, right);
+            }
+
+            // Put pivot in the right location.
+            Swap(keys, values, left, (hi - 1));
+            return left;
+        }
+
+        private static void Heapsort(TKey[] keys, TValue[] values, int lo, int hi)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(values != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi > lo);
+            Debug.Assert(hi < keys.Length);
+
+            int n = hi - lo + 1;
+            for (int i = n / 2; i >= 1; i = i - 1)
+            {
+                DownHeap(keys, values, i, n, lo);
+            }
+            for (int i = n; i > 1; i = i - 1)
+            {
+                Swap(keys, values, lo, lo + i - 1);
+                DownHeap(keys, values, 1, i - 1, lo);
+            }
+        }
+
+        private static void DownHeap(TKey[] keys, TValue[] values, int i, int n, int lo)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(lo < keys.Length);
+
+            TKey d = keys[lo + i - 1];
+            TValue dValue = values[lo + i - 1];
+            int child;
+            while (i <= n / 2)
+            {
+                child = 2 * i;
+                if (child < n && (keys[lo + child - 1] == null || keys[lo + child - 1].CompareTo(keys[lo + child]) < 0))
+                {
+                    child++;
+                }
+                if (keys[lo + child - 1] == null || keys[lo + child - 1].CompareTo(d) < 0)
+                    break;
+                keys[lo + i - 1] = keys[lo + child - 1];
+                values[lo + i - 1] = values[lo + child - 1];
+                i = child;
+            }
+            keys[lo + i - 1] = d;
+            values[lo + i - 1] = dValue;
+        }
+
+        private static void InsertionSort(TKey[] keys, TValue[] values, int lo, int hi)
+        {
+            Debug.Assert(keys != null);
+            Debug.Assert(values != null);
+            Debug.Assert(lo >= 0);
+            Debug.Assert(hi >= lo);
+            Debug.Assert(hi <= keys.Length);
+
+            int i, j;
+            TKey t;
+            TValue tValue;
+            for (i = lo; i < hi; i++)
+            {
+                j = i;
+                t = keys[i + 1];
+                tValue = values[i + 1];
+                while (j >= lo && (t == null || t.CompareTo(keys[j]) < 0))
+                {
+                    keys[j + 1] = keys[j];
+                    values[j + 1] = values[j];
+                    j--;
+                }
+                keys[j + 1] = t;
+                values[j + 1] = tValue;
+            }
+        }
+    }
+
+    #endregion
+}
diff --git a/src/System.Private.CoreLib/src/System/Collections/Generic/Comparer.cs b/src/System.Private.CoreLib/src/System/Collections/Generic/Comparer.cs
new file mode 100644
index 0000000000..d5d2e9165f
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Collections/Generic/Comparer.cs
@@ -0,0 +1,256 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.Serialization;
+
+namespace System.Collections.Generic
+{
+    [Serializable]
+    [TypeDependencyAttribute("System.Collections.Generic.ObjectComparer`1")]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")] 
+    public abstract class Comparer<T> : IComparer, IComparer<T>
+    {
+        // To minimize generic instantiation overhead of creating the comparer per type, we keep the generic portion of the code as small
+        // as possible and define most of the creation logic in a non-generic class.
+        public static Comparer<T> Default { get; } = (Comparer<T>)ComparerHelpers.CreateDefaultComparer(typeof(T));
+
+        public static Comparer<T> Create(Comparison<T> comparison)
+        {
+            if (comparison == null)
+                throw new ArgumentNullException(nameof(comparison));
+
+            return new ComparisonComparer<T>(comparison);
+        }
+
+        public abstract int Compare(T x, T y);
+
+        int IComparer.Compare(object x, object y)
+        {
+            if (x == null) return y == null ? 0 : -1;
+            if (y == null) return 1;
+            if (x is T && y is T) return Compare((T)x, (T)y);
+            ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidArgumentForComparison);
+            return 0;
+        }
+    }
+
+    // Note: although there is a lot of shared code in the following
+    // comparers, we do not incorporate it into a base class for perf
+    // reasons. Adding another base class (even one with no fields)
+    // means another generic instantiation, which can be costly esp.
+    // for value types.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    // Needs to be public to support binary serialization compatibility
+    public sealed class GenericComparer<T> : Comparer<T> where T : IComparable<T>
+    {
+        public override int Compare(T x, T y)
+        {
+            if (x != null)
+            {
+                if (y != null) return x.CompareTo(y);
+                return 1;
+            }
+            if (y != null) return -1;
+            return 0;
+        }
+
+        // Equals method for the comparer itself. 
+        public override bool Equals(object obj) =>
+            obj != null && GetType() == obj.GetType();
+
+        public override int GetHashCode() =>
+            GetType().GetHashCode();
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    // Needs to be public to support binary serialization compatibility
+    public sealed class NullableComparer<T> : Comparer<T?> where T : struct, IComparable<T>
+    {
+        public override int Compare(T? x, T? y)
+        {
+            if (x.HasValue)
+            {
+                if (y.HasValue) return x.value.CompareTo(y.value);
+                return 1;
+            }
+            if (y.HasValue) return -1;
+            return 0;
+        }
+
+        // Equals method for the comparer itself. 
+        public override bool Equals(object obj) =>
+            obj != null && GetType() == obj.GetType();
+
+        public override int GetHashCode() =>
+            GetType().GetHashCode();
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    // Needs to be public to support binary serialization compatibility
+    public sealed class ObjectComparer<T> : Comparer<T>
+    {
+        public override int Compare(T x, T y)
+        {
+            return System.Collections.Comparer.Default.Compare(x, y);
+        }
+
+        // Equals method for the comparer itself. 
+        public override bool Equals(object obj) =>
+            obj != null && GetType() == obj.GetType();
+
+        public override int GetHashCode() =>
+            GetType().GetHashCode();
+    }
+
+    internal sealed class ComparisonComparer<T> : Comparer<T>
+    {
+        private readonly Comparison<T> _comparison;
+
+        public ComparisonComparer(Comparison<T> comparison)
+        {
+            _comparison = comparison;
+        }
+
+        public override int Compare(T x, T y)
+        {
+            return _comparison(x, y);
+        }
+    }
+
+    // Enum comparers (specialized to avoid boxing)
+    // NOTE: Each of these needs to implement ISerializable
+    // and have a SerializationInfo/StreamingContext ctor,
+    // since we want to serialize as ObjectComparer for
+    // back-compat reasons (see below).
+    [Serializable]
+    internal sealed class Int32EnumComparer<T> : Comparer<T>, ISerializable where T : struct
+    {
+        public Int32EnumComparer()
+        {
+            Debug.Assert(typeof(T).IsEnum);
+        }
+
+        // Used by the serialization engine.
+        private Int32EnumComparer(SerializationInfo info, StreamingContext context) { }
+
+        public override int Compare(T x, T y)
+        {
+            int ix = JitHelpers.UnsafeEnumCast(x);
+            int iy = JitHelpers.UnsafeEnumCast(y);
+            return ix.CompareTo(iy);
+        }
+
+        // Equals method for the comparer itself. 
+        public override bool Equals(object obj) =>
+            obj != null && GetType() == obj.GetType();
+
+        public override int GetHashCode() =>
+            GetType().GetHashCode();
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            // Previously Comparer<T> was not specialized for enums,
+            // and instead fell back to ObjectComparer which uses boxing.
+            // Set the type as ObjectComparer here so code that serializes
+            // Comparer for enums will not break.
+            info.SetType(typeof(ObjectComparer<T>));
+        }
+    }
+
+    [Serializable]
+    internal sealed class UInt32EnumComparer<T> : Comparer<T>, ISerializable where T : struct
+    {
+        public UInt32EnumComparer()
+        {
+            Debug.Assert(typeof(T).IsEnum);
+        }
+
+        // Used by the serialization engine.
+        private UInt32EnumComparer(SerializationInfo info, StreamingContext context) { }
+
+        public override int Compare(T x, T y)
+        {
+            uint ix = (uint)JitHelpers.UnsafeEnumCast(x);
+            uint iy = (uint)JitHelpers.UnsafeEnumCast(y);
+            return ix.CompareTo(iy);
+        }
+
+        // Equals method for the comparer itself. 
+        public override bool Equals(object obj) =>
+            obj != null && GetType() == obj.GetType();
+
+        public override int GetHashCode() =>
+            GetType().GetHashCode();
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            info.SetType(typeof(ObjectComparer<T>));
+        }
+    }
+
+    [Serializable]
+    internal sealed class Int64EnumComparer<T> : Comparer<T>, ISerializable where T : struct
+    {
+        public Int64EnumComparer()
+        {
+            Debug.Assert(typeof(T).IsEnum);
+        }
+
+        public override int Compare(T x, T y)
+        {
+            long lx = JitHelpers.UnsafeEnumCastLong(x);
+            long ly = JitHelpers.UnsafeEnumCastLong(y);
+            return lx.CompareTo(ly);
+        }
+
+        // Equals method for the comparer itself. 
+        public override bool Equals(object obj) =>
+            obj != null && GetType() == obj.GetType();
+
+        public override int GetHashCode() =>
+            GetType().GetHashCode();
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            info.SetType(typeof(ObjectComparer<T>));
+        }
+    }
+
+    [Serializable]
+    internal sealed class UInt64EnumComparer<T> : Comparer<T>, ISerializable where T : struct
+    {
+        public UInt64EnumComparer()
+        {
+            Debug.Assert(typeof(T).IsEnum);
+        }
+
+        // Used by the serialization engine.
+        private UInt64EnumComparer(SerializationInfo info, StreamingContext context) { }
+
+        public override int Compare(T x, T y)
+        {
+            ulong lx = (ulong)JitHelpers.UnsafeEnumCastLong(x);
+            ulong ly = (ulong)JitHelpers.UnsafeEnumCastLong(y);
+            return lx.CompareTo(ly);
+        }
+
+        // Equals method for the comparer itself. 
+        public override bool Equals(object obj) =>
+            obj != null && GetType() == obj.GetType();
+
+        public override int GetHashCode() =>
+            GetType().GetHashCode();
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            info.SetType(typeof(ObjectComparer<T>));
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Collections/Generic/ComparerHelpers.cs b/src/System.Private.CoreLib/src/System/Collections/Generic/ComparerHelpers.cs
new file mode 100644
index 0000000000..2575d4e346
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Collections/Generic/ComparerHelpers.cs
@@ -0,0 +1,207 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using static System.RuntimeTypeHandle;
+
+namespace System.Collections.Generic
+{
+    /// <summary>
+    /// Helper class for creating the default <see cref="Comparer{T}"/> and <see cref="EqualityComparer{T}"/>.
+    /// </summary>
+    /// <remarks>
+    /// This class is intentionally type-unsafe and non-generic to minimize the generic instantiation overhead of creating
+    /// the default comparer/equality comparer for a new type parameter. Efficiency of the methods in here does not matter too
+    /// much since they will only be run once per type parameter, but generic code involved in creating the comparers needs to be
+    /// kept to a minimum.
+    /// </remarks>
+    internal static class ComparerHelpers
+    {
+        /// <summary>
+        /// Creates the default <see cref="Comparer{T}"/>.
+        /// </summary>
+        /// <param name="type">The type to create the default comparer for.</param>
+        /// <remarks>
+        /// The logic in this method is replicated in vm/compile.cpp to ensure that NGen saves the right instantiations,
+        /// and in vm/jitinterface.cpp so the jit can model the behavior of this method.
+        /// </remarks>
+        internal static object CreateDefaultComparer(Type type)
+        {
+            Debug.Assert(type != null && type is RuntimeType);
+
+            object result = null;
+            var runtimeType = (RuntimeType)type;
+
+            // If T implements IComparable<T> return a GenericComparer<T>
+            if (typeof(IComparable<>).MakeGenericType(type).IsAssignableFrom(type))
+            {
+                result = CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(GenericComparer<int>), runtimeType);
+            }
+            // Nullable does not implement IComparable<T?> directly because that would add an extra interface call per comparison.
+            // Instead, it relies on Comparer<T?>.Default to specialize for nullables and do the lifted comparisons if T implements IComparable.
+            else if (type.IsGenericType)
+            {
+                if (type.GetGenericTypeDefinition() == typeof(Nullable<>))
+                {
+                    result = TryCreateNullableComparer(runtimeType);
+                }
+            }
+            // The comparer for enums is specialized to avoid boxing.
+            else if (type.IsEnum)
+            {
+                result = TryCreateEnumComparer(runtimeType);
+            }
+            
+            return result ?? CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(ObjectComparer<object>), runtimeType);
+        }
+
+        /// <summary>
+        /// Creates the default <see cref="Comparer{T}"/> for a nullable type.
+        /// </summary>
+        /// <param name="nullableType">The nullable type to create the default comparer for.</param>
+        private static object TryCreateNullableComparer(RuntimeType nullableType)
+        {
+            Debug.Assert(nullableType != null);
+            Debug.Assert(nullableType.IsGenericType && nullableType.GetGenericTypeDefinition() == typeof(Nullable<>));
+            
+            var embeddedType = (RuntimeType)nullableType.GetGenericArguments()[0];
+
+            if (typeof(IComparable<>).MakeGenericType(embeddedType).IsAssignableFrom(embeddedType))
+            {
+                return RuntimeTypeHandle.CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(NullableComparer<int>), embeddedType);
+            }
+
+            return null;
+        }
+
+        /// <summary>
+        /// Creates the default <see cref="Comparer{T}"/> for an enum type.
+        /// </summary>
+        /// <param name="enumType">The enum type to create the default comparer for.</param>
+        private static object TryCreateEnumComparer(RuntimeType enumType)
+        {
+            Debug.Assert(enumType != null);
+            Debug.Assert(enumType.IsEnum);
+
+            // Explicitly call Enum.GetUnderlyingType here. Although GetTypeCode
+            // ends up doing this anyway, we end up avoiding an unnecessary P/Invoke
+            // and virtual method call.
+            TypeCode underlyingTypeCode = Type.GetTypeCode(Enum.GetUnderlyingType(enumType));
+            
+            // Depending on the enum type, we need to special case the comparers so that we avoid boxing.
+            // Specialize differently for signed/unsigned types so we avoid problems with large numbers.
+            switch (underlyingTypeCode)
+            {
+                case TypeCode.SByte:
+                case TypeCode.Int16:
+                case TypeCode.Int32:
+                    return RuntimeTypeHandle.CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(Int32EnumComparer<int>), enumType);
+                case TypeCode.Byte:
+                case TypeCode.UInt16:
+                case TypeCode.UInt32:
+                    return RuntimeTypeHandle.CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(UInt32EnumComparer<uint>), enumType);
+                // 64-bit enums: Use `UnsafeEnumCastLong`
+                case TypeCode.Int64:
+                    return RuntimeTypeHandle.CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(Int64EnumComparer<long>), enumType);
+                case TypeCode.UInt64:
+                    return RuntimeTypeHandle.CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(UInt64EnumComparer<ulong>), enumType);
+            }
+            
+            return null;
+        }
+
+        /// <summary>
+        /// Creates the default <see cref="EqualityComparer{T}"/>.
+        /// </summary>
+        /// <param name="type">The type to create the default equality comparer for.</param>
+        /// <remarks>
+        /// The logic in this method is replicated in vm/compile.cpp to ensure that NGen saves the right instantiations.
+        /// </remarks>
+        internal static object CreateDefaultEqualityComparer(Type type)
+        {
+            Debug.Assert(type != null && type is RuntimeType);
+
+            object result = null;
+            var runtimeType = (RuntimeType)type;
+
+            // Specialize for byte so Array.IndexOf is faster.
+            if (type == typeof(byte))
+            {
+                result = new ByteEqualityComparer();
+            }
+            // If T implements IEquatable<T> return a GenericEqualityComparer<T>
+            else if (typeof(IEquatable<>).MakeGenericType(type).IsAssignableFrom(type))
+            {
+                result = CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(GenericEqualityComparer<int>), runtimeType);
+            }
+            // Nullable does not implement IEquatable<T?> directly because that would add an extra interface call per comparison.
+            // Instead, it relies on EqualityComparer<T?>.Default to specialize for nullables and do the lifted comparisons if T implements IEquatable.
+            else if (type.IsGenericType)
+            {
+                if (type.GetGenericTypeDefinition() == typeof(Nullable<>))
+                {
+                    result = TryCreateNullableEqualityComparer(runtimeType);
+                }
+            }
+            // The equality comparer for enums is specialized to avoid boxing.
+            else if (type.IsEnum)
+            {
+                result = TryCreateEnumEqualityComparer(runtimeType);
+            }
+            
+            return result ?? CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(ObjectEqualityComparer<object>), runtimeType);
+        }
+
+        /// <summary>
+        /// Creates the default <see cref="EqualityComparer{T}"/> for a nullable type.
+        /// </summary>
+        /// <param name="nullableType">The nullable type to create the default equality comparer for.</param>
+        private static object TryCreateNullableEqualityComparer(RuntimeType nullableType)
+        {
+            Debug.Assert(nullableType != null);
+            Debug.Assert(nullableType.IsGenericType && nullableType.GetGenericTypeDefinition() == typeof(Nullable<>));
+
+            var embeddedType = (RuntimeType)nullableType.GetGenericArguments()[0];
+
+            if (typeof(IEquatable<>).MakeGenericType(embeddedType).IsAssignableFrom(embeddedType))
+            {
+                return RuntimeTypeHandle.CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(NullableEqualityComparer<int>), embeddedType);
+            }
+            
+            return null;
+        }
+
+        /// <summary>
+        /// Creates the default <see cref="EqualityComparer{T}"/> for an enum type.
+        /// </summary>
+        /// <param name="enumType">The enum type to create the default equality comparer for.</param>
+        private static object TryCreateEnumEqualityComparer(RuntimeType enumType)
+        {
+            Debug.Assert(enumType != null);
+            Debug.Assert(enumType.IsEnum);
+
+            // See the METHOD__JIT_HELPERS__UNSAFE_ENUM_CAST and METHOD__JIT_HELPERS__UNSAFE_ENUM_CAST_LONG cases in getILIntrinsicImplementation
+            // for how we cast the enum types to integral values in the comparer without boxing.
+
+            TypeCode underlyingTypeCode = Type.GetTypeCode(Enum.GetUnderlyingType(enumType));
+
+            // Depending on the enum type, we need to special case the comparers so that we avoid boxing.
+            switch (underlyingTypeCode)
+            {
+                case TypeCode.Int32:
+                case TypeCode.UInt32:
+                case TypeCode.SByte:
+                case TypeCode.Byte:
+                case TypeCode.Int16:
+                case TypeCode.UInt16:
+                    return RuntimeTypeHandle.CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(EnumEqualityComparer<int>), enumType);
+                case TypeCode.Int64:
+                case TypeCode.UInt64:
+                    return RuntimeTypeHandle.CreateInstanceForAnotherGenericParameter((RuntimeType)typeof(LongEnumEqualityComparer<long>), enumType);
+            }
+            
+            return null;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Collections/Generic/EqualityComparer.cs b/src/System.Private.CoreLib/src/System/Collections/Generic/EqualityComparer.cs
new file mode 100644
index 0000000000..4c7a70553e
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Collections/Generic/EqualityComparer.cs
@@ -0,0 +1,439 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Security;
+
+using System.Globalization;
+using System.Runtime;
+using System.Runtime.CompilerServices;
+using System.Runtime.Serialization;
+
+namespace System.Collections.Generic
+{
+    [Serializable]
+    [TypeDependencyAttribute("System.Collections.Generic.ObjectEqualityComparer`1")]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")] 
+    public abstract class EqualityComparer<T> : IEqualityComparer, IEqualityComparer<T>
+    {
+        // To minimize generic instantiation overhead of creating the comparer per type, we keep the generic portion of the code as small
+        // as possible and define most of the creation logic in a non-generic class.
+        public static EqualityComparer<T> Default { [Intrinsic] get; } = (EqualityComparer<T>)ComparerHelpers.CreateDefaultEqualityComparer(typeof(T));
+
+        public abstract bool Equals(T x, T y);
+        public abstract int GetHashCode(T obj);
+
+        internal virtual int IndexOf(T[] array, T value, int startIndex, int count)
+        {
+            int endIndex = startIndex + count;
+            for (int i = startIndex; i < endIndex; i++)
+            {
+                if (Equals(array[i], value)) return i;
+            }
+            return -1;
+        }
+
+        internal virtual int LastIndexOf(T[] array, T value, int startIndex, int count)
+        {
+            int endIndex = startIndex - count + 1;
+            for (int i = startIndex; i >= endIndex; i--)
+            {
+                if (Equals(array[i], value)) return i;
+            }
+            return -1;
+        }
+
+        int IEqualityComparer.GetHashCode(object obj)
+        {
+            if (obj == null) return 0;
+            if (obj is T) return GetHashCode((T)obj);
+            ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidArgumentForComparison);
+            return 0;
+        }
+
+        bool IEqualityComparer.Equals(object x, object y)
+        {
+            if (x == y) return true;
+            if (x == null || y == null) return false;
+            if ((x is T) && (y is T)) return Equals((T)x, (T)y);
+            ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidArgumentForComparison);
+            return false;
+        }
+    }
+
+    // The methods in this class look identical to the inherited methods, but the calls
+    // to Equal bind to IEquatable<T>.Equals(T) instead of Object.Equals(Object)
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    // Needs to be public to support binary serialization compatibility
+    public sealed class GenericEqualityComparer<T> : EqualityComparer<T> where T : IEquatable<T>
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override bool Equals(T x, T y)
+        {
+            if (x != null)
+            {
+                if (y != null) return x.Equals(y);
+                return false;
+            }
+            if (y != null) return false;
+            return true;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override int GetHashCode(T obj) => obj?.GetHashCode() ?? 0;
+
+        internal override int IndexOf(T[] array, T value, int startIndex, int count)
+        {
+            int endIndex = startIndex + count;
+            if (value == null)
+            {
+                for (int i = startIndex; i < endIndex; i++)
+                {
+                    if (array[i] == null) return i;
+                }
+            }
+            else
+            {
+                for (int i = startIndex; i < endIndex; i++)
+                {
+                    if (array[i] != null && array[i].Equals(value)) return i;
+                }
+            }
+            return -1;
+        }
+
+        internal override int LastIndexOf(T[] array, T value, int startIndex, int count)
+        {
+            int endIndex = startIndex - count + 1;
+            if (value == null)
+            {
+                for (int i = startIndex; i >= endIndex; i--)
+                {
+                    if (array[i] == null) return i;
+                }
+            }
+            else
+            {
+                for (int i = startIndex; i >= endIndex; i--)
+                {
+                    if (array[i] != null && array[i].Equals(value)) return i;
+                }
+            }
+            return -1;
+        }
+
+        // Equals method for the comparer itself.
+        // If in the future this type is made sealed, change the is check to obj != null && GetType() == obj.GetType().
+        public override bool Equals(object obj) =>
+            obj is GenericEqualityComparer<T>;
+
+        // If in the future this type is made sealed, change typeof(...) to GetType().
+        public override int GetHashCode() =>
+            typeof(GenericEqualityComparer<T>).GetHashCode();
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    // Needs to be public to support binary serialization compatibility
+    public sealed class NullableEqualityComparer<T> : EqualityComparer<T?> where T : struct, IEquatable<T>
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override bool Equals(T? x, T? y)
+        {
+            if (x.HasValue)
+            {
+                if (y.HasValue) return x.value.Equals(y.value);
+                return false;
+            }
+            if (y.HasValue) return false;
+            return true;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override int GetHashCode(T? obj) => obj.GetHashCode();
+
+        internal override int IndexOf(T?[] array, T? value, int startIndex, int count)
+        {
+            int endIndex = startIndex + count;
+            if (!value.HasValue)
+            {
+                for (int i = startIndex; i < endIndex; i++)
+                {
+                    if (!array[i].HasValue) return i;
+                }
+            }
+            else
+            {
+                for (int i = startIndex; i < endIndex; i++)
+                {
+                    if (array[i].HasValue && array[i].value.Equals(value.value)) return i;
+                }
+            }
+            return -1;
+        }
+
+        internal override int LastIndexOf(T?[] array, T? value, int startIndex, int count)
+        {
+            int endIndex = startIndex - count + 1;
+            if (!value.HasValue)
+            {
+                for (int i = startIndex; i >= endIndex; i--)
+                {
+                    if (!array[i].HasValue) return i;
+                }
+            }
+            else
+            {
+                for (int i = startIndex; i >= endIndex; i--)
+                {
+                    if (array[i].HasValue && array[i].value.Equals(value.value)) return i;
+                }
+            }
+            return -1;
+        }
+
+        // Equals method for the comparer itself.
+        public override bool Equals(object obj) =>
+            obj != null && GetType() == obj.GetType();
+
+        public override int GetHashCode() =>
+            GetType().GetHashCode();
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    // Needs to be public to support binary serialization compatibility
+    public sealed class ObjectEqualityComparer<T> : EqualityComparer<T>
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override bool Equals(T x, T y)
+        {
+            if (x != null)
+            {
+                if (y != null) return x.Equals(y);
+                return false;
+            }
+            if (y != null) return false;
+            return true;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override int GetHashCode(T obj) => obj?.GetHashCode() ?? 0;
+
+        internal override int IndexOf(T[] array, T value, int startIndex, int count)
+        {
+            int endIndex = startIndex + count;
+            if (value == null)
+            {
+                for (int i = startIndex; i < endIndex; i++)
+                {
+                    if (array[i] == null) return i;
+                }
+            }
+            else
+            {
+                for (int i = startIndex; i < endIndex; i++)
+                {
+                    if (array[i] != null && array[i].Equals(value)) return i;
+                }
+            }
+            return -1;
+        }
+
+        internal override int LastIndexOf(T[] array, T value, int startIndex, int count)
+        {
+            int endIndex = startIndex - count + 1;
+            if (value == null)
+            {
+                for (int i = startIndex; i >= endIndex; i--)
+                {
+                    if (array[i] == null) return i;
+                }
+            }
+            else
+            {
+                for (int i = startIndex; i >= endIndex; i--)
+                {
+                    if (array[i] != null && array[i].Equals(value)) return i;
+                }
+            }
+            return -1;
+        }
+
+        // Equals method for the comparer itself.
+        public override bool Equals(object obj) =>
+            obj != null && GetType() == obj.GetType();
+
+        public override int GetHashCode() =>
+            GetType().GetHashCode();
+    }
+
+    // Performance of IndexOf on byte array is very important for some scenarios.
+    // We will call the C runtime function memchr, which is optimized.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    // Needs to be public to support binary serialization compatibility
+    public sealed class ByteEqualityComparer : EqualityComparer<byte>
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override bool Equals(byte x, byte y)
+        {
+            return x == y;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override int GetHashCode(byte b)
+        {
+            return b.GetHashCode();
+        }
+
+        internal unsafe override int IndexOf(byte[] array, byte value, int startIndex, int count)
+        {
+            int found = new ReadOnlySpan<byte>(array, startIndex, count).IndexOf(value);
+            return (found >= 0) ? (startIndex + found) : found;
+        }
+
+        internal override int LastIndexOf(byte[] array, byte value, int startIndex, int count)
+        {
+            int endIndex = startIndex - count + 1;
+            int found = new ReadOnlySpan<byte>(array, endIndex, count).LastIndexOf(value);
+            return (found >= 0) ? (endIndex + found) : found;
+        }
+
+        // Equals method for the comparer itself.
+        public override bool Equals(object obj) =>
+            obj != null && GetType() == obj.GetType();
+
+        public override int GetHashCode() =>
+            GetType().GetHashCode();
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    // Needs to be public to support binary serialization compatibility
+    public sealed class EnumEqualityComparer<T> : EqualityComparer<T>, ISerializable where T : struct
+    {
+        internal EnumEqualityComparer() { }
+
+        // This is used by the serialization engine.
+        private EnumEqualityComparer(SerializationInfo information, StreamingContext context) { }
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            // For back-compat we need to serialize the comparers for enums with underlying types other than int as ObjectEqualityComparer 
+            if (Type.GetTypeCode(Enum.GetUnderlyingType(typeof(T))) != TypeCode.Int32) {
+                info.SetType(typeof(ObjectEqualityComparer<T>));
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override bool Equals(T x, T y)
+        {
+            int x_final = System.Runtime.CompilerServices.JitHelpers.UnsafeEnumCast(x);
+            int y_final = System.Runtime.CompilerServices.JitHelpers.UnsafeEnumCast(y);
+            return x_final == y_final;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override int GetHashCode(T obj)
+        {
+            return obj.GetHashCode();
+        }
+
+        // Equals method for the comparer itself.
+        public override bool Equals(object obj) =>
+            obj != null && GetType() == obj.GetType();
+
+        public override int GetHashCode() =>
+            GetType().GetHashCode();
+
+        internal override int IndexOf(T[] array, T value, int startIndex, int count)
+        {
+            int toFind = JitHelpers.UnsafeEnumCast(value);
+            int endIndex = startIndex + count;
+            for (int i = startIndex; i < endIndex; i++)
+            {
+                int current = JitHelpers.UnsafeEnumCast(array[i]);
+                if (toFind == current) return i;
+            }
+            return -1;
+        }
+
+        internal override int LastIndexOf(T[] array, T value, int startIndex, int count)
+        {
+            int toFind = JitHelpers.UnsafeEnumCast(value);
+            int endIndex = startIndex - count + 1;
+            for (int i = startIndex; i >= endIndex; i--)
+            {
+                int current = JitHelpers.UnsafeEnumCast(array[i]);
+                if (toFind == current) return i;
+            }
+            return -1;
+        }
+    }
+
+    [Serializable]
+    internal sealed class LongEnumEqualityComparer<T> : EqualityComparer<T>, ISerializable where T : struct
+    {
+        internal LongEnumEqualityComparer() { }
+
+        // This is used by the serialization engine.
+        private LongEnumEqualityComparer(SerializationInfo information, StreamingContext context) { }
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            // The LongEnumEqualityComparer does not exist on 4.0 so we need to serialize this comparer as ObjectEqualityComparer
+            // to allow for roundtrip between 4.0 and 4.5.
+            info.SetType(typeof(ObjectEqualityComparer<T>));
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override bool Equals(T x, T y)
+        {
+            long x_final = System.Runtime.CompilerServices.JitHelpers.UnsafeEnumCastLong(x);
+            long y_final = System.Runtime.CompilerServices.JitHelpers.UnsafeEnumCastLong(y);
+            return x_final == y_final;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override int GetHashCode(T obj)
+        {
+            return obj.GetHashCode();
+        }
+
+        // Equals method for the comparer itself.
+        public override bool Equals(object obj) =>
+            obj != null && GetType() == obj.GetType();
+
+        public override int GetHashCode() =>
+            GetType().GetHashCode();
+
+        internal override int IndexOf(T[] array, T value, int startIndex, int count)
+        {
+            long toFind = JitHelpers.UnsafeEnumCastLong(value);
+            int endIndex = startIndex + count;
+            for (int i = startIndex; i < endIndex; i++)
+            {
+                long current = JitHelpers.UnsafeEnumCastLong(array[i]);
+                if (toFind == current) return i;
+            }
+            return -1;
+        }
+
+        internal override int LastIndexOf(T[] array, T value, int startIndex, int count)
+        {
+            long toFind = JitHelpers.UnsafeEnumCastLong(value);
+            int endIndex = startIndex - count + 1;
+            for (int i = startIndex; i >= endIndex; i--)
+            {
+                long current = JitHelpers.UnsafeEnumCastLong(array[i]);
+                if (toFind == current) return i;
+            }
+            return -1;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Collections/ObjectModel/ReadOnlyDictionary.cs b/src/System.Private.CoreLib/src/System/Collections/ObjectModel/ReadOnlyDictionary.cs
new file mode 100644
index 0000000000..25d03355e4
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Collections/ObjectModel/ReadOnlyDictionary.cs
@@ -0,0 +1,731 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+** Purpose: Read-only wrapper for another generic dictionary.
+**
+===========================================================*/
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System.Collections.ObjectModel
+{
+    [DebuggerTypeProxy(typeof(IDictionaryDebugView<,>))]
+    [DebuggerDisplay("Count = {Count}")]
+    internal class ReadOnlyDictionary<TKey, TValue> : IDictionary<TKey, TValue>, IDictionary, IReadOnlyDictionary<TKey, TValue>
+    {
+        private readonly IDictionary<TKey, TValue> m_dictionary;
+        private Object m_syncRoot;
+        private KeyCollection m_keys;
+        private ValueCollection m_values;
+
+        public ReadOnlyDictionary(IDictionary<TKey, TValue> dictionary)
+        {
+            if (dictionary == null)
+            {
+                throw new ArgumentNullException(nameof(dictionary));
+            }
+            m_dictionary = dictionary;
+        }
+
+        protected IDictionary<TKey, TValue> Dictionary
+        {
+            get { return m_dictionary; }
+        }
+
+        public KeyCollection Keys
+        {
+            get
+            {
+                if (m_keys == null)
+                {
+                    m_keys = new KeyCollection(m_dictionary.Keys);
+                }
+                return m_keys;
+            }
+        }
+
+        public ValueCollection Values
+        {
+            get
+            {
+                if (m_values == null)
+                {
+                    m_values = new ValueCollection(m_dictionary.Values);
+                }
+                return m_values;
+            }
+        }
+
+        #region IDictionary<TKey, TValue> Members
+
+        public bool ContainsKey(TKey key)
+        {
+            return m_dictionary.ContainsKey(key);
+        }
+
+        ICollection<TKey> IDictionary<TKey, TValue>.Keys
+        {
+            get
+            {
+                return Keys;
+            }
+        }
+
+        public bool TryGetValue(TKey key, out TValue value)
+        {
+            return m_dictionary.TryGetValue(key, out value);
+        }
+
+        ICollection<TValue> IDictionary<TKey, TValue>.Values
+        {
+            get
+            {
+                return Values;
+            }
+        }
+
+        public TValue this[TKey key]
+        {
+            get
+            {
+                return m_dictionary[key];
+            }
+        }
+
+        void IDictionary<TKey, TValue>.Add(TKey key, TValue value)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+
+        bool IDictionary<TKey, TValue>.Remove(TKey key)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            return false;
+        }
+
+        TValue IDictionary<TKey, TValue>.this[TKey key]
+        {
+            get
+            {
+                return m_dictionary[key];
+            }
+            set
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+        }
+
+        #endregion
+
+        #region ICollection<KeyValuePair<TKey, TValue>> Members
+
+        public int Count
+        {
+            get { return m_dictionary.Count; }
+        }
+
+        bool ICollection<KeyValuePair<TKey, TValue>>.Contains(KeyValuePair<TKey, TValue> item)
+        {
+            return m_dictionary.Contains(item);
+        }
+
+        void ICollection<KeyValuePair<TKey, TValue>>.CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
+        {
+            m_dictionary.CopyTo(array, arrayIndex);
+        }
+
+        bool ICollection<KeyValuePair<TKey, TValue>>.IsReadOnly
+        {
+            get { return true; }
+        }
+
+        void ICollection<KeyValuePair<TKey, TValue>>.Add(KeyValuePair<TKey, TValue> item)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+
+        void ICollection<KeyValuePair<TKey, TValue>>.Clear()
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+
+        bool ICollection<KeyValuePair<TKey, TValue>>.Remove(KeyValuePair<TKey, TValue> item)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            return false;
+        }
+
+        #endregion
+
+        #region IEnumerable<KeyValuePair<TKey, TValue>> Members
+
+        public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
+        {
+            return m_dictionary.GetEnumerator();
+        }
+
+        #endregion
+
+        #region IEnumerable Members
+
+        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
+        {
+            return ((IEnumerable)m_dictionary).GetEnumerator();
+        }
+
+        #endregion
+
+        #region IDictionary Members
+
+        private static bool IsCompatibleKey(object key)
+        {
+            if (key == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
+            }
+            return key is TKey;
+        }
+
+        void IDictionary.Add(object key, object value)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+
+        void IDictionary.Clear()
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+
+        bool IDictionary.Contains(object key)
+        {
+            return IsCompatibleKey(key) && ContainsKey((TKey)key);
+        }
+
+        IDictionaryEnumerator IDictionary.GetEnumerator()
+        {
+            IDictionary d = m_dictionary as IDictionary;
+            if (d != null)
+            {
+                return d.GetEnumerator();
+            }
+            return new DictionaryEnumerator(m_dictionary);
+        }
+
+        bool IDictionary.IsFixedSize
+        {
+            get { return true; }
+        }
+
+        bool IDictionary.IsReadOnly
+        {
+            get { return true; }
+        }
+
+        ICollection IDictionary.Keys
+        {
+            get
+            {
+                return Keys;
+            }
+        }
+
+        void IDictionary.Remove(object key)
+        {
+            ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+        }
+
+        ICollection IDictionary.Values
+        {
+            get
+            {
+                return Values;
+            }
+        }
+
+        object IDictionary.this[object key]
+        {
+            get
+            {
+                if (IsCompatibleKey(key))
+                {
+                    return this[(TKey)key];
+                }
+                return null;
+            }
+            set
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+        }
+
+        void ICollection.CopyTo(Array array, int index)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (array.Rank != 1)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
+            }
+
+            if (array.GetLowerBound(0) != 0)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NonZeroLowerBound);
+            }
+
+            if (index < 0 || index > array.Length)
+            {
+                ThrowHelper.ThrowIndexArgumentOutOfRange_NeedNonNegNumException();
+            }
+
+            if (array.Length - index < Count)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall);
+            }
+
+            KeyValuePair<TKey, TValue>[] pairs = array as KeyValuePair<TKey, TValue>[];
+            if (pairs != null)
+            {
+                m_dictionary.CopyTo(pairs, index);
+            }
+            else
+            {
+                DictionaryEntry[] dictEntryArray = array as DictionaryEntry[];
+                if (dictEntryArray != null)
+                {
+                    foreach (var item in m_dictionary)
+                    {
+                        dictEntryArray[index++] = new DictionaryEntry(item.Key, item.Value);
+                    }
+                }
+                else
+                {
+                    object[] objects = array as object[];
+                    if (objects == null)
+                    {
+                        ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                    }
+
+                    try
+                    {
+                        foreach (var item in m_dictionary)
+                        {
+                            objects[index++] = new KeyValuePair<TKey, TValue>(item.Key, item.Value);
+                        }
+                    }
+                    catch (ArrayTypeMismatchException)
+                    {
+                        ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                    }
+                }
+            }
+        }
+
+        bool ICollection.IsSynchronized
+        {
+            get { return false; }
+        }
+
+        object ICollection.SyncRoot
+        {
+            get
+            {
+                if (m_syncRoot == null)
+                {
+                    ICollection c = m_dictionary as ICollection;
+                    if (c != null)
+                    {
+                        m_syncRoot = c.SyncRoot;
+                    }
+                    else
+                    {
+                        System.Threading.Interlocked.CompareExchange<Object>(ref m_syncRoot, new Object(), null);
+                    }
+                }
+                return m_syncRoot;
+            }
+        }
+
+        private struct DictionaryEnumerator : IDictionaryEnumerator
+        {
+            private readonly IDictionary<TKey, TValue> m_dictionary;
+            private IEnumerator<KeyValuePair<TKey, TValue>> m_enumerator;
+
+            public DictionaryEnumerator(IDictionary<TKey, TValue> dictionary)
+            {
+                m_dictionary = dictionary;
+                m_enumerator = m_dictionary.GetEnumerator();
+            }
+
+            public DictionaryEntry Entry
+            {
+                get { return new DictionaryEntry(m_enumerator.Current.Key, m_enumerator.Current.Value); }
+            }
+
+            public object Key
+            {
+                get { return m_enumerator.Current.Key; }
+            }
+
+            public object Value
+            {
+                get { return m_enumerator.Current.Value; }
+            }
+
+            public object Current
+            {
+                get { return Entry; }
+            }
+
+            public bool MoveNext()
+            {
+                return m_enumerator.MoveNext();
+            }
+
+            public void Reset()
+            {
+                m_enumerator.Reset();
+            }
+        }
+
+        #endregion
+
+        #region IReadOnlyDictionary members
+
+        IEnumerable<TKey> IReadOnlyDictionary<TKey, TValue>.Keys
+        {
+            get
+            {
+                return Keys;
+            }
+        }
+
+        IEnumerable<TValue> IReadOnlyDictionary<TKey, TValue>.Values
+        {
+            get
+            {
+                return Values;
+            }
+        }
+
+        #endregion IReadOnlyDictionary members
+
+        [DebuggerTypeProxy(typeof(ICollectionDebugView<>))]
+        [DebuggerDisplay("Count = {Count}")]
+        public sealed class KeyCollection : ICollection<TKey>, ICollection, IReadOnlyCollection<TKey>
+        {
+            private readonly ICollection<TKey> m_collection;
+            private Object m_syncRoot;
+
+            internal KeyCollection(ICollection<TKey> collection)
+            {
+                if (collection == null)
+                {
+                    ThrowHelper.ThrowArgumentNullException(ExceptionArgument.collection);
+                }
+                m_collection = collection;
+            }
+
+            #region ICollection<T> Members
+
+            void ICollection<TKey>.Add(TKey item)
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+
+            void ICollection<TKey>.Clear()
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+
+            bool ICollection<TKey>.Contains(TKey item)
+            {
+                return m_collection.Contains(item);
+            }
+
+            public void CopyTo(TKey[] array, int arrayIndex)
+            {
+                m_collection.CopyTo(array, arrayIndex);
+            }
+
+            public int Count
+            {
+                get { return m_collection.Count; }
+            }
+
+            bool ICollection<TKey>.IsReadOnly
+            {
+                get { return true; }
+            }
+
+            bool ICollection<TKey>.Remove(TKey item)
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+                return false;
+            }
+
+            #endregion
+
+            #region IEnumerable<T> Members
+
+            public IEnumerator<TKey> GetEnumerator()
+            {
+                return m_collection.GetEnumerator();
+            }
+
+            #endregion
+
+            #region IEnumerable Members
+
+            System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
+            {
+                return ((IEnumerable)m_collection).GetEnumerator();
+            }
+
+            #endregion
+
+            #region ICollection Members
+
+            void ICollection.CopyTo(Array array, int index)
+            {
+                ReadOnlyDictionaryHelpers.CopyToNonGenericICollectionHelper<TKey>(m_collection, array, index);
+            }
+
+            bool ICollection.IsSynchronized
+            {
+                get { return false; }
+            }
+
+            object ICollection.SyncRoot
+            {
+                get
+                {
+                    if (m_syncRoot == null)
+                    {
+                        ICollection c = m_collection as ICollection;
+                        if (c != null)
+                        {
+                            m_syncRoot = c.SyncRoot;
+                        }
+                        else
+                        {
+                            System.Threading.Interlocked.CompareExchange<Object>(ref m_syncRoot, new Object(), null);
+                        }
+                    }
+                    return m_syncRoot;
+                }
+            }
+
+            #endregion
+        }
+
+        [DebuggerTypeProxy(typeof(ICollectionDebugView<>))]
+        [DebuggerDisplay("Count = {Count}")]
+        public sealed class ValueCollection : ICollection<TValue>, ICollection, IReadOnlyCollection<TValue>
+        {
+            private readonly ICollection<TValue> m_collection;
+            private Object m_syncRoot;
+
+            internal ValueCollection(ICollection<TValue> collection)
+            {
+                if (collection == null)
+                {
+                    ThrowHelper.ThrowArgumentNullException(ExceptionArgument.collection);
+                }
+                m_collection = collection;
+            }
+
+            #region ICollection<T> Members
+
+            void ICollection<TValue>.Add(TValue item)
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+
+            void ICollection<TValue>.Clear()
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+            }
+
+            bool ICollection<TValue>.Contains(TValue item)
+            {
+                return m_collection.Contains(item);
+            }
+
+            public void CopyTo(TValue[] array, int arrayIndex)
+            {
+                m_collection.CopyTo(array, arrayIndex);
+            }
+
+            public int Count
+            {
+                get { return m_collection.Count; }
+            }
+
+            bool ICollection<TValue>.IsReadOnly
+            {
+                get { return true; }
+            }
+
+            bool ICollection<TValue>.Remove(TValue item)
+            {
+                ThrowHelper.ThrowNotSupportedException(ExceptionResource.NotSupported_ReadOnlyCollection);
+                return false;
+            }
+
+            #endregion
+
+            #region IEnumerable<T> Members
+
+            public IEnumerator<TValue> GetEnumerator()
+            {
+                return m_collection.GetEnumerator();
+            }
+
+            #endregion
+
+            #region IEnumerable Members
+
+            System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
+            {
+                return ((IEnumerable)m_collection).GetEnumerator();
+            }
+
+            #endregion
+
+            #region ICollection Members
+
+            void ICollection.CopyTo(Array array, int index)
+            {
+                ReadOnlyDictionaryHelpers.CopyToNonGenericICollectionHelper<TValue>(m_collection, array, index);
+            }
+
+            bool ICollection.IsSynchronized
+            {
+                get { return false; }
+            }
+
+            object ICollection.SyncRoot
+            {
+                get
+                {
+                    if (m_syncRoot == null)
+                    {
+                        ICollection c = m_collection as ICollection;
+                        if (c != null)
+                        {
+                            m_syncRoot = c.SyncRoot;
+                        }
+                        else
+                        {
+                            System.Threading.Interlocked.CompareExchange<Object>(ref m_syncRoot, new Object(), null);
+                        }
+                    }
+                    return m_syncRoot;
+                }
+            }
+
+            #endregion ICollection Members
+        }
+    }
+
+    // To share code when possible, use a non-generic class to get rid of irrelevant type parameters.
+    internal static class ReadOnlyDictionaryHelpers
+    {
+        #region Helper method for our KeyCollection and ValueCollection
+
+        // Abstracted away to avoid redundant implementations.
+        internal static void CopyToNonGenericICollectionHelper<T>(ICollection<T> collection, Array array, int index)
+        {
+            if (array == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
+            }
+
+            if (array.Rank != 1)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
+            }
+
+            if (array.GetLowerBound(0) != 0)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_NonZeroLowerBound);
+            }
+
+            if (index < 0)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.arrayIndex, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (array.Length - index < collection.Count)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_ArrayPlusOffTooSmall);
+            }
+
+            // Easy out if the ICollection<T> implements the non-generic ICollection
+            ICollection nonGenericCollection = collection as ICollection;
+            if (nonGenericCollection != null)
+            {
+                nonGenericCollection.CopyTo(array, index);
+                return;
+            }
+
+            T[] items = array as T[];
+            if (items != null)
+            {
+                collection.CopyTo(items, index);
+            }
+            else
+            {
+                //
+                // Catch the obvious case assignment will fail.
+                // We can found all possible problems by doing the check though.
+                // For example, if the element type of the Array is derived from T,
+                // we can't figure out if we can successfully copy the element beforehand.
+                //
+                Type targetType = array.GetType().GetElementType();
+                Type sourceType = typeof(T);
+                if (!(targetType.IsAssignableFrom(sourceType) || sourceType.IsAssignableFrom(targetType)))
+                {
+                    ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                }
+
+                //
+                // We can't cast array of value type to object[], so we don't support 
+                // widening of primitive types here.
+                //
+                object[] objects = array as object[];
+                if (objects == null)
+                {
+                    ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                }
+
+                try
+                {
+                    foreach (var item in collection)
+                    {
+                        objects[index++] = item;
+                    }
+                }
+                catch (ArrayTypeMismatchException)
+                {
+                    ThrowHelper.ThrowArgumentException_Argument_InvalidArrayType();
+                }
+            }
+        }
+
+        #endregion Helper method for our KeyCollection and ValueCollection
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Currency.cs b/src/System.Private.CoreLib/src/System/Currency.cs
new file mode 100644
index 0000000000..4b735bbfe3
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Currency.cs
@@ -0,0 +1,63 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    internal struct Currency
+    {
+        internal long m_value;
+
+        // Constructs a Currency from a Decimal value.
+        //
+        public Currency(Decimal value)
+        {
+            m_value = Decimal.ToCurrency(value).m_value;
+        }
+
+        // Constructs a Currency from a long value without scaling. The
+        // ignored parameter exists only to distinguish this constructor
+        // from the constructor that takes a long.  Used only in the System 
+        // package, especially in Variant.
+        internal Currency(long value, int ignored)
+        {
+            m_value = value;
+        }
+
+        // Creates a Currency from an OLE Automation Currency.  This method
+        // applies no scaling to the Currency value, essentially doing a bitwise
+        // copy.
+        // 
+        public static Currency FromOACurrency(long cy)
+        {
+            return new Currency(cy, 0);
+        }
+
+        //Creates an OLE Automation Currency from a Currency instance.  This 
+        // method applies no scaling to the Currency value, essentially doing 
+        // a bitwise copy.
+        // 
+        public long ToOACurrency()
+        {
+            return m_value;
+        }
+
+        // Converts a Currency to a Decimal.
+        //
+        public static Decimal ToDecimal(Currency c)
+        {
+            Decimal result = new Decimal();
+            FCallToDecimal(ref result, c);
+            return result;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void FCallToDecimal(ref Decimal result, Currency c);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/CurrentSystemTimeZone.Cache.cs b/src/System.Private.CoreLib/src/System/CurrentSystemTimeZone.Cache.cs
new file mode 100644
index 0000000000..744c697124
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/CurrentSystemTimeZone.Cache.cs
@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.Globalization;
+
+namespace System
+{
+    internal partial class CurrentSystemTimeZone
+    {
+        private DaylightTime GetCachedDaylightChanges(int year)
+        {
+            Object objYear = (Object)year;
+
+            if (!m_CachedDaylightChanges.Contains(objYear))
+            {
+                DaylightTime currentDaylightChanges = CreateDaylightChanges(year);
+                lock (m_CachedDaylightChanges)
+                {
+                    if (!m_CachedDaylightChanges.Contains(objYear))
+                    {
+                        m_CachedDaylightChanges.Add(objYear, currentDaylightChanges);
+                    }
+                }
+            }
+
+            return (DaylightTime)m_CachedDaylightChanges[objYear];
+        }
+
+        // The per-year information is cached in in this instance value. As a result it can
+        // be cleaned up by CultureInfo.ClearCachedData, which will clear the instance of this object
+        private readonly Hashtable m_CachedDaylightChanges = new Hashtable();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/DateTime.CoreCLR.cs b/src/System.Private.CoreLib/src/System/DateTime.CoreCLR.cs
new file mode 100644
index 0000000000..84cda1d813
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/DateTime.CoreCLR.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    public readonly partial struct DateTime
+    {
+        public static DateTime UtcNow
+        {
+            get
+            {
+                // following code is tuned for speed. Don't change it without running benchmark.
+                long ticks = 0;
+                ticks = GetSystemTimeAsFileTime();
+
+                return new DateTime(((UInt64)(ticks + FileTimeOffset)) | KindUtc);
+            }
+        }
+
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern long GetSystemTimeAsFileTime();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Decimal.DecCalc.cs b/src/System.Private.CoreLib/src/System/Decimal.DecCalc.cs
new file mode 100644
index 0000000000..6d1a7a50c5
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Decimal.DecCalc.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System
+{
+    public partial struct Decimal
+    {
+        internal static uint DecDivMod1E9(ref decimal value)
+        {
+            return D32DivMod1E9(D32DivMod1E9(D32DivMod1E9(0,
+                                                          ref Unsafe.As<int, uint>(ref value.hi)),
+                                             ref Unsafe.As<int, uint>(ref value.mid)),
+                                ref Unsafe.As<int, uint>(ref value.lo));
+
+            uint D32DivMod1E9(uint hi32, ref uint lo32)
+            {
+                ulong n = (ulong)hi32 << 32 | lo32;
+                lo32 = (uint)(n / 1000000000);
+                return (uint)(n % 1000000000);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Decimal.cs b/src/System.Private.CoreLib/src/System/Decimal.cs
new file mode 100644
index 0000000000..baab51c0dc
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Decimal.cs
@@ -0,0 +1,1351 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System;
+using System.Globalization;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Runtime.ConstrainedExecution;
+using System.Runtime.Versioning;
+using System.Runtime.Serialization;
+using System.Diagnostics;
+
+namespace System
+{
+    // Implements the Decimal data type. The Decimal data type can
+    // represent values ranging from -79,228,162,514,264,337,593,543,950,335 to
+    // 79,228,162,514,264,337,593,543,950,335 with 28 significant digits. The
+    // Decimal data type is ideally suited to financial calculations that
+    // require a large number of significant digits and no round-off errors.
+    //
+    // The finite set of values of type Decimal are of the form m
+    // / 10e, where m is an integer such that
+    // -296 <; m <; 296, and e is an integer
+    // between 0 and 28 inclusive.
+    //
+    // Contrary to the float and double data types, decimal
+    // fractional numbers such as 0.1 can be represented exactly in the
+    // Decimal representation. In the float and double
+    // representations, such numbers are often infinite fractions, making those
+    // representations more prone to round-off errors.
+    //
+    // The Decimal class implements widening conversions from the
+    // ubyte, char, short, int, and long types
+    // to Decimal. These widening conversions never loose any information
+    // and never throw exceptions. The Decimal class also implements
+    // narrowing conversions from Decimal to ubyte, char,
+    // short, int, and long. These narrowing conversions round
+    // the Decimal value towards zero to the nearest integer, and then
+    // converts that integer to the destination type. An OverflowException
+    // is thrown if the result is not within the range of the destination type.
+    //
+    // The Decimal class provides a widening conversion from
+    // Currency to Decimal. This widening conversion never loses any
+    // information and never throws exceptions. The Currency class provides
+    // a narrowing conversion from Decimal to Currency. This
+    // narrowing conversion rounds the Decimal to four decimals and then
+    // converts that number to a Currency. An OverflowException
+    // is thrown if the result is not within the range of the Currency type.
+    //
+    // The Decimal class provides narrowing conversions to and from the
+    // float and double types. A conversion from Decimal to
+    // float or double may loose precision, but will not loose
+    // information about the overall magnitude of the numeric value, and will never
+    // throw an exception. A conversion from float or double to
+    // Decimal throws an OverflowException if the value is not within
+    // the range of the Decimal type.
+    [StructLayout(LayoutKind.Sequential)]
+    [Serializable]
+    [System.Runtime.Versioning.NonVersionable] // This only applies to field layout
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public partial struct Decimal : IFormattable, IComparable, IConvertible, IComparable<Decimal>, IEquatable<Decimal>, IDeserializationCallback, ISpanFormattable
+    {
+        // Sign mask for the flags field. A value of zero in this bit indicates a
+        // positive Decimal value, and a value of one in this bit indicates a
+        // negative Decimal value.
+        // 
+        // Look at OleAut's DECIMAL_NEG constant to check for negative values
+        // in native code.
+        private const int SignMask = unchecked((int)0x80000000);
+        private const byte DECIMAL_NEG = 0x80;
+        private const byte DECIMAL_ADD = 0x00;
+
+        // Scale mask for the flags field. This byte in the flags field contains
+        // the power of 10 to divide the Decimal value by. The scale byte must
+        // contain a value between 0 and 28 inclusive.
+        private const int ScaleMask = 0x00FF0000;
+
+        // Number of bits scale is shifted by.
+        private const int ScaleShift = 16;
+
+        // The maximum power of 10 that a 32 bit integer can store
+        private const Int32 MaxInt32Scale = 9;
+
+        // Fast access for 10^n where n is 0-9        
+        private static UInt32[] Powers10 = new UInt32[] {
+            1,
+            10,
+            100,
+            1000,
+            10000,
+            100000,
+            1000000,
+            10000000,
+            100000000,
+            1000000000
+        };
+
+        // Constant representing the Decimal value 0.
+        public const Decimal Zero = 0m;
+
+        // Constant representing the Decimal value 1.
+        public const Decimal One = 1m;
+
+        // Constant representing the Decimal value -1.
+        public const Decimal MinusOne = -1m;
+
+        // Constant representing the largest possible Decimal value. The value of
+        // this constant is 79,228,162,514,264,337,593,543,950,335.
+        public const Decimal MaxValue = 79228162514264337593543950335m;
+
+        // Constant representing the smallest possible Decimal value. The value of
+        // this constant is -79,228,162,514,264,337,593,543,950,335.
+        public const Decimal MinValue = -79228162514264337593543950335m;
+
+
+        // Constant representing the negative number that is the closest possible
+        // Decimal value to -0m.
+        private const Decimal NearNegativeZero = -0.000000000000000000000000001m;
+
+        // Constant representing the positive number that is the closest possible
+        // Decimal value to +0m.
+        private const Decimal NearPositiveZero = +0.000000000000000000000000001m;
+
+        // The lo, mid, hi, and flags fields contain the representation of the
+        // Decimal value. The lo, mid, and hi fields contain the 96-bit integer
+        // part of the Decimal. Bits 0-15 (the lower word) of the flags field are
+        // unused and must be zero; bits 16-23 contain must contain a value between
+        // 0 and 28, indicating the power of 10 to divide the 96-bit integer part
+        // by to produce the Decimal value; bits 24-30 are unused and must be zero;
+        // and finally bit 31 indicates the sign of the Decimal value, 0 meaning
+        // positive and 1 meaning negative.
+        //
+        // NOTE: Do not change the order in which these fields are declared. The
+        // native methods in this class rely on this particular order. 
+        // Do not rename (binary serialization).
+        private int flags;
+        private int hi;
+        private int lo;
+        private int mid;
+
+        internal uint High => (uint)hi;
+        internal uint Low => (uint)lo;
+        internal uint Mid => (uint)mid;
+
+        // Constructs a zero Decimal.
+        //public Decimal() {
+        //    lo = 0;
+        //    mid = 0;
+        //    hi = 0;
+        //    flags = 0;
+        //}
+
+        // Constructs a Decimal from an integer value.
+        //
+        public Decimal(int value)
+        {
+            //  JIT today can't inline methods that contains "starg" opcode.
+            //  For more details, see DevDiv Bugs 81184: x86 JIT CQ: Removing the inline striction of "starg".
+            int value_copy = value;
+            if (value_copy >= 0)
+            {
+                flags = 0;
+            }
+            else
+            {
+                flags = SignMask;
+                value_copy = -value_copy;
+            }
+            lo = value_copy;
+            mid = 0;
+            hi = 0;
+        }
+
+        // Constructs a Decimal from an unsigned integer value.
+        //
+        [CLSCompliant(false)]
+        public Decimal(uint value)
+        {
+            flags = 0;
+            lo = (int)value;
+            mid = 0;
+            hi = 0;
+        }
+
+        // Constructs a Decimal from a long value.
+        //
+        public Decimal(long value)
+        {
+            //  JIT today can't inline methods that contains "starg" opcode.
+            //  For more details, see DevDiv Bugs 81184: x86 JIT CQ: Removing the inline striction of "starg".
+            long value_copy = value;
+            if (value_copy >= 0)
+            {
+                flags = 0;
+            }
+            else
+            {
+                flags = SignMask;
+                value_copy = -value_copy;
+            }
+            lo = (int)value_copy;
+            mid = (int)(value_copy >> 32);
+            hi = 0;
+        }
+
+        // Constructs a Decimal from an unsigned long value.
+        //
+        [CLSCompliant(false)]
+        public Decimal(ulong value)
+        {
+            flags = 0;
+            lo = (int)value;
+            mid = (int)(value >> 32);
+            hi = 0;
+        }
+
+        // Constructs a Decimal from a float value.
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern Decimal(float value);
+
+        // Constructs a Decimal from a double value.
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern Decimal(double value);
+
+        // Constructs a Decimal from a Currency value.
+        //
+        internal Decimal(Currency value)
+        {
+            this = Currency.ToDecimal(value);
+        }
+
+        // Don't remove these 2 methods below. They are required by the fx when the are dealing with Currency in their
+        // databases
+        public static long ToOACurrency(Decimal value)
+        {
+            return new Currency(value).ToOACurrency();
+        }
+
+        public static Decimal FromOACurrency(long cy)
+        {
+            return Currency.ToDecimal(Currency.FromOACurrency(cy));
+        }
+
+
+        // Constructs a Decimal from an integer array containing a binary
+        // representation. The bits argument must be a non-null integer
+        // array with four elements. bits[0], bits[1], and
+        // bits[2] contain the low, middle, and high 32 bits of the 96-bit
+        // integer part of the Decimal. bits[3] contains the scale factor
+        // and sign of the Decimal: bits 0-15 (the lower word) are unused and must
+        // be zero; bits 16-23 must contain a value between 0 and 28, indicating
+        // the power of 10 to divide the 96-bit integer part by to produce the
+        // Decimal value; bits 24-30 are unused and must be zero; and finally bit
+        // 31 indicates the sign of the Decimal value, 0 meaning positive and 1
+        // meaning negative.
+        //
+        // Note that there are several possible binary representations for the
+        // same numeric value. For example, the value 1 can be represented as {1,
+        // 0, 0, 0} (integer value 1 with a scale factor of 0) and equally well as
+        // {1000, 0, 0, 0x30000} (integer value 1000 with a scale factor of 3).
+        // The possible binary representations of a particular value are all
+        // equally valid, and all are numerically equivalent.
+        //
+        public Decimal(int[] bits)
+        {
+            lo = 0;
+            mid = 0;
+            hi = 0;
+            flags = 0;
+            SetBits(bits);
+        }
+
+        private void SetBits(int[] bits)
+        {
+            if (bits == null)
+                throw new ArgumentNullException(nameof(bits));
+            if (bits.Length == 4)
+            {
+                int f = bits[3];
+                if ((f & ~(SignMask | ScaleMask)) == 0 && (f & ScaleMask) <= (28 << 16))
+                {
+                    lo = bits[0];
+                    mid = bits[1];
+                    hi = bits[2];
+                    flags = f;
+                    return;
+                }
+            }
+            throw new ArgumentException(SR.Arg_DecBitCtor);
+        }
+
+        // Constructs a Decimal from its constituent parts.
+        // 
+        public Decimal(int lo, int mid, int hi, bool isNegative, byte scale)
+        {
+            if (scale > 28)
+                throw new ArgumentOutOfRangeException(nameof(scale), SR.ArgumentOutOfRange_DecimalScale);
+            this.lo = lo;
+            this.mid = mid;
+            this.hi = hi;
+            flags = ((int)scale) << 16;
+            if (isNegative)
+                flags |= SignMask;
+        }
+
+        [OnSerializing]
+        private void OnSerializing(StreamingContext ctx)
+        {
+            // OnSerializing is called before serialization of an object
+            try
+            {
+                SetBits(GetBits(this));
+            }
+            catch (ArgumentException e)
+            {
+                throw new SerializationException(SR.Overflow_Decimal, e);
+            }
+        }
+
+        void IDeserializationCallback.OnDeserialization(Object sender)
+        {
+            // OnDeserialization is called after each instance of this class is deserialized.
+            // This callback method performs decimal validation after being deserialized.
+            try
+            {
+                SetBits(GetBits(this));
+            }
+            catch (ArgumentException e)
+            {
+                throw new SerializationException(SR.Overflow_Decimal, e);
+            }
+        }
+
+        // Constructs a Decimal from its constituent parts.
+        private Decimal(int lo, int mid, int hi, int flags)
+        {
+            if ((flags & ~(SignMask | ScaleMask)) == 0 && (flags & ScaleMask) <= (28 << 16))
+            {
+                this.lo = lo;
+                this.mid = mid;
+                this.hi = hi;
+                this.flags = flags;
+                return;
+            }
+            throw new ArgumentException(SR.Arg_DecBitCtor);
+        }
+
+        // Returns the absolute value of the given Decimal. If d is
+        // positive, the result is d. If d is negative, the result
+        // is -d.
+        //
+        internal static Decimal Abs(ref Decimal d)
+        {
+            return new Decimal(d.lo, d.mid, d.hi, d.flags & ~SignMask);
+        }
+
+        // Adds two Decimal values.
+        //
+        public static Decimal Add(Decimal d1, Decimal d2)
+        {
+            FCallAddSub(ref d1, ref d2, DECIMAL_ADD);
+            return d1;
+        }
+
+        internal bool IsNegative => (flags & SignMask) != 0;
+
+        internal int Scale => (byte)((uint)flags >> ScaleShift);
+
+        // FCallAddSub adds or subtracts two decimal values.  On return, d1 contains the result
+        // of the operation.  Passing in DECIMAL_ADD or DECIMAL_NEG for bSign indicates
+        // addition or subtraction, respectively.
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void FCallAddSub(ref Decimal d1, ref Decimal d2, byte bSign);
+
+        // Rounds a Decimal to an integer value. The Decimal argument is rounded
+        // towards positive infinity.
+        public static Decimal Ceiling(Decimal d)
+        {
+            return (-(Decimal.Floor(-d)));
+        }
+
+        // Compares two Decimal values, returning an integer that indicates their
+        // relationship.
+        //
+        public static int Compare(Decimal d1, Decimal d2)
+        {
+            return FCallCompare(ref d1, ref d2);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int FCallCompare(ref Decimal d1, ref Decimal d2);
+
+        // Compares this object to another object, returning an integer that
+        // indicates the relationship. 
+        // Returns a value less than zero if this  object
+        // null is considered to be less than any instance.
+        // If object is not of type Decimal, this method throws an ArgumentException.
+        // 
+        public int CompareTo(Object value)
+        {
+            if (value == null)
+                return 1;
+            if (!(value is Decimal))
+                throw new ArgumentException(SR.Arg_MustBeDecimal);
+
+            Decimal other = (Decimal)value;
+            return FCallCompare(ref this, ref other);
+        }
+
+        public int CompareTo(Decimal value)
+        {
+            return FCallCompare(ref this, ref value);
+        }
+
+        // Divides two Decimal values.
+        //
+        public static Decimal Divide(Decimal d1, Decimal d2)
+        {
+            FCallDivide(ref d1, ref d2);
+            return d1;
+        }
+
+        // FCallDivide divides two decimal values.  On return, d1 contains the result
+        // of the operation.
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void FCallDivide(ref Decimal d1, ref Decimal d2);
+
+
+        // Checks if this Decimal is equal to a given object. Returns true
+        // if the given object is a boxed Decimal and its value is equal to the
+        // value of this Decimal. Returns false otherwise.
+        //
+        public override bool Equals(Object value)
+        {
+            if (value is Decimal)
+            {
+                Decimal other = (Decimal)value;
+                return FCallCompare(ref this, ref other) == 0;
+            }
+            return false;
+        }
+
+        public bool Equals(Decimal value)
+        {
+            return FCallCompare(ref this, ref value) == 0;
+        }
+
+        // Returns the hash code for this Decimal.
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern override int GetHashCode();
+
+        // Compares two Decimal values for equality. Returns true if the two
+        // Decimal values are equal, or false if they are not equal.
+        //
+        public static bool Equals(Decimal d1, Decimal d2)
+        {
+            return FCallCompare(ref d1, ref d2) == 0;
+        }
+
+        // Rounds a Decimal to an integer value. The Decimal argument is rounded
+        // towards negative infinity.
+        //
+        public static Decimal Floor(Decimal d)
+        {
+            FCallFloor(ref d);
+            return d;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void FCallFloor(ref Decimal d);
+
+        // Converts this Decimal to a string. The resulting string consists of an
+        // optional minus sign ("-") followed to a sequence of digits ("0" - "9"),
+        // optionally followed by a decimal point (".") and another sequence of
+        // digits.
+        //
+        public override String ToString()
+        {
+            return Number.FormatDecimal(this, null, NumberFormatInfo.CurrentInfo);
+        }
+
+        public String ToString(String format)
+        {
+            return Number.FormatDecimal(this, format, NumberFormatInfo.CurrentInfo);
+        }
+
+        public String ToString(IFormatProvider provider)
+        {
+            return Number.FormatDecimal(this, null, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public String ToString(String format, IFormatProvider provider)
+        {
+            return Number.FormatDecimal(this, format, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider provider = null)
+        {
+            return Number.TryFormatDecimal(this, format, NumberFormatInfo.GetInstance(provider), destination, out charsWritten);
+        }
+
+        // Converts a string to a Decimal. The string must consist of an optional
+        // minus sign ("-") followed by a sequence of digits ("0" - "9"). The
+        // sequence of digits may optionally contain a single decimal point (".")
+        // character. Leading and trailing whitespace characters are allowed.
+        // Parse also allows a currency symbol, a trailing negative sign, and
+        // parentheses in the number.
+        //
+        public static Decimal Parse(String s)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseDecimal(s, NumberStyles.Number, NumberFormatInfo.CurrentInfo);
+        }
+
+        public static Decimal Parse(String s, NumberStyles style)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseDecimal(s, style, NumberFormatInfo.CurrentInfo);
+        }
+
+        public static Decimal Parse(String s, IFormatProvider provider)
+        {
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseDecimal(s, NumberStyles.Number, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public static Decimal Parse(String s, NumberStyles style, IFormatProvider provider)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            if (s == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.s);
+            return Number.ParseDecimal(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public static decimal Parse(ReadOnlySpan<char> s, NumberStyles style = NumberStyles.Number, IFormatProvider provider = null)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            return Number.ParseDecimal(s, style, NumberFormatInfo.GetInstance(provider));
+        }
+
+        public static Boolean TryParse(String s, out Decimal result)
+        {
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return Number.TryParseDecimal(s, NumberStyles.Number, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, out decimal result)
+        {
+            return Number.TryParseDecimal(s, NumberStyles.Number, NumberFormatInfo.CurrentInfo, out result);
+        }
+
+        public static Boolean TryParse(String s, NumberStyles style, IFormatProvider provider, out Decimal result)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+
+            if (s == null)
+            {
+                result = 0;
+                return false;
+            }
+
+            return Number.TryParseDecimal(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider provider, out decimal result)
+        {
+            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            return Number.TryParseDecimal(s, style, NumberFormatInfo.GetInstance(provider), out result);
+        }
+
+        // Returns a binary representation of a Decimal. The return value is an
+        // integer array with four elements. Elements 0, 1, and 2 contain the low,
+        // middle, and high 32 bits of the 96-bit integer part of the Decimal.
+        // Element 3 contains the scale factor and sign of the Decimal: bits 0-15
+        // (the lower word) are unused; bits 16-23 contain a value between 0 and
+        // 28, indicating the power of 10 to divide the 96-bit integer part by to
+        // produce the Decimal value; bits 24-30 are unused; and finally bit 31
+        // indicates the sign of the Decimal value, 0 meaning positive and 1
+        // meaning negative.
+        //
+        public static int[] GetBits(Decimal d)
+        {
+            return new int[] { d.lo, d.mid, d.hi, d.flags };
+        }
+
+        internal static void GetBytes(Decimal d, byte[] buffer)
+        {
+            Debug.Assert((buffer != null && buffer.Length >= 16), "[GetBytes]buffer != null && buffer.Length >= 16");
+            buffer[0] = (byte)d.lo;
+            buffer[1] = (byte)(d.lo >> 8);
+            buffer[2] = (byte)(d.lo >> 16);
+            buffer[3] = (byte)(d.lo >> 24);
+
+            buffer[4] = (byte)d.mid;
+            buffer[5] = (byte)(d.mid >> 8);
+            buffer[6] = (byte)(d.mid >> 16);
+            buffer[7] = (byte)(d.mid >> 24);
+
+            buffer[8] = (byte)d.hi;
+            buffer[9] = (byte)(d.hi >> 8);
+            buffer[10] = (byte)(d.hi >> 16);
+            buffer[11] = (byte)(d.hi >> 24);
+
+            buffer[12] = (byte)d.flags;
+            buffer[13] = (byte)(d.flags >> 8);
+            buffer[14] = (byte)(d.flags >> 16);
+            buffer[15] = (byte)(d.flags >> 24);
+        }
+
+        internal static decimal ToDecimal(byte[] buffer)
+        {
+            Debug.Assert((buffer != null && buffer.Length >= 16), "[ToDecimal]buffer != null && buffer.Length >= 16");
+            int lo = ((int)buffer[0]) | ((int)buffer[1] << 8) | ((int)buffer[2] << 16) | ((int)buffer[3] << 24);
+            int mid = ((int)buffer[4]) | ((int)buffer[5] << 8) | ((int)buffer[6] << 16) | ((int)buffer[7] << 24);
+            int hi = ((int)buffer[8]) | ((int)buffer[9] << 8) | ((int)buffer[10] << 16) | ((int)buffer[11] << 24);
+            int flags = ((int)buffer[12]) | ((int)buffer[13] << 8) | ((int)buffer[14] << 16) | ((int)buffer[15] << 24);
+            return new Decimal(lo, mid, hi, flags);
+        }
+
+        // This method does a 'raw' and 'unchecked' addition of a UInt32 to a Decimal in place. 
+        // 'raw' means that it operates on the internal 96-bit unsigned integer value and 
+        // ingores the sign and scale. This means that it is not equivalent to just adding
+        // that number, as the sign and scale are effectively applied to the UInt32 value also.
+        // 'unchecked' means that it does not fail if you overflow the 96 bit value.
+        private static void InternalAddUInt32RawUnchecked(ref Decimal value, UInt32 i)
+        {
+            UInt32 v;
+            UInt32 sum;
+            v = (UInt32)value.lo;
+            sum = v + i;
+            value.lo = (Int32)sum;
+            if (sum < v || sum < i)
+            {
+                v = (UInt32)value.mid;
+                sum = v + 1;
+                value.mid = (Int32)sum;
+                if (sum < v || sum < 1)
+                {
+                    value.hi = (Int32)((UInt32)value.hi + 1);
+                }
+            }
+        }
+
+        // This method does an in-place division of a decimal by a UInt32, returning the remainder. 
+        // Although it does not operate on the sign or scale, this does not result in any 
+        // caveat for the result. It is equivalent to dividing by that number.
+        private static UInt32 InternalDivRemUInt32(ref Decimal value, UInt32 divisor)
+        {
+            UInt32 remainder = 0;
+            UInt64 n;
+            if (value.hi != 0)
+            {
+                n = ((UInt32)value.hi);
+                value.hi = (Int32)((UInt32)(n / divisor));
+                remainder = (UInt32)(n % divisor);
+            }
+            if (value.mid != 0 || remainder != 0)
+            {
+                n = ((UInt64)remainder << 32) | (UInt32)value.mid;
+                value.mid = (Int32)((UInt32)(n / divisor));
+                remainder = (UInt32)(n % divisor);
+            }
+            if (value.lo != 0 || remainder != 0)
+            {
+                n = ((UInt64)remainder << 32) | (UInt32)value.lo;
+                value.lo = (Int32)((UInt32)(n / divisor));
+                remainder = (UInt32)(n % divisor);
+            }
+            return remainder;
+        }
+
+        // Does an in-place round the specified number of digits, rounding mid-point values
+        // away from zero
+        private static void InternalRoundFromZero(ref Decimal d, int decimalCount)
+        {
+            Int32 scale = (d.flags & ScaleMask) >> ScaleShift;
+            Int32 scaleDifference = scale - decimalCount;
+            if (scaleDifference <= 0)
+            {
+                return;
+            }
+            // Divide the value by 10^scaleDifference
+            UInt32 lastRemainder;
+            UInt32 lastDivisor;
+            do
+            {
+                Int32 diffChunk = (scaleDifference > MaxInt32Scale) ? MaxInt32Scale : scaleDifference;
+                lastDivisor = Powers10[diffChunk];
+                lastRemainder = InternalDivRemUInt32(ref d, lastDivisor);
+                scaleDifference -= diffChunk;
+            } while (scaleDifference > 0);
+
+            // Round away from zero at the mid point
+            if (lastRemainder >= (lastDivisor >> 1))
+            {
+                InternalAddUInt32RawUnchecked(ref d, 1);
+            }
+
+            // the scale becomes the desired decimal count
+            d.flags = ((decimalCount << ScaleShift) & ScaleMask) | (d.flags & SignMask);
+        }
+
+        // Returns the larger of two Decimal values.
+        //
+        internal static Decimal Max(ref Decimal d1, ref Decimal d2)
+        {
+            return FCallCompare(ref d1, ref d2) >= 0 ? d1 : d2;
+        }
+
+        // Returns the smaller of two Decimal values.
+        //
+        internal static Decimal Min(ref Decimal d1, ref Decimal d2)
+        {
+            return FCallCompare(ref d1, ref d2) < 0 ? d1 : d2;
+        }
+
+        public static Decimal Remainder(Decimal d1, Decimal d2)
+        {
+            // OleAut doesn't provide a VarDecMod.            
+
+            // In the operation x % y the sign of y does not matter. Result will have the sign of x.
+            d2.flags = (d2.flags & ~SignMask) | (d1.flags & SignMask);
+
+
+            // This piece of code is to work around the fact that Dividing a decimal with 28 digits number by decimal which causes
+            // causes the result to be 28 digits, can cause to be incorrectly rounded up.
+            // eg. Decimal.MaxValue / 2 * Decimal.MaxValue will overflow since the division by 2 was rounded instead of being truncked.
+            if (Math.Abs(d1) < Math.Abs(d2))
+            {
+                return d1;
+            }
+            d1 -= d2;
+
+            if (d1 == 0)
+            {
+                // The sign of D1 will be wrong here. Fall through so that we still get a DivideByZeroException
+                d1.flags = (d1.flags & ~SignMask) | (d2.flags & SignMask);
+            }
+
+            // Formula:  d1 - (RoundTowardsZero(d1 / d2) * d2)            
+            Decimal dividedResult = Truncate(d1 / d2);
+            Decimal multipliedResult = dividedResult * d2;
+            Decimal result = d1 - multipliedResult;
+            // See if the result has crossed 0
+            if ((d1.flags & SignMask) != (result.flags & SignMask))
+            {
+                if (NearNegativeZero <= result && result <= NearPositiveZero)
+                {
+                    // Certain Remainder operations on decimals with 28 significant digits round
+                    // to [+-]0.000000000000000000000000001m instead of [+-]0m during the intermediate calculations. 
+                    // 'zero' results just need their sign corrected.
+                    result.flags = (result.flags & ~SignMask) | (d1.flags & SignMask);
+                }
+                else
+                {
+                    // If the division rounds up because it runs out of digits, the multiplied result can end up with a larger
+                    // absolute value and the result of the formula crosses 0. To correct it can add the divisor back.
+                    result += d2;
+                }
+            }
+
+            return result;
+        }
+
+        // Multiplies two Decimal values.
+        //
+        public static Decimal Multiply(Decimal d1, Decimal d2)
+        {
+            FCallMultiply(ref d1, ref d2);
+            return d1;
+        }
+
+        // FCallMultiply multiples two decimal values.  On return, d1 contains the result
+        // of the operation.
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void FCallMultiply(ref Decimal d1, ref Decimal d2);
+
+        // Returns the negated value of the given Decimal. If d is non-zero,
+        // the result is -d. If d is zero, the result is zero.
+        //
+        public static Decimal Negate(Decimal d)
+        {
+            return new Decimal(d.lo, d.mid, d.hi, d.flags ^ SignMask);
+        }
+
+        // Rounds a Decimal value to a given number of decimal places. The value
+        // given by d is rounded to the number of decimal places given by
+        // decimals. The decimals argument must be an integer between
+        // 0 and 28 inclusive.
+        //
+        // By default a mid-point value is rounded to the nearest even number. If the mode is
+        // passed in, it can also round away from zero.
+
+        public static Decimal Round(Decimal d)
+        {
+            return Round(d, 0);
+        }
+
+        public static Decimal Round(Decimal d, int decimals)
+        {
+            FCallRound(ref d, decimals);
+            return d;
+        }
+
+        public static Decimal Round(Decimal d, MidpointRounding mode)
+        {
+            return Round(d, 0, mode);
+        }
+
+        public static Decimal Round(Decimal d, int decimals, MidpointRounding mode)
+        {
+            if ((decimals < 0) || (decimals > 28))
+                throw new ArgumentOutOfRangeException(nameof(decimals), SR.ArgumentOutOfRange_DecimalRound);
+            if (mode < MidpointRounding.ToEven || mode > MidpointRounding.AwayFromZero)
+            {
+                throw new ArgumentException(SR.Format(SR.Argument_InvalidEnumValue, mode, nameof(MidpointRounding)), nameof(mode));
+            }
+
+            if (mode == MidpointRounding.ToEven)
+            {
+                FCallRound(ref d, decimals);
+            }
+            else
+            {
+                InternalRoundFromZero(ref d, decimals);
+            }
+            return d;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void FCallRound(ref Decimal d, int decimals);
+
+        internal static int Sign(ref decimal d) => (d.lo | d.mid | d.hi) == 0 ? 0 : (d.flags >> 31) | 1;
+
+        // Subtracts two Decimal values.
+        //
+        public static Decimal Subtract(Decimal d1, Decimal d2)
+        {
+            FCallAddSub(ref d1, ref d2, DECIMAL_NEG);
+            return d1;
+        }
+
+        // Converts a Decimal to an unsigned byte. The Decimal value is rounded
+        // towards zero to the nearest integer value, and the result of this
+        // operation is returned as a byte.
+        //
+        public static byte ToByte(Decimal value)
+        {
+            uint temp;
+            try
+            {
+                temp = ToUInt32(value);
+            }
+            catch (OverflowException e)
+            {
+                throw new OverflowException(SR.Overflow_Byte, e);
+            }
+            if (temp < Byte.MinValue || temp > Byte.MaxValue) throw new OverflowException(SR.Overflow_Byte);
+            return (byte)temp;
+        }
+
+        // Converts a Decimal to a signed byte. The Decimal value is rounded
+        // towards zero to the nearest integer value, and the result of this
+        // operation is returned as a byte.
+        //
+        [CLSCompliant(false)]
+        public static sbyte ToSByte(Decimal value)
+        {
+            int temp;
+            try
+            {
+                temp = ToInt32(value);
+            }
+            catch (OverflowException e)
+            {
+                throw new OverflowException(SR.Overflow_SByte, e);
+            }
+            if (temp < SByte.MinValue || temp > SByte.MaxValue) throw new OverflowException(SR.Overflow_SByte);
+            return (sbyte)temp;
+        }
+
+        // Converts a Decimal to a short. The Decimal value is
+        // rounded towards zero to the nearest integer value, and the result of
+        // this operation is returned as a short.
+        //
+        public static short ToInt16(Decimal value)
+        {
+            int temp;
+            try
+            {
+                temp = ToInt32(value);
+            }
+            catch (OverflowException e)
+            {
+                throw new OverflowException(SR.Overflow_Int16, e);
+            }
+            if (temp < Int16.MinValue || temp > Int16.MaxValue) throw new OverflowException(SR.Overflow_Int16);
+            return (short)temp;
+        }
+
+
+        // Converts a Decimal to a Currency. Since a Currency
+        // has fewer significant digits than a Decimal, this operation may
+        // produce round-off errors.
+        //
+        internal static Currency ToCurrency(Decimal d)
+        {
+            Currency result = new Currency();
+            FCallToCurrency(ref result, d);
+            return result;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void FCallToCurrency(ref Currency result, Decimal d);
+
+        // Converts a Decimal to a double. Since a double has fewer significant
+        // digits than a Decimal, this operation may produce round-off errors.
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern double ToDouble(Decimal d);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int FCallToInt32(Decimal d);
+
+        // Converts a Decimal to an integer. The Decimal value is rounded towards
+        // zero to the nearest integer value, and the result of this operation is
+        // returned as an integer.
+        //
+        public static int ToInt32(Decimal d)
+        {
+            if ((d.flags & ScaleMask) != 0) FCallTruncate(ref d);
+            if (d.hi == 0 && d.mid == 0)
+            {
+                int i = d.lo;
+                if (d.flags >= 0)
+                {
+                    if (i >= 0) return i;
+                }
+                else
+                {
+                    i = -i;
+                    if (i <= 0) return i;
+                }
+            }
+            throw new OverflowException(SR.Overflow_Int32);
+        }
+
+        // Converts a Decimal to a long. The Decimal value is rounded towards zero
+        // to the nearest integer value, and the result of this operation is
+        // returned as a long.
+        //
+        public static long ToInt64(Decimal d)
+        {
+            if ((d.flags & ScaleMask) != 0) FCallTruncate(ref d);
+            if (d.hi == 0)
+            {
+                long l = d.lo & 0xFFFFFFFFL | (long)d.mid << 32;
+                if (d.flags >= 0)
+                {
+                    if (l >= 0) return l;
+                }
+                else
+                {
+                    l = -l;
+                    if (l <= 0) return l;
+                }
+            }
+            throw new OverflowException(SR.Overflow_Int64);
+        }
+
+        // Converts a Decimal to an ushort. The Decimal 
+        // value is rounded towards zero to the nearest integer value, and the 
+        // result of this operation is returned as an ushort.
+        //
+        [CLSCompliant(false)]
+        public static ushort ToUInt16(Decimal value)
+        {
+            uint temp;
+            try
+            {
+                temp = ToUInt32(value);
+            }
+            catch (OverflowException e)
+            {
+                throw new OverflowException(SR.Overflow_UInt16, e);
+            }
+            if (temp < UInt16.MinValue || temp > UInt16.MaxValue) throw new OverflowException(SR.Overflow_UInt16);
+            return (ushort)temp;
+        }
+
+        // Converts a Decimal to an unsigned integer. The Decimal 
+        // value is rounded towards zero to the nearest integer value, and the 
+        // result of this operation is returned as an unsigned integer.
+        //
+        [CLSCompliant(false)]
+        public static uint ToUInt32(Decimal d)
+        {
+            if ((d.flags & ScaleMask) != 0) FCallTruncate(ref d);
+            if (d.hi == 0 && d.mid == 0)
+            {
+                uint i = (uint)d.lo;
+                if (d.flags >= 0 || i == 0)
+                    return i;
+            }
+            throw new OverflowException(SR.Overflow_UInt32);
+        }
+
+        // Converts a Decimal to an unsigned long. The Decimal 
+        // value is rounded towards zero to the nearest integer value, and the 
+        // result of this operation is returned as a long.
+        //
+        [CLSCompliant(false)]
+        public static ulong ToUInt64(Decimal d)
+        {
+            if ((d.flags & ScaleMask) != 0) FCallTruncate(ref d);
+            if (d.hi == 0)
+            {
+                ulong l = ((ulong)(uint)d.lo) | ((ulong)(uint)d.mid << 32);
+                if (d.flags >= 0 || l == 0)
+                    return l;
+            }
+            throw new OverflowException(SR.Overflow_UInt64);
+        }
+
+        // Converts a Decimal to a float. Since a float has fewer significant
+        // digits than a Decimal, this operation may produce round-off errors.
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern float ToSingle(Decimal d);
+
+        // Truncates a Decimal to an integer value. The Decimal argument is rounded
+        // towards zero to the nearest integer value, corresponding to removing all
+        // digits after the decimal point.
+        //
+        public static Decimal Truncate(Decimal d)
+        {
+            FCallTruncate(ref d);
+            return d;
+        }
+
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void FCallTruncate(ref Decimal d);
+
+
+        public static implicit operator Decimal(byte value)
+        {
+            return new Decimal(value);
+        }
+
+        [CLSCompliant(false)]
+        public static implicit operator Decimal(sbyte value)
+        {
+            return new Decimal(value);
+        }
+
+        public static implicit operator Decimal(short value)
+        {
+            return new Decimal(value);
+        }
+
+        [CLSCompliant(false)]
+        public static implicit operator Decimal(ushort value)
+        {
+            return new Decimal(value);
+        }
+
+        public static implicit operator Decimal(char value)
+        {
+            return new Decimal(value);
+        }
+
+        public static implicit operator Decimal(int value)
+        {
+            return new Decimal(value);
+        }
+
+        [CLSCompliant(false)]
+        public static implicit operator Decimal(uint value)
+        {
+            return new Decimal(value);
+        }
+
+        public static implicit operator Decimal(long value)
+        {
+            return new Decimal(value);
+        }
+
+        [CLSCompliant(false)]
+        public static implicit operator Decimal(ulong value)
+        {
+            return new Decimal(value);
+        }
+
+
+        public static explicit operator Decimal(float value)
+        {
+            return new Decimal(value);
+        }
+
+        public static explicit operator Decimal(double value)
+        {
+            return new Decimal(value);
+        }
+
+        public static explicit operator byte(Decimal value)
+        {
+            return ToByte(value);
+        }
+
+        [CLSCompliant(false)]
+        public static explicit operator sbyte(Decimal value)
+        {
+            return ToSByte(value);
+        }
+
+        public static explicit operator char(Decimal value)
+        {
+            UInt16 temp;
+            try
+            {
+                temp = ToUInt16(value);
+            }
+            catch (OverflowException e)
+            {
+                throw new OverflowException(SR.Overflow_Char, e);
+            }
+            return (char)temp;
+        }
+
+        public static explicit operator short(Decimal value)
+        {
+            return ToInt16(value);
+        }
+
+        [CLSCompliant(false)]
+        public static explicit operator ushort(Decimal value)
+        {
+            return ToUInt16(value);
+        }
+
+        public static explicit operator int(Decimal value)
+        {
+            return ToInt32(value);
+        }
+
+        [CLSCompliant(false)]
+        public static explicit operator uint(Decimal value)
+        {
+            return ToUInt32(value);
+        }
+
+        public static explicit operator long(Decimal value)
+        {
+            return ToInt64(value);
+        }
+
+        [CLSCompliant(false)]
+        public static explicit operator ulong(Decimal value)
+        {
+            return ToUInt64(value);
+        }
+
+        public static explicit operator float(Decimal value)
+        {
+            return ToSingle(value);
+        }
+
+        public static explicit operator double(Decimal value)
+        {
+            return ToDouble(value);
+        }
+
+        public static Decimal operator +(Decimal d)
+        {
+            return d;
+        }
+
+        public static Decimal operator -(Decimal d)
+        {
+            return Negate(d);
+        }
+
+        public static Decimal operator ++(Decimal d)
+        {
+            return Add(d, One);
+        }
+
+        public static Decimal operator --(Decimal d)
+        {
+            return Subtract(d, One);
+        }
+
+        public static Decimal operator +(Decimal d1, Decimal d2)
+        {
+            FCallAddSub(ref d1, ref d2, DECIMAL_ADD);
+            return d1;
+        }
+
+        public static Decimal operator -(Decimal d1, Decimal d2)
+        {
+            FCallAddSub(ref d1, ref d2, DECIMAL_NEG);
+            return d1;
+        }
+
+        public static Decimal operator *(Decimal d1, Decimal d2)
+        {
+            FCallMultiply(ref d1, ref d2);
+            return d1;
+        }
+
+        public static Decimal operator /(Decimal d1, Decimal d2)
+        {
+            FCallDivide(ref d1, ref d2);
+            return d1;
+        }
+
+        public static Decimal operator %(Decimal d1, Decimal d2)
+        {
+            return Remainder(d1, d2);
+        }
+
+        public static bool operator ==(Decimal d1, Decimal d2)
+        {
+            return FCallCompare(ref d1, ref d2) == 0;
+        }
+
+        public static bool operator !=(Decimal d1, Decimal d2)
+        {
+            return FCallCompare(ref d1, ref d2) != 0;
+        }
+
+        public static bool operator <(Decimal d1, Decimal d2)
+        {
+            return FCallCompare(ref d1, ref d2) < 0;
+        }
+
+        public static bool operator <=(Decimal d1, Decimal d2)
+        {
+            return FCallCompare(ref d1, ref d2) <= 0;
+        }
+
+        public static bool operator >(Decimal d1, Decimal d2)
+        {
+            return FCallCompare(ref d1, ref d2) > 0;
+        }
+
+        public static bool operator >=(Decimal d1, Decimal d2)
+        {
+            return FCallCompare(ref d1, ref d2) >= 0;
+        }
+
+        //
+        // IConvertible implementation
+        //
+
+        public TypeCode GetTypeCode()
+        {
+            return TypeCode.Decimal;
+        }
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            return Convert.ToBoolean(this);
+        }
+
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Decimal", "Char"));
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return Convert.ToSByte(this);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return Convert.ToByte(this);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return Convert.ToInt16(this);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return Convert.ToUInt16(this);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return Convert.ToInt32(this);
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return Convert.ToUInt32(this);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return Convert.ToInt64(this);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return Convert.ToUInt64(this);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            return Convert.ToSingle(this);
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            return Convert.ToDouble(this);
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            return this;
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Decimal", "DateTime"));
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/DefaultBinder.CanConvert.cs b/src/System.Private.CoreLib/src/System/DefaultBinder.CanConvert.cs
new file mode 100644
index 0000000000..09c7298a3d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/DefaultBinder.CanConvert.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    internal partial class DefaultBinder : Binder
+    {
+        // CanChangePrimitive
+        // This will determine if the source can be converted to the target type
+        private static bool CanChangePrimitive(Type source, Type target) => CanConvertPrimitive((RuntimeType)source, (RuntimeType)target);
+
+        // CanChangePrimitiveObjectToType
+        private static bool CanChangePrimitiveObjectToType(object source, Type type) => CanConvertPrimitiveObjectToType(source, (RuntimeType)type);
+
+        // CanConvertPrimitive
+        // This will determine if the source can be converted to the target type
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern bool CanConvertPrimitive(RuntimeType source, RuntimeType target);
+
+        // CanConvertPrimitiveObjectToType
+        // This method will determine if the primitive object can be converted
+        //  to a type.
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern bool CanConvertPrimitiveObjectToType(object source, RuntimeType type);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Delegate.cs b/src/System.Private.CoreLib/src/System/Delegate.cs
new file mode 100644
index 0000000000..690fafb819
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Delegate.cs
@@ -0,0 +1,689 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    using System;
+    using System.Reflection;
+    using System.Runtime;
+    using System.Threading;
+    using System.Runtime.Serialization;
+    using System.Runtime.InteropServices;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.Versioning;
+    using System.Diagnostics;
+
+    [ClassInterface(ClassInterfaceType.AutoDual)]
+    [System.Runtime.InteropServices.ComVisible(true)]
+    public abstract class Delegate : ICloneable, ISerializable
+    {
+        // _target is the object we will invoke on
+        internal Object _target;
+
+        // MethodBase, either cached after first request or assigned from a DynamicMethod
+        // For open delegates to collectible types, this may be a LoaderAllocator object
+        internal Object _methodBase;
+
+        // _methodPtr is a pointer to the method we will invoke
+        // It could be a small thunk if this is a static or UM call
+        internal IntPtr _methodPtr;
+
+        // In the case of a static method passed to a delegate, this field stores
+        // whatever _methodPtr would have stored: and _methodPtr points to a
+        // small thunk which removes the "this" pointer before going on
+        // to _methodPtrAux.
+        internal IntPtr _methodPtrAux;
+
+        // This constructor is called from the class generated by the
+        //  compiler generated code
+        protected Delegate(Object target, String method)
+        {
+            if (target == null)
+                throw new ArgumentNullException(nameof(target));
+
+            if (method == null)
+                throw new ArgumentNullException(nameof(method));
+
+            // This API existed in v1/v1.1 and only expected to create closed
+            // instance delegates. Constrain the call to BindToMethodName to
+            // such and don't allow relaxed signature matching (which could make
+            // the choice of target method ambiguous) for backwards
+            // compatibility. The name matching was case sensitive and we
+            // preserve that as well.
+            if (!BindToMethodName(target, (RuntimeType)target.GetType(), method,
+                                  DelegateBindingFlags.InstanceMethodOnly |
+                                  DelegateBindingFlags.ClosedDelegateOnly))
+                throw new ArgumentException(SR.Arg_DlgtTargMeth);
+        }
+
+        // This constructor is called from a class to generate a 
+        // delegate based upon a static method name and the Type object
+        // for the class defining the method.
+        protected unsafe Delegate(Type target, String method)
+        {
+            if (target == null)
+                throw new ArgumentNullException(nameof(target));
+
+            if (target.ContainsGenericParameters)
+                throw new ArgumentException(SR.Arg_UnboundGenParam, nameof(target));
+
+            if (method == null)
+                throw new ArgumentNullException(nameof(method));
+
+            RuntimeType rtTarget = target as RuntimeType;
+            if (rtTarget == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType, nameof(target));
+
+            // This API existed in v1/v1.1 and only expected to create open
+            // static delegates. Constrain the call to BindToMethodName to such
+            // and don't allow relaxed signature matching (which could make the
+            // choice of target method ambiguous) for backwards compatibility.
+            // The name matching was case insensitive (no idea why this is
+            // different from the constructor above) and we preserve that as
+            // well.
+            BindToMethodName(null, rtTarget, method,
+                             DelegateBindingFlags.StaticMethodOnly |
+                             DelegateBindingFlags.OpenDelegateOnly |
+                             DelegateBindingFlags.CaselessMatching);
+        }
+
+        // Protect the default constructor so you can't build a delegate
+        private Delegate()
+        {
+        }
+
+        public Object DynamicInvoke(params Object[] args)
+        {
+            // Theoretically we should set up a LookForMyCaller stack mark here and pass that along.
+            // But to maintain backward compatibility we can't switch to calling an 
+            // internal overload of DynamicInvokeImpl that takes a stack mark.
+            // Fortunately the stack walker skips all the reflection invocation frames including this one.
+            // So this method will never be returned by the stack walker as the caller.
+            // See SystemDomain::CallersMethodCallbackWithStackMark in AppDomain.cpp.
+            return DynamicInvokeImpl(args);
+        }
+
+        protected virtual object DynamicInvokeImpl(object[] args)
+        {
+            RuntimeMethodHandleInternal method = new RuntimeMethodHandleInternal(GetInvokeMethod());
+            RuntimeMethodInfo invoke = (RuntimeMethodInfo)RuntimeType.GetMethodBase((RuntimeType)this.GetType(), method);
+
+            return invoke.Invoke(this, BindingFlags.Default, null, args, null);
+        }
+
+
+        public override bool Equals(Object obj)
+        {
+            if (obj == null || !InternalEqualTypes(this, obj))
+                return false;
+
+            Delegate d = (Delegate)obj;
+
+            // do an optimistic check first. This is hopefully cheap enough to be worth
+            if (_target == d._target && _methodPtr == d._methodPtr && _methodPtrAux == d._methodPtrAux)
+                return true;
+
+            // even though the fields were not all equals the delegates may still match
+            // When target carries the delegate itself the 2 targets (delegates) may be different instances
+            // but the delegates are logically the same
+            // It may also happen that the method pointer was not jitted when creating one delegate and jitted in the other 
+            // if that's the case the delegates may still be equals but we need to make a more complicated check
+
+            if (_methodPtrAux == IntPtr.Zero)
+            {
+                if (d._methodPtrAux != IntPtr.Zero)
+                    return false; // different delegate kind
+                // they are both closed over the first arg
+                if (_target != d._target)
+                    return false;
+                // fall through method handle check
+            }
+            else
+            {
+                if (d._methodPtrAux == IntPtr.Zero)
+                    return false; // different delegate kind
+
+                // Ignore the target as it will be the delegate instance, though it may be a different one
+                /*
+                if (_methodPtr != d._methodPtr)
+                    return false;
+                    */
+
+                if (_methodPtrAux == d._methodPtrAux)
+                    return true;
+                // fall through method handle check
+            }
+
+            // method ptrs don't match, go down long path
+            // 
+            if (_methodBase == null || d._methodBase == null || !(_methodBase is MethodInfo) || !(d._methodBase is MethodInfo))
+                return Delegate.InternalEqualMethodHandles(this, d);
+            else
+                return _methodBase.Equals(d._methodBase);
+        }
+
+        public override int GetHashCode()
+        {
+            //
+            // this is not right in the face of a method being jitted in one delegate and not in another
+            // in that case the delegate is the same and Equals will return true but GetHashCode returns a
+            // different hashcode which is not true.
+            /*
+            if (_methodPtrAux == IntPtr.Zero)
+                return unchecked((int)((long)this._methodPtr));
+            else
+                return unchecked((int)((long)this._methodPtrAux));
+            */
+            if (_methodPtrAux == IntPtr.Zero)
+                return ( _target != null ? RuntimeHelpers.GetHashCode(_target) * 33 : 0) + GetType().GetHashCode();
+            else
+                return GetType().GetHashCode();
+        }
+
+        public static Delegate Combine(Delegate a, Delegate b)
+        {
+            if ((Object)a == null) // cast to object for a more efficient test
+                return b;
+
+            return a.CombineImpl(b);
+        }
+
+        public static Delegate Combine(params Delegate[] delegates)
+        {
+            if (delegates == null || delegates.Length == 0)
+                return null;
+
+            Delegate d = delegates[0];
+            for (int i = 1; i < delegates.Length; i++)
+                d = Combine(d, delegates[i]);
+
+            return d;
+        }
+
+        public virtual Delegate[] GetInvocationList()
+        {
+            Delegate[] d = new Delegate[1];
+            d[0] = this;
+            return d;
+        }
+
+        // This routine will return the method
+        public MethodInfo Method
+        {
+            get
+            {
+                return GetMethodImpl();
+            }
+        }
+
+        protected virtual MethodInfo GetMethodImpl()
+        {
+            if ((_methodBase == null) || !(_methodBase is MethodInfo))
+            {
+                IRuntimeMethodInfo method = FindMethodHandle();
+                RuntimeType declaringType = RuntimeMethodHandle.GetDeclaringType(method);
+                // need a proper declaring type instance method on a generic type
+                if (RuntimeTypeHandle.IsGenericTypeDefinition(declaringType) || RuntimeTypeHandle.HasInstantiation(declaringType))
+                {
+                    bool isStatic = (RuntimeMethodHandle.GetAttributes(method) & MethodAttributes.Static) != (MethodAttributes)0;
+                    if (!isStatic)
+                    {
+                        if (_methodPtrAux == IntPtr.Zero)
+                        {
+                            // The target may be of a derived type that doesn't have visibility onto the
+                            // target method. We don't want to call RuntimeType.GetMethodBase below with that
+                            // or reflection can end up generating a MethodInfo where the ReflectedType cannot
+                            // see the MethodInfo itself and that breaks an important invariant. But the
+                            // target type could include important generic type information we need in order
+                            // to work out what the exact instantiation of the method's declaring type is. So
+                            // we'll walk up the inheritance chain (which will yield exactly instantiated
+                            // types at each step) until we find the declaring type. Since the declaring type
+                            // we get from the method is probably shared and those in the hierarchy we're
+                            // walking won't be we compare using the generic type definition forms instead.
+                            Type currentType = _target.GetType();
+                            Type targetType = declaringType.GetGenericTypeDefinition();
+                            while (currentType != null)
+                            {
+                                if (currentType.IsGenericType &&
+                                    currentType.GetGenericTypeDefinition() == targetType)
+                                {
+                                    declaringType = currentType as RuntimeType;
+                                    break;
+                                }
+                                currentType = currentType.BaseType;
+                            }
+
+                            // RCWs don't need to be "strongly-typed" in which case we don't find a base type
+                            // that matches the declaring type of the method. This is fine because interop needs
+                            // to work with exact methods anyway so declaringType is never shared at this point.
+                            Debug.Assert(currentType != null || _target.GetType().IsCOMObject, "The class hierarchy should declare the method");
+                        }
+                        else
+                        {
+                            // it's an open one, need to fetch the first arg of the instantiation
+                            MethodInfo invoke = this.GetType().GetMethod("Invoke");
+                            declaringType = (RuntimeType)invoke.GetParameters()[0].ParameterType;
+                        }
+                    }
+                }
+                _methodBase = (MethodInfo)RuntimeType.GetMethodBase(declaringType, method);
+            }
+            return (MethodInfo)_methodBase;
+        }
+
+        public Object Target
+        {
+            get
+            {
+                return GetTarget();
+            }
+        }
+
+
+        public static Delegate Remove(Delegate source, Delegate value)
+        {
+            if (source == null)
+                return null;
+
+            if (value == null)
+                return source;
+
+            if (!InternalEqualTypes(source, value))
+                throw new ArgumentException(SR.Arg_DlgtTypeMis);
+
+            return source.RemoveImpl(value);
+        }
+
+        public static Delegate RemoveAll(Delegate source, Delegate value)
+        {
+            Delegate newDelegate = null;
+
+            do
+            {
+                newDelegate = source;
+                source = Remove(source, value);
+            }
+            while (newDelegate != source);
+
+            return newDelegate;
+        }
+
+        protected virtual Delegate CombineImpl(Delegate d)
+        {
+            throw new MulticastNotSupportedException(SR.Multicast_Combine);
+        }
+
+        protected virtual Delegate RemoveImpl(Delegate d)
+        {
+            return (d.Equals(this)) ? null : this;
+        }
+
+
+        public virtual Object Clone()
+        {
+            return MemberwiseClone();
+        }
+
+        // V1 API.
+        public static Delegate CreateDelegate(Type type, Object target, String method)
+        {
+            return CreateDelegate(type, target, method, false, true);
+        }
+
+        // V1 API.
+        public static Delegate CreateDelegate(Type type, Object target, String method, bool ignoreCase)
+        {
+            return CreateDelegate(type, target, method, ignoreCase, true);
+        }
+
+        // V1 API.
+        public static Delegate CreateDelegate(Type type, Object target, String method, bool ignoreCase, bool throwOnBindFailure)
+        {
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+            if (target == null)
+                throw new ArgumentNullException(nameof(target));
+            if (method == null)
+                throw new ArgumentNullException(nameof(method));
+
+            RuntimeType rtType = type as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType, nameof(type));
+            if (!rtType.IsDelegate())
+                throw new ArgumentException(SR.Arg_MustBeDelegate, nameof(type));
+
+            Delegate d = InternalAlloc(rtType);
+            // This API existed in v1/v1.1 and only expected to create closed
+            // instance delegates. Constrain the call to BindToMethodName to such
+            // and don't allow relaxed signature matching (which could make the
+            // choice of target method ambiguous) for backwards compatibility.
+            // We never generate a closed over null delegate and this is
+            // actually enforced via the check on target above, but we pass
+            // NeverCloseOverNull anyway just for clarity.
+            if (!d.BindToMethodName(target, (RuntimeType)target.GetType(), method,
+                                    DelegateBindingFlags.InstanceMethodOnly |
+                                    DelegateBindingFlags.ClosedDelegateOnly |
+                                    DelegateBindingFlags.NeverCloseOverNull |
+                                    (ignoreCase ? DelegateBindingFlags.CaselessMatching : 0)))
+            {
+                if (throwOnBindFailure)
+                    throw new ArgumentException(SR.Arg_DlgtTargMeth);
+                d = null;
+            }
+
+            return d;
+        }
+
+        // V1 API.
+        public static Delegate CreateDelegate(Type type, Type target, String method)
+        {
+            return CreateDelegate(type, target, method, false, true);
+        }
+
+        // V1 API.
+        public static Delegate CreateDelegate(Type type, Type target, String method, bool ignoreCase)
+        {
+            return CreateDelegate(type, target, method, ignoreCase, true);
+        }
+
+        // V1 API.
+        public static Delegate CreateDelegate(Type type, Type target, String method, bool ignoreCase, bool throwOnBindFailure)
+        {
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+            if (target == null)
+                throw new ArgumentNullException(nameof(target));
+            if (target.ContainsGenericParameters)
+                throw new ArgumentException(SR.Arg_UnboundGenParam, nameof(target));
+            if (method == null)
+                throw new ArgumentNullException(nameof(method));
+
+            RuntimeType rtType = type as RuntimeType;
+            RuntimeType rtTarget = target as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType, nameof(type));
+            if (rtTarget == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType, nameof(target));
+            if (!rtType.IsDelegate())
+                throw new ArgumentException(SR.Arg_MustBeDelegate, nameof(type));
+
+            Delegate d = InternalAlloc(rtType);
+            // This API existed in v1/v1.1 and only expected to create open
+            // static delegates. Constrain the call to BindToMethodName to such
+            // and don't allow relaxed signature matching (which could make the
+            // choice of target method ambiguous) for backwards compatibility.
+            if (!d.BindToMethodName(null, rtTarget, method,
+                                    DelegateBindingFlags.StaticMethodOnly |
+                                    DelegateBindingFlags.OpenDelegateOnly |
+                                    (ignoreCase ? DelegateBindingFlags.CaselessMatching : 0)))
+            {
+                if (throwOnBindFailure)
+                    throw new ArgumentException(SR.Arg_DlgtTargMeth);
+                d = null;
+            }
+
+            return d;
+        }
+
+        // V1 API.
+        public static Delegate CreateDelegate(Type type, MethodInfo method, bool throwOnBindFailure)
+        {
+            // Validate the parameters.
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+            if (method == null)
+                throw new ArgumentNullException(nameof(method));
+
+            RuntimeType rtType = type as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType, nameof(type));
+
+            RuntimeMethodInfo rmi = method as RuntimeMethodInfo;
+            if (rmi == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeMethodInfo, nameof(method));
+
+            if (!rtType.IsDelegate())
+                throw new ArgumentException(SR.Arg_MustBeDelegate, nameof(type));
+
+            // This API existed in v1/v1.1 and only expected to create closed
+            // instance delegates. Constrain the call to BindToMethodInfo to
+            // open delegates only for backwards compatibility. But we'll allow
+            // relaxed signature checking and open static delegates because
+            // there's no ambiguity there (the caller would have to explicitly
+            // pass us a static method or a method with a non-exact signature
+            // and the only change in behavior from v1.1 there is that we won't
+            // fail the call).
+            Delegate d = CreateDelegateInternal(
+                rtType,
+                rmi,
+                null,
+                DelegateBindingFlags.OpenDelegateOnly | DelegateBindingFlags.RelaxedSignature);
+
+            if (d == null && throwOnBindFailure)
+                throw new ArgumentException(SR.Arg_DlgtTargMeth);
+
+            return d;
+        }
+
+        // V2 API.
+        public static Delegate CreateDelegate(Type type, Object firstArgument, MethodInfo method)
+        {
+            return CreateDelegate(type, firstArgument, method, true);
+        }
+
+        // V2 API.
+        public static Delegate CreateDelegate(Type type, Object firstArgument, MethodInfo method, bool throwOnBindFailure)
+        {
+            // Validate the parameters.
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+            if (method == null)
+                throw new ArgumentNullException(nameof(method));
+
+            RuntimeType rtType = type as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType, nameof(type));
+
+            RuntimeMethodInfo rmi = method as RuntimeMethodInfo;
+            if (rmi == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeMethodInfo, nameof(method));
+
+            if (!rtType.IsDelegate())
+                throw new ArgumentException(SR.Arg_MustBeDelegate, nameof(type));
+
+            // This API is new in Whidbey and allows the full range of delegate
+            // flexability (open or closed delegates binding to static or
+            // instance methods with relaxed signature checking. The delegate
+            // can also be closed over null. There's no ambiguity with all these
+            // options since the caller is providing us a specific MethodInfo.
+            Delegate d = CreateDelegateInternal(
+                rtType,
+                rmi,
+                firstArgument,
+                DelegateBindingFlags.RelaxedSignature);
+
+            if (d == null && throwOnBindFailure)
+                throw new ArgumentException(SR.Arg_DlgtTargMeth);
+
+            return d;
+        }
+
+        public static bool operator ==(Delegate d1, Delegate d2)
+        {
+            if ((Object)d1 == null)
+                return (Object)d2 == null;
+
+            return d1.Equals(d2);
+        }
+
+        public static bool operator !=(Delegate d1, Delegate d2)
+        {
+            if ((Object)d1 == null)
+                return (Object)d2 != null;
+
+            return !d1.Equals(d2);
+        }
+
+        //
+        // Implementation of ISerializable
+        //
+
+        public virtual void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            throw new PlatformNotSupportedException();
+        }
+
+        //
+        // internal implementation details (FCALLS and utilities)
+        //
+
+        // V2 internal API.
+        // This is Critical because it skips the security check when creating the delegate.
+        internal static unsafe Delegate CreateDelegateNoSecurityCheck(Type type, Object target, RuntimeMethodHandle method)
+        {
+            // Validate the parameters.
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+
+            if (method.IsNullHandle())
+                throw new ArgumentNullException(nameof(method));
+
+            RuntimeType rtType = type as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType, nameof(type));
+
+            if (!rtType.IsDelegate())
+                throw new ArgumentException(SR.Arg_MustBeDelegate, nameof(type));
+
+            // Initialize the method...
+            Delegate d = InternalAlloc(rtType);
+            // This is a new internal API added in Whidbey. Currently it's only
+            // used by the dynamic method code to generate a wrapper delegate.
+            // Allow flexible binding options since the target method is
+            // unambiguously provided to us.
+
+            if (!d.BindToMethodInfo(target,
+                                    method.GetMethodInfo(),
+                                    RuntimeMethodHandle.GetDeclaringType(method.GetMethodInfo()),
+                                    DelegateBindingFlags.RelaxedSignature | DelegateBindingFlags.SkipSecurityChecks))
+                throw new ArgumentException(SR.Arg_DlgtTargMeth);
+            return d;
+        }
+
+        // Caution: this method is intended for deserialization only, no security checks are performed.
+        internal static Delegate CreateDelegateNoSecurityCheck(RuntimeType type, Object firstArgument, MethodInfo method)
+        {
+            // Validate the parameters.
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+            if (method == null)
+                throw new ArgumentNullException(nameof(method));
+
+
+            RuntimeMethodInfo rtMethod = method as RuntimeMethodInfo;
+            if (rtMethod == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeMethodInfo, nameof(method));
+
+            if (!type.IsDelegate())
+                throw new ArgumentException(SR.Arg_MustBeDelegate, nameof(type));
+
+            // This API is used by the formatters when deserializing a delegate.
+            // They pass us the specific target method (that was already the
+            // target in a valid delegate) so we should bind with the most
+            // relaxed rules available (the result will never be ambiguous, it
+            // just increases the chance of success with minor (compatible)
+            // signature changes). We explicitly skip security checks here --
+            // we're not really constructing a delegate, we're cloning an
+            // existing instance which already passed its checks.
+            Delegate d = CreateDelegateInternal(type, rtMethod, firstArgument,
+                                              DelegateBindingFlags.SkipSecurityChecks |
+                                              DelegateBindingFlags.RelaxedSignature);
+
+            if (d == null)
+                throw new ArgumentException(SR.Arg_DlgtTargMeth);
+
+            return d;
+        }
+
+        // V1 API.
+        public static Delegate CreateDelegate(Type type, MethodInfo method)
+        {
+            return CreateDelegate(type, method, true);
+        }
+
+        internal static Delegate CreateDelegateInternal(RuntimeType rtType, RuntimeMethodInfo rtMethod, Object firstArgument, DelegateBindingFlags flags)
+        {
+            Delegate d = InternalAlloc(rtType);
+
+            if (d.BindToMethodInfo(firstArgument, rtMethod, rtMethod.GetDeclaringTypeInternal(), flags))
+                return d;
+            else
+                return null;
+        }
+
+        //
+        // internal implementation details (FCALLS and utilities)
+        //
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern bool BindToMethodName(Object target, RuntimeType methodType, String method, DelegateBindingFlags flags);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern bool BindToMethodInfo(Object target, IRuntimeMethodInfo method, RuntimeType methodType, DelegateBindingFlags flags);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern MulticastDelegate InternalAlloc(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern MulticastDelegate InternalAllocLike(Delegate d);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool InternalEqualTypes(object a, object b);
+
+        // Used by the ctor. Do not call directly.
+        // The name of this function will appear in managed stacktraces as delegate constructor.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern void DelegateConstruct(Object target, IntPtr slot);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern IntPtr GetMulticastInvoke();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern IntPtr GetInvokeMethod();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern IRuntimeMethodInfo FindMethodHandle();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool InternalEqualMethodHandles(Delegate left, Delegate right);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern IntPtr AdjustTarget(Object target, IntPtr methodPtr);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern IntPtr GetCallStub(IntPtr methodPtr);
+
+        internal virtual Object GetTarget()
+        {
+            return (_methodPtrAux == IntPtr.Zero) ? _target : null;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool CompareUnmanagedFunctionPtrs(Delegate d1, Delegate d2);
+    }
+
+    // These flags effect the way BindToMethodInfo and BindToMethodName are allowed to bind a delegate to a target method. Their
+    // values must be kept in sync with the definition in vm\comdelegate.h.
+    internal enum DelegateBindingFlags
+    {
+        StaticMethodOnly = 0x00000001, // Can only bind to static target methods
+        InstanceMethodOnly = 0x00000002, // Can only bind to instance (including virtual) methods
+        OpenDelegateOnly = 0x00000004, // Only allow the creation of delegates open over the 1st argument
+        ClosedDelegateOnly = 0x00000008, // Only allow the creation of delegates closed over the 1st argument
+        NeverCloseOverNull = 0x00000010, // A null target will never been considered as a possible null 1st argument
+        CaselessMatching = 0x00000020, // Use case insensitive lookup for methods matched by name
+        SkipSecurityChecks = 0x00000040, // Skip security checks (visibility, link demand etc.)
+        RelaxedSignature = 0x00000080, // Allow relaxed signature matching (co/contra variance)
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/Contracts/Contracts.cs b/src/System.Private.CoreLib/src/System/Diagnostics/Contracts/Contracts.cs
new file mode 100644
index 0000000000..5547684b04
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/Contracts/Contracts.cs
@@ -0,0 +1,665 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+**
+** Purpose: The contract class allows for expressing preconditions,
+** postconditions, and object invariants about methods in source
+** code for runtime checking & static analysis.
+**
+** Two classes (Contract and ContractHelper) are split into partial classes
+** in order to share the public front for multiple platforms (this file)
+** while providing separate implementation details for each platform.
+**
+===========================================================*/
+#define DEBUG // The behavior of this contract library should be consistent regardless of build type.
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Diagnostics.Contracts;
+
+namespace System.Diagnostics.Contracts
+{
+    #region Attributes
+
+    /// <summary>
+    /// Methods and classes marked with this attribute can be used within calls to Contract methods. Such methods not make any visible state changes.
+    /// </summary>
+    [Conditional("CONTRACTS_FULL")]
+    [AttributeUsage(AttributeTargets.Constructor | AttributeTargets.Method | AttributeTargets.Property | AttributeTargets.Event | AttributeTargets.Delegate | AttributeTargets.Class | AttributeTargets.Parameter, AllowMultiple = false, Inherited = true)]
+    public sealed class PureAttribute : Attribute
+    {
+    }
+
+    /// <summary>
+    /// Types marked with this attribute specify that a separate type contains the contracts for this type.
+    /// </summary>
+    [Conditional("CONTRACTS_FULL")]
+    [Conditional("DEBUG")]
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface | AttributeTargets.Delegate, AllowMultiple = false, Inherited = false)]
+    public sealed class ContractClassAttribute : Attribute
+    {
+        private Type _typeWithContracts;
+
+        public ContractClassAttribute(Type typeContainingContracts)
+        {
+            _typeWithContracts = typeContainingContracts;
+        }
+
+        public Type TypeContainingContracts
+        {
+            get { return _typeWithContracts; }
+        }
+    }
+
+    /// <summary>
+    /// Types marked with this attribute specify that they are a contract for the type that is the argument of the constructor.
+    /// </summary>
+    [Conditional("CONTRACTS_FULL")]
+    [AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = false)]
+    public sealed class ContractClassForAttribute : Attribute
+    {
+        private Type _typeIAmAContractFor;
+
+        public ContractClassForAttribute(Type typeContractsAreFor)
+        {
+            _typeIAmAContractFor = typeContractsAreFor;
+        }
+
+        public Type TypeContractsAreFor
+        {
+            get { return _typeIAmAContractFor; }
+        }
+    }
+
+    /// <summary>
+    /// This attribute is used to mark a method as being the invariant
+    /// method for a class. The method can have any name, but it must
+    /// return "void" and take no parameters. The body of the method
+    /// must consist solely of one or more calls to the method
+    /// Contract.Invariant. A suggested name for the method is 
+    /// "ObjectInvariant".
+    /// </summary>
+    [Conditional("CONTRACTS_FULL")]
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = false)]
+    public sealed class ContractInvariantMethodAttribute : Attribute
+    {
+    }
+
+    /// <summary>
+    /// Attribute that specifies that an assembly is a reference assembly with contracts.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Assembly)]
+    public sealed class ContractReferenceAssemblyAttribute : Attribute
+    {
+    }
+
+    /// <summary>
+    /// Methods (and properties) marked with this attribute can be used within calls to Contract methods, but have no runtime behavior associated with them.
+    /// </summary>
+    [Conditional("CONTRACTS_FULL")]
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
+    public sealed class ContractRuntimeIgnoredAttribute : Attribute
+    {
+    }
+
+    /// <summary>
+    /// Instructs downstream tools whether to assume the correctness of this assembly, type or member without performing any verification or not.
+    /// Can use [ContractVerification(false)] to explicitly mark assembly, type or member as one to *not* have verification performed on it.
+    /// Most specific element found (member, type, then assembly) takes precedence.
+    /// (That is useful if downstream tools allow a user to decide which polarity is the default, unmarked case.)
+    /// </summary>
+    /// <remarks>
+    /// Apply this attribute to a type to apply to all members of the type, including nested types.
+    /// Apply this attribute to an assembly to apply to all types and members of the assembly.
+    /// Apply this attribute to a property to apply to both the getter and setter.
+    /// </remarks>
+    [Conditional("CONTRACTS_FULL")]
+    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Property)]
+    public sealed class ContractVerificationAttribute : Attribute
+    {
+        private bool _value;
+
+        public ContractVerificationAttribute(bool value) { _value = value; }
+
+        public bool Value
+        {
+            get { return _value; }
+        }
+    }
+
+    /// <summary>
+    /// Allows a field f to be used in the method contracts for a method m when f has less visibility than m.
+    /// For instance, if the method is public, but the field is private.
+    /// </summary>
+    [Conditional("CONTRACTS_FULL")]
+    [AttributeUsage(AttributeTargets.Field)]
+    public sealed class ContractPublicPropertyNameAttribute : Attribute
+    {
+        private String _publicName;
+
+        public ContractPublicPropertyNameAttribute(String name)
+        {
+            _publicName = name;
+        }
+
+        public String Name
+        {
+            get { return _publicName; }
+        }
+    }
+
+    /// <summary>
+    /// Enables factoring legacy if-then-throw into separate methods for reuse and full control over
+    /// thrown exception and arguments
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
+    [Conditional("CONTRACTS_FULL")]
+    public sealed class ContractArgumentValidatorAttribute : Attribute
+    {
+    }
+
+    /// <summary>
+    /// Enables writing abbreviations for contracts that get copied to other methods
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
+    [Conditional("CONTRACTS_FULL")]
+    public sealed class ContractAbbreviatorAttribute : Attribute
+    {
+    }
+
+    /// <summary>
+    /// Allows setting contract and tool options at assembly, type, or method granularity.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.All, AllowMultiple = true, Inherited = false)]
+    [Conditional("CONTRACTS_FULL")]
+    public sealed class ContractOptionAttribute : Attribute
+    {
+        private String _category;
+        private String _setting;
+        private bool _enabled;
+        private String _value;
+
+        public ContractOptionAttribute(String category, String setting, bool enabled)
+        {
+            _category = category;
+            _setting = setting;
+            _enabled = enabled;
+        }
+
+        public ContractOptionAttribute(String category, String setting, String value)
+        {
+            _category = category;
+            _setting = setting;
+            _value = value;
+        }
+
+        public String Category
+        {
+            get { return _category; }
+        }
+
+        public String Setting
+        {
+            get { return _setting; }
+        }
+
+        public bool Enabled
+        {
+            get { return _enabled; }
+        }
+
+        public String Value
+        {
+            get { return _value; }
+        }
+    }
+
+    #endregion Attributes
+
+    /// <summary>
+    /// Contains static methods for representing program contracts such as preconditions, postconditions, and invariants.
+    /// </summary>
+    /// <remarks>
+    /// WARNING: A binary rewriter must be used to insert runtime enforcement of these contracts.
+    /// Otherwise some contracts like Ensures can only be checked statically and will not throw exceptions during runtime when contracts are violated.
+    /// Please note this class uses conditional compilation to help avoid easy mistakes.  Defining the preprocessor
+    /// symbol CONTRACTS_PRECONDITIONS will include all preconditions expressed using Contract.Requires in your 
+    /// build.  The symbol CONTRACTS_FULL will include postconditions and object invariants, and requires the binary rewriter.
+    /// </remarks>
+    public static partial class Contract
+    {
+        #region User Methods
+
+        #region Assume
+
+        /// <summary>
+        /// Instructs code analysis tools to assume the expression <paramref name="condition"/> is true even if it can not be statically proven to always be true.
+        /// </summary>
+        /// <param name="condition">Expression to assume will always be true.</param>
+        /// <remarks>
+        /// At runtime this is equivalent to an <seealso cref="System.Diagnostics.Contracts.Debug.Assert(bool)"/>.
+        /// </remarks>
+        [Pure]
+        [Conditional("DEBUG")]
+        [Conditional("CONTRACTS_FULL")]
+        public static void Assume(bool condition)
+        {
+            if (!condition)
+            {
+                ReportFailure(ContractFailureKind.Assume, null, null, null);
+            }
+        }
+
+        /// <summary>
+        /// Instructs code analysis tools to assume the expression <paramref name="condition"/> is true even if it can not be statically proven to always be true.
+        /// </summary>
+        /// <param name="condition">Expression to assume will always be true.</param>
+        /// <param name="userMessage">If it is not a constant string literal, then the contract may not be understood by tools.</param>
+        /// <remarks>
+        /// At runtime this is equivalent to an <seealso cref="System.Diagnostics.Contracts.Debug.Assert(bool)"/>.
+        /// </remarks>
+        [Pure]
+        [Conditional("DEBUG")]
+        [Conditional("CONTRACTS_FULL")]
+        public static void Assume(bool condition, String userMessage)
+        {
+            if (!condition)
+            {
+                ReportFailure(ContractFailureKind.Assume, userMessage, null, null);
+            }
+        }
+
+        #endregion Assume
+
+        #region Assert
+
+        /// <summary>
+        /// In debug builds, perform a runtime check that <paramref name="condition"/> is true.
+        /// </summary>
+        /// <param name="condition">Expression to check to always be true.</param>
+        [Pure]
+        [Conditional("DEBUG")]
+        [Conditional("CONTRACTS_FULL")]
+        public static void Assert(bool condition)
+        {
+            if (!condition)
+                ReportFailure(ContractFailureKind.Assert, null, null, null);
+        }
+
+        /// <summary>
+        /// In debug builds, perform a runtime check that <paramref name="condition"/> is true.
+        /// </summary>
+        /// <param name="condition">Expression to check to always be true.</param>
+        /// <param name="userMessage">If it is not a constant string literal, then the contract may not be understood by tools.</param>
+        [Pure]
+        [Conditional("DEBUG")]
+        [Conditional("CONTRACTS_FULL")]
+        public static void Assert(bool condition, String userMessage)
+        {
+            if (!condition)
+                ReportFailure(ContractFailureKind.Assert, userMessage, null, null);
+        }
+
+        #endregion Assert
+
+        #region Requires
+
+        /// <summary>
+        /// Specifies a contract such that the expression <paramref name="condition"/> must be true before the enclosing method or property is invoked.
+        /// </summary>
+        /// <param name="condition">Boolean expression representing the contract.</param>
+        /// <remarks>
+        /// This call must happen at the beginning of a method or property before any other code.
+        /// This contract is exposed to clients so must only reference members at least as visible as the enclosing method.
+        /// Use this form when backward compatibility does not force you to throw a particular exception.
+        /// </remarks>
+        [Pure]
+        [Conditional("CONTRACTS_FULL")]
+        public static void Requires(bool condition)
+        {
+            AssertMustUseRewriter(ContractFailureKind.Precondition, "Requires");
+        }
+
+        /// <summary>
+        /// Specifies a contract such that the expression <paramref name="condition"/> must be true before the enclosing method or property is invoked.
+        /// </summary>
+        /// <param name="condition">Boolean expression representing the contract.</param>
+        /// <param name="userMessage">If it is not a constant string literal, then the contract may not be understood by tools.</param>
+        /// <remarks>
+        /// This call must happen at the beginning of a method or property before any other code.
+        /// This contract is exposed to clients so must only reference members at least as visible as the enclosing method.
+        /// Use this form when backward compatibility does not force you to throw a particular exception.
+        /// </remarks>
+        [Pure]
+        [Conditional("CONTRACTS_FULL")]
+        public static void Requires(bool condition, String userMessage)
+        {
+            AssertMustUseRewriter(ContractFailureKind.Precondition, "Requires");
+        }
+
+        /// <summary>
+        /// Specifies a contract such that the expression <paramref name="condition"/> must be true before the enclosing method or property is invoked.
+        /// </summary>
+        /// <param name="condition">Boolean expression representing the contract.</param>
+        /// <remarks>
+        /// This call must happen at the beginning of a method or property before any other code.
+        /// This contract is exposed to clients so must only reference members at least as visible as the enclosing method.
+        /// Use this form when you want to throw a particular exception.
+        /// </remarks>
+        [Pure]
+        public static void Requires<TException>(bool condition) where TException : Exception
+        {
+            AssertMustUseRewriter(ContractFailureKind.Precondition, "Requires<TException>");
+        }
+
+        /// <summary>
+        /// Specifies a contract such that the expression <paramref name="condition"/> must be true before the enclosing method or property is invoked.
+        /// </summary>
+        /// <param name="condition">Boolean expression representing the contract.</param>
+        /// <param name="userMessage">If it is not a constant string literal, then the contract may not be understood by tools.</param>
+        /// <remarks>
+        /// This call must happen at the beginning of a method or property before any other code.
+        /// This contract is exposed to clients so must only reference members at least as visible as the enclosing method.
+        /// Use this form when you want to throw a particular exception.
+        /// </remarks>
+        [Pure]
+        public static void Requires<TException>(bool condition, String userMessage) where TException : Exception
+        {
+            AssertMustUseRewriter(ContractFailureKind.Precondition, "Requires<TException>");
+        }
+
+        #endregion Requires
+
+        #region Ensures
+
+        /// <summary>
+        /// Specifies a public contract such that the expression <paramref name="condition"/> will be true when the enclosing method or property returns normally.
+        /// </summary>
+        /// <param name="condition">Boolean expression representing the contract.  May include <seealso cref="OldValue"/> and <seealso cref="Result"/>.</param>
+        /// <remarks>
+        /// This call must happen at the beginning of a method or property before any other code.
+        /// This contract is exposed to clients so must only reference members at least as visible as the enclosing method.
+        /// The contract rewriter must be used for runtime enforcement of this postcondition.
+        /// </remarks>
+        [Pure]
+        [Conditional("CONTRACTS_FULL")]
+        public static void Ensures(bool condition)
+        {
+            AssertMustUseRewriter(ContractFailureKind.Postcondition, "Ensures");
+        }
+
+        /// <summary>
+        /// Specifies a public contract such that the expression <paramref name="condition"/> will be true when the enclosing method or property returns normally.
+        /// </summary>
+        /// <param name="condition">Boolean expression representing the contract.  May include <seealso cref="OldValue"/> and <seealso cref="Result"/>.</param>
+        /// <param name="userMessage">If it is not a constant string literal, then the contract may not be understood by tools.</param>
+        /// <remarks>
+        /// This call must happen at the beginning of a method or property before any other code.
+        /// This contract is exposed to clients so must only reference members at least as visible as the enclosing method.
+        /// The contract rewriter must be used for runtime enforcement of this postcondition.
+        /// </remarks>
+        [Pure]
+        [Conditional("CONTRACTS_FULL")]
+        public static void Ensures(bool condition, String userMessage)
+        {
+            AssertMustUseRewriter(ContractFailureKind.Postcondition, "Ensures");
+        }
+
+        /// <summary>
+        /// Specifies a contract such that if an exception of type <typeparamref name="TException"/> is thrown then the expression <paramref name="condition"/> will be true when the enclosing method or property terminates abnormally.
+        /// </summary>
+        /// <typeparam name="TException">Type of exception related to this postcondition.</typeparam>
+        /// <param name="condition">Boolean expression representing the contract.  May include <seealso cref="OldValue"/> and <seealso cref="Result"/>.</param>
+        /// <remarks>
+        /// This call must happen at the beginning of a method or property before any other code.
+        /// This contract is exposed to clients so must only reference types and members at least as visible as the enclosing method.
+        /// The contract rewriter must be used for runtime enforcement of this postcondition.
+        /// </remarks>
+        [Pure]
+        [Conditional("CONTRACTS_FULL")]
+        public static void EnsuresOnThrow<TException>(bool condition) where TException : Exception
+        {
+            AssertMustUseRewriter(ContractFailureKind.PostconditionOnException, "EnsuresOnThrow");
+        }
+
+        /// <summary>
+        /// Specifies a contract such that if an exception of type <typeparamref name="TException"/> is thrown then the expression <paramref name="condition"/> will be true when the enclosing method or property terminates abnormally.
+        /// </summary>
+        /// <typeparam name="TException">Type of exception related to this postcondition.</typeparam>
+        /// <param name="condition">Boolean expression representing the contract.  May include <seealso cref="OldValue"/> and <seealso cref="Result"/>.</param>
+        /// <param name="userMessage">If it is not a constant string literal, then the contract may not be understood by tools.</param>
+        /// <remarks>
+        /// This call must happen at the beginning of a method or property before any other code.
+        /// This contract is exposed to clients so must only reference types and members at least as visible as the enclosing method.
+        /// The contract rewriter must be used for runtime enforcement of this postcondition.
+        /// </remarks>
+        [Pure]
+        [Conditional("CONTRACTS_FULL")]
+        public static void EnsuresOnThrow<TException>(bool condition, String userMessage) where TException : Exception
+        {
+            AssertMustUseRewriter(ContractFailureKind.PostconditionOnException, "EnsuresOnThrow");
+        }
+
+        #region Old, Result, and Out Parameters
+
+        /// <summary>
+        /// Represents the result (a.k.a. return value) of a method or property.
+        /// </summary>
+        /// <typeparam name="T">Type of return value of the enclosing method or property.</typeparam>
+        /// <returns>Return value of the enclosing method or property.</returns>
+        /// <remarks>
+        /// This method can only be used within the argument to the <seealso cref="Ensures(bool)"/> contract.
+        /// </remarks>
+        [Pure]
+        public static T Result<T>() { return default(T); }
+
+        /// <summary>
+        /// Represents the final (output) value of an out parameter when returning from a method.
+        /// </summary>
+        /// <typeparam name="T">Type of the out parameter.</typeparam>
+        /// <param name="value">The out parameter.</param>
+        /// <returns>The output value of the out parameter.</returns>
+        /// <remarks>
+        /// This method can only be used within the argument to the <seealso cref="Ensures(bool)"/> contract.
+        /// </remarks>
+        [Pure]
+        public static T ValueAtReturn<T>(out T value) { value = default(T); return value; }
+
+        /// <summary>
+        /// Represents the value of <paramref name="value"/> as it was at the start of the method or property.
+        /// </summary>
+        /// <typeparam name="T">Type of <paramref name="value"/>.  This can be inferred.</typeparam>
+        /// <param name="value">Value to represent.  This must be a field or parameter.</param>
+        /// <returns>Value of <paramref name="value"/> at the start of the method or property.</returns>
+        /// <remarks>
+        /// This method can only be used within the argument to the <seealso cref="Ensures(bool)"/> contract.
+        /// </remarks>
+        [Pure]
+        public static T OldValue<T>(T value) { return default(T); }
+
+        #endregion Old, Result, and Out Parameters
+
+        #endregion Ensures
+
+        #region Invariant
+
+        /// <summary>
+        /// Specifies a contract such that the expression <paramref name="condition"/> will be true after every method or property on the enclosing class.
+        /// </summary>
+        /// <param name="condition">Boolean expression representing the contract.</param>
+        /// <remarks>
+        /// This contact can only be specified in a dedicated invariant method declared on a class.
+        /// This contract is not exposed to clients so may reference members less visible as the enclosing method.
+        /// The contract rewriter must be used for runtime enforcement of this invariant.
+        /// </remarks>
+        [Pure]
+        [Conditional("CONTRACTS_FULL")]
+        public static void Invariant(bool condition)
+        {
+            AssertMustUseRewriter(ContractFailureKind.Invariant, "Invariant");
+        }
+
+        /// <summary>
+        /// Specifies a contract such that the expression <paramref name="condition"/> will be true after every method or property on the enclosing class.
+        /// </summary>
+        /// <param name="condition">Boolean expression representing the contract.</param>
+        /// <param name="userMessage">If it is not a constant string literal, then the contract may not be understood by tools.</param>
+        /// <remarks>
+        /// This contact can only be specified in a dedicated invariant method declared on a class.
+        /// This contract is not exposed to clients so may reference members less visible as the enclosing method.
+        /// The contract rewriter must be used for runtime enforcement of this invariant.
+        /// </remarks>
+        [Pure]
+        [Conditional("CONTRACTS_FULL")]
+        public static void Invariant(bool condition, String userMessage)
+        {
+            AssertMustUseRewriter(ContractFailureKind.Invariant, "Invariant");
+        }
+
+        #endregion Invariant
+
+        #region Quantifiers
+
+        #region ForAll
+
+        /// <summary>
+        /// Returns whether the <paramref name="predicate"/> returns <c>true</c> 
+        /// for all integers starting from <paramref name="fromInclusive"/> to <paramref name="toExclusive"/> - 1.
+        /// </summary>
+        /// <param name="fromInclusive">First integer to pass to <paramref name="predicate"/>.</param>
+        /// <param name="toExclusive">One greater than the last integer to pass to <paramref name="predicate"/>.</param>
+        /// <param name="predicate">Function that is evaluated from <paramref name="fromInclusive"/> to <paramref name="toExclusive"/> - 1.</param>
+        /// <returns><c>true</c> if <paramref name="predicate"/> returns <c>true</c> for all integers 
+        /// starting from <paramref name="fromInclusive"/> to <paramref name="toExclusive"/> - 1.</returns>
+        /// <seealso cref="System.Collections.Generic.List&lt;T&gt;.TrueForAll"/>
+        [Pure]
+        public static bool ForAll(int fromInclusive, int toExclusive, Predicate<int> predicate)
+        {
+            if (fromInclusive > toExclusive)
+#if CORECLR
+                throw new ArgumentException(SR.Argument_ToExclusiveLessThanFromExclusive);
+#else
+                throw new ArgumentException("fromInclusive must be less than or equal to toExclusive.");
+#endif
+            if (predicate == null)
+                throw new ArgumentNullException(nameof(predicate));
+
+            for (int i = fromInclusive; i < toExclusive; i++)
+                if (!predicate(i)) return false;
+            return true;
+        }
+
+
+        /// <summary>
+        /// Returns whether the <paramref name="predicate"/> returns <c>true</c> 
+        /// for all elements in the <paramref name="collection"/>.
+        /// </summary>
+        /// <param name="collection">The collection from which elements will be drawn from to pass to <paramref name="predicate"/>.</param>
+        /// <param name="predicate">Function that is evaluated on elements from <paramref name="collection"/>.</param>
+        /// <returns><c>true</c> if and only if <paramref name="predicate"/> returns <c>true</c> for all elements in
+        /// <paramref name="collection"/>.</returns>
+        /// <seealso cref="System.Collections.Generic.List&lt;T&gt;.TrueForAll"/>
+        [Pure]
+        public static bool ForAll<T>(IEnumerable<T> collection, Predicate<T> predicate)
+        {
+            if (collection == null)
+                throw new ArgumentNullException(nameof(collection));
+            if (predicate == null)
+                throw new ArgumentNullException(nameof(predicate));
+
+            foreach (T t in collection)
+                if (!predicate(t)) return false;
+            return true;
+        }
+
+        #endregion ForAll
+
+        #region Exists
+
+        /// <summary>
+        /// Returns whether the <paramref name="predicate"/> returns <c>true</c> 
+        /// for any integer starting from <paramref name="fromInclusive"/> to <paramref name="toExclusive"/> - 1.
+        /// </summary>
+        /// <param name="fromInclusive">First integer to pass to <paramref name="predicate"/>.</param>
+        /// <param name="toExclusive">One greater than the last integer to pass to <paramref name="predicate"/>.</param>
+        /// <param name="predicate">Function that is evaluated from <paramref name="fromInclusive"/> to <paramref name="toExclusive"/> - 1.</param>
+        /// <returns><c>true</c> if <paramref name="predicate"/> returns <c>true</c> for any integer
+        /// starting from <paramref name="fromInclusive"/> to <paramref name="toExclusive"/> - 1.</returns>
+        /// <seealso cref="System.Collections.Generic.List&lt;T&gt;.Exists"/>
+        [Pure]
+        public static bool Exists(int fromInclusive, int toExclusive, Predicate<int> predicate)
+        {
+            if (fromInclusive > toExclusive)
+#if CORECLR
+                throw new ArgumentException(SR.Argument_ToExclusiveLessThanFromExclusive);
+#else
+                throw new ArgumentException("fromInclusive must be less than or equal to toExclusive.");
+#endif
+            if (predicate == null)
+                throw new ArgumentNullException(nameof(predicate));
+
+            for (int i = fromInclusive; i < toExclusive; i++)
+                if (predicate(i)) return true;
+            return false;
+        }
+
+        /// <summary>
+        /// Returns whether the <paramref name="predicate"/> returns <c>true</c> 
+        /// for any element in the <paramref name="collection"/>.
+        /// </summary>
+        /// <param name="collection">The collection from which elements will be drawn from to pass to <paramref name="predicate"/>.</param>
+        /// <param name="predicate">Function that is evaluated on elements from <paramref name="collection"/>.</param>
+        /// <returns><c>true</c> if and only if <paramref name="predicate"/> returns <c>true</c> for an element in
+        /// <paramref name="collection"/>.</returns>
+        /// <seealso cref="System.Collections.Generic.List&lt;T&gt;.Exists"/>
+        [Pure]
+        public static bool Exists<T>(IEnumerable<T> collection, Predicate<T> predicate)
+        {
+            if (collection == null)
+                throw new ArgumentNullException(nameof(collection));
+            if (predicate == null)
+                throw new ArgumentNullException(nameof(predicate));
+
+            foreach (T t in collection)
+                if (predicate(t)) return true;
+            return false;
+        }
+
+        #endregion Exists
+
+        #endregion Quantifiers
+
+        #region Pointers
+        #endregion
+
+        #region Misc.
+
+        /// <summary>
+        /// Marker to indicate the end of the contract section of a method.
+        /// </summary>
+        [Conditional("CONTRACTS_FULL")]
+        public static void EndContractBlock() { }
+
+        #endregion
+
+        #endregion User Methods
+    }
+
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public enum ContractFailureKind
+    {
+        Precondition,
+        Postcondition,
+        PostconditionOnException,
+        Invariant,
+        Assert,
+        Assume,
+    }
+}  // namespace System.Runtime.CompilerServices
+
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/Contracts/ContractsBCL.cs b/src/System.Private.CoreLib/src/System/Diagnostics/Contracts/ContractsBCL.cs
new file mode 100644
index 0000000000..e12bb5141f
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/Contracts/ContractsBCL.cs
@@ -0,0 +1,388 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+**
+** Implementation details of CLR Contracts.
+**
+===========================================================*/
+#define DEBUG // The behavior of this contract library should be consistent regardless of build type.
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Diagnostics.Contracts;
+using System.Reflection;
+
+namespace System.Diagnostics.Contracts
+{
+    public static partial class Contract
+    {
+        #region Private Methods
+
+        /// <summary>
+        /// This method is used internally to trigger a failure indicating to the "programmer" that he is using the interface incorrectly.
+        /// It is NEVER used to indicate failure of actual contracts at runtime.
+        /// </summary>
+        static void AssertMustUseRewriter(ContractFailureKind kind, String contractKind)
+        {
+            // For better diagnostics, report which assembly is at fault.  Walk up stack and
+            // find the first non-mscorlib assembly.
+            Assembly thisAssembly = typeof(Contract).Assembly;  // In case we refactor mscorlib, use Contract class instead of Object.
+            StackTrace stack = new StackTrace();
+            Assembly probablyNotRewritten = null;
+            for (int i = 0; i < stack.FrameCount; i++)
+            {
+                Assembly caller = stack.GetFrame(i).GetMethod().DeclaringType.Assembly;
+                if (caller != thisAssembly)
+                {
+                    probablyNotRewritten = caller;
+                    break;
+                }
+            }
+
+            if (probablyNotRewritten == null)
+                probablyNotRewritten = thisAssembly;
+            String simpleName = probablyNotRewritten.GetName().Name;
+            System.Runtime.CompilerServices.ContractHelper.TriggerFailure(kind, SR.Format(SR.MustUseCCRewrite, contractKind, simpleName), null, null, null);
+        }
+
+        #endregion Private Methods
+
+        #region Failure Behavior
+
+        /// <summary>
+        /// Without contract rewriting, failing Assert/Assumes end up calling this method.
+        /// Code going through the contract rewriter never calls this method. Instead, the rewriter produced failures call
+        /// System.Runtime.CompilerServices.ContractHelper.RaiseContractFailedEvent, followed by 
+        /// System.Runtime.CompilerServices.ContractHelper.TriggerFailure.
+        /// </summary>
+        [System.Diagnostics.DebuggerNonUserCode]
+        static void ReportFailure(ContractFailureKind failureKind, String userMessage, String conditionText, Exception innerException)
+        {
+            if (failureKind < ContractFailureKind.Precondition || failureKind > ContractFailureKind.Assume)
+                throw new ArgumentException(SR.Format(SR.Arg_EnumIllegalVal, failureKind), nameof(failureKind));
+
+            // displayMessage == null means: yes we handled it. Otherwise it is the localized failure message
+            var displayMessage = System.Runtime.CompilerServices.ContractHelper.RaiseContractFailedEvent(failureKind, userMessage, conditionText, innerException);
+
+            if (displayMessage == null) return;
+
+            System.Runtime.CompilerServices.ContractHelper.TriggerFailure(failureKind, displayMessage, userMessage, conditionText, innerException);
+        }
+
+        /// <summary>
+        /// Allows a managed application environment such as an interactive interpreter (IronPython)
+        /// to be notified of contract failures and 
+        /// potentially "handle" them, either by throwing a particular exception type, etc.  If any of the
+        /// event handlers sets the Cancel flag in the ContractFailedEventArgs, then the Contract class will
+        /// not pop up an assert dialog box or trigger escalation policy.  Hooking this event requires 
+        /// full trust, because it will inform you of bugs in the appdomain and because the event handler
+        /// could allow you to continue execution.
+        /// </summary>
+        public static event EventHandler<ContractFailedEventArgs> ContractFailed
+        {
+            add
+            {
+                System.Runtime.CompilerServices.ContractHelper.InternalContractFailed += value;
+            }
+            remove
+            {
+                System.Runtime.CompilerServices.ContractHelper.InternalContractFailed -= value;
+            }
+        }
+        #endregion FailureBehavior
+    }
+
+    public sealed class ContractFailedEventArgs : EventArgs
+    {
+        private ContractFailureKind _failureKind;
+        private String _message;
+        private String _condition;
+        private Exception _originalException;
+        private bool _handled;
+        private bool _unwind;
+
+        internal Exception thrownDuringHandler;
+
+        public ContractFailedEventArgs(ContractFailureKind failureKind, String message, String condition, Exception originalException)
+        {
+            Debug.Assert(originalException == null || failureKind == ContractFailureKind.PostconditionOnException);
+            _failureKind = failureKind;
+            _message = message;
+            _condition = condition;
+            _originalException = originalException;
+        }
+
+        public String Message { get { return _message; } }
+        public String Condition { get { return _condition; } }
+        public ContractFailureKind FailureKind { get { return _failureKind; } }
+        public Exception OriginalException { get { return _originalException; } }
+
+        // Whether the event handler "handles" this contract failure, or to fail via escalation policy.
+        public bool Handled
+        {
+            get { return _handled; }
+        }
+
+        public void SetHandled()
+        {
+            _handled = true;
+        }
+
+        public bool Unwind
+        {
+            get { return _unwind; }
+        }
+
+        public void SetUnwind()
+        {
+            _unwind = true;
+        }
+    }
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    // Needs to be public to support binary serialization compatibility
+    public sealed class ContractException : Exception
+    {
+        private readonly ContractFailureKind _kind;
+        private readonly string _userMessage;
+        private readonly string _condition;
+
+        public ContractFailureKind Kind { get { return _kind; } }
+        public string Failure { get { return this.Message; } }
+        public string UserMessage { get { return _userMessage; } }
+        public string Condition { get { return _condition; } }
+
+        // Called by COM Interop, if we see COR_E_CODECONTRACTFAILED as an HRESULT.
+        private ContractException()
+        {
+            HResult = System.Runtime.CompilerServices.ContractHelper.COR_E_CODECONTRACTFAILED;
+        }
+
+        public ContractException(ContractFailureKind kind, string failure, string userMessage, string condition, Exception innerException)
+            : base(failure, innerException)
+        {
+            HResult = System.Runtime.CompilerServices.ContractHelper.COR_E_CODECONTRACTFAILED;
+            _kind = kind;
+            _userMessage = userMessage;
+            _condition = condition;
+        }
+
+        private ContractException(System.Runtime.Serialization.SerializationInfo info, System.Runtime.Serialization.StreamingContext context)
+            : base(info, context)
+        {
+            _kind = (ContractFailureKind)info.GetInt32("Kind");
+            _userMessage = info.GetString("UserMessage");
+            _condition = info.GetString("Condition");
+        }
+
+
+        public override void GetObjectData(System.Runtime.Serialization.SerializationInfo info, System.Runtime.Serialization.StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("Kind", _kind);
+            info.AddValue("UserMessage", _userMessage);
+            info.AddValue("Condition", _condition);
+        }
+    }
+}
+
+
+namespace System.Runtime.CompilerServices
+{
+    public static partial class ContractHelper
+    {
+#region Private fields
+
+        private static volatile EventHandler<ContractFailedEventArgs> contractFailedEvent;
+        private static readonly Object lockObject = new Object();
+
+        internal const int COR_E_CODECONTRACTFAILED = unchecked((int)0x80131542);
+
+#endregion
+
+        /// <summary>
+        /// Allows a managed application environment such as an interactive interpreter (IronPython) or a
+        /// web browser host (Jolt hosting Silverlight in IE) to be notified of contract failures and 
+        /// potentially "handle" them, either by throwing a particular exception type, etc.  If any of the
+        /// event handlers sets the Cancel flag in the ContractFailedEventArgs, then the Contract class will
+        /// not pop up an assert dialog box or trigger escalation policy.  Hooking this event requires 
+        /// full trust.
+        /// </summary>
+        internal static event EventHandler<ContractFailedEventArgs> InternalContractFailed
+        {
+            add
+            {
+                // Eagerly prepare each event handler _marked with a reliability contract_, to 
+                // attempt to reduce out of memory exceptions while reporting contract violations.
+                // This only works if the new handler obeys the constraints placed on 
+                // constrained execution regions.  Eagerly preparing non-reliable event handlers
+                // would be a perf hit and wouldn't significantly improve reliability.
+                // UE: Please mention reliable event handlers should also be marked with the 
+                // PrePrepareMethodAttribute to avoid CER eager preparation work when ngen'ed.
+                System.Runtime.CompilerServices.RuntimeHelpers.PrepareContractedDelegate(value);
+                lock (lockObject)
+                {
+                    contractFailedEvent += value;
+                }
+            }
+            remove
+            {
+                lock (lockObject)
+                {
+                    contractFailedEvent -= value;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Rewriter will call this method on a contract failure to allow listeners to be notified.
+        /// The method should not perform any failure (assert/throw) itself.
+        /// This method has 3 functions:
+        /// 1. Call any contract hooks (such as listeners to Contract failed events)
+        /// 2. Determine if the listeners deem the failure as handled (then resultFailureMessage should be set to null)
+        /// 3. Produce a localized resultFailureMessage used in advertising the failure subsequently.
+        /// </summary>
+        /// On exit: null if the event was handled and should not trigger a failure.
+        ///          Otherwise, returns the localized failure message</param>
+        [System.Diagnostics.DebuggerNonUserCode]
+        public static string RaiseContractFailedEvent(ContractFailureKind failureKind, String userMessage, String conditionText, Exception innerException)
+        {
+            if (failureKind < ContractFailureKind.Precondition || failureKind > ContractFailureKind.Assume)
+                throw new ArgumentException(SR.Format(SR.Arg_EnumIllegalVal, failureKind), nameof(failureKind));
+
+            string returnValue;
+            String displayMessage = "contract failed.";  // Incomplete, but in case of OOM during resource lookup...
+            ContractFailedEventArgs eventArgs = null;  // In case of OOM.
+
+            try
+            {
+                displayMessage = GetDisplayMessage(failureKind, userMessage, conditionText);
+                EventHandler<ContractFailedEventArgs> contractFailedEventLocal = contractFailedEvent;
+                if (contractFailedEventLocal != null)
+                {
+                    eventArgs = new ContractFailedEventArgs(failureKind, displayMessage, conditionText, innerException);
+                    foreach (EventHandler<ContractFailedEventArgs> handler in contractFailedEventLocal.GetInvocationList())
+                    {
+                        try
+                        {
+                            handler(null, eventArgs);
+                        }
+                        catch (Exception e)
+                        {
+                            eventArgs.thrownDuringHandler = e;
+                            eventArgs.SetUnwind();
+                        }
+                    }
+                    if (eventArgs.Unwind)
+                    {
+                        // unwind
+                        if (innerException == null) { innerException = eventArgs.thrownDuringHandler; }
+                        throw new ContractException(failureKind, displayMessage, userMessage, conditionText, innerException);
+                    }
+                }
+            }
+            finally
+            {
+                if (eventArgs != null && eventArgs.Handled)
+                {
+                    returnValue = null; // handled
+                }
+                else
+                {
+                    returnValue = displayMessage;
+                }
+            }
+            return returnValue;
+        }
+
+        /// <summary>
+        /// Rewriter calls this method to get the default failure behavior.
+        /// </summary>
+        [System.Diagnostics.DebuggerNonUserCode]
+        public static void TriggerFailure(ContractFailureKind kind, String displayMessage, String userMessage, String conditionText, Exception innerException)
+        {
+            if (string.IsNullOrEmpty(displayMessage))
+            {
+                displayMessage = GetDisplayMessage(kind, userMessage, conditionText);
+            }
+
+            System.Diagnostics.Debug.ContractFailure(false, displayMessage, string.Empty, GetResourceNameForFailure(kind));
+        }
+
+        private static String GetResourceNameForFailure(ContractFailureKind failureKind)
+        {
+            String resourceName = null;
+            switch (failureKind)
+            {
+                case ContractFailureKind.Assert:
+                    resourceName = "AssertionFailed";
+                    break;
+
+                case ContractFailureKind.Assume:
+                    resourceName = "AssumptionFailed";
+                    break;
+
+                case ContractFailureKind.Precondition:
+                    resourceName = "PreconditionFailed";
+                    break;
+
+                case ContractFailureKind.Postcondition:
+                    resourceName = "PostconditionFailed";
+                    break;
+
+                case ContractFailureKind.Invariant:
+                    resourceName = "InvariantFailed";
+                    break;
+
+                case ContractFailureKind.PostconditionOnException:
+                    resourceName = "PostconditionOnExceptionFailed";
+                    break;
+
+                default:
+                    Debug.Fail("Unreachable code");
+                    resourceName = "AssumptionFailed";
+                    break;
+            }
+            return resourceName;
+        }
+
+        private static String GetDisplayMessage(ContractFailureKind failureKind, String userMessage, String conditionText)
+        {
+            String failureMessage;
+            // Well-formatted English messages will take one of four forms.  A sentence ending in
+            // either a period or a colon, the condition string, then the message tacked 
+            // on to the end with two spaces in front.
+            // Note that both the conditionText and userMessage may be null.  Also, 
+            // on Silverlight we may not be able to look up a friendly string for the
+            // error message.  Let's leverage Silverlight's default error message there. 
+            if (!String.IsNullOrEmpty(conditionText))
+            {
+                String resourceName = GetResourceNameForFailure(failureKind); 
+                resourceName += "_Cnd";
+                failureMessage = SR.Format(SR.GetResourceString(resourceName), conditionText);
+            }
+            else
+            {
+                failureMessage = "";
+            }
+
+            // Now add in the user message, if present.
+            if (!String.IsNullOrEmpty(userMessage))
+            {
+                return failureMessage + "  " + userMessage;
+            }
+            else
+            {
+                return failureMessage;
+            }
+        }
+    }
+}  // namespace System.Runtime.CompilerServices
+
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/Debug.Windows.cs b/src/System.Private.CoreLib/src/System/Diagnostics/Debug.Windows.cs
new file mode 100644
index 0000000000..7649991011
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/Debug.Windows.cs
@@ -0,0 +1,77 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Diagnostics
+{
+    public static partial class Debug
+    {
+        private static void ShowDialog(string stackTrace, string message, string detailMessage, string errorSource)
+        {
+            if (Debugger.IsAttached)
+            {
+                Debugger.Break();
+            }
+            else
+            {
+                // In Core, we do not show a dialog.
+                // Fail in order to avoid anyone catching an exception and masking
+                // an assert failure.
+                DebugAssertException ex;
+                if (message == String.Empty) 
+                {
+                    ex = new DebugAssertException(stackTrace);
+                }
+                else if (detailMessage == String.Empty) 
+                {
+                    ex = new DebugAssertException(message, stackTrace);
+                }
+                else
+                {
+                    ex = new DebugAssertException(message, detailMessage, stackTrace);
+                }
+                Environment.FailFast(ex.Message, ex, errorSource);
+            }
+        }
+
+        private static readonly object s_ForLock = new Object();
+
+        private static void WriteCore(string message)
+        {
+            // really huge messages mess up both VS and dbmon, so we chop it up into 
+            // reasonable chunks if it's too big. This is the number of characters 
+            // that OutputDebugstring chunks at.
+            const int WriteChunkLength = 4091;
+
+            // We don't want output from multiple threads to be interleaved.
+            lock (s_ForLock)
+            {
+                if (message == null || message.Length <= WriteChunkLength)
+                {
+                    WriteToDebugger(message);
+                }
+                else
+                {
+                    int offset;
+                    for (offset = 0; offset < message.Length - WriteChunkLength; offset += WriteChunkLength)
+                    {
+                        WriteToDebugger(message.Substring(offset, WriteChunkLength));
+                    }
+                    WriteToDebugger(message.Substring(offset));
+                }
+            }
+        }
+
+        private static void WriteToDebugger(string message)
+        {
+            if (Debugger.IsLogging())
+            {
+                Debugger.Log(0, null, message);
+            }
+            else
+            {
+                Interop.Kernel32.OutputDebugString(message ?? string.Empty);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/Debugger.cs b/src/System.Private.CoreLib/src/System/Diagnostics/Debugger.cs
new file mode 100644
index 0000000000..cda3c4e729
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/Debugger.cs
@@ -0,0 +1,95 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// The Debugger class is a part of the System.Diagnostics package
+// and is used for communicating with a debugger.
+
+using System.Runtime.CompilerServices;
+
+namespace System.Diagnostics
+{
+    public static class Debugger
+    {
+        // Break causes a breakpoint to be signalled to an attached debugger.  If no debugger
+        // is attached, the user is asked if he wants to attach a debugger. If yes, then the
+        // debugger is launched.
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        public static void Break() => BreakInternal();
+
+        // The VM depends on this private method.
+        private static void BreakCanThrow() => BreakInternal();
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern void BreakInternal();
+
+        // Launch launches & attaches a debugger to the process. If a debugger is already attached,
+        // nothing happens.
+        //
+        public static bool Launch() => IsAttached ? true : LaunchInternal();
+
+        // This class implements code:ICustomDebuggerNotification and provides a type to be used to notify
+        // the debugger that execution is about to enter a path that involves a cross-thread dependency.
+        // See code:NotifyOfCrossThreadDependency for more details.
+        private class CrossThreadDependencyNotification : ICustomDebuggerNotification { }
+
+        // Do not inline the slow path
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void NotifyOfCrossThreadDependencySlow() =>
+            CustomNotification(new CrossThreadDependencyNotification());
+
+        // Sends a notification to the debugger to indicate that execution is about to enter a path
+        // involving a cross thread dependency. A debugger that has opted into this type of notification
+        // can take appropriate action on receipt. For example, performing a funceval normally requires
+        // freezing all threads but the one performing the funceval. If the funceval requires execution on
+        // more than one thread, as might occur in remoting scenarios, the funceval will block. This
+        // notification will apprise the debugger that it will need  to slip a thread or abort the funceval
+        // in such a situation. The notification is subject to collection after this function returns.
+        //
+        public static void NotifyOfCrossThreadDependency()
+        {
+            if (IsAttached)
+            {
+                NotifyOfCrossThreadDependencySlow();
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern bool LaunchInternal();
+
+        // Returns whether or not a debugger is attached to the process.
+        //
+        public static extern bool IsAttached
+        {
+            [MethodImpl(MethodImplOptions.InternalCall)]
+            get;
+        }
+
+        // Constants representing the importance level of messages to be logged.
+        //
+        // An attached debugger can enable or disable which messages will
+        // actually be reported to the user through the COM+ debugger
+        // services API.  This info is communicated to the runtime so only
+        // desired events are actually reported to the debugger.
+        //
+        // Constant representing the default category
+        public static readonly string DefaultCategory = null;
+
+        // Posts a message for the attached debugger.  If there is no
+        // debugger attached, has no effect.  The debugger may or may not
+        // report the message depending on its settings.
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern void Log(int level, string category, string message);
+
+        // Checks to see if an attached debugger has logging enabled
+        //
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern bool IsLogging();
+
+        // Posts a custom notification for the attached debugger.  If there is no
+        // debugger attached, has no effect.  The debugger may or may not
+        // report the notification depending on its settings.
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern void CustomNotification(ICustomDebuggerNotification data);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/EditAndContinueHelper.cs b/src/System.Private.CoreLib/src/System/Diagnostics/EditAndContinueHelper.cs
new file mode 100644
index 0000000000..6b8c150ab8
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/EditAndContinueHelper.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Helper for EditAndContinue
+**
+**
+=============================================================================*/
+
+
+using System;
+
+namespace System.Diagnostics
+{
+    internal sealed class EditAndContinueHelper
+    {
+#pragma warning disable 169
+#pragma warning disable 414  // Field is not used from managed.
+        private Object _objectReference;
+#pragma warning restore 414
+#pragma warning restore 169
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventPipe.cs b/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventPipe.cs
new file mode 100644
index 0000000000..58091be27f
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventPipe.cs
@@ -0,0 +1,180 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Security;
+using Microsoft.Win32;
+
+namespace System.Diagnostics.Tracing
+{
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct EventPipeProviderConfiguration
+    {
+        [MarshalAs(UnmanagedType.LPWStr)]
+        private string m_providerName;
+        private ulong m_keywords;
+        private uint m_loggingLevel;
+
+        internal EventPipeProviderConfiguration(
+            string providerName,
+            ulong keywords,
+            uint loggingLevel)
+        {
+            if(string.IsNullOrEmpty(providerName))
+            {
+                throw new ArgumentNullException(nameof(providerName));
+            }
+            if(loggingLevel > 5) // 5 == Verbose, the highest value in EventPipeLoggingLevel.
+            {
+                throw new ArgumentOutOfRangeException(nameof(loggingLevel));
+            }
+            m_providerName = providerName;
+            m_keywords = keywords;
+            m_loggingLevel = loggingLevel;
+        }
+
+        internal string ProviderName
+        {
+            get { return m_providerName; }
+        }
+
+        internal ulong Keywords
+        {
+            get { return m_keywords; }
+        }
+
+        internal uint LoggingLevel
+        {
+            get { return m_loggingLevel; }
+        }
+    }
+
+    internal sealed class EventPipeConfiguration
+    {
+        private string m_outputFile;
+        private uint m_circularBufferSizeInMB;
+        private List<EventPipeProviderConfiguration> m_providers;
+        private TimeSpan m_minTimeBetweenSamples = TimeSpan.FromMilliseconds(1);
+
+        internal EventPipeConfiguration(
+            string outputFile,
+            uint circularBufferSizeInMB)
+        {
+            if(string.IsNullOrEmpty(outputFile))
+            {
+                throw new ArgumentNullException(nameof(outputFile));
+            }
+            if(circularBufferSizeInMB == 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(circularBufferSizeInMB));
+            }
+            m_outputFile = outputFile;
+            m_circularBufferSizeInMB = circularBufferSizeInMB;
+            m_providers = new List<EventPipeProviderConfiguration>();
+        }
+
+        internal string OutputFile
+        {
+            get { return m_outputFile; }
+        }
+
+        internal uint CircularBufferSizeInMB
+        {
+            get { return m_circularBufferSizeInMB; }
+        }
+
+        internal EventPipeProviderConfiguration[] Providers
+        {
+            get { return m_providers.ToArray(); }
+        }
+
+        internal long ProfilerSamplingRateInNanoseconds
+        {
+            // 100 nanoseconds == 1 tick.
+            get { return m_minTimeBetweenSamples.Ticks * 100; }
+        }
+
+        internal void EnableProvider(string providerName, ulong keywords, uint loggingLevel)
+        {
+            m_providers.Add(new EventPipeProviderConfiguration(
+                providerName,
+                keywords,
+                loggingLevel));
+        }
+
+        internal void SetProfilerSamplingRate(TimeSpan minTimeBetweenSamples)
+        {
+            if(minTimeBetweenSamples.Ticks <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(minTimeBetweenSamples));
+            }
+
+            m_minTimeBetweenSamples = minTimeBetweenSamples;
+        }
+    }
+
+    internal static class EventPipe
+    {
+        internal static void Enable(EventPipeConfiguration configuration)
+        {
+            if(configuration == null)
+            {
+                throw new ArgumentNullException(nameof(configuration));
+            }
+
+            if(configuration.Providers == null)
+            {
+                throw new ArgumentNullException(nameof(configuration.Providers));
+            }
+
+            EventPipeProviderConfiguration[] providers = configuration.Providers;
+
+            EventPipeInternal.Enable(
+                configuration.OutputFile,
+                configuration.CircularBufferSizeInMB,
+                configuration.ProfilerSamplingRateInNanoseconds,
+                providers,
+                providers.Length);
+        }
+
+        internal static void Disable()
+        {
+            EventPipeInternal.Disable();
+        }
+    }
+
+    internal static class EventPipeInternal
+    {
+        //
+        // These PInvokes are used by the configuration APIs to interact with EventPipe.
+        //
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void Enable(string outputFile, uint circularBufferSizeInMB, long profilerSamplingRateInNanoseconds, EventPipeProviderConfiguration[] providers, int numProviders);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void Disable();
+
+        //
+        // These PInvokes are used by EventSource to interact with the EventPipe.
+        //
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern IntPtr CreateProvider(string providerName, UnsafeNativeMethods.ManifestEtw.EtwEnableCallback callbackFunc);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern unsafe IntPtr DefineEvent(IntPtr provHandle, uint eventID, long keywords, uint eventVersion, uint level, void *pMetadata, uint metadataLength);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void DeleteProvider(IntPtr provHandle);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern int EventActivityIdControl(uint controlCode, ref Guid activityId);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern unsafe void WriteEvent(IntPtr eventHandle, uint eventID, void* pData, uint length, Guid* activityId, Guid* relatedActivityId);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern unsafe void WriteEventData(IntPtr eventHandle, uint eventID, EventProvider.EventData* pEventData, uint dataCount, Guid* activityId, Guid* relatedActivityId);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventPipeEventProvider.cs b/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventPipeEventProvider.cs
new file mode 100644
index 0000000000..42061df043
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventPipeEventProvider.cs
@@ -0,0 +1,96 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+using System.Collections.Concurrent;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Security;
+using Microsoft.Win32;
+using System.Diagnostics;
+using System.Collections.Generic;
+
+namespace System.Diagnostics.Tracing
+{
+    internal sealed class EventPipeEventProvider : IEventProvider
+    {
+        // The EventPipeProvider handle.
+        private IntPtr m_provHandle = IntPtr.Zero;
+
+        // Register an event provider.
+        unsafe uint IEventProvider.EventRegister(
+            EventSource eventSource,
+            UnsafeNativeMethods.ManifestEtw.EtwEnableCallback enableCallback,
+            void* callbackContext,
+            ref long registrationHandle)
+        {
+            uint returnStatus = 0;
+            m_provHandle = EventPipeInternal.CreateProvider(eventSource.Name, enableCallback);
+            if(m_provHandle != IntPtr.Zero)
+            {
+                // Fixed registration handle because a new EventPipeEventProvider
+                // will be created for each new EventSource.
+                registrationHandle = 1;
+            }
+            else
+            {
+                // Unable to create the provider.
+                returnStatus = 1;
+            }
+
+            return returnStatus;
+        }
+
+        // Unregister an event provider.
+        uint IEventProvider.EventUnregister(long registrationHandle)
+        {
+            EventPipeInternal.DeleteProvider(m_provHandle);
+            return 0;
+        }
+
+        // Write an event.
+        unsafe int IEventProvider.EventWriteTransferWrapper(
+            long registrationHandle,
+            ref EventDescriptor eventDescriptor,
+            IntPtr eventHandle,
+            Guid* activityId,
+            Guid* relatedActivityId,
+            int userDataCount,
+            EventProvider.EventData* userData)
+        {
+            uint eventID = (uint)eventDescriptor.EventId;
+            if(eventID != 0 && eventHandle != IntPtr.Zero)
+            {
+                if (userDataCount == 0)
+                {
+                    EventPipeInternal.WriteEventData(eventHandle, eventID, null, 0, activityId, relatedActivityId);
+                    return 0;
+                }
+
+                // If Channel == 11, this is a TraceLogging event.
+                // The first 3 descriptors contain event metadata that is emitted for ETW and should be discarded on EventPipe.
+                // EventPipe metadata is provided via the EventPipeEventProvider.DefineEventHandle.
+                if (eventDescriptor.Channel == 11)
+                {
+                    userData = userData + 3;
+                    userDataCount = userDataCount - 3;
+                    Debug.Assert(userDataCount >= 0);
+                }
+                EventPipeInternal.WriteEventData(eventHandle, eventID, userData, (uint) userDataCount, activityId, relatedActivityId);
+            }
+            return 0;
+        }
+
+        // Get or set the per-thread activity ID.
+        int IEventProvider.EventActivityIdControl(UnsafeNativeMethods.ManifestEtw.ActivityControl ControlCode, ref Guid ActivityId)
+        {
+            return EventPipeInternal.EventActivityIdControl((uint)ControlCode, ref ActivityId);
+        }
+
+        // Define an EventPipeEvent handle.
+        unsafe IntPtr IEventProvider.DefineEventHandle(uint eventID, string eventName, Int64 keywords, uint eventVersion, uint level, byte *pMetadata, uint metadataLength)
+        {
+            IntPtr eventHandlePtr = EventPipeInternal.DefineEvent(m_provHandle, eventID, keywords, eventVersion, level, pMetadata, metadataLength);
+            return eventHandlePtr;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventPipeMetadataGenerator.cs b/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventPipeMetadataGenerator.cs
new file mode 100644
index 0000000000..d18610d922
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventPipeMetadataGenerator.cs
@@ -0,0 +1,392 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+using System;
+using System.Reflection;
+using EventMetadata = System.Diagnostics.Tracing.EventSource.EventMetadata;
+
+namespace System.Diagnostics.Tracing
+{
+#if FEATURE_PERFTRACING
+
+    internal sealed class EventPipeMetadataGenerator
+    {
+        public static EventPipeMetadataGenerator Instance = new EventPipeMetadataGenerator();
+
+        private EventPipeMetadataGenerator() { }
+
+        public unsafe byte[] GenerateEventMetadata(EventMetadata eventMetadata)
+        {
+            ParameterInfo[] parameters = eventMetadata.Parameters;
+            EventParameterInfo[] eventParams = new EventParameterInfo[parameters.Length];
+            for(int i=0; i<parameters.Length; i++)
+            {
+                eventParams[i].SetInfo(parameters[i].Name, parameters[i].ParameterType);
+            }
+
+            return GenerateMetadata(
+                eventMetadata.Descriptor.EventId,
+                eventMetadata.Name,
+                eventMetadata.Descriptor.Keywords,
+                eventMetadata.Descriptor.Level,
+                eventMetadata.Descriptor.Version,
+                eventParams);
+        }
+
+        public unsafe byte[] GenerateEventMetadata(
+            int eventId,
+            string eventName,
+            EventKeywords keywords,
+            EventLevel level,
+            uint version,
+            TraceLoggingEventTypes eventTypes)
+        {
+            TraceLoggingTypeInfo[] typeInfos = eventTypes.typeInfos;
+            string[] paramNames = eventTypes.paramNames;
+            EventParameterInfo[] eventParams = new EventParameterInfo[typeInfos.Length];
+            for(int i=0; i<typeInfos.Length; i++)
+            {
+                string paramName = string.Empty;
+                if(paramNames != null)
+                {
+                    paramName = paramNames[i];
+                }
+                eventParams[i].SetInfo(paramName, typeInfos[i].DataType, typeInfos[i]);
+            }
+
+            return GenerateMetadata(eventId, eventName, (long)keywords, (uint)level, version, eventParams);
+        }
+
+        private unsafe byte[] GenerateMetadata(
+            int eventId,
+            string eventName,
+            long keywords,
+            uint level,
+            uint version,
+            EventParameterInfo[] parameters)
+        {
+            byte[] metadata = null;
+            try
+            {
+                // eventID          : 4 bytes
+                // eventName        : (eventName.Length + 1) * 2 bytes
+                // keywords         : 8 bytes
+                // eventVersion     : 4 bytes
+                // level            : 4 bytes
+                // parameterCount   : 4 bytes
+                uint metadataLength = 24 + ((uint)eventName.Length + 1) * 2;
+
+                // Check for an empty payload.
+                // Write<T> calls with no arguments by convention have a parameter of
+                // type NullTypeInfo which is serialized as nothing.
+                if ((parameters.Length == 1) && (parameters[0].ParameterType == typeof(EmptyStruct)))
+                {
+                    parameters = Array.Empty<EventParameterInfo>();
+                }
+
+                // Increase the metadataLength for parameters.
+                foreach (var parameter in parameters)
+                {
+                    metadataLength = metadataLength + parameter.GetMetadataLength();
+                }
+
+                metadata = new byte[metadataLength];
+
+                // Write metadata: eventID, eventName, keywords, eventVersion, level, parameterCount, param1 type, param1 name...
+                fixed (byte* pMetadata = metadata)
+                {
+                    uint offset = 0;
+                    WriteToBuffer(pMetadata, metadataLength, ref offset, (uint)eventId);
+                    fixed (char* pEventName = eventName)
+                    {
+                        WriteToBuffer(pMetadata, metadataLength, ref offset, (byte*)pEventName, ((uint)eventName.Length + 1) * 2);
+                    }
+                    WriteToBuffer(pMetadata, metadataLength, ref offset, keywords);
+                    WriteToBuffer(pMetadata, metadataLength, ref offset, version);
+                    WriteToBuffer(pMetadata, metadataLength, ref offset, level);
+                    WriteToBuffer(pMetadata, metadataLength, ref offset, (uint)parameters.Length);
+                    foreach (var parameter in parameters)
+                    {
+                        parameter.GenerateMetadata(pMetadata, ref offset, metadataLength);
+                    }
+                    Debug.Assert(metadataLength == offset);
+                }
+            }
+            catch
+            {
+                // If a failure occurs during metadata generation, make sure that we don't return
+                // malformed metadata.  Instead, return a null metadata blob.
+                // Consumers can either build in knowledge of the event or skip it entirely.
+                metadata = null;
+            }
+
+            return metadata;
+        }
+
+        // Copy src to buffer and modify the offset.
+        // Note: We know the buffer size ahead of time to make sure no buffer overflow.
+        internal static unsafe void WriteToBuffer(byte *buffer, uint bufferLength, ref uint offset, byte *src, uint srcLength)
+        {
+            Debug.Assert(bufferLength >= (offset + srcLength));
+            for (int i = 0; i < srcLength; i++)
+            {
+                *(byte *)(buffer + offset + i) = *(byte *)(src + i);
+            }
+            offset += srcLength;
+        }
+
+        // Copy uint value to buffer.
+        internal static unsafe void WriteToBuffer(byte *buffer, uint bufferLength, ref uint offset, uint value)
+        {
+            Debug.Assert(bufferLength >= (offset + 4));
+            *(uint *)(buffer + offset) = value;
+            offset += 4;
+        }
+
+        // Copy long value to buffer.
+        internal static unsafe void WriteToBuffer(byte *buffer, uint bufferLength, ref uint offset, long value)
+        {
+            Debug.Assert(bufferLength >= (offset + 8));
+            *(long *)(buffer + offset) = value;
+            offset += 8;
+        }
+
+        // Copy char value to buffer.
+        internal static unsafe void WriteToBuffer(byte *buffer, uint bufferLength, ref uint offset, char value)
+        {
+            Debug.Assert(bufferLength >= (offset + 2));
+            *(char *)(buffer + offset) = value;
+            offset += 2;
+        }
+
+    }
+
+    internal struct EventParameterInfo
+    {
+        internal string ParameterName;
+        internal Type ParameterType;
+        internal TraceLoggingTypeInfo TypeInfo;
+
+        internal void SetInfo(string name, Type type, TraceLoggingTypeInfo typeInfo = null)
+        {
+            ParameterName = name;
+            ParameterType = type;
+            TypeInfo = typeInfo;
+        }
+
+        internal unsafe void GenerateMetadata(byte* pMetadataBlob, ref uint offset, uint blobSize)
+        {
+            TypeCode typeCode = GetTypeCodeExtended(ParameterType);
+            if(typeCode == TypeCode.Object)
+            {
+                // Each nested struct is serialized as:
+                //     TypeCode.Object              : 4 bytes
+                //     Number of properties         : 4 bytes
+                //     Property description 0...N
+                //     Nested struct property name  : NULL-terminated string.
+                EventPipeMetadataGenerator.WriteToBuffer(pMetadataBlob, blobSize, ref offset, (uint)TypeCode.Object);
+
+                InvokeTypeInfo invokeTypeInfo = TypeInfo as InvokeTypeInfo;
+                if(invokeTypeInfo == null)
+                {
+                    throw new NotSupportedException();
+                }
+
+                // Get the set of properties to be serialized.
+                PropertyAnalysis[] properties = invokeTypeInfo.properties;
+                if(properties != null)
+                {
+                    // Write the count of serializable properties.
+                    EventPipeMetadataGenerator.WriteToBuffer(pMetadataBlob, blobSize, ref offset, (uint)properties.Length);
+
+                    foreach(PropertyAnalysis prop in properties)
+                    {
+                        GenerateMetadataForProperty(prop, pMetadataBlob, ref offset, blobSize);
+                    }
+                }
+                else
+                {
+                    // This struct has zero serializable properties so we just write the property count.
+                    EventPipeMetadataGenerator.WriteToBuffer(pMetadataBlob, blobSize, ref offset, (uint)0);
+                }
+
+                // Top-level structs don't have a property name, but for simplicity we write a NULL-char to represent the name.
+                EventPipeMetadataGenerator.WriteToBuffer(pMetadataBlob, blobSize, ref offset, '\0');
+               
+            }
+            else
+            {
+                // Write parameter type.
+                EventPipeMetadataGenerator.WriteToBuffer(pMetadataBlob, blobSize, ref offset, (uint)typeCode);
+
+                // Write parameter name.
+                fixed (char *pParameterName = ParameterName)
+                {
+                    EventPipeMetadataGenerator.WriteToBuffer(pMetadataBlob, blobSize, ref offset, (byte *)pParameterName, ((uint)ParameterName.Length + 1) * 2);
+                }
+            }
+        }
+
+        private static unsafe void GenerateMetadataForProperty(PropertyAnalysis property, byte* pMetadataBlob, ref uint offset, uint blobSize)
+        {
+            Debug.Assert(property != null);
+            Debug.Assert(pMetadataBlob != null);
+
+            // Check if this property is a nested struct.
+            InvokeTypeInfo invokeTypeInfo = property.typeInfo as InvokeTypeInfo;
+            if(invokeTypeInfo != null)
+            {
+                // Each nested struct is serialized as:
+                //     TypeCode.Object              : 4 bytes
+                //     Number of properties         : 4 bytes
+                //     Property description 0...N
+                //     Nested struct property name  : NULL-terminated string.
+                EventPipeMetadataGenerator.WriteToBuffer(pMetadataBlob, blobSize, ref offset, (uint)TypeCode.Object);
+
+                // Get the set of properties to be serialized.
+                PropertyAnalysis[] properties = invokeTypeInfo.properties;
+                if(properties != null)
+                {
+                    // Write the count of serializable properties.
+                    EventPipeMetadataGenerator.WriteToBuffer(pMetadataBlob, blobSize, ref offset, (uint)properties.Length);
+
+                    foreach(PropertyAnalysis prop in properties)
+                    {
+                        GenerateMetadataForProperty(prop, pMetadataBlob, ref offset, blobSize);
+                    }
+                }
+                else
+                {
+                    // This struct has zero serializable properties so we just write the property count.
+                    EventPipeMetadataGenerator.WriteToBuffer(pMetadataBlob, blobSize, ref offset, (uint)0);
+                }
+
+                // Write the property name.
+                fixed(char *pPropertyName = property.name)
+                {
+                    EventPipeMetadataGenerator.WriteToBuffer(pMetadataBlob, blobSize, ref offset, (byte *)pPropertyName, ((uint)property.name.Length + 1) * 2);
+                }
+            }
+            else
+            {
+                // Each primitive type is serialized as:
+                //     TypeCode : 4 bytes
+                //     PropertyName : NULL-terminated string
+                TypeCode typeCode = GetTypeCodeExtended(property.typeInfo.DataType);
+
+                // EventPipe does not support this type.  Throw, which will cause no metadata to be registered for this event.
+                if(typeCode == TypeCode.Object)
+                {
+                    throw new NotSupportedException();
+                }
+
+                // Write the type code.
+                EventPipeMetadataGenerator.WriteToBuffer(pMetadataBlob, blobSize, ref offset, (uint)typeCode);
+
+                // Write the property name.
+                fixed(char *pPropertyName = property.name)
+                {
+                    EventPipeMetadataGenerator.WriteToBuffer(pMetadataBlob, blobSize, ref offset, (byte *)pPropertyName, ((uint)property.name.Length + 1) * 2);
+                }
+            }
+        }
+
+
+        internal unsafe uint GetMetadataLength()
+        {
+            uint ret = 0;
+
+            TypeCode typeCode = GetTypeCodeExtended(ParameterType);
+            if(typeCode == TypeCode.Object)
+            {
+                InvokeTypeInfo typeInfo = TypeInfo as InvokeTypeInfo;
+                if(typeInfo == null)
+                {
+                    throw new NotSupportedException();
+                }
+
+                // Each nested struct is serialized as:
+                //     TypeCode.Object      : 4 bytes
+                //     Number of properties : 4 bytes
+                //     Property description 0...N
+                //     Nested struct property name  : NULL-terminated string.
+                ret += sizeof(uint)  // TypeCode
+                     + sizeof(uint); // Property count
+
+                // Get the set of properties to be serialized.
+                PropertyAnalysis[] properties = typeInfo.properties;
+                if(properties != null)
+                {
+                    foreach(PropertyAnalysis prop in properties)
+                    {
+                        ret += GetMetadataLengthForProperty(prop);
+                    }
+                }
+
+                // For simplicity when writing a reader, we write a NULL char
+                // after the metadata for a top-level struct (for its name) so that 
+                // readers don't have do special case the outer-most struct.
+                ret += sizeof(char);
+            }
+            else
+            {
+                ret += (uint)(sizeof(uint) + ((ParameterName.Length + 1) * 2));
+            }
+
+            return ret;
+        }
+
+        private static uint GetMetadataLengthForProperty(PropertyAnalysis property)
+        {
+            Debug.Assert(property != null);
+
+            uint ret = 0;
+
+            // Check if this property is a nested struct.
+            InvokeTypeInfo invokeTypeInfo = property.typeInfo as InvokeTypeInfo;
+            if(invokeTypeInfo != null)
+            {
+                // Each nested struct is serialized as:
+                //     TypeCode.Object      : 4 bytes
+                //     Number of properties : 4 bytes
+                //     Property description 0...N
+                //     Nested struct property name  : NULL-terminated string.
+                ret += sizeof(uint)  // TypeCode
+                     + sizeof(uint); // Property count
+
+                // Get the set of properties to be serialized.
+                PropertyAnalysis[] properties = invokeTypeInfo.properties;
+                if(properties != null)
+                {
+                    foreach(PropertyAnalysis prop in properties)
+                    {
+                        ret += GetMetadataLengthForProperty(prop);
+                    }
+                }
+
+                // Add the size of the property name.
+                ret += (uint)((property.name.Length + 1) * 2);
+            }
+            else
+            {
+                ret += (uint)(sizeof(uint) + ((property.name.Length + 1) * 2));
+            }
+
+            return ret;
+        }
+
+        private static TypeCode GetTypeCodeExtended(Type parameterType)
+        {
+            // Guid is not part of TypeCode, we decided to use 17 to represent it, as it's the "free slot"
+            // see https://github.com/dotnet/coreclr/issues/16105#issuecomment-361749750 for more
+            const TypeCode GuidTypeCode = (TypeCode)17;
+
+            if (parameterType == typeof(Guid)) // Guid is not a part of TypeCode enum
+                return GuidTypeCode;
+
+            return Type.GetTypeCode(parameterType);
+        }
+    }
+
+#endif // FEATURE_PERFTRACING
+}
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventSource_CoreCLR.cs b/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventSource_CoreCLR.cs
new file mode 100644
index 0000000000..4233e46bbd
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventSource_CoreCLR.cs
@@ -0,0 +1,230 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
+using Microsoft.Reflection;
+using Microsoft.Win32;
+
+namespace System.Diagnostics.Tracing
+{
+    public partial class EventSource
+    {
+        // ActivityID support (see also WriteEventWithRelatedActivityIdCore)
+        /// <summary>
+        /// When a thread starts work that is on behalf of 'something else' (typically another 
+        /// thread or network request) it should mark the thread as working on that other work.
+        /// This API marks the current thread as working on activity 'activityID'. This API
+        /// should be used when the caller knows the thread's current activity (the one being
+        /// overwritten) has completed. Otherwise, callers should prefer the overload that
+        /// return the oldActivityThatWillContinue (below).
+        /// 
+        /// All events created with the EventSource on this thread are also tagged with the 
+        /// activity ID of the thread. 
+        /// 
+        /// It is common, and good practice after setting the thread to an activity to log an event
+        /// with a 'start' opcode to indicate that precise time/thread where the new activity 
+        /// started.
+        /// </summary>
+        /// <param name="activityId">A Guid that represents the new activity with which to mark 
+        /// the current thread</param>
+        public static void SetCurrentThreadActivityId(Guid activityId)
+        {
+            if (TplEtwProvider.Log != null)
+                TplEtwProvider.Log.SetActivityId(activityId);
+
+            // We ignore errors to keep with the convention that EventSources do not throw errors.
+            // Note we can't access m_throwOnWrites because this is a static method.  
+#if FEATURE_MANAGED_ETW
+#if FEATURE_PERFTRACING
+            // Set the activity id via EventPipe.
+            EventPipeInternal.EventActivityIdControl(
+                (uint)UnsafeNativeMethods.ManifestEtw.ActivityControl.EVENT_ACTIVITY_CTRL_SET_ID,
+                ref activityId);
+#endif // FEATURE_PERFTRACING
+#if PLATFORM_WINDOWS
+            // Set the activity id via ETW.
+            UnsafeNativeMethods.ManifestEtw.EventActivityIdControl(
+                UnsafeNativeMethods.ManifestEtw.ActivityControl.EVENT_ACTIVITY_CTRL_SET_ID,
+                ref activityId);
+#endif // PLATFORM_WINDOWS
+#endif // FEATURE_MANAGED_ETW
+        }
+
+        /// <summary>
+        /// When a thread starts work that is on behalf of 'something else' (typically another 
+        /// thread or network request) it should mark the thread as working on that other work.
+        /// This API marks the current thread as working on activity 'activityID'. It returns 
+        /// whatever activity the thread was previously marked with. There is a convention that
+        /// callers can assume that callees restore this activity mark before the callee returns. 
+        /// To encourage this, this API returns the old activity, so that it can be restored later.
+        /// 
+        /// All events created with the EventSource on this thread are also tagged with the 
+        /// activity ID of the thread. 
+        /// 
+        /// It is common, and good practice after setting the thread to an activity to log an event
+        /// with a 'start' opcode to indicate that precise time/thread where the new activity 
+        /// started.
+        /// </summary>
+        /// <param name="activityId">A Guid that represents the new activity with which to mark 
+        /// the current thread</param>
+        /// <param name="oldActivityThatWillContinue">The Guid that represents the current activity  
+        /// which will continue at some point in the future, on the current thread</param>
+        public static void SetCurrentThreadActivityId(Guid activityId, out Guid oldActivityThatWillContinue)
+        {
+            oldActivityThatWillContinue = activityId;
+#if FEATURE_MANAGED_ETW
+            // We ignore errors to keep with the convention that EventSources do not throw errors.
+            // Note we can't access m_throwOnWrites because this is a static method.  
+
+#if FEATURE_PERFTRACING && PLATFORM_WINDOWS
+            EventPipeInternal.EventActivityIdControl(
+                (uint)UnsafeNativeMethods.ManifestEtw.ActivityControl.EVENT_ACTIVITY_CTRL_SET_ID,
+                    ref oldActivityThatWillContinue);
+#elif FEATURE_PERFTRACING
+            EventPipeInternal.EventActivityIdControl(
+                (uint)UnsafeNativeMethods.ManifestEtw.ActivityControl.EVENT_ACTIVITY_CTRL_GET_SET_ID,
+                    ref oldActivityThatWillContinue);
+#endif // FEATURE_PERFTRACING && PLATFORM_WINDOWS
+
+#if PLATFORM_WINDOWS
+            UnsafeNativeMethods.ManifestEtw.EventActivityIdControl(
+                UnsafeNativeMethods.ManifestEtw.ActivityControl.EVENT_ACTIVITY_CTRL_GET_SET_ID,
+                    ref oldActivityThatWillContinue);
+#endif // PLATFORM_WINDOWS
+#endif // FEATURE_MANAGED_ETW
+
+            // We don't call the activityDying callback here because the caller has declared that
+            // it is not dying.  
+            if (TplEtwProvider.Log != null)
+                TplEtwProvider.Log.SetActivityId(activityId);
+        }
+
+        /// <summary>
+        /// Retrieves the ETW activity ID associated with the current thread.
+        /// </summary>
+        public static Guid CurrentThreadActivityId
+        {
+            get
+            {
+                // We ignore errors to keep with the convention that EventSources do not throw 
+                // errors. Note we can't access m_throwOnWrites because this is a static method.
+                Guid retVal = new Guid();
+#if FEATURE_MANAGED_ETW
+#if PLATFORM_WINDOWS
+                UnsafeNativeMethods.ManifestEtw.EventActivityIdControl(
+                    UnsafeNativeMethods.ManifestEtw.ActivityControl.EVENT_ACTIVITY_CTRL_GET_ID,
+                    ref retVal);
+#elif FEATURE_PERFTRACING
+                EventPipeInternal.EventActivityIdControl(
+                    (uint)UnsafeNativeMethods.ManifestEtw.ActivityControl.EVENT_ACTIVITY_CTRL_GET_ID,
+                    ref retVal);
+#endif // PLATFORM_WINDOWS
+#endif // FEATURE_MANAGED_ETW
+                return retVal;
+            }
+        }
+
+        private int GetParameterCount(EventMetadata eventData)
+        {
+            return eventData.Parameters.Length;
+        }
+
+        private Type GetDataType(EventMetadata eventData, int parameterId)
+        {
+            return eventData.Parameters[parameterId].ParameterType;
+        }
+
+        private static string GetResourceString(string key, params object[] args)
+        {
+            return SR.Format(SR.GetResourceString(key), args);
+        }
+
+        private static readonly bool m_EventSourcePreventRecursion = false;
+    }
+
+    internal partial class ManifestBuilder
+    {
+        private string GetTypeNameHelper(Type type)
+        {
+            switch (type.GetTypeCode())
+            {
+                case TypeCode.Boolean:
+                    return "win:Boolean";
+                case TypeCode.Byte:
+                    return "win:UInt8";
+                case TypeCode.Char:
+                case TypeCode.UInt16:
+                    return "win:UInt16";
+                case TypeCode.UInt32:
+                    return "win:UInt32";
+                case TypeCode.UInt64:
+                    return "win:UInt64";
+                case TypeCode.SByte:
+                    return "win:Int8";
+                case TypeCode.Int16:
+                    return "win:Int16";
+                case TypeCode.Int32:
+                    return "win:Int32";
+                case TypeCode.Int64:
+                    return "win:Int64";
+                case TypeCode.String:
+                    return "win:UnicodeString";
+                case TypeCode.Single:
+                    return "win:Float";
+                case TypeCode.Double:
+                    return "win:Double";
+                case TypeCode.DateTime:
+                    return "win:FILETIME";
+                default:
+                    if (type == typeof(Guid))
+                        return "win:GUID";
+                    else if (type == typeof(IntPtr))
+                        return "win:Pointer";
+                    else if ((type.IsArray || type.IsPointer) && type.GetElementType() == typeof(byte))
+                        return "win:Binary";
+
+                    ManifestError(Resources.GetResourceString("EventSource_UnsupportedEventTypeInManifest", type.Name), true);
+                    return string.Empty;
+            }
+        }
+    }
+
+    internal partial class EventProvider
+    {
+        internal unsafe int SetInformation(
+            UnsafeNativeMethods.ManifestEtw.EVENT_INFO_CLASS eventInfoClass,
+            IntPtr data,
+            uint dataSize)
+        {
+            int status = UnsafeNativeMethods.ManifestEtw.ERROR_NOT_SUPPORTED;
+
+            if (!m_setInformationMissing)
+            {
+                try
+                {
+                    status = UnsafeNativeMethods.ManifestEtw.EventSetInformation(
+                        m_regHandle,
+                        eventInfoClass,
+                        (void*)data,
+                        (int)dataSize);
+                }
+                catch (TypeLoadException)
+                {
+                    m_setInformationMissing = true;
+                }
+            }
+
+            return status;
+        }
+    }
+
+    internal static class Resources
+    {
+        internal static string GetResourceString(string key, params object[] args)
+        {
+            return SR.Format(SR.GetResourceString(key), args);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/FrameworkEventSource.cs b/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/FrameworkEventSource.cs
new file mode 100644
index 0000000000..a1fbc1a6b9
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/FrameworkEventSource.cs
@@ -0,0 +1,745 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+// ResourcesEtwProvider.cs
+//
+//
+// Managed event source for things that can version with MSCORLIB.  
+//
+
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Reflection;
+using System.Text;
+using System.Runtime.CompilerServices;
+
+namespace System.Diagnostics.Tracing
+{
+    // To use the framework provider
+    // 
+    //     \\clrmain\tools\Perfmonitor /nokernel /noclr /provider:8E9F5090-2D75-4d03-8A81-E5AFBF85DAF1 start
+    //     Run run your app
+    //     \\clrmain\tools\Perfmonitor stop
+    //     \\clrmain\tools\Perfmonitor print
+    //
+    // This will produce an XML file, where each event is pretty-printed with all its arguments nicely parsed.
+    //
+    // [FriendAccessAllowed]
+    [EventSource(Guid = "8E9F5090-2D75-4d03-8A81-E5AFBF85DAF1", Name = "System.Diagnostics.Eventing.FrameworkEventSource")]
+    sealed internal class FrameworkEventSource : EventSource
+    {
+        // Defines the singleton instance for the Resources ETW provider
+        public static readonly FrameworkEventSource Log = new FrameworkEventSource();
+
+        // Keyword definitions.  These represent logical groups of events that can be turned on and off independently
+        // Often each task has a keyword, but where tasks are determined by subsystem, keywords are determined by
+        // usefulness to end users to filter.  Generally users don't mind extra events if they are not high volume
+        // so grouping low volume events together in a single keywords is OK (users can post-filter by task if desired)
+        public static class Keywords
+        {
+            public const EventKeywords Loader = (EventKeywords)0x0001; // This is bit 0
+            public const EventKeywords ThreadPool = (EventKeywords)0x0002;
+            public const EventKeywords NetClient = (EventKeywords)0x0004;
+            //
+            // This is a private event we do not want to expose to customers.  It is to be used for profiling
+            // uses of dynamic type loading by ProjectN applications running on the desktop CLR
+            //
+            public const EventKeywords DynamicTypeUsage = (EventKeywords)0x0008;
+            public const EventKeywords ThreadTransfer = (EventKeywords)0x0010;
+        }
+
+        /// <summary>ETW tasks that have start/stop events.</summary>
+        public static class Tasks // this name is important for EventSource
+        {
+            /// <summary>Begin / End - GetResponse.</summary>
+            public const EventTask GetResponse = (EventTask)1;
+            /// <summary>Begin / End - GetRequestStream</summary>
+            public const EventTask GetRequestStream = (EventTask)2;
+            /// <summary>Send / Receive - begin transfer/end transfer</summary>
+            public const EventTask ThreadTransfer = (EventTask)3;
+        }
+
+        public static class Opcodes
+        {
+            public const EventOpcode ReceiveHandled = (EventOpcode)11;
+        }
+
+        // This predicate is used by consumers of this class to deteremine if the class has actually been initialized,
+        // and therefore if the public statics are available for use. This is typically not a problem... if the static
+        // class constructor fails, then attempts to access the statics (or even this property) will result in a 
+        // TypeInitializationException. However, that is not the case while the class loader is actually trying to construct
+        // the TypeInitializationException instance to represent that failure, and some consumers of this class are on
+        // that code path, specifically the resource manager. 
+        public static bool IsInitialized
+        {
+            get
+            {
+                return Log != null;
+            }
+        }
+
+        // The FrameworkEventSource GUID is {8E9F5090-2D75-4d03-8A81-E5AFBF85DAF1}
+        private FrameworkEventSource() : base(new Guid(0x8e9f5090, 0x2d75, 0x4d03, 0x8a, 0x81, 0xe5, 0xaf, 0xbf, 0x85, 0xda, 0xf1), "System.Diagnostics.Eventing.FrameworkEventSource") { }
+
+        // WriteEvent overloads (to avoid the "params" EventSource.WriteEvent
+
+        // optimized for common signatures (used by the ThreadTransferSend/Receive events)
+        [NonEvent]
+#if !CORECLR
+        [System.Security.SecuritySafeCritical]
+#endif // !CORECLR
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        private unsafe void WriteEvent(int eventId, long arg1, int arg2, string arg3, bool arg4)
+        {
+            if (IsEnabled())
+            {
+                if (arg3 == null) arg3 = "";
+                fixed (char* string3Bytes = arg3)
+                {
+                    EventSource.EventData* descrs = stackalloc EventSource.EventData[4];
+                    descrs[0].DataPointer = (IntPtr)(&arg1);
+                    descrs[0].Size = 8;
+                    descrs[0].Reserved = 0;
+                    descrs[1].DataPointer = (IntPtr)(&arg2);
+                    descrs[1].Size = 4;
+                    descrs[1].Reserved = 0;
+                    descrs[2].DataPointer = (IntPtr)string3Bytes;
+                    descrs[2].Size = ((arg3.Length + 1) * 2);
+                    descrs[2].Reserved = 0;
+                    descrs[3].DataPointer = (IntPtr)(&arg4);
+                    descrs[3].Size = 4;
+                    descrs[3].Reserved = 0;
+                    WriteEventCore(eventId, 4, descrs);
+                }
+            }
+        }
+
+        // optimized for common signatures (used by the ThreadTransferSend/Receive events)
+        [NonEvent]
+#if !CORECLR
+        [System.Security.SecuritySafeCritical]
+#endif // !CORECLR
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        private unsafe void WriteEvent(int eventId, long arg1, int arg2, string arg3)
+        {
+            if (IsEnabled())
+            {
+                if (arg3 == null) arg3 = "";
+                fixed (char* string3Bytes = arg3)
+                {
+                    EventSource.EventData* descrs = stackalloc EventSource.EventData[3];
+                    descrs[0].DataPointer = (IntPtr)(&arg1);
+                    descrs[0].Size = 8;
+                    descrs[0].Reserved = 0;
+                    descrs[1].DataPointer = (IntPtr)(&arg2);
+                    descrs[1].Size = 4;
+                    descrs[1].Reserved = 0;
+                    descrs[2].DataPointer = (IntPtr)string3Bytes;
+                    descrs[2].Size = ((arg3.Length + 1) * 2);
+                    descrs[2].Reserved = 0;
+                    WriteEventCore(eventId, 3, descrs);
+                }
+            }
+        }
+
+        // optimized for common signatures (used by the BeginGetResponse/BeginGetRequestStream events)
+        [NonEvent]
+#if !CORECLR
+        [System.Security.SecuritySafeCritical]
+#endif // !CORECLR
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        private unsafe void WriteEvent(int eventId, long arg1, string arg2, bool arg3, bool arg4)
+        {
+            if (IsEnabled())
+            {
+                if (arg2 == null) arg2 = "";
+                fixed (char* string2Bytes = arg2)
+                {
+                    EventSource.EventData* descrs = stackalloc EventSource.EventData[4];
+                    descrs[0].DataPointer = (IntPtr)(&arg1);
+                    descrs[0].Size = 8;
+                    descrs[0].Reserved = 0;
+                    descrs[1].DataPointer = (IntPtr)string2Bytes;
+                    descrs[1].Size = ((arg2.Length + 1) * 2);
+                    descrs[1].Reserved = 0;
+                    descrs[2].DataPointer = (IntPtr)(&arg3);
+                    descrs[2].Size = 4;
+                    descrs[2].Reserved = 0;
+                    descrs[3].DataPointer = (IntPtr)(&arg4);
+                    descrs[3].Size = 4;
+                    descrs[3].Reserved = 0;
+                    WriteEventCore(eventId, 4, descrs);
+                }
+            }
+        }
+
+        // optimized for common signatures (used by the EndGetRequestStream event)
+        [NonEvent]
+#if !CORECLR
+        [System.Security.SecuritySafeCritical]
+#endif // !CORECLR
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        private unsafe void WriteEvent(int eventId, long arg1, bool arg2, bool arg3)
+        {
+            if (IsEnabled())
+            {
+                EventSource.EventData* descrs = stackalloc EventSource.EventData[3];
+                descrs[0].DataPointer = (IntPtr)(&arg1);
+                descrs[0].Size = 8;
+                descrs[0].Reserved = 0;
+                descrs[1].DataPointer = (IntPtr)(&arg2);
+                descrs[1].Size = 4;
+                descrs[1].Reserved = 0;
+                descrs[2].DataPointer = (IntPtr)(&arg3);
+                descrs[2].Size = 4;
+                descrs[2].Reserved = 0;
+                WriteEventCore(eventId, 3, descrs);
+            }
+        }
+
+        // optimized for common signatures (used by the EndGetResponse event)
+        [NonEvent]
+#if !CORECLR
+        [System.Security.SecuritySafeCritical]
+#endif // !CORECLR
+        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "This does not need to be correct when racing with other threads")]
+        private unsafe void WriteEvent(int eventId, long arg1, bool arg2, bool arg3, int arg4)
+        {
+            if (IsEnabled())
+            {
+                EventSource.EventData* descrs = stackalloc EventSource.EventData[4];
+                descrs[0].DataPointer = (IntPtr)(&arg1);
+                descrs[0].Size = 8;
+                descrs[0].Reserved = 0;
+                descrs[1].DataPointer = (IntPtr)(&arg2);
+                descrs[1].Size = 4;
+                descrs[1].Reserved = 0;
+                descrs[2].DataPointer = (IntPtr)(&arg3);
+                descrs[2].Size = 4;
+                descrs[2].Reserved = 0;
+                descrs[3].DataPointer = (IntPtr)(&arg4);
+                descrs[3].Size = 4;
+                descrs[3].Reserved = 0;
+                WriteEventCore(eventId, 4, descrs);
+            }
+        }
+
+        // ResourceManager Event Definitions 
+
+        [Event(1, Level = EventLevel.Informational, Keywords = Keywords.Loader)]
+        public void ResourceManagerLookupStarted(String baseName, String mainAssemblyName, String cultureName)
+        {
+            WriteEvent(1, baseName, mainAssemblyName, cultureName);
+        }
+
+        [Event(2, Level = EventLevel.Informational, Keywords = Keywords.Loader)]
+        public void ResourceManagerLookingForResourceSet(String baseName, String mainAssemblyName, String cultureName)
+        {
+            if (IsEnabled())
+                WriteEvent(2, baseName, mainAssemblyName, cultureName);
+        }
+
+        [Event(3, Level = EventLevel.Informational, Keywords = Keywords.Loader)]
+        public void ResourceManagerFoundResourceSetInCache(String baseName, String mainAssemblyName, String cultureName)
+        {
+            if (IsEnabled())
+                WriteEvent(3, baseName, mainAssemblyName, cultureName);
+        }
+
+        // After loading a satellite assembly, we already have the ResourceSet for this culture in
+        // the cache. This can happen if you have an assembly load callback that called into this
+        // instance of the ResourceManager.
+        [Event(4, Level = EventLevel.Warning, Keywords = Keywords.Loader)]
+        public void ResourceManagerFoundResourceSetInCacheUnexpected(String baseName, String mainAssemblyName, String cultureName)
+        {
+            if (IsEnabled())
+                WriteEvent(4, baseName, mainAssemblyName, cultureName);
+        }
+
+        // manifest resource stream lookup succeeded
+        [Event(5, Level = EventLevel.Informational, Keywords = Keywords.Loader)]
+        public void ResourceManagerStreamFound(String baseName, String mainAssemblyName, String cultureName, String loadedAssemblyName, String resourceFileName)
+        {
+            if (IsEnabled())
+                WriteEvent(5, baseName, mainAssemblyName, cultureName, loadedAssemblyName, resourceFileName);
+        }
+
+        // manifest resource stream lookup failed
+        [Event(6, Level = EventLevel.Warning, Keywords = Keywords.Loader)]
+        public void ResourceManagerStreamNotFound(String baseName, String mainAssemblyName, String cultureName, String loadedAssemblyName, String resourceFileName)
+        {
+            if (IsEnabled())
+                WriteEvent(6, baseName, mainAssemblyName, cultureName, loadedAssemblyName, resourceFileName);
+        }
+
+        [Event(7, Level = EventLevel.Informational, Keywords = Keywords.Loader)]
+        public void ResourceManagerGetSatelliteAssemblySucceeded(String baseName, String mainAssemblyName, String cultureName, String assemblyName)
+        {
+            if (IsEnabled())
+                WriteEvent(7, baseName, mainAssemblyName, cultureName, assemblyName);
+        }
+
+        [Event(8, Level = EventLevel.Warning, Keywords = Keywords.Loader)]
+        public void ResourceManagerGetSatelliteAssemblyFailed(String baseName, String mainAssemblyName, String cultureName, String assemblyName)
+        {
+            if (IsEnabled())
+                WriteEvent(8, baseName, mainAssemblyName, cultureName, assemblyName);
+        }
+
+        [Event(9, Level = EventLevel.Informational, Keywords = Keywords.Loader)]
+        public void ResourceManagerCaseInsensitiveResourceStreamLookupSucceeded(String baseName, String mainAssemblyName, String assemblyName, String resourceFileName)
+        {
+            if (IsEnabled())
+                WriteEvent(9, baseName, mainAssemblyName, assemblyName, resourceFileName);
+        }
+
+        [Event(10, Level = EventLevel.Warning, Keywords = Keywords.Loader)]
+        public void ResourceManagerCaseInsensitiveResourceStreamLookupFailed(String baseName, String mainAssemblyName, String assemblyName, String resourceFileName)
+        {
+            if (IsEnabled())
+                WriteEvent(10, baseName, mainAssemblyName, assemblyName, resourceFileName);
+        }
+
+        // Could not access the manifest resource the assembly
+        [Event(11, Level = EventLevel.Error, Keywords = Keywords.Loader)]
+        public void ResourceManagerManifestResourceAccessDenied(String baseName, String mainAssemblyName, String assemblyName, String canonicalName)
+        {
+            if (IsEnabled())
+                WriteEvent(11, baseName, mainAssemblyName, assemblyName, canonicalName);
+        }
+
+        // Neutral resources are sufficient for this culture. Skipping satellites
+        [Event(12, Level = EventLevel.Informational, Keywords = Keywords.Loader)]
+        public void ResourceManagerNeutralResourcesSufficient(String baseName, String mainAssemblyName, String cultureName)
+        {
+            if (IsEnabled())
+                WriteEvent(12, baseName, mainAssemblyName, cultureName);
+        }
+
+        [Event(13, Level = EventLevel.Warning, Keywords = Keywords.Loader)]
+        public void ResourceManagerNeutralResourceAttributeMissing(String mainAssemblyName)
+        {
+            if (IsEnabled())
+                WriteEvent(13, mainAssemblyName);
+        }
+
+        [Event(14, Level = EventLevel.Informational, Keywords = Keywords.Loader)]
+        public void ResourceManagerCreatingResourceSet(String baseName, String mainAssemblyName, String cultureName, String fileName)
+        {
+            if (IsEnabled())
+                WriteEvent(14, baseName, mainAssemblyName, cultureName, fileName);
+        }
+
+        [Event(15, Level = EventLevel.Informational, Keywords = Keywords.Loader)]
+        public void ResourceManagerNotCreatingResourceSet(String baseName, String mainAssemblyName, String cultureName)
+        {
+            if (IsEnabled())
+                WriteEvent(15, baseName, mainAssemblyName, cultureName);
+        }
+
+        [Event(16, Level = EventLevel.Warning, Keywords = Keywords.Loader)]
+        public void ResourceManagerLookupFailed(String baseName, String mainAssemblyName, String cultureName)
+        {
+            if (IsEnabled())
+                WriteEvent(16, baseName, mainAssemblyName, cultureName);
+        }
+
+        [Event(17, Level = EventLevel.Informational, Keywords = Keywords.Loader)]
+        public void ResourceManagerReleasingResources(String baseName, String mainAssemblyName)
+        {
+            if (IsEnabled())
+                WriteEvent(17, baseName, mainAssemblyName);
+        }
+
+        [Event(18, Level = EventLevel.Warning, Keywords = Keywords.Loader)]
+        public void ResourceManagerNeutralResourcesNotFound(String baseName, String mainAssemblyName, String resName)
+        {
+            if (IsEnabled())
+                WriteEvent(18, baseName, mainAssemblyName, resName);
+        }
+
+        [Event(19, Level = EventLevel.Informational, Keywords = Keywords.Loader)]
+        public void ResourceManagerNeutralResourcesFound(String baseName, String mainAssemblyName, String resName)
+        {
+            if (IsEnabled())
+                WriteEvent(19, baseName, mainAssemblyName, resName);
+        }
+
+        [Event(20, Level = EventLevel.Informational, Keywords = Keywords.Loader)]
+        public void ResourceManagerAddingCultureFromConfigFile(String baseName, String mainAssemblyName, String cultureName)
+        {
+            if (IsEnabled())
+                WriteEvent(20, baseName, mainAssemblyName, cultureName);
+        }
+
+        [Event(21, Level = EventLevel.Informational, Keywords = Keywords.Loader)]
+        public void ResourceManagerCultureNotFoundInConfigFile(String baseName, String mainAssemblyName, String cultureName)
+        {
+            if (IsEnabled())
+                WriteEvent(21, baseName, mainAssemblyName, cultureName);
+        }
+
+        [Event(22, Level = EventLevel.Informational, Keywords = Keywords.Loader)]
+        public void ResourceManagerCultureFoundInConfigFile(String baseName, String mainAssemblyName, String cultureName)
+        {
+            if (IsEnabled())
+                WriteEvent(22, baseName, mainAssemblyName, cultureName);
+        }
+
+
+        // ResourceManager Event Wrappers
+
+        [NonEvent]
+        public void ResourceManagerLookupStarted(String baseName, Assembly mainAssembly, String cultureName)
+        {
+            if (IsEnabled())
+                ResourceManagerLookupStarted(baseName, GetName(mainAssembly), cultureName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerLookingForResourceSet(String baseName, Assembly mainAssembly, String cultureName)
+        {
+            if (IsEnabled())
+                ResourceManagerLookingForResourceSet(baseName, GetName(mainAssembly), cultureName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerFoundResourceSetInCache(String baseName, Assembly mainAssembly, String cultureName)
+        {
+            if (IsEnabled())
+                ResourceManagerFoundResourceSetInCache(baseName, GetName(mainAssembly), cultureName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerFoundResourceSetInCacheUnexpected(String baseName, Assembly mainAssembly, String cultureName)
+        {
+            if (IsEnabled())
+                ResourceManagerFoundResourceSetInCacheUnexpected(baseName, GetName(mainAssembly), cultureName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerStreamFound(String baseName, Assembly mainAssembly, String cultureName, Assembly loadedAssembly, String resourceFileName)
+        {
+            if (IsEnabled())
+                ResourceManagerStreamFound(baseName, GetName(mainAssembly), cultureName, GetName(loadedAssembly), resourceFileName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerStreamNotFound(String baseName, Assembly mainAssembly, String cultureName, Assembly loadedAssembly, String resourceFileName)
+        {
+            if (IsEnabled())
+                ResourceManagerStreamNotFound(baseName, GetName(mainAssembly), cultureName, GetName(loadedAssembly), resourceFileName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerGetSatelliteAssemblySucceeded(String baseName, Assembly mainAssembly, String cultureName, String assemblyName)
+        {
+            if (IsEnabled())
+                ResourceManagerGetSatelliteAssemblySucceeded(baseName, GetName(mainAssembly), cultureName, assemblyName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerGetSatelliteAssemblyFailed(String baseName, Assembly mainAssembly, String cultureName, String assemblyName)
+        {
+            if (IsEnabled())
+                ResourceManagerGetSatelliteAssemblyFailed(baseName, GetName(mainAssembly), cultureName, assemblyName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerCaseInsensitiveResourceStreamLookupSucceeded(String baseName, Assembly mainAssembly, String assemblyName, String resourceFileName)
+        {
+            if (IsEnabled())
+                ResourceManagerCaseInsensitiveResourceStreamLookupSucceeded(baseName, GetName(mainAssembly), assemblyName, resourceFileName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerCaseInsensitiveResourceStreamLookupFailed(String baseName, Assembly mainAssembly, String assemblyName, String resourceFileName)
+        {
+            if (IsEnabled())
+                ResourceManagerCaseInsensitiveResourceStreamLookupFailed(baseName, GetName(mainAssembly), assemblyName, resourceFileName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerManifestResourceAccessDenied(String baseName, Assembly mainAssembly, String assemblyName, String canonicalName)
+        {
+            if (IsEnabled())
+                ResourceManagerManifestResourceAccessDenied(baseName, GetName(mainAssembly), assemblyName, canonicalName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerNeutralResourcesSufficient(String baseName, Assembly mainAssembly, String cultureName)
+        {
+            if (IsEnabled())
+                ResourceManagerNeutralResourcesSufficient(baseName, GetName(mainAssembly), cultureName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerNeutralResourceAttributeMissing(Assembly mainAssembly)
+        {
+            if (IsEnabled())
+                ResourceManagerNeutralResourceAttributeMissing(GetName(mainAssembly));
+        }
+
+        [NonEvent]
+        public void ResourceManagerCreatingResourceSet(String baseName, Assembly mainAssembly, String cultureName, String fileName)
+        {
+            if (IsEnabled())
+                ResourceManagerCreatingResourceSet(baseName, GetName(mainAssembly), cultureName, fileName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerNotCreatingResourceSet(String baseName, Assembly mainAssembly, String cultureName)
+        {
+            if (IsEnabled())
+                ResourceManagerNotCreatingResourceSet(baseName, GetName(mainAssembly), cultureName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerLookupFailed(String baseName, Assembly mainAssembly, String cultureName)
+        {
+            if (IsEnabled())
+                ResourceManagerLookupFailed(baseName, GetName(mainAssembly), cultureName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerReleasingResources(String baseName, Assembly mainAssembly)
+        {
+            if (IsEnabled())
+                ResourceManagerReleasingResources(baseName, GetName(mainAssembly));
+        }
+
+        [NonEvent]
+        public void ResourceManagerNeutralResourcesNotFound(String baseName, Assembly mainAssembly, String resName)
+        {
+            if (IsEnabled())
+                ResourceManagerNeutralResourcesNotFound(baseName, GetName(mainAssembly), resName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerNeutralResourcesFound(String baseName, Assembly mainAssembly, String resName)
+        {
+            if (IsEnabled())
+                ResourceManagerNeutralResourcesFound(baseName, GetName(mainAssembly), resName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerAddingCultureFromConfigFile(String baseName, Assembly mainAssembly, String cultureName)
+        {
+            if (IsEnabled())
+                ResourceManagerAddingCultureFromConfigFile(baseName, GetName(mainAssembly), cultureName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerCultureNotFoundInConfigFile(String baseName, Assembly mainAssembly, String cultureName)
+        {
+            if (IsEnabled())
+                ResourceManagerCultureNotFoundInConfigFile(baseName, GetName(mainAssembly), cultureName);
+        }
+
+        [NonEvent]
+        public void ResourceManagerCultureFoundInConfigFile(String baseName, Assembly mainAssembly, String cultureName)
+        {
+            if (IsEnabled())
+                ResourceManagerCultureFoundInConfigFile(baseName, GetName(mainAssembly), cultureName);
+        }
+
+        private static string GetName(Assembly assembly)
+        {
+            if (assembly == null)
+                return "<<NULL>>";
+            else
+                return assembly.FullName;
+        }
+
+        [Event(30, Level = EventLevel.Verbose, Keywords = Keywords.ThreadPool | Keywords.ThreadTransfer)]
+        public void ThreadPoolEnqueueWork(long workID)
+        {
+            WriteEvent(30, workID);
+        }
+        [NonEvent]
+#if !CORECLR
+        [System.Security.SecuritySafeCritical]
+#endif // !CORECLR
+        public unsafe void ThreadPoolEnqueueWorkObject(object workID)
+        {
+            // convert the Object Id to a long
+            ThreadPoolEnqueueWork((long)*((void**)JitHelpers.UnsafeCastToStackPointer(ref workID)));
+        }
+
+        [Event(31, Level = EventLevel.Verbose, Keywords = Keywords.ThreadPool | Keywords.ThreadTransfer)]
+        public void ThreadPoolDequeueWork(long workID)
+        {
+            WriteEvent(31, workID);
+        }
+
+        [NonEvent]
+#if !CORECLR
+        [System.Security.SecuritySafeCritical]
+#endif // !CORECLR
+        public unsafe void ThreadPoolDequeueWorkObject(object workID)
+        {
+            // convert the Object Id to a long
+            ThreadPoolDequeueWork((long)*((void**)JitHelpers.UnsafeCastToStackPointer(ref workID)));
+        }
+
+        // In the desktop runtime they don't use Tasks for the point at which the response happens, which means that the
+        // Activity ID created by start using implicit activity IDs does not match.   Thus disable implicit activities (until we fix that)
+        [Event(140, Level = EventLevel.Informational, Keywords = Keywords.NetClient, ActivityOptions = EventActivityOptions.Disable,
+         Task = Tasks.GetResponse, Opcode = EventOpcode.Start, Version = 1)]
+        private void GetResponseStart(long id, string uri, bool success, bool synchronous)
+        {
+            WriteEvent(140, id, uri, success, synchronous);
+        }
+
+        [Event(141, Level = EventLevel.Informational, Keywords = Keywords.NetClient, ActivityOptions = EventActivityOptions.Disable,
+         Task = Tasks.GetResponse, Opcode = EventOpcode.Stop, Version = 1)]
+        private void GetResponseStop(long id, bool success, bool synchronous, int statusCode)
+        {
+            WriteEvent(141, id, success, synchronous, statusCode);
+        }
+
+        // In the desktop runtime they don't use Tasks for the point at which the response happens, which means that the
+        // Activity ID created by start using implicit activity IDs does not match.   Thus disable implicit activities (until we fix that)
+        [Event(142, Level = EventLevel.Informational, Keywords = Keywords.NetClient, ActivityOptions = EventActivityOptions.Disable,
+         Task = Tasks.GetRequestStream, Opcode = EventOpcode.Start, Version = 1)]
+        private void GetRequestStreamStart(long id, string uri, bool success, bool synchronous)
+        {
+            WriteEvent(142, id, uri, success, synchronous);
+        }
+
+        [Event(143, Level = EventLevel.Informational, Keywords = Keywords.NetClient, ActivityOptions = EventActivityOptions.Disable,
+         Task = Tasks.GetRequestStream, Opcode = EventOpcode.Stop, Version = 1)]
+        private void GetRequestStreamStop(long id, bool success, bool synchronous)
+        {
+            WriteEvent(143, id, success, synchronous);
+        }
+
+        [NonEvent]
+#if !CORECLR
+        [System.Security.SecuritySafeCritical]
+#endif // !CORECLR
+        public unsafe void BeginGetResponse(object id, string uri, bool success, bool synchronous)
+        {
+            if (IsEnabled())
+                GetResponseStart(IdForObject(id), uri, success, synchronous);
+        }
+
+        [NonEvent]
+#if !CORECLR
+        [System.Security.SecuritySafeCritical]
+#endif // !CORECLR
+        public unsafe void EndGetResponse(object id, bool success, bool synchronous, int statusCode)
+        {
+            if (IsEnabled())
+                GetResponseStop(IdForObject(id), success, synchronous, statusCode);
+        }
+
+        [NonEvent]
+#if !CORECLR
+        [System.Security.SecuritySafeCritical]
+#endif // !CORECLR
+        public unsafe void BeginGetRequestStream(object id, string uri, bool success, bool synchronous)
+        {
+            if (IsEnabled())
+                GetRequestStreamStart(IdForObject(id), uri, success, synchronous);
+        }
+
+        [NonEvent]
+#if !CORECLR
+        [System.Security.SecuritySafeCritical]
+#endif // !CORECLR
+        public unsafe void EndGetRequestStream(object id, bool success, bool synchronous)
+        {
+            if (IsEnabled())
+                GetRequestStreamStop(IdForObject(id), success, synchronous);
+        }
+
+        // id -   represents a correlation ID that allows correlation of two activities, one stamped by 
+        //        ThreadTransferSend, the other by ThreadTransferReceive
+        // kind - identifies the transfer: values below 64 are reserved for the runtime. Currently used values:
+        //        1 - managed Timers ("roaming" ID)
+        //        2 - managed async IO operations (FileStream, PipeStream, a.o.)
+        //        3 - WinRT dispatch operations
+        // info - any additional information user code might consider interesting
+        [Event(150, Level = EventLevel.Informational, Keywords = Keywords.ThreadTransfer, Task = Tasks.ThreadTransfer, Opcode = EventOpcode.Send)]
+        public void ThreadTransferSend(long id, int kind, string info, bool multiDequeues)
+        {
+            if (IsEnabled())
+                WriteEvent(150, id, kind, info, multiDequeues);
+        }
+        // id - is a managed object. it gets translated to the object's address. ETW listeners must
+        //      keep track of GC movements in order to correlate the value passed to XyzSend with the
+        //      (possibly changed) value passed to XyzReceive
+        [NonEvent]
+#if !CORECLR
+        [System.Security.SecuritySafeCritical]
+#endif // !CORECLR
+        public unsafe void ThreadTransferSendObj(object id, int kind, string info, bool multiDequeues)
+        {
+            ThreadTransferSend((long)*((void**)JitHelpers.UnsafeCastToStackPointer(ref id)), kind, info, multiDequeues);
+        }
+
+        // id -   represents a correlation ID that allows correlation of two activities, one stamped by 
+        //        ThreadTransferSend, the other by ThreadTransferReceive
+        // kind - identifies the transfer: values below 64 are reserved for the runtime. Currently used values:
+        //        1 - managed Timers ("roaming" ID)
+        //        2 - managed async IO operations (FileStream, PipeStream, a.o.)
+        //        3 - WinRT dispatch operations
+        // info - any additional information user code might consider interesting
+        [Event(151, Level = EventLevel.Informational, Keywords = Keywords.ThreadTransfer, Task = Tasks.ThreadTransfer, Opcode = EventOpcode.Receive)]
+        public void ThreadTransferReceive(long id, int kind, string info)
+        {
+            if (IsEnabled())
+                WriteEvent(151, id, kind, info);
+        }
+        // id - is a managed object. it gets translated to the object's address. ETW listeners must
+        //      keep track of GC movements in order to correlate the value passed to XyzSend with the
+        //      (possibly changed) value passed to XyzReceive
+        [NonEvent]
+#if !CORECLR
+        [System.Security.SecuritySafeCritical]
+#endif // !CORECLR
+        public unsafe void ThreadTransferReceiveObj(object id, int kind, string info)
+        {
+            ThreadTransferReceive((long)*((void**)JitHelpers.UnsafeCastToStackPointer(ref id)), kind, info);
+        }
+
+        // id -   represents a correlation ID that allows correlation of two activities, one stamped by 
+        //        ThreadTransferSend, the other by ThreadTransferReceive
+        // kind - identifies the transfer: values below 64 are reserved for the runtime. Currently used values:
+        //        1 - managed Timers ("roaming" ID)
+        //        2 - managed async IO operations (FileStream, PipeStream, a.o.)
+        //        3 - WinRT dispatch operations
+        // info - any additional information user code might consider interesting
+        [Event(152, Level = EventLevel.Informational, Keywords = Keywords.ThreadTransfer, Task = Tasks.ThreadTransfer, Opcode = Opcodes.ReceiveHandled)]
+        public void ThreadTransferReceiveHandled(long id, int kind, string info)
+        {
+            if (IsEnabled())
+                WriteEvent(152, id, kind, info);
+        }
+        // id - is a managed object. it gets translated to the object's address. ETW listeners must
+        //      keep track of GC movements in order to correlate the value passed to XyzSend with the
+        //      (possibly changed) value passed to XyzReceive
+        [NonEvent]
+#if !CORECLR
+        [System.Security.SecuritySafeCritical]
+#endif // !CORECLR
+        public unsafe void ThreadTransferReceiveHandledObj(object id, int kind, string info)
+        {
+            ThreadTransferReceive((long)*((void**)JitHelpers.UnsafeCastToStackPointer(ref id)), kind, info);
+        }
+
+        // return a stable ID for a an object.  We use the hash code which is not truely unique but is 
+        // close enough for now at least. we add to it 0x7FFFFFFF00000000 to make it distinguishable
+        // from the style of ID that simply casts the object reference to a long (since old versions of the 
+        // runtime will emit IDs of that form).  
+        private static long IdForObject(object obj)
+        {
+            return obj.GetHashCode() + 0x7FFFFFFF00000000;
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/XplatEventLogger.cs b/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/XplatEventLogger.cs
new file mode 100644
index 0000000000..31f79f5218
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/Eventing/XplatEventLogger.cs
@@ -0,0 +1,193 @@
+using System;
+using System.Runtime.CompilerServices;
+using System.Collections.ObjectModel;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Text;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+#if FEATURE_EVENTSOURCE_XPLAT
+
+namespace System.Diagnostics.Tracing
+{
+    internal  class XplatEventLogger : EventListener
+    {
+        private static Lazy<string> eventSourceNameFilter = new Lazy<string>(() => CompatibilitySwitch.GetValueInternal("EventSourceFilter"));
+        private static Lazy<string> eventSourceEventFilter = new Lazy<string>(() => CompatibilitySwitch.GetValueInternal("EventNameFilter"));
+        
+        public XplatEventLogger() {}
+
+        private static bool initializedPersistentListener = false;
+
+        public static EventListener InitializePersistentListener()
+        {
+            try{
+                if (!initializedPersistentListener && XplatEventLogger.IsEventSourceLoggingEnabled())
+                {
+                    initializedPersistentListener = true;
+                    return new XplatEventLogger();
+                }
+            }
+            catch(Exception){}
+
+            return null;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern bool IsEventSourceLoggingEnabled();
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void LogEventSource(int eventID, string eventName, string eventSourceName, string payload);
+
+        static List<char> escape_seq = new List<char> { '\b', '\f', '\n', '\r', '\t', '\"', '\\' };
+        static Dictionary<char, string> seq_mapping = new Dictionary<char, string>()
+        {
+            {'\b', "b"},
+            {'\f', "f"},
+            {'\n', "n"},
+            {'\r', "r"},
+            {'\t', "t"},
+            {'\"', "\\\""},
+            {'\\', "\\\\"}
+        };
+
+        private static void minimalJsonserializer(string payload, StringBuilder sb)
+        {
+            foreach( var elem in payload)
+            {
+                if (escape_seq.Contains(elem))
+                {
+                    sb.Append("\\\\");
+                    sb.Append(seq_mapping[elem]);
+                }
+                else
+                {
+                    sb.Append(elem);
+                }
+            }
+        }
+
+        private static string Serialize(ReadOnlyCollection<string> payloadName, ReadOnlyCollection<object> payload, string eventMessage)
+        {
+            if (payloadName == null || payload == null )
+                return String.Empty;
+
+            if (payloadName.Count == 0 || payload.Count == 0)
+                return String.Empty;
+
+            int eventDataCount = payloadName.Count;
+
+            if(payloadName.Count != payload.Count)
+            {
+               eventDataCount = Math.Min(payloadName.Count, payload.Count);
+            }
+
+            var sb = StringBuilderCache.Acquire();
+
+            sb.Append('{');
+
+            // If the event has a message, send that as well as a pseudo-field
+            if (!string.IsNullOrEmpty(eventMessage)) 
+            {
+                sb.Append("\\\"EventSource_Message\\\":\\\"");
+                minimalJsonserializer(eventMessage,sb);
+                sb.Append("\\\"");
+                if (eventDataCount != 0)
+                    sb.Append(", ");
+            }
+
+            for (int i = 0; i < eventDataCount; i++)
+            {
+                if (i != 0)
+                    sb.Append(", ");
+
+                var fieldstr = payloadName[i].ToString();
+
+                sb.Append("\\\"");
+                sb.Append(fieldstr);
+                sb.Append("\\\"");
+                sb.Append(':');
+
+                switch(payload[i])
+                {
+                    case string str:
+                    {
+                        sb.Append("\\\"");
+                        minimalJsonserializer(str, sb);
+                        sb.Append("\\\"");
+                        break;
+                    }
+                    case byte[] byteArr:
+                    {
+                        sb.Append("\\\"");
+                        AppendByteArrayAsHexString(sb, byteArr);
+                        sb.Append("\\\"");
+                        break;
+                    }
+                    default:
+                    {
+                        if(payload[i] != null)
+                        {
+                            sb.Append(payload[i].ToString());
+                        }
+                        break;
+                    }
+                }
+            }
+            sb.Append('}');
+            return StringBuilderCache.GetStringAndRelease(sb);
+        }
+
+        private static void AppendByteArrayAsHexString(StringBuilder builder, byte[] byteArray)
+        {
+            Debug.Assert(builder != null);
+            Debug.Assert(byteArray != null);
+
+            ReadOnlySpan<char> hexFormat = "X2";
+            Span<char> hex = stackalloc char[2];
+            for(int i=0; i<byteArray.Length; i++)
+            {
+                byteArray[i].TryFormat(hex, out int charsWritten, hexFormat);
+                Debug.Assert(charsWritten == 2);
+                builder.Append(hex);
+            }
+        }
+
+        internal protected  override void OnEventSourceCreated(EventSource eventSource)
+        {
+            string eventSourceFilter = eventSourceNameFilter.Value;
+            if (String.IsNullOrEmpty(eventSourceFilter) || (eventSource.Name.IndexOf(eventSourceFilter, StringComparison.OrdinalIgnoreCase) >= 0))
+            {   
+                EnableEvents(eventSource, EventLevel.LogAlways, EventKeywords.All, null);
+            }
+        }
+
+        internal protected  override void OnEventWritten(EventWrittenEventArgs eventData)
+        {
+            string eventFilter = eventSourceEventFilter.Value;
+            if (String.IsNullOrEmpty(eventFilter) || (eventData.EventName.IndexOf(eventFilter, StringComparison.OrdinalIgnoreCase) >= 0))
+            {
+                LogOnEventWritten(eventData);
+            }
+        }
+
+        private void LogOnEventWritten(EventWrittenEventArgs eventData)
+        {
+            string payload = "";
+            if (eventData.Payload != null)
+            {
+                try{
+                    payload = Serialize(eventData.PayloadNames, eventData.Payload, eventData.Message);
+                }
+                catch (Exception ex)
+                {
+                    payload = "XplatEventLogger failed with Exception " + ex.ToString();
+                }
+            }
+
+            LogEventSource( eventData.EventId, eventData.EventName,eventData.EventSource.Name,payload);
+        }
+    }
+}
+#endif //FEATURE_EVENTSOURCE_XPLAT
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/ICustomDebuggerNotification.cs b/src/System.Private.CoreLib/src/System/Diagnostics/ICustomDebuggerNotification.cs
new file mode 100644
index 0000000000..e7f41051f2
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/ICustomDebuggerNotification.cs
@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+** This interface is implemented by classes that support custom debugger notifications.
+**
+===========================================================*/
+
+using System;
+
+namespace System.Diagnostics
+{
+    // Defines an interface indicating that a custom debugger notification is requested under specific 
+    // conditions. Users should implement this interface to be used as an argument to 
+    // System.Diagnostics.Debugger.CustomNotification.  
+    internal interface ICustomDebuggerNotification
+    {
+        // Interface does not need to be marked with the serializable attribute
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/Stackframe.cs b/src/System.Private.CoreLib/src/System/Diagnostics/Stackframe.cs
new file mode 100644
index 0000000000..884188d071
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/Stackframe.cs
@@ -0,0 +1,285 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System.Text;
+using System;
+using System.IO;
+using System.Reflection;
+
+namespace System.Diagnostics
+{
+    // There is no good reason for the methods of this class to be virtual.
+    public class StackFrame
+    {
+        private MethodBase method;
+        private int offset;
+        private int ILOffset;
+        private String strFileName;
+        private int iLineNumber;
+        private int iColumnNumber;
+
+        [System.Runtime.Serialization.OptionalField]
+        private bool fIsLastFrameFromForeignExceptionStackTrace;
+
+        internal void InitMembers()
+        {
+            method = null;
+            offset = OFFSET_UNKNOWN;
+            ILOffset = OFFSET_UNKNOWN;
+            strFileName = null;
+            iLineNumber = 0;
+            iColumnNumber = 0;
+            fIsLastFrameFromForeignExceptionStackTrace = false;
+        }
+
+        // Constructs a StackFrame corresponding to the active stack frame.
+        public StackFrame()
+        {
+            InitMembers();
+            BuildStackFrame(0 + StackTrace.METHODS_TO_SKIP, false);// iSkipFrames=0
+        }
+
+        // Constructs a StackFrame corresponding to the active stack frame.
+        public StackFrame(bool fNeedFileInfo)
+        {
+            InitMembers();
+            BuildStackFrame(0 + StackTrace.METHODS_TO_SKIP, fNeedFileInfo);// iSkipFrames=0
+        }
+
+        // Constructs a StackFrame corresponding to a calling stack frame.
+        // 
+        public StackFrame(int skipFrames)
+        {
+            InitMembers();
+            BuildStackFrame(skipFrames + StackTrace.METHODS_TO_SKIP, false);
+        }
+
+        // Constructs a StackFrame corresponding to a calling stack frame.
+        // 
+        public StackFrame(int skipFrames, bool fNeedFileInfo)
+        {
+            InitMembers();
+            BuildStackFrame(skipFrames + StackTrace.METHODS_TO_SKIP, fNeedFileInfo);
+        }
+
+
+        // Called from the class "StackTrace"
+        // 
+        internal StackFrame(bool DummyFlag1, bool DummyFlag2)
+        {
+            InitMembers();
+        }
+
+        // Constructs a "fake" stack frame, just containing the given file
+        // name and line number.  Use when you don't want to use the 
+        // debugger's line mapping logic.
+        //
+        public StackFrame(String fileName, int lineNumber)
+        {
+            InitMembers();
+            BuildStackFrame(StackTrace.METHODS_TO_SKIP, false);
+            strFileName = fileName;
+            iLineNumber = lineNumber;
+            iColumnNumber = 0;
+        }
+
+
+        // Constructs a "fake" stack frame, just containing the given file
+        // name, line number and column number.  Use when you don't want to 
+        // use the debugger's line mapping logic.
+        //
+        public StackFrame(String fileName, int lineNumber, int colNumber)
+        {
+            InitMembers();
+            BuildStackFrame(StackTrace.METHODS_TO_SKIP, false);
+            strFileName = fileName;
+            iLineNumber = lineNumber;
+            iColumnNumber = colNumber;
+        }
+
+
+        // Constant returned when the native or IL offset is unknown
+        public const int OFFSET_UNKNOWN = -1;
+
+
+        internal virtual void SetMethodBase(MethodBase mb)
+        {
+            method = mb;
+        }
+
+        internal virtual void SetOffset(int iOffset)
+        {
+            offset = iOffset;
+        }
+
+        internal virtual void SetILOffset(int iOffset)
+        {
+            ILOffset = iOffset;
+        }
+
+        internal virtual void SetFileName(String strFName)
+        {
+            strFileName = strFName;
+        }
+
+        internal virtual void SetLineNumber(int iLine)
+        {
+            iLineNumber = iLine;
+        }
+
+        internal virtual void SetColumnNumber(int iCol)
+        {
+            iColumnNumber = iCol;
+        }
+
+        internal virtual void SetIsLastFrameFromForeignExceptionStackTrace(bool fIsLastFrame)
+        {
+            fIsLastFrameFromForeignExceptionStackTrace = fIsLastFrame;
+        }
+
+        internal virtual bool GetIsLastFrameFromForeignExceptionStackTrace()
+        {
+            return fIsLastFrameFromForeignExceptionStackTrace;
+        }
+
+        // Returns the method the frame is executing
+        // 
+        public virtual MethodBase GetMethod()
+        {
+            return method;
+        }
+
+        // Returns the offset from the start of the native (jitted) code for the
+        // method being executed
+        // 
+        public virtual int GetNativeOffset()
+        {
+            return offset;
+        }
+
+
+        // Returns the offset from the start of the IL code for the
+        // method being executed.  This offset may be approximate depending
+        // on whether the jitter is generating debuggable code or not.
+        // 
+        public virtual int GetILOffset()
+        {
+            return ILOffset;
+        }
+
+        // Returns the file name containing the code being executed.  This 
+        // information is normally extracted from the debugging symbols
+        // for the executable.
+        //
+        public virtual String GetFileName()
+        {
+            return strFileName;
+        }
+
+        // Returns the line number in the file containing the code being executed.  
+        // This information is normally extracted from the debugging symbols
+        // for the executable.
+        //
+        public virtual int GetFileLineNumber()
+        {
+            return iLineNumber;
+        }
+
+        // Returns the column number in the line containing the code being executed.  
+        // This information is normally extracted from the debugging symbols
+        // for the executable.
+        //
+        public virtual int GetFileColumnNumber()
+        {
+            return iColumnNumber;
+        }
+
+
+        // Builds a readable representation of the stack frame
+        //
+        public override String ToString()
+        {
+            StringBuilder sb = new StringBuilder(255);
+
+            if (method != null)
+            {
+                sb.Append(method.Name);
+
+                // deal with the generic portion of the method
+                if (method is MethodInfo && ((MethodInfo)method).IsGenericMethod)
+                {
+                    Type[] typars = ((MethodInfo)method).GetGenericArguments();
+
+                    sb.Append('<');
+                    int k = 0;
+                    bool fFirstTyParam = true;
+                    while (k < typars.Length)
+                    {
+                        if (fFirstTyParam == false)
+                            sb.Append(',');
+                        else
+                            fFirstTyParam = false;
+
+                        sb.Append(typars[k].Name);
+                        k++;
+                    }
+
+                    sb.Append('>');
+                }
+
+                sb.Append(" at offset ");
+                if (offset == OFFSET_UNKNOWN)
+                    sb.Append("<offset unknown>");
+                else
+                    sb.Append(offset);
+
+                sb.Append(" in file:line:column ");
+
+                bool useFileName = (strFileName != null);
+
+                if (!useFileName)
+                    sb.Append("<filename unknown>");
+                else
+                    sb.Append(strFileName);
+                sb.Append(':');
+                sb.Append(iLineNumber);
+                sb.Append(':');
+                sb.Append(iColumnNumber);
+            }
+            else
+            {
+                sb.Append("<null>");
+            }
+            sb.Append(Environment.NewLine);
+
+            return sb.ToString();
+        }
+
+
+        private void BuildStackFrame(int skipFrames, bool fNeedFileInfo)
+        {
+            StackFrameHelper StackF = new StackFrameHelper(null);
+
+            StackF.InitializeSourceInfo(0, fNeedFileInfo, null);
+
+            int iNumOfFrames = StackF.GetNumberOfFrames();
+
+            skipFrames += StackTrace.CalculateFramesToSkip(StackF, iNumOfFrames);
+
+            if ((iNumOfFrames - skipFrames) > 0)
+            {
+                method = StackF.GetMethodBase(skipFrames);
+                offset = StackF.GetOffset(skipFrames);
+                ILOffset = StackF.GetILOffset(skipFrames);
+                if (fNeedFileInfo)
+                {
+                    strFileName = StackF.GetFilename(skipFrames);
+                    iLineNumber = StackF.GetLineNumber(skipFrames);
+                    iColumnNumber = StackF.GetColumnNumber(skipFrames);
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/Stacktrace.cs b/src/System.Private.CoreLib/src/System/Diagnostics/Stacktrace.cs
new file mode 100644
index 0000000000..0535f02049
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/Stacktrace.cs
@@ -0,0 +1,674 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Text;
+using System.Threading;
+using System.Security;
+using System.IO;
+using System.Reflection;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Globalization;
+using System.Runtime.Versioning;
+
+namespace System.Diagnostics
+{
+    // READ ME:
+    // Modifying the order or fields of this object may require other changes 
+    // to the unmanaged definition of the StackFrameHelper class, in 
+    // VM\DebugDebugger.h. The binder will catch some of these layout problems.
+    internal class StackFrameHelper
+    {
+        private Thread targetThread;
+        private int[] rgiOffset;
+        private int[] rgiILOffset;
+
+#pragma warning disable 414
+        // dynamicMethods is an array of System.Resolver objects, used to keep
+        // DynamicMethodDescs alive for the lifetime of StackFrameHelper.
+        private Object dynamicMethods; // Field is not used from managed.        
+
+        private IntPtr[] rgMethodHandle;
+        private String[] rgAssemblyPath;
+        private IntPtr[] rgLoadedPeAddress;
+        private int[] rgiLoadedPeSize;
+        private IntPtr[] rgInMemoryPdbAddress;
+        private int[] rgiInMemoryPdbSize;
+        // if rgiMethodToken[i] == 0, then don't attempt to get the portable PDB source/info
+        private int[] rgiMethodToken;
+        private String[] rgFilename;
+        private int[] rgiLineNumber;
+        private int[] rgiColumnNumber;
+        private bool[] rgiLastFrameFromForeignExceptionStackTrace;
+        private int iFrameCount;
+#pragma warning restore 414
+
+        private delegate void GetSourceLineInfoDelegate(string assemblyPath, IntPtr loadedPeAddress, int loadedPeSize,
+            IntPtr inMemoryPdbAddress, int inMemoryPdbSize, int methodToken, int ilOffset,
+            out string sourceFile, out int sourceLine, out int sourceColumn);
+
+        private static GetSourceLineInfoDelegate s_getSourceLineInfo = null;
+
+        [ThreadStatic]
+        private static int t_reentrancy = 0;
+
+        public StackFrameHelper(Thread target)
+        {
+            targetThread = target;
+            rgMethodHandle = null;
+            rgiMethodToken = null;
+            rgiOffset = null;
+            rgiILOffset = null;
+            rgAssemblyPath = null;
+            rgLoadedPeAddress = null;
+            rgiLoadedPeSize = null;
+            rgInMemoryPdbAddress = null;
+            rgiInMemoryPdbSize = null;
+            dynamicMethods = null;
+            rgFilename = null;
+            rgiLineNumber = null;
+            rgiColumnNumber = null;
+
+            rgiLastFrameFromForeignExceptionStackTrace = null;
+
+            // 0 means capture all frames.  For StackTraces from an Exception, the EE always
+            // captures all frames.  For other uses of StackTraces, we can abort stack walking after
+            // some limit if we want to by setting this to a non-zero value.  In Whidbey this was 
+            // hard-coded to 512, but some customers complained.  There shouldn't be any need to limit
+            // this as memory/CPU is no longer allocated up front.  If there is some reason to provide a
+            // limit in the future, then we should expose it in the managed API so applications can 
+            // override it.
+            iFrameCount = 0;
+        }
+
+        //
+        // Initializes the stack trace helper. If fNeedFileInfo is true, initializes rgFilename, 
+        // rgiLineNumber and rgiColumnNumber fields using the portable PDB reader if not already
+        // done by GetStackFramesInternal (on Windows for old PDB format).
+        //
+        internal void InitializeSourceInfo(int iSkip, bool fNeedFileInfo, Exception exception)
+        {
+            StackTrace.GetStackFramesInternal(this, iSkip, fNeedFileInfo, exception);
+
+            if (!fNeedFileInfo)
+                return;
+
+            // Check if this function is being reentered because of an exception in the code below
+            if (t_reentrancy > 0)
+                return;
+
+            t_reentrancy++;
+            try
+            {
+                if (s_getSourceLineInfo == null)
+                {
+                    Type symbolsType = Type.GetType(
+                        "System.Diagnostics.StackTraceSymbols, System.Diagnostics.StackTrace, Version=4.0.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a",
+                        throwOnError: false);
+
+                    if (symbolsType == null)
+                    {
+                        return;
+                    }
+
+                    MethodInfo symbolsMethodInfo = symbolsType.GetMethod("GetSourceLineInfo", BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance);
+                    if (symbolsMethodInfo == null)
+                    {
+                        return;
+                    }
+
+                    // Create an instance of System.Diagnostics.Stacktrace.Symbols
+                    object target = Activator.CreateInstance(symbolsType);
+
+                    // Create an instance delegate for the GetSourceLineInfo method
+                    GetSourceLineInfoDelegate getSourceLineInfo = (GetSourceLineInfoDelegate)symbolsMethodInfo.CreateDelegate(typeof(GetSourceLineInfoDelegate), target);
+
+                    // We could race with another thread. It doesn't matter if we win or lose, the losing instance will be GC'ed and all threads including this one will
+                    // use the winning instance
+                    Interlocked.CompareExchange(ref s_getSourceLineInfo, getSourceLineInfo, null);
+                }
+
+                for (int index = 0; index < iFrameCount; index++)
+                {
+                    // If there was some reason not to try get the symbols from the portable PDB reader like the module was
+                    // ENC or the source/line info was already retrieved, the method token is 0.
+                    if (rgiMethodToken[index] != 0)
+                    {
+                        s_getSourceLineInfo(rgAssemblyPath[index], rgLoadedPeAddress[index], rgiLoadedPeSize[index],
+                            rgInMemoryPdbAddress[index], rgiInMemoryPdbSize[index], rgiMethodToken[index],
+                            rgiILOffset[index], out rgFilename[index], out rgiLineNumber[index], out rgiColumnNumber[index]);
+                    }
+                }
+            }
+            catch
+            {
+            }
+            finally
+            {
+                t_reentrancy--;
+            }
+        }
+
+        public virtual MethodBase GetMethodBase(int i)
+        {
+            // There may be a better way to do this.
+            // we got RuntimeMethodHandles here and we need to go to MethodBase
+            // but we don't know whether the reflection info has been initialized
+            // or not. So we call GetMethods and GetConstructors on the type
+            // and then we fetch the proper MethodBase!!
+            IntPtr mh = rgMethodHandle[i];
+
+            if (mh == IntPtr.Zero)
+                return null;
+
+            IRuntimeMethodInfo mhReal = RuntimeMethodHandle.GetTypicalMethodDefinition(new RuntimeMethodInfoStub(mh, this));
+
+            return RuntimeType.GetMethodBase(mhReal);
+        }
+
+        public virtual int GetOffset(int i) { return rgiOffset[i]; }
+        public virtual int GetILOffset(int i) { return rgiILOffset[i]; }
+        public virtual String GetFilename(int i) { return rgFilename == null ? null : rgFilename[i]; }
+        public virtual int GetLineNumber(int i) { return rgiLineNumber == null ? 0 : rgiLineNumber[i]; }
+        public virtual int GetColumnNumber(int i) { return rgiColumnNumber == null ? 0 : rgiColumnNumber[i]; }
+
+        public virtual bool IsLastFrameFromForeignExceptionStackTrace(int i)
+        {
+            return (rgiLastFrameFromForeignExceptionStackTrace == null) ? false : rgiLastFrameFromForeignExceptionStackTrace[i];
+        }
+
+        public virtual int GetNumberOfFrames() { return iFrameCount; }
+    }
+
+
+    // Class which represents a description of a stack trace
+    // There is no good reason for the methods of this class to be virtual.  
+    public class StackTrace
+    {
+        private StackFrame[] frames;
+        private int m_iNumOfFrames;
+        public const int METHODS_TO_SKIP = 0;
+        private int m_iMethodsToSkip;
+
+        // Constructs a stack trace from the current location.
+        public StackTrace()
+        {
+            m_iNumOfFrames = 0;
+            m_iMethodsToSkip = 0;
+            CaptureStackTrace(METHODS_TO_SKIP, false, null, null);
+        }
+
+        // Constructs a stack trace from the current location.
+        //
+        public StackTrace(bool fNeedFileInfo)
+        {
+            m_iNumOfFrames = 0;
+            m_iMethodsToSkip = 0;
+            CaptureStackTrace(METHODS_TO_SKIP, fNeedFileInfo, null, null);
+        }
+
+        // Constructs a stack trace from the current location, in a caller's
+        // frame
+        //
+        public StackTrace(int skipFrames)
+        {
+            if (skipFrames < 0)
+                throw new ArgumentOutOfRangeException(nameof(skipFrames),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            m_iNumOfFrames = 0;
+            m_iMethodsToSkip = 0;
+
+            CaptureStackTrace(skipFrames + METHODS_TO_SKIP, false, null, null);
+        }
+
+        // Constructs a stack trace from the current location, in a caller's
+        // frame
+        //
+        public StackTrace(int skipFrames, bool fNeedFileInfo)
+        {
+            if (skipFrames < 0)
+                throw new ArgumentOutOfRangeException(nameof(skipFrames),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            m_iNumOfFrames = 0;
+            m_iMethodsToSkip = 0;
+
+            CaptureStackTrace(skipFrames + METHODS_TO_SKIP, fNeedFileInfo, null, null);
+        }
+
+
+        // Constructs a stack trace from the current location.
+        public StackTrace(Exception e)
+        {
+            if (e == null)
+                throw new ArgumentNullException(nameof(e));
+
+            m_iNumOfFrames = 0;
+            m_iMethodsToSkip = 0;
+            CaptureStackTrace(METHODS_TO_SKIP, false, null, e);
+        }
+
+        // Constructs a stack trace from the current location.
+        //
+        public StackTrace(Exception e, bool fNeedFileInfo)
+        {
+            if (e == null)
+                throw new ArgumentNullException(nameof(e));
+
+            m_iNumOfFrames = 0;
+            m_iMethodsToSkip = 0;
+            CaptureStackTrace(METHODS_TO_SKIP, fNeedFileInfo, null, e);
+        }
+
+        // Constructs a stack trace from the current location, in a caller's
+        // frame
+        //
+        public StackTrace(Exception e, int skipFrames)
+        {
+            if (e == null)
+                throw new ArgumentNullException(nameof(e));
+
+            if (skipFrames < 0)
+                throw new ArgumentOutOfRangeException(nameof(skipFrames),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            m_iNumOfFrames = 0;
+            m_iMethodsToSkip = 0;
+
+            CaptureStackTrace(skipFrames + METHODS_TO_SKIP, false, null, e);
+        }
+
+        // Constructs a stack trace from the current location, in a caller's
+        // frame
+        //
+        public StackTrace(Exception e, int skipFrames, bool fNeedFileInfo)
+        {
+            if (e == null)
+                throw new ArgumentNullException(nameof(e));
+
+            if (skipFrames < 0)
+                throw new ArgumentOutOfRangeException(nameof(skipFrames),
+                    SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            m_iNumOfFrames = 0;
+            m_iMethodsToSkip = 0;
+
+            CaptureStackTrace(skipFrames + METHODS_TO_SKIP, fNeedFileInfo, null, e);
+        }
+
+
+        // Constructs a "fake" stack trace, just containing a single frame.  
+        // Does not have the overhead of a full stack trace.
+        //
+        public StackTrace(StackFrame frame)
+        {
+            frames = new StackFrame[1];
+            frames[0] = frame;
+            m_iMethodsToSkip = 0;
+            m_iNumOfFrames = 1;
+        }
+
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void GetStackFramesInternal(StackFrameHelper sfh, int iSkip, bool fNeedFileInfo, Exception e);
+
+        internal static int CalculateFramesToSkip(StackFrameHelper StackF, int iNumFrames)
+        {
+            int iRetVal = 0;
+            String PackageName = "System.Diagnostics";
+
+            // Check if this method is part of the System.Diagnostics
+            // package. If so, increment counter keeping track of 
+            // System.Diagnostics functions
+            for (int i = 0; i < iNumFrames; i++)
+            {
+                MethodBase mb = StackF.GetMethodBase(i);
+                if (mb != null)
+                {
+                    Type t = mb.DeclaringType;
+                    if (t == null)
+                        break;
+                    String ns = t.Namespace;
+                    if (ns == null)
+                        break;
+                    if (String.Compare(ns, PackageName, StringComparison.Ordinal) != 0)
+                        break;
+                }
+                iRetVal++;
+            }
+
+            return iRetVal;
+        }
+
+        // Retrieves an object with stack trace information encoded.
+        // It leaves out the first "iSkip" lines of the stacktrace.
+        //
+        private void CaptureStackTrace(int iSkip, bool fNeedFileInfo, Thread targetThread, Exception e)
+        {
+            m_iMethodsToSkip += iSkip;
+
+            StackFrameHelper StackF = new StackFrameHelper(targetThread);
+            
+            StackF.InitializeSourceInfo(0, fNeedFileInfo, e);
+
+            m_iNumOfFrames = StackF.GetNumberOfFrames();
+
+            if (m_iMethodsToSkip > m_iNumOfFrames)
+                m_iMethodsToSkip = m_iNumOfFrames;
+
+            if (m_iNumOfFrames != 0)
+            {
+                frames = new StackFrame[m_iNumOfFrames];
+
+                for (int i = 0; i < m_iNumOfFrames; i++)
+                {
+                    bool fDummy1 = true;
+                    bool fDummy2 = true;
+                    StackFrame sfTemp = new StackFrame(fDummy1, fDummy2);
+
+                    sfTemp.SetMethodBase(StackF.GetMethodBase(i));
+                    sfTemp.SetOffset(StackF.GetOffset(i));
+                    sfTemp.SetILOffset(StackF.GetILOffset(i));
+
+                    sfTemp.SetIsLastFrameFromForeignExceptionStackTrace(StackF.IsLastFrameFromForeignExceptionStackTrace(i));
+
+                    if (fNeedFileInfo)
+                    {
+                        sfTemp.SetFileName(StackF.GetFilename(i));
+                        sfTemp.SetLineNumber(StackF.GetLineNumber(i));
+                        sfTemp.SetColumnNumber(StackF.GetColumnNumber(i));
+                    }
+
+                    frames[i] = sfTemp;
+                }
+
+                // CalculateFramesToSkip skips all frames in the System.Diagnostics namespace,
+                // but this is not desired if building a stack trace from an exception.
+                if (e == null)
+                    m_iMethodsToSkip += CalculateFramesToSkip(StackF, m_iNumOfFrames);
+
+                m_iNumOfFrames -= m_iMethodsToSkip;
+                if (m_iNumOfFrames < 0)
+                {
+                    m_iNumOfFrames = 0;
+                }
+            }
+
+            // In case this is the same object being re-used, set frames to null
+            else
+            {
+                frames = null;
+            }
+        }
+
+        // Property to get the number of frames in the stack trace
+        //
+        public virtual int FrameCount
+        {
+            get { return m_iNumOfFrames; }
+        }
+
+
+        // Returns a given stack frame.  Stack frames are numbered starting at
+        // zero, which is the last stack frame pushed.
+        //
+        public virtual StackFrame GetFrame(int index)
+        {
+            if ((frames != null) && (index < m_iNumOfFrames) && (index >= 0))
+                return frames[index + m_iMethodsToSkip];
+
+            return null;
+        }
+
+        // Returns an array of all stack frames for this stacktrace.
+        // The array is ordered and sized such that GetFrames()[i] == GetFrame(i)
+        // The nth element of this array is the same as GetFrame(n). 
+        // The length of the array is the same as FrameCount.
+        // 
+        public virtual StackFrame[] GetFrames()
+        {
+            if (frames == null || m_iNumOfFrames <= 0)
+                return null;
+
+            // We have to return a subset of the array. Unfortunately this
+            // means we have to allocate a new array and copy over.
+            StackFrame[] array = new StackFrame[m_iNumOfFrames];
+            Array.Copy(frames, m_iMethodsToSkip, array, 0, m_iNumOfFrames);
+            return array;
+        }
+
+        // Builds a readable representation of the stack trace
+        //
+        public override String ToString()
+        {
+            // Include a trailing newline for backwards compatibility
+            return ToString(TraceFormat.TrailingNewLine);
+        }
+
+        // TraceFormat is Used to specify options for how the 
+        // string-representation of a StackTrace should be generated.
+        internal enum TraceFormat
+        {
+            Normal,
+            TrailingNewLine,        // include a trailing new line character
+            NoResourceLookup    // to prevent infinite resource recusion
+        }
+
+        // Builds a readable representation of the stack trace, specifying 
+        // the format for backwards compatibility.
+        internal String ToString(TraceFormat traceFormat)
+        {
+            bool displayFilenames = true;   // we'll try, but demand may fail
+            String word_At = "at";
+            String inFileLineNum = "in {0}:line {1}";
+
+            if (traceFormat != TraceFormat.NoResourceLookup)
+            {
+                word_At = SR.Word_At;
+                inFileLineNum = SR.StackTrace_InFileLineNumber;
+            }
+
+            bool fFirstFrame = true;
+            StringBuilder sb = new StringBuilder(255);
+            for (int iFrameIndex = 0; iFrameIndex < m_iNumOfFrames; iFrameIndex++)
+            {
+                StackFrame sf = GetFrame(iFrameIndex);
+                MethodBase mb = sf.GetMethod();
+                if (mb != null && (ShowInStackTrace(mb) || 
+                                   (iFrameIndex == m_iNumOfFrames - 1))) // Don't filter last frame
+                {
+                    // We want a newline at the end of every line except for the last
+                    if (fFirstFrame)
+                        fFirstFrame = false;
+                    else
+                        sb.Append(Environment.NewLine);
+
+                    sb.AppendFormat(CultureInfo.InvariantCulture, "   {0} ", word_At);
+
+                    bool isAsync = false;
+                    Type declaringType = mb.DeclaringType;
+                    string methodName = mb.Name;
+                    bool methodChanged = false;
+                    if (declaringType != null && declaringType.IsDefined(typeof(CompilerGeneratedAttribute)))
+                    {
+                        isAsync = typeof(IAsyncStateMachine).IsAssignableFrom(declaringType);
+                        if (isAsync || typeof(IEnumerator).IsAssignableFrom(declaringType))
+                        {
+                            methodChanged = TryResolveStateMachineMethod(ref mb, out declaringType);
+                        }
+                    }
+
+                    // if there is a type (non global method) print it
+                    // ResolveStateMachineMethod may have set declaringType to null
+                    if (declaringType != null)
+                    {
+                        // Append t.FullName, replacing '+' with '.'
+                        string fullName = declaringType.FullName;
+                        for (int i = 0; i < fullName.Length; i++)
+                        {
+                            char ch = fullName[i];
+                            sb.Append(ch == '+' ? '.' : ch);
+                        }
+                        sb.Append('.');
+                    }
+                    sb.Append(mb.Name);
+
+                    // deal with the generic portion of the method
+                    if (mb is MethodInfo && ((MethodInfo)mb).IsGenericMethod)
+                    {
+                        Type[] typars = ((MethodInfo)mb).GetGenericArguments();
+                        sb.Append('[');
+                        int k = 0;
+                        bool fFirstTyParam = true;
+                        while (k < typars.Length)
+                        {
+                            if (fFirstTyParam == false)
+                                sb.Append(',');
+                            else
+                                fFirstTyParam = false;
+
+                            sb.Append(typars[k].Name);
+                            k++;
+                        }
+                        sb.Append(']');
+                    }
+
+                    ParameterInfo[] pi = null;
+                    try
+                    {
+                        pi = mb.GetParameters();
+                    }
+                    catch
+                    {
+                        // The parameter info cannot be loaded, so we don't
+                        // append the parameter list.
+                    }
+                    if (pi != null)
+                    {
+                        // arguments printing
+                        sb.Append('(');
+                        bool fFirstParam = true;
+                        for (int j = 0; j < pi.Length; j++)
+                        {
+                            if (fFirstParam == false)
+                                sb.Append(", ");
+                            else
+                                fFirstParam = false;
+
+                            String typeName = "<UnknownType>";
+                            if (pi[j].ParameterType != null)
+                                typeName = pi[j].ParameterType.Name;
+                            sb.Append(typeName);
+                            sb.Append(' ');
+                            sb.Append(pi[j].Name);
+                        }
+                        sb.Append(')');
+                    }
+
+                    if (methodChanged)
+                    {
+                        // Append original method name e.g. +MoveNext()
+                        sb.Append("+");
+                        sb.Append(methodName);
+                        sb.Append("()");
+                    }
+
+                    // source location printing
+                    if (displayFilenames && (sf.GetILOffset() != -1))
+                    {
+                        // If we don't have a PDB or PDB-reading is disabled for the module,
+                        // then the file name will be null.
+                        String fileName = null;
+
+                        // Getting the filename from a StackFrame is a privileged operation - we won't want
+                        // to disclose full path names to arbitrarily untrusted code.  Rather than just omit
+                        // this we could probably trim to just the filename so it's still mostly usefull.
+                        try
+                        {
+                            fileName = sf.GetFileName();
+                        }
+                        catch (SecurityException)
+                        {
+                            // If the demand for displaying filenames fails, then it won't
+                            // succeed later in the loop.  Avoid repeated exceptions by not trying again.
+                            displayFilenames = false;
+                        }
+
+                        if (fileName != null)
+                        {
+                            // tack on " in c:\tmp\MyFile.cs:line 5"
+                            sb.Append(' ');
+                            sb.AppendFormat(CultureInfo.InvariantCulture, inFileLineNum, fileName, sf.GetFileLineNumber());
+                        }
+                    }
+
+                    if (sf.GetIsLastFrameFromForeignExceptionStackTrace() &&
+                        !isAsync) // Skip EDI boundary for async
+                    {
+                        sb.Append(Environment.NewLine);
+                        sb.Append(SR.Exception_EndStackTraceFromPreviousThrow);
+                    }
+                }
+            }
+
+            if (traceFormat == TraceFormat.TrailingNewLine)
+                sb.Append(Environment.NewLine);
+
+            return sb.ToString();
+        }
+
+        private static bool ShowInStackTrace(MethodBase mb)
+        {
+            Debug.Assert(mb != null);
+            return !(mb.IsDefined(typeof(StackTraceHiddenAttribute)) || (mb.DeclaringType?.IsDefined(typeof(StackTraceHiddenAttribute)) ?? false));
+        }
+
+        private static bool TryResolveStateMachineMethod(ref MethodBase method, out Type declaringType)
+        {
+            Debug.Assert(method != null);
+            Debug.Assert(method.DeclaringType != null);
+
+            declaringType = method.DeclaringType;
+
+            Type parentType = declaringType.DeclaringType;
+            if (parentType == null)
+            {
+                return false;
+            }
+
+            MethodInfo[] methods = parentType.GetMethods(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance | BindingFlags.DeclaredOnly);
+            if (methods == null)
+            {
+                return false;
+            }
+
+            foreach (MethodInfo candidateMethod in methods)
+            {
+                IEnumerable<StateMachineAttribute> attributes = candidateMethod.GetCustomAttributes<StateMachineAttribute>();
+                if (attributes == null)
+                {
+                    continue;
+                }
+
+                foreach (StateMachineAttribute asma in attributes)
+                {
+                    if (asma.StateMachineType == declaringType)
+                    {
+                        method = candidateMethod;
+                        declaringType = candidateMethod.DeclaringType;
+                        // Mark the iterator as changed; so it gets the + annotation of the original method
+                        // async statemachines resolve directly to their builder methods so aren't marked as changed
+                        return asma is IteratorStateMachineAttribute;
+                    }
+                }
+            }
+
+            return false;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/SymbolStore/ISymDocumentWriter.cs b/src/System.Private.CoreLib/src/System/Diagnostics/SymbolStore/ISymDocumentWriter.cs
new file mode 100644
index 0000000000..09a7a3b0b0
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/SymbolStore/ISymDocumentWriter.cs
@@ -0,0 +1,31 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Represents a document referenced by a symbol store. A document is
+** defined by a URL and a document type GUID. Document source can
+** optionally be stored in the symbol store.
+**
+** 
+===========================================================*/
+
+using System;
+
+namespace System.Diagnostics.SymbolStore
+{
+    // Interface does not need to be marked with the serializable attribute
+    public interface ISymbolDocumentWriter
+    {
+        // SetSource will store the raw source for a document into the
+        // symbol store. An array of unsigned bytes is used instead of
+        // character data to accommodate a wider variety of "source".
+        void SetSource(byte[] source);
+
+        // Check sum support.
+        void SetCheckSum(Guid algorithmId, byte[] checkSum);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/SymbolStore/ISymWriter.cs b/src/System.Private.CoreLib/src/System/Diagnostics/SymbolStore/ISymWriter.cs
new file mode 100644
index 0000000000..fa2a59797a
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/SymbolStore/ISymWriter.cs
@@ -0,0 +1,111 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Represents a symbol writer for managed code. Provides methods to
+** define documents, sequence points, lexical scopes, and variables.
+**
+** 
+===========================================================*/
+
+using System;
+using System.Text;
+using System.Reflection;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace System.Diagnostics.SymbolStore
+{
+    // Interface does not need to be marked with the serializable attribute
+    internal interface ISymbolWriter
+    {
+        // Define a source document. Guid's will be provided for the
+        // languages, vendors, and document types that we currently know
+        // about.
+        ISymbolDocumentWriter DefineDocument(String url,
+                                          Guid language,
+                                          Guid languageVendor,
+                                          Guid documentType);
+
+        // Open a method to emit symbol information into. The given method
+        // becomes the current method for calls do define sequence points,
+        // parameters and lexical scopes. There is an implicit lexical
+        // scope around the entire method. Re-opening a method that has
+        // been previously closed effectivley erases any previously
+        // defined symbols for that method.
+        //
+        // There can be only one open method at a time.
+        void OpenMethod(SymbolToken method);
+
+        // Close the current method. Once a method is closed, no more
+        // symbols can be defined within it.
+        void CloseMethod();
+
+        // Define a group of sequence points within the current method.
+        // Each line/column defines the start of a statement within a
+        // method. The arrays should be sorted by offset. The offset is
+        // always the offset from the start of the method, in bytes.
+        void DefineSequencePoints(ISymbolDocumentWriter document,
+                                  int[] offsets,
+                                  int[] lines,
+                                  int[] columns,
+                                  int[] endLines,
+                                  int[] endColumns);
+
+        // Open a new lexical scope in the current method. The scope
+        // becomes the new current scope and is effectivley pushed onto a
+        // stack of scopes. startOffset is the offset, in bytes from the
+        // beginning of the method, of the first instruction in the
+        // lexical scope. Scopes must form a hierarchy. Siblings are not
+        // allowed to overlap.
+        //
+        // OpenScope returns an opaque scope id that can be used with
+        // SetScopeRange to define a scope's start/end offset at a later
+        // time. In this case, the offsets passed to OpenScope and
+        // CloseScope are ignored.
+        //
+        // Note: scope id's are only valid in the current method.
+        //
+
+        int OpenScope(int startOffset);
+
+        // Close the current lexical scope. Once a scope is closed no more
+        // variables can be defined within it. endOffset points past the
+        // last instruction in the scope.
+        void CloseScope(int endOffset);
+
+        // Define a single variable in the current lexical
+        // scope. startOffset and endOffset are optional. If 0, then they
+        // are ignored and the variable is defined over the entire
+        // scope. If non-zero, then they must fall within the offsets of
+        // the current scope. This can be called multiple times for a
+        // variable of the same name that has multiple homes throughout a
+        // scope. (Note: start/end offsets must not overlap in such a
+        // case.)
+        void DefineLocalVariable(String name,
+                                        FieldAttributes attributes,
+                                        byte[] signature,
+                                        SymAddressKind addrKind,
+                                        int addr1,
+                                        int addr2,
+                                        int addr3,
+                                        int startOffset,
+                                        int endOffset);
+
+        // Defines a custom attribute based upon its name. Not to be
+        // confused with Metadata custom attributes, these attributes are
+        // held in the symbol store.
+        void SetSymAttribute(SymbolToken parent, String name, byte[] data);
+
+        // Specifies that the given, fully qualified namespace name is
+        // being used within the currently open lexical scope. Closing the
+        // current scope will also stop using the namespace, and the
+        // namespace will be in use in all scopes that inherit from the
+        // currently open scope.
+        void UsingNamespace(String fullName);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/SymbolStore/SymAddressKind.cs b/src/System.Private.CoreLib/src/System/Diagnostics/SymbolStore/SymAddressKind.cs
new file mode 100644
index 0000000000..15b3c7f4f7
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/SymbolStore/SymAddressKind.cs
@@ -0,0 +1,52 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Represents address Kinds used with local variables, parameters, and
+** fields.
+**
+** 
+===========================================================*/
+// Only statics, does not need to be marked with the serializable attribute    
+
+using System;
+
+namespace System.Diagnostics.SymbolStore
+{
+    internal enum SymAddressKind
+    {
+        // ILOffset: addr1 = IL local var or param index.
+        ILOffset = 1,
+
+        // NativeRVA: addr1 = RVA into module.
+        NativeRVA = 2,
+
+        // NativeRegister: addr1 = register the var is stored in.
+        NativeRegister = 3,
+
+        // NativeRegisterRelative: addr1 = register, addr2 = offset.
+        NativeRegisterRelative = 4,
+
+        // NativeOffset: addr1 = offset from start of parent.
+        NativeOffset = 5,
+
+        // NativeRegisterRegister: addr1 = reg low, addr2 = reg high.
+        NativeRegisterRegister = 6,
+
+        // NativeRegisterStack: addr1 = reg low, addr2 = reg stk, addr3 = offset.
+        NativeRegisterStack = 7,
+
+        // NativeStackRegister: addr1 = reg stk, addr2 = offset, addr3 = reg high.
+        NativeStackRegister = 8,
+
+        // BitField: addr1 = field start, addr = field length.
+        BitField = 9,
+
+        // NativeSectionOffset: addr1 = section, addr = offset
+        NativeSectionOffset = 10,
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/SymbolStore/Token.cs b/src/System.Private.CoreLib/src/System/Diagnostics/SymbolStore/Token.cs
new file mode 100644
index 0000000000..a6e6fdc0ef
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/SymbolStore/Token.cs
@@ -0,0 +1,41 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+** Small value class used by the SymbolStore package for passing
+** around metadata tokens.
+**
+===========================================================*/
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace System.Diagnostics.SymbolStore
+{
+    internal struct SymbolToken
+    {
+        internal int m_token;
+
+        public SymbolToken(int val) { m_token = val; }
+
+        public int GetToken() { return m_token; }
+
+        public override int GetHashCode() { return m_token; }
+
+        public override bool Equals(Object obj)
+        {
+            if (obj is SymbolToken)
+                return Equals((SymbolToken)obj);
+            else
+                return false;
+        }
+
+        public bool Equals(SymbolToken obj)
+        {
+            return obj.m_token == m_token;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Enum.cs b/src/System.Private.CoreLib/src/System/Enum.cs
new file mode 100644
index 0000000000..eae46cf3de
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Enum.cs
@@ -0,0 +1,1209 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+using System.Text;
+using System.Collections;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+using System.Diagnostics;
+
+// The code below includes partial support for float/double and
+// pointer sized enums.
+//
+// The type loader does not prohibit such enums, and older versions of
+// the ECMA spec include them as possible enum types.
+//
+// However there are many things broken throughout the stack for
+// float/double/intptr/uintptr enums. There was a conscious decision
+// made to not fix the whole stack to work well for them because of
+// the right behavior is often unclear, and it is hard to test and
+// very low value because of such enums cannot be expressed in C#.
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public abstract class Enum : ValueType, IComparable, IFormattable, IConvertible
+    {
+        #region Private Constants
+        private const char enumSeparatorChar = ',';
+        private const String enumSeparatorString = ", ";
+        #endregion
+
+        #region Private Static Methods
+        private static TypeValuesAndNames GetCachedValuesAndNames(RuntimeType enumType, bool getNames)
+        {
+            TypeValuesAndNames entry = enumType.GenericCache as TypeValuesAndNames;
+
+            if (entry == null || (getNames && entry.Names == null))
+            {
+                ulong[] values = null;
+                String[] names = null;
+                bool isFlags = enumType.IsDefined(typeof(System.FlagsAttribute), false);
+
+                GetEnumValuesAndNames(
+                    enumType.GetTypeHandleInternal(),
+                    JitHelpers.GetObjectHandleOnStack(ref values),
+                    JitHelpers.GetObjectHandleOnStack(ref names),
+                    getNames);
+
+                entry = new TypeValuesAndNames(isFlags, values, names);
+                enumType.GenericCache = entry;
+            }
+
+            return entry;
+        }
+
+        private unsafe String InternalFormattedHexString()
+        {
+            fixed (void* pValue = &JitHelpers.GetPinningHelper(this).m_data)
+            {
+                switch (InternalGetCorElementType())
+                {
+                    case CorElementType.I1:
+                    case CorElementType.U1:
+                        return (*(byte*)pValue).ToString("X2", null);
+                    case CorElementType.Boolean:
+                        // direct cast from bool to byte is not allowed
+                        return Convert.ToByte(*(bool*)pValue).ToString("X2", null);
+                    case CorElementType.I2:
+                    case CorElementType.U2:
+                    case CorElementType.Char:
+                        return (*(ushort*)pValue).ToString("X4", null);
+                    case CorElementType.I4:
+                    case CorElementType.U4:
+                        return (*(uint*)pValue).ToString("X8", null);
+                    case CorElementType.I8:
+                    case CorElementType.U8:
+                        return (*(ulong*)pValue).ToString("X16", null);
+                    default:
+                        throw new InvalidOperationException(SR.InvalidOperation_UnknownEnumType);
+                }
+            }
+        }
+
+        private static String InternalFormattedHexString(object value)
+        {
+            TypeCode typeCode = Convert.GetTypeCode(value);
+
+            switch (typeCode)
+            {
+                case TypeCode.SByte:
+                    return ((byte)(sbyte)value).ToString("X2", null);
+                case TypeCode.Byte:
+                    return ((byte)value).ToString("X2", null);
+                case TypeCode.Boolean:
+                    // direct cast from bool to byte is not allowed
+                    return Convert.ToByte((bool)value).ToString("X2", null);
+                case TypeCode.Int16:
+                    return ((UInt16)(Int16)value).ToString("X4", null);
+                case TypeCode.UInt16:
+                    return ((UInt16)value).ToString("X4", null);
+                case TypeCode.Char:
+                    return ((UInt16)(Char)value).ToString("X4", null);
+                case TypeCode.UInt32:
+                    return ((UInt32)value).ToString("X8", null);
+                case TypeCode.Int32:
+                    return ((UInt32)(Int32)value).ToString("X8", null);
+                case TypeCode.UInt64:
+                    return ((UInt64)value).ToString("X16", null);
+                case TypeCode.Int64:
+                    return ((UInt64)(Int64)value).ToString("X16", null);
+                // All unsigned types will be directly cast
+                default:
+                    throw new InvalidOperationException(SR.InvalidOperation_UnknownEnumType);
+            }
+        }
+
+        internal static String GetEnumName(RuntimeType eT, ulong ulValue)
+        {
+            Debug.Assert(eT != null);
+            ulong[] ulValues = Enum.InternalGetValues(eT);
+            int index = Array.BinarySearch(ulValues, ulValue);
+
+            if (index >= 0)
+            {
+                string[] names = Enum.InternalGetNames(eT);
+                return names[index];
+            }
+
+            return null; // return null so the caller knows to .ToString() the input
+        }
+
+        private static String InternalFormat(RuntimeType eT, ulong value)
+        {
+            Debug.Assert(eT != null);
+
+            // These values are sorted by value. Don't change this
+            TypeValuesAndNames entry = GetCachedValuesAndNames(eT, true);
+
+            if (!entry.IsFlag) // Not marked with Flags attribute
+            {
+                return Enum.GetEnumName(eT, value);
+            }
+            else // These are flags OR'ed together (We treat everything as unsigned types)
+            {
+                return InternalFlagsFormat(eT, entry, value);
+            }
+        }
+
+        private static String InternalFlagsFormat(RuntimeType eT, ulong result)
+        {
+            // These values are sorted by value. Don't change this
+            TypeValuesAndNames entry = GetCachedValuesAndNames(eT, true);
+
+            return InternalFlagsFormat(eT, entry, result);
+        }
+
+        private static String InternalFlagsFormat(RuntimeType eT, TypeValuesAndNames entry, ulong result)
+        {
+            Debug.Assert(eT != null);
+
+            String[] names = entry.Names;
+            ulong[] values = entry.Values;
+            Debug.Assert(names.Length == values.Length);
+
+            int index = values.Length - 1;
+            StringBuilder sb = StringBuilderCache.Acquire();
+            bool firstTime = true;
+            ulong saveResult = result;
+
+            // We will not optimize this code further to keep it maintainable. There are some boundary checks that can be applied
+            // to minimize the comparsions required. This code works the same for the best/worst case. In general the number of
+            // items in an enum are sufficiently small and not worth the optimization.
+            while (index >= 0)
+            {
+                if ((index == 0) && (values[index] == 0))
+                    break;
+
+                if ((result & values[index]) == values[index])
+                {
+                    result -= values[index];
+                    if (!firstTime)
+                        sb.Insert(0, enumSeparatorString);
+
+                    sb.Insert(0, names[index]);
+                    firstTime = false;
+                }
+
+                index--;
+            }
+
+            string returnString;
+            if (result != 0)
+            {
+                // We were unable to represent this number as a bitwise or of valid flags
+                returnString = null; // return null so the caller knows to .ToString() the input
+            }
+            else if (saveResult == 0)
+            {
+                // For the cases when we have zero
+                if (values.Length > 0 && values[0] == 0)
+                {
+                    returnString = names[0]; // Zero was one of the enum values.
+                }
+                else
+                {
+                    returnString = "0";
+                }
+            }
+            else
+            {
+                returnString = sb.ToString(); // Return the string representation
+            }
+
+            StringBuilderCache.Release(sb);
+            return returnString;
+        }
+
+        internal static ulong ToUInt64(Object value)
+        {
+            // Helper function to silently convert the value to UInt64 from the other base types for enum without throwing an exception.
+            // This is need since the Convert functions do overflow checks.
+            TypeCode typeCode = Convert.GetTypeCode(value);
+
+            ulong result;
+            switch (typeCode)
+            {
+                case TypeCode.SByte:
+                    result = (ulong)(sbyte)value;
+                    break;
+                case TypeCode.Byte:
+                    result = (byte)value;
+                    break;
+                case TypeCode.Boolean:
+                    // direct cast from bool to byte is not allowed
+                    result = Convert.ToByte((bool)value);
+                    break;
+                case TypeCode.Int16:
+                    result = (ulong)(Int16)value;
+                    break;
+                case TypeCode.UInt16:
+                    result = (UInt16)value;
+                    break;
+                case TypeCode.Char:
+                    result = (UInt16)(Char)value;
+                    break;
+                case TypeCode.UInt32:
+                    result = (UInt32)value;
+                    break;
+                case TypeCode.Int32:
+                    result = (ulong)(int)value;
+                    break;
+                case TypeCode.UInt64:
+                    result = (ulong)value;
+                    break;
+                case TypeCode.Int64:
+                    result = (ulong)(Int64)value;
+                    break;
+                // All unsigned types will be directly cast
+                default:
+                    throw new InvalidOperationException(SR.InvalidOperation_UnknownEnumType);
+            }
+
+            return result;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int InternalCompareTo(Object o1, Object o2);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern RuntimeType InternalGetUnderlyingType(RuntimeType enumType);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetEnumValuesAndNames(RuntimeTypeHandle enumType, ObjectHandleOnStack values, ObjectHandleOnStack names, bool getNames);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern Object InternalBoxEnum(RuntimeType enumType, long value);
+        #endregion
+
+        #region Public Static Methods
+        private enum ParseFailureKind
+        {
+            None = 0,
+            Argument = 1,
+            ArgumentNull = 2,
+            ArgumentWithParameter = 3,
+            UnhandledException = 4
+        }
+
+        // This will store the result of the parsing.
+        private struct EnumResult
+        {
+            internal object parsedEnum;
+            internal bool canThrow;
+            internal ParseFailureKind m_failure;
+            internal string m_failureMessageID;
+            internal string m_failureParameter;
+            internal object m_failureMessageFormatArgument;
+            internal Exception m_innerException;
+
+            internal void SetFailure(Exception unhandledException)
+            {
+                m_failure = ParseFailureKind.UnhandledException;
+                m_innerException = unhandledException;
+            }
+            internal void SetFailure(ParseFailureKind failure, string failureParameter)
+            {
+                m_failure = failure;
+                m_failureParameter = failureParameter;
+                if (canThrow)
+                    throw GetEnumParseException();
+            }
+            internal void SetFailure(ParseFailureKind failure, string failureMessageID, object failureMessageFormatArgument)
+            {
+                m_failure = failure;
+                m_failureMessageID = failureMessageID;
+                m_failureMessageFormatArgument = failureMessageFormatArgument;
+                if (canThrow)
+                    throw GetEnumParseException();
+            }
+            internal Exception GetEnumParseException()
+            {
+                switch (m_failure)
+                {
+                    case ParseFailureKind.Argument:
+                        return new ArgumentException(SR.GetResourceString(m_failureMessageID));
+
+                    case ParseFailureKind.ArgumentNull:
+                        return new ArgumentNullException(m_failureParameter);
+
+                    case ParseFailureKind.ArgumentWithParameter:
+                        return new ArgumentException(SR.Format(SR.GetResourceString(m_failureMessageID), m_failureMessageFormatArgument));
+
+                    case ParseFailureKind.UnhandledException:
+                        return m_innerException;
+
+                    default:
+                        Debug.Fail("Unknown EnumParseFailure: " + m_failure);
+                        return new ArgumentException(SR.Arg_EnumValueNotFound);
+                }
+            }
+        }
+
+        public static bool TryParse(Type enumType, String value, out Object result)
+        {
+            return TryParse(enumType, value, false, out result);
+        }
+
+        public static bool TryParse(Type enumType, String value, bool ignoreCase, out Object result)
+        {
+            result = null;
+            EnumResult parseResult = new EnumResult();
+            bool retValue;
+
+            if (retValue = TryParseEnum(enumType, value, ignoreCase, ref parseResult))
+                result = parseResult.parsedEnum;
+            return retValue;
+        }
+
+        public static bool TryParse<TEnum>(String value, out TEnum result) where TEnum : struct
+        {
+            return TryParse(value, false, out result);
+        }
+
+        public static bool TryParse<TEnum>(String value, bool ignoreCase, out TEnum result) where TEnum : struct
+        {
+            result = default(TEnum);
+            EnumResult parseResult = new EnumResult();
+            bool retValue;
+
+            if (retValue = TryParseEnum(typeof(TEnum), value, ignoreCase, ref parseResult))
+                result = (TEnum)parseResult.parsedEnum;
+            return retValue;
+        }
+
+        public static Object Parse(Type enumType, String value)
+        {
+            return Parse(enumType, value, false);
+        }
+
+        public static Object Parse(Type enumType, String value, bool ignoreCase)
+        {
+            EnumResult parseResult = new EnumResult() { canThrow = true };
+            if (TryParseEnum(enumType, value, ignoreCase, ref parseResult))
+                return parseResult.parsedEnum;
+            else
+                throw parseResult.GetEnumParseException();
+        }
+
+        public static TEnum Parse<TEnum>(String value) where TEnum : struct
+        {
+            return Parse<TEnum>(value, false);
+        }
+
+        public static TEnum Parse<TEnum>(String value, bool ignoreCase) where TEnum : struct
+        {
+            EnumResult parseResult = new EnumResult() { canThrow = true };
+            if (TryParseEnum(typeof(TEnum), value, ignoreCase, ref parseResult))
+                return (TEnum)parseResult.parsedEnum;
+            else
+                throw parseResult.GetEnumParseException();
+        }
+
+        private static bool TryParseEnum(Type enumType, String value, bool ignoreCase, ref EnumResult parseResult)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+
+            RuntimeType rtType = enumType as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(enumType));
+
+            if (!enumType.IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, nameof(enumType));
+
+            if (value == null)
+            {
+                parseResult.SetFailure(ParseFailureKind.ArgumentNull, nameof(value));
+                return false;
+            }
+
+            int firstNonWhitespaceIndex = -1;
+            for (int i = 0; i < value.Length; i++)
+            {
+                if (!Char.IsWhiteSpace(value[i]))
+                {
+                    firstNonWhitespaceIndex = i;
+                    break;
+                }
+            }
+            if (firstNonWhitespaceIndex == -1)
+            {
+                parseResult.SetFailure(ParseFailureKind.Argument, nameof(SR.Arg_MustContainEnumInfo), null);
+                return false;
+            }
+
+            // We have 2 code paths here. One if they are values else if they are Strings.
+            // values will have the first character as as number or a sign.
+            ulong result = 0;
+
+            char firstNonWhitespaceChar = value[firstNonWhitespaceIndex];
+            if (Char.IsDigit(firstNonWhitespaceChar) || firstNonWhitespaceChar == '-' || firstNonWhitespaceChar == '+')
+            {
+                Type underlyingType = GetUnderlyingType(enumType);
+                Object temp;
+
+                try
+                {
+                    value = value.Trim();
+                    temp = Convert.ChangeType(value, underlyingType, CultureInfo.InvariantCulture);
+                    parseResult.parsedEnum = ToObject(enumType, temp);
+                    return true;
+                }
+                catch (FormatException)
+                { // We need to Parse this as a String instead. There are cases
+                  // when you tlbimp enums that can have values of the form "3D".
+                  // Don't fix this code.
+                }
+                catch (Exception ex)
+                {
+                    if (parseResult.canThrow)
+                        throw;
+                    else
+                    {
+                        parseResult.SetFailure(ex);
+                        return false;
+                    }
+                }
+            }
+
+            // Find the field. Let's assume that these are always static classes 
+            // because the class is an enum.
+            TypeValuesAndNames entry = GetCachedValuesAndNames(rtType, true);
+            String[] enumNames = entry.Names;
+            ulong[] enumValues = entry.Values;
+
+            StringComparison comparison = ignoreCase ?
+                StringComparison.OrdinalIgnoreCase :
+                StringComparison.Ordinal;
+
+            int valueIndex = firstNonWhitespaceIndex;
+            while (valueIndex <= value.Length) // '=' is to handle invalid case of an ending comma
+            {
+                // Find the next separator, if there is one, otherwise the end of the string.
+                int endIndex = value.IndexOf(enumSeparatorChar, valueIndex);
+                if (endIndex == -1)
+                {
+                    endIndex = value.Length;
+                }
+
+                // Shift the starting and ending indices to eliminate whitespace
+                int endIndexNoWhitespace = endIndex;
+                while (valueIndex < endIndex && Char.IsWhiteSpace(value[valueIndex])) valueIndex++;
+                while (endIndexNoWhitespace > valueIndex && Char.IsWhiteSpace(value[endIndexNoWhitespace - 1])) endIndexNoWhitespace--;
+                int valueSubstringLength = endIndexNoWhitespace - valueIndex;
+
+                // Try to match this substring against each enum name
+                bool success = false;
+                for (int i = 0; i < enumNames.Length; i++)
+                {
+                    if (enumNames[i].Length == valueSubstringLength &&
+                        string.Compare(enumNames[i], 0, value, valueIndex, valueSubstringLength, comparison) == 0)
+                    {
+                        result |= enumValues[i];
+                        success = true;
+                        break;
+                    }
+                }
+
+                // If we couldn't find a match, throw an argument exception.
+                if (!success)
+                {
+                    // Not found, throw an argument exception.
+                    parseResult.SetFailure(ParseFailureKind.ArgumentWithParameter, nameof(SR.Arg_EnumValueNotFound), value);
+                    return false;
+                }
+
+                // Move our pointer to the ending index to go again.
+                valueIndex = endIndex + 1;
+            }
+
+            try
+            {
+                parseResult.parsedEnum = ToObject(enumType, result);
+                return true;
+            }
+            catch (Exception ex)
+            {
+                if (parseResult.canThrow)
+                    throw;
+                else
+                {
+                    parseResult.SetFailure(ex);
+                    return false;
+                }
+            }
+        }
+
+        public static Type GetUnderlyingType(Type enumType)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+
+            return enumType.GetEnumUnderlyingType();
+        }
+
+        public static Array GetValues(Type enumType)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+
+            return enumType.GetEnumValues();
+        }
+
+        internal static ulong[] InternalGetValues(RuntimeType enumType)
+        {
+            // Get all of the values
+            return GetCachedValuesAndNames(enumType, false).Values;
+        }
+
+        public static String GetName(Type enumType, Object value)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+
+            return enumType.GetEnumName(value);
+        }
+
+        public static String[] GetNames(Type enumType)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+
+            return enumType.GetEnumNames();
+        }
+
+        internal static String[] InternalGetNames(RuntimeType enumType)
+        {
+            // Get all of the names
+            return GetCachedValuesAndNames(enumType, true).Names;
+        }
+
+        public static Object ToObject(Type enumType, Object value)
+        {
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            // Delegate rest of error checking to the other functions
+            TypeCode typeCode = Convert.GetTypeCode(value);
+
+            switch (typeCode)
+            {
+                case TypeCode.Int32:
+                    return ToObject(enumType, (int)value);
+
+                case TypeCode.SByte:
+                    return ToObject(enumType, (sbyte)value);
+
+                case TypeCode.Int16:
+                    return ToObject(enumType, (short)value);
+
+                case TypeCode.Int64:
+                    return ToObject(enumType, (long)value);
+
+                case TypeCode.UInt32:
+                    return ToObject(enumType, (uint)value);
+
+                case TypeCode.Byte:
+                    return ToObject(enumType, (byte)value);
+
+                case TypeCode.UInt16:
+                    return ToObject(enumType, (ushort)value);
+
+                case TypeCode.UInt64:
+                    return ToObject(enumType, (ulong)value);
+
+                case TypeCode.Char:
+                    return ToObject(enumType, (char)value);
+
+                case TypeCode.Boolean:
+                    return ToObject(enumType, (bool)value);
+
+                default:
+                    // All unsigned types will be directly cast
+                    throw new ArgumentException(SR.Arg_MustBeEnumBaseTypeOrEnum, nameof(value));
+            }
+        }
+
+        public static bool IsDefined(Type enumType, Object value)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+
+            return enumType.IsEnumDefined(value);
+        }
+
+        public static String Format(Type enumType, Object value, String format)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+
+            if (!enumType.IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, nameof(enumType));
+
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            if (format == null)
+                throw new ArgumentNullException(nameof(format));
+
+            RuntimeType rtType = enumType as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(enumType));
+
+            // Check if both of them are of the same type
+            Type valueType = value.GetType();
+
+            Type underlyingType = GetUnderlyingType(enumType);
+
+            // If the value is an Enum then we need to extract the underlying value from it
+            if (valueType.IsEnum)
+            {
+                if (!valueType.IsEquivalentTo(enumType))
+                    throw new ArgumentException(SR.Format(SR.Arg_EnumAndObjectMustBeSameType, valueType.ToString(), enumType.ToString()));
+
+                if (format.Length != 1)
+                {
+                    // all acceptable format string are of length 1
+                    throw new FormatException(SR.Format_InvalidEnumFormatSpecification);
+                }
+                return ((Enum)value).ToString(format);
+            }
+            // The value must be of the same type as the Underlying type of the Enum
+            else if (valueType != underlyingType)
+            {
+                throw new ArgumentException(SR.Format(SR.Arg_EnumFormatUnderlyingTypeAndObjectMustBeSameType, valueType.ToString(), underlyingType.ToString()));
+            }
+            if (format.Length != 1)
+            {
+                // all acceptable format string are of length 1
+                throw new FormatException(SR.Format_InvalidEnumFormatSpecification);
+            }
+
+            char formatCh = format[0];
+            if (formatCh == 'G' || formatCh == 'g')
+                return GetEnumName(rtType, ToUInt64(value)) ?? value.ToString();
+
+            if (formatCh == 'D' || formatCh == 'd')
+                return value.ToString();
+
+            if (formatCh == 'X' || formatCh == 'x')
+                return InternalFormattedHexString(value);
+
+            if (formatCh == 'F' || formatCh == 'f')
+                return Enum.InternalFlagsFormat(rtType, ToUInt64(value)) ?? value.ToString();
+
+            throw new FormatException(SR.Format_InvalidEnumFormatSpecification);
+        }
+
+        #endregion
+
+        #region Definitions
+        private class TypeValuesAndNames
+        {
+            // Each entry contains a list of sorted pair of enum field names and values, sorted by values
+            public TypeValuesAndNames(bool isFlag, ulong[] values, String[] names)
+            {
+                this.IsFlag = isFlag;
+                this.Values = values;
+                this.Names = names;
+            }
+
+            public bool IsFlag;
+            public ulong[] Values;
+            public String[] Names;
+        }
+        #endregion
+
+        #region Private Methods
+        internal unsafe Object GetValue()
+        {
+            fixed (void* pValue = &JitHelpers.GetPinningHelper(this).m_data)
+            {
+                switch (InternalGetCorElementType())
+                {
+                    case CorElementType.I1:
+                        return *(sbyte*)pValue;
+                    case CorElementType.U1:
+                        return *(byte*)pValue;
+                    case CorElementType.Boolean:
+                        return *(bool*)pValue;
+                    case CorElementType.I2:
+                        return *(short*)pValue;
+                    case CorElementType.U2:
+                        return *(ushort*)pValue;
+                    case CorElementType.Char:
+                        return *(char*)pValue;
+                    case CorElementType.I4:
+                        return *(int*)pValue;
+                    case CorElementType.U4:
+                        return *(uint*)pValue;
+                    case CorElementType.R4:
+                        return *(float*)pValue;
+                    case CorElementType.I8:
+                        return *(long*)pValue;
+                    case CorElementType.U8:
+                        return *(ulong*)pValue;
+                    case CorElementType.R8:
+                        return *(double*)pValue;
+                    case CorElementType.I:
+                        return *(IntPtr*)pValue;
+                    case CorElementType.U:
+                        return *(UIntPtr*)pValue;
+                    default:
+                        Debug.Fail("Invalid primitive type");
+                        return null;
+                }
+            }
+        }
+
+        private unsafe ulong ToUInt64()
+        {
+            fixed (void* pValue = &JitHelpers.GetPinningHelper(this).m_data)
+            {
+                switch (InternalGetCorElementType())
+                {
+                    case CorElementType.I1:
+                        return (ulong)*(sbyte*)pValue;
+                    case CorElementType.U1:
+                        return *(byte*)pValue;
+                    case CorElementType.Boolean:
+                        return Convert.ToUInt64(*(bool*)pValue, CultureInfo.InvariantCulture);
+                    case CorElementType.I2:
+                        return (ulong)*(short*)pValue;
+                    case CorElementType.U2:
+                    case CorElementType.Char:
+                        return *(ushort*)pValue;
+                    case CorElementType.I4:
+                        return (ulong)*(int*)pValue;
+                    case CorElementType.U4:
+                    case CorElementType.R4:
+                        return *(uint*)pValue;
+                    case CorElementType.I8:
+                        return (ulong)*(long*)pValue;
+                    case CorElementType.U8:
+                    case CorElementType.R8:
+                        return *(ulong*)pValue;
+                    case CorElementType.I:
+                        if (IntPtr.Size == 8)
+                        {
+                            return *(ulong*)pValue;
+                        }
+                        else
+                        {
+                            return (ulong)*(int*)pValue;
+                        }
+                    case CorElementType.U:
+                        if (IntPtr.Size == 8)
+                        {
+                            return *(ulong*)pValue;
+                        }
+                        else
+                        {
+                            return *(uint*)pValue;
+                        }
+                    default:
+                        Debug.Fail("Invalid primitive type");
+                        return 0;
+                }
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern bool InternalHasFlag(Enum flags);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern CorElementType InternalGetCorElementType();
+
+        #endregion
+
+        #region Object Overrides
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern override bool Equals(Object obj);
+
+        public override unsafe int GetHashCode()
+        {
+            // CONTRACT with the runtime: GetHashCode of enum types is implemented as GetHashCode of the underlying type.
+            // The runtime can bypass calls to Enum::GetHashCode and call the underlying type's GetHashCode directly
+            // to avoid boxing the enum.
+
+            fixed (void* pValue = &JitHelpers.GetPinningHelper(this).m_data)
+            {
+                switch (InternalGetCorElementType())
+                {
+                    case CorElementType.I1:
+                        return (*(sbyte*)pValue).GetHashCode();
+                    case CorElementType.U1:
+                        return (*(byte*)pValue).GetHashCode();
+                    case CorElementType.Boolean:
+                        return (*(bool*)pValue).GetHashCode();
+                    case CorElementType.I2:
+                        return (*(short*)pValue).GetHashCode();
+                    case CorElementType.U2:
+                        return (*(ushort*)pValue).GetHashCode();
+                    case CorElementType.Char:
+                        return (*(char*)pValue).GetHashCode();
+                    case CorElementType.I4:
+                        return (*(int*)pValue).GetHashCode();
+                    case CorElementType.U4:
+                        return (*(uint*)pValue).GetHashCode();
+                    case CorElementType.R4:
+                        return (*(float*)pValue).GetHashCode();
+                    case CorElementType.I8:
+                        return (*(long*)pValue).GetHashCode();
+                    case CorElementType.U8:
+                        return (*(ulong*)pValue).GetHashCode();
+                    case CorElementType.R8:
+                        return (*(double*)pValue).GetHashCode();
+                    case CorElementType.I:
+                        return (*(IntPtr*)pValue).GetHashCode();
+                    case CorElementType.U:
+                        return (*(UIntPtr*)pValue).GetHashCode();
+                    default:
+                        Debug.Fail("Invalid primitive type");
+                        return 0;
+                }
+            }
+        }
+
+        public override String ToString()
+        {
+            // Returns the value in a human readable format.  For PASCAL style enums who's value maps directly the name of the field is returned.
+            // For PASCAL style enums who's values do not map directly the decimal value of the field is returned.
+            // For BitFlags (indicated by the Flags custom attribute): If for each bit that is set in the value there is a corresponding constant
+            //(a pure power of 2), then the  OR string (ie "Red | Yellow") is returned. Otherwise, if the value is zero or if you can't create a string that consists of
+            // pure powers of 2 OR-ed together, you return a hex value
+
+
+            // Try to see if its one of the enum values, then we return a String back else the value
+            return Enum.InternalFormat((RuntimeType)GetType(), ToUInt64()) ?? GetValue().ToString();
+        }
+        #endregion
+
+        #region IFormattable
+        [Obsolete("The provider argument is not used. Please use ToString(String).")]
+        public String ToString(String format, IFormatProvider provider)
+        {
+            return ToString(format);
+        }
+        #endregion
+
+        #region IComparable
+        public int CompareTo(Object target)
+        {
+            const int retIncompatibleMethodTables = 2;  // indicates that the method tables did not match
+            const int retInvalidEnumType = 3; // indicates that the enum was of an unknown/unsupported underlying type
+
+            if (this == null)
+                throw new NullReferenceException();
+
+            int ret = InternalCompareTo(this, target);
+
+            if (ret < retIncompatibleMethodTables)
+            {
+                // -1, 0 and 1 are the normal return codes
+                return ret;
+            }
+            else if (ret == retIncompatibleMethodTables)
+            {
+                Type thisType = this.GetType();
+                Type targetType = target.GetType();
+
+                throw new ArgumentException(SR.Format(SR.Arg_EnumAndObjectMustBeSameType, targetType.ToString(), thisType.ToString()));
+            }
+            else
+            {
+                // assert valid return code (3)
+                Debug.Assert(ret == retInvalidEnumType, "Enum.InternalCompareTo return code was invalid");
+
+                throw new InvalidOperationException(SR.InvalidOperation_UnknownEnumType);
+            }
+        }
+        #endregion
+
+        #region Public Methods
+        public String ToString(String format)
+        {
+            char formatCh;
+            if (format == null || format.Length == 0)
+                formatCh = 'G';
+            else if (format.Length != 1)
+                throw new FormatException(SR.Format_InvalidEnumFormatSpecification);
+            else
+                formatCh = format[0];
+
+            if (formatCh == 'G' || formatCh == 'g')
+                return ToString();
+
+            if (formatCh == 'D' || formatCh == 'd')
+                return GetValue().ToString();
+
+            if (formatCh == 'X' || formatCh == 'x')
+                return InternalFormattedHexString();
+
+            if (formatCh == 'F' || formatCh == 'f')
+                return InternalFlagsFormat((RuntimeType)GetType(), ToUInt64()) ?? GetValue().ToString();
+
+            throw new FormatException(SR.Format_InvalidEnumFormatSpecification);
+        }
+
+        [Obsolete("The provider argument is not used. Please use ToString().")]
+        public String ToString(IFormatProvider provider)
+        {
+            return ToString();
+        }
+
+        [Intrinsic]
+        public Boolean HasFlag(Enum flag)
+        {
+            if (flag == null)
+                throw new ArgumentNullException(nameof(flag));
+
+            if (!this.GetType().IsEquivalentTo(flag.GetType()))
+            {
+                throw new ArgumentException(SR.Format(SR.Argument_EnumTypeDoesNotMatch, flag.GetType(), this.GetType()));
+            }
+
+            return InternalHasFlag(flag);
+        }
+
+        #endregion
+
+        #region IConvertable
+        public TypeCode GetTypeCode()
+        {
+            switch (InternalGetCorElementType())
+            {
+                case CorElementType.I1:
+                    return TypeCode.SByte;
+                case CorElementType.U1:
+                    return TypeCode.Byte;
+                case CorElementType.Boolean:
+                    return TypeCode.Boolean;
+                case CorElementType.I2:
+                    return TypeCode.Int16;
+                case CorElementType.U2:
+                    return TypeCode.UInt16;
+                case CorElementType.Char:
+                    return TypeCode.Char;
+                case CorElementType.I4:
+                    return TypeCode.Int32;
+                case CorElementType.U4:
+                    return TypeCode.UInt32;
+                case CorElementType.I8:
+                    return TypeCode.Int64;
+                case CorElementType.U8:
+                    return TypeCode.UInt64;
+                default:
+                    throw new InvalidOperationException(SR.InvalidOperation_UnknownEnumType);
+            }
+        }
+
+        bool IConvertible.ToBoolean(IFormatProvider provider)
+        {
+            return Convert.ToBoolean(GetValue(), CultureInfo.CurrentCulture);
+        }
+
+        char IConvertible.ToChar(IFormatProvider provider)
+        {
+            return Convert.ToChar(GetValue(), CultureInfo.CurrentCulture);
+        }
+
+        sbyte IConvertible.ToSByte(IFormatProvider provider)
+        {
+            return Convert.ToSByte(GetValue(), CultureInfo.CurrentCulture);
+        }
+
+        byte IConvertible.ToByte(IFormatProvider provider)
+        {
+            return Convert.ToByte(GetValue(), CultureInfo.CurrentCulture);
+        }
+
+        short IConvertible.ToInt16(IFormatProvider provider)
+        {
+            return Convert.ToInt16(GetValue(), CultureInfo.CurrentCulture);
+        }
+
+        ushort IConvertible.ToUInt16(IFormatProvider provider)
+        {
+            return Convert.ToUInt16(GetValue(), CultureInfo.CurrentCulture);
+        }
+
+        int IConvertible.ToInt32(IFormatProvider provider)
+        {
+            return Convert.ToInt32(GetValue(), CultureInfo.CurrentCulture);
+        }
+
+        uint IConvertible.ToUInt32(IFormatProvider provider)
+        {
+            return Convert.ToUInt32(GetValue(), CultureInfo.CurrentCulture);
+        }
+
+        long IConvertible.ToInt64(IFormatProvider provider)
+        {
+            return Convert.ToInt64(GetValue(), CultureInfo.CurrentCulture);
+        }
+
+        ulong IConvertible.ToUInt64(IFormatProvider provider)
+        {
+            return Convert.ToUInt64(GetValue(), CultureInfo.CurrentCulture);
+        }
+
+        float IConvertible.ToSingle(IFormatProvider provider)
+        {
+            return Convert.ToSingle(GetValue(), CultureInfo.CurrentCulture);
+        }
+
+        double IConvertible.ToDouble(IFormatProvider provider)
+        {
+            return Convert.ToDouble(GetValue(), CultureInfo.CurrentCulture);
+        }
+
+        Decimal IConvertible.ToDecimal(IFormatProvider provider)
+        {
+            return Convert.ToDecimal(GetValue(), CultureInfo.CurrentCulture);
+        }
+
+        DateTime IConvertible.ToDateTime(IFormatProvider provider)
+        {
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_FromTo, "Enum", "DateTime"));
+        }
+
+        Object IConvertible.ToType(Type type, IFormatProvider provider)
+        {
+            return Convert.DefaultToType((IConvertible)this, type, provider);
+        }
+        #endregion
+
+        #region ToObject
+        [CLSCompliant(false)]
+        public static Object ToObject(Type enumType, sbyte value)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+            if (!enumType.IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, nameof(enumType));
+            RuntimeType rtType = enumType as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(enumType));
+            return InternalBoxEnum(rtType, value);
+        }
+
+        public static Object ToObject(Type enumType, short value)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+            if (!enumType.IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, nameof(enumType));
+            RuntimeType rtType = enumType as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(enumType));
+            return InternalBoxEnum(rtType, value);
+        }
+
+        public static Object ToObject(Type enumType, int value)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+            if (!enumType.IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, nameof(enumType));
+            RuntimeType rtType = enumType as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(enumType));
+            return InternalBoxEnum(rtType, value);
+        }
+
+        public static Object ToObject(Type enumType, byte value)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+            if (!enumType.IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, nameof(enumType));
+            RuntimeType rtType = enumType as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(enumType));
+            return InternalBoxEnum(rtType, value);
+        }
+
+        [CLSCompliant(false)]
+        public static Object ToObject(Type enumType, ushort value)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+            if (!enumType.IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, nameof(enumType));
+            RuntimeType rtType = enumType as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(enumType));
+            return InternalBoxEnum(rtType, value);
+        }
+
+        [CLSCompliant(false)]
+        public static Object ToObject(Type enumType, uint value)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+            if (!enumType.IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, nameof(enumType));
+            RuntimeType rtType = enumType as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(enumType));
+            return InternalBoxEnum(rtType, value);
+        }
+
+        public static Object ToObject(Type enumType, long value)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+            if (!enumType.IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, nameof(enumType));
+            RuntimeType rtType = enumType as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(enumType));
+            return InternalBoxEnum(rtType, value);
+        }
+
+        [CLSCompliant(false)]
+        public static Object ToObject(Type enumType, ulong value)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+            if (!enumType.IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, nameof(enumType));
+            RuntimeType rtType = enumType as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(enumType));
+            return InternalBoxEnum(rtType, unchecked((long)value));
+        }
+
+        private static Object ToObject(Type enumType, char value)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+            if (!enumType.IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, nameof(enumType));
+            RuntimeType rtType = enumType as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(enumType));
+            return InternalBoxEnum(rtType, value);
+        }
+
+        private static Object ToObject(Type enumType, bool value)
+        {
+            if (enumType == null)
+                throw new ArgumentNullException(nameof(enumType));
+            if (!enumType.IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, nameof(enumType));
+            RuntimeType rtType = enumType as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(enumType));
+            return InternalBoxEnum(rtType, value ? 1 : 0);
+        }
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Environment.Windows.cs b/src/System.Private.CoreLib/src/System/Environment.Windows.cs
new file mode 100644
index 0000000000..5bf7bea158
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Environment.Windows.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.IO;
+
+namespace System
+{
+    internal static partial class Environment
+    {
+        internal static string SystemDirectory
+        {
+            get
+            {
+                // The path will likely be under 32 characters, e.g. C:\Windows\system32
+                Span<char> buffer = stackalloc char[32];
+                int requiredSize = Interop.Kernel32.GetSystemDirectoryW(buffer);
+
+                if (requiredSize > buffer.Length)
+                {
+                    buffer = new char[requiredSize];
+                    requiredSize = Interop.Kernel32.GetSystemDirectoryW(buffer);
+                }
+
+                if (requiredSize == 0)
+                {
+                    throw Win32Marshal.GetExceptionForLastWin32Error();
+                }
+
+                return new string(buffer.Slice(0, requiredSize));
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Environment.cs b/src/System.Private.CoreLib/src/System/Environment.cs
new file mode 100644
index 0000000000..902c6769ac
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Environment.cs
@@ -0,0 +1,705 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Provides some basic access to some environment 
+** functionality.
+**
+**
+============================================================*/
+
+namespace System
+{
+    using System.Buffers;
+    using System.IO;
+    using System.Security;
+    using System.Resources;
+    using System.Globalization;
+    using System.Collections;
+    using System.Collections.Generic;
+    using System.Text;
+    using System.Configuration.Assemblies;
+    using System.Runtime.InteropServices;
+    using System.Reflection;
+    using System.Diagnostics;
+    using Microsoft.Win32;
+    using System.Runtime.CompilerServices;
+    using System.Threading;
+    using System.Runtime.ConstrainedExecution;
+    using System.Runtime.Versioning;
+
+    public enum EnvironmentVariableTarget
+    {
+        Process = 0,
+        User = 1,
+        Machine = 2,
+    }
+
+    internal static partial class Environment
+    {
+        // Assume the following constants include the terminating '\0' - use <, not <=
+
+        // System environment variables are stored in the registry, and have 
+        // a size restriction that is separate from both normal environment 
+        // variables and registry value name lengths, according to MSDN.
+        // MSDN doesn't detail whether the name is limited to 1024, or whether
+        // that includes the contents of the environment variable.
+        private const int MaxSystemEnvVariableLength = 1024;
+        private const int MaxUserEnvVariableLength = 255;
+        private const int MaxMachineNameLength = 256;
+
+        // Looks up the resource string value for key.
+        // 
+        // if you change this method's signature then you must change the code that calls it
+        // in excep.cpp and probably you will have to visit mscorlib.h to add the new signature
+        // as well as metasig.h to create the new signature type
+        internal static String GetResourceStringLocal(String key)
+        {
+            return SR.GetResourceString(key);
+        }
+
+        /*==================================TickCount===================================
+        **Action: Gets the number of ticks since the system was started.
+        **Returns: The number of ticks since the system was started.
+        **Arguments: None
+        **Exceptions: None
+        ==============================================================================*/
+        public static extern int TickCount
+        {
+            [MethodImplAttribute(MethodImplOptions.InternalCall)]
+            get;
+        }
+
+        // Terminates this process with the given exit code.
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void _Exit(int exitCode);
+
+        public static void Exit(int exitCode)
+        {
+            _Exit(exitCode);
+        }
+
+
+        public static extern int ExitCode
+        {
+            [MethodImplAttribute(MethodImplOptions.InternalCall)]
+            get;
+
+            [MethodImplAttribute(MethodImplOptions.InternalCall)]
+            set;
+        }
+
+        // Note: The CLR's Watson bucketization code looks at the caller of the FCALL method
+        // to assign blame for crashes.  Don't mess with this, such as by making it call 
+        // another managed helper method, unless you consult with some CLR Watson experts.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void FailFast(String message);
+
+        // This overload of FailFast will allow you to specify the exception object
+        // whose bucket details *could* be used when undergoing the failfast process.
+        // To be specific:
+        //
+        // 1) When invoked from within a managed EH clause (fault/finally/catch),
+        //    if the exception object is preallocated, the runtime will try to find its buckets
+        //    and use them. If the exception object is not preallocated, it will use the bucket
+        //    details contained in the object (if any).
+        //
+        // 2) When invoked from outside the managed EH clauses (fault/finally/catch),
+        //    if the exception object is preallocated, the runtime will use the callsite's
+        //    IP for bucketing. If the exception object is not preallocated, it will use the bucket
+        //    details contained in the object (if any).
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void FailFast(String message, Exception exception);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void FailFast(String message, Exception exception, String errorMessage);
+
+#if FEATURE_WIN32_REGISTRY
+        // This is only used by RegistryKey on Windows.
+        public static String ExpandEnvironmentVariables(String name)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            if (name.Length == 0)
+            {
+                return name;
+            }
+
+            int currentSize = 100;
+            StringBuilder blob = new StringBuilder(currentSize); // A somewhat reasonable default size
+
+            int size;
+
+            blob.Length = 0;
+            size = Win32Native.ExpandEnvironmentStrings(name, blob, currentSize);
+            if (size == 0)
+                Marshal.ThrowExceptionForHR(Marshal.GetHRForLastWin32Error());
+
+            while (size > currentSize)
+            {
+                currentSize = size;
+                blob.Capacity = currentSize;
+                blob.Length = 0;
+
+                size = Win32Native.ExpandEnvironmentStrings(name, blob, currentSize);
+                if (size == 0)
+                    Marshal.ThrowExceptionForHR(Marshal.GetHRForLastWin32Error());
+            }
+
+            return blob.ToString();
+        }
+#endif // FEATURE_WIN32_REGISTRY
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern Int32 GetProcessorCount();
+
+        public static int ProcessorCount
+        {
+            get
+            {
+                return GetProcessorCount();
+            }
+        }
+
+        /*==============================GetCommandLineArgs==============================
+        **Action: Gets the command line and splits it appropriately to deal with whitespace,
+        **        quotes, and escape characters.
+        **Returns: A string array containing your command line arguments.
+        **Arguments: None
+        **Exceptions: None.
+        ==============================================================================*/
+        public static String[] GetCommandLineArgs()
+        {
+            /*
+             * There are multiple entry points to a hosted app.
+             * The host could use ::ExecuteAssembly() or ::CreateDelegate option
+             * ::ExecuteAssembly() -> In this particular case, the runtime invokes the main 
+               method based on the arguments set by the host, and we return those arguments
+             *
+             * ::CreateDelegate() -> In this particular case, the host is asked to create a 
+             * delegate based on the appDomain, assembly and methodDesc passed to it.
+             * which the caller uses to invoke the method. In this particular case we do not have
+             * any information on what arguments would be passed to the delegate.
+             * So our best bet is to simply use the commandLine that was used to invoke the process.
+             * in case it is present.
+             */
+            if (s_CommandLineArgs != null)
+                return (string[])s_CommandLineArgs.Clone();
+
+            return GetCommandLineArgsNative();
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern String[] GetCommandLineArgsNative();
+
+        private static string[] s_CommandLineArgs = null;
+        private static void SetCommandLineArgs(string[] cmdLineArgs)
+        {
+            s_CommandLineArgs = cmdLineArgs;
+        }
+
+        private static unsafe char[] GetEnvironmentCharArray()
+        {
+            char[] block = null;
+
+            RuntimeHelpers.PrepareConstrainedRegions();
+
+            char* pStrings = null;
+
+            try
+            {
+                pStrings = Win32Native.GetEnvironmentStrings();
+                if (pStrings == null)
+                {
+                    throw new OutOfMemoryException();
+                }
+
+                // Format for GetEnvironmentStrings is:
+                // [=HiddenVar=value\0]* [Variable=value\0]* \0
+                // See the description of Environment Blocks in MSDN's
+                // CreateProcess page (null-terminated array of null-terminated strings).
+
+                // Search for terminating \0\0 (two unicode \0's).
+                char* p = pStrings;
+                while (!(*p == '\0' && *(p + 1) == '\0'))
+                    p++;
+
+                int len = (int)(p - pStrings + 1);
+                block = new char[len];
+
+                fixed (char* pBlock = block)
+                    string.wstrcpy(pBlock, pStrings, len);
+            }
+            finally
+            {
+                if (pStrings != null)
+                    Win32Native.FreeEnvironmentStrings(pStrings);
+            }
+
+            return block;
+        }
+
+        /*===================================NewLine====================================
+        **Action: A property which returns the appropriate newline string for the given
+        **        platform.
+        **Returns: \r\n on Win32.
+        **Arguments: None.
+        **Exceptions: None.
+        ==============================================================================*/
+        public static String NewLine
+        {
+            get
+            {
+#if PLATFORM_WINDOWS
+                return "\r\n";
+#else
+                return "\n";
+#endif // PLATFORM_WINDOWS
+            }
+        }
+
+
+        /*===================================Version====================================
+        **Action: Returns the COM+ version struct, describing the build number.
+        **Returns:
+        **Arguments:
+        **Exceptions:
+        ==============================================================================*/
+        public static Version Version
+        {
+            get
+            {
+                // Previously this represented the File version of mscorlib.dll.  Many other libraries in the framework and outside took dependencies on the first three parts of this version 
+                // remaining constant throughout 4.x.  From 4.0 to 4.5.2 this was fine since the file version only incremented the last part.Starting with 4.6 we switched to a file versioning
+                // scheme that matched the product version.  In order to preserve compatibility with existing libraries, this needs to be hard-coded.
+
+                return new Version(4, 0, 30319, 42000);
+            }
+        }
+
+#if !FEATURE_PAL
+        private static Lazy<bool> s_IsWindows8OrAbove = new Lazy<bool>(() => 
+        {
+            ulong conditionMask = Win32Native.VerSetConditionMask(0, Win32Native.VER_MAJORVERSION, Win32Native.VER_GREATER_EQUAL);
+            conditionMask = Win32Native.VerSetConditionMask(conditionMask, Win32Native.VER_MINORVERSION, Win32Native.VER_GREATER_EQUAL);
+            conditionMask = Win32Native.VerSetConditionMask(conditionMask, Win32Native.VER_SERVICEPACKMAJOR, Win32Native.VER_GREATER_EQUAL);
+            conditionMask = Win32Native.VerSetConditionMask(conditionMask, Win32Native.VER_SERVICEPACKMINOR, Win32Native.VER_GREATER_EQUAL);
+
+            // Windows 8 version is 6.2
+            var version = new Win32Native.OSVERSIONINFOEX { MajorVersion = 6, MinorVersion = 2, ServicePackMajor = 0, ServicePackMinor = 0 };
+                
+            return Win32Native.VerifyVersionInfoW(version, 
+                       Win32Native.VER_MAJORVERSION | Win32Native.VER_MINORVERSION | Win32Native.VER_SERVICEPACKMAJOR | Win32Native.VER_SERVICEPACKMINOR,
+                       conditionMask);
+        });
+        internal static bool IsWindows8OrAbove => s_IsWindows8OrAbove.Value;
+#endif
+        
+#if FEATURE_COMINTEROP
+        // Does the current version of Windows have Windows Runtime suppport?
+        private static Lazy<bool> s_IsWinRTSupported = new Lazy<bool>(() =>
+        {
+            return WinRTSupported();
+        });
+
+        internal static bool IsWinRTSupported => s_IsWinRTSupported.Value;
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static extern bool WinRTSupported();
+#endif // FEATURE_COMINTEROP
+
+
+        /*==================================StackTrace==================================
+        **Action:
+        **Returns:
+        **Arguments:
+        **Exceptions:
+        ==============================================================================*/
+        public static String StackTrace
+        {
+            [MethodImpl(MethodImplOptions.NoInlining)] // Prevent inlining from affecting where the stacktrace starts
+            get
+            {
+                return Internal.Runtime.Augments.EnvironmentAugments.StackTrace;
+            }
+        }
+
+        internal static String GetStackTrace(Exception e, bool needFileInfo)
+        {
+            // Note: Setting needFileInfo to true will start up COM and set our
+            // apartment state.  Try to not call this when passing "true" 
+            // before the EE's ExecuteMainMethod has had a chance to set up the
+            // apartment state.  -- 
+            StackTrace st;
+            if (e == null)
+                st = new StackTrace(needFileInfo);
+            else
+                st = new StackTrace(e, needFileInfo);
+
+            // Do no include a trailing newline for backwards compatibility
+            return st.ToString(System.Diagnostics.StackTrace.TraceFormat.Normal);
+        }
+
+        public static extern bool HasShutdownStarted
+        {
+            [MethodImplAttribute(MethodImplOptions.InternalCall)]
+            get;
+        }
+
+        internal static bool UserInteractive
+        {
+            get
+            {
+                return true;
+            }
+        }
+        public static int CurrentManagedThreadId
+        {
+            get
+            {
+                return Thread.CurrentThread.ManagedThreadId;
+            }
+        }
+
+        public static string GetEnvironmentVariable(string variable)
+        {
+            if (variable == null)
+            {
+                throw new ArgumentNullException(nameof(variable));
+            }
+
+            // separated from the EnvironmentVariableTarget overload to help with tree shaking in common case
+            return GetEnvironmentVariableCore(variable);
+        }
+
+        internal static string GetEnvironmentVariable(string variable, EnvironmentVariableTarget target)
+        {
+            if (variable == null)
+            {
+                throw new ArgumentNullException(nameof(variable));
+            }
+
+            ValidateTarget(target);
+
+            return GetEnvironmentVariableCore(variable, target);
+        }
+
+        public static void SetEnvironmentVariable(string variable, string value)
+        {
+            ValidateVariableAndValue(variable, ref value);
+
+            // separated from the EnvironmentVariableTarget overload to help with tree shaking in common case
+            SetEnvironmentVariableCore(variable, value);
+        }
+
+        internal static void SetEnvironmentVariable(string variable, string value, EnvironmentVariableTarget target)
+        {
+            ValidateVariableAndValue(variable, ref value);
+            ValidateTarget(target);
+
+            SetEnvironmentVariableCore(variable, value, target);
+        }
+
+        private static void ValidateVariableAndValue(string variable, ref string value)
+        {
+            if (variable == null)
+            {
+                throw new ArgumentNullException(nameof(variable));
+            }
+            if (variable.Length == 0)
+            {
+                throw new ArgumentException(SR.Argument_StringZeroLength, nameof(variable));
+            }
+            if (variable[0] == '\0')
+            {
+                throw new ArgumentException(SR.Argument_StringFirstCharIsZero, nameof(variable));
+            }
+            if (variable.IndexOf('=') != -1)
+            {
+                throw new ArgumentException(SR.Argument_IllegalEnvVarName, nameof(variable));
+            }
+
+            if (string.IsNullOrEmpty(value) || value[0] == '\0')
+            {
+                // Explicitly null out value if it's empty
+                value = null;
+            }
+        }
+
+        private static void ValidateTarget(EnvironmentVariableTarget target)
+        {
+            if (target != EnvironmentVariableTarget.Process &&
+                target != EnvironmentVariableTarget.Machine &&
+                target != EnvironmentVariableTarget.User)
+            {
+                throw new ArgumentOutOfRangeException(nameof(target), target, SR.Format(SR.Arg_EnumIllegalVal, target));
+            }
+        }
+
+        private static string GetEnvironmentVariableCore(string variable)
+        {
+            Span<char> buffer = stackalloc char[128]; // A somewhat reasonable default size
+            return GetEnvironmentVariableCoreHelper(variable, buffer);
+        }
+
+        private static string GetEnvironmentVariableCoreHelper(string variable, Span<char> buffer)
+        {
+            int requiredSize = Win32Native.GetEnvironmentVariable(variable, buffer);
+
+            if (requiredSize == 0 && Marshal.GetLastWin32Error() == Interop.Errors.ERROR_ENVVAR_NOT_FOUND)
+            {
+                return null;
+            }
+
+            if (requiredSize > buffer.Length)
+            {
+                char[] chars = ArrayPool<char>.Shared.Rent(requiredSize);
+                try
+                {
+                    return GetEnvironmentVariableCoreHelper(variable, chars);
+                }
+                finally
+                {
+                    ArrayPool<char>.Shared.Return(chars);
+                }
+            }
+
+            return new string(buffer.Slice(0, requiredSize));
+        }
+
+        private static string GetEnvironmentVariableCore(string variable, EnvironmentVariableTarget target)
+        {
+            if (target == EnvironmentVariableTarget.Process)
+                return GetEnvironmentVariableCore(variable);
+
+#if FEATURE_WIN32_REGISTRY
+            if (AppDomain.IsAppXModel())
+#endif
+            {
+                return null;
+            }
+#if FEATURE_WIN32_REGISTRY
+            RegistryKey baseKey;
+            string keyName;
+
+            if (target == EnvironmentVariableTarget.Machine)
+            {
+                baseKey = Registry.LocalMachine;
+                keyName = @"System\CurrentControlSet\Control\Session Manager\Environment";
+            }
+            else if (target == EnvironmentVariableTarget.User)
+            {
+                baseKey = Registry.CurrentUser;
+                keyName = "Environment";
+            }
+            else
+            {
+                throw new ArgumentException(SR.Format(SR.Arg_EnumIllegalVal, (int)target));
+            }
+
+            using (RegistryKey environmentKey = baseKey.OpenSubKey(keyName, writable: false))
+            {
+                return environmentKey?.GetValue(variable) as string;
+            }
+#endif
+        }
+
+        internal static IEnumerable<KeyValuePair<string, string>> EnumerateEnvironmentVariables()
+        {
+            // Format for GetEnvironmentStrings is:
+            // (=HiddenVar=value\0 | Variable=value\0)* \0
+            // See the description of Environment Blocks in MSDN's
+            // CreateProcess page (null-terminated array of null-terminated strings).
+            // Note the =HiddenVar's aren't always at the beginning.
+
+            // Copy strings out, parsing into pairs and inserting into the table.
+            // The first few environment variable entries start with an '='.
+            // The current working directory of every drive (except for those drives
+            // you haven't cd'ed into in your DOS window) are stored in the 
+            // environment block (as =C:=pwd) and the program's exit code is 
+            // as well (=ExitCode=00000000).
+
+            char[] block = GetEnvironmentCharArray();
+            for (int i = 0; i < block.Length; i++)
+            {
+                int startKey = i;
+
+                // Skip to key. On some old OS, the environment block can be corrupted.
+                // Some will not have '=', so we need to check for '\0'. 
+                while (block[i] != '=' && block[i] != '\0')
+                    i++;
+                if (block[i] == '\0')
+                    continue;
+
+                // Skip over environment variables starting with '='
+                if (i - startKey == 0)
+                {
+                    while (block[i] != 0)
+                        i++;
+                    continue;
+                }
+
+                string key = new string(block, startKey, i - startKey);
+                i++;  // skip over '='
+
+                int startValue = i;
+                while (block[i] != 0)
+                    i++; // Read to end of this entry 
+                string value = new string(block, startValue, i - startValue); // skip over 0 handled by for loop's i++
+
+                yield return new KeyValuePair<string, string>(key, value);
+            }
+        }
+
+        internal static IEnumerable<KeyValuePair<string, string>> EnumerateEnvironmentVariables(EnvironmentVariableTarget target)
+        {
+            if (target == EnvironmentVariableTarget.Process)
+                return EnumerateEnvironmentVariables();
+            return EnumerateEnvironmentVariablesFromRegistry(target);
+        }
+
+        internal static IEnumerable<KeyValuePair<string, string>> EnumerateEnvironmentVariablesFromRegistry(EnvironmentVariableTarget target)
+        {
+#if FEATURE_WIN32_REGISTRY
+            if (AppDomain.IsAppXModel())
+#endif
+            {
+                // Without registry support we have nothing to return
+                ValidateTarget(target);
+                yield break;
+            }
+#if FEATURE_WIN32_REGISTRY
+            RegistryKey baseKey;
+            string keyName;
+            if (target == EnvironmentVariableTarget.Machine)
+            {
+                baseKey = Registry.LocalMachine;
+                keyName = @"System\CurrentControlSet\Control\Session Manager\Environment";
+            }
+            else if (target == EnvironmentVariableTarget.User)
+            {
+                baseKey = Registry.CurrentUser;
+                keyName = @"Environment";
+            }
+            else
+            {
+                throw new ArgumentOutOfRangeException(nameof(target), target, SR.Format(SR.Arg_EnumIllegalVal, target));
+            }
+
+            using (RegistryKey environmentKey = baseKey.OpenSubKey(keyName, writable: false))
+            {
+                if (environmentKey != null)
+                {
+                    foreach (string name in environmentKey.GetValueNames())
+                    {
+                        string value = environmentKey.GetValue(name, "").ToString();
+                        yield return new KeyValuePair<string, string>(name, value);
+                    }
+                }
+            }
+#endif // FEATURE_WIN32_REGISTRY
+        }
+
+        private static void SetEnvironmentVariableCore(string variable, string value)
+        {
+            // explicitly null out value if is the empty string.
+            if (string.IsNullOrEmpty(value) || value[0] == '\0')
+                value = null;
+
+            if (!Win32Native.SetEnvironmentVariable(variable, value))
+            {
+                int errorCode = Marshal.GetLastWin32Error();
+
+                switch (errorCode)
+                {
+                    case Interop.Errors.ERROR_ENVVAR_NOT_FOUND:
+                        // Allow user to try to clear a environment variable
+                        return;
+                    case Interop.Errors.ERROR_FILENAME_EXCED_RANGE:
+                        // The error message from Win32 is "The filename or extension is too long",
+                        // which is not accurate.
+                        throw new ArgumentException(SR.Format(SR.Argument_LongEnvVarValue));
+                    case Interop.Errors.ERROR_NOT_ENOUGH_MEMORY:
+                    case Interop.Errors.ERROR_NO_SYSTEM_RESOURCES:
+                        throw new OutOfMemoryException(Interop.Kernel32.GetMessage(errorCode));
+                    default:
+                        throw new ArgumentException(Interop.Kernel32.GetMessage(errorCode));
+                }
+            }
+        }
+
+        private static void SetEnvironmentVariableCore(string variable, string value, EnvironmentVariableTarget target)
+        {
+            if (target == EnvironmentVariableTarget.Process)
+            {
+                SetEnvironmentVariableCore(variable, value);
+                return;
+            }
+
+#if FEATURE_WIN32_REGISTRY
+            if (AppDomain.IsAppXModel())
+#endif
+            {
+                // other targets ignored
+                return;
+            }
+#if FEATURE_WIN32_REGISTRY
+            // explicitly null out value if is the empty string.
+            if (string.IsNullOrEmpty(value) || value[0] == '\0')
+                value = null;
+
+            RegistryKey baseKey;
+            string keyName;
+
+            if (target == EnvironmentVariableTarget.Machine)
+            {
+                baseKey = Registry.LocalMachine;
+                keyName = @"System\CurrentControlSet\Control\Session Manager\Environment";
+            }
+            else if (target == EnvironmentVariableTarget.User)
+            {
+                // User-wide environment variables stored in the registry are limited to 255 chars for the environment variable name.
+                const int MaxUserEnvVariableLength = 255;
+                if (variable.Length >= MaxUserEnvVariableLength)
+                {
+                    throw new ArgumentException(SR.Argument_LongEnvVarValue, nameof(variable));
+                }
+
+                baseKey = Registry.CurrentUser;
+                keyName = "Environment";
+            }
+            else
+            {
+                throw new ArgumentException(SR.Format(SR.Arg_EnumIllegalVal, (int)target));
+            }
+
+            using (RegistryKey environmentKey = baseKey.OpenSubKey(keyName, writable: true))
+            {
+                if (environmentKey != null)
+                {
+                    if (value == null)
+                    {
+                        environmentKey.DeleteValue(variable, throwOnMissingValue: false);
+                    }
+                    else
+                    {
+                        environmentKey.SetValue(variable, value);
+                    }
+                }
+            }
+
+            // send a WM_SETTINGCHANGE message to all windows
+            IntPtr r = Interop.User32.SendMessageTimeout(new IntPtr(Interop.User32.HWND_BROADCAST),
+                Interop.User32.WM_SETTINGCHANGE, IntPtr.Zero, "Environment", 0, 1000, IntPtr.Zero);
+
+            Debug.Assert(r != IntPtr.Zero, "SetEnvironmentVariable failed: " + Marshal.GetLastWin32Error());
+#endif // FEATURE_WIN32_REGISTRY
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Exception.cs b/src/System.Private.CoreLib/src/System/Exception.cs
new file mode 100644
index 0000000000..abb9af814b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Exception.cs
@@ -0,0 +1,783 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: The base class for all exceptional conditions.
+**
+**
+=============================================================================*/
+
+namespace System
+{
+    using System;
+    using System.Runtime.InteropServices;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.Serialization;
+    using System.Runtime.Versioning;
+    using System.Diagnostics;
+    using System.Security;
+    using System.IO;
+    using System.Text;
+    using System.Reflection;
+    using System.Collections;
+    using System.Globalization;
+
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class Exception : ISerializable
+    {
+        private void Init()
+        {
+            _message = null;
+            _stackTrace = null;
+            _dynamicMethods = null;
+            HResult = HResults.COR_E_EXCEPTION;
+            _xcode = _COMPlusExceptionCode;
+            _xptrs = (IntPtr)0;
+
+            // Initialize the WatsonBuckets to be null
+            _watsonBuckets = null;
+
+            // Initialize the watson bucketing IP
+            _ipForWatsonBuckets = UIntPtr.Zero;
+        }
+
+        public Exception()
+        {
+            Init();
+        }
+
+        public Exception(String message)
+        {
+            Init();
+            _message = message;
+        }
+
+        // Creates a new Exception.  All derived classes should 
+        // provide this constructor.
+        // Note: the stack trace is not started until the exception 
+        // is thrown
+        // 
+        public Exception(String message, Exception innerException)
+        {
+            Init();
+            _message = message;
+            _innerException = innerException;
+        }
+
+        protected Exception(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+                throw new ArgumentNullException(nameof(info));
+
+            _className = info.GetString("ClassName"); // Do not rename (binary serialization)
+            _message = info.GetString("Message"); // Do not rename (binary serialization)
+            _data = (IDictionary)(info.GetValueNoThrow("Data", typeof(IDictionary))); // Do not rename (binary serialization)
+            _innerException = (Exception)(info.GetValue("InnerException", typeof(Exception))); // Do not rename (binary serialization)
+            _helpURL = info.GetString("HelpURL"); // Do not rename (binary serialization)
+            _stackTraceString = info.GetString("StackTraceString"); // Do not rename (binary serialization)
+            _remoteStackTraceString = info.GetString("RemoteStackTraceString"); // Do not rename (binary serialization)
+            _remoteStackIndex = info.GetInt32("RemoteStackIndex"); // Do not rename (binary serialization)
+
+            HResult = info.GetInt32("HResult"); // Do not rename (binary serialization)
+            _source = info.GetString("Source"); // Do not rename (binary serialization)
+
+            // Get the WatsonBuckets that were serialized - this is particularly
+            // done to support exceptions going across AD transitions.
+            // 
+            // We use the no throw version since we could be deserializing a pre-V4
+            // exception object that may not have this entry. In such a case, we would
+            // get null.
+            _watsonBuckets = (Object)info.GetValueNoThrow("WatsonBuckets", typeof(byte[])); // Do not rename (binary serialization)
+
+
+            if (_className == null || HResult == 0)
+                throw new SerializationException(SR.Serialization_InsufficientState);
+
+            // If we are constructing a new exception after a cross-appdomain call...
+            if (context.State == StreamingContextStates.CrossAppDomain)
+            {
+                // ...this new exception may get thrown.  It is logically a re-throw, but 
+                //  physically a brand-new exception.  Since the stack trace is cleared 
+                //  on a new exception, the "_remoteStackTraceString" is provided to 
+                //  effectively import a stack trace from a "remote" exception.  So,
+                //  move the _stackTraceString into the _remoteStackTraceString.  Note
+                //  that if there is an existing _remoteStackTraceString, it will be 
+                //  preserved at the head of the new string, so everything works as 
+                //  expected.
+                // Even if this exception is NOT thrown, things will still work as expected
+                //  because the StackTrace property returns the concatenation of the
+                //  _remoteStackTraceString and the _stackTraceString.
+                _remoteStackTraceString = _remoteStackTraceString + _stackTraceString;
+                _stackTraceString = null;
+            }
+        }
+
+
+        public virtual String Message
+        {
+            get
+            {
+                if (_message == null)
+                {
+                    if (_className == null)
+                    {
+                        _className = GetClassName();
+                    }
+                    return SR.Format(SR.Exception_WasThrown, _className);
+                }
+                else
+                {
+                    return _message;
+                }
+            }
+        }
+
+        public virtual IDictionary Data
+        {
+            get
+            {
+                if (_data == null)
+                    if (IsImmutableAgileException(this))
+                        _data = new EmptyReadOnlyDictionaryInternal();
+                    else
+                        _data = new ListDictionaryInternal();
+
+                return _data;
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool IsImmutableAgileException(Exception e);
+
+#if FEATURE_COMINTEROP
+        //
+        // Exception requires anything to be added into Data dictionary is serializable
+        // This wrapper is made serializable to satisfy this requirement but does NOT serialize 
+        // the object and simply ignores it during serialization, because we only need 
+        // the exception instance in the app to hold the error object alive.
+        // Once the exception is serialized to debugger, debugger only needs the error reference string
+        //
+        [Serializable]
+        internal class __RestrictedErrorObject
+        {
+            // Hold the error object instance but don't serialize/deserialize it
+            [NonSerialized]
+            private object _realErrorObject;
+
+            internal __RestrictedErrorObject(object errorObject)
+            {
+                _realErrorObject = errorObject;
+            }
+
+            public object RealErrorObject
+            {
+                get
+                {
+                    return _realErrorObject;
+                }
+            }
+        }
+
+        // [FriendAccessAllowed]
+        internal void AddExceptionDataForRestrictedErrorInfo(
+            string restrictedError,
+            string restrictedErrorReference,
+            string restrictedCapabilitySid,
+            object restrictedErrorObject,
+            bool hasrestrictedLanguageErrorObject = false)
+        {
+            IDictionary dict = Data;
+            if (dict != null)
+            {
+                dict.Add("RestrictedDescription", restrictedError);
+                dict.Add("RestrictedErrorReference", restrictedErrorReference);
+                dict.Add("RestrictedCapabilitySid", restrictedCapabilitySid);
+
+                // Keep the error object alive so that user could retrieve error information
+                // using Data["RestrictedErrorReference"]
+                dict.Add("__RestrictedErrorObject", (restrictedErrorObject == null ? null : new __RestrictedErrorObject(restrictedErrorObject)));
+                dict.Add("__HasRestrictedLanguageErrorObject", hasrestrictedLanguageErrorObject);
+            }
+        }
+
+        internal bool TryGetRestrictedLanguageErrorObject(out object restrictedErrorObject)
+        {
+            restrictedErrorObject = null;
+            if (Data != null && Data.Contains("__HasRestrictedLanguageErrorObject"))
+            {
+                if (Data.Contains("__RestrictedErrorObject"))
+                {
+                    __RestrictedErrorObject restrictedObject = Data["__RestrictedErrorObject"] as __RestrictedErrorObject;
+                    if (restrictedObject != null)
+                        restrictedErrorObject = restrictedObject.RealErrorObject;
+                }
+                return (bool)Data["__HasRestrictedLanguageErrorObject"];
+            }
+
+            return false;
+        }
+#endif // FEATURE_COMINTEROP
+
+        private string GetClassName()
+        {
+            // Will include namespace but not full instantiation and assembly name.
+            if (_className == null)
+                _className = GetType().ToString();
+
+            return _className;
+        }
+
+        // Retrieves the lowest exception (inner most) for the given Exception.
+        // This will traverse exceptions using the innerException property.
+        //
+        public virtual Exception GetBaseException()
+        {
+            Exception inner = InnerException;
+            Exception back = this;
+
+            while (inner != null)
+            {
+                back = inner;
+                inner = inner.InnerException;
+            }
+
+            return back;
+        }
+
+        // Returns the inner exception contained in this exception
+        // 
+        public Exception InnerException
+        {
+            get { return _innerException; }
+        }
+
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        static private extern IRuntimeMethodInfo GetMethodFromStackTrace(Object stackTrace);
+
+        private MethodBase GetExceptionMethodFromStackTrace()
+        {
+            IRuntimeMethodInfo method = GetMethodFromStackTrace(_stackTrace);
+
+            // Under certain race conditions when exceptions are re-used, this can be null
+            if (method == null)
+                return null;
+
+            return RuntimeType.GetMethodBase(method);
+        }
+
+        public MethodBase TargetSite
+        {
+            get
+            {
+                return GetTargetSiteInternal();
+            }
+        }
+
+
+        // this function is provided as a private helper to avoid the security demand
+        private MethodBase GetTargetSiteInternal()
+        {
+            if (_exceptionMethod != null)
+            {
+                return _exceptionMethod;
+            }
+            if (_stackTrace == null)
+            {
+                return null;
+            }
+            
+            _exceptionMethod = GetExceptionMethodFromStackTrace();
+            return _exceptionMethod;
+        }
+
+        // Returns the stack trace as a string.  If no stack trace is
+        // available, null is returned.
+        public virtual String StackTrace
+        {
+            get
+            {
+                // By default attempt to include file and line number info
+                return GetStackTrace(true);
+            }
+        }
+
+        // Computes and returns the stack trace as a string
+        // Attempts to get source file and line number information if needFileInfo
+        // is true.  Note that this requires FileIOPermission(PathDiscovery), and so
+        // will usually fail in CoreCLR.  To avoid the demand and resulting
+        // SecurityException we can explicitly not even try to get fileinfo.
+        private string GetStackTrace(bool needFileInfo)
+        {
+            string stackTraceString = _stackTraceString;
+            string remoteStackTraceString = _remoteStackTraceString;
+
+            // if no stack trace, try to get one
+            if (stackTraceString != null)
+            {
+                return remoteStackTraceString + stackTraceString;
+            }
+            if (_stackTrace == null)
+            {
+                return remoteStackTraceString;
+            }
+
+            // Obtain the stack trace string. Note that since Environment.GetStackTrace
+            // will add the path to the source file if the PDB is present and a demand
+            // for FileIOPermission(PathDiscovery) succeeds, we need to make sure we 
+            // don't store the stack trace string in the _stackTraceString member variable.
+            String tempStackTraceString = Environment.GetStackTrace(this, needFileInfo);
+            return remoteStackTraceString + tempStackTraceString;
+        }
+
+        // [FriendAccessAllowed]
+        internal void SetErrorCode(int hr)
+        {
+            HResult = hr;
+        }
+
+        // Sets the help link for this exception.
+        // This should be in a URL/URN form, such as:
+        // "file:///C:/Applications/Bazzal/help.html#ErrorNum42"
+        // Changed to be a read-write String and not return an exception
+        public virtual String HelpLink
+        {
+            get
+            {
+                return _helpURL;
+            }
+            set
+            {
+                _helpURL = value;
+            }
+        }
+
+        public virtual String Source
+        {
+            get
+            {
+                if (_source == null)
+                {
+                    StackTrace st = new StackTrace(this, true);
+                    if (st.FrameCount > 0)
+                    {
+                        StackFrame sf = st.GetFrame(0);
+                        MethodBase method = sf.GetMethod();
+
+                        Module module = method.Module;
+
+                        RuntimeModule rtModule = module as RuntimeModule;
+
+                        if (rtModule == null)
+                        {
+                            System.Reflection.Emit.ModuleBuilder moduleBuilder = module as System.Reflection.Emit.ModuleBuilder;
+                            if (moduleBuilder != null)
+                                rtModule = moduleBuilder.InternalModule;
+                            else
+                                throw new ArgumentException(SR.Argument_MustBeRuntimeReflectionObject);
+                        }
+
+                        _source = rtModule.GetRuntimeAssembly().GetSimpleName();
+                    }
+                }
+
+                return _source;
+            }
+            set { _source = value; }
+        }
+
+        public override String ToString()
+        {
+            return ToString(true, true);
+        }
+
+        private String ToString(bool needFileLineInfo, bool needMessage)
+        {
+            String message = (needMessage ? Message : null);
+            String s;
+
+            if (message == null || message.Length <= 0)
+            {
+                s = GetClassName();
+            }
+            else
+            {
+                s = GetClassName() + ": " + message;
+            }
+
+            if (_innerException != null)
+            {
+                s = s + " ---> " + _innerException.ToString(needFileLineInfo, needMessage) + Environment.NewLine +
+                "   " + SR.Exception_EndOfInnerExceptionStack;
+            }
+
+            string stackTrace = GetStackTrace(needFileLineInfo);
+            if (stackTrace != null)
+            {
+                s += Environment.NewLine + stackTrace;
+            }
+
+            return s;
+        }
+
+        protected event EventHandler<SafeSerializationEventArgs> SerializeObjectState
+        {
+            add { throw new PlatformNotSupportedException(SR.PlatformNotSupported_SecureBinarySerialization); }
+            remove { throw new PlatformNotSupportedException(SR.PlatformNotSupported_SecureBinarySerialization); }
+        }
+
+        public virtual void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+
+            String tempStackTraceString = _stackTraceString;
+
+            if (_stackTrace != null)
+            {
+                if (tempStackTraceString == null)
+                {
+                    tempStackTraceString = Environment.GetStackTrace(this, true);
+                }
+                if (_exceptionMethod == null)
+                {
+                    _exceptionMethod = GetExceptionMethodFromStackTrace();
+                }
+            }
+
+            if (_source == null)
+            {
+                _source = Source; // Set the Source information correctly before serialization
+            }
+
+            info.AddValue("ClassName", GetClassName(), typeof(String)); // Do not rename (binary serialization)
+            info.AddValue("Message", _message, typeof(String)); // Do not rename (binary serialization)
+            info.AddValue("Data", _data, typeof(IDictionary)); // Do not rename (binary serialization)
+            info.AddValue("InnerException", _innerException, typeof(Exception)); // Do not rename (binary serialization)
+            info.AddValue("HelpURL", _helpURL, typeof(String)); // Do not rename (binary serialization)
+            info.AddValue("StackTraceString", tempStackTraceString, typeof(String)); // Do not rename (binary serialization)
+            info.AddValue("RemoteStackTraceString", _remoteStackTraceString, typeof(String)); // Do not rename (binary serialization)
+            info.AddValue("RemoteStackIndex", _remoteStackIndex, typeof(Int32)); // Do not rename (binary serialization)
+            info.AddValue("ExceptionMethod", null, typeof(String)); // Do not rename (binary serialization)
+            info.AddValue("HResult", HResult); // Do not rename (binary serialization)
+            info.AddValue("Source", _source, typeof(String)); // Do not rename (binary serialization)
+
+            // Serialize the Watson bucket details as well
+            info.AddValue("WatsonBuckets", _watsonBuckets, typeof(byte[])); // Do not rename (binary serialization)
+        }
+
+        // This method will clear the _stackTrace of the exception object upon deserialization
+        // to ensure that references from another AD/Process dont get accidentally used.
+        [OnDeserialized]
+        private void OnDeserialized(StreamingContext context)
+        {
+            _stackTrace = null;
+
+            // We wont serialize or deserialize the IP for Watson bucketing since
+            // we dont know where the deserialized object will be used in.
+            // Using it across process or an AppDomain could be invalid and result
+            // in AV in the runtime.
+            //
+            // Hence, we set it to zero when deserialization takes place. 
+            _ipForWatsonBuckets = UIntPtr.Zero;
+        }
+
+        // This is used by the runtime when re-throwing a managed exception.  It will
+        //  copy the stack trace to _remoteStackTraceString.
+        internal void InternalPreserveStackTrace()
+        {
+            string tmpStackTraceString;
+
+#if FEATURE_APPX
+            if (AppDomain.IsAppXModel())
+            {
+                // Call our internal GetStackTrace in AppX so we can parse the result should
+                // we need to strip file/line info from it to make it PII-free. Calling the
+                // public and overridable StackTrace getter here was probably not intended.
+                tmpStackTraceString = GetStackTrace(true);
+
+                // Make sure that the _source field is initialized if Source is not overriden.
+                // We want it to contain the original faulting point.
+                string source = Source;
+            }
+            else
+#else // FEATURE_APPX
+            // Preinitialize _source on CoreSystem as well. The legacy behavior is not ideal and
+            // we keep it for back compat but we can afford to make the change on the Phone.
+            string source = Source;
+#endif // FEATURE_APPX
+            {
+                // Call the StackTrace getter in classic for compat.
+                tmpStackTraceString = StackTrace;
+            }
+
+            if (tmpStackTraceString != null && tmpStackTraceString.Length > 0)
+            {
+                _remoteStackTraceString = tmpStackTraceString + Environment.NewLine;
+            }
+
+            _stackTrace = null;
+            _stackTraceString = null;
+        }
+
+
+        // This is the object against which a lock will be taken
+        // when attempt to restore the EDI. Since its static, its possible
+        // that unrelated exception object restorations could get blocked
+        // for a small duration but that sounds reasonable considering
+        // such scenarios are going to be extremely rare, where timing
+        // matches precisely.
+        [OptionalField]
+        private static object s_EDILock = new object();
+
+        internal UIntPtr IPForWatsonBuckets
+        {
+            get
+            {
+                return _ipForWatsonBuckets;
+            }
+        }
+
+        internal object WatsonBuckets
+        {
+            get
+            {
+                return _watsonBuckets;
+            }
+        }
+
+        internal string RemoteStackTrace
+        {
+            get
+            {
+                return _remoteStackTraceString;
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void PrepareForForeignExceptionRaise();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void GetStackTracesDeepCopy(Exception exception, out object currentStackTrace, out object dynamicMethodArray);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void SaveStackTracesFromDeepCopy(Exception exception, object currentStackTrace, object dynamicMethodArray);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern object CopyStackTrace(object currentStackTrace);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern object CopyDynamicMethods(object currentDynamicMethods);
+
+        internal object DeepCopyStackTrace(object currentStackTrace)
+        {
+            if (currentStackTrace != null)
+            {
+                return CopyStackTrace(currentStackTrace);
+            }
+            else
+            {
+                return null;
+            }
+        }
+
+        internal object DeepCopyDynamicMethods(object currentDynamicMethods)
+        {
+            if (currentDynamicMethods != null)
+            {
+                return CopyDynamicMethods(currentDynamicMethods);
+            }
+            else
+            {
+                return null;
+            }
+        }
+
+        internal void GetStackTracesDeepCopy(out object currentStackTrace, out object dynamicMethodArray)
+        {
+            GetStackTracesDeepCopy(this, out currentStackTrace, out dynamicMethodArray);
+        }
+
+        // This is invoked by ExceptionDispatchInfo.Throw to restore the exception stack trace, corresponding to the original throw of the
+        // exception, just before the exception is "rethrown".
+        internal void RestoreExceptionDispatchInfo(System.Runtime.ExceptionServices.ExceptionDispatchInfo exceptionDispatchInfo)
+        {
+            bool fCanProcessException = !(IsImmutableAgileException(this));
+            // Restore only for non-preallocated exceptions
+            if (fCanProcessException)
+            {
+                // Take a lock to ensure only one thread can restore the details
+                // at a time against this exception object that could have
+                // multiple ExceptionDispatchInfo instances associated with it.
+                //
+                // We do this inside a finally clause to ensure ThreadAbort cannot
+                // be injected while we have taken the lock. This is to prevent
+                // unrelated exception restorations from getting blocked due to TAE.
+                try { }
+                finally
+                {
+                    // When restoring back the fields, we again create a copy and set reference to them
+                    // in the exception object. This will ensure that when this exception is thrown and these
+                    // fields are modified, then EDI's references remain intact.
+                    //
+                    // Since deep copying can throw on OOM, try to get the copies
+                    // outside the lock.
+                    object _stackTraceCopy = (exceptionDispatchInfo.BinaryStackTraceArray == null) ? null : DeepCopyStackTrace(exceptionDispatchInfo.BinaryStackTraceArray);
+                    object _dynamicMethodsCopy = (exceptionDispatchInfo.DynamicMethodArray == null) ? null : DeepCopyDynamicMethods(exceptionDispatchInfo.DynamicMethodArray);
+
+                    // Finally, restore the information. 
+                    //
+                    // Since EDI can be created at various points during exception dispatch (e.g. at various frames on the stack) for the same exception instance,
+                    // they can have different data to be restored. Thus, to ensure atomicity of restoration from each EDI, perform the restore under a lock.
+                    lock (Exception.s_EDILock)
+                    {
+                        _watsonBuckets = exceptionDispatchInfo.WatsonBuckets;
+                        _ipForWatsonBuckets = exceptionDispatchInfo.IPForWatsonBuckets;
+                        _remoteStackTraceString = exceptionDispatchInfo.RemoteStackTrace;
+                        SaveStackTracesFromDeepCopy(this, _stackTraceCopy, _dynamicMethodsCopy);
+                    }
+                    _stackTraceString = null;
+
+                    // Marks the TES state to indicate we have restored foreign exception
+                    // dispatch information.
+                    Exception.PrepareForForeignExceptionRaise();
+                }
+            }
+        }
+
+        private String _className;  //Needed for serialization.  
+        private MethodBase _exceptionMethod;  //Needed for serialization.  
+        internal String _message;
+        private IDictionary _data;
+        private Exception _innerException;
+        private String _helpURL;
+        private Object _stackTrace;
+        [OptionalField] // This isnt present in pre-V4 exception objects that would be serialized.
+        private Object _watsonBuckets;
+        private String _stackTraceString; //Needed for serialization.  
+        private String _remoteStackTraceString;
+        private int _remoteStackIndex;
+#pragma warning disable 414  // Field is not used from managed.        
+        // _dynamicMethods is an array of System.Resolver objects, used to keep
+        // DynamicMethodDescs alive for the lifetime of the exception. We do this because
+        // the _stackTrace field holds MethodDescs, and a DynamicMethodDesc can be destroyed
+        // unless a System.Resolver object roots it.
+        private Object _dynamicMethods;
+#pragma warning restore 414
+
+        // @MANAGED: HResult is used from within the EE!  Rename with care - check VM directory
+        internal int _HResult;     // HResult
+
+        public int HResult
+        {
+            get
+            {
+                return _HResult;
+            }
+            protected set
+            {
+                _HResult = value;
+            }
+        }
+
+        private String _source;         // Mainly used by VB. 
+        // WARNING: Don't delete/rename _xptrs and _xcode - used by functions
+        // on Marshal class.  Native functions are in COMUtilNative.cpp & AppDomain
+        private IntPtr _xptrs;             // Internal EE stuff 
+#pragma warning disable 414  // Field is not used from managed.
+        private int _xcode;             // Internal EE stuff 
+#pragma warning restore 414
+        [OptionalField]
+        private UIntPtr _ipForWatsonBuckets; // Used to persist the IP for Watson Bucketing
+
+
+        // See src\inc\corexcep.h's EXCEPTION_COMPLUS definition:
+        private const int _COMPlusExceptionCode = unchecked((int)0xe0434352);   // Win32 exception code for COM+ exceptions
+
+        // InternalToString is called by the runtime to get the exception text 
+        // and create a corresponding CrossAppDomainMarshaledException
+        internal virtual String InternalToString()
+        {
+            // Get the current stack trace string. 
+            return ToString(true, true);
+        }
+
+        // this method is required so Object.GetType is not made virtual by the compiler
+        // _Exception.GetType()
+        public new Type GetType()
+        {
+            return base.GetType();
+        }
+
+        internal bool IsTransient
+        {
+            get
+            {
+                return nIsTransient(_HResult);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool nIsTransient(int hr);
+
+
+        // This piece of infrastructure exists to help avoid deadlocks 
+        // between parts of mscorlib that might throw an exception while 
+        // holding a lock that are also used by mscorlib's ResourceManager
+        // instance.  As a special case of code that may throw while holding
+        // a lock, we also need to fix our asynchronous exceptions to use
+        // Win32 resources as well (assuming we ever call a managed 
+        // constructor on instances of them).  We should grow this set of
+        // exception messages as we discover problems, then move the resources
+        // involved to native code.
+        internal enum ExceptionMessageKind
+        {
+            ThreadAbort = 1,
+            ThreadInterrupted = 2,
+            OutOfMemory = 3
+        }
+
+        // See comment on ExceptionMessageKind
+        internal static String GetMessageFromNativeResources(ExceptionMessageKind kind)
+        {
+            string retMesg = null;
+            GetMessageFromNativeResources(kind, JitHelpers.GetStringHandleOnStack(ref retMesg));
+            return retMesg;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetMessageFromNativeResources(ExceptionMessageKind kind, StringHandleOnStack retMesg);
+    }
+
+    //--------------------------------------------------------------------------
+    // Telesto: Telesto doesn't support appdomain marshaling of objects so
+    // managed exceptions that leak across appdomain boundaries are flatted to
+    // its ToString() output and rethrown as an CrossAppDomainMarshaledException.
+    // The Message field is set to the ToString() output of the original exception.
+    //--------------------------------------------------------------------------
+
+    internal sealed class CrossAppDomainMarshaledException : SystemException
+    {
+        public CrossAppDomainMarshaledException(String message, int errorCode)
+            : base(message)
+        {
+            HResult = errorCode;
+        }
+
+        // Normally, only Telesto's UEF will see these exceptions.
+        // This override prints out the original Exception's ToString()
+        // output and hides the fact that it is wrapped inside another excepton.
+        internal override String InternalToString()
+        {
+            return Message;
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/GC.cs b/src/System.Private.CoreLib/src/System/GC.cs
new file mode 100644
index 0000000000..848141f006
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/GC.cs
@@ -0,0 +1,513 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Exposes features of the Garbage Collector through
+** the class libraries.  This is a class which cannot be
+** instantiated.
+**
+**
+===========================================================*/
+//This class only static members and doesn't require the serializable keyword.
+
+using System;
+using System.Reflection;
+using System.Security;
+using System.Threading;
+using System.Runtime;
+using System.Runtime.CompilerServices;
+using System.Runtime.ConstrainedExecution;
+using System.Globalization;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+using System.Diagnostics;
+
+namespace System
+{
+    public enum GCCollectionMode
+    {
+        Default = 0,
+        Forced = 1,
+        Optimized = 2
+    }
+
+    // !!!!!!!!!!!!!!!!!!!!!!!
+    // make sure you change the def in vm\gc.h 
+    // if you change this!
+    internal enum InternalGCCollectionMode
+    {
+        NonBlocking = 0x00000001,
+        Blocking = 0x00000002,
+        Optimized = 0x00000004,
+        Compacting = 0x00000008,
+    }
+
+    // !!!!!!!!!!!!!!!!!!!!!!!
+    // make sure you change the def in vm\gc.h 
+    // if you change this!
+    public enum GCNotificationStatus
+    {
+        Succeeded = 0,
+        Failed = 1,
+        Canceled = 2,
+        Timeout = 3,
+        NotApplicable = 4
+    }
+
+    public static class GC
+    {
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int GetGCLatencyMode();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int SetGCLatencyMode(int newLatencyMode);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void GetMemoryInfo(out uint highMemLoadThreshold,
+                                                  out ulong totalPhysicalMem,
+                                                  out uint lastRecordedMemLoad,
+                                                  // The next two are size_t
+                                                  out UIntPtr lastRecordedHeapSize,
+                                                  out UIntPtr lastRecordedFragmentation);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern int _StartNoGCRegion(long totalSize, bool lohSizeKnown, long lohSize, bool disallowFullBlockingGC);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern int _EndNoGCRegion();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int GetLOHCompactionMode();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void SetLOHCompactionMode(int newLOHCompactionMode);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int GetGenerationWR(IntPtr handle);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern long GetTotalMemory();
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void _Collect(int generation, int mode);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int GetMaxGeneration();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int _CollectionCount(int generation, int getSpecialGCCount);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsServerGC();
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void _AddMemoryPressure(UInt64 bytesAllocated);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void _RemoveMemoryPressure(UInt64 bytesAllocated);
+
+        public static void AddMemoryPressure(long bytesAllocated)
+        {
+            if (bytesAllocated <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(bytesAllocated),
+                        SR.ArgumentOutOfRange_NeedPosNum);
+            }
+
+            if ((4 == IntPtr.Size) && (bytesAllocated > Int32.MaxValue))
+            {
+                throw new ArgumentOutOfRangeException("pressure",
+                    SR.ArgumentOutOfRange_MustBeNonNegInt32);
+            }
+
+            _AddMemoryPressure((ulong)bytesAllocated);
+        }
+
+        public static void RemoveMemoryPressure(long bytesAllocated)
+        {
+            if (bytesAllocated <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(bytesAllocated),
+                    SR.ArgumentOutOfRange_NeedPosNum);
+            }
+
+            if ((4 == IntPtr.Size) && (bytesAllocated > Int32.MaxValue))
+            {
+                throw new ArgumentOutOfRangeException(nameof(bytesAllocated),
+                    SR.ArgumentOutOfRange_MustBeNonNegInt32);
+            }
+
+            _RemoveMemoryPressure((ulong)bytesAllocated);
+        }
+
+
+        // Returns the generation that obj is currently in.
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern int GetGeneration(Object obj);
+
+
+        // Forces a collection of all generations from 0 through Generation.
+        //
+        public static void Collect(int generation)
+        {
+            Collect(generation, GCCollectionMode.Default);
+        }
+
+        // Garbage Collect all generations.
+        //
+        public static void Collect()
+        {
+            //-1 says to GC all generations.
+            _Collect(-1, (int)InternalGCCollectionMode.Blocking);
+        }
+
+        public static void Collect(int generation, GCCollectionMode mode)
+        {
+            Collect(generation, mode, true);
+        }
+
+        public static void Collect(int generation, GCCollectionMode mode, bool blocking)
+        {
+            Collect(generation, mode, blocking, false);
+        }
+
+        public static void Collect(int generation, GCCollectionMode mode, bool blocking, bool compacting)
+        {
+            if (generation < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(generation), SR.ArgumentOutOfRange_GenericPositive);
+            }
+
+            if ((mode < GCCollectionMode.Default) || (mode > GCCollectionMode.Optimized))
+            {
+                throw new ArgumentOutOfRangeException(nameof(mode), SR.ArgumentOutOfRange_Enum);
+            }
+
+
+            int iInternalModes = 0;
+
+            if (mode == GCCollectionMode.Optimized)
+            {
+                iInternalModes |= (int)InternalGCCollectionMode.Optimized;
+            }
+
+            if (compacting)
+                iInternalModes |= (int)InternalGCCollectionMode.Compacting;
+
+            if (blocking)
+            {
+                iInternalModes |= (int)InternalGCCollectionMode.Blocking;
+            }
+            else if (!compacting)
+            {
+                iInternalModes |= (int)InternalGCCollectionMode.NonBlocking;
+            }
+
+            _Collect(generation, iInternalModes);
+        }
+
+        public static int CollectionCount(int generation)
+        {
+            if (generation < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(generation), SR.ArgumentOutOfRange_GenericPositive);
+            }
+            return _CollectionCount(generation, 0);
+        }
+
+        // This method DOES NOT DO ANYTHING in and of itself.  It's used to 
+        // prevent a finalizable object from losing any outstanding references 
+        // a touch too early.  The JIT is very aggressive about keeping an 
+        // object's lifetime to as small a window as possible, to the point
+        // where a 'this' pointer isn't considered live in an instance method
+        // unless you read a value from the instance.  So for finalizable 
+        // objects that store a handle or pointer and provide a finalizer that 
+        // cleans them up, this can cause subtle race conditions with the finalizer 
+        // thread.  This isn't just about handles - it can happen with just 
+        // about any finalizable resource.
+        //
+        // Users should insert a call to this method right after the last line
+        // of their code where their code still needs the object to be kept alive.
+        // The object which reference is passed into this method will not
+        // be eligible for collection until the call to this method happens.
+        // Once the call to this method has happened the object may immediately
+        // become eligible for collection. Here is an example:
+        // 
+        // "...all you really need is one object with a Finalize method, and a 
+        // second object with a Close/Dispose/Done method.  Such as the following 
+        // contrived example:
+        //
+        // class Foo {
+        //    Stream stream = ...;
+        //    protected void Finalize() { stream.Close(); }
+        //    void Problem() { stream.MethodThatSpansGCs(); }
+        //    static void Main() { new Foo().Problem(); }
+        // }
+        // 
+        //
+        // In this code, Foo will be finalized in the middle of 
+        // stream.MethodThatSpansGCs, thus closing a stream still in use."
+        //
+        // If we insert a call to GC.KeepAlive(this) at the end of Problem(), then
+        // Foo doesn't get finalized and the stream stays open.
+        [MethodImplAttribute(MethodImplOptions.NoInlining)] // disable optimizations
+        public static void KeepAlive(Object obj)
+        {
+        }
+
+        // Returns the generation in which wo currently resides.
+        //
+        public static int GetGeneration(WeakReference wo)
+        {
+            int result = GetGenerationWR(wo.m_handle);
+            KeepAlive(wo);
+            return result;
+        }
+
+        // Returns the maximum GC generation.  Currently assumes only 1 heap.
+        //
+        public static int MaxGeneration
+        {
+            get { return GetMaxGeneration(); }
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void _WaitForPendingFinalizers();
+
+        public static void WaitForPendingFinalizers()
+        {
+            // QCalls can not be exposed from mscorlib directly, need to wrap it.
+            _WaitForPendingFinalizers();
+        }
+
+        // Indicates that the system should not call the Finalize() method on
+        // an object that would normally require this call.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _SuppressFinalize(Object o);
+
+        public static void SuppressFinalize(Object obj)
+        {
+            if (obj == null)
+                throw new ArgumentNullException(nameof(obj));
+            _SuppressFinalize(obj);
+        }
+
+        // Indicates that the system should call the Finalize() method on an object
+        // for which SuppressFinalize has already been called. The other situation 
+        // where calling ReRegisterForFinalize is useful is inside a finalizer that 
+        // needs to resurrect itself or an object that it references.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _ReRegisterForFinalize(Object o);
+
+        public static void ReRegisterForFinalize(Object obj)
+        {
+            if (obj == null)
+                throw new ArgumentNullException(nameof(obj));
+            _ReRegisterForFinalize(obj);
+        }
+
+        // Returns the total number of bytes currently in use by live objects in
+        // the GC heap.  This does not return the total size of the GC heap, but
+        // only the live objects in the GC heap.
+        //
+        public static long GetTotalMemory(bool forceFullCollection)
+        {
+            long size = GetTotalMemory();
+            if (!forceFullCollection)
+                return size;
+            // If we force a full collection, we will run the finalizers on all 
+            // existing objects and do a collection until the value stabilizes.
+            // The value is "stable" when either the value is within 5% of the 
+            // previous call to GetTotalMemory, or if we have been sitting
+            // here for more than x times (we don't want to loop forever here).
+            int reps = 20;  // Number of iterations
+            long newSize = size;
+            float diff;
+            do
+            {
+                GC.WaitForPendingFinalizers();
+                GC.Collect();
+                size = newSize;
+                newSize = GetTotalMemory();
+                diff = ((float)(newSize - size)) / size;
+            } while (reps-- > 0 && !(-.05 < diff && diff < .05));
+            return newSize;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern long _GetAllocatedBytesForCurrentThread();
+
+        public static long GetAllocatedBytesForCurrentThread()
+        {
+            return _GetAllocatedBytesForCurrentThread();
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool _RegisterForFullGCNotification(int maxGenerationPercentage, int largeObjectHeapPercentage);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool _CancelFullGCNotification();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int _WaitForFullGCApproach(int millisecondsTimeout);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int _WaitForFullGCComplete(int millisecondsTimeout);
+
+        public static void RegisterForFullGCNotification(int maxGenerationThreshold, int largeObjectHeapThreshold)
+        {
+            if ((maxGenerationThreshold <= 0) || (maxGenerationThreshold >= 100))
+            {
+                throw new ArgumentOutOfRangeException(nameof(maxGenerationThreshold),
+                                                      String.Format(
+                                                          CultureInfo.CurrentCulture,
+                                                          SR.ArgumentOutOfRange_Bounds_Lower_Upper,
+                                                          1,
+                                                          99));
+            }
+
+            if ((largeObjectHeapThreshold <= 0) || (largeObjectHeapThreshold >= 100))
+            {
+                throw new ArgumentOutOfRangeException(nameof(largeObjectHeapThreshold),
+                                                      String.Format(
+                                                          CultureInfo.CurrentCulture,
+                                                          SR.ArgumentOutOfRange_Bounds_Lower_Upper,
+                                                          1,
+                                                          99));
+            }
+
+            if (!_RegisterForFullGCNotification(maxGenerationThreshold, largeObjectHeapThreshold))
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_NotWithConcurrentGC);
+            }
+        }
+
+        public static void CancelFullGCNotification()
+        {
+            if (!_CancelFullGCNotification())
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_NotWithConcurrentGC);
+            }
+        }
+
+        public static GCNotificationStatus WaitForFullGCApproach()
+        {
+            return (GCNotificationStatus)_WaitForFullGCApproach(-1);
+        }
+
+        public static GCNotificationStatus WaitForFullGCApproach(int millisecondsTimeout)
+        {
+            if (millisecondsTimeout < -1)
+                throw new ArgumentOutOfRangeException(nameof(millisecondsTimeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+
+            return (GCNotificationStatus)_WaitForFullGCApproach(millisecondsTimeout);
+        }
+
+        public static GCNotificationStatus WaitForFullGCComplete()
+        {
+            return (GCNotificationStatus)_WaitForFullGCComplete(-1);
+        }
+
+        public static GCNotificationStatus WaitForFullGCComplete(int millisecondsTimeout)
+        {
+            if (millisecondsTimeout < -1)
+                throw new ArgumentOutOfRangeException(nameof(millisecondsTimeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            return (GCNotificationStatus)_WaitForFullGCComplete(millisecondsTimeout);
+        }
+
+        private enum StartNoGCRegionStatus
+        {
+            Succeeded = 0,
+            NotEnoughMemory = 1,
+            AmountTooLarge = 2,
+            AlreadyInProgress = 3
+        }
+
+        private enum EndNoGCRegionStatus
+        {
+            Succeeded = 0,
+            NotInProgress = 1,
+            GCInduced = 2,
+            AllocationExceeded = 3
+        }
+
+        private static bool StartNoGCRegionWorker(long totalSize, bool hasLohSize, long lohSize, bool disallowFullBlockingGC)
+        {
+            if (totalSize <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(totalSize), "totalSize can't be zero or negative");
+            }
+
+            if (hasLohSize)
+            {
+                if (lohSize <= 0)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(lohSize), "lohSize can't be zero or negative");
+                }
+
+                if (lohSize > totalSize)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(lohSize), "lohSize can't be greater than totalSize");
+                }
+            }
+
+            StartNoGCRegionStatus status = (StartNoGCRegionStatus)_StartNoGCRegion(totalSize, hasLohSize, lohSize, disallowFullBlockingGC);
+            switch (status)
+            {
+                case StartNoGCRegionStatus.NotEnoughMemory:
+                    return false;
+                case StartNoGCRegionStatus.AlreadyInProgress:
+                    throw new InvalidOperationException("The NoGCRegion mode was already in progress");
+                case StartNoGCRegionStatus.AmountTooLarge:
+                    throw new ArgumentOutOfRangeException(nameof(totalSize),
+                        "totalSize is too large. For more information about setting the maximum size, see \"Latency Modes\" in http://go.microsoft.com/fwlink/?LinkId=522706");
+            }
+
+            Debug.Assert(status == StartNoGCRegionStatus.Succeeded);
+            return true;
+        }
+
+        public static bool TryStartNoGCRegion(long totalSize)
+        {
+            return StartNoGCRegionWorker(totalSize, false, 0, false);
+        }
+
+        public static bool TryStartNoGCRegion(long totalSize, long lohSize)
+        {
+            return StartNoGCRegionWorker(totalSize, true, lohSize, false);
+        }
+
+        public static bool TryStartNoGCRegion(long totalSize, bool disallowFullBlockingGC)
+        {
+            return StartNoGCRegionWorker(totalSize, false, 0, disallowFullBlockingGC);
+        }
+
+        public static bool TryStartNoGCRegion(long totalSize, long lohSize, bool disallowFullBlockingGC)
+        {
+            return StartNoGCRegionWorker(totalSize, true, lohSize, disallowFullBlockingGC);
+        }
+
+        private static EndNoGCRegionStatus EndNoGCRegionWorker()
+        {
+            EndNoGCRegionStatus status = (EndNoGCRegionStatus)_EndNoGCRegion();
+            if (status == EndNoGCRegionStatus.NotInProgress)
+                throw new InvalidOperationException("NoGCRegion mode must be set");
+            else if (status == EndNoGCRegionStatus.GCInduced)
+                throw new InvalidOperationException("Garbage collection was induced in NoGCRegion mode");
+            else if (status == EndNoGCRegionStatus.AllocationExceeded)
+                throw new InvalidOperationException("Allocated memory exceeds specified memory for NoGCRegion mode");
+
+            return EndNoGCRegionStatus.Succeeded;
+        }
+
+        public static void EndNoGCRegion()
+        {
+            EndNoGCRegionWorker();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Globalization/CharUnicodeInfoData.cs b/src/System.Private.CoreLib/src/System/Globalization/CharUnicodeInfoData.cs
new file mode 100644
index 0000000000..b1bef8146e
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Globalization/CharUnicodeInfoData.cs
@@ -0,0 +1,1247 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Globalization
+{
+    public static partial class CharUnicodeInfo
+    {
+        // THE FOLLOWING DATA IS AUTO GENERATED BY GenUnicodeProp.pl SCRIPT UNDER THE TOOLS FOLDER
+        // PLEASE DON'T MODIFY BY HAND
+
+
+        // 12:4:4 index table of the Unicode cateogry data.
+        private static ushort[] s_pCategoryLevel1Index = new ushort[]
+        {
+            0x1100, 0x1110, 0x1120, 0x1130, 0x1140, 0x1150, 0x1160, 0x1170, 0x1180, 0x1190, 0x11a0, 0x11b0, 0x11c0, 0x11d0, 0x11e0, 0x11f0,
+            0x1200, 0x1210, 0x1220, 0x1230, 0x1240, 0x1210, 0x1250, 0x1260, 0x1270, 0x1280, 0x1290, 0x12a0, 0x12b0, 0x12c0, 0x12d0, 0x12e0,
+            0x12f0, 0x1300, 0x1310, 0x1320, 0x1330, 0x1340, 0x1350, 0x1360, 0x1370, 0x1380, 0x1390, 0x13a0, 0x13b0, 0x13c0, 0x13d0, 0x13e0,
+            0x13f0, 0x1400, 0x1410, 0x1420, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210,
+            0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1430, 0x1210, 0x1210,
+            0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210,
+            0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210, 0x1210,
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+            0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x19b0, 0x19b0, 0x19c0, 0x19c0, 0x1e08, 0x2a10,
+            0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bd0, 0x1bd0, 0x1bd0, 0x28f0,
+            0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1fd8, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x21e0, 0x21e0, 0x21e0, 0x21e0, 0x21e0, 0x21e0, 0x2a18, 0x2a20, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0,
+            0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x2600, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x1bd0, 0x1bd0, 0x1fa0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x2388, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x1bd0, 0x1bd0, 0x1bd0, 0x28f0, 0x1bd0, 0x1fa0, 0x2570, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bd0, 0x1fc0, 0x2a28,
+            0x1bd0, 0x1bd0, 0x1bd0, 0x2a30, 0x2a38, 0x2a40, 0x2a48, 0x2a50, 0x1bd0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1fc8, 0x2a58, 0x2a60, 0x2a68, 0x28d8, 0x2a70, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x2a78, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x2420, 0x1e20, 0x28f0, 0x2a80, 0x2a88, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x2240, 0x2240, 0x2240, 0x2240, 0x2240, 0x2240, 0x2240, 0x2240, 0x2240, 0x2240, 0x2240, 0x2240, 0x2240, 0x2240, 0x2240, 0x2a90,
+            0x2240, 0x2240, 0x2a98, 0x2240, 0x2240, 0x2240, 0x2aa0, 0x2aa8, 0x2ab0, 0x2240, 0x2ab8, 0x2240, 0x2240, 0x2240, 0x2ac0, 0x1bb0,
+            0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x2ac8, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x2278, 0x2718, 0x2ad0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x19b0, 0x2ad8, 0x19c0, 0x2ae0, 0x2ae8, 0x2af0, 0x20e8, 0x19b0, 0x2af8, 0x2b00, 0x2b08, 0x2b10, 0x2b18, 0x19b0, 0x2ad8, 0x19c0,
+            0x2b20, 0x2b28, 0x19c0, 0x2b30, 0x2b38, 0x2b40, 0x2b48, 0x19b0, 0x2b50, 0x19c0, 0x19b0, 0x2ad8, 0x19c0, 0x2ae0, 0x2ae8, 0x19c0,
+            0x20e8, 0x19b0, 0x2af8, 0x2b48, 0x19b0, 0x2b50, 0x19c0, 0x19b0, 0x2ad8, 0x19c0, 0x2b58, 0x19b0, 0x2b60, 0x2b68, 0x2b70, 0x2b78,
+            0x19c0, 0x2b80, 0x19b0, 0x2b88, 0x2b90, 0x2b98, 0x2ba0, 0x19c0, 0x2ba8, 0x19b0, 0x2bb0, 0x19c0, 0x2bb8, 0x2bc0, 0x2bc0, 0x2bc0,
+            0x1a68, 0x1a68, 0x1a68, 0x2bc8, 0x1a68, 0x1a68, 0x2bd0, 0x2bd8, 0x2be0, 0x2be8, 0x1ad8, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x1af0, 0x1af0, 0x1af0, 0x1af0, 0x1af0, 0x1af0, 0x1af0, 0x1af0, 0x1af0, 0x1af0, 0x1af0, 0x1af0, 0x2bf0, 0x2bf8, 0x1bb0, 0x1bb0,
+            0x2c00, 0x1b18, 0x2c08, 0x2c10, 0x2c18, 0x2c20, 0x2c28, 0x2c30, 0x2c38, 0x2c40, 0x2c48, 0x2c40, 0x1bb0, 0x1bb0, 0x1bb0, 0x2c50,
+            0x1fe8, 0x1fe8, 0x23d8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x23c8, 0x2c58, 0x2c60, 0x2c60, 0x2c60, 0x1fe8, 0x23d0,
+            0x2c68, 0x2240, 0x2460, 0x2240, 0x2240, 0x2240, 0x2c70, 0x2240, 0x2240, 0x2c78, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x2c80, 0x2240,
+            0x2c88, 0x2240, 0x2240, 0x2c78, 0x2ac0, 0x2c90, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x2c98,
+            0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8,
+            0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x23c0, 0x1fe8, 0x1fe8, 0x2ca0, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8,
+            0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x2740, 0x2ca8, 0x23c8,
+            0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x23c8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x1fe8, 0x2cb0, 0x1bb0, 0x1bb0,
+            0x23d8, 0x1fe8, 0x1fe8, 0x1fe8, 0x2cb8, 0x1ee8, 0x1fe8, 0x1fe8, 0x2cb8, 0x1fe8, 0x2cc0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x1bb0, 0x2cc8, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x2cb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x2740, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x2388, 0x1bb0, 0x1bb0,
+            0x1bd0, 0x1bd0, 0x1bd0, 0x1fc8, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0,
+            0x1bd0, 0x1fc0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0,
+            0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x1bd0, 0x2a78, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x1bd0, 0x1fc0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x2cd0, 0x1bb0, 0x2cd8, 0x2cd8, 0x2cd8, 0x2cd8, 0x2cd8, 0x2cd8, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0, 0x1bb0,
+            0x1a68, 0x1a68, 0x1a68, 0x1a68, 0x1a68, 0x1a68, 0x1a68, 0x1a68, 0x1a68, 0x1a68, 0x1a68, 0x1a68, 0x1a68, 0x1a68, 0x1a68, 0x1bb0,
+            0x2618, 0x2618, 0x2618, 0x2618, 0x2618, 0x2618, 0x2618, 0x2618, 0x2618, 0x2618, 0x2618, 0x2618, 0x2618, 0x2618, 0x2618, 0x2ce0,
+            0x0101, 0x0101, 0x0101, 0x0101, 0x0201, 0x0203, 0x0304, 0x0101, 0x0101, 0x0101, 0x0101, 0x0101, 0x0101, 0x0101, 0x0303, 0x0203,
+            0x0605, 0x0706, 0x0708, 0x0606, 0x0a09, 0x0b06, 0x0d0c, 0x0c0c, 0x0e0e, 0x0e0e, 0x0e0e, 0x0e0e, 0x0e0e, 0x060c, 0x0f0f, 0x060f,
+            0x1006, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x0910, 0x0a06, 0x1211,
+            0x1311, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x0913, 0x0a0f, 0x010f,
+            0x0101, 0x0101, 0x0301, 0x0101, 0x0101, 0x0101, 0x0101, 0x0101, 0x0101, 0x0101, 0x0101, 0x0101, 0x0101, 0x0101, 0x0101, 0x0101,
+            0x0614, 0x0808, 0x0808, 0x0615, 0x1511, 0x1716, 0x180f, 0x1115, 0x1a19, 0x1b1b, 0x1311, 0x0606, 0x1b11, 0x1c16, 0x1d1d, 0x061d,
+            0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x0f10, 0x1010, 0x1010, 0x1010, 0x1310,
+            0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x0f13, 0x1313, 0x1313, 0x1313, 0x1313,
+            0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1013, 0x1013, 0x1013, 0x1013,
+            0x1013, 0x1013, 0x1013, 0x1013, 0x1313, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1010, 0x1013, 0x1013, 0x1313,
+            0x1013, 0x1310, 0x1310, 0x1010, 0x1013, 0x1010, 0x1313, 0x1010, 0x1010, 0x1013, 0x1310, 0x1010, 0x1310, 0x1313, 0x1010, 0x1013,
+            0x1310, 0x1310, 0x1310, 0x1010, 0x1013, 0x1313, 0x1310, 0x1010, 0x1013, 0x1010, 0x1013, 0x1013, 0x1310, 0x1613, 0x1310, 0x1313,
+            0x1616, 0x1616, 0x1e10, 0x1013, 0x131e, 0x1e10, 0x1013, 0x1013, 0x1013, 0x1013, 0x1013, 0x1013, 0x1013, 0x1013, 0x1313, 0x1310,
+            0x1013, 0x131e, 0x1310, 0x1010, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1313, 0x1313, 0x1313, 0x1010, 0x1013, 0x1310,
+            0x1013, 0x1013, 0x1010, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1313, 0x1313, 0x1316, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313,
+            0x1f1f, 0x1f1f, 0x1f1f, 0x1f1f, 0x201f, 0x1f20, 0x1f1f, 0x1f1f, 0x1f1f, 0x1111, 0x1111, 0x2020, 0x2020, 0x2020, 0x2020, 0x2020,
+            0x1f1f, 0x1111, 0x1111, 0x1111, 0x1111, 0x1111, 0x1111, 0x1111, 0x1f1f, 0x1f1f, 0x111f, 0x1111, 0x1111, 0x1111, 0x1120, 0x111f,
+            0x1111, 0x1111, 0x1111, 0x1111, 0x1111, 0x1111, 0x1111, 0x1111, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121,
+            0x1310, 0x1310, 0x1120, 0x1310, 0x0000, 0x131f, 0x1313, 0x1006, 0x0000, 0x0000, 0x1111, 0x0610, 0x1010, 0x0010, 0x0010, 0x1010,
+            0x1013, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1000, 0x1010, 0x1010, 0x1010, 0x1010, 0x1313, 0x1313,
+            0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1013, 0x1313, 0x1010, 0x1310, 0x1313, 0x1310, 0x1310, 0x1310, 0x1310,
+            0x1313, 0x1313, 0x1310, 0x100f, 0x1013, 0x1310, 0x1013, 0x1010, 0x1310, 0x2122, 0x2121, 0x2121, 0x2323, 0x1310, 0x1310, 0x1310,
+            0x1010, 0x1013, 0x1013, 0x1013, 0x1013, 0x1013, 0x1013, 0x1313, 0x1000, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010,
+            0x1010, 0x1010, 0x1010, 0x0010, 0x1f00, 0x2424, 0x2424, 0x2424, 0x1300, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313,
+            0x1313, 0x1313, 0x1313, 0x1313, 0x2400, 0x0025, 0x1500, 0x0815, 0x2100, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121,
+            0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x2126, 0x2127, 0x2721, 0x2121, 0x2127, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x0028, 0x0000, 0x0000,
+            0x2828, 0x2728, 0x0027, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x2929, 0x2929, 0x2929, 0x0f0f, 0x072a, 0x2b07, 0x2c0c, 0x1515,
+            0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x2c21, 0x002d, 0x2c2c, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e,
+            0x2e2f, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x212e, 0x2121, 0x2121, 0x3030, 0x3030, 0x3030, 0x3030, 0x3030, 0x3107, 0x2c31, 0x2e2e,
+            0x2e21, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2c, 0x2121, 0x2121, 0x2121, 0x2921, 0x2115,
+            0x2121, 0x2121, 0x2f21, 0x212f, 0x1521, 0x2121, 0x2121, 0x2e2e, 0x0e0e, 0x0e0e, 0x0e0e, 0x0e0e, 0x0e0e, 0x2e2e, 0x322e, 0x2e32,
+            0x2c2c, 0x2c2c, 0x2c2c, 0x2c2c, 0x2c2c, 0x2c2c, 0x2c2c, 0x2d00, 0x212e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e,
+            0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x0021, 0x2e00, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121,
+            0x2e21, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x3333, 0x3333, 0x3333, 0x3333, 0x3333, 0x2828, 0x2828, 0x2828,
+            0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2128, 0x2121, 0x2121, 0x2121, 0x2121, 0x3434, 0x0615, 0x0606, 0x0034, 0x0000, 0x0000,
+            0x2828, 0x2828, 0x2828, 0x2121, 0x2121, 0x2134, 0x2121, 0x2121, 0x2121, 0x2121, 0x2134, 0x2121, 0x2134, 0x2121, 0x2121, 0x0000,
+            0x2727, 0x2727, 0x2727, 0x2727, 0x2727, 0x2727, 0x2727, 0x0027, 0x2828, 0x2828, 0x2828, 0x2828, 0x2128, 0x2121, 0x0000, 0x0027,
+            0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x2e2e, 0x2e2e, 0x002e, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x0000, 0x2100, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x3521, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616,
+            0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x3521, 0x1621, 0x3535,
+            0x2135, 0x2121, 0x2121, 0x2121, 0x3521, 0x3535, 0x2135, 0x3535, 0x2116, 0x2121, 0x2121, 0x2121, 0x1616, 0x1616, 0x1616, 0x1616,
+            0x1616, 0x2121, 0x2424, 0x3636, 0x3636, 0x3636, 0x3636, 0x3636, 0x1f24, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616,
+            0x2116, 0x3535, 0x1600, 0x1616, 0x1616, 0x1616, 0x0016, 0x1600, 0x0016, 0x1600, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616,
+            0x1616, 0x1616, 0x1616, 0x1616, 0x0016, 0x1616, 0x1616, 0x1616, 0x0016, 0x0016, 0x0000, 0x1616, 0x1616, 0x0000, 0x1621, 0x3535,
+            0x2135, 0x2121, 0x0021, 0x3500, 0x0035, 0x3500, 0x2135, 0x0016, 0x0000, 0x0000, 0x0000, 0x3500, 0x0000, 0x0000, 0x1616, 0x1600,
+            0x1616, 0x2121, 0x0000, 0x3636, 0x3636, 0x3636, 0x3636, 0x3636, 0x1616, 0x0808, 0x3737, 0x3737, 0x3737, 0x0822, 0x0000, 0x0000,
+            0x2100, 0x3521, 0x1600, 0x1616, 0x1616, 0x0016, 0x0000, 0x1600, 0x0016, 0x1616, 0x1600, 0x0016, 0x1616, 0x0000, 0x0021, 0x3535,
+            0x2135, 0x0021, 0x0000, 0x2100, 0x0021, 0x2100, 0x2121, 0x0000, 0x2100, 0x0000, 0x0000, 0x0000, 0x1600, 0x1616, 0x0016, 0x0016,
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+            0x1d1d, 0x1d1d, 0x1d1d, 0x1d1d, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x2222, 0x2222,
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+            0x1d1d, 0x1d1d, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x0f0f, 0x0f0f, 0x090f, 0x0f0a, 0x0f0f, 0x0f0f, 0x0f0f, 0x0f0f,
+            0x0f0f, 0x0f0f, 0x0f0f, 0x0a09, 0x0a09, 0x0a09, 0x0a09, 0x0a09, 0x0f0f, 0x090f, 0x090a, 0x090a, 0x090a, 0x090a, 0x090a, 0x090a,
+            0x090a, 0x090a, 0x090a, 0x090a, 0x0f0a, 0x0f0f, 0x0f0f, 0x0f0f, 0x0f0f, 0x0f0f, 0x0f0f, 0x0f0f, 0x0a09, 0x0a09, 0x0f0f, 0x0f0f,
+            0x0f0f, 0x0f0f, 0x0f0f, 0x0f0f, 0x0f0f, 0x0f0f, 0x0a09, 0x0f0f, 0x0f0f, 0x0f0f, 0x150f, 0x0f15, 0x0f0f, 0x0f0f, 0x150f, 0x1515,
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+            0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x0010, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x0013,
+            0x1310, 0x1010, 0x1310, 0x1013, 0x1013, 0x1013, 0x1013, 0x1010, 0x1310, 0x1310, 0x1013, 0x1313, 0x1313, 0x1313, 0x1f1f, 0x1010,
+            0x1310, 0x1310, 0x1513, 0x1515, 0x1515, 0x1015, 0x1013, 0x2113, 0x2121, 0x1310, 0x0000, 0x0000, 0x0600, 0x0606, 0x1d06, 0x0606,
+            0x1313, 0x1313, 0x1313, 0x1300, 0x0000, 0x0000, 0x1300, 0x0000, 0x1616, 0x1616, 0x1616, 0x1616, 0x0000, 0x0000, 0x0000, 0x1f00,
+            0x0024, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x2100, 0x1616, 0x1616, 0x1616, 0x0016, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x1616, 0x1616, 0x1616, 0x0016, 0x1616, 0x1616, 0x1616, 0x0016, 0x0606, 0x1c17, 0x1c17, 0x0606, 0x1706, 0x061c, 0x1c17, 0x0606,
+            0x0606, 0x0606, 0x0606, 0x2506, 0x0606, 0x0625, 0x1c17, 0x0606, 0x1c17, 0x0a09, 0x0a09, 0x0a09, 0x0a09, 0x0606, 0x0606, 0x2006,
+            0x0606, 0x0606, 0x0606, 0x0606, 0x0606, 0x2525, 0x0606, 0x0606, 0x0625, 0x0009, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1500, 0x1515, 0x1515, 0x1515, 0x1515, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x1515, 0x1515, 0x1515, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x0000, 0x0000,
+            0x0605, 0x0606, 0x1f15, 0x3916, 0x0a09, 0x0a09, 0x0a09, 0x0a09, 0x0a09, 0x1515, 0x0a09, 0x0a09, 0x0a09, 0x0a09, 0x0925, 0x0a0a,
+            0x3915, 0x3939, 0x3939, 0x3939, 0x3939, 0x2121, 0x2121, 0x3535, 0x1f25, 0x1f1f, 0x1f1f, 0x1515, 0x3939, 0x1f39, 0x0616, 0x1515,
+            0x1616, 0x1616, 0x1616, 0x0016, 0x2100, 0x1121, 0x1f11, 0x161f, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x0616, 0x1f1f, 0x161f,
+            0x0000, 0x0000, 0x1600, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x2222, 0x3737, 0x3737, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222,
+            0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x0016, 0x0000, 0x0000, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x1522, 0x0015,
+            0x3737, 0x3737, 0x3737, 0x3737, 0x3737, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x3737, 0x3737, 0x3737, 0x3737,
+            0x1d15, 0x1d1d, 0x1d1d, 0x1d1d, 0x1d1d, 0x1d1d, 0x1d1d, 0x1d1d, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x1515, 0x2215,
+            0x1d22, 0x1d1d, 0x1d1d, 0x1d1d, 0x1d1d, 0x1d1d, 0x1d1d, 0x1d1d, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x1515, 0x1515,
+            0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x0022, 0x2222, 0x2222, 0x2222, 0x1522, 0x1515, 0x2215, 0x2222, 0x2222,
+            0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x1515, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x1522,
+            0x1616, 0x1616, 0x1f16, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x061f, 0x0606,
+            0x3636, 0x3636, 0x3636, 0x3636, 0x3636, 0x1616, 0x0000, 0x0000, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x2116,
+            0x2323, 0x0623, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x2006, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1f1f, 0x2121,
+            0x1616, 0x1616, 0x1616, 0x3939, 0x3939, 0x3939, 0x3939, 0x3939, 0x2121, 0x2424, 0x2424, 0x2424, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x1111, 0x1111, 0x1111, 0x2011, 0x2020, 0x2020, 0x2020, 0x2020, 0x1111, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310,
+            0x1313, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x131f, 0x1313, 0x1313, 0x1313, 0x1013, 0x1013, 0x1013, 0x1310,
+            0x1310, 0x1310, 0x1310, 0x1310, 0x4820, 0x1048, 0x1013, 0x1613, 0x1310, 0x1310, 0x1313, 0x1310, 0x1310, 0x1310, 0x1310, 0x1310,
+            0x1310, 0x1310, 0x1310, 0x1310, 0x1310, 0x1010, 0x1010, 0x0000, 0x1010, 0x1010, 0x1310, 0x1310, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x0000, 0x0000, 0x0000, 0x1600, 0x1f1f, 0x1613, 0x1616, 0x1616, 0x1616, 0x1621, 0x1616, 0x1621, 0x1616, 0x2116, 0x1616, 0x1616,
+            0x1616, 0x3516, 0x2135, 0x3521, 0x1515, 0x1515, 0x0000, 0x0000, 0x3737, 0x3737, 0x3737, 0x2222, 0x1908, 0x0000, 0x0000, 0x0000,
+            0x1616, 0x1616, 0x0606, 0x0606, 0x0000, 0x0000, 0x0000, 0x0000, 0x3535, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616,
+            0x1616, 0x1616, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x0021, 0x0000, 0x0000, 0x0000, 0x0000, 0x2424,
+            0x2121, 0x1616, 0x1616, 0x1616, 0x2424, 0x1624, 0x1624, 0x0000, 0x1616, 0x1616, 0x1616, 0x2121, 0x2121, 0x2121, 0x2121, 0x2424,
+            0x1616, 0x1616, 0x1616, 0x2116, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x3535, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x2400,
+            0x1616, 0x2116, 0x3535, 0x2121, 0x2121, 0x3535, 0x3521, 0x3535, 0x2435, 0x2424, 0x2424, 0x2424, 0x2424, 0x2424, 0x2424, 0x1f00,
+            0x3636, 0x3636, 0x3636, 0x3636, 0x3636, 0x0000, 0x0000, 0x2424, 0x1616, 0x1616, 0x2116, 0x161f, 0x1616, 0x1616, 0x1616, 0x1616,
+            0x3636, 0x3636, 0x3636, 0x3636, 0x3636, 0x1616, 0x1616, 0x0016, 0x1616, 0x1616, 0x1616, 0x1616, 0x2116, 0x2121, 0x2121, 0x3521,
+            0x2135, 0x3521, 0x2135, 0x0021, 0x0000, 0x0000, 0x0000, 0x0000, 0x1616, 0x2116, 0x1616, 0x1616, 0x1616, 0x1616, 0x3521, 0x0000,
+            0x3636, 0x3636, 0x3636, 0x3636, 0x3636, 0x0000, 0x2424, 0x2424, 0x161f, 0x1616, 0x1616, 0x2216, 0x2222, 0x3516, 0x3521, 0x1616,
+            0x1621, 0x2121, 0x1621, 0x2116, 0x1621, 0x1616, 0x1616, 0x2121, 0x2116, 0x0016, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1600, 0x1f16, 0x2424, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x3516, 0x2121, 0x3535,
+            0x2424, 0x1f16, 0x351f, 0x0021, 0x0000, 0x0000, 0x0000, 0x0000, 0x1600, 0x1616, 0x1616, 0x0016, 0x1600, 0x1616, 0x1616, 0x0016,
+            0x1600, 0x1616, 0x1616, 0x0016, 0x0000, 0x0000, 0x0000, 0x0000, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x4813, 0x1f1f, 0x1f1f,
+            0x1313, 0x1313, 0x1313, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1616, 0x3516, 0x2135, 0x3535, 0x3521, 0x2435, 0x2135, 0x0000,
+            0x1616, 0x1616, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1616, 0x1616, 0x1616, 0x0016, 0x0000, 0x1600, 0x1616, 0x1616,
+            0x4949, 0x4949, 0x4949, 0x4949, 0x4949, 0x4949, 0x4949, 0x4949, 0x4a4a, 0x4a4a, 0x4a4a, 0x4a4a, 0x4a4a, 0x4a4a, 0x4a4a, 0x4a4a,
+            0x1313, 0x1313, 0x1313, 0x0013, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1300, 0x1313, 0x1313, 0x0000, 0x0000, 0x2800, 0x2821,
+            0x2828, 0x2828, 0x2828, 0x2828, 0x0b28, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x0028, 0x2828, 0x2828, 0x0028, 0x0028,
+            0x2828, 0x2800, 0x0028, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2e2e, 0x4b4b, 0x4b4b, 0x4b4b, 0x4b4b, 0x4b4b, 0x4b4b, 0x4b4b,
+            0x4b4b, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x2e00, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e,
+            0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x090a, 0x0000, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e,
+            0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x0000, 0x0000, 0x0000, 0x0000, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x152b, 0x0000,
+            0x0606, 0x0606, 0x0606, 0x0906, 0x060a, 0x0000, 0x0000, 0x0000, 0x2506, 0x1225, 0x0912, 0x090a, 0x090a, 0x090a, 0x090a, 0x090a,
+            0x090a, 0x090a, 0x060a, 0x0906, 0x060a, 0x0606, 0x1206, 0x1212, 0x060c, 0x000c, 0x0c06, 0x0606, 0x0925, 0x090a, 0x090a, 0x070a,
+            0x0606, 0x0d0b, 0x0f0f, 0x000f, 0x0806, 0x0607, 0x0000, 0x0000, 0x2e2e, 0x2e2e, 0x002e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e,
+            0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x002e, 0x1800, 0x0600, 0x0706, 0x0708, 0x0606, 0x0a09, 0x0b06, 0x0d0c, 0x0c0c,
+            0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x0913, 0x0a0f, 0x090f, 0x060a, 0x0a09, 0x0606, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616,
+            0x161f, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1f1f,
+            0x0000, 0x1616, 0x1616, 0x1616, 0x0000, 0x1616, 0x1616, 0x1616, 0x0000, 0x1616, 0x1616, 0x1616, 0x0000, 0x1616, 0x0016, 0x0000,
+            0x0808, 0x110f, 0x0815, 0x0008, 0x0f15, 0x0f0f, 0x150f, 0x0015, 0x0000, 0x0000, 0x0000, 0x0000, 0x4c00, 0x4c4c, 0x1515, 0x0000,
+            0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1600, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x0016, 0x1616, 0x1600,
+            0x0624, 0x0024, 0x0000, 0x3700, 0x3737, 0x3737, 0x3737, 0x3737, 0x3737, 0x3737, 0x3737, 0x3737, 0x3737, 0x3737, 0x3737, 0x3737,
+            0x3737, 0x3737, 0x0000, 0x2200, 0x2222, 0x2222, 0x2222, 0x2222, 0x4d4d, 0x4d4d, 0x4d4d, 0x4d4d, 0x4d4d, 0x4d4d, 0x4d4d, 0x4d4d,
+            0x4d4d, 0x4d4d, 0x1d4d, 0x1d1d, 0x151d, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1d1d, 0x0015, 0x0000,
+            0x0015, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2122, 0x0000,
+            0x1b21, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x0000, 0x0000,
+            0x3737, 0x3737, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x3916, 0x1616, 0x1616, 0x1616, 0x1616, 0x0039, 0x0000, 0x0000,
+            0x1616, 0x1616, 0x1616, 0x2121, 0x2121, 0x0021, 0x0000, 0x0000, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x2400,
+            0x1616, 0x1616, 0x0000, 0x0000, 0x1616, 0x1616, 0x1616, 0x1616, 0x3924, 0x3939, 0x3939, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x1010, 0x1010, 0x1010, 0x1010, 0x1313, 0x1313, 0x1313, 0x1313, 0x1616, 0x1616, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x2400,
+            0x2828, 0x2828, 0x2828, 0x0000, 0x0028, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2800, 0x0028, 0x0000, 0x0028, 0x2800,
+            0x2828, 0x2828, 0x2828, 0x2700, 0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e, 0x2828, 0x2828, 0x2828, 0x4f28, 0x4e4f, 0x4e4e, 0x4e4e, 0x4e4e,
+            0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x0028, 0x0000, 0x0000, 0x0000, 0x4e00, 0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e,
+            0x2828, 0x0028, 0x2828, 0x0000, 0x0000, 0x4e00, 0x4e4e, 0x4e4e, 0x2828, 0x2828, 0x2828, 0x4e4e, 0x4e4e, 0x4e4e, 0x0000, 0x0600,
+            0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x0000, 0x0000, 0x2700, 0x2828, 0x2828, 0x2828, 0x2828, 0x0000, 0x0000, 0x4e4e, 0x2828,
+            0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e, 0x0000, 0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e,
+            0x2128, 0x2121, 0x2100, 0x0021, 0x0000, 0x0000, 0x2121, 0x2121, 0x2828, 0x2828, 0x2800, 0x2828, 0x2800, 0x2828, 0x2828, 0x2828,
+            0x2828, 0x2828, 0x0000, 0x0000, 0x2121, 0x0021, 0x0000, 0x2100, 0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x2727, 0x2727, 0x2727, 0x2727, 0x0027, 0x0000, 0x0000, 0x0000, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x4e28, 0x274e,
+            0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x2828, 0x4e28, 0x4e4e, 0x2828, 0x2828, 0x2828, 0x2828, 0x284f, 0x2828, 0x2828, 0x2828,
+            0x2828, 0x2828, 0x2128, 0x0021, 0x0000, 0x4e00, 0x4e4e, 0x4e4e, 0x2727, 0x2727, 0x2727, 0x0027, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x2828, 0x2828, 0x2828, 0x0000, 0x0600, 0x0606, 0x0606, 0x0606, 0x2828, 0x2828, 0x2828, 0x0000, 0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e,
+            0x2828, 0x0028, 0x0000, 0x0000, 0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e, 0x2828, 0x0000, 0x0000, 0x0000, 0x2700, 0x2727, 0x0027, 0x0000,
+            0x0000, 0x0000, 0x0000, 0x0000, 0x4e00, 0x4e4e, 0x4e4e, 0x4e4e, 0x2828, 0x2828, 0x2828, 0x2828, 0x0028, 0x0000, 0x0000, 0x0000,
+            0x5050, 0x5050, 0x5050, 0x5050, 0x5050, 0x5050, 0x5050, 0x5050, 0x5050, 0x0050, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x5151, 0x5151, 0x5151, 0x5151, 0x5151, 0x5151, 0x5151, 0x5151, 0x5151, 0x0051, 0x0000, 0x0000, 0x0000, 0x4e4e, 0x4e4e, 0x4e4e,
+            0x5252, 0x5252, 0x5252, 0x5252, 0x5252, 0x5252, 0x5252, 0x5252, 0x5252, 0x5252, 0x5252, 0x5252, 0x5252, 0x5252, 0x5252, 0x0052,
+            0x2135, 0x1635, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x2121, 0x2121, 0x2121, 0x2121,
+            0x2121, 0x2121, 0x2121, 0x2421, 0x2424, 0x2424, 0x2424, 0x0000, 0x0000, 0x1d1d, 0x1d1d, 0x1d1d, 0x1d1d, 0x1d1d, 0x1d1d, 0x1d1d,
+            0x1d1d, 0x1d1d, 0x1d1d, 0x3636, 0x3636, 0x3636, 0x3636, 0x3636, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x2100,
+            0x3535, 0x2135, 0x2121, 0x3521, 0x2135, 0x2421, 0x3a24, 0x2424, 0x2424, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x1616, 0x1616, 0x1616, 0x1616, 0x0016, 0x0000, 0x0000, 0x0000, 0x2121, 0x1621, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616,
+            0x1616, 0x1616, 0x1616, 0x2116, 0x2121, 0x2121, 0x2135, 0x2121, 0x2121, 0x2121, 0x0021, 0x3636, 0x3636, 0x3636, 0x3636, 0x3636,
+            0x2424, 0x2424, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1616, 0x2116, 0x2424, 0x0016, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x1616, 0x3516, 0x3535, 0x2121, 0x2121, 0x2121, 0x2121, 0x3521, 0x1635, 0x1616, 0x2416, 0x2424, 0x2424, 0x2121, 0x2421, 0x0000,
+            0x3636, 0x3636, 0x3636, 0x3636, 0x3636, 0x2416, 0x2416, 0x2424, 0x3700, 0x3737, 0x3737, 0x3737, 0x3737, 0x3737, 0x3737, 0x3737,
+            0x3737, 0x3737, 0x0037, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x3535, 0x2135,
+            0x2121, 0x3535, 0x3521, 0x2121, 0x2424, 0x2424, 0x2424, 0x0000, 0x1616, 0x1616, 0x1616, 0x0016, 0x0016, 0x1616, 0x1616, 0x1600,
+            0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1600, 0x1616, 0x1616, 0x1616, 0x1616, 0x2416, 0x0000, 0x0000, 0x0000,
+            0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x2116, 0x3535, 0x2135, 0x2121, 0x2121, 0x2121, 0x0021, 0x0000, 0x0000,
+            0x2121, 0x3535, 0x1600, 0x1616, 0x1616, 0x1616, 0x0016, 0x1600, 0x3521, 0x3535, 0x0035, 0x3500, 0x0035, 0x3500, 0x3535, 0x0000,
+            0x0016, 0x0000, 0x0000, 0x3500, 0x0000, 0x0000, 0x1600, 0x1616, 0x1616, 0x3535, 0x0000, 0x2121, 0x2121, 0x2121, 0x0021, 0x0000,
+            0x2121, 0x2121, 0x0021, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x3535, 0x2135, 0x2121, 0x2121, 0x3521, 0x3521, 0x3535, 0x2135,
+            0x3521, 0x2121, 0x1616, 0x1624, 0x0000, 0x0000, 0x0000, 0x0000, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x3516,
+            0x3535, 0x2121, 0x2121, 0x0000, 0x3535, 0x3535, 0x2121, 0x2135, 0x2421, 0x2424, 0x2424, 0x2424, 0x2424, 0x2424, 0x2424, 0x2424,
+            0x2424, 0x2424, 0x2424, 0x2424, 0x1616, 0x1616, 0x2121, 0x0000, 0x3535, 0x2135, 0x2121, 0x2121, 0x2121, 0x3521, 0x2135, 0x2135,
+            0x2421, 0x2424, 0x0016, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x2116, 0x2135, 0x3535,
+            0x2121, 0x2121, 0x2121, 0x2135, 0x0000, 0x0000, 0x0000, 0x0000, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x0000, 0x2100, 0x2121,
+            0x3535, 0x2121, 0x2121, 0x2135, 0x2121, 0x2121, 0x0000, 0x0000, 0x3636, 0x3636, 0x3636, 0x3636, 0x3636, 0x3737, 0x2424, 0x2224,
+            0x3737, 0x0037, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1600, 0x3939, 0x3939, 0x3939, 0x3939, 0x3939, 0x3939, 0x3939, 0x0039,
+            0x2424, 0x2424, 0x0024, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x2121, 0x2121, 0x2421, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x2121, 0x2121, 0x2121, 0x2421, 0x2424, 0x2424, 0x2222, 0x2222, 0x1f1f, 0x1f1f, 0x2224, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x3636, 0x3636, 0x3636, 0x3636, 0x3636, 0x3700, 0x3737, 0x3737, 0x3737, 0x1600, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x1616,
+            0x1616, 0x1616, 0x1616, 0x1616, 0x0000, 0x0000, 0x1600, 0x1616, 0x3516, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535,
+            0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x3535, 0x0035,
+            0x2121, 0x1f21, 0x1f1f, 0x1f1f, 0x1f1f, 0x1f1f, 0x1f1f, 0x1f1f, 0x1616, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x1616, 0x1616, 0x1616, 0x1616, 0x1616, 0x0000, 0x2122, 0x2421, 0x1818, 0x1818, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x2222, 0x2222, 0x2222, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x2222, 0x2222, 0x2222, 0x0022, 0x2200, 0x2222, 0x2222, 0x2222,
+            0x2222, 0x2222, 0x3522, 0x2135, 0x2121, 0x2222, 0x3522, 0x3535, 0x3535, 0x1835, 0x1818, 0x1818, 0x1818, 0x2118, 0x2121, 0x2121,
+            0x2121, 0x2221, 0x2122, 0x2121, 0x2121, 0x2121, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2121, 0x2121, 0x2222,
+            0x2222, 0x2222, 0x2222, 0x2222, 0x0022, 0x0000, 0x0000, 0x0000, 0x1515, 0x2121, 0x1521, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x3737, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1313, 0x1313, 0x1313,
+            0x1313, 0x1313, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1313,
+            0x1313, 0x1313, 0x0013, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1010, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313,
+            0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x0010, 0x1010, 0x0000, 0x0010, 0x1000, 0x0010, 0x1000, 0x1010, 0x0010, 0x1010,
+            0x1010, 0x1010, 0x1010, 0x1313, 0x1313, 0x1300, 0x1300, 0x1313, 0x1313, 0x1313, 0x1300, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313,
+            0x1313, 0x1313, 0x1010, 0x1000, 0x1010, 0x0010, 0x1000, 0x1010, 0x1010, 0x1010, 0x0010, 0x1010, 0x1010, 0x1010, 0x0010, 0x1313,
+            0x1313, 0x1313, 0x1313, 0x1313, 0x1010, 0x1000, 0x1010, 0x0010, 0x1010, 0x1010, 0x0010, 0x0010, 0x0000, 0x1010, 0x1010, 0x1010,
+            0x0010, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1010, 0x1010,
+            0x1010, 0x1010, 0x1010, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x0000, 0x1010, 0x1010, 0x1010, 0x1010,
+            0x5310, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x0f13, 0x1313, 0x1313,
+            0x1313, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x5310, 0x1313, 0x1313,
+            0x1313, 0x1313, 0x0f13, 0x1313, 0x1313, 0x1313, 0x1010, 0x1010, 0x1010, 0x1010, 0x5310, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313,
+            0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x1313, 0x0f13, 0x1313, 0x1313, 0x1313, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010,
+            0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x1010, 0x5310, 0x1313, 0x1313, 0x1313, 0x1313, 0x0f13, 0x1313, 0x1313, 0x1313,
+            0x1010, 0x1010, 0x1010, 0x1010, 0x5310, 0x1313, 0x1313, 0x1313, 0x1313, 0x0f13, 0x1313, 0x1313, 0x1313, 0x1310, 0x0000, 0x0e0e,
+            0x0e0e, 0x0e0e, 0x0e0e, 0x0e0e, 0x0e0e, 0x0e0e, 0x0e0e, 0x0e0e, 0x2121, 0x2121, 0x2121, 0x2221, 0x2222, 0x2122, 0x2121, 0x2121,
+            0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x2121, 0x2221, 0x2222, 0x2222, 0x2222, 0x2122, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222,
+            0x2222, 0x2222, 0x2221, 0x2422, 0x2424, 0x2424, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x2100, 0x2121, 0x2121,
+            0x2828, 0x2828, 0x0028, 0x4e00, 0x4e4e, 0x4e4e, 0x4e4e, 0x4e4e, 0x2121, 0x2121, 0x2121, 0x0021, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x2e2e, 0x2e2e, 0x2e00, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e00, 0x002e, 0x002e, 0x2e00, 0x2e00, 0x2e2e, 0x2e2e, 0x2e2e,
+            0x2e2e, 0x002e, 0x2e2e, 0x2e2e, 0x2e00, 0x2e00, 0x0000, 0x0000, 0x0000, 0x002e, 0x0000, 0x2e00, 0x2e00, 0x2e00, 0x2e00, 0x2e2e,
+            0x2e00, 0x002e, 0x002e, 0x2e00, 0x2e00, 0x2e00, 0x2e00, 0x2e00, 0x2e00, 0x002e, 0x002e, 0x2e00, 0x2e2e, 0x002e, 0x2e2e, 0x2e2e,
+            0x2e2e, 0x002e, 0x2e2e, 0x2e2e, 0x2e00, 0x2e2e, 0x002e, 0x002e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e00, 0x2e2e, 0x2e2e,
+            0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x2e2e, 0x0000, 0x0000, 0x2e00, 0x2e2e, 0x2e00, 0x2e2e, 0x2e2e, 0x2e00, 0x2e2e, 0x2e2e,
+            0x0f0f, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x0015,
+            0x1500, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1b1b, 0x1d1b, 0x001d, 0x0000,
+            0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x1515, 0x0000, 0x0000, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x0022, 0x0000, 0x0000,
+            0x0000, 0x0000, 0x0000, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x2222, 0x0022, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x2222, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1115, 0x1111, 0x1111,
+            0x1515, 0x1515, 0x1500, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x0015, 0x0000,
+            0x1515, 0x1515, 0x0015, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1515, 0x1515, 0x1515, 0x1515, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x1515, 0x0000, 0x1515, 0x1515, 0x1515, 0x1515, 0x0015, 0x0000, 0x0000, 0x0000,
+            0x1800, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1818, 0x1818, 0x1818, 0x1818, 0x1818, 0x1818, 0x1818, 0x1818,
+            0x4a4a, 0x4a4a, 0x4a4a, 0x4a4a, 0x4a4a, 0x4a4a, 0x4a4a, 0x0000, 0xeeee, 0xeeee
+        };
+
+        private static byte[] s_pCategoriesValue = new byte[]
+        {
+            0x1d, 0x00, 0x0e, 0x0e, 0x0e, 0x10, 0x0e, 0x0f, 0x0e, 0x11, 0x0b, 0x11, 0x18, 0x12, 0x18, 0x0a,
+            0x1a, 0x0a, 0x14, 0x12, 0x15, 0x12, 0x19, 0x09, 0x18, 0x0c, 0x13, 0x09, 0x08, 0x08, 0x19, 0x12,
+            0x00, 0x00, 0x1b, 0x12, 0x12, 0x12, 0x01, 0x00, 0x0b, 0x0c, 0x1c, 0x12, 0x04, 0x00, 0x16, 0x12,
+            0x0f, 0x0e, 0x1c, 0x0a, 0x19, 0x0a, 0x0a, 0x08, 0x17, 0x12, 0x0a, 0x12, 0x02, 0x00, 0x03, 0x00,
+            0x03, 0x12, 0x05, 0x0d, 0x1c, 0x00, 0x07, 0x0d, 0x18, 0x00, 0x13, 0x12, 0x13, 0x03, 0x18, 0x03,
+            0x04, 0x03, 0x0f, 0x0b, 0x19, 0x04, 0x1a, 0x04, 0x18, 0x04, 0x0f, 0x04, 0x04, 0x04, 0x03, 0x04,
+            0x08, 0x0b, 0x18, 0x0b, 0x1c, 0x04, 0x08, 0x03, 0x03, 0x03, 0x06, 0x00, 0x08, 0x00, 0x0a, 0x00,
+            0x05, 0x00, 0x09, 0x00, 0x0f, 0x00, 0x0f, 0x03, 0x0c, 0x11, 0x0d, 0x0f, 0x0f, 0x01, 0x0f, 0x05,
+            0x0f, 0x07, 0x0f, 0x02, 0x0f, 0x06, 0x19, 0x0c, 0x0f, 0x13, 0x0f, 0x14, 0x0f, 0x15, 0x0f, 0x16,
+            0x1b, 0x00, 0x10, 0x00, 0x11, 0x00, 0x1b, 0x04, 0x0f, 0x12, 0x09, 0x12, 0x0a, 0x03, 0x1c, 0x03,
+            0x00, 0x03, 0x01, 0x03, 0x0a, 0x0b, 0x19, 0x00
+        };
+        // 12:4:4 index table of the Unicode numeric data.
+        private static ushort[] s_pNumericLevel1Index = new ushort[]
+        {
+            0x1100, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1120, 0x1130, 0x1110, 0x1140, 0x1150, 0x1160, 0x1170, 0x1180, 0x1190, 0x11a0,
+            0x11b0, 0x1110, 0x1110, 0x11c0, 0x1110, 0x1110, 0x11d0, 0x11e0, 0x11f0, 0x1200, 0x1210, 0x1220, 0x1230, 0x1110, 0x1110, 0x1110,
+            0x1240, 0x1250, 0x1110, 0x1110, 0x1260, 0x1110, 0x1110, 0x1270, 0x1110, 0x1110, 0x1110, 0x1110, 0x1280, 0x1110, 0x1110, 0x1110,
+            0x1290, 0x12a0, 0x12b0, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110,
+            0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110,
+            0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110,
+            0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110,
+            0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110,
+            0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110,
+            0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110,
+            0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x12c0, 0x1110, 0x12d0, 0x12e0, 0x12f0, 0x1300, 0x1110, 0x1110, 0x1110, 0x1110,
+            0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110,
+            0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110, 0x1110,
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+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x1550, 0x1558, 0x1560, 0x1568, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x1570, 0x1578,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x1580, 0x1588, 0x1590, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x1598,
+            0x15a0, 0x14a0, 0x15a8, 0x15b0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x15b8, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x15c0, 0x14a0, 0x15c8, 0x15d0, 0x14a0, 0x14a0, 0x15c0, 0x14a0, 0x14a0, 0x15d8, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a8, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x15e0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x15e8, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a8, 0x14a0, 0x14a0,
+            0x14a8, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a8, 0x14a0, 0x14a8,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a8, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a8,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x15f0, 0x15f8, 0x14a0, 0x14a0, 0x14a0, 0x1600, 0x14a0, 0x1608, 0x14a0, 0x1610,
+            0x1618, 0x1620, 0x1628, 0x1630, 0x1638, 0x1640, 0x1648, 0x1650, 0x1658, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x1660, 0x1668,
+            0x14a0, 0x14a0, 0x1670, 0x14a0, 0x1678, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x1680, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a8, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x1688, 0x14a0, 0x1690, 0x14a0, 0x14a0, 0x1698, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x16a0,
+            0x14a0, 0x16a8, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x16b0, 0x16b8, 0x16c0, 0x16c8, 0x16d0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x16d8, 0x14a0, 0x14a0, 0x16e0, 0x14a0, 0x16e8, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x16a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x16f0, 0x14a0, 0x16f0, 0x14a0, 0x14a0, 0x16f8, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x1700,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x1708, 0x1710, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x1718, 0x1720, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a8,
+            0x14a0, 0x14a0, 0x14a0, 0x14b8, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a8, 0x1660, 0x1728,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a8, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a8, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a8, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x1730, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x1738, 0x1740,
+            0x1748, 0x1750, 0x1758, 0x1760, 0x1768, 0x1770, 0x1778, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a8, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x1780, 0x1788, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x16b8, 0x1790, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x1798, 0x17a0, 0x17a8, 0x17b0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x1618, 0x14a0, 0x14a0, 0x14a0,
+            0x17b8, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x17c0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0, 0x14a0,
+            0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0201, 0x0403, 0x0605, 0x0807, 0x0a09, 0x0000, 0x0000, 0x0000,
+            0x0000, 0x0c0b, 0x0000, 0x0000, 0x0d00, 0x0000, 0x0f0e, 0x0010, 0x0000, 0x0000, 0x0000, 0x0201, 0x0403, 0x0605, 0x0807, 0x0a09,
+            0x0000, 0x0000, 0x1211, 0x0e13, 0x1410, 0x0000, 0x0000, 0x0000, 0x0000, 0x0f0e, 0x1110, 0x1312, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x1615, 0x0017, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1918, 0x1b1a, 0x1a19, 0x001b,
+            0x1615, 0x0e17, 0x100f, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0201, 0x0403, 0x0605, 0x0807, 0x0a09, 0x1c0f, 0x1e1d, 0x201f,
+            0x2221, 0x2423, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0d00, 0x0c0b, 0x2625, 0x2827,
+            0x2a29, 0x2b15, 0x2d2c, 0x2f2e, 0x3130, 0x1632, 0x0033, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x3534,
+            0x0036, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1918, 0x1b1a, 0x3837, 0x3a39, 0x3c3b, 0x0000, 0x0000, 0x0000,
+            0x0201, 0x0403, 0x0605, 0x0807, 0x0a09, 0x000d, 0x0000, 0x0000, 0x003d, 0x0000, 0x2625, 0x2827, 0x2a29, 0x0000, 0x0000, 0x0000,
+            0x0d3d, 0x0c0b, 0x2625, 0x2827, 0x2a29, 0x0000, 0x0000, 0x0000, 0x3f3e, 0x4140, 0x4342, 0x4544, 0x4746, 0x1248, 0x4a49, 0x194b,
+            0x1a19, 0x371b, 0x3938, 0x3b3a, 0x153c, 0x4d4c, 0x162e, 0x174e, 0x4f17, 0x0033, 0x3900, 0x502e, 0x1851, 0x0000, 0x0000, 0x0000,
+            0x0b0d, 0x250c, 0x2726, 0x2928, 0x152a, 0x4d4c, 0x5352, 0x1454, 0x3534, 0x2b36, 0x0b0d, 0x250c, 0x2726, 0x2928, 0x152a, 0x4d4c,
+            0x5352, 0x1454, 0x3534, 0x2b36, 0x0b0d, 0x250c, 0x2726, 0x2928, 0x152a, 0x4d4c, 0x5352, 0x1454, 0x3534, 0x2b36, 0x0000, 0x0000,
+            0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x4c3d, 0x524d, 0x5453, 0x3414, 0x3635, 0x0d2b, 0x0c0b, 0x2625, 0x2827, 0x2a29, 0x3d15,
+            0x0000, 0x0000, 0x0000, 0x0b0d, 0x250c, 0x2726, 0x2928, 0x152a, 0x0b0d, 0x250c, 0x2726, 0x2928, 0x152a, 0x0b0d, 0x250c, 0x2726,
+            0x2928, 0x152a, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0f00, 0x0000,
+            0x0000, 0x0000, 0x0000, 0x1800, 0x0000, 0x0000, 0x0000, 0x0000, 0x1900, 0x1b1a, 0x3837, 0x3a39, 0x3c3b, 0x0000, 0x0000, 0x0000,
+            0x0000, 0x0000, 0x0000, 0x0000, 0x2b15, 0x002c, 0x0000, 0x0000, 0x0000, 0x1a19, 0x371b, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x1a19, 0x371b, 0x3938, 0x3b3a, 0x153c, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x2b15, 0x2d2c, 0x2f2e, 0x3130,
+            0x5500, 0x5756, 0x5958, 0x5b5a, 0x5d5c, 0x5e2c, 0x605f, 0x6261, 0x6300, 0x6564, 0x2d66, 0x6867, 0x6a69, 0x6c6b, 0x6e6d, 0x2e6f,
+            0x0000, 0x0000, 0x0000, 0x1a19, 0x371b, 0x3938, 0x3b3a, 0x183c, 0x0f0e, 0x1110, 0x1312, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1b00, 0x0000, 0x0000, 0x0000, 0x1500, 0x0000, 0x0000, 0x001a, 0x0000, 0x0000, 0x0000,
+            0x0000, 0x0018, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x3900, 0x3900, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1500, 0x0000, 0x0000, 0x0000, 0x0000, 0x1900, 0x1b1a, 0x3837, 0x3a39, 0x3c3b,
+            0x2b15, 0x2d2c, 0x2f2e, 0x3130, 0x1632, 0x7170, 0x4e72, 0x7473, 0x7675, 0x7717, 0x7978, 0x7a4f, 0x7c7b, 0x337d, 0x7f7e, 0x5080,
+            0x8281, 0x8483, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0f0e, 0x3819, 0x4e2e, 0x504f, 0x1538, 0x162e, 0x174e, 0x384f,
+            0x2e15, 0x4e16, 0x3317, 0x1550, 0x1919, 0x1a19, 0x1a1a, 0x381a, 0x1515, 0x1515, 0x2c15, 0x2e2e, 0x2e2e, 0x7116, 0x4e4e, 0x4e4e,
+            0x174e, 0x384f, 0x0f2e, 0x420f, 0x0010, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0e18, 0x0000, 0x0000,
+            0x1900, 0x1b1a, 0x3837, 0x3a39, 0x3c3b, 0x2b15, 0x2d2c, 0x2f2e, 0x3130, 0x1632, 0x7170, 0x4e72, 0x7473, 0x7675, 0x0000, 0x0000,
+            0x3819, 0x2e15, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x3200, 0x0000, 0x0000, 0x0000, 0x0000, 0x0076, 0x0000, 0x0000,
+            0x1900, 0x151a, 0x162b, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1a19, 0x151b, 0x162b, 0x3317,
+            0x0000, 0x0000, 0x0000, 0x0000, 0x1900, 0x1b1a, 0x3837, 0x2b15, 0x0000, 0x0000, 0x0000, 0x1900, 0x1b1a, 0x3737, 0x1538, 0x162b,
+            0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1900, 0x1538, 0x162b, 0x0000, 0x0000, 0x0000, 0x1519, 0x162b, 0x1b1a, 0x0000, 0x0000,
+            0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0f85, 0x0000, 0x1a19, 0x371b, 0x3938, 0x3b3a, 0x153c, 0x2c2b, 0x2e2d, 0x302f,
+            0x0000, 0x7016, 0x7271, 0x734e, 0x7574, 0x1776, 0x7877, 0x4f79, 0x7b7a, 0x7d7c, 0x7e33, 0x807f, 0x8150, 0x8382, 0x5184, 0x8786,
+            0x8988, 0x8b8a, 0x8d8c, 0x8f8e, 0x9190, 0x9392, 0x9594, 0x9796, 0x0b0d, 0x250c, 0x2b15, 0x1716, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1900, 0x002e, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1900, 0x2b15,
+            0x0000, 0x0000, 0x0000, 0x0000, 0x1a19, 0x371b, 0x2b15, 0x1716, 0x0000, 0x0000, 0x0000, 0x0000, 0x1900, 0x1b1a, 0x1537, 0x162b,
+            0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x3819, 0x2e15, 0x1716, 0x0b0d, 0x250c, 0x2726, 0x2928, 0x152a, 0x2c2b, 0x2e2d, 0x302f,
+            0x3231, 0x7016, 0x7271, 0x734e, 0x7574, 0x0f76, 0x410e, 0x0042, 0x0000, 0x0b0d, 0x250c, 0x2726, 0x2928, 0x152a, 0x2c2b, 0x2e2d,
+            0x302f, 0x3231, 0x1716, 0x0201, 0x0403, 0x0605, 0x0807, 0x0a09, 0x3130, 0x1632, 0x0017, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x0201, 0x0403, 0x0605, 0x0807, 0x0a09, 0x2b15, 0x0000, 0x0000, 0x0201, 0x0403, 0x0605, 0x0807, 0x0a09, 0x2b15, 0x2d2c, 0x2f2e,
+            0x3130, 0x0032, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x1b1a, 0x3837, 0x3a39, 0x3c3b, 0x371b, 0x3938, 0x3b3a, 0x373c,
+            0x3938, 0x3b3a, 0x193c, 0x1b1a, 0x3837, 0x3a39, 0x3c3b, 0x1a19, 0x371b, 0x1a38, 0x1b1b, 0x3837, 0x3a39, 0x3c3b, 0x1a19, 0x1b1b,
+            0x3837, 0x9998, 0x1a19, 0x1b1b, 0x3837, 0x1b1b, 0x3737, 0x3737, 0x3a39, 0x3a3a, 0x3b3b, 0x3c3c, 0x3c3c, 0x1b1a, 0x3837, 0x1939,
+            0x1b1a, 0x3737, 0x3838, 0x1b1a, 0x1a19, 0x4241, 0x4148, 0x1242, 0x470e, 0x0e0e, 0x410f, 0x2d42, 0x372e, 0x3938, 0x3b3a, 0x003c,
+            0x0201, 0x0403, 0x0605, 0x0807, 0x0a09, 0x1500, 0x3316, 0x9b9a, 0x9d9c, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
+            0x3231, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0201,
+            0x0403, 0x0605, 0x0807, 0x0a09, 0x0201, 0x0403, 0x0605, 0x0807, 0x0a09, 0x0201, 0x0403, 0x0605, 0x0807, 0x0a09, 0x0201, 0x0403,
+            0x0605, 0x0807, 0x0a09, 0x0201, 0x0403, 0x0605, 0x0807, 0x0a09, 0x3d3d, 0x0b0d, 0x250c, 0x2726, 0x2928, 0x182a, 0x0018, 0x0000,
+            0x003c, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0xeeee, 0xeeee, 0xeeee, 0xeeee
+        };
+        // Every item contains the value for numeric value.
+        private static byte[] s_pNumericValues = new byte[]
+        {
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf0, 0xbf, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf0, 0x3f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x08, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x14, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x18, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1c, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x20, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x22, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x08, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf0, 0x3f,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xd0, 0x3f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xe0, 0x3f,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xe8, 0x3f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xb0, 0x3f,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xc0, 0x3f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xc8, 0x3f,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x30, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x24, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x59, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x8f, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf0, 0x3f,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x08, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf8, 0x3f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0c, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x12, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x16, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1a, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1e, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x21, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xe0, 0xbf, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x14, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x18, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1c, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x20, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x22, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x34, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3e, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x44, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x49, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x4e, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x51, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x54, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x56, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x88, 0xc3, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x31, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x32, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x33, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x14, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x18, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1c, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x20, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x22, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x92, 0x24, 0x49, 0x92, 0x24, 0x49, 0xc2, 0x3f, 0x1c, 0xc7, 0x71, 0x1c, 0xc7, 0x71, 0xbc, 0x3f,
+            0x9a, 0x99, 0x99, 0x99, 0x99, 0x99, 0xb9, 0x3f, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0xd5, 0x3f,
+            0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0xe5, 0x3f, 0x9a, 0x99, 0x99, 0x99, 0x99, 0x99, 0xc9, 0x3f,
+            0x9a, 0x99, 0x99, 0x99, 0x99, 0x99, 0xd9, 0x3f, 0x33, 0x33, 0x33, 0x33, 0x33, 0x33, 0xe3, 0x3f,
+            0x9a, 0x99, 0x99, 0x99, 0x99, 0x99, 0xe9, 0x3f, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0xc5, 0x3f,
+            0xab, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xea, 0x3f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xd8, 0x3f,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xe4, 0x3f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xec, 0x3f,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x26, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x28, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x7f, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x88, 0xb3, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x6a, 0xe8, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x6a, 0xf8, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2a, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2c, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2e, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x35, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x36, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x37, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x38, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x39, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3a, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3b, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3c, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3d, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3f, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x40, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x41, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x41, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x42, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x42, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x43, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x43, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x44, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x45, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x45, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x46, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x46, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x47, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x47, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x48, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x48, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x69, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0xc0, 0x72, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0xc0, 0x82, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0xe0, 0x85, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x89, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x20, 0x8c, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x9f, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x70, 0xa7, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0xaf, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x70, 0xb7, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x58, 0xbb, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0xbf, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x94, 0xc1, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x88, 0xd3, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x4c, 0xdd, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x88, 0xe3, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x4c, 0xed, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x17, 0xf1, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x88, 0xf3, 0x40,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0xf9, 0xf5, 0x40, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0xed, 0x3f,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x6a, 0x08, 0x41, 0x00, 0x00, 0x00, 0x00, 0x80, 0x4f, 0x12, 0x41,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x6a, 0x18, 0x41, 0x00, 0x00, 0x00, 0x00, 0x80, 0x84, 0x1e, 0x41,
+            0x00, 0x00, 0x00, 0x00, 0x80, 0x4f, 0x22, 0x41, 0x00, 0x00, 0x00, 0x00, 0xc0, 0x5c, 0x25, 0x41,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x6a, 0x28, 0x41, 0x00, 0x00, 0x00, 0x00, 0x40, 0x77, 0x2b, 0x41,
+            0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0xb5, 0x3f, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0xc5, 0x3f,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xd0, 0x3f, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0xd5, 0x3f,
+            0xab, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xda, 0x3f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xe0, 0x3f,
+            0xab, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xe2, 0x3f, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0xe5, 0x3f,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xe8, 0x3f, 0xab, 0xaa, 0xaa, 0xaa, 0xaa, 0xaa, 0xea, 0x3f,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x5e, 0x0a, 0x41, 0x00, 0x00, 0x00, 0x00, 0x00, 0x5e, 0x1a, 0x41,
+            0x00, 0x00, 0x00, 0x00, 0x80, 0x84, 0x2e, 0x41, 0x00, 0x00, 0x00, 0x00, 0x84, 0xd7, 0x97, 0x41,
+            0x00, 0x00, 0x00, 0x20, 0x5f, 0xa0, 0x02, 0x42, 0x00, 0x00, 0x00, 0xa2, 0x94, 0x1a, 0x6d, 0x42
+        };
+
+        private static ushort[] s_pDigitValues = new ushort []
+        {
+            0xffff, 0x0000, 0x0101, 0x0202, 0x0303, 0x0404, 0x0505, 0x0606,
+            0x0707, 0x0808, 0x0909, 0xff02, 0xff03, 0xff01, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xff04, 0xff05, 0xff06,
+            0xff07, 0xff08, 0xff09, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xff00, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff,
+            0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0x0000, 0x0000
+        };
+
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Globalization/CultureInfo.Unix.cs b/src/System.Private.CoreLib/src/System/Globalization/CultureInfo.Unix.cs
new file mode 100644
index 0000000000..719cc7532f
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Globalization/CultureInfo.Unix.cs
@@ -0,0 +1,120 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Threading;
+
+namespace System.Globalization
+{
+    public partial class CultureInfo : IFormatProvider
+    {
+        private static CultureInfo GetUserDefaultCultureCacheOverride()
+        {
+            return null; // ICU doesn't provide a user override
+        }        
+
+        internal static CultureInfo GetUserDefaultCulture()
+        {
+            if (GlobalizationMode.Invariant)
+                return CultureInfo.InvariantCulture;
+
+            CultureInfo cultureInfo = null;
+            string localeName;
+            if (CultureData.GetDefaultLocaleName(out localeName))
+            {
+                cultureInfo = GetCultureByName(localeName, true);
+                cultureInfo._isReadOnly = true;
+            }
+            else
+            {
+                cultureInfo = CultureInfo.InvariantCulture;
+            }
+
+            return cultureInfo;
+        }
+
+        private static CultureInfo GetUserDefaultUICulture()
+        {
+            return GetUserDefaultCulture();
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  CurrentCulture
+        //
+        //  This instance provides methods based on the current user settings.
+        //  These settings are volatile and may change over the lifetime of the
+        //  thread.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        //
+        // We use the following order to return CurrentCulture and CurrentUICulture
+        //      o   use current thread culture if the user already set one using CurrentCulture/CurrentUICulture
+        //      o   use thread culture if the user already set one using DefaultThreadCurrentCulture
+        //          or DefaultThreadCurrentUICulture
+        //      o   Use NLS default user culture
+        //      o   Use NLS default system culture
+        //      o   Use Invariant culture
+        //
+        public static CultureInfo CurrentCulture
+        {
+            get
+            {
+                if (Thread.m_CurrentCulture != null)
+                {
+                    return Thread.m_CurrentCulture;
+                }
+
+                CultureInfo ci = s_DefaultThreadCurrentCulture;
+                if (ci != null)
+                {
+                    return ci;
+                }
+
+                return s_userDefaultCulture ?? InitializeUserDefaultCulture();
+            }
+
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value));
+                }
+                
+                if (s_asyncLocalCurrentCulture == null)
+                {
+                    Interlocked.CompareExchange(ref s_asyncLocalCurrentCulture, new AsyncLocal<CultureInfo>(AsyncLocalSetCurrentCulture), null);
+                }
+                s_asyncLocalCurrentCulture.Value = value;
+            }
+        }
+
+        public static CultureInfo CurrentUICulture
+        {
+            get
+            {
+                return GetCurrentUICultureNoAppX();
+            }
+
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value));
+                }
+
+                CultureInfo.VerifyCultureName(value, true);
+                if (s_asyncLocalCurrentUICulture == null)
+                {
+                    Interlocked.CompareExchange(ref s_asyncLocalCurrentUICulture, new AsyncLocal<CultureInfo>(AsyncLocalSetCurrentUICulture), null);
+                }
+
+                // this one will set s_currentThreadUICulture too
+                s_asyncLocalCurrentUICulture.Value = value;               
+            }
+        }
+        
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Globalization/CultureInfo.Windows.cs b/src/System.Private.CoreLib/src/System/Globalization/CultureInfo.Windows.cs
new file mode 100644
index 0000000000..d9ce874ad4
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Globalization/CultureInfo.Windows.cs
@@ -0,0 +1,269 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+#if ENABLE_WINRT
+using Internal.Runtime.Augments;
+#endif
+
+using System.Threading;
+#if FEATURE_APPX
+using System.Resources;
+#endif
+
+namespace System.Globalization
+{
+    public partial class CultureInfo : IFormatProvider
+    {
+#if FEATURE_APPX
+        // When running under AppX, we use this to get some information about the language list
+        private static volatile WindowsRuntimeResourceManagerBase s_WindowsRuntimeResourceManager;
+
+        [ThreadStatic]
+        private static bool ts_IsDoingAppXCultureInfoLookup;
+#endif
+
+        /// <summary>
+        /// Gets the default user culture from WinRT, if available.
+        /// </summary>
+        /// <remarks>
+        /// This method may return null, if there is no default user culture or if WinRT isn't available.
+        /// </remarks>
+        private static CultureInfo GetUserDefaultCultureCacheOverride()
+        {
+#if ENABLE_WINRT
+            WinRTInteropCallbacks callbacks = WinRTInterop.UnsafeCallbacks;
+            if (callbacks != null && callbacks.IsAppxModel())
+            {
+                return (CultureInfo)callbacks.GetUserDefaultCulture();
+            }
+#endif
+
+            return null;
+        }
+
+        internal static CultureInfo GetUserDefaultCulture()
+        {
+            if (GlobalizationMode.Invariant)
+                return CultureInfo.InvariantCulture;
+            
+            const uint LOCALE_SNAME = 0x0000005c;
+            const string LOCALE_NAME_USER_DEFAULT = null;
+            const string LOCALE_NAME_SYSTEM_DEFAULT = "!x-sys-default-locale";
+
+            string strDefault = CultureData.GetLocaleInfoEx(LOCALE_NAME_USER_DEFAULT, LOCALE_SNAME);
+            if (strDefault == null)
+            {
+                strDefault = CultureData.GetLocaleInfoEx(LOCALE_NAME_SYSTEM_DEFAULT, LOCALE_SNAME);
+
+                if (strDefault == null)
+                {
+                    // If system default doesn't work, use invariant
+                    return CultureInfo.InvariantCulture;
+                }
+            }
+
+            CultureInfo temp = GetCultureByName(strDefault, true);
+
+            temp._isReadOnly = true;
+
+            return temp;
+        }
+
+        private static CultureInfo GetUserDefaultUICulture()
+        {
+            if (GlobalizationMode.Invariant)
+                return CultureInfo.InvariantCulture;
+
+            const uint MUI_LANGUAGE_NAME = 0x8;    // Use ISO language (culture) name convention
+            uint langCount = 0;
+            uint bufLen = 0;
+
+            if (Interop.Kernel32.GetUserPreferredUILanguages(MUI_LANGUAGE_NAME, out langCount, null, ref bufLen))
+            {
+                char [] languages = new char[bufLen];
+                if (Interop.Kernel32.GetUserPreferredUILanguages(MUI_LANGUAGE_NAME, out langCount, languages, ref bufLen))
+                {
+                    int index = 0;
+                    while (languages[index] != (char) 0 && index<languages.Length)
+                    {
+                        index++;
+                    }
+
+                    CultureInfo temp = GetCultureByName(new String(languages, 0, index), true);
+                    temp._isReadOnly = true;
+                    return temp;
+                }
+            }
+
+            return GetUserDefaultCulture();
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  CurrentCulture
+        //
+        //  This instance provides methods based on the current user settings.
+        //  These settings are volatile and may change over the lifetime of the
+        //  thread.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        //
+        // We use the following order to return CurrentCulture and CurrentUICulture
+        //      o   Use WinRT to return the current user profile language
+        //      o   use current thread culture if the user already set one using CurrentCulture/CurrentUICulture
+        //      o   use thread culture if the user already set one using DefaultThreadCurrentCulture
+        //          or DefaultThreadCurrentUICulture
+        //      o   Use NLS default user culture
+        //      o   Use NLS default system culture
+        //      o   Use Invariant culture
+        //
+        public static CultureInfo CurrentCulture
+        {
+            get
+            {
+#if FEATURE_APPX
+                if (AppDomain.IsAppXModel())
+                {
+                    CultureInfo culture = GetCultureInfoForUserPreferredLanguageInAppX();
+                    if (culture != null)
+                        return culture;
+                }
+#endif
+                CultureInfo ci = GetUserDefaultCultureCacheOverride();
+                if (ci != null)
+                {
+                    return ci;
+                }
+
+                if (Thread.m_CurrentCulture != null)
+                {
+                    return Thread.m_CurrentCulture;
+                }
+
+                ci = s_DefaultThreadCurrentCulture;
+                if (ci != null)
+                {
+                    return ci;
+                }
+
+                return s_userDefaultCulture ?? InitializeUserDefaultCulture();
+            }
+
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value));
+                }
+                
+#if FEATURE_APPX
+                if (AppDomain.IsAppXModel())
+                {
+                    if (SetCultureInfoForUserPreferredLanguageInAppX(value))
+                    {
+                        // successfully set the culture, otherwise fallback to legacy path
+                        return; 
+                    }
+                }
+#endif
+                if (s_asyncLocalCurrentCulture == null)
+                {
+                    Interlocked.CompareExchange(ref s_asyncLocalCurrentCulture, new AsyncLocal<CultureInfo>(AsyncLocalSetCurrentCulture), null);
+                }
+                s_asyncLocalCurrentCulture.Value = value;
+            }
+        }
+
+        public static CultureInfo CurrentUICulture
+        {
+            get
+            {
+#if FEATURE_APPX
+                if (AppDomain.IsAppXModel())
+                {
+                    CultureInfo culture = GetCultureInfoForUserPreferredLanguageInAppX();
+                    if (culture != null)
+                        return culture;
+                }
+#endif
+                return GetCurrentUICultureNoAppX();
+            }
+
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value));
+                }
+
+                CultureInfo.VerifyCultureName(value, true);
+#if FEATURE_APPX
+                if (AppDomain.IsAppXModel())
+                {
+                    if (SetCultureInfoForUserPreferredLanguageInAppX(value))
+                    {
+                        // successfully set the culture, otherwise fallback to legacy path
+                        return; 
+                    }
+                }
+#endif
+                if (s_asyncLocalCurrentUICulture == null)
+                {
+                    Interlocked.CompareExchange(ref s_asyncLocalCurrentUICulture, new AsyncLocal<CultureInfo>(AsyncLocalSetCurrentUICulture), null);
+                }
+
+                // this one will set s_currentThreadUICulture too
+                s_asyncLocalCurrentUICulture.Value = value;               
+            }
+        }
+
+#if FEATURE_APPX
+        internal static CultureInfo GetCultureInfoForUserPreferredLanguageInAppX()
+        {
+            // If a call to GetCultureInfoForUserPreferredLanguageInAppX() generated a recursive
+            // call to itself, return null, since we don't want to stack overflow.  For example, 
+            // this can happen if some code in this method ends up calling CultureInfo.CurrentCulture.
+            // In this case, returning null will mean CultureInfo.CurrentCulture gets the default Win32 
+            // value, which should be fine. 
+            if (ts_IsDoingAppXCultureInfoLookup)
+            {
+                return null;
+            }
+
+            CultureInfo toReturn = null;
+
+            try 
+            {
+                ts_IsDoingAppXCultureInfoLookup = true;
+
+                if (s_WindowsRuntimeResourceManager == null)
+                {
+                    s_WindowsRuntimeResourceManager = ResourceManager.GetWinRTResourceManager();
+                }
+
+                toReturn = s_WindowsRuntimeResourceManager.GlobalResourceContextBestFitCultureInfo;
+            } 
+            finally 
+            {
+               ts_IsDoingAppXCultureInfoLookup = false;
+            }
+ 
+            return toReturn;
+        }
+
+        internal static bool SetCultureInfoForUserPreferredLanguageInAppX(CultureInfo ci)
+        {
+            if (s_WindowsRuntimeResourceManager == null)
+            {
+                s_WindowsRuntimeResourceManager = ResourceManager.GetWinRTResourceManager();
+            }
+
+            return s_WindowsRuntimeResourceManager.SetGlobalResourceContextDefaultCulture(ci);
+        }
+#endif
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Globalization/CultureInfo.cs b/src/System.Private.CoreLib/src/System/Globalization/CultureInfo.cs
new file mode 100644
index 0000000000..83a261fc65
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Globalization/CultureInfo.cs
@@ -0,0 +1,1372 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////
+//
+//
+//
+//  Purpose:  This class represents the software preferences of a particular
+//            culture or community.  It includes information such as the
+//            language, writing system, and a calendar used by the culture
+//            as well as methods for common operations such as printing
+//            dates and sorting strings.
+//
+//
+//
+//  !!!! NOTE WHEN CHANGING THIS CLASS !!!!
+//
+//  If adding or removing members to this class, please update CultureInfoBaseObject
+//  in ndp/clr/src/vm/object.h. Note, the "actual" layout of the class may be
+//  different than the order in which members are declared. For instance, all
+//  reference types will come first in the class before value types (like ints, bools, etc)
+//  regardless of the order in which they are declared. The best way to see the
+//  actual order of the class is to do a !dumpobj on an instance of the managed
+//  object inside of the debugger.
+//
+////////////////////////////////////////////////////////////////////////////
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Threading;
+
+namespace System.Globalization
+{
+#if CORECLR
+    using StringCultureInfoDictionary = Dictionary<string, CultureInfo>;
+    using StringLcidDictionary = Dictionary<int, CultureInfo>;
+    
+    using Lock = Object;
+#else
+    using StringCultureInfoDictionary = LowLevelDictionary<string, CultureInfo>;
+    using StringLcidDictionary = LowLevelDictionary<int, CultureInfo>;
+#endif
+
+    public partial class CultureInfo : IFormatProvider, ICloneable
+    {
+        //--------------------------------------------------------------------//
+        //                        Internal Information                        //
+        //--------------------------------------------------------------------//
+
+        // We use an RFC4646 type string to construct CultureInfo.
+        // This string is stored in _name and is authoritative.
+        // We use the _cultureData to get the data for our object
+
+        private bool _isReadOnly;
+        private CompareInfo compareInfo;
+        private TextInfo textInfo;
+        internal NumberFormatInfo numInfo;
+        internal DateTimeFormatInfo dateTimeInfo;
+        private Calendar calendar;
+        //
+        // The CultureData instance that we are going to read data from.
+        // For supported culture, this will be the CultureData instance that read data from mscorlib assembly.
+        // For customized culture, this will be the CultureData instance that read data from user customized culture binary file.
+        //
+        internal CultureData _cultureData;
+
+        internal bool _isInherited;
+
+        private CultureInfo _consoleFallbackCulture;
+
+        // Names are confusing.  Here are 3 names we have:
+        //
+        //  new CultureInfo()   _name          _nonSortName    _sortName
+        //      en-US           en-US           en-US           en-US
+        //      de-de_phoneb    de-DE_phoneb    de-DE           de-DE_phoneb
+        //      fj-fj (custom)  fj-FJ           fj-FJ           en-US (if specified sort is en-US)
+        //      en              en              
+        //
+        // Note that in Silverlight we ask the OS for the text and sort behavior, so the 
+        // textinfo and compareinfo names are the same as the name
+
+        // This has a de-DE, de-DE_phoneb or fj-FJ style name
+        internal string _name;
+
+        // This will hold the non sorting name to be returned from CultureInfo.Name property.
+        // This has a de-DE style name even for de-DE_phoneb type cultures
+        private string _nonSortName;
+
+        // This will hold the sorting name to be returned from CultureInfo.SortName property.
+        // This might be completely unrelated to the culture name if a custom culture.  Ie en-US for fj-FJ.
+        // Otherwise its the sort name, ie: de-DE or de-DE_phoneb
+        private string _sortName;
+
+        //--------------------------------------------------------------------//
+        //
+        // Static data members
+        //
+        //--------------------------------------------------------------------//
+
+        //Get the current user default culture.  This one is almost always used, so we create it by default.
+        private static volatile CultureInfo s_userDefaultCulture;
+
+        //The culture used in the user interface. This is mostly used to load correct localized resources.
+        private static volatile CultureInfo s_userDefaultUICulture;
+        //
+        // All of the following will be created on demand.
+        //
+
+        // WARNING: We allow diagnostic tools to directly inspect these three members (s_InvariantCultureInfo, s_DefaultThreadCurrentUICulture and s_DefaultThreadCurrentCulture)
+        // See https://github.com/dotnet/corert/blob/master/Documentation/design-docs/diagnostics/diagnostics-tools-contract.md for more details. 
+        // Please do not change the type, the name, or the semantic usage of this member without understanding the implication for tools. 
+        // Get in touch with the diagnostics team if you have questions.
+
+        //The Invariant culture;
+        private static readonly CultureInfo s_InvariantCultureInfo = new CultureInfo(CultureData.Invariant, isReadOnly: true);
+
+        //These are defaults that we use if a thread has not opted into having an explicit culture
+        private static volatile CultureInfo s_DefaultThreadCurrentUICulture;
+        private static volatile CultureInfo s_DefaultThreadCurrentCulture;
+
+        internal static AsyncLocal<CultureInfo> s_asyncLocalCurrentCulture; 
+        internal static AsyncLocal<CultureInfo> s_asyncLocalCurrentUICulture;
+
+        internal static void AsyncLocalSetCurrentCulture(AsyncLocalValueChangedArgs<CultureInfo> args)
+        {
+            Thread.m_CurrentCulture = args.CurrentValue;
+        }
+
+        internal static void AsyncLocalSetCurrentUICulture(AsyncLocalValueChangedArgs<CultureInfo> args)
+        {
+            Thread.m_CurrentUICulture = args.CurrentValue;
+        }
+
+        private static readonly Lock _lock = new Lock();
+        private static volatile StringCultureInfoDictionary s_NameCachedCultures;
+        private static volatile StringLcidDictionary s_LcidCachedCultures;       
+
+        //The parent culture.
+        private CultureInfo _parent;
+
+        // LOCALE constants of interest to us internally and privately for LCID functions
+        // (ie: avoid using these and use names if possible)
+        internal const int LOCALE_NEUTRAL        = 0x0000;
+        private  const int LOCALE_USER_DEFAULT   = 0x0400;
+        private  const int LOCALE_SYSTEM_DEFAULT = 0x0800;
+        internal const int LOCALE_CUSTOM_UNSPECIFIED = 0x1000;
+        internal const int LOCALE_CUSTOM_DEFAULT  = 0x0c00;
+        internal const int LOCALE_INVARIANT       = 0x007F;
+
+        private static CultureInfo InitializeUserDefaultCulture()
+        {
+            Interlocked.CompareExchange(ref s_userDefaultCulture, GetUserDefaultCulture(), null);
+            return s_userDefaultCulture;
+        }
+
+        private static CultureInfo InitializeUserDefaultUICulture()
+        {
+            Interlocked.CompareExchange(ref s_userDefaultUICulture, GetUserDefaultUICulture(), null);
+            return s_userDefaultUICulture;
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  CultureInfo Constructors
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        public CultureInfo(String name)
+            : this(name, true)
+        {
+        }
+
+
+        public CultureInfo(String name, bool useUserOverride)
+        {
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(name),
+                    SR.ArgumentNull_String);
+            }
+
+            InitializeFromName(name, useUserOverride);
+        }
+
+        private CultureInfo(CultureData cultureData, bool isReadOnly = false)
+        {
+            Debug.Assert(cultureData != null);
+            _cultureData = cultureData;
+            _name = cultureData.CultureName;
+            _isInherited = false;
+            _isReadOnly = isReadOnly;
+        }
+
+        private static CultureInfo CreateCultureInfoNoThrow(string name, bool useUserOverride)
+        {
+            Debug.Assert(name != null);
+            CultureData cultureData = CultureData.GetCultureData(name, useUserOverride);
+            if (cultureData == null)
+            {
+                return null;
+            }
+
+            return new CultureInfo(cultureData);
+        } 
+        public CultureInfo(int culture) : this(culture, true) 
+        {
+        }
+
+        public CultureInfo(int culture, bool useUserOverride)
+        {
+            // We don't check for other invalid LCIDS here...
+            if (culture < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(culture), SR.ArgumentOutOfRange_NeedPosNum);
+            }
+
+            InitializeFromCultureId(culture, useUserOverride);
+        }
+
+        private void InitializeFromCultureId(int culture, bool useUserOverride)
+        {
+            switch (culture)
+            {
+                case LOCALE_CUSTOM_DEFAULT:
+                case LOCALE_SYSTEM_DEFAULT:
+                case LOCALE_NEUTRAL:
+                case LOCALE_USER_DEFAULT:
+                case LOCALE_CUSTOM_UNSPECIFIED:
+                    // Can't support unknown custom cultures and we do not support neutral or
+                    // non-custom user locales.
+                    throw new CultureNotFoundException(nameof(culture), culture, SR.Argument_CultureNotSupported);
+
+                default:
+                    // Now see if this LCID is supported in the system default CultureData table.
+                    _cultureData = CultureData.GetCultureData(culture, useUserOverride);
+                    break;
+            }
+            _isInherited = (this.GetType() != typeof(System.Globalization.CultureInfo));
+            _name = _cultureData.CultureName;
+        }
+
+        private void InitializeFromName(string name, bool useUserOverride)
+        {
+            // Get our data providing record
+            _cultureData = CultureData.GetCultureData(name, useUserOverride);
+
+            if (_cultureData == null)
+            {
+                throw new CultureNotFoundException(nameof(name), name, SR.Argument_CultureNotSupported);
+            }
+
+            _name = _cultureData.CultureName;
+            _isInherited = (this.GetType() != typeof(System.Globalization.CultureInfo));
+        }
+
+        // Constructor called by SQL Server's special munged culture - creates a culture with
+        // a TextInfo and CompareInfo that come from a supplied alternate source. This object
+        // is ALWAYS read-only.
+        // Note that we really cannot use an LCID version of this override as the cached
+        // name we create for it has to include both names, and the logic for this is in
+        // the GetCultureInfo override *only*.
+        internal CultureInfo(String cultureName, String textAndCompareCultureName)
+        {
+            if (cultureName == null)
+            {
+                throw new ArgumentNullException(nameof(cultureName),SR.ArgumentNull_String);
+            }
+
+            _cultureData = CultureData.GetCultureData(cultureName, false);
+            if (_cultureData == null)
+                throw new CultureNotFoundException(nameof(cultureName), cultureName, SR.Argument_CultureNotSupported);
+            
+            _name = _cultureData.CultureName;
+
+            CultureInfo altCulture = GetCultureInfo(textAndCompareCultureName);
+            compareInfo = altCulture.CompareInfo;
+            textInfo = altCulture.TextInfo;
+        }
+
+        // We do this to try to return the system UI language and the default user languages
+        // This method will fallback if this fails (like Invariant)
+        //
+        // TODO: It would appear that this is only ever called with userOveride = true
+        // and this method only has one caller.  Can we fold it into the caller?
+        private static CultureInfo GetCultureByName(String name, bool userOverride)
+        {
+            CultureInfo ci = null;
+            // Try to get our culture
+            try
+            {
+                ci = userOverride ? new CultureInfo(name) : CultureInfo.GetCultureInfo(name);
+            }
+            catch (ArgumentException)
+            {
+            }
+
+            if (ci == null)
+            {
+                ci = InvariantCulture;
+            }
+
+            return ci;
+        }
+
+        //
+        // Return a specific culture.  A tad irrelevent now since we always return valid data
+        // for neutral locales.
+        //
+        // Note that there's interesting behavior that tries to find a smaller name, ala RFC4647,
+        // if we can't find a bigger name.  That doesn't help with things like "zh" though, so
+        // the approach is of questionable value
+        //
+        public static CultureInfo CreateSpecificCulture(String name)
+        {
+            CultureInfo culture;
+
+            try
+            {
+                culture = new CultureInfo(name);
+            }
+            catch (ArgumentException)
+            {
+                // When CultureInfo throws this exception, it may be because someone passed the form
+                // like "az-az" because it came out of an http accept lang. We should try a little
+                // parsing to perhaps fall back to "az" here and use *it* to create the neutral.
+
+                int idx;
+
+                culture = null;
+                for (idx = 0; idx < name.Length; idx++)
+                {
+                    if ('-' == name[idx])
+                    {
+                        try
+                        {
+                            culture = new CultureInfo(name.Substring(0, idx));
+                            break;
+                        }
+                        catch (ArgumentException)
+                        {
+                            // throw the original exception so the name in the string will be right
+                            throw;
+                        }
+                    }
+                }
+
+                if (culture == null)
+                {
+                    // nothing to save here; throw the original exception
+                    throw;
+                }
+            }
+
+            // In the most common case, they've given us a specific culture, so we'll just return that.
+            if (!(culture.IsNeutralCulture))
+            {
+                return culture;
+            }
+
+            return (new CultureInfo(culture._cultureData.SSPECIFICCULTURE));
+        }
+
+        internal static bool VerifyCultureName(String cultureName, bool throwException)
+        {
+            // This function is used by ResourceManager.GetResourceFileName().
+            // ResourceManager searches for resource using CultureInfo.Name,
+            // so we should check against CultureInfo.Name.
+
+            for (int i = 0; i < cultureName.Length; i++)
+            {
+                char c = cultureName[i];
+                // TODO: Names can only be RFC4646 names (ie: a-zA-Z0-9) while this allows any unicode letter/digit
+                if (Char.IsLetterOrDigit(c) || c == '-' || c == '_')
+                {
+                    continue;
+                }
+                if (throwException)
+                {
+                    throw new ArgumentException(SR.Format(SR.Argument_InvalidResourceCultureName, cultureName));
+                }
+                return false;
+            }
+            return true;
+        }
+
+        internal static bool VerifyCultureName(CultureInfo culture, bool throwException)
+        {
+            //If we have an instance of one of our CultureInfos, the user can't have changed the
+            //name and we know that all names are valid in files.
+            if (!culture._isInherited)
+            {
+                return true;
+            }
+
+            return VerifyCultureName(culture.Name, throwException);
+        }
+
+        // We need to store the override from the culture data record.
+        private bool _useUserOverride;
+        
+        internal static CultureInfo GetCurrentUICultureNoAppX()
+        {
+            CultureInfo ci = GetUserDefaultCultureCacheOverride();
+            if (ci != null)
+            {
+                return ci;
+            }
+
+            if (Thread.m_CurrentUICulture != null)
+            {
+                return Thread.m_CurrentUICulture;
+            }
+
+            ci = s_DefaultThreadCurrentUICulture;
+            if (ci != null)
+            {
+                return ci;
+            }
+
+            return UserDefaultUICulture;
+        }
+
+        internal static CultureInfo UserDefaultUICulture => s_userDefaultUICulture ?? InitializeUserDefaultUICulture();
+
+        public static CultureInfo InstalledUICulture => s_userDefaultCulture ?? InitializeUserDefaultCulture();
+
+        public static CultureInfo DefaultThreadCurrentCulture
+        {
+            get { return s_DefaultThreadCurrentCulture; }
+            set
+            {
+                // If you add pre-conditions to this method, check to see if you also need to
+                // add them to Thread.CurrentCulture.set.
+
+                s_DefaultThreadCurrentCulture = value;
+            }
+        }
+
+        public static CultureInfo DefaultThreadCurrentUICulture
+        {
+            get { return s_DefaultThreadCurrentUICulture; }
+            set
+            {
+                //If they're trying to use a Culture with a name that we can't use in resource lookup,
+                //don't even let them set it on the thread.
+
+                // If you add more pre-conditions to this method, check to see if you also need to
+                // add them to Thread.CurrentUICulture.set.
+
+                if (value != null)
+                {
+                    CultureInfo.VerifyCultureName(value, true);
+                }
+
+                s_DefaultThreadCurrentUICulture = value;
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  InvariantCulture
+        //
+        //  This instance provides methods, for example for casing and sorting,
+        //  that are independent of the system and current user settings.  It
+        //  should be used only by processes such as some system services that
+        //  require such invariant results (eg. file systems).  In general,
+        //  the results are not linguistically correct and do not match any
+        //  culture info.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+
+        public static CultureInfo InvariantCulture
+        {
+            get
+            {
+                Debug.Assert(s_InvariantCultureInfo != null);
+                return (s_InvariantCultureInfo);
+            }
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  Parent
+        //
+        //  Return the parent CultureInfo for the current instance.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        public virtual CultureInfo Parent
+        {
+            get
+            {
+                if (null == _parent)
+                {
+                    string parentName = _cultureData.SPARENT;
+
+                    if (String.IsNullOrEmpty(parentName))
+                    {
+                        _parent = InvariantCulture;
+                    }
+                    else
+                    {
+                        _parent = CreateCultureInfoNoThrow(parentName, _cultureData.UseUserOverride);
+                        if (_parent == null)
+                        {
+                            // For whatever reason our IPARENT or SPARENT wasn't correct, so use invariant
+                            // We can't allow ourselves to fail.  In case of custom cultures the parent of the
+                            // current custom culture isn't installed.
+                            _parent = InvariantCulture;
+                        }
+                    }
+                }
+                return _parent;
+            }
+        }
+
+        public virtual int LCID
+        {
+            get
+            {
+                return (this._cultureData.ILANGUAGE);
+            }
+        }
+
+        public virtual int KeyboardLayoutId
+        {
+            get
+            {
+                return _cultureData.IINPUTLANGUAGEHANDLE;
+            }
+        }
+
+        public static CultureInfo[] GetCultures(CultureTypes types)
+        {
+            // internally we treat UserCustomCultures as Supplementals but v2
+            // treats as Supplementals and Replacements
+            if ((types & CultureTypes.UserCustomCulture) == CultureTypes.UserCustomCulture)
+            {
+                types |= CultureTypes.ReplacementCultures;
+            }
+            return (CultureData.GetCultures(types));
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  Name
+        //
+        //  Returns the full name of the CultureInfo. The name is in format like
+        //  "en-US"  This version does NOT include sort information in the name.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String Name
+        {
+            get
+            {
+                // We return non sorting name here.
+                if (_nonSortName == null)
+                {
+                    _nonSortName = _cultureData.SNAME;
+                    if (_nonSortName == null)
+                    {
+                        _nonSortName = String.Empty;
+                    }
+                }
+                return _nonSortName;
+            }
+        }
+
+        // This one has the sort information (ie: de-DE_phoneb)
+        internal String SortName
+        {
+            get
+            {
+                if (_sortName == null)
+                {
+                    _sortName = _cultureData.SCOMPAREINFO;
+                }
+
+                return _sortName;
+            }
+        }
+
+        public string IetfLanguageTag
+        {
+            get
+            {
+                // special case the compatibility cultures
+                switch (this.Name)
+                {
+                    case "zh-CHT":
+                        return "zh-Hant";
+                    case "zh-CHS":
+                        return "zh-Hans";
+                    default:
+                        return this.Name;
+                }
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  DisplayName
+        //
+        //  Returns the full name of the CultureInfo in the localized language.
+        //  For example, if the localized language of the runtime is Spanish and the CultureInfo is
+        //  US English, "Ingles (Estados Unidos)" will be returned.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String DisplayName
+        {
+            get
+            {
+                Debug.Assert(_name != null, "[CultureInfo.DisplayName] Always expect _name to be set");
+
+                return _cultureData.SLOCALIZEDDISPLAYNAME;
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetNativeName
+        //
+        //  Returns the full name of the CultureInfo in the native language.
+        //  For example, if the CultureInfo is US English, "English
+        //  (United States)" will be returned.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String NativeName
+        {
+            get
+            {
+                return (_cultureData.SNATIVEDISPLAYNAME);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetEnglishName
+        //
+        //  Returns the full name of the CultureInfo in English.
+        //  For example, if the CultureInfo is US English, "English
+        //  (United States)" will be returned.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String EnglishName
+        {
+            get
+            {
+                return (_cultureData.SENGDISPLAYNAME);
+            }
+        }
+
+        // ie: en
+        public virtual String TwoLetterISOLanguageName
+        {
+            get
+            {
+                return (_cultureData.SISO639LANGNAME);
+            }
+        }
+
+        // ie: eng
+        public virtual String ThreeLetterISOLanguageName
+        {
+            get
+            {
+                return _cultureData.SISO639LANGNAME2;
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  ThreeLetterWindowsLanguageName
+        //
+        //  Returns the 3 letter windows language name for the current instance.  eg: "ENU"
+        //  The ISO names are much preferred
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual String ThreeLetterWindowsLanguageName
+        {
+            get
+            {
+                return _cultureData.SABBREVLANGNAME;
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  CompareInfo               Read-Only Property
+        //
+        //  Gets the CompareInfo for this culture.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual CompareInfo CompareInfo
+        {
+            get
+            {
+                if (this.compareInfo == null)
+                {
+                    // Since CompareInfo's don't have any overrideable properties, get the CompareInfo from
+                    // the Non-Overridden CultureInfo so that we only create one CompareInfo per culture
+                    this.compareInfo = UseUserOverride
+                                        ? GetCultureInfo(this._name).CompareInfo
+                                        : new CompareInfo(this);
+                }
+                return (compareInfo);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  TextInfo
+        //
+        //  Gets the TextInfo for this culture.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual TextInfo TextInfo
+        {
+            get
+            {
+                if (textInfo == null)
+                {
+                    // Make a new textInfo
+                    TextInfo tempTextInfo = new TextInfo(_cultureData);
+                    tempTextInfo.SetReadOnlyState(_isReadOnly);
+                    textInfo = tempTextInfo;
+                }
+                return (textInfo);
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  Equals
+        //
+        //  Implements Object.Equals().  Returns a boolean indicating whether
+        //  or not object refers to the same CultureInfo as the current instance.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+
+        public override bool Equals(Object value)
+        {
+            if (Object.ReferenceEquals(this, value))
+                return true;
+
+            CultureInfo that = value as CultureInfo;
+
+            if (that != null)
+            {
+                // using CompareInfo to verify the data passed through the constructor
+                // CultureInfo(String cultureName, String textAndCompareCultureName)
+
+                return (this.Name.Equals(that.Name) && this.CompareInfo.Equals(that.CompareInfo));
+            }
+
+            return (false);
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  GetHashCode
+        //
+        //  Implements Object.GetHashCode().  Returns the hash code for the
+        //  CultureInfo.  The hash code is guaranteed to be the same for CultureInfo A
+        //  and B where A.Equals(B) is true.
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+        public override int GetHashCode()
+        {
+            return (this.Name.GetHashCode() + this.CompareInfo.GetHashCode());
+        }
+
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        //  ToString
+        //
+        //  Implements Object.ToString().  Returns the name of the CultureInfo,
+        //  eg. "de-DE_phoneb", "en-US", or "fj-FJ".
+        //
+        ////////////////////////////////////////////////////////////////////////
+
+
+        public override String ToString()
+        {
+            return _name;
+        }
+
+
+        public virtual Object GetFormat(Type formatType)
+        {
+            if (formatType == typeof(NumberFormatInfo))
+                return (NumberFormat);
+            if (formatType == typeof(DateTimeFormatInfo))
+                return (DateTimeFormat);
+            return (null);
+        }
+
+        public virtual bool IsNeutralCulture
+        {
+            get
+            {
+                return _cultureData.IsNeutralCulture;
+            }
+        }
+
+        public CultureTypes CultureTypes
+        {
+            get
+            {
+                CultureTypes types = 0;
+
+                if (_cultureData.IsNeutralCulture)
+                    types |= CultureTypes.NeutralCultures;
+                else
+                    types |= CultureTypes.SpecificCultures;
+
+                types |= _cultureData.IsWin32Installed ? CultureTypes.InstalledWin32Cultures : 0;
+
+                // Disable  warning 618: System.Globalization.CultureTypes.FrameworkCultures' is obsolete
+#pragma warning disable 618
+                types |= _cultureData.IsFramework ? CultureTypes.FrameworkCultures : 0;
+
+#pragma warning restore 618
+                types |= _cultureData.IsSupplementalCustomCulture ? CultureTypes.UserCustomCulture : 0;
+                types |= _cultureData.IsReplacementCulture ? CultureTypes.ReplacementCultures | CultureTypes.UserCustomCulture : 0;
+
+                return types;
+            }
+        }
+
+        public virtual NumberFormatInfo NumberFormat
+        {
+            get
+            {
+                if (numInfo == null)
+                {
+                    NumberFormatInfo temp = new NumberFormatInfo(_cultureData);
+                    temp.isReadOnly = _isReadOnly;
+                    Interlocked.CompareExchange(ref numInfo, temp, null);
+                }
+                return (numInfo);
+            }
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value), SR.ArgumentNull_Obj);
+                }
+                VerifyWritable();
+                numInfo = value;
+            }
+        }
+
+        ////////////////////////////////////////////////////////////////////////
+        //
+        // GetDateTimeFormatInfo
+        //
+        // Create a DateTimeFormatInfo, and fill in the properties according to
+        // the CultureID.
+        //
+        ////////////////////////////////////////////////////////////////////////
+        public virtual DateTimeFormatInfo DateTimeFormat
+        {
+            get
+            {
+                if (dateTimeInfo == null)
+                {
+                    // Change the calendar of DTFI to the specified calendar of this CultureInfo.
+                    DateTimeFormatInfo temp = new DateTimeFormatInfo(_cultureData, this.Calendar);
+                    temp._isReadOnly = _isReadOnly;
+                    Interlocked.CompareExchange(ref dateTimeInfo, temp, null);
+                }
+                return (dateTimeInfo);
+            }
+
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value), SR.ArgumentNull_Obj);
+                }
+                VerifyWritable();
+                dateTimeInfo = value;
+            }
+        }
+
+        public void ClearCachedData()
+        {
+            // reset the default culture values
+            s_userDefaultCulture = GetUserDefaultCulture();
+            s_userDefaultUICulture = GetUserDefaultUICulture();
+
+            RegionInfo.s_currentRegionInfo = null;
+            #pragma warning disable 0618 // disable the obsolete warning 
+            TimeZone.ResetTimeZone();
+            #pragma warning restore 0618
+            TimeZoneInfo.ClearCachedData();
+            s_LcidCachedCultures = null;
+            s_NameCachedCultures = null;
+
+            CultureData.ClearCachedData();
+        }
+
+        /*=================================GetCalendarInstance==========================
+        **Action: Map a Win32 CALID to an instance of supported calendar.
+        **Returns: An instance of calendar.
+        **Arguments: calType    The Win32 CALID
+        **Exceptions:
+        **      Shouldn't throw exception since the calType value is from our data table or from Win32 registry.
+        **      If we are in trouble (like getting a weird value from Win32 registry), just return the GregorianCalendar.
+        ============================================================================*/
+        internal static Calendar GetCalendarInstance(CalendarId calType)
+        {
+            if (calType == CalendarId.GREGORIAN)
+            {
+                return (new GregorianCalendar());
+            }
+            return GetCalendarInstanceRare(calType);
+        }
+
+        //This function exists as a shortcut to prevent us from loading all of the non-gregorian
+        //calendars unless they're required.
+        internal static Calendar GetCalendarInstanceRare(CalendarId calType)
+        {
+            Debug.Assert(calType != CalendarId.GREGORIAN, "calType!=CalendarId.GREGORIAN");
+
+            switch (calType)
+            {
+                case CalendarId.GREGORIAN_US:               // Gregorian (U.S.) calendar
+                case CalendarId.GREGORIAN_ME_FRENCH:        // Gregorian Middle East French calendar
+                case CalendarId.GREGORIAN_ARABIC:           // Gregorian Arabic calendar
+                case CalendarId.GREGORIAN_XLIT_ENGLISH:     // Gregorian Transliterated English calendar
+                case CalendarId.GREGORIAN_XLIT_FRENCH:      // Gregorian Transliterated French calendar
+                    return (new GregorianCalendar((GregorianCalendarTypes)calType));
+                case CalendarId.TAIWAN:                     // Taiwan Era calendar
+                    return (new TaiwanCalendar());
+                case CalendarId.JAPAN:                      // Japanese Emperor Era calendar
+                    return (new JapaneseCalendar());
+                case CalendarId.KOREA:                      // Korean Tangun Era calendar
+                    return (new KoreanCalendar());
+                case CalendarId.THAI:                       // Thai calendar
+                    return (new ThaiBuddhistCalendar());
+                case CalendarId.HIJRI:                      // Hijri (Arabic Lunar) calendar
+                    return (new HijriCalendar());
+                case CalendarId.HEBREW:                     // Hebrew (Lunar) calendar
+                    return (new HebrewCalendar());
+                case CalendarId.UMALQURA:
+                    return (new UmAlQuraCalendar());
+                case CalendarId.PERSIAN:
+                    return (new PersianCalendar());
+            }
+            return (new GregorianCalendar());
+        }
+
+        /*=================================Calendar==========================
+        **Action: Return/set the default calendar used by this culture.
+        ** This value can be overridden by regional option if this is a current culture.
+        **Returns:
+        **Arguments:
+        **Exceptions:
+        **  ArgumentNull_Obj if the set value is null.
+        ============================================================================*/
+        public virtual Calendar Calendar
+        {
+            get
+            {
+                if (calendar == null)
+                {
+                    Debug.Assert(_cultureData.CalendarIds.Length > 0, "_cultureData.CalendarIds.Length > 0");
+                    // Get the default calendar for this culture.  Note that the value can be
+                    // from registry if this is a user default culture.
+                    Calendar newObj = _cultureData.DefaultCalendar;
+
+                    System.Threading.Interlocked.MemoryBarrier();
+                    newObj.SetReadOnlyState(_isReadOnly);
+                    calendar = newObj;
+                }
+                return (calendar);
+            }
+        }
+
+        /*=================================OptionCalendars==========================
+        **Action: Return an array of the optional calendar for this culture.
+        **Returns: an array of Calendar.
+        **Arguments:
+        **Exceptions:
+        ============================================================================*/
+
+
+        public virtual Calendar[] OptionalCalendars
+        {
+            get
+            {
+                //
+                // This property always returns a new copy of the calendar array.
+                //
+                CalendarId[] calID = _cultureData.CalendarIds;
+                Calendar[] cals = new Calendar[calID.Length];
+                for (int i = 0; i < cals.Length; i++)
+                {
+                    cals[i] = GetCalendarInstance(calID[i]);
+                }
+                return (cals);
+            }
+        }
+
+        public bool UseUserOverride
+        {
+            get
+            {
+                return _cultureData.UseUserOverride;
+            }
+        }
+
+        public CultureInfo GetConsoleFallbackUICulture()
+        {
+            CultureInfo temp = _consoleFallbackCulture;
+            if (temp == null)
+            {
+                temp = CreateSpecificCulture(_cultureData.SCONSOLEFALLBACKNAME);
+                temp._isReadOnly = true;
+                _consoleFallbackCulture = temp;
+            }
+            return (temp);
+        }
+
+        public virtual Object Clone()
+        {
+            CultureInfo ci = (CultureInfo)MemberwiseClone();
+            ci._isReadOnly = false;
+
+            //If this is exactly our type, we can make certain optimizations so that we don't allocate NumberFormatInfo or DTFI unless
+            //they've already been allocated.  If this is a derived type, we'll take a more generic codepath.
+            if (!_isInherited)
+            {
+                if (this.dateTimeInfo != null)
+                {
+                    ci.dateTimeInfo = (DateTimeFormatInfo)this.dateTimeInfo.Clone();
+                }
+                if (this.numInfo != null)
+                {
+                    ci.numInfo = (NumberFormatInfo)this.numInfo.Clone();
+                }
+            }
+            else
+            {
+                ci.DateTimeFormat = (DateTimeFormatInfo)this.DateTimeFormat.Clone();
+                ci.NumberFormat = (NumberFormatInfo)this.NumberFormat.Clone();
+            }
+
+            if (textInfo != null)
+            {
+                ci.textInfo = (TextInfo)textInfo.Clone();
+            }
+
+            if (calendar != null)
+            {
+                ci.calendar = (Calendar)calendar.Clone();
+            }
+
+            return (ci);
+        }
+
+        public static CultureInfo ReadOnly(CultureInfo ci)
+        {
+            if (ci == null)
+            {
+                throw new ArgumentNullException(nameof(ci));
+            }
+
+            if (ci.IsReadOnly)
+            {
+                return (ci);
+            }
+            CultureInfo newInfo = (CultureInfo)(ci.MemberwiseClone());
+
+            if (!ci.IsNeutralCulture)
+            {
+                //If this is exactly our type, we can make certain optimizations so that we don't allocate NumberFormatInfo or DTFI unless
+                //they've already been allocated.  If this is a derived type, we'll take a more generic codepath.
+                if (!ci._isInherited)
+                {
+                    if (ci.dateTimeInfo != null)
+                    {
+                        newInfo.dateTimeInfo = DateTimeFormatInfo.ReadOnly(ci.dateTimeInfo);
+                    }
+                    if (ci.numInfo != null)
+                    {
+                        newInfo.numInfo = NumberFormatInfo.ReadOnly(ci.numInfo);
+                    }
+                }
+                else
+                {
+                    newInfo.DateTimeFormat = DateTimeFormatInfo.ReadOnly(ci.DateTimeFormat);
+                    newInfo.NumberFormat = NumberFormatInfo.ReadOnly(ci.NumberFormat);
+                }
+            }
+
+            if (ci.textInfo != null)
+            {
+                newInfo.textInfo = TextInfo.ReadOnly(ci.textInfo);
+            }
+
+            if (ci.calendar != null)
+            {
+                newInfo.calendar = Calendar.ReadOnly(ci.calendar);
+            }
+
+            // Don't set the read-only flag too early.
+            // We should set the read-only flag here.  Otherwise, info.DateTimeFormat will not be able to set.
+            newInfo._isReadOnly = true;
+
+            return (newInfo);
+        }
+
+
+        public bool IsReadOnly
+        {
+            get
+            {
+                return (_isReadOnly);
+            }
+        }
+
+        private void VerifyWritable()
+        {
+            if (_isReadOnly)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_ReadOnly);
+            }
+        }
+
+        // For resource lookup, we consider a culture the invariant culture by name equality. 
+        // We perform this check frequently during resource lookup, so adding a property for
+        // improved readability.
+        internal bool HasInvariantCultureName
+        {
+            get { return Name == CultureInfo.InvariantCulture.Name; }
+        }
+
+        // Helper function both both overloads of GetCachedReadOnlyCulture.  If lcid is 0, we use the name.
+        // If lcid is -1, use the altName and create one of those special SQL cultures.
+        internal static CultureInfo GetCultureInfoHelper(int lcid, string name, string altName)
+        {
+            // retval is our return value.
+            CultureInfo retval;
+
+            // Temporary hashtable for the names.
+            StringCultureInfoDictionary tempNameHT = s_NameCachedCultures;
+
+            if (name != null)
+            {
+                name = CultureData.AnsiToLower(name);
+            }
+
+            if (altName != null)
+            {
+                altName = CultureData.AnsiToLower(altName);
+            }
+
+            // We expect the same result for both hashtables, but will test individually for added safety.
+            if (tempNameHT == null)
+            {
+                tempNameHT = new StringCultureInfoDictionary();
+            }
+            else
+            {
+                // If we are called by name, check if the object exists in the hashtable.  If so, return it.
+                if (lcid == -1 || lcid == 0)
+                {
+                    bool ret;
+                    lock (_lock)
+                    {
+                        ret = tempNameHT.TryGetValue(lcid == 0 ? name : name + '\xfffd' + altName, out retval);
+                    }
+
+                    if (ret && retval != null)
+                    {
+                        return retval;
+                    }
+                }
+            }
+
+            // Next, the Lcid table.
+            StringLcidDictionary tempLcidHT = s_LcidCachedCultures;
+
+            if (tempLcidHT == null)
+            {
+                // Case insensitive is not an issue here, save the constructor call.
+                tempLcidHT = new StringLcidDictionary();
+            }
+            else
+            {
+                // If we were called by Lcid, check if the object exists in the table.  If so, return it.
+                if (lcid > 0)
+                {
+                    bool ret;
+                    lock (_lock)
+                    {
+                        ret = tempLcidHT.TryGetValue(lcid, out retval);
+                    }
+                    if (ret && retval != null)
+                    {
+                        return retval;
+                    }
+                }
+            }
+
+            // We now have two temporary hashtables and the desired object was not found.
+            // We'll construct it.  We catch any exceptions from the constructor call and return null.
+            try
+            {
+                switch (lcid)
+                {
+                    case -1:
+                        // call the private constructor
+                        retval = new CultureInfo(name, altName);
+                        break;
+
+                    case 0:
+                        retval = new CultureInfo(name, false);
+                        break;
+
+                    default:
+                        retval = new CultureInfo(lcid, false);
+                        break;
+                }
+            }
+            catch (ArgumentException)
+            {
+                return null;
+            }
+
+            // Set it to read-only
+            retval._isReadOnly = true;
+
+            if (lcid == -1)
+            {
+                lock (_lock)
+                {
+                    // This new culture will be added only to the name hash table.
+                    tempNameHT[name + '\xfffd' + altName] = retval;
+                }
+                // when lcid == -1 then TextInfo object is already get created and we need to set it as read only.
+                retval.TextInfo.SetReadOnlyState(true);
+            }
+            else if (lcid == 0)
+            {
+                // Remember our name (as constructed).  Do NOT use alternate sort name versions because
+                // we have internal state representing the sort.  (So someone would get the wrong cached version)
+                string newName = CultureData.AnsiToLower(retval._name);
+
+                // We add this new culture info object to both tables.
+                lock (_lock)
+                {
+                    tempNameHT[newName] = retval;
+                }
+            } 
+            else
+            {
+                lock (_lock)
+                {
+                    tempLcidHT[lcid] = retval;
+                }
+            }
+
+            // Copy the two hashtables to the corresponding member variables.  This will potentially overwrite
+            // new tables simultaneously created by a new thread, but maximizes thread safety.
+            if (-1 != lcid)
+            {
+                // Only when we modify the lcid hash table, is there a need to overwrite.
+                s_LcidCachedCultures = tempLcidHT;
+            }
+
+            s_NameCachedCultures = tempNameHT;
+
+            // Finally, return our new CultureInfo object.
+            return retval;
+        }
+
+        // Gets a cached copy of the specified culture from an internal hashtable (or creates it
+        // if not found).  (LCID version)... use named version
+        public static CultureInfo GetCultureInfo(int culture)
+        {
+            // Must check for -1 now since the helper function uses the value to signal
+            // the altCulture code path for SQL Server.
+            // Also check for zero as this would fail trying to add as a key to the hash.
+            if (culture <= 0) 
+            {
+                throw new ArgumentOutOfRangeException(nameof(culture), SR.ArgumentOutOfRange_NeedPosNum);
+            }
+            CultureInfo retval = GetCultureInfoHelper(culture, null, null);
+            if (null == retval)
+            {
+                throw new CultureNotFoundException(nameof(culture), culture, SR.Argument_CultureNotSupported);
+            }
+            return retval;
+        }
+
+        // Gets a cached copy of the specified culture from an internal hashtable (or creates it
+        // if not found).  (Named version)
+        public static CultureInfo GetCultureInfo(string name)
+        {
+            // Make sure we have a valid, non-zero length string as name
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
+            CultureInfo retval = GetCultureInfoHelper(0, name, null);
+            if (retval == null)
+            {
+                throw new CultureNotFoundException(
+                    nameof(name), name, SR.Argument_CultureNotSupported);
+            }
+            return retval;
+        }
+
+        // Gets a cached copy of the specified culture from an internal hashtable (or creates it
+        // if not found).
+        public static CultureInfo GetCultureInfo(string name, string altName)
+        {
+            // Make sure we have a valid, non-zero length string as name
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
+            if (altName == null)
+            {
+                throw new ArgumentNullException(nameof(altName));
+            }
+            
+
+            CultureInfo retval = GetCultureInfoHelper(-1, name, altName);
+            if (retval == null)
+            {
+                throw new CultureNotFoundException("name or altName",
+                                        SR.Format(SR.Argument_OneOfCulturesNotSupported, name, altName));
+            }
+            return retval;
+        }
+
+        // This function is deprecated, we don't like it
+        public static CultureInfo GetCultureInfoByIetfLanguageTag(string name)
+        {
+            // Disallow old zh-CHT/zh-CHS names
+            if (name == "zh-CHT" || name == "zh-CHS")
+            {
+                throw new CultureNotFoundException(nameof(name), SR.Format(SR.Argument_CultureIetfNotSupported, name));
+            }
+
+            CultureInfo ci = GetCultureInfo(name);
+
+            // Disallow alt sorts and es-es_TS
+            if (ci.LCID > 0xffff || ci.LCID == 0x040a)
+            {
+                throw new CultureNotFoundException(nameof(name), SR.Format(SR.Argument_CultureIetfNotSupported, name));
+            }
+
+            return ci;
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Globalization/GlobalizationMode.Unix.cs b/src/System.Private.CoreLib/src/System/Globalization/GlobalizationMode.Unix.cs
new file mode 100644
index 0000000000..95a54fd5e3
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Globalization/GlobalizationMode.Unix.cs
@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Globalization
+{
+    internal sealed partial class GlobalizationMode
+    {
+        private static bool GetGlobalizationInvariantMode()
+        {
+            bool invariantEnabled = GetInvariantSwitchValue();
+            if (!invariantEnabled)
+            {
+                if (Interop.Globalization.LoadICU() == 0)
+                {
+                    string message = "Couldn't find a valid ICU package installed on the system. " +
+                                    "Set the configuration flag System.Globalization.Invariant to true if you want to run with no globalization support.";
+                    Environment.FailFast(message);
+                }
+            }
+            return invariantEnabled;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Globalization/GlobalizationMode.Windows.cs b/src/System.Private.CoreLib/src/System/Globalization/GlobalizationMode.Windows.cs
new file mode 100644
index 0000000000..2738d5b4ba
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Globalization/GlobalizationMode.Windows.cs
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Globalization
+{
+    internal sealed partial class GlobalizationMode
+    {
+        private static bool GetGlobalizationInvariantMode()
+        {
+            return GetInvariantSwitchValue();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Globalization/GlobalizationMode.cs b/src/System.Private.CoreLib/src/System/Globalization/GlobalizationMode.cs
new file mode 100644
index 0000000000..a9d30eb61b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Globalization/GlobalizationMode.cs
@@ -0,0 +1,31 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Globalization
+{
+    internal sealed partial class GlobalizationMode
+    {
+        internal static bool Invariant { get; } = GetGlobalizationInvariantMode();
+
+        // GetInvariantSwitchValue calls CLRConfig first to detect if the switch is defined in the config file.
+        // if the switch is defined we just use the value of this switch. otherwise, we'll try to get the switch
+        // value from the environment variable if it is defined.
+        internal static bool GetInvariantSwitchValue()
+        {
+            bool exist;
+            bool ret = CLRConfig.GetBoolValue("System.Globalization.Invariant", out exist);
+            if (!exist)
+            {
+                // Linux doesn't support environment variable names include dots
+                string switchValue = Environment.GetEnvironmentVariable("DOTNET_SYSTEM_GLOBALIZATION_INVARIANT");
+                if (switchValue != null)
+                {
+                    ret = switchValue.Equals("true", StringComparison.OrdinalIgnoreCase) || switchValue.Equals("1");
+                }
+            }
+
+            return ret;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/IO/BinaryReader.cs b/src/System.Private.CoreLib/src/System/IO/BinaryReader.cs
new file mode 100644
index 0000000000..fc7dba4a3f
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/IO/BinaryReader.cs
@@ -0,0 +1,661 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Wraps a stream and provides convenient read functionality
+** for strings and primitive types.
+**
+**
+============================================================*/
+
+using System;
+using System.Runtime;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Globalization;
+using System.Diagnostics;
+using System.Security;
+
+namespace System.IO
+{
+    public class BinaryReader : IDisposable
+    {
+        private const int MaxCharBytesSize = 128;
+
+        private Stream _stream;
+        private byte[] _buffer;
+        private Decoder _decoder;
+        private byte[] _charBytes;
+        private char[] _singleChar;
+        private char[] _charBuffer;
+        private int _maxCharsSize;  // From MaxCharBytesSize & Encoding
+
+        // Performance optimization for Read() w/ Unicode.  Speeds us up by ~40% 
+        private bool _2BytesPerChar;
+        private bool _isMemoryStream; // "do we sit on MemoryStream?" for Read/ReadInt32 perf
+        private bool _leaveOpen;
+
+        public BinaryReader(Stream input) : this(input, Encoding.UTF8, false)
+        {
+        }
+
+        public BinaryReader(Stream input, Encoding encoding) : this(input, encoding, false)
+        {
+        }
+
+        public BinaryReader(Stream input, Encoding encoding, bool leaveOpen)
+        {
+            if (input == null)
+            {
+                throw new ArgumentNullException(nameof(input));
+            }
+            if (encoding == null)
+            {
+                throw new ArgumentNullException(nameof(encoding));
+            }
+            if (!input.CanRead)
+                throw new ArgumentException(SR.Argument_StreamNotReadable);
+            _stream = input;
+            _decoder = encoding.GetDecoder();
+            _maxCharsSize = encoding.GetMaxCharCount(MaxCharBytesSize);
+            int minBufferSize = encoding.GetMaxByteCount(1);  // max bytes per one char
+            if (minBufferSize < 16)
+                minBufferSize = 16;
+            _buffer = new byte[minBufferSize];
+            // _charBuffer and _charBytes will be left null.
+
+            // For Encodings that always use 2 bytes per char (or more), 
+            // special case them here to make Read() & Peek() faster.
+            _2BytesPerChar = encoding is UnicodeEncoding;
+            // check if BinaryReader is based on MemoryStream, and keep this for it's life
+            // we cannot use "as" operator, since derived classes are not allowed
+            _isMemoryStream = (_stream.GetType() == typeof(MemoryStream));
+            _leaveOpen = leaveOpen;
+
+            Debug.Assert(_decoder != null, "[BinaryReader.ctor]_decoder!=null");
+        }
+
+        public virtual Stream BaseStream
+        {
+            get
+            {
+                return _stream;
+            }
+        }
+
+        public virtual void Close()
+        {
+            Dispose(true);
+        }
+
+        protected virtual void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                Stream copyOfStream = _stream;
+                _stream = null;
+                if (copyOfStream != null && !_leaveOpen)
+                    copyOfStream.Close();
+            }
+            _stream = null;
+            _buffer = null;
+            _decoder = null;
+            _charBytes = null;
+            _singleChar = null;
+            _charBuffer = null;
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+        }
+
+        public virtual int PeekChar()
+        {
+            if (_stream == null) throw Error.GetFileNotOpen();
+
+            if (!_stream.CanSeek)
+                return -1;
+            long origPos = _stream.Position;
+            int ch = Read();
+            _stream.Position = origPos;
+            return ch;
+        }
+
+        public virtual int Read()
+        {
+            if (_stream == null)
+            {
+                throw Error.GetFileNotOpen();
+            }
+            return InternalReadOneChar();
+        }
+
+        public virtual bool ReadBoolean()
+        {
+            FillBuffer(1);
+            return (_buffer[0] != 0);
+        }
+
+        public virtual byte ReadByte()
+        {
+            // Inlined to avoid some method call overhead with FillBuffer.
+            if (_stream == null) throw Error.GetFileNotOpen();
+
+            int b = _stream.ReadByte();
+            if (b == -1)
+                throw Error.GetEndOfFile();
+            return (byte)b;
+        }
+
+        [CLSCompliant(false)]
+        public virtual sbyte ReadSByte()
+        {
+            FillBuffer(1);
+            return (sbyte)(_buffer[0]);
+        }
+
+        public virtual char ReadChar()
+        {
+            int value = Read();
+            if (value == -1)
+            {
+                throw Error.GetEndOfFile();
+            }
+            return (char)value;
+        }
+
+        public virtual short ReadInt16()
+        {
+            FillBuffer(2);
+            return (short)(_buffer[0] | _buffer[1] << 8);
+        }
+
+        [CLSCompliant(false)]
+        public virtual ushort ReadUInt16()
+        {
+            FillBuffer(2);
+            return (ushort)(_buffer[0] | _buffer[1] << 8);
+        }
+
+        public virtual int ReadInt32()
+        {
+            if (_isMemoryStream)
+            {
+                if (_stream == null) throw Error.GetFileNotOpen();
+                // read directly from MemoryStream buffer
+                MemoryStream mStream = _stream as MemoryStream;
+                Debug.Assert(mStream != null, "_stream as MemoryStream != null");
+
+                return mStream.InternalReadInt32();
+            }
+            else
+            {
+                FillBuffer(4);
+                return (int)(_buffer[0] | _buffer[1] << 8 | _buffer[2] << 16 | _buffer[3] << 24);
+            }
+        }
+
+        [CLSCompliant(false)]
+        public virtual uint ReadUInt32()
+        {
+            FillBuffer(4);
+            return (uint)(_buffer[0] | _buffer[1] << 8 | _buffer[2] << 16 | _buffer[3] << 24);
+        }
+
+        public virtual long ReadInt64()
+        {
+            FillBuffer(8);
+            uint lo = (uint)(_buffer[0] | _buffer[1] << 8 |
+                             _buffer[2] << 16 | _buffer[3] << 24);
+            uint hi = (uint)(_buffer[4] | _buffer[5] << 8 |
+                             _buffer[6] << 16 | _buffer[7] << 24);
+            return (long)((ulong)hi) << 32 | lo;
+        }
+
+        [CLSCompliant(false)]
+        public virtual ulong ReadUInt64()
+        {
+            FillBuffer(8);
+            uint lo = (uint)(_buffer[0] | _buffer[1] << 8 |
+                             _buffer[2] << 16 | _buffer[3] << 24);
+            uint hi = (uint)(_buffer[4] | _buffer[5] << 8 |
+                             _buffer[6] << 16 | _buffer[7] << 24);
+            return ((ulong)hi) << 32 | lo;
+        }
+
+        public virtual unsafe float ReadSingle()
+        {
+            FillBuffer(4);
+            uint tmpBuffer = (uint)(_buffer[0] | _buffer[1] << 8 | _buffer[2] << 16 | _buffer[3] << 24);
+            return *((float*)&tmpBuffer);
+        }
+
+        public virtual unsafe double ReadDouble()
+        {
+            FillBuffer(8);
+            uint lo = (uint)(_buffer[0] | _buffer[1] << 8 |
+                _buffer[2] << 16 | _buffer[3] << 24);
+            uint hi = (uint)(_buffer[4] | _buffer[5] << 8 |
+                _buffer[6] << 16 | _buffer[7] << 24);
+
+            ulong tmpBuffer = ((ulong)hi) << 32 | lo;
+            return *((double*)&tmpBuffer);
+        }
+
+        public virtual decimal ReadDecimal()
+        {
+            FillBuffer(16);
+            try
+            {
+                return Decimal.ToDecimal(_buffer);
+            }
+            catch (ArgumentException e)
+            {
+                // ReadDecimal cannot leak out ArgumentException
+                throw new IOException(SR.Arg_DecBitCtor, e);
+            }
+        }
+
+        public virtual String ReadString()
+        {
+            if (_stream == null)
+                throw Error.GetFileNotOpen();
+
+            int currPos = 0;
+            int n;
+            int stringLength;
+            int readLength;
+            int charsRead;
+
+            // Length of the string in bytes, not chars
+            stringLength = Read7BitEncodedInt();
+            if (stringLength < 0)
+            {
+                throw new IOException(SR.Format(SR.IO_InvalidStringLen_Len, stringLength));
+            }
+
+            if (stringLength == 0)
+            {
+                return String.Empty;
+            }
+
+            if (_charBytes == null)
+            {
+                _charBytes = new byte[MaxCharBytesSize];
+            }
+
+            if (_charBuffer == null)
+            {
+                _charBuffer = new char[_maxCharsSize];
+            }
+
+            StringBuilder sb = null;
+            do
+            {
+                readLength = ((stringLength - currPos) > MaxCharBytesSize) ? MaxCharBytesSize : (stringLength - currPos);
+
+                n = _stream.Read(_charBytes, 0, readLength);
+                if (n == 0)
+                {
+                    throw Error.GetEndOfFile();
+                }
+
+                charsRead = _decoder.GetChars(_charBytes, 0, n, _charBuffer, 0);
+
+                if (currPos == 0 && n == stringLength)
+                    return new String(_charBuffer, 0, charsRead);
+
+                if (sb == null)
+                    sb = StringBuilderCache.Acquire(stringLength); // Actual string length in chars may be smaller.
+                sb.Append(_charBuffer, 0, charsRead);
+                currPos += n;
+            } while (currPos < stringLength);
+
+            return StringBuilderCache.GetStringAndRelease(sb);
+        }
+
+        public virtual int Read(char[] buffer, int index, int count)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            }
+            if (index < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (buffer.Length - index < count)
+            {
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+            }
+
+            if (_stream == null)
+                throw Error.GetFileNotOpen();
+
+            // SafeCritical: index and count have already been verified to be a valid range for the buffer
+            return InternalReadChars(new Span<char>(buffer, index, count));
+        }
+
+        public virtual int Read(Span<char> buffer)
+        {
+            if (_stream == null)
+                throw Error.GetFileNotOpen();
+
+            return InternalReadChars(buffer);
+        }
+
+        private int InternalReadChars(Span<char> buffer)
+        {
+            Debug.Assert(_stream != null);
+
+            int numBytes = 0;
+            int index = 0;
+            int charsRemaining = buffer.Length;
+
+            if (_charBytes == null)
+            {
+                _charBytes = new byte[MaxCharBytesSize];
+            }
+
+            while (charsRemaining > 0)
+            {
+                int charsRead = 0;
+                // We really want to know what the minimum number of bytes per char
+                // is for our encoding.  Otherwise for UnicodeEncoding we'd have to
+                // do ~1+log(n) reads to read n characters.
+                numBytes = charsRemaining;
+
+                // special case for DecoderNLS subclasses when there is a hanging byte from the previous loop
+                DecoderNLS decoder = _decoder as DecoderNLS;
+                if (decoder != null && decoder.HasState && numBytes > 1)
+                {
+                    numBytes -= 1;
+                }
+
+                if (_2BytesPerChar)
+                    numBytes <<= 1;
+                if (numBytes > MaxCharBytesSize)
+                    numBytes = MaxCharBytesSize;
+
+                int position = 0;
+                byte[] byteBuffer = null;
+                if (_isMemoryStream)
+                {
+                    MemoryStream mStream = _stream as MemoryStream;
+                    Debug.Assert(mStream != null, "_stream as MemoryStream != null");
+
+                    position = mStream.InternalGetPosition();
+                    numBytes = mStream.InternalEmulateRead(numBytes);
+                    byteBuffer = mStream.InternalGetBuffer();
+                }
+                else
+                {
+                    numBytes = _stream.Read(_charBytes, 0, numBytes);
+                    byteBuffer = _charBytes;
+                }
+
+                if (numBytes == 0)
+                {
+                    return (buffer.Length - charsRemaining);
+                }
+
+                Debug.Assert(byteBuffer != null, "expected byteBuffer to be non-null");
+
+                checked
+                {
+                    if (position < 0 || numBytes < 0 || position > byteBuffer.Length - numBytes)
+                    {
+                        throw new ArgumentOutOfRangeException(nameof(numBytes));
+                    }
+                    if (index < 0 || charsRemaining < 0 || index > buffer.Length - charsRemaining)
+                    {
+                        throw new ArgumentOutOfRangeException(nameof(charsRemaining));
+                    }
+                    unsafe
+                    {
+                        fixed (byte* pBytes = byteBuffer)
+                        fixed (char* pChars = &MemoryMarshal.GetReference(buffer))
+                        {
+                            charsRead = _decoder.GetChars(pBytes + position, numBytes, pChars + index, charsRemaining, flush: false);
+                        }
+                    }
+                }
+
+                charsRemaining -= charsRead;
+                index += charsRead;
+            }
+
+            // this should never fail
+            Debug.Assert(charsRemaining >= 0, "We read too many characters.");
+
+            // we may have read fewer than the number of characters requested if end of stream reached 
+            // or if the encoding makes the char count too big for the buffer (e.g. fallback sequence)
+            return (buffer.Length - charsRemaining);
+        }
+
+        private int InternalReadOneChar()
+        {
+            // I know having a separate InternalReadOneChar method seems a little 
+            // redundant, but this makes a scenario like the security parser code
+            // 20% faster, in addition to the optimizations for UnicodeEncoding I
+            // put in InternalReadChars.   
+            int charsRead = 0;
+            int numBytes = 0;
+            long posSav = posSav = 0;
+
+            if (_stream.CanSeek)
+                posSav = _stream.Position;
+
+            if (_charBytes == null)
+            {
+                _charBytes = new byte[MaxCharBytesSize];
+            }
+            if (_singleChar == null)
+            {
+                _singleChar = new char[1];
+            }
+
+            while (charsRead == 0)
+            {
+                // We really want to know what the minimum number of bytes per char
+                // is for our encoding.  Otherwise for UnicodeEncoding we'd have to
+                // do ~1+log(n) reads to read n characters.
+                // Assume 1 byte can be 1 char unless _2BytesPerChar is true.
+                numBytes = _2BytesPerChar ? 2 : 1;
+
+                int r = _stream.ReadByte();
+                _charBytes[0] = (byte)r;
+                if (r == -1)
+                    numBytes = 0;
+                if (numBytes == 2)
+                {
+                    r = _stream.ReadByte();
+                    _charBytes[1] = (byte)r;
+                    if (r == -1)
+                        numBytes = 1;
+                }
+
+                if (numBytes == 0)
+                {
+                    // Console.WriteLine("Found no bytes.  We're outta here.");
+                    return -1;
+                }
+
+                Debug.Assert(numBytes == 1 || numBytes == 2, "BinaryReader::InternalReadOneChar assumes it's reading one or 2 bytes only.");
+
+                try
+                {
+                    charsRead = _decoder.GetChars(_charBytes, 0, numBytes, _singleChar, 0);
+                }
+                catch
+                {
+                    // Handle surrogate char 
+
+                    if (_stream.CanSeek)
+                        _stream.Seek((posSav - _stream.Position), SeekOrigin.Current);
+                    // else - we can't do much here
+
+                    throw;
+                }
+
+                Debug.Assert(charsRead < 2, "InternalReadOneChar - assuming we only got 0 or 1 char, not 2!");
+                //                Console.WriteLine("That became: " + charsRead + " characters.");
+            }
+            if (charsRead == 0)
+                return -1;
+            return _singleChar[0];
+        }
+
+        public virtual char[] ReadChars(int count)
+        {
+            if (count < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            if (_stream == null)
+            {
+                throw Error.GetFileNotOpen();
+            }
+
+            if (count == 0)
+            {
+                return Array.Empty<Char>();
+            }
+
+            // SafeCritical: we own the chars buffer, and therefore can guarantee that the index and count are valid
+            char[] chars = new char[count];
+            int n = InternalReadChars(new Span<char>(chars));
+            if (n != count)
+            {
+                char[] copy = new char[n];
+                Buffer.BlockCopy(chars, 0, copy, 0, 2 * n); // sizeof(char)
+                chars = copy;
+            }
+
+            return chars;
+        }
+
+        public virtual int Read(byte[] buffer, int index, int count)
+        {
+            if (buffer == null)
+                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (buffer.Length - index < count)
+                throw new ArgumentException(SR.Argument_InvalidOffLen);
+
+            if (_stream == null) throw Error.GetFileNotOpen();
+            return _stream.Read(buffer, index, count);
+        }
+
+        public virtual int Read(Span<byte> buffer)
+        {
+            if (_stream == null)
+                throw Error.GetFileNotOpen();
+
+            return _stream.Read(buffer);
+        }
+
+        public virtual byte[] ReadBytes(int count)
+        {
+            if (count < 0) throw new ArgumentOutOfRangeException(nameof(count), SR.ArgumentOutOfRange_NeedNonNegNum);
+            if (_stream == null) throw Error.GetFileNotOpen();
+
+            if (count == 0)
+            {
+                return Array.Empty<Byte>();
+            }
+
+            byte[] result = new byte[count];
+
+            int numRead = 0;
+            do
+            {
+                int n = _stream.Read(result, numRead, count);
+                if (n == 0)
+                    break;
+                numRead += n;
+                count -= n;
+            } while (count > 0);
+
+            if (numRead != result.Length)
+            {
+                // Trim array.  This should happen on EOF & possibly net streams.
+                byte[] copy = new byte[numRead];
+                Buffer.BlockCopy(result, 0, copy, 0, numRead);
+                result = copy;
+            }
+
+            return result;
+        }
+
+        protected virtual void FillBuffer(int numBytes)
+        {
+            if (_buffer != null && (numBytes < 0 || numBytes > _buffer.Length))
+            {
+                throw new ArgumentOutOfRangeException(nameof(numBytes), SR.ArgumentOutOfRange_BinaryReaderFillBuffer);
+            }
+            int bytesRead = 0;
+            int n = 0;
+
+            if (_stream == null) throw Error.GetFileNotOpen();
+
+            // Need to find a good threshold for calling ReadByte() repeatedly
+            // vs. calling Read(byte[], int, int) for both buffered & unbuffered
+            // streams.
+            if (numBytes == 1)
+            {
+                n = _stream.ReadByte();
+                if (n == -1)
+                    throw Error.GetEndOfFile();
+                _buffer[0] = (byte)n;
+                return;
+            }
+
+            do
+            {
+                n = _stream.Read(_buffer, bytesRead, numBytes - bytesRead);
+                if (n == 0)
+                {
+                    throw Error.GetEndOfFile();
+                }
+                bytesRead += n;
+            } while (bytesRead < numBytes);
+        }
+
+        internal protected int Read7BitEncodedInt()
+        {
+            // Read out an Int32 7 bits at a time.  The high bit
+            // of the byte when on means to continue reading more bytes.
+            int count = 0;
+            int shift = 0;
+            byte b;
+            do
+            {
+                // Check for a corrupted stream.  Read a max of 5 bytes.
+                // In a future version, add a DataFormatException.
+                if (shift == 5 * 7)  // 5 bytes max per Int32, shift += 7
+                    throw new FormatException(SR.Format_Bad7BitInt32);
+
+                // ReadByte handles end of stream cases for us.
+                b = ReadByte();
+                count |= (b & 0x7F) << shift;
+                shift += 7;
+            } while ((b & 0x80) != 0);
+            return count;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/IO/FileLoadException.CoreCLR.cs b/src/System.Private.CoreLib/src/System/IO/FileLoadException.CoreCLR.cs
new file mode 100644
index 0000000000..b839ddb52d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/IO/FileLoadException.CoreCLR.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Security;
+
+namespace System.IO
+{
+    public partial class FileLoadException
+    {
+        // Do not delete: this is invoked from native code.
+        private FileLoadException(string fileName, string fusionLog, int hResult)
+            : base(null)
+        {
+            HResult = hResult;
+            FileName = fileName;
+            FusionLog = fusionLog;
+            _message = FormatFileLoadExceptionMessage(FileName, HResult);
+        }
+
+        internal static string FormatFileLoadExceptionMessage(string fileName, int hResult)
+        {
+            string format = null;
+            GetFileLoadExceptionMessage(hResult, JitHelpers.GetStringHandleOnStack(ref format));
+
+            string message = null;
+            if (hResult == System.HResults.COR_E_BADEXEFORMAT)
+                message = SR.Arg_BadImageFormatException;
+            else 
+                GetMessageForHR(hResult, JitHelpers.GetStringHandleOnStack(ref message));
+
+            return string.Format(CultureInfo.CurrentCulture, format, fileName, message);
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetFileLoadExceptionMessage(int hResult, StringHandleOnStack retString);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetMessageForHR(int hresult, StringHandleOnStack retString);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/IO/FileNotFoundException.CoreCLR.cs b/src/System.Private.CoreLib/src/System/IO/FileNotFoundException.CoreCLR.cs
new file mode 100644
index 0000000000..99645f0f2d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/IO/FileNotFoundException.CoreCLR.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.IO
+{
+    public partial class FileNotFoundException
+    {
+        // Do not delete: this is invoked from native code.
+        private FileNotFoundException(string fileName, string fusionLog, int hResult)
+            : base(null)
+        {
+            HResult = hResult;
+            FileName = fileName;
+            FusionLog = fusionLog;
+            SetMessageField();
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/IO/SearchOption.cs b/src/System.Private.CoreLib/src/System/IO/SearchOption.cs
new file mode 100644
index 0000000000..c2f7e0db6e
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/IO/SearchOption.cs
@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Enum:   SearchOption
+** 
+** 
+**
+**
+** Purpose: Enum describing whether the search operation should  
+** retrieve files/directories from the current directory alone  
+** or should include all the subdirectories also.
+**
+**
+===========================================================*/
+
+using System;
+
+namespace System.IO
+{
+    internal enum SearchOption
+    {
+        // Include only the current directory in the search operation
+        TopDirectoryOnly,
+
+        // Include the current directory and all the sub-directories
+        // underneath it including reparse points in the search operation. 
+        // This will traverse reparse points (i.e, mounted points and symbolic links)
+        // recursively. If the directory structure searched contains a loop
+        // because of hard links, the search operation will go on for ever. 
+        AllDirectories,
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/IO/Stream.cs b/src/System.Private.CoreLib/src/System/IO/Stream.cs
new file mode 100644
index 0000000000..4cf8435f2b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/IO/Stream.cs
@@ -0,0 +1,1356 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Abstract base class for all Streams.  Provides
+** default implementations of asynchronous reads & writes, in
+** terms of the synchronous reads & writes (and vice versa).
+**
+**
+===========================================================*/
+
+using System;
+using System.Buffers;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Runtime;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Runtime.ExceptionServices;
+using System.Security;
+using System.Diagnostics;
+using System.Reflection;
+
+namespace System.IO
+{
+    public abstract class Stream : MarshalByRefObject, IDisposable
+    {
+        public static readonly Stream Null = new NullStream();
+
+        //We pick a value that is the largest multiple of 4096 that is still smaller than the large object heap threshold (85K).
+        // The CopyTo/CopyToAsync buffer is short-lived and is likely to be collected at Gen0, and it offers a significant
+        // improvement in Copy performance.
+        private const int _DefaultCopyBufferSize = 81920;
+
+        // To implement Async IO operations on streams that don't support async IO
+
+        private ReadWriteTask _activeReadWriteTask;
+        private SemaphoreSlim _asyncActiveSemaphore;
+
+        internal SemaphoreSlim EnsureAsyncActiveSemaphoreInitialized()
+        {
+            // Lazily-initialize _asyncActiveSemaphore.  As we're never accessing the SemaphoreSlim's
+            // WaitHandle, we don't need to worry about Disposing it.
+            return LazyInitializer.EnsureInitialized(ref _asyncActiveSemaphore, () => new SemaphoreSlim(1, 1));
+        }
+
+        public abstract bool CanRead
+        {
+            get;
+        }
+
+        // If CanSeek is false, Position, Seek, Length, and SetLength should throw.
+        public abstract bool CanSeek
+        {
+            get;
+        }
+
+        public virtual bool CanTimeout
+        {
+            get
+            {
+                return false;
+            }
+        }
+
+        public abstract bool CanWrite
+        {
+            get;
+        }
+
+        public abstract long Length
+        {
+            get;
+        }
+
+        public abstract long Position
+        {
+            get;
+            set;
+        }
+
+        public virtual int ReadTimeout
+        {
+            get
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_TimeoutsNotSupported);
+            }
+            set
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_TimeoutsNotSupported);
+            }
+        }
+
+        public virtual int WriteTimeout
+        {
+            get
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_TimeoutsNotSupported);
+            }
+            set
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_TimeoutsNotSupported);
+            }
+        }
+
+        public Task CopyToAsync(Stream destination)
+        {
+            int bufferSize = GetCopyBufferSize();
+
+            return CopyToAsync(destination, bufferSize);
+        }
+
+        public Task CopyToAsync(Stream destination, Int32 bufferSize)
+        {
+            return CopyToAsync(destination, bufferSize, CancellationToken.None);
+        }
+
+        public Task CopyToAsync(Stream destination, CancellationToken cancellationToken)
+        {
+            int bufferSize = GetCopyBufferSize();
+
+            return CopyToAsync(destination, bufferSize, cancellationToken);
+        }
+
+        public virtual Task CopyToAsync(Stream destination, Int32 bufferSize, CancellationToken cancellationToken)
+        {
+            StreamHelpers.ValidateCopyToArgs(this, destination, bufferSize);
+
+            return CopyToAsyncInternal(destination, bufferSize, cancellationToken);
+        }
+
+        private async Task CopyToAsyncInternal(Stream destination, Int32 bufferSize, CancellationToken cancellationToken)
+        {
+            byte[] buffer = ArrayPool<byte>.Shared.Rent(bufferSize);
+            try
+            {
+                while (true)
+                {
+                    int bytesRead = await ReadAsync(new Memory<byte>(buffer), cancellationToken).ConfigureAwait(false);
+                    if (bytesRead == 0) break;
+                    await destination.WriteAsync(new ReadOnlyMemory<byte>(buffer, 0, bytesRead), cancellationToken).ConfigureAwait(false);
+                }
+            }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(buffer);
+            }
+        }
+
+        // Reads the bytes from the current stream and writes the bytes to
+        // the destination stream until all bytes are read, starting at
+        // the current position.
+        public void CopyTo(Stream destination)
+        {
+            int bufferSize = GetCopyBufferSize();
+
+            CopyTo(destination, bufferSize);
+        }
+
+        public virtual void CopyTo(Stream destination, int bufferSize)
+        {
+            StreamHelpers.ValidateCopyToArgs(this, destination, bufferSize);
+
+            byte[] buffer = ArrayPool<byte>.Shared.Rent(bufferSize);
+            try
+            {
+                int read;
+                while ((read = Read(buffer, 0, buffer.Length)) != 0)
+                {
+                    destination.Write(buffer, 0, read);
+                }
+            }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(buffer);
+            }
+        }
+
+        private int GetCopyBufferSize()
+        {
+            int bufferSize = _DefaultCopyBufferSize;
+
+            if (CanSeek)
+            {
+                long length = Length;
+                long position = Position;
+                if (length <= position) // Handles negative overflows
+                {
+                    // There are no bytes left in the stream to copy.
+                    // However, because CopyTo{Async} is virtual, we need to
+                    // ensure that any override is still invoked to provide its
+                    // own validation, so we use the smallest legal buffer size here.
+                    bufferSize = 1;
+                }
+                else
+                {
+                    long remaining = length - position;
+                    if (remaining > 0)
+                    {
+                        // In the case of a positive overflow, stick to the default size
+                        bufferSize = (int)Math.Min(bufferSize, remaining);
+                    }
+                }
+            }
+
+            return bufferSize;
+        }
+
+        // Stream used to require that all cleanup logic went into Close(),
+        // which was thought up before we invented IDisposable.  However, we
+        // need to follow the IDisposable pattern so that users can write 
+        // sensible subclasses without needing to inspect all their base 
+        // classes, and without worrying about version brittleness, from a
+        // base class switching to the Dispose pattern.  We're moving
+        // Stream to the Dispose(bool) pattern - that's where all subclasses 
+        // should put their cleanup starting in V2.
+        public virtual void Close()
+        {
+            // Ideally we would assert CanRead == CanWrite == CanSeek = false, 
+            // but we'd have to fix PipeStream & NetworkStream very carefully.
+
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        public void Dispose()
+        {
+            // Ideally we would assert CanRead == CanWrite == CanSeek = false, 
+            // but we'd have to fix PipeStream & NetworkStream very carefully.
+
+            Close();
+        }
+
+
+        protected virtual void Dispose(bool disposing)
+        {
+            // Note: Never change this to call other virtual methods on Stream
+            // like Write, since the state on subclasses has already been 
+            // torn down.  This is the last code to run on cleanup for a stream.
+        }
+
+        public abstract void Flush();
+
+        public Task FlushAsync()
+        {
+            return FlushAsync(CancellationToken.None);
+        }
+
+        public virtual Task FlushAsync(CancellationToken cancellationToken)
+        {
+            return Task.Factory.StartNew(state => ((Stream)state).Flush(), this,
+                cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+        }
+
+        [Obsolete("CreateWaitHandle will be removed eventually.  Please use \"new ManualResetEvent(false)\" instead.")]
+        protected virtual WaitHandle CreateWaitHandle()
+        {
+            return new ManualResetEvent(false);
+        }
+
+        public virtual IAsyncResult BeginRead(byte[] buffer, int offset, int count, AsyncCallback callback, Object state)
+        {
+            return BeginReadInternal(buffer, offset, count, callback, state, serializeAsynchronously: false, apm: true);
+        }
+
+        internal IAsyncResult BeginReadInternal(
+            byte[] buffer, int offset, int count, AsyncCallback callback, Object state,
+            bool serializeAsynchronously, bool apm)
+        {
+            if (!CanRead) throw Error.GetReadNotSupported();
+
+            // To avoid a race with a stream's position pointer & generating race conditions 
+            // with internal buffer indexes in our own streams that 
+            // don't natively support async IO operations when there are multiple 
+            // async requests outstanding, we will block the application's main
+            // thread if it does a second IO request until the first one completes.
+            var semaphore = EnsureAsyncActiveSemaphoreInitialized();
+            Task semaphoreTask = null;
+            if (serializeAsynchronously)
+            {
+                semaphoreTask = semaphore.WaitAsync();
+            }
+            else
+            {
+                semaphore.Wait();
+            }
+
+            // Create the task to asynchronously do a Read.  This task serves both
+            // as the asynchronous work item and as the IAsyncResult returned to the user.
+            var asyncResult = new ReadWriteTask(true /*isRead*/, apm, delegate
+            {
+                // The ReadWriteTask stores all of the parameters to pass to Read.
+                // As we're currently inside of it, we can get the current task
+                // and grab the parameters from it.
+                var thisTask = Task.InternalCurrent as ReadWriteTask;
+                Debug.Assert(thisTask != null, "Inside ReadWriteTask, InternalCurrent should be the ReadWriteTask");
+
+                try
+                {
+                    // Do the Read and return the number of bytes read
+                    return thisTask._stream.Read(thisTask._buffer, thisTask._offset, thisTask._count);
+                }
+                finally
+                {
+                    // If this implementation is part of Begin/EndXx, then the EndXx method will handle
+                    // finishing the async operation.  However, if this is part of XxAsync, then there won't
+                    // be an end method, and this task is responsible for cleaning up.
+                    if (!thisTask._apm)
+                    {
+                        thisTask._stream.FinishTrackingAsyncOperation();
+                    }
+
+                    thisTask.ClearBeginState(); // just to help alleviate some memory pressure
+                }
+            }, state, this, buffer, offset, count, callback);
+
+            // Schedule it
+            if (semaphoreTask != null)
+                RunReadWriteTaskWhenReady(semaphoreTask, asyncResult);
+            else
+                RunReadWriteTask(asyncResult);
+
+
+            return asyncResult; // return it
+        }
+
+        public virtual int EndRead(IAsyncResult asyncResult)
+        {
+            if (asyncResult == null)
+                throw new ArgumentNullException(nameof(asyncResult));
+
+            var readTask = _activeReadWriteTask;
+
+            if (readTask == null)
+            {
+                throw new ArgumentException(SR.InvalidOperation_WrongAsyncResultOrEndReadCalledMultiple);
+            }
+            else if (readTask != asyncResult)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_WrongAsyncResultOrEndReadCalledMultiple);
+            }
+            else if (!readTask._isRead)
+            {
+                throw new ArgumentException(SR.InvalidOperation_WrongAsyncResultOrEndReadCalledMultiple);
+            }
+
+            try
+            {
+                return readTask.GetAwaiter().GetResult(); // block until completion, then get result / propagate any exception
+            }
+            finally
+            {
+                FinishTrackingAsyncOperation();
+            }
+        }
+
+        public Task<int> ReadAsync(Byte[] buffer, int offset, int count)
+        {
+            return ReadAsync(buffer, offset, count, CancellationToken.None);
+        }
+
+        public virtual Task<int> ReadAsync(Byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            // If cancellation was requested, bail early with an already completed task.
+            // Otherwise, return a task that represents the Begin/End methods.
+            return cancellationToken.IsCancellationRequested
+                        ? Task.FromCanceled<int>(cancellationToken)
+                        : BeginEndReadAsync(buffer, offset, count);
+        }
+
+        public virtual ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            if (MemoryMarshal.TryGetArray(buffer, out ArraySegment<byte> array))
+            {
+                return new ValueTask<int>(ReadAsync(array.Array, array.Offset, array.Count, cancellationToken));
+            }
+            else
+            {
+                byte[] sharedBuffer = ArrayPool<byte>.Shared.Rent(buffer.Length);
+                return FinishReadAsync(ReadAsync(sharedBuffer, 0, buffer.Length, cancellationToken), sharedBuffer, buffer);
+
+                async ValueTask<int> FinishReadAsync(Task<int> readTask, byte[] localBuffer, Memory<byte> localDestination)
+                {
+                    try
+                    {
+                        int result = await readTask.ConfigureAwait(false);
+                        new Span<byte>(localBuffer, 0, result).CopyTo(localDestination.Span);
+                        return result;
+                    }
+                    finally
+                    {
+                        ArrayPool<byte>.Shared.Return(localBuffer);
+                    }
+                }
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern bool HasOverriddenBeginEndRead();
+
+        private Task<Int32> BeginEndReadAsync(Byte[] buffer, Int32 offset, Int32 count)
+        {
+            if (!HasOverriddenBeginEndRead())
+            {
+                // If the Stream does not override Begin/EndRead, then we can take an optimized path
+                // that skips an extra layer of tasks / IAsyncResults.
+                return (Task<Int32>)BeginReadInternal(buffer, offset, count, null, null, serializeAsynchronously: true, apm: false);
+            }
+
+            // Otherwise, we need to wrap calls to Begin/EndWrite to ensure we use the derived type's functionality.
+            return TaskFactory<Int32>.FromAsyncTrim(
+                        this, new ReadWriteParameters { Buffer = buffer, Offset = offset, Count = count },
+                        (stream, args, callback, state) => stream.BeginRead(args.Buffer, args.Offset, args.Count, callback, state), // cached by compiler
+                        (stream, asyncResult) => stream.EndRead(asyncResult)); // cached by compiler
+        }
+
+        private struct ReadWriteParameters // struct for arguments to Read and Write calls
+        {
+            internal byte[] Buffer;
+            internal int Offset;
+            internal int Count;
+        }
+
+
+
+        public virtual IAsyncResult BeginWrite(byte[] buffer, int offset, int count, AsyncCallback callback, Object state)
+        {
+            return BeginWriteInternal(buffer, offset, count, callback, state, serializeAsynchronously: false, apm: true);
+        }
+
+        internal IAsyncResult BeginWriteInternal(
+            byte[] buffer, int offset, int count, AsyncCallback callback, Object state,
+            bool serializeAsynchronously, bool apm)
+        {
+            if (!CanWrite) throw Error.GetWriteNotSupported();
+
+            // To avoid a race condition with a stream's position pointer & generating conditions 
+            // with internal buffer indexes in our own streams that 
+            // don't natively support async IO operations when there are multiple 
+            // async requests outstanding, we will block the application's main
+            // thread if it does a second IO request until the first one completes.
+            var semaphore = EnsureAsyncActiveSemaphoreInitialized();
+            Task semaphoreTask = null;
+            if (serializeAsynchronously)
+            {
+                semaphoreTask = semaphore.WaitAsync(); // kick off the asynchronous wait, but don't block
+            }
+            else
+            {
+                semaphore.Wait(); // synchronously wait here
+            }
+
+            // Create the task to asynchronously do a Write.  This task serves both
+            // as the asynchronous work item and as the IAsyncResult returned to the user.
+            var asyncResult = new ReadWriteTask(false /*isRead*/, apm, delegate
+            {
+                // The ReadWriteTask stores all of the parameters to pass to Write.
+                // As we're currently inside of it, we can get the current task
+                // and grab the parameters from it.
+                var thisTask = Task.InternalCurrent as ReadWriteTask;
+                Debug.Assert(thisTask != null, "Inside ReadWriteTask, InternalCurrent should be the ReadWriteTask");
+
+                try
+                {
+                    // Do the Write
+                    thisTask._stream.Write(thisTask._buffer, thisTask._offset, thisTask._count);
+                    return 0; // not used, but signature requires a value be returned
+                }
+                finally
+                {
+                    // If this implementation is part of Begin/EndXx, then the EndXx method will handle
+                    // finishing the async operation.  However, if this is part of XxAsync, then there won't
+                    // be an end method, and this task is responsible for cleaning up.
+                    if (!thisTask._apm)
+                    {
+                        thisTask._stream.FinishTrackingAsyncOperation();
+                    }
+
+                    thisTask.ClearBeginState(); // just to help alleviate some memory pressure
+                }
+            }, state, this, buffer, offset, count, callback);
+
+            // Schedule it
+            if (semaphoreTask != null)
+                RunReadWriteTaskWhenReady(semaphoreTask, asyncResult);
+            else
+                RunReadWriteTask(asyncResult);
+
+            return asyncResult; // return it
+        }
+
+        private void RunReadWriteTaskWhenReady(Task asyncWaiter, ReadWriteTask readWriteTask)
+        {
+            Debug.Assert(readWriteTask != null);
+            Debug.Assert(asyncWaiter != null);
+
+            // If the wait has already completed, run the task.
+            if (asyncWaiter.IsCompleted)
+            {
+                Debug.Assert(asyncWaiter.IsCompletedSuccessfully, "The semaphore wait should always complete successfully.");
+                RunReadWriteTask(readWriteTask);
+            }
+            else  // Otherwise, wait for our turn, and then run the task.
+            {
+                asyncWaiter.ContinueWith((t, state) =>
+                {
+                    Debug.Assert(t.IsCompletedSuccessfully, "The semaphore wait should always complete successfully.");
+                    var rwt = (ReadWriteTask)state;
+                    rwt._stream.RunReadWriteTask(rwt); // RunReadWriteTask(readWriteTask);
+                }, readWriteTask, default(CancellationToken), TaskContinuationOptions.ExecuteSynchronously, TaskScheduler.Default);
+            }
+        }
+
+        private void RunReadWriteTask(ReadWriteTask readWriteTask)
+        {
+            Debug.Assert(readWriteTask != null);
+            Debug.Assert(_activeReadWriteTask == null, "Expected no other readers or writers");
+
+            // Schedule the task.  ScheduleAndStart must happen after the write to _activeReadWriteTask to avoid a race.
+            // Internally, we're able to directly call ScheduleAndStart rather than Start, avoiding
+            // two interlocked operations.  However, if ReadWriteTask is ever changed to use
+            // a cancellation token, this should be changed to use Start.
+            _activeReadWriteTask = readWriteTask; // store the task so that EndXx can validate it's given the right one
+            readWriteTask.m_taskScheduler = TaskScheduler.Default;
+            readWriteTask.ScheduleAndStart(needsProtection: false);
+        }
+
+        private void FinishTrackingAsyncOperation()
+        {
+            _activeReadWriteTask = null;
+            Debug.Assert(_asyncActiveSemaphore != null, "Must have been initialized in order to get here.");
+            _asyncActiveSemaphore.Release();
+        }
+
+        public virtual void EndWrite(IAsyncResult asyncResult)
+        {
+            if (asyncResult == null)
+                throw new ArgumentNullException(nameof(asyncResult));
+
+            var writeTask = _activeReadWriteTask;
+            if (writeTask == null)
+            {
+                throw new ArgumentException(SR.InvalidOperation_WrongAsyncResultOrEndWriteCalledMultiple);
+            }
+            else if (writeTask != asyncResult)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_WrongAsyncResultOrEndWriteCalledMultiple);
+            }
+            else if (writeTask._isRead)
+            {
+                throw new ArgumentException(SR.InvalidOperation_WrongAsyncResultOrEndWriteCalledMultiple);
+            }
+
+            try
+            {
+                writeTask.GetAwaiter().GetResult(); // block until completion, then propagate any exceptions
+                Debug.Assert(writeTask.Status == TaskStatus.RanToCompletion);
+            }
+            finally
+            {
+                FinishTrackingAsyncOperation();
+            }
+        }
+
+        // Task used by BeginRead / BeginWrite to do Read / Write asynchronously.
+        // A single instance of this task serves four purposes:
+        // 1. The work item scheduled to run the Read / Write operation
+        // 2. The state holding the arguments to be passed to Read / Write
+        // 3. The IAsyncResult returned from BeginRead / BeginWrite
+        // 4. The completion action that runs to invoke the user-provided callback.
+        // This last item is a bit tricky.  Before the AsyncCallback is invoked, the
+        // IAsyncResult must have completed, so we can't just invoke the handler
+        // from within the task, since it is the IAsyncResult, and thus it's not
+        // yet completed.  Instead, we use AddCompletionAction to install this
+        // task as its own completion handler.  That saves the need to allocate
+        // a separate completion handler, it guarantees that the task will
+        // have completed by the time the handler is invoked, and it allows
+        // the handler to be invoked synchronously upon the completion of the
+        // task.  This all enables BeginRead / BeginWrite to be implemented
+        // with a single allocation.
+        private sealed class ReadWriteTask : Task<int>, ITaskCompletionAction
+        {
+            internal readonly bool _isRead;
+            internal readonly bool _apm; // true if this is from Begin/EndXx; false if it's from XxAsync
+            internal Stream _stream;
+            internal byte[] _buffer;
+            internal readonly int _offset;
+            internal readonly int _count;
+            private AsyncCallback _callback;
+            private ExecutionContext _context;
+
+            internal void ClearBeginState() // Used to allow the args to Read/Write to be made available for GC
+            {
+                _stream = null;
+                _buffer = null;
+            }
+
+            public ReadWriteTask(
+                bool isRead,
+                bool apm,
+                Func<object, int> function, object state,
+                Stream stream, byte[] buffer, int offset, int count, AsyncCallback callback) :
+                base(function, state, CancellationToken.None, TaskCreationOptions.DenyChildAttach)
+            {
+                Debug.Assert(function != null);
+                Debug.Assert(stream != null);
+                Debug.Assert(buffer != null);
+
+                // Store the arguments
+                _isRead = isRead;
+                _apm = apm;
+                _stream = stream;
+                _buffer = buffer;
+                _offset = offset;
+                _count = count;
+
+                // If a callback was provided, we need to:
+                // - Store the user-provided handler
+                // - Capture an ExecutionContext under which to invoke the handler
+                // - Add this task as its own completion handler so that the Invoke method
+                //   will run the callback when this task completes.
+                if (callback != null)
+                {
+                    _callback = callback;
+                    _context = ExecutionContext.Capture();
+                    base.AddCompletionAction(this);
+                }
+            }
+
+            private static void InvokeAsyncCallback(object completedTask)
+            {
+                var rwc = (ReadWriteTask)completedTask;
+                var callback = rwc._callback;
+                rwc._callback = null;
+                callback(rwc);
+            }
+
+            private static ContextCallback s_invokeAsyncCallback;
+
+            void ITaskCompletionAction.Invoke(Task completingTask)
+            {
+                // Get the ExecutionContext.  If there is none, just run the callback
+                // directly, passing in the completed task as the IAsyncResult.
+                // If there is one, process it with ExecutionContext.Run.
+                var context = _context;
+                if (context == null)
+                {
+                    var callback = _callback;
+                    _callback = null;
+                    callback(completingTask);
+                }
+                else
+                {
+                    _context = null;
+
+                    var invokeAsyncCallback = s_invokeAsyncCallback;
+                    if (invokeAsyncCallback == null) s_invokeAsyncCallback = invokeAsyncCallback = InvokeAsyncCallback; // benign race condition
+
+                    ExecutionContext.RunInternal(context, invokeAsyncCallback, this);
+                }
+            }
+
+            bool ITaskCompletionAction.InvokeMayRunArbitraryCode { get { return true; } }
+        }
+
+        public Task WriteAsync(Byte[] buffer, int offset, int count)
+        {
+            return WriteAsync(buffer, offset, count, CancellationToken.None);
+        }
+
+        public virtual Task WriteAsync(Byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        {
+            // If cancellation was requested, bail early with an already completed task.
+            // Otherwise, return a task that represents the Begin/End methods.
+            return cancellationToken.IsCancellationRequested
+                        ? Task.FromCanceled(cancellationToken)
+                        : BeginEndWriteAsync(buffer, offset, count);
+        }
+
+        public virtual ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            if (MemoryMarshal.TryGetArray(buffer, out ArraySegment<byte> array))
+            {
+                return new ValueTask(WriteAsync(array.Array, array.Offset, array.Count, cancellationToken));
+            }
+            else
+            {
+                byte[] sharedBuffer = ArrayPool<byte>.Shared.Rent(buffer.Length);
+                buffer.Span.CopyTo(sharedBuffer);
+                return new ValueTask(FinishWriteAsync(WriteAsync(sharedBuffer, 0, buffer.Length, cancellationToken), sharedBuffer));
+            }
+        }
+
+        private async Task FinishWriteAsync(Task writeTask, byte[] localBuffer)
+        {
+            try
+            {
+                await writeTask.ConfigureAwait(false);
+            }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(localBuffer);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern bool HasOverriddenBeginEndWrite();
+
+        private Task BeginEndWriteAsync(Byte[] buffer, Int32 offset, Int32 count)
+        {
+            if (!HasOverriddenBeginEndWrite())
+            {
+                // If the Stream does not override Begin/EndWrite, then we can take an optimized path
+                // that skips an extra layer of tasks / IAsyncResults.
+                return (Task)BeginWriteInternal(buffer, offset, count, null, null, serializeAsynchronously: true, apm: false);
+            }
+
+            // Otherwise, we need to wrap calls to Begin/EndWrite to ensure we use the derived type's functionality.
+            return TaskFactory<VoidTaskResult>.FromAsyncTrim(
+                        this, new ReadWriteParameters { Buffer = buffer, Offset = offset, Count = count },
+                        (stream, args, callback, state) => stream.BeginWrite(args.Buffer, args.Offset, args.Count, callback, state), // cached by compiler
+                        (stream, asyncResult) => // cached by compiler
+                        {
+                            stream.EndWrite(asyncResult);
+                            return default(VoidTaskResult);
+                        });
+        }
+
+        public abstract long Seek(long offset, SeekOrigin origin);
+
+        public abstract void SetLength(long value);
+
+        public abstract int Read(byte[] buffer, int offset, int count);
+
+        public virtual int Read(Span<byte> buffer)
+        {
+            byte[] sharedBuffer = ArrayPool<byte>.Shared.Rent(buffer.Length);
+            try
+            {
+                int numRead = Read(sharedBuffer, 0, buffer.Length);
+                if ((uint)numRead > buffer.Length)
+                {
+                    throw new IOException(SR.IO_StreamTooLong);
+                }
+                new Span<byte>(sharedBuffer, 0, numRead).CopyTo(buffer);
+                return numRead;
+            }
+            finally { ArrayPool<byte>.Shared.Return(sharedBuffer); }
+        }
+
+        // Reads one byte from the stream by calling Read(byte[], int, int). 
+        // Will return an unsigned byte cast to an int or -1 on end of stream.
+        // This implementation does not perform well because it allocates a new
+        // byte[] each time you call it, and should be overridden by any 
+        // subclass that maintains an internal buffer.  Then, it can help perf
+        // significantly for people who are reading one byte at a time.
+        public virtual int ReadByte()
+        {
+            byte[] oneByteArray = new byte[1];
+            int r = Read(oneByteArray, 0, 1);
+            if (r == 0)
+                return -1;
+            return oneByteArray[0];
+        }
+
+        public abstract void Write(byte[] buffer, int offset, int count);
+
+        public virtual void Write(ReadOnlySpan<byte> buffer)
+        {
+            byte[] sharedBuffer = ArrayPool<byte>.Shared.Rent(buffer.Length);
+            try
+            {
+                buffer.CopyTo(sharedBuffer);
+                Write(sharedBuffer, 0, buffer.Length);
+            }
+            finally { ArrayPool<byte>.Shared.Return(sharedBuffer); }
+        }
+
+        // Writes one byte from the stream by calling Write(byte[], int, int).
+        // This implementation does not perform well because it allocates a new
+        // byte[] each time you call it, and should be overridden by any 
+        // subclass that maintains an internal buffer.  Then, it can help perf
+        // significantly for people who are writing one byte at a time.
+        public virtual void WriteByte(byte value)
+        {
+            byte[] oneByteArray = new byte[1];
+            oneByteArray[0] = value;
+            Write(oneByteArray, 0, 1);
+        }
+
+        public static Stream Synchronized(Stream stream)
+        {
+            if (stream == null)
+                throw new ArgumentNullException(nameof(stream));
+            if (stream is SyncStream)
+                return stream;
+
+            return new SyncStream(stream);
+        }
+
+        [Obsolete("Do not call or override this method.")]
+        protected virtual void ObjectInvariant()
+        {
+        }
+
+        internal IAsyncResult BlockingBeginRead(byte[] buffer, int offset, int count, AsyncCallback callback, Object state)
+        {
+            // To avoid a race with a stream's position pointer & generating conditions
+            // with internal buffer indexes in our own streams that 
+            // don't natively support async IO operations when there are multiple 
+            // async requests outstanding, we will block the application's main
+            // thread and do the IO synchronously.  
+            // This can't perform well - use a different approach.
+            SynchronousAsyncResult asyncResult;
+            try
+            {
+                int numRead = Read(buffer, offset, count);
+                asyncResult = new SynchronousAsyncResult(numRead, state);
+            }
+            catch (IOException ex)
+            {
+                asyncResult = new SynchronousAsyncResult(ex, state, isWrite: false);
+            }
+
+            if (callback != null)
+            {
+                callback(asyncResult);
+            }
+
+            return asyncResult;
+        }
+
+        internal static int BlockingEndRead(IAsyncResult asyncResult)
+        {
+            return SynchronousAsyncResult.EndRead(asyncResult);
+        }
+
+        internal IAsyncResult BlockingBeginWrite(byte[] buffer, int offset, int count, AsyncCallback callback, Object state)
+        {
+            // To avoid a race condition with a stream's position pointer & generating conditions 
+            // with internal buffer indexes in our own streams that 
+            // don't natively support async IO operations when there are multiple 
+            // async requests outstanding, we will block the application's main
+            // thread and do the IO synchronously.  
+            // This can't perform well - use a different approach.
+            SynchronousAsyncResult asyncResult;
+            try
+            {
+                Write(buffer, offset, count);
+                asyncResult = new SynchronousAsyncResult(state);
+            }
+            catch (IOException ex)
+            {
+                asyncResult = new SynchronousAsyncResult(ex, state, isWrite: true);
+            }
+
+            if (callback != null)
+            {
+                callback(asyncResult);
+            }
+
+            return asyncResult;
+        }
+
+        internal static void BlockingEndWrite(IAsyncResult asyncResult)
+        {
+            SynchronousAsyncResult.EndWrite(asyncResult);
+        }
+
+        private sealed class NullStream : Stream
+        {
+            internal NullStream() { }
+
+            public override bool CanRead
+            {
+                get { return true; }
+            }
+
+            public override bool CanWrite
+            {
+                get { return true; }
+            }
+
+            public override bool CanSeek
+            {
+                get { return true; }
+            }
+
+            public override long Length
+            {
+                get { return 0; }
+            }
+
+            public override long Position
+            {
+                get { return 0; }
+                set { }
+            }
+
+            public override void CopyTo(Stream destination, int bufferSize)
+            {
+                StreamHelpers.ValidateCopyToArgs(this, destination, bufferSize);
+
+                // After we validate arguments this is a nop.
+            }
+
+            public override Task CopyToAsync(Stream destination, int bufferSize, CancellationToken cancellationToken)
+            {
+                // Validate arguments here for compat, since previously this method
+                // was inherited from Stream (which did check its arguments).
+                StreamHelpers.ValidateCopyToArgs(this, destination, bufferSize);
+
+                return cancellationToken.IsCancellationRequested ?
+                    Task.FromCanceled(cancellationToken) :
+                    Task.CompletedTask;
+            }
+
+            protected override void Dispose(bool disposing)
+            {
+                // Do nothing - we don't want NullStream singleton (static) to be closable
+            }
+
+            public override void Flush()
+            {
+            }
+
+            public override Task FlushAsync(CancellationToken cancellationToken)
+            {
+                return cancellationToken.IsCancellationRequested ?
+                    Task.FromCanceled(cancellationToken) :
+                    Task.CompletedTask;
+            }
+
+            public override IAsyncResult BeginRead(byte[] buffer, int offset, int count, AsyncCallback callback, Object state)
+            {
+                if (!CanRead) throw Error.GetReadNotSupported();
+
+                return BlockingBeginRead(buffer, offset, count, callback, state);
+            }
+
+            public override int EndRead(IAsyncResult asyncResult)
+            {
+                if (asyncResult == null)
+                    throw new ArgumentNullException(nameof(asyncResult));
+
+                return BlockingEndRead(asyncResult);
+            }
+
+            public override IAsyncResult BeginWrite(byte[] buffer, int offset, int count, AsyncCallback callback, Object state)
+            {
+                if (!CanWrite) throw Error.GetWriteNotSupported();
+
+                return BlockingBeginWrite(buffer, offset, count, callback, state);
+            }
+
+            public override void EndWrite(IAsyncResult asyncResult)
+            {
+                if (asyncResult == null)
+                    throw new ArgumentNullException(nameof(asyncResult));
+
+                BlockingEndWrite(asyncResult);
+            }
+
+            public override int Read(byte[] buffer, int offset, int count)
+            {
+                return 0;
+            }
+
+            public override int Read(Span<byte> buffer)
+            {
+                return 0;
+            }
+
+            public override Task<int> ReadAsync(Byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+            {
+                return AsyncTaskMethodBuilder<int>.s_defaultResultTask;
+            }
+
+            public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken))
+            {
+                return new ValueTask<int>(0);
+            }
+
+            public override int ReadByte()
+            {
+                return -1;
+            }
+
+            public override void Write(byte[] buffer, int offset, int count)
+            {
+            }
+
+            public override void Write(ReadOnlySpan<byte> buffer)
+            {
+            }
+
+            public override Task WriteAsync(Byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+            {
+                return cancellationToken.IsCancellationRequested ?
+                    Task.FromCanceled(cancellationToken) :
+                    Task.CompletedTask;
+            }
+
+            public override ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken cancellationToken = default(CancellationToken))
+            {
+                return cancellationToken.IsCancellationRequested ?
+                    new ValueTask(Task.FromCanceled(cancellationToken)) :
+                    default;
+            }
+
+            public override void WriteByte(byte value)
+            {
+            }
+
+            public override long Seek(long offset, SeekOrigin origin)
+            {
+                return 0;
+            }
+
+            public override void SetLength(long length)
+            {
+            }
+        }
+
+
+        /// <summary>Used as the IAsyncResult object when using asynchronous IO methods on the base Stream class.</summary>
+        internal sealed class SynchronousAsyncResult : IAsyncResult
+        {
+            private readonly Object _stateObject;
+            private readonly bool _isWrite;
+            private ManualResetEvent _waitHandle;
+            private ExceptionDispatchInfo _exceptionInfo;
+
+            private bool _endXxxCalled;
+            private Int32 _bytesRead;
+
+            internal SynchronousAsyncResult(Int32 bytesRead, Object asyncStateObject)
+            {
+                _bytesRead = bytesRead;
+                _stateObject = asyncStateObject;
+                //_isWrite = false;
+            }
+
+            internal SynchronousAsyncResult(Object asyncStateObject)
+            {
+                _stateObject = asyncStateObject;
+                _isWrite = true;
+            }
+
+            internal SynchronousAsyncResult(Exception ex, Object asyncStateObject, bool isWrite)
+            {
+                _exceptionInfo = ExceptionDispatchInfo.Capture(ex);
+                _stateObject = asyncStateObject;
+                _isWrite = isWrite;
+            }
+
+            public bool IsCompleted
+            {
+                // We never hand out objects of this type to the user before the synchronous IO completed:
+                get { return true; }
+            }
+
+            public WaitHandle AsyncWaitHandle
+            {
+                get
+                {
+                    return LazyInitializer.EnsureInitialized(ref _waitHandle, () => new ManualResetEvent(true));
+                }
+            }
+
+            public Object AsyncState
+            {
+                get { return _stateObject; }
+            }
+
+            public bool CompletedSynchronously
+            {
+                get { return true; }
+            }
+
+            internal void ThrowIfError()
+            {
+                if (_exceptionInfo != null)
+                    _exceptionInfo.Throw();
+            }
+
+            internal static Int32 EndRead(IAsyncResult asyncResult)
+            {
+                SynchronousAsyncResult ar = asyncResult as SynchronousAsyncResult;
+                if (ar == null || ar._isWrite)
+                    throw new ArgumentException(SR.Arg_WrongAsyncResult);
+
+                if (ar._endXxxCalled)
+                    throw new ArgumentException(SR.InvalidOperation_EndReadCalledMultiple);
+
+                ar._endXxxCalled = true;
+
+                ar.ThrowIfError();
+                return ar._bytesRead;
+            }
+
+            internal static void EndWrite(IAsyncResult asyncResult)
+            {
+                SynchronousAsyncResult ar = asyncResult as SynchronousAsyncResult;
+                if (ar == null || !ar._isWrite)
+                    throw new ArgumentException(SR.Arg_WrongAsyncResult);
+
+                if (ar._endXxxCalled)
+                    throw new ArgumentException(SR.InvalidOperation_EndWriteCalledMultiple);
+
+                ar._endXxxCalled = true;
+
+                ar.ThrowIfError();
+            }
+        }   // class SynchronousAsyncResult
+
+
+        // SyncStream is a wrapper around a stream that takes 
+        // a lock for every operation making it thread safe.
+        internal sealed class SyncStream : Stream, IDisposable
+        {
+            private Stream _stream;
+
+            internal SyncStream(Stream stream)
+            {
+                if (stream == null)
+                    throw new ArgumentNullException(nameof(stream));
+                _stream = stream;
+            }
+
+            public override bool CanRead
+            {
+                get { return _stream.CanRead; }
+            }
+
+            public override bool CanWrite
+            {
+                get { return _stream.CanWrite; }
+            }
+
+            public override bool CanSeek
+            {
+                get { return _stream.CanSeek; }
+            }
+
+            public override bool CanTimeout
+            {
+                get
+                {
+                    return _stream.CanTimeout;
+                }
+            }
+
+            public override long Length
+            {
+                get
+                {
+                    lock (_stream)
+                    {
+                        return _stream.Length;
+                    }
+                }
+            }
+
+            public override long Position
+            {
+                get
+                {
+                    lock (_stream)
+                    {
+                        return _stream.Position;
+                    }
+                }
+                set
+                {
+                    lock (_stream)
+                    {
+                        _stream.Position = value;
+                    }
+                }
+            }
+
+            public override int ReadTimeout
+            {
+                get
+                {
+                    return _stream.ReadTimeout;
+                }
+                set
+                {
+                    _stream.ReadTimeout = value;
+                }
+            }
+
+            public override int WriteTimeout
+            {
+                get
+                {
+                    return _stream.WriteTimeout;
+                }
+                set
+                {
+                    _stream.WriteTimeout = value;
+                }
+            }
+
+            // In the off chance that some wrapped stream has different 
+            // semantics for Close vs. Dispose, let's preserve that.
+            public override void Close()
+            {
+                lock (_stream)
+                {
+                    try
+                    {
+                        _stream.Close();
+                    }
+                    finally
+                    {
+                        base.Dispose(true);
+                    }
+                }
+            }
+
+            protected override void Dispose(bool disposing)
+            {
+                lock (_stream)
+                {
+                    try
+                    {
+                        // Explicitly pick up a potentially methodimpl'ed Dispose
+                        if (disposing)
+                            ((IDisposable)_stream).Dispose();
+                    }
+                    finally
+                    {
+                        base.Dispose(disposing);
+                    }
+                }
+            }
+
+            public override void Flush()
+            {
+                lock (_stream)
+                    _stream.Flush();
+            }
+
+            public override int Read(byte[] bytes, int offset, int count)
+            {
+                lock (_stream)
+                    return _stream.Read(bytes, offset, count);
+            }
+
+            public override int Read(Span<byte> buffer)
+            {
+                lock (_stream)
+                    return _stream.Read(buffer);
+            }
+
+            public override int ReadByte()
+            {
+                lock (_stream)
+                    return _stream.ReadByte();
+            }
+
+            public override IAsyncResult BeginRead(byte[] buffer, int offset, int count, AsyncCallback callback, Object state)
+            {
+                bool overridesBeginRead = _stream.HasOverriddenBeginEndRead();
+
+                lock (_stream)
+                {
+                    // If the Stream does have its own BeginRead implementation, then we must use that override.
+                    // If it doesn't, then we'll use the base implementation, but we'll make sure that the logic
+                    // which ensures only one asynchronous operation does so with an asynchronous wait rather
+                    // than a synchronous wait.  A synchronous wait will result in a deadlock condition, because
+                    // the EndXx method for the outstanding async operation won't be able to acquire the lock on
+                    // _stream due to this call blocked while holding the lock.
+                    return overridesBeginRead ?
+                        _stream.BeginRead(buffer, offset, count, callback, state) :
+                        _stream.BeginReadInternal(buffer, offset, count, callback, state, serializeAsynchronously: true, apm: true);
+                }
+            }
+
+            public override int EndRead(IAsyncResult asyncResult)
+            {
+                if (asyncResult == null)
+                    throw new ArgumentNullException(nameof(asyncResult));
+
+                lock (_stream)
+                    return _stream.EndRead(asyncResult);
+            }
+
+            public override long Seek(long offset, SeekOrigin origin)
+            {
+                lock (_stream)
+                    return _stream.Seek(offset, origin);
+            }
+
+            public override void SetLength(long length)
+            {
+                lock (_stream)
+                    _stream.SetLength(length);
+            }
+
+            public override void Write(byte[] bytes, int offset, int count)
+            {
+                lock (_stream)
+                    _stream.Write(bytes, offset, count);
+            }
+
+            public override void Write(ReadOnlySpan<byte> buffer)
+            {
+                lock (_stream)
+                    _stream.Write(buffer);
+            }
+
+            public override void WriteByte(byte b)
+            {
+                lock (_stream)
+                    _stream.WriteByte(b);
+            }
+
+            public override IAsyncResult BeginWrite(byte[] buffer, int offset, int count, AsyncCallback callback, Object state)
+            {
+                bool overridesBeginWrite = _stream.HasOverriddenBeginEndWrite();
+
+                lock (_stream)
+                {
+                    // If the Stream does have its own BeginWrite implementation, then we must use that override.
+                    // If it doesn't, then we'll use the base implementation, but we'll make sure that the logic
+                    // which ensures only one asynchronous operation does so with an asynchronous wait rather
+                    // than a synchronous wait.  A synchronous wait will result in a deadlock condition, because
+                    // the EndXx method for the outstanding async operation won't be able to acquire the lock on
+                    // _stream due to this call blocked while holding the lock.
+                    return overridesBeginWrite ?
+                        _stream.BeginWrite(buffer, offset, count, callback, state) :
+                        _stream.BeginWriteInternal(buffer, offset, count, callback, state, serializeAsynchronously: true, apm: true);
+                }
+            }
+
+            public override void EndWrite(IAsyncResult asyncResult)
+            {
+                if (asyncResult == null)
+                    throw new ArgumentNullException(nameof(asyncResult));
+
+                lock (_stream)
+                    _stream.EndWrite(asyncResult);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/InsufficientMemoryException.cs b/src/System.Private.CoreLib/src/System/InsufficientMemoryException.cs
new file mode 100644
index 0000000000..b5f369ef9b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/InsufficientMemoryException.cs
@@ -0,0 +1,51 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: The exception class for running out of memory
+** but most likely in a non-fatal way that shouldn't 
+** be affected by escalation policy.  Use this for cases
+** like MemoryFailPoint or a TryAllocate method, where you 
+** expect OOM's with no shared state corruption and you
+** want to recover from these errors.
+**
+**
+=============================================================================*/
+
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public sealed class InsufficientMemoryException : OutOfMemoryException
+    {
+        public InsufficientMemoryException()
+            : base(GetMessageFromNativeResources(ExceptionMessageKind.OutOfMemory))
+        {
+            HResult = HResults.COR_E_INSUFFICIENTMEMORY;
+        }
+
+        public InsufficientMemoryException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_INSUFFICIENTMEMORY;
+        }
+
+        public InsufficientMemoryException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_INSUFFICIENTMEMORY;
+        }
+
+        private InsufficientMemoryException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Internal.cs b/src/System.Private.CoreLib/src/System/Internal.cs
new file mode 100644
index 0000000000..1534326921
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Internal.cs
@@ -0,0 +1,357 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** This file exists to contain miscellaneous module-level attributes
+** and other miscellaneous stuff.
+**
+**
+** 
+===========================================================*/
+
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Collections.Generic;
+using System.Reflection;
+using System.Security;
+using System.StubHelpers;
+using System.Threading.Tasks;
+
+#if FEATURE_COMINTEROP
+using System.Runtime.InteropServices.WindowsRuntime;
+#endif // FEATURE_COMINTEROP
+
+[assembly: DefaultDependencyAttribute(LoadHint.Always)]
+// mscorlib would like to have its literal strings frozen if possible
+[assembly: System.Runtime.CompilerServices.StringFreezingAttribute()]
+
+namespace System
+{
+    static class CommonlyUsedGenericInstantiations
+    {
+        // This method is purely an aid for NGen to statically deduce which
+        // instantiations to save in the ngen image.
+        // Otherwise, the JIT-compiler gets used, which is bad for working-set.
+        // Note that IBC can provide this information too.
+        // However, this helps in keeping the JIT-compiler out even for
+        // test scenarios which do not use IBC.
+        // This can be removed after V2, when we implement other schemes
+        // of keeping the JIT-compiler out for generic instantiations.
+
+        // Method marked as NoOptimization as we don't want the JIT to
+        // inline any methods or take any short-circuit paths since the 
+        // instantiation closure process is driven by "fixup" references 
+        // left in the final code stream.
+        [MethodImplAttribute(MethodImplOptions.NoOptimization)]
+        static CommonlyUsedGenericInstantiations()
+        {
+            // Make absolutely sure we include some of the most common 
+            // instantiations here in mscorlib's ngen image.
+            // Note that reference type instantiations are already included
+            // automatically for us.
+
+            // Need to sort non null, len > 1 array or paths will short-circuit
+            Array.Sort<double>(new double[1]);
+            Array.Sort<int>(new int[1]);
+            Array.Sort<IntPtr>(new IntPtr[1]);
+
+            new ArraySegment<byte>(new byte[1], 0, 0);
+
+            new Dictionary<Char, Object>();
+            new Dictionary<Guid, Byte>();
+            new Dictionary<Guid, Object>();
+            new Dictionary<Guid, Guid>(); // Added for Visual Studio 2010
+            new Dictionary<Int16, IntPtr>();
+            new Dictionary<Int32, Byte>();
+            new Dictionary<Int32, Int32>();
+            new Dictionary<Int32, Object>();
+            new Dictionary<IntPtr, Boolean>();
+            new Dictionary<IntPtr, Int16>();
+            new Dictionary<Object, Boolean>();
+            new Dictionary<Object, Char>();
+            new Dictionary<Object, Guid>();
+            new Dictionary<Object, Int32>();
+            new Dictionary<Object, Int64>(); // Added for Visual Studio 2010
+            new Dictionary<uint, WeakReference>();  // NCL team needs this
+            new Dictionary<Object, UInt32>();
+            new Dictionary<UInt32, Object>();
+            new Dictionary<Int64, Object>();
+
+            // to genereate mdil for Dictionary instantiation when key is user defined value type
+            new Dictionary<Guid, Int32>();
+
+            // Microsoft.Windows.Design
+            new Dictionary<System.Reflection.MemberTypes, Object>();
+            new EnumEqualityComparer<System.Reflection.MemberTypes>();
+
+            // Microsoft.Expression.DesignModel
+            new Dictionary<Object, KeyValuePair<Object, Object>>();
+            new Dictionary<KeyValuePair<Object, Object>, Object>();
+
+            NullableHelper<Boolean>();
+            NullableHelper<Byte>();
+            NullableHelper<Char>();
+            NullableHelper<DateTime>();
+            NullableHelper<Decimal>();
+            NullableHelper<Double>();
+            NullableHelper<Guid>();
+            NullableHelper<Int16>();
+            NullableHelper<Int32>();
+            NullableHelper<Int64>();
+            NullableHelper<Single>();
+            NullableHelper<TimeSpan>();
+            NullableHelper<DateTimeOffset>();  // For SQL
+
+            new List<Boolean>();
+            new List<Byte>();
+            new List<Char>();
+            new List<DateTime>();
+            new List<Decimal>();
+            new List<Double>();
+            new List<Guid>();
+            new List<Int16>();
+            new List<Int32>();
+            new List<Int64>();
+            new List<TimeSpan>();
+            new List<SByte>();
+            new List<Single>();
+            new List<UInt16>();
+            new List<UInt32>();
+            new List<UInt64>();
+            new List<IntPtr>();
+            new List<KeyValuePair<Object, Object>>();
+            new List<GCHandle>();  // NCL team needs this
+            new List<DateTimeOffset>();
+
+            new KeyValuePair<Char, UInt16>('\0', UInt16.MinValue);
+            new KeyValuePair<UInt16, Double>(UInt16.MinValue, Double.MinValue);
+            new KeyValuePair<Object, Int32>(String.Empty, Int32.MinValue);
+            new KeyValuePair<Int32, Int32>(Int32.MinValue, Int32.MinValue);
+            SZArrayHelper<Boolean>(null);
+            SZArrayHelper<Byte>(null);
+            SZArrayHelper<DateTime>(null);
+            SZArrayHelper<Decimal>(null);
+            SZArrayHelper<Double>(null);
+            SZArrayHelper<Guid>(null);
+            SZArrayHelper<Int16>(null);
+            SZArrayHelper<Int32>(null);
+            SZArrayHelper<Int64>(null);
+            SZArrayHelper<TimeSpan>(null);
+            SZArrayHelper<SByte>(null);
+            SZArrayHelper<Single>(null);
+            SZArrayHelper<UInt16>(null);
+            SZArrayHelper<UInt32>(null);
+            SZArrayHelper<UInt64>(null);
+            SZArrayHelper<DateTimeOffset>(null);
+
+            SZArrayHelper<CustomAttributeTypedArgument>(null);
+            SZArrayHelper<CustomAttributeNamedArgument>(null);
+
+#pragma warning disable 4014
+            // This is necessary to generate MDIL for AsyncVoidMethodBuilder
+            AsyncHelper<int>();
+            AsyncHelper2<int>();
+            AsyncHelper3();
+#pragma warning restore 4014
+        }
+
+        private static T NullableHelper<T>() where T : struct
+        {
+            Nullable.Compare<T>(null, null);
+            Nullable.Equals<T>(null, null);
+            Nullable<T> nullable = new Nullable<T>();
+            return nullable.GetValueOrDefault();
+        }
+
+        private static void SZArrayHelper<T>(SZArrayHelper oSZArrayHelper)
+        {
+            // Instantiate common methods for IList implementation on Array
+            oSZArrayHelper.get_Count<T>();
+            oSZArrayHelper.get_Item<T>(0);
+            oSZArrayHelper.GetEnumerator<T>();
+        }
+
+        // System.Runtime.CompilerServices.AsyncVoidMethodBuilder
+        // System.Runtime.CompilerServices.TaskAwaiter
+        private static async void AsyncHelper<T>()
+        {
+            await Task.Delay(1);
+        }
+        // System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1[System.__Canon]
+        // System.Runtime.CompilerServices.TaskAwaiter'[System.__Canon]
+        private static async Task<String> AsyncHelper2<T>()
+        {
+            return await Task.FromResult<string>("");
+        }
+
+        // System.Runtime.CompilerServices.AsyncTaskMethodBuilder
+        // System.Runtime.CompilerServices.AsyncTaskMethodBuilder'1[VoidTaskResult]
+        private static async Task AsyncHelper3()
+        {
+            await Task.FromResult<string>("");
+        }
+
+#if FEATURE_COMINTEROP
+
+        // Similar to CommonlyUsedGenericInstantiations but for instantiations of marshaling stubs used
+        // for WinRT redirected interfaces. Note that we do care about reference types here as well because,
+        // say, IList<string> and IList<object> cannot share marshaling stubs.
+        // The methods below "call" most commonly used stub methods on redirected interfaces and take arguments
+        // typed as matching instantiations of mscorlib copies of WinRT interfaces (IIterable<T>, IVector<T>,
+        // IMap<K, V>, ...) which is necessary to generate all required IL stubs.
+
+        private static void CommonlyUsedWinRTRedirectedInterfaceStubs()
+        {
+            WinRT_IEnumerable<byte>(null, null, null);
+            WinRT_IEnumerable<char>(null, null, null);
+            WinRT_IEnumerable<short>(null, null, null);
+            WinRT_IEnumerable<ushort>(null, null, null);
+            WinRT_IEnumerable<int>(null, null, null);
+            WinRT_IEnumerable<uint>(null, null, null);
+            WinRT_IEnumerable<long>(null, null, null);
+            WinRT_IEnumerable<ulong>(null, null, null);
+            WinRT_IEnumerable<float>(null, null, null);
+            WinRT_IEnumerable<double>(null, null, null);
+
+            // The underlying WinRT types for shared instantiations have to be referenced explicitly. 
+            // They are not guaranteeed to be created indirectly because of generic code sharing.
+            WinRT_IEnumerable<string>(null, null, null); typeof(IIterable<string>).ToString(); typeof(IIterator<string>).ToString();
+            WinRT_IEnumerable<object>(null, null, null); typeof(IIterable<object>).ToString(); typeof(IIterator<object>).ToString();
+
+            WinRT_IList<int>(null, null, null, null);
+            WinRT_IList<string>(null, null, null, null); typeof(IVector<string>).ToString();
+            WinRT_IList<object>(null, null, null, null); typeof(IVector<object>).ToString();
+
+            WinRT_IReadOnlyList<int>(null, null, null);
+            WinRT_IReadOnlyList<string>(null, null, null); typeof(IVectorView<string>).ToString();
+            WinRT_IReadOnlyList<object>(null, null, null); typeof(IVectorView<object>).ToString();
+
+            WinRT_IDictionary<string, int>(null, null, null, null); typeof(IMap<string, int>).ToString();
+            WinRT_IDictionary<string, string>(null, null, null, null); typeof(IMap<string, string>).ToString();
+            WinRT_IDictionary<string, object>(null, null, null, null); typeof(IMap<string, object>).ToString();
+            WinRT_IDictionary<object, object>(null, null, null, null); typeof(IMap<object, object>).ToString();
+
+            WinRT_IReadOnlyDictionary<string, int>(null, null, null, null); typeof(IMapView<string, int>).ToString();
+            WinRT_IReadOnlyDictionary<string, string>(null, null, null, null); typeof(IMapView<string, string>).ToString();
+            WinRT_IReadOnlyDictionary<string, object>(null, null, null, null); typeof(IMapView<string, object>).ToString();
+            WinRT_IReadOnlyDictionary<object, object>(null, null, null, null); typeof(IMapView<object, object>).ToString();
+
+            WinRT_Nullable<bool>();
+            WinRT_Nullable<byte>();
+            WinRT_Nullable<int>();
+            WinRT_Nullable<uint>();
+            WinRT_Nullable<long>();
+            WinRT_Nullable<ulong>();
+            WinRT_Nullable<float>();
+            WinRT_Nullable<double>();
+        }
+
+        private static void WinRT_IEnumerable<T>(IterableToEnumerableAdapter iterableToEnumerableAdapter, EnumerableToIterableAdapter enumerableToIterableAdapter, IIterable<T> iterable)
+        {
+            // instantiate stubs for the one method on IEnumerable<T> and the one method on IIterable<T>
+            iterableToEnumerableAdapter.GetEnumerator_Stub<T>();
+            enumerableToIterableAdapter.First_Stub<T>();
+        }
+
+        private static void WinRT_IList<T>(VectorToListAdapter vectorToListAdapter, VectorToCollectionAdapter vectorToCollectionAdapter, ListToVectorAdapter listToVectorAdapter, IVector<T> vector)
+        {
+            WinRT_IEnumerable<T>(null, null, null);
+
+            // instantiate stubs for commonly used methods on IList<T> and ICollection<T>
+            vectorToListAdapter.Indexer_Get<T>(0);
+            vectorToListAdapter.Indexer_Set<T>(0, default(T));
+            vectorToListAdapter.Insert<T>(0, default(T));
+            vectorToListAdapter.RemoveAt<T>(0);
+            vectorToCollectionAdapter.Count<T>();
+            vectorToCollectionAdapter.Add<T>(default(T));
+            vectorToCollectionAdapter.Clear<T>();
+
+            // instantiate stubs for commonly used methods on IVector<T>
+            listToVectorAdapter.GetAt<T>(0);
+            listToVectorAdapter.Size<T>();
+            listToVectorAdapter.SetAt<T>(0, default(T));
+            listToVectorAdapter.InsertAt<T>(0, default(T));
+            listToVectorAdapter.RemoveAt<T>(0);
+            listToVectorAdapter.Append<T>(default(T));
+            listToVectorAdapter.RemoveAtEnd<T>();
+            listToVectorAdapter.Clear<T>();
+        }
+
+        private static void WinRT_IReadOnlyCollection<T>(VectorViewToReadOnlyCollectionAdapter vectorViewToReadOnlyCollectionAdapter)
+        {
+            WinRT_IEnumerable<T>(null, null, null);
+
+            // instantiate stubs for commonly used methods on IReadOnlyCollection<T>
+            vectorViewToReadOnlyCollectionAdapter.Count<T>();
+        }
+
+        private static void WinRT_IReadOnlyList<T>(IVectorViewToIReadOnlyListAdapter vectorToListAdapter, IReadOnlyListToIVectorViewAdapter listToVectorAdapter, IVectorView<T> vectorView)
+        {
+            WinRT_IEnumerable<T>(null, null, null);
+            WinRT_IReadOnlyCollection<T>(null);
+
+            // instantiate stubs for commonly used methods on IReadOnlyList<T>
+            vectorToListAdapter.Indexer_Get<T>(0);
+
+            // instantiate stubs for commonly used methods on IVectorView<T>
+            listToVectorAdapter.GetAt<T>(0);
+            listToVectorAdapter.Size<T>();
+        }
+
+        private static void WinRT_IDictionary<K, V>(MapToDictionaryAdapter mapToDictionaryAdapter, MapToCollectionAdapter mapToCollectionAdapter, DictionaryToMapAdapter dictionaryToMapAdapter, IMap<K, V> map)
+        {
+            WinRT_IEnumerable<KeyValuePair<K, V>>(null, null, null);
+
+            // instantiate stubs for commonly used methods on IDictionary<K, V> and ICollection<KeyValuePair<K, V>>
+            V dummy;
+            mapToDictionaryAdapter.Indexer_Get<K, V>(default(K));
+            mapToDictionaryAdapter.Indexer_Set<K, V>(default(K), default(V));
+            mapToDictionaryAdapter.ContainsKey<K, V>(default(K));
+            mapToDictionaryAdapter.Add<K, V>(default(K), default(V));
+            mapToDictionaryAdapter.Remove<K, V>(default(K));
+            mapToDictionaryAdapter.TryGetValue<K, V>(default(K), out dummy);
+            mapToCollectionAdapter.Count<K, V>();
+            mapToCollectionAdapter.Add<K, V>(new KeyValuePair<K, V>(default(K), default(V)));
+            mapToCollectionAdapter.Clear<K, V>();
+
+            // instantiate stubs for commonly used methods on IMap<K, V>
+            dictionaryToMapAdapter.Lookup<K, V>(default(K));
+            dictionaryToMapAdapter.Size<K, V>();
+            dictionaryToMapAdapter.HasKey<K, V>(default(K));
+            dictionaryToMapAdapter.Insert<K, V>(default(K), default(V));
+            dictionaryToMapAdapter.Remove<K, V>(default(K));
+            dictionaryToMapAdapter.Clear<K, V>();
+        }
+
+        private static void WinRT_IReadOnlyDictionary<K, V>(IMapViewToIReadOnlyDictionaryAdapter mapToDictionaryAdapter, IReadOnlyDictionaryToIMapViewAdapter dictionaryToMapAdapter, IMapView<K, V> mapView, MapViewToReadOnlyCollectionAdapter mapViewToReadOnlyCollectionAdapter)
+        {
+            WinRT_IEnumerable<KeyValuePair<K, V>>(null, null, null);
+            WinRT_IReadOnlyCollection<KeyValuePair<K, V>>(null);
+
+            // instantiate stubs for commonly used methods on IReadOnlyDictionary<K, V>
+            V dummy;
+            mapToDictionaryAdapter.Indexer_Get<K, V>(default(K));
+            mapToDictionaryAdapter.ContainsKey<K, V>(default(K));
+            mapToDictionaryAdapter.TryGetValue<K, V>(default(K), out dummy);
+
+            // instantiate stubs for commonly used methods in IReadOnlyCollection<T>
+            mapViewToReadOnlyCollectionAdapter.Count<K, V>();
+
+            // instantiate stubs for commonly used methods on IMapView<K, V>
+            dictionaryToMapAdapter.Lookup<K, V>(default(K));
+            dictionaryToMapAdapter.Size<K, V>();
+            dictionaryToMapAdapter.HasKey<K, V>(default(K));
+        }
+
+        private static void WinRT_Nullable<T>() where T : struct
+        {
+            Nullable<T> nullable = new Nullable<T>();
+            NullableMarshaler.ConvertToNative(ref nullable);
+            NullableMarshaler.ConvertToManagedRetVoid(IntPtr.Zero, ref nullable);
+        }
+
+#endif // FEATURE_COMINTEROP
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Math.CoreCLR.cs b/src/System.Private.CoreLib/src/System/Math.CoreCLR.cs
new file mode 100644
index 0000000000..e4c85f92a0
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Math.CoreCLR.cs
@@ -0,0 +1,97 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Some floating-point math operations
+**
+** 
+===========================================================*/
+
+//This class contains only static members and doesn't require serialization.
+
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    public static partial class Math
+    {
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Abs(double value);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Abs(float value);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Acos(double d);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Acosh(double d);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Asin(double d);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Asinh(double d);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Atan(double d);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Atan2(double y, double x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Atanh(double d);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Cbrt(double d);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Ceiling(double a);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Cos(double d);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Cosh(double value);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Exp(double d);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Floor(double d);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Log(double d);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Log10(double d);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Pow(double x, double y);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Sin(double a);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Sinh(double value);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Sqrt(double d);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Tan(double a);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double Tanh(double value);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern double FMod(double x, double y);
+        
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern unsafe double ModF(double x, double* intptr);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/MathF.CoreCLR.cs b/src/System.Private.CoreLib/src/System/MathF.CoreCLR.cs
new file mode 100644
index 0000000000..1abc040e98
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/MathF.CoreCLR.cs
@@ -0,0 +1,88 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Purpose: Some single-precision floating-point math operations
+**
+===========================================================*/
+
+//This class contains only static members and doesn't require serialization.
+
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    public static partial class MathF
+    {
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Acos(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Acosh(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Asin(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Asinh(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Atan(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Atan2(float y, float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Atanh(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Cbrt(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Ceiling(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Cos(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Cosh(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Exp(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Floor(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Log(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Log10(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Pow(float x, float y);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Sin(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Sinh(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Sqrt(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Tan(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern float Tanh(float x);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern float FMod(float x, float y);
+        
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern unsafe float ModF(float x, float* intptr);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/MissingFieldException.cs b/src/System.Private.CoreLib/src/System/MissingFieldException.cs
new file mode 100644
index 0000000000..0225414a38
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/MissingFieldException.cs
@@ -0,0 +1,72 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+** Purpose: The exception class for class loading failures.
+**
+=============================================================================*/
+
+
+using System;
+using System.Runtime.Serialization;
+using System.Runtime.CompilerServices;
+using System.Globalization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class MissingFieldException : MissingMemberException, ISerializable
+    {
+        public MissingFieldException()
+            : base(SR.Arg_MissingFieldException)
+        {
+            HResult = HResults.COR_E_MISSINGFIELD;
+        }
+
+        public MissingFieldException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_MISSINGFIELD;
+        }
+
+        public MissingFieldException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_MISSINGFIELD;
+        }
+
+        protected MissingFieldException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+
+        public override String Message
+        {
+            get
+            {
+                if (ClassName == null)
+                {
+                    return base.Message;
+                }
+                else
+                {
+                    // do any desired fixups to classname here.
+                    return SR.Format(SR.MissingField_Name, (Signature != null ? FormatSignature(Signature) + " " : "") + ClassName + "." + MemberName);
+                }
+            }
+        }
+
+        public MissingFieldException(String className, String fieldName)
+        {
+            ClassName = className;
+            MemberName = fieldName;
+        }
+
+        // If ClassName != null, Message will construct on the fly using it
+        // and the other variables. This allows customization of the
+        // format depending on the language environment.
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/MissingMemberException.cs b/src/System.Private.CoreLib/src/System/MissingMemberException.cs
new file mode 100644
index 0000000000..ba16b27680
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/MissingMemberException.cs
@@ -0,0 +1,91 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: The exception class for versioning problems with DLLS.
+**
+**
+=============================================================================*/
+
+
+using System.Runtime.Serialization;
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class MissingMemberException : MemberAccessException, ISerializable
+    {
+        public MissingMemberException()
+            : base(SR.Arg_MissingMemberException)
+        {
+            HResult = HResults.COR_E_MISSINGMEMBER;
+        }
+
+        public MissingMemberException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_MISSINGMEMBER;
+        }
+
+        public MissingMemberException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_MISSINGMEMBER;
+        }
+
+        protected MissingMemberException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+            ClassName = info.GetString("MMClassName");
+            MemberName = info.GetString("MMMemberName");
+            Signature = (byte[])info.GetValue("MMSignature", typeof(byte[]));
+        }
+
+        public override String Message
+        {
+            get
+            {
+                if (ClassName == null)
+                {
+                    return base.Message;
+                }
+                else
+                {
+                    // do any desired fixups to classname here.
+                    return SR.Format(SR.MissingMember_Name, ClassName + "." + MemberName + (Signature != null ? " " + FormatSignature(Signature) : ""));
+                }
+            }
+        }
+
+        // Called to format signature
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern String FormatSignature(byte[] signature);
+
+        public MissingMemberException(String className, String memberName)
+        {
+            ClassName = className;
+            MemberName = memberName;
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("MMClassName", ClassName, typeof(string));
+            info.AddValue("MMMemberName", MemberName, typeof(string));
+            info.AddValue("MMSignature", Signature, typeof(byte[]));
+        }
+
+
+        // If ClassName != null, GetMessage will construct on the fly using it
+        // and the other variables. This allows customization of the
+        // format depending on the language environment.
+        protected String ClassName;
+        protected String MemberName;
+        protected byte[] Signature;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/MulticastDelegate.cs b/src/System.Private.CoreLib/src/System/MulticastDelegate.cs
new file mode 100644
index 0000000000..ef630bc158
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/MulticastDelegate.cs
@@ -0,0 +1,631 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Reflection;
+using System.Runtime.Serialization;
+using System.Diagnostics;
+using System.Reflection.Emit;
+using Internal.Runtime.CompilerServices;
+
+namespace System
+{
+    [System.Runtime.InteropServices.ComVisible(true)]
+    public abstract class MulticastDelegate : Delegate
+    {
+        // This is set under 3 circumstances
+        // 1. Multicast delegate
+        // 2. Secure/Wrapper delegate
+        // 3. Inner delegate of secure delegate where the secure delegate security context is a collectible method
+        private Object _invocationList;
+        private IntPtr _invocationCount;
+
+        // This constructor is called from the class generated by the
+        //    compiler generated code (This must match the constructor
+        //    in Delegate
+        protected MulticastDelegate(Object target, String method) : base(target, method)
+        {
+        }
+
+        // This constructor is called from a class to generate a 
+        // delegate based upon a static method name and the Type object
+        // for the class defining the method.
+        protected MulticastDelegate(Type target, String method) : base(target, method)
+        {
+        }
+
+        internal bool IsUnmanagedFunctionPtr()
+        {
+            return (_invocationCount == (IntPtr)(-1));
+        }
+
+        internal bool InvocationListLogicallyNull()
+        {
+            return (_invocationList == null) || (_invocationList is LoaderAllocator) || (_invocationList is DynamicResolver);
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            throw new SerializationException(SR.Serialization_DelegatesNotSupported);
+        }
+
+        // equals returns true IIF the delegate is not null and has the
+        //    same target, method and invocation list as this object
+        public override sealed bool Equals(Object obj)
+        {
+            if (obj == null)
+                return false;
+            if (object.ReferenceEquals(this, obj))
+                return true;
+            if (!InternalEqualTypes(this, obj))
+                return false;
+
+            // Since this is a MulticastDelegate and we know
+            // the types are the same, obj should also be a
+            // MulticastDelegate
+            Debug.Assert(obj is MulticastDelegate, "Shouldn't have failed here since we already checked the types are the same!");
+            var d = Unsafe.As<MulticastDelegate>(obj);
+
+            if (_invocationCount != (IntPtr)0)
+            {
+                // there are 4 kind of delegate kinds that fall into this bucket
+                // 1- Multicast (_invocationList is Object[])
+                // 2- Secure/Wrapper (_invocationList is Delegate)
+                // 3- Unmanaged FntPtr (_invocationList == null)
+                // 4- Open virtual (_invocationCount == MethodDesc of target, _invocationList == null, LoaderAllocator, or DynamicResolver)
+
+                if (InvocationListLogicallyNull())
+                {
+                    if (IsUnmanagedFunctionPtr())
+                    {
+                        if (!d.IsUnmanagedFunctionPtr())
+                            return false;
+
+                        return CompareUnmanagedFunctionPtrs(this, d);
+                    }
+
+                    // now we know 'this' is not a special one, so we can work out what the other is
+                    if ((d._invocationList as Delegate) != null)
+                        // this is a secure/wrapper delegate so we need to unwrap and check the inner one
+                        return Equals(d._invocationList);
+
+                    return base.Equals(obj);
+                }
+                else
+                {
+                    if ((_invocationList as Delegate) != null)
+                    {
+                        // this is a secure/wrapper delegate so we need to unwrap and check the inner one
+                        return _invocationList.Equals(obj);
+                    }
+                    else
+                    {
+                        Debug.Assert((_invocationList as Object[]) != null, "empty invocation list on multicast delegate");
+                        return InvocationListEquals(d);
+                    }
+                }
+            }
+            else
+            {
+                // among the several kind of delegates falling into this bucket one has got a non
+                // empty _invocationList (open static with special sig)
+                // to be equals we need to check that _invocationList matches (both null is fine)
+                // and call the base.Equals()
+                if (!InvocationListLogicallyNull())
+                {
+                    if (!_invocationList.Equals(d._invocationList))
+                        return false;
+                    return base.Equals(d);
+                }
+
+                // now we know 'this' is not a special one, so we can work out what the other is
+                if ((d._invocationList as Delegate) != null)
+                    // this is a secure/wrapper delegate so we need to unwrap and check the inner one
+                    return Equals(d._invocationList);
+
+                // now we can call on the base
+                return base.Equals(d);
+            }
+        }
+
+        // Recursive function which will check for equality of the invocation list.
+        private bool InvocationListEquals(MulticastDelegate d)
+        {
+            Debug.Assert(d != null && (_invocationList as Object[]) != null, "bogus delegate in multicast list comparison");
+            Object[] invocationList = _invocationList as Object[];
+            if (d._invocationCount != _invocationCount)
+                return false;
+
+            int invocationCount = (int)_invocationCount;
+            for (int i = 0; i < invocationCount; i++)
+            {
+                Delegate dd = (Delegate)invocationList[i];
+                Object[] dInvocationList = d._invocationList as Object[];
+                if (!dd.Equals(dInvocationList[i]))
+                    return false;
+            }
+            return true;
+        }
+
+        private bool TrySetSlot(Object[] a, int index, Object o)
+        {
+            if (a[index] == null && System.Threading.Interlocked.CompareExchange<Object>(ref a[index], o, null) == null)
+                return true;
+
+            // The slot may be already set because we have added and removed the same method before.
+            // Optimize this case, because it's cheaper than copying the array.
+            if (a[index] != null)
+            {
+                MulticastDelegate d = (MulticastDelegate)o;
+                MulticastDelegate dd = (MulticastDelegate)a[index];
+
+                if (dd._methodPtr == d._methodPtr &&
+                    dd._target == d._target &&
+                    dd._methodPtrAux == d._methodPtrAux)
+                {
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        private MulticastDelegate NewMulticastDelegate(Object[] invocationList, int invocationCount, bool thisIsMultiCastAlready)
+        {
+            // First, allocate a new multicast delegate just like this one, i.e. same type as the this object
+            MulticastDelegate result = (MulticastDelegate)InternalAllocLike(this);
+
+            // Performance optimization - if this already points to a true multicast delegate,
+            // copy _methodPtr and _methodPtrAux fields rather than calling into the EE to get them
+            if (thisIsMultiCastAlready)
+            {
+                result._methodPtr = this._methodPtr;
+                result._methodPtrAux = this._methodPtrAux;
+            }
+            else
+            {
+                result._methodPtr = GetMulticastInvoke();
+                result._methodPtrAux = GetInvokeMethod();
+            }
+            result._target = result;
+            result._invocationList = invocationList;
+            result._invocationCount = (IntPtr)invocationCount;
+
+            return result;
+        }
+
+        internal MulticastDelegate NewMulticastDelegate(Object[] invocationList, int invocationCount)
+        {
+            return NewMulticastDelegate(invocationList, invocationCount, false);
+        }
+
+        internal void StoreDynamicMethod(MethodInfo dynamicMethod)
+        {
+            if (_invocationCount != (IntPtr)0)
+            {
+                Debug.Assert(!IsUnmanagedFunctionPtr(), "dynamic method and unmanaged fntptr delegate combined");
+                // must be a secure/wrapper one, unwrap and save
+                MulticastDelegate d = (MulticastDelegate)_invocationList;
+                d._methodBase = dynamicMethod;
+            }
+            else
+                _methodBase = dynamicMethod;
+        }
+
+        // This method will combine this delegate with the passed delegate
+        //    to form a new delegate.
+        protected override sealed Delegate CombineImpl(Delegate follow)
+        {
+            if ((Object)follow == null) // cast to object for a more efficient test
+                return this;
+
+            // Verify that the types are the same...
+            if (!InternalEqualTypes(this, follow))
+                throw new ArgumentException(SR.Arg_DlgtTypeMis);
+
+            MulticastDelegate dFollow = (MulticastDelegate)follow;
+            Object[] resultList;
+            int followCount = 1;
+            Object[] followList = dFollow._invocationList as Object[];
+            if (followList != null)
+                followCount = (int)dFollow._invocationCount;
+
+            int resultCount;
+            Object[] invocationList = _invocationList as Object[];
+            if (invocationList == null)
+            {
+                resultCount = 1 + followCount;
+                resultList = new Object[resultCount];
+                resultList[0] = this;
+                if (followList == null)
+                {
+                    resultList[1] = dFollow;
+                }
+                else
+                {
+                    for (int i = 0; i < followCount; i++)
+                        resultList[1 + i] = followList[i];
+                }
+                return NewMulticastDelegate(resultList, resultCount);
+            }
+            else
+            {
+                int invocationCount = (int)_invocationCount;
+                resultCount = invocationCount + followCount;
+                resultList = null;
+                if (resultCount <= invocationList.Length)
+                {
+                    resultList = invocationList;
+                    if (followList == null)
+                    {
+                        if (!TrySetSlot(resultList, invocationCount, dFollow))
+                            resultList = null;
+                    }
+                    else
+                    {
+                        for (int i = 0; i < followCount; i++)
+                        {
+                            if (!TrySetSlot(resultList, invocationCount + i, followList[i]))
+                            {
+                                resultList = null;
+                                break;
+                            }
+                        }
+                    }
+                }
+
+                if (resultList == null)
+                {
+                    int allocCount = invocationList.Length;
+                    while (allocCount < resultCount)
+                        allocCount *= 2;
+
+                    resultList = new Object[allocCount];
+
+                    for (int i = 0; i < invocationCount; i++)
+                        resultList[i] = invocationList[i];
+
+                    if (followList == null)
+                    {
+                        resultList[invocationCount] = dFollow;
+                    }
+                    else
+                    {
+                        for (int i = 0; i < followCount; i++)
+                            resultList[invocationCount + i] = followList[i];
+                    }
+                }
+                return NewMulticastDelegate(resultList, resultCount, true);
+            }
+        }
+
+        private Object[] DeleteFromInvocationList(Object[] invocationList, int invocationCount, int deleteIndex, int deleteCount)
+        {
+            Object[] thisInvocationList = _invocationList as Object[];
+            int allocCount = thisInvocationList.Length;
+            while (allocCount / 2 >= invocationCount - deleteCount)
+                allocCount /= 2;
+
+            Object[] newInvocationList = new Object[allocCount];
+
+            for (int i = 0; i < deleteIndex; i++)
+                newInvocationList[i] = invocationList[i];
+
+            for (int i = deleteIndex + deleteCount; i < invocationCount; i++)
+                newInvocationList[i - deleteCount] = invocationList[i];
+
+            return newInvocationList;
+        }
+
+        private bool EqualInvocationLists(Object[] a, Object[] b, int start, int count)
+        {
+            for (int i = 0; i < count; i++)
+            {
+                if (!(a[start + i].Equals(b[i])))
+                    return false;
+            }
+            return true;
+        }
+
+        // This method currently looks backward on the invocation list
+        //    for an element that has Delegate based equality with value.  (Doesn't
+        //    look at the invocation list.)  If this is found we remove it from
+        //    this list and return a new delegate.  If its not found a copy of the
+        //    current list is returned.
+        protected override sealed Delegate RemoveImpl(Delegate value)
+        {
+            // There is a special case were we are removing using a delegate as
+            //    the value we need to check for this case
+            //
+            MulticastDelegate v = value as MulticastDelegate;
+
+            if (v == null)
+                return this;
+            if (v._invocationList as Object[] == null)
+            {
+                Object[] invocationList = _invocationList as Object[];
+                if (invocationList == null)
+                {
+                    // they are both not real Multicast
+                    if (this.Equals(value))
+                        return null;
+                }
+                else
+                {
+                    int invocationCount = (int)_invocationCount;
+                    for (int i = invocationCount; --i >= 0;)
+                    {
+                        if (value.Equals(invocationList[i]))
+                        {
+                            if (invocationCount == 2)
+                            {
+                                // Special case - only one value left, either at the beginning or the end
+                                return (Delegate)invocationList[1 - i];
+                            }
+                            else
+                            {
+                                Object[] list = DeleteFromInvocationList(invocationList, invocationCount, i, 1);
+                                return NewMulticastDelegate(list, invocationCount - 1, true);
+                            }
+                        }
+                    }
+                }
+            }
+            else
+            {
+                Object[] invocationList = _invocationList as Object[];
+                if (invocationList != null)
+                {
+                    int invocationCount = (int)_invocationCount;
+                    int vInvocationCount = (int)v._invocationCount;
+                    for (int i = invocationCount - vInvocationCount; i >= 0; i--)
+                    {
+                        if (EqualInvocationLists(invocationList, v._invocationList as Object[], i, vInvocationCount))
+                        {
+                            if (invocationCount - vInvocationCount == 0)
+                            {
+                                // Special case - no values left
+                                return null;
+                            }
+                            else if (invocationCount - vInvocationCount == 1)
+                            {
+                                // Special case - only one value left, either at the beginning or the end
+                                return (Delegate)invocationList[i != 0 ? 0 : invocationCount - 1];
+                            }
+                            else
+                            {
+                                Object[] list = DeleteFromInvocationList(invocationList, invocationCount, i, vInvocationCount);
+                                return NewMulticastDelegate(list, invocationCount - vInvocationCount, true);
+                            }
+                        }
+                    }
+                }
+            }
+
+            return this;
+        }
+
+        // This method returns the Invocation list of this multicast delegate.
+        public override sealed Delegate[] GetInvocationList()
+        {
+            Delegate[] del;
+            Object[] invocationList = _invocationList as Object[];
+            if (invocationList == null)
+            {
+                del = new Delegate[1];
+                del[0] = this;
+            }
+            else
+            {
+                // Create an array of delegate copies and each
+                //    element into the array
+                del = new Delegate[(int)_invocationCount];
+
+                for (int i = 0; i < del.Length; i++)
+                    del[i] = (Delegate)invocationList[i];
+            }
+            return del;
+        }
+
+        public static bool operator ==(MulticastDelegate d1, MulticastDelegate d2)
+        {
+            if (ReferenceEquals(d1, d2))
+            {
+                return true;
+            }
+
+            return d1 is null ? false : d1.Equals(d2);
+        }
+
+        public static bool operator !=(MulticastDelegate d1, MulticastDelegate d2)
+        {
+            if (ReferenceEquals(d1, d2))
+            {
+                return false;
+            }
+
+            return d1 is null ? true : !d1.Equals(d2);
+        }
+
+        public override sealed int GetHashCode()
+        {
+            if (IsUnmanagedFunctionPtr())
+                return ValueType.GetHashCodeOfPtr(_methodPtr) ^ ValueType.GetHashCodeOfPtr(_methodPtrAux);
+
+            if (_invocationCount != (IntPtr)0)
+            {
+                var t = _invocationList as Delegate;
+
+                if (t != null)
+                {
+                    // this is a secure/wrapper delegate so we need to unwrap and check the inner one
+                    return t.GetHashCode();
+                }
+            }
+
+            Object[] invocationList = _invocationList as Object[];
+            if (invocationList == null)
+            {
+                return base.GetHashCode();
+            }
+            else
+            {
+                int hash = 0;
+                for (int i = 0; i < (int)_invocationCount; i++)
+                {
+                    hash = hash * 33 + invocationList[i].GetHashCode();
+                }
+
+                return hash;
+            }
+        }
+
+        internal override Object GetTarget()
+        {
+            if (_invocationCount != (IntPtr)0)
+            {
+                // _invocationCount != 0 we are in one of these cases:
+                // - Multicast -> return the target of the last delegate in the list
+                // - Secure/wrapper delegate -> return the target of the inner delegate
+                // - unmanaged function pointer - return null
+                // - virtual open delegate - return null
+                if (InvocationListLogicallyNull())
+                {
+                    // both open virtual and ftn pointer return null for the target
+                    return null;
+                }
+                else
+                {
+                    Object[] invocationList = _invocationList as Object[];
+                    if (invocationList != null)
+                    {
+                        int invocationCount = (int)_invocationCount;
+                        return ((Delegate)invocationList[invocationCount - 1]).GetTarget();
+                    }
+                    else
+                    {
+                        Delegate receiver = _invocationList as Delegate;
+                        if (receiver != null)
+                            return receiver.GetTarget();
+                    }
+                }
+            }
+            return base.GetTarget();
+        }
+
+        protected override MethodInfo GetMethodImpl()
+        {
+            if (_invocationCount != (IntPtr)0 && _invocationList != null)
+            {
+                // multicast case
+                Object[] invocationList = _invocationList as Object[];
+                if (invocationList != null)
+                {
+                    int index = (int)_invocationCount - 1;
+                    return ((Delegate)invocationList[index]).Method;
+                }
+                MulticastDelegate innerDelegate = _invocationList as MulticastDelegate;
+                if (innerDelegate != null)
+                {
+                    // must be a secure/wrapper delegate
+                    return innerDelegate.GetMethodImpl();
+                }
+            }
+            else if (IsUnmanagedFunctionPtr())
+            {
+                // we handle unmanaged function pointers here because the generic ones (used for WinRT) would otherwise
+                // be treated as open delegates by the base implementation, resulting in failure to get the MethodInfo
+                if ((_methodBase == null) || !(_methodBase is MethodInfo))
+                {
+                    IRuntimeMethodInfo method = FindMethodHandle();
+                    RuntimeType declaringType = RuntimeMethodHandle.GetDeclaringType(method);
+
+                    // need a proper declaring type instance method on a generic type
+                    if (RuntimeTypeHandle.IsGenericTypeDefinition(declaringType) || RuntimeTypeHandle.HasInstantiation(declaringType))
+                    {
+                        // we are returning the 'Invoke' method of this delegate so use this.GetType() for the exact type
+                        RuntimeType reflectedType = GetType() as RuntimeType;
+                        declaringType = reflectedType;
+                    }
+                    _methodBase = (MethodInfo)RuntimeType.GetMethodBase(declaringType, method);
+                }
+                return (MethodInfo)_methodBase;
+            }
+
+            // Otherwise, must be an inner delegate of a SecureDelegate of an open virtual method. In that case, call base implementation
+            return base.GetMethodImpl();
+        }
+
+        // this should help inlining
+        [System.Diagnostics.DebuggerNonUserCode]
+        private void ThrowNullThisInDelegateToInstance()
+        {
+            throw new ArgumentException(SR.Arg_DlgtNullInst);
+        }
+
+        [System.Diagnostics.DebuggerNonUserCode]
+        private void CtorClosed(Object target, IntPtr methodPtr)
+        {
+            if (target == null)
+                ThrowNullThisInDelegateToInstance();
+            this._target = target;
+            this._methodPtr = methodPtr;
+        }
+
+        [System.Diagnostics.DebuggerNonUserCode]
+        private void CtorClosedStatic(Object target, IntPtr methodPtr)
+        {
+            this._target = target;
+            this._methodPtr = methodPtr;
+        }
+
+        [System.Diagnostics.DebuggerNonUserCode]
+        private void CtorRTClosed(Object target, IntPtr methodPtr)
+        {
+            this._target = target;
+            this._methodPtr = AdjustTarget(target, methodPtr);
+        }
+
+        [System.Diagnostics.DebuggerNonUserCode]
+        private void CtorOpened(Object target, IntPtr methodPtr, IntPtr shuffleThunk)
+        {
+            this._target = this;
+            this._methodPtr = shuffleThunk;
+            this._methodPtrAux = methodPtr;
+        }
+
+        [System.Diagnostics.DebuggerNonUserCode]
+        private void CtorVirtualDispatch(Object target, IntPtr methodPtr, IntPtr shuffleThunk)
+        {
+            this._target = this;
+            this._methodPtr = shuffleThunk;
+            this._methodPtrAux = GetCallStub(methodPtr);
+        }
+
+        [System.Diagnostics.DebuggerNonUserCode]
+        private void CtorCollectibleClosedStatic(Object target, IntPtr methodPtr, IntPtr gchandle)
+        {
+            this._target = target;
+            this._methodPtr = methodPtr;
+            this._methodBase = System.Runtime.InteropServices.GCHandle.InternalGet(gchandle);
+        }
+
+        [System.Diagnostics.DebuggerNonUserCode]
+        private void CtorCollectibleOpened(Object target, IntPtr methodPtr, IntPtr shuffleThunk, IntPtr gchandle)
+        {
+            this._target = this;
+            this._methodPtr = shuffleThunk;
+            this._methodPtrAux = methodPtr;
+            this._methodBase = System.Runtime.InteropServices.GCHandle.InternalGet(gchandle);
+        }
+
+        [System.Diagnostics.DebuggerNonUserCode]
+        private void CtorCollectibleVirtualDispatch(Object target, IntPtr methodPtr, IntPtr shuffleThunk, IntPtr gchandle)
+        {
+            this._target = this;
+            this._methodPtr = shuffleThunk;
+            this._methodPtrAux = GetCallStub(methodPtr);
+            this._methodBase = System.Runtime.InteropServices.GCHandle.InternalGet(gchandle);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Number.CoreCLR.cs b/src/System.Private.CoreLib/src/System/Number.CoreCLR.cs
new file mode 100644
index 0000000000..e14db02762
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Number.CoreCLR.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+    internal static partial class Number
+    {
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern void DoubleToNumber(double value, int precision, ref NumberBuffer number);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern double NumberToDouble(ref NumberBuffer number);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern bool NumberBufferToDecimal(ref NumberBuffer number, ref decimal value);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Numerics/Hashing/HashHelpers.cs b/src/System.Private.CoreLib/src/System/Numerics/Hashing/HashHelpers.cs
new file mode 100644
index 0000000000..f017309a90
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Numerics/Hashing/HashHelpers.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Numerics.Hashing
+{
+    // Please change the corresponding file in corefx if this is changed.
+
+    internal static class HashHelpers
+    {
+        public static readonly int RandomSeed = new Random().Next(Int32.MinValue, Int32.MaxValue);
+
+        public static int Combine(int h1, int h2)
+        {
+            // RyuJIT optimizes this to use the ROL instruction
+            // Related GitHub pull request: dotnet/coreclr#1830
+            uint rol5 = ((uint)h1 << 5) | ((uint)h1 >> 27);
+            return ((int)rol5 + h1) ^ h2;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Object.cs b/src/System.Private.CoreLib/src/System/Object.cs
new file mode 100644
index 0000000000..8d74aaeed0
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Object.cs
@@ -0,0 +1,224 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Object is the root class for all CLR objects.  This class
+** defines only the basics.
+**
+** 
+===========================================================*/
+
+namespace System
+{
+    using System;
+    using System.Diagnostics;
+    using System.Runtime;
+    using System.Runtime.InteropServices;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.ConstrainedExecution;
+    using System.Runtime.Versioning;
+    using CultureInfo = System.Globalization.CultureInfo;
+    using FieldInfo = System.Reflection.FieldInfo;
+    using BindingFlags = System.Reflection.BindingFlags;
+
+    // The Object is the root class for all object in the CLR System. Object 
+    // is the super class for all other CLR objects and provide a set of methods and low level
+    // services to subclasses.  These services include object synchronization and support for clone
+    // operations.
+    // 
+    //This class contains no data and does not need to be serializable 
+    [Serializable]
+    [ClassInterface(ClassInterfaceType.AutoDual)]
+    [System.Runtime.InteropServices.ComVisible(true)]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class Object
+    {
+        // Creates a new instance of an Object.
+        [System.Runtime.Versioning.NonVersionable]
+        public Object()
+        {
+        }
+
+        // Returns a String which represents the object instance.  The default
+        // for an object is to return the fully qualified name of the class.
+        // 
+        public virtual String ToString()
+        {
+            return GetType().ToString();
+        }
+
+        // Returns a boolean indicating if the passed in object obj is 
+        // Equal to this.  Equality is defined as object equality for reference
+        // types and bitwise equality for value types using a loader trick to
+        // replace Equals with EqualsValue for value types).
+        // 
+
+        public virtual bool Equals(Object obj)
+        {
+            return RuntimeHelpers.Equals(this, obj);
+        }
+
+        public static bool Equals(Object objA, Object objB)
+        {
+            if (objA == objB)
+            {
+                return true;
+            }
+            if (objA == null || objB == null)
+            {
+                return false;
+            }
+            return objA.Equals(objB);
+        }
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static bool ReferenceEquals(Object objA, Object objB)
+        {
+            return objA == objB;
+        }
+
+        // GetHashCode is intended to serve as a hash function for this object.
+        // Based on the contents of the object, the hash function will return a suitable
+        // value with a relatively random distribution over the various inputs.
+        //
+        // The default implementation returns the sync block index for this instance.
+        // Calling it on the same object multiple times will return the same value, so
+        // it will technically meet the needs of a hash function, but it's less than ideal.
+        // Objects (& especially value classes) should override this method.
+        // 
+        public virtual int GetHashCode()
+        {
+            return RuntimeHelpers.GetHashCode(this);
+        }
+
+        // Returns a Type object which represent this object instance.
+        // 
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern Type GetType();
+
+        // Allow an object to free resources before the object is reclaimed by the GC.
+        // 
+        [System.Runtime.Versioning.NonVersionable]
+        ~Object()
+        {
+        }
+
+        // Returns a new object instance that is a memberwise copy of this 
+        // object.  This is always a shallow copy of the instance. The method is protected
+        // so that other object may only call this method on themselves.  It is entended to
+        // support the ICloneable interface.
+        // 
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        protected extern Object MemberwiseClone();
+
+
+        // Sets the value specified in the variant on the field
+        // 
+        private void FieldSetter(String typeName, String fieldName, Object val)
+        {
+            Debug.Assert(typeName != null);
+            Debug.Assert(fieldName != null);
+
+            // Extract the field info object
+            FieldInfo fldInfo = GetFieldInfo(typeName, fieldName);
+
+            if (fldInfo.IsInitOnly)
+                throw new FieldAccessException(SR.FieldAccess_InitOnly);
+
+            // Make sure that the value is compatible with the type
+            // of field
+            Type pt = fldInfo.FieldType;
+            if (pt.IsByRef)
+            {
+                pt = pt.GetElementType();
+            }
+
+            if (!pt.IsInstanceOfType(val))
+            {
+                val = Convert.ChangeType(val, pt, CultureInfo.InvariantCulture);
+            }
+
+            // Set the value
+            fldInfo.SetValue(this, val);
+        }
+
+        // Gets the value specified in the variant on the field
+        // 
+        private void FieldGetter(String typeName, String fieldName, ref Object val)
+        {
+            Debug.Assert(typeName != null);
+            Debug.Assert(fieldName != null);
+
+            // Extract the field info object
+            FieldInfo fldInfo = GetFieldInfo(typeName, fieldName);
+
+            // Get the value
+            val = fldInfo.GetValue(this);
+        }
+
+        // Gets the field info object given the type name and field name.
+        // 
+        private FieldInfo GetFieldInfo(String typeName, String fieldName)
+        {
+            Debug.Assert(typeName != null);
+            Debug.Assert(fieldName != null);
+
+            Type t = GetType();
+            while (null != t)
+            {
+                if (t.FullName.Equals(typeName))
+                {
+                    break;
+                }
+
+                t = t.BaseType;
+            }
+
+            if (null == t)
+            {
+                throw new ArgumentException();
+            }
+
+            FieldInfo fldInfo = t.GetField(fieldName, BindingFlags.Public |
+                                                      BindingFlags.Instance |
+                                                      BindingFlags.IgnoreCase);
+            if (null == fldInfo)
+            {
+                throw new ArgumentException();
+            }
+
+            return fldInfo;
+        }
+    }
+
+
+    // Internal methodtable used to instantiate the "canonical" methodtable for generic instantiations.
+    // The name "__Canon" will never been seen by users but it will appear a lot in debugger stack traces
+    // involving generics so it is kept deliberately short as to avoid being a nuisance.
+
+    [ClassInterface(ClassInterfaceType.AutoDual)]
+    [System.Runtime.InteropServices.ComVisible(true)]
+    internal class __Canon
+    {
+    }
+
+    // This class is used to define the name of the base class library
+    internal class CoreLib
+    {
+        public const string Name = "System.Private.CoreLib";
+
+        public static string FixupCoreLibName(string strToFixup)
+        {
+            if (!String.IsNullOrEmpty(strToFixup))
+            {
+                strToFixup = strToFixup.Replace("mscorlib", System.CoreLib.Name);
+            }
+
+            return strToFixup;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/OleAutBinder.cs b/src/System.Private.CoreLib/src/System/OleAutBinder.cs
new file mode 100644
index 0000000000..3a9f03c5f0
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/OleAutBinder.cs
@@ -0,0 +1,91 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// This class represents the Ole Automation binder.
+
+// #define DISPLAY_DEBUG_INFO
+
+namespace System
+{
+    using System;
+    using System.Runtime.InteropServices;
+    using System.Reflection;
+    using Microsoft.Win32;
+    using CultureInfo = System.Globalization.CultureInfo;
+
+    // Made serializable in anticipation of this class eventually having state.
+    internal class OleAutBinder : DefaultBinder
+    {
+        // ChangeType
+        // This binder uses OLEAUT to change the type of the variant.
+        public override Object ChangeType(Object value, Type type, CultureInfo cultureInfo)
+        {
+            Variant myValue = new Variant(value);
+            if (cultureInfo == null)
+                cultureInfo = CultureInfo.CurrentCulture;
+
+#if DISPLAY_DEBUG_INFO
+            Console.WriteLine("In OleAutBinder::ChangeType converting variant of type: {0} to type: {1}", myValue.VariantType, type.Name);
+#endif
+
+            if (type.IsByRef)
+            {
+#if DISPLAY_DEBUG_INFO
+                Console.WriteLine("Stripping byref from the type to convert to.");
+#endif
+                type = type.GetElementType();
+            }
+
+            // If we are trying to convert from an object to another type then we don't
+            // need the OLEAUT change type, we can just use the normal COM+ mechanisms.
+            if (!type.IsPrimitive && type.IsInstanceOfType(value))
+            {
+#if DISPLAY_DEBUG_INFO
+                Console.WriteLine("Source variant can be assigned to destination type");
+#endif
+                return value;
+            }
+
+            Type srcType = value.GetType();
+
+            // Handle converting primitives to enums.
+            if (type.IsEnum && srcType.IsPrimitive)
+            {
+#if DISPLAY_DEBUG_INFO
+                Console.WriteLine("Converting primitive to enum");
+#endif
+                return Enum.Parse(type, value.ToString());
+            }
+
+            // Use the OA variant lib to convert primitive types.
+            try
+            {
+#if DISPLAY_DEBUG_INFO      
+                Console.WriteLine("Using OAVariantLib.ChangeType() to do the conversion");
+#endif      
+                // Specify the LocalBool flag to have BOOL values converted to local language rather
+                // than 0 or -1.
+                Object RetObj = OAVariantLib.ChangeType(myValue, type, OAVariantLib.LocalBool, cultureInfo).ToObject();
+
+#if DISPLAY_DEBUG_INFO      
+                Console.WriteLine("Object returned from ChangeType is of type: " + RetObj.GetType().Name);
+#endif
+
+                return RetObj;
+            }
+#if DISPLAY_DEBUG_INFO      
+            catch(NotSupportedException e)
+#else
+            catch (NotSupportedException)
+#endif      
+            {
+#if DISPLAY_DEBUG_INFO      
+                Console.Write("Exception thrown: ");
+                Console.WriteLine(e);
+#endif      
+                throw new COMException(SR.Interop_COM_TypeMismatch, unchecked((int)0x80020005));
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/OutOfMemoryException.cs b/src/System.Private.CoreLib/src/System/OutOfMemoryException.cs
new file mode 100644
index 0000000000..33cf6399e4
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/OutOfMemoryException.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: The exception class for OOM.
+**
+**
+=============================================================================*/
+
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class OutOfMemoryException : SystemException
+    {
+        public OutOfMemoryException()
+            : base(GetMessageFromNativeResources(ExceptionMessageKind.OutOfMemory))
+        {
+            HResult = HResults.COR_E_OUTOFMEMORY;
+        }
+
+        public OutOfMemoryException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_OUTOFMEMORY;
+        }
+
+        public OutOfMemoryException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_OUTOFMEMORY;
+        }
+
+        protected OutOfMemoryException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/PinnableBufferCache.cs b/src/System.Private.CoreLib/src/System/PinnableBufferCache.cs
new file mode 100644
index 0000000000..1bfd2cf07b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/PinnableBufferCache.cs
@@ -0,0 +1,445 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+#define ENABLE
+#define MINBUFFERS
+
+using System;
+using System.Runtime.InteropServices;
+using System.Runtime.ConstrainedExecution;
+using System.Collections.Generic;
+using System.Collections.Concurrent;
+using System.Threading;
+using System.Runtime.CompilerServices;
+using System.Diagnostics;
+
+#if PINNABLEBUFFERCACHE_MSCORLIB
+namespace System.Threading
+#else
+namespace System
+#endif
+{
+    internal sealed class PinnableBufferCache
+    {
+        /// <summary>
+        /// Create a PinnableBufferCache that works on any object (it is intended for OverlappedData)
+        /// This is only used in mscorlib.
+        /// </summary>
+        internal PinnableBufferCache(string cacheName, Func<object> factory)
+        {
+            m_NotGen2 = new List<object>(DefaultNumberOfBuffers);
+            m_factory = factory;
+#if ENABLE
+            // Check to see if we should disable the cache.
+            string envVarName = "PinnableBufferCache_" + cacheName + "_Disabled";
+            try
+            {
+                string envVar = Environment.GetEnvironmentVariable(envVarName);
+                if (envVar != null)
+                {
+                    PinnableBufferCacheEventSource.Log.DebugMessage("Creating " + cacheName + " PinnableBufferCacheDisabled=" + envVar);
+                    int index = envVar.IndexOf(cacheName, StringComparison.OrdinalIgnoreCase);
+                    if (0 <= index)
+                    {
+                        // The cache is disabled because we haven't set the cache name.
+                        PinnableBufferCacheEventSource.Log.DebugMessage("Disabling " + cacheName);
+                        return;
+                    }
+                }
+            }
+            catch
+            {
+                // Ignore failures when reading the environment variable.
+            }
+#endif
+#if MINBUFFERS
+            // Allow the environment to specify a minimum buffer count.
+            string minEnvVarName = "PinnableBufferCache_" + cacheName + "_MinCount";
+            try
+            {
+                string minEnvVar = Environment.GetEnvironmentVariable(minEnvVarName);
+                if (minEnvVar != null)
+                {
+                    if (int.TryParse(minEnvVar, out m_minBufferCount))
+                        CreateNewBuffers();
+                }
+            }
+            catch
+            {
+                // Ignore failures when reading the environment variable.
+            }
+#endif
+
+            PinnableBufferCacheEventSource.Log.Create(cacheName);
+            m_CacheName = cacheName;
+        }
+
+        /// <summary>
+        /// Get a object from the buffer manager.  If no buffers exist, allocate a new one.
+        /// </summary>
+        internal object Allocate()
+        {
+#if ENABLE
+            // Check to see whether or not the cache is disabled.
+            if (m_CacheName == null)
+                return m_factory();
+#endif
+            // Fast path, get it from our Gen2 aged m_FreeList.  
+            object returnBuffer;
+            if (!m_FreeList.TryPop(out returnBuffer))
+                Restock(out returnBuffer);
+
+            // Computing free count is expensive enough that we don't want to compute it unless logging is on.
+            if (PinnableBufferCacheEventSource.Log.IsEnabled())
+            {
+                int numAllocCalls = Interlocked.Increment(ref m_numAllocCalls);
+                if (numAllocCalls >= 1024)
+                {
+                    lock (this)
+                    {
+                        int previousNumAllocCalls = Interlocked.Exchange(ref m_numAllocCalls, 0);
+                        if (previousNumAllocCalls >= 1024)
+                        {
+                            int nonGen2Count = 0;
+                            foreach (object o in m_FreeList)
+                            {
+                                if (GC.GetGeneration(o) < GC.MaxGeneration)
+                                {
+                                    nonGen2Count++;
+                                }
+                            }
+
+                            PinnableBufferCacheEventSource.Log.WalkFreeListResult(m_CacheName, m_FreeList.Count, nonGen2Count);
+                        }
+                    }
+                }
+
+                PinnableBufferCacheEventSource.Log.AllocateBuffer(m_CacheName, PinnableBufferCacheEventSource.AddressOf(returnBuffer), returnBuffer.GetHashCode(), GC.GetGeneration(returnBuffer), m_FreeList.Count);
+            }
+            return returnBuffer;
+        }
+
+        /// <summary>
+        /// Return a buffer back to the buffer manager.
+        /// </summary>
+        internal void Free(object buffer)
+        {
+#if ENABLE
+            // Check to see whether or not the cache is disabled.
+            if (m_CacheName == null)
+                return;
+#endif
+            if (PinnableBufferCacheEventSource.Log.IsEnabled())
+                PinnableBufferCacheEventSource.Log.FreeBuffer(m_CacheName, PinnableBufferCacheEventSource.AddressOf(buffer), buffer.GetHashCode(), m_FreeList.Count);
+
+
+            // After we've done 3 gen1 GCs, assume that all buffers have aged into gen2 on the free path.
+            if ((m_gen1CountAtLastRestock + 3) > GC.CollectionCount(GC.MaxGeneration - 1))
+            {
+                lock (this)
+                {
+                    if (GC.GetGeneration(buffer) < GC.MaxGeneration)
+                    {
+                        // The buffer is not aged, so put it in the non-aged free list.
+                        m_moreThanFreeListNeeded = true;
+                        PinnableBufferCacheEventSource.Log.FreeBufferStillTooYoung(m_CacheName, m_NotGen2.Count);
+                        m_NotGen2.Add(buffer);
+                        m_gen1CountAtLastRestock = GC.CollectionCount(GC.MaxGeneration - 1);
+                        return;
+                    }
+                }
+            }
+
+            // If we discovered that it is indeed Gen2, great, put it in the Gen2 list.  
+            m_FreeList.Push(buffer);
+        }
+
+        #region Private
+
+        /// <summary>
+        /// Called when we don't have any buffers in our free list to give out.    
+        /// </summary>
+        /// <returns></returns>
+        private void Restock(out object returnBuffer)
+        {
+            lock (this)
+            {
+                // Try again after getting the lock as another thread could have just filled the free list.  If we don't check
+                // then we unnecessarily grab a new set of buffers because we think we are out.     
+                if (m_FreeList.TryPop(out returnBuffer))
+                    return;
+
+                // Lazy init, Ask that TrimFreeListIfNeeded be called on every Gen 2 GC.  
+                if (m_restockSize == 0)
+                    Gen2GcCallback.Register(Gen2GcCallbackFunc, this);
+
+                // Indicate to the trimming policy that the free list is insufficent.   
+                m_moreThanFreeListNeeded = true;
+                PinnableBufferCacheEventSource.Log.AllocateBufferFreeListEmpty(m_CacheName, m_NotGen2.Count);
+
+                // Get more buffers if needed.
+                if (m_NotGen2.Count == 0)
+                    CreateNewBuffers();
+
+                // We have no buffers in the aged freelist, so get one from the newer list.   Try to pick the best one.
+                // Debug.Assert(m_NotGen2.Count != 0);
+                int idx = m_NotGen2.Count - 1;
+                if (GC.GetGeneration(m_NotGen2[idx]) < GC.MaxGeneration && GC.GetGeneration(m_NotGen2[0]) == GC.MaxGeneration)
+                    idx = 0;
+                returnBuffer = m_NotGen2[idx];
+                m_NotGen2.RemoveAt(idx);
+
+                // Remember any sub-optimial buffer so we don't put it on the free list when it gets freed.   
+                if (PinnableBufferCacheEventSource.Log.IsEnabled() && GC.GetGeneration(returnBuffer) < GC.MaxGeneration)
+                {
+                    PinnableBufferCacheEventSource.Log.AllocateBufferFromNotGen2(m_CacheName, m_NotGen2.Count);
+                }
+
+                // If we have a Gen1 collection, then everything on m_NotGen2 should have aged.  Move them to the m_Free list.  
+                if (!AgePendingBuffers())
+                {
+                    // Before we could age at set of buffers, we have handed out half of them.
+                    // This implies we should be proactive about allocating more (since we will trim them if we over-allocate).  
+                    if (m_NotGen2.Count == m_restockSize / 2)
+                    {
+                        PinnableBufferCacheEventSource.Log.DebugMessage("Proactively adding more buffers to aging pool");
+                        CreateNewBuffers();
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// See if we can promote the buffers to the free list.  Returns true if successful. 
+        /// </summary>
+        private bool AgePendingBuffers()
+        {
+            if (m_gen1CountAtLastRestock < GC.CollectionCount(GC.MaxGeneration - 1))
+            {
+                // Allocate a temp list of buffers that are not actually in gen2, and swap it in once
+                // we're done scanning all buffers.
+                int promotedCount = 0;
+                List<object> notInGen2 = new List<object>();
+                PinnableBufferCacheEventSource.Log.AllocateBufferAged(m_CacheName, m_NotGen2.Count);
+                for (int i = 0; i < m_NotGen2.Count; i++)
+                {
+                    // We actually check every object to ensure that we aren't putting non-aged buffers into the free list.
+                    object currentBuffer = m_NotGen2[i];
+                    if (GC.GetGeneration(currentBuffer) >= GC.MaxGeneration)
+                    {
+                        m_FreeList.Push(currentBuffer);
+                        promotedCount++;
+                    }
+                    else
+                    {
+                        notInGen2.Add(currentBuffer);
+                    }
+                }
+                PinnableBufferCacheEventSource.Log.AgePendingBuffersResults(m_CacheName, promotedCount, notInGen2.Count);
+                m_NotGen2 = notInGen2;
+
+                return true;
+            }
+            return false;
+        }
+
+        /// <summary>
+        /// Generates some buffers to age into Gen2.
+        /// </summary>
+        private void CreateNewBuffers()
+        {
+            // We choose a very modest number of buffers initially because for the client case.  This is often enough.
+            if (m_restockSize == 0)
+                m_restockSize = 4;
+            else if (m_restockSize < DefaultNumberOfBuffers)
+                m_restockSize = DefaultNumberOfBuffers;
+            else if (m_restockSize < 256)
+                m_restockSize = m_restockSize * 2;                // Grow quickly at small sizes
+            else if (m_restockSize < 4096)
+                m_restockSize = m_restockSize * 3 / 2;            // Less agressively at large ones
+            else
+                m_restockSize = 4096;                             // Cap how agressive we are
+
+            // Ensure we hit our minimums
+            if (m_minBufferCount > m_buffersUnderManagement)
+                m_restockSize = Math.Max(m_restockSize, m_minBufferCount - m_buffersUnderManagement);
+
+            PinnableBufferCacheEventSource.Log.AllocateBufferCreatingNewBuffers(m_CacheName, m_buffersUnderManagement, m_restockSize);
+            for (int i = 0; i < m_restockSize; i++)
+            {
+                // Make a new buffer.
+                object newBuffer = m_factory();
+
+                // Create space between the objects.  We do this because otherwise it forms a single plug (group of objects)
+                // and the GC pins the entire plug making them NOT move to Gen1 and Gen2.   by putting space between them
+                // we ensure that object get a chance to move independently (even if some are pinned).  
+                var dummyObject = new object();
+                m_NotGen2.Add(newBuffer);
+            }
+            m_buffersUnderManagement += m_restockSize;
+            m_gen1CountAtLastRestock = GC.CollectionCount(GC.MaxGeneration - 1);
+        }
+
+        /// <summary>
+        /// This is the static function that is called from the gen2 GC callback.
+        /// The input object is the cache itself.
+        /// NOTE: The reason that we make this functionstatic and take the cache as a parameter is that
+        /// otherwise, we root the cache to the Gen2GcCallback object, and leak the cache even when
+        /// the application no longer needs it.
+        /// </summary>
+        private static bool Gen2GcCallbackFunc(object targetObj)
+        {
+            return ((PinnableBufferCache)(targetObj)).TrimFreeListIfNeeded();
+        }
+
+        /// <summary>
+        /// This is called on every gen2 GC to see if we need to trim the free list.
+        /// NOTE: DO NOT CALL THIS DIRECTLY FROM THE GEN2GCCALLBACK.  INSTEAD CALL IT VIA A STATIC FUNCTION (SEE ABOVE).
+        /// If you register a non-static function as a callback, then this object will be leaked.
+        /// </summary>
+        private bool TrimFreeListIfNeeded()
+        {
+            int curMSec = Environment.TickCount;
+            int deltaMSec = curMSec - m_msecNoUseBeyondFreeListSinceThisTime;
+            PinnableBufferCacheEventSource.Log.TrimCheck(m_CacheName, m_buffersUnderManagement, m_moreThanFreeListNeeded, deltaMSec);
+
+            // If we needed more than just the set of aged buffers since the last time we were called,
+            // we obviously should not be trimming any memory, so do nothing except reset the flag 
+            if (m_moreThanFreeListNeeded)
+            {
+                m_moreThanFreeListNeeded = false;
+                m_trimmingExperimentInProgress = false;
+                m_msecNoUseBeyondFreeListSinceThisTime = curMSec;
+                return true;
+            }
+
+            // We require a minimum amount of clock time to pass  (10 seconds) before we trim.  Ideally this time
+            // is larger than the typical buffer hold time.  
+            if (0 <= deltaMSec && deltaMSec < 10000)
+                return true;
+
+            // If we got here we have spend the last few second without needing to lengthen the free list.   Thus
+            // we have 'enough' buffers, but maybe we have too many. 
+            // See if we can trim
+            lock (this)
+            {
+                // Hit a race, try again later.  
+                if (m_moreThanFreeListNeeded)
+                {
+                    m_moreThanFreeListNeeded = false;
+                    m_trimmingExperimentInProgress = false;
+                    m_msecNoUseBeyondFreeListSinceThisTime = curMSec;
+                    return true;
+                }
+
+                var freeCount = m_FreeList.Count;   // This is expensive to fetch, do it once.
+
+                // If there is something in m_NotGen2 it was not used for the last few seconds, it is trimable.  
+                if (m_NotGen2.Count > 0)
+                {
+                    // If we are not performing an experiment and we have stuff that is waiting to go into the
+                    // free list but has not made it there, it could be becasue the 'slow path' of restocking
+                    // has not happened, so force this (which should flush the list) and start over.  
+                    if (!m_trimmingExperimentInProgress)
+                    {
+                        PinnableBufferCacheEventSource.Log.TrimFlush(m_CacheName, m_buffersUnderManagement, freeCount, m_NotGen2.Count);
+                        AgePendingBuffers();
+                        m_trimmingExperimentInProgress = true;
+                        return true;
+                    }
+
+                    PinnableBufferCacheEventSource.Log.TrimFree(m_CacheName, m_buffersUnderManagement, freeCount, m_NotGen2.Count);
+                    m_buffersUnderManagement -= m_NotGen2.Count;
+
+                    // Possibly revise the restocking down.  We don't want to grow agressively if we are trimming.  
+                    var newRestockSize = m_buffersUnderManagement / 4;
+                    if (newRestockSize < m_restockSize)
+                        m_restockSize = Math.Max(newRestockSize, DefaultNumberOfBuffers);
+
+                    m_NotGen2.Clear();
+                    m_trimmingExperimentInProgress = false;
+                    return true;
+                }
+
+                // Set up an experiment where we use 25% less buffers in our free list.   We put them in 
+                // m_NotGen2, and if they are needed they will be put back in the free list again.  
+                var trimSize = freeCount / 4 + 1;
+
+                // We are OK with a 15% overhead, do nothing in that case.  
+                if (freeCount * 15 <= m_buffersUnderManagement || m_buffersUnderManagement - trimSize <= m_minBufferCount)
+                {
+                    PinnableBufferCacheEventSource.Log.TrimFreeSizeOK(m_CacheName, m_buffersUnderManagement, freeCount);
+                    return true;
+                }
+
+                // Move buffers from the free list back to the non-aged list.  If we don't use them by next time, then we'll consider trimming them.
+                PinnableBufferCacheEventSource.Log.TrimExperiment(m_CacheName, m_buffersUnderManagement, freeCount, trimSize);
+                object buffer;
+                for (int i = 0; i < trimSize; i++)
+                {
+                    if (m_FreeList.TryPop(out buffer))
+                        m_NotGen2.Add(buffer);
+                }
+                m_msecNoUseBeyondFreeListSinceThisTime = curMSec;
+                m_trimmingExperimentInProgress = true;
+            }
+
+            // Indicate that we want to be called back on the next Gen 2 GC.  
+            return true;
+        }
+
+        private const int DefaultNumberOfBuffers = 16;
+        private string m_CacheName;
+        private Func<object> m_factory;
+
+        /// <summary>
+        /// Contains 'good' buffers to reuse.  They are guaranteed to be Gen 2 ENFORCED!
+        /// </summary>
+        private ConcurrentStack<object> m_FreeList = new ConcurrentStack<object>();
+        /// <summary>
+        /// Contains buffers that are not gen 2 and thus we do not wish to give out unless we have to.
+        /// To implement trimming we sometimes put aged buffers in here as a place to 'park' them
+        /// before true deletion.  
+        /// </summary>
+        private List<object> m_NotGen2;
+        /// <summary>
+        /// What was the gen 1 count the last time re restocked?  If it is now greater, then
+        /// we know that all objects are in Gen 2 so we don't have to check.  Should be updated
+        /// every time something gets added to the m_NotGen2 list.
+        /// </summary>
+        private int m_gen1CountAtLastRestock;
+
+        /// <summary>
+        /// Used to ensure we have a minimum time between trimmings.  
+        /// </summary>
+        private int m_msecNoUseBeyondFreeListSinceThisTime;
+        /// <summary>
+        /// To trim, we remove things from the free list (which is Gen 2) and see if we 'hit bottom'
+        /// This flag indicates that we hit bottom (we really needed a bigger free list).
+        /// </summary>
+        private bool m_moreThanFreeListNeeded;
+        /// <summary>
+        /// The total number of buffers that this cache has ever allocated.
+        /// Used in trimming heuristics. 
+        /// </summary>
+        private int m_buffersUnderManagement;
+        /// <summary>
+        /// The number of buffers we added the last time we restocked.
+        /// </summary>
+        private int m_restockSize;
+        /// <summary>
+        /// Did we put some buffers into m_NotGen2 to see if we can trim?
+        /// </summary>
+        private bool m_trimmingExperimentInProgress;
+        /// <summary>
+        /// A forced minimum number of buffers.
+        /// </summary>
+        private int m_minBufferCount;
+        /// <summary>
+        /// The number of calls to Allocate.
+        /// </summary>
+        private int m_numAllocCalls;
+
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/PinnableBufferCacheEventSource.cs b/src/System.Private.CoreLib/src/System/PinnableBufferCacheEventSource.cs
new file mode 100644
index 0000000000..7d382f3c12
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/PinnableBufferCacheEventSource.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics.Tracing;
+
+namespace System
+{
+    internal sealed class PinnableBufferCacheEventSource
+    {
+        public static readonly PinnableBufferCacheEventSource Log = new PinnableBufferCacheEventSource();
+
+        public bool IsEnabled() { return false; }
+        public void DebugMessage(string message) { }
+        public void Create(string cacheName) { }
+        public void AllocateBuffer(string cacheName, ulong objectId, int objectHash, int objectGen, int freeCountAfter) { }
+        public void AllocateBufferFromNotGen2(string cacheName, int notGen2CountAfter) { }
+        public void AllocateBufferCreatingNewBuffers(string cacheName, int totalBuffsBefore, int objectCount) { }
+        public void AllocateBufferAged(string cacheName, int agedCount) { }
+        public void AllocateBufferFreeListEmpty(string cacheName, int notGen2CountBefore) { }
+        public void FreeBuffer(string cacheName, ulong objectId, int objectHash, int freeCountBefore) { }
+        public void FreeBufferStillTooYoung(string cacheName, int notGen2CountBefore) { }
+        public void TrimCheck(string cacheName, int totalBuffs, bool neededMoreThanFreeList, int deltaMSec) { }
+        public void TrimFree(string cacheName, int totalBuffs, int freeListCount, int toBeFreed) { }
+        public void TrimExperiment(string cacheName, int totalBuffs, int freeListCount, int numTrimTrial) { }
+        public void TrimFreeSizeOK(string cacheName, int totalBuffs, int freeListCount) { }
+        public void TrimFlush(string cacheName, int totalBuffs, int freeListCount, int notGen2CountBefore) { }
+        public void AgePendingBuffersResults(string cacheName, int promotedToFreeListCount, int heldBackCount) { }
+        public void WalkFreeListResult(string cacheName, int freeListCount, int gen0BuffersInFreeList) { }
+
+        internal static ulong AddressOf(object obj)
+        {
+            return 0;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Assembly.CoreCLR.cs b/src/System.Private.CoreLib/src/System/Reflection/Assembly.CoreCLR.cs
new file mode 100644
index 0000000000..0931e3ccdc
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Assembly.CoreCLR.cs
@@ -0,0 +1,234 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.IO;
+using System.Configuration.Assemblies;
+using StackCrawlMark = System.Threading.StackCrawlMark;
+using System.Runtime.Serialization;
+using System.Runtime.Loader;
+
+namespace System.Reflection
+{
+    public abstract partial class Assembly : ICustomAttributeProvider, ISerializable
+    {
+        private static volatile bool s_LoadFromResolveHandlerSetup = false;
+        private static object s_syncRootLoadFrom = new object();
+        private static List<string> s_LoadFromAssemblyList = new List<string>();
+        private static object s_syncLoadFromAssemblyList = new object();
+
+        private static Assembly LoadFromResolveHandler(object sender, ResolveEventArgs args)
+        {
+            Assembly requestingAssembly = args.RequestingAssembly;
+            if (requestingAssembly == null)
+            {
+                return null;
+            }
+
+            // Requesting assembly for LoadFrom is always loaded in defaultContext - proceed only if that
+            // is the case.
+            if (AssemblyLoadContext.Default != AssemblyLoadContext.GetLoadContext(requestingAssembly))
+                return null;
+
+            // Get the path where requesting assembly lives and check if it is in the list
+            // of assemblies for which LoadFrom was invoked.
+            bool fRequestorLoadedViaLoadFrom = false;
+            string requestorPath = Path.GetFullPath(requestingAssembly.Location);
+            if (string.IsNullOrEmpty(requestorPath))
+                return null;
+
+            lock(s_syncLoadFromAssemblyList)
+            {
+                fRequestorLoadedViaLoadFrom = s_LoadFromAssemblyList.Contains(requestorPath);
+            }
+            
+            // If the requestor assembly was not loaded using LoadFrom, exit.
+            if (!fRequestorLoadedViaLoadFrom)
+                return null;
+
+            // Requestor assembly was loaded using loadFrom, so look for its dependencies
+            // in the same folder as it.
+            // Form the name of the assembly using the path of the assembly that requested its load.
+            AssemblyName requestedAssemblyName = new AssemblyName(args.Name);
+            string requestedAssemblyPath = Path.Combine(Path.GetDirectoryName(requestorPath), requestedAssemblyName.Name+".dll");
+
+            // Load the dependency via LoadFrom so that it goes through the same path of being in the LoadFrom list.
+            Assembly resolvedAssembly = null;
+
+            try
+            {
+                resolvedAssembly = Assembly.LoadFrom(requestedAssemblyPath);
+            }
+            catch(FileNotFoundException)
+            {
+                // Catch FileNotFoundException when attempting to resolve assemblies via this handler to account for missing assemblies.
+                resolvedAssembly = null;
+            }
+
+            return resolvedAssembly;
+        }
+
+        public static Assembly LoadFrom(String assemblyFile)
+        {
+            if (assemblyFile == null)
+                throw new ArgumentNullException(nameof(assemblyFile));
+            
+            string fullPath = Path.GetFullPath(assemblyFile);
+
+            if (!s_LoadFromResolveHandlerSetup)
+            {
+                lock (s_syncRootLoadFrom)
+                {
+                    if (!s_LoadFromResolveHandlerSetup)
+                    {
+                        AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(LoadFromResolveHandler);
+                        s_LoadFromResolveHandlerSetup = true;
+                    }
+                }
+            }
+
+            // Add the path to the LoadFrom path list which we will consult
+            // before handling the resolves in our handler.
+            lock(s_syncLoadFromAssemblyList)
+            {
+                if (!s_LoadFromAssemblyList.Contains(fullPath))
+                {
+                    s_LoadFromAssemblyList.Add(fullPath);
+                }
+            }
+
+            return AssemblyLoadContext.Default.LoadFromAssemblyPath(fullPath);
+        }
+
+        public static Assembly LoadFrom(String assemblyFile,
+                                        byte[] hashValue,
+                                        AssemblyHashAlgorithm hashAlgorithm)
+        {
+            throw new NotSupportedException(SR.NotSupported_AssemblyLoadFromHash);
+        }
+
+        // Locate an assembly by the long form of the assembly name. 
+        // eg. "Toolbox.dll, version=1.1.10.1220, locale=en, publickey=1234567890123456789012345678901234567890"
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public static Assembly Load(String assemblyString)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return RuntimeAssembly.InternalLoad(assemblyString, ref stackMark);
+        }
+
+        // Locate an assembly by its name. The name can be strong or
+        // weak. The assembly is loaded into the domain of the caller.
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public static Assembly Load(AssemblyName assemblyRef)
+        {
+            AssemblyName modifiedAssemblyRef = null;
+            if (assemblyRef != null && assemblyRef.CodeBase != null)
+            {
+                modifiedAssemblyRef = (AssemblyName)assemblyRef.Clone();
+                modifiedAssemblyRef.CodeBase = null;
+            }
+            else
+            {
+                modifiedAssemblyRef = assemblyRef;
+            }
+            
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return RuntimeAssembly.InternalLoadAssemblyName(modifiedAssemblyRef, null, ref stackMark, true /*thrownOnFileNotFound*/);
+        }
+
+        // Locate an assembly by its name. The name can be strong or
+        // weak. The assembly is loaded into the domain of the caller.
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        internal static Assembly Load(AssemblyName assemblyRef, IntPtr ptrLoadContextBinder)
+        {
+            AssemblyName modifiedAssemblyRef = null;
+            if (assemblyRef != null && assemblyRef.CodeBase != null)
+            {
+                modifiedAssemblyRef = (AssemblyName)assemblyRef.Clone();
+                modifiedAssemblyRef.CodeBase = null;
+            }
+            else
+            {
+                modifiedAssemblyRef = assemblyRef;
+            }
+
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return RuntimeAssembly.InternalLoadAssemblyName(modifiedAssemblyRef, null, ref stackMark, true /*thrownOnFileNotFound*/, ptrLoadContextBinder);
+        }
+
+        // Loads the assembly with a COFF based IMAGE containing
+        // an emitted assembly. The assembly is loaded into the domain
+        // of the caller. The second parameter is the raw bytes
+        // representing the symbol store that matches the assembly.
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public static Assembly Load(byte[] rawAssembly,
+                                    byte[] rawSymbolStore)
+        {
+            AppDomain.CheckLoadByteArraySupported();
+
+            if (rawAssembly == null)
+                throw new ArgumentNullException(nameof(rawAssembly));
+            AssemblyLoadContext alc = new IndividualAssemblyLoadContext();
+            MemoryStream assemblyStream = new MemoryStream(rawAssembly);
+            MemoryStream symbolStream = (rawSymbolStore != null) ? new MemoryStream(rawSymbolStore) : null;
+            return alc.LoadFromStream(assemblyStream, symbolStream);
+        }
+
+        private static Dictionary<string, Assembly> s_loadfile = new Dictionary<string, Assembly>();
+
+        public static Assembly LoadFile(String path)
+        {
+            AppDomain.CheckLoadFileSupported();
+
+            Assembly result = null;
+            if (path == null)
+                throw new ArgumentNullException(nameof(path));
+
+            if (PathInternal.IsPartiallyQualified(path))
+            {
+                throw new ArgumentException(SR.Argument_AbsolutePathRequired, nameof(path));
+            }
+
+            string normalizedPath = Path.GetFullPath(path);
+
+            lock (s_loadfile)
+            {
+                if (s_loadfile.TryGetValue(normalizedPath, out result))
+                    return result;
+                AssemblyLoadContext alc = new IndividualAssemblyLoadContext();
+                result = alc.LoadFromAssemblyPath(normalizedPath);
+                s_loadfile.Add(normalizedPath, result);
+            }
+            return result;
+        }
+
+        /*
+         * Get the assembly that the current code is running from.
+         */
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod 
+        public static Assembly GetExecutingAssembly()
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return RuntimeAssembly.GetExecutingAssembly(ref stackMark);
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public static Assembly GetCallingAssembly()
+        {
+            // LookForMyCallersCaller is not guarantee to return the correct stack frame
+            // because of inlining, tail calls, etc. As a result GetCallingAssembly is not 
+            // ganranteed to return the correct result. We should document it as such.
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCallersCaller;
+            return RuntimeAssembly.GetExecutingAssembly(ref stackMark);
+        }
+
+        public static Assembly GetEntryAssembly()
+        {
+            AppDomainManager domainManager = AppDomain.CurrentDomain.DomainManager;
+            if (domainManager == null)
+                domainManager = new AppDomainManager();
+            return domainManager.EntryAssembly;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/AssemblyName.cs b/src/System.Private.CoreLib/src/System/Reflection/AssemblyName.cs
new file mode 100644
index 0000000000..9a6728c6d5
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/AssemblyName.cs
@@ -0,0 +1,661 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+** 
+**
+**
+** Purpose: Used for binding and retrieving info about an assembly
+**
+**
+===========================================================*/
+
+namespace System.Reflection
+{
+    using System;
+    using System.IO;
+    using System.Configuration.Assemblies;
+    using System.Runtime.CompilerServices;
+    using CultureInfo = System.Globalization.CultureInfo;
+    using System.Runtime.Serialization;
+    using System.Runtime.InteropServices;
+    using System.Runtime.Versioning;
+    using System.Text;
+
+    public sealed class AssemblyName : ICloneable, ISerializable, IDeserializationCallback
+    {
+        //
+        // READ ME
+        // If you modify any of these fields, you must also update the 
+        // AssemblyBaseObject structure in object.h
+        //
+        private String _Name;                  // Name
+        private byte[] _PublicKey;
+        private byte[] _PublicKeyToken;
+        private CultureInfo _CultureInfo;
+        private String _CodeBase;              // Potential location to get the file
+        private Version _Version;
+
+        private StrongNameKeyPair _StrongNameKeyPair;
+
+        private SerializationInfo m_siInfo; //A temporary variable which we need during deserialization.
+
+        private byte[] _HashForControl;
+        private AssemblyHashAlgorithm _HashAlgorithm;
+        private AssemblyHashAlgorithm _HashAlgorithmForControl;
+
+        private AssemblyVersionCompatibility _VersionCompatibility;
+        private AssemblyNameFlags _Flags;
+
+        public AssemblyName()
+        {
+            _HashAlgorithm = AssemblyHashAlgorithm.None;
+            _VersionCompatibility = AssemblyVersionCompatibility.SameMachine;
+            _Flags = AssemblyNameFlags.None;
+        }
+
+        // Set and get the name of the assembly. If this is a weak Name
+        // then it optionally contains a site. For strong assembly names, 
+        // the name partitions up the strong name's namespace
+        public String Name
+        {
+            get { return _Name; }
+            set { _Name = value; }
+        }
+
+        public Version Version
+        {
+            get
+            {
+                return _Version;
+            }
+            set
+            {
+                _Version = value;
+            }
+        }
+
+        // Locales, internally the LCID is used for the match.
+        public CultureInfo CultureInfo
+        {
+            get
+            {
+                return _CultureInfo;
+            }
+            set
+            {
+                _CultureInfo = value;
+            }
+        }
+
+        public String CultureName
+        {
+            get
+            {
+                return (_CultureInfo == null) ? null : _CultureInfo.Name;
+            }
+            set
+            {
+                _CultureInfo = (value == null) ? null : new CultureInfo(value);
+            }
+        }
+
+        public String CodeBase
+        {
+            get { return _CodeBase; }
+            set { _CodeBase = value; }
+        }
+
+        public String EscapedCodeBase
+        {
+            get
+            {
+                if (_CodeBase == null)
+                    return null;
+                else
+                    return EscapeCodeBase(_CodeBase);
+            }
+        }
+
+        public ProcessorArchitecture ProcessorArchitecture
+        {
+            get
+            {
+                int x = (((int)_Flags) & 0x70) >> 4;
+                if (x > 5)
+                    x = 0;
+                return (ProcessorArchitecture)x;
+            }
+            set
+            {
+                int x = ((int)value) & 0x07;
+                if (x <= 5)
+                {
+                    _Flags = (AssemblyNameFlags)((int)_Flags & 0xFFFFFF0F);
+                    _Flags |= (AssemblyNameFlags)(x << 4);
+                }
+            }
+        }
+
+        public AssemblyContentType ContentType
+        {
+            get
+            {
+                int x = (((int)_Flags) & 0x00000E00) >> 9;
+                if (x > 1)
+                    x = 0;
+                return (AssemblyContentType)x;
+            }
+            set
+            {
+                int x = ((int)value) & 0x07;
+                if (x <= 1)
+                {
+                    _Flags = (AssemblyNameFlags)((int)_Flags & 0xFFFFF1FF);
+                    _Flags |= (AssemblyNameFlags)(x << 9);
+                }
+            }
+        }
+
+
+
+        // Make a copy of this assembly name.
+        public Object Clone()
+        {
+            AssemblyName name = new AssemblyName();
+            name.Init(_Name,
+                      _PublicKey,
+                      _PublicKeyToken,
+                      _Version,
+                      _CultureInfo,
+                      _HashAlgorithm,
+                      _VersionCompatibility,
+                      _CodeBase,
+                      _Flags,
+                      _StrongNameKeyPair);
+            name._HashForControl = _HashForControl;
+            name._HashAlgorithmForControl = _HashAlgorithmForControl;
+            return name;
+        }
+
+        /*
+         * Get the AssemblyName for a given file. This will only work
+         * if the file contains an assembly manifest. This method causes
+         * the file to be opened and closed.
+         */
+        public static AssemblyName GetAssemblyName(String assemblyFile)
+        {
+            if (assemblyFile == null)
+                throw new ArgumentNullException(nameof(assemblyFile));
+
+            // Assembly.GetNameInternal() will not demand path discovery 
+            //  permission, so do that first.
+            string fullPath = Path.GetFullPath(assemblyFile);
+            return nGetFileInformation(fullPath);
+        }
+
+        internal void SetHashControl(byte[] hash, AssemblyHashAlgorithm hashAlgorithm)
+        {
+            _HashForControl = hash;
+            _HashAlgorithmForControl = hashAlgorithm;
+        }
+
+        // The public key that is used to verify an assemblies
+        // inclusion into the namespace. If the public key associated
+        // with the namespace cannot verify the assembly the assembly
+        // will fail to load.
+        public byte[] GetPublicKey()
+        {
+            return _PublicKey;
+        }
+
+        public void SetPublicKey(byte[] publicKey)
+        {
+            _PublicKey = publicKey;
+
+            if (publicKey == null)
+                _Flags &= ~AssemblyNameFlags.PublicKey;
+            else
+                _Flags |= AssemblyNameFlags.PublicKey;
+        }
+
+        // The compressed version of the public key formed from a truncated hash.
+        // Will throw a SecurityException if _PublicKey is invalid
+        public byte[] GetPublicKeyToken()
+        {
+            if (_PublicKeyToken == null)
+                _PublicKeyToken = nGetPublicKeyToken();
+            return _PublicKeyToken;
+        }
+
+        public void SetPublicKeyToken(byte[] publicKeyToken)
+        {
+            _PublicKeyToken = publicKeyToken;
+        }
+
+        // Flags modifying the name. So far the only flag is PublicKey, which
+        // indicates that a full public key and not the compressed version is
+        // present. 
+        // Processor Architecture flags are set only through ProcessorArchitecture
+        // property and can't be set or retrieved directly
+        // Content Type flags are set only through ContentType property and can't be 
+        // set or retrieved directly
+        public AssemblyNameFlags Flags
+        {
+            get { return (AssemblyNameFlags)((uint)_Flags & 0xFFFFF10F); }
+            set
+            {
+                _Flags &= unchecked((AssemblyNameFlags)0x00000EF0);
+                _Flags |= (value & unchecked((AssemblyNameFlags)0xFFFFF10F));
+            }
+        }
+
+        public AssemblyHashAlgorithm HashAlgorithm
+        {
+            get { return _HashAlgorithm; }
+            set { _HashAlgorithm = value; }
+        }
+
+        public AssemblyVersionCompatibility VersionCompatibility
+        {
+            get { return _VersionCompatibility; }
+            set { _VersionCompatibility = value; }
+        }
+
+        public StrongNameKeyPair KeyPair
+        {
+            get { return _StrongNameKeyPair; }
+            set { _StrongNameKeyPair = value; }
+        }
+
+        public String FullName
+        {
+            get
+            {
+                if (this.Name == null)
+                    return string.Empty;
+                // Do not call GetPublicKeyToken() here - that latches the result into AssemblyName which isn't a side effect we want.
+                byte[] pkt = _PublicKeyToken ?? nGetPublicKeyToken();
+                return AssemblyNameFormatter.ComputeDisplayName(Name, Version, CultureName, pkt, Flags, ContentType);
+            }
+        }
+
+        // Returns the stringized version of the assembly name.
+        public override String ToString()
+        {
+            String s = FullName;
+            if (s == null)
+                return base.ToString();
+            else
+                return s;
+        }
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            throw new PlatformNotSupportedException();
+        }
+
+        public void OnDeserialization(Object sender)
+        {
+            throw new PlatformNotSupportedException();
+        }
+
+        public AssemblyName(String assemblyName)
+        {
+            if (assemblyName == null)
+                throw new ArgumentNullException(nameof(assemblyName));
+            if ((assemblyName.Length == 0) ||
+                (assemblyName[0] == '\0'))
+                throw new ArgumentException(SR.Format_StringZeroLength);
+
+            _Name = assemblyName;
+            nInit();
+        }
+
+        /// <summary>
+        /// Compares the simple names disregarding Version, Culture and PKT. While this clearly does not
+        /// match the intent of this api, this api has been broken this way since its debut and we cannot
+        /// change its behavior now.
+        /// </summary>
+        public static bool ReferenceMatchesDefinition(AssemblyName reference, AssemblyName definition)
+        {
+            if (object.ReferenceEquals(reference, definition))
+                return true;
+
+            if (reference == null)
+                throw new ArgumentNullException(nameof(reference));
+
+            if (definition == null)
+                throw new ArgumentNullException(nameof(definition));
+
+            string refName = reference.Name ?? string.Empty;
+            string defName = definition.Name ?? string.Empty;
+            return refName.Equals(defName, StringComparison.OrdinalIgnoreCase);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern void nInit(out RuntimeAssembly assembly, bool raiseResolveEvent);
+
+        internal void nInit()
+        {
+            RuntimeAssembly dummy = null;
+            nInit(out dummy, false);
+        }
+
+        internal void SetProcArchIndex(PortableExecutableKinds pek, ImageFileMachine ifm)
+        {
+            ProcessorArchitecture = CalculateProcArchIndex(pek, ifm, _Flags);
+        }
+
+        internal static ProcessorArchitecture CalculateProcArchIndex(PortableExecutableKinds pek, ImageFileMachine ifm, AssemblyNameFlags flags)
+        {
+            if (((uint)flags & 0xF0) == 0x70)
+                return ProcessorArchitecture.None;
+
+            if ((pek & System.Reflection.PortableExecutableKinds.PE32Plus) == System.Reflection.PortableExecutableKinds.PE32Plus)
+            {
+                switch (ifm)
+                {
+                    case System.Reflection.ImageFileMachine.IA64:
+                        return ProcessorArchitecture.IA64;
+                    case System.Reflection.ImageFileMachine.AMD64:
+                        return ProcessorArchitecture.Amd64;
+                    case System.Reflection.ImageFileMachine.I386:
+                        if ((pek & System.Reflection.PortableExecutableKinds.ILOnly) == System.Reflection.PortableExecutableKinds.ILOnly)
+                            return ProcessorArchitecture.MSIL;
+                        break;
+                }
+            }
+            else
+            {
+                if (ifm == System.Reflection.ImageFileMachine.I386)
+                {
+                    if ((pek & System.Reflection.PortableExecutableKinds.Required32Bit) == System.Reflection.PortableExecutableKinds.Required32Bit)
+                        return ProcessorArchitecture.X86;
+
+                    if ((pek & System.Reflection.PortableExecutableKinds.ILOnly) == System.Reflection.PortableExecutableKinds.ILOnly)
+                        return ProcessorArchitecture.MSIL;
+
+                    return ProcessorArchitecture.X86;
+                }
+                if (ifm == System.Reflection.ImageFileMachine.ARM)
+                {
+                    return ProcessorArchitecture.Arm;
+                }
+            }
+            return ProcessorArchitecture.None;
+        }
+
+        internal void Init(String name,
+                           byte[] publicKey,
+                           byte[] publicKeyToken,
+                           Version version,
+                           CultureInfo cultureInfo,
+                           AssemblyHashAlgorithm hashAlgorithm,
+                           AssemblyVersionCompatibility versionCompatibility,
+                           String codeBase,
+                           AssemblyNameFlags flags,
+                           StrongNameKeyPair keyPair) // Null if ref, matching Assembly if def
+        {
+            _Name = name;
+
+            if (publicKey != null)
+            {
+                _PublicKey = new byte[publicKey.Length];
+                Array.Copy(publicKey, _PublicKey, publicKey.Length);
+            }
+
+            if (publicKeyToken != null)
+            {
+                _PublicKeyToken = new byte[publicKeyToken.Length];
+                Array.Copy(publicKeyToken, _PublicKeyToken, publicKeyToken.Length);
+            }
+
+            if (version != null)
+                _Version = (Version)version.Clone();
+
+            _CultureInfo = cultureInfo;
+            _HashAlgorithm = hashAlgorithm;
+            _VersionCompatibility = versionCompatibility;
+            _CodeBase = codeBase;
+            _Flags = flags;
+            _StrongNameKeyPair = keyPair;
+        }
+
+        // This call opens and closes the file, but does not add the
+        // assembly to the domain.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern AssemblyName nGetFileInformation(String s);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern byte[] nGetPublicKeyToken();
+
+        internal static String EscapeCodeBase(String codebase)
+        {
+            if (codebase == null)
+                return string.Empty;
+
+            int position = 0;
+            char[] dest = EscapeString(codebase, 0, codebase.Length, null, ref position, true, c_DummyChar, c_DummyChar, c_DummyChar);
+            if (dest == null)
+                return codebase;
+
+            return new string(dest, 0, position);
+        }
+
+        // This implementation of EscapeString has been copied from System.Private.Uri from corefx repo
+        // - forceX characters are always escaped if found
+        // - rsvd character will remain unescaped
+        //
+        // start    - starting offset from input
+        // end      - the exclusive ending offset in input
+        // destPos  - starting offset in dest for output, on return this will be an exclusive "end" in the output.
+        //
+        // In case "dest" has lack of space it will be reallocated by preserving the _whole_ content up to current destPos
+        //
+        // Returns null if nothing has to be escaped AND passed dest was null, otherwise the resulting array with the updated destPos
+        //
+        internal static unsafe char[] EscapeString(string input, int start, int end, char[] dest, ref int destPos,
+            bool isUriString, char force1, char force2, char rsvd)
+        {
+            int i = start;
+            int prevInputPos = start;
+            byte* bytes = stackalloc byte[c_MaxUnicodeCharsReallocate * c_MaxUTF_8BytesPerUnicodeChar];   // 40*4=160
+
+            fixed (char* pStr = input)
+            {
+                for (; i < end; ++i)
+                {
+                    char ch = pStr[i];
+
+                    // a Unicode ?
+                    if (ch > '\x7F')
+                    {
+                        short maxSize = (short)Math.Min(end - i, (int)c_MaxUnicodeCharsReallocate - 1);
+
+                        short count = 1;
+                        for (; count < maxSize && pStr[i + count] > '\x7f'; ++count)
+                            ;
+
+                        // Is the last a high surrogate?
+                        if (pStr[i + count - 1] >= 0xD800 && pStr[i + count - 1] <= 0xDBFF)
+                        {
+                            // Should be a rare case where the app tries to feed an invalid Unicode surrogates pair
+                            if (count == 1 || count == end - i)
+                                throw new FormatException(SR.Arg_FormatException);
+                            // need to grab one more char as a Surrogate except when it's a bogus input
+                            ++count;
+                        }
+
+                        dest = EnsureDestinationSize(pStr, dest, i,
+                            (short)(count * c_MaxUTF_8BytesPerUnicodeChar * c_EncodedCharsPerByte),
+                            c_MaxUnicodeCharsReallocate * c_MaxUTF_8BytesPerUnicodeChar * c_EncodedCharsPerByte,
+                            ref destPos, prevInputPos);
+
+                        short numberOfBytes = (short)Encoding.UTF8.GetBytes(pStr + i, count, bytes,
+                            c_MaxUnicodeCharsReallocate * c_MaxUTF_8BytesPerUnicodeChar);
+
+                        // This is the only exception that built in UriParser can throw after a Uri ctor.
+                        // Should not happen unless the app tries to feed an invalid Unicode String
+                        if (numberOfBytes == 0)
+                            throw new FormatException(SR.Arg_FormatException);
+
+                        i += (count - 1);
+
+                        for (count = 0; count < numberOfBytes; ++count)
+                            EscapeAsciiChar((char)bytes[count], dest, ref destPos);
+
+                        prevInputPos = i + 1;
+                    }
+                    else if (ch == '%' && rsvd == '%')
+                    {
+                        // Means we don't reEncode '%' but check for the possible escaped sequence
+                        dest = EnsureDestinationSize(pStr, dest, i, c_EncodedCharsPerByte,
+                            c_MaxAsciiCharsReallocate * c_EncodedCharsPerByte, ref destPos, prevInputPos);
+                        if (i + 2 < end && EscapedAscii(pStr[i + 1], pStr[i + 2]) != c_DummyChar)
+                        {
+                            // leave it escaped
+                            dest[destPos++] = '%';
+                            dest[destPos++] = pStr[i + 1];
+                            dest[destPos++] = pStr[i + 2];
+                            i += 2;
+                        }
+                        else
+                        {
+                            EscapeAsciiChar('%', dest, ref destPos);
+                        }
+                        prevInputPos = i + 1;
+                    }
+                    else if (ch == force1 || ch == force2)
+                    {
+                        dest = EnsureDestinationSize(pStr, dest, i, c_EncodedCharsPerByte,
+                            c_MaxAsciiCharsReallocate * c_EncodedCharsPerByte, ref destPos, prevInputPos);
+                        EscapeAsciiChar(ch, dest, ref destPos);
+                        prevInputPos = i + 1;
+                    }
+                    else if (ch != rsvd && (isUriString ? !IsReservedUnreservedOrHash(ch) : !IsUnreserved(ch)))
+                    {
+                        dest = EnsureDestinationSize(pStr, dest, i, c_EncodedCharsPerByte,
+                            c_MaxAsciiCharsReallocate * c_EncodedCharsPerByte, ref destPos, prevInputPos);
+                        EscapeAsciiChar(ch, dest, ref destPos);
+                        prevInputPos = i + 1;
+                    }
+                }
+
+                if (prevInputPos != i)
+                {
+                    // need to fill up the dest array ?
+                    if (prevInputPos != start || dest != null)
+                        dest = EnsureDestinationSize(pStr, dest, i, 0, 0, ref destPos, prevInputPos);
+                }
+            }
+
+            return dest;
+        }
+
+        //
+        // ensure destination array has enough space and contains all the needed input stuff
+        //
+        private static unsafe char[] EnsureDestinationSize(char* pStr, char[] dest, int currentInputPos,
+            short charsToAdd, short minReallocateChars, ref int destPos, int prevInputPos)
+        {
+            if ((object)dest == null || dest.Length < destPos + (currentInputPos - prevInputPos) + charsToAdd)
+            {
+                // allocating or reallocating array by ensuring enough space based on maxCharsToAdd.
+                char[] newresult = new char[destPos + (currentInputPos - prevInputPos) + minReallocateChars];
+
+                if ((object)dest != null && destPos != 0)
+                    Buffer.BlockCopy(dest, 0, newresult, 0, destPos << 1);
+                dest = newresult;
+            }
+
+            // ensuring we copied everything form the input string left before last escaping
+            while (prevInputPos != currentInputPos)
+                dest[destPos++] = pStr[prevInputPos++];
+            return dest;
+        }
+
+        internal static void EscapeAsciiChar(char ch, char[] to, ref int pos)
+        {
+            to[pos++] = '%';
+            to[pos++] = s_hexUpperChars[(ch & 0xf0) >> 4];
+            to[pos++] = s_hexUpperChars[ch & 0xf];
+        }
+
+        internal static char EscapedAscii(char digit, char next)
+        {
+            if (!(((digit >= '0') && (digit <= '9'))
+                || ((digit >= 'A') && (digit <= 'F'))
+                || ((digit >= 'a') && (digit <= 'f'))))
+            {
+                return c_DummyChar;
+            }
+
+            int res = (digit <= '9')
+                ? ((int)digit - (int)'0')
+                : (((digit <= 'F')
+                ? ((int)digit - (int)'A')
+                : ((int)digit - (int)'a'))
+                   + 10);
+
+            if (!(((next >= '0') && (next <= '9'))
+                || ((next >= 'A') && (next <= 'F'))
+                || ((next >= 'a') && (next <= 'f'))))
+            {
+                return c_DummyChar;
+            }
+
+            return (char)((res << 4) + ((next <= '9')
+                    ? ((int)next - (int)'0')
+                    : (((next <= 'F')
+                        ? ((int)next - (int)'A')
+                        : ((int)next - (int)'a'))
+                       + 10)));
+        }
+
+        private static unsafe bool IsReservedUnreservedOrHash(char c)
+        {
+            if (IsUnreserved(c))
+            {
+                return true;
+            }
+            return (RFC3986ReservedMarks.IndexOf(c) >= 0);
+        }
+
+        internal static unsafe bool IsUnreserved(char c)
+        {
+            if (IsAsciiLetterOrDigit(c))
+            {
+                return true;
+            }
+            return (RFC3986UnreservedMarks.IndexOf(c) >= 0);
+        }
+
+        //Only consider ASCII characters
+        internal static bool IsAsciiLetter(char character)
+        {
+            return (character >= 'a' && character <= 'z') ||
+                   (character >= 'A' && character <= 'Z');
+        }
+
+        internal static bool IsAsciiLetterOrDigit(char character)
+        {
+            return IsAsciiLetter(character) || (character >= '0' && character <= '9');
+        }
+
+        private static readonly char[] s_hexUpperChars = {
+                                   '0', '1', '2', '3', '4', '5', '6', '7',
+                                   '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
+        internal const char c_DummyChar = (char)0xFFFF;     //An Invalid Unicode character used as a dummy char passed into the parameter                                   
+        private const short c_MaxAsciiCharsReallocate = 40;
+        private const short c_MaxUnicodeCharsReallocate = 40;
+        private const short c_MaxUTF_8BytesPerUnicodeChar = 4;
+        private const short c_EncodedCharsPerByte = 3;
+        private const string RFC3986ReservedMarks = @":/?#[]@!$&'()*+,;=";
+        private const string RFC3986UnreservedMarks = @"-._~";
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Associates.cs b/src/System.Private.CoreLib/src/System/Reflection/Associates.cs
new file mode 100644
index 0000000000..381146bf5e
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Associates.cs
@@ -0,0 +1,209 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System.Reflection
+{
+    internal static class Associates
+    {
+        [Flags]
+        internal enum Attributes
+        {
+            ComposedOfAllVirtualMethods = 0x1,
+            ComposedOfAllPrivateMethods = 0x2,
+            ComposedOfNoPublicMembers = 0x4,
+            ComposedOfNoStaticMembers = 0x8,
+        }
+
+        internal static bool IncludeAccessor(MethodInfo associate, bool nonPublic)
+        {
+            if ((object)associate == null)
+                return false;
+
+            if (nonPublic)
+                return true;
+
+            if (associate.IsPublic)
+                return true;
+
+            return false;
+        }
+
+        private static unsafe RuntimeMethodInfo AssignAssociates(
+            int tkMethod,
+            RuntimeType declaredType,
+            RuntimeType reflectedType)
+        {
+            if (MetadataToken.IsNullToken(tkMethod))
+                return null;
+
+            Debug.Assert(declaredType != null);
+            Debug.Assert(reflectedType != null);
+
+            bool isInherited = declaredType != reflectedType;
+
+            IntPtr[] genericArgumentHandles = null;
+            int genericArgumentCount = 0;
+            RuntimeType[] genericArguments = declaredType.GetTypeHandleInternal().GetInstantiationInternal();
+            if (genericArguments != null)
+            {
+                genericArgumentCount = genericArguments.Length;
+                genericArgumentHandles = new IntPtr[genericArguments.Length];
+                for (int i = 0; i < genericArguments.Length; i++)
+                {
+                    genericArgumentHandles[i] = genericArguments[i].GetTypeHandleInternal().Value;
+                }
+            }
+
+            RuntimeMethodHandleInternal associateMethodHandle = ModuleHandle.ResolveMethodHandleInternalCore(RuntimeTypeHandle.GetModule(declaredType), tkMethod, genericArgumentHandles, genericArgumentCount, null, 0);
+            Debug.Assert(!associateMethodHandle.IsNullHandle(), "Failed to resolve associateRecord methodDef token");
+
+            if (isInherited)
+            {
+                MethodAttributes methAttr = RuntimeMethodHandle.GetAttributes(associateMethodHandle);
+
+                // ECMA MethodSemantics: "All methods for a given Property or Event shall have the same accessibility 
+                //(ie the MemberAccessMask subfield of their Flags row) and cannot be CompilerControlled  [CLS]"
+                // Consequently, a property may be composed of public and private methods. If the declared type !=
+                // the reflected type, the private methods should not be exposed. Note that this implies that the 
+                // identity of a property includes it's reflected type.
+
+                if ((methAttr & MethodAttributes.MemberAccessMask) == MethodAttributes.Private)
+                    return null;
+
+                // Note this is the first time the property was encountered walking from the most derived class 
+                // towards the base class. It would seem to follow that any associated methods would not
+                // be overriden -- but this is not necessarily true. A more derived class may have overriden a
+                // virtual method associated with a property in a base class without associating the override with 
+                // the same or any property in the derived class. 
+                if ((methAttr & MethodAttributes.Virtual) != 0)
+                {
+                    bool declaringTypeIsClass =
+                        (RuntimeTypeHandle.GetAttributes(declaredType) & TypeAttributes.ClassSemanticsMask) == TypeAttributes.Class;
+
+                    // It makes no sense to search for a virtual override of a method declared on an interface.
+                    if (declaringTypeIsClass)
+                    {
+                        int slot = RuntimeMethodHandle.GetSlot(associateMethodHandle);
+
+                        // Find the override visible from the reflected type
+                        associateMethodHandle = RuntimeTypeHandle.GetMethodAt(reflectedType, slot);
+                    }
+                }
+            }
+
+            RuntimeMethodInfo associateMethod =
+                RuntimeType.GetMethodBase(reflectedType, associateMethodHandle) as RuntimeMethodInfo;
+
+            // suppose a property was mapped to a method not in the derivation hierarchy of the reflectedTypeHandle
+            if (associateMethod == null)
+                associateMethod = reflectedType.Module.ResolveMethod(tkMethod, null, null) as RuntimeMethodInfo;
+
+            return associateMethod;
+        }
+
+        internal static unsafe void AssignAssociates(
+            MetadataImport scope,
+            int mdPropEvent,
+            RuntimeType declaringType,
+            RuntimeType reflectedType,
+            out RuntimeMethodInfo addOn,
+            out RuntimeMethodInfo removeOn,
+            out RuntimeMethodInfo fireOn,
+            out RuntimeMethodInfo getter,
+            out RuntimeMethodInfo setter,
+            out MethodInfo[] other,
+            out bool composedOfAllPrivateMethods,
+            out BindingFlags bindingFlags)
+        {
+            addOn = removeOn = fireOn = getter = setter = null;
+
+            Attributes attributes =
+                Attributes.ComposedOfAllPrivateMethods |
+                Attributes.ComposedOfAllVirtualMethods |
+                Attributes.ComposedOfNoPublicMembers |
+                Attributes.ComposedOfNoStaticMembers;
+
+            while (RuntimeTypeHandle.IsGenericVariable(reflectedType))
+                reflectedType = (RuntimeType)reflectedType.BaseType;
+
+            bool isInherited = declaringType != reflectedType;
+
+            List<MethodInfo> otherList = null;
+
+            MetadataEnumResult associatesData;
+            scope.Enum(MetadataTokenType.MethodDef, mdPropEvent, out associatesData);
+
+            int cAssociates = associatesData.Length / 2;
+
+            for (int i = 0; i < cAssociates; i++)
+            {
+                int methodDefToken = associatesData[i * 2];
+                MethodSemanticsAttributes semantics = (MethodSemanticsAttributes)associatesData[i * 2 + 1];
+
+                #region Assign each associate
+                RuntimeMethodInfo associateMethod =
+                    AssignAssociates(methodDefToken, declaringType, reflectedType);
+
+                if (associateMethod == null)
+                    continue;
+
+                MethodAttributes methAttr = associateMethod.Attributes;
+                bool isPrivate = (methAttr & MethodAttributes.MemberAccessMask) == MethodAttributes.Private;
+                bool isVirtual = (methAttr & MethodAttributes.Virtual) != 0;
+
+                MethodAttributes visibility = methAttr & MethodAttributes.MemberAccessMask;
+                bool isPublic = visibility == MethodAttributes.Public;
+                bool isStatic = (methAttr & MethodAttributes.Static) != 0;
+
+                if (isPublic)
+                {
+                    attributes &= ~Attributes.ComposedOfNoPublicMembers;
+                    attributes &= ~Attributes.ComposedOfAllPrivateMethods;
+                }
+                else if (!isPrivate)
+                {
+                    attributes &= ~Attributes.ComposedOfAllPrivateMethods;
+                }
+
+                if (isStatic)
+                    attributes &= ~Attributes.ComposedOfNoStaticMembers;
+
+                if (!isVirtual)
+                    attributes &= ~Attributes.ComposedOfAllVirtualMethods;
+                #endregion
+
+                if (semantics == MethodSemanticsAttributes.Setter)
+                    setter = associateMethod;
+                else if (semantics == MethodSemanticsAttributes.Getter)
+                    getter = associateMethod;
+                else if (semantics == MethodSemanticsAttributes.Fire)
+                    fireOn = associateMethod;
+                else if (semantics == MethodSemanticsAttributes.AddOn)
+                    addOn = associateMethod;
+                else if (semantics == MethodSemanticsAttributes.RemoveOn)
+                    removeOn = associateMethod;
+                else
+                {
+                    if (otherList == null)
+                        otherList = new List<MethodInfo>(cAssociates);
+                    otherList.Add(associateMethod);
+                }
+            }
+
+            bool isPseudoPublic = (attributes & Attributes.ComposedOfNoPublicMembers) == 0;
+            bool isPseudoStatic = (attributes & Attributes.ComposedOfNoStaticMembers) == 0;
+            bindingFlags = RuntimeType.FilterPreCalculate(isPseudoPublic, isInherited, isPseudoStatic);
+
+            composedOfAllPrivateMethods = (attributes & Attributes.ComposedOfAllPrivateMethods) != 0;
+
+            other = (otherList != null) ? otherList.ToArray() : null;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/ConstructorInfo.CoreCLR.cs b/src/System.Private.CoreLib/src/System/Reflection/ConstructorInfo.CoreCLR.cs
new file mode 100644
index 0000000000..c96bfb5ac1
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/ConstructorInfo.CoreCLR.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public abstract partial class ConstructorInfo : MethodBase
+    {
+        internal virtual Type GetReturnType() { throw new NotImplementedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/CustomAttribute.cs b/src/System.Private.CoreLib/src/System/Reflection/CustomAttribute.cs
new file mode 100644
index 0000000000..fb102c128d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/CustomAttribute.cs
@@ -0,0 +1,2332 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Collections;
+using System.Collections.Generic;
+using System.Resources;
+using System.Diagnostics;
+using System.Diagnostics.Tracing;
+using System.Globalization;
+using System.Security;
+using System.Runtime.ConstrainedExecution;
+using System.Runtime.Versioning;
+
+namespace System.Reflection
+{
+    public class CustomAttributeData
+    {
+        #region Public Static Members
+        public static IList<CustomAttributeData> GetCustomAttributes(MemberInfo target)
+        {
+            if (target == null)
+                throw new ArgumentNullException(nameof(target));
+
+            return target.GetCustomAttributesData();
+        }
+
+        public static IList<CustomAttributeData> GetCustomAttributes(Module target)
+        {
+            if (target == null)
+                throw new ArgumentNullException(nameof(target));
+
+            return target.GetCustomAttributesData();
+        }
+
+        public static IList<CustomAttributeData> GetCustomAttributes(Assembly target)
+        {
+            if (target == null)
+                throw new ArgumentNullException(nameof(target));
+
+            return target.GetCustomAttributesData();
+        }
+
+        public static IList<CustomAttributeData> GetCustomAttributes(ParameterInfo target)
+        {
+            if (target == null)
+                throw new ArgumentNullException(nameof(target));
+
+            return target.GetCustomAttributesData();
+        }
+        #endregion
+
+        #region Internal Static Members
+        internal static IList<CustomAttributeData> GetCustomAttributesInternal(RuntimeType target)
+        {
+            Debug.Assert(target != null);
+
+            IList<CustomAttributeData> cad = GetCustomAttributes(target.GetRuntimeModule(), target.MetadataToken);
+
+            Attribute[] a = PseudoCustomAttribute.GetCustomAttributes((RuntimeType)target, typeof(object) as RuntimeType, out int pcaCount);
+
+            if (pcaCount == 0)
+                return cad;
+
+            CustomAttributeData[] pca = new CustomAttributeData[cad.Count + pcaCount];
+            cad.CopyTo(pca, pcaCount);
+            for (int i = 0; i < pcaCount; i++)
+            {
+                pca[i] = new CustomAttributeData(a[i]);
+            }
+
+            return Array.AsReadOnly(pca);
+        }
+
+        internal static IList<CustomAttributeData> GetCustomAttributesInternal(RuntimeFieldInfo target)
+        {
+            Debug.Assert(target != null);
+
+            IList<CustomAttributeData> cad = GetCustomAttributes(target.GetRuntimeModule(), target.MetadataToken);
+
+            Attribute[] a = PseudoCustomAttribute.GetCustomAttributes((RuntimeFieldInfo)target, typeof(object) as RuntimeType, out int pcaCount);
+
+            if (pcaCount == 0)
+                return cad;
+
+            CustomAttributeData[] pca = new CustomAttributeData[cad.Count + pcaCount];
+            cad.CopyTo(pca, pcaCount);
+            for (int i = 0; i < pcaCount; i++)
+            {
+                pca[i] = new CustomAttributeData(a[i]);
+            }
+
+            return Array.AsReadOnly(pca);
+        }
+
+        internal static IList<CustomAttributeData> GetCustomAttributesInternal(RuntimeMethodInfo target)
+        {
+            Debug.Assert(target != null);
+
+            IList<CustomAttributeData> cad = GetCustomAttributes(target.GetRuntimeModule(), target.MetadataToken);
+
+            Attribute[] a = PseudoCustomAttribute.GetCustomAttributes((RuntimeMethodInfo)target, typeof(object) as RuntimeType, out int pcaCount);
+
+            if (pcaCount == 0)
+                return cad;
+
+            CustomAttributeData[] pca = new CustomAttributeData[cad.Count + pcaCount];
+            cad.CopyTo(pca, pcaCount);
+            for (int i = 0; i < pcaCount; i++)
+            {
+                pca[i] = new CustomAttributeData(a[i]);
+            }
+
+            return Array.AsReadOnly(pca);
+        }
+
+        internal static IList<CustomAttributeData> GetCustomAttributesInternal(RuntimeConstructorInfo target)
+        {
+            Debug.Assert(target != null);
+
+            return GetCustomAttributes(target.GetRuntimeModule(), target.MetadataToken);
+        }
+
+        internal static IList<CustomAttributeData> GetCustomAttributesInternal(RuntimeEventInfo target)
+        {
+            Debug.Assert(target != null);
+
+            return GetCustomAttributes(target.GetRuntimeModule(), target.MetadataToken);
+        }
+
+        internal static IList<CustomAttributeData> GetCustomAttributesInternal(RuntimePropertyInfo target)
+        {
+            Debug.Assert(target != null);
+
+            return GetCustomAttributes(target.GetRuntimeModule(), target.MetadataToken);
+        }
+
+        internal static IList<CustomAttributeData> GetCustomAttributesInternal(RuntimeModule target)
+        {
+            Debug.Assert(target != null);
+
+            if (target.IsResource())
+                return new List<CustomAttributeData>();
+
+            return GetCustomAttributes(target, target.MetadataToken);
+        }
+
+        internal static IList<CustomAttributeData> GetCustomAttributesInternal(RuntimeAssembly target)
+        {
+            Debug.Assert(target != null);
+
+            IList<CustomAttributeData> cad = GetCustomAttributes((RuntimeModule)target.ManifestModule, RuntimeAssembly.GetToken(target.GetNativeHandle()));
+
+            Attribute[] a = PseudoCustomAttribute.GetCustomAttributes(target, typeof(object) as RuntimeType, out int pcaCount);
+
+            if (pcaCount == 0)
+                return cad;
+
+            CustomAttributeData[] pca = new CustomAttributeData[cad.Count + pcaCount];
+            cad.CopyTo(pca, pcaCount);
+            for (int i = 0; i < pcaCount; i++)
+            {
+                pca[i] = new CustomAttributeData(a[i]);
+            }
+
+            return Array.AsReadOnly(pca);
+        }
+
+        internal static IList<CustomAttributeData> GetCustomAttributesInternal(RuntimeParameterInfo target)
+        {
+            Debug.Assert(target != null);
+
+            IList<CustomAttributeData> cad = GetCustomAttributes(target.GetRuntimeModule(), target.MetadataToken);
+
+            Attribute[] a = PseudoCustomAttribute.GetCustomAttributes(target, typeof(object) as RuntimeType, out int pcaCount);
+
+            if (pcaCount == 0)
+                return cad;
+
+            CustomAttributeData[] pca = new CustomAttributeData[cad.Count + pcaCount];
+            cad.CopyTo(pca, pcaCount);
+            for (int i = 0; i < pcaCount; i++)
+                pca[i] = new CustomAttributeData(a[i]);
+
+            return Array.AsReadOnly(pca);
+        }
+        #endregion
+
+        #region Private Static Methods
+        private static CustomAttributeEncoding TypeToCustomAttributeEncoding(RuntimeType type)
+        {
+            if (type == typeof(int))
+                return CustomAttributeEncoding.Int32;
+
+            if (type.IsEnum)
+                return CustomAttributeEncoding.Enum;
+
+            if (type == typeof(string))
+                return CustomAttributeEncoding.String;
+
+            if (type == typeof(Type))
+                return CustomAttributeEncoding.Type;
+
+            if (type == typeof(object))
+                return CustomAttributeEncoding.Object;
+
+            if (type.IsArray)
+                return CustomAttributeEncoding.Array;
+
+            if (type == typeof(char))
+                return CustomAttributeEncoding.Char;
+
+            if (type == typeof(bool))
+                return CustomAttributeEncoding.Boolean;
+
+            if (type == typeof(byte))
+                return CustomAttributeEncoding.Byte;
+
+            if (type == typeof(sbyte))
+                return CustomAttributeEncoding.SByte;
+
+            if (type == typeof(short))
+                return CustomAttributeEncoding.Int16;
+
+            if (type == typeof(ushort))
+                return CustomAttributeEncoding.UInt16;
+
+            if (type == typeof(uint))
+                return CustomAttributeEncoding.UInt32;
+
+            if (type == typeof(long))
+                return CustomAttributeEncoding.Int64;
+
+            if (type == typeof(ulong))
+                return CustomAttributeEncoding.UInt64;
+
+            if (type == typeof(float))
+                return CustomAttributeEncoding.Float;
+
+            if (type == typeof(double))
+                return CustomAttributeEncoding.Double;
+
+            // System.Enum is neither an Enum nor a Class
+            if (type == typeof(Enum))
+                return CustomAttributeEncoding.Object;
+
+            if (type.IsClass)
+                return CustomAttributeEncoding.Object;
+
+            if (type.IsInterface)
+                return CustomAttributeEncoding.Object;
+
+            if (type.IsValueType)
+                return CustomAttributeEncoding.Undefined;
+
+            throw new ArgumentException(SR.Argument_InvalidKindOfTypeForCA, nameof(type));
+        }
+        private static CustomAttributeType InitCustomAttributeType(RuntimeType parameterType)
+        {
+            CustomAttributeEncoding encodedType = CustomAttributeData.TypeToCustomAttributeEncoding(parameterType);
+            CustomAttributeEncoding encodedArrayType = CustomAttributeEncoding.Undefined;
+            CustomAttributeEncoding encodedEnumType = CustomAttributeEncoding.Undefined;
+            string enumName = null;
+
+            if (encodedType == CustomAttributeEncoding.Array)
+            {
+                parameterType = (RuntimeType)parameterType.GetElementType();
+                encodedArrayType = CustomAttributeData.TypeToCustomAttributeEncoding(parameterType);
+            }
+
+            if (encodedType == CustomAttributeEncoding.Enum || encodedArrayType == CustomAttributeEncoding.Enum)
+            {
+                encodedEnumType = TypeToCustomAttributeEncoding((RuntimeType)Enum.GetUnderlyingType(parameterType));
+                enumName = parameterType.AssemblyQualifiedName;
+            }
+
+            return new CustomAttributeType(encodedType, encodedArrayType, encodedEnumType, enumName);
+        }
+        private static IList<CustomAttributeData> GetCustomAttributes(RuntimeModule module, int tkTarget)
+        {
+            CustomAttributeRecord[] records = GetCustomAttributeRecords(module, tkTarget);
+
+            CustomAttributeData[] customAttributes = new CustomAttributeData[records.Length];
+            for (int i = 0; i < records.Length; i++)
+                customAttributes[i] = new CustomAttributeData(module, records[i]);
+
+            return Array.AsReadOnly(customAttributes);
+        }
+        #endregion
+
+        #region Internal Static Members
+        internal static unsafe CustomAttributeRecord[] GetCustomAttributeRecords(RuntimeModule module, int targetToken)
+        {
+            MetadataImport scope = module.MetadataImport;
+
+            MetadataEnumResult tkCustomAttributeTokens;
+            scope.EnumCustomAttributes(targetToken, out tkCustomAttributeTokens);
+
+            if (tkCustomAttributeTokens.Length == 0)
+            {
+                return Array.Empty<CustomAttributeRecord>();
+            }
+
+            CustomAttributeRecord[] records = new CustomAttributeRecord[tkCustomAttributeTokens.Length];
+
+            for (int i = 0; i < records.Length; i++)
+            {
+                scope.GetCustomAttributeProps(
+                    tkCustomAttributeTokens[i], out records[i].tkCtor.Value, out records[i].blob);
+            }
+
+            return records;
+        }
+
+        internal static CustomAttributeTypedArgument Filter(IList<CustomAttributeData> attrs, Type caType, int parameter)
+        {
+            for (int i = 0; i < attrs.Count; i++)
+            {
+                if (attrs[i].Constructor.DeclaringType == caType)
+                {
+                    return attrs[i].ConstructorArguments[parameter];
+                }
+            }
+
+            return new CustomAttributeTypedArgument();
+        }
+        #endregion
+
+        #region Private Data Members
+        private ConstructorInfo m_ctor;
+        private RuntimeModule m_scope;
+        private MemberInfo[] m_members;
+        private CustomAttributeCtorParameter[] m_ctorParams;
+        private CustomAttributeNamedParameter[] m_namedParams;
+        private IList<CustomAttributeTypedArgument> m_typedCtorArgs;
+        private IList<CustomAttributeNamedArgument> m_namedArgs;
+        #endregion
+
+        #region Constructor
+        protected CustomAttributeData()
+        {
+        }
+
+        private CustomAttributeData(RuntimeModule scope, CustomAttributeRecord caRecord)
+        {
+            m_scope = scope;
+            m_ctor = (RuntimeConstructorInfo)RuntimeType.GetMethodBase(scope, caRecord.tkCtor);
+
+            ParameterInfo[] parameters = m_ctor.GetParametersNoCopy();
+            m_ctorParams = new CustomAttributeCtorParameter[parameters.Length];
+            for (int i = 0; i < parameters.Length; i++)
+                m_ctorParams[i] = new CustomAttributeCtorParameter(InitCustomAttributeType((RuntimeType)parameters[i].ParameterType));
+
+            FieldInfo[] fields = m_ctor.DeclaringType.GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
+            PropertyInfo[] properties = m_ctor.DeclaringType.GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
+            m_namedParams = new CustomAttributeNamedParameter[properties.Length + fields.Length];
+            for (int i = 0; i < fields.Length; i++)
+                m_namedParams[i] = new CustomAttributeNamedParameter(
+                    fields[i].Name, CustomAttributeEncoding.Field, InitCustomAttributeType((RuntimeType)fields[i].FieldType));
+            for (int i = 0; i < properties.Length; i++)
+                m_namedParams[i + fields.Length] = new CustomAttributeNamedParameter(
+                    properties[i].Name, CustomAttributeEncoding.Property, InitCustomAttributeType((RuntimeType)properties[i].PropertyType));
+
+            m_members = new MemberInfo[fields.Length + properties.Length];
+            fields.CopyTo(m_members, 0);
+            properties.CopyTo(m_members, fields.Length);
+
+            CustomAttributeEncodedArgument.ParseAttributeArguments(caRecord.blob, ref m_ctorParams, ref m_namedParams, m_scope);
+        }
+        #endregion
+
+        #region Pseudo Custom Attribute Constructor
+        internal CustomAttributeData(Attribute attribute)
+        {
+            if (attribute is DllImportAttribute)
+                Init((DllImportAttribute)attribute);
+            else if (attribute is FieldOffsetAttribute)
+                Init((FieldOffsetAttribute)attribute);
+            else if (attribute is MarshalAsAttribute)
+                Init((MarshalAsAttribute)attribute);
+            else if (attribute is TypeForwardedToAttribute)
+                Init((TypeForwardedToAttribute)attribute);
+            else
+                Init(attribute);
+        }
+        private void Init(DllImportAttribute dllImport)
+        {
+            Type type = typeof(DllImportAttribute);
+            m_ctor = type.GetConstructors(BindingFlags.Public | BindingFlags.Instance)[0];
+            m_typedCtorArgs = Array.AsReadOnly(new CustomAttributeTypedArgument[]
+            {
+                new CustomAttributeTypedArgument(dllImport.Value),
+            });
+
+            m_namedArgs = Array.AsReadOnly(new CustomAttributeNamedArgument[]
+            {
+                new CustomAttributeNamedArgument(type.GetField("EntryPoint"), dllImport.EntryPoint),
+                new CustomAttributeNamedArgument(type.GetField("CharSet"), dllImport.CharSet),
+                new CustomAttributeNamedArgument(type.GetField("ExactSpelling"), dllImport.ExactSpelling),
+                new CustomAttributeNamedArgument(type.GetField("SetLastError"), dllImport.SetLastError),
+                new CustomAttributeNamedArgument(type.GetField("PreserveSig"), dllImport.PreserveSig),
+                new CustomAttributeNamedArgument(type.GetField("CallingConvention"), dllImport.CallingConvention),
+                new CustomAttributeNamedArgument(type.GetField("BestFitMapping"), dllImport.BestFitMapping),
+                new CustomAttributeNamedArgument(type.GetField("ThrowOnUnmappableChar"), dllImport.ThrowOnUnmappableChar)
+});
+        }
+        private void Init(FieldOffsetAttribute fieldOffset)
+        {
+            m_ctor = typeof(FieldOffsetAttribute).GetConstructors(BindingFlags.Public | BindingFlags.Instance)[0];
+            m_typedCtorArgs = Array.AsReadOnly(new CustomAttributeTypedArgument[] {
+                new CustomAttributeTypedArgument(fieldOffset.Value)
+            });
+            m_namedArgs = Array.AsReadOnly(Array.Empty<CustomAttributeNamedArgument>());
+        }
+        private void Init(MarshalAsAttribute marshalAs)
+        {
+            Type type = typeof(MarshalAsAttribute);
+            m_ctor = type.GetConstructors(BindingFlags.Public | BindingFlags.Instance)[0];
+            m_typedCtorArgs = Array.AsReadOnly(new CustomAttributeTypedArgument[]
+            {
+                new CustomAttributeTypedArgument(marshalAs.Value),
+            });
+
+            int i = 3; // ArraySubType, SizeParamIndex, SizeConst
+            if (marshalAs.MarshalType != null) i++;
+            if (marshalAs.MarshalTypeRef != null) i++;
+            if (marshalAs.MarshalCookie != null) i++;
+            i++; // IidParameterIndex
+            i++; // SafeArraySubType
+            if (marshalAs.SafeArrayUserDefinedSubType != null) i++;
+            CustomAttributeNamedArgument[] namedArgs = new CustomAttributeNamedArgument[i];
+
+            // For compatibility with previous runtimes, we always include the following 5 attributes, regardless
+            // of if they apply to the UnmanagedType being marshaled or not.
+            i = 0;
+            namedArgs[i++] = new CustomAttributeNamedArgument(type.GetField("ArraySubType"), marshalAs.ArraySubType);
+            namedArgs[i++] = new CustomAttributeNamedArgument(type.GetField("SizeParamIndex"), marshalAs.SizeParamIndex);
+            namedArgs[i++] = new CustomAttributeNamedArgument(type.GetField("SizeConst"), marshalAs.SizeConst);
+            namedArgs[i++] = new CustomAttributeNamedArgument(type.GetField("IidParameterIndex"), marshalAs.IidParameterIndex);
+            namedArgs[i++] = new CustomAttributeNamedArgument(type.GetField("SafeArraySubType"), marshalAs.SafeArraySubType);
+            if (marshalAs.MarshalType != null)
+                namedArgs[i++] = new CustomAttributeNamedArgument(type.GetField("MarshalType"), marshalAs.MarshalType);
+            if (marshalAs.MarshalTypeRef != null)
+                namedArgs[i++] = new CustomAttributeNamedArgument(type.GetField("MarshalTypeRef"), marshalAs.MarshalTypeRef);
+            if (marshalAs.MarshalCookie != null)
+                namedArgs[i++] = new CustomAttributeNamedArgument(type.GetField("MarshalCookie"), marshalAs.MarshalCookie);
+            if (marshalAs.SafeArrayUserDefinedSubType != null)
+                namedArgs[i++] = new CustomAttributeNamedArgument(type.GetField("SafeArrayUserDefinedSubType"), marshalAs.SafeArrayUserDefinedSubType);
+
+            m_namedArgs = Array.AsReadOnly(namedArgs);
+        }
+        private void Init(TypeForwardedToAttribute forwardedTo)
+        {
+            Type type = typeof(TypeForwardedToAttribute);
+
+            Type[] sig = new Type[] { typeof(Type) };
+            m_ctor = type.GetConstructor(BindingFlags.Public | BindingFlags.Instance, null, sig, null);
+
+            CustomAttributeTypedArgument[] typedArgs = new CustomAttributeTypedArgument[1];
+            typedArgs[0] = new CustomAttributeTypedArgument(typeof(Type), forwardedTo.Destination);
+            m_typedCtorArgs = Array.AsReadOnly(typedArgs);
+
+            CustomAttributeNamedArgument[] namedArgs = Array.Empty<CustomAttributeNamedArgument>();
+            m_namedArgs = Array.AsReadOnly(namedArgs);
+        }
+        private void Init(object pca)
+        {
+            m_ctor = pca.GetType().GetConstructors(BindingFlags.Public | BindingFlags.Instance)[0];
+            m_typedCtorArgs = Array.AsReadOnly(Array.Empty<CustomAttributeTypedArgument>());
+            m_namedArgs = Array.AsReadOnly(Array.Empty<CustomAttributeNamedArgument>());
+        }
+        #endregion
+
+        #region Object Override
+        public override string ToString()
+        {
+            string ctorArgs = "";
+            for (int i = 0; i < ConstructorArguments.Count; i++)
+                ctorArgs += String.Format(CultureInfo.CurrentCulture, i == 0 ? "{0}" : ", {0}", ConstructorArguments[i]);
+
+            string namedArgs = "";
+            for (int i = 0; i < NamedArguments.Count; i++)
+                namedArgs += String.Format(CultureInfo.CurrentCulture, i == 0 && ctorArgs.Length == 0 ? "{0}" : ", {0}", NamedArguments[i]);
+
+            return String.Format(CultureInfo.CurrentCulture, "[{0}({1}{2})]", Constructor.DeclaringType.FullName, ctorArgs, namedArgs);
+        }
+        public override int GetHashCode()
+        {
+            return base.GetHashCode();
+        }
+        public override bool Equals(object obj)
+        {
+            return obj == (object)this;
+        }
+        #endregion
+
+        #region Public Members
+        public Type AttributeType { get { return Constructor.DeclaringType; } }
+
+        public virtual ConstructorInfo Constructor { get { return m_ctor; } }
+
+        public virtual IList<CustomAttributeTypedArgument> ConstructorArguments
+        {
+            get
+            {
+                if (m_typedCtorArgs == null)
+                {
+                    CustomAttributeTypedArgument[] typedCtorArgs = new CustomAttributeTypedArgument[m_ctorParams.Length];
+
+                    for (int i = 0; i < typedCtorArgs.Length; i++)
+                    {
+                        CustomAttributeEncodedArgument encodedArg = m_ctorParams[i].CustomAttributeEncodedArgument;
+
+                        typedCtorArgs[i] = new CustomAttributeTypedArgument(m_scope, m_ctorParams[i].CustomAttributeEncodedArgument);
+                    }
+
+                    m_typedCtorArgs = Array.AsReadOnly(typedCtorArgs);
+                }
+
+                return m_typedCtorArgs;
+            }
+        }
+
+        public virtual IList<CustomAttributeNamedArgument> NamedArguments
+        {
+            get
+            {
+                if (m_namedArgs == null)
+                {
+                    if (m_namedParams == null)
+                        return null;
+
+                    int cNamedArgs = 0;
+                    for (int i = 0; i < m_namedParams.Length; i++)
+                    {
+                        if (m_namedParams[i].EncodedArgument.CustomAttributeType.EncodedType != CustomAttributeEncoding.Undefined)
+                            cNamedArgs++;
+                    }
+
+                    CustomAttributeNamedArgument[] namedArgs = new CustomAttributeNamedArgument[cNamedArgs];
+
+                    for (int i = 0, j = 0; i < m_namedParams.Length; i++)
+                    {
+                        if (m_namedParams[i].EncodedArgument.CustomAttributeType.EncodedType != CustomAttributeEncoding.Undefined)
+                            namedArgs[j++] = new CustomAttributeNamedArgument(
+                                m_members[i], new CustomAttributeTypedArgument(m_scope, m_namedParams[i].EncodedArgument));
+                    }
+
+                    m_namedArgs = Array.AsReadOnly(namedArgs);
+                }
+
+                return m_namedArgs;
+            }
+        }
+        #endregion
+    }
+
+    public struct CustomAttributeNamedArgument
+    {
+        #region Public Static Members
+        public static bool operator ==(CustomAttributeNamedArgument left, CustomAttributeNamedArgument right)
+        {
+            return left.Equals(right);
+        }
+        public static bool operator !=(CustomAttributeNamedArgument left, CustomAttributeNamedArgument right)
+        {
+            return !left.Equals(right);
+        }
+        #endregion
+
+        #region Private Data Members
+        private MemberInfo m_memberInfo;
+        private CustomAttributeTypedArgument m_value;
+        #endregion
+
+        #region Constructor
+        public CustomAttributeNamedArgument(MemberInfo memberInfo, object value)
+        {
+            if (memberInfo == null)
+                throw new ArgumentNullException(nameof(memberInfo));
+
+            Type type = null;
+            FieldInfo field = memberInfo as FieldInfo;
+            PropertyInfo property = memberInfo as PropertyInfo;
+
+            if (field != null)
+                type = field.FieldType;
+            else if (property != null)
+                type = property.PropertyType;
+            else
+                throw new ArgumentException(SR.Argument_InvalidMemberForNamedArgument);
+
+            m_memberInfo = memberInfo;
+            m_value = new CustomAttributeTypedArgument(type, value);
+        }
+
+        public CustomAttributeNamedArgument(MemberInfo memberInfo, CustomAttributeTypedArgument typedArgument)
+        {
+            if (memberInfo == null)
+                throw new ArgumentNullException(nameof(memberInfo));
+
+            m_memberInfo = memberInfo;
+            m_value = typedArgument;
+        }
+        #endregion
+
+        #region Object Override
+        public override string ToString()
+        {
+            if (m_memberInfo == null)
+                return base.ToString();
+
+            return String.Format(CultureInfo.CurrentCulture, "{0} = {1}", MemberInfo.Name, TypedValue.ToString(ArgumentType != typeof(object)));
+        }
+        public override int GetHashCode()
+        {
+            return base.GetHashCode();
+        }
+        public override bool Equals(object obj)
+        {
+            return obj == (object)this;
+        }
+        #endregion
+
+        #region Internal Members
+        internal Type ArgumentType
+        {
+            get
+            {
+                return m_memberInfo is FieldInfo ?
+                    ((FieldInfo)m_memberInfo).FieldType :
+                    ((PropertyInfo)m_memberInfo).PropertyType;
+            }
+        }
+        #endregion
+
+        #region Public Members
+        public MemberInfo MemberInfo { get { return m_memberInfo; } }
+        public CustomAttributeTypedArgument TypedValue { get { return m_value; } }
+        public string MemberName { get { return MemberInfo.Name; } }
+        public bool IsField { get { return MemberInfo is FieldInfo; } }
+        #endregion
+
+    }
+
+    public struct CustomAttributeTypedArgument
+    {
+        #region Public Static Members
+        public static bool operator ==(CustomAttributeTypedArgument left, CustomAttributeTypedArgument right)
+        {
+            return left.Equals(right);
+        }
+        public static bool operator !=(CustomAttributeTypedArgument left, CustomAttributeTypedArgument right)
+        {
+            return !left.Equals(right);
+        }
+        #endregion
+
+        #region Private Static Methods
+        private static Type CustomAttributeEncodingToType(CustomAttributeEncoding encodedType)
+        {
+            switch (encodedType)
+            {
+                case (CustomAttributeEncoding.Enum):
+                    return typeof(Enum);
+
+                case (CustomAttributeEncoding.Int32):
+                    return typeof(int);
+
+                case (CustomAttributeEncoding.String):
+                    return typeof(string);
+
+                case (CustomAttributeEncoding.Type):
+                    return typeof(Type);
+
+                case (CustomAttributeEncoding.Array):
+                    return typeof(Array);
+
+                case (CustomAttributeEncoding.Char):
+                    return typeof(char);
+
+                case (CustomAttributeEncoding.Boolean):
+                    return typeof(bool);
+
+                case (CustomAttributeEncoding.SByte):
+                    return typeof(sbyte);
+
+                case (CustomAttributeEncoding.Byte):
+                    return typeof(byte);
+
+                case (CustomAttributeEncoding.Int16):
+                    return typeof(short);
+
+                case (CustomAttributeEncoding.UInt16):
+                    return typeof(ushort);
+
+                case (CustomAttributeEncoding.UInt32):
+                    return typeof(uint);
+
+                case (CustomAttributeEncoding.Int64):
+                    return typeof(long);
+
+                case (CustomAttributeEncoding.UInt64):
+                    return typeof(ulong);
+
+                case (CustomAttributeEncoding.Float):
+                    return typeof(float);
+
+                case (CustomAttributeEncoding.Double):
+                    return typeof(double);
+
+                case (CustomAttributeEncoding.Object):
+                    return typeof(object);
+
+                default:
+                    throw new ArgumentException(SR.Format(SR.Arg_EnumIllegalVal, (int)encodedType), nameof(encodedType));
+            }
+        }
+
+        private static object EncodedValueToRawValue(long val, CustomAttributeEncoding encodedType)
+        {
+            switch (encodedType)
+            {
+                case CustomAttributeEncoding.Boolean:
+                    return (byte)val != 0;
+
+                case CustomAttributeEncoding.Char:
+                    return (char)val;
+
+                case CustomAttributeEncoding.Byte:
+                    return (byte)val;
+
+                case CustomAttributeEncoding.SByte:
+                    return (sbyte)val;
+
+                case CustomAttributeEncoding.Int16:
+                    return (short)val;
+
+                case CustomAttributeEncoding.UInt16:
+                    return (ushort)val;
+
+                case CustomAttributeEncoding.Int32:
+                    return (int)val;
+
+                case CustomAttributeEncoding.UInt32:
+                    return (uint)val;
+
+                case CustomAttributeEncoding.Int64:
+                    return (long)val;
+
+                case CustomAttributeEncoding.UInt64:
+                    return (ulong)val;
+
+                case CustomAttributeEncoding.Float:
+                    unsafe { return *(float*)&val; }
+
+                case CustomAttributeEncoding.Double:
+                    unsafe { return *(double*)&val; }
+
+                default:
+                    throw new ArgumentException(SR.Format(SR.Arg_EnumIllegalVal, (int)val), nameof(val));
+            }
+        }
+        private static RuntimeType ResolveType(RuntimeModule scope, string typeName)
+        {
+            RuntimeType type = RuntimeTypeHandle.GetTypeByNameUsingCARules(typeName, scope);
+
+            if (type == null)
+                throw new InvalidOperationException(
+                    String.Format(CultureInfo.CurrentUICulture, SR.Arg_CATypeResolutionFailed, typeName));
+
+            return type;
+        }
+        #endregion
+
+        #region Private Data Members
+        private object m_value;
+        private Type m_argumentType;
+        #endregion
+
+        #region Constructor
+        public CustomAttributeTypedArgument(Type argumentType, object value)
+        {
+            // value can be null.
+            if (argumentType == null)
+                throw new ArgumentNullException(nameof(argumentType));
+
+            m_value = (value == null) ? null : CanonicalizeValue(value);
+            m_argumentType = argumentType;
+        }
+
+        public CustomAttributeTypedArgument(object value)
+        {
+            // value cannot be null.
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            m_value = CanonicalizeValue(value);
+            m_argumentType = value.GetType();
+        }
+
+        private static object CanonicalizeValue(object value)
+        {
+            Debug.Assert(value != null);
+
+            if (value.GetType().IsEnum)
+            {
+                return ((Enum)value).GetValue();
+            }
+            return value;
+        }
+
+        internal CustomAttributeTypedArgument(RuntimeModule scope, CustomAttributeEncodedArgument encodedArg)
+        {
+            CustomAttributeEncoding encodedType = encodedArg.CustomAttributeType.EncodedType;
+
+            if (encodedType == CustomAttributeEncoding.Undefined)
+                throw new ArgumentException(null, nameof(encodedArg));
+
+            else if (encodedType == CustomAttributeEncoding.Enum)
+            {
+                m_argumentType = ResolveType(scope, encodedArg.CustomAttributeType.EnumName);
+                m_value = EncodedValueToRawValue(encodedArg.PrimitiveValue, encodedArg.CustomAttributeType.EncodedEnumType);
+            }
+            else if (encodedType == CustomAttributeEncoding.String)
+            {
+                m_argumentType = typeof(string);
+                m_value = encodedArg.StringValue;
+            }
+            else if (encodedType == CustomAttributeEncoding.Type)
+            {
+                m_argumentType = typeof(Type);
+
+                m_value = null;
+
+                if (encodedArg.StringValue != null)
+                    m_value = ResolveType(scope, encodedArg.StringValue);
+            }
+            else if (encodedType == CustomAttributeEncoding.Array)
+            {
+                encodedType = encodedArg.CustomAttributeType.EncodedArrayType;
+                Type elementType;
+
+                if (encodedType == CustomAttributeEncoding.Enum)
+                {
+                    elementType = ResolveType(scope, encodedArg.CustomAttributeType.EnumName);
+                }
+                else
+                {
+                    elementType = CustomAttributeEncodingToType(encodedType);
+                }
+
+                m_argumentType = elementType.MakeArrayType();
+
+                if (encodedArg.ArrayValue == null)
+                {
+                    m_value = null;
+                }
+                else
+                {
+                    CustomAttributeTypedArgument[] arrayValue = new CustomAttributeTypedArgument[encodedArg.ArrayValue.Length];
+                    for (int i = 0; i < arrayValue.Length; i++)
+                        arrayValue[i] = new CustomAttributeTypedArgument(scope, encodedArg.ArrayValue[i]);
+
+                    m_value = Array.AsReadOnly(arrayValue);
+                }
+            }
+            else
+            {
+                m_argumentType = CustomAttributeEncodingToType(encodedType);
+                m_value = EncodedValueToRawValue(encodedArg.PrimitiveValue, encodedType);
+            }
+        }
+        #endregion
+
+        #region Object Overrides
+        public override string ToString() { return ToString(false); }
+
+        internal string ToString(bool typed)
+        {
+            if (m_argumentType == null)
+                return base.ToString();
+
+            if (ArgumentType.IsEnum)
+                return String.Format(CultureInfo.CurrentCulture, typed ? "{0}" : "({1}){0}", Value, ArgumentType.FullName);
+
+            else if (Value == null)
+                return String.Format(CultureInfo.CurrentCulture, typed ? "null" : "({0})null", ArgumentType.Name);
+
+            else if (ArgumentType == typeof(string))
+                return String.Format(CultureInfo.CurrentCulture, "\"{0}\"", Value);
+
+            else if (ArgumentType == typeof(char))
+                return String.Format(CultureInfo.CurrentCulture, "'{0}'", Value);
+
+            else if (ArgumentType == typeof(Type))
+                return String.Format(CultureInfo.CurrentCulture, "typeof({0})", ((Type)Value).FullName);
+
+            else if (ArgumentType.IsArray)
+            {
+                string result = null;
+                IList<CustomAttributeTypedArgument> array = Value as IList<CustomAttributeTypedArgument>;
+
+                Type elementType = ArgumentType.GetElementType();
+                result = String.Format(CultureInfo.CurrentCulture, @"new {0}[{1}] {{ ", elementType.IsEnum ? elementType.FullName : elementType.Name, array.Count);
+
+                for (int i = 0; i < array.Count; i++)
+                    result += String.Format(CultureInfo.CurrentCulture, i == 0 ? "{0}" : ", {0}", array[i].ToString(elementType != typeof(object)));
+
+                return result += " }";
+            }
+
+            return String.Format(CultureInfo.CurrentCulture, typed ? "{0}" : "({1}){0}", Value, ArgumentType.Name);
+        }
+
+        public override int GetHashCode()
+        {
+            return base.GetHashCode();
+        }
+        public override bool Equals(object obj)
+        {
+            return obj == (object)this;
+        }
+        #endregion
+
+        #region Public Members
+        public Type ArgumentType
+        {
+            get
+            {
+                return m_argumentType;
+            }
+        }
+        public object Value
+        {
+            get
+            {
+                return m_value;
+            }
+        }
+        #endregion
+    }
+
+    internal struct CustomAttributeRecord
+    {
+        internal ConstArray blob;
+        internal MetadataToken tkCtor;
+    }
+
+    internal enum CustomAttributeEncoding : int
+    {
+        Undefined = 0,
+        Boolean = CorElementType.Boolean,
+        Char = CorElementType.Char,
+        SByte = CorElementType.I1,
+        Byte = CorElementType.U1,
+        Int16 = CorElementType.I2,
+        UInt16 = CorElementType.U2,
+        Int32 = CorElementType.I4,
+        UInt32 = CorElementType.U4,
+        Int64 = CorElementType.I8,
+        UInt64 = CorElementType.U8,
+        Float = CorElementType.R4,
+        Double = CorElementType.R8,
+        String = CorElementType.String,
+        Array = CorElementType.SzArray,
+        Type = 0x50,
+        Object = 0x51,
+        Field = 0x53,
+        Property = 0x54,
+        Enum = 0x55
+    }
+
+    [StructLayout(LayoutKind.Auto)]
+    internal struct CustomAttributeEncodedArgument
+    {
+        #region Parser
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void ParseAttributeArguments(
+            IntPtr pCa,
+            int cCa,
+            ref CustomAttributeCtorParameter[] CustomAttributeCtorParameters,
+            ref CustomAttributeNamedParameter[] CustomAttributeTypedArgument,
+            RuntimeAssembly assembly);
+
+        internal static void ParseAttributeArguments(ConstArray attributeBlob,
+            ref CustomAttributeCtorParameter[] customAttributeCtorParameters,
+            ref CustomAttributeNamedParameter[] customAttributeNamedParameters,
+            RuntimeModule customAttributeModule)
+        {
+            if (customAttributeModule == null)
+                throw new ArgumentNullException(nameof(customAttributeModule));
+
+            Debug.Assert(customAttributeCtorParameters != null);
+            Debug.Assert(customAttributeNamedParameters != null);
+
+            if (customAttributeCtorParameters.Length != 0 || customAttributeNamedParameters.Length != 0)
+            {
+                unsafe
+                {
+                    ParseAttributeArguments(
+                        attributeBlob.Signature,
+                        (int)attributeBlob.Length,
+                        ref customAttributeCtorParameters,
+                        ref customAttributeNamedParameters,
+                        (RuntimeAssembly)customAttributeModule.Assembly);
+                }
+            }
+        }
+        #endregion
+
+        #region Private Data Members
+        private long m_primitiveValue;
+        private CustomAttributeEncodedArgument[] m_arrayValue;
+        private string m_stringValue;
+        private CustomAttributeType m_type;
+        #endregion
+
+        #region Public Members
+        public CustomAttributeType CustomAttributeType { get { return m_type; } }
+        public long PrimitiveValue { get { return m_primitiveValue; } }
+        public CustomAttributeEncodedArgument[] ArrayValue { get { return m_arrayValue; } }
+        public string StringValue { get { return m_stringValue; } }
+        #endregion
+    }
+
+    [StructLayout(LayoutKind.Auto)]
+    internal struct CustomAttributeNamedParameter
+    {
+        #region Private Data Members
+        private string m_argumentName;
+        private CustomAttributeEncoding m_fieldOrProperty;
+        private CustomAttributeEncoding m_padding;
+        private CustomAttributeType m_type;
+        private CustomAttributeEncodedArgument m_encodedArgument;
+        #endregion
+
+        #region Constructor
+        public CustomAttributeNamedParameter(string argumentName, CustomAttributeEncoding fieldOrProperty, CustomAttributeType type)
+        {
+            if (argumentName == null)
+                throw new ArgumentNullException(nameof(argumentName));
+
+            m_argumentName = argumentName;
+            m_fieldOrProperty = fieldOrProperty;
+            m_padding = fieldOrProperty;
+            m_type = type;
+            m_encodedArgument = new CustomAttributeEncodedArgument();
+        }
+        #endregion
+
+        #region Public Members
+        public CustomAttributeEncodedArgument EncodedArgument { get { return m_encodedArgument; } }
+        #endregion
+    }
+
+    [StructLayout(LayoutKind.Auto)]
+    internal struct CustomAttributeCtorParameter
+    {
+        #region Private Data Members
+        private CustomAttributeType m_type;
+        private CustomAttributeEncodedArgument m_encodedArgument;
+        #endregion
+
+        #region Constructor
+        public CustomAttributeCtorParameter(CustomAttributeType type)
+        {
+            m_type = type;
+            m_encodedArgument = new CustomAttributeEncodedArgument();
+        }
+        #endregion
+
+        #region Public Members
+        public CustomAttributeEncodedArgument CustomAttributeEncodedArgument { get { return m_encodedArgument; } }
+        #endregion
+    }
+
+    [StructLayout(LayoutKind.Auto)]
+    internal struct CustomAttributeType
+    {
+        #region Private Data Members
+        /// The most complicated type is an enum[] in which case...
+        private string m_enumName; // ...enum name
+        private CustomAttributeEncoding m_encodedType; // ...array
+        private CustomAttributeEncoding m_encodedEnumType; // ...enum
+        private CustomAttributeEncoding m_encodedArrayType; // ...enum type
+        private CustomAttributeEncoding m_padding;
+        #endregion
+
+        #region Constructor
+        public CustomAttributeType(CustomAttributeEncoding encodedType, CustomAttributeEncoding encodedArrayType,
+            CustomAttributeEncoding encodedEnumType, string enumName)
+        {
+            m_encodedType = encodedType;
+            m_encodedArrayType = encodedArrayType;
+            m_encodedEnumType = encodedEnumType;
+            m_enumName = enumName;
+            m_padding = m_encodedType;
+        }
+        #endregion
+
+        #region Public Members
+        public CustomAttributeEncoding EncodedType { get { return m_encodedType; } }
+        public CustomAttributeEncoding EncodedEnumType { get { return m_encodedEnumType; } }
+        public CustomAttributeEncoding EncodedArrayType { get { return m_encodedArrayType; } }
+        public string EnumName { get { return m_enumName; } }
+        #endregion
+    }
+
+    internal static unsafe class CustomAttribute
+    {
+        #region Private Data Members
+        private static RuntimeType Type_RuntimeType = (RuntimeType)typeof(RuntimeType);
+        private static RuntimeType Type_Type = (RuntimeType)typeof(Type);
+        #endregion
+
+        #region Internal Static Members
+        internal static bool IsDefined(RuntimeType type, RuntimeType caType, bool inherit)
+        {
+            Debug.Assert(type != null);
+
+            if (type.GetElementType() != null)
+                return false;
+
+            if (PseudoCustomAttribute.IsDefined(type, caType))
+                return true;
+
+            if (IsCustomAttributeDefined(type.GetRuntimeModule(), type.MetadataToken, caType))
+                return true;
+
+            if (!inherit)
+                return false;
+
+            type = type.BaseType as RuntimeType;
+
+            while (type != null)
+            {
+                if (IsCustomAttributeDefined(type.GetRuntimeModule(), type.MetadataToken, caType, 0, inherit))
+                    return true;
+
+                type = type.BaseType as RuntimeType;
+            }
+
+            return false;
+        }
+
+        internal static bool IsDefined(RuntimeMethodInfo method, RuntimeType caType, bool inherit)
+        {
+            Debug.Assert(method != null);
+            Debug.Assert(caType != null);
+
+            if (PseudoCustomAttribute.IsDefined(method, caType))
+                return true;
+
+            if (IsCustomAttributeDefined(method.GetRuntimeModule(), method.MetadataToken, caType))
+                return true;
+
+            if (!inherit)
+                return false;
+
+            method = method.GetParentDefinition();
+
+            while (method != null)
+            {
+                if (IsCustomAttributeDefined(method.GetRuntimeModule(), method.MetadataToken, caType, 0, inherit))
+                    return true;
+
+                method = method.GetParentDefinition();
+            }
+
+            return false;
+        }
+
+        internal static bool IsDefined(RuntimeConstructorInfo ctor, RuntimeType caType)
+        {
+            Debug.Assert(ctor != null);
+            Debug.Assert(caType != null);
+
+            if (PseudoCustomAttribute.IsDefined(ctor, caType))
+                return true;
+
+            return IsCustomAttributeDefined(ctor.GetRuntimeModule(), ctor.MetadataToken, caType);
+        }
+
+        internal static bool IsDefined(RuntimePropertyInfo property, RuntimeType caType)
+        {
+            Debug.Assert(property != null);
+            Debug.Assert(caType != null);
+
+            if (PseudoCustomAttribute.IsDefined(property, caType))
+                return true;
+
+            return IsCustomAttributeDefined(property.GetRuntimeModule(), property.MetadataToken, caType);
+        }
+
+        internal static bool IsDefined(RuntimeEventInfo e, RuntimeType caType)
+        {
+            Debug.Assert(e != null);
+            Debug.Assert(caType != null);
+
+            if (PseudoCustomAttribute.IsDefined(e, caType))
+                return true;
+
+            return IsCustomAttributeDefined(e.GetRuntimeModule(), e.MetadataToken, caType);
+        }
+
+        internal static bool IsDefined(RuntimeFieldInfo field, RuntimeType caType)
+        {
+            Debug.Assert(field != null);
+            Debug.Assert(caType != null);
+
+            if (PseudoCustomAttribute.IsDefined(field, caType))
+                return true;
+
+            return IsCustomAttributeDefined(field.GetRuntimeModule(), field.MetadataToken, caType);
+        }
+
+        internal static bool IsDefined(RuntimeParameterInfo parameter, RuntimeType caType)
+        {
+            Debug.Assert(parameter != null);
+            Debug.Assert(caType != null);
+
+            if (PseudoCustomAttribute.IsDefined(parameter, caType))
+                return true;
+
+            return IsCustomAttributeDefined(parameter.GetRuntimeModule(), parameter.MetadataToken, caType);
+        }
+
+        internal static bool IsDefined(RuntimeAssembly assembly, RuntimeType caType)
+        {
+            Debug.Assert(assembly != null);
+            Debug.Assert(caType != null);
+
+            if (PseudoCustomAttribute.IsDefined(assembly, caType))
+                return true;
+
+            return IsCustomAttributeDefined(assembly.ManifestModule as RuntimeModule, RuntimeAssembly.GetToken(assembly.GetNativeHandle()), caType);
+        }
+
+        internal static bool IsDefined(RuntimeModule module, RuntimeType caType)
+        {
+            Debug.Assert(module != null);
+            Debug.Assert(caType != null);
+
+            if (PseudoCustomAttribute.IsDefined(module, caType))
+                return true;
+
+            return IsCustomAttributeDefined(module, module.MetadataToken, caType);
+        }
+
+        internal static Object[] GetCustomAttributes(RuntimeType type, RuntimeType caType, bool inherit)
+        {
+            Debug.Assert(type != null);
+            Debug.Assert(caType != null);
+
+            if (type.GetElementType() != null)
+                return (caType.IsValueType) ? Array.Empty<Object>() : CreateAttributeArrayHelper(caType, 0);
+
+            if (type.IsGenericType && !type.IsGenericTypeDefinition)
+                type = type.GetGenericTypeDefinition() as RuntimeType;
+
+            Attribute[] pca = PseudoCustomAttribute.GetCustomAttributes(type, caType, out int pcaCount);
+
+            // if we are asked to go up the hierarchy chain we have to do it now and regardless of the
+            // attribute usage for the specific attribute because a derived attribute may override the usage...           
+            // ... however if the attribute is sealed we can rely on the attribute usage
+            if (!inherit || (caType.IsSealed && !CustomAttribute.GetAttributeUsage(caType).Inherited))
+            {
+                object[] attributes = GetCustomAttributes(type.GetRuntimeModule(), type.MetadataToken, pcaCount, caType);
+                if (pcaCount > 0) Array.Copy(pca, 0, attributes, attributes.Length - pcaCount, pcaCount);
+                return attributes;
+            }
+
+            List<object> result = new List<object>();
+            bool mustBeInheritable = false;
+            bool useObjectArray = (caType == null || caType.IsValueType || caType.ContainsGenericParameters);
+            Type arrayType = useObjectArray ? typeof(object) : caType;
+
+            while (pcaCount > 0)
+                result.Add(pca[--pcaCount]);
+
+            while (type != (RuntimeType)typeof(object) && type != null)
+            {
+                object[] attributes = GetCustomAttributes(type.GetRuntimeModule(), type.MetadataToken, 0, caType, mustBeInheritable, result);
+                mustBeInheritable = true;
+                for (int i = 0; i < attributes.Length; i++)
+                    result.Add(attributes[i]);
+
+                type = type.BaseType as RuntimeType;
+            }
+
+            object[] typedResult = CreateAttributeArrayHelper(arrayType, result.Count);
+            Array.Copy(result.ToArray(), 0, typedResult, 0, result.Count);
+            return typedResult;
+        }
+
+        internal static Object[] GetCustomAttributes(RuntimeMethodInfo method, RuntimeType caType, bool inherit)
+        {
+            Debug.Assert(method != null);
+            Debug.Assert(caType != null);
+
+            if (method.IsGenericMethod && !method.IsGenericMethodDefinition)
+                method = method.GetGenericMethodDefinition() as RuntimeMethodInfo;
+
+            Attribute[] pca = PseudoCustomAttribute.GetCustomAttributes(method, caType, out int pcaCount);
+
+            // if we are asked to go up the hierarchy chain we have to do it now and regardless of the
+            // attribute usage for the specific attribute because a derived attribute may override the usage...           
+            // ... however if the attribute is sealed we can rely on the attribute usage
+            if (!inherit || (caType.IsSealed && !CustomAttribute.GetAttributeUsage(caType).Inherited))
+            {
+                object[] attributes = GetCustomAttributes(method.GetRuntimeModule(), method.MetadataToken, pcaCount, caType);
+                if (pcaCount > 0) Array.Copy(pca, 0, attributes, attributes.Length - pcaCount, pcaCount);
+                return attributes;
+            }
+
+            List<object> result = new List<object>();
+            bool mustBeInheritable = false;
+            bool useObjectArray = (caType == null || caType.IsValueType || caType.ContainsGenericParameters);
+            Type arrayType = useObjectArray ? typeof(object) : caType;
+
+            while (pcaCount > 0)
+                result.Add(pca[--pcaCount]);
+
+            while (method != null)
+            {
+                object[] attributes = GetCustomAttributes(method.GetRuntimeModule(), method.MetadataToken, 0, caType, mustBeInheritable, result);
+                mustBeInheritable = true;
+                for (int i = 0; i < attributes.Length; i++)
+                    result.Add(attributes[i]);
+
+                method = method.GetParentDefinition();
+            }
+
+            object[] typedResult = CreateAttributeArrayHelper(arrayType, result.Count);
+            Array.Copy(result.ToArray(), 0, typedResult, 0, result.Count);
+            return typedResult;
+        }
+
+        internal static Object[] GetCustomAttributes(RuntimeConstructorInfo ctor, RuntimeType caType)
+        {
+            Debug.Assert(ctor != null);
+            Debug.Assert(caType != null);
+
+            Attribute[] pca = PseudoCustomAttribute.GetCustomAttributes(ctor, caType, out int pcaCount);
+            object[] attributes = GetCustomAttributes(ctor.GetRuntimeModule(), ctor.MetadataToken, pcaCount, caType);
+            if (pcaCount > 0) Array.Copy(pca, 0, attributes, attributes.Length - pcaCount, pcaCount);
+            return attributes;
+        }
+
+        internal static Object[] GetCustomAttributes(RuntimePropertyInfo property, RuntimeType caType)
+        {
+            Debug.Assert(property != null);
+            Debug.Assert(caType != null);
+
+            Attribute[] pca = PseudoCustomAttribute.GetCustomAttributes(property, caType, out int pcaCount);
+
+            object[] attributes = GetCustomAttributes(property.GetRuntimeModule(), property.MetadataToken, pcaCount, caType);
+            if (pcaCount > 0) Array.Copy(pca, 0, attributes, attributes.Length - pcaCount, pcaCount);
+            return attributes;
+        }
+
+        internal static Object[] GetCustomAttributes(RuntimeEventInfo e, RuntimeType caType)
+        {
+            Debug.Assert(e != null);
+            Debug.Assert(caType != null);
+
+            Attribute[] pca = PseudoCustomAttribute.GetCustomAttributes(e, caType, out int pcaCount);
+            object[] attributes = GetCustomAttributes(e.GetRuntimeModule(), e.MetadataToken, pcaCount, caType);
+            if (pcaCount > 0) Array.Copy(pca, 0, attributes, attributes.Length - pcaCount, pcaCount);
+            return attributes;
+        }
+
+        internal static Object[] GetCustomAttributes(RuntimeFieldInfo field, RuntimeType caType)
+        {
+            Debug.Assert(field != null);
+            Debug.Assert(caType != null);
+
+            Attribute[] pca = PseudoCustomAttribute.GetCustomAttributes(field, caType, out int pcaCount);
+            object[] attributes = GetCustomAttributes(field.GetRuntimeModule(), field.MetadataToken, pcaCount, caType);
+            if (pcaCount > 0) Array.Copy(pca, 0, attributes, attributes.Length - pcaCount, pcaCount);
+            return attributes;
+        }
+
+        internal static Object[] GetCustomAttributes(RuntimeParameterInfo parameter, RuntimeType caType)
+        {
+            Debug.Assert(parameter != null);
+            Debug.Assert(caType != null);
+
+            Attribute[] pca = PseudoCustomAttribute.GetCustomAttributes(parameter, caType, out int pcaCount);
+            object[] attributes = GetCustomAttributes(parameter.GetRuntimeModule(), parameter.MetadataToken, pcaCount, caType);
+            if (pcaCount > 0) Array.Copy(pca, 0, attributes, attributes.Length - pcaCount, pcaCount);
+            return attributes;
+        }
+
+        internal static Object[] GetCustomAttributes(RuntimeAssembly assembly, RuntimeType caType)
+        {
+            Debug.Assert(assembly != null);
+            Debug.Assert(caType != null);
+
+            Attribute[] pca = PseudoCustomAttribute.GetCustomAttributes(assembly, caType, out int pcaCount);
+            int assemblyToken = RuntimeAssembly.GetToken(assembly.GetNativeHandle());
+            object[] attributes = GetCustomAttributes(assembly.ManifestModule as RuntimeModule, assemblyToken, pcaCount, caType);
+            if (pcaCount > 0) Array.Copy(pca, 0, attributes, attributes.Length - pcaCount, pcaCount);
+            return attributes;
+        }
+
+        internal static Object[] GetCustomAttributes(RuntimeModule module, RuntimeType caType)
+        {
+            Debug.Assert(module != null);
+            Debug.Assert(caType != null);
+
+            Attribute[] pca = PseudoCustomAttribute.GetCustomAttributes(module, caType, out int pcaCount);
+            object[] attributes = GetCustomAttributes(module, module.MetadataToken, pcaCount, caType);
+            if (pcaCount > 0) Array.Copy(pca, 0, attributes, attributes.Length - pcaCount, pcaCount);
+            return attributes;
+        }
+
+        internal static bool IsAttributeDefined(RuntimeModule decoratedModule, int decoratedMetadataToken, int attributeCtorToken)
+        {
+            return IsCustomAttributeDefined(decoratedModule, decoratedMetadataToken, null, attributeCtorToken, false);
+        }
+
+        private static bool IsCustomAttributeDefined(
+            RuntimeModule decoratedModule, int decoratedMetadataToken, RuntimeType attributeFilterType)
+        {
+            return IsCustomAttributeDefined(decoratedModule, decoratedMetadataToken, attributeFilterType, 0, false);
+        }
+
+        private static bool IsCustomAttributeDefined(
+            RuntimeModule decoratedModule, int decoratedMetadataToken, RuntimeType attributeFilterType, int attributeCtorToken, bool mustBeInheritable)
+        {
+            if (decoratedModule.Assembly.ReflectionOnly)
+                throw new InvalidOperationException(SR.Arg_ReflectionOnlyCA);
+
+            CustomAttributeRecord[] car = CustomAttributeData.GetCustomAttributeRecords(decoratedModule, decoratedMetadataToken);
+
+            if (attributeFilterType != null)
+            {
+                Debug.Assert(attributeCtorToken == 0);
+
+                MetadataImport scope = decoratedModule.MetadataImport;
+                RuntimeType attributeType;
+                IRuntimeMethodInfo ctor;
+                bool ctorHasParameters, isVarArg;
+
+                // Optimization for the case where attributes decorate entities in the same assembly in which case 
+                // we can cache the successful APTCA check between the decorated and the declared assembly.
+                Assembly lastAptcaOkAssembly = null;
+
+                for (int i = 0; i < car.Length; i++)
+                {
+                    CustomAttributeRecord caRecord = car[i];
+
+                    if (FilterCustomAttributeRecord(caRecord, scope, ref lastAptcaOkAssembly,
+                        decoratedModule, decoratedMetadataToken, attributeFilterType, mustBeInheritable, null, null,
+                        out attributeType, out ctor, out ctorHasParameters, out isVarArg))
+                        return true;
+                }
+            }
+            else
+            {
+                Debug.Assert(attributeFilterType == null);
+                Debug.Assert(!MetadataToken.IsNullToken(attributeCtorToken));
+
+                for (int i = 0; i < car.Length; i++)
+                {
+                    CustomAttributeRecord caRecord = car[i];
+
+                    if (caRecord.tkCtor == attributeCtorToken)
+                        return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static unsafe object[] GetCustomAttributes(
+            RuntimeModule decoratedModule, int decoratedMetadataToken, int pcaCount, RuntimeType attributeFilterType)
+        {
+            return GetCustomAttributes(decoratedModule, decoratedMetadataToken, pcaCount, attributeFilterType, false, null);
+        }
+
+        private static unsafe object[] GetCustomAttributes(
+            RuntimeModule decoratedModule, int decoratedMetadataToken, int pcaCount,
+            RuntimeType attributeFilterType, bool mustBeInheritable, IList derivedAttributes)
+        {
+            if (decoratedModule.Assembly.ReflectionOnly)
+                throw new InvalidOperationException(SR.Arg_ReflectionOnlyCA);
+
+            MetadataImport scope = decoratedModule.MetadataImport;
+            CustomAttributeRecord[] car = CustomAttributeData.GetCustomAttributeRecords(decoratedModule, decoratedMetadataToken);
+
+            bool useObjectArray = (attributeFilterType == null || attributeFilterType.IsValueType || attributeFilterType.ContainsGenericParameters);
+            Type arrayType = useObjectArray ? typeof(object) : attributeFilterType;
+
+            if (attributeFilterType == null && car.Length == 0)
+                return CreateAttributeArrayHelper(arrayType, 0);
+
+            object[] attributes = CreateAttributeArrayHelper(arrayType, car.Length);
+            int cAttributes = 0;
+
+            // Optimization for the case where attributes decorate entities in the same assembly in which case 
+            // we can cache the successful APTCA check between the decorated and the declared assembly.
+            Assembly lastAptcaOkAssembly = null;
+
+            for (int i = 0; i < car.Length; i++)
+            {
+                object attribute = null;
+                CustomAttributeRecord caRecord = car[i];
+
+                IRuntimeMethodInfo ctor = null;
+                RuntimeType attributeType = null;
+                bool ctorHasParameters, isVarArg;
+                int cNamedArgs = 0;
+
+                IntPtr blobStart = caRecord.blob.Signature;
+                IntPtr blobEnd = (IntPtr)((byte*)blobStart + caRecord.blob.Length);
+                int blobLen = (int)((byte*)blobEnd - (byte*)blobStart);
+
+                if (!FilterCustomAttributeRecord(caRecord, scope, ref lastAptcaOkAssembly,
+                                                 decoratedModule, decoratedMetadataToken, attributeFilterType, mustBeInheritable,
+                                                 attributes, derivedAttributes,
+                                                 out attributeType, out ctor, out ctorHasParameters, out isVarArg))
+                    continue;
+
+                // Leverage RuntimeConstructorInfo standard .ctor verfication
+                RuntimeConstructorInfo.CheckCanCreateInstance(attributeType, isVarArg);
+
+                // Create custom attribute object
+                if (ctorHasParameters)
+                {
+                    attribute = CreateCaObject(decoratedModule, attributeType, ctor, ref blobStart, blobEnd, out cNamedArgs);
+                }
+                else
+                {
+                    attribute = RuntimeTypeHandle.CreateCaInstance(attributeType, ctor);
+
+                    // It is allowed by the ECMA spec to have an empty signature blob
+                    if (blobLen == 0)
+                        cNamedArgs = 0;
+                    else
+                    {
+                        // Metadata is always written in little-endian format. Must account for this on
+                        // big-endian platforms.
+#if BIGENDIAN
+                        const int CustomAttributeVersion = 0x0100;
+#else
+                        const int CustomAttributeVersion = 0x0001;
+#endif
+                        if (Marshal.ReadInt16(blobStart) != CustomAttributeVersion)
+                            throw new CustomAttributeFormatException();
+                        blobStart = (IntPtr)((byte*)blobStart + 2); // skip version prefix
+
+                        cNamedArgs = Marshal.ReadInt16(blobStart);
+                        blobStart = (IntPtr)((byte*)blobStart + 2); // skip namedArgs count
+#if BIGENDIAN
+                        cNamedArgs = ((cNamedArgs & 0xff00) >> 8) | ((cNamedArgs & 0x00ff) << 8);
+#endif
+                    }
+                }
+
+                for (int j = 0; j < cNamedArgs; j++)
+                {
+                    #region // Initialize named properties and fields
+                    string name;
+                    bool isProperty;
+                    RuntimeType type;
+                    object value;
+
+                    IntPtr blobItr = caRecord.blob.Signature;
+
+                    GetPropertyOrFieldData(decoratedModule, ref blobStart, blobEnd, out name, out isProperty, out type, out value);
+
+                    try
+                    {
+                        if (isProperty)
+                        {
+                            #region // Initialize property
+                            if (type == null && value != null)
+                            {
+                                type = (RuntimeType)value.GetType();
+                                if (type == Type_RuntimeType)
+                                    type = Type_Type;
+                            }
+
+                            RuntimePropertyInfo property = null;
+
+                            if (type == null)
+                                property = attributeType.GetProperty(name) as RuntimePropertyInfo;
+                            else
+                                property = attributeType.GetProperty(name, type, Type.EmptyTypes) as RuntimePropertyInfo;
+
+                            // Did we get a valid property reference?
+                            if (property == null)
+                            {
+                                throw new CustomAttributeFormatException(
+                                    String.Format(CultureInfo.CurrentUICulture, 
+                                        isProperty ? SR.RFLCT_InvalidPropFail : SR.RFLCT_InvalidFieldFail, name));
+                            }
+
+                            RuntimeMethodInfo setMethod = property.GetSetMethod(true) as RuntimeMethodInfo;
+
+                            // Public properties may have non-public setter methods
+                            if (!setMethod.IsPublic)
+                                continue;
+
+                            setMethod.Invoke(attribute, BindingFlags.Default, null, new object[] { value }, null);
+                            #endregion
+                        }
+                        else
+                        {
+                            RtFieldInfo field = attributeType.GetField(name) as RtFieldInfo;
+
+                            field.CheckConsistency(attribute);
+                            field.UnsafeSetValue(attribute, value, BindingFlags.Default, Type.DefaultBinder, null);
+                        }
+                    }
+                    catch (Exception e)
+                    {
+                        throw new CustomAttributeFormatException(
+                            String.Format(CultureInfo.CurrentUICulture,
+                                isProperty ? SR.RFLCT_InvalidPropFail : SR.RFLCT_InvalidFieldFail, name), e);
+                    }
+                    #endregion
+                }
+
+                if (blobStart != blobEnd)
+                    throw new CustomAttributeFormatException();
+
+                attributes[cAttributes++] = attribute;
+            }
+
+            if (cAttributes == car.Length && pcaCount == 0)
+                return attributes;
+
+            object[] result = CreateAttributeArrayHelper(arrayType, cAttributes + pcaCount);
+            Array.Copy(attributes, 0, result, 0, cAttributes);
+            return result;
+        }
+
+        private static unsafe bool FilterCustomAttributeRecord(
+            CustomAttributeRecord caRecord,
+            MetadataImport scope,
+            ref Assembly lastAptcaOkAssembly,
+            RuntimeModule decoratedModule,
+            MetadataToken decoratedToken,
+            RuntimeType attributeFilterType,
+            bool mustBeInheritable,
+            object[] attributes,
+            IList derivedAttributes,
+            out RuntimeType attributeType,
+            out IRuntimeMethodInfo ctor,
+            out bool ctorHasParameters,
+            out bool isVarArg)
+        {
+            ctor = null;
+            attributeType = null;
+            ctorHasParameters = false;
+            isVarArg = false;
+
+            IntPtr blobStart = caRecord.blob.Signature;
+            IntPtr blobEnd = (IntPtr)((byte*)blobStart + caRecord.blob.Length);
+
+            // Resolve attribute type from ctor parent token found in decorated decoratedModule scope
+            attributeType = decoratedModule.ResolveType(scope.GetParentToken(caRecord.tkCtor), null, null) as RuntimeType;
+
+
+            // Test attribute type against user provided attribute type filter
+            if (!(attributeFilterType.IsAssignableFrom(attributeType)))
+                return false;
+
+            // Ensure if attribute type must be inheritable that it is inhertiable
+            // Ensure that to consider a duplicate attribute type AllowMultiple is true
+            if (!AttributeUsageCheck(attributeType, mustBeInheritable, attributes, derivedAttributes))
+                return false;
+
+            // Windows Runtime attributes aren't real types - they exist to be read as metadata only, and as such
+            // should be filtered out of the GetCustomAttributes path.
+            if ((attributeType.Attributes & TypeAttributes.WindowsRuntime) == TypeAttributes.WindowsRuntime)
+            {
+                return false;
+            }
+
+            // Resolve the attribute ctor
+            ConstArray ctorSig = scope.GetMethodSignature(caRecord.tkCtor);
+            isVarArg = (ctorSig[0] & 0x05) != 0;
+            ctorHasParameters = ctorSig[1] != 0;
+
+            if (ctorHasParameters)
+            {
+                // Resolve method ctor token found in decorated decoratedModule scope
+                ctor = decoratedModule.ResolveMethod(caRecord.tkCtor, attributeType.GenericTypeArguments, null).MethodHandle.GetMethodInfo();
+            }
+            else
+            {
+                // Resolve method ctor token from decorated decoratedModule scope
+                ctor = attributeType.GetTypeHandleInternal().GetDefaultConstructor();
+
+                if (ctor == null && !attributeType.IsValueType)
+                    throw new MissingMethodException(".ctor");
+            }
+
+            // Visibility checks
+            MetadataToken tkParent = new MetadataToken();
+
+            if (decoratedToken.IsParamDef)
+            {
+                tkParent = new MetadataToken(scope.GetParentToken(decoratedToken));
+                tkParent = new MetadataToken(scope.GetParentToken(tkParent));
+            }
+            else if (decoratedToken.IsMethodDef || decoratedToken.IsProperty || decoratedToken.IsEvent || decoratedToken.IsFieldDef)
+            {
+                tkParent = new MetadataToken(scope.GetParentToken(decoratedToken));
+            }
+            else if (decoratedToken.IsTypeDef)
+            {
+                tkParent = decoratedToken;
+            }
+            else if (decoratedToken.IsGenericPar)
+            {
+                tkParent = new MetadataToken(scope.GetParentToken(decoratedToken));
+
+                // decoratedToken is a generic parameter on a method. Get the declaring Type of the method.
+                if (tkParent.IsMethodDef)
+                    tkParent = new MetadataToken(scope.GetParentToken(tkParent));
+            }
+            else
+            {
+                // We need to relax this when we add support for other types of decorated tokens.
+                Debug.Assert(decoratedToken.IsModule || decoratedToken.IsAssembly,
+                                "The decoratedToken must be either an assembly, a module, a type, or a member.");
+            }
+
+            // If the attribute is on a type, member, or parameter we check access against the (declaring) type,
+            // otherwise we check access against the module.
+            RuntimeTypeHandle parentTypeHandle = tkParent.IsTypeDef ?
+                                                    decoratedModule.ModuleHandle.ResolveTypeHandle(tkParent) :
+                                                    new RuntimeTypeHandle();
+
+            return RuntimeMethodHandle.IsCAVisibleFromDecoratedType(attributeType.TypeHandle, ctor, parentTypeHandle, decoratedModule);
+        }
+        #endregion
+
+        #region Private Static Methods
+        private static bool AttributeUsageCheck(
+            RuntimeType attributeType, bool mustBeInheritable, object[] attributes, IList derivedAttributes)
+        {
+            AttributeUsageAttribute attributeUsageAttribute = null;
+
+            if (mustBeInheritable)
+            {
+                attributeUsageAttribute = CustomAttribute.GetAttributeUsage(attributeType);
+
+                if (!attributeUsageAttribute.Inherited)
+                    return false;
+            }
+
+            // Legacy: AllowMultiple ignored for none inheritable attributes
+
+            if (derivedAttributes == null)
+                return true;
+
+            for (int i = 0; i < derivedAttributes.Count; i++)
+            {
+                if (derivedAttributes[i].GetType() == attributeType)
+                {
+                    if (attributeUsageAttribute == null)
+                        attributeUsageAttribute = CustomAttribute.GetAttributeUsage(attributeType);
+
+                    return attributeUsageAttribute.AllowMultiple;
+                }
+            }
+
+            return true;
+        }
+
+        internal static AttributeUsageAttribute GetAttributeUsage(RuntimeType decoratedAttribute)
+        {
+            RuntimeModule decoratedModule = decoratedAttribute.GetRuntimeModule();
+            MetadataImport scope = decoratedModule.MetadataImport;
+            CustomAttributeRecord[] car = CustomAttributeData.GetCustomAttributeRecords(decoratedModule, decoratedAttribute.MetadataToken);
+
+            AttributeUsageAttribute attributeUsageAttribute = null;
+
+            for (int i = 0; i < car.Length; i++)
+            {
+                CustomAttributeRecord caRecord = car[i];
+                RuntimeType attributeType = decoratedModule.ResolveType(scope.GetParentToken(caRecord.tkCtor), null, null) as RuntimeType;
+
+                if (attributeType != (RuntimeType)typeof(AttributeUsageAttribute))
+                    continue;
+
+                if (attributeUsageAttribute != null)
+                    throw new FormatException(String.Format(
+                        CultureInfo.CurrentUICulture, SR.Format_AttributeUsage, attributeType));
+
+                AttributeTargets targets;
+                bool inherited, allowMultiple;
+                ParseAttributeUsageAttribute(caRecord.blob, out targets, out inherited, out allowMultiple);
+                attributeUsageAttribute = new AttributeUsageAttribute(targets, allowMultiple, inherited);
+            }
+
+            if (attributeUsageAttribute == null)
+                return AttributeUsageAttribute.Default;
+
+            return attributeUsageAttribute;
+        }
+        #endregion
+
+        #region Private Static FCalls
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _ParseAttributeUsageAttribute(
+            IntPtr pCa, int cCa, out int targets, out bool inherited, out bool allowMultiple);
+        private static void ParseAttributeUsageAttribute(
+            ConstArray ca, out AttributeTargets targets, out bool inherited, out bool allowMultiple)
+        {
+            int _targets;
+            _ParseAttributeUsageAttribute(ca.Signature, ca.Length, out _targets, out inherited, out allowMultiple);
+            targets = (AttributeTargets)_targets;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe Object _CreateCaObject(RuntimeModule pModule, RuntimeType type, IRuntimeMethodInfo pCtor, byte** ppBlob, byte* pEndBlob, int* pcNamedArgs);
+        private static unsafe Object CreateCaObject(RuntimeModule module, RuntimeType type, IRuntimeMethodInfo ctor, ref IntPtr blob, IntPtr blobEnd, out int namedArgs)
+        {
+            byte* pBlob = (byte*)blob;
+            byte* pBlobEnd = (byte*)blobEnd;
+            int cNamedArgs;
+            object ca = _CreateCaObject(module, type, ctor, &pBlob, pBlobEnd, &cNamedArgs);
+            blob = (IntPtr)pBlob;
+            namedArgs = cNamedArgs;
+            return ca;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe void _GetPropertyOrFieldData(
+            RuntimeModule pModule, byte** ppBlobStart, byte* pBlobEnd, out string name, out bool bIsProperty, out RuntimeType type, out object value);
+        private static unsafe void GetPropertyOrFieldData(
+            RuntimeModule module, ref IntPtr blobStart, IntPtr blobEnd, out string name, out bool isProperty, out RuntimeType type, out object value)
+        {
+            byte* pBlobStart = (byte*)blobStart;
+            _GetPropertyOrFieldData(
+                module.GetNativeHandle(), &pBlobStart, (byte*)blobEnd, out name, out isProperty, out type, out value);
+            blobStart = (IntPtr)pBlobStart;
+        }
+
+        private static object[] CreateAttributeArrayHelper(Type elementType, int elementCount)
+        {
+            return (object[])Array.UnsafeCreateInstance(elementType, elementCount);
+        }
+        #endregion
+    }
+
+    internal static class PseudoCustomAttribute
+    {
+        #region Private Static Data Members
+        // Here we can avoid the need to take a lock when using Dictionary by rearranging
+        // the only method that adds values to the Dictionary. For more details on 
+        // Dictionary versus Hashtable thread safety:
+        // See code:Dictionary#DictionaryVersusHashtableThreadSafety
+        private static readonly Dictionary<RuntimeType, RuntimeType> s_pca = CreatePseudoCustomAttributeDictionary();
+        #endregion
+
+        #region Static Constructor
+        static Dictionary<RuntimeType, RuntimeType> CreatePseudoCustomAttributeDictionary()
+        {
+            Type[] pcas = new Type[]
+            {
+                // See https://github.com/dotnet/coreclr/blob/master/src/md/compiler/custattr_emit.cpp
+                typeof(FieldOffsetAttribute), // field
+                typeof(SerializableAttribute), // class, struct, enum, delegate
+                typeof(MarshalAsAttribute), // parameter, field, return-value
+                typeof(ComImportAttribute), // class, interface 
+                typeof(NonSerializedAttribute), // field, inherited
+                typeof(InAttribute), // parameter
+                typeof(OutAttribute), // parameter
+                typeof(OptionalAttribute), // parameter
+                typeof(DllImportAttribute), // method
+                typeof(PreserveSigAttribute), // method
+                typeof(TypeForwardedToAttribute), // assembly
+            };
+
+            Dictionary<RuntimeType, RuntimeType> dict = new Dictionary<RuntimeType, RuntimeType>(pcas.Length);
+            foreach (RuntimeType runtimeType in pcas)
+            {
+                VerifyPseudoCustomAttribute(runtimeType);
+                dict[runtimeType] = runtimeType;
+            }
+            return dict;
+        }
+
+        [Conditional("DEBUG")]
+        private static void VerifyPseudoCustomAttribute(RuntimeType pca)
+        {
+            // If any of these are invariants are no longer true will have to 
+            // re-architect the PCA product logic and test cases -- you've been warned!
+            Debug.Assert(pca.BaseType == typeof(Attribute), "Pseudo CA Error");
+            AttributeUsageAttribute usage = CustomAttribute.GetAttributeUsage(pca);
+            Debug.Assert(usage.Inherited == false, "Pseudo CA Error");
+            //AllowMultiple is true for TypeForwardedToAttribute
+            //Debug.Assert(usage.AllowMultiple == false, "Pseudo CA Error");
+        }
+        #endregion
+
+        #region Internal Static
+        internal static Attribute[] GetCustomAttributes(RuntimeType type, RuntimeType caType, out int count)
+        {
+            Debug.Assert(type != null);
+            Debug.Assert(caType != null);
+
+            count = 0;
+
+            bool all = caType == typeof(object) || caType == typeof(Attribute);
+            if (!all && !s_pca.ContainsKey(caType))
+                return null;
+
+            Attribute[] pcas = new Attribute[all ? 2 : 1];
+
+            if (all || caType == typeof(SerializableAttribute))
+            {
+                if ((type.Attributes & TypeAttributes.Serializable) != 0)
+                    pcas[count++] = new SerializableAttribute();
+            }
+            if (all || caType == typeof(ComImportAttribute))
+            {
+                if ((type.Attributes & TypeAttributes.Import) != 0)
+                    pcas[count++] = new ComImportAttribute();
+            }
+
+            return pcas;
+        }
+        internal static bool IsDefined(RuntimeType type, RuntimeType caType)
+        {
+            bool all = caType == typeof(object) || caType == typeof(Attribute);
+            if (!all && !s_pca.ContainsKey(caType))
+                return false;
+
+            if (all || caType == typeof(SerializableAttribute))
+            {
+                if ((type.Attributes & TypeAttributes.Serializable) != 0)
+                    return true;
+            }
+            if (all || caType == typeof(ComImportAttribute))
+            {
+                if ((type.Attributes & TypeAttributes.Import) != 0)
+                    return true;
+            }
+
+            return false;
+        }
+
+        internal static Attribute[] GetCustomAttributes(RuntimeMethodInfo method, RuntimeType caType, out int count)
+        {
+            Debug.Assert(method != null);
+            Debug.Assert(caType != null);
+
+            count = 0;
+
+            bool all = caType == typeof(object) || caType == typeof(Attribute);
+            if (!all && !s_pca.ContainsKey(caType))
+                return null;
+
+            Attribute[] pcas = new Attribute[all ? 2 : 1];
+            Attribute pca;
+
+            if (all || caType == typeof(DllImportAttribute))
+            {
+                pca = GetDllImportCustomAttribute(method);
+                if (pca != null) pcas[count++] = pca;
+            }
+            if (all || caType == typeof(PreserveSigAttribute))
+            {
+                if ((method.GetMethodImplementationFlags() & MethodImplAttributes.PreserveSig) != 0)
+                    pcas[count++] = new PreserveSigAttribute();
+            }
+
+            return pcas;
+        }
+        internal static bool IsDefined(RuntimeMethodInfo method, RuntimeType caType)
+        {
+            bool all = caType == typeof(object) || caType == typeof(Attribute);
+            if (!all && !s_pca.ContainsKey(caType))
+                return false;
+
+            if (all || caType == typeof(DllImportAttribute))
+            {
+                if ((method.Attributes & MethodAttributes.PinvokeImpl) != 0)
+                    return true;
+            }
+            if (all || caType == typeof(PreserveSigAttribute))
+            {
+                if ((method.GetMethodImplementationFlags() & MethodImplAttributes.PreserveSig) != 0)
+                    return true;
+            }
+
+            return false;
+        }
+
+        internal static Attribute[] GetCustomAttributes(RuntimeParameterInfo parameter, RuntimeType caType, out int count)
+        {
+            Debug.Assert(parameter != null);
+            Debug.Assert(caType != null);
+
+            count = 0;
+
+            bool all = caType == typeof(object) || caType == typeof(Attribute);
+            if (!all && !s_pca.ContainsKey(caType))
+                return null;
+
+            Attribute[] pcas = new Attribute[all ? 4 : 1];
+            Attribute pca;
+
+            if (all || caType == typeof(InAttribute))
+            {
+                if (parameter.IsIn)
+                    pcas[count++] = new InAttribute();
+            }
+            if (all || caType == typeof(OutAttribute))
+            {
+                if (parameter.IsOut)
+                    pcas[count++] = new OutAttribute();
+            }
+            if (all || caType == typeof(OptionalAttribute))
+            {
+                if (parameter.IsOptional)
+                    pcas[count++] = new OptionalAttribute();
+            }
+            if (all || caType == typeof(MarshalAsAttribute))
+            {
+                pca = GetMarshalAsCustomAttribute(parameter);
+                if (pca != null) pcas[count++] = pca;
+            }
+            return pcas;
+        }
+        internal static bool IsDefined(RuntimeParameterInfo parameter, RuntimeType caType)
+        {
+            bool all = caType == typeof(object) || caType == typeof(Attribute);
+            if (!all && !s_pca.ContainsKey(caType))
+                return false;
+
+            if (all || caType == typeof(InAttribute))
+            {
+                if (parameter.IsIn) return true;
+            }
+            if (all || caType == typeof(OutAttribute))
+            {
+                if (parameter.IsOut) return true;
+            }
+            if (all || caType == typeof(OptionalAttribute))
+            {
+                if (parameter.IsOptional) return true;
+            }
+            if (all || caType == typeof(MarshalAsAttribute))
+            {
+                if (GetMarshalAsCustomAttribute(parameter) != null) return true;
+            }
+
+            return false;
+        }
+
+        internal static Attribute[] GetCustomAttributes(RuntimeAssembly assembly, RuntimeType caType, out int count)
+        {
+            count = 0;
+            return null;
+        }
+        internal static bool IsDefined(RuntimeAssembly assembly, RuntimeType caType)
+        {
+            return false;
+        }
+
+        internal static Attribute[] GetCustomAttributes(RuntimeModule module, RuntimeType caType, out int count)
+        {
+            count = 0;
+            return null;
+        }
+        internal static bool IsDefined(RuntimeModule module, RuntimeType caType)
+        {
+            return false;
+        }
+
+        internal static Attribute[] GetCustomAttributes(RuntimeFieldInfo field, RuntimeType caType, out int count)
+        {
+            Debug.Assert(field != null);
+            Debug.Assert(caType != null);
+
+            count = 0;
+
+            bool all = caType == typeof(object) || caType == typeof(Attribute);
+            if (!all && !s_pca.ContainsKey(caType))
+                return null;
+
+            Attribute[] pcas = new Attribute[all ? 3 : 1];
+            Attribute pca;
+
+            if (all || caType == typeof(MarshalAsAttribute))
+            {
+                pca = GetMarshalAsCustomAttribute(field);
+                if (pca != null) pcas[count++] = pca;
+            }
+            if (all || caType == typeof(FieldOffsetAttribute))
+            {
+                pca = GetFieldOffsetCustomAttribute(field);
+                if (pca != null) pcas[count++] = pca;
+            }
+            if (all || caType == typeof(NonSerializedAttribute))
+            {
+                if ((field.Attributes & FieldAttributes.NotSerialized) != 0)
+                    pcas[count++] = new NonSerializedAttribute();
+            }
+            return pcas;
+        }
+        internal static bool IsDefined(RuntimeFieldInfo field, RuntimeType caType)
+        {
+            bool all = caType == typeof(object) || caType == typeof(Attribute);
+            if (!all && !s_pca.ContainsKey(caType))
+                return false;
+
+            if (all || caType == typeof(MarshalAsAttribute))
+            {
+                if (GetMarshalAsCustomAttribute(field) != null) return true;
+            }
+            if (all || caType == typeof(FieldOffsetAttribute))
+            {
+                if (GetFieldOffsetCustomAttribute(field) != null) return true;
+            }
+            if (all || caType == typeof(NonSerializedAttribute))
+            {
+                if ((field.Attributes & FieldAttributes.NotSerialized) != 0)
+                    return true;
+            }
+
+            return false;
+        }
+
+        internal static Attribute[] GetCustomAttributes(RuntimeConstructorInfo ctor, RuntimeType caType, out int count)
+        {
+            count = 0;
+            return null;
+        }
+        internal static bool IsDefined(RuntimeConstructorInfo ctor, RuntimeType caType)
+        {
+            return false;
+        }
+
+        internal static Attribute[] GetCustomAttributes(RuntimePropertyInfo property, RuntimeType caType, out int count)
+        {
+            count = 0;
+            return null;
+        }
+        internal static bool IsDefined(RuntimePropertyInfo property, RuntimeType caType)
+        {
+            return false;
+        }
+
+        internal static Attribute[] GetCustomAttributes(RuntimeEventInfo e, RuntimeType caType, out int count)
+        {
+            count = 0;
+            return null;
+        }
+        internal static bool IsDefined(RuntimeEventInfo e, RuntimeType caType)
+        {
+            return false;
+        }
+        #endregion
+
+        private static DllImportAttribute GetDllImportCustomAttribute(RuntimeMethodInfo method)
+        {
+            if ((method.Attributes & MethodAttributes.PinvokeImpl) == 0)
+                return null;
+
+            MetadataImport scope = ModuleHandle.GetMetadataImport(method.Module.ModuleHandle.GetRuntimeModule());
+            string entryPoint, dllName = null;
+            int token = method.MetadataToken;
+            PInvokeAttributes flags = 0;
+
+            scope.GetPInvokeMap(token, out flags, out entryPoint, out dllName);
+
+            CharSet charSet = CharSet.None;
+
+            switch (flags & PInvokeAttributes.CharSetMask)
+            {
+                case PInvokeAttributes.CharSetNotSpec: charSet = CharSet.None; break;
+                case PInvokeAttributes.CharSetAnsi: charSet = CharSet.Ansi; break;
+                case PInvokeAttributes.CharSetUnicode: charSet = CharSet.Unicode; break;
+                case PInvokeAttributes.CharSetAuto: charSet = CharSet.Auto; break;
+
+                // Invalid: default to CharSet.None
+                default: break;
+            }
+
+            CallingConvention callingConvention = CallingConvention.Cdecl;
+
+            switch (flags & PInvokeAttributes.CallConvMask)
+            {
+                case PInvokeAttributes.CallConvWinapi: callingConvention = CallingConvention.Winapi; break;
+                case PInvokeAttributes.CallConvCdecl: callingConvention = CallingConvention.Cdecl; break;
+                case PInvokeAttributes.CallConvStdcall: callingConvention = CallingConvention.StdCall; break;
+                case PInvokeAttributes.CallConvThiscall: callingConvention = CallingConvention.ThisCall; break;
+                case PInvokeAttributes.CallConvFastcall: callingConvention = CallingConvention.FastCall; break;
+
+                // Invalid: default to CallingConvention.Cdecl
+                default: break;
+            }
+
+            DllImportAttribute attribute = new DllImportAttribute(dllName);
+
+            attribute.EntryPoint = entryPoint;
+            attribute.CharSet = charSet;
+            attribute.SetLastError = (flags & PInvokeAttributes.SupportsLastError) != 0;
+            attribute.ExactSpelling = (flags & PInvokeAttributes.NoMangle) != 0;
+            attribute.PreserveSig = (method.GetMethodImplementationFlags() & MethodImplAttributes.PreserveSig) != 0;
+            attribute.CallingConvention = callingConvention;
+            attribute.BestFitMapping = (flags & PInvokeAttributes.BestFitMask) == PInvokeAttributes.BestFitEnabled;
+            attribute.ThrowOnUnmappableChar = (flags & PInvokeAttributes.ThrowOnUnmappableCharMask) == PInvokeAttributes.ThrowOnUnmappableCharEnabled;
+
+            return attribute;
+        }
+
+
+        private static MarshalAsAttribute GetMarshalAsCustomAttribute(RuntimeParameterInfo parameter)
+        {
+            return GetMarshalAsCustomAttribute(parameter.MetadataToken, parameter.GetRuntimeModule());
+        }
+        private static MarshalAsAttribute GetMarshalAsCustomAttribute(RuntimeFieldInfo field)
+        {
+            return GetMarshalAsCustomAttribute(field.MetadataToken, field.GetRuntimeModule());
+        }
+
+        private static MarshalAsAttribute GetMarshalAsCustomAttribute(int token, RuntimeModule scope)
+        {
+            UnmanagedType unmanagedType, arraySubType;
+            VarEnum safeArraySubType;
+            int sizeParamIndex = 0, sizeConst = 0;
+            string marshalTypeName = null, marshalCookie = null, safeArrayUserDefinedTypeName = null;
+            int iidParamIndex = 0;
+            ConstArray nativeType = ModuleHandle.GetMetadataImport(scope.GetNativeHandle()).GetFieldMarshal(token);
+
+            if (nativeType.Length == 0)
+                return null;
+
+            MetadataImport.GetMarshalAs(nativeType,
+                out unmanagedType, out safeArraySubType, out safeArrayUserDefinedTypeName, out arraySubType, out sizeParamIndex,
+                out sizeConst, out marshalTypeName, out marshalCookie, out iidParamIndex);
+
+            RuntimeType safeArrayUserDefinedType = safeArrayUserDefinedTypeName == null || safeArrayUserDefinedTypeName.Length == 0 ? null :
+                RuntimeTypeHandle.GetTypeByNameUsingCARules(safeArrayUserDefinedTypeName, scope);
+            RuntimeType marshalTypeRef = null;
+
+            try
+            {
+                marshalTypeRef = marshalTypeName == null ? null : RuntimeTypeHandle.GetTypeByNameUsingCARules(marshalTypeName, scope);
+            }
+            catch (System.TypeLoadException)
+            {
+                // The user may have supplied a bad type name string causing this TypeLoadException
+                // Regardless, we return the bad type name
+                Debug.Assert(marshalTypeName != null);
+            }
+
+            MarshalAsAttribute attribute = new MarshalAsAttribute(unmanagedType);
+
+            attribute.SafeArraySubType = safeArraySubType;
+            attribute.SafeArrayUserDefinedSubType = safeArrayUserDefinedType;
+            attribute.IidParameterIndex = iidParamIndex;
+            attribute.ArraySubType = arraySubType;
+            attribute.SizeParamIndex = (short)sizeParamIndex;
+            attribute.SizeConst = sizeConst;
+            attribute.MarshalType = marshalTypeName;
+            attribute.MarshalTypeRef = marshalTypeRef;
+            attribute.MarshalCookie = marshalCookie;
+
+            return attribute;
+        }
+
+        private static FieldOffsetAttribute GetFieldOffsetCustomAttribute(RuntimeFieldInfo field)
+        {
+            int fieldOffset;
+
+            if (field.DeclaringType != null &&
+                field.GetRuntimeModule().MetadataImport.GetFieldOffset(field.DeclaringType.MetadataToken, field.MetadataToken, out fieldOffset))
+                return new FieldOffsetAttribute(fieldOffset);
+
+            return null;
+        }
+
+        internal static StructLayoutAttribute GetStructLayoutCustomAttribute(RuntimeType type)
+        {
+            if (type.IsInterface || type.HasElementType || type.IsGenericParameter)
+                return null;
+
+            int pack = 0, size = 0;
+            LayoutKind layoutKind = LayoutKind.Auto;
+            switch (type.Attributes & TypeAttributes.LayoutMask)
+            {
+                case TypeAttributes.ExplicitLayout: layoutKind = LayoutKind.Explicit; break;
+                case TypeAttributes.AutoLayout: layoutKind = LayoutKind.Auto; break;
+                case TypeAttributes.SequentialLayout: layoutKind = LayoutKind.Sequential; break;
+                default: Debug.Fail("Unreachable code"); break;
+            }
+
+            CharSet charSet = CharSet.None;
+            switch (type.Attributes & TypeAttributes.StringFormatMask)
+            {
+                case TypeAttributes.AnsiClass: charSet = CharSet.Ansi; break;
+                case TypeAttributes.AutoClass: charSet = CharSet.Auto; break;
+                case TypeAttributes.UnicodeClass: charSet = CharSet.Unicode; break;
+                default: Debug.Fail("Unreachable code"); break;
+            }
+            type.GetRuntimeModule().MetadataImport.GetClassLayout(type.MetadataToken, out pack, out size);
+
+            // Metadata parameter checking should not have allowed 0 for packing size.
+            // The runtime later converts a packing size of 0 to 8 so do the same here
+            // because it's more useful from a user perspective. 
+            if (pack == 0)
+                pack = 8; // DEFAULT_PACKING_SIZE
+
+            StructLayoutAttribute attribute = new StructLayoutAttribute(layoutKind);
+
+            attribute.Pack = pack;
+            attribute.Size = size;
+            attribute.CharSet = charSet;
+
+            return attribute;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/CustomAttributeExtensions.cs b/src/System.Private.CoreLib/src/System/Reflection/CustomAttributeExtensions.cs
new file mode 100644
index 0000000000..24e5055b8d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/CustomAttributeExtensions.cs
@@ -0,0 +1,175 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+
+namespace System.Reflection
+{
+    public static class CustomAttributeExtensions
+    {
+        #region APIs that return a single attribute
+        public static Attribute GetCustomAttribute(this Assembly element, Type attributeType)
+        {
+            return Attribute.GetCustomAttribute(element, attributeType);
+        }
+        public static Attribute GetCustomAttribute(this Module element, Type attributeType)
+        {
+            return Attribute.GetCustomAttribute(element, attributeType);
+        }
+        public static Attribute GetCustomAttribute(this MemberInfo element, Type attributeType)
+        {
+            return Attribute.GetCustomAttribute(element, attributeType);
+        }
+        public static Attribute GetCustomAttribute(this ParameterInfo element, Type attributeType)
+        {
+            return Attribute.GetCustomAttribute(element, attributeType);
+        }
+
+        public static T GetCustomAttribute<T>(this Assembly element) where T : Attribute
+        {
+            return (T)GetCustomAttribute(element, typeof(T));
+        }
+        public static T GetCustomAttribute<T>(this Module element) where T : Attribute
+        {
+            return (T)GetCustomAttribute(element, typeof(T));
+        }
+        public static T GetCustomAttribute<T>(this MemberInfo element) where T : Attribute
+        {
+            return (T)GetCustomAttribute(element, typeof(T));
+        }
+        public static T GetCustomAttribute<T>(this ParameterInfo element) where T : Attribute
+        {
+            return (T)GetCustomAttribute(element, typeof(T));
+        }
+
+        public static Attribute GetCustomAttribute(this MemberInfo element, Type attributeType, bool inherit)
+        {
+            return Attribute.GetCustomAttribute(element, attributeType, inherit);
+        }
+        public static Attribute GetCustomAttribute(this ParameterInfo element, Type attributeType, bool inherit)
+        {
+            return Attribute.GetCustomAttribute(element, attributeType, inherit);
+        }
+
+        public static T GetCustomAttribute<T>(this MemberInfo element, bool inherit) where T : Attribute
+        {
+            return (T)GetCustomAttribute(element, typeof(T), inherit);
+        }
+        public static T GetCustomAttribute<T>(this ParameterInfo element, bool inherit) where T : Attribute
+        {
+            return (T)GetCustomAttribute(element, typeof(T), inherit);
+        }
+        #endregion
+
+        #region APIs that return all attributes
+        public static IEnumerable<Attribute> GetCustomAttributes(this Assembly element)
+        {
+            return Attribute.GetCustomAttributes(element);
+        }
+        public static IEnumerable<Attribute> GetCustomAttributes(this Module element)
+        {
+            return Attribute.GetCustomAttributes(element);
+        }
+        public static IEnumerable<Attribute> GetCustomAttributes(this MemberInfo element)
+        {
+            return Attribute.GetCustomAttributes(element);
+        }
+        public static IEnumerable<Attribute> GetCustomAttributes(this ParameterInfo element)
+        {
+            return Attribute.GetCustomAttributes(element);
+        }
+
+        public static IEnumerable<Attribute> GetCustomAttributes(this MemberInfo element, bool inherit)
+        {
+            return Attribute.GetCustomAttributes(element, inherit);
+        }
+        public static IEnumerable<Attribute> GetCustomAttributes(this ParameterInfo element, bool inherit)
+        {
+            return Attribute.GetCustomAttributes(element, inherit);
+        }
+        #endregion
+
+        #region APIs that return all attributes of a particular type
+        public static IEnumerable<Attribute> GetCustomAttributes(this Assembly element, Type attributeType)
+        {
+            return Attribute.GetCustomAttributes(element, attributeType);
+        }
+        public static IEnumerable<Attribute> GetCustomAttributes(this Module element, Type attributeType)
+        {
+            return Attribute.GetCustomAttributes(element, attributeType);
+        }
+        public static IEnumerable<Attribute> GetCustomAttributes(this MemberInfo element, Type attributeType)
+        {
+            return Attribute.GetCustomAttributes(element, attributeType);
+        }
+        public static IEnumerable<Attribute> GetCustomAttributes(this ParameterInfo element, Type attributeType)
+        {
+            return Attribute.GetCustomAttributes(element, attributeType);
+        }
+
+        public static IEnumerable<T> GetCustomAttributes<T>(this Assembly element) where T : Attribute
+        {
+            return (IEnumerable<T>)GetCustomAttributes(element, typeof(T));
+        }
+        public static IEnumerable<T> GetCustomAttributes<T>(this Module element) where T : Attribute
+        {
+            return (IEnumerable<T>)GetCustomAttributes(element, typeof(T));
+        }
+        public static IEnumerable<T> GetCustomAttributes<T>(this MemberInfo element) where T : Attribute
+        {
+            return (IEnumerable<T>)GetCustomAttributes(element, typeof(T));
+        }
+        public static IEnumerable<T> GetCustomAttributes<T>(this ParameterInfo element) where T : Attribute
+        {
+            return (IEnumerable<T>)GetCustomAttributes(element, typeof(T));
+        }
+
+        public static IEnumerable<Attribute> GetCustomAttributes(this MemberInfo element, Type attributeType, bool inherit)
+        {
+            return Attribute.GetCustomAttributes(element, attributeType, inherit);
+        }
+        public static IEnumerable<Attribute> GetCustomAttributes(this ParameterInfo element, Type attributeType, bool inherit)
+        {
+            return Attribute.GetCustomAttributes(element, attributeType, inherit);
+        }
+
+        public static IEnumerable<T> GetCustomAttributes<T>(this MemberInfo element, bool inherit) where T : Attribute
+        {
+            return (IEnumerable<T>)GetCustomAttributes(element, typeof(T), inherit);
+        }
+        public static IEnumerable<T> GetCustomAttributes<T>(this ParameterInfo element, bool inherit) where T : Attribute
+        {
+            return (IEnumerable<T>)GetCustomAttributes(element, typeof(T), inherit);
+        }
+        #endregion
+
+        #region IsDefined
+        public static bool IsDefined(this Assembly element, Type attributeType)
+        {
+            return Attribute.IsDefined(element, attributeType);
+        }
+        public static bool IsDefined(this Module element, Type attributeType)
+        {
+            return Attribute.IsDefined(element, attributeType);
+        }
+        public static bool IsDefined(this MemberInfo element, Type attributeType)
+        {
+            return Attribute.IsDefined(element, attributeType);
+        }
+        public static bool IsDefined(this ParameterInfo element, Type attributeType)
+        {
+            return Attribute.IsDefined(element, attributeType);
+        }
+
+        public static bool IsDefined(this MemberInfo element, Type attributeType, bool inherit)
+        {
+            return Attribute.IsDefined(element, attributeType, inherit);
+        }
+        public static bool IsDefined(this ParameterInfo element, Type attributeType, bool inherit)
+        {
+            return Attribute.IsDefined(element, attributeType, inherit);
+        }
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/AQNBuilder.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/AQNBuilder.cs
new file mode 100644
index 0000000000..fa53c10dcb
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/AQNBuilder.cs
@@ -0,0 +1,164 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+using System.Runtime.InteropServices;
+using System.Security;
+
+namespace System.Reflection.Emit
+{
+    // TypeNameBuilder is NOT thread safe NOR reliable
+    internal class TypeNameBuilder
+    {
+        internal enum Format
+        {
+            ToString,
+            FullName,
+            AssemblyQualifiedName,
+        }
+
+        #region QCalls
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern IntPtr CreateTypeNameBuilder();
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void ReleaseTypeNameBuilder(IntPtr pAQN);
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void OpenGenericArguments(IntPtr tnb);
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void CloseGenericArguments(IntPtr tnb);
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void OpenGenericArgument(IntPtr tnb);
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void CloseGenericArgument(IntPtr tnb);
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void AddName(IntPtr tnb, string name);
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void AddPointer(IntPtr tnb);
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void AddByRef(IntPtr tnb);
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void AddSzArray(IntPtr tnb);
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void AddArray(IntPtr tnb, int rank);
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void AddAssemblySpec(IntPtr tnb, string assemblySpec);
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void ToString(IntPtr tnb, StringHandleOnStack retString);
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void Clear(IntPtr tnb);
+        #endregion
+
+        #region Static Members
+
+        // TypeNameBuilder is NOT thread safe NOR reliable
+        internal static string ToString(Type type, Format format)
+        {
+            if (format == Format.FullName || format == Format.AssemblyQualifiedName)
+            {
+                if (!type.IsGenericTypeDefinition && type.ContainsGenericParameters)
+                    return null;
+            }
+
+            TypeNameBuilder tnb = new TypeNameBuilder(CreateTypeNameBuilder());
+            tnb.Clear();
+            tnb.ConstructAssemblyQualifiedNameWorker(type, format);
+            string toString = tnb.ToString();
+            tnb.Dispose();
+            return toString;
+        }
+        #endregion
+
+        #region Private Data Members
+        private IntPtr m_typeNameBuilder;
+        #endregion
+
+        #region Constructor
+        private TypeNameBuilder(IntPtr typeNameBuilder) { m_typeNameBuilder = typeNameBuilder; }
+        internal void Dispose() { ReleaseTypeNameBuilder(m_typeNameBuilder); }
+        #endregion
+
+        #region private Members
+        private void AddElementType(Type elementType)
+        {
+            if (elementType.HasElementType)
+                AddElementType(elementType.GetElementType());
+
+            if (elementType.IsPointer)
+                AddPointer();
+
+            else if (elementType.IsByRef)
+                AddByRef();
+
+            else if (elementType.IsSZArray)
+                AddSzArray();
+
+            else if (elementType.IsArray)
+                AddArray(elementType.GetArrayRank());
+        }
+
+        private void ConstructAssemblyQualifiedNameWorker(Type type, Format format)
+        {
+            Type rootType = type;
+
+            while (rootType.HasElementType)
+                rootType = rootType.GetElementType();
+
+            // Append namespace + nesting + name
+            List<Type> nestings = new List<Type>();
+            for (Type t = rootType; t != null; t = t.IsGenericParameter ? null : t.DeclaringType)
+                nestings.Add(t);
+
+            for (int i = nestings.Count - 1; i >= 0; i--)
+            {
+                Type enclosingType = nestings[i];
+                string name = enclosingType.Name;
+
+                if (i == nestings.Count - 1 && enclosingType.Namespace != null && enclosingType.Namespace.Length != 0)
+                    name = enclosingType.Namespace + "." + name;
+
+                AddName(name);
+            }
+
+            // Append generic arguments
+            if (rootType.IsGenericType && (!rootType.IsGenericTypeDefinition || format == Format.ToString))
+            {
+                Type[] genericArguments = rootType.GetGenericArguments();
+
+                OpenGenericArguments();
+                for (int i = 0; i < genericArguments.Length; i++)
+                {
+                    Format genericArgumentsFormat = format == Format.FullName ? Format.AssemblyQualifiedName : format;
+
+                    OpenGenericArgument();
+                    ConstructAssemblyQualifiedNameWorker(genericArguments[i], genericArgumentsFormat);
+                    CloseGenericArgument();
+                }
+                CloseGenericArguments();
+            }
+
+            // Append pointer, byRef and array qualifiers
+            AddElementType(type);
+
+            if (format == Format.AssemblyQualifiedName)
+                AddAssemblySpec(type.Module.Assembly.FullName);
+        }
+
+        private void OpenGenericArguments() { OpenGenericArguments(m_typeNameBuilder); }
+        private void CloseGenericArguments() { CloseGenericArguments(m_typeNameBuilder); }
+        private void OpenGenericArgument() { OpenGenericArgument(m_typeNameBuilder); }
+        private void CloseGenericArgument() { CloseGenericArgument(m_typeNameBuilder); }
+        private void AddName(string name) { AddName(m_typeNameBuilder, name); }
+        private void AddPointer() { AddPointer(m_typeNameBuilder); }
+        private void AddByRef() { AddByRef(m_typeNameBuilder); }
+        private void AddSzArray() { AddSzArray(m_typeNameBuilder); }
+        private void AddArray(int rank) { AddArray(m_typeNameBuilder, rank); }
+        private void AddAssemblySpec(string assemblySpec) { AddAssemblySpec(m_typeNameBuilder, assemblySpec); }
+        public override string ToString() { string ret = null; ToString(m_typeNameBuilder, JitHelpers.GetStringHandleOnStack(ref ret)); return ret; }
+        private void Clear() { Clear(m_typeNameBuilder); }
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilder.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilder.cs
new file mode 100644
index 0000000000..2c446f7ecb
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilder.cs
@@ -0,0 +1,749 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+//*************************************************************************************************************
+// For each dynamic assembly there will be two AssemblyBuilder objects: the "internal" 
+// AssemblyBuilder object and the "external" AssemblyBuilder object.
+//  1.  The "internal" object is the real assembly object that the VM creates and knows about. However, 
+//      you can perform RefEmit operations on it only if you have its granted permission. From the AppDomain 
+//      and other "internal" objects like the "internal" ModuleBuilders and runtime types, you can only
+//      get the "internal" objects. This is to prevent low-trust code from getting a hold of the dynamic
+//      AssemblyBuilder/ModuleBuilder/TypeBuilder/MethodBuilder/etc other people have created by simply 
+//      enumerating the AppDomain and inject code in it.
+//  2.  The "external" object is merely an wrapper of the "internal" object and all operations on it
+//      are directed to the internal object. This is the one you get by calling DefineDynamicAssembly
+//      on AppDomain and the one you can always perform RefEmit operations on. You can get other "external"
+//      objects from the "external" AssemblyBuilder, ModuleBuilder, TypeBuilder, MethodBuilder, etc. Note
+//      that VM doesn't know about this object. So every time we call into the VM we need to pass in the
+//      "internal" object.
+//
+// "internal" and "external" ModuleBuilders are similar
+//*************************************************************************************************************
+
+namespace System.Reflection.Emit
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Diagnostics;
+    using System.Diagnostics.SymbolStore;
+    using CultureInfo = System.Globalization.CultureInfo;
+    using System.IO;
+    using System.Reflection;
+    using System.Resources;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.InteropServices;
+    using System.Runtime.Serialization;
+    using System.Runtime.Versioning;
+    using System.Security;
+    using System.Threading;
+
+    // When the user calls AppDomain.DefineDynamicAssembly the loader creates a new InternalAssemblyBuilder. 
+    // This InternalAssemblyBuilder can be retrieved via a call to Assembly.GetAssemblies() by untrusted code.
+    // In the past, when InternalAssemblyBuilder was AssemblyBuilder, the untrusted user could down cast the
+    // Assembly to an AssemblyBuilder and emit code with the elevated permissions of the trusted code which 
+    // originally created the AssemblyBuilder via DefineDynamicAssembly. Today, this can no longer happen
+    // because the Assembly returned via AssemblyGetAssemblies() will be an InternalAssemblyBuilder.
+
+    // Only the caller of DefineDynamicAssembly will get an AssemblyBuilder. 
+    // There is a 1-1 relationship between InternalAssemblyBuilder and AssemblyBuilder. 
+    // AssemblyBuilder is composed of its InternalAssemblyBuilder.
+    // The AssemblyBuilder data members (e.g. m_foo) were changed to properties which then delegate 
+    // the access to the composed InternalAssemblyBuilder. This way, AssemblyBuilder simply wraps 
+    // InternalAssemblyBuilder and still operates on InternalAssemblyBuilder members. 
+    // This also makes the change transparent to the loader. This is good because most of the complexity
+    // of Assembly building is in the loader code so not touching that code reduces the chance of 
+    // introducing new bugs.
+    internal sealed class InternalAssemblyBuilder : RuntimeAssembly
+    {
+        private InternalAssemblyBuilder() { }
+
+        #region object overrides
+        public override bool Equals(object obj)
+        {
+            if (obj == null)
+                return false;
+
+            if (obj is InternalAssemblyBuilder)
+                return ((object)this == obj);
+
+            return obj.Equals(this);
+        }
+        // Need a dummy GetHashCode to pair with Equals
+        public override int GetHashCode() { return base.GetHashCode(); }
+        #endregion
+
+        // Assembly methods that are overridden by AssemblyBuilder should be overridden by InternalAssemblyBuilder too
+        #region Methods inherited from Assembly
+        public override String[] GetManifestResourceNames()
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicAssembly);
+        }
+
+        public override FileStream GetFile(String name)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicAssembly);
+        }
+
+        public override FileStream[] GetFiles(bool getResourceModules)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicAssembly);
+        }
+
+        public override Stream GetManifestResourceStream(Type type, String name)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicAssembly);
+        }
+
+        public override Stream GetManifestResourceStream(String name)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicAssembly);
+        }
+
+        public override ManifestResourceInfo GetManifestResourceInfo(String resourceName)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicAssembly);
+        }
+
+        public override String Location
+        {
+            get
+            {
+                throw new NotSupportedException(SR.NotSupported_DynamicAssembly);
+            }
+        }
+
+        public override String CodeBase
+        {
+            get
+            {
+                throw new NotSupportedException(SR.NotSupported_DynamicAssembly);
+            }
+        }
+
+        public override Type[] GetExportedTypes()
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicAssembly);
+        }
+
+        public override String ImageRuntimeVersion
+        {
+            get
+            {
+                return RuntimeEnvironment.GetSystemVersion();
+            }
+        }
+        #endregion
+    }
+
+    // AssemblyBuilder class.
+    // deliberately not [serializable]
+    public sealed class AssemblyBuilder : Assembly
+    {
+        #region FCALL
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern RuntimeModule GetInMemoryAssemblyModule(RuntimeAssembly assembly);
+
+        private Module nGetInMemoryAssemblyModule()
+        {
+            return AssemblyBuilder.GetInMemoryAssemblyModule(GetNativeHandle());
+        }
+
+        #endregion
+
+        #region Internal Data Members
+        // This is only valid in the "external" AssemblyBuilder
+        internal AssemblyBuilderData m_assemblyData;
+        private InternalAssemblyBuilder m_internalAssemblyBuilder;
+        private ModuleBuilder m_manifestModuleBuilder;
+        // Set to true if the manifest module was returned by code:DefineDynamicModule to the user
+        private bool m_fManifestModuleUsedAsDefinedModule;
+        internal const string MANIFEST_MODULE_NAME = "RefEmit_InMemoryManifestModule";
+
+        internal ModuleBuilder GetModuleBuilder(InternalModuleBuilder module)
+        {
+            Debug.Assert(module != null);
+            Debug.Assert(this.InternalAssembly == module.Assembly);
+
+            lock (SyncRoot)
+            {
+                // in CoreCLR there is only one module in each dynamic assembly, the manifest module
+                if (m_manifestModuleBuilder.InternalModule == module)
+                    return m_manifestModuleBuilder;
+
+                throw new ArgumentException(null, nameof(module));
+            }
+        }
+
+        internal object SyncRoot
+        {
+            get
+            {
+                return InternalAssembly.SyncRoot;
+            }
+        }
+
+        internal InternalAssemblyBuilder InternalAssembly
+        {
+            get
+            {
+                return m_internalAssemblyBuilder;
+            }
+        }
+
+        internal RuntimeAssembly GetNativeHandle()
+        {
+            return InternalAssembly.GetNativeHandle();
+        }
+        #endregion
+
+        #region Constructor
+        internal AssemblyBuilder(AppDomain domain,
+                                 AssemblyName name,
+                                 AssemblyBuilderAccess access,
+                                 ref StackCrawlMark stackMark,
+                                 IEnumerable<CustomAttributeBuilder> unsafeAssemblyAttributes)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            if (access != AssemblyBuilderAccess.Run
+                && access != AssemblyBuilderAccess.RunAndCollect
+                )
+            {
+                throw new ArgumentException(SR.Format(SR.Arg_EnumIllegalVal, (int)access), nameof(access));
+            }
+
+            // Clone the name in case the caller modifies it underneath us.
+            name = (AssemblyName)name.Clone();
+
+            // Scan the assembly level attributes for any attributes which modify how we create the
+            // assembly. Currently, we look for any attribute which modifies the security transparency
+            // of the assembly.
+            List<CustomAttributeBuilder> assemblyAttributes = null;
+            if (unsafeAssemblyAttributes != null)
+            {
+                // Create a copy to ensure that it cannot be modified from another thread
+                // as it is used further below.
+                assemblyAttributes = new List<CustomAttributeBuilder>(unsafeAssemblyAttributes);
+            }
+
+            m_internalAssemblyBuilder = (InternalAssemblyBuilder)nCreateDynamicAssembly(domain,
+                                                                                        name,
+                                                                                        ref stackMark,
+                                                                                        access);
+
+            m_assemblyData = new AssemblyBuilderData(m_internalAssemblyBuilder,
+                                                     name.Name,
+                                                     access);
+
+            // Make sure that ManifestModule is properly initialized
+            // We need to do this before setting any CustomAttribute
+            InitManifestModule();
+
+            if (assemblyAttributes != null)
+            {
+                foreach (CustomAttributeBuilder assemblyAttribute in assemblyAttributes)
+                    SetCustomAttribute(assemblyAttribute);
+            }
+        }
+
+        private void InitManifestModule()
+        {
+            InternalModuleBuilder modBuilder = (InternalModuleBuilder)nGetInMemoryAssemblyModule();
+
+            // Note that this ModuleBuilder cannot be used for RefEmit yet
+            // because it hasn't been initialized.
+            // However, it can be used to set the custom attribute on the Assembly
+            m_manifestModuleBuilder = new ModuleBuilder(this, modBuilder);
+
+            // We are only setting the name in the managed ModuleBuilderData here.
+            // The name in the underlying metadata will be set when the
+            // manifest module is created during nCreateDynamicAssembly.
+
+            // This name needs to stay in sync with that used in
+            // Assembly::Init to call ReflectionModule::Create (in VM)
+            m_manifestModuleBuilder.Init(AssemblyBuilder.MANIFEST_MODULE_NAME, null, 0);
+
+            m_fManifestModuleUsedAsDefinedModule = false;
+        }
+        #endregion
+
+        #region DefineDynamicAssembly
+
+        /**********************************************
+        * If an AssemblyName has a public key specified, the assembly is assumed
+        * to have a strong name and a hash will be computed when the assembly
+        * is saved.
+        **********************************************/
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public static AssemblyBuilder DefineDynamicAssembly(
+            AssemblyName name,
+            AssemblyBuilderAccess access)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return InternalDefineDynamicAssembly(name, access,
+                                                 ref stackMark, null);
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public static AssemblyBuilder DefineDynamicAssembly(
+            AssemblyName name,
+            AssemblyBuilderAccess access,
+            IEnumerable<CustomAttributeBuilder> assemblyAttributes)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return InternalDefineDynamicAssembly(name,
+                                                 access,
+                                                 ref stackMark,
+                                                 assemblyAttributes);
+        }
+
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern Assembly nCreateDynamicAssembly(AppDomain domain,
+                                                              AssemblyName name,
+                                                              ref StackCrawlMark stackMark,
+                                                              AssemblyBuilderAccess access);
+
+        private class AssemblyBuilderLock { }
+
+        internal static AssemblyBuilder InternalDefineDynamicAssembly(
+            AssemblyName name,
+            AssemblyBuilderAccess access,
+            ref StackCrawlMark stackMark,
+            IEnumerable<CustomAttributeBuilder> unsafeAssemblyAttributes)
+        {
+            lock (typeof(AssemblyBuilderLock))
+            {
+                // we can only create dynamic assemblies in the current domain
+                return new AssemblyBuilder(AppDomain.CurrentDomain,
+                                           name,
+                                           access,
+                                           ref stackMark,
+                                           unsafeAssemblyAttributes);
+            } //lock(typeof(AssemblyBuilderLock))
+        }
+        #endregion
+
+        #region DefineDynamicModule
+        /**********************************************
+        *
+        * Defines a named dynamic module. It is an error to define multiple 
+        * modules within an Assembly with the same name. This dynamic module is
+        * a transient module.
+        * 
+        **********************************************/
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public ModuleBuilder DefineDynamicModule(
+            String name)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return DefineDynamicModuleInternal(name, false, ref stackMark);
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public ModuleBuilder DefineDynamicModule(
+            String name,
+            bool emitSymbolInfo)         // specify if emit symbol info or not
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return DefineDynamicModuleInternal(name, emitSymbolInfo, ref stackMark);
+        }
+
+        private ModuleBuilder DefineDynamicModuleInternal(
+            String name,
+            bool emitSymbolInfo,         // specify if emit symbol info or not
+            ref StackCrawlMark stackMark)
+        {
+            lock (SyncRoot)
+            {
+                return DefineDynamicModuleInternalNoLock(name, emitSymbolInfo, ref stackMark);
+            }
+        }
+
+        private ModuleBuilder DefineDynamicModuleInternalNoLock(
+            String name,
+            bool emitSymbolInfo,         // specify if emit symbol info or not
+            ref StackCrawlMark stackMark)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+            if (name.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(name));
+            if (name[0] == '\0')
+                throw new ArgumentException(SR.Argument_InvalidName, nameof(name));
+
+            Debug.Assert(m_assemblyData != null, "m_assemblyData is null in DefineDynamicModuleInternal");
+
+            ModuleBuilder dynModule;
+            ISymbolWriter writer = null;
+            IntPtr pInternalSymWriter = new IntPtr();
+
+            // create the dynamic module- only one ModuleBuilder per AssemblyBuilder can be created
+            if (m_fManifestModuleUsedAsDefinedModule == true)
+                throw new InvalidOperationException(SR.InvalidOperation_NoMultiModuleAssembly);
+
+            // Init(...) has already been called on m_manifestModuleBuilder in InitManifestModule()
+            dynModule = m_manifestModuleBuilder;
+
+            // Create the symbol writer
+            if (emitSymbolInfo)
+            {
+                writer = SymWrapperCore.SymWriter.CreateSymWriter();
+
+                String fileName = "Unused"; // this symfile is never written to disk so filename does not matter.
+
+                // Pass the "real" module to the VM
+                pInternalSymWriter = ModuleBuilder.nCreateISymWriterForDynamicModule(dynModule.InternalModule, fileName);
+
+                // In Telesto, we took the SetUnderlyingWriter method private as it's a very rickety method.
+                // This might someday be a good move for the desktop CLR too.
+                ((SymWrapperCore.SymWriter)writer).InternalSetUnderlyingWriter(pInternalSymWriter);
+            } // Creating the symbol writer
+
+            dynModule.SetSymWriter(writer);
+            m_assemblyData.AddModule(dynModule);
+
+            if (dynModule == m_manifestModuleBuilder)
+            {   // We are reusing manifest module as user-defined dynamic module
+                m_fManifestModuleUsedAsDefinedModule = true;
+            }
+
+            return dynModule;
+        } // DefineDynamicModuleInternalNoLock
+
+        #endregion
+
+        internal void CheckContext(params Type[][] typess)
+        {
+            if (typess == null)
+                return;
+
+            foreach (Type[] types in typess)
+                if (types != null)
+                    CheckContext(types);
+        }
+
+        internal void CheckContext(params Type[] types)
+        {
+            if (types == null)
+                return;
+
+            foreach (Type type in types)
+            {
+                if (type == null)
+                    continue;
+
+                if (type.Module == null || type.Module.Assembly == null)
+                    throw new ArgumentException(SR.Argument_TypeNotValid);
+
+                if (type.Module.Assembly == typeof(object).Module.Assembly)
+                    continue;
+
+                if (type.Module.Assembly.ReflectionOnly && !ReflectionOnly)
+                    throw new InvalidOperationException(SR.Format(SR.Arugment_EmitMixedContext1, type.AssemblyQualifiedName));
+
+                if (!type.Module.Assembly.ReflectionOnly && ReflectionOnly)
+                    throw new InvalidOperationException(SR.Format(SR.Arugment_EmitMixedContext2, type.AssemblyQualifiedName));
+            }
+        }
+
+        #region object overrides
+        public override bool Equals(object obj)
+        {
+            return InternalAssembly.Equals(obj);
+        }
+        // Need a dummy GetHashCode to pair with Equals
+        public override int GetHashCode() { return InternalAssembly.GetHashCode(); }
+        #endregion
+
+        #region ICustomAttributeProvider Members
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            return InternalAssembly.GetCustomAttributes(inherit);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            return InternalAssembly.GetCustomAttributes(attributeType, inherit);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            return InternalAssembly.IsDefined(attributeType, inherit);
+        }
+
+        public override IList<CustomAttributeData> GetCustomAttributesData()
+        {
+            return InternalAssembly.GetCustomAttributesData();
+        }
+        #endregion
+
+        #region Assembly overrides
+        // Returns the names of all the resources
+        public override String[] GetManifestResourceNames()
+        {
+            return InternalAssembly.GetManifestResourceNames();
+        }
+
+        public override FileStream GetFile(String name)
+        {
+            return InternalAssembly.GetFile(name);
+        }
+
+        public override FileStream[] GetFiles(bool getResourceModules)
+        {
+            return InternalAssembly.GetFiles(getResourceModules);
+        }
+
+        public override Stream GetManifestResourceStream(Type type, String name)
+        {
+            return InternalAssembly.GetManifestResourceStream(type, name);
+        }
+
+        public override Stream GetManifestResourceStream(String name)
+        {
+            return InternalAssembly.GetManifestResourceStream(name);
+        }
+
+        public override ManifestResourceInfo GetManifestResourceInfo(String resourceName)
+        {
+            return InternalAssembly.GetManifestResourceInfo(resourceName);
+        }
+
+        public override String Location
+        {
+            get
+            {
+                return InternalAssembly.Location;
+            }
+        }
+
+        public override String ImageRuntimeVersion
+        {
+            get
+            {
+                return InternalAssembly.ImageRuntimeVersion;
+            }
+        }
+
+        public override String CodeBase
+        {
+            get
+            {
+                return InternalAssembly.CodeBase;
+            }
+        }
+
+        // Override the EntryPoint method on Assembly.
+        // This doesn't need to be synchronized because it is simple enough
+        public override MethodInfo EntryPoint
+        {
+            get
+            {
+                return m_assemblyData.m_entryPointMethod;
+            }
+        }
+
+        // Get an array of all the public types defined in this assembly
+        public override Type[] GetExportedTypes()
+        {
+            return InternalAssembly.GetExportedTypes();
+        }
+
+        public override AssemblyName GetName(bool copiedName)
+        {
+            return InternalAssembly.GetName(copiedName);
+        }
+
+        public override String FullName
+        {
+            get
+            {
+                return InternalAssembly.FullName;
+            }
+        }
+
+        public override Type GetType(String name, bool throwOnError, bool ignoreCase)
+        {
+            return InternalAssembly.GetType(name, throwOnError, ignoreCase);
+        }
+
+        public override Module ManifestModule
+        {
+            get
+            {
+                return m_manifestModuleBuilder.InternalModule;
+            }
+        }
+
+        public override bool ReflectionOnly
+        {
+            get
+            {
+                return InternalAssembly.ReflectionOnly;
+            }
+        }
+
+        public override Module GetModule(String name)
+        {
+            return InternalAssembly.GetModule(name);
+        }
+
+        public override AssemblyName[] GetReferencedAssemblies()
+        {
+            return InternalAssembly.GetReferencedAssemblies();
+        }
+
+        public override bool GlobalAssemblyCache
+        {
+            get
+            {
+                return InternalAssembly.GlobalAssemblyCache;
+            }
+        }
+
+        public override Int64 HostContext
+        {
+            get
+            {
+                return InternalAssembly.HostContext;
+            }
+        }
+
+        public override Module[] GetModules(bool getResourceModules)
+        {
+            return InternalAssembly.GetModules(getResourceModules);
+        }
+
+        public override Module[] GetLoadedModules(bool getResourceModules)
+        {
+            return InternalAssembly.GetLoadedModules(getResourceModules);
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public override Assembly GetSatelliteAssembly(CultureInfo culture)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return InternalAssembly.InternalGetSatelliteAssembly(culture, null, ref stackMark);
+        }
+
+        // Useful for binding to a very specific version of a satellite assembly
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public override Assembly GetSatelliteAssembly(CultureInfo culture, Version version)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return InternalAssembly.InternalGetSatelliteAssembly(culture, version, ref stackMark);
+        }
+
+        public override bool IsDynamic
+        {
+            get
+            {
+                return true;
+            }
+        }
+        #endregion
+
+
+        /**********************************************
+        *
+        * return a dynamic module with the specified name.
+        *
+        **********************************************/
+        public ModuleBuilder GetDynamicModule(
+            String name)                   // the name of module for the look up
+        {
+            lock (SyncRoot)
+            {
+                return GetDynamicModuleNoLock(name);
+            }
+        }
+
+        private ModuleBuilder GetDynamicModuleNoLock(
+            String name)                   // the name of module for the look up
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+            if (name.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(name));
+
+            int size = m_assemblyData.m_moduleBuilderList.Count;
+            for (int i = 0; i < size; i++)
+            {
+                ModuleBuilder moduleBuilder = (ModuleBuilder)m_assemblyData.m_moduleBuilderList[i];
+                if (moduleBuilder.m_moduleData.m_strModuleName.Equals(name))
+                {
+                    return moduleBuilder;
+                }
+            }
+            return null;
+        }
+
+
+        /**********************************************
+        * Use this function if client decides to form the custom attribute blob themselves
+        **********************************************/
+        public void SetCustomAttribute(ConstructorInfo con, byte[] binaryAttribute)
+        {
+            if (con == null)
+                throw new ArgumentNullException(nameof(con));
+            if (binaryAttribute == null)
+                throw new ArgumentNullException(nameof(binaryAttribute));
+
+            lock (SyncRoot)
+            {
+                SetCustomAttributeNoLock(con, binaryAttribute);
+            }
+        }
+
+        private void SetCustomAttributeNoLock(ConstructorInfo con, byte[] binaryAttribute)
+        {
+            TypeBuilder.DefineCustomAttribute(
+                m_manifestModuleBuilder,     // pass in the in-memory assembly module
+                AssemblyBuilderData.m_tkAssembly,           // This is the AssemblyDef token
+                m_manifestModuleBuilder.GetConstructorToken(con).Token,
+                binaryAttribute,
+                false,
+                typeof(System.Diagnostics.DebuggableAttribute) == con.DeclaringType);
+
+            // Track the CA for persistence
+            if (m_assemblyData.m_access != AssemblyBuilderAccess.Run)
+            {
+                // tracking the CAs for persistence
+                m_assemblyData.AddCustomAttribute(con, binaryAttribute);
+            }
+        }
+
+        /**********************************************
+        * Use this function if client wishes to build CustomAttribute using CustomAttributeBuilder
+        **********************************************/
+        public void SetCustomAttribute(CustomAttributeBuilder customBuilder)
+        {
+            if (customBuilder == null)
+            {
+                throw new ArgumentNullException(nameof(customBuilder));
+            }
+
+            lock (SyncRoot)
+            {
+                SetCustomAttributeNoLock(customBuilder);
+            }
+        }
+
+        private void SetCustomAttributeNoLock(CustomAttributeBuilder customBuilder)
+        {
+            customBuilder.CreateCustomAttribute(
+                m_manifestModuleBuilder,
+                AssemblyBuilderData.m_tkAssembly);          // This is the AssemblyDef token 
+
+            // Track the CA for persistence
+            if (m_assemblyData.m_access != AssemblyBuilderAccess.Run)
+            {
+                m_assemblyData.AddCustomAttribute(customBuilder);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilderAccess.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilderAccess.cs
new file mode 100644
index 0000000000..b096960406
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilderAccess.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+// This enumeration defines the access modes for a dynamic assembly.
+// EE uses these enum values..look for m_dwDynamicAssemblyAccess in Assembly.hpp
+
+namespace System.Reflection.Emit
+{
+    [Flags]
+    public enum AssemblyBuilderAccess
+    {
+        Run = 1,
+        RunAndCollect = 8 | Run
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilderData.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilderData.cs
new file mode 100644
index 0000000000..ea1f6994e9
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilderData.cs
@@ -0,0 +1,192 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+// 
+
+namespace System.Reflection.Emit
+{
+    using System;
+    using IList = System.Collections.IList;
+    using System.Collections.Generic;
+    using System.Reflection;
+    using System.Security;
+    using System.Diagnostics;
+    using CultureInfo = System.Globalization.CultureInfo;
+    using System.IO;
+    using System.Runtime.Versioning;
+    using System.Diagnostics.SymbolStore;
+
+    // This is a package private class. This class hold all of the managed
+    // data member for AssemblyBuilder. Note that what ever data members added to
+    // this class cannot be accessed from the EE.
+    internal class AssemblyBuilderData
+    {
+        internal AssemblyBuilderData(
+            InternalAssemblyBuilder assembly,
+            String strAssemblyName,
+            AssemblyBuilderAccess access)
+        {
+            m_assembly = assembly;
+            m_strAssemblyName = strAssemblyName;
+            m_access = access;
+            m_moduleBuilderList = new List<ModuleBuilder>();
+            m_resWriterList = new List<ResWriterData>();
+
+            m_peFileKind = PEFileKinds.Dll;
+        }
+
+        // Helper to add a dynamic module into the tracking list
+        internal void AddModule(ModuleBuilder dynModule)
+        {
+            m_moduleBuilderList.Add(dynModule);
+        }
+
+
+        // Helper to track CAs to persist onto disk
+        internal void AddCustomAttribute(CustomAttributeBuilder customBuilder)
+        {
+            // make sure we have room for this CA
+            if (m_CABuilders == null)
+            {
+                m_CABuilders = new CustomAttributeBuilder[m_iInitialSize];
+            }
+            if (m_iCABuilder == m_CABuilders.Length)
+            {
+                CustomAttributeBuilder[] tempCABuilders = new CustomAttributeBuilder[m_iCABuilder * 2];
+                Array.Copy(m_CABuilders, 0, tempCABuilders, 0, m_iCABuilder);
+                m_CABuilders = tempCABuilders;
+            }
+            m_CABuilders[m_iCABuilder] = customBuilder;
+
+            m_iCABuilder++;
+        }
+
+        // Helper to track CAs to persist onto disk
+        internal void AddCustomAttribute(ConstructorInfo con, byte[] binaryAttribute)
+        {
+            // make sure we have room for this CA
+            if (m_CABytes == null)
+            {
+                m_CABytes = new byte[m_iInitialSize][];
+                m_CACons = new ConstructorInfo[m_iInitialSize];
+            }
+            if (m_iCAs == m_CABytes.Length)
+            {
+                // enlarge the arrays
+                byte[][] temp = new byte[m_iCAs * 2][];
+                ConstructorInfo[] tempCon = new ConstructorInfo[m_iCAs * 2];
+                for (int i = 0; i < m_iCAs; i++)
+                {
+                    temp[i] = m_CABytes[i];
+                    tempCon[i] = m_CACons[i];
+                }
+                m_CABytes = temp;
+                m_CACons = tempCon;
+            }
+
+            byte[] attrs = new byte[binaryAttribute.Length];
+            Buffer.BlockCopy(binaryAttribute, 0, attrs, 0, binaryAttribute.Length);
+            m_CABytes[m_iCAs] = attrs;
+            m_CACons[m_iCAs] = con;
+            m_iCAs++;
+        }
+
+        // Helper to ensure the type name is unique underneath assemblyBuilder
+        internal void CheckTypeNameConflict(String strTypeName, TypeBuilder enclosingType)
+        {
+            for (int i = 0; i < m_moduleBuilderList.Count; i++)
+            {
+                ModuleBuilder curModule = m_moduleBuilderList[i];
+                curModule.CheckTypeNameConflict(strTypeName, enclosingType);
+            }
+
+            // Right now dynamic modules can only be added to dynamic assemblies in which
+            // all modules are dynamic. Otherwise we would also need to check loaded types.
+            // We only need to make this test for non-nested types since any
+            // duplicates in nested types will be caught at the top level.
+            //      if (enclosingType == null && m_assembly.GetType(strTypeName, false, false) != null)
+            //      {
+            //          // Cannot have two types with the same name
+            //          throw new ArgumentException(SR.Argument_DuplicateTypeName);
+            //      }
+        }
+
+        internal List<ModuleBuilder> m_moduleBuilderList;
+        internal List<ResWriterData> m_resWriterList;
+        internal String m_strAssemblyName;
+        internal AssemblyBuilderAccess m_access;
+        private InternalAssemblyBuilder m_assembly;
+
+        internal Type[] m_publicComTypeList;
+        internal int m_iPublicComTypeCount;
+
+        internal bool m_isSaved;
+        internal const int m_iInitialSize = 16;
+
+        // hard coding the assembly def token
+        internal const int m_tkAssembly = 0x20000001;
+
+        // tracking AssemblyDef's CAs for persistence to disk
+        internal CustomAttributeBuilder[] m_CABuilders;
+        internal int m_iCABuilder;
+        internal byte[][] m_CABytes;
+        internal ConstructorInfo[] m_CACons;
+        internal int m_iCAs;
+        internal PEFileKinds m_peFileKind;           // assembly file kind
+        internal MethodInfo m_entryPointMethod;
+        internal Assembly m_ISymWrapperAssembly;
+
+        // For unmanaged resources
+        internal String m_strResourceFileName;
+        internal byte[] m_resourceBytes;
+        internal NativeVersionInfo m_nativeVersion;
+        internal bool m_hasUnmanagedVersionInfo;
+        internal bool m_OverrideUnmanagedVersionInfo;
+    }
+
+
+    /**********************************************
+    *
+    * Internal structure to track the list of ResourceWriter for
+    * AssemblyBuilder & ModuleBuilder.
+    *
+    **********************************************/
+    internal class ResWriterData
+    {
+        internal String m_strName;
+        internal String m_strFileName;
+        internal String m_strFullFileName;
+        internal Stream m_memoryStream;
+        internal ResWriterData m_nextResWriter;
+        internal ResourceAttributes m_attribute;
+    }
+
+    internal class NativeVersionInfo
+    {
+        internal NativeVersionInfo()
+        {
+            m_strDescription = null;
+            m_strCompany = null;
+            m_strTitle = null;
+            m_strCopyright = null;
+            m_strTrademark = null;
+            m_strProduct = null;
+            m_strProductVersion = null;
+            m_strFileVersion = null;
+            m_lcid = -1;
+        }
+
+        internal String m_strDescription;
+        internal String m_strCompany;
+        internal String m_strTitle;
+        internal String m_strCopyright;
+        internal String m_strTrademark;
+        internal String m_strProduct;
+        internal String m_strProductVersion;
+        internal String m_strFileVersion;
+        internal int m_lcid;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/ConstructorBuilder.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/ConstructorBuilder.cs
new file mode 100644
index 0000000000..b333dc3922
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/ConstructorBuilder.cs
@@ -0,0 +1,236 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+namespace System.Reflection.Emit
+{
+    using System;
+    using System.Reflection;
+    using CultureInfo = System.Globalization.CultureInfo;
+    using System.Collections.Generic;
+    using System.Diagnostics.SymbolStore;
+    using System.Security;
+    using System.Runtime.InteropServices;
+
+    public sealed class ConstructorBuilder : ConstructorInfo
+    {
+        private readonly MethodBuilder m_methodBuilder;
+        internal bool m_isDefaultConstructor;
+
+        #region Constructor
+
+        internal ConstructorBuilder(String name, MethodAttributes attributes, CallingConventions callingConvention,
+            Type[] parameterTypes, Type[][] requiredCustomModifiers, Type[][] optionalCustomModifiers, ModuleBuilder mod, TypeBuilder type)
+        {
+            int sigLength;
+            byte[] sigBytes;
+            MethodToken token;
+
+            m_methodBuilder = new MethodBuilder(name, attributes, callingConvention, null, null, null,
+                parameterTypes, requiredCustomModifiers, optionalCustomModifiers, mod, type, false);
+
+            type.m_listMethods.Add(m_methodBuilder);
+
+            sigBytes = m_methodBuilder.GetMethodSignature().InternalGetSignature(out sigLength);
+
+            token = m_methodBuilder.GetToken();
+        }
+
+        internal ConstructorBuilder(String name, MethodAttributes attributes, CallingConventions callingConvention,
+            Type[] parameterTypes, ModuleBuilder mod, TypeBuilder type) :
+            this(name, attributes, callingConvention, parameterTypes, null, null, mod, type)
+        {
+        }
+
+        #endregion
+
+        #region Internal
+        internal override Type[] GetParameterTypes()
+        {
+            return m_methodBuilder.GetParameterTypes();
+        }
+
+        private TypeBuilder GetTypeBuilder()
+        {
+            return m_methodBuilder.GetTypeBuilder();
+        }
+        #endregion
+
+        #region Object Overrides
+        public override String ToString()
+        {
+            return m_methodBuilder.ToString();
+        }
+
+        #endregion
+
+        #region MemberInfo Overrides
+        internal int MetadataTokenInternal
+        {
+            get { return m_methodBuilder.MetadataTokenInternal; }
+        }
+
+        public override Module Module
+        {
+            get { return m_methodBuilder.Module; }
+        }
+
+        public override Type ReflectedType
+        {
+            get { return m_methodBuilder.ReflectedType; }
+        }
+
+        public override Type DeclaringType
+        {
+            get { return m_methodBuilder.DeclaringType; }
+        }
+
+        public override String Name
+        {
+            get { return m_methodBuilder.Name; }
+        }
+
+        #endregion
+
+        #region MethodBase Overrides
+        public override Object Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override ParameterInfo[] GetParameters()
+        {
+            ConstructorInfo rci = GetTypeBuilder().GetConstructor(m_methodBuilder.m_parameterTypes);
+            return rci.GetParameters();
+        }
+
+        public override MethodAttributes Attributes
+        {
+            get { return m_methodBuilder.Attributes; }
+        }
+
+        public override MethodImplAttributes GetMethodImplementationFlags()
+        {
+            return m_methodBuilder.GetMethodImplementationFlags();
+        }
+
+        public override RuntimeMethodHandle MethodHandle
+        {
+            get { return m_methodBuilder.MethodHandle; }
+        }
+
+        #endregion
+
+        #region ConstructorInfo Overrides
+        public override Object Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        #endregion
+
+        #region ICustomAttributeProvider Implementation
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            return m_methodBuilder.GetCustomAttributes(inherit);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            return m_methodBuilder.GetCustomAttributes(attributeType, inherit);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            return m_methodBuilder.IsDefined(attributeType, inherit);
+        }
+
+        #endregion
+
+        #region Public Members
+        public MethodToken GetToken()
+        {
+            return m_methodBuilder.GetToken();
+        }
+
+        public ParameterBuilder DefineParameter(int iSequence, ParameterAttributes attributes, String strParamName)
+        {
+            // Theoretically we shouldn't allow iSequence to be 0 because in reflection ctors don't have 
+            // return parameters. But we'll allow it for backward compatibility with V2. The attributes 
+            // defined on the return parameters won't be very useful but won't do much harm either.
+
+            // MD will assert if we try to set the reserved bits explicitly
+            attributes = attributes & ~ParameterAttributes.ReservedMask;
+            return m_methodBuilder.DefineParameter(iSequence, attributes, strParamName);
+        }
+
+        public ILGenerator GetILGenerator()
+        {
+            if (m_isDefaultConstructor)
+                throw new InvalidOperationException(SR.InvalidOperation_DefaultConstructorILGen);
+
+            return m_methodBuilder.GetILGenerator();
+        }
+
+        public ILGenerator GetILGenerator(int streamSize)
+        {
+            if (m_isDefaultConstructor)
+                throw new InvalidOperationException(SR.InvalidOperation_DefaultConstructorILGen);
+
+            return m_methodBuilder.GetILGenerator(streamSize);
+        }
+
+        public override CallingConventions CallingConvention
+        {
+            get
+            {
+                if (DeclaringType.IsGenericType)
+                    return CallingConventions.HasThis;
+
+                return CallingConventions.Standard;
+            }
+        }
+
+        public Module GetModule()
+        {
+            return m_methodBuilder.GetModule();
+        }
+
+        // This always returns null. Is that what we want?
+        internal override Type GetReturnType()
+        {
+            return m_methodBuilder.ReturnType;
+        }
+
+        public String Signature
+        {
+            get { return m_methodBuilder.Signature; }
+        }
+
+        public void SetCustomAttribute(ConstructorInfo con, byte[] binaryAttribute)
+        {
+            m_methodBuilder.SetCustomAttribute(con, binaryAttribute);
+        }
+
+        public void SetCustomAttribute(CustomAttributeBuilder customBuilder)
+        {
+            m_methodBuilder.SetCustomAttribute(customBuilder);
+        }
+
+        public void SetImplementationFlags(MethodImplAttributes attributes)
+        {
+            m_methodBuilder.SetImplementationFlags(attributes);
+        }
+
+        public bool InitLocals
+        {
+            get { return m_methodBuilder.InitLocals; }
+            set { m_methodBuilder.InitLocals = value; }
+        }
+
+        #endregion
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/CustomAttributeBuilder.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/CustomAttributeBuilder.cs
new file mode 100644
index 0000000000..f48a07251a
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/CustomAttributeBuilder.cs
@@ -0,0 +1,565 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** CustomAttributeBuilder is a helper class to help building custom attribute.
+**
+** 
+===========================================================*/
+
+
+using System;
+using System.Reflection;
+using System.IO;
+using System.Text;
+using System.Runtime.InteropServices;
+using System.Globalization;
+using System.Diagnostics;
+
+namespace System.Reflection.Emit
+{
+    public class CustomAttributeBuilder
+    {
+        // public constructor to form the custom attribute with constructor and constructor
+        // parameters.
+        public CustomAttributeBuilder(ConstructorInfo con, Object[] constructorArgs)
+        {
+            InitCustomAttributeBuilder(con, constructorArgs,
+                                       new PropertyInfo[] { }, new Object[] { },
+                                       new FieldInfo[] { }, new Object[] { });
+        }
+
+        // public constructor to form the custom attribute with constructor, constructor
+        // parameters and named properties.
+        public CustomAttributeBuilder(ConstructorInfo con, Object[] constructorArgs,
+                                      PropertyInfo[] namedProperties, Object[] propertyValues)
+        {
+            InitCustomAttributeBuilder(con, constructorArgs, namedProperties,
+                                       propertyValues, new FieldInfo[] { }, new Object[] { });
+        }
+
+        // public constructor to form the custom attribute with constructor and constructor
+        // parameters.
+        public CustomAttributeBuilder(ConstructorInfo con, Object[] constructorArgs,
+                                      FieldInfo[] namedFields, Object[] fieldValues)
+        {
+            InitCustomAttributeBuilder(con, constructorArgs, new PropertyInfo[] { },
+                                       new Object[] { }, namedFields, fieldValues);
+        }
+
+        // public constructor to form the custom attribute with constructor and constructor
+        // parameters.
+        public CustomAttributeBuilder(ConstructorInfo con, Object[] constructorArgs,
+                                      PropertyInfo[] namedProperties, Object[] propertyValues,
+                                      FieldInfo[] namedFields, Object[] fieldValues)
+        {
+            InitCustomAttributeBuilder(con, constructorArgs, namedProperties,
+                                       propertyValues, namedFields, fieldValues);
+        }
+
+        // Check that a type is suitable for use in a custom attribute.
+        private bool ValidateType(Type t)
+        {
+            if (t.IsPrimitive)
+            {
+                return t != typeof(IntPtr) && t != typeof(UIntPtr);
+            }
+            if (t == typeof(String) || t == typeof(Type))
+            {
+                return true;
+            }
+            if (t.IsEnum)
+            {
+                switch (Type.GetTypeCode(Enum.GetUnderlyingType(t)))
+                {
+                    case TypeCode.SByte:
+                    case TypeCode.Byte:
+                    case TypeCode.Int16:
+                    case TypeCode.UInt16:
+                    case TypeCode.Int32:
+                    case TypeCode.UInt32:
+                    case TypeCode.Int64:
+                    case TypeCode.UInt64:
+                        return true;
+                    default:
+                        return false;
+                }
+            }
+            if (t.IsArray)
+            {
+                if (t.GetArrayRank() != 1)
+                    return false;
+                return ValidateType(t.GetElementType());
+            }
+            return t == typeof(Object);
+        }
+
+        internal void InitCustomAttributeBuilder(ConstructorInfo con, Object[] constructorArgs,
+                                                 PropertyInfo[] namedProperties, Object[] propertyValues,
+                                                 FieldInfo[] namedFields, Object[] fieldValues)
+        {
+            if (con == null)
+                throw new ArgumentNullException(nameof(con));
+            if (constructorArgs == null)
+                throw new ArgumentNullException(nameof(constructorArgs));
+            if (namedProperties == null)
+                throw new ArgumentNullException(nameof(namedProperties));
+            if (propertyValues == null)
+                throw new ArgumentNullException(nameof(propertyValues));
+            if (namedFields == null)
+                throw new ArgumentNullException(nameof(namedFields));
+            if (fieldValues == null)
+                throw new ArgumentNullException(nameof(fieldValues));
+            if (namedProperties.Length != propertyValues.Length)
+                throw new ArgumentException(SR.Arg_ArrayLengthsDiffer, "namedProperties, propertyValues");
+            if (namedFields.Length != fieldValues.Length)
+                throw new ArgumentException(SR.Arg_ArrayLengthsDiffer, "namedFields, fieldValues");
+
+            if ((con.Attributes & MethodAttributes.Static) == MethodAttributes.Static ||
+                (con.Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Private)
+                throw new ArgumentException(SR.Argument_BadConstructor);
+
+            if ((con.CallingConvention & CallingConventions.Standard) != CallingConventions.Standard)
+                throw new ArgumentException(SR.Argument_BadConstructorCallConv);
+
+            // Cache information used elsewhere.
+            m_con = con;
+            m_constructorArgs = new Object[constructorArgs.Length];
+            Array.Copy(constructorArgs, 0, m_constructorArgs, 0, constructorArgs.Length);
+
+            Type[] paramTypes;
+            int i;
+
+            // Get the types of the constructor's formal parameters.
+            paramTypes = con.GetParameterTypes();
+
+            // Since we're guaranteed a non-var calling convention, the number of arguments must equal the number of parameters.
+            if (paramTypes.Length != constructorArgs.Length)
+                throw new ArgumentException(SR.Argument_BadParameterCountsForConstructor);
+
+            // Verify that the constructor has a valid signature (custom attributes only support a subset of our type system).
+            for (i = 0; i < paramTypes.Length; i++)
+                if (!ValidateType(paramTypes[i]))
+                    throw new ArgumentException(SR.Argument_BadTypeInCustomAttribute);
+
+            // Now verify that the types of the actual parameters are compatible with the types of the formal parameters.
+            for (i = 0; i < paramTypes.Length; i++)
+            {
+                object constructorArg = constructorArgs[i];
+                if (constructorArg == null)
+                {
+                    if (paramTypes[i].IsValueType)
+                    {
+                        throw new ArgumentNullException($"{nameof(constructorArgs)}[{i}]");
+                    }
+                    continue;
+                }
+                VerifyTypeAndPassedObjectType(paramTypes[i], constructorArg.GetType(), $"{nameof(constructorArgs)}[{i}]");
+            }
+
+            // Allocate a memory stream to represent the CA blob in the metadata and a binary writer to help format it.
+            MemoryStream stream = new MemoryStream();
+            BinaryWriter writer = new BinaryWriter(stream);
+
+            // Write the blob protocol version (currently 1).
+            writer.Write((ushort)1);
+
+            // Now emit the constructor argument values (no need for types, they're inferred from the constructor signature).
+            for (i = 0; i < constructorArgs.Length; i++)
+                EmitValue(writer, paramTypes[i], constructorArgs[i]);
+
+            // Next a short with the count of properties and fields.
+            writer.Write((ushort)(namedProperties.Length + namedFields.Length));
+
+            // Emit all the property sets.
+            for (i = 0; i < namedProperties.Length; i++)
+            {
+                // Validate the property.
+                PropertyInfo property = namedProperties[i];
+                if (property == null)
+                    throw new ArgumentNullException("namedProperties[" + i + "]");
+
+                // Allow null for non-primitive types only.
+                Type propType = property.PropertyType;
+                object propertyValue = propertyValues[i];
+                if (propertyValue == null && propType.IsValueType)
+                    throw new ArgumentNullException("propertyValues[" + i + "]");
+
+                // Validate property type.
+                if (!ValidateType(propType))
+                    throw new ArgumentException(SR.Argument_BadTypeInCustomAttribute);
+
+                // Property has to be writable.
+                if (!property.CanWrite)
+                    throw new ArgumentException(SR.Argument_NotAWritableProperty);
+
+                // Property has to be from the same class or base class as ConstructorInfo.
+                if (property.DeclaringType != con.DeclaringType
+                    && (!(con.DeclaringType is TypeBuilderInstantiation))
+                    && !con.DeclaringType.IsSubclassOf(property.DeclaringType))
+                {
+                    // Might have failed check because one type is a XXXBuilder
+                    // and the other is not. Deal with these special cases
+                    // separately.
+                    if (!TypeBuilder.IsTypeEqual(property.DeclaringType, con.DeclaringType))
+                    {
+                        // IsSubclassOf is overloaded to do the right thing if
+                        // the constructor is a TypeBuilder, but we still need
+                        // to deal with the case where the property's declaring
+                        // type is one.
+                        if (!(property.DeclaringType is TypeBuilder) ||
+                            !con.DeclaringType.IsSubclassOf(((TypeBuilder)property.DeclaringType).BakedRuntimeType))
+                            throw new ArgumentException(SR.Argument_BadPropertyForConstructorBuilder);
+                    }
+                }
+
+                // Make sure the property's type can take the given value.
+                // Note that there will be no coersion.
+                if (propertyValue != null)
+                {
+                    VerifyTypeAndPassedObjectType(propType, propertyValue.GetType(), $"{nameof(propertyValues)}[{i}]");
+                }
+
+                // First a byte indicating that this is a property.
+                writer.Write((byte)CustomAttributeEncoding.Property);
+
+                // Emit the property type, name and value.
+                EmitType(writer, propType);
+                EmitString(writer, namedProperties[i].Name);
+                EmitValue(writer, propType, propertyValue);
+            }
+
+            // Emit all the field sets.
+            for (i = 0; i < namedFields.Length; i++)
+            {
+                // Validate the field.
+                FieldInfo namedField = namedFields[i];
+                if (namedField == null)
+                    throw new ArgumentNullException("namedFields[" + i + "]");
+
+                // Allow null for non-primitive types only.
+                Type fldType = namedField.FieldType;
+                object fieldValue = fieldValues[i];
+                if (fieldValue == null && fldType.IsValueType)
+                    throw new ArgumentNullException("fieldValues[" + i + "]");
+
+                // Validate field type.
+                if (!ValidateType(fldType))
+                    throw new ArgumentException(SR.Argument_BadTypeInCustomAttribute);
+
+                // Field has to be from the same class or base class as ConstructorInfo.
+                if (namedField.DeclaringType != con.DeclaringType
+                    && (!(con.DeclaringType is TypeBuilderInstantiation))
+                    && !con.DeclaringType.IsSubclassOf(namedField.DeclaringType))
+                {
+                    // Might have failed check because one type is a XXXBuilder
+                    // and the other is not. Deal with these special cases
+                    // separately.
+                    if (!TypeBuilder.IsTypeEqual(namedField.DeclaringType, con.DeclaringType))
+                    {
+                        // IsSubclassOf is overloaded to do the right thing if
+                        // the constructor is a TypeBuilder, but we still need
+                        // to deal with the case where the field's declaring
+                        // type is one.
+                        if (!(namedField.DeclaringType is TypeBuilder) ||
+                            !con.DeclaringType.IsSubclassOf(((TypeBuilder)namedFields[i].DeclaringType).BakedRuntimeType))
+                            throw new ArgumentException(SR.Argument_BadFieldForConstructorBuilder);
+                    }
+                }
+
+                // Make sure the field's type can take the given value.
+                // Note that there will be no coersion.
+                if (fieldValue != null)
+                {
+                    VerifyTypeAndPassedObjectType(fldType, fieldValue.GetType(), $"{nameof(fieldValues)}[{i}]");
+                }
+
+                // First a byte indicating that this is a field.
+                writer.Write((byte)CustomAttributeEncoding.Field);
+
+                // Emit the field type, name and value.
+                EmitType(writer, fldType);
+                EmitString(writer, namedField.Name);
+                EmitValue(writer, fldType, fieldValue);
+            }
+
+            // Create the blob array.
+            m_blob = ((MemoryStream)writer.BaseStream).ToArray();
+        }
+
+        private static void VerifyTypeAndPassedObjectType(Type type, Type passedType, string paramName)
+        {
+            if (type != typeof(object) && Type.GetTypeCode(passedType) != Type.GetTypeCode(type))
+            {
+                throw new ArgumentException(SR.Argument_ConstantDoesntMatch);
+            }
+            if (passedType == typeof(IntPtr) || passedType == typeof(UIntPtr))
+            {
+                throw new ArgumentException(SR.Format(SR.Argument_BadParameterTypeForCAB, passedType.ToString()), paramName);
+            }
+        }
+
+        private void EmitType(BinaryWriter writer, Type type)
+        {
+            if (type.IsPrimitive)
+            {
+                switch (Type.GetTypeCode(type))
+                {
+                    case TypeCode.SByte:
+                        writer.Write((byte)CustomAttributeEncoding.SByte);
+                        break;
+                    case TypeCode.Byte:
+                        writer.Write((byte)CustomAttributeEncoding.Byte);
+                        break;
+                    case TypeCode.Char:
+                        writer.Write((byte)CustomAttributeEncoding.Char);
+                        break;
+                    case TypeCode.Boolean:
+                        writer.Write((byte)CustomAttributeEncoding.Boolean);
+                        break;
+                    case TypeCode.Int16:
+                        writer.Write((byte)CustomAttributeEncoding.Int16);
+                        break;
+                    case TypeCode.UInt16:
+                        writer.Write((byte)CustomAttributeEncoding.UInt16);
+                        break;
+                    case TypeCode.Int32:
+                        writer.Write((byte)CustomAttributeEncoding.Int32);
+                        break;
+                    case TypeCode.UInt32:
+                        writer.Write((byte)CustomAttributeEncoding.UInt32);
+                        break;
+                    case TypeCode.Int64:
+                        writer.Write((byte)CustomAttributeEncoding.Int64);
+                        break;
+                    case TypeCode.UInt64:
+                        writer.Write((byte)CustomAttributeEncoding.UInt64);
+                        break;
+                    case TypeCode.Single:
+                        writer.Write((byte)CustomAttributeEncoding.Float);
+                        break;
+                    case TypeCode.Double:
+                        writer.Write((byte)CustomAttributeEncoding.Double);
+                        break;
+                    default:
+                        Debug.Fail("Invalid primitive type");
+                        break;
+                }
+            }
+            else if (type.IsEnum)
+            {
+                writer.Write((byte)CustomAttributeEncoding.Enum);
+                EmitString(writer, type.AssemblyQualifiedName);
+            }
+            else if (type == typeof(String))
+            {
+                writer.Write((byte)CustomAttributeEncoding.String);
+            }
+            else if (type == typeof(Type))
+            {
+                writer.Write((byte)CustomAttributeEncoding.Type);
+            }
+            else if (type.IsArray)
+            {
+                writer.Write((byte)CustomAttributeEncoding.Array);
+                EmitType(writer, type.GetElementType());
+            }
+            else
+            {
+                // Tagged object case.
+                writer.Write((byte)CustomAttributeEncoding.Object);
+            }
+        }
+
+        private void EmitString(BinaryWriter writer, String str)
+        {
+            // Strings are emitted with a length prefix in a compressed format (1, 2 or 4 bytes) as used internally by metadata.
+            byte[] utf8Str = Encoding.UTF8.GetBytes(str);
+            uint length = (uint)utf8Str.Length;
+            if (length <= 0x7f)
+            {
+                writer.Write((byte)length);
+            }
+            else if (length <= 0x3fff)
+            {
+                writer.Write((byte)((length >> 8) | 0x80));
+                writer.Write((byte)(length & 0xff));
+            }
+            else
+            {
+                writer.Write((byte)((length >> 24) | 0xc0));
+                writer.Write((byte)((length >> 16) & 0xff));
+                writer.Write((byte)((length >> 8) & 0xff));
+                writer.Write((byte)(length & 0xff));
+            }
+            writer.Write(utf8Str);
+        }
+
+        private void EmitValue(BinaryWriter writer, Type type, Object value)
+        {
+            if (type.IsEnum)
+            {
+                switch (Type.GetTypeCode(Enum.GetUnderlyingType(type)))
+                {
+                    case TypeCode.SByte:
+                        writer.Write((sbyte)value);
+                        break;
+                    case TypeCode.Byte:
+                        writer.Write((byte)value);
+                        break;
+                    case TypeCode.Int16:
+                        writer.Write((short)value);
+                        break;
+                    case TypeCode.UInt16:
+                        writer.Write((ushort)value);
+                        break;
+                    case TypeCode.Int32:
+                        writer.Write((int)value);
+                        break;
+                    case TypeCode.UInt32:
+                        writer.Write((uint)value);
+                        break;
+                    case TypeCode.Int64:
+                        writer.Write((long)value);
+                        break;
+                    case TypeCode.UInt64:
+                        writer.Write((ulong)value);
+                        break;
+                    default:
+                        Debug.Fail("Invalid enum base type");
+                        break;
+                }
+            }
+            else if (type == typeof(String))
+            {
+                if (value == null)
+                    writer.Write((byte)0xff);
+                else
+                    EmitString(writer, (String)value);
+            }
+            else if (type == typeof(Type))
+            {
+                if (value == null)
+                    writer.Write((byte)0xff);
+                else
+                {
+                    String typeName = TypeNameBuilder.ToString((Type)value, TypeNameBuilder.Format.AssemblyQualifiedName);
+                    if (typeName == null)
+                        throw new ArgumentException(SR.Format(SR.Argument_InvalidTypeForCA, value.GetType()));
+                    EmitString(writer, typeName);
+                }
+            }
+            else if (type.IsArray)
+            {
+                if (value == null)
+                    writer.Write((uint)0xffffffff);
+                else
+                {
+                    Array a = (Array)value;
+                    Type et = type.GetElementType();
+                    writer.Write(a.Length);
+                    for (int i = 0; i < a.Length; i++)
+                        EmitValue(writer, et, a.GetValue(i));
+                }
+            }
+            else if (type.IsPrimitive)
+            {
+                switch (Type.GetTypeCode(type))
+                {
+                    case TypeCode.SByte:
+                        writer.Write((sbyte)value);
+                        break;
+                    case TypeCode.Byte:
+                        writer.Write((byte)value);
+                        break;
+                    case TypeCode.Char:
+                        writer.Write(Convert.ToUInt16((char)value));
+                        break;
+                    case TypeCode.Boolean:
+                        writer.Write((byte)((bool)value ? 1 : 0));
+                        break;
+                    case TypeCode.Int16:
+                        writer.Write((short)value);
+                        break;
+                    case TypeCode.UInt16:
+                        writer.Write((ushort)value);
+                        break;
+                    case TypeCode.Int32:
+                        writer.Write((int)value);
+                        break;
+                    case TypeCode.UInt32:
+                        writer.Write((uint)value);
+                        break;
+                    case TypeCode.Int64:
+                        writer.Write((long)value);
+                        break;
+                    case TypeCode.UInt64:
+                        writer.Write((ulong)value);
+                        break;
+                    case TypeCode.Single:
+                        writer.Write((float)value);
+                        break;
+                    case TypeCode.Double:
+                        writer.Write((double)value);
+                        break;
+                    default:
+                        Debug.Fail("Invalid primitive type");
+                        break;
+                }
+            }
+            else if (type == typeof(object))
+            {
+                // Tagged object case. Type instances aren't actually Type, they're some subclass (such as RuntimeType or
+                // TypeBuilder), so we need to canonicalize this case back to Type. If we have a null value we follow the convention
+                // used by C# and emit a null typed as a string (it doesn't really matter what type we pick as long as it's a
+                // reference type).
+                Type ot = value == null ? typeof(String) : value is Type ? typeof(Type) : value.GetType();
+
+                // value cannot be a "System.Object" object.
+                // If we allow this we will get into an infinite recursion
+                if (ot == typeof(object))
+                    throw new ArgumentException(SR.Format(SR.Argument_BadParameterTypeForCAB, ot.ToString()));
+
+                EmitType(writer, ot);
+                EmitValue(writer, ot, value);
+            }
+            else
+            {
+                string typename = "null";
+
+                if (value != null)
+                    typename = value.GetType().ToString();
+
+                throw new ArgumentException(SR.Format(SR.Argument_BadParameterTypeForCAB, typename));
+            }
+        }
+
+
+
+
+        // return the byte interpretation of the custom attribute
+        internal void CreateCustomAttribute(ModuleBuilder mod, int tkOwner)
+        {
+            CreateCustomAttribute(mod, tkOwner, mod.GetConstructorToken(m_con).Token, false);
+        }
+
+        //*************************************************
+        // Call this function with toDisk=1, after on disk module has been snapped.
+        //*************************************************
+        internal void CreateCustomAttribute(ModuleBuilder mod, int tkOwner, int tkAttrib, bool toDisk)
+        {
+            TypeBuilder.DefineCustomAttribute(mod, tkOwner, tkAttrib, m_blob, toDisk,
+                                                      typeof(System.Diagnostics.DebuggableAttribute) == m_con.DeclaringType);
+        }
+
+        internal ConstructorInfo m_con;
+        internal Object[] m_constructorArgs;
+        internal byte[] m_blob;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/DynamicILGenerator.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/DynamicILGenerator.cs
new file mode 100644
index 0000000000..5ecf0bef80
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/DynamicILGenerator.cs
@@ -0,0 +1,1066 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+namespace System.Reflection.Emit
+{
+    using System;
+    using System.Globalization;
+    using System.Diagnostics.SymbolStore;
+    using System.Runtime.InteropServices;
+    using System.Reflection;
+    using System.Collections;
+    using System.Collections.Generic;
+    using System.Threading;
+    using System.Diagnostics;
+    using System.Diagnostics.CodeAnalysis;
+    using System.Security;
+
+    internal class DynamicILGenerator : ILGenerator
+    {
+        internal DynamicScope m_scope;
+        private int m_methodSigToken;
+
+        internal unsafe DynamicILGenerator(DynamicMethod method, byte[] methodSignature, int size)
+            : base(method, size)
+        {
+            m_scope = new DynamicScope();
+
+            m_methodSigToken = m_scope.GetTokenFor(methodSignature);
+        }
+
+
+        internal void GetCallableMethod(RuntimeModule module, DynamicMethod dm)
+        {
+            dm.m_methodHandle = ModuleHandle.GetDynamicMethod(dm,
+                                          module,
+                                          m_methodBuilder.Name,
+                                          (byte[])m_scope[m_methodSigToken],
+                                          new DynamicResolver(this));
+        }
+
+        // *** ILGenerator api ***
+
+        public override LocalBuilder DeclareLocal(Type localType, bool pinned)
+        {
+            LocalBuilder localBuilder;
+            if (localType == null)
+                throw new ArgumentNullException(nameof(localType));
+
+            RuntimeType rtType = localType as RuntimeType;
+
+            if (rtType == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType);
+
+            localBuilder = new LocalBuilder(m_localCount, localType, m_methodBuilder);
+            // add the localType to local signature
+            m_localSignature.AddArgument(localType, pinned);
+            m_localCount++;
+            return localBuilder;
+        }
+
+        //
+        //
+        // Token resolution calls
+        //
+        //
+        public override void Emit(OpCode opcode, MethodInfo meth)
+        {
+            if (meth == null)
+                throw new ArgumentNullException(nameof(meth));
+
+            int stackchange = 0;
+            int token = 0;
+            DynamicMethod dynMeth = meth as DynamicMethod;
+            if (dynMeth == null)
+            {
+                RuntimeMethodInfo rtMeth = meth as RuntimeMethodInfo;
+                if (rtMeth == null)
+                    throw new ArgumentException(SR.Argument_MustBeRuntimeMethodInfo, nameof(meth));
+
+                RuntimeType declaringType = rtMeth.GetRuntimeType();
+                if (declaringType != null && (declaringType.IsGenericType || declaringType.IsArray))
+                    token = GetTokenFor(rtMeth, declaringType);
+                else
+                    token = GetTokenFor(rtMeth);
+            }
+            else
+            {
+                // rule out not allowed operations on DynamicMethods
+                if (opcode.Equals(OpCodes.Ldtoken) || opcode.Equals(OpCodes.Ldftn) || opcode.Equals(OpCodes.Ldvirtftn))
+                {
+                    throw new ArgumentException(SR.Argument_InvalidOpCodeOnDynamicMethod);
+                }
+                token = GetTokenFor(dynMeth);
+            }
+
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+
+            if (opcode.StackBehaviourPush == StackBehaviour.Varpush
+                && meth.ReturnType != typeof(void))
+            {
+                stackchange++;
+            }
+            if (opcode.StackBehaviourPop == StackBehaviour.Varpop)
+            {
+                stackchange -= meth.GetParametersNoCopy().Length;
+            }
+            // Pop the "this" parameter if the method is non-static,
+            //  and the instruction is not newobj/ldtoken/ldftn.
+            if (!meth.IsStatic &&
+                !(opcode.Equals(OpCodes.Newobj) || opcode.Equals(OpCodes.Ldtoken) || opcode.Equals(OpCodes.Ldftn)))
+            {
+                stackchange--;
+            }
+
+            UpdateStackSize(opcode, stackchange);
+
+            PutInteger4(token);
+        }
+
+        public override void Emit(OpCode opcode, ConstructorInfo con)
+        {
+            if (con == null)
+                throw new ArgumentNullException(nameof(con));
+
+            RuntimeConstructorInfo rtConstructor = con as RuntimeConstructorInfo;
+            if (rtConstructor == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeMethodInfo, nameof(con));
+
+            RuntimeType declaringType = rtConstructor.GetRuntimeType();
+            int token;
+
+            if (declaringType != null && (declaringType.IsGenericType || declaringType.IsArray))
+                // need to sort out the stack size story
+                token = GetTokenFor(rtConstructor, declaringType);
+            else
+                token = GetTokenFor(rtConstructor);
+
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+
+            // need to sort out the stack size story
+            UpdateStackSize(opcode, 1);
+
+            PutInteger4(token);
+        }
+
+        public override void Emit(OpCode opcode, Type type)
+        {
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+
+            RuntimeType rtType = type as RuntimeType;
+
+            if (rtType == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType);
+
+            int token = GetTokenFor(rtType);
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+            PutInteger4(token);
+        }
+
+        public override void Emit(OpCode opcode, FieldInfo field)
+        {
+            if (field == null)
+                throw new ArgumentNullException(nameof(field));
+
+            RuntimeFieldInfo runtimeField = field as RuntimeFieldInfo;
+            if (runtimeField == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeFieldInfo, nameof(field));
+
+            int token;
+            if (field.DeclaringType == null)
+                token = GetTokenFor(runtimeField);
+            else
+                token = GetTokenFor(runtimeField, runtimeField.GetRuntimeType());
+
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+            PutInteger4(token);
+        }
+
+        public override void Emit(OpCode opcode, String str)
+        {
+            if (str == null)
+                throw new ArgumentNullException(nameof(str));
+
+            int tempVal = GetTokenForString(str);
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+            PutInteger4(tempVal);
+        }
+
+        //
+        //
+        // Signature related calls (vararg, calli)
+        //
+        //
+        public override void EmitCalli(OpCode opcode,
+                                       CallingConventions callingConvention,
+                                       Type returnType,
+                                       Type[] parameterTypes,
+                                       Type[] optionalParameterTypes)
+        {
+            int stackchange = 0;
+            SignatureHelper sig;
+            if (optionalParameterTypes != null)
+                if ((callingConvention & CallingConventions.VarArgs) == 0)
+
+                    throw new InvalidOperationException(SR.InvalidOperation_NotAVarArgCallingConvention);
+
+            sig = GetMemberRefSignature(callingConvention,
+                                        returnType,
+                                        parameterTypes,
+                                        optionalParameterTypes);
+
+            EnsureCapacity(7);
+            Emit(OpCodes.Calli);
+
+            // If there is a non-void return type, push one.
+            if (returnType != typeof(void))
+                stackchange++;
+            // Pop off arguments if any.
+            if (parameterTypes != null)
+                stackchange -= parameterTypes.Length;
+            // Pop off vararg arguments.
+            if (optionalParameterTypes != null)
+                stackchange -= optionalParameterTypes.Length;
+            // Pop the this parameter if the method has a this parameter.
+            if ((callingConvention & CallingConventions.HasThis) == CallingConventions.HasThis)
+                stackchange--;
+            // Pop the native function pointer.
+            stackchange--;
+            UpdateStackSize(OpCodes.Calli, stackchange);
+
+            int token = GetTokenForSig(sig.GetSignature(true));
+            PutInteger4(token);
+        }
+
+        public override void EmitCalli(OpCode opcode, CallingConvention unmanagedCallConv, Type returnType, Type[] parameterTypes)
+        {
+            int stackchange = 0;
+            int cParams = 0;
+            int i;
+            SignatureHelper sig;
+
+            if (parameterTypes != null)
+                cParams = parameterTypes.Length;
+
+            sig = SignatureHelper.GetMethodSigHelper(unmanagedCallConv, returnType);
+
+            if (parameterTypes != null)
+                for (i = 0; i < cParams; i++)
+                    sig.AddArgument(parameterTypes[i]);
+
+            // If there is a non-void return type, push one. 
+            if (returnType != typeof(void))
+                stackchange++;
+
+            // Pop off arguments if any.
+            if (parameterTypes != null)
+                stackchange -= cParams;
+
+            // Pop the native function pointer.
+            stackchange--;
+            UpdateStackSize(OpCodes.Calli, stackchange);
+
+            EnsureCapacity(7);
+            Emit(OpCodes.Calli);
+
+            int token = GetTokenForSig(sig.GetSignature(true));
+            PutInteger4(token);
+        }
+
+        public override void EmitCall(OpCode opcode, MethodInfo methodInfo, Type[] optionalParameterTypes)
+        {
+            if (methodInfo == null)
+                throw new ArgumentNullException(nameof(methodInfo));
+
+            if (!(opcode.Equals(OpCodes.Call) || opcode.Equals(OpCodes.Callvirt) || opcode.Equals(OpCodes.Newobj)))
+                throw new ArgumentException(SR.Argument_NotMethodCallOpcode, nameof(opcode));
+
+            if (methodInfo.ContainsGenericParameters)
+                throw new ArgumentException(SR.Argument_GenericsInvalid, nameof(methodInfo));
+
+            if (methodInfo.DeclaringType != null && methodInfo.DeclaringType.ContainsGenericParameters)
+                throw new ArgumentException(SR.Argument_GenericsInvalid, nameof(methodInfo));
+
+            int tk;
+            int stackchange = 0;
+
+            tk = GetMemberRefToken(methodInfo, optionalParameterTypes);
+
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+
+            // Push the return value if there is one.
+            if (methodInfo.ReturnType != typeof(void))
+                stackchange++;
+            // Pop the parameters.
+            stackchange -= methodInfo.GetParameterTypes().Length;
+            // Pop the this parameter if the method is non-static and the
+            // instruction is not newobj.
+            if (!(methodInfo is SymbolMethod) && methodInfo.IsStatic == false && !(opcode.Equals(OpCodes.Newobj)))
+                stackchange--;
+            // Pop the optional parameters off the stack.
+            if (optionalParameterTypes != null)
+                stackchange -= optionalParameterTypes.Length;
+            UpdateStackSize(opcode, stackchange);
+
+            PutInteger4(tk);
+        }
+
+        public override void Emit(OpCode opcode, SignatureHelper signature)
+        {
+            if (signature == null)
+                throw new ArgumentNullException(nameof(signature));
+
+            int stackchange = 0;
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+
+            // The only IL instruction that has VarPop behaviour, that takes a
+            // Signature token as a parameter is calli.  Pop the parameters and
+            // the native function pointer.  To be conservative, do not pop the
+            // this pointer since this information is not easily derived from
+            // SignatureHelper.
+            if (opcode.StackBehaviourPop == StackBehaviour.Varpop)
+            {
+                Debug.Assert(opcode.Equals(OpCodes.Calli),
+                                "Unexpected opcode encountered for StackBehaviour VarPop.");
+                // Pop the arguments..
+                stackchange -= signature.ArgumentCount;
+                // Pop native function pointer off the stack.
+                stackchange--;
+                UpdateStackSize(opcode, stackchange);
+            }
+
+            int token = GetTokenForSig(signature.GetSignature(true));
+            PutInteger4(token);
+        }
+
+        //
+        //
+        // Exception related generation
+        //
+        //
+        public override void BeginExceptFilterBlock()
+        {
+            // Begins an exception filter block. Emits a branch instruction to the end of the current exception block.
+
+            if (CurrExcStackCount == 0)
+                throw new NotSupportedException(SR.Argument_NotInExceptionBlock);
+
+            __ExceptionInfo current = CurrExcStack[CurrExcStackCount - 1];
+
+            Label endLabel = current.GetEndLabel();
+            Emit(OpCodes.Leave, endLabel);
+            UpdateStackSize(OpCodes.Nop, 1);
+
+            current.MarkFilterAddr(ILOffset);
+        }
+
+        public override void BeginCatchBlock(Type exceptionType)
+        {
+            if (CurrExcStackCount == 0)
+                throw new NotSupportedException(SR.Argument_NotInExceptionBlock);
+
+            __ExceptionInfo current = CurrExcStack[CurrExcStackCount - 1];
+
+            RuntimeType rtType = exceptionType as RuntimeType;
+
+            if (current.GetCurrentState() == __ExceptionInfo.State_Filter)
+            {
+                if (exceptionType != null)
+                {
+                    throw new ArgumentException(SR.Argument_ShouldNotSpecifyExceptionType);
+                }
+
+                this.Emit(OpCodes.Endfilter);
+
+                current.MarkCatchAddr(ILOffset, null);
+            }
+            else
+            {
+                // execute this branch if previous clause is Catch or Fault
+                if (exceptionType == null)
+                    throw new ArgumentNullException(nameof(exceptionType));
+
+                if (rtType == null)
+                    throw new ArgumentException(SR.Argument_MustBeRuntimeType);
+
+                Label endLabel = current.GetEndLabel();
+                this.Emit(OpCodes.Leave, endLabel);
+
+                // if this is a catch block the exception will be pushed on the stack and we need to update the stack info
+                UpdateStackSize(OpCodes.Nop, 1);
+
+                current.MarkCatchAddr(ILOffset, exceptionType);
+
+
+                // this is relying on too much implementation details of the base and so it's highly breaking
+                // Need to have a more integrated story for exceptions
+                current.m_filterAddr[current.m_currentCatch - 1] = GetTokenFor(rtType);
+            }
+        }
+
+        //
+        //
+        // debugger related calls. 
+        //
+        //
+        public override void UsingNamespace(String ns)
+        {
+            throw new NotSupportedException(SR.InvalidOperation_NotAllowedInDynamicMethod);
+        }
+
+        public override void MarkSequencePoint(ISymbolDocumentWriter document,
+                                               int startLine,
+                                               int startColumn,
+                                               int endLine,
+                                               int endColumn)
+        {
+            throw new NotSupportedException(SR.InvalidOperation_NotAllowedInDynamicMethod);
+        }
+
+        public override void BeginScope()
+        {
+            throw new NotSupportedException(SR.InvalidOperation_NotAllowedInDynamicMethod);
+        }
+
+        public override void EndScope()
+        {
+            throw new NotSupportedException(SR.InvalidOperation_NotAllowedInDynamicMethod);
+        }
+
+        private int GetMemberRefToken(MethodBase methodInfo, Type[] optionalParameterTypes)
+        {
+            Type[] parameterTypes;
+
+            if (optionalParameterTypes != null && (methodInfo.CallingConvention & CallingConventions.VarArgs) == 0)
+                throw new InvalidOperationException(SR.InvalidOperation_NotAVarArgCallingConvention);
+
+            RuntimeMethodInfo rtMeth = methodInfo as RuntimeMethodInfo;
+            DynamicMethod dm = methodInfo as DynamicMethod;
+
+            if (rtMeth == null && dm == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeMethodInfo, nameof(methodInfo));
+
+            ParameterInfo[] paramInfo = methodInfo.GetParametersNoCopy();
+            if (paramInfo != null && paramInfo.Length != 0)
+            {
+                parameterTypes = new Type[paramInfo.Length];
+                for (int i = 0; i < paramInfo.Length; i++)
+                    parameterTypes[i] = paramInfo[i].ParameterType;
+            }
+            else
+            {
+                parameterTypes = null;
+            }
+
+            SignatureHelper sig = GetMemberRefSignature(methodInfo.CallingConvention,
+                                                     MethodBuilder.GetMethodBaseReturnType(methodInfo),
+                                                     parameterTypes,
+                                                     optionalParameterTypes);
+
+            if (rtMeth != null)
+                return GetTokenForVarArgMethod(rtMeth, sig);
+            else
+                return GetTokenForVarArgMethod(dm, sig);
+        }
+
+        internal override SignatureHelper GetMemberRefSignature(
+                                                CallingConventions call,
+                                                Type returnType,
+                                                Type[] parameterTypes,
+                                                Type[] optionalParameterTypes)
+        {
+            SignatureHelper sig = SignatureHelper.GetMethodSigHelper(call, returnType);
+            if (parameterTypes != null)
+            {
+                foreach (Type t in parameterTypes)
+                    sig.AddArgument(t);
+            }
+            if (optionalParameterTypes != null && optionalParameterTypes.Length != 0)
+            {
+                // add the sentinel
+                sig.AddSentinel();
+                foreach (Type t in optionalParameterTypes)
+                    sig.AddArgument(t);
+            }
+            return sig;
+        }
+
+        internal override void RecordTokenFixup()
+        {
+            // DynamicMethod doesn't need fixup.
+        }
+
+        #region GetTokenFor helpers
+        private int GetTokenFor(RuntimeType rtType)
+        {
+            return m_scope.GetTokenFor(rtType.TypeHandle);
+        }
+
+        private int GetTokenFor(RuntimeFieldInfo runtimeField)
+        {
+            return m_scope.GetTokenFor(runtimeField.FieldHandle);
+        }
+
+        private int GetTokenFor(RuntimeFieldInfo runtimeField, RuntimeType rtType)
+        {
+            return m_scope.GetTokenFor(runtimeField.FieldHandle, rtType.TypeHandle);
+        }
+
+        private int GetTokenFor(RuntimeConstructorInfo rtMeth)
+        {
+            return m_scope.GetTokenFor(rtMeth.MethodHandle);
+        }
+
+        private int GetTokenFor(RuntimeConstructorInfo rtMeth, RuntimeType rtType)
+        {
+            return m_scope.GetTokenFor(rtMeth.MethodHandle, rtType.TypeHandle);
+        }
+
+        private int GetTokenFor(RuntimeMethodInfo rtMeth)
+        {
+            return m_scope.GetTokenFor(rtMeth.MethodHandle);
+        }
+
+        private int GetTokenFor(RuntimeMethodInfo rtMeth, RuntimeType rtType)
+        {
+            return m_scope.GetTokenFor(rtMeth.MethodHandle, rtType.TypeHandle);
+        }
+
+        private int GetTokenFor(DynamicMethod dm)
+        {
+            return m_scope.GetTokenFor(dm);
+        }
+
+        private int GetTokenForVarArgMethod(RuntimeMethodInfo rtMeth, SignatureHelper sig)
+        {
+            VarArgMethod varArgMeth = new VarArgMethod(rtMeth, sig);
+            return m_scope.GetTokenFor(varArgMeth);
+        }
+
+        private int GetTokenForVarArgMethod(DynamicMethod dm, SignatureHelper sig)
+        {
+            VarArgMethod varArgMeth = new VarArgMethod(dm, sig);
+            return m_scope.GetTokenFor(varArgMeth);
+        }
+
+        private int GetTokenForString(String s)
+        {
+            return m_scope.GetTokenFor(s);
+        }
+
+        private int GetTokenForSig(byte[] sig)
+        {
+            return m_scope.GetTokenFor(sig);
+        }
+        #endregion
+
+    }
+
+    internal class DynamicResolver : Resolver
+    {
+        #region Private Data Members
+        private __ExceptionInfo[] m_exceptions;
+        private byte[] m_exceptionHeader;
+        private DynamicMethod m_method;
+        private byte[] m_code;
+        private byte[] m_localSignature;
+        private int m_stackSize;
+        private DynamicScope m_scope;
+        #endregion
+
+        #region Internal Methods
+        internal DynamicResolver(DynamicILGenerator ilGenerator)
+        {
+            m_stackSize = ilGenerator.GetMaxStackSize();
+            m_exceptions = ilGenerator.GetExceptions();
+            m_code = ilGenerator.BakeByteArray();
+            m_localSignature = ilGenerator.m_localSignature.InternalGetSignatureArray();
+            m_scope = ilGenerator.m_scope;
+
+            m_method = (DynamicMethod)ilGenerator.m_methodBuilder;
+            m_method.m_resolver = this;
+        }
+
+        internal DynamicResolver(DynamicILInfo dynamicILInfo)
+        {
+            m_stackSize = dynamicILInfo.MaxStackSize;
+            m_code = dynamicILInfo.Code;
+            m_localSignature = dynamicILInfo.LocalSignature;
+            m_exceptionHeader = dynamicILInfo.Exceptions;
+            //m_exceptions = dynamicILInfo.Exceptions;
+            m_scope = dynamicILInfo.DynamicScope;
+
+            m_method = dynamicILInfo.DynamicMethod;
+            m_method.m_resolver = this;
+        }
+
+        //
+        // We can destroy the unmanaged part of dynamic method only after the managed part is definitely gone and thus
+        // nobody can call the dynamic method anymore. A call to finalizer alone does not guarantee that the managed 
+        // part is gone. A malicious code can keep a reference to DynamicMethod in long weak reference that survives finalization,
+        // or we can be running during shutdown where everything is finalized.
+        //
+        // The unmanaged resolver keeps a reference to the managed resolver in long weak handle. If the long weak handle 
+        // is null, we can be sure that the managed part of the dynamic method is definitely gone and that it is safe to 
+        // destroy the unmanaged part. (Note that the managed finalizer has to be on the same object that the long weak handle 
+        // points to in order for this to work.) Unfortunately, we can not perform the above check when out finalizer 
+        // is called - the long weak handle won't be cleared yet. Instead, we create a helper scout object that will attempt 
+        // to do the destruction after next GC.
+        //
+        // The finalization does not have to be done using CriticalFinalizerObject. We have to go over all DynamicMethodDescs 
+        // during AppDomain shutdown anyway to avoid leaks e.g. if somebody stores reference to DynamicMethod in static.
+        //
+        ~DynamicResolver()
+        {
+            DynamicMethod method = m_method;
+
+            if (method == null)
+                return;
+
+            if (method.m_methodHandle == null)
+                return;
+
+            DestroyScout scout = null;
+            try
+            {
+                scout = new DestroyScout();
+            }
+            catch
+            {
+                // We go over all DynamicMethodDesc during AppDomain shutdown and make sure
+                // that everything associated with them is released. So it is ok to skip reregistration
+                // for finalization during appdomain shutdown
+                if (!Environment.HasShutdownStarted &&
+                    !AppDomain.CurrentDomain.IsFinalizingForUnload())
+                {
+                    // Try again later.
+                    GC.ReRegisterForFinalize(this);
+                }
+                return;
+            }
+
+            // We can never ever have two active destroy scouts for the same method. We need to initialize the scout
+            // outside the try/reregister block to avoid possibility of reregistration for finalization with active scout.
+            scout.m_methodHandle = method.m_methodHandle.Value;
+        }
+
+        private class DestroyScout
+        {
+            internal RuntimeMethodHandleInternal m_methodHandle;
+
+            ~DestroyScout()
+            {
+                if (m_methodHandle.IsNullHandle())
+                    return;
+
+                // It is not safe to destroy the method if the managed resolver is alive.
+                if (RuntimeMethodHandle.GetResolver(m_methodHandle) != null)
+                {
+                    if (!Environment.HasShutdownStarted &&
+                        !AppDomain.CurrentDomain.IsFinalizingForUnload())
+                    {
+                        // Somebody might have been holding a reference on us via weak handle.
+                        // We will keep trying. It will be hopefully released eventually.
+                        GC.ReRegisterForFinalize(this);
+                    }
+                    return;
+                }
+
+                RuntimeMethodHandle.Destroy(m_methodHandle);
+            }
+        }
+
+        // Keep in sync with vm/dynamicmethod.h
+        [Flags]
+        internal enum SecurityControlFlags
+        {
+            Default = 0x0,
+            SkipVisibilityChecks = 0x1,
+            RestrictedSkipVisibilityChecks = 0x2,
+            HasCreationContext = 0x4,
+            CanSkipCSEvaluation = 0x8,
+        }
+
+        internal override RuntimeType GetJitContext(ref int securityControlFlags)
+        {
+            RuntimeType typeOwner;
+
+            SecurityControlFlags flags = SecurityControlFlags.Default;
+
+            if (m_method.m_restrictedSkipVisibility)
+                flags |= SecurityControlFlags.RestrictedSkipVisibilityChecks;
+            else if (m_method.m_skipVisibility)
+                flags |= SecurityControlFlags.SkipVisibilityChecks;
+
+            typeOwner = m_method.m_typeOwner;
+
+
+            securityControlFlags = (int)flags;
+
+            return typeOwner;
+        }
+
+        private static int CalculateNumberOfExceptions(__ExceptionInfo[] excp)
+        {
+            int num = 0;
+            if (excp == null)
+                return 0;
+            for (int i = 0; i < excp.Length; i++)
+                num += excp[i].GetNumberOfCatches();
+            return num;
+        }
+
+        internal override byte[] GetCodeInfo(
+            ref int stackSize, ref int initLocals, ref int EHCount)
+        {
+            stackSize = m_stackSize;
+            if (m_exceptionHeader != null && m_exceptionHeader.Length != 0)
+            {
+                if (m_exceptionHeader.Length < 4)
+                    throw new FormatException();
+
+                byte header = m_exceptionHeader[0];
+
+                if ((header & 0x40) != 0) // Fat
+                {
+                    byte[] size = new byte[4];
+                    for (int q = 0; q < 3; q++)
+                        size[q] = m_exceptionHeader[q + 1];
+                    EHCount = (BitConverter.ToInt32(size, 0) - 4) / 24;
+                }
+                else
+                    EHCount = (m_exceptionHeader[1] - 2) / 12;
+            }
+            else
+            {
+                EHCount = CalculateNumberOfExceptions(m_exceptions);
+            }
+            initLocals = (m_method.InitLocals) ? 1 : 0;
+            return m_code;
+        }
+
+        internal override byte[] GetLocalsSignature()
+        {
+            return m_localSignature;
+        }
+
+        internal override unsafe byte[] GetRawEHInfo()
+        {
+            return m_exceptionHeader;
+        }
+
+        internal override unsafe void GetEHInfo(int excNumber, void* exc)
+        {
+            CORINFO_EH_CLAUSE* exception = (CORINFO_EH_CLAUSE*)exc;
+            for (int i = 0; i < m_exceptions.Length; i++)
+            {
+                int excCount = m_exceptions[i].GetNumberOfCatches();
+                if (excNumber < excCount)
+                {
+                    // found the right exception block
+                    exception->Flags = m_exceptions[i].GetExceptionTypes()[excNumber];
+                    exception->TryOffset = m_exceptions[i].GetStartAddress();
+                    if ((exception->Flags & __ExceptionInfo.Finally) != __ExceptionInfo.Finally)
+                        exception->TryLength = m_exceptions[i].GetEndAddress() - exception->TryOffset;
+                    else
+                        exception->TryLength = m_exceptions[i].GetFinallyEndAddress() - exception->TryOffset;
+                    exception->HandlerOffset = m_exceptions[i].GetCatchAddresses()[excNumber];
+                    exception->HandlerLength = m_exceptions[i].GetCatchEndAddresses()[excNumber] - exception->HandlerOffset;
+                    // this is cheating because the filter address is the token of the class only for light code gen
+                    exception->ClassTokenOrFilterOffset = m_exceptions[i].GetFilterAddresses()[excNumber];
+                    break;
+                }
+                excNumber -= excCount;
+            }
+        }
+
+        internal override String GetStringLiteral(int token) { return m_scope.GetString(token); }
+
+
+        internal override void ResolveToken(int token, out IntPtr typeHandle, out IntPtr methodHandle, out IntPtr fieldHandle)
+        {
+            typeHandle = new IntPtr();
+            methodHandle = new IntPtr();
+            fieldHandle = new IntPtr();
+
+            Object handle = m_scope[token];
+
+            if (handle == null)
+                throw new InvalidProgramException();
+
+            if (handle is RuntimeTypeHandle)
+            {
+                typeHandle = ((RuntimeTypeHandle)handle).Value;
+                return;
+            }
+
+            if (handle is RuntimeMethodHandle)
+            {
+                methodHandle = ((RuntimeMethodHandle)handle).Value;
+                return;
+            }
+
+            if (handle is RuntimeFieldHandle)
+            {
+                fieldHandle = ((RuntimeFieldHandle)handle).Value;
+                return;
+            }
+
+            DynamicMethod dm = handle as DynamicMethod;
+            if (dm != null)
+            {
+                methodHandle = dm.GetMethodDescriptor().Value;
+                return;
+            }
+
+            GenericMethodInfo gmi = handle as GenericMethodInfo;
+            if (gmi != null)
+            {
+                methodHandle = gmi.m_methodHandle.Value;
+                typeHandle = gmi.m_context.Value;
+                return;
+            }
+
+            GenericFieldInfo gfi = handle as GenericFieldInfo;
+            if (gfi != null)
+            {
+                fieldHandle = gfi.m_fieldHandle.Value;
+                typeHandle = gfi.m_context.Value;
+                return;
+            }
+
+            VarArgMethod vaMeth = handle as VarArgMethod;
+            if (vaMeth != null)
+            {
+                if (vaMeth.m_dynamicMethod == null)
+                {
+                    methodHandle = vaMeth.m_method.MethodHandle.Value;
+                    typeHandle = vaMeth.m_method.GetDeclaringTypeInternal().GetTypeHandleInternal().Value;
+                }
+                else
+                    methodHandle = vaMeth.m_dynamicMethod.GetMethodDescriptor().Value;
+
+                return;
+            }
+        }
+
+        internal override byte[] ResolveSignature(int token, int fromMethod)
+        {
+            return m_scope.ResolveSignature(token, fromMethod);
+        }
+
+        internal override MethodInfo GetDynamicMethod()
+        {
+            return m_method.GetMethodInfo();
+        }
+        #endregion
+    }
+
+
+    internal class DynamicILInfo
+    {
+        #region Private Data Members
+        private DynamicMethod m_method;
+        private DynamicScope m_scope;
+        private byte[] m_exceptions;
+        private byte[] m_code;
+        private byte[] m_localSignature;
+        private int m_maxStackSize;
+        private int m_methodSignature;
+        #endregion
+
+        #region Internal Methods
+        internal void GetCallableMethod(RuntimeModule module, DynamicMethod dm)
+        {
+            dm.m_methodHandle = ModuleHandle.GetDynamicMethod(dm,
+                module, m_method.Name, (byte[])m_scope[m_methodSignature], new DynamicResolver(this));
+        }
+
+        internal byte[] LocalSignature
+        {
+            get
+            {
+                if (m_localSignature == null)
+                    m_localSignature = SignatureHelper.GetLocalVarSigHelper().InternalGetSignatureArray();
+
+                return m_localSignature;
+            }
+        }
+        internal byte[] Exceptions { get { return m_exceptions; } }
+        internal byte[] Code { get { return m_code; } }
+        internal int MaxStackSize { get { return m_maxStackSize; } }
+        #endregion
+
+        #region Public ILGenerator Methods
+        public DynamicMethod DynamicMethod { get { return m_method; } }
+        internal DynamicScope DynamicScope { get { return m_scope; } }
+
+        #endregion
+        #region Public Scope Methods
+        #endregion
+    }
+
+    internal class DynamicScope
+    {
+        #region Private Data Members
+        internal List<Object> m_tokens;
+        #endregion
+
+        #region Constructor
+        internal unsafe DynamicScope()
+        {
+            m_tokens = new List<Object>();
+            m_tokens.Add(null);
+        }
+        #endregion
+
+        #region Internal Methods
+        internal object this[int token]
+        {
+            get
+            {
+                token &= 0x00FFFFFF;
+
+                if (token < 0 || token > m_tokens.Count)
+                    return null;
+
+                return m_tokens[token];
+            }
+        }
+
+        internal int GetTokenFor(VarArgMethod varArgMethod)
+        {
+            m_tokens.Add(varArgMethod);
+            return m_tokens.Count - 1 | (int)MetadataTokenType.MemberRef;
+        }
+        internal string GetString(int token) { return this[token] as string; }
+
+        internal byte[] ResolveSignature(int token, int fromMethod)
+        {
+            if (fromMethod == 0)
+                return (byte[])this[token];
+
+            VarArgMethod vaMethod = this[token] as VarArgMethod;
+
+            if (vaMethod == null)
+                return null;
+
+            return vaMethod.m_signature.GetSignature(true);
+        }
+        #endregion
+
+        #region Public Methods
+        public int GetTokenFor(RuntimeMethodHandle method)
+        {
+            IRuntimeMethodInfo methodReal = method.GetMethodInfo();
+            RuntimeMethodHandleInternal rmhi = methodReal.Value;
+
+            if (methodReal != null && !RuntimeMethodHandle.IsDynamicMethod(rmhi))
+            {
+                RuntimeType type = RuntimeMethodHandle.GetDeclaringType(rmhi);
+                if ((type != null) && RuntimeTypeHandle.HasInstantiation(type))
+                {
+                    // Do we really need to retrieve this much info just to throw an exception?
+                    MethodBase m = RuntimeType.GetMethodBase(methodReal);
+                    Type t = m.DeclaringType.GetGenericTypeDefinition();
+
+                    throw new ArgumentException(String.Format(
+                        CultureInfo.CurrentCulture, SR.Argument_MethodDeclaringTypeGenericLcg, m, t));
+                }
+            }
+
+            m_tokens.Add(method);
+            return m_tokens.Count - 1 | (int)MetadataTokenType.MethodDef;
+        }
+        public int GetTokenFor(RuntimeMethodHandle method, RuntimeTypeHandle typeContext)
+        {
+            m_tokens.Add(new GenericMethodInfo(method, typeContext));
+            return m_tokens.Count - 1 | (int)MetadataTokenType.MethodDef;
+        }
+        public int GetTokenFor(DynamicMethod method)
+        {
+            m_tokens.Add(method);
+            return m_tokens.Count - 1 | (int)MetadataTokenType.MethodDef;
+        }
+        public int GetTokenFor(RuntimeFieldHandle field)
+        {
+            m_tokens.Add(field);
+            return m_tokens.Count - 1 | (int)MetadataTokenType.FieldDef;
+        }
+        public int GetTokenFor(RuntimeFieldHandle field, RuntimeTypeHandle typeContext)
+        {
+            m_tokens.Add(new GenericFieldInfo(field, typeContext));
+            return m_tokens.Count - 1 | (int)MetadataTokenType.FieldDef;
+        }
+        public int GetTokenFor(RuntimeTypeHandle type)
+        {
+            m_tokens.Add(type);
+            return m_tokens.Count - 1 | (int)MetadataTokenType.TypeDef;
+        }
+        public int GetTokenFor(string literal)
+        {
+            m_tokens.Add(literal);
+            return m_tokens.Count - 1 | (int)MetadataTokenType.String;
+        }
+        public int GetTokenFor(byte[] signature)
+        {
+            m_tokens.Add(signature);
+            return m_tokens.Count - 1 | (int)MetadataTokenType.Signature;
+        }
+        #endregion
+    }
+
+    internal sealed class GenericMethodInfo
+    {
+        internal RuntimeMethodHandle m_methodHandle;
+        internal RuntimeTypeHandle m_context;
+
+        internal GenericMethodInfo(RuntimeMethodHandle methodHandle, RuntimeTypeHandle context)
+        {
+            m_methodHandle = methodHandle;
+            m_context = context;
+        }
+    }
+
+    internal sealed class GenericFieldInfo
+    {
+        internal RuntimeFieldHandle m_fieldHandle;
+        internal RuntimeTypeHandle m_context;
+
+        internal GenericFieldInfo(RuntimeFieldHandle fieldHandle, RuntimeTypeHandle context)
+        {
+            m_fieldHandle = fieldHandle;
+            m_context = context;
+        }
+    }
+
+    internal sealed class VarArgMethod
+    {
+        internal RuntimeMethodInfo m_method;
+        internal DynamicMethod m_dynamicMethod;
+        internal SignatureHelper m_signature;
+
+        internal VarArgMethod(DynamicMethod dm, SignatureHelper signature)
+        {
+            m_dynamicMethod = dm;
+            m_signature = signature;
+        }
+
+        internal VarArgMethod(RuntimeMethodInfo method, SignatureHelper signature)
+        {
+            m_method = method;
+            m_signature = signature;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/DynamicMethod.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/DynamicMethod.cs
new file mode 100644
index 0000000000..00ee65d9f0
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/DynamicMethod.cs
@@ -0,0 +1,774 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+namespace System.Reflection.Emit
+{
+    using System;
+    using System.Collections.Generic;
+    using CultureInfo = System.Globalization.CultureInfo;
+    using System.Reflection;
+    using System.Security;
+    using System.Threading;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.Versioning;
+    using System.Diagnostics;
+    using System.Runtime.InteropServices;
+
+    public sealed class DynamicMethod : MethodInfo
+    {
+        private RuntimeType[] m_parameterTypes;
+        internal IRuntimeMethodInfo m_methodHandle;
+        private RuntimeType m_returnType;
+        private DynamicILGenerator m_ilGenerator;
+        private DynamicILInfo m_DynamicILInfo;
+        private bool m_fInitLocals;
+        private RuntimeModule m_module;
+        internal bool m_skipVisibility;
+        internal RuntimeType m_typeOwner; // can be null
+
+        // We want the creator of the DynamicMethod to control who has access to the
+        // DynamicMethod (just like we do for delegates). However, a user can get to
+        // the corresponding RTDynamicMethod using Exception.TargetSite, StackFrame.GetMethod, etc.
+        // If we allowed use of RTDynamicMethod, the creator of the DynamicMethod would
+        // not be able to bound access to the DynamicMethod. Hence, we need to ensure that 
+        // we do not allow direct use of RTDynamicMethod.
+        private RTDynamicMethod m_dynMethod;
+
+        // needed to keep the object alive during jitting
+        // assigned by the DynamicResolver ctor
+        internal DynamicResolver m_resolver;
+
+        internal bool m_restrictedSkipVisibility;
+        // The context when the method was created. We use this to do the RestrictedMemberAccess checks.
+        // These checks are done when the method is compiled. This can happen at an arbitrary time,
+        // when CreateDelegate or Invoke is called, or when another DynamicMethod executes OpCodes.Call.
+        // We capture the creation context so that we can do the checks against the same context,
+        // irrespective of when the method gets compiled. Note that the DynamicMethod does not know when
+        // it is ready for use since there is not API which indictates that IL generation has completed.
+        private static volatile InternalModuleBuilder s_anonymouslyHostedDynamicMethodsModule;
+        private static readonly object s_anonymouslyHostedDynamicMethodsModuleLock = new object();
+
+        //
+        // class initialization (ctor and init)
+        //
+
+        public DynamicMethod(string name,
+                             Type returnType,
+                             Type[] parameterTypes)
+        {
+            Init(name,
+                MethodAttributes.Public | MethodAttributes.Static,
+                CallingConventions.Standard,
+                returnType,
+                parameterTypes,
+                null,   // owner
+                null,   // m
+                false,  // skipVisibility
+                true);
+        }
+
+        public DynamicMethod(string name,
+                             Type returnType,
+                             Type[] parameterTypes,
+                             bool restrictedSkipVisibility)
+        {
+            Init(name,
+                MethodAttributes.Public | MethodAttributes.Static,
+                CallingConventions.Standard,
+                returnType,
+                parameterTypes,
+                null,   // owner
+                null,   // m
+                restrictedSkipVisibility,
+                true);
+        }
+
+        public DynamicMethod(string name,
+                             Type returnType,
+                             Type[] parameterTypes,
+                             Module m)
+        {
+            if (m == null)
+                throw new ArgumentNullException(nameof(m));
+
+            Init(name,
+                MethodAttributes.Public | MethodAttributes.Static,
+                CallingConventions.Standard,
+                returnType,
+                parameterTypes,
+                null,   // owner
+                m,      // m
+                false,  // skipVisibility
+                false);
+        }
+
+        public DynamicMethod(string name,
+                             Type returnType,
+                             Type[] parameterTypes,
+                             Module m,
+                             bool skipVisibility)
+        {
+            if (m == null)
+                throw new ArgumentNullException(nameof(m));
+
+            Init(name,
+                MethodAttributes.Public | MethodAttributes.Static,
+                CallingConventions.Standard,
+                returnType,
+                parameterTypes,
+                null,   // owner
+                m,      // m
+                skipVisibility,
+                false);
+        }
+
+        public DynamicMethod(string name,
+                             MethodAttributes attributes,
+                             CallingConventions callingConvention,
+                             Type returnType,
+                             Type[] parameterTypes,
+                             Module m,
+                             bool skipVisibility)
+        {
+            if (m == null)
+                throw new ArgumentNullException(nameof(m));
+
+            Init(name,
+                attributes,
+                callingConvention,
+                returnType,
+                parameterTypes,
+                null,   // owner
+                m,      // m
+                skipVisibility,
+                false);
+        }
+
+        public DynamicMethod(string name,
+                             Type returnType,
+                             Type[] parameterTypes,
+                             Type owner)
+        {
+            if (owner == null)
+                throw new ArgumentNullException(nameof(owner));
+
+            Init(name,
+                MethodAttributes.Public | MethodAttributes.Static,
+                CallingConventions.Standard,
+                returnType,
+                parameterTypes,
+                owner,  // owner
+                null,   // m
+                false,  // skipVisibility
+                false);
+        }
+
+        public DynamicMethod(string name,
+                             Type returnType,
+                             Type[] parameterTypes,
+                             Type owner,
+                             bool skipVisibility)
+        {
+            if (owner == null)
+                throw new ArgumentNullException(nameof(owner));
+
+            Init(name,
+                MethodAttributes.Public | MethodAttributes.Static,
+                CallingConventions.Standard,
+                returnType,
+                parameterTypes,
+                owner,  // owner
+                null,   // m
+                skipVisibility,
+                false);
+        }
+
+        public DynamicMethod(string name,
+                             MethodAttributes attributes,
+                             CallingConventions callingConvention,
+                             Type returnType,
+                             Type[] parameterTypes,
+                             Type owner,
+                             bool skipVisibility)
+        {
+            if (owner == null)
+                throw new ArgumentNullException(nameof(owner));
+
+            Init(name,
+                attributes,
+                callingConvention,
+                returnType,
+                parameterTypes,
+                owner,  // owner
+                null,   // m
+                skipVisibility,
+                false);
+        }
+
+        // helpers for intialization
+
+        private static void CheckConsistency(MethodAttributes attributes, CallingConventions callingConvention)
+        {
+            // only public static for method attributes
+            if ((attributes & ~MethodAttributes.MemberAccessMask) != MethodAttributes.Static)
+                throw new NotSupportedException(SR.NotSupported_DynamicMethodFlags);
+            if ((attributes & MethodAttributes.MemberAccessMask) != MethodAttributes.Public)
+                throw new NotSupportedException(SR.NotSupported_DynamicMethodFlags);
+
+            // only standard or varargs supported
+            if (callingConvention != CallingConventions.Standard && callingConvention != CallingConventions.VarArgs)
+                throw new NotSupportedException(SR.NotSupported_DynamicMethodFlags);
+
+            // vararg is not supported at the moment
+            if (callingConvention == CallingConventions.VarArgs)
+                throw new NotSupportedException(SR.NotSupported_DynamicMethodFlags);
+        }
+
+        // We create a transparent assembly to host DynamicMethods. Since the assembly does not have any
+        // non-public fields (or any fields at all), it is a safe anonymous assembly to host DynamicMethods
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        private static RuntimeModule GetDynamicMethodsModule()
+        {
+            if (s_anonymouslyHostedDynamicMethodsModule != null)
+                return s_anonymouslyHostedDynamicMethodsModule;
+
+            lock (s_anonymouslyHostedDynamicMethodsModuleLock)
+            {
+                if (s_anonymouslyHostedDynamicMethodsModule != null)
+                    return s_anonymouslyHostedDynamicMethodsModule;
+
+                ConstructorInfo transparencyCtor = typeof(SecurityTransparentAttribute).GetConstructor(Type.EmptyTypes);
+                CustomAttributeBuilder transparencyAttribute = new CustomAttributeBuilder(transparencyCtor, Array.Empty<Object>());
+                List<CustomAttributeBuilder> assemblyAttributes = new List<CustomAttributeBuilder>();
+                assemblyAttributes.Add(transparencyAttribute);
+
+                AssemblyName assemblyName = new AssemblyName("Anonymously Hosted DynamicMethods Assembly");
+                StackCrawlMark stackMark = StackCrawlMark.LookForMe;
+
+                AssemblyBuilder assembly = AssemblyBuilder.InternalDefineDynamicAssembly(
+                    assemblyName,
+                    AssemblyBuilderAccess.Run,
+                    ref stackMark,
+                    assemblyAttributes);
+
+                AppDomain.PublishAnonymouslyHostedDynamicMethodsAssembly(assembly.GetNativeHandle());
+
+                // this always gets the internal module.
+                s_anonymouslyHostedDynamicMethodsModule = (InternalModuleBuilder)assembly.ManifestModule;
+            }
+
+            return s_anonymouslyHostedDynamicMethodsModule;
+        }
+
+        private unsafe void Init(String name,
+                                 MethodAttributes attributes,
+                                 CallingConventions callingConvention,
+                                 Type returnType,
+                                 Type[] signature,
+                                 Type owner,
+                                 Module m,
+                                 bool skipVisibility,
+                                 bool transparentMethod)
+        {
+            DynamicMethod.CheckConsistency(attributes, callingConvention);
+
+            // check and store the signature
+            if (signature != null)
+            {
+                m_parameterTypes = new RuntimeType[signature.Length];
+                for (int i = 0; i < signature.Length; i++)
+                {
+                    if (signature[i] == null)
+                        throw new ArgumentException(SR.Arg_InvalidTypeInSignature);
+                    m_parameterTypes[i] = signature[i].UnderlyingSystemType as RuntimeType;
+                    if (m_parameterTypes[i] == null || m_parameterTypes[i] == typeof(void))
+                        throw new ArgumentException(SR.Arg_InvalidTypeInSignature);
+                }
+            }
+            else
+            {
+                m_parameterTypes = Array.Empty<RuntimeType>();
+            }
+
+            // check and store the return value
+            m_returnType = (returnType == null) ? (RuntimeType)typeof(void) : returnType.UnderlyingSystemType as RuntimeType;
+            if (m_returnType == null)
+                throw new NotSupportedException(SR.Arg_InvalidTypeInRetType);
+
+            if (transparentMethod)
+            {
+                Debug.Assert(owner == null && m == null, "owner and m cannot be set for transparent methods");
+                m_module = GetDynamicMethodsModule();
+                if (skipVisibility)
+                {
+                    m_restrictedSkipVisibility = true;
+                }
+            }
+            else
+            {
+                Debug.Assert(m != null || owner != null, "Constructor should ensure that either m or owner is set");
+                Debug.Assert(m == null || !m.Equals(s_anonymouslyHostedDynamicMethodsModule), "The user cannot explicitly use this assembly");
+                Debug.Assert(m == null || owner == null, "m and owner cannot both be set");
+
+                if (m != null)
+                    m_module = m.ModuleHandle.GetRuntimeModule(); // this returns the underlying module for all RuntimeModule and ModuleBuilder objects.
+                else
+                {
+                    RuntimeType rtOwner = null;
+                    if (owner != null)
+                        rtOwner = owner.UnderlyingSystemType as RuntimeType;
+
+                    if (rtOwner != null)
+                    {
+                        if (rtOwner.HasElementType || rtOwner.ContainsGenericParameters
+                            || rtOwner.IsGenericParameter || rtOwner.IsInterface)
+                            throw new ArgumentException(SR.Argument_InvalidTypeForDynamicMethod);
+
+                        m_typeOwner = rtOwner;
+                        m_module = rtOwner.GetRuntimeModule();
+                    }
+                }
+
+                m_skipVisibility = skipVisibility;
+            }
+
+            // initialize remaining fields
+            m_ilGenerator = null;
+            m_fInitLocals = true;
+            m_methodHandle = null;
+
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            m_dynMethod = new RTDynamicMethod(this, name, attributes, callingConvention);
+        }
+
+        //
+        // Delegate and method creation
+        //
+
+        public sealed override Delegate CreateDelegate(Type delegateType)
+        {
+            if (m_restrictedSkipVisibility)
+            {
+                // Compile the method since accessibility checks are done as part of compilation.
+                GetMethodDescriptor();
+                System.Runtime.CompilerServices.RuntimeHelpers._CompileMethod(m_methodHandle);
+            }
+
+            MulticastDelegate d = (MulticastDelegate)Delegate.CreateDelegateNoSecurityCheck(delegateType, null, GetMethodDescriptor());
+            // stash this MethodInfo by brute force.  
+            d.StoreDynamicMethod(GetMethodInfo());
+            return d;
+        }
+
+        public sealed override Delegate CreateDelegate(Type delegateType, Object target)
+        {
+            if (m_restrictedSkipVisibility)
+            {
+                // Compile the method since accessibility checks are done as part of compilation
+                GetMethodDescriptor();
+                System.Runtime.CompilerServices.RuntimeHelpers._CompileMethod(m_methodHandle);
+            }
+
+            MulticastDelegate d = (MulticastDelegate)Delegate.CreateDelegateNoSecurityCheck(delegateType, target, GetMethodDescriptor());
+            // stash this MethodInfo by brute force. 
+            d.StoreDynamicMethod(GetMethodInfo());
+            return d;
+        }
+
+        // This is guaranteed to return a valid handle
+        internal unsafe RuntimeMethodHandle GetMethodDescriptor()
+        {
+            if (m_methodHandle == null)
+            {
+                lock (this)
+                {
+                    if (m_methodHandle == null)
+                    {
+                        if (m_DynamicILInfo != null)
+                            m_DynamicILInfo.GetCallableMethod(m_module, this);
+                        else
+                        {
+                            if (m_ilGenerator == null || m_ilGenerator.ILOffset == 0)
+                                throw new InvalidOperationException(SR.Format(SR.InvalidOperation_BadEmptyMethodBody, Name));
+
+                            m_ilGenerator.GetCallableMethod(m_module, this);
+                        }
+                    }
+                }
+            }
+            return new RuntimeMethodHandle(m_methodHandle);
+        }
+
+        //
+        // MethodInfo api. They mostly forward to RTDynamicMethod
+        //
+
+        public override String ToString() { return m_dynMethod.ToString(); }
+
+        public override String Name { get { return m_dynMethod.Name; } }
+
+        public override Type DeclaringType { get { return m_dynMethod.DeclaringType; } }
+
+        public override Type ReflectedType { get { return m_dynMethod.ReflectedType; } }
+
+        public override Module Module { get { return m_dynMethod.Module; } }
+
+        // we cannot return a MethodHandle because we cannot track it via GC so this method is off limits
+        public override RuntimeMethodHandle MethodHandle { get { throw new InvalidOperationException(SR.InvalidOperation_NotAllowedInDynamicMethod); } }
+
+        public override MethodAttributes Attributes { get { return m_dynMethod.Attributes; } }
+
+        public override CallingConventions CallingConvention { get { return m_dynMethod.CallingConvention; } }
+
+        public override MethodInfo GetBaseDefinition() { return this; }
+
+        public override ParameterInfo[] GetParameters() { return m_dynMethod.GetParameters(); }
+
+        public override MethodImplAttributes GetMethodImplementationFlags() { return m_dynMethod.GetMethodImplementationFlags(); }
+
+        //
+        // Security transparency accessors
+        //
+        // Since the dynamic method may not be JITed yet, we don't always have the runtime method handle
+        // which is needed to determine the official runtime transparency status of the dynamic method.  We
+        // fall back to saying that the dynamic method matches the transparency of its containing module
+        // until we get a JITed version, since dynamic methods cannot have attributes of their own.
+        //
+
+        public override bool IsSecurityCritical
+        {
+            get { return true; }
+        }
+
+        public override bool IsSecuritySafeCritical
+        {
+            get { return false; }
+        }
+
+        public override bool IsSecurityTransparent
+        {
+            get { return false; }
+        }
+
+        public override Object Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
+        {
+            if ((CallingConvention & CallingConventions.VarArgs) == CallingConventions.VarArgs)
+                throw new NotSupportedException(SR.NotSupported_CallToVarArg);
+
+            //
+            // We do not demand any permission here because the caller already has access
+            // to the current DynamicMethod object, and it could just as easily emit another 
+            // Transparent DynamicMethod to call the current DynamicMethod.
+            //
+
+            RuntimeMethodHandle method = GetMethodDescriptor();
+            // ignore obj since it's a static method
+
+            // create a signature object
+            Signature sig = new Signature(
+                this.m_methodHandle, m_parameterTypes, m_returnType, CallingConvention);
+
+
+            // verify arguments
+            int formalCount = sig.Arguments.Length;
+            int actualCount = (parameters != null) ? parameters.Length : 0;
+            if (formalCount != actualCount)
+                throw new TargetParameterCountException(SR.Arg_ParmCnt);
+
+            // if we are here we passed all the previous checks. Time to look at the arguments
+            bool wrapExceptions = (invokeAttr & BindingFlags.DoNotWrapExceptions) == 0;
+            Object retValue = null;
+            if (actualCount > 0)
+            {
+                Object[] arguments = CheckArguments(parameters, binder, invokeAttr, culture, sig);
+                retValue = RuntimeMethodHandle.InvokeMethod(null, arguments, sig, false, wrapExceptions);
+                // copy out. This should be made only if ByRef are present.
+                for (int index = 0; index < arguments.Length; index++)
+                    parameters[index] = arguments[index];
+            }
+            else
+            {
+                retValue = RuntimeMethodHandle.InvokeMethod(null, null, sig, false, wrapExceptions);
+            }
+
+            GC.KeepAlive(this);
+            return retValue;
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            return m_dynMethod.GetCustomAttributes(attributeType, inherit);
+        }
+
+        public override Object[] GetCustomAttributes(bool inherit) { return m_dynMethod.GetCustomAttributes(inherit); }
+
+        public override bool IsDefined(Type attributeType, bool inherit) { return m_dynMethod.IsDefined(attributeType, inherit); }
+
+        public override Type ReturnType { get { return m_dynMethod.ReturnType; } }
+
+        public override ParameterInfo ReturnParameter { get { return m_dynMethod.ReturnParameter; } }
+
+        public override ICustomAttributeProvider ReturnTypeCustomAttributes { get { return m_dynMethod.ReturnTypeCustomAttributes; } }
+
+        //
+        // DynamicMethod specific methods
+        //
+
+        public ParameterBuilder DefineParameter(int position, ParameterAttributes attributes, String parameterName)
+        {
+            if (position < 0 || position > m_parameterTypes.Length)
+                throw new ArgumentOutOfRangeException(SR.ArgumentOutOfRange_ParamSequence);
+            position--; // it's 1 based. 0 is the return value
+
+            if (position >= 0)
+            {
+                RuntimeParameterInfo[] parameters = m_dynMethod.LoadParameters();
+                parameters[position].SetName(parameterName);
+                parameters[position].SetAttributes(attributes);
+            }
+            return null;
+        }
+
+        public ILGenerator GetILGenerator()
+        {
+            return GetILGenerator(64);
+        }
+
+        public ILGenerator GetILGenerator(int streamSize)
+        {
+            if (m_ilGenerator == null)
+            {
+                byte[] methodSignature = SignatureHelper.GetMethodSigHelper(
+                    null, CallingConvention, ReturnType, null, null, m_parameterTypes, null, null).GetSignature(true);
+                m_ilGenerator = new DynamicILGenerator(this, methodSignature, streamSize);
+            }
+            return m_ilGenerator;
+        }
+
+        public bool InitLocals
+        {
+            get { return m_fInitLocals; }
+            set { m_fInitLocals = value; }
+        }
+
+        //
+        // Internal API
+        //
+
+        internal MethodInfo GetMethodInfo()
+        {
+            return m_dynMethod;
+        }
+
+        //////////////////////////////////////////////////////////////////////////////////////////////
+        // RTDynamicMethod
+        //
+        // this is actually the real runtime instance of a method info that gets used for invocation
+        // We need this so we never leak the DynamicMethod out via an exception.
+        // This way the DynamicMethod creator is the only one responsible for DynamicMethod access,
+        // and can control exactly who gets access to it.
+        //
+        internal sealed class RTDynamicMethod : MethodInfo
+        {
+            internal DynamicMethod m_owner;
+            private RuntimeParameterInfo[] m_parameters;
+            private String m_name;
+            private MethodAttributes m_attributes;
+            private CallingConventions m_callingConvention;
+
+            internal RTDynamicMethod(DynamicMethod owner, String name, MethodAttributes attributes, CallingConventions callingConvention)
+            {
+                m_owner = owner;
+                m_name = name;
+                m_attributes = attributes;
+                m_callingConvention = callingConvention;
+            }
+
+            //
+            // MethodInfo api
+            //
+            public override String ToString()
+            {
+                return ReturnType.FormatTypeName() + " " + FormatNameAndSig();
+            }
+
+            public override String Name
+            {
+                get { return m_name; }
+            }
+
+            public override Type DeclaringType
+            {
+                get { return null; }
+            }
+
+            public override Type ReflectedType
+            {
+                get { return null; }
+            }
+
+            public override Module Module
+            {
+                get { return m_owner.m_module; }
+            }
+
+            public override RuntimeMethodHandle MethodHandle
+            {
+                get { throw new InvalidOperationException(SR.InvalidOperation_NotAllowedInDynamicMethod); }
+            }
+
+            public override MethodAttributes Attributes
+            {
+                get { return m_attributes; }
+            }
+
+            public override CallingConventions CallingConvention
+            {
+                get { return m_callingConvention; }
+            }
+
+            public override MethodInfo GetBaseDefinition()
+            {
+                return this;
+            }
+
+            public override ParameterInfo[] GetParameters()
+            {
+                ParameterInfo[] privateParameters = LoadParameters();
+                ParameterInfo[] parameters = new ParameterInfo[privateParameters.Length];
+                Array.Copy(privateParameters, 0, parameters, 0, privateParameters.Length);
+                return parameters;
+            }
+
+            public override MethodImplAttributes GetMethodImplementationFlags()
+            {
+                return MethodImplAttributes.IL | MethodImplAttributes.NoInlining;
+            }
+
+            public override Object Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
+            {
+                // We want the creator of the DynamicMethod to control who has access to the
+                // DynamicMethod (just like we do for delegates). However, a user can get to
+                // the corresponding RTDynamicMethod using Exception.TargetSite, StackFrame.GetMethod, etc.
+                // If we allowed use of RTDynamicMethod, the creator of the DynamicMethod would
+                // not be able to bound access to the DynamicMethod. Hence, we do not allow
+                // direct use of RTDynamicMethod.
+                throw new ArgumentException(SR.Argument_MustBeRuntimeMethodInfo, "this");
+            }
+
+            public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+            {
+                if (attributeType == null)
+                    throw new ArgumentNullException(nameof(attributeType));
+
+                if (attributeType.IsAssignableFrom(typeof(MethodImplAttribute)))
+                    return new Object[] { new MethodImplAttribute((MethodImplOptions)GetMethodImplementationFlags()) };
+                else
+                    return Array.Empty<Object>();
+            }
+
+            public override Object[] GetCustomAttributes(bool inherit)
+            {
+                // support for MethodImplAttribute PCA
+                return new Object[] { new MethodImplAttribute((MethodImplOptions)GetMethodImplementationFlags()) };
+            }
+
+            public override bool IsDefined(Type attributeType, bool inherit)
+            {
+                if (attributeType == null)
+                    throw new ArgumentNullException(nameof(attributeType));
+
+                if (attributeType.IsAssignableFrom(typeof(MethodImplAttribute)))
+                    return true;
+                else
+                    return false;
+            }
+
+            public override bool IsSecurityCritical
+            {
+                get { return m_owner.IsSecurityCritical; }
+            }
+
+            public override bool IsSecuritySafeCritical
+            {
+                get { return m_owner.IsSecuritySafeCritical; }
+            }
+
+            public override bool IsSecurityTransparent
+            {
+                get { return m_owner.IsSecurityTransparent; }
+            }
+
+            public override Type ReturnType
+            {
+                get
+                {
+                    return m_owner.m_returnType;
+                }
+            }
+
+            public override ParameterInfo ReturnParameter
+            {
+                get { return null; }
+            }
+
+            public override ICustomAttributeProvider ReturnTypeCustomAttributes
+            {
+                get { return GetEmptyCAHolder(); }
+            }
+
+            //
+            // private implementation
+            //
+
+            internal RuntimeParameterInfo[] LoadParameters()
+            {
+                if (m_parameters == null)
+                {
+                    Type[] parameterTypes = m_owner.m_parameterTypes;
+                    RuntimeParameterInfo[] parameters = new RuntimeParameterInfo[parameterTypes.Length];
+                    for (int i = 0; i < parameterTypes.Length; i++)
+                        parameters[i] = new RuntimeParameterInfo(this, null, parameterTypes[i], i);
+                    if (m_parameters == null)
+                        // should we interlockexchange?
+                        m_parameters = parameters;
+                }
+                return m_parameters;
+            }
+
+            // private implementation of CA for the return type
+            private ICustomAttributeProvider GetEmptyCAHolder()
+            {
+                return new EmptyCAHolder();
+            }
+
+            ///////////////////////////////////////////////////
+            // EmptyCAHolder
+            private class EmptyCAHolder : ICustomAttributeProvider
+            {
+                internal EmptyCAHolder() { }
+
+                Object[] ICustomAttributeProvider.GetCustomAttributes(Type attributeType, bool inherit)
+                {
+                    return Array.Empty<Object>();
+                }
+
+                Object[] ICustomAttributeProvider.GetCustomAttributes(bool inherit)
+                {
+                    return Array.Empty<Object>();
+                }
+
+                bool ICustomAttributeProvider.IsDefined(Type attributeType, bool inherit)
+                {
+                    return false;
+                }
+            }
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/EnumBuilder.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/EnumBuilder.cs
new file mode 100644
index 0000000000..38aaab220d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/EnumBuilder.cs
@@ -0,0 +1,417 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** EnumBuilder is a helper class to build Enum ( a special type ). 
+**
+** 
+===========================================================*/
+
+namespace System.Reflection.Emit
+{
+    using System;
+    using System.Diagnostics.CodeAnalysis;
+    using System.Reflection;
+    using System.Runtime.InteropServices;
+    using CultureInfo = System.Globalization.CultureInfo;
+
+    sealed public class EnumBuilder : TypeInfo
+    {
+        public override bool IsAssignableFrom(System.Reflection.TypeInfo typeInfo)
+        {
+            if (typeInfo == null) return false;
+            return IsAssignableFrom(typeInfo.AsType());
+        }
+
+        // Define literal for enum
+
+        public FieldBuilder DefineLiteral(String literalName, Object literalValue)
+        {
+            // Define the underlying field for the enum. It will be a non-static, private field with special name bit set. 
+            FieldBuilder fieldBuilder = m_typeBuilder.DefineField(
+                literalName,
+                this,
+                FieldAttributes.Public | FieldAttributes.Static | FieldAttributes.Literal);
+            fieldBuilder.SetConstant(literalValue);
+            return fieldBuilder;
+        }
+
+        public TypeInfo CreateTypeInfo()
+        {
+            return m_typeBuilder.CreateTypeInfo();
+        }
+
+        // CreateType cause EnumBuilder to be baked.
+        public Type CreateType()
+        {
+            return m_typeBuilder.CreateType();
+        }
+
+        // Get the internal metadata token for this class.
+        public TypeToken TypeToken
+        {
+            get { return m_typeBuilder.TypeToken; }
+        }
+
+
+        // return the underlying field for the enum
+        public FieldBuilder UnderlyingField
+        {
+            get { return m_underlyingField; }
+        }
+
+        public override String Name
+        {
+            get { return m_typeBuilder.Name; }
+        }
+
+        /****************************************************
+         * 
+         * abstract methods defined in the base class
+         * 
+         */
+        public override Guid GUID
+        {
+            get
+            {
+                return m_typeBuilder.GUID;
+            }
+        }
+
+        public override Object InvokeMember(
+            String name,
+            BindingFlags invokeAttr,
+            Binder binder,
+            Object target,
+            Object[] args,
+            ParameterModifier[] modifiers,
+            CultureInfo culture,
+            String[] namedParameters)
+        {
+            return m_typeBuilder.InvokeMember(name, invokeAttr, binder, target, args, modifiers, culture, namedParameters);
+        }
+
+        public override Module Module
+        {
+            get { return m_typeBuilder.Module; }
+        }
+
+        public override Assembly Assembly
+        {
+            get { return m_typeBuilder.Assembly; }
+        }
+
+        public override RuntimeTypeHandle TypeHandle
+        {
+            get { return m_typeBuilder.TypeHandle; }
+        }
+
+        public override String FullName
+        {
+            get { return m_typeBuilder.FullName; }
+        }
+
+        public override String AssemblyQualifiedName
+        {
+            get
+            {
+                return m_typeBuilder.AssemblyQualifiedName;
+            }
+        }
+
+        public override String Namespace
+        {
+            get { return m_typeBuilder.Namespace; }
+        }
+
+        public override Type BaseType
+        {
+            get { return m_typeBuilder.BaseType; }
+        }
+
+        protected override ConstructorInfo GetConstructorImpl(BindingFlags bindingAttr, Binder binder,
+                CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            return m_typeBuilder.GetConstructor(bindingAttr, binder, callConvention,
+                            types, modifiers);
+        }
+
+        public override ConstructorInfo[] GetConstructors(BindingFlags bindingAttr)
+        {
+            return m_typeBuilder.GetConstructors(bindingAttr);
+        }
+
+        protected override MethodInfo GetMethodImpl(String name, BindingFlags bindingAttr, Binder binder,
+                CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            if (types == null)
+                return m_typeBuilder.GetMethod(name, bindingAttr);
+            else
+                return m_typeBuilder.GetMethod(name, bindingAttr, binder, callConvention, types, modifiers);
+        }
+
+        public override MethodInfo[] GetMethods(BindingFlags bindingAttr)
+        {
+            return m_typeBuilder.GetMethods(bindingAttr);
+        }
+
+        public override FieldInfo GetField(String name, BindingFlags bindingAttr)
+        {
+            return m_typeBuilder.GetField(name, bindingAttr);
+        }
+
+        public override FieldInfo[] GetFields(BindingFlags bindingAttr)
+        {
+            return m_typeBuilder.GetFields(bindingAttr);
+        }
+
+        public override Type GetInterface(String name, bool ignoreCase)
+        {
+            return m_typeBuilder.GetInterface(name, ignoreCase);
+        }
+
+        public override Type[] GetInterfaces()
+        {
+            return m_typeBuilder.GetInterfaces();
+        }
+
+        public override EventInfo GetEvent(String name, BindingFlags bindingAttr)
+        {
+            return m_typeBuilder.GetEvent(name, bindingAttr);
+        }
+
+        public override EventInfo[] GetEvents()
+        {
+            return m_typeBuilder.GetEvents();
+        }
+
+        protected override PropertyInfo GetPropertyImpl(String name, BindingFlags bindingAttr, Binder binder,
+                Type returnType, Type[] types, ParameterModifier[] modifiers)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override PropertyInfo[] GetProperties(BindingFlags bindingAttr)
+        {
+            return m_typeBuilder.GetProperties(bindingAttr);
+        }
+
+        public override Type[] GetNestedTypes(BindingFlags bindingAttr)
+        {
+            return m_typeBuilder.GetNestedTypes(bindingAttr);
+        }
+
+        public override Type GetNestedType(String name, BindingFlags bindingAttr)
+        {
+            return m_typeBuilder.GetNestedType(name, bindingAttr);
+        }
+
+        public override MemberInfo[] GetMember(String name, MemberTypes type, BindingFlags bindingAttr)
+        {
+            return m_typeBuilder.GetMember(name, type, bindingAttr);
+        }
+
+        public override MemberInfo[] GetMembers(BindingFlags bindingAttr)
+        {
+            return m_typeBuilder.GetMembers(bindingAttr);
+        }
+
+        public override InterfaceMapping GetInterfaceMap(Type interfaceType)
+        {
+            return m_typeBuilder.GetInterfaceMap(interfaceType);
+        }
+
+        public override EventInfo[] GetEvents(BindingFlags bindingAttr)
+        {
+            return m_typeBuilder.GetEvents(bindingAttr);
+        }
+
+        protected override TypeAttributes GetAttributeFlagsImpl()
+        {
+            return m_typeBuilder.Attributes;
+        }
+
+        public override bool IsTypeDefinition => true;
+
+        public override bool IsSZArray => false;
+
+        protected override bool IsArrayImpl()
+        {
+            return false;
+        }
+        protected override bool IsPrimitiveImpl()
+        {
+            return false;
+        }
+
+        protected override bool IsValueTypeImpl()
+        {
+            return true;
+        }
+
+        protected override bool IsByRefImpl()
+        {
+            return false;
+        }
+
+        protected override bool IsPointerImpl()
+        {
+            return false;
+        }
+
+        protected override bool IsCOMObjectImpl()
+        {
+            return false;
+        }
+
+        public override bool IsConstructedGenericType
+        {
+            get
+            {
+                return false;
+            }
+        }
+
+        public override Type GetElementType()
+        {
+            return m_typeBuilder.GetElementType();
+        }
+
+        protected override bool HasElementTypeImpl()
+        {
+            return m_typeBuilder.HasElementType;
+        }
+
+        // Legacy: JScript needs it.
+        public override Type GetEnumUnderlyingType()
+        {
+            return m_underlyingField.FieldType;
+        }
+
+        public override Type UnderlyingSystemType
+        {
+            get
+            {
+                return GetEnumUnderlyingType();
+            }
+        }
+
+        //ICustomAttributeProvider
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            return m_typeBuilder.GetCustomAttributes(inherit);
+        }
+
+        // Return a custom attribute identified by Type
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            return m_typeBuilder.GetCustomAttributes(attributeType, inherit);
+        }
+
+        // Use this function if client decides to form the custom attribute blob themselves
+
+        public void SetCustomAttribute(ConstructorInfo con, byte[] binaryAttribute)
+        {
+            m_typeBuilder.SetCustomAttribute(con, binaryAttribute);
+        }
+
+        // Use this function if client wishes to build CustomAttribute using CustomAttributeBuilder
+        public void SetCustomAttribute(CustomAttributeBuilder customBuilder)
+        {
+            m_typeBuilder.SetCustomAttribute(customBuilder);
+        }
+
+        // Return the class that declared this Field.
+        public override Type DeclaringType
+        {
+            get { return m_typeBuilder.DeclaringType; }
+        }
+
+        // Return the class that was used to obtain this field.
+
+        public override Type ReflectedType
+        {
+            get { return m_typeBuilder.ReflectedType; }
+        }
+
+
+        // Returns true if one or more instance of attributeType is defined on this member. 
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            return m_typeBuilder.IsDefined(attributeType, inherit);
+        }
+
+        /*****************************************************
+         * 
+         * private/protected functions
+         * 
+         */
+
+        public override Type MakePointerType()
+        {
+            return SymbolType.FormCompoundType("*", this, 0);
+        }
+
+        public override Type MakeByRefType()
+        {
+            return SymbolType.FormCompoundType("&", this, 0);
+        }
+
+        public override Type MakeArrayType()
+        {
+            return SymbolType.FormCompoundType("[]", this, 0);
+        }
+
+        public override Type MakeArrayType(int rank)
+        {
+            if (rank <= 0)
+                throw new IndexOutOfRangeException();
+
+            string szrank = "";
+            if (rank == 1)
+            {
+                szrank = "*";
+            }
+            else
+            {
+                for (int i = 1; i < rank; i++)
+                    szrank += ",";
+            }
+
+            string s = String.Format(CultureInfo.InvariantCulture, "[{0}]", szrank); // [,,]
+            return SymbolType.FormCompoundType(s, this, 0);
+        }
+
+
+        // Constructs a EnumBuilder.
+        // EnumBuilder can only be a top-level (not nested) enum type.
+        internal EnumBuilder(
+            String name,                       // name of type
+            Type underlyingType,             // underlying type for an Enum
+            TypeAttributes visibility,              // any bits on TypeAttributes.VisibilityMask)
+            ModuleBuilder module)                     // module containing this type
+        {
+            // Client should not set any bits other than the visibility bits.
+            if ((visibility & ~TypeAttributes.VisibilityMask) != 0)
+                throw new ArgumentException(SR.Argument_ShouldOnlySetVisibilityFlags, nameof(name));
+            m_typeBuilder = new TypeBuilder(name, visibility | TypeAttributes.Sealed, typeof(System.Enum), null, module, PackingSize.Unspecified, TypeBuilder.UnspecifiedTypeSize, null);
+
+            // Define the underlying field for the enum. It will be a non-static, private field with special name bit set. 
+            m_underlyingField = m_typeBuilder.DefineField("value__", underlyingType, FieldAttributes.Public | FieldAttributes.SpecialName | FieldAttributes.RTSpecialName);
+        }
+
+        /*****************************************************
+         * 
+         * private data members
+         * 
+         */
+        internal TypeBuilder m_typeBuilder;
+        private FieldBuilder m_underlyingField;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/EventBuilder.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/EventBuilder.cs
new file mode 100644
index 0000000000..c67d5559fd
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/EventBuilder.cs
@@ -0,0 +1,123 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Eventbuilder is for client to define eevnts for a class
+**
+** 
+===========================================================*/
+
+using System;
+using System.Reflection;
+using System.Runtime.InteropServices;
+
+namespace System.Reflection.Emit
+{
+    // 
+    // A EventBuilder is always associated with a TypeBuilder.  The TypeBuilder.DefineEvent
+    // method will return a new EventBuilder to a client.
+    // 
+    public sealed class EventBuilder
+    {
+        // Constructs a EventBuilder.  
+        //
+        internal EventBuilder(
+            ModuleBuilder mod,                    // the module containing this EventBuilder        
+            String name,                    // Event name
+            EventAttributes attr,                    // event attribute such as Public, Private, and Protected defined above
+                                                     //int            eventType,                // event type
+            TypeBuilder type,                    // containing type
+            EventToken evToken)
+        {
+            m_name = name;
+            m_module = mod;
+            m_attributes = attr;
+            m_evToken = evToken;
+            m_type = type;
+        }
+
+        // Return the Token for this event within the TypeBuilder that the
+        // event is defined within.
+        public EventToken GetEventToken()
+        {
+            return m_evToken;
+        }
+
+        private void SetMethodSemantics(MethodBuilder mdBuilder, MethodSemanticsAttributes semantics)
+        {
+            if (mdBuilder == null)
+            {
+                throw new ArgumentNullException(nameof(mdBuilder));
+            }
+
+            m_type.ThrowIfCreated();
+            TypeBuilder.DefineMethodSemantics(
+                m_module.GetNativeHandle(),
+                m_evToken.Token,
+                semantics,
+                mdBuilder.GetToken().Token);
+        }
+
+        public void SetAddOnMethod(MethodBuilder mdBuilder)
+        {
+            SetMethodSemantics(mdBuilder, MethodSemanticsAttributes.AddOn);
+        }
+
+        public void SetRemoveOnMethod(MethodBuilder mdBuilder)
+        {
+            SetMethodSemantics(mdBuilder, MethodSemanticsAttributes.RemoveOn);
+        }
+
+        public void SetRaiseMethod(MethodBuilder mdBuilder)
+        {
+            SetMethodSemantics(mdBuilder, MethodSemanticsAttributes.Fire);
+        }
+
+        public void AddOtherMethod(MethodBuilder mdBuilder)
+        {
+            SetMethodSemantics(mdBuilder, MethodSemanticsAttributes.Other);
+        }
+
+        // Use this function if client decides to form the custom attribute blob themselves
+
+        public void SetCustomAttribute(ConstructorInfo con, byte[] binaryAttribute)
+        {
+            if (con == null)
+                throw new ArgumentNullException(nameof(con));
+            if (binaryAttribute == null)
+                throw new ArgumentNullException(nameof(binaryAttribute));
+            m_type.ThrowIfCreated();
+
+            TypeBuilder.DefineCustomAttribute(
+                m_module,
+                m_evToken.Token,
+                m_module.GetConstructorToken(con).Token,
+                binaryAttribute,
+                false, false);
+        }
+
+        // Use this function if client wishes to build CustomAttribute using CustomAttributeBuilder
+        public void SetCustomAttribute(CustomAttributeBuilder customBuilder)
+        {
+            if (customBuilder == null)
+            {
+                throw new ArgumentNullException(nameof(customBuilder));
+            }
+            m_type.ThrowIfCreated();
+            customBuilder.CreateCustomAttribute(m_module, m_evToken.Token);
+        }
+
+        // These are package private so that TypeBuilder can access them.
+        private String m_name;         // The name of the event
+        private EventToken m_evToken;      // The token of this event
+        private ModuleBuilder m_module;
+        private EventAttributes m_attributes;
+        private TypeBuilder m_type;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/EventToken.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/EventToken.cs
new file mode 100644
index 0000000000..e44dc3d0ce
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/EventToken.cs
@@ -0,0 +1,65 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Propertybuilder is for client to define properties for a class
+**
+** 
+===========================================================*/
+
+using System;
+using System.Reflection;
+
+namespace System.Reflection.Emit
+{
+    public struct EventToken
+    {
+        public static readonly EventToken Empty = new EventToken();
+
+        internal int m_event;
+
+        internal EventToken(int str)
+        {
+            m_event = str;
+        }
+
+        public int Token
+        {
+            get { return m_event; }
+        }
+
+        public override int GetHashCode()
+        {
+            return m_event;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (obj is EventToken)
+                return Equals((EventToken)obj);
+            else
+                return false;
+        }
+
+        public bool Equals(EventToken obj)
+        {
+            return obj.m_event == m_event;
+        }
+
+        public static bool operator ==(EventToken a, EventToken b)
+        {
+            return a.Equals(b);
+        }
+
+        public static bool operator !=(EventToken a, EventToken b)
+        {
+            return !(a == b);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/FieldBuilder.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/FieldBuilder.cs
new file mode 100644
index 0000000000..78a1ed5bb5
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/FieldBuilder.cs
@@ -0,0 +1,222 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+namespace System.Reflection.Emit
+{
+    using System.Runtime.InteropServices;
+    using System;
+    using CultureInfo = System.Globalization.CultureInfo;
+    using System.Reflection;
+
+    public sealed class FieldBuilder : FieldInfo
+    {
+        #region Private Data Members
+        private int m_fieldTok;
+        private FieldToken m_tkField;
+        private TypeBuilder m_typeBuilder;
+        private String m_fieldName;
+        private FieldAttributes m_Attributes;
+        private Type m_fieldType;
+        #endregion
+
+        #region Constructor
+        internal FieldBuilder(TypeBuilder typeBuilder, String fieldName, Type type,
+            Type[] requiredCustomModifiers, Type[] optionalCustomModifiers, FieldAttributes attributes)
+        {
+            if (fieldName == null)
+                throw new ArgumentNullException(nameof(fieldName));
+
+            if (fieldName.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(fieldName));
+
+            if (fieldName[0] == '\0')
+                throw new ArgumentException(SR.Argument_IllegalName, nameof(fieldName));
+
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+
+            if (type == typeof(void))
+                throw new ArgumentException(SR.Argument_BadFieldType);
+
+            m_fieldName = fieldName;
+            m_typeBuilder = typeBuilder;
+            m_fieldType = type;
+            m_Attributes = attributes & ~FieldAttributes.ReservedMask;
+
+            SignatureHelper sigHelp = SignatureHelper.GetFieldSigHelper(m_typeBuilder.Module);
+            sigHelp.AddArgument(type, requiredCustomModifiers, optionalCustomModifiers);
+
+            int sigLength;
+            byte[] signature = sigHelp.InternalGetSignature(out sigLength);
+
+            m_fieldTok = TypeBuilder.DefineField(m_typeBuilder.GetModuleBuilder().GetNativeHandle(),
+                typeBuilder.TypeToken.Token, fieldName, signature, sigLength, m_Attributes);
+
+            m_tkField = new FieldToken(m_fieldTok, type);
+        }
+
+        #endregion
+
+        #region Internal Members
+        internal void SetData(byte[] data, int size)
+        {
+            ModuleBuilder.SetFieldRVAContent(m_typeBuilder.GetModuleBuilder().GetNativeHandle(), m_tkField.Token, data, size);
+        }
+        #endregion
+
+        #region MemberInfo Overrides
+        internal int MetadataTokenInternal
+        {
+            get { return m_fieldTok; }
+        }
+
+        public override Module Module
+        {
+            get { return m_typeBuilder.Module; }
+        }
+
+        public override String Name
+        {
+            get { return m_fieldName; }
+        }
+
+        public override Type DeclaringType
+        {
+            get
+            {
+                if (m_typeBuilder.m_isHiddenGlobalType == true)
+                    return null;
+
+                return m_typeBuilder;
+            }
+        }
+
+        public override Type ReflectedType
+        {
+            get
+            {
+                if (m_typeBuilder.m_isHiddenGlobalType == true)
+                    return null;
+
+                return m_typeBuilder;
+            }
+        }
+
+        #endregion
+
+        #region FieldInfo Overrides
+        public override Type FieldType
+        {
+            get { return m_fieldType; }
+        }
+
+        public override Object GetValue(Object obj)
+        {
+            // NOTE!!  If this is implemented, make sure that this throws 
+            // a NotSupportedException for Save-only dynamic assemblies.
+            // Otherwise, it could cause the .cctor to be executed.
+
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override void SetValue(Object obj, Object val, BindingFlags invokeAttr, Binder binder, CultureInfo culture)
+        {
+            // NOTE!!  If this is implemented, make sure that this throws 
+            // a NotSupportedException for Save-only dynamic assemblies.
+            // Otherwise, it could cause the .cctor to be executed.
+
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override RuntimeFieldHandle FieldHandle
+        {
+            get { throw new NotSupportedException(SR.NotSupported_DynamicModule); }
+        }
+
+        public override FieldAttributes Attributes
+        {
+            get { return m_Attributes; }
+        }
+
+        #endregion
+
+        #region ICustomAttributeProvider Implementation
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        #endregion
+
+        #region Public Members
+        public FieldToken GetToken()
+        {
+            return m_tkField;
+        }
+
+        public void SetOffset(int iOffset)
+        {
+            m_typeBuilder.ThrowIfCreated();
+
+            TypeBuilder.SetFieldLayoutOffset(m_typeBuilder.GetModuleBuilder().GetNativeHandle(), GetToken().Token, iOffset);
+        }
+
+        public void SetConstant(Object defaultValue)
+        {
+            m_typeBuilder.ThrowIfCreated();
+
+            if (defaultValue == null && m_fieldType.IsValueType)
+            {
+                // nullable types can hold null value.
+                if (!(m_fieldType.IsGenericType && m_fieldType.GetGenericTypeDefinition() == typeof(Nullable<>)))
+                    throw new ArgumentException(SR.Argument_ConstantNull);
+            }
+
+            TypeBuilder.SetConstantValue(m_typeBuilder.GetModuleBuilder(), GetToken().Token, m_fieldType, defaultValue);
+        }
+
+
+        public void SetCustomAttribute(ConstructorInfo con, byte[] binaryAttribute)
+        {
+            if (con == null)
+                throw new ArgumentNullException(nameof(con));
+
+            if (binaryAttribute == null)
+                throw new ArgumentNullException(nameof(binaryAttribute));
+
+            ModuleBuilder module = m_typeBuilder.Module as ModuleBuilder;
+
+            m_typeBuilder.ThrowIfCreated();
+
+            TypeBuilder.DefineCustomAttribute(module,
+                m_tkField.Token, module.GetConstructorToken(con).Token, binaryAttribute, false, false);
+        }
+
+        public void SetCustomAttribute(CustomAttributeBuilder customBuilder)
+        {
+            if (customBuilder == null)
+                throw new ArgumentNullException(nameof(customBuilder));
+
+            m_typeBuilder.ThrowIfCreated();
+
+            ModuleBuilder module = m_typeBuilder.Module as ModuleBuilder;
+
+            customBuilder.CreateCustomAttribute(module, m_tkField.Token);
+        }
+
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/FieldToken.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/FieldToken.cs
new file mode 100644
index 0000000000..c7450ca301
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/FieldToken.cs
@@ -0,0 +1,85 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Represents a Field to the ILGenerator Class
+**
+** 
+===========================================================*/
+
+using System;
+using System.Reflection;
+
+namespace System.Reflection.Emit
+{
+    // The FieldToken class is an opaque representation of the Token returned
+    // by the Metadata to represent the field.  FieldTokens are generated by 
+    // Module.GetFieldToken().  There are no meaningful accessors on this class,
+    // but it can be passed to ILGenerator which understands it's internals.
+    public struct FieldToken
+    {
+        public static readonly FieldToken Empty = new FieldToken();
+
+        internal int m_fieldTok;
+        internal Object m_class;
+
+        // Creates an empty FieldToken.  A publicly visible constructor so that
+        // it can be created on the stack.
+        //public FieldToken() {
+        //    m_fieldTok=0;
+        //    m_attributes=0;
+        //    m_class=null;
+        //}
+        // The actual constructor.  Sets the field, attributes and class
+        // variables
+
+        internal FieldToken(int field, Type fieldClass)
+        {
+            m_fieldTok = field;
+            m_class = fieldClass;
+        }
+
+        public int Token
+        {
+            get { return m_fieldTok; }
+        }
+
+
+        // Generates the hash code for this field. 
+        public override int GetHashCode()
+        {
+            return (m_fieldTok);
+        }
+
+        // Returns true if obj is an instance of FieldToken and is 
+        // equal to this instance.
+        public override bool Equals(Object obj)
+        {
+            if (obj is FieldToken)
+                return Equals((FieldToken)obj);
+            else
+                return false;
+        }
+
+        public bool Equals(FieldToken obj)
+        {
+            return obj.m_fieldTok == m_fieldTok && obj.m_class == m_class;
+        }
+
+        public static bool operator ==(FieldToken a, FieldToken b)
+        {
+            return a.Equals(b);
+        }
+
+        public static bool operator !=(FieldToken a, FieldToken b)
+        {
+            return !(a == b);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/FlowControl.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/FlowControl.cs
new file mode 100644
index 0000000000..8905a7f1d9
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/FlowControl.cs
@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Enumeration: FlowControl
+**
+** Purpose: Exposes FlowControl Attribute of IL.
+**
+** THIS FILE IS AUTOMATICALLY GENERATED. DO NOT EDIT BY HAND!
+** See $(RepoRoot)\src\inc\OpCodeGen.pl for more information.**
+==============================================================*/
+
+using System;
+
+namespace System.Reflection.Emit
+{
+    public enum FlowControl
+    {
+        Branch = 0,
+        Break = 1,
+        Call = 2,
+        Cond_Branch = 3,
+        Meta = 4,
+        Next = 5,
+        [Obsolete("This API has been deprecated. http://go.microsoft.com/fwlink/?linkid=14202")]
+        Phi = 6,
+        Return = 7,
+        Throw = 8,
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/GenericTypeParameterBuilder.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/GenericTypeParameterBuilder.cs
new file mode 100644
index 0000000000..4da7b650a0
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/GenericTypeParameterBuilder.cs
@@ -0,0 +1,242 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+using System;
+using System.Reflection;
+using System.Collections;
+using System.Collections.Generic;
+using System.Globalization;
+
+namespace System.Reflection.Emit
+{
+    public sealed class GenericTypeParameterBuilder : TypeInfo
+    {
+        public override bool IsAssignableFrom(System.Reflection.TypeInfo typeInfo)
+        {
+            if (typeInfo == null) return false;
+            return IsAssignableFrom(typeInfo.AsType());
+        }
+
+        #region Private Data Members
+        internal TypeBuilder m_type;
+        #endregion
+
+        #region Constructor
+        internal GenericTypeParameterBuilder(TypeBuilder type)
+        {
+            m_type = type;
+        }
+        #endregion
+
+        #region Object Overrides
+        public override String ToString()
+        {
+            return m_type.Name;
+        }
+        public override bool Equals(object o)
+        {
+            GenericTypeParameterBuilder g = o as GenericTypeParameterBuilder;
+
+            if (g == null)
+                return false;
+
+            return object.ReferenceEquals(g.m_type, m_type);
+        }
+        public override int GetHashCode() { return m_type.GetHashCode(); }
+        #endregion
+
+        #region MemberInfo Overrides
+        public override Type DeclaringType { get { return m_type.DeclaringType; } }
+
+        public override Type ReflectedType { get { return m_type.ReflectedType; } }
+
+        public override String Name { get { return m_type.Name; } }
+
+        public override Module Module { get { return m_type.Module; } }
+
+        internal int MetadataTokenInternal { get { return m_type.MetadataTokenInternal; } }
+        #endregion
+
+        #region Type Overrides
+
+        public override Type MakePointerType()
+        {
+            return SymbolType.FormCompoundType("*", this, 0);
+        }
+
+        public override Type MakeByRefType()
+        {
+            return SymbolType.FormCompoundType("&", this, 0);
+        }
+
+        public override Type MakeArrayType()
+        {
+            return SymbolType.FormCompoundType("[]", this, 0);
+        }
+
+        public override Type MakeArrayType(int rank)
+        {
+            if (rank <= 0)
+                throw new IndexOutOfRangeException();
+
+            string szrank = "";
+            if (rank == 1)
+            {
+                szrank = "*";
+            }
+            else
+            {
+                for (int i = 1; i < rank; i++)
+                    szrank += ",";
+            }
+
+            string s = String.Format(CultureInfo.InvariantCulture, "[{0}]", szrank); // [,,]
+            SymbolType st = SymbolType.FormCompoundType(s, this, 0) as SymbolType;
+            return st;
+        }
+
+        public override Guid GUID { get { throw new NotSupportedException(); } }
+
+        public override Object InvokeMember(String name, BindingFlags invokeAttr, Binder binder, Object target, Object[] args, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParameters) { throw new NotSupportedException(); }
+
+        public override Assembly Assembly { get { return m_type.Assembly; } }
+
+        public override RuntimeTypeHandle TypeHandle { get { throw new NotSupportedException(); } }
+
+        public override String FullName { get { return null; } }
+
+        public override String Namespace { get { return null; } }
+
+        public override String AssemblyQualifiedName { get { return null; } }
+
+        public override Type BaseType { get { return m_type.BaseType; } }
+
+        protected override ConstructorInfo GetConstructorImpl(BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers) { throw new NotSupportedException(); }
+
+        public override ConstructorInfo[] GetConstructors(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+
+        protected override MethodInfo GetMethodImpl(String name, BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers) { throw new NotSupportedException(); }
+
+        public override MethodInfo[] GetMethods(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+
+        public override FieldInfo GetField(String name, BindingFlags bindingAttr) { throw new NotSupportedException(); }
+
+        public override FieldInfo[] GetFields(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+
+        public override Type GetInterface(String name, bool ignoreCase) { throw new NotSupportedException(); }
+
+        public override Type[] GetInterfaces() { throw new NotSupportedException(); }
+
+        public override EventInfo GetEvent(String name, BindingFlags bindingAttr) { throw new NotSupportedException(); }
+
+        public override EventInfo[] GetEvents() { throw new NotSupportedException(); }
+
+        protected override PropertyInfo GetPropertyImpl(String name, BindingFlags bindingAttr, Binder binder, Type returnType, Type[] types, ParameterModifier[] modifiers) { throw new NotSupportedException(); }
+
+        public override PropertyInfo[] GetProperties(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+
+        public override Type[] GetNestedTypes(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+
+        public override Type GetNestedType(String name, BindingFlags bindingAttr) { throw new NotSupportedException(); }
+
+        public override MemberInfo[] GetMember(String name, MemberTypes type, BindingFlags bindingAttr) { throw new NotSupportedException(); }
+
+        public override InterfaceMapping GetInterfaceMap(Type interfaceType) { throw new NotSupportedException(); }
+
+        public override EventInfo[] GetEvents(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+
+        public override MemberInfo[] GetMembers(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+
+        protected override TypeAttributes GetAttributeFlagsImpl() { return TypeAttributes.Public; }
+
+        public override bool IsTypeDefinition => false;
+
+        public override bool IsSZArray => false;
+
+        protected override bool IsArrayImpl() { return false; }
+
+        protected override bool IsByRefImpl() { return false; }
+
+        protected override bool IsPointerImpl() { return false; }
+
+        protected override bool IsPrimitiveImpl() { return false; }
+
+        protected override bool IsCOMObjectImpl() { return false; }
+
+        public override Type GetElementType() { throw new NotSupportedException(); }
+
+        protected override bool HasElementTypeImpl() { return false; }
+
+        public override Type UnderlyingSystemType { get { return this; } }
+
+        public override Type[] GetGenericArguments() { throw new InvalidOperationException(); }
+
+        public override bool IsGenericTypeDefinition { get { return false; } }
+
+        public override bool IsGenericType { get { return false; } }
+
+        public override bool IsGenericParameter { get { return true; } }
+
+        public override bool IsConstructedGenericType { get { return false; } }
+
+        public override int GenericParameterPosition { get { return m_type.GenericParameterPosition; } }
+
+        public override bool ContainsGenericParameters { get { return m_type.ContainsGenericParameters; } }
+
+        public override GenericParameterAttributes GenericParameterAttributes { get { return m_type.GenericParameterAttributes; } }
+
+        public override MethodBase DeclaringMethod { get { return m_type.DeclaringMethod; } }
+
+        public override Type GetGenericTypeDefinition() { throw new InvalidOperationException(); }
+
+        public override Type MakeGenericType(params Type[] typeArguments) { throw new InvalidOperationException(SR.Format(SR.Arg_NotGenericTypeDefinition, this)); }
+
+        protected override bool IsValueTypeImpl() { return false; }
+
+        public override bool IsAssignableFrom(Type c) { throw new NotSupportedException(); }
+
+        public override bool IsSubclassOf(Type c) { throw new NotSupportedException(); }
+        #endregion
+
+        #region ICustomAttributeProvider Implementation
+        public override Object[] GetCustomAttributes(bool inherit) { throw new NotSupportedException(); }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit) { throw new NotSupportedException(); }
+
+        public override bool IsDefined(Type attributeType, bool inherit) { throw new NotSupportedException(); }
+        #endregion
+
+        #region Public Members
+        public void SetCustomAttribute(ConstructorInfo con, byte[] binaryAttribute)
+        {
+            m_type.SetGenParamCustomAttribute(con, binaryAttribute);
+        }
+
+        public void SetCustomAttribute(CustomAttributeBuilder customBuilder)
+        {
+            m_type.SetGenParamCustomAttribute(customBuilder);
+        }
+
+        public void SetBaseTypeConstraint(Type baseTypeConstraint)
+        {
+            m_type.CheckContext(baseTypeConstraint);
+            m_type.SetParent(baseTypeConstraint);
+        }
+
+        public void SetInterfaceConstraints(params Type[] interfaceConstraints)
+        {
+            m_type.CheckContext(interfaceConstraints);
+            m_type.SetInterfaces(interfaceConstraints);
+        }
+
+        public void SetGenericParameterAttributes(GenericParameterAttributes genericParameterAttributes)
+        {
+            m_type.SetGenParamAttributes(genericParameterAttributes);
+        }
+        #endregion
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs
new file mode 100644
index 0000000000..a1cee10ba3
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/ILGenerator.cs
@@ -0,0 +1,1985 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+using System;
+using System.Diagnostics.SymbolStore;
+using System.Runtime.InteropServices;
+using System.Reflection;
+using System.Globalization;
+using System.Diagnostics;
+using System.Diagnostics.Contracts;
+
+namespace System.Reflection.Emit
+{
+    public class ILGenerator
+    {
+        #region Const Members
+        private const int defaultSize = 16;
+        private const int DefaultFixupArraySize = 8;
+        private const int DefaultLabelArraySize = 4;
+        private const int DefaultExceptionArraySize = 2;
+        #endregion
+
+        #region Internal Statics
+        internal static T[] EnlargeArray<T>(T[] incoming)
+        {
+            return EnlargeArray(incoming, incoming.Length * 2);
+        }
+
+        internal static T[] EnlargeArray<T>(T[] incoming, int requiredSize)
+        {
+            Debug.Assert(incoming != null);
+
+            T[] temp = new T[requiredSize];
+            Array.Copy(incoming, 0, temp, 0, incoming.Length);
+            return temp;
+        }
+
+        private static byte[] EnlargeArray(byte[] incoming)
+        {
+            return EnlargeArray(incoming, incoming.Length * 2);
+        }
+
+        private static byte[] EnlargeArray(byte[] incoming, int requiredSize)
+        {
+            Debug.Assert(incoming != null);
+
+            byte[] temp = new byte[requiredSize];
+            Buffer.BlockCopy(incoming, 0, temp, 0, incoming.Length);
+            return temp;
+        }
+        #endregion
+
+        #region Internal Data Members
+        private int m_length;
+        private byte[] m_ILStream;
+
+        private int[] m_labelList;
+        private int m_labelCount;
+
+        private __FixupData[] m_fixupData;
+
+        private int m_fixupCount;
+
+        private int[] m_RelocFixupList;
+        private int m_RelocFixupCount;
+
+        private int m_exceptionCount;
+        private int m_currExcStackCount;
+        private __ExceptionInfo[] m_exceptions;           //This is the list of all of the exceptions in this ILStream.
+        private __ExceptionInfo[] m_currExcStack;         //This is the stack of exceptions which we're currently in.
+
+        internal ScopeTree m_ScopeTree;            // this variable tracks all debugging scope information
+        internal LineNumberInfo m_LineNumberInfo;       // this variable tracks all line number information
+
+        internal MethodInfo m_methodBuilder;
+        internal int m_localCount;
+        internal SignatureHelper m_localSignature;
+
+        private int m_maxStackSize = 0;     // Maximum stack size not counting the exceptions.
+
+        private int m_maxMidStack = 0;      // Maximum stack size for a given basic block.
+        private int m_maxMidStackCur = 0;   // Running count of the maximum stack size for the current basic block.
+
+        internal int CurrExcStackCount
+        {
+            get { return m_currExcStackCount; }
+        }
+
+        internal __ExceptionInfo[] CurrExcStack
+        {
+            get { return m_currExcStack; }
+        }
+        #endregion
+
+        #region Constructor
+        // package private constructor. This code path is used when client create
+        // ILGenerator through MethodBuilder.
+        internal ILGenerator(MethodInfo methodBuilder) : this(methodBuilder, 64)
+        {
+        }
+
+        internal ILGenerator(MethodInfo methodBuilder, int size)
+        {
+            Debug.Assert(methodBuilder != null);
+            Debug.Assert(methodBuilder is MethodBuilder || methodBuilder is DynamicMethod);
+
+            if (size < defaultSize)
+            {
+                m_ILStream = new byte[defaultSize];
+            }
+            else
+            {
+                m_ILStream = new byte[size];
+            }
+
+            m_length = 0;
+
+            m_labelCount = 0;
+            m_fixupCount = 0;
+            m_labelList = null;
+
+            m_fixupData = null;
+
+            m_exceptions = null;
+            m_exceptionCount = 0;
+            m_currExcStack = null;
+            m_currExcStackCount = 0;
+
+            m_RelocFixupList = null;
+            m_RelocFixupCount = 0;
+
+            // initialize the scope tree
+            m_ScopeTree = new ScopeTree();
+            m_LineNumberInfo = new LineNumberInfo();
+            m_methodBuilder = methodBuilder;
+
+            // initialize local signature
+            m_localCount = 0;
+            MethodBuilder mb = m_methodBuilder as MethodBuilder;
+            if (mb == null)
+                m_localSignature = SignatureHelper.GetLocalVarSigHelper(null);
+            else
+                m_localSignature = SignatureHelper.GetLocalVarSigHelper(mb.GetTypeBuilder().Module);
+        }
+
+        #endregion
+
+        #region Internal Members
+        internal virtual void RecordTokenFixup()
+        {
+            if (m_RelocFixupList == null)
+                m_RelocFixupList = new int[DefaultFixupArraySize];
+            else if (m_RelocFixupList.Length <= m_RelocFixupCount)
+                m_RelocFixupList = EnlargeArray(m_RelocFixupList);
+
+            m_RelocFixupList[m_RelocFixupCount++] = m_length;
+        }
+
+        internal void InternalEmit(OpCode opcode)
+        {
+            if (opcode.Size != 1)
+            {
+                m_ILStream[m_length++] = (byte)(opcode.Value >> 8);
+            }
+
+            m_ILStream[m_length++] = (byte)opcode.Value;
+
+            UpdateStackSize(opcode, opcode.StackChange());
+        }
+
+        internal void UpdateStackSize(OpCode opcode, int stackchange)
+        {
+            // Updates internal variables for keeping track of the stack size
+            // requirements for the function.  stackchange specifies the amount
+            // by which the stacksize needs to be updated.
+
+            // Special case for the Return.  Returns pops 1 if there is a
+            // non-void return value.
+
+            // Update the running stacksize.  m_maxMidStack specifies the maximum
+            // amount of stack required for the current basic block irrespective of
+            // where you enter the block.
+            m_maxMidStackCur += stackchange;
+            if (m_maxMidStackCur > m_maxMidStack)
+                m_maxMidStack = m_maxMidStackCur;
+            else if (m_maxMidStackCur < 0)
+                m_maxMidStackCur = 0;
+
+            // If the current instruction signifies end of a basic, which basically
+            // means an unconditional branch, add m_maxMidStack to m_maxStackSize.
+            // m_maxStackSize will eventually be the sum of the stack requirements for
+            // each basic block.
+            if (opcode.EndsUncondJmpBlk())
+            {
+                m_maxStackSize += m_maxMidStack;
+                m_maxMidStack = 0;
+                m_maxMidStackCur = 0;
+            }
+        }
+
+        private int GetMethodToken(MethodBase method, Type[] optionalParameterTypes, bool useMethodDef)
+        {
+            return ((ModuleBuilder)m_methodBuilder.Module).GetMethodTokenInternal(method, optionalParameterTypes, useMethodDef);
+        }
+
+        internal virtual SignatureHelper GetMemberRefSignature(CallingConventions call, Type returnType,
+            Type[] parameterTypes, Type[] optionalParameterTypes)
+        {
+            return GetMemberRefSignature(call, returnType, parameterTypes, optionalParameterTypes, 0);
+        }
+
+        private SignatureHelper GetMemberRefSignature(CallingConventions call, Type returnType,
+            Type[] parameterTypes, Type[] optionalParameterTypes, int cGenericParameters)
+        {
+            return ((ModuleBuilder)m_methodBuilder.Module).GetMemberRefSignature(call, returnType, parameterTypes, optionalParameterTypes, cGenericParameters);
+        }
+
+        internal byte[] BakeByteArray()
+        {
+            // BakeByteArray is an internal function designed to be called by MethodBuilder to do
+            // all of the fixups and return a new byte array representing the byte stream with labels resolved, etc.
+
+            int newSize;
+            int updateAddr;
+            byte[] newBytes;
+
+            if (m_currExcStackCount != 0)
+            {
+                throw new ArgumentException(SR.Argument_UnclosedExceptionBlock);
+            }
+            if (m_length == 0)
+                return null;
+
+            //Calculate the size of the new array.
+            newSize = m_length;
+
+            //Allocate space for the new array.
+            newBytes = new byte[newSize];
+
+            //Copy the data from the old array
+            Buffer.BlockCopy(m_ILStream, 0, newBytes, 0, newSize);
+
+            //Do the fixups.
+            //This involves iterating over all of the labels and
+            //replacing them with their proper values.
+            for (int i = 0; i < m_fixupCount; i++)
+            {
+                updateAddr = GetLabelPos(m_fixupData[i].m_fixupLabel) - (m_fixupData[i].m_fixupPos + m_fixupData[i].m_fixupInstSize);
+
+                //Handle single byte instructions
+                //Throw an exception if they're trying to store a jump in a single byte instruction that doesn't fit.
+                if (m_fixupData[i].m_fixupInstSize == 1)
+                {
+                    //Verify that our one-byte arg will fit into a Signed Byte.
+                    if (updateAddr < SByte.MinValue || updateAddr > SByte.MaxValue)
+                    {
+                        throw new NotSupportedException(SR.Format(SR.NotSupported_IllegalOneByteBranch, m_fixupData[i].m_fixupPos, updateAddr));
+                    }
+
+                    //Place the one-byte arg
+                    if (updateAddr < 0)
+                    {
+                        newBytes[m_fixupData[i].m_fixupPos] = (byte)(256 + updateAddr);
+                    }
+                    else
+                    {
+                        newBytes[m_fixupData[i].m_fixupPos] = (byte)updateAddr;
+                    }
+                }
+                else
+                {
+                    //Place the four-byte arg
+                    PutInteger4InArray(updateAddr, m_fixupData[i].m_fixupPos, newBytes);
+                }
+            }
+            return newBytes;
+        }
+
+        internal __ExceptionInfo[] GetExceptions()
+        {
+            __ExceptionInfo[] temp;
+            if (m_currExcStackCount != 0)
+            {
+                throw new NotSupportedException(SR.Argument_UnclosedExceptionBlock);
+            }
+
+            if (m_exceptionCount == 0)
+            {
+                return null;
+            }
+
+            temp = new __ExceptionInfo[m_exceptionCount];
+            Array.Copy(m_exceptions, 0, temp, 0, m_exceptionCount);
+            SortExceptions(temp);
+            return temp;
+        }
+
+        internal void EnsureCapacity(int size)
+        {
+            // Guarantees an array capable of holding at least size elements.
+            if (m_length + size >= m_ILStream.Length)
+            {
+                if (m_length + size >= 2 * m_ILStream.Length)
+                {
+                    m_ILStream = EnlargeArray(m_ILStream, m_length + size);
+                }
+                else
+                {
+                    m_ILStream = EnlargeArray(m_ILStream);
+                }
+            }
+        }
+
+        internal void PutInteger4(int value)
+        {
+            m_length = PutInteger4InArray(value, m_length, m_ILStream);
+        }
+
+        private static int PutInteger4InArray(int value, int startPos, byte[] array)
+        {
+            // Puts an Int32 onto the stream. This is an internal routine, so it does not do any error checking.
+
+            array[startPos++] = (byte)value;
+            array[startPos++] = (byte)(value >> 8);
+            array[startPos++] = (byte)(value >> 16);
+            array[startPos++] = (byte)(value >> 24);
+            return startPos;
+        }
+
+        private int GetLabelPos(Label lbl)
+        {
+            // Gets the position in the stream of a particular label.
+            // Verifies that the label exists and that it has been given a value.
+
+            int index = lbl.GetLabelValue();
+
+            if (index < 0 || index >= m_labelCount)
+                throw new ArgumentException(SR.Argument_BadLabel);
+
+            if (m_labelList[index] < 0)
+                throw new ArgumentException(SR.Argument_BadLabelContent);
+
+            return m_labelList[index];
+        }
+
+        private void AddFixup(Label lbl, int pos, int instSize)
+        {
+            // Notes the label, position, and instruction size of a new fixup.  Expands
+            // all of the fixup arrays as appropriate.
+
+            if (m_fixupData == null)
+            {
+                m_fixupData = new __FixupData[DefaultFixupArraySize];
+            }
+            else if (m_fixupData.Length <= m_fixupCount)
+            {
+                m_fixupData = EnlargeArray(m_fixupData);
+            }
+
+            m_fixupData[m_fixupCount].m_fixupPos = pos;
+            m_fixupData[m_fixupCount].m_fixupLabel = lbl;
+            m_fixupData[m_fixupCount].m_fixupInstSize = instSize;
+
+            m_fixupCount++;
+        }
+
+        internal int GetMaxStackSize()
+        {
+            return m_maxStackSize;
+        }
+
+        private static void SortExceptions(__ExceptionInfo[] exceptions)
+        {
+            // In order to call exceptions properly we have to sort them in ascending order by their end position.
+            // Just a cheap insertion sort.  We don't expect many exceptions (<10), where InsertionSort beats QuickSort.
+            // If we have more exceptions than this in real life, we should consider moving to a QuickSort.
+
+            for (int i = 0; i < exceptions.Length; i++)
+            {
+                int least = i;
+                for (int j = i + 1; j < exceptions.Length; j++)
+                {
+                    if (exceptions[least].IsInner(exceptions[j]))
+                    {
+                        least = j;
+                    }
+                }
+                __ExceptionInfo temp = exceptions[i];
+                exceptions[i] = exceptions[least];
+                exceptions[least] = temp;
+            }
+        }
+
+        internal int[] GetTokenFixups()
+        {
+            if (m_RelocFixupCount == 0)
+            {
+                Debug.Assert(m_RelocFixupList == null);
+                return null;
+            }
+
+            int[] narrowTokens = new int[m_RelocFixupCount];
+            Array.Copy(m_RelocFixupList, 0, narrowTokens, 0, m_RelocFixupCount);
+            return narrowTokens;
+        }
+        #endregion
+
+        #region Public Members
+
+        #region Emit
+        public virtual void Emit(OpCode opcode)
+        {
+            EnsureCapacity(3);
+            InternalEmit(opcode);
+        }
+
+        public virtual void Emit(OpCode opcode, byte arg)
+        {
+            EnsureCapacity(4);
+            InternalEmit(opcode);
+            m_ILStream[m_length++] = arg;
+        }
+
+        [CLSCompliant(false)]
+        public void Emit(OpCode opcode, sbyte arg)
+        {
+            // Puts opcode onto the stream of instructions followed by arg
+
+            EnsureCapacity(4);
+            InternalEmit(opcode);
+            if (arg < 0)
+            {
+                m_ILStream[m_length++] = (byte)(256 + arg);
+            }
+            else
+            {
+                m_ILStream[m_length++] = (byte)arg;
+            }
+        }
+
+        public virtual void Emit(OpCode opcode, short arg)
+        {
+            // Puts opcode onto the stream of instructions followed by arg
+            EnsureCapacity(5);
+            InternalEmit(opcode);
+            m_ILStream[m_length++] = (byte)arg;
+            m_ILStream[m_length++] = (byte)(arg >> 8);
+        }
+
+        public virtual void Emit(OpCode opcode, int arg)
+        {
+            // Puts opcode onto the stream of instructions followed by arg
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+            PutInteger4(arg);
+        }
+
+        public virtual void Emit(OpCode opcode, MethodInfo meth)
+        {
+            if (meth == null)
+                throw new ArgumentNullException(nameof(meth));
+
+            if (opcode.Equals(OpCodes.Call) || opcode.Equals(OpCodes.Callvirt) || opcode.Equals(OpCodes.Newobj))
+            {
+                EmitCall(opcode, meth, null);
+            }
+            else
+            {
+                int stackchange = 0;
+
+                // Reflection doesn't distinguish between these two concepts:
+                //   1. A generic method definition: Foo`1
+                //   2. A generic method definition instantiated over its own generic arguments: Foo`1<!!0>
+                // In RefEmit, we always want 1 for Ld* opcodes and 2 for Call* and Newobj.
+                bool useMethodDef = opcode.Equals(OpCodes.Ldtoken) || opcode.Equals(OpCodes.Ldftn) || opcode.Equals(OpCodes.Ldvirtftn);
+                int tk = GetMethodToken(meth, null, useMethodDef);
+
+                EnsureCapacity(7);
+                InternalEmit(opcode);
+
+                UpdateStackSize(opcode, stackchange);
+                RecordTokenFixup();
+                PutInteger4(tk);
+            }
+        }
+
+
+        public virtual void EmitCalli(OpCode opcode, CallingConventions callingConvention,
+            Type returnType, Type[] parameterTypes, Type[] optionalParameterTypes)
+        {
+            int stackchange = 0;
+            SignatureHelper sig;
+            if (optionalParameterTypes != null)
+            {
+                if ((callingConvention & CallingConventions.VarArgs) == 0)
+                {
+                    // Client should not supply optional parameter in default calling convention
+                    throw new InvalidOperationException(SR.InvalidOperation_NotAVarArgCallingConvention);
+                }
+            }
+
+            ModuleBuilder modBuilder = (ModuleBuilder)m_methodBuilder.Module;
+            sig = GetMemberRefSignature(callingConvention,
+                                        returnType,
+                                        parameterTypes,
+                                        optionalParameterTypes);
+
+            EnsureCapacity(7);
+            Emit(OpCodes.Calli);
+
+            // If there is a non-void return type, push one.
+            if (returnType != typeof(void))
+                stackchange++;
+            // Pop off arguments if any.
+            if (parameterTypes != null)
+                stackchange -= parameterTypes.Length;
+            // Pop off vararg arguments.
+            if (optionalParameterTypes != null)
+                stackchange -= optionalParameterTypes.Length;
+            // Pop the this parameter if the method has a this parameter.
+            if ((callingConvention & CallingConventions.HasThis) == CallingConventions.HasThis)
+                stackchange--;
+            // Pop the native function pointer.
+            stackchange--;
+            UpdateStackSize(OpCodes.Calli, stackchange);
+
+            RecordTokenFixup();
+            PutInteger4(modBuilder.GetSignatureToken(sig).Token);
+        }
+
+        public virtual void EmitCalli(OpCode opcode, CallingConvention unmanagedCallConv, Type returnType, Type[] parameterTypes)
+        {
+            int stackchange = 0;
+            int cParams = 0;
+            int i;
+            SignatureHelper sig;
+
+            ModuleBuilder modBuilder = (ModuleBuilder)m_methodBuilder.Module;
+
+            if (parameterTypes != null)
+            {
+                cParams = parameterTypes.Length;
+            }
+
+            sig = SignatureHelper.GetMethodSigHelper(
+                modBuilder,
+                unmanagedCallConv,
+                returnType);
+
+            if (parameterTypes != null)
+            {
+                for (i = 0; i < cParams; i++)
+                {
+                    sig.AddArgument(parameterTypes[i]);
+                }
+            }
+
+            // If there is a non-void return type, push one.
+            if (returnType != typeof(void))
+                stackchange++;
+
+            // Pop off arguments if any.
+            if (parameterTypes != null)
+                stackchange -= cParams;
+
+            // Pop the native function pointer.
+            stackchange--;
+            UpdateStackSize(OpCodes.Calli, stackchange);
+
+            EnsureCapacity(7);
+            Emit(OpCodes.Calli);
+            RecordTokenFixup();
+            PutInteger4(modBuilder.GetSignatureToken(sig).Token);
+        }
+
+        public virtual void EmitCall(OpCode opcode, MethodInfo methodInfo, Type[] optionalParameterTypes)
+        {
+            if (methodInfo == null)
+                throw new ArgumentNullException(nameof(methodInfo));
+
+            if (!(opcode.Equals(OpCodes.Call) || opcode.Equals(OpCodes.Callvirt) || opcode.Equals(OpCodes.Newobj)))
+                throw new ArgumentException(SR.Argument_NotMethodCallOpcode, nameof(opcode));
+
+
+            int stackchange = 0;
+            int tk = GetMethodToken(methodInfo, optionalParameterTypes, false);
+
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+
+            // Push the return value if there is one.
+            if (methodInfo.ReturnType != typeof(void))
+                stackchange++;
+            // Pop the parameters.
+            Type[] parameters = methodInfo.GetParameterTypes();
+            if (parameters != null)
+                stackchange -= parameters.Length;
+
+            // Pop the this parameter if the method is non-static and the
+            // instruction is not newobj.
+            if (!(methodInfo is SymbolMethod) && methodInfo.IsStatic == false && !(opcode.Equals(OpCodes.Newobj)))
+                stackchange--;
+            // Pop the optional parameters off the stack.
+            if (optionalParameterTypes != null)
+                stackchange -= optionalParameterTypes.Length;
+            UpdateStackSize(opcode, stackchange);
+
+            RecordTokenFixup();
+            PutInteger4(tk);
+        }
+
+        public virtual void Emit(OpCode opcode, SignatureHelper signature)
+        {
+            if (signature == null)
+                throw new ArgumentNullException(nameof(signature));
+
+            int stackchange = 0;
+            ModuleBuilder modBuilder = (ModuleBuilder)m_methodBuilder.Module;
+            SignatureToken sig = modBuilder.GetSignatureToken(signature);
+
+            int tempVal = sig.Token;
+
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+
+            // The only IL instruction that has VarPop behaviour, that takes a
+            // Signature token as a parameter is calli.  Pop the parameters and
+            // the native function pointer.  To be conservative, do not pop the
+            // this pointer since this information is not easily derived from
+            // SignatureHelper.
+            if (opcode.StackBehaviourPop == StackBehaviour.Varpop)
+            {
+                Debug.Assert(opcode.Equals(OpCodes.Calli),
+                                "Unexpected opcode encountered for StackBehaviour VarPop.");
+                // Pop the arguments..
+                stackchange -= signature.ArgumentCount;
+                // Pop native function pointer off the stack.
+                stackchange--;
+                UpdateStackSize(opcode, stackchange);
+            }
+
+            RecordTokenFixup();
+            PutInteger4(tempVal);
+        }
+
+        public virtual void Emit(OpCode opcode, ConstructorInfo con)
+        {
+            if (con == null)
+                throw new ArgumentNullException(nameof(con));
+
+            int stackchange = 0;
+
+            // Constructors cannot be generic so the value of UseMethodDef doesn't matter.
+            int tk = GetMethodToken(con, null, true);
+
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+
+            // Make a conservative estimate by assuming a return type and no
+            // this parameter.
+            if (opcode.StackBehaviourPush == StackBehaviour.Varpush)
+            {
+                // Instruction must be one of call or callvirt.
+                Debug.Assert(opcode.Equals(OpCodes.Call) ||
+                                opcode.Equals(OpCodes.Callvirt),
+                                "Unexpected opcode encountered for StackBehaviour of VarPush.");
+                stackchange++;
+            }
+            if (opcode.StackBehaviourPop == StackBehaviour.Varpop)
+            {
+                // Instruction must be one of call, callvirt or newobj.
+                Debug.Assert(opcode.Equals(OpCodes.Call) ||
+                                opcode.Equals(OpCodes.Callvirt) ||
+                                opcode.Equals(OpCodes.Newobj),
+                                "Unexpected opcode encountered for StackBehaviour of VarPop.");
+
+                Type[] parameters = con.GetParameterTypes();
+                if (parameters != null)
+                    stackchange -= parameters.Length;
+            }
+            UpdateStackSize(opcode, stackchange);
+
+            RecordTokenFixup();
+            PutInteger4(tk);
+        }
+
+        public virtual void Emit(OpCode opcode, Type cls)
+        {
+            // Puts opcode onto the stream and then the metadata token represented
+            // by cls.  The location of cls is recorded so that the token can be
+            // patched if necessary when persisting the module to a PE.
+
+            int tempVal = 0;
+            ModuleBuilder modBuilder = (ModuleBuilder)m_methodBuilder.Module;
+            if (opcode == OpCodes.Ldtoken && cls != null && cls.IsGenericTypeDefinition)
+            {
+                // This gets the token for the generic type definition if cls is one.
+                tempVal = modBuilder.GetTypeToken(cls).Token;
+            }
+            else
+            {
+                // This gets the token for the generic type instantiated on the formal parameters
+                // if cls is a generic type definition.
+                tempVal = modBuilder.GetTypeTokenInternal(cls).Token;
+            }
+
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+            RecordTokenFixup();
+            PutInteger4(tempVal);
+        }
+
+        public virtual void Emit(OpCode opcode, long arg)
+        {
+            EnsureCapacity(11);
+            InternalEmit(opcode);
+            m_ILStream[m_length++] = (byte)arg;
+            m_ILStream[m_length++] = (byte)(arg >> 8);
+            m_ILStream[m_length++] = (byte)(arg >> 16);
+            m_ILStream[m_length++] = (byte)(arg >> 24);
+            m_ILStream[m_length++] = (byte)(arg >> 32);
+            m_ILStream[m_length++] = (byte)(arg >> 40);
+            m_ILStream[m_length++] = (byte)(arg >> 48);
+            m_ILStream[m_length++] = (byte)(arg >> 56);
+        }
+
+        public unsafe virtual void Emit(OpCode opcode, float arg)
+        {
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+            uint tempVal = *(uint*)&arg;
+            m_ILStream[m_length++] = (byte)tempVal;
+            m_ILStream[m_length++] = (byte)(tempVal >> 8);
+            m_ILStream[m_length++] = (byte)(tempVal >> 16);
+            m_ILStream[m_length++] = (byte)(tempVal >> 24);
+        }
+
+        public unsafe virtual void Emit(OpCode opcode, double arg)
+        {
+            EnsureCapacity(11);
+            InternalEmit(opcode);
+            ulong tempVal = *(ulong*)&arg;
+            m_ILStream[m_length++] = (byte)tempVal;
+            m_ILStream[m_length++] = (byte)(tempVal >> 8);
+            m_ILStream[m_length++] = (byte)(tempVal >> 16);
+            m_ILStream[m_length++] = (byte)(tempVal >> 24);
+            m_ILStream[m_length++] = (byte)(tempVal >> 32);
+            m_ILStream[m_length++] = (byte)(tempVal >> 40);
+            m_ILStream[m_length++] = (byte)(tempVal >> 48);
+            m_ILStream[m_length++] = (byte)(tempVal >> 56);
+        }
+
+        public virtual void Emit(OpCode opcode, Label label)
+        {
+            // Puts opcode onto the stream and leaves space to include label
+            // when fixups are done.  Labels are created using ILGenerator.DefineLabel and
+            // their location within the stream is fixed by using ILGenerator.MarkLabel.
+            // If a single-byte instruction (designated by the _S suffix in OpCodes.cs) is used,
+            // the label can represent a jump of at most 127 bytes along the stream.
+            //
+            // opcode must represent a branch instruction (although we don't explicitly
+            // verify this).  Since branches are relative instructions, label will be replaced with the
+            // correct offset to branch during the fixup process.
+
+            int tempVal = label.GetLabelValue();
+            EnsureCapacity(7);
+
+
+            InternalEmit(opcode);
+            if (OpCodes.TakesSingleByteArgument(opcode))
+            {
+                AddFixup(label, m_length, 1);
+                m_length++;
+            }
+            else
+            {
+                AddFixup(label, m_length, 4);
+                m_length += 4;
+            }
+        }
+
+        public virtual void Emit(OpCode opcode, Label[] labels)
+        {
+            if (labels == null)
+                throw new ArgumentNullException(nameof(labels));
+
+            // Emitting a switch table
+
+            int i;
+            int remaining;                  // number of bytes remaining for this switch instruction to be substracted
+            // for computing the offset
+
+            int count = labels.Length;
+
+            EnsureCapacity(count * 4 + 7);
+            InternalEmit(opcode);
+            PutInteger4(count);
+            for (remaining = count * 4, i = 0; remaining > 0; remaining -= 4, i++)
+            {
+                AddFixup(labels[i], m_length, remaining);
+                m_length += 4;
+            }
+        }
+
+        public virtual void Emit(OpCode opcode, FieldInfo field)
+        {
+            ModuleBuilder modBuilder = (ModuleBuilder)m_methodBuilder.Module;
+            int tempVal = modBuilder.GetFieldToken(field).Token;
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+            RecordTokenFixup();
+            PutInteger4(tempVal);
+        }
+
+        public virtual void Emit(OpCode opcode, String str)
+        {
+            // Puts the opcode onto the IL stream followed by the metadata token
+            // represented by str.  The location of str is recorded for future
+            // fixups if the module is persisted to a PE.
+
+            ModuleBuilder modBuilder = (ModuleBuilder)m_methodBuilder.Module;
+            int tempVal = modBuilder.GetStringConstant(str).Token;
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+            PutInteger4(tempVal);
+        }
+
+        public virtual void Emit(OpCode opcode, LocalBuilder local)
+        {
+            // Puts the opcode onto the IL stream followed by the information for local variable local.
+
+            if (local == null)
+            {
+                throw new ArgumentNullException(nameof(local));
+            }
+            int tempVal = local.GetLocalIndex();
+            if (local.GetMethodBuilder() != m_methodBuilder)
+            {
+                throw new ArgumentException(SR.Argument_UnmatchedMethodForLocal, nameof(local));
+            }
+            // If the instruction is a ldloc, ldloca a stloc, morph it to the optimal form.
+            if (opcode.Equals(OpCodes.Ldloc))
+            {
+                switch (tempVal)
+                {
+                    case 0:
+                        opcode = OpCodes.Ldloc_0;
+                        break;
+                    case 1:
+                        opcode = OpCodes.Ldloc_1;
+                        break;
+                    case 2:
+                        opcode = OpCodes.Ldloc_2;
+                        break;
+                    case 3:
+                        opcode = OpCodes.Ldloc_3;
+                        break;
+                    default:
+                        if (tempVal <= 255)
+                            opcode = OpCodes.Ldloc_S;
+                        break;
+                }
+            }
+            else if (opcode.Equals(OpCodes.Stloc))
+            {
+                switch (tempVal)
+                {
+                    case 0:
+                        opcode = OpCodes.Stloc_0;
+                        break;
+                    case 1:
+                        opcode = OpCodes.Stloc_1;
+                        break;
+                    case 2:
+                        opcode = OpCodes.Stloc_2;
+                        break;
+                    case 3:
+                        opcode = OpCodes.Stloc_3;
+                        break;
+                    default:
+                        if (tempVal <= 255)
+                            opcode = OpCodes.Stloc_S;
+                        break;
+                }
+            }
+            else if (opcode.Equals(OpCodes.Ldloca))
+            {
+                if (tempVal <= 255)
+                    opcode = OpCodes.Ldloca_S;
+            }
+
+            EnsureCapacity(7);
+            InternalEmit(opcode);
+
+            if (opcode.OperandType == OperandType.InlineNone)
+                return;
+            else if (!OpCodes.TakesSingleByteArgument(opcode))
+            {
+                m_ILStream[m_length++] = (byte)tempVal;
+                m_ILStream[m_length++] = (byte)(tempVal >> 8);
+            }
+            else
+            {
+                //Handle stloc_1, ldloc_1
+                if (tempVal > Byte.MaxValue)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_BadInstructionOrIndexOutOfBound);
+                }
+                m_ILStream[m_length++] = (byte)tempVal;
+            }
+        }
+        #endregion
+
+        #region Exceptions
+        public virtual Label BeginExceptionBlock()
+        {
+            // Begin an Exception block.  Creating an Exception block records some information,
+            // but does not actually emit any IL onto the stream.  Exceptions should be created and
+            // marked in the following form:
+            //
+            // Emit Some IL
+            // BeginExceptionBlock
+            // Emit the IL which should appear within the "try" block
+            // BeginCatchBlock
+            // Emit the IL which should appear within the "catch" block
+            // Optional: BeginCatchBlock (this can be repeated an arbitrary number of times
+            // EndExceptionBlock
+
+            // Delay init
+            if (m_exceptions == null)
+            {
+                m_exceptions = new __ExceptionInfo[DefaultExceptionArraySize];
+            }
+
+            if (m_currExcStack == null)
+            {
+                m_currExcStack = new __ExceptionInfo[DefaultExceptionArraySize];
+            }
+
+            if (m_exceptionCount >= m_exceptions.Length)
+            {
+                m_exceptions = EnlargeArray(m_exceptions);
+            }
+
+            if (m_currExcStackCount >= m_currExcStack.Length)
+            {
+                m_currExcStack = EnlargeArray(m_currExcStack);
+            }
+
+            Label endLabel = DefineLabel();
+            __ExceptionInfo exceptionInfo = new __ExceptionInfo(m_length, endLabel);
+
+            // add the exception to the tracking list
+            m_exceptions[m_exceptionCount++] = exceptionInfo;
+
+            // Make this exception the current active exception
+            m_currExcStack[m_currExcStackCount++] = exceptionInfo;
+            return endLabel;
+        }
+
+        public virtual void EndExceptionBlock()
+        {
+            if (m_currExcStackCount == 0)
+            {
+                throw new NotSupportedException(SR.Argument_NotInExceptionBlock);
+            }
+
+            // Pop the current exception block
+            __ExceptionInfo current = m_currExcStack[m_currExcStackCount - 1];
+            m_currExcStack[m_currExcStackCount - 1] = null;
+            m_currExcStackCount--;
+
+            Label endLabel = current.GetEndLabel();
+            int state = current.GetCurrentState();
+
+            if (state == __ExceptionInfo.State_Filter ||
+                state == __ExceptionInfo.State_Try)
+            {
+                throw new InvalidOperationException(SR.Argument_BadExceptionCodeGen);
+            }
+
+            if (state == __ExceptionInfo.State_Catch)
+            {
+                this.Emit(OpCodes.Leave, endLabel);
+            }
+            else if (state == __ExceptionInfo.State_Finally || state == __ExceptionInfo.State_Fault)
+            {
+                this.Emit(OpCodes.Endfinally);
+            }
+
+            //Check if we've alredy set this label.
+            //The only reason why we might have set this is if we have a finally block.
+            if (m_labelList[endLabel.GetLabelValue()] == -1)
+            {
+                MarkLabel(endLabel);
+            }
+            else
+            {
+                MarkLabel(current.GetFinallyEndLabel());
+            }
+
+            current.Done(m_length);
+        }
+
+        public virtual void BeginExceptFilterBlock()
+        {
+            // Begins an exception filter block.  Emits a branch instruction to the end of the current exception block.
+
+            if (m_currExcStackCount == 0)
+                throw new NotSupportedException(SR.Argument_NotInExceptionBlock);
+
+            __ExceptionInfo current = m_currExcStack[m_currExcStackCount - 1];
+
+            Label endLabel = current.GetEndLabel();
+            this.Emit(OpCodes.Leave, endLabel);
+
+            current.MarkFilterAddr(m_length);
+        }
+
+        public virtual void BeginCatchBlock(Type exceptionType)
+        {
+            // Begins a catch block.  Emits a branch instruction to the end of the current exception block.
+
+            if (m_currExcStackCount == 0)
+            {
+                throw new NotSupportedException(SR.Argument_NotInExceptionBlock);
+            }
+            __ExceptionInfo current = m_currExcStack[m_currExcStackCount - 1];
+
+            if (current.GetCurrentState() == __ExceptionInfo.State_Filter)
+            {
+                if (exceptionType != null)
+                {
+                    throw new ArgumentException(SR.Argument_ShouldNotSpecifyExceptionType);
+                }
+
+                this.Emit(OpCodes.Endfilter);
+            }
+            else
+            {
+                // execute this branch if previous clause is Catch or Fault
+                if (exceptionType == null)
+                {
+                    throw new ArgumentNullException(nameof(exceptionType));
+                }
+
+                Label endLabel = current.GetEndLabel();
+                this.Emit(OpCodes.Leave, endLabel);
+            }
+
+            current.MarkCatchAddr(m_length, exceptionType);
+        }
+
+        public virtual void BeginFaultBlock()
+        {
+            if (m_currExcStackCount == 0)
+            {
+                throw new NotSupportedException(SR.Argument_NotInExceptionBlock);
+            }
+            __ExceptionInfo current = m_currExcStack[m_currExcStackCount - 1];
+
+            // emit the leave for the clause before this one.
+            Label endLabel = current.GetEndLabel();
+            this.Emit(OpCodes.Leave, endLabel);
+
+            current.MarkFaultAddr(m_length);
+        }
+
+        public virtual void BeginFinallyBlock()
+        {
+            if (m_currExcStackCount == 0)
+            {
+                throw new NotSupportedException(SR.Argument_NotInExceptionBlock);
+            }
+            __ExceptionInfo current = m_currExcStack[m_currExcStackCount - 1];
+            int state = current.GetCurrentState();
+            Label endLabel = current.GetEndLabel();
+            int catchEndAddr = 0;
+            if (state != __ExceptionInfo.State_Try)
+            {
+                // generate leave for any preceeding catch clause
+                this.Emit(OpCodes.Leave, endLabel);
+                catchEndAddr = m_length;
+            }
+
+            MarkLabel(endLabel);
+
+
+            Label finallyEndLabel = this.DefineLabel();
+            current.SetFinallyEndLabel(finallyEndLabel);
+
+            // generate leave for try clause                                                  
+            this.Emit(OpCodes.Leave, finallyEndLabel);
+            if (catchEndAddr == 0)
+                catchEndAddr = m_length;
+            current.MarkFinallyAddr(m_length, catchEndAddr);
+        }
+
+        #endregion
+
+        #region Labels
+        public virtual Label DefineLabel()
+        {
+            // Declares a new Label.  This is just a token and does not yet represent any particular location
+            // within the stream.  In order to set the position of the label within the stream, you must call
+            // Mark Label.
+
+            // Delay init the lable array in case we dont use it
+            if (m_labelList == null)
+            {
+                m_labelList = new int[DefaultLabelArraySize];
+            }
+
+            if (m_labelCount >= m_labelList.Length)
+            {
+                m_labelList = EnlargeArray(m_labelList);
+            }
+            m_labelList[m_labelCount] = -1;
+            return new Label(m_labelCount++);
+        }
+
+        public virtual void MarkLabel(Label loc)
+        {
+            // Defines a label by setting the position where that label is found within the stream.
+            // Does not allow a label to be defined more than once.
+
+            int labelIndex = loc.GetLabelValue();
+
+            //This should never happen.
+            if (labelIndex < 0 || labelIndex >= m_labelList.Length)
+            {
+                throw new ArgumentException(SR.Argument_InvalidLabel);
+            }
+
+            if (m_labelList[labelIndex] != -1)
+            {
+                throw new ArgumentException(SR.Argument_RedefinedLabel);
+            }
+
+            m_labelList[labelIndex] = m_length;
+        }
+
+        #endregion
+
+        #region IL Macros
+        public virtual void ThrowException(Type excType)
+        {
+            // Emits the il to throw an exception
+
+            if (excType == null)
+            {
+                throw new ArgumentNullException(nameof(excType));
+            }
+
+            if (!excType.IsSubclassOf(typeof(Exception)) && excType != typeof(Exception))
+            {
+                throw new ArgumentException(SR.Argument_NotExceptionType);
+            }
+            ConstructorInfo con = excType.GetConstructor(Type.EmptyTypes);
+            if (con == null)
+            {
+                throw new ArgumentException(SR.Argument_MissingDefaultConstructor);
+            }
+            this.Emit(OpCodes.Newobj, con);
+            this.Emit(OpCodes.Throw);
+        }
+
+        private static Type GetConsoleType()
+        {
+            return Type.GetType("System.Console, System.Console", throwOnError: true);
+        }
+
+        public virtual void EmitWriteLine(String value)
+        {
+            // Emits the IL to call Console.WriteLine with a string.
+
+            Emit(OpCodes.Ldstr, value);
+            Type[] parameterTypes = new Type[1];
+            parameterTypes[0] = typeof(String);
+            MethodInfo mi = GetConsoleType().GetMethod("WriteLine", parameterTypes);
+            Emit(OpCodes.Call, mi);
+        }
+
+        public virtual void EmitWriteLine(LocalBuilder localBuilder)
+        {
+            // Emits the IL necessary to call WriteLine with lcl.  It is
+            // an error to call EmitWriteLine with a lcl which is not of
+            // one of the types for which Console.WriteLine implements overloads. (e.g.
+            // we do *not* call ToString on the locals.
+
+            Object cls;
+            if (m_methodBuilder == null)
+            {
+                throw new ArgumentException(SR.InvalidOperation_BadILGeneratorUsage);
+            }
+
+            MethodInfo prop = GetConsoleType().GetMethod("get_Out");
+            Emit(OpCodes.Call, prop);
+            Emit(OpCodes.Ldloc, localBuilder);
+            Type[] parameterTypes = new Type[1];
+            cls = localBuilder.LocalType;
+            if (cls is TypeBuilder || cls is EnumBuilder)
+            {
+                throw new ArgumentException(SR.NotSupported_OutputStreamUsingTypeBuilder);
+            }
+            parameterTypes[0] = (Type)cls;
+            MethodInfo mi = prop.ReturnType.GetMethod("WriteLine", parameterTypes);
+            if (mi == null)
+            {
+                throw new ArgumentException(SR.Argument_EmitWriteLineType, nameof(localBuilder));
+            }
+
+            Emit(OpCodes.Callvirt, mi);
+        }
+
+        public virtual void EmitWriteLine(FieldInfo fld)
+        {
+            // Emits the IL necessary to call WriteLine with fld.  It is
+            // an error to call EmitWriteLine with a fld which is not of
+            // one of the types for which Console.WriteLine implements overloads. (e.g.
+            // we do *not* call ToString on the fields.
+
+            Object cls;
+
+            if (fld == null)
+            {
+                throw new ArgumentNullException(nameof(fld));
+            }
+
+            MethodInfo prop = GetConsoleType().GetMethod("get_Out");
+            Emit(OpCodes.Call, prop);
+
+            if ((fld.Attributes & FieldAttributes.Static) != 0)
+            {
+                Emit(OpCodes.Ldsfld, fld);
+            }
+            else
+            {
+                Emit(OpCodes.Ldarg, (short)0); //Load the this ref.
+                Emit(OpCodes.Ldfld, fld);
+            }
+            Type[] parameterTypes = new Type[1];
+            cls = fld.FieldType;
+            if (cls is TypeBuilder || cls is EnumBuilder)
+            {
+                throw new NotSupportedException(SR.NotSupported_OutputStreamUsingTypeBuilder);
+            }
+            parameterTypes[0] = (Type)cls;
+            MethodInfo mi = prop.ReturnType.GetMethod("WriteLine", parameterTypes);
+            if (mi == null)
+            {
+                throw new ArgumentException(SR.Argument_EmitWriteLineType, nameof(fld));
+            }
+            Emit(OpCodes.Callvirt, mi);
+        }
+
+        #endregion
+
+        #region Debug API
+        public virtual LocalBuilder DeclareLocal(Type localType)
+        {
+            return DeclareLocal(localType, false);
+        }
+
+        public virtual LocalBuilder DeclareLocal(Type localType, bool pinned)
+        {
+            // Declare a local of type "local". The current active lexical scope
+            // will be the scope that local will live.
+
+            LocalBuilder localBuilder;
+
+            MethodBuilder methodBuilder = m_methodBuilder as MethodBuilder;
+            if (methodBuilder == null)
+                throw new NotSupportedException();
+
+            if (methodBuilder.IsTypeCreated())
+            {
+                // cannot change method after its containing type has been created
+                throw new InvalidOperationException(SR.InvalidOperation_TypeHasBeenCreated);
+            }
+
+            if (localType == null)
+            {
+                throw new ArgumentNullException(nameof(localType));
+            }
+
+            if (methodBuilder.m_bIsBaked)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_MethodBaked);
+            }
+
+            // add the localType to local signature
+            m_localSignature.AddArgument(localType, pinned);
+
+            localBuilder = new LocalBuilder(m_localCount, localType, methodBuilder, pinned);
+            m_localCount++;
+            return localBuilder;
+        }
+
+        public virtual void UsingNamespace(String usingNamespace)
+        {
+            // Specifying the namespace to be used in evaluating locals and watches
+            // for the current active lexical scope.
+
+            if (usingNamespace == null)
+                throw new ArgumentNullException(nameof(usingNamespace));
+
+            if (usingNamespace.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(usingNamespace));
+
+            int index;
+            MethodBuilder methodBuilder = m_methodBuilder as MethodBuilder;
+            if (methodBuilder == null)
+                throw new NotSupportedException();
+
+            index = methodBuilder.GetILGenerator().m_ScopeTree.GetCurrentActiveScopeIndex();
+            if (index == -1)
+            {
+                methodBuilder.m_localSymInfo.AddUsingNamespace(usingNamespace);
+            }
+            else
+            {
+                m_ScopeTree.AddUsingNamespaceToCurrentScope(usingNamespace);
+            }
+        }
+
+        public virtual void MarkSequencePoint(
+            ISymbolDocumentWriter document,
+            int startLine,       // line number is 1 based
+            int startColumn,     // column is 0 based
+            int endLine,         // line number is 1 based
+            int endColumn)       // column is 0 based
+        {
+            if (startLine == 0 || startLine < 0 || endLine == 0 || endLine < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(startLine));
+            }
+            m_LineNumberInfo.AddLineNumberInfo(document, m_length, startLine, startColumn, endLine, endColumn);
+        }
+
+        public virtual void BeginScope()
+        {
+            m_ScopeTree.AddScopeInfo(ScopeAction.Open, m_length);
+        }
+
+        public virtual void EndScope()
+        {
+            m_ScopeTree.AddScopeInfo(ScopeAction.Close, m_length);
+        }
+
+        public virtual int ILOffset
+        {
+            get
+            {
+                return m_length;
+            }
+        }
+
+        #endregion
+
+        #endregion
+    }
+
+    internal struct __FixupData
+    {
+        internal Label m_fixupLabel;
+        internal int m_fixupPos;
+
+        internal int m_fixupInstSize;
+    }
+
+    internal sealed class __ExceptionInfo
+    {
+        internal const int None = 0x0000;  //COR_ILEXCEPTION_CLAUSE_NONE
+        internal const int Filter = 0x0001;  //COR_ILEXCEPTION_CLAUSE_FILTER
+        internal const int Finally = 0x0002;  //COR_ILEXCEPTION_CLAUSE_FINALLY
+        internal const int Fault = 0x0004;  //COR_ILEXCEPTION_CLAUSE_FAULT
+        internal const int PreserveStack = 0x0004;  //COR_ILEXCEPTION_CLAUSE_PRESERVESTACK
+
+        internal const int State_Try = 0;
+        internal const int State_Filter = 1;
+        internal const int State_Catch = 2;
+        internal const int State_Finally = 3;
+        internal const int State_Fault = 4;
+        internal const int State_Done = 5;
+
+        internal int m_startAddr;
+        internal int[] m_filterAddr;
+        internal int[] m_catchAddr;
+        internal int[] m_catchEndAddr;
+        internal int[] m_type;
+        internal Type[] m_catchClass;
+        internal Label m_endLabel;
+        internal Label m_finallyEndLabel;
+        internal int m_endAddr;
+        internal int m_endFinally;
+        internal int m_currentCatch;
+
+        private int m_currentState;
+
+        internal __ExceptionInfo(int startAddr, Label endLabel)
+        {
+            m_startAddr = startAddr;
+            m_endAddr = -1;
+            m_filterAddr = new int[4];
+            m_catchAddr = new int[4];
+            m_catchEndAddr = new int[4];
+            m_catchClass = new Type[4];
+            m_currentCatch = 0;
+            m_endLabel = endLabel;
+            m_type = new int[4];
+            m_endFinally = -1;
+            m_currentState = State_Try;
+        }
+
+        private void MarkHelper(
+            int catchorfilterAddr,      // the starting address of a clause
+            int catchEndAddr,           // the end address of a previous catch clause. Only use when finally is following a catch
+            Type catchClass,             // catch exception type
+            int type)                   // kind of clause
+        {
+            if (m_currentCatch >= m_catchAddr.Length)
+            {
+                m_filterAddr = ILGenerator.EnlargeArray(m_filterAddr);
+                m_catchAddr = ILGenerator.EnlargeArray(m_catchAddr);
+                m_catchEndAddr = ILGenerator.EnlargeArray(m_catchEndAddr);
+                m_catchClass = ILGenerator.EnlargeArray(m_catchClass);
+                m_type = ILGenerator.EnlargeArray(m_type);
+            }
+            if (type == Filter)
+            {
+                m_type[m_currentCatch] = type;
+                m_filterAddr[m_currentCatch] = catchorfilterAddr;
+                m_catchAddr[m_currentCatch] = -1;
+                if (m_currentCatch > 0)
+                {
+                    Debug.Assert(m_catchEndAddr[m_currentCatch - 1] == -1, "m_catchEndAddr[m_currentCatch-1] == -1");
+                    m_catchEndAddr[m_currentCatch - 1] = catchorfilterAddr;
+                }
+            }
+            else
+            {
+                // catch or Fault clause
+                m_catchClass[m_currentCatch] = catchClass;
+                if (m_type[m_currentCatch] != Filter)
+                {
+                    m_type[m_currentCatch] = type;
+                }
+                m_catchAddr[m_currentCatch] = catchorfilterAddr;
+                if (m_currentCatch > 0)
+                {
+                    if (m_type[m_currentCatch] != Filter)
+                    {
+                        Debug.Assert(m_catchEndAddr[m_currentCatch - 1] == -1, "m_catchEndAddr[m_currentCatch-1] == -1");
+                        m_catchEndAddr[m_currentCatch - 1] = catchEndAddr;
+                    }
+                }
+                m_catchEndAddr[m_currentCatch] = -1;
+                m_currentCatch++;
+            }
+
+            if (m_endAddr == -1)
+            {
+                m_endAddr = catchorfilterAddr;
+            }
+        }
+
+        internal void MarkFilterAddr(int filterAddr)
+        {
+            m_currentState = State_Filter;
+            MarkHelper(filterAddr, filterAddr, null, Filter);
+        }
+
+        internal void MarkFaultAddr(int faultAddr)
+        {
+            m_currentState = State_Fault;
+            MarkHelper(faultAddr, faultAddr, null, Fault);
+        }
+
+        internal void MarkCatchAddr(int catchAddr, Type catchException)
+        {
+            m_currentState = State_Catch;
+            MarkHelper(catchAddr, catchAddr, catchException, None);
+        }
+
+        internal void MarkFinallyAddr(int finallyAddr, int endCatchAddr)
+        {
+            if (m_endFinally != -1)
+            {
+                throw new ArgumentException(SR.Argument_TooManyFinallyClause);
+            }
+            else
+            {
+                m_currentState = State_Finally;
+                m_endFinally = finallyAddr;
+            }
+            MarkHelper(finallyAddr, endCatchAddr, null, Finally);
+        }
+
+        internal void Done(int endAddr)
+        {
+            Debug.Assert(m_currentCatch > 0, "m_currentCatch > 0");
+            Debug.Assert(m_catchAddr[m_currentCatch - 1] > 0, "m_catchAddr[m_currentCatch-1] > 0");
+            Debug.Assert(m_catchEndAddr[m_currentCatch - 1] == -1, "m_catchEndAddr[m_currentCatch-1] == -1");
+            m_catchEndAddr[m_currentCatch - 1] = endAddr;
+            m_currentState = State_Done;
+        }
+
+        internal int GetStartAddress()
+        {
+            return m_startAddr;
+        }
+
+        internal int GetEndAddress()
+        {
+            return m_endAddr;
+        }
+
+        internal int GetFinallyEndAddress()
+        {
+            return m_endFinally;
+        }
+
+        internal Label GetEndLabel()
+        {
+            return m_endLabel;
+        }
+
+        internal int[] GetFilterAddresses()
+        {
+            return m_filterAddr;
+        }
+
+        internal int[] GetCatchAddresses()
+        {
+            return m_catchAddr;
+        }
+
+        internal int[] GetCatchEndAddresses()
+        {
+            return m_catchEndAddr;
+        }
+
+        internal Type[] GetCatchClass()
+        {
+            return m_catchClass;
+        }
+
+        internal int GetNumberOfCatches()
+        {
+            return m_currentCatch;
+        }
+
+        internal int[] GetExceptionTypes()
+        {
+            return m_type;
+        }
+
+        internal void SetFinallyEndLabel(Label lbl)
+        {
+            m_finallyEndLabel = lbl;
+        }
+
+        internal Label GetFinallyEndLabel()
+        {
+            return m_finallyEndLabel;
+        }
+
+        // Specifies whether exc is an inner exception for "this".  The way
+        // its determined is by comparing the end address for the last catch
+        // clause for both exceptions.  If they're the same, the start address
+        // for the exception is compared.
+        // WARNING: This is not a generic function to determine the innerness
+        // of an exception.  This is somewhat of a mis-nomer.  This gives a
+        // random result for cases where the two exceptions being compared do
+        // not having a nesting relation. 
+        internal bool IsInner(__ExceptionInfo exc)
+        {
+            Debug.Assert(exc != null);
+            Debug.Assert(m_currentCatch > 0, "m_currentCatch > 0");
+            Debug.Assert(exc.m_currentCatch > 0, "exc.m_currentCatch > 0");
+
+            int exclast = exc.m_currentCatch - 1;
+            int last = m_currentCatch - 1;
+
+            if (exc.m_catchEndAddr[exclast] < m_catchEndAddr[last])
+                return true;
+            else if (exc.m_catchEndAddr[exclast] == m_catchEndAddr[last])
+            {
+                Debug.Assert(exc.GetEndAddress() != GetEndAddress(),
+                                "exc.GetEndAddress() != GetEndAddress()");
+                if (exc.GetEndAddress() > GetEndAddress())
+                    return true;
+            }
+            return false;
+        }
+
+        // 0 indicates in a try block
+        // 1 indicates in a filter block
+        // 2 indicates in a catch block
+        // 3 indicates in a finally block
+        // 4 indicates Done
+        internal int GetCurrentState()
+        {
+            return m_currentState;
+        }
+    }
+
+
+    /***************************
+    *
+    * Scope Tree is a class that track the scope structure within a method body
+    * It keeps track two parallel array. m_ScopeAction keeps track the action. It can be
+    * OpenScope or CloseScope. m_iOffset records the offset where the action
+    * takes place.
+    *
+    ***************************/
+    internal enum ScopeAction
+    {
+        Open = 0x0,
+        Close = 0x1,
+    }
+
+    internal sealed class ScopeTree
+    {
+        internal ScopeTree()
+        {
+            // initialize data variables
+            m_iOpenScopeCount = 0;
+            m_iCount = 0;
+        }
+
+        /***************************
+        *
+        * Find the current active lexical scope. For example, if we have
+        * "Open Open Open Close",
+        * we will return 1 as the second BeginScope is currently active.
+        *
+        ***************************/
+        internal int GetCurrentActiveScopeIndex()
+        {
+            int cClose = 0;
+            int i = m_iCount - 1;
+
+            if (m_iCount == 0)
+            {
+                return -1;
+            }
+            for (; cClose > 0 || m_ScopeActions[i] == ScopeAction.Close; i--)
+            {
+                if (m_ScopeActions[i] == ScopeAction.Open)
+                {
+                    cClose--;
+                }
+                else
+                    cClose++;
+            }
+
+            return i;
+        }
+
+        internal void AddLocalSymInfoToCurrentScope(
+            String strName,
+            byte[] signature,
+            int slot,
+            int startOffset,
+            int endOffset)
+        {
+            int i = GetCurrentActiveScopeIndex();
+            if (m_localSymInfos[i] == null)
+            {
+                m_localSymInfos[i] = new LocalSymInfo();
+            }
+            m_localSymInfos[i].AddLocalSymInfo(strName, signature, slot, startOffset, endOffset);
+        }
+
+        internal void AddUsingNamespaceToCurrentScope(
+            String strNamespace)
+        {
+            int i = GetCurrentActiveScopeIndex();
+            if (m_localSymInfos[i] == null)
+            {
+                m_localSymInfos[i] = new LocalSymInfo();
+            }
+            m_localSymInfos[i].AddUsingNamespace(strNamespace);
+        }
+
+        internal void AddScopeInfo(ScopeAction sa, int iOffset)
+        {
+            if (sa == ScopeAction.Close && m_iOpenScopeCount <= 0)
+            {
+                throw new ArgumentException(SR.Argument_UnmatchingSymScope);
+            }
+
+            // make sure that arrays are large enough to hold addition info
+            EnsureCapacity();
+
+
+            m_ScopeActions[m_iCount] = sa;
+            m_iOffsets[m_iCount] = iOffset;
+            m_localSymInfos[m_iCount] = null;
+            checked { m_iCount++; }
+            if (sa == ScopeAction.Open)
+            {
+                m_iOpenScopeCount++;
+            }
+            else
+                m_iOpenScopeCount--;
+        }
+
+        /**************************
+        *
+        * Helper to ensure arrays are large enough
+        *
+        **************************/
+        internal void EnsureCapacity()
+        {
+            if (m_iCount == 0)
+            {
+                // First time. Allocate the arrays.
+                m_iOffsets = new int[InitialSize];
+                m_ScopeActions = new ScopeAction[InitialSize];
+                m_localSymInfos = new LocalSymInfo[InitialSize];
+            }
+            else if (m_iCount == m_iOffsets.Length)
+            {
+                // the arrays are full. Enlarge the arrays
+                // It would probably be simpler to just use Lists here.
+                int newSize = checked(m_iCount * 2);
+                int[] temp = new int[newSize];
+                Array.Copy(m_iOffsets, 0, temp, 0, m_iCount);
+                m_iOffsets = temp;
+
+                ScopeAction[] tempSA = new ScopeAction[newSize];
+                Array.Copy(m_ScopeActions, 0, tempSA, 0, m_iCount);
+                m_ScopeActions = tempSA;
+
+                LocalSymInfo[] tempLSI = new LocalSymInfo[newSize];
+                Array.Copy(m_localSymInfos, 0, tempLSI, 0, m_iCount);
+                m_localSymInfos = tempLSI;
+            }
+        }
+
+        internal void EmitScopeTree(ISymbolWriter symWriter)
+        {
+            int i;
+            for (i = 0; i < m_iCount; i++)
+            {
+                if (m_ScopeActions[i] == ScopeAction.Open)
+                {
+                    symWriter.OpenScope(m_iOffsets[i]);
+                }
+                else
+                {
+                    symWriter.CloseScope(m_iOffsets[i]);
+                }
+                if (m_localSymInfos[i] != null)
+                {
+                    m_localSymInfos[i].EmitLocalSymInfo(symWriter);
+                }
+            }
+        }
+
+        internal int[] m_iOffsets;                 // array of offsets
+        internal ScopeAction[] m_ScopeActions;             // array of scope actions
+        internal int m_iCount;                   // how many entries in the arrays are occupied
+        internal int m_iOpenScopeCount;          // keep track how many scopes are open
+        internal const int InitialSize = 16;
+        internal LocalSymInfo[] m_localSymInfos;            // keep track debugging local information
+    }
+
+
+    /***************************
+    *
+    * This class tracks the line number info
+    *
+    ***************************/
+    internal sealed class LineNumberInfo
+    {
+        internal LineNumberInfo()
+        {
+            // initialize data variables
+            m_DocumentCount = 0;
+            m_iLastFound = 0;
+        }
+
+        internal void AddLineNumberInfo(
+            ISymbolDocumentWriter document,
+            int iOffset,
+            int iStartLine,
+            int iStartColumn,
+            int iEndLine,
+            int iEndColumn)
+        {
+            int i;
+
+            // make sure that arrays are large enough to hold addition info
+            i = FindDocument(document);
+
+            Debug.Assert(i < m_DocumentCount, "Bad document look up!");
+            m_Documents[i].AddLineNumberInfo(document, iOffset, iStartLine, iStartColumn, iEndLine, iEndColumn);
+        }
+
+        // Find a REDocument representing document. If we cannot find one, we will add a new entry into
+        // the REDocument array.
+        private int FindDocument(ISymbolDocumentWriter document)
+        {
+            int i;
+
+            // This is an optimization. The chance that the previous line is coming from the same
+            // document is very high.
+            if (m_iLastFound < m_DocumentCount && m_Documents[m_iLastFound].m_document == document)
+                return m_iLastFound;
+
+            for (i = 0; i < m_DocumentCount; i++)
+            {
+                if (m_Documents[i].m_document == document)
+                {
+                    m_iLastFound = i;
+                    return m_iLastFound;
+                }
+            }
+
+            // cannot find an existing document so add one to the array                                       
+            EnsureCapacity();
+            m_iLastFound = m_DocumentCount;
+            m_Documents[m_iLastFound] = new REDocument(document);
+            checked { m_DocumentCount++; }
+            return m_iLastFound;
+        }
+
+        /**************************
+        *
+        * Helper to ensure arrays are large enough
+        *
+        **************************/
+        private void EnsureCapacity()
+        {
+            if (m_DocumentCount == 0)
+            {
+                // First time. Allocate the arrays.
+                m_Documents = new REDocument[InitialSize];
+            }
+            else if (m_DocumentCount == m_Documents.Length)
+            {
+                // the arrays are full. Enlarge the arrays
+                REDocument[] temp = new REDocument[m_DocumentCount * 2];
+                Array.Copy(m_Documents, 0, temp, 0, m_DocumentCount);
+                m_Documents = temp;
+            }
+        }
+
+        internal void EmitLineNumberInfo(ISymbolWriter symWriter)
+        {
+            for (int i = 0; i < m_DocumentCount; i++)
+                m_Documents[i].EmitLineNumberInfo(symWriter);
+        }
+
+        private int m_DocumentCount;         // how many documents that we have right now
+        private REDocument[] m_Documents;             // array of documents
+        private const int InitialSize = 16;
+        private int m_iLastFound;
+    }
+
+
+    /***************************
+    *
+    * This class tracks the line number info
+    *
+    ***************************/
+    internal sealed class REDocument
+    {
+        internal REDocument(ISymbolDocumentWriter document)
+        {
+            // initialize data variables
+            m_iLineNumberCount = 0;
+            m_document = document;
+        }
+
+        internal void AddLineNumberInfo(
+            ISymbolDocumentWriter document,
+            int iOffset,
+            int iStartLine,
+            int iStartColumn,
+            int iEndLine,
+            int iEndColumn)
+        {
+            Debug.Assert(document == m_document, "Bad document look up!");
+
+            // make sure that arrays are large enough to hold addition info
+            EnsureCapacity();
+
+            m_iOffsets[m_iLineNumberCount] = iOffset;
+            m_iLines[m_iLineNumberCount] = iStartLine;
+            m_iColumns[m_iLineNumberCount] = iStartColumn;
+            m_iEndLines[m_iLineNumberCount] = iEndLine;
+            m_iEndColumns[m_iLineNumberCount] = iEndColumn;
+            checked { m_iLineNumberCount++; }
+        }
+
+        /**************************
+        *
+        * Helper to ensure arrays are large enough
+        *
+        **************************/
+        private void EnsureCapacity()
+        {
+            if (m_iLineNumberCount == 0)
+            {
+                // First time. Allocate the arrays.
+                m_iOffsets = new int[InitialSize];
+                m_iLines = new int[InitialSize];
+                m_iColumns = new int[InitialSize];
+                m_iEndLines = new int[InitialSize];
+                m_iEndColumns = new int[InitialSize];
+            }
+            else if (m_iLineNumberCount == m_iOffsets.Length)
+            {
+                // the arrays are full. Enlarge the arrays
+                // It would probably be simpler to just use Lists here
+                int newSize = checked(m_iLineNumberCount * 2);
+                int[] temp = new int[newSize];
+                Array.Copy(m_iOffsets, 0, temp, 0, m_iLineNumberCount);
+                m_iOffsets = temp;
+
+                temp = new int[newSize];
+                Array.Copy(m_iLines, 0, temp, 0, m_iLineNumberCount);
+                m_iLines = temp;
+
+                temp = new int[newSize];
+                Array.Copy(m_iColumns, 0, temp, 0, m_iLineNumberCount);
+                m_iColumns = temp;
+
+                temp = new int[newSize];
+                Array.Copy(m_iEndLines, 0, temp, 0, m_iLineNumberCount);
+                m_iEndLines = temp;
+
+                temp = new int[newSize];
+                Array.Copy(m_iEndColumns, 0, temp, 0, m_iLineNumberCount);
+                m_iEndColumns = temp;
+            }
+        }
+
+        internal void EmitLineNumberInfo(ISymbolWriter symWriter)
+        {
+            int[] iOffsetsTemp;
+            int[] iLinesTemp;
+            int[] iColumnsTemp;
+            int[] iEndLinesTemp;
+            int[] iEndColumnsTemp;
+
+            if (m_iLineNumberCount == 0)
+                return;
+            // reduce the array size to be exact
+            iOffsetsTemp = new int[m_iLineNumberCount];
+            Array.Copy(m_iOffsets, 0, iOffsetsTemp, 0, m_iLineNumberCount);
+
+            iLinesTemp = new int[m_iLineNumberCount];
+            Array.Copy(m_iLines, 0, iLinesTemp, 0, m_iLineNumberCount);
+
+            iColumnsTemp = new int[m_iLineNumberCount];
+            Array.Copy(m_iColumns, 0, iColumnsTemp, 0, m_iLineNumberCount);
+
+            iEndLinesTemp = new int[m_iLineNumberCount];
+            Array.Copy(m_iEndLines, 0, iEndLinesTemp, 0, m_iLineNumberCount);
+
+            iEndColumnsTemp = new int[m_iLineNumberCount];
+            Array.Copy(m_iEndColumns, 0, iEndColumnsTemp, 0, m_iLineNumberCount);
+
+            symWriter.DefineSequencePoints(m_document, iOffsetsTemp, iLinesTemp, iColumnsTemp, iEndLinesTemp, iEndColumnsTemp);
+        }
+
+        private int[] m_iOffsets;                 // array of offsets
+        private int[] m_iLines;                   // array of offsets
+        private int[] m_iColumns;                 // array of offsets
+        private int[] m_iEndLines;                // array of offsets
+        private int[] m_iEndColumns;              // array of offsets
+        internal ISymbolDocumentWriter m_document;       // The ISymbolDocumentWriter that this REDocument is tracking.
+        private int m_iLineNumberCount;         // how many entries in the arrays are occupied
+        private const int InitialSize = 16;
+    }       // end of REDocument
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/ISymWrapperCore.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/ISymWrapperCore.cs
new file mode 100644
index 0000000000..cda651c9ce
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/ISymWrapperCore.cs
@@ -0,0 +1,539 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Security;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Diagnostics.SymbolStore;
+
+namespace System.Reflection.Emit
+{
+    //-----------------------------------------------------------------------------------
+    // On Telesto, we don't ship the ISymWrapper.dll assembly. However, ReflectionEmit
+    // relies on that assembly to write out managed PDBs.
+    //
+    // This file implements the minimum subset of ISymWrapper.dll required to restore
+    // that functionality. Namely, the SymWriter and SymDocumentWriter objects.
+    // 
+    // Ideally we wouldn't need ISymWrapper.dll on desktop either - it's an ugly piece
+    // of legacy.  We could just use this (or COM-interop code) everywhere, but we might
+    // have to worry about compatibility.
+    // 
+    // We've now got a real implementation even when no debugger is attached.  It's
+    // up to the runtime to ensure it doesn't provide us with an insecure writer 
+    // (eg. diasymreader) in the no-trust scenarios (no debugger, partial-trust code).
+    //-----------------------------------------------------------------------------------
+
+
+    //------------------------------------------------------------------------------
+    // SymWrapperCore is never instantiated and is used as an encapsulation class.
+    // It is our "ISymWrapper.dll" assembly within an assembly.
+    //------------------------------------------------------------------------------
+    internal class SymWrapperCore
+    {
+        //------------------------------------------------------------------------------
+        // Block instantiation
+        //------------------------------------------------------------------------------
+        private SymWrapperCore()
+        {
+        }
+
+        //------------------------------------------------------------------------------
+        // Implements Telesto's version of SymDocumentWriter (in the desktop world,
+        // this type is exposed from ISymWrapper.dll.)
+        //
+        // The only thing user code can do with this wrapper is to receive it from
+        // SymWriter.DefineDocument and pass it back to SymWriter.DefineSequencePoints.
+        //------------------------------------------------------------------------------
+        private unsafe class SymDocumentWriter : ISymbolDocumentWriter
+        {
+            //------------------------------------------------------------------------------
+            // Ctor
+            //------------------------------------------------------------------------------
+            internal SymDocumentWriter(PunkSafeHandle pDocumentWriterSafeHandle)
+            {
+                m_pDocumentWriterSafeHandle = pDocumentWriterSafeHandle;
+                // The handle is actually a pointer to a native ISymUnmanagedDocumentWriter.
+                m_pDocWriter = (ISymUnmanagedDocumentWriter*)m_pDocumentWriterSafeHandle.DangerousGetHandle();
+                m_vtable = (ISymUnmanagedDocumentWriterVTable)(Marshal.PtrToStructure(m_pDocWriter->m_unmanagedVTable, typeof(ISymUnmanagedDocumentWriterVTable)));
+            }
+
+            //------------------------------------------------------------------------------
+            // Returns the underlying ISymUnmanagedDocumentWriter* (as a safehandle.)
+            //------------------------------------------------------------------------------
+            internal PunkSafeHandle GetUnmanaged()
+            {
+                return m_pDocumentWriterSafeHandle;
+            }
+
+
+            //=========================================================================================
+            // Public interface methods start here. (Well actually, they're all NotSupported
+            // stubs since that's what they are on the real ISymWrapper.dll.)
+            //=========================================================================================
+
+            //------------------------------------------------------------------------------
+            // SetSource() wrapper
+            //------------------------------------------------------------------------------
+            void ISymbolDocumentWriter.SetSource(byte[] source)
+            {
+                throw new NotSupportedException();   // Intentionally not supported to match desktop CLR
+            }
+
+            //------------------------------------------------------------------------------
+            // SetCheckSum() wrapper
+            //------------------------------------------------------------------------------
+            void ISymbolDocumentWriter.SetCheckSum(Guid algorithmId, byte[] checkSum)
+            {
+                int hr = m_vtable.SetCheckSum(m_pDocWriter, algorithmId, (uint)checkSum.Length, checkSum);
+                if (hr < 0)
+                {
+                    throw Marshal.GetExceptionForHR(hr);
+                }
+            }
+
+            private delegate int DSetCheckSum(ISymUnmanagedDocumentWriter* pThis, Guid algorithmId, uint checkSumSize, [In] byte[] checkSum);
+
+            //------------------------------------------------------------------------------
+            // This layout must match the unmanaged ISymUnmanagedDocumentWriter* COM vtable
+            // exactly. If a member is declared as an IntPtr rather than a delegate, it means
+            // we don't call that particular member.
+            //------------------------------------------------------------------------------
+            [StructLayout(LayoutKind.Sequential)]
+            private struct ISymUnmanagedDocumentWriterVTable
+            {
+                internal IntPtr QueryInterface;
+                internal IntPtr AddRef;
+                internal IntPtr Release;
+
+                internal IntPtr SetSource;
+                internal DSetCheckSum SetCheckSum;
+            }
+
+            //------------------------------------------------------------------------------
+            // This layout must match the (start) of the unmanaged ISymUnmanagedDocumentWriter
+            // COM object.
+            //------------------------------------------------------------------------------
+            [StructLayout(LayoutKind.Sequential)]
+            private struct ISymUnmanagedDocumentWriter
+            {
+                internal IntPtr m_unmanagedVTable;
+            }
+
+            //------------------------------------------------------------------------------
+            // Stores underlying ISymUnmanagedDocumentWriter* pointer (wrapped in a safehandle.)
+            //------------------------------------------------------------------------------
+            private PunkSafeHandle m_pDocumentWriterSafeHandle;
+
+            private ISymUnmanagedDocumentWriter* m_pDocWriter;
+
+            //------------------------------------------------------------------------------
+            // Stores the "managed vtable" (actually a structure full of delegates that
+            // P/Invoke to the corresponding unmanaged COM methods.)
+            //------------------------------------------------------------------------------
+            private ISymUnmanagedDocumentWriterVTable m_vtable;
+        } // class SymDocumentWriter
+
+
+        //------------------------------------------------------------------------------
+        // Implements Telesto's version of SymWriter (in the desktop world,
+        // this type is expored from ISymWrapper.dll.)
+        //------------------------------------------------------------------------------
+        internal unsafe class SymWriter : ISymbolWriter
+        {
+            //------------------------------------------------------------------------------
+            // Creates a SymWriter. The SymWriter is a managed wrapper around the unmanaged 
+            // symbol writer provided by the runtime (ildbsymlib or diasymreader.dll).
+            //------------------------------------------------------------------------------
+            internal static ISymbolWriter CreateSymWriter()
+            {
+                return new SymWriter();
+            }
+
+
+            //------------------------------------------------------------------------------
+            // Basic ctor. You'd think this ctor would take the unmanaged symwriter object as an argument
+            // but to fit in with existing desktop code, the unmanaged writer is passed in 
+            // through a subsequent call to InternalSetUnderlyingWriter
+            //------------------------------------------------------------------------------
+            private SymWriter()
+            {
+            }
+
+            //------------------------------------------------------------------------------
+            // DefineDocument() wrapper
+            //------------------------------------------------------------------------------
+            ISymbolDocumentWriter ISymbolWriter.DefineDocument(String url,
+                                                               Guid language,
+                                                               Guid languageVendor,
+                                                               Guid documentType)
+            {
+                PunkSafeHandle psymUnmanagedDocumentWriter = new PunkSafeHandle();
+
+                int hr = m_vtable.DefineDocument(m_pWriter, url, ref language, ref languageVendor, ref documentType, out psymUnmanagedDocumentWriter);
+                if (hr < 0)
+                {
+                    throw Marshal.GetExceptionForHR(hr);
+                }
+                if (psymUnmanagedDocumentWriter.IsInvalid)
+                {
+                    return null;
+                }
+                return new SymDocumentWriter(psymUnmanagedDocumentWriter);
+            }
+
+            //------------------------------------------------------------------------------
+            // OpenMethod() wrapper
+            //------------------------------------------------------------------------------
+            void ISymbolWriter.OpenMethod(SymbolToken method)
+            {
+                int hr = m_vtable.OpenMethod(m_pWriter, method.GetToken());
+                if (hr < 0)
+                {
+                    throw Marshal.GetExceptionForHR(hr);
+                }
+            }
+
+            //------------------------------------------------------------------------------
+            // CloseMethod() wrapper
+            //------------------------------------------------------------------------------
+            void ISymbolWriter.CloseMethod()
+            {
+                int hr = m_vtable.CloseMethod(m_pWriter);
+                if (hr < 0)
+                {
+                    throw Marshal.GetExceptionForHR(hr);
+                }
+            }
+
+            //------------------------------------------------------------------------------
+            // DefineSequencePoints() wrapper
+            //------------------------------------------------------------------------------
+            void ISymbolWriter.DefineSequencePoints(ISymbolDocumentWriter document,
+                                                    int[] offsets,
+                                                    int[] lines,
+                                                    int[] columns,
+                                                    int[] endLines,
+                                                    int[] endColumns)
+            {
+                int spCount = 0;
+                if (offsets != null)
+                {
+                    spCount = offsets.Length;
+                }
+                else if (lines != null)
+                {
+                    spCount = lines.Length;
+                }
+                else if (columns != null)
+                {
+                    spCount = columns.Length;
+                }
+                else if (endLines != null)
+                {
+                    spCount = endLines.Length;
+                }
+                else if (endColumns != null)
+                {
+                    spCount = endColumns.Length;
+                }
+                if (spCount == 0)
+                {
+                    return;
+                }
+                if ((offsets != null && offsets.Length != spCount) ||
+                     (lines != null && lines.Length != spCount) ||
+                     (columns != null && columns.Length != spCount) ||
+                     (endLines != null && endLines.Length != spCount) ||
+                     (endColumns != null && endColumns.Length != spCount))
+                {
+                    throw new ArgumentException();
+                }
+
+                // Sure, claim to accept any type that implements ISymbolDocumentWriter but the only one that actually
+                // works is the one returned by DefineDocument. The desktop ISymWrapper commits the same signature fraud.
+                // Ideally we'd just return a sealed opaque cookie type, which had an internal accessor to
+                // get the writer out.
+                // Regardless, this cast is important for security - we cannot allow our caller to provide
+                // arbitrary instances of this interface.
+                SymDocumentWriter docwriter = (SymDocumentWriter)document;
+                int hr = m_vtable.DefineSequencePoints(m_pWriter, docwriter.GetUnmanaged(), spCount, offsets, lines, columns, endLines, endColumns);
+                if (hr < 0)
+                {
+                    throw Marshal.GetExceptionForHR(hr);
+                }
+            }
+
+            //------------------------------------------------------------------------------
+            // OpenScope() wrapper
+            //------------------------------------------------------------------------------
+            int ISymbolWriter.OpenScope(int startOffset)
+            {
+                int ret;
+                int hr = m_vtable.OpenScope(m_pWriter, startOffset, out ret);
+                if (hr < 0)
+                {
+                    throw Marshal.GetExceptionForHR(hr);
+                }
+                return ret;
+            }
+
+            //------------------------------------------------------------------------------
+            // CloseScope() wrapper
+            //------------------------------------------------------------------------------
+            void ISymbolWriter.CloseScope(int endOffset)
+            {
+                int hr = m_vtable.CloseScope(m_pWriter, endOffset);
+                if (hr < 0)
+                {
+                    throw Marshal.GetExceptionForHR(hr);
+                }
+            }
+
+            //------------------------------------------------------------------------------
+            // DefineLocalVariable() wrapper
+            //------------------------------------------------------------------------------
+            void ISymbolWriter.DefineLocalVariable(String name,
+                                                   FieldAttributes attributes,
+                                                   byte[] signature,
+                                                   SymAddressKind addrKind,
+                                                   int addr1,
+                                                   int addr2,
+                                                   int addr3,
+                                                   int startOffset,
+                                                   int endOffset)
+            {
+                int hr = m_vtable.DefineLocalVariable(m_pWriter,
+                                                      name,
+                                                      (int)attributes,
+                                                      signature.Length,
+                                                      signature,
+                                                      (int)addrKind,
+                                                      addr1,
+                                                      addr2,
+                                                      addr3,
+                                                      startOffset,
+                                                      endOffset);
+                if (hr < 0)
+                {
+                    throw Marshal.GetExceptionForHR(hr);
+                }
+            }
+
+            //------------------------------------------------------------------------------
+            // SetSymAttribute() wrapper
+            //------------------------------------------------------------------------------
+            void ISymbolWriter.SetSymAttribute(SymbolToken parent, String name, byte[] data)
+            {
+                int hr = m_vtable.SetSymAttribute(m_pWriter, parent.GetToken(), name, data.Length, data);
+                if (hr < 0)
+                {
+                    throw Marshal.GetExceptionForHR(hr);
+                }
+            }
+
+            //------------------------------------------------------------------------------
+            // UsingNamespace() wrapper
+            //------------------------------------------------------------------------------
+            void ISymbolWriter.UsingNamespace(String name)
+            {
+                int hr = m_vtable.UsingNamespace(m_pWriter, name);
+                if (hr < 0)
+                {
+                    throw Marshal.GetExceptionForHR(hr);
+                }
+            }
+
+            //------------------------------------------------------------------------------
+            // InternalSetUnderlyingWriter() wrapper.
+            //
+            // Furnishes the native ISymUnmanagedWriter* pointer. 
+            //
+            // The parameter is actually a pointer to a pointer to an ISymUnmanagedWriter. As
+            // with the real ISymWrapper.dll, ISymWrapper performs *no* Release (or AddRef) on pointers
+            // furnished through SetUnderlyingWriter. Lifetime management is entirely up to the caller.
+            //------------------------------------------------------------------------------
+            internal void InternalSetUnderlyingWriter(IntPtr ppUnderlyingWriter)
+            {
+                m_pWriter = *((ISymUnmanagedWriter**)ppUnderlyingWriter);
+                m_vtable = (ISymUnmanagedWriterVTable)(Marshal.PtrToStructure(m_pWriter->m_unmanagedVTable, typeof(ISymUnmanagedWriterVTable)));
+            }
+
+            //------------------------------------------------------------------------------
+            // Define delegates for the unmanaged COM methods we invoke.
+            //------------------------------------------------------------------------------
+            private delegate int DInitialize(ISymUnmanagedWriter* pthis,
+                                             IntPtr emitter,  //IUnknown*
+                                             [MarshalAs(UnmanagedType.LPWStr)] String filename, //WCHAR*
+                                             IntPtr pIStream, //IStream*
+                                             [MarshalAs(UnmanagedType.Bool)] bool fFullBuild
+                                             );
+
+            private delegate int DDefineDocument(ISymUnmanagedWriter* pthis,
+                                                 [MarshalAs(UnmanagedType.LPWStr)] String url,
+                                                 [In] ref Guid language,
+                                                 [In] ref Guid languageVender,
+                                                 [In] ref Guid documentType,
+                                                 [Out] out PunkSafeHandle ppsymUnmanagedDocumentWriter
+                                                );
+
+            private delegate int DSetUserEntryPoint(ISymUnmanagedWriter* pthis, int entryMethod);
+            private delegate int DOpenMethod(ISymUnmanagedWriter* pthis, int entryMethod);
+            private delegate int DCloseMethod(ISymUnmanagedWriter* pthis);
+
+            private delegate int DDefineSequencePoints(ISymUnmanagedWriter* pthis,
+                                                       PunkSafeHandle document,
+                                                       int spCount,
+                                                       [In] int[] offsets,
+                                                       [In] int[] lines,
+                                                       [In] int[] columns,
+                                                       [In] int[] endLines,
+                                                       [In] int[] endColumns);
+
+            private delegate int DOpenScope(ISymUnmanagedWriter* pthis, int startOffset, [Out] out int pretval);
+            private delegate int DCloseScope(ISymUnmanagedWriter* pthis, int endOffset);
+
+            private delegate int DSetScopeRange(ISymUnmanagedWriter* pthis, int scopeID, int startOffset, int endOffset);
+
+            private delegate int DDefineLocalVariable(ISymUnmanagedWriter* pthis,
+                                                      [MarshalAs(UnmanagedType.LPWStr)] String name,
+                                                      int attributes,
+                                                      int cSig,
+                                                      [In] byte[] signature,
+                                                      int addrKind,
+                                                      int addr1,
+                                                      int addr2,
+                                                      int addr3,
+                                                      int startOffset,
+                                                      int endOffset
+                                                     );
+
+            private delegate int DClose(ISymUnmanagedWriter* pthis);
+
+            private delegate int DSetSymAttribute(ISymUnmanagedWriter* pthis,
+                                                  int parent,
+                                                  [MarshalAs(UnmanagedType.LPWStr)] String name,
+                                                  int cData,
+                                                  [In] byte[] data
+                                                 );
+
+
+            private delegate int DOpenNamespace(ISymUnmanagedWriter* pthis, [MarshalAs(UnmanagedType.LPWStr)] String name);
+            private delegate int DCloseNamespace(ISymUnmanagedWriter* pthis);
+            private delegate int DUsingNamespace(ISymUnmanagedWriter* pthis, [MarshalAs(UnmanagedType.LPWStr)] String name);
+
+
+
+            //------------------------------------------------------------------------------
+            // This layout must match the unmanaged ISymUnmanagedWriter* COM vtable
+            // exactly. If a member is declared as an IntPtr rather than a delegate, it means
+            // we don't call that particular member.
+            //------------------------------------------------------------------------------
+            [StructLayout(LayoutKind.Sequential)]
+            private struct ISymUnmanagedWriterVTable
+            {
+                internal IntPtr QueryInterface;
+                internal IntPtr AddRef;
+                internal IntPtr Release;
+
+                internal DDefineDocument DefineDocument;
+                internal DSetUserEntryPoint SetUserEntryPoint;
+
+                internal DOpenMethod OpenMethod;
+                internal DCloseMethod CloseMethod;
+
+                internal DOpenScope OpenScope;
+                internal DCloseScope CloseScope;
+
+                internal DSetScopeRange SetScopeRange;
+
+                internal DDefineLocalVariable DefineLocalVariable;
+                internal IntPtr DefineParameter;
+                internal IntPtr DefineField;
+                internal IntPtr DefineGlobalVariable;
+
+                internal DClose Close;
+                internal DSetSymAttribute SetSymAttribute;
+
+                internal DOpenNamespace OpenNamespace;
+                internal DCloseNamespace CloseNamespace;
+                internal DUsingNamespace UsingNamespace;
+
+                internal IntPtr SetMethodSourceRange;
+                internal DInitialize Initialize;
+                internal IntPtr GetDebugInfo;
+                internal DDefineSequencePoints DefineSequencePoints;
+            }
+
+            //------------------------------------------------------------------------------
+            // This layout must match the (start) of the unmanaged ISymUnmanagedWriter
+            // COM object.
+            //------------------------------------------------------------------------------
+            [StructLayout(LayoutKind.Sequential)]
+            private struct ISymUnmanagedWriter
+            {
+                internal IntPtr m_unmanagedVTable;
+            }
+
+            //------------------------------------------------------------------------------
+            // Stores native ISymUnmanagedWriter* pointer.
+            //
+            // As with the real ISymWrapper.dll, ISymWrapper performs *no* Release (or AddRef) on this pointer.
+            // Managing lifetime is up to the caller (coreclr.dll).
+            //------------------------------------------------------------------------------
+            private ISymUnmanagedWriter* m_pWriter;
+
+            //------------------------------------------------------------------------------
+            // Stores the "managed vtable" (actually a structure full of delegates that
+            // P/Invoke to the corresponding unmanaged COM methods.)
+            //------------------------------------------------------------------------------
+            private ISymUnmanagedWriterVTable m_vtable;
+        } // class SymWriter
+    } //class SymWrapperCore
+
+
+
+    //--------------------------------------------------------------------------------------
+    // SafeHandle for RAW MTA IUnknown's.
+    //
+    // ! Because the Release occurs in the finalizer thread, this safehandle really takes
+    // ! an ostrich approach to apartment issues. We only tolerate this here because we're emulating
+    // ! the desktop CLR's use of ISymWrapper which also pays lip service to COM apartment rules.
+    // !
+    // ! However, think twice about pulling this safehandle out for other uses.
+    //
+    // Had to make this a non-nested class since FCall's don't like to bind to nested classes.
+    //--------------------------------------------------------------------------------------
+    internal sealed class PunkSafeHandle : SafeHandle
+    {
+        internal PunkSafeHandle()
+            : base((IntPtr)0, true)
+        {
+        }
+
+        override protected bool ReleaseHandle()
+        {
+            m_Release(handle);
+            return true;
+        }
+
+        public override bool IsInvalid
+        {
+            get { return handle == ((IntPtr)0); }
+        }
+
+        private delegate void DRelease(IntPtr punk);         // Delegate type for P/Invoking to coreclr.dll and doing an IUnknown::Release()
+        private static DRelease m_Release;
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern IntPtr nGetDReleaseTarget();     // FCall gets us the native DRelease target (so we don't need named dllexport from coreclr.dll)
+
+        static PunkSafeHandle()
+        {
+            m_Release = (DRelease)(Marshal.GetDelegateForFunctionPointer(nGetDReleaseTarget(), typeof(DRelease)));
+            m_Release((IntPtr)0); // make one call to make sure the delegate is fully prepped before we're in the critical finalizer situation.
+        }
+    } // PunkSafeHandle
+} //namespace System.Reflection.Emit
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/Label.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/Label.cs
new file mode 100644
index 0000000000..d67c0e6a19
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/Label.cs
@@ -0,0 +1,75 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**  
+**
+** Purpose: Represents a Label to the ILGenerator class.
+**
+** 
+===========================================================*/
+
+using System;
+using System.Reflection;
+using System.Runtime.InteropServices;
+
+namespace System.Reflection.Emit
+{
+    // The Label class is an opaque representation of a label used by the 
+    // ILGenerator class.  The token is used to mark where labels occur in the IL
+    // stream and then the necessary offsets are put back in the code when the ILGenerator 
+    // is passed to the MethodWriter.
+    // Labels are created by using ILGenerator.CreateLabel and their position is set
+    // by using ILGenerator.MarkLabel.
+    public struct Label
+    {
+        internal int m_label;
+
+        //public Label() {
+        //    m_label=0;
+        //}
+
+        internal Label(int label)
+        {
+            m_label = label;
+        }
+
+        internal int GetLabelValue()
+        {
+            return m_label;
+        }
+
+        public override int GetHashCode()
+        {
+            return m_label;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (obj is Label)
+                return Equals((Label)obj);
+            else
+                return false;
+        }
+
+        public bool Equals(Label obj)
+        {
+            return obj.m_label == m_label;
+        }
+
+        public static bool operator ==(Label a, Label b)
+        {
+            return a.Equals(b);
+        }
+
+        public static bool operator !=(Label a, Label b)
+        {
+            return !(a == b);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/LocalBuilder.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/LocalBuilder.cs
new file mode 100644
index 0000000000..1e07f3a4e0
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/LocalBuilder.cs
@@ -0,0 +1,124 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Reflection;
+using System.Runtime.InteropServices;
+
+namespace System.Reflection.Emit
+{
+    public sealed class LocalBuilder : LocalVariableInfo
+    {
+        #region Private Data Members
+        private int m_localIndex;
+        private Type m_localType;
+        private MethodInfo m_methodBuilder;
+        private bool m_isPinned;
+        #endregion
+
+        #region Constructor
+        internal LocalBuilder(int localIndex, Type localType, MethodInfo methodBuilder)
+            : this(localIndex, localType, methodBuilder, false) { }
+        internal LocalBuilder(int localIndex, Type localType, MethodInfo methodBuilder, bool isPinned)
+        {
+            m_isPinned = isPinned;
+            m_localIndex = localIndex;
+            m_localType = localType;
+            m_methodBuilder = methodBuilder;
+        }
+        #endregion
+
+        #region Internal Members
+        internal int GetLocalIndex()
+        {
+            return m_localIndex;
+        }
+        internal MethodInfo GetMethodBuilder()
+        {
+            return m_methodBuilder;
+        }
+        #endregion
+
+        #region LocalVariableInfo Override
+        public override bool IsPinned { get { return m_isPinned; } }
+        public override Type LocalType
+        {
+            get
+            {
+                return m_localType;
+            }
+        }
+        public override int LocalIndex { get { return m_localIndex; } }
+        #endregion
+
+        #region Public Members
+        public void SetLocalSymInfo(String name)
+        {
+            SetLocalSymInfo(name, 0, 0);
+        }
+
+        public void SetLocalSymInfo(String name, int startOffset, int endOffset)
+        {
+            ModuleBuilder dynMod;
+            SignatureHelper sigHelp;
+            int sigLength;
+            byte[] signature;
+            byte[] mungedSig;
+            int index;
+
+            MethodBuilder methodBuilder = m_methodBuilder as MethodBuilder;
+            if (methodBuilder == null)
+                // it's a light code gen entity
+                throw new NotSupportedException();
+            dynMod = (ModuleBuilder)methodBuilder.Module;
+            if (methodBuilder.IsTypeCreated())
+            {
+                // cannot change method after its containing type has been created
+                throw new InvalidOperationException(SR.InvalidOperation_TypeHasBeenCreated);
+            }
+
+            // set the name and range of offset for the local
+            if (dynMod.GetSymWriter() == null)
+            {
+                // cannot set local name if not debug module
+                throw new InvalidOperationException(SR.InvalidOperation_NotADebugModule);
+            }
+
+            sigHelp = SignatureHelper.GetFieldSigHelper(dynMod);
+            sigHelp.AddArgument(m_localType);
+            signature = sigHelp.InternalGetSignature(out sigLength);
+
+            // The symbol store doesn't want the calling convention on the
+            // front of the signature, but InternalGetSignature returns
+            // the callinging convention. So we strip it off. This is a
+            // bit unfortunate, since it means that we need to allocate
+            // yet another array of bytes...  
+            mungedSig = new byte[sigLength - 1];
+            Buffer.BlockCopy(signature, 1, mungedSig, 0, sigLength - 1);
+
+            index = methodBuilder.GetILGenerator().m_ScopeTree.GetCurrentActiveScopeIndex();
+            if (index == -1)
+            {
+                // top level scope information is kept with methodBuilder
+                methodBuilder.m_localSymInfo.AddLocalSymInfo(
+                     name,
+                     mungedSig,
+                     m_localIndex,
+                     startOffset,
+                     endOffset);
+            }
+            else
+            {
+                methodBuilder.GetILGenerator().m_ScopeTree.AddLocalSymInfoToCurrentScope(
+                     name,
+                     mungedSig,
+                     m_localIndex,
+                     startOffset,
+                     endOffset);
+            }
+        }
+        #endregion
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/MethodBuilder.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/MethodBuilder.cs
new file mode 100644
index 0000000000..70b5b66d65
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/MethodBuilder.cs
@@ -0,0 +1,1203 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+namespace System.Reflection.Emit
+{
+    using System.Text;
+    using System;
+    using CultureInfo = System.Globalization.CultureInfo;
+    using System.Diagnostics.SymbolStore;
+    using System.Reflection;
+    using System.Security;
+    using System.Collections;
+    using System.Collections.Generic;
+    using System.Runtime.InteropServices;
+    using System.Diagnostics;
+
+    public sealed class MethodBuilder : MethodInfo
+    {
+        #region Private Data Members
+        // Identity
+        internal String m_strName; // The name of the method
+        private MethodToken m_tkMethod; // The token of this method
+        private ModuleBuilder m_module;
+        internal TypeBuilder m_containingType;
+
+        // IL
+        private int[] m_mdMethodFixups;              // The location of all of the token fixups. Null means no fixups.
+        private byte[] m_localSignature;             // Local signature if set explicitly via DefineBody. Null otherwise.
+        internal LocalSymInfo m_localSymInfo;        // keep track debugging local information
+        internal ILGenerator m_ilGenerator;          // Null if not used.
+        private byte[] m_ubBody;                     // The IL for the method
+        private ExceptionHandler[] m_exceptions; // Exception handlers or null if there are none.
+        private const int DefaultMaxStack = 16;
+        private int m_maxStack = DefaultMaxStack;
+
+        // Flags
+        internal bool m_bIsBaked;
+        private bool m_bIsGlobalMethod;
+        private bool m_fInitLocals; // indicating if the method stack frame will be zero initialized or not.
+
+        // Attributes
+        private MethodAttributes m_iAttributes;
+        private CallingConventions m_callingConvention;
+        private MethodImplAttributes m_dwMethodImplFlags;
+
+        // Parameters
+        private SignatureHelper m_signature;
+        internal Type[] m_parameterTypes;
+        private Type m_returnType;
+        private Type[] m_returnTypeRequiredCustomModifiers;
+        private Type[] m_returnTypeOptionalCustomModifiers;
+        private Type[][] m_parameterTypeRequiredCustomModifiers;
+        private Type[][] m_parameterTypeOptionalCustomModifiers;
+
+        // Generics
+        private GenericTypeParameterBuilder[] m_inst;
+        private bool m_bIsGenMethDef;
+        #endregion
+
+        #region Constructor
+
+        internal MethodBuilder(String name, MethodAttributes attributes, CallingConventions callingConvention,
+            Type returnType, Type[] returnTypeRequiredCustomModifiers, Type[] returnTypeOptionalCustomModifiers,
+            Type[] parameterTypes, Type[][] parameterTypeRequiredCustomModifiers, Type[][] parameterTypeOptionalCustomModifiers,
+            ModuleBuilder mod, TypeBuilder type, bool bIsGlobalMethod)
+        {
+            Init(name, attributes, callingConvention,
+                returnType, returnTypeRequiredCustomModifiers, returnTypeOptionalCustomModifiers,
+                parameterTypes, parameterTypeRequiredCustomModifiers, parameterTypeOptionalCustomModifiers,
+                mod, type, bIsGlobalMethod);
+        }
+
+        private void Init(String name, MethodAttributes attributes, CallingConventions callingConvention,
+            Type returnType, Type[] returnTypeRequiredCustomModifiers, Type[] returnTypeOptionalCustomModifiers,
+            Type[] parameterTypes, Type[][] parameterTypeRequiredCustomModifiers, Type[][] parameterTypeOptionalCustomModifiers,
+            ModuleBuilder mod, TypeBuilder type, bool bIsGlobalMethod)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            if (name.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(name));
+
+            if (name[0] == '\0')
+                throw new ArgumentException(SR.Argument_IllegalName, nameof(name));
+
+            if (mod == null)
+                throw new ArgumentNullException(nameof(mod));
+
+            if (parameterTypes != null)
+            {
+                foreach (Type t in parameterTypes)
+                {
+                    if (t == null)
+                        throw new ArgumentNullException(nameof(parameterTypes));
+                }
+            }
+
+            m_strName = name;
+            m_module = mod;
+            m_containingType = type;
+
+            // 
+            //if (returnType == null)
+            //{
+            //    m_returnType = typeof(void);
+            //}
+            //else
+            {
+                m_returnType = returnType;
+            }
+
+            if ((attributes & MethodAttributes.Static) == 0)
+            {
+                // turn on the has this calling convention
+                callingConvention = callingConvention | CallingConventions.HasThis;
+            }
+            else if ((attributes & MethodAttributes.Virtual) != 0)
+            {
+                // A method can't be both static and virtual
+                throw new ArgumentException(SR.Arg_NoStaticVirtual);
+            }
+
+#if !FEATURE_DEFAULT_INTERFACES
+            if ((attributes & MethodAttributes.SpecialName) != MethodAttributes.SpecialName)
+            {
+                if ((type.Attributes & TypeAttributes.Interface) == TypeAttributes.Interface)
+                {
+                    // methods on interface have to be abstract + virtual except special name methods such as type initializer
+                    if ((attributes & (MethodAttributes.Abstract | MethodAttributes.Virtual)) !=
+                        (MethodAttributes.Abstract | MethodAttributes.Virtual) &&
+                        (attributes & MethodAttributes.Static) == 0)
+                        throw new ArgumentException(SR.Argument_BadAttributeOnInterfaceMethod);
+                }
+            }
+#endif
+
+            m_callingConvention = callingConvention;
+
+            if (parameterTypes != null)
+            {
+                m_parameterTypes = new Type[parameterTypes.Length];
+                Array.Copy(parameterTypes, 0, m_parameterTypes, 0, parameterTypes.Length);
+            }
+            else
+            {
+                m_parameterTypes = null;
+            }
+
+            m_returnTypeRequiredCustomModifiers = returnTypeRequiredCustomModifiers;
+            m_returnTypeOptionalCustomModifiers = returnTypeOptionalCustomModifiers;
+            m_parameterTypeRequiredCustomModifiers = parameterTypeRequiredCustomModifiers;
+            m_parameterTypeOptionalCustomModifiers = parameterTypeOptionalCustomModifiers;
+
+            //            m_signature = SignatureHelper.GetMethodSigHelper(mod, callingConvention, 
+            //                returnType, returnTypeRequiredCustomModifiers, returnTypeOptionalCustomModifiers,
+            //                parameterTypes, parameterTypeRequiredCustomModifiers, parameterTypeOptionalCustomModifiers);
+
+            m_iAttributes = attributes;
+            m_bIsGlobalMethod = bIsGlobalMethod;
+            m_bIsBaked = false;
+            m_fInitLocals = true;
+
+            m_localSymInfo = new LocalSymInfo();
+            m_ubBody = null;
+            m_ilGenerator = null;
+
+            // Default is managed IL. Manged IL has bit flag 0x0020 set off
+            m_dwMethodImplFlags = MethodImplAttributes.IL;
+        }
+
+        #endregion
+
+        #region Internal Members
+
+        internal void CheckContext(params Type[][] typess)
+        {
+            m_module.CheckContext(typess);
+        }
+
+        internal void CheckContext(params Type[] types)
+        {
+            m_module.CheckContext(types);
+        }
+
+        internal void CreateMethodBodyHelper(ILGenerator il)
+        {
+            // Sets the IL of the method.  An ILGenerator is passed as an argument and the method
+            // queries this instance to get all of the information which it needs.
+            if (il == null)
+            {
+                throw new ArgumentNullException(nameof(il));
+            }
+
+            __ExceptionInfo[] excp;
+            int counter = 0;
+            int[] filterAddrs;
+            int[] catchAddrs;
+            int[] catchEndAddrs;
+            Type[] catchClass;
+            int[] type;
+            int numCatch;
+            int start, end;
+            ModuleBuilder dynMod = (ModuleBuilder)m_module;
+
+            m_containingType.ThrowIfCreated();
+
+            if (m_bIsBaked)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_MethodHasBody);
+            }
+
+            if (il.m_methodBuilder != this && il.m_methodBuilder != null)
+            {
+                // you don't need to call DefineBody when you get your ILGenerator
+                // through MethodBuilder::GetILGenerator.
+                //
+
+                throw new InvalidOperationException(SR.InvalidOperation_BadILGeneratorUsage);
+            }
+
+            ThrowIfShouldNotHaveBody();
+
+            if (il.m_ScopeTree.m_iOpenScopeCount != 0)
+            {
+                // There are still unclosed local scope
+                throw new InvalidOperationException(SR.InvalidOperation_OpenLocalVariableScope);
+            }
+
+
+            m_ubBody = il.BakeByteArray();
+
+            m_mdMethodFixups = il.GetTokenFixups();
+
+            //Okay, now the fun part.  Calculate all of the exceptions.
+            excp = il.GetExceptions();
+            int numExceptions = CalculateNumberOfExceptions(excp);
+            if (numExceptions > 0)
+            {
+                m_exceptions = new ExceptionHandler[numExceptions];
+
+                for (int i = 0; i < excp.Length; i++)
+                {
+                    filterAddrs = excp[i].GetFilterAddresses();
+                    catchAddrs = excp[i].GetCatchAddresses();
+                    catchEndAddrs = excp[i].GetCatchEndAddresses();
+                    catchClass = excp[i].GetCatchClass();
+
+                    numCatch = excp[i].GetNumberOfCatches();
+                    start = excp[i].GetStartAddress();
+                    end = excp[i].GetEndAddress();
+                    type = excp[i].GetExceptionTypes();
+                    for (int j = 0; j < numCatch; j++)
+                    {
+                        int tkExceptionClass = 0;
+                        if (catchClass[j] != null)
+                        {
+                            tkExceptionClass = dynMod.GetTypeTokenInternal(catchClass[j]).Token;
+                        }
+
+                        switch (type[j])
+                        {
+                            case __ExceptionInfo.None:
+                            case __ExceptionInfo.Fault:
+                            case __ExceptionInfo.Filter:
+                                m_exceptions[counter++] = new ExceptionHandler(start, end, filterAddrs[j], catchAddrs[j], catchEndAddrs[j], type[j], tkExceptionClass);
+                                break;
+
+                            case __ExceptionInfo.Finally:
+                                m_exceptions[counter++] = new ExceptionHandler(start, excp[i].GetFinallyEndAddress(), filterAddrs[j], catchAddrs[j], catchEndAddrs[j], type[j], tkExceptionClass);
+                                break;
+                        }
+                    }
+                }
+            }
+
+
+            m_bIsBaked = true;
+
+            if (dynMod.GetSymWriter() != null)
+            {
+                // set the debugging information such as scope and line number
+                // if it is in a debug module
+                //
+                SymbolToken tk = new SymbolToken(MetadataTokenInternal);
+                ISymbolWriter symWriter = dynMod.GetSymWriter();
+
+                // call OpenMethod to make this method the current method
+                symWriter.OpenMethod(tk);
+
+                // call OpenScope because OpenMethod no longer implicitly creating
+                // the top-levelsmethod scope
+                //
+                symWriter.OpenScope(0);
+
+                if (m_symCustomAttrs != null)
+                {
+                    foreach (SymCustomAttr symCustomAttr in m_symCustomAttrs)
+                        dynMod.GetSymWriter().SetSymAttribute(
+                        new SymbolToken(MetadataTokenInternal),
+                            symCustomAttr.m_name,
+                            symCustomAttr.m_data);
+                }
+
+                if (m_localSymInfo != null)
+                    m_localSymInfo.EmitLocalSymInfo(symWriter);
+                il.m_ScopeTree.EmitScopeTree(symWriter);
+                il.m_LineNumberInfo.EmitLineNumberInfo(symWriter);
+                symWriter.CloseScope(il.ILOffset);
+                symWriter.CloseMethod();
+            }
+        }
+
+        // This is only called from TypeBuilder.CreateType after the method has been created
+        internal void ReleaseBakedStructures()
+        {
+            if (!m_bIsBaked)
+            {
+                // We don't need to do anything here if we didn't baked the method body
+                return;
+            }
+
+            m_ubBody = null;
+            m_localSymInfo = null;
+            m_mdMethodFixups = null;
+            m_localSignature = null;
+            m_exceptions = null;
+        }
+
+        internal override Type[] GetParameterTypes()
+        {
+            if (m_parameterTypes == null)
+                m_parameterTypes = Array.Empty<Type>();
+
+            return m_parameterTypes;
+        }
+
+        internal static Type GetMethodBaseReturnType(MethodBase method)
+        {
+            MethodInfo mi = null;
+            ConstructorInfo ci = null;
+
+            if ((mi = method as MethodInfo) != null)
+            {
+                return mi.ReturnType;
+            }
+            else if ((ci = method as ConstructorInfo) != null)
+            {
+                return ci.GetReturnType();
+            }
+            else
+            {
+                Debug.Fail("We should never get here!");
+                return null;
+            }
+        }
+
+        internal byte[] GetBody()
+        {
+            // Returns the il bytes of this method.
+            // This il is not valid until somebody has called BakeByteArray
+            return m_ubBody;
+        }
+
+        internal int[] GetTokenFixups()
+        {
+            return m_mdMethodFixups;
+        }
+
+        internal SignatureHelper GetMethodSignature()
+        {
+            if (m_parameterTypes == null)
+                m_parameterTypes = Array.Empty<Type>();
+
+            m_signature = SignatureHelper.GetMethodSigHelper(m_module, m_callingConvention, m_inst != null ? m_inst.Length : 0,
+                m_returnType == null ? typeof(void) : m_returnType, m_returnTypeRequiredCustomModifiers, m_returnTypeOptionalCustomModifiers,
+                m_parameterTypes, m_parameterTypeRequiredCustomModifiers, m_parameterTypeOptionalCustomModifiers);
+
+            return m_signature;
+        }
+
+        // Returns a buffer whose initial signatureLength bytes contain encoded local signature.
+        internal byte[] GetLocalSignature(out int signatureLength)
+        {
+            if (m_localSignature != null)
+            {
+                signatureLength = m_localSignature.Length;
+                return m_localSignature;
+            }
+
+            if (m_ilGenerator != null)
+            {
+                if (m_ilGenerator.m_localCount != 0)
+                {
+                    // If user is using ILGenerator::DeclareLocal, then get local signaturefrom there.
+                    return m_ilGenerator.m_localSignature.InternalGetSignature(out signatureLength);
+                }
+            }
+
+            return SignatureHelper.GetLocalVarSigHelper(m_module).InternalGetSignature(out signatureLength);
+        }
+
+        internal int GetMaxStack()
+        {
+            if (m_ilGenerator != null)
+            {
+                return m_ilGenerator.GetMaxStackSize() + ExceptionHandlerCount;
+            }
+            else
+            {
+                // this is the case when client provide an array of IL byte stream rather than going through ILGenerator.
+                return m_maxStack;
+            }
+        }
+
+        internal ExceptionHandler[] GetExceptionHandlers()
+        {
+            return m_exceptions;
+        }
+
+        internal int ExceptionHandlerCount
+        {
+            get { return m_exceptions != null ? m_exceptions.Length : 0; }
+        }
+
+        internal int CalculateNumberOfExceptions(__ExceptionInfo[] excp)
+        {
+            int num = 0;
+
+            if (excp == null)
+            {
+                return 0;
+            }
+
+            for (int i = 0; i < excp.Length; i++)
+            {
+                num += excp[i].GetNumberOfCatches();
+            }
+
+            return num;
+        }
+
+        internal bool IsTypeCreated()
+        {
+            return (m_containingType != null && m_containingType.IsCreated());
+        }
+
+        internal TypeBuilder GetTypeBuilder()
+        {
+            return m_containingType;
+        }
+
+        internal ModuleBuilder GetModuleBuilder()
+        {
+            return m_module;
+        }
+        #endregion
+
+        #region Object Overrides
+        public override bool Equals(Object obj)
+        {
+            if (!(obj is MethodBuilder))
+            {
+                return false;
+            }
+            if (!(this.m_strName.Equals(((MethodBuilder)obj).m_strName)))
+            {
+                return false;
+            }
+
+            if (m_iAttributes != (((MethodBuilder)obj).m_iAttributes))
+            {
+                return false;
+            }
+
+            SignatureHelper thatSig = ((MethodBuilder)obj).GetMethodSignature();
+            if (thatSig.Equals(GetMethodSignature()))
+            {
+                return true;
+            }
+            return false;
+        }
+
+        public override int GetHashCode()
+        {
+            return this.m_strName.GetHashCode();
+        }
+
+        public override String ToString()
+        {
+            StringBuilder sb = new StringBuilder(1000);
+            sb.Append("Name: " + m_strName + " " + Environment.NewLine);
+            sb.Append("Attributes: " + (int)m_iAttributes + Environment.NewLine);
+            sb.Append("Method Signature: " + GetMethodSignature() + Environment.NewLine);
+            sb.Append(Environment.NewLine);
+            return sb.ToString();
+        }
+
+        #endregion
+
+        #region MemberInfo Overrides
+        public override String Name
+        {
+            get
+            {
+                return m_strName;
+            }
+        }
+
+        internal int MetadataTokenInternal
+        {
+            get
+            {
+                return GetToken().Token;
+            }
+        }
+
+        public override Module Module
+        {
+            get
+            {
+                return m_containingType.Module;
+            }
+        }
+
+        public override Type DeclaringType
+        {
+            get
+            {
+                if (m_containingType.m_isHiddenGlobalType == true)
+                    return null;
+                return m_containingType;
+            }
+        }
+
+        public override ICustomAttributeProvider ReturnTypeCustomAttributes
+        {
+            get
+            {
+                return null;
+            }
+        }
+
+        public override Type ReflectedType
+        {
+            get
+            {
+                return DeclaringType;
+            }
+        }
+
+        #endregion
+
+        #region MethodBase Overrides
+        public override Object Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override MethodImplAttributes GetMethodImplementationFlags()
+        {
+            return m_dwMethodImplFlags;
+        }
+
+        public override MethodAttributes Attributes
+        {
+            get { return m_iAttributes; }
+        }
+
+        public override CallingConventions CallingConvention
+        {
+            get { return m_callingConvention; }
+        }
+
+        public override RuntimeMethodHandle MethodHandle
+        {
+            get { throw new NotSupportedException(SR.NotSupported_DynamicModule); }
+        }
+
+        public override bool IsSecurityCritical
+        {
+            get { return true; }
+        }
+
+        public override bool IsSecuritySafeCritical
+        {
+            get { return false; }
+        }
+
+        public override bool IsSecurityTransparent
+        {
+            get { return false; }
+        }
+        #endregion
+
+        #region MethodInfo Overrides
+        public override MethodInfo GetBaseDefinition()
+        {
+            return this;
+        }
+
+        public override Type ReturnType
+        {
+            get
+            {
+                return m_returnType;
+            }
+        }
+
+        public override ParameterInfo[] GetParameters()
+        {
+            if (!m_bIsBaked || m_containingType == null || m_containingType.BakedRuntimeType == null)
+                throw new NotSupportedException(SR.InvalidOperation_TypeNotCreated);
+
+            MethodInfo rmi = m_containingType.GetMethod(m_strName, m_parameterTypes);
+
+            return rmi.GetParameters();
+        }
+
+        public override ParameterInfo ReturnParameter
+        {
+            get
+            {
+                if (!m_bIsBaked || m_containingType == null || m_containingType.BakedRuntimeType == null)
+                    throw new InvalidOperationException(SR.InvalidOperation_TypeNotCreated);
+
+                MethodInfo rmi = m_containingType.GetMethod(m_strName, m_parameterTypes);
+
+                return rmi.ReturnParameter;
+            }
+        }
+        #endregion
+
+        #region ICustomAttributeProvider Implementation
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        #endregion
+
+        #region Generic Members
+        public override bool IsGenericMethodDefinition { get { return m_bIsGenMethDef; } }
+
+        public override bool ContainsGenericParameters { get { throw new NotSupportedException(); } }
+
+        public override MethodInfo GetGenericMethodDefinition() { if (!IsGenericMethod) throw new InvalidOperationException(); return this; }
+
+        public override bool IsGenericMethod { get { return m_inst != null; } }
+
+        public override Type[] GetGenericArguments() { return m_inst; }
+
+        public override MethodInfo MakeGenericMethod(params Type[] typeArguments)
+        {
+            return MethodBuilderInstantiation.MakeGenericMethod(this, typeArguments);
+        }
+
+
+        public GenericTypeParameterBuilder[] DefineGenericParameters(params string[] names)
+        {
+            if (names == null)
+                throw new ArgumentNullException(nameof(names));
+
+            if (names.Length == 0)
+                throw new ArgumentException(SR.Arg_EmptyArray, nameof(names));
+
+            if (m_inst != null)
+                throw new InvalidOperationException(SR.InvalidOperation_GenericParametersAlreadySet);
+
+            for (int i = 0; i < names.Length; i++)
+                if (names[i] == null)
+                    throw new ArgumentNullException(nameof(names));
+
+            if (m_tkMethod.Token != 0)
+                throw new InvalidOperationException(SR.InvalidOperation_MethodBuilderBaked);
+
+            m_bIsGenMethDef = true;
+            m_inst = new GenericTypeParameterBuilder[names.Length];
+            for (int i = 0; i < names.Length; i++)
+                m_inst[i] = new GenericTypeParameterBuilder(new TypeBuilder(names[i], i, this));
+
+            return m_inst;
+        }
+
+        internal void ThrowIfGeneric() { if (IsGenericMethod && !IsGenericMethodDefinition) throw new InvalidOperationException(); }
+        #endregion
+
+        #region Public Members
+        public MethodToken GetToken()
+        {
+            // We used to always "tokenize" a MethodBuilder when it is constructed. After change list 709498
+            // we only "tokenize" a method when requested. But the order in which the methods are tokenized
+            // didn't change: the same order the MethodBuilders are constructed. The recursion introduced
+            // will overflow the stack when there are many methods on the same type (10000 in my experiment).
+            // The change also introduced race conditions. Before the code change GetToken is called from
+            // the MethodBuilder .ctor which is protected by lock(ModuleBuilder.SyncRoot). Now it
+            // could be called more than once on the the same method introducing duplicate (invalid) tokens.
+            // I don't fully understand this change. So I will keep the logic and only fix the recursion and 
+            // the race condition.
+
+            if (m_tkMethod.Token != 0)
+            {
+                return m_tkMethod;
+            }
+
+            MethodBuilder currentMethod = null;
+            MethodToken currentToken = new MethodToken(0);
+            int i;
+
+            // We need to lock here to prevent a method from being "tokenized" twice.
+            // We don't need to synchronize this with Type.DefineMethod because it only appends newly
+            // constructed MethodBuilders to the end of m_listMethods
+            lock (m_containingType.m_listMethods)
+            {
+                if (m_tkMethod.Token != 0)
+                {
+                    return m_tkMethod;
+                }
+
+                // If m_tkMethod is still 0 when we obtain the lock, m_lastTokenizedMethod must be smaller
+                // than the index of the current method.
+                for (i = m_containingType.m_lastTokenizedMethod + 1; i < m_containingType.m_listMethods.Count; ++i)
+                {
+                    currentMethod = m_containingType.m_listMethods[i];
+                    currentToken = currentMethod.GetTokenNoLock();
+
+                    if (currentMethod == this)
+                        break;
+                }
+
+                m_containingType.m_lastTokenizedMethod = i;
+            }
+
+            Debug.Assert(currentMethod == this, "We should have found this method in m_containingType.m_listMethods");
+            Debug.Assert(currentToken.Token != 0, "The token should not be 0");
+
+            return currentToken;
+        }
+
+        private MethodToken GetTokenNoLock()
+        {
+            Debug.Assert(m_tkMethod.Token == 0, "m_tkMethod should not have been initialized");
+
+            int sigLength;
+            byte[] sigBytes = GetMethodSignature().InternalGetSignature(out sigLength);
+
+            int token = TypeBuilder.DefineMethod(m_module.GetNativeHandle(), m_containingType.MetadataTokenInternal, m_strName, sigBytes, sigLength, Attributes);
+            m_tkMethod = new MethodToken(token);
+
+            if (m_inst != null)
+                foreach (GenericTypeParameterBuilder tb in m_inst)
+                    if (!tb.m_type.IsCreated()) tb.m_type.CreateType();
+
+            TypeBuilder.SetMethodImpl(m_module.GetNativeHandle(), token, m_dwMethodImplFlags);
+
+            return m_tkMethod;
+        }
+
+        public void SetParameters(params Type[] parameterTypes)
+        {
+            CheckContext(parameterTypes);
+
+            SetSignature(null, null, null, parameterTypes, null, null);
+        }
+
+        public void SetReturnType(Type returnType)
+        {
+            CheckContext(returnType);
+
+            SetSignature(returnType, null, null, null, null, null);
+        }
+
+        public void SetSignature(
+            Type returnType, Type[] returnTypeRequiredCustomModifiers, Type[] returnTypeOptionalCustomModifiers,
+            Type[] parameterTypes, Type[][] parameterTypeRequiredCustomModifiers, Type[][] parameterTypeOptionalCustomModifiers)
+        {
+            // We should throw InvalidOperation_MethodBuilderBaked here if the method signature has been baked.
+            // But we cannot because that would be a breaking change from V2.
+            if (m_tkMethod.Token != 0)
+                return;
+
+            CheckContext(returnType);
+            CheckContext(returnTypeRequiredCustomModifiers, returnTypeOptionalCustomModifiers, parameterTypes);
+            CheckContext(parameterTypeRequiredCustomModifiers);
+            CheckContext(parameterTypeOptionalCustomModifiers);
+
+            ThrowIfGeneric();
+
+            if (returnType != null)
+            {
+                m_returnType = returnType;
+            }
+
+            if (parameterTypes != null)
+            {
+                m_parameterTypes = new Type[parameterTypes.Length];
+                Array.Copy(parameterTypes, 0, m_parameterTypes, 0, parameterTypes.Length);
+            }
+
+            m_returnTypeRequiredCustomModifiers = returnTypeRequiredCustomModifiers;
+            m_returnTypeOptionalCustomModifiers = returnTypeOptionalCustomModifiers;
+            m_parameterTypeRequiredCustomModifiers = parameterTypeRequiredCustomModifiers;
+            m_parameterTypeOptionalCustomModifiers = parameterTypeOptionalCustomModifiers;
+        }
+
+
+        public ParameterBuilder DefineParameter(int position, ParameterAttributes attributes, String strParamName)
+        {
+            if (position < 0)
+                throw new ArgumentOutOfRangeException(SR.ArgumentOutOfRange_ParamSequence);
+
+            ThrowIfGeneric();
+            m_containingType.ThrowIfCreated();
+
+            if (position > 0 && (m_parameterTypes == null || position > m_parameterTypes.Length))
+                throw new ArgumentOutOfRangeException(SR.ArgumentOutOfRange_ParamSequence);
+
+            attributes = attributes & ~ParameterAttributes.ReservedMask;
+            return new ParameterBuilder(this, position, attributes, strParamName);
+        }
+
+        private List<SymCustomAttr> m_symCustomAttrs;
+        private struct SymCustomAttr
+        {
+            public String m_name;
+            public byte[] m_data;
+        }
+
+        public void SetImplementationFlags(MethodImplAttributes attributes)
+        {
+            ThrowIfGeneric();
+
+            m_containingType.ThrowIfCreated();
+
+            m_dwMethodImplFlags = attributes;
+
+            m_canBeRuntimeImpl = true;
+
+            TypeBuilder.SetMethodImpl(m_module.GetNativeHandle(), MetadataTokenInternal, attributes);
+        }
+
+        public ILGenerator GetILGenerator()
+        {
+            ThrowIfGeneric();
+            ThrowIfShouldNotHaveBody();
+
+            if (m_ilGenerator == null)
+                m_ilGenerator = new ILGenerator(this);
+            return m_ilGenerator;
+        }
+
+        public ILGenerator GetILGenerator(int size)
+        {
+            ThrowIfGeneric();
+            ThrowIfShouldNotHaveBody();
+
+            if (m_ilGenerator == null)
+                m_ilGenerator = new ILGenerator(this, size);
+            return m_ilGenerator;
+        }
+
+        private void ThrowIfShouldNotHaveBody()
+        {
+            if ((m_dwMethodImplFlags & MethodImplAttributes.CodeTypeMask) != MethodImplAttributes.IL ||
+                (m_dwMethodImplFlags & MethodImplAttributes.Unmanaged) != 0 ||
+                (m_iAttributes & MethodAttributes.PinvokeImpl) != 0 ||
+                m_isDllImport)
+            {
+                // cannot attach method body if methodimpl is marked not marked as managed IL
+                //
+                throw new InvalidOperationException(SR.InvalidOperation_ShouldNotHaveMethodBody);
+            }
+        }
+
+
+        public bool InitLocals
+        {
+            // Property is set to true if user wishes to have zero initialized stack frame for this method. Default to false.
+            get { ThrowIfGeneric(); return m_fInitLocals; }
+            set { ThrowIfGeneric(); m_fInitLocals = value; }
+        }
+
+        public Module GetModule()
+        {
+            return GetModuleBuilder();
+        }
+
+        public String Signature
+        {
+            get
+            {
+                return GetMethodSignature().ToString();
+            }
+        }
+
+
+        public void SetCustomAttribute(ConstructorInfo con, byte[] binaryAttribute)
+        {
+            if (con == null)
+                throw new ArgumentNullException(nameof(con));
+            if (binaryAttribute == null)
+                throw new ArgumentNullException(nameof(binaryAttribute));
+
+            ThrowIfGeneric();
+
+            TypeBuilder.DefineCustomAttribute(m_module, MetadataTokenInternal,
+                ((ModuleBuilder)m_module).GetConstructorToken(con).Token,
+                binaryAttribute,
+                false, false);
+
+            if (IsKnownCA(con))
+                ParseCA(con, binaryAttribute);
+        }
+
+        public void SetCustomAttribute(CustomAttributeBuilder customBuilder)
+        {
+            if (customBuilder == null)
+                throw new ArgumentNullException(nameof(customBuilder));
+
+            ThrowIfGeneric();
+
+            customBuilder.CreateCustomAttribute((ModuleBuilder)m_module, MetadataTokenInternal);
+
+            if (IsKnownCA(customBuilder.m_con))
+                ParseCA(customBuilder.m_con, customBuilder.m_blob);
+        }
+
+        // this method should return true for any and every ca that requires more work
+        // than just setting the ca
+        private bool IsKnownCA(ConstructorInfo con)
+        {
+            Type caType = con.DeclaringType;
+            if (caType == typeof(System.Runtime.CompilerServices.MethodImplAttribute)) return true;
+            else if (caType == typeof(DllImportAttribute)) return true;
+            else return false;
+        }
+
+        private void ParseCA(ConstructorInfo con, byte[] blob)
+        {
+            Type caType = con.DeclaringType;
+            if (caType == typeof(System.Runtime.CompilerServices.MethodImplAttribute))
+            {
+                // dig through the blob looking for the MethodImplAttributes flag
+                // that must be in the MethodCodeType field
+
+                // for now we simply set a flag that relaxes the check when saving and
+                // allows this method to have no body when any kind of MethodImplAttribute is present
+                m_canBeRuntimeImpl = true;
+            }
+            else if (caType == typeof(DllImportAttribute))
+            {
+                m_canBeRuntimeImpl = true;
+                m_isDllImport = true;
+            }
+        }
+
+        internal bool m_canBeRuntimeImpl = false;
+        internal bool m_isDllImport = false;
+
+        #endregion
+    }
+
+    internal class LocalSymInfo
+    {
+        // This class tracks the local variable's debugging information 
+        // and namespace information with a given active lexical scope.
+
+        #region Internal Data Members
+        internal String[] m_strName;
+        internal byte[][] m_ubSignature;
+        internal int[] m_iLocalSlot;
+        internal int[] m_iStartOffset;
+        internal int[] m_iEndOffset;
+        internal int m_iLocalSymCount;         // how many entries in the arrays are occupied
+        internal String[] m_namespace;
+        internal int m_iNameSpaceCount;
+        internal const int InitialSize = 16;
+        #endregion
+
+        #region Constructor
+        internal LocalSymInfo()
+        {
+            // initialize data variables
+            m_iLocalSymCount = 0;
+            m_iNameSpaceCount = 0;
+        }
+        #endregion
+
+        #region Private Members
+        private void EnsureCapacityNamespace()
+        {
+            if (m_iNameSpaceCount == 0)
+            {
+                m_namespace = new String[InitialSize];
+            }
+            else if (m_iNameSpaceCount == m_namespace.Length)
+            {
+                String[] strTemp = new String[checked(m_iNameSpaceCount * 2)];
+                Array.Copy(m_namespace, 0, strTemp, 0, m_iNameSpaceCount);
+                m_namespace = strTemp;
+            }
+        }
+
+        private void EnsureCapacity()
+        {
+            if (m_iLocalSymCount == 0)
+            {
+                // First time. Allocate the arrays.
+                m_strName = new String[InitialSize];
+                m_ubSignature = new byte[InitialSize][];
+                m_iLocalSlot = new int[InitialSize];
+                m_iStartOffset = new int[InitialSize];
+                m_iEndOffset = new int[InitialSize];
+            }
+            else if (m_iLocalSymCount == m_strName.Length)
+            {
+                // the arrays are full. Enlarge the arrays
+                // why aren't we just using lists here?
+                int newSize = checked(m_iLocalSymCount * 2);
+                int[] temp = new int[newSize];
+                Array.Copy(m_iLocalSlot, 0, temp, 0, m_iLocalSymCount);
+                m_iLocalSlot = temp;
+
+                temp = new int[newSize];
+                Array.Copy(m_iStartOffset, 0, temp, 0, m_iLocalSymCount);
+                m_iStartOffset = temp;
+
+                temp = new int[newSize];
+                Array.Copy(m_iEndOffset, 0, temp, 0, m_iLocalSymCount);
+                m_iEndOffset = temp;
+
+                String[] strTemp = new String[newSize];
+                Array.Copy(m_strName, 0, strTemp, 0, m_iLocalSymCount);
+                m_strName = strTemp;
+
+                byte[][] ubTemp = new byte[newSize][];
+                Array.Copy(m_ubSignature, 0, ubTemp, 0, m_iLocalSymCount);
+                m_ubSignature = ubTemp;
+            }
+        }
+
+        #endregion
+
+        #region Internal Members
+        internal void AddLocalSymInfo(String strName, byte[] signature, int slot, int startOffset, int endOffset)
+        {
+            // make sure that arrays are large enough to hold addition info
+            EnsureCapacity();
+            m_iStartOffset[m_iLocalSymCount] = startOffset;
+            m_iEndOffset[m_iLocalSymCount] = endOffset;
+            m_iLocalSlot[m_iLocalSymCount] = slot;
+            m_strName[m_iLocalSymCount] = strName;
+            m_ubSignature[m_iLocalSymCount] = signature;
+            checked { m_iLocalSymCount++; }
+        }
+
+        internal void AddUsingNamespace(String strNamespace)
+        {
+            EnsureCapacityNamespace();
+            m_namespace[m_iNameSpaceCount] = strNamespace;
+            checked { m_iNameSpaceCount++; }
+        }
+
+        internal virtual void EmitLocalSymInfo(ISymbolWriter symWriter)
+        {
+            int i;
+
+            for (i = 0; i < m_iLocalSymCount; i++)
+            {
+                symWriter.DefineLocalVariable(
+                            m_strName[i],
+                            FieldAttributes.PrivateScope,
+                            m_ubSignature[i],
+                            SymAddressKind.ILOffset,
+                            m_iLocalSlot[i],
+                            0,          // addr2 is not used yet
+                            0,          // addr3 is not used
+                            m_iStartOffset[i],
+                            m_iEndOffset[i]);
+            }
+            for (i = 0; i < m_iNameSpaceCount; i++)
+            {
+                symWriter.UsingNamespace(m_namespace[i]);
+            }
+        }
+
+        #endregion
+    }
+
+    /// <summary>
+    /// Describes exception handler in a method body.
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    internal readonly struct ExceptionHandler : IEquatable<ExceptionHandler>
+    {
+        // Keep in sync with unmanged structure. 
+        internal readonly int m_exceptionClass;
+        internal readonly int m_tryStartOffset;
+        internal readonly int m_tryEndOffset;
+        internal readonly int m_filterOffset;
+        internal readonly int m_handlerStartOffset;
+        internal readonly int m_handlerEndOffset;
+        internal readonly ExceptionHandlingClauseOptions m_kind;
+
+        #region Constructors
+
+        internal ExceptionHandler(int tryStartOffset, int tryEndOffset, int filterOffset, int handlerStartOffset, int handlerEndOffset,
+            int kind, int exceptionTypeToken)
+        {
+            Debug.Assert(tryStartOffset >= 0);
+            Debug.Assert(tryEndOffset >= 0);
+            Debug.Assert(filterOffset >= 0);
+            Debug.Assert(handlerStartOffset >= 0);
+            Debug.Assert(handlerEndOffset >= 0);
+            Debug.Assert(IsValidKind((ExceptionHandlingClauseOptions)kind));
+            Debug.Assert(kind != (int)ExceptionHandlingClauseOptions.Clause || (exceptionTypeToken & 0x00FFFFFF) != 0);
+
+            m_tryStartOffset = tryStartOffset;
+            m_tryEndOffset = tryEndOffset;
+            m_filterOffset = filterOffset;
+            m_handlerStartOffset = handlerStartOffset;
+            m_handlerEndOffset = handlerEndOffset;
+            m_kind = (ExceptionHandlingClauseOptions)kind;
+            m_exceptionClass = exceptionTypeToken;
+        }
+
+        private static bool IsValidKind(ExceptionHandlingClauseOptions kind)
+        {
+            switch (kind)
+            {
+                case ExceptionHandlingClauseOptions.Clause:
+                case ExceptionHandlingClauseOptions.Filter:
+                case ExceptionHandlingClauseOptions.Finally:
+                case ExceptionHandlingClauseOptions.Fault:
+                    return true;
+
+                default:
+                    return false;
+            }
+        }
+
+        #endregion
+
+        #region Equality
+
+        public override int GetHashCode()
+        {
+            return m_exceptionClass ^ m_tryStartOffset ^ m_tryEndOffset ^ m_filterOffset ^ m_handlerStartOffset ^ m_handlerEndOffset ^ (int)m_kind;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            return obj is ExceptionHandler && Equals((ExceptionHandler)obj);
+        }
+
+        public bool Equals(ExceptionHandler other)
+        {
+            return
+                other.m_exceptionClass == m_exceptionClass &&
+                other.m_tryStartOffset == m_tryStartOffset &&
+                other.m_tryEndOffset == m_tryEndOffset &&
+                other.m_filterOffset == m_filterOffset &&
+                other.m_handlerStartOffset == m_handlerStartOffset &&
+                other.m_handlerEndOffset == m_handlerEndOffset &&
+                other.m_kind == m_kind;
+        }
+
+        public static bool operator ==(ExceptionHandler left, ExceptionHandler right)
+        {
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(ExceptionHandler left, ExceptionHandler right)
+        {
+            return !left.Equals(right);
+        }
+
+        #endregion
+    }
+}
+
+
+
+
+
+
+
+
+
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/MethodBuilderInstantiation.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/MethodBuilderInstantiation.cs
new file mode 100644
index 0000000000..63f299a511
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/MethodBuilderInstantiation.cs
@@ -0,0 +1,138 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+using System;
+using System.Reflection;
+using System.Collections;
+using System.Globalization;
+
+namespace System.Reflection.Emit
+{
+    internal sealed class MethodBuilderInstantiation : MethodInfo
+    {
+        #region Static Members
+        internal static MethodInfo MakeGenericMethod(MethodInfo method, Type[] inst)
+        {
+            if (!method.IsGenericMethodDefinition)
+                throw new InvalidOperationException();
+
+            return new MethodBuilderInstantiation(method, inst);
+        }
+
+        #endregion
+
+        #region Private Data Members
+        internal MethodInfo m_method;
+        private Type[] m_inst;
+        #endregion
+
+        #region Constructor
+        internal MethodBuilderInstantiation(MethodInfo method, Type[] inst)
+        {
+            m_method = method;
+            m_inst = inst;
+        }
+        #endregion
+
+        internal override Type[] GetParameterTypes()
+        {
+            return m_method.GetParameterTypes();
+        }
+
+        #region MemberBase
+        public override MemberTypes MemberType { get { return m_method.MemberType; } }
+        public override String Name { get { return m_method.Name; } }
+        public override Type DeclaringType { get { return m_method.DeclaringType; } }
+        public override Type ReflectedType { get { return m_method.ReflectedType; } }
+        public override Object[] GetCustomAttributes(bool inherit) { return m_method.GetCustomAttributes(inherit); }
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit) { return m_method.GetCustomAttributes(attributeType, inherit); }
+        public override bool IsDefined(Type attributeType, bool inherit) { return m_method.IsDefined(attributeType, inherit); }
+        public override Module Module { get { return m_method.Module; } }
+        #endregion
+
+        #region MethodBase Members
+        public override ParameterInfo[] GetParameters() { throw new NotSupportedException(); }
+        public override MethodImplAttributes GetMethodImplementationFlags() { return m_method.GetMethodImplementationFlags(); }
+        public override RuntimeMethodHandle MethodHandle { get { throw new NotSupportedException(SR.NotSupported_DynamicModule); } }
+        public override MethodAttributes Attributes { get { return m_method.Attributes; } }
+        public override Object Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
+        {
+            throw new NotSupportedException();
+        }
+        public override CallingConventions CallingConvention { get { return m_method.CallingConvention; } }
+        public override Type[] GetGenericArguments() { return m_inst; }
+        public override MethodInfo GetGenericMethodDefinition() { return m_method; }
+        public override bool IsGenericMethodDefinition { get { return false; } }
+        public override bool ContainsGenericParameters
+        {
+            get
+            {
+                for (int i = 0; i < m_inst.Length; i++)
+                {
+                    if (m_inst[i].ContainsGenericParameters)
+                        return true;
+                }
+
+                if (DeclaringType != null && DeclaringType.ContainsGenericParameters)
+                    return true;
+
+                return false;
+            }
+        }
+
+        public override MethodInfo MakeGenericMethod(params Type[] arguments)
+        {
+            throw new InvalidOperationException(SR.Format(SR.Arg_NotGenericMethodDefinition, this));
+        }
+
+        public override bool IsGenericMethod { get { return true; } }
+
+        #endregion
+
+        #region Public Abstract\Virtual Members
+        public override Type ReturnType
+        {
+            get
+            {
+                return m_method.ReturnType;
+            }
+        }
+
+        public override ParameterInfo ReturnParameter { get { throw new NotSupportedException(); } }
+        public override ICustomAttributeProvider ReturnTypeCustomAttributes { get { throw new NotSupportedException(); } }
+        public override MethodInfo GetBaseDefinition() { throw new NotSupportedException(); }
+        #endregion
+    }
+}
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/MethodToken.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/MethodToken.cs
new file mode 100644
index 0000000000..9698b07333
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/MethodToken.cs
@@ -0,0 +1,64 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Represents a Method to the ILGenerator class.
+**
+** 
+===========================================================*/
+
+using System;
+using System.Reflection;
+
+namespace System.Reflection.Emit
+{
+    public struct MethodToken
+    {
+        public static readonly MethodToken Empty = new MethodToken();
+        internal int m_method;
+
+        internal MethodToken(int str)
+        {
+            m_method = str;
+        }
+
+        public int Token
+        {
+            get { return m_method; }
+        }
+
+        public override int GetHashCode()
+        {
+            return m_method;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (obj is MethodToken)
+                return Equals((MethodToken)obj);
+            else
+                return false;
+        }
+
+        public bool Equals(MethodToken obj)
+        {
+            return obj.m_method == m_method;
+        }
+
+        public static bool operator ==(MethodToken a, MethodToken b)
+        {
+            return a.Equals(b);
+        }
+
+        public static bool operator !=(MethodToken a, MethodToken b)
+        {
+            return !(a == b);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/ModuleBuilder.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/ModuleBuilder.cs
new file mode 100644
index 0000000000..9b2d878d38
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/ModuleBuilder.cs
@@ -0,0 +1,1670 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+namespace System.Reflection.Emit
+{
+    using System.Runtime.InteropServices;
+    using System;
+    using System.Collections.Generic;
+    using System.Diagnostics.SymbolStore;
+    using System.Globalization;
+    using System.Reflection;
+    using System.IO;
+    using System.Resources;
+    using System.Security;
+    using System.Runtime.Serialization;
+    using System.Text;
+    using System.Threading;
+    using System.Runtime.Versioning;
+    using System.Runtime.CompilerServices;
+    using System.Diagnostics;
+
+    internal sealed class InternalModuleBuilder : RuntimeModule
+    {
+        #region Private Data Members
+        // WARNING!! WARNING!!
+        // InternalModuleBuilder should not contain any data members as its reflectbase is the same as Module.
+        #endregion
+
+        private InternalModuleBuilder() { }
+
+        #region object overrides
+        public override bool Equals(object obj)
+        {
+            if (obj == null)
+                return false;
+
+            if (obj is InternalModuleBuilder)
+                return ((object)this == obj);
+
+            return obj.Equals(this);
+        }
+        // Need a dummy GetHashCode to pair with Equals
+        public override int GetHashCode() { return base.GetHashCode(); }
+        #endregion
+    }
+
+    // deliberately not [serializable]
+    public class ModuleBuilder : Module
+    {
+        #region FCalls
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr nCreateISymWriterForDynamicModule(Module module, String filename);
+
+        #endregion
+
+        #region Internal Static Members
+        internal static String UnmangleTypeName(String typeName)
+        {
+            // Gets the original type name, without '+' name mangling.
+
+            int i = typeName.Length - 1;
+            while (true)
+            {
+                i = typeName.LastIndexOf('+', i);
+                if (i == -1)
+                    break;
+
+                bool evenSlashes = true;
+                int iSlash = i;
+                while (typeName[--iSlash] == '\\')
+                    evenSlashes = !evenSlashes;
+
+                // Even number of slashes means this '+' is a name separator
+                if (evenSlashes)
+                    break;
+
+                i = iSlash;
+            }
+
+            return typeName.Substring(i + 1);
+        }
+
+        #endregion
+
+        #region Internal Data Members
+        // m_TypeBuilder contains both TypeBuilder and EnumBuilder objects
+        private Dictionary<string, Type> m_TypeBuilderDict;
+        private ISymbolWriter m_iSymWriter;
+        internal ModuleBuilderData m_moduleData;
+        internal InternalModuleBuilder m_internalModuleBuilder;
+        // This is the "external" AssemblyBuilder
+        // only the "external" ModuleBuilder has this set
+        private AssemblyBuilder m_assemblyBuilder;
+        internal AssemblyBuilder ContainingAssemblyBuilder { get { return m_assemblyBuilder; } }
+        #endregion
+
+        #region Constructor
+        internal ModuleBuilder(AssemblyBuilder assemblyBuilder, InternalModuleBuilder internalModuleBuilder)
+        {
+            m_internalModuleBuilder = internalModuleBuilder;
+            m_assemblyBuilder = assemblyBuilder;
+        }
+        #endregion
+
+        #region Private Members
+        internal void AddType(string name, Type type)
+        {
+            m_TypeBuilderDict.Add(name, type);
+        }
+
+        internal void CheckTypeNameConflict(String strTypeName, Type enclosingType)
+        {
+            Type foundType = null;
+            if (m_TypeBuilderDict.TryGetValue(strTypeName, out foundType) &&
+                object.ReferenceEquals(foundType.DeclaringType, enclosingType))
+            {
+                // Cannot have two types with the same name
+                throw new ArgumentException(SR.Argument_DuplicateTypeName);
+            }
+        }
+
+        private Type GetType(String strFormat, Type baseType)
+        {
+            // This function takes a string to describe the compound type, such as "[,][]", and a baseType.
+
+            if (strFormat == null || strFormat.Equals(String.Empty))
+            {
+                return baseType;
+            }
+
+            // convert the format string to byte array and then call FormCompoundType
+            return SymbolType.FormCompoundType(strFormat, baseType, 0);
+        }
+
+
+        internal void CheckContext(params Type[][] typess)
+        {
+            ContainingAssemblyBuilder.CheckContext(typess);
+        }
+        internal void CheckContext(params Type[] types)
+        {
+            ContainingAssemblyBuilder.CheckContext(types);
+        }
+
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern int GetTypeRef(RuntimeModule module, String strFullName, RuntimeModule refedModule, String strRefedModuleFileName, int tkResolution);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern int GetMemberRef(RuntimeModule module, RuntimeModule refedModule, int tr, int defToken);
+
+        private int GetMemberRef(Module refedModule, int tr, int defToken)
+        {
+            return GetMemberRef(GetNativeHandle(), GetRuntimeModuleFromModule(refedModule).GetNativeHandle(), tr, defToken);
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern int GetMemberRefFromSignature(RuntimeModule module, int tr, String methodName, byte[] signature, int length);
+
+        private int GetMemberRefFromSignature(int tr, String methodName, byte[] signature, int length)
+        {
+            return GetMemberRefFromSignature(GetNativeHandle(), tr, methodName, signature, length);
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern int GetMemberRefOfMethodInfo(RuntimeModule module, int tr, IRuntimeMethodInfo method);
+
+        private int GetMemberRefOfMethodInfo(int tr, RuntimeMethodInfo method)
+        {
+            Debug.Assert(method != null);
+
+            return GetMemberRefOfMethodInfo(GetNativeHandle(), tr, method);
+        }
+
+        private int GetMemberRefOfMethodInfo(int tr, RuntimeConstructorInfo method)
+        {
+            Debug.Assert(method != null);
+
+            return GetMemberRefOfMethodInfo(GetNativeHandle(), tr, method);
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern int GetMemberRefOfFieldInfo(RuntimeModule module, int tkType, RuntimeTypeHandle declaringType, int tkField);
+
+        private int GetMemberRefOfFieldInfo(int tkType, RuntimeTypeHandle declaringType, RuntimeFieldInfo runtimeField)
+        {
+            Debug.Assert(runtimeField != null);
+
+            return GetMemberRefOfFieldInfo(GetNativeHandle(), tkType, declaringType, runtimeField.MetadataToken);
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern int GetTokenFromTypeSpec(RuntimeModule pModule, byte[] signature, int length);
+
+        private int GetTokenFromTypeSpec(byte[] signature, int length)
+        {
+            return GetTokenFromTypeSpec(GetNativeHandle(), signature, length);
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern int GetArrayMethodToken(RuntimeModule module, int tkTypeSpec, String methodName, byte[] signature, int sigLength);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern int GetStringConstant(RuntimeModule module, String str, int length);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void SetFieldRVAContent(RuntimeModule module, int fdToken, byte[] data, int length);
+
+        #endregion
+
+        #region Internal Members
+        internal virtual Type FindTypeBuilderWithName(String strTypeName, bool ignoreCase)
+        {
+            if (ignoreCase)
+            {
+                foreach (string name in m_TypeBuilderDict.Keys)
+                {
+                    if (String.Compare(name, strTypeName, (StringComparison.OrdinalIgnoreCase)) == 0)
+                        return m_TypeBuilderDict[name];
+                }
+            }
+            else
+            {
+                Type foundType;
+                if (m_TypeBuilderDict.TryGetValue(strTypeName, out foundType))
+                    return foundType;
+            }
+
+            return null;
+        }
+
+        private int GetTypeRefNested(Type type, Module refedModule, String strRefedModuleFileName)
+        {
+            // This function will generate correct TypeRef token for top level type and nested type.
+
+            Type enclosingType = type.DeclaringType;
+            int tkResolution = 0;
+            String typeName = type.FullName;
+
+            if (enclosingType != null)
+            {
+                tkResolution = GetTypeRefNested(enclosingType, refedModule, strRefedModuleFileName);
+                typeName = UnmangleTypeName(typeName);
+            }
+
+            Debug.Assert(!type.IsByRef, "Must not be ByRef.");
+            Debug.Assert(!type.IsGenericType || type.IsGenericTypeDefinition, "Must not have generic arguments.");
+
+            return GetTypeRef(GetNativeHandle(), typeName, GetRuntimeModuleFromModule(refedModule).GetNativeHandle(), strRefedModuleFileName, tkResolution);
+        }
+
+        internal MethodToken InternalGetConstructorToken(ConstructorInfo con, bool usingRef)
+        {
+            // Helper to get constructor token. If usingRef is true, we will never use the def token
+
+            if (con == null)
+                throw new ArgumentNullException(nameof(con));
+
+            int tr;
+            int mr = 0;
+
+            ConstructorBuilder conBuilder = null;
+            ConstructorOnTypeBuilderInstantiation conOnTypeBuilderInst = null;
+            RuntimeConstructorInfo rtCon = null;
+
+            if ((conBuilder = con as ConstructorBuilder) != null)
+            {
+                if (usingRef == false && conBuilder.Module.Equals(this))
+                    return conBuilder.GetToken();
+
+                // constructor is defined in a different module
+                tr = GetTypeTokenInternal(con.ReflectedType).Token;
+                mr = GetMemberRef(con.ReflectedType.Module, tr, conBuilder.GetToken().Token);
+            }
+            else if ((conOnTypeBuilderInst = con as ConstructorOnTypeBuilderInstantiation) != null)
+            {
+                if (usingRef == true) throw new InvalidOperationException();
+
+                tr = GetTypeTokenInternal(con.DeclaringType).Token;
+                mr = GetMemberRef(con.DeclaringType.Module, tr, conOnTypeBuilderInst.MetadataTokenInternal);
+            }
+            else if ((rtCon = con as RuntimeConstructorInfo) != null && con.ReflectedType.IsArray == false)
+            {
+                // constructor is not a dynamic field
+                // We need to get the TypeRef tokens
+
+                tr = GetTypeTokenInternal(con.ReflectedType).Token;
+                mr = GetMemberRefOfMethodInfo(tr, rtCon);
+            }
+            else
+            {
+                // some user derived ConstructorInfo
+                // go through the slower code path, i.e. retrieve parameters and form signature helper.
+                ParameterInfo[] parameters = con.GetParameters();
+                if (parameters == null)
+                    throw new ArgumentException(SR.Argument_InvalidConstructorInfo);
+
+                Type[] parameterTypes = new Type[parameters.Length];
+                Type[][] requiredCustomModifiers = new Type[parameters.Length][];
+                Type[][] optionalCustomModifiers = new Type[parameters.Length][];
+
+                for (int i = 0; i < parameters.Length; i++)
+                {
+                    if (parameters[i] == null)
+                        throw new ArgumentException(SR.Argument_InvalidConstructorInfo);
+
+                    parameterTypes[i] = parameters[i].ParameterType;
+                    requiredCustomModifiers[i] = parameters[i].GetRequiredCustomModifiers();
+                    optionalCustomModifiers[i] = parameters[i].GetOptionalCustomModifiers();
+                }
+
+                tr = GetTypeTokenInternal(con.ReflectedType).Token;
+
+                SignatureHelper sigHelp = SignatureHelper.GetMethodSigHelper(this, con.CallingConvention, null, null, null, parameterTypes, requiredCustomModifiers, optionalCustomModifiers);
+                int length;
+                byte[] sigBytes = sigHelp.InternalGetSignature(out length);
+
+                mr = GetMemberRefFromSignature(tr, con.Name, sigBytes, length);
+            }
+
+            return new MethodToken(mr);
+        }
+
+        internal void Init(String strModuleName, String strFileName, int tkFile)
+        {
+            m_moduleData = new ModuleBuilderData(this, strModuleName, strFileName, tkFile);
+            m_TypeBuilderDict = new Dictionary<string, Type>();
+        }
+
+        internal void SetSymWriter(ISymbolWriter writer)
+        {
+            m_iSymWriter = writer;
+        }
+
+        internal object SyncRoot
+        {
+            get
+            {
+                return ContainingAssemblyBuilder.SyncRoot;
+            }
+        }
+
+        #endregion
+
+        #region Module Overrides
+
+        // m_internalModuleBuilder is null iff this is a "internal" ModuleBuilder
+        internal InternalModuleBuilder InternalModule
+        {
+            get
+            {
+                return m_internalModuleBuilder;
+            }
+        }
+
+        protected override ModuleHandle GetModuleHandleImpl()
+        {
+            return new ModuleHandle(GetNativeHandle());
+        }
+
+        internal RuntimeModule GetNativeHandle()
+        {
+            return InternalModule.GetNativeHandle();
+        }
+
+        private static RuntimeModule GetRuntimeModuleFromModule(Module m)
+        {
+            ModuleBuilder mb = m as ModuleBuilder;
+            if (mb != null)
+            {
+                return mb.InternalModule;
+            }
+
+            return m as RuntimeModule;
+        }
+
+        private int GetMemberRefToken(MethodBase method, IEnumerable<Type> optionalParameterTypes)
+        {
+            Type[] parameterTypes;
+            Type returnType;
+            int tkParent;
+            int cGenericParameters = 0;
+
+            if (method.IsGenericMethod)
+            {
+                if (!method.IsGenericMethodDefinition)
+                    throw new InvalidOperationException();
+
+                cGenericParameters = method.GetGenericArguments().Length;
+            }
+
+            if (optionalParameterTypes != null)
+            {
+                if ((method.CallingConvention & CallingConventions.VarArgs) == 0)
+                {
+                    // Client should not supply optional parameter in default calling convention
+                    throw new InvalidOperationException(SR.InvalidOperation_NotAVarArgCallingConvention);
+                }
+            }
+
+            MethodInfo masmi = method as MethodInfo;
+
+            if (method.DeclaringType.IsGenericType)
+            {
+                MethodBase methDef = null; // methodInfo = G<Foo>.M<Bar> ==> methDef = G<T>.M<S>
+
+                MethodOnTypeBuilderInstantiation motbi;
+                ConstructorOnTypeBuilderInstantiation cotbi;
+
+                if ((motbi = method as MethodOnTypeBuilderInstantiation) != null)
+                {
+                    methDef = motbi.m_method;
+                }
+                else if ((cotbi = method as ConstructorOnTypeBuilderInstantiation) != null)
+                {
+                    methDef = cotbi.m_ctor;
+                }
+                else if (method is MethodBuilder || method is ConstructorBuilder)
+                {
+                    // methodInfo must be GenericMethodDefinition; trying to emit G<?>.M<S>
+                    methDef = method;
+                }
+                else
+                {
+                    Debug.Assert(method is RuntimeMethodInfo || method is RuntimeConstructorInfo);
+
+                    if (method.IsGenericMethod)
+                    {
+                        Debug.Assert(masmi != null);
+
+                        methDef = masmi.GetGenericMethodDefinition();
+                        methDef = methDef.Module.ResolveMethod(
+                            method.MetadataToken,
+                            methDef.DeclaringType != null ? methDef.DeclaringType.GetGenericArguments() : null,
+                            methDef.GetGenericArguments());
+                    }
+                    else
+                    {
+                        methDef = method.Module.ResolveMethod(
+                            method.MetadataToken,
+                            method.DeclaringType != null ? method.DeclaringType.GetGenericArguments() : null,
+                            null);
+                    }
+                }
+
+                parameterTypes = methDef.GetParameterTypes();
+                returnType = MethodBuilder.GetMethodBaseReturnType(methDef);
+            }
+            else
+            {
+                parameterTypes = method.GetParameterTypes();
+                returnType = MethodBuilder.GetMethodBaseReturnType(method);
+            }
+
+            int sigLength;
+            byte[] sigBytes = GetMemberRefSignature(method.CallingConvention, returnType, parameterTypes,
+                optionalParameterTypes, cGenericParameters).InternalGetSignature(out sigLength);
+
+            if (method.DeclaringType.IsGenericType)
+            {
+                int length;
+                byte[] sig = SignatureHelper.GetTypeSigToken(this, method.DeclaringType).InternalGetSignature(out length);
+                tkParent = GetTokenFromTypeSpec(sig, length);
+            }
+            else if (!method.Module.Equals(this))
+            {
+                // Use typeRef as parent because the method's declaringType lives in a different assembly                
+                tkParent = GetTypeToken(method.DeclaringType).Token;
+            }
+            else
+            {
+                // Use methodDef as parent because the method lives in this assembly and its declaringType has no generic arguments
+                if (masmi != null)
+                    tkParent = GetMethodToken(masmi).Token;
+                else
+                    tkParent = GetConstructorToken(method as ConstructorInfo).Token;
+            }
+
+            return GetMemberRefFromSignature(tkParent, method.Name, sigBytes, sigLength);
+        }
+
+        internal SignatureHelper GetMemberRefSignature(CallingConventions call, Type returnType,
+            Type[] parameterTypes, IEnumerable<Type> optionalParameterTypes, int cGenericParameters)
+        {
+            SignatureHelper sig = SignatureHelper.GetMethodSigHelper(this, call, returnType, cGenericParameters);
+
+            if (parameterTypes != null)
+            {
+                foreach (Type t in parameterTypes)
+                {
+                    sig.AddArgument(t);
+                }
+            }
+
+            if (optionalParameterTypes != null)
+            {
+                int i = 0;
+                foreach (Type type in optionalParameterTypes)
+                {
+                    // add the sentinel
+                    if (i == 0)
+                    {
+                        sig.AddSentinel();
+                    }
+
+                    sig.AddArgument(type);
+                    i++;
+                }
+            }
+
+            return sig;
+        }
+
+        #endregion
+
+        #region object overrides
+        public override bool Equals(object obj)
+        {
+            return InternalModule.Equals(obj);
+        }
+        // Need a dummy GetHashCode to pair with Equals
+        public override int GetHashCode() { return InternalModule.GetHashCode(); }
+        #endregion
+
+        #region ICustomAttributeProvider Members
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            return InternalModule.GetCustomAttributes(inherit);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            return InternalModule.GetCustomAttributes(attributeType, inherit);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            return InternalModule.IsDefined(attributeType, inherit);
+        }
+
+        public override IList<CustomAttributeData> GetCustomAttributesData()
+        {
+            return InternalModule.GetCustomAttributesData();
+        }
+        #endregion
+
+        #region Module Overrides
+
+        public override Type[] GetTypes()
+        {
+            lock (SyncRoot)
+            {
+                return GetTypesNoLock();
+            }
+        }
+
+        internal Type[] GetTypesNoLock()
+        {
+            int size = m_TypeBuilderDict.Count;
+            Type[] typeList = new Type[m_TypeBuilderDict.Count];
+            int i = 0;
+
+            foreach (Type builder in m_TypeBuilderDict.Values)
+            {
+                EnumBuilder enumBldr = builder as EnumBuilder;
+                TypeBuilder tmpTypeBldr;
+
+                if (enumBldr != null)
+                    tmpTypeBldr = enumBldr.m_typeBuilder;
+                else
+                    tmpTypeBldr = (TypeBuilder)builder;
+
+                // We should not return TypeBuilders.
+                // Otherwise anyone can emit code in it.
+                if (tmpTypeBldr.IsCreated())
+                    typeList[i++] = tmpTypeBldr.UnderlyingSystemType;
+                else
+                    typeList[i++] = builder;
+            }
+
+            return typeList;
+        }
+
+        public override Type GetType(String className)
+        {
+            return GetType(className, false, false);
+        }
+
+        public override Type GetType(String className, bool ignoreCase)
+        {
+            return GetType(className, false, ignoreCase);
+        }
+
+        public override Type GetType(String className, bool throwOnError, bool ignoreCase)
+        {
+            lock (SyncRoot)
+            {
+                return GetTypeNoLock(className, throwOnError, ignoreCase);
+            }
+        }
+
+        private Type GetTypeNoLock(String className, bool throwOnError, bool ignoreCase)
+        {
+            // public API to to a type. The reason that we need this function override from module
+            // is because clients might need to get foo[] when foo is being built. For example, if 
+            // foo class contains a data member of type foo[].
+            // This API first delegate to the Module.GetType implementation. If succeeded, great! 
+            // If not, we have to look up the current module to find the TypeBuilder to represent the base
+            // type and form the Type object for "foo[,]".
+
+            // Module.GetType() will verify className.                
+            Type baseType = InternalModule.GetType(className, throwOnError, ignoreCase);
+            if (baseType != null)
+                return baseType;
+
+            // Now try to see if we contain a TypeBuilder for this type or not.
+            // Might have a compound type name, indicated via an unescaped
+            // '[', '*' or '&'. Split the name at this point.
+            String baseName = null;
+            String parameters = null;
+            int startIndex = 0;
+
+            while (startIndex <= className.Length)
+            {
+                // Are there any possible special characters left?
+                int i = className.IndexOfAny(new char[] { '[', '*', '&' }, startIndex);
+                if (i == -1)
+                {
+                    // No, type name is simple.
+                    baseName = className;
+                    parameters = null;
+                    break;
+                }
+
+                // Found a potential special character, but it might be escaped.
+                int slashes = 0;
+                for (int j = i - 1; j >= 0 && className[j] == '\\'; j--)
+                    slashes++;
+
+                // Odd number of slashes indicates escaping.
+                if (slashes % 2 == 1)
+                {
+                    startIndex = i + 1;
+                    continue;
+                }
+
+                // Found the end of the base type name.
+                baseName = className.Substring(0, i);
+                parameters = className.Substring(i);
+                break;
+            }
+
+            // If we didn't find a basename yet, the entire class name is
+            // the base name and we don't have a composite type.
+            if (baseName == null)
+            {
+                baseName = className;
+                parameters = null;
+            }
+
+            baseName = baseName.Replace(@"\\", @"\").Replace(@"\[", @"[").Replace(@"\*", @"*").Replace(@"\&", @"&");
+
+            if (parameters != null)
+            {
+                // try to see if reflection can find the base type. It can be such that reflection
+                // does not support the complex format string yet!
+
+                baseType = InternalModule.GetType(baseName, false, ignoreCase);
+            }
+
+            if (baseType == null)
+            {
+                // try to find it among the unbaked types.
+                // starting with the current module first of all.
+                baseType = FindTypeBuilderWithName(baseName, ignoreCase);
+                if (baseType == null && Assembly is AssemblyBuilder)
+                {
+                    // now goto Assembly level to find the type.
+                    int size;
+                    List<ModuleBuilder> modList;
+
+                    modList = ContainingAssemblyBuilder.m_assemblyData.m_moduleBuilderList;
+                    size = modList.Count;
+                    for (int i = 0; i < size && baseType == null; i++)
+                    {
+                        ModuleBuilder mBuilder = modList[i];
+                        baseType = mBuilder.FindTypeBuilderWithName(baseName, ignoreCase);
+                    }
+                }
+                if (baseType == null)
+                    return null;
+            }
+
+            if (parameters == null)
+                return baseType;
+
+            return GetType(parameters, baseType);
+        }
+
+        public override String FullyQualifiedName
+        {
+            get
+            {
+                return m_moduleData.m_strFileName;
+            }
+        }
+
+        public override byte[] ResolveSignature(int metadataToken)
+        {
+            return InternalModule.ResolveSignature(metadataToken);
+        }
+
+        public override MethodBase ResolveMethod(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
+        {
+            return InternalModule.ResolveMethod(metadataToken, genericTypeArguments, genericMethodArguments);
+        }
+
+        public override FieldInfo ResolveField(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
+        {
+            return InternalModule.ResolveField(metadataToken, genericTypeArguments, genericMethodArguments);
+        }
+
+        public override Type ResolveType(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
+        {
+            return InternalModule.ResolveType(metadataToken, genericTypeArguments, genericMethodArguments);
+        }
+
+        public override MemberInfo ResolveMember(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
+        {
+            return InternalModule.ResolveMember(metadataToken, genericTypeArguments, genericMethodArguments);
+        }
+
+        public override string ResolveString(int metadataToken)
+        {
+            return InternalModule.ResolveString(metadataToken);
+        }
+
+        public override void GetPEKind(out PortableExecutableKinds peKind, out ImageFileMachine machine)
+        {
+            InternalModule.GetPEKind(out peKind, out machine);
+        }
+
+        public override int MDStreamVersion
+        {
+            get
+            {
+                return InternalModule.MDStreamVersion;
+            }
+        }
+
+        public override Guid ModuleVersionId
+        {
+            get
+            {
+                return InternalModule.ModuleVersionId;
+            }
+        }
+
+        public override int MetadataToken
+        {
+            get
+            {
+                return InternalModule.MetadataToken;
+            }
+        }
+
+        public override bool IsResource()
+        {
+            return InternalModule.IsResource();
+        }
+
+        public override FieldInfo[] GetFields(BindingFlags bindingFlags)
+        {
+            return InternalModule.GetFields(bindingFlags);
+        }
+
+        public override FieldInfo GetField(String name, BindingFlags bindingAttr)
+        {
+            return InternalModule.GetField(name, bindingAttr);
+        }
+
+        public override MethodInfo[] GetMethods(BindingFlags bindingFlags)
+        {
+            return InternalModule.GetMethods(bindingFlags);
+        }
+
+        protected override MethodInfo GetMethodImpl(String name, BindingFlags bindingAttr, Binder binder,
+            CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            // Cannot call InternalModule.GetMethods because it doesn't allow types to be null
+            return InternalModule.GetMethodInternal(name, bindingAttr, binder, callConvention, types, modifiers);
+        }
+
+        public override String ScopeName
+        {
+            get
+            {
+                return InternalModule.ScopeName;
+            }
+        }
+
+        public override String Name
+        {
+            get
+            {
+                return InternalModule.Name;
+            }
+        }
+
+        public override Assembly Assembly
+        {
+            get
+            {
+                return m_assemblyBuilder;
+            }
+        }
+
+        #endregion
+
+        #region Public Members
+
+        #region Define Type
+        public TypeBuilder DefineType(String name)
+        {
+            lock (SyncRoot)
+            {
+                return DefineTypeNoLock(name, TypeAttributes.NotPublic, null, null, PackingSize.Unspecified, TypeBuilder.UnspecifiedTypeSize);
+            }
+        }
+
+        public TypeBuilder DefineType(String name, TypeAttributes attr)
+        {
+            lock (SyncRoot)
+            {
+                return DefineTypeNoLock(name, attr, null, null, PackingSize.Unspecified, TypeBuilder.UnspecifiedTypeSize);
+            }
+        }
+
+        public TypeBuilder DefineType(String name, TypeAttributes attr, Type parent)
+        {
+            lock (SyncRoot)
+            {
+                // Why do we only call CheckContext here? Why don't we call it in the other overloads?
+                CheckContext(parent);
+
+                return DefineTypeNoLock(name, attr, parent, null, PackingSize.Unspecified, TypeBuilder.UnspecifiedTypeSize);
+            }
+        }
+
+        public TypeBuilder DefineType(String name, TypeAttributes attr, Type parent, int typesize)
+        {
+            lock (SyncRoot)
+            {
+                return DefineTypeNoLock(name, attr, parent, null, PackingSize.Unspecified, typesize);
+            }
+        }
+
+        public TypeBuilder DefineType(String name, TypeAttributes attr, Type parent, PackingSize packingSize, int typesize)
+        {
+            lock (SyncRoot)
+            {
+                return DefineTypeNoLock(name, attr, parent, null, packingSize, typesize);
+            }
+        }
+
+        public TypeBuilder DefineType(String name, TypeAttributes attr, Type parent, Type[] interfaces)
+        {
+            lock (SyncRoot)
+            {
+                return DefineTypeNoLock(name, attr, parent, interfaces, PackingSize.Unspecified, TypeBuilder.UnspecifiedTypeSize);
+            }
+        }
+
+        private TypeBuilder DefineTypeNoLock(String name, TypeAttributes attr, Type parent, Type[] interfaces, PackingSize packingSize, int typesize)
+        {
+            return new TypeBuilder(name, attr, parent, interfaces, this, packingSize, typesize, null); ;
+        }
+
+        public TypeBuilder DefineType(String name, TypeAttributes attr, Type parent, PackingSize packsize)
+        {
+            lock (SyncRoot)
+            {
+                return DefineTypeNoLock(name, attr, parent, packsize);
+            }
+        }
+
+        private TypeBuilder DefineTypeNoLock(String name, TypeAttributes attr, Type parent, PackingSize packsize)
+        {
+            return new TypeBuilder(name, attr, parent, null, this, packsize, TypeBuilder.UnspecifiedTypeSize, null);
+        }
+
+        #endregion
+
+        #region Define Enum
+
+        // This API can only be used to construct a top-level (not nested) enum type.
+        // Nested enum types can be defined manually using ModuleBuilder.DefineType.
+        public EnumBuilder DefineEnum(String name, TypeAttributes visibility, Type underlyingType)
+        {
+            CheckContext(underlyingType);
+            lock (SyncRoot)
+            {
+                EnumBuilder enumBuilder = DefineEnumNoLock(name, visibility, underlyingType);
+
+                // This enum is not generic, nested, and cannot have any element type.
+
+                // We ought to be able to make the following assertions:
+                //
+                //  Debug.Assert(name == enumBuilder.FullName);
+                //  Debug.Assert(enumBuilder.m_typeBuilder == m_TypeBuilderDict[name]);
+                //
+                // but we can't because an embedded null ('\0') in the name will cause it to be truncated
+                // incorrectly.  Fixing that would be a breaking change.
+
+                // Replace the TypeBuilder object in m_TypeBuilderDict with this EnumBuilder object.
+                m_TypeBuilderDict[name] = enumBuilder;
+
+                return enumBuilder;
+            }
+        }
+
+        private EnumBuilder DefineEnumNoLock(String name, TypeAttributes visibility, Type underlyingType)
+        {
+            return new EnumBuilder(name, underlyingType, visibility, this);
+        }
+
+        #endregion
+
+        #region Define Resource
+
+        #endregion
+
+        #region Define Global Method
+        public MethodBuilder DefineGlobalMethod(String name, MethodAttributes attributes, Type returnType, Type[] parameterTypes)
+        {
+            return DefineGlobalMethod(name, attributes, CallingConventions.Standard, returnType, parameterTypes);
+        }
+
+        public MethodBuilder DefineGlobalMethod(String name, MethodAttributes attributes, CallingConventions callingConvention,
+            Type returnType, Type[] parameterTypes)
+        {
+            return DefineGlobalMethod(name, attributes, callingConvention, returnType, null, null, parameterTypes, null, null);
+        }
+
+        public MethodBuilder DefineGlobalMethod(String name, MethodAttributes attributes, CallingConventions callingConvention,
+            Type returnType, Type[] requiredReturnTypeCustomModifiers, Type[] optionalReturnTypeCustomModifiers,
+            Type[] parameterTypes, Type[][] requiredParameterTypeCustomModifiers, Type[][] optionalParameterTypeCustomModifiers)
+        {
+            lock (SyncRoot)
+            {
+                return DefineGlobalMethodNoLock(name, attributes, callingConvention, returnType,
+                                                requiredReturnTypeCustomModifiers, optionalReturnTypeCustomModifiers,
+                                                parameterTypes, requiredParameterTypeCustomModifiers, optionalParameterTypeCustomModifiers);
+            }
+        }
+
+        private MethodBuilder DefineGlobalMethodNoLock(String name, MethodAttributes attributes, CallingConventions callingConvention,
+            Type returnType, Type[] requiredReturnTypeCustomModifiers, Type[] optionalReturnTypeCustomModifiers,
+            Type[] parameterTypes, Type[][] requiredParameterTypeCustomModifiers, Type[][] optionalParameterTypeCustomModifiers)
+        {
+            if (m_moduleData.m_fGlobalBeenCreated == true)
+                throw new InvalidOperationException(SR.InvalidOperation_GlobalsHaveBeenCreated);
+
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            if (name.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(name));
+
+            if ((attributes & MethodAttributes.Static) == 0)
+                throw new ArgumentException(SR.Argument_GlobalFunctionHasToBeStatic);
+
+            CheckContext(returnType);
+            CheckContext(requiredReturnTypeCustomModifiers, optionalReturnTypeCustomModifiers, parameterTypes);
+            CheckContext(requiredParameterTypeCustomModifiers);
+            CheckContext(optionalParameterTypeCustomModifiers);
+
+            m_moduleData.m_fHasGlobal = true;
+
+            return m_moduleData.m_globalTypeBuilder.DefineMethod(name, attributes, callingConvention,
+                returnType, requiredReturnTypeCustomModifiers, optionalReturnTypeCustomModifiers,
+                parameterTypes, requiredParameterTypeCustomModifiers, optionalParameterTypeCustomModifiers);
+        }
+
+        public void CreateGlobalFunctions()
+        {
+            lock (SyncRoot)
+            {
+                CreateGlobalFunctionsNoLock();
+            }
+        }
+
+        private void CreateGlobalFunctionsNoLock()
+        {
+            if (m_moduleData.m_fGlobalBeenCreated)
+            {
+                // cannot create globals twice
+                throw new InvalidOperationException(SR.InvalidOperation_NotADebugModule);
+            }
+            m_moduleData.m_globalTypeBuilder.CreateType();
+            m_moduleData.m_fGlobalBeenCreated = true;
+        }
+
+        #endregion
+
+        #region Define Data
+
+        public FieldBuilder DefineInitializedData(String name, byte[] data, FieldAttributes attributes)
+        {
+            // This method will define an initialized Data in .sdata. 
+            // We will create a fake TypeDef to represent the data with size. This TypeDef
+            // will be the signature for the Field.         
+
+            lock (SyncRoot)
+            {
+                return DefineInitializedDataNoLock(name, data, attributes);
+            }
+        }
+
+        private FieldBuilder DefineInitializedDataNoLock(String name, byte[] data, FieldAttributes attributes)
+        {
+            // This method will define an initialized Data in .sdata. 
+            // We will create a fake TypeDef to represent the data with size. This TypeDef
+            // will be the signature for the Field.
+            if (m_moduleData.m_fGlobalBeenCreated == true)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_GlobalsHaveBeenCreated);
+            }
+
+            m_moduleData.m_fHasGlobal = true;
+            return m_moduleData.m_globalTypeBuilder.DefineInitializedData(name, data, attributes);
+        }
+
+        public FieldBuilder DefineUninitializedData(String name, int size, FieldAttributes attributes)
+        {
+            lock (SyncRoot)
+            {
+                return DefineUninitializedDataNoLock(name, size, attributes);
+            }
+        }
+
+        private FieldBuilder DefineUninitializedDataNoLock(String name, int size, FieldAttributes attributes)
+        {
+            // This method will define an uninitialized Data in .sdata. 
+            // We will create a fake TypeDef to represent the data with size. This TypeDef
+            // will be the signature for the Field. 
+
+            if (m_moduleData.m_fGlobalBeenCreated == true)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_GlobalsHaveBeenCreated);
+            }
+
+            m_moduleData.m_fHasGlobal = true;
+            return m_moduleData.m_globalTypeBuilder.DefineUninitializedData(name, size, attributes);
+        }
+
+        #endregion
+
+        #region GetToken
+        // For a generic type definition, we should return the token for the generic type definition itself in two cases: 
+        //   1. GetTypeToken
+        //   2. ldtoken (see ILGenerator)
+        // For all other occasions we should return the generic type instantiated on its formal parameters.
+        internal TypeToken GetTypeTokenInternal(Type type)
+        {
+            return GetTypeTokenInternal(type, false);
+        }
+
+        private TypeToken GetTypeTokenInternal(Type type, bool getGenericDefinition)
+        {
+            lock (SyncRoot)
+            {
+                return GetTypeTokenWorkerNoLock(type, getGenericDefinition);
+            }
+        }
+
+        public TypeToken GetTypeToken(Type type)
+        {
+            return GetTypeTokenInternal(type, true);
+        }
+
+        private TypeToken GetTypeTokenWorkerNoLock(Type type, bool getGenericDefinition)
+        {
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+
+            CheckContext(type);
+
+            // Return a token for the class relative to the Module.  Tokens
+            // are used to indentify objects when the objects are used in IL
+            // instructions.  Tokens are always relative to the Module.  For example,
+            // the token value for System.String is likely to be different from
+            // Module to Module.  Calling GetTypeToken will cause a reference to be
+            // added to the Module.  This reference becomes a perminate part of the Module,
+            // multiple calles to this method with the same class have no additional side affects.
+            // This function is optimized to use the TypeDef token if Type is within the same module.
+            // We should also be aware of multiple dynamic modules and multiple implementation of Type!!!
+
+            if (type.IsByRef)
+                throw new ArgumentException(SR.Argument_CannotGetTypeTokenForByRef);
+
+            if ((type.IsGenericType && (!type.IsGenericTypeDefinition || !getGenericDefinition)) ||
+                type.IsGenericParameter ||
+                type.IsArray ||
+                type.IsPointer)
+            {
+                int length;
+                byte[] sig = SignatureHelper.GetTypeSigToken(this, type).InternalGetSignature(out length);
+                return new TypeToken(GetTokenFromTypeSpec(sig, length));
+            }
+
+            Module refedModule = type.Module;
+
+            if (refedModule.Equals(this))
+            {
+                // no need to do anything additional other than defining the TypeRef Token
+                TypeBuilder typeBuilder = null;
+                GenericTypeParameterBuilder paramBuilder = null;
+
+                EnumBuilder enumBuilder = type as EnumBuilder;
+                if (enumBuilder != null)
+                    typeBuilder = enumBuilder.m_typeBuilder;
+                else
+                    typeBuilder = type as TypeBuilder;
+
+                if (typeBuilder != null)
+                {
+                    // optimization: if the type is defined in this module,
+                    // just return the token
+                    //
+                    return typeBuilder.TypeToken;
+                }
+                else if ((paramBuilder = type as GenericTypeParameterBuilder) != null)
+                {
+                    return new TypeToken(paramBuilder.MetadataTokenInternal);
+                }
+
+                return new TypeToken(GetTypeRefNested(type, this, String.Empty));
+            }
+
+            // After this point, the referenced module is not the same as the referencing
+            // module.
+            //
+            ModuleBuilder refedModuleBuilder = refedModule as ModuleBuilder;
+
+            String strRefedModuleFileName = String.Empty;
+            if (refedModule.Assembly.Equals(this.Assembly))
+            {
+                // if the referenced module is in the same assembly, the resolution
+                // scope of the type token will be a module ref, we will need
+                // the file name of the referenced module for that.
+                // if the refed module is in a different assembly, the resolution
+                // scope of the type token will be an assembly ref. We don't need
+                // the file name of the referenced module.
+                if (refedModuleBuilder == null)
+                {
+                    refedModuleBuilder = this.ContainingAssemblyBuilder.GetModuleBuilder((InternalModuleBuilder)refedModule);
+                }
+                strRefedModuleFileName = refedModuleBuilder.m_moduleData.m_strFileName;
+            }
+
+            return new TypeToken(GetTypeRefNested(type, refedModule, strRefedModuleFileName));
+        }
+
+        public TypeToken GetTypeToken(String name)
+        {
+            // Return a token for the class relative to the Module. 
+            // Module.GetType() verifies name
+
+            // Unfortunately, we will need to load the Type and then call GetTypeToken in 
+            // order to correctly track the assembly reference information.
+
+            return GetTypeToken(InternalModule.GetType(name, false, true));
+        }
+
+        public MethodToken GetMethodToken(MethodInfo method)
+        {
+            lock (SyncRoot)
+            {
+                return GetMethodTokenNoLock(method, true);
+            }
+        }
+
+        internal MethodToken GetMethodTokenInternal(MethodInfo method)
+        {
+            lock (SyncRoot)
+            {
+                return GetMethodTokenNoLock(method, false);
+            }
+        }
+
+        // For a method on a generic type, we should return the methoddef token on the generic type definition in two cases
+        //   1. GetMethodToken
+        //   2. ldtoken (see ILGenerator)
+        // For all other occasions we should return the method on the generic type instantiated on the formal parameters.
+        private MethodToken GetMethodTokenNoLock(MethodInfo method, bool getGenericTypeDefinition)
+        {
+            // Return a MemberRef token if MethodInfo is not defined in this module. Or 
+            // return the MethodDef token. 
+            if (method == null)
+                throw new ArgumentNullException(nameof(method));
+
+            int tr;
+            int mr = 0;
+
+            SymbolMethod symMethod = null;
+            MethodBuilder methBuilder = null;
+
+            if ((methBuilder = method as MethodBuilder) != null)
+            {
+                int methodToken = methBuilder.MetadataTokenInternal;
+                if (method.Module.Equals(this))
+                    return new MethodToken(methodToken);
+
+                if (method.DeclaringType == null)
+                    throw new InvalidOperationException(SR.InvalidOperation_CannotImportGlobalFromDifferentModule);
+
+                // method is defined in a different module
+                tr = getGenericTypeDefinition ? GetTypeToken(method.DeclaringType).Token : GetTypeTokenInternal(method.DeclaringType).Token;
+                mr = GetMemberRef(method.DeclaringType.Module, tr, methodToken);
+            }
+            else if (method is MethodOnTypeBuilderInstantiation)
+            {
+                return new MethodToken(GetMemberRefToken(method, null));
+            }
+            else if ((symMethod = method as SymbolMethod) != null)
+            {
+                if (symMethod.GetModule() == this)
+                    return symMethod.GetToken();
+
+                // form the method token
+                return symMethod.GetToken(this);
+            }
+            else
+            {
+                Type declaringType = method.DeclaringType;
+
+                // We need to get the TypeRef tokens
+                if (declaringType == null)
+                    throw new InvalidOperationException(SR.InvalidOperation_CannotImportGlobalFromDifferentModule);
+
+                RuntimeMethodInfo rtMeth = null;
+
+                if (declaringType.IsArray == true)
+                {
+                    // use reflection to build signature to work around the E_T_VAR problem in EEClass
+                    ParameterInfo[] paramInfo = method.GetParameters();
+
+                    Type[] tt = new Type[paramInfo.Length];
+
+                    for (int i = 0; i < paramInfo.Length; i++)
+                        tt[i] = paramInfo[i].ParameterType;
+
+                    return GetArrayMethodToken(declaringType, method.Name, method.CallingConvention, method.ReturnType, tt);
+                }
+                else if ((rtMeth = method as RuntimeMethodInfo) != null)
+                {
+                    tr = getGenericTypeDefinition ? GetTypeToken(method.DeclaringType).Token : GetTypeTokenInternal(method.DeclaringType).Token;
+                    mr = GetMemberRefOfMethodInfo(tr, rtMeth);
+                }
+                else
+                {
+                    // some user derived ConstructorInfo
+                    // go through the slower code path, i.e. retrieve parameters and form signature helper.
+                    ParameterInfo[] parameters = method.GetParameters();
+
+                    Type[] parameterTypes = new Type[parameters.Length];
+                    Type[][] requiredCustomModifiers = new Type[parameterTypes.Length][];
+                    Type[][] optionalCustomModifiers = new Type[parameterTypes.Length][];
+
+                    for (int i = 0; i < parameters.Length; i++)
+                    {
+                        parameterTypes[i] = parameters[i].ParameterType;
+                        requiredCustomModifiers[i] = parameters[i].GetRequiredCustomModifiers();
+                        optionalCustomModifiers[i] = parameters[i].GetOptionalCustomModifiers();
+                    }
+
+                    tr = getGenericTypeDefinition ? GetTypeToken(method.DeclaringType).Token : GetTypeTokenInternal(method.DeclaringType).Token;
+
+                    SignatureHelper sigHelp;
+
+                    try
+                    {
+                        sigHelp = SignatureHelper.GetMethodSigHelper(
+                        this, method.CallingConvention, method.ReturnType,
+                        method.ReturnParameter.GetRequiredCustomModifiers(), method.ReturnParameter.GetOptionalCustomModifiers(),
+                        parameterTypes, requiredCustomModifiers, optionalCustomModifiers);
+                    }
+                    catch (NotImplementedException)
+                    {
+                        // Legacy code deriving from MethodInfo may not have implemented ReturnParameter.
+                        sigHelp = SignatureHelper.GetMethodSigHelper(this, method.ReturnType, parameterTypes);
+                    }
+
+                    int length;
+                    byte[] sigBytes = sigHelp.InternalGetSignature(out length);
+                    mr = GetMemberRefFromSignature(tr, method.Name, sigBytes, length);
+                }
+            }
+
+            return new MethodToken(mr);
+        }
+
+        internal int GetMethodTokenInternal(MethodBase method, IEnumerable<Type> optionalParameterTypes, bool useMethodDef)
+        {
+            int tk = 0;
+            MethodInfo methodInfo = method as MethodInfo;
+
+            if (method.IsGenericMethod)
+            {
+                // Constructors cannot be generic.
+                Debug.Assert(methodInfo != null);
+
+                // Given M<Bar> unbind to M<S>
+                MethodInfo methodInfoUnbound = methodInfo;
+                bool isGenericMethodDef = methodInfo.IsGenericMethodDefinition;
+
+                if (!isGenericMethodDef)
+                {
+                    methodInfoUnbound = methodInfo.GetGenericMethodDefinition();
+                }
+
+                if (!this.Equals(methodInfoUnbound.Module)
+                    || (methodInfoUnbound.DeclaringType != null && methodInfoUnbound.DeclaringType.IsGenericType))
+                {
+                    tk = GetMemberRefToken(methodInfoUnbound, null);
+                }
+                else
+                {
+                    tk = GetMethodTokenInternal(methodInfoUnbound).Token;
+                }
+
+                // For Ldtoken, Ldftn, and Ldvirtftn, we should emit the method def/ref token for a generic method definition.
+                if (isGenericMethodDef && useMethodDef)
+                {
+                    return tk;
+                }
+
+                // Create signature of method instantiation M<Bar>
+                int sigLength;
+                byte[] sigBytes = SignatureHelper.GetMethodSpecSigHelper(
+                    this, methodInfo.GetGenericArguments()).InternalGetSignature(out sigLength);
+
+                // Create MethodSepc M<Bar> with parent G?.M<S> 
+                tk = TypeBuilder.DefineMethodSpec(this.GetNativeHandle(), tk, sigBytes, sigLength);
+            }
+            else
+            {
+                if (((method.CallingConvention & CallingConventions.VarArgs) == 0) &&
+                    (method.DeclaringType == null || !method.DeclaringType.IsGenericType))
+                {
+                    if (methodInfo != null)
+                    {
+                        tk = GetMethodTokenInternal(methodInfo).Token;
+                    }
+                    else
+                    {
+                        tk = GetConstructorToken(method as ConstructorInfo).Token;
+                    }
+                }
+                else
+                {
+                    tk = GetMemberRefToken(method, optionalParameterTypes);
+                }
+            }
+
+            return tk;
+        }
+
+        public MethodToken GetArrayMethodToken(Type arrayClass, String methodName, CallingConventions callingConvention,
+            Type returnType, Type[] parameterTypes)
+        {
+            lock (SyncRoot)
+            {
+                return GetArrayMethodTokenNoLock(arrayClass, methodName, callingConvention, returnType, parameterTypes);
+            }
+        }
+
+        private MethodToken GetArrayMethodTokenNoLock(Type arrayClass, String methodName, CallingConventions callingConvention,
+            Type returnType, Type[] parameterTypes)
+        {
+            if (arrayClass == null)
+                throw new ArgumentNullException(nameof(arrayClass));
+
+            if (methodName == null)
+                throw new ArgumentNullException(nameof(methodName));
+
+            if (methodName.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(methodName));
+
+            if (arrayClass.IsArray == false)
+                throw new ArgumentException(SR.Argument_HasToBeArrayClass);
+
+            CheckContext(returnType, arrayClass);
+            CheckContext(parameterTypes);
+
+            // Return a token for the MethodInfo for a method on an Array.  This is primarily
+            // used to get the LoadElementAddress method. 
+
+            int length;
+
+            SignatureHelper sigHelp = SignatureHelper.GetMethodSigHelper(
+                this, callingConvention, returnType, null, null, parameterTypes, null, null);
+
+            byte[] sigBytes = sigHelp.InternalGetSignature(out length);
+
+            TypeToken typeSpec = GetTypeTokenInternal(arrayClass);
+
+            return new MethodToken(GetArrayMethodToken(GetNativeHandle(),
+                typeSpec.Token, methodName, sigBytes, length));
+        }
+
+        public MethodInfo GetArrayMethod(Type arrayClass, String methodName, CallingConventions callingConvention,
+            Type returnType, Type[] parameterTypes)
+        {
+            CheckContext(returnType, arrayClass);
+            CheckContext(parameterTypes);
+
+            // GetArrayMethod is useful when you have an array of a type whose definition has not been completed and 
+            // you want to access methods defined on Array. For example, you might define a type and want to define a 
+            // method that takes an array of the type as a parameter. In order to access the elements of the array, 
+            // you will need to call methods of the Array class.
+
+            MethodToken token = GetArrayMethodToken(arrayClass, methodName, callingConvention, returnType, parameterTypes);
+
+            return new SymbolMethod(this, token, arrayClass, methodName, callingConvention, returnType, parameterTypes);
+        }
+
+        public MethodToken GetConstructorToken(ConstructorInfo con)
+        {
+            // Return a token for the ConstructorInfo relative to the Module. 
+            return InternalGetConstructorToken(con, false);
+        }
+
+        public FieldToken GetFieldToken(FieldInfo field)
+        {
+            lock (SyncRoot)
+            {
+                return GetFieldTokenNoLock(field);
+            }
+        }
+
+        private FieldToken GetFieldTokenNoLock(FieldInfo field)
+        {
+            if (field == null)
+            {
+                throw new ArgumentNullException(nameof(field));
+            }
+
+            int tr;
+            int mr = 0;
+
+            FieldBuilder fdBuilder = null;
+            RuntimeFieldInfo rtField = null;
+            FieldOnTypeBuilderInstantiation fOnTB = null;
+
+            if ((fdBuilder = field as FieldBuilder) != null)
+            {
+                if (field.DeclaringType != null && field.DeclaringType.IsGenericType)
+                {
+                    int length;
+                    byte[] sig = SignatureHelper.GetTypeSigToken(this, field.DeclaringType).InternalGetSignature(out length);
+                    tr = GetTokenFromTypeSpec(sig, length);
+                    mr = GetMemberRef(this, tr, fdBuilder.GetToken().Token);
+                }
+                else if (fdBuilder.Module.Equals(this))
+                {
+                    // field is defined in the same module
+                    return fdBuilder.GetToken();
+                }
+                else
+                {
+                    // field is defined in a different module
+                    if (field.DeclaringType == null)
+                    {
+                        throw new InvalidOperationException(SR.InvalidOperation_CannotImportGlobalFromDifferentModule);
+                    }
+                    tr = GetTypeTokenInternal(field.DeclaringType).Token;
+                    mr = GetMemberRef(field.ReflectedType.Module, tr, fdBuilder.GetToken().Token);
+                }
+            }
+            else if ((rtField = field as RuntimeFieldInfo) != null)
+            {
+                // FieldInfo is not an dynamic field
+
+                // We need to get the TypeRef tokens
+                if (field.DeclaringType == null)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_CannotImportGlobalFromDifferentModule);
+                }
+
+                if (field.DeclaringType != null && field.DeclaringType.IsGenericType)
+                {
+                    int length;
+                    byte[] sig = SignatureHelper.GetTypeSigToken(this, field.DeclaringType).InternalGetSignature(out length);
+                    tr = GetTokenFromTypeSpec(sig, length);
+                    mr = GetMemberRefOfFieldInfo(tr, field.DeclaringType.GetTypeHandleInternal(), rtField);
+                }
+                else
+                {
+                    tr = GetTypeTokenInternal(field.DeclaringType).Token;
+                    mr = GetMemberRefOfFieldInfo(tr, field.DeclaringType.GetTypeHandleInternal(), rtField);
+                }
+            }
+            else if ((fOnTB = field as FieldOnTypeBuilderInstantiation) != null)
+            {
+                FieldInfo fb = fOnTB.FieldInfo;
+                int length;
+                byte[] sig = SignatureHelper.GetTypeSigToken(this, field.DeclaringType).InternalGetSignature(out length);
+                tr = GetTokenFromTypeSpec(sig, length);
+                mr = GetMemberRef(fb.ReflectedType.Module, tr, fOnTB.MetadataTokenInternal);
+            }
+            else
+            {
+                // user defined FieldInfo
+                tr = GetTypeTokenInternal(field.ReflectedType).Token;
+
+                SignatureHelper sigHelp = SignatureHelper.GetFieldSigHelper(this);
+
+                sigHelp.AddArgument(field.FieldType, field.GetRequiredCustomModifiers(), field.GetOptionalCustomModifiers());
+
+                int length;
+                byte[] sigBytes = sigHelp.InternalGetSignature(out length);
+
+                mr = GetMemberRefFromSignature(tr, field.Name, sigBytes, length);
+            }
+
+            return new FieldToken(mr, field.GetType());
+        }
+
+        public StringToken GetStringConstant(String str)
+        {
+            if (str == null)
+            {
+                throw new ArgumentNullException(nameof(str));
+            }
+
+            // Returns a token representing a String constant.  If the string 
+            // value has already been defined, the existing token will be returned.
+            return new StringToken(GetStringConstant(GetNativeHandle(), str, str.Length));
+        }
+
+        public SignatureToken GetSignatureToken(SignatureHelper sigHelper)
+        {
+            // Define signature token given a signature helper. This will define a metadata
+            // token for the signature described by SignatureHelper.
+
+            if (sigHelper == null)
+            {
+                throw new ArgumentNullException(nameof(sigHelper));
+            }
+
+            int sigLength;
+            byte[] sigBytes;
+
+            // get the signature in byte form
+            sigBytes = sigHelper.InternalGetSignature(out sigLength);
+            return new SignatureToken(TypeBuilder.GetTokenFromSig(GetNativeHandle(), sigBytes, sigLength), this);
+        }
+        public SignatureToken GetSignatureToken(byte[] sigBytes, int sigLength)
+        {
+            if (sigBytes == null)
+                throw new ArgumentNullException(nameof(sigBytes));
+
+            byte[] localSigBytes = new byte[sigBytes.Length];
+            Buffer.BlockCopy(sigBytes, 0, localSigBytes, 0, sigBytes.Length);
+
+            return new SignatureToken(TypeBuilder.GetTokenFromSig(GetNativeHandle(), localSigBytes, sigLength), this);
+        }
+
+        #endregion
+
+        #region Other
+
+        public void SetCustomAttribute(ConstructorInfo con, byte[] binaryAttribute)
+        {
+            if (con == null)
+                throw new ArgumentNullException(nameof(con));
+            if (binaryAttribute == null)
+                throw new ArgumentNullException(nameof(binaryAttribute));
+
+            TypeBuilder.DefineCustomAttribute(
+                this,
+                1,                                          // This is hard coding the module token to 1
+                this.GetConstructorToken(con).Token,
+                binaryAttribute,
+                false, false);
+        }
+
+        public void SetCustomAttribute(CustomAttributeBuilder customBuilder)
+        {
+            if (customBuilder == null)
+            {
+                throw new ArgumentNullException(nameof(customBuilder));
+            }
+
+            customBuilder.CreateCustomAttribute(this, 1);   // This is hard coding the module token to 1
+        }
+
+        // This API returns the symbol writer being used to write debug symbols for this 
+        // module (if any).
+        // 
+        // WARNING: It is unlikely this API can be used correctly by applications in any 
+        // reasonable way.  It may be called internally from within TypeBuilder.CreateType.
+        // 
+        // Specifically:
+        // 1. The underlying symbol writer (written in unmanaged code) is not necessarily well
+        // hardenned and fuzz-tested against malicious API calls.  The security of partial-trust
+        // symbol writing is improved by restricting usage of the writer APIs to the well-structured
+        // uses in ModuleBuilder. 
+        // 2. TypeBuilder.CreateType emits all the symbols for the type.  This will effectively 
+        // overwrite anything someone may have written manually about the type (specifically 
+        // ISymbolWriter.OpenMethod is specced to clear anything previously written for the 
+        // specified method)
+        // 3. Someone could technically update the symbols for a method after CreateType is 
+        // called, but the debugger (which uses these symbols) assumes that they are only 
+        // updated at TypeBuilder.CreateType time.  The changes wouldn't be visible (committed 
+        // to the underlying stream) until another type was baked.
+        // 4. Access to the writer is supposed to be synchronized (the underlying COM API is 
+        // not thread safe, and these are only thin wrappers on top of them).  Exposing this 
+        // directly allows the synchronization to be violated.  We know that concurrent symbol 
+        // writer access can cause AVs and other problems.  The writer APIs should not be callable
+        // directly by partial-trust code, but if they could this would be a security hole.  
+        // Regardless, this is a reliability bug.  
+        // 
+        // For these reasons, we should consider making this API internal in Arrowhead
+        // (as it is in Silverlight), and consider validating that we're within a call
+        // to TypeBuilder.CreateType whenever this is used.
+        internal ISymbolWriter GetSymWriter()
+        {
+            return m_iSymWriter;
+        }
+
+        public ISymbolDocumentWriter DefineDocument(String url, Guid language, Guid languageVendor, Guid documentType)
+        {
+            // url cannot be null but can be an empty string 
+            if (url == null)
+                throw new ArgumentNullException(nameof(url));
+
+            lock (SyncRoot)
+            {
+                return DefineDocumentNoLock(url, language, languageVendor, documentType);
+            }
+        }
+
+        private ISymbolDocumentWriter DefineDocumentNoLock(String url, Guid language, Guid languageVendor, Guid documentType)
+        {
+            if (m_iSymWriter == null)
+            {
+                // Cannot DefineDocument when it is not a debug module
+                throw new InvalidOperationException(SR.InvalidOperation_NotADebugModule);
+            }
+
+            return m_iSymWriter.DefineDocument(url, language, languageVendor, documentType);
+        }
+
+        public bool IsTransient()
+        {
+            return InternalModule.IsTransientInternal();
+        }
+
+        #endregion
+
+        #endregion    
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/ModuleBuilderData.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/ModuleBuilderData.cs
new file mode 100644
index 0000000000..0364ae52ab
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/ModuleBuilderData.cs
@@ -0,0 +1,62 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+using System.Globalization;
+using System.IO;
+using System.Reflection;
+using System.Runtime.Versioning;
+
+namespace System.Reflection.Emit
+{
+    // This is a package private class. This class hold all of the managed
+    // data member for ModuleBuilder. Note that what ever data members added to
+    // this class cannot be accessed from the EE.
+    internal class ModuleBuilderData
+    {
+        internal ModuleBuilderData(ModuleBuilder module, String strModuleName, String strFileName, int tkFile)
+        {
+            m_globalTypeBuilder = new TypeBuilder(module);
+            m_module = module;
+            m_tkFile = tkFile;
+
+            InitNames(strModuleName, strFileName);
+        }
+
+        // Initialize module and file names.
+        private void InitNames(String strModuleName, String strFileName)
+        {
+            m_strModuleName = strModuleName;
+            if (strFileName == null)
+            {
+                // fake a transient module file name
+                m_strFileName = strModuleName;
+            }
+            else
+            {
+                String strExtension = Path.GetExtension(strFileName);
+                if (strExtension == null || strExtension == String.Empty)
+                {
+                    // This is required by our loader. It cannot load module file that does not have file extension.
+                    throw new ArgumentException(SR.Format(SR.Argument_NoModuleFileExtension, strFileName));
+                }
+                m_strFileName = strFileName;
+            }
+        }
+
+        internal String m_strModuleName;     // scope name (can be different from file name)
+        internal String m_strFileName;
+        internal bool m_fGlobalBeenCreated;
+        internal bool m_fHasGlobal;
+        internal TypeBuilder m_globalTypeBuilder;
+        internal ModuleBuilder m_module;
+
+        private int m_tkFile;
+        internal bool m_isSaved;
+        internal const String MULTI_BYTE_VALUE_CLASS = "$ArrayType$";
+        internal String m_strResourceFileName;
+        internal byte[] m_resourceBytes;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/OpCodeType.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/OpCodeType.cs
new file mode 100644
index 0000000000..17435c5768
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/OpCodeType.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Enumeration: OpCodeType
+**
+** Purpose: Exposes OpCodeType Attribute of IL.
+**
+** THIS FILE IS AUTOMATICALLY GENERATED. DO NOT EDIT BY HAND!
+** See $(RepoRoot)\src\inc\OpCodeGen.pl for more information.**
+==============================================================*/
+
+using System;
+
+namespace System.Reflection.Emit
+{
+    public enum OpCodeType
+    {
+        [Obsolete("This API has been deprecated. http://go.microsoft.com/fwlink/?linkid=14202")]
+        Annotation = 0,
+        Macro = 1,
+        Nternal = 2,
+        Objmodel = 3,
+        Prefix = 4,
+        Primitive = 5,
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/OpCodes.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/OpCodes.cs
new file mode 100644
index 0000000000..81257bdd4b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/OpCodes.cs
@@ -0,0 +1,2552 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Class: OpCodes
+**
+** Purpose: Exposes all of the IL instructions supported by the runtime.
+**
+** THIS FILE IS AUTOMATICALLY GENERATED. DO NOT EDIT BY HAND!
+** See $(RepoRoot)\src\inc\OpCodeGen.pl for more information.**
+==============================================================*/
+
+using System;
+
+namespace System.Reflection.Emit
+{
+    ///<summary>
+    /// Internal enum OpCodeValues for opcode values.
+    ///</summary>
+    ///<remarks>
+    /// Note that the value names are used to construct publicly visible
+    /// ilasm-compatible opcode names, so their exact form is important!
+    ///</remarks>
+    internal enum OpCodeValues
+    {
+        Nop = 0x00,
+        Break = 0x01,
+        Ldarg_0 = 0x02,
+        Ldarg_1 = 0x03,
+        Ldarg_2 = 0x04,
+        Ldarg_3 = 0x05,
+        Ldloc_0 = 0x06,
+        Ldloc_1 = 0x07,
+        Ldloc_2 = 0x08,
+        Ldloc_3 = 0x09,
+        Stloc_0 = 0x0a,
+        Stloc_1 = 0x0b,
+        Stloc_2 = 0x0c,
+        Stloc_3 = 0x0d,
+        Ldarg_S = 0x0e,
+        Ldarga_S = 0x0f,
+        Starg_S = 0x10,
+        Ldloc_S = 0x11,
+        Ldloca_S = 0x12,
+        Stloc_S = 0x13,
+        Ldnull = 0x14,
+        Ldc_I4_M1 = 0x15,
+        Ldc_I4_0 = 0x16,
+        Ldc_I4_1 = 0x17,
+        Ldc_I4_2 = 0x18,
+        Ldc_I4_3 = 0x19,
+        Ldc_I4_4 = 0x1a,
+        Ldc_I4_5 = 0x1b,
+        Ldc_I4_6 = 0x1c,
+        Ldc_I4_7 = 0x1d,
+        Ldc_I4_8 = 0x1e,
+        Ldc_I4_S = 0x1f,
+        Ldc_I4 = 0x20,
+        Ldc_I8 = 0x21,
+        Ldc_R4 = 0x22,
+        Ldc_R8 = 0x23,
+        Dup = 0x25,
+        Pop = 0x26,
+        Jmp = 0x27,
+        Call = 0x28,
+        Calli = 0x29,
+        Ret = 0x2a,
+        Br_S = 0x2b,
+        Brfalse_S = 0x2c,
+        Brtrue_S = 0x2d,
+        Beq_S = 0x2e,
+        Bge_S = 0x2f,
+        Bgt_S = 0x30,
+        Ble_S = 0x31,
+        Blt_S = 0x32,
+        Bne_Un_S = 0x33,
+        Bge_Un_S = 0x34,
+        Bgt_Un_S = 0x35,
+        Ble_Un_S = 0x36,
+        Blt_Un_S = 0x37,
+        Br = 0x38,
+        Brfalse = 0x39,
+        Brtrue = 0x3a,
+        Beq = 0x3b,
+        Bge = 0x3c,
+        Bgt = 0x3d,
+        Ble = 0x3e,
+        Blt = 0x3f,
+        Bne_Un = 0x40,
+        Bge_Un = 0x41,
+        Bgt_Un = 0x42,
+        Ble_Un = 0x43,
+        Blt_Un = 0x44,
+        Switch = 0x45,
+        Ldind_I1 = 0x46,
+        Ldind_U1 = 0x47,
+        Ldind_I2 = 0x48,
+        Ldind_U2 = 0x49,
+        Ldind_I4 = 0x4a,
+        Ldind_U4 = 0x4b,
+        Ldind_I8 = 0x4c,
+        Ldind_I = 0x4d,
+        Ldind_R4 = 0x4e,
+        Ldind_R8 = 0x4f,
+        Ldind_Ref = 0x50,
+        Stind_Ref = 0x51,
+        Stind_I1 = 0x52,
+        Stind_I2 = 0x53,
+        Stind_I4 = 0x54,
+        Stind_I8 = 0x55,
+        Stind_R4 = 0x56,
+        Stind_R8 = 0x57,
+        Add = 0x58,
+        Sub = 0x59,
+        Mul = 0x5a,
+        Div = 0x5b,
+        Div_Un = 0x5c,
+        Rem = 0x5d,
+        Rem_Un = 0x5e,
+        And = 0x5f,
+        Or = 0x60,
+        Xor = 0x61,
+        Shl = 0x62,
+        Shr = 0x63,
+        Shr_Un = 0x64,
+        Neg = 0x65,
+        Not = 0x66,
+        Conv_I1 = 0x67,
+        Conv_I2 = 0x68,
+        Conv_I4 = 0x69,
+        Conv_I8 = 0x6a,
+        Conv_R4 = 0x6b,
+        Conv_R8 = 0x6c,
+        Conv_U4 = 0x6d,
+        Conv_U8 = 0x6e,
+        Callvirt = 0x6f,
+        Cpobj = 0x70,
+        Ldobj = 0x71,
+        Ldstr = 0x72,
+        Newobj = 0x73,
+        Castclass = 0x74,
+        Isinst = 0x75,
+        Conv_R_Un = 0x76,
+        Unbox = 0x79,
+        Throw = 0x7a,
+        Ldfld = 0x7b,
+        Ldflda = 0x7c,
+        Stfld = 0x7d,
+        Ldsfld = 0x7e,
+        Ldsflda = 0x7f,
+        Stsfld = 0x80,
+        Stobj = 0x81,
+        Conv_Ovf_I1_Un = 0x82,
+        Conv_Ovf_I2_Un = 0x83,
+        Conv_Ovf_I4_Un = 0x84,
+        Conv_Ovf_I8_Un = 0x85,
+        Conv_Ovf_U1_Un = 0x86,
+        Conv_Ovf_U2_Un = 0x87,
+        Conv_Ovf_U4_Un = 0x88,
+        Conv_Ovf_U8_Un = 0x89,
+        Conv_Ovf_I_Un = 0x8a,
+        Conv_Ovf_U_Un = 0x8b,
+        Box = 0x8c,
+        Newarr = 0x8d,
+        Ldlen = 0x8e,
+        Ldelema = 0x8f,
+        Ldelem_I1 = 0x90,
+        Ldelem_U1 = 0x91,
+        Ldelem_I2 = 0x92,
+        Ldelem_U2 = 0x93,
+        Ldelem_I4 = 0x94,
+        Ldelem_U4 = 0x95,
+        Ldelem_I8 = 0x96,
+        Ldelem_I = 0x97,
+        Ldelem_R4 = 0x98,
+        Ldelem_R8 = 0x99,
+        Ldelem_Ref = 0x9a,
+        Stelem_I = 0x9b,
+        Stelem_I1 = 0x9c,
+        Stelem_I2 = 0x9d,
+        Stelem_I4 = 0x9e,
+        Stelem_I8 = 0x9f,
+        Stelem_R4 = 0xa0,
+        Stelem_R8 = 0xa1,
+        Stelem_Ref = 0xa2,
+        Ldelem = 0xa3,
+        Stelem = 0xa4,
+        Unbox_Any = 0xa5,
+        Conv_Ovf_I1 = 0xb3,
+        Conv_Ovf_U1 = 0xb4,
+        Conv_Ovf_I2 = 0xb5,
+        Conv_Ovf_U2 = 0xb6,
+        Conv_Ovf_I4 = 0xb7,
+        Conv_Ovf_U4 = 0xb8,
+        Conv_Ovf_I8 = 0xb9,
+        Conv_Ovf_U8 = 0xba,
+        Refanyval = 0xc2,
+        Ckfinite = 0xc3,
+        Mkrefany = 0xc6,
+        Ldtoken = 0xd0,
+        Conv_U2 = 0xd1,
+        Conv_U1 = 0xd2,
+        Conv_I = 0xd3,
+        Conv_Ovf_I = 0xd4,
+        Conv_Ovf_U = 0xd5,
+        Add_Ovf = 0xd6,
+        Add_Ovf_Un = 0xd7,
+        Mul_Ovf = 0xd8,
+        Mul_Ovf_Un = 0xd9,
+        Sub_Ovf = 0xda,
+        Sub_Ovf_Un = 0xdb,
+        Endfinally = 0xdc,
+        Leave = 0xdd,
+        Leave_S = 0xde,
+        Stind_I = 0xdf,
+        Conv_U = 0xe0,
+        Prefix7 = 0xf8,
+        Prefix6 = 0xf9,
+        Prefix5 = 0xfa,
+        Prefix4 = 0xfb,
+        Prefix3 = 0xfc,
+        Prefix2 = 0xfd,
+        Prefix1 = 0xfe,
+        Prefixref = 0xff,
+        Arglist = 0xfe00,
+        Ceq = 0xfe01,
+        Cgt = 0xfe02,
+        Cgt_Un = 0xfe03,
+        Clt = 0xfe04,
+        Clt_Un = 0xfe05,
+        Ldftn = 0xfe06,
+        Ldvirtftn = 0xfe07,
+        Ldarg = 0xfe09,
+        Ldarga = 0xfe0a,
+        Starg = 0xfe0b,
+        Ldloc = 0xfe0c,
+        Ldloca = 0xfe0d,
+        Stloc = 0xfe0e,
+        Localloc = 0xfe0f,
+        Endfilter = 0xfe11,
+        Unaligned_ = 0xfe12,
+        Volatile_ = 0xfe13,
+        Tail_ = 0xfe14,
+        Initobj = 0xfe15,
+        Constrained_ = 0xfe16,
+        Cpblk = 0xfe17,
+        Initblk = 0xfe18,
+        Rethrow = 0xfe1a,
+        Sizeof = 0xfe1c,
+        Refanytype = 0xfe1d,
+        Readonly_ = 0xfe1e,
+    }
+
+    /// <summary>
+    ///    <para>
+    ///       The IL instruction opcodes supported by the runtime.
+    ///       The Specification of IL Instruction describes each Opcode.
+    ///    </para>
+    /// </summary>
+    /// <seealso topic='IL Instruction Set Specification'/>
+    public class OpCodes
+    {
+        private OpCodes()
+        {
+        }
+
+        public static readonly OpCode Nop = new OpCode(OpCodeValues.Nop,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Break = new OpCode(OpCodeValues.Break,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Break << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldarg_0 = new OpCode(OpCodeValues.Ldarg_0,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldarg_1 = new OpCode(OpCodeValues.Ldarg_1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldarg_2 = new OpCode(OpCodeValues.Ldarg_2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldarg_3 = new OpCode(OpCodeValues.Ldarg_3,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldloc_0 = new OpCode(OpCodeValues.Ldloc_0,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldloc_1 = new OpCode(OpCodeValues.Ldloc_1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldloc_2 = new OpCode(OpCodeValues.Ldloc_2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldloc_3 = new OpCode(OpCodeValues.Ldloc_3,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stloc_0 = new OpCode(OpCodeValues.Stloc_0,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stloc_1 = new OpCode(OpCodeValues.Stloc_1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stloc_2 = new OpCode(OpCodeValues.Stloc_2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stloc_3 = new OpCode(OpCodeValues.Stloc_3,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldarg_S = new OpCode(OpCodeValues.Ldarg_S,
+            ((int)OperandType.ShortInlineVar) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldarga_S = new OpCode(OpCodeValues.Ldarga_S,
+            ((int)OperandType.ShortInlineVar) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Starg_S = new OpCode(OpCodeValues.Starg_S,
+            ((int)OperandType.ShortInlineVar) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldloc_S = new OpCode(OpCodeValues.Ldloc_S,
+            ((int)OperandType.ShortInlineVar) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldloca_S = new OpCode(OpCodeValues.Ldloca_S,
+            ((int)OperandType.ShortInlineVar) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stloc_S = new OpCode(OpCodeValues.Stloc_S,
+            ((int)OperandType.ShortInlineVar) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldnull = new OpCode(OpCodeValues.Ldnull,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushref << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_I4_M1 = new OpCode(OpCodeValues.Ldc_I4_M1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_I4_0 = new OpCode(OpCodeValues.Ldc_I4_0,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_I4_1 = new OpCode(OpCodeValues.Ldc_I4_1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_I4_2 = new OpCode(OpCodeValues.Ldc_I4_2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_I4_3 = new OpCode(OpCodeValues.Ldc_I4_3,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_I4_4 = new OpCode(OpCodeValues.Ldc_I4_4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_I4_5 = new OpCode(OpCodeValues.Ldc_I4_5,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_I4_6 = new OpCode(OpCodeValues.Ldc_I4_6,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_I4_7 = new OpCode(OpCodeValues.Ldc_I4_7,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_I4_8 = new OpCode(OpCodeValues.Ldc_I4_8,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_I4_S = new OpCode(OpCodeValues.Ldc_I4_S,
+            ((int)OperandType.ShortInlineI) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_I4 = new OpCode(OpCodeValues.Ldc_I4,
+            ((int)OperandType.InlineI) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_I8 = new OpCode(OpCodeValues.Ldc_I8,
+            ((int)OperandType.InlineI8) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_R4 = new OpCode(OpCodeValues.Ldc_R4,
+            ((int)OperandType.ShortInlineR) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushr4 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldc_R8 = new OpCode(OpCodeValues.Ldc_R8,
+            ((int)OperandType.InlineR) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushr8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Dup = new OpCode(OpCodeValues.Dup,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1_push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Pop = new OpCode(OpCodeValues.Pop,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Jmp = new OpCode(OpCodeValues.Jmp,
+            ((int)OperandType.InlineMethod) |
+            ((int)FlowControl.Call << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            OpCode.EndsUncondJmpBlkFlag |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Call = new OpCode(OpCodeValues.Call,
+            ((int)OperandType.InlineMethod) |
+            ((int)FlowControl.Call << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Varpop << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Varpush << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Calli = new OpCode(OpCodeValues.Calli,
+            ((int)OperandType.InlineSig) |
+            ((int)FlowControl.Call << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Varpop << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Varpush << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ret = new OpCode(OpCodeValues.Ret,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Return << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Varpop << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            OpCode.EndsUncondJmpBlkFlag |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Br_S = new OpCode(OpCodeValues.Br_S,
+            ((int)OperandType.ShortInlineBrTarget) |
+            ((int)FlowControl.Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            OpCode.EndsUncondJmpBlkFlag |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Brfalse_S = new OpCode(OpCodeValues.Brfalse_S,
+            ((int)OperandType.ShortInlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Brtrue_S = new OpCode(OpCodeValues.Brtrue_S,
+            ((int)OperandType.ShortInlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Beq_S = new OpCode(OpCodeValues.Beq_S,
+            ((int)OperandType.ShortInlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Bge_S = new OpCode(OpCodeValues.Bge_S,
+            ((int)OperandType.ShortInlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Bgt_S = new OpCode(OpCodeValues.Bgt_S,
+            ((int)OperandType.ShortInlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ble_S = new OpCode(OpCodeValues.Ble_S,
+            ((int)OperandType.ShortInlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Blt_S = new OpCode(OpCodeValues.Blt_S,
+            ((int)OperandType.ShortInlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Bne_Un_S = new OpCode(OpCodeValues.Bne_Un_S,
+            ((int)OperandType.ShortInlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Bge_Un_S = new OpCode(OpCodeValues.Bge_Un_S,
+            ((int)OperandType.ShortInlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Bgt_Un_S = new OpCode(OpCodeValues.Bgt_Un_S,
+            ((int)OperandType.ShortInlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ble_Un_S = new OpCode(OpCodeValues.Ble_Un_S,
+            ((int)OperandType.ShortInlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Blt_Un_S = new OpCode(OpCodeValues.Blt_Un_S,
+            ((int)OperandType.ShortInlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Br = new OpCode(OpCodeValues.Br,
+            ((int)OperandType.InlineBrTarget) |
+            ((int)FlowControl.Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            OpCode.EndsUncondJmpBlkFlag |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Brfalse = new OpCode(OpCodeValues.Brfalse,
+            ((int)OperandType.InlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Brtrue = new OpCode(OpCodeValues.Brtrue,
+            ((int)OperandType.InlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Beq = new OpCode(OpCodeValues.Beq,
+            ((int)OperandType.InlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Bge = new OpCode(OpCodeValues.Bge,
+            ((int)OperandType.InlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Bgt = new OpCode(OpCodeValues.Bgt,
+            ((int)OperandType.InlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ble = new OpCode(OpCodeValues.Ble,
+            ((int)OperandType.InlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Blt = new OpCode(OpCodeValues.Blt,
+            ((int)OperandType.InlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Bne_Un = new OpCode(OpCodeValues.Bne_Un,
+            ((int)OperandType.InlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Bge_Un = new OpCode(OpCodeValues.Bge_Un,
+            ((int)OperandType.InlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Bgt_Un = new OpCode(OpCodeValues.Bgt_Un,
+            ((int)OperandType.InlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ble_Un = new OpCode(OpCodeValues.Ble_Un,
+            ((int)OperandType.InlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Blt_Un = new OpCode(OpCodeValues.Blt_Un,
+            ((int)OperandType.InlineBrTarget) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Macro << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Switch = new OpCode(OpCodeValues.Switch,
+            ((int)OperandType.InlineSwitch) |
+            ((int)FlowControl.Cond_Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldind_I1 = new OpCode(OpCodeValues.Ldind_I1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldind_U1 = new OpCode(OpCodeValues.Ldind_U1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldind_I2 = new OpCode(OpCodeValues.Ldind_I2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldind_U2 = new OpCode(OpCodeValues.Ldind_U2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldind_I4 = new OpCode(OpCodeValues.Ldind_I4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldind_U4 = new OpCode(OpCodeValues.Ldind_U4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldind_I8 = new OpCode(OpCodeValues.Ldind_I8,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldind_I = new OpCode(OpCodeValues.Ldind_I,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldind_R4 = new OpCode(OpCodeValues.Ldind_R4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushr4 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldind_R8 = new OpCode(OpCodeValues.Ldind_R8,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushr8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldind_Ref = new OpCode(OpCodeValues.Ldind_Ref,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushref << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stind_Ref = new OpCode(OpCodeValues.Stind_Ref,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stind_I1 = new OpCode(OpCodeValues.Stind_I1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stind_I2 = new OpCode(OpCodeValues.Stind_I2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stind_I4 = new OpCode(OpCodeValues.Stind_I4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stind_I8 = new OpCode(OpCodeValues.Stind_I8,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi_popi8 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stind_R4 = new OpCode(OpCodeValues.Stind_R4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi_popr4 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stind_R8 = new OpCode(OpCodeValues.Stind_R8,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi_popr8 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Add = new OpCode(OpCodeValues.Add,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Sub = new OpCode(OpCodeValues.Sub,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Mul = new OpCode(OpCodeValues.Mul,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Div = new OpCode(OpCodeValues.Div,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Div_Un = new OpCode(OpCodeValues.Div_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Rem = new OpCode(OpCodeValues.Rem,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Rem_Un = new OpCode(OpCodeValues.Rem_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode And = new OpCode(OpCodeValues.And,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Or = new OpCode(OpCodeValues.Or,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Xor = new OpCode(OpCodeValues.Xor,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Shl = new OpCode(OpCodeValues.Shl,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Shr = new OpCode(OpCodeValues.Shr,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Shr_Un = new OpCode(OpCodeValues.Shr_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Neg = new OpCode(OpCodeValues.Neg,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Not = new OpCode(OpCodeValues.Not,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_I1 = new OpCode(OpCodeValues.Conv_I1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_I2 = new OpCode(OpCodeValues.Conv_I2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_I4 = new OpCode(OpCodeValues.Conv_I4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_I8 = new OpCode(OpCodeValues.Conv_I8,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_R4 = new OpCode(OpCodeValues.Conv_R4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushr4 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_R8 = new OpCode(OpCodeValues.Conv_R8,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushr8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_U4 = new OpCode(OpCodeValues.Conv_U4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_U8 = new OpCode(OpCodeValues.Conv_U8,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Callvirt = new OpCode(OpCodeValues.Callvirt,
+            ((int)OperandType.InlineMethod) |
+            ((int)FlowControl.Call << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Varpop << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Varpush << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Cpobj = new OpCode(OpCodeValues.Cpobj,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldobj = new OpCode(OpCodeValues.Ldobj,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldstr = new OpCode(OpCodeValues.Ldstr,
+            ((int)OperandType.InlineString) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushref << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Newobj = new OpCode(OpCodeValues.Newobj,
+            ((int)OperandType.InlineMethod) |
+            ((int)FlowControl.Call << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Varpop << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushref << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Castclass = new OpCode(OpCodeValues.Castclass,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushref << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Isinst = new OpCode(OpCodeValues.Isinst,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_R_Un = new OpCode(OpCodeValues.Conv_R_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushr8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Unbox = new OpCode(OpCodeValues.Unbox,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Throw = new OpCode(OpCodeValues.Throw,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Throw << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            OpCode.EndsUncondJmpBlkFlag |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldfld = new OpCode(OpCodeValues.Ldfld,
+            ((int)OperandType.InlineField) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldflda = new OpCode(OpCodeValues.Ldflda,
+            ((int)OperandType.InlineField) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stfld = new OpCode(OpCodeValues.Stfld,
+            ((int)OperandType.InlineField) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldsfld = new OpCode(OpCodeValues.Ldsfld,
+            ((int)OperandType.InlineField) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldsflda = new OpCode(OpCodeValues.Ldsflda,
+            ((int)OperandType.InlineField) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stsfld = new OpCode(OpCodeValues.Stsfld,
+            ((int)OperandType.InlineField) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stobj = new OpCode(OpCodeValues.Stobj,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_I1_Un = new OpCode(OpCodeValues.Conv_Ovf_I1_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_I2_Un = new OpCode(OpCodeValues.Conv_Ovf_I2_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_I4_Un = new OpCode(OpCodeValues.Conv_Ovf_I4_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_I8_Un = new OpCode(OpCodeValues.Conv_Ovf_I8_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_U1_Un = new OpCode(OpCodeValues.Conv_Ovf_U1_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_U2_Un = new OpCode(OpCodeValues.Conv_Ovf_U2_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_U4_Un = new OpCode(OpCodeValues.Conv_Ovf_U4_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_U8_Un = new OpCode(OpCodeValues.Conv_Ovf_U8_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_I_Un = new OpCode(OpCodeValues.Conv_Ovf_I_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_U_Un = new OpCode(OpCodeValues.Conv_Ovf_U_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Box = new OpCode(OpCodeValues.Box,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushref << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Newarr = new OpCode(OpCodeValues.Newarr,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushref << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldlen = new OpCode(OpCodeValues.Ldlen,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldelema = new OpCode(OpCodeValues.Ldelema,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldelem_I1 = new OpCode(OpCodeValues.Ldelem_I1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldelem_U1 = new OpCode(OpCodeValues.Ldelem_U1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldelem_I2 = new OpCode(OpCodeValues.Ldelem_I2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldelem_U2 = new OpCode(OpCodeValues.Ldelem_U2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldelem_I4 = new OpCode(OpCodeValues.Ldelem_I4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldelem_U4 = new OpCode(OpCodeValues.Ldelem_U4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldelem_I8 = new OpCode(OpCodeValues.Ldelem_I8,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldelem_I = new OpCode(OpCodeValues.Ldelem_I,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldelem_R4 = new OpCode(OpCodeValues.Ldelem_R4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushr4 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldelem_R8 = new OpCode(OpCodeValues.Ldelem_R8,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushr8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldelem_Ref = new OpCode(OpCodeValues.Ldelem_Ref,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushref << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stelem_I = new OpCode(OpCodeValues.Stelem_I,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-3 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stelem_I1 = new OpCode(OpCodeValues.Stelem_I1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-3 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stelem_I2 = new OpCode(OpCodeValues.Stelem_I2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-3 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stelem_I4 = new OpCode(OpCodeValues.Stelem_I4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-3 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stelem_I8 = new OpCode(OpCodeValues.Stelem_I8,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi_popi8 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-3 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stelem_R4 = new OpCode(OpCodeValues.Stelem_R4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi_popr4 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-3 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stelem_R8 = new OpCode(OpCodeValues.Stelem_R8,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi_popr8 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-3 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stelem_Ref = new OpCode(OpCodeValues.Stelem_Ref,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi_popref << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-3 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldelem = new OpCode(OpCodeValues.Ldelem,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stelem = new OpCode(OpCodeValues.Stelem,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref_popi_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Unbox_Any = new OpCode(OpCodeValues.Unbox_Any,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_I1 = new OpCode(OpCodeValues.Conv_Ovf_I1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_U1 = new OpCode(OpCodeValues.Conv_Ovf_U1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_I2 = new OpCode(OpCodeValues.Conv_Ovf_I2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_U2 = new OpCode(OpCodeValues.Conv_Ovf_U2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_I4 = new OpCode(OpCodeValues.Conv_Ovf_I4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_U4 = new OpCode(OpCodeValues.Conv_Ovf_U4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_I8 = new OpCode(OpCodeValues.Conv_Ovf_I8,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_U8 = new OpCode(OpCodeValues.Conv_Ovf_U8,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Refanyval = new OpCode(OpCodeValues.Refanyval,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ckfinite = new OpCode(OpCodeValues.Ckfinite,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushr8 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Mkrefany = new OpCode(OpCodeValues.Mkrefany,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldtoken = new OpCode(OpCodeValues.Ldtoken,
+            ((int)OperandType.InlineTok) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_U2 = new OpCode(OpCodeValues.Conv_U2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_U1 = new OpCode(OpCodeValues.Conv_U1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_I = new OpCode(OpCodeValues.Conv_I,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_I = new OpCode(OpCodeValues.Conv_Ovf_I,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_Ovf_U = new OpCode(OpCodeValues.Conv_Ovf_U,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Add_Ovf = new OpCode(OpCodeValues.Add_Ovf,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Add_Ovf_Un = new OpCode(OpCodeValues.Add_Ovf_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Mul_Ovf = new OpCode(OpCodeValues.Mul_Ovf,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Mul_Ovf_Un = new OpCode(OpCodeValues.Mul_Ovf_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Sub_Ovf = new OpCode(OpCodeValues.Sub_Ovf,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Sub_Ovf_Un = new OpCode(OpCodeValues.Sub_Ovf_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Endfinally = new OpCode(OpCodeValues.Endfinally,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Return << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            OpCode.EndsUncondJmpBlkFlag |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Leave = new OpCode(OpCodeValues.Leave,
+            ((int)OperandType.InlineBrTarget) |
+            ((int)FlowControl.Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            OpCode.EndsUncondJmpBlkFlag |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Leave_S = new OpCode(OpCodeValues.Leave_S,
+            ((int)OperandType.ShortInlineBrTarget) |
+            ((int)FlowControl.Branch << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            OpCode.EndsUncondJmpBlkFlag |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stind_I = new OpCode(OpCodeValues.Stind_I,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (-2 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Conv_U = new OpCode(OpCodeValues.Conv_U,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Prefix7 = new OpCode(OpCodeValues.Prefix7,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Meta << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Nternal << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Prefix6 = new OpCode(OpCodeValues.Prefix6,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Meta << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Nternal << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Prefix5 = new OpCode(OpCodeValues.Prefix5,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Meta << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Nternal << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Prefix4 = new OpCode(OpCodeValues.Prefix4,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Meta << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Nternal << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Prefix3 = new OpCode(OpCodeValues.Prefix3,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Meta << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Nternal << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Prefix2 = new OpCode(OpCodeValues.Prefix2,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Meta << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Nternal << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Prefix1 = new OpCode(OpCodeValues.Prefix1,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Meta << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Nternal << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Prefixref = new OpCode(OpCodeValues.Prefixref,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Meta << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Nternal << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (1 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Arglist = new OpCode(OpCodeValues.Arglist,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ceq = new OpCode(OpCodeValues.Ceq,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Cgt = new OpCode(OpCodeValues.Cgt,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Cgt_Un = new OpCode(OpCodeValues.Cgt_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Clt = new OpCode(OpCodeValues.Clt,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Clt_Un = new OpCode(OpCodeValues.Clt_Un,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1_pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldftn = new OpCode(OpCodeValues.Ldftn,
+            ((int)OperandType.InlineMethod) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldvirtftn = new OpCode(OpCodeValues.Ldvirtftn,
+            ((int)OperandType.InlineMethod) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popref << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldarg = new OpCode(OpCodeValues.Ldarg,
+            ((int)OperandType.InlineVar) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldarga = new OpCode(OpCodeValues.Ldarga,
+            ((int)OperandType.InlineVar) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Starg = new OpCode(OpCodeValues.Starg,
+            ((int)OperandType.InlineVar) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldloc = new OpCode(OpCodeValues.Ldloc,
+            ((int)OperandType.InlineVar) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push1 << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Ldloca = new OpCode(OpCodeValues.Ldloca,
+            ((int)OperandType.InlineVar) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Stloc = new OpCode(OpCodeValues.Stloc,
+            ((int)OperandType.InlineVar) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Localloc = new OpCode(OpCodeValues.Localloc,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Endfilter = new OpCode(OpCodeValues.Endfilter,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Return << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            OpCode.EndsUncondJmpBlkFlag |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Unaligned = new OpCode(OpCodeValues.Unaligned_,
+            ((int)OperandType.ShortInlineI) |
+            ((int)FlowControl.Meta << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Prefix << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Volatile = new OpCode(OpCodeValues.Volatile_,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Meta << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Prefix << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Tailcall = new OpCode(OpCodeValues.Tail_,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Meta << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Prefix << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Initobj = new OpCode(OpCodeValues.Initobj,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (-1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Constrained = new OpCode(OpCodeValues.Constrained_,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Meta << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Prefix << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Cpblk = new OpCode(OpCodeValues.Cpblk,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi_popi_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (-3 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Initblk = new OpCode(OpCodeValues.Initblk,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Popi_popi_popi << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (-3 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Rethrow = new OpCode(OpCodeValues.Rethrow,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Throw << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Objmodel << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            OpCode.EndsUncondJmpBlkFlag |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Sizeof = new OpCode(OpCodeValues.Sizeof,
+            ((int)OperandType.InlineType) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (1 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Refanytype = new OpCode(OpCodeValues.Refanytype,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Next << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Primitive << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop1 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Pushi << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+        public static readonly OpCode Readonly = new OpCode(OpCodeValues.Readonly_,
+            ((int)OperandType.InlineNone) |
+            ((int)FlowControl.Meta << OpCode.FlowControlShift) |
+            ((int)OpCodeType.Prefix << OpCode.OpCodeTypeShift) |
+            ((int)StackBehaviour.Pop0 << OpCode.StackBehaviourPopShift) |
+            ((int)StackBehaviour.Push0 << OpCode.StackBehaviourPushShift) |
+            (2 << OpCode.SizeShift) |
+            (0 << OpCode.StackChangeShift)
+        );
+
+
+        public static bool TakesSingleByteArgument(OpCode inst)
+        {
+            switch (inst.OperandType)
+            {
+                case OperandType.ShortInlineBrTarget:
+                case OperandType.ShortInlineI:
+                case OperandType.ShortInlineVar:
+                    return true;
+            };
+            return false;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/Opcode.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/Opcode.cs
new file mode 100644
index 0000000000..72967cdfca
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/Opcode.cs
@@ -0,0 +1,192 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading;
+
+namespace System.Reflection.Emit
+{
+    public struct OpCode
+    {
+        //
+        // Use packed bitfield for flags to avoid code bloat
+        //
+
+        internal const int OperandTypeMask = 0x1F;         // 000000000000000000000000000XXXXX
+
+        internal const int FlowControlShift = 5;            // 00000000000000000000000XXXX00000
+        internal const int FlowControlMask = 0x0F;
+
+        internal const int OpCodeTypeShift = 9;            // 00000000000000000000XXX000000000
+        internal const int OpCodeTypeMask = 0x07;
+
+        internal const int StackBehaviourPopShift = 12;           // 000000000000000XXXXX000000000000
+        internal const int StackBehaviourPushShift = 17;           // 0000000000XXXXX00000000000000000
+        internal const int StackBehaviourMask = 0x1F;
+
+        internal const int SizeShift = 22;           // 00000000XX0000000000000000000000
+        internal const int SizeMask = 0x03;
+
+        internal const int EndsUncondJmpBlkFlag = 0x01000000;   // 0000000X000000000000000000000000
+
+        // unused                                                       // 0000XXX0000000000000000000000000
+
+        internal const int StackChangeShift = 28;           // XXXX0000000000000000000000000000
+
+        private OpCodeValues m_value;
+        private int m_flags;
+
+        internal OpCode(OpCodeValues value, int flags)
+        {
+            m_value = value;
+            m_flags = flags;
+        }
+
+        internal bool EndsUncondJmpBlk()
+        {
+            return (m_flags & EndsUncondJmpBlkFlag) != 0;
+        }
+
+        internal int StackChange()
+        {
+            return (m_flags >> StackChangeShift);
+        }
+
+        public OperandType OperandType
+        {
+            get
+            {
+                return (OperandType)(m_flags & OperandTypeMask);
+            }
+        }
+
+        public FlowControl FlowControl
+        {
+            get
+            {
+                return (FlowControl)((m_flags >> FlowControlShift) & FlowControlMask);
+            }
+        }
+
+        public OpCodeType OpCodeType
+        {
+            get
+            {
+                return (OpCodeType)((m_flags >> OpCodeTypeShift) & OpCodeTypeMask);
+            }
+        }
+
+        public StackBehaviour StackBehaviourPop
+        {
+            get
+            {
+                return (StackBehaviour)((m_flags >> StackBehaviourPopShift) & StackBehaviourMask);
+            }
+        }
+
+        public StackBehaviour StackBehaviourPush
+        {
+            get
+            {
+                return (StackBehaviour)((m_flags >> StackBehaviourPushShift) & StackBehaviourMask);
+            }
+        }
+
+        public int Size
+        {
+            get
+            {
+                return (m_flags >> SizeShift) & SizeMask;
+            }
+        }
+
+        public short Value
+        {
+            get
+            {
+                return (short)m_value;
+            }
+        }
+
+        private static volatile string[] g_nameCache;
+
+        public String Name
+        {
+            get
+            {
+                if (Size == 0)
+                    return null;
+
+                // Create and cache the opcode names lazily. They should be rarely used (only for logging, etc.)
+                // Note that we do not any locks here because of we always get the same names. The last one wins.
+                string[] nameCache = g_nameCache;
+                if (nameCache == null)
+                {
+                    nameCache = new String[0x11f];
+                    g_nameCache = nameCache;
+                }
+
+                OpCodeValues opCodeValue = (OpCodeValues)(ushort)Value;
+
+                int idx = (int)opCodeValue;
+                if (idx > 0xFF)
+                {
+                    if (idx >= 0xfe00 && idx <= 0xfe1e)
+                    {
+                        // Transform two byte opcode value to lower range that's suitable
+                        // for array index
+                        idx = 0x100 + (idx - 0xfe00);
+                    }
+                    else
+                    {
+                        // Unknown opcode
+                        return null;
+                    }
+                }
+
+                String name = Volatile.Read(ref nameCache[idx]);
+                if (name != null)
+                    return name;
+
+                // Create ilasm style name from the enum value name.
+                name = Enum.GetName(typeof(OpCodeValues), opCodeValue).ToLowerInvariant().Replace("_", ".");
+                Volatile.Write(ref nameCache[idx], name);
+                return name;
+            }
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (obj is OpCode)
+                return Equals((OpCode)obj);
+            else
+                return false;
+        }
+
+        public bool Equals(OpCode obj)
+        {
+            return obj.Value == Value;
+        }
+
+        public static bool operator ==(OpCode a, OpCode b)
+        {
+            return a.Equals(b);
+        }
+
+        public static bool operator !=(OpCode a, OpCode b)
+        {
+            return !(a == b);
+        }
+
+        public override int GetHashCode()
+        {
+            return Value;
+        }
+
+        public override String ToString()
+        {
+            return Name;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/OperandType.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/OperandType.cs
new file mode 100644
index 0000000000..6257c56745
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/OperandType.cs
@@ -0,0 +1,41 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Enumeration: OperandType
+**
+** Purpose: Exposes OperandType Attribute of IL.
+**
+** THIS FILE IS AUTOMATICALLY GENERATED. DO NOT EDIT BY HAND!
+** See $(RepoRoot)\src\inc\OpCodeGen.pl for more information.**
+==============================================================*/
+
+using System;
+
+namespace System.Reflection.Emit
+{
+    public enum OperandType
+    {
+        InlineBrTarget = 0,
+        InlineField = 1,
+        InlineI = 2,
+        InlineI8 = 3,
+        InlineMethod = 4,
+        InlineNone = 5,
+        [Obsolete("This API has been deprecated. http://go.microsoft.com/fwlink/?linkid=14202")]
+        InlinePhi = 6,
+        InlineR = 7,
+        InlineSig = 9,
+        InlineString = 10,
+        InlineSwitch = 11,
+        InlineTok = 12,
+        InlineType = 13,
+        InlineVar = 14,
+        ShortInlineBrTarget = 15,
+        ShortInlineI = 16,
+        ShortInlineR = 17,
+        ShortInlineVar = 18,
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/PEFileKinds.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/PEFileKinds.cs
new file mode 100644
index 0000000000..f6606c477a
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/PEFileKinds.cs
@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System;
+
+namespace System.Reflection.Emit
+{
+    // This Enum matchs the CorFieldAttr defined in CorHdr.h
+    public enum PEFileKinds
+    {
+        Dll = 0x0001,
+        ConsoleApplication = 0x0002,
+        WindowApplication = 0x0003,
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/ParameterBuilder.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/ParameterBuilder.cs
new file mode 100644
index 0000000000..a875e3b943
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/ParameterBuilder.cs
@@ -0,0 +1,119 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** ParameterBuilder is used to create/associate parameter information
+**
+** 
+===========================================================*/
+
+using System.Runtime.InteropServices;
+using System;
+using System.Reflection;
+
+namespace System.Reflection.Emit
+{
+    public class ParameterBuilder
+    {
+        // Set the default value of the parameter
+        public virtual void SetConstant(Object defaultValue)
+        {
+            TypeBuilder.SetConstantValue(
+                m_methodBuilder.GetModuleBuilder(),
+                m_pdToken.Token,
+                m_iPosition == 0 ? m_methodBuilder.ReturnType : m_methodBuilder.m_parameterTypes[m_iPosition - 1],
+                defaultValue);
+        }
+
+        // Use this function if client decides to form the custom attribute blob themselves
+
+        public void SetCustomAttribute(ConstructorInfo con, byte[] binaryAttribute)
+        {
+            if (con == null)
+                throw new ArgumentNullException(nameof(con));
+            if (binaryAttribute == null)
+                throw new ArgumentNullException(nameof(binaryAttribute));
+
+            TypeBuilder.DefineCustomAttribute(
+                m_methodBuilder.GetModuleBuilder(),
+                m_pdToken.Token,
+                ((ModuleBuilder)m_methodBuilder.GetModule()).GetConstructorToken(con).Token,
+                binaryAttribute,
+                false, false);
+        }
+
+        // Use this function if client wishes to build CustomAttribute using CustomAttributeBuilder
+        public void SetCustomAttribute(CustomAttributeBuilder customBuilder)
+        {
+            if (customBuilder == null)
+            {
+                throw new ArgumentNullException(nameof(customBuilder));
+            }
+            customBuilder.CreateCustomAttribute((ModuleBuilder)(m_methodBuilder.GetModule()), m_pdToken.Token);
+        }
+
+        internal ParameterBuilder(
+            MethodBuilder methodBuilder,
+            int sequence,
+            ParameterAttributes attributes,
+            String strParamName)            // can be NULL string
+        {
+            m_iPosition = sequence;
+            m_strParamName = strParamName;
+            m_methodBuilder = methodBuilder;
+            m_strParamName = strParamName;
+            m_attributes = attributes;
+            m_pdToken = new ParameterToken(TypeBuilder.SetParamInfo(
+                        m_methodBuilder.GetModuleBuilder().GetNativeHandle(),
+                        m_methodBuilder.GetToken().Token,
+                        sequence,
+                        attributes,
+                        strParamName));
+        }
+
+        public virtual ParameterToken GetToken()
+        {
+            return m_pdToken;
+        }
+
+        public virtual String Name
+        {
+            get { return m_strParamName; }
+        }
+
+        public virtual int Position
+        {
+            get { return m_iPosition; }
+        }
+
+        public virtual int Attributes
+        {
+            get { return (int)m_attributes; }
+        }
+
+        public bool IsIn
+        {
+            get { return ((m_attributes & ParameterAttributes.In) != 0); }
+        }
+        public bool IsOut
+        {
+            get { return ((m_attributes & ParameterAttributes.Out) != 0); }
+        }
+        public bool IsOptional
+        {
+            get { return ((m_attributes & ParameterAttributes.Optional) != 0); }
+        }
+
+        private String m_strParamName;
+        private int m_iPosition;
+        private ParameterAttributes m_attributes;
+        private MethodBuilder m_methodBuilder;
+        private ParameterToken m_pdToken;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/ParameterToken.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/ParameterToken.cs
new file mode 100644
index 0000000000..067bc2d010
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/ParameterToken.cs
@@ -0,0 +1,67 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: metadata tokens for a parameter
+**
+** 
+===========================================================*/
+
+using System;
+using System.Reflection;
+
+namespace System.Reflection.Emit
+{
+    // The ParameterToken class is an opaque representation of the Token returned
+    // by the Metadata to represent the parameter. 
+    public struct ParameterToken
+    {
+        public static readonly ParameterToken Empty = new ParameterToken();
+        internal int m_tkParameter;
+
+
+        internal ParameterToken(int tkParam)
+        {
+            m_tkParameter = tkParam;
+        }
+
+        public int Token
+        {
+            get { return m_tkParameter; }
+        }
+
+        public override int GetHashCode()
+        {
+            return m_tkParameter;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (obj is ParameterToken)
+                return Equals((ParameterToken)obj);
+            else
+                return false;
+        }
+
+        public bool Equals(ParameterToken obj)
+        {
+            return obj.m_tkParameter == m_tkParameter;
+        }
+
+        public static bool operator ==(ParameterToken a, ParameterToken b)
+        {
+            return a.Equals(b);
+        }
+
+        public static bool operator !=(ParameterToken a, ParameterToken b)
+        {
+            return !(a == b);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/PropertyBuilder.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/PropertyBuilder.cs
new file mode 100644
index 0000000000..0fbdd8371b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/PropertyBuilder.cs
@@ -0,0 +1,261 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Propertybuilder is for client to define properties for a class
+**
+** 
+===========================================================*/
+
+namespace System.Reflection.Emit
+{
+    using System;
+    using System.Reflection;
+    using CultureInfo = System.Globalization.CultureInfo;
+    using System.Runtime.InteropServices;
+
+    // 
+    // A PropertyBuilder is always associated with a TypeBuilder.  The TypeBuilder.DefineProperty
+    // method will return a new PropertyBuilder to a client.
+    // 
+    public sealed class PropertyBuilder : PropertyInfo
+    {
+        // Constructs a PropertyBuilder.  
+        //
+        internal PropertyBuilder(
+            ModuleBuilder mod,            // the module containing this PropertyBuilder
+            String name,           // property name
+            SignatureHelper sig,            // property signature descriptor info
+            PropertyAttributes attr,           // property attribute such as DefaultProperty, Bindable, DisplayBind, etc
+            Type returnType,     // return type of the property.
+            PropertyToken prToken,        // the metadata token for this property
+            TypeBuilder containingType) // the containing type
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+            if (name.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(name));
+            if (name[0] == '\0')
+                throw new ArgumentException(SR.Argument_IllegalName, nameof(name));
+
+            m_name = name;
+            m_moduleBuilder = mod;
+            m_signature = sig;
+            m_attributes = attr;
+            m_returnType = returnType;
+            m_prToken = prToken;
+            m_tkProperty = prToken.Token;
+            m_containingType = containingType;
+        }
+
+        //************************************************
+        // Set the default value of the Property
+        //************************************************
+        public void SetConstant(Object defaultValue)
+        {
+            m_containingType.ThrowIfCreated();
+
+            TypeBuilder.SetConstantValue(
+                m_moduleBuilder,
+                m_prToken.Token,
+                m_returnType,
+                defaultValue);
+        }
+
+
+        // Return the Token for this property within the TypeBuilder that the
+        // property is defined within.
+        public PropertyToken PropertyToken
+        {
+            get { return m_prToken; }
+        }
+
+        public override Module Module
+        {
+            get
+            {
+                return m_containingType.Module;
+            }
+        }
+
+        private void SetMethodSemantics(MethodBuilder mdBuilder, MethodSemanticsAttributes semantics)
+        {
+            if (mdBuilder == null)
+            {
+                throw new ArgumentNullException(nameof(mdBuilder));
+            }
+
+            m_containingType.ThrowIfCreated();
+            TypeBuilder.DefineMethodSemantics(
+                m_moduleBuilder.GetNativeHandle(),
+                m_prToken.Token,
+                semantics,
+                mdBuilder.GetToken().Token);
+        }
+
+        public void SetGetMethod(MethodBuilder mdBuilder)
+        {
+            SetMethodSemantics(mdBuilder, MethodSemanticsAttributes.Getter);
+            m_getMethod = mdBuilder;
+        }
+
+        public void SetSetMethod(MethodBuilder mdBuilder)
+        {
+            SetMethodSemantics(mdBuilder, MethodSemanticsAttributes.Setter);
+            m_setMethod = mdBuilder;
+        }
+
+        public void AddOtherMethod(MethodBuilder mdBuilder)
+        {
+            SetMethodSemantics(mdBuilder, MethodSemanticsAttributes.Other);
+        }
+
+        // Use this function if client decides to form the custom attribute blob themselves
+
+        public void SetCustomAttribute(ConstructorInfo con, byte[] binaryAttribute)
+        {
+            if (con == null)
+                throw new ArgumentNullException(nameof(con));
+            if (binaryAttribute == null)
+                throw new ArgumentNullException(nameof(binaryAttribute));
+
+            m_containingType.ThrowIfCreated();
+            TypeBuilder.DefineCustomAttribute(
+                m_moduleBuilder,
+                m_prToken.Token,
+                m_moduleBuilder.GetConstructorToken(con).Token,
+                binaryAttribute,
+                false, false);
+        }
+
+        // Use this function if client wishes to build CustomAttribute using CustomAttributeBuilder
+        public void SetCustomAttribute(CustomAttributeBuilder customBuilder)
+        {
+            if (customBuilder == null)
+            {
+                throw new ArgumentNullException(nameof(customBuilder));
+            }
+            m_containingType.ThrowIfCreated();
+            customBuilder.CreateCustomAttribute(m_moduleBuilder, m_prToken.Token);
+        }
+
+        // Not supported functions in dynamic module.
+        public override Object GetValue(Object obj, Object[] index)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override Object GetValue(Object obj, BindingFlags invokeAttr, Binder binder, Object[] index, CultureInfo culture)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override void SetValue(Object obj, Object value, Object[] index)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override void SetValue(Object obj, Object value, BindingFlags invokeAttr, Binder binder, Object[] index, CultureInfo culture)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override MethodInfo[] GetAccessors(bool nonPublic)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override MethodInfo GetGetMethod(bool nonPublic)
+        {
+            if (nonPublic || m_getMethod == null)
+                return m_getMethod;
+            // now check to see if m_getMethod is public
+            if ((m_getMethod.Attributes & MethodAttributes.Public) == MethodAttributes.Public)
+                return m_getMethod;
+            return null;
+        }
+
+        public override MethodInfo GetSetMethod(bool nonPublic)
+        {
+            if (nonPublic || m_setMethod == null)
+                return m_setMethod;
+            // now check to see if m_setMethod is public
+            if ((m_setMethod.Attributes & MethodAttributes.Public) == MethodAttributes.Public)
+                return m_setMethod;
+            return null;
+        }
+
+        public override ParameterInfo[] GetIndexParameters()
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override Type PropertyType
+        {
+            get { return m_returnType; }
+        }
+
+        public override PropertyAttributes Attributes
+        {
+            get { return m_attributes; }
+        }
+
+        public override bool CanRead
+        {
+            get { if (m_getMethod != null) return true; else return false; }
+        }
+
+        public override bool CanWrite
+        {
+            get { if (m_setMethod != null) return true; else return false; }
+        }
+
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override String Name
+        {
+            get { return m_name; }
+        }
+
+        public override Type DeclaringType
+        {
+            get { return m_containingType; }
+        }
+
+        public override Type ReflectedType
+        {
+            get { return m_containingType; }
+        }
+
+        // These are package private so that TypeBuilder can access them.
+        private String m_name;                // The name of the property
+        private PropertyToken m_prToken;            // The token of this property
+        private int m_tkProperty;
+        private ModuleBuilder m_moduleBuilder;
+        private SignatureHelper m_signature;
+        private PropertyAttributes m_attributes;        // property's attribute flags
+        private Type m_returnType;        // property's return type
+        private MethodInfo m_getMethod;
+        private MethodInfo m_setMethod;
+        private TypeBuilder m_containingType;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/PropertyToken.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/PropertyToken.cs
new file mode 100644
index 0000000000..02f34881f4
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/PropertyToken.cs
@@ -0,0 +1,67 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Propertybuilder is for client to define properties for a class
+**
+** 
+===========================================================*/
+
+using System;
+using System.Reflection;
+
+namespace System.Reflection.Emit
+{
+    public struct PropertyToken
+    {
+        public static readonly PropertyToken Empty = new PropertyToken();
+
+        internal int m_property;
+
+        internal PropertyToken(int str)
+        {
+            m_property = str;
+        }
+
+        public int Token
+        {
+            get { return m_property; }
+        }
+
+        // Satisfy value class requirements
+        public override int GetHashCode()
+        {
+            return m_property;
+        }
+
+        // Satisfy value class requirements
+        public override bool Equals(Object obj)
+        {
+            if (obj is PropertyToken)
+                return Equals((PropertyToken)obj);
+            else
+                return false;
+        }
+
+        public bool Equals(PropertyToken obj)
+        {
+            return obj.m_property == m_property;
+        }
+
+        public static bool operator ==(PropertyToken a, PropertyToken b)
+        {
+            return a.Equals(b);
+        }
+
+        public static bool operator !=(PropertyToken a, PropertyToken b)
+        {
+            return !(a == b);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/SignatureHelper.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/SignatureHelper.cs
new file mode 100644
index 0000000000..94d2b12dce
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/SignatureHelper.cs
@@ -0,0 +1,943 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+using System.Text;
+using System;
+using System.Diagnostics;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace System.Reflection.Emit
+{
+    public sealed class SignatureHelper
+    {
+        #region Consts Fields
+        private const int NO_SIZE_IN_SIG = -1;
+        #endregion
+
+        #region Static Members
+        public static SignatureHelper GetMethodSigHelper(Module mod, Type returnType, Type[] parameterTypes)
+        {
+            return GetMethodSigHelper(mod, CallingConventions.Standard, returnType, null, null, parameterTypes, null, null);
+        }
+
+        internal static SignatureHelper GetMethodSigHelper(Module mod, CallingConventions callingConvention, Type returnType, int cGenericParam)
+        {
+            return GetMethodSigHelper(mod, callingConvention, cGenericParam, returnType, null, null, null, null, null);
+        }
+
+        public static SignatureHelper GetMethodSigHelper(Module mod, CallingConventions callingConvention, Type returnType)
+        {
+            return GetMethodSigHelper(mod, callingConvention, returnType, null, null, null, null, null);
+        }
+
+        internal static SignatureHelper GetMethodSpecSigHelper(Module scope, Type[] inst)
+        {
+            SignatureHelper sigHelp = new SignatureHelper(scope, MdSigCallingConvention.GenericInst);
+            sigHelp.AddData(inst.Length);
+            foreach (Type t in inst)
+                sigHelp.AddArgument(t);
+            return sigHelp;
+        }
+
+        internal static SignatureHelper GetMethodSigHelper(
+            Module scope, CallingConventions callingConvention,
+            Type returnType, Type[] requiredReturnTypeCustomModifiers, Type[] optionalReturnTypeCustomModifiers,
+            Type[] parameterTypes, Type[][] requiredParameterTypeCustomModifiers, Type[][] optionalParameterTypeCustomModifiers)
+        {
+            return GetMethodSigHelper(scope, callingConvention, 0, returnType, requiredReturnTypeCustomModifiers,
+                optionalReturnTypeCustomModifiers, parameterTypes, requiredParameterTypeCustomModifiers, optionalParameterTypeCustomModifiers);
+        }
+
+        internal static SignatureHelper GetMethodSigHelper(
+            Module scope, CallingConventions callingConvention, int cGenericParam,
+            Type returnType, Type[] requiredReturnTypeCustomModifiers, Type[] optionalReturnTypeCustomModifiers,
+            Type[] parameterTypes, Type[][] requiredParameterTypeCustomModifiers, Type[][] optionalParameterTypeCustomModifiers)
+        {
+            SignatureHelper sigHelp;
+            MdSigCallingConvention intCall;
+
+            if (returnType == null)
+            {
+                returnType = typeof(void);
+            }
+
+            intCall = MdSigCallingConvention.Default;
+
+            if ((callingConvention & CallingConventions.VarArgs) == CallingConventions.VarArgs)
+                intCall = MdSigCallingConvention.Vararg;
+
+            if (cGenericParam > 0)
+            {
+                intCall |= MdSigCallingConvention.Generic;
+            }
+
+            if ((callingConvention & CallingConventions.HasThis) == CallingConventions.HasThis)
+                intCall |= MdSigCallingConvention.HasThis;
+
+            sigHelp = new SignatureHelper(scope, intCall, cGenericParam, returnType,
+                                            requiredReturnTypeCustomModifiers, optionalReturnTypeCustomModifiers);
+            sigHelp.AddArguments(parameterTypes, requiredParameterTypeCustomModifiers, optionalParameterTypeCustomModifiers);
+
+            return sigHelp;
+        }
+
+        public static SignatureHelper GetMethodSigHelper(Module mod, CallingConvention unmanagedCallConv, Type returnType)
+        {
+            SignatureHelper sigHelp;
+            MdSigCallingConvention intCall;
+
+            if (returnType == null)
+                returnType = typeof(void);
+
+            if (unmanagedCallConv == CallingConvention.Cdecl)
+            {
+                intCall = MdSigCallingConvention.C;
+            }
+            else if (unmanagedCallConv == CallingConvention.StdCall || unmanagedCallConv == CallingConvention.Winapi)
+            {
+                intCall = MdSigCallingConvention.StdCall;
+            }
+            else if (unmanagedCallConv == CallingConvention.ThisCall)
+            {
+                intCall = MdSigCallingConvention.ThisCall;
+            }
+            else if (unmanagedCallConv == CallingConvention.FastCall)
+            {
+                intCall = MdSigCallingConvention.FastCall;
+            }
+            else
+            {
+                throw new ArgumentException(SR.Argument_UnknownUnmanagedCallConv, nameof(unmanagedCallConv));
+            }
+
+            sigHelp = new SignatureHelper(mod, intCall, returnType, null, null);
+
+            return sigHelp;
+        }
+
+        public static SignatureHelper GetLocalVarSigHelper()
+        {
+            return GetLocalVarSigHelper(null);
+        }
+
+        public static SignatureHelper GetMethodSigHelper(CallingConventions callingConvention, Type returnType)
+        {
+            return GetMethodSigHelper(null, callingConvention, returnType);
+        }
+
+        public static SignatureHelper GetMethodSigHelper(CallingConvention unmanagedCallingConvention, Type returnType)
+        {
+            return GetMethodSigHelper(null, unmanagedCallingConvention, returnType);
+        }
+
+        public static SignatureHelper GetLocalVarSigHelper(Module mod)
+        {
+            return new SignatureHelper(mod, MdSigCallingConvention.LocalSig);
+        }
+
+        public static SignatureHelper GetFieldSigHelper(Module mod)
+        {
+            return new SignatureHelper(mod, MdSigCallingConvention.Field);
+        }
+
+        public static SignatureHelper GetPropertySigHelper(Module mod, Type returnType, Type[] parameterTypes)
+        {
+            return GetPropertySigHelper(mod, returnType, null, null, parameterTypes, null, null);
+        }
+
+        public static SignatureHelper GetPropertySigHelper(Module mod,
+            Type returnType, Type[] requiredReturnTypeCustomModifiers, Type[] optionalReturnTypeCustomModifiers,
+            Type[] parameterTypes, Type[][] requiredParameterTypeCustomModifiers, Type[][] optionalParameterTypeCustomModifiers)
+        {
+            return GetPropertySigHelper(mod, (CallingConventions)0, returnType, requiredReturnTypeCustomModifiers, optionalReturnTypeCustomModifiers,
+                parameterTypes, requiredParameterTypeCustomModifiers, optionalParameterTypeCustomModifiers);
+        }
+        public static SignatureHelper GetPropertySigHelper(Module mod, CallingConventions callingConvention,
+            Type returnType, Type[] requiredReturnTypeCustomModifiers, Type[] optionalReturnTypeCustomModifiers,
+            Type[] parameterTypes, Type[][] requiredParameterTypeCustomModifiers, Type[][] optionalParameterTypeCustomModifiers)
+        {
+            SignatureHelper sigHelp;
+
+            if (returnType == null)
+            {
+                returnType = typeof(void);
+            }
+
+            MdSigCallingConvention intCall = MdSigCallingConvention.Property;
+
+            if ((callingConvention & CallingConventions.HasThis) == CallingConventions.HasThis)
+                intCall |= MdSigCallingConvention.HasThis;
+
+            sigHelp = new SignatureHelper(mod, intCall,
+                returnType, requiredReturnTypeCustomModifiers, optionalReturnTypeCustomModifiers);
+            sigHelp.AddArguments(parameterTypes, requiredParameterTypeCustomModifiers, optionalParameterTypeCustomModifiers);
+
+            return sigHelp;
+        }
+
+        internal static SignatureHelper GetTypeSigToken(Module module, Type type)
+        {
+            if (module == null)
+                throw new ArgumentNullException(nameof(module));
+
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+
+            return new SignatureHelper(module, type);
+        }
+        #endregion
+
+        #region Private Data Members
+        private byte[] m_signature;
+        private int m_currSig; // index into m_signature buffer for next available byte
+        private int m_sizeLoc; // index into m_signature buffer to put m_argCount (will be NO_SIZE_IN_SIG if no arg count is needed)
+        private ModuleBuilder m_module;
+        private bool m_sigDone;
+        private int m_argCount; // tracking number of arguments in the signature
+        #endregion
+
+        #region Constructor
+        private SignatureHelper(Module mod, MdSigCallingConvention callingConvention)
+        {
+            // Use this constructor to instantiate a local var sig  or Field where return type is not applied.
+            Init(mod, callingConvention);
+        }
+
+        private SignatureHelper(Module mod, MdSigCallingConvention callingConvention, int cGenericParameters,
+            Type returnType, Type[] requiredCustomModifiers, Type[] optionalCustomModifiers)
+        {
+            // Use this constructor to instantiate a any signatures that will require a return type.
+            Init(mod, callingConvention, cGenericParameters);
+
+            if (callingConvention == MdSigCallingConvention.Field)
+                throw new ArgumentException(SR.Argument_BadFieldSig);
+
+            AddOneArgTypeHelper(returnType, requiredCustomModifiers, optionalCustomModifiers);
+        }
+
+        private SignatureHelper(Module mod, MdSigCallingConvention callingConvention,
+            Type returnType, Type[] requiredCustomModifiers, Type[] optionalCustomModifiers)
+            : this(mod, callingConvention, 0, returnType, requiredCustomModifiers, optionalCustomModifiers)
+        {
+        }
+
+        private SignatureHelper(Module mod, Type type)
+        {
+            Init(mod);
+
+            AddOneArgTypeHelper(type);
+        }
+
+        private void Init(Module mod)
+        {
+            m_signature = new byte[32];
+            m_currSig = 0;
+            m_module = mod as ModuleBuilder;
+            m_argCount = 0;
+            m_sigDone = false;
+            m_sizeLoc = NO_SIZE_IN_SIG;
+
+            if (m_module == null && mod != null)
+                throw new ArgumentException(SR.NotSupported_MustBeModuleBuilder);
+        }
+
+        private void Init(Module mod, MdSigCallingConvention callingConvention)
+        {
+            Init(mod, callingConvention, 0);
+        }
+
+        private void Init(Module mod, MdSigCallingConvention callingConvention, int cGenericParam)
+        {
+            Init(mod);
+
+            AddData((byte)callingConvention);
+
+            if (callingConvention == MdSigCallingConvention.Field ||
+                callingConvention == MdSigCallingConvention.GenericInst)
+            {
+                m_sizeLoc = NO_SIZE_IN_SIG;
+            }
+            else
+            {
+                if (cGenericParam > 0)
+                    AddData(cGenericParam);
+
+                m_sizeLoc = m_currSig++;
+            }
+        }
+
+        #endregion
+
+        #region Private Members
+        private void AddOneArgTypeHelper(Type argument, bool pinned)
+        {
+            if (pinned)
+                AddElementType(CorElementType.Pinned);
+
+            AddOneArgTypeHelper(argument);
+        }
+
+        private void AddOneArgTypeHelper(Type clsArgument, Type[] requiredCustomModifiers, Type[] optionalCustomModifiers)
+        {
+            // This function will not increase the argument count. It only fills in bytes 
+            // in the signature based on clsArgument. This helper is called for return type.
+
+            Debug.Assert(clsArgument != null);
+            Debug.Assert((optionalCustomModifiers == null && requiredCustomModifiers == null) || !clsArgument.ContainsGenericParameters);
+
+            if (optionalCustomModifiers != null)
+            {
+                for (int i = 0; i < optionalCustomModifiers.Length; i++)
+                {
+                    Type t = optionalCustomModifiers[i];
+
+                    if (t == null)
+                        throw new ArgumentNullException(nameof(optionalCustomModifiers));
+
+                    if (t.HasElementType)
+                        throw new ArgumentException(SR.Argument_ArraysInvalid, nameof(optionalCustomModifiers));
+
+                    if (t.ContainsGenericParameters)
+                        throw new ArgumentException(SR.Argument_GenericsInvalid, nameof(optionalCustomModifiers));
+
+                    AddElementType(CorElementType.CModOpt);
+
+                    int token = m_module.GetTypeToken(t).Token;
+                    Debug.Assert(!MetadataToken.IsNullToken(token));
+                    AddToken(token);
+                }
+            }
+
+            if (requiredCustomModifiers != null)
+            {
+                for (int i = 0; i < requiredCustomModifiers.Length; i++)
+                {
+                    Type t = requiredCustomModifiers[i];
+
+                    if (t == null)
+                        throw new ArgumentNullException(nameof(requiredCustomModifiers));
+
+                    if (t.HasElementType)
+                        throw new ArgumentException(SR.Argument_ArraysInvalid, nameof(requiredCustomModifiers));
+
+                    if (t.ContainsGenericParameters)
+                        throw new ArgumentException(SR.Argument_GenericsInvalid, nameof(requiredCustomModifiers));
+
+                    AddElementType(CorElementType.CModReqd);
+
+                    int token = m_module.GetTypeToken(t).Token;
+                    Debug.Assert(!MetadataToken.IsNullToken(token));
+                    AddToken(token);
+                }
+            }
+
+            AddOneArgTypeHelper(clsArgument);
+        }
+
+        private void AddOneArgTypeHelper(Type clsArgument) { AddOneArgTypeHelperWorker(clsArgument, false); }
+        private void AddOneArgTypeHelperWorker(Type clsArgument, bool lastWasGenericInst)
+        {
+            if (clsArgument.IsGenericParameter)
+            {
+                if (clsArgument.DeclaringMethod != null)
+                    AddElementType(CorElementType.MVar);
+                else
+                    AddElementType(CorElementType.Var);
+
+                AddData(clsArgument.GenericParameterPosition);
+            }
+            else if (clsArgument.IsGenericType && (!clsArgument.IsGenericTypeDefinition || !lastWasGenericInst))
+            {
+                AddElementType(CorElementType.GenericInst);
+
+                AddOneArgTypeHelperWorker(clsArgument.GetGenericTypeDefinition(), true);
+
+                Type[] args = clsArgument.GetGenericArguments();
+
+                AddData(args.Length);
+
+                foreach (Type t in args)
+                    AddOneArgTypeHelper(t);
+            }
+            else if (clsArgument is TypeBuilder)
+            {
+                TypeBuilder clsBuilder = (TypeBuilder)clsArgument;
+                TypeToken tkType;
+
+                if (clsBuilder.Module.Equals(m_module))
+                {
+                    tkType = clsBuilder.TypeToken;
+                }
+                else
+                {
+                    tkType = m_module.GetTypeToken(clsArgument);
+                }
+
+                if (clsArgument.IsValueType)
+                {
+                    InternalAddTypeToken(tkType, CorElementType.ValueType);
+                }
+                else
+                {
+                    InternalAddTypeToken(tkType, CorElementType.Class);
+                }
+            }
+            else if (clsArgument is EnumBuilder)
+            {
+                TypeBuilder clsBuilder = ((EnumBuilder)clsArgument).m_typeBuilder;
+                TypeToken tkType;
+
+                if (clsBuilder.Module.Equals(m_module))
+                {
+                    tkType = clsBuilder.TypeToken;
+                }
+                else
+                {
+                    tkType = m_module.GetTypeToken(clsArgument);
+                }
+
+                if (clsArgument.IsValueType)
+                {
+                    InternalAddTypeToken(tkType, CorElementType.ValueType);
+                }
+                else
+                {
+                    InternalAddTypeToken(tkType, CorElementType.Class);
+                }
+            }
+            else if (clsArgument.IsByRef)
+            {
+                AddElementType(CorElementType.ByRef);
+                clsArgument = clsArgument.GetElementType();
+                AddOneArgTypeHelper(clsArgument);
+            }
+            else if (clsArgument.IsPointer)
+            {
+                AddElementType(CorElementType.Ptr);
+                AddOneArgTypeHelper(clsArgument.GetElementType());
+            }
+            else if (clsArgument.IsArray)
+            {
+                if (clsArgument.IsSZArray)
+                {
+                    AddElementType(CorElementType.SzArray);
+
+                    AddOneArgTypeHelper(clsArgument.GetElementType());
+                }
+                else
+                {
+                    AddElementType(CorElementType.Array);
+
+                    AddOneArgTypeHelper(clsArgument.GetElementType());
+
+                    // put the rank information
+                    int rank = clsArgument.GetArrayRank();
+                    AddData(rank);     // rank
+                    AddData(0);     // upper bounds
+                    AddData(rank);  // lower bound
+                    for (int i = 0; i < rank; i++)
+                        AddData(0);
+                }
+            }
+            else
+            {
+                CorElementType type = CorElementType.Max;
+
+                if (clsArgument is RuntimeType)
+                {
+                    type = RuntimeTypeHandle.GetCorElementType((RuntimeType)clsArgument);
+
+                    //GetCorElementType returns CorElementType.Class for both object and string
+                    if (type == CorElementType.Class)
+                    {
+                        if (clsArgument == typeof(object))
+                            type = CorElementType.Object;
+                        else if (clsArgument == typeof(string))
+                            type = CorElementType.String;
+                    }
+                }
+
+                if (IsSimpleType(type))
+                {
+                    AddElementType(type);
+                }
+                else if (m_module == null)
+                {
+                    InternalAddRuntimeType(clsArgument);
+                }
+                else if (clsArgument.IsValueType)
+                {
+                    InternalAddTypeToken(m_module.GetTypeToken(clsArgument), CorElementType.ValueType);
+                }
+                else
+                {
+                    InternalAddTypeToken(m_module.GetTypeToken(clsArgument), CorElementType.Class);
+                }
+            }
+        }
+
+        private void AddData(int data)
+        {
+            // A managed representation of CorSigCompressData; 
+
+            if (m_currSig + 4 > m_signature.Length)
+            {
+                m_signature = ExpandArray(m_signature);
+            }
+
+            if (data <= 0x7F)
+            {
+                m_signature[m_currSig++] = (byte)(data & 0xFF);
+            }
+            else if (data <= 0x3FFF)
+            {
+                m_signature[m_currSig++] = (byte)((data >> 8) | 0x80);
+                m_signature[m_currSig++] = (byte)(data & 0xFF);
+            }
+            else if (data <= 0x1FFFFFFF)
+            {
+                m_signature[m_currSig++] = (byte)((data >> 24) | 0xC0);
+                m_signature[m_currSig++] = (byte)((data >> 16) & 0xFF);
+                m_signature[m_currSig++] = (byte)((data >> 8) & 0xFF);
+                m_signature[m_currSig++] = (byte)((data) & 0xFF);
+            }
+            else
+            {
+                throw new ArgumentException(SR.Argument_LargeInteger);
+            }
+        }
+
+        private void AddElementType(CorElementType cvt)
+        {
+            // Adds an element to the signature.  A managed represenation of CorSigCompressElement
+            if (m_currSig + 1 > m_signature.Length)
+                m_signature = ExpandArray(m_signature);
+
+            m_signature[m_currSig++] = (byte)cvt;
+        }
+
+        private void AddToken(int token)
+        {
+            // A managed represenation of CompressToken
+            // Pulls the token appart to get a rid, adds some appropriate bits
+            // to the token and then adds this to the signature.
+
+            int rid = (token & 0x00FFFFFF); //This is RidFromToken;
+            MetadataTokenType type = (MetadataTokenType)(token & unchecked((int)0xFF000000)); //This is TypeFromToken;
+
+            if (rid > 0x3FFFFFF)
+            {
+                // token is too big to be compressed    
+                throw new ArgumentException(SR.Argument_LargeInteger);
+            }
+
+            rid = (rid << 2);
+
+            // TypeDef is encoded with low bits 00  
+            // TypeRef is encoded with low bits 01  
+            // TypeSpec is encoded with low bits 10    
+            if (type == MetadataTokenType.TypeRef)
+            {
+                //if type is mdtTypeRef
+                rid |= 0x1;
+            }
+            else if (type == MetadataTokenType.TypeSpec)
+            {
+                //if type is mdtTypeSpec
+                rid |= 0x2;
+            }
+
+            AddData(rid);
+        }
+
+        private void InternalAddTypeToken(TypeToken clsToken, CorElementType CorType)
+        {
+            // Add a type token into signature. CorType will be either CorElementType.Class or CorElementType.ValueType
+            AddElementType(CorType);
+            AddToken(clsToken.Token);
+        }
+
+        private unsafe void InternalAddRuntimeType(Type type)
+        {
+            // Add a runtime type into the signature. 
+
+            AddElementType(CorElementType.Internal);
+
+            IntPtr handle = type.GetTypeHandleInternal().Value;
+
+            // Internal types must have their pointer written into the signature directly (we don't
+            // want to convert to little-endian format on big-endian machines because the value is
+            // going to be extracted and used directly as a pointer (and only within this process)).
+
+            if (m_currSig + sizeof(void*) > m_signature.Length)
+                m_signature = ExpandArray(m_signature);
+
+            byte* phandle = (byte*)&handle;
+            for (int i = 0; i < sizeof(void*); i++)
+                m_signature[m_currSig++] = phandle[i];
+        }
+
+        private byte[] ExpandArray(byte[] inArray)
+        {
+            // Expand the signature buffer size
+            return ExpandArray(inArray, inArray.Length * 2);
+        }
+
+        private byte[] ExpandArray(byte[] inArray, int requiredLength)
+        {
+            // Expand the signature buffer size
+
+            if (requiredLength < inArray.Length)
+                requiredLength = inArray.Length * 2;
+
+            byte[] outArray = new byte[requiredLength];
+            Buffer.BlockCopy(inArray, 0, outArray, 0, inArray.Length);
+            return outArray;
+        }
+
+        private void IncrementArgCounts()
+        {
+            if (m_sizeLoc == NO_SIZE_IN_SIG)
+            {
+                //We don't have a size if this is a field.
+                return;
+            }
+
+            m_argCount++;
+        }
+
+        private void SetNumberOfSignatureElements(bool forceCopy)
+        {
+            // For most signatures, this will set the number of elements in a byte which we have reserved for it.
+            // However, if we have a field signature, we don't set the length and return.
+            // If we have a signature with more than 128 arguments, we can't just set the number of elements,
+            // we actually have to allocate more space (e.g. shift everything in the array one or more spaces to the
+            // right.  We do this by making a copy of the array and leaving the correct number of blanks.  This new
+            // array is now set to be m_signature and we use the AddData method to set the number of elements properly.
+            // The forceCopy argument can be used to force SetNumberOfSignatureElements to make a copy of
+            // the array.  This is useful for GetSignature which promises to trim the array to be the correct size anyway.
+
+            byte[] temp;
+            int newSigSize;
+            int currSigHolder = m_currSig;
+
+            if (m_sizeLoc == NO_SIZE_IN_SIG)
+                return;
+
+            //If we have fewer than 128 arguments and we haven't been told to copy the
+            //array, we can just set the appropriate bit and return.
+            if (m_argCount < 0x80 && !forceCopy)
+            {
+                m_signature[m_sizeLoc] = (byte)m_argCount;
+                return;
+            }
+
+            //We need to have more bytes for the size.  Figure out how many bytes here.
+            //Since we need to copy anyway, we're just going to take the cost of doing a
+            //new allocation.
+            if (m_argCount < 0x80)
+            {
+                newSigSize = 1;
+            }
+            else if (m_argCount < 0x4000)
+            {
+                newSigSize = 2;
+            }
+            else
+            {
+                newSigSize = 4;
+            }
+
+            //Allocate the new array.
+            temp = new byte[m_currSig + newSigSize - 1];
+
+            //Copy the calling convention.  The calling convention is always just one byte
+            //so we just copy that byte.  Then copy the rest of the array, shifting everything
+            //to make room for the new number of elements.
+            temp[0] = m_signature[0];
+            Buffer.BlockCopy(m_signature, m_sizeLoc + 1, temp, m_sizeLoc + newSigSize, currSigHolder - (m_sizeLoc + 1));
+            m_signature = temp;
+
+            //Use the AddData method to add the number of elements appropriately compressed.
+            m_currSig = m_sizeLoc;
+            AddData(m_argCount);
+            m_currSig = currSigHolder + (newSigSize - 1);
+        }
+
+        #endregion
+
+        #region Internal Members
+        internal int ArgumentCount
+        {
+            get
+            {
+                return m_argCount;
+            }
+        }
+
+        internal static bool IsSimpleType(CorElementType type)
+        {
+            if (type <= CorElementType.String)
+                return true;
+
+            if (type == CorElementType.TypedByRef || type == CorElementType.I || type == CorElementType.U || type == CorElementType.Object)
+                return true;
+
+            return false;
+        }
+
+        internal byte[] InternalGetSignature(out int length)
+        {
+            // An internal method to return the signature.  Does not trim the
+            // array, but passes out the length of the array in an out parameter.
+            // This is the actual array -- not a copy -- so the callee must agree
+            // to not copy it.
+            //
+            // param length : an out param indicating the length of the array.
+            // return : A reference to the internal ubyte array.
+
+            if (!m_sigDone)
+            {
+                m_sigDone = true;
+
+                // If we have more than 128 variables, we can't just set the length, we need 
+                // to compress it.  Unfortunately, this means that we need to copy the entire 
+                // array.  Bummer, eh?
+                SetNumberOfSignatureElements(false);
+            }
+
+            length = m_currSig;
+            return m_signature;
+        }
+
+
+
+
+        internal byte[] InternalGetSignatureArray()
+        {
+            int argCount = m_argCount;
+            int currSigLength = m_currSig;
+            int newSigSize = currSigLength;
+
+            //Allocate the new array.
+            if (argCount < 0x7F)
+                newSigSize += 1;
+            else if (argCount < 0x3FFF)
+                newSigSize += 2;
+            else
+                newSigSize += 4;
+            byte[] temp = new byte[newSigSize];
+
+            // copy the sig
+            int sigCopyIndex = 0;
+            // calling convention
+            temp[sigCopyIndex++] = m_signature[0];
+            // arg size
+            if (argCount <= 0x7F)
+                temp[sigCopyIndex++] = (byte)(argCount & 0xFF);
+            else if (argCount <= 0x3FFF)
+            {
+                temp[sigCopyIndex++] = (byte)((argCount >> 8) | 0x80);
+                temp[sigCopyIndex++] = (byte)(argCount & 0xFF);
+            }
+            else if (argCount <= 0x1FFFFFFF)
+            {
+                temp[sigCopyIndex++] = (byte)((argCount >> 24) | 0xC0);
+                temp[sigCopyIndex++] = (byte)((argCount >> 16) & 0xFF);
+                temp[sigCopyIndex++] = (byte)((argCount >> 8) & 0xFF);
+                temp[sigCopyIndex++] = (byte)((argCount) & 0xFF);
+            }
+            else
+                throw new ArgumentException(SR.Argument_LargeInteger);
+            // copy the sig part of the sig
+            Buffer.BlockCopy(m_signature, 2, temp, sigCopyIndex, currSigLength - 2);
+            // mark the end of sig
+            temp[newSigSize - 1] = (byte)CorElementType.End;
+
+            return temp;
+        }
+
+        #endregion
+
+        #region Public Methods
+        public void AddArgument(Type clsArgument)
+        {
+            AddArgument(clsArgument, null, null);
+        }
+
+        public void AddArgument(Type argument, bool pinned)
+        {
+            if (argument == null)
+                throw new ArgumentNullException(nameof(argument));
+
+            IncrementArgCounts();
+            AddOneArgTypeHelper(argument, pinned);
+        }
+
+        public void AddArguments(Type[] arguments, Type[][] requiredCustomModifiers, Type[][] optionalCustomModifiers)
+        {
+            if (requiredCustomModifiers != null && (arguments == null || requiredCustomModifiers.Length != arguments.Length))
+                throw new ArgumentException(SR.Format(SR.Argument_MismatchedArrays, nameof(requiredCustomModifiers), nameof(arguments)));
+
+            if (optionalCustomModifiers != null && (arguments == null || optionalCustomModifiers.Length != arguments.Length))
+                throw new ArgumentException(SR.Format(SR.Argument_MismatchedArrays, nameof(optionalCustomModifiers), nameof(arguments)));
+
+            if (arguments != null)
+            {
+                for (int i = 0; i < arguments.Length; i++)
+                {
+                    AddArgument(arguments[i],
+                        requiredCustomModifiers == null ? null : requiredCustomModifiers[i],
+                        optionalCustomModifiers == null ? null : optionalCustomModifiers[i]);
+                }
+            }
+        }
+
+        public void AddArgument(Type argument, Type[] requiredCustomModifiers, Type[] optionalCustomModifiers)
+        {
+            if (m_sigDone)
+                throw new ArgumentException(SR.Argument_SigIsFinalized);
+
+            if (argument == null)
+                throw new ArgumentNullException(nameof(argument));
+
+            IncrementArgCounts();
+
+            // Add an argument to the signature. Takes a Type and determines whether it
+            // is one of the primitive types of which we have special knowledge or a more
+            // general class.  In the former case, we only add the appropriate short cut encoding, 
+            // otherwise we will calculate proper description for the type.
+            AddOneArgTypeHelper(argument, requiredCustomModifiers, optionalCustomModifiers);
+        }
+
+        public void AddSentinel()
+        {
+            AddElementType(CorElementType.Sentinel);
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (!(obj is SignatureHelper))
+            {
+                return false;
+            }
+
+            SignatureHelper temp = (SignatureHelper)obj;
+
+            if (!temp.m_module.Equals(m_module) || temp.m_currSig != m_currSig || temp.m_sizeLoc != m_sizeLoc || temp.m_sigDone != m_sigDone)
+            {
+                return false;
+            }
+
+            for (int i = 0; i < m_currSig; i++)
+            {
+                if (m_signature[i] != temp.m_signature[i])
+                    return false;
+            }
+            return true;
+        }
+
+        public override int GetHashCode()
+        {
+            // Start the hash code with the hash code of the module and the values of the member variables.
+            int HashCode = m_module.GetHashCode() + m_currSig + m_sizeLoc;
+
+            // Add one if the sig is done.
+            if (m_sigDone)
+                HashCode += 1;
+
+            // Then add the hash code of all the arguments.
+            for (int i = 0; i < m_currSig; i++)
+                HashCode += m_signature[i].GetHashCode();
+
+            return HashCode;
+        }
+
+        public byte[] GetSignature()
+        {
+            return GetSignature(false);
+        }
+
+        internal byte[] GetSignature(bool appendEndOfSig)
+        {
+            // Chops the internal signature to the appropriate length.  Adds the 
+            // end token to the signature and marks the signature as finished so that
+            // no further tokens can be added. Return the full signature in a trimmed array.
+            if (!m_sigDone)
+            {
+                if (appendEndOfSig)
+                    AddElementType(CorElementType.End);
+                SetNumberOfSignatureElements(true);
+                m_sigDone = true;
+            }
+
+            // This case will only happen if the user got the signature through 
+            // InternalGetSignature first and then called GetSignature.
+            if (m_signature.Length > m_currSig)
+            {
+                byte[] temp = new byte[m_currSig];
+                Array.Copy(m_signature, 0, temp, 0, m_currSig);
+                m_signature = temp;
+            }
+
+            return m_signature;
+        }
+
+        public override String ToString()
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append("Length: " + m_currSig + Environment.NewLine);
+
+            if (m_sizeLoc != -1)
+            {
+                sb.Append("Arguments: " + m_signature[m_sizeLoc] + Environment.NewLine);
+            }
+            else
+            {
+                sb.Append("Field Signature" + Environment.NewLine);
+            }
+
+            sb.Append("Signature: " + Environment.NewLine);
+            for (int i = 0; i <= m_currSig; i++)
+            {
+                sb.Append(m_signature[i] + "  ");
+            }
+
+            sb.Append(Environment.NewLine);
+            return sb.ToString();
+        }
+
+        #endregion
+    }
+}
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/SignatureToken.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/SignatureToken.cs
new file mode 100644
index 0000000000..e17e0c955e
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/SignatureToken.cs
@@ -0,0 +1,68 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Signature:  SignatureToken
+** 
+** 
+**
+**
+** Purpose: Represents a Signature to the ILGenerator signature.
+**
+** 
+===========================================================*/
+
+using System;
+using System.Reflection;
+
+namespace System.Reflection.Emit
+{
+    public struct SignatureToken
+    {
+        public static readonly SignatureToken Empty = new SignatureToken();
+
+        internal int m_signature;
+        internal ModuleBuilder m_moduleBuilder;
+
+        internal SignatureToken(int str, ModuleBuilder mod)
+        {
+            m_signature = str;
+            m_moduleBuilder = mod;
+        }
+
+        public int Token
+        {
+            get { return m_signature; }
+        }
+
+        public override int GetHashCode()
+        {
+            return m_signature;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (obj is SignatureToken)
+                return Equals((SignatureToken)obj);
+            else
+                return false;
+        }
+
+        public bool Equals(SignatureToken obj)
+        {
+            return obj.m_signature == m_signature;
+        }
+
+        public static bool operator ==(SignatureToken a, SignatureToken b)
+        {
+            return a.Equals(b);
+        }
+
+        public static bool operator !=(SignatureToken a, SignatureToken b)
+        {
+            return !(a == b);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/StackBehaviour.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/StackBehaviour.cs
new file mode 100644
index 0000000000..3e64b48798
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/StackBehaviour.cs
@@ -0,0 +1,51 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** Enumeration: StackBehaviour
+**
+** Purpose: Exposes StackBehaviour Attribute of IL.
+**
+** THIS FILE IS AUTOMATICALLY GENERATED. DO NOT EDIT BY HAND!
+** See $(RepoRoot)\src\inc\OpCodeGen.pl for more information.**
+==============================================================*/
+
+using System;
+
+namespace System.Reflection.Emit
+{
+    public enum StackBehaviour
+    {
+        Pop0 = 0,
+        Pop1 = 1,
+        Pop1_pop1 = 2,
+        Popi = 3,
+        Popi_pop1 = 4,
+        Popi_popi = 5,
+        Popi_popi8 = 6,
+        Popi_popi_popi = 7,
+        Popi_popr4 = 8,
+        Popi_popr8 = 9,
+        Popref = 10,
+        Popref_pop1 = 11,
+        Popref_popi = 12,
+        Popref_popi_popi = 13,
+        Popref_popi_popi8 = 14,
+        Popref_popi_popr4 = 15,
+        Popref_popi_popr8 = 16,
+        Popref_popi_popref = 17,
+        Push0 = 18,
+        Push1 = 19,
+        Push1_push1 = 20,
+        Pushi = 21,
+        Pushi8 = 22,
+        Pushr4 = 23,
+        Pushr8 = 24,
+        Pushref = 25,
+        Varpop = 26,
+        Varpush = 27,
+        Popref_popi_pop1 = 28,
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/StringToken.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/StringToken.cs
new file mode 100644
index 0000000000..cc5b734ae8
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/StringToken.cs
@@ -0,0 +1,70 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Represents a String to the ILGenerator class.
+**
+** 
+===========================================================*/
+
+using System;
+using System.Reflection;
+
+namespace System.Reflection.Emit
+{
+    public struct StringToken
+    {
+        internal int m_string;
+
+        //public StringToken() {
+        //    m_string=0;
+        //}
+
+        internal StringToken(int str)
+        {
+            m_string = str;
+        }
+
+        // Returns the metadata token for this particular string.  
+        // Generated by a call to Module.GetStringConstant().
+        //
+        public int Token
+        {
+            get { return m_string; }
+        }
+
+        public override int GetHashCode()
+        {
+            return m_string;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (obj is StringToken)
+                return Equals((StringToken)obj);
+            else
+                return false;
+        }
+
+        public bool Equals(StringToken obj)
+        {
+            return obj.m_string == m_string;
+        }
+
+        public static bool operator ==(StringToken a, StringToken b)
+        {
+            return a.Equals(b);
+        }
+
+        public static bool operator !=(StringToken a, StringToken b)
+        {
+            return !(a == b);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/SymbolMethod.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/SymbolMethod.cs
new file mode 100644
index 0000000000..5e5668ac7b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/SymbolMethod.cs
@@ -0,0 +1,181 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+namespace System.Reflection.Emit
+{
+    using System.Runtime.InteropServices;
+    using System;
+    using System.Reflection;
+    using CultureInfo = System.Globalization.CultureInfo;
+
+    internal sealed class SymbolMethod : MethodInfo
+    {
+        #region Private Data Members
+        private ModuleBuilder m_module;
+        private Type m_containingType;
+        private String m_name;
+        private CallingConventions m_callingConvention;
+        private Type m_returnType;
+        private MethodToken m_mdMethod;
+        private Type[] m_parameterTypes;
+        private SignatureHelper m_signature;
+        #endregion
+
+        #region Constructor
+        internal SymbolMethod(ModuleBuilder mod, MethodToken token, Type arrayClass, String methodName,
+            CallingConventions callingConvention, Type returnType, Type[] parameterTypes)
+        {
+            // This is a kind of MethodInfo to represent methods for array type of unbaked type
+
+            // Another way to look at this class is as a glorified MethodToken wrapper. At the time of this comment
+            // this class is only constructed inside ModuleBuilder.GetArrayMethod and the only interesting thing 
+            // passed into it is this MethodToken. The MethodToken was forged using a TypeSpec for an Array type and
+            // the name of the method on Array. 
+            // As none of the methods on Array have CustomModifiers their is no need to pass those around in here.
+            m_mdMethod = token;
+
+            // The ParameterTypes are also a bit interesting in that they may be unbaked TypeBuilders.
+            m_returnType = returnType;
+            if (parameterTypes != null)
+            {
+                m_parameterTypes = new Type[parameterTypes.Length];
+                Array.Copy(parameterTypes, 0, m_parameterTypes, 0, parameterTypes.Length);
+            }
+            else
+            {
+                m_parameterTypes = Array.Empty<Type>();
+            }
+
+            m_module = mod;
+            m_containingType = arrayClass;
+            m_name = methodName;
+            m_callingConvention = callingConvention;
+
+            m_signature = SignatureHelper.GetMethodSigHelper(
+                mod, callingConvention, returnType, null, null, parameterTypes, null, null);
+        }
+        #endregion
+
+        #region Internal Members
+        internal override Type[] GetParameterTypes()
+        {
+            return m_parameterTypes;
+        }
+
+        internal MethodToken GetToken(ModuleBuilder mod)
+        {
+            return mod.GetArrayMethodToken(m_containingType, m_name, m_callingConvention, m_returnType, m_parameterTypes);
+        }
+
+        #endregion
+
+        #region MemberInfo Overrides
+        public override Module Module
+        {
+            get { return m_module; }
+        }
+
+        public override Type ReflectedType
+        {
+            get { return m_containingType as Type; }
+        }
+
+        public override String Name
+        {
+            get { return m_name; }
+        }
+
+        public override Type DeclaringType
+        {
+            get { return m_containingType; }
+        }
+        #endregion
+
+        #region MethodBase Overrides
+        public override ParameterInfo[] GetParameters()
+        {
+            throw new NotSupportedException(SR.NotSupported_SymbolMethod);
+        }
+
+        public override MethodImplAttributes GetMethodImplementationFlags()
+        {
+            throw new NotSupportedException(SR.NotSupported_SymbolMethod);
+        }
+
+        public override MethodAttributes Attributes
+        {
+            get { throw new NotSupportedException(SR.NotSupported_SymbolMethod); }
+        }
+
+        public override CallingConventions CallingConvention
+        {
+            get { return m_callingConvention; }
+        }
+
+        public override RuntimeMethodHandle MethodHandle
+        {
+            get { throw new NotSupportedException(SR.NotSupported_SymbolMethod); }
+        }
+
+        #endregion
+
+        #region MethodInfo Overrides
+        public override Type ReturnType
+        {
+            get
+            {
+                return m_returnType;
+            }
+        }
+
+        public override ICustomAttributeProvider ReturnTypeCustomAttributes
+        {
+            get { return null; }
+        }
+
+        public override Object Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
+        {
+            throw new NotSupportedException(SR.NotSupported_SymbolMethod);
+        }
+
+        public override MethodInfo GetBaseDefinition()
+        {
+            return this;
+        }
+        #endregion
+
+        #region ICustomAttributeProvider Implementation
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_SymbolMethod);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_SymbolMethod);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_SymbolMethod);
+        }
+
+        #endregion
+
+        #region Public Members
+        public Module GetModule()
+        {
+            return m_module;
+        }
+
+        public MethodToken GetToken()
+        {
+            return m_mdMethod;
+        }
+
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/SymbolType.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/SymbolType.cs
new file mode 100644
index 0000000000..6057c1da72
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/SymbolType.cs
@@ -0,0 +1,591 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+namespace System.Reflection.Emit
+{
+    using System.Runtime.InteropServices;
+    using System;
+    using System.Reflection;
+    using CultureInfo = System.Globalization.CultureInfo;
+
+    internal enum TypeKind
+    {
+        IsArray = 1,
+        IsPointer = 2,
+        IsByRef = 3,
+    }
+
+    // This is a kind of Type object that will represent the compound expression of a parameter type or field type.
+    internal sealed class SymbolType : TypeInfo
+    {
+        public override bool IsAssignableFrom(System.Reflection.TypeInfo typeInfo)
+        {
+            if (typeInfo == null) return false;
+            return IsAssignableFrom(typeInfo.AsType());
+        }
+
+        #region Static Members
+        internal static Type FormCompoundType(string format, Type baseType, int curIndex)
+        {
+            // This function takes a string to describe the compound type, such as "[,][]", and a baseType.
+            // 
+            // Example: [2..4]  - one dimension array with lower bound 2 and size of 3
+            // Example: [3, 5, 6] - three dimension array with lower bound 3, 5, 6
+            // Example: [-3, ] [] - one dimensional array of two dimensional array (with lower bound -3 for 
+            //          the first dimension)
+            // Example: []* - pointer to a one dimensional array
+            // Example: *[] - one dimensional array. The element type is a pointer to the baseType
+            // Example: []& - ByRef of a single dimensional array. Only one & is allowed and it must appear the last!
+            // Example: [?] - Array with unknown bound
+
+            SymbolType symbolType;
+            int iLowerBound;
+            int iUpperBound;
+
+            if (format == null || curIndex == format.Length)
+            {
+                // we have consumed all of the format string
+                return baseType;
+            }
+
+
+
+
+            if (format[curIndex] == '&')
+            {
+                // ByRef case
+
+                symbolType = new SymbolType(TypeKind.IsByRef);
+                symbolType.SetFormat(format, curIndex, 1);
+                curIndex++;
+
+                if (curIndex != format.Length)
+                    // ByRef has to be the last char!!
+                    throw new ArgumentException(SR.Argument_BadSigFormat);
+
+                symbolType.SetElementType(baseType);
+                return symbolType;
+            }
+
+            if (format[curIndex] == '[')
+            {
+                // Array type.
+                symbolType = new SymbolType(TypeKind.IsArray);
+                int startIndex = curIndex;
+                curIndex++;
+
+                iLowerBound = 0;
+                iUpperBound = -1;
+
+                // Example: [2..4]  - one dimension array with lower bound 2 and size of 3
+                // Example: [3, 5, 6] - three dimension array with lower bound 3, 5, 6
+                // Example: [-3, ] [] - one dimensional array of two dimensional array (with lower bound -3 sepcified)
+
+                while (format[curIndex] != ']')
+                {
+                    if (format[curIndex] == '*')
+                    {
+                        symbolType.m_isSzArray = false;
+                        curIndex++;
+                    }
+                    // consume, one dimension at a time
+                    if ((format[curIndex] >= '0' && format[curIndex] <= '9') || format[curIndex] == '-')
+                    {
+                        bool isNegative = false;
+                        if (format[curIndex] == '-')
+                        {
+                            isNegative = true;
+                            curIndex++;
+                        }
+
+                        // lower bound is specified. Consume the low bound
+                        while (format[curIndex] >= '0' && format[curIndex] <= '9')
+                        {
+                            iLowerBound = iLowerBound * 10;
+                            iLowerBound += format[curIndex] - '0';
+                            curIndex++;
+                        }
+
+                        if (isNegative)
+                        {
+                            iLowerBound = 0 - iLowerBound;
+                        }
+
+                        // set the upper bound to be less than LowerBound to indicate that upper bound it not specified yet!
+                        iUpperBound = iLowerBound - 1;
+                    }
+                    if (format[curIndex] == '.')
+                    {
+                        // upper bound is specified
+
+                        // skip over ".."
+                        curIndex++;
+                        if (format[curIndex] != '.')
+                        {
+                            // bad format!! Throw exception
+                            throw new ArgumentException(SR.Argument_BadSigFormat);
+                        }
+
+                        curIndex++;
+                        // consume the upper bound
+                        if ((format[curIndex] >= '0' && format[curIndex] <= '9') || format[curIndex] == '-')
+                        {
+                            bool isNegative = false;
+                            iUpperBound = 0;
+                            if (format[curIndex] == '-')
+                            {
+                                isNegative = true;
+                                curIndex++;
+                            }
+
+                            // lower bound is specified. Consume the low bound
+                            while (format[curIndex] >= '0' && format[curIndex] <= '9')
+                            {
+                                iUpperBound = iUpperBound * 10;
+                                iUpperBound += format[curIndex] - '0';
+                                curIndex++;
+                            }
+                            if (isNegative)
+                            {
+                                iUpperBound = 0 - iUpperBound;
+                            }
+                            if (iUpperBound < iLowerBound)
+                            {
+                                // User specified upper bound less than lower bound, this is an error.
+                                // Throw error exception.
+                                throw new ArgumentException(SR.Argument_BadSigFormat);
+                            }
+                        }
+                    }
+
+                    if (format[curIndex] == ',')
+                    {
+                        // We have more dimension to deal with.
+                        // now set the lower bound, the size, and increase the dimension count!
+                        curIndex++;
+                        symbolType.SetBounds(iLowerBound, iUpperBound);
+
+                        // clear the lower and upper bound information for next dimension
+                        iLowerBound = 0;
+                        iUpperBound = -1;
+                    }
+                    else if (format[curIndex] != ']')
+                    {
+                        throw new ArgumentException(SR.Argument_BadSigFormat);
+                    }
+                }
+
+                // The last dimension information
+                symbolType.SetBounds(iLowerBound, iUpperBound);
+
+                // skip over ']'
+                curIndex++;
+
+                symbolType.SetFormat(format, startIndex, curIndex - startIndex);
+
+                // set the base type of array
+                symbolType.SetElementType(baseType);
+                return FormCompoundType(format, symbolType, curIndex);
+            }
+            else if (format[curIndex] == '*')
+            {
+                // pointer type.
+
+                symbolType = new SymbolType(TypeKind.IsPointer);
+                symbolType.SetFormat(format, curIndex, 1);
+                curIndex++;
+                symbolType.SetElementType(baseType);
+                return FormCompoundType(format, symbolType, curIndex);
+            }
+
+            return null;
+        }
+
+        #endregion
+
+        #region Data Members
+        internal TypeKind m_typeKind;
+        internal Type m_baseType;
+        internal int m_cRank;        // count of dimension
+        // If LowerBound and UpperBound is equal, that means one element. 
+        // If UpperBound is less than LowerBound, then the size is not specified.
+        internal int[] m_iaLowerBound;
+        internal int[] m_iaUpperBound; // count of dimension
+        private string m_format;      // format string to form the full name.
+        private bool m_isSzArray = true;
+        #endregion
+
+        #region Constructor
+        internal SymbolType(TypeKind typeKind)
+        {
+            m_typeKind = typeKind;
+            m_iaLowerBound = new int[4];
+            m_iaUpperBound = new int[4];
+        }
+
+        #endregion
+
+        #region Internal Members
+        internal void SetElementType(Type baseType)
+        {
+            if (baseType == null)
+                throw new ArgumentNullException(nameof(baseType));
+
+            m_baseType = baseType;
+        }
+
+        private void SetBounds(int lower, int upper)
+        {
+            // Increase the rank, set lower and upper bound
+
+            if (lower != 0 || upper != -1)
+                m_isSzArray = false;
+
+            if (m_iaLowerBound.Length <= m_cRank)
+            {
+                // resize the bound array
+                int[] iaTemp = new int[m_cRank * 2];
+                Array.Copy(m_iaLowerBound, 0, iaTemp, 0, m_cRank);
+                m_iaLowerBound = iaTemp;
+                Array.Copy(m_iaUpperBound, 0, iaTemp, 0, m_cRank);
+                m_iaUpperBound = iaTemp;
+            }
+
+            m_iaLowerBound[m_cRank] = lower;
+            m_iaUpperBound[m_cRank] = upper;
+            m_cRank++;
+        }
+
+        internal void SetFormat(string format, int curIndex, int length)
+        {
+            // Cache the text display format for this SymbolType
+
+            m_format = format.Substring(curIndex, length);
+        }
+        #endregion
+
+        #region Type Overrides
+
+        public override bool IsTypeDefinition => false;
+
+        public override bool IsSZArray => m_cRank <= 1 && m_isSzArray;
+
+        public override Type MakePointerType()
+        {
+            return SymbolType.FormCompoundType(m_format + "*", m_baseType, 0);
+        }
+
+        public override Type MakeByRefType()
+        {
+            return SymbolType.FormCompoundType(m_format + "&", m_baseType, 0);
+        }
+
+        public override Type MakeArrayType()
+        {
+            return SymbolType.FormCompoundType(m_format + "[]", m_baseType, 0);
+        }
+
+        public override Type MakeArrayType(int rank)
+        {
+            if (rank <= 0)
+                throw new IndexOutOfRangeException();
+
+            string szrank = "";
+            if (rank == 1)
+            {
+                szrank = "*";
+            }
+            else
+            {
+                for (int i = 1; i < rank; i++)
+                    szrank += ",";
+            }
+
+            string s = String.Format(CultureInfo.InvariantCulture, "[{0}]", szrank); // [,,]
+            SymbolType st = SymbolType.FormCompoundType(m_format + s, m_baseType, 0) as SymbolType;
+            return st;
+        }
+
+        public override int GetArrayRank()
+        {
+            if (!IsArray)
+                throw new NotSupportedException(SR.NotSupported_SubclassOverride);
+
+            return m_cRank;
+        }
+
+        public override Guid GUID
+        {
+            get { throw new NotSupportedException(SR.NotSupported_NonReflectedType); }
+        }
+
+        public override Object InvokeMember(String name, BindingFlags invokeAttr, Binder binder, Object target,
+            Object[] args, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParameters)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override Module Module
+        {
+            get
+            {
+                Type baseType;
+
+                for (baseType = m_baseType; baseType is SymbolType; baseType = ((SymbolType)baseType).m_baseType) ;
+
+                return baseType.Module;
+            }
+        }
+        public override Assembly Assembly
+        {
+            get
+            {
+                Type baseType;
+
+                for (baseType = m_baseType; baseType is SymbolType; baseType = ((SymbolType)baseType).m_baseType) ;
+
+                return baseType.Assembly;
+            }
+        }
+
+        public override RuntimeTypeHandle TypeHandle
+        {
+            get { throw new NotSupportedException(SR.NotSupported_NonReflectedType); }
+        }
+
+        public override String Name
+        {
+            get
+            {
+                Type baseType;
+                String sFormat = m_format;
+
+                for (baseType = m_baseType; baseType is SymbolType; baseType = ((SymbolType)baseType).m_baseType)
+                    sFormat = ((SymbolType)baseType).m_format + sFormat;
+
+                return baseType.Name + sFormat;
+            }
+        }
+
+        public override String FullName
+        {
+            get
+            {
+                return TypeNameBuilder.ToString(this, TypeNameBuilder.Format.FullName);
+            }
+        }
+
+        public override String AssemblyQualifiedName
+        {
+            get
+            {
+                return TypeNameBuilder.ToString(this, TypeNameBuilder.Format.AssemblyQualifiedName);
+            }
+        }
+
+        public override String ToString()
+        {
+            return TypeNameBuilder.ToString(this, TypeNameBuilder.Format.ToString);
+        }
+
+        public override String Namespace
+        {
+            get { return m_baseType.Namespace; }
+        }
+
+        public override Type BaseType
+        {
+            get { return typeof(System.Array); }
+        }
+
+        protected override ConstructorInfo GetConstructorImpl(BindingFlags bindingAttr, Binder binder,
+                CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override ConstructorInfo[] GetConstructors(BindingFlags bindingAttr)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        protected override MethodInfo GetMethodImpl(String name, BindingFlags bindingAttr, Binder binder,
+                CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override MethodInfo[] GetMethods(BindingFlags bindingAttr)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override FieldInfo GetField(String name, BindingFlags bindingAttr)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override FieldInfo[] GetFields(BindingFlags bindingAttr)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override Type GetInterface(String name, bool ignoreCase)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override Type[] GetInterfaces()
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override EventInfo GetEvent(String name, BindingFlags bindingAttr)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override EventInfo[] GetEvents()
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        protected override PropertyInfo GetPropertyImpl(String name, BindingFlags bindingAttr, Binder binder,
+                Type returnType, Type[] types, ParameterModifier[] modifiers)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override PropertyInfo[] GetProperties(BindingFlags bindingAttr)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override Type[] GetNestedTypes(BindingFlags bindingAttr)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override Type GetNestedType(String name, BindingFlags bindingAttr)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override MemberInfo[] GetMember(String name, MemberTypes type, BindingFlags bindingAttr)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override MemberInfo[] GetMembers(BindingFlags bindingAttr)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override InterfaceMapping GetInterfaceMap(Type interfaceType)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override EventInfo[] GetEvents(BindingFlags bindingAttr)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        protected override TypeAttributes GetAttributeFlagsImpl()
+        {
+            // Return the attribute flags of the base type?
+            Type baseType;
+            for (baseType = m_baseType; baseType is SymbolType; baseType = ((SymbolType)baseType).m_baseType) ;
+            return baseType.Attributes;
+        }
+
+        protected override bool IsArrayImpl()
+        {
+            return m_typeKind == TypeKind.IsArray;
+        }
+
+        protected override bool IsPointerImpl()
+        {
+            return m_typeKind == TypeKind.IsPointer;
+        }
+
+        protected override bool IsByRefImpl()
+        {
+            return m_typeKind == TypeKind.IsByRef;
+        }
+
+        protected override bool IsPrimitiveImpl()
+        {
+            return false;
+        }
+
+        protected override bool IsValueTypeImpl()
+        {
+            return false;
+        }
+
+        protected override bool IsCOMObjectImpl()
+        {
+            return false;
+        }
+
+        public override bool IsConstructedGenericType
+        {
+            get
+            {
+                return false;
+            }
+        }
+
+        public override Type GetElementType()
+        {
+            return m_baseType;
+        }
+
+        protected override bool HasElementTypeImpl()
+        {
+            return m_baseType != null;
+        }
+
+        public override Type UnderlyingSystemType
+        {
+            get { return this; }
+        }
+
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            throw new NotSupportedException(SR.NotSupported_NonReflectedType);
+        }
+        #endregion
+    }
+}
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/TypeBuilder.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/TypeBuilder.cs
new file mode 100644
index 0000000000..f517decc1d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/TypeBuilder.cs
@@ -0,0 +1,2128 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+// 
+
+namespace System.Reflection.Emit
+{
+    using System;
+    using System.Reflection;
+    using System.Security;
+    using System.Runtime.InteropServices;
+    using System.Runtime.CompilerServices;
+    using System.Collections.Generic;
+    using CultureInfo = System.Globalization.CultureInfo;
+    using System.Threading;
+    using System.Runtime.Versioning;
+    using System.Diagnostics;
+
+
+    public enum PackingSize
+    {
+        Unspecified = 0,
+        Size1 = 1,
+        Size2 = 2,
+        Size4 = 4,
+        Size8 = 8,
+        Size16 = 16,
+        Size32 = 32,
+        Size64 = 64,
+        Size128 = 128,
+    }
+
+    public sealed class TypeBuilder : TypeInfo
+    {
+        public override bool IsAssignableFrom(System.Reflection.TypeInfo typeInfo)
+        {
+            if (typeInfo == null) return false;
+            return IsAssignableFrom(typeInfo.AsType());
+        }
+
+        #region Declarations
+        private class CustAttr
+        {
+            private ConstructorInfo m_con;
+            private byte[] m_binaryAttribute;
+            private CustomAttributeBuilder m_customBuilder;
+
+            public CustAttr(ConstructorInfo con, byte[] binaryAttribute)
+            {
+                if (con == null)
+                    throw new ArgumentNullException(nameof(con));
+
+                if (binaryAttribute == null)
+                    throw new ArgumentNullException(nameof(binaryAttribute));
+
+                m_con = con;
+                m_binaryAttribute = binaryAttribute;
+            }
+
+            public CustAttr(CustomAttributeBuilder customBuilder)
+            {
+                if (customBuilder == null)
+                    throw new ArgumentNullException(nameof(customBuilder));
+
+                m_customBuilder = customBuilder;
+            }
+
+            public void Bake(ModuleBuilder module, int token)
+            {
+                if (m_customBuilder == null)
+                {
+                    TypeBuilder.DefineCustomAttribute(module, token, module.GetConstructorToken(m_con).Token,
+                        m_binaryAttribute, false, false);
+                }
+                else
+                {
+                    m_customBuilder.CreateCustomAttribute(module, token);
+                }
+            }
+        }
+        #endregion
+
+        #region Public Static Methods
+        public static MethodInfo GetMethod(Type type, MethodInfo method)
+        {
+            if (!(type is TypeBuilder) && !(type is TypeBuilderInstantiation))
+                throw new ArgumentException(SR.Argument_MustBeTypeBuilder);
+
+            // The following checks establishes invariants that more simply put require type to be generic and 
+            // method to be a generic method definition declared on the generic type definition of type.
+            // To create generic method G<Foo>.M<Bar> these invariants require that G<Foo>.M<S> be created by calling 
+            // this function followed by MakeGenericMethod on the resulting MethodInfo to finally get G<Foo>.M<Bar>.
+            // We could also allow G<T>.M<Bar> to be created before G<Foo>.M<Bar> (BindGenParm followed by this method) 
+            // if we wanted to but that just complicates things so these checks are designed to prevent that scenario.
+
+            if (method.IsGenericMethod && !method.IsGenericMethodDefinition)
+                throw new ArgumentException(SR.Argument_NeedGenericMethodDefinition, nameof(method));
+
+            if (method.DeclaringType == null || !method.DeclaringType.IsGenericTypeDefinition)
+                throw new ArgumentException(SR.Argument_MethodNeedGenericDeclaringType, nameof(method));
+
+            if (type.GetGenericTypeDefinition() != method.DeclaringType)
+                throw new ArgumentException(SR.Argument_InvalidMethodDeclaringType, nameof(type));
+
+            // The following converts from Type or TypeBuilder of G<T> to TypeBuilderInstantiation G<T>. These types
+            // both logically represent the same thing. The runtime displays a similar convention by having 
+            // G<M>.M() be encoded by a typeSpec whose parent is the typeDef for G<M> and whose instantiation is also G<M>.
+            if (type.IsGenericTypeDefinition)
+                type = type.MakeGenericType(type.GetGenericArguments());
+
+            if (!(type is TypeBuilderInstantiation))
+                throw new ArgumentException(SR.Argument_NeedNonGenericType, nameof(type));
+
+            return MethodOnTypeBuilderInstantiation.GetMethod(method, type as TypeBuilderInstantiation);
+        }
+        public static ConstructorInfo GetConstructor(Type type, ConstructorInfo constructor)
+        {
+            if (!(type is TypeBuilder) && !(type is TypeBuilderInstantiation))
+                throw new ArgumentException(SR.Argument_MustBeTypeBuilder);
+
+            if (!constructor.DeclaringType.IsGenericTypeDefinition)
+                throw new ArgumentException(SR.Argument_ConstructorNeedGenericDeclaringType, nameof(constructor));
+
+            if (!(type is TypeBuilderInstantiation))
+                throw new ArgumentException(SR.Argument_NeedNonGenericType, nameof(type));
+
+            // TypeBuilder G<T> ==> TypeBuilderInstantiation G<T>
+            if (type is TypeBuilder && type.IsGenericTypeDefinition)
+                type = type.MakeGenericType(type.GetGenericArguments());
+
+            if (type.GetGenericTypeDefinition() != constructor.DeclaringType)
+                throw new ArgumentException(SR.Argument_InvalidConstructorDeclaringType, nameof(type));
+
+            return ConstructorOnTypeBuilderInstantiation.GetConstructor(constructor, type as TypeBuilderInstantiation);
+        }
+        public static FieldInfo GetField(Type type, FieldInfo field)
+        {
+            if (!(type is TypeBuilder) && !(type is TypeBuilderInstantiation))
+                throw new ArgumentException(SR.Argument_MustBeTypeBuilder);
+
+            if (!field.DeclaringType.IsGenericTypeDefinition)
+                throw new ArgumentException(SR.Argument_FieldNeedGenericDeclaringType, nameof(field));
+
+            if (!(type is TypeBuilderInstantiation))
+                throw new ArgumentException(SR.Argument_NeedNonGenericType, nameof(type));
+
+            // TypeBuilder G<T> ==> TypeBuilderInstantiation G<T>
+            if (type is TypeBuilder && type.IsGenericTypeDefinition)
+                type = type.MakeGenericType(type.GetGenericArguments());
+
+            if (type.GetGenericTypeDefinition() != field.DeclaringType)
+                throw new ArgumentException(SR.Argument_InvalidFieldDeclaringType, nameof(type));
+
+            return FieldOnTypeBuilderInstantiation.GetField(field, type as TypeBuilderInstantiation);
+        }
+        #endregion
+
+        #region Public Const
+        public const int UnspecifiedTypeSize = 0;
+        #endregion
+
+        #region Private Static FCalls
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void SetParentType(RuntimeModule module, int tdTypeDef, int tkParent);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void AddInterfaceImpl(RuntimeModule module, int tdTypeDef, int tkInterface);
+        #endregion
+
+        #region Internal Static FCalls
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern int DefineMethod(RuntimeModule module, int tkParent, String name, byte[] signature, int sigLength,
+            MethodAttributes attributes);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern int DefineMethodSpec(RuntimeModule module, int tkParent, byte[] signature, int sigLength);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern int DefineField(RuntimeModule module, int tkParent, String name, byte[] signature, int sigLength,
+            FieldAttributes attributes);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void SetMethodIL(RuntimeModule module, int tk, bool isInitLocals,
+            byte[] body, int bodyLength,
+            byte[] LocalSig, int sigLength,
+            int maxStackSize,
+            ExceptionHandler[] exceptions, int numExceptions,
+            int[] tokenFixups, int numTokenFixups);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void DefineCustomAttribute(RuntimeModule module, int tkAssociate, int tkConstructor,
+            byte[] attr, int attrLength, bool toDisk, bool updateCompilerFlags);
+
+        internal static void DefineCustomAttribute(ModuleBuilder module, int tkAssociate, int tkConstructor,
+            byte[] attr, bool toDisk, bool updateCompilerFlags)
+        {
+            byte[] localAttr = null;
+
+            if (attr != null)
+            {
+                localAttr = new byte[attr.Length];
+                Buffer.BlockCopy(attr, 0, localAttr, 0, attr.Length);
+            }
+
+            DefineCustomAttribute(module.GetNativeHandle(), tkAssociate, tkConstructor,
+                localAttr, (localAttr != null) ? localAttr.Length : 0, toDisk, updateCompilerFlags);
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern int DefineProperty(RuntimeModule module, int tkParent, String name, PropertyAttributes attributes,
+            byte[] signature, int sigLength);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern int DefineEvent(RuntimeModule module, int tkParent, String name, EventAttributes attributes, int tkEventType);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void DefineMethodSemantics(RuntimeModule module, int tkAssociation,
+            MethodSemanticsAttributes semantics, int tkMethod);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void DefineMethodImpl(RuntimeModule module, int tkType, int tkBody, int tkDecl);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void SetMethodImpl(RuntimeModule module, int tkMethod, MethodImplAttributes MethodImplAttributes);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern int SetParamInfo(RuntimeModule module, int tkMethod, int iSequence,
+            ParameterAttributes iParamAttributes, String strParamName);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern int GetTokenFromSig(RuntimeModule module, byte[] signature, int sigLength);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void SetFieldLayoutOffset(RuntimeModule module, int fdToken, int iOffset);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void SetClassLayout(RuntimeModule module, int tk, PackingSize iPackingSize, int iTypeSize);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern unsafe void SetConstantValue(RuntimeModule module, int tk, int corType, void* pValue);
+
+        #endregion
+        #region Internal\Private Static Members
+
+        internal static bool IsTypeEqual(Type t1, Type t2)
+        {
+            // Maybe we are lucky that they are equal in the first place
+            if (t1 == t2)
+                return true;
+            TypeBuilder tb1 = null;
+            TypeBuilder tb2 = null;
+            Type runtimeType1 = null;
+            Type runtimeType2 = null;
+
+            // set up the runtimeType and TypeBuilder type corresponding to t1 and t2
+            if (t1 is TypeBuilder)
+            {
+                tb1 = (TypeBuilder)t1;
+                // This will be null if it is not baked.
+                runtimeType1 = tb1.m_bakedRuntimeType;
+            }
+            else
+            {
+                runtimeType1 = t1;
+            }
+
+            if (t2 is TypeBuilder)
+            {
+                tb2 = (TypeBuilder)t2;
+                // This will be null if it is not baked.
+                runtimeType2 = tb2.m_bakedRuntimeType;
+            }
+            else
+            {
+                runtimeType2 = t2;
+            }
+
+            // If the type builder view is eqaul then it is equal                
+            if (tb1 != null && tb2 != null && Object.ReferenceEquals(tb1, tb2))
+                return true;
+
+            // if the runtimetype view is eqaul than it is equal                
+            if (runtimeType1 != null && runtimeType2 != null && runtimeType1 == runtimeType2)
+                return true;
+
+            return false;
+        }
+
+        internal static unsafe void SetConstantValue(ModuleBuilder module, int tk, Type destType, Object value)
+        {
+            // This is a helper function that is used by ParameterBuilder, PropertyBuilder,
+            // and FieldBuilder to validate a default value and save it in the meta-data.
+
+            if (value != null)
+            {
+                Type type = value.GetType();
+
+                // We should allow setting a constant value on a ByRef parameter
+                if (destType.IsByRef)
+                    destType = destType.GetElementType();
+
+                if (destType.IsEnum)
+                {
+                    //                                   |  UnderlyingSystemType     |  Enum.GetUnderlyingType() |  IsEnum
+                    // ----------------------------------|---------------------------|---------------------------|---------
+                    // runtime Enum Type                 |  self                     |  underlying type of enum  |  TRUE
+                    // EnumBuilder                       |  underlying type of enum  |  underlying type of enum* |  TRUE
+                    // TypeBuilder of enum types**       |  underlying type of enum  |  Exception                |  TRUE
+                    // TypeBuilder of enum types (baked) |  runtime enum type        |  Exception                |  TRUE
+
+                    //  *: the behavior of Enum.GetUnderlyingType(EnumBuilder) might change in the future
+                    //     so let's not depend on it.
+                    // **: created with System.Enum as the parent type.
+
+                    // The above behaviors might not be the most consistent but we have to live with them.
+
+                    Type underlyingType;
+                    EnumBuilder enumBldr;
+                    TypeBuilder typeBldr;
+                    if ((enumBldr = destType as EnumBuilder) != null)
+                    {
+                        underlyingType = enumBldr.GetEnumUnderlyingType();
+
+                        // The constant value supplied should match either the baked enum type or its underlying type
+                        // we don't need to compare it with the EnumBuilder itself because you can never have an object of that type
+                        if (type != enumBldr.m_typeBuilder.m_bakedRuntimeType && type != underlyingType)
+                            throw new ArgumentException(SR.Argument_ConstantDoesntMatch);
+                    }
+                    else if ((typeBldr = destType as TypeBuilder) != null)
+                    {
+                        underlyingType = typeBldr.m_enumUnderlyingType;
+
+                        // The constant value supplied should match either the baked enum type or its underlying type
+                        // typeBldr.m_enumUnderlyingType is null if the user hasn't created a "value__" field on the enum
+                        if (underlyingType == null || (type != typeBldr.UnderlyingSystemType && type != underlyingType))
+                            throw new ArgumentException(SR.Argument_ConstantDoesntMatch);
+                    }
+                    else // must be a runtime Enum Type
+                    {
+                        Debug.Assert(destType is RuntimeType, "destType is not a runtime type, an EnumBuilder, or a TypeBuilder.");
+
+                        underlyingType = Enum.GetUnderlyingType(destType);
+
+                        // The constant value supplied should match either the enum itself or its underlying type
+                        if (type != destType && type != underlyingType)
+                            throw new ArgumentException(SR.Argument_ConstantDoesntMatch);
+                    }
+
+                    type = underlyingType;
+                }
+                else
+                {
+                    // Note that it is non CLS compliant if destType != type. But RefEmit never guarantees CLS-Compliance.
+                    if (!destType.IsAssignableFrom(type))
+                        throw new ArgumentException(SR.Argument_ConstantDoesntMatch);
+                }
+
+                CorElementType corType = RuntimeTypeHandle.GetCorElementType((RuntimeType)type);
+
+                switch (corType)
+                {
+                    case CorElementType.I1:
+                    case CorElementType.U1:
+                    case CorElementType.Boolean:
+                    case CorElementType.I2:
+                    case CorElementType.U2:
+                    case CorElementType.Char:
+                    case CorElementType.I4:
+                    case CorElementType.U4:
+                    case CorElementType.R4:
+                    case CorElementType.I8:
+                    case CorElementType.U8:
+                    case CorElementType.R8:
+                        fixed (byte* pData = &JitHelpers.GetPinningHelper(value).m_data)
+                            SetConstantValue(module.GetNativeHandle(), tk, (int)corType, pData);
+                        break;
+
+                    default:
+                        if (type == typeof(String))
+                        {
+                            fixed (char* pString = (string)value)
+                                SetConstantValue(module.GetNativeHandle(), tk, (int)CorElementType.String, pString);
+                        }
+                        else if (type == typeof(DateTime))
+                        {
+                            //date is a I8 representation
+                            long ticks = ((DateTime)value).Ticks;
+                            SetConstantValue(module.GetNativeHandle(), tk, (int)CorElementType.I8, &ticks);
+                        }
+                        else
+                        {
+                            throw new ArgumentException(SR.Format(SR.Argument_ConstantNotSupported, type.ToString()));
+                        }
+                        break;
+                }
+            }
+            else
+            {
+                // A null default value in metadata is permissible even for non-nullable value types.
+                // (See ECMA-335 II.15.4.1.4 "The .param directive" and II.22.9 "Constant" for details.)
+                // This is how the Roslyn compilers generally encode `default(TValueType)` default values.
+
+                SetConstantValue(module.GetNativeHandle(), tk, (int)CorElementType.Class, null);
+            }
+        }
+
+        #endregion
+
+        #region Private Data Members
+        private List<CustAttr> m_ca;
+        private TypeToken m_tdType;
+        private ModuleBuilder m_module;
+        private String m_strName;
+        private String m_strNameSpace;
+        private String m_strFullQualName;
+        private Type m_typeParent;
+        private List<Type> m_typeInterfaces;
+        private TypeAttributes m_iAttr;
+        private GenericParameterAttributes m_genParamAttributes;
+        internal List<MethodBuilder> m_listMethods;
+        internal int m_lastTokenizedMethod;
+        private int m_constructorCount;
+        private int m_iTypeSize;
+        private PackingSize m_iPackingSize;
+        private TypeBuilder m_DeclaringType;
+
+        // We cannot store this on EnumBuilder because users can define enum types manually using TypeBuilder.
+        private Type m_enumUnderlyingType;
+        internal bool m_isHiddenGlobalType;
+        private bool m_hasBeenCreated;
+        private RuntimeType m_bakedRuntimeType;
+
+        private int m_genParamPos;
+        private GenericTypeParameterBuilder[] m_inst;
+        private bool m_bIsGenParam;
+        private MethodBuilder m_declMeth;
+        private TypeBuilder m_genTypeDef;
+        #endregion
+
+        #region Constructor
+        // ctor for the global (module) type
+        internal TypeBuilder(ModuleBuilder module)
+        {
+            m_tdType = new TypeToken((int)MetadataTokenType.TypeDef);
+            m_isHiddenGlobalType = true;
+            m_module = (ModuleBuilder)module;
+            m_listMethods = new List<MethodBuilder>();
+            // No token has been created so let's initialize it to -1
+            // The first time we call MethodBuilder.GetToken this will incremented.
+            m_lastTokenizedMethod = -1;
+        }
+
+        // ctor for generic method parameter
+        internal TypeBuilder(string szName, int genParamPos, MethodBuilder declMeth)
+        {
+            Debug.Assert(declMeth != null);
+            m_declMeth = declMeth;
+            m_DeclaringType = m_declMeth.GetTypeBuilder();
+            m_module = declMeth.GetModuleBuilder();
+            InitAsGenericParam(szName, genParamPos);
+        }
+
+        // ctor for generic type parameter
+        private TypeBuilder(string szName, int genParamPos, TypeBuilder declType)
+        {
+            Debug.Assert(declType != null);
+            m_DeclaringType = declType;
+            m_module = declType.GetModuleBuilder();
+            InitAsGenericParam(szName, genParamPos);
+        }
+
+        private void InitAsGenericParam(string szName, int genParamPos)
+        {
+            m_strName = szName;
+            m_genParamPos = genParamPos;
+            m_bIsGenParam = true;
+            m_typeInterfaces = new List<Type>();
+        }
+
+        internal TypeBuilder(
+            String name,
+            TypeAttributes attr,
+            Type parent,
+            Type[] interfaces,
+            ModuleBuilder module,
+            PackingSize iPackingSize,
+            int iTypeSize,
+            TypeBuilder enclosingType)
+        {
+            Init(name, attr, parent, interfaces, module, iPackingSize, iTypeSize, enclosingType);
+        }
+
+        private void Init(String fullname, TypeAttributes attr, Type parent, Type[] interfaces, ModuleBuilder module,
+            PackingSize iPackingSize, int iTypeSize, TypeBuilder enclosingType)
+        {
+            if (fullname == null)
+                throw new ArgumentNullException(nameof(fullname));
+
+            if (fullname.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(fullname));
+
+            if (fullname[0] == '\0')
+                throw new ArgumentException(SR.Argument_IllegalName, nameof(fullname));
+
+
+            if (fullname.Length > 1023)
+                throw new ArgumentException(SR.Argument_TypeNameTooLong, nameof(fullname));
+
+            int i;
+            m_module = module;
+            m_DeclaringType = enclosingType;
+            AssemblyBuilder containingAssem = m_module.ContainingAssemblyBuilder;
+
+            // cannot have two types within the same assembly of the same name
+            containingAssem.m_assemblyData.CheckTypeNameConflict(fullname, enclosingType);
+
+            if (enclosingType != null)
+            {
+                // Nested Type should have nested attribute set.
+                // If we are renumbering TypeAttributes' bit, we need to change the logic here.
+                if (((attr & TypeAttributes.VisibilityMask) == TypeAttributes.Public) || ((attr & TypeAttributes.VisibilityMask) == TypeAttributes.NotPublic))
+                    throw new ArgumentException(SR.Argument_BadNestedTypeFlags, nameof(attr));
+            }
+
+            int[] interfaceTokens = null;
+            if (interfaces != null)
+            {
+                for (i = 0; i < interfaces.Length; i++)
+                {
+                    if (interfaces[i] == null)
+                    {
+                        // cannot contain null in the interface list
+                        throw new ArgumentNullException(nameof(interfaces));
+                    }
+                }
+                interfaceTokens = new int[interfaces.Length + 1];
+                for (i = 0; i < interfaces.Length; i++)
+                {
+                    interfaceTokens[i] = m_module.GetTypeTokenInternal(interfaces[i]).Token;
+                }
+            }
+
+            int iLast = fullname.LastIndexOf('.');
+            if (iLast == -1 || iLast == 0)
+            {
+                // no name space
+                m_strNameSpace = String.Empty;
+                m_strName = fullname;
+            }
+            else
+            {
+                // split the name space
+                m_strNameSpace = fullname.Substring(0, iLast);
+                m_strName = fullname.Substring(iLast + 1);
+            }
+
+            VerifyTypeAttributes(attr);
+
+            m_iAttr = attr;
+
+            SetParent(parent);
+
+            m_listMethods = new List<MethodBuilder>();
+            m_lastTokenizedMethod = -1;
+
+            SetInterfaces(interfaces);
+
+            int tkParent = 0;
+            if (m_typeParent != null)
+                tkParent = m_module.GetTypeTokenInternal(m_typeParent).Token;
+
+            int tkEnclosingType = 0;
+            if (enclosingType != null)
+            {
+                tkEnclosingType = enclosingType.m_tdType.Token;
+            }
+
+            m_tdType = new TypeToken(DefineType(m_module.GetNativeHandle(),
+                fullname, tkParent, m_iAttr, tkEnclosingType, interfaceTokens));
+
+            m_iPackingSize = iPackingSize;
+            m_iTypeSize = iTypeSize;
+            if ((m_iPackingSize != 0) || (m_iTypeSize != 0))
+                SetClassLayout(GetModuleBuilder().GetNativeHandle(), m_tdType.Token, m_iPackingSize, m_iTypeSize);
+
+            m_module.AddType(FullName, this);
+        }
+
+        #endregion
+        #region Private Members
+
+        private FieldBuilder DefineDataHelper(String name, byte[] data, int size, FieldAttributes attributes)
+        {
+            String strValueClassName;
+            TypeBuilder valueClassType;
+            FieldBuilder fdBuilder;
+            TypeAttributes typeAttributes;
+
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            if (name.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(name));
+
+            if (size <= 0 || size >= 0x003f0000)
+                throw new ArgumentException(SR.Argument_BadSizeForData);
+
+            ThrowIfCreated();
+
+            // form the value class name
+            strValueClassName = ModuleBuilderData.MULTI_BYTE_VALUE_CLASS + size.ToString();
+
+            // Is this already defined in this module?
+            Type temp = m_module.FindTypeBuilderWithName(strValueClassName, false);
+            valueClassType = temp as TypeBuilder;
+
+            if (valueClassType == null)
+            {
+                typeAttributes = TypeAttributes.Public | TypeAttributes.ExplicitLayout | TypeAttributes.Class | TypeAttributes.Sealed | TypeAttributes.AnsiClass;
+
+                // Define the backing value class
+                valueClassType = m_module.DefineType(strValueClassName, typeAttributes, typeof(System.ValueType), PackingSize.Size1, size);
+                valueClassType.CreateType();
+            }
+
+            fdBuilder = DefineField(name, valueClassType, (attributes | FieldAttributes.Static));
+
+            // now we need to set the RVA
+            fdBuilder.SetData(data, size);
+            return fdBuilder;
+        }
+
+        private void VerifyTypeAttributes(TypeAttributes attr)
+        {
+            // Verify attr consistency for Nesting or otherwise.
+            if (DeclaringType == null)
+            {
+                // Not a nested class.
+                if (((attr & TypeAttributes.VisibilityMask) != TypeAttributes.NotPublic) && ((attr & TypeAttributes.VisibilityMask) != TypeAttributes.Public))
+                {
+                    throw new ArgumentException(SR.Argument_BadTypeAttrNestedVisibilityOnNonNestedType);
+                }
+            }
+            else
+            {
+                // Nested class.
+                if (((attr & TypeAttributes.VisibilityMask) == TypeAttributes.NotPublic) || ((attr & TypeAttributes.VisibilityMask) == TypeAttributes.Public))
+                {
+                    throw new ArgumentException(SR.Argument_BadTypeAttrNonNestedVisibilityNestedType);
+                }
+            }
+
+            // Verify that the layout mask is valid.
+            if (((attr & TypeAttributes.LayoutMask) != TypeAttributes.AutoLayout) && ((attr & TypeAttributes.LayoutMask) != TypeAttributes.SequentialLayout) && ((attr & TypeAttributes.LayoutMask) != TypeAttributes.ExplicitLayout))
+            {
+                throw new ArgumentException(SR.Argument_BadTypeAttrInvalidLayout);
+            }
+
+            // Check if the user attempted to set any reserved bits.
+            if ((attr & TypeAttributes.ReservedMask) != 0)
+            {
+                throw new ArgumentException(SR.Argument_BadTypeAttrReservedBitsSet);
+            }
+        }
+
+        public bool IsCreated()
+        {
+            return m_hasBeenCreated;
+        }
+
+        #endregion
+
+        #region FCalls
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern int DefineType(RuntimeModule module,
+            String fullname, int tkParent, TypeAttributes attributes, int tkEnclosingType, int[] interfaceTokens);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern int DefineGenericParam(RuntimeModule module,
+            String name, int tkParent, GenericParameterAttributes attributes, int position, int[] constraints);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void TermCreateClass(RuntimeModule module, int tk, ObjectHandleOnStack type);
+        #endregion
+
+        #region Internal Methods
+        internal void ThrowIfCreated()
+        {
+            if (IsCreated())
+                throw new InvalidOperationException(SR.InvalidOperation_TypeHasBeenCreated);
+        }
+
+        internal object SyncRoot
+        {
+            get
+            {
+                return m_module.SyncRoot;
+            }
+        }
+
+        internal ModuleBuilder GetModuleBuilder()
+        {
+            return m_module;
+        }
+
+        internal RuntimeType BakedRuntimeType
+        {
+            get
+            {
+                return m_bakedRuntimeType;
+            }
+        }
+
+        internal void SetGenParamAttributes(GenericParameterAttributes genericParameterAttributes)
+        {
+            m_genParamAttributes = genericParameterAttributes;
+        }
+
+        internal void SetGenParamCustomAttribute(ConstructorInfo con, byte[] binaryAttribute)
+        {
+            CustAttr ca = new CustAttr(con, binaryAttribute);
+
+            lock (SyncRoot)
+            {
+                SetGenParamCustomAttributeNoLock(ca);
+            }
+        }
+
+        internal void SetGenParamCustomAttribute(CustomAttributeBuilder customBuilder)
+        {
+            CustAttr ca = new CustAttr(customBuilder);
+
+            lock (SyncRoot)
+            {
+                SetGenParamCustomAttributeNoLock(ca);
+            }
+        }
+
+        private void SetGenParamCustomAttributeNoLock(CustAttr ca)
+        {
+            if (m_ca == null)
+                m_ca = new List<TypeBuilder.CustAttr>();
+
+            m_ca.Add(ca);
+        }
+        #endregion
+
+        #region Object Overrides
+        public override String ToString()
+        {
+            return TypeNameBuilder.ToString(this, TypeNameBuilder.Format.ToString);
+        }
+
+        #endregion
+
+        #region MemberInfo Overrides
+        public override Type DeclaringType
+        {
+            get { return m_DeclaringType; }
+        }
+
+        public override Type ReflectedType
+        {
+            // Return the class that was used to obtain this field.
+
+            get { return m_DeclaringType; }
+        }
+
+        public override String Name
+        {
+            get { return m_strName; }
+        }
+
+        public override Module Module
+        {
+            get { return GetModuleBuilder(); }
+        }
+
+        internal int MetadataTokenInternal
+        {
+            get { return m_tdType.Token; }
+        }
+
+        #endregion
+
+        #region Type Overrides
+        public override Guid GUID
+        {
+            get
+            {
+                if (!IsCreated())
+                    throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+                return m_bakedRuntimeType.GUID;
+            }
+        }
+
+        public override Object InvokeMember(String name, BindingFlags invokeAttr, Binder binder, Object target,
+            Object[] args, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParameters)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.InvokeMember(name, invokeAttr, binder, target, args, modifiers, culture, namedParameters);
+        }
+
+        public override Assembly Assembly
+        {
+            get { return m_module.Assembly; }
+        }
+
+        public override RuntimeTypeHandle TypeHandle
+        {
+            get { throw new NotSupportedException(SR.NotSupported_DynamicModule); }
+        }
+
+        public override String FullName
+        {
+            get
+            {
+                if (m_strFullQualName == null)
+                    m_strFullQualName = TypeNameBuilder.ToString(this, TypeNameBuilder.Format.FullName);
+
+                return m_strFullQualName;
+            }
+        }
+
+        public override String Namespace
+        {
+            get { return m_strNameSpace; }
+        }
+
+        public override String AssemblyQualifiedName
+        {
+            get
+            {
+                return TypeNameBuilder.ToString(this, TypeNameBuilder.Format.AssemblyQualifiedName);
+            }
+        }
+
+        public override Type BaseType
+        {
+            get { return m_typeParent; }
+        }
+
+        protected override ConstructorInfo GetConstructorImpl(BindingFlags bindingAttr, Binder binder,
+                CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetConstructor(bindingAttr, binder, callConvention, types, modifiers);
+        }
+
+        public override ConstructorInfo[] GetConstructors(BindingFlags bindingAttr)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetConstructors(bindingAttr);
+        }
+
+        protected override MethodInfo GetMethodImpl(String name, BindingFlags bindingAttr, Binder binder,
+                CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            if (types == null)
+            {
+                return m_bakedRuntimeType.GetMethod(name, bindingAttr);
+            }
+            else
+            {
+                return m_bakedRuntimeType.GetMethod(name, bindingAttr, binder, callConvention, types, modifiers);
+            }
+        }
+
+        public override MethodInfo[] GetMethods(BindingFlags bindingAttr)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetMethods(bindingAttr);
+        }
+
+        public override FieldInfo GetField(String name, BindingFlags bindingAttr)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetField(name, bindingAttr);
+        }
+
+        public override FieldInfo[] GetFields(BindingFlags bindingAttr)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetFields(bindingAttr);
+        }
+
+        public override Type GetInterface(String name, bool ignoreCase)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetInterface(name, ignoreCase);
+        }
+
+        public override Type[] GetInterfaces()
+        {
+            if (m_bakedRuntimeType != null)
+            {
+                return m_bakedRuntimeType.GetInterfaces();
+            }
+
+            if (m_typeInterfaces == null)
+            {
+                return Array.Empty<Type>();
+            }
+
+            return m_typeInterfaces.ToArray();
+        }
+
+        public override EventInfo GetEvent(String name, BindingFlags bindingAttr)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetEvent(name, bindingAttr);
+        }
+
+        public override EventInfo[] GetEvents()
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetEvents();
+        }
+
+        protected override PropertyInfo GetPropertyImpl(String name, BindingFlags bindingAttr, Binder binder,
+                Type returnType, Type[] types, ParameterModifier[] modifiers)
+        {
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        public override PropertyInfo[] GetProperties(BindingFlags bindingAttr)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetProperties(bindingAttr);
+        }
+
+        public override Type[] GetNestedTypes(BindingFlags bindingAttr)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetNestedTypes(bindingAttr);
+        }
+
+        public override Type GetNestedType(String name, BindingFlags bindingAttr)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetNestedType(name, bindingAttr);
+        }
+
+        public override MemberInfo[] GetMember(String name, MemberTypes type, BindingFlags bindingAttr)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetMember(name, type, bindingAttr);
+        }
+
+        public override InterfaceMapping GetInterfaceMap(Type interfaceType)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetInterfaceMap(interfaceType);
+        }
+
+        public override EventInfo[] GetEvents(BindingFlags bindingAttr)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetEvents(bindingAttr);
+        }
+
+        public override MemberInfo[] GetMembers(BindingFlags bindingAttr)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return m_bakedRuntimeType.GetMembers(bindingAttr);
+        }
+
+        public override bool IsAssignableFrom(Type c)
+        {
+            if (TypeBuilder.IsTypeEqual(c, this))
+                return true;
+
+            Type fromRuntimeType = null;
+            TypeBuilder fromTypeBuilder = c as TypeBuilder;
+
+            if (fromTypeBuilder != null)
+                fromRuntimeType = fromTypeBuilder.m_bakedRuntimeType;
+            else
+                fromRuntimeType = c;
+
+            if (fromRuntimeType != null && fromRuntimeType is RuntimeType)
+            {
+                // fromType is baked. So if this type is not baked, it cannot be assignable to!
+                if (m_bakedRuntimeType == null)
+                    return false;
+
+                // since toType is also baked, delegate to the base
+                return m_bakedRuntimeType.IsAssignableFrom(fromRuntimeType);
+            }
+
+            // So if c is not a runtimeType nor TypeBuilder. We don't know how to deal with it. 
+            // return false then.
+            if (fromTypeBuilder == null)
+                return false;
+
+            // If fromTypeBuilder is a subclass of this class, then c can be cast to this type.
+            if (fromTypeBuilder.IsSubclassOf(this))
+                return true;
+
+            if (this.IsInterface == false)
+                return false;
+
+            // now is This type a base type on one of the interface impl?
+            Type[] interfaces = fromTypeBuilder.GetInterfaces();
+            for (int i = 0; i < interfaces.Length; i++)
+            {
+                // unfortunately, IsSubclassOf does not cover the case when they are the same type.
+                if (TypeBuilder.IsTypeEqual(interfaces[i], this))
+                    return true;
+
+                if (interfaces[i].IsSubclassOf(this))
+                    return true;
+            }
+            return false;
+        }
+
+        protected override TypeAttributes GetAttributeFlagsImpl()
+        {
+            return m_iAttr;
+        }
+
+        public override bool IsTypeDefinition => true;
+
+        public override bool IsSZArray => false;
+
+        protected override bool IsArrayImpl()
+        {
+            return false;
+        }
+        protected override bool IsByRefImpl()
+        {
+            return false;
+        }
+        protected override bool IsPointerImpl()
+        {
+            return false;
+        }
+        protected override bool IsPrimitiveImpl()
+        {
+            return false;
+        }
+
+        protected override bool IsCOMObjectImpl()
+        {
+            return ((GetAttributeFlagsImpl() & TypeAttributes.Import) != 0) ? true : false;
+        }
+
+        public override Type GetElementType()
+        {
+            // You will never have to deal with a TypeBuilder if you are just referring to arrays.
+            throw new NotSupportedException(SR.NotSupported_DynamicModule);
+        }
+
+        protected override bool HasElementTypeImpl()
+        {
+            return false;
+        }
+
+        public override bool IsSecurityCritical
+        {
+            get { return true; }
+        }
+
+        public override bool IsSecuritySafeCritical
+        {
+            get { return false; }
+        }
+
+        public override bool IsSecurityTransparent
+        {
+            get { return false; }
+        }
+
+        public override bool IsSubclassOf(Type c)
+        {
+            Type p = this;
+
+            if (TypeBuilder.IsTypeEqual(p, c))
+                return false;
+
+            p = p.BaseType;
+
+            while (p != null)
+            {
+                if (TypeBuilder.IsTypeEqual(p, c))
+                    return true;
+
+                p = p.BaseType;
+            }
+
+            return false;
+        }
+
+        public override Type UnderlyingSystemType
+        {
+            get
+            {
+                if (m_bakedRuntimeType != null)
+                    return m_bakedRuntimeType;
+
+                if (IsEnum)
+                {
+                    if (m_enumUnderlyingType == null)
+                        throw new InvalidOperationException(SR.InvalidOperation_NoUnderlyingTypeOnEnum);
+
+                    return m_enumUnderlyingType;
+                }
+                else
+                {
+                    return this;
+                }
+            }
+        }
+
+        public override Type MakePointerType()
+        {
+            return SymbolType.FormCompoundType("*", this, 0);
+        }
+
+        public override Type MakeByRefType()
+        {
+            return SymbolType.FormCompoundType("&", this, 0);
+        }
+
+        public override Type MakeArrayType()
+        {
+            return SymbolType.FormCompoundType("[]", this, 0);
+        }
+
+        public override Type MakeArrayType(int rank)
+        {
+            if (rank <= 0)
+                throw new IndexOutOfRangeException();
+
+            string szrank = "";
+            if (rank == 1)
+            {
+                szrank = "*";
+            }
+            else
+            {
+                for (int i = 1; i < rank; i++)
+                    szrank += ",";
+            }
+
+            string s = String.Format(CultureInfo.InvariantCulture, "[{0}]", szrank); // [,,]
+            return SymbolType.FormCompoundType(s, this, 0);
+        }
+
+        #endregion
+
+        #region ICustomAttributeProvider Implementation
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            return CustomAttribute.GetCustomAttributes(m_bakedRuntimeType, typeof(object) as RuntimeType, inherit);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.GetCustomAttributes(m_bakedRuntimeType, attributeRuntimeType, inherit);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            if (!IsCreated())
+                throw new NotSupportedException(SR.NotSupported_TypeNotYetCreated);
+
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.IsDefined(m_bakedRuntimeType, attributeRuntimeType, inherit);
+        }
+
+        #endregion
+
+        #region Public Member
+
+        #region DefineType
+        public override GenericParameterAttributes GenericParameterAttributes { get { return m_genParamAttributes; } }
+
+        internal void SetInterfaces(params Type[] interfaces)
+        {
+            ThrowIfCreated();
+
+            m_typeInterfaces = new List<Type>();
+            if (interfaces != null)
+            {
+                m_typeInterfaces.AddRange(interfaces);
+            }
+        }
+
+
+        public GenericTypeParameterBuilder[] DefineGenericParameters(params string[] names)
+        {
+            if (names == null)
+                throw new ArgumentNullException(nameof(names));
+
+            if (names.Length == 0)
+                throw new ArgumentException();
+
+            for (int i = 0; i < names.Length; i++)
+                if (names[i] == null)
+                    throw new ArgumentNullException(nameof(names));
+
+            if (m_inst != null)
+                throw new InvalidOperationException();
+
+            m_inst = new GenericTypeParameterBuilder[names.Length];
+            for (int i = 0; i < names.Length; i++)
+                m_inst[i] = new GenericTypeParameterBuilder(new TypeBuilder(names[i], i, this));
+
+            return m_inst;
+        }
+
+
+        public override Type MakeGenericType(params Type[] typeArguments)
+        {
+            CheckContext(typeArguments);
+
+            return TypeBuilderInstantiation.MakeGenericType(this, typeArguments);
+        }
+
+        public override Type[] GetGenericArguments() { return m_inst; }
+        // If a TypeBuilder is generic, it must be a generic type definition
+        // All instantiated generic types are TypeBuilderInstantiation.
+        public override bool IsGenericTypeDefinition { get { return IsGenericType; } }
+        public override bool IsGenericType { get { return m_inst != null; } }
+        public override bool IsGenericParameter { get { return m_bIsGenParam; } }
+        public override bool IsConstructedGenericType { get { return false; } }
+
+        public override int GenericParameterPosition { get { return m_genParamPos; } }
+        public override MethodBase DeclaringMethod { get { return m_declMeth; } }
+        public override Type GetGenericTypeDefinition() { if (IsGenericTypeDefinition) return this; if (m_genTypeDef == null) throw new InvalidOperationException(); return m_genTypeDef; }
+        #endregion
+
+        #region Define Method
+        public void DefineMethodOverride(MethodInfo methodInfoBody, MethodInfo methodInfoDeclaration)
+        {
+            lock (SyncRoot)
+            {
+                DefineMethodOverrideNoLock(methodInfoBody, methodInfoDeclaration);
+            }
+        }
+
+        private void DefineMethodOverrideNoLock(MethodInfo methodInfoBody, MethodInfo methodInfoDeclaration)
+        {
+            if (methodInfoBody == null)
+                throw new ArgumentNullException(nameof(methodInfoBody));
+
+            if (methodInfoDeclaration == null)
+                throw new ArgumentNullException(nameof(methodInfoDeclaration));
+
+            ThrowIfCreated();
+
+            if (!object.ReferenceEquals(methodInfoBody.DeclaringType, this))
+                // Loader restriction: body method has to be from this class
+                throw new ArgumentException(SR.ArgumentException_BadMethodImplBody);
+
+            MethodToken tkBody;
+            MethodToken tkDecl;
+
+            tkBody = m_module.GetMethodTokenInternal(methodInfoBody);
+            tkDecl = m_module.GetMethodTokenInternal(methodInfoDeclaration);
+
+            DefineMethodImpl(m_module.GetNativeHandle(), m_tdType.Token, tkBody.Token, tkDecl.Token);
+        }
+
+        public MethodBuilder DefineMethod(String name, MethodAttributes attributes, Type returnType, Type[] parameterTypes)
+        {
+            return DefineMethod(name, attributes, CallingConventions.Standard, returnType, parameterTypes);
+        }
+
+        public MethodBuilder DefineMethod(String name, MethodAttributes attributes)
+        {
+            return DefineMethod(name, attributes, CallingConventions.Standard, null, null);
+        }
+
+        public MethodBuilder DefineMethod(String name, MethodAttributes attributes, CallingConventions callingConvention)
+        {
+            return DefineMethod(name, attributes, callingConvention, null, null);
+        }
+
+        public MethodBuilder DefineMethod(String name, MethodAttributes attributes, CallingConventions callingConvention,
+            Type returnType, Type[] parameterTypes)
+        {
+            return DefineMethod(name, attributes, callingConvention, returnType, null, null, parameterTypes, null, null);
+        }
+
+        public MethodBuilder DefineMethod(String name, MethodAttributes attributes, CallingConventions callingConvention,
+            Type returnType, Type[] returnTypeRequiredCustomModifiers, Type[] returnTypeOptionalCustomModifiers,
+            Type[] parameterTypes, Type[][] parameterTypeRequiredCustomModifiers, Type[][] parameterTypeOptionalCustomModifiers)
+        {
+            lock (SyncRoot)
+            {
+                return DefineMethodNoLock(name, attributes, callingConvention, returnType, returnTypeRequiredCustomModifiers,
+                                          returnTypeOptionalCustomModifiers, parameterTypes, parameterTypeRequiredCustomModifiers,
+                                          parameterTypeOptionalCustomModifiers);
+            }
+        }
+
+        private MethodBuilder DefineMethodNoLock(String name, MethodAttributes attributes, CallingConventions callingConvention,
+            Type returnType, Type[] returnTypeRequiredCustomModifiers, Type[] returnTypeOptionalCustomModifiers,
+            Type[] parameterTypes, Type[][] parameterTypeRequiredCustomModifiers, Type[][] parameterTypeOptionalCustomModifiers)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            if (name.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(name));
+
+            CheckContext(returnType);
+            CheckContext(returnTypeRequiredCustomModifiers, returnTypeOptionalCustomModifiers, parameterTypes);
+            CheckContext(parameterTypeRequiredCustomModifiers);
+            CheckContext(parameterTypeOptionalCustomModifiers);
+
+            if (parameterTypes != null)
+            {
+                if (parameterTypeOptionalCustomModifiers != null && parameterTypeOptionalCustomModifiers.Length != parameterTypes.Length)
+                    throw new ArgumentException(SR.Format(SR.Argument_MismatchedArrays, nameof(parameterTypeOptionalCustomModifiers), nameof(parameterTypes)));
+
+                if (parameterTypeRequiredCustomModifiers != null && parameterTypeRequiredCustomModifiers.Length != parameterTypes.Length)
+                    throw new ArgumentException(SR.Format(SR.Argument_MismatchedArrays, nameof(parameterTypeRequiredCustomModifiers), nameof(parameterTypes)));
+            }
+
+            ThrowIfCreated();
+
+#if !FEATURE_DEFAULT_INTERFACES
+            if (!m_isHiddenGlobalType)
+            {
+                if (((m_iAttr & TypeAttributes.ClassSemanticsMask) == TypeAttributes.Interface) &&
+                   (attributes & MethodAttributes.Abstract) == 0 && (attributes & MethodAttributes.Static) == 0)
+                    throw new ArgumentException(SR.Argument_BadAttributeOnInterfaceMethod);
+            }
+#endif
+
+            // pass in Method attributes
+            MethodBuilder method = new MethodBuilder(
+                name, attributes, callingConvention,
+                returnType, returnTypeRequiredCustomModifiers, returnTypeOptionalCustomModifiers,
+                parameterTypes, parameterTypeRequiredCustomModifiers, parameterTypeOptionalCustomModifiers,
+                m_module, this, false);
+
+            if (!m_isHiddenGlobalType)
+            {
+                //If this method is declared to be a constructor, increment our constructor count.
+                if ((method.Attributes & MethodAttributes.SpecialName) != 0 && method.Name.Equals(ConstructorInfo.ConstructorName))
+                {
+                    m_constructorCount++;
+                }
+            }
+
+            m_listMethods.Add(method);
+
+            return method;
+        }
+
+        #endregion
+
+        #region Define Constructor
+        public ConstructorBuilder DefineTypeInitializer()
+        {
+            lock (SyncRoot)
+            {
+                return DefineTypeInitializerNoLock();
+            }
+        }
+
+        private ConstructorBuilder DefineTypeInitializerNoLock()
+        {
+            ThrowIfCreated();
+
+            // change the attributes and the class constructor's name
+            MethodAttributes attr = MethodAttributes.Private | MethodAttributes.Static | MethodAttributes.SpecialName;
+
+            ConstructorBuilder constBuilder = new ConstructorBuilder(
+                ConstructorInfo.TypeConstructorName, attr, CallingConventions.Standard, null, m_module, this);
+
+            return constBuilder;
+        }
+
+        public ConstructorBuilder DefineDefaultConstructor(MethodAttributes attributes)
+        {
+            if ((m_iAttr & TypeAttributes.Interface) == TypeAttributes.Interface)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_ConstructorNotAllowedOnInterface);
+            }
+
+            lock (SyncRoot)
+            {
+                return DefineDefaultConstructorNoLock(attributes);
+            }
+        }
+
+        private ConstructorBuilder DefineDefaultConstructorNoLock(MethodAttributes attributes)
+        {
+            ConstructorBuilder constBuilder;
+
+            // get the parent class's default constructor
+            // We really don't want(BindingFlags.Instance|BindingFlags.Public|BindingFlags.NonPublic) here.  We really want
+            // constructors visible from the subclass, but that is not currently
+            // available in BindingFlags.  This more open binding is open to
+            // runtime binding failures(like if we resolve to a private
+            // constructor).
+            ConstructorInfo con = null;
+
+            if (m_typeParent is TypeBuilderInstantiation)
+            {
+                Type genericTypeDefinition = m_typeParent.GetGenericTypeDefinition();
+
+                if (genericTypeDefinition is TypeBuilder)
+                    genericTypeDefinition = ((TypeBuilder)genericTypeDefinition).m_bakedRuntimeType;
+
+                if (genericTypeDefinition == null)
+                    throw new NotSupportedException(SR.NotSupported_DynamicModule);
+
+                Type inst = genericTypeDefinition.MakeGenericType(m_typeParent.GetGenericArguments());
+
+                if (inst is TypeBuilderInstantiation)
+                    con = TypeBuilder.GetConstructor(inst, genericTypeDefinition.GetConstructor(
+                        BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, Type.EmptyTypes, null));
+                else
+                    con = inst.GetConstructor(
+                        BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, Type.EmptyTypes, null);
+            }
+
+            if (con == null)
+            {
+                con = m_typeParent.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, Type.EmptyTypes, null);
+            }
+
+            if (con == null)
+                throw new NotSupportedException(SR.NotSupported_NoParentDefaultConstructor);
+
+            // Define the constructor Builder
+            constBuilder = DefineConstructor(attributes, CallingConventions.Standard, null);
+            m_constructorCount++;
+
+            // generate the code to call the parent's default constructor
+            ILGenerator il = constBuilder.GetILGenerator();
+            il.Emit(OpCodes.Ldarg_0);
+            il.Emit(OpCodes.Call, con);
+            il.Emit(OpCodes.Ret);
+
+            constBuilder.m_isDefaultConstructor = true;
+            return constBuilder;
+        }
+
+        public ConstructorBuilder DefineConstructor(MethodAttributes attributes, CallingConventions callingConvention, Type[] parameterTypes)
+        {
+            return DefineConstructor(attributes, callingConvention, parameterTypes, null, null);
+        }
+
+        public ConstructorBuilder DefineConstructor(MethodAttributes attributes, CallingConventions callingConvention,
+            Type[] parameterTypes, Type[][] requiredCustomModifiers, Type[][] optionalCustomModifiers)
+        {
+            if ((m_iAttr & TypeAttributes.Interface) == TypeAttributes.Interface && (attributes & MethodAttributes.Static) != MethodAttributes.Static)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_ConstructorNotAllowedOnInterface);
+            }
+
+            lock (SyncRoot)
+            {
+                return DefineConstructorNoLock(attributes, callingConvention, parameterTypes, requiredCustomModifiers, optionalCustomModifiers);
+            }
+        }
+
+        private ConstructorBuilder DefineConstructorNoLock(MethodAttributes attributes, CallingConventions callingConvention,
+            Type[] parameterTypes, Type[][] requiredCustomModifiers, Type[][] optionalCustomModifiers)
+        {
+            CheckContext(parameterTypes);
+            CheckContext(requiredCustomModifiers);
+            CheckContext(optionalCustomModifiers);
+
+            ThrowIfCreated();
+
+            String name;
+
+            if ((attributes & MethodAttributes.Static) == 0)
+            {
+                name = ConstructorInfo.ConstructorName;
+            }
+            else
+            {
+                name = ConstructorInfo.TypeConstructorName;
+            }
+
+            attributes = attributes | MethodAttributes.SpecialName;
+
+            ConstructorBuilder constBuilder =
+                new ConstructorBuilder(name, attributes, callingConvention,
+                    parameterTypes, requiredCustomModifiers, optionalCustomModifiers, m_module, this);
+
+            m_constructorCount++;
+
+            return constBuilder;
+        }
+
+        #endregion
+
+        #region Define Nested Type
+        public TypeBuilder DefineNestedType(String name)
+        {
+            lock (SyncRoot)
+            {
+                return DefineNestedTypeNoLock(name, TypeAttributes.NestedPrivate, null, null, PackingSize.Unspecified, UnspecifiedTypeSize);
+            }
+        }
+
+        public TypeBuilder DefineNestedType(String name, TypeAttributes attr, Type parent, Type[] interfaces)
+        {
+            lock (SyncRoot)
+            {
+                // Why do we only call CheckContext here? Why don't we call it in the other overloads?
+                CheckContext(parent);
+                CheckContext(interfaces);
+
+                return DefineNestedTypeNoLock(name, attr, parent, interfaces, PackingSize.Unspecified, UnspecifiedTypeSize);
+            }
+        }
+
+        public TypeBuilder DefineNestedType(String name, TypeAttributes attr, Type parent)
+        {
+            lock (SyncRoot)
+            {
+                return DefineNestedTypeNoLock(name, attr, parent, null, PackingSize.Unspecified, UnspecifiedTypeSize);
+            }
+        }
+
+        public TypeBuilder DefineNestedType(String name, TypeAttributes attr)
+        {
+            lock (SyncRoot)
+            {
+                return DefineNestedTypeNoLock(name, attr, null, null, PackingSize.Unspecified, UnspecifiedTypeSize);
+            }
+        }
+
+        public TypeBuilder DefineNestedType(String name, TypeAttributes attr, Type parent, int typeSize)
+        {
+            lock (SyncRoot)
+            {
+                return DefineNestedTypeNoLock(name, attr, parent, null, PackingSize.Unspecified, typeSize);
+            }
+        }
+
+        public TypeBuilder DefineNestedType(String name, TypeAttributes attr, Type parent, PackingSize packSize)
+        {
+            lock (SyncRoot)
+            {
+                return DefineNestedTypeNoLock(name, attr, parent, null, packSize, UnspecifiedTypeSize);
+            }
+        }
+
+        public TypeBuilder DefineNestedType(String name, TypeAttributes attr, Type parent, PackingSize packSize, int typeSize)
+        {
+            lock (SyncRoot)
+            {
+                return DefineNestedTypeNoLock(name, attr, parent, null, packSize, typeSize);
+            }
+        }
+
+        private TypeBuilder DefineNestedTypeNoLock(String name, TypeAttributes attr, Type parent, Type[] interfaces, PackingSize packSize, int typeSize)
+        {
+            return new TypeBuilder(name, attr, parent, interfaces, m_module, packSize, typeSize, this);
+        }
+
+        #endregion
+
+        #region Define Field
+        public FieldBuilder DefineField(String fieldName, Type type, FieldAttributes attributes)
+        {
+            return DefineField(fieldName, type, null, null, attributes);
+        }
+
+        public FieldBuilder DefineField(String fieldName, Type type, Type[] requiredCustomModifiers,
+            Type[] optionalCustomModifiers, FieldAttributes attributes)
+        {
+            lock (SyncRoot)
+            {
+                return DefineFieldNoLock(fieldName, type, requiredCustomModifiers, optionalCustomModifiers, attributes);
+            }
+        }
+
+        private FieldBuilder DefineFieldNoLock(String fieldName, Type type, Type[] requiredCustomModifiers,
+            Type[] optionalCustomModifiers, FieldAttributes attributes)
+        {
+            ThrowIfCreated();
+            CheckContext(type);
+            CheckContext(requiredCustomModifiers);
+
+            if (m_enumUnderlyingType == null && IsEnum == true)
+            {
+                if ((attributes & FieldAttributes.Static) == 0)
+                {
+                    // remember the underlying type for enum type
+                    m_enumUnderlyingType = type;
+                }
+            }
+
+            return new FieldBuilder(this, fieldName, type, requiredCustomModifiers, optionalCustomModifiers, attributes);
+        }
+
+        public FieldBuilder DefineInitializedData(String name, byte[] data, FieldAttributes attributes)
+        {
+            lock (SyncRoot)
+            {
+                return DefineInitializedDataNoLock(name, data, attributes);
+            }
+        }
+
+        private FieldBuilder DefineInitializedDataNoLock(String name, byte[] data, FieldAttributes attributes)
+        {
+            if (data == null)
+                throw new ArgumentNullException(nameof(data));
+
+            // This method will define an initialized Data in .sdata.
+            // We will create a fake TypeDef to represent the data with size. This TypeDef
+            // will be the signature for the Field.
+
+            return DefineDataHelper(name, data, data.Length, attributes);
+        }
+
+        public FieldBuilder DefineUninitializedData(String name, int size, FieldAttributes attributes)
+        {
+            lock (SyncRoot)
+            {
+                return DefineUninitializedDataNoLock(name, size, attributes);
+            }
+        }
+
+        private FieldBuilder DefineUninitializedDataNoLock(String name, int size, FieldAttributes attributes)
+        {
+            // This method will define an uninitialized Data in .sdata.
+            // We will create a fake TypeDef to represent the data with size. This TypeDef
+            // will be the signature for the Field.
+            return DefineDataHelper(name, null, size, attributes);
+        }
+
+        #endregion
+
+        #region Define Properties and Events
+        public PropertyBuilder DefineProperty(String name, PropertyAttributes attributes, Type returnType, Type[] parameterTypes)
+        {
+            return DefineProperty(name, attributes, returnType, null, null, parameterTypes, null, null);
+        }
+
+        public PropertyBuilder DefineProperty(String name, PropertyAttributes attributes,
+            CallingConventions callingConvention, Type returnType, Type[] parameterTypes)
+        {
+            return DefineProperty(name, attributes, callingConvention, returnType, null, null, parameterTypes, null, null);
+        }
+
+
+        public PropertyBuilder DefineProperty(String name, PropertyAttributes attributes,
+            Type returnType, Type[] returnTypeRequiredCustomModifiers, Type[] returnTypeOptionalCustomModifiers,
+            Type[] parameterTypes, Type[][] parameterTypeRequiredCustomModifiers, Type[][] parameterTypeOptionalCustomModifiers)
+        {
+            return DefineProperty(name, attributes, (CallingConventions)0, returnType,
+                returnTypeRequiredCustomModifiers, returnTypeOptionalCustomModifiers,
+                parameterTypes, parameterTypeRequiredCustomModifiers, parameterTypeOptionalCustomModifiers);
+        }
+
+        public PropertyBuilder DefineProperty(String name, PropertyAttributes attributes, CallingConventions callingConvention,
+            Type returnType, Type[] returnTypeRequiredCustomModifiers, Type[] returnTypeOptionalCustomModifiers,
+            Type[] parameterTypes, Type[][] parameterTypeRequiredCustomModifiers, Type[][] parameterTypeOptionalCustomModifiers)
+        {
+            lock (SyncRoot)
+            {
+                return DefinePropertyNoLock(name, attributes, callingConvention, returnType, returnTypeRequiredCustomModifiers, returnTypeOptionalCustomModifiers,
+                                            parameterTypes, parameterTypeRequiredCustomModifiers, parameterTypeOptionalCustomModifiers);
+            }
+        }
+
+        private PropertyBuilder DefinePropertyNoLock(String name, PropertyAttributes attributes, CallingConventions callingConvention,
+            Type returnType, Type[] returnTypeRequiredCustomModifiers, Type[] returnTypeOptionalCustomModifiers,
+            Type[] parameterTypes, Type[][] parameterTypeRequiredCustomModifiers, Type[][] parameterTypeOptionalCustomModifiers)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+            if (name.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(name));
+
+            CheckContext(returnType);
+            CheckContext(returnTypeRequiredCustomModifiers, returnTypeOptionalCustomModifiers, parameterTypes);
+            CheckContext(parameterTypeRequiredCustomModifiers);
+            CheckContext(parameterTypeOptionalCustomModifiers);
+
+            SignatureHelper sigHelper;
+            int sigLength;
+            byte[] sigBytes;
+
+            ThrowIfCreated();
+
+            // get the signature in SignatureHelper form
+            sigHelper = SignatureHelper.GetPropertySigHelper(
+                m_module, callingConvention,
+                returnType, returnTypeRequiredCustomModifiers, returnTypeOptionalCustomModifiers,
+                parameterTypes, parameterTypeRequiredCustomModifiers, parameterTypeOptionalCustomModifiers);
+
+            // get the signature in byte form
+            sigBytes = sigHelper.InternalGetSignature(out sigLength);
+
+            PropertyToken prToken = new PropertyToken(DefineProperty(
+                m_module.GetNativeHandle(),
+                m_tdType.Token,
+                name,
+                attributes,
+                sigBytes,
+                sigLength));
+
+            // create the property builder now.
+            return new PropertyBuilder(
+                    m_module,
+                    name,
+                    sigHelper,
+                    attributes,
+                    returnType,
+                    prToken,
+                    this);
+        }
+
+        public EventBuilder DefineEvent(String name, EventAttributes attributes, Type eventtype)
+        {
+            lock (SyncRoot)
+            {
+                return DefineEventNoLock(name, attributes, eventtype);
+            }
+        }
+
+        private EventBuilder DefineEventNoLock(String name, EventAttributes attributes, Type eventtype)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+            if (name.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(name));
+            if (name[0] == '\0')
+                throw new ArgumentException(SR.Argument_IllegalName, nameof(name));
+
+            int tkType;
+            EventToken evToken;
+
+            CheckContext(eventtype);
+
+            ThrowIfCreated();
+
+            tkType = m_module.GetTypeTokenInternal(eventtype).Token;
+
+            // Internal helpers to define property records
+            evToken = new EventToken(DefineEvent(
+                m_module.GetNativeHandle(),
+                m_tdType.Token,
+                name,
+                attributes,
+                tkType));
+
+            // create the property builder now.
+            return new EventBuilder(
+                    m_module,
+                    name,
+                    attributes,
+                    //tkType,
+                    this,
+                    evToken);
+        }
+
+        #endregion
+
+        #region Create Type
+
+        public TypeInfo CreateTypeInfo()
+        {
+            lock (SyncRoot)
+            {
+                return CreateTypeNoLock();
+            }
+        }
+
+        public Type CreateType()
+        {
+            lock (SyncRoot)
+            {
+                return CreateTypeNoLock();
+            }
+        }
+
+        internal void CheckContext(params Type[][] typess)
+        {
+            m_module.CheckContext(typess);
+        }
+        internal void CheckContext(params Type[] types)
+        {
+            m_module.CheckContext(types);
+        }
+
+        private TypeInfo CreateTypeNoLock()
+        {
+            if (IsCreated())
+                return m_bakedRuntimeType;
+
+            ThrowIfCreated();
+
+            if (m_typeInterfaces == null)
+                m_typeInterfaces = new List<Type>();
+
+            int[] interfaceTokens = new int[m_typeInterfaces.Count];
+            for (int i = 0; i < m_typeInterfaces.Count; i++)
+            {
+                interfaceTokens[i] = m_module.GetTypeTokenInternal(m_typeInterfaces[i]).Token;
+            }
+
+            int tkParent = 0;
+            if (m_typeParent != null)
+                tkParent = m_module.GetTypeTokenInternal(m_typeParent).Token;
+
+            if (IsGenericParameter)
+            {
+                int[] constraints; // Array of token constrains terminated by null token
+
+                if (m_typeParent != null)
+                {
+                    constraints = new int[m_typeInterfaces.Count + 2];
+                    constraints[constraints.Length - 2] = tkParent;
+                }
+                else
+                {
+                    constraints = new int[m_typeInterfaces.Count + 1];
+                }
+
+                for (int i = 0; i < m_typeInterfaces.Count; i++)
+                {
+                    constraints[i] = m_module.GetTypeTokenInternal(m_typeInterfaces[i]).Token;
+                }
+
+                int declMember = m_declMeth == null ? m_DeclaringType.m_tdType.Token : m_declMeth.GetToken().Token;
+                m_tdType = new TypeToken(DefineGenericParam(m_module.GetNativeHandle(),
+                    m_strName, declMember, m_genParamAttributes, m_genParamPos, constraints));
+
+                if (m_ca != null)
+                {
+                    foreach (CustAttr ca in m_ca)
+                        ca.Bake(m_module, MetadataTokenInternal);
+                }
+
+                m_hasBeenCreated = true;
+
+                // Baking a generic parameter does not put sufficient information into the metadata to actually be able to load it as a type,
+                // the associated generic type/method needs to be baked first. So we return this rather than the baked type.
+                return this;
+            }
+            else
+            {
+                // Check for global typebuilder
+                if (((m_tdType.Token & 0x00FFFFFF) != 0) && ((tkParent & 0x00FFFFFF) != 0))
+                    SetParentType(m_module.GetNativeHandle(), m_tdType.Token, tkParent);
+
+                if (m_inst != null)
+                    foreach (Type tb in m_inst)
+                        if (tb is GenericTypeParameterBuilder)
+                            ((GenericTypeParameterBuilder)tb).m_type.CreateType();
+            }
+
+            byte[] body;
+            MethodAttributes methodAttrs;
+
+            if (!m_isHiddenGlobalType)
+            {
+                // create a public default constructor if this class has no constructor.
+                // except if the type is Interface, ValueType, Enum, or a static class.
+                if (m_constructorCount == 0 && ((m_iAttr & TypeAttributes.Interface) == 0) && !IsValueType && ((m_iAttr & (TypeAttributes.Abstract | TypeAttributes.Sealed)) != (TypeAttributes.Abstract | TypeAttributes.Sealed)))
+                {
+                    DefineDefaultConstructor(MethodAttributes.Public);
+                }
+            }
+
+            int size = m_listMethods.Count;
+
+            for (int i = 0; i < size; i++)
+            {
+                MethodBuilder meth = m_listMethods[i];
+
+
+                if (meth.IsGenericMethodDefinition)
+                    meth.GetToken(); // Doubles as "CreateMethod" for MethodBuilder -- analagous to CreateType()
+
+                methodAttrs = meth.Attributes;
+
+                // Any of these flags in the implemenation flags is set, we will not attach the IL method body
+                if (((meth.GetMethodImplementationFlags() & (MethodImplAttributes.CodeTypeMask | MethodImplAttributes.PreserveSig | MethodImplAttributes.Unmanaged)) != MethodImplAttributes.IL) ||
+                    ((methodAttrs & MethodAttributes.PinvokeImpl) != (MethodAttributes)0))
+                {
+                    continue;
+                }
+
+                int sigLength;
+                byte[] localSig = meth.GetLocalSignature(out sigLength);
+
+                // Check that they haven't declared an abstract method on a non-abstract class
+                if (((methodAttrs & MethodAttributes.Abstract) != 0) && ((m_iAttr & TypeAttributes.Abstract) == 0))
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_BadTypeAttributesNotAbstract);
+                }
+
+                body = meth.GetBody();
+
+                // If this is an abstract method or an interface, we don't need to set the IL.
+
+                if ((methodAttrs & MethodAttributes.Abstract) != 0)
+                {
+                    // We won't check on Interface because we can have class static initializer on interface.
+                    // We will just let EE or validator to catch the problem.
+
+                    //((m_iAttr & TypeAttributes.ClassSemanticsMask) == TypeAttributes.Interface))
+
+                    if (body != null)
+                        throw new InvalidOperationException(SR.Format(SR.InvalidOperation_BadMethodBody, meth.Name));
+                }
+                else if (body == null || body.Length == 0)
+                {
+                    // If it's not an abstract or an interface, set the IL.
+                    if (meth.m_ilGenerator != null)
+                    {
+                        // we need to bake the method here.
+                        meth.CreateMethodBodyHelper(meth.GetILGenerator());
+                    }
+
+                    body = meth.GetBody();
+
+                    if ((body == null || body.Length == 0) && !meth.m_canBeRuntimeImpl)
+                        throw new InvalidOperationException(
+                            SR.Format(SR.InvalidOperation_BadEmptyMethodBody, meth.Name));
+                }
+
+                int maxStack = meth.GetMaxStack();
+
+                ExceptionHandler[] exceptions = meth.GetExceptionHandlers();
+                int[] tokenFixups = meth.GetTokenFixups();
+
+                SetMethodIL(m_module.GetNativeHandle(), meth.GetToken().Token, meth.InitLocals,
+                    body, (body != null) ? body.Length : 0,
+                    localSig, sigLength, maxStack,
+                    exceptions, (exceptions != null) ? exceptions.Length : 0,
+                    tokenFixups, (tokenFixups != null) ? tokenFixups.Length : 0);
+
+                if (m_module.ContainingAssemblyBuilder.m_assemblyData.m_access == AssemblyBuilderAccess.Run)
+                {
+                    // if we don't need the data structures to build the method any more
+                    // throw them away.
+                    meth.ReleaseBakedStructures();
+                }
+            }
+
+            m_hasBeenCreated = true;
+
+            // Terminate the process.
+            RuntimeType cls = null;
+            TermCreateClass(m_module.GetNativeHandle(), m_tdType.Token, JitHelpers.GetObjectHandleOnStack(ref cls));
+
+            if (!m_isHiddenGlobalType)
+            {
+                m_bakedRuntimeType = cls;
+
+                // if this type is a nested type, we need to invalidate the cached nested runtime type on the nesting type
+                if (m_DeclaringType != null && m_DeclaringType.m_bakedRuntimeType != null)
+                {
+                    m_DeclaringType.m_bakedRuntimeType.InvalidateCachedNestedType();
+                }
+
+                return cls;
+            }
+            else
+            {
+                return null;
+            }
+        }
+
+        #endregion
+
+        #region Misc
+        public int Size
+        {
+            get { return m_iTypeSize; }
+        }
+
+        public PackingSize PackingSize
+        {
+            get { return m_iPackingSize; }
+        }
+
+        public void SetParent(Type parent)
+        {
+            ThrowIfCreated();
+
+            if (parent != null)
+            {
+                CheckContext(parent);
+
+                if (parent.IsInterface)
+                    throw new ArgumentException(SR.Argument_CannotSetParentToInterface);
+
+                m_typeParent = parent;
+            }
+            else
+            {
+                if ((m_iAttr & TypeAttributes.Interface) != TypeAttributes.Interface)
+                {
+                    m_typeParent = typeof(Object);
+                }
+                else
+                {
+                    if ((m_iAttr & TypeAttributes.Abstract) == 0)
+                        throw new InvalidOperationException(SR.InvalidOperation_BadInterfaceNotAbstract);
+
+                    // there is no extends for interface class
+                    m_typeParent = null;
+                }
+            }
+        }
+
+        public void AddInterfaceImplementation(Type interfaceType)
+        {
+            if (interfaceType == null)
+            {
+                throw new ArgumentNullException(nameof(interfaceType));
+            }
+
+            CheckContext(interfaceType);
+
+            ThrowIfCreated();
+
+            TypeToken tkInterface = m_module.GetTypeTokenInternal(interfaceType);
+            AddInterfaceImpl(m_module.GetNativeHandle(), m_tdType.Token, tkInterface.Token);
+
+            m_typeInterfaces.Add(interfaceType);
+        }
+
+        public TypeToken TypeToken
+        {
+            get
+            {
+                if (IsGenericParameter)
+                    ThrowIfCreated();
+
+                return m_tdType;
+            }
+        }
+
+
+        public void SetCustomAttribute(ConstructorInfo con, byte[] binaryAttribute)
+        {
+            if (con == null)
+                throw new ArgumentNullException(nameof(con));
+
+            if (binaryAttribute == null)
+                throw new ArgumentNullException(nameof(binaryAttribute));
+
+            TypeBuilder.DefineCustomAttribute(m_module, m_tdType.Token, ((ModuleBuilder)m_module).GetConstructorToken(con).Token,
+                binaryAttribute, false, false);
+        }
+
+        public void SetCustomAttribute(CustomAttributeBuilder customBuilder)
+        {
+            if (customBuilder == null)
+                throw new ArgumentNullException(nameof(customBuilder));
+
+            customBuilder.CreateCustomAttribute((ModuleBuilder)m_module, m_tdType.Token);
+        }
+
+        #endregion
+
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/TypeBuilderInstantiation.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/TypeBuilderInstantiation.cs
new file mode 100644
index 0000000000..d674f349da
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/TypeBuilderInstantiation.cs
@@ -0,0 +1,275 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+using System;
+using System.Reflection;
+using System.Collections;
+using System.Globalization;
+using System.Diagnostics;
+
+namespace System.Reflection.Emit
+{
+    internal sealed class TypeBuilderInstantiation : TypeInfo
+    {
+        public override bool IsAssignableFrom(System.Reflection.TypeInfo typeInfo)
+        {
+            if (typeInfo == null) return false;
+            return IsAssignableFrom(typeInfo.AsType());
+        }
+
+        #region Static Members
+        internal static Type MakeGenericType(Type type, Type[] typeArguments)
+        {
+            Debug.Assert(type != null, "this is only called from RuntimeType.MakeGenericType and TypeBuilder.MakeGenericType so 'type' cannot be null");
+
+            if (!type.IsGenericTypeDefinition)
+                throw new InvalidOperationException();
+
+            if (typeArguments == null)
+                throw new ArgumentNullException(nameof(typeArguments));
+
+            foreach (Type t in typeArguments)
+            {
+                if (t == null)
+                    throw new ArgumentNullException(nameof(typeArguments));
+            }
+
+            return new TypeBuilderInstantiation(type, typeArguments);
+        }
+
+        #endregion
+
+        #region Private Data Members
+        private Type m_type;
+        private Type[] m_inst;
+        private string m_strFullQualName;
+        internal Hashtable m_hashtable = new Hashtable();
+
+        #endregion
+
+        #region Constructor
+        private TypeBuilderInstantiation(Type type, Type[] inst)
+        {
+            m_type = type;
+            m_inst = inst;
+            m_hashtable = new Hashtable();
+        }
+        #endregion
+
+        #region Object Overrides
+        public override String ToString()
+        {
+            return TypeNameBuilder.ToString(this, TypeNameBuilder.Format.ToString);
+        }
+        #endregion
+
+        #region MemberInfo Overrides
+        public override Type DeclaringType { get { return m_type.DeclaringType; } }
+
+        public override Type ReflectedType { get { return m_type.ReflectedType; } }
+
+        public override String Name { get { return m_type.Name; } }
+
+        public override Module Module { get { return m_type.Module; } }
+        #endregion
+
+        #region Type Overrides
+        public override Type MakePointerType()
+        {
+            return SymbolType.FormCompoundType("*", this, 0);
+        }
+        public override Type MakeByRefType()
+        {
+            return SymbolType.FormCompoundType("&", this, 0);
+        }
+        public override Type MakeArrayType()
+        {
+            return SymbolType.FormCompoundType("[]", this, 0);
+        }
+        public override Type MakeArrayType(int rank)
+        {
+            if (rank <= 0)
+                throw new IndexOutOfRangeException();
+
+            string comma = "";
+            for (int i = 1; i < rank; i++)
+                comma += ",";
+
+            string s = String.Format(CultureInfo.InvariantCulture, "[{0}]", comma);
+            return SymbolType.FormCompoundType(s, this, 0);
+        }
+        public override Guid GUID { get { throw new NotSupportedException(); } }
+        public override Object InvokeMember(String name, BindingFlags invokeAttr, Binder binder, Object target, Object[] args, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParameters) { throw new NotSupportedException(); }
+        public override Assembly Assembly { get { return m_type.Assembly; } }
+        public override RuntimeTypeHandle TypeHandle { get { throw new NotSupportedException(); } }
+        public override String FullName
+        {
+            get
+            {
+                if (m_strFullQualName == null)
+                    m_strFullQualName = TypeNameBuilder.ToString(this, TypeNameBuilder.Format.FullName);
+                return m_strFullQualName;
+            }
+        }
+        public override String Namespace { get { return m_type.Namespace; } }
+        public override String AssemblyQualifiedName { get { return TypeNameBuilder.ToString(this, TypeNameBuilder.Format.AssemblyQualifiedName); } }
+        private Type Substitute(Type[] substitutes)
+        {
+            Type[] inst = GetGenericArguments();
+            Type[] instSubstituted = new Type[inst.Length];
+
+            for (int i = 0; i < instSubstituted.Length; i++)
+            {
+                Type t = inst[i];
+
+                if (t is TypeBuilderInstantiation)
+                {
+                    instSubstituted[i] = (t as TypeBuilderInstantiation).Substitute(substitutes);
+                }
+                else if (t is GenericTypeParameterBuilder)
+                {
+                    // Substitute
+                    instSubstituted[i] = substitutes[t.GenericParameterPosition];
+                }
+                else
+                {
+                    instSubstituted[i] = t;
+                }
+            }
+
+            return GetGenericTypeDefinition().MakeGenericType(instSubstituted);
+        }
+        public override Type BaseType
+        {
+            // B<A,B,C>
+            // D<T,S> : B<S,List<T>,char>
+
+            // D<string,int> : B<int,List<string>,char>
+            // D<S,T> : B<T,List<S>,char>        
+            // D<S,string> : B<string,List<S>,char>        
+            get
+            {
+                Type typeBldrBase = m_type.BaseType;
+
+                if (typeBldrBase == null)
+                    return null;
+
+                TypeBuilderInstantiation typeBldrBaseAs = typeBldrBase as TypeBuilderInstantiation;
+
+                if (typeBldrBaseAs == null)
+                    return typeBldrBase;
+
+                return typeBldrBaseAs.Substitute(GetGenericArguments());
+            }
+        }
+        protected override ConstructorInfo GetConstructorImpl(BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers) { throw new NotSupportedException(); }
+
+        public override ConstructorInfo[] GetConstructors(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+        protected override MethodInfo GetMethodImpl(String name, BindingFlags bindingAttr, Binder binder, CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers) { throw new NotSupportedException(); }
+        public override MethodInfo[] GetMethods(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+        public override FieldInfo GetField(String name, BindingFlags bindingAttr) { throw new NotSupportedException(); }
+        public override FieldInfo[] GetFields(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+        public override Type GetInterface(String name, bool ignoreCase) { throw new NotSupportedException(); }
+        public override Type[] GetInterfaces() { throw new NotSupportedException(); }
+        public override EventInfo GetEvent(String name, BindingFlags bindingAttr) { throw new NotSupportedException(); }
+        public override EventInfo[] GetEvents() { throw new NotSupportedException(); }
+        protected override PropertyInfo GetPropertyImpl(String name, BindingFlags bindingAttr, Binder binder, Type returnType, Type[] types, ParameterModifier[] modifiers) { throw new NotSupportedException(); }
+        public override PropertyInfo[] GetProperties(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+        public override Type[] GetNestedTypes(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+        public override Type GetNestedType(String name, BindingFlags bindingAttr) { throw new NotSupportedException(); }
+        public override MemberInfo[] GetMember(String name, MemberTypes type, BindingFlags bindingAttr) { throw new NotSupportedException(); }
+
+        public override InterfaceMapping GetInterfaceMap(Type interfaceType) { throw new NotSupportedException(); }
+        public override EventInfo[] GetEvents(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+        public override MemberInfo[] GetMembers(BindingFlags bindingAttr) { throw new NotSupportedException(); }
+        protected override TypeAttributes GetAttributeFlagsImpl() { return m_type.Attributes; }
+
+        public override bool IsTypeDefinition => false;
+        public override bool IsSZArray => false;
+
+        protected override bool IsArrayImpl() { return false; }
+        protected override bool IsByRefImpl() { return false; }
+        protected override bool IsPointerImpl() { return false; }
+        protected override bool IsPrimitiveImpl() { return false; }
+        protected override bool IsCOMObjectImpl() { return false; }
+        public override Type GetElementType() { throw new NotSupportedException(); }
+        protected override bool HasElementTypeImpl() { return false; }
+        public override Type UnderlyingSystemType { get { return this; } }
+        public override Type[] GetGenericArguments() { return m_inst; }
+        public override bool IsGenericTypeDefinition { get { return false; } }
+        public override bool IsGenericType { get { return true; } }
+        public override bool IsConstructedGenericType { get { return true; } }
+        public override bool IsGenericParameter { get { return false; } }
+        public override int GenericParameterPosition { get { throw new InvalidOperationException(); } }
+        protected override bool IsValueTypeImpl() { return m_type.IsValueType; }
+        public override bool ContainsGenericParameters
+        {
+            get
+            {
+                for (int i = 0; i < m_inst.Length; i++)
+                {
+                    if (m_inst[i].ContainsGenericParameters)
+                        return true;
+                }
+
+                return false;
+            }
+        }
+        public override MethodBase DeclaringMethod { get { return null; } }
+        public override Type GetGenericTypeDefinition() { return m_type; }
+        public override Type MakeGenericType(params Type[] inst) { throw new InvalidOperationException(SR.Format(SR.Arg_NotGenericTypeDefinition, this)); }
+        public override bool IsAssignableFrom(Type c) { throw new NotSupportedException(); }
+
+        public override bool IsSubclassOf(Type c)
+        {
+            throw new NotSupportedException();
+        }
+        #endregion
+
+        #region ICustomAttributeProvider Implementation
+        public override Object[] GetCustomAttributes(bool inherit) { throw new NotSupportedException(); }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit) { throw new NotSupportedException(); }
+
+        public override bool IsDefined(Type attributeType, bool inherit) { throw new NotSupportedException(); }
+        #endregion
+    }
+}
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/TypeToken.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/TypeToken.cs
new file mode 100644
index 0000000000..15a0816a50
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/TypeToken.cs
@@ -0,0 +1,68 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Represents a Class to the ILGenerator class.
+**
+** 
+===========================================================*/
+
+using System;
+using System.Reflection;
+using System.Threading;
+
+namespace System.Reflection.Emit
+{
+    public struct TypeToken
+    {
+        public static readonly TypeToken Empty = new TypeToken();
+
+        internal int m_class;
+
+
+        internal TypeToken(int str)
+        {
+            m_class = str;
+        }
+
+        public int Token
+        {
+            get { return m_class; }
+        }
+
+        public override int GetHashCode()
+        {
+            return m_class;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (obj is TypeToken)
+                return Equals((TypeToken)obj);
+            else
+                return false;
+        }
+
+        public bool Equals(TypeToken obj)
+        {
+            return obj.m_class == m_class;
+        }
+
+        public static bool operator ==(TypeToken a, TypeToken b)
+        {
+            return a.Equals(b);
+        }
+
+        public static bool operator !=(TypeToken a, TypeToken b)
+        {
+            return !(a == b);
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Emit/XXXOnTypeBuilderInstantiation.cs b/src/System.Private.CoreLib/src/System/Reflection/Emit/XXXOnTypeBuilderInstantiation.cs
new file mode 100644
index 0000000000..715fe01f54
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Emit/XXXOnTypeBuilderInstantiation.cs
@@ -0,0 +1,312 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+using System;
+using System.Reflection;
+using System.Collections;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Diagnostics;
+
+namespace System.Reflection.Emit
+{
+    internal sealed class MethodOnTypeBuilderInstantiation : MethodInfo
+    {
+        #region Private Static Members
+        internal static MethodInfo GetMethod(MethodInfo method, TypeBuilderInstantiation type)
+        {
+            return new MethodOnTypeBuilderInstantiation(method, type);
+        }
+        #endregion
+
+        #region Private Data Members
+        internal MethodInfo m_method;
+        private TypeBuilderInstantiation m_type;
+        #endregion
+
+        #region Constructor
+        internal MethodOnTypeBuilderInstantiation(MethodInfo method, TypeBuilderInstantiation type)
+        {
+            Debug.Assert(method is MethodBuilder || method is RuntimeMethodInfo);
+
+            m_method = method;
+            m_type = type;
+        }
+        #endregion
+
+        internal override Type[] GetParameterTypes()
+        {
+            return m_method.GetParameterTypes();
+        }
+
+        #region MemberInfo Overrides
+        public override MemberTypes MemberType { get { return m_method.MemberType; } }
+        public override String Name { get { return m_method.Name; } }
+        public override Type DeclaringType { get { return m_type; } }
+        public override Type ReflectedType { get { return m_type; } }
+        public override Object[] GetCustomAttributes(bool inherit) { return m_method.GetCustomAttributes(inherit); }
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit) { return m_method.GetCustomAttributes(attributeType, inherit); }
+        public override bool IsDefined(Type attributeType, bool inherit) { return m_method.IsDefined(attributeType, inherit); }
+        public override Module Module { get { return m_method.Module; } }
+        #endregion
+
+        #region MethodBase Members
+        public override ParameterInfo[] GetParameters() { return m_method.GetParameters(); }
+        public override MethodImplAttributes GetMethodImplementationFlags() { return m_method.GetMethodImplementationFlags(); }
+        public override RuntimeMethodHandle MethodHandle { get { return m_method.MethodHandle; } }
+        public override MethodAttributes Attributes { get { return m_method.Attributes; } }
+        public override Object Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
+        {
+            throw new NotSupportedException();
+        }
+        public override CallingConventions CallingConvention { get { return m_method.CallingConvention; } }
+        public override Type[] GetGenericArguments() { return m_method.GetGenericArguments(); }
+        public override MethodInfo GetGenericMethodDefinition() { return m_method; }
+        public override bool IsGenericMethodDefinition { get { return m_method.IsGenericMethodDefinition; } }
+        public override bool ContainsGenericParameters { get { return m_method.ContainsGenericParameters; } }
+        public override MethodInfo MakeGenericMethod(params Type[] typeArgs)
+        {
+            if (!IsGenericMethodDefinition)
+                throw new InvalidOperationException(SR.Format(SR.Arg_NotGenericMethodDefinition, this));
+
+            return MethodBuilderInstantiation.MakeGenericMethod(this, typeArgs);
+        }
+
+        public override bool IsGenericMethod { get { return m_method.IsGenericMethod; } }
+
+        #endregion
+
+        #region Public Abstract\Virtual Members
+        public override Type ReturnType { get { return m_method.ReturnType; } }
+        public override ParameterInfo ReturnParameter { get { throw new NotSupportedException(); } }
+        public override ICustomAttributeProvider ReturnTypeCustomAttributes { get { throw new NotSupportedException(); } }
+        public override MethodInfo GetBaseDefinition() { throw new NotSupportedException(); }
+        #endregion    
+    }
+
+    internal sealed class ConstructorOnTypeBuilderInstantiation : ConstructorInfo
+    {
+        #region Private Static Members
+        internal static ConstructorInfo GetConstructor(ConstructorInfo Constructor, TypeBuilderInstantiation type)
+        {
+            return new ConstructorOnTypeBuilderInstantiation(Constructor, type);
+        }
+        #endregion
+
+        #region Private Data Members
+        internal ConstructorInfo m_ctor;
+        private TypeBuilderInstantiation m_type;
+        #endregion
+
+        #region Constructor
+        internal ConstructorOnTypeBuilderInstantiation(ConstructorInfo constructor, TypeBuilderInstantiation type)
+        {
+            Debug.Assert(constructor is ConstructorBuilder || constructor is RuntimeConstructorInfo);
+
+            m_ctor = constructor;
+            m_type = type;
+        }
+        #endregion
+
+        internal override Type[] GetParameterTypes()
+        {
+            return m_ctor.GetParameterTypes();
+        }
+
+        internal override Type GetReturnType()
+        {
+            return DeclaringType;
+        }
+
+        #region MemberInfo Overrides
+        public override MemberTypes MemberType { get { return m_ctor.MemberType; } }
+        public override String Name { get { return m_ctor.Name; } }
+        public override Type DeclaringType { get { return m_type; } }
+        public override Type ReflectedType { get { return m_type; } }
+        public override Object[] GetCustomAttributes(bool inherit) { return m_ctor.GetCustomAttributes(inherit); }
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit) { return m_ctor.GetCustomAttributes(attributeType, inherit); }
+        public override bool IsDefined(Type attributeType, bool inherit) { return m_ctor.IsDefined(attributeType, inherit); }
+        internal int MetadataTokenInternal
+        {
+            get
+            {
+                ConstructorBuilder cb = m_ctor as ConstructorBuilder;
+
+                if (cb != null)
+                    return cb.MetadataTokenInternal;
+                else
+                {
+                    Debug.Assert(m_ctor is RuntimeConstructorInfo);
+                    return m_ctor.MetadataToken;
+                }
+            }
+        }
+        public override Module Module { get { return m_ctor.Module; } }
+        #endregion
+
+        #region MethodBase Members
+        public override ParameterInfo[] GetParameters() { return m_ctor.GetParameters(); }
+        public override MethodImplAttributes GetMethodImplementationFlags() { return m_ctor.GetMethodImplementationFlags(); }
+        public override RuntimeMethodHandle MethodHandle { get { return m_ctor.MethodHandle; } }
+        public override MethodAttributes Attributes { get { return m_ctor.Attributes; } }
+        public override Object Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
+        {
+            throw new NotSupportedException();
+        }
+        public override CallingConventions CallingConvention { get { return m_ctor.CallingConvention; } }
+        public override Type[] GetGenericArguments() { return m_ctor.GetGenericArguments(); }
+        public override bool IsGenericMethodDefinition { get { return false; } }
+        public override bool ContainsGenericParameters { get { return false; } }
+
+        public override bool IsGenericMethod { get { return false; } }
+        #endregion
+
+        #region ConstructorInfo Members
+        public override Object Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
+        {
+            throw new InvalidOperationException();
+        }
+        #endregion
+    }
+
+    internal sealed class FieldOnTypeBuilderInstantiation : FieldInfo
+    {
+        #region Private Static Members
+        internal static FieldInfo GetField(FieldInfo Field, TypeBuilderInstantiation type)
+        {
+            FieldInfo m = null;
+
+            // This ifdef was introduced when non-generic collections were pulled from
+            // silverlight. See code:Dictionary#DictionaryVersusHashtableThreadSafety
+            // for information about this change.
+            //
+            // There is a pre-existing race condition in this code with the side effect
+            // that the second thread's value clobbers the first in the hashtable. This is 
+            // an acceptable race condition since we make no guarantees that this will return the
+            // same object.
+            //
+            // We're not entirely sure if this cache helps any specific scenarios, so 
+            // long-term, one could investigate whether it's needed. In any case, this
+            // method isn't expected to be on any critical paths for performance.
+            if (type.m_hashtable.Contains(Field))
+            {
+                m = type.m_hashtable[Field] as FieldInfo;
+            }
+            else
+            {
+                m = new FieldOnTypeBuilderInstantiation(Field, type);
+                type.m_hashtable[Field] = m;
+            }
+
+            return m;
+        }
+        #endregion
+
+        #region Private Data Members
+        private FieldInfo m_field;
+        private TypeBuilderInstantiation m_type;
+        #endregion
+
+        #region Constructor
+        internal FieldOnTypeBuilderInstantiation(FieldInfo field, TypeBuilderInstantiation type)
+        {
+            Debug.Assert(field is FieldBuilder || field is RuntimeFieldInfo);
+
+            m_field = field;
+            m_type = type;
+        }
+        #endregion
+
+        internal FieldInfo FieldInfo { get { return m_field; } }
+
+        #region MemberInfo Overrides
+        public override MemberTypes MemberType { get { return System.Reflection.MemberTypes.Field; } }
+        public override String Name { get { return m_field.Name; } }
+        public override Type DeclaringType { get { return m_type; } }
+        public override Type ReflectedType { get { return m_type; } }
+        public override Object[] GetCustomAttributes(bool inherit) { return m_field.GetCustomAttributes(inherit); }
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit) { return m_field.GetCustomAttributes(attributeType, inherit); }
+        public override bool IsDefined(Type attributeType, bool inherit) { return m_field.IsDefined(attributeType, inherit); }
+        internal int MetadataTokenInternal
+        {
+            get
+            {
+                FieldBuilder fb = m_field as FieldBuilder;
+
+                if (fb != null)
+                    return fb.MetadataTokenInternal;
+                else
+                {
+                    Debug.Assert(m_field is RuntimeFieldInfo);
+                    return m_field.MetadataToken;
+                }
+            }
+        }
+        public override Module Module { get { return m_field.Module; } }
+        #endregion
+
+        #region Public Abstract\Virtual Members
+        public override Type[] GetRequiredCustomModifiers() { return m_field.GetRequiredCustomModifiers(); }
+        public override Type[] GetOptionalCustomModifiers() { return m_field.GetOptionalCustomModifiers(); }
+        public override void SetValueDirect(TypedReference obj, Object value)
+        {
+            throw new NotImplementedException();
+        }
+        public override Object GetValueDirect(TypedReference obj)
+        {
+            throw new NotImplementedException();
+        }
+        public override RuntimeFieldHandle FieldHandle
+        {
+            get { throw new NotImplementedException(); }
+        }
+        public override Type FieldType { get { throw new NotImplementedException(); } }
+        public override Object GetValue(Object obj) { throw new InvalidOperationException(); }
+        public override void SetValue(Object obj, Object value, BindingFlags invokeAttr, Binder binder, CultureInfo culture) { throw new InvalidOperationException(); }
+        public override FieldAttributes Attributes { get { return m_field.Attributes; } }
+        #endregion
+    }
+}
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/ExceptionHandlingClause.cs b/src/System.Private.CoreLib/src/System/Reflection/ExceptionHandlingClause.cs
new file mode 100644
index 0000000000..66ad4eb7a9
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/ExceptionHandlingClause.cs
@@ -0,0 +1,91 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+
+namespace System.Reflection
+{
+    public class ExceptionHandlingClause
+    {
+        #region constructor
+        // This class can only be created from inside the EE.
+        protected ExceptionHandlingClause() { }
+        #endregion
+
+        #region Private Data Members
+        private MethodBody m_methodBody;
+        private ExceptionHandlingClauseOptions m_flags;
+        private int m_tryOffset;
+        private int m_tryLength;
+        private int m_handlerOffset;
+        private int m_handlerLength;
+        private int m_catchMetadataToken;
+        private int m_filterOffset;
+        #endregion
+
+        #region Public Members
+        public virtual ExceptionHandlingClauseOptions Flags { get { return m_flags; } }
+        public virtual int TryOffset { get { return m_tryOffset; } }
+        public virtual int TryLength { get { return m_tryLength; } }
+        public virtual int HandlerOffset { get { return m_handlerOffset; } }
+        public virtual int HandlerLength { get { return m_handlerLength; } }
+
+        public virtual int FilterOffset
+        {
+            get
+            {
+                if (m_flags != ExceptionHandlingClauseOptions.Filter)
+                    throw new InvalidOperationException(SR.Arg_EHClauseNotFilter);
+
+                return m_filterOffset;
+            }
+        }
+
+        public virtual Type CatchType
+        {
+            get
+            {
+                if (m_flags != ExceptionHandlingClauseOptions.Clause)
+                    throw new InvalidOperationException(SR.Arg_EHClauseNotClause);
+
+                Type type = null;
+
+                if (!MetadataToken.IsNullToken(m_catchMetadataToken))
+                {
+                    Type declaringType = m_methodBody.m_methodBase.DeclaringType;
+                    Module module = (declaringType == null) ? m_methodBody.m_methodBase.Module : declaringType.Module;
+                    type = module.ResolveType(m_catchMetadataToken, (declaringType == null) ? null : declaringType.GetGenericArguments(),
+                        m_methodBody.m_methodBase is MethodInfo ? m_methodBody.m_methodBase.GetGenericArguments() : null);
+                }
+
+                return type;
+            }
+        }
+        #endregion
+
+        #region Object Overrides
+        public override string ToString()
+        {
+            if (Flags == ExceptionHandlingClauseOptions.Clause)
+            {
+                return String.Format(CultureInfo.CurrentUICulture,
+                    "Flags={0}, TryOffset={1}, TryLength={2}, HandlerOffset={3}, HandlerLength={4}, CatchType={5}",
+                    Flags, TryOffset, TryLength, HandlerOffset, HandlerLength, CatchType);
+            }
+
+            if (Flags == ExceptionHandlingClauseOptions.Filter)
+            {
+                return String.Format(CultureInfo.CurrentUICulture,
+                    "Flags={0}, TryOffset={1}, TryLength={2}, HandlerOffset={3}, HandlerLength={4}, FilterOffset={5}",
+                    Flags, TryOffset, TryLength, HandlerOffset, HandlerLength, FilterOffset);
+            }
+
+            return String.Format(CultureInfo.CurrentUICulture,
+                "Flags={0}, TryOffset={1}, TryLength={2}, HandlerOffset={3}, HandlerLength={4}",
+                Flags, TryOffset, TryLength, HandlerOffset, HandlerLength);
+        }
+        #endregion
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/FieldInfo.CoreCLR.cs b/src/System.Private.CoreLib/src/System/Reflection/FieldInfo.CoreCLR.cs
new file mode 100644
index 0000000000..bcda3418fa
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/FieldInfo.CoreCLR.cs
@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Globalization;
+
+namespace System.Reflection
+{
+    public abstract partial class FieldInfo : MemberInfo
+    {
+        public static FieldInfo GetFieldFromHandle(RuntimeFieldHandle handle)
+        {
+            if (handle.IsNullHandle())
+                throw new ArgumentException(SR.Argument_InvalidHandle, nameof(handle));
+
+            FieldInfo f = RuntimeType.GetFieldInfo(handle.GetRuntimeFieldInfo());
+
+            Type declaringType = f.DeclaringType;
+            if (declaringType != null && declaringType.IsGenericType)
+                throw new ArgumentException(String.Format(
+                    CultureInfo.CurrentCulture, SR.Argument_FieldDeclaringTypeGeneric,
+                    f.Name, declaringType.GetGenericTypeDefinition()));
+
+            return f;
+        }
+
+        public static FieldInfo GetFieldFromHandle(RuntimeFieldHandle handle, RuntimeTypeHandle declaringType)
+        {
+            if (handle.IsNullHandle())
+                throw new ArgumentException(SR.Argument_InvalidHandle);
+
+            return RuntimeType.GetFieldInfo(declaringType.GetRuntimeType(), handle.GetRuntimeFieldInfo());
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/INVOCATION_FLAGS.cs b/src/System.Private.CoreLib/src/System/Reflection/INVOCATION_FLAGS.cs
new file mode 100644
index 0000000000..eb28f4e209
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/INVOCATION_FLAGS.cs
@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    //
+    // Invocation cached flags. Those are used in unmanaged code as well
+    // so be careful if you change them
+    //
+    [Flags]
+    internal enum INVOCATION_FLAGS : uint
+    {
+        INVOCATION_FLAGS_UNKNOWN = 0x00000000,
+        INVOCATION_FLAGS_INITIALIZED = 0x00000001,
+        // it's used for both method and field to signify that no access is allowed
+        INVOCATION_FLAGS_NO_INVOKE = 0x00000002,
+        /* unused 0x00000004 */
+        // Set for static ctors and ctors on abstract types, which
+        // can be invoked only if the "this" object is provided (even if it's null).
+        INVOCATION_FLAGS_NO_CTOR_INVOKE = 0x00000008,
+        // because field and method are different we can reuse the same bits
+        // method
+        INVOCATION_FLAGS_IS_CTOR = 0x00000010,
+        /* unused 0x00000020 */
+        /* unused 0x00000040 */
+        INVOCATION_FLAGS_IS_DELEGATE_CTOR = 0x00000080,
+        INVOCATION_FLAGS_CONTAINS_STACK_POINTERS = 0x00000100,
+        // field
+        INVOCATION_FLAGS_SPECIAL_FIELD = 0x00000010,
+        INVOCATION_FLAGS_FIELD_SPECIAL_CAST = 0x00000020,
+
+        // temporary flag used for flagging invocation of method vs ctor
+        // this flag never appears on the instance m_invocationFlag and is simply
+        // passed down from within ConstructorInfo.Invoke()
+        INVOCATION_FLAGS_CONSTRUCTOR_INVOKE = 0x10000000,
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/LoaderAllocator.cs b/src/System.Private.CoreLib/src/System/Reflection/LoaderAllocator.cs
new file mode 100644
index 0000000000..54477734c2
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/LoaderAllocator.cs
@@ -0,0 +1,82 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+using System;
+using System.Reflection;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Security;
+using System.Collections.Generic;
+
+
+namespace System.Reflection
+{
+    //
+    // We can destroy the unmanaged part of collectible type only after the managed part is definitely gone and thus
+    // nobody can call/allocate/reference anything related to the collectible assembly anymore. A call to finalizer 
+    // alone does not guarantee that the managed part is gone. A malicious code can keep a reference to some object
+    // in a way that that survives finalization, or we can be running during shutdown where everything is finalized.
+    //
+    // The unmanaged LoaderAllocator keeps a reference to the managed LoaderAllocator in long weak handle. If the long 
+    // weak handle is null, we can be sure that the managed part of the LoaderAllocator is definitely gone and that it 
+    // is safe to destroy the unmanaged part. Unfortunately, we can not perform the above check in a finalizer on the
+    // LoaderAllocator, but it can be performed on a helper object. 
+    //
+    // The finalization does not have to be done using CriticalFinalizerObject. We have to go over all LoaderAllocators 
+    // during AppDomain shutdown anyway to avoid leaks e.g. if somebody stores reference to LoaderAllocator in a static.
+    //
+    internal sealed class LoaderAllocatorScout
+    {
+        // This field is set by the VM to atomically transfer the ownership to the managed loader allocator
+        internal IntPtr m_nativeLoaderAllocator;
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern bool Destroy(IntPtr nativeLoaderAllocator);
+
+        ~LoaderAllocatorScout()
+        {
+            if (m_nativeLoaderAllocator == IntPtr.Zero)
+                return;
+
+            // Assemblies and LoaderAllocators will be cleaned up during AppDomain shutdown in
+            // unmanaged code
+            // So it is ok to skip reregistration and cleanup for finalization during appdomain shutdown.
+            // We also avoid early finalization of LoaderAllocatorScout due to AD unload when the object was inside DelayedFinalizationList.
+            if (!Environment.HasShutdownStarted &&
+                !AppDomain.CurrentDomain.IsFinalizingForUnload())
+            {
+                // Destroy returns false if the managed LoaderAllocator is still alive.
+                if (!Destroy(m_nativeLoaderAllocator))
+                {
+                    // Somebody might have been holding a reference on us via weak handle.
+                    // We will keep trying. It will be hopefully released eventually.
+                    GC.ReRegisterForFinalize(this);
+                }
+            }
+        }
+    }
+
+    internal sealed class LoaderAllocator
+    {
+        private LoaderAllocator()
+        {
+            m_slots = new object[5];
+            // m_slotsUsed = 0;
+
+            m_scout = new LoaderAllocatorScout();
+        }
+
+#pragma warning disable 169
+#pragma warning disable 414
+        private LoaderAllocatorScout m_scout;
+        private object[] m_slots;
+        internal CerHashtable<RuntimeMethodInfo, RuntimeMethodInfo> m_methodInstantiations;
+        private int m_slotsUsed;
+#pragma warning restore 414
+#pragma warning restore 169
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/LocalVariableInfo.cs b/src/System.Private.CoreLib/src/System/Reflection/LocalVariableInfo.cs
new file mode 100644
index 0000000000..241a3c4de6
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/LocalVariableInfo.cs
@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Reflection
+{
+    public class LocalVariableInfo
+    {
+        #region Private Data Members
+        private RuntimeType m_type;
+        private int m_isPinned;
+        private int m_localIndex;
+        #endregion
+
+        #region Constructor
+        protected LocalVariableInfo() { }
+        #endregion
+
+        #region Object Overrides
+        public override string ToString()
+        {
+            string toString = LocalType.ToString() + " (" + LocalIndex + ")";
+
+            if (IsPinned)
+                toString += " (pinned)";
+
+            return toString;
+        }
+        #endregion
+
+        #region Public Members
+        public virtual Type LocalType { get { Debug.Assert(m_type != null, "type must be set!"); return m_type; } }
+        public virtual bool IsPinned { get { return m_isPinned != 0; } }
+        public virtual int LocalIndex { get { return m_localIndex; } }
+        #endregion
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/MdConstant.cs b/src/System.Private.CoreLib/src/System/Reflection/MdConstant.cs
new file mode 100644
index 0000000000..5284bcae0b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/MdConstant.cs
@@ -0,0 +1,173 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+using System;
+
+namespace System.Reflection
+{
+    internal static class MdConstant
+    {
+        public static unsafe Object GetValue(MetadataImport scope, int token, RuntimeTypeHandle fieldTypeHandle, bool raw)
+        {
+            CorElementType corElementType = 0;
+            long buffer = 0;
+            int length;
+            String stringVal;
+
+            stringVal = scope.GetDefaultValue(token, out buffer, out length, out corElementType);
+
+            RuntimeType fieldType = fieldTypeHandle.GetRuntimeType();
+
+            if (fieldType.IsEnum && raw == false)
+            {
+                long defaultValue = 0;
+
+                switch (corElementType)
+                {
+                    #region Switch
+
+                    case CorElementType.Void:
+                        return DBNull.Value;
+
+                    case CorElementType.Char:
+                        defaultValue = *(char*)&buffer;
+                        break;
+
+                    case CorElementType.I1:
+                        defaultValue = *(sbyte*)&buffer;
+                        break;
+
+                    case CorElementType.U1:
+                        defaultValue = *(byte*)&buffer;
+                        break;
+
+                    case CorElementType.I2:
+                        defaultValue = *(short*)&buffer;
+                        break;
+
+                    case CorElementType.U2:
+                        defaultValue = *(ushort*)&buffer;
+                        break;
+
+                    case CorElementType.I4:
+                        defaultValue = *(int*)&buffer;
+                        break;
+
+                    case CorElementType.U4:
+                        defaultValue = *(uint*)&buffer;
+                        break;
+
+                    case CorElementType.I8:
+                        defaultValue = buffer;
+                        break;
+
+                    case CorElementType.U8:
+                        defaultValue = buffer;
+                        break;
+
+                    case CorElementType.Class:
+                        return null;
+
+                    default:
+                        throw new FormatException(SR.Arg_BadLiteralFormat);
+                        #endregion
+                }
+
+                return RuntimeType.CreateEnum(fieldType, defaultValue);
+            }
+            else if (fieldType == typeof(DateTime))
+            {
+                long defaultValue = 0;
+
+                switch (corElementType)
+                {
+                    #region Switch
+
+                    case CorElementType.Void:
+                        return DBNull.Value;
+
+                    case CorElementType.I8:
+                        defaultValue = buffer;
+                        break;
+
+                    case CorElementType.U8:
+                        defaultValue = buffer;
+                        break;
+
+                    case CorElementType.Class:
+                        return null;
+
+                    default:
+                        throw new FormatException(SR.Arg_BadLiteralFormat);
+                        #endregion
+                }
+
+                return new DateTime(defaultValue);
+            }
+            else
+            {
+                switch (corElementType)
+                {
+                    #region Switch
+
+                    case CorElementType.Void:
+                        return DBNull.Value;
+
+                    case CorElementType.Char:
+                        return *(char*)&buffer;
+
+                    case CorElementType.I1:
+                        return *(sbyte*)&buffer;
+
+                    case CorElementType.U1:
+                        return *(byte*)&buffer;
+
+                    case CorElementType.I2:
+                        return *(short*)&buffer;
+
+                    case CorElementType.U2:
+                        return *(ushort*)&buffer;
+
+                    case CorElementType.I4:
+                        return *(int*)&buffer;
+
+                    case CorElementType.U4:
+                        return *(uint*)&buffer;
+
+                    case CorElementType.I8:
+                        return buffer;
+
+                    case CorElementType.U8:
+                        return (ulong)buffer;
+
+                    case CorElementType.Boolean:
+                        // The boolean value returned from the metadata engine is stored as a
+                        // BOOL, which actually maps to an int. We need to read it out as an int
+                        // to avoid problems on big-endian machines.
+                        return (*(int*)&buffer != 0);
+
+                    case CorElementType.R4:
+                        return *(float*)&buffer;
+
+                    case CorElementType.R8:
+                        return *(double*)&buffer;
+
+                    case CorElementType.String:
+                        // A string constant can be empty but never null.
+                        // A nullref constant can only be type CorElementType.Class.
+                        return stringVal == null ? String.Empty : stringVal;
+
+                    case CorElementType.Class:
+                        return null;
+
+                    default:
+                        throw new FormatException(SR.Arg_BadLiteralFormat);
+                        #endregion
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/MdFieldInfo.cs b/src/System.Private.CoreLib/src/System/Reflection/MdFieldInfo.cs
new file mode 100644
index 0000000000..94416d7aa3
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/MdFieldInfo.cs
@@ -0,0 +1,139 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Globalization;
+using RuntimeTypeCache = System.RuntimeType.RuntimeTypeCache;
+
+namespace System.Reflection
+{
+    internal sealed unsafe class MdFieldInfo : RuntimeFieldInfo
+    {
+        #region Private Data Members
+        private int m_tkField;
+        private string m_name;
+        private RuntimeType m_fieldType;
+        private FieldAttributes m_fieldAttributes;
+        #endregion
+
+        #region Constructor
+        internal MdFieldInfo(
+        int tkField, FieldAttributes fieldAttributes, RuntimeTypeHandle declaringTypeHandle, RuntimeTypeCache reflectedTypeCache, BindingFlags bindingFlags)
+            : base(reflectedTypeCache, declaringTypeHandle.GetRuntimeType(), bindingFlags)
+        {
+            m_tkField = tkField;
+            m_name = null;
+            m_fieldAttributes = fieldAttributes;
+        }
+        #endregion
+
+        #region Internal Members
+        internal override bool CacheEquals(object o)
+        {
+            MdFieldInfo m = o as MdFieldInfo;
+
+            if ((object)m == null)
+                return false;
+
+            return m.m_tkField == m_tkField &&
+                m_declaringType.GetTypeHandleInternal().GetModuleHandle().Equals(
+                    m.m_declaringType.GetTypeHandleInternal().GetModuleHandle());
+        }
+        #endregion
+
+        #region MemberInfo Overrides
+        public override String Name
+        {
+            get
+            {
+                if (m_name == null)
+                    m_name = GetRuntimeModule().MetadataImport.GetName(m_tkField).ToString();
+
+                return m_name;
+            }
+        }
+
+        public override int MetadataToken { get { return m_tkField; } }
+        internal override RuntimeModule GetRuntimeModule() { return m_declaringType.GetRuntimeModule(); }
+        #endregion
+
+        #region FieldInfo Overrides
+        public override RuntimeFieldHandle FieldHandle { get { throw new NotSupportedException(); } }
+        public override FieldAttributes Attributes { get { return m_fieldAttributes; } }
+
+        public override bool IsSecurityCritical { get { return DeclaringType.IsSecurityCritical; } }
+        public override bool IsSecuritySafeCritical { get { return DeclaringType.IsSecuritySafeCritical; } }
+        public override bool IsSecurityTransparent { get { return DeclaringType.IsSecurityTransparent; } }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public override Object GetValueDirect(TypedReference obj)
+        {
+            return GetValue(null);
+        }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public override void SetValueDirect(TypedReference obj, Object value)
+        {
+            throw new FieldAccessException(SR.Acc_ReadOnly);
+        }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public unsafe override Object GetValue(Object obj)
+        {
+            return GetValue(false);
+        }
+
+        public unsafe override Object GetRawConstantValue() { return GetValue(true); }
+
+        private unsafe Object GetValue(bool raw)
+        {
+            // Cannot cache these because they could be user defined non-agile enumerations
+
+            Object value = MdConstant.GetValue(GetRuntimeModule().MetadataImport, m_tkField, FieldType.GetTypeHandleInternal(), raw);
+
+            if (value == DBNull.Value)
+                throw new NotSupportedException(SR.Arg_EnumLitValueNotFound);
+
+            return value;
+        }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public override void SetValue(Object obj, Object value, BindingFlags invokeAttr, Binder binder, CultureInfo culture)
+        {
+            throw new FieldAccessException(SR.Acc_ReadOnly);
+        }
+
+        public override Type FieldType
+        {
+            get
+            {
+                if (m_fieldType == null)
+                {
+                    ConstArray fieldMarshal = GetRuntimeModule().MetadataImport.GetSigOfFieldDef(m_tkField);
+
+                    m_fieldType = new Signature(fieldMarshal.Signature.ToPointer(),
+                        (int)fieldMarshal.Length, m_declaringType).FieldType;
+                }
+
+                return m_fieldType;
+            }
+        }
+
+        public override Type[] GetRequiredCustomModifiers()
+        {
+            return Array.Empty<Type>();
+        }
+
+        public override Type[] GetOptionalCustomModifiers()
+        {
+            return Array.Empty<Type>();
+        }
+
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/MdImport.cs b/src/System.Private.CoreLib/src/System/Reflection/MdImport.cs
new file mode 100644
index 0000000000..8589e14d42
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/MdImport.cs
@@ -0,0 +1,671 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// 
+
+using System;
+using System.Reflection;
+using System.Globalization;
+using System.Threading;
+using System.Diagnostics;
+using System.Collections;
+using System.Runtime.CompilerServices;
+using System.Security;
+using System.Text;
+using System.Runtime.InteropServices;
+using System.Configuration.Assemblies;
+using System.Runtime.Versioning;
+
+namespace System.Reflection
+{
+    internal enum CorElementType : byte
+    {
+        End = 0x00,
+        Void = 0x01,
+        Boolean = 0x02,
+        Char = 0x03,
+        I1 = 0x04,
+        U1 = 0x05,
+        I2 = 0x06,
+        U2 = 0x07,
+        I4 = 0x08,
+        U4 = 0x09,
+        I8 = 0x0A,
+        U8 = 0x0B,
+        R4 = 0x0C,
+        R8 = 0x0D,
+        String = 0x0E,
+        Ptr = 0x0F,
+        ByRef = 0x10,
+        ValueType = 0x11,
+        Class = 0x12,
+        Var = 0x13,
+        Array = 0x14,
+        GenericInst = 0x15,
+        TypedByRef = 0x16,
+        I = 0x18,
+        U = 0x19,
+        FnPtr = 0x1B,
+        Object = 0x1C,
+        SzArray = 0x1D,
+        MVar = 0x1E,
+        CModReqd = 0x1F,
+        CModOpt = 0x20,
+        Internal = 0x21,
+        Max = 0x22,
+        Modifier = 0x40,
+        Sentinel = 0x41,
+        Pinned = 0x45,
+    }
+
+    [Flags()]
+    internal enum MdSigCallingConvention : byte
+    {
+        CallConvMask = 0x0f,  // Calling convention is bottom 4 bits 
+
+        Default = 0x00,
+        C = 0x01,
+        StdCall = 0x02,
+        ThisCall = 0x03,
+        FastCall = 0x04,
+        Vararg = 0x05,
+        Field = 0x06,
+        LocalSig = 0x07,
+        Property = 0x08,
+        Unmgd = 0x09,
+        GenericInst = 0x0a,  // generic method instantiation
+
+        Generic = 0x10,  // Generic method sig with explicit number of type arguments (precedes ordinary parameter count)
+        HasThis = 0x20,  // Top bit indicates a 'this' parameter    
+        ExplicitThis = 0x40,  // This parameter is explicitly in the signature
+    }
+
+
+    [Flags()]
+    internal enum PInvokeAttributes
+    {
+        NoMangle = 0x0001,
+
+
+        CharSetMask = 0x0006,
+        CharSetNotSpec = 0x0000,
+        CharSetAnsi = 0x0002,
+        CharSetUnicode = 0x0004,
+        CharSetAuto = 0x0006,
+
+
+        BestFitUseAssem = 0x0000,
+        BestFitEnabled = 0x0010,
+        BestFitDisabled = 0x0020,
+        BestFitMask = 0x0030,
+
+        ThrowOnUnmappableCharUseAssem = 0x0000,
+        ThrowOnUnmappableCharEnabled = 0x1000,
+        ThrowOnUnmappableCharDisabled = 0x2000,
+        ThrowOnUnmappableCharMask = 0x3000,
+
+        SupportsLastError = 0x0040,
+
+        CallConvMask = 0x0700,
+        CallConvWinapi = 0x0100,
+        CallConvCdecl = 0x0200,
+        CallConvStdcall = 0x0300,
+        CallConvThiscall = 0x0400,
+        CallConvFastcall = 0x0500,
+
+        MaxValue = 0xFFFF,
+    }
+
+
+    [Flags()]
+    internal enum MethodSemanticsAttributes
+    {
+        Setter = 0x0001,
+        Getter = 0x0002,
+        Other = 0x0004,
+        AddOn = 0x0008,
+        RemoveOn = 0x0010,
+        Fire = 0x0020,
+    }
+
+
+    internal enum MetadataTokenType
+    {
+        Module = 0x00000000,
+        TypeRef = 0x01000000,
+        TypeDef = 0x02000000,
+        FieldDef = 0x04000000,
+        MethodDef = 0x06000000,
+        ParamDef = 0x08000000,
+        InterfaceImpl = 0x09000000,
+        MemberRef = 0x0a000000,
+        CustomAttribute = 0x0c000000,
+        Permission = 0x0e000000,
+        Signature = 0x11000000,
+        Event = 0x14000000,
+        Property = 0x17000000,
+        ModuleRef = 0x1a000000,
+        TypeSpec = 0x1b000000,
+        Assembly = 0x20000000,
+        AssemblyRef = 0x23000000,
+        File = 0x26000000,
+        ExportedType = 0x27000000,
+        ManifestResource = 0x28000000,
+        GenericPar = 0x2a000000,
+        MethodSpec = 0x2b000000,
+        String = 0x70000000,
+        Name = 0x71000000,
+        BaseType = 0x72000000,
+        Invalid = 0x7FFFFFFF,
+    }
+
+    internal struct ConstArray
+    {
+        public IntPtr Signature { get { return m_constArray; } }
+        public int Length { get { return m_length; } }
+        public byte this[int index]
+        {
+            get
+            {
+                if (index < 0 || index >= m_length)
+                    throw new IndexOutOfRangeException();
+
+                unsafe
+                {
+                    return ((byte*)m_constArray.ToPointer())[index];
+                }
+            }
+        }
+
+        // Keep the definition in sync with vm\ManagedMdImport.hpp
+        internal int m_length;
+        internal IntPtr m_constArray;
+    }
+
+    internal struct MetadataToken
+    {
+        #region Implicit Cast Operators
+        public static implicit operator int(MetadataToken token) { return token.Value; }
+        public static implicit operator MetadataToken(int token) { return new MetadataToken(token); }
+        #endregion
+
+        #region Public Static Members
+        public static bool IsTokenOfType(int token, params MetadataTokenType[] types)
+        {
+            for (int i = 0; i < types.Length; i++)
+            {
+                if ((int)(token & 0xFF000000) == (int)types[i])
+                    return true;
+            }
+
+            return false;
+        }
+
+        public static bool IsNullToken(int token)
+        {
+            return (token & 0x00FFFFFF) == 0;
+        }
+        #endregion
+
+        #region Public Data Members
+        public int Value;
+        #endregion
+
+        #region Constructor
+        public MetadataToken(int token) { Value = token; }
+        #endregion
+
+        #region Public Members
+        public bool IsGlobalTypeDefToken { get { return (Value == 0x02000001); } }
+        public MetadataTokenType TokenType { get { return (MetadataTokenType)(Value & 0xFF000000); } }
+        public bool IsTypeRef { get { return TokenType == MetadataTokenType.TypeRef; } }
+        public bool IsTypeDef { get { return TokenType == MetadataTokenType.TypeDef; } }
+        public bool IsFieldDef { get { return TokenType == MetadataTokenType.FieldDef; } }
+        public bool IsMethodDef { get { return TokenType == MetadataTokenType.MethodDef; } }
+        public bool IsMemberRef { get { return TokenType == MetadataTokenType.MemberRef; } }
+        public bool IsEvent { get { return TokenType == MetadataTokenType.Event; } }
+        public bool IsProperty { get { return TokenType == MetadataTokenType.Property; } }
+        public bool IsParamDef { get { return TokenType == MetadataTokenType.ParamDef; } }
+        public bool IsTypeSpec { get { return TokenType == MetadataTokenType.TypeSpec; } }
+        public bool IsMethodSpec { get { return TokenType == MetadataTokenType.MethodSpec; } }
+        public bool IsString { get { return TokenType == MetadataTokenType.String; } }
+        public bool IsSignature { get { return TokenType == MetadataTokenType.Signature; } }
+        public bool IsModule { get { return TokenType == MetadataTokenType.Module; } }
+        public bool IsAssembly { get { return TokenType == MetadataTokenType.Assembly; } }
+        public bool IsGenericPar { get { return TokenType == MetadataTokenType.GenericPar; } }
+        #endregion
+
+        #region Object Overrides
+        public override string ToString() { return String.Format(CultureInfo.InvariantCulture, "0x{0:x8}", Value); }
+        #endregion
+    }
+
+    internal unsafe struct MetadataEnumResult
+    {
+        // Keep the definition in sync with vm\ManagedMdImport.hpp
+        private int[] largeResult;
+        private int length;
+        private fixed int smallResult[16];
+
+        public int Length
+        {
+            get
+            {
+                return length;
+            }
+        }
+
+        public int this[int index]
+        {
+            get
+            {
+                Debug.Assert(0 <= index && index < Length);
+                if (largeResult != null)
+                    return largeResult[index];
+
+                fixed (int* p = smallResult)
+                    return p[index];
+            }
+        }
+    }
+
+    internal struct MetadataImport
+    {
+        #region Private Data Members
+        private IntPtr m_metadataImport2;
+        private object m_keepalive;
+        #endregion
+
+        #region Override methods from Object
+        internal static readonly MetadataImport EmptyImport = new MetadataImport((IntPtr)0, null);
+
+        public override int GetHashCode()
+        {
+            return ValueType.GetHashCodeOfPtr(m_metadataImport2);
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (!(obj is MetadataImport))
+                return false;
+            return Equals((MetadataImport)obj);
+        }
+
+        private bool Equals(MetadataImport import)
+        {
+            return import.m_metadataImport2 == m_metadataImport2;
+        }
+
+        #endregion
+
+        #region Static Members
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _GetMarshalAs(IntPtr pNativeType, int cNativeType, out int unmanagedType, out int safeArraySubType, out string safeArrayUserDefinedSubType,
+            out int arraySubType, out int sizeParamIndex, out int sizeConst, out string marshalType, out string marshalCookie,
+            out int iidParamIndex);
+        internal static void GetMarshalAs(ConstArray nativeType,
+            out UnmanagedType unmanagedType, out VarEnum safeArraySubType, out string safeArrayUserDefinedSubType,
+            out UnmanagedType arraySubType, out int sizeParamIndex, out int sizeConst, out string marshalType, out string marshalCookie,
+            out int iidParamIndex)
+        {
+            int _unmanagedType, _safeArraySubType, _arraySubType;
+
+            _GetMarshalAs(nativeType.Signature, (int)nativeType.Length,
+                out _unmanagedType, out _safeArraySubType, out safeArrayUserDefinedSubType,
+                out _arraySubType, out sizeParamIndex, out sizeConst, out marshalType, out marshalCookie,
+                out iidParamIndex);
+            unmanagedType = (UnmanagedType)_unmanagedType;
+            safeArraySubType = (VarEnum)_safeArraySubType;
+            arraySubType = (UnmanagedType)_arraySubType;
+        }
+        #endregion
+
+        #region Internal Static Members
+        internal static void ThrowError(int hResult)
+        {
+            throw new MetadataException(hResult);
+        }
+        #endregion
+
+        #region Constructor
+        internal MetadataImport(IntPtr metadataImport2, object keepalive)
+        {
+            m_metadataImport2 = metadataImport2;
+            m_keepalive = keepalive;
+        }
+        #endregion
+
+        #region FCalls
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe void _Enum(IntPtr scope, int type, int parent, out MetadataEnumResult result);
+
+        public unsafe void Enum(MetadataTokenType type, int parent, out MetadataEnumResult result)
+        {
+            _Enum(m_metadataImport2, (int)type, parent, out result);
+        }
+
+        public unsafe void EnumNestedTypes(int mdTypeDef, out MetadataEnumResult result)
+        {
+            Enum(MetadataTokenType.TypeDef, mdTypeDef, out result);
+        }
+
+        public unsafe void EnumCustomAttributes(int mdToken, out MetadataEnumResult result)
+        {
+            Enum(MetadataTokenType.CustomAttribute, mdToken, out result);
+        }
+
+        public unsafe void EnumParams(int mdMethodDef, out MetadataEnumResult result)
+        {
+            Enum(MetadataTokenType.ParamDef, mdMethodDef, out result);
+        }
+
+        public unsafe void EnumFields(int mdTypeDef, out MetadataEnumResult result)
+        {
+            Enum(MetadataTokenType.FieldDef, mdTypeDef, out result);
+        }
+
+        public unsafe void EnumProperties(int mdTypeDef, out MetadataEnumResult result)
+        {
+            Enum(MetadataTokenType.Property, mdTypeDef, out result);
+        }
+
+        public unsafe void EnumEvents(int mdTypeDef, out MetadataEnumResult result)
+        {
+            Enum(MetadataTokenType.Event, mdTypeDef, out result);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern String _GetDefaultValue(IntPtr scope, int mdToken, out long value, out int length, out int corElementType);
+        public String GetDefaultValue(int mdToken, out long value, out int length, out CorElementType corElementType)
+        {
+            int _corElementType;
+            String stringVal;
+            stringVal = _GetDefaultValue(m_metadataImport2, mdToken, out value, out length, out _corElementType);
+            corElementType = (CorElementType)_corElementType;
+            return stringVal;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe void _GetUserString(IntPtr scope, int mdToken, void** name, out int length);
+        public unsafe String GetUserString(int mdToken)
+        {
+            void* name;
+            int length;
+            _GetUserString(m_metadataImport2, mdToken, &name, out length);
+
+            if (name == null)
+                return null;
+
+            char[] c = new char[length];
+            for (int i = 0; i < c.Length; i++)
+            {
+#if ALIGN_ACCESS
+                c[i] = (char)Marshal.ReadInt16( (IntPtr) (((char*)name) + i) );
+#else
+                c[i] = ((char*)name)[i];
+#endif
+            }
+
+            return new String(c);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe void _GetName(IntPtr scope, int mdToken, void** name);
+        public unsafe MdUtf8String GetName(int mdToken)
+        {
+            void* name;
+            _GetName(m_metadataImport2, mdToken, &name);
+
+            return new MdUtf8String(name);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe void _GetNamespace(IntPtr scope, int mdToken, void** namesp);
+        public unsafe MdUtf8String GetNamespace(int mdToken)
+        {
+            void* namesp;
+            _GetNamespace(m_metadataImport2, mdToken, &namesp);
+
+            return new MdUtf8String(namesp);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe void _GetEventProps(IntPtr scope, int mdToken, void** name, out int eventAttributes);
+        public unsafe void GetEventProps(int mdToken, out void* name, out EventAttributes eventAttributes)
+        {
+            int _eventAttributes;
+            void* _name;
+            _GetEventProps(m_metadataImport2, mdToken, &_name, out _eventAttributes);
+            name = _name;
+            eventAttributes = (EventAttributes)_eventAttributes;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _GetFieldDefProps(IntPtr scope, int mdToken, out int fieldAttributes);
+        public void GetFieldDefProps(int mdToken, out FieldAttributes fieldAttributes)
+        {
+            int _fieldAttributes;
+            _GetFieldDefProps(m_metadataImport2, mdToken, out _fieldAttributes);
+            fieldAttributes = (FieldAttributes)_fieldAttributes;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe void _GetPropertyProps(IntPtr scope,
+            int mdToken, void** name, out int propertyAttributes, out ConstArray signature);
+        public unsafe void GetPropertyProps(int mdToken, out void* name, out PropertyAttributes propertyAttributes, out ConstArray signature)
+        {
+            int _propertyAttributes;
+            void* _name;
+            _GetPropertyProps(m_metadataImport2, mdToken, &_name, out _propertyAttributes, out signature);
+            name = _name;
+            propertyAttributes = (PropertyAttributes)_propertyAttributes;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _GetParentToken(IntPtr scope,
+            int mdToken, out int tkParent);
+        public int GetParentToken(int tkToken)
+        {
+            int tkParent;
+            _GetParentToken(m_metadataImport2, tkToken, out tkParent);
+            return tkParent;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _GetParamDefProps(IntPtr scope,
+            int parameterToken, out int sequence, out int attributes);
+        public void GetParamDefProps(int parameterToken, out int sequence, out ParameterAttributes attributes)
+        {
+            int _attributes;
+
+            _GetParamDefProps(m_metadataImport2, parameterToken, out sequence, out _attributes);
+
+            attributes = (ParameterAttributes)_attributes;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _GetGenericParamProps(IntPtr scope,
+            int genericParameter,
+            out int flags);
+
+        public void GetGenericParamProps(
+            int genericParameter,
+            out GenericParameterAttributes attributes)
+        {
+            int _attributes;
+            _GetGenericParamProps(m_metadataImport2, genericParameter, out _attributes);
+            attributes = (GenericParameterAttributes)_attributes;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _GetScopeProps(IntPtr scope,
+            out Guid mvid);
+
+        public void GetScopeProps(
+            out Guid mvid)
+        {
+            _GetScopeProps(m_metadataImport2, out mvid);
+        }
+
+
+        public ConstArray GetMethodSignature(MetadataToken token)
+        {
+            if (token.IsMemberRef)
+                return GetMemberRefProps(token);
+
+            return GetSigOfMethodDef(token);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _GetSigOfMethodDef(IntPtr scope,
+            int methodToken,
+            ref ConstArray signature);
+
+        public ConstArray GetSigOfMethodDef(int methodToken)
+        {
+            ConstArray signature = new ConstArray();
+
+            _GetSigOfMethodDef(m_metadataImport2, methodToken, ref signature);
+
+            return signature;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _GetSignatureFromToken(IntPtr scope,
+            int methodToken,
+            ref ConstArray signature);
+
+        public ConstArray GetSignatureFromToken(int token)
+        {
+            ConstArray signature = new ConstArray();
+
+            _GetSignatureFromToken(m_metadataImport2, token, ref signature);
+
+            return signature;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _GetMemberRefProps(IntPtr scope,
+            int memberTokenRef,
+            out ConstArray signature);
+
+        public ConstArray GetMemberRefProps(int memberTokenRef)
+        {
+            ConstArray signature = new ConstArray();
+
+            _GetMemberRefProps(m_metadataImport2, memberTokenRef, out signature);
+
+            return signature;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _GetCustomAttributeProps(IntPtr scope,
+            int customAttributeToken,
+            out int constructorToken,
+            out ConstArray signature);
+
+        public void GetCustomAttributeProps(
+            int customAttributeToken,
+            out int constructorToken,
+            out ConstArray signature)
+        {
+            _GetCustomAttributeProps(m_metadataImport2, customAttributeToken,
+                out constructorToken, out signature);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _GetClassLayout(IntPtr scope,
+            int typeTokenDef, out int packSize, out int classSize);
+        public void GetClassLayout(
+            int typeTokenDef,
+            out int packSize,
+            out int classSize)
+        {
+            _GetClassLayout(m_metadataImport2, typeTokenDef, out packSize, out classSize);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool _GetFieldOffset(IntPtr scope,
+            int typeTokenDef, int fieldTokenDef, out int offset);
+        public bool GetFieldOffset(
+            int typeTokenDef,
+            int fieldTokenDef,
+            out int offset)
+        {
+            return _GetFieldOffset(m_metadataImport2, typeTokenDef, fieldTokenDef, out offset);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _GetSigOfFieldDef(IntPtr scope,
+            int fieldToken,
+            ref ConstArray fieldMarshal);
+
+        public ConstArray GetSigOfFieldDef(int fieldToken)
+        {
+            ConstArray fieldMarshal = new ConstArray();
+
+            _GetSigOfFieldDef(m_metadataImport2, fieldToken, ref fieldMarshal);
+
+            return fieldMarshal;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _GetFieldMarshal(IntPtr scope,
+            int fieldToken,
+            ref ConstArray fieldMarshal);
+
+        public ConstArray GetFieldMarshal(int fieldToken)
+        {
+            ConstArray fieldMarshal = new ConstArray();
+
+            _GetFieldMarshal(m_metadataImport2, fieldToken, ref fieldMarshal);
+
+            return fieldMarshal;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe void _GetPInvokeMap(IntPtr scope,
+            int token,
+            out int attributes,
+            void** importName,
+            void** importDll);
+
+        public unsafe void GetPInvokeMap(
+            int token,
+            out PInvokeAttributes attributes,
+            out String importName,
+            out String importDll)
+        {
+            int _attributes;
+            void* _importName, _importDll;
+            _GetPInvokeMap(m_metadataImport2, token, out _attributes, &_importName, &_importDll);
+            importName = new MdUtf8String(_importName).ToString();
+            importDll = new MdUtf8String(_importDll).ToString();
+
+            attributes = (PInvokeAttributes)_attributes;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool _IsValidToken(IntPtr scope, int token);
+        public bool IsValidToken(int token)
+        {
+            return _IsValidToken(m_metadataImport2, token);
+        }
+        #endregion
+    }
+
+
+    internal class MetadataException : Exception
+    {
+        private int m_hr;
+        internal MetadataException(int hr) { m_hr = hr; }
+
+        public override string ToString()
+        {
+            return String.Format(CultureInfo.CurrentCulture, "MetadataException HResult = {0:x}.", m_hr);
+        }
+    }
+}
+
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/MemberInfo.Internal.cs b/src/System.Private.CoreLib/src/System/Reflection/MemberInfo.Internal.cs
new file mode 100644
index 0000000000..9bb7b57413
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/MemberInfo.Internal.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Reflection
+{
+    public abstract partial class MemberInfo
+    {
+        internal virtual bool CacheEquals(object o) { throw new NotImplementedException(); }
+
+        internal bool HasSameMetadataDefinitionAsCore<TOther>(MemberInfo other) where TOther : MemberInfo
+        {
+            if (other == null)
+                throw new ArgumentNullException(nameof(other));
+
+            // Ensure that "other" is a runtime-implemented MemberInfo. Do this check before calling any methods on it!
+            if (!(other is TOther)) 
+                return false;
+
+            if (MetadataToken != other.MetadataToken)
+                return false;
+
+            if (!(Module.Equals(other.Module)))
+                return false;
+
+            return true;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/Metadata/AssemblyExtensions.cs b/src/System.Private.CoreLib/src/System/Reflection/Metadata/AssemblyExtensions.cs
new file mode 100644
index 0000000000..2b6e5b2ffe
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/Metadata/AssemblyExtensions.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Security;
+
+namespace System.Reflection.Metadata
+{
+    public static class AssemblyExtensions
+    {
+        [DllImport(JitHelpers.QCall)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static extern unsafe bool InternalTryGetRawMetadata(RuntimeAssembly assembly, ref byte* blob, ref int length);
+
+        // Retrieves the metadata section of the assembly, for use with System.Reflection.Metadata.MetadataReader.
+        //   - Returns false upon failure. Metadata might not be available for some assemblies, such as AssemblyBuilder, .NET
+        //     native images, etc.
+        //   - Callers should not write to the metadata blob
+        //   - The metadata blob pointer will remain valid as long as the AssemblyLoadContext with which the assembly is
+        //     associated, is alive. The caller is responsible for keeping the assembly object alive while accessing the
+        //     metadata blob.
+        [CLSCompliant(false)] // out byte* blob
+        public static unsafe bool TryGetRawMetadata(this Assembly assembly, out byte* blob, out int length)
+        {
+            if (assembly == null)
+            {
+                throw new ArgumentNullException(nameof(assembly));
+            }
+
+            blob = null;
+            length = 0;
+
+            var runtimeAssembly = assembly as RuntimeAssembly;
+            if (runtimeAssembly == null)
+            {
+                return false;
+            }
+
+            return InternalTryGetRawMetadata(runtimeAssembly, ref blob, ref length);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/MethodBase.CoreCLR.cs b/src/System.Private.CoreLib/src/System/Reflection/MethodBase.CoreCLR.cs
new file mode 100644
index 0000000000..3afd396471
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/MethodBase.CoreCLR.cs
@@ -0,0 +1,157 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Globalization;
+using System.Text;
+using System.Threading;
+
+namespace System.Reflection
+{
+    public abstract partial class MethodBase : MemberInfo
+    {
+        #region Static Members
+        public static MethodBase GetMethodFromHandle(RuntimeMethodHandle handle)
+        {
+            if (handle.IsNullHandle())
+                throw new ArgumentException(SR.Argument_InvalidHandle);
+
+            MethodBase m = RuntimeType.GetMethodBase(handle.GetMethodInfo());
+
+            Type declaringType = m.DeclaringType;
+            if (declaringType != null && declaringType.IsGenericType)
+                throw new ArgumentException(String.Format(
+                    CultureInfo.CurrentCulture, SR.Argument_MethodDeclaringTypeGeneric,
+                    m, declaringType.GetGenericTypeDefinition()));
+
+            return m;
+        }
+
+        public static MethodBase GetMethodFromHandle(RuntimeMethodHandle handle, RuntimeTypeHandle declaringType)
+        {
+            if (handle.IsNullHandle())
+                throw new ArgumentException(SR.Argument_InvalidHandle);
+
+            return RuntimeType.GetMethodBase(declaringType.GetRuntimeType(), handle.GetMethodInfo());
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public static MethodBase GetCurrentMethod()
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return RuntimeMethodInfo.InternalGetCurrentMethod(ref stackMark);
+        }
+        #endregion
+
+        #region Internal Members
+        // used by EE
+        private IntPtr GetMethodDesc() { return MethodHandle.Value; }
+
+        internal virtual ParameterInfo[] GetParametersNoCopy() { return GetParameters(); }
+        #endregion
+
+        #region Internal Methods
+        // helper method to construct the string representation of the parameter list
+
+        internal static string ConstructParameters(Type[] parameterTypes, CallingConventions callingConvention, bool serialization)
+        {
+            StringBuilder sbParamList = new StringBuilder();
+            string comma = "";
+
+            for (int i = 0; i < parameterTypes.Length; i++)
+            {
+                Type t = parameterTypes[i];
+
+                sbParamList.Append(comma);
+
+                string typeName = t.FormatTypeName(serialization);
+
+                // Legacy: Why use "ByRef" for by ref parameters? What language is this? 
+                // VB uses "ByRef" but it should precede (not follow) the parameter name.
+                // Why don't we just use "&"?
+                if (t.IsByRef && !serialization)
+                {
+                    sbParamList.Append(typeName.TrimEnd('&'));
+                    sbParamList.Append(" ByRef");
+                }
+                else
+                {
+                    sbParamList.Append(typeName);
+                }
+
+                comma = ", ";
+            }
+
+            if ((callingConvention & CallingConventions.VarArgs) == CallingConventions.VarArgs)
+            {
+                sbParamList.Append(comma);
+                sbParamList.Append("...");
+            }
+
+            return sbParamList.ToString();
+        }
+
+        internal string FullName
+        {
+            get
+            {
+                return String.Format("{0}.{1}", DeclaringType.FullName, FormatNameAndSig());
+            }
+        }
+        internal string FormatNameAndSig()
+        {
+            return FormatNameAndSig(false);
+        }
+
+        internal virtual string FormatNameAndSig(bool serialization)
+        {
+            // Serialization uses ToString to resolve MethodInfo overloads.
+            StringBuilder sbName = new StringBuilder(Name);
+
+            sbName.Append("(");
+            sbName.Append(ConstructParameters(GetParameterTypes(), CallingConvention, serialization));
+            sbName.Append(")");
+
+            return sbName.ToString();
+        }
+
+        internal virtual Type[] GetParameterTypes()
+        {
+            ParameterInfo[] paramInfo = GetParametersNoCopy();
+
+            Type[] parameterTypes = new Type[paramInfo.Length];
+            for (int i = 0; i < paramInfo.Length; i++)
+                parameterTypes[i] = paramInfo[i].ParameterType;
+
+            return parameterTypes;
+        }
+
+        internal Object[] CheckArguments(Object[] parameters, Binder binder,
+            BindingFlags invokeAttr, CultureInfo culture, Signature sig)
+        {
+            // copy the arguments in a different array so we detach from any user changes 
+            Object[] copyOfParameters = new Object[parameters.Length];
+
+            ParameterInfo[] p = null;
+            for (int i = 0; i < parameters.Length; i++)
+            {
+                Object arg = parameters[i];
+                RuntimeType argRT = sig.Arguments[i];
+
+                if (arg == Type.Missing)
+                {
+                    if (p == null)
+                        p = GetParametersNoCopy();
+                    if (p[i].DefaultValue == System.DBNull.Value)
+                        throw new ArgumentException(SR.Arg_VarMissNull, nameof(parameters));
+                    arg = p[i].DefaultValue;
+                }
+                copyOfParameters[i] = argRT.CheckValue(arg, binder, culture, invokeAttr);
+            }
+
+            return copyOfParameters;
+        }
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/MethodBody.cs b/src/System.Private.CoreLib/src/System/Reflection/MethodBody.cs
new file mode 100644
index 0000000000..e1d18bf375
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/MethodBody.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+
+namespace System.Reflection
+{
+    public class MethodBody
+    {
+        #region constructor
+        // This class can only be created from inside the EE.
+        protected MethodBody() { }
+        #endregion
+
+        #region Private Data Members
+        private byte[] m_IL;
+        private ExceptionHandlingClause[] m_exceptionHandlingClauses;
+        private LocalVariableInfo[] m_localVariables;
+        internal MethodBase m_methodBase;
+        private int m_localSignatureMetadataToken;
+        private int m_maxStackSize;
+        private bool m_initLocals;
+        #endregion
+
+        #region Public Members
+        public virtual int LocalSignatureMetadataToken { get { return m_localSignatureMetadataToken; } }
+        public virtual IList<LocalVariableInfo> LocalVariables { get { return Array.AsReadOnly(m_localVariables); } }
+        public virtual int MaxStackSize { get { return m_maxStackSize; } }
+        public virtual bool InitLocals { get { return m_initLocals; } }
+        public virtual byte[] GetILAsByteArray() { return m_IL; }
+        public virtual IList<ExceptionHandlingClause> ExceptionHandlingClauses { get { return Array.AsReadOnly(m_exceptionHandlingClauses); } }
+        #endregion
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Reflection/RtFieldInfo.cs b/src/System.Private.CoreLib/src/System/Reflection/RtFieldInfo.cs
new file mode 100644
index 0000000000..fedffad5d5
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/RtFieldInfo.cs
@@ -0,0 +1,363 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using RuntimeTypeCache = System.RuntimeType.RuntimeTypeCache;
+
+namespace System.Reflection
+{
+    internal unsafe sealed class RtFieldInfo : RuntimeFieldInfo, IRuntimeFieldInfo
+    {
+        #region Private Data Members
+        // agressive caching
+        private IntPtr m_fieldHandle;
+        private FieldAttributes m_fieldAttributes;
+        // lazy caching
+        private string m_name;
+        private RuntimeType m_fieldType;
+        private INVOCATION_FLAGS m_invocationFlags;
+
+        internal INVOCATION_FLAGS InvocationFlags
+        {
+            get
+            {
+                if ((m_invocationFlags & INVOCATION_FLAGS.INVOCATION_FLAGS_INITIALIZED) == 0)
+                {
+                    Type declaringType = DeclaringType;
+                    bool fIsReflectionOnlyType = (declaringType is ReflectionOnlyType);
+
+                    INVOCATION_FLAGS invocationFlags = 0;
+
+                    // first take care of all the NO_INVOKE cases
+                    if (
+                        (declaringType != null && declaringType.ContainsGenericParameters) ||
+                        (declaringType == null && Module.Assembly.ReflectionOnly) ||
+                        (fIsReflectionOnlyType)
+                       )
+                    {
+                        invocationFlags |= INVOCATION_FLAGS.INVOCATION_FLAGS_NO_INVOKE;
+                    }
+
+                    // If the invocationFlags are still 0, then
+                    // this should be an usable field, determine the other flags 
+                    if (invocationFlags == 0)
+                    {
+                        if ((m_fieldAttributes & FieldAttributes.InitOnly) != (FieldAttributes)0)
+                            invocationFlags |= INVOCATION_FLAGS.INVOCATION_FLAGS_SPECIAL_FIELD;
+
+                        if ((m_fieldAttributes & FieldAttributes.HasFieldRVA) != (FieldAttributes)0)
+                            invocationFlags |= INVOCATION_FLAGS.INVOCATION_FLAGS_SPECIAL_FIELD;
+
+                        // find out if the field type is one of the following: Primitive, Enum or Pointer
+                        Type fieldType = FieldType;
+                        if (fieldType.IsPointer || fieldType.IsEnum || fieldType.IsPrimitive)
+                            invocationFlags |= INVOCATION_FLAGS.INVOCATION_FLAGS_FIELD_SPECIAL_CAST;
+                    }
+
+                    // must be last to avoid threading problems
+                    m_invocationFlags = invocationFlags | INVOCATION_FLAGS.INVOCATION_FLAGS_INITIALIZED;
+                }
+
+                return m_invocationFlags;
+            }
+        }
+        #endregion
+
+        #region Constructor
+        internal RtFieldInfo(
+            RuntimeFieldHandleInternal handle, RuntimeType declaringType, RuntimeTypeCache reflectedTypeCache, BindingFlags bindingFlags)
+            : base(reflectedTypeCache, declaringType, bindingFlags)
+        {
+            m_fieldHandle = handle.Value;
+            m_fieldAttributes = RuntimeFieldHandle.GetAttributes(handle);
+        }
+        #endregion
+
+        #region Private Members
+        RuntimeFieldHandleInternal IRuntimeFieldInfo.Value
+        {
+            get
+            {
+                return new RuntimeFieldHandleInternal(m_fieldHandle);
+            }
+        }
+
+        #endregion
+
+        #region Internal Members
+        internal void CheckConsistency(Object target)
+        {
+            // only test instance fields
+            if ((m_fieldAttributes & FieldAttributes.Static) != FieldAttributes.Static)
+            {
+                if (!m_declaringType.IsInstanceOfType(target))
+                {
+                    if (target == null)
+                    {
+                        throw new TargetException(SR.RFLCT_Targ_StatFldReqTarg);
+                    }
+                    else
+                    {
+                        throw new ArgumentException(
+                            String.Format(CultureInfo.CurrentUICulture, SR.Arg_FieldDeclTarget,
+                                Name, m_declaringType, target.GetType()));
+                    }
+                }
+            }
+        }
+
+        internal override bool CacheEquals(object o)
+        {
+            RtFieldInfo m = o as RtFieldInfo;
+
+            if ((object)m == null)
+                return false;
+
+            return m.m_fieldHandle == m_fieldHandle;
+        }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        internal void InternalSetValue(Object obj, Object value, BindingFlags invokeAttr, Binder binder, CultureInfo culture, ref StackCrawlMark stackMark)
+        {
+            INVOCATION_FLAGS invocationFlags = InvocationFlags;
+            RuntimeType declaringType = DeclaringType as RuntimeType;
+
+            if ((invocationFlags & INVOCATION_FLAGS.INVOCATION_FLAGS_NO_INVOKE) != 0)
+            {
+                if (declaringType != null && declaringType.ContainsGenericParameters)
+                    throw new InvalidOperationException(SR.Arg_UnboundGenField);
+
+                if ((declaringType == null && Module.Assembly.ReflectionOnly) || declaringType is ReflectionOnlyType)
+                    throw new InvalidOperationException(SR.Arg_ReflectionOnlyField);
+
+                throw new FieldAccessException();
+            }
+
+            CheckConsistency(obj);
+
+            RuntimeType fieldType = (RuntimeType)FieldType;
+            value = fieldType.CheckValue(value, binder, culture, invokeAttr);
+
+            bool domainInitialized = false;
+            if (declaringType == null)
+            {
+                RuntimeFieldHandle.SetValue(this, obj, value, fieldType, m_fieldAttributes, null, ref domainInitialized);
+            }
+            else
+            {
+                domainInitialized = declaringType.DomainInitialized;
+                RuntimeFieldHandle.SetValue(this, obj, value, fieldType, m_fieldAttributes, declaringType, ref domainInitialized);
+                declaringType.DomainInitialized = domainInitialized;
+            }
+        }
+
+        // UnsafeSetValue doesn't perform any consistency or visibility check.
+        // It is the caller's responsibility to ensure the operation is safe.
+        // When the caller needs to perform visibility checks they should call
+        // InternalSetValue() instead. When the caller needs to perform 
+        // consistency checks they should call CheckConsistency() before 
+        // calling this method.
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        internal void UnsafeSetValue(Object obj, Object value, BindingFlags invokeAttr, Binder binder, CultureInfo culture)
+        {
+            RuntimeType declaringType = DeclaringType as RuntimeType;
+            RuntimeType fieldType = (RuntimeType)FieldType;
+            value = fieldType.CheckValue(value, binder, culture, invokeAttr);
+
+            bool domainInitialized = false;
+            if (declaringType == null)
+            {
+                RuntimeFieldHandle.SetValue(this, obj, value, fieldType, m_fieldAttributes, null, ref domainInitialized);
+            }
+            else
+            {
+                domainInitialized = declaringType.DomainInitialized;
+                RuntimeFieldHandle.SetValue(this, obj, value, fieldType, m_fieldAttributes, declaringType, ref domainInitialized);
+                declaringType.DomainInitialized = domainInitialized;
+            }
+        }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        internal Object InternalGetValue(Object obj, ref StackCrawlMark stackMark)
+        {
+            INVOCATION_FLAGS invocationFlags = InvocationFlags;
+            RuntimeType declaringType = DeclaringType as RuntimeType;
+
+            if ((invocationFlags & INVOCATION_FLAGS.INVOCATION_FLAGS_NO_INVOKE) != 0)
+            {
+                if (declaringType != null && DeclaringType.ContainsGenericParameters)
+                    throw new InvalidOperationException(SR.Arg_UnboundGenField);
+
+                if ((declaringType == null && Module.Assembly.ReflectionOnly) || declaringType is ReflectionOnlyType)
+                    throw new InvalidOperationException(SR.Arg_ReflectionOnlyField);
+
+                throw new FieldAccessException();
+            }
+
+            CheckConsistency(obj);
+
+            return UnsafeGetValue(obj);
+        }
+
+        // UnsafeGetValue doesn't perform any consistency or visibility check.
+        // It is the caller's responsibility to ensure the operation is safe.
+        // When the caller needs to perform visibility checks they should call
+        // InternalGetValue() instead. When the caller needs to perform 
+        // consistency checks they should call CheckConsistency() before 
+        // calling this method.
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        internal Object UnsafeGetValue(Object obj)
+        {
+            RuntimeType declaringType = DeclaringType as RuntimeType;
+
+            RuntimeType fieldType = (RuntimeType)FieldType;
+
+            bool domainInitialized = false;
+            if (declaringType == null)
+            {
+                return RuntimeFieldHandle.GetValue(this, obj, fieldType, null, ref domainInitialized);
+            }
+            else
+            {
+                domainInitialized = declaringType.DomainInitialized;
+                object retVal = RuntimeFieldHandle.GetValue(this, obj, fieldType, declaringType, ref domainInitialized);
+                declaringType.DomainInitialized = domainInitialized;
+                return retVal;
+            }
+        }
+
+        #endregion
+
+        #region MemberInfo Overrides
+        public override String Name
+        {
+            get
+            {
+                if (m_name == null)
+                    m_name = RuntimeFieldHandle.GetName(this);
+
+                return m_name;
+            }
+        }
+
+        internal String FullName
+        {
+            get
+            {
+                return String.Format("{0}.{1}", DeclaringType.FullName, Name);
+            }
+        }
+
+        public override int MetadataToken
+        {
+            get { return RuntimeFieldHandle.GetToken(this); }
+        }
+
+        internal override RuntimeModule GetRuntimeModule()
+        {
+            return RuntimeTypeHandle.GetModule(RuntimeFieldHandle.GetApproxDeclaringType(this));
+        }
+
+        #endregion
+
+        #region FieldInfo Overrides        
+        public override Object GetValue(Object obj)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return InternalGetValue(obj, ref stackMark);
+        }
+
+        public override object GetRawConstantValue() { throw new InvalidOperationException(); }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public override Object GetValueDirect(TypedReference obj)
+        {
+            if (obj.IsNull)
+                throw new ArgumentException(SR.Arg_TypedReference_Null);
+
+            unsafe
+            {
+                // Passing TypedReference by reference is easier to make correct in native code
+                return RuntimeFieldHandle.GetValueDirect(this, (RuntimeType)FieldType, &obj, (RuntimeType)DeclaringType);
+            }
+        }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public override void SetValue(Object obj, Object value, BindingFlags invokeAttr, Binder binder, CultureInfo culture)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            InternalSetValue(obj, value, invokeAttr, binder, culture, ref stackMark);
+        }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public override void SetValueDirect(TypedReference obj, Object value)
+        {
+            if (obj.IsNull)
+                throw new ArgumentException(SR.Arg_TypedReference_Null);
+
+            unsafe
+            {
+                // Passing TypedReference by reference is easier to make correct in native code
+                RuntimeFieldHandle.SetValueDirect(this, (RuntimeType)FieldType, &obj, value, (RuntimeType)DeclaringType);
+            }
+        }
+
+        public override RuntimeFieldHandle FieldHandle
+        {
+            get
+            {
+                Type declaringType = DeclaringType;
+                if ((declaringType == null && Module.Assembly.ReflectionOnly) || declaringType is ReflectionOnlyType)
+                    throw new InvalidOperationException(SR.InvalidOperation_NotAllowedInReflectionOnly);
+                return new RuntimeFieldHandle(this);
+            }
+        }
+
+        internal IntPtr GetFieldHandle()
+        {
+            return m_fieldHandle;
+        }
+
+        public override FieldAttributes Attributes
+        {
+            get
+            {
+                return m_fieldAttributes;
+            }
+        }
+
+        public override Type FieldType
+        {
+            get
+            {
+                if (m_fieldType == null)
+                    m_fieldType = new Signature(this, m_declaringType).FieldType;
+
+                return m_fieldType;
+            }
+        }
+
+        public override Type[] GetRequiredCustomModifiers()
+        {
+            return new Signature(this, m_declaringType).GetCustomModifiers(1, true);
+        }
+
+        public override Type[] GetOptionalCustomModifiers()
+        {
+            return new Signature(this, m_declaringType).GetCustomModifiers(1, false);
+        }
+
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs b/src/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs
new file mode 100644
index 0000000000..17910e192d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs
@@ -0,0 +1,851 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using CultureInfo = System.Globalization.CultureInfo;
+using System.Security;
+using System.IO;
+using StringBuilder = System.Text.StringBuilder;
+using System.Configuration.Assemblies;
+using StackCrawlMark = System.Threading.StackCrawlMark;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Runtime.Serialization;
+using System.Threading;
+
+namespace System.Reflection
+{
+    internal class RuntimeAssembly : Assembly
+    {
+        internal RuntimeAssembly() { throw new NotSupportedException(); }
+
+        #region private data members
+        private event ModuleResolveEventHandler _ModuleResolve;
+        private string m_fullname;
+        private object m_syncRoot;   // Used to keep collectible types alive and as the syncroot for reflection.emit
+        private IntPtr m_assembly;    // slack for ptr datum on unmanaged side
+
+        #endregion
+
+        internal object SyncRoot
+        {
+            get
+            {
+                if (m_syncRoot == null)
+                {
+                    Interlocked.CompareExchange<object>(ref m_syncRoot, new object(), null);
+                }
+                return m_syncRoot;
+            }
+        }
+
+        public override event ModuleResolveEventHandler ModuleResolve
+        {
+            add
+            {
+                _ModuleResolve += value;
+            }
+            remove
+            {
+                _ModuleResolve -= value;
+            }
+        }
+
+        private const String s_localFilePrefix = "file:";
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetCodeBase(RuntimeAssembly assembly,
+                                               bool copiedName,
+                                               StringHandleOnStack retString);
+
+        internal String GetCodeBase(bool copiedName)
+        {
+            String codeBase = null;
+            GetCodeBase(GetNativeHandle(), copiedName, JitHelpers.GetStringHandleOnStack(ref codeBase));
+            return codeBase;
+        }
+
+        public override String CodeBase
+        {
+            get
+            {
+                String codeBase = GetCodeBase(false);
+                return codeBase;
+            }
+        }
+
+        internal RuntimeAssembly GetNativeHandle()
+        {
+            return this;
+        }
+
+        // If the assembly is copied before it is loaded, the codebase will be set to the
+        // actual file loaded if copiedName is true. If it is false, then the original code base
+        // is returned.
+        public override AssemblyName GetName(bool copiedName)
+        {
+            AssemblyName an = new AssemblyName();
+
+            String codeBase = GetCodeBase(copiedName);
+
+            an.Init(GetSimpleName(),
+                    GetPublicKey(),
+                    null, // public key token
+                    GetVersion(),
+                    GetLocale(),
+                    GetHashAlgorithm(),
+                    AssemblyVersionCompatibility.SameMachine,
+                    codeBase,
+                    GetFlags() | AssemblyNameFlags.PublicKey,
+                    null); // strong name key pair
+
+            PortableExecutableKinds pek;
+            ImageFileMachine ifm;
+
+            Module manifestModule = ManifestModule;
+            if (manifestModule != null)
+            {
+                if (manifestModule.MDStreamVersion > 0x10000)
+                {
+                    ManifestModule.GetPEKind(out pek, out ifm);
+                    an.SetProcArchIndex(pek, ifm);
+                }
+            }
+            return an;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetFullName(RuntimeAssembly assembly, StringHandleOnStack retString);
+
+        public override String FullName
+        {
+            get
+            {
+                // If called by Object.ToString(), return val may be NULL.
+                if (m_fullname == null)
+                {
+                    string s = null;
+                    GetFullName(GetNativeHandle(), JitHelpers.GetStringHandleOnStack(ref s));
+                    Interlocked.CompareExchange<string>(ref m_fullname, s, null);
+                }
+
+                return m_fullname;
+            }
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetEntryPoint(RuntimeAssembly assembly, ObjectHandleOnStack retMethod);
+
+        public override MethodInfo EntryPoint
+        {
+            get
+            {
+                IRuntimeMethodInfo methodHandle = null;
+                GetEntryPoint(GetNativeHandle(), JitHelpers.GetObjectHandleOnStack(ref methodHandle));
+
+                if (methodHandle == null)
+                    return null;
+
+                return (MethodInfo)RuntimeType.GetMethodBase(methodHandle);
+            }
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetType(RuntimeAssembly assembly,
+                                                        String name,
+                                                        bool throwOnError,
+                                                        bool ignoreCase,
+                                                        ObjectHandleOnStack type,
+                                                        ObjectHandleOnStack keepAlive);
+
+        public override Type GetType(String name, bool throwOnError, bool ignoreCase)
+        {
+            // throw on null strings regardless of the value of "throwOnError"
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            RuntimeType type = null;
+            Object keepAlive = null;
+            GetType(GetNativeHandle(), name, throwOnError, ignoreCase, JitHelpers.GetObjectHandleOnStack(ref type), JitHelpers.GetObjectHandleOnStack(ref keepAlive));
+            GC.KeepAlive(keepAlive);
+
+            return type;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetExportedTypes(RuntimeAssembly assembly, ObjectHandleOnStack retTypes);
+
+        public override Type[] GetExportedTypes()
+        {
+            Type[] types = null;
+            GetExportedTypes(GetNativeHandle(), JitHelpers.GetObjectHandleOnStack(ref types));
+            return types;
+        }
+
+        public override IEnumerable<TypeInfo> DefinedTypes
+        {
+            get
+            {
+                List<RuntimeType> rtTypes = new List<RuntimeType>();
+
+                RuntimeModule[] modules = GetModulesInternal(true, false);
+
+                for (int i = 0; i < modules.Length; i++)
+                {
+                    rtTypes.AddRange(modules[i].GetDefinedTypes());
+                }
+
+                return rtTypes.ToArray();
+            }
+        }
+
+        // Load a resource based on the NameSpace of the type.
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public override Stream GetManifestResourceStream(Type type, String name)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return GetManifestResourceStream(type, name, false, ref stackMark);
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public override Stream GetManifestResourceStream(String name)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return GetManifestResourceStream(name, ref stackMark, false);
+        }
+
+        // ISerializable implementation
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            throw new PlatformNotSupportedException();
+        }
+
+        public override Module ManifestModule
+        {
+            get
+            {
+                // We don't need to return the "external" ModuleBuilder because
+                // it is meant to be read-only
+                return RuntimeAssembly.GetManifestModule(GetNativeHandle());
+            }
+        }
+
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            return CustomAttribute.GetCustomAttributes(this, typeof(object) as RuntimeType);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.GetCustomAttributes(this, attributeRuntimeType);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.IsDefined(this, attributeRuntimeType);
+        }
+
+        public override IList<CustomAttributeData> GetCustomAttributesData()
+        {
+            return CustomAttributeData.GetCustomAttributesInternal(this);
+        }
+
+        // Wrapper function to wrap the typical use of InternalLoad.
+        internal static RuntimeAssembly InternalLoad(String assemblyString,
+                                                     ref StackCrawlMark stackMark)
+        {
+            return InternalLoad(assemblyString, ref stackMark, IntPtr.Zero);
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        internal static RuntimeAssembly InternalLoad(String assemblyString,
+                                                     ref StackCrawlMark stackMark,
+                                                     IntPtr pPrivHostBinder)
+        {
+            RuntimeAssembly assembly;
+            AssemblyName an = CreateAssemblyName(assemblyString, out assembly);
+
+            if (assembly != null)
+            {
+                // The assembly was returned from ResolveAssemblyEvent
+                return assembly;
+            }
+
+            return InternalLoadAssemblyName(an, null, ref stackMark,
+                                            pPrivHostBinder,
+                                            true  /*thrownOnFileNotFound*/);
+        }
+
+        // Creates AssemblyName. Fills assembly if AssemblyResolve event has been raised.
+        internal static AssemblyName CreateAssemblyName(
+            String assemblyString,
+            out RuntimeAssembly assemblyFromResolveEvent)
+        {
+            if (assemblyString == null)
+                throw new ArgumentNullException(nameof(assemblyString));
+
+            if ((assemblyString.Length == 0) ||
+                (assemblyString[0] == '\0'))
+                throw new ArgumentException(SR.Format_StringZeroLength);
+
+            AssemblyName an = new AssemblyName();
+
+            an.Name = assemblyString;
+            an.nInit(out assemblyFromResolveEvent, true);
+
+            return an;
+        }
+
+        // Wrapper function to wrap the typical use of InternalLoadAssemblyName.
+        internal static RuntimeAssembly InternalLoadAssemblyName(
+            AssemblyName assemblyRef,
+            RuntimeAssembly reqAssembly,
+            ref StackCrawlMark stackMark,
+            bool throwOnFileNotFound,
+            IntPtr ptrLoadContextBinder = default(IntPtr))
+        {
+            return InternalLoadAssemblyName(assemblyRef, reqAssembly, ref stackMark, IntPtr.Zero, true /*throwOnError*/, ptrLoadContextBinder);
+        }
+
+        internal static RuntimeAssembly InternalLoadAssemblyName(
+            AssemblyName assemblyRef,
+            RuntimeAssembly reqAssembly,
+            ref StackCrawlMark stackMark,
+            IntPtr pPrivHostBinder,
+            bool throwOnFileNotFound,
+            IntPtr ptrLoadContextBinder = default(IntPtr))
+        {
+            if (assemblyRef == null)
+                throw new ArgumentNullException(nameof(assemblyRef));
+
+            if (assemblyRef.CodeBase != null)
+            {
+                AppDomain.CheckLoadFromSupported();
+            }
+
+            assemblyRef = (AssemblyName)assemblyRef.Clone();
+            if (assemblyRef.ProcessorArchitecture != ProcessorArchitecture.None)
+            {
+                // PA does not have a semantics for by-name binds for execution
+                assemblyRef.ProcessorArchitecture = ProcessorArchitecture.None;
+            }
+
+            String codeBase = VerifyCodeBase(assemblyRef.CodeBase);
+
+            return nLoad(assemblyRef, codeBase, reqAssembly, ref stackMark,
+                pPrivHostBinder,
+                throwOnFileNotFound, ptrLoadContextBinder);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern RuntimeAssembly nLoad(AssemblyName fileName,
+                                                    String codeBase,
+                                                    RuntimeAssembly locationHint,
+                                                    ref StackCrawlMark stackMark,
+                                                    IntPtr pPrivHostBinder,
+                                                    bool throwOnFileNotFound,
+                                                    IntPtr ptrLoadContextBinder = default(IntPtr));
+
+        public override bool ReflectionOnly
+        {
+            get
+            {
+                return false;
+            }
+        }
+
+        // Returns the module in this assembly with name 'name'
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetModule(RuntimeAssembly assembly, String name, ObjectHandleOnStack retModule);
+
+        public override Module GetModule(String name)
+        {
+            Module retModule = null;
+            GetModule(GetNativeHandle(), name, JitHelpers.GetObjectHandleOnStack(ref retModule));
+            return retModule;
+        }
+
+        // Returns the file in the File table of the manifest that matches the
+        // given name.  (Name should not include path.)
+        public override FileStream GetFile(String name)
+        {
+            RuntimeModule m = (RuntimeModule)GetModule(name);
+            if (m == null)
+                return null;
+
+            return new FileStream(m.GetFullyQualifiedName(),
+                                  FileMode.Open,
+                                  FileAccess.Read, FileShare.Read, FileStream.DefaultBufferSize, false);
+        }
+
+        public override FileStream[] GetFiles(bool getResourceModules)
+        {
+            Module[] m = GetModules(getResourceModules);
+            FileStream[] fs = new FileStream[m.Length];
+
+            for (int i = 0; i < fs.Length; i++)
+            {
+                fs[i] = new FileStream(((RuntimeModule)m[i]).GetFullyQualifiedName(),
+                                       FileMode.Open,
+                                       FileAccess.Read, FileShare.Read, FileStream.DefaultBufferSize, false);
+            }
+
+            return fs;
+        }
+
+        // Returns the names of all the resources
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern String[] GetManifestResourceNames(RuntimeAssembly assembly);
+
+        // Returns the names of all the resources
+        public override String[] GetManifestResourceNames()
+        {
+            return GetManifestResourceNames(GetNativeHandle());
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetExecutingAssembly(StackCrawlMarkHandle stackMark, ObjectHandleOnStack retAssembly);
+
+        internal static RuntimeAssembly GetExecutingAssembly(ref StackCrawlMark stackMark)
+        {
+            RuntimeAssembly retAssembly = null;
+            GetExecutingAssembly(JitHelpers.GetStackCrawlMarkHandle(ref stackMark), JitHelpers.GetObjectHandleOnStack(ref retAssembly));
+            return retAssembly;
+        }
+
+        // Returns the names of all the resources
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern AssemblyName[] GetReferencedAssemblies(RuntimeAssembly assembly);
+
+        public override AssemblyName[] GetReferencedAssemblies()
+        {
+            return GetReferencedAssemblies(GetNativeHandle());
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern int GetManifestResourceInfo(RuntimeAssembly assembly,
+                                                          String resourceName,
+                                                          ObjectHandleOnStack assemblyRef,
+                                                          StringHandleOnStack retFileName,
+                                                          StackCrawlMarkHandle stackMark);
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public override ManifestResourceInfo GetManifestResourceInfo(String resourceName)
+        {
+            RuntimeAssembly retAssembly = null;
+            String fileName = null;
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            int location = GetManifestResourceInfo(GetNativeHandle(), resourceName,
+                                                   JitHelpers.GetObjectHandleOnStack(ref retAssembly),
+                                                   JitHelpers.GetStringHandleOnStack(ref fileName),
+                                                   JitHelpers.GetStackCrawlMarkHandle(ref stackMark));
+
+            if (location == -1)
+                return null;
+
+            return new ManifestResourceInfo(retAssembly, fileName,
+                                                (ResourceLocation)location);
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetLocation(RuntimeAssembly assembly, StringHandleOnStack retString);
+
+        public override String Location
+        {
+            get
+            {
+                String location = null;
+
+                GetLocation(GetNativeHandle(), JitHelpers.GetStringHandleOnStack(ref location));
+
+                return location;
+            }
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetImageRuntimeVersion(RuntimeAssembly assembly, StringHandleOnStack retString);
+
+        public override String ImageRuntimeVersion
+        {
+            get
+            {
+                String s = null;
+                GetImageRuntimeVersion(GetNativeHandle(), JitHelpers.GetStringHandleOnStack(ref s));
+                return s;
+            }
+        }
+
+        public override bool GlobalAssemblyCache
+        {
+            get
+            {
+                return false;
+            }
+        }
+
+        public override Int64 HostContext
+        {
+            get
+            {
+                return 0;
+            }
+        }
+
+        private static String VerifyCodeBase(String codebase)
+        {
+            if (codebase == null)
+                return null;
+
+            int len = codebase.Length;
+            if (len == 0)
+                return null;
+
+
+            int j = codebase.IndexOf(':');
+            // Check to see if the url has a prefix
+            if ((j != -1) &&
+                (j + 2 < len) &&
+                ((codebase[j + 1] == '/') || (codebase[j + 1] == '\\')) &&
+                ((codebase[j + 2] == '/') || (codebase[j + 2] == '\\')))
+                return codebase;
+#if PLATFORM_WINDOWS
+            else if ((len > 2) && (codebase[0] == '\\') && (codebase[1] == '\\'))
+                return "file://" + codebase;
+            else
+                return "file:///" + Path.GetFullPath(codebase);
+#else
+            else
+                return "file://" + Path.GetFullPath(codebase);
+#endif // PLATFORM_WINDOWS
+        }
+
+        internal Stream GetManifestResourceStream(
+            Type type,
+            String name,
+            bool skipSecurityCheck,
+            ref StackCrawlMark stackMark)
+        {
+            StringBuilder sb = new StringBuilder();
+            if (type == null)
+            {
+                if (name == null)
+                    throw new ArgumentNullException(nameof(type));
+            }
+            else
+            {
+                String nameSpace = type.Namespace;
+                if (nameSpace != null)
+                {
+                    sb.Append(nameSpace);
+                    if (name != null)
+                        sb.Append(Type.Delimiter);
+                }
+            }
+
+            if (name != null)
+                sb.Append(name);
+
+            return GetManifestResourceStream(sb.ToString(), ref stackMark, skipSecurityCheck);
+        }
+
+        // GetResource will return a pointer to the resources in memory.
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern unsafe byte* GetResource(RuntimeAssembly assembly,
+                                                       String resourceName,
+                                                       out ulong length,
+                                                       StackCrawlMarkHandle stackMark,
+                                                       bool skipSecurityCheck);
+
+        internal unsafe Stream GetManifestResourceStream(String name, ref StackCrawlMark stackMark, bool skipSecurityCheck)
+        {
+            ulong length = 0;
+            byte* pbInMemoryResource = GetResource(GetNativeHandle(), name, out length, JitHelpers.GetStackCrawlMarkHandle(ref stackMark), skipSecurityCheck);
+
+            if (pbInMemoryResource != null)
+            {
+                //Console.WriteLine("Creating an unmanaged memory stream of length "+length);
+                if (length > Int64.MaxValue)
+                    throw new NotImplementedException(SR.NotImplemented_ResourcesLongerThanInt64Max);
+
+                return new UnmanagedMemoryStream(pbInMemoryResource, (long)length, (long)length, FileAccess.Read);
+            }
+
+            //Console.WriteLine("GetManifestResourceStream: Blob "+name+" not found...");
+            return null;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetVersion(RuntimeAssembly assembly,
+                                              out int majVer,
+                                              out int minVer,
+                                              out int buildNum,
+                                              out int revNum);
+
+        internal Version GetVersion()
+        {
+            int majorVer, minorVer, build, revision;
+            GetVersion(GetNativeHandle(), out majorVer, out minorVer, out build, out revision);
+            return new Version(majorVer, minorVer, build, revision);
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetLocale(RuntimeAssembly assembly, StringHandleOnStack retString);
+
+        internal CultureInfo GetLocale()
+        {
+            String locale = null;
+
+            GetLocale(GetNativeHandle(), JitHelpers.GetStringHandleOnStack(ref locale));
+
+            if (locale == null)
+                return CultureInfo.InvariantCulture;
+
+            return new CultureInfo(locale);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool FCallIsDynamic(RuntimeAssembly assembly);
+
+        public override bool IsDynamic
+        {
+            get
+            {
+                return FCallIsDynamic(GetNativeHandle());
+            }
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetSimpleName(RuntimeAssembly assembly, StringHandleOnStack retSimpleName);
+
+        internal String GetSimpleName()
+        {
+            string name = null;
+            GetSimpleName(GetNativeHandle(), JitHelpers.GetStringHandleOnStack(ref name));
+            return name;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern AssemblyHashAlgorithm GetHashAlgorithm(RuntimeAssembly assembly);
+
+        private AssemblyHashAlgorithm GetHashAlgorithm()
+        {
+            return GetHashAlgorithm(GetNativeHandle());
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern AssemblyNameFlags GetFlags(RuntimeAssembly assembly);
+
+        private AssemblyNameFlags GetFlags()
+        {
+            return GetFlags(GetNativeHandle());
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetPublicKey(RuntimeAssembly assembly, ObjectHandleOnStack retPublicKey);
+
+        internal byte[] GetPublicKey()
+        {
+            byte[] publicKey = null;
+            GetPublicKey(GetNativeHandle(), JitHelpers.GetObjectHandleOnStack(ref publicKey));
+            return publicKey;
+        }
+
+        // This method is called by the VM.
+        private RuntimeModule OnModuleResolveEvent(String moduleName)
+        {
+            ModuleResolveEventHandler moduleResolve = _ModuleResolve;
+            if (moduleResolve == null)
+                return null;
+
+            foreach (ModuleResolveEventHandler handler in moduleResolve.GetInvocationList())
+            {
+                RuntimeModule ret = (RuntimeModule)handler(this, new ResolveEventArgs(moduleName, this));
+                if (ret != null)
+                    return ret;
+            }
+
+            return null;
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod  
+        public override Assembly GetSatelliteAssembly(CultureInfo culture)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return InternalGetSatelliteAssembly(culture, null, ref stackMark);
+        }
+
+        // Useful for binding to a very specific version of a satellite assembly
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod  
+        public override Assembly GetSatelliteAssembly(CultureInfo culture, Version version)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return InternalGetSatelliteAssembly(culture, version, ref stackMark);
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod  
+        internal Assembly InternalGetSatelliteAssembly(CultureInfo culture,
+                                                       Version version,
+                                                       ref StackCrawlMark stackMark)
+        {
+            if (culture == null)
+                throw new ArgumentNullException(nameof(culture));
+
+
+            String name = GetSimpleName() + ".resources";
+            return InternalGetSatelliteAssembly(name, culture, version, true, ref stackMark);
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod  
+        internal RuntimeAssembly InternalGetSatelliteAssembly(String name,
+                                                              CultureInfo culture,
+                                                              Version version,
+                                                              bool throwOnFileNotFound,
+                                                              ref StackCrawlMark stackMark)
+        {
+            AssemblyName an = new AssemblyName();
+
+            an.SetPublicKey(GetPublicKey());
+            an.Flags = GetFlags() | AssemblyNameFlags.PublicKey;
+
+            if (version == null)
+                an.Version = GetVersion();
+            else
+                an.Version = version;
+
+            an.CultureInfo = culture;
+            an.Name = name;
+
+            RuntimeAssembly retAssembly = nLoad(an, null, this, ref stackMark,
+                                IntPtr.Zero,
+                                throwOnFileNotFound);
+
+            if (retAssembly == this || (retAssembly == null && throwOnFileNotFound))
+            {
+                throw new FileNotFoundException(String.Format(culture, SR.IO_FileNotFound_FileName, an.Name));
+            }
+
+            return retAssembly;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetModules(RuntimeAssembly assembly,
+                                              bool loadIfNotFound,
+                                              bool getResourceModules,
+                                              ObjectHandleOnStack retModuleHandles);
+
+        private RuntimeModule[] GetModulesInternal(bool loadIfNotFound,
+                                     bool getResourceModules)
+        {
+            RuntimeModule[] modules = null;
+            GetModules(GetNativeHandle(), loadIfNotFound, getResourceModules, JitHelpers.GetObjectHandleOnStack(ref modules));
+            return modules;
+        }
+
+        public override Module[] GetModules(bool getResourceModules)
+        {
+            return GetModulesInternal(true, getResourceModules);
+        }
+
+        public override Module[] GetLoadedModules(bool getResourceModules)
+        {
+            return GetModulesInternal(false, getResourceModules);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern RuntimeModule GetManifestModule(RuntimeAssembly assembly);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int GetToken(RuntimeAssembly assembly);
+
+        public sealed override Type[] GetForwardedTypes()
+        {
+            List<Type> types = new List<Type>();
+            List<Exception> exceptions = new List<Exception>();
+
+            MetadataImport scope = GetManifestModule(GetNativeHandle()).MetadataImport;
+            scope.Enum(MetadataTokenType.ExportedType, 0, out MetadataEnumResult enumResult);
+            for (int i = 0; i < enumResult.Length; i++)
+            {
+                MetadataToken mdtExternalType = enumResult[i];
+                Type type = null;
+                Exception exception = null;
+                ObjectHandleOnStack pType = JitHelpers.GetObjectHandleOnStack(ref type);
+                try
+                {
+                    GetForwardedType(this, mdtExternalType, pType);
+                    if (type == null)
+                        continue;  // mdtExternalType was not a forwarder entry.
+                }
+                catch (Exception e)
+                {
+                    type = null;
+                    exception = e;
+                }
+
+                Debug.Assert((type != null) != (exception != null)); // Exactly one of these must be non-null.
+
+                if (type != null)
+                {
+                    types.Add(type);
+                    AddPublicNestedTypes(type, types, exceptions);
+                }
+                else
+                {
+                    exceptions.Add(exception);
+                }
+            }
+
+            if (exceptions.Count != 0)
+            {
+                int numTypes = types.Count;
+                int numExceptions = exceptions.Count;
+                types.AddRange(new Type[numExceptions]); // add one null Type for each exception.
+                exceptions.InsertRange(0, new Exception[numTypes]); // align the Exceptions with the null Types.
+                throw new ReflectionTypeLoadException(types.ToArray(), exceptions.ToArray());
+            }
+
+            return types.ToArray();
+        }
+
+        private static void AddPublicNestedTypes(Type type, List<Type> types, List<Exception> exceptions)
+        {
+            Type[] nestedTypes;
+            try
+            {
+                nestedTypes = type.GetNestedTypes(BindingFlags.Public);
+            }
+            catch (Exception e)
+            {
+                exceptions.Add(e);
+                return;
+            }
+            foreach (Type nestedType in nestedTypes)
+            {
+                types.Add(nestedType);
+                AddPublicNestedTypes(nestedType, types, exceptions);
+            }
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetForwardedType(RuntimeAssembly assembly, MetadataToken mdtExternalType, ObjectHandleOnStack type);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/RuntimeConstructorInfo.cs b/src/System.Private.CoreLib/src/System/Reflection/RuntimeConstructorInfo.cs
new file mode 100644
index 0000000000..ad9a1a43cc
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/RuntimeConstructorInfo.cs
@@ -0,0 +1,442 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using RuntimeTypeCache = System.RuntimeType.RuntimeTypeCache;
+
+namespace System.Reflection
+{
+    internal sealed class RuntimeConstructorInfo : ConstructorInfo, IRuntimeMethodInfo
+    {
+        #region Private Data Members
+        private volatile RuntimeType m_declaringType;
+        private RuntimeTypeCache m_reflectedTypeCache;
+        private string m_toString;
+        private ParameterInfo[] m_parameters = null; // Created lazily when GetParameters() is called.
+#pragma warning disable 169
+        private object _empty1; // These empties are used to ensure that RuntimeConstructorInfo and RuntimeMethodInfo are have a layout which is sufficiently similar
+        private object _empty2;
+        private object _empty3;
+#pragma warning restore 169
+        private IntPtr m_handle;
+        private MethodAttributes m_methodAttributes;
+        private BindingFlags m_bindingFlags;
+        private volatile Signature m_signature;
+        private INVOCATION_FLAGS m_invocationFlags;
+
+        internal INVOCATION_FLAGS InvocationFlags
+        {
+            get
+            {
+                if ((m_invocationFlags & INVOCATION_FLAGS.INVOCATION_FLAGS_INITIALIZED) == 0)
+                {
+                    INVOCATION_FLAGS invocationFlags = INVOCATION_FLAGS.INVOCATION_FLAGS_IS_CTOR; // this is a given
+
+                    Type declaringType = DeclaringType;
+
+                    //
+                    // first take care of all the NO_INVOKE cases. 
+                    if (declaringType == typeof(void) ||
+                         (declaringType != null && declaringType.ContainsGenericParameters) ||
+                         ((CallingConvention & CallingConventions.VarArgs) == CallingConventions.VarArgs))
+                    {
+                        // We don't need other flags if this method cannot be invoked
+                        invocationFlags |= INVOCATION_FLAGS.INVOCATION_FLAGS_NO_INVOKE;
+                    }
+                    else if (IsStatic || declaringType != null && declaringType.IsAbstract)
+                    {
+                        invocationFlags |= INVOCATION_FLAGS.INVOCATION_FLAGS_NO_CTOR_INVOKE;
+                    }
+                    else
+                    {
+                        // Check for byref-like types
+                        if (declaringType != null && declaringType.IsByRefLike)
+                            invocationFlags |= INVOCATION_FLAGS.INVOCATION_FLAGS_CONTAINS_STACK_POINTERS;
+
+                        // Check for attempt to create a delegate class.
+                        if (typeof(Delegate).IsAssignableFrom(DeclaringType))
+                            invocationFlags |= INVOCATION_FLAGS.INVOCATION_FLAGS_IS_DELEGATE_CTOR;
+                    }
+
+                    m_invocationFlags = invocationFlags | INVOCATION_FLAGS.INVOCATION_FLAGS_INITIALIZED;
+                }
+
+                return m_invocationFlags;
+            }
+        }
+        #endregion
+
+        #region Constructor
+        internal RuntimeConstructorInfo(
+            RuntimeMethodHandleInternal handle, RuntimeType declaringType, RuntimeTypeCache reflectedTypeCache,
+            MethodAttributes methodAttributes, BindingFlags bindingFlags)
+        {
+            m_bindingFlags = bindingFlags;
+            m_reflectedTypeCache = reflectedTypeCache;
+            m_declaringType = declaringType;
+            m_handle = handle.Value;
+            m_methodAttributes = methodAttributes;
+        }
+        #endregion
+
+        #region NonPublic Methods
+        RuntimeMethodHandleInternal IRuntimeMethodInfo.Value
+        {
+            get
+            {
+                return new RuntimeMethodHandleInternal(m_handle);
+            }
+        }
+
+        internal override bool CacheEquals(object o)
+        {
+            RuntimeConstructorInfo m = o as RuntimeConstructorInfo;
+
+            if ((object)m == null)
+                return false;
+
+            return m.m_handle == m_handle;
+        }
+
+        private Signature Signature
+        {
+            get
+            {
+                if (m_signature == null)
+                    m_signature = new Signature(this, m_declaringType);
+
+                return m_signature;
+            }
+        }
+
+        private RuntimeType ReflectedTypeInternal
+        {
+            get
+            {
+                return m_reflectedTypeCache.GetRuntimeType();
+            }
+        }
+
+        private void CheckConsistency(Object target)
+        {
+            if (target == null && IsStatic)
+                return;
+
+            if (!m_declaringType.IsInstanceOfType(target))
+            {
+                if (target == null)
+                    throw new TargetException(SR.RFLCT_Targ_StatMethReqTarg);
+
+                throw new TargetException(SR.RFLCT_Targ_ITargMismatch);
+            }
+        }
+
+        internal BindingFlags BindingFlags { get { return m_bindingFlags; } }
+        #endregion
+
+        #region Object Overrides
+        public override String ToString()
+        {
+            // "Void" really doesn't make sense here. But we'll keep it for compat reasons.
+            if (m_toString == null)
+                m_toString = "Void " + FormatNameAndSig();
+
+            return m_toString;
+        }
+        #endregion
+
+        #region ICustomAttributeProvider
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            return CustomAttribute.GetCustomAttributes(this, typeof(object) as RuntimeType);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.GetCustomAttributes(this, attributeRuntimeType);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.IsDefined(this, attributeRuntimeType);
+        }
+
+        public override IList<CustomAttributeData> GetCustomAttributesData()
+        {
+            return CustomAttributeData.GetCustomAttributesInternal(this);
+        }
+        #endregion
+
+
+        #region MemberInfo Overrides
+        public override String Name
+        {
+            get { return RuntimeMethodHandle.GetName(this); }
+        }
+        public override MemberTypes MemberType { get { return MemberTypes.Constructor; } }
+
+        public override Type DeclaringType
+        {
+            get
+            {
+                return m_reflectedTypeCache.IsGlobal ? null : m_declaringType;
+            }
+        }
+
+        public sealed override bool HasSameMetadataDefinitionAs(MemberInfo other) => HasSameMetadataDefinitionAsCore<RuntimeConstructorInfo>(other);
+
+        public override Type ReflectedType
+        {
+            get
+            {
+                return m_reflectedTypeCache.IsGlobal ? null : ReflectedTypeInternal;
+            }
+        }
+
+        public override int MetadataToken
+        {
+            get { return RuntimeMethodHandle.GetMethodDef(this); }
+        }
+        public override Module Module
+        {
+            get { return GetRuntimeModule(); }
+        }
+
+        internal RuntimeType GetRuntimeType() { return m_declaringType; }
+        internal RuntimeModule GetRuntimeModule() { return RuntimeTypeHandle.GetModule(m_declaringType); }
+        internal RuntimeAssembly GetRuntimeAssembly() { return GetRuntimeModule().GetRuntimeAssembly(); }
+        #endregion
+
+        #region MethodBase Overrides
+
+        // This seems to always returns System.Void.
+        internal override Type GetReturnType() { return Signature.ReturnType; }
+
+        internal override ParameterInfo[] GetParametersNoCopy()
+        {
+            if (m_parameters == null)
+                m_parameters = RuntimeParameterInfo.GetParameters(this, this, Signature);
+
+            return m_parameters;
+        }
+
+        public override ParameterInfo[] GetParameters()
+        {
+            ParameterInfo[] parameters = GetParametersNoCopy();
+
+            if (parameters.Length == 0)
+                return parameters;
+
+            ParameterInfo[] ret = new ParameterInfo[parameters.Length];
+            Array.Copy(parameters, ret, parameters.Length);
+            return ret;
+        }
+
+        public override MethodImplAttributes GetMethodImplementationFlags()
+        {
+            return RuntimeMethodHandle.GetImplAttributes(this);
+        }
+
+        public override RuntimeMethodHandle MethodHandle
+        {
+            get
+            {
+                Type declaringType = DeclaringType;
+                if ((declaringType == null && Module.Assembly.ReflectionOnly) || declaringType is ReflectionOnlyType)
+                    throw new InvalidOperationException(SR.InvalidOperation_NotAllowedInReflectionOnly);
+                return new RuntimeMethodHandle(this);
+            }
+        }
+
+        public override MethodAttributes Attributes
+        {
+            get
+            {
+                return m_methodAttributes;
+            }
+        }
+
+        public override CallingConventions CallingConvention
+        {
+            get
+            {
+                return Signature.CallingConvention;
+            }
+        }
+
+        internal static void CheckCanCreateInstance(Type declaringType, bool isVarArg)
+        {
+            if (declaringType == null)
+                throw new ArgumentNullException(nameof(declaringType));
+
+            // ctor is ReflectOnly
+            if (declaringType is ReflectionOnlyType)
+                throw new InvalidOperationException(SR.Arg_ReflectionOnlyInvoke);
+
+            // ctor is declared on interface class
+            else if (declaringType.IsInterface)
+                throw new MemberAccessException(
+                    String.Format(CultureInfo.CurrentUICulture, SR.Acc_CreateInterfaceEx, declaringType));
+
+            // ctor is on an abstract class
+            else if (declaringType.IsAbstract)
+                throw new MemberAccessException(
+                    String.Format(CultureInfo.CurrentUICulture, SR.Acc_CreateAbstEx, declaringType));
+
+            // ctor is on a class that contains stack pointers
+            else if (declaringType.GetRootElementType() == typeof(ArgIterator))
+                throw new NotSupportedException();
+
+            // ctor is vararg
+            else if (isVarArg)
+                throw new NotSupportedException();
+
+            // ctor is generic or on a generic class
+            else if (declaringType.ContainsGenericParameters)
+            {
+                throw new MemberAccessException(
+                    String.Format(CultureInfo.CurrentUICulture, SR.Acc_CreateGenericEx, declaringType));
+            }
+
+            // ctor is declared on System.Void
+            else if (declaringType == typeof(void))
+                throw new MemberAccessException(SR.Access_Void);
+        }
+
+        internal void ThrowNoInvokeException()
+        {
+            CheckCanCreateInstance(DeclaringType, (CallingConvention & CallingConventions.VarArgs) == CallingConventions.VarArgs);
+
+            // ctor is .cctor
+            if ((Attributes & MethodAttributes.Static) == MethodAttributes.Static)
+                throw new MemberAccessException(SR.Acc_NotClassInit);
+
+            throw new TargetException();
+        }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public override Object Invoke(
+            Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
+        {
+            INVOCATION_FLAGS invocationFlags = InvocationFlags;
+
+            if ((invocationFlags & INVOCATION_FLAGS.INVOCATION_FLAGS_NO_INVOKE) != 0)
+                ThrowNoInvokeException();
+
+            // check basic method consistency. This call will throw if there are problems in the target/method relationship
+            CheckConsistency(obj);
+
+            Signature sig = Signature;
+
+            // get the signature
+            int formalCount = sig.Arguments.Length;
+            int actualCount = (parameters != null) ? parameters.Length : 0;
+            if (formalCount != actualCount)
+                throw new TargetParameterCountException(SR.Arg_ParmCnt);
+
+            // if we are here we passed all the previous checks. Time to look at the arguments
+            bool wrapExceptions = (invokeAttr & BindingFlags.DoNotWrapExceptions) == 0;
+            if (actualCount > 0)
+            {
+                Object[] arguments = CheckArguments(parameters, binder, invokeAttr, culture, sig);
+                Object retValue = RuntimeMethodHandle.InvokeMethod(obj, arguments, sig, false, wrapExceptions);
+                // copy out. This should be made only if ByRef are present.
+                for (int index = 0; index < arguments.Length; index++)
+                    parameters[index] = arguments[index];
+                return retValue;
+            }
+            return RuntimeMethodHandle.InvokeMethod(obj, null, sig, false, wrapExceptions);
+        }
+
+        public override MethodBody GetMethodBody()
+        {
+            MethodBody mb = RuntimeMethodHandle.GetMethodBody(this, ReflectedTypeInternal);
+            if (mb != null)
+                mb.m_methodBase = this;
+            return mb;
+        }
+
+        public override bool IsSecurityCritical
+        {
+            get { return true; }
+        }
+
+        public override bool IsSecuritySafeCritical
+        {
+            get { return false; }
+        }
+
+        public override bool IsSecurityTransparent
+        {
+            get { return false; }
+        }
+
+        public override bool ContainsGenericParameters
+        {
+            get
+            {
+                return (DeclaringType != null && DeclaringType.ContainsGenericParameters);
+            }
+        }
+        #endregion
+
+        #region ConstructorInfo Overrides
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public override Object Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
+        {
+            INVOCATION_FLAGS invocationFlags = InvocationFlags;
+
+            // get the declaring TypeHandle early for consistent exceptions in IntrospectionOnly context
+            RuntimeTypeHandle declaringTypeHandle = m_declaringType.TypeHandle;
+
+            if ((invocationFlags & (INVOCATION_FLAGS.INVOCATION_FLAGS_NO_INVOKE | INVOCATION_FLAGS.INVOCATION_FLAGS_CONTAINS_STACK_POINTERS | INVOCATION_FLAGS.INVOCATION_FLAGS_NO_CTOR_INVOKE)) != 0)
+                ThrowNoInvokeException();
+
+            // get the signature
+            Signature sig = Signature;
+
+            int formalCount = sig.Arguments.Length;
+            int actualCount = (parameters != null) ? parameters.Length : 0;
+            if (formalCount != actualCount)
+                throw new TargetParameterCountException(SR.Arg_ParmCnt);
+
+            // We don't need to explicitly invoke the class constructor here,
+            // JIT/NGen will insert the call to .cctor in the instance ctor.
+
+            // if we are here we passed all the previous checks. Time to look at the arguments
+            bool wrapExceptions = (invokeAttr & BindingFlags.DoNotWrapExceptions) == 0;
+            if (actualCount > 0)
+            {
+                Object[] arguments = CheckArguments(parameters, binder, invokeAttr, culture, sig);
+                Object retValue = RuntimeMethodHandle.InvokeMethod(null, arguments, sig, true, wrapExceptions);
+                // copy out. This should be made only if ByRef are present.
+                for (int index = 0; index < arguments.Length; index++)
+                    parameters[index] = arguments[index];
+                return retValue;
+            }
+            return RuntimeMethodHandle.InvokeMethod(null, null, sig, true, wrapExceptions);
+        }
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/RuntimeEventInfo.cs b/src/System.Private.CoreLib/src/System/Reflection/RuntimeEventInfo.cs
new file mode 100644
index 0000000000..4152f2bdd6
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/RuntimeEventInfo.cs
@@ -0,0 +1,205 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using RuntimeTypeCache = System.RuntimeType.RuntimeTypeCache;
+
+namespace System.Reflection
+{
+    internal unsafe sealed class RuntimeEventInfo : EventInfo
+    {
+        #region Private Data Members
+        private int m_token;
+        private EventAttributes m_flags;
+        private string m_name;
+        private void* m_utf8name;
+        private RuntimeTypeCache m_reflectedTypeCache;
+        private RuntimeMethodInfo m_addMethod;
+        private RuntimeMethodInfo m_removeMethod;
+        private RuntimeMethodInfo m_raiseMethod;
+        private MethodInfo[] m_otherMethod;
+        private RuntimeType m_declaringType;
+        private BindingFlags m_bindingFlags;
+        #endregion
+
+        #region Constructor
+        internal RuntimeEventInfo()
+        {
+            // Used for dummy head node during population
+        }
+        internal RuntimeEventInfo(int tkEvent, RuntimeType declaredType, RuntimeTypeCache reflectedTypeCache, out bool isPrivate)
+        {
+            Debug.Assert(declaredType != null);
+            Debug.Assert(reflectedTypeCache != null);
+            Debug.Assert(!reflectedTypeCache.IsGlobal);
+
+            MetadataImport scope = declaredType.GetRuntimeModule().MetadataImport;
+
+            m_token = tkEvent;
+            m_reflectedTypeCache = reflectedTypeCache;
+            m_declaringType = declaredType;
+
+
+            RuntimeType reflectedType = reflectedTypeCache.GetRuntimeType();
+
+            scope.GetEventProps(tkEvent, out m_utf8name, out m_flags);
+
+            RuntimeMethodInfo dummy;
+            Associates.AssignAssociates(scope, tkEvent, declaredType, reflectedType,
+                out m_addMethod, out m_removeMethod, out m_raiseMethod,
+                out dummy, out dummy, out m_otherMethod, out isPrivate, out m_bindingFlags);
+        }
+        #endregion
+
+        #region Internal Members
+        internal override bool CacheEquals(object o)
+        {
+            RuntimeEventInfo m = o as RuntimeEventInfo;
+
+            if ((object)m == null)
+                return false;
+
+            return m.m_token == m_token &&
+                RuntimeTypeHandle.GetModule(m_declaringType).Equals(
+                    RuntimeTypeHandle.GetModule(m.m_declaringType));
+        }
+
+        internal BindingFlags BindingFlags { get { return m_bindingFlags; } }
+        #endregion
+
+        #region Object Overrides
+        public override String ToString()
+        {
+            if (m_addMethod == null || m_addMethod.GetParametersNoCopy().Length == 0)
+                throw new InvalidOperationException(SR.InvalidOperation_NoPublicAddMethod);
+
+            return m_addMethod.GetParametersNoCopy()[0].ParameterType.FormatTypeName() + " " + Name;
+        }
+        #endregion
+
+        #region ICustomAttributeProvider
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            return CustomAttribute.GetCustomAttributes(this, typeof(object) as RuntimeType);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.GetCustomAttributes(this, attributeRuntimeType);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.IsDefined(this, attributeRuntimeType);
+        }
+
+        public override IList<CustomAttributeData> GetCustomAttributesData()
+        {
+            return CustomAttributeData.GetCustomAttributesInternal(this);
+        }
+        #endregion
+
+        #region MemberInfo Overrides
+        public override MemberTypes MemberType { get { return MemberTypes.Event; } }
+        public override String Name
+        {
+            get
+            {
+                if (m_name == null)
+                    m_name = new MdUtf8String(m_utf8name).ToString();
+
+                return m_name;
+            }
+        }
+        public override Type DeclaringType { get { return m_declaringType; } }
+        public sealed override bool HasSameMetadataDefinitionAs(MemberInfo other) => HasSameMetadataDefinitionAsCore<RuntimeEventInfo>(other);
+        public override Type ReflectedType
+        {
+            get
+            {
+                return ReflectedTypeInternal;
+            }
+        }
+
+        private RuntimeType ReflectedTypeInternal
+        {
+            get
+            {
+                return m_reflectedTypeCache.GetRuntimeType();
+            }
+        }
+
+        public override int MetadataToken { get { return m_token; } }
+        public override Module Module { get { return GetRuntimeModule(); } }
+        internal RuntimeModule GetRuntimeModule() { return m_declaringType.GetRuntimeModule(); }
+        #endregion
+
+        #region EventInfo Overrides
+        public override MethodInfo[] GetOtherMethods(bool nonPublic)
+        {
+            List<MethodInfo> ret = new List<MethodInfo>();
+
+            if ((object)m_otherMethod == null)
+                return new MethodInfo[0];
+
+            for (int i = 0; i < m_otherMethod.Length; i++)
+            {
+                if (Associates.IncludeAccessor((MethodInfo)m_otherMethod[i], nonPublic))
+                    ret.Add(m_otherMethod[i]);
+            }
+
+            return ret.ToArray();
+        }
+
+        public override MethodInfo GetAddMethod(bool nonPublic)
+        {
+            if (!Associates.IncludeAccessor(m_addMethod, nonPublic))
+                return null;
+
+            return m_addMethod;
+        }
+
+        public override MethodInfo GetRemoveMethod(bool nonPublic)
+        {
+            if (!Associates.IncludeAccessor(m_removeMethod, nonPublic))
+                return null;
+
+            return m_removeMethod;
+        }
+
+        public override MethodInfo GetRaiseMethod(bool nonPublic)
+        {
+            if (!Associates.IncludeAccessor(m_raiseMethod, nonPublic))
+                return null;
+
+            return m_raiseMethod;
+        }
+
+        public override EventAttributes Attributes
+        {
+            get
+            {
+                return m_flags;
+            }
+        }
+        #endregion    
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/RuntimeFieldInfo.cs b/src/System.Private.CoreLib/src/System/Reflection/RuntimeFieldInfo.cs
new file mode 100644
index 0000000000..56f89e618f
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/RuntimeFieldInfo.cs
@@ -0,0 +1,122 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using RuntimeTypeCache = System.RuntimeType.RuntimeTypeCache;
+
+namespace System.Reflection
+{
+    internal abstract class RuntimeFieldInfo : FieldInfo
+    {
+        #region Private Data Members
+        private BindingFlags m_bindingFlags;
+        protected RuntimeTypeCache m_reflectedTypeCache;
+        protected RuntimeType m_declaringType;
+        #endregion
+
+        #region Constructor
+        protected RuntimeFieldInfo()
+        {
+            // Used for dummy head node during population
+        }
+        protected RuntimeFieldInfo(RuntimeTypeCache reflectedTypeCache, RuntimeType declaringType, BindingFlags bindingFlags)
+        {
+            m_bindingFlags = bindingFlags;
+            m_declaringType = declaringType;
+            m_reflectedTypeCache = reflectedTypeCache;
+        }
+        #endregion
+
+        #region NonPublic Members
+        internal BindingFlags BindingFlags { get { return m_bindingFlags; } }
+        private RuntimeType ReflectedTypeInternal
+        {
+            get
+            {
+                return m_reflectedTypeCache.GetRuntimeType();
+            }
+        }
+
+        internal RuntimeType GetDeclaringTypeInternal()
+        {
+            return m_declaringType;
+        }
+
+        internal RuntimeType GetRuntimeType() { return m_declaringType; }
+        internal abstract RuntimeModule GetRuntimeModule();
+        #endregion
+
+        #region MemberInfo Overrides
+        public override MemberTypes MemberType { get { return MemberTypes.Field; } }
+        public override Type ReflectedType
+        {
+            get
+            {
+                return m_reflectedTypeCache.IsGlobal ? null : ReflectedTypeInternal;
+            }
+        }
+
+        public override Type DeclaringType
+        {
+            get
+            {
+                return m_reflectedTypeCache.IsGlobal ? null : m_declaringType;
+            }
+        }
+
+        public sealed override bool HasSameMetadataDefinitionAs(MemberInfo other) => HasSameMetadataDefinitionAsCore<RuntimeFieldInfo>(other);
+
+        public override Module Module { get { return GetRuntimeModule(); } }
+        #endregion
+
+        #region Object Overrides
+        public unsafe override String ToString()
+        {
+            return FieldType.FormatTypeName() + " " + Name;
+        }
+        #endregion
+
+        #region ICustomAttributeProvider
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            return CustomAttribute.GetCustomAttributes(this, typeof(object) as RuntimeType);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.GetCustomAttributes(this, attributeRuntimeType);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.IsDefined(this, attributeRuntimeType);
+        }
+
+        public override IList<CustomAttributeData> GetCustomAttributesData()
+        {
+            return CustomAttributeData.GetCustomAttributesInternal(this);
+        }
+        #endregion
+
+        #region FieldInfo Overrides
+        // All implemented on derived classes
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/RuntimeMethodInfo.cs b/src/System.Private.CoreLib/src/System/Reflection/RuntimeMethodInfo.cs
new file mode 100644
index 0000000000..8bebfb3e70
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/RuntimeMethodInfo.cs
@@ -0,0 +1,741 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using System.Security;
+using System.Text;
+using System.Threading;
+using RuntimeTypeCache = System.RuntimeType.RuntimeTypeCache;
+
+namespace System.Reflection
+{
+    internal sealed class RuntimeMethodInfo : MethodInfo, IRuntimeMethodInfo
+    {
+        #region Private Data Members
+        private IntPtr m_handle;
+        private RuntimeTypeCache m_reflectedTypeCache;
+        private string m_name;
+        private string m_toString;
+        private ParameterInfo[] m_parameters;
+        private ParameterInfo m_returnParameter;
+        private BindingFlags m_bindingFlags;
+        private MethodAttributes m_methodAttributes;
+        private Signature m_signature;
+        private RuntimeType m_declaringType;
+        private object m_keepalive;
+        private INVOCATION_FLAGS m_invocationFlags;
+
+        internal INVOCATION_FLAGS InvocationFlags
+        {
+            get
+            {
+                if ((m_invocationFlags & INVOCATION_FLAGS.INVOCATION_FLAGS_INITIALIZED) == 0)
+                {
+                    INVOCATION_FLAGS invocationFlags = INVOCATION_FLAGS.INVOCATION_FLAGS_UNKNOWN;
+
+                    Type declaringType = DeclaringType;
+
+                    //
+                    // first take care of all the NO_INVOKE cases. 
+                    if (ContainsGenericParameters ||
+                         IsDisallowedByRefType(ReturnType) ||
+                         (declaringType != null && declaringType.ContainsGenericParameters) ||
+                         ((CallingConvention & CallingConventions.VarArgs) == CallingConventions.VarArgs))
+                    {
+                        // We don't need other flags if this method cannot be invoked
+                        invocationFlags = INVOCATION_FLAGS.INVOCATION_FLAGS_NO_INVOKE;
+                    }
+                    else
+                    {
+                        // Check for byref-like types
+                        if ((declaringType != null && declaringType.IsByRefLike) || ReturnType.IsByRefLike)
+                            invocationFlags |= INVOCATION_FLAGS.INVOCATION_FLAGS_CONTAINS_STACK_POINTERS;
+                    }
+
+                    m_invocationFlags = invocationFlags | INVOCATION_FLAGS.INVOCATION_FLAGS_INITIALIZED;
+                }
+
+                return m_invocationFlags;
+            }
+        }
+
+        private bool IsDisallowedByRefType(Type type)
+        {
+            if (!type.IsByRef)
+                return false;
+
+            Type elementType = type.GetElementType();
+            return elementType.IsByRefLike || elementType == typeof(void);
+        }
+        #endregion
+
+        #region Constructor
+        internal RuntimeMethodInfo(
+            RuntimeMethodHandleInternal handle, RuntimeType declaringType,
+            RuntimeTypeCache reflectedTypeCache, MethodAttributes methodAttributes, BindingFlags bindingFlags, object keepalive)
+        {
+            Debug.Assert(!handle.IsNullHandle());
+            Debug.Assert(methodAttributes == RuntimeMethodHandle.GetAttributes(handle));
+
+            m_bindingFlags = bindingFlags;
+            m_declaringType = declaringType;
+            m_keepalive = keepalive;
+            m_handle = handle.Value;
+            m_reflectedTypeCache = reflectedTypeCache;
+            m_methodAttributes = methodAttributes;
+        }
+        #endregion
+
+        #region Private Methods
+        RuntimeMethodHandleInternal IRuntimeMethodInfo.Value
+        {
+            get
+            {
+                return new RuntimeMethodHandleInternal(m_handle);
+            }
+        }
+
+        private RuntimeType ReflectedTypeInternal
+        {
+            get
+            {
+                return m_reflectedTypeCache.GetRuntimeType();
+            }
+        }
+
+        private ParameterInfo[] FetchNonReturnParameters()
+        {
+            if (m_parameters == null)
+                m_parameters = RuntimeParameterInfo.GetParameters(this, this, Signature);
+
+            return m_parameters;
+        }
+
+        private ParameterInfo FetchReturnParameter()
+        {
+            if (m_returnParameter == null)
+                m_returnParameter = RuntimeParameterInfo.GetReturnParameter(this, this, Signature);
+
+            return m_returnParameter;
+        }
+        #endregion
+
+        #region Internal Members
+        internal override string FormatNameAndSig(bool serialization)
+        {
+            // Serialization uses ToString to resolve MethodInfo overloads.
+            StringBuilder sbName = new StringBuilder(Name);
+
+            // serialization == true: use unambiguous (except for assembly name) type names to distinguish between overloads.
+            // serialization == false: use basic format to maintain backward compatibility of MethodInfo.ToString().
+            TypeNameFormatFlags format = serialization ? TypeNameFormatFlags.FormatSerialization : TypeNameFormatFlags.FormatBasic;
+
+            if (IsGenericMethod)
+                sbName.Append(RuntimeMethodHandle.ConstructInstantiation(this, format));
+
+            sbName.Append("(");
+            sbName.Append(ConstructParameters(GetParameterTypes(), CallingConvention, serialization));
+            sbName.Append(")");
+
+            return sbName.ToString();
+        }
+
+        internal override bool CacheEquals(object o)
+        {
+            RuntimeMethodInfo m = o as RuntimeMethodInfo;
+
+            if ((object)m == null)
+                return false;
+
+            return m.m_handle == m_handle;
+        }
+
+        internal Signature Signature
+        {
+            get
+            {
+                if (m_signature == null)
+                    m_signature = new Signature(this, m_declaringType);
+
+                return m_signature;
+            }
+        }
+
+        internal BindingFlags BindingFlags { get { return m_bindingFlags; } }
+
+        internal RuntimeMethodInfo GetParentDefinition()
+        {
+            if (!IsVirtual || m_declaringType.IsInterface)
+                return null;
+
+            RuntimeType parent = (RuntimeType)m_declaringType.BaseType;
+
+            if (parent == null)
+                return null;
+
+            int slot = RuntimeMethodHandle.GetSlot(this);
+
+            if (RuntimeTypeHandle.GetNumVirtuals(parent) <= slot)
+                return null;
+
+            return (RuntimeMethodInfo)RuntimeType.GetMethodBase(parent, RuntimeTypeHandle.GetMethodAt(parent, slot));
+        }
+
+        // Unlike DeclaringType, this will return a valid type even for global methods
+        internal RuntimeType GetDeclaringTypeInternal()
+        {
+            return m_declaringType;
+        }
+
+        internal sealed override int GenericParameterCount => RuntimeMethodHandle.GetGenericParameterCount(this);
+        #endregion
+
+        #region Object Overrides
+        public override String ToString()
+        {
+            if (m_toString == null)
+                m_toString = ReturnType.FormatTypeName() + " " + FormatNameAndSig();
+
+            return m_toString;
+        }
+
+        public override int GetHashCode()
+        {
+            // See RuntimeMethodInfo.Equals() below.
+            if (IsGenericMethod)
+                return ValueType.GetHashCodeOfPtr(m_handle);
+            else
+                return base.GetHashCode();
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (!IsGenericMethod)
+                return obj == (object)this;
+
+            // We cannot do simple object identity comparisons for generic methods.
+            // Equals will be called in CerHashTable when RuntimeType+RuntimeTypeCache.GetGenericMethodInfo()
+            // retrieve items from and insert items into s_methodInstantiations which is a CerHashtable.
+
+            RuntimeMethodInfo mi = obj as RuntimeMethodInfo;
+
+            if (mi == null || !mi.IsGenericMethod)
+                return false;
+
+            // now we know that both operands are generic methods
+
+            IRuntimeMethodInfo handle1 = RuntimeMethodHandle.StripMethodInstantiation(this);
+            IRuntimeMethodInfo handle2 = RuntimeMethodHandle.StripMethodInstantiation(mi);
+            if (handle1.Value.Value != handle2.Value.Value)
+                return false;
+
+            Type[] lhs = GetGenericArguments();
+            Type[] rhs = mi.GetGenericArguments();
+
+            if (lhs.Length != rhs.Length)
+                return false;
+
+            for (int i = 0; i < lhs.Length; i++)
+            {
+                if (lhs[i] != rhs[i])
+                    return false;
+            }
+
+            if (DeclaringType != mi.DeclaringType)
+                return false;
+
+            if (ReflectedType != mi.ReflectedType)
+                return false;
+
+            return true;
+        }
+        #endregion
+
+        #region ICustomAttributeProvider
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            return CustomAttribute.GetCustomAttributes(this, typeof(object) as RuntimeType as RuntimeType, inherit);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.GetCustomAttributes(this, attributeRuntimeType, inherit);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.IsDefined(this, attributeRuntimeType, inherit);
+        }
+
+        public override IList<CustomAttributeData> GetCustomAttributesData()
+        {
+            return CustomAttributeData.GetCustomAttributesInternal(this);
+        }
+        #endregion
+
+        #region MemberInfo Overrides
+        public override String Name
+        {
+            get
+            {
+                if (m_name == null)
+                    m_name = RuntimeMethodHandle.GetName(this);
+
+                return m_name;
+            }
+        }
+
+        public override Type DeclaringType
+        {
+            get
+            {
+                if (m_reflectedTypeCache.IsGlobal)
+                    return null;
+
+                return m_declaringType;
+            }
+        }
+
+        public sealed override bool HasSameMetadataDefinitionAs(MemberInfo other) => HasSameMetadataDefinitionAsCore<RuntimeMethodInfo>(other);
+
+        public override Type ReflectedType
+        {
+            get
+            {
+                if (m_reflectedTypeCache.IsGlobal)
+                    return null;
+
+                return m_reflectedTypeCache.GetRuntimeType();
+            }
+        }
+
+        public override MemberTypes MemberType { get { return MemberTypes.Method; } }
+        public override int MetadataToken
+        {
+            get { return RuntimeMethodHandle.GetMethodDef(this); }
+        }
+        public override Module Module { get { return GetRuntimeModule(); } }
+        internal RuntimeType GetRuntimeType() { return m_declaringType; }
+        internal RuntimeModule GetRuntimeModule() { return m_declaringType.GetRuntimeModule(); }
+        internal RuntimeAssembly GetRuntimeAssembly() { return GetRuntimeModule().GetRuntimeAssembly(); }
+
+        public override bool IsSecurityCritical
+        {
+            get { return true; }
+        }
+        public override bool IsSecuritySafeCritical
+        {
+            get { return false; }
+        }
+        public override bool IsSecurityTransparent
+        {
+            get { return false; }
+        }
+        #endregion
+
+        #region MethodBase Overrides
+        internal override ParameterInfo[] GetParametersNoCopy()
+        {
+            FetchNonReturnParameters();
+
+            return m_parameters;
+        }
+
+        public override ParameterInfo[] GetParameters()
+        {
+            FetchNonReturnParameters();
+
+            if (m_parameters.Length == 0)
+                return m_parameters;
+
+            ParameterInfo[] ret = new ParameterInfo[m_parameters.Length];
+
+            Array.Copy(m_parameters, ret, m_parameters.Length);
+
+            return ret;
+        }
+
+        public override MethodImplAttributes GetMethodImplementationFlags()
+        {
+            return RuntimeMethodHandle.GetImplAttributes(this);
+        }
+
+        public override RuntimeMethodHandle MethodHandle
+        {
+            get
+            {
+                Type declaringType = DeclaringType;
+                if ((declaringType == null && Module.Assembly.ReflectionOnly) || declaringType is ReflectionOnlyType)
+                    throw new InvalidOperationException(SR.InvalidOperation_NotAllowedInReflectionOnly);
+                return new RuntimeMethodHandle(this);
+            }
+        }
+
+        public override MethodAttributes Attributes { get { return m_methodAttributes; } }
+
+        public override CallingConventions CallingConvention
+        {
+            get
+            {
+                return Signature.CallingConvention;
+            }
+        }
+
+        public override MethodBody GetMethodBody()
+        {
+            MethodBody mb = RuntimeMethodHandle.GetMethodBody(this, ReflectedTypeInternal);
+            if (mb != null)
+                mb.m_methodBase = this;
+            return mb;
+        }
+        #endregion
+
+        #region Invocation Logic(On MemberBase)
+        private void CheckConsistency(Object target)
+        {
+            // only test instance methods
+            if ((m_methodAttributes & MethodAttributes.Static) != MethodAttributes.Static)
+            {
+                if (!m_declaringType.IsInstanceOfType(target))
+                {
+                    if (target == null)
+                        throw new TargetException(SR.RFLCT_Targ_StatMethReqTarg);
+                    else
+                        throw new TargetException(SR.RFLCT_Targ_ITargMismatch);
+                }
+            }
+        }
+
+        private void ThrowNoInvokeException()
+        {
+            // method is ReflectionOnly
+            Type declaringType = DeclaringType;
+            if ((declaringType == null && Module.Assembly.ReflectionOnly) || declaringType is ReflectionOnlyType)
+            {
+                throw new InvalidOperationException(SR.Arg_ReflectionOnlyInvoke);
+            }
+            // method is on a class that contains stack pointers
+            else if ((InvocationFlags & INVOCATION_FLAGS.INVOCATION_FLAGS_CONTAINS_STACK_POINTERS) != 0)
+            {
+                throw new NotSupportedException();
+            }
+            // method is vararg
+            else if ((CallingConvention & CallingConventions.VarArgs) == CallingConventions.VarArgs)
+            {
+                throw new NotSupportedException();
+            }
+            // method is generic or on a generic class
+            else if (DeclaringType.ContainsGenericParameters || ContainsGenericParameters)
+            {
+                throw new InvalidOperationException(SR.Arg_UnboundGenParam);
+            }
+            // method is abstract class
+            else if (IsAbstract)
+            {
+                throw new MemberAccessException();
+            }
+            else if (ReturnType.IsByRef)
+            {
+                Type elementType = ReturnType.GetElementType();
+                if (elementType.IsByRefLike)
+                    throw new NotSupportedException(SR.NotSupported_ByRefToByRefLikeReturn);    
+                if (elementType == typeof(void))
+                    throw new NotSupportedException(SR.NotSupported_ByRefToVoidReturn);
+            }
+
+            throw new TargetException();
+        }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public override Object Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
+        {
+            object[] arguments = InvokeArgumentsCheck(obj, invokeAttr, binder, parameters, culture);
+
+            bool wrapExceptions = (invokeAttr & BindingFlags.DoNotWrapExceptions) == 0;
+            if (arguments == null || arguments.Length == 0)
+                return RuntimeMethodHandle.InvokeMethod(obj, null, Signature, false, wrapExceptions);
+            else
+            {
+                Object retValue = RuntimeMethodHandle.InvokeMethod(obj, arguments, Signature, false, wrapExceptions);
+
+                // copy out. This should be made only if ByRef are present.
+                for (int index = 0; index < arguments.Length; index++)
+                    parameters[index] = arguments[index];
+
+                return retValue;
+            }
+        }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        private object[] InvokeArgumentsCheck(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
+        {
+            Signature sig = Signature;
+
+            // get the signature 
+            int formalCount = sig.Arguments.Length;
+            int actualCount = (parameters != null) ? parameters.Length : 0;
+
+            INVOCATION_FLAGS invocationFlags = InvocationFlags;
+
+            // INVOCATION_FLAGS_CONTAINS_STACK_POINTERS means that the struct (either the declaring type or the return type)
+            // contains pointers that point to the stack. This is either a ByRef or a TypedReference. These structs cannot
+            // be boxed and thus cannot be invoked through reflection which only deals with boxed value type objects.
+            if ((invocationFlags & (INVOCATION_FLAGS.INVOCATION_FLAGS_NO_INVOKE | INVOCATION_FLAGS.INVOCATION_FLAGS_CONTAINS_STACK_POINTERS)) != 0)
+                ThrowNoInvokeException();
+
+            // check basic method consistency. This call will throw if there are problems in the target/method relationship
+            CheckConsistency(obj);
+
+            if (formalCount != actualCount)
+                throw new TargetParameterCountException(SR.Arg_ParmCnt);
+
+            if (actualCount != 0)
+                return CheckArguments(parameters, binder, invokeAttr, culture, sig);
+            else
+                return null;
+        }
+
+        #endregion
+
+        #region MethodInfo Overrides
+        public override Type ReturnType
+        {
+            get { return Signature.ReturnType; }
+        }
+
+        public override ICustomAttributeProvider ReturnTypeCustomAttributes
+        {
+            get { return ReturnParameter; }
+        }
+
+        public override ParameterInfo ReturnParameter
+        {
+            get
+            {
+                FetchReturnParameter();
+                return m_returnParameter as ParameterInfo;
+            }
+        }
+
+        public override MethodInfo GetBaseDefinition()
+        {
+            if (!IsVirtual || IsStatic || m_declaringType == null || m_declaringType.IsInterface)
+                return this;
+
+            int slot = RuntimeMethodHandle.GetSlot(this);
+            RuntimeType declaringType = (RuntimeType)DeclaringType;
+            RuntimeType baseDeclaringType = declaringType;
+            RuntimeMethodHandleInternal baseMethodHandle = new RuntimeMethodHandleInternal();
+
+            do
+            {
+                int cVtblSlots = RuntimeTypeHandle.GetNumVirtuals(declaringType);
+
+                if (cVtblSlots <= slot)
+                    break;
+
+                baseMethodHandle = RuntimeTypeHandle.GetMethodAt(declaringType, slot);
+                baseDeclaringType = declaringType;
+
+                declaringType = (RuntimeType)declaringType.BaseType;
+            } while (declaringType != null);
+
+            return (MethodInfo)RuntimeType.GetMethodBase(baseDeclaringType, baseMethodHandle);
+        }
+
+        public override Delegate CreateDelegate(Type delegateType)
+        {
+            // This API existed in v1/v1.1 and only expected to create closed
+            // instance delegates. Constrain the call to BindToMethodInfo to
+            // open delegates only for backwards compatibility. But we'll allow
+            // relaxed signature checking and open static delegates because
+            // there's no ambiguity there (the caller would have to explicitly
+            // pass us a static method or a method with a non-exact signature
+            // and the only change in behavior from v1.1 there is that we won't
+            // fail the call).
+            return CreateDelegateInternal(
+                delegateType,
+                null,
+                DelegateBindingFlags.OpenDelegateOnly | DelegateBindingFlags.RelaxedSignature);
+        }
+
+        public override Delegate CreateDelegate(Type delegateType, Object target)
+        {
+            // This API is new in Whidbey and allows the full range of delegate
+            // flexability (open or closed delegates binding to static or
+            // instance methods with relaxed signature checking). The delegate
+            // can also be closed over null. There's no ambiguity with all these
+            // options since the caller is providing us a specific MethodInfo.
+            return CreateDelegateInternal(
+                delegateType,
+                target,
+                DelegateBindingFlags.RelaxedSignature);
+        }
+
+        private Delegate CreateDelegateInternal(Type delegateType, Object firstArgument, DelegateBindingFlags bindingFlags)
+        {
+            // Validate the parameters.
+            if (delegateType == null)
+                throw new ArgumentNullException(nameof(delegateType));
+
+            RuntimeType rtType = delegateType as RuntimeType;
+            if (rtType == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType, nameof(delegateType));
+
+            if (!rtType.IsDelegate())
+                throw new ArgumentException(SR.Arg_MustBeDelegate, nameof(delegateType));
+
+            Delegate d = Delegate.CreateDelegateInternal(rtType, this, firstArgument, bindingFlags);
+            if (d == null)
+            {
+                throw new ArgumentException(SR.Arg_DlgtTargMeth);
+            }
+
+            return d;
+        }
+
+        #endregion
+
+        #region Generics
+        public override MethodInfo MakeGenericMethod(params Type[] methodInstantiation)
+        {
+            if (methodInstantiation == null)
+                throw new ArgumentNullException(nameof(methodInstantiation));
+
+            RuntimeType[] methodInstantionRuntimeType = new RuntimeType[methodInstantiation.Length];
+
+            if (!IsGenericMethodDefinition)
+                throw new InvalidOperationException(
+                    SR.Format(SR.Arg_NotGenericMethodDefinition, this));
+
+            for (int i = 0; i < methodInstantiation.Length; i++)
+            {
+                Type methodInstantiationElem = methodInstantiation[i];
+
+                if (methodInstantiationElem == null)
+                    throw new ArgumentNullException();
+
+                RuntimeType rtMethodInstantiationElem = methodInstantiationElem as RuntimeType;
+
+                if (rtMethodInstantiationElem == null)
+                {
+                    Type[] methodInstantiationCopy = new Type[methodInstantiation.Length];
+                    for (int iCopy = 0; iCopy < methodInstantiation.Length; iCopy++)
+                        methodInstantiationCopy[iCopy] = methodInstantiation[iCopy];
+                    methodInstantiation = methodInstantiationCopy;
+                    return System.Reflection.Emit.MethodBuilderInstantiation.MakeGenericMethod(this, methodInstantiation);
+                }
+
+                methodInstantionRuntimeType[i] = rtMethodInstantiationElem;
+            }
+
+            RuntimeType[] genericParameters = GetGenericArgumentsInternal();
+
+            RuntimeType.SanityCheckGenericArguments(methodInstantionRuntimeType, genericParameters);
+
+            MethodInfo ret = null;
+
+            try
+            {
+                ret = RuntimeType.GetMethodBase(ReflectedTypeInternal,
+                    RuntimeMethodHandle.GetStubIfNeeded(new RuntimeMethodHandleInternal(m_handle), m_declaringType, methodInstantionRuntimeType)) as MethodInfo;
+            }
+            catch (VerificationException e)
+            {
+                RuntimeType.ValidateGenericArguments(this, methodInstantionRuntimeType, e);
+                throw;
+            }
+
+            return ret;
+        }
+
+        internal RuntimeType[] GetGenericArgumentsInternal()
+        {
+            return RuntimeMethodHandle.GetMethodInstantiationInternal(this);
+        }
+
+        public override Type[] GetGenericArguments()
+        {
+            Type[] types = RuntimeMethodHandle.GetMethodInstantiationPublic(this);
+
+            if (types == null)
+            {
+                types = Array.Empty<Type>();
+            }
+            return types;
+        }
+
+        public override MethodInfo GetGenericMethodDefinition()
+        {
+            if (!IsGenericMethod)
+                throw new InvalidOperationException();
+
+            return RuntimeType.GetMethodBase(m_declaringType, RuntimeMethodHandle.StripMethodInstantiation(this)) as MethodInfo;
+        }
+
+        public override bool IsGenericMethod
+        {
+            get { return RuntimeMethodHandle.HasMethodInstantiation(this); }
+        }
+
+        public override bool IsGenericMethodDefinition
+        {
+            get { return RuntimeMethodHandle.IsGenericMethodDefinition(this); }
+        }
+
+        public override bool ContainsGenericParameters
+        {
+            get
+            {
+                if (DeclaringType != null && DeclaringType.ContainsGenericParameters)
+                    return true;
+
+                if (!IsGenericMethod)
+                    return false;
+
+                Type[] pis = GetGenericArguments();
+                for (int i = 0; i < pis.Length; i++)
+                {
+                    if (pis[i].ContainsGenericParameters)
+                        return true;
+                }
+
+                return false;
+            }
+        }
+        #endregion
+
+        #region Legacy Internal
+        internal static MethodBase InternalGetCurrentMethod(ref StackCrawlMark stackMark)
+        {
+            IRuntimeMethodInfo method = RuntimeMethodHandle.GetCurrentMethod(ref stackMark);
+
+            if (method == null)
+                return null;
+
+            return RuntimeType.GetMethodBase(method);
+        }
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/RuntimeModule.cs b/src/System.Private.CoreLib/src/System/Reflection/RuntimeModule.cs
new file mode 100644
index 0000000000..e4b1135db3
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/RuntimeModule.cs
@@ -0,0 +1,588 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+using System.Runtime.Serialization;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Security;
+using System.Globalization;
+
+namespace System.Reflection
+{
+    internal class RuntimeModule : Module
+    {
+        internal RuntimeModule() { throw new NotSupportedException(); }
+
+        #region FCalls
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetType(RuntimeModule module, String className, bool throwOnError, bool ignoreCase, ObjectHandleOnStack type, ObjectHandleOnStack keepAlive);
+
+        [DllImport(JitHelpers.QCall)]
+        private static extern bool nIsTransientInternal(RuntimeModule module);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetScopeName(RuntimeModule module, StringHandleOnStack retString);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetFullyQualifiedName(RuntimeModule module, StringHandleOnStack retString);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern RuntimeType[] GetTypes(RuntimeModule module);
+
+        internal RuntimeType[] GetDefinedTypes()
+        {
+            return GetTypes(GetNativeHandle());
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool IsResource(RuntimeModule module);
+        #endregion
+
+        #region Module overrides
+        private static RuntimeTypeHandle[] ConvertToTypeHandleArray(Type[] genericArguments)
+        {
+            if (genericArguments == null)
+                return null;
+
+            int size = genericArguments.Length;
+            RuntimeTypeHandle[] typeHandleArgs = new RuntimeTypeHandle[size];
+            for (int i = 0; i < size; i++)
+            {
+                Type typeArg = genericArguments[i];
+                if (typeArg == null)
+                    throw new ArgumentException(SR.Argument_InvalidGenericInstArray);
+                typeArg = typeArg.UnderlyingSystemType;
+                if (typeArg == null)
+                    throw new ArgumentException(SR.Argument_InvalidGenericInstArray);
+                if (!(typeArg is RuntimeType))
+                    throw new ArgumentException(SR.Argument_InvalidGenericInstArray);
+                typeHandleArgs[i] = typeArg.GetTypeHandleInternal();
+            }
+            return typeHandleArgs;
+        }
+
+        public override byte[] ResolveSignature(int metadataToken)
+        {
+            MetadataToken tk = new MetadataToken(metadataToken);
+
+            if (!MetadataImport.IsValidToken(tk))
+                throw new ArgumentOutOfRangeException(nameof(metadataToken),
+                    SR.Format(SR.Argument_InvalidToken, tk, this));
+
+            if (!tk.IsMemberRef && !tk.IsMethodDef && !tk.IsTypeSpec && !tk.IsSignature && !tk.IsFieldDef)
+                throw new ArgumentException(SR.Format(SR.Argument_InvalidToken, tk, this),
+                                            nameof(metadataToken));
+
+            ConstArray signature;
+            if (tk.IsMemberRef)
+                signature = MetadataImport.GetMemberRefProps(metadataToken);
+            else
+                signature = MetadataImport.GetSignatureFromToken(metadataToken);
+
+            byte[] sig = new byte[signature.Length];
+
+            for (int i = 0; i < signature.Length; i++)
+                sig[i] = signature[i];
+
+            return sig;
+        }
+
+        public override MethodBase ResolveMethod(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
+        {
+            MetadataToken tk = new MetadataToken(metadataToken);
+
+            if (!MetadataImport.IsValidToken(tk))
+                throw new ArgumentOutOfRangeException(nameof(metadataToken),
+                    SR.Format(SR.Argument_InvalidToken, tk, this));
+
+            RuntimeTypeHandle[] typeArgs = ConvertToTypeHandleArray(genericTypeArguments);
+            RuntimeTypeHandle[] methodArgs = ConvertToTypeHandleArray(genericMethodArguments);
+
+            try
+            {
+                if (!tk.IsMethodDef && !tk.IsMethodSpec)
+                {
+                    if (!tk.IsMemberRef)
+                        throw new ArgumentException(SR.Format(SR.Argument_ResolveMethod, tk, this),
+                            nameof(metadataToken));
+
+                    unsafe
+                    {
+                        ConstArray sig = MetadataImport.GetMemberRefProps(tk);
+
+                        if (*(MdSigCallingConvention*)sig.Signature.ToPointer() == MdSigCallingConvention.Field)
+                            throw new ArgumentException(SR.Format(SR.Argument_ResolveMethod, tk, this),
+                                nameof(metadataToken));
+                    }
+                }
+
+                IRuntimeMethodInfo methodHandle = ModuleHandle.ResolveMethodHandleInternal(GetNativeHandle(), tk, typeArgs, methodArgs);
+                Type declaringType = RuntimeMethodHandle.GetDeclaringType(methodHandle);
+
+                if (declaringType.IsGenericType || declaringType.IsArray)
+                {
+                    MetadataToken tkDeclaringType = new MetadataToken(MetadataImport.GetParentToken(tk));
+
+                    if (tk.IsMethodSpec)
+                        tkDeclaringType = new MetadataToken(MetadataImport.GetParentToken(tkDeclaringType));
+
+                    declaringType = ResolveType(tkDeclaringType, genericTypeArguments, genericMethodArguments);
+                }
+
+                return System.RuntimeType.GetMethodBase(declaringType as RuntimeType, methodHandle);
+            }
+            catch (BadImageFormatException e)
+            {
+                throw new ArgumentException(SR.Argument_BadImageFormatExceptionResolve, e);
+            }
+        }
+
+        private FieldInfo ResolveLiteralField(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
+        {
+            MetadataToken tk = new MetadataToken(metadataToken);
+
+            if (!MetadataImport.IsValidToken(tk) || !tk.IsFieldDef)
+                throw new ArgumentOutOfRangeException(nameof(metadataToken),
+                    String.Format(CultureInfo.CurrentUICulture, SR.Format(SR.Argument_InvalidToken, tk, this)));
+
+            int tkDeclaringType;
+            string fieldName;
+
+            fieldName = MetadataImport.GetName(tk).ToString();
+            tkDeclaringType = MetadataImport.GetParentToken(tk);
+
+            Type declaringType = ResolveType(tkDeclaringType, genericTypeArguments, genericMethodArguments);
+
+            declaringType.GetFields();
+
+            try
+            {
+                return declaringType.GetField(fieldName,
+                    BindingFlags.Static | BindingFlags.Instance |
+                    BindingFlags.Public | BindingFlags.NonPublic |
+                    BindingFlags.DeclaredOnly);
+            }
+            catch
+            {
+                throw new ArgumentException(SR.Format(SR.Argument_ResolveField, tk, this), nameof(metadataToken));
+            }
+        }
+
+        public override FieldInfo ResolveField(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
+        {
+            MetadataToken tk = new MetadataToken(metadataToken);
+
+            if (!MetadataImport.IsValidToken(tk))
+                throw new ArgumentOutOfRangeException(nameof(metadataToken),
+                    SR.Format(SR.Argument_InvalidToken, tk, this));
+
+            RuntimeTypeHandle[] typeArgs = ConvertToTypeHandleArray(genericTypeArguments);
+            RuntimeTypeHandle[] methodArgs = ConvertToTypeHandleArray(genericMethodArguments);
+
+            try
+            {
+                IRuntimeFieldInfo fieldHandle = null;
+
+                if (!tk.IsFieldDef)
+                {
+                    if (!tk.IsMemberRef)
+                        throw new ArgumentException(SR.Format(SR.Argument_ResolveField, tk, this),
+                            nameof(metadataToken));
+
+                    unsafe
+                    {
+                        ConstArray sig = MetadataImport.GetMemberRefProps(tk);
+
+                        if (*(MdSigCallingConvention*)sig.Signature.ToPointer() != MdSigCallingConvention.Field)
+                            throw new ArgumentException(SR.Format(SR.Argument_ResolveField, tk, this),
+                                nameof(metadataToken));
+                    }
+
+                    fieldHandle = ModuleHandle.ResolveFieldHandleInternal(GetNativeHandle(), tk, typeArgs, methodArgs);
+                }
+
+                fieldHandle = ModuleHandle.ResolveFieldHandleInternal(GetNativeHandle(), metadataToken, typeArgs, methodArgs);
+                RuntimeType declaringType = RuntimeFieldHandle.GetApproxDeclaringType(fieldHandle.Value);
+
+                if (declaringType.IsGenericType || declaringType.IsArray)
+                {
+                    int tkDeclaringType = ModuleHandle.GetMetadataImport(GetNativeHandle()).GetParentToken(metadataToken);
+                    declaringType = (RuntimeType)ResolveType(tkDeclaringType, genericTypeArguments, genericMethodArguments);
+                }
+
+                return System.RuntimeType.GetFieldInfo(declaringType, fieldHandle);
+            }
+            catch (MissingFieldException)
+            {
+                return ResolveLiteralField(tk, genericTypeArguments, genericMethodArguments);
+            }
+            catch (BadImageFormatException e)
+            {
+                throw new ArgumentException(SR.Argument_BadImageFormatExceptionResolve, e);
+            }
+        }
+
+        public override Type ResolveType(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
+        {
+            MetadataToken tk = new MetadataToken(metadataToken);
+
+            if (tk.IsGlobalTypeDefToken)
+                throw new ArgumentException(SR.Format(SR.Argument_ResolveModuleType, tk), nameof(metadataToken));
+
+            if (!MetadataImport.IsValidToken(tk))
+                throw new ArgumentOutOfRangeException(nameof(metadataToken),
+                    SR.Format(SR.Argument_InvalidToken, tk, this));
+
+            if (!tk.IsTypeDef && !tk.IsTypeSpec && !tk.IsTypeRef)
+                throw new ArgumentException(SR.Format(SR.Argument_ResolveType, tk, this), nameof(metadataToken));
+
+            RuntimeTypeHandle[] typeArgs = ConvertToTypeHandleArray(genericTypeArguments);
+            RuntimeTypeHandle[] methodArgs = ConvertToTypeHandleArray(genericMethodArguments);
+
+            try
+            {
+                Type t = GetModuleHandleImpl().ResolveTypeHandle(metadataToken, typeArgs, methodArgs).GetRuntimeType();
+
+                if (t == null)
+                    throw new ArgumentException(SR.Format(SR.Argument_ResolveType, tk, this), nameof(metadataToken));
+
+                return t;
+            }
+            catch (BadImageFormatException e)
+            {
+                throw new ArgumentException(SR.Argument_BadImageFormatExceptionResolve, e);
+            }
+        }
+
+        public override MemberInfo ResolveMember(int metadataToken, Type[] genericTypeArguments, Type[] genericMethodArguments)
+        {
+            MetadataToken tk = new MetadataToken(metadataToken);
+
+            if (tk.IsProperty)
+                throw new ArgumentException(SR.InvalidOperation_PropertyInfoNotAvailable);
+
+            if (tk.IsEvent)
+                throw new ArgumentException(SR.InvalidOperation_EventInfoNotAvailable);
+
+            if (tk.IsMethodSpec || tk.IsMethodDef)
+                return ResolveMethod(metadataToken, genericTypeArguments, genericMethodArguments);
+
+            if (tk.IsFieldDef)
+                return ResolveField(metadataToken, genericTypeArguments, genericMethodArguments);
+
+            if (tk.IsTypeRef || tk.IsTypeDef || tk.IsTypeSpec)
+                return ResolveType(metadataToken, genericTypeArguments, genericMethodArguments);
+
+            if (tk.IsMemberRef)
+            {
+                if (!MetadataImport.IsValidToken(tk))
+                    throw new ArgumentOutOfRangeException(nameof(metadataToken),
+                        SR.Format(SR.Argument_InvalidToken, tk, this));
+
+                ConstArray sig = MetadataImport.GetMemberRefProps(tk);
+
+                unsafe
+                {
+                    if (*(MdSigCallingConvention*)sig.Signature.ToPointer() == MdSigCallingConvention.Field)
+                    {
+                        return ResolveField(tk, genericTypeArguments, genericMethodArguments);
+                    }
+                    else
+                    {
+                        return ResolveMethod(tk, genericTypeArguments, genericMethodArguments);
+                    }
+                }
+            }
+
+            throw new ArgumentException(SR.Format(SR.Argument_ResolveMember, tk, this),
+                nameof(metadataToken));
+        }
+
+        public override string ResolveString(int metadataToken)
+        {
+            MetadataToken tk = new MetadataToken(metadataToken);
+            if (!tk.IsString)
+                throw new ArgumentException(
+                    String.Format(CultureInfo.CurrentUICulture, SR.Argument_ResolveString, metadataToken, ToString()));
+
+            if (!MetadataImport.IsValidToken(tk))
+                throw new ArgumentOutOfRangeException(nameof(metadataToken),
+                    String.Format(CultureInfo.CurrentUICulture, SR.Format(SR.Argument_InvalidToken, tk, this)));
+
+            string str = MetadataImport.GetUserString(metadataToken);
+
+            if (str == null)
+                throw new ArgumentException(
+                    String.Format(CultureInfo.CurrentUICulture, SR.Argument_ResolveString, metadataToken, ToString()));
+
+            return str;
+        }
+
+        public override void GetPEKind(out PortableExecutableKinds peKind, out ImageFileMachine machine)
+        {
+            ModuleHandle.GetPEKind(GetNativeHandle(), out peKind, out machine);
+        }
+
+        public override int MDStreamVersion
+        {
+            get
+            {
+                return ModuleHandle.GetMDStreamVersion(GetNativeHandle());
+            }
+        }
+        #endregion
+
+        #region Data Members
+#pragma warning disable 169
+        // If you add any data members, you need to update the native declaration ReflectModuleBaseObject.
+        private RuntimeType m_runtimeType;
+        private RuntimeAssembly m_runtimeAssembly;
+        private IntPtr m_pRefClass;
+        private IntPtr m_pData;
+        private IntPtr m_pGlobals;
+        private IntPtr m_pFields;
+#pragma warning restore 169
+        #endregion
+
+        #region Protected Virtuals
+        protected override MethodInfo GetMethodImpl(String name, BindingFlags bindingAttr, Binder binder,
+            CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            return GetMethodInternal(name, bindingAttr, binder, callConvention, types, modifiers);
+        }
+
+        internal MethodInfo GetMethodInternal(String name, BindingFlags bindingAttr, Binder binder,
+            CallingConventions callConvention, Type[] types, ParameterModifier[] modifiers)
+        {
+            if (RuntimeType == null)
+                return null;
+
+            if (types == null)
+            {
+                return RuntimeType.GetMethod(name, bindingAttr);
+            }
+            else
+            {
+                return RuntimeType.GetMethod(name, bindingAttr, binder, callConvention, types, modifiers);
+            }
+        }
+        #endregion
+
+        #region Internal Members
+        internal RuntimeType RuntimeType
+        {
+            get
+            {
+                if (m_runtimeType == null)
+                    m_runtimeType = ModuleHandle.GetModuleType(GetNativeHandle());
+
+                return m_runtimeType;
+            }
+        }
+
+        internal bool IsTransientInternal()
+        {
+            return RuntimeModule.nIsTransientInternal(this.GetNativeHandle());
+        }
+
+        internal MetadataImport MetadataImport
+        {
+            get
+            {
+                unsafe
+                {
+                    return ModuleHandle.GetMetadataImport(GetNativeHandle());
+                }
+            }
+        }
+        #endregion
+
+        #region ICustomAttributeProvider Members
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            return CustomAttribute.GetCustomAttributes(this, typeof(object) as RuntimeType);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.GetCustomAttributes(this, attributeRuntimeType);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.IsDefined(this, attributeRuntimeType);
+        }
+
+        public override IList<CustomAttributeData> GetCustomAttributesData()
+        {
+            return CustomAttributeData.GetCustomAttributesInternal(this);
+        }
+        #endregion
+
+        #region Public Virtuals
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            throw new PlatformNotSupportedException();
+        }
+
+        public override Type GetType(String className, bool throwOnError, bool ignoreCase)
+        {
+            // throw on null strings regardless of the value of "throwOnError"
+            if (className == null)
+                throw new ArgumentNullException(nameof(className));
+
+            RuntimeType retType = null;
+            Object keepAlive = null;
+            GetType(GetNativeHandle(), className, throwOnError, ignoreCase, JitHelpers.GetObjectHandleOnStack(ref retType), JitHelpers.GetObjectHandleOnStack(ref keepAlive));
+            GC.KeepAlive(keepAlive);
+            return retType;
+        }
+
+        internal string GetFullyQualifiedName()
+        {
+            String fullyQualifiedName = null;
+            GetFullyQualifiedName(GetNativeHandle(), JitHelpers.GetStringHandleOnStack(ref fullyQualifiedName));
+            return fullyQualifiedName;
+        }
+
+        public override String FullyQualifiedName
+        {
+            get
+            {
+                return GetFullyQualifiedName();
+            }
+        }
+
+        public override Type[] GetTypes()
+        {
+            return GetTypes(GetNativeHandle());
+        }
+
+        #endregion
+
+        #region Public Members
+
+        public override Guid ModuleVersionId
+        {
+            get
+            {
+                unsafe
+                {
+                    Guid mvid;
+                    MetadataImport.GetScopeProps(out mvid);
+                    return mvid;
+                }
+            }
+        }
+
+        public override int MetadataToken
+        {
+            get
+            {
+                return ModuleHandle.GetToken(GetNativeHandle());
+            }
+        }
+
+        public override bool IsResource()
+        {
+            return IsResource(GetNativeHandle());
+        }
+
+        public override FieldInfo[] GetFields(BindingFlags bindingFlags)
+        {
+            if (RuntimeType == null)
+                return new FieldInfo[0];
+
+            return RuntimeType.GetFields(bindingFlags);
+        }
+
+        public override FieldInfo GetField(String name, BindingFlags bindingAttr)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            if (RuntimeType == null)
+                return null;
+
+            return RuntimeType.GetField(name, bindingAttr);
+        }
+
+        public override MethodInfo[] GetMethods(BindingFlags bindingFlags)
+        {
+            if (RuntimeType == null)
+                return new MethodInfo[0];
+
+            return RuntimeType.GetMethods(bindingFlags);
+        }
+
+        public override String ScopeName
+        {
+            get
+            {
+                string scopeName = null;
+                GetScopeName(GetNativeHandle(), JitHelpers.GetStringHandleOnStack(ref scopeName));
+                return scopeName;
+            }
+        }
+
+        public override String Name
+        {
+            get
+            {
+                String s = GetFullyQualifiedName();
+
+#if !FEATURE_PAL
+                int i = s.LastIndexOf('\\');
+#else
+                int i = s.LastIndexOf(System.IO.Path.DirectorySeparatorChar);
+#endif
+                if (i == -1)
+                    return s;
+
+                return s.Substring(i + 1);
+            }
+        }
+
+        public override Assembly Assembly
+        {
+            get
+            {
+                return GetRuntimeAssembly();
+            }
+        }
+
+        internal RuntimeAssembly GetRuntimeAssembly()
+        {
+            return m_runtimeAssembly;
+        }
+
+        protected override ModuleHandle GetModuleHandleImpl()
+        {
+            return new ModuleHandle(this);
+        }
+
+        internal RuntimeModule GetNativeHandle()
+        {
+            return this;
+        }
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/RuntimeParameterInfo.cs b/src/System.Private.CoreLib/src/System/Reflection/RuntimeParameterInfo.cs
new file mode 100644
index 0000000000..1bd053ee82
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/RuntimeParameterInfo.cs
@@ -0,0 +1,554 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using MdToken = System.Reflection.MetadataToken;
+
+namespace System.Reflection
+{
+    internal unsafe sealed class RuntimeParameterInfo : ParameterInfo
+    {
+        #region Static Members
+        internal static unsafe ParameterInfo[] GetParameters(IRuntimeMethodInfo method, MemberInfo member, Signature sig)
+        {
+            Debug.Assert(method is RuntimeMethodInfo || method is RuntimeConstructorInfo);
+
+            ParameterInfo dummy;
+            return GetParameters(method, member, sig, out dummy, false);
+        }
+
+        internal static unsafe ParameterInfo GetReturnParameter(IRuntimeMethodInfo method, MemberInfo member, Signature sig)
+        {
+            Debug.Assert(method is RuntimeMethodInfo || method is RuntimeConstructorInfo);
+
+            ParameterInfo returnParameter;
+            GetParameters(method, member, sig, out returnParameter, true);
+            return returnParameter;
+        }
+
+        internal static unsafe ParameterInfo[] GetParameters(
+            IRuntimeMethodInfo methodHandle, MemberInfo member, Signature sig, out ParameterInfo returnParameter, bool fetchReturnParameter)
+        {
+            returnParameter = null;
+            int sigArgCount = sig.Arguments.Length;
+            ParameterInfo[] args = fetchReturnParameter ? null : new ParameterInfo[sigArgCount];
+
+            int tkMethodDef = RuntimeMethodHandle.GetMethodDef(methodHandle);
+            int cParamDefs = 0;
+
+            // Not all methods have tokens. Arrays, pointers and byRef types do not have tokens as they
+            // are generated on the fly by the runtime. 
+            if (!MdToken.IsNullToken(tkMethodDef))
+            {
+                MetadataImport scope = RuntimeTypeHandle.GetMetadataImport(RuntimeMethodHandle.GetDeclaringType(methodHandle));
+
+                MetadataEnumResult tkParamDefs;
+                scope.EnumParams(tkMethodDef, out tkParamDefs);
+
+                cParamDefs = tkParamDefs.Length;
+
+                // Not all parameters have tokens. Parameters may have no token 
+                // if they have no name and no attributes.
+                if (cParamDefs > sigArgCount + 1 /* return type */)
+                    throw new BadImageFormatException(SR.BadImageFormat_ParameterSignatureMismatch);
+
+                for (int i = 0; i < cParamDefs; i++)
+                {
+                    #region Populate ParameterInfos
+                    ParameterAttributes attr;
+                    int position, tkParamDef = tkParamDefs[i];
+
+                    scope.GetParamDefProps(tkParamDef, out position, out attr);
+
+                    position--;
+
+                    if (fetchReturnParameter == true && position == -1)
+                    {
+                        // more than one return parameter?
+                        if (returnParameter != null)
+                            throw new BadImageFormatException(SR.BadImageFormat_ParameterSignatureMismatch);
+
+                        returnParameter = new RuntimeParameterInfo(sig, scope, tkParamDef, position, attr, member);
+                    }
+                    else if (fetchReturnParameter == false && position >= 0)
+                    {
+                        // position beyong sigArgCount?
+                        if (position >= sigArgCount)
+                            throw new BadImageFormatException(SR.BadImageFormat_ParameterSignatureMismatch);
+
+                        args[position] = new RuntimeParameterInfo(sig, scope, tkParamDef, position, attr, member);
+                    }
+                    #endregion
+                }
+            }
+
+            // Fill in empty ParameterInfos for those without tokens
+            if (fetchReturnParameter)
+            {
+                if (returnParameter == null)
+                {
+                    returnParameter = new RuntimeParameterInfo(sig, MetadataImport.EmptyImport, 0, -1, (ParameterAttributes)0, member);
+                }
+            }
+            else
+            {
+                if (cParamDefs < args.Length + 1)
+                {
+                    for (int i = 0; i < args.Length; i++)
+                    {
+                        if (args[i] != null)
+                            continue;
+
+                        args[i] = new RuntimeParameterInfo(sig, MetadataImport.EmptyImport, 0, i, (ParameterAttributes)0, member);
+                    }
+                }
+            }
+
+            return args;
+        }
+        #endregion
+
+        #region Private Statics
+        private static readonly Type s_DecimalConstantAttributeType = typeof(DecimalConstantAttribute);
+        private static readonly Type s_CustomConstantAttributeType = typeof(CustomConstantAttribute);
+        #endregion
+
+        #region Private Data Members
+        private int m_tkParamDef;
+        private MetadataImport m_scope;
+        private Signature m_signature;
+        private volatile bool m_nameIsCached = false;
+        private readonly bool m_noMetadata = false;
+        private bool m_noDefaultValue = false;
+        private MethodBase m_originalMember = null;
+        #endregion
+
+        #region Internal Properties
+        internal MethodBase DefiningMethod
+        {
+            get
+            {
+                MethodBase result = m_originalMember != null ? m_originalMember : MemberImpl as MethodBase;
+                Debug.Assert(result != null);
+                return result;
+            }
+        }
+        #endregion
+
+        #region Internal Methods
+        internal void SetName(string name)
+        {
+            NameImpl = name;
+        }
+
+        internal void SetAttributes(ParameterAttributes attributes)
+        {
+            AttrsImpl = attributes;
+        }
+        #endregion
+
+        #region Constructor
+        // used by RuntimePropertyInfo
+        internal RuntimeParameterInfo(RuntimeParameterInfo accessor, RuntimePropertyInfo property)
+            : this(accessor, (MemberInfo)property)
+        {
+            m_signature = property.Signature;
+        }
+
+        private RuntimeParameterInfo(RuntimeParameterInfo accessor, MemberInfo member)
+        {
+            // Change ownership
+            MemberImpl = member;
+
+            // The original owner should always be a method, because this method is only used to 
+            // change the owner from a method to a property.
+            m_originalMember = accessor.MemberImpl as MethodBase;
+            Debug.Assert(m_originalMember != null);
+
+            // Populate all the caches -- we inherit this behavior from RTM
+            NameImpl = accessor.Name;
+            m_nameIsCached = true;
+            ClassImpl = accessor.ParameterType;
+            PositionImpl = accessor.Position;
+            AttrsImpl = accessor.Attributes;
+
+            // Strictly speeking, property's don't contain paramter tokens
+            // However we need this to make ca's work... oh well...
+            m_tkParamDef = MdToken.IsNullToken(accessor.MetadataToken) ? (int)MetadataTokenType.ParamDef : accessor.MetadataToken;
+            m_scope = accessor.m_scope;
+        }
+
+        private RuntimeParameterInfo(
+            Signature signature, MetadataImport scope, int tkParamDef,
+            int position, ParameterAttributes attributes, MemberInfo member)
+        {
+            Debug.Assert(member != null);
+            Debug.Assert(MdToken.IsNullToken(tkParamDef) == scope.Equals(MetadataImport.EmptyImport));
+            Debug.Assert(MdToken.IsNullToken(tkParamDef) || MdToken.IsTokenOfType(tkParamDef, MetadataTokenType.ParamDef));
+
+            PositionImpl = position;
+            MemberImpl = member;
+            m_signature = signature;
+            m_tkParamDef = MdToken.IsNullToken(tkParamDef) ? (int)MetadataTokenType.ParamDef : tkParamDef;
+            m_scope = scope;
+            AttrsImpl = attributes;
+
+            ClassImpl = null;
+            NameImpl = null;
+        }
+
+        // ctor for no metadata MethodInfo in the DynamicMethod and RuntimeMethodInfo cases
+        internal RuntimeParameterInfo(MethodInfo owner, String name, Type parameterType, int position)
+        {
+            MemberImpl = owner;
+            NameImpl = name;
+            m_nameIsCached = true;
+            m_noMetadata = true;
+            ClassImpl = parameterType;
+            PositionImpl = position;
+            AttrsImpl = ParameterAttributes.None;
+            m_tkParamDef = (int)MetadataTokenType.ParamDef;
+            m_scope = MetadataImport.EmptyImport;
+        }
+        #endregion
+
+        #region Public Methods
+        public override Type ParameterType
+        {
+            get
+            {
+                // only instance of ParameterInfo has ClassImpl, all its subclasses don't
+                if (ClassImpl == null)
+                {
+                    RuntimeType parameterType;
+                    if (PositionImpl == -1)
+                        parameterType = m_signature.ReturnType;
+                    else
+                        parameterType = m_signature.Arguments[PositionImpl];
+
+                    Debug.Assert(parameterType != null);
+                    // different thread could only write ClassImpl to the same value, so a race condition is not a problem here
+                    ClassImpl = parameterType;
+                }
+
+                return ClassImpl;
+            }
+        }
+
+        public override String Name
+        {
+            get
+            {
+                if (!m_nameIsCached)
+                {
+                    if (!MdToken.IsNullToken(m_tkParamDef))
+                    {
+                        string name;
+                        name = m_scope.GetName(m_tkParamDef).ToString();
+                        NameImpl = name;
+                    }
+
+                    // other threads could only write it to true, so a race condition is OK
+                    // this field is volatile, so the write ordering is guaranteed
+                    m_nameIsCached = true;
+                }
+
+                // name may be null
+                return NameImpl;
+            }
+        }
+
+        public override bool HasDefaultValue
+        {
+            get
+            {
+                if (m_noMetadata || m_noDefaultValue)
+                    return false;
+
+                object defaultValue = GetDefaultValueInternal(false);
+
+                return (defaultValue != DBNull.Value);
+            }
+        }
+
+        public override Object DefaultValue { get { return GetDefaultValue(false); } }
+        public override Object RawDefaultValue { get { return GetDefaultValue(true); } }
+
+        private Object GetDefaultValue(bool raw)
+        {
+            // OLD COMMENT (Is this even true?)
+            // Cannot cache because default value could be non-agile user defined enumeration.
+            // OLD COMMENT ends
+            if (m_noMetadata)
+                return null;
+
+            // for dynamic method we pretend to have cached the value so we do not go to metadata
+            object defaultValue = GetDefaultValueInternal(raw);
+
+            if (defaultValue == DBNull.Value)
+            {
+                #region Handle case if no default value was found
+                if (IsOptional)
+                {
+                    // If the argument is marked as optional then the default value is Missing.Value.
+                    defaultValue = Type.Missing;
+                }
+                #endregion
+            }
+
+            return defaultValue;
+        }
+
+        // returns DBNull.Value if the parameter doesn't have a default value
+        private Object GetDefaultValueInternal(bool raw)
+        {
+            Debug.Assert(!m_noMetadata);
+
+            if (m_noDefaultValue)
+                return DBNull.Value;
+
+            object defaultValue = null;
+
+            // Why check the parameter type only for DateTime and only for the ctor arguments? 
+            // No check on the parameter type is done for named args and for Decimal.
+
+            // We should move this after MdToken.IsNullToken(m_tkParamDef) and combine it 
+            // with the other custom attribute logic. But will that be a breaking change?
+            // For a DateTime parameter on which both an md constant and a ca constant are set,
+            // which one should win?
+            if (ParameterType == typeof(DateTime))
+            {
+                if (raw)
+                {
+                    CustomAttributeTypedArgument value =
+                        CustomAttributeData.Filter(
+                            CustomAttributeData.GetCustomAttributes(this), typeof(DateTimeConstantAttribute), 0);
+
+                    if (value.ArgumentType != null)
+                        return new DateTime((long)value.Value);
+                }
+                else
+                {
+                    object[] dt = GetCustomAttributes(typeof(DateTimeConstantAttribute), false);
+                    if (dt != null && dt.Length != 0)
+                        return ((DateTimeConstantAttribute)dt[0]).Value;
+                }
+            }
+
+            #region Look for a default value in metadata
+            if (!MdToken.IsNullToken(m_tkParamDef))
+            {
+                // This will return DBNull.Value if no constant value is defined on m_tkParamDef in the metadata.
+                defaultValue = MdConstant.GetValue(m_scope, m_tkParamDef, ParameterType.GetTypeHandleInternal(), raw);
+            }
+            #endregion
+
+            if (defaultValue == DBNull.Value)
+            {
+                #region Look for a default value in the custom attributes
+                if (raw)
+                {
+                    foreach (CustomAttributeData attr in CustomAttributeData.GetCustomAttributes(this))
+                    {
+                        Type attrType = attr.Constructor.DeclaringType;
+
+                        if (attrType == typeof(DateTimeConstantAttribute))
+                        {
+                            defaultValue = GetRawDateTimeConstant(attr);
+                        }
+                        else if (attrType == typeof(DecimalConstantAttribute))
+                        {
+                            defaultValue = GetRawDecimalConstant(attr);
+                        }
+                        else if (attrType.IsSubclassOf(s_CustomConstantAttributeType))
+                        {
+                            defaultValue = GetRawConstant(attr);
+                        }
+                    }
+                }
+                else
+                {
+                    Object[] CustomAttrs = GetCustomAttributes(s_CustomConstantAttributeType, false);
+                    if (CustomAttrs.Length != 0)
+                    {
+                        defaultValue = ((CustomConstantAttribute)CustomAttrs[0]).Value;
+                    }
+                    else
+                    {
+                        CustomAttrs = GetCustomAttributes(s_DecimalConstantAttributeType, false);
+                        if (CustomAttrs.Length != 0)
+                        {
+                            defaultValue = ((DecimalConstantAttribute)CustomAttrs[0]).Value;
+                        }
+                    }
+                }
+                #endregion
+            }
+
+            if (defaultValue == DBNull.Value)
+                m_noDefaultValue = true;
+
+            return defaultValue;
+        }
+
+        private static Decimal GetRawDecimalConstant(CustomAttributeData attr)
+        {
+            Debug.Assert(attr.Constructor.DeclaringType == typeof(DecimalConstantAttribute));
+
+            foreach (CustomAttributeNamedArgument namedArgument in attr.NamedArguments)
+            {
+                if (namedArgument.MemberInfo.Name.Equals("Value"))
+                {
+                    // This is not possible because Decimal cannot be represented directly in the metadata.
+                    Debug.Fail("Decimal cannot be represented directly in the metadata.");
+                    return (Decimal)namedArgument.TypedValue.Value;
+                }
+            }
+
+            ParameterInfo[] parameters = attr.Constructor.GetParameters();
+            Debug.Assert(parameters.Length == 5);
+
+            System.Collections.Generic.IList<CustomAttributeTypedArgument> args = attr.ConstructorArguments;
+            Debug.Assert(args.Count == 5);
+
+            if (parameters[2].ParameterType == typeof(uint))
+            {
+                // DecimalConstantAttribute(byte scale, byte sign, uint hi, uint mid, uint low)
+                int low = (int)(UInt32)args[4].Value;
+                int mid = (int)(UInt32)args[3].Value;
+                int hi = (int)(UInt32)args[2].Value;
+                byte sign = (byte)args[1].Value;
+                byte scale = (byte)args[0].Value;
+
+                return new System.Decimal(low, mid, hi, (sign != 0), scale);
+            }
+            else
+            {
+                // DecimalConstantAttribute(byte scale, byte sign, int hi, int mid, int low)
+                int low = (int)args[4].Value;
+                int mid = (int)args[3].Value;
+                int hi = (int)args[2].Value;
+                byte sign = (byte)args[1].Value;
+                byte scale = (byte)args[0].Value;
+
+                return new System.Decimal(low, mid, hi, (sign != 0), scale);
+            }
+        }
+
+        private static DateTime GetRawDateTimeConstant(CustomAttributeData attr)
+        {
+            Debug.Assert(attr.Constructor.DeclaringType == typeof(DateTimeConstantAttribute));
+            Debug.Assert(attr.ConstructorArguments.Count == 1);
+
+            foreach (CustomAttributeNamedArgument namedArgument in attr.NamedArguments)
+            {
+                if (namedArgument.MemberInfo.Name.Equals("Value"))
+                {
+                    return new DateTime((long)namedArgument.TypedValue.Value);
+                }
+            }
+
+            // Look at the ctor argument if the "Value" property was not explicitly defined.
+            return new DateTime((long)attr.ConstructorArguments[0].Value);
+        }
+
+        private static object GetRawConstant(CustomAttributeData attr)
+        {
+            foreach (CustomAttributeNamedArgument namedArgument in attr.NamedArguments)
+            {
+                if (namedArgument.MemberInfo.Name.Equals("Value"))
+                    return namedArgument.TypedValue.Value;
+            }
+
+            // Return DBNull to indicate that no default value is available.
+            // Not to be confused with a null return which indicates a null default value.
+            return DBNull.Value;
+        }
+
+        internal RuntimeModule GetRuntimeModule()
+        {
+            RuntimeMethodInfo method = Member as RuntimeMethodInfo;
+            RuntimeConstructorInfo constructor = Member as RuntimeConstructorInfo;
+            RuntimePropertyInfo property = Member as RuntimePropertyInfo;
+
+            if (method != null)
+                return method.GetRuntimeModule();
+            else if (constructor != null)
+                return constructor.GetRuntimeModule();
+            else if (property != null)
+                return property.GetRuntimeModule();
+            else
+                return null;
+        }
+
+        public override int MetadataToken
+        {
+            get
+            {
+                return m_tkParamDef;
+            }
+        }
+
+        public override Type[] GetRequiredCustomModifiers()
+        {
+            return m_signature.GetCustomModifiers(PositionImpl + 1, true);
+        }
+
+        public override Type[] GetOptionalCustomModifiers()
+        {
+            return m_signature.GetCustomModifiers(PositionImpl + 1, false);
+        }
+
+        #endregion
+
+        #region ICustomAttributeProvider
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            if (MdToken.IsNullToken(m_tkParamDef))
+                return Array.Empty<Object>();
+
+            return CustomAttribute.GetCustomAttributes(this, typeof(object) as RuntimeType);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            if (MdToken.IsNullToken(m_tkParamDef))
+                return Array.Empty<Object>();
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.GetCustomAttributes(this, attributeRuntimeType);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            if (MdToken.IsNullToken(m_tkParamDef))
+                return false;
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.IsDefined(this, attributeRuntimeType);
+        }
+
+        public override IList<CustomAttributeData> GetCustomAttributesData()
+        {
+            return CustomAttributeData.GetCustomAttributesInternal(this);
+        }
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Reflection/RuntimePropertyInfo.cs b/src/System.Private.CoreLib/src/System/Reflection/RuntimePropertyInfo.cs
new file mode 100644
index 0000000000..1e64da2123
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Reflection/RuntimePropertyInfo.cs
@@ -0,0 +1,448 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using System.Text;
+using RuntimeTypeCache = System.RuntimeType.RuntimeTypeCache;
+
+namespace System.Reflection
+{
+    internal unsafe sealed class RuntimePropertyInfo : PropertyInfo
+    {
+        #region Private Data Members
+        private int m_token;
+        private string m_name;
+        private void* m_utf8name;
+        private PropertyAttributes m_flags;
+        private RuntimeTypeCache m_reflectedTypeCache;
+        private RuntimeMethodInfo m_getterMethod;
+        private RuntimeMethodInfo m_setterMethod;
+        private MethodInfo[] m_otherMethod;
+        private RuntimeType m_declaringType;
+        private BindingFlags m_bindingFlags;
+        private Signature m_signature;
+        private ParameterInfo[] m_parameters;
+        #endregion
+
+        #region Constructor
+        internal RuntimePropertyInfo(
+            int tkProperty, RuntimeType declaredType, RuntimeTypeCache reflectedTypeCache, out bool isPrivate)
+        {
+            Debug.Assert(declaredType != null);
+            Debug.Assert(reflectedTypeCache != null);
+            Debug.Assert(!reflectedTypeCache.IsGlobal);
+
+            MetadataImport scope = declaredType.GetRuntimeModule().MetadataImport;
+
+            m_token = tkProperty;
+            m_reflectedTypeCache = reflectedTypeCache;
+            m_declaringType = declaredType;
+
+            ConstArray sig;
+            scope.GetPropertyProps(tkProperty, out m_utf8name, out m_flags, out sig);
+
+            RuntimeMethodInfo dummy;
+            Associates.AssignAssociates(scope, tkProperty, declaredType, reflectedTypeCache.GetRuntimeType(),
+                out dummy, out dummy, out dummy,
+                out m_getterMethod, out m_setterMethod, out m_otherMethod,
+                out isPrivate, out m_bindingFlags);
+        }
+        #endregion
+
+        #region Internal Members
+        internal override bool CacheEquals(object o)
+        {
+            RuntimePropertyInfo m = o as RuntimePropertyInfo;
+
+            if ((object)m == null)
+                return false;
+
+            return m.m_token == m_token &&
+                RuntimeTypeHandle.GetModule(m_declaringType).Equals(
+                    RuntimeTypeHandle.GetModule(m.m_declaringType));
+        }
+
+        internal Signature Signature
+        {
+            get
+            {
+                if (m_signature == null)
+                {
+                    PropertyAttributes flags;
+                    ConstArray sig;
+
+                    void* name;
+                    GetRuntimeModule().MetadataImport.GetPropertyProps(
+                        m_token, out name, out flags, out sig);
+
+                    m_signature = new Signature(sig.Signature.ToPointer(), (int)sig.Length, m_declaringType);
+                }
+
+                return m_signature;
+            }
+        }
+        internal bool EqualsSig(RuntimePropertyInfo target)
+        {
+            //@Asymmetry - Legacy policy is to remove duplicate properties, including hidden properties. 
+            //             The comparison is done by name and by sig. The EqualsSig comparison is expensive 
+            //             but forutnetly it is only called when an inherited property is hidden by name or
+            //             when an interfaces declare properies with the same signature. 
+            //             Note that we intentionally don't resolve generic arguments so that we don't treat
+            //             signatures that only match in certain instantiations as duplicates. This has the
+            //             down side of treating overriding and overriden properties as different properties
+            //             in some cases. But PopulateProperties in rttype.cs should have taken care of that
+            //             by comparing VTable slots.
+            //
+            //             Class C1(Of T, Y)
+            //                 Property Prop1(ByVal t1 As T) As Integer
+            //                     Get
+            //                         ... ...
+            //                     End Get
+            //                 End Property
+            //                 Property Prop1(ByVal y1 As Y) As Integer
+            //                     Get
+            //                         ... ...
+            //                     End Get
+            //                 End Property
+            //             End Class
+            //
+
+            Debug.Assert(Name.Equals(target.Name));
+            Debug.Assert(this != target);
+            Debug.Assert(this.ReflectedType == target.ReflectedType);
+
+            return Signature.CompareSig(this.Signature, target.Signature);
+        }
+        internal BindingFlags BindingFlags { get { return m_bindingFlags; } }
+        #endregion
+
+        #region Object Overrides
+        public override String ToString()
+        {
+            return FormatNameAndSig(false);
+        }
+
+        private string FormatNameAndSig(bool serialization)
+        {
+            StringBuilder sbName = new StringBuilder(PropertyType.FormatTypeName(serialization));
+
+            sbName.Append(" ");
+            sbName.Append(Name);
+
+            RuntimeType[] arguments = Signature.Arguments;
+            if (arguments.Length > 0)
+            {
+                sbName.Append(" [");
+                sbName.Append(MethodBase.ConstructParameters(arguments, Signature.CallingConvention, serialization));
+                sbName.Append("]");
+            }
+
+            return sbName.ToString();
+        }
+        #endregion
+
+        #region ICustomAttributeProvider
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            return CustomAttribute.GetCustomAttributes(this, typeof(object) as RuntimeType);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.GetCustomAttributes(this, attributeRuntimeType);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            if (attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.IsDefined(this, attributeRuntimeType);
+        }
+
+        public override IList<CustomAttributeData> GetCustomAttributesData()
+        {
+            return CustomAttributeData.GetCustomAttributesInternal(this);
+        }
+        #endregion
+
+        #region MemberInfo Overrides
+        public override MemberTypes MemberType { get { return MemberTypes.Property; } }
+        public override String Name
+        {
+            get
+            {
+                if (m_name == null)
+                    m_name = new MdUtf8String(m_utf8name).ToString();
+
+                return m_name;
+            }
+        }
+        public override Type DeclaringType
+        {
+            get
+            {
+                return m_declaringType;
+            }
+        }
+
+        public sealed override bool HasSameMetadataDefinitionAs(MemberInfo other) => HasSameMetadataDefinitionAsCore<RuntimePropertyInfo>(other);
+
+        public override Type ReflectedType
+        {
+            get
+            {
+                return ReflectedTypeInternal;
+            }
+        }
+
+        private RuntimeType ReflectedTypeInternal
+        {
+            get
+            {
+                return m_reflectedTypeCache.GetRuntimeType();
+            }
+        }
+
+        public override int MetadataToken { get { return m_token; } }
+
+        public override Module Module { get { return GetRuntimeModule(); } }
+        internal RuntimeModule GetRuntimeModule() { return m_declaringType.GetRuntimeModule(); }
+        #endregion
+
+        #region PropertyInfo Overrides
+
+        #region Non Dynamic
+
+        public override Type[] GetRequiredCustomModifiers()
+        {
+            return Signature.GetCustomModifiers(0, true);
+        }
+
+        public override Type[] GetOptionalCustomModifiers()
+        {
+            return Signature.GetCustomModifiers(0, false);
+        }
+
+        internal object GetConstantValue(bool raw)
+        {
+            Object defaultValue = MdConstant.GetValue(GetRuntimeModule().MetadataImport, m_token, PropertyType.GetTypeHandleInternal(), raw);
+
+            if (defaultValue == DBNull.Value)
+                // Arg_EnumLitValueNotFound -> "Literal value was not found."
+                throw new InvalidOperationException(SR.Arg_EnumLitValueNotFound);
+
+            return defaultValue;
+        }
+
+        public override object GetConstantValue() { return GetConstantValue(false); }
+
+        public override object GetRawConstantValue() { return GetConstantValue(true); }
+
+        public override MethodInfo[] GetAccessors(bool nonPublic)
+        {
+            List<MethodInfo> accessorList = new List<MethodInfo>();
+
+            if (Associates.IncludeAccessor(m_getterMethod, nonPublic))
+                accessorList.Add(m_getterMethod);
+
+            if (Associates.IncludeAccessor(m_setterMethod, nonPublic))
+                accessorList.Add(m_setterMethod);
+
+            if ((object)m_otherMethod != null)
+            {
+                for (int i = 0; i < m_otherMethod.Length; i++)
+                {
+                    if (Associates.IncludeAccessor(m_otherMethod[i] as MethodInfo, nonPublic))
+                        accessorList.Add(m_otherMethod[i]);
+                }
+            }
+            return accessorList.ToArray();
+        }
+
+        public override Type PropertyType
+        {
+            get { return Signature.ReturnType; }
+        }
+
+        public override MethodInfo GetGetMethod(bool nonPublic)
+        {
+            if (!Associates.IncludeAccessor(m_getterMethod, nonPublic))
+                return null;
+
+            return m_getterMethod;
+        }
+
+        public override MethodInfo GetSetMethod(bool nonPublic)
+        {
+            if (!Associates.IncludeAccessor(m_setterMethod, nonPublic))
+                return null;
+
+            return m_setterMethod;
+        }
+
+        public override ParameterInfo[] GetIndexParameters()
+        {
+            ParameterInfo[] indexParams = GetIndexParametersNoCopy();
+
+            int numParams = indexParams.Length;
+
+            if (numParams == 0)
+                return indexParams;
+
+            ParameterInfo[] ret = new ParameterInfo[numParams];
+
+            Array.Copy(indexParams, ret, numParams);
+
+            return ret;
+        }
+
+        internal ParameterInfo[] GetIndexParametersNoCopy()
+        {
+            // @History - Logic ported from RTM
+
+            // No need to lock because we don't guarantee the uniqueness of ParameterInfo objects
+            if (m_parameters == null)
+            {
+                int numParams = 0;
+                ParameterInfo[] methParams = null;
+
+                // First try to get the Get method.
+                MethodInfo m = GetGetMethod(true);
+                if (m != null)
+                {
+                    // There is a Get method so use it.
+                    methParams = m.GetParametersNoCopy();
+                    numParams = methParams.Length;
+                }
+                else
+                {
+                    // If there is no Get method then use the Set method.
+                    m = GetSetMethod(true);
+
+                    if (m != null)
+                    {
+                        methParams = m.GetParametersNoCopy();
+                        numParams = methParams.Length - 1;
+                    }
+                }
+
+                // Now copy over the parameter info's and change their 
+                // owning member info to the current property info.
+
+                ParameterInfo[] propParams = new ParameterInfo[numParams];
+
+                for (int i = 0; i < numParams; i++)
+                    propParams[i] = new RuntimeParameterInfo((RuntimeParameterInfo)methParams[i], this);
+
+                m_parameters = propParams;
+            }
+
+            return m_parameters;
+        }
+
+        public override PropertyAttributes Attributes
+        {
+            get
+            {
+                return m_flags;
+            }
+        }
+
+        public override bool CanRead
+        {
+            get
+            {
+                return m_getterMethod != null;
+            }
+        }
+
+        public override bool CanWrite
+        {
+            get
+            {
+                return m_setterMethod != null;
+            }
+        }
+        #endregion
+
+        #region Dynamic
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public override Object GetValue(Object obj, Object[] index)
+        {
+            return GetValue(obj, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Static,
+                null, index, null);
+        }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public override Object GetValue(Object obj, BindingFlags invokeAttr, Binder binder, Object[] index, CultureInfo culture)
+        {
+            MethodInfo m = GetGetMethod(true);
+            if (m == null)
+                throw new ArgumentException(System.SR.Arg_GetMethNotFnd);
+            return m.Invoke(obj, invokeAttr, binder, index, null);
+        }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public override void SetValue(Object obj, Object value, Object[] index)
+        {
+            SetValue(obj,
+                    value,
+                    BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Static,
+                    null,
+                    index,
+                    null);
+        }
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public override void SetValue(Object obj, Object value, BindingFlags invokeAttr, Binder binder, Object[] index, CultureInfo culture)
+        {
+            MethodInfo m = GetSetMethod(true);
+
+            if (m == null)
+                throw new ArgumentException(System.SR.Arg_SetMethNotFnd);
+
+            Object[] args = null;
+
+            if (index != null)
+            {
+                args = new Object[index.Length + 1];
+
+                for (int i = 0; i < index.Length; i++)
+                    args[i] = index[i];
+
+                args[index.Length] = value;
+            }
+            else
+            {
+                args = new Object[1];
+                args[0] = value;
+            }
+
+            m.Invoke(obj, invokeAttr, binder, args, culture);
+        }
+        #endregion
+
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Resources/FileBasedResourceGroveler.cs b/src/System.Private.CoreLib/src/System/Resources/FileBasedResourceGroveler.cs
new file mode 100644
index 0000000000..1546c5e5cc
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Resources/FileBasedResourceGroveler.cs
@@ -0,0 +1,124 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+** Purpose: Searches for resources on disk, used for file-
+** based resource lookup.
+**
+** 
+===========================================================*/
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using System.IO;
+using System.Threading;
+
+using Internal.IO;
+
+namespace System.Resources
+{
+    internal class FileBasedResourceGroveler : IResourceGroveler
+    {
+        private ResourceManager.ResourceManagerMediator _mediator;
+
+        public FileBasedResourceGroveler(ResourceManager.ResourceManagerMediator mediator)
+        {
+            Debug.Assert(mediator != null, "mediator shouldn't be null; check caller");
+            _mediator = mediator;
+        }
+
+        // Consider modifying IResourceGroveler interface (hence this method signature) when we figure out 
+        // serialization compat story for moving ResourceManager members to either file-based or 
+        // manifest-based classes. Want to continue tightening the design to get rid of unused params.
+        public ResourceSet GrovelForResourceSet(CultureInfo culture, Dictionary<String, ResourceSet> localResourceSets, bool tryParents, bool createIfNotExists, ref StackCrawlMark stackMark)
+        {
+            Debug.Assert(culture != null, "culture shouldn't be null; check caller");
+
+            String fileName = null;
+            ResourceSet rs = null;
+
+            // Don't use Assembly manifest, but grovel on disk for a file.
+
+            // Create new ResourceSet, if a file exists on disk for it.
+            String tempFileName = _mediator.GetResourceFileName(culture);
+            fileName = FindResourceFile(culture, tempFileName);
+            if (fileName == null)
+            {
+                if (tryParents)
+                {
+                    // If we've hit top of the Culture tree, return.
+                    if (culture.HasInvariantCultureName)
+                    {
+                        // We really don't think this should happen - we always
+                        // expect the neutral locale's resources to be present.
+                        throw new MissingManifestResourceException(SR.MissingManifestResource_NoNeutralDisk + Environment.NewLine + "baseName: " + _mediator.BaseNameField + "  locationInfo: " + (_mediator.LocationInfo == null ? "<null>" : _mediator.LocationInfo.FullName) + "  fileName: " + _mediator.GetResourceFileName(culture));
+                    }
+                }
+            }
+            else
+            {
+                rs = CreateResourceSet(fileName);
+            }
+            return rs;
+        }
+
+        // Given a CultureInfo, it generates the path &; file name for 
+        // the .resources file for that CultureInfo.  This method will grovel
+        // the disk looking for the correct file name & path.  Uses CultureInfo's
+        // Name property.  If the module directory was set in the ResourceManager 
+        // constructor, we'll look there first.  If it couldn't be found in the module
+        // diretory or the module dir wasn't provided, look in the current
+        // directory.
+
+        private String FindResourceFile(CultureInfo culture, String fileName)
+        {
+            Debug.Assert(culture != null, "culture shouldn't be null; check caller");
+            Debug.Assert(fileName != null, "fileName shouldn't be null; check caller");
+
+            // If we have a moduleDir, check there first.  Get module fully 
+            // qualified name, append path to that.
+            if (_mediator.ModuleDir != null)
+            {
+                String path = Path.Combine(_mediator.ModuleDir, fileName);
+                if (File.Exists(path))
+                {
+                    return path;
+                }
+            }
+
+            // look in .
+            if (File.Exists(fileName))
+                return fileName;
+
+            return null;  // give up.
+        }
+
+        // Constructs a new ResourceSet for a given file name.
+        private ResourceSet CreateResourceSet(String file)
+        {
+            Debug.Assert(file != null, "file shouldn't be null; check caller");
+
+            if (_mediator.UserResourceSet == null)
+            {
+                return new RuntimeResourceSet(file);
+            }
+            else
+            {
+                Object[] args = new Object[1];
+                args[0] = file;
+                try
+                {
+                    return (ResourceSet)Activator.CreateInstance(_mediator.UserResourceSet, args);
+                }
+                catch (MissingMethodException e)
+                {
+                    throw new InvalidOperationException(SR.Format(SR.InvalidOperation_ResMgrBadResSet_Type, _mediator.UserResourceSet.AssemblyQualifiedName), e);
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Resources/IResourceGroveler.cs b/src/System.Private.CoreLib/src/System/Resources/IResourceGroveler.cs
new file mode 100644
index 0000000000..bdd8826c77
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Resources/IResourceGroveler.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Interface for resource grovelers
+**
+** 
+===========================================================*/
+
+using System;
+using System.Globalization;
+using System.Threading;
+using System.Collections.Generic;
+using System.Runtime.Versioning;
+
+namespace System.Resources
+{
+    internal interface IResourceGroveler
+    {
+        ResourceSet GrovelForResourceSet(CultureInfo culture, Dictionary<String, ResourceSet> localResourceSets, bool tryParents,
+            bool createIfNotExists, ref StackCrawlMark stackMark);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Resources/ManifestBasedResourceGroveler.cs b/src/System.Private.CoreLib/src/System/Resources/ManifestBasedResourceGroveler.cs
new file mode 100644
index 0000000000..1dc986bfd4
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Resources/ManifestBasedResourceGroveler.cs
@@ -0,0 +1,526 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Searches for resources in Assembly manifest, used
+** for assembly-based resource lookup.
+**
+** 
+===========================================================*/
+
+namespace System.Resources
+{
+    using System;
+    using System.Collections;
+    using System.Collections.Generic;
+    using System.Globalization;
+    using System.IO;
+    using System.Reflection;
+    using System.Runtime.InteropServices;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.Versioning;
+    using System.Text;
+    using System.Threading;
+    using System.Diagnostics;
+    using Microsoft.Win32;
+
+    //
+    // Note: this type is integral to the construction of exception objects,
+    // and sometimes this has to be done in low memory situtations (OOM) or
+    // to create TypeInitializationExceptions due to failure of a static class
+    // constructor. This type needs to be extremely careful and assume that 
+    // any type it references may have previously failed to construct, so statics
+    // belonging to that type may not be initialized. FrameworkEventSource.Log
+    // is one such example.
+    //
+    internal class ManifestBasedResourceGroveler : IResourceGroveler
+    {
+        private ResourceManager.ResourceManagerMediator _mediator;
+
+        public ManifestBasedResourceGroveler(ResourceManager.ResourceManagerMediator mediator)
+        {
+            // here and below: convert asserts to preconditions where appropriate when we get
+            // contracts story in place.
+            Debug.Assert(mediator != null, "mediator shouldn't be null; check caller");
+            _mediator = mediator;
+        }
+
+        public ResourceSet GrovelForResourceSet(CultureInfo culture, Dictionary<String, ResourceSet> localResourceSets, bool tryParents, bool createIfNotExists, ref StackCrawlMark stackMark)
+        {
+            Debug.Assert(culture != null, "culture shouldn't be null; check caller");
+            Debug.Assert(localResourceSets != null, "localResourceSets shouldn't be null; check caller");
+
+            ResourceSet rs = null;
+            Stream stream = null;
+            RuntimeAssembly satellite = null;
+
+            // 1. Fixups for ultimate fallbacks
+            CultureInfo lookForCulture = UltimateFallbackFixup(culture);
+
+            // 2. Look for satellite assembly or main assembly, as appropriate
+            if (lookForCulture.HasInvariantCultureName && _mediator.FallbackLoc == UltimateResourceFallbackLocation.MainAssembly)
+            {
+                // don't bother looking in satellites in this case
+                satellite = _mediator.MainAssembly;
+            }
+#if RESOURCE_SATELLITE_CONFIG
+            // If our config file says the satellite isn't here, don't ask for it.
+            else if (!lookForCulture.HasInvariantCultureName && !_mediator.TryLookingForSatellite(lookForCulture))
+            {
+                satellite = null;
+            }
+#endif
+            else
+            {
+                satellite = GetSatelliteAssembly(lookForCulture, ref stackMark);
+
+                if (satellite == null)
+                {
+                    bool raiseException = (culture.HasInvariantCultureName && (_mediator.FallbackLoc == UltimateResourceFallbackLocation.Satellite));
+                    // didn't find satellite, give error if necessary
+                    if (raiseException)
+                    {
+                        HandleSatelliteMissing();
+                    }
+                }
+            }
+
+            // get resource file name we'll search for. Note, be careful if you're moving this statement
+            // around because lookForCulture may be modified from originally requested culture above.
+            String fileName = _mediator.GetResourceFileName(lookForCulture);
+
+            // 3. If we identified an assembly to search; look in manifest resource stream for resource file
+            if (satellite != null)
+            {
+                // Handle case in here where someone added a callback for assembly load events.
+                // While no other threads have called into GetResourceSet, our own thread can!
+                // At that point, we could already have an RS in our hash table, and we don't 
+                // want to add it twice.
+                lock (localResourceSets)
+                {
+                    localResourceSets.TryGetValue(culture.Name, out rs);
+                }
+
+                stream = GetManifestResourceStream(satellite, fileName, ref stackMark);
+            }
+
+            // 4a. Found a stream; create a ResourceSet if possible
+            if (createIfNotExists && stream != null && rs == null)
+            {
+                rs = CreateResourceSet(stream, satellite);
+            }
+            else if (stream == null && tryParents)
+            {
+                // 4b. Didn't find stream; give error if necessary
+                bool raiseException = culture.HasInvariantCultureName;
+                if (raiseException)
+                {
+                    HandleResourceStreamMissing(fileName);
+                }
+            }
+
+            return rs;
+        }
+
+        private CultureInfo UltimateFallbackFixup(CultureInfo lookForCulture)
+        {
+            CultureInfo returnCulture = lookForCulture;
+
+            // If our neutral resources were written in this culture AND we know the main assembly
+            // does NOT contain neutral resources, don't probe for this satellite.
+            if (lookForCulture.Name == _mediator.NeutralResourcesCulture.Name &&
+                _mediator.FallbackLoc == UltimateResourceFallbackLocation.MainAssembly)
+            {
+                returnCulture = CultureInfo.InvariantCulture;
+            }
+            else if (lookForCulture.HasInvariantCultureName && _mediator.FallbackLoc == UltimateResourceFallbackLocation.Satellite)
+            {
+                returnCulture = _mediator.NeutralResourcesCulture;
+            }
+
+            return returnCulture;
+        }
+
+        internal static CultureInfo GetNeutralResourcesLanguage(Assembly a, ref UltimateResourceFallbackLocation fallbackLocation)
+        {
+            Debug.Assert(a != null, "assembly != null");
+            string cultureName = null;
+            short fallback = 0;
+            if (GetNeutralResourcesLanguageAttribute(((RuntimeAssembly)a).GetNativeHandle(),
+                                                        JitHelpers.GetStringHandleOnStack(ref cultureName),
+                                                        out fallback))
+            {
+                if ((UltimateResourceFallbackLocation)fallback < UltimateResourceFallbackLocation.MainAssembly || (UltimateResourceFallbackLocation)fallback > UltimateResourceFallbackLocation.Satellite)
+                {
+                    throw new ArgumentException(SR.Format(SR.Arg_InvalidNeutralResourcesLanguage_FallbackLoc, fallback));
+                }
+                fallbackLocation = (UltimateResourceFallbackLocation)fallback;
+            }
+            else
+            {
+                fallbackLocation = UltimateResourceFallbackLocation.MainAssembly;
+                return CultureInfo.InvariantCulture;
+            }
+
+            try
+            {
+                CultureInfo c = CultureInfo.GetCultureInfo(cultureName);
+                return c;
+            }
+            catch (ArgumentException e)
+            { // we should catch ArgumentException only.
+                // Note we could go into infinite loops if mscorlib's 
+                // NeutralResourcesLanguageAttribute is mangled.  If this assert
+                // fires, please fix the build process for the BCL directory.
+                if (a == typeof(Object).Assembly)
+                {
+                    Debug.Fail(System.CoreLib.Name + "'s NeutralResourcesLanguageAttribute is a malformed culture name! name: \"" + cultureName + "\"  Exception: " + e);
+                    return CultureInfo.InvariantCulture;
+                }
+
+                throw new ArgumentException(SR.Format(SR.Arg_InvalidNeutralResourcesLanguage_Asm_Culture, a.ToString(), cultureName), e);
+            }
+        }
+
+        // Constructs a new ResourceSet for a given file name.
+        // Use the assembly to resolve assembly manifest resource references.
+        // Note that is can be null, but probably shouldn't be.
+        // This method could use some refactoring. One thing at a time.
+        internal ResourceSet CreateResourceSet(Stream store, Assembly assembly)
+        {
+            Debug.Assert(store != null, "I need a Stream!");
+            // Check to see if this is a Stream the ResourceManager understands,
+            // and check for the correct resource reader type.
+            if (store.CanSeek && store.Length > 4)
+            {
+                long startPos = store.Position;
+
+                // not disposing because we want to leave stream open
+                BinaryReader br = new BinaryReader(store);
+
+                // Look for our magic number as a little endian Int32.
+                int bytes = br.ReadInt32();
+                if (bytes == ResourceManager.MagicNumber)
+                {
+                    int resMgrHeaderVersion = br.ReadInt32();
+                    String readerTypeName = null, resSetTypeName = null;
+                    if (resMgrHeaderVersion == ResourceManager.HeaderVersionNumber)
+                    {
+                        br.ReadInt32();  // We don't want the number of bytes to skip.
+                        readerTypeName = System.CoreLib.FixupCoreLibName(br.ReadString());
+                        resSetTypeName = System.CoreLib.FixupCoreLibName(br.ReadString());
+                    }
+                    else if (resMgrHeaderVersion > ResourceManager.HeaderVersionNumber)
+                    {
+                        // Assume that the future ResourceManager headers will
+                        // have two strings for us - the reader type name and
+                        // resource set type name.  Read those, then use the num
+                        // bytes to skip field to correct our position.
+                        int numBytesToSkip = br.ReadInt32();
+                        long endPosition = br.BaseStream.Position + numBytesToSkip;
+
+                        readerTypeName = System.CoreLib.FixupCoreLibName(br.ReadString());
+                        resSetTypeName = System.CoreLib.FixupCoreLibName(br.ReadString());
+
+                        br.BaseStream.Seek(endPosition, SeekOrigin.Begin);
+                    }
+                    else
+                    {
+                        // resMgrHeaderVersion is older than this ResMgr version.
+                        // We should add in backwards compatibility support here.
+
+                        throw new NotSupportedException(SR.Format(SR.NotSupported_ObsoleteResourcesFile, _mediator.MainAssembly.GetSimpleName()));
+                    }
+
+                    store.Position = startPos;
+                    // Perf optimization - Don't use Reflection for our defaults.
+                    // Note there are two different sets of strings here - the
+                    // assembly qualified strings emitted by ResourceWriter, and
+                    // the abbreviated ones emitted by InternalResGen.
+                    if (CanUseDefaultResourceClasses(readerTypeName, resSetTypeName))
+                    {
+                        return new RuntimeResourceSet(store);
+                    }
+                    else
+                    {
+                        // we do not want to use partial binding here.
+                        Type readerType = Type.GetType(readerTypeName, true);
+                        Object[] args = new Object[1];
+                        args[0] = store;
+                        IResourceReader reader = (IResourceReader)Activator.CreateInstance(readerType, args);
+
+                        Object[] resourceSetArgs = new Object[1];
+                        resourceSetArgs[0] = reader;
+
+                        Type resSetType;
+                        if (_mediator.UserResourceSet == null)
+                        {
+                            Debug.Assert(resSetTypeName != null, "We should have a ResourceSet type name from the custom resource file here.");
+                            resSetType = Type.GetType(resSetTypeName, true, false);
+                        }
+                        else
+                            resSetType = _mediator.UserResourceSet;
+                        ResourceSet rs = (ResourceSet)Activator.CreateInstance(resSetType,
+                                                                                BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.CreateInstance,
+                                                                                null,
+                                                                                resourceSetArgs,
+                                                                                null,
+                                                                                null);
+                        return rs;
+                    }
+                }
+                else
+                {
+                    store.Position = startPos;
+                }
+            }
+
+            if (_mediator.UserResourceSet == null)
+            {
+                return new RuntimeResourceSet(store);
+            }
+            else
+            {
+                Object[] args = new Object[2];
+                args[0] = store;
+                args[1] = assembly;
+                try
+                {
+                    ResourceSet rs = null;
+                    // Add in a check for a constructor taking in an assembly first.
+                    try
+                    {
+                        rs = (ResourceSet)Activator.CreateInstance(_mediator.UserResourceSet, args);
+                        return rs;
+                    }
+                    catch (MissingMethodException) { }
+
+                    args = new Object[1];
+                    args[0] = store;
+                    rs = (ResourceSet)Activator.CreateInstance(_mediator.UserResourceSet, args);
+
+                    return rs;
+                }
+                catch (MissingMethodException e)
+                {
+                    throw new InvalidOperationException(SR.Format(SR.InvalidOperation_ResMgrBadResSet_Type, _mediator.UserResourceSet.AssemblyQualifiedName), e);
+                }
+            }
+        }
+
+        private Stream GetManifestResourceStream(RuntimeAssembly satellite, String fileName, ref StackCrawlMark stackMark)
+        {
+            Debug.Assert(satellite != null, "satellite shouldn't be null; check caller");
+            Debug.Assert(fileName != null, "fileName shouldn't be null; check caller");
+
+            // If we're looking in the main assembly AND if the main assembly was the person who
+            // created the ResourceManager, skip a security check for private manifest resources.
+            bool canSkipSecurityCheck = (_mediator.MainAssembly == satellite)
+                                        && (_mediator.CallingAssembly == _mediator.MainAssembly);
+
+            Stream stream = satellite.GetManifestResourceStream(_mediator.LocationInfo, fileName, canSkipSecurityCheck, ref stackMark);
+            if (stream == null)
+            {
+                stream = CaseInsensitiveManifestResourceStreamLookup(satellite, fileName);
+            }
+
+            return stream;
+        }
+
+        // Looks up a .resources file in the assembly manifest using 
+        // case-insensitive lookup rules.  Yes, this is slow.  The metadata
+        // dev lead refuses to make all assembly manifest resource lookups case-insensitive,
+        // even optionally case-insensitive.        
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        private Stream CaseInsensitiveManifestResourceStreamLookup(RuntimeAssembly satellite, String name)
+        {
+            Debug.Assert(satellite != null, "satellite shouldn't be null; check caller");
+            Debug.Assert(name != null, "name shouldn't be null; check caller");
+
+            StringBuilder sb = new StringBuilder();
+            if (_mediator.LocationInfo != null)
+            {
+                String nameSpace = _mediator.LocationInfo.Namespace;
+                if (nameSpace != null)
+                {
+                    sb.Append(nameSpace);
+                    if (name != null)
+                        sb.Append(Type.Delimiter);
+                }
+            }
+            sb.Append(name);
+
+            String givenName = sb.ToString();
+            String canonicalName = null;
+            foreach (String existingName in satellite.GetManifestResourceNames())
+            {
+                if (String.Equals(existingName, givenName, StringComparison.InvariantCultureIgnoreCase))
+                {
+                    if (canonicalName == null)
+                    {
+                        canonicalName = existingName;
+                    }
+                    else
+                    {
+                        throw new MissingManifestResourceException(SR.Format(SR.MissingManifestResource_MultipleBlobs, givenName, satellite.ToString()));
+                    }
+                }
+            }
+
+            if (canonicalName == null)
+            {
+                return null;
+            }
+
+            // If we're looking in the main assembly AND if the main
+            // assembly was the person who created the ResourceManager,
+            // skip a security check for private manifest resources.
+            bool canSkipSecurityCheck = _mediator.MainAssembly == satellite && _mediator.CallingAssembly == _mediator.MainAssembly;
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return satellite.GetManifestResourceStream(canonicalName, ref stackMark, canSkipSecurityCheck);
+        }
+
+        private RuntimeAssembly GetSatelliteAssembly(CultureInfo lookForCulture, ref StackCrawlMark stackMark)
+        {
+            if (!_mediator.LookedForSatelliteContractVersion)
+            {
+                _mediator.SatelliteContractVersion = _mediator.ObtainSatelliteContractVersion(_mediator.MainAssembly);
+                _mediator.LookedForSatelliteContractVersion = true;
+            }
+
+            RuntimeAssembly satellite = null;
+            String satAssemblyName = GetSatelliteAssemblyName();
+
+            // Look up the satellite assembly, but don't let problems
+            // like a partially signed satellite assembly stop us from
+            // doing fallback and displaying something to the user.
+            // Yet also somehow log this error for a developer.
+            try
+            {
+                satellite = _mediator.MainAssembly.InternalGetSatelliteAssembly(satAssemblyName, lookForCulture, _mediator.SatelliteContractVersion, false, ref stackMark);
+            }
+
+            // Jun 08: for cases other than ACCESS_DENIED, we'll assert instead of throw to give release builds more opportunity to fallback.
+
+            catch (FileLoadException fle)
+            {
+                // Ignore cases where the loader gets an access
+                // denied back from the OS.  This showed up for
+                // href-run exe's at one point.  
+                int hr = fle._HResult;
+                if (hr != Win32Marshal.MakeHRFromErrorCode(Interop.Errors.ERROR_ACCESS_DENIED))
+                {
+                    Debug.Fail("[This assert catches satellite assembly build/deployment problems - report this message to your build lab & loc engineer]" + Environment.NewLine + "GetSatelliteAssembly failed for culture " + lookForCulture.Name + " and version " + (_mediator.SatelliteContractVersion == null ? _mediator.MainAssembly.GetVersion().ToString() : _mediator.SatelliteContractVersion.ToString()) + " of assembly " + _mediator.MainAssembly.GetSimpleName() + " with error code 0x" + hr.ToString("X", CultureInfo.InvariantCulture) + Environment.NewLine + "Exception: " + fle);
+                }
+            }
+
+            // Don't throw for zero-length satellite assemblies, for compat with v1
+            catch (BadImageFormatException bife)
+            {
+                Debug.Fail("[This assert catches satellite assembly build/deployment problems - report this message to your build lab & loc engineer]" + Environment.NewLine + "GetSatelliteAssembly failed for culture " + lookForCulture.Name + " and version " + (_mediator.SatelliteContractVersion == null ? _mediator.MainAssembly.GetVersion().ToString() : _mediator.SatelliteContractVersion.ToString()) + " of assembly " + _mediator.MainAssembly.GetSimpleName() + Environment.NewLine + "Exception: " + bife);
+            }
+
+            return satellite;
+        }
+
+        // Perf optimization - Don't use Reflection for most cases with
+        // our .resources files.  This makes our code run faster and we can
+        // creating a ResourceReader via Reflection.  This would incur
+        // a security check (since the link-time check on the constructor that
+        // takes a String is turned into a full demand with a stack walk)
+        // and causes partially trusted localized apps to fail.
+        private bool CanUseDefaultResourceClasses(String readerTypeName, String resSetTypeName)
+        {
+            Debug.Assert(readerTypeName != null, "readerTypeName shouldn't be null; check caller");
+            Debug.Assert(resSetTypeName != null, "resSetTypeName shouldn't be null; check caller");
+
+            if (_mediator.UserResourceSet != null)
+                return false;
+
+            // Ignore the actual version of the ResourceReader and 
+            // RuntimeResourceSet classes.  Let those classes deal with
+            // versioning themselves.
+            AssemblyName mscorlib = new AssemblyName(ResourceManager.MscorlibName);
+
+            if (readerTypeName != null)
+            {
+                if (!ResourceManager.CompareNames(readerTypeName, ResourceManager.ResReaderTypeName, mscorlib))
+                    return false;
+            }
+
+            if (resSetTypeName != null)
+            {
+                if (!ResourceManager.CompareNames(resSetTypeName, ResourceManager.ResSetTypeName, mscorlib))
+                    return false;
+            }
+
+            return true;
+        }
+
+        private String GetSatelliteAssemblyName()
+        {
+            String satAssemblyName = _mediator.MainAssembly.GetSimpleName();
+            satAssemblyName += ".resources";
+            return satAssemblyName;
+        }
+
+        private void HandleSatelliteMissing()
+        {
+            String satAssemName = _mediator.MainAssembly.GetSimpleName() + ".resources.dll";
+            if (_mediator.SatelliteContractVersion != null)
+            {
+                satAssemName += ", Version=" + _mediator.SatelliteContractVersion.ToString();
+            }
+
+            AssemblyName an = new AssemblyName();
+            an.SetPublicKey(_mediator.MainAssembly.GetPublicKey());
+            byte[] token = an.GetPublicKeyToken();
+
+            int iLen = token.Length;
+            StringBuilder publicKeyTok = new StringBuilder(iLen * 2);
+            for (int i = 0; i < iLen; i++)
+            {
+                publicKeyTok.Append(token[i].ToString("x", CultureInfo.InvariantCulture));
+            }
+            satAssemName += ", PublicKeyToken=" + publicKeyTok;
+
+            String missingCultureName = _mediator.NeutralResourcesCulture.Name;
+            if (missingCultureName.Length == 0)
+            {
+                missingCultureName = "<invariant>";
+            }
+            throw new MissingSatelliteAssemblyException(SR.Format(SR.MissingSatelliteAssembly_Culture_Name, _mediator.NeutralResourcesCulture, satAssemName), missingCultureName);
+        }
+
+        private void HandleResourceStreamMissing(String fileName)
+        {
+            // Keep people from bothering me about resources problems
+            if (_mediator.MainAssembly == typeof(Object).Assembly && _mediator.BaseName.Equals(System.CoreLib.Name))
+            {
+                // This would break CultureInfo & all our exceptions.
+                Debug.Fail("Couldn't get " + System.CoreLib.Name + ResourceManager.ResFileExtension + " from " + System.CoreLib.Name + "'s assembly" + Environment.NewLine + Environment.NewLine + "Are you building the runtime on your machine?  Chances are the BCL directory didn't build correctly.  Type 'build -c' in the BCL directory.  If you get build errors, look at buildd.log.  If you then can't figure out what's wrong (and you aren't changing the assembly-related metadata code), ask a BCL dev.\n\nIf you did NOT build the runtime, you shouldn't be seeing this and you've found a bug.");
+
+                // We cannot continue further - simply FailFast.
+                string mesgFailFast = System.CoreLib.Name + ResourceManager.ResFileExtension + " couldn't be found!  Large parts of the BCL won't work!";
+                System.Environment.FailFast(mesgFailFast);
+            }
+            // We really don't think this should happen - we always
+            // expect the neutral locale's resources to be present.
+            String resName = String.Empty;
+            if (_mediator.LocationInfo != null && _mediator.LocationInfo.Namespace != null)
+                resName = _mediator.LocationInfo.Namespace + Type.Delimiter;
+            resName += fileName;
+            throw new MissingManifestResourceException(SR.Format(SR.MissingManifestResource_NoNeutralAsm, resName, _mediator.MainAssembly.GetSimpleName()));
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern bool GetNeutralResourcesLanguageAttribute(RuntimeAssembly assemblyHandle, StringHandleOnStack cultureName, out short fallbackLocation);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Resources/ResourceManager.cs b/src/System.Private.CoreLib/src/System/Resources/ResourceManager.cs
new file mode 100644
index 0000000000..f17dc753aa
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Resources/ResourceManager.cs
@@ -0,0 +1,1338 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Default way to access String and Object resources
+** from an assembly.
+**
+** 
+===========================================================*/
+
+namespace System.Resources
+{
+    using System;
+    using System.IO;
+    using System.Globalization;
+    using System.Collections;
+    using System.Text;
+    using System.Reflection;
+    using System.Security;
+    using System.Threading;
+    using System.Runtime.InteropServices;
+    using System.Runtime.CompilerServices;
+    using Microsoft.Win32;
+    using System.Collections.Generic;
+    using System.Runtime.Versioning;
+    using System.Diagnostics;
+
+#if FEATURE_APPX
+    //
+    // This is implemented in System.Runtime.WindowsRuntime as function System.Resources.WindowsRuntimeResourceManager,
+    // allowing us to ask for a WinRT-specific ResourceManager.
+    // It is important to have WindowsRuntimeResourceManagerBase as regular class with virtual methods and default implementations. 
+    // Defining WindowsRuntimeResourceManagerBase as abstract class or interface will cause issues when adding more methods to it 
+    // because it'll create dependency between mscorlib and System.Runtime.WindowsRuntime which will require always shipping both DLLs together. 
+    //
+    // [FriendAccessAllowed]
+    internal abstract class WindowsRuntimeResourceManagerBase
+    {
+        public abstract bool Initialize(string libpath, string reswFilename, out PRIExceptionInfo exceptionInfo);
+
+        public abstract String GetString(String stringName, String startingCulture, String neutralResourcesCulture);
+
+        public abstract CultureInfo GlobalResourceContextBestFitCultureInfo
+        {
+            get;
+        }
+
+        public abstract bool SetGlobalResourceContextDefaultCulture(CultureInfo ci);
+    }
+
+    // [FriendAccessAllowed]
+    internal class PRIExceptionInfo
+    {
+        public string _PackageSimpleName;
+        public string _ResWFile;
+    }
+#endif // FEATURE_APPX
+
+    // Resource Manager exposes an assembly's resources to an application for
+    // the correct CultureInfo.  An example would be localizing text for a 
+    // user-visible message.  Create a set of resource files listing a name 
+    // for a message and its value, compile them using ResGen, put them in
+    // an appropriate place (your assembly manifest(?)), then create a Resource 
+    // Manager and query for the name of the message you want.  The Resource
+    // Manager will use CultureInfo.GetCurrentUICulture() to look
+    // up a resource for your user's locale settings.
+    // 
+    // Users should ideally create a resource file for every culture, or
+    // at least a meaningful subset.  The filenames will follow the naming 
+    // scheme:
+    // 
+    // basename.culture name.resources
+    // 
+    // The base name can be the name of your application, or depending on 
+    // the granularity desired, possibly the name of each class.  The culture 
+    // name is determined from CultureInfo's Name property.  
+    // An example file name may be MyApp.en-US.resources for
+    // MyApp's US English resources.
+    // 
+    // -----------------
+    // Refactoring Notes
+    // -----------------
+    // In Feb 08, began first step of refactoring ResourceManager to improve
+    // maintainability (sd changelist 3012100). This resulted in breaking
+    // apart the InternalGetResourceSet "big loop" so that the file-based
+    // and manifest-based lookup was located in separate methods. 
+    // In Apr 08, continued refactoring so that file-based and manifest-based
+    // concerns are encapsulated by separate classes. At construction, the
+    // ResourceManager creates one of these classes based on whether the 
+    // RM will need to use file-based or manifest-based resources, and 
+    // afterwards refers to this through the interface IResourceGroveler.
+    // 
+    // Serialization Compat: Ideally, we could have refactored further but
+    // this would have broken serialization compat. For example, the
+    // ResourceManager member UseManifest and UseSatelliteAssem are no 
+    // longer relevant on ResourceManager. Similarly, other members could
+    // ideally be moved to the file-based or manifest-based classes 
+    // because they are only relevant for those types of lookup.
+    //
+    // Solution now / in the future: 
+    // For now, we simply use a mediator class so that we can keep these
+    // members on ResourceManager but allow the file-based and manifest-
+    // based classes to access/set these members in a uniform way. See
+    // ResourceManagerMediator.
+    // We encapsulate fallback logic in a fallback iterator class, so that 
+    // this logic isn't duplicated in several methods.
+    // 
+    // In the future, we can also look into further factoring and better
+    // design of IResourceGroveler interface to accommodate unused parameters
+    // that don't make sense for either file-based or manifest-based lookup paths.
+    //
+    // Benefits of this refactoring:
+    // - Makes it possible to understand what the ResourceManager does, 
+    // which is key for maintainability. 
+    // - Makes the ResourceManager more extensible by identifying and
+    // encapsulating what varies
+    // - Unearthed a bug that's been lurking a while in file-based 
+    // lookup paths for InternalGetResourceSet if createIfNotExists is
+    // false.
+    // - Reuses logic, e.g. by breaking apart the culture fallback into 
+    // the fallback iterator class, we don't have to repeat the 
+    // sometimes confusing fallback logic across multiple methods
+    // - Fxcop violations reduced to 1/5th of original count. Most 
+    // importantly, code complexity violations disappeared.
+    // - Finally, it got rid of dead code paths. Because the big loop was
+    // so confusing, it masked unused chunks of code. Also, dividing 
+    // between file-based and manifest-based allowed functionaliy 
+    // unused in silverlight to fall out.
+    // 
+    // Note: this type is integral to the construction of exception objects,
+    // and sometimes this has to be done in low memory situtations (OOM) or
+    // to create TypeInitializationExceptions due to failure of a static class
+    // constructor. This type needs to be extremely careful and assume that 
+    // any type it references may have previously failed to construct, so statics
+    // belonging to that type may not be initialized. FrameworkEventSource.Log
+    // is one such example.
+    //
+
+    public class ResourceManager
+    {
+        internal class CultureNameResourceSetPair
+        {
+            public String lastCultureName;
+            public ResourceSet lastResourceSet;
+        }
+
+        protected String BaseNameField;
+        // Sets is a many-to-one table of CultureInfos mapped to ResourceSets.
+        // Don't synchronize ResourceSets - too fine-grained a lock to be effective
+        [Obsolete("call InternalGetResourceSet instead")]
+        internal Hashtable ResourceSets;
+
+
+        private Dictionary<String, ResourceSet> _resourceSets;
+        private String moduleDir;      // For assembly-ignorant directory location
+        protected Assembly MainAssembly;   // Need the assembly manifest sometimes.
+        private Type _locationInfo;    // For Assembly or type-based directory layout
+        private Type _userResourceSet;  // Which ResourceSet instance to create
+        private CultureInfo _neutralResourcesCulture;  // For perf optimizations.
+
+        private CultureNameResourceSetPair _lastUsedResourceCache;
+
+        private bool _ignoreCase;   // Whether case matters in GetString & GetObject
+
+        private bool UseManifest;  // Use Assembly manifest, or grovel disk.
+
+#if RESOURCE_SATELLITE_CONFIG
+        private static volatile Hashtable _installedSatelliteInfo;  // Give the user the option  
+                                                                    // to prevent certain satellite assembly probes via a config file.
+                                                                    // Note that config files are per-appdomain, not per-assembly nor process
+        private static volatile bool _checkedConfigFile;  // Did we read the app's config file?
+#endif
+
+        // Whether to fall back to the main assembly or a particular 
+        // satellite for the neutral resources.
+        private UltimateResourceFallbackLocation _fallbackLoc;
+        // Version number of satellite assemblies to look for.  May be null.
+        private Version _satelliteContractVersion;
+        private bool _lookedForSatelliteContractVersion;
+
+        private RuntimeAssembly _callingAssembly;  // Assembly who created the ResMgr.
+
+        private IResourceGroveler resourceGroveler;
+
+        public static readonly int MagicNumber = unchecked((int)0xBEEFCACE);  // If only hex had a K...
+
+        // Version number so ResMgr can get the ideal set of classes for you.
+        // ResMgr header is:
+        // 1) MagicNumber (little endian Int32)
+        // 2) HeaderVersionNumber (little endian Int32)
+        // 3) Num Bytes to skip past ResMgr header (little endian Int32)
+        // 4) IResourceReader type name for this file (bytelength-prefixed UTF-8 String)
+        // 5) ResourceSet type name for this file (bytelength-prefixed UTF8 String)
+        public static readonly int HeaderVersionNumber = 1;
+
+        //
+        //It would be better if we could use _neutralCulture instead of calling
+        //CultureInfo.InvariantCulture everywhere, but we run into problems with the .cctor.  CultureInfo 
+        //initializes assembly, which initializes ResourceManager, which tries to get a CultureInfo which isn't
+        //there yet because CultureInfo's class initializer hasn't finished.  If we move SystemResMgr off of
+        //Assembly (or at least make it an internal property) we should be able to circumvent this problem.
+        //
+        //      private static CultureInfo _neutralCulture = null;
+
+        // This is our min required ResourceSet type.
+        private static readonly Type _minResourceSet = typeof(ResourceSet);
+        // These Strings are used to avoid using Reflection in CreateResourceSet.
+        // The first set are used by ResourceWriter.  The second are used by
+        // InternalResGen.
+        internal static readonly String ResReaderTypeName = typeof(ResourceReader).FullName;
+        internal static readonly String ResSetTypeName = typeof(RuntimeResourceSet).FullName;
+        internal static readonly String MscorlibName = typeof(ResourceReader).Assembly.FullName;
+        internal const String ResFileExtension = ".resources";
+        internal const int ResFileExtensionLength = 10;
+
+        private static volatile bool s_IsAppXModel;
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        private void Init()
+        {
+            _callingAssembly = (RuntimeAssembly)Assembly.GetCallingAssembly();
+        }
+
+        protected ResourceManager()
+        {
+            Init();
+
+            _lastUsedResourceCache = new CultureNameResourceSetPair();
+            ResourceManagerMediator mediator = new ResourceManagerMediator(this);
+            resourceGroveler = new ManifestBasedResourceGroveler(mediator);
+        }
+
+        // Constructs a Resource Manager for files beginning with 
+        // baseName in the directory specified by resourceDir
+        // or in the current directory.  This Assembly-ignorant constructor is 
+        // mostly useful for testing your own ResourceSet implementation.
+        //
+        // A good example of a baseName might be "Strings".  BaseName 
+        // should not end in ".resources".
+        //
+        // Note: System.Windows.Forms uses this method at design time.
+        // 
+        private ResourceManager(String baseName, String resourceDir, Type usingResourceSet)
+        {
+            if (null == baseName)
+                throw new ArgumentNullException(nameof(baseName));
+            if (null == resourceDir)
+                throw new ArgumentNullException(nameof(resourceDir));
+
+            BaseNameField = baseName;
+
+            moduleDir = resourceDir;
+            _userResourceSet = usingResourceSet;
+#pragma warning disable 618
+            ResourceSets = new Hashtable(); // for backward compatibility
+#pragma warning restore 618
+            _resourceSets = new Dictionary<String, ResourceSet>();
+            _lastUsedResourceCache = new CultureNameResourceSetPair();
+            UseManifest = false;
+
+            ResourceManagerMediator mediator = new ResourceManagerMediator(this);
+            resourceGroveler = new FileBasedResourceGroveler(mediator);
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public ResourceManager(String baseName, Assembly assembly)
+        {
+            if (null == baseName)
+                throw new ArgumentNullException(nameof(baseName));
+
+            if (null == assembly)
+                throw new ArgumentNullException(nameof(assembly));
+
+            if (!(assembly is RuntimeAssembly))
+                throw new ArgumentException(SR.Argument_MustBeRuntimeAssembly);
+
+            MainAssembly = assembly;
+            BaseNameField = baseName;
+
+            SetAppXConfiguration();
+
+            CommonAssemblyInit();
+
+            _callingAssembly = (RuntimeAssembly)Assembly.GetCallingAssembly();
+            // Special case for mscorlib - protect mscorlib's private resources.
+            // This isn't for security reasons, but to ensure we can make
+            // breaking changes to mscorlib's internal resources without 
+            // assuming users may have taken a dependency on them.
+            if (assembly == typeof(Object).Assembly && _callingAssembly != assembly)
+            {
+                _callingAssembly = null;
+            }
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public ResourceManager(String baseName, Assembly assembly, Type usingResourceSet)
+        {
+            if (null == baseName)
+                throw new ArgumentNullException(nameof(baseName));
+            if (null == assembly)
+                throw new ArgumentNullException(nameof(assembly));
+
+            if (!(assembly is RuntimeAssembly))
+                throw new ArgumentException(SR.Argument_MustBeRuntimeAssembly);
+
+            MainAssembly = assembly;
+            BaseNameField = baseName;
+
+            if (usingResourceSet != null && (usingResourceSet != _minResourceSet) && !(usingResourceSet.IsSubclassOf(_minResourceSet)))
+                throw new ArgumentException(SR.Arg_ResMgrNotResSet, nameof(usingResourceSet));
+            _userResourceSet = usingResourceSet;
+
+            CommonAssemblyInit();
+            _callingAssembly = (RuntimeAssembly)Assembly.GetCallingAssembly();
+            // Special case for mscorlib - protect mscorlib's private resources.
+            // This isn't for security reasons, but to ensure we can make
+            // breaking changes to mscorlib's internal resources without 
+            // assuming users may have taken a dependency on them.
+            if (assembly == typeof(Object).Assembly && _callingAssembly != assembly)
+                _callingAssembly = null;
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public ResourceManager(Type resourceSource)
+        {
+            if (null == resourceSource)
+                throw new ArgumentNullException(nameof(resourceSource));
+
+            if (!(resourceSource is RuntimeType))
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType);
+
+            _locationInfo = resourceSource;
+            MainAssembly = _locationInfo.Assembly;
+            BaseNameField = resourceSource.Name;
+
+            SetAppXConfiguration();
+
+            CommonAssemblyInit();
+
+            _callingAssembly = (RuntimeAssembly)Assembly.GetCallingAssembly();
+            // Special case for mscorlib - protect mscorlib's private resources.
+            if (MainAssembly == typeof(Object).Assembly && _callingAssembly != MainAssembly)
+            {
+                _callingAssembly = null;
+            }
+        }
+
+        // Trying to unify code as much as possible, even though having to do a
+        // security check in each constructor prevents it.
+        private void CommonAssemblyInit()
+        {
+            // Now we can use the managed resources even when using PRI's to support the APIs GetObject, GetStream...etc.
+            UseManifest = true;
+
+            _resourceSets = new Dictionary<String, ResourceSet>();
+            _lastUsedResourceCache = new CultureNameResourceSetPair();
+
+            _fallbackLoc = UltimateResourceFallbackLocation.MainAssembly;
+
+            ResourceManagerMediator mediator = new ResourceManagerMediator(this);
+            resourceGroveler = new ManifestBasedResourceGroveler(mediator);
+
+            _neutralResourcesCulture = ManifestBasedResourceGroveler.GetNeutralResourcesLanguage(MainAssembly, ref _fallbackLoc);
+        }
+
+        // Gets the base name for the ResourceManager.
+        public virtual String BaseName
+        {
+            get { return BaseNameField; }
+        }
+
+        // Whether we should ignore the capitalization of resources when calling
+        // GetString or GetObject.
+        public virtual bool IgnoreCase
+        {
+            get { return _ignoreCase; }
+            set { _ignoreCase = value; }
+        }
+
+        // Returns the Type of the ResourceSet the ResourceManager uses
+        // to construct ResourceSets.
+        public virtual Type ResourceSetType
+        {
+            get { return (_userResourceSet == null) ? typeof(RuntimeResourceSet) : _userResourceSet; }
+        }
+
+        protected UltimateResourceFallbackLocation FallbackLocation
+        {
+            get { return _fallbackLoc; }
+            set { _fallbackLoc = value; }
+        }
+
+        // Tells the ResourceManager to call Close on all ResourceSets and 
+        // release all resources.  This will shrink your working set by
+        // potentially a substantial amount in a running application.  Any
+        // future resource lookups on this ResourceManager will be as 
+        // expensive as the very first lookup, since it will need to search
+        // for files and load resources again.
+        // 
+        // This may be useful in some complex threading scenarios, where 
+        // creating a new ResourceManager isn't quite the correct behavior.
+        public virtual void ReleaseAllResources()
+        {
+            Dictionary<String, ResourceSet> localResourceSets = _resourceSets;
+
+            // If any calls to Close throw, at least leave ourselves in a
+            // consistent state.
+            _resourceSets = new Dictionary<String, ResourceSet>();
+            _lastUsedResourceCache = new CultureNameResourceSetPair();
+
+            lock (localResourceSets)
+            {
+                foreach ((_, ResourceSet resourceSet) in localResourceSets)
+                {
+                    resourceSet.Close();
+                }
+            }
+        }
+
+        public static ResourceManager CreateFileBasedResourceManager(String baseName, String resourceDir, Type usingResourceSet)
+        {
+            return new ResourceManager(baseName, resourceDir, usingResourceSet);
+        }
+
+        // Given a CultureInfo, GetResourceFileName generates the name for 
+        // the binary file for the given CultureInfo.  This method uses 
+        // CultureInfo's Name property as part of the file name for all cultures
+        // other than the invariant culture.  This method does not touch the disk, 
+        // and is used only to construct what a resource file name (suitable for
+        // passing to the ResourceReader constructor) or a manifest resource file
+        // name should look like.
+        // 
+        // This method can be overriden to look for a different extension,
+        // such as ".ResX", or a completely different format for naming files.
+        protected virtual String GetResourceFileName(CultureInfo culture)
+        {
+            // If this is the neutral culture, don't include the culture name.
+            if (culture.HasInvariantCultureName)
+            {
+                return BaseNameField + ResFileExtension;
+            }
+            else
+            {
+                CultureInfo.VerifyCultureName(culture.Name, throwException: true);
+                return BaseNameField + "." + culture.Name + ResFileExtension;
+            }
+        }
+
+        // WARNING: This function must be kept in sync with ResourceFallbackManager.GetEnumerator()
+        // Return the first ResourceSet, based on the first culture ResourceFallbackManager would return
+        internal ResourceSet GetFirstResourceSet(CultureInfo culture)
+        {
+            // Logic from ResourceFallbackManager.GetEnumerator()
+            if (_neutralResourcesCulture != null && culture.Name == _neutralResourcesCulture.Name)
+            {
+                culture = CultureInfo.InvariantCulture;
+            }
+
+            if (_lastUsedResourceCache != null)
+            {
+                lock (_lastUsedResourceCache)
+                {
+                    if (culture.Name == _lastUsedResourceCache.lastCultureName)
+                        return _lastUsedResourceCache.lastResourceSet;
+                }
+            }
+
+            // Look in the ResourceSet table
+            Dictionary<String, ResourceSet> localResourceSets = _resourceSets;
+            ResourceSet rs = null;
+            if (localResourceSets != null)
+            {
+                lock (localResourceSets)
+                {
+                    localResourceSets.TryGetValue(culture.Name, out rs);
+                }
+            }
+
+            if (rs != null)
+            {
+                // update the cache with the most recent ResourceSet
+                if (_lastUsedResourceCache != null)
+                {
+                    lock (_lastUsedResourceCache)
+                    {
+                        _lastUsedResourceCache.lastCultureName = culture.Name;
+                        _lastUsedResourceCache.lastResourceSet = rs;
+                    }
+                }
+                return rs;
+            }
+
+            return null;
+        }
+
+        // Looks up a set of resources for a particular CultureInfo.  This is
+        // not useful for most users of the ResourceManager - call 
+        // GetString() or GetObject() instead.  
+        //
+        // The parameters let you control whether the ResourceSet is created 
+        // if it hasn't yet been loaded and if parent CultureInfos should be 
+        // loaded as well for resource inheritance.
+        //         
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public virtual ResourceSet GetResourceSet(CultureInfo culture, bool createIfNotExists, bool tryParents)
+        {
+            if (null == culture)
+                throw new ArgumentNullException(nameof(culture));
+
+            Dictionary<String, ResourceSet> localResourceSets = _resourceSets;
+            ResourceSet rs;
+            if (localResourceSets != null)
+            {
+                lock (localResourceSets)
+                {
+                    if (localResourceSets.TryGetValue(culture.Name, out rs))
+                        return rs;
+                }
+            }
+
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+
+            if (UseManifest && culture.HasInvariantCultureName)
+            {
+                string fileName = GetResourceFileName(culture);
+                RuntimeAssembly mainAssembly = (RuntimeAssembly)MainAssembly;
+                Stream stream = mainAssembly.GetManifestResourceStream(_locationInfo, fileName, _callingAssembly == MainAssembly, ref stackMark);
+                if (createIfNotExists && stream != null)
+                {
+                    rs = ((ManifestBasedResourceGroveler)resourceGroveler).CreateResourceSet(stream, MainAssembly);
+                    AddResourceSet(localResourceSets, culture.Name, ref rs);
+                    return rs;
+                }
+            }
+
+            // Note: ideally we could plumb through the stack crawl mark here, but we must
+            // call the virtual 3-argument InternalGetResourceSet method for compatibility.
+            // Security-wise, we're not overly interested in protecting access to resources,
+            // since full-trust callers can get them already and most resources are public.
+            // Also, the JIT inliner could always inline a caller into another assembly's
+            // method.
+            // So if we happen to return some resources in cases where we should really be
+            // doing a demand for member access permissions, we're not overly concerned.
+            return InternalGetResourceSet(culture, createIfNotExists, tryParents);
+        }
+
+        // InternalGetResourceSet is a non-threadsafe method where all the logic
+        // for getting a resource set lives.  Access to it is controlled by
+        // threadsafe methods such as GetResourceSet, GetString, & GetObject.  
+        // This will take a minimal number of locks.
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        protected virtual ResourceSet InternalGetResourceSet(CultureInfo culture, bool createIfNotExists, bool tryParents)
+        {
+            Debug.Assert(culture != null, "culture != null");
+
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return InternalGetResourceSet(culture, createIfNotExists, tryParents, ref stackMark);
+        }
+
+        // InternalGetResourceSet is a non-threadsafe method where all the logic
+        // for getting a resource set lives.  Access to it is controlled by
+        // threadsafe methods such as GetResourceSet, GetString, & GetObject.  
+        // This will take a minimal number of locks.
+        private ResourceSet InternalGetResourceSet(CultureInfo requestedCulture, bool createIfNotExists, bool tryParents, ref StackCrawlMark stackMark)
+        {
+            Dictionary<String, ResourceSet> localResourceSets = _resourceSets;
+            ResourceSet rs = null;
+            CultureInfo foundCulture = null;
+            lock (localResourceSets)
+            {
+                if (localResourceSets.TryGetValue(requestedCulture.Name, out rs))
+                {
+                    return rs;
+                }
+            }
+
+            ResourceFallbackManager mgr = new ResourceFallbackManager(requestedCulture, _neutralResourcesCulture, tryParents);
+
+            foreach (CultureInfo currentCultureInfo in mgr)
+            {
+                lock (localResourceSets)
+                {
+                    if (localResourceSets.TryGetValue(currentCultureInfo.Name, out rs))
+                    {
+                        // we need to update the cache if we fellback
+                        if (requestedCulture != currentCultureInfo) foundCulture = currentCultureInfo;
+                        break;
+                    }
+                }
+
+                // InternalGetResourceSet will never be threadsafe.  However, it must
+                // be protected against reentrancy from the SAME THREAD.  (ie, calling
+                // GetSatelliteAssembly may send some window messages or trigger the
+                // Assembly load event, which could fail then call back into the 
+                // ResourceManager).  It's happened.
+
+                rs = resourceGroveler.GrovelForResourceSet(currentCultureInfo, localResourceSets,
+                                                           tryParents, createIfNotExists, ref stackMark);
+
+                // found a ResourceSet; we're done
+                if (rs != null)
+                {
+                    foundCulture = currentCultureInfo;
+                    break;
+                }
+            }
+
+            if (rs != null && foundCulture != null)
+            {
+                // add entries to the cache for the cultures we have gone through
+
+                // currentCultureInfo now refers to the culture that had resources.
+                // update cultures starting from requested culture up to the culture
+                // that had resources.
+                foreach (CultureInfo updateCultureInfo in mgr)
+                {
+                    AddResourceSet(localResourceSets, updateCultureInfo.Name, ref rs);
+
+                    // stop when we've added current or reached invariant (top of chain)
+                    if (updateCultureInfo == foundCulture)
+                    {
+                        break;
+                    }
+                }
+            }
+
+            return rs;
+        }
+
+        // Simple helper to ease maintenance and improve readability.
+        private static void AddResourceSet(Dictionary<String, ResourceSet> localResourceSets, String cultureName, ref ResourceSet rs)
+        {
+            // InternalGetResourceSet is both recursive and reentrant - 
+            // assembly load callbacks in particular are a way we can call
+            // back into the ResourceManager in unexpectedly on the same thread.
+            lock (localResourceSets)
+            {
+                // If another thread added this culture, return that.
+                ResourceSet lostRace;
+                if (localResourceSets.TryGetValue(cultureName, out lostRace))
+                {
+                    if (!Object.ReferenceEquals(lostRace, rs))
+                    {
+                        // Note: In certain cases, we can be trying to add a ResourceSet for multiple
+                        // cultures on one thread, while a second thread added another ResourceSet for one
+                        // of those cultures.  If there is a race condition we must make sure our ResourceSet 
+                        // isn't in our dictionary before closing it.
+                        if (!localResourceSets.ContainsValue(rs))
+                            rs.Dispose();
+                        rs = lostRace;
+                    }
+                }
+                else
+                {
+                    localResourceSets.Add(cultureName, rs);
+                }
+            }
+        }
+
+        protected static Version GetSatelliteContractVersion(Assembly a)
+        {
+            // Ensure that the assembly reference is not null
+            if (a == null)
+            {
+                throw new ArgumentNullException(nameof(a), SR.ArgumentNull_Assembly);
+            }
+
+            // Return null. The calling code will use the assembly version instead to avoid potential type
+            // and library loads caused by CA lookup. NetCF uses the assembly version always.
+            return null;
+        }
+
+        protected static CultureInfo GetNeutralResourcesLanguage(Assembly a)
+        {
+            // This method should be obsolete - replace it with the one below.
+            // Unfortunately, we made it protected.
+            UltimateResourceFallbackLocation ignoringUsefulData = UltimateResourceFallbackLocation.MainAssembly;
+            CultureInfo culture = ManifestBasedResourceGroveler.GetNeutralResourcesLanguage(a, ref ignoringUsefulData);
+            return culture;
+        }
+
+        // IGNORES VERSION
+        internal static bool CompareNames(String asmTypeName1,
+                                          String typeName2,
+                                          AssemblyName asmName2)
+        {
+            Debug.Assert(asmTypeName1 != null, "asmTypeName1 was unexpectedly null");
+
+            // First, compare type names
+            int comma = asmTypeName1.IndexOf(',');
+            if (((comma == -1) ? asmTypeName1.Length : comma) != typeName2.Length)
+                return false;
+
+            // case sensitive
+            if (String.Compare(asmTypeName1, 0, typeName2, 0, typeName2.Length, StringComparison.Ordinal) != 0)
+                return false;
+            if (comma == -1)
+                return true;
+
+            // Now, compare assembly display names (IGNORES VERSION AND PROCESSORARCHITECTURE)
+            // also, for  mscorlib ignores everything, since that's what the binder is going to do
+            while (Char.IsWhiteSpace(asmTypeName1[++comma])) ;
+
+            // case insensitive
+            AssemblyName an1 = new AssemblyName(asmTypeName1.Substring(comma));
+            if (String.Compare(an1.Name, asmName2.Name, StringComparison.OrdinalIgnoreCase) != 0)
+                return false;
+
+            // to match IsMscorlib() in VM
+            if (String.Compare(an1.Name, System.CoreLib.Name, StringComparison.OrdinalIgnoreCase) == 0)
+                return true;
+
+
+            if ((an1.CultureInfo != null) && (asmName2.CultureInfo != null) &&
+#if FEATURE_USE_LCID                
+                (an1.CultureInfo.LCID != asmName2.CultureInfo.LCID)
+#else
+                (an1.CultureInfo.Name != asmName2.CultureInfo.Name)
+#endif                
+                )
+                return false;
+
+            byte[] pkt1 = an1.GetPublicKeyToken();
+            byte[] pkt2 = asmName2.GetPublicKeyToken();
+            if ((pkt1 != null) && (pkt2 != null))
+            {
+                if (pkt1.Length != pkt2.Length)
+                    return false;
+
+                for (int i = 0; i < pkt1.Length; i++)
+                {
+                    if (pkt1[i] != pkt2[i])
+                        return false;
+                }
+            }
+
+            return true;
+        }
+
+#if FEATURE_APPX
+        private string GetStringFromPRI(String stringName, String startingCulture, String neutralResourcesCulture)
+        {
+            Debug.Assert(_bUsingModernResourceManagement);
+            Debug.Assert(_WinRTResourceManager != null);
+            Debug.Assert(_PRIonAppXInitialized);
+            Debug.Assert(AppDomain.IsAppXModel());
+
+            if (stringName.Length == 0)
+                return null;
+
+            string resourceString = null;
+
+            // Do not handle exceptions. See the comment in SetAppXConfiguration about throwing
+            // exception types that the ResourceManager class is not documented to throw.
+            resourceString = _WinRTResourceManager.GetString(
+                                       stringName,
+                                       String.IsNullOrEmpty(startingCulture) ? null : startingCulture,
+                                       String.IsNullOrEmpty(neutralResourcesCulture) ? null : neutralResourcesCulture);
+
+            return resourceString;
+        }
+
+        // Since we can't directly reference System.Runtime.WindowsRuntime from mscorlib, we have to get the type via reflection.
+        // It would be better if we could just implement WindowsRuntimeResourceManager in mscorlib, but we can't, because
+        // we can do very little with WinRT in mscorlib.
+        internal static WindowsRuntimeResourceManagerBase GetWinRTResourceManager()
+        {
+            Type WinRTResourceManagerType = Type.GetType("System.Resources.WindowsRuntimeResourceManager, System.Runtime.WindowsRuntime", throwOnError: true);
+            return (WindowsRuntimeResourceManagerBase)Activator.CreateInstance(WinRTResourceManagerType, true);
+        }
+#endif
+
+        private bool _bUsingModernResourceManagement; // Written only by SetAppXConfiguration
+
+#if FEATURE_APPX
+        private WindowsRuntimeResourceManagerBase _WinRTResourceManager; // Written only by SetAppXConfiguration
+
+        private bool _PRIonAppXInitialized; // Written only by SetAppXConfiguration
+
+        private PRIExceptionInfo _PRIExceptionInfo; // Written only by SetAppXConfiguration
+
+        // When running under AppX, the following rules apply for resource lookup:
+        //
+        // 1) For Framework assemblies, we always use satellite assembly based lookup.
+        // 2) For non-FX assemblies:
+        //    
+        //    a) If the assembly lives under PLATFORM_RESOURCE_ROOTS (as specified by the host during AppDomain creation),
+        //       then we will use satellite assembly based lookup in assemblies like *.resources.dll.
+        //   
+        //    b) For any other non-FX assembly, we will use the modern resource manager with the premise that app package
+        //       contains the PRI resources.
+        private bool ShouldUseSatelliteAssemblyResourceLookupUnderAppX(RuntimeAssembly resourcesAssembly)
+        {
+            bool fUseSatelliteAssemblyResourceLookupUnderAppX = typeof(Object).Assembly == resourcesAssembly;
+
+            if (!fUseSatelliteAssemblyResourceLookupUnderAppX)
+            {
+                // Check to see if the assembly is under PLATFORM_RESOURCE_ROOTS. If it is, then we should use satellite assembly lookup for it.
+                String platformResourceRoots = (String)(AppDomain.CurrentDomain.GetData("PLATFORM_RESOURCE_ROOTS"));
+                if ((platformResourceRoots != null) && (platformResourceRoots != String.Empty))
+                {
+                    string resourceAssemblyPath = resourcesAssembly.Location;
+
+                    // Loop through the PLATFORM_RESOURCE_ROOTS and see if the assembly is contained in it.
+                    foreach (string pathPlatformResourceRoot in platformResourceRoots.Split(Path.PathSeparator))
+                    {
+                        if (resourceAssemblyPath.StartsWith(pathPlatformResourceRoot, StringComparison.CurrentCultureIgnoreCase))
+                        {
+                            // Found the resource assembly to be present in one of the PLATFORM_RESOURCE_ROOT, so stop the enumeration loop.
+                            fUseSatelliteAssemblyResourceLookupUnderAppX = true;
+                            break;
+                        }
+                    }
+                }
+            }
+
+            return fUseSatelliteAssemblyResourceLookupUnderAppX;
+        }
+#endif // FEATURE_APPX
+
+        // Only call SetAppXConfiguration from ResourceManager constructors, and nowhere else.
+        // Throws MissingManifestResourceException and WinRT HResults
+
+        private void SetAppXConfiguration()
+        {
+            Debug.Assert(_bUsingModernResourceManagement == false); // Only this function writes to this member
+#if FEATURE_APPX
+            Debug.Assert(_WinRTResourceManager == null); // Only this function writes to this member
+            Debug.Assert(_PRIonAppXInitialized == false); // Only this function writes to this member
+            Debug.Assert(_PRIExceptionInfo == null); // Only this function writes to this member
+
+            bool bUsingSatelliteAssembliesUnderAppX = false;
+
+            RuntimeAssembly resourcesAssembly = (RuntimeAssembly)MainAssembly;
+
+            if (resourcesAssembly == null)
+                resourcesAssembly = _callingAssembly;
+
+            if (resourcesAssembly != null)
+            {
+                if (resourcesAssembly != typeof(Object).Assembly) // We are not loading resources for mscorlib
+                {
+                    // Cannot load the WindowsRuntimeResourceManager when in a compilation process, since it
+                    // lives in System.Runtime.WindowsRuntime and only mscorlib may be loaded for execution.
+                    if (AppDomain.IsAppXModel())
+                    {
+                        s_IsAppXModel = true;
+
+                        // If we have the type information from the ResourceManager(Type) constructor, we use it. Otherwise, we use BaseNameField.
+                        String reswFilename = _locationInfo == null ? BaseNameField : _locationInfo.FullName;
+
+                        // The only way this can happen is if a class inherited from ResourceManager and
+                        // did not set the BaseNameField before calling the protected ResourceManager() constructor.
+                        // For other constructors, we would already have thrown an ArgumentNullException by now.
+                        // Throwing an ArgumentNullException now is not the right thing to do because technically
+                        // ResourceManager() takes no arguments, and because it is not documented as throwing
+                        // any exceptions. Instead, let's go through the rest of the initialization with this set to
+                        // an empty string. We may in fact fail earlier for another reason, but otherwise we will
+                        // throw a MissingManifestResourceException when GetString is called indicating that a
+                        // resW filename called "" could not be found.
+                        if (reswFilename == null)
+                            reswFilename = String.Empty;
+
+                        WindowsRuntimeResourceManagerBase WRRM = null;
+                        bool bWRRM_Initialized = false;
+
+                        if (AppDomain.IsAppXDesignMode())
+                        {
+                            WRRM = GetWinRTResourceManager();
+                            try
+                            {
+                                PRIExceptionInfo exceptionInfo; // If the exception info is filled in, we will ignore it.
+                                bWRRM_Initialized = WRRM.Initialize(resourcesAssembly.Location, reswFilename, out exceptionInfo);
+                                bUsingSatelliteAssembliesUnderAppX = !bWRRM_Initialized;
+                            }
+                            catch (Exception e)
+                            {
+                                bUsingSatelliteAssembliesUnderAppX = true;
+                                if (e.IsTransient)
+                                    throw;
+                            }
+                        }
+
+                        if (!bUsingSatelliteAssembliesUnderAppX)
+                        {
+                            _bUsingModernResourceManagement = !ShouldUseSatelliteAssemblyResourceLookupUnderAppX(resourcesAssembly);
+
+                            if (_bUsingModernResourceManagement)
+                            {
+                                // Only now are we certain that we need the PRI file.
+
+                                // Note that if IsAppXDesignMode is false, we haven't checked if the PRI file exists.
+                                // This is by design. We will find out in the call to WindowsRuntimeResourceManager.Initialize below.
+
+                                // At this point it is important NOT to set _bUsingModernResourceManagement to false
+                                // if the PRI file does not exist because we are now certain we need to load PRI
+                                // resources. We want to fail by throwing a MissingManifestResourceException
+                                // if WindowsRuntimeResourceManager.Initialize fails to locate the PRI file. We do not
+                                // want to fall back to using satellite assemblies anymore. Note that we would not throw
+                                // the MissingManifestResourceException from this function, but from GetString. See the
+                                // comment below on the reason for this.
+
+                                if (WRRM != null && bWRRM_Initialized)
+                                {
+                                    // Reuse the one successfully created earlier
+                                    _WinRTResourceManager = WRRM;
+                                    _PRIonAppXInitialized = true;
+                                }
+                                else
+                                {
+                                    _WinRTResourceManager = GetWinRTResourceManager();
+
+                                    try
+                                    {
+                                        _PRIonAppXInitialized = _WinRTResourceManager.Initialize(resourcesAssembly.Location, reswFilename, out _PRIExceptionInfo);
+
+                                        // Note that _PRIExceptionInfo might be null - this is OK.
+                                        // In that case we will just throw the generic
+                                        // MissingManifestResource_NoPRIresources exception.
+                                        // See the implementation of GetString for more details.
+                                    }
+                                    // We would like to be able to throw a MissingManifestResourceException here if PRI resources
+                                    // could not be loaded for a recognized reason. However, the ResourceManager constructors
+                                    // that call SetAppXConfiguration are not documented as throwing MissingManifestResourceException,
+                                    // and since they are part of the portable profile, we cannot start throwing a new exception type
+                                    // as that would break existing portable libraries. Hence we must save the exception information
+                                    // now and throw the exception on the first call to GetString.
+                                    catch (FileNotFoundException)
+                                    {
+                                        // We will throw MissingManifestResource_NoPRIresources from GetString
+                                        // when we see that _PRIonAppXInitialized is false.
+                                    }
+                                    catch (Exception e)
+                                    {
+                                        // ERROR_MRM_MAP_NOT_FOUND can be thrown by the call to ResourceManager.get_AllResourceMaps
+                                        // in WindowsRuntimeResourceManager.Initialize.
+                                        // In this case _PRIExceptionInfo is now null and we will just throw the generic
+                                        // MissingManifestResource_NoPRIresources exception.
+                                        // See the implementation of GetString for more details.
+                                        if (e.HResult != HResults.ERROR_MRM_MAP_NOT_FOUND)
+                                            throw; // Unexpected exception code. Bubble it up to the caller.
+                                    }
+
+                                    if (!_PRIonAppXInitialized)
+                                    {
+                                        _bUsingModernResourceManagement = false;
+                                    }
+                                    // Allow all other exception types to bubble up to the caller.
+
+                                    // Yes, this causes us to potentially throw exception types that are not documented.
+
+                                    // Ultimately the tradeoff is the following:
+                                    // -We could ignore unknown exceptions or rethrow them as inner exceptions
+                                    // of exceptions that the ResourceManager class is already documented as throwing.
+                                    // This would allow existing portable libraries to gracefully recover if they don't care
+                                    // too much about the ResourceManager object they are using. However it could
+                                    // mask potentially fatal errors that we are not aware of, such as a disk drive failing.
+
+
+                                    // The alternative, which we chose, is to throw unknown exceptions. This may tear
+                                    // down the process if the portable library and app don't expect this exception type.
+                                    // On the other hand, this won't mask potentially fatal errors we don't know about.
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+            // resourcesAssembly == null should not happen but it can. See the comment on Assembly.GetCallingAssembly.
+            // However for the sake of 100% backwards compatibility on Win7 and below, we must leave
+            // _bUsingModernResourceManagement as false.
+#endif // FEATURE_APPX            
+        }
+
+        // Looks up a resource value for a particular name.  Looks in the 
+        // current thread's CultureInfo, and if not found, all parent CultureInfos.
+        // Returns null if the resource wasn't found.
+        // 
+        public virtual String GetString(String name)
+        {
+            return GetString(name, (CultureInfo)null);
+        }
+
+        // Looks up a resource value for a particular name.  Looks in the 
+        // specified CultureInfo, and if not found, all parent CultureInfos.
+        // Returns null if the resource wasn't found.
+        // 
+        public virtual String GetString(String name, CultureInfo culture)
+        {
+            if (null == name)
+                throw new ArgumentNullException(nameof(name));
+
+#if FEATURE_APPX
+            if (s_IsAppXModel)
+            {
+                // If the caller explictily passed in a culture that was obtained by calling CultureInfo.CurrentUICulture,
+                // null it out, so that we re-compute it.  If we use modern resource lookup, we may end up getting a "better"
+                // match, since CultureInfo objects can't represent all the different languages the AppX resource model supports.
+                // For classic resources, this causes us to ignore the languages list and instead use the older Win32 behavior,
+                // which is the design choice we've made. (See the call a little later to GetCurrentUICultureNoAppX()).
+                if (Object.ReferenceEquals(culture, CultureInfo.CurrentUICulture))
+                {
+                    culture = null;
+                }
+            }
+
+            if (_bUsingModernResourceManagement)
+            {
+                if (_PRIonAppXInitialized == false)
+                {
+                    // Always throw if we did not fully succeed in initializing the WinRT Resource Manager.
+
+                    if (_PRIExceptionInfo != null && _PRIExceptionInfo._PackageSimpleName != null && _PRIExceptionInfo._ResWFile != null)
+                        throw new MissingManifestResourceException(SR.Format(SR.MissingManifestResource_ResWFileNotLoaded, _PRIExceptionInfo._ResWFile, _PRIExceptionInfo._PackageSimpleName));
+
+                    throw new MissingManifestResourceException(SR.MissingManifestResource_NoPRIresources);
+                }
+
+                // Throws WinRT hresults.
+                return GetStringFromPRI(name,
+                                        culture == null ? null : culture.Name,
+                                        _neutralResourcesCulture.Name);
+            }
+            else
+#endif // FEATURE_APPX
+            {
+                if (culture == null)
+                {
+                    // When running inside AppX we want to ignore the languages list when trying to come up with our CurrentUICulture.
+                    // This line behaves the same way as CultureInfo.CurrentUICulture would have in .NET 4
+                    culture = CultureInfo.CurrentUICulture;
+                }
+
+                ResourceSet last = GetFirstResourceSet(culture);
+
+                if (last != null)
+                {
+                    String value = last.GetString(name, _ignoreCase);
+                    if (value != null)
+                        return value;
+                }
+
+
+                // This is the CultureInfo hierarchy traversal code for resource 
+                // lookups, similar but necessarily orthogonal to the ResourceSet 
+                // lookup logic.
+                ResourceFallbackManager mgr = new ResourceFallbackManager(culture, _neutralResourcesCulture, true);
+                foreach (CultureInfo currentCultureInfo in mgr)
+                {
+                    ResourceSet rs = InternalGetResourceSet(currentCultureInfo, true, true);
+                    if (rs == null)
+                        break;
+
+                    if (rs != last)
+                    {
+                        String value = rs.GetString(name, _ignoreCase);
+                        if (value != null)
+                        {
+                            // update last used ResourceSet
+                            if (_lastUsedResourceCache != null)
+                            {
+                                lock (_lastUsedResourceCache)
+                                {
+                                    _lastUsedResourceCache.lastCultureName = currentCultureInfo.Name;
+                                    _lastUsedResourceCache.lastResourceSet = rs;
+                                }
+                            }
+                            return value;
+                        }
+
+                        last = rs;
+                    }
+                }
+            }
+
+            return null;
+        }
+
+
+        // Looks up a resource value for a particular name.  Looks in the 
+        // current thread's CultureInfo, and if not found, all parent CultureInfos.
+        // Returns null if the resource wasn't found.
+        // 
+        public virtual Object GetObject(String name)
+        {
+            return GetObject(name, (CultureInfo)null, true);
+        }
+
+        // Looks up a resource value for a particular name.  Looks in the 
+        // specified CultureInfo, and if not found, all parent CultureInfos.
+        // Returns null if the resource wasn't found.
+        public virtual Object GetObject(String name, CultureInfo culture)
+        {
+            return GetObject(name, culture, true);
+        }
+
+        private Object GetObject(String name, CultureInfo culture, bool wrapUnmanagedMemStream)
+        {
+            if (null == name)
+                throw new ArgumentNullException(nameof(name));
+
+#if FEATURE_APPX
+            if (s_IsAppXModel)
+            {
+                // If the caller explictily passed in a culture that was obtained by calling CultureInfo.CurrentUICulture,
+                // null it out, so that we re-compute it based on the Win32 value and not the AppX language list value.
+                // (See the call a little later to GetCurrentUICultureNoAppX()).
+                if (Object.ReferenceEquals(culture, CultureInfo.CurrentUICulture))
+                {
+                    culture = null;
+                }
+            }
+#endif
+
+            if (null == culture)
+            {
+                // When running inside AppX we want to ignore the languages list when trying to come up with our CurrentUICulture.
+                // This line behaves the same way as CultureInfo.CurrentUICulture would have in .NET 4
+                culture = CultureInfo.GetCurrentUICultureNoAppX();
+            }
+
+            ResourceSet last = GetFirstResourceSet(culture);
+            if (last != null)
+            {
+                Object value = last.GetObject(name, _ignoreCase);
+
+                if (value != null)
+                {
+                    UnmanagedMemoryStream stream = value as UnmanagedMemoryStream;
+                    if (stream != null && wrapUnmanagedMemStream)
+                        return new UnmanagedMemoryStreamWrapper(stream);
+                    else
+                        return value;
+                }
+            }
+
+            // This is the CultureInfo hierarchy traversal code for resource 
+            // lookups, similar but necessarily orthogonal to the ResourceSet 
+            // lookup logic.
+            ResourceFallbackManager mgr = new ResourceFallbackManager(culture, _neutralResourcesCulture, true);
+
+            foreach (CultureInfo currentCultureInfo in mgr)
+            {
+                // Note: Technically this method should be passed in a stack crawl mark that we then pass
+                // to InternalGetResourceSet for ensuring we demand permissions to read your private resources
+                // if you're reading resources from an assembly other than yourself.  But, we must call our
+                // three argument overload (without the stack crawl mark) for compatibility.  After 
+                // consideration, we aren't worried about the security impact.
+                ResourceSet rs = InternalGetResourceSet(currentCultureInfo, true, true);
+                if (rs == null)
+                    break;
+
+                if (rs != last)
+                {
+                    Object value = rs.GetObject(name, _ignoreCase);
+                    if (value != null)
+                    {
+                        // update the last used ResourceSet
+                        if (_lastUsedResourceCache != null)
+                        {
+                            lock (_lastUsedResourceCache)
+                            {
+                                _lastUsedResourceCache.lastCultureName = currentCultureInfo.Name;
+                                _lastUsedResourceCache.lastResourceSet = rs;
+                            }
+                        }
+
+                        UnmanagedMemoryStream stream = value as UnmanagedMemoryStream;
+                        if (stream != null && wrapUnmanagedMemStream)
+                            return new UnmanagedMemoryStreamWrapper(stream);
+                        else
+                            return value;
+                    }
+
+                    last = rs;
+                }
+            }
+
+            return null;
+        }
+
+        public UnmanagedMemoryStream GetStream(String name)
+        {
+            return GetStream(name, (CultureInfo)null);
+        }
+
+        public UnmanagedMemoryStream GetStream(String name, CultureInfo culture)
+        {
+            Object obj = GetObject(name, culture, false);
+            UnmanagedMemoryStream ums = obj as UnmanagedMemoryStream;
+            if (ums == null && obj != null)
+                throw new InvalidOperationException(SR.Format(SR.InvalidOperation_ResourceNotStream_Name, name));
+            return ums;
+        }
+
+#if RESOURCE_SATELLITE_CONFIG
+        // Internal helper method - gives an end user the ability to prevent
+        // satellite assembly probes for certain cultures via a config file.
+        private bool TryLookingForSatellite(CultureInfo lookForCulture)
+        {
+            if (!_checkedConfigFile)
+            {
+                lock (this)
+                {
+                    if (!_checkedConfigFile)
+                    {
+                        _checkedConfigFile = true;
+                        _installedSatelliteInfo = GetSatelliteAssembliesFromConfig();
+                    }
+                }
+            }
+
+            if (_installedSatelliteInfo == null)
+                return true;
+
+            String[] installedSatellites = (String[])_installedSatelliteInfo[MainAssembly.FullName];
+
+            if (installedSatellites == null)
+                return true;
+
+            // The config file told us what satellites might be installed.
+            int pos = Array.IndexOf(installedSatellites, lookForCulture.Name);
+
+            return pos >= 0;
+        }
+
+        // Note: There is one config file per appdomain.  This is not 
+        // per-process nor per-assembly.
+        private Hashtable GetSatelliteAssembliesFromConfig()
+        {
+            return null;
+        }
+#endif  // RESOURCE_SATELLITE_CONFIG
+
+        internal class ResourceManagerMediator
+        {
+            private ResourceManager _rm;
+
+            internal ResourceManagerMediator(ResourceManager rm)
+            {
+                if (rm == null)
+                {
+                    throw new ArgumentNullException(nameof(rm));
+                }
+                _rm = rm;
+            }
+
+            // NEEDED ONLY BY FILE-BASED
+            internal String ModuleDir
+            {
+                get { return _rm.moduleDir; }
+            }
+
+            // NEEDED BOTH BY FILE-BASED  AND ASSEMBLY-BASED
+            internal Type LocationInfo
+            {
+                get { return _rm._locationInfo; }
+            }
+
+            internal Type UserResourceSet
+            {
+                get { return _rm._userResourceSet; }
+            }
+
+            internal String BaseNameField
+            {
+                get { return _rm.BaseNameField; }
+            }
+
+            internal CultureInfo NeutralResourcesCulture
+            {
+                get { return _rm._neutralResourcesCulture; }
+                set { _rm._neutralResourcesCulture = value; }
+            }
+
+            internal String GetResourceFileName(CultureInfo culture)
+            {
+                return _rm.GetResourceFileName(culture);
+            }
+
+            // NEEDED ONLY BY ASSEMBLY-BASED
+            internal bool LookedForSatelliteContractVersion
+            {
+                get { return _rm._lookedForSatelliteContractVersion; }
+                set { _rm._lookedForSatelliteContractVersion = value; }
+            }
+
+            internal Version SatelliteContractVersion
+            {
+                get { return _rm._satelliteContractVersion; }
+                set { _rm._satelliteContractVersion = value; }
+            }
+
+            internal Version ObtainSatelliteContractVersion(Assembly a)
+            {
+                return ResourceManager.GetSatelliteContractVersion(a);
+            }
+
+            internal UltimateResourceFallbackLocation FallbackLoc
+            {
+                get { return _rm.FallbackLocation; }
+                set { _rm._fallbackLoc = value; }
+            }
+
+            internal RuntimeAssembly CallingAssembly
+            {
+                get { return _rm._callingAssembly; }
+            }
+
+            internal RuntimeAssembly MainAssembly
+            {
+                get { return (RuntimeAssembly)_rm.MainAssembly; }
+            }
+
+            // this is weird because we have BaseNameField accessor above, but we're sticking
+            // with it for compat.
+            internal String BaseName
+            {
+                get { return _rm.BaseName; }
+            }
+
+
+#if RESOURCE_SATELLITE_CONFIG
+            internal bool TryLookingForSatellite(CultureInfo lookForCulture)
+            {
+                return _rm.TryLookingForSatellite(lookForCulture);
+            }
+#endif
+
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Resources/ResourceReader.cs b/src/System.Private.CoreLib/src/System/Resources/ResourceReader.cs
new file mode 100644
index 0000000000..75c17686b3
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Resources/ResourceReader.cs
@@ -0,0 +1,1192 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Default way to read streams of resources on 
+** demand.
+**
+**         Version 2 support on October 6, 2003
+** 
+===========================================================*/
+
+namespace System.Resources
+{
+    using System;
+    using System.IO;
+    using System.Text;
+    using System.Collections;
+    using System.Collections.Generic;
+    using System.Reflection;
+    using System.Security;
+    using System.Globalization;
+    using System.Configuration.Assemblies;
+    using System.Runtime.Versioning;
+    using System.Diagnostics;
+    using System.Diagnostics.Contracts;
+
+    // Provides the default implementation of IResourceReader, reading
+    // .resources file from the system default binary format.  This class
+    // can be treated as an enumerator once.
+    // 
+    // See the RuntimeResourceSet overview for details on the system 
+    // default file format.
+    // 
+
+    internal struct ResourceLocator
+    {
+        internal Object _value;  // Can be null.  Consider WeakReference instead?
+        internal int _dataPos;
+
+        internal ResourceLocator(int dataPos, Object value)
+        {
+            _dataPos = dataPos;
+            _value = value;
+        }
+
+        internal int DataPosition
+        {
+            get { return _dataPos; }
+            //set { _dataPos = value; }
+        }
+
+        // Allows adding in profiling data in a future version, or a special
+        // resource profiling build.  We could also use WeakReference.
+        internal Object Value
+        {
+            get { return _value; }
+            set { _value = value; }
+        }
+
+        internal static bool CanCache(ResourceTypeCode value)
+        {
+            Debug.Assert(value >= 0, "negative ResourceTypeCode.  What?");
+            return value <= ResourceTypeCode.LastPrimitive;
+        }
+    }
+
+
+    public sealed class ResourceReader : IResourceReader
+    {
+        // A reasonable default buffer size for reading from files, especially
+        // when we will likely be seeking frequently.  Could be smaller, but does
+        // it make sense to use anything less than one page?
+        private const int DefaultFileStreamBufferSize = 4096;
+
+        private BinaryReader _store;    // backing store we're reading from.
+        // Used by RuntimeResourceSet and this class's enumerator.  Maps
+        // resource name to a value, a ResourceLocator, or a 
+        // LooselyLinkedManifestResource.
+        internal Dictionary<String, ResourceLocator> _resCache;
+        private long _nameSectionOffset;  // Offset to name section of file.
+        private long _dataSectionOffset;  // Offset to Data section of file.
+
+        // Note this class is tightly coupled with UnmanagedMemoryStream.
+        // At runtime when getting an embedded resource from an assembly, 
+        // we're given an UnmanagedMemoryStream referring to the mmap'ed portion
+        // of the assembly.  The pointers here are pointers into that block of
+        // memory controlled by the OS's loader.
+        private int[] _nameHashes;    // hash values for all names.
+        private unsafe int* _nameHashesPtr;  // In case we're using UnmanagedMemoryStream
+        private int[] _namePositions; // relative locations of names
+        private unsafe int* _namePositionsPtr;  // If we're using UnmanagedMemoryStream
+        private RuntimeType[] _typeTable;    // Lazy array of Types for resource values.
+        private int[] _typeNamePositions;  // To delay initialize type table
+        private int _numResources;    // Num of resources files, in case arrays aren't allocated.        
+
+        // We'll include a separate code path that uses UnmanagedMemoryStream to
+        // avoid allocating String objects and the like.
+        private UnmanagedMemoryStream _ums;
+
+        // Version number of .resources file, for compatibility
+        private int _version;
+
+
+        public ResourceReader(String fileName)
+        {
+            _resCache = new Dictionary<String, ResourceLocator>(FastResourceComparer.Default);
+            _store = new BinaryReader(new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read, DefaultFileStreamBufferSize, FileOptions.RandomAccess), Encoding.UTF8);
+
+            try
+            {
+                ReadResources();
+            }
+            catch
+            {
+                _store.Close(); // If we threw an exception, close the file.
+                throw;
+            }
+        }
+
+        public ResourceReader(Stream stream)
+        {
+            if (stream == null)
+                throw new ArgumentNullException(nameof(stream));
+            if (!stream.CanRead)
+                throw new ArgumentException(SR.Argument_StreamNotReadable);
+
+            _resCache = new Dictionary<String, ResourceLocator>(FastResourceComparer.Default);
+            _store = new BinaryReader(stream, Encoding.UTF8);
+            // We have a faster code path for reading resource files from an assembly.
+            _ums = stream as UnmanagedMemoryStream;
+
+            ReadResources();
+        }
+
+        // This is the constructor the RuntimeResourceSet calls,
+        // passing in the stream to read from and the RuntimeResourceSet's 
+        // internal hash table (hash table of names with file offsets
+        // and values, coupled to this ResourceReader).
+        internal ResourceReader(Stream stream, Dictionary<String, ResourceLocator> resCache)
+        {
+            Debug.Assert(stream != null, "Need a stream!");
+            Debug.Assert(stream.CanRead, "Stream should be readable!");
+            Debug.Assert(resCache != null, "Need a Dictionary!");
+
+            _resCache = resCache;
+            _store = new BinaryReader(stream, Encoding.UTF8);
+
+            _ums = stream as UnmanagedMemoryStream;
+
+            ReadResources();
+        }
+
+
+        public void Close()
+        {
+            Dispose(true);
+        }
+
+        public void Dispose()
+        {
+            Close();
+        }
+
+        private unsafe void Dispose(bool disposing)
+        {
+            if (_store != null)
+            {
+                _resCache = null;
+                if (disposing)
+                {
+                    // Close the stream in a thread-safe way.  This fix means 
+                    // that we may call Close n times, but that's safe.
+                    BinaryReader copyOfStore = _store;
+                    _store = null;
+                    if (copyOfStore != null)
+                        copyOfStore.Close();
+                }
+                _store = null;
+                _namePositions = null;
+                _nameHashes = null;
+                _ums = null;
+                _namePositionsPtr = null;
+                _nameHashesPtr = null;
+            }
+        }
+
+        internal static unsafe int ReadUnalignedI4(int* p)
+        {
+            byte* buffer = (byte*)p;
+            // Unaligned, little endian format
+            return buffer[0] | (buffer[1] << 8) | (buffer[2] << 16) | (buffer[3] << 24);
+        }
+
+
+        private void SkipString()
+        {
+            int stringLength = _store.Read7BitEncodedInt();
+            if (stringLength < 0)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_NegativeStringLength);
+            }
+            _store.BaseStream.Seek(stringLength, SeekOrigin.Current);
+        }
+
+        private unsafe int GetNameHash(int index)
+        {
+            Debug.Assert(index >= 0 && index < _numResources, "Bad index into hash array.  index: " + index);
+            Debug.Assert((_ums == null && _nameHashes != null && _nameHashesPtr == null) ||
+                            (_ums != null && _nameHashes == null && _nameHashesPtr != null), "Internal state mangled.");
+            if (_ums == null)
+                return _nameHashes[index];
+            else
+                return ReadUnalignedI4(&_nameHashesPtr[index]);
+        }
+
+        private unsafe int GetNamePosition(int index)
+        {
+            Debug.Assert(index >= 0 && index < _numResources, "Bad index into name position array.  index: " + index);
+            Debug.Assert((_ums == null && _namePositions != null && _namePositionsPtr == null) ||
+                            (_ums != null && _namePositions == null && _namePositionsPtr != null), "Internal state mangled.");
+            int r;
+            if (_ums == null)
+                r = _namePositions[index];
+            else
+                r = ReadUnalignedI4(&_namePositionsPtr[index]);
+            if (r < 0 || r > _dataSectionOffset - _nameSectionOffset)
+            {
+                throw new FormatException(SR.Format(SR.BadImageFormat_ResourcesNameInvalidOffset, r));
+            }
+            return r;
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+
+        public IDictionaryEnumerator GetEnumerator()
+        {
+            if (_resCache == null)
+                throw new InvalidOperationException(SR.ResourceReaderIsClosed);
+            return new ResourceEnumerator(this);
+        }
+
+        internal ResourceEnumerator GetEnumeratorInternal()
+        {
+            return new ResourceEnumerator(this);
+        }
+
+        // From a name, finds the associated virtual offset for the data.
+        // To read the data, seek to _dataSectionOffset + dataPos, then
+        // read the resource type & data.
+        // This does a binary search through the names.
+        internal int FindPosForResource(String name)
+        {
+            Debug.Assert(_store != null, "ResourceReader is closed!");
+            int hash = FastResourceComparer.HashFunction(name);
+
+            // Binary search over the hashes.  Use the _namePositions array to 
+            // determine where they exist in the underlying stream.
+            int lo = 0;
+            int hi = _numResources - 1;
+            int index = -1;
+            bool success = false;
+            while (lo <= hi)
+            {
+                index = (lo + hi) >> 1;
+                // Do NOT use subtraction here, since it will wrap for large
+                // negative numbers. 
+                int currentHash = GetNameHash(index);
+                int c;
+                if (currentHash == hash)
+                    c = 0;
+                else if (currentHash < hash)
+                    c = -1;
+                else
+                    c = 1;
+
+                if (c == 0)
+                {
+                    success = true;
+                    break;
+                }
+                if (c < 0)
+                    lo = index + 1;
+                else
+                    hi = index - 1;
+            }
+            if (!success)
+            {
+                return -1;
+            }
+
+            // index is the location in our hash array that corresponds with a 
+            // value in the namePositions array.
+            // There could be collisions in our hash function.  Check on both sides 
+            // of index to find the range of hash values that are equal to the
+            // target hash value.
+            if (lo != index)
+            {
+                lo = index;
+                while (lo > 0 && GetNameHash(lo - 1) == hash)
+                    lo--;
+            }
+            if (hi != index)
+            {
+                hi = index;
+                while (hi < _numResources - 1 && GetNameHash(hi + 1) == hash)
+                    hi++;
+            }
+
+            lock (this)
+            {
+                for (int i = lo; i <= hi; i++)
+                {
+                    _store.BaseStream.Seek(_nameSectionOffset + GetNamePosition(i), SeekOrigin.Begin);
+                    if (CompareStringEqualsName(name))
+                    {
+                        int dataPos = _store.ReadInt32();
+                        if (dataPos < 0 || dataPos >= _store.BaseStream.Length - _dataSectionOffset)
+                        {
+                            throw new FormatException(SR.Format(SR.BadImageFormat_ResourcesDataInvalidOffset, dataPos));
+                        }
+                        return dataPos;
+                    }
+                }
+            }
+            return -1;
+        }
+
+        // This compares the String in the .resources file at the current position
+        // with the string you pass in. 
+        // Whoever calls this method should make sure that they take a lock
+        // so no one else can cause us to seek in the stream.
+        private unsafe bool CompareStringEqualsName(String name)
+        {
+            Debug.Assert(_store != null, "ResourceReader is closed!");
+            int byteLen = _store.Read7BitEncodedInt();
+            if (byteLen < 0)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_NegativeStringLength);
+            }
+            if (_ums != null)
+            {
+                byte* bytes = _ums.PositionPointer;
+                // Skip over the data in the Stream, positioning ourselves right after it.
+                _ums.Seek(byteLen, SeekOrigin.Current);
+                if (_ums.Position > _ums.Length)
+                {
+                    throw new BadImageFormatException(SR.BadImageFormat_ResourcesNameTooLong);
+                }
+
+                // On 64-bit machines, these char*'s may be misaligned.  Use a
+                // byte-by-byte comparison instead.
+                //return FastResourceComparer.CompareOrdinal((char*)bytes, byteLen/2, name) == 0;
+                return FastResourceComparer.CompareOrdinal(bytes, byteLen, name) == 0;
+            }
+            else
+            {
+                // This code needs to be fast
+                byte[] bytes = new byte[byteLen];
+                int numBytesToRead = byteLen;
+                while (numBytesToRead > 0)
+                {
+                    int n = _store.Read(bytes, byteLen - numBytesToRead, numBytesToRead);
+                    if (n == 0)
+                        throw new BadImageFormatException(SR.BadImageFormat_ResourceNameCorrupted);
+                    numBytesToRead -= n;
+                }
+                return FastResourceComparer.CompareOrdinal(bytes, byteLen / 2, name) == 0;
+            }
+        }
+
+        // This is used in the enumerator.  The enumerator iterates from 0 to n
+        // of our resources and this returns the resource name for a particular
+        // index.  The parameter is NOT a virtual offset.
+        private unsafe String AllocateStringForNameIndex(int index, out int dataOffset)
+        {
+            Debug.Assert(_store != null, "ResourceReader is closed!");
+            byte[] bytes;
+            int byteLen;
+            long nameVA = GetNamePosition(index);
+            lock (this)
+            {
+                _store.BaseStream.Seek(nameVA + _nameSectionOffset, SeekOrigin.Begin);
+                // Can't use _store.ReadString, since it's using UTF-8!
+                byteLen = _store.Read7BitEncodedInt();
+                if (byteLen < 0)
+                {
+                    throw new BadImageFormatException(SR.BadImageFormat_NegativeStringLength);
+                }
+
+                if (_ums != null)
+                {
+                    if (_ums.Position > _ums.Length - byteLen)
+                        throw new BadImageFormatException(SR.Format(SR.BadImageFormat_ResourcesIndexTooLong, index));
+
+                    String s = null;
+                    char* charPtr = (char*)_ums.PositionPointer;
+
+                    s = new String(charPtr, 0, byteLen / 2);
+
+                    _ums.Position += byteLen;
+                    dataOffset = _store.ReadInt32();
+                    if (dataOffset < 0 || dataOffset >= _store.BaseStream.Length - _dataSectionOffset)
+                    {
+                        throw new FormatException(SR.Format(SR.BadImageFormat_ResourcesDataInvalidOffset, dataOffset));
+                    }
+                    return s;
+                }
+
+                bytes = new byte[byteLen];
+                // We must read byteLen bytes, or we have a corrupted file.
+                // Use a blocking read in case the stream doesn't give us back
+                // everything immediately.
+                int count = byteLen;
+                while (count > 0)
+                {
+                    int n = _store.Read(bytes, byteLen - count, count);
+                    if (n == 0)
+                        throw new EndOfStreamException(SR.Format(SR.BadImageFormat_ResourceNameCorrupted_NameIndex, index));
+                    count -= n;
+                }
+                dataOffset = _store.ReadInt32();
+                if (dataOffset < 0 || dataOffset >= _store.BaseStream.Length - _dataSectionOffset)
+                {
+                    throw new FormatException(SR.Format(SR.BadImageFormat_ResourcesDataInvalidOffset, dataOffset));
+                }
+            }
+            return Encoding.Unicode.GetString(bytes, 0, byteLen);
+        }
+
+        // This is used in the enumerator.  The enumerator iterates from 0 to n
+        // of our resources and this returns the resource value for a particular
+        // index.  The parameter is NOT a virtual offset.
+        private Object GetValueForNameIndex(int index)
+        {
+            Debug.Assert(_store != null, "ResourceReader is closed!");
+            long nameVA = GetNamePosition(index);
+            lock (this)
+            {
+                _store.BaseStream.Seek(nameVA + _nameSectionOffset, SeekOrigin.Begin);
+                SkipString();
+
+                int dataPos = _store.ReadInt32();
+                if (dataPos < 0 || dataPos >= _store.BaseStream.Length - _dataSectionOffset)
+                {
+                    throw new FormatException(SR.Format(SR.BadImageFormat_ResourcesDataInvalidOffset, dataPos));
+                }
+
+                ResourceTypeCode junk;
+                if (_version == 1)
+                    return LoadObjectV1(dataPos);
+                else
+                    return LoadObjectV2(dataPos, out junk);
+            }
+        }
+
+        // This takes a virtual offset into the data section and reads a String
+        // from that location.
+        // Anyone who calls LoadObject should make sure they take a lock so 
+        // no one can cause us to do a seek in here.
+        internal String LoadString(int pos)
+        {
+            Debug.Assert(_store != null, "ResourceReader is closed!");
+            _store.BaseStream.Seek(_dataSectionOffset + pos, SeekOrigin.Begin);
+            String s = null;
+            int typeIndex = _store.Read7BitEncodedInt();
+            if (_version == 1)
+            {
+                if (typeIndex == -1)
+                    return null;
+                if (FindType(typeIndex) != typeof(String))
+                    throw new InvalidOperationException(SR.Format(SR.InvalidOperation_ResourceNotString_Type, FindType(typeIndex).FullName));
+                s = _store.ReadString();
+            }
+            else
+            {
+                ResourceTypeCode typeCode = (ResourceTypeCode)typeIndex;
+                if (typeCode != ResourceTypeCode.String && typeCode != ResourceTypeCode.Null)
+                {
+                    String typeString;
+                    if (typeCode < ResourceTypeCode.StartOfUserTypes)
+                        typeString = typeCode.ToString();
+                    else
+                        typeString = FindType(typeCode - ResourceTypeCode.StartOfUserTypes).FullName;
+                    throw new InvalidOperationException(SR.Format(SR.InvalidOperation_ResourceNotString_Type, typeString));
+                }
+                if (typeCode == ResourceTypeCode.String) // ignore Null
+                    s = _store.ReadString();
+            }
+
+            return s;
+        }
+
+        // Called from RuntimeResourceSet
+        internal Object LoadObject(int pos)
+        {
+            if (_version == 1)
+                return LoadObjectV1(pos);
+            ResourceTypeCode typeCode;
+            return LoadObjectV2(pos, out typeCode);
+        }
+
+        internal Object LoadObject(int pos, out ResourceTypeCode typeCode)
+        {
+            if (_version == 1)
+            {
+                Object o = LoadObjectV1(pos);
+                typeCode = (o is String) ? ResourceTypeCode.String : ResourceTypeCode.StartOfUserTypes;
+                return o;
+            }
+            return LoadObjectV2(pos, out typeCode);
+        }
+
+        // This takes a virtual offset into the data section and reads an Object
+        // from that location.
+        // Anyone who calls LoadObject should make sure they take a lock so 
+        // no one can cause us to do a seek in here.
+        internal Object LoadObjectV1(int pos)
+        {
+            Debug.Assert(_store != null, "ResourceReader is closed!");
+            Debug.Assert(_version == 1, ".resources file was not a V1 .resources file!");
+
+            try
+            {
+                // mega try-catch performs exceptionally bad on x64; factored out body into 
+                // _LoadObjectV1 and wrap here.
+                return _LoadObjectV1(pos);
+            }
+            catch (EndOfStreamException eof)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_TypeMismatch, eof);
+            }
+            catch (ArgumentOutOfRangeException e)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_TypeMismatch, e);
+            }
+        }
+
+        private Object _LoadObjectV1(int pos)
+        {
+            _store.BaseStream.Seek(_dataSectionOffset + pos, SeekOrigin.Begin);
+            int typeIndex = _store.Read7BitEncodedInt();
+            if (typeIndex == -1)
+                return null;
+            RuntimeType type = FindType(typeIndex);
+            // Consider putting in logic to see if this type is a 
+            // primitive or a value type first, so we can reach the 
+            // deserialization code faster for arbitrary objects.
+
+            if (type == typeof(String))
+                return _store.ReadString();
+            else if (type == typeof(Int32))
+                return _store.ReadInt32();
+            else if (type == typeof(Byte))
+                return _store.ReadByte();
+            else if (type == typeof(SByte))
+                return _store.ReadSByte();
+            else if (type == typeof(Int16))
+                return _store.ReadInt16();
+            else if (type == typeof(Int64))
+                return _store.ReadInt64();
+            else if (type == typeof(UInt16))
+                return _store.ReadUInt16();
+            else if (type == typeof(UInt32))
+                return _store.ReadUInt32();
+            else if (type == typeof(UInt64))
+                return _store.ReadUInt64();
+            else if (type == typeof(Single))
+                return _store.ReadSingle();
+            else if (type == typeof(Double))
+                return _store.ReadDouble();
+            else if (type == typeof(DateTime))
+            {
+                // Ideally we should use DateTime's ToBinary & FromBinary,
+                // but we can't for compatibility reasons.
+                return new DateTime(_store.ReadInt64());
+            }
+            else if (type == typeof(TimeSpan))
+                return new TimeSpan(_store.ReadInt64());
+            else if (type == typeof(Decimal))
+            {
+                int[] bits = new int[4];
+                for (int i = 0; i < bits.Length; i++)
+                    bits[i] = _store.ReadInt32();
+                return new Decimal(bits);
+            }
+            else
+            {
+                throw new NotSupportedException(SR.NotSupported_ResourceObjectSerialization);
+            }
+        }
+
+        internal Object LoadObjectV2(int pos, out ResourceTypeCode typeCode)
+        {
+            Debug.Assert(_store != null, "ResourceReader is closed!");
+            Debug.Assert(_version >= 2, ".resources file was not a V2 (or higher) .resources file!");
+
+            try
+            {
+                // mega try-catch performs exceptionally bad on x64; factored out body into 
+                // _LoadObjectV2 and wrap here.
+                return _LoadObjectV2(pos, out typeCode);
+            }
+            catch (EndOfStreamException eof)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_TypeMismatch, eof);
+            }
+            catch (ArgumentOutOfRangeException e)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_TypeMismatch, e);
+            }
+        }
+
+        private Object _LoadObjectV2(int pos, out ResourceTypeCode typeCode)
+        {
+            _store.BaseStream.Seek(_dataSectionOffset + pos, SeekOrigin.Begin);
+            typeCode = (ResourceTypeCode)_store.Read7BitEncodedInt();
+
+            switch (typeCode)
+            {
+                case ResourceTypeCode.Null:
+                    return null;
+
+                case ResourceTypeCode.String:
+                    return _store.ReadString();
+
+                case ResourceTypeCode.Boolean:
+                    return _store.ReadBoolean();
+
+                case ResourceTypeCode.Char:
+                    return (char)_store.ReadUInt16();
+
+                case ResourceTypeCode.Byte:
+                    return _store.ReadByte();
+
+                case ResourceTypeCode.SByte:
+                    return _store.ReadSByte();
+
+                case ResourceTypeCode.Int16:
+                    return _store.ReadInt16();
+
+                case ResourceTypeCode.UInt16:
+                    return _store.ReadUInt16();
+
+                case ResourceTypeCode.Int32:
+                    return _store.ReadInt32();
+
+                case ResourceTypeCode.UInt32:
+                    return _store.ReadUInt32();
+
+                case ResourceTypeCode.Int64:
+                    return _store.ReadInt64();
+
+                case ResourceTypeCode.UInt64:
+                    return _store.ReadUInt64();
+
+                case ResourceTypeCode.Single:
+                    return _store.ReadSingle();
+
+                case ResourceTypeCode.Double:
+                    return _store.ReadDouble();
+
+                case ResourceTypeCode.Decimal:
+                    return _store.ReadDecimal();
+
+                case ResourceTypeCode.DateTime:
+                    // Use DateTime's ToBinary & FromBinary.
+                    Int64 data = _store.ReadInt64();
+                    return DateTime.FromBinary(data);
+
+                case ResourceTypeCode.TimeSpan:
+                    Int64 ticks = _store.ReadInt64();
+                    return new TimeSpan(ticks);
+
+                // Special types
+                case ResourceTypeCode.ByteArray:
+                    {
+                        int len = _store.ReadInt32();
+                        if (len < 0)
+                        {
+                            throw new BadImageFormatException(SR.Format(SR.BadImageFormat_ResourceDataLengthInvalid, len));
+                        }
+
+                        if (_ums == null)
+                        {
+                            if (len > _store.BaseStream.Length)
+                            {
+                                throw new BadImageFormatException(SR.Format(SR.BadImageFormat_ResourceDataLengthInvalid, len));
+                            }
+                            return _store.ReadBytes(len);
+                        }
+
+                        if (len > _ums.Length - _ums.Position)
+                        {
+                            throw new BadImageFormatException(SR.Format(SR.BadImageFormat_ResourceDataLengthInvalid, len));
+                        }
+
+                        byte[] bytes = new byte[len];
+                        int r = _ums.Read(bytes, 0, len);
+                        Debug.Assert(r == len, "ResourceReader needs to use a blocking read here.  (Call _store.ReadBytes(len)?)");
+                        return bytes;
+                    }
+
+                case ResourceTypeCode.Stream:
+                    {
+                        int len = _store.ReadInt32();
+                        if (len < 0)
+                        {
+                            throw new BadImageFormatException(SR.Format(SR.BadImageFormat_ResourceDataLengthInvalid, len));
+                        }
+                        if (_ums == null)
+                        {
+                            byte[] bytes = _store.ReadBytes(len);
+                            // Lifetime of memory == lifetime of this stream.
+                            return new PinnedBufferMemoryStream(bytes);
+                        }
+
+                        // make sure we don't create an UnmanagedMemoryStream that is longer than the resource stream. 
+                        if (len > _ums.Length - _ums.Position)
+                        {
+                            throw new BadImageFormatException(SR.Format(SR.BadImageFormat_ResourceDataLengthInvalid, len));
+                        }
+
+                        // For the case that we've memory mapped in the .resources
+                        // file, just return a Stream pointing to that block of memory.
+                        unsafe
+                        {
+                            return new UnmanagedMemoryStream(_ums.PositionPointer, len, len, FileAccess.Read);
+                        }
+                    }
+
+                default:
+                    if (typeCode < ResourceTypeCode.StartOfUserTypes)
+                    {
+                        throw new BadImageFormatException(SR.BadImageFormat_TypeMismatch);
+                    }
+                    break;
+            }
+
+            // Normal serialized objects
+            throw new NotSupportedException(SR.NotSupported_ResourceObjectSerialization);
+        }
+
+
+
+        // Reads in the header information for a .resources file.  Verifies some
+        // of the assumptions about this resource set, and builds the class table
+        // for the default resource file format.
+        private void ReadResources()
+        {
+            Debug.Assert(_store != null, "ResourceReader is closed!");
+
+            try
+            {
+                // mega try-catch performs exceptionally bad on x64; factored out body into 
+                // _ReadResources and wrap here.
+                _ReadResources();
+            }
+            catch (EndOfStreamException eof)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_ResourcesHeaderCorrupted, eof);
+            }
+            catch (IndexOutOfRangeException e)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_ResourcesHeaderCorrupted, e);
+            }
+        }
+
+        private void _ReadResources()
+        {
+            // Read ResourceManager header
+            // Check for magic number
+            int magicNum = _store.ReadInt32();
+            if (magicNum != ResourceManager.MagicNumber)
+                throw new ArgumentException(SR.Resources_StreamNotValid);
+            // Assuming this is ResourceManager header V1 or greater, hopefully
+            // after the version number there is a number of bytes to skip
+            // to bypass the rest of the ResMgr header. For V2 or greater, we
+            // use this to skip to the end of the header
+            int resMgrHeaderVersion = _store.ReadInt32();
+            int numBytesToSkip = _store.ReadInt32();
+            if (numBytesToSkip < 0 || resMgrHeaderVersion < 0)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_ResourcesHeaderCorrupted);
+            }
+            if (resMgrHeaderVersion > 1)
+            {
+                _store.BaseStream.Seek(numBytesToSkip, SeekOrigin.Current);
+            }
+            else
+            {
+                // We don't care about numBytesToSkip; read the rest of the header
+
+                // Read in type name for a suitable ResourceReader
+                // Note ResourceWriter & InternalResGen use different Strings.
+                String readerType = _store.ReadString();
+                readerType = System.CoreLib.FixupCoreLibName(readerType);
+                AssemblyName mscorlib = new AssemblyName(ResourceManager.MscorlibName);
+
+                if (!ResourceManager.CompareNames(readerType, ResourceManager.ResReaderTypeName, mscorlib))
+                    throw new NotSupportedException(SR.Format(SR.NotSupported_WrongResourceReader_Type, readerType));
+
+                // Skip over type name for a suitable ResourceSet
+                SkipString();
+            }
+
+            // Read RuntimeResourceSet header
+            // Do file version check
+            int version = _store.ReadInt32();
+            if (version != RuntimeResourceSet.Version && version != 1)
+                throw new ArgumentException(SR.Format(SR.Arg_ResourceFileUnsupportedVersion, RuntimeResourceSet.Version, version));
+            _version = version;
+
+            _numResources = _store.ReadInt32();
+            if (_numResources < 0)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_ResourcesHeaderCorrupted);
+            }
+
+            // Read type positions into type positions array.
+            // But delay initialize the type table.
+            int numTypes = _store.ReadInt32();
+            if (numTypes < 0)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_ResourcesHeaderCorrupted);
+            }
+            _typeTable = new RuntimeType[numTypes];
+            _typeNamePositions = new int[numTypes];
+            for (int i = 0; i < numTypes; i++)
+            {
+                _typeNamePositions[i] = (int)_store.BaseStream.Position;
+
+                // Skip over the Strings in the file.  Don't create types.
+                SkipString();
+            }
+
+            // Prepare to read in the array of name hashes
+            //  Note that the name hashes array is aligned to 8 bytes so 
+            //  we can use pointers into it on 64 bit machines. (4 bytes 
+            //  may be sufficient, but let's plan for the future)
+            //  Skip over alignment stuff.  All public .resources files
+            //  should be aligned   No need to verify the byte values.
+            long pos = _store.BaseStream.Position;
+            int alignBytes = ((int)pos) & 7;
+            if (alignBytes != 0)
+            {
+                for (int i = 0; i < 8 - alignBytes; i++)
+                {
+                    _store.ReadByte();
+                }
+            }
+
+            // Read in the array of name hashes
+            if (_ums == null)
+            {
+                _nameHashes = new int[_numResources];
+                for (int i = 0; i < _numResources; i++)
+                {
+                    _nameHashes[i] = _store.ReadInt32();
+                }
+            }
+            else
+            {
+                int seekPos = unchecked(4 * _numResources);
+                if (seekPos < 0)
+                {
+                    throw new BadImageFormatException(SR.BadImageFormat_ResourcesHeaderCorrupted);
+                }
+                unsafe
+                {
+                    _nameHashesPtr = (int*)_ums.PositionPointer;
+                    // Skip over the array of nameHashes.
+                    _ums.Seek(seekPos, SeekOrigin.Current);
+                    // get the position pointer once more to check that the whole table is within the stream
+                    byte* junk = _ums.PositionPointer;
+                }
+            }
+
+            // Read in the array of relative positions for all the names.
+            if (_ums == null)
+            {
+                _namePositions = new int[_numResources];
+                for (int i = 0; i < _numResources; i++)
+                {
+                    int namePosition = _store.ReadInt32();
+                    if (namePosition < 0)
+                    {
+                        throw new BadImageFormatException(SR.BadImageFormat_ResourcesHeaderCorrupted);
+                    }
+
+                    _namePositions[i] = namePosition;
+                }
+            }
+            else
+            {
+                int seekPos = unchecked(4 * _numResources);
+                if (seekPos < 0)
+                {
+                    throw new BadImageFormatException(SR.BadImageFormat_ResourcesHeaderCorrupted);
+                }
+                unsafe
+                {
+                    _namePositionsPtr = (int*)_ums.PositionPointer;
+                    // Skip over the array of namePositions.
+                    _ums.Seek(seekPos, SeekOrigin.Current);
+                    // get the position pointer once more to check that the whole table is within the stream
+                    byte* junk = _ums.PositionPointer;
+                }
+            }
+
+            // Read location of data section.
+            _dataSectionOffset = _store.ReadInt32();
+            if (_dataSectionOffset < 0)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_ResourcesHeaderCorrupted);
+            }
+
+            // Store current location as start of name section
+            _nameSectionOffset = _store.BaseStream.Position;
+
+            // _nameSectionOffset should be <= _dataSectionOffset; if not, it's corrupt
+            if (_dataSectionOffset < _nameSectionOffset)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_ResourcesHeaderCorrupted);
+            }
+        }
+
+        // This allows us to delay-initialize the Type[].  This might be a 
+        // good startup time savings, since we might have to load assemblies
+        // and initialize Reflection.
+        private RuntimeType FindType(int typeIndex)
+        {
+            if (typeIndex < 0 || typeIndex >= _typeTable.Length)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_InvalidType);
+            }
+            if (_typeTable[typeIndex] == null)
+            {
+                long oldPos = _store.BaseStream.Position;
+                try
+                {
+                    _store.BaseStream.Position = _typeNamePositions[typeIndex];
+                    String typeName = _store.ReadString();
+                    _typeTable[typeIndex] = (RuntimeType)Type.GetType(typeName, true);
+                }
+                // If serialization isn't supported, we convert FileNotFoundException to 
+                // NotSupportedException for consistency with v2. This is a corner-case, but the 
+                // idea is that we want to give the user a more accurate error message. Even if
+                // the dependency were found, we know it will require serialization since it
+                // can't be one of the types we special case. So if the dependency were found,
+                // it would go down the serialization code path, resulting in NotSupported for 
+                // SKUs without serialization.
+                //
+                // We don't want to regress the expected case by checking the type info before 
+                // getting to Type.GetType -- this is costly with v1 resource formats.
+                catch (FileNotFoundException)
+                {
+                    throw new NotSupportedException(SR.NotSupported_ResourceObjectSerialization);
+                }
+                finally
+                {
+                    _store.BaseStream.Position = oldPos;
+                }
+            }
+            Debug.Assert(_typeTable[typeIndex] != null, "Should have found a type!");
+            return _typeTable[typeIndex];
+        }
+
+
+        public void GetResourceData(String resourceName, out String resourceType, out byte[] resourceData)
+        {
+            if (resourceName == null)
+                throw new ArgumentNullException(nameof(resourceName));
+            if (_resCache == null)
+                throw new InvalidOperationException(SR.ResourceReaderIsClosed);
+
+            // Get the type information from the data section.  Also,
+            // sort all of the data section's indexes to compute length of
+            // the serialized data for this type (making sure to subtract
+            // off the length of the type code).
+            int[] sortedDataPositions = new int[_numResources];
+            int dataPos = FindPosForResource(resourceName);
+            if (dataPos == -1)
+            {
+                throw new ArgumentException(SR.Format(SR.Arg_ResourceNameNotExist, resourceName));
+            }
+
+            lock (this)
+            {
+                // Read all the positions of data within the data section.
+                for (int i = 0; i < _numResources; i++)
+                {
+                    _store.BaseStream.Position = _nameSectionOffset + GetNamePosition(i);
+                    // Skip over name of resource
+                    int numBytesToSkip = _store.Read7BitEncodedInt();
+                    if (numBytesToSkip < 0)
+                    {
+                        throw new FormatException(SR.Format(SR.BadImageFormat_ResourcesNameInvalidOffset, numBytesToSkip));
+                    }
+                    _store.BaseStream.Position += numBytesToSkip;
+
+                    int dPos = _store.ReadInt32();
+                    if (dPos < 0 || dPos >= _store.BaseStream.Length - _dataSectionOffset)
+                    {
+                        throw new FormatException(SR.Format(SR.BadImageFormat_ResourcesDataInvalidOffset, dPos));
+                    }
+                    sortedDataPositions[i] = dPos;
+                }
+                Array.Sort(sortedDataPositions);
+
+                int index = Array.BinarySearch(sortedDataPositions, dataPos);
+                Debug.Assert(index >= 0 && index < _numResources, "Couldn't find data position within sorted data positions array!");
+                long nextData = (index < _numResources - 1) ? sortedDataPositions[index + 1] + _dataSectionOffset : _store.BaseStream.Length;
+                int len = (int)(nextData - (dataPos + _dataSectionOffset));
+                Debug.Assert(len >= 0 && len <= (int)_store.BaseStream.Length - dataPos + _dataSectionOffset, "Length was negative or outside the bounds of the file!");
+
+                // Read type code then byte[]
+                _store.BaseStream.Position = _dataSectionOffset + dataPos;
+                ResourceTypeCode typeCode = (ResourceTypeCode)_store.Read7BitEncodedInt();
+                if (typeCode < 0 || typeCode >= ResourceTypeCode.StartOfUserTypes + _typeTable.Length)
+                {
+                    throw new BadImageFormatException(SR.BadImageFormat_InvalidType);
+                }
+                resourceType = TypeNameFromTypeCode(typeCode);
+
+                // The length must be adjusted to subtract off the number 
+                // of bytes in the 7 bit encoded type code.
+                len -= (int)(_store.BaseStream.Position - (_dataSectionOffset + dataPos));
+                byte[] bytes = _store.ReadBytes(len);
+                if (bytes.Length != len)
+                    throw new FormatException(SR.BadImageFormat_ResourceNameCorrupted);
+                resourceData = bytes;
+            }
+        }
+
+        private String TypeNameFromTypeCode(ResourceTypeCode typeCode)
+        {
+            Debug.Assert(typeCode >= 0, "can't be negative");
+            if (typeCode < ResourceTypeCode.StartOfUserTypes)
+            {
+                Debug.Assert(!String.Equals(typeCode.ToString(), "LastPrimitive"), "Change ResourceTypeCode metadata order so LastPrimitive isn't what Enum.ToString prefers.");
+                return "ResourceTypeCode." + typeCode.ToString();
+            }
+            else
+            {
+                int typeIndex = typeCode - ResourceTypeCode.StartOfUserTypes;
+                Debug.Assert(typeIndex >= 0 && typeIndex < _typeTable.Length, "TypeCode is broken or corrupted!");
+                long oldPos = _store.BaseStream.Position;
+                try
+                {
+                    _store.BaseStream.Position = _typeNamePositions[typeIndex];
+                    return _store.ReadString();
+                }
+                finally
+                {
+                    _store.BaseStream.Position = oldPos;
+                }
+            }
+        }
+
+
+
+        internal sealed class ResourceEnumerator : IDictionaryEnumerator
+        {
+            private const int ENUM_DONE = Int32.MinValue;
+            private const int ENUM_NOT_STARTED = -1;
+
+            private ResourceReader _reader;
+            private bool _currentIsValid;
+            private int _currentName;
+            private int _dataPosition; // cached for case-insensitive table
+
+            internal ResourceEnumerator(ResourceReader reader)
+            {
+                _currentName = ENUM_NOT_STARTED;
+                _reader = reader;
+                _dataPosition = -2;
+            }
+
+            public bool MoveNext()
+            {
+                if (_currentName == _reader._numResources - 1 || _currentName == ENUM_DONE)
+                {
+                    _currentIsValid = false;
+                    _currentName = ENUM_DONE;
+                    return false;
+                }
+                _currentIsValid = true;
+                _currentName++;
+                return true;
+            }
+
+            public Object Key
+            {
+                get
+                {
+                    if (_currentName == ENUM_DONE) throw new InvalidOperationException(SR.InvalidOperation_EnumEnded);
+                    if (!_currentIsValid) throw new InvalidOperationException(SR.InvalidOperation_EnumNotStarted);
+                    if (_reader._resCache == null) throw new InvalidOperationException(SR.ResourceReaderIsClosed);
+
+                    return _reader.AllocateStringForNameIndex(_currentName, out _dataPosition);
+                }
+            }
+
+            public Object Current
+            {
+                get
+                {
+                    return Entry;
+                }
+            }
+
+            // Warning: This requires that you call the Key or Entry property FIRST before calling it!
+            internal int DataPosition
+            {
+                get
+                {
+                    return _dataPosition;
+                }
+            }
+
+            public DictionaryEntry Entry
+            {
+                get
+                {
+                    if (_currentName == ENUM_DONE) throw new InvalidOperationException(SR.InvalidOperation_EnumEnded);
+                    if (!_currentIsValid) throw new InvalidOperationException(SR.InvalidOperation_EnumNotStarted);
+                    if (_reader._resCache == null) throw new InvalidOperationException(SR.ResourceReaderIsClosed);
+
+                    String key;
+                    Object value = null;
+                    lock (_reader)
+                    { // locks should be taken in the same order as in RuntimeResourceSet.GetObject to avoid deadlock
+                        lock (_reader._resCache)
+                        {
+                            key = _reader.AllocateStringForNameIndex(_currentName, out _dataPosition); // AllocateStringForNameIndex could lock on _reader
+                            ResourceLocator locator;
+                            if (_reader._resCache.TryGetValue(key, out locator))
+                            {
+                                value = locator.Value;
+                            }
+                            if (value == null)
+                            {
+                                if (_dataPosition == -1)
+                                    value = _reader.GetValueForNameIndex(_currentName);
+                                else
+                                    value = _reader.LoadObject(_dataPosition);
+                                // If enumeration and subsequent lookups happen very
+                                // frequently in the same process, add a ResourceLocator
+                                // to _resCache here.  But WinForms enumerates and
+                                // just about everyone else does lookups.  So caching
+                                // here may bloat working set.
+                            }
+                        }
+                    }
+                    return new DictionaryEntry(key, value);
+                }
+            }
+
+            public Object Value
+            {
+                get
+                {
+                    if (_currentName == ENUM_DONE) throw new InvalidOperationException(SR.InvalidOperation_EnumEnded);
+                    if (!_currentIsValid) throw new InvalidOperationException(SR.InvalidOperation_EnumNotStarted);
+                    if (_reader._resCache == null) throw new InvalidOperationException(SR.ResourceReaderIsClosed);
+
+                    // Consider using _resCache here, eventually, if
+                    // this proves to be an interesting perf scenario.
+                    // But mixing lookups and enumerators shouldn't be
+                    // particularly compelling.
+                    return _reader.GetValueForNameIndex(_currentName);
+                }
+            }
+
+            public void Reset()
+            {
+                if (_reader._resCache == null) throw new InvalidOperationException(SR.ResourceReaderIsClosed);
+                _currentIsValid = false;
+                _currentName = ENUM_NOT_STARTED;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Resources/ResourceSet.cs b/src/System.Private.CoreLib/src/System/Resources/ResourceSet.cs
new file mode 100644
index 0000000000..9e5a72c431
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Resources/ResourceSet.cs
@@ -0,0 +1,262 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+** 
+**
+**
+** Purpose: Culture-specific collection of resources.
+**
+** 
+===========================================================*/
+
+using System.Collections;
+using System.IO;
+using System.Reflection;
+
+namespace System.Resources
+{
+    // A ResourceSet stores all the resources defined in one particular CultureInfo.
+    // 
+    // The method used to load resources is straightforward - this class
+    // enumerates over an IResourceReader, loading every name and value, and 
+    // stores them in a hash table.  Custom IResourceReaders can be used.
+    //
+    public class ResourceSet : IDisposable, IEnumerable
+    {
+        protected IResourceReader Reader;
+        internal Hashtable Table;
+
+        private Hashtable _caseInsensitiveTable;  // For case-insensitive lookups.
+
+        protected ResourceSet()
+        {
+            // To not inconvenience people subclassing us, we should allocate a new
+            // hashtable here just so that Table is set to something.
+            CommonInit();
+        }
+
+        // For RuntimeResourceSet, ignore the Table parameter - it's a wasted 
+        // allocation.
+        internal ResourceSet(bool junk)
+        {
+        }
+
+        // Creates a ResourceSet using the system default ResourceReader
+        // implementation.  Use this constructor to open & read from a file 
+        // on disk.
+        // 
+        public ResourceSet(String fileName)
+        {
+            Reader = new ResourceReader(fileName);
+            CommonInit();
+            ReadResources();
+        }
+
+        // Creates a ResourceSet using the system default ResourceReader
+        // implementation.  Use this constructor to read from an open stream 
+        // of data.
+        // 
+        public ResourceSet(Stream stream)
+        {
+            Reader = new ResourceReader(stream);
+            CommonInit();
+            ReadResources();
+        }
+
+        public ResourceSet(IResourceReader reader)
+        {
+            if (reader == null)
+                throw new ArgumentNullException(nameof(reader));
+            Reader = reader;
+            CommonInit();
+            ReadResources();
+        }
+
+        private void CommonInit()
+        {
+            Table = new Hashtable();
+        }
+
+        // Closes and releases any resources used by this ResourceSet, if any.
+        // All calls to methods on the ResourceSet after a call to close may 
+        // fail.  Close is guaranteed to be safely callable multiple times on a 
+        // particular ResourceSet, and all subclasses must support these semantics.
+        public virtual void Close()
+        {
+            Dispose(true);
+        }
+
+        protected virtual void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                // Close the Reader in a thread-safe way.
+                IResourceReader copyOfReader = Reader;
+                Reader = null;
+                if (copyOfReader != null)
+                    copyOfReader.Close();
+            }
+            Reader = null;
+            _caseInsensitiveTable = null;
+            Table = null;
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+        }
+
+        // Returns the preferred IResourceReader class for this kind of ResourceSet.
+        // Subclasses of ResourceSet using their own Readers &; should override
+        // GetDefaultReader and GetDefaultWriter.
+        public virtual Type GetDefaultReader()
+        {
+            return typeof(ResourceReader);
+        }
+
+        // Returns the preferred IResourceWriter class for this kind of ResourceSet.
+        // Subclasses of ResourceSet using their own Readers &; should override
+        // GetDefaultReader and GetDefaultWriter.
+        public virtual Type GetDefaultWriter()
+        {
+            Assembly resourceWriterAssembly = Assembly.Load("System.Resources.Writer, Version=4.0.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a");
+            return resourceWriterAssembly.GetType("System.Resources.ResourceWriter", true);
+        }
+
+        public virtual IDictionaryEnumerator GetEnumerator()
+        {
+            return GetEnumeratorHelper();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumeratorHelper();
+        }
+
+        private IDictionaryEnumerator GetEnumeratorHelper()
+        {
+            Hashtable copyOfTable = Table;  // Avoid a race with Dispose
+            if (copyOfTable == null)
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ResourceSet);
+            return copyOfTable.GetEnumerator();
+        }
+
+        // Look up a string value for a resource given its name.
+        // 
+        public virtual String GetString(String name)
+        {
+            Object obj = GetObjectInternal(name);
+            try
+            {
+                return (String)obj;
+            }
+            catch (InvalidCastException)
+            {
+                throw new InvalidOperationException(SR.Format(SR.InvalidOperation_ResourceNotString_Name, name));
+            }
+        }
+
+        public virtual String GetString(String name, bool ignoreCase)
+        {
+            Object obj;
+            String s;
+
+            // Case-sensitive lookup
+            obj = GetObjectInternal(name);
+            try
+            {
+                s = (String)obj;
+            }
+            catch (InvalidCastException)
+            {
+                throw new InvalidOperationException(SR.Format(SR.InvalidOperation_ResourceNotString_Name, name));
+            }
+
+            // case-sensitive lookup succeeded
+            if (s != null || !ignoreCase)
+            {
+                return s;
+            }
+
+            // Try doing a case-insensitive lookup
+            obj = GetCaseInsensitiveObjectInternal(name);
+            try
+            {
+                return (String)obj;
+            }
+            catch (InvalidCastException)
+            {
+                throw new InvalidOperationException(SR.Format(SR.InvalidOperation_ResourceNotString_Name, name));
+            }
+        }
+
+        // Look up an object value for a resource given its name.
+        // 
+        public virtual Object GetObject(String name)
+        {
+            return GetObjectInternal(name);
+        }
+
+        public virtual Object GetObject(String name, bool ignoreCase)
+        {
+            Object obj = GetObjectInternal(name);
+
+            if (obj != null || !ignoreCase)
+                return obj;
+
+            return GetCaseInsensitiveObjectInternal(name);
+        }
+
+        protected virtual void ReadResources()
+        {
+            IDictionaryEnumerator en = Reader.GetEnumerator();
+            while (en.MoveNext())
+            {
+                Object value = en.Value;
+                Table.Add(en.Key, value);
+            }
+            // While technically possible to close the Reader here, don't close it
+            // to help with some WinRes lifetime issues.
+        }
+
+        private Object GetObjectInternal(String name)
+        {
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            Hashtable copyOfTable = Table;  // Avoid a race with Dispose
+
+            if (copyOfTable == null)
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ResourceSet);
+
+            return copyOfTable[name];
+        }
+
+        private Object GetCaseInsensitiveObjectInternal(String name)
+        {
+            Hashtable copyOfTable = Table;  // Avoid a race with Dispose
+
+            if (copyOfTable == null)
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_ResourceSet);
+
+            Hashtable caseTable = _caseInsensitiveTable;  // Avoid a race condition with Close
+            if (caseTable == null)
+            {
+                caseTable = new Hashtable(StringComparer.OrdinalIgnoreCase);
+
+                IDictionaryEnumerator en = copyOfTable.GetEnumerator();
+                while (en.MoveNext())
+                {
+                    caseTable.Add(en.Key, en.Value);
+                }
+                _caseInsensitiveTable = caseTable;
+            }
+
+            return caseTable[name];
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Resources/__FastResourceComparer.cs b/src/System.Private.CoreLib/src/System/Resources/__FastResourceComparer.cs
new file mode 100644
index 0000000000..b9e2f8198d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Resources/__FastResourceComparer.cs
@@ -0,0 +1,142 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: A collection of quick methods for comparing 
+**          resource keys (strings)
+**
+** 
+===========================================================*/
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System.Resources
+{
+    internal sealed class FastResourceComparer : IComparer, IEqualityComparer, IComparer<String>, IEqualityComparer<String>
+    {
+        internal static readonly FastResourceComparer Default = new FastResourceComparer();
+
+        // Implements IHashCodeProvider too, due to Hashtable requirements.
+        public int GetHashCode(Object key)
+        {
+            String s = (String)key;
+            return FastResourceComparer.HashFunction(s);
+        }
+
+        public int GetHashCode(String key)
+        {
+            return FastResourceComparer.HashFunction(key);
+        }
+
+        // This hash function MUST be publically documented with the resource
+        // file format, AND we may NEVER change this hash function's return 
+        // value (without changing the file format).
+        internal static int HashFunction(String key)
+        {
+            // Never change this hash function.  We must standardize it so that 
+            // others can read & write our .resources files.  Additionally, we
+            // have a copy of it in InternalResGen as well.
+            uint hash = 5381;
+            for (int i = 0; i < key.Length; i++)
+                hash = ((hash << 5) + hash) ^ key[i];
+            return (int)hash;
+        }
+
+        // Compares Strings quickly in a case-sensitive way
+        public int Compare(Object a, Object b)
+        {
+            if (a == b) return 0;
+            String sa = (String)a;
+            String sb = (String)b;
+            return String.CompareOrdinal(sa, sb);
+        }
+
+        public int Compare(String a, String b)
+        {
+            return String.CompareOrdinal(a, b);
+        }
+
+        public bool Equals(String a, String b)
+        {
+            return String.Equals(a, b);
+        }
+
+        public new bool Equals(Object a, Object b)
+        {
+            if (a == b) return true;
+            String sa = (String)a;
+            String sb = (String)b;
+            return String.Equals(sa, sb);
+        }
+
+        // Input is one string to compare with, and a byte[] containing chars in 
+        // little endian unicode.  Pass in the number of valid chars.
+        public static unsafe int CompareOrdinal(String a, byte[] bytes, int bCharLength)
+        {
+            Debug.Assert(a != null && bytes != null, "FastResourceComparer::CompareOrdinal must have non-null params");
+            Debug.Assert(bCharLength * 2 <= bytes.Length, "FastResourceComparer::CompareOrdinal - numChars is too big!");
+            // This is a managed version of strcmp, but I can't take advantage
+            // of a terminating 0, unlike strcmp in C.
+            int i = 0;
+            int r = 0;
+            // Compare the min length # of characters, then return length diffs.
+            int numChars = a.Length;
+            if (numChars > bCharLength)
+                numChars = bCharLength;
+            if (bCharLength == 0)   // Can't use fixed on a 0-element array.
+                return (a.Length == 0) ? 0 : -1;
+            fixed (byte* pb = bytes)
+            {
+                byte* pChar = pb;
+                while (i < numChars && r == 0)
+                {
+                    // little endian format
+                    int b = pChar[0] | pChar[1] << 8;
+                    r = a[i++] - b;
+                    pChar += sizeof(char);
+                }
+            }
+            if (r != 0) return r;
+            return a.Length - bCharLength;
+        }
+
+        public static int CompareOrdinal(byte[] bytes, int aCharLength, String b)
+        {
+            return -CompareOrdinal(b, bytes, aCharLength);
+        }
+
+        // This method is to handle potentially misaligned data accesses.
+        // The byte* must point to little endian Unicode characters.
+        internal static unsafe int CompareOrdinal(byte* a, int byteLen, String b)
+        {
+            Debug.Assert((byteLen & 1) == 0, "CompareOrdinal is expecting a UTF-16 string length, which must be even!");
+            Debug.Assert(a != null && b != null, "Null args not allowed.");
+            Debug.Assert(byteLen >= 0, "byteLen must be non-negative.");
+
+            int r = 0;
+            int i = 0;
+            // Compare the min length # of characters, then return length diffs.
+            int numChars = byteLen >> 1;
+            if (numChars > b.Length)
+                numChars = b.Length;
+            while (i < numChars && r == 0)
+            {
+                // Must compare character by character, not byte by byte.
+                char aCh = (char)(*a++ | (*a++ << 8));
+                r = aCh - b[i++];
+            }
+            if (r != 0) return r;
+            return byteLen - b.Length * 2;
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/RtType.cs b/src/System.Private.CoreLib/src/System/RtType.cs
new file mode 100644
index 0000000000..ca25f85315
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/RtType.cs
@@ -0,0 +1,5186 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+//
+//
+// Implements System.RuntimeType
+//
+// ======================================================================================
+
+
+using System;
+using System.Reflection;
+using System.Runtime.ConstrainedExecution;
+using System.Globalization;
+using System.Threading;
+using System.Diagnostics;
+using System.Collections;
+using System.Collections.Generic;
+using System.Runtime;
+using System.Runtime.CompilerServices;
+using System.Security;
+using System.Text;
+using MdSigCallingConvention = System.Signature.MdSigCallingConvention;
+using RuntimeTypeCache = System.RuntimeType.RuntimeTypeCache;
+using System.Runtime.InteropServices;
+using DebuggerStepThroughAttribute = System.Diagnostics.DebuggerStepThroughAttribute;
+using MdToken = System.Reflection.MetadataToken;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    // this is a work around to get the concept of a calli. It's not as fast but it would be interesting to 
+    // see how it compares to the current implementation. 
+    // This delegate will disappear at some point in favor of calli 
+
+    internal delegate void CtorDelegate(Object instance);
+
+    // Keep this in sync with FormatFlags defined in typestring.h
+    internal enum TypeNameFormatFlags
+    {
+        FormatBasic = 0x00000000, // Not a bitmask, simply the tersest flag settings possible
+        FormatNamespace = 0x00000001, // Include namespace and/or enclosing class names in type names
+        FormatFullInst = 0x00000002, // Include namespace and assembly in generic types (regardless of other flag settings)
+        FormatAssembly = 0x00000004, // Include assembly display name in type names
+        FormatSignature = 0x00000008, // Include signature in method names
+        FormatNoVersion = 0x00000010, // Suppress version and culture information in all assembly names
+#if DEBUG
+        FormatDebug = 0x00000020, // For debug printing of types only
+#endif
+        FormatAngleBrackets = 0x00000040, // Whether generic types are C<T> or C[T]
+        FormatStubInfo = 0x00000080, // Include stub info like {unbox-stub}
+        FormatGenericParam = 0x00000100, // Use !name and !!name for generic type and method parameters
+
+        // If we want to be able to distinguish between overloads whose parameter types have the same name but come from different assemblies,
+        // we can add FormatAssembly | FormatNoVersion to FormatSerialization. But we are omitting it because it is not a useful scenario
+        // and including the assembly name will normally increase the size of the serialized data and also decrease the performance.
+        FormatSerialization = FormatNamespace |
+                              FormatGenericParam |
+                              FormatFullInst
+    }
+
+    internal enum TypeNameKind
+    {
+        Name,
+        ToString,
+        SerializationName,
+        FullName,
+    }
+
+    internal class RuntimeType :
+        System.Reflection.TypeInfo, ICloneable
+    {
+        #region Definitions
+
+        internal enum MemberListType
+        {
+            All,
+            CaseSensitive,
+            CaseInsensitive,
+            HandleToInfo
+        }
+
+        // Helper to build lists of MemberInfos. Special cased to avoid allocations for lists of one element.
+        private struct ListBuilder<T> where T : class
+        {
+            private T[] _items;
+            private T _item;
+            private int _count;
+            private int _capacity;
+
+            public ListBuilder(int capacity)
+            {
+                _items = null;
+                _item = null;
+                _count = 0;
+                _capacity = capacity;
+            }
+
+            public T this[int index]
+            {
+                get
+                {
+                    Debug.Assert(index < Count);
+                    return (_items != null) ? _items[index] : _item;
+                }
+            }
+
+            public T[] ToArray()
+            {
+                if (_count == 0)
+                    return Array.Empty<T>();
+                if (_count == 1)
+                    return new T[1] { _item };
+
+                Array.Resize(ref _items, _count);
+                _capacity = _count;
+                return _items;
+            }
+
+            public void CopyTo(Object[] array, int index)
+            {
+                if (_count == 0)
+                    return;
+
+                if (_count == 1)
+                {
+                    array[index] = _item;
+                    return;
+                }
+
+                Array.Copy(_items, 0, array, index, _count);
+            }
+
+            public int Count
+            {
+                get
+                {
+                    return _count;
+                }
+            }
+
+            public void Add(T item)
+            {
+                if (_count == 0)
+                {
+                    _item = item;
+                }
+                else
+                {
+                    if (_count == 1)
+                    {
+                        if (_capacity < 2)
+                            _capacity = 4;
+                        _items = new T[_capacity];
+                        _items[0] = _item;
+                    }
+                    else
+                    if (_capacity == _count)
+                    {
+                        int newCapacity = 2 * _capacity;
+                        Array.Resize(ref _items, newCapacity);
+                        _capacity = newCapacity;
+                    }
+
+                    _items[_count] = item;
+                }
+                _count++;
+            }
+        }
+
+        internal class RuntimeTypeCache
+        {
+            private const int MAXNAMELEN = 1024;
+
+            #region Definitions
+            internal enum CacheType
+            {
+                Method,
+                Constructor,
+                Field,
+                Property,
+                Event,
+                Interface,
+                NestedType
+            }
+
+            private struct Filter
+            {
+                private MdUtf8String m_name;
+                private MemberListType m_listType;
+                private uint m_nameHash;
+
+                public unsafe Filter(byte* pUtf8Name, int cUtf8Name, MemberListType listType)
+                {
+                    m_name = new MdUtf8String((void*)pUtf8Name, cUtf8Name);
+                    m_listType = listType;
+                    m_nameHash = 0;
+
+                    if (RequiresStringComparison())
+                    {
+                        m_nameHash = m_name.HashCaseInsensitive();
+                    }
+                }
+
+                public bool Match(MdUtf8String name)
+                {
+                    bool retVal = true;
+
+                    if (m_listType == MemberListType.CaseSensitive)
+                        retVal = m_name.Equals(name);
+                    else if (m_listType == MemberListType.CaseInsensitive)
+                        retVal = m_name.EqualsCaseInsensitive(name);
+
+                    // Currently the callers of UsesStringComparison assume that if it returns false
+                    // then the match always succeeds and can be skipped.  Assert that this is maintained.
+                    Debug.Assert(retVal || RequiresStringComparison());
+
+                    return retVal;
+                }
+
+                // Does the current match type require a string comparison?
+                // If not, we know Match will always return true and the call can be skipped
+                // If so, we know we can have a valid hash to check against from GetHashToMatch
+                public bool RequiresStringComparison()
+                {
+                    return (m_listType == MemberListType.CaseSensitive) ||
+                           (m_listType == MemberListType.CaseInsensitive);
+                }
+
+                public bool CaseSensitive()
+                {
+                    return (m_listType == MemberListType.CaseSensitive);
+                }
+
+                public uint GetHashToMatch()
+                {
+                    Debug.Assert(RequiresStringComparison());
+
+                    return m_nameHash;
+                }
+            }
+
+            private class MemberInfoCache<T> where T : MemberInfo
+            {
+                #region Private Data Members
+
+                // MemberInfo caches
+                private CerHashtable<string, T[]> m_csMemberInfos;
+                private CerHashtable<string, T[]> m_cisMemberInfos;
+                // List of MemberInfos given out. When m_cacheComplete is false, it may have null entries at the end to avoid
+                // reallocating the list every time a new entry is added.
+                private T[] m_allMembers;
+                private bool m_cacheComplete;
+
+                // This is the strong reference back to the cache
+                private RuntimeTypeCache m_runtimeTypeCache;
+                #endregion
+
+                #region Constructor
+#if MDA_SUPPORTED
+#endif
+                internal MemberInfoCache(RuntimeTypeCache runtimeTypeCache)
+                {
+#if MDA_SUPPORTED
+                    Mda.MemberInfoCacheCreation();
+#endif
+                    m_runtimeTypeCache = runtimeTypeCache;
+                }
+
+                internal MethodBase AddMethod(RuntimeType declaringType, RuntimeMethodHandleInternal method, CacheType cacheType)
+                {
+                    T[] list = null;
+                    MethodAttributes methodAttributes = RuntimeMethodHandle.GetAttributes(method);
+                    bool isPublic = (methodAttributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Public;
+                    bool isStatic = (methodAttributes & MethodAttributes.Static) != 0;
+                    bool isInherited = declaringType != ReflectedType;
+                    BindingFlags bindingFlags = RuntimeType.FilterPreCalculate(isPublic, isInherited, isStatic);
+                    switch (cacheType)
+                    {
+                        case CacheType.Method:
+                            list = (T[])(object)new RuntimeMethodInfo[1] {
+                            new RuntimeMethodInfo(method, declaringType, m_runtimeTypeCache, methodAttributes, bindingFlags, null)
+                        };
+                            break;
+                        case CacheType.Constructor:
+                            list = (T[])(object)new RuntimeConstructorInfo[1] {
+                            new RuntimeConstructorInfo(method, declaringType, m_runtimeTypeCache, methodAttributes, bindingFlags)
+                        };
+                            break;
+                    }
+
+                    Insert(ref list, null, MemberListType.HandleToInfo);
+
+                    return (MethodBase)(object)list[0];
+                }
+
+                internal FieldInfo AddField(RuntimeFieldHandleInternal field)
+                {
+                    // create the runtime field info
+                    FieldAttributes fieldAttributes = RuntimeFieldHandle.GetAttributes(field);
+                    bool isPublic = (fieldAttributes & FieldAttributes.FieldAccessMask) == FieldAttributes.Public;
+                    bool isStatic = (fieldAttributes & FieldAttributes.Static) != 0;
+                    RuntimeType approxDeclaringType = RuntimeFieldHandle.GetApproxDeclaringType(field);
+                    bool isInherited = RuntimeFieldHandle.AcquiresContextFromThis(field) ?
+                        !RuntimeTypeHandle.CompareCanonicalHandles(approxDeclaringType, ReflectedType) :
+                        approxDeclaringType != ReflectedType;
+
+                    BindingFlags bindingFlags = RuntimeType.FilterPreCalculate(isPublic, isInherited, isStatic);
+
+                    T[] list = (T[])(object)new RuntimeFieldInfo[1] {
+                        new RtFieldInfo(field, ReflectedType, m_runtimeTypeCache, bindingFlags)
+                    };
+
+                    Insert(ref list, null, MemberListType.HandleToInfo);
+
+                    return (FieldInfo)(object)list[0];
+                }
+
+                private unsafe T[] Populate(string name, MemberListType listType, CacheType cacheType)
+                {
+                    T[] list = null;
+
+                    if (name == null || name.Length == 0 ||
+                        (cacheType == CacheType.Constructor && name[0] != '.' && name[0] != '*'))
+                    {
+                        list = GetListByName(null, 0, null, 0, listType, cacheType);
+                    }
+                    else
+                    {
+                        int cNameLen = name.Length;
+                        fixed (char* pName = name)
+                        {
+                            int cUtf8Name = Encoding.UTF8.GetByteCount(pName, cNameLen);
+                            // allocating on the stack is faster than allocating on the GC heap
+                            // but we surely don't want to cause a stack overflow
+                            // no one should be looking for a member whose name is longer than 1024
+                            if (cUtf8Name > MAXNAMELEN)
+                            {
+                                byte[] utf8Name = new byte[cUtf8Name];
+                                fixed (byte* pUtf8Name = &utf8Name[0])
+                                {
+                                    list = GetListByName(pName, cNameLen, pUtf8Name, cUtf8Name, listType, cacheType);
+                                }
+                            }
+                            else
+                            {
+                                byte* pUtf8Name = stackalloc byte[cUtf8Name];
+                                list = GetListByName(pName, cNameLen, pUtf8Name, cUtf8Name, listType, cacheType);
+                            }
+                        }
+                    }
+
+                    Insert(ref list, name, listType);
+
+                    return list;
+                }
+
+                private unsafe T[] GetListByName(char* pName, int cNameLen, byte* pUtf8Name, int cUtf8Name, MemberListType listType, CacheType cacheType)
+                {
+                    if (cNameLen != 0)
+                        Encoding.UTF8.GetBytes(pName, cNameLen, pUtf8Name, cUtf8Name);
+
+                    Filter filter = new Filter(pUtf8Name, cUtf8Name, listType);
+                    Object list = null;
+
+                    switch (cacheType)
+                    {
+                        case CacheType.Method:
+                            list = PopulateMethods(filter);
+                            break;
+                        case CacheType.Field:
+                            list = PopulateFields(filter);
+                            break;
+                        case CacheType.Constructor:
+                            list = PopulateConstructors(filter);
+                            break;
+                        case CacheType.Property:
+                            list = PopulateProperties(filter);
+                            break;
+                        case CacheType.Event:
+                            list = PopulateEvents(filter);
+                            break;
+                        case CacheType.NestedType:
+                            list = PopulateNestedClasses(filter);
+                            break;
+                        case CacheType.Interface:
+                            list = PopulateInterfaces(filter);
+                            break;
+                        default:
+                            Debug.Fail("Invalid CacheType");
+                            break;
+                    }
+
+                    return (T[])list;
+                }
+
+                // May replace the list with a new one if certain cache
+                // lookups succeed.  Also, may modify the contents of the list
+                // after merging these new data structures with cached ones.
+                internal void Insert(ref T[] list, string name, MemberListType listType)
+                {
+                    bool lockTaken = false;
+
+                    RuntimeHelpers.PrepareConstrainedRegions();
+                    try
+                    {
+                        Monitor.Enter(this, ref lockTaken);
+
+                        switch (listType)
+                        {
+                            case MemberListType.CaseSensitive:
+                                {
+                                    // Ensure we always return a list that has 
+                                    // been merged with the global list.
+                                    T[] cachedList = m_csMemberInfos[name];
+                                    if (cachedList == null)
+                                    {
+                                        MergeWithGlobalList(list);
+                                        m_csMemberInfos[name] = list;
+                                    }
+                                    else
+                                        list = cachedList;
+                                }
+                                break;
+
+                            case MemberListType.CaseInsensitive:
+                                {
+                                    // Ensure we always return a list that has 
+                                    // been merged with the global list.
+                                    T[] cachedList = m_cisMemberInfos[name];
+                                    if (cachedList == null)
+                                    {
+                                        MergeWithGlobalList(list);
+                                        m_cisMemberInfos[name] = list;
+                                    }
+                                    else
+                                        list = cachedList;
+                                }
+                                break;
+
+                            case MemberListType.All:
+                                if (!m_cacheComplete)
+                                {
+                                    MergeWithGlobalList(list);
+
+                                    // Trim null entries at the end of m_allMembers array
+                                    int memberCount = m_allMembers.Length;
+                                    while (memberCount > 0)
+                                    {
+                                        if (m_allMembers[memberCount - 1] != null)
+                                            break;
+                                        memberCount--;
+                                    }
+                                    Array.Resize(ref m_allMembers, memberCount);
+
+                                    Volatile.Write(ref m_cacheComplete, true);
+                                }
+
+                                list = m_allMembers;
+                                break;
+
+                            default:
+                                MergeWithGlobalList(list);
+                                break;
+                        }
+                    }
+                    finally
+                    {
+                        if (lockTaken)
+                        {
+                            Monitor.Exit(this);
+                        }
+                    }
+                }
+
+                // Modifies the existing list.
+                private void MergeWithGlobalList(T[] list)
+                {
+                    T[] cachedMembers = m_allMembers;
+
+                    if (cachedMembers == null)
+                    {
+                        m_allMembers = list;
+                        return;
+                    }
+
+                    int cachedCount = cachedMembers.Length;
+                    int freeSlotIndex = 0;
+
+                    for (int i = 0; i < list.Length; i++)
+                    {
+                        T newMemberInfo = list[i];
+                        bool foundInCache = false;
+
+                        int cachedIndex;
+                        for (cachedIndex = 0; cachedIndex < cachedCount; cachedIndex++)
+                        {
+                            T cachedMemberInfo = cachedMembers[cachedIndex];
+                            if (cachedMemberInfo == null)
+                                break;
+
+                            if (newMemberInfo.CacheEquals(cachedMemberInfo))
+                            {
+                                list[i] = cachedMemberInfo;
+                                foundInCache = true;
+                                break;
+                            }
+                        }
+
+                        if (!foundInCache)
+                        {
+                            if (freeSlotIndex == 0)
+                                freeSlotIndex = cachedIndex;
+
+                            if (freeSlotIndex >= cachedMembers.Length)
+                            {
+                                int newSize;
+                                if (m_cacheComplete)
+                                {
+                                    //
+                                    // In theory, we should never add more elements to the cache when it is complete.
+                                    //
+                                    // Unfortunately, we shipped with bugs that cause changes of the complete cache (DevDiv #339308).
+                                    // Grow the list by exactly one element in this case to avoid null entries at the end.
+                                    //
+
+                                    Debug.Assert(false);
+
+                                    newSize = cachedMembers.Length + 1;
+                                }
+                                else
+                                {
+                                    newSize = Math.Max(Math.Max(4, 2 * cachedMembers.Length), list.Length);
+                                }
+
+                                // Use different variable for ref argument to Array.Resize to allow enregistration of cachedMembers by the JIT
+                                T[] cachedMembers2 = cachedMembers;
+                                Array.Resize(ref cachedMembers2, newSize);
+                                cachedMembers = cachedMembers2;
+                            }
+
+                            Debug.Assert(cachedMembers[freeSlotIndex] == null);
+                            cachedMembers[freeSlotIndex] = newMemberInfo;
+                            freeSlotIndex++;
+                        }
+                    }
+
+                    m_allMembers = cachedMembers;
+                }
+                #endregion
+
+                #region Population Logic
+
+                private unsafe RuntimeMethodInfo[] PopulateMethods(Filter filter)
+                {
+                    ListBuilder<RuntimeMethodInfo> list = new ListBuilder<RuntimeMethodInfo>();
+
+                    RuntimeType declaringType = ReflectedType;
+                    Debug.Assert(declaringType != null);
+
+                    if (RuntimeTypeHandle.IsInterface(declaringType))
+                    {
+                        #region IsInterface
+
+                        foreach (RuntimeMethodHandleInternal methodHandle in RuntimeTypeHandle.GetIntroducedMethods(declaringType))
+                        {
+                            if (filter.RequiresStringComparison())
+                            {
+                                if (!RuntimeMethodHandle.MatchesNameHash(methodHandle, filter.GetHashToMatch()))
+                                {
+                                    Debug.Assert(!filter.Match(RuntimeMethodHandle.GetUtf8Name(methodHandle)));
+                                    continue;
+                                }
+
+                                if (!filter.Match(RuntimeMethodHandle.GetUtf8Name(methodHandle)))
+                                    continue;
+                            }
+
+                            #region Loop through all methods on the interface
+                            Debug.Assert(!methodHandle.IsNullHandle());
+
+                            MethodAttributes methodAttributes = RuntimeMethodHandle.GetAttributes(methodHandle);
+
+                            #region Continue if this is a constructor
+                            Debug.Assert(
+                                (RuntimeMethodHandle.GetAttributes(methodHandle) & MethodAttributes.RTSpecialName) == 0 ||
+                                RuntimeMethodHandle.GetName(methodHandle).Equals(".cctor"));
+
+                            if ((methodAttributes & MethodAttributes.RTSpecialName) != 0)
+                                continue;
+                            #endregion
+
+                            #region Calculate Binding Flags
+                            bool isPublic = (methodAttributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Public;
+                            bool isStatic = (methodAttributes & MethodAttributes.Static) != 0;
+                            bool isInherited = false;
+                            BindingFlags bindingFlags = RuntimeType.FilterPreCalculate(isPublic, isInherited, isStatic);
+                            #endregion
+
+                            // get the unboxing stub or instantiating stub if needed
+                            RuntimeMethodHandleInternal instantiatedHandle = RuntimeMethodHandle.GetStubIfNeeded(methodHandle, declaringType, null);
+
+                            RuntimeMethodInfo runtimeMethodInfo = new RuntimeMethodInfo(
+                            instantiatedHandle, declaringType, m_runtimeTypeCache, methodAttributes, bindingFlags, null);
+
+                            list.Add(runtimeMethodInfo);
+                            #endregion  
+                        }
+                        #endregion
+                    }
+                    else
+                    {
+                        #region IsClass or GenericParameter
+                        while (RuntimeTypeHandle.IsGenericVariable(declaringType))
+                            declaringType = declaringType.GetBaseType();
+
+                        int numVirtuals = RuntimeTypeHandle.GetNumVirtuals(declaringType);
+
+                        bool* overrides = stackalloc bool[numVirtuals];
+                        new Span<bool>(overrides, numVirtuals).Clear();
+
+                        bool isValueType = declaringType.IsValueType;
+
+                        do
+                        {
+                            int vtableSlots = RuntimeTypeHandle.GetNumVirtuals(declaringType);
+
+                            foreach (RuntimeMethodHandleInternal methodHandle in RuntimeTypeHandle.GetIntroducedMethods(declaringType))
+                            {
+                                if (filter.RequiresStringComparison())
+                                {
+                                    if (!RuntimeMethodHandle.MatchesNameHash(methodHandle, filter.GetHashToMatch()))
+                                    {
+                                        Debug.Assert(!filter.Match(RuntimeMethodHandle.GetUtf8Name(methodHandle)));
+                                        continue;
+                                    }
+
+                                    if (!filter.Match(RuntimeMethodHandle.GetUtf8Name(methodHandle)))
+                                        continue;
+                                }
+
+                                #region Loop through all methods on the current type
+                                Debug.Assert(!methodHandle.IsNullHandle());
+
+                                MethodAttributes methodAttributes = RuntimeMethodHandle.GetAttributes(methodHandle);
+                                MethodAttributes methodAccess = methodAttributes & MethodAttributes.MemberAccessMask;
+
+                                #region Continue if this is a constructor
+                                Debug.Assert(
+                                    (RuntimeMethodHandle.GetAttributes(methodHandle) & MethodAttributes.RTSpecialName) == 0 ||
+                                    RuntimeMethodHandle.GetName(methodHandle).Equals(".ctor") ||
+                                    RuntimeMethodHandle.GetName(methodHandle).Equals(".cctor"));
+
+                                if ((methodAttributes & MethodAttributes.RTSpecialName) != 0)
+                                    continue;
+                                #endregion
+
+                                #region Continue if this is a private declared on a base type
+                                bool isVirtual = false;
+                                int methodSlot = 0;
+                                if ((methodAttributes & MethodAttributes.Virtual) != 0)
+                                {
+                                    // only virtual if actually in the vtableslot range, but GetSlot will
+                                    // assert if an EnC method, which can't be virtual, so narrow down first
+                                    // before calling GetSlot
+                                    methodSlot = RuntimeMethodHandle.GetSlot(methodHandle);
+                                    isVirtual = (methodSlot < vtableSlots);
+                                }
+
+                                bool isInherited = declaringType != ReflectedType;
+
+                                bool isPrivate = methodAccess == MethodAttributes.Private;
+                                if (isInherited && isPrivate && !isVirtual)
+                                    continue;
+
+                                #endregion
+
+                                #region Continue if this is a virtual and is already overridden
+                                if (isVirtual)
+                                {
+                                    Debug.Assert(
+                                        (methodAttributes & MethodAttributes.Abstract) != 0 ||
+                                        (methodAttributes & MethodAttributes.Virtual) != 0 ||
+                                        RuntimeMethodHandle.GetDeclaringType(methodHandle) != declaringType);
+
+                                    if (overrides[methodSlot] == true)
+                                        continue;
+
+                                    overrides[methodSlot] = true;
+                                }
+                                else if (isValueType)
+                                {
+                                    if ((methodAttributes & (MethodAttributes.Virtual | MethodAttributes.Abstract)) != 0)
+                                        continue;
+                                }
+                                else
+                                {
+                                    Debug.Assert((methodAttributes & (MethodAttributes.Virtual | MethodAttributes.Abstract)) == 0);
+                                }
+                                #endregion
+
+                                #region Calculate Binding Flags
+                                bool isPublic = methodAccess == MethodAttributes.Public;
+                                bool isStatic = (methodAttributes & MethodAttributes.Static) != 0;
+                                BindingFlags bindingFlags = RuntimeType.FilterPreCalculate(isPublic, isInherited, isStatic);
+                                #endregion
+
+                                // get the unboxing stub or instantiating stub if needed
+                                RuntimeMethodHandleInternal instantiatedHandle = RuntimeMethodHandle.GetStubIfNeeded(methodHandle, declaringType, null);
+
+                                RuntimeMethodInfo runtimeMethodInfo = new RuntimeMethodInfo(
+                                instantiatedHandle, declaringType, m_runtimeTypeCache, methodAttributes, bindingFlags, null);
+
+                                list.Add(runtimeMethodInfo);
+                                #endregion
+                            }
+
+                            declaringType = RuntimeTypeHandle.GetBaseType(declaringType);
+                        } while (declaringType != null);
+                        #endregion
+                    }
+
+                    return list.ToArray();
+                }
+
+                private RuntimeConstructorInfo[] PopulateConstructors(Filter filter)
+                {
+                    if (ReflectedType.IsGenericParameter)
+                    {
+                        return Array.Empty<RuntimeConstructorInfo>();
+                    }
+
+                    ListBuilder<RuntimeConstructorInfo> list = new ListBuilder<RuntimeConstructorInfo>();
+
+                    RuntimeType declaringType = ReflectedType;
+
+                    foreach (RuntimeMethodHandleInternal methodHandle in RuntimeTypeHandle.GetIntroducedMethods(declaringType))
+                    {
+                        if (filter.RequiresStringComparison())
+                        {
+                            if (!RuntimeMethodHandle.MatchesNameHash(methodHandle, filter.GetHashToMatch()))
+                            {
+                                Debug.Assert(!filter.Match(RuntimeMethodHandle.GetUtf8Name(methodHandle)));
+                                continue;
+                            }
+
+                            if (!filter.Match(RuntimeMethodHandle.GetUtf8Name(methodHandle)))
+                                continue;
+                        }
+
+                        MethodAttributes methodAttributes = RuntimeMethodHandle.GetAttributes(methodHandle);
+
+                        Debug.Assert(!methodHandle.IsNullHandle());
+
+                        if ((methodAttributes & MethodAttributes.RTSpecialName) == 0)
+                            continue;
+
+                        // Constructors should not be virtual or abstract
+                        Debug.Assert(
+                            (methodAttributes & MethodAttributes.Abstract) == 0 &&
+                            (methodAttributes & MethodAttributes.Virtual) == 0);
+
+                        #region Calculate Binding Flags
+                        bool isPublic = (methodAttributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Public;
+                        bool isStatic = (methodAttributes & MethodAttributes.Static) != 0;
+                        bool isInherited = false;
+                        BindingFlags bindingFlags = RuntimeType.FilterPreCalculate(isPublic, isInherited, isStatic);
+                        #endregion
+
+                        // get the unboxing stub or instantiating stub if needed
+                        RuntimeMethodHandleInternal instantiatedHandle = RuntimeMethodHandle.GetStubIfNeeded(methodHandle, declaringType, null);
+
+                        RuntimeConstructorInfo runtimeConstructorInfo =
+                        new RuntimeConstructorInfo(instantiatedHandle, ReflectedType, m_runtimeTypeCache, methodAttributes, bindingFlags);
+
+                        list.Add(runtimeConstructorInfo);
+                    }
+
+                    return list.ToArray();
+                }
+
+                private unsafe RuntimeFieldInfo[] PopulateFields(Filter filter)
+                {
+                    ListBuilder<RuntimeFieldInfo> list = new ListBuilder<RuntimeFieldInfo>();
+
+                    RuntimeType declaringType = ReflectedType;
+
+                    #region Populate all static, instance and literal fields
+                    while (RuntimeTypeHandle.IsGenericVariable(declaringType))
+                        declaringType = declaringType.GetBaseType();
+
+                    while (declaringType != null)
+                    {
+                        PopulateRtFields(filter, declaringType, ref list);
+
+                        PopulateLiteralFields(filter, declaringType, ref list);
+
+                        declaringType = RuntimeTypeHandle.GetBaseType(declaringType);
+                    }
+                    #endregion
+
+                    #region Populate Literal Fields on Interfaces
+                    if (ReflectedType.IsGenericParameter)
+                    {
+                        Type[] interfaces = ReflectedType.BaseType.GetInterfaces();
+
+                        for (int i = 0; i < interfaces.Length; i++)
+                        {
+                            // Populate literal fields defined on any of the interfaces implemented by the declaring type
+                            PopulateLiteralFields(filter, (RuntimeType)interfaces[i], ref list);
+                            PopulateRtFields(filter, (RuntimeType)interfaces[i], ref list);
+                        }
+                    }
+                    else
+                    {
+                        Type[] interfaces = RuntimeTypeHandle.GetInterfaces(ReflectedType);
+
+                        if (interfaces != null)
+                        {
+                            for (int i = 0; i < interfaces.Length; i++)
+                            {
+                                // Populate literal fields defined on any of the interfaces implemented by the declaring type
+                                PopulateLiteralFields(filter, (RuntimeType)interfaces[i], ref list);
+                                PopulateRtFields(filter, (RuntimeType)interfaces[i], ref list);
+                            }
+                        }
+                    }
+                    #endregion
+
+                    return list.ToArray();
+                }
+
+                private unsafe void PopulateRtFields(Filter filter, RuntimeType declaringType, ref ListBuilder<RuntimeFieldInfo> list)
+                {
+                    IntPtr* pResult = stackalloc IntPtr[64];
+                    int count = 64;
+
+                    if (!RuntimeTypeHandle.GetFields(declaringType, pResult, &count))
+                    {
+                        fixed (IntPtr* pBigResult = new IntPtr[count])
+                        {
+                            RuntimeTypeHandle.GetFields(declaringType, pBigResult, &count);
+                            PopulateRtFields(filter, pBigResult, count, declaringType, ref list);
+                        }
+                    }
+                    else if (count > 0)
+                    {
+                        PopulateRtFields(filter, pResult, count, declaringType, ref list);
+                    }
+                }
+
+                private unsafe void PopulateRtFields(Filter filter,
+                    IntPtr* ppFieldHandles, int count, RuntimeType declaringType, ref ListBuilder<RuntimeFieldInfo> list)
+                {
+                    Debug.Assert(declaringType != null);
+                    Debug.Assert(ReflectedType != null);
+
+                    bool needsStaticFieldForGeneric = RuntimeTypeHandle.HasInstantiation(declaringType) && !RuntimeTypeHandle.ContainsGenericVariables(declaringType);
+                    bool isInherited = declaringType != ReflectedType;
+
+                    for (int i = 0; i < count; i++)
+                    {
+                        RuntimeFieldHandleInternal runtimeFieldHandle = new RuntimeFieldHandleInternal(ppFieldHandles[i]);
+
+                        if (filter.RequiresStringComparison())
+                        {
+                            if (!RuntimeFieldHandle.MatchesNameHash(runtimeFieldHandle, filter.GetHashToMatch()))
+                            {
+                                Debug.Assert(!filter.Match(RuntimeFieldHandle.GetUtf8Name(runtimeFieldHandle)));
+                                continue;
+                            }
+
+                            if (!filter.Match(RuntimeFieldHandle.GetUtf8Name(runtimeFieldHandle)))
+                                continue;
+                        }
+
+                        Debug.Assert(!runtimeFieldHandle.IsNullHandle());
+
+                        FieldAttributes fieldAttributes = RuntimeFieldHandle.GetAttributes(runtimeFieldHandle);
+                        FieldAttributes fieldAccess = fieldAttributes & FieldAttributes.FieldAccessMask;
+
+                        if (isInherited)
+                        {
+                            if (fieldAccess == FieldAttributes.Private)
+                                continue;
+                        }
+
+                        #region Calculate Binding Flags
+                        bool isPublic = fieldAccess == FieldAttributes.Public;
+                        bool isStatic = (fieldAttributes & FieldAttributes.Static) != 0;
+                        BindingFlags bindingFlags = RuntimeType.FilterPreCalculate(isPublic, isInherited, isStatic);
+                        #endregion
+
+                        // correct the FieldDesc if needed
+                        if (needsStaticFieldForGeneric && isStatic)
+                            runtimeFieldHandle = RuntimeFieldHandle.GetStaticFieldForGenericType(runtimeFieldHandle, declaringType);
+
+                        RuntimeFieldInfo runtimeFieldInfo =
+                            new RtFieldInfo(runtimeFieldHandle, declaringType, m_runtimeTypeCache, bindingFlags);
+
+                        list.Add(runtimeFieldInfo);
+                    }
+                }
+
+                private unsafe void PopulateLiteralFields(Filter filter, RuntimeType declaringType, ref ListBuilder<RuntimeFieldInfo> list)
+                {
+                    Debug.Assert(declaringType != null);
+                    Debug.Assert(ReflectedType != null);
+
+                    int tkDeclaringType = RuntimeTypeHandle.GetToken(declaringType);
+
+                    // Our policy is that TypeDescs do not have metadata tokens
+                    if (MdToken.IsNullToken(tkDeclaringType))
+                        return;
+
+                    MetadataImport scope = RuntimeTypeHandle.GetMetadataImport(declaringType);
+
+                    MetadataEnumResult tkFields;
+                    scope.EnumFields(tkDeclaringType, out tkFields);
+
+                    for (int i = 0; i < tkFields.Length; i++)
+                    {
+                        int tkField = tkFields[i];
+                        Debug.Assert(MdToken.IsTokenOfType(tkField, MetadataTokenType.FieldDef));
+                        Debug.Assert(!MdToken.IsNullToken(tkField));
+
+                        FieldAttributes fieldAttributes;
+                        scope.GetFieldDefProps(tkField, out fieldAttributes);
+
+                        FieldAttributes fieldAccess = fieldAttributes & FieldAttributes.FieldAccessMask;
+
+                        if ((fieldAttributes & FieldAttributes.Literal) != 0)
+                        {
+                            bool isInherited = declaringType != ReflectedType;
+                            if (isInherited)
+                            {
+                                bool isPrivate = fieldAccess == FieldAttributes.Private;
+                                if (isPrivate)
+                                    continue;
+                            }
+
+                            if (filter.RequiresStringComparison())
+                            {
+                                MdUtf8String name;
+                                name = scope.GetName(tkField);
+
+                                if (!filter.Match(name))
+                                    continue;
+                            }
+
+                            #region Calculate Binding Flags
+                            bool isPublic = fieldAccess == FieldAttributes.Public;
+                            bool isStatic = (fieldAttributes & FieldAttributes.Static) != 0;
+                            BindingFlags bindingFlags = RuntimeType.FilterPreCalculate(isPublic, isInherited, isStatic);
+                            #endregion
+
+                            RuntimeFieldInfo runtimeFieldInfo =
+                            new MdFieldInfo(tkField, fieldAttributes, declaringType.GetTypeHandleInternal(), m_runtimeTypeCache, bindingFlags);
+
+                            list.Add(runtimeFieldInfo);
+                        }
+                    }
+                }
+
+                private void AddSpecialInterface(ref ListBuilder<RuntimeType> list, Filter filter, RuntimeType iList, bool addSubInterface)
+                {
+                    if (iList.IsAssignableFrom(ReflectedType))
+                    {
+                        if (filter.Match(RuntimeTypeHandle.GetUtf8Name(iList)))
+                            list.Add(iList);
+
+                        if (addSubInterface)
+                        {
+                            Type[] iFaces = iList.GetInterfaces();
+                            for (int j = 0; j < iFaces.Length; j++)
+                            {
+                                RuntimeType iFace = (RuntimeType)iFaces[j];
+                                if (iFace.IsGenericType && filter.Match(RuntimeTypeHandle.GetUtf8Name(iFace)))
+                                    list.Add(iFace);
+                            }
+                        }
+                    }
+                }
+
+                private RuntimeType[] PopulateInterfaces(Filter filter)
+                {
+                    ListBuilder<RuntimeType> list = new ListBuilder<RuntimeType>();
+
+                    RuntimeType declaringType = ReflectedType;
+
+                    if (!RuntimeTypeHandle.IsGenericVariable(declaringType))
+                    {
+                        Type[] ifaces = RuntimeTypeHandle.GetInterfaces(declaringType);
+
+                        if (ifaces != null)
+                        {
+                            for (int i = 0; i < ifaces.Length; i++)
+                            {
+                                RuntimeType interfaceType = (RuntimeType)ifaces[i];
+
+                                if (filter.RequiresStringComparison())
+                                {
+                                    if (!filter.Match(RuntimeTypeHandle.GetUtf8Name(interfaceType)))
+                                        continue;
+                                }
+
+                                Debug.Assert(interfaceType.IsInterface);
+                                list.Add(interfaceType);
+                            }
+                        }
+
+                        if (ReflectedType.IsSZArray)
+                        {
+                            RuntimeType arrayType = (RuntimeType)ReflectedType.GetElementType();
+
+                            if (!arrayType.IsPointer)
+                            {
+                                AddSpecialInterface(ref list, filter, (RuntimeType)typeof(IList<>).MakeGenericType(arrayType), true);
+
+                                // To avoid adding a duplicate IEnumerable<T>, we don't add the sub interfaces of IReadOnlyList.
+                                // Instead, we add IReadOnlyCollection<T> separately.
+                                AddSpecialInterface(ref list, filter, (RuntimeType)typeof(IReadOnlyList<>).MakeGenericType(arrayType), false);
+                                AddSpecialInterface(ref list, filter, (RuntimeType)typeof(IReadOnlyCollection<>).MakeGenericType(arrayType), false);
+                            }
+                        }
+                    }
+                    else
+                    {
+                        List<RuntimeType> al = new List<RuntimeType>();
+
+                        // Get all constraints
+                        Type[] constraints = declaringType.GetGenericParameterConstraints();
+
+                        // Populate transitive closure of all interfaces in constraint set
+                        for (int i = 0; i < constraints.Length; i++)
+                        {
+                            RuntimeType constraint = (RuntimeType)constraints[i];
+                            if (constraint.IsInterface)
+                                al.Add(constraint);
+
+                            Type[] temp = constraint.GetInterfaces();
+                            for (int j = 0; j < temp.Length; j++)
+                                al.Add(temp[j] as RuntimeType);
+                        }
+
+                        // Remove duplicates
+                        Dictionary<RuntimeType, RuntimeType> ht = new Dictionary<RuntimeType, RuntimeType>();
+                        for (int i = 0; i < al.Count; i++)
+                        {
+                            RuntimeType constraint = al[i];
+                            if (!ht.ContainsKey(constraint))
+                                ht[constraint] = constraint;
+                        }
+
+                        RuntimeType[] interfaces = new RuntimeType[ht.Values.Count];
+                        ht.Values.CopyTo(interfaces, 0);
+
+                        // Populate link-list
+                        for (int i = 0; i < interfaces.Length; i++)
+                        {
+                            if (filter.RequiresStringComparison())
+                            {
+                                if (!filter.Match(RuntimeTypeHandle.GetUtf8Name(interfaces[i])))
+                                    continue;
+                            }
+
+                            list.Add(interfaces[i]);
+                        }
+                    }
+
+                    return list.ToArray();
+                }
+
+                private unsafe RuntimeType[] PopulateNestedClasses(Filter filter)
+                {
+                    RuntimeType declaringType = ReflectedType;
+
+                    while (RuntimeTypeHandle.IsGenericVariable(declaringType))
+                    {
+                        declaringType = declaringType.GetBaseType();
+                    }
+
+                    int tkEnclosingType = RuntimeTypeHandle.GetToken(declaringType);
+
+                    // For example, TypeDescs do not have metadata tokens
+                    if (MdToken.IsNullToken(tkEnclosingType))
+                        return Array.Empty<RuntimeType>();
+
+                    ListBuilder<RuntimeType> list = new ListBuilder<RuntimeType>();
+
+                    RuntimeModule moduleHandle = RuntimeTypeHandle.GetModule(declaringType);
+                    MetadataImport scope = ModuleHandle.GetMetadataImport(moduleHandle);
+
+                    MetadataEnumResult tkNestedClasses;
+                    scope.EnumNestedTypes(tkEnclosingType, out tkNestedClasses);
+
+                    for (int i = 0; i < tkNestedClasses.Length; i++)
+                    {
+                        RuntimeType nestedType = null;
+
+                        try
+                        {
+                            nestedType = ModuleHandle.ResolveTypeHandleInternal(moduleHandle, tkNestedClasses[i], null, null);
+                        }
+                        catch (System.TypeLoadException)
+                        {
+                            // In a reflection emit scenario, we may have a token for a class which 
+                            // has not been baked and hence cannot be loaded. 
+                            continue;
+                        }
+
+                        if (filter.RequiresStringComparison())
+                        {
+                            if (!filter.Match(RuntimeTypeHandle.GetUtf8Name(nestedType)))
+                                continue;
+                        }
+
+                        list.Add(nestedType);
+                    }
+
+                    return list.ToArray();
+                }
+
+                private unsafe RuntimeEventInfo[] PopulateEvents(Filter filter)
+                {
+                    Debug.Assert(ReflectedType != null);
+
+                    // Do not create the dictionary if we are filtering the properties by name already
+                    Dictionary<String, RuntimeEventInfo> csEventInfos = filter.CaseSensitive() ? null :
+                        new Dictionary<String, RuntimeEventInfo>();
+
+                    RuntimeType declaringType = ReflectedType;
+                    ListBuilder<RuntimeEventInfo> list = new ListBuilder<RuntimeEventInfo>();
+
+                    if (!RuntimeTypeHandle.IsInterface(declaringType))
+                    {
+                        while (RuntimeTypeHandle.IsGenericVariable(declaringType))
+                            declaringType = declaringType.GetBaseType();
+
+                        // Populate associates off of the class hierarchy
+                        while (declaringType != null)
+                        {
+                            PopulateEvents(filter, declaringType, csEventInfos, ref list);
+                            declaringType = RuntimeTypeHandle.GetBaseType(declaringType);
+                        }
+                    }
+                    else
+                    {
+                        // Populate associates for this interface 
+                        PopulateEvents(filter, declaringType, csEventInfos, ref list);
+                    }
+
+                    return list.ToArray();
+                }
+
+                private unsafe void PopulateEvents(
+                    Filter filter, RuntimeType declaringType, Dictionary<String, RuntimeEventInfo> csEventInfos, ref ListBuilder<RuntimeEventInfo> list)
+                {
+                    int tkDeclaringType = RuntimeTypeHandle.GetToken(declaringType);
+
+                    // Arrays, Pointers, ByRef types and others generated only the fly by the RT do not have tokens.
+                    if (MdToken.IsNullToken(tkDeclaringType))
+                        return;
+
+                    MetadataImport scope = RuntimeTypeHandle.GetMetadataImport(declaringType);
+
+                    MetadataEnumResult tkEvents;
+                    scope.EnumEvents(tkDeclaringType, out tkEvents);
+
+                    for (int i = 0; i < tkEvents.Length; i++)
+                    {
+                        int tkEvent = tkEvents[i];
+                        bool isPrivate;
+
+                        Debug.Assert(!MdToken.IsNullToken(tkEvent));
+                        Debug.Assert(MdToken.IsTokenOfType(tkEvent, MetadataTokenType.Event));
+
+                        if (filter.RequiresStringComparison())
+                        {
+                            MdUtf8String name;
+                            name = scope.GetName(tkEvent);
+
+                            if (!filter.Match(name))
+                                continue;
+                        }
+
+                        RuntimeEventInfo eventInfo = new RuntimeEventInfo(
+                            tkEvent, declaringType, m_runtimeTypeCache, out isPrivate);
+
+                        #region Remove Inherited Privates
+                        if (declaringType != m_runtimeTypeCache.GetRuntimeType() && isPrivate)
+                            continue;
+                        #endregion
+
+                        #region Remove Duplicates
+                        if (csEventInfos != null)
+                        {
+                            string name = eventInfo.Name;
+
+                            if (csEventInfos.ContainsKey(name))
+                                continue;
+
+                            csEventInfos[name] = eventInfo;
+                        }
+                        else
+                        {
+                            if (list.Count > 0)
+                                break;
+                        }
+                        #endregion
+
+                        list.Add(eventInfo);
+                    }
+                }
+
+                private unsafe RuntimePropertyInfo[] PopulateProperties(Filter filter)
+                {
+                    Debug.Assert(ReflectedType != null);
+
+                    // m_csMemberInfos can be null at this point. It will be initialized when Insert
+                    // is called in Populate after this returns.
+
+                    RuntimeType declaringType = ReflectedType;
+                    Debug.Assert(declaringType != null);
+
+                    ListBuilder<RuntimePropertyInfo> list = new ListBuilder<RuntimePropertyInfo>();
+
+                    if (!RuntimeTypeHandle.IsInterface(declaringType))
+                    {
+                        while (RuntimeTypeHandle.IsGenericVariable(declaringType))
+                            declaringType = declaringType.GetBaseType();
+
+                        // Do not create the dictionary if we are filtering the properties by name already
+                        Dictionary<String, List<RuntimePropertyInfo>> csPropertyInfos = filter.CaseSensitive() ? null :
+                            new Dictionary<String, List<RuntimePropertyInfo>>();
+
+                        // All elements automatically initialized to false.
+                        bool[] usedSlots = new bool[RuntimeTypeHandle.GetNumVirtuals(declaringType)];
+
+                        // Populate associates off of the class hierarchy
+                        do
+                        {
+                            PopulateProperties(filter, declaringType, csPropertyInfos, usedSlots, ref list);
+                            declaringType = RuntimeTypeHandle.GetBaseType(declaringType);
+                        } while (declaringType != null);
+                    }
+                    else
+                    {
+                        // Populate associates for this interface 
+                        PopulateProperties(filter, declaringType, null, null, ref list);
+                    }
+
+                    return list.ToArray();
+                }
+
+                private unsafe void PopulateProperties(
+                    Filter filter,
+                    RuntimeType declaringType,
+                    Dictionary<String, List<RuntimePropertyInfo>> csPropertyInfos,
+                    bool[] usedSlots,
+                    ref ListBuilder<RuntimePropertyInfo> list)
+                {
+                    int tkDeclaringType = RuntimeTypeHandle.GetToken(declaringType);
+
+                    // Arrays, Pointers, ByRef types and others generated only the fly by the RT do not have tokens.
+                    if (MdToken.IsNullToken(tkDeclaringType))
+                        return;
+
+                    MetadataImport scope = RuntimeTypeHandle.GetMetadataImport(declaringType);
+
+                    MetadataEnumResult tkProperties;
+                    scope.EnumProperties(tkDeclaringType, out tkProperties);
+
+                    RuntimeModule declaringModuleHandle = RuntimeTypeHandle.GetModule(declaringType);
+
+                    int numVirtuals = RuntimeTypeHandle.GetNumVirtuals(declaringType);
+
+                    Debug.Assert((declaringType.IsInterface && usedSlots == null && csPropertyInfos == null) ||
+                                    (!declaringType.IsInterface && usedSlots != null && usedSlots.Length >= numVirtuals));
+
+                    for (int i = 0; i < tkProperties.Length; i++)
+                    {
+                        int tkProperty = tkProperties[i];
+                        bool isPrivate;
+
+                        Debug.Assert(!MdToken.IsNullToken(tkProperty));
+                        Debug.Assert(MdToken.IsTokenOfType(tkProperty, MetadataTokenType.Property));
+
+                        if (filter.RequiresStringComparison())
+                        {
+                            if (!ModuleHandle.ContainsPropertyMatchingHash(declaringModuleHandle, tkProperty, filter.GetHashToMatch()))
+                            {
+                                Debug.Assert(!filter.Match(declaringType.GetRuntimeModule().MetadataImport.GetName(tkProperty)));
+                                continue;
+                            }
+
+                            MdUtf8String name;
+                            name = declaringType.GetRuntimeModule().MetadataImport.GetName(tkProperty);
+
+                            if (!filter.Match(name))
+                                continue;
+                        }
+
+                        RuntimePropertyInfo propertyInfo =
+                            new RuntimePropertyInfo(
+                            tkProperty, declaringType, m_runtimeTypeCache, out isPrivate);
+
+                        // If this is a class, not an interface
+                        if (usedSlots != null)
+                        {
+                            #region Remove Privates
+                            if (declaringType != ReflectedType && isPrivate)
+                                continue;
+                            #endregion
+
+                            #region Duplicate check based on vtable slots
+
+                            // The inheritance of properties are defined by the inheritance of their 
+                            // getters and setters.
+                            // A property on a base type is "overriden" by a property on a sub type
+                            // if the getter/setter of the latter occupies the same vtable slot as 
+                            // the getter/setter of the former.
+
+                            MethodInfo associateMethod = propertyInfo.GetGetMethod();
+                            if (associateMethod == null)
+                            {
+                                // We only need to examine the setter if a getter doesn't exist.
+                                // It is not logical for the getter to be virtual but not the setter.
+                                associateMethod = propertyInfo.GetSetMethod();
+                            }
+
+                            if (associateMethod != null)
+                            {
+                                int slot = RuntimeMethodHandle.GetSlot((RuntimeMethodInfo)associateMethod);
+
+                                if (slot < numVirtuals)
+                                {
+                                    Debug.Assert(associateMethod.IsVirtual);
+                                    if (usedSlots[slot] == true)
+                                        continue;
+                                    else
+                                        usedSlots[slot] = true;
+                                }
+                            }
+                            #endregion
+
+                            #region Duplicate check based on name and signature
+
+                            // For backward compatibility, even if the vtable slots don't match, we will still treat
+                            // a property as duplicate if the names and signatures match.
+
+                            if (csPropertyInfos != null)
+                            {
+                                string name = propertyInfo.Name;
+                                List<RuntimePropertyInfo> cache;
+                                if (!csPropertyInfos.TryGetValue(name, out cache))
+                                {
+                                    cache = new List<RuntimePropertyInfo>(1);
+                                    csPropertyInfos[name] = cache;
+                                }
+
+                                for (int j = 0; j < cache.Count; j++)
+                                {
+                                    if (propertyInfo.EqualsSig(cache[j]))
+                                    {
+                                        cache = null;
+                                        break;
+                                    }
+                                }
+
+                                if (cache == null)
+                                    continue;
+
+                                cache.Add(propertyInfo);
+                            }
+                            else
+                            {
+                                bool duplicate = false;
+
+                                for (int j = 0; j < list.Count; j++)
+                                {
+                                    if (propertyInfo.EqualsSig(list[j]))
+                                    {
+                                        duplicate = true;
+                                        break;
+                                    }
+                                }
+
+                                if (duplicate)
+                                    continue;
+                            }
+                            #endregion
+                        }
+
+                        list.Add(propertyInfo);
+                    }
+                }
+                #endregion
+
+                #region NonPrivate Members
+                internal T[] GetMemberList(MemberListType listType, string name, CacheType cacheType)
+                {
+                    T[] list = null;
+
+                    switch (listType)
+                    {
+                        case MemberListType.CaseSensitive:
+                            list = m_csMemberInfos[name];
+                            if (list != null)
+                                return list;
+
+                            return Populate(name, listType, cacheType);
+
+                        case MemberListType.CaseInsensitive:
+                            list = m_cisMemberInfos[name];
+                            if (list != null)
+                                return list;
+
+                            return Populate(name, listType, cacheType);
+
+                        default:
+                            Debug.Assert(listType == MemberListType.All);
+                            if (Volatile.Read(ref m_cacheComplete))
+                                return m_allMembers;
+
+                            return Populate(null, listType, cacheType);
+                    }
+                }
+
+                internal RuntimeType ReflectedType
+                {
+                    get
+                    {
+                        return m_runtimeTypeCache.GetRuntimeType();
+                    }
+                }
+                #endregion
+            }
+            #endregion
+
+            #region Private Data Members
+            private RuntimeType m_runtimeType;
+            private RuntimeType m_enclosingType;
+            private TypeCode m_typeCode;
+            private string m_name;
+            private string m_fullname;
+            private string m_toString;
+            private string m_namespace;
+            private string m_serializationname;
+            private bool m_isGlobal;
+            private bool m_bIsDomainInitialized;
+            private MemberInfoCache<RuntimeMethodInfo> m_methodInfoCache;
+            private MemberInfoCache<RuntimeConstructorInfo> m_constructorInfoCache;
+            private MemberInfoCache<RuntimeFieldInfo> m_fieldInfoCache;
+            private MemberInfoCache<RuntimeType> m_interfaceCache;
+            private MemberInfoCache<RuntimeType> m_nestedClassesCache;
+            private MemberInfoCache<RuntimePropertyInfo> m_propertyInfoCache;
+            private MemberInfoCache<RuntimeEventInfo> m_eventInfoCache;
+            private static CerHashtable<RuntimeMethodInfo, RuntimeMethodInfo> s_methodInstantiations;
+            private static Object s_methodInstantiationsLock;
+            private string m_defaultMemberName;
+            private Object m_genericCache; // Generic cache for rare scenario specific data. It is used to cache Enum names and values.
+            #endregion
+
+            #region Constructor
+            internal RuntimeTypeCache(RuntimeType runtimeType)
+            {
+                m_typeCode = TypeCode.Empty;
+                m_runtimeType = runtimeType;
+                m_isGlobal = RuntimeTypeHandle.GetModule(runtimeType).RuntimeType == runtimeType;
+            }
+            #endregion
+
+            #region Private Members
+            private string ConstructName(ref string name, TypeNameFormatFlags formatFlags)
+            {
+                if (name == null)
+                {
+                    name = new RuntimeTypeHandle(m_runtimeType).ConstructName(formatFlags);
+                }
+                return name;
+            }
+
+            private T[] GetMemberList<T>(ref MemberInfoCache<T> m_cache, MemberListType listType, string name, CacheType cacheType)
+                where T : MemberInfo
+            {
+                MemberInfoCache<T> existingCache = GetMemberCache<T>(ref m_cache);
+                return existingCache.GetMemberList(listType, name, cacheType);
+            }
+
+            private MemberInfoCache<T> GetMemberCache<T>(ref MemberInfoCache<T> m_cache)
+                where T : MemberInfo
+            {
+                MemberInfoCache<T> existingCache = m_cache;
+
+                if (existingCache == null)
+                {
+                    MemberInfoCache<T> newCache = new MemberInfoCache<T>(this);
+                    existingCache = Interlocked.CompareExchange(ref m_cache, newCache, null);
+                    if (existingCache == null)
+                        existingCache = newCache;
+                }
+
+                return existingCache;
+            }
+            #endregion
+
+            #region Internal Members
+
+            internal Object GenericCache
+            {
+                get { return m_genericCache; }
+                set { m_genericCache = value; }
+            }
+
+            internal bool DomainInitialized
+            {
+                get { return m_bIsDomainInitialized; }
+                set { m_bIsDomainInitialized = value; }
+            }
+
+            internal string GetName(TypeNameKind kind)
+            {
+                switch (kind)
+                {
+                    case TypeNameKind.Name:
+                        // No namespace, full instantiation, and assembly.
+                        return ConstructName(ref m_name, TypeNameFormatFlags.FormatBasic);
+
+                    case TypeNameKind.FullName:
+                        // We exclude the types that contain generic parameters because their names cannot be roundtripped.
+                        // We allow generic type definitions (and their refs, ptrs, and arrays) because their names can be roundtriped.
+                        // Theoretically generic types instantiated with generic type definitions can be roundtripped, e.g. List`1<Dictionary`2>.
+                        // But these kind of types are useless, rare, and hard to identity. We would need to recursively examine all the 
+                        // generic arguments with the same criteria. We will exclude them unless we see a real user scenario.
+                        if (!m_runtimeType.GetRootElementType().IsGenericTypeDefinition && m_runtimeType.ContainsGenericParameters)
+                            return null;
+
+                        // No assembly.
+                        return ConstructName(ref m_fullname, TypeNameFormatFlags.FormatNamespace | TypeNameFormatFlags.FormatFullInst);
+
+                    case TypeNameKind.ToString:
+                        // No full instantiation and assembly.
+                        return ConstructName(ref m_toString, TypeNameFormatFlags.FormatNamespace);
+
+                    case TypeNameKind.SerializationName:
+                        // Use FormatGenericParam in serialization. Otherwise we won't be able 
+                        // to distinguish between a generic parameter and a normal type with the same name.
+                        // e.g. Foo<T>.Bar(T t), the parameter type T could be !1 or a real type named "T".
+                        // Excluding the version number in the assembly name for VTS.
+                        return ConstructName(ref m_serializationname, TypeNameFormatFlags.FormatSerialization);
+
+                    default:
+                        throw new InvalidOperationException();
+                }
+            }
+
+            internal unsafe string GetNameSpace()
+            {
+                // @Optimization - Use ConstructName to populate m_namespace
+                if (m_namespace == null)
+                {
+                    Type type = m_runtimeType;
+                    type = type.GetRootElementType();
+
+                    while (type.IsNested)
+                        type = type.DeclaringType;
+
+                    m_namespace = RuntimeTypeHandle.GetMetadataImport((RuntimeType)type).GetNamespace(type.MetadataToken).ToString();
+                }
+
+                return m_namespace;
+            }
+
+            internal TypeCode TypeCode
+            {
+                get { return m_typeCode; }
+                set { m_typeCode = value; }
+            }
+
+            internal unsafe RuntimeType GetEnclosingType()
+            {
+                if (m_enclosingType == null)
+                {
+                    // Use void as a marker of null enclosing type
+                    RuntimeType enclosingType = RuntimeTypeHandle.GetDeclaringType(GetRuntimeType());
+                    Debug.Assert(enclosingType != typeof(void));
+                    m_enclosingType = enclosingType ?? (RuntimeType)typeof(void);
+                }
+
+                return (m_enclosingType == typeof(void)) ? null : m_enclosingType;
+            }
+
+            internal RuntimeType GetRuntimeType()
+            {
+                return m_runtimeType;
+            }
+
+            internal bool IsGlobal
+            {
+                get { return m_isGlobal; }
+            }
+
+            internal void InvalidateCachedNestedType()
+            {
+                m_nestedClassesCache = null;
+            }
+
+            internal string GetDefaultMemberName()
+            {
+                if (m_defaultMemberName == null)
+                {
+                    CustomAttributeData attr = null;
+                    Type DefaultMemberAttrType = typeof(DefaultMemberAttribute);
+                    for (RuntimeType t = m_runtimeType; t != null; t = t.GetBaseType())
+                    {
+                        IList<CustomAttributeData> attrs = CustomAttributeData.GetCustomAttributes(t);
+                        for (int i = 0; i < attrs.Count; i++)
+                        {
+                            if (Object.ReferenceEquals(attrs[i].Constructor.DeclaringType, DefaultMemberAttrType))
+                            {
+                                attr = attrs[i];
+                                break;
+                            }
+                        }
+
+                        if (attr != null)
+                        {
+                            m_defaultMemberName = attr.ConstructorArguments[0].Value as string;
+                            break;
+                        }
+                    }
+                }
+
+                return m_defaultMemberName;
+            }
+            #endregion
+
+            #region Caches Accessors
+            internal MethodInfo GetGenericMethodInfo(RuntimeMethodHandleInternal genericMethod)
+            {
+                LoaderAllocator la = RuntimeMethodHandle.GetLoaderAllocator(genericMethod);
+
+                RuntimeMethodInfo rmi = new RuntimeMethodInfo(
+                    genericMethod, RuntimeMethodHandle.GetDeclaringType(genericMethod), this,
+                    RuntimeMethodHandle.GetAttributes(genericMethod), (BindingFlags)(-1), la);
+
+                RuntimeMethodInfo crmi;
+                if (la != null)
+                {
+                    crmi = la.m_methodInstantiations[rmi];
+                }
+                else
+                {
+                    crmi = s_methodInstantiations[rmi];
+                }
+                if (crmi != null)
+                    return crmi;
+
+                if (s_methodInstantiationsLock == null)
+                    Interlocked.CompareExchange(ref s_methodInstantiationsLock, new Object(), null);
+
+                bool lockTaken = false;
+                RuntimeHelpers.PrepareConstrainedRegions();
+                try
+                {
+                    Monitor.Enter(s_methodInstantiationsLock, ref lockTaken);
+
+                    if (la != null)
+                    {
+                        crmi = la.m_methodInstantiations[rmi];
+                        if (crmi != null)
+                            return crmi;
+                        la.m_methodInstantiations[rmi] = rmi;
+                    }
+                    else
+                    {
+                        crmi = s_methodInstantiations[rmi];
+                        if (crmi != null)
+                            return crmi;
+                        s_methodInstantiations[rmi] = rmi;
+                    }
+                }
+                finally
+                {
+                    if (lockTaken)
+                    {
+                        Monitor.Exit(s_methodInstantiationsLock);
+                    }
+                }
+
+                return rmi;
+            }
+
+            internal RuntimeMethodInfo[] GetMethodList(MemberListType listType, string name)
+            {
+                return GetMemberList<RuntimeMethodInfo>(ref m_methodInfoCache, listType, name, CacheType.Method);
+            }
+
+            internal RuntimeConstructorInfo[] GetConstructorList(MemberListType listType, string name)
+            {
+                return GetMemberList<RuntimeConstructorInfo>(ref m_constructorInfoCache, listType, name, CacheType.Constructor);
+            }
+
+            internal RuntimePropertyInfo[] GetPropertyList(MemberListType listType, string name)
+            {
+                return GetMemberList<RuntimePropertyInfo>(ref m_propertyInfoCache, listType, name, CacheType.Property);
+            }
+
+            internal RuntimeEventInfo[] GetEventList(MemberListType listType, string name)
+            {
+                return GetMemberList<RuntimeEventInfo>(ref m_eventInfoCache, listType, name, CacheType.Event);
+            }
+
+            internal RuntimeFieldInfo[] GetFieldList(MemberListType listType, string name)
+            {
+                return GetMemberList<RuntimeFieldInfo>(ref m_fieldInfoCache, listType, name, CacheType.Field);
+            }
+
+            internal RuntimeType[] GetInterfaceList(MemberListType listType, string name)
+            {
+                return GetMemberList<RuntimeType>(ref m_interfaceCache, listType, name, CacheType.Interface);
+            }
+
+            internal RuntimeType[] GetNestedTypeList(MemberListType listType, string name)
+            {
+                return GetMemberList<RuntimeType>(ref m_nestedClassesCache, listType, name, CacheType.NestedType);
+            }
+
+            internal MethodBase GetMethod(RuntimeType declaringType, RuntimeMethodHandleInternal method)
+            {
+                GetMemberCache<RuntimeMethodInfo>(ref m_methodInfoCache);
+                return m_methodInfoCache.AddMethod(declaringType, method, CacheType.Method);
+            }
+
+            internal MethodBase GetConstructor(RuntimeType declaringType, RuntimeMethodHandleInternal constructor)
+            {
+                GetMemberCache<RuntimeConstructorInfo>(ref m_constructorInfoCache);
+                return m_constructorInfoCache.AddMethod(declaringType, constructor, CacheType.Constructor);
+            }
+
+            internal FieldInfo GetField(RuntimeFieldHandleInternal field)
+            {
+                GetMemberCache<RuntimeFieldInfo>(ref m_fieldInfoCache);
+                return m_fieldInfoCache.AddField(field);
+            }
+
+            #endregion
+        }
+        #endregion
+
+        #region Static Members
+
+        #region Internal
+        internal static RuntimeType GetType(String typeName, bool throwOnError, bool ignoreCase, bool reflectionOnly,
+            ref StackCrawlMark stackMark)
+        {
+            if (typeName == null)
+                throw new ArgumentNullException(nameof(typeName));
+
+            return RuntimeTypeHandle.GetTypeByName(
+                typeName, throwOnError, ignoreCase, reflectionOnly, ref stackMark, false);
+        }
+
+        internal static MethodBase GetMethodBase(RuntimeModule scope, int typeMetadataToken)
+        {
+            return GetMethodBase(ModuleHandle.ResolveMethodHandleInternal(scope, typeMetadataToken));
+        }
+
+        internal static MethodBase GetMethodBase(IRuntimeMethodInfo methodHandle)
+        {
+            return GetMethodBase(null, methodHandle);
+        }
+
+        internal static MethodBase GetMethodBase(RuntimeType reflectedType, IRuntimeMethodInfo methodHandle)
+        {
+            MethodBase retval = RuntimeType.GetMethodBase(reflectedType, methodHandle.Value);
+            GC.KeepAlive(methodHandle);
+            return retval;
+        }
+
+        internal static unsafe MethodBase GetMethodBase(RuntimeType reflectedType, RuntimeMethodHandleInternal methodHandle)
+        {
+            Debug.Assert(!methodHandle.IsNullHandle());
+
+            if (RuntimeMethodHandle.IsDynamicMethod(methodHandle))
+            {
+                Resolver resolver = RuntimeMethodHandle.GetResolver(methodHandle);
+
+                if (resolver != null)
+                    return resolver.GetDynamicMethod();
+
+                return null;
+            }
+
+            // verify the type/method relationship
+            RuntimeType declaredType = RuntimeMethodHandle.GetDeclaringType(methodHandle);
+
+            RuntimeType[] methodInstantiation = null;
+
+            if (reflectedType == null)
+                reflectedType = declaredType as RuntimeType;
+
+            if (reflectedType != declaredType && !reflectedType.IsSubclassOf(declaredType))
+            {
+                // object[] is assignable from string[].
+                if (reflectedType.IsArray)
+                {
+                    // The whole purpose of this chunk of code is not only for error checking.
+                    // GetMember has a side effect of populating the member cache of reflectedType,
+                    // doing so will ensure we construct the correct MethodInfo/ConstructorInfo objects.
+                    // Without this the reflectedType.Cache.GetMethod call below may return a MethodInfo
+                    // object whose ReflectedType is string[] and DeclaringType is object[]. That would
+                    // be (arguabally) incorrect because string[] is not a subclass of object[].
+                    MethodBase[] methodBases = reflectedType.GetMember(
+                        RuntimeMethodHandle.GetName(methodHandle), MemberTypes.Constructor | MemberTypes.Method,
+                        BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance) as MethodBase[];
+
+                    bool loaderAssuredCompatible = false;
+                    for (int i = 0; i < methodBases.Length; i++)
+                    {
+                        IRuntimeMethodInfo rmi = (IRuntimeMethodInfo)methodBases[i];
+                        if (rmi.Value.Value == methodHandle.Value)
+                            loaderAssuredCompatible = true;
+                    }
+
+                    if (!loaderAssuredCompatible)
+                        throw new ArgumentException(String.Format(
+                            CultureInfo.CurrentCulture, SR.Argument_ResolveMethodHandle,
+                            reflectedType.ToString(), declaredType.ToString()));
+                }
+                // Action<in string> is assignable from, but not a subclass of Action<in object>.
+                else if (declaredType.IsGenericType)
+                {
+                    // ignoring instantiation is the ReflectedType a subtype of the DeclaringType
+                    RuntimeType declaringDefinition = (RuntimeType)declaredType.GetGenericTypeDefinition();
+
+                    RuntimeType baseType = reflectedType;
+
+                    while (baseType != null)
+                    {
+                        RuntimeType baseDefinition = baseType;
+
+                        if (baseDefinition.IsGenericType && !baseType.IsGenericTypeDefinition)
+                            baseDefinition = (RuntimeType)baseDefinition.GetGenericTypeDefinition();
+
+                        if (baseDefinition == declaringDefinition)
+                            break;
+
+                        baseType = baseType.GetBaseType();
+                    }
+
+                    if (baseType == null)
+                    {
+                        // ignoring instantiation is the ReflectedType is not a subtype of the DeclaringType
+                        throw new ArgumentException(String.Format(
+                            CultureInfo.CurrentCulture, SR.Argument_ResolveMethodHandle,
+                            reflectedType.ToString(), declaredType.ToString()));
+                    }
+
+                    // remap the method to same method on the subclass ReflectedType
+                    declaredType = baseType;
+
+                    // if the original methodHandle was the definition then we don't need to rebind generic method arguments
+                    // because all RuntimeMethodHandles retrieved off of the canonical method table are definitions. That's 
+                    // why for everything else we need to rebind the generic method arguments. 
+                    if (!RuntimeMethodHandle.IsGenericMethodDefinition(methodHandle))
+                    {
+                        methodInstantiation = RuntimeMethodHandle.GetMethodInstantiationInternal(methodHandle);
+                    }
+
+                    // lookup via v-table slot the RuntimeMethodHandle on the new declaring type
+                    methodHandle = RuntimeMethodHandle.GetMethodFromCanonical(methodHandle, declaredType);
+                }
+                else if (!declaredType.IsAssignableFrom(reflectedType))
+                {
+                    // declaredType is not Array, not generic, and not assignable from reflectedType
+                    throw new ArgumentException(String.Format(
+                        CultureInfo.CurrentCulture, SR.Argument_ResolveMethodHandle,
+                        reflectedType.ToString(), declaredType.ToString()));
+                }
+            }
+
+            // If methodInstantiation is not null, GetStubIfNeeded will rebind the generic method arguments
+            // if declaredType is an instantiated generic type and methodHandle is not generic, get the instantiated MethodDesc (if needed)
+            // if declaredType is a value type, get the unboxing stub (if needed)
+
+            // this is so that our behavior here is consistent with that of Type.GetMethod
+            // See MemberInfoCache<RuntimeConstructorInfo>.PopulateMethods and MemberInfoCache<RuntimeMethodInfoInfo>.PopulateConstructors
+
+            methodHandle = RuntimeMethodHandle.GetStubIfNeeded(methodHandle, declaredType, methodInstantiation);
+            MethodBase retval;
+
+            if (RuntimeMethodHandle.IsConstructor(methodHandle))
+            {
+                // Constructor case: constructors cannot be generic
+                retval = reflectedType.Cache.GetConstructor(declaredType, methodHandle);
+            }
+            else
+            {
+                // Method case
+                if (RuntimeMethodHandle.HasMethodInstantiation(methodHandle) && !RuntimeMethodHandle.IsGenericMethodDefinition(methodHandle))
+                    retval = reflectedType.Cache.GetGenericMethodInfo(methodHandle);
+                else
+                    retval = reflectedType.Cache.GetMethod(declaredType, methodHandle);
+            }
+
+            GC.KeepAlive(methodInstantiation);
+            return retval;
+        }
+
+        internal Object GenericCache
+        {
+            get { return Cache.GenericCache; }
+            set { Cache.GenericCache = value; }
+        }
+
+        internal bool DomainInitialized
+        {
+            get { return Cache.DomainInitialized; }
+            set { Cache.DomainInitialized = value; }
+        }
+
+        internal static unsafe FieldInfo GetFieldInfo(IRuntimeFieldInfo fieldHandle)
+        {
+            return GetFieldInfo(RuntimeFieldHandle.GetApproxDeclaringType(fieldHandle), fieldHandle);
+        }
+
+        internal static unsafe FieldInfo GetFieldInfo(RuntimeType reflectedType, IRuntimeFieldInfo field)
+        {
+            RuntimeFieldHandleInternal fieldHandle = field.Value;
+
+            // verify the type/method relationship
+            if (reflectedType == null)
+            {
+                reflectedType = RuntimeFieldHandle.GetApproxDeclaringType(fieldHandle);
+            }
+            else
+            {
+                RuntimeType declaredType = RuntimeFieldHandle.GetApproxDeclaringType(fieldHandle);
+                if (reflectedType != declaredType)
+                {
+                    if (!RuntimeFieldHandle.AcquiresContextFromThis(fieldHandle) ||
+                        !RuntimeTypeHandle.CompareCanonicalHandles(declaredType, reflectedType))
+                    {
+                        throw new ArgumentException(String.Format(
+                            CultureInfo.CurrentCulture, SR.Argument_ResolveFieldHandle,
+                            reflectedType.ToString(),
+                            declaredType.ToString()));
+                    }
+                }
+            }
+
+            FieldInfo retVal = reflectedType.Cache.GetField(fieldHandle);
+            GC.KeepAlive(field);
+            return retVal;
+        }
+
+        // Called internally
+        private static unsafe PropertyInfo GetPropertyInfo(RuntimeType reflectedType, int tkProperty)
+        {
+            RuntimePropertyInfo property = null;
+            RuntimePropertyInfo[] candidates =
+                reflectedType.Cache.GetPropertyList(MemberListType.All, null);
+
+            for (int i = 0; i < candidates.Length; i++)
+            {
+                property = candidates[i];
+                if (property.MetadataToken == tkProperty)
+                    return property;
+            }
+
+            Debug.Fail("Unreachable code");
+            throw new SystemException();
+        }
+
+        private static void ThrowIfTypeNeverValidGenericArgument(RuntimeType type)
+        {
+            if (type.IsPointer || type.IsByRef || type == typeof(void))
+                throw new ArgumentException(
+                    SR.Format(SR.Argument_NeverValidGenericArgument, type.ToString()));
+        }
+
+
+        internal static void SanityCheckGenericArguments(RuntimeType[] genericArguments, RuntimeType[] genericParamters)
+        {
+            if (genericArguments == null)
+                throw new ArgumentNullException();
+
+            for (int i = 0; i < genericArguments.Length; i++)
+            {
+                if (genericArguments[i] == null)
+                    throw new ArgumentNullException();
+
+                ThrowIfTypeNeverValidGenericArgument(genericArguments[i]);
+            }
+
+            if (genericArguments.Length != genericParamters.Length)
+                throw new ArgumentException(
+                    SR.Format(SR.Argument_NotEnoughGenArguments, genericArguments.Length, genericParamters.Length));
+        }
+
+        internal static void ValidateGenericArguments(MemberInfo definition, RuntimeType[] genericArguments, Exception e)
+        {
+            RuntimeType[] typeContext = null;
+            RuntimeType[] methodContext = null;
+            RuntimeType[] genericParamters = null;
+
+            if (definition is Type)
+            {
+                RuntimeType genericTypeDefinition = (RuntimeType)definition;
+                genericParamters = genericTypeDefinition.GetGenericArgumentsInternal();
+                typeContext = genericArguments;
+            }
+            else
+            {
+                RuntimeMethodInfo genericMethodDefinition = (RuntimeMethodInfo)definition;
+                genericParamters = genericMethodDefinition.GetGenericArgumentsInternal();
+                methodContext = genericArguments;
+
+                RuntimeType declaringType = (RuntimeType)genericMethodDefinition.DeclaringType;
+                if (declaringType != null)
+                {
+                    typeContext = declaringType.GetTypeHandleInternal().GetInstantiationInternal();
+                }
+            }
+
+            for (int i = 0; i < genericArguments.Length; i++)
+            {
+                Type genericArgument = genericArguments[i];
+                Type genericParameter = genericParamters[i];
+
+                if (!RuntimeTypeHandle.SatisfiesConstraints(genericParameter.GetTypeHandleInternal().GetTypeChecked(),
+                    typeContext, methodContext, genericArgument.GetTypeHandleInternal().GetTypeChecked()))
+                {
+                    throw new ArgumentException(
+                        SR.Format(SR.Argument_GenConstraintViolation, i.ToString(CultureInfo.CurrentCulture), genericArgument.ToString(), definition.ToString(), genericParameter.ToString()), e);
+                }
+            }
+        }
+
+        private static void SplitName(string fullname, out string name, out string ns)
+        {
+            name = null;
+            ns = null;
+
+            if (fullname == null)
+                return;
+
+            // Get namespace
+            int nsDelimiter = fullname.LastIndexOf(".", StringComparison.Ordinal);
+            if (nsDelimiter != -1)
+            {
+                ns = fullname.Substring(0, nsDelimiter);
+                int nameLength = fullname.Length - ns.Length - 1;
+                if (nameLength != 0)
+                    name = fullname.Substring(nsDelimiter + 1, nameLength);
+                else
+                    name = "";
+                Debug.Assert(fullname.Equals(ns + "." + name));
+            }
+            else
+            {
+                name = fullname;
+            }
+        }
+        #endregion
+
+        #region Filters
+        internal static BindingFlags FilterPreCalculate(bool isPublic, bool isInherited, bool isStatic)
+        {
+            BindingFlags bindingFlags = isPublic ? BindingFlags.Public : BindingFlags.NonPublic;
+
+            if (isInherited)
+            {
+                // We arrange things so the DeclaredOnly flag means "include inherited members"
+                bindingFlags |= BindingFlags.DeclaredOnly;
+
+                if (isStatic)
+                {
+                    bindingFlags |= BindingFlags.Static | BindingFlags.FlattenHierarchy;
+                }
+                else
+                {
+                    bindingFlags |= BindingFlags.Instance;
+                }
+            }
+            else
+            {
+                if (isStatic)
+                {
+                    bindingFlags |= BindingFlags.Static;
+                }
+                else
+                {
+                    bindingFlags |= BindingFlags.Instance;
+                }
+            }
+
+            return bindingFlags;
+        }
+
+        // Calculate prefixLookup, ignoreCase, and listType for use by GetXXXCandidates
+        private static void FilterHelper(
+            BindingFlags bindingFlags, ref string name, bool allowPrefixLookup, out bool prefixLookup,
+            out bool ignoreCase, out MemberListType listType)
+        {
+            prefixLookup = false;
+            ignoreCase = false;
+
+            if (name != null)
+            {
+                if ((bindingFlags & BindingFlags.IgnoreCase) != 0)
+                {
+                    name = name.ToLower(CultureInfo.InvariantCulture);
+                    ignoreCase = true;
+                    listType = MemberListType.CaseInsensitive;
+                }
+                else
+                {
+                    listType = MemberListType.CaseSensitive;
+                }
+
+                if (allowPrefixLookup && name.EndsWith("*", StringComparison.Ordinal))
+                {
+                    // We set prefixLookup to true if name ends with a "*".
+                    // We will also set listType to All so that all members are included in 
+                    // the candidates which are later filtered by FilterApplyPrefixLookup.
+                    name = name.Substring(0, name.Length - 1);
+                    prefixLookup = true;
+                    listType = MemberListType.All;
+                }
+            }
+            else
+            {
+                listType = MemberListType.All;
+            }
+        }
+
+        // Used by the singular GetXXX APIs (Event, Field, Interface, NestedType) where prefixLookup is not supported.
+        private static void FilterHelper(BindingFlags bindingFlags, ref string name, out bool ignoreCase, out MemberListType listType)
+        {
+            bool prefixLookup;
+            FilterHelper(bindingFlags, ref name, false, out prefixLookup, out ignoreCase, out listType);
+        }
+
+        // Only called by GetXXXCandidates, GetInterfaces, and GetNestedTypes when FilterHelper has set "prefixLookup" to true.
+        // Most of the plural GetXXX methods allow prefix lookups while the singular GetXXX methods mostly do not.
+        private static bool FilterApplyPrefixLookup(MemberInfo memberInfo, string name, bool ignoreCase)
+        {
+            Debug.Assert(name != null);
+
+            if (ignoreCase)
+            {
+                if (!memberInfo.Name.StartsWith(name, StringComparison.OrdinalIgnoreCase))
+                    return false;
+            }
+            else
+            {
+                if (!memberInfo.Name.StartsWith(name, StringComparison.Ordinal))
+                    return false;
+            }
+
+            return true;
+        }
+
+
+        // Used by FilterApplyType to perform all the filtering based on name and BindingFlags
+        private static bool FilterApplyBase(
+            MemberInfo memberInfo, BindingFlags bindingFlags, bool isPublic, bool isNonProtectedInternal, bool isStatic,
+            string name, bool prefixLookup)
+        {
+            #region Preconditions
+            Debug.Assert(memberInfo != null);
+            Debug.Assert(name == null || (bindingFlags & BindingFlags.IgnoreCase) == 0 || (name.ToLower(CultureInfo.InvariantCulture).Equals(name)));
+            #endregion
+
+            #region Filter by Public & Private
+            if (isPublic)
+            {
+                if ((bindingFlags & BindingFlags.Public) == 0)
+                    return false;
+            }
+            else
+            {
+                if ((bindingFlags & BindingFlags.NonPublic) == 0)
+                    return false;
+            }
+            #endregion
+
+            bool isInherited = !Object.ReferenceEquals(memberInfo.DeclaringType, memberInfo.ReflectedType);
+
+            #region Filter by DeclaredOnly
+            if ((bindingFlags & BindingFlags.DeclaredOnly) != 0 && isInherited)
+                return false;
+            #endregion
+
+            #region Filter by Static & Instance
+            if (memberInfo.MemberType != MemberTypes.TypeInfo &&
+                memberInfo.MemberType != MemberTypes.NestedType)
+            {
+                if (isStatic)
+                {
+                    if ((bindingFlags & BindingFlags.FlattenHierarchy) == 0 && isInherited)
+                        return false;
+
+                    if ((bindingFlags & BindingFlags.Static) == 0)
+                        return false;
+                }
+                else
+                {
+                    if ((bindingFlags & BindingFlags.Instance) == 0)
+                        return false;
+                }
+            }
+            #endregion
+
+            #region Filter by name wrt prefixLookup and implicitly by case sensitivity
+            if (prefixLookup == true)
+            {
+                if (!FilterApplyPrefixLookup(memberInfo, name, (bindingFlags & BindingFlags.IgnoreCase) != 0))
+                    return false;
+            }
+            #endregion
+
+            #region Asymmetries
+            // @Asymmetry - Internal, inherited, instance, non-protected, non-virtual, non-abstract members returned 
+            //              iff BindingFlags !DeclaredOnly, Instance and Public are present except for fields
+            if (((bindingFlags & BindingFlags.DeclaredOnly) == 0) &&        // DeclaredOnly not present
+                 isInherited &&                                            // Is inherited Member
+
+                (isNonProtectedInternal) &&                                 // Is non-protected internal member
+                ((bindingFlags & BindingFlags.NonPublic) != 0) &&           // BindingFlag.NonPublic present 
+
+                (!isStatic) &&                                              // Is instance member
+                ((bindingFlags & BindingFlags.Instance) != 0))              // BindingFlag.Instance present 
+            {
+                MethodInfo methodInfo = memberInfo as MethodInfo;
+
+                if (methodInfo == null)
+                    return false;
+
+                if (!methodInfo.IsVirtual && !methodInfo.IsAbstract)
+                    return false;
+            }
+            #endregion
+
+            return true;
+        }
+
+
+        // Used by GetInterface and GetNestedType(s) which don't need parameter type filtering.
+        private static bool FilterApplyType(
+            Type type, BindingFlags bindingFlags, string name, bool prefixLookup, string ns)
+        {
+            Debug.Assert((object)type != null);
+            Debug.Assert(type is RuntimeType);
+
+            bool isPublic = type.IsNestedPublic || type.IsPublic;
+            bool isStatic = false;
+
+            if (!RuntimeType.FilterApplyBase(type, bindingFlags, isPublic, type.IsNestedAssembly, isStatic, name, prefixLookup))
+                return false;
+
+            if (ns != null && !type.Namespace.Equals(ns))
+                return false;
+
+            return true;
+        }
+
+
+        private static bool FilterApplyMethodInfo(
+            RuntimeMethodInfo method, BindingFlags bindingFlags, CallingConventions callConv, Type[] argumentTypes)
+        {
+            // Optimization: Pre-Calculate the method binding flags to avoid casting.
+            return FilterApplyMethodBase(method, method.BindingFlags, bindingFlags, callConv, argumentTypes);
+        }
+
+        private static bool FilterApplyConstructorInfo(
+            RuntimeConstructorInfo constructor, BindingFlags bindingFlags, CallingConventions callConv, Type[] argumentTypes)
+        {
+            // Optimization: Pre-Calculate the method binding flags to avoid casting.
+            return FilterApplyMethodBase(constructor, constructor.BindingFlags, bindingFlags, callConv, argumentTypes);
+        }
+
+        // Used by GetMethodCandidates/GetConstructorCandidates, InvokeMember, and CreateInstanceImpl to perform the necessary filtering.
+        // Should only be called by FilterApplyMethodInfo and FilterApplyConstructorInfo.
+        private static bool FilterApplyMethodBase(
+            MethodBase methodBase, BindingFlags methodFlags, BindingFlags bindingFlags, CallingConventions callConv, Type[] argumentTypes)
+        {
+            Debug.Assert(methodBase != null);
+
+            bindingFlags ^= BindingFlags.DeclaredOnly;
+
+            #region Apply Base Filter
+            if ((bindingFlags & methodFlags) != methodFlags)
+                return false;
+            #endregion
+
+            #region Check CallingConvention
+            if ((callConv & CallingConventions.Any) == 0)
+            {
+                if ((callConv & CallingConventions.VarArgs) != 0 &&
+                    (methodBase.CallingConvention & CallingConventions.VarArgs) == 0)
+                    return false;
+
+                if ((callConv & CallingConventions.Standard) != 0 &&
+                    (methodBase.CallingConvention & CallingConventions.Standard) == 0)
+                    return false;
+            }
+            #endregion
+
+            #region If argumentTypes supplied
+            if (argumentTypes != null)
+            {
+                ParameterInfo[] parameterInfos = methodBase.GetParametersNoCopy();
+
+                if (argumentTypes.Length != parameterInfos.Length)
+                {
+                    #region Invoke Member, Get\Set & Create Instance specific case
+                    // If the number of supplied arguments differs than the number in the signature AND
+                    // we are not filtering for a dynamic call -- InvokeMethod or CreateInstance -- filter out the method.
+                    if ((bindingFlags &
+                        (BindingFlags.InvokeMethod | BindingFlags.CreateInstance | BindingFlags.GetProperty | BindingFlags.SetProperty)) == 0)
+                        return false;
+
+                    bool testForParamArray = false;
+                    bool excessSuppliedArguments = argumentTypes.Length > parameterInfos.Length;
+
+                    if (excessSuppliedArguments)
+                    { // more supplied arguments than parameters, additional arguments could be vararg
+                        #region Varargs
+                        // If method is not vararg, additional arguments can not be passed as vararg
+                        if ((methodBase.CallingConvention & CallingConventions.VarArgs) == 0)
+                        {
+                            testForParamArray = true;
+                        }
+                        else
+                        {
+                            // If Binding flags did not include varargs we would have filtered this vararg method.
+                            // This Invariant established during callConv check.
+                            Debug.Assert((callConv & CallingConventions.VarArgs) != 0);
+                        }
+                        #endregion
+                    }
+                    else
+                    {// fewer supplied arguments than parameters, missing arguments could be optional
+                        #region OptionalParamBinding
+                        if ((bindingFlags & BindingFlags.OptionalParamBinding) == 0)
+                        {
+                            testForParamArray = true;
+                        }
+                        else
+                        {
+                            // From our existing code, our policy here is that if a parameterInfo 
+                            // is optional then all subsequent parameterInfos shall be optional. 
+
+                            // Thus, iff the first parameterInfo is not optional then this MethodInfo is no longer a canidate.
+                            if (!parameterInfos[argumentTypes.Length].IsOptional)
+                                testForParamArray = true;
+                        }
+                        #endregion
+                    }
+
+                    #region ParamArray
+                    if (testForParamArray)
+                    {
+                        if (parameterInfos.Length == 0)
+                            return false;
+
+                        // The last argument of the signature could be a param array. 
+                        bool shortByMoreThanOneSuppliedArgument = argumentTypes.Length < parameterInfos.Length - 1;
+
+                        if (shortByMoreThanOneSuppliedArgument)
+                            return false;
+
+                        ParameterInfo lastParameter = parameterInfos[parameterInfos.Length - 1];
+
+                        if (!lastParameter.ParameterType.IsArray)
+                            return false;
+
+                        if (!lastParameter.IsDefined(typeof(ParamArrayAttribute), false))
+                            return false;
+                    }
+                    #endregion
+
+                    #endregion
+                }
+                else
+                {
+                    #region Exact Binding
+                    if ((bindingFlags & BindingFlags.ExactBinding) != 0)
+                    {
+                        // Legacy behavior is to ignore ExactBinding when InvokeMember is specified.
+                        // Why filter by InvokeMember? If the answer is we leave this to the binder then why not leave
+                        // all the rest of this  to the binder too? Further, what other semanitc would the binder
+                        // use for BindingFlags.ExactBinding besides this one? Further, why not include CreateInstance 
+                        // in this if statement? That's just InvokeMethod with a constructor, right?
+                        if ((bindingFlags & (BindingFlags.InvokeMethod)) == 0)
+                        {
+                            for (int i = 0; i < parameterInfos.Length; i++)
+                            {
+                                // a null argument type implies a null arg which is always a perfect match
+                                if ((object)argumentTypes[i] != null && !argumentTypes[i].MatchesParameterTypeExactly(parameterInfos[i]))
+                                    return false;
+                            }
+                        }
+                    }
+                    #endregion
+                }
+            }
+            #endregion
+
+            return true;
+        }
+
+        #endregion
+
+        #endregion
+
+        #region Private Data Members
+        private object m_keepalive; // This will be filled with a LoaderAllocator reference when this RuntimeType represents a collectible type
+        private IntPtr m_cache;
+        internal IntPtr m_handle;
+
+        internal static readonly RuntimeType ValueType = (RuntimeType)typeof(System.ValueType);
+
+        private static readonly RuntimeType ObjectType = (RuntimeType)typeof(System.Object);
+        private static readonly RuntimeType StringType = (RuntimeType)typeof(System.String);
+        #endregion
+
+        #region Constructor
+        internal RuntimeType() { throw new NotSupportedException(); }
+        #endregion
+
+        #region Private\Internal Members
+        internal override bool CacheEquals(object o)
+        {
+            return (o is RuntimeType t) && (t.m_handle == m_handle);
+        }
+
+        private RuntimeTypeCache Cache
+        {
+            get
+            {
+                if (m_cache == IntPtr.Zero)
+                {
+                    IntPtr newgcHandle = new RuntimeTypeHandle(this).GetGCHandle(GCHandleType.WeakTrackResurrection);
+                    IntPtr gcHandle = Interlocked.CompareExchange(ref m_cache, newgcHandle, IntPtr.Zero);
+                    // Leak the handle if the type is collectible. It will be reclaimed when
+                    // the type goes away.
+                    if (gcHandle != IntPtr.Zero && !IsCollectible)
+                        GCHandle.InternalFree(newgcHandle);
+                }
+
+                RuntimeTypeCache cache = GCHandle.InternalGet(m_cache) as RuntimeTypeCache;
+                if (cache == null)
+                {
+                    cache = new RuntimeTypeCache(this);
+                    RuntimeTypeCache existingCache = GCHandle.InternalCompareExchange(m_cache, cache, null, false) as RuntimeTypeCache;
+                    if (existingCache != null)
+                        cache = existingCache;
+                }
+
+                Debug.Assert(cache != null);
+                return cache;
+            }
+        }
+
+        private string GetDefaultMemberName()
+        {
+            return Cache.GetDefaultMemberName();
+        }
+        #endregion
+
+        #region Type Overrides
+
+        #region Get XXXInfo Candidates
+
+        private const int GenericParameterCountAny = -1;
+
+        private ListBuilder<MethodInfo> GetMethodCandidates(
+            String name, int genericParameterCount, BindingFlags bindingAttr, CallingConventions callConv,
+            Type[] types, bool allowPrefixLookup)
+        {
+            bool prefixLookup, ignoreCase;
+            MemberListType listType;
+            RuntimeType.FilterHelper(bindingAttr, ref name, allowPrefixLookup, out prefixLookup, out ignoreCase, out listType);
+
+            RuntimeMethodInfo[] cache = Cache.GetMethodList(listType, name);
+
+            ListBuilder<MethodInfo> candidates = new ListBuilder<MethodInfo>(cache.Length);
+            for (int i = 0; i < cache.Length; i++)
+            {
+                RuntimeMethodInfo methodInfo = cache[i];
+                if (genericParameterCount != GenericParameterCountAny && genericParameterCount != methodInfo.GenericParameterCount)
+                    continue;
+
+                if (FilterApplyMethodInfo(methodInfo, bindingAttr, callConv, types) &&
+                    (!prefixLookup || RuntimeType.FilterApplyPrefixLookup(methodInfo, name, ignoreCase)))
+                {
+                    candidates.Add(methodInfo);
+                }
+            }
+
+            return candidates;
+        }
+
+        private ListBuilder<ConstructorInfo> GetConstructorCandidates(
+            string name, BindingFlags bindingAttr, CallingConventions callConv,
+            Type[] types, bool allowPrefixLookup)
+        {
+            bool prefixLookup, ignoreCase;
+            MemberListType listType;
+            RuntimeType.FilterHelper(bindingAttr, ref name, allowPrefixLookup, out prefixLookup, out ignoreCase, out listType);
+
+            RuntimeConstructorInfo[] cache = Cache.GetConstructorList(listType, name);
+
+            ListBuilder<ConstructorInfo> candidates = new ListBuilder<ConstructorInfo>(cache.Length);
+            for (int i = 0; i < cache.Length; i++)
+            {
+                RuntimeConstructorInfo constructorInfo = cache[i];
+                if (FilterApplyConstructorInfo(constructorInfo, bindingAttr, callConv, types) &&
+                    (!prefixLookup || RuntimeType.FilterApplyPrefixLookup(constructorInfo, name, ignoreCase)))
+                {
+                    candidates.Add(constructorInfo);
+                }
+            }
+
+            return candidates;
+        }
+
+
+        private ListBuilder<PropertyInfo> GetPropertyCandidates(
+            String name, BindingFlags bindingAttr, Type[] types, bool allowPrefixLookup)
+        {
+            bool prefixLookup, ignoreCase;
+            MemberListType listType;
+            RuntimeType.FilterHelper(bindingAttr, ref name, allowPrefixLookup, out prefixLookup, out ignoreCase, out listType);
+
+            RuntimePropertyInfo[] cache = Cache.GetPropertyList(listType, name);
+
+            bindingAttr ^= BindingFlags.DeclaredOnly;
+
+            ListBuilder<PropertyInfo> candidates = new ListBuilder<PropertyInfo>(cache.Length);
+            for (int i = 0; i < cache.Length; i++)
+            {
+                RuntimePropertyInfo propertyInfo = cache[i];
+                if ((bindingAttr & propertyInfo.BindingFlags) == propertyInfo.BindingFlags &&
+                    (!prefixLookup || RuntimeType.FilterApplyPrefixLookup(propertyInfo, name, ignoreCase)) &&
+                    (types == null || (propertyInfo.GetIndexParameters().Length == types.Length)))
+                {
+                    candidates.Add(propertyInfo);
+                }
+            }
+
+            return candidates;
+        }
+
+        private ListBuilder<EventInfo> GetEventCandidates(String name, BindingFlags bindingAttr, bool allowPrefixLookup)
+        {
+            bool prefixLookup, ignoreCase;
+            MemberListType listType;
+            RuntimeType.FilterHelper(bindingAttr, ref name, allowPrefixLookup, out prefixLookup, out ignoreCase, out listType);
+
+            RuntimeEventInfo[] cache = Cache.GetEventList(listType, name);
+
+            bindingAttr ^= BindingFlags.DeclaredOnly;
+
+            ListBuilder<EventInfo> candidates = new ListBuilder<EventInfo>(cache.Length);
+            for (int i = 0; i < cache.Length; i++)
+            {
+                RuntimeEventInfo eventInfo = cache[i];
+                if ((bindingAttr & eventInfo.BindingFlags) == eventInfo.BindingFlags &&
+                    (!prefixLookup || RuntimeType.FilterApplyPrefixLookup(eventInfo, name, ignoreCase)))
+                {
+                    candidates.Add(eventInfo);
+                }
+            }
+
+            return candidates;
+        }
+
+        private ListBuilder<FieldInfo> GetFieldCandidates(String name, BindingFlags bindingAttr, bool allowPrefixLookup)
+        {
+            bool prefixLookup, ignoreCase;
+            MemberListType listType;
+            RuntimeType.FilterHelper(bindingAttr, ref name, allowPrefixLookup, out prefixLookup, out ignoreCase, out listType);
+
+            RuntimeFieldInfo[] cache = Cache.GetFieldList(listType, name);
+
+            bindingAttr ^= BindingFlags.DeclaredOnly;
+
+            ListBuilder<FieldInfo> candidates = new ListBuilder<FieldInfo>(cache.Length);
+            for (int i = 0; i < cache.Length; i++)
+            {
+                RuntimeFieldInfo fieldInfo = cache[i];
+                if ((bindingAttr & fieldInfo.BindingFlags) == fieldInfo.BindingFlags &&
+                    (!prefixLookup || FilterApplyPrefixLookup(fieldInfo, name, ignoreCase)))
+                {
+                    candidates.Add(fieldInfo);
+                }
+            }
+
+            return candidates;
+        }
+
+        private ListBuilder<Type> GetNestedTypeCandidates(String fullname, BindingFlags bindingAttr, bool allowPrefixLookup)
+        {
+            bool prefixLookup, ignoreCase;
+            bindingAttr &= ~BindingFlags.Static;
+            string name, ns;
+            MemberListType listType;
+            SplitName(fullname, out name, out ns);
+            RuntimeType.FilterHelper(bindingAttr, ref name, allowPrefixLookup, out prefixLookup, out ignoreCase, out listType);
+
+            RuntimeType[] cache = Cache.GetNestedTypeList(listType, name);
+
+            ListBuilder<Type> candidates = new ListBuilder<Type>(cache.Length);
+            for (int i = 0; i < cache.Length; i++)
+            {
+                RuntimeType nestedClass = cache[i];
+                if (RuntimeType.FilterApplyType(nestedClass, bindingAttr, name, prefixLookup, ns))
+                {
+                    candidates.Add(nestedClass);
+                }
+            }
+
+            return candidates;
+        }
+        #endregion
+
+        #region Get All XXXInfos
+        public override MethodInfo[] GetMethods(BindingFlags bindingAttr)
+        {
+            return GetMethodCandidates(null, GenericParameterCountAny, bindingAttr, CallingConventions.Any, null, false).ToArray();
+        }
+
+        public override ConstructorInfo[] GetConstructors(BindingFlags bindingAttr)
+        {
+            return GetConstructorCandidates(null, bindingAttr, CallingConventions.Any, null, false).ToArray();
+        }
+
+        public override PropertyInfo[] GetProperties(BindingFlags bindingAttr)
+        {
+            return GetPropertyCandidates(null, bindingAttr, null, false).ToArray();
+        }
+
+        public override EventInfo[] GetEvents(BindingFlags bindingAttr)
+        {
+            return GetEventCandidates(null, bindingAttr, false).ToArray();
+        }
+
+        public override FieldInfo[] GetFields(BindingFlags bindingAttr)
+        {
+            return GetFieldCandidates(null, bindingAttr, false).ToArray();
+        }
+
+        public override Type[] GetInterfaces()
+        {
+            RuntimeType[] candidates = this.Cache.GetInterfaceList(MemberListType.All, null);
+            Type[] interfaces = new Type[candidates.Length];
+            for (int i = 0; i < candidates.Length; i++)
+                JitHelpers.UnsafeSetArrayElement(interfaces, i, candidates[i]);
+
+            return interfaces;
+        }
+
+        public override Type[] GetNestedTypes(BindingFlags bindingAttr)
+        {
+            return GetNestedTypeCandidates(null, bindingAttr, false).ToArray();
+        }
+
+        public override MemberInfo[] GetMembers(BindingFlags bindingAttr)
+        {
+            ListBuilder<MethodInfo> methods = GetMethodCandidates(null, GenericParameterCountAny, bindingAttr, CallingConventions.Any, null, false);
+            ListBuilder<ConstructorInfo> constructors = GetConstructorCandidates(null, bindingAttr, CallingConventions.Any, null, false);
+            ListBuilder<PropertyInfo> properties = GetPropertyCandidates(null, bindingAttr, null, false);
+            ListBuilder<EventInfo> events = GetEventCandidates(null, bindingAttr, false);
+            ListBuilder<FieldInfo> fields = GetFieldCandidates(null, bindingAttr, false);
+            ListBuilder<Type> nestedTypes = GetNestedTypeCandidates(null, bindingAttr, false);
+            // Interfaces are excluded from the result of GetMembers
+
+            MemberInfo[] members = new MemberInfo[
+                methods.Count +
+                constructors.Count +
+                properties.Count +
+                events.Count +
+                fields.Count +
+                nestedTypes.Count];
+
+            int i = 0;
+            methods.CopyTo(members, i); i += methods.Count;
+            constructors.CopyTo(members, i); i += constructors.Count;
+            properties.CopyTo(members, i); i += properties.Count;
+            events.CopyTo(members, i); i += events.Count;
+            fields.CopyTo(members, i); i += fields.Count;
+            nestedTypes.CopyTo(members, i); i += nestedTypes.Count;
+            Debug.Assert(i == members.Length);
+
+            return members;
+        }
+
+        public override InterfaceMapping GetInterfaceMap(Type ifaceType)
+        {
+            if (IsGenericParameter)
+                throw new InvalidOperationException(SR.Arg_GenericParameter);
+
+            if ((object)ifaceType == null)
+                throw new ArgumentNullException(nameof(ifaceType));
+
+            RuntimeType ifaceRtType = ifaceType as RuntimeType;
+
+            if (ifaceRtType == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType, nameof(ifaceType));
+
+            RuntimeTypeHandle ifaceRtTypeHandle = ifaceRtType.GetTypeHandleInternal();
+
+            GetTypeHandleInternal().VerifyInterfaceIsImplemented(ifaceRtTypeHandle);
+            Debug.Assert(ifaceType.IsInterface);  // VerifyInterfaceIsImplemented enforces this invariant
+            Debug.Assert(!IsInterface); // VerifyInterfaceIsImplemented enforces this invariant
+
+            // SZArrays implement the methods on IList`1, IEnumerable`1, and ICollection`1 with
+            // SZArrayHelper and some runtime magic. We don't have accurate interface maps for them.
+            if (IsSZArray && ifaceType.IsGenericType)
+                throw new ArgumentException(SR.Argument_ArrayGetInterfaceMap);
+
+            int ifaceInstanceMethodCount = RuntimeTypeHandle.GetNumVirtuals(ifaceRtType);
+
+            InterfaceMapping im;
+            im.InterfaceType = ifaceType;
+            im.TargetType = this;
+            im.InterfaceMethods = new MethodInfo[ifaceInstanceMethodCount];
+            im.TargetMethods = new MethodInfo[ifaceInstanceMethodCount];
+
+            for (int i = 0; i < ifaceInstanceMethodCount; i++)
+            {
+                RuntimeMethodHandleInternal ifaceRtMethodHandle = RuntimeTypeHandle.GetMethodAt(ifaceRtType, i);
+
+                // GetMethodBase will convert this to the instantiating/unboxing stub if necessary
+                MethodBase ifaceMethodBase = RuntimeType.GetMethodBase(ifaceRtType, ifaceRtMethodHandle);
+                Debug.Assert(ifaceMethodBase is RuntimeMethodInfo);
+                im.InterfaceMethods[i] = (MethodInfo)ifaceMethodBase;
+
+                // If the impl is null, then virtual stub dispatch is active.
+                RuntimeMethodHandleInternal classRtMethodHandle = GetTypeHandleInternal().GetInterfaceMethodImplementation(ifaceRtTypeHandle, ifaceRtMethodHandle);
+
+                if (classRtMethodHandle.IsNullHandle())
+                    continue;
+
+                // If we resolved to an interface method, use the interface type as reflected type. Otherwise use `this`.
+                RuntimeType reflectedType = RuntimeMethodHandle.GetDeclaringType(classRtMethodHandle);
+                if (!reflectedType.IsInterface)
+                    reflectedType = this;
+
+                // GetMethodBase will convert this to the instantiating/unboxing stub if necessary
+                MethodBase rtTypeMethodBase = RuntimeType.GetMethodBase(reflectedType, classRtMethodHandle);
+                // a class may not implement all the methods of an interface (abstract class) so null is a valid value 
+                Debug.Assert(rtTypeMethodBase == null || rtTypeMethodBase is RuntimeMethodInfo);
+                im.TargetMethods[i] = (MethodInfo)rtTypeMethodBase;
+            }
+
+            return im;
+        }
+        #endregion
+
+        #region Find XXXInfo
+
+        protected override MethodInfo GetMethodImpl(
+            String name, BindingFlags bindingAttr, Binder binder, CallingConventions callConv,
+            Type[] types, ParameterModifier[] modifiers)
+        {
+            return GetMethodImplCommon(name, GenericParameterCountAny, bindingAttr, binder, callConv, types, modifiers);
+        }
+
+        protected override MethodInfo GetMethodImpl(
+            String name, int genericParameterCount, BindingFlags bindingAttr, Binder binder, CallingConventions callConv,
+            Type[] types, ParameterModifier[] modifiers)
+        {
+            return GetMethodImplCommon(name, genericParameterCount, bindingAttr, binder, callConv, types, modifiers);
+        }
+
+        private MethodInfo GetMethodImplCommon(
+            String name, int genericParameterCount, BindingFlags bindingAttr, Binder binder, CallingConventions callConv,
+            Type[] types, ParameterModifier[] modifiers)
+        {
+            ListBuilder<MethodInfo> candidates = GetMethodCandidates(name, genericParameterCount, bindingAttr, callConv, types, false);
+
+            if (candidates.Count == 0)
+                return null;
+
+            if (types == null || types.Length == 0)
+            {
+                MethodInfo firstCandidate = candidates[0];
+
+                if (candidates.Count == 1)
+                {
+                    return firstCandidate;
+                }
+                else if (types == null)
+                {
+                    for (int j = 1; j < candidates.Count; j++)
+                    {
+                        MethodInfo methodInfo = candidates[j];
+                        if (!System.DefaultBinder.CompareMethodSig(methodInfo, firstCandidate))
+                        {
+                            throw new AmbiguousMatchException(SR.Arg_AmbiguousMatchException);
+                        }
+                    }
+
+                    // All the methods have the exact same name and sig so return the most derived one.
+                    return System.DefaultBinder.FindMostDerivedNewSlotMeth(candidates.ToArray(), candidates.Count) as MethodInfo;
+                }
+            }
+
+            if (binder == null)
+                binder = DefaultBinder;
+
+            return binder.SelectMethod(bindingAttr, candidates.ToArray(), types, modifiers) as MethodInfo;
+        }
+
+
+        protected override ConstructorInfo GetConstructorImpl(
+            BindingFlags bindingAttr, Binder binder, CallingConventions callConvention,
+            Type[] types, ParameterModifier[] modifiers)
+        {
+            ListBuilder<ConstructorInfo> candidates = GetConstructorCandidates(null, bindingAttr, CallingConventions.Any, types, false);
+
+            if (candidates.Count == 0)
+                return null;
+
+            if (types.Length == 0 && candidates.Count == 1)
+            {
+                ConstructorInfo firstCandidate = candidates[0];
+
+                ParameterInfo[] parameters = firstCandidate.GetParametersNoCopy();
+                if (parameters == null || parameters.Length == 0)
+                {
+                    return firstCandidate;
+                }
+            }
+
+            if ((bindingAttr & BindingFlags.ExactBinding) != 0)
+                return System.DefaultBinder.ExactBinding(candidates.ToArray(), types, modifiers) as ConstructorInfo;
+
+            if (binder == null)
+                binder = DefaultBinder;
+
+            return binder.SelectMethod(bindingAttr, candidates.ToArray(), types, modifiers) as ConstructorInfo;
+        }
+
+
+        protected override PropertyInfo GetPropertyImpl(
+            String name, BindingFlags bindingAttr, Binder binder, Type returnType, Type[] types, ParameterModifier[] modifiers)
+        {
+            if (name == null) throw new ArgumentNullException();
+
+            ListBuilder<PropertyInfo> candidates = GetPropertyCandidates(name, bindingAttr, types, false);
+
+            if (candidates.Count == 0)
+                return null;
+
+            if (types == null || types.Length == 0)
+            {
+                // no arguments
+                if (candidates.Count == 1)
+                {
+                    PropertyInfo firstCandidate = candidates[0];
+
+                    if ((object)returnType != null && !returnType.IsEquivalentTo(firstCandidate.PropertyType))
+                        return null;
+
+                    return firstCandidate;
+                }
+                else
+                {
+                    if ((object)returnType == null)
+                        // if we are here we have no args or property type to select over and we have more than one property with that name
+                        throw new AmbiguousMatchException(SR.Arg_AmbiguousMatchException);
+                }
+            }
+
+            if ((bindingAttr & BindingFlags.ExactBinding) != 0)
+                return System.DefaultBinder.ExactPropertyBinding(candidates.ToArray(), returnType, types, modifiers);
+
+            if (binder == null)
+                binder = DefaultBinder;
+
+            return binder.SelectProperty(bindingAttr, candidates.ToArray(), returnType, types, modifiers);
+        }
+
+
+        public override EventInfo GetEvent(String name, BindingFlags bindingAttr)
+        {
+            if (name == null) throw new ArgumentNullException();
+
+            bool ignoreCase;
+            MemberListType listType;
+            RuntimeType.FilterHelper(bindingAttr, ref name, out ignoreCase, out listType);
+
+            RuntimeEventInfo[] cache = Cache.GetEventList(listType, name);
+            EventInfo match = null;
+
+            bindingAttr ^= BindingFlags.DeclaredOnly;
+
+            for (int i = 0; i < cache.Length; i++)
+            {
+                RuntimeEventInfo eventInfo = cache[i];
+                if ((bindingAttr & eventInfo.BindingFlags) == eventInfo.BindingFlags)
+                {
+                    if (match != null)
+                        throw new AmbiguousMatchException(SR.Arg_AmbiguousMatchException);
+
+                    match = eventInfo;
+                }
+            }
+
+            return match;
+        }
+
+        public override FieldInfo GetField(String name, BindingFlags bindingAttr)
+        {
+            if (name == null) throw new ArgumentNullException();
+
+            bool ignoreCase;
+            MemberListType listType;
+            RuntimeType.FilterHelper(bindingAttr, ref name, out ignoreCase, out listType);
+
+            RuntimeFieldInfo[] cache = Cache.GetFieldList(listType, name);
+            FieldInfo match = null;
+
+            bindingAttr ^= BindingFlags.DeclaredOnly;
+            bool multipleStaticFieldMatches = false;
+
+            for (int i = 0; i < cache.Length; i++)
+            {
+                RuntimeFieldInfo fieldInfo = cache[i];
+                if ((bindingAttr & fieldInfo.BindingFlags) == fieldInfo.BindingFlags)
+                {
+                    if (match != null)
+                    {
+                        if (Object.ReferenceEquals(fieldInfo.DeclaringType, match.DeclaringType))
+                            throw new AmbiguousMatchException(SR.Arg_AmbiguousMatchException);
+
+                        if ((match.DeclaringType.IsInterface == true) && (fieldInfo.DeclaringType.IsInterface == true))
+                            multipleStaticFieldMatches = true;
+                    }
+
+                    if (match == null || fieldInfo.DeclaringType.IsSubclassOf(match.DeclaringType) || match.DeclaringType.IsInterface)
+                        match = fieldInfo;
+                }
+            }
+
+            if (multipleStaticFieldMatches && match.DeclaringType.IsInterface)
+                throw new AmbiguousMatchException(SR.Arg_AmbiguousMatchException);
+
+            return match;
+        }
+
+        public override Type GetInterface(String fullname, bool ignoreCase)
+        {
+            if (fullname == null) throw new ArgumentNullException();
+
+            BindingFlags bindingAttr = BindingFlags.Public | BindingFlags.NonPublic;
+
+            bindingAttr &= ~BindingFlags.Static;
+
+            if (ignoreCase)
+                bindingAttr |= BindingFlags.IgnoreCase;
+
+            string name, ns;
+            MemberListType listType;
+            SplitName(fullname, out name, out ns);
+            RuntimeType.FilterHelper(bindingAttr, ref name, out ignoreCase, out listType);
+
+            RuntimeType[] cache = Cache.GetInterfaceList(listType, name);
+
+            RuntimeType match = null;
+
+            for (int i = 0; i < cache.Length; i++)
+            {
+                RuntimeType iface = cache[i];
+                if (RuntimeType.FilterApplyType(iface, bindingAttr, name, false, ns))
+                {
+                    if (match != null)
+                        throw new AmbiguousMatchException(SR.Arg_AmbiguousMatchException);
+
+                    match = iface;
+                }
+            }
+
+            return match;
+        }
+
+        public override Type GetNestedType(String fullname, BindingFlags bindingAttr)
+        {
+            if (fullname == null) throw new ArgumentNullException();
+
+            bool ignoreCase;
+            bindingAttr &= ~BindingFlags.Static;
+            string name, ns;
+            MemberListType listType;
+            SplitName(fullname, out name, out ns);
+            RuntimeType.FilterHelper(bindingAttr, ref name, out ignoreCase, out listType);
+
+            RuntimeType[] cache = Cache.GetNestedTypeList(listType, name);
+
+            RuntimeType match = null;
+
+            for (int i = 0; i < cache.Length; i++)
+            {
+                RuntimeType nestedType = cache[i];
+                if (RuntimeType.FilterApplyType(nestedType, bindingAttr, name, false, ns))
+                {
+                    if (match != null)
+                        throw new AmbiguousMatchException(SR.Arg_AmbiguousMatchException);
+
+                    match = nestedType;
+                }
+            }
+
+            return match;
+        }
+
+        public override MemberInfo[] GetMember(String name, MemberTypes type, BindingFlags bindingAttr)
+        {
+            if (name == null) throw new ArgumentNullException();
+
+            ListBuilder<MethodInfo> methods = new ListBuilder<MethodInfo>();
+            ListBuilder<ConstructorInfo> constructors = new ListBuilder<ConstructorInfo>();
+            ListBuilder<PropertyInfo> properties = new ListBuilder<PropertyInfo>();
+            ListBuilder<EventInfo> events = new ListBuilder<EventInfo>();
+            ListBuilder<FieldInfo> fields = new ListBuilder<FieldInfo>();
+            ListBuilder<Type> nestedTypes = new ListBuilder<Type>();
+
+            int totalCount = 0;
+
+            // Methods
+            if ((type & MemberTypes.Method) != 0)
+            {
+                methods = GetMethodCandidates(name, GenericParameterCountAny, bindingAttr, CallingConventions.Any, null, true);
+                if (type == MemberTypes.Method)
+                    return methods.ToArray();
+                totalCount += methods.Count;
+            }
+
+            // Constructors
+            if ((type & MemberTypes.Constructor) != 0)
+            {
+                constructors = GetConstructorCandidates(name, bindingAttr, CallingConventions.Any, null, true);
+                if (type == MemberTypes.Constructor)
+                    return constructors.ToArray();
+                totalCount += constructors.Count;
+            }
+
+            // Properties
+            if ((type & MemberTypes.Property) != 0)
+            {
+                properties = GetPropertyCandidates(name, bindingAttr, null, true);
+                if (type == MemberTypes.Property)
+                    return properties.ToArray();
+                totalCount += properties.Count;
+            }
+
+            // Events
+            if ((type & MemberTypes.Event) != 0)
+            {
+                events = GetEventCandidates(name, bindingAttr, true);
+                if (type == MemberTypes.Event)
+                    return events.ToArray();
+                totalCount += events.Count;
+            }
+
+            // Fields
+            if ((type & MemberTypes.Field) != 0)
+            {
+                fields = GetFieldCandidates(name, bindingAttr, true);
+                if (type == MemberTypes.Field)
+                    return fields.ToArray();
+                totalCount += fields.Count;
+            }
+
+            // NestedTypes
+            if ((type & (MemberTypes.NestedType | MemberTypes.TypeInfo)) != 0)
+            {
+                nestedTypes = GetNestedTypeCandidates(name, bindingAttr, true);
+                if (type == MemberTypes.NestedType || type == MemberTypes.TypeInfo)
+                    return nestedTypes.ToArray();
+                totalCount += nestedTypes.Count;
+            }
+
+            MemberInfo[] compressMembers = (type == (MemberTypes.Method | MemberTypes.Constructor)) ?
+                new MethodBase[totalCount] : new MemberInfo[totalCount];
+
+            int i = 0;
+            methods.CopyTo(compressMembers, i); i += methods.Count;
+            constructors.CopyTo(compressMembers, i); i += constructors.Count;
+            properties.CopyTo(compressMembers, i); i += properties.Count;
+            events.CopyTo(compressMembers, i); i += events.Count;
+            fields.CopyTo(compressMembers, i); i += fields.Count;
+            nestedTypes.CopyTo(compressMembers, i); i += nestedTypes.Count;
+            Debug.Assert(i == compressMembers.Length);
+
+            return compressMembers;
+        }
+        #endregion
+
+        #region Identity
+        public override Module Module
+        {
+            get
+            {
+                return GetRuntimeModule();
+            }
+        }
+
+        internal RuntimeModule GetRuntimeModule()
+        {
+            return RuntimeTypeHandle.GetModule(this);
+        }
+
+        public override Assembly Assembly
+        {
+            get
+            {
+                return GetRuntimeAssembly();
+            }
+        }
+
+        internal RuntimeAssembly GetRuntimeAssembly()
+        {
+            return RuntimeTypeHandle.GetAssembly(this);
+        }
+
+        public override RuntimeTypeHandle TypeHandle
+        {
+            get
+            {
+                return new RuntimeTypeHandle(this);
+            }
+        }
+
+        internal sealed override RuntimeTypeHandle GetTypeHandleInternal()
+        {
+            return new RuntimeTypeHandle(this);
+        }
+
+        public sealed override bool IsCollectible => RuntimeTypeHandle.IsCollectible(GetTypeHandleInternal());
+
+        protected override TypeCode GetTypeCodeImpl()
+        {
+            TypeCode typeCode = Cache.TypeCode;
+
+            if (typeCode != TypeCode.Empty)
+                return typeCode;
+
+            CorElementType corElementType = RuntimeTypeHandle.GetCorElementType(this);
+            switch (corElementType)
+            {
+                case CorElementType.Boolean:
+                    typeCode = TypeCode.Boolean; break;
+                case CorElementType.Char:
+                    typeCode = TypeCode.Char; break;
+                case CorElementType.I1:
+                    typeCode = TypeCode.SByte; break;
+                case CorElementType.U1:
+                    typeCode = TypeCode.Byte; break;
+                case CorElementType.I2:
+                    typeCode = TypeCode.Int16; break;
+                case CorElementType.U2:
+                    typeCode = TypeCode.UInt16; break;
+                case CorElementType.I4:
+                    typeCode = TypeCode.Int32; break;
+                case CorElementType.U4:
+                    typeCode = TypeCode.UInt32; break;
+                case CorElementType.I8:
+                    typeCode = TypeCode.Int64; break;
+                case CorElementType.U8:
+                    typeCode = TypeCode.UInt64; break;
+                case CorElementType.R4:
+                    typeCode = TypeCode.Single; break;
+                case CorElementType.R8:
+                    typeCode = TypeCode.Double; break;
+                case CorElementType.String:
+                    typeCode = TypeCode.String; break;
+                case CorElementType.ValueType:
+                    if (this == Convert.ConvertTypes[(int)TypeCode.Decimal])
+                        typeCode = TypeCode.Decimal;
+                    else if (this == Convert.ConvertTypes[(int)TypeCode.DateTime])
+                        typeCode = TypeCode.DateTime;
+                    else if (this.IsEnum)
+                        typeCode = Type.GetTypeCode(Enum.GetUnderlyingType(this));
+                    else
+                        typeCode = TypeCode.Object;
+                    break;
+                default:
+                    if (this == Convert.ConvertTypes[(int)TypeCode.DBNull])
+                        typeCode = TypeCode.DBNull;
+                    else if (this == Convert.ConvertTypes[(int)TypeCode.String])
+                        typeCode = TypeCode.String;
+                    else
+                        typeCode = TypeCode.Object;
+                    break;
+            }
+
+            Cache.TypeCode = typeCode;
+
+            return typeCode;
+        }
+
+        public override MethodBase DeclaringMethod
+        {
+            get
+            {
+                if (!IsGenericParameter)
+                    throw new InvalidOperationException(SR.Arg_NotGenericParameter);
+
+                IRuntimeMethodInfo declaringMethod = RuntimeTypeHandle.GetDeclaringMethod(this);
+
+                if (declaringMethod == null)
+                    return null;
+
+                return GetMethodBase(RuntimeMethodHandle.GetDeclaringType(declaringMethod), declaringMethod);
+            }
+        }
+        #endregion
+
+        #region Hierarchy
+        public override bool IsInstanceOfType(Object o)
+        {
+            return RuntimeTypeHandle.IsInstanceOfType(this, o);
+        }
+
+        public override bool IsSubclassOf(Type type)
+        {
+            if ((object)type == null)
+                throw new ArgumentNullException(nameof(type));
+            RuntimeType rtType = type as RuntimeType;
+            if (rtType == null)
+                return false;
+
+            RuntimeType baseType = GetBaseType();
+
+            while (baseType != null)
+            {
+                if (baseType == rtType)
+                    return true;
+
+                baseType = baseType.GetBaseType();
+            }
+
+            // pretty much everything is a subclass of object, even interfaces
+            // notice that interfaces are really odd because they do not have a BaseType
+            // yet IsSubclassOf(typeof(object)) returns true
+            if (rtType == RuntimeType.ObjectType && rtType != this)
+                return true;
+
+            return false;
+        }
+
+        public override bool IsAssignableFrom(System.Reflection.TypeInfo typeInfo)
+        {
+            if (typeInfo == null) return false;
+            return IsAssignableFrom(typeInfo.AsType());
+        }
+
+        public override bool IsAssignableFrom(Type c)
+        {
+            if ((object)c == null)
+                return false;
+
+            if (Object.ReferenceEquals(c, this))
+                return true;
+
+            RuntimeType fromType = c.UnderlyingSystemType as RuntimeType;
+
+            // For runtime type, let the VM decide.
+            if (fromType != null)
+            {
+                // both this and c (or their underlying system types) are runtime types
+                return RuntimeTypeHandle.CanCastTo(fromType, this);
+            }
+
+            // Special case for TypeBuilder to be backward-compatible.
+            if (c is System.Reflection.Emit.TypeBuilder)
+            {
+                // If c is a subclass of this class, then c can be cast to this type.
+                if (c.IsSubclassOf(this))
+                    return true;
+
+                if (this.IsInterface)
+                {
+                    return c.ImplementInterface(this);
+                }
+                else if (this.IsGenericParameter)
+                {
+                    Type[] constraints = GetGenericParameterConstraints();
+                    for (int i = 0; i < constraints.Length; i++)
+                        if (!constraints[i].IsAssignableFrom(c))
+                            return false;
+
+                    return true;
+                }
+            }
+
+            // For anything else we return false.
+            return false;
+        }
+
+        public override Type BaseType
+        {
+            get
+            {
+                return GetBaseType();
+            }
+        }
+
+        private RuntimeType GetBaseType()
+        {
+            if (IsInterface)
+                return null;
+
+            if (RuntimeTypeHandle.IsGenericVariable(this))
+            {
+                Type[] constraints = GetGenericParameterConstraints();
+
+                RuntimeType baseType = RuntimeType.ObjectType;
+
+                for (int i = 0; i < constraints.Length; i++)
+                {
+                    RuntimeType constraint = (RuntimeType)constraints[i];
+
+                    if (constraint.IsInterface)
+                        continue;
+
+                    if (constraint.IsGenericParameter)
+                    {
+                        GenericParameterAttributes special;
+                        special = constraint.GenericParameterAttributes & GenericParameterAttributes.SpecialConstraintMask;
+
+                        if ((special & GenericParameterAttributes.ReferenceTypeConstraint) == 0 &&
+                            (special & GenericParameterAttributes.NotNullableValueTypeConstraint) == 0)
+                            continue;
+                    }
+
+                    baseType = constraint;
+                }
+
+                if (baseType == RuntimeType.ObjectType)
+                {
+                    GenericParameterAttributes special;
+                    special = GenericParameterAttributes & GenericParameterAttributes.SpecialConstraintMask;
+                    if ((special & GenericParameterAttributes.NotNullableValueTypeConstraint) != 0)
+                        baseType = RuntimeType.ValueType;
+                }
+
+                return baseType;
+            }
+
+            return RuntimeTypeHandle.GetBaseType(this);
+        }
+
+        public override Type UnderlyingSystemType
+        {
+            get
+            {
+                return this;
+            }
+        }
+        #endregion
+
+        #region Name
+        public override String FullName
+        {
+            get
+            {
+                return GetCachedName(TypeNameKind.FullName);
+            }
+        }
+
+        public override String AssemblyQualifiedName
+        {
+            get
+            {
+                string fullname = FullName;
+
+                // FullName is null if this type contains generic parameters but is not a generic type definition.
+                if (fullname == null)
+                    return null;
+
+                return Assembly.CreateQualifiedName(this.Assembly.FullName, fullname);
+            }
+        }
+
+        public override String Namespace
+        {
+            get
+            {
+                string ns = Cache.GetNameSpace();
+
+                if (ns == null || ns.Length == 0)
+                    return null;
+
+                return ns;
+            }
+        }
+        #endregion
+
+        #region Attributes
+        protected override TypeAttributes GetAttributeFlagsImpl()
+        {
+            return RuntimeTypeHandle.GetAttributes(this);
+        }
+
+        public override Guid GUID
+        {
+            get
+            {
+                Guid result = new Guid();
+                GetGUID(ref result);
+                return result;
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern void GetGUID(ref Guid result);
+
+        protected override bool IsContextfulImpl()
+        {
+            return false;
+        }
+
+        protected override bool IsByRefImpl()
+        {
+            return RuntimeTypeHandle.IsByRef(this);
+        }
+
+        protected override bool IsPrimitiveImpl()
+        {
+            return RuntimeTypeHandle.IsPrimitive(this);
+        }
+
+        protected override bool IsPointerImpl()
+        {
+            return RuntimeTypeHandle.IsPointer(this);
+        }
+
+        protected override bool IsCOMObjectImpl()
+        {
+            return RuntimeTypeHandle.IsComObject(this, false);
+        }
+
+        public sealed override bool IsByRefLike => RuntimeTypeHandle.IsByRefLike(this);
+
+#if FEATURE_COMINTEROP
+        internal override bool IsWindowsRuntimeObjectImpl()
+        {
+            return IsWindowsRuntimeObjectType(this);
+        }
+
+        internal override bool IsExportedToWindowsRuntimeImpl()
+        {
+            return IsTypeExportedToWindowsRuntime(this);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool IsWindowsRuntimeObjectType(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool IsTypeExportedToWindowsRuntime(RuntimeType type);
+
+#endif // FEATURE_COMINTEROP
+
+        internal bool IsDelegate()
+        {
+            return GetBaseType() == typeof(System.MulticastDelegate);
+        }
+
+        protected override bool IsValueTypeImpl()
+        {
+            // We need to return true for generic parameters with the ValueType constraint.
+            // So we cannot use the faster RuntimeTypeHandle.IsValueType because it returns 
+            // false for all generic parameters.
+            if (this == typeof(ValueType) || this == typeof(Enum))
+                return false;
+
+            return IsSubclassOf(typeof(ValueType));
+        }
+
+        protected override bool HasElementTypeImpl()
+        {
+            return RuntimeTypeHandle.HasElementType(this);
+        }
+
+        public override GenericParameterAttributes GenericParameterAttributes
+        {
+            get
+            {
+                if (!IsGenericParameter)
+                    throw new InvalidOperationException(SR.Arg_NotGenericParameter);
+
+                GenericParameterAttributes attributes;
+
+                RuntimeTypeHandle.GetMetadataImport(this).GetGenericParamProps(MetadataToken, out attributes);
+
+                return attributes;
+            }
+        }
+
+        public override bool IsSecurityCritical
+        {
+            get { return true; }
+        }
+        public override bool IsSecuritySafeCritical
+        {
+            get { return false; }
+        }
+        public override bool IsSecurityTransparent
+        {
+            get { return false; }
+        }
+        #endregion
+
+        #region Arrays
+        public sealed override bool IsSZArray
+        {
+            get
+            {
+                return RuntimeTypeHandle.IsSZArray(this);
+            }
+        }
+
+        protected override bool IsArrayImpl()
+        {
+            return RuntimeTypeHandle.IsArray(this);
+        }
+
+        public override int GetArrayRank()
+        {
+            if (!IsArrayImpl())
+                throw new ArgumentException(SR.Argument_HasToBeArrayClass);
+
+            return RuntimeTypeHandle.GetArrayRank(this);
+        }
+
+        public override Type GetElementType()
+        {
+            return RuntimeTypeHandle.GetElementType(this);
+        }
+        #endregion
+
+        #region Enums
+        public override string[] GetEnumNames()
+        {
+            if (!IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
+
+            String[] ret = Enum.InternalGetNames(this);
+
+            // Make a copy since we can't hand out the same array since users can modify them
+            String[] retVal = new String[ret.Length];
+
+            Array.Copy(ret, retVal, ret.Length);
+
+            return retVal;
+        }
+
+        public override Array GetEnumValues()
+        {
+            if (!IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
+
+            // Get all of the values
+            ulong[] values = Enum.InternalGetValues(this);
+
+            // Create a generic Array
+            Array ret = Array.UnsafeCreateInstance(this, values.Length);
+
+            for (int i = 0; i < values.Length; i++)
+            {
+                Object val = Enum.ToObject(this, values[i]);
+                ret.SetValue(val, i);
+            }
+
+            return ret;
+        }
+
+        public override Type GetEnumUnderlyingType()
+        {
+            if (!IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
+
+            return Enum.InternalGetUnderlyingType(this);
+        }
+
+        public override bool IsEnumDefined(object value)
+        {
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            // Check if both of them are of the same type
+            RuntimeType valueType = (RuntimeType)value.GetType();
+
+            // If the value is an Enum then we need to extract the underlying value from it
+            if (valueType.IsEnum)
+            {
+                if (!valueType.IsEquivalentTo(this))
+                    throw new ArgumentException(SR.Format(SR.Arg_EnumAndObjectMustBeSameType, valueType.ToString(), this.ToString()));
+
+                valueType = (RuntimeType)valueType.GetEnumUnderlyingType();
+            }
+
+            // If a string is passed in
+            if (valueType == RuntimeType.StringType)
+            {
+                // Get all of the Fields, calling GetHashEntry directly to avoid copying
+                string[] names = Enum.InternalGetNames(this);
+                if (Array.IndexOf(names, value) >= 0)
+                    return true;
+                else
+                    return false;
+            }
+
+            // If an enum or integer value is passed in
+            if (Type.IsIntegerType(valueType))
+            {
+                RuntimeType underlyingType = Enum.InternalGetUnderlyingType(this);
+                if (underlyingType != valueType)
+                    throw new ArgumentException(SR.Format(SR.Arg_EnumUnderlyingTypeAndObjectMustBeSameType, valueType.ToString(), underlyingType.ToString()));
+
+                ulong[] ulValues = Enum.InternalGetValues(this);
+                ulong ulValue = Enum.ToUInt64(value);
+
+                return (Array.BinarySearch(ulValues, ulValue) >= 0);
+            }
+            else
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_UnknownEnumType);
+            }
+        }
+
+        public override string GetEnumName(object value)
+        {
+            if (value == null)
+                throw new ArgumentNullException(nameof(value));
+
+            Type valueType = value.GetType();
+
+            if (!(valueType.IsEnum || IsIntegerType(valueType)))
+                throw new ArgumentException(SR.Arg_MustBeEnumBaseTypeOrEnum, nameof(value));
+
+            ulong ulValue = Enum.ToUInt64(value);
+
+            return Enum.GetEnumName(this, ulValue);
+        }
+        #endregion
+
+        #region Generics
+        internal RuntimeType[] GetGenericArgumentsInternal()
+        {
+            return GetRootElementType().GetTypeHandleInternal().GetInstantiationInternal();
+        }
+
+        public override Type[] GetGenericArguments()
+        {
+            Type[] types = GetRootElementType().GetTypeHandleInternal().GetInstantiationPublic();
+
+            if (types == null)
+                types = Array.Empty<Type>();
+
+            return types;
+        }
+
+        public override Type MakeGenericType(Type[] instantiation)
+        {
+            if (instantiation == null)
+                throw new ArgumentNullException(nameof(instantiation));
+
+            RuntimeType[] instantiationRuntimeType = new RuntimeType[instantiation.Length];
+
+            if (!IsGenericTypeDefinition)
+                throw new InvalidOperationException(
+                    SR.Format(SR.Arg_NotGenericTypeDefinition, this));
+
+            if (GetGenericArguments().Length != instantiation.Length)
+                throw new ArgumentException(SR.Argument_GenericArgsCount, nameof(instantiation));
+
+            bool foundSigType = false;
+            bool foundNonRuntimeType = false;
+            for (int i = 0; i < instantiation.Length; i++)
+            {
+                Type instantiationElem = instantiation[i];
+                if (instantiationElem == null)
+                    throw new ArgumentNullException();
+
+                RuntimeType rtInstantiationElem = instantiationElem as RuntimeType;
+
+                if (rtInstantiationElem == null)
+                {
+                    foundNonRuntimeType = true;
+                    if (instantiationElem.IsSignatureType)
+                    {
+                        foundSigType = true;
+                    }
+                }
+
+                instantiationRuntimeType[i] = rtInstantiationElem;
+            }
+
+            if (foundNonRuntimeType)
+            {
+                if (foundSigType)
+                    return new SignatureConstructedGenericType(this, instantiation);
+
+                return System.Reflection.Emit.TypeBuilderInstantiation.MakeGenericType(this, (Type[])(instantiation.Clone()));
+            }
+
+            RuntimeType[] genericParameters = GetGenericArgumentsInternal();
+
+            SanityCheckGenericArguments(instantiationRuntimeType, genericParameters);
+
+            Type ret = null;
+            try
+            {
+                ret = new RuntimeTypeHandle(this).Instantiate(instantiationRuntimeType);
+            }
+            catch (TypeLoadException e)
+            {
+                ValidateGenericArguments(this, instantiationRuntimeType, e);
+                throw e;
+            }
+
+            return ret;
+        }
+
+        public override bool IsGenericTypeDefinition
+        {
+            get { return RuntimeTypeHandle.IsGenericTypeDefinition(this); }
+        }
+
+        public override bool IsGenericParameter
+        {
+            get { return RuntimeTypeHandle.IsGenericVariable(this); }
+        }
+
+        public override int GenericParameterPosition
+        {
+            get
+            {
+                if (!IsGenericParameter)
+                    throw new InvalidOperationException(SR.Arg_NotGenericParameter);
+
+                return new RuntimeTypeHandle(this).GetGenericVariableIndex();
+            }
+        }
+
+        public override Type GetGenericTypeDefinition()
+        {
+            if (!IsGenericType)
+                throw new InvalidOperationException(SR.InvalidOperation_NotGenericType);
+
+            return RuntimeTypeHandle.GetGenericTypeDefinition(this);
+        }
+
+        public override bool IsGenericType
+        {
+            get { return RuntimeTypeHandle.HasInstantiation(this); }
+        }
+
+        public override bool IsConstructedGenericType
+        {
+            get { return IsGenericType && !IsGenericTypeDefinition; }
+        }
+
+        public override bool ContainsGenericParameters
+        {
+            get { return GetRootElementType().GetTypeHandleInternal().ContainsGenericVariables(); }
+        }
+
+        public override Type[] GetGenericParameterConstraints()
+        {
+            if (!IsGenericParameter)
+                throw new InvalidOperationException(SR.Arg_NotGenericParameter);
+
+            Type[] constraints = new RuntimeTypeHandle(this).GetConstraints();
+
+            if (constraints == null)
+                constraints = Array.Empty<Type>();
+
+            return constraints;
+        }
+        #endregion
+
+        #region Misc
+        public sealed override bool HasSameMetadataDefinitionAs(MemberInfo other) => HasSameMetadataDefinitionAsCore<RuntimeType>(other);
+
+        public override bool IsTypeDefinition
+        {
+            get { return RuntimeTypeHandle.IsTypeDefinition(this); }
+        }
+
+        public override Type MakePointerType() { return new RuntimeTypeHandle(this).MakePointer(); }
+        public override Type MakeByRefType() { return new RuntimeTypeHandle(this).MakeByRef(); }
+        public override Type MakeArrayType() { return new RuntimeTypeHandle(this).MakeSZArray(); }
+        public override Type MakeArrayType(int rank)
+        {
+            if (rank <= 0)
+                throw new IndexOutOfRangeException();
+
+            return new RuntimeTypeHandle(this).MakeArray(rank);
+        }
+        public override StructLayoutAttribute StructLayoutAttribute
+        {
+            get
+            {
+                return PseudoCustomAttribute.GetStructLayoutCustomAttribute(this);
+            }
+        }
+        #endregion
+
+        #region Invoke Member
+        private const BindingFlags MemberBindingMask = (BindingFlags)0x000000FF;
+        private const BindingFlags InvocationMask = (BindingFlags)0x0000FF00;
+        private const BindingFlags BinderNonCreateInstance = BindingFlags.InvokeMethod | BinderGetSetField | BinderGetSetProperty;
+        private const BindingFlags BinderGetSetProperty = BindingFlags.GetProperty | BindingFlags.SetProperty;
+        private const BindingFlags BinderSetInvokeProperty = BindingFlags.InvokeMethod | BindingFlags.SetProperty;
+        private const BindingFlags BinderGetSetField = BindingFlags.GetField | BindingFlags.SetField;
+        private const BindingFlags BinderSetInvokeField = BindingFlags.SetField | BindingFlags.InvokeMethod;
+        private const BindingFlags BinderNonFieldGetSet = (BindingFlags)0x00FFF300;
+        private const BindingFlags ClassicBindingMask =
+            BindingFlags.InvokeMethod | BindingFlags.GetProperty | BindingFlags.SetProperty |
+            BindingFlags.PutDispProperty | BindingFlags.PutRefDispProperty;
+        private static RuntimeType s_typedRef = (RuntimeType)typeof(TypedReference);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool CanValueSpecialCast(RuntimeType valueType, RuntimeType targetType);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern Object AllocateValueType(RuntimeType type, object value, bool fForceTypeChange);
+
+        internal unsafe Object CheckValue(Object value, Binder binder, CultureInfo culture, BindingFlags invokeAttr)
+        {
+            // this method is used by invocation in reflection to check whether a value can be assigned to type.
+            if (IsInstanceOfType(value))
+            {
+                // Since this cannot be a generic parameter, we use RuntimeTypeHandle.IsValueType here
+                // because it is faster than RuntimeType.IsValueType
+                Debug.Assert(!IsGenericParameter);
+
+                Type type = value.GetType();
+
+                if (!Object.ReferenceEquals(type, this) && RuntimeTypeHandle.IsValueType(this))
+                {
+                    // must be an equivalent type, re-box to the target type
+                    return AllocateValueType(this, value, true);
+                }
+                else
+                {
+                    return value;
+                }
+            }
+
+            // if this is a ByRef get the element type and check if it's compatible
+            bool isByRef = IsByRef;
+            if (isByRef)
+            {
+                RuntimeType elementType = RuntimeTypeHandle.GetElementType(this);
+                if (elementType.IsInstanceOfType(value) || value == null)
+                {
+                    // need to create an instance of the ByRef if null was provided, but only if primitive, enum or value type
+                    return AllocateValueType(elementType, value, false);
+                }
+            }
+            else if (value == null)
+                return value;
+            else if (this == s_typedRef)
+                // everything works for a typedref
+                return value;
+
+            // check the strange ones courtesy of reflection:
+            // - implicit cast between primitives
+            // - enum treated as underlying type
+            // - IntPtr and System.Reflection.Pointer to pointer types
+            bool needsSpecialCast = IsPointer || IsEnum || IsPrimitive;
+            if (needsSpecialCast)
+            {
+                RuntimeType valueType;
+                Pointer pointer = value as Pointer;
+                if (pointer != null)
+                    valueType = (RuntimeType)pointer.GetPointerType();
+                else
+                    valueType = (RuntimeType)value.GetType();
+
+                if (CanValueSpecialCast(valueType, this))
+                {
+                    if (pointer != null)
+                        return pointer.GetPointerValue();
+                    else
+                        return value;
+                }
+            }
+
+            if ((invokeAttr & BindingFlags.ExactBinding) == BindingFlags.ExactBinding)
+                throw new ArgumentException(String.Format(CultureInfo.CurrentUICulture, SR.Arg_ObjObjEx, value.GetType(), this));
+
+            return TryChangeType(value, binder, culture, needsSpecialCast);
+        }
+
+        // Factored out of CheckValue to reduce code complexity.
+        private Object TryChangeType(Object value, Binder binder, CultureInfo culture, bool needsSpecialCast)
+        {
+            if (binder != null && binder != Type.DefaultBinder)
+            {
+                value = binder.ChangeType(value, this, culture);
+                if (IsInstanceOfType(value))
+                    return value;
+                // if this is a ByRef get the element type and check if it's compatible
+                if (IsByRef)
+                {
+                    RuntimeType elementType = RuntimeTypeHandle.GetElementType(this);
+                    if (elementType.IsInstanceOfType(value) || value == null)
+                        return AllocateValueType(elementType, value, false);
+                }
+                else if (value == null)
+                    return value;
+                if (needsSpecialCast)
+                {
+                    RuntimeType valueType;
+                    Pointer pointer = value as Pointer;
+                    if (pointer != null)
+                        valueType = (RuntimeType)pointer.GetPointerType();
+                    else
+                        valueType = (RuntimeType)value.GetType();
+
+                    if (CanValueSpecialCast(valueType, this))
+                    {
+                        if (pointer != null)
+                            return pointer.GetPointerValue();
+                        else
+                            return value;
+                    }
+                }
+            }
+
+            throw new ArgumentException(String.Format(CultureInfo.CurrentUICulture, SR.Arg_ObjObjEx, value.GetType(), this));
+        }
+
+        // GetDefaultMembers
+        // This will return a MemberInfo that has been marked with the [DefaultMemberAttribute]
+        public override MemberInfo[] GetDefaultMembers()
+        {
+            // See if we have cached the default member name
+            MemberInfo[] members = null;
+
+            String defaultMemberName = GetDefaultMemberName();
+            if (defaultMemberName != null)
+            {
+                members = GetMember(defaultMemberName);
+            }
+
+            if (members == null)
+                members = Array.Empty<MemberInfo>();
+
+            return members;
+        }
+
+#if FEATURE_COMINTEROP
+#endif
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        public override Object InvokeMember(
+            String name, BindingFlags bindingFlags, Binder binder, Object target,
+            Object[] providedArgs, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParams)
+        {
+            if (IsGenericParameter)
+                throw new InvalidOperationException(SR.Arg_GenericParameter);
+
+            #region Preconditions
+            if ((bindingFlags & InvocationMask) == 0)
+                // "Must specify binding flags describing the invoke operation required."
+                throw new ArgumentException(SR.Arg_NoAccessSpec, nameof(bindingFlags));
+
+            // Provide a default binding mask if none is provided 
+            if ((bindingFlags & MemberBindingMask) == 0)
+            {
+                bindingFlags |= BindingFlags.Instance | BindingFlags.Public;
+
+                if ((bindingFlags & BindingFlags.CreateInstance) == 0)
+                    bindingFlags |= BindingFlags.Static;
+            }
+
+            // There must not be more named parameters than provided arguments
+            if (namedParams != null)
+            {
+                if (providedArgs != null)
+                {
+                    if (namedParams.Length > providedArgs.Length)
+                        // "Named parameter array can not be bigger than argument array."
+                        throw new ArgumentException(SR.Arg_NamedParamTooBig, nameof(namedParams));
+                }
+                else
+                {
+                    if (namedParams.Length != 0)
+                        // "Named parameter array can not be bigger than argument array."
+                        throw new ArgumentException(SR.Arg_NamedParamTooBig, nameof(namedParams));
+                }
+            }
+            #endregion
+
+            #region COM Interop
+#if FEATURE_COMINTEROP && FEATURE_USE_LCID
+            if (target != null && target.GetType().IsCOMObject)
+            {
+                #region Preconditions
+                if ((bindingFlags & ClassicBindingMask) == 0)
+                    throw new ArgumentException(SR.Arg_COMAccess, nameof(bindingFlags));
+
+                if ((bindingFlags & BindingFlags.GetProperty) != 0 && (bindingFlags & ClassicBindingMask & ~(BindingFlags.GetProperty | BindingFlags.InvokeMethod)) != 0)
+                    throw new ArgumentException(SR.Arg_PropSetGet, nameof(bindingFlags));
+
+                if ((bindingFlags & BindingFlags.InvokeMethod) != 0 && (bindingFlags & ClassicBindingMask & ~(BindingFlags.GetProperty | BindingFlags.InvokeMethod)) != 0)
+                    throw new ArgumentException(SR.Arg_PropSetInvoke, nameof(bindingFlags));
+
+                if ((bindingFlags & BindingFlags.SetProperty) != 0 && (bindingFlags & ClassicBindingMask & ~BindingFlags.SetProperty) != 0)
+                    throw new ArgumentException(SR.Arg_COMPropSetPut, nameof(bindingFlags));
+
+                if ((bindingFlags & BindingFlags.PutDispProperty) != 0 && (bindingFlags & ClassicBindingMask & ~BindingFlags.PutDispProperty) != 0)
+                    throw new ArgumentException(SR.Arg_COMPropSetPut, nameof(bindingFlags));
+
+                if ((bindingFlags & BindingFlags.PutRefDispProperty) != 0 && (bindingFlags & ClassicBindingMask & ~BindingFlags.PutRefDispProperty) != 0)
+                    throw new ArgumentException(SR.Arg_COMPropSetPut, nameof(bindingFlags));
+                #endregion
+
+                {
+                    #region Non-TransparentProxy case
+                    if (name == null)
+                        throw new ArgumentNullException(nameof(name));
+
+                    bool[] isByRef = modifiers == null ? null : modifiers[0].IsByRefArray;
+
+                    // pass LCID_ENGLISH_US if no explicit culture is specified to match the behavior of VB
+                    int lcid = (culture == null ? 0x0409 : culture.LCID);
+
+                    return InvokeDispMethod(name, bindingFlags, target, providedArgs, isByRef, lcid, namedParams);
+                    #endregion
+                }
+            }
+#endif // FEATURE_COMINTEROP && FEATURE_USE_LCID
+            #endregion
+
+            #region Check that any named parameters are not null
+            if (namedParams != null && Array.IndexOf(namedParams, null) != -1)
+                // "Named parameter value must not be null."
+                throw new ArgumentException(SR.Arg_NamedParamNull, nameof(namedParams));
+            #endregion
+
+            int argCnt = (providedArgs != null) ? providedArgs.Length : 0;
+
+            #region Get a Binder
+            if (binder == null)
+                binder = DefaultBinder;
+
+            bool bDefaultBinder = (binder == DefaultBinder);
+            #endregion
+
+            #region Delegate to Activator.CreateInstance
+            if ((bindingFlags & BindingFlags.CreateInstance) != 0)
+            {
+                if ((bindingFlags & BindingFlags.CreateInstance) != 0 && (bindingFlags & BinderNonCreateInstance) != 0)
+                    // "Can not specify both CreateInstance and another access type."
+                    throw new ArgumentException(SR.Arg_CreatInstAccess, nameof(bindingFlags));
+
+                return Activator.CreateInstance(this, bindingFlags, binder, providedArgs, culture);
+            }
+            #endregion
+
+            // PutDispProperty and\or PutRefDispProperty ==> SetProperty.
+            if ((bindingFlags & (BindingFlags.PutDispProperty | BindingFlags.PutRefDispProperty)) != 0)
+                bindingFlags |= BindingFlags.SetProperty;
+
+            #region Name
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+
+            if (name.Length == 0 || name.Equals(@"[DISPID=0]"))
+            {
+                name = GetDefaultMemberName();
+
+                if (name == null)
+                {
+                    // in InvokeMember we always pretend there is a default member if none is provided and we make it ToString
+                    name = "ToString";
+                }
+            }
+            #endregion
+
+            #region GetField or SetField
+            bool IsGetField = (bindingFlags & BindingFlags.GetField) != 0;
+            bool IsSetField = (bindingFlags & BindingFlags.SetField) != 0;
+
+            if (IsGetField || IsSetField)
+            {
+                #region Preconditions
+                if (IsGetField)
+                {
+                    if (IsSetField)
+                        // "Can not specify both Get and Set on a field."
+                        throw new ArgumentException(SR.Arg_FldSetGet, nameof(bindingFlags));
+
+                    if ((bindingFlags & BindingFlags.SetProperty) != 0)
+                        // "Can not specify both GetField and SetProperty."
+                        throw new ArgumentException(SR.Arg_FldGetPropSet, nameof(bindingFlags));
+                }
+                else
+                {
+                    Debug.Assert(IsSetField);
+
+                    if (providedArgs == null)
+                        throw new ArgumentNullException(nameof(providedArgs));
+
+                    if ((bindingFlags & BindingFlags.GetProperty) != 0)
+                        // "Can not specify both SetField and GetProperty."
+                        throw new ArgumentException(SR.Arg_FldSetPropGet, nameof(bindingFlags));
+
+                    if ((bindingFlags & BindingFlags.InvokeMethod) != 0)
+                        // "Can not specify Set on a Field and Invoke on a method."
+                        throw new ArgumentException(SR.Arg_FldSetInvoke, nameof(bindingFlags));
+                }
+                #endregion
+
+                #region Lookup Field
+                FieldInfo selFld = null;
+                FieldInfo[] flds = GetMember(name, MemberTypes.Field, bindingFlags) as FieldInfo[];
+
+                Debug.Assert(flds != null);
+
+                if (flds.Length == 1)
+                {
+                    selFld = flds[0];
+                }
+                else if (flds.Length > 0)
+                {
+                    selFld = binder.BindToField(bindingFlags, flds, IsGetField ? Empty.Value : providedArgs[0], culture);
+                }
+                #endregion
+
+                if (selFld != null)
+                {
+                    #region Invocation on a field
+                    if (selFld.FieldType.IsArray || Object.ReferenceEquals(selFld.FieldType, typeof(System.Array)))
+                    {
+                        #region Invocation of an array Field
+                        int idxCnt;
+
+                        if ((bindingFlags & BindingFlags.GetField) != 0)
+                        {
+                            idxCnt = argCnt;
+                        }
+                        else
+                        {
+                            idxCnt = argCnt - 1;
+                        }
+
+                        if (idxCnt > 0)
+                        {
+                            // Verify that all of the index values are ints
+                            int[] idx = new int[idxCnt];
+                            for (int i = 0; i < idxCnt; i++)
+                            {
+                                try
+                                {
+                                    idx[i] = ((IConvertible)providedArgs[i]).ToInt32(null);
+                                }
+                                catch (InvalidCastException)
+                                {
+                                    throw new ArgumentException(SR.Arg_IndexMustBeInt);
+                                }
+                            }
+
+                            // Set or get the value...
+                            Array a = (Array)selFld.GetValue(target);
+
+                            // Set or get the value in the array
+                            if ((bindingFlags & BindingFlags.GetField) != 0)
+                            {
+                                return a.GetValue(idx);
+                            }
+                            else
+                            {
+                                a.SetValue(providedArgs[idxCnt], idx);
+                                return null;
+                            }
+                        }
+                        #endregion
+                    }
+
+                    if (IsGetField)
+                    {
+                        #region Get the field value
+                        if (argCnt != 0)
+                            throw new ArgumentException(SR.Arg_FldGetArgErr, nameof(bindingFlags));
+
+                        return selFld.GetValue(target);
+                        #endregion
+                    }
+                    else
+                    {
+                        #region Set the field Value
+                        if (argCnt != 1)
+                            throw new ArgumentException(SR.Arg_FldSetArgErr, nameof(bindingFlags));
+
+                        selFld.SetValue(target, providedArgs[0], bindingFlags, binder, culture);
+
+                        return null;
+                        #endregion
+                    }
+                    #endregion
+                }
+
+                if ((bindingFlags & BinderNonFieldGetSet) == 0)
+                    throw new MissingFieldException(FullName, name);
+            }
+            #endregion                    
+
+            #region Caching Logic
+            /*
+            bool useCache = false;
+
+            // Note that when we add something to the cache, we are careful to ensure
+            // that the actual providedArgs matches the parameters of the method.  Otherwise,
+            // some default argument processing has occurred.  We don't want anyone
+            // else with the same (insufficient) number of actual arguments to get a
+            // cache hit because then they would bypass the default argument processing
+            // and the invocation would fail.
+            if (bDefaultBinder && namedParams == null && argCnt < 6)
+                useCache = true;
+
+            if (useCache)
+            {
+                MethodBase invokeMethod = GetMethodFromCache (name, bindingFlags, argCnt, providedArgs);
+
+                if (invokeMethod != null)
+                    return ((MethodInfo) invokeMethod).Invoke(target, bindingFlags, binder, providedArgs, culture);
+            }
+            */
+            #endregion
+
+            #region Property PreConditions
+            // @Legacy - This is RTM behavior
+            bool isGetProperty = (bindingFlags & BindingFlags.GetProperty) != 0;
+            bool isSetProperty = (bindingFlags & BindingFlags.SetProperty) != 0;
+
+            if (isGetProperty || isSetProperty)
+            {
+                #region Preconditions
+                if (isGetProperty)
+                {
+                    Debug.Assert(!IsSetField);
+
+                    if (isSetProperty)
+                        throw new ArgumentException(SR.Arg_PropSetGet, nameof(bindingFlags));
+                }
+                else
+                {
+                    Debug.Assert(isSetProperty);
+
+                    Debug.Assert(!IsGetField);
+
+                    if ((bindingFlags & BindingFlags.InvokeMethod) != 0)
+                        throw new ArgumentException(SR.Arg_PropSetInvoke, nameof(bindingFlags));
+                }
+                #endregion
+            }
+            #endregion
+
+            MethodInfo[] finalists = null;
+            MethodInfo finalist = null;
+
+            #region BindingFlags.InvokeMethod
+            if ((bindingFlags & BindingFlags.InvokeMethod) != 0)
+            {
+                #region Lookup Methods
+                MethodInfo[] semiFinalists = GetMember(name, MemberTypes.Method, bindingFlags) as MethodInfo[];
+                List<MethodInfo> results = null;
+
+                for (int i = 0; i < semiFinalists.Length; i++)
+                {
+                    MethodInfo semiFinalist = semiFinalists[i];
+                    Debug.Assert(semiFinalist != null);
+
+                    if (!FilterApplyMethodInfo((RuntimeMethodInfo)semiFinalist, bindingFlags, CallingConventions.Any, new Type[argCnt]))
+                        continue;
+
+                    if (finalist == null)
+                    {
+                        finalist = semiFinalist;
+                    }
+                    else
+                    {
+                        if (results == null)
+                        {
+                            results = new List<MethodInfo>(semiFinalists.Length);
+                            results.Add(finalist);
+                        }
+
+                        results.Add(semiFinalist);
+                    }
+                }
+
+                if (results != null)
+                {
+                    Debug.Assert(results.Count > 1);
+                    finalists = new MethodInfo[results.Count];
+                    results.CopyTo(finalists);
+                }
+                #endregion
+            }
+            #endregion
+
+            Debug.Assert(finalists == null || finalist != null);
+
+            #region BindingFlags.GetProperty or BindingFlags.SetProperty
+            if (finalist == null && isGetProperty || isSetProperty)
+            {
+                #region Lookup Property
+                PropertyInfo[] semiFinalists = GetMember(name, MemberTypes.Property, bindingFlags) as PropertyInfo[];
+                List<MethodInfo> results = null;
+
+                for (int i = 0; i < semiFinalists.Length; i++)
+                {
+                    MethodInfo semiFinalist = null;
+
+                    if (isSetProperty)
+                    {
+                        semiFinalist = semiFinalists[i].GetSetMethod(true);
+                    }
+                    else
+                    {
+                        semiFinalist = semiFinalists[i].GetGetMethod(true);
+                    }
+
+                    if (semiFinalist == null)
+                        continue;
+
+                    if (!FilterApplyMethodInfo((RuntimeMethodInfo)semiFinalist, bindingFlags, CallingConventions.Any, new Type[argCnt]))
+                        continue;
+
+                    if (finalist == null)
+                    {
+                        finalist = semiFinalist;
+                    }
+                    else
+                    {
+                        if (results == null)
+                        {
+                            results = new List<MethodInfo>(semiFinalists.Length);
+                            results.Add(finalist);
+                        }
+
+                        results.Add(semiFinalist);
+                    }
+                }
+
+                if (results != null)
+                {
+                    Debug.Assert(results.Count > 1);
+                    finalists = new MethodInfo[results.Count];
+                    results.CopyTo(finalists);
+                }
+                #endregion            
+            }
+            #endregion
+
+            if (finalist != null)
+            {
+                #region Invoke
+                if (finalists == null &&
+                    argCnt == 0 &&
+                    finalist.GetParametersNoCopy().Length == 0 &&
+                    (bindingFlags & BindingFlags.OptionalParamBinding) == 0)
+                {
+                    //if (useCache && argCnt == props[0].GetParameters().Length)
+                    //    AddMethodToCache(name, bindingFlags, argCnt, providedArgs, props[0]);
+
+                    return finalist.Invoke(target, bindingFlags, binder, providedArgs, culture);
+                }
+
+                if (finalists == null)
+                    finalists = new MethodInfo[] { finalist };
+
+                if (providedArgs == null)
+                    providedArgs = Array.Empty<Object>();
+
+                Object state = null;
+
+
+                MethodBase invokeMethod = null;
+
+                try { invokeMethod = binder.BindToMethod(bindingFlags, finalists, ref providedArgs, modifiers, culture, namedParams, out state); }
+                catch (MissingMethodException) { }
+
+                if (invokeMethod == null)
+                    throw new MissingMethodException(FullName, name);
+
+                //if (useCache && argCnt == invokeMethod.GetParameters().Length)
+                //    AddMethodToCache(name, bindingFlags, argCnt, providedArgs, invokeMethod);
+
+                Object result = ((MethodInfo)invokeMethod).Invoke(target, bindingFlags, binder, providedArgs, culture);
+
+                if (state != null)
+                    binder.ReorderArgumentArray(ref providedArgs, state);
+
+                return result;
+                #endregion
+            }
+
+            throw new MissingMethodException(FullName, name);
+        }
+        #endregion
+
+        #endregion
+
+        #region Object Overrides
+        public override bool Equals(object obj)
+        {
+            // ComObjects are identified by the instance of the Type object and not the TypeHandle.
+            return obj == (object)this;
+        }
+
+        public override int GetHashCode()
+        {
+            return RuntimeHelpers.GetHashCode(this);
+        }
+
+        public override String ToString()
+        {
+            return GetCachedName(TypeNameKind.ToString);
+        }
+        #endregion
+
+        #region ICloneable
+        public Object Clone()
+        {
+            return this;
+        }
+        #endregion
+
+        #region ICustomAttributeProvider
+        public override Object[] GetCustomAttributes(bool inherit)
+        {
+            return CustomAttribute.GetCustomAttributes(this, RuntimeType.ObjectType, inherit);
+        }
+
+        public override Object[] GetCustomAttributes(Type attributeType, bool inherit)
+        {
+            if ((object)attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.GetCustomAttributes(this, attributeRuntimeType, inherit);
+        }
+
+        public override bool IsDefined(Type attributeType, bool inherit)
+        {
+            if ((object)attributeType == null)
+                throw new ArgumentNullException(nameof(attributeType));
+
+            RuntimeType attributeRuntimeType = attributeType.UnderlyingSystemType as RuntimeType;
+
+            if (attributeRuntimeType == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
+
+            return CustomAttribute.IsDefined(this, attributeRuntimeType, inherit);
+        }
+
+        public override IList<CustomAttributeData> GetCustomAttributesData()
+        {
+            return CustomAttributeData.GetCustomAttributesInternal(this);
+        }
+        #endregion
+
+        #region MemberInfo Overrides
+        public override String Name
+        {
+            get
+            {
+                return GetCachedName(TypeNameKind.Name);
+            }
+        }
+
+        // This is used by the ToString() overrides of all reflection types. The legacy behavior has the following problems:
+        //  1. Use only Name for nested types, which can be confused with global types and generic parameters of the same name.
+        //  2. Use only Name for generic parameters, which can be confused with nested types and global types of the same name.
+        //  3. Remove the namespace ("System") for all primitive types, which is not language neutral.
+        //  4. MethodBase.ToString() use "ByRef" for byref parameters which is different than Type.ToString().
+        //  5. ConstructorInfo.ToString() outputs "Void" as the return type. Why Void?
+        // Since it could be a breaking changes to fix these legacy behaviors, we only use the better and more unambiguous format
+        // in serialization (MemberInfoSerializationHolder).
+        internal override string FormatTypeName(bool serialization)
+        {
+            if (serialization)
+            {
+                return GetCachedName(TypeNameKind.SerializationName);
+            }
+            else
+            {
+                Type elementType = GetRootElementType();
+
+                // Legacy: this doesn't make sense, why use only Name for nested types but otherwise
+                // ToString() which contains namespace.
+                if (elementType.IsNested)
+                    return Name;
+
+                string typeName = ToString();
+
+                // Legacy: why removing "System"? Is it just because C# has keywords for these types?
+                // If so why don't we change it to lower case to match the C# keyword casing?
+                if (elementType.IsPrimitive ||
+                    elementType == typeof(void) ||
+                    elementType == typeof(TypedReference))
+                {
+                    typeName = typeName.Substring(@"System.".Length);
+                }
+
+                return typeName;
+            }
+        }
+
+        private string GetCachedName(TypeNameKind kind)
+        {
+            return Cache.GetName(kind);
+        }
+
+        public override MemberTypes MemberType
+        {
+            get
+            {
+                if (this.IsPublic || this.IsNotPublic)
+                    return MemberTypes.TypeInfo;
+                else
+                    return MemberTypes.NestedType;
+            }
+        }
+
+        public override Type DeclaringType
+        {
+            get
+            {
+                return Cache.GetEnclosingType();
+            }
+        }
+
+        public override Type ReflectedType
+        {
+            get
+            {
+                return DeclaringType;
+            }
+        }
+
+        public override int MetadataToken
+        {
+            get
+            {
+                return RuntimeTypeHandle.GetToken(this);
+            }
+        }
+        #endregion
+
+        #region Legacy Internal
+        private void CreateInstanceCheckThis()
+        {
+            if (this is ReflectionOnlyType)
+                throw new ArgumentException(SR.Arg_ReflectionOnlyInvoke);
+
+            if (ContainsGenericParameters)
+                throw new ArgumentException(
+                    SR.Format(SR.Acc_CreateGenericEx, this));
+
+            Type elementType = this.GetRootElementType();
+
+            if (Object.ReferenceEquals(elementType, typeof(ArgIterator)))
+                throw new NotSupportedException(SR.Acc_CreateArgIterator);
+
+            if (Object.ReferenceEquals(elementType, typeof(void)))
+                throw new NotSupportedException(SR.Acc_CreateVoid);
+        }
+
+        internal Object CreateInstanceImpl(
+            BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
+        {
+            CreateInstanceCheckThis();
+
+            Object server = null;
+
+            if (args == null)
+                args = Array.Empty<Object>();
+
+            int argCnt = args.Length;
+
+            // Without a binder we need to do use the default binder...
+            if (binder == null)
+                binder = DefaultBinder;
+
+            // deal with the __COMObject case first. It is very special because from a reflection point of view it has no ctors
+            // so a call to GetMemberCons would fail
+            bool publicOnly = (bindingAttr & BindingFlags.NonPublic) == 0;
+            bool wrapExceptions = (bindingAttr & BindingFlags.DoNotWrapExceptions) == 0;
+            if (argCnt == 0 && (bindingAttr & BindingFlags.Public) != 0 && (bindingAttr & BindingFlags.Instance) != 0
+                && (IsGenericCOMObjectImpl() || IsValueType))
+            {
+                server = CreateInstanceDefaultCtor(publicOnly, false, true, wrapExceptions);
+            }
+            else
+            {
+                ConstructorInfo[] candidates = GetConstructors(bindingAttr);
+                List<MethodBase> matches = new List<MethodBase>(candidates.Length);
+
+                // We cannot use Type.GetTypeArray here because some of the args might be null
+                Type[] argsType = new Type[argCnt];
+                for (int i = 0; i < argCnt; i++)
+                {
+                    if (args[i] != null)
+                    {
+                        argsType[i] = args[i].GetType();
+                    }
+                }
+
+                for (int i = 0; i < candidates.Length; i++)
+                {
+                    if (FilterApplyConstructorInfo((RuntimeConstructorInfo)candidates[i], bindingAttr, CallingConventions.Any, argsType))
+                        matches.Add(candidates[i]);
+                }
+
+                MethodBase[] cons = new MethodBase[matches.Count];
+                matches.CopyTo(cons);
+                if (cons != null && cons.Length == 0)
+                    cons = null;
+
+                if (cons == null)
+                {
+                    throw new MissingMethodException(SR.Format(SR.MissingConstructor_Name, FullName));
+                }
+
+                MethodBase invokeMethod;
+                Object state = null;
+
+                try
+                {
+                    invokeMethod = binder.BindToMethod(bindingAttr, cons, ref args, null, culture, null, out state);
+                }
+                catch (MissingMethodException) { invokeMethod = null; }
+
+                if (invokeMethod == null)
+                {
+                    throw new MissingMethodException(SR.Format(SR.MissingConstructor_Name, FullName));
+                }
+
+                if (invokeMethod.GetParametersNoCopy().Length == 0)
+                {
+                    if (args.Length != 0)
+                    {
+                        Debug.Assert((invokeMethod.CallingConvention & CallingConventions.VarArgs) ==
+                                            CallingConventions.VarArgs);
+                        throw new NotSupportedException(String.Format(CultureInfo.CurrentCulture,
+                            SR.NotSupported_CallToVarArg));
+                    }
+
+                    // fast path??
+                    server = Activator.CreateInstance(this, nonPublic: true, wrapExceptions: wrapExceptions);
+                }
+                else
+                {
+                    server = ((ConstructorInfo)invokeMethod).Invoke(bindingAttr, binder, args, culture);
+                    if (state != null)
+                        binder.ReorderArgumentArray(ref args, state);
+                }
+            }
+
+            return server;
+        }
+
+        // the cache entry
+        private class ActivatorCacheEntry
+        {
+            // the type to cache
+            internal readonly RuntimeType m_type;
+            // the delegate containing the call to the ctor, will be replaced by an IntPtr to feed a calli with
+            internal volatile CtorDelegate m_ctor;
+            internal readonly RuntimeMethodHandleInternal m_hCtorMethodHandle;
+            internal readonly MethodAttributes m_ctorAttributes;
+            // Lazy initialization was performed
+            internal volatile bool m_bFullyInitialized;
+
+            internal ActivatorCacheEntry(RuntimeType t, RuntimeMethodHandleInternal rmh)
+            {
+                m_type = t;
+                m_hCtorMethodHandle = rmh;
+                if (!m_hCtorMethodHandle.IsNullHandle())
+                    m_ctorAttributes = RuntimeMethodHandle.GetAttributes(m_hCtorMethodHandle);
+            }
+        }
+
+        //ActivatorCache
+        private class ActivatorCache
+        {
+            private const int CACHE_SIZE = 16;
+            private volatile int hash_counter; //Counter for wrap around
+            private readonly ActivatorCacheEntry[] cache = new ActivatorCacheEntry[CACHE_SIZE];
+
+            private volatile ConstructorInfo delegateCtorInfo;
+
+            private void InitializeDelegateCreator()
+            {
+                ConstructorInfo ctorInfo = typeof(CtorDelegate).GetConstructor(new Type[] { typeof(Object), typeof(IntPtr) });
+                delegateCtorInfo = ctorInfo; // this assignment should be last
+            }
+
+            private void InitializeCacheEntry(ActivatorCacheEntry ace)
+            {
+                if (!ace.m_type.IsValueType)
+                {
+                    Debug.Assert(!ace.m_hCtorMethodHandle.IsNullHandle(), "Expected the default ctor method handle for a reference type.");
+
+                    if (delegateCtorInfo == null)
+                        InitializeDelegateCreator();
+
+                    // No synchronization needed here. In the worst case we create extra garbage
+                    CtorDelegate ctor = (CtorDelegate)delegateCtorInfo.Invoke(new Object[] { null, RuntimeMethodHandle.GetFunctionPointer(ace.m_hCtorMethodHandle) });
+                    ace.m_ctor = ctor;
+                }
+                ace.m_bFullyInitialized = true;
+            }
+
+            internal ActivatorCacheEntry GetEntry(RuntimeType t)
+            {
+                int index = hash_counter;
+                for (int i = 0; i < CACHE_SIZE; i++)
+                {
+                    ActivatorCacheEntry ace = Volatile.Read(ref cache[index]);
+                    if (ace != null && ace.m_type == t) //check for type match..
+                    {
+                        if (!ace.m_bFullyInitialized)
+                            InitializeCacheEntry(ace);
+                        return ace;
+                    }
+                    index = (index + 1) & (ActivatorCache.CACHE_SIZE - 1);
+                }
+                return null;
+            }
+
+            internal void SetEntry(ActivatorCacheEntry ace)
+            {
+                // fill the array backwards to hit the most recently filled entries first in GetEntry
+                int index = (hash_counter - 1) & (ActivatorCache.CACHE_SIZE - 1);
+                hash_counter = index;
+                Volatile.Write(ref cache[index], ace);
+            }
+        }
+
+        private static volatile ActivatorCache s_ActivatorCache;
+
+        // the slow path of CreateInstanceDefaultCtor
+        internal Object CreateInstanceSlow(bool publicOnly, bool wrapExceptions, bool skipCheckThis, bool fillCache)
+        {
+            RuntimeMethodHandleInternal runtime_ctor = default(RuntimeMethodHandleInternal);
+            bool bCanBeCached = false;
+
+            if (!skipCheckThis)
+                CreateInstanceCheckThis();
+
+            Object instance = RuntimeTypeHandle.CreateInstance(this, publicOnly, wrapExceptions, ref bCanBeCached, ref runtime_ctor);
+
+            if (bCanBeCached && fillCache)
+            {
+                ActivatorCache activatorCache = s_ActivatorCache;
+                if (activatorCache == null)
+                {
+                    // No synchronization needed here. In the worst case we create extra garbage
+                    activatorCache = new ActivatorCache();
+                    s_ActivatorCache = activatorCache;
+                }
+
+                // cache the ctor
+                ActivatorCacheEntry ace = new ActivatorCacheEntry(this, runtime_ctor);
+                activatorCache.SetEntry(ace);
+            }
+
+            return instance;
+        }
+
+        // Helper to invoke the default (parameterless) ctor.
+        // fillCache is set in the SL2/3 compat mode or when called from Marshal.PtrToStructure.
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        internal Object CreateInstanceDefaultCtor(bool publicOnly, bool skipCheckThis, bool fillCache, bool wrapExceptions)
+        {
+            if (GetType() == typeof(ReflectionOnlyType))
+                throw new InvalidOperationException(SR.InvalidOperation_NotAllowedInReflectionOnly);
+
+            ActivatorCache activatorCache = s_ActivatorCache;
+            if (activatorCache != null)
+            {
+                ActivatorCacheEntry ace = activatorCache.GetEntry(this);
+                if (ace != null)
+                {
+                    if (publicOnly)
+                    {
+                        if (ace.m_ctor != null &&
+                            (ace.m_ctorAttributes & MethodAttributes.MemberAccessMask) != MethodAttributes.Public)
+                        {
+                            throw new MissingMethodException(SR.Arg_NoDefCTor);
+                        }
+                    }
+
+                    // Allocate empty object
+                    Object instance = RuntimeTypeHandle.Allocate(this);
+
+                    // if m_ctor is null, this type doesn't have a default ctor
+                    Debug.Assert(ace.m_ctor != null || this.IsValueType);
+
+                    if (ace.m_ctor != null)
+                    {
+                        // Call ctor (value types wont have any)
+                        try
+                        {
+                            ace.m_ctor(instance);
+                        }
+                        catch (Exception e) when (wrapExceptions)
+                        {
+                            throw new TargetInvocationException(e);
+                        }
+                    }
+                    return instance;
+                }
+            }
+            return CreateInstanceSlow(publicOnly, wrapExceptions, skipCheckThis, fillCache);
+        }
+
+        internal void InvalidateCachedNestedType()
+        {
+            Cache.InvalidateCachedNestedType();
+        }
+
+        internal bool IsGenericCOMObjectImpl()
+        {
+            return RuntimeTypeHandle.IsComObject(this, true);
+        }
+        #endregion
+
+        #region Legacy internal static
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern Object _CreateEnum(RuntimeType enumType, long value);
+        internal static Object CreateEnum(RuntimeType enumType, long value)
+        {
+            return _CreateEnum(enumType, value);
+        }
+
+#if FEATURE_COMINTEROP       
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern Object InvokeDispMethod(
+            String name, BindingFlags invokeAttr, Object target, Object[] args,
+            bool[] byrefModifiers, int culture, String[] namedParameters);
+#endif // FEATURE_COMINTEROP        
+
+#if FEATURE_COMINTEROP_UNMANAGED_ACTIVATION
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Type GetTypeFromProgIDImpl(String progID, String server, bool throwOnError);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Type GetTypeFromCLSIDImpl(Guid clsid, String server, bool throwOnError);
+#else // FEATURE_COMINTEROP_UNMANAGED_ACTIVATION
+        internal static Type GetTypeFromProgIDImpl(String progID, String server, bool throwOnError)
+        {
+            throw new NotImplementedException("CoreCLR_REMOVED -- Unmanaged activation removed");
+        }
+
+        internal static Type GetTypeFromCLSIDImpl(Guid clsid, String server, bool throwOnError)
+        {
+            throw new NotImplementedException("CoreCLR_REMOVED -- Unmanaged activation removed"); 
+        }
+#endif // FEATURE_COMINTEROP_UNMANAGED_ACTIVATION
+
+        #endregion
+
+        #region COM
+        #endregion
+    }
+
+    // this is the introspection only type. This type overrides all the functions with runtime semantics
+    // and throws an exception.
+    // The idea behind this type is that it relieves RuntimeType from doing honerous checks about ReflectionOnly
+    // context.
+    // This type should not derive from RuntimeType but it's doing so for convinience.
+    // That should not present a security threat though it is risky as a direct call to one of the base method
+    // method (RuntimeType) and an instance of this type will work around the reason to have this type in the 
+    // first place. However given RuntimeType is not public all its methods are protected and require full trust
+    // to be accessed
+    internal class ReflectionOnlyType : RuntimeType
+    {
+        private ReflectionOnlyType() { }
+
+        // always throw
+        public override RuntimeTypeHandle TypeHandle
+        {
+            get
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_NotAllowedInReflectionOnly);
+            }
+        }
+    }
+
+    #region Library
+    internal unsafe struct MdUtf8String
+    {
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe bool EqualsCaseSensitive(void* szLhs, void* szRhs, int cSz);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern unsafe bool EqualsCaseInsensitive(void* szLhs, void* szRhs, int cSz);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern unsafe uint HashCaseInsensitive(void* sz, int cSz);
+
+        private static int GetUtf8StringByteLength(void* pUtf8String)
+        {
+            int len = 0;
+
+            unsafe
+            {
+                byte* pItr = (byte*)pUtf8String;
+
+                while (*pItr != 0)
+                {
+                    len++;
+                    pItr++;
+                }
+            }
+
+            return len;
+        }
+
+        private void* m_pStringHeap;        // This is the raw UTF8 string.
+        private int m_StringHeapByteLength;
+
+        internal MdUtf8String(void* pStringHeap)
+        {
+            m_pStringHeap = pStringHeap;
+            if (pStringHeap != null)
+            {
+                m_StringHeapByteLength = GetUtf8StringByteLength(pStringHeap);
+            }
+            else
+            {
+                m_StringHeapByteLength = 0;
+            }
+        }
+
+        internal unsafe MdUtf8String(void* pUtf8String, int cUtf8String)
+        {
+            m_pStringHeap = pUtf8String;
+            m_StringHeapByteLength = cUtf8String;
+        }
+
+        internal unsafe bool Equals(MdUtf8String s)
+        {
+            if (m_pStringHeap == null)
+            {
+                return s.m_StringHeapByteLength == 0;
+            }
+            if ((s.m_StringHeapByteLength == m_StringHeapByteLength) && (m_StringHeapByteLength != 0))
+            {
+                return MdUtf8String.EqualsCaseSensitive(s.m_pStringHeap, m_pStringHeap, m_StringHeapByteLength);
+            }
+            return false;
+        }
+
+        internal unsafe bool EqualsCaseInsensitive(MdUtf8String s)
+        {
+            if (m_pStringHeap == null)
+            {
+                return s.m_StringHeapByteLength == 0;
+            }
+            if ((s.m_StringHeapByteLength == m_StringHeapByteLength) && (m_StringHeapByteLength != 0))
+            {
+                return MdUtf8String.EqualsCaseInsensitive(s.m_pStringHeap, m_pStringHeap, m_StringHeapByteLength);
+            }
+            return false;
+        }
+
+        internal unsafe uint HashCaseInsensitive()
+        {
+            return MdUtf8String.HashCaseInsensitive(m_pStringHeap, m_StringHeapByteLength);
+        }
+
+        public override string ToString()
+        {
+            unsafe
+            {
+                byte* buf = stackalloc byte[m_StringHeapByteLength];
+                byte* pItr = (byte*)m_pStringHeap;
+
+                for (int currentPos = 0; currentPos < m_StringHeapByteLength; currentPos++)
+                {
+                    buf[currentPos] = *pItr;
+                    pItr++;
+                }
+
+                if (m_StringHeapByteLength == 0)
+                    return "";
+
+                int cResult = Encoding.UTF8.GetCharCount(buf, m_StringHeapByteLength);
+                char* result = stackalloc char[cResult];
+                Encoding.UTF8.GetChars(buf, m_StringHeapByteLength, result, cResult);
+                return new string(result, 0, cResult);
+            }
+        }
+    }
+    #endregion
+}
+
+namespace System.Reflection
+{
+    // Reliable hashtable thread safe for multiple readers and single writer. Note that the reliability goes together with thread
+    // safety. Thread safety for multiple readers requires atomic update of the state that also makes makes the table
+    // reliable in the presence of asynchronous exceptions.
+    internal struct CerHashtable<K, V> where K : class
+    {
+        private class Table
+        {
+            // Note that m_keys and m_values arrays are immutable to allow lock-free reads. A new instance 
+            // of CerHashtable has to be allocated to grow the size of the hashtable.
+            internal K[] m_keys;
+            internal V[] m_values;
+            internal int m_count;
+
+            internal Table(int size)
+            {
+                size = HashHelpers.GetPrime(size);
+                m_keys = new K[size];
+                m_values = new V[size];
+            }
+
+            internal void Insert(K key, V value)
+            {
+                int hashcode = GetHashCodeHelper(key);
+                if (hashcode < 0)
+                    hashcode = ~hashcode;
+
+                K[] keys = m_keys;
+                int index = hashcode % keys.Length;
+
+                while (true)
+                {
+                    K hit = keys[index];
+
+                    if (hit == null)
+                    {
+                        m_count++;
+                        m_values[index] = value;
+
+                        // This volatile write has to be last. It is going to publish the result atomically.
+                        //
+                        // Note that incrementing the count or setting the value does not do any harm without setting the key. The inconsistency will be ignored 
+                        // and it will go away completely during next rehash.
+                        Volatile.Write(ref keys[index], key);
+
+                        break;
+                    }
+                    else
+                    {
+                        Debug.Assert(!hit.Equals(key), "Key was already in CerHashtable!  Potential race condition (or bug) in the Reflection cache?");
+
+                        index++;
+                        if (index >= keys.Length)
+                            index -= keys.Length;
+                    }
+                }
+            }
+        }
+
+        private Table m_Table;
+
+        private const int MinSize = 7;
+
+        private static int GetHashCodeHelper(K key)
+        {
+            string sKey = key as string;
+
+            // For strings we don't want the key to differ across domains as CerHashtable might be shared.
+            if (sKey == null)
+            {
+                return key.GetHashCode();
+            }
+            else
+            {
+                return sKey.GetLegacyNonRandomizedHashCode();
+            }
+        }
+
+        private void Rehash(int newSize)
+        {
+            Table newTable = new Table(newSize);
+
+            Table oldTable = m_Table;
+            if (oldTable != null)
+            {
+                K[] keys = oldTable.m_keys;
+                V[] values = oldTable.m_values;
+
+                for (int i = 0; i < keys.Length; i++)
+                {
+                    K key = keys[i];
+
+                    if (key != null)
+                    {
+                        newTable.Insert(key, values[i]);
+                    }
+                }
+            }
+
+            // Publish the new table atomically
+            Volatile.Write(ref m_Table, newTable);
+        }
+
+        internal V this[K key]
+        {
+            set
+            {
+                Table table = m_Table;
+
+                if (table != null)
+                {
+                    int requiredSize = 2 * (table.m_count + 1);
+                    if (requiredSize >= table.m_keys.Length)
+                        Rehash(requiredSize);
+                }
+                else
+                {
+                    Rehash(MinSize);
+                }
+
+                m_Table.Insert(key, value);
+            }
+            get
+            {
+                Table table = Volatile.Read(ref m_Table);
+                if (table == null)
+                    return default(V);
+
+                int hashcode = GetHashCodeHelper(key);
+                if (hashcode < 0)
+                    hashcode = ~hashcode;
+
+                K[] keys = table.m_keys;
+                int index = hashcode % keys.Length;
+
+                while (true)
+                {
+                    // This volatile read has to be first. It is reading the atomically published result.
+                    K hit = Volatile.Read(ref keys[index]);
+
+                    if (hit != null)
+                    {
+                        if (hit.Equals(key))
+                            return table.m_values[index];
+
+                        index++;
+                        if (index >= keys.Length)
+                            index -= keys.Length;
+                    }
+                    else
+                    {
+                        return default(V);
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncMethodBuilder.cs b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncMethodBuilder.cs
new file mode 100644
index 0000000000..f247d10ffc
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncMethodBuilder.cs
@@ -0,0 +1,1063 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// Compiler-targeted types that build tasks for use as the return types of asynchronous methods.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Diagnostics;
+using System.Diagnostics.Tracing;
+using System.Reflection;
+using System.Runtime.ExceptionServices;
+#if FEATURE_COMINTEROP
+using System.Runtime.InteropServices.WindowsRuntime;
+#endif // FEATURE_COMINTEROP
+using System.Threading;
+using System.Threading.Tasks;
+using System.Text;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Provides a builder for asynchronous methods that return void.
+    /// This type is intended for compiler use only.
+    /// </summary>
+    public struct AsyncVoidMethodBuilder
+    {
+        /// <summary>The synchronization context associated with this operation.</summary>
+        private SynchronizationContext _synchronizationContext;
+        /// <summary>The builder this void builder wraps.</summary>
+        private AsyncTaskMethodBuilder _builder; // mutable struct: must not be readonly
+
+        /// <summary>Initializes a new <see cref="AsyncVoidMethodBuilder"/>.</summary>
+        /// <returns>The initialized <see cref="AsyncVoidMethodBuilder"/>.</returns>
+        public static AsyncVoidMethodBuilder Create()
+        {
+            SynchronizationContext sc = SynchronizationContext.Current;
+            sc?.OperationStarted();
+            return new AsyncVoidMethodBuilder() { _synchronizationContext = sc };
+        }
+
+        /// <summary>Initiates the builder's execution with the associated state machine.</summary>
+        /// <typeparam name="TStateMachine">Specifies the type of the state machine.</typeparam>
+        /// <param name="stateMachine">The state machine instance, passed by reference.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="stateMachine"/> argument was null (Nothing in Visual Basic).</exception>
+        [DebuggerStepThrough]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Start<TStateMachine>(ref TStateMachine stateMachine) where TStateMachine : IAsyncStateMachine =>
+            AsyncMethodBuilderCore.Start(ref stateMachine);
+
+        /// <summary>Associates the builder with the state machine it represents.</summary>
+        /// <param name="stateMachine">The heap-allocated state machine object.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="stateMachine"/> argument was null (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.InvalidOperationException">The builder is incorrectly initialized.</exception>
+        public void SetStateMachine(IAsyncStateMachine stateMachine) =>
+            _builder.SetStateMachine(stateMachine);
+
+        /// <summary>
+        /// Schedules the specified state machine to be pushed forward when the specified awaiter completes.
+        /// </summary>
+        /// <typeparam name="TAwaiter">Specifies the type of the awaiter.</typeparam>
+        /// <typeparam name="TStateMachine">Specifies the type of the state machine.</typeparam>
+        /// <param name="awaiter">The awaiter.</param>
+        /// <param name="stateMachine">The state machine.</param>
+        public void AwaitOnCompleted<TAwaiter, TStateMachine>(
+            ref TAwaiter awaiter, ref TStateMachine stateMachine)
+            where TAwaiter : INotifyCompletion
+            where TStateMachine : IAsyncStateMachine =>
+            _builder.AwaitOnCompleted(ref awaiter, ref stateMachine);
+
+        /// <summary>
+        /// Schedules the specified state machine to be pushed forward when the specified awaiter completes.
+        /// </summary>
+        /// <typeparam name="TAwaiter">Specifies the type of the awaiter.</typeparam>
+        /// <typeparam name="TStateMachine">Specifies the type of the state machine.</typeparam>
+        /// <param name="awaiter">The awaiter.</param>
+        /// <param name="stateMachine">The state machine.</param>
+        public void AwaitUnsafeOnCompleted<TAwaiter, TStateMachine>(
+            ref TAwaiter awaiter, ref TStateMachine stateMachine)
+            where TAwaiter : ICriticalNotifyCompletion
+            where TStateMachine : IAsyncStateMachine =>
+            _builder.AwaitUnsafeOnCompleted(ref awaiter, ref stateMachine);
+
+        /// <summary>Completes the method builder successfully.</summary>
+        public void SetResult()
+        {
+            if (AsyncCausalityTracer.LoggingOn)
+            {
+                AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, this.Task.Id, AsyncCausalityStatus.Completed);
+            }
+
+            // Mark the builder as completed.  As this is a void-returning method, this mostly
+            // doesn't matter, but it can affect things like debug events related to finalization.
+            _builder.SetResult();
+
+            if (_synchronizationContext != null)
+            {
+                NotifySynchronizationContextOfCompletion();
+            }
+        }
+
+        /// <summary>Faults the method builder with an exception.</summary>
+        /// <param name="exception">The exception that is the cause of this fault.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="exception"/> argument is null (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.InvalidOperationException">The builder is not initialized.</exception>
+        public void SetException(Exception exception)
+        {
+            if (exception == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.exception);
+            }
+
+            if (AsyncCausalityTracer.LoggingOn)
+            {
+                AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, this.Task.Id, AsyncCausalityStatus.Error);
+            }
+
+            if (_synchronizationContext != null)
+            {
+                // If we captured a synchronization context, Post the throwing of the exception to it 
+                // and decrement its outstanding operation count.
+                try
+                {
+                    AsyncMethodBuilderCore.ThrowAsync(exception, targetContext: _synchronizationContext);
+                }
+                finally
+                {
+                    NotifySynchronizationContextOfCompletion();
+                }
+            }
+            else
+            {
+                // Otherwise, queue the exception to be thrown on the ThreadPool.  This will
+                // result in a crash unless legacy exception behavior is enabled by a config
+                // file or a CLR host.
+                AsyncMethodBuilderCore.ThrowAsync(exception, targetContext: null);
+            }
+
+            // The exception was propagated already; we don't need or want to fault the builder, just mark it as completed.
+            _builder.SetResult();
+        }
+
+        /// <summary>Notifies the current synchronization context that the operation completed.</summary>
+        private void NotifySynchronizationContextOfCompletion()
+        {
+            Debug.Assert(_synchronizationContext != null, "Must only be used with a non-null context.");
+            try
+            {
+                _synchronizationContext.OperationCompleted();
+            }
+            catch (Exception exc)
+            {
+                // If the interaction with the SynchronizationContext goes awry,
+                // fall back to propagating on the ThreadPool.
+                AsyncMethodBuilderCore.ThrowAsync(exc, targetContext: null);
+            }
+        }
+
+        /// <summary>Lazily instantiate the Task in a non-thread-safe manner.</summary>
+        private Task Task => _builder.Task;
+
+        /// <summary>
+        /// Gets an object that may be used to uniquely identify this builder to the debugger.
+        /// </summary>
+        /// <remarks>
+        /// This property lazily instantiates the ID in a non-thread-safe manner.  
+        /// It must only be used by the debugger and AsyncCausalityTracer in a single-threaded manner.
+        /// </remarks>
+        internal object ObjectIdForDebugger => _builder.ObjectIdForDebugger;
+    }
+
+    /// <summary>
+    /// Provides a builder for asynchronous methods that return <see cref="System.Threading.Tasks.Task"/>.
+    /// This type is intended for compiler use only.
+    /// </summary>
+    /// <remarks>
+    /// AsyncTaskMethodBuilder is a value type, and thus it is copied by value.
+    /// Prior to being copied, one of its Task, SetResult, or SetException members must be accessed,
+    /// or else the copies may end up building distinct Task instances.
+    /// </remarks>
+    public struct AsyncTaskMethodBuilder
+    {
+        /// <summary>A cached VoidTaskResult task used for builders that complete synchronously.</summary>
+        private readonly static Task<VoidTaskResult> s_cachedCompleted = AsyncTaskMethodBuilder<VoidTaskResult>.s_defaultResultTask;
+
+        /// <summary>The generic builder object to which this non-generic instance delegates.</summary>
+        private AsyncTaskMethodBuilder<VoidTaskResult> m_builder; // mutable struct: must not be readonly. Debugger depends on the exact name of this field.
+
+        /// <summary>Initializes a new <see cref="AsyncTaskMethodBuilder"/>.</summary>
+        /// <returns>The initialized <see cref="AsyncTaskMethodBuilder"/>.</returns>
+        public static AsyncTaskMethodBuilder Create() => default(AsyncTaskMethodBuilder);
+
+        /// <summary>Initiates the builder's execution with the associated state machine.</summary>
+        /// <typeparam name="TStateMachine">Specifies the type of the state machine.</typeparam>
+        /// <param name="stateMachine">The state machine instance, passed by reference.</param>
+        [DebuggerStepThrough]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Start<TStateMachine>(ref TStateMachine stateMachine) where TStateMachine : IAsyncStateMachine =>
+            AsyncMethodBuilderCore.Start(ref stateMachine);
+
+        /// <summary>Associates the builder with the state machine it represents.</summary>
+        /// <param name="stateMachine">The heap-allocated state machine object.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="stateMachine"/> argument was null (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.InvalidOperationException">The builder is incorrectly initialized.</exception>
+        public void SetStateMachine(IAsyncStateMachine stateMachine) =>
+            m_builder.SetStateMachine(stateMachine);
+
+        /// <summary>
+        /// Schedules the specified state machine to be pushed forward when the specified awaiter completes.
+        /// </summary>
+        /// <typeparam name="TAwaiter">Specifies the type of the awaiter.</typeparam>
+        /// <typeparam name="TStateMachine">Specifies the type of the state machine.</typeparam>
+        /// <param name="awaiter">The awaiter.</param>
+        /// <param name="stateMachine">The state machine.</param>
+        public void AwaitOnCompleted<TAwaiter, TStateMachine>(
+            ref TAwaiter awaiter, ref TStateMachine stateMachine)
+            where TAwaiter : INotifyCompletion
+            where TStateMachine : IAsyncStateMachine =>
+            m_builder.AwaitOnCompleted(ref awaiter, ref stateMachine);
+
+        /// <summary>
+        /// Schedules the specified state machine to be pushed forward when the specified awaiter completes.
+        /// </summary>
+        /// <typeparam name="TAwaiter">Specifies the type of the awaiter.</typeparam>
+        /// <typeparam name="TStateMachine">Specifies the type of the state machine.</typeparam>
+        /// <param name="awaiter">The awaiter.</param>
+        /// <param name="stateMachine">The state machine.</param>
+        public void AwaitUnsafeOnCompleted<TAwaiter, TStateMachine>(
+            ref TAwaiter awaiter, ref TStateMachine stateMachine)
+            where TAwaiter : ICriticalNotifyCompletion
+            where TStateMachine : IAsyncStateMachine =>
+            m_builder.AwaitUnsafeOnCompleted(ref awaiter, ref stateMachine);
+
+        /// <summary>Gets the <see cref="System.Threading.Tasks.Task"/> for this builder.</summary>
+        /// <returns>The <see cref="System.Threading.Tasks.Task"/> representing the builder's asynchronous operation.</returns>
+        /// <exception cref="System.InvalidOperationException">The builder is not initialized.</exception>
+        public Task Task
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => m_builder.Task;
+        }
+
+        /// <summary>
+        /// Completes the <see cref="System.Threading.Tasks.Task"/> in the 
+        /// <see cref="System.Threading.Tasks.TaskStatus">RanToCompletion</see> state.
+        /// </summary>
+        /// <exception cref="System.InvalidOperationException">The builder is not initialized.</exception>
+        /// <exception cref="System.InvalidOperationException">The task has already completed.</exception>
+        public void SetResult() => m_builder.SetResult(s_cachedCompleted); // Using s_cachedCompleted is faster than using s_defaultResultTask.
+
+        /// <summary>
+        /// Completes the <see cref="System.Threading.Tasks.Task"/> in the 
+        /// <see cref="System.Threading.Tasks.TaskStatus">Faulted</see> state with the specified exception.
+        /// </summary>
+        /// <param name="exception">The <see cref="System.Exception"/> to use to fault the task.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="exception"/> argument is null (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.InvalidOperationException">The builder is not initialized.</exception>
+        /// <exception cref="System.InvalidOperationException">The task has already completed.</exception>
+        public void SetException(Exception exception) => m_builder.SetException(exception);
+
+        /// <summary>
+        /// Called by the debugger to request notification when the first wait operation
+        /// (await, Wait, Result, etc.) on this builder's task completes.
+        /// </summary>
+        /// <param name="enabled">
+        /// true to enable notification; false to disable a previously set notification.
+        /// </param>
+        internal void SetNotificationForWaitCompletion(bool enabled) => m_builder.SetNotificationForWaitCompletion(enabled);
+
+        /// <summary>
+        /// Gets an object that may be used to uniquely identify this builder to the debugger.
+        /// </summary>
+        /// <remarks>
+        /// This property lazily instantiates the ID in a non-thread-safe manner.  
+        /// It must only be used by the debugger and tracing purposes, and only in a single-threaded manner
+        /// when no other threads are in the middle of accessing this property or this.Task.
+        /// </remarks>
+        internal object ObjectIdForDebugger => m_builder.ObjectIdForDebugger;
+    }
+
+    /// <summary>
+    /// Provides a builder for asynchronous methods that return <see cref="System.Threading.Tasks.Task{TResult}"/>.
+    /// This type is intended for compiler use only.
+    /// </summary>
+    /// <remarks>
+    /// AsyncTaskMethodBuilder{TResult} is a value type, and thus it is copied by value.
+    /// Prior to being copied, one of its Task, SetResult, or SetException members must be accessed,
+    /// or else the copies may end up building distinct Task instances.
+    /// </remarks>
+    public struct AsyncTaskMethodBuilder<TResult>
+    {
+        /// <summary>A cached task for default(TResult).</summary>
+        internal readonly static Task<TResult> s_defaultResultTask = AsyncTaskCache.CreateCacheableTask(default(TResult));
+
+        /// <summary>The lazily-initialized built task.</summary>
+        private Task<TResult> m_task; // lazily-initialized: must not be readonly. Debugger depends on the exact name of this field.
+
+        /// <summary>Initializes a new <see cref="AsyncTaskMethodBuilder"/>.</summary>
+        /// <returns>The initialized <see cref="AsyncTaskMethodBuilder"/>.</returns>
+        public static AsyncTaskMethodBuilder<TResult> Create()
+        {
+            return default(AsyncTaskMethodBuilder<TResult>);
+            // NOTE: If this method is ever updated to perform more initialization,
+            //       other Create methods like AsyncTaskMethodBuilder.Create and
+            //       AsyncValueTaskMethodBuilder.Create must be updated to call this.
+        }
+
+        /// <summary>Initiates the builder's execution with the associated state machine.</summary>
+        /// <typeparam name="TStateMachine">Specifies the type of the state machine.</typeparam>
+        /// <param name="stateMachine">The state machine instance, passed by reference.</param>
+        [DebuggerStepThrough]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Start<TStateMachine>(ref TStateMachine stateMachine) where TStateMachine : IAsyncStateMachine =>
+            AsyncMethodBuilderCore.Start(ref stateMachine);
+
+        /// <summary>Associates the builder with the state machine it represents.</summary>
+        /// <param name="stateMachine">The heap-allocated state machine object.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="stateMachine"/> argument was null (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.InvalidOperationException">The builder is incorrectly initialized.</exception>
+        public void SetStateMachine(IAsyncStateMachine stateMachine)
+        {
+            if (stateMachine == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.stateMachine);
+            }
+
+            if (m_task != null)
+            {
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.AsyncMethodBuilder_InstanceNotInitialized);
+            }
+
+            // SetStateMachine was originally needed in order to store the boxed state machine reference into
+            // the boxed copy.  Now that a normal box is no longer used, SetStateMachine is also legacy.  We need not
+            // do anything here, and thus assert to ensure we're not calling this from our own implementations.
+            Debug.Fail("SetStateMachine should not be used.");
+        }
+
+        /// <summary>
+        /// Schedules the specified state machine to be pushed forward when the specified awaiter completes.
+        /// </summary>
+        /// <typeparam name="TAwaiter">Specifies the type of the awaiter.</typeparam>
+        /// <typeparam name="TStateMachine">Specifies the type of the state machine.</typeparam>
+        /// <param name="awaiter">The awaiter.</param>
+        /// <param name="stateMachine">The state machine.</param>
+        public void AwaitOnCompleted<TAwaiter, TStateMachine>(
+            ref TAwaiter awaiter, ref TStateMachine stateMachine)
+            where TAwaiter : INotifyCompletion
+            where TStateMachine : IAsyncStateMachine
+        {
+            try
+            {
+                awaiter.OnCompleted(GetStateMachineBox(ref stateMachine).MoveNextAction);
+            }
+            catch (Exception e)
+            {
+                AsyncMethodBuilderCore.ThrowAsync(e, targetContext: null);
+            }
+        }
+
+        /// <summary>
+        /// Schedules the specified state machine to be pushed forward when the specified awaiter completes.
+        /// </summary>
+        /// <typeparam name="TAwaiter">Specifies the type of the awaiter.</typeparam>
+        /// <typeparam name="TStateMachine">Specifies the type of the state machine.</typeparam>
+        /// <param name="awaiter">The awaiter.</param>
+        /// <param name="stateMachine">The state machine.</param>
+        public void AwaitUnsafeOnCompleted<TAwaiter, TStateMachine>(
+            ref TAwaiter awaiter, ref TStateMachine stateMachine)
+            where TAwaiter : ICriticalNotifyCompletion
+            where TStateMachine : IAsyncStateMachine
+        {
+            IAsyncStateMachineBox box = GetStateMachineBox(ref stateMachine);
+
+            // The null tests here ensure that the jit can optimize away the interface
+            // tests when TAwaiter is a ref type.
+
+            if ((null != (object)default(TAwaiter)) && (awaiter is ITaskAwaiter))
+            {
+                ref TaskAwaiter ta = ref Unsafe.As<TAwaiter, TaskAwaiter>(ref awaiter); // relies on TaskAwaiter/TaskAwaiter<T> having the same layout
+                TaskAwaiter.UnsafeOnCompletedInternal(ta.m_task, box, continueOnCapturedContext: true);
+            }
+            else if ((null != (object)default(TAwaiter)) && (awaiter is IConfiguredTaskAwaiter))
+            {
+                ref ConfiguredTaskAwaitable.ConfiguredTaskAwaiter ta = ref Unsafe.As<TAwaiter, ConfiguredTaskAwaitable.ConfiguredTaskAwaiter>(ref awaiter);
+                TaskAwaiter.UnsafeOnCompletedInternal(ta.m_task, box, ta.m_continueOnCapturedContext);
+            }
+            else if ((null != (object)default(TAwaiter)) && (awaiter is IStateMachineBoxAwareAwaiter))
+            {
+                try
+                {
+                    ((IStateMachineBoxAwareAwaiter)awaiter).AwaitUnsafeOnCompleted(box);
+                }
+                catch (Exception e)
+                {
+                    // Whereas with Task the code that hooks up and invokes the continuation is all local to corelib,
+                    // with ValueTaskAwaiter we may be calling out to an arbitrary implementation of IValueTaskSource
+                    // wrapped in the ValueTask, and as such we protect against errant exceptions that may emerge.
+                    // We don't want such exceptions propagating back into the async method, which can't handle
+                    // exceptions well at that location in the state machine, especially if the exception may occur
+                    // after the ValueTaskAwaiter already successfully hooked up the callback, in which case it's possible
+                    // two different flows of execution could end up happening in the same async method call.
+                    AsyncMethodBuilderCore.ThrowAsync(e, targetContext: null);
+                }
+            }
+            else
+            {
+                // The awaiter isn't specially known. Fall back to doing a normal await.
+                try
+                {
+                    awaiter.UnsafeOnCompleted(box.MoveNextAction);
+                }
+                catch (Exception e)
+                {
+                    AsyncMethodBuilderCore.ThrowAsync(e, targetContext: null);
+                }
+            }
+        }
+
+        /// <summary>Gets the "boxed" state machine object.</summary>
+        /// <typeparam name="TStateMachine">Specifies the type of the async state machine.</typeparam>
+        /// <param name="stateMachine">The state machine.</param>
+        /// <returns>The "boxed" state machine.</returns>
+        private IAsyncStateMachineBox GetStateMachineBox<TStateMachine>(
+            ref TStateMachine stateMachine)
+            where TStateMachine : IAsyncStateMachine
+        {
+            ExecutionContext currentContext = ExecutionContext.Capture();
+
+            // Check first for the most common case: not the first yield in an async method.
+            // In this case, the first yield will have already "boxed" the state machine in
+            // a strongly-typed manner into an AsyncStateMachineBox.  It will already contain
+            // the state machine as well as a MoveNextDelegate and a context.  The only thing
+            // we might need to do is update the context if that's changed since it was stored.
+            if (m_task is AsyncStateMachineBox<TStateMachine> stronglyTypedBox)
+            {
+                if (stronglyTypedBox.Context != currentContext)
+                {
+                    stronglyTypedBox.Context = currentContext;
+                }
+                return stronglyTypedBox;
+            }
+
+            // The least common case: we have a weakly-typed boxed.  This results if the debugger
+            // or some other use of reflection accesses a property like ObjectIdForDebugger or a
+            // method like SetNotificationForWaitCompletion prior to the first await happening.  In
+            // such situations, we need to get an object to represent the builder, but we don't yet
+            // know the type of the state machine, and thus can't use TStateMachine.  Instead, we
+            // use the IAsyncStateMachine interface, which all TStateMachines implement.  This will
+            // result in a boxing allocation when storing the TStateMachine if it's a struct, but
+            // this only happens in active debugging scenarios where such performance impact doesn't
+            // matter.
+            if (m_task is AsyncStateMachineBox<IAsyncStateMachine> weaklyTypedBox)
+            {
+                // If this is the first await, we won't yet have a state machine, so store it.
+                if (weaklyTypedBox.StateMachine == null)
+                {
+                    Debugger.NotifyOfCrossThreadDependency(); // same explanation as with usage below
+                    weaklyTypedBox.StateMachine = stateMachine;
+                }
+
+                // Update the context.  This only happens with a debugger, so no need to spend
+                // extra IL checking for equality before doing the assignment.
+                weaklyTypedBox.Context = currentContext;
+                return weaklyTypedBox;
+            }
+
+            // Alert a listening debugger that we can't make forward progress unless it slips threads.
+            // If we don't do this, and a method that uses "await foo;" is invoked through funceval,
+            // we could end up hooking up a callback to push forward the async method's state machine,
+            // the debugger would then abort the funceval after it takes too long, and then continuing
+            // execution could result in another callback being hooked up.  At that point we have
+            // multiple callbacks registered to push the state machine, which could result in bad behavior.
+            Debugger.NotifyOfCrossThreadDependency();
+
+            // At this point, m_task should really be null, in which case we want to create the box.
+            // However, in a variety of debugger-related (erroneous) situations, it might be non-null,
+            // e.g. if the Task property is examined in a Watch window, forcing it to be lazily-intialized
+            // as a Task<TResult> rather than as an AsyncStateMachineBox.  The worst that happens in such
+            // cases is we lose the ability to properly step in the debugger, as the debugger uses that
+            // object's identity to track this specific builder/state machine.  As such, we proceed to
+            // overwrite whatever's there anyway, even if it's non-null.
+            var box = AsyncMethodBuilderCore.TrackAsyncMethodCompletion ?
+                new DebugFinalizableAsyncStateMachineBox<TStateMachine>() :
+                new AsyncStateMachineBox<TStateMachine>();
+            m_task = box; // important: this must be done before storing stateMachine into box.StateMachine!
+            box.StateMachine = stateMachine;
+            box.Context = currentContext;
+            return box;
+        }
+
+        /// <summary>
+        /// Provides an async state machine box with a finalizer that will fire an EventSource
+        /// event about the state machine if it's being finalized without having been completed.
+        /// </summary>
+        /// <typeparam name="TStateMachine">Specifies the type of the state machine.</typeparam>
+        private sealed class DebugFinalizableAsyncStateMachineBox<TStateMachine> :
+            AsyncStateMachineBox<TStateMachine>
+            where TStateMachine : IAsyncStateMachine
+        {
+            ~DebugFinalizableAsyncStateMachineBox()
+            {
+                // If the state machine is being finalized, something went wrong during its processing,
+                // e.g. it awaited something that got collected without itself having been completed.
+                // Fire an event with details about the state machine to help with debugging.
+                if (!IsCompleted) // double-check it's not completed, just to help minimize false positives
+                {
+                    TplEtwProvider.Log.IncompleteAsyncMethod(this);
+                }
+            }
+        }
+
+        /// <summary>A strongly-typed box for Task-based async state machines.</summary>
+        /// <typeparam name="TStateMachine">Specifies the type of the state machine.</typeparam>
+        /// <typeparam name="TResult">Specifies the type of the Task's result.</typeparam>
+        private class AsyncStateMachineBox<TStateMachine> :
+            Task<TResult>, IAsyncStateMachineBox
+            where TStateMachine : IAsyncStateMachine
+        {
+            /// <summary>Delegate used to invoke on an ExecutionContext when passed an instance of this box type.</summary>
+            private static readonly ContextCallback s_callback = s => ((AsyncStateMachineBox<TStateMachine>)s).StateMachine.MoveNext();
+
+            /// <summary>A delegate to the <see cref="MoveNext"/> method.</summary>
+            private Action _moveNextAction;
+            /// <summary>The state machine itself.</summary>
+            public TStateMachine StateMachine; // mutable struct; do not make this readonly
+            /// <summary>Captured ExecutionContext with which to invoke <see cref="MoveNextAction"/>; may be null.</summary>
+            public ExecutionContext Context;
+
+            /// <summary>A delegate to the <see cref="MoveNext"/> method.</summary>
+            public Action MoveNextAction => _moveNextAction ?? (_moveNextAction = new Action(MoveNext));
+
+            /// <summary>Calls MoveNext on <see cref="StateMachine"/></summary>
+            public void MoveNext()
+            {
+                bool loggingOn = AsyncCausalityTracer.LoggingOn;
+                if (loggingOn)
+                {
+                    AsyncCausalityTracer.TraceSynchronousWorkStart(CausalityTraceLevel.Required, Id, CausalitySynchronousWork.Execution);
+                }
+
+                ExecutionContext context = Context;
+                if (context == null)
+                {
+                    StateMachine.MoveNext();
+                }
+                else
+                {
+                    ExecutionContext.RunInternal(context, s_callback, this);
+                }
+
+                // In case this is a state machine box with a finalizer, suppress its finalization
+                // if it's now complete.  We only need the finalizer to run if the box is collected
+                // without having been completed.
+                if (IsCompleted && AsyncMethodBuilderCore.TrackAsyncMethodCompletion)
+                {
+                    GC.SuppressFinalize(this);
+                }
+
+                if (loggingOn)
+                {
+                    AsyncCausalityTracer.TraceSynchronousWorkCompletion(CausalityTraceLevel.Required, CausalitySynchronousWork.Execution);
+                }
+            }
+
+            /// <summary>Gets the state machine as a boxed object.  This should only be used for debugging purposes.</summary>
+            IAsyncStateMachine IAsyncStateMachineBox.GetStateMachineObject() => StateMachine; // likely boxes, only use for debugging
+        }
+
+        /// <summary>Gets the <see cref="System.Threading.Tasks.Task{TResult}"/> for this builder.</summary>
+        /// <returns>The <see cref="System.Threading.Tasks.Task{TResult}"/> representing the builder's asynchronous operation.</returns>
+        public Task<TResult> Task
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => m_task ?? InitializeTaskAsPromise();
+        }
+
+        /// <summary>
+        /// Initializes the task, which must not yet be initialized.  Used only when the Task is being forced into
+        /// existence when no state machine is needed, e.g. when the builder is being synchronously completed with
+        /// an exception, when the builder is being used out of the context of an async method, etc.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private Task<TResult> InitializeTaskAsPromise()
+        {
+            Debug.Assert(m_task == null);
+            return (m_task = new Task<TResult>());
+        }
+
+        /// <summary>
+        /// Initializes the task, which must not yet be initialized.  Used only when the Task is being forced into
+        /// existence due to the debugger trying to enable step-out/step-over/etc. prior to the first await yielding
+        /// in an async method.  In that case, we don't know the actual TStateMachine type, so we're forced to
+        /// use IAsyncStateMachine instead.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private Task<TResult> InitializeTaskAsStateMachineBox()
+        {
+            Debug.Assert(m_task == null);
+            return (m_task = AsyncMethodBuilderCore.TrackAsyncMethodCompletion ?
+                new DebugFinalizableAsyncStateMachineBox<IAsyncStateMachine>() :
+                new AsyncStateMachineBox<IAsyncStateMachine>());
+        }
+
+        /// <summary>
+        /// Completes the <see cref="System.Threading.Tasks.Task{TResult}"/> in the 
+        /// <see cref="System.Threading.Tasks.TaskStatus">RanToCompletion</see> state with the specified result.
+        /// </summary>
+        /// <param name="result">The result to use to complete the task.</param>
+        /// <exception cref="System.InvalidOperationException">The task has already completed.</exception>
+        public void SetResult(TResult result)
+        {
+            // Get the currently stored task, which will be non-null if get_Task has already been accessed.
+            // If there isn't one, get a task and store it.
+            if (m_task == null)
+            {
+                m_task = GetTaskForResult(result);
+                Debug.Assert(m_task != null, $"{nameof(GetTaskForResult)} should never return null");
+            }
+            else
+            {
+                // Slow path: complete the existing task.
+                SetExistingTaskResult(result);
+            }
+        }
+
+        /// <summary>Completes the already initialized task with the specified result.</summary>
+        /// <param name="result">The result to use to complete the task.</param>
+        private void SetExistingTaskResult(TResult result)
+        {
+            Debug.Assert(m_task != null, "Expected non-null task");
+
+            if (AsyncCausalityTracer.LoggingOn || System.Threading.Tasks.Task.s_asyncDebuggingEnabled)
+            {
+                LogExistingTaskCompletion();
+            }
+
+            if (!m_task.TrySetResult(result))
+            {
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.TaskT_TransitionToFinal_AlreadyCompleted);
+            }
+        }
+
+        /// <summary>Handles logging for the successful completion of an operation.</summary>
+        private void LogExistingTaskCompletion()
+        {
+            Debug.Assert(m_task != null);
+
+            if (AsyncCausalityTracer.LoggingOn)
+            {
+                AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, m_task.Id, AsyncCausalityStatus.Completed);
+            }
+
+            // only log if we have a real task that was previously created
+            if (System.Threading.Tasks.Task.s_asyncDebuggingEnabled)
+            {
+                System.Threading.Tasks.Task.RemoveFromActiveTasks(m_task.Id);
+            }
+        }
+
+        /// <summary>
+        /// Completes the builder by using either the supplied completed task, or by completing
+        /// the builder's previously accessed task using default(TResult).
+        /// </summary>
+        /// <param name="completedTask">A task already completed with the value default(TResult).</param>
+        /// <exception cref="System.InvalidOperationException">The task has already completed.</exception>
+        internal void SetResult(Task<TResult> completedTask)
+        {
+            Debug.Assert(completedTask != null, "Expected non-null task");
+            Debug.Assert(completedTask.IsCompletedSuccessfully, "Expected a successfully completed task");
+
+            // Get the currently stored task, which will be non-null if get_Task has already been accessed.
+            // If there isn't one, store the supplied completed task.
+            if (m_task == null)
+            {
+                m_task = completedTask;
+            }
+            else
+            {
+                // Otherwise, complete the task that's there.
+                SetExistingTaskResult(default(TResult));
+            }
+        }
+
+        /// <summary>
+        /// Completes the <see cref="System.Threading.Tasks.Task{TResult}"/> in the 
+        /// <see cref="System.Threading.Tasks.TaskStatus">Faulted</see> state with the specified exception.
+        /// </summary>
+        /// <param name="exception">The <see cref="System.Exception"/> to use to fault the task.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="exception"/> argument is null (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.InvalidOperationException">The task has already completed.</exception>
+        public void SetException(Exception exception)
+        {
+            if (exception == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.exception);
+            }
+
+            // Get the task, forcing initialization if it hasn't already been initialized.
+            Task<TResult> task = this.Task;
+
+            // If the exception represents cancellation, cancel the task.  Otherwise, fault the task.
+            var oce = exception as OperationCanceledException;
+            bool successfullySet = oce != null ?
+                task.TrySetCanceled(oce.CancellationToken, oce) :
+                task.TrySetException(exception);
+
+            // Unlike with TaskCompletionSource, we do not need to spin here until _taskAndStateMachine is completed,
+            // since AsyncTaskMethodBuilder.SetException should not be immediately followed by any code
+            // that depends on the task having completely completed.  Moreover, with correct usage, 
+            // SetResult or SetException should only be called once, so the Try* methods should always
+            // return true, so no spinning would be necessary anyway (the spinning in TCS is only relevant
+            // if another thread completes the task first).
+            if (!successfullySet)
+            {
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.TaskT_TransitionToFinal_AlreadyCompleted);
+            }
+        }
+
+        /// <summary>
+        /// Called by the debugger to request notification when the first wait operation
+        /// (await, Wait, Result, etc.) on this builder's task completes.
+        /// </summary>
+        /// <param name="enabled">
+        /// true to enable notification; false to disable a previously set notification.
+        /// </param>
+        /// <remarks>
+        /// This should only be invoked from within an asynchronous method,
+        /// and only by the debugger.
+        /// </remarks>
+        internal void SetNotificationForWaitCompletion(bool enabled)
+        {
+            // Get the task (forcing initialization if not already initialized), and set debug notification
+            (m_task ?? InitializeTaskAsStateMachineBox()).SetNotificationForWaitCompletion(enabled);
+
+            // NOTE: It's important that the debugger use builder.SetNotificationForWaitCompletion
+            // rather than builder.Task.SetNotificationForWaitCompletion.  Even though the latter will
+            // lazily-initialize the task as well, it'll initialize it to a Task<T> (which is important
+            // to minimize size for cases where an ATMB is used directly by user code to avoid the
+            // allocation overhead of a TaskCompletionSource).  If that's done prior to the first await,
+            // the GetMoveNextDelegate code, which needs an AsyncStateMachineBox, will end up creating
+            // a new box and overwriting the previously created task.  That'll change the object identity
+            // of the task being used for wait completion notification, and no notification will
+            // ever arrive, breaking step-out behavior when stepping out before the first yielding await.
+        }
+
+        /// <summary>
+        /// Gets an object that may be used to uniquely identify this builder to the debugger.
+        /// </summary>
+        /// <remarks>
+        /// This property lazily instantiates the ID in a non-thread-safe manner.  
+        /// It must only be used by the debugger and tracing purposes, and only in a single-threaded manner
+        /// when no other threads are in the middle of accessing this or other members that lazily initialize the task.
+        /// </remarks>
+        internal object ObjectIdForDebugger => m_task ?? InitializeTaskAsStateMachineBox();
+
+        /// <summary>
+        /// Gets a task for the specified result.  This will either
+        /// be a cached or new task, never null.
+        /// </summary>
+        /// <param name="result">The result for which we need a task.</param>
+        /// <returns>The completed task containing the result.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)] // method looks long, but for a given TResult it results in a relatively small amount of asm
+        internal static Task<TResult> GetTaskForResult(TResult result)
+        {
+            // The goal of this function is to be give back a cached task if possible,
+            // or to otherwise give back a new task.  To give back a cached task,
+            // we need to be able to evaluate the incoming result value, and we need
+            // to avoid as much overhead as possible when doing so, as this function
+            // is invoked as part of the return path from every async method.
+            // Most tasks won't be cached, and thus we need the checks for those that are 
+            // to be as close to free as possible. This requires some trickiness given the 
+            // lack of generic specialization in .NET.
+            //
+            // Be very careful when modifying this code.  It has been tuned
+            // to comply with patterns recognized by both 32-bit and 64-bit JITs.
+            // If changes are made here, be sure to look at the generated assembly, as
+            // small tweaks can have big consequences for what does and doesn't get optimized away.
+            //
+            // Note that this code only ever accesses a static field when it knows it'll
+            // find a cached value, since static fields (even if readonly and integral types) 
+            // require special access helpers in this NGEN'd and domain-neutral.
+
+            if (null != (object)default(TResult)) // help the JIT avoid the value type branches for ref types
+            {
+                // Special case simple value types:
+                // - Boolean
+                // - Byte, SByte
+                // - Char
+                // - Int32, UInt32
+                // - Int64, UInt64
+                // - Int16, UInt16
+                // - IntPtr, UIntPtr
+                // As of .NET 4.5, the (Type)(object)result pattern used below
+                // is recognized and optimized by both 32-bit and 64-bit JITs.
+
+                // For Boolean, we cache all possible values.
+                if (typeof(TResult) == typeof(Boolean)) // only the relevant branches are kept for each value-type generic instantiation
+                {
+                    Boolean value = (Boolean)(object)result;
+                    Task<Boolean> task = value ? AsyncTaskCache.TrueTask : AsyncTaskCache.FalseTask;
+                    return Unsafe.As<Task<TResult>>(task); // UnsafeCast avoids type check we know will succeed
+                }
+                // For Int32, we cache a range of common values, e.g. [-1,4).
+                else if (typeof(TResult) == typeof(Int32))
+                {
+                    // Compare to constants to avoid static field access if outside of cached range.
+                    // We compare to the upper bound first, as we're more likely to cache miss on the upper side than on the 
+                    // lower side, due to positive values being more common than negative as return values.
+                    Int32 value = (Int32)(object)result;
+                    if (value < AsyncTaskCache.EXCLUSIVE_INT32_MAX &&
+                        value >= AsyncTaskCache.INCLUSIVE_INT32_MIN)
+                    {
+                        Task<Int32> task = AsyncTaskCache.Int32Tasks[value - AsyncTaskCache.INCLUSIVE_INT32_MIN];
+                        return Unsafe.As<Task<TResult>>(task); // UnsafeCast avoids a type check we know will succeed
+                    }
+                }
+                // For other known value types, we only special-case 0 / default(TResult).
+                else if (
+                    (typeof(TResult) == typeof(UInt32) && default(UInt32) == (UInt32)(object)result) ||
+                    (typeof(TResult) == typeof(Byte) && default(Byte) == (Byte)(object)result) ||
+                    (typeof(TResult) == typeof(SByte) && default(SByte) == (SByte)(object)result) ||
+                    (typeof(TResult) == typeof(Char) && default(Char) == (Char)(object)result) ||
+                    (typeof(TResult) == typeof(Int64) && default(Int64) == (Int64)(object)result) ||
+                    (typeof(TResult) == typeof(UInt64) && default(UInt64) == (UInt64)(object)result) ||
+                    (typeof(TResult) == typeof(Int16) && default(Int16) == (Int16)(object)result) ||
+                    (typeof(TResult) == typeof(UInt16) && default(UInt16) == (UInt16)(object)result) ||
+                    (typeof(TResult) == typeof(IntPtr) && default(IntPtr) == (IntPtr)(object)result) ||
+                    (typeof(TResult) == typeof(UIntPtr) && default(UIntPtr) == (UIntPtr)(object)result))
+                {
+                    return s_defaultResultTask;
+                }
+            }
+            else if (result == null) // optimized away for value types
+            {
+                return s_defaultResultTask;
+            }
+
+            // No cached task is available.  Manufacture a new one for this result.
+            return new Task<TResult>(result);
+        }
+    }
+
+    /// <summary>Provides a cache of closed generic tasks for async methods.</summary>
+    internal static class AsyncTaskCache
+    {
+        // All static members are initialized inline to ensure type is beforefieldinit
+
+        /// <summary>A cached Task{Boolean}.Result == true.</summary>
+        internal readonly static Task<Boolean> TrueTask = CreateCacheableTask(true);
+        /// <summary>A cached Task{Boolean}.Result == false.</summary>
+        internal readonly static Task<Boolean> FalseTask = CreateCacheableTask(false);
+
+        /// <summary>The cache of Task{Int32}.</summary>
+        internal readonly static Task<Int32>[] Int32Tasks = CreateInt32Tasks();
+        /// <summary>The minimum value, inclusive, for which we want a cached task.</summary>
+        internal const Int32 INCLUSIVE_INT32_MIN = -1;
+        /// <summary>The maximum value, exclusive, for which we want a cached task.</summary>
+        internal const Int32 EXCLUSIVE_INT32_MAX = 9;
+        /// <summary>Creates an array of cached tasks for the values in the range [INCLUSIVE_MIN,EXCLUSIVE_MAX).</summary>
+        private static Task<Int32>[] CreateInt32Tasks()
+        {
+            Debug.Assert(EXCLUSIVE_INT32_MAX >= INCLUSIVE_INT32_MIN, "Expected max to be at least min");
+            var tasks = new Task<Int32>[EXCLUSIVE_INT32_MAX - INCLUSIVE_INT32_MIN];
+            for (int i = 0; i < tasks.Length; i++)
+            {
+                tasks[i] = CreateCacheableTask(i + INCLUSIVE_INT32_MIN);
+            }
+            return tasks;
+        }
+
+        /// <summary>Creates a non-disposable task.</summary>
+        /// <typeparam name="TResult">Specifies the result type.</typeparam>
+        /// <param name="result">The result for the task.</param>
+        /// <returns>The cacheable task.</returns>
+        internal static Task<TResult> CreateCacheableTask<TResult>(TResult result) =>
+            new Task<TResult>(false, result, (TaskCreationOptions)InternalTaskOptions.DoNotDispose, default(CancellationToken));
+    }
+
+    /// <summary>
+    /// An interface implemented by all <see cref="AsyncStateMachineBox{TStateMachine, TResult}"/> instances, regardless of generics.
+    /// </summary>
+    internal interface IAsyncStateMachineBox
+    {
+        /// <summary>Move the state machine forward.</summary>
+        void MoveNext();
+
+        /// <summary>
+        /// Gets an action for moving forward the contained state machine.
+        /// This will lazily-allocate the delegate as needed.
+        /// </summary>
+        Action MoveNextAction { get; }
+
+        /// <summary>Gets the state machine as a boxed object.  This should only be used for debugging purposes.</summary>
+        IAsyncStateMachine GetStateMachineObject();
+    }
+
+    /// <summary>Shared helpers for manipulating state related to async state machines.</summary>
+    internal static class AsyncMethodBuilderCore // debugger depends on this exact name
+    {
+        /// <summary>Initiates the builder's execution with the associated state machine.</summary>
+        /// <typeparam name="TStateMachine">Specifies the type of the state machine.</typeparam>
+        /// <param name="stateMachine">The state machine instance, passed by reference.</param>
+        [DebuggerStepThrough]
+        public static void Start<TStateMachine>(ref TStateMachine stateMachine) where TStateMachine : IAsyncStateMachine
+        {
+            if (stateMachine == null) // TStateMachines are generally non-nullable value types, so this check will be elided
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.stateMachine);
+            }
+
+            // enregistrer variables with 0 post-fix so they can be used in registers without EH forcing them to stack
+            // Capture references to Thread Contexts
+            Thread currentThread0 = Thread.CurrentThread;
+            Thread currentThread = currentThread0;
+            ExecutionContext previousExecutionCtx0 = currentThread0.ExecutionContext;
+
+            // Store current ExecutionContext and SynchronizationContext as "previousXxx".
+            // This allows us to restore them and undo any Context changes made in stateMachine.MoveNext
+            // so that they won't "leak" out of the first await.
+            ExecutionContext previousExecutionCtx = previousExecutionCtx0;
+            SynchronizationContext previousSyncCtx = currentThread0.SynchronizationContext;
+
+            try
+            {
+                stateMachine.MoveNext();
+            }
+            finally
+            {
+                // Re-enregistrer variables post EH with 1 post-fix so they can be used in registers rather than from stack
+                SynchronizationContext previousSyncCtx1 = previousSyncCtx;
+                Thread currentThread1 = currentThread;
+                // The common case is that these have not changed, so avoid the cost of a write barrier if not needed.
+                if (previousSyncCtx1 != currentThread1.SynchronizationContext)
+                {
+                    // Restore changed SynchronizationContext back to previous
+                    currentThread1.SynchronizationContext = previousSyncCtx1;
+                }
+
+                ExecutionContext previousExecutionCtx1 = previousExecutionCtx;
+                ExecutionContext currentExecutionCtx1 = currentThread1.ExecutionContext;
+                if (previousExecutionCtx1 != currentExecutionCtx1)
+                {
+                    // Restore changed ExecutionContext back to previous
+                    currentThread1.ExecutionContext = previousExecutionCtx1;
+                    if ((currentExecutionCtx1 != null && currentExecutionCtx1.HasChangeNotifications) ||
+                        (previousExecutionCtx1 != null && previousExecutionCtx1.HasChangeNotifications))
+                    {
+                        // There are change notifications; trigger any affected
+                        ExecutionContext.OnValuesChanged(currentExecutionCtx1, previousExecutionCtx1);
+                    }
+                }
+            }
+        }
+
+        /// <summary>Gets whether we should be tracking async method completions for eventing.</summary>
+        internal static bool TrackAsyncMethodCompletion
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => TplEtwProvider.Log.IsEnabled(EventLevel.Warning, TplEtwProvider.Keywords.AsyncMethod);
+        }
+
+        /// <summary>Gets a description of the state of the state machine object, suitable for debug purposes.</summary>
+        /// <param name="stateMachine">The state machine object.</param>
+        /// <returns>A description of the state machine.</returns>
+        internal static string GetAsyncStateMachineDescription(IAsyncStateMachine stateMachine)
+        {
+            Debug.Assert(stateMachine != null);
+
+            Type stateMachineType = stateMachine.GetType();
+            FieldInfo[] fields = stateMachineType.GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
+
+            var sb = new StringBuilder();
+            sb.AppendLine(stateMachineType.FullName);
+            foreach (FieldInfo fi in fields)
+            {
+                sb.AppendLine($"    {fi.Name}: {fi.GetValue(stateMachine)}");
+            }
+            return sb.ToString();
+        }
+
+        internal static Action CreateContinuationWrapper(Action continuation, Action<Action,Task> invokeAction, Task innerTask) =>
+            new ContinuationWrapper(continuation, invokeAction, innerTask).Invoke;
+
+        internal static Action TryGetStateMachineForDebugger(Action action) // debugger depends on this exact name/signature
+        {
+            object target = action.Target;
+            return
+                target is IAsyncStateMachineBox sm ? sm.GetStateMachineObject().MoveNext :
+                target is ContinuationWrapper cw ? TryGetStateMachineForDebugger(cw._continuation) :
+                action;
+        }
+
+        internal static Task TryGetContinuationTask(Action continuation) =>
+            (continuation?.Target as ContinuationWrapper)?._innerTask;
+
+        /// <summary>Throws the exception on the ThreadPool.</summary>
+        /// <param name="exception">The exception to propagate.</param>
+        /// <param name="targetContext">The target context on which to propagate the exception.  Null to use the ThreadPool.</param>
+        internal static void ThrowAsync(Exception exception, SynchronizationContext targetContext)
+        {
+            // Capture the exception into an ExceptionDispatchInfo so that its 
+            // stack trace and Watson bucket info will be preserved
+            var edi = ExceptionDispatchInfo.Capture(exception);
+
+            // If the user supplied a SynchronizationContext...
+            if (targetContext != null)
+            {
+                try
+                {
+                    // Post the throwing of the exception to that context, and return.
+                    targetContext.Post(state => ((ExceptionDispatchInfo)state).Throw(), edi);
+                    return;
+                }
+                catch (Exception postException)
+                {
+                    // If something goes horribly wrong in the Post, we'll 
+                    // propagate both exceptions on the ThreadPool
+                    edi = ExceptionDispatchInfo.Capture(new AggregateException(exception, postException));
+                }
+            }
+
+            // If we have the new error reporting APIs, report this error.  Otherwise, Propagate the exception(s) on the ThreadPool
+#if FEATURE_COMINTEROP
+            if (!WindowsRuntimeMarshal.ReportUnhandledError(edi.SourceException))
+#endif // FEATURE_COMINTEROP
+            {
+                ThreadPool.QueueUserWorkItem(state => ((ExceptionDispatchInfo)state).Throw(), edi);
+            }
+        }
+
+        /// <summary>
+        /// Logically we pass just an Action (delegate) to a task for its action to 'ContinueWith' when it completes.
+        /// However debuggers and profilers need more information about what that action is. (In particular what 
+        /// the action after that is and after that.   To solve this problem we create a 'ContinuationWrapper 
+        /// which when invoked just does the original action (the invoke action), but also remembers other information
+        /// (like the action after that (which is also a ContinuationWrapper and thus form a linked list).  
+        //  We also store that task if the action is associate with at task.  
+        /// </summary>
+        private sealed class ContinuationWrapper
+        {
+            private readonly Action<Action, Task> _invokeAction; // This wrapper is an action that wraps another action, this is that Action.  
+            internal readonly Action _continuation;              // This is continuation which will happen after m_invokeAction  (and is probably a ContinuationWrapper)
+            internal readonly Task _innerTask;                   // If the continuation is logically going to invoke a task, this is that task (may be null)
+
+            internal ContinuationWrapper(Action continuation, Action<Action, Task> invokeAction, Task innerTask)
+            {
+                Debug.Assert(continuation != null, "Expected non-null continuation");
+                Debug.Assert(invokeAction != null, "Expected non-null continuation");
+
+                _invokeAction = invokeAction;
+                _continuation = continuation;
+                _innerTask = innerTask ?? TryGetContinuationTask(continuation); // if we don't have a task, see if our continuation is a wrapper and use that.
+            }
+
+            internal void Invoke() => _invokeAction(_continuation, _innerTask);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/ConditionalWeakTable.cs b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/ConditionalWeakTable.cs
new file mode 100644
index 0000000000..2bbed367fb
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/ConditionalWeakTable.cs
@@ -0,0 +1,1012 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+** 
+**
+** Description: Compiler support for runtime-generated "object fields."
+**
+**    Lets DLR and other language compilers expose the ability to
+**    attach arbitrary "properties" to instanced managed objects at runtime.
+**
+**    We expose this support as a dictionary whose keys are the
+**    instanced objects and the values are the "properties."
+**
+**    Unlike a regular dictionary, ConditionalWeakTables will not
+**    keep keys alive.
+**
+**
+** Lifetimes of keys and values:
+**
+**    Inserting a key and value into the dictonary will not
+**    prevent the key from dying, even if the key is strongly reachable
+**    from the value.
+**
+**    Prior to ConditionalWeakTable, the CLR did not expose
+**    the functionality needed to implement this guarantee.
+**
+**    Once the key dies, the dictionary automatically removes
+**    the key/value entry.
+**
+**
+** Relationship between ConditionalWeakTable and Dictionary:
+**
+**    ConditionalWeakTable mirrors the form and functionality
+**    of the IDictionary interface for the sake of api consistency.
+**
+**    Unlike Dictionary, ConditionalWeakTable is fully thread-safe
+**    and requires no additional locking to be done by callers.
+**
+**    ConditionalWeakTable defines equality as Object.ReferenceEquals().
+**    ConditionalWeakTable does not invoke GetHashCode() overrides.
+**
+**    It is not intended to be a general purpose collection
+**    and it does not formally implement IDictionary or
+**    expose the full public surface area.
+**
+**
+** Thread safety guarantees:
+**
+**    ConditionalWeakTable is fully thread-safe and requires no
+**    additional locking to be done by callers.
+**
+**
+** OOM guarantees:
+**
+**    Will not corrupt unmanaged handle table on OOM. No guarantees
+**    about managed weak table consistency. Native handles reclamation
+**    may be delayed until appdomain shutdown.
+===========================================================*/
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Threading;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.CompilerServices
+{
+    #region ConditionalWeakTable
+    public sealed class ConditionalWeakTable<TKey, TValue> : IEnumerable<KeyValuePair<TKey, TValue>>
+        where TKey : class
+        where TValue : class
+    {
+        #region Fields
+        private const int InitialCapacity = 8;  // Initial length of the table. Must be a power of two.
+        private readonly object _lock;          // This lock protects all mutation of data in the table.  Readers do not take this lock.
+        private volatile Container _container;  // The actual storage for the table; swapped out as the table grows.
+        private int _activeEnumeratorRefCount;  // The number of outstanding enumerators on the table
+        #endregion
+
+        #region Constructors
+        public ConditionalWeakTable()
+        {
+            _lock = new object();
+            _container = new Container(this);
+        }
+        #endregion
+
+        #region Public Members
+        //--------------------------------------------------------------------------------------------
+        // key:   key of the value to find. Cannot be null.
+        // value: if the key is found, contains the value associated with the key upon method return.
+        //        if the key is not found, contains default(TValue).
+        //
+        // Method returns "true" if key was found, "false" otherwise.
+        //
+        // Note: The key may get garbaged collected during the TryGetValue operation. If so, TryGetValue
+        // may at its discretion, return "false" and set "value" to the default (as if the key was not present.)
+        //--------------------------------------------------------------------------------------------
+        public bool TryGetValue(TKey key, out TValue value)
+        {
+            if (key == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
+            }
+
+            return _container.TryGetValueWorker(key, out value);
+        }
+
+        //--------------------------------------------------------------------------------------------
+        // key: key to add. May not be null.
+        // value: value to associate with key.
+        //
+        // If the key is already entered into the dictionary, this method throws an exception.
+        //
+        // Note: The key may get garbage collected during the Add() operation. If so, Add()
+        // has the right to consider any prior entries successfully removed and add a new entry without
+        // throwing an exception.
+        //--------------------------------------------------------------------------------------------
+        public void Add(TKey key, TValue value)
+        {
+            if (key == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
+            }
+
+            lock (_lock)
+            {
+                object otherValue;
+                int entryIndex = _container.FindEntry(key, out otherValue);
+                if (entryIndex != -1)
+                {
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_AddingDuplicate);
+                }
+
+                CreateEntry(key, value);
+            }
+        }
+
+        //--------------------------------------------------------------------------------------------
+        // key: key to add or update. May not be null.
+        // value: value to associate with key.
+        //
+        // If the key is already entered into the dictionary, this method will update the value associated with key.
+        //--------------------------------------------------------------------------------------------
+        public void AddOrUpdate(TKey key, TValue value)
+        {
+            if (key == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
+            }
+
+            lock (_lock)
+            {
+                object otherValue;
+                int entryIndex = _container.FindEntry(key, out otherValue);
+
+                // if we found a key we should just update, if no we should create a new entry.
+                if (entryIndex != -1)
+                {
+                    _container.UpdateValue(entryIndex, value);
+                }
+                else
+                {
+                    CreateEntry(key, value);
+                }
+            }
+        }
+
+        //--------------------------------------------------------------------------------------------
+        // key: key to remove. May not be null.
+        //
+        // Returns true if the key is found and removed. Returns false if the key was not in the dictionary.
+        //
+        // Note: The key may get garbage collected during the Remove() operation. If so,
+        // Remove() will not fail or throw, however, the return value can be either true or false
+        // depending on who wins the race.
+        //--------------------------------------------------------------------------------------------
+        public bool Remove(TKey key)
+        {
+            if (key == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
+            }
+
+            lock (_lock)
+            {
+                return _container.Remove(key);
+            }
+        }
+
+        //--------------------------------------------------------------------------------------------
+        // Clear all the key/value pairs
+        //--------------------------------------------------------------------------------------------
+        public void Clear()
+        {
+            lock (_lock)
+            {
+                // To clear, we would prefer to simply drop the existing container
+                // and replace it with an empty one, as that's overall more efficient.
+                // However, if there are any active enumerators, we don't want to do
+                // that as it will end up removing all of the existing entries and
+                // allowing new items to be added at the same indices when the container
+                // is filled and replaced, and one of the guarantees we try to make with
+                // enumeration is that new items added after enumeration starts won't be
+                // included in the enumeration. As such, if there are active enumerators,
+                // we simply use the container's removal functionality to remove all of the
+                // keys; then when the table is resized, if there are still active enumerators,
+                // these empty slots will be maintained.
+                if (_activeEnumeratorRefCount > 0)
+                {
+                    _container.RemoveAllKeys();
+                }
+                else
+                {
+                    _container = new Container(this);
+                }
+            }
+        }
+
+        //--------------------------------------------------------------------------------------------
+        // key:                 key of the value to find. Cannot be null.
+        // createValueCallback: callback that creates value for key. Cannot be null.
+        //
+        // Atomically tests if key exists in table. If so, returns corresponding value. If not,
+        // invokes createValueCallback() passing it the key. The returned value is bound to the key in the table
+        // and returned as the result of GetValue().
+        //
+        // If multiple threads try to initialize the same key, the table may invoke createValueCallback
+        // multiple times with the same key. Exactly one of these calls will succeed and the returned
+        // value of that call will be the one added to the table and returned by all the racing GetValue() calls.
+        // 
+        // This rule permits the table to invoke createValueCallback outside the internal table lock
+        // to prevent deadlocks.
+        //--------------------------------------------------------------------------------------------
+        public TValue GetValue(TKey key, CreateValueCallback createValueCallback)
+        {
+            // key is validated by TryGetValue
+
+            if (createValueCallback == null)
+            {
+                throw new ArgumentNullException(nameof(createValueCallback));
+            }
+
+            TValue existingValue;
+            return TryGetValue(key, out existingValue) ?
+                existingValue :
+                GetValueLocked(key, createValueCallback);
+        }
+
+        private TValue GetValueLocked(TKey key, CreateValueCallback createValueCallback)
+        {
+            // If we got here, the key was not in the table. Invoke the callback (outside the lock)
+            // to generate the new value for the key. 
+            TValue newValue = createValueCallback(key);
+
+            lock (_lock)
+            {
+                // Now that we've taken the lock, must recheck in case we lost a race to add the key.
+                TValue existingValue;
+                if (_container.TryGetValueWorker(key, out existingValue))
+                {
+                    return existingValue;
+                }
+                else
+                {
+                    // Verified in-lock that we won the race to add the key. Add it now.
+                    CreateEntry(key, newValue);
+                    return newValue;
+                }
+            }
+        }
+
+        //--------------------------------------------------------------------------------------------
+        // key:                 key of the value to find. Cannot be null.
+        //
+        // Helper method to call GetValue without passing a creation delegate.  Uses Activator.CreateInstance
+        // to create new instances as needed.  If TValue does not have a default constructor, this will
+        // throw.
+        //--------------------------------------------------------------------------------------------
+
+        public TValue GetOrCreateValue(TKey key) => GetValue(key, _ => Activator.CreateInstance<TValue>());
+
+        public delegate TValue CreateValueCallback(TKey key);
+
+        //--------------------------------------------------------------------------------------------
+        // Gets an enumerator for the table.  The returned enumerator will not extend the lifetime of
+        // any object pairs in the table, other than the one that's Current.  It will not return entries
+        // that have already been collected, nor will it return entries added after the enumerator was
+        // retrieved.  It may not return all entries that were present when the enumerat was retrieved,
+        // however, such as not returning entries that were collected or removed after the enumerator
+        // was retrieved but before they were enumerated.
+        //--------------------------------------------------------------------------------------------
+        IEnumerator<KeyValuePair<TKey, TValue>> IEnumerable<KeyValuePair<TKey, TValue>>.GetEnumerator()
+        {
+            lock (_lock)
+            {
+                Container c = _container;
+                return c == null || c.FirstFreeEntry == 0 ?
+                    ((IEnumerable<KeyValuePair<TKey, TValue>>)Array.Empty<KeyValuePair<TKey, TValue>>()).GetEnumerator() :
+                    new Enumerator(this);
+            }
+        }
+
+        IEnumerator IEnumerable.GetEnumerator() => ((IEnumerable<KeyValuePair<TKey, TValue>>)this).GetEnumerator();
+
+        /// <summary>Provides an enumerator for the table.</summary>
+        private sealed class Enumerator : IEnumerator<KeyValuePair<TKey, TValue>>
+        {
+            // The enumerator would ideally hold a reference to the Container and the end index within that
+            // container.  However, the safety of the CWT depends on the only reference to the Container being
+            // from the CWT itself; the Container then employs a two-phase finalization scheme, where the first
+            // phase nulls out that parent CWT's reference, guaranteeing that the second time it's finalized there
+            // can be no other existing references to it in use that would allow for concurrent usage of the
+            // native handles with finalization.  We would break that if we allowed this Enumerator to hold a
+            // reference to the Container.  Instead, the Enumerator holds a reference to the CWT rather than to
+            // the Container, and it maintains the CWT._activeEnumeratorRefCount field to track whether there
+            // are outstanding enumerators that have yet to be disposed/finalized.  If there aren't any, the CWT
+            // behaves as it normally does.  If there are, certain operations are affected, in particular resizes.
+            // Normally when the CWT is resized, it enumerates the contents of the table looking for indices that
+            // contain entries which have been collected or removed, and it frees those up, effectively moving
+            // down all subsequent entries in the container (not in the existing container, but in a replacement).
+            // This, however, would cause the enumerator's understanding of indices to break.  So, as long as
+            // there is any outstanding enumerator, no compaction is performed.
+
+            private ConditionalWeakTable<TKey, TValue> _table; // parent table, set to null when disposed
+            private readonly int _maxIndexInclusive;           // last index in the container that should be enumerated
+            private int _currentIndex = -1;                    // the current index into the container
+            private KeyValuePair<TKey, TValue> _current;       // the current entry set by MoveNext and returned from Current
+
+            public Enumerator(ConditionalWeakTable<TKey, TValue> table)
+            {
+                Debug.Assert(table != null, "Must provide a valid table");
+                Debug.Assert(Monitor.IsEntered(table._lock), "Must hold the _lock lock to construct the enumerator");
+                Debug.Assert(table._container != null, "Should not be used on a finalized table");
+                Debug.Assert(table._container.FirstFreeEntry > 0, "Should have returned an empty enumerator instead");
+
+                // Store a reference to the parent table and increase its active enumerator count.
+                _table = table;
+                Debug.Assert(table._activeEnumeratorRefCount >= 0, "Should never have a negative ref count before incrementing");
+                table._activeEnumeratorRefCount++;
+
+                // Store the max index to be enumerated.
+                _maxIndexInclusive = table._container.FirstFreeEntry - 1;
+                _currentIndex = -1;
+            }
+
+            ~Enumerator() { Dispose(); }
+
+            public void Dispose()
+            {
+                // Use an interlocked operation to ensure that only one thread can get access to
+                // the _table for disposal and thus only decrement the ref count once.
+                ConditionalWeakTable<TKey, TValue> table = Interlocked.Exchange(ref _table, null);
+                if (table != null)
+                {
+                    // Ensure we don't keep the last current alive unnecessarily
+                    _current = default(KeyValuePair<TKey, TValue>);
+
+                    // Decrement the ref count that was incremented when constructed
+                    lock (table._lock)
+                    {
+                        table._activeEnumeratorRefCount--;
+                        Debug.Assert(table._activeEnumeratorRefCount >= 0, "Should never have a negative ref count after decrementing");
+                    }
+
+                    // Finalization is purely to decrement the ref count.  We can suppress it now.
+                    GC.SuppressFinalize(this);
+                }
+            }
+
+            public bool MoveNext()
+            {
+                // Start by getting the current table.  If it's already been disposed, it will be null.
+                ConditionalWeakTable<TKey, TValue> table = _table;
+                if (table != null)
+                {
+                    // Once have the table, we need to lock to synchronize with other operations on
+                    // the table, like adding.
+                    lock (table._lock)
+                    {
+                        // From the table, we have to get the current container.  This could have changed
+                        // since we grabbed the enumerator, but the index-to-pair mapping should not have
+                        // due to there being at least one active enumerator.  If the table (or rather its
+                        // container at the time) has already been finalized, this will be null.
+                        Container c = table._container;
+                        if (c != null)
+                        {
+                            // We have the container.  Find the next entry to return, if there is one.
+                            // We need to loop as we may try to get an entry that's already been removed
+                            // or collected, in which case we try again.
+                            while (_currentIndex < _maxIndexInclusive)
+                            {
+                                _currentIndex++;
+                                TKey key;
+                                TValue value;
+                                if (c.TryGetEntry(_currentIndex, out key, out value))
+                                {
+                                    _current = new KeyValuePair<TKey, TValue>(key, value);
+                                    return true;
+                                }
+                            }
+                        }
+                    }
+                }
+
+                // Nothing more to enumerate.
+                return false;
+            }
+
+            public KeyValuePair<TKey, TValue> Current
+            {
+                get
+                {
+                    if (_currentIndex < 0)
+                    {
+                        ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumOpCantHappen();
+                    }
+                    return _current;
+                }
+            }
+
+            object IEnumerator.Current => Current;
+
+            public void Reset() { }
+        }
+
+        #endregion
+
+        #region Private Members
+
+        //----------------------------------------------------------------------------------------
+        // Worker for adding a new key/value pair.
+        // Will resize the container if it is full
+        //
+        // Preconditions:
+        //     Must hold _lock.
+        //     Key already validated as non-null and not already in table.
+        //----------------------------------------------------------------------------------------
+        private void CreateEntry(TKey key, TValue value)
+        {
+            Debug.Assert(Monitor.IsEntered(_lock));
+
+            Container c = _container;
+            if (!c.HasCapacity)
+            {
+                _container = c = c.Resize();
+            }
+            c.CreateEntryNoResize(key, value);
+        }
+
+        private static bool IsPowerOfTwo(int value) => (value > 0) && ((value & (value - 1)) == 0);
+
+        #endregion
+
+        #region Private Data Members
+        //--------------------------------------------------------------------------------------------
+        // Entry can be in one of four states:
+        //
+        //    - Unused (stored with an index _firstFreeEntry and above)
+        //         depHnd.IsAllocated == false
+        //         hashCode == <dontcare>
+        //         next == <dontcare>)
+        //
+        //    - Used with live key (linked into a bucket list where _buckets[hashCode & (_buckets.Length - 1)] points to first entry)
+        //         depHnd.IsAllocated == true, depHnd.GetPrimary() != null
+        //         hashCode == RuntimeHelpers.GetHashCode(depHnd.GetPrimary()) & Int32.MaxValue
+        //         next links to next Entry in bucket. 
+        //                          
+        //    - Used with dead key (linked into a bucket list where _buckets[hashCode & (_buckets.Length - 1)] points to first entry)
+        //         depHnd.IsAllocated == true, depHnd.GetPrimary() == null
+        //         hashCode == <notcare> 
+        //         next links to next Entry in bucket. 
+        //
+        //    - Has been removed from the table (by a call to Remove)
+        //         depHnd.IsAllocated == true, depHnd.GetPrimary() == <notcare>
+        //         hashCode == -1 
+        //         next links to next Entry in bucket. 
+        //
+        // The only difference between "used with live key" and "used with dead key" is that
+        // depHnd.GetPrimary() returns null. The transition from "used with live key" to "used with dead key"
+        // happens asynchronously as a result of normal garbage collection. The dictionary itself
+        // receives no notification when this happens.
+        //
+        // When the dictionary grows the _entries table, it scours it for expired keys and does not
+        // add those to the new container.
+        //--------------------------------------------------------------------------------------------
+        private struct Entry
+        {
+            public DependentHandle depHnd;      // Holds key and value using a weak reference for the key and a strong reference
+                                                // for the value that is traversed only if the key is reachable without going through the value.
+            public int HashCode;    // Cached copy of key's hashcode
+            public int Next;        // Index of next entry, -1 if last
+        }
+
+        //
+        // Container holds the actual data for the table.  A given instance of Container always has the same capacity.  When we need
+        // more capacity, we create a new Container, copy the old one into the new one, and discard the old one.  This helps enable lock-free
+        // reads from the table, as readers never need to deal with motion of entries due to rehashing.
+        //
+        private sealed class Container
+        {
+            private readonly ConditionalWeakTable<TKey, TValue> _parent;  // the ConditionalWeakTable with which this container is associated
+            private int[] _buckets;                // _buckets[hashcode & (_buckets.Length - 1)] contains index of the first entry in bucket (-1 if empty)
+            private Entry[] _entries;              // the table entries containing the stored dependency handles
+            private int _firstFreeEntry;           // _firstFreeEntry < _entries.Length => table has capacity,  entries grow from the bottom of the table.
+            private bool _invalid;                 // flag detects if OOM or other background exception threw us out of the lock.
+            private bool _finalized;               // set to true when initially finalized
+            private volatile object _oldKeepAlive; // used to ensure the next allocated container isn't finalized until this one is GC'd
+
+            internal Container(ConditionalWeakTable<TKey, TValue> parent)
+            {
+                Debug.Assert(parent != null);
+                Debug.Assert(IsPowerOfTwo(InitialCapacity));
+
+                int size = InitialCapacity;
+                _buckets = new int[size];
+                for (int i = 0; i < _buckets.Length; i++)
+                {
+                    _buckets[i] = -1;
+                }
+                _entries = new Entry[size];
+
+                // Only store the parent after all of the allocations have happened successfully.
+                // Otherwise, as part of growing or clearing the container, we could end up allocating
+                // a new Container that fails (OOMs) part way through construction but that gets finalized
+                // and ends up clearing out some other container present in the associated CWT.
+                _parent = parent;
+            }
+
+            private Container(ConditionalWeakTable<TKey, TValue> parent, int[] buckets, Entry[] entries, int firstFreeEntry)
+            {
+                Debug.Assert(parent != null);
+                Debug.Assert(buckets != null);
+                Debug.Assert(entries != null);
+                Debug.Assert(buckets.Length == entries.Length);
+                Debug.Assert(IsPowerOfTwo(buckets.Length));
+
+                _parent = parent;
+                _buckets = buckets;
+                _entries = entries;
+                _firstFreeEntry = firstFreeEntry;
+            }
+
+            internal bool HasCapacity => _firstFreeEntry < _entries.Length;
+
+            internal int FirstFreeEntry => _firstFreeEntry;
+
+            //----------------------------------------------------------------------------------------
+            // Worker for adding a new key/value pair.
+            // Preconditions:
+            //     Container must NOT be full
+            //----------------------------------------------------------------------------------------
+            internal void CreateEntryNoResize(TKey key, TValue value)
+            {
+                Debug.Assert(HasCapacity);
+
+                VerifyIntegrity();
+                _invalid = true;
+
+                int hashCode = RuntimeHelpers.GetHashCode(key) & int.MaxValue;
+                int newEntry = _firstFreeEntry++;
+
+                _entries[newEntry].HashCode = hashCode;
+                _entries[newEntry].depHnd = new DependentHandle(key, value);
+                int bucket = hashCode & (_buckets.Length - 1);
+                _entries[newEntry].Next = _buckets[bucket];
+
+                // This write must be volatile, as we may be racing with concurrent readers.  If they see
+                // the new entry, they must also see all of the writes earlier in this method.
+                Volatile.Write(ref _buckets[bucket], newEntry);
+
+                _invalid = false;
+            }
+
+            //----------------------------------------------------------------------------------------
+            // Worker for finding a key/value pair
+            //
+            // Preconditions:
+            //     Must hold _lock.
+            //     Key already validated as non-null
+            //----------------------------------------------------------------------------------------
+            internal bool TryGetValueWorker(TKey key, out TValue value)
+            {
+                object secondary;
+                int entryIndex = FindEntry(key, out secondary);
+                value = Unsafe.As<TValue>(secondary);
+                return entryIndex != -1;
+            }
+
+            //----------------------------------------------------------------------------------------
+            // Returns -1 if not found (if key expires during FindEntry, this can be treated as "not found.")
+            //
+            // Preconditions:
+            //     Must hold _lock, or be prepared to retry the search while holding _lock.
+            //     Key already validated as non-null.
+            //----------------------------------------------------------------------------------------
+            internal int FindEntry(TKey key, out object value)
+            {
+                int hashCode = RuntimeHelpers.GetHashCode(key) & int.MaxValue;
+                int bucket = hashCode & (_buckets.Length - 1);
+                for (int entriesIndex = Volatile.Read(ref _buckets[bucket]); entriesIndex != -1; entriesIndex = _entries[entriesIndex].Next)
+                {
+                    if (_entries[entriesIndex].HashCode == hashCode && _entries[entriesIndex].depHnd.GetPrimaryAndSecondary(out value) == key)
+                    {
+                        GC.KeepAlive(this); // ensure we don't get finalized while accessing DependentHandles.
+                        return entriesIndex;
+                    }
+                }
+
+                GC.KeepAlive(this); // ensure we don't get finalized while accessing DependentHandles.
+                value = null;
+                return -1;
+            }
+
+            //----------------------------------------------------------------------------------------
+            // Gets the entry at the specified entry index.
+            //----------------------------------------------------------------------------------------
+            internal bool TryGetEntry(int index, out TKey key, out TValue value)
+            {
+                if (index < _entries.Length)
+                {
+                    object oKey, oValue;
+                    oKey = _entries[index].depHnd.GetPrimaryAndSecondary(out oValue);
+                    GC.KeepAlive(this); // ensure we don't get finalized while accessing DependentHandles.
+
+                    if (oKey != null)
+                    {
+                        key = Unsafe.As<TKey>(oKey);
+                        value = Unsafe.As<TValue>(oValue);
+                        return true;
+                    }
+                }
+
+                key = default(TKey);
+                value = default(TValue);
+                return false;
+            }
+
+            //----------------------------------------------------------------------------------------
+            // Removes all of the keys in the table.
+            //----------------------------------------------------------------------------------------
+            internal void RemoveAllKeys()
+            {
+                for (int i = 0; i < _firstFreeEntry; i++)
+                {
+                    RemoveIndex(i);
+                }
+            }
+
+            //----------------------------------------------------------------------------------------
+            // Removes the specified key from the table, if it exists.
+            //----------------------------------------------------------------------------------------
+            internal bool Remove(TKey key)
+            {
+                VerifyIntegrity();
+
+                object value;
+                int entryIndex = FindEntry(key, out value);
+                if (entryIndex != -1)
+                {
+                    RemoveIndex(entryIndex);
+                    return true;
+                }
+
+                return false;
+            }
+
+            private void RemoveIndex(int entryIndex)
+            {
+                Debug.Assert(entryIndex >= 0 && entryIndex < _firstFreeEntry);
+
+                ref Entry entry = ref _entries[entryIndex];
+
+                // We do not free the handle here, as we may be racing with readers who already saw the hash code.
+                // Instead, we simply overwrite the entry's hash code, so subsequent reads will ignore it.
+                // The handle will be free'd in Container's finalizer, after the table is resized or discarded.
+                Volatile.Write(ref entry.HashCode, -1);
+
+                // Also, clear the key to allow GC to collect objects pointed to by the entry
+                entry.depHnd.SetPrimary(null);
+            }
+
+            internal void UpdateValue(int entryIndex, TValue newValue)
+            {
+                Debug.Assert(entryIndex != -1);
+
+                VerifyIntegrity();
+                _invalid = true;
+
+                _entries[entryIndex].depHnd.SetSecondary(newValue);
+
+                _invalid = false;
+            }
+
+            //----------------------------------------------------------------------------------------
+            // This does two things: resize and scrub expired keys off bucket lists.
+            //
+            // Precondition:
+            //      Must hold _lock.
+            //
+            // Postcondition:
+            //      _firstEntry is less than _entries.Length on exit, that is, the table has at least one free entry.
+            //----------------------------------------------------------------------------------------
+            internal Container Resize()
+            {
+                Debug.Assert(!HasCapacity);
+
+                bool hasExpiredEntries = false;
+                int newSize = _buckets.Length;
+
+                if (_parent == null || _parent._activeEnumeratorRefCount == 0)
+                {
+                    // If any expired or removed keys exist, we won't resize.
+                    // If there any active enumerators, though, we don't want
+                    // to compact and thus have no expired entries.
+                    for (int entriesIndex = 0; entriesIndex < _entries.Length; entriesIndex++)
+                    {
+                        ref Entry entry = ref _entries[entriesIndex];
+
+                        if (entry.HashCode == -1)
+                        {
+                            // the entry was removed
+                            hasExpiredEntries = true;
+                            break;
+                        }
+
+                        if (entry.depHnd.IsAllocated && entry.depHnd.GetPrimary() == null)
+                        {
+                            // the entry has expired
+                            hasExpiredEntries = true;
+                            break;
+                        }
+                    }
+                }
+
+                if (!hasExpiredEntries)
+                {
+                    // Not necessary to check for overflow here, the attempt to allocate new arrays will throw
+                    newSize = _buckets.Length * 2;
+                }
+
+                return Resize(newSize);
+            }
+
+            internal Container Resize(int newSize)
+            {
+                Debug.Assert(newSize >= _buckets.Length);
+                Debug.Assert(IsPowerOfTwo(newSize));
+
+                // Reallocate both buckets and entries and rebuild the bucket and entries from scratch.
+                // This serves both to scrub entries with expired keys and to put the new entries in the proper bucket.
+                int[] newBuckets = new int[newSize];
+                for (int bucketIndex = 0; bucketIndex < newBuckets.Length; bucketIndex++)
+                {
+                    newBuckets[bucketIndex] = -1;
+                }
+                Entry[] newEntries = new Entry[newSize];
+                int newEntriesIndex = 0;
+                bool activeEnumerators = _parent != null && _parent._activeEnumeratorRefCount > 0;
+
+                // Migrate existing entries to the new table.
+                if (activeEnumerators)
+                {
+                    // There's at least one active enumerator, which means we don't want to
+                    // remove any expired/removed entries, in order to not affect existing
+                    // entries indices.  Copy over the entries while rebuilding the buckets list,
+                    // as the buckets are dependent on the buckets list length, which is changing.
+                    for (; newEntriesIndex < _entries.Length; newEntriesIndex++)
+                    {
+                        ref Entry oldEntry = ref _entries[newEntriesIndex];
+                        ref Entry newEntry = ref newEntries[newEntriesIndex];
+                        int hashCode = oldEntry.HashCode;
+
+                        newEntry.HashCode = hashCode;
+                        newEntry.depHnd = oldEntry.depHnd;
+                        int bucket = hashCode & (newBuckets.Length - 1);
+                        newEntry.Next = newBuckets[bucket];
+                        newBuckets[bucket] = newEntriesIndex;
+                    }
+                }
+                else
+                {
+                    // There are no active enumerators, which means we want to compact by
+                    // removing expired/removed entries.
+                    for (int entriesIndex = 0; entriesIndex < _entries.Length; entriesIndex++)
+                    {
+                        ref Entry oldEntry = ref _entries[entriesIndex];
+                        int hashCode = oldEntry.HashCode;
+                        DependentHandle depHnd = oldEntry.depHnd;
+                        if (hashCode != -1 && depHnd.IsAllocated)
+                        {
+                            if (depHnd.GetPrimary() != null)
+                            {
+                                ref Entry newEntry = ref newEntries[newEntriesIndex];
+
+                                // Entry is used and has not expired. Link it into the appropriate bucket list.
+                                newEntry.HashCode = hashCode;
+                                newEntry.depHnd = depHnd;
+                                int bucket = hashCode & (newBuckets.Length - 1);
+                                newEntry.Next = newBuckets[bucket];
+                                newBuckets[bucket] = newEntriesIndex;
+                                newEntriesIndex++;
+                            }
+                            else
+                            {
+                                // Pretend the item was removed, so that this container's finalizer
+                                // will clean up this dependent handle.
+                                Volatile.Write(ref oldEntry.HashCode, -1);
+                            }
+                        }
+                    }
+                }
+
+                // Create the new container.  We want to transfer the responsibility of freeing the handles from
+                // the old container to the new container, and also ensure that the new container isn't finalized
+                // while the old container may still be in use.  As such, we store a reference from the old container
+                // to the new one, which will keep the new container alive as long as the old one is.
+                var newContainer = new Container(_parent, newBuckets, newEntries, newEntriesIndex);
+                if (activeEnumerators)
+                {
+                    // If there are active enumerators, both the old container and the new container may be storing
+                    // the same entries with -1 hash codes, which the finalizer will clean up even if the container
+                    // is not the active container for the table.  To prevent that, we want to stop the old container
+                    // from being finalized, as it no longer has any responsibility for any cleanup.
+                    GC.SuppressFinalize(this);
+                }
+                _oldKeepAlive = newContainer; // once this is set, the old container's finalizer will not free transferred dependent handles
+
+                GC.KeepAlive(this); // ensure we don't get finalized while accessing DependentHandles.
+
+                return newContainer;
+            }
+
+            //----------------------------------------------------------------------------------------
+            // Precondition:
+            //     Must hold _lock.
+            //----------------------------------------------------------------------------------------
+            private void VerifyIntegrity()
+            {
+                if (_invalid)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_CollectionCorrupted);
+                }
+            }
+
+            //----------------------------------------------------------------------------------------
+            // Finalizer.
+            //----------------------------------------------------------------------------------------
+            ~Container()
+            {
+                // We're just freeing per-appdomain unmanaged handles here. If we're already shutting down the AD,
+                // don't bother. (Despite its name, Environment.HasShutdownStart also returns true if the current
+                // AD is finalizing.)  We also skip doing anything if the container is invalid, including if someone
+                // the container object was allocated but its associated table never set.
+                if (Environment.HasShutdownStarted || _invalid || _parent == null)
+                {
+                    return;
+                }
+
+                // It's possible that the ConditionalWeakTable could have been resurrected, in which case code could
+                // be accessing this Container as it's being finalized.  We don't support usage after finalization,
+                // but we also don't want to potentially corrupt state by allowing dependency handles to be used as
+                // or after they've been freed.  To avoid that, if it's at all possible that another thread has a
+                // reference to this container via the CWT, we remove such a reference and then re-register for
+                // finalization: the next time around, we can be sure that no references remain to this and we can
+                // clean up the dependency handles without fear of corruption.
+                if (!_finalized)
+                {
+                    _finalized = true;
+                    lock (_parent._lock)
+                    {
+                        if (_parent._container == this)
+                        {
+                            _parent._container = null;
+                        }
+                    }
+                    GC.ReRegisterForFinalize(this); // next time it's finalized, we'll be sure there are no remaining refs
+                    return;
+                }
+
+                Entry[] entries = _entries;
+                _invalid = true;
+                _entries = null;
+                _buckets = null;
+
+                if (entries != null)
+                {
+                    for (int entriesIndex = 0; entriesIndex < entries.Length; entriesIndex++)
+                    {
+                        // We need to free handles in two cases:
+                        // - If this container still owns the dependency handle (meaning ownership hasn't been transferred
+                        //   to another container that replaced this one), then it should be freed.
+                        // - If this container had the entry removed, then even if in general ownership was transferred to
+                        //   another container, removed entries are not, therefore this container must free them.
+                        if (_oldKeepAlive == null || entries[entriesIndex].HashCode == -1)
+                        {
+                            entries[entriesIndex].depHnd.Free();
+                        }
+                    }
+                }
+            }
+        }
+        #endregion
+    }
+    #endregion
+
+    #region DependentHandle
+    //=========================================================================================
+    // This struct collects all operations on native DependentHandles. The DependentHandle
+    // merely wraps an IntPtr so this struct serves mainly as a "managed typedef."
+    //
+    // DependentHandles exist in one of two states:
+    //
+    //    IsAllocated == false
+    //        No actual handle is allocated underneath. Illegal to call GetPrimary
+    //        or GetPrimaryAndSecondary(). Ok to call Free().
+    //
+    //        Initializing a DependentHandle using the nullary ctor creates a DependentHandle
+    //        that's in the !IsAllocated state.
+    //        (! Right now, we get this guarantee for free because (IntPtr)0 == NULL unmanaged handle.
+    //         ! If that assertion ever becomes false, we'll have to add an _isAllocated field
+    //         ! to compensate.)
+    //        
+    //
+    //    IsAllocated == true
+    //        There's a handle allocated underneath. You must call Free() on this eventually
+    //        or you cause a native handle table leak.
+    //
+    // This struct intentionally does no self-synchronization. It's up to the caller to
+    // to use DependentHandles in a thread-safe way.
+    //=========================================================================================
+    internal struct DependentHandle
+    {
+        #region Constructors
+        public DependentHandle(object primary, object secondary)
+        {
+            // no need to check for null result: nInitialize expected to throw OOM.
+            _handle = nInitialize(primary, secondary);
+        }
+        #endregion
+
+        #region Public Members
+        public bool IsAllocated => _handle != IntPtr.Zero;
+
+        // Getting the secondary object is more expensive than getting the first so
+        // we provide a separate primary-only accessor for those times we only want the
+        // primary.
+        public object GetPrimary()
+        {
+            return nGetPrimary(_handle);
+        }
+
+        public object GetPrimaryAndSecondary(out object secondary)
+        {
+            return nGetPrimaryAndSecondary(_handle, out secondary);
+        }
+
+        public void SetPrimary(object primary)
+        {
+            nSetPrimary(_handle, primary);
+        }
+
+        public void SetSecondary(object secondary)
+        {
+            nSetSecondary(_handle, secondary);
+        }
+
+        //----------------------------------------------------------------------
+        // Forces dependentHandle back to non-allocated state (if not already there)
+        // and frees the handle if needed.
+        //----------------------------------------------------------------------
+        public void Free()
+        {
+            if (_handle != (IntPtr)0)
+            {
+                IntPtr handle = _handle;
+                _handle = (IntPtr)0;
+                nFree(handle);
+            }
+        }
+        #endregion
+
+        #region Private Members
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern IntPtr nInitialize(object primary, object secondary);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern object nGetPrimary(IntPtr dependentHandle);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern object nGetPrimaryAndSecondary(IntPtr dependentHandle, out object secondary);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern void nSetPrimary(IntPtr dependentHandle, object primary);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern void nSetSecondary(IntPtr dependentHandle, object secondary);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern void nFree(IntPtr dependentHandle);
+        #endregion
+
+        #region Private Data Member
+        private IntPtr _handle;
+        #endregion
+
+    } // struct DependentHandle
+    #endregion
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/ICastable.cs b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/ICastable.cs
new file mode 100644
index 0000000000..e2b76ed973
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/ICastable.cs
@@ -0,0 +1,82 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+
+//
+// Support for dynamic interface casting. Specifically implementing this interface on a type will allow the
+// type to support interfaces (for the purposes of casting and interface dispatch) that do not appear in its
+// interface map.
+//
+
+using System;
+
+namespace System.Runtime.CompilerServices
+{
+    public interface ICastable
+    {
+        // This is called if casting this object to the given interface type would otherwise fail. Casting
+        // here means the IL isinst and castclass instructions in the case where they are given an interface
+        // type as the target type.
+        //
+        // A return value of true indicates the cast is valid.
+        //
+        // If false is returned when this is called as part of a castclass then the usual InvalidCastException
+        // will be thrown unless an alternate exception is assigned to the castError output parameter. This
+        // parameter is ignored on successful casts or during the evaluation of an isinst (which returns null
+        // rather than throwing on error).
+        //
+        // No exception should be thrown from this method (it will cause unpredictable effects, including the
+        // possibility of an immediate failfast).
+        //
+        // The results of this call are not cached, so it is advisable to provide a performant implementation.
+        //
+        // The results of this call should be invariant for the same class, interface type pair. That is
+        // because this is the only guard placed before an interface invocation at runtime. If a type decides
+        // it no longer wants to implement a given interface it has no way to synchronize with callers that
+        // have already cached this relationship and can invoke directly via the interface pointer.
+        bool IsInstanceOfInterface(RuntimeTypeHandle interfaceType, out Exception castError);
+
+        // This is called as part of the interface dispatch mechanism when the dispatcher logic cannot find
+        // the given interface type in the interface map of this object.
+        //
+        // It allows the implementor to return an alternate class type which does implement the interface. The
+        // interface lookup shall be performed again on this type (failure to find the interface this time
+        // resulting in a fail fast) and the corresponding implemented method on that class called instead.
+        //
+        // Naturally, since the call is dispatched to a method on a class which does not match the type of the
+        // this pointer, extreme care must be taken in the implementation of the interface methods of this
+        // surrogate type.
+        //
+        // No exception should be thrown from this method (it will cause unpredictable effects, including the
+        // possibility of an immediate failfast).
+        //
+        // There is no error path defined here. By construction all interface dispatches will already have
+        // been verified via the castclass/isinst mechanism (and thus a call to IsInstanceOfInterface above)
+        // so this method is expected to succeed in all cases. The contract for interface dispatch does not
+        // include any errors from the infrastructure, of which this is a part.
+        //
+        // The results of this lookup are cached so computation of the result is not as perf-sensitive as
+        // IsInstanceOfInterface.
+        RuntimeTypeHandle GetImplType(RuntimeTypeHandle interfaceType);
+    }
+
+    /// <summary>
+    /// Helpers that allows VM to call into ICastable methods without having to deal with RuntimeTypeHandle.
+    /// RuntimeTypeHandle is a struct and is always passed in stack in x86, which our VM call helpers don't
+    /// particularly like.
+    /// </summary>
+    internal class ICastableHelpers
+    {
+        internal static bool IsInstanceOfInterface(ICastable castable, RuntimeType type, out Exception castError)
+        {
+            return castable.IsInstanceOfInterface(new RuntimeTypeHandle(type), out castError);
+        }
+
+        internal static RuntimeType GetImplType(ICastable castable, RuntimeType interfaceType)
+        {
+            return castable.GetImplType(new RuntimeTypeHandle(interfaceType)).GetRuntimeType();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.cs b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.cs
new file mode 100644
index 0000000000..8f06008bb4
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.cs
@@ -0,0 +1,199 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+//
+// RuntimeHelpers
+//    This class defines a set of static methods that provide support for compilers.
+//
+//
+
+namespace System.Runtime.CompilerServices
+{
+    using System;
+    using System.Security;
+    using System.Runtime;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.InteropServices;
+    using System.Runtime.ConstrainedExecution;
+    using System.Runtime.Serialization;
+    using System.Threading;
+    using System.Runtime.Versioning;
+
+    public static class RuntimeHelpers
+    {
+        // Exposed here as a more appropriate place than on FormatterServices itself,
+        // which is a high level reflection heavy type.
+        public static Object GetUninitializedObject(Type type)
+        {
+            return FormatterServices.GetUninitializedObject(type);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void InitializeArray(Array array, RuntimeFieldHandle fldHandle);
+
+        // GetObjectValue is intended to allow value classes to be manipulated as 'Object'
+        // but have aliasing behavior of a value class.  The intent is that you would use
+        // this function just before an assignment to a variable of type 'Object'.  If the
+        // value being assigned is a mutable value class, then a shallow copy is returned 
+        // (because value classes have copy semantics), but otherwise the object itself
+        // is returned.  
+        //
+        // Note: VB calls this method when they're about to assign to an Object
+        // or pass it as a parameter.  The goal is to make sure that boxed 
+        // value types work identical to unboxed value types - ie, they get 
+        // cloned when you pass them around, and are always passed by value.  
+        // Of course, reference types are not cloned.
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern Object GetObjectValue(Object obj);
+
+        // RunClassConstructor causes the class constructor for the given type to be triggered
+        // in the current domain.  After this call returns, the class constructor is guaranteed to
+        // have at least been started by some thread.  In the absence of class constructor
+        // deadlock conditions, the call is further guaranteed to have completed.
+        //
+        // This call will generate an exception if the specified class constructor threw an 
+        // exception when it ran. 
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _RunClassConstructor(RuntimeType type);
+
+        public static void RunClassConstructor(RuntimeTypeHandle type)
+        {
+            _RunClassConstructor(type.GetRuntimeType());
+        }
+
+        // RunModuleConstructor causes the module constructor for the given type to be triggered
+        // in the current domain.  After this call returns, the module constructor is guaranteed to
+        // have at least been started by some thread.  In the absence of module constructor
+        // deadlock conditions, the call is further guaranteed to have completed.
+        //
+        // This call will generate an exception if the specified module constructor threw an 
+        // exception when it ran. 
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void _RunModuleConstructor(System.Reflection.RuntimeModule module);
+
+        public static void RunModuleConstructor(ModuleHandle module)
+        {
+            _RunModuleConstructor(module.GetRuntimeModule());
+        }
+
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void _CompileMethod(IRuntimeMethodInfo method);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe void _PrepareMethod(IRuntimeMethodInfo method, IntPtr* pInstantiation, int cInstantiation);
+
+        public static void PrepareMethod(RuntimeMethodHandle method) 
+        {
+            unsafe
+            {
+                _PrepareMethod(method.GetMethodInfo(), null, 0);
+            }
+        }
+
+        public static void PrepareMethod(RuntimeMethodHandle method, RuntimeTypeHandle[] instantiation)
+        {
+            unsafe
+            {
+                int length;
+                IntPtr[] instantiationHandles = RuntimeTypeHandle.CopyRuntimeTypeHandles(instantiation, out length);
+                fixed (IntPtr* pInstantiation = instantiationHandles)
+                {
+                    _PrepareMethod(method.GetMethodInfo(), pInstantiation, length);
+                    GC.KeepAlive(instantiation);
+                }
+            }
+        }
+
+        public static void PrepareContractedDelegate(Delegate d) { }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void PrepareDelegate(Delegate d);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern int GetHashCode(Object o);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public new static extern bool Equals(Object o1, Object o2);
+
+        public static int OffsetToStringData
+        {
+            // This offset is baked in by string indexer intrinsic, so there is no harm
+            // in getting it baked in here as well.
+            [System.Runtime.Versioning.NonVersionable]
+            get
+            {
+                // Number of bytes from the address pointed to by a reference to
+                // a String to the first 16-bit character in the String.  Skip 
+                // over the MethodTable pointer, & String 
+                // length.  Of course, the String reference points to the memory 
+                // after the sync block, so don't count that.  
+                // This property allows C#'s fixed statement to work on Strings.
+                // On 64 bit platforms, this should be 12 (8+4) and on 32 bit 8 (4+4).
+#if BIT64
+                return 12;
+#else // 32
+                return 8;
+#endif // BIT64
+            }
+        }
+
+        // This method ensures that there is sufficient stack to execute the average Framework function.
+        // If there is not enough stack, then it throws System.InsufficientExecutionStackException.
+        // Note: this method is not part of the CER support, and is not to be confused with ProbeForSufficientStack
+        // below.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void EnsureSufficientExecutionStack();
+
+        // This method ensures that there is sufficient stack to execute the average Framework function.
+        // If there is not enough stack, then it return false.
+        // Note: this method is not part of the CER support, and is not to be confused with ProbeForSufficientStack
+        // below.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern bool TryEnsureSufficientExecutionStack();
+
+        public static void ProbeForSufficientStack()
+        {
+        }
+
+        // This method is a marker placed immediately before a try clause to mark the corresponding catch and finally blocks as
+        // constrained. There's no code here other than the probe because most of the work is done at JIT time when we spot a call to this routine.
+        public static void PrepareConstrainedRegions()
+        {
+            ProbeForSufficientStack();
+        }
+
+        // When we detect a CER with no calls, we can point the JIT to this non-probing version instead
+        // as we don't need to probe.
+        public static void PrepareConstrainedRegionsNoOP()
+        {
+        }
+
+        public delegate void TryCode(Object userData);
+
+        public delegate void CleanupCode(Object userData, bool exceptionThrown);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData);
+
+        internal static void ExecuteBackoutCodeHelper(Object backoutCode, Object userData, bool exceptionThrown)
+        {
+            ((CleanupCode)backoutCode)(userData, exceptionThrown);
+        }
+
+        /// <returns>true if given type is reference type or value type that contains references</returns>
+        public static bool IsReferenceOrContainsReferences<T>()
+        {
+            // The body of this function will be replaced by the EE with unsafe code!!!
+            // See getILIntrinsicImplementation for how this happens.
+            throw new InvalidOperationException();
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/TaskAwaiter.cs b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/TaskAwaiter.cs
new file mode 100644
index 0000000000..487a311abe
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/TaskAwaiter.cs
@@ -0,0 +1,574 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// Types for awaiting Task and Task<T>. These types are emitted from Task{<T>}.GetAwaiter 
+// and Task{<T>}.ConfigureAwait.  They are meant to be used only by the compiler, e.g.
+// 
+//   await nonGenericTask;
+//   =====================
+//       var $awaiter = nonGenericTask.GetAwaiter();
+//       if (!$awaiter.IsCompleted)
+//       {
+//           SPILL:
+//           $builder.AwaitUnsafeOnCompleted(ref $awaiter, ref this);
+//           return;
+//           Label:
+//           UNSPILL;
+//       }
+//       $awaiter.GetResult();
+//
+//   result += await genericTask.ConfigureAwait(false);
+//   ===================================================================================
+//       var $awaiter = genericTask.ConfigureAwait(false).GetAwaiter();
+//       if (!$awaiter.IsCompleted)
+//       {
+//           SPILL;
+//           $builder.AwaitUnsafeOnCompleted(ref $awaiter, ref this);
+//           return;
+//           Label:
+//           UNSPILL;
+//       }
+//       result += $awaiter.GetResult();
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Security;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Diagnostics.Tracing;
+
+// NOTE: For performance reasons, initialization is not verified.  If a developer
+//       incorrectly initializes a task awaiter, which should only be done by the compiler,
+//       NullReferenceExceptions may be generated (the alternative would be for us to detect
+//       this case and then throw a different exception instead).  This is the same tradeoff
+//       that's made with other compiler-focused value types like List<T>.Enumerator.
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>Provides an awaiter for awaiting a <see cref="System.Threading.Tasks.Task"/>.</summary>
+    /// <remarks>This type is intended for compiler use only.</remarks>
+    public readonly struct TaskAwaiter : ICriticalNotifyCompletion, ITaskAwaiter
+    {
+        // WARNING: Unsafe.As is used to access the generic TaskAwaiter<> as TaskAwaiter.
+        // Its layout must remain the same.
+
+        /// <summary>The task being awaited.</summary>
+        internal readonly Task m_task;
+
+        /// <summary>Initializes the <see cref="TaskAwaiter"/>.</summary>
+        /// <param name="task">The <see cref="System.Threading.Tasks.Task"/> to be awaited.</param>
+        internal TaskAwaiter(Task task)
+        {
+            Debug.Assert(task != null, "Constructing an awaiter requires a task to await.");
+            m_task = task;
+        }
+
+        /// <summary>Gets whether the task being awaited is completed.</summary>
+        /// <remarks>This property is intended for compiler user rather than use directly in code.</remarks>
+        /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+        public bool IsCompleted
+        {
+            get { return m_task.IsCompleted; }
+        }
+
+        /// <summary>Schedules the continuation onto the <see cref="System.Threading.Tasks.Task"/> associated with this <see cref="TaskAwaiter"/>.</summary>
+        /// <param name="continuation">The action to invoke when the await operation completes.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.InvalidOperationException">The awaiter was not properly initialized.</exception>
+        /// <remarks>This method is intended for compiler user rather than use directly in code.</remarks>
+        public void OnCompleted(Action continuation)
+        {
+            OnCompletedInternal(m_task, continuation, continueOnCapturedContext: true, flowExecutionContext: true);
+        }
+
+        /// <summary>Schedules the continuation onto the <see cref="System.Threading.Tasks.Task"/> associated with this <see cref="TaskAwaiter"/>.</summary>
+        /// <param name="continuation">The action to invoke when the await operation completes.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.InvalidOperationException">The awaiter was not properly initialized.</exception>
+        /// <remarks>This method is intended for compiler user rather than use directly in code.</remarks>
+        public void UnsafeOnCompleted(Action continuation)
+        {
+            OnCompletedInternal(m_task, continuation, continueOnCapturedContext: true, flowExecutionContext: false);
+        }
+
+        /// <summary>Ends the await on the completed <see cref="System.Threading.Tasks.Task"/>.</summary>
+        /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+        /// <exception cref="System.Threading.Tasks.TaskCanceledException">The task was canceled.</exception>
+        /// <exception cref="System.Exception">The task completed in a Faulted state.</exception>
+        [StackTraceHidden]
+        public void GetResult()
+        {
+            ValidateEnd(m_task);
+        }
+
+        /// <summary>
+        /// Fast checks for the end of an await operation to determine whether more needs to be done
+        /// prior to completing the await.
+        /// </summary>
+        /// <param name="task">The awaited task.</param>
+        [StackTraceHidden]
+        internal static void ValidateEnd(Task task)
+        {
+            // Fast checks that can be inlined.
+            if (task.IsWaitNotificationEnabledOrNotRanToCompletion)
+            {
+                // If either the end await bit is set or we're not completed successfully,
+                // fall back to the slower path.
+                HandleNonSuccessAndDebuggerNotification(task);
+            }
+        }
+
+        /// <summary>
+        /// Ensures the task is completed, triggers any necessary debugger breakpoints for completing 
+        /// the await on the task, and throws an exception if the task did not complete successfully.
+        /// </summary>
+        /// <param name="task">The awaited task.</param>
+        [StackTraceHidden]
+        private static void HandleNonSuccessAndDebuggerNotification(Task task)
+        {
+            // NOTE: The JIT refuses to inline ValidateEnd when it contains the contents
+            // of HandleNonSuccessAndDebuggerNotification, hence the separation.
+
+            // Synchronously wait for the task to complete.  When used by the compiler,
+            // the task will already be complete.  This code exists only for direct GetResult use,
+            // for cases where the same exception propagation semantics used by "await" are desired,
+            // but where for one reason or another synchronous rather than asynchronous waiting is needed.
+            if (!task.IsCompleted)
+            {
+                bool taskCompleted = task.InternalWait(Timeout.Infinite, default(CancellationToken));
+                Debug.Assert(taskCompleted, "With an infinite timeout, the task should have always completed.");
+            }
+
+            // Now that we're done, alert the debugger if so requested
+            task.NotifyDebuggerOfWaitCompletionIfNecessary();
+
+            // And throw an exception if the task is faulted or canceled.
+            if (!task.IsCompletedSuccessfully) ThrowForNonSuccess(task);
+        }
+
+        /// <summary>Throws an exception to handle a task that completed in a state other than RanToCompletion.</summary>
+        [StackTraceHidden]
+        private static void ThrowForNonSuccess(Task task)
+        {
+            Debug.Assert(task.IsCompleted, "Task must have been completed by now.");
+            Debug.Assert(task.Status != TaskStatus.RanToCompletion, "Task should not be completed successfully.");
+
+            // Handle whether the task has been canceled or faulted
+            switch (task.Status)
+            {
+                // If the task completed in a canceled state, throw an OperationCanceledException.
+                // This will either be the OCE that actually caused the task to cancel, or it will be a new
+                // TaskCanceledException. TCE derives from OCE, and by throwing it we automatically pick up the
+                // completed task's CancellationToken if it has one, including that CT in the OCE.
+                case TaskStatus.Canceled:
+                    var oceEdi = task.GetCancellationExceptionDispatchInfo();
+                    if (oceEdi != null)
+                    {
+                        oceEdi.Throw();
+                        Debug.Fail("Throw() should have thrown");
+                    }
+                    throw new TaskCanceledException(task);
+
+                // If the task faulted, throw its first exception,
+                // even if it contained more than one.
+                case TaskStatus.Faulted:
+                    var edis = task.GetExceptionDispatchInfos();
+                    if (edis.Count > 0)
+                    {
+                        edis[0].Throw();
+                        Debug.Fail("Throw() should have thrown");
+                        break; // Necessary to compile: non-reachable, but compiler can't determine that
+                    }
+                    else
+                    {
+                        Debug.Fail("There should be exceptions if we're Faulted.");
+                        throw task.Exception;
+                    }
+            }
+        }
+
+        /// <summary>Schedules the continuation onto the <see cref="System.Threading.Tasks.Task"/> associated with this <see cref="TaskAwaiter"/>.</summary>
+        /// <param name="task">The task being awaited.</param>
+        /// <param name="continuation">The action to invoke when the await operation completes.</param>
+        /// <param name="continueOnCapturedContext">Whether to capture and marshal back to the current context.</param>
+        /// <param name="flowExecutionContext">Whether to flow ExecutionContext across the await.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+        /// <remarks>This method is intended for compiler user rather than use directly in code.</remarks>
+        internal static void OnCompletedInternal(Task task, Action continuation, bool continueOnCapturedContext, bool flowExecutionContext)
+        {
+            if (continuation == null) throw new ArgumentNullException(nameof(continuation));
+
+            // If TaskWait* ETW events are enabled, trace a beginning event for this await
+            // and set up an ending event to be traced when the asynchronous await completes.
+            if (TplEtwProvider.Log.IsEnabled() || Task.s_asyncDebuggingEnabled)
+            {
+                continuation = OutputWaitEtwEvents(task, continuation);
+            }
+
+            // Set the continuation onto the awaited task.
+            task.SetContinuationForAwait(continuation, continueOnCapturedContext, flowExecutionContext);
+        }
+
+        /// <summary>Schedules the continuation onto the <see cref="System.Threading.Tasks.Task"/> associated with this <see cref="TaskAwaiter"/>.</summary>
+        /// <param name="task">The task being awaited.</param>
+        /// <param name="continuation">The action to invoke when the await operation completes.</param>
+        /// <param name="continueOnCapturedContext">Whether to capture and marshal back to the current context.</param>
+        /// <param name="flowExecutionContext">Whether to flow ExecutionContext across the await.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+        /// <remarks>This method is intended for compiler user rather than use directly in code.</remarks>
+        internal static void UnsafeOnCompletedInternal(Task task, IAsyncStateMachineBox stateMachineBox, bool continueOnCapturedContext)
+        {
+            Debug.Assert(stateMachineBox != null);
+
+            // If TaskWait* ETW events are enabled, trace a beginning event for this await
+            // and set up an ending event to be traced when the asynchronous await completes.
+            if (TplEtwProvider.Log.IsEnabled() || Task.s_asyncDebuggingEnabled)
+            {
+                task.SetContinuationForAwait(OutputWaitEtwEvents(task, stateMachineBox.MoveNextAction), continueOnCapturedContext, flowExecutionContext: false);
+            }
+            else
+            {
+                task.UnsafeSetContinuationForAwait(stateMachineBox, continueOnCapturedContext);
+            }
+        }
+
+        /// <summary>
+        /// Outputs a WaitBegin ETW event, and augments the continuation action to output a WaitEnd ETW event.
+        /// </summary>
+        /// <param name="task">The task being awaited.</param>
+        /// <param name="continuation">The action to invoke when the await operation completes.</param>
+        /// <returns>The action to use as the actual continuation.</returns>
+        private static Action OutputWaitEtwEvents(Task task, Action continuation)
+        {
+            Debug.Assert(task != null, "Need a task to wait on");
+            Debug.Assert(continuation != null, "Need a continuation to invoke when the wait completes");
+
+            if (Task.s_asyncDebuggingEnabled)
+            {
+                Task.AddToActiveTasks(task);
+            }
+
+            var etwLog = TplEtwProvider.Log;
+
+            if (etwLog.IsEnabled())
+            {
+                // ETW event for Task Wait Begin
+                var currentTaskAtBegin = Task.InternalCurrent;
+
+                // If this task's continuation is another task, get it.
+                var continuationTask = AsyncMethodBuilderCore.TryGetContinuationTask(continuation);
+                etwLog.TaskWaitBegin(
+                    (currentTaskAtBegin != null ? currentTaskAtBegin.m_taskScheduler.Id : TaskScheduler.Default.Id),
+                    (currentTaskAtBegin != null ? currentTaskAtBegin.Id : 0),
+                    task.Id, TplEtwProvider.TaskWaitBehavior.Asynchronous,
+                    (continuationTask != null ? continuationTask.Id : 0));
+            }
+
+            // Create a continuation action that outputs the end event and then invokes the user
+            // provided delegate.  This incurs the allocations for the closure/delegate, but only if the event
+            // is enabled, and in doing so it allows us to pass the awaited task's information into the end event
+            // in a purely pay-for-play manner (the alternatively would be to increase the size of TaskAwaiter
+            // just for this ETW purpose, not pay-for-play, since GetResult would need to know whether a real yield occurred).
+            return AsyncMethodBuilderCore.CreateContinuationWrapper(continuation, (innerContinuation,innerTask) =>
+            {
+                if (Task.s_asyncDebuggingEnabled)
+                {
+                    Task.RemoveFromActiveTasks(innerTask.Id);
+                }
+
+                TplEtwProvider innerEtwLog = TplEtwProvider.Log;
+
+                // ETW event for Task Wait End.
+                Guid prevActivityId = new Guid();
+                bool bEtwLogEnabled = innerEtwLog.IsEnabled();
+                if (bEtwLogEnabled)
+                {
+                    var currentTaskAtEnd = Task.InternalCurrent;
+                    innerEtwLog.TaskWaitEnd(
+                        (currentTaskAtEnd != null ? currentTaskAtEnd.m_taskScheduler.Id : TaskScheduler.Default.Id),
+                        (currentTaskAtEnd != null ? currentTaskAtEnd.Id : 0),
+                        innerTask.Id);
+
+                    // Ensure the continuation runs under the activity ID of the task that completed for the
+                    // case the antecendent is a promise (in the other cases this is already the case).
+                    if (innerEtwLog.TasksSetActivityIds && (innerTask.Options & (TaskCreationOptions)InternalTaskOptions.PromiseTask) != 0)
+                        EventSource.SetCurrentThreadActivityId(TplEtwProvider.CreateGuidForTaskID(innerTask.Id), out prevActivityId);
+                }
+
+                // Invoke the original continuation provided to OnCompleted.
+                innerContinuation();
+
+                if (bEtwLogEnabled)
+                {
+                    innerEtwLog.TaskWaitContinuationComplete(innerTask.Id);
+                    if (innerEtwLog.TasksSetActivityIds && (innerTask.Options & (TaskCreationOptions)InternalTaskOptions.PromiseTask) != 0)
+                        EventSource.SetCurrentThreadActivityId(prevActivityId);
+                }
+            }, task);
+        }
+    }
+
+    /// <summary>Provides an awaiter for awaiting a <see cref="System.Threading.Tasks.Task{TResult}"/>.</summary>
+    /// <remarks>This type is intended for compiler use only.</remarks>
+    public readonly struct TaskAwaiter<TResult> : ICriticalNotifyCompletion, ITaskAwaiter
+    {
+        // WARNING: Unsafe.As is used to access TaskAwaiter<> as the non-generic TaskAwaiter.
+        // Its layout must remain the same.
+
+        /// <summary>The task being awaited.</summary>
+        private readonly Task<TResult> m_task;
+
+        /// <summary>Initializes the <see cref="TaskAwaiter{TResult}"/>.</summary>
+        /// <param name="task">The <see cref="System.Threading.Tasks.Task{TResult}"/> to be awaited.</param>
+        internal TaskAwaiter(Task<TResult> task)
+        {
+            Debug.Assert(task != null, "Constructing an awaiter requires a task to await.");
+            m_task = task;
+        }
+
+        /// <summary>Gets whether the task being awaited is completed.</summary>
+        /// <remarks>This property is intended for compiler user rather than use directly in code.</remarks>
+        /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+        public bool IsCompleted
+        {
+            get { return m_task.IsCompleted; }
+        }
+
+        /// <summary>Schedules the continuation onto the <see cref="System.Threading.Tasks.Task"/> associated with this <see cref="TaskAwaiter"/>.</summary>
+        /// <param name="continuation">The action to invoke when the await operation completes.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+        /// <remarks>This method is intended for compiler user rather than use directly in code.</remarks>
+        public void OnCompleted(Action continuation)
+        {
+            TaskAwaiter.OnCompletedInternal(m_task, continuation, continueOnCapturedContext: true, flowExecutionContext: true);
+        }
+
+        /// <summary>Schedules the continuation onto the <see cref="System.Threading.Tasks.Task"/> associated with this <see cref="TaskAwaiter"/>.</summary>
+        /// <param name="continuation">The action to invoke when the await operation completes.</param>
+        /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+        /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+        /// <remarks>This method is intended for compiler user rather than use directly in code.</remarks>
+        public void UnsafeOnCompleted(Action continuation)
+        {
+            TaskAwaiter.OnCompletedInternal(m_task, continuation, continueOnCapturedContext: true, flowExecutionContext: false);
+        }
+
+        /// <summary>Ends the await on the completed <see cref="System.Threading.Tasks.Task{TResult}"/>.</summary>
+        /// <returns>The result of the completed <see cref="System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+        /// <exception cref="System.Threading.Tasks.TaskCanceledException">The task was canceled.</exception>
+        /// <exception cref="System.Exception">The task completed in a Faulted state.</exception>
+        [StackTraceHidden]
+        public TResult GetResult()
+        {
+            TaskAwaiter.ValidateEnd(m_task);
+            return m_task.ResultOnSuccess;
+        }
+    }
+
+    /// <summary>
+    /// Marker interface used to know whether a particular awaiter is either a
+    /// TaskAwaiter or a TaskAwaiter`1.  It must not be implemented by any other
+    /// awaiters.
+    /// </summary>
+    internal interface ITaskAwaiter { }
+
+    /// <summary>
+    /// Marker interface used to know whether a particular awaiter is either a
+    /// CTA.ConfiguredTaskAwaiter or a CTA`1.ConfiguredTaskAwaiter.  It must not
+    /// be implemented by any other awaiters.
+    /// </summary>
+    internal interface IConfiguredTaskAwaiter { }
+
+    /// <summary>Provides an awaitable object that allows for configured awaits on <see cref="System.Threading.Tasks.Task"/>.</summary>
+    /// <remarks>This type is intended for compiler use only.</remarks>
+    public readonly struct ConfiguredTaskAwaitable
+    {
+        /// <summary>The task being awaited.</summary>
+        private readonly ConfiguredTaskAwaitable.ConfiguredTaskAwaiter m_configuredTaskAwaiter;
+
+        /// <summary>Initializes the <see cref="ConfiguredTaskAwaitable"/>.</summary>
+        /// <param name="task">The awaitable <see cref="System.Threading.Tasks.Task"/>.</param>
+        /// <param name="continueOnCapturedContext">
+        /// true to attempt to marshal the continuation back to the original context captured; otherwise, false.
+        /// </param>
+        internal ConfiguredTaskAwaitable(Task task, bool continueOnCapturedContext)
+        {
+            Debug.Assert(task != null, "Constructing an awaitable requires a task to await.");
+            m_configuredTaskAwaiter = new ConfiguredTaskAwaitable.ConfiguredTaskAwaiter(task, continueOnCapturedContext);
+        }
+
+        /// <summary>Gets an awaiter for this awaitable.</summary>
+        /// <returns>The awaiter.</returns>
+        public ConfiguredTaskAwaitable.ConfiguredTaskAwaiter GetAwaiter()
+        {
+            return m_configuredTaskAwaiter;
+        }
+
+        /// <summary>Provides an awaiter for a <see cref="ConfiguredTaskAwaitable"/>.</summary>
+        /// <remarks>This type is intended for compiler use only.</remarks>
+        public readonly struct ConfiguredTaskAwaiter : ICriticalNotifyCompletion, IConfiguredTaskAwaiter
+        {
+            // WARNING: Unsafe.As is used to access the generic ConfiguredTaskAwaiter as this.
+            // Its layout must remain the same.
+
+            /// <summary>The task being awaited.</summary>
+            internal readonly Task m_task;
+            /// <summary>Whether to attempt marshaling back to the original context.</summary>
+            internal readonly bool m_continueOnCapturedContext;
+
+            /// <summary>Initializes the <see cref="ConfiguredTaskAwaiter"/>.</summary>
+            /// <param name="task">The <see cref="System.Threading.Tasks.Task"/> to await.</param>
+            /// <param name="continueOnCapturedContext">
+            /// true to attempt to marshal the continuation back to the original context captured
+            /// when BeginAwait is called; otherwise, false.
+            /// </param>
+            internal ConfiguredTaskAwaiter(Task task, bool continueOnCapturedContext)
+            {
+                Debug.Assert(task != null, "Constructing an awaiter requires a task to await.");
+                m_task = task;
+                m_continueOnCapturedContext = continueOnCapturedContext;
+            }
+
+            /// <summary>Gets whether the task being awaited is completed.</summary>
+            /// <remarks>This property is intended for compiler user rather than use directly in code.</remarks>
+            /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+            public bool IsCompleted
+            {
+                get { return m_task.IsCompleted; }
+            }
+
+            /// <summary>Schedules the continuation onto the <see cref="System.Threading.Tasks.Task"/> associated with this <see cref="TaskAwaiter"/>.</summary>
+            /// <param name="continuation">The action to invoke when the await operation completes.</param>
+            /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+            /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+            /// <remarks>This method is intended for compiler user rather than use directly in code.</remarks>
+            public void OnCompleted(Action continuation)
+            {
+                TaskAwaiter.OnCompletedInternal(m_task, continuation, m_continueOnCapturedContext, flowExecutionContext: true);
+            }
+
+            /// <summary>Schedules the continuation onto the <see cref="System.Threading.Tasks.Task"/> associated with this <see cref="TaskAwaiter"/>.</summary>
+            /// <param name="continuation">The action to invoke when the await operation completes.</param>
+            /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+            /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+            /// <remarks>This method is intended for compiler user rather than use directly in code.</remarks>
+            public void UnsafeOnCompleted(Action continuation)
+            {
+                TaskAwaiter.OnCompletedInternal(m_task, continuation, m_continueOnCapturedContext, flowExecutionContext: false);
+            }
+
+            /// <summary>Ends the await on the completed <see cref="System.Threading.Tasks.Task"/>.</summary>
+            /// <returns>The result of the completed <see cref="System.Threading.Tasks.Task{TResult}"/>.</returns>
+            /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+            /// <exception cref="System.Threading.Tasks.TaskCanceledException">The task was canceled.</exception>
+            /// <exception cref="System.Exception">The task completed in a Faulted state.</exception>
+            [StackTraceHidden]
+            public void GetResult()
+            {
+                TaskAwaiter.ValidateEnd(m_task);
+            }
+        }
+    }
+
+    /// <summary>Provides an awaitable object that allows for configured awaits on <see cref="System.Threading.Tasks.Task{TResult}"/>.</summary>
+    /// <remarks>This type is intended for compiler use only.</remarks>
+    public readonly struct ConfiguredTaskAwaitable<TResult>
+    {
+        /// <summary>The underlying awaitable on whose logic this awaitable relies.</summary>
+        private readonly ConfiguredTaskAwaitable<TResult>.ConfiguredTaskAwaiter m_configuredTaskAwaiter;
+
+        /// <summary>Initializes the <see cref="ConfiguredTaskAwaitable{TResult}"/>.</summary>
+        /// <param name="task">The awaitable <see cref="System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="continueOnCapturedContext">
+        /// true to attempt to marshal the continuation back to the original context captured; otherwise, false.
+        /// </param>
+        internal ConfiguredTaskAwaitable(Task<TResult> task, bool continueOnCapturedContext)
+        {
+            m_configuredTaskAwaiter = new ConfiguredTaskAwaitable<TResult>.ConfiguredTaskAwaiter(task, continueOnCapturedContext);
+        }
+
+        /// <summary>Gets an awaiter for this awaitable.</summary>
+        /// <returns>The awaiter.</returns>
+        public ConfiguredTaskAwaitable<TResult>.ConfiguredTaskAwaiter GetAwaiter()
+        {
+            return m_configuredTaskAwaiter;
+        }
+
+        /// <summary>Provides an awaiter for a <see cref="ConfiguredTaskAwaitable{TResult}"/>.</summary>
+        /// <remarks>This type is intended for compiler use only.</remarks>
+        public readonly struct ConfiguredTaskAwaiter : ICriticalNotifyCompletion, IConfiguredTaskAwaiter
+        {
+            // WARNING: Unsafe.As is used to access this as the non-generic ConfiguredTaskAwaiter.
+            // Its layout must remain the same.
+
+            /// <summary>The task being awaited.</summary>
+            private readonly Task<TResult> m_task;
+            /// <summary>Whether to attempt marshaling back to the original context.</summary>
+            private readonly bool m_continueOnCapturedContext;
+
+            /// <summary>Initializes the <see cref="ConfiguredTaskAwaiter"/>.</summary>
+            /// <param name="task">The awaitable <see cref="System.Threading.Tasks.Task{TResult}"/>.</param>
+            /// <param name="continueOnCapturedContext">
+            /// true to attempt to marshal the continuation back to the original context captured; otherwise, false.
+            /// </param>
+            internal ConfiguredTaskAwaiter(Task<TResult> task, bool continueOnCapturedContext)
+            {
+                Debug.Assert(task != null, "Constructing an awaiter requires a task to await.");
+                m_task = task;
+                m_continueOnCapturedContext = continueOnCapturedContext;
+            }
+
+            /// <summary>Gets whether the task being awaited is completed.</summary>
+            /// <remarks>This property is intended for compiler user rather than use directly in code.</remarks>
+            /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+            public bool IsCompleted
+            {
+                get { return m_task.IsCompleted; }
+            }
+
+            /// <summary>Schedules the continuation onto the <see cref="System.Threading.Tasks.Task"/> associated with this <see cref="TaskAwaiter"/>.</summary>
+            /// <param name="continuation">The action to invoke when the await operation completes.</param>
+            /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+            /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+            /// <remarks>This method is intended for compiler user rather than use directly in code.</remarks>
+            public void OnCompleted(Action continuation)
+            {
+                TaskAwaiter.OnCompletedInternal(m_task, continuation, m_continueOnCapturedContext, flowExecutionContext: true);
+            }
+
+            /// <summary>Schedules the continuation onto the <see cref="System.Threading.Tasks.Task"/> associated with this <see cref="TaskAwaiter"/>.</summary>
+            /// <param name="continuation">The action to invoke when the await operation completes.</param>
+            /// <exception cref="System.ArgumentNullException">The <paramref name="continuation"/> argument is null (Nothing in Visual Basic).</exception>
+            /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+            /// <remarks>This method is intended for compiler user rather than use directly in code.</remarks>
+            public void UnsafeOnCompleted(Action continuation)
+            {
+                TaskAwaiter.OnCompletedInternal(m_task, continuation, m_continueOnCapturedContext, flowExecutionContext: false);
+            }
+
+            /// <summary>Ends the await on the completed <see cref="System.Threading.Tasks.Task{TResult}"/>.</summary>
+            /// <returns>The result of the completed <see cref="System.Threading.Tasks.Task{TResult}"/>.</returns>
+            /// <exception cref="System.NullReferenceException">The awaiter was not properly initialized.</exception>
+            /// <exception cref="System.Threading.Tasks.TaskCanceledException">The task was canceled.</exception>
+            /// <exception cref="System.Exception">The task completed in a Faulted state.</exception>
+            [StackTraceHidden]
+            public TResult GetResult()
+            {
+                TaskAwaiter.ValidateEnd(m_task);
+                return m_task.ResultOnSuccess;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/TypeDependencyAttribute.cs b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/TypeDependencyAttribute.cs
new file mode 100644
index 0000000000..3e386fa8b7
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/TypeDependencyAttribute.cs
@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Runtime.CompilerServices
+{
+    // We might want to make this inherited someday.  But I suspect it shouldn't
+    // be necessary.
+    [AttributeUsage(AttributeTargets.Struct | AttributeTargets.Class | AttributeTargets.Interface, AllowMultiple = true, Inherited = false)]
+    internal sealed class TypeDependencyAttribute : Attribute
+    {
+        private string typeName;
+
+        public TypeDependencyAttribute(string typeName)
+        {
+            if (typeName == null) throw new ArgumentNullException(nameof(typeName));
+            this.typeName = typeName;
+        }
+    }
+}
+
+
+
diff --git a/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/jithelpers.cs b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/jithelpers.cs
new file mode 100644
index 0000000000..42fe79d83b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/CompilerServices/jithelpers.cs
@@ -0,0 +1,195 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////////
+// JitHelpers
+//    Low-level Jit Helpers
+////////////////////////////////////////////////////////////////////////////////
+
+using System;
+using System.Threading;
+using System.Runtime;
+using System.Runtime.Versioning;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Security;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.CompilerServices
+{
+    // Wrapper for address of a string variable on stack
+    internal struct StringHandleOnStack
+    {
+        private IntPtr m_ptr;
+
+        internal StringHandleOnStack(IntPtr pString)
+        {
+            m_ptr = pString;
+        }
+    }
+
+    // Wrapper for address of a object variable on stack
+    internal struct ObjectHandleOnStack
+    {
+        private IntPtr m_ptr;
+
+        internal ObjectHandleOnStack(IntPtr pObject)
+        {
+            m_ptr = pObject;
+        }
+    }
+
+    // Wrapper for StackCrawlMark
+    internal struct StackCrawlMarkHandle
+    {
+        private IntPtr m_ptr;
+
+        internal StackCrawlMarkHandle(IntPtr stackMark)
+        {
+            m_ptr = stackMark;
+        }
+    }
+
+    // Helper class to assist with unsafe pinning of arbitrary objects. The typical usage pattern is:
+    // fixed (byte * pData = &JitHelpers.GetPinningHelper(value).m_data)
+    // {
+    //    ... pData is what Object::GetData() returns in VM ...
+    // }
+    internal class PinningHelper
+    {
+        public byte m_data;
+    }
+
+    internal class ArrayPinningHelper
+    {
+        public IntPtr m_lengthAndPadding;
+        public byte m_arrayData;
+    }
+
+    internal static class JitHelpers
+    {
+        // The special dll name to be used for DllImport of QCalls
+        internal const string QCall = "QCall";
+
+        // Wraps object variable into a handle. Used to return managed strings from QCalls.
+        // s has to be a local variable on the stack.
+        internal static StringHandleOnStack GetStringHandleOnStack(ref string s)
+        {
+            return new StringHandleOnStack(UnsafeCastToStackPointer(ref s));
+        }
+
+        // Wraps object variable into a handle. Used to pass managed object references in and out of QCalls.
+        // o has to be a local variable on the stack.
+        internal static ObjectHandleOnStack GetObjectHandleOnStack<T>(ref T o) where T : class
+        {
+            return new ObjectHandleOnStack(UnsafeCastToStackPointer(ref o));
+        }
+
+        // Wraps StackCrawlMark into a handle. Used to pass StackCrawlMark to QCalls.
+        // stackMark has to be a local variable on the stack.
+        internal static StackCrawlMarkHandle GetStackCrawlMarkHandle(ref StackCrawlMark stackMark)
+        {
+            return new StackCrawlMarkHandle(UnsafeCastToStackPointer(ref stackMark));
+        }
+
+#if DEBUG
+        internal static int UnsafeEnumCast<T>(T val) where T : struct		// Actually T must be 4 byte (or less) enum
+        {
+            Debug.Assert(typeof(T).IsEnum
+                              && (Enum.GetUnderlyingType(typeof(T)) == typeof(int)
+                                  || Enum.GetUnderlyingType(typeof(T)) == typeof(uint)
+                                  || Enum.GetUnderlyingType(typeof(T)) == typeof(short)
+                                  || Enum.GetUnderlyingType(typeof(T)) == typeof(ushort)
+                                  || Enum.GetUnderlyingType(typeof(T)) == typeof(byte)
+                                  || Enum.GetUnderlyingType(typeof(T)) == typeof(sbyte)),
+                "Error, T must be an 4 byte (or less) enum JitHelpers.UnsafeEnumCast!");
+            return UnsafeEnumCastInternal<T>(val);
+        }
+
+        private static int UnsafeEnumCastInternal<T>(T val) where T : struct		// Actually T must be 4 (or less) byte enum
+        {
+            // should be return (int) val; but C# does not allow, runtime does this magically
+            // See getILIntrinsicImplementation for how this happens.  
+            throw new InvalidOperationException();
+        }
+
+        internal static long UnsafeEnumCastLong<T>(T val) where T : struct		// Actually T must be 8 byte enum
+        {
+            Debug.Assert(typeof(T).IsEnum
+                              && (Enum.GetUnderlyingType(typeof(T)) == typeof(long)
+                                  || Enum.GetUnderlyingType(typeof(T)) == typeof(ulong)),
+                "Error, T must be an 8 byte enum JitHelpers.UnsafeEnumCastLong!");
+            return UnsafeEnumCastLongInternal<T>(val);
+        }
+
+        private static long UnsafeEnumCastLongInternal<T>(T val) where T : struct	// Actually T must be 8 byte enum
+        {
+            // should be return (int) val; but C# does not allow, runtime does this magically
+            // See getILIntrinsicImplementation for how this happens.  
+            throw new InvalidOperationException();
+        }
+
+        // Internal method for getting a raw pointer for handles in JitHelpers.
+        // The reference has to point into a local stack variable in order so it can not be moved by the GC.
+        internal static IntPtr UnsafeCastToStackPointer<T>(ref T val)
+        {
+            IntPtr p = UnsafeCastToStackPointerInternal<T>(ref val);
+            Debug.Assert(IsAddressInStack(p), "Pointer not in the stack!");
+            return p;
+        }
+
+        private static IntPtr UnsafeCastToStackPointerInternal<T>(ref T val)
+        {
+            // The body of this function will be replaced by the EE with unsafe code that just returns val!!!
+            // See getILIntrinsicImplementation for how this happens.  
+            throw new InvalidOperationException();
+        }
+#else // DEBUG
+
+        internal static int UnsafeEnumCast<T>(T val) where T : struct		// Actually T must be 4 byte (or less) enum
+        {
+            // should be return (int) val; but C# does not allow, runtime does this magically
+            // See getILIntrinsicImplementation for how this happens.  
+            throw new InvalidOperationException();
+        }
+
+        internal static long UnsafeEnumCastLong<T>(T val) where T : struct	// Actually T must be 8 byte enum
+        {
+            // should be return (long) val; but C# does not allow, runtime does this magically
+            // See getILIntrinsicImplementation for how this happens.  
+            throw new InvalidOperationException();
+        }
+
+        internal static IntPtr UnsafeCastToStackPointer<T>(ref T val)
+        {
+            // The body of this function will be replaced by the EE with unsafe code that just returns o!!!
+            // See getILIntrinsicImplementation for how this happens.  
+            throw new InvalidOperationException();
+        }
+#endif // DEBUG
+
+        // Set the given element in the array without any type or range checks
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void UnsafeSetArrayElement(Object[] target, int index, Object element);
+
+        // Used for unsafe pinning of arbitrary objects.
+        internal static PinningHelper GetPinningHelper(Object o)
+        {
+            return Unsafe.As<PinningHelper>(o);
+        }
+
+#if DEBUG
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool IsAddressInStack(IntPtr ptr);
+#endif
+
+        internal static ref byte GetRawSzArrayData(this Array array)
+        {
+            // The body of this function will be replaced by the EE with unsafe code!!!
+            // See getILIntrinsicImplementation for how this happens.
+            typeof(ArrayPinningHelper).ToString(); // Type used by the actual method body
+            throw new InvalidOperationException();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/ExceptionServices/ExceptionDispatchInfo.cs b/src/System.Private.CoreLib/src/System/Runtime/ExceptionServices/ExceptionDispatchInfo.cs
new file mode 100644
index 0000000000..0a379667d7
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/ExceptionServices/ExceptionDispatchInfo.cs
@@ -0,0 +1,139 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Contains common usage support entities for advanced exception
+**          handling/processing scenarios.
+**
+** Created: 11/2/2010
+** 
+** 
+** 
+=============================================================================*/
+
+using System;
+using System.Diagnostics;
+
+namespace System.Runtime.ExceptionServices
+{
+    // This class defines support for seperating the exception dispatch details
+    // (like stack trace, watson buckets, etc) from the actual managed exception
+    // object. This allows us to track error (via the exception object) independent
+    // of the path the error takes.
+    //
+    // This is particularly useful for frameworks like PFX, APM, etc that wish to
+    // propagate exceptions (i.e. errors to be precise) across threads.
+    public sealed class ExceptionDispatchInfo
+    {
+        // Private members that will hold the relevant details.
+        private Exception m_Exception;
+        private string m_remoteStackTrace;
+        private object m_stackTrace;
+        private object m_dynamicMethods;
+        private UIntPtr m_IPForWatsonBuckets;
+        private Object m_WatsonBuckets;
+
+        private ExceptionDispatchInfo(Exception exception)
+        {
+            // Copy over the details we need to save.
+            m_Exception = exception;
+            m_remoteStackTrace = exception.RemoteStackTrace;
+
+            // NOTE: don't be tempted to pass the fields for the out params; the containing object
+            //       might be relocated during the call so the pointers will no longer be valid.
+            object stackTrace;
+            object dynamicMethods;
+            m_Exception.GetStackTracesDeepCopy(out stackTrace, out dynamicMethods);
+            m_stackTrace = stackTrace;
+            m_dynamicMethods = dynamicMethods;
+
+            m_IPForWatsonBuckets = exception.IPForWatsonBuckets;
+            m_WatsonBuckets = exception.WatsonBuckets;
+        }
+
+        internal UIntPtr IPForWatsonBuckets
+        {
+            get
+            {
+                return m_IPForWatsonBuckets;
+            }
+        }
+
+        internal object WatsonBuckets
+        {
+            get
+            {
+                return m_WatsonBuckets;
+            }
+        }
+
+        internal object BinaryStackTraceArray
+        {
+            get
+            {
+                return m_stackTrace;
+            }
+        }
+
+        internal object DynamicMethodArray
+        {
+            get
+            {
+                return m_dynamicMethods;
+            }
+        }
+
+        internal string RemoteStackTrace
+        {
+            get
+            {
+                return m_remoteStackTrace;
+            }
+        }
+
+        // This static method is used to create an instance of ExceptionDispatchInfo for
+        // the specified exception object and save all the required details that maybe
+        // needed to be propagated when the exception is "rethrown" on a different thread.
+        public static ExceptionDispatchInfo Capture(Exception source)
+        {
+            if (source == null)
+            {
+                throw new ArgumentNullException(nameof(source), SR.ArgumentNull_Obj);
+            }
+
+            return new ExceptionDispatchInfo(source);
+        }
+
+        // Return the exception object represented by this ExceptionDispatchInfo instance
+        public Exception SourceException
+        {
+            get
+            {
+                return m_Exception;
+            }
+        }
+
+        // When a framework needs to "Rethrow" an exception on a thread different (but not necessarily so) from
+        // where it was thrown, it should invoke this method against the ExceptionDispatchInfo (EDI)
+        // created for the exception in question.
+        //
+        // This method will restore the original stack trace and bucketing details before throwing
+        // the exception so that it is easy, from debugging standpoint, to understand what really went wrong on
+        // the original thread.
+        [StackTraceHidden]
+        public void Throw()
+        {
+            // Restore the exception dispatch details before throwing the exception.
+            m_Exception.RestoreExceptionDispatchInfo(this);
+            throw m_Exception;
+        }
+
+        // Throws the source exception, maintaining the original bucketing details and augmenting
+        // rather than replacing the original stack trace.
+        public static void Throw(Exception source) => Capture(source).Throw();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/GcSettings.cs b/src/System.Private.CoreLib/src/System/Runtime/GcSettings.cs
new file mode 100644
index 0000000000..6e08aa3dc5
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/GcSettings.cs
@@ -0,0 +1,86 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.ConstrainedExecution;
+
+namespace System.Runtime
+{
+    // These settings are the same format as in clr\src\vm\gcpriv.h
+    // make sure you change that file if you change this file!
+
+    public enum GCLargeObjectHeapCompactionMode
+    {
+        Default = 1,
+        CompactOnce = 2
+    }
+
+    public enum GCLatencyMode
+    {
+        Batch = 0,
+        Interactive = 1,
+        LowLatency = 2,
+        SustainedLowLatency = 3,
+        NoGCRegion = 4
+    }
+
+    public static class GCSettings
+    {
+        private enum SetLatencyModeStatus
+        {
+            Succeeded = 0,
+            NoGCInProgress = 1 // NoGCRegion is in progress, can't change pause mode.
+        };
+
+        public static GCLatencyMode LatencyMode
+        {
+            get
+            {
+                return (GCLatencyMode)(GC.GetGCLatencyMode());
+            }
+
+            // We don't want to allow this API when hosted.
+            set
+            {
+                if ((value < GCLatencyMode.Batch) || (value > GCLatencyMode.SustainedLowLatency))
+                {
+                    throw new ArgumentOutOfRangeException(SR.ArgumentOutOfRange_Enum);
+                }
+
+                if (GC.SetGCLatencyMode((int)value) == (int)SetLatencyModeStatus.NoGCInProgress)
+                    throw new InvalidOperationException("The NoGCRegion mode is in progress. End it and then set a different mode.");
+            }
+        }
+
+        public static GCLargeObjectHeapCompactionMode LargeObjectHeapCompactionMode
+        {
+            get
+            {
+                return (GCLargeObjectHeapCompactionMode)(GC.GetLOHCompactionMode());
+            }
+
+            // We don't want to allow this API when hosted.
+            set
+            {
+                if ((value < GCLargeObjectHeapCompactionMode.Default) ||
+                    (value > GCLargeObjectHeapCompactionMode.CompactOnce))
+                {
+                    throw new ArgumentOutOfRangeException(SR.ArgumentOutOfRange_Enum);
+                }
+
+                GC.SetLOHCompactionMode((int)value);
+            }
+        }
+
+        public static bool IsServerGC
+        {
+            get
+            {
+                return GC.IsServerGC();
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ArrayWithOffset.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ArrayWithOffset.cs
new file mode 100644
index 0000000000..e009db277f
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ArrayWithOffset.cs
@@ -0,0 +1,72 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+
+namespace System.Runtime.InteropServices
+{
+    public struct ArrayWithOffset
+    {
+        //private ArrayWithOffset()
+        //{
+        //    throw new Exception();
+        //}
+
+        public ArrayWithOffset(Object array, int offset)
+        {
+            m_array = array;
+            m_offset = offset;
+            m_count = 0;
+            m_count = CalculateCount();
+        }
+
+        public Object GetArray()
+        {
+            return m_array;
+        }
+
+        public int GetOffset()
+        {
+            return m_offset;
+        }
+
+        public override int GetHashCode()
+        {
+            return m_count + m_offset;
+        }
+
+        public override bool Equals(Object obj)
+        {
+            if (obj is ArrayWithOffset)
+                return Equals((ArrayWithOffset)obj);
+            else
+                return false;
+        }
+
+        public bool Equals(ArrayWithOffset obj)
+        {
+            return obj.m_array == m_array && obj.m_offset == m_offset && obj.m_count == m_count;
+        }
+
+        public static bool operator ==(ArrayWithOffset a, ArrayWithOffset b)
+        {
+            return a.Equals(b);
+        }
+
+        public static bool operator !=(ArrayWithOffset a, ArrayWithOffset b)
+        {
+            return !(a == b);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern int CalculateCount();
+
+        private Object m_array;
+        private int m_offset;
+        private int m_count;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/Attributes.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/Attributes.cs
new file mode 100644
index 0000000000..4141202129
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/Attributes.cs
@@ -0,0 +1,177 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+
+using System;
+using System.Reflection;
+using System.Diagnostics;
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Interface | AttributeTargets.Enum | AttributeTargets.Struct | AttributeTargets.Delegate, AllowMultiple = false, Inherited = false)]
+    public sealed class TypeIdentifierAttribute : Attribute
+    {
+        public TypeIdentifierAttribute() { }
+        public TypeIdentifierAttribute(string scope, string identifier) { Scope_ = scope; Identifier_ = identifier; }
+
+        public String Scope { get { return Scope_; } }
+        public String Identifier { get { return Identifier_; } }
+
+        internal String Scope_;
+        internal String Identifier_;
+    }
+
+    // To be used on methods that sink reverse P/Invoke calls.
+    // This attribute is a CoreCLR-only security measure, currently ignored by the desktop CLR.
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = false)]
+    public sealed class AllowReversePInvokeCallsAttribute : Attribute
+    {
+        public AllowReversePInvokeCallsAttribute()
+        {
+        }
+    }
+
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Field | AttributeTargets.Property | AttributeTargets.Event, Inherited = false)]
+    public sealed class DispIdAttribute : Attribute
+    {
+        internal int _val;
+        public DispIdAttribute(int dispId)
+        {
+            _val = dispId;
+        }
+        public int Value { get { return _val; } }
+    }
+
+    public enum ComInterfaceType
+    {
+        InterfaceIsDual = 0,
+        InterfaceIsIUnknown = 1,
+        InterfaceIsIDispatch = 2,
+
+        InterfaceIsIInspectable = 3,
+    }
+
+    [AttributeUsage(AttributeTargets.Interface, Inherited = false)]
+    public sealed class InterfaceTypeAttribute : Attribute
+    {
+        internal ComInterfaceType _val;
+        public InterfaceTypeAttribute(ComInterfaceType interfaceType)
+        {
+            _val = interfaceType;
+        }
+        public InterfaceTypeAttribute(short interfaceType)
+        {
+            _val = (ComInterfaceType)interfaceType;
+        }
+        public ComInterfaceType Value { get { return _val; } }
+    }
+
+    [AttributeUsage(AttributeTargets.Class, Inherited = false)]
+    public sealed class ComDefaultInterfaceAttribute : Attribute
+    {
+        internal Type _val;
+
+        public ComDefaultInterfaceAttribute(Type defaultInterface)
+        {
+            _val = defaultInterface;
+        }
+
+        public Type Value { get { return _val; } }
+    }
+
+    public enum ClassInterfaceType
+    {
+        None = 0,
+        AutoDispatch = 1,
+        AutoDual = 2
+    }
+
+    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class, Inherited = false)]
+    public sealed class ClassInterfaceAttribute : Attribute
+    {
+        internal ClassInterfaceType _val;
+        public ClassInterfaceAttribute(ClassInterfaceType classInterfaceType)
+        {
+            _val = classInterfaceType;
+        }
+        public ClassInterfaceAttribute(short classInterfaceType)
+        {
+            _val = (ClassInterfaceType)classInterfaceType;
+        }
+        public ClassInterfaceType Value { get { return _val; } }
+    }
+
+    [AttributeUsage(AttributeTargets.Method, Inherited = false)]
+    public sealed class LCIDConversionAttribute : Attribute
+    {
+        internal int _val;
+        public LCIDConversionAttribute(int lcid)
+        {
+            _val = lcid;
+        }
+        public int Value { get { return _val; } }
+    }
+
+    [AttributeUsage(AttributeTargets.Class, Inherited = false)]
+    public sealed class ProgIdAttribute : Attribute
+    {
+        internal String _val;
+        public ProgIdAttribute(String progId)
+        {
+            _val = progId;
+        }
+        public String Value { get { return _val; } }
+    }
+
+    [AttributeUsage(AttributeTargets.Class, Inherited = true)]
+    public sealed class ComSourceInterfacesAttribute : Attribute
+    {
+        internal String _val;
+        public ComSourceInterfacesAttribute(String sourceInterfaces)
+        {
+            _val = sourceInterfaces;
+        }
+        public ComSourceInterfacesAttribute(Type sourceInterface)
+        {
+            _val = sourceInterface.FullName;
+        }
+        public ComSourceInterfacesAttribute(Type sourceInterface1, Type sourceInterface2)
+        {
+            _val = sourceInterface1.FullName + "\0" + sourceInterface2.FullName;
+        }
+        public ComSourceInterfacesAttribute(Type sourceInterface1, Type sourceInterface2, Type sourceInterface3)
+        {
+            _val = sourceInterface1.FullName + "\0" + sourceInterface2.FullName + "\0" + sourceInterface3.FullName;
+        }
+        public ComSourceInterfacesAttribute(Type sourceInterface1, Type sourceInterface2, Type sourceInterface3, Type sourceInterface4)
+        {
+            _val = sourceInterface1.FullName + "\0" + sourceInterface2.FullName + "\0" + sourceInterface3.FullName + "\0" + sourceInterface4.FullName;
+        }
+        public String Value { get { return _val; } }
+    }
+
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface, Inherited = false)]
+    public sealed class ComImportAttribute : Attribute
+    {
+        public ComImportAttribute()
+        {
+        }
+    }
+
+    [AttributeUsage(AttributeTargets.Interface, Inherited = false)]
+    public sealed class CoClassAttribute : Attribute
+    {
+        internal Type _CoClass;
+
+        public CoClassAttribute(Type coClass)
+        {
+            _CoClass = coClass;
+        }
+
+        public Type CoClass { get { return _CoClass; } }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/BStrWrapper.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/BStrWrapper.cs
new file mode 100644
index 0000000000..586b03b366
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/BStrWrapper.cs
@@ -0,0 +1,42 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Wrapper that is converted to a variant with VT_BSTR.
+**
+**
+=============================================================================*/
+
+
+using System;
+using System.Security;
+
+namespace System.Runtime.InteropServices
+{
+    public sealed class BStrWrapper
+    {
+        public BStrWrapper(String value)
+        {
+            m_WrappedObject = value;
+        }
+
+        public BStrWrapper(Object value)
+        {
+            m_WrappedObject = (String)value;
+        }
+
+        public String WrappedObject
+        {
+            get
+            {
+                return m_WrappedObject;
+            }
+        }
+
+        private String m_WrappedObject;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/COMException.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/COMException.cs
new file mode 100644
index 0000000000..c31a1576c4
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/COMException.cs
@@ -0,0 +1,82 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception class for all errors from COM Interop where we don't
+** recognize the HResult.
+**
+**
+=============================================================================*/
+
+using System;
+using System.Runtime.Serialization;
+using System.Globalization;
+using System.Security;
+using Microsoft.Win32;
+
+namespace System.Runtime.InteropServices
+{
+    // Exception for COM Interop errors where we don't recognize the HResult.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class COMException : ExternalException
+    {
+        public COMException()
+            : base(SR.Arg_COMException)
+        {
+            HResult = HResults.E_FAIL;
+        }
+
+        public COMException(String message)
+            : base(message)
+        {
+            HResult = HResults.E_FAIL;
+        }
+
+        public COMException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.E_FAIL;
+        }
+
+        public COMException(String message, int errorCode)
+            : base(message)
+        {
+            HResult = errorCode;
+        }
+
+        protected COMException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+
+        public override String ToString()
+        {
+            String message = Message;
+            String s;
+            String _className = GetType().ToString();
+            s = _className + " (0x" + HResult.ToString("X8", CultureInfo.InvariantCulture) + ")";
+
+            if (!(message == null || message.Length <= 0))
+            {
+                s = s + ": " + message;
+            }
+
+            Exception _innerException = InnerException;
+
+            if (_innerException != null)
+            {
+                s = s + " ---> " + _innerException.ToString();
+            }
+
+
+            if (StackTrace != null)
+                s += Environment.NewLine + StackTrace;
+
+            return s;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsHelper.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsHelper.cs
new file mode 100644
index 0000000000..50e9ea6fee
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsHelper.cs
@@ -0,0 +1,195 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+/*============================================================
+**
+**
+** Purpose: ComEventHelpers APIs allow binding 
+** managed delegates to COM's connection point based events.
+**
+**/
+//
+// #ComEventsFeature
+// 
+// code:#ComEventsFeature defines two public methods allowing to add/remove .NET delegates handling
+// events from COM objects. Those methods are defined as part of code:ComEventsHelper static class
+// * code:ComEventsHelper.Combine - will create/reuse-an-existing COM event sink and register the
+//     specified delegate to be raised when corresponding COM event is raised
+// * code:ComEventsHelper.Remove
+// 
+// 
+// To bind an event handler to the COM object you need to provide the following data:
+//  * rcw - the instance of the COM object you want to bind to
+//  * iid - Guid of the source interface you want the sink to implement
+//  * dispid - dispatch identifier of the event on the source interface you are interested in
+//  * d - delegate to invoked when corresponding COM event is raised.
+// 
+// #ComEventsArchitecture:
+// In COM world, events are handled by so-called event sinks. What these are? COM-based Object Models
+// (OMs) define "source" interfaces that need to be implemented by the COM clients to receive events. So,
+// event sinks are COM objects implementing a source interfaces. Once an event sink is passed to the COM
+// server (through a mechanism known as 'binding/advising to connection point'), COM server will be
+// calling source interface methods to "fire events" (advising, connection points, firing events etc. -
+// is all COM jargon).
+// 
+// There are few interesting obervations about source interfaces. Usually source interfaces are defined
+// as 'dispinterface' - meaning that only late-bound invocations on this interface are allowed. Even
+// though it is not illegal to use early bound invocations on source interfaces - the practice is
+// discouraged because of versioning concerns.
+// 
+// Notice also that each COM server object might define multiple source interfaces and hence have
+// multiple connection points (each CP handles exactly one source interface). COM objects that want to
+// fire events are required to implement IConnectionPointContainer interface which is used by the COM
+// clients to discovery connection poitns - objects implementing IConnectionPoint interface. Once
+// connection point is found - clients can bind to it using IConnectionPoint::Advise (see
+// code:ComEventsSink.Advise).
+// 
+// The idea behind code:#ComEventsFeature is to write a "universal event sink" COM component that is
+// generic enough to handle all late-bound event firings and invoke corresponding COM delegates (through
+// reflection).
+// 
+// When delegate is registered (using code:ComEventsHelper.Combine) we will verify we have corresponding
+// event sink created and bound.
+// 
+// But what happens when COM events are fired? code:ComEventsSink.Invoke implements IDispatch::Invoke method
+// and this is the entry point that is called. Once our event sink is invoked, we need to find the
+// corresponding delegate to invoke . We need to match the dispid of the call that is coming in to a
+// dispid of .NET delegate that has been registered for this object. Once this is found we do call the
+// delegates using reflection (code:ComEventsMethod.Invoke).
+// 
+// #ComEventsArgsMarshalling
+// Notice, that we may not have a delegate registered against every method on the source interface. If we
+// were to marshal all the input parameters for methods that do not reach user code - we would end up
+// generatic RCWs that are not reachable for user code (the inconvenience it might create is there will
+// be RCWs that users can not call Marshal.ReleaseComObject on to explicitly manage the lifetime of these
+// COM objects). The above behavior was one of the shortcoimings of legacy TLBIMP's implementation of COM
+// event sinking. In our code we will not marshal any data if there is no delegate registered to handle
+// the event. (code:ComEventsMethod.Invoke)
+// 
+// #ComEventsFinalization:
+// Additional area of interest is when COM sink should be unadvised from the connection point. Legacy
+// TLBIMP's implementation of COM event sinks will unadvises the sink when corresponding RCW is GCed.
+// This is achieved by rooting the event sinks in a finalizable object stored in RCW's property bag
+// (using Marshal.SetComObjectData). Hence, once RCW is no longer reachable - the finalizer is called and
+// it would unadvise all the event sinks. We are employing the same strategy here. See storing an
+// instance in the RCW at code:ComEventsInfo.FromObject and undadvsing the sinks at
+// code:ComEventsInfo.~ComEventsInfo
+// 
+// Classes of interest:
+// * code:ComEventsHelpers - defines public methods but there are also a number of internal classes that
+//     implement the actual COM event sink:
+// * code:ComEventsInfo - represents a finalizable container for all event sinks for a particular RCW.
+//     Lifetime of this instance corresponds to the lifetime of the RCW object
+// * code:ComEventsSink - represents a single event sink. Maintains an internal pointer to the next
+//     instance (in a singly linked list). A collection of code:ComEventsSink is stored at
+//     code:ComEventsInfo._sinks
+// * code:ComEventsMethod - represents a single method from the source interface which has .NET delegates
+//     attached to it. Maintains an internal pointer to the next instance (in a singly linked list). A
+//     collection of code:ComEventMethod is stored at code:ComEventsSink._methods
+//     
+// #ComEventsRetValIssue:
+// Issue: normally, COM events would not return any value. However, it may happen as described in
+// http://support.microsoft.com/kb/810228. Such design might represent a problem for us - e.g. what is
+// the return value of a chain of delegates - is it the value of the last call in the chain or the the
+// first one? As the above KB article indicates, in cases where OM has events returning values, it is
+// suggested that people implement their event sink by explicitly implementing the source interface. This
+// means that the problem is already quite complex and we should not be dealing with it - see
+// code:ComEventsMethod.Invoke
+
+using System;
+
+namespace System.Runtime.InteropServices
+{
+    /// <summary>
+    /// The static methods provided in ComEventsHelper allow using .NET delegates to subscribe to events
+    /// raised COM objects.
+    /// </summary>
+    public static class ComEventsHelper
+    {
+        /// <summary>
+        /// Adds a delegate to the invocation list of events originating from the COM object.
+        /// </summary>
+        /// <param name="rcw">COM object firing the events the caller would like to respond to</param>
+        /// <param name="iid">identifier of the source interface used by COM object to fire events</param>
+        /// <param name="dispid">dispatch identifier of the method on the source interface</param>
+        /// <param name="d">delegate to invoke when specified COM event is fired</param>
+        public static void Combine(object rcw, Guid iid, int dispid, System.Delegate d)
+        {
+            rcw = UnwrapIfTransparentProxy(rcw);
+
+            lock (rcw)
+            {
+                ComEventsInfo eventsInfo = ComEventsInfo.FromObject(rcw);
+
+                ComEventsSink sink = eventsInfo.FindSink(ref iid);
+                if (sink == null)
+                {
+                    sink = eventsInfo.AddSink(ref iid);
+                }
+
+
+                ComEventsMethod method = sink.FindMethod(dispid);
+                if (method == null)
+                {
+                    method = sink.AddMethod(dispid);
+                }
+
+                method.AddDelegate(d);
+            }
+        }
+
+        /// <summary>
+        /// Removes a delegate from the invocation list of events originating from the COM object.
+        /// </summary>
+        /// <param name="rcw">COM object the delegate is attached to</param>
+        /// <param name="iid">identifier of the source interface used by COM object to fire events</param>
+        /// <param name="dispid">dispatch identifier of the method on the source interface</param>
+        /// <param name="d">delegate to remove from the invocation list</param>
+        /// <returns></returns>
+        public static Delegate Remove(object rcw, Guid iid, int dispid, System.Delegate d)
+        {
+            rcw = UnwrapIfTransparentProxy(rcw);
+
+            lock (rcw)
+            {
+                ComEventsInfo eventsInfo = ComEventsInfo.Find(rcw);
+                if (eventsInfo == null)
+                    return null;
+                ComEventsSink sink = eventsInfo.FindSink(ref iid);
+                if (sink == null)
+                    return null;
+                ComEventsMethod method = sink.FindMethod(dispid);
+                if (method == null)
+                    return null;
+
+                method.RemoveDelegate(d);
+
+                if (method.Empty)
+                {
+                    // removed the last event handler for this dispid - need to remove dispid handler
+                    method = sink.RemoveMethod(method);
+                }
+                if (method == null)
+                {
+                    // removed last dispid handler for this sink - need to remove the sink
+                    sink = eventsInfo.RemoveSink(sink);
+                }
+                if (sink == null)
+                {
+                    // removed last sink for this rcw - need to remove all traces of event info
+                    Marshal.SetComObjectData(rcw, typeof(ComEventsInfo), null);
+                    GC.SuppressFinalize(eventsInfo);
+                }
+
+                return d;
+            }
+        }
+
+        internal static object UnwrapIfTransparentProxy(object rcw)
+        {
+            return rcw;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsInfo.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsInfo.cs
new file mode 100644
index 0000000000..0fbe34db8d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsInfo.cs
@@ -0,0 +1,93 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+/*============================================================
+**
+**
+** Purpose: part of ComEventHelpers APIs which allow binding 
+** managed delegates to COM's connection point based events.
+**
+**/
+
+namespace System.Runtime.InteropServices
+{
+    using System;
+    using ComTypes = System.Runtime.InteropServices.ComTypes;
+
+    // see code:ComEventsHelper#ComEventsArchitecture
+    internal class ComEventsInfo
+    {
+        #region fields
+
+        private ComEventsSink _sinks;
+        private object _rcw;
+
+        #endregion
+
+
+        #region ctor/dtor
+
+        private ComEventsInfo(object rcw)
+        {
+            _rcw = rcw;
+        }
+
+        ~ComEventsInfo()
+        {
+            // see code:ComEventsHelper#ComEventsFinalization
+            _sinks = ComEventsSink.RemoveAll(_sinks);
+        }
+
+        #endregion
+
+
+        #region static methods
+
+        internal static ComEventsInfo Find(object rcw)
+        {
+            return (ComEventsInfo)Marshal.GetComObjectData(rcw, typeof(ComEventsInfo));
+        }
+
+        // it is caller's responsibility to call this method under lock(rcw)
+        internal static ComEventsInfo FromObject(object rcw)
+        {
+            ComEventsInfo eventsInfo = Find(rcw);
+            if (eventsInfo == null)
+            {
+                eventsInfo = new ComEventsInfo(rcw);
+                Marshal.SetComObjectData(rcw, typeof(ComEventsInfo), eventsInfo);
+            }
+            return eventsInfo;
+        }
+
+        #endregion
+
+
+        #region internal methods
+
+        internal ComEventsSink FindSink(ref Guid iid)
+        {
+            return ComEventsSink.Find(_sinks, ref iid);
+        }
+
+        // it is caller's responsibility to call this method under lock(rcw)
+        internal ComEventsSink AddSink(ref Guid iid)
+        {
+            ComEventsSink sink = new ComEventsSink(_rcw, iid);
+            _sinks = ComEventsSink.Add(_sinks, sink);
+
+            return _sinks;
+        }
+
+        // it is caller's responsibility to call this method under lock(rcw)
+        internal ComEventsSink RemoveSink(ComEventsSink sink)
+        {
+            _sinks = ComEventsSink.Remove(_sinks, sink);
+            return _sinks;
+        }
+
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsMethod.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsMethod.cs
new file mode 100644
index 0000000000..8b1bcdcfab
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsMethod.cs
@@ -0,0 +1,198 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+/*============================================================
+**
+**
+** Purpose: part of ComEventHelpers APIs which allow binding 
+** managed delegates to COM's connection point based events.
+**
+**/
+
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Reflection;
+
+
+namespace System.Runtime.InteropServices
+{
+    // see code:ComEventsHelper#ComEventsArchitecture
+    internal class ComEventsMethod
+    {
+        // This delegate wrapper class handles dynamic invocation of delegates. The reason for the wrapper's
+        // existence is that under certain circumstances we need to coerce arguments to types expected by the
+        // delegates signature. Normally, reflection (Delegate.DynamicInvoke) handles types coercion
+        // correctly but one known case is when the expected signature is 'ref Enum' - in this case
+        // reflection by design does not do the coercion. Since we need to be compatible with COM interop
+        // handling of this scenario - we are pre-processing delegate's signature by looking for 'ref enums'
+        // and cache the types required for such coercion.
+        internal class DelegateWrapper
+        {
+            private Delegate _d;
+
+            public DelegateWrapper(Delegate d)
+            {
+                _d = d;
+            }
+
+            public Delegate Delegate
+            {
+                get { return _d; }
+                set { _d = value; }
+            }
+        }
+
+        #region private fields
+
+        /// <summary>
+        /// Invoking ComEventsMethod means invoking a multi-cast delegate attached to it.
+        /// Since multicast delegate's built-in chaining supports only chaining instances of the same type,
+        /// we need to complement this design by using an explicit linked list data structure.
+        /// </summary>
+        private DelegateWrapper[] _delegateWrappers;
+
+        private int _dispid;
+        private ComEventsMethod _next;
+
+        #endregion
+
+
+        #region ctor
+
+        internal ComEventsMethod(int dispid)
+        {
+            _delegateWrappers = null;
+            _dispid = dispid;
+        }
+
+        #endregion
+
+
+        #region internal static methods
+
+        internal static ComEventsMethod Find(ComEventsMethod methods, int dispid)
+        {
+            while (methods != null && methods._dispid != dispid)
+            {
+                methods = methods._next;
+            }
+            return methods;
+        }
+
+        internal static ComEventsMethod Add(ComEventsMethod methods, ComEventsMethod method)
+        {
+            method._next = methods;
+            return method;
+        }
+
+        internal static ComEventsMethod Remove(ComEventsMethod methods, ComEventsMethod method)
+        {
+            if (methods == method)
+            {
+                methods = methods._next;
+            }
+            else
+            {
+                ComEventsMethod current = methods;
+                while (current != null && current._next != method)
+                    current = current._next;
+                if (current != null)
+                    current._next = method._next;
+            }
+
+            return methods;
+        }
+
+        #endregion
+        #region public properties / methods
+
+        internal bool Empty
+        {
+            get { return _delegateWrappers == null || _delegateWrappers.Length == 0; }
+        }
+
+        internal void AddDelegate(Delegate d)
+        {
+            int count = 0;
+            if (_delegateWrappers != null)
+            {
+                count = _delegateWrappers.Length;
+            }
+
+            for (int i = 0; i < count; i++)
+            {
+                if (_delegateWrappers[i].Delegate.GetType() == d.GetType())
+                {
+                    _delegateWrappers[i].Delegate = Delegate.Combine(_delegateWrappers[i].Delegate, d);
+                    return;
+                }
+            }
+
+            DelegateWrapper[] newDelegateWrappers = new DelegateWrapper[count + 1];
+            if (count > 0)
+            {
+                _delegateWrappers.CopyTo(newDelegateWrappers, 0);
+            }
+
+            DelegateWrapper wrapper = new DelegateWrapper(d);
+            newDelegateWrappers[count] = wrapper;
+
+            _delegateWrappers = newDelegateWrappers;
+        }
+
+        internal void RemoveDelegate(Delegate d)
+        {
+            int count = _delegateWrappers.Length;
+            int removeIdx = -1;
+
+            for (int i = 0; i < count; i++)
+            {
+                if (_delegateWrappers[i].Delegate.GetType() == d.GetType())
+                {
+                    removeIdx = i;
+                    break;
+                }
+            }
+
+            if (removeIdx < 0)
+                return;
+
+            Delegate newDelegate = Delegate.Remove(_delegateWrappers[removeIdx].Delegate, d);
+            if (newDelegate != null)
+            {
+                _delegateWrappers[removeIdx].Delegate = newDelegate;
+                return;
+            }
+
+            // now remove the found entry from the _delegates array
+
+            if (count == 1)
+            {
+                _delegateWrappers = null;
+                return;
+            }
+
+            DelegateWrapper[] newDelegateWrappers = new DelegateWrapper[count - 1];
+            int j = 0;
+            while (j < removeIdx)
+            {
+                newDelegateWrappers[j] = _delegateWrappers[j];
+                j++;
+            }
+            while (j < count - 1)
+            {
+                newDelegateWrappers[j] = _delegateWrappers[j + 1];
+                j++;
+            }
+
+            _delegateWrappers = newDelegateWrappers;
+        }
+
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsSink.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsSink.cs
new file mode 100644
index 0000000000..b9f10bc5cb
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComEventsSink.cs
@@ -0,0 +1,183 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+/*============================================================
+**
+**
+** Purpose: part of ComEventHelpers APIs which allow binding 
+** managed delegates to COM's connection point based events.
+**
+**/
+
+using System;
+using System.Diagnostics;
+
+namespace System.Runtime.InteropServices
+{
+    // see code:ComEventsHelper#ComEventsArchitecture
+    internal class ComEventsSink : ICustomQueryInterface
+    {
+        #region private fields
+
+        private Guid _iidSourceItf;
+        private ComTypes.IConnectionPoint _connectionPoint;
+        private int _cookie;
+        private ComEventsMethod _methods;
+        private ComEventsSink _next;
+
+        #endregion
+
+
+        #region ctor
+
+        internal ComEventsSink(object rcw, Guid iid)
+        {
+            _iidSourceItf = iid;
+            this.Advise(rcw);
+        }
+
+        #endregion
+
+
+        #region static members
+
+        internal static ComEventsSink Find(ComEventsSink sinks, ref Guid iid)
+        {
+            ComEventsSink sink = sinks;
+            while (sink != null && sink._iidSourceItf != iid)
+            {
+                sink = sink._next;
+            }
+
+            return sink;
+        }
+
+        internal static ComEventsSink Add(ComEventsSink sinks, ComEventsSink sink)
+        {
+            sink._next = sinks;
+            return sink;
+        }
+
+        internal static ComEventsSink RemoveAll(ComEventsSink sinks)
+        {
+            while (sinks != null)
+            {
+                sinks.Unadvise();
+                sinks = sinks._next;
+            }
+
+            return null;
+        }
+
+        internal static ComEventsSink Remove(ComEventsSink sinks, ComEventsSink sink)
+        {
+            Debug.Assert(sinks != null, "removing event sink from empty sinks collection");
+            Debug.Assert(sink != null, "specify event sink is null");
+
+            if (sink == sinks)
+            {
+                sinks = sinks._next;
+            }
+            else
+            {
+                ComEventsSink current = sinks;
+                while (current != null && current._next != sink)
+                    current = current._next;
+
+                if (current != null)
+                {
+                    current._next = sink._next;
+                }
+            }
+
+            sink.Unadvise();
+
+            return sinks;
+        }
+
+        #endregion
+
+
+        #region public methods
+
+        public ComEventsMethod RemoveMethod(ComEventsMethod method)
+        {
+            _methods = ComEventsMethod.Remove(_methods, method);
+            return _methods;
+        }
+
+        public ComEventsMethod FindMethod(int dispid)
+        {
+            return ComEventsMethod.Find(_methods, dispid);
+        }
+
+        public ComEventsMethod AddMethod(int dispid)
+        {
+            ComEventsMethod method = new ComEventsMethod(dispid);
+            _methods = ComEventsMethod.Add(_methods, method);
+            return method;
+        }
+
+        #endregion
+
+        private static Guid IID_IManagedObject = new Guid("{C3FCC19E-A970-11D2-8B5A-00A0C9B7C9C4}");
+
+        CustomQueryInterfaceResult ICustomQueryInterface.GetInterface(ref Guid iid, out IntPtr ppv)
+        {
+            ppv = IntPtr.Zero;
+            if (iid == _iidSourceItf || iid == typeof(NativeMethods.IDispatch).GUID)
+            {
+                ppv = Marshal.GetComInterfaceForObject(this, typeof(NativeMethods.IDispatch), CustomQueryInterfaceMode.Ignore);
+                return CustomQueryInterfaceResult.Handled;
+            }
+            else if (iid == IID_IManagedObject)
+            {
+                return CustomQueryInterfaceResult.Failed;
+            }
+
+            return CustomQueryInterfaceResult.NotHandled;
+        }
+
+        #region private methods
+
+
+        private void Advise(object rcw)
+        {
+            Debug.Assert(_connectionPoint == null, "comevent sink is already advised");
+
+            ComTypes.IConnectionPointContainer cpc = (ComTypes.IConnectionPointContainer)rcw;
+            ComTypes.IConnectionPoint cp;
+            cpc.FindConnectionPoint(ref _iidSourceItf, out cp);
+
+            object sinkObject = this;
+
+            cp.Advise(sinkObject, out _cookie);
+
+            _connectionPoint = cp;
+        }
+
+        private void Unadvise()
+        {
+            Debug.Assert(_connectionPoint != null, "can not unadvise from empty connection point");
+
+            try
+            {
+                _connectionPoint.Unadvise(_cookie);
+                Marshal.ReleaseComObject(_connectionPoint);
+            }
+            catch (System.Exception)
+            {
+                // swallow all exceptions on unadvise
+                // the host may not be available at this point
+            }
+            finally
+            {
+                _connectionPoint = null;
+            }
+        }
+
+        #endregion
+    };
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComMemberType.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComMemberType.cs
new file mode 100644
index 0000000000..2de01465d3
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComMemberType.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+
+using System;
+
+namespace System.Runtime.InteropServices
+{
+    public enum ComMemberType
+    {
+        Method = 0,
+        PropGet = 1,
+        PropSet = 2
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IBindCtx.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IBindCtx.cs
new file mode 100644
index 0000000000..152f1cd655
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IBindCtx.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: IBindCtx interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    [StructLayout(LayoutKind.Sequential)]
+
+    public struct BIND_OPTS
+    {
+        public int cbStruct;
+        public int grfFlags;
+        public int grfMode;
+        public int dwTickCountDeadline;
+    }
+
+    [Guid("0000000e-0000-0000-C000-000000000046")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface IBindCtx
+    {
+        void RegisterObjectBound([MarshalAs(UnmanagedType.Interface)] Object punk);
+        void RevokeObjectBound([MarshalAs(UnmanagedType.Interface)] Object punk);
+        void ReleaseBoundObjects();
+        void SetBindOptions([In()] ref BIND_OPTS pbindopts);
+        void GetBindOptions(ref BIND_OPTS pbindopts);
+        void GetRunningObjectTable(out IRunningObjectTable pprot);
+        void RegisterObjectParam([MarshalAs(UnmanagedType.LPWStr)] String pszKey, [MarshalAs(UnmanagedType.Interface)] Object punk);
+        void GetObjectParam([MarshalAs(UnmanagedType.LPWStr)] String pszKey, [MarshalAs(UnmanagedType.Interface)] out Object ppunk);
+        void EnumObjectParam(out IEnumString ppenum);
+        [PreserveSig]
+        int RevokeObjectParam([MarshalAs(UnmanagedType.LPWStr)] String pszKey);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IConnectionPoint.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IConnectionPoint.cs
new file mode 100644
index 0000000000..3933d528a9
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IConnectionPoint.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: IConnectionPoint interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    [Guid("B196B286-BAB4-101A-B69C-00AA00341D07")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface IConnectionPoint
+    {
+        void GetConnectionInterface(out Guid pIID);
+        void GetConnectionPointContainer(out IConnectionPointContainer ppCPC);
+        void Advise([MarshalAs(UnmanagedType.Interface)] Object pUnkSink, out int pdwCookie);
+        void Unadvise(int dwCookie);
+        void EnumConnections(out IEnumConnections ppEnum);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IConnectionPointContainer.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IConnectionPointContainer.cs
new file mode 100644
index 0000000000..881dd8acfe
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IConnectionPointContainer.cs
@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: IConnectionPointContainer interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    [Guid("B196B284-BAB4-101A-B69C-00AA00341D07")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface IConnectionPointContainer
+    {
+        void EnumConnectionPoints(out IEnumConnectionPoints ppEnum);
+        void FindConnectionPoint([In] ref Guid riid, out IConnectionPoint ppCP);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumConnectionPoints.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumConnectionPoints.cs
new file mode 100644
index 0000000000..32ad1f7f06
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumConnectionPoints.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: IEnumConnectionPoints interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    [Guid("B196B285-BAB4-101A-B69C-00AA00341D07")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface IEnumConnectionPoints
+    {
+        [PreserveSig]
+        int Next(int celt, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 0), Out] IConnectionPoint[] rgelt, IntPtr pceltFetched);
+        [PreserveSig]
+        int Skip(int celt);
+        void Reset();
+        void Clone(out IEnumConnectionPoints ppenum);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumConnections.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumConnections.cs
new file mode 100644
index 0000000000..1acfe54657
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumConnections.cs
@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: IEnumConnections interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+
+    public struct CONNECTDATA
+    {
+        [MarshalAs(UnmanagedType.Interface)]
+        public Object pUnk;
+        public int dwCookie;
+    }
+
+    [Guid("B196B287-BAB4-101A-B69C-00AA00341D07")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface IEnumConnections
+    {
+        [PreserveSig]
+        int Next(int celt, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 0), Out] CONNECTDATA[] rgelt, IntPtr pceltFetched);
+        [PreserveSig]
+        int Skip(int celt);
+        void Reset();
+        void Clone(out IEnumConnections ppenum);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumMoniker.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumMoniker.cs
new file mode 100644
index 0000000000..4513bc86ff
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumMoniker.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: IEnumMoniker interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    [Guid("00000102-0000-0000-C000-000000000046")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface IEnumMoniker
+    {
+        [PreserveSig]
+        int Next(int celt, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 0), Out] IMoniker[] rgelt, IntPtr pceltFetched);
+        [PreserveSig]
+        int Skip(int celt);
+        void Reset();
+        void Clone(out IEnumMoniker ppenum);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumString.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumString.cs
new file mode 100644
index 0000000000..5738a42751
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumString.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: IEnumString interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    [Guid("00000101-0000-0000-C000-000000000046")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface IEnumString
+    {
+        [PreserveSig]
+        int Next(int celt, [MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.LPWStr, SizeParamIndex = 0), Out] String[] rgelt, IntPtr pceltFetched);
+        [PreserveSig]
+        int Skip(int celt);
+        void Reset();
+        void Clone(out IEnumString ppenum);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumVARIANT.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumVARIANT.cs
new file mode 100644
index 0000000000..b94ac5e4c9
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IEnumVARIANT.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: IEnumVARIANT interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    [Guid("00020404-0000-0000-C000-000000000046")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface IEnumVARIANT
+    {
+        [PreserveSig]
+        int Next(int celt, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 0), Out] object[] rgVar, IntPtr pceltFetched);
+
+        [PreserveSig]
+        int Skip(int celt);
+
+        [PreserveSig]
+        int Reset();
+
+        IEnumVARIANT Clone();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IMoniker.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IMoniker.cs
new file mode 100644
index 0000000000..ea45149b29
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IMoniker.cs
@@ -0,0 +1,61 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: IMoniker interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    [StructLayout(LayoutKind.Sequential)]
+
+    public struct FILETIME
+    {
+        public int dwLowDateTime;
+        public int dwHighDateTime;
+    }
+
+    [Guid("0000000f-0000-0000-C000-000000000046")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface IMoniker
+    {
+        // IPersist portion
+        void GetClassID(out Guid pClassID);
+
+        // IPersistStream portion
+        [PreserveSig]
+        int IsDirty();
+        void Load(IStream pStm);
+        void Save(IStream pStm, [MarshalAs(UnmanagedType.Bool)] bool fClearDirty);
+        void GetSizeMax(out Int64 pcbSize);
+
+        // IMoniker portion
+        void BindToObject(IBindCtx pbc, IMoniker pmkToLeft, [In()] ref Guid riidResult, [MarshalAs(UnmanagedType.Interface)] out Object ppvResult);
+        void BindToStorage(IBindCtx pbc, IMoniker pmkToLeft, [In()] ref Guid riid, [MarshalAs(UnmanagedType.Interface)] out Object ppvObj);
+        void Reduce(IBindCtx pbc, int dwReduceHowFar, ref IMoniker ppmkToLeft, out IMoniker ppmkReduced);
+        void ComposeWith(IMoniker pmkRight, [MarshalAs(UnmanagedType.Bool)] bool fOnlyIfNotGeneric, out IMoniker ppmkComposite);
+        void Enum([MarshalAs(UnmanagedType.Bool)] bool fForward, out IEnumMoniker ppenumMoniker);
+        [PreserveSig]
+        int IsEqual(IMoniker pmkOtherMoniker);
+        void Hash(out int pdwHash);
+        [PreserveSig]
+        int IsRunning(IBindCtx pbc, IMoniker pmkToLeft, IMoniker pmkNewlyRunning);
+        void GetTimeOfLastChange(IBindCtx pbc, IMoniker pmkToLeft, out FILETIME pFileTime);
+        void Inverse(out IMoniker ppmk);
+        void CommonPrefixWith(IMoniker pmkOther, out IMoniker ppmkPrefix);
+        void RelativePathTo(IMoniker pmkOther, out IMoniker ppmkRelPath);
+        void GetDisplayName(IBindCtx pbc, IMoniker pmkToLeft, [MarshalAs(UnmanagedType.LPWStr)] out String ppszDisplayName);
+        void ParseDisplayName(IBindCtx pbc, IMoniker pmkToLeft, [MarshalAs(UnmanagedType.LPWStr)] String pszDisplayName, out int pchEaten, out IMoniker ppmkOut);
+        [PreserveSig]
+        int IsSystemMoniker(out int pdwMksys);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IPersistFile.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IPersistFile.cs
new file mode 100644
index 0000000000..467a9e3a6a
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IPersistFile.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: IPersistFile interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    [Guid("0000010b-0000-0000-C000-000000000046")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface IPersistFile
+    {
+        // IPersist portion
+        void GetClassID(out Guid pClassID);
+
+        // IPersistFile portion
+        [PreserveSig]
+        int IsDirty();
+        void Load([MarshalAs(UnmanagedType.LPWStr)] String pszFileName, int dwMode);
+        void Save([MarshalAs(UnmanagedType.LPWStr)] String pszFileName, [MarshalAs(UnmanagedType.Bool)] bool fRemember);
+        void SaveCompleted([MarshalAs(UnmanagedType.LPWStr)] String pszFileName);
+        void GetCurFile([MarshalAs(UnmanagedType.LPWStr)] out String ppszFileName);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IRunningObjectTable.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IRunningObjectTable.cs
new file mode 100644
index 0000000000..ffca35ae83
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IRunningObjectTable.cs
@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: IRunningObjectTable interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    [Guid("00000010-0000-0000-C000-000000000046")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface IRunningObjectTable
+    {
+        int Register(int grfFlags, [MarshalAs(UnmanagedType.Interface)] Object punkObject, IMoniker pmkObjectName);
+        void Revoke(int dwRegister);
+        [PreserveSig]
+        int IsRunning(IMoniker pmkObjectName);
+        [PreserveSig]
+        int GetObject(IMoniker pmkObjectName, [MarshalAs(UnmanagedType.Interface)] out Object ppunkObject);
+        void NoteChangeTime(int dwRegister, ref FILETIME pfiletime);
+        [PreserveSig]
+        int GetTimeOfLastChange(IMoniker pmkObjectName, out FILETIME pfiletime);
+        void EnumRunning(out IEnumMoniker ppenumMoniker);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IStream.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IStream.cs
new file mode 100644
index 0000000000..1a2d81f7ea
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/IStream.cs
@@ -0,0 +1,55 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: IStream interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+
+    public struct STATSTG
+    {
+        public String pwcsName;
+        public int type;
+        public Int64 cbSize;
+        public FILETIME mtime;
+        public FILETIME ctime;
+        public FILETIME atime;
+        public int grfMode;
+        public int grfLocksSupported;
+        public Guid clsid;
+        public int grfStateBits;
+        public int reserved;
+    }
+
+    [Guid("0000000c-0000-0000-C000-000000000046")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface IStream
+    {
+        // ISequentialStream portion
+        void Read([MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1), Out] Byte[] pv, int cb, IntPtr pcbRead);
+        void Write([MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1)] Byte[] pv, int cb, IntPtr pcbWritten);
+
+        // IStream portion
+        void Seek(Int64 dlibMove, int dwOrigin, IntPtr plibNewPosition);
+        void SetSize(Int64 libNewSize);
+        void CopyTo(IStream pstm, Int64 cb, IntPtr pcbRead, IntPtr pcbWritten);
+        void Commit(int grfCommitFlags);
+        void Revert();
+        void LockRegion(Int64 libOffset, Int64 cb, int dwLockType);
+        void UnlockRegion(Int64 libOffset, Int64 cb, int dwLockType);
+        void Stat(out STATSTG pstatstg, int grfStatFlag);
+        void Clone(out IStream ppstm);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeComp.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeComp.cs
new file mode 100644
index 0000000000..ae403d138c
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeComp.cs
@@ -0,0 +1,48 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: ITypeComp interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    public enum DESCKIND
+    {
+        DESCKIND_NONE = 0,
+        DESCKIND_FUNCDESC = DESCKIND_NONE + 1,
+        DESCKIND_VARDESC = DESCKIND_FUNCDESC + 1,
+        DESCKIND_TYPECOMP = DESCKIND_VARDESC + 1,
+        DESCKIND_IMPLICITAPPOBJ = DESCKIND_TYPECOMP + 1,
+        DESCKIND_MAX = DESCKIND_IMPLICITAPPOBJ + 1
+    }
+
+    [StructLayout(LayoutKind.Explicit, CharSet = CharSet.Unicode)]
+
+    public struct BINDPTR
+    {
+        [FieldOffset(0)]
+        public IntPtr lpfuncdesc;
+        [FieldOffset(0)]
+        public IntPtr lpvardesc;
+        [FieldOffset(0)]
+        public IntPtr lptcomp;
+    }
+
+    [Guid("00020403-0000-0000-C000-000000000046")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface ITypeComp
+    {
+        void Bind([MarshalAs(UnmanagedType.LPWStr)] String szName, int lHashVal, Int16 wFlags, out ITypeInfo ppTInfo, out DESCKIND pDescKind, out BINDPTR pBindPtr);
+        void BindType([MarshalAs(UnmanagedType.LPWStr)] String szName, int lHashVal, out ITypeInfo ppTInfo, out ITypeComp ppTComp);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeInfo.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeInfo.cs
new file mode 100644
index 0000000000..4cd102f76e
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeInfo.cs
@@ -0,0 +1,324 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: ITypeInfo interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    public enum TYPEKIND
+    {
+        TKIND_ENUM = 0,
+        TKIND_RECORD = TKIND_ENUM + 1,
+        TKIND_MODULE = TKIND_RECORD + 1,
+        TKIND_INTERFACE = TKIND_MODULE + 1,
+        TKIND_DISPATCH = TKIND_INTERFACE + 1,
+        TKIND_COCLASS = TKIND_DISPATCH + 1,
+        TKIND_ALIAS = TKIND_COCLASS + 1,
+        TKIND_UNION = TKIND_ALIAS + 1,
+        TKIND_MAX = TKIND_UNION + 1
+    }
+
+    [Flags()]
+    public enum TYPEFLAGS : short
+    {
+        TYPEFLAG_FAPPOBJECT = 0x1,
+        TYPEFLAG_FCANCREATE = 0x2,
+        TYPEFLAG_FLICENSED = 0x4,
+        TYPEFLAG_FPREDECLID = 0x8,
+        TYPEFLAG_FHIDDEN = 0x10,
+        TYPEFLAG_FCONTROL = 0x20,
+        TYPEFLAG_FDUAL = 0x40,
+        TYPEFLAG_FNONEXTENSIBLE = 0x80,
+        TYPEFLAG_FOLEAUTOMATION = 0x100,
+        TYPEFLAG_FRESTRICTED = 0x200,
+        TYPEFLAG_FAGGREGATABLE = 0x400,
+        TYPEFLAG_FREPLACEABLE = 0x800,
+        TYPEFLAG_FDISPATCHABLE = 0x1000,
+        TYPEFLAG_FREVERSEBIND = 0x2000,
+        TYPEFLAG_FPROXY = 0x4000
+    }
+
+    [Flags()]
+    public enum IMPLTYPEFLAGS
+    {
+        IMPLTYPEFLAG_FDEFAULT = 0x1,
+        IMPLTYPEFLAG_FSOURCE = 0x2,
+        IMPLTYPEFLAG_FRESTRICTED = 0x4,
+        IMPLTYPEFLAG_FDEFAULTVTABLE = 0x8,
+    }
+
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+
+    public struct TYPEATTR
+    {
+        // Constant used with the memid fields.
+        public const int MEMBER_ID_NIL = unchecked((int)0xFFFFFFFF);
+
+        // Actual fields of the TypeAttr struct.
+        public Guid guid;
+        public Int32 lcid;
+        public Int32 dwReserved;
+        public Int32 memidConstructor;
+        public Int32 memidDestructor;
+        public IntPtr lpstrSchema;
+        public Int32 cbSizeInstance;
+        public TYPEKIND typekind;
+        public Int16 cFuncs;
+        public Int16 cVars;
+        public Int16 cImplTypes;
+        public Int16 cbSizeVft;
+        public Int16 cbAlignment;
+        public TYPEFLAGS wTypeFlags;
+        public Int16 wMajorVerNum;
+        public Int16 wMinorVerNum;
+        public TYPEDESC tdescAlias;
+        public IDLDESC idldescType;
+    }
+
+    [StructLayout(LayoutKind.Sequential)]
+
+    public struct FUNCDESC
+    {
+        public int memid;                   //MEMBERID memid;
+        public IntPtr lprgscode;            // /* [size_is(cScodes)] */ SCODE RPC_FAR *lprgscode;
+        public IntPtr lprgelemdescParam;    // /* [size_is(cParams)] */ ELEMDESC __RPC_FAR *lprgelemdescParam;
+        public FUNCKIND funckind;           //FUNCKIND funckind;
+        public INVOKEKIND invkind;          //INVOKEKIND invkind;
+        public CALLCONV callconv;           //CALLCONV callconv;
+        public Int16 cParams;               //short cParams;
+        public Int16 cParamsOpt;            //short cParamsOpt;
+        public Int16 oVft;                  //short oVft;
+        public Int16 cScodes;               //short cScodes;
+        public ELEMDESC elemdescFunc;       //ELEMDESC elemdescFunc;
+        public Int16 wFuncFlags;            //WORD wFuncFlags;
+    }
+
+    [Flags()]
+    public enum IDLFLAG : short
+    {
+        IDLFLAG_NONE = PARAMFLAG.PARAMFLAG_NONE,
+        IDLFLAG_FIN = PARAMFLAG.PARAMFLAG_FIN,
+        IDLFLAG_FOUT = PARAMFLAG.PARAMFLAG_FOUT,
+        IDLFLAG_FLCID = PARAMFLAG.PARAMFLAG_FLCID,
+        IDLFLAG_FRETVAL = PARAMFLAG.PARAMFLAG_FRETVAL
+    }
+
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+
+    public struct IDLDESC
+    {
+        public IntPtr dwReserved;
+        public IDLFLAG wIDLFlags;
+    }
+
+    [Flags()]
+    public enum PARAMFLAG : short
+    {
+        PARAMFLAG_NONE = 0,
+        PARAMFLAG_FIN = 0x1,
+        PARAMFLAG_FOUT = 0x2,
+        PARAMFLAG_FLCID = 0x4,
+        PARAMFLAG_FRETVAL = 0x8,
+        PARAMFLAG_FOPT = 0x10,
+        PARAMFLAG_FHASDEFAULT = 0x20,
+        PARAMFLAG_FHASCUSTDATA = 0x40
+    }
+
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+
+    public struct PARAMDESC
+    {
+        public IntPtr lpVarValue;
+        public PARAMFLAG wParamFlags;
+    }
+
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+
+    public struct TYPEDESC
+    {
+        public IntPtr lpValue;
+        public Int16 vt;
+    }
+
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+
+    public struct ELEMDESC
+    {
+        public TYPEDESC tdesc;
+
+        [System.Runtime.InteropServices.StructLayout(LayoutKind.Explicit, CharSet = CharSet.Unicode)]
+
+        public struct DESCUNION
+        {
+            [FieldOffset(0)]
+            public IDLDESC idldesc;
+            [FieldOffset(0)]
+            public PARAMDESC paramdesc;
+        };
+        public DESCUNION desc;
+    }
+
+    public enum VARKIND : int
+    {
+        VAR_PERINSTANCE = 0x0,
+        VAR_STATIC = 0x1,
+        VAR_CONST = 0x2,
+        VAR_DISPATCH = 0x3
+    }
+
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+
+    public struct VARDESC
+    {
+        public int memid;
+        public String lpstrSchema;
+
+        [System.Runtime.InteropServices.StructLayout(LayoutKind.Explicit, CharSet = CharSet.Unicode)]
+
+        public struct DESCUNION
+        {
+            [FieldOffset(0)]
+            public int oInst;
+            [FieldOffset(0)]
+            public IntPtr lpvarValue;
+        };
+
+        public DESCUNION desc;
+
+        public ELEMDESC elemdescVar;
+        public short wVarFlags;
+        public VARKIND varkind;
+    }
+
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+
+    public struct DISPPARAMS
+    {
+        public IntPtr rgvarg;
+        public IntPtr rgdispidNamedArgs;
+        public int cArgs;
+        public int cNamedArgs;
+    }
+
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+
+    public struct EXCEPINFO
+    {
+        public Int16 wCode;
+        public Int16 wReserved;
+        [MarshalAs(UnmanagedType.BStr)] public String bstrSource;
+        [MarshalAs(UnmanagedType.BStr)] public String bstrDescription;
+        [MarshalAs(UnmanagedType.BStr)] public String bstrHelpFile;
+        public int dwHelpContext;
+        public IntPtr pvReserved;
+        public IntPtr pfnDeferredFillIn;
+        public Int32 scode;
+    }
+
+    public enum FUNCKIND : int
+    {
+        FUNC_VIRTUAL = 0,
+        FUNC_PUREVIRTUAL = 1,
+        FUNC_NONVIRTUAL = 2,
+        FUNC_STATIC = 3,
+        FUNC_DISPATCH = 4
+    }
+
+    [Flags]
+    public enum INVOKEKIND : int
+    {
+        INVOKE_FUNC = 0x1,
+        INVOKE_PROPERTYGET = 0x2,
+        INVOKE_PROPERTYPUT = 0x4,
+        INVOKE_PROPERTYPUTREF = 0x8
+    }
+
+    public enum CALLCONV : int
+    {
+        CC_CDECL = 1,
+        CC_MSCPASCAL = 2,
+        CC_PASCAL = CC_MSCPASCAL,
+        CC_MACPASCAL = 3,
+        CC_STDCALL = 4,
+        CC_RESERVED = 5,
+        CC_SYSCALL = 6,
+        CC_MPWCDECL = 7,
+        CC_MPWPASCAL = 8,
+        CC_MAX = 9
+    }
+
+    [Flags()]
+    public enum FUNCFLAGS : short
+    {
+        FUNCFLAG_FRESTRICTED = 0x1,
+        FUNCFLAG_FSOURCE = 0x2,
+        FUNCFLAG_FBINDABLE = 0x4,
+        FUNCFLAG_FREQUESTEDIT = 0x8,
+        FUNCFLAG_FDISPLAYBIND = 0x10,
+        FUNCFLAG_FDEFAULTBIND = 0x20,
+        FUNCFLAG_FHIDDEN = 0x40,
+        FUNCFLAG_FUSESGETLASTERROR = 0x80,
+        FUNCFLAG_FDEFAULTCOLLELEM = 0x100,
+        FUNCFLAG_FUIDEFAULT = 0x200,
+        FUNCFLAG_FNONBROWSABLE = 0x400,
+        FUNCFLAG_FREPLACEABLE = 0x800,
+        FUNCFLAG_FIMMEDIATEBIND = 0x1000
+    }
+
+    [Flags()]
+    public enum VARFLAGS : short
+    {
+        VARFLAG_FREADONLY = 0x1,
+        VARFLAG_FSOURCE = 0x2,
+        VARFLAG_FBINDABLE = 0x4,
+        VARFLAG_FREQUESTEDIT = 0x8,
+        VARFLAG_FDISPLAYBIND = 0x10,
+        VARFLAG_FDEFAULTBIND = 0x20,
+        VARFLAG_FHIDDEN = 0x40,
+        VARFLAG_FRESTRICTED = 0x80,
+        VARFLAG_FDEFAULTCOLLELEM = 0x100,
+        VARFLAG_FUIDEFAULT = 0x200,
+        VARFLAG_FNONBROWSABLE = 0x400,
+        VARFLAG_FREPLACEABLE = 0x800,
+        VARFLAG_FIMMEDIATEBIND = 0x1000
+    }
+
+    [Guid("00020401-0000-0000-C000-000000000046")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface ITypeInfo
+    {
+        void GetTypeAttr(out IntPtr ppTypeAttr);
+        void GetTypeComp(out ITypeComp ppTComp);
+        void GetFuncDesc(int index, out IntPtr ppFuncDesc);
+        void GetVarDesc(int index, out IntPtr ppVarDesc);
+        void GetNames(int memid, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 2), Out] String[] rgBstrNames, int cMaxNames, out int pcNames);
+        void GetRefTypeOfImplType(int index, out int href);
+        void GetImplTypeFlags(int index, out IMPLTYPEFLAGS pImplTypeFlags);
+        void GetIDsOfNames([MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.LPWStr, SizeParamIndex = 1), In] String[] rgszNames, int cNames, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1), Out] int[] pMemId);
+        void Invoke([MarshalAs(UnmanagedType.IUnknown)] Object pvInstance, int memid, Int16 wFlags, ref DISPPARAMS pDispParams, IntPtr pVarResult, IntPtr pExcepInfo, out int puArgErr);
+        void GetDocumentation(int index, out String strName, out String strDocString, out int dwHelpContext, out String strHelpFile);
+        void GetDllEntry(int memid, INVOKEKIND invKind, IntPtr pBstrDllName, IntPtr pBstrName, IntPtr pwOrdinal);
+        void GetRefTypeInfo(int hRef, out ITypeInfo ppTI);
+        void AddressOfMember(int memid, INVOKEKIND invKind, out IntPtr ppv);
+        void CreateInstance([MarshalAs(UnmanagedType.IUnknown)] Object pUnkOuter, [In] ref Guid riid, [MarshalAs(UnmanagedType.IUnknown), Out] out Object ppvObj);
+        void GetMops(int memid, out String pBstrMops);
+        void GetContainingTypeLib(out ITypeLib ppTLB, out int pIndex);
+        [PreserveSig]
+        void ReleaseTypeAttr(IntPtr pTypeAttr);
+        [PreserveSig]
+        void ReleaseFuncDesc(IntPtr pFuncDesc);
+        [PreserveSig]
+        void ReleaseVarDesc(IntPtr pVarDesc);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeInfo2.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeInfo2.cs
new file mode 100644
index 0000000000..7bb7138c46
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeInfo2.cs
@@ -0,0 +1,62 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: ITypeInfo2 interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    [Guid("00020412-0000-0000-C000-000000000046")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface ITypeInfo2 : ITypeInfo
+    {
+        new void GetTypeAttr(out IntPtr ppTypeAttr);
+        new void GetTypeComp(out ITypeComp ppTComp);
+        new void GetFuncDesc(int index, out IntPtr ppFuncDesc);
+        new void GetVarDesc(int index, out IntPtr ppVarDesc);
+        new void GetNames(int memid, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 2), Out] String[] rgBstrNames, int cMaxNames, out int pcNames);
+        new void GetRefTypeOfImplType(int index, out int href);
+        new void GetImplTypeFlags(int index, out IMPLTYPEFLAGS pImplTypeFlags);
+        new void GetIDsOfNames([MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.LPWStr, SizeParamIndex = 1), In] String[] rgszNames, int cNames, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1), Out] int[] pMemId);
+        new void Invoke([MarshalAs(UnmanagedType.IUnknown)] Object pvInstance, int memid, Int16 wFlags, ref DISPPARAMS pDispParams, IntPtr pVarResult, IntPtr pExcepInfo, out int puArgErr);
+        new void GetDocumentation(int index, out String strName, out String strDocString, out int dwHelpContext, out String strHelpFile);
+        new void GetDllEntry(int memid, INVOKEKIND invKind, IntPtr pBstrDllName, IntPtr pBstrName, IntPtr pwOrdinal);
+        new void GetRefTypeInfo(int hRef, out ITypeInfo ppTI);
+        new void AddressOfMember(int memid, INVOKEKIND invKind, out IntPtr ppv);
+        new void CreateInstance([MarshalAs(UnmanagedType.IUnknown)] Object pUnkOuter, [In] ref Guid riid, [MarshalAs(UnmanagedType.IUnknown), Out] out Object ppvObj);
+        new void GetMops(int memid, out String pBstrMops);
+        new void GetContainingTypeLib(out ITypeLib ppTLB, out int pIndex);
+        [PreserveSig]
+        new void ReleaseTypeAttr(IntPtr pTypeAttr);
+        [PreserveSig]
+        new void ReleaseFuncDesc(IntPtr pFuncDesc);
+        [PreserveSig]
+        new void ReleaseVarDesc(IntPtr pVarDesc);
+        void GetTypeKind(out TYPEKIND pTypeKind);
+        void GetTypeFlags(out int pTypeFlags);
+        void GetFuncIndexOfMemId(int memid, INVOKEKIND invKind, out int pFuncIndex);
+        void GetVarIndexOfMemId(int memid, out int pVarIndex);
+        void GetCustData(ref Guid guid, out Object pVarVal);
+        void GetFuncCustData(int index, ref Guid guid, out Object pVarVal);
+        void GetParamCustData(int indexFunc, int indexParam, ref Guid guid, out Object pVarVal);
+        void GetVarCustData(int index, ref Guid guid, out Object pVarVal);
+        void GetImplTypeCustData(int index, ref Guid guid, out Object pVarVal);
+        [LCIDConversionAttribute(1)]
+        void GetDocumentation2(int memid, out String pbstrHelpString, out int pdwHelpStringContext, out String pbstrHelpStringDll);
+        void GetAllCustData(IntPtr pCustData);
+        void GetAllFuncCustData(int index, IntPtr pCustData);
+        void GetAllParamCustData(int indexFunc, int indexParam, IntPtr pCustData);
+        void GetAllVarCustData(int index, IntPtr pCustData);
+        void GetAllImplTypeCustData(int index, IntPtr pCustData);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeLib.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeLib.cs
new file mode 100644
index 0000000000..05a9e3f176
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeLib.cs
@@ -0,0 +1,65 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: ITypeLib interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    public enum SYSKIND
+    {
+        SYS_WIN16 = 0,
+        SYS_WIN32 = SYS_WIN16 + 1,
+        SYS_MAC = SYS_WIN32 + 1,
+        SYS_WIN64 = SYS_MAC + 1
+    }
+
+    [Flags()]
+    public enum LIBFLAGS : short
+    {
+        LIBFLAG_FRESTRICTED = 0x1,
+        LIBFLAG_FCONTROL = 0x2,
+        LIBFLAG_FHIDDEN = 0x4,
+        LIBFLAG_FHASDISKIMAGE = 0x8
+    }
+
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+    public struct TYPELIBATTR
+    {
+        public Guid guid;
+        public int lcid;
+        public SYSKIND syskind;
+        public Int16 wMajorVerNum;
+        public Int16 wMinorVerNum;
+        public LIBFLAGS wLibFlags;
+    }
+
+    [Guid("00020402-0000-0000-C000-000000000046")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface ITypeLib
+    {
+        [PreserveSig]
+        int GetTypeInfoCount();
+        void GetTypeInfo(int index, out ITypeInfo ppTI);
+        void GetTypeInfoType(int index, out TYPEKIND pTKind);
+        void GetTypeInfoOfGuid(ref Guid guid, out ITypeInfo ppTInfo);
+        void GetLibAttr(out IntPtr ppTLibAttr);
+        void GetTypeComp(out ITypeComp ppTComp);
+        void GetDocumentation(int index, out String strName, out String strDocString, out int dwHelpContext, out String strHelpFile);
+        [return: MarshalAs(UnmanagedType.Bool)]
+        bool IsName([MarshalAs(UnmanagedType.LPWStr)] String szNameBuf, int lHashVal);
+        void FindName([MarshalAs(UnmanagedType.LPWStr)] String szNameBuf, int lHashVal, [MarshalAs(UnmanagedType.LPArray), Out] ITypeInfo[] ppTInfo, [MarshalAs(UnmanagedType.LPArray), Out] int[] rgMemId, ref Int16 pcFound);
+        [PreserveSig]
+        void ReleaseTLibAttr(IntPtr pTLibAttr);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeLib2.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeLib2.cs
new file mode 100644
index 0000000000..48f4fb3782
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ComTypes/ITypeLib2.cs
@@ -0,0 +1,42 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: ITypeLib2 interface definition.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices.ComTypes
+{
+    [Guid("00020411-0000-0000-C000-000000000046")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
+    [ComImport]
+    public interface ITypeLib2 : ITypeLib
+    {
+        [PreserveSig]
+        new int GetTypeInfoCount();
+        new void GetTypeInfo(int index, out ITypeInfo ppTI);
+        new void GetTypeInfoType(int index, out TYPEKIND pTKind);
+        new void GetTypeInfoOfGuid(ref Guid guid, out ITypeInfo ppTInfo);
+        new void GetLibAttr(out IntPtr ppTLibAttr);
+        new void GetTypeComp(out ITypeComp ppTComp);
+        new void GetDocumentation(int index, out String strName, out String strDocString, out int dwHelpContext, out String strHelpFile);
+        [return: MarshalAs(UnmanagedType.Bool)]
+        new bool IsName([MarshalAs(UnmanagedType.LPWStr)] String szNameBuf, int lHashVal);
+        new void FindName([MarshalAs(UnmanagedType.LPWStr)] String szNameBuf, int lHashVal, [MarshalAs(UnmanagedType.LPArray), Out] ITypeInfo[] ppTInfo, [MarshalAs(UnmanagedType.LPArray), Out] int[] rgMemId, ref Int16 pcFound);
+        [PreserveSig]
+        new void ReleaseTLibAttr(IntPtr pTLibAttr);
+        void GetCustData(ref Guid guid, out Object pVarVal);
+        [LCIDConversionAttribute(1)]
+        void GetDocumentation2(int index, out String pbstrHelpString, out int pdwHelpStringContext, out String pbstrHelpStringDll);
+        void GetLibStatistics(IntPtr pcUniqueNames, out int pcchUniqueNames);
+        void GetAllCustData(IntPtr pCustData);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/CriticalHandle.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/CriticalHandle.cs
new file mode 100644
index 0000000000..da7cb3e3fc
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/CriticalHandle.cs
@@ -0,0 +1,230 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** A specially designed handle wrapper to ensure we never leak
+** an OS handle.  The runtime treats this class specially during
+** P/Invoke marshaling and finalization.  Users should write
+** subclasses of CriticalHandle for each distinct handle type.
+** This class is similar to SafeHandle, but lacks the ref counting
+** behavior on marshaling that prevents handle recycling errors
+** or security holes. This lowers the overhead of using the handle
+** considerably, but leaves the onus on the caller to protect
+** themselves from any recycling effects.
+**
+** **** NOTE ****
+**
+** Since there are no ref counts tracking handle usage there is
+** no thread safety either. Your application must ensure that
+** usages of the handle do not cross with attempts to close the
+** handle (or tolerate such crossings). Normal GC mechanics will
+** prevent finalization until the handle class isn't used any more,
+** but explicit Close or Dispose operations may be initiated at any
+** time.
+**
+** Similarly, multiple calls to Close or Dispose on different
+** threads at the same time may cause the ReleaseHandle method to be
+** called more than once.
+**
+** In general (and as might be inferred from the lack of handle
+** recycle protection) you should be very cautious about exposing
+** CriticalHandle instances directly or indirectly to untrusted users.
+** At a minimum you should restrict their ability to queue multiple
+** operations against a single handle at the same time or block their
+** access to Close and Dispose unless you are very comfortable with the
+** semantics of passing an invalid (or possibly invalidated and
+** reallocated) to the unamanged routines you marshal your handle to
+** (and the effects of closing such a handle while those calls are in
+** progress). The runtime cannot protect you from undefined program
+** behvior that might result from such scenarios. You have been warned.
+**
+** 
+===========================================================*/
+
+using System;
+using System.Reflection;
+using System.Threading;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+using System.Runtime.ConstrainedExecution;
+using System.IO;
+
+/*
+  Problems addressed by the CriticalHandle class:
+  1) Critical finalization - ensure we never leak OS resources in SQL.  Done
+     without running truly arbitrary & unbounded amounts of managed code.
+  2) Reduced graph promotion - during finalization, keep object graph small
+  3) GC.KeepAlive behavior - P/Invoke vs. finalizer thread race condition (HandleRef)
+  4) Enforcement of the above via the type system - Don't use IntPtr anymore.
+
+  Subclasses of CriticalHandle will implement the ReleaseHandle
+  abstract method used to execute any code required to free the
+  handle. This method will be prepared as a constrained execution
+  region at instance construction time (along with all the methods in
+  its statically determinable call graph). This implies that we won't
+  get any inconvenient jit allocation errors or rude thread abort
+  interrupts while releasing the handle but the user must still write
+  careful code to avoid injecting fault paths of their own (see the
+  CER spec for more details). In particular, any sub-methods you call
+  should be decorated with a reliability contract of the appropriate
+  level. In most cases this should be:
+    ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)
+
+  Subclasses must also implement the IsInvalid property so that the
+  infrastructure can tell when critical finalization is actually required.
+  Again, this method is prepared ahead of time. It's envisioned that direct
+  subclasses of CriticalHandle will provide an IsInvalid implementation that suits
+  the general type of handle they support (null is invalid, -1 is invalid etc.)
+  and then these classes will be further derived for specific handle types.
+
+  Most classes using CriticalHandle should not provide a finalizer.  If they do
+  need to do so (ie, for flushing out file buffers, needing to write some data
+  back into memory, etc), then they can provide a finalizer that will be 
+  guaranteed to run before the CriticalHandle's critical finalizer.
+
+  Subclasses are expected to be written as follows (note that
+  SuppressUnmanagedCodeSecurity should always be used on any P/Invoke methods
+  invoked as part of ReleaseHandle, in order to switch the security check from
+  runtime to jit time and thus remove a possible failure path from the
+  invocation of the method):
+
+  internal sealed MyCriticalHandleSubclass : CriticalHandle {
+      // Called by P/Invoke when returning CriticalHandles
+      private MyCriticalHandleSubclass() : base(IntPtr.Zero)
+      {
+      }
+
+      // Do not provide a finalizer - CriticalHandle's critical finalizer will
+      // call ReleaseHandle for you.
+
+      public override bool IsInvalid {
+          get { return handle == IntPtr.Zero; }
+      }
+
+      [DllImport(Interop.Libraries.Kernel32), SuppressUnmanagedCodeSecurity, ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
+      private static extern bool CloseHandle(IntPtr handle);
+
+      override protected bool ReleaseHandle()
+      {
+          return CloseHandle(handle);
+      }
+  }
+
+  Then elsewhere to create one of these CriticalHandles, define a method
+  with the following type of signature (CreateFile follows this model).
+  Note that when returning a CriticalHandle like this, P/Invoke will call your
+  classes default constructor.
+
+      [DllImport(Interop.Libraries.Kernel32)]
+      private static extern MyCriticalHandleSubclass CreateHandle(int someState);
+
+ */
+
+namespace System.Runtime.InteropServices
+{
+    // This class should not be serializable - it's a handle
+    public abstract class CriticalHandle : CriticalFinalizerObject, IDisposable
+    {
+        // ! Do not add or rearrange fields as the EE depends on this layout.
+        //------------------------------------------------------------------
+        protected IntPtr handle;    // This must be protected so derived classes can use out params. 
+        private bool _isClosed;     // Set by SetHandleAsInvalid or Close/Dispose/finalization.
+
+        // Creates a CriticalHandle class.  Users must then set the Handle property or allow P/Invoke marshaling to set it implicitly.
+        protected CriticalHandle(IntPtr invalidHandleValue)
+        {
+            handle = invalidHandleValue;
+            _isClosed = false;
+        }
+
+        ~CriticalHandle()
+        {
+            Dispose(false);
+        }
+
+        private void Cleanup()
+        {
+            if (IsClosed)
+                return;
+            _isClosed = true;
+
+            if (IsInvalid)
+                return;
+
+            // Save last error from P/Invoke in case the implementation of
+            // ReleaseHandle trashes it (important because this ReleaseHandle could
+            // occur implicitly as part of unmarshaling another P/Invoke).
+            int lastError = Marshal.GetLastWin32Error();
+
+            if (!ReleaseHandle())
+                FireCustomerDebugProbe();
+
+            Marshal.SetLastWin32Error(lastError);
+
+            GC.SuppressFinalize(this);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern void FireCustomerDebugProbe();
+
+        protected void SetHandle(IntPtr handle)
+        {
+            this.handle = handle;
+        }
+
+        // Returns whether the handle has been explicitly marked as closed
+        // (Close/Dispose) or invalid (SetHandleAsInvalid).
+        public bool IsClosed
+        {
+            get { return _isClosed; }
+        }
+
+        // Returns whether the handle looks like an invalid value (i.e. matches one
+        // of the handle's designated illegal values). CriticalHandle itself doesn't
+        // know what an invalid handle looks like, so this method is abstract and
+        // must be provided by a derived type.
+        public abstract bool IsInvalid
+        {
+            get;
+        }
+
+        public void Close()
+        {
+            Dispose(true);
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+        }
+
+        protected virtual void Dispose(bool disposing)
+        {
+            Cleanup();
+        }
+
+        // This should only be called for cases when you know for a fact that
+        // your handle is invalid and you want to record that information.
+        // An example is calling a syscall and getting back ERROR_INVALID_HANDLE.
+        // This method will normally leak handles!
+        public void SetHandleAsInvalid()
+        {
+            _isClosed = true;
+            GC.SuppressFinalize(this);
+        }
+
+        // Implement this abstract method in your derived class to specify how to
+        // free the handle. Be careful not write any code that's subject to faults
+        // in this method (the runtime will prepare the infrastructure for you so
+        // that no jit allocations etc. will occur, but don't allocate memory unless
+        // you can deal with the failure and still free the handle).
+        // The boolean returned should be true for success and false if a
+        // catastrophic error occurred and you wish to trigger a diagnostic for
+        // debugging purposes (the SafeHandleCriticalFailure MDA).
+        protected abstract bool ReleaseHandle();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/CurrencyWrapper.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/CurrencyWrapper.cs
new file mode 100644
index 0000000000..590925aafe
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/CurrencyWrapper.cs
@@ -0,0 +1,43 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Wrapper that is converted to a variant with VT_CURRENCY.
+**
+**
+=============================================================================*/
+
+
+using System;
+
+namespace System.Runtime.InteropServices
+{
+    public sealed class CurrencyWrapper
+    {
+        public CurrencyWrapper(Decimal obj)
+        {
+            m_WrappedObject = obj;
+        }
+
+        public CurrencyWrapper(Object obj)
+        {
+            if (!(obj is Decimal))
+                throw new ArgumentException(SR.Arg_MustBeDecimal, nameof(obj));
+            m_WrappedObject = (Decimal)obj;
+        }
+
+        public Decimal WrappedObject
+        {
+            get
+            {
+                return m_WrappedObject;
+            }
+        }
+
+        private Decimal m_WrappedObject;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/DispatchWrapper.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/DispatchWrapper.cs
new file mode 100644
index 0000000000..5fb78c56ad
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/DispatchWrapper.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Wrapper that is converted to a variant with VT_DISPATCH.
+**
+**
+=============================================================================*/
+
+
+using System;
+using System.Security;
+
+namespace System.Runtime.InteropServices
+{
+    public sealed class DispatchWrapper
+    {
+        public DispatchWrapper(Object obj)
+        {
+            if (obj != null)
+            {
+                // Make sure this guy has an IDispatch
+                IntPtr pdisp = Marshal.GetIDispatchForObject(obj);
+
+                // If we got here without throwing an exception, the QI for IDispatch succeeded.
+                Marshal.Release(pdisp);
+            }
+            m_WrappedObject = obj;
+        }
+
+        public Object WrappedObject
+        {
+            get
+            {
+                return m_WrappedObject;
+            }
+        }
+
+        private Object m_WrappedObject;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ErrorWrapper.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ErrorWrapper.cs
new file mode 100644
index 0000000000..34237d539a
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ErrorWrapper.cs
@@ -0,0 +1,48 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Wrapper that is converted to a variant with VT_ERROR.
+**
+**
+=============================================================================*/
+
+
+using System;
+
+namespace System.Runtime.InteropServices
+{
+    public sealed class ErrorWrapper
+    {
+        public ErrorWrapper(int errorCode)
+        {
+            m_ErrorCode = errorCode;
+        }
+
+        public ErrorWrapper(Object errorCode)
+        {
+            if (!(errorCode is int))
+                throw new ArgumentException(SR.Arg_MustBeInt32, nameof(errorCode));
+            m_ErrorCode = (int)errorCode;
+        }
+
+        public ErrorWrapper(Exception e)
+        {
+            m_ErrorCode = Marshal.GetHRForException(e);
+        }
+
+        public int ErrorCode
+        {
+            get
+            {
+                return m_ErrorCode;
+            }
+        }
+
+        private int m_ErrorCode;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/Expando/IExpando.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/Expando/IExpando.cs
new file mode 100644
index 0000000000..2bd398b7a9
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/Expando/IExpando.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+//
+// IExpando is an interface which allows Objects implemeningt this interface 
+//    support the ability to modify the object by adding and removing members, 
+//    represented by MemberInfo objects.
+//
+//
+// The IExpando Interface.
+
+using System;
+using System.Reflection;
+
+namespace System.Runtime.InteropServices.Expando
+{
+    [Guid("AFBF15E6-C37C-11d2-B88E-00A0C9B471B8")]
+    internal interface IExpando : IReflect
+    {
+        // Add a new Field to the reflection object.  The field has
+        // name as its name.
+        FieldInfo AddField(String name);
+
+        // Removes the specified member.
+        void RemoveMember(MemberInfo m);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/GCHandleCookieTable.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/GCHandleCookieTable.cs
new file mode 100644
index 0000000000..9e813d9bd9
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/GCHandleCookieTable.cs
@@ -0,0 +1,219 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#if MDA_SUPPORTED
+
+namespace System.Runtime.InteropServices
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Threading;
+
+    using ObjectHandle = IntPtr;
+    using GCHandleCookie = IntPtr;
+
+    // Internal class used to map a GCHandle to an IntPtr. Instead of handing out the underlying CLR
+    // handle, we now hand out a cookie that can later be converted back to the CLR handle it 
+    // is associated with.
+
+    // NOTE:
+    // this implementation uses a single lock between FindOrAddHandle and RemoveHandleIfPresent which
+    // could create some scalability issues when this MDA is turned on.  if this is affecting perf
+    // then additional tuning work will be required.
+
+    internal class GCHandleCookieTable
+    {
+        private const int InitialHandleCount = 10;
+        private const int MaxListSize = 0xFFFFFF;
+        private const uint CookieMaskIndex = 0x00FFFFFF;
+        private const uint CookieMaskSentinal = 0xFF000000;
+
+        internal GCHandleCookieTable()
+        {
+            m_HandleList = new ObjectHandle[InitialHandleCount];
+            m_CycleCounts = new byte[InitialHandleCount];
+            m_HandleToCookieMap = new Dictionary<ObjectHandle, GCHandleCookie>(InitialHandleCount);
+            m_syncObject = new object();
+
+            for (int i = 0; i < InitialHandleCount; i++)
+            {
+                m_HandleList[i] = ObjectHandle.Zero;
+                m_CycleCounts[i] = 0;
+            }
+        }
+
+        // Retrieve a cookie for the passed in handle. If no cookie has yet been allocated for 
+        // this handle, one will be created. This method is thread safe.
+        internal GCHandleCookie FindOrAddHandle(ObjectHandle handle)
+        {
+            // Don't accept a null object handle
+            if (handle == ObjectHandle.Zero)
+                return GCHandleCookie.Zero;
+
+            GCHandleCookie cookie = GCHandleCookie.Zero;
+
+            lock (m_syncObject)
+            {
+                // First see if we already have a cookie for this handle.
+                if (m_HandleToCookieMap.ContainsKey(handle))
+                    return m_HandleToCookieMap[handle];
+
+                if ((m_FreeIndex < m_HandleList.Length) && (Volatile.Read(ref m_HandleList[m_FreeIndex]) == ObjectHandle.Zero))
+                {
+                    Volatile.Write(ref m_HandleList[m_FreeIndex],  handle);
+                    cookie = GetCookieFromData((uint)m_FreeIndex, m_CycleCounts[m_FreeIndex]);
+
+                    // Set our next guess just one higher as this index is now in use.
+                    // it's ok if this sets m_FreeIndex > m_HandleList.Length as this condition is
+                    // checked at the beginning of the if statement.
+                    ++m_FreeIndex;
+                }
+                else
+                {
+                    for (m_FreeIndex = 0; m_FreeIndex < MaxListSize; ++m_FreeIndex)
+                    {
+                        if (m_HandleList[m_FreeIndex] == ObjectHandle.Zero)
+                        {
+                            Volatile.Write(ref m_HandleList[m_FreeIndex], handle);
+                            cookie = GetCookieFromData((uint)m_FreeIndex, m_CycleCounts[m_FreeIndex]);
+
+                            // this will be our next guess for a free index.
+                            // it's ok if this sets m_FreeIndex > m_HandleList.Length
+                            // since we check for this condition in the if statement.
+                            ++m_FreeIndex;
+                            break;
+                        }
+
+                        if (m_FreeIndex + 1 == m_HandleList.Length)
+                            GrowArrays();
+                    }
+                }
+
+                if (cookie == GCHandleCookie.Zero)
+                    throw new OutOfMemoryException(SR.OutOfMemory_GCHandleMDA);
+
+                // This handle hasn't been added to the map yet so add it.
+                m_HandleToCookieMap.Add(handle, cookie);
+            }
+
+            return cookie;
+        }
+
+        // Get a handle.
+        internal ObjectHandle GetHandle(GCHandleCookie cookie)
+        {
+            ObjectHandle oh = ObjectHandle.Zero;
+
+            if (!ValidateCookie(cookie))
+                return ObjectHandle.Zero;
+
+            oh = Volatile.Read(ref m_HandleList[GetIndexFromCookie(cookie)]);
+
+            return oh;
+        }
+
+        // Remove the handle from the cookie table if it is present. 
+        //
+        internal void RemoveHandleIfPresent(ObjectHandle handle)
+        {
+            if (handle == ObjectHandle.Zero)
+                return;
+
+            lock (m_syncObject)
+            {
+                if (m_HandleToCookieMap.ContainsKey(handle))
+                {
+                    GCHandleCookie cookie = m_HandleToCookieMap[handle];
+
+                    // Remove it from the array first
+                    if (!ValidateCookie(cookie))
+                        return;
+
+                    int index = GetIndexFromCookie(cookie);
+
+                    m_CycleCounts[index]++;
+                    Volatile.Write(ref m_HandleList[index], ObjectHandle.Zero);
+
+                    // Remove it from the hashtable last
+                    m_HandleToCookieMap.Remove(handle);
+
+                    // Update our guess
+                    m_FreeIndex = index;
+                }
+            }
+        }
+
+        private bool ValidateCookie(GCHandleCookie cookie)
+        {
+            int index;
+            byte xorData;
+
+            GetDataFromCookie(cookie, out index, out xorData);
+
+            // Validate the index
+            if (index >= MaxListSize)
+                return false;
+
+            if (index >= m_HandleList.Length)
+                return false;
+
+            if (Volatile.Read(ref m_HandleList[index]) == ObjectHandle.Zero)
+                return false;
+
+            // Validate the xorData byte (this contains the cycle count and appdomain id).
+            byte ADID = (byte)(AppDomain.CurrentDomain.Id % 0xFF);
+            byte goodData = (byte)(Volatile.Read(ref m_CycleCounts[index]) ^ ADID);
+            if (xorData != goodData)
+                return false;
+
+            return true;
+        }
+
+        // Double the size of our arrays - must be called with the lock taken.
+        private void GrowArrays()
+        {
+            int CurrLength = m_HandleList.Length;
+
+            ObjectHandle[] newHandleList = new ObjectHandle[CurrLength * 2];
+            byte[] newCycleCounts = new byte[CurrLength * 2];
+
+            Array.Copy(m_HandleList, newHandleList, CurrLength);
+            Array.Copy(m_CycleCounts, newCycleCounts, CurrLength);
+
+            m_HandleList = newHandleList;
+            m_CycleCounts = newCycleCounts;
+        }
+
+        // Generate a cookie based on the index, cyclecount, and current domain id.
+        private GCHandleCookie GetCookieFromData(uint index, byte cycleCount)
+        {
+            byte ADID = (byte)(AppDomain.CurrentDomain.Id % 0xFF);
+            return (GCHandleCookie)(((cycleCount ^ ADID) << 24) + index + 1);
+        }
+
+        // Break down the cookie into its parts
+        private void GetDataFromCookie(GCHandleCookie cookie, out int index, out byte xorData)
+        {
+            uint intCookie = (uint)cookie;
+            index = (int)(intCookie & CookieMaskIndex) - 1;
+            xorData = (byte)((intCookie & CookieMaskSentinal) >> 24);
+        }
+
+        // Just get the index from the cookie
+        private int GetIndexFromCookie(GCHandleCookie cookie)
+        {
+            uint intCookie = (uint)cookie;
+            return (int)(intCookie & CookieMaskIndex) - 1;
+        }
+
+        private Dictionary<ObjectHandle, GCHandleCookie> m_HandleToCookieMap;
+        private volatile ObjectHandle[] m_HandleList;
+        private volatile byte[] m_CycleCounts;
+        private int m_FreeIndex;
+        private readonly object m_syncObject;
+    }
+}
+
+#endif
+
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/GcHandle.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/GcHandle.cs
new file mode 100644
index 0000000000..cec32bbd8c
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/GcHandle.cs
@@ -0,0 +1,291 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    using System;
+    using System.Runtime.CompilerServices;
+    using System.Threading;
+#if BIT64
+    using nint = System.Int64;
+#else
+    using nint = System.Int32;
+#endif
+
+    // These are the types of handles used by the EE.  
+    // IMPORTANT: These must match the definitions in ObjectHandle.h in the EE. 
+    // IMPORTANT: If new values are added to the enum the GCHandle::MaxHandleType
+    //            constant must be updated.
+    public enum GCHandleType
+    {
+        Weak = 0,
+        WeakTrackResurrection = 1,
+        Normal = 2,
+        Pinned = 3
+    }
+
+    // This class allows you to create an opaque, GC handle to any 
+    // COM+ object. A GC handle is used when an object reference must be
+    // reachable from unmanaged memory.  There are 3 kinds of roots:
+    // Normal - keeps the object from being collected.
+    // Weak - allows object to be collected and handle contents will be zeroed.
+    //          Weak references are zeroed before the finalizer runs, so if the
+    //          object is resurrected in the finalizer the weak reference is
+    //          still zeroed.
+    // WeakTrackResurrection - Same as weak, but stays until after object is
+    //          really gone.
+    // Pinned - same as normal, but allows the address of the actual object
+    //          to be taken.
+    //
+
+    [StructLayout(LayoutKind.Sequential)]
+    public struct GCHandle
+    {
+        // IMPORTANT: This must be kept in sync with the GCHandleType enum.
+        private const GCHandleType MaxHandleType = GCHandleType.Pinned;
+
+#if MDA_SUPPORTED
+        static GCHandle()
+        {
+            s_probeIsActive = Mda.IsInvalidGCHandleCookieProbeEnabled();
+            if (s_probeIsActive)
+                s_cookieTable = new GCHandleCookieTable();
+        }
+#endif
+
+        // Allocate a handle storing the object and the type.
+        internal GCHandle(Object value, GCHandleType type)
+        {
+            // Make sure the type parameter is within the valid range for the enum.
+            if ((uint)type > (uint)MaxHandleType)
+                ThrowArgumentOutOfRangeException_ArgumentOutOfRange_Enum();
+
+            IntPtr handle = InternalAlloc(value, type);
+
+            if (type == GCHandleType.Pinned)
+            {
+                // Record if the handle is pinned.
+                handle = (IntPtr)((nint)handle | 1);
+            }
+
+            m_handle = handle;
+        }
+
+        // Used in the conversion functions below.
+        internal GCHandle(IntPtr handle)
+        {
+            m_handle = handle;
+        }
+
+        // Creates a new GC handle for an object.
+        //
+        // value - The object that the GC handle is created for.
+        // type - The type of GC handle to create.
+        // 
+        // returns a new GC handle that protects the object.
+        public static GCHandle Alloc(Object value)
+        {
+            return new GCHandle(value, GCHandleType.Normal);
+        }
+
+        public static GCHandle Alloc(Object value, GCHandleType type)
+        {
+            return new GCHandle(value, type);
+        }
+
+        // Frees a GC handle.
+        public void Free()
+        {
+            // Free the handle if it hasn't already been freed.
+            IntPtr handle = Interlocked.Exchange(ref m_handle, IntPtr.Zero);
+            ValidateHandle(handle);
+#if MDA_SUPPORTED
+            // If this handle was passed out to unmanaged code, we need to remove it
+            // from the cookie table.
+            // NOTE: the entry in the cookie table must be released before the
+            // internal handle is freed to prevent a race with reusing GC handles.
+            if (s_probeIsActive)
+                s_cookieTable.RemoveHandleIfPresent(handle);
+#endif
+            InternalFree(GetHandleValue(handle));
+        }
+
+        // Target property - allows getting / updating of the handle's referent.
+        public Object Target
+        {
+            get
+            {
+                ValidateHandle();
+                return InternalGet(GetHandleValue());
+            }
+
+            set
+            {
+                ValidateHandle();
+                InternalSet(GetHandleValue(), value, IsPinned());
+            }
+        }
+
+        // Retrieve the address of an object in a Pinned handle.  This throws
+        // an exception if the handle is any type other than Pinned.
+        public IntPtr AddrOfPinnedObject()
+        {
+            // Check if the handle was not a pinned handle.
+            if (!IsPinned())
+            {
+                ValidateHandle();
+
+                // You can only get the address of pinned handles.
+                throw new InvalidOperationException(SR.InvalidOperation_HandleIsNotPinned);
+            }
+
+            // Get the address.
+            return InternalAddrOfPinnedObject(GetHandleValue());
+        }
+
+        // Determine whether this handle has been allocated or not.
+        public bool IsAllocated => m_handle != IntPtr.Zero;
+
+        // Used to create a GCHandle from an int.  This is intended to
+        // be used with the reverse conversion.
+        public static explicit operator GCHandle(IntPtr value)
+        {
+            ValidateHandle(value);
+            return new GCHandle(value);
+        }
+
+        public static GCHandle FromIntPtr(IntPtr value)
+        {
+            ValidateHandle(value);
+
+#if MDA_SUPPORTED
+            IntPtr handle = value;
+            if (s_probeIsActive)
+            {
+                // Make sure this cookie matches up with a GCHandle we've passed out a cookie for.
+                handle = s_cookieTable.GetHandle(value);
+                if (IntPtr.Zero == handle)
+                {
+                    // Fire an MDA if we were unable to retrieve the GCHandle.
+                    Mda.FireInvalidGCHandleCookieProbe(value);
+                    return new GCHandle(IntPtr.Zero);
+                }
+                return new GCHandle(handle);
+            }
+#endif
+            return new GCHandle(value);
+        }
+
+        // Used to get the internal integer representation of the handle out.
+        public static explicit operator IntPtr(GCHandle value)
+        {
+            return ToIntPtr(value);
+        }
+
+        public static IntPtr ToIntPtr(GCHandle value)
+        {
+#if MDA_SUPPORTED
+            if (s_probeIsActive)
+            {
+                // Remember that we passed this GCHandle out by storing the cookie we returned so we
+                //  can later validate.
+                return s_cookieTable.FindOrAddHandle(value.m_handle);
+            }
+#endif
+            return value.m_handle;
+        }
+
+        public override int GetHashCode()
+        {
+            return m_handle.GetHashCode();
+        }
+
+        public override bool Equals(Object o)
+        {
+            GCHandle hnd;
+
+            // Check that o is a GCHandle first
+            if (o == null || !(o is GCHandle))
+                return false;
+            else
+                hnd = (GCHandle)o;
+
+            return m_handle == hnd.m_handle;
+        }
+
+        public static bool operator ==(GCHandle a, GCHandle b)
+        {
+            return a.m_handle == b.m_handle;
+        }
+
+        public static bool operator !=(GCHandle a, GCHandle b)
+        {
+            return a.m_handle != b.m_handle;
+        }
+
+        internal IntPtr GetHandleValue()
+        {
+            return GetHandleValue(m_handle);
+        }
+
+        private static IntPtr GetHandleValue(IntPtr handle)
+        {
+            // Remove Pin flag
+            return new IntPtr((nint)handle & ~(nint)1);
+        }
+
+        internal bool IsPinned()
+        {
+            // Check Pin flag
+            return ((nint)m_handle & 1) != 0;
+        }
+
+        // Internal native calls that this implementation uses.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr InternalAlloc(Object value, GCHandleType type);
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void InternalFree(IntPtr handle);
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Object InternalGet(IntPtr handle);
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void InternalSet(IntPtr handle, Object value, bool isPinned);
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Object InternalCompareExchange(IntPtr handle, Object value, Object oldValue, bool isPinned);
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr InternalAddrOfPinnedObject(IntPtr handle);
+
+        // The actual integer handle value that the EE uses internally.
+        private IntPtr m_handle;
+
+#if MDA_SUPPORTED
+        // The GCHandle cookie table.
+        private static volatile GCHandleCookieTable s_cookieTable = null;
+        private static volatile bool s_probeIsActive = false;
+#endif
+
+        private void ValidateHandle()
+        {
+            // Check if the handle was never initialized or was freed.
+            if (m_handle == IntPtr.Zero)
+                ThrowInvalidOperationException_HandleIsNotInitialized();
+        }
+
+        private static void ValidateHandle(IntPtr handle)
+        {
+            // Check if the handle was never initialized or was freed.
+            if (handle == IntPtr.Zero)
+                ThrowInvalidOperationException_HandleIsNotInitialized();
+        }
+
+        private static void ThrowArgumentOutOfRangeException_ArgumentOutOfRange_Enum()
+        {
+            throw ThrowHelper.GetArgumentOutOfRangeException(ExceptionArgument.type, ExceptionResource.ArgumentOutOfRange_Enum);
+        }
+
+        private static void ThrowInvalidOperationException_HandleIsNotInitialized()
+        {
+            throw ThrowHelper.GetInvalidOperationException(ExceptionResource.InvalidOperation_HandleIsNotInitialized);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ICustomAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ICustomAdapter.cs
new file mode 100644
index 0000000000..f47d348699
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ICustomAdapter.cs
@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: This the base interface that custom adapters can chose to implement
+**          when they want to expose the underlying object.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices
+{
+    public interface ICustomAdapter
+    {
+        [return: MarshalAs(UnmanagedType.IUnknown)] Object GetUnderlyingObject();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ICustomFactory.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ICustomFactory.cs
new file mode 100644
index 0000000000..e7bfc47281
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ICustomFactory.cs
@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+
+using System;
+
+namespace System.Runtime.InteropServices
+{
+    public interface ICustomFactory
+    {
+        MarshalByRefObject CreateInstance(Type serverType);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ICustomMarshaler.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ICustomMarshaler.cs
new file mode 100644
index 0000000000..571d78dfe3
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ICustomMarshaler.cs
@@ -0,0 +1,31 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: This the base interface that must be implemented by all custom
+**          marshalers.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices
+{
+    public interface ICustomMarshaler
+    {
+        Object MarshalNativeToManaged(IntPtr pNativeData);
+
+        IntPtr MarshalManagedToNative(Object ManagedObj);
+
+        void CleanUpNativeData(IntPtr pNativeData);
+
+        void CleanUpManagedData(Object ManagedObj);
+
+        int GetNativeDataSize();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ICustomQueryInterface.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ICustomQueryInterface.cs
new file mode 100644
index 0000000000..f0aa35e7dd
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/ICustomQueryInterface.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: This the interface that be implemented by class that want to 
+**          customize the behavior of QueryInterface.
+**
+**
+=============================================================================*/
+
+using System;
+
+namespace System.Runtime.InteropServices
+{
+    //====================================================================
+    // The enum of the return value of IQuerable.GetInterface
+    //====================================================================
+    public enum CustomQueryInterfaceResult
+    {
+        Handled = 0,
+        NotHandled = 1,
+        Failed = 2,
+    }
+
+    //====================================================================
+    // The interface for customizing IQueryInterface
+    //====================================================================
+    public interface ICustomQueryInterface
+    {
+        CustomQueryInterfaceResult GetInterface([In]ref Guid iid, out IntPtr ppv);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/IException.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/IException.cs
new file mode 100644
index 0000000000..895aa54781
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/IException.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+** Interface: _Exception
+**
+**
+** Purpose: COM backwards compatibility with v1 Exception
+**        object layout.
+**
+**
+=============================================================================*/
+
+namespace System.Runtime.InteropServices {
+    using System;
+    using System.Reflection;
+    using System.Runtime.Serialization;
+    
+    [GuidAttribute("b36b5c63-42ef-38bc-a07e-0b34c98f164a")]
+    [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsDual)]
+    [CLSCompliant(false)]
+    internal interface _Exception
+    {
+        //
+        // This method is intentionally included in CoreCLR to make Exception.get_InnerException "newslot virtual final".
+        // Some phone apps include MEF from desktop Silverlight. MEF's ComposablePartException depends on implicit interface 
+        // implementations of get_InnerException to be provided by the base class. It works only if Exception.get_InnerException
+        // is virtual.
+        //
+        Exception InnerException {
+            get;
+        }
+   }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/InvalidComObjectException.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/InvalidComObjectException.cs
new file mode 100644
index 0000000000..d1ae2e2a91
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/InvalidComObjectException.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+** Purpose: This exception is thrown when an invalid COM object is used. This
+**            happens when a the __ComObject type is used directly without
+**            having a backing class factory.
+**
+=============================================================================*/
+
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System.Runtime.InteropServices
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class InvalidComObjectException : SystemException
+    {
+        public InvalidComObjectException()
+            : base(SR.Arg_InvalidComObjectException)
+        {
+            HResult = HResults.COR_E_INVALIDCOMOBJECT;
+        }
+
+        public InvalidComObjectException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_INVALIDCOMOBJECT;
+        }
+
+        public InvalidComObjectException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_INVALIDCOMOBJECT;
+        }
+
+        protected InvalidComObjectException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/InvalidOleVariantTypeException.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/InvalidOleVariantTypeException.cs
new file mode 100644
index 0000000000..74029081ad
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/InvalidOleVariantTypeException.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+** Purpose: The type of an OLE variant that was passed into the runtime is 
+**            invalid.
+**
+=============================================================================*/
+
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System.Runtime.InteropServices
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class InvalidOleVariantTypeException : SystemException
+    {
+        public InvalidOleVariantTypeException()
+            : base(SR.Arg_InvalidOleVariantTypeException)
+        {
+            HResult = HResults.COR_E_INVALIDOLEVARIANTTYPE;
+        }
+
+        public InvalidOleVariantTypeException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_INVALIDOLEVARIANTTYPE;
+        }
+
+        public InvalidOleVariantTypeException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_INVALIDOLEVARIANTTYPE;
+        }
+
+        protected InvalidOleVariantTypeException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.cs
new file mode 100644
index 0000000000..52ca18c40a
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.cs
@@ -0,0 +1,1875 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: This class contains methods that are mainly used to marshal 
+**          between unmanaged and managed types.
+**
+**
+=============================================================================*/
+
+namespace System.Runtime.InteropServices
+{
+    using System;
+    using System.Runtime;
+    using System.Collections.Generic;
+    using System.Reflection;
+    using System.Reflection.Emit;
+    using System.Security;
+    using System.Text;
+    using System.Threading;
+    using System.Runtime.CompilerServices;
+    using System.Globalization;
+    using System.Runtime.ConstrainedExecution;
+    using System.Runtime.Versioning;
+    using Win32Native = Microsoft.Win32.Win32Native;
+    using Microsoft.Win32.SafeHandles;
+    using System.Diagnostics;
+    using System.Runtime.InteropServices.ComTypes;
+    using System.StubHelpers;
+
+    public enum CustomQueryInterfaceMode
+    {
+        Ignore = 0,
+        Allow = 1
+    }
+
+    //========================================================================
+    // All public methods, including PInvoke, are protected with linkchecks.  
+    // Remove the default demands for all PInvoke methods with this global 
+    // declaration on the class.
+    //========================================================================
+
+    public static partial class Marshal
+    {
+        //====================================================================
+        // Defines used inside the Marshal class.
+        //====================================================================
+        private const int LMEM_FIXED = 0;
+        private const int LMEM_MOVEABLE = 2;
+#if !FEATURE_PAL
+        private const long HIWORDMASK = unchecked((long)0xffffffffffff0000L);
+#endif //!FEATURE_PAL
+#if FEATURE_COMINTEROP
+        private static Guid IID_IUnknown = new Guid("00000000-0000-0000-C000-000000000046");
+#endif //FEATURE_COMINTEROP
+
+        // Win32 has the concept of Atoms, where a pointer can either be a pointer
+        // or an int.  If it's less than 64K, this is guaranteed to NOT be a 
+        // pointer since the bottom 64K bytes are reserved in a process' page table.
+        // We should be careful about deallocating this stuff.  Extracted to
+        // a function to avoid C# problems with lack of support for IntPtr.
+        // We have 2 of these methods for slightly different semantics for NULL.
+        private static bool IsWin32Atom(IntPtr ptr)
+        {
+#if FEATURE_PAL
+            return false;
+#else
+            long lPtr = (long)ptr;
+            return 0 == (lPtr & HIWORDMASK);
+#endif
+        }
+
+        private static bool IsNotWin32Atom(IntPtr ptr)
+        {
+#if FEATURE_PAL
+            return true;
+#else
+            long lPtr = (long)ptr;
+            return 0 != (lPtr & HIWORDMASK);
+#endif
+        }
+
+        //====================================================================
+        // The default character size for the system. This is always 2 because
+        // the framework only runs on UTF-16 systems.
+        //====================================================================
+        public static readonly int SystemDefaultCharSize = 2;
+
+        //====================================================================
+        // The max DBCS character size for the system.
+        //====================================================================
+        public static readonly int SystemMaxDBCSCharSize = GetSystemMaxDBCSCharSize();
+
+
+        //====================================================================
+        // The name, title and description of the assembly that will contain 
+        // the dynamically generated interop types. 
+        //====================================================================
+        private const String s_strConvertedTypeInfoAssemblyName = "InteropDynamicTypes";
+        private const String s_strConvertedTypeInfoAssemblyTitle = "Interop Dynamic Types";
+        private const String s_strConvertedTypeInfoAssemblyDesc = "Type dynamically generated from ITypeInfo's";
+        private const String s_strConvertedTypeInfoNameSpace = "InteropDynamicTypes";
+
+
+        //====================================================================
+        // Helper method to retrieve the system's maximum DBCS character size.
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int GetSystemMaxDBCSCharSize();
+
+        public static unsafe String PtrToStringAnsi(IntPtr ptr)
+        {
+            if (IntPtr.Zero == ptr)
+            {
+                return null;
+            }
+            else if (IsWin32Atom(ptr))
+            {
+                return null;
+            }
+            else
+            {
+                int nb = Win32Native.lstrlenA(ptr);
+                if (nb == 0)
+                {
+                    return string.Empty;
+                }
+                else
+                {
+                    return new String((sbyte*)ptr);
+                }
+            }
+        }
+
+        public static unsafe String PtrToStringAnsi(IntPtr ptr, int len)
+        {
+            if (ptr == IntPtr.Zero)
+                throw new ArgumentNullException(nameof(ptr));
+            if (len < 0)
+                throw new ArgumentException(null, nameof(len));
+
+            return new String((sbyte*)ptr, 0, len);
+        }
+
+        public static unsafe String PtrToStringUni(IntPtr ptr, int len)
+        {
+            if (ptr == IntPtr.Zero)
+                throw new ArgumentNullException(nameof(ptr));
+            if (len < 0)
+                throw new ArgumentException(null, nameof(len));
+
+            return new String((char*)ptr, 0, len);
+        }
+
+        public static String PtrToStringAuto(IntPtr ptr, int len)
+        {
+            // Ansi platforms are no longer supported
+            return PtrToStringUni(ptr, len);
+        }
+
+        public static unsafe String PtrToStringUni(IntPtr ptr)
+        {
+            if (IntPtr.Zero == ptr)
+            {
+                return null;
+            }
+            else if (IsWin32Atom(ptr))
+            {
+                return null;
+            }
+            else
+            {
+                return new String((char*)ptr);
+            }
+        }
+
+        public static String PtrToStringAuto(IntPtr ptr)
+        {
+            // Ansi platforms are no longer supported
+            return PtrToStringUni(ptr);
+        }
+
+        public static unsafe String PtrToStringUTF8(IntPtr ptr)
+        {
+            if (IntPtr.Zero == ptr)
+            {
+                return null;
+            }
+            else
+            {
+                int nbBytes = System.StubHelpers.StubHelpers.strlen((sbyte*)ptr.ToPointer());
+                return PtrToStringUTF8(ptr, nbBytes);
+            }
+        }
+
+        public static unsafe String PtrToStringUTF8(IntPtr ptr, int byteLen)
+        {
+            if (byteLen < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(byteLen), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+            else if (IntPtr.Zero == ptr)
+            {
+                return null;
+            }
+            else if (IsWin32Atom(ptr))
+            {
+                return null;
+            }
+            else if (byteLen == 0)
+            {
+                return string.Empty;
+            }
+            else
+            {
+                byte* pByte = (byte*)ptr.ToPointer();
+                return Encoding.UTF8.GetString(pByte, byteLen);
+            }
+        }
+
+        //====================================================================
+        // SizeOf()
+        //====================================================================
+        public static int SizeOf(Object structure)
+        {
+            if (structure == null)
+                throw new ArgumentNullException(nameof(structure));
+            // we never had a check for generics here
+
+            return SizeOfHelper(structure.GetType(), true);
+        }
+
+        public static int SizeOf<T>(T structure)
+        {
+            return SizeOf((object)structure);
+        }
+
+        public static int SizeOf(Type t)
+        {
+            if (t == null)
+                throw new ArgumentNullException(nameof(t));
+            if (!(t is RuntimeType))
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType, nameof(t));
+            if (t.IsGenericType)
+                throw new ArgumentException(SR.Argument_NeedNonGenericType, nameof(t));
+
+            return SizeOfHelper(t, true);
+        }
+
+        public static int SizeOf<T>()
+        {
+            return SizeOf(typeof(T));
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int SizeOfHelper(Type t, bool throwIfNotMarshalable);
+
+        //====================================================================
+        // OffsetOf()
+        //====================================================================
+        public static IntPtr OffsetOf(Type t, String fieldName)
+        {
+            if (t == null)
+                throw new ArgumentNullException(nameof(t));
+
+            FieldInfo f = t.GetField(fieldName, BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
+            if (f == null)
+                throw new ArgumentException(SR.Format(SR.Argument_OffsetOfFieldNotFound, t.FullName), nameof(fieldName));
+            RtFieldInfo rtField = f as RtFieldInfo;
+            if (rtField == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeFieldInfo, nameof(fieldName));
+
+            return OffsetOfHelper(rtField);
+        }
+        public static IntPtr OffsetOf<T>(string fieldName)
+        {
+            return OffsetOf(typeof(T), fieldName);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern IntPtr OffsetOfHelper(IRuntimeFieldInfo f);
+
+        //====================================================================
+        // UnsafeAddrOfPinnedArrayElement()
+        //
+        // IMPORTANT NOTICE: This method does not do any verification on the
+        // array. It must be used with EXTREME CAUTION since passing in 
+        // an array that is not pinned or in the fixed heap can cause 
+        // unexpected results !
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern IntPtr UnsafeAddrOfPinnedArrayElement(Array arr, int index);
+
+        public static IntPtr UnsafeAddrOfPinnedArrayElement<T>(T[] arr, int index)
+        {
+            return UnsafeAddrOfPinnedArrayElement((Array)arr, index);
+        }
+
+        //====================================================================
+        // Copy blocks from CLR arrays to native memory.
+        //====================================================================
+        public static void Copy(int[] source, int startIndex, IntPtr destination, int length)
+        {
+            CopyToNative(source, startIndex, destination, length);
+        }
+        public static void Copy(char[] source, int startIndex, IntPtr destination, int length)
+        {
+            CopyToNative(source, startIndex, destination, length);
+        }
+        public static void Copy(short[] source, int startIndex, IntPtr destination, int length)
+        {
+            CopyToNative(source, startIndex, destination, length);
+        }
+        public static void Copy(long[] source, int startIndex, IntPtr destination, int length)
+        {
+            CopyToNative(source, startIndex, destination, length);
+        }
+        public static void Copy(float[] source, int startIndex, IntPtr destination, int length)
+        {
+            CopyToNative(source, startIndex, destination, length);
+        }
+        public static void Copy(double[] source, int startIndex, IntPtr destination, int length)
+        {
+            CopyToNative(source, startIndex, destination, length);
+        }
+        public static void Copy(byte[] source, int startIndex, IntPtr destination, int length)
+        {
+            CopyToNative(source, startIndex, destination, length);
+        }
+        public static void Copy(IntPtr[] source, int startIndex, IntPtr destination, int length)
+        {
+            CopyToNative(source, startIndex, destination, length);
+        }
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void CopyToNative(Object source, int startIndex, IntPtr destination, int length);
+
+        //====================================================================
+        // Copy blocks from native memory to CLR arrays
+        //====================================================================
+        public static void Copy(IntPtr source, int[] destination, int startIndex, int length)
+        {
+            CopyToManaged(source, destination, startIndex, length);
+        }
+        public static void Copy(IntPtr source, char[] destination, int startIndex, int length)
+        {
+            CopyToManaged(source, destination, startIndex, length);
+        }
+        public static void Copy(IntPtr source, short[] destination, int startIndex, int length)
+        {
+            CopyToManaged(source, destination, startIndex, length);
+        }
+        public static void Copy(IntPtr source, long[] destination, int startIndex, int length)
+        {
+            CopyToManaged(source, destination, startIndex, length);
+        }
+        public static void Copy(IntPtr source, float[] destination, int startIndex, int length)
+        {
+            CopyToManaged(source, destination, startIndex, length);
+        }
+        public static void Copy(IntPtr source, double[] destination, int startIndex, int length)
+        {
+            CopyToManaged(source, destination, startIndex, length);
+        }
+        public static void Copy(IntPtr source, byte[] destination, int startIndex, int length)
+        {
+            CopyToManaged(source, destination, startIndex, length);
+        }
+        public static void Copy(IntPtr source, IntPtr[] destination, int startIndex, int length)
+        {
+            CopyToManaged(source, destination, startIndex, length);
+        }
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void CopyToManaged(IntPtr source, Object destination, int startIndex, int length);
+
+        //====================================================================
+        // Read from memory
+        //====================================================================
+        public static byte ReadByte(Object ptr, int ofs)
+        {
+            return ReadValueSlow(ptr, ofs, (IntPtr nativeHome, int offset) => Marshal.ReadByte(nativeHome, offset));
+        }
+
+        public static unsafe byte ReadByte(IntPtr ptr, int ofs)
+        {
+            try
+            {
+                byte* addr = (byte*)ptr + ofs;
+                return *addr;
+            }
+            catch (NullReferenceException)
+            {
+                // this method is documented to throw AccessViolationException on any AV
+                throw new AccessViolationException();
+            }
+        }
+
+        public static byte ReadByte(IntPtr ptr)
+        {
+            return ReadByte(ptr, 0);
+        }
+
+        public static short ReadInt16(Object ptr, int ofs)
+        {
+            return ReadValueSlow(ptr, ofs, (IntPtr nativeHome, int offset) => Marshal.ReadInt16(nativeHome, offset));
+        }
+
+        public static unsafe short ReadInt16(IntPtr ptr, int ofs)
+        {
+            try
+            {
+                byte* addr = (byte*)ptr + ofs;
+                if ((unchecked((int)addr) & 0x1) == 0)
+                {
+                    // aligned read
+                    return *((short*)addr);
+                }
+                else
+                {
+                    // unaligned read
+                    short val;
+                    byte* valPtr = (byte*)&val;
+                    valPtr[0] = addr[0];
+                    valPtr[1] = addr[1];
+                    return val;
+                }
+            }
+            catch (NullReferenceException)
+            {
+                // this method is documented to throw AccessViolationException on any AV
+                throw new AccessViolationException();
+            }
+        }
+
+        public static short ReadInt16(IntPtr ptr)
+        {
+            return ReadInt16(ptr, 0);
+        }
+
+        public static int ReadInt32(object ptr, int ofs)
+        {
+            return ReadValueSlow(ptr, ofs, (IntPtr nativeHome, int offset) => Marshal.ReadInt32(nativeHome, offset));
+        }
+
+        public static unsafe int ReadInt32(IntPtr ptr, int ofs)
+        {
+            try
+            {
+                byte* addr = (byte*)ptr + ofs;
+                if ((unchecked((int)addr) & 0x3) == 0)
+                {
+                    // aligned read
+                    return *((int*)addr);
+                }
+                else
+                {
+                    // unaligned read
+                    int val;
+                    byte* valPtr = (byte*)&val;
+                    valPtr[0] = addr[0];
+                    valPtr[1] = addr[1];
+                    valPtr[2] = addr[2];
+                    valPtr[3] = addr[3];
+                    return val;
+                }
+            }
+            catch (NullReferenceException)
+            {
+                // this method is documented to throw AccessViolationException on any AV
+                throw new AccessViolationException();
+            }
+        }
+
+        public static int ReadInt32(IntPtr ptr)
+        {
+            return ReadInt32(ptr, 0);
+        }
+
+        public static IntPtr ReadIntPtr(Object ptr, int ofs)
+        {
+#if BIT64
+            return (IntPtr)ReadInt64(ptr, ofs);
+#else // 32
+                return (IntPtr) ReadInt32(ptr, ofs);
+#endif
+        }
+
+        public static IntPtr ReadIntPtr(IntPtr ptr, int ofs)
+        {
+#if BIT64
+            return (IntPtr)ReadInt64(ptr, ofs);
+#else // 32
+                return (IntPtr) ReadInt32(ptr, ofs);
+#endif
+        }
+
+        public static IntPtr ReadIntPtr(IntPtr ptr)
+        {
+#if BIT64
+            return (IntPtr)ReadInt64(ptr, 0);
+#else // 32
+                return (IntPtr) ReadInt32(ptr, 0);
+#endif
+        }
+
+        public static long ReadInt64([MarshalAs(UnmanagedType.AsAny), In] Object ptr, int ofs)
+        {
+            return ReadValueSlow(ptr, ofs, (IntPtr nativeHome, int offset) => Marshal.ReadInt64(nativeHome, offset));
+        }
+
+        public static unsafe long ReadInt64(IntPtr ptr, int ofs)
+        {
+            try
+            {
+                byte* addr = (byte*)ptr + ofs;
+                if ((unchecked((int)addr) & 0x7) == 0)
+                {
+                    // aligned read
+                    return *((long*)addr);
+                }
+                else
+                {
+                    // unaligned read
+                    long val;
+                    byte* valPtr = (byte*)&val;
+                    valPtr[0] = addr[0];
+                    valPtr[1] = addr[1];
+                    valPtr[2] = addr[2];
+                    valPtr[3] = addr[3];
+                    valPtr[4] = addr[4];
+                    valPtr[5] = addr[5];
+                    valPtr[6] = addr[6];
+                    valPtr[7] = addr[7];
+                    return val;
+                }
+            }
+            catch (NullReferenceException)
+            {
+                // this method is documented to throw AccessViolationException on any AV
+                throw new AccessViolationException();
+            }
+        }
+
+        public static long ReadInt64(IntPtr ptr)
+        {
+            return ReadInt64(ptr, 0);
+        }
+
+        //====================================================================
+        // Read value from marshaled object (marshaled using AsAny)
+        // It's quite slow and can return back dangling pointers
+        // It's only there for backcompact
+        // I don't think we should spend time optimizing it
+        // People should really call the IntPtr overload instead
+        //====================================================================
+        private static unsafe T ReadValueSlow<T>(object ptr, int ofs, Func<IntPtr, int, T> readValueHelper)
+        {
+            // We AV on desktop if passing NULL. So this is technically a breaking change but is an improvement
+            if (ptr == null)
+                throw new ArgumentNullException(nameof(ptr));
+
+            int dwFlags = 
+                (int)AsAnyMarshaler.AsAnyFlags.In | 
+                (int)AsAnyMarshaler.AsAnyFlags.IsAnsi | 
+                (int)AsAnyMarshaler.AsAnyFlags.IsBestFit;
+
+            MngdNativeArrayMarshaler.MarshalerState nativeArrayMarshalerState = new MngdNativeArrayMarshaler.MarshalerState();                
+            AsAnyMarshaler marshaler = new AsAnyMarshaler(new IntPtr(&nativeArrayMarshalerState));
+                
+            IntPtr pNativeHome = IntPtr.Zero;
+
+            try
+            {
+                pNativeHome = marshaler.ConvertToNative(ptr, dwFlags);
+                return readValueHelper(pNativeHome, ofs);
+            }
+            finally
+            {
+                marshaler.ClearNative(pNativeHome);
+            }    
+        }
+
+
+
+        //====================================================================
+        // Write to memory
+        //====================================================================
+        public static unsafe void WriteByte(IntPtr ptr, int ofs, byte val)
+        {
+            try
+            {
+                byte* addr = (byte*)ptr + ofs;
+                *addr = val;
+            }
+            catch (NullReferenceException)
+            {
+                // this method is documented to throw AccessViolationException on any AV
+                throw new AccessViolationException();
+            }
+        }
+
+        public static void WriteByte(Object ptr, int ofs, byte val)
+        {
+            WriteValueSlow(ptr, ofs, val, (IntPtr nativeHome, int offset, byte value) => Marshal.WriteByte(nativeHome, offset, value));
+        }
+
+        public static void WriteByte(IntPtr ptr, byte val)
+        {
+            WriteByte(ptr, 0, val);
+        }
+
+        public static unsafe void WriteInt16(IntPtr ptr, int ofs, short val)
+        {
+            try
+            {
+                byte* addr = (byte*)ptr + ofs;
+                if ((unchecked((int)addr) & 0x1) == 0)
+                {
+                    // aligned write
+                    *((short*)addr) = val;
+                }
+                else
+                {
+                    // unaligned write
+                    byte* valPtr = (byte*)&val;
+                    addr[0] = valPtr[0];
+                    addr[1] = valPtr[1];
+                }
+            }
+            catch (NullReferenceException)
+            {
+                // this method is documented to throw AccessViolationException on any AV
+                throw new AccessViolationException();
+            }
+        }
+
+        public static void WriteInt16(Object ptr, int ofs, short val)
+        {
+            WriteValueSlow(ptr, ofs, val, (IntPtr nativeHome, int offset, short value) => Marshal.WriteInt16(nativeHome, offset, value));
+        }
+
+        public static void WriteInt16(IntPtr ptr, short val)
+        {
+            WriteInt16(ptr, 0, val);
+        }
+
+        public static void WriteInt16(IntPtr ptr, int ofs, char val)
+        {
+            WriteInt16(ptr, ofs, (short)val);
+        }
+
+        public static void WriteInt16([In, Out]Object ptr, int ofs, char val)
+        {
+            WriteInt16(ptr, ofs, (short)val);
+        }
+
+        public static void WriteInt16(IntPtr ptr, char val)
+        {
+            WriteInt16(ptr, 0, (short)val);
+        }
+
+        public static unsafe void WriteInt32(IntPtr ptr, int ofs, int val)
+        {
+            try
+            {
+                byte* addr = (byte*)ptr + ofs;
+                if ((unchecked((int)addr) & 0x3) == 0)
+                {
+                    // aligned write
+                    *((int*)addr) = val;
+                }
+                else
+                {
+                    // unaligned write
+                    byte* valPtr = (byte*)&val;
+                    addr[0] = valPtr[0];
+                    addr[1] = valPtr[1];
+                    addr[2] = valPtr[2];
+                    addr[3] = valPtr[3];
+                }
+            }
+            catch (NullReferenceException)
+            {
+                // this method is documented to throw AccessViolationException on any AV
+                throw new AccessViolationException();
+            }
+        }
+
+        public static void WriteInt32(Object ptr, int ofs, int val)
+        {
+            WriteValueSlow(ptr, ofs, val, (IntPtr nativeHome, int offset, int value) => Marshal.WriteInt32(nativeHome, offset, value));
+        }
+
+        public static void WriteInt32(IntPtr ptr, int val)
+        {
+            WriteInt32(ptr, 0, val);
+        }
+
+        public static void WriteIntPtr(IntPtr ptr, int ofs, IntPtr val)
+        {
+#if BIT64
+            WriteInt64(ptr, ofs, (long)val);
+#else // 32
+                WriteInt32(ptr, ofs, (int)val);
+#endif
+        }
+
+        public static void WriteIntPtr(Object ptr, int ofs, IntPtr val)
+        {
+#if BIT64
+            WriteInt64(ptr, ofs, (long)val);
+#else // 32
+                WriteInt32(ptr, ofs, (int)val);
+#endif
+        }
+
+        public static void WriteIntPtr(IntPtr ptr, IntPtr val)
+        {
+#if BIT64
+            WriteInt64(ptr, 0, (long)val);
+#else // 32
+                WriteInt32(ptr, 0, (int)val);
+#endif
+        }
+
+        public static unsafe void WriteInt64(IntPtr ptr, int ofs, long val)
+        {
+            try
+            {
+                byte* addr = (byte*)ptr + ofs;
+                if ((unchecked((int)addr) & 0x7) == 0)
+                {
+                    // aligned write
+                    *((long*)addr) = val;
+                }
+                else
+                {
+                    // unaligned write
+                    byte* valPtr = (byte*)&val;
+                    addr[0] = valPtr[0];
+                    addr[1] = valPtr[1];
+                    addr[2] = valPtr[2];
+                    addr[3] = valPtr[3];
+                    addr[4] = valPtr[4];
+                    addr[5] = valPtr[5];
+                    addr[6] = valPtr[6];
+                    addr[7] = valPtr[7];
+                }
+            }
+            catch (NullReferenceException)
+            {
+                // this method is documented to throw AccessViolationException on any AV
+                throw new AccessViolationException();
+            }
+        }
+
+        public static void WriteInt64(Object ptr, int ofs, long val)
+        {
+            WriteValueSlow(ptr, ofs, val, (IntPtr nativeHome, int offset, long value) => Marshal.WriteInt64(nativeHome, offset, value));
+        }
+
+        public static void WriteInt64(IntPtr ptr, long val)
+        {
+            WriteInt64(ptr, 0, val);
+        }
+
+        //====================================================================
+        // Write value into marshaled object (marshaled using AsAny) and
+        // propagate the value back
+        // It's quite slow and is only there for backcompact
+        // I don't think we should spend time optimizing it
+        // People should really call the IntPtr overload instead
+        //====================================================================
+        private static unsafe void WriteValueSlow<T>(object ptr, int ofs, T val, Action<IntPtr, int, T> writeValueHelper)
+        {
+            // We AV on desktop if passing NULL. So this is technically a breaking change but is an improvement
+            if (ptr == null)
+                throw new ArgumentNullException(nameof(ptr));
+                            
+            int dwFlags = 
+                (int)AsAnyMarshaler.AsAnyFlags.In | 
+                (int)AsAnyMarshaler.AsAnyFlags.Out | 
+                (int)AsAnyMarshaler.AsAnyFlags.IsAnsi | 
+                (int)AsAnyMarshaler.AsAnyFlags.IsBestFit;
+
+            MngdNativeArrayMarshaler.MarshalerState nativeArrayMarshalerState = new MngdNativeArrayMarshaler.MarshalerState();                
+            AsAnyMarshaler marshaler = new AsAnyMarshaler(new IntPtr(&nativeArrayMarshalerState));
+                
+            IntPtr pNativeHome = IntPtr.Zero;
+
+            try
+            {
+                pNativeHome = marshaler.ConvertToNative(ptr, dwFlags);
+                writeValueHelper(pNativeHome, ofs, val);
+                marshaler.ConvertToManaged(ptr, pNativeHome);
+            }
+            finally
+            {
+                marshaler.ClearNative(pNativeHome);
+            }            
+        }
+
+        //====================================================================
+        // GetLastWin32Error
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern int GetLastWin32Error();
+
+
+        //====================================================================
+        // SetLastWin32Error
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void SetLastWin32Error(int error);
+
+
+        //====================================================================
+        // GetHRForLastWin32Error
+        //====================================================================
+        public static int GetHRForLastWin32Error()
+        {
+            int dwLastError = GetLastWin32Error();
+            if ((dwLastError & 0x80000000) == 0x80000000)
+                return dwLastError;
+            else
+                return (dwLastError & 0x0000FFFF) | unchecked((int)0x80070000);
+        }
+
+
+        //====================================================================
+        // Prelink
+        //====================================================================
+        public static void Prelink(MethodInfo m)
+        {
+            if (m == null)
+                throw new ArgumentNullException(nameof(m));
+
+            RuntimeMethodInfo rmi = m as RuntimeMethodInfo;
+
+            if (rmi == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeMethodInfo);
+
+            InternalPrelink(rmi);
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void InternalPrelink(IRuntimeMethodInfo m);
+
+        public static void PrelinkAll(Type c)
+        {
+            if (c == null)
+                throw new ArgumentNullException(nameof(c));
+
+            MethodInfo[] mi = c.GetMethods();
+            if (mi != null)
+            {
+                for (int i = 0; i < mi.Length; i++)
+                {
+                    Prelink(mi[i]);
+                }
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern /* struct _EXCEPTION_POINTERS* */ IntPtr GetExceptionPointers();
+        
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern int GetExceptionCode();
+
+
+        //====================================================================
+        // Marshals data from a structure class to a native memory block.
+        // If the structure contains pointers to allocated blocks and
+        // "fDeleteOld" is true, this routine will call DestroyStructure() first. 
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall), ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
+        public static extern void StructureToPtr(Object structure, IntPtr ptr, bool fDeleteOld);
+
+        public static void StructureToPtr<T>(T structure, IntPtr ptr, bool fDeleteOld)
+        {
+            StructureToPtr((object)structure, ptr, fDeleteOld);
+        }
+
+        //====================================================================
+        // Marshals data from a native memory block to a preallocated structure class.
+        //====================================================================
+        public static void PtrToStructure(IntPtr ptr, Object structure)
+        {
+            PtrToStructureHelper(ptr, structure, false);
+        }
+
+        public static void PtrToStructure<T>(IntPtr ptr, T structure)
+        {
+            PtrToStructure(ptr, (object)structure);
+        }
+
+        //====================================================================
+        // Creates a new instance of "structuretype" and marshals data from a
+        // native memory block to it.
+        //====================================================================
+        public static Object PtrToStructure(IntPtr ptr, Type structureType)
+        {
+            if (ptr == IntPtr.Zero) return null;
+
+            if (structureType == null)
+                throw new ArgumentNullException(nameof(structureType));
+
+            if (structureType.IsGenericType)
+                throw new ArgumentException(SR.Argument_NeedNonGenericType, nameof(structureType));
+
+            RuntimeType rt = structureType.UnderlyingSystemType as RuntimeType;
+
+            if (rt == null)
+                throw new ArgumentException(SR.Arg_MustBeType, nameof(structureType));
+
+            Object structure = rt.CreateInstanceDefaultCtor(false /*publicOnly*/, false /*skipCheckThis*/, false /*fillCache*/, true /*wrapExceptions*/);
+            PtrToStructureHelper(ptr, structure, true);
+            return structure;
+        }
+
+        public static T PtrToStructure<T>(IntPtr ptr)
+        {
+            return (T)PtrToStructure(ptr, typeof(T));
+        }
+
+        //====================================================================
+        // Helper function to copy a pointer into a preallocated structure.
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void PtrToStructureHelper(IntPtr ptr, Object structure, bool allowValueClasses);
+
+
+        //====================================================================
+        // Freeds all substructures pointed to by the native memory block.
+        // "structureclass" is used to provide layout information.
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void DestroyStructure(IntPtr ptr, Type structuretype);
+
+        public static void DestroyStructure<T>(IntPtr ptr)
+        {
+            DestroyStructure(ptr, typeof(T));
+        }
+
+#if FEATURE_COMINTEROP
+        //====================================================================
+        // Returns the HInstance for this module.  Returns -1 if the module 
+        // doesn't have an HInstance.  In Memory (Dynamic) Modules won't have 
+        // an HInstance.
+        //====================================================================
+        public static IntPtr GetHINSTANCE(Module m)
+        {
+            if (m == null)
+                throw new ArgumentNullException(nameof(m));
+
+            RuntimeModule rtModule = m as RuntimeModule;
+            if (rtModule == null)
+            {
+                ModuleBuilder mb = m as ModuleBuilder;
+                if (mb != null)
+                    rtModule = mb.InternalModule;
+            }
+
+            if (rtModule == null)
+                throw new ArgumentNullException(nameof(m), SR.Argument_MustBeRuntimeModule);
+
+            return GetHINSTANCE(rtModule.GetNativeHandle());
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern IntPtr GetHINSTANCE(RuntimeModule m);
+
+#endif // FEATURE_COMINTEROP
+        //====================================================================
+        // Throws a CLR exception based on the HRESULT.
+        //====================================================================
+        public static void ThrowExceptionForHR(int errorCode)
+        {
+            if (errorCode < 0)
+                ThrowExceptionForHRInternal(errorCode, IntPtr.Zero);
+        }
+        public static void ThrowExceptionForHR(int errorCode, IntPtr errorInfo)
+        {
+            if (errorCode < 0)
+                ThrowExceptionForHRInternal(errorCode, errorInfo);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ThrowExceptionForHRInternal(int errorCode, IntPtr errorInfo);
+
+
+        //====================================================================
+        // Converts the HRESULT to a CLR exception.
+        //====================================================================
+        public static Exception GetExceptionForHR(int errorCode)
+        {
+            if (errorCode < 0)
+                return GetExceptionForHRInternal(errorCode, IntPtr.Zero);
+            else
+                return null;
+        }
+        public static Exception GetExceptionForHR(int errorCode, IntPtr errorInfo)
+        {
+            if (errorCode < 0)
+                return GetExceptionForHRInternal(errorCode, errorInfo);
+            else
+                return null;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Exception GetExceptionForHRInternal(int errorCode, IntPtr errorInfo);
+
+
+        //====================================================================
+        // Memory allocation and deallocation.
+        //====================================================================
+        public static IntPtr AllocHGlobal(IntPtr cb)
+        {
+            // For backwards compatibility on 32 bit platforms, ensure we pass values between 
+            // Int32.MaxValue and UInt32.MaxValue to Windows.  If the binary has had the 
+            // LARGEADDRESSAWARE bit set in the PE header, it may get 3 or 4 GB of user mode
+            // address space.  It is remotely that those allocations could have succeeded,
+            // though I couldn't reproduce that.  In either case, that means we should continue
+            // throwing an OOM instead of an ArgumentOutOfRangeException for "negative" amounts of memory.
+            UIntPtr numBytes;
+#if BIT64
+            numBytes = new UIntPtr(unchecked((ulong)cb.ToInt64()));
+#else // 32
+            numBytes = new UIntPtr(unchecked((uint)cb.ToInt32()));
+#endif
+
+            IntPtr pNewMem = Win32Native.LocalAlloc_NoSafeHandle(LMEM_FIXED, unchecked(numBytes));
+
+            if (pNewMem == IntPtr.Zero)
+            {
+                throw new OutOfMemoryException();
+            }
+            return pNewMem;
+        }
+
+        public static IntPtr AllocHGlobal(int cb)
+        {
+            return AllocHGlobal((IntPtr)cb);
+        }
+
+        public static void FreeHGlobal(IntPtr hglobal)
+        {
+            if (IsNotWin32Atom(hglobal))
+            {
+                if (IntPtr.Zero != Win32Native.LocalFree(hglobal))
+                {
+                    ThrowExceptionForHR(GetHRForLastWin32Error());
+                }
+            }
+        }
+
+        public static IntPtr ReAllocHGlobal(IntPtr pv, IntPtr cb)
+        {
+            IntPtr pNewMem = Win32Native.LocalReAlloc(pv, cb, LMEM_MOVEABLE);
+            if (pNewMem == IntPtr.Zero)
+            {
+                throw new OutOfMemoryException();
+            }
+            return pNewMem;
+        }
+
+
+        //====================================================================
+        // String convertions.
+        //====================================================================          
+        public static unsafe IntPtr StringToHGlobalAnsi(String s)
+        {
+            if (s == null)
+            {
+                return IntPtr.Zero;
+            }
+            else
+            {
+                int nb = (s.Length + 1) * SystemMaxDBCSCharSize;
+
+                // Overflow checking
+                if (nb < s.Length)
+                    throw new ArgumentOutOfRangeException(nameof(s));
+
+                UIntPtr len = new UIntPtr((uint)nb);
+                IntPtr hglobal = Win32Native.LocalAlloc_NoSafeHandle(LMEM_FIXED, len);
+
+                if (hglobal == IntPtr.Zero)
+                {
+                    throw new OutOfMemoryException();
+                }
+                else
+                {
+                    s.ConvertToAnsi((byte*)hglobal, nb, false, false);
+                    return hglobal;
+                }
+            }
+        }
+
+        public static unsafe IntPtr StringToHGlobalUni(String s)
+        {
+            if (s == null)
+            {
+                return IntPtr.Zero;
+            }
+            else
+            {
+                int nb = (s.Length + 1) * 2;
+
+                // Overflow checking
+                if (nb < s.Length)
+                    throw new ArgumentOutOfRangeException(nameof(s));
+
+                UIntPtr len = new UIntPtr((uint)nb);
+                IntPtr hglobal = Win32Native.LocalAlloc_NoSafeHandle(LMEM_FIXED, len);
+
+                if (hglobal == IntPtr.Zero)
+                {
+                    throw new OutOfMemoryException();
+                }
+                else
+                {
+                    fixed (char* firstChar = s)
+                    {
+                        String.wstrcpy((char*)hglobal, firstChar, s.Length + 1);
+                    }
+                    return hglobal;
+                }
+            }
+        }
+
+        public static IntPtr StringToHGlobalAuto(String s)
+        {
+            // Ansi platforms are no longer supported
+            return StringToHGlobalUni(s);
+        }
+
+#if FEATURE_COMINTEROP
+
+        //====================================================================
+        // Converts the CLR exception to an HRESULT. This function also sets
+        // up an IErrorInfo for the exception.
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern int GetHRForException(Exception e);
+
+        //====================================================================
+        // Converts the CLR exception to an HRESULT. This function also sets
+        // up an IErrorInfo for the exception.
+        // This function is only used in WinRT and converts ObjectDisposedException
+        // to RO_E_CLOSED
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int GetHRForException_WinRT(Exception e);
+
+        internal static readonly Guid ManagedNameGuid = new Guid("{0F21F359-AB84-41E8-9A78-36D110E6D2F9}");
+
+        //====================================================================
+        // Given a managed object that wraps an ITypeInfo, return its name
+        //====================================================================
+        public static String GetTypeInfoName(ITypeInfo typeInfo)
+        {
+            if (typeInfo == null)
+                throw new ArgumentNullException(nameof(typeInfo));
+
+            String strTypeLibName = null;
+            String strDocString = null;
+            int dwHelpContext = 0;
+            String strHelpFile = null;
+
+            typeInfo.GetDocumentation(-1, out strTypeLibName, out strDocString, out dwHelpContext, out strHelpFile);
+
+            return strTypeLibName;
+        }
+
+        // This method is identical to Type.GetTypeFromCLSID. Since it's interop specific, we expose it
+        // on Marshal for more consistent API surface.
+        public static Type GetTypeFromCLSID(Guid clsid)
+        {
+            return RuntimeType.GetTypeFromCLSIDImpl(clsid, null, false);
+        }
+
+        //====================================================================
+        // return the IUnknown* for an Object if the current context
+        // is the one where the RCW was first seen. Will return null 
+        // otherwise.
+        //====================================================================
+        public static IntPtr /* IUnknown* */ GetIUnknownForObject(Object o)
+        {
+            return GetIUnknownForObjectNative(o, false);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern IntPtr /* IUnknown* */ GetIUnknownForObjectNative(Object o, bool onlyInContext);
+
+        //====================================================================
+        // return the raw IUnknown* for a COM Object not related to current 
+        // context
+        // Does not call AddRef
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr /* IUnknown* */ GetRawIUnknownForComObjectNoAddRef(Object o);
+#endif // FEATURE_COMINTEROP
+
+        //====================================================================
+        // return the IDispatch* for an Object
+        //====================================================================
+        public static IntPtr /* IDispatch */ GetIDispatchForObject(Object o)
+        {
+            throw new PlatformNotSupportedException();
+        }
+
+#if FEATURE_COMINTEROP
+
+        //====================================================================
+        // return the IUnknown* representing the interface for the Object
+        // Object o should support Type T
+        //====================================================================
+        public static IntPtr /* IUnknown* */ GetComInterfaceForObject(Object o, Type T)
+        {
+            return GetComInterfaceForObjectNative(o, T, false, true);
+        }
+
+        public static IntPtr GetComInterfaceForObject<T, TInterface>(T o)
+        {
+            return GetComInterfaceForObject(o, typeof(TInterface));
+        }
+
+        //====================================================================
+        // return the IUnknown* representing the interface for the Object
+        // Object o should support Type T, it refer the value of mode to 
+        // invoke customized QueryInterface or not
+        //====================================================================
+        public static IntPtr /* IUnknown* */ GetComInterfaceForObject(Object o, Type T, CustomQueryInterfaceMode mode)
+        {
+            bool bEnableCustomizedQueryInterface = ((mode == CustomQueryInterfaceMode.Allow) ? true : false);
+            return GetComInterfaceForObjectNative(o, T, false, bEnableCustomizedQueryInterface);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern IntPtr /* IUnknown* */ GetComInterfaceForObjectNative(Object o, Type t, bool onlyInContext, bool fEnalbeCustomizedQueryInterface);
+
+        //====================================================================
+        // return an Object for IUnknown
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern Object GetObjectForIUnknown(IntPtr /* IUnknown* */ pUnk);
+
+        //====================================================================
+        // Return a unique Object given an IUnknown.  This ensures that you
+        //  receive a fresh object (we will not look in the cache to match up this
+        //  IUnknown to an already existing object).  This is useful in cases
+        //  where you want to be able to call ReleaseComObject on a RCW
+        //  and not worry about other active uses of said RCW.
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern Object GetUniqueObjectForIUnknown(IntPtr unknown);
+
+        //====================================================================
+        // return an Object for IUnknown, using the Type T, 
+        //  NOTE: 
+        //  Type T should be either a COM imported Type or a sub-type of COM 
+        //  imported Type
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern Object GetTypedObjectForIUnknown(IntPtr /* IUnknown* */ pUnk, Type t);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern IntPtr CreateAggregatedObject(IntPtr pOuter, Object o);
+
+        public static IntPtr CreateAggregatedObject<T>(IntPtr pOuter, T o)
+        {
+            return CreateAggregatedObject(pOuter, (object)o);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void CleanupUnusedObjectsInCurrentContext();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern bool AreComObjectsAvailableForCleanup();
+
+        //====================================================================
+        // check if the object is classic COM component
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern bool IsComObject(Object o);
+
+#endif // FEATURE_COMINTEROP
+
+        public static IntPtr AllocCoTaskMem(int cb)
+        {
+            IntPtr pNewMem = Win32Native.CoTaskMemAlloc(new UIntPtr((uint)cb));
+            if (pNewMem == IntPtr.Zero)
+            {
+                throw new OutOfMemoryException();
+            }
+            return pNewMem;
+        }
+
+        public static unsafe IntPtr StringToCoTaskMemUni(String s)
+        {
+            if (s == null)
+            {
+                return IntPtr.Zero;
+            }
+            else
+            {
+                int nb = (s.Length + 1) * 2;
+
+                // Overflow checking
+                if (nb < s.Length)
+                    throw new ArgumentOutOfRangeException(nameof(s));
+
+                IntPtr hglobal = Win32Native.CoTaskMemAlloc(new UIntPtr((uint)nb));
+
+                if (hglobal == IntPtr.Zero)
+                {
+                    throw new OutOfMemoryException();
+                }
+                else
+                {
+                    fixed (char* firstChar = s)
+                    {
+                        String.wstrcpy((char*)hglobal, firstChar, s.Length + 1);
+                    }
+                    return hglobal;
+                }
+            }
+        }
+
+        public static unsafe IntPtr StringToCoTaskMemUTF8(String s)
+        {
+            if (s == null)
+            {
+                return IntPtr.Zero;
+            }
+            else
+            {
+                int nb = Encoding.UTF8.GetMaxByteCount(s.Length);
+
+                IntPtr pMem = Win32Native.CoTaskMemAlloc(new UIntPtr((uint)nb + 1));
+
+                if (pMem == IntPtr.Zero)
+                {
+                    throw new OutOfMemoryException();
+                }
+                else
+                {
+                    fixed (char* firstChar = s)
+                    {
+                        byte* pbMem = (byte*)pMem;
+                        int nbWritten = Encoding.UTF8.GetBytes(firstChar, s.Length, pbMem, nb);
+                        pbMem[nbWritten] = 0;
+                    }
+                    return pMem;
+                }
+            }
+        }
+
+        public static IntPtr StringToCoTaskMemAuto(String s)
+        {
+            // Ansi platforms are no longer supported
+            return StringToCoTaskMemUni(s);
+        }
+
+        public static unsafe IntPtr StringToCoTaskMemAnsi(String s)
+        {
+            if (s == null)
+            {
+                return IntPtr.Zero;
+            }
+            else
+            {
+                int nb = (s.Length + 1) * SystemMaxDBCSCharSize;
+
+                // Overflow checking
+                if (nb < s.Length)
+                    throw new ArgumentOutOfRangeException(nameof(s));
+
+                IntPtr hglobal = Win32Native.CoTaskMemAlloc(new UIntPtr((uint)nb));
+
+                if (hglobal == IntPtr.Zero)
+                {
+                    throw new OutOfMemoryException();
+                }
+                else
+                {
+                    s.ConvertToAnsi((byte*)hglobal, nb, false, false);
+                    return hglobal;
+                }
+            }
+        }
+
+        public static void FreeCoTaskMem(IntPtr ptr)
+        {
+            if (IsNotWin32Atom(ptr))
+            {
+                Win32Native.CoTaskMemFree(ptr);
+            }
+        }
+
+        public static IntPtr ReAllocCoTaskMem(IntPtr pv, int cb)
+        {
+            IntPtr pNewMem = Win32Native.CoTaskMemRealloc(pv, new UIntPtr((uint)cb));
+            if (pNewMem == IntPtr.Zero && cb != 0)
+            {
+                throw new OutOfMemoryException();
+            }
+            return pNewMem;
+        }
+
+        //====================================================================
+        // BSTR allocation and dealocation.
+        //====================================================================      
+        public static void FreeBSTR(IntPtr ptr)
+        {
+            if (IsNotWin32Atom(ptr))
+            {
+                Win32Native.SysFreeString(ptr);
+            }
+        }
+
+        public static IntPtr StringToBSTR(String s)
+        {
+            if (s == null)
+                return IntPtr.Zero;
+
+            // Overflow checking
+            if (s.Length + 1 < s.Length)
+                throw new ArgumentOutOfRangeException(nameof(s));
+
+            IntPtr bstr = Win32Native.SysAllocStringLen(s, s.Length);
+            if (bstr == IntPtr.Zero)
+                throw new OutOfMemoryException();
+
+            return bstr;
+        }
+
+        public static String PtrToStringBSTR(IntPtr ptr)
+        {
+            return PtrToStringUni(ptr, (int)Win32Native.SysStringLen(ptr));
+        }
+
+#if FEATURE_COMINTEROP
+        //====================================================================
+        // release the COM component and if the reference hits 0 zombie this object
+        // further usage of this Object might throw an exception
+        //====================================================================
+        public static int ReleaseComObject(Object o)
+        {
+            __ComObject co = null;
+
+            // Make sure the obj is an __ComObject.
+            try
+            {
+                co = (__ComObject)o;
+            }
+            catch (InvalidCastException)
+            {
+                throw new ArgumentException(SR.Argument_ObjNotComObject, nameof(o));
+            }
+
+            return co.ReleaseSelf();
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int InternalReleaseComObject(Object o);
+
+
+        //====================================================================
+        // release the COM component and zombie this object
+        // further usage of this Object might throw an exception
+        //====================================================================
+        public static Int32 FinalReleaseComObject(Object o)
+        {
+            if (o == null)
+                throw new ArgumentNullException(nameof(o));
+
+            __ComObject co = null;
+
+            // Make sure the obj is an __ComObject.
+            try
+            {
+                co = (__ComObject)o;
+            }
+            catch (InvalidCastException)
+            {
+                throw new ArgumentException(SR.Argument_ObjNotComObject, nameof(o));
+            }
+
+            co.FinalReleaseSelf();
+
+            return 0;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void InternalFinalReleaseComObject(Object o);
+#endif // FEATURE_COMINTEROP
+
+        //====================================================================
+        // This method retrieves data from the COM object.
+        //====================================================================
+        public static Object GetComObjectData(Object obj, Object key)
+        {
+            throw new PlatformNotSupportedException(SR.Arg_PlatformNotSupported);
+        }
+
+        //====================================================================
+        // This method sets data on the COM object. The data can only be set 
+        // once for a given key and cannot be removed. This function returns
+        // true if the data has been added, false if the data could not be
+        // added because there already was data for the specified key.
+        //====================================================================
+        public static bool SetComObjectData(Object obj, Object key, Object data)
+        {
+            throw new PlatformNotSupportedException(SR.Arg_PlatformNotSupported);
+        }
+
+#if FEATURE_COMINTEROP
+        //====================================================================
+        // This method takes the given COM object and wraps it in an object
+        // of the specified type. The type must be derived from __ComObject.
+        //====================================================================
+        public static Object CreateWrapperOfType(Object o, Type t)
+        {
+            // Validate the arguments.
+            if (t == null)
+                throw new ArgumentNullException(nameof(t));
+            if (!t.IsCOMObject)
+                throw new ArgumentException(SR.Argument_TypeNotComObject, nameof(t));
+            if (t.IsGenericType)
+                throw new ArgumentException(SR.Argument_NeedNonGenericType, nameof(t));
+
+            if (t.IsWindowsRuntimeObject)
+                throw new ArgumentException(SR.Argument_TypeIsWinRTType, nameof(t));
+
+            // Check for the null case.
+            if (o == null)
+                return null;
+
+            // Make sure the object is a COM object.
+            if (!o.GetType().IsCOMObject)
+                throw new ArgumentException(SR.Argument_ObjNotComObject, nameof(o));
+            if (o.GetType().IsWindowsRuntimeObject)
+                throw new ArgumentException(SR.Argument_ObjIsWinRTObject, nameof(o));
+
+            // Check to see if the type of the object is the requested type.
+            if (o.GetType() == t)
+                return o;
+
+            // Check to see if we already have a cached wrapper for this type.
+            Object Wrapper = GetComObjectData(o, t);
+            if (Wrapper == null)
+            {
+                // Create the wrapper for the specified type.
+                Wrapper = InternalCreateWrapperOfType(o, t);
+
+                // Attempt to cache the wrapper on the object.
+                if (!SetComObjectData(o, t, Wrapper))
+                {
+                    // Another thead already cached the wrapper so use that one instead.
+                    Wrapper = GetComObjectData(o, t);
+                }
+            }
+
+            return Wrapper;
+        }
+
+        public static TWrapper CreateWrapperOfType<T, TWrapper>(T o)
+        {
+            return (TWrapper)CreateWrapperOfType(o, typeof(TWrapper));
+        }
+
+        //====================================================================
+        // Helper method called from CreateWrapperOfType.
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern Object InternalCreateWrapperOfType(Object o, Type t);
+
+        //====================================================================
+        // IUnknown Helpers
+        //====================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern int /* HRESULT */ QueryInterface(IntPtr /* IUnknown */ pUnk, ref Guid iid, out IntPtr ppv);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern int /* ULONG */ AddRef(IntPtr /* IUnknown */ pUnk);
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern int /* ULONG */ Release(IntPtr /* IUnknown */ pUnk);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void GetNativeVariantForObject(Object obj, /* VARIANT * */ IntPtr pDstNativeVariant);
+
+        public static void GetNativeVariantForObject<T>(T obj, IntPtr pDstNativeVariant)
+        {
+            GetNativeVariantForObject((object)obj, pDstNativeVariant);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern Object GetObjectForNativeVariant(/* VARIANT * */ IntPtr pSrcNativeVariant);
+
+        public static T GetObjectForNativeVariant<T>(IntPtr pSrcNativeVariant)
+        {
+            return (T)GetObjectForNativeVariant(pSrcNativeVariant);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern Object[] GetObjectsForNativeVariants(/* VARIANT * */ IntPtr aSrcNativeVariant, int cVars);
+
+        public static T[] GetObjectsForNativeVariants<T>(IntPtr aSrcNativeVariant, int cVars)
+        {
+            object[] objects = GetObjectsForNativeVariants(aSrcNativeVariant, cVars);
+            T[] result = null;
+
+            if (objects != null)
+            {
+                result = new T[objects.Length];
+                Array.Copy(objects, result, objects.Length);
+            }
+
+            return result;
+        }
+
+        /// <summary>
+        /// <para>Returns the first valid COM slot that GetMethodInfoForSlot will work on
+        /// This will be 3 for IUnknown based interfaces and 7 for IDispatch based interfaces. </para>
+        /// </summary>
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern int GetStartComSlot(Type t);
+
+#endif // FEATURE_COMINTEROP
+
+        //====================================================================
+        // This method generates a GUID for the specified type. If the type
+        // has a GUID in the metadata then it is returned otherwise a stable
+        // guid GUID is generated based on the fully qualified name of the 
+        // type.
+        //====================================================================
+        public static Guid GenerateGuidForType(Type type)
+        {
+            return type.GUID;
+        }
+
+        //====================================================================
+        // This method generates a PROGID for the specified type. If the type
+        // has a PROGID in the metadata then it is returned otherwise a stable
+        // PROGID is generated based on the fully qualified name of the 
+        // type.
+        //====================================================================
+        public static String GenerateProgIdForType(Type type)
+        {
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+            if (type.IsImport)
+                throw new ArgumentException(SR.Argument_TypeMustNotBeComImport, nameof(type));
+            if (type.IsGenericType)
+                throw new ArgumentException(SR.Argument_NeedNonGenericType, nameof(type));
+
+            IList<CustomAttributeData> cas = CustomAttributeData.GetCustomAttributes(type);
+            for (int i = 0; i < cas.Count; i++)
+            {
+                if (cas[i].Constructor.DeclaringType == typeof(ProgIdAttribute))
+                {
+                    // Retrieve the PROGID string from the ProgIdAttribute.
+                    IList<CustomAttributeTypedArgument> caConstructorArgs = cas[i].ConstructorArguments;
+                    Debug.Assert(caConstructorArgs.Count == 1, "caConstructorArgs.Count == 1");
+
+                    CustomAttributeTypedArgument progIdConstructorArg = caConstructorArgs[0];
+                    Debug.Assert(progIdConstructorArg.ArgumentType == typeof(String), "progIdConstructorArg.ArgumentType == typeof(String)");
+
+                    String strProgId = (String)progIdConstructorArg.Value;
+
+                    if (strProgId == null)
+                        strProgId = String.Empty;
+
+                    return strProgId;
+                }
+            }
+
+            // If there is no prog ID attribute then use the full name of the type as the prog id.
+            return type.FullName;
+        }
+
+#if FEATURE_COMINTEROP
+        //====================================================================
+        // This method binds to the specified moniker.
+        //====================================================================
+        public static Object BindToMoniker(String monikerName)
+        {
+            Object obj = null;
+            IBindCtx bindctx = null;
+            CreateBindCtx(0, out bindctx);
+
+            UInt32 cbEaten;
+            IMoniker pmoniker = null;
+            MkParseDisplayName(bindctx, monikerName, out cbEaten, out pmoniker);
+
+            BindMoniker(pmoniker, 0, ref IID_IUnknown, out obj);
+            return obj;
+        }
+
+        [DllImport(Interop.Libraries.Ole32, PreserveSig = false)]
+        private static extern void CreateBindCtx(UInt32 reserved, out IBindCtx ppbc);
+
+        [DllImport(Interop.Libraries.Ole32, PreserveSig = false)]
+        private static extern void MkParseDisplayName(IBindCtx pbc, [MarshalAs(UnmanagedType.LPWStr)] String szUserName, out UInt32 pchEaten, out IMoniker ppmk);
+
+        [DllImport(Interop.Libraries.Ole32, PreserveSig = false)]
+        private static extern void BindMoniker(IMoniker pmk, UInt32 grfOpt, ref Guid iidResult, [MarshalAs(UnmanagedType.Interface)] out Object ppvResult);
+
+        //========================================================================
+        // Private method called from EE upon use of license/ICF2 marshaling.
+        //========================================================================
+        private static IntPtr LoadLicenseManager()
+        {
+            Type t = Type.GetType("System.ComponentModel.LicenseManager, System", throwOnError: true);
+            return t.TypeHandle.Value;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void ChangeWrapperHandleStrength(Object otp, bool fIsWeak);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void InitializeWrapperForWinRT(object o, ref IntPtr pUnk);
+
+#if FEATURE_COMINTEROP_WINRT_MANAGED_ACTIVATION
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void InitializeManagedWinRTFactoryObject(object o, RuntimeType runtimeClassType);
+#endif
+
+        //========================================================================
+        // Create activation factory and wraps it with a unique RCW
+        //========================================================================
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern object GetNativeActivationFactory(Type type);
+
+#endif // FEATURE_COMINTEROP
+
+        public static Delegate GetDelegateForFunctionPointer(IntPtr ptr, Type t)
+        {
+            // Validate the parameters
+            if (ptr == IntPtr.Zero)
+                throw new ArgumentNullException(nameof(ptr));
+
+            if (t == null)
+                throw new ArgumentNullException(nameof(t));
+
+            if ((t as RuntimeType) == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType, nameof(t));
+
+            if (t.IsGenericType)
+                throw new ArgumentException(SR.Argument_NeedNonGenericType, nameof(t));
+
+            Type c = t.BaseType;
+            if (c == null || (c != typeof(Delegate) && c != typeof(MulticastDelegate)))
+                throw new ArgumentException(SR.Arg_MustBeDelegate, nameof(t));
+
+            return GetDelegateForFunctionPointerInternal(ptr, t);
+        }
+
+        public static TDelegate GetDelegateForFunctionPointer<TDelegate>(IntPtr ptr)
+        {
+            return (TDelegate)(object)GetDelegateForFunctionPointer(ptr, typeof(TDelegate));
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Delegate GetDelegateForFunctionPointerInternal(IntPtr ptr, Type t);
+
+        public static IntPtr GetFunctionPointerForDelegate(Delegate d)
+        {
+            if (d == null)
+                throw new ArgumentNullException(nameof(d));
+
+            return GetFunctionPointerForDelegateInternal(d);
+        }
+
+        public static IntPtr GetFunctionPointerForDelegate<TDelegate>(TDelegate d)
+        {
+            return GetFunctionPointerForDelegate((Delegate)(object)d);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr GetFunctionPointerForDelegateInternal(Delegate d);
+
+        public static IntPtr SecureStringToBSTR(SecureString s)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+
+            return s.MarshalToBSTR();
+        }
+
+        public static IntPtr SecureStringToCoTaskMemAnsi(SecureString s)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+
+            return s.MarshalToString(globalAlloc: false, unicode: false);
+        }
+
+        public static IntPtr SecureStringToCoTaskMemUnicode(SecureString s)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+
+            return s.MarshalToString(globalAlloc: false, unicode: true);
+        }
+        
+        public static void ZeroFreeBSTR(IntPtr s)
+        {
+            RuntimeImports.RhZeroMemory(s, (UIntPtr)(Win32Native.SysStringLen(s) * 2));
+            FreeBSTR(s);
+        }
+
+        public static void ZeroFreeCoTaskMemAnsi(IntPtr s)
+        {
+            RuntimeImports.RhZeroMemory(s, (UIntPtr)(Win32Native.lstrlenA(s)));
+            FreeCoTaskMem(s);
+        }
+
+        public static void ZeroFreeCoTaskMemUnicode(IntPtr s)
+        {
+            RuntimeImports.RhZeroMemory(s, (UIntPtr)(Win32Native.lstrlenW(s) * 2));
+            FreeCoTaskMem(s);
+        }
+
+        public static unsafe void ZeroFreeCoTaskMemUTF8(IntPtr s)
+        {
+            RuntimeImports.RhZeroMemory(s, (UIntPtr)System.StubHelpers.StubHelpers.strlen((sbyte*)s));
+            FreeCoTaskMem(s);
+        }
+
+        public static IntPtr SecureStringToGlobalAllocAnsi(SecureString s)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+
+            return s.MarshalToString(globalAlloc: true, unicode: false);
+        }
+
+        public static IntPtr SecureStringToGlobalAllocUnicode(SecureString s)
+        {
+            if (s == null)
+            {
+                throw new ArgumentNullException(nameof(s));
+            }
+
+            return s.MarshalToString(globalAlloc: true, unicode: true); ;
+        }
+
+        public static void ZeroFreeGlobalAllocAnsi(IntPtr s)
+        {
+            RuntimeImports.RhZeroMemory(s, (UIntPtr)(Win32Native.lstrlenA(s)));
+            FreeHGlobal(s);
+        }
+
+        public static void ZeroFreeGlobalAllocUnicode(IntPtr s)
+        {
+            RuntimeImports.RhZeroMemory(s, (UIntPtr)(Win32Native.lstrlenW(s) * 2));
+            FreeHGlobal(s);
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/NativeCallableAttribute.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/NativeCallableAttribute.cs
new file mode 100644
index 0000000000..d0ab0d9460
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/NativeCallableAttribute.cs
@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+** Any method marked with NativeCallableAttribute can be directly called from 
+** native code.The function token can be loaded to a local variable using LDFTN and
+** passed as a callback to native method.
+=============================================================================*/
+
+using System;
+using System.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices
+{
+    [AttributeUsage(AttributeTargets.Method)]
+    public sealed class NativeCallableAttribute : Attribute
+    {
+        public NativeCallableAttribute()
+        {
+        }
+        // Optional. If omitted , compiler will choose one for you.
+        public CallingConvention CallingConvention;
+        // Optional. If omitted, then the method is native callable, but no EAT is emitted.
+        public string EntryPoint;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/NativeMethods.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/NativeMethods.cs
new file mode 100644
index 0000000000..ccc8d2015d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/NativeMethods.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+/*============================================================
+**
+**
+** Purpose: part of ComEventHelpers APIs which allow binding 
+** managed delegates to COM's connection point based events.
+**
+**/
+#if FEATURE_COMINTEROP
+
+namespace System.Runtime.InteropServices
+{
+    internal static class NativeMethods
+    {
+        [
+        ComImport,
+        InterfaceType(ComInterfaceType.InterfaceIsIUnknown),
+        Guid("00020400-0000-0000-C000-000000000046")
+        ]
+        internal interface IDispatch
+        {
+        }
+    }
+}
+
+#endif
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/NonPortable.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/NonPortable.cs
new file mode 100644
index 0000000000..59229ed528
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/NonPortable.cs
@@ -0,0 +1,210 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// Dummy implementations of non-portable interop methods that just throw PlatformNotSupportedException
+
+namespace System.Runtime.InteropServices
+{
+    public  static partial class Marshal
+    {
+        public static int GetHRForException(Exception e)
+        {
+            return (e != null) ? e.HResult : 0;
+        }
+
+        public static int AddRef(System.IntPtr pUnk)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static bool AreComObjectsAvailableForCleanup()
+        { 
+            return false;
+        }
+
+        public static System.IntPtr CreateAggregatedObject(System.IntPtr pOuter, object o)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static Object BindToMoniker(String monikerName)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+        
+        public static void CleanupUnusedObjectsInCurrentContext()
+        {
+           return;
+        }
+
+        public static System.IntPtr CreateAggregatedObject<T>(System.IntPtr pOuter, T o)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static object CreateWrapperOfType(object o, System.Type t)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static TWrapper CreateWrapperOfType<T, TWrapper>(T o)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static void ChangeWrapperHandleStrength(Object otp, bool fIsWeak)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }           
+
+        public static int FinalReleaseComObject(object o)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static System.IntPtr GetComInterfaceForObject(object o, System.Type T)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static System.IntPtr GetComInterfaceForObject(object o, System.Type T, System.Runtime.InteropServices.CustomQueryInterfaceMode mode)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static System.IntPtr GetComInterfaceForObject<T, TInterface>(T o)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static System.IntPtr GetHINSTANCE(System.Reflection.Module m)
+        {
+            if (m == null)
+            {
+                throw new ArgumentNullException(nameof(m));
+            }
+            return (System.IntPtr) (-1);
+        }           
+
+        public static System.IntPtr GetIUnknownForObject(object o)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static void GetNativeVariantForObject(object obj, System.IntPtr pDstNativeVariant)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static void GetNativeVariantForObject<T>(T obj, System.IntPtr pDstNativeVariant)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static Object GetTypedObjectForIUnknown(System.IntPtr pUnk, System.Type t)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static object GetObjectForIUnknown(System.IntPtr pUnk)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static object GetObjectForNativeVariant(System.IntPtr pSrcNativeVariant)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static T GetObjectForNativeVariant<T>(System.IntPtr pSrcNativeVariant)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static object[] GetObjectsForNativeVariants(System.IntPtr aSrcNativeVariant, int cVars)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static T[] GetObjectsForNativeVariants<T>(System.IntPtr aSrcNativeVariant, int cVars)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static int GetStartComSlot(System.Type t)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static System.Type GetTypeFromCLSID(System.Guid clsid) 
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static string GetTypeInfoName(System.Runtime.InteropServices.ComTypes.ITypeInfo typeInfo)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static object GetUniqueObjectForIUnknown(System.IntPtr unknown)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static bool IsComObject(object o)
+        {
+            if (o == null)
+            {
+                throw new ArgumentNullException(nameof(o));
+            }
+
+            return false;
+        }
+
+        public static int QueryInterface(System.IntPtr pUnk, ref System.Guid iid, out System.IntPtr ppv)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static int Release(System.IntPtr pUnk)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static int ReleaseComObject(object o)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+    }
+
+    public class DispatchWrapper
+    {
+        public DispatchWrapper(object obj)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public object WrappedObject
+        {
+            get
+            {
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+            }
+        }
+    }
+
+    public static class ComEventsHelper
+    {
+        public static void Combine(object rcw, System.Guid iid, int dispid, System.Delegate d)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+
+        public static System.Delegate Remove(object rcw, System.Guid iid, int dispid, System.Delegate d)
+        {
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_ComInterop);
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/PInvokeMap.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/PInvokeMap.cs
new file mode 100644
index 0000000000..33f1b5f09c
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/PInvokeMap.cs
@@ -0,0 +1,49 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+//
+// PInvokeMap is an enum that defines the PInvoke attributes.  These
+//  values are defined in CorHdr.h.
+//
+//
+
+using System.Runtime.InteropServices;
+using System;
+
+namespace System.Runtime.InteropServices
+{
+    // This Enum matchs the CorPinvokeMap defined in CorHdr.h
+    internal enum PInvokeMap
+    {
+        NoMangle = 0x0001,   // Pinvoke is to use the member name as specified.
+        CharSetMask = 0x0006,   // Heuristic used in data type & name mapping.
+        CharSetNotSpec = 0x0000,
+        CharSetAnsi = 0x0002,
+        CharSetUnicode = 0x0004,
+        CharSetAuto = 0x0006,
+
+        PinvokeOLE = 0x0020,   // Heuristic: pinvoke will return hresult, with return value becoming the retval param. Not relevant for fields. 
+        SupportsLastError = 0x0040,   // Information about target function. Not relevant for fields.
+
+        BestFitMask = 0x0030,
+        BestFitEnabled = 0x0010,
+        BestFitDisabled = 0x0020,
+        BestFitUseAsm = 0x0030,
+
+        ThrowOnUnmappableCharMask = 0x3000,
+        ThrowOnUnmappableCharEnabled = 0x1000,
+        ThrowOnUnmappableCharDisabled = 0x2000,
+        ThrowOnUnmappableCharUseAsm = 0x3000,
+
+        // None of the calling convention flags is relevant for fields.
+        CallConvMask = 0x0700,
+        CallConvWinapi = 0x0100,   // Pinvoke will use native callconv appropriate to target windows platform.
+        CallConvCdecl = 0x0200,
+        CallConvStdcall = 0x0300,
+        CallConvThiscall = 0x0400,   // In M9, pinvoke will raise exception.
+        CallConvFastcall = 0x0500,
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/PInvokeMarshal.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/PInvokeMarshal.cs
new file mode 100644
index 0000000000..9eb60bdce7
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/PInvokeMarshal.cs
@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32;
+
+namespace System.Runtime.InteropServices
+{
+    internal static class PInvokeMarshal
+    {
+        public static IntPtr AllocBSTR(int length)
+        {
+            IntPtr bstr = Win32Native.SysAllocStringLen(null, length);
+            if (bstr == IntPtr.Zero)
+                throw new OutOfMemoryException();
+            return bstr;
+        }
+
+        public static void FreeBSTR(IntPtr ptr)
+        {
+            Win32Native.SysFreeString(ptr);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/RuntimeEnvironment.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/RuntimeEnvironment.cs
new file mode 100644
index 0000000000..d421636c4b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/RuntimeEnvironment.cs
@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Runtime information
+**          
+**
+=============================================================================*/
+
+using System;
+using System.Text;
+using System.IO;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Security;
+using System.Reflection;
+using Microsoft.Win32;
+using System.Runtime.Versioning;
+using StackCrawlMark = System.Threading.StackCrawlMark;
+
+namespace System.Runtime.InteropServices
+{
+    internal static class RuntimeEnvironment
+    {
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern String GetModuleFileName();
+
+        public static String GetSystemVersion()
+        {
+            return Assembly.GetExecutingAssembly().ImageRuntimeVersion;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/SEHException.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/SEHException.cs
new file mode 100644
index 0000000000..039059e7e8
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/SEHException.cs
@@ -0,0 +1,60 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Exception class for all Structured Exception Handling code.
+**
+**
+=============================================================================*/
+
+using System.Runtime.InteropServices;
+using System;
+using System.Runtime.Serialization;
+
+namespace System.Runtime.InteropServices
+{
+    // Exception for Structured Exception Handler exceptions.
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class SEHException : ExternalException
+    {
+        public SEHException()
+            : base()
+        {
+            HResult = HResults.E_FAIL;
+        }
+
+        public SEHException(String message)
+            : base(message)
+        {
+            HResult = HResults.E_FAIL;
+        }
+
+        public SEHException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.E_FAIL;
+        }
+
+        protected SEHException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+
+        // Exceptions can be resumable, meaning a filtered exception 
+        // handler can correct the problem that caused the exception,
+        // and the code will continue from the point that threw the 
+        // exception.
+        // 
+        // Resumable exceptions aren't implemented in this version,
+        // but this method exists and always returns false.
+        // 
+        public virtual bool CanResume()
+        {
+            return false;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/SafeArrayRankMismatchException.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/SafeArrayRankMismatchException.cs
new file mode 100644
index 0000000000..7f6a24f593
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/SafeArrayRankMismatchException.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+** Purpose: This exception is thrown when the runtime rank of a safe array
+**            is different than the array rank specified in the metadata.
+**
+=============================================================================*/
+
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System.Runtime.InteropServices
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class SafeArrayRankMismatchException : SystemException
+    {
+        public SafeArrayRankMismatchException()
+            : base(SR.Arg_SafeArrayRankMismatchException)
+        {
+            HResult = HResults.COR_E_SAFEARRAYRANKMISMATCH;
+        }
+
+        public SafeArrayRankMismatchException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_SAFEARRAYRANKMISMATCH;
+        }
+
+        public SafeArrayRankMismatchException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_SAFEARRAYRANKMISMATCH;
+        }
+
+        protected SafeArrayRankMismatchException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/SafeArrayTypeMismatchException.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/SafeArrayTypeMismatchException.cs
new file mode 100644
index 0000000000..e155dcf64d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/SafeArrayTypeMismatchException.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+** Purpose: This exception is thrown when the runtime type of an array
+**            is different than the safe array sub type specified in the 
+**            metadata.
+**
+=============================================================================*/
+
+
+using System;
+using System.Runtime.Serialization;
+
+namespace System.Runtime.InteropServices
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class SafeArrayTypeMismatchException : SystemException
+    {
+        public SafeArrayTypeMismatchException()
+            : base(SR.Arg_SafeArrayTypeMismatchException)
+        {
+            HResult = HResults.COR_E_SAFEARRAYTYPEMISMATCH;
+        }
+
+        public SafeArrayTypeMismatchException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_SAFEARRAYTYPEMISMATCH;
+        }
+
+        public SafeArrayTypeMismatchException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_SAFEARRAYTYPEMISMATCH;
+        }
+
+        protected SafeArrayTypeMismatchException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/SafeHandle.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/SafeHandle.cs
new file mode 100644
index 0000000000..a8bfbdcaea
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/SafeHandle.cs
@@ -0,0 +1,278 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** A specially designed handle wrapper to ensure we never leak
+** an OS handle.  The runtime treats this class specially during
+** P/Invoke marshaling and finalization.  Users should write
+** subclasses of SafeHandle for each distinct handle type.
+**
+** 
+===========================================================*/
+
+namespace System.Runtime.InteropServices
+{
+    using System;
+    using System.Diagnostics;
+    using System.Reflection;
+    using System.Threading;
+    using System.Runtime;
+    using System.Runtime.CompilerServices;
+    using System.IO;
+    using System.Runtime.ConstrainedExecution;
+    using System.Runtime.Versioning;
+
+    /*
+      Problems addressed by the SafeHandle class:
+      1) Critical finalization - ensure we never leak OS resources in SQL.  Done
+         without running truly arbitrary & unbounded amounts of managed code.
+      2) Reduced graph promotion - during finalization, keep object graph small
+      3) GC.KeepAlive behavior - P/Invoke vs. finalizer thread race conditions (HandleRef)
+      4) Elimination of security race conditions w/ explicit calls to Close (HandleProtector)
+      5) Enforcement of the above via the type system - Don't use IntPtr anymore.
+      6) Allows the handle lifetime to be controlled externally via a boolean.
+
+      Subclasses of SafeHandle will implement the ReleaseHandle abstract method
+      used to execute any code required to free the handle. This method will be
+      prepared as a constrained execution region at instance construction time
+      (along with all the methods in its statically determinable call graph). This
+      implies that we won't get any inconvenient jit allocation errors or rude
+      thread abort interrupts while releasing the handle but the user must still
+      write careful code to avoid injecting fault paths of their own (see the CER
+      spec for more details). In particular, any sub-methods you call should be
+      decorated with a reliability contract of the appropriate level. In most cases
+      this should be:
+        ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)
+
+      The GC will run ReleaseHandle methods after any normal finalizers have been
+      run for objects that were collected at the same time. This ensures classes
+      like FileStream can run a normal finalizer to flush out existing buffered
+      data. This is key - it means adding this class to a class like FileStream does
+      not alter our current semantics w.r.t. finalization today.
+
+      Subclasses must also implement the IsInvalid property so that the
+      infrastructure can tell when critical finalization is actually required.
+      Again, this method is prepared ahead of time. It's envisioned that direct
+      subclasses of SafeHandle will provide an IsInvalid implementation that suits
+      the general type of handle they support (null is invalid, -1 is invalid etc.)
+      and then these classes will be further derived for specific safe handle types.
+
+      Most classes using SafeHandle should not provide a finalizer.  If they do
+      need to do so (ie, for flushing out file buffers, needing to write some data
+      back into memory, etc), then they can provide a finalizer that will be 
+      guaranteed to run before the SafeHandle's critical finalizer.  
+
+      Note that SafeHandle's ReleaseHandle is called from a constrained execution 
+      region, and is eagerly prepared before we create your class.  This means you
+      should only call methods with an appropriate reliability contract from your
+      ReleaseHandle method.
+
+      Subclasses are expected to be written as follows (note that
+      SuppressUnmanagedCodeSecurity should always be used on any P/Invoke methods
+      invoked as part of ReleaseHandle, in order to switch the security check from
+      runtime to jit time and thus remove a possible failure path from the
+      invocation of the method):
+
+      internal sealed MySafeHandleSubclass : SafeHandle {
+          // Called by P/Invoke when returning SafeHandles
+          private MySafeHandleSubclass() : base(IntPtr.Zero, true)
+          {
+          }
+
+          // If & only if you need to support user-supplied handles
+          internal MySafeHandleSubclass(IntPtr preexistingHandle, bool ownsHandle) : base(IntPtr.Zero, ownsHandle)
+          {
+              SetHandle(preexistingHandle);
+          }
+
+          // Do not provide a finalizer - SafeHandle's critical finalizer will
+          // call ReleaseHandle for you.
+
+          public override bool IsInvalid {
+              get { return handle == IntPtr.Zero; }
+          }
+
+          override protected bool ReleaseHandle()
+          {
+              return MyNativeMethods.CloseHandle(handle);
+          }
+      }
+
+      Then elsewhere to create one of these SafeHandles, define a method
+      with the following type of signature (CreateFile follows this model).
+      Note that when returning a SafeHandle like this, P/Invoke will call your
+      class's default constructor.  Also, you probably want to define CloseHandle
+      somewhere, and remember to apply a reliability contract to it.
+
+      internal static class MyNativeMethods {
+          [DllImport("kernel32")]
+          private static extern MySafeHandleSubclass CreateHandle(int someState);
+
+          [DllImport("kernel32", SetLastError=true), ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
+          private static extern bool CloseHandle(IntPtr handle);
+      }
+
+      Drawbacks with this implementation:
+      1) Requires some magic to run the critical finalizer.
+      2) Requires more memory than just an IntPtr.
+      3) If you use DangerousAddRef and forget to call DangerousRelease, you can leak a SafeHandle.  Use CER's & don't do that.
+     */
+
+
+    // This class should not be serializable - it's a handle.  We require unmanaged
+    // code permission to subclass SafeHandle to prevent people from writing a 
+    // subclass and suddenly being able to run arbitrary native code with the
+    // same signature as CloseHandle.  This is technically a little redundant, but
+    // we'll do this to ensure we've cut off all attack vectors.  Similarly, all
+    // methods have a link demand to ensure untrusted code cannot directly edit
+    // or alter a handle.
+    public abstract class SafeHandle : CriticalFinalizerObject, IDisposable
+    {
+        // ! Do not add or rearrange fields as the EE depends on this layout.
+        //------------------------------------------------------------------
+        protected IntPtr handle;   // this must be protected so derived classes can use out params. 
+        private int _state;   // Combined ref count and closed/disposed flags (so we can atomically modify them).
+        private bool _ownsHandle;  // Whether we can release this handle.
+#pragma warning disable 414
+        private bool _fullyInitialized;  // Whether constructor completed.
+#pragma warning restore 414
+
+        // Creates a SafeHandle class.  Users must then set the Handle property.
+        // To prevent the SafeHandle from being freed, write a subclass that
+        // doesn't define a finalizer.
+        protected SafeHandle(IntPtr invalidHandleValue, bool ownsHandle)
+        {
+            handle = invalidHandleValue;
+            _state = 4; // Ref count 1 and not closed or disposed.
+            _ownsHandle = ownsHandle;
+
+            if (!ownsHandle)
+                GC.SuppressFinalize(this);
+
+            // Set this last to prevent SafeHandle's finalizer from freeing an
+            // invalid handle.  This means we don't have to worry about 
+            // ThreadAbortExceptions interrupting this constructor or the managed
+            // constructors on subclasses that call this constructor.
+            _fullyInitialized = true;
+        }
+
+        // Migrating InheritanceDemands requires this default ctor, so we can mark it critical
+        protected SafeHandle()
+        {
+            Debug.Fail("SafeHandle's protected default ctor should never be used!");
+            throw new NotImplementedException();
+        }
+
+        ~SafeHandle()
+        {
+            Dispose(false);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern void InternalFinalize();
+
+        protected void SetHandle(IntPtr handle)
+        {
+            this.handle = handle;
+        }
+
+        // This method is necessary for getting an IntPtr out of a SafeHandle.
+        // Used to tell whether a call to create the handle succeeded by comparing
+        // the handle against a known invalid value, and for backwards 
+        // compatibility to support the handle properties returning IntPtrs on
+        // many of our Framework classes.
+        // Note that this method is dangerous for two reasons:
+        //  1) If the handle has been marked invalid with SetHandleasInvalid,
+        //     DangerousGetHandle will still return the original handle value.
+        //  2) The handle returned may be recycled at any point. At best this means
+        //     the handle might stop working suddenly. At worst, if the handle or
+        //     the resource the handle represents is exposed to untrusted code in
+        //     any way, this can lead to a handle recycling security attack (i.e. an
+        //     untrusted caller can query data on the handle you've just returned
+        //     and get back information for an entirely unrelated resource).
+        public IntPtr DangerousGetHandle()
+        {
+            return handle;
+        }
+
+        public bool IsClosed
+        {
+            get { return (_state & 1) == 1; }
+        }
+
+        public abstract bool IsInvalid
+        {
+            get;
+        }
+
+        public void Close()
+        {
+            Dispose(true);
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+        }
+
+        protected virtual void Dispose(bool disposing)
+        {
+            if (disposing)
+                InternalDispose();
+            else
+                InternalFinalize();
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern void InternalDispose();
+
+        // This should only be called for cases when you know for a fact that
+        // your handle is invalid and you want to record that information.
+        // An example is calling a syscall and getting back ERROR_INVALID_HANDLE.
+        // This method will normally leak handles!
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern void SetHandleAsInvalid();
+
+        // Implement this abstract method in your derived class to specify how to
+        // free the handle. Be careful not write any code that's subject to faults
+        // in this method (the runtime will prepare the infrastructure for you so
+        // that no jit allocations etc. will occur, but don't allocate memory unless
+        // you can deal with the failure and still free the handle).
+        // The boolean returned should be true for success and false if the runtime
+        // should fire a SafeHandleCriticalFailure MDA (CustomerDebugProbe) if that
+        // MDA is enabled.
+        protected abstract bool ReleaseHandle();
+
+        // Add a reason why this handle should not be relinquished (i.e. have
+        // ReleaseHandle called on it). This method has dangerous in the name since
+        // it must always be used carefully (e.g. called within a CER) to avoid
+        // leakage of the handle. It returns a boolean indicating whether the
+        // increment was actually performed to make it easy for program logic to
+        // back out in failure cases (i.e. is a call to DangerousRelease needed).
+        // It is passed back via a ref parameter rather than as a direct return so
+        // that callers need not worry about the atomicity of calling the routine
+        // and assigning the return value to a variable (the variable should be
+        // explicitly set to false prior to the call). The only failure cases are
+        // when the method is interrupted prior to processing by a thread abort or
+        // when the handle has already been (or is in the process of being)
+        // released.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern void DangerousAddRef(ref bool success);
+
+        // Partner to DangerousAddRef. This should always be successful when used in
+        // a correct manner (i.e. matching a successful DangerousAddRef and called
+        // from a region such as a CER where a thread abort cannot interrupt
+        // processing). In the same way that unbalanced DangerousAddRef calls can
+        // cause resource leakage, unbalanced DangerousRelease calls may cause
+        // invalid handle states to become visible to other threads. This
+        // constitutes a potential security hole (via handle recycling) as well as a
+        // correctness problem -- so don't ever expose Dangerous* calls out to
+        // untrusted code.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern void DangerousRelease();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/UnknownWrapper.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/UnknownWrapper.cs
new file mode 100644
index 0000000000..de06cbf1a8
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/UnknownWrapper.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Wrapper that is converted to a variant with VT_UNKNOWN.
+**
+**
+=============================================================================*/
+
+
+using System;
+
+namespace System.Runtime.InteropServices
+{
+    public sealed class UnknownWrapper
+    {
+        public UnknownWrapper(Object obj)
+        {
+            m_WrappedObject = obj;
+        }
+
+        public Object WrappedObject
+        {
+            get
+            {
+                return m_WrappedObject;
+            }
+        }
+
+        private Object m_WrappedObject;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/VariantWrapper.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/VariantWrapper.cs
new file mode 100644
index 0000000000..455f0759fe
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/VariantWrapper.cs
@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Wrapper that is converted to a variant with VT_BYREF | VT_VARIANT.
+**
+**
+=============================================================================*/
+
+
+using System;
+
+namespace System.Runtime.InteropServices
+{
+    public sealed class VariantWrapper
+    {
+        public VariantWrapper(Object obj)
+        {
+            m_WrappedObject = obj;
+        }
+
+        public Object WrappedObject
+        {
+            get
+            {
+                return m_WrappedObject;
+            }
+        }
+
+        private Object m_WrappedObject;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/Attributes.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/Attributes.cs
new file mode 100644
index 0000000000..d11b436b3c
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/Attributes.cs
@@ -0,0 +1,122 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // DefaultInterfaceAttribute marks a WinRT class (or interface group) that has its default interface specified.
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface, AllowMultiple = false, Inherited = false)]
+    public sealed class DefaultInterfaceAttribute : Attribute
+    {
+        private Type m_defaultInterface;
+
+        public DefaultInterfaceAttribute(Type defaultInterface)
+        {
+            m_defaultInterface = defaultInterface;
+        }
+
+        public Type DefaultInterface
+        {
+            get { return m_defaultInterface; }
+        }
+    }
+
+    // WindowsRuntimeImport is a pseudo custom attribute which causes us to emit the tdWindowsRuntime bit
+    // onto types which are decorated with the attribute.  This is needed to mark Windows Runtime types
+    // which are redefined in mscorlib.dll and System.Runtime.WindowsRuntime.dll, as the C# compiler does
+    // not have a built in syntax to mark tdWindowsRuntime.   These two assemblies are special as they
+    // implement the CLR's support for WinRT, so this type is internal as marking tdWindowsRuntime should
+    // generally be done via winmdexp for user code.
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface | AttributeTargets.Enum | AttributeTargets.Struct | AttributeTargets.Delegate, Inherited = false)]
+    // [System.Runtime.CompilerServices.FriendAccessAllowed]
+    internal sealed class WindowsRuntimeImportAttribute : Attribute
+    {
+        internal WindowsRuntimeImportAttribute()
+        { }
+    }
+
+    // This attribute is applied to class interfaces in a generated projection assembly.  It is used by Visual Studio
+    // and other tools to find out what version of a component (eg. Windows) a WinRT class began to implement
+    // a particular interfaces.
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface, Inherited = false, AllowMultiple = true)]
+    public sealed class InterfaceImplementedInVersionAttribute : Attribute
+    {
+        public InterfaceImplementedInVersionAttribute(Type interfaceType, byte majorVersion, byte minorVersion, byte buildVersion, byte revisionVersion)
+        {
+            m_interfaceType = interfaceType;
+            m_majorVersion = majorVersion;
+            m_minorVersion = minorVersion;
+            m_buildVersion = buildVersion;
+            m_revisionVersion = revisionVersion;
+        }
+
+        public Type InterfaceType
+        {
+            get { return m_interfaceType; }
+        }
+
+        public byte MajorVersion
+        {
+            get { return m_majorVersion; }
+        }
+
+        public byte MinorVersion
+        {
+            get { return m_minorVersion; }
+        }
+
+        public byte BuildVersion
+        {
+            get { return m_buildVersion; }
+        }
+
+        public byte RevisionVersion
+        {
+            get { return m_revisionVersion; }
+        }
+
+        private Type m_interfaceType;
+        private byte m_majorVersion;
+        private byte m_minorVersion;
+        private byte m_buildVersion;
+        private byte m_revisionVersion;
+    }
+
+    // Applies to read-only array parameters
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = false, AllowMultiple = false)]
+    public sealed class ReadOnlyArrayAttribute : Attribute
+    {
+        public ReadOnlyArrayAttribute() { }
+    }
+
+    // Applies to write-only array parameters
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = false, AllowMultiple = false)]
+    public sealed class WriteOnlyArrayAttribute : Attribute
+    {
+        public WriteOnlyArrayAttribute() { }
+    }
+
+
+
+    // This attribute is applied on the return value to specify the name of the return value. 
+    // In WindowsRuntime all parameters including return value need to have unique names.
+    // This is essential in JS as one of the ways to get at the results of a method in JavaScript is via a Dictionary object keyed by parameter name.
+    [AttributeUsage(AttributeTargets.ReturnValue | AttributeTargets.Delegate, AllowMultiple = false, Inherited = false)]
+    public sealed class ReturnValueNameAttribute : Attribute
+    {
+        private string m_Name;
+        public ReturnValueNameAttribute(string name)
+        {
+            m_Name = name;
+        }
+
+        public string Name
+        {
+            get { return m_Name; }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/BindableVectorToCollectionAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/BindableVectorToCollectionAdapter.cs
new file mode 100644
index 0000000000..e34e4f62fa
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/BindableVectorToCollectionAdapter.cs
@@ -0,0 +1,101 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Runtime;
+using System.Security;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // This is a set of stub methods implementing the support for the ICollection interface on WinRT
+    // objects that support IBindableVector. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not BindableVectorToCollectionAdapter objects. Rather, they are
+    // of type IBindableVector. No actual BindableVectorToCollectionAdapter object is ever instantiated.
+    // Thus, you will see a lot of expressions that cast "this" to "IBindableVector".
+    internal sealed class BindableVectorToCollectionAdapter
+    {
+        private BindableVectorToCollectionAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // int Count { get }
+        internal int Count()
+        {
+            IBindableVector _this = Unsafe.As<IBindableVector>(this);
+            uint size = _this.Size;
+            if (((uint)Int32.MaxValue) < size)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_CollectionBackingListTooLarge);
+            }
+
+            return (int)size;
+        }
+
+        // bool IsSynchronized { get }
+        internal bool IsSynchronized()
+        {
+            return false;
+        }
+
+        // object SyncRoot { get }
+        internal object SyncRoot()
+        {
+            return this;
+        }
+
+        // void CopyTo(Array array, int index)
+        internal void CopyTo(Array array, int arrayIndex)
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array));
+
+            // ICollection expects the destination array to be single-dimensional.
+            if (array.Rank != 1)
+                throw new ArgumentException(SR.Arg_RankMultiDimNotSupported);
+
+            int destLB = array.GetLowerBound(0);
+
+            int srcLen = Count();
+            int destLen = array.GetLength(0);
+
+            if (arrayIndex < destLB)
+                throw new ArgumentOutOfRangeException(nameof(arrayIndex));
+
+            // Does the dimension in question have sufficient space to copy the expected number of entries?
+            // We perform this check before valid index check to ensure the exception message is in sync with
+            // the following snippet that uses regular framework code:
+            //
+            // ArrayList list = new ArrayList();
+            // list.Add(1);
+            // Array items = Array.CreateInstance(typeof(object), new int[] { 1 }, new int[] { -1 });
+            // list.CopyTo(items, 0);
+
+            if (srcLen > (destLen - (arrayIndex - destLB)))
+                throw new ArgumentException(SR.Argument_InsufficientSpaceToCopyCollection);
+
+            if (arrayIndex - destLB > destLen)
+                throw new ArgumentException(SR.Argument_IndexOutOfArrayBounds);
+
+            // We need to verify the index as we;
+            IBindableVector _this = Unsafe.As<IBindableVector>(this);
+
+            for (uint i = 0; i < srcLen; i++)
+            {
+                array.SetValue(_this.GetAt(i), i + arrayIndex);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/BindableVectorToListAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/BindableVectorToListAdapter.cs
new file mode 100644
index 0000000000..eb9fbc4f1c
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/BindableVectorToListAdapter.cs
@@ -0,0 +1,229 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Runtime;
+using System.Security;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // This is a set of stub methods implementing the support for the IList interface on WinRT
+    // objects that support IBindableVector. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not BindableVectorToListAdapter objects. Rather, they are
+    // of type IBindableVector. No actual BindableVectorToListAdapter object is ever instantiated.
+    // Thus, you will see a lot of expressions that cast "this" to "IBindableVector".
+    internal sealed class BindableVectorToListAdapter
+    {
+        private BindableVectorToListAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // object this[int index] { get }
+        internal object Indexer_Get(int index)
+        {
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index));
+
+            IBindableVector _this = Unsafe.As<IBindableVector>(this);
+            return GetAt(_this, (uint)index);
+        }
+
+        // object this[int index] { set }
+        internal void Indexer_Set(int index, object value)
+        {
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index));
+
+            IBindableVector _this = Unsafe.As<IBindableVector>(this);
+            SetAt(_this, (uint)index, value);
+        }
+
+        // int Add(object value)
+        internal int Add(object value)
+        {
+            IBindableVector _this = Unsafe.As<IBindableVector>(this);
+            _this.Append(value);
+
+            uint size = _this.Size;
+            if (((uint)Int32.MaxValue) < size)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_CollectionBackingListTooLarge);
+            }
+
+            return (int)(size - 1);
+        }
+
+        // bool Contains(object item)
+        internal bool Contains(object item)
+        {
+            IBindableVector _this = Unsafe.As<IBindableVector>(this);
+
+            uint index;
+            return _this.IndexOf(item, out index);
+        }
+
+        // void Clear()
+        internal void Clear()
+        {
+            IBindableVector _this = Unsafe.As<IBindableVector>(this);
+            _this.Clear();
+        }
+
+        // bool IsFixedSize { get }
+        internal bool IsFixedSize()
+        {
+            return false;
+        }
+
+        // bool IsReadOnly { get }
+        internal bool IsReadOnly()
+        {
+            return false;
+        }
+
+        // int IndexOf(object item)
+        internal int IndexOf(object item)
+        {
+            IBindableVector _this = Unsafe.As<IBindableVector>(this);
+
+            uint index;
+            bool exists = _this.IndexOf(item, out index);
+
+            if (!exists)
+                return -1;
+
+            if (((uint)Int32.MaxValue) < index)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_CollectionBackingListTooLarge);
+            }
+
+            return (int)index;
+        }
+
+        // void Insert(int index, object item)
+        internal void Insert(int index, object item)
+        {
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index));
+
+            IBindableVector _this = Unsafe.As<IBindableVector>(this);
+            InsertAtHelper(_this, (uint)index, item);
+        }
+
+        // bool Remove(object item)
+        internal void Remove(object item)
+        {
+            IBindableVector _this = Unsafe.As<IBindableVector>(this);
+
+            uint index;
+            bool exists = _this.IndexOf(item, out index);
+
+            if (exists)
+            {
+                if (((uint)Int32.MaxValue) < index)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_CollectionBackingListTooLarge);
+                }
+
+                RemoveAtHelper(_this, index);
+            }
+        }
+
+        // void RemoveAt(int index)
+        internal void RemoveAt(int index)
+        {
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index));
+
+            IBindableVector _this = Unsafe.As<IBindableVector>(this);
+            RemoveAtHelper(_this, (uint)index);
+        }
+
+        // Helpers:
+
+        private static object GetAt(IBindableVector _this, uint index)
+        {
+            try
+            {
+                return _this.GetAt(index);
+
+                // We delegate bounds checking to the underlying collection and if it detected a fault,
+                // we translate it to the right exception:
+            }
+            catch (Exception ex)
+            {
+                if (HResults.E_BOUNDS == ex._HResult)
+                    throw new ArgumentOutOfRangeException(nameof(index));
+
+                throw;
+            }
+        }
+
+        private static void SetAt(IBindableVector _this, uint index, object value)
+        {
+            try
+            {
+                _this.SetAt(index, value);
+
+                // We delegate bounds checking to the underlying collection and if it detected a fault,
+                // we translate it to the right exception:
+            }
+            catch (Exception ex)
+            {
+                if (HResults.E_BOUNDS == ex._HResult)
+                    throw new ArgumentOutOfRangeException(nameof(index));
+
+                throw;
+            }
+        }
+
+        private static void InsertAtHelper(IBindableVector _this, uint index, object item)
+        {
+            try
+            {
+                _this.InsertAt(index, item);
+
+                // We delegate bounds checking to the underlying collection and if it detected a fault,
+                // we translate it to the right exception:
+            }
+            catch (Exception ex)
+            {
+                if (HResults.E_BOUNDS == ex._HResult)
+                    throw new ArgumentOutOfRangeException(nameof(index));
+
+                throw;
+            }
+        }
+
+        private static void RemoveAtHelper(IBindableVector _this, uint index)
+        {
+            try
+            {
+                _this.RemoveAt(index);
+
+                // We delegate bounds checking to the underlying collection and if it detected a fault,
+                // we translate it to the right exception:
+            }
+            catch (Exception ex)
+            {
+                if (HResults.E_BOUNDS == ex._HResult)
+                    throw new ArgumentOutOfRangeException(nameof(index));
+
+                throw;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/CLRIKeyValuePairImpl.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/CLRIKeyValuePairImpl.cs
new file mode 100644
index 0000000000..92c78f9ea2
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/CLRIKeyValuePairImpl.cs
@@ -0,0 +1,63 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // Provides access to a System.Collections.Generic.KeyValuePair<K, V> via the IKeyValuePair<K, V> WinRT interface.
+    internal sealed class CLRIKeyValuePairImpl<K, V> : IKeyValuePair<K, V>,
+                                                       IGetProxyTarget
+    {
+        private readonly KeyValuePair<K, V> _pair;
+
+        public CLRIKeyValuePairImpl([In] ref KeyValuePair<K, V> pair)
+        {
+            _pair = pair;
+        }
+
+        // IKeyValuePair<K, V> implementation
+        public K Key
+        {
+            get { return _pair.Key; }
+        }
+
+        public V Value
+        {
+            get { return _pair.Value; }
+        }
+
+        // Called from the VM to wrap a boxed KeyValuePair with a CLRIKeyValuePairImpl.
+        internal static object BoxHelper(object pair)
+        {
+            Debug.Assert(pair != null);
+
+            KeyValuePair<K, V> unboxedPair = (KeyValuePair<K, V>)pair;
+            return new CLRIKeyValuePairImpl<K, V>(ref unboxedPair);
+        }
+
+        // Called from the VM to get a boxed KeyValuePair out of a CLRIKeyValuePairImpl.
+        internal static object UnboxHelper(object wrapper)
+        {
+            Debug.Assert(wrapper != null);
+
+            CLRIKeyValuePairImpl<K, V> reference = (CLRIKeyValuePairImpl<K, V>)wrapper;
+            return reference._pair;
+        }
+
+        public override string ToString()
+        {
+            return _pair.ToString();
+        }
+
+        object IGetProxyTarget.GetTarget()
+        {
+            return _pair;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/CLRIPropertyValueImpl.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/CLRIPropertyValueImpl.cs
new file mode 100644
index 0000000000..2d15e31c26
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/CLRIPropertyValueImpl.cs
@@ -0,0 +1,533 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Security;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    internal class CLRIPropertyValueImpl : IPropertyValue
+    {
+        private PropertyType _type;
+        private Object _data;
+
+        // Numeric scalar types which participate in coersion
+        private static volatile Tuple<Type, PropertyType>[] s_numericScalarTypes;
+
+        internal CLRIPropertyValueImpl(PropertyType type, Object data)
+        {
+            _type = type;
+            _data = data;
+        }
+
+        private static Tuple<Type, PropertyType>[] NumericScalarTypes
+        {
+            get
+            {
+                if (s_numericScalarTypes == null)
+                {
+                    Tuple<Type, PropertyType>[] numericScalarTypes = new Tuple<Type, PropertyType>[] {
+                        new Tuple<Type, PropertyType>(typeof(Byte), PropertyType.UInt8),
+                        new Tuple<Type, PropertyType>(typeof(Int16), PropertyType.Int16),
+                        new Tuple<Type, PropertyType>(typeof(UInt16), PropertyType.UInt16),
+                        new Tuple<Type, PropertyType>(typeof(Int32), PropertyType.Int32),
+                        new Tuple<Type, PropertyType>(typeof(UInt32), PropertyType.UInt32),
+                        new Tuple<Type, PropertyType>(typeof(Int64), PropertyType.Int64),
+                        new Tuple<Type, PropertyType>(typeof(UInt64), PropertyType.UInt64),
+                        new Tuple<Type, PropertyType>(typeof(Single), PropertyType.Single),
+                        new Tuple<Type, PropertyType>(typeof(Double), PropertyType.Double)
+                    };
+
+                    s_numericScalarTypes = numericScalarTypes;
+                }
+
+                return s_numericScalarTypes;
+            }
+        }
+
+        public PropertyType Type
+        {
+            get { return _type; }
+        }
+
+        public bool IsNumericScalar
+        {
+            get
+            {
+                return IsNumericScalarImpl(_type, _data);
+            }
+        }
+
+        public override string ToString()
+        {
+            if (_data != null)
+            {
+                return _data.ToString();
+            }
+            else
+            {
+                return base.ToString();
+            }
+        }
+
+        public Byte GetUInt8()
+        {
+            return CoerceScalarValue<Byte>(PropertyType.UInt8);
+        }
+
+        public Int16 GetInt16()
+        {
+            return CoerceScalarValue<Int16>(PropertyType.Int16);
+        }
+
+        public UInt16 GetUInt16()
+        {
+            return CoerceScalarValue<UInt16>(PropertyType.UInt16);
+        }
+
+        public Int32 GetInt32()
+        {
+            return CoerceScalarValue<Int32>(PropertyType.Int32);
+        }
+
+        public UInt32 GetUInt32()
+        {
+            return CoerceScalarValue<UInt32>(PropertyType.UInt32);
+        }
+
+        public Int64 GetInt64()
+        {
+            return CoerceScalarValue<Int64>(PropertyType.Int64);
+        }
+
+        public UInt64 GetUInt64()
+        {
+            return CoerceScalarValue<UInt64>(PropertyType.UInt64);
+        }
+
+        public Single GetSingle()
+        {
+            return CoerceScalarValue<Single>(PropertyType.Single);
+        }
+
+        public Double GetDouble()
+        {
+            return CoerceScalarValue<Double>(PropertyType.Double);
+        }
+
+        public char GetChar16()
+        {
+            if (this.Type != PropertyType.Char16)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "Char16"), HResults.TYPE_E_TYPEMISMATCH);
+            return (char)_data;
+        }
+
+        public Boolean GetBoolean()
+        {
+            if (this.Type != PropertyType.Boolean)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "Boolean"), HResults.TYPE_E_TYPEMISMATCH);
+            return (bool)_data;
+        }
+
+        public String GetString()
+        {
+            return CoerceScalarValue<String>(PropertyType.String);
+        }
+
+
+        public Guid GetGuid()
+        {
+            return CoerceScalarValue<Guid>(PropertyType.Guid);
+        }
+
+
+        public DateTimeOffset GetDateTime()
+        {
+            if (this.Type != PropertyType.DateTime)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "DateTime"), HResults.TYPE_E_TYPEMISMATCH);
+            return (DateTimeOffset)_data;
+        }
+
+        public TimeSpan GetTimeSpan()
+        {
+            if (this.Type != PropertyType.TimeSpan)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "TimeSpan"), HResults.TYPE_E_TYPEMISMATCH);
+            return (TimeSpan)_data;
+        }
+
+        public Point GetPoint()
+        {
+            if (this.Type != PropertyType.Point)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "Point"), HResults.TYPE_E_TYPEMISMATCH);
+
+            return Unbox<Point>(IReferenceFactory.s_pointType);
+        }
+
+        public Size GetSize()
+        {
+            if (this.Type != PropertyType.Size)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "Size"), HResults.TYPE_E_TYPEMISMATCH);
+
+            return Unbox<Size>(IReferenceFactory.s_sizeType);
+        }
+
+        public Rect GetRect()
+        {
+            if (this.Type != PropertyType.Rect)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "Rect"), HResults.TYPE_E_TYPEMISMATCH);
+
+            return Unbox<Rect>(IReferenceFactory.s_rectType);
+        }
+
+        public Byte[] GetUInt8Array()
+        {
+            return CoerceArrayValue<Byte>(PropertyType.UInt8Array);
+        }
+
+        public Int16[] GetInt16Array()
+        {
+            return CoerceArrayValue<Int16>(PropertyType.Int16Array);
+        }
+
+        public UInt16[] GetUInt16Array()
+        {
+            return CoerceArrayValue<UInt16>(PropertyType.UInt16Array);
+        }
+
+        public Int32[] GetInt32Array()
+        {
+            return CoerceArrayValue<Int32>(PropertyType.Int32Array);
+        }
+
+        public UInt32[] GetUInt32Array()
+        {
+            return CoerceArrayValue<UInt32>(PropertyType.UInt32Array);
+        }
+
+        public Int64[] GetInt64Array()
+        {
+            return CoerceArrayValue<Int64>(PropertyType.Int64Array);
+        }
+
+        public UInt64[] GetUInt64Array()
+        {
+            return CoerceArrayValue<UInt64>(PropertyType.UInt64Array);
+        }
+
+        public Single[] GetSingleArray()
+        {
+            return CoerceArrayValue<Single>(PropertyType.SingleArray);
+        }
+
+        public Double[] GetDoubleArray()
+        {
+            return CoerceArrayValue<Double>(PropertyType.DoubleArray);
+        }
+
+        public char[] GetChar16Array()
+        {
+            if (this.Type != PropertyType.Char16Array)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "Char16[]"), HResults.TYPE_E_TYPEMISMATCH);
+            return (char[])_data;
+        }
+
+        public Boolean[] GetBooleanArray()
+        {
+            if (this.Type != PropertyType.BooleanArray)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "Boolean[]"), HResults.TYPE_E_TYPEMISMATCH);
+            return (bool[])_data;
+        }
+
+        public String[] GetStringArray()
+        {
+            return CoerceArrayValue<String>(PropertyType.StringArray);
+        }
+
+        public Object[] GetInspectableArray()
+        {
+            if (this.Type != PropertyType.InspectableArray)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "Inspectable[]"), HResults.TYPE_E_TYPEMISMATCH);
+            return (Object[])_data;
+        }
+
+        public Guid[] GetGuidArray()
+        {
+            return CoerceArrayValue<Guid>(PropertyType.GuidArray);
+        }
+
+        public DateTimeOffset[] GetDateTimeArray()
+        {
+            if (this.Type != PropertyType.DateTimeArray)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "DateTimeOffset[]"), HResults.TYPE_E_TYPEMISMATCH);
+            return (DateTimeOffset[])_data;
+        }
+
+        public TimeSpan[] GetTimeSpanArray()
+        {
+            if (this.Type != PropertyType.TimeSpanArray)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "TimeSpan[]"), HResults.TYPE_E_TYPEMISMATCH);
+            return (TimeSpan[])_data;
+        }
+
+        public Point[] GetPointArray()
+        {
+            if (this.Type != PropertyType.PointArray)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "Point[]"), HResults.TYPE_E_TYPEMISMATCH);
+
+            return UnboxArray<Point>(IReferenceFactory.s_pointType);
+        }
+
+        public Size[] GetSizeArray()
+        {
+            if (this.Type != PropertyType.SizeArray)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "Size[]"), HResults.TYPE_E_TYPEMISMATCH);
+
+
+            return UnboxArray<Size>(IReferenceFactory.s_sizeType);
+        }
+
+        public Rect[] GetRectArray()
+        {
+            if (this.Type != PropertyType.RectArray)
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, "Rect[]"), HResults.TYPE_E_TYPEMISMATCH);
+
+            return UnboxArray<Rect>(IReferenceFactory.s_rectType);
+        }
+
+        private T[] CoerceArrayValue<T>(PropertyType unboxType)
+        {
+            // If we contain the type being looked for directly, then take the fast-path
+            if (Type == unboxType)
+            {
+                return (T[])_data;
+            }
+
+            // Make sure we have an array to begin with
+            Array dataArray = _data as Array;
+            if (dataArray == null)
+            {
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, this.Type, typeof (T).MakeArrayType().Name), HResults.TYPE_E_TYPEMISMATCH);
+            }
+
+            // Array types are 1024 larger than their equivilent scalar counterpart
+            Debug.Assert((int)Type > 1024, "Unexpected array PropertyType value");
+            PropertyType scalarType = Type - 1024;
+
+            // If we do not have the correct array type, then we need to convert the array element-by-element
+            // to a new array of the requested type
+            T[] coercedArray = new T[dataArray.Length];
+            for (int i = 0; i < dataArray.Length; ++i)
+            {
+                try
+                {
+                    coercedArray[i] = CoerceScalarValue<T>(scalarType, dataArray.GetValue(i));
+                }
+                catch (InvalidCastException elementCastException)
+                {
+                    Exception e = new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueArrayCoersion, this.Type, typeof (T).MakeArrayType().Name, i, elementCastException.Message), elementCastException);
+                    e.SetErrorCode(elementCastException._HResult);
+                    throw e;
+                }
+            }
+
+            return coercedArray;
+        }
+
+        private T CoerceScalarValue<T>(PropertyType unboxType)
+        {
+            // If we are just a boxed version of the requested type, then take the fast path out
+            if (Type == unboxType)
+            {
+                return (T)_data;
+            }
+
+            return CoerceScalarValue<T>(Type, _data);
+        }
+
+        private static T CoerceScalarValue<T>(PropertyType type, object value)
+        {
+            // If the property type is neither one of the coercable numeric types nor IInspectable, we
+            // should not attempt coersion, even if the underlying value is technically convertable
+            if (!IsCoercable(type, value) && type != PropertyType.Inspectable)
+            {
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, type, typeof (T).Name), HResults.TYPE_E_TYPEMISMATCH);
+            }
+
+            try
+            {
+                // Try to coerce:
+                //  * String <--> Guid
+                //  * Numeric scalars
+                if (type == PropertyType.String && typeof(T) == typeof(Guid))
+                {
+                    return (T)(object)Guid.Parse((string)value);
+                }
+                else if (type == PropertyType.Guid && typeof(T) == typeof(String))
+                {
+                    return (T)(object)((Guid)value).ToString("D", System.Globalization.CultureInfo.InvariantCulture);
+                }
+                else
+                {
+                    // Iterate over the numeric scalars, to see if we have a match for one of the known conversions
+                    foreach (Tuple<Type, PropertyType> numericScalar in NumericScalarTypes)
+                    {
+                        if (numericScalar.Item1 == typeof(T))
+                        {
+                            return (T)Convert.ChangeType(value, typeof(T), System.Globalization.CultureInfo.InvariantCulture);
+                        }
+                    }
+                }
+            }
+            catch (FormatException)
+            {
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, type, typeof (T).Name), HResults.TYPE_E_TYPEMISMATCH);
+            }
+            catch (InvalidCastException)
+            {
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, type, typeof (T).Name), HResults.TYPE_E_TYPEMISMATCH);
+            }
+            catch (OverflowException)
+            {
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueCoersion, type, value, typeof (T).Name), HResults.DISP_E_OVERFLOW);
+            }
+
+            // If the property type is IInspectable, and we have a nested IPropertyValue, then we need
+            // to pass along the request to coerce the value.
+            IPropertyValue ipv = value as IPropertyValue;
+            if (type == PropertyType.Inspectable && ipv != null)
+            {
+                if (typeof(T) == typeof(Byte))
+                {
+                    return (T)(object)ipv.GetUInt8();
+                }
+                else if (typeof(T) == typeof(Int16))
+                {
+                    return (T)(object)ipv.GetInt16();
+                }
+                else if (typeof(T) == typeof(UInt16))
+                {
+                    return (T)(object)ipv.GetUInt16();
+                }
+                else if (typeof(T) == typeof(Int32))
+                {
+                    return (T)(object)ipv.GetUInt32();
+                }
+                else if (typeof(T) == typeof(UInt32))
+                {
+                    return (T)(object)ipv.GetUInt32();
+                }
+                else if (typeof(T) == typeof(Int64))
+                {
+                    return (T)(object)ipv.GetInt64();
+                }
+                else if (typeof(T) == typeof(UInt64))
+                {
+                    return (T)(object)ipv.GetUInt64();
+                }
+                else if (typeof(T) == typeof(Single))
+                {
+                    return (T)(object)ipv.GetSingle();
+                }
+                else if (typeof(T) == typeof(Double))
+                {
+                    return (T)(object)ipv.GetDouble();
+                }
+                else
+                {
+                    Debug.Fail("T in coersion function wasn't understood as a type that can be coerced - make sure that CoerceScalarValue and NumericScalarTypes are in sync");
+                }
+            }
+
+            // Otherwise, this is an invalid coersion
+            throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, type, typeof (T).Name), HResults.TYPE_E_TYPEMISMATCH);
+        }
+
+        private static bool IsCoercable(PropertyType type, object data)
+        {
+            // String <--> Guid is allowed
+            if (type == PropertyType.Guid || type == PropertyType.String)
+            {
+                return true;
+            }
+
+            // All numeric scalars can also be coerced
+            return IsNumericScalarImpl(type, data);
+        }
+
+        private static bool IsNumericScalarImpl(PropertyType type, object data)
+        {
+            if (data.GetType().IsEnum)
+            {
+                return true;
+            }
+
+            foreach (Tuple<Type, PropertyType> numericScalar in NumericScalarTypes)
+            {
+                if (numericScalar.Item2 == type)
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        // Unbox the data stored in the property value to a structurally equivilent type
+        private unsafe T Unbox<T>(Type expectedBoxedType) where T : struct
+        {
+            Debug.Assert(expectedBoxedType != null);
+            Debug.Assert(Marshal.SizeOf(expectedBoxedType) == Marshal.SizeOf(typeof(T)));
+
+            if (_data.GetType() != expectedBoxedType)
+            {
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, _data.GetType(), expectedBoxedType.Name), HResults.TYPE_E_TYPEMISMATCH);
+            }
+
+            T unboxed = new T();
+
+            fixed (byte* pData = &JitHelpers.GetPinningHelper(_data).m_data)
+            {
+                byte* pUnboxed = (byte*)JitHelpers.UnsafeCastToStackPointer(ref unboxed);
+                Buffer.Memcpy(pUnboxed, pData, Marshal.SizeOf(unboxed));
+            }
+
+            return unboxed;
+        }
+
+        // Convert the array stored in the property value to a structurally equivilent array type
+        private unsafe T[] UnboxArray<T>(Type expectedArrayElementType) where T : struct
+        {
+            Debug.Assert(expectedArrayElementType != null);
+            Debug.Assert(Marshal.SizeOf(expectedArrayElementType) == Marshal.SizeOf(typeof(T)));
+
+            Array dataArray = _data as Array;
+            if (dataArray == null || _data.GetType().GetElementType() != expectedArrayElementType)
+            {
+                throw new InvalidCastException(SR.Format(SR.InvalidCast_WinRTIPropertyValueElement, _data.GetType(), expectedArrayElementType.MakeArrayType().Name), HResults.TYPE_E_TYPEMISMATCH);
+            }
+
+            T[] converted = new T[dataArray.Length];
+
+            if (converted.Length > 0)
+            {
+                fixed (byte* dataPin = &JitHelpers.GetPinningHelper(dataArray).m_data)
+                {
+                    fixed (byte* convertedPin = &JitHelpers.GetPinningHelper(converted).m_data)
+                    {
+                        byte* pData = (byte*)Marshal.UnsafeAddrOfPinnedArrayElement(dataArray, 0);
+                        byte* pConverted = (byte*)Marshal.UnsafeAddrOfPinnedArrayElement(converted, 0);
+
+                        Buffer.Memcpy(pConverted, pData, checked(Marshal.SizeOf(typeof(T)) * converted.Length));
+                    }
+                }
+            }
+
+            return converted;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/CLRIReferenceImpl.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/CLRIReferenceImpl.cs
new file mode 100644
index 0000000000..9e1a9f39e5
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/CLRIReferenceImpl.cs
@@ -0,0 +1,401 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Collections;
+using System.Diagnostics;
+using System.Reflection;
+using System.Security;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    internal sealed class CLRIReferenceImpl<T> : CLRIPropertyValueImpl, IReference<T>, IGetProxyTarget
+    {
+        private T _value;
+
+        public CLRIReferenceImpl(PropertyType type, T obj)
+            : base(type, obj)
+        {
+            Debug.Assert(obj != null, "Must not be null");
+            _value = obj;
+        }
+
+        public T Value
+        {
+            get { return _value; }
+        }
+
+        public override string ToString()
+        {
+            if (_value != null)
+            {
+                return _value.ToString();
+            }
+            else
+            {
+                return base.ToString();
+            }
+        }
+
+        object IGetProxyTarget.GetTarget()
+        {
+            return (object)_value;
+        }
+
+        // We have T in an IReference<T>.  Need to QI for IReference<T> with the appropriate GUID, call
+        // the get_Value property, allocate an appropriately-sized managed object, marshal the native object
+        // to the managed object, and free the native method.  Also we want the return value boxed (aka normal value type boxing).
+        //
+        // This method is called by VM.
+        internal static Object UnboxHelper(Object wrapper)
+        {
+            Debug.Assert(wrapper != null);
+            IReference<T> reference = (IReference<T>)wrapper;
+            Debug.Assert(reference != null, "CLRIReferenceImpl::UnboxHelper - QI'ed for IReference<" + typeof(T) + ">, but that failed.");
+            return reference.Value;
+        }
+    }
+
+    // T can be any WinRT-compatible type
+    internal sealed class CLRIReferenceArrayImpl<T> : CLRIPropertyValueImpl,
+                                                      IGetProxyTarget,
+                                                      IReferenceArray<T>,
+                                                      IList                     // Jupiter data binding needs IList/IEnumerable
+    {
+        private T[] _value;
+        private IList _list;
+
+        public CLRIReferenceArrayImpl(PropertyType type, T[] obj)
+            : base(type, obj)
+        {
+            Debug.Assert(obj != null, "Must not be null");
+
+            _value = obj;
+
+            _list = (IList)_value;
+        }
+
+        public T[] Value
+        {
+            get { return _value; }
+        }
+
+        public override string ToString()
+        {
+            if (_value != null)
+            {
+                return _value.ToString();
+            }
+            else
+            {
+                return base.ToString();
+            }
+        }
+
+        //
+        // IEnumerable methods. Used by data-binding in Jupiter when you try to data bind
+        // against a managed array
+        //
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return ((IEnumerable)_value).GetEnumerator();
+        }
+
+        //
+        // IList & ICollection methods. 
+        // This enables two-way data binding and index access in Jupiter
+        //
+        Object IList.this[int index]
+        {
+            get
+            {
+                return _list[index];
+            }
+
+            set
+            {
+                _list[index] = value;
+            }
+        }
+
+        int IList.Add(Object value)
+        {
+            return _list.Add(value);
+        }
+
+        bool IList.Contains(Object value)
+        {
+            return _list.Contains(value);
+        }
+
+        void IList.Clear()
+        {
+            _list.Clear();
+        }
+
+        bool IList.IsReadOnly
+        {
+            get
+            {
+                return _list.IsReadOnly;
+            }
+        }
+
+        bool IList.IsFixedSize
+        {
+            get
+            {
+                return _list.IsFixedSize;
+            }
+        }
+
+        int IList.IndexOf(Object value)
+        {
+            return _list.IndexOf(value);
+        }
+
+        void IList.Insert(int index, Object value)
+        {
+            _list.Insert(index, value);
+        }
+
+        void IList.Remove(Object value)
+        {
+            _list.Remove(value);
+        }
+
+        void IList.RemoveAt(int index)
+        {
+            _list.RemoveAt(index);
+        }
+
+        void ICollection.CopyTo(Array array, int index)
+        {
+            _list.CopyTo(array, index);
+        }
+
+        int ICollection.Count
+        {
+            get
+            {
+                return _list.Count;
+            }
+        }
+
+        Object ICollection.SyncRoot
+        {
+            get
+            {
+                return _list.SyncRoot;
+            }
+        }
+
+        bool ICollection.IsSynchronized
+        {
+            get
+            {
+                return _list.IsSynchronized;
+            }
+        }
+
+        object IGetProxyTarget.GetTarget()
+        {
+            return (object)_value;
+        }
+
+        // We have T in an IReferenceArray<T>.  Need to QI for IReferenceArray<T> with the appropriate GUID, call
+        // the get_Value property, allocate an appropriately-sized managed object, marshal the native object
+        // to the managed object, and free the native method.
+        //
+        // This method is called by VM.
+        internal static Object UnboxHelper(Object wrapper)
+        {
+            Debug.Assert(wrapper != null);
+            IReferenceArray<T> reference = (IReferenceArray<T>)wrapper;
+            Debug.Assert(reference != null, "CLRIReferenceArrayImpl::UnboxHelper - QI'ed for IReferenceArray<" + typeof(T) + ">, but that failed.");
+            T[] marshaled = reference.Value;
+            return marshaled;
+        }
+    }
+
+    // For creating instances of Windows Runtime's IReference<T> and IReferenceArray<T>.
+    internal static class IReferenceFactory
+    {
+        internal static readonly Type s_pointType = Type.GetType("Windows.Foundation.Point, System.Runtime.WindowsRuntime");
+        internal static readonly Type s_rectType = Type.GetType("Windows.Foundation.Rect, System.Runtime.WindowsRuntime");
+        internal static readonly Type s_sizeType = Type.GetType("Windows.Foundation.Size, System.Runtime.WindowsRuntime");
+
+        internal static Object CreateIReference(Object obj)
+        {
+            Debug.Assert(obj != null, "Null should not be boxed.");
+
+            Type type = obj.GetType();
+
+            if (type.IsArray)
+                return CreateIReferenceArray((Array)obj);
+
+            if (type == typeof(int))
+                return new CLRIReferenceImpl<int>(PropertyType.Int32, (int)obj);
+            if (type == typeof(String))
+                return new CLRIReferenceImpl<String>(PropertyType.String, (String)obj);
+            if (type == typeof(byte))
+                return new CLRIReferenceImpl<byte>(PropertyType.UInt8, (byte)obj);
+            if (type == typeof(short))
+                return new CLRIReferenceImpl<short>(PropertyType.Int16, (short)obj);
+            if (type == typeof(ushort))
+                return new CLRIReferenceImpl<ushort>(PropertyType.UInt16, (ushort)obj);
+            if (type == typeof(uint))
+                return new CLRIReferenceImpl<uint>(PropertyType.UInt32, (uint)obj);
+            if (type == typeof(long))
+                return new CLRIReferenceImpl<long>(PropertyType.Int64, (long)obj);
+            if (type == typeof(ulong))
+                return new CLRIReferenceImpl<ulong>(PropertyType.UInt64, (ulong)obj);
+            if (type == typeof(float))
+                return new CLRIReferenceImpl<float>(PropertyType.Single, (float)obj);
+            if (type == typeof(double))
+                return new CLRIReferenceImpl<double>(PropertyType.Double, (double)obj);
+            if (type == typeof(char))
+                return new CLRIReferenceImpl<char>(PropertyType.Char16, (char)obj);
+            if (type == typeof(bool))
+                return new CLRIReferenceImpl<bool>(PropertyType.Boolean, (bool)obj);
+            if (type == typeof(Guid))
+                return new CLRIReferenceImpl<Guid>(PropertyType.Guid, (Guid)obj);
+            if (type == typeof(DateTimeOffset))
+                return new CLRIReferenceImpl<DateTimeOffset>(PropertyType.DateTime, (DateTimeOffset)obj);
+            if (type == typeof(TimeSpan))
+                return new CLRIReferenceImpl<TimeSpan>(PropertyType.TimeSpan, (TimeSpan)obj);
+            if (type == typeof(Object))
+                return new CLRIReferenceImpl<Object>(PropertyType.Inspectable, (Object)obj);
+            if (type == typeof(RuntimeType))
+            {   // If the type is System.RuntimeType, we want to use System.Type marshaler (it's parent of the type)
+                return new CLRIReferenceImpl<Type>(PropertyType.Other, (Type)obj);
+            }
+
+            // Handle arbitrary WinRT-compatible value types, and recognize a few special types.
+            PropertyType? propType = null;
+            if (type == s_pointType)
+            {
+                propType = PropertyType.Point;
+            }
+            else if (type == s_rectType)
+            {
+                propType = PropertyType.Rect;
+            }
+            else if (type == s_sizeType)
+            {
+                propType = PropertyType.Size;
+            }
+            else if (type.IsValueType || obj is Delegate)
+            {
+                propType = PropertyType.Other;
+            }
+
+            if (propType.HasValue)
+            {
+                Type specificType = typeof(CLRIReferenceImpl<>).MakeGenericType(type);
+                return Activator.CreateInstance(specificType, new Object[] { propType.Value, obj });
+            }
+
+            Debug.Fail("We should not see non-WinRT type here");
+            return null;
+        }
+
+        internal static Object CreateIReferenceArray(Array obj)
+        {
+            Debug.Assert(obj != null);
+            Debug.Assert(obj.GetType().IsArray);
+
+            Type type = obj.GetType().GetElementType();
+
+            Debug.Assert(obj.Rank == 1 && obj.GetLowerBound(0) == 0 && !type.IsArray);
+
+            if (type == typeof(int))
+                return new CLRIReferenceArrayImpl<int>(PropertyType.Int32Array, (int[])obj);
+            if (type == typeof(String))
+                return new CLRIReferenceArrayImpl<String>(PropertyType.StringArray, (String[])obj);
+            if (type == typeof(byte))
+                return new CLRIReferenceArrayImpl<byte>(PropertyType.UInt8Array, (byte[])obj);
+            if (type == typeof(short))
+                return new CLRIReferenceArrayImpl<short>(PropertyType.Int16Array, (short[])obj);
+            if (type == typeof(ushort))
+                return new CLRIReferenceArrayImpl<ushort>(PropertyType.UInt16Array, (ushort[])obj);
+            if (type == typeof(uint))
+                return new CLRIReferenceArrayImpl<uint>(PropertyType.UInt32Array, (uint[])obj);
+            if (type == typeof(long))
+                return new CLRIReferenceArrayImpl<long>(PropertyType.Int64Array, (long[])obj);
+            if (type == typeof(ulong))
+                return new CLRIReferenceArrayImpl<ulong>(PropertyType.UInt64Array, (ulong[])obj);
+            if (type == typeof(float))
+                return new CLRIReferenceArrayImpl<float>(PropertyType.SingleArray, (float[])obj);
+            if (type == typeof(double))
+                return new CLRIReferenceArrayImpl<double>(PropertyType.DoubleArray, (double[])obj);
+            if (type == typeof(char))
+                return new CLRIReferenceArrayImpl<char>(PropertyType.Char16Array, (char[])obj);
+            if (type == typeof(bool))
+                return new CLRIReferenceArrayImpl<bool>(PropertyType.BooleanArray, (bool[])obj);
+            if (type == typeof(Guid))
+                return new CLRIReferenceArrayImpl<Guid>(PropertyType.GuidArray, (Guid[])obj);
+            if (type == typeof(DateTimeOffset))
+                return new CLRIReferenceArrayImpl<DateTimeOffset>(PropertyType.DateTimeArray, (DateTimeOffset[])obj);
+            if (type == typeof(TimeSpan))
+                return new CLRIReferenceArrayImpl<TimeSpan>(PropertyType.TimeSpanArray, (TimeSpan[])obj);
+            if (type == typeof(Type))
+            {   // Note: The array type will be System.Type, not System.RuntimeType
+                return new CLRIReferenceArrayImpl<Type>(PropertyType.OtherArray, (Type[])obj);
+            }
+
+            PropertyType? propType = null;
+            if (type == s_pointType)
+            {
+                propType = PropertyType.PointArray;
+            }
+            else if (type == s_rectType)
+            {
+                propType = PropertyType.RectArray;
+            }
+            else if (type == s_sizeType)
+            {
+                propType = PropertyType.SizeArray;
+            }
+            else if (type.IsValueType)
+            {
+                // note that KeyValuePair`2 is a reference type on the WinRT side so the array
+                // must be wrapped with CLRIReferenceArrayImpl<Object>
+                if (type.IsGenericType &&
+                    type.GetGenericTypeDefinition() == typeof(System.Collections.Generic.KeyValuePair<,>))
+                {
+                    Object[] objArray = new Object[obj.Length];
+                    for (int i = 0; i < objArray.Length; i++)
+                    {
+                        objArray[i] = obj.GetValue(i);
+                    }
+                    obj = objArray;
+                }
+                else
+                {
+                    propType = PropertyType.OtherArray;
+                }
+            }
+            else if (typeof(Delegate).IsAssignableFrom(type))
+            {
+                propType = PropertyType.OtherArray;
+            }
+
+
+            if (propType.HasValue)
+            {
+                // All WinRT value type will be Property.Other
+                Type specificType = typeof(CLRIReferenceArrayImpl<>).MakeGenericType(type);
+                return Activator.CreateInstance(specificType, new Object[] { propType.Value, obj });
+            }
+            else
+            {
+                // All WinRT reference type (including arbitary managed type) will be PropertyType.ObjectArray
+                return new CLRIReferenceArrayImpl<Object>(PropertyType.InspectableArray, (Object[])obj);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ConstantSplittableMap.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ConstantSplittableMap.cs
new file mode 100644
index 0000000000..85b6c39811
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ConstantSplittableMap.cs
@@ -0,0 +1,231 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics.Contracts;
+using System.Runtime.InteropServices;
+
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    /// <summary>
+    /// This is a constant map aimed to efficiently support a Split operation (map decomposition).
+    /// A Split operation returns two non-overlapping, non-empty views of the existing map (or both
+    /// values are set to NULL). The two views returned should contain roughly the same number of elements.
+    /// This map is backed by a sorted array. Thus, split operations are O(1) and enumerations are fast;
+    /// however, look-up in the map are O(log n).
+    /// </summary>
+    /// <typeparam name="TKey">Type of objects that act as keys.</typeparam>    
+    /// <typeparam name="TValue">Type of objects that act as entries / values.</typeparam>
+    [DebuggerDisplay("Count = {Count}")]
+    internal sealed class ConstantSplittableMap<TKey, TValue> : IMapView<TKey, TValue>
+    {
+        private class KeyValuePairComparator : IComparer<KeyValuePair<TKey, TValue>>
+        {
+            private static readonly IComparer<TKey> keyComparator = Comparer<TKey>.Default;
+
+            public Int32 Compare(KeyValuePair<TKey, TValue> x, KeyValuePair<TKey, TValue> y)
+            {
+                return keyComparator.Compare(x.Key, y.Key);
+            }
+        }  // private class KeyValuePairComparator
+
+
+        private static readonly KeyValuePairComparator keyValuePairComparator = new KeyValuePairComparator();
+
+        private readonly KeyValuePair<TKey, TValue>[] items;
+        private readonly int firstItemIndex;
+        private readonly int lastItemIndex;
+
+        internal ConstantSplittableMap(IReadOnlyDictionary<TKey, TValue> data)
+        {
+            if (data == null)
+                throw new ArgumentNullException(nameof(data));
+
+            firstItemIndex = 0;
+            lastItemIndex = data.Count - 1;
+            items = CreateKeyValueArray(data.Count, data.GetEnumerator());
+        }
+
+
+        private ConstantSplittableMap(KeyValuePair<TKey, TValue>[] items, Int32 firstItemIndex, Int32 lastItemIndex)
+        {
+            this.items = items;
+            this.firstItemIndex = firstItemIndex;
+            this.lastItemIndex = lastItemIndex;
+        }
+
+
+        private KeyValuePair<TKey, TValue>[] CreateKeyValueArray(Int32 count, IEnumerator<KeyValuePair<TKey, TValue>> data)
+        {
+            KeyValuePair<TKey, TValue>[] kvArray = new KeyValuePair<TKey, TValue>[count];
+
+            Int32 i = 0;
+            while (data.MoveNext())
+                kvArray[i++] = data.Current;
+
+            Array.Sort(kvArray, keyValuePairComparator);
+
+            return kvArray;
+        }
+
+
+        public int Count
+        {
+            get
+            {
+                return lastItemIndex - firstItemIndex + 1;
+            }
+        }
+
+
+        // [CLSCompliant(false)]
+        public UInt32 Size
+        {
+            get
+            {
+                return (UInt32)(lastItemIndex - firstItemIndex + 1);
+            }
+        }
+
+
+        public TValue Lookup(TKey key)
+        {
+            TValue value;
+            bool found = TryGetValue(key, out value);
+
+            if (!found)
+            {
+                Exception e = new KeyNotFoundException(SR.Format(SR.Arg_KeyNotFoundWithKey, key.ToString()));
+                e.SetErrorCode(HResults.E_BOUNDS);
+                throw e;
+            }
+
+            return value;
+        }
+
+
+        public bool HasKey(TKey key)
+        {
+            TValue value;
+            bool hasKey = TryGetValue(key, out value);
+            return hasKey;
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return ((IEnumerable<IKeyValuePair<TKey, TValue>>)this).GetEnumerator();
+        }
+
+        public IIterator<IKeyValuePair<TKey, TValue>> First()
+        {
+            return new EnumeratorToIteratorAdapter<IKeyValuePair<TKey, TValue>>(GetEnumerator());
+        }
+
+        public IEnumerator<IKeyValuePair<TKey, TValue>> GetEnumerator()
+        {
+            return new IKeyValuePairEnumerator(items, firstItemIndex, lastItemIndex);
+        }
+
+        public void Split(out IMapView<TKey, TValue> firstPartition, out IMapView<TKey, TValue> secondPartition)
+        {
+            if (Count < 2)
+            {
+                firstPartition = null;
+                secondPartition = null;
+                return;
+            }
+
+            int pivot = (Int32)(((Int64)firstItemIndex + (Int64)lastItemIndex) / (Int64)2);
+
+            firstPartition = new ConstantSplittableMap<TKey, TValue>(items, firstItemIndex, pivot);
+            secondPartition = new ConstantSplittableMap<TKey, TValue>(items, pivot + 1, lastItemIndex);
+        }
+
+        #region IReadOnlyDictionary members
+
+        public bool TryGetValue(TKey key, out TValue value)
+        {
+            KeyValuePair<TKey, TValue> searchKey = new KeyValuePair<TKey, TValue>(key, default(TValue));
+            int index = Array.BinarySearch(items, firstItemIndex, Count, searchKey, keyValuePairComparator);
+
+            if (index < 0)
+            {
+                value = default(TValue);
+                return false;
+            }
+
+            value = items[index].Value;
+            return true;
+        }
+
+        #endregion IReadOnlyDictionary members
+
+        #region IKeyValuePair Enumerator
+
+        internal struct IKeyValuePairEnumerator : IEnumerator<IKeyValuePair<TKey, TValue>>
+        {
+            private KeyValuePair<TKey, TValue>[] _array;
+            private int _start;
+            private int _end;
+            private int _current;
+
+            internal IKeyValuePairEnumerator(KeyValuePair<TKey, TValue>[] items, int first, int end)
+            {
+                Debug.Assert(items != null);
+                Debug.Assert(first >= 0);
+                Debug.Assert(end >= 0);
+                Debug.Assert(first < items.Length);
+                Debug.Assert(end < items.Length);
+
+                _array = items;
+                _start = first;
+                _end = end;
+                _current = _start - 1;
+            }
+
+            public bool MoveNext()
+            {
+                if (_current < _end)
+                {
+                    _current++;
+                    return true;
+                }
+                return false;
+            }
+
+            public IKeyValuePair<TKey, TValue> Current
+            {
+                get
+                {
+                    if (_current < _start) throw new InvalidOperationException(SR.InvalidOperation_EnumNotStarted);
+                    if (_current > _end) throw new InvalidOperationException(SR.InvalidOperation_EnumEnded);
+                    return new CLRIKeyValuePairImpl<TKey, TValue>(ref _array[_current]);
+                }
+            }
+
+            Object IEnumerator.Current
+            {
+                get
+                {
+                    return Current;
+                }
+            }
+
+            void IEnumerator.Reset()
+            {
+                _current = _start - 1;
+            }
+
+            public void Dispose()
+            {
+            }
+        }
+
+        #endregion IKeyValuePair Enumerator
+    }  // internal ConstantSplittableMap<TKey, TValue>
+}  // namespace System.Runtime.InteropServices.WindowsRuntime
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/CustomPropertyImpl.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/CustomPropertyImpl.cs
new file mode 100644
index 0000000000..1d7a5dfb9d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/CustomPropertyImpl.cs
@@ -0,0 +1,136 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Reflection;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Runtime.Serialization;
+using System.StubHelpers;
+using System.Globalization;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    //
+    // ICustomProperty implementation - basically a wrapper of PropertyInfo
+    //
+    internal sealed class CustomPropertyImpl : ICustomProperty
+    {
+        private PropertyInfo m_property;
+
+        //
+        // Constructor
+        //
+        public CustomPropertyImpl(PropertyInfo propertyInfo)
+        {
+            if (propertyInfo == null)
+                throw new ArgumentNullException(nameof(propertyInfo));
+
+            m_property = propertyInfo;
+        }
+
+        //
+        // ICustomProperty interface implementation
+        //
+
+        public string Name
+        {
+            get
+            {
+                return m_property.Name;
+            }
+        }
+
+        public bool CanRead
+        {
+            get
+            {
+                // Return false if the getter is not public
+                return m_property.GetGetMethod() != null;
+            }
+        }
+
+        public bool CanWrite
+        {
+            get
+            {
+                // Return false if the setter is not public
+                return m_property.GetSetMethod() != null;
+            }
+        }
+
+        public object GetValue(object target)
+        {
+            return InvokeInternal(target, null, true);
+        }
+
+        // Unlike normal .Net, Jupiter properties can have at most one indexer parameter. A null
+        // indexValue here means that the property has an indexer argument and its value is null.
+        public object GetValue(object target, object indexValue)
+        {
+            return InvokeInternal(target, new object[] { indexValue }, true);
+        }
+
+        public void SetValue(object target, object value)
+        {
+            InvokeInternal(target, new object[] { value }, false);
+        }
+
+        // Unlike normal .Net, Jupiter properties can have at most one indexer parameter. A null
+        // indexValue here means that the property has an indexer argument and its value is null.
+        public void SetValue(object target, object value, object indexValue)
+        {
+            InvokeInternal(target, new object[] { indexValue, value }, false);
+        }
+
+        private object InvokeInternal(object target, object[] args, bool getValue)
+        {
+            // Forward to the right object if we are dealing with a proxy
+            IGetProxyTarget proxy = target as IGetProxyTarget;
+            if (proxy != null)
+            {
+                target = proxy.GetTarget();
+            }
+
+            // You can get PropertyInfo for properties with a private getter/public setter (or vice versa) 
+            // even if you pass BindingFlags.Public only. And in this case, passing binding flags to 
+            // GetValue/SetValue won't work as the default binder ignores those values
+            // Use GetGetMethod/GetSetMethod instead
+
+            // We get non-public accessors just so that we can throw the correct exception.
+            MethodInfo accessor = getValue ? m_property.GetGetMethod(true) : m_property.GetSetMethod(true);
+
+            if (accessor == null)
+                throw new ArgumentException(getValue ? SR.Arg_GetMethNotFnd : SR.Arg_SetMethNotFnd);
+
+            if (!accessor.IsPublic)
+                throw new MethodAccessException(
+                    String.Format(
+                        CultureInfo.CurrentCulture,
+                        SR.Arg_MethodAccessException_WithMethodName,
+                        accessor.ToString(),
+                        accessor.DeclaringType.FullName));
+
+            RuntimeMethodInfo rtMethod = accessor as RuntimeMethodInfo;
+            if (rtMethod == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeMethodInfo);
+
+            // We can safely skip access check because this is only used in full trust scenarios.
+            // And we have already verified that the property accessor is public.
+            return rtMethod.Invoke(target, BindingFlags.Default, null, args, null);
+        }
+
+        public Type Type
+        {
+            get
+            {
+                return m_property.PropertyType;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryKeyCollection.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryKeyCollection.cs
new file mode 100644
index 0000000000..f2434ce91d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryKeyCollection.cs
@@ -0,0 +1,126 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    [DebuggerDisplay("Count = {Count}")]
+    internal sealed class DictionaryKeyCollection<TKey, TValue> : ICollection<TKey>
+    {
+        private readonly IDictionary<TKey, TValue> dictionary;
+
+        public DictionaryKeyCollection(IDictionary<TKey, TValue> dictionary)
+        {
+            if (dictionary == null)
+                throw new ArgumentNullException(nameof(dictionary));
+
+            this.dictionary = dictionary;
+        }
+
+        public void CopyTo(TKey[] array, int index)
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array));
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index));
+            if (array.Length <= index && this.Count > 0)
+                throw new ArgumentException(SR.Arg_IndexOutOfRangeException);
+            if (array.Length - index < dictionary.Count)
+                throw new ArgumentException(SR.Argument_InsufficientSpaceToCopyCollection);
+
+            int i = index;
+            foreach (KeyValuePair<TKey, TValue> mapping in dictionary)
+            {
+                array[i++] = mapping.Key;
+            }
+        }
+
+        public int Count
+        {
+            get { return dictionary.Count; }
+        }
+
+        bool ICollection<TKey>.IsReadOnly
+        {
+            get { return true; }
+        }
+
+        void ICollection<TKey>.Add(TKey item)
+        {
+            throw new NotSupportedException(SR.NotSupported_KeyCollectionSet);
+        }
+
+        void ICollection<TKey>.Clear()
+        {
+            throw new NotSupportedException(SR.NotSupported_KeyCollectionSet);
+        }
+
+        public bool Contains(TKey item)
+        {
+            return dictionary.ContainsKey(item);
+        }
+
+        bool ICollection<TKey>.Remove(TKey item)
+        {
+            throw new NotSupportedException(SR.NotSupported_KeyCollectionSet);
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return ((IEnumerable<TKey>)this).GetEnumerator();
+        }
+
+        public IEnumerator<TKey> GetEnumerator()
+        {
+            return new DictionaryKeyEnumerator<TKey, TValue>(dictionary);
+        }
+    }  // public class DictionaryKeyCollection<TKey, TValue>
+
+
+    internal sealed class DictionaryKeyEnumerator<TKey, TValue> : IEnumerator<TKey>
+    {
+        private readonly IDictionary<TKey, TValue> dictionary;
+        private IEnumerator<KeyValuePair<TKey, TValue>> enumeration;
+
+        public DictionaryKeyEnumerator(IDictionary<TKey, TValue> dictionary)
+        {
+            if (dictionary == null)
+                throw new ArgumentNullException(nameof(dictionary));
+
+            this.dictionary = dictionary;
+            enumeration = dictionary.GetEnumerator();
+        }
+
+        void IDisposable.Dispose()
+        {
+            enumeration.Dispose();
+        }
+
+        public bool MoveNext()
+        {
+            return enumeration.MoveNext();
+        }
+
+        Object IEnumerator.Current
+        {
+            get { return ((IEnumerator<TKey>)this).Current; }
+        }
+
+        public TKey Current
+        {
+            get { return enumeration.Current.Key; }
+        }
+
+        public void Reset()
+        {
+            enumeration = dictionary.GetEnumerator();
+        }
+    }  // class DictionaryKeyEnumerator<TKey, TValue>
+}
+
+// DictionaryKeyCollection.cs
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryToMapAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryToMapAdapter.cs
new file mode 100644
index 0000000000..b83916b833
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryToMapAdapter.cs
@@ -0,0 +1,112 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Reflection;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // This is a set of stub methods implementing the support for the IMap`2 interface on managed
+    // objects that implement IDictionary`2. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not DictionaryToMapAdapter objects. Rather, they are of type
+    // IDictionary<K, V>. No actual DictionaryToMapAdapter object is ever instantiated. Thus, you will
+    // see a lot of expressions that cast "this" to "IDictionary<K, V>". 
+    internal sealed class DictionaryToMapAdapter
+    {
+        private DictionaryToMapAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // V Lookup(K key)
+        internal V Lookup<K, V>(K key)
+        {
+            IDictionary<K, V> _this = Unsafe.As<IDictionary<K, V>>(this);
+            V value;
+            bool keyFound = _this.TryGetValue(key, out value);
+
+            if (!keyFound)
+            {
+                Exception e = new KeyNotFoundException(SR.Format(SR.Arg_KeyNotFoundWithKey, key.ToString()));
+                e.SetErrorCode(HResults.E_BOUNDS);
+                throw e;
+            }
+
+            return value;
+        }
+
+        // uint Size { get }
+        internal uint Size<K, V>()
+        {
+            IDictionary<K, V> _this = Unsafe.As<IDictionary<K, V>>(this);
+            return (uint)_this.Count;
+        }
+
+        // bool HasKey(K key)
+        internal bool HasKey<K, V>(K key)
+        {
+            IDictionary<K, V> _this = Unsafe.As<IDictionary<K, V>>(this);
+            return _this.ContainsKey(key);
+        }
+
+        // IMapView<K, V> GetView()
+        internal IReadOnlyDictionary<K, V> GetView<K, V>()
+        {
+            IDictionary<K, V> _this = Unsafe.As<IDictionary<K, V>>(this);
+            Debug.Assert(_this != null);
+
+            // Note: This dictionary is not really read-only - you could QI for a modifiable
+            // dictionary.  We gain some perf by doing this.  We believe this is acceptable.
+            IReadOnlyDictionary<K, V> roDictionary = _this as IReadOnlyDictionary<K, V>;
+            if (roDictionary == null)
+            {
+                roDictionary = new ReadOnlyDictionary<K, V>(_this);
+            }
+            return roDictionary;
+        }
+
+        // bool Insert(K key, V value)
+        internal bool Insert<K, V>(K key, V value)
+        {
+            IDictionary<K, V> _this = Unsafe.As<IDictionary<K, V>>(this);
+            bool replacing = _this.ContainsKey(key);
+            _this[key] = value;
+            return replacing;
+        }
+
+        // void Remove(K key)
+        internal void Remove<K, V>(K key)
+        {
+            IDictionary<K, V> _this = Unsafe.As<IDictionary<K, V>>(this);
+            bool removed = _this.Remove(key);
+
+            if (!removed)
+            {
+                Exception e = new KeyNotFoundException(SR.Format(SR.Arg_KeyNotFoundWithKey, key.ToString()));
+                e.SetErrorCode(HResults.E_BOUNDS);
+                throw e;
+            }
+        }
+
+        // void Clear()
+        internal void Clear<K, V>()
+        {
+            IDictionary<K, V> _this = Unsafe.As<IDictionary<K, V>>(this);
+            _this.Clear();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryValueCollection.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryValueCollection.cs
new file mode 100644
index 0000000000..d441a2fbf8
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/DictionaryValueCollection.cs
@@ -0,0 +1,133 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.InteropServices.WindowsRuntime;
+
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    [DebuggerDisplay("Count = {Count}")]
+    internal sealed class DictionaryValueCollection<TKey, TValue> : ICollection<TValue>
+    {
+        private readonly IDictionary<TKey, TValue> dictionary;
+
+        public DictionaryValueCollection(IDictionary<TKey, TValue> dictionary)
+        {
+            if (dictionary == null)
+                throw new ArgumentNullException(nameof(dictionary));
+
+            this.dictionary = dictionary;
+        }
+
+        public void CopyTo(TValue[] array, int index)
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array));
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index));
+            if (array.Length <= index && this.Count > 0)
+                throw new ArgumentException(SR.Arg_IndexOutOfRangeException);
+            if (array.Length - index < dictionary.Count)
+                throw new ArgumentException(SR.Argument_InsufficientSpaceToCopyCollection);
+
+            int i = index;
+            foreach (KeyValuePair<TKey, TValue> mapping in dictionary)
+            {
+                array[i++] = mapping.Value;
+            }
+        }
+
+        public int Count
+        {
+            get { return dictionary.Count; }
+        }
+
+        bool ICollection<TValue>.IsReadOnly
+        {
+            get { return true; }
+        }
+
+        void ICollection<TValue>.Add(TValue item)
+        {
+            throw new NotSupportedException(SR.NotSupported_ValueCollectionSet);
+        }
+
+        void ICollection<TValue>.Clear()
+        {
+            throw new NotSupportedException(SR.NotSupported_ValueCollectionSet);
+        }
+
+        public bool Contains(TValue item)
+        {
+            EqualityComparer<TValue> comparer = EqualityComparer<TValue>.Default;
+            foreach (TValue value in this)
+                if (comparer.Equals(item, value))
+                    return true;
+            return false;
+        }
+
+        bool ICollection<TValue>.Remove(TValue item)
+        {
+            throw new NotSupportedException(SR.NotSupported_ValueCollectionSet);
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return ((IEnumerable<TValue>)this).GetEnumerator();
+        }
+
+        public IEnumerator<TValue> GetEnumerator()
+        {
+            return new DictionaryValueEnumerator<TKey, TValue>(dictionary);
+        }
+    }  // public class DictionaryValueCollection<TKey, TValue>
+
+
+    internal sealed class DictionaryValueEnumerator<TKey, TValue> : IEnumerator<TValue>
+    {
+        private readonly IDictionary<TKey, TValue> dictionary;
+        private IEnumerator<KeyValuePair<TKey, TValue>> enumeration;
+
+        public DictionaryValueEnumerator(IDictionary<TKey, TValue> dictionary)
+        {
+            if (dictionary == null)
+                throw new ArgumentNullException(nameof(dictionary));
+
+            this.dictionary = dictionary;
+            enumeration = dictionary.GetEnumerator();
+        }
+
+        void IDisposable.Dispose()
+        {
+            enumeration.Dispose();
+        }
+
+        public bool MoveNext()
+        {
+            return enumeration.MoveNext();
+        }
+
+        Object IEnumerator.Current
+        {
+            get { return ((IEnumerator<TValue>)this).Current; }
+        }
+
+        public TValue Current
+        {
+            get { return enumeration.Current.Value; }
+        }
+
+        public void Reset()
+        {
+            enumeration = dictionary.GetEnumerator();
+        }
+    }  // class DictionaryValueEnumerator<TKey, TValue>
+}
+
+// DictionaryValueCollection.cs
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/EnumeratorToIteratorAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/EnumeratorToIteratorAdapter.cs
new file mode 100644
index 0000000000..861ee6e4b7
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/EnumeratorToIteratorAdapter.cs
@@ -0,0 +1,167 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // This is a set of stub methods implementing the support for the IIterable`1 interface on managed
+    // objects that implement IEnumerable`1. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not EnumerableToIterableAdapter objects. Rather, they are of type
+    // IEnumerable<T>. No actual EnumerableToIterableAdapter object is ever instantiated. Thus, you will
+    // see a lot of expressions that cast "this" to "IEnumerable<T>". 
+    internal sealed class EnumerableToIterableAdapter
+    {
+        private EnumerableToIterableAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // This method is invoked when First is called on a managed implementation of IIterable<T>.
+        internal IIterator<T> First_Stub<T>()
+        {
+            IEnumerable<T> _this = Unsafe.As<IEnumerable<T>>(this);
+            return new EnumeratorToIteratorAdapter<T>(_this.GetEnumerator());
+        }
+    }
+
+    internal sealed class EnumerableToBindableIterableAdapter
+    {
+        private EnumerableToBindableIterableAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        internal sealed class NonGenericToGenericEnumerator : IEnumerator<object>
+        {
+            private IEnumerator enumerator;
+
+            public NonGenericToGenericEnumerator(IEnumerator enumerator)
+            { this.enumerator = enumerator; }
+
+            public object Current { get { return enumerator.Current; } }
+            public bool MoveNext() { return enumerator.MoveNext(); }
+            public void Reset() { enumerator.Reset(); }
+            public void Dispose() { }
+        }
+
+        // This method is invoked when First is called on a managed implementation of IBindableIterable.
+        internal IBindableIterator First_Stub()
+        {
+            IEnumerable _this = Unsafe.As<IEnumerable>(this);
+            return new EnumeratorToIteratorAdapter<object>(new NonGenericToGenericEnumerator(_this.GetEnumerator()));
+        }
+    }
+
+    // Adapter class which holds a managed IEnumerator<T>, exposing it as a Windows Runtime IIterator<T>
+    internal sealed class EnumeratorToIteratorAdapter<T> : IIterator<T>, IBindableIterator
+    {
+        private IEnumerator<T> m_enumerator;
+        private bool m_firstItem = true;
+        private bool m_hasCurrent;
+
+        internal EnumeratorToIteratorAdapter(IEnumerator<T> enumerator)
+        {
+            Debug.Assert(enumerator != null);
+            m_enumerator = enumerator;
+        }
+
+        public T Current
+        {
+            get
+            {
+                // IEnumerator starts at item -1, while IIterators start at item 0.  Therefore, if this is the
+                // first access to the iterator we need to advance to the first item.
+                if (m_firstItem)
+                {
+                    m_firstItem = false;
+                    MoveNext();
+                }
+
+                if (!m_hasCurrent)
+                {
+                    throw WindowsRuntimeMarshal.GetExceptionForHR(HResults.E_BOUNDS, null);
+                }
+
+                return m_enumerator.Current;
+            }
+        }
+
+        object IBindableIterator.Current
+        {
+            get
+            {
+                return (object)((IIterator<T>)this).Current;
+            }
+        }
+
+        public bool HasCurrent
+        {
+            get
+            {
+                // IEnumerator starts at item -1, while IIterators start at item 0.  Therefore, if this is the
+                // first access to the iterator we need to advance to the first item.
+                if (m_firstItem)
+                {
+                    m_firstItem = false;
+                    MoveNext();
+                }
+
+                return m_hasCurrent;
+            }
+        }
+
+        public bool MoveNext()
+        {
+            try
+            {
+                m_hasCurrent = m_enumerator.MoveNext();
+            }
+            catch (InvalidOperationException e)
+            {
+                throw WindowsRuntimeMarshal.GetExceptionForHR(HResults.E_CHANGED_STATE, e);
+            }
+
+            return m_hasCurrent;
+        }
+
+        public int GetMany(T[] items)
+        {
+            if (items == null)
+            {
+                return 0;
+            }
+
+            int index = 0;
+            while (index < items.Length && HasCurrent)
+            {
+                items[index] = Current;
+                MoveNext();
+                ++index;
+            }
+
+            if (typeof(T) == typeof(string))
+            {
+                string[] stringItems = items as string[];
+
+                // Fill the rest of the array with String.Empty to avoid marshaling failure
+                for (int i = index; i < items.Length; ++i)
+                    stringItems[i] = String.Empty;
+            }
+
+            return index;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/EventRegistrationToken.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/EventRegistrationToken.cs
new file mode 100644
index 0000000000..2aeeb44beb
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/EventRegistrationToken.cs
@@ -0,0 +1,63 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // Event registration tokens are 64 bit opaque structures returned from WinRT style event adders, in order
+    // to signify a registration of a particular delegate to an event.  The token's only real use is to
+    // unregister the same delgate from the event at a later time.
+    public struct EventRegistrationToken : IEquatable<EventRegistrationToken>
+    {
+        internal ulong m_value;
+
+        internal EventRegistrationToken(ulong value)
+        {
+            m_value = value;
+        }
+
+        internal ulong Value
+        {
+            get { return m_value; }
+        }
+
+        public static bool operator ==(EventRegistrationToken left, EventRegistrationToken right)
+        {
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(EventRegistrationToken left, EventRegistrationToken right)
+        {
+            return !left.Equals(right);
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (!(obj is EventRegistrationToken))
+            {
+                return false;
+            }
+
+            return ((EventRegistrationToken)obj).Value == Value;
+        }
+
+        public override int GetHashCode()
+        {
+            return m_value.GetHashCode();
+        }
+
+        bool IEquatable<EventRegistrationToken>.Equals(EventRegistrationToken other)
+        {
+            return Equals(other);
+        }
+
+        private bool Equals(EventRegistrationToken other)
+        {
+            return other.m_value == m_value;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/EventRegistrationTokenTable.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/EventRegistrationTokenTable.cs
new file mode 100644
index 0000000000..1a210a05cb
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/EventRegistrationTokenTable.cs
@@ -0,0 +1,255 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Threading;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // An event registration token table stores mappings from delegates to event tokens, in order to support
+    // sourcing WinRT style events from managed code.
+    public sealed class EventRegistrationTokenTable<T> where T : class
+    {
+        // Note this dictionary is also used as the synchronization object for this table
+        private Dictionary<EventRegistrationToken, T> m_tokens = new Dictionary<EventRegistrationToken, T>();
+
+        // Cached multicast delegate which will invoke all of the currently registered delegates.  This
+        // will be accessed frequently in common coding paterns, so we don't want to calculate it repeatedly.
+        private volatile T m_invokeList;
+
+        public EventRegistrationTokenTable()
+        {
+            // T must be a delegate type, but we cannot constrain on being a delegate.  Therefore, we'll do a
+            // static check at construction time
+            if (!typeof(Delegate).IsAssignableFrom(typeof(T)))
+            {
+                throw new InvalidOperationException(SR.Format(SR.InvalidOperation_EventTokenTableRequiresDelegate, typeof (T)));
+            }
+        }
+
+        // The InvocationList property provides access to a delegate which will invoke every registered event handler
+        // in this table.  If the property is set, the new value will replace any existing token registrations.
+        public T InvocationList
+        {
+            get
+            {
+                return m_invokeList;
+            }
+
+            set
+            {
+                lock (m_tokens)
+                {
+                    // The value being set replaces any of the existing values
+                    m_tokens.Clear();
+                    m_invokeList = null;
+
+                    if (value != null)
+                    {
+                        AddEventHandlerNoLock(value);
+                    }
+                }
+            }
+        }
+
+        public EventRegistrationToken AddEventHandler(T handler)
+        {
+            // Windows Runtime allows null handlers.  Assign those a token value of 0 for easy identity
+            if (handler == null)
+            {
+                return new EventRegistrationToken(0);
+            }
+
+            lock (m_tokens)
+            {
+                return AddEventHandlerNoLock(handler);
+            }
+        }
+
+        private EventRegistrationToken AddEventHandlerNoLock(T handler)
+        {
+            Debug.Assert(handler != null);
+
+            // Get a registration token, making sure that we haven't already used the value.  This should be quite
+            // rare, but in the case it does happen, just keep trying until we find one that's unused.
+            EventRegistrationToken token = GetPreferredToken(handler);
+            while (m_tokens.ContainsKey(token))
+            {
+                token = new EventRegistrationToken(token.Value + 1);
+            }
+            m_tokens[token] = handler;
+
+            // Update the current invocation list to include the newly added delegate
+            Delegate invokeList = (Delegate)(object)m_invokeList;
+            invokeList = MulticastDelegate.Combine(invokeList, (Delegate)(object)handler);
+            m_invokeList = (T)(object)invokeList;
+
+            return token;
+        }
+
+        // Get the delegate associated with an event registration token if it exists.  Additionally,
+        // remove the registration from the table at the same time.  If the token is not registered,
+        // Extract returns null and does not modify the table.
+        // [System.Runtime.CompilerServices.FriendAccessAllowed]
+        internal T ExtractHandler(EventRegistrationToken token)
+        {
+            T handler = null;
+            lock (m_tokens)
+            {
+                if (m_tokens.TryGetValue(token, out handler))
+                {
+                    RemoveEventHandlerNoLock(token);
+                }
+            }
+
+            return handler;
+        }
+
+        // Generate a token that may be used for a particular event handler.  We will frequently be called
+        // upon to look up a token value given only a delegate to start from.  Therefore, we want to make
+        // an initial token value that is easily determined using only the delegate instance itself.  Although
+        // in the common case this token value will be used to uniquely identify the handler, it is not
+        // the only possible token that can represent the handler.
+        //
+        // This means that both:
+        //  * if there is a handler assigned to the generated initial token value, it is not necessarily
+        //    this handler.
+        //  * if there is no handler assigned to the generated initial token value, the handler may still
+        //    be registered under a different token
+        //
+        // Effectively the only reasonable thing to do with this value is either to:
+        //  1. Use it as a good starting point for generating a token for handler
+        //  2. Use it as a guess to quickly see if the handler was really assigned this token value
+        private static EventRegistrationToken GetPreferredToken(T handler)
+        {
+            Debug.Assert(handler != null);
+
+            // We want to generate a token value that has the following properties:
+            //  1. is quickly obtained from the handler instance
+            //  2. uses bits in the upper 32 bits of the 64 bit value, in order to avoid bugs where code
+            //     may assume the value is realy just 32 bits
+            //  3. uses bits in the bottom 32 bits of the 64 bit value, in order to ensure that code doesn't
+            //     take a dependency on them always being 0.
+            //
+            // The simple algorithm chosen here is to simply assign the upper 32 bits the metadata token of the
+            // event handler type, and the lower 32 bits the hash code of the handler instance itself. Using the
+            // metadata token for the upper 32 bits gives us at least a small chance of being able to identify a
+            // totally corrupted token if we ever come across one in a minidump or other scenario.
+            //
+            // The hash code of a unicast delegate is not tied to the method being invoked, so in the case
+            // of a unicast delegate, the hash code of the target method is used instead of the full delegate
+            // hash code.
+            //
+            // While calculating this initial value will be somewhat more expensive than just using a counter
+            // for events that have few registrations, it will also gives us a shot at preventing unregistration
+            // from becoming an O(N) operation.
+            //
+            // We should feel free to change this algorithm as other requirements / optimizations become
+            // available.  This implementation is sufficiently random that code cannot simply guess the value to
+            // take a dependency upon it.  (Simply applying the hash-value algorithm directly won't work in the
+            // case of collisions, where we'll use a different token value).
+
+            uint handlerHashCode = 0;
+            Delegate[] invocationList = ((Delegate)(object)handler).GetInvocationList();
+            if (invocationList.Length == 1)
+            {
+                handlerHashCode = (uint)invocationList[0].Method.GetHashCode();
+            }
+            else
+            {
+                handlerHashCode = (uint)handler.GetHashCode();
+            }
+
+            ulong tokenValue = ((ulong)(uint)typeof(T).MetadataToken << 32) | handlerHashCode;
+            return new EventRegistrationToken(tokenValue);
+        }
+
+        public void RemoveEventHandler(EventRegistrationToken token)
+        {
+            // The 0 token is assigned to null handlers, so there's nothing to do
+            if (token.Value == 0)
+            {
+                return;
+            }
+
+            lock (m_tokens)
+            {
+                RemoveEventHandlerNoLock(token);
+            }
+        }
+
+        public void RemoveEventHandler(T handler)
+        {
+            // To match the Windows Runtime behaivor when adding a null handler, removing one is a no-op
+            if (handler == null)
+            {
+                return;
+            }
+
+            lock (m_tokens)
+            {
+                // Fast path - if the delegate is stored with its preferred token, then there's no need to do
+                // a full search of the table for it.  Note that even if we find something stored using the
+                // preferred token value, it's possible we have a collision and another delegate was using that
+                // value.  Therefore we need to make sure we really have the handler we want before taking the
+                // fast path.
+                EventRegistrationToken preferredToken = GetPreferredToken(handler);
+                T registeredHandler;
+                if (m_tokens.TryGetValue(preferredToken, out registeredHandler))
+                {
+                    if (registeredHandler == handler)
+                    {
+                        RemoveEventHandlerNoLock(preferredToken);
+                        return;
+                    }
+                }
+
+                // Slow path - we didn't find the delegate with its preferred token, so we need to fall
+                // back to a search of the table
+                foreach (KeyValuePair<EventRegistrationToken, T> registration in m_tokens)
+                {
+                    if (registration.Value == (T)(object)handler)
+                    {
+                        RemoveEventHandlerNoLock(registration.Key);
+
+                        // If a delegate has been added multiple times to handle an event, then it
+                        // needs to be removed the same number of times to stop handling the event.
+                        // Stop after the first one we find.
+                        return;
+                    }
+                }
+
+                // Note that falling off the end of the loop is not an error, as removing a registration
+                // for a handler that is not currently registered is simply a no-op
+            }
+        }
+
+        private void RemoveEventHandlerNoLock(EventRegistrationToken token)
+        {
+            T handler;
+            if (m_tokens.TryGetValue(token, out handler))
+            {
+                m_tokens.Remove(token);
+
+                // Update the current invocation list to remove the delegate
+                Delegate invokeList = (Delegate)(object)m_invokeList;
+                invokeList = MulticastDelegate.Remove(invokeList, (Delegate)(object)handler);
+                m_invokeList = (T)(object)invokeList;
+            }
+        }
+
+        public static EventRegistrationTokenTable<T> GetOrCreateEventRegistrationTokenTable(ref EventRegistrationTokenTable<T> refEventTable)
+        {
+            if (refEventTable == null)
+            {
+                Interlocked.CompareExchange(ref refEventTable, new EventRegistrationTokenTable<T>(), null);
+            }
+            return refEventTable;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IActivationFactory.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IActivationFactory.cs
new file mode 100644
index 0000000000..0ce01f8653
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IActivationFactory.cs
@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    [ComImport]
+    [Guid("00000035-0000-0000-C000-000000000046")]
+    [WindowsRuntimeImport]
+    public interface IActivationFactory
+    {
+        object ActivateInstance();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IClosable.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IClosable.cs
new file mode 100644
index 0000000000..7891fd4666
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IClosable.cs
@@ -0,0 +1,54 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Collections;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // Local definition of Windows.Foundation.IClosable
+    [ComImport]
+    [Guid("30d5a829-7fa4-4026-83bb-d75bae4ea99e")]
+    [WindowsRuntimeImport]
+    internal interface IClosable
+    {
+        void Close();
+    }
+
+    // Adapter class - converts IClosable.Close calls to Disposable.Dispose
+    internal sealed class IDisposableToIClosableAdapter
+    {
+        private IDisposableToIClosableAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        public void Close()
+        {
+            IDisposable _this = Unsafe.As<IDisposable>(this);
+            _this.Dispose();
+        }
+    }
+
+    // Adapter class which converts IDisposable.Dispose calls into IClosable.Close
+    internal sealed class IClosableToIDisposableAdapter
+    {
+        private IClosableToIDisposableAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        private void Dispose()
+        {
+            IClosable _this = Unsafe.As<IClosable>(this);
+            _this.Close();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ICustomProperty.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ICustomProperty.cs
new file mode 100644
index 0000000000..07fb8f171a
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ICustomProperty.cs
@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    [ComImport]
+    [Guid("30DA92C0-23E8-42A0-AE7C-734A0E5D2782")]
+    [WindowsRuntimeImport]
+    internal interface ICustomProperty
+    {
+        Type Type
+        {
+            get;
+        }
+
+        string Name
+        {
+            get;
+        }
+
+        object GetValue(object target);
+
+        void SetValue(object target, object value);
+
+        object GetValue(object target, object indexValue);
+
+        void SetValue(object target, object value, object indexValue);
+
+        bool CanWrite
+        {
+            get;
+        }
+
+        bool CanRead
+        {
+            get;
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ICustomPropertyProvider.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ICustomPropertyProvider.cs
new file mode 100644
index 0000000000..bcc8590bb2
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ICustomPropertyProvider.cs
@@ -0,0 +1,535 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.StubHelpers;
+using System.Reflection;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Collections;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Security;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    //
+    // ICustomProperty Implementation helpers
+    //
+    internal static class ICustomPropertyProviderImpl
+    {
+        //
+        // Creates a ICustomProperty implementation for Jupiter
+        // Called from ICustomPropertyProvider_GetProperty from within runtime
+        //
+        internal static ICustomProperty CreateProperty(object target, string propertyName)
+        {
+            Debug.Assert(target != null);
+            Debug.Assert(propertyName != null);
+
+            IGetProxyTarget proxy = target as IGetProxyTarget;
+            if (proxy != null)
+                target = proxy.GetTarget();
+
+            // Only return public instance/static properties
+            PropertyInfo propertyInfo = target.GetType().GetProperty(
+                propertyName,
+                BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public);
+
+            if (propertyInfo == null)
+                return null;
+            else
+                return new CustomPropertyImpl(propertyInfo);
+        }
+
+        //
+        // Creates a ICustomProperty implementation for Jupiter
+        // Called from ICustomPropertyProvider_GetIndexedProperty from within runtime
+        //               
+        internal static unsafe ICustomProperty CreateIndexedProperty(object target, string propertyName, TypeNameNative* pIndexedParamType)
+        {
+            Debug.Assert(target != null);
+            Debug.Assert(propertyName != null);
+
+            Type indexedParamType = null;
+            SystemTypeMarshaler.ConvertToManaged(pIndexedParamType, ref indexedParamType);
+
+            return CreateIndexedProperty(target, propertyName, indexedParamType);
+        }
+
+        internal static ICustomProperty CreateIndexedProperty(object target, string propertyName, Type indexedParamType)
+        {
+            Debug.Assert(target != null);
+            Debug.Assert(propertyName != null);
+
+            IGetProxyTarget proxy = target as IGetProxyTarget;
+            if (proxy != null)
+                target = proxy.GetTarget();
+
+            // Only return public instance/static properties
+            PropertyInfo propertyInfo = target.GetType().GetProperty(
+                propertyName,
+                BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public,
+                null,                                                                   // default binder
+                null,                                                                   // ignore return type
+                new Type[] { indexedParamType },                                        // indexed parameter type
+                null                                                                    // ignore type modifier
+                );
+
+            if (propertyInfo == null)
+                return null;
+            else
+                return new CustomPropertyImpl(propertyInfo);
+        }
+
+        internal static unsafe void GetType(object target, TypeNameNative* pIndexedParamType)
+        {
+            IGetProxyTarget proxy = target as IGetProxyTarget;
+            if (proxy != null)
+                target = proxy.GetTarget();
+
+            SystemTypeMarshaler.ConvertToNative(target.GetType(), pIndexedParamType);
+        }
+    }
+
+    [Flags]
+    internal enum InterfaceForwardingSupport
+    {
+        None = 0,
+        IBindableVector = 0x1,              // IBindableVector -> IBindableVector
+        IVector = 0x2,              // IBindableVector -> IVector<T>
+        IBindableVectorView = 0x4,              // IBindableVectorView -> IBindableVectorView
+        IVectorView = 0x8,              // IBindableVectorView -> IVectorView<T>
+        IBindableIterableOrIIterable = 0x10              // IBindableIterable -> IBindableIterable/IIterable<T>
+    }
+
+    //
+    // Interface for data binding code (CustomPropertyImpl) to retreive the target object
+    // See CustomPropertyImpl.InvokeInternal for details
+    //
+    internal interface IGetProxyTarget
+    {
+        object GetTarget();
+    }
+
+    //
+    // Proxy that supports data binding on another object
+    //
+    // This serves two purposes:
+    //
+    // 1. Delegate data binding interfaces to another object
+    // Note that this proxy implements the native interfaces directly to avoid unnecessary overhead 
+    // (such as the adapter code that addresses behavior differences between IBindableVector & List
+    // as well as simplify forwarding code (except for IEnumerable)
+    //
+    // 2. ICLRServices.CreateManagedReference will hand out ICCW* of a new instance of this object
+    // and will hold the other object alive
+    //
+    //
+    internal class ICustomPropertyProviderProxy<T1, T2> : IGetProxyTarget,
+                                                          ICustomQueryInterface,
+                                                          IEnumerable,          // IBindableIterable -> IBindableIterable/IIterable<T>
+                                                          IBindableVector,      // IBindableVector -> IBindableVector/IVector<T>
+                                                          IBindableVectorView   // IBindableVectorView -> IBindableVectorView/IVectorView<T>
+    {
+        private object _target;
+        private InterfaceForwardingSupport _flags;
+
+        internal ICustomPropertyProviderProxy(object target, InterfaceForwardingSupport flags)
+        {
+            _target = target;
+            _flags = flags;
+        }
+
+        //
+        // Creates a new instance of ICustomPropertyProviderProxy<T1, T2> and assign appropriate
+        // flags
+        //
+        internal static object CreateInstance(object target)
+        {
+            InterfaceForwardingSupport supportFlags = InterfaceForwardingSupport.None;
+
+            //
+            // QI and figure out the right flags
+            //
+            if (target as IList != null)
+                supportFlags |= InterfaceForwardingSupport.IBindableVector;
+
+            // NOTE: We need to use the directed type here
+            // If we use IVector_Raw<T1> here, it derives from a different IIterable<T> which the runtime
+            // doesn't recognize, and therefore IEnumerable cast won't be able to take advantage of this QI
+            if (target as IList<T1> != null)
+                supportFlags |= InterfaceForwardingSupport.IVector;
+
+            if (target as IBindableVectorView != null)
+                supportFlags |= InterfaceForwardingSupport.IBindableVectorView;
+
+            // NOTE: We need to use the redirected type here
+            // If we use IVector_Raw<T1> here, it derives from a different IIterable<T> which the runtime
+            // doesn't recognize, and therefore IEnumerable cast won't be able to take advantage of this QI
+            if (target as IReadOnlyList<T2> != null)
+                supportFlags |= InterfaceForwardingSupport.IVectorView;
+
+            // Verify IEnumerable last because the first few QIs might succeed and we need
+            // IEnumerable cast to use that cache (instead of having ICustomPropertyProvider to
+            // forward it manually)
+            // For example, if we try to shoot in the dark by trying IVector<IInspectable> and it 
+            // succeeded, IEnumerable needs to know that
+            if (target as IEnumerable != null)
+                supportFlags |= InterfaceForwardingSupport.IBindableIterableOrIIterable;
+
+            return new ICustomPropertyProviderProxy<T1, T2>(target, supportFlags);
+        }
+
+
+        //
+        // override ToString() to make sure callers get correct IStringable.ToString() behavior in native code
+        //
+        public override string ToString()
+        {
+            return WindowsRuntime.IStringableHelper.ToString(_target);
+        }
+
+        //
+        // IGetProxyTarget - unwraps the target object and use it for data binding
+        // 
+        object IGetProxyTarget.GetTarget()
+        {
+            return _target;
+        }
+
+        // 
+        // ICustomQueryInterface methods
+        //    
+        public CustomQueryInterfaceResult GetInterface([In]ref Guid iid, out IntPtr ppv)
+        {
+            ppv = IntPtr.Zero;
+
+            if (iid == typeof(IBindableIterable).GUID)
+            {
+                // Reject the QI if target doesn't implement IEnumerable
+                if ((_flags & (InterfaceForwardingSupport.IBindableIterableOrIIterable)) == 0)
+                    return CustomQueryInterfaceResult.Failed;
+            }
+
+            if (iid == typeof(IBindableVector).GUID)
+            {
+                // Reject the QI if target doesn't implement IBindableVector/IVector
+                if ((_flags & (InterfaceForwardingSupport.IBindableVector | InterfaceForwardingSupport.IVector)) == 0)
+                    return CustomQueryInterfaceResult.Failed;
+            }
+
+            if (iid == typeof(IBindableVectorView).GUID)
+            {
+                // Reject the QI if target doesn't implement IBindableVectorView/IVectorView
+                if ((_flags & (InterfaceForwardingSupport.IBindableVectorView | InterfaceForwardingSupport.IVectorView)) == 0)
+                    return CustomQueryInterfaceResult.Failed;
+            }
+
+            return CustomQueryInterfaceResult.NotHandled;
+        }
+
+        //
+        // IEnumerable methods
+        //
+        public IEnumerator GetEnumerator()
+        {
+            return ((IEnumerable)_target).GetEnumerator();
+        }
+
+        //
+        // IBindableVector implementation (forwards to IBindableVector / IVector<T>)
+        //        
+        object IBindableVector.GetAt(uint index)
+        {
+            IBindableVector bindableVector = GetIBindableVectorNoThrow();
+            if (bindableVector != null)
+            {
+                // IBindableVector -> IBindableVector
+                return bindableVector.GetAt(index);
+            }
+            else
+            {
+                // IBindableVector -> IVector<T>
+                return GetVectorOfT().GetAt(index);
+            }
+        }
+
+        uint IBindableVector.Size
+        {
+            get
+            {
+                IBindableVector bindableVector = GetIBindableVectorNoThrow();
+                if (bindableVector != null)
+                {
+                    // IBindableVector -> IBindableVector
+                    return bindableVector.Size;
+                }
+                else
+                {
+                    // IBindableVector -> IVector<T>
+                    return GetVectorOfT().Size;
+                }
+            }
+        }
+
+        IBindableVectorView IBindableVector.GetView()
+        {
+            IBindableVector bindableVector = GetIBindableVectorNoThrow();
+            if (bindableVector != null)
+            {
+                // IBindableVector -> IBindableVector
+                return bindableVector.GetView();
+            }
+            else
+            {
+                // IBindableVector -> IVector<T>
+                return new IVectorViewToIBindableVectorViewAdapter<T1>(GetVectorOfT().GetView());
+            }
+        }
+
+        private sealed class IVectorViewToIBindableVectorViewAdapter<T> : IBindableVectorView
+        {
+            private IVectorView<T> _vectorView;
+
+            public IVectorViewToIBindableVectorViewAdapter(IVectorView<T> vectorView)
+            {
+                _vectorView = vectorView;
+            }
+
+            object IBindableVectorView.GetAt(uint index)
+            {
+                return _vectorView.GetAt(index);
+            }
+
+            uint IBindableVectorView.Size
+            {
+                get
+                {
+                    return _vectorView.Size;
+                }
+            }
+
+            bool IBindableVectorView.IndexOf(object value, out uint index)
+            {
+                return _vectorView.IndexOf(ConvertTo<T>(value), out index);
+            }
+
+            IBindableIterator IBindableIterable.First()
+            {
+                return new IteratorOfTToIteratorAdapter<T>(_vectorView.First());
+            }
+        }
+
+        bool IBindableVector.IndexOf(object value, out uint index)
+        {
+            IBindableVector bindableVector = GetIBindableVectorNoThrow();
+            if (bindableVector != null)
+            {
+                // IBindableVector -> IBindableVector
+                return bindableVector.IndexOf(value, out index);
+            }
+            else
+            {
+                // IBindableVector -> IVector<T>
+                return GetVectorOfT().IndexOf(ConvertTo<T1>(value), out index);
+            }
+        }
+
+        void IBindableVector.SetAt(uint index, object value)
+        {
+            IBindableVector bindableVector = GetIBindableVectorNoThrow();
+            if (bindableVector != null)
+            {
+                // IBindableVector -> IBindableVector
+                bindableVector.SetAt(index, value);
+            }
+            else
+            {
+                // IBindableVector -> IVector<T>
+                GetVectorOfT().SetAt(index, ConvertTo<T1>(value));
+            }
+        }
+
+        void IBindableVector.InsertAt(uint index, object value)
+        {
+            IBindableVector bindableVector = GetIBindableVectorNoThrow();
+            if (bindableVector != null)
+            {
+                // IBindableVector -> IBindableVector
+                bindableVector.InsertAt(index, value);
+            }
+            else
+            {
+                // IBindableVector -> IVector<T>
+                GetVectorOfT().InsertAt(index, ConvertTo<T1>(value));
+            }
+        }
+
+        void IBindableVector.RemoveAt(uint index)
+        {
+            IBindableVector bindableVector = GetIBindableVectorNoThrow();
+            if (bindableVector != null)
+            {
+                // IBindableVector -> IBindableVector
+                bindableVector.RemoveAt(index);
+            }
+            else
+            {
+                // IBindableVector -> IVector<T>
+                GetVectorOfT().RemoveAt(index);
+            }
+        }
+
+        void IBindableVector.Append(object value)
+        {
+            IBindableVector bindableVector = GetIBindableVectorNoThrow();
+            if (bindableVector != null)
+            {
+                // IBindableVector -> IBindableVector
+                bindableVector.Append(value);
+            }
+            else
+            {
+                // IBindableVector -> IVector<T>
+                GetVectorOfT().Append(ConvertTo<T1>(value));
+            }
+        }
+
+        void IBindableVector.RemoveAtEnd()
+        {
+            IBindableVector bindableVector = GetIBindableVectorNoThrow();
+            if (bindableVector != null)
+            {
+                // IBindableVector -> IBindableVector
+                bindableVector.RemoveAtEnd();
+            }
+            else
+            {
+                // IBindableVector -> IVector<T>
+                GetVectorOfT().RemoveAtEnd();
+            }
+        }
+
+        void IBindableVector.Clear()
+        {
+            IBindableVector bindableVector = GetIBindableVectorNoThrow();
+            if (bindableVector != null)
+            {
+                // IBindableVector -> IBindableVector
+                bindableVector.Clear();
+            }
+            else
+            {
+                // IBindableVector -> IVector<T>
+                GetVectorOfT().Clear();
+            }
+        }
+
+        private IBindableVector GetIBindableVectorNoThrow()
+        {
+            if ((_flags & InterfaceForwardingSupport.IBindableVector) != 0)
+                return Unsafe.As<IBindableVector>(_target);
+            else
+                return null;
+        }
+
+        private IVector_Raw<T1> GetVectorOfT()
+        {
+            if ((_flags & InterfaceForwardingSupport.IVector) != 0)
+                return Unsafe.As<IVector_Raw<T1>>(_target);
+            else
+                throw new InvalidOperationException();  // We should not go down this path, unless Jupiter pass this out to managed code
+                                                        // and managed code use reflection to do the cast
+        }
+
+        //
+        // IBindableVectorView implementation (forwarding to IBindableVectorView or IVectorView<T>)
+        //
+        object IBindableVectorView.GetAt(uint index)
+        {
+            IBindableVectorView bindableVectorView = GetIBindableVectorViewNoThrow();
+            if (bindableVectorView != null)
+                return bindableVectorView.GetAt(index);
+            else
+                return GetVectorViewOfT().GetAt(index);
+        }
+
+        uint IBindableVectorView.Size
+        {
+            get
+            {
+                IBindableVectorView bindableVectorView = GetIBindableVectorViewNoThrow();
+                if (bindableVectorView != null)
+                    return bindableVectorView.Size;
+                else
+                    return GetVectorViewOfT().Size;
+            }
+        }
+
+        bool IBindableVectorView.IndexOf(object value, out uint index)
+        {
+            IBindableVectorView bindableVectorView = GetIBindableVectorViewNoThrow();
+            if (bindableVectorView != null)
+                return bindableVectorView.IndexOf(value, out index);
+            else
+                return GetVectorViewOfT().IndexOf(ConvertTo<T2>(value), out index);
+        }
+
+        IBindableIterator IBindableIterable.First()
+        {
+            IBindableVectorView bindableVectorView = GetIBindableVectorViewNoThrow();
+            if (bindableVectorView != null)
+                return bindableVectorView.First();
+            else
+                return new IteratorOfTToIteratorAdapter<T2>(GetVectorViewOfT().First());
+        }
+
+        private sealed class IteratorOfTToIteratorAdapter<T> : IBindableIterator
+        {
+            private IIterator<T> _iterator;
+
+            public IteratorOfTToIteratorAdapter(IIterator<T> iterator)
+            { _iterator = iterator; }
+
+            public bool HasCurrent { get { return _iterator.HasCurrent; } }
+            public object Current { get { return (object)_iterator.Current; } }
+            public bool MoveNext() { return _iterator.MoveNext(); }
+        }
+
+        private IBindableVectorView GetIBindableVectorViewNoThrow()
+        {
+            if ((_flags & InterfaceForwardingSupport.IBindableVectorView) != 0)
+                return Unsafe.As<IBindableVectorView>(_target);
+            else
+                return null;
+        }
+
+        private IVectorView<T2> GetVectorViewOfT()
+        {
+            if ((_flags & InterfaceForwardingSupport.IVectorView) != 0)
+                return Unsafe.As<IVectorView<T2>>(_target);
+            else
+                throw new InvalidOperationException();  // We should not go down this path, unless Jupiter pass this out to managed code
+                                                        // and managed code use reflection to do the cast
+        }
+
+        //
+        // Convert to type T
+        //
+        private static T ConvertTo<T>(object value)
+        {
+            // Throw ArgumentNullException if value is null (otherwise we'll throw NullReferenceException
+            // when casting value to T)
+            ThrowHelper.IfNullAndNullsAreIllegalThenThrow<T>(value, ExceptionArgument.value);
+
+            // No coersion support needed. If we need coersion later, this is the place
+            return (T)value;
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IIterable.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IIterable.cs
new file mode 100644
index 0000000000..a44591245f
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IIterable.cs
@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Collections.Generic;
+
+// Windows.Foundation.Collections.IIterable`1 cannot be referenced from managed code because it's hidden
+// by the metadata adapter. We redeclare the interface manually to be able to talk to native WinRT objects.
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    [ComImport]
+    [Guid("faa585ea-6214-4217-afda-7f46de5869b3")]
+    [WindowsRuntimeImport]
+    internal interface IIterable<T> : IEnumerable<T>
+    {
+        IIterator<T> First();
+    }
+
+    [ComImport]
+    [Guid("036d2c08-df29-41af-8aa2-d774be62ba6f")]
+    [WindowsRuntimeImport]
+    internal interface IBindableIterable
+    {
+        IBindableIterator First();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IIterator.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IIterator.cs
new file mode 100644
index 0000000000..00d622b711
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IIterator.cs
@@ -0,0 +1,48 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    [ComImport]
+    [WindowsRuntimeImport]
+    [Guid("6a79e863-4300-459a-9966-cbb660963ee1")]
+    internal interface IIterator<T>
+    {
+        T Current
+        {
+            get;
+        }
+
+        bool HasCurrent
+        {
+            get;
+        }
+
+        bool MoveNext();
+
+        int GetMany([Out] T[] items);
+    }
+
+    [ComImport]
+    [WindowsRuntimeImport]
+    [Guid("6a1d6c07-076d-49f2-8314-f52c9c9a8331")]
+    internal interface IBindableIterator
+    {
+        object Current
+        {
+            get;
+        }
+
+        bool HasCurrent
+        {
+            get;
+        }
+
+        bool MoveNext();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IMap.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IMap.cs
new file mode 100644
index 0000000000..02dff54eac
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IMap.cs
@@ -0,0 +1,49 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Collections.Generic;
+
+// Windows.Foundation.Collections.IMap`2, IMapView`2, and IKeyValuePair`2 cannot be referenced from
+// managed code because they're hidden by the metadata adapter. We redeclare the interfaces manually
+// to be able to talk to native WinRT objects.
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    [ComImport]
+    [Guid("3c2925fe-8519-45c1-aa79-197b6718c1c1")]
+    [WindowsRuntimeImport]
+    internal interface IMap<K, V> : IIterable<IKeyValuePair<K, V>>
+    {
+        V Lookup(K key);
+        uint Size { get; }
+        bool HasKey(K key);
+        IReadOnlyDictionary<K, V> GetView();  // Really an IMapView<K, V>
+        bool Insert(K key, V value);
+        void Remove(K key);
+        void Clear();
+    }
+
+    [ComImport]
+    [Guid("e480ce40-a338-4ada-adcf-272272e48cb9")]
+    [WindowsRuntimeImport]
+    internal interface IMapView<K, V> : IIterable<IKeyValuePair<K, V>>
+    {
+        V Lookup(K key);
+        uint Size { get; }
+        bool HasKey(K key);
+        void Split(out IMapView<K, V> first, out IMapView<K, V> second);
+    }
+
+    [ComImport]
+    [Guid("02b51929-c1c4-4a7e-8940-0312b5c18500")]
+    [WindowsRuntimeImport]
+    internal interface IKeyValuePair<K, V>
+    {
+        K Key { get; }
+        V Value { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IMapViewToIReadOnlyDictionaryAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IMapViewToIReadOnlyDictionaryAdapter.cs
new file mode 100644
index 0000000000..e131d5651b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IMapViewToIReadOnlyDictionaryAdapter.cs
@@ -0,0 +1,316 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // This is a set of stub methods implementing the support for the IReadOnlyDictionary`2 interface on WinRT
+    // objects that support IMapView`2. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not IMapViewToIReadOnlyDictionaryAdapter objects. Rather, they are of type
+    // IMapView<K, V>. No actual IMapViewToIReadOnlyDictionaryAdapter object is ever instantiated. Thus, you will see
+    // a lot of expressions that cast "this" to "IMapView<K, V>".
+    [DebuggerDisplay("Count = {Count}")]
+    internal sealed class IMapViewToIReadOnlyDictionaryAdapter
+    {
+        private IMapViewToIReadOnlyDictionaryAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // V this[K key] { get }
+        internal V Indexer_Get<K, V>(K key)
+        {
+            if (key == null)
+                throw new ArgumentNullException(nameof(key));
+
+            IMapView<K, V> _this = Unsafe.As<IMapView<K, V>>(this);
+            return Lookup(_this, key);
+        }
+
+        // IEnumerable<K> Keys { get }
+        internal IEnumerable<K> Keys<K, V>()
+        {
+            IMapView<K, V> _this = Unsafe.As<IMapView<K, V>>(this);
+            IReadOnlyDictionary<K, V> roDictionary = (IReadOnlyDictionary<K, V>)_this;
+            return new ReadOnlyDictionaryKeyCollection<K, V>(roDictionary);
+        }
+
+        // IEnumerable<V> Values { get }
+        internal IEnumerable<V> Values<K, V>()
+        {
+            IMapView<K, V> _this = Unsafe.As<IMapView<K, V>>(this);
+            IReadOnlyDictionary<K, V> roDictionary = (IReadOnlyDictionary<K, V>)_this;
+            return new ReadOnlyDictionaryValueCollection<K, V>(roDictionary);
+        }
+
+        // bool ContainsKey(K key)
+        internal bool ContainsKey<K, V>(K key)
+        {
+            if (key == null)
+                throw new ArgumentNullException(nameof(key));
+
+            IMapView<K, V> _this = Unsafe.As<IMapView<K, V>>(this);
+            return _this.HasKey(key);
+        }
+
+        // bool TryGetValue(TKey key, out TValue value)
+        internal bool TryGetValue<K, V>(K key, out V value)
+        {
+            if (key == null)
+                throw new ArgumentNullException(nameof(key));
+
+            IMapView<K, V> _this = Unsafe.As<IMapView<K, V>>(this);
+
+            // It may be faster to call HasKey then Lookup.  On failure, we would otherwise
+            // throw an exception from Lookup.
+            if (!_this.HasKey(key))
+            {
+                value = default(V);
+                return false;
+            }
+
+            try
+            {
+                value = _this.Lookup(key);
+                return true;
+            }
+            catch (Exception ex)  // Still may hit this case due to a race condition
+            {
+                if (HResults.E_BOUNDS == ex._HResult)
+                {
+                    value = default(V);
+                    return false;
+                }
+                throw;
+            }
+        }
+
+        #region Helpers
+
+        private static V Lookup<K, V>(IMapView<K, V> _this, K key)
+        {
+            Debug.Assert(null != key);
+
+            try
+            {
+                return _this.Lookup(key);
+            }
+            catch (Exception ex)
+            {
+                if (HResults.E_BOUNDS == ex._HResult)
+                    throw new KeyNotFoundException(SR.Format(SR.Arg_KeyNotFoundWithKey, key.ToString()));
+                throw;
+            }
+        }
+
+        #endregion Helpers
+    }
+
+    // Note: One day we may make these return IReadOnlyCollection<T>
+    [DebuggerDisplay("Count = {Count}")]
+    internal sealed class ReadOnlyDictionaryKeyCollection<TKey, TValue> : IEnumerable<TKey>
+    {
+        private readonly IReadOnlyDictionary<TKey, TValue> dictionary;
+
+        public ReadOnlyDictionaryKeyCollection(IReadOnlyDictionary<TKey, TValue> dictionary)
+        {
+            if (dictionary == null)
+                throw new ArgumentNullException(nameof(dictionary));
+
+            this.dictionary = dictionary;
+        }
+
+        /*
+        public void CopyTo(TKey[] array, int index)
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array));
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index));
+            if (array.Length <= index && this.Count > 0)
+                throw new ArgumentException(SR.Arg_IndexOutOfRangeException);
+            if (array.Length - index < dictionary.Count)
+                throw new ArgumentException(SR.Argument_InsufficientSpaceToCopyCollection);
+
+            int i = index;
+            foreach (KeyValuePair<TKey, TValue> mapping in dictionary)
+            {
+                array[i++] = mapping.Key;
+            }
+        }
+        
+        public int Count {
+            get { return dictionary.Count; }
+        }
+
+        public bool Contains(TKey item)
+        {
+            return dictionary.ContainsKey(item);
+        }
+        */
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return ((IEnumerable<TKey>)this).GetEnumerator();
+        }
+
+        public IEnumerator<TKey> GetEnumerator()
+        {
+            return new ReadOnlyDictionaryKeyEnumerator<TKey, TValue>(dictionary);
+        }
+    }  // public class ReadOnlyDictionaryKeyCollection<TKey, TValue>
+
+
+    internal sealed class ReadOnlyDictionaryKeyEnumerator<TKey, TValue> : IEnumerator<TKey>
+    {
+        private readonly IReadOnlyDictionary<TKey, TValue> dictionary;
+        private IEnumerator<KeyValuePair<TKey, TValue>> enumeration;
+
+        public ReadOnlyDictionaryKeyEnumerator(IReadOnlyDictionary<TKey, TValue> dictionary)
+        {
+            if (dictionary == null)
+                throw new ArgumentNullException(nameof(dictionary));
+
+            this.dictionary = dictionary;
+            enumeration = dictionary.GetEnumerator();
+        }
+
+        void IDisposable.Dispose()
+        {
+            enumeration.Dispose();
+        }
+
+        public bool MoveNext()
+        {
+            return enumeration.MoveNext();
+        }
+
+        Object IEnumerator.Current
+        {
+            get { return ((IEnumerator<TKey>)this).Current; }
+        }
+
+        public TKey Current
+        {
+            get { return enumeration.Current.Key; }
+        }
+
+        public void Reset()
+        {
+            enumeration = dictionary.GetEnumerator();
+        }
+    }  // class ReadOnlyDictionaryKeyEnumerator<TKey, TValue>
+
+
+    [DebuggerDisplay("Count = {Count}")]
+    internal sealed class ReadOnlyDictionaryValueCollection<TKey, TValue> : IEnumerable<TValue>
+    {
+        private readonly IReadOnlyDictionary<TKey, TValue> dictionary;
+
+        public ReadOnlyDictionaryValueCollection(IReadOnlyDictionary<TKey, TValue> dictionary)
+        {
+            if (dictionary == null)
+                throw new ArgumentNullException(nameof(dictionary));
+
+            this.dictionary = dictionary;
+        }
+
+        /*
+        public void CopyTo(TValue[] array, int index)
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array));
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index));
+            if (array.Length <= index && this.Count > 0)
+                throw new ArgumentException(SR.Arg_IndexOutOfRangeException);
+            if (array.Length - index < dictionary.Count)
+                throw new ArgumentException(SR.Argument_InsufficientSpaceToCopyCollection);
+
+            int i = index;
+            foreach (KeyValuePair<TKey, TValue> mapping in dictionary)
+            {
+                array[i++] = mapping.Value;
+            }
+        }
+
+        public int Count {
+            get { return dictionary.Count; }
+        }
+
+        public bool Contains(TValue item)
+        {
+            EqualityComparer<TValue> comparer = EqualityComparer<TValue>.Default;
+            foreach (TValue value in this)
+                if (comparer.Equals(item, value))
+                    return true;
+            return false;
+        }
+        */
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return ((IEnumerable<TValue>)this).GetEnumerator();
+        }
+
+        public IEnumerator<TValue> GetEnumerator()
+        {
+            return new ReadOnlyDictionaryValueEnumerator<TKey, TValue>(dictionary);
+        }
+    }  // public class ReadOnlyDictionaryValueCollection<TKey, TValue>
+
+
+    internal sealed class ReadOnlyDictionaryValueEnumerator<TKey, TValue> : IEnumerator<TValue>
+    {
+        private readonly IReadOnlyDictionary<TKey, TValue> dictionary;
+        private IEnumerator<KeyValuePair<TKey, TValue>> enumeration;
+
+        public ReadOnlyDictionaryValueEnumerator(IReadOnlyDictionary<TKey, TValue> dictionary)
+        {
+            if (dictionary == null)
+                throw new ArgumentNullException(nameof(dictionary));
+
+            this.dictionary = dictionary;
+            enumeration = dictionary.GetEnumerator();
+        }
+
+        void IDisposable.Dispose()
+        {
+            enumeration.Dispose();
+        }
+
+        public bool MoveNext()
+        {
+            return enumeration.MoveNext();
+        }
+
+        Object IEnumerator.Current
+        {
+            get { return ((IEnumerator<TValue>)this).Current; }
+        }
+
+        public TValue Current
+        {
+            get { return enumeration.Current.Value; }
+        }
+
+        public void Reset()
+        {
+            enumeration = dictionary.GetEnumerator();
+        }
+    }  // class ReadOnlyDictionaryValueEnumerator<TKey, TValue>
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IPropertyValue.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IPropertyValue.cs
new file mode 100644
index 0000000000..8a67119496
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IPropertyValue.cs
@@ -0,0 +1,129 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    [ComImport]
+    [Guid("4bd682dd-7554-40e9-9a9b-82654ede7e62")]
+    [WindowsRuntimeImport]
+    internal interface IPropertyValue
+    {
+        PropertyType Type
+        {
+            get;
+        }
+
+        bool IsNumericScalar
+        {
+            get;
+        }
+
+        Byte GetUInt8();
+
+        Int16 GetInt16();
+
+        UInt16 GetUInt16();
+
+        Int32 GetInt32();
+
+        UInt32 GetUInt32();
+
+        Int64 GetInt64();
+
+        UInt64 GetUInt64();
+
+        Single GetSingle();
+
+        Double GetDouble();
+
+        char GetChar16();
+
+        Boolean GetBoolean();
+
+        String GetString();
+
+        Guid GetGuid();
+
+        DateTimeOffset GetDateTime();
+
+        TimeSpan GetTimeSpan();
+
+        Point GetPoint();
+
+        Size GetSize();
+
+        Rect GetRect();
+
+        Byte[] GetUInt8Array();
+
+        Int16[] GetInt16Array();
+
+        UInt16[] GetUInt16Array();
+
+        Int32[] GetInt32Array();
+
+        UInt32[] GetUInt32Array();
+
+        Int64[] GetInt64Array();
+
+        UInt64[] GetUInt64Array();
+
+        Single[] GetSingleArray();
+
+        Double[] GetDoubleArray();
+
+        char[] GetChar16Array();
+
+        Boolean[] GetBooleanArray();
+
+        String[] GetStringArray();
+
+        object[] GetInspectableArray();
+
+        Guid[] GetGuidArray();
+
+        DateTimeOffset[] GetDateTimeArray();
+
+        TimeSpan[] GetTimeSpanArray();
+
+        Point[] GetPointArray();
+
+        Size[] GetSizeArray();
+
+        Rect[] GetRectArray();
+    }
+
+    // Specify size directly instead of fields to avoid warnings
+    [StructLayoutAttribute(LayoutKind.Sequential, Size = 8)]
+    [WindowsRuntimeImport]
+    internal struct Point
+    {
+        // float X;
+        // float Y;        
+    }
+
+    // Specify size directly instead of fields to avoid warnings
+    [StructLayoutAttribute(LayoutKind.Sequential, Size = 8)]
+    [WindowsRuntimeImport]
+    internal struct Size
+    {
+        // float Width;
+        // float Height;   
+    }
+
+    // Specify size directly instead of fields to avoid warnings
+    [StructLayoutAttribute(LayoutKind.Sequential, Size = 16)]
+    [WindowsRuntimeImport]
+    internal struct Rect
+    {
+        // float X;
+        // float Y;
+        // float Width;
+        // float Height;        
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IReadOnlyDictionaryToIMapViewAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IReadOnlyDictionaryToIMapViewAdapter.cs
new file mode 100644
index 0000000000..0c8462f340
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IReadOnlyDictionaryToIMapViewAdapter.cs
@@ -0,0 +1,85 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // This is a set of stub methods implementing the support for the IMapView`2 interface on managed
+    // objects that implement IReadOnlyDictionary`2. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not IReadOnlyDictionaryToIMapViewAdapter objects. Rather, they are of type
+    // IReadOnlyDictionary<K, V>. No actual IReadOnlyDictionaryToIMapViewAdapter object is ever instantiated. Thus, you will
+    // see a lot of expressions that cast "this" to "IReadOnlyDictionary<K, V>". 
+    [DebuggerDisplay("Size = {Size}")]
+    internal sealed class IReadOnlyDictionaryToIMapViewAdapter
+    {
+        private IReadOnlyDictionaryToIMapViewAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // V Lookup(K key)
+        internal V Lookup<K, V>(K key)
+        {
+            IReadOnlyDictionary<K, V> _this = Unsafe.As<IReadOnlyDictionary<K, V>>(this);
+            V value;
+            bool keyFound = _this.TryGetValue(key, out value);
+
+            if (!keyFound)
+            {
+                Exception e = new KeyNotFoundException(SR.Format(SR.Arg_KeyNotFoundWithKey, key.ToString()));
+                e.SetErrorCode(HResults.E_BOUNDS);
+                throw e;
+            }
+
+            return value;
+        }
+
+        // uint Size { get }
+        internal uint Size<K, V>()
+        {
+            IReadOnlyDictionary<K, V> _this = Unsafe.As<IReadOnlyDictionary<K, V>>(this);
+            return (uint)_this.Count;
+        }
+
+        // bool HasKey(K key)
+        internal bool HasKey<K, V>(K key)
+        {
+            IReadOnlyDictionary<K, V> _this = Unsafe.As<IReadOnlyDictionary<K, V>>(this);
+            return _this.ContainsKey(key);
+        }
+
+        // void Split(out IMapView<K, V> first, out IMapView<K, V> second)
+        internal void Split<K, V>(out IMapView<K, V> first, out IMapView<K, V> second)
+        {
+            IReadOnlyDictionary<K, V> _this = Unsafe.As<IReadOnlyDictionary<K, V>>(this);
+
+            if (_this.Count < 2)
+            {
+                first = null;
+                second = null;
+                return;
+            }
+
+            ConstantSplittableMap<K, V> splittableMap = _this as ConstantSplittableMap<K, V>;
+
+            if (splittableMap == null)
+                splittableMap = new ConstantSplittableMap<K, V>(_this);
+
+            splittableMap.Split(out first, out second);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IReadOnlyListToIVectorViewAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IReadOnlyListToIVectorViewAdapter.cs
new file mode 100644
index 0000000000..be52bce681
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IReadOnlyListToIVectorViewAdapter.cs
@@ -0,0 +1,137 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // This is a set of stub methods implementing the support for the IVectorView`1 interface on managed
+    // objects that implement IReadOnlyList`1. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not IReadOnlyListToIVectorViewAdapter objects. Rather, they are of type
+    // IReadOnlyList<T>. No actual IReadOnlyListToIVectorViewAdapter object is ever instantiated. Thus, you will
+    // see a lot of expressions that cast "this" to "IReadOnlyList<T>". 
+    [DebuggerDisplay("Size = {Size}")]
+    internal sealed class IReadOnlyListToIVectorViewAdapter
+    {
+        private IReadOnlyListToIVectorViewAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // T GetAt(uint index)
+        internal T GetAt<T>(uint index)
+        {
+            IReadOnlyList<T> _this = Unsafe.As<IReadOnlyList<T>>(this);
+            EnsureIndexInt32(index, _this.Count);
+
+            try
+            {
+                return _this[(int)index];
+            }
+            catch (ArgumentOutOfRangeException ex)
+            {
+                ex.SetErrorCode(HResults.E_BOUNDS);
+                throw;
+            }
+        }
+
+        // uint Size { get }
+        internal uint Size<T>()
+        {
+            IReadOnlyList<T> _this = Unsafe.As<IReadOnlyList<T>>(this);
+            return (uint)_this.Count;
+        }
+
+        // bool IndexOf(T value, out uint index)
+        internal bool IndexOf<T>(T value, out uint index)
+        {
+            IReadOnlyList<T> _this = Unsafe.As<IReadOnlyList<T>>(this);
+
+            int ind = -1;
+            int max = _this.Count;
+            for (int i = 0; i < max; i++)
+            {
+                if (EqualityComparer<T>.Default.Equals(value, _this[i]))
+                {
+                    ind = i;
+                    break;
+                }
+            }
+
+            if (-1 == ind)
+            {
+                index = 0;
+                return false;
+            }
+
+            index = (uint)ind;
+            return true;
+        }
+
+        // uint GetMany(uint startIndex, T[] items)
+        internal uint GetMany<T>(uint startIndex, T[] items)
+        {
+            IReadOnlyList<T> _this = Unsafe.As<IReadOnlyList<T>>(this);
+
+            // REX spec says "calling GetMany with startIndex equal to the length of the vector 
+            // (last valid index + 1) and any specified capacity will succeed and return zero actual
+            // elements".
+            if (startIndex == _this.Count)
+                return 0;
+
+            EnsureIndexInt32(startIndex, _this.Count);
+
+            if (items == null)
+            {
+                return 0;
+            }
+
+            uint itemCount = Math.Min((uint)items.Length, (uint)_this.Count - startIndex);
+
+            for (uint i = 0; i < itemCount; ++i)
+            {
+                items[i] = _this[(int)(i + startIndex)];
+            }
+
+            if (typeof(T) == typeof(string))
+            {
+                string[] stringItems = items as string[];
+
+                // Fill in the rest of the array with String.Empty to avoid marshaling failure
+                for (uint i = itemCount; i < items.Length; ++i)
+                    stringItems[i] = String.Empty;
+            }
+
+            return itemCount;
+        }
+
+        #region Helpers
+
+        private static void EnsureIndexInt32(uint index, int listCapacity)
+        {
+            // We use '<=' and not '<' because Int32.MaxValue == index would imply
+            // that Size > Int32.MaxValue:
+            if (((uint)Int32.MaxValue) <= index || index >= (uint)listCapacity)
+            {
+                Exception e = new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_IndexLargerThanMaxValue);
+                e.SetErrorCode(HResults.E_BOUNDS);
+                throw e;
+            }
+        }
+
+        #endregion Helpers
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IReference.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IReference.cs
new file mode 100644
index 0000000000..d0101dafc9
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IReference.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    [ComImport]
+    [Guid("61c17706-2d65-11e0-9ae8-d48564015472")]
+    [WindowsRuntimeImport]
+    // Note that ideally, T should be constrained to be a value type.  However, Windows uses IReference<HSTRING>
+    // and the projection may not be exactly pretty.
+    internal interface IReference<T> : IPropertyValue
+    {
+        T Value { get; }
+    }
+
+    [ComImport]
+    [Guid("61c17707-2d65-11e0-9ae8-d48564015472")]
+    [WindowsRuntimeImport]
+    // T can be any WinRT-compatible type, including reference types.
+    internal interface IReferenceArray<T> : IPropertyValue
+    {
+        T[] Value { get; }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IRestrictedErrorInfo.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IRestrictedErrorInfo.cs
new file mode 100644
index 0000000000..ca19d94c76
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IRestrictedErrorInfo.cs
@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // [System.Runtime.CompilerServices.FriendAccessAllowed]
+    [ComImport]
+    [Guid("82BA7092-4C88-427D-A7BC-16DD93FEB67E")]
+    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
+    internal interface IRestrictedErrorInfo
+    {
+        void GetErrorDetails([MarshalAs(UnmanagedType.BStr)] out string description,
+                             out int error,
+                             [MarshalAs(UnmanagedType.BStr)] out string restrictedDescription,
+                             [MarshalAs(UnmanagedType.BStr)] out string capabilitySid);
+
+        void GetReference([MarshalAs(UnmanagedType.BStr)] out string reference);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IVector.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IVector.cs
new file mode 100644
index 0000000000..f00a7d3504
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IVector.cs
@@ -0,0 +1,90 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Collections.Generic;
+
+// Windows.Foundation.Collections.IVector`1 and IVectorView`1 cannot be referenced from managed
+// code because they're hidden by the metadata adapter. We redeclare the interfaces manually
+// to be able to talk to native WinRT objects.
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    [ComImport]
+    [Guid("913337e9-11a1-4345-a3a2-4e7f956e222d")]
+    [WindowsRuntimeImport]
+    internal interface IVector<T> : IIterable<T>
+    {
+        T GetAt(uint index);
+        uint Size { get; }
+        IReadOnlyList<T> GetView();  // Really an IVectorView<T>.
+        bool IndexOf(T value, out uint index);
+        void SetAt(uint index, T value);
+        void InsertAt(uint index, T value);
+        void RemoveAt(uint index);
+        void Append(T value);
+        void RemoveAtEnd();
+        void Clear();
+        uint GetMany(uint startIndex, [Out] T[] items);
+        void ReplaceAll(T[] items);
+    }
+
+    // Same as IVector - the only difference is that GetView returns IVectorView<T>
+    [ComImport]
+    [Guid("913337e9-11a1-4345-a3a2-4e7f956e222d")]
+    [WindowsRuntimeImport]
+    internal interface IVector_Raw<T> : IIterable<T>
+    {
+        T GetAt(uint index);
+        uint Size { get; }
+        IVectorView<T> GetView();
+        bool IndexOf(T value, out uint index);
+        void SetAt(uint index, T value);
+        void InsertAt(uint index, T value);
+        void RemoveAt(uint index);
+        void Append(T value);
+        void RemoveAtEnd();
+        void Clear();
+    }
+
+    [ComImport]
+    [Guid("bbe1fa4c-b0e3-4583-baef-1f1b2e483e56")]
+    [WindowsRuntimeImport]
+    internal interface IVectorView<T> : IIterable<T>
+    {
+        T GetAt(uint index);
+        uint Size { get; }
+        bool IndexOf(T value, out uint index);
+        uint GetMany(uint startIndex, [Out] T[] items);
+    }
+
+    [ComImport]
+    [Guid("393de7de-6fd0-4c0d-bb71-47244a113e93")]
+    [WindowsRuntimeImport]
+    internal interface IBindableVector : IBindableIterable
+    {
+        object GetAt(uint index);
+        uint Size { get; }
+        IBindableVectorView GetView();
+        bool IndexOf(object value, out uint index);
+        void SetAt(uint index, object value);
+        void InsertAt(uint index, object value);
+        void RemoveAt(uint index);
+        void Append(object value);
+        void RemoveAtEnd();
+        void Clear();
+    }
+
+    [ComImport]
+    [Guid("346dd6e7-976e-4bc3-815d-ece243bc0f33")]
+    [WindowsRuntimeImport]
+    internal interface IBindableVectorView : IBindableIterable
+    {
+        object GetAt(uint index);
+        uint Size { get; }
+        bool IndexOf(object value, out uint index);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IVectorViewToIReadOnlyListAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IVectorViewToIReadOnlyListAdapter.cs
new file mode 100644
index 0000000000..83889d0326
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IVectorViewToIReadOnlyListAdapter.cs
@@ -0,0 +1,82 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    internal delegate T Indexer_Get_Delegate<out T>(int index);
+
+    // This is a set of stub methods implementing the support for the IReadOnlyList`1 interface on WinRT
+    // objects that support IVectorView`1. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not IVectorViewToIReadOnlyListAdapter objects. Rather, they are of type
+    // IVectorView<T>. No actual IVectorViewToIReadOnlyListAdapter object is ever instantiated. Thus, you will see
+    // a lot of expressions that cast "this" to "IVectorView<T>".
+    [DebuggerDisplay("Count = {Count}")]
+    internal sealed class IVectorViewToIReadOnlyListAdapter
+    {
+        private IVectorViewToIReadOnlyListAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // T this[int index] { get }
+        internal T Indexer_Get<T>(int index)
+        {
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index));
+
+            IVectorView<T> _this = Unsafe.As<IVectorView<T>>(this);
+
+            try
+            {
+                return _this.GetAt((uint)index);
+
+                // We delegate bounds checking to the underlying collection and if it detected a fault,
+                // we translate it to the right exception:
+            }
+            catch (Exception ex)
+            {
+                if (HResults.E_BOUNDS == ex._HResult)
+                    throw new ArgumentOutOfRangeException(nameof(index));
+
+                throw;
+            }
+        }
+
+        // T this[int index] { get }
+        internal T Indexer_Get_Variance<T>(int index) where T : class
+        {
+            bool fUseString;
+            Delegate target = System.StubHelpers.StubHelpers.GetTargetForAmbiguousVariantCall(
+                this,
+                typeof(IReadOnlyList<T>).TypeHandle.Value,
+                out fUseString);
+
+            if (target != null)
+            {
+                return (Unsafe.As<Indexer_Get_Delegate<T>>(target))(index);
+            }
+
+            if (fUseString)
+            {
+                return Unsafe.As<T>(Indexer_Get<string>(index));
+            }
+
+            return Indexer_Get<T>(index);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IteratorToEnumeratorAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IteratorToEnumeratorAdapter.cs
new file mode 100644
index 0000000000..d49836c46a
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/IteratorToEnumeratorAdapter.cs
@@ -0,0 +1,207 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Security;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    internal delegate IEnumerator<T> GetEnumerator_Delegate<out T>();
+
+    // This is a set of stub methods implementing the support for the IEnumerable`1 interface on WinRT
+    // objects that implement IIterable`1. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not IterableToEnumerableAdapter objects. Rather, they are of type
+    // IIterable<T>. No actual IterableToEnumerableAdapter object is ever instantiated. Thus, you will
+    // see a lot of expressions that cast "this" to "IIterable<T>". 
+    internal sealed class IterableToEnumerableAdapter
+    {
+        private IterableToEnumerableAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // This method is invoked when GetEnumerator is called on a WinRT-backed implementation of IEnumerable<T>.
+        internal IEnumerator<T> GetEnumerator_Stub<T>()
+        {
+            IIterable<T> _this = Unsafe.As<IIterable<T>>(this);
+            return new IteratorToEnumeratorAdapter<T>(_this.First());
+        }
+
+        // This method is invoked when GetEnumerator is called on a WinRT-backed implementation of IEnumerable<T>
+        // and it is possible that the implementation supports IEnumerable<Type>/IEnumerable<string>/IEnumerable<Exception>/
+        // IEnumerable<array>/IEnumerable<delegate> rather than IEnumerable<T> because T is assignable from Type/string/
+        // Exception/array/delegate via co-variance.
+        internal IEnumerator<T> GetEnumerator_Variance_Stub<T>() where T : class
+        {
+            bool fUseString;
+            Delegate target = System.StubHelpers.StubHelpers.GetTargetForAmbiguousVariantCall(
+                this,
+                typeof(IEnumerable<T>).TypeHandle.Value,
+                out fUseString);
+
+            if (target != null)
+            {
+                return (Unsafe.As<GetEnumerator_Delegate<T>>(target))();
+            }
+
+            if (fUseString)
+            {
+                return Unsafe.As<IEnumerator<T>>(GetEnumerator_Stub<string>());
+            }
+
+            return GetEnumerator_Stub<T>();
+        }
+    }
+
+    internal sealed class BindableIterableToEnumerableAdapter
+    {
+        private BindableIterableToEnumerableAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        private sealed class NonGenericToGenericIterator : IIterator<object>
+        {
+            private IBindableIterator iterator;
+
+            public NonGenericToGenericIterator(IBindableIterator iterator)
+            { this.iterator = iterator; }
+
+            public object Current { get { return iterator.Current; } }
+            public bool HasCurrent { get { return iterator.HasCurrent; } }
+            public bool MoveNext() { return iterator.MoveNext(); }
+            public int GetMany(object[] items) { throw new NotSupportedException(); }
+        }
+
+        // This method is invoked when GetEnumerator is called on a WinRT-backed implementation of IEnumerable.
+        internal IEnumerator GetEnumerator_Stub()
+        {
+            IBindableIterable _this = Unsafe.As<IBindableIterable>(this);
+            return new IteratorToEnumeratorAdapter<object>(new NonGenericToGenericIterator(_this.First()));
+        }
+    }
+
+    // Adapter class which holds a Windows Runtime IIterator<T>, exposing it as a managed IEnumerator<T>
+
+
+    // There are a few implementation differences between the Iterator and IEnumerator which need to be 
+    // addressed. Iterator starts at index 0 while IEnumerator starts at index -1 as a result of which 
+    // the first call to IEnumerator.Current is correct only after calling MoveNext(). 
+    // Also IEnumerator throws an exception when we call Current after reaching the end of collection.
+    internal sealed class IteratorToEnumeratorAdapter<T> : IEnumerator<T>
+    {
+        private IIterator<T> m_iterator;
+        private bool m_hadCurrent;
+        private T m_current;
+        private bool m_isInitialized;
+
+        internal IteratorToEnumeratorAdapter(IIterator<T> iterator)
+        {
+            Debug.Assert(iterator != null);
+            m_iterator = iterator;
+            m_hadCurrent = true;
+            m_isInitialized = false;
+        }
+
+        public T Current
+        {
+            get
+            {
+                // The enumerator has not been advanced to the first element yet.
+                if (!m_isInitialized)
+                    ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumNotStarted();
+                // The enumerator has reached the end of the collection
+                if (!m_hadCurrent)
+                    ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumEnded();
+                return m_current;
+            }
+        }
+
+        object IEnumerator.Current
+        {
+            get
+            {
+                // The enumerator has not been advanced to the first element yet.
+                if (!m_isInitialized)
+                    ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumNotStarted();
+                // The enumerator has reached the end of the collection
+                if (!m_hadCurrent)
+                    ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumEnded();
+                return m_current;
+            }
+        }
+
+        public bool MoveNext()
+        {
+            // If we've passed the end of the iteration, IEnumerable<T> should return false, while
+            // IIterable will fail the interface call
+            if (!m_hadCurrent)
+            {
+                return false;
+            }
+
+            // IIterators start at index 0, rather than -1.  If this is the first call, we need to just
+            // check HasCurrent rather than actually moving to the next element
+            try
+            {
+                if (!m_isInitialized)
+                {
+                    m_hadCurrent = m_iterator.HasCurrent;
+                    m_isInitialized = true;
+                }
+                else
+                {
+                    m_hadCurrent = m_iterator.MoveNext();
+                }
+
+                // We want to save away the current value for two reasons:
+                //  1. Accessing .Current is cheap on other iterators, so having it be a property which is a
+                //     simple field access preserves the expected performance characteristics (as opposed to
+                //     triggering a COM call every time the property is accessed)
+                //
+                //  2. This allows us to preserve the same semantics as generic collection iteration when iterating
+                //     beyond the end of the collection - namely that Current continues to return the last value
+                //     of the collection
+                if (m_hadCurrent)
+                {
+                    m_current = m_iterator.Current;
+                }
+            }
+            catch (Exception e)
+            {
+                // Translate E_CHANGED_STATE into an InvalidOperationException for an updated enumeration
+                if (Marshal.GetHRForException(e) == HResults.E_CHANGED_STATE)
+                {
+                    ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion();
+                }
+                else
+                {
+                    throw;
+                }
+            }
+
+            return m_hadCurrent;
+        }
+
+        public void Reset()
+        {
+            throw new NotSupportedException();
+        }
+
+        public void Dispose()
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ListToBindableVectorAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ListToBindableVectorAdapter.cs
new file mode 100644
index 0000000000..b1bde19d06
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ListToBindableVectorAdapter.cs
@@ -0,0 +1,179 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Reflection;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // This is a set of stub methods implementing the support for the IBindableVector interface on managed
+    // objects that implement IList. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not ListToBindableVectorAdapter objects. Rather, they are of type
+    // IList. No actual ListToVectorBindableAdapter object is ever instantiated. Thus, you will
+    // see a lot of expressions that cast "this" to "IList". 
+    internal sealed class ListToBindableVectorAdapter
+    {
+        private ListToBindableVectorAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // object GetAt(uint index)
+        internal object GetAt(uint index)
+        {
+            IList _this = Unsafe.As<IList>(this);
+            EnsureIndexInt32(index, _this.Count);
+
+            try
+            {
+                return _this[(Int32)index];
+            }
+            catch (ArgumentOutOfRangeException ex)
+            {
+                throw WindowsRuntimeMarshal.GetExceptionForHR(HResults.E_BOUNDS, ex, "ArgumentOutOfRange_IndexOutOfRange");
+            }
+        }
+
+        // uint Size { get }
+        internal uint Size()
+        {
+            IList _this = Unsafe.As<IList>(this);
+            return (uint)_this.Count;
+        }
+
+        // IBindableVectorView GetView()
+        internal IBindableVectorView GetView()
+        {
+            IList _this = Unsafe.As<IList>(this);
+            return new ListToBindableVectorViewAdapter(_this);
+        }
+
+        // bool IndexOf(object value, out uint index)
+        internal bool IndexOf(object value, out uint index)
+        {
+            IList _this = Unsafe.As<IList>(this);
+            int ind = _this.IndexOf(value);
+
+            if (-1 == ind)
+            {
+                index = 0;
+                return false;
+            }
+
+            index = (uint)ind;
+            return true;
+        }
+
+        // void SetAt(uint index, object value)
+        internal void SetAt(uint index, object value)
+        {
+            IList _this = Unsafe.As<IList>(this);
+            EnsureIndexInt32(index, _this.Count);
+
+            try
+            {
+                _this[(int)index] = value;
+            }
+            catch (ArgumentOutOfRangeException ex)
+            {
+                throw WindowsRuntimeMarshal.GetExceptionForHR(HResults.E_BOUNDS, ex, "ArgumentOutOfRange_IndexOutOfRange");
+            }
+        }
+
+        // void InsertAt(uint index, object value)
+        internal void InsertAt(uint index, object value)
+        {
+            IList _this = Unsafe.As<IList>(this);
+
+            // Inserting at an index one past the end of the list is equivalent to appending
+            // so we need to ensure that we're within (0, count + 1).
+            EnsureIndexInt32(index, _this.Count + 1);
+
+            try
+            {
+                _this.Insert((int)index, value);
+            }
+            catch (ArgumentOutOfRangeException ex)
+            {
+                // Change error code to match what WinRT expects
+                ex.SetErrorCode(HResults.E_BOUNDS);
+                throw;
+            }
+        }
+
+        // void RemoveAt(uint index)
+        internal void RemoveAt(uint index)
+        {
+            IList _this = Unsafe.As<IList>(this);
+            EnsureIndexInt32(index, _this.Count);
+
+            try
+            {
+                _this.RemoveAt((Int32)index);
+            }
+            catch (ArgumentOutOfRangeException ex)
+            {
+                // Change error code to match what WinRT expects
+                ex.SetErrorCode(HResults.E_BOUNDS);
+                throw;
+            }
+        }
+
+        // void Append(object value)
+        internal void Append(object value)
+        {
+            IList _this = Unsafe.As<IList>(this);
+            _this.Add(value);
+        }
+
+        // void RemoveAtEnd()
+        internal void RemoveAtEnd()
+        {
+            IList _this = Unsafe.As<IList>(this);
+            if (_this.Count == 0)
+            {
+                Exception e = new InvalidOperationException(SR.InvalidOperation_CannotRemoveLastFromEmptyCollection);
+                e.SetErrorCode(HResults.E_BOUNDS);
+                throw e;
+            }
+
+            uint size = (uint)_this.Count;
+            RemoveAt(size - 1);
+        }
+
+        // void Clear()
+        internal void Clear()
+        {
+            IList _this = Unsafe.As<IList>(this);
+            _this.Clear();
+        }
+
+        // Helpers:
+
+        private static void EnsureIndexInt32(uint index, int listCapacity)
+        {
+            // We use '<=' and not '<' becasue Int32.MaxValue == index would imply
+            // that Size > Int32.MaxValue:
+            if (((uint)Int32.MaxValue) <= index || index >= (uint)listCapacity)
+            {
+                Exception e = new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_IndexLargerThanMaxValue);
+                e.SetErrorCode(HResults.E_BOUNDS);
+                throw e;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ListToBindableVectorViewAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ListToBindableVectorViewAdapter.cs
new file mode 100644
index 0000000000..e92b879b1d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ListToBindableVectorViewAdapter.cs
@@ -0,0 +1,91 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Reflection;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    /// A Windows Runtime IBindableVectorView implementation that wraps around a managed IList exposing
+    /// it to Windows runtime interop.
+    internal sealed class ListToBindableVectorViewAdapter : IBindableVectorView
+    {
+        private readonly IList list;
+
+        internal ListToBindableVectorViewAdapter(IList list)
+        {
+            if (list == null)
+                throw new ArgumentNullException(nameof(list));
+
+
+            this.list = list;
+        }
+
+        private static void EnsureIndexInt32(uint index, int listCapacity)
+        {
+            // We use '<=' and not '<' becasue Int32.MaxValue == index would imply
+            // that Size > Int32.MaxValue:
+            if (((uint)Int32.MaxValue) <= index || index >= (uint)listCapacity)
+            {
+                Exception e = new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_IndexLargerThanMaxValue);
+                e.SetErrorCode(HResults.E_BOUNDS);
+                throw e;
+            }
+        }
+
+        // IBindableIterable implementation:
+
+        public IBindableIterator First()
+        {
+            IEnumerator enumerator = list.GetEnumerator();
+            return new EnumeratorToIteratorAdapter<object>(new EnumerableToBindableIterableAdapter.NonGenericToGenericEnumerator(enumerator));
+        }
+
+        // IBindableVectorView implementation:
+
+        public object GetAt(uint index)
+        {
+            EnsureIndexInt32(index, list.Count);
+
+            try
+            {
+                return list[(int)index];
+            }
+            catch (ArgumentOutOfRangeException ex)
+            {
+                throw WindowsRuntimeMarshal.GetExceptionForHR(HResults.E_BOUNDS, ex, "ArgumentOutOfRange_IndexOutOfRange");
+            }
+        }
+
+        public uint Size
+        {
+            get
+            {
+                return (uint)list.Count;
+            }
+        }
+
+        public bool IndexOf(object value, out uint index)
+        {
+            int ind = list.IndexOf(value);
+
+            if (-1 == ind)
+            {
+                index = 0;
+                return false;
+            }
+
+            index = (uint)ind;
+            return true;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ListToVectorAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ListToVectorAdapter.cs
new file mode 100644
index 0000000000..12ba36632e
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ListToVectorAdapter.cs
@@ -0,0 +1,244 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Reflection;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // This is a set of stub methods implementing the support for the IVector`1 interface on managed
+    // objects that implement IList`1. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not ListToVectorAdapter objects. Rather, they are of type
+    // IList<T>. No actual ListToVectorAdapter object is ever instantiated. Thus, you will
+    // see a lot of expressions that cast "this" to "IList<T>". 
+    internal sealed class ListToVectorAdapter
+    {
+        private ListToVectorAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // T GetAt(uint index)
+        internal T GetAt<T>(uint index)
+        {
+            IList<T> _this = Unsafe.As<IList<T>>(this);
+            EnsureIndexInt32(index, _this.Count);
+
+            try
+            {
+                return _this[(Int32)index];
+            }
+            catch (ArgumentOutOfRangeException ex)
+            {
+                throw WindowsRuntimeMarshal.GetExceptionForHR(HResults.E_BOUNDS, ex, "ArgumentOutOfRange_IndexOutOfRange");
+            }
+        }
+
+        // uint Size { get }
+        internal uint Size<T>()
+        {
+            IList<T> _this = Unsafe.As<IList<T>>(this);
+            return (uint)_this.Count;
+        }
+
+        // IVectorView<T> GetView()
+        internal IReadOnlyList<T> GetView<T>()
+        {
+            IList<T> _this = Unsafe.As<IList<T>>(this);
+            Debug.Assert(_this != null);
+
+            // Note: This list is not really read-only - you could QI for a modifiable
+            // list.  We gain some perf by doing this.  We believe this is acceptable.
+            IReadOnlyList<T> roList = _this as IReadOnlyList<T>;
+            if (roList == null)
+            {
+                roList = new ReadOnlyCollection<T>(_this);
+            }
+            return roList;
+        }
+
+        // bool IndexOf(T value, out uint index)
+        internal bool IndexOf<T>(T value, out uint index)
+        {
+            IList<T> _this = Unsafe.As<IList<T>>(this);
+            int ind = _this.IndexOf(value);
+
+            if (-1 == ind)
+            {
+                index = 0;
+                return false;
+            }
+
+            index = (uint)ind;
+            return true;
+        }
+
+        // void SetAt(uint index, T value)
+        internal void SetAt<T>(uint index, T value)
+        {
+            IList<T> _this = Unsafe.As<IList<T>>(this);
+            EnsureIndexInt32(index, _this.Count);
+
+            try
+            {
+                _this[(int)index] = value;
+            }
+            catch (ArgumentOutOfRangeException ex)
+            {
+                throw WindowsRuntimeMarshal.GetExceptionForHR(HResults.E_BOUNDS, ex, "ArgumentOutOfRange_IndexOutOfRange");
+            }
+        }
+
+        // void InsertAt(uint index, T value)
+        internal void InsertAt<T>(uint index, T value)
+        {
+            IList<T> _this = Unsafe.As<IList<T>>(this);
+
+            // Inserting at an index one past the end of the list is equivalent to appending
+            // so we need to ensure that we're within (0, count + 1).
+            EnsureIndexInt32(index, _this.Count + 1);
+
+            try
+            {
+                _this.Insert((int)index, value);
+            }
+            catch (ArgumentOutOfRangeException ex)
+            {
+                // Change error code to match what WinRT expects
+                ex.SetErrorCode(HResults.E_BOUNDS);
+                throw;
+            }
+        }
+
+        // void RemoveAt(uint index)
+        internal void RemoveAt<T>(uint index)
+        {
+            IList<T> _this = Unsafe.As<IList<T>>(this);
+            EnsureIndexInt32(index, _this.Count);
+
+            try
+            {
+                _this.RemoveAt((Int32)index);
+            }
+            catch (ArgumentOutOfRangeException ex)
+            {
+                // Change error code to match what WinRT expects
+                ex.SetErrorCode(HResults.E_BOUNDS);
+                throw;
+            }
+        }
+
+        // void Append(T value)
+        internal void Append<T>(T value)
+        {
+            IList<T> _this = Unsafe.As<IList<T>>(this);
+            _this.Add(value);
+        }
+
+        // void RemoveAtEnd()
+        internal void RemoveAtEnd<T>()
+        {
+            IList<T> _this = Unsafe.As<IList<T>>(this);
+            if (_this.Count == 0)
+            {
+                Exception e = new InvalidOperationException(SR.InvalidOperation_CannotRemoveLastFromEmptyCollection);
+                e.SetErrorCode(HResults.E_BOUNDS);
+                throw e;
+            }
+
+            uint size = (uint)_this.Count;
+            RemoveAt<T>(size - 1);
+        }
+
+        // void Clear()
+        internal void Clear<T>()
+        {
+            IList<T> _this = Unsafe.As<IList<T>>(this);
+            _this.Clear();
+        }
+
+        // uint GetMany(uint startIndex, T[] items)
+        internal uint GetMany<T>(uint startIndex, T[] items)
+        {
+            IList<T> _this = Unsafe.As<IList<T>>(this);
+            return GetManyHelper<T>(_this, startIndex, items);
+        }
+
+        // void ReplaceAll(T[] items)
+        internal void ReplaceAll<T>(T[] items)
+        {
+            IList<T> _this = Unsafe.As<IList<T>>(this);
+            _this.Clear();
+
+            if (items != null)
+            {
+                foreach (T item in items)
+                {
+                    _this.Add(item);
+                }
+            }
+        }
+
+        // Helpers:
+
+        private static void EnsureIndexInt32(uint index, int listCapacity)
+        {
+            // We use '<=' and not '<' becasue Int32.MaxValue == index would imply
+            // that Size > Int32.MaxValue:
+            if (((uint)Int32.MaxValue) <= index || index >= (uint)listCapacity)
+            {
+                Exception e = new ArgumentOutOfRangeException(nameof(index), SR.ArgumentOutOfRange_IndexLargerThanMaxValue);
+                e.SetErrorCode(HResults.E_BOUNDS);
+                throw e;
+            }
+        }
+
+        private static uint GetManyHelper<T>(IList<T> sourceList, uint startIndex, T[] items)
+        {
+            // Calling GetMany with a start index equal to the size of the list should always
+            // return 0 elements, regardless of the input item size
+            if (startIndex == sourceList.Count)
+            {
+                return 0;
+            }
+
+            EnsureIndexInt32(startIndex, sourceList.Count);
+
+            if (items == null)
+            {
+                return 0;
+            }
+
+            uint itemCount = Math.Min((uint)items.Length, (uint)sourceList.Count - startIndex);
+            for (uint i = 0; i < itemCount; ++i)
+            {
+                items[i] = sourceList[(int)(i + startIndex)];
+            }
+
+            if (typeof(T) == typeof(string))
+            {
+                string[] stringItems = items as string[];
+
+                // Fill in rest of the array with String.Empty to avoid marshaling failure
+                for (uint i = itemCount; i < items.Length; ++i)
+                    stringItems[i] = String.Empty;
+            }
+
+            return itemCount;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ManagedActivationFactory.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ManagedActivationFactory.cs
new file mode 100644
index 0000000000..82ef71c783
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/ManagedActivationFactory.cs
@@ -0,0 +1,74 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Reflection;
+using System.Runtime.InteropServices;
+using System.Security;
+using System.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    [ComImport]
+    [Guid("60D27C8D-5F61-4CCE-B751-690FAE66AA53")]
+    [WindowsRuntimeImport]
+    internal interface IManagedActivationFactory
+    {
+        void RunClassConstructor();
+    }
+
+    // A ManangedActivationFactory provides the IActivationFactory implementation for managed types which are
+    // constructable via Windows Runtime. Implementation of specialized factory and static WinRT interfaces is
+    // provided using VM functionality (see Marshal.InitializeWinRTFactoryObject for details).
+    //
+    // In order to be activatable via the ManagedActivationFactory type, the type must be decorated with either
+    // ActivatableAttribute, or StaticAttribute.
+    [ComVisible(true)]
+    [ClassInterface(ClassInterfaceType.None)]
+    internal sealed class ManagedActivationFactory : IActivationFactory, IManagedActivationFactory
+    {
+        private Type m_type;
+
+        internal ManagedActivationFactory(Type type)
+        {
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+
+            // Check whether the type is "exported to WinRT", i.e. it is declared in a managed .winmd and is decorated
+            // with at least one ActivatableAttribute or StaticAttribute.
+            if (!(type is RuntimeType) || !type.IsExportedToWindowsRuntime)
+                throw new ArgumentException(SR.Format(SR.Argument_TypeNotActivatableViaWindowsRuntime, type), nameof(type));
+
+            m_type = type;
+        }
+
+        // Activate an instance of the managed type by using its default constructor.
+        public object ActivateInstance()
+        {
+            try
+            {
+                return Activator.CreateInstance(m_type);
+            }
+            catch (MissingMethodException)
+            {
+                // If the type doesn't expose a default constructor, then we fail with E_NOTIMPL
+                throw new NotImplementedException();
+            }
+            catch (TargetInvocationException e)
+            {
+                throw e.InnerException;
+            }
+        }
+
+        // Runs the class constructor
+        // Currently only Jupiter use this to run class constructor in order to 
+        // initialize DependencyProperty objects and do necessary work
+        void IManagedActivationFactory.RunClassConstructor()
+        {
+            RuntimeHelpers.RunClassConstructor(m_type.TypeHandle);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapToCollectionAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapToCollectionAdapter.cs
new file mode 100644
index 0000000000..c64703b80a
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapToCollectionAdapter.cs
@@ -0,0 +1,184 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // These stubs will be used when a call via ICollection<KeyValuePair<K, V>> is made in managed code.
+    // This can mean two things - either the underlying unmanaged object implements IMap<K, V> or it
+    // implements IVector<IKeyValuePair<K, V>> and we cannot determine this statically in the general
+    // case so we have to cast at run-time. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not MapToCollectionAdapter objects. Rather, they are of type
+    // IVector<KeyValuePair<K, V>> or IMap<K, V>. No actual MapToCollectionAdapter object is ever
+    // instantiated. Thus, you will see a lot of expressions that cast "this" to "IVector<KeyValuePair<K, V>>"
+    // or "IMap<K, V>".
+    internal sealed class MapToCollectionAdapter
+    {
+        private MapToCollectionAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // int Count { get }
+        internal int Count<K, V>()
+        {
+            object _this = Unsafe.As<object>(this);
+
+            IMap<K, V> _this_map = _this as IMap<K, V>;
+            if (_this_map != null)
+            {
+                uint size = _this_map.Size;
+
+                if (((uint)Int32.MaxValue) < size)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_CollectionBackingDictionaryTooLarge);
+                }
+
+                return (int)size;
+            }
+            else
+            {
+                IVector<KeyValuePair<K, V>> _this_vector = Unsafe.As<IVector<KeyValuePair<K, V>>>(this);
+                uint size = _this_vector.Size;
+
+                if (((uint)Int32.MaxValue) < size)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_CollectionBackingListTooLarge);
+                }
+
+                return (int)size;
+            }
+        }
+
+        // bool IsReadOnly { get }
+        internal bool IsReadOnly<K, V>()
+        {
+            return false;
+        }
+
+        // void Add(T item)
+        internal void Add<K, V>(KeyValuePair<K, V> item)
+        {
+            object _this = Unsafe.As<object>(this);
+
+            IDictionary<K, V> _this_dictionary = _this as IDictionary<K, V>;
+            if (_this_dictionary != null)
+            {
+                _this_dictionary.Add(item.Key, item.Value);
+            }
+            else
+            {
+                IVector<KeyValuePair<K, V>> _this_vector = Unsafe.As<IVector<KeyValuePair<K, V>>>(this);
+                _this_vector.Append(item);
+            }
+        }
+
+        // void Clear()
+        internal void Clear<K, V>()
+        {
+            object _this = Unsafe.As<object>(this);
+
+            IMap<K, V> _this_map = _this as IMap<K, V>;
+            if (_this_map != null)
+            {
+                _this_map.Clear();
+            }
+            else
+            {
+                IVector<KeyValuePair<K, V>> _this_vector = Unsafe.As<IVector<KeyValuePair<K, V>>>(this);
+                _this_vector.Clear();
+            }
+        }
+
+        // bool Contains(T item)
+        internal bool Contains<K, V>(KeyValuePair<K, V> item)
+        {
+            object _this = Unsafe.As<object>(this);
+
+            IDictionary<K, V> _this_dictionary = _this as IDictionary<K, V>;
+            if (_this_dictionary != null)
+            {
+                V value;
+                bool hasKey = _this_dictionary.TryGetValue(item.Key, out value);
+
+                if (!hasKey)
+                    return false;
+
+                return EqualityComparer<V>.Default.Equals(value, item.Value);
+            }
+            else
+            {
+                IVector<KeyValuePair<K, V>> _this_vector = Unsafe.As<IVector<KeyValuePair<K, V>>>(this);
+
+                uint index;
+                return _this_vector.IndexOf(item, out index);
+            }
+        }
+
+        // void CopyTo(T[] array, int arrayIndex)
+        internal void CopyTo<K, V>(KeyValuePair<K, V>[] array, int arrayIndex)
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array));
+
+            if (arrayIndex < 0)
+                throw new ArgumentOutOfRangeException(nameof(arrayIndex));
+
+            if (array.Length <= arrayIndex && Count<K, V>() > 0)
+                throw new ArgumentException(SR.Argument_IndexOutOfArrayBounds);
+
+            if (array.Length - arrayIndex < Count<K, V>())
+                throw new ArgumentException(SR.Argument_InsufficientSpaceToCopyCollection);
+
+
+            IIterable<KeyValuePair<K, V>> _this = Unsafe.As<IIterable<KeyValuePair<K, V>>>(this);
+            foreach (KeyValuePair<K, V> mapping in _this)
+            {
+                array[arrayIndex++] = mapping;
+            }
+        }
+
+        // bool Remove(T item)
+        internal bool Remove<K, V>(KeyValuePair<K, V> item)
+        {
+            object _this = Unsafe.As<object>(this);
+
+            IDictionary<K, V> _this_dictionary = _this as IDictionary<K, V>;
+            if (_this_dictionary != null)
+            {
+                return _this_dictionary.Remove(item.Key);
+            }
+            else
+            {
+                IVector<KeyValuePair<K, V>> _this_vector = Unsafe.As<IVector<KeyValuePair<K, V>>>(this);
+                uint index;
+                bool exists = _this_vector.IndexOf(item, out index);
+
+                if (!exists)
+                    return false;
+
+                if (((uint)Int32.MaxValue) < index)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_CollectionBackingListTooLarge);
+                }
+
+                VectorToListAdapter.RemoveAtHelper<KeyValuePair<K, V>>(_this_vector, index);
+                return true;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapToDictionaryAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapToDictionaryAdapter.cs
new file mode 100644
index 0000000000..cbac962099
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapToDictionaryAdapter.cs
@@ -0,0 +1,170 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // This is a set of stub methods implementing the support for the IDictionary`2 interface on WinRT
+    // objects that support IMap`2. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not MapToDictionaryAdapter objects. Rather, they are of type
+    // IMap<K, V>. No actual MapToDictionaryAdapter object is ever instantiated. Thus, you will see
+    // a lot of expressions that cast "this" to "IMap<K, V>".
+    internal sealed class MapToDictionaryAdapter
+    {
+        private MapToDictionaryAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // V this[K key] { get }
+        internal V Indexer_Get<K, V>(K key)
+        {
+            if (key == null)
+                throw new ArgumentNullException(nameof(key));
+
+
+            IMap<K, V> _this = Unsafe.As<IMap<K, V>>(this);
+            return Lookup(_this, key);
+        }
+
+        // V this[K key] { set }
+        internal void Indexer_Set<K, V>(K key, V value)
+        {
+            if (key == null)
+                throw new ArgumentNullException(nameof(key));
+
+
+            IMap<K, V> _this = Unsafe.As<IMap<K, V>>(this);
+            Insert(_this, key, value);
+        }
+
+        // ICollection<K> Keys { get }
+        internal ICollection<K> Keys<K, V>()
+        {
+            IMap<K, V> _this = Unsafe.As<IMap<K, V>>(this);
+            IDictionary<K, V> dictionary = (IDictionary<K, V>)_this;
+            return new DictionaryKeyCollection<K, V>(dictionary);
+        }
+
+        // ICollection<V> Values { get }
+        internal ICollection<V> Values<K, V>()
+        {
+            IMap<K, V> _this = Unsafe.As<IMap<K, V>>(this);
+            IDictionary<K, V> dictionary = (IDictionary<K, V>)_this;
+            return new DictionaryValueCollection<K, V>(dictionary);
+        }
+
+        // bool ContainsKey(K key)
+        internal bool ContainsKey<K, V>(K key)
+        {
+            if (key == null)
+                throw new ArgumentNullException(nameof(key));
+
+            IMap<K, V> _this = Unsafe.As<IMap<K, V>>(this);
+            return _this.HasKey(key);
+        }
+
+        // void Add(K key, V value)
+        internal void Add<K, V>(K key, V value)
+        {
+            if (key == null)
+                throw new ArgumentNullException(nameof(key));
+
+            if (ContainsKey<K, V>(key))
+                throw new ArgumentException(SR.Argument_AddingDuplicate);
+
+
+            IMap<K, V> _this = Unsafe.As<IMap<K, V>>(this);
+            Insert(_this, key, value);
+        }
+
+        // bool Remove(TKey key)
+        internal bool Remove<K, V>(K key)
+        {
+            if (key == null)
+                throw new ArgumentNullException(nameof(key));
+
+            IMap<K, V> _this = Unsafe.As<IMap<K, V>>(this);
+            if (!_this.HasKey(key))
+                return false;
+
+            try
+            {
+                _this.Remove(key);
+                return true;
+            }
+            catch (Exception ex)
+            {
+                if (HResults.E_BOUNDS == ex._HResult)
+                    return false;
+
+                throw;
+            }
+        }
+
+        // bool TryGetValue(TKey key, out TValue value)
+        internal bool TryGetValue<K, V>(K key, out V value)
+        {
+            if (key == null)
+                throw new ArgumentNullException(nameof(key));
+
+            IMap<K, V> _this = Unsafe.As<IMap<K, V>>(this);
+            if (!_this.HasKey(key))
+            {
+                value = default(V);
+                return false;
+            }
+
+            try
+            {
+                value = Lookup(_this, key);
+                return true;
+            }
+            catch (KeyNotFoundException)
+            {
+                value = default(V);
+                return false;
+            }
+        }
+
+        // Helpers:
+
+        private static V Lookup<K, V>(IMap<K, V> _this, K key)
+        {
+            Debug.Assert(null != key);
+
+            try
+            {
+                return _this.Lookup(key);
+            }
+            catch (Exception ex)
+            {
+                if (HResults.E_BOUNDS == ex._HResult)
+                    throw new KeyNotFoundException(SR.Arg_KeyNotFound);
+                throw;
+            }
+        }
+
+        private static bool Insert<K, V>(IMap<K, V> _this, K key, V value)
+        {
+            Debug.Assert(null != key);
+
+            bool replaced = _this.Insert(key, value);
+            return replaced;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapViewToReadOnlyCollectionAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapViewToReadOnlyCollectionAdapter.cs
new file mode 100644
index 0000000000..e1323dade4
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/MapViewToReadOnlyCollectionAdapter.cs
@@ -0,0 +1,67 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // These stubs will be used when a call via IReadOnlyCollection<KeyValuePair<K, V>> is made in managed code.
+    // This can mean two things - either the underlying unmanaged object implements IMapView<K, V> or it
+    // implements IVectorView<IKeyValuePair<K, V>> and we cannot determine this statically in the general
+    // case so we have to cast at run-time. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not MapViewToReadOnlyCollectionAdapter objects. Rather, they are of type
+    // IVectorView<KeyValuePair<K, V>> or IMapView<K, V>. No actual MapViewToReadOnlyCollectionAdapter object is ever
+    // instantiated. Thus, you will see a lot of expressions that cast "this" to "IVectorView<KeyValuePair<K, V>>"
+    // or "IMapView<K, V>".
+    internal sealed class MapViewToReadOnlyCollectionAdapter
+    {
+        private MapViewToReadOnlyCollectionAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // int Count { get }
+        internal int Count<K, V>()
+        {
+            object _this = Unsafe.As<object>(this);
+
+            IMapView<K, V> _this_map = _this as IMapView<K, V>;
+            if (_this_map != null)
+            {
+                uint size = _this_map.Size;
+
+                if (((uint)Int32.MaxValue) < size)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_CollectionBackingDictionaryTooLarge);
+                }
+
+                return (int)size;
+            }
+            else
+            {
+                IVectorView<KeyValuePair<K, V>> _this_vector = Unsafe.As<IVectorView<KeyValuePair<K, V>>>(this);
+                uint size = _this_vector.Size;
+
+                if (((uint)Int32.MaxValue) < size)
+                {
+                    throw new InvalidOperationException(SR.InvalidOperation_CollectionBackingListTooLarge);
+                }
+
+                return (int)size;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/NativeMethods.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/NativeMethods.cs
new file mode 100644
index 0000000000..201f4b132b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/NativeMethods.cs
@@ -0,0 +1,51 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Runtime.InteropServices;
+using System.Security;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+#if BIT64
+    [StructLayout(LayoutKind.Explicit, Size = 24)]
+#else
+    [StructLayout(LayoutKind.Explicit, Size = 20)]
+#endif
+    internal unsafe struct HSTRING_HEADER
+    {
+    }
+
+    internal static class UnsafeNativeMethods
+    {
+        [DllImport("api-ms-win-core-winrt-error-l1-1-0.dll", PreserveSig = false)]
+        internal static extern IRestrictedErrorInfo GetRestrictedErrorInfo();
+
+        [DllImport("api-ms-win-core-winrt-error-l1-1-1.dll")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern bool RoOriginateLanguageException(int error, [MarshalAs(UnmanagedType.HString)]string message, IntPtr languageException);
+
+        [DllImport("api-ms-win-core-winrt-error-l1-1-1.dll", PreserveSig = false)]
+        internal static extern void RoReportUnhandledError(IRestrictedErrorInfo error);
+
+        [DllImport("api-ms-win-core-winrt-string-l1-1-0.dll", CallingConvention = CallingConvention.StdCall)]
+        internal static extern unsafe int WindowsCreateString([MarshalAs(UnmanagedType.LPWStr)] string sourceString,
+                                                              int length,
+                                                              [Out] IntPtr* hstring);
+
+        [DllImport("api-ms-win-core-winrt-string-l1-1-0.dll", CallingConvention = CallingConvention.StdCall)]
+        internal static extern unsafe int WindowsCreateStringReference(char* sourceString,
+                                                                       int length,
+                                                                       [Out] HSTRING_HEADER* hstringHeader,
+                                                                       [Out] IntPtr* hstring);
+
+        [DllImport("api-ms-win-core-winrt-string-l1-1-0.dll", CallingConvention = CallingConvention.StdCall)]
+        internal static extern int WindowsDeleteString(IntPtr hstring);
+
+        [DllImport("api-ms-win-core-winrt-string-l1-1-0.dll", CallingConvention = CallingConvention.StdCall)]
+        internal static extern unsafe char* WindowsGetStringRawBuffer(IntPtr hstring, [Out] uint* length);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/PropertyValue.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/PropertyValue.cs
new file mode 100644
index 0000000000..f083eb29b8
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/PropertyValue.cs
@@ -0,0 +1,63 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Security;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // Note this is a copy of the PropertyType enumeration from Windows.Foundation.winmd
+    internal enum PropertyType
+    {
+        // WARNING: These values have to match enum Windows.Foundation.PropertyType !!!
+        Empty = 0,
+        UInt8 = 1,
+        Int16 = 2,
+        UInt16 = 3,
+        Int32 = 4,
+        UInt32 = 5,
+        Int64 = 6,
+        UInt64 = 7,
+        Single = 8,
+        Double = 9,
+        Char16 = 10,
+        Boolean = 11,
+        String = 12,
+        Inspectable = 13,
+        DateTime = 14,
+        TimeSpan = 15,
+        Guid = 16,
+        Point = 17,
+        Size = 18,
+        Rect = 19,
+
+        Other = 20,
+
+        UInt8Array = UInt8 + 1024,
+        Int16Array = Int16 + 1024,
+        UInt16Array = UInt16 + 1024,
+        Int32Array = Int32 + 1024,
+        UInt32Array = UInt32 + 1024,
+        Int64Array = Int64 + 1024,
+        UInt64Array = UInt64 + 1024,
+        SingleArray = Single + 1024,
+        DoubleArray = Double + 1024,
+        Char16Array = Char16 + 1024,
+        BooleanArray = Boolean + 1024,
+        StringArray = String + 1024,
+        InspectableArray = Inspectable + 1024,
+        DateTimeArray = DateTime + 1024,
+        TimeSpanArray = TimeSpan + 1024,
+        GuidArray = Guid + 1024,
+        PointArray = Point + 1024,
+        SizeArray = Size + 1024,
+        RectArray = Rect + 1024,
+        OtherArray = Other + 1024,
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/RuntimeClass.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/RuntimeClass.cs
new file mode 100644
index 0000000000..fdc0d22632
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/RuntimeClass.cs
@@ -0,0 +1,113 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** RuntimeClass is the base class of all WinRT types
+**
+** 
+===========================================================*/
+
+using System;
+using System.Runtime.InteropServices;
+using System.Runtime.InteropServices.WindowsRuntime;
+using System.Runtime.CompilerServices;
+using System.Security;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // Local definition of Windows.Foundation.IStringable
+    [ComImport]
+    [Guid("96369f54-8eb6-48f0-abce-c1b211e627c3")]
+    [WindowsRuntimeImport]
+    internal interface IStringable
+    {
+        string ToString();
+    }
+
+    internal class IStringableHelper
+    {
+        internal static string ToString(object obj)
+        {
+            IGetProxyTarget proxy = obj as IGetProxyTarget;
+            if (proxy != null)
+                obj = proxy.GetTarget();
+
+            // Check whether the type implements IStringable.
+            IStringable stringableType = obj as IStringable;
+            if (stringableType != null)
+            {
+                return stringableType.ToString();
+            }
+
+            return obj.ToString();
+        }
+    }
+
+    //
+    // Base class for every WinRT class
+    // We'll make it a ComImport and WindowsRuntimeImport in the type loader
+    // as C# compiler won't allow putting code in ComImport type
+    //
+    internal abstract class RuntimeClass : __ComObject
+    {
+        //
+        // Support for ToString/GetHashCode/Equals override
+        //        
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal extern IntPtr GetRedirectedGetHashCodeMD();
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal extern int RedirectGetHashCode(IntPtr pMD);
+
+        public override int GetHashCode()
+        {
+            IntPtr pMD = GetRedirectedGetHashCodeMD();
+            if (pMD == IntPtr.Zero)
+                return base.GetHashCode();
+            return RedirectGetHashCode(pMD);
+        }
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal extern IntPtr GetRedirectedToStringMD();
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal extern string RedirectToString(IntPtr pMD);
+
+        public override string ToString()
+        {
+            // Check whether the type implements IStringable.
+            IStringable stringableType = this as IStringable;
+            if (stringableType != null)
+            {
+                return stringableType.ToString();
+            }
+            else
+            {
+                IntPtr pMD = GetRedirectedToStringMD();
+
+                if (pMD == IntPtr.Zero)
+                    return base.ToString();
+
+                return RedirectToString(pMD);
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal extern IntPtr GetRedirectedEqualsMD();
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal extern bool RedirectEquals(object obj, IntPtr pMD);
+
+        public override bool Equals(object obj)
+        {
+            IntPtr pMD = GetRedirectedEqualsMD();
+            if (pMD == IntPtr.Zero)
+                return base.Equals(obj);
+            return RedirectEquals(obj, pMD);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/VectorToCollectionAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/VectorToCollectionAdapter.cs
new file mode 100644
index 0000000000..35b77b26d3
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/VectorToCollectionAdapter.cs
@@ -0,0 +1,119 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // This is a set of stub methods implementing the support for the ICollection`1 interface on WinRT
+    // objects that support IVector`1. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not VectorToCollectionAdapter objects. Rather, they are of type
+    // IVector<T>. No actual VectorToCollectionAdapter object is ever instantiated. Thus, you will see
+    // a lot of expressions that cast "this" to "IVector<T>".
+    internal sealed class VectorToCollectionAdapter
+    {
+        private VectorToCollectionAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // int Count { get }
+        internal int Count<T>()
+        {
+            IVector<T> _this = Unsafe.As<IVector<T>>(this);
+            uint size = _this.Size;
+            if (((uint)Int32.MaxValue) < size)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_CollectionBackingListTooLarge);
+            }
+
+            return (int)size;
+        }
+
+        // bool IsReadOnly { get }
+        internal bool IsReadOnly<T>()
+        {
+            return false;
+        }
+
+        // void Add(T item)
+        internal void Add<T>(T item)
+        {
+            IVector<T> _this = Unsafe.As<IVector<T>>(this);
+            _this.Append(item);
+        }
+
+        // void Clear()
+        internal void Clear<T>()
+        {
+            IVector<T> _this = Unsafe.As<IVector<T>>(this);
+            _this.Clear();
+        }
+
+        // bool Contains(T item)
+        internal bool Contains<T>(T item)
+        {
+            IVector<T> _this = Unsafe.As<IVector<T>>(this);
+
+            uint index;
+            return _this.IndexOf(item, out index);
+        }
+
+        // void CopyTo(T[] array, int arrayIndex)
+        internal void CopyTo<T>(T[] array, int arrayIndex)
+        {
+            if (array == null)
+                throw new ArgumentNullException(nameof(array));
+
+            if (arrayIndex < 0)
+                throw new ArgumentOutOfRangeException(nameof(arrayIndex));
+
+            if (array.Length <= arrayIndex && Count<T>() > 0)
+                throw new ArgumentException(SR.Argument_IndexOutOfArrayBounds);
+
+            if (array.Length - arrayIndex < Count<T>())
+                throw new ArgumentException(SR.Argument_InsufficientSpaceToCopyCollection);
+
+
+            IVector<T> _this = Unsafe.As<IVector<T>>(this);
+            int count = Count<T>();
+            for (int i = 0; i < count; i++)
+            {
+                array[i + arrayIndex] = VectorToListAdapter.GetAt<T>(_this, (uint)i);
+            }
+        }
+
+        // bool Remove(T item)
+        internal bool Remove<T>(T item)
+        {
+            IVector<T> _this = Unsafe.As<IVector<T>>(this);
+
+            uint index;
+            bool exists = _this.IndexOf(item, out index);
+
+            if (!exists)
+                return false;
+
+            if (((uint)Int32.MaxValue) < index)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_CollectionBackingListTooLarge);
+            }
+
+            VectorToListAdapter.RemoveAtHelper<T>(_this, index);
+            return true;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/VectorToListAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/VectorToListAdapter.cs
new file mode 100644
index 0000000000..ab3cb9c635
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/VectorToListAdapter.cs
@@ -0,0 +1,166 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // This is a set of stub methods implementing the support for the IList`1 interface on WinRT
+    // objects that support IVector`1. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not VectorToListAdapter objects. Rather, they are of type
+    // IVector<T>. No actual VectorToListAdapter object is ever instantiated. Thus, you will see
+    // a lot of expressions that cast "this" to "IVector<T>".
+    internal sealed class VectorToListAdapter
+    {
+        private VectorToListAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // T this[int index] { get }
+        internal T Indexer_Get<T>(int index)
+        {
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index));
+
+            IVector<T> _this = Unsafe.As<IVector<T>>(this);
+            return GetAt(_this, (uint)index);
+        }
+
+        // T this[int index] { set }
+        internal void Indexer_Set<T>(int index, T value)
+        {
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index));
+
+            IVector<T> _this = Unsafe.As<IVector<T>>(this);
+            SetAt(_this, (uint)index, value);
+        }
+
+        // int IndexOf(T item)
+        internal int IndexOf<T>(T item)
+        {
+            IVector<T> _this = Unsafe.As<IVector<T>>(this);
+
+            uint index;
+            bool exists = _this.IndexOf(item, out index);
+
+            if (!exists)
+                return -1;
+
+            if (((uint)Int32.MaxValue) < index)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_CollectionBackingListTooLarge);
+            }
+
+            return (int)index;
+        }
+
+        // void Insert(int index, T item)
+        internal void Insert<T>(int index, T item)
+        {
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index));
+
+            IVector<T> _this = Unsafe.As<IVector<T>>(this);
+            InsertAtHelper<T>(_this, (uint)index, item);
+        }
+
+        // void RemoveAt(int index)
+        internal void RemoveAt<T>(int index)
+        {
+            if (index < 0)
+                throw new ArgumentOutOfRangeException(nameof(index));
+
+            IVector<T> _this = Unsafe.As<IVector<T>>(this);
+            RemoveAtHelper<T>(_this, (uint)index);
+        }
+
+        // Helpers:
+
+        internal static T GetAt<T>(IVector<T> _this, uint index)
+        {
+            try
+            {
+                return _this.GetAt(index);
+
+                // We delegate bounds checking to the underlying collection and if it detected a fault,
+                // we translate it to the right exception:
+            }
+            catch (Exception ex)
+            {
+                if (HResults.E_BOUNDS == ex._HResult)
+                    throw new ArgumentOutOfRangeException(nameof(index));
+
+                throw;
+            }
+        }
+
+        private static void SetAt<T>(IVector<T> _this, UInt32 index, T value)
+        {
+            try
+            {
+                _this.SetAt(index, value);
+
+                // We deligate bounds checking to the underlying collection and if it detected a fault,
+                // we translate it to the right exception:
+            }
+            catch (Exception ex)
+            {
+                if (HResults.E_BOUNDS == ex._HResult)
+                    throw new ArgumentOutOfRangeException(nameof(index));
+
+                throw;
+            }
+        }
+
+        private static void InsertAtHelper<T>(IVector<T> _this, uint index, T item)
+        {
+            try
+            {
+                _this.InsertAt(index, item);
+
+                // We delegate bounds checking to the underlying collection and if it detected a fault,
+                // we translate it to the right exception:
+            }
+            catch (Exception ex)
+            {
+                if (HResults.E_BOUNDS == ex._HResult)
+                    throw new ArgumentOutOfRangeException(nameof(index));
+
+                throw;
+            }
+        }
+
+        internal static void RemoveAtHelper<T>(IVector<T> _this, uint index)
+        {
+            try
+            {
+                _this.RemoveAt(index);
+
+                // We delegate bounds checking to the underlying collection and if it detected a fault,
+                // we translate it to the right exception:
+            }
+            catch (Exception ex)
+            {
+                if (HResults.E_BOUNDS == ex._HResult)
+                    throw new ArgumentOutOfRangeException(nameof(index));
+
+                throw;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/VectorViewToReadOnlyCollectionAdapter.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/VectorViewToReadOnlyCollectionAdapter.cs
new file mode 100644
index 0000000000..58ec1dda92
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/VectorViewToReadOnlyCollectionAdapter.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Security;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // This is a set of stub methods implementing the support for the IReadOnlyCollection<T> interface on WinRT
+    // objects that support IVectorView<T>. Used by the interop mashaling infrastructure.
+    //
+    // The methods on this class must be written VERY carefully to avoid introducing security holes.
+    // That's because they are invoked with special "this"! The "this" object
+    // for all of these methods are not VectorViewToReadOnlyCollectionAdapter objects. Rather, they are of type
+    // IVectorView<T>. No actual VectorViewToReadOnlyCollectionAdapter object is ever instantiated. Thus, you will see
+    // a lot of expressions that cast "this" to "IVectorView<T>".
+    internal sealed class VectorViewToReadOnlyCollectionAdapter
+    {
+        private VectorViewToReadOnlyCollectionAdapter()
+        {
+            Debug.Fail("This class is never instantiated");
+        }
+
+        // int Count { get }
+        internal int Count<T>()
+        {
+            IVectorView<T> _this = Unsafe.As<IVectorView<T>>(this);
+            uint size = _this.Size;
+            if (((uint)Int32.MaxValue) < size)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_CollectionBackingListTooLarge);
+            }
+
+            return (int)size;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/WindowsFoundationEventHandler.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/WindowsFoundationEventHandler.cs
new file mode 100644
index 0000000000..1f6e373842
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/WindowsFoundationEventHandler.cs
@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // WindowsFoundationEventHandler<T> a copy of the definition for the Windows.Foundation.EventHandler<T> delegate
+    [Guid("9de1c535-6ae1-11e0-84e1-18a905bcc53f")]
+    [WindowsRuntimeImport]
+    internal delegate void WindowsFoundationEventHandler<T>(object sender, T args);
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/WindowsRuntimeMarshal.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/WindowsRuntimeMarshal.cs
new file mode 100644
index 0000000000..1cdb85598c
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/WindowsRuntimeMarshal.cs
@@ -0,0 +1,1286 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Security;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    // Helper functions to manually marshal data between .NET and WinRT
+    public static class WindowsRuntimeMarshal
+    {
+        // Add an event handler to a Windows Runtime style event, such that it can be removed via a delegate
+        // lookup at a later time.  This method adds the handler to the add method using the supplied
+        // delegate.  It then stores the corresponding token in a dictionary for easy access by RemoveEventHandler
+        // later.  Note that the dictionary is indexed by the remove method that will be used for RemoveEventHandler
+        // so the removeMethod given here must match the remove method supplied there exactly.
+        public static void AddEventHandler<T>(Func<T, EventRegistrationToken> addMethod,
+                                              Action<EventRegistrationToken> removeMethod,
+                                              T handler)
+        {
+            if (addMethod == null)
+                throw new ArgumentNullException(nameof(addMethod));
+            if (removeMethod == null)
+                throw new ArgumentNullException(nameof(removeMethod));
+
+            // Managed code allows adding a null event handler, the effect is a no-op.  To match this behavior
+            // for WinRT events, we simply ignore attempts to add null.
+            if (handler == null)
+            {
+                return;
+            }
+
+            // Delegate to managed event registration implementation or native event registration implementation
+            // They have completely different implementation because native side has its own unique problem to solve -
+            // there could be more than one RCW for the same COM object
+            // it would be more confusing and less-performant if we were to merge them together
+            object target = removeMethod.Target;
+            if (target == null || Marshal.IsComObject(target))
+                NativeOrStaticEventRegistrationImpl.AddEventHandler<T>(addMethod, removeMethod, handler);
+            else
+                ManagedEventRegistrationImpl.AddEventHandler<T>(addMethod, removeMethod, handler);
+        }
+
+        // Remove the delegate handler from the Windows Runtime style event registration by looking for
+        // its token, previously stored via AddEventHandler<T>
+        public static void RemoveEventHandler<T>(Action<EventRegistrationToken> removeMethod, T handler)
+        {
+            if (removeMethod == null)
+                throw new ArgumentNullException(nameof(removeMethod));
+
+            // Managed code allows removing a null event handler, the effect is a no-op.  To match this behavior
+            // for WinRT events, we simply ignore attempts to remove null.
+            if (handler == null)
+            {
+                return;
+            }
+
+            // Delegate to managed event registration implementation or native event registration implementation
+            // They have completely different implementation because native side has its own unique problem to solve -
+            // there could be more than one RCW for the same COM object
+            // it would be more confusing and less-performant if we were to merge them together
+            object target = removeMethod.Target;
+            if (target == null || Marshal.IsComObject(target))
+                NativeOrStaticEventRegistrationImpl.RemoveEventHandler<T>(removeMethod, handler);
+            else
+                ManagedEventRegistrationImpl.RemoveEventHandler<T>(removeMethod, handler);
+        }
+
+        public static void RemoveAllEventHandlers(Action<EventRegistrationToken> removeMethod)
+        {
+            if (removeMethod == null)
+                throw new ArgumentNullException(nameof(removeMethod));
+
+            // Delegate to managed event registration implementation or native event registration implementation
+            // They have completely different implementation because native side has its own unique problem to solve -
+            // there could be more than one RCW for the same COM object
+            // it would be more confusing and less-performant if we were to merge them together
+            object target = removeMethod.Target;
+            if (target == null || Marshal.IsComObject(target))
+                NativeOrStaticEventRegistrationImpl.RemoveAllEventHandlers(removeMethod);
+            else
+                ManagedEventRegistrationImpl.RemoveAllEventHandlers(removeMethod);
+        }
+
+        // Returns the total cache size
+        // Used by test only to verify we don't leak event cache
+        internal static int GetRegistrationTokenCacheSize()
+        {
+            int count = 0;
+
+            if (ManagedEventRegistrationImpl.s_eventRegistrations != null)
+            {
+                lock (ManagedEventRegistrationImpl.s_eventRegistrations)
+                {
+                    foreach (var item in ManagedEventRegistrationImpl.s_eventRegistrations)
+                        count++;
+                }
+            }
+
+            if (NativeOrStaticEventRegistrationImpl.s_eventRegistrations != null)
+            {
+                lock (NativeOrStaticEventRegistrationImpl.s_eventRegistrations)
+                {
+                    count += NativeOrStaticEventRegistrationImpl.s_eventRegistrations.Count;
+                }
+            }
+
+            return count;
+        }
+
+        //
+        // Optimized version of List of EventRegistrationToken
+        // It is made a struct to reduce overhead
+        //
+        internal struct EventRegistrationTokenList
+        {
+            private EventRegistrationToken firstToken;     // Optimization for common case where there is only one token
+            private List<EventRegistrationToken> restTokens;     // Rest of the tokens
+
+            internal EventRegistrationTokenList(EventRegistrationToken token)
+            {
+                firstToken = token;
+                restTokens = null;
+            }
+
+            // Push a new token into this list
+            // Returns true if you need to copy back this list into the dictionary (so that you 
+            // don't lose change outside the dictionary). false otherwise.
+            public bool Push(EventRegistrationToken token)
+            {
+                bool needCopy = false;
+
+                if (restTokens == null)
+                {
+                    restTokens = new List<EventRegistrationToken>();
+                    needCopy = true;
+                }
+
+                restTokens.Add(token);
+
+                return needCopy;
+            }
+
+            // Pops the last token
+            // Returns false if no more tokens left, true otherwise
+            public bool Pop(out EventRegistrationToken token)
+            {
+                // Only 1 token in this list and we just removed the last token
+                if (restTokens == null || restTokens.Count == 0)
+                {
+                    token = firstToken;
+                    return false;
+                }
+
+                int last = restTokens.Count - 1;
+                token = restTokens[last];
+                restTokens.RemoveAt(last);
+
+                return true;
+            }
+
+            public void CopyTo(List<EventRegistrationToken> tokens)
+            {
+                tokens.Add(firstToken);
+                if (restTokens != null)
+                    tokens.AddRange(restTokens);
+            }
+        }
+
+        //
+        // Event registration support for managed objects events & static events
+        //
+        internal static class ManagedEventRegistrationImpl
+        {
+            // Mappings of delegates registered for events -> their registration tokens.
+            // These mappings are stored indexed by the remove method which can be used to undo the registrations.
+            //
+            // The full structure of this table is:
+            //   object the event is being registered on ->
+            //      Table [RemoveMethod] -> 
+            //        Table [Handler] -> Token
+            //
+            // Note: There are a couple of optimizations I didn't do here because they don't make sense for managed events:
+            // 1.  Flatten the event cache (see EventCacheKey in native WinRT event implementation below)
+            //
+            //     This is because managed events use ConditionalWeakTable to hold Objects->(Event->(Handler->Tokens)), 
+            //     and when object goes away everything else will be nicely cleaned up. If I flatten it like native WinRT events, 
+            //     I'll have to use Dictionary (as ConditionalWeakTable won't work - nobody will hold the new key alive anymore) 
+            //     instead, and that means I'll have to add more code from native WinRT events into managed WinRT event to support 
+            //     self-cleanup in the finalization, as well as reader/writer lock to protect against race conditions in the finalization, 
+            //     which adds a lot more complexity and doesn't really worth it.
+            // 
+            // 2.  Use conditionalWeakTable to hold Handler->Tokens. 
+            // 
+            //     The reason is very simple - managed object use dictionary (see EventRegistrationTokenTable) to hold delegates alive. 
+            //     If the delegates aren't alive, it means either they have been unsubscribed, or the object itself is gone, 
+            //     and in either case, they've been already taken care of.
+            // 
+            internal volatile static
+                ConditionalWeakTable<object, Dictionary<MethodInfo, Dictionary<object, EventRegistrationTokenList>>> s_eventRegistrations =
+                    new ConditionalWeakTable<object, Dictionary<MethodInfo, Dictionary<object, EventRegistrationTokenList>>>();
+
+            internal static void AddEventHandler<T>(Func<T, EventRegistrationToken> addMethod,
+                                                  Action<EventRegistrationToken> removeMethod,
+                                                  T handler)
+            {
+                Debug.Assert(addMethod != null);
+                Debug.Assert(removeMethod != null);
+
+                // Add the method, and make a note of the token -> delegate mapping.
+                object instance = removeMethod.Target;
+                Dictionary<object, EventRegistrationTokenList> registrationTokens = GetEventRegistrationTokenTable(instance, removeMethod);
+                EventRegistrationToken token = addMethod(handler);
+                lock (registrationTokens)
+                {
+                    EventRegistrationTokenList tokens;
+                    if (!registrationTokens.TryGetValue(handler, out tokens))
+                    {
+                        tokens = new EventRegistrationTokenList(token);
+                        registrationTokens[handler] = tokens;
+                    }
+                    else
+                    {
+                        bool needCopy = tokens.Push(token);
+
+                        // You need to copy back this list into the dictionary (so that you don't lose change outside dictionary)
+                        if (needCopy)
+                            registrationTokens[handler] = tokens;
+                    }
+
+                    Log("[WinRT_Eventing] Event subscribed for managed instance = " + instance + ", handler = " + handler + "\n");
+                }
+            }
+
+            // Get the event registration token table for an event.  These are indexed by the remove method of the event.
+            private static Dictionary<object, EventRegistrationTokenList> GetEventRegistrationTokenTable(object instance, Action<EventRegistrationToken> removeMethod)
+            {
+                Debug.Assert(instance != null);
+                Debug.Assert(removeMethod != null);
+                Debug.Assert(s_eventRegistrations != null);
+
+                lock (s_eventRegistrations)
+                {
+                    Dictionary<MethodInfo, Dictionary<object, EventRegistrationTokenList>> instanceMap = null;
+                    if (!s_eventRegistrations.TryGetValue(instance, out instanceMap))
+                    {
+                        instanceMap = new Dictionary<MethodInfo, Dictionary<object, EventRegistrationTokenList>>();
+                        s_eventRegistrations.Add(instance, instanceMap);
+                    }
+
+                    Dictionary<object, EventRegistrationTokenList> tokens = null;
+                    if (!instanceMap.TryGetValue(removeMethod.Method, out tokens))
+                    {
+                        tokens = new Dictionary<object, EventRegistrationTokenList>();
+                        instanceMap.Add(removeMethod.Method, tokens);
+                    }
+
+                    return tokens;
+                }
+            }
+
+            internal static void RemoveEventHandler<T>(Action<EventRegistrationToken> removeMethod, T handler)
+            {
+                Debug.Assert(removeMethod != null);
+
+                object instance = removeMethod.Target;
+                Dictionary<object, EventRegistrationTokenList> registrationTokens = GetEventRegistrationTokenTable(instance, removeMethod);
+                EventRegistrationToken token;
+
+                lock (registrationTokens)
+                {
+                    EventRegistrationTokenList tokens;
+
+                    // Failure to find a registration for a token is not an error - it's simply a no-op.
+                    if (!registrationTokens.TryGetValue(handler, out tokens))
+                    {
+                        Log("[WinRT_Eventing] no registrationTokens found for instance=" + instance + ", handler= " + handler + "\n");
+
+                        return;
+                    }
+
+                    // Select a registration token to unregister
+                    // We don't care which one but I'm returning the last registered token to be consistent
+                    // with native event registration implementation                    
+                    bool moreItems = tokens.Pop(out token);
+                    if (!moreItems)
+                    {
+                        // Remove it from cache if this list become empty
+                        // This must be done because EventRegistrationTokenList now becomes invalid 
+                        // (mostly because there is no safe default value for EventRegistrationToken to express 'no token')
+                        // NOTE: We should try to remove registrationTokens itself from cache if it is empty, otherwise
+                        // we could run into a race condition where one thread removes it from cache and another thread adds
+                        // into the empty registrationToken table
+                        registrationTokens.Remove(handler);
+                    }
+                }
+
+                removeMethod(token);
+
+                Log("[WinRT_Eventing] Event unsubscribed for managed instance = " + instance + ", handler = " + handler + ", token = " + token.m_value + "\n");
+            }
+
+            internal static void RemoveAllEventHandlers(Action<EventRegistrationToken> removeMethod)
+            {
+                Debug.Assert(removeMethod != null);
+
+                object instance = removeMethod.Target;
+                Dictionary<object, EventRegistrationTokenList> registrationTokens = GetEventRegistrationTokenTable(instance, removeMethod);
+
+                List<EventRegistrationToken> tokensToRemove = new List<EventRegistrationToken>();
+
+                lock (registrationTokens)
+                {
+                    // Copy all tokens to tokensToRemove array which later we'll call removeMethod on
+                    // outside this lock
+                    foreach (EventRegistrationTokenList tokens in registrationTokens.Values)
+                    {
+                        tokens.CopyTo(tokensToRemove);
+                    }
+
+                    // Clear the dictionary - at this point all event handlers are no longer in the cache
+                    // but they are not removed yet
+                    registrationTokens.Clear();
+                    Log("[WinRT_Eventing] Cache cleared for managed instance = " + instance + "\n");
+                }
+
+                //
+                // Remove all handlers outside the lock
+                //
+                Log("[WinRT_Eventing] Start removing all events for instance = " + instance + "\n");
+                CallRemoveMethods(removeMethod, tokensToRemove);
+                Log("[WinRT_Eventing] Finished removing all events for instance = " + instance + "\n");
+            }
+        }
+
+        //
+        // WinRT event registration implementation code
+        //
+        internal static class NativeOrStaticEventRegistrationImpl
+        {
+            //
+            // Key = (target object, event)
+            // We use a key of object+event to save an extra dictionary
+            //
+            internal struct EventCacheKey : IEquatable<EventCacheKey>
+            {
+                internal object target;
+                internal MethodInfo method;
+
+                public override string ToString()
+                {
+                    return "(" + target + ", " + method + ")";
+                }
+
+                public bool Equals(EventCacheKey other)
+                {
+                    return (Object.Equals(target, other.target) && Object.Equals(method, other.method));
+                }
+
+                public int GetHashCode(EventCacheKey key)
+                {
+                    return key.target.GetHashCode() ^ key.method.GetHashCode();
+                }
+            }
+
+            //
+            // EventRegistrationTokenListWithCount
+            // 
+            // A list of EventRegistrationTokens that maintains a count
+            //
+            // The reason this needs to be a separate class is that we need a finalizer for this class
+            // If the delegate is collected, it will take this list away with it (due to dependent handles), 
+            // and we need to remove the PerInstancEntry from cache
+            // See ~EventRegistrationTokenListWithCount for more details
+            //
+            internal class EventRegistrationTokenListWithCount
+            {
+                private TokenListCount _tokenListCount;
+                private EventRegistrationTokenList _tokenList;
+
+                internal EventRegistrationTokenListWithCount(TokenListCount tokenListCount, EventRegistrationToken token)
+                {
+                    _tokenListCount = tokenListCount;
+                    _tokenListCount.Inc();
+
+                    _tokenList = new EventRegistrationTokenList(token);
+                }
+
+                ~EventRegistrationTokenListWithCount()
+                {
+                    // Decrement token list count
+                    // This is need to correctly keep trace of number of tokens for EventCacheKey
+                    // and remove it from cache when the token count drop to 0
+                    // we don't need to take locks for decrement the count - we only need to take a global
+                    // lock when we decide to destroy cache for the IUnknown */type instance
+                    Log("[WinRT_Eventing] Finalizing EventRegistrationTokenList for " + _tokenListCount.Key + "\n");
+                    _tokenListCount.Dec();
+                }
+
+                public void Push(EventRegistrationToken token)
+                {
+                    // Since EventRegistrationTokenListWithCount is a reference type, there is no need
+                    // to copy back. Ignore the return value
+                    _tokenList.Push(token);
+                }
+
+                public bool Pop(out EventRegistrationToken token)
+                {
+                    return _tokenList.Pop(out token);
+                }
+
+                public void CopyTo(List<EventRegistrationToken> tokens)
+                {
+                    _tokenList.CopyTo(tokens);
+                }
+            }
+
+            //
+            // Maintains the number of tokens for a particular EventCacheKey
+            // TokenListCount is a class for two reasons:
+            // 1. Efficient update in the Dictionary to avoid lookup twice to update the value
+            // 2. Update token count without taking a global lock. Only takes a global lock when drop to 0
+            //
+            internal class TokenListCount
+            {
+                private int _count;
+                private EventCacheKey _key;
+
+                internal TokenListCount(EventCacheKey key)
+                {
+                    _key = key;
+                }
+
+                internal EventCacheKey Key
+                {
+                    get { return _key; }
+                }
+
+                internal void Inc()
+                {
+                    int newCount = Interlocked.Increment(ref _count);
+                    Log("[WinRT_Eventing] Incremented TokenListCount for " + _key + ", Value = " + newCount + "\n");
+                }
+
+                internal void Dec()
+                {
+                    // Avoid racing with Add/Remove event entries into the cache
+                    // You don't want this removing the key in the middle of a Add/Remove
+                    s_eventCacheRWLock.AcquireWriterLock(Timeout.Infinite);
+                    try
+                    {
+                        int newCount = Interlocked.Decrement(ref _count);
+                        Log("[WinRT_Eventing] Decremented TokenListCount for " + _key + ", Value = " + newCount + "\n");
+                        if (newCount == 0)
+                            CleanupCache();
+                    }
+                    finally
+                    {
+                        s_eventCacheRWLock.ReleaseWriterLock();
+                    }
+                }
+
+                private void CleanupCache()
+                {
+                    // Time to destroy cache for this IUnknown */type instance
+                    // because the total token list count has dropped to 0 and we don't have any events subscribed
+                    Debug.Assert(s_eventRegistrations != null);
+
+                    Log("[WinRT_Eventing] Removing " + _key + " from cache" + "\n");
+                    s_eventRegistrations.Remove(_key);
+                    Log("[WinRT_Eventing] s_eventRegistrations size = " + s_eventRegistrations.Count + "\n");
+                }
+            }
+
+            internal struct EventCacheEntry
+            {
+                // [Handler] -> Token
+                internal ConditionalWeakTable<object, EventRegistrationTokenListWithCount> registrationTable;
+
+                // Maintains current total count for the EventRegistrationTokenListWithCount for this event cache key
+                internal TokenListCount tokenListCount;
+            }
+
+            // Mappings of delegates registered for events -> their registration tokens.
+            // These mappings are stored indexed by the remove method which can be used to undo the registrations.
+            //
+            // The full structure of this table is:
+            //   EventCacheKey (instanceKey, eventMethod) -> EventCacheEntry (Handler->tokens)
+            //   
+            // A InstanceKey is the IUnknown * or static type instance
+            //
+            // Couple of things to note:
+            // 1. We need to use IUnknown* because we want to be able to unscribe to the event for another RCW
+            // based on the same COM object. For example:
+            //    m_canvas.GetAt(0).Event += Func;
+            //    m_canvas.GetAt(0).Event -= Func;  // GetAt(0) might create a new RCW
+            // 
+            // 2. Handler->Token is a ConditionalWeakTable because we don't want to keep the delegate alive
+            // and we want EventRegistrationTokenListWithCount to be finalized after the delegate is no longer alive 
+            // 3. It is possible another COM object is created at the same address
+            // before the entry in cache is destroyed. More specifically, 
+            //   a. The same delegate is being unsubscribed. In this case we'll give them a 
+            //   stale token - unlikely to be a problem
+            //   b. The same delegate is subscribed then unsubscribed. We need to make sure give
+            //   them the latest token in this case. This is guaranteed by always giving the last token and always use equality to
+            //   add/remove event handlers
+            internal volatile static Dictionary<EventCacheKey, EventCacheEntry> s_eventRegistrations =
+                new Dictionary<EventCacheKey, EventCacheEntry>();
+
+            // Prevent add/remove handler code to run at the same with with cache cleanup code
+            private volatile static MyReaderWriterLock s_eventCacheRWLock = new MyReaderWriterLock();
+
+            // Get InstanceKey to use in the cache
+            private static object GetInstanceKey(Action<EventRegistrationToken> removeMethod)
+            {
+                object target = removeMethod.Target;
+                Debug.Assert(target == null || Marshal.IsComObject(target), "Must be null or a RCW");
+                if (target == null)
+                    return removeMethod.Method.DeclaringType;
+
+                // Need the "Raw" IUnknown pointer for the RCW that is not bound to the current context
+                return (object)Marshal.GetRawIUnknownForComObjectNoAddRef(target);
+            }
+
+            private static object FindEquivalentKeyUnsafe(ConditionalWeakTable<object, EventRegistrationTokenListWithCount> registrationTable, object handler, out EventRegistrationTokenListWithCount tokens)
+            {
+                foreach (KeyValuePair<object, EventRegistrationTokenListWithCount> item in registrationTable)
+                {
+                    if (Object.Equals(item.Key, handler))
+                    {
+                        tokens = item.Value;
+                        return item.Key;
+                    }
+                }
+                tokens = null;
+                return null;
+            }
+
+            internal static void AddEventHandler<T>(Func<T, EventRegistrationToken> addMethod,
+                                                  Action<EventRegistrationToken> removeMethod,
+                                                  T handler)
+            {
+                // The instanceKey will be IUnknown * of the target object
+                object instanceKey = GetInstanceKey(removeMethod);
+
+                // Call addMethod outside of RW lock
+                // At this point we don't need to worry about race conditions and we can avoid deadlocks 
+                // if addMethod waits on finalizer thread
+                // If we later throw we need to remove the method
+                EventRegistrationToken token = addMethod(handler);
+
+                bool tokenAdded = false;
+
+                try
+                {
+                    EventRegistrationTokenListWithCount tokens;
+
+                    //
+                    // The whole add/remove code has to be protected by a reader/writer lock
+                    // Add/Remove cannot run at the same time with cache cleanup but Add/Remove can run at the same time
+                    //
+                    s_eventCacheRWLock.AcquireReaderLock(Timeout.Infinite);
+                    try
+                    {
+                        // Add the method, and make a note of the delegate -> token mapping.
+                        TokenListCount tokenListCount;
+                        ConditionalWeakTable<object, EventRegistrationTokenListWithCount> registrationTokens = GetOrCreateEventRegistrationTokenTable(instanceKey, removeMethod, out tokenListCount);
+                        lock (registrationTokens)
+                        {
+                            //
+                            // We need to find the key that equals to this handler
+                            // Suppose we have 3 handlers A, B, C that are equal (refer to the same object and method),
+                            // the first handler (let's say A) will be used as the key and holds all the tokens. 
+                            // We don't need to hold onto B and C, because the COM object itself will keep them alive,
+                            // and they won't die anyway unless the COM object dies or they get unsubscribed.
+                            // It may appear that it is fine to hold A, B, C, and add them and their corresponding tokens
+                            // into registrationTokens table. However, this is very dangerous, because this COM object
+                            // may die, but A, B, C might not get collected yet, and another COM object comes into life
+                            // with the same IUnknown address, and we subscribe event B. In this case, the right token
+                            // will be added into B's token list, but once we unsubscribe B, we might end up removing
+                            // the last token in C, and that may lead to crash.
+                            //
+                            object key = FindEquivalentKeyUnsafe(registrationTokens, handler, out tokens);
+                            if (key == null)
+                            {
+                                tokens = new EventRegistrationTokenListWithCount(tokenListCount, token);
+                                registrationTokens.Add(handler, tokens);
+                            }
+                            else
+                            {
+                                tokens.Push(token);
+                            }
+
+                            tokenAdded = true;
+                        }
+                    }
+                    finally
+                    {
+                        s_eventCacheRWLock.ReleaseReaderLock();
+                    }
+
+                    Log("[WinRT_Eventing] Event subscribed for instance = " + instanceKey + ", handler = " + handler + "\n");
+                }
+                catch (Exception)
+                {
+                    // If we've already added the token and go there, we don't need to "UNDO" anything
+                    if (!tokenAdded)
+                    {
+                        // Otherwise, "Undo" addMethod if any exception occurs
+                        // There is no need to cleanup our data structure as we haven't added the token yet
+                        removeMethod(token);
+                    }
+
+
+                    throw;
+                }
+            }
+
+            private static ConditionalWeakTable<object, EventRegistrationTokenListWithCount> GetEventRegistrationTokenTableNoCreate(object instance, Action<EventRegistrationToken> removeMethod, out TokenListCount tokenListCount)
+            {
+                Debug.Assert(instance != null);
+                Debug.Assert(removeMethod != null);
+
+                return GetEventRegistrationTokenTableInternal(instance, removeMethod, out tokenListCount, /* createIfNotFound = */ false);
+            }
+
+            private static ConditionalWeakTable<object, EventRegistrationTokenListWithCount> GetOrCreateEventRegistrationTokenTable(object instance, Action<EventRegistrationToken> removeMethod, out TokenListCount tokenListCount)
+            {
+                Debug.Assert(instance != null);
+                Debug.Assert(removeMethod != null);
+
+                return GetEventRegistrationTokenTableInternal(instance, removeMethod, out tokenListCount, /* createIfNotFound = */ true);
+            }
+
+            // Get the event registration token table for an event.  These are indexed by the remove method of the event.
+            private static ConditionalWeakTable<object, EventRegistrationTokenListWithCount> GetEventRegistrationTokenTableInternal(object instance, Action<EventRegistrationToken> removeMethod, out TokenListCount tokenListCount, bool createIfNotFound)
+            {
+                Debug.Assert(instance != null);
+                Debug.Assert(removeMethod != null);
+                Debug.Assert(s_eventRegistrations != null);
+
+                EventCacheKey eventCacheKey;
+                eventCacheKey.target = instance;
+                eventCacheKey.method = removeMethod.Method;
+
+                lock (s_eventRegistrations)
+                {
+                    EventCacheEntry eventCacheEntry;
+                    if (!s_eventRegistrations.TryGetValue(eventCacheKey, out eventCacheEntry))
+                    {
+                        if (!createIfNotFound)
+                        {
+                            // No need to create an entry in this case
+                            tokenListCount = null;
+                            return null;
+                        }
+
+                        Log("[WinRT_Eventing] Adding (" + instance + "," + removeMethod.Method + ") into cache" + "\n");
+
+                        eventCacheEntry = new EventCacheEntry();
+                        eventCacheEntry.registrationTable = new ConditionalWeakTable<object, EventRegistrationTokenListWithCount>();
+                        eventCacheEntry.tokenListCount = new TokenListCount(eventCacheKey);
+
+                        s_eventRegistrations.Add(eventCacheKey, eventCacheEntry);
+                    }
+
+                    tokenListCount = eventCacheEntry.tokenListCount;
+
+                    return eventCacheEntry.registrationTable;
+                }
+            }
+
+            internal static void RemoveEventHandler<T>(Action<EventRegistrationToken> removeMethod, T handler)
+            {
+                object instanceKey = GetInstanceKey(removeMethod);
+
+                EventRegistrationToken token;
+
+                //
+                // The whole add/remove code has to be protected by a reader/writer lock
+                // Add/Remove cannot run at the same time with cache cleanup but Add/Remove can run at the same time
+                //
+                s_eventCacheRWLock.AcquireReaderLock(Timeout.Infinite);
+                try
+                {
+                    TokenListCount tokenListCount;
+                    ConditionalWeakTable<object, EventRegistrationTokenListWithCount> registrationTokens = GetEventRegistrationTokenTableNoCreate(instanceKey, removeMethod, out tokenListCount);
+                    if (registrationTokens == null)
+                    {
+                        // We have no information regarding this particular instance (IUnknown*/type) - just return
+                        // This is necessary to avoid leaking empty dictionary/conditionalWeakTables for this instance
+                        Log("[WinRT_Eventing] no registrationTokens found for instance=" + instanceKey + ", handler= " + handler + "\n");
+                        return;
+                    }
+
+                    lock (registrationTokens)
+                    {
+                        EventRegistrationTokenListWithCount tokens;
+
+                        // Note:
+                        // When unsubscribing events, we allow subscribing the event using a different delegate
+                        // (but with the same object/method), so we need to find the first delegate that matches
+                        // and unsubscribe it
+                        // It actually doesn't matter which delegate - as long as it matches
+                        // Note that inside TryGetValueWithValueEquality we assumes that any delegate 
+                        // with the same value equality would have the same hash code
+                        object key = FindEquivalentKeyUnsafe(registrationTokens, handler, out tokens);
+                        Debug.Assert((key != null && tokens != null) || (key == null && tokens == null),
+                                        "key and tokens must be both null or non-null");
+                        if (tokens == null)
+                        {
+                            // Failure to find a registration for a token is not an error - it's simply a no-op.
+                            Log("[WinRT_Eventing] no token list found for instance=" + instanceKey + ", handler= " + handler + "\n");
+                            return;
+                        }
+
+                        // Select a registration token to unregister
+                        // Note that we need to always get the last token just in case another COM object
+                        // is created at the same address before the entry for the old one goes away.
+                        // See comments above s_eventRegistrations for more details
+                        bool moreItems = tokens.Pop(out token);
+
+                        // If the last token is removed from token list, we need to remove it from the cache
+                        // otherwise FindEquivalentKeyUnsafe may found this empty token list even though there could be other
+                        // equivalent keys in there with non-0 token list
+                        if (!moreItems)
+                        {
+                            // Remove it from (handler)->(tokens)
+                            // NOTE: We should not check whether registrationTokens has 0 entries and remove it from the cache
+                            // (just like managed event implementation), because this might have raced with the finalizer of 
+                            // EventRegistrationTokenList
+                            registrationTokens.Remove(key);
+                        }
+
+                        Log("[WinRT_Eventing] Event unsubscribed for managed instance = " + instanceKey + ", handler = " + handler + ", token = " + token.m_value + "\n");
+                    }
+                }
+                finally
+                {
+                    s_eventCacheRWLock.ReleaseReaderLock();
+                }
+
+                // Call removeMethod outside of RW lock
+                // At this point we don't need to worry about race conditions and we can avoid deadlocks 
+                // if removeMethod waits on finalizer thread
+                removeMethod(token);
+            }
+
+            internal static void RemoveAllEventHandlers(Action<EventRegistrationToken> removeMethod)
+            {
+                object instanceKey = GetInstanceKey(removeMethod);
+
+                List<EventRegistrationToken> tokensToRemove = new List<EventRegistrationToken>();
+
+                //
+                // The whole add/remove code has to be protected by a reader/writer lock
+                // Add/Remove cannot run at the same time with cache cleanup but Add/Remove can run at the same time
+                //
+                s_eventCacheRWLock.AcquireReaderLock(Timeout.Infinite);
+                try
+                {
+                    TokenListCount tokenListCount;
+                    ConditionalWeakTable<object, EventRegistrationTokenListWithCount> registrationTokens = GetEventRegistrationTokenTableNoCreate(instanceKey, removeMethod, out tokenListCount);
+                    if (registrationTokens == null)
+                    {
+                        // We have no information regarding this particular instance (IUnknown*/type) - just return
+                        // This is necessary to avoid leaking empty dictionary/conditionalWeakTables for this instance
+                        return;
+                    }
+
+                    lock (registrationTokens)
+                    {
+                        // Copy all tokens to tokensToRemove array which later we'll call removeMethod on
+                        // outside this lock
+                        foreach (KeyValuePair<object, EventRegistrationTokenListWithCount> item in registrationTokens)
+                        {
+                            item.Value.CopyTo(tokensToRemove);
+                        }
+
+                        // Clear the table - at this point all event handlers are no longer in the cache
+                        // but they are not removed yet
+                        registrationTokens.Clear();
+                        Log("[WinRT_Eventing] Cache cleared for managed instance = " + instanceKey + "\n");
+                    }
+                }
+                finally
+                {
+                    s_eventCacheRWLock.ReleaseReaderLock();
+                }
+
+                //
+                // Remove all handlers outside the lock
+                //
+                Log("[WinRT_Eventing] Start removing all events for instance = " + instanceKey + "\n");
+                CallRemoveMethods(removeMethod, tokensToRemove);
+                Log("[WinRT_Eventing] Finished removing all events for instance = " + instanceKey + "\n");
+            }
+
+
+            internal class ReaderWriterLockTimedOutException : ApplicationException
+            {
+            }
+
+            /// Discussed @ https://blogs.msdn.microsoft.com/vancem/2006/03/29/analysis-of-reader-writer-lock/
+            ///
+            /// <summary>
+            /// A reader-writer lock implementation that is intended to be simple, yet very
+            /// efficient.  In particular only 1 interlocked operation is taken for any lock 
+            /// operation (we use spin locks to achieve this).  The spin lock is never held
+            /// for more than a few instructions (in particular, we never call event APIs
+            /// or in fact any non-trivial API while holding the spin lock).   
+            /// 
+            /// Currently this ReaderWriterLock does not support recursion, however it is 
+            /// not hard to add 
+            /// </summary>
+            internal class MyReaderWriterLock
+            {
+                // Lock specifiation for myLock:  This lock protects exactly the local fields associted
+                // instance of MyReaderWriterLock.  It does NOT protect the memory associted with the
+                // the events that hang off this lock (eg writeEvent, readEvent upgradeEvent).
+                private int myLock;
+
+                // Who owns the lock owners > 0 => readers
+                // owners = -1 means there is one writer.  Owners must be >= -1.  
+                private int owners;
+
+                // These variables allow use to avoid Setting events (which is expensive) if we don't have to. 
+                private uint numWriteWaiters;        // maximum number of threads that can be doing a WaitOne on the writeEvent 
+                private uint numReadWaiters;         // maximum number of threads that can be doing a WaitOne on the readEvent
+
+                // conditions we wait on. 
+                private EventWaitHandle writeEvent;    // threads waiting to aquire a write lock go here.
+                private EventWaitHandle readEvent;     // threads waiting to aquire a read lock go here (will be released in bulk)
+
+                internal MyReaderWriterLock()
+                {
+                    // All state can start out zeroed. 
+                }
+
+                internal void AcquireReaderLock(int millisecondsTimeout)
+                {
+                    EnterMyLock();
+                    for (;;)
+                    {
+                        // We can enter a read lock if there are only read-locks have been given out
+                        // and a writer is not trying to get in.  
+                        if (owners >= 0 && numWriteWaiters == 0)
+                        {
+                            // Good case, there is no contention, we are basically done
+                            owners++;       // Indicate we have another reader
+                            break;
+                        }
+
+                        // Drat, we need to wait.  Mark that we have waiters and wait.  
+                        if (readEvent == null)      // Create the needed event 
+                        {
+                            LazyCreateEvent(ref readEvent, false);
+                            continue;   // since we left the lock, start over. 
+                        }
+
+                        WaitOnEvent(readEvent, ref numReadWaiters, millisecondsTimeout);
+                    }
+                    ExitMyLock();
+                }
+
+                internal void AcquireWriterLock(int millisecondsTimeout)
+                {
+                    EnterMyLock();
+                    for (;;)
+                    {
+                        if (owners == 0)
+                        {
+                            // Good case, there is no contention, we are basically done
+                            owners = -1;    // indicate we have a writer.
+                            break;
+                        }
+
+                        // Drat, we need to wait.  Mark that we have waiters and wait.
+                        if (writeEvent == null)     // create the needed event.
+                        {
+                            LazyCreateEvent(ref writeEvent, true);
+                            continue;   // since we left the lock, start over. 
+                        }
+
+                        WaitOnEvent(writeEvent, ref numWriteWaiters, millisecondsTimeout);
+                    }
+                    ExitMyLock();
+                }
+
+                internal void ReleaseReaderLock()
+                {
+                    EnterMyLock();
+                    Debug.Assert(owners > 0, "ReleasingReaderLock: releasing lock and no read lock taken");
+                    --owners;
+                    ExitAndWakeUpAppropriateWaiters();
+                }
+
+                internal void ReleaseWriterLock()
+                {
+                    EnterMyLock();
+                    Debug.Assert(owners == -1, "Calling ReleaseWriterLock when no write lock is held");
+                    owners++;
+                    ExitAndWakeUpAppropriateWaiters();
+                }
+
+                /// <summary>
+                /// A routine for lazily creating a event outside the lock (so if errors
+                /// happen they are outside the lock and that we don't do much work
+                /// while holding a spin lock).  If all goes well, reenter the lock and
+                /// set 'waitEvent' 
+                /// </summary>
+                private void LazyCreateEvent(ref EventWaitHandle waitEvent, bool makeAutoResetEvent)
+                {
+                    Debug.Assert(myLock != 0, "Lock must be held");
+                    Debug.Assert(waitEvent == null, "Wait event must be null");
+
+                    ExitMyLock();
+                    EventWaitHandle newEvent;
+                    if (makeAutoResetEvent)
+                        newEvent = new AutoResetEvent(false);
+                    else
+                        newEvent = new ManualResetEvent(false);
+                    EnterMyLock();
+                    if (waitEvent == null)          // maybe someone snuck in. 
+                        waitEvent = newEvent;
+                }
+
+                /// <summary>
+                /// Waits on 'waitEvent' with a timeout of 'millisceondsTimeout.  
+                /// Before the wait 'numWaiters' is incremented and is restored before leaving this routine.
+                /// </summary>
+                private void WaitOnEvent(EventWaitHandle waitEvent, ref uint numWaiters, int millisecondsTimeout)
+                {
+                    Debug.Assert(myLock != 0, "Lock must be held");
+
+                    waitEvent.Reset();
+                    numWaiters++;
+
+                    bool waitSuccessful = false;
+                    ExitMyLock();      // Do the wait outside of any lock 
+                    try
+                    {
+                        if (!waitEvent.WaitOne(millisecondsTimeout, false))
+                            throw new ReaderWriterLockTimedOutException();
+
+                        waitSuccessful = true;
+                    }
+                    finally
+                    {
+                        EnterMyLock();
+                        --numWaiters;
+                        if (!waitSuccessful)        // We are going to throw for some reason.  Exit myLock. 
+                            ExitMyLock();
+                    }
+                }
+
+                /// <summary>
+                /// Determines the appropriate events to set, leaves the locks, and sets the events. 
+                /// </summary>
+                private void ExitAndWakeUpAppropriateWaiters()
+                {
+                    Debug.Assert(myLock != 0, "Lock must be held");
+
+                    if (owners == 0 && numWriteWaiters > 0)
+                    {
+                        ExitMyLock();      // Exit before signaling to improve efficiency (wakee will need the lock)
+                        writeEvent.Set();   // release one writer. 
+                    }
+                    else if (owners >= 0 && numReadWaiters != 0)
+                    {
+                        ExitMyLock();    // Exit before signaling to improve efficiency (wakee will need the lock)
+                        readEvent.Set();  // release all readers. 
+                    }
+                    else
+                        ExitMyLock();
+                }
+
+                private void EnterMyLock()
+                {
+                    if (Interlocked.CompareExchange(ref myLock, 1, 0) != 0)
+                        EnterMyLockSpin();
+                }
+
+                private void EnterMyLockSpin()
+                {
+                    for (int i = 0; ; i++)
+                    {
+                        if (i < 3 && Environment.ProcessorCount > 1)
+                            Thread.SpinWait(20);    // Wait a few dozen instructions to let another processor release lock. 
+                        else
+                            Thread.Sleep(0);        // Give up my quantum.  
+
+                        if (Interlocked.CompareExchange(ref myLock, 1, 0) == 0)
+                            return;
+                    }
+                }
+                private void ExitMyLock()
+                {
+                    Debug.Assert(myLock != 0, "Exiting spin lock that is not held");
+                    myLock = 0;
+                }
+            };
+        }
+
+        //
+        // Call removeMethod on each token and aggregate all exceptions thrown from removeMethod into one in case of failure
+        //
+        internal static void CallRemoveMethods(Action<EventRegistrationToken> removeMethod, List<EventRegistrationToken> tokensToRemove)
+        {
+            List<Exception> exceptions = new List<Exception>();
+
+            foreach (EventRegistrationToken token in tokensToRemove)
+            {
+                try
+                {
+                    removeMethod(token);
+                }
+                catch (Exception ex)
+                {
+                    exceptions.Add(ex);
+                }
+
+                Log("[WinRT_Eventing] Event unsubscribed for token = " + token.m_value + "\n");
+            }
+
+            if (exceptions.Count > 0)
+                throw new AggregateException(exceptions.ToArray());
+        }
+
+        internal static unsafe string HStringToString(IntPtr hstring)
+        {
+            Debug.Assert(Environment.IsWinRTSupported);
+
+            // There is no difference between a null and empty HSTRING
+            if (hstring == IntPtr.Zero)
+            {
+                return String.Empty;
+            }
+
+            unsafe
+            {
+                uint length;
+                char* rawBuffer = UnsafeNativeMethods.WindowsGetStringRawBuffer(hstring, &length);
+                return new String(rawBuffer, 0, checked((int)length));
+            }
+        }
+
+        internal static Exception GetExceptionForHR(int hresult, Exception innerException, string messageResource)
+        {
+            Exception e = null;
+            if (innerException != null)
+            {
+                string message = innerException.Message;
+                if (message == null && messageResource != null)
+                {
+                    message = SR.GetResourceString(messageResource);
+                }
+                e = new Exception(message, innerException);
+            }
+            else
+            {
+                string message = (messageResource != null ? SR.GetResourceString(messageResource): null);
+                e = new Exception(message);
+            }
+
+            e.SetErrorCode(hresult);
+            return e;
+        }
+
+        internal static Exception GetExceptionForHR(int hresult, Exception innerException)
+        {
+            return GetExceptionForHR(hresult, innerException, null);
+        }
+
+        private static bool s_haveBlueErrorApis = true;
+
+        private static bool RoOriginateLanguageException(int error, string message, IntPtr languageException)
+        {
+            if (s_haveBlueErrorApis)
+            {
+                try
+                {
+                    return UnsafeNativeMethods.RoOriginateLanguageException(error, message, languageException);
+                }
+                catch (EntryPointNotFoundException)
+                {
+                    s_haveBlueErrorApis = false;
+                }
+            }
+
+            return false;
+        }
+
+        private static void RoReportUnhandledError(IRestrictedErrorInfo error)
+        {
+            if (s_haveBlueErrorApis)
+            {
+                try
+                {
+                    UnsafeNativeMethods.RoReportUnhandledError(error);
+                }
+                catch (EntryPointNotFoundException)
+                {
+                    s_haveBlueErrorApis = false;
+                }
+            }
+        }
+
+        private static Guid s_iidIErrorInfo = new Guid(0x1CF2B120, 0x547D, 0x101B, 0x8E, 0x65, 0x08, 0x00, 0x2B, 0x2B, 0xD1, 0x19);
+
+        /// <summary>
+        /// Report that an exception has occurred which went user unhandled.  This allows the global error handler
+        /// for the application to be invoked to process the error.
+        /// </summary>
+        /// <returns>true if the error was reported, false if not (ie running on Win8)</returns>
+        // [FriendAccessAllowed]
+        internal static bool ReportUnhandledError(Exception e)
+        {
+            // Only report to the WinRT global exception handler in modern apps
+            if (!AppDomain.IsAppXModel())
+            {
+                return false;
+            }
+
+            // If we don't have the capability to report to the global error handler, early out
+            if (!s_haveBlueErrorApis)
+            {
+                return false;
+            }
+
+            if (e != null)
+            {
+                IntPtr exceptionIUnknown = IntPtr.Zero;
+                IntPtr exceptionIErrorInfo = IntPtr.Zero;
+                try
+                {
+                    // Get an IErrorInfo for the current exception and originate it as a langauge error in order to have
+                    // Windows generate an IRestrictedErrorInfo corresponding to the exception object.  We can then
+                    // notify the global error handler that this IRestrictedErrorInfo instance represents an exception that
+                    // went unhandled in managed code.
+                    //
+                    // Note that we need to get an IUnknown for the exception object and then QI for IErrorInfo since Exception
+                    // doesn't implement IErrorInfo in managed code - only its CCW does.
+                    exceptionIUnknown = Marshal.GetIUnknownForObject(e);
+                    if (exceptionIUnknown != IntPtr.Zero)
+                    {
+                        Marshal.QueryInterface(exceptionIUnknown, ref s_iidIErrorInfo, out exceptionIErrorInfo);
+                        if (exceptionIErrorInfo != IntPtr.Zero)
+                        {
+                            if (RoOriginateLanguageException(Marshal.GetHRForException_WinRT(e), e.Message, exceptionIErrorInfo))
+                            {
+                                IRestrictedErrorInfo restrictedError = UnsafeNativeMethods.GetRestrictedErrorInfo();
+                                if (restrictedError != null)
+                                {
+                                    RoReportUnhandledError(restrictedError);
+                                    return true;
+                                }
+                            }
+                        }
+                    }
+                }
+                finally
+                {
+                    if (exceptionIErrorInfo != IntPtr.Zero)
+                    {
+                        Marshal.Release(exceptionIErrorInfo);
+                    }
+
+                    if (exceptionIUnknown != IntPtr.Zero)
+                    {
+                        Marshal.Release(exceptionIUnknown);
+                    }
+                }
+            }
+
+            // If we got here, then some step of the marshaling failed, which means the GEH was not invoked
+            return false;
+        }
+
+#if FEATURE_COMINTEROP_WINRT_MANAGED_ACTIVATION
+        // Get an IActivationFactory * for a managed type
+        internal static IntPtr GetActivationFactoryForType(Type type)
+        {
+            ManagedActivationFactory activationFactory = GetManagedActivationFactory(type);
+            return Marshal.GetComInterfaceForObject(activationFactory, typeof(IActivationFactory));
+        }
+
+        internal static ManagedActivationFactory GetManagedActivationFactory(Type type)
+        {
+            ManagedActivationFactory activationFactory = new ManagedActivationFactory(type);
+
+            // If the type has any associated factory interfaces (i.e. supports non-default activation
+            // or has statics), the CCW for this instance of ManagedActivationFactory must support them.
+            Marshal.InitializeManagedWinRTFactoryObject(activationFactory, (RuntimeType)type);
+            return activationFactory;
+        }
+
+
+#endif // FEATURE_COMINTEROP_WINRT_MANAGED_ACTIVATION
+
+        //
+        // Get activation factory object for a specified WinRT type
+        // If the WinRT type is a native type, we'll always create a unique RCW for it,
+        // This is necessary because WinRT factories are often implemented as a singleton, 
+        // and getting back a RCW for such WinRT factory would usually get back a RCW from 
+        // another apartment, even if the interface pointe returned from GetActivationFactory
+        // is a raw pointer. As a result, user would randomly get back RCWs for activation
+        // factories from other apartments and make transiton to those apartments and cause
+        // deadlocks and create objects in incorrect apartments
+        //
+        public static IActivationFactory GetActivationFactory(Type type)
+        {
+            if (type == null)
+                throw new ArgumentNullException(nameof(type));
+
+            if (type.IsWindowsRuntimeObject && type.IsImport)
+            {
+                return (IActivationFactory)Marshal.GetNativeActivationFactory(type);
+            }
+            else
+            {
+#if FEATURE_COMINTEROP_WINRT_MANAGED_ACTIVATION
+                return GetManagedActivationFactory(type);
+#else 
+                // Managed factories are not supported so as to minimize public surface (and test effort)
+                throw new NotSupportedException();
+#endif
+            }
+        }
+
+        // HSTRING marshaling methods:
+
+        public static IntPtr StringToHString(String s)
+        {
+            if (!Environment.IsWinRTSupported)
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_WinRT);
+
+            if (s == null)
+                throw new ArgumentNullException(nameof(s));
+
+            unsafe
+            {
+                IntPtr hstring;
+                int hrCreate = UnsafeNativeMethods.WindowsCreateString(s, s.Length, &hstring);
+                Marshal.ThrowExceptionForHR(hrCreate, new IntPtr(-1));
+                return hstring;
+            }
+        }
+
+        public static String PtrToStringHString(IntPtr ptr)
+        {
+            if (!Environment.IsWinRTSupported)
+            {
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_WinRT);
+            }
+
+            return HStringToString(ptr);
+        }
+
+        public static void FreeHString(IntPtr ptr)
+        {
+            if (!Environment.IsWinRTSupported)
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_WinRT);
+
+            if (ptr != IntPtr.Zero)
+            {
+                UnsafeNativeMethods.WindowsDeleteString(ptr);
+            }
+        }
+
+        [Conditional("_LOGGING")]
+        private static void Log(string s)
+        {
+            // Internal.Console.WriteLine(s);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/WindowsRuntimeMetadata.cs b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/WindowsRuntimeMetadata.cs
new file mode 100644
index 0000000000..ecc1916ba0
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/InteropServices/WindowsRuntime/WindowsRuntimeMetadata.cs
@@ -0,0 +1,77 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Reflection;
+using System.Reflection.Emit;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Security;
+
+namespace System.Runtime.InteropServices.WindowsRuntime
+{
+    internal static class WindowsRuntimeMetadata
+    {
+        private static EventHandler<DesignerNamespaceResolveEventArgs> DesignerNamespaceResolve;
+
+        internal static string[] OnDesignerNamespaceResolveEvent(AppDomain appDomain, string namespaceName)
+        {
+            EventHandler<DesignerNamespaceResolveEventArgs> eventHandler = DesignerNamespaceResolve;
+            if (eventHandler != null)
+            {
+                foreach (EventHandler<DesignerNamespaceResolveEventArgs> handler in eventHandler.GetInvocationList())
+                {
+                    DesignerNamespaceResolveEventArgs eventArgs = new DesignerNamespaceResolveEventArgs(namespaceName);
+
+                    handler(appDomain, eventArgs);
+
+                    Collection<string> assemblyFilesCollection = eventArgs.ResolvedAssemblyFiles;
+                    if (assemblyFilesCollection.Count > 0)
+                    {
+                        string[] retAssemblyFiles = new string[assemblyFilesCollection.Count];
+                        int retIndex = 0;
+                        foreach (string assemblyFile in assemblyFilesCollection)
+                        {
+                            if (String.IsNullOrEmpty(assemblyFile))
+                            {   // DesignerNamespaceResolve event returned null or empty file name - that is not allowed
+                                throw new ArgumentException(SR.Arg_EmptyOrNullString, "DesignerNamespaceResolveEventArgs.ResolvedAssemblyFiles");
+                            }
+                            retAssemblyFiles[retIndex] = assemblyFile;
+                            retIndex++;
+                        }
+
+                        return retAssemblyFiles;
+                    }
+                }
+            }
+
+            return null;
+        }
+    }
+
+
+    internal class DesignerNamespaceResolveEventArgs : EventArgs
+    {
+        private string _NamespaceName;
+        private Collection<string> _ResolvedAssemblyFiles;
+
+        public Collection<string> ResolvedAssemblyFiles
+        {
+            get
+            {
+                return _ResolvedAssemblyFiles;
+            }
+        }
+
+        public DesignerNamespaceResolveEventArgs(string namespaceName)
+        {
+            _NamespaceName = namespaceName;
+            _ResolvedAssemblyFiles = new Collection<string>();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Aes.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Aes.PlatformNotSupported.cs
new file mode 100644
index 0000000000..0ad9634d19
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Aes.PlatformNotSupported.cs
@@ -0,0 +1,40 @@
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.Arm.Arm64
+{
+    /// <summary>
+    /// This class provides access to the Arm64 AES Crypto intrinsics
+    ///
+    /// Arm64 CPU indicate support for this feature by setting
+    /// ID_AA64ISAR0_EL1.AES is 1 or better
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Aes
+    {
+        public static bool IsSupported {  get { return false; } }
+        // <summary>
+        /// Performs AES single round decryption
+        /// vaesdq_u8 (uint8x16_t data, uint8x16_t key)
+        ///</summary>
+        public static Vector128<byte> Decrypt(Vector128<byte> value, Vector128<byte> roundKey) { throw new PlatformNotSupportedException(); }
+
+        // <summary>
+        /// Performs AES single round encryption
+        /// vaeseq_u8 (uint8x16_t data, uint8x16_t key)
+        ///</summary>
+        public static Vector128<byte> Encrypt(Vector128<byte> value, Vector128<byte> roundKey) { throw new PlatformNotSupportedException(); }
+
+        // <summary>
+        /// Performs AES  Mix Columns
+        /// vaesmcq_u8 (uint8x16_t data)
+        ///</summary>
+        public static Vector128<byte> MixColumns(Vector128<byte> value) { throw new PlatformNotSupportedException(); }
+
+        // <summary>
+        /// Performs AES inverse mix columns
+        /// vaesimcq_u8  (uint8x16_t data)
+        ///</summary>
+        public static Vector128<byte> InverseMixColumns(Vector128<byte> value) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Aes.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Aes.cs
new file mode 100644
index 0000000000..24c9342d91
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Aes.cs
@@ -0,0 +1,40 @@
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.Arm.Arm64
+{
+    /// <summary>
+    /// This class provides access to the Arm64 AES Crypto intrinsics
+    ///
+    /// Arm64 CPU indicate support for this feature by setting
+    /// ID_AA64ISAR0_EL1.AES is 1 or better
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Aes
+    {
+        public static bool IsSupported { get => IsSupported; }
+        // <summary>
+        /// Performs AES single round decryption
+        /// vaesdq_u8 (uint8x16_t data, uint8x16_t key)
+        ///</summary>
+        public static Vector128<byte> Decrypt(Vector128<byte> value, Vector128<byte> roundKey) => Decrypt(value, roundKey);
+
+        // <summary>
+        /// Performs AES single round encryption
+        /// vaeseq_u8 (uint8x16_t data, uint8x16_t key)
+        ///</summary>
+        public static Vector128<byte> Encrypt(Vector128<byte> value, Vector128<byte> roundKey) => Encrypt(value, roundKey);
+
+        // <summary>
+        /// Performs AES  Mix Columns
+        /// vaesmcq_u8 (uint8x16_t data)
+        ///</summary>
+        public static Vector128<byte> MixColumns(Vector128<byte> value) => MixColumns(value);
+
+        // <summary>
+        /// Performs AES inverse mix columns
+        /// vaesimcq_u8  (uint8x16_t data)
+        ///</summary>
+        public static Vector128<byte> InverseMixColumns(Vector128<byte> value) => InverseMixColumns(value);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Base.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Base.PlatformNotSupported.cs
new file mode 100644
index 0000000000..0a13828ee0
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Base.PlatformNotSupported.cs
@@ -0,0 +1,33 @@
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+
+namespace System.Runtime.Intrinsics.Arm.Arm64
+{
+    /// <summary>
+    /// This class provides access to the Arm64 Base intrinsics
+    ///
+    /// These intrinsics are supported by all Arm64 CPUs
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Base
+    {
+        public static bool IsSupported { get { return false; }}
+
+        /// <summary>
+        /// Vector LeadingSignCount
+        /// Corresponds to integer forms of ARM64 CLS
+        /// </summary>
+        public static int LeadingSignCount(int  value) { throw new PlatformNotSupportedException(); }
+        public static int LeadingSignCount(long value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector LeadingZeroCount
+        /// Corresponds to integer forms of ARM64 CLZ
+        /// </summary>
+        public static int LeadingZeroCount(int   value) { throw new PlatformNotSupportedException(); }
+        public static int LeadingZeroCount(uint  value) { throw new PlatformNotSupportedException(); }
+        public static int LeadingZeroCount(long  value) { throw new PlatformNotSupportedException(); }
+        public static int LeadingZeroCount(ulong value) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Base.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Base.cs
new file mode 100644
index 0000000000..fc0a19055e
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Base.cs
@@ -0,0 +1,33 @@
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+
+namespace System.Runtime.Intrinsics.Arm.Arm64
+{
+    /// <summary>
+    /// This class provides access to the Arm64 Base intrinsics
+    ///
+    /// These intrinsics are supported by all Arm64 CPUs
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Base
+    {
+        public static bool IsSupported { get { return false; }}
+
+        /// <summary>
+        /// Vector LeadingSignCount
+        /// Corresponds to integer forms of ARM64 CLS
+        /// </summary>
+        public static int LeadingSignCount(int  value) => LeadingSignCount(value);
+        public static int LeadingSignCount(long value) => LeadingSignCount(value);
+
+        /// <summary>
+        /// Vector LeadingZeroCount
+        /// Corresponds to integer forms of ARM64 CLZ
+        /// </summary>
+        public static int LeadingZeroCount(int   value) => LeadingZeroCount(value);
+        public static int LeadingZeroCount(uint  value) => LeadingZeroCount(value);
+        public static int LeadingZeroCount(long  value) => LeadingZeroCount(value);
+        public static int LeadingZeroCount(ulong value) => LeadingZeroCount(value);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Sha1.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Sha1.PlatformNotSupported.cs
new file mode 100644
index 0000000000..9b6c5aac63
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Sha1.PlatformNotSupported.cs
@@ -0,0 +1,54 @@
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.Arm.Arm64
+{
+    /// <summary>
+    /// This class provides access to the Arm64 SHA1 Crypto intrinsics
+    ///
+    /// Arm64 CPU indicate support for this feature by setting
+    /// ID_AA64ISAR0_EL1.SHA1 is 1 or better
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Sha1
+    {
+
+        public static bool IsSupported {  get { return false; } }
+
+        // <summary>
+        /// Performs SHA1 hash update choose form.
+        /// vsha1cq_u32 (uint32x4_t hash_abcd, uint32_t hash_e, uint32x4_t wk)
+        ///</summary>
+        public static Vector128<uint> HashChoose(Vector128<uint> hash_abcd, uint hash_e, Vector128<uint>wk) { throw new PlatformNotSupportedException(); }
+
+        // <summary>
+        /// Performs SHA1 hash update majority form.
+        /// vsha1mq_u32 (uint32x4_t hash_abcd, uint32_t hash_e, uint32x4_t wk)
+        ///</summary>
+        public static Vector128<uint> HashMajority(Vector128<uint> hash_abcd, uint hash_e, Vector128<uint>wk) { throw new PlatformNotSupportedException(); }
+
+        // <summary>
+        /// Performs SHA1 hash update parity form.
+        /// vsha1pq_u32 (uint32x4_t hash_abcd, uint32_t hash_e, uint32x4_t wk)
+        ///</summary>
+        public static Vector128<uint> HashParity(Vector128<uint> hash_abcd, uint hash_e, Vector128<uint>wk) { throw new PlatformNotSupportedException(); }
+
+        // <summary>
+        /// Performs SHA1 fixed rotate
+        /// vsha1h_u32 (uint32_t hash_e)
+        ///</summary>
+        public static uint FixedRotate(uint hash_e) { throw new PlatformNotSupportedException(); }
+
+        // <summary>
+        /// Performs SHA1 schedule update 0
+        /// vsha1su0q_u32 (uint32x4_t w0_3, uint32x4_t w4_7, uint32x4_t w8_11)
+        ///</summary>
+        public static Vector128<uint> SchedulePart1(Vector128<uint> w0_3, Vector128<uint> w4_7, Vector128<uint> w8_11) { throw new PlatformNotSupportedException(); }
+
+        // <summary>
+        /// Performs SHA1 schedule update 1
+        /// vsha1su1q_u32 (uint32x4_t tw0_3, uint32x4_t w12_15)
+        ///</summary>
+        public static Vector128<uint> SchedulePart2(Vector128<uint> tw0_3, Vector128<uint> w12_15) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Sha1.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Sha1.cs
new file mode 100644
index 0000000000..28cc397ceb
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Sha1.cs
@@ -0,0 +1,53 @@
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.Arm.Arm64
+{
+    /// <summary>
+    /// This class provides access to the Arm64 SHA1 Crypto intrinsics
+    ///
+    /// Arm64 CPU indicate support for this feature by setting
+    /// ID_AA64ISAR0_EL1.SHA1 is 1 or better
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Sha1
+    {
+        public static bool IsSupported {  get => IsSupported; }
+
+        // <summary>
+        /// Performs SHA1 hash update choose form.
+        /// vsha1cq_u32 (uint32x4_t hash_abcd, uint32_t hash_e, uint32x4_t wk)
+        ///</summary>
+        public static Vector128<uint> HashChoose(Vector128<uint> hash_abcd, uint hash_e, Vector128<uint>wk) => HashChoose(hash_abcd, hash_e, wk);
+
+        // <summary>
+        /// Performs SHA1 hash update majority form.
+        /// vsha1mq_u32 (uint32x4_t hash_abcd, uint32_t hash_e, uint32x4_t wk)
+        ///</summary>
+        public static Vector128<uint> HashMajority(Vector128<uint> hash_abcd, uint hash_e, Vector128<uint>wk) => HashMajority(hash_abcd, hash_e, wk);
+
+        // <summary>
+        /// Performs SHA1 hash update parity form.
+        /// vsha1pq_u32 (uint32x4_t hash_abcd, uint32_t hash_e, uint32x4_t wk)
+        ///</summary>
+        public static Vector128<uint> HashParity(Vector128<uint> hash_abcd, uint hash_e, Vector128<uint>wk) => HashParity(hash_abcd, hash_e, wk);
+
+        // <summary>
+        /// Performs SHA1 fixed rotate
+        /// vsha1h_u32 (uint32_t hash_e)
+        ///</summary>
+        public static uint FixedRotate(uint hash_e) => FixedRotate(hash_e);
+
+        // <summary>
+        /// Performs SHA1 schedule update 0
+        /// vsha1su0q_u32 (uint32x4_t w0_3, uint32x4_t w4_7, uint32x4_t w8_11)
+        ///</summary>
+        public static Vector128<uint> SchedulePart1(Vector128<uint> w0_3, Vector128<uint> w4_7, Vector128<uint> w8_11) => SchedulePart1(w0_3, w4_7, w8_11);
+
+        // <summary>
+        /// Performs SHA1 schedule update 1
+        /// vsha1su1q_u32 (uint32x4_t tw0_3, uint32x4_t w12_15)
+        ///</summary>
+        public static Vector128<uint> SchedulePart2(Vector128<uint> tw0_3, Vector128<uint> w12_15)  => SchedulePart2(tw0_3, w12_15);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Sha256.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Sha256.PlatformNotSupported.cs
new file mode 100644
index 0000000000..052a1d236b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Sha256.PlatformNotSupported.cs
@@ -0,0 +1,41 @@
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.Arm.Arm64
+{
+    /// <summary>
+    /// This class provides access to the Arm64 SHA256 Crypto intrinsics
+    ///
+    /// Arm64 CPU indicate support for this feature by setting
+    /// ID_AA64ISAR0_EL1.SHA2 is 1 or better
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Sha256
+    {
+        public static bool IsSupported { get { return false; } }
+
+        // <summary>
+        /// Performs SHA256 hash update (part 1).
+        /// vsha256hq_u32 (uint32x4_t hash_abcd, uint32x4_t hash_efgh, uint32x4_t wk)
+        ///</summary>
+        public static Vector128<uint> HashLower(Vector128<uint> hash_abcd, Vector128<uint> hash_efgh, Vector128<uint> wk) { throw new PlatformNotSupportedException(); }
+
+        // <summary>
+        /// Performs SHA256 hash update (part 2).
+        /// vsha256h2q_u32 (uint32x4_t hash_efgh, uint32x4_t hash_abcd, uint32x4_t wk)
+        ///</summary>
+        public static Vector128<uint> HashUpper(Vector128<uint> hash_efgh, Vector128<uint> hash_abcd, Vector128<uint> wk) { throw new PlatformNotSupportedException(); }
+
+        // <summary>
+        /// Performs SHA256 schedule update 0
+        /// vsha256su0q_u32 (uint32x4_t w0_3, uint32x4_t w4_7)
+        ///</summary>
+        public static Vector128<uint> SchedulePart1(Vector128<uint> w0_3, Vector128<uint> w4_7) { throw new PlatformNotSupportedException(); }
+
+        // <summary>
+        /// Performs SHA256 schedule update 1
+        /// vsha256su1q_u32 (uint32x4_t w0_3, uint32x4_t w8_11, uint32x4_t w12_15)
+        ///</summary>
+        public static Vector128<uint> SchedulePart2(Vector128<uint> w0_3, Vector128<uint> w8_11, Vector128<uint> w12_15) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Sha256.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Sha256.cs
new file mode 100644
index 0000000000..4e7e51db30
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Sha256.cs
@@ -0,0 +1,41 @@
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.Arm.Arm64
+{
+    /// <summary>
+    /// This class provides access to the Arm64 SHA256 Crypto intrinsics
+    ///
+    /// Arm64 CPU indicate support for this feature by setting
+    /// ID_AA64ISAR0_EL1.SHA2 is 1 or better
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Sha256
+    {
+        public static bool IsSupported { get => IsSupported; }
+
+        // <summary>
+        /// Performs SHA256 hash update (part 1).
+        /// vsha256hq_u32 (uint32x4_t hash_abcd, uint32x4_t hash_efgh, uint32x4_t wk)
+        ///</summary>
+        public static Vector128<uint> HashLower(Vector128<uint> hash_abcd, Vector128<uint> hash_efgh, Vector128<uint> wk) => HashLower(hash_abcd, hash_efgh, wk);
+
+        // <summary>
+        /// Performs SHA256 hash update (part 2).
+        /// vsha256h2q_u32 (uint32x4_t hash_efgh, uint32x4_t hash_abcd, uint32x4_t wk)
+        ///</summary>
+        public static Vector128<uint> HashUpper(Vector128<uint> hash_efgh, Vector128<uint> hash_abcd, Vector128<uint> wk) => HashUpper(hash_efgh, hash_abcd, wk);
+
+        // <summary>
+        /// Performs SHA256 schedule update 0
+        /// vsha256su0q_u32 (uint32x4_t w0_3, uint32x4_t w4_7)
+        ///</summary>
+        public static Vector128<uint> SchedulePart1(Vector128<uint> w0_3, Vector128<uint> w4_7) => SchedulePart1(w0_3, w4_7);
+
+        // <summary>
+        /// Performs SHA256 schedule update 1
+        /// vsha256su1q_u32 (uint32x4_t tw0_3, uint32x4_t w8_11, uint32x4_t w12_15)
+        ///</summary>
+        public static Vector128<uint> SchedulePart2(Vector128<uint> w0_3, Vector128<uint> w8_11, Vector128<uint> w12_15) => SchedulePart2(w0_3, w8_11, w12_15);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Simd.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Simd.PlatformNotSupported.cs
new file mode 100644
index 0000000000..4b377902c7
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Simd.PlatformNotSupported.cs
@@ -0,0 +1,344 @@
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+
+namespace System.Runtime.Intrinsics.Arm.Arm64
+{
+    /// <summary>
+    /// This class provides access to the Arm64 AdvSIMD intrinsics
+    ///
+    /// Arm64 CPU indicate support for this feature by setting
+    /// ID_AA64PFR0_EL1.AdvSIMD == 0 or better.
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Simd
+    {
+        /// <summary>
+        /// IsSupported property indicates whether any method provided
+        /// by this class is supported by the current runtime.
+        /// </summary>
+        public static bool IsSupported { get { return false; }}
+
+        /// <summary>
+        /// Vector abs
+        /// Corresponds to vector forms of ARM64 ABS & FABS
+        /// </summary>
+        public static Vector64<byte>    Abs(Vector64<sbyte>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector64<ushort>  Abs(Vector64<short>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector64<uint>    Abs(Vector64<int>     value) { throw new PlatformNotSupportedException(); }
+        public static Vector64<float>   Abs(Vector64<float>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<byte>   Abs(Vector128<sbyte>  value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<ushort> Abs(Vector128<short>  value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<uint>   Abs(Vector128<int>    value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<ulong>  Abs(Vector128<long>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<float>  Abs(Vector128<float>  value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<double> Abs(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector add
+        /// Corresponds to vector forms of ARM64 ADD & FADD
+        /// </summary>
+        public static Vector64<T>  Add<T>(Vector64<T>  left, Vector64<T>  right) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> Add<T>(Vector128<T> left, Vector128<T> right) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector and
+        /// Corresponds to vector forms of ARM64 AND
+        /// </summary>
+        public static Vector64<T>  And<T>(Vector64<T>  left, Vector64<T>  right) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> And<T>(Vector128<T> left, Vector128<T> right) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector and not
+        /// Corresponds to vector forms of ARM64 BIC
+        /// </summary>
+        public static Vector64<T>  AndNot<T>(Vector64<T>  left, Vector64<T>  right) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> AndNot<T>(Vector128<T> left, Vector128<T> right) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector BitwiseSelect
+        /// For each bit in the vector result[bit] = sel[bit] ? left[bit] : right[bit]
+        /// Corresponds to vector forms of ARM64 BSL (Also BIF & BIT)
+        /// </summary>
+        public static Vector64<T>  BitwiseSelect<T>(Vector64<T>  sel, Vector64<T>  left, Vector64<T>  right) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> BitwiseSelect<T>(Vector128<T> sel, Vector128<T> left, Vector128<T> right) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector CompareEqual
+        /// For each element result[elem] = (left[elem] == right[elem]) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMEQ & FCMEQ
+        /// </summary>
+        public static Vector64<T>  CompareEqual<T>(Vector64<T>  left, Vector64<T>  right) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> CompareEqual<T>(Vector128<T> left, Vector128<T> right) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector CompareEqualZero
+        /// For each element result[elem] = (left[elem] == 0) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMEQ & FCMEQ
+        /// </summary>
+        public static Vector64<T>  CompareEqualZero<T>(Vector64<T>  value) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> CompareEqualZero<T>(Vector128<T> value) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector CompareGreaterThan
+        /// For each element result[elem] = (left[elem] > right[elem]) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMGT/CMHI & FCMGT
+        /// </summary>
+        public static Vector64<T>  CompareGreaterThan<T>(Vector64<T>  left, Vector64<T>  right) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> CompareGreaterThan<T>(Vector128<T> left, Vector128<T> right) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector CompareGreaterThanZero
+        /// For each element result[elem] = (left[elem] > 0) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMGT & FCMGT
+        /// </summary>
+        public static Vector64<T>  CompareGreaterThanZero<T>(Vector64<T>  value) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> CompareGreaterThanZero<T>(Vector128<T> value) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector CompareGreaterThanOrEqual
+        /// For each element result[elem] = (left[elem] >= right[elem]) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMGE/CMHS & FCMGE
+        /// </summary>
+        public static Vector64<T>  CompareGreaterThanOrEqual<T>(Vector64<T>  left, Vector64<T>    right) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> CompareGreaterThanOrEqual<T>(Vector128<T> left, Vector128<T>   right) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector CompareGreaterThanOrEqualZero
+        /// For each element result[elem] = (left[elem] >= 0) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMGE & FCMGE
+        /// </summary>
+        public static Vector64<T>  CompareGreaterThanOrEqualZero<T>(Vector64<T>  value) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> CompareGreaterThanOrEqualZero<T>(Vector128<T> value) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector CompareLessThanZero
+        /// For each element result[elem] = (left[elem] < 0) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMGT & FCMGT
+        /// </summary>
+        public static Vector64<T>  CompareLessThanZero<T>(Vector64<T>  value) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> CompareLessThanZero<T>(Vector128<T> value) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector CompareLessThanOrEqualZero
+        /// For each element result[elem] = (left[elem] < 0) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMGT & FCMGT
+        /// </summary>
+        public static Vector64<T>  CompareLessThanOrEqualZero<T>(Vector64<T>  value) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> CompareLessThanOrEqualZero<T>(Vector128<T> value) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector CompareTest
+        /// For each element result[elem] = (left[elem] & right[elem]) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMTST
+        /// </summary>
+        public static Vector64<T>  CompareTest<T>(Vector64<T>  left, Vector64<T>  right) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> CompareTest<T>(Vector128<T> left, Vector128<T> right) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// TBD Convert...
+
+        /// <summary>
+        /// Vector Divide
+        /// Corresponds to vector forms of ARM64 FDIV
+        /// </summary>
+        public static Vector64<float>   Divide(Vector64<float>   left, Vector64<float>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<float>  Divide(Vector128<float>  left, Vector128<float>  right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<double> Divide(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector extract item
+        ///
+        /// result = vector[index]
+        ///
+        /// Note: In order to be inlined, index must be a JIT time const expression which can be used to
+        /// populate the literal immediate field.  Use of a non constant will result in generation of a switch table
+        ///
+        /// Corresponds to vector forms of ARM64 MOV
+        /// </summary>
+        public static T Extract<T>(Vector64<T>  vector, byte index) where T : struct { throw new PlatformNotSupportedException(); }
+        public static T Extract<T>(Vector128<T> vector, byte index) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector insert item
+        ///
+        /// result = vector;
+        /// result[index] = data;
+        ///
+        /// Note: In order to be inlined, index must be a JIT time const expression which can be used to
+        /// populate the literal immediate field.  Use of a non constant will result in generation of a switch table
+        ///
+        /// Corresponds to vector forms of ARM64 INS
+        /// </summary>
+        public static Vector64<T>  Insert<T>(Vector64<T>  vector, byte index, T data) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> Insert<T>(Vector128<T> vector, byte index, T data) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector LeadingSignCount
+        /// Corresponds to vector forms of ARM64 CLS
+        /// </summary>
+        public static Vector64<sbyte>  LeadingSignCount(Vector64<sbyte>  value) { throw new PlatformNotSupportedException(); }
+        public static Vector64<short>  LeadingSignCount(Vector64<short>  value) { throw new PlatformNotSupportedException(); }
+        public static Vector64<int>    LeadingSignCount(Vector64<int>    value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<sbyte> LeadingSignCount(Vector128<sbyte> value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<short> LeadingSignCount(Vector128<short> value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<int>   LeadingSignCount(Vector128<int>   value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector LeadingZeroCount
+        /// Corresponds to vector forms of ARM64 CLZ
+        /// </summary>
+        public static Vector64<byte>    LeadingZeroCount(Vector64<byte>    value) { throw new PlatformNotSupportedException(); }
+        public static Vector64<sbyte>   LeadingZeroCount(Vector64<sbyte>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector64<ushort>  LeadingZeroCount(Vector64<ushort>  value) { throw new PlatformNotSupportedException(); }
+        public static Vector64<short>   LeadingZeroCount(Vector64<short>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector64<uint>    LeadingZeroCount(Vector64<uint>    value) { throw new PlatformNotSupportedException(); }
+        public static Vector64<int>     LeadingZeroCount(Vector64<int>     value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<byte>   LeadingZeroCount(Vector128<byte>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<sbyte>  LeadingZeroCount(Vector128<sbyte>  value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<ushort> LeadingZeroCount(Vector128<ushort> value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<short>  LeadingZeroCount(Vector128<short>  value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<uint>   LeadingZeroCount(Vector128<uint>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<int>    LeadingZeroCount(Vector128<int>    value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector max
+        /// Corresponds to vector forms of ARM64 SMAX, UMAX & FMAX
+        /// </summary>
+        public static Vector64<byte>    Max(Vector64<byte>    left, Vector64<byte>    right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<sbyte>   Max(Vector64<sbyte>   left, Vector64<sbyte>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<ushort>  Max(Vector64<ushort>  left, Vector64<ushort>  right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<short>   Max(Vector64<short>   left, Vector64<short>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<uint>    Max(Vector64<uint>    left, Vector64<uint>    right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<int>     Max(Vector64<int>     left, Vector64<int>     right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<float>   Max(Vector64<float>   left, Vector64<float>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<byte>   Max(Vector128<byte>   left, Vector128<byte>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<sbyte>  Max(Vector128<sbyte>  left, Vector128<sbyte>  right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<ushort> Max(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<short>  Max(Vector128<short>  left, Vector128<short>  right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<uint>   Max(Vector128<uint>   left, Vector128<uint>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<int>    Max(Vector128<int>    left, Vector128<int>    right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<float>  Max(Vector128<float>  left, Vector128<float>  right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<double> Max(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector min
+        /// Corresponds to vector forms of ARM64 SMIN, UMIN & FMIN
+        /// </summary>
+        public static Vector64<byte>    Min(Vector64<byte>    left, Vector64<byte>    right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<sbyte>   Min(Vector64<sbyte>   left, Vector64<sbyte>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<ushort>  Min(Vector64<ushort>  left, Vector64<ushort>  right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<short>   Min(Vector64<short>   left, Vector64<short>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<uint>    Min(Vector64<uint>    left, Vector64<uint>    right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<int>     Min(Vector64<int>     left, Vector64<int>     right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<float>   Min(Vector64<float>   left, Vector64<float>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<byte>   Min(Vector128<byte>   left, Vector128<byte>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<sbyte>  Min(Vector128<sbyte>  left, Vector128<sbyte>  right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<ushort> Min(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<short>  Min(Vector128<short>  left, Vector128<short>  right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<uint>   Min(Vector128<uint>   left, Vector128<uint>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<int>    Min(Vector128<int>    left, Vector128<int>    right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<float>  Min(Vector128<float>  left, Vector128<float>  right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<double> Min(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// TBD MOV, FMOV
+
+        /// <summary>
+        /// Vector multiply
+        ///
+        /// For each element result[elem] = left[elem] * right[elem]
+        ///
+        /// Corresponds to vector forms of ARM64 MUL & FMUL
+        /// </summary>
+        public static Vector64<byte>    Multiply(Vector64<byte>    left, Vector64<byte>    right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<sbyte>   Multiply(Vector64<sbyte>   left, Vector64<sbyte>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<ushort>  Multiply(Vector64<ushort>  left, Vector64<ushort>  right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<short>   Multiply(Vector64<short>   left, Vector64<short>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<uint>    Multiply(Vector64<uint>    left, Vector64<uint>    right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<int>     Multiply(Vector64<int>     left, Vector64<int>     right) { throw new PlatformNotSupportedException(); }
+        public static Vector64<float>   Multiply(Vector64<float>   left, Vector64<float>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<byte>   Multiply(Vector128<byte>   left, Vector128<byte>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<sbyte>  Multiply(Vector128<sbyte>  left, Vector128<sbyte>  right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<ushort> Multiply(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<short>  Multiply(Vector128<short>  left, Vector128<short>  right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<uint>   Multiply(Vector128<uint>   left, Vector128<uint>   right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<int>    Multiply(Vector128<int>    left, Vector128<int>    right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<float>  Multiply(Vector128<float>  left, Vector128<float>  right) { throw new PlatformNotSupportedException(); }
+        public static Vector128<double> Multiply(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector negate
+        /// Corresponds to vector forms of ARM64 NEG & FNEG
+        /// </summary>
+        public static Vector64<sbyte>   Negate(Vector64<sbyte>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector64<short>   Negate(Vector64<short>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector64<int>     Negate(Vector64<int>     value) { throw new PlatformNotSupportedException(); }
+        public static Vector64<float>   Negate(Vector64<float>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<sbyte>  Negate(Vector128<sbyte>  value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<short>  Negate(Vector128<short>  value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<int>    Negate(Vector128<int>    value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<long>   Negate(Vector128<long>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<float>  Negate(Vector128<float>  value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<double> Negate(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector not
+        /// Corresponds to vector forms of ARM64 NOT
+        /// </summary>
+        public static Vector64<T>  Not<T>(Vector64<T>  value) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> Not<T>(Vector128<T> value) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector or
+        /// Corresponds to vector forms of ARM64 ORR
+        /// </summary>
+        public static Vector64<T>  Or<T>(Vector64<T>  left, Vector64<T>  right) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> Or<T>(Vector128<T> left, Vector128<T> right) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector or not
+        /// Corresponds to vector forms of ARM64 ORN
+        /// </summary>
+        public static Vector64<T>  OrNot<T>(Vector64<T>  left, Vector64<T>  right) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> OrNot<T>(Vector128<T> left, Vector128<T> right) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector PopCount
+        /// Corresponds to vector forms of ARM64 CNT
+        /// </summary>
+        public static Vector64<byte>    PopCount(Vector64<byte>    value) { throw new PlatformNotSupportedException(); }
+        public static Vector64<sbyte>   PopCount(Vector64<sbyte>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<byte>   PopCount(Vector128<byte>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<sbyte>  PopCount(Vector128<sbyte>  value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// SetVector* Fill vector elements by replicating element value
+        ///
+        /// Corresponds to vector forms of ARM64 DUP (general), DUP (element 0), FMOV (vector, immediate)
+        /// </summary>
+        public static Vector64<T>    SetAllVector64<T>(T value) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T>   SetAllVector128<T>(T value) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector square root
+        /// Corresponds to vector forms of ARM64 FRSQRT
+        /// </summary>
+        public static Vector64<float>   Sqrt(Vector64<float>   value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<float>  Sqrt(Vector128<float>  value) { throw new PlatformNotSupportedException(); }
+        public static Vector128<double> Sqrt(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// Vector subtract
+        /// Corresponds to vector forms of ARM64 SUB & FSUB
+        /// </summary>
+        public static Vector64<T>  Subtract<T>(Vector64<T>  left, Vector64<T>  right) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> Subtract<T>(Vector128<T> left, Vector128<T> right) where T : struct { throw new PlatformNotSupportedException(); }
+
+
+        /// <summary>
+        /// Vector exclusive or
+        /// Corresponds to vector forms of ARM64 EOR
+        /// </summary>
+        public static Vector64<T>  Xor<T>(Vector64<T>  left, Vector64<T>  right) where T : struct { throw new PlatformNotSupportedException(); }
+        public static Vector128<T> Xor<T>(Vector128<T> left, Vector128<T> right) where T : struct { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Simd.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Simd.cs
new file mode 100644
index 0000000000..f162483daf
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/Arm64/Simd.cs
@@ -0,0 +1,344 @@
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+
+namespace System.Runtime.Intrinsics.Arm.Arm64
+{
+    /// <summary>
+    /// This class provides access to the Arm64 AdvSIMD intrinsics
+    ///
+    /// Arm64 CPU indicate support for this feature by setting
+    /// ID_AA64PFR0_EL1.AdvSIMD == 0 or better.
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Simd
+    {
+        /// <summary>
+        /// IsSupported property indicates whether any method provided
+        /// by this class is supported by the current runtime.
+        /// </summary>
+        public static bool IsSupported { get => IsSupported; }
+
+        /// <summary>
+        /// Vector abs
+        /// Corresponds to vector forms of ARM64 ABS & FABS
+        /// </summary>
+        public static Vector64<byte>    Abs(Vector64<sbyte>   value) => Abs(value);
+        public static Vector64<ushort>  Abs(Vector64<short>   value) => Abs(value);
+        public static Vector64<uint>    Abs(Vector64<int>     value) => Abs(value);
+        public static Vector64<float>   Abs(Vector64<float>   value) => Abs(value);
+        public static Vector128<byte>   Abs(Vector128<sbyte>  value) => Abs(value);
+        public static Vector128<ushort> Abs(Vector128<short>  value) => Abs(value);
+        public static Vector128<uint>   Abs(Vector128<int>    value) => Abs(value);
+        public static Vector128<ulong>  Abs(Vector128<long>   value) => Abs(value);
+        public static Vector128<float>  Abs(Vector128<float>  value) => Abs(value);
+        public static Vector128<double> Abs(Vector128<double> value) => Abs(value);
+
+        /// <summary>
+        /// Vector add
+        /// Corresponds to vector forms of ARM64 ADD & FADD
+        /// </summary>
+        public static Vector64<T>  Add<T>(Vector64<T>  left, Vector64<T>  right) where T : struct => Add(left, right);
+        public static Vector128<T> Add<T>(Vector128<T> left, Vector128<T> right) where T : struct => Add(left, right);
+
+        /// <summary>
+        /// Vector and
+        /// Corresponds to vector forms of ARM64 AND
+        /// </summary>
+        public static Vector64<T>  And<T>(Vector64<T>  left, Vector64<T>  right) where T : struct => And(left, right);
+        public static Vector128<T> And<T>(Vector128<T> left, Vector128<T> right) where T : struct => And(left, right);
+
+        /// <summary>
+        /// Vector and not
+        /// Corresponds to vector forms of ARM64 BIC
+        /// </summary>
+        public static Vector64<T>  AndNot<T>(Vector64<T>  left, Vector64<T>  right) where T : struct => AndNot(left, right);
+        public static Vector128<T> AndNot<T>(Vector128<T> left, Vector128<T> right) where T : struct => AndNot(left, right);
+
+        /// <summary>
+        /// Vector BitwiseSelect
+        /// For each bit in the vector result[bit] = sel[bit] ? left[bit] : right[bit]
+        /// Corresponds to vector forms of ARM64 BSL (Also BIF & BIT)
+        /// </summary>
+        public static Vector64<T>  BitwiseSelect<T>(Vector64<T>  sel, Vector64<T>  left, Vector64<T>  right) where T : struct => BitwiseSelect(sel, left, right);
+        public static Vector128<T> BitwiseSelect<T>(Vector128<T> sel, Vector128<T> left, Vector128<T> right) where T : struct => BitwiseSelect(sel, left, right);
+
+        /// <summary>
+        /// Vector CompareEqual
+        /// For each element result[elem] = (left[elem] == right[elem]) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMEQ & FCMEQ
+        /// </summary>
+        public static Vector64<T>  CompareEqual<T>(Vector64<T>  left, Vector64<T>  right) where T : struct => CompareEqual(left, right);
+        public static Vector128<T> CompareEqual<T>(Vector128<T> left, Vector128<T> right) where T : struct => CompareEqual(left, right);
+
+        /// <summary>
+        /// Vector CompareEqualZero
+        /// For each element result[elem] = (left[elem] == 0) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMEQ & FCMEQ
+        /// </summary>
+        public static Vector64<T>  CompareEqualZero<T>(Vector64<T>  value) where T : struct => CompareEqualZero(value);
+        public static Vector128<T> CompareEqualZero<T>(Vector128<T> value) where T : struct => CompareEqualZero(value);
+
+        /// <summary>
+        /// Vector CompareGreaterThan
+        /// For each element result[elem] = (left[elem] > right[elem]) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMGT/CMHI & FCMGT
+        /// </summary>
+        public static Vector64<T>  CompareGreaterThan<T>(Vector64<T>  left, Vector64<T>  right) where T : struct => CompareGreaterThan(left, right);
+        public static Vector128<T> CompareGreaterThan<T>(Vector128<T> left, Vector128<T> right) where T : struct => CompareGreaterThan(left, right);
+
+        /// <summary>
+        /// Vector CompareGreaterThanZero
+        /// For each element result[elem] = (left[elem] > 0) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMGT & FCMGT
+        /// </summary>
+        public static Vector64<T>  CompareGreaterThanZero<T>(Vector64<T>  value) where T : struct => CompareGreaterThanZero(value);
+        public static Vector128<T> CompareGreaterThanZero<T>(Vector128<T> value) where T : struct => CompareGreaterThanZero(value);
+
+        /// <summary>
+        /// Vector CompareGreaterThanOrEqual
+        /// For each element result[elem] = (left[elem] >= right[elem]) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMGE/CMHS & FCMGE
+        /// </summary>
+        public static Vector64<T>  CompareGreaterThanOrEqual<T>(Vector64<T>  left, Vector64<T>    right) where T : struct => CompareGreaterThanOrEqual(left, right);
+        public static Vector128<T> CompareGreaterThanOrEqual<T>(Vector128<T> left, Vector128<T>   right) where T : struct => CompareGreaterThanOrEqual(left, right);
+
+        /// <summary>
+        /// Vector CompareGreaterThanOrEqualZero
+        /// For each element result[elem] = (left[elem] >= 0) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMGE & FCMGE
+        /// </summary>
+        public static Vector64<T>  CompareGreaterThanOrEqualZero<T>(Vector64<T>  value) where T : struct => CompareGreaterThanOrEqualZero(value);
+        public static Vector128<T> CompareGreaterThanOrEqualZero<T>(Vector128<T> value) where T : struct => CompareGreaterThanOrEqualZero(value);
+
+        /// <summary>
+        /// Vector CompareLessThanZero
+        /// For each element result[elem] = (left[elem] < 0) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMGT & FCMGT
+        /// </summary>
+        public static Vector64<T>  CompareLessThanZero<T>(Vector64<T>  value) where T : struct => CompareLessThanZero(value);
+        public static Vector128<T> CompareLessThanZero<T>(Vector128<T> value) where T : struct => CompareLessThanZero(value);
+
+        /// <summary>
+        /// Vector CompareLessThanOrEqualZero
+        /// For each element result[elem] = (left[elem] < 0) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMGT & FCMGT
+        /// </summary>
+        public static Vector64<T>  CompareLessThanOrEqualZero<T>(Vector64<T>  value) where T : struct => CompareLessThanOrEqualZero(value);
+        public static Vector128<T> CompareLessThanOrEqualZero<T>(Vector128<T> value) where T : struct => CompareLessThanOrEqualZero(value);
+
+        /// <summary>
+        /// Vector CompareTest
+        /// For each element result[elem] = (left[elem] & right[elem]) ? ~0 : 0
+        /// Corresponds to vector forms of ARM64 CMTST
+        /// </summary>
+        public static Vector64<T>  CompareTest<T>(Vector64<T>  left, Vector64<T>  right) where T : struct => CompareTest(left, right);
+        public static Vector128<T> CompareTest<T>(Vector128<T> left, Vector128<T> right) where T : struct => CompareTest(left, right);
+
+        /// TBD Convert...
+
+        /// <summary>
+        /// Vector Divide
+        /// Corresponds to vector forms of ARM64 FDIV
+        /// </summary>
+        public static Vector64<float>   Divide(Vector64<float>   left, Vector64<float>   right) => Divide(left, right);
+        public static Vector128<float>  Divide(Vector128<float>  left, Vector128<float>  right) => Divide(left, right);
+        public static Vector128<double> Divide(Vector128<double> left, Vector128<double> right) => Divide(left, right);
+
+        /// <summary>
+        /// Vector extract item
+        ///
+        /// result = vector[index]
+        ///
+        /// Note: In order to be inlined, index must be a JIT time const expression which can be used to
+        /// populate the literal immediate field.  Use of a non constant will result in generation of a switch table
+        ///
+        /// Corresponds to vector forms of ARM64 MOV
+        /// </summary>
+        public static T Extract<T>(Vector64<T>  vector, byte index) where T : struct => Extract(vector, index);
+        public static T Extract<T>(Vector128<T> vector, byte index) where T : struct => Extract(vector, index);
+
+        /// <summary>
+        /// Vector insert item
+        ///
+        /// result = vector;
+        /// result[index] = data;
+        ///
+        /// Note: In order to be inlined, index must be a JIT time const expression which can be used to
+        /// populate the literal immediate field.  Use of a non constant will result in generation of a switch table
+        ///
+        /// Corresponds to vector forms of ARM64 INS
+        /// </summary>
+        public static Vector64<T>  Insert<T>(Vector64<T>  vector, byte index, T data) where T : struct => Insert(vector, index, data);
+        public static Vector128<T> Insert<T>(Vector128<T> vector, byte index, T data) where T : struct => Insert(vector, index, data);
+
+        /// <summary>
+        /// Vector LeadingSignCount
+        /// Corresponds to vector forms of ARM64 CLS
+        /// </summary>
+        public static Vector64<sbyte>  LeadingSignCount(Vector64<sbyte>  value) => LeadingSignCount(value);
+        public static Vector64<short>  LeadingSignCount(Vector64<short>  value) => LeadingSignCount(value);
+        public static Vector64<int>    LeadingSignCount(Vector64<int>    value) => LeadingSignCount(value);
+        public static Vector128<sbyte> LeadingSignCount(Vector128<sbyte> value) => LeadingSignCount(value);
+        public static Vector128<short> LeadingSignCount(Vector128<short> value) => LeadingSignCount(value);
+        public static Vector128<int>   LeadingSignCount(Vector128<int>   value) => LeadingSignCount(value);
+
+        /// <summary>
+        /// Vector LeadingZeroCount
+        /// Corresponds to vector forms of ARM64 CLZ
+        /// </summary>
+        public static Vector64<byte>    LeadingZeroCount(Vector64<byte>    value) => LeadingZeroCount(value);
+        public static Vector64<sbyte>   LeadingZeroCount(Vector64<sbyte>   value) => LeadingZeroCount(value);
+        public static Vector64<ushort>  LeadingZeroCount(Vector64<ushort>  value) => LeadingZeroCount(value);
+        public static Vector64<short>   LeadingZeroCount(Vector64<short>   value) => LeadingZeroCount(value);
+        public static Vector64<uint>    LeadingZeroCount(Vector64<uint>    value) => LeadingZeroCount(value);
+        public static Vector64<int>     LeadingZeroCount(Vector64<int>     value) => LeadingZeroCount(value);
+        public static Vector128<byte>   LeadingZeroCount(Vector128<byte>   value) => LeadingZeroCount(value);
+        public static Vector128<sbyte>  LeadingZeroCount(Vector128<sbyte>  value) => LeadingZeroCount(value);
+        public static Vector128<ushort> LeadingZeroCount(Vector128<ushort> value) => LeadingZeroCount(value);
+        public static Vector128<short>  LeadingZeroCount(Vector128<short>  value) => LeadingZeroCount(value);
+        public static Vector128<uint>   LeadingZeroCount(Vector128<uint>   value) => LeadingZeroCount(value);
+        public static Vector128<int>    LeadingZeroCount(Vector128<int>    value) => LeadingZeroCount(value);
+
+        /// <summary>
+        /// Vector max
+        /// Corresponds to vector forms of ARM64 SMAX, UMAX & FMAX
+        /// </summary>
+        public static Vector64<byte>    Max(Vector64<byte>    left, Vector64<byte>    right) => Max(left, right);
+        public static Vector64<sbyte>   Max(Vector64<sbyte>   left, Vector64<sbyte>   right) => Max(left, right);
+        public static Vector64<ushort>  Max(Vector64<ushort>  left, Vector64<ushort>  right) => Max(left, right);
+        public static Vector64<short>   Max(Vector64<short>   left, Vector64<short>   right) => Max(left, right);
+        public static Vector64<uint>    Max(Vector64<uint>    left, Vector64<uint>    right) => Max(left, right);
+        public static Vector64<int>     Max(Vector64<int>     left, Vector64<int>     right) => Max(left, right);
+        public static Vector64<float>   Max(Vector64<float>   left, Vector64<float>   right) => Max(left, right);
+        public static Vector128<byte>   Max(Vector128<byte>   left, Vector128<byte>   right) => Max(left, right);
+        public static Vector128<sbyte>  Max(Vector128<sbyte>  left, Vector128<sbyte>  right) => Max(left, right);
+        public static Vector128<ushort> Max(Vector128<ushort> left, Vector128<ushort> right) => Max(left, right);
+        public static Vector128<short>  Max(Vector128<short>  left, Vector128<short>  right) => Max(left, right);
+        public static Vector128<uint>   Max(Vector128<uint>   left, Vector128<uint>   right) => Max(left, right);
+        public static Vector128<int>    Max(Vector128<int>    left, Vector128<int>    right) => Max(left, right);
+        public static Vector128<float>  Max(Vector128<float>  left, Vector128<float>  right) => Max(left, right);
+        public static Vector128<double> Max(Vector128<double> left, Vector128<double> right) => Max(left, right);
+
+        /// <summary>
+        /// Vector min
+        /// Corresponds to vector forms of ARM64 SMIN, UMIN & FMIN
+        /// </summary>
+        public static Vector64<byte>    Min(Vector64<byte>    left, Vector64<byte>    right) => Min(left, right);
+        public static Vector64<sbyte>   Min(Vector64<sbyte>   left, Vector64<sbyte>   right) => Min(left, right);
+        public static Vector64<ushort>  Min(Vector64<ushort>  left, Vector64<ushort>  right) => Min(left, right);
+        public static Vector64<short>   Min(Vector64<short>   left, Vector64<short>   right) => Min(left, right);
+        public static Vector64<uint>    Min(Vector64<uint>    left, Vector64<uint>    right) => Min(left, right);
+        public static Vector64<int>     Min(Vector64<int>     left, Vector64<int>     right) => Min(left, right);
+        public static Vector64<float>   Min(Vector64<float>   left, Vector64<float>   right) => Min(left, right);
+        public static Vector128<byte>   Min(Vector128<byte>   left, Vector128<byte>   right) => Min(left, right);
+        public static Vector128<sbyte>  Min(Vector128<sbyte>  left, Vector128<sbyte>  right) => Min(left, right);
+        public static Vector128<ushort> Min(Vector128<ushort> left, Vector128<ushort> right) => Min(left, right);
+        public static Vector128<short>  Min(Vector128<short>  left, Vector128<short>  right) => Min(left, right);
+        public static Vector128<uint>   Min(Vector128<uint>   left, Vector128<uint>   right) => Min(left, right);
+        public static Vector128<int>    Min(Vector128<int>    left, Vector128<int>    right) => Min(left, right);
+        public static Vector128<float>  Min(Vector128<float>  left, Vector128<float>  right) => Min(left, right);
+        public static Vector128<double> Min(Vector128<double> left, Vector128<double> right) => Min(left, right);
+
+        /// TBD MOV, FMOV
+
+        /// <summary>
+        /// Vector multiply
+        ///
+        /// For each element result[elem] = left[elem] * right[elem]
+        ///
+        /// Corresponds to vector forms of ARM64 MUL & FMUL
+        /// </summary>
+        public static Vector64<byte>    Multiply(Vector64<byte>    left, Vector64<byte>    right) => Multiply(left, right);
+        public static Vector64<sbyte>   Multiply(Vector64<sbyte>   left, Vector64<sbyte>   right) => Multiply(left, right);
+        public static Vector64<ushort>  Multiply(Vector64<ushort>  left, Vector64<ushort>  right) => Multiply(left, right);
+        public static Vector64<short>   Multiply(Vector64<short>   left, Vector64<short>   right) => Multiply(left, right);
+        public static Vector64<uint>    Multiply(Vector64<uint>    left, Vector64<uint>    right) => Multiply(left, right);
+        public static Vector64<int>     Multiply(Vector64<int>     left, Vector64<int>     right) => Multiply(left, right);
+        public static Vector64<float>   Multiply(Vector64<float>   left, Vector64<float>   right) => Multiply(left, right);
+        public static Vector128<byte>   Multiply(Vector128<byte>   left, Vector128<byte>   right) => Multiply(left, right);
+        public static Vector128<sbyte>  Multiply(Vector128<sbyte>  left, Vector128<sbyte>  right) => Multiply(left, right);
+        public static Vector128<ushort> Multiply(Vector128<ushort> left, Vector128<ushort> right) => Multiply(left, right);
+        public static Vector128<short>  Multiply(Vector128<short>  left, Vector128<short>  right) => Multiply(left, right);
+        public static Vector128<uint>   Multiply(Vector128<uint>   left, Vector128<uint>   right) => Multiply(left, right);
+        public static Vector128<int>    Multiply(Vector128<int>    left, Vector128<int>    right) => Multiply(left, right);
+        public static Vector128<float>  Multiply(Vector128<float>  left, Vector128<float>  right) => Multiply(left, right);
+        public static Vector128<double> Multiply(Vector128<double> left, Vector128<double> right) => Multiply(left, right);
+
+        /// <summary>
+        /// Vector negate
+        /// Corresponds to vector forms of ARM64 NEG & FNEG
+        /// </summary>
+        public static Vector64<sbyte>   Negate(Vector64<sbyte>   value) => Negate(value);
+        public static Vector64<short>   Negate(Vector64<short>   value) => Negate(value);
+        public static Vector64<int>     Negate(Vector64<int>     value) => Negate(value);
+        public static Vector64<float>   Negate(Vector64<float>   value) => Negate(value);
+        public static Vector128<sbyte>  Negate(Vector128<sbyte>  value) => Negate(value);
+        public static Vector128<short>  Negate(Vector128<short>  value) => Negate(value);
+        public static Vector128<int>    Negate(Vector128<int>    value) => Negate(value);
+        public static Vector128<long>   Negate(Vector128<long>   value) => Negate(value);
+        public static Vector128<float>  Negate(Vector128<float>  value) => Negate(value);
+        public static Vector128<double> Negate(Vector128<double> value) => Negate(value);
+
+        /// <summary>
+        /// Vector not
+        /// Corresponds to vector forms of ARM64 NOT
+        /// </summary>
+        public static Vector64<T>  Not<T>(Vector64<T>  value) where T : struct => Not(value);
+        public static Vector128<T> Not<T>(Vector128<T> value) where T : struct => Not(value);
+
+        /// <summary>
+        /// Vector or
+        /// Corresponds to vector forms of ARM64 ORR
+        /// </summary>
+        public static Vector64<T>  Or<T>(Vector64<T>  left, Vector64<T>  right) where T : struct => Or(left, right);
+        public static Vector128<T> Or<T>(Vector128<T> left, Vector128<T> right) where T : struct => Or(left, right);
+
+        /// <summary>
+        /// Vector or not
+        /// Corresponds to vector forms of ARM64 ORN
+        /// </summary>
+        public static Vector64<T>  OrNot<T>(Vector64<T>  left, Vector64<T>  right) where T : struct => OrNot(left, right);
+        public static Vector128<T> OrNot<T>(Vector128<T> left, Vector128<T> right) where T : struct => OrNot(left, right);
+
+        /// <summary>
+        /// Vector PopCount
+        /// Corresponds to vector forms of ARM64 CNT
+        /// </summary>
+        public static Vector64<byte>    PopCount(Vector64<byte>    value) => PopCount(value);
+        public static Vector64<sbyte>   PopCount(Vector64<sbyte>   value) => PopCount(value);
+        public static Vector128<byte>   PopCount(Vector128<byte>   value) => PopCount(value);
+        public static Vector128<sbyte>  PopCount(Vector128<sbyte>  value) => PopCount(value);
+
+        /// <summary>
+        /// SetVector* Fill vector elements by replicating element value
+        ///
+        /// Corresponds to vector forms of ARM64 DUP (general), DUP (element 0), FMOV (vector, immediate)
+        /// </summary>
+        public static Vector64<T>    SetAllVector64<T>(T value)  where T : struct => SetAllVector64(value);
+        public static Vector128<T>   SetAllVector128<T>(T value) where T : struct => SetAllVector128(value);
+
+        /// <summary>
+        /// Vector square root
+        /// Corresponds to vector forms of ARM64 FRSQRT
+        /// </summary>
+        public static Vector64<float>   Sqrt(Vector64<float>   value) => Sqrt(value);
+        public static Vector128<float>  Sqrt(Vector128<float>  value) => Sqrt(value);
+        public static Vector128<double> Sqrt(Vector128<double> value) => Sqrt(value);
+
+        /// <summary>
+        /// Vector subtract
+        /// Corresponds to vector forms of ARM64 SUB & FSUB
+        /// </summary>
+        public static Vector64<T>  Subtract<T>(Vector64<T>  left, Vector64<T>  right) where T : struct => Subtract(left, right);
+        public static Vector128<T> Subtract<T>(Vector128<T> left, Vector128<T> right) where T : struct => Subtract(left, right);
+
+
+        /// <summary>
+        /// Vector exclusive or
+        /// Corresponds to vector forms of ARM64 EOR
+        /// </summary>
+        public static Vector64<T>  Xor<T>(Vector64<T>  left, Vector64<T>  right) where T : struct => Xor(left, right);
+        public static Vector128<T> Xor<T>(Vector128<T> left, Vector128<T> right) where T : struct => Xor(left, right);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector128.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector128.cs
new file mode 100644
index 0000000000..f61310e4e9
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector128.cs
@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.Intrinsics
+{
+    [Intrinsic]
+    [DebuggerDisplay("{DisplayString,nq}")]
+    [DebuggerTypeProxy(typeof(Vector128DebugView<>))]
+    [StructLayout(LayoutKind.Sequential, Size = 16)]
+    public struct Vector128<T> where T : struct
+    {
+        // These fields exist to ensure the alignment is 8, rather than 1.
+        // This also allows the debug view to work https://github.com/dotnet/coreclr/issues/15694)
+        private ulong _00;
+        private ulong _01;
+
+        private unsafe string DisplayString
+        {
+            get
+            {
+                // The IsPrimitive check ends up working for `bool`, `char`, `IntPtr`, and `UIntPtr`
+                // which are not actually supported by any current architecture. This shouldn't be
+                // an issue however and greatly simplifies the check
+
+                if (typeof(T).IsPrimitive)
+                {
+                    var items = new T[16 / Unsafe.SizeOf<T>()];
+                    Unsafe.WriteUnaligned(ref Unsafe.As<T, byte>(ref items[0]), this);
+                    return $"({string.Join(", ", items)})";
+                }
+                else
+                {
+                    return SR.NotSupported_Type;
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector128DebugView.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector128DebugView.cs
new file mode 100644
index 0000000000..7119757b79
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector128DebugView.cs
@@ -0,0 +1,118 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.Intrinsics
+{
+    internal struct Vector128DebugView<T> where T : struct
+    {
+        private Vector128<T> _value;
+
+        public Vector128DebugView(Vector128<T> value)
+        {
+            _value = value;
+        }
+
+        public byte[] ByteView
+        {
+            get
+            {
+                var items = new byte[16];
+                Unsafe.WriteUnaligned(ref items[0], _value);
+                return items;
+            }
+        }
+
+        public double[] DoubleView
+        {
+            get
+            {
+                var items = new double[2];
+                Unsafe.WriteUnaligned(ref Unsafe.As<double, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public short[] Int16View
+        {
+            get
+            {
+                var items = new short[8];
+                Unsafe.WriteUnaligned(ref Unsafe.As<short, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public int[] Int32View
+        {
+            get
+            {
+                var items = new int[4];
+                Unsafe.WriteUnaligned(ref Unsafe.As<int, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public long[] Int64View
+        {
+            get
+            {
+                var items = new long[2];
+                Unsafe.WriteUnaligned(ref Unsafe.As<long, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public sbyte[] SByteView
+        {
+            get
+            {
+                var items = new sbyte[16];
+                Unsafe.WriteUnaligned(ref Unsafe.As<sbyte, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public float[] SingleView
+        {
+            get
+            {
+                var items = new float[4];
+                Unsafe.WriteUnaligned(ref Unsafe.As<float, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public ushort[] UInt16View
+        {
+            get
+            {
+                var items = new ushort[8];
+                Unsafe.WriteUnaligned(ref Unsafe.As<ushort, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public uint[] UInt32View
+        {
+            get
+            {
+                var items = new uint[4];
+                Unsafe.WriteUnaligned(ref Unsafe.As<uint, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public ulong[] UInt64View
+        {
+            get
+            {
+                var items = new ulong[2];
+                Unsafe.WriteUnaligned(ref Unsafe.As<ulong, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector256.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector256.cs
new file mode 100644
index 0000000000..88fd9973e3
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector256.cs
@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.Intrinsics
+{
+    [Intrinsic]
+    [DebuggerDisplay("{DisplayString,nq}")]
+    [DebuggerTypeProxy(typeof(Vector256DebugView<>))]
+    [StructLayout(LayoutKind.Sequential, Size = 32)]
+    public struct Vector256<T> where T : struct
+    {
+        // These fields exist to ensure the alignment is 8, rather than 1.
+        // This also allows the debug view to work https://github.com/dotnet/coreclr/issues/15694)
+        private ulong _00;
+        private ulong _01;
+        private ulong _02;
+        private ulong _03;
+
+        private unsafe string DisplayString
+        {
+            get
+            {
+                // The IsPrimitive check ends up working for `bool`, `char`, `IntPtr`, and `UIntPtr`
+                // which are not actually supported by any current architecture. This shouldn't be
+                // an issue however and greatly simplifies the check
+
+                if (typeof(T).IsPrimitive)
+                {
+                    var items = new T[32 / Unsafe.SizeOf<T>()];
+                    Unsafe.WriteUnaligned(ref Unsafe.As<T, byte>(ref items[0]), this);
+                    return $"({string.Join(", ", items)})";
+                }
+                else
+                {
+                    return SR.NotSupported_Type;
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector256DebugView.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector256DebugView.cs
new file mode 100644
index 0000000000..f07277604c
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector256DebugView.cs
@@ -0,0 +1,118 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.Intrinsics
+{
+    internal struct Vector256DebugView<T> where T : struct
+    {
+        private Vector256<T> _value;
+
+        public Vector256DebugView(Vector256<T> value)
+        {
+            _value = value;
+        }
+
+        public byte[] ByteView
+        {
+            get
+            {
+                var items = new byte[32];
+                Unsafe.WriteUnaligned(ref items[0], _value);
+                return items;
+            }
+        }
+
+        public double[] DoubleView
+        {
+            get
+            {
+                var items = new double[4];
+                Unsafe.WriteUnaligned(ref Unsafe.As<double, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public short[] Int16View
+        {
+            get
+            {
+                var items = new short[16];
+                Unsafe.WriteUnaligned(ref Unsafe.As<short, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public int[] Int32View
+        {
+            get
+            {
+                var items = new int[8];
+                Unsafe.WriteUnaligned(ref Unsafe.As<int, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public long[] Int64View
+        {
+            get
+            {
+                var items = new long[4];
+                Unsafe.WriteUnaligned(ref Unsafe.As<long, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public sbyte[] SByteView
+        {
+            get
+            {
+                var items = new sbyte[32];
+                Unsafe.WriteUnaligned(ref Unsafe.As<sbyte, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public float[] SingleView
+        {
+            get
+            {
+                var items = new float[8];
+                Unsafe.WriteUnaligned(ref Unsafe.As<float, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public ushort[] UInt16View
+        {
+            get
+            {
+                var items = new ushort[16];
+                Unsafe.WriteUnaligned(ref Unsafe.As<ushort, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public uint[] UInt32View
+        {
+            get
+            {
+                var items = new uint[8];
+                Unsafe.WriteUnaligned(ref Unsafe.As<uint, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public ulong[] UInt64View
+        {
+            get
+            {
+                var items = new ulong[4];
+                Unsafe.WriteUnaligned(ref Unsafe.As<ulong, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector64.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector64.cs
new file mode 100644
index 0000000000..776fe2017d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector64.cs
@@ -0,0 +1,43 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.Intrinsics
+{
+    [Intrinsic]
+    [DebuggerDisplay("{DisplayString,nq}")]
+    [DebuggerTypeProxy(typeof(Vector64DebugView<>))]
+    [StructLayout(LayoutKind.Sequential, Size = 8)]
+    public struct Vector64<T> where T : struct
+    {
+        // These fields exist to ensure the alignment is 8, rather than 1.
+        // This also allows the debug view to work https://github.com/dotnet/coreclr/issues/15694)
+        private ulong _00;
+
+        private unsafe string DisplayString
+        {
+            get
+            {
+                // The IsPrimitive check ends up working for `bool`, `char`, `IntPtr`, and `UIntPtr`
+                // which are not actually supported by any current architecture. This shouldn't be
+                // an issue however and greatly simplifies the check
+
+                if (typeof(T).IsPrimitive)
+                {
+                    var items = new T[8 / Unsafe.SizeOf<T>()];
+                    Unsafe.WriteUnaligned(ref Unsafe.As<T, byte>(ref items[0]), this);
+                    return $"({string.Join(", ", items)})";
+                }
+                else
+                {
+                    return SR.NotSupported_Type;
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector64DebugView.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector64DebugView.cs
new file mode 100644
index 0000000000..129832a3c3
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector64DebugView.cs
@@ -0,0 +1,118 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Internal.Runtime.CompilerServices;
+
+namespace System.Runtime.Intrinsics
+{
+    internal struct Vector64DebugView<T> where T : struct
+    {
+        private Vector64<T> _value;
+
+        public Vector64DebugView(Vector64<T> value)
+        {
+            _value = value;
+        }
+
+        public byte[] ByteView
+        {
+            get
+            {
+                var items = new byte[8];
+                Unsafe.WriteUnaligned(ref items[0], _value);
+                return items;
+            }
+        }
+
+        public double[] DoubleView
+        {
+            get
+            {
+                var items = new double[1];
+                Unsafe.WriteUnaligned(ref Unsafe.As<double, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public short[] Int16View
+        {
+            get
+            {
+                var items = new short[4];
+                Unsafe.WriteUnaligned(ref Unsafe.As<short, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public int[] Int32View
+        {
+            get
+            {
+                var items = new int[2];
+                Unsafe.WriteUnaligned(ref Unsafe.As<int, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public long[] Int64View
+        {
+            get
+            {
+                var items = new long[1];
+                Unsafe.WriteUnaligned(ref Unsafe.As<long, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public sbyte[] SByteView
+        {
+            get
+            {
+                var items = new sbyte[8];
+                Unsafe.WriteUnaligned(ref Unsafe.As<sbyte, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public float[] SingleView
+        {
+            get
+            {
+                var items = new float[2];
+                Unsafe.WriteUnaligned(ref Unsafe.As<float, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public ushort[] UInt16View
+        {
+            get
+            {
+                var items = new ushort[4];
+                Unsafe.WriteUnaligned(ref Unsafe.As<ushort, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public uint[] UInt32View
+        {
+            get
+            {
+                var items = new uint[2];
+                Unsafe.WriteUnaligned(ref Unsafe.As<uint, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+
+        public ulong[] UInt64View
+        {
+            get
+            {
+                var items = new ulong[1];
+                Unsafe.WriteUnaligned(ref Unsafe.As<ulong, byte>(ref items[0]), _value);
+                return items;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Aes.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Aes.PlatformNotSupported.cs
new file mode 100644
index 0000000000..5df8f266df
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Aes.PlatformNotSupported.cs
@@ -0,0 +1,86 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel AES hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Aes 
+    {
+        public static bool IsSupported { get { return false; } }
+        
+        /// <summary>
+        /// __m128i _mm_aesdec_si128 (__m128i a, __m128i RoundKey)
+        ///   AESDEC xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Decrypt(Vector128<sbyte> value, Vector128<sbyte> roundKey) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_aesdec_si128 (__m128i a, __m128i RoundKey)
+        ///   AESDEC xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Decrypt(Vector128<byte> value, Vector128<byte> roundKey) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_aesdeclast_si128 (__m128i a, __m128i RoundKey)
+        ///   AESDECLAST xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> DecryptLast(Vector128<sbyte> value, Vector128<sbyte> roundKey) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_aesdeclast_si128 (__m128i a, __m128i RoundKey)
+        ///   AESDECLAST xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> DecryptLast(Vector128<byte> value, Vector128<byte> roundKey) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_aesenc_si128 (__m128i a, __m128i RoundKey)
+        ///   AESENC xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Encrypt(Vector128<sbyte> value, Vector128<sbyte> roundKey) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_aesenc_si128 (__m128i a, __m128i RoundKey)
+        ///   AESENC xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Encrypt(Vector128<byte> value, Vector128<byte> roundKey) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_aesenclast_si128 (__m128i a, __m128i RoundKey)
+        ///   AESENCLAST xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> EncryptLast(Vector128<sbyte> value, Vector128<sbyte> roundKey) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_aesenclast_si128 (__m128i a, __m128i RoundKey)
+        ///   AESENCLAST xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> EncryptLast(Vector128<byte> value, Vector128<byte> roundKey) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_aesimc_si128 (__m128i a)
+        ///   AESIMC xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> InvisibleMixColumn(Vector128<sbyte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_aesimc_si128 (__m128i a)
+        ///   AESIMC xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> InvisibleMixColumn(Vector128<byte> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_aeskeygenassist_si128 (__m128i a, const int imm8)
+        ///   AESKEYGENASSIST xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<sbyte> KeygenAssist(Vector128<sbyte> value, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_aeskeygenassist_si128 (__m128i a, const int imm8)
+        ///   AESKEYGENASSIST xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> KeygenAssist(Vector128<byte> value, byte control) { throw new PlatformNotSupportedException(); }
+
+    }
+
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Aes.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Aes.cs
new file mode 100644
index 0000000000..349919a21c
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Aes.cs
@@ -0,0 +1,86 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel AES hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Aes 
+    {
+        public static bool IsSupported { get => IsSupported; }
+        
+        /// <summary>
+        /// __m128i _mm_aesdec_si128 (__m128i a, __m128i RoundKey)
+        ///   AESDEC xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Decrypt(Vector128<sbyte> value, Vector128<sbyte> roundKey) => Decrypt(value, roundKey);
+        /// <summary>
+        /// __m128i _mm_aesdec_si128 (__m128i a, __m128i RoundKey)
+        ///   AESDEC xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Decrypt(Vector128<byte> value, Vector128<byte> roundKey) => Decrypt(value, roundKey);
+
+        /// <summary>
+        /// __m128i _mm_aesdeclast_si128 (__m128i a, __m128i RoundKey)
+        ///   AESDECLAST xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> DecryptLast(Vector128<sbyte> value, Vector128<sbyte> roundKey) => DecryptLast(value, roundKey);
+        /// <summary>
+        /// __m128i _mm_aesdeclast_si128 (__m128i a, __m128i RoundKey)
+        ///   AESDECLAST xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> DecryptLast(Vector128<byte> value, Vector128<byte> roundKey) => DecryptLast(value, roundKey);
+
+        /// <summary>
+        /// __m128i _mm_aesenc_si128 (__m128i a, __m128i RoundKey)
+        ///   AESENC xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Encrypt(Vector128<sbyte> value, Vector128<sbyte> roundKey) => Encrypt(value, roundKey);
+        /// <summary>
+        /// __m128i _mm_aesenc_si128 (__m128i a, __m128i RoundKey)
+        ///   AESENC xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Encrypt(Vector128<byte> value, Vector128<byte> roundKey) => Encrypt(value, roundKey);
+
+        /// <summary>
+        /// __m128i _mm_aesenclast_si128 (__m128i a, __m128i RoundKey)
+        ///   AESENCLAST xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> EncryptLast(Vector128<sbyte> value, Vector128<sbyte> roundKey) => EncryptLast(value, roundKey);
+        /// <summary>
+        /// __m128i _mm_aesenclast_si128 (__m128i a, __m128i RoundKey)
+        ///   AESENCLAST xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> EncryptLast(Vector128<byte> value, Vector128<byte> roundKey) => EncryptLast(value, roundKey);
+
+        /// <summary>
+        /// __m128i _mm_aesimc_si128 (__m128i a)
+        ///   AESIMC xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> InvisibleMixColumn(Vector128<sbyte> value) => InvisibleMixColumn(value);
+        /// <summary>
+        /// __m128i _mm_aesimc_si128 (__m128i a)
+        ///   AESIMC xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> InvisibleMixColumn(Vector128<byte> value) => InvisibleMixColumn(value);
+
+        /// <summary>
+        /// __m128i _mm_aeskeygenassist_si128 (__m128i a, const int imm8)
+        ///   AESKEYGENASSIST xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<sbyte> KeygenAssist(Vector128<sbyte> value, byte control) => KeygenAssist(value, control);
+        /// <summary>
+        /// __m128i _mm_aeskeygenassist_si128 (__m128i a, const int imm8)
+        ///   AESKEYGENASSIST xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> KeygenAssist(Vector128<byte> value, byte control) => KeygenAssist(value, control);
+
+    }
+
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Avx.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Avx.PlatformNotSupported.cs
new file mode 100644
index 0000000000..1fd61ec3e1
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Avx.PlatformNotSupported.cs
@@ -0,0 +1,1238 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel AVX hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Avx
+    {
+        public static bool IsSupported { get { return false; } }
+        
+        /// <summary>
+        /// __m256 _mm256_add_ps (__m256 a, __m256 b)
+        ///   VADDPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Add(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_add_pd (__m256d a, __m256d b)
+        ///   VADDPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Add(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_addsub_ps (__m256 a, __m256 b)
+        ///   VADDSUBPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> AddSubtract(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_addsub_pd (__m256d a, __m256d b)
+        ///   VADDSUBPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> AddSubtract(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_and_ps (__m256 a, __m256 b)
+        ///   VANDPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> And(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_and_pd (__m256d a, __m256d b)
+        ///   VANDPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> And(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_andnot_ps (__m256 a, __m256 b)
+        ///   VANDNPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> AndNot(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_andnot_pd (__m256d a, __m256d b)
+        ///   VANDNPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> AndNot(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_blend_ps (__m256 a, __m256 b, const int imm8)
+        ///   VBLENDPS ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<float> Blend(Vector256<float> left, Vector256<float> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_blend_pd (__m256d a, __m256d b, const int imm8)
+        ///   VBLENDPD ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<double> Blend(Vector256<double> left, Vector256<double> right, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_blendv_ps (__m256 a, __m256 b, __m256 mask)
+        ///   VBLENDVPS ymm, ymm, ymm/m256, ymm
+        /// </summary>
+        public static Vector256<float> BlendVariable(Vector256<float> left, Vector256<float> right, Vector256<float> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_blendv_pd (__m256d a, __m256d b, __m256d mask)
+        ///   VBLENDVPD ymm, ymm, ymm/m256, ymm
+        /// </summary>
+        public static Vector256<double> BlendVariable(Vector256<double> left, Vector256<double> right, Vector256<double> mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_broadcast_ss (float const * mem_addr)
+        ///   VBROADCASTSS xmm, m32
+        /// </summary>
+        public static unsafe Vector128<float> BroadcastScalarToVector128(float* source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_broadcast_ss (float const * mem_addr)
+        ///   VBROADCASTSS ymm, m32
+        /// </summary>
+        public static unsafe Vector256<float> BroadcastScalarToVector256(float* source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_broadcast_sd (double const * mem_addr)
+        ///   VBROADCASTSD ymm, m64
+        /// </summary>
+        public static unsafe Vector256<double> BroadcastScalarToVector256(double* source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_broadcast_ps (__m128 const * mem_addr)
+        ///   VBROADCASTF128, ymm, m128
+        /// </summary>
+        public static unsafe Vector256<float> BroadcastVector128ToVector256(float* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_broadcast_pd (__m128d const * mem_addr)
+        ///   VBROADCASTF128, ymm, m128
+        /// </summary>
+        public static unsafe Vector256<double> BroadcastVector128ToVector256(double* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_ceil_ps (__m256 a)
+        ///   VROUNDPS ymm, ymm/m256, imm8(10)
+        /// </summary>
+        public static Vector256<float> Ceiling(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_ceil_pd (__m256d a)
+        ///   VROUNDPD ymm, ymm/m256, imm8(10)
+        /// </summary>
+        public static Vector256<double> Ceiling(Vector256<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmp_ps (__m128 a, __m128 b, const int imm8)
+        ///   VCMPPS xmm, xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<float> Compare(Vector128<float> left, Vector128<float> right, FloatComparisonMode mode) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_cmp_pd (__m128d a, __m128d b, const int imm8)
+        ///   VCMPPD xmm, xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<double> Compare(Vector128<double> left, Vector128<double> right, FloatComparisonMode mode) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_cmp_ps (__m256 a, __m256 b, const int imm8)
+        ///   VCMPPS ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<float> Compare(Vector256<float> left, Vector256<float> right, FloatComparisonMode mode) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_cmp_pd (__m256d a, __m256d b, const int imm8)
+        ///   VCMPPD ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<double> Compare(Vector256<double> left, Vector256<double> right, FloatComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmp_sd (__m128d a, __m128d b, const int imm8)
+        ///   VCMPSS xmm, xmm, xmm/m32, imm8
+        /// </summary>
+        public static Vector128<double> CompareScalar(Vector128<double> left, Vector128<double> right, FloatComparisonMode mode) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_cmp_ss (__m128 a, __m128 b, const int imm8)
+        ///   VCMPSD xmm, xmm, xmm/m64, imm8
+        /// </summary>
+        public static Vector128<float> CompareScalar(Vector128<float> left, Vector128<float> right, FloatComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// float _mm256_cvtss_f32 (__m256 a)
+        ///   HELPER: VMOVSS
+        /// </summary>
+        public static float ConvertToSingle(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm256_cvtpd_epi32 (__m256d a)
+        ///   VCVTPD2DQ xmm, ymm/m256
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32(Vector256<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm256_cvtpd_ps (__m256d a)
+        ///   VCVTPD2PS xmm, ymm/m256
+        /// </summary>
+        public static Vector128<float> ConvertToVector128Single(Vector256<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cvtps_epi32 (__m256 a)
+        ///   VCVTPS2DQ ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> ConvertToVector256Int32(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_cvtepi32_ps (__m256i a)
+        ///   VCVTDQ2PS ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> ConvertToVector256Single(Vector256<int> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_cvtps_pd (__m128 a)
+        ///   VCVTPS2PD ymm, xmm/m128
+        /// </summary>
+        public static Vector256<double> ConvertToVector256Double(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_cvtepi32_pd (__m128i a)
+        ///   VCVTDQ2PD ymm, xmm/m128
+        /// </summary>
+        public static Vector256<double> ConvertToVector256Double(Vector128<int> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm256_cvttpd_epi32 (__m256d a)
+        ///   VCVTTPD2DQ xmm, ymm/m256
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32WithTruncation(Vector256<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cvttps_epi32 (__m256 a)
+        ///   VCVTTPS2DQ ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> ConvertToVector256Int32WithTruncation(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_div_ps (__m256 a, __m256 b)
+        ///   VDIVPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Divide(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_div_pd (__m256d a, __m256d b)
+        ///   VDIVPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Divide(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_dp_ps (__m256 a, __m256 b, const int imm8)
+        ///   VDPPS ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<float> DotProduct(Vector256<float> left, Vector256<float> right, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_moveldup_ps (__m256 a)
+        ///   VMOVSLDUP ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> DuplicateEvenIndexed(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_movedup_pd (__m256d a)
+        ///   VMOVDDUP ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> DuplicateEvenIndexed(Vector256<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_movehdup_ps (__m256 a)
+        ///   VMOVSHDUP ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> DuplicateOddIndexed(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __int8 _mm256_extract_epi8 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static sbyte Extract(Vector256<sbyte> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int8 _mm256_extract_epi8 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static byte Extract(Vector256<byte> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int16 _mm256_extract_epi16 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static short Extract(Vector256<short> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int16 _mm256_extract_epi16 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static ushort Extract(Vector256<ushort> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int32 _mm256_extract_epi32 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static int Extract(Vector256<int> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int32 _mm256_extract_epi32 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static uint Extract(Vector256<uint> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int64 _mm256_extract_epi64 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static long Extract(Vector256<long> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int64 _mm256_extract_epi64 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static ulong Extract(Vector256<ulong> value, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm256_extractf128_ps (__m256 a, const int imm8)
+        ///   VEXTRACTF128 xmm/m128, ymm, imm8
+        /// __m128d _mm256_extractf128_pd (__m256d a, const int imm8)
+        ///   VEXTRACTF128 xmm/m128, ymm, imm8
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 xmm/m128, ymm, imm8
+        /// </summary>
+        public static Vector128<T> ExtractVector128<T>(Vector256<T> value, byte index) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(byte* address, Vector256<byte> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(sbyte* address, Vector256<sbyte> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(short* address, Vector256<short> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(ushort* address, Vector256<ushort> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(int* address, Vector256<int> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(uint* address, Vector256<uint> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(long* address, Vector256<long> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(ulong* address, Vector256<ulong> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm256_extractf128_ps (__m256 a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(float* address, Vector256<float> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm256_extractf128_pd (__m256d a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(double* address, Vector256<double> value, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256d _mm256_castpd128_pd256 (__m128d a)
+        ///   HELPER - No Codegen
+        /// __m256 _mm256_castps128_ps256 (__m128 a)
+        ///   HELPER - No Codegen
+        /// __m256i _mm256_castsi128_si256 (__m128i a)
+        ///   HELPER - No Codegen
+        /// </summary>
+        public static Vector256<T> ExtendToVector256<T>(Vector128<T> value) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_floor_ps (__m256 a)
+        ///   VROUNDPS ymm, ymm/m256, imm8(9)
+        /// </summary>
+        public static Vector256<float> Floor(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_floor_pd (__m256d a)
+        ///   VROUNDPS ymm, ymm/m256, imm8(9)
+        /// </summary>
+        public static Vector256<double> Floor(Vector256<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm256_castpd256_pd128 (__m256d a)
+        ///   HELPER - No Codegen
+        /// __m128 _mm256_castps256_ps128 (__m256 a)
+        ///   HELPER - No Codegen
+        /// __m128i _mm256_castsi256_si128 (__m256i a)
+        ///   HELPER - No Codegen
+        /// </summary>
+        public static Vector128<T> GetLowerHalf<T>(Vector256<T> value) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_hadd_ps (__m256 a, __m256 b)
+        ///   VHADDPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> HorizontalAdd(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_hadd_pd (__m256d a, __m256d b)
+        ///   VHADDPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> HorizontalAdd(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_hsub_ps (__m256 a, __m256 b)
+        ///   VHSUBPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> HorizontalSubtract(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_hsub_pd (__m256d a, __m256d b)
+        ///   VHSUBPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> HorizontalSubtract(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_insert_epi8 (__m256i a, __int8 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<sbyte> Insert(Vector256<sbyte> value, sbyte data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_insert_epi8 (__m256i a, __int8 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<byte> Insert(Vector256<byte> value, byte data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_insert_epi16 (__m256i a, __int16 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<short> Insert(Vector256<short> value, short data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_insert_epi16 (__m256i a, __int16 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<ushort> Insert(Vector256<ushort> value, ushort data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_insert_epi32 (__m256i a, __int32 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<int> Insert(Vector256<int> value, int data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_insert_epi32 (__m256i a, __int32 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<uint> Insert(Vector256<uint> value, uint data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_insert_epi64 (__m256i a, __int64 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<long> Insert(Vector256<long> value, long data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_insert_epi64 (__m256i a, __int64 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<ulong> Insert(Vector256<ulong> value, ulong data, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_insertf128_ps (__m256 a, __m128 b, int imm8)
+        ///   VINSERTF128 ymm, ymm, xmm/m128, imm8
+        /// __m256d _mm256_insertf128_pd (__m256d a, __m128d b, int imm8)
+        ///   VINSERTF128 ymm, ymm, xmm/m128, imm8
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, xmm/m128, imm8
+        /// </summary>
+        public static Vector256<T> InsertVector128<T>(Vector256<T> value, Vector128<T> data, byte index) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<sbyte> InsertVector128(Vector256<sbyte> value, sbyte* address, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<byte> InsertVector128(Vector256<byte> value, byte* address, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<short> InsertVector128(Vector256<short> value, short* address, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<ushort> InsertVector128(Vector256<ushort> value, ushort* address, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<int> InsertVector128(Vector256<int> value, int* address, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<uint> InsertVector128(Vector256<uint> value, uint* address, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<long> InsertVector128(Vector256<long> value, long* address, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<ulong> InsertVector128(Vector256<ulong> value, ulong* address, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_insertf128_ps (__m256 a, __m128 b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<float> InsertVector128(Vector256<float> value, float* address, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_insertf128_pd (__m256d a, __m128d b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<double> InsertVector128(Vector256<double> value, double* address, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<sbyte> LoadVector256(sbyte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<byte> LoadVector256(byte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<short> LoadVector256(short* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ushort> LoadVector256(ushort* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<int> LoadVector256(int* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<uint> LoadVector256(uint* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<long> LoadVector256(long* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ulong> LoadVector256(ulong* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_loadu_ps (float const * mem_addr)
+        ///   VMOVUPS ymm, ymm/m256
+        /// </summary>
+        public static unsafe Vector256<float> LoadVector256(float* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_loadu_pd (double const * mem_addr)
+        ///   VMOVUPD ymm, ymm/m256
+        /// </summary>
+        public static unsafe Vector256<double> LoadVector256(double* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<sbyte> LoadAlignedVector256(sbyte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<byte> LoadAlignedVector256(byte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<short> LoadAlignedVector256(short* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ushort> LoadAlignedVector256(ushort* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<int> LoadAlignedVector256(int* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<uint> LoadAlignedVector256(uint* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<long> LoadAlignedVector256(long* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ulong> LoadAlignedVector256(ulong* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_load_ps (float const * mem_addr)
+        ///   VMOVAPS ymm, ymm/m256
+        /// </summary>
+        public static unsafe Vector256<float> LoadAlignedVector256(float* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_load_pd (double const * mem_addr)
+        ///   VMOVAPD ymm, ymm/m256
+        /// </summary>
+        public static unsafe Vector256<double> LoadAlignedVector256(double* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<sbyte> LoadDquVector256(sbyte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<byte> LoadDquVector256(byte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<short> LoadDquVector256(short* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ushort> LoadDquVector256(ushort* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<int> LoadDquVector256(int* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<uint> LoadDquVector256(uint* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<long> LoadDquVector256(long* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ulong> LoadDquVector256(ulong* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_maskload_ps (float const * mem_addr, __m128i mask)
+        ///   VMASKMOVPS xmm, xmm, m128
+        /// </summary>
+        public static unsafe Vector128<float> MaskLoad(float* address, Vector128<uint> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_maskload_pd (double const * mem_addr, __m128i mask)
+        ///   VMASKMOVPD xmm, xmm, m128
+        /// </summary>
+        public static unsafe Vector128<double> MaskLoad(double* address, Vector128<ulong> mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_maskload_ps (float const * mem_addr, __m256i mask)
+        ///   VMASKMOVPS ymm, ymm, m256
+        /// </summary>
+        public static unsafe Vector256<float> MaskLoad(float* address, Vector256<uint> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_maskload_pd (double const * mem_addr, __m256i mask)
+        ///   VMASKMOVPD ymm, ymm, m256
+        /// </summary>
+        public static unsafe Vector256<double> MaskLoad(double* address, Vector256<ulong> mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_maskstore_ps (float * mem_addr, __m128i mask, __m128 a)
+        ///   VMASKMOVPS m128, xmm, xmm
+        /// </summary>
+        public static unsafe void MaskStore(float* address, Vector128<float> mask, Vector128<uint> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_maskstore_pd (double * mem_addr, __m128i mask, __m128d a)
+        ///   VMASKMOVPD m128, xmm, xmm
+        /// </summary>
+        public static unsafe void MaskStore(double* address, Vector128<double> mask, Vector128<ulong> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm256_maskstore_ps (float * mem_addr, __m256i mask, __m256 a)
+        ///   VMASKMOVPS m256, ymm, ymm
+        /// </summary>
+        public static unsafe void MaskStore(float* address, Vector256<float> mask, Vector256<uint> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_maskstore_pd (double * mem_addr, __m256i mask, __m256d a)
+        ///   VMASKMOVPD m256, ymm, ymm
+        /// </summary>
+        public static unsafe void MaskStore(double* address, Vector256<double> mask, Vector256<ulong> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_max_ps (__m256 a, __m256 b)
+        ///   VMAXPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Max(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_max_pd (__m256d a, __m256d b)
+        ///   VMAXPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Max(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_min_ps (__m256 a, __m256 b)
+        ///   VMINPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Min(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_min_pd (__m256d a, __m256d b)
+        ///   VMINPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Min(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm256_movemask_ps (__m256 a)
+        ///   VMOVMSKPS reg, ymm
+        /// </summary>
+        public static int MoveMask(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm256_movemask_pd (__m256d a)
+        ///   VMOVMSKPD reg, ymm
+        /// </summary>
+        public static int MoveMask(Vector256<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_mul_ps (__m256 a, __m256 b)
+        ///   VMULPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Multiply(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_mul_pd (__m256d a, __m256d b)
+        ///   VMULPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Multiply(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_or_ps (__m256 a, __m256 b)
+        ///   VORPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Or(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_or_pd (__m256d a, __m256d b)
+        ///   VORPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Or(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_permute_ps (__m128 a, int imm8)
+        ///   VPERMILPS xmm, xmm, imm8
+        /// </summary>
+        public static Vector128<float> Permute(Vector128<float> value, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_permute_pd (__m128d a, int imm8)
+        ///   VPERMILPD xmm, xmm, imm8
+        /// </summary>
+        public static Vector128<double> Permute(Vector128<double> value, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_permute_ps (__m256 a, int imm8)
+        ///   VPERMILPS ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<float> Permute(Vector256<float> value, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_permute_pd (__m256d a, int imm8)
+        ///   VPERMILPD ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<double> Permute(Vector256<double> value, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_permute2f128_ps (__m256 a, __m256 b, int imm8)
+        ///   VPERM2F128 ymm, ymm, ymm/m256, imm8
+        /// __m256d _mm256_permute2f128_pd (__m256d a, __m256d b, int imm8)
+        ///   VPERM2F128 ymm, ymm, ymm/m256, imm8
+        /// __m256i _mm256_permute2f128_si256 (__m256i a, __m256i b, int imm8)
+        ///   VPERM2F128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<T> Permute2x128<T>(Vector256<T> left, Vector256<T> right, byte control) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_permutevar_ps (__m128 a, __m128i b)
+        ///   VPERMILPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> PermuteVar(Vector128<float> left, Vector128<float> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_permutevar_pd (__m128d a, __m128i b)
+        ///   VPERMILPD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> PermuteVar(Vector128<double> left, Vector128<double> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_permutevar_ps (__m256 a, __m256i b)
+        ///   VPERMILPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> PermuteVar(Vector256<float> left, Vector256<float> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_permutevar_pd (__m256d a, __m256i b)
+        ///   VPERMILPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> PermuteVar(Vector256<double> left, Vector256<double> mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_rcp_ps (__m256 a)
+        ///   VRCPPS ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Reciprocal(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_rsqrt_ps (__m256 a)
+        ///   VRSQRTPS ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> ReciprocalSqrt(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_round_ps (__m256 a, _MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC)
+        ///   VROUNDPS ymm, ymm/m256, imm8(8)
+        /// </summary>
+        public static Vector256<float> RoundToNearestInteger(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_round_ps (__m256 a, _MM_FROUND_TO_NEG_INF | _MM_FROUND_NO_EXC)
+        ///   VROUNDPS ymm, ymm/m256, imm8(9)
+        /// </summary>
+        public static Vector256<float> RoundToNegativeInfinity(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_round_ps (__m256 a, _MM_FROUND_TO_POS_INF | _MM_FROUND_NO_EXC)
+        ///   VROUNDPS ymm, ymm/m256, imm8(10)
+        /// </summary>
+        public static Vector256<float> RoundToPositiveInfinity(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_round_ps (__m256 a, _MM_FROUND_TO_ZERO | _MM_FROUND_NO_EXC)
+        ///   VROUNDPS ymm, ymm/m256, imm8(11)
+        /// </summary>
+        public static Vector256<float> RoundToZero(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_round_ps (__m256 a, _MM_FROUND_CUR_DIRECTION)
+        ///   VROUNDPS ymm, ymm/m256, imm8(4)
+        /// </summary>
+        public static Vector256<float> RoundCurrentDirection(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256d _mm256_round_pd (__m256d a, _MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC)
+        ///   VROUNDPD ymm, ymm/m256, imm8(8)
+        /// </summary>
+        public static Vector256<double> RoundToNearestInteger(Vector256<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_round_pd (__m256d a, _MM_FROUND_TO_NEG_INF | _MM_FROUND_NO_EXC)
+        ///   VROUNDPD ymm, ymm/m256, imm8(9)
+        /// </summary>
+        public static Vector256<double> RoundToNegativeInfinity(Vector256<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_round_pd (__m256d a, _MM_FROUND_TO_POS_INF | _MM_FROUND_NO_EXC)
+        ///   VROUNDPD ymm, ymm/m256, imm8(10)
+        /// </summary>
+        public static Vector256<double> RoundToPositiveInfinity(Vector256<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_round_pd (__m256d a, _MM_FROUND_TO_ZERO | _MM_FROUND_NO_EXC)
+        ///   VROUNDPD ymm, ymm/m256, imm8(11)
+        /// </summary>
+        public static Vector256<double> RoundToZero(Vector256<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_round_pd (__m256d a, _MM_FROUND_CUR_DIRECTION)
+        ///   VROUNDPD ymm, ymm/m256, imm8(4)
+        /// </summary>
+        public static Vector256<double> RoundCurrentDirection(Vector256<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_set_epi8 (char e31, char e30, char e29, char e28, char e27, char e26, char e25, char e24, char e23, char e22, char e21, char e20, char e19, char e18, char e17, char e16, char e15, char e14, char e13, char e12, char e11, char e10, char e9, char e8, char e7, char e6, char e5, char e4, char e3, char e2, char e1, char e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<sbyte> SetVector256(sbyte e31, sbyte e30, sbyte e29, sbyte e28, sbyte e27, sbyte e26, sbyte e25, sbyte e24, sbyte e23, sbyte e22, sbyte e21, sbyte e20, sbyte e19, sbyte e18, sbyte e17, sbyte e16, sbyte e15, sbyte e14, sbyte e13, sbyte e12, sbyte e11, sbyte e10, sbyte e9, sbyte e8, sbyte e7, sbyte e6, sbyte e5, sbyte e4, sbyte e3, sbyte e2, sbyte e1, sbyte e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_set_epi8 (char e31, char e30, char e29, char e28, char e27, char e26, char e25, char e24, char e23, char e22, char e21, char e20, char e19, char e18, char e17, char e16, char e15, char e14, char e13, char e12, char e11, char e10, char e9, char e8, char e7, char e6, char e5, char e4, char e3, char e2, char e1, char e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<byte> SetVector256(byte e31, byte e30, byte e29, byte e28, byte e27, byte e26, byte e25, byte e24, byte e23, byte e22, byte e21, byte e20, byte e19, byte e18, byte e17, byte e16, byte e15, byte e14, byte e13, byte e12, byte e11, byte e10, byte e9, byte e8, byte e7, byte e6, byte e5, byte e4, byte e3, byte e2, byte e1, byte e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_set_epi16 (short e15, short e14, short e13, short e12, short e11, short e10, short e9, short e8, short e7, short e6, short e5, short e4, short e3, short e2, short e1, short e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<short> SetVector256(short e15, short e14, short e13, short e12, short e11, short e10, short e9, short e8, short e7, short e6, short e5, short e4, short e3, short e2, short e1, short e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_set_epi16 (short e15, short e14, short e13, short e12, short e11, short e10, short e9, short e8, short e7, short e6, short e5, short e4, short e3, short e2, short e1, short e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<ushort> SetVector256(ushort e15, ushort e14, ushort e13, ushort e12, ushort e11, ushort e10, ushort e9, ushort e8, ushort e7, ushort e6, ushort e5, ushort e4, ushort e3, ushort e2, ushort e1, ushort e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_set_epi32 (int e7, int e6, int e5, int e4, int e3, int e2, int e1, int e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<int> SetVector256(int e7, int e6, int e5, int e4, int e3, int e2, int e1, int e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_set_epi32 (int e7, int e6, int e5, int e4, int e3, int e2, int e1, int e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<uint> SetVector256(uint e7, uint e6, uint e5, uint e4, uint e3, uint e2, uint e1, uint e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_set_epi64x (__int64 e3, __int64 e2, __int64 e1, __int64 e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<long> SetVector256(long e3, long e2, long e1, long e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_set_epi64x (__int64 e3, __int64 e2, __int64 e1, __int64 e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<ulong> SetVector256(ulong e3, ulong e2, ulong e1, ulong e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_set_ps (float e7, float e6, float e5, float e4, float e3, float e2, float e1, float e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<float> SetVector256(float e7, float e6, float e5, float e4, float e3, float e2, float e1, float e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_set_pd (double e3, double e2, double e1, double e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<double> SetVector256(double e3, double e2, double e1, double e0) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_set1_epi8 (char a)
+        ///   HELPER
+        /// __m256i _mm256_set1_epi16 (short a)
+        ///   HELPER
+        /// __m256i _mm256_set1_epi32 (int a)
+        ///   HELPER
+        /// __m256i _mm256_set1_epi64x (long long a)
+        ///   HELPER
+        /// __m256 _mm256_set1_ps (float a)
+        ///   HELPER
+        /// __m256d _mm256_set1_pd (double a)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<T> SetAllVector256<T>(T value) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_set_m128 (__m128 hi, __m128 lo)
+        ///   HELPER
+        /// __m256d _mm256_set_m128d (__m128d hi, __m128d lo)
+        ///   HELPER
+        /// __m256i _mm256_set_m128i (__m128i hi, __m128i lo)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<T> SetHighLow<T>(Vector128<T> hi, Vector128<T> lo) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_setzero_si256 (void)
+        ///   HELPER
+        /// __m256 _mm256_setzero_ps (void)
+        ///   HELPER
+        /// __m256d _mm256_setzero_pd (void)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<T> SetZeroVector256<T>() where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_shuffle_ps (__m256 a, __m256 b, const int imm8)
+        ///   VSHUFPS ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<float> Shuffle(Vector256<float> value, Vector256<float> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_shuffle_pd (__m256d a, __m256d b, const int imm8)
+        ///   VSHUFPD ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<double> Shuffle(Vector256<double> value, Vector256<double> right, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_sqrt_ps (__m256 a)
+        ///   VSQRTPS ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Sqrt(Vector256<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_sqrt_pd (__m256d a)
+        ///   VSQRTPD ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Sqrt(Vector256<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_castpd_ps (__m256d a)
+        ///   HELPER - No Codegen
+        /// __m256i _mm256_castpd_si256 (__m256d a)
+        ///   HELPER - No Codegen
+        /// __m256d _mm256_castps_pd (__m256 a)
+        ///   HELPER - No Codegen
+        /// __m256i _mm256_castps_si256 (__m256 a)
+        ///   HELPER - No Codegen
+        /// __m256d _mm256_castsi256_pd (__m256i a)
+        ///   HELPER - No Codegen
+        /// __m256 _mm256_castsi256_ps (__m256i a)
+        ///   HELPER - No Codegen
+        /// </summary>
+        public static Vector256<U> StaticCast<T, U>(Vector256<T> value) where T : struct where U : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(sbyte* address, Vector256<sbyte> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(byte* address, Vector256<byte> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(short* address, Vector256<short> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(ushort* address, Vector256<ushort> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(int* address, Vector256<int> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(uint* address, Vector256<uint> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(long* address, Vector256<long> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(ulong* address, Vector256<ulong> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_store_ps (float * mem_addr, __m256 a)
+        ///   VMOVAPS m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(float* address, Vector256<float> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_store_pd (double * mem_addr, __m256d a)
+        ///   VMOVAPD m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(double* address, Vector256<double> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(sbyte* address, Vector256<sbyte> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(byte* address, Vector256<byte> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(short* address, Vector256<short> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(ushort* address, Vector256<ushort> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(int* address, Vector256<int> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(uint* address, Vector256<uint> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(long* address, Vector256<long> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(ulong* address, Vector256<ulong> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_stream_ps (float * mem_addr, __m256 a)
+        ///   MOVNTPS m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(float* address, Vector256<float> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_stream_pd (double * mem_addr, __m256d a)
+        ///   MOVNTPD m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(double* address, Vector256<double> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(sbyte* address, Vector256<sbyte> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(byte* address, Vector256<byte> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(short* address, Vector256<short> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(ushort* address, Vector256<ushort> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(int* address, Vector256<int> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(uint* address, Vector256<uint> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(long* address, Vector256<long> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(ulong* address, Vector256<ulong> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_storeu_ps (float * mem_addr, __m256 a)
+        ///   MOVUPS m256, ymm
+        /// </summary>
+        public static unsafe void Store(float* address, Vector256<float> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_storeu_pd (double * mem_addr, __m256d a)
+        ///   MOVUPD m256, ymm
+        /// </summary>
+        public static unsafe void Store(double* address, Vector256<double> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_sub_ps (__m256 a, __m256 b)
+        ///   VSUBPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Subtract(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_sub_pd (__m256d a, __m256d b)
+        ///   VSUBPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Subtract(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_testc_ps (__m128 a, __m128 b)
+        ///   VTESTPS xmm, xmm/m128
+        /// </summary>
+        public static bool TestC(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm_testc_pd (__m128d a, __m128d b)
+        ///   VTESTPD xmm, xmm/m128
+        /// </summary>
+        public static bool TestC(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm256_testc_si256 (__m256i a, __m256i b)
+        ///   VPTEST ymm, ymm/m256
+        /// int _mm256_testc_ps (__m256 a, __m256 b)
+        ///   VTESTPS ymm, ymm/m256
+        /// int _mm256_testc_pd (__m256d a, __m256d b)
+        ///   VTESTPS ymm, ymm/m256
+        /// </summary>
+        public static bool TestC<T>(Vector256<T> left, Vector256<T> right) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_testnzc_ps (__m128 a, __m128 b)
+        ///   VTESTPS xmm, xmm/m128
+        /// </summary>
+        public static bool TestNotZAndNotC(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm_testnzc_pd (__m128d a, __m128d b)
+        ///   VTESTPD xmm, xmm/m128
+        /// </summary>
+        public static bool TestNotZAndNotC(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm256_testnzc_si256 (__m256i a, __m256i b)
+        ///   VPTEST ymm, ymm/m256
+        /// int _mm256_testnzc_ps (__m256 a, __m256 b)
+        ///   VTESTPS ymm, ymm/m256
+        /// int _mm256_testnzc_pd (__m256d a, __m256d b)
+        ///   VTESTPD ymm, ymm/m256
+        /// </summary>
+        public static bool TestNotZAndNotC<T>(Vector256<T> left, Vector256<T> right) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_testz_ps (__m128 a, __m128 b)
+        ///   VTESTPS xmm, xmm/m128
+        /// </summary>
+        public static bool TestZ(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm_testz_pd (__m128d a, __m128d b)
+        ///   VTESTPD xmm, xmm/m128
+        /// </summary>
+        public static bool TestZ(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm256_testz_si256 (__m256i a, __m256i b)
+        ///   VPTEST ymm, ymm/m256
+        /// int _mm256_testz_ps (__m256 a, __m256 b)
+        ///   VTESTPS ymm, ymm/m256
+        /// int _mm256_testz_pd (__m256d a, __m256d b)
+        ///   VTESTPD ymm, ymm/m256
+        /// </summary>
+        public static bool TestZ<T>(Vector256<T> left, Vector256<T> right) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_unpackhi_ps (__m256 a, __m256 b)
+        ///   VUNPCKHPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> UnpackHigh(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_unpackhi_pd (__m256d a, __m256d b)
+        ///   VUNPCKHPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> UnpackHigh(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_unpacklo_ps (__m256 a, __m256 b)
+        ///   VUNPCKLPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> UnpackLow(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_unpacklo_pd (__m256d a, __m256d b)
+        ///   VUNPCKLPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> UnpackLow(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256 _mm256_xor_ps (__m256 a, __m256 b)
+        ///   VXORPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Xor(Vector256<float> left, Vector256<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_xor_pd (__m256d a, __m256d b)
+        ///   VXORPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Xor(Vector256<double> left, Vector256<double> right) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Avx.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Avx.cs
new file mode 100644
index 0000000000..fdb349b120
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Avx.cs
@@ -0,0 +1,1449 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+using System.Runtime.CompilerServices;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel AVX hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Avx
+    {
+        public static bool IsSupported { get => IsSupported; }
+
+        /// <summary>
+        /// __m256 _mm256_add_ps (__m256 a, __m256 b)
+        ///   VADDPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Add(Vector256<float> left, Vector256<float> right) => Add(left, right);
+        /// <summary>
+        /// __m256d _mm256_add_pd (__m256d a, __m256d b)
+        ///   VADDPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Add(Vector256<double> left, Vector256<double> right) => Add(left, right);
+
+        /// <summary>
+        /// __m256 _mm256_addsub_ps (__m256 a, __m256 b)
+        ///   VADDSUBPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> AddSubtract(Vector256<float> left, Vector256<float> right) => AddSubtract(left, right);
+        /// <summary>
+        /// __m256d _mm256_addsub_pd (__m256d a, __m256d b)
+        ///   VADDSUBPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> AddSubtract(Vector256<double> left, Vector256<double> right) => AddSubtract(left, right);
+
+        /// <summary>
+        /// __m256 _mm256_and_ps (__m256 a, __m256 b)
+        ///   VANDPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> And(Vector256<float> left, Vector256<float> right) => And(left, right);
+        /// <summary>
+        /// __m256d _mm256_and_pd (__m256d a, __m256d b)
+        ///   VANDPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> And(Vector256<double> left, Vector256<double> right) => And(left, right);
+
+        /// <summary>
+        /// __m256 _mm256_andnot_ps (__m256 a, __m256 b)
+        ///   VANDNPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> AndNot(Vector256<float> left, Vector256<float> right) => AndNot(left, right);
+        /// <summary>
+        /// __m256d _mm256_andnot_pd (__m256d a, __m256d b)
+        ///   VANDNPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> AndNot(Vector256<double> left, Vector256<double> right) => AndNot(left, right);
+
+        /// <summary>
+        /// __m256 _mm256_blend_ps (__m256 a, __m256 b, const int imm8)
+        ///   VBLENDPS ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<float> Blend(Vector256<float> left, Vector256<float> right, byte control) => Blend(left, right, control);
+        /// <summary>
+        /// __m256d _mm256_blend_pd (__m256d a, __m256d b, const int imm8)
+        ///   VBLENDPD ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<double> Blend(Vector256<double> left, Vector256<double> right, byte control) => Blend(left, right, control);
+
+        /// <summary>
+        /// __m256 _mm256_blendv_ps (__m256 a, __m256 b, __m256 mask)
+        ///   VBLENDVPS ymm, ymm, ymm/m256, ymm
+        /// </summary>
+        public static Vector256<float> BlendVariable(Vector256<float> left, Vector256<float> right, Vector256<float> mask) => BlendVariable(left, right, mask);
+        /// <summary>
+        /// __m256d _mm256_blendv_pd (__m256d a, __m256d b, __m256d mask)
+        ///   VBLENDVPD ymm, ymm, ymm/m256, ymm
+        /// </summary>
+        public static Vector256<double> BlendVariable(Vector256<double> left, Vector256<double> right, Vector256<double> mask) => BlendVariable(left, right, mask);
+
+        /// <summary>
+        /// __m128 _mm_broadcast_ss (float const * mem_addr)
+        ///   VBROADCASTSS xmm, m32
+        /// </summary>
+        public static unsafe Vector128<float> BroadcastScalarToVector128(float* source) => BroadcastScalarToVector128(source);
+
+        /// <summary>
+        /// __m256 _mm256_broadcast_ss (float const * mem_addr)
+        ///   VBROADCASTSS ymm, m32
+        /// </summary>
+        public static unsafe Vector256<float> BroadcastScalarToVector256(float* source) => BroadcastScalarToVector256(source);
+        /// <summary>
+        /// __m256d _mm256_broadcast_sd (double const * mem_addr)
+        ///   VBROADCASTSD ymm, m64
+        /// </summary>
+        public static unsafe Vector256<double> BroadcastScalarToVector256(double* source) => BroadcastScalarToVector256(source);
+
+        /// <summary>
+        /// __m256 _mm256_broadcast_ps (__m128 const * mem_addr)
+        ///   VBROADCASTF128, ymm, m128
+        /// </summary>
+        public static unsafe Vector256<float> BroadcastVector128ToVector256(float* address) => BroadcastVector128ToVector256(address);
+        /// <summary>
+        /// __m256d _mm256_broadcast_pd (__m128d const * mem_addr)
+        ///   VBROADCASTF128, ymm, m128
+        /// </summary>
+        public static unsafe Vector256<double> BroadcastVector128ToVector256(double* address) => BroadcastVector128ToVector256(address);
+
+        /// <summary>
+        /// __m256 _mm256_ceil_ps (__m256 a)
+        ///   VROUNDPS ymm, ymm/m256, imm8(10)
+        /// </summary>
+        public static Vector256<float> Ceiling(Vector256<float> value) => Ceiling(value);
+        /// <summary>
+        /// __m256d _mm256_ceil_pd (__m256d a)
+        ///   VROUNDPD ymm, ymm/m256, imm8(10)
+        /// </summary>
+        public static Vector256<double> Ceiling(Vector256<double> value) => Ceiling(value);
+
+        /// <summary>
+        /// __m128 _mm_cmp_ps (__m128 a, __m128 b, const int imm8)
+        ///   VCMPPS xmm, xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<float> Compare(Vector128<float> left, Vector128<float> right, FloatComparisonMode mode) => Compare(left, right, mode);
+        /// <summary>
+        /// __m128d _mm_cmp_pd (__m128d a, __m128d b, const int imm8)
+        ///   VCMPPD xmm, xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<double> Compare(Vector128<double> left, Vector128<double> right, FloatComparisonMode mode) => Compare(left, right, mode);
+        /// <summary>
+        /// __m256 _mm256_cmp_ps (__m256 a, __m256 b, const int imm8)
+        ///   VCMPPS ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<float> Compare(Vector256<float> left, Vector256<float> right, FloatComparisonMode mode) => Compare(left, right, mode);
+        /// <summary>
+        /// __m256d _mm256_cmp_pd (__m256d a, __m256d b, const int imm8)
+        ///   VCMPPD ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<double> Compare(Vector256<double> left, Vector256<double> right, FloatComparisonMode mode) => Compare(left, right, mode);
+
+        /// <summary>
+        /// __m128d _mm_cmp_sd (__m128d a, __m128d b, const int imm8)
+        ///   VCMPSS xmm, xmm, xmm/m32, imm8
+        /// </summary>
+        public static Vector128<double> CompareScalar(Vector128<double> left, Vector128<double> right, FloatComparisonMode mode) => CompareScalar(left, right, mode);
+        /// <summary>
+        /// __m128 _mm_cmp_ss (__m128 a, __m128 b, const int imm8)
+        ///   VCMPSD xmm, xmm, xmm/m64, imm8
+        /// </summary>
+        public static Vector128<float> CompareScalar(Vector128<float> left, Vector128<float> right, FloatComparisonMode mode) => CompareScalar(left, right, mode);
+
+        /// <summary>
+        /// float _mm256_cvtss_f32 (__m256 a)
+        ///   HELPER: VMOVSS
+        /// </summary>
+        public static float ConvertToSingle(Vector256<float> value) => ConvertToSingle(value);
+
+        /// <summary>
+        /// __m128i _mm256_cvtpd_epi32 (__m256d a)
+        ///   VCVTPD2DQ xmm, ymm/m256
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32(Vector256<double> value) => ConvertToVector128Int32(value);
+        /// <summary>
+        /// __m128 _mm256_cvtpd_ps (__m256d a)
+        ///   VCVTPD2PS xmm, ymm/m256
+        /// </summary>
+        public static Vector128<float> ConvertToVector128Single(Vector256<double> value) => ConvertToVector128Single(value);
+        /// <summary>
+        /// __m256i _mm256_cvtps_epi32 (__m256 a)
+        ///   VCVTPS2DQ ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> ConvertToVector256Int32(Vector256<float> value) => ConvertToVector256Int32(value);
+        /// <summary>
+        /// __m256 _mm256_cvtepi32_ps (__m256i a)
+        ///   VCVTDQ2PS ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> ConvertToVector256Single(Vector256<int> value) => ConvertToVector256Single(value);
+        /// <summary>
+        /// __m256d _mm256_cvtps_pd (__m128 a)
+        ///   VCVTPS2PD ymm, xmm/m128
+        /// </summary>
+        public static Vector256<double> ConvertToVector256Double(Vector128<float> value) => ConvertToVector256Double(value);
+        /// <summary>
+        /// __m256d _mm256_cvtepi32_pd (__m128i a)
+        ///   VCVTDQ2PD ymm, xmm/m128
+        /// </summary>
+        public static Vector256<double> ConvertToVector256Double(Vector128<int> value) => ConvertToVector256Double(value);
+
+        /// <summary>
+        /// __m128i _mm256_cvttpd_epi32 (__m256d a)
+        ///   VCVTTPD2DQ xmm, ymm/m256
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32WithTruncation(Vector256<double> value) => ConvertToVector128Int32WithTruncation(value);
+        /// <summary>
+        /// __m256i _mm256_cvttps_epi32 (__m256 a)
+        ///   VCVTTPS2DQ ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> ConvertToVector256Int32WithTruncation(Vector256<float> value) => ConvertToVector256Int32WithTruncation(value);
+
+        /// <summary>
+        /// __m256 _mm256_div_ps (__m256 a, __m256 b)
+        ///   VDIVPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Divide(Vector256<float> left, Vector256<float> right) => Divide(left, right);
+        /// <summary>
+        /// __m256d _mm256_div_pd (__m256d a, __m256d b)
+        ///   VDIVPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Divide(Vector256<double> left, Vector256<double> right) => Divide(left, right);
+
+        /// <summary>
+        /// __m256 _mm256_dp_ps (__m256 a, __m256 b, const int imm8)
+        ///   VDPPS ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<float> DotProduct(Vector256<float> left, Vector256<float> right, byte control) => DotProduct(left, right, control);
+
+        /// <summary>
+        /// __m256 _mm256_moveldup_ps (__m256 a)
+        ///   VMOVSLDUP ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> DuplicateEvenIndexed(Vector256<float> value) => DuplicateEvenIndexed(value);
+        /// <summary>
+        /// __m256d _mm256_movedup_pd (__m256d a)
+        ///   VMOVDDUP ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> DuplicateEvenIndexed(Vector256<double> value) => DuplicateEvenIndexed(value);
+
+        /// <summary>
+        /// __m256 _mm256_movehdup_ps (__m256 a)
+        ///   VMOVSHDUP ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> DuplicateOddIndexed(Vector256<float> value) => DuplicateOddIndexed(value);
+
+        /// <summary>
+        /// __int8 _mm256_extract_epi8 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static sbyte Extract(Vector256<sbyte> value, byte index)
+        {
+            unsafe
+            {
+                index &= 0x1F;
+                sbyte* buffer = stackalloc sbyte[32];
+                Store(buffer, value);
+                return buffer[index];
+            }
+        }
+
+        /// <summary>
+        /// __int8 _mm256_extract_epi8 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static byte Extract(Vector256<byte> value, byte index)
+        {
+            unsafe
+            {
+                index &= 0x1F;
+                byte* buffer = stackalloc byte[32];
+                Store(buffer, value);
+                return buffer[index];   
+            }
+        }
+
+        /// <summary>
+        /// __int16 _mm256_extract_epi16 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static short Extract(Vector256<short> value, byte index)
+        {
+            unsafe
+            {
+                index &= 0xF;
+                short* buffer = stackalloc short[16];
+                Store(buffer, value);
+                return buffer[index];
+            }   
+        }
+
+        /// <summary>
+        /// __int16 _mm256_extract_epi16 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static ushort Extract(Vector256<ushort> value, byte index)
+        {
+            unsafe
+            {
+                index &= 0xF;
+                ushort* buffer = stackalloc ushort[16];
+                Store(buffer, value);
+                return buffer[index];
+            }
+        }
+
+        /// <summary>
+        /// __int32 _mm256_extract_epi32 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static int Extract(Vector256<int> value, byte index)
+        {
+            unsafe
+            {
+                index &= 0x7;
+                int* buffer = stackalloc int[8];
+                Store(buffer, value);
+                return buffer[index];
+            }
+        }
+
+        /// <summary>
+        /// __int32 _mm256_extract_epi32 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static uint Extract(Vector256<uint> value, byte index)
+        {
+            unsafe
+            {
+                index &= 0x7;
+                uint* buffer = stackalloc uint[8];
+                Store(buffer, value);
+                return buffer[index];
+            }
+        }
+
+        /// <summary>
+        /// __int64 _mm256_extract_epi64 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static long Extract(Vector256<long> value, byte index)
+        {
+            if (IntPtr.Size != 8)
+            {
+                throw new PlatformNotSupportedException();
+            }
+            unsafe
+            {
+                index &= 0x3;
+                long* buffer = stackalloc long[4];
+                Store(buffer, value);
+                return buffer[index];
+            }
+        }
+
+        /// <summary>
+        /// __int64 _mm256_extract_epi64 (__m256i a, const int index)
+        ///   HELPER
+        /// </summary>
+        public static ulong Extract(Vector256<ulong> value, byte index)
+        {
+            if (IntPtr.Size != 8)
+            {
+                throw new PlatformNotSupportedException();
+            }
+            unsafe
+            {
+                index &= 0x3;
+                ulong* buffer = stackalloc ulong[4];
+                Store(buffer, value);
+                return buffer[index];
+            }
+        }
+
+        /// <summary>
+        /// __m128 _mm256_extractf128_ps (__m256 a, const int imm8)
+        ///   VEXTRACTF128 xmm/m128, ymm, imm8
+        /// __m128d _mm256_extractf128_pd (__m256d a, const int imm8)
+        ///   VEXTRACTF128 xmm/m128, ymm, imm8
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 xmm/m128, ymm, imm8
+        /// </summary>
+        public static Vector128<T> ExtractVector128<T>(Vector256<T> value, byte index) where T : struct
+        {
+            return ExtractVector128<T>(value, index);
+        }
+
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(byte* address, Vector256<byte> value, byte index) => ExtractVector128(address, value, index);
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(sbyte* address, Vector256<sbyte> value, byte index) => ExtractVector128(address, value, index);
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(short* address, Vector256<short> value, byte index) => ExtractVector128(address, value, index);
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(ushort* address, Vector256<ushort> value, byte index) => ExtractVector128(address, value, index);
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(int* address, Vector256<int> value, byte index) => ExtractVector128(address, value, index);
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(uint* address, Vector256<uint> value, byte index) => ExtractVector128(address, value, index);
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(long* address, Vector256<long> value, byte index) => ExtractVector128(address, value, index);
+        /// <summary>
+        /// __m128i _mm256_extractf128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(ulong* address, Vector256<ulong> value, byte index) => ExtractVector128(address, value, index);
+        /// <summary>
+        /// __m128 _mm256_extractf128_ps (__m256 a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(float* address, Vector256<float> value, byte index) => ExtractVector128(address, value, index);
+        /// <summary>
+        /// __m128d _mm256_extractf128_pd (__m256d a, const int imm8)
+        ///   VEXTRACTF128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(double* address, Vector256<double> value, byte index) => ExtractVector128(address, value, index);
+
+        /// <summary>
+        /// __m256d _mm256_castpd128_pd256 (__m128d a)
+        ///   HELPER - No Codegen
+        /// __m256 _mm256_castps128_ps256 (__m128 a)
+        ///   HELPER - No Codegen
+        /// __m256i _mm256_castsi128_si256 (__m128i a)
+        ///   HELPER - No Codegen
+        /// </summary>
+        public static Vector256<T> ExtendToVector256<T>(Vector128<T> value) where T : struct
+        {
+            return ExtendToVector256<T>(value);
+        }
+
+        /// <summary>
+        /// __m256 _mm256_floor_ps (__m256 a)
+        ///   VROUNDPS ymm, ymm/m256, imm8(9)
+        /// </summary>
+        public static Vector256<float> Floor(Vector256<float> value) => Floor(value);
+        /// <summary>
+        /// __m256d _mm256_floor_pd (__m256d a)
+        ///   VROUNDPS ymm, ymm/m256, imm8(9)
+        /// </summary>
+        public static Vector256<double> Floor(Vector256<double> value) => Floor(value);
+
+        /// <summary>
+        /// __m128d _mm256_castpd256_pd128 (__m256d a)
+        ///   HELPER - No Codegen
+        /// __m128 _mm256_castps256_ps128 (__m256 a)
+        ///   HELPER - No Codegen
+        /// __m128i _mm256_castsi256_si128 (__m256i a)
+        ///   HELPER - No Codegen
+        /// </summary>
+        public static Vector128<T> GetLowerHalf<T>(Vector256<T> value) where T : struct
+        {
+            return GetLowerHalf<T>(value);
+        }
+
+        /// <summary>
+        /// __m256 _mm256_hadd_ps (__m256 a, __m256 b)
+        ///   VHADDPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> HorizontalAdd(Vector256<float> left, Vector256<float> right) => HorizontalAdd(left, right);
+        /// <summary>
+        /// __m256d _mm256_hadd_pd (__m256d a, __m256d b)
+        ///   VHADDPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> HorizontalAdd(Vector256<double> left, Vector256<double> right) => HorizontalAdd(left, right);
+
+        /// <summary>
+        /// __m256 _mm256_hsub_ps (__m256 a, __m256 b)
+        ///   VHSUBPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> HorizontalSubtract(Vector256<float> left, Vector256<float> right) => HorizontalSubtract(left, right);
+        /// <summary>
+        /// __m256d _mm256_hsub_pd (__m256d a, __m256d b)
+        ///   VHSUBPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> HorizontalSubtract(Vector256<double> left, Vector256<double> right) => HorizontalSubtract(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_insert_epi8 (__m256i a, __int8 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<sbyte> Insert(Vector256<sbyte> value, sbyte data, byte index)
+        {
+            unsafe
+            {
+                index &= 0x1F;
+                sbyte* buffer = stackalloc sbyte[32];
+                Store(buffer, value);
+                buffer[index] = data;
+                return LoadVector256(buffer);
+            }
+        }
+
+        /// <summary>
+        /// __m256i _mm256_insert_epi8 (__m256i a, __int8 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<byte> Insert(Vector256<byte> value, byte data, byte index)
+        {
+            unsafe
+            {
+                index &= 0x1F;
+                byte* buffer = stackalloc byte[32];
+                Store(buffer, value);
+                buffer[index] = data;
+                return LoadVector256(buffer);
+            }
+        }
+        
+        /// <summary>
+        /// __m256i _mm256_insert_epi16 (__m256i a, __int16 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<short> Insert(Vector256<short> value, short data, byte index)
+        {
+            unsafe
+            {
+                index &= 0xF;
+                short* buffer = stackalloc short[16];
+                Store(buffer, value);
+                buffer[index] = data;
+                return LoadVector256(buffer);
+            }
+        }
+
+        /// <summary>
+        /// __m256i _mm256_insert_epi16 (__m256i a, __int16 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<ushort> Insert(Vector256<ushort> value, ushort data, byte index)
+        {
+            unsafe
+            {
+                index &= 0xF;
+                ushort* buffer = stackalloc ushort[16];
+                Store(buffer, value);
+                buffer[index] = data;
+                return LoadVector256(buffer);
+            }
+        }
+
+        /// <summary>
+        /// __m256i _mm256_insert_epi32 (__m256i a, __int32 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<int> Insert(Vector256<int> value, int data, byte index)
+        {
+            unsafe
+            {
+                index &= 0x7;
+                int* buffer = stackalloc int[8];
+                Store(buffer, value);
+                buffer[index] = data;
+                return LoadVector256(buffer);
+            }
+        }
+        
+        /// <summary>
+        /// __m256i _mm256_insert_epi32 (__m256i a, __int32 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<uint> Insert(Vector256<uint> value, uint data, byte index)
+        {
+            unsafe
+            {
+                index &= 0x7;
+                uint* buffer = stackalloc uint[8];
+                Store(buffer, value);
+                buffer[index] = data;
+                return LoadVector256(buffer);
+            }
+        }
+
+        /// <summary>
+        /// __m256i _mm256_insert_epi64 (__m256i a, __int64 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<long> Insert(Vector256<long> value, long data, byte index)
+        {
+            unsafe
+            {
+                index &= 0x3;
+                long* buffer = stackalloc long[4];
+                Store(buffer, value);
+                buffer[index] = data;
+                return LoadVector256(buffer);
+            }
+        }
+
+        /// <summary>
+        /// __m256i _mm256_insert_epi64 (__m256i a, __int64 i, const int index)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<ulong> Insert(Vector256<ulong> value, ulong data, byte index)
+        {
+            unsafe
+            {
+                index &= 0x3;
+                ulong* buffer = stackalloc ulong[4];
+                Store(buffer, value);
+                buffer[index] = data;
+                return LoadVector256(buffer);
+            }
+        }
+
+        /// <summary>
+        /// __m256 _mm256_insertf128_ps (__m256 a, __m128 b, int imm8)
+        ///   VINSERTF128 ymm, ymm, xmm/m128, imm8
+        /// __m256d _mm256_insertf128_pd (__m256d a, __m128d b, int imm8)
+        ///   VINSERTF128 ymm, ymm, xmm/m128, imm8
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, xmm/m128, imm8
+        /// </summary>
+        public static Vector256<T> InsertVector128<T>(Vector256<T> value, Vector128<T> data, byte index) where T : struct
+        {
+            return InsertVector128<T>(value, data, index);
+        }
+
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<sbyte> InsertVector128(Vector256<sbyte> value, sbyte* address, byte index) => InsertVector128(value, address, index);
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<byte> InsertVector128(Vector256<byte> value, byte* address, byte index) => InsertVector128(value, address, index);
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<short> InsertVector128(Vector256<short> value, short* address, byte index) => InsertVector128(value, address, index);
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<ushort> InsertVector128(Vector256<ushort> value, ushort* address, byte index) => InsertVector128(value, address, index);
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<int> InsertVector128(Vector256<int> value, int* address, byte index) => InsertVector128(value, address, index);
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<uint> InsertVector128(Vector256<uint> value, uint* address, byte index) => InsertVector128(value, address, index);
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<long> InsertVector128(Vector256<long> value, long* address, byte index) => InsertVector128(value, address, index);
+        /// <summary>
+        /// __m256i _mm256_insertf128_si256 (__m256i a, __m128i b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<ulong> InsertVector128(Vector256<ulong> value, ulong* address, byte index) => InsertVector128(value, address, index);
+        /// <summary>
+        /// __m256 _mm256_insertf128_ps (__m256 a, __m128 b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<float> InsertVector128(Vector256<float> value, float* address, byte index) => InsertVector128(value, address, index);
+        /// <summary>
+        /// __m256d _mm256_insertf128_pd (__m256d a, __m128d b, int imm8)
+        ///   VINSERTF128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<double> InsertVector128(Vector256<double> value, double* address, byte index) => InsertVector128(value, address, index);
+
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<sbyte> LoadVector256(sbyte* address) => LoadVector256(address);
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<byte> LoadVector256(byte* address) => LoadVector256(address);
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<short> LoadVector256(short* address) => LoadVector256(address);
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ushort> LoadVector256(ushort* address) => LoadVector256(address);
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<int> LoadVector256(int* address) => LoadVector256(address);
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<uint> LoadVector256(uint* address) => LoadVector256(address);
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<long> LoadVector256(long* address) => LoadVector256(address);
+        /// <summary>
+        /// __m256i _mm256_loadu_si256 (__m256i const * mem_addr)
+        ///   VMOVDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ulong> LoadVector256(ulong* address) => LoadVector256(address);
+        /// <summary>
+        /// __m256 _mm256_loadu_ps (float const * mem_addr)
+        ///   VMOVUPS ymm, ymm/m256
+        /// </summary>
+        public static unsafe Vector256<float> LoadVector256(float* address) => LoadVector256(address);
+        /// <summary>
+        /// __m256d _mm256_loadu_pd (double const * mem_addr)
+        ///   VMOVUPD ymm, ymm/m256
+        /// </summary>
+        public static unsafe Vector256<double> LoadVector256(double* address) => LoadVector256(address);
+
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<sbyte> LoadAlignedVector256(sbyte* address) => LoadAlignedVector256(address);
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<byte> LoadAlignedVector256(byte* address) => LoadAlignedVector256(address);
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<short> LoadAlignedVector256(short* address) => LoadAlignedVector256(address);
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ushort> LoadAlignedVector256(ushort* address) => LoadAlignedVector256(address);
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<int> LoadAlignedVector256(int* address) => LoadAlignedVector256(address);
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<uint> LoadAlignedVector256(uint* address) => LoadAlignedVector256(address);
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<long> LoadAlignedVector256(long* address) => LoadAlignedVector256(address);
+        /// <summary>
+        /// __m256i _mm256_load_si256 (__m256i const * mem_addr)
+        ///   VMOVDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ulong> LoadAlignedVector256(ulong* address) => LoadAlignedVector256(address);
+        /// <summary>
+        /// __m256 _mm256_load_ps (float const * mem_addr)
+        ///   VMOVAPS ymm, ymm/m256
+        /// </summary>
+        public static unsafe Vector256<float> LoadAlignedVector256(float* address) => LoadAlignedVector256(address);
+        /// <summary>
+        /// __m256d _mm256_load_pd (double const * mem_addr)
+        ///   VMOVAPD ymm, ymm/m256
+        /// </summary>
+        public static unsafe Vector256<double> LoadAlignedVector256(double* address) => LoadAlignedVector256(address);
+
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<sbyte> LoadDquVector256(sbyte* address) => LoadDquVector256(address);
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<byte> LoadDquVector256(byte* address) => LoadDquVector256(address);
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<short> LoadDquVector256(short* address) => LoadDquVector256(address);
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ushort> LoadDquVector256(ushort* address) => LoadDquVector256(address);
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<int> LoadDquVector256(int* address) => LoadDquVector256(address);
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<uint> LoadDquVector256(uint* address) => LoadDquVector256(address);
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<long> LoadDquVector256(long* address) => LoadDquVector256(address);
+        /// <summary>
+        /// __m256i _mm256_lddqu_si256 (__m256i const * mem_addr)
+        ///   VLDDQU ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ulong> LoadDquVector256(ulong* address) => LoadDquVector256(address);
+
+        /// <summary>
+        /// __m128 _mm_maskload_ps (float const * mem_addr, __m128i mask)
+        ///   VMASKMOVPS xmm, xmm, m128
+        /// </summary>
+        public static unsafe Vector128<float> MaskLoad(float* address, Vector128<uint> mask) => MaskLoad(address, mask);
+        /// <summary>
+        /// __m128d _mm_maskload_pd (double const * mem_addr, __m128i mask)
+        ///   VMASKMOVPD xmm, xmm, m128
+        /// </summary>
+        public static unsafe Vector128<double> MaskLoad(double* address, Vector128<ulong> mask) => MaskLoad(address, mask);
+
+        /// <summary>
+        /// __m256 _mm256_maskload_ps (float const * mem_addr, __m256i mask)
+        ///   VMASKMOVPS ymm, ymm, m256
+        /// </summary>
+        public static unsafe Vector256<float> MaskLoad(float* address, Vector256<uint> mask) => MaskLoad(address, mask);
+        /// <summary>
+        /// __m256d _mm256_maskload_pd (double const * mem_addr, __m256i mask)
+        ///   VMASKMOVPD ymm, ymm, m256
+        /// </summary>
+        public static unsafe Vector256<double> MaskLoad(double* address, Vector256<ulong> mask) => MaskLoad(address, mask);
+
+        /// <summary>
+        /// void _mm_maskstore_ps (float * mem_addr, __m128i mask, __m128 a)
+        ///   VMASKMOVPS m128, xmm, xmm
+        /// </summary>
+        public static unsafe void MaskStore(float* address, Vector128<float> mask, Vector128<uint> source) => MaskStore(address, mask, source);
+        /// <summary>
+        /// void _mm_maskstore_pd (double * mem_addr, __m128i mask, __m128d a)
+        ///   VMASKMOVPD m128, xmm, xmm
+        /// </summary>
+        public static unsafe void MaskStore(double* address, Vector128<double> mask, Vector128<ulong> source) => MaskStore(address, mask, source);
+
+        /// <summary>
+        /// void _mm256_maskstore_ps (float * mem_addr, __m256i mask, __m256 a)
+        ///   VMASKMOVPS m256, ymm, ymm
+        /// </summary>
+        public static unsafe void MaskStore(float* address, Vector256<float> mask, Vector256<uint> source) => MaskStore(address, mask, source);
+        /// <summary>
+        /// void _mm256_maskstore_pd (double * mem_addr, __m256i mask, __m256d a)
+        ///   VMASKMOVPD m256, ymm, ymm
+        /// </summary>
+        public static unsafe void MaskStore(double* address, Vector256<double> mask, Vector256<ulong> source) => MaskStore(address, mask, source);
+
+        /// <summary>
+        /// __m256 _mm256_max_ps (__m256 a, __m256 b)
+        ///   VMAXPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Max(Vector256<float> left, Vector256<float> right) => Max(left, right);
+        /// <summary>
+        /// __m256d _mm256_max_pd (__m256d a, __m256d b)
+        ///   VMAXPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Max(Vector256<double> left, Vector256<double> right) => Max(left, right);
+
+        /// <summary>
+        /// __m256 _mm256_min_ps (__m256 a, __m256 b)
+        ///   VMINPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Min(Vector256<float> left, Vector256<float> right) => Min(left, right);
+        /// <summary>
+        /// __m256d _mm256_min_pd (__m256d a, __m256d b)
+        ///   VMINPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Min(Vector256<double> left, Vector256<double> right) => Min(left, right);
+
+        /// <summary>
+        /// int _mm256_movemask_ps (__m256 a)
+        ///   VMOVMSKPS reg, ymm
+        /// </summary>
+        public static int MoveMask(Vector256<float> value) => MoveMask(value);
+        /// <summary>
+        /// int _mm256_movemask_pd (__m256d a)
+        ///   VMOVMSKPD reg, ymm
+        /// </summary>
+        public static int MoveMask(Vector256<double> value) => MoveMask(value);
+
+        /// <summary>
+        /// __m256 _mm256_mul_ps (__m256 a, __m256 b)
+        ///   VMULPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Multiply(Vector256<float> left, Vector256<float> right) => Multiply(left, right);
+        /// <summary>
+        /// __m256d _mm256_mul_pd (__m256d a, __m256d b)
+        ///   VMULPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Multiply(Vector256<double> left, Vector256<double> right) => Multiply(left, right);
+
+        /// <summary>
+        /// __m256 _mm256_or_ps (__m256 a, __m256 b)
+        ///   VORPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Or(Vector256<float> left, Vector256<float> right) => Or(left, right);
+        /// <summary>
+        /// __m256d _mm256_or_pd (__m256d a, __m256d b)
+        ///   VORPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Or(Vector256<double> left, Vector256<double> right) => Or(left, right);
+
+        /// <summary>
+        /// __m128 _mm_permute_ps (__m128 a, int imm8)
+        ///   VPERMILPS xmm, xmm, imm8
+        /// </summary>
+        public static Vector128<float> Permute(Vector128<float> value, byte control) => Permute(value, control);
+        /// <summary>
+        /// __m128d _mm_permute_pd (__m128d a, int imm8)
+        ///   VPERMILPD xmm, xmm, imm8
+        /// </summary>
+        public static Vector128<double> Permute(Vector128<double> value, byte control) => Permute(value, control);
+
+        /// <summary>
+        /// __m256 _mm256_permute_ps (__m256 a, int imm8)
+        ///   VPERMILPS ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<float> Permute(Vector256<float> value, byte control) => Permute(value, control);
+        /// <summary>
+        /// __m256d _mm256_permute_pd (__m256d a, int imm8)
+        ///   VPERMILPD ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<double> Permute(Vector256<double> value, byte control) => Permute(value, control);
+
+        /// <summary>
+        /// __m256 _mm256_permute2f128_ps (__m256 a, __m256 b, int imm8)
+        ///   VPERM2F128 ymm, ymm, ymm/m256, imm8
+        /// __m256d _mm256_permute2f128_pd (__m256d a, __m256d b, int imm8)
+        ///   VPERM2F128 ymm, ymm, ymm/m256, imm8
+        /// __m256i _mm256_permute2f128_si256 (__m256i a, __m256i b, int imm8)
+        ///   VPERM2F128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<T> Permute2x128<T>(Vector256<T> left, Vector256<T> right, byte control) where T : struct
+        {
+            return Permute2x128<T>(left, right, control);
+        }
+
+        /// <summary>
+        /// __m128 _mm_permutevar_ps (__m128 a, __m128i b)
+        ///   VPERMILPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> PermuteVar(Vector128<float> left, Vector128<float> mask) => PermuteVar(left, mask);
+        /// <summary>
+        /// __m128d _mm_permutevar_pd (__m128d a, __m128i b)
+        ///   VPERMILPD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> PermuteVar(Vector128<double> left, Vector128<double> mask) => PermuteVar(left, mask);
+        /// <summary>
+        /// __m256 _mm256_permutevar_ps (__m256 a, __m256i b)
+        ///   VPERMILPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> PermuteVar(Vector256<float> left, Vector256<float> mask) => PermuteVar(left, mask);
+        /// <summary>
+        /// __m256d _mm256_permutevar_pd (__m256d a, __m256i b)
+        ///   VPERMILPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> PermuteVar(Vector256<double> left, Vector256<double> mask) => PermuteVar(left, mask);
+
+        /// <summary>
+        /// __m256 _mm256_rcp_ps (__m256 a)
+        ///   VRCPPS ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Reciprocal(Vector256<float> value) => Reciprocal(value);
+
+        /// <summary>
+        /// __m256 _mm256_rsqrt_ps (__m256 a)
+        ///   VRSQRTPS ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> ReciprocalSqrt(Vector256<float> value) => ReciprocalSqrt(value);
+
+        /// <summary>
+        /// __m256 _mm256_round_ps (__m256 a, _MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC)
+        ///   VROUNDPS ymm, ymm/m256, imm8(8)
+        /// </summary>
+        public static Vector256<float> RoundToNearestInteger(Vector256<float> value) => RoundToNearestInteger(value);
+        /// <summary>
+        /// __m256 _mm256_round_ps (__m256 a, _MM_FROUND_TO_NEG_INF | _MM_FROUND_NO_EXC)
+        ///   VROUNDPS ymm, ymm/m256, imm8(9)
+        /// </summary>
+        public static Vector256<float> RoundToNegativeInfinity(Vector256<float> value) => RoundToNegativeInfinity(value);
+        /// <summary>
+        /// __m256 _mm256_round_ps (__m256 a, _MM_FROUND_TO_POS_INF | _MM_FROUND_NO_EXC)
+        ///   VROUNDPS ymm, ymm/m256, imm8(10)
+        /// </summary>
+        public static Vector256<float> RoundToPositiveInfinity(Vector256<float> value) => RoundToPositiveInfinity(value);
+        /// <summary>
+        /// __m256 _mm256_round_ps (__m256 a, _MM_FROUND_TO_ZERO | _MM_FROUND_NO_EXC)
+        ///   VROUNDPS ymm, ymm/m256, imm8(11)
+        /// </summary>
+        public static Vector256<float> RoundToZero(Vector256<float> value) => RoundToZero(value);
+        /// <summary>
+        /// __m256 _mm256_round_ps (__m256 a, _MM_FROUND_CUR_DIRECTION)
+        ///   VROUNDPS ymm, ymm/m256, imm8(4)
+        /// </summary>
+        public static Vector256<float> RoundCurrentDirection(Vector256<float> value) => RoundCurrentDirection(value);
+
+        /// <summary>
+        /// __m256d _mm256_round_pd (__m256d a, _MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC)
+        ///   VROUNDPD ymm, ymm/m256, imm8(8)
+        /// </summary>
+        public static Vector256<double> RoundToNearestInteger(Vector256<double> value) => RoundToNearestInteger(value);
+        /// <summary>
+        /// __m256d _mm256_round_pd (__m256d a, _MM_FROUND_TO_NEG_INF | _MM_FROUND_NO_EXC)
+        ///   VROUNDPD ymm, ymm/m256, imm8(9)
+        /// </summary>
+        public static Vector256<double> RoundToNegativeInfinity(Vector256<double> value) => RoundToNegativeInfinity(value);
+        /// <summary>
+        /// __m256d _mm256_round_pd (__m256d a, _MM_FROUND_TO_POS_INF | _MM_FROUND_NO_EXC)
+        ///   VROUNDPD ymm, ymm/m256, imm8(10)
+        /// </summary>
+        public static Vector256<double> RoundToPositiveInfinity(Vector256<double> value) => RoundToPositiveInfinity(value);
+        /// <summary>
+        /// __m256d _mm256_round_pd (__m256d a, _MM_FROUND_TO_ZERO | _MM_FROUND_NO_EXC)
+        ///   VROUNDPD ymm, ymm/m256, imm8(11)
+        /// </summary>
+        public static Vector256<double> RoundToZero(Vector256<double> value) => RoundToZero(value);
+        /// <summary>
+        /// __m256d _mm256_round_pd (__m256d a, _MM_FROUND_CUR_DIRECTION)
+        ///   VROUNDPD ymm, ymm/m256, imm8(4)
+        /// </summary>
+        public static Vector256<double> RoundCurrentDirection(Vector256<double> value) => RoundCurrentDirection(value);
+
+        /// <summary>
+        /// __m256i _mm256_set_epi8 (char e31, char e30, char e29, char e28, char e27, char e26, char e25, char e24, char e23, char e22, char e21, char e20, char e19, char e18, char e17, char e16, char e15, char e14, char e13, char e12, char e11, char e10, char e9, char e8, char e7, char e6, char e5, char e4, char e3, char e2, char e1, char e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<sbyte> SetVector256(sbyte e31, sbyte e30, sbyte e29, sbyte e28, sbyte e27, sbyte e26, sbyte e25, sbyte e24, sbyte e23, sbyte e22, sbyte e21, sbyte e20, sbyte e19, sbyte e18, sbyte e17, sbyte e16, sbyte e15, sbyte e14, sbyte e13, sbyte e12, sbyte e11, sbyte e10, sbyte e9, sbyte e8, sbyte e7, sbyte e6, sbyte e5, sbyte e4, sbyte e3, sbyte e2, sbyte e1, sbyte e0) => SetVector256(e31, e30, e29, e28, e27, e26, e25, e24, e23, e22, e21, e20, e19, e18, e17, e16, e15, e14, e13, e12, e11, e10, e9, e8, e7, e6, e5, e4, e3, e2, e1, e0);
+        /// <summary>
+        /// __m256i _mm256_set_epi8 (char e31, char e30, char e29, char e28, char e27, char e26, char e25, char e24, char e23, char e22, char e21, char e20, char e19, char e18, char e17, char e16, char e15, char e14, char e13, char e12, char e11, char e10, char e9, char e8, char e7, char e6, char e5, char e4, char e3, char e2, char e1, char e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<byte> SetVector256(byte e31, byte e30, byte e29, byte e28, byte e27, byte e26, byte e25, byte e24, byte e23, byte e22, byte e21, byte e20, byte e19, byte e18, byte e17, byte e16, byte e15, byte e14, byte e13, byte e12, byte e11, byte e10, byte e9, byte e8, byte e7, byte e6, byte e5, byte e4, byte e3, byte e2, byte e1, byte e0) => SetVector256(e31, e30, e29, e28, e27, e26, e25, e24, e23, e22, e21, e20, e19, e18, e17, e16, e15, e14, e13, e12, e11, e10, e9, e8, e7, e6, e5, e4, e3, e2, e1, e0);
+        /// <summary>
+        /// __m256i _mm256_set_epi16 (short e15, short e14, short e13, short e12, short e11, short e10, short e9, short e8, short e7, short e6, short e5, short e4, short e3, short e2, short e1, short e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<short> SetVector256(short e15, short e14, short e13, short e12, short e11, short e10, short e9, short e8, short e7, short e6, short e5, short e4, short e3, short e2, short e1, short e0) => SetVector256(e15, e14, e13, e12, e11, e10, e9, e8, e7, e6, e5, e4, e3, e2, e1, e0);
+        /// <summary>
+        /// __m256i _mm256_set_epi16 (short e15, short e14, short e13, short e12, short e11, short e10, short e9, short e8, short e7, short e6, short e5, short e4, short e3, short e2, short e1, short e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<ushort> SetVector256(ushort e15, ushort e14, ushort e13, ushort e12, ushort e11, ushort e10, ushort e9, ushort e8, ushort e7, ushort e6, ushort e5, ushort e4, ushort e3, ushort e2, ushort e1, ushort e0) => SetVector256(e15, e14, e13, e12, e11, e10, e9, e8, e7, e6, e5, e4, e3, e2, e1, e0);
+        /// <summary>
+        /// __m256i _mm256_set_epi32 (int e7, int e6, int e5, int e4, int e3, int e2, int e1, int e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<int> SetVector256(int e7, int e6, int e5, int e4, int e3, int e2, int e1, int e0) => SetVector256(e7, e6, e5, e4, e3, e2, e1, e0);
+        /// <summary>
+        /// __m256i _mm256_set_epi32 (int e7, int e6, int e5, int e4, int e3, int e2, int e1, int e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<uint> SetVector256(uint e7, uint e6, uint e5, uint e4, uint e3, uint e2, uint e1, uint e0) => SetVector256(e7, e6, e5, e4, e3, e2, e1, e0);
+        /// <summary>
+        /// __m256i _mm256_set_epi64x (__int64 e3, __int64 e2, __int64 e1, __int64 e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<long> SetVector256(long e3, long e2, long e1, long e0) => SetVector256(e3, e2, e1, e0);
+        /// <summary>
+        /// __m256i _mm256_set_epi64x (__int64 e3, __int64 e2, __int64 e1, __int64 e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<ulong> SetVector256(ulong e3, ulong e2, ulong e1, ulong e0) => SetVector256(e3, e2, e1, e0);
+        /// <summary>
+        /// __m256 _mm256_set_ps (float e7, float e6, float e5, float e4, float e3, float e2, float e1, float e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<float> SetVector256(float e7, float e6, float e5, float e4, float e3, float e2, float e1, float e0) => SetVector256(e7, e6, e5, e4, e3, e2, e1, e0);
+        /// <summary>
+        /// __m256d _mm256_set_pd (double e3, double e2, double e1, double e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<double> SetVector256(double e3, double e2, double e1, double e0) => SetVector256(e3, e2, e1, e0);
+
+        /// <summary>
+        /// __m256i _mm256_set1_epi8 (char a)
+        ///   HELPER
+        /// __m256i _mm256_set1_epi16 (short a)
+        ///   HELPER
+        /// __m256i _mm256_set1_epi32 (int a)
+        ///   HELPER
+        /// __m256i _mm256_set1_epi64x (long long a)
+        ///   HELPER
+        /// __m256 _mm256_set1_ps (float a)
+        ///   HELPER
+        /// __m256d _mm256_set1_pd (double a)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<T> SetAllVector256<T>(T value) where T : struct
+        {
+            return SetAllVector256<T>(value);
+        }
+
+        /// <summary>
+        /// __m256 _mm256_set_m128 (__m128 hi, __m128 lo)
+        ///   HELPER
+        /// __m256d _mm256_set_m128d (__m128d hi, __m128d lo)
+        ///   HELPER
+        /// __m256i _mm256_set_m128i (__m128i hi, __m128i lo)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<T> SetHighLow<T>(Vector128<T> hi, Vector128<T> lo) where T : struct
+        {
+            return SetHighLow<T>(hi, lo);
+        }
+
+        /// <summary>
+        /// __m256i _mm256_setzero_si256 (void)
+        ///   HELPER
+        /// __m256 _mm256_setzero_ps (void)
+        ///   HELPER
+        /// __m256d _mm256_setzero_pd (void)
+        ///   HELPER
+        /// </summary>
+        public static Vector256<T> SetZeroVector256<T>() where T : struct
+        {
+            return SetZeroVector256<T>();
+        }
+
+        /// <summary>
+        /// __m256 _mm256_shuffle_ps (__m256 a, __m256 b, const int imm8)
+        ///   VSHUFPS ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<float> Shuffle(Vector256<float> value, Vector256<float> right, byte control) => Shuffle(value, right, control);
+        /// <summary>
+        /// __m256d _mm256_shuffle_pd (__m256d a, __m256d b, const int imm8)
+        ///   VSHUFPD ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<double> Shuffle(Vector256<double> value, Vector256<double> right, byte control) => Shuffle(value, right, control);
+
+        /// <summary>
+        /// __m256 _mm256_sqrt_ps (__m256 a)
+        ///   VSQRTPS ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Sqrt(Vector256<float> value) => Sqrt(value);
+        /// <summary>
+        /// __m256d _mm256_sqrt_pd (__m256d a)
+        ///   VSQRTPD ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Sqrt(Vector256<double> value) => Sqrt(value);
+
+        /// <summary>
+        /// __m256 _mm256_castpd_ps (__m256d a)
+        ///   HELPER - No Codegen
+        /// __m256i _mm256_castpd_si256 (__m256d a)
+        ///   HELPER - No Codegen
+        /// __m256d _mm256_castps_pd (__m256 a)
+        ///   HELPER - No Codegen
+        /// __m256i _mm256_castps_si256 (__m256 a)
+        ///   HELPER - No Codegen
+        /// __m256d _mm256_castsi256_pd (__m256i a)
+        ///   HELPER - No Codegen
+        /// __m256 _mm256_castsi256_ps (__m256i a)
+        ///   HELPER - No Codegen
+        /// </summary>
+        public static Vector256<U> StaticCast<T, U>(Vector256<T> value) where T : struct where U : struct
+        {
+            return StaticCast<T, U>(value);
+        }
+
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(sbyte* address, Vector256<sbyte> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(byte* address, Vector256<byte> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(short* address, Vector256<short> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(ushort* address, Vector256<ushort> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(int* address, Vector256<int> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(uint* address, Vector256<uint> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(long* address, Vector256<long> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm256_store_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQA m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(ulong* address, Vector256<ulong> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm256_store_ps (float * mem_addr, __m256 a)
+        ///   VMOVAPS m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(float* address, Vector256<float> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm256_store_pd (double * mem_addr, __m256d a)
+        ///   VMOVAPD m256, ymm
+        /// </summary>
+        public static unsafe void StoreAligned(double* address, Vector256<double> source) => StoreAligned(address, source);
+
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(sbyte* address, Vector256<sbyte> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(byte* address, Vector256<byte> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(short* address, Vector256<short> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(ushort* address, Vector256<ushort> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(int* address, Vector256<int> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(uint* address, Vector256<uint> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(long* address, Vector256<long> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm256_stream_si256 (__m256i * mem_addr, __m256i a)
+        ///   VMOVNTDQ m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(ulong* address, Vector256<ulong> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm256_stream_ps (float * mem_addr, __m256 a)
+        ///   MOVNTPS m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(float* address, Vector256<float> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm256_stream_pd (double * mem_addr, __m256d a)
+        ///   MOVNTPD m256, ymm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(double* address, Vector256<double> source) => StoreAlignedNonTemporal(address, source);
+
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(sbyte* address, Vector256<sbyte> source) => Store(address, source);
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(byte* address, Vector256<byte> source) => Store(address, source);
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(short* address, Vector256<short> source) => Store(address, source);
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(ushort* address, Vector256<ushort> source) => Store(address, source);
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(int* address, Vector256<int> source) => Store(address, source);
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(uint* address, Vector256<uint> source) => Store(address, source);
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(long* address, Vector256<long> source) => Store(address, source);
+        /// <summary>
+        /// void _mm256_storeu_si256 (__m256i * mem_addr, __m256i a)
+        ///   MOVDQU m256, ymm
+        /// </summary>
+        public static unsafe void Store(ulong* address, Vector256<ulong> source) => Store(address, source);
+        /// <summary>
+        /// void _mm256_storeu_ps (float * mem_addr, __m256 a)
+        ///   MOVUPS m256, ymm
+        /// </summary>
+        public static unsafe void Store(float* address, Vector256<float> source) => Store(address, source);
+        /// <summary>
+        /// void _mm256_storeu_pd (double * mem_addr, __m256d a)
+        ///   MOVUPD m256, ymm
+        /// </summary>
+        public static unsafe void Store(double* address, Vector256<double> source) => Store(address, source);
+
+        /// <summary>
+        /// __m256 _mm256_sub_ps (__m256 a, __m256 b)
+        ///   VSUBPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Subtract(Vector256<float> left, Vector256<float> right) => Subtract(left, right);
+        /// <summary>
+        /// __m256d _mm256_sub_pd (__m256d a, __m256d b)
+        ///   VSUBPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Subtract(Vector256<double> left, Vector256<double> right) => Subtract(left, right);
+
+        /// <summary>
+        /// int _mm_testc_ps (__m128 a, __m128 b)
+        ///   VTESTPS xmm, xmm/m128
+        /// </summary>
+        public static bool TestC(Vector128<float> left, Vector128<float> right) => TestC(left, right);
+        /// <summary>
+        /// int _mm_testc_pd (__m128d a, __m128d b)
+        ///   VTESTPD xmm, xmm/m128
+        /// </summary>
+        public static bool TestC(Vector128<double> left, Vector128<double> right) => TestC(left, right);
+
+        /// <summary>
+        /// int _mm256_testc_si256 (__m256i a, __m256i b)
+        ///   VPTEST ymm, ymm/m256
+        /// int _mm256_testc_ps (__m256 a, __m256 b)
+        ///   VTESTPS ymm, ymm/m256
+        /// int _mm256_testc_pd (__m256d a, __m256d b)
+        ///   VTESTPS ymm, ymm/m256
+        /// </summary>
+        public static bool TestC<T>(Vector256<T> left, Vector256<T> right) where T : struct
+        {
+            return TestC<T>(left, right);
+        }
+
+        /// <summary>
+        /// int _mm_testnzc_ps (__m128 a, __m128 b)
+        ///   VTESTPS xmm, xmm/m128
+        /// </summary>
+        public static bool TestNotZAndNotC(Vector128<float> left, Vector128<float> right) => TestNotZAndNotC(left, right);
+        /// <summary>
+        /// int _mm_testnzc_pd (__m128d a, __m128d b)
+        ///   VTESTPD xmm, xmm/m128
+        /// </summary>
+        public static bool TestNotZAndNotC(Vector128<double> left, Vector128<double> right) => TestNotZAndNotC(left, right);
+
+        /// <summary>
+        /// int _mm256_testnzc_si256 (__m256i a, __m256i b)
+        ///   VPTEST ymm, ymm/m256
+        /// int _mm256_testnzc_ps (__m256 a, __m256 b)
+        ///   VTESTPS ymm, ymm/m256
+        /// int _mm256_testnzc_pd (__m256d a, __m256d b)
+        ///   VTESTPD ymm, ymm/m256
+        /// </summary>
+        public static bool TestNotZAndNotC<T>(Vector256<T> left, Vector256<T> right) where T : struct
+        {
+            return TestNotZAndNotC<T>(left, right);
+        }
+
+        /// <summary>
+        /// int _mm_testz_ps (__m128 a, __m128 b)
+        ///   VTESTPS xmm, xmm/m128
+        /// </summary>
+        public static bool TestZ(Vector128<float> left, Vector128<float> right) => TestZ(left, right);
+        /// <summary>
+        /// int _mm_testz_pd (__m128d a, __m128d b)
+        ///   VTESTPD xmm, xmm/m128
+        /// </summary>
+        public static bool TestZ(Vector128<double> left, Vector128<double> right) => TestZ(left, right);
+
+        /// <summary>
+        /// int _mm256_testz_si256 (__m256i a, __m256i b)
+        ///   VPTEST ymm, ymm/m256
+        /// int _mm256_testz_ps (__m256 a, __m256 b)
+        ///   VTESTPS ymm, ymm/m256
+        /// int _mm256_testz_pd (__m256d a, __m256d b)
+        ///   VTESTPD ymm, ymm/m256
+        /// </summary>
+        public static bool TestZ<T>(Vector256<T> left, Vector256<T> right) where T : struct
+        {
+            return TestZ<T>(left, right);
+        }
+
+        /// <summary>
+        /// __m256 _mm256_unpackhi_ps (__m256 a, __m256 b)
+        ///   VUNPCKHPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> UnpackHigh(Vector256<float> left, Vector256<float> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m256d _mm256_unpackhi_pd (__m256d a, __m256d b)
+        ///   VUNPCKHPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> UnpackHigh(Vector256<double> left, Vector256<double> right) => UnpackHigh(left, right);
+
+        /// <summary>
+        /// __m256 _mm256_unpacklo_ps (__m256 a, __m256 b)
+        ///   VUNPCKLPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> UnpackLow(Vector256<float> left, Vector256<float> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m256d _mm256_unpacklo_pd (__m256d a, __m256d b)
+        ///   VUNPCKLPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> UnpackLow(Vector256<double> left, Vector256<double> right) => UnpackLow(left, right);
+
+        /// <summary>
+        /// __m256 _mm256_xor_ps (__m256 a, __m256 b)
+        ///   VXORPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> Xor(Vector256<float> left, Vector256<float> right) => Xor(left, right);
+        /// <summary>
+        /// __m256d _mm256_xor_pd (__m256d a, __m256d b)
+        ///   VXORPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> Xor(Vector256<double> left, Vector256<double> right) => Xor(left, right);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Avx2.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Avx2.PlatformNotSupported.cs
new file mode 100644
index 0000000000..495f371c5e
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Avx2.PlatformNotSupported.cs
@@ -0,0 +1,1865 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel AVX2 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Avx2
+    {
+        public static bool IsSupported { get { return false; } }
+
+        /// <summary>
+        /// __m256i _mm256_abs_epi8 (__m256i a)
+        ///   VPABSB ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Abs(Vector256<sbyte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_abs_epi16 (__m256i a)
+        ///   VPABSW ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Abs(Vector256<short> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_abs_epi32 (__m256i a)
+        ///   VPABSD ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Abs(Vector256<int> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_add_epi8 (__m256i a, __m256i b)
+        ///   VPADDB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Add(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_add_epi8 (__m256i a, __m256i b)
+        ///   VPADDB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Add(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_add_epi16 (__m256i a, __m256i b)
+        ///   VPADDW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> Add(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_add_epi16 (__m256i a, __m256i b)
+        ///   VPADDW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Add(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_add_epi32 (__m256i a, __m256i b)
+        ///   VPADDD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Add(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_add_epi32 (__m256i a, __m256i b)
+        ///   VPADDD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Add(Vector256<uint> left, Vector256<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_add_epi64 (__m256i a, __m256i b)
+        ///   VPADDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> Add(Vector256<long> left, Vector256<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_add_epi64 (__m256i a, __m256i b)
+        ///   VPADDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> Add(Vector256<ulong> left, Vector256<ulong> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_adds_epi8 (__m256i a, __m256i b)
+        ///   VPADDSB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> AddSaturate(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_adds_epu8 (__m256i a, __m256i b)
+        ///   VPADDUSB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> AddSaturate(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_adds_epi16 (__m256i a, __m256i b)
+        ///   VPADDSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> AddSaturate(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_adds_epu16 (__m256i a, __m256i b)
+        ///   VPADDUSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> AddSaturate(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_alignr_epi8 (__m256i a, __m256i b, const int count)
+        ///   VPALIGNR ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<sbyte> AlignRight(Vector256<sbyte> left, Vector256<sbyte> right, byte mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> And(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> And(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> And(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> And(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> And(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> And(Vector256<uint> left, Vector256<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> And(Vector256<long> left, Vector256<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> And(Vector256<ulong> left, Vector256<ulong> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> AndNot(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> AndNot(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> AndNot(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> AndNot(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> AndNot(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> AndNot(Vector256<uint> left, Vector256<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> AndNot(Vector256<long> left, Vector256<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> AndNot(Vector256<ulong> left, Vector256<ulong> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_avg_epu8 (__m256i a, __m256i b)
+        ///   VPAVGB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Average(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_avg_epu16 (__m256i a, __m256i b)
+        ///   VPAVGW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Average(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_blend_epi32 (__m128i a, __m128i b, const int imm8)
+        ///   VPBLENDD xmm, xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<int> Blend(Vector128<int> left, Vector128<int> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_blend_epi32 (__m128i a, __m128i b, const int imm8)
+        ///   VPBLENDD xmm, xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<uint> Blend(Vector128<uint> left, Vector128<uint> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_blend_epi16 (__m256i a, __m256i b, const int imm8)
+        ///   VPBLENDW ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<short> Blend(Vector256<short> left, Vector256<short> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_blend_epi16 (__m256i a, __m256i b, const int imm8)
+        ///   VPBLENDW ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<ushort> Blend(Vector256<ushort> left, Vector256<ushort> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_blend_epi32 (__m256i a, __m256i b, const int imm8)
+        ///   VPBLENDD ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<int> Blend(Vector256<int> left, Vector256<int> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_blend_epi32 (__m256i a, __m256i b, const int imm8)
+        ///   VPBLENDD ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<uint> Blend(Vector256<uint> left, Vector256<uint> right, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_blendv_epi8 (__m256i a, __m256i b, __m256i mask)
+        ///   PBLENDVB ymm, ymm, ymm/m256, ymm
+        /// </summary>
+        public static Vector256<sbyte> BlendVariable(Vector256<sbyte> left, Vector256<sbyte> right, Vector256<sbyte> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_blendv_epi8 (__m256i a, __m256i b, __m256i mask)
+        ///   PBLENDVB ymm, ymm, ymm/m256, ymm
+        /// </summary>
+        public static Vector256<byte> BlendVariable(Vector256<byte> left, Vector256<byte> right, Vector256<byte> mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_broadcastb_epi8 (__m128i a)
+        ///   VPBROADCASTB xmm, xmm
+        /// __m128i _mm_broadcastw_epi16 (__m128i a)
+        ///   VPBROADCASTW xmm, xmm
+        /// __m128i _mm_broadcastd_epi32 (__m128i a)
+        ///   VPBROADCASTD xmm, xmm
+        /// __m128i _mm_broadcastq_epi64 (__m128i a)
+        ///   VPBROADCASTQ xmm, xmm
+        /// __m128 _mm_broadcastss_ps (__m128 a)
+        ///   VBROADCASTSS xmm, xmm
+        /// __m128d _mm_broadcastsd_pd (__m128d a)
+        ///   VMOVDDUP xmm, xmm
+        /// </summary>
+        public static Vector128<T> BroadcastScalarToVector128<T>(Vector128<T> value) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_broadcastb_epi8 (__m128i a)
+        ///   VPBROADCASTB ymm, xmm
+        /// __m256i _mm256_broadcastw_epi16 (__m128i a)
+        ///   VPBROADCASTW ymm, xmm
+        /// __m256i _mm256_broadcastd_epi32 (__m128i a)
+        ///   VPBROADCASTD ymm, xmm
+        /// __m256i _mm256_broadcastq_epi64 (__m128i a)
+        ///   VPBROADCASTQ ymm, xmm
+        /// __m256 _mm256_broadcastss_ps (__m128 a)
+        ///   VBROADCASTSS ymm, xmm
+        /// __m256d _mm256_broadcastsd_pd (__m128d a)
+        ///   VBROADCASTSD ymm, xmm
+        /// </summary>
+        public static Vector256<T> BroadcastScalarToVector256<T>(Vector128<T> value) where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m8
+        /// </summary>
+        public static unsafe Vector256<sbyte> BroadcastVector128ToVector256(sbyte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m8
+        /// </summary>
+        public static unsafe Vector256<byte> BroadcastVector128ToVector256(byte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m16
+        /// </summary>
+        public static unsafe Vector256<short> BroadcastVector128ToVector256(short* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m16
+        /// </summary>
+        public static unsafe Vector256<ushort> BroadcastVector128ToVector256(ushort* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m32
+        /// </summary>
+        public static unsafe Vector256<int> BroadcastVector128ToVector256(int* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m32
+        /// </summary>
+        public static unsafe Vector256<uint> BroadcastVector128ToVector256(uint* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m64
+        /// </summary>
+        public static unsafe Vector256<long> BroadcastVector128ToVector256(long* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m64
+        /// </summary>
+        public static unsafe Vector256<ulong> BroadcastVector128ToVector256(ulong* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi8 (__m256i a, __m256i b)
+        ///   VPCMPEQB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> CompareEqual(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi8 (__m256i a, __m256i b)
+        ///   VPCMPEQB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> CompareEqual(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi16 (__m256i a, __m256i b)
+        ///   VPCMPEQW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> CompareEqual(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi16 (__m256i a, __m256i b)
+        ///   VPCMPEQW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> CompareEqual(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi32 (__m256i a, __m256i b)
+        ///   VPCMPEQD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> CompareEqual(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi32 (__m256i a, __m256i b)
+        ///   VPCMPEQD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> CompareEqual(Vector256<uint> left, Vector256<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi64 (__m256i a, __m256i b)
+        ///   VPCMPEQQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> CompareEqual(Vector256<long> left, Vector256<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi64 (__m256i a, __m256i b)
+        ///   VPCMPEQQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> CompareEqual(Vector256<ulong> left, Vector256<ulong> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_cmpgt_epi8 (__m256i a, __m256i b)
+        ///   VPCMPGTB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> CompareGreaterThan(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cmpgt_epi16 (__m256i a, __m256i b)
+        ///   VPCMPGTW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> CompareGreaterThan(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cmpgt_epi32 (__m256i a, __m256i b)
+        ///   VPCMPGTD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> CompareGreaterThan(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cmpgt_epi64 (__m256i a, __m256i b)
+        ///   VPCMPGTQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> CompareGreaterThan(Vector256<long> left, Vector256<long> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// double _mm256_cvtsd_f64 (__m256d a)
+        ///   HELPER: MOVSD
+        /// </summary>
+        public static double ConvertToDouble(Vector256<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm256_cvtsi256_si32 (__m256i a)
+        ///   MOVD reg/m32, xmm
+        /// </summary>
+        public static int ConvertToInt32(Vector256<int> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm256_cvtsi256_si32 (__m256i a)
+        ///   MOVD reg/m32, xmm
+        /// </summary>
+        public static uint ConvertToUInt32(Vector256<uint> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_cvtepi8_epi16 (__m128i a)
+        ///   VPMOVSXBW ymm, xmm/m128
+        /// </summary>
+        public static Vector256<short> ConvertToVector256Int16(Vector128<sbyte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cvtepu8_epi16 (__m128i a)
+        ///   VPMOVZXBW ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ushort> ConvertToVector256UInt16(Vector128<byte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cvtepi8_epi32 (__m128i a)
+        ///   VPMOVSXBD ymm, xmm/m128
+        /// </summary>
+        public static Vector256<int> ConvertToVector256Int32(Vector128<sbyte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cvtepi16_epi32 (__m128i a)
+        ///   VPMOVSXWD ymm, xmm/m128
+        /// </summary>
+        public static Vector256<int> ConvertToVector256Int32(Vector128<short> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cvtepu8_epi32 (__m128i a)
+        ///   VPMOVZXBD ymm, xmm/m128
+        /// </summary>
+        public static Vector256<uint> ConvertToVector256UInt32(Vector128<byte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cvtepu16_epi32 (__m128i a)
+        ///   VPMOVZXWD ymm, xmm/m128
+        /// </summary>
+        public static Vector256<uint> ConvertToVector256UInt32(Vector128<ushort> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cvtepi8_epi64 (__m128i a)
+        ///   VPMOVSXBQ ymm, xmm/m128
+        /// </summary>
+        public static Vector256<long> ConvertToVector256Int64(Vector128<sbyte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cvtepi16_epi64 (__m128i a)
+        ///   VPMOVSXWQ ymm, xmm/m128
+        /// </summary>
+        public static Vector256<long> ConvertToVector256Int64(Vector128<short> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cvtepi32_epi64 (__m128i a)
+        ///   VPMOVSXDQ ymm, xmm/m128
+        /// </summary>
+        public static Vector256<long> ConvertToVector256Int64(Vector128<int> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cvtepu8_epi64 (__m128i a)
+        ///   VPMOVZXBQ ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ulong> ConvertToVector256UInt64(Vector128<byte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cvtepu16_epi64 (__m128i a)
+        ///   VPMOVZXWQ ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ulong> ConvertToVector256UInt64(Vector128<ushort> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_cvtepu32_epi64 (__m128i a)
+        ///   VPMOVZXDQ ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ulong> ConvertToVector256UInt64(Vector128<uint> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<sbyte> ExtractVector128(Vector256<sbyte> value, byte index) { throw new PlatformNotSupportedException(); }
+        // <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(sbyte* address, Vector256<sbyte> value, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<byte> ExtractVector128(Vector256<byte> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(byte* address, Vector256<byte> value, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<short> ExtractVector128(Vector256<short> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(short* address, Vector256<short> value, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<ushort> ExtractVector128(Vector256<ushort> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(ushort* address, Vector256<ushort> value, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<int> ExtractVector128(Vector256<int> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(int* address, Vector256<int> value, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<uint> ExtractVector128(Vector256<uint> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(uint* address, Vector256<uint> value, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<long> ExtractVector128(Vector256<long> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(long* address, Vector256<long> value, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<ulong> ExtractVector128(Vector256<ulong> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(ulong* address, Vector256<ulong> value, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_i32gather_epi32 (int const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERDD xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<int> GatherVector128(int* baseAddress, Vector128<int> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_i32gather_epi32 (int const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERDD xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<uint> GatherVector128(uint* baseAddress, Vector128<int> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_i32gather_epi64 (__int64 const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERDQ xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<long> GatherVector128(long* baseAddress, Vector128<int> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_i32gather_epi64 (__int64 const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERDQ xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<ulong> GatherVector128(ulong* baseAddress, Vector128<int> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_i32gather_ps (float const* base_addr, __m128i vindex, const int scale)
+        ///   VGATHERDPS xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<float> GatherVector128(float* baseAddress, Vector128<int> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_i32gather_pd (double const* base_addr, __m128i vindex, const int scale)
+        ///   VGATHERDPD xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<double> GatherVector128(double* baseAddress, Vector128<int> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_i64gather_epi32 (int const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERQD xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<int> GatherVector128(int* baseAddress, Vector128<long> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_i64gather_epi32 (int const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERQD xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<uint> GatherVector128(uint* baseAddress, Vector128<long> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_i64gather_epi64 (__int64 const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERQQ xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<long> GatherVector128(long* baseAddress, Vector128<long> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_i64gather_epi64 (__int64 const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERQQ xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<ulong> GatherVector128(ulong* baseAddress, Vector128<long> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_i64gather_ps (float const* base_addr, __m128i vindex, const int scale)
+        ///   VGATHERQPS xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<float> GatherVector128(float* baseAddress, Vector128<long> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_i64gather_pd (double const* base_addr, __m128i vindex, const int scale)
+        ///   VGATHERQPD xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<double> GatherVector128(double* baseAddress, Vector128<long> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_i32gather_epi32 (int const* base_addr, __m256i vindex, const int scale)
+        ///   VPGATHERDD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<int> GatherVector256(int* baseAddress, Vector256<int> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_i32gather_epi32 (int const* base_addr, __m256i vindex, const int scale)
+        ///   VPGATHERDD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<uint> GatherVector256(uint* baseAddress, Vector256<int> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_i32gather_epi64 (__int64 const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERDQ ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<long> GatherVector256(long* baseAddress, Vector128<int> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_i32gather_epi64 (__int64 const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERDQ ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<ulong> GatherVector256(ulong* baseAddress, Vector128<int> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_i32gather_ps (float const* base_addr, __m256i vindex, const int scale)
+        ///   VGATHERDPS ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<float> GatherVector256(float* baseAddress, Vector256<int> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_i32gather_pd (double const* base_addr, __m128i vindex, const int scale)
+        ///   VGATHERDPD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<double> GatherVector256(double* baseAddress, Vector128<int> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_i64gather_epi32 (int const* base_addr, __m256i vindex, const int scale)
+        ///   VPGATHERQD ymm, vm64y, ymm
+        /// </summary>
+        public static unsafe Vector128<int> GatherVector128(int* baseAddress, Vector256<long> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_i64gather_epi32 (int const* base_addr, __m256i vindex, const int scale)
+        ///   VPGATHERQD ymm, vm64y, ymm
+        /// </summary>
+        public static unsafe Vector128<uint> GatherVector128(uint* baseAddress, Vector256<long> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_i64gather_epi64 (__int64 const* base_addr, __m256i vindex, const int scale)
+        ///   VPGATHERQQ ymm, vm64y, ymm
+        /// </summary>
+        public static unsafe Vector256<long> GatherVector256(long* baseAddress, Vector256<long> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_i64gather_epi64 (__int64 const* base_addr, __m256i vindex, const int scale)
+        ///   VPGATHERQQ ymm, vm64y, ymm
+        /// </summary>
+        public static unsafe Vector256<ulong> GatherVector256(ulong* baseAddress, Vector256<long> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm256_i64gather_ps (float const* base_addr, __m256i vindex, const int scale)
+        ///   VGATHERQPS ymm, vm64y, ymm
+        /// </summary>
+        public static unsafe Vector128<float> GatherVector128(float* baseAddress, Vector256<long> index, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_i64gather_pd (double const* base_addr, __m256i vindex, const int scale)
+        ///   VGATHERQPD ymm, vm64y, ymm
+        /// </summary>
+        public static unsafe Vector256<double> GatherVector256(double* baseAddress, Vector256<long> index, byte scale) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_mask_i32gather_epi32 (__m128i src, int const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERDD xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<int> GatherMaskVector128(Vector128<int> source, int* baseAddress, Vector128<int> index, Vector128<int> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_mask_i32gather_epi32 (__m128i src, int const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERDD xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<uint> GatherMaskVector128(Vector128<uint> source, uint* baseAddress, Vector128<int> index, Vector128<uint> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_mask_i32gather_epi64 (__m128i src, __int64 const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERDQ xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<long> GatherMaskVector128(Vector128<long> source, long* baseAddress, Vector128<int> index, Vector128<long> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_mask_i32gather_epi64 (__m128i src, __int64 const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERDQ xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<ulong> GatherMaskVector128(Vector128<ulong> source, ulong* baseAddress, Vector128<int> index, Vector128<ulong> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_mask_i32gather_ps (__m128 src, float const* base_addr, __m128i vindex, __m128 mask, const int scale)
+        ///   VGATHERDPS xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<float> GatherMaskVector128(Vector128<float> source, float* baseAddress, Vector128<int> index, Vector128<float> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_mask_i32gather_pd (__m128d src, double const* base_addr, __m128i vindex, __m128d mask, const int scale)
+        ///   VGATHERDPD xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<double> GatherMaskVector128(Vector128<double> source, double* baseAddress, Vector128<int> index, Vector128<double> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_mask_i64gather_epi32 (__m128i src, int const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERQD xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<int> GatherMaskVector128(Vector128<int> source, int* baseAddress, Vector128<long> index, Vector128<int> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_mask_i64gather_epi32 (__m128i src, int const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERQD xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<uint> GatherMaskVector128(Vector128<uint> source, uint* baseAddress, Vector128<long> index, Vector128<uint> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_mask_i64gather_epi64 (__m128i src, __int64 const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERQQ xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<long> GatherMaskVector128(Vector128<long> source, long* baseAddress, Vector128<long> index, Vector128<long> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_mask_i64gather_epi64 (__m128i src, __int64 const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERQQ xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<ulong> GatherMaskVector128(Vector128<ulong> source, ulong* baseAddress, Vector128<long> index, Vector128<ulong> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_mask_i64gather_ps (__m128 src, float const* base_addr, __m128i vindex, __m128 mask, const int scale)
+        ///   VPGATHERQPS xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<float> GatherMaskVector128(Vector128<float> source, float* baseAddress, Vector128<long> index, Vector128<float> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_mask_i64gather_pd (__m128d src, double const* base_addr, __m128i vindex, __m128d mask, const int scale)
+        ///   VPGATHERQPD xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<double> GatherMaskVector128(Vector128<double> source, double* baseAddress, Vector128<long> index, Vector128<double> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_mask_i32gather_epi32 (__m256i src, int const* base_addr, __m256i vindex, __m256i mask, const int scale)
+        ///   VPGATHERDD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<int> GatherMaskVector256(Vector256<int> source, int* baseAddress, Vector256<int> index, Vector256<int> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_mask_i32gather_epi32 (__m256i src, int const* base_addr, __m256i vindex, __m256i mask, const int scale)
+        ///   VPGATHERDD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<uint> GatherMaskVector256(Vector256<uint> source, uint* baseAddress, Vector256<int> index, Vector256<uint> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_mask_i32gather_epi64 (__m256i src, __int64 const* base_addr, __m128i vindex, __m256i mask, const int scale)
+        ///   VPGATHERDQ ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<long> GatherMaskVector256(Vector256<long> source, long* baseAddress, Vector128<int> index, Vector256<long> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_mask_i32gather_epi64 (__m256i src, __int64 const* base_addr, __m128i vindex, __m256i mask, const int scale)
+        ///   VPGATHERDQ ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<ulong> GatherMaskVector256(Vector256<ulong> source, ulong* baseAddress, Vector128<int> index, Vector256<ulong> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_mask_i32gather_ps (__m256 src, float const* base_addr, __m256i vindex, __m256 mask, const int scale)
+        ///   VPGATHERDPS ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<float> GatherMaskVector256(Vector256<float> source, float* baseAddress, Vector256<int> index, Vector256<float> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_mask_i32gather_pd (__m256d src, double const* base_addr, __m128i vindex, __m256d mask, const int scale)
+        ///   VPGATHERDPD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<double> GatherMaskVector256(Vector256<double> source, double* baseAddress, Vector128<int> index, Vector256<double> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_mask_i64gather_epi32 (__m128i src, int const* base_addr, __m256i vindex, __m128i mask, const int scale)
+        ///   VPGATHERQD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector128<int> GatherMaskVector128(Vector128<int> source, int* baseAddress, Vector256<long> index, Vector128<int> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm256_mask_i64gather_epi32 (__m128i src, int const* base_addr, __m256i vindex, __m128i mask, const int scale)
+        ///   VPGATHERQD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector128<uint> GatherMaskVector128(Vector128<uint> source, uint* baseAddress, Vector256<long> index, Vector128<uint> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_mask_i64gather_epi64 (__m256i src, __int64 const* base_addr, __m256i vindex, __m256i mask, const int scale)
+        ///   VPGATHERQQ ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<long> GatherMaskVector256(Vector256<long> source, long* baseAddress, Vector256<long> index, Vector256<long> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_mask_i64gather_epi64 (__m256i src, __int64 const* base_addr, __m256i vindex, __m256i mask, const int scale)
+        ///   VPGATHERQQ ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<ulong> GatherMaskVector256(Vector256<ulong> source, ulong* baseAddress, Vector256<long> index, Vector256<ulong> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm256_mask_i64gather_ps (__m128 src, float const* base_addr, __m256i vindex, __m128 mask, const int scale)
+        ///   VPGATHERQPS ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector128<float> GatherMaskVector128(Vector128<float> source, float* baseAddress, Vector256<long> index, Vector128<float> mask, byte scale) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_mask_i64gather_pd (__m256d src, double const* base_addr, __m256i vindex, __m256d mask, const int scale)
+        ///   VPGATHERQPD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<double> GatherMaskVector256(Vector256<double> source, double* baseAddress, Vector256<long> index, Vector256<double> mask, byte scale) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_hadd_epi16 (__m256i a, __m256i b)
+        ///   VPHADDW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> HorizontalAdd(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_hadd_epi32 (__m256i a, __m256i b)
+        ///   VPHADDD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> HorizontalAdd(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_hadds_epi16 (__m256i a, __m256i b)
+        ///   VPHADDSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> HorizontalAddSaturate(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_hsub_epi16 (__m256i a, __m256i b)
+        ///   VPHSUBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> HorizontalSubtract(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_hsub_epi32 (__m256i a, __m256i b)
+        ///   VPHSUBD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> HorizontalSubtract(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_hsubs_epi16 (__m256i a, __m256i b)
+        ///   VPHSUBSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> HorizontalSubtractSaturate(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<sbyte> InsertVector128(Vector256<sbyte> value, Vector128<sbyte> data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xm128, imm8
+        /// </summary>
+        public static unsafe Vector256<sbyte> InsertVector128(Vector256<sbyte> value, sbyte* address, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<byte> InsertVector128(Vector256<byte> value, Vector128<byte> data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<byte> InsertVector128(Vector256<byte> value, byte* address, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<short> InsertVector128(Vector256<short> value, Vector128<short> data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<short> InsertVector128(Vector256<short> value, short* address, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<ushort> InsertVector128(Vector256<ushort> value, Vector128<ushort> data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<ushort> InsertVector128(Vector256<ushort> value, ushort* address, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<int> InsertVector128(Vector256<int> value, Vector128<int> data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<int> InsertVector128(Vector256<int> value, int* address, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<uint> InsertVector128(Vector256<uint> value, Vector128<uint> data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<uint> InsertVector128(Vector256<uint> value, uint* address, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<long> InsertVector128(Vector256<long> value, Vector128<long> data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<long> InsertVector128(Vector256<long> value, long* address, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<ulong> InsertVector128(Vector256<ulong> value, Vector128<ulong> data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<ulong> InsertVector128(Vector256<ulong> value, ulong* address, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<sbyte> LoadAlignedVector256NonTemporal(sbyte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<byte> LoadAlignedVector256NonTemporal(byte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<short> LoadAlignedVector256NonTemporal(short* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ushort> LoadAlignedVector256NonTemporal(ushort* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<int> LoadAlignedVector256NonTemporal(int* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<uint> LoadAlignedVector256NonTemporal(uint* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<long> LoadAlignedVector256NonTemporal(long* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ulong> LoadAlignedVector256NonTemporal(ulong* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_maskload_epi32 (int const* mem_addr, __m128i mask)
+        ///   VPMASKMOVD xmm, xmm, m128
+        /// </summary>
+        public static unsafe Vector128<int> MaskLoad(int* address, Vector128<int> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_maskload_epi32 (int const* mem_addr, __m128i mask)
+        ///   VPMASKMOVD xmm, xmm, m128
+        /// </summary>
+        public static unsafe Vector128<uint> MaskLoad(uint* address, Vector128<uint> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_maskload_epi64 (__int64 const* mem_addr, __m128i mask)
+        ///   VPMASKMOVQ xmm, xmm, m128
+        /// </summary>
+        public static unsafe Vector128<long> MaskLoad(long* address, Vector128<long> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_maskload_epi64 (__int64 const* mem_addr, __m128i mask)
+        ///   VPMASKMOVQ xmm, xmm, m128
+        /// </summary>
+        public static unsafe Vector128<ulong> MaskLoad(ulong* address, Vector128<ulong> mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_maskload_epi32 (int const* mem_addr, __m256i mask)
+        ///   VPMASKMOVD ymm, ymm, m256
+        /// </summary>
+        public static unsafe Vector256<int> MaskLoad(int* address, Vector256<int> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_maskload_epi32 (int const* mem_addr, __m256i mask)
+        ///   VPMASKMOVD ymm, ymm, m256
+        /// </summary>
+        public static unsafe Vector256<uint> MaskLoad(uint* address, Vector256<uint> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_maskload_epi64 (__int64 const* mem_addr, __m256i mask)
+        ///   VPMASKMOVQ ymm, ymm, m256
+        /// </summary>
+        public static unsafe Vector256<long> MaskLoad(long* address, Vector256<long> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_maskload_epi64 (__int64 const* mem_addr, __m256i mask)
+        ///   VPMASKMOVQ ymm, ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ulong> MaskLoad(ulong* address, Vector256<ulong> mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_maskstore_epi32 (int* mem_addr, __m128i mask, __m128i a)
+        ///   VPMASKMOVD m128, xmm, xmm
+        /// </summary>
+        public static unsafe void MaskStore(int* address, Vector128<int> mask, Vector128<int> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_maskstore_epi32 (int* mem_addr, __m128i mask, __m128i a)
+        ///   VPMASKMOVD m128, xmm, xmm
+        /// </summary>
+        public static unsafe void MaskStore(uint* address, Vector128<uint> mask, Vector128<uint> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_maskstore_epi64 (__int64* mem_addr, __m128i mask, __m128i a)
+        ///   VPMASKMOVQ m128, xmm, xmm
+        /// </summary>
+        public static unsafe void MaskStore(long* address, Vector128<long> mask, Vector128<long> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_maskstore_epi64 (__int64* mem_addr, __m128i mask, __m128i a)
+        ///   VPMASKMOVQ m128, xmm, xmm
+        /// </summary>
+        public static unsafe void MaskStore(ulong* address, Vector128<ulong> mask, Vector128<ulong> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm256_maskstore_epi32 (int* mem_addr, __m256i mask, __m256i a)
+        ///   VPMASKMOVD m256, ymm, ymm
+        /// </summary>
+        public static unsafe void MaskStore(int* address, Vector256<int> mask, Vector256<int> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_maskstore_epi32 (int* mem_addr, __m256i mask, __m256i a)
+        ///   VPMASKMOVD m256, ymm, ymm
+        /// </summary>
+        public static unsafe void MaskStore(uint* address, Vector256<uint> mask, Vector256<uint> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_maskstore_epi64 (__int64* mem_addr, __m256i mask, __m256i a)
+        ///   VPMASKMOVQ m256, ymm, ymm
+        /// </summary>
+        public static unsafe void MaskStore(long* address, Vector256<long> mask, Vector256<long> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm256_maskstore_epi64 (__int64* mem_addr, __m256i mask, __m256i a)
+        ///   VPMASKMOVQ m256, ymm, ymm
+        /// </summary>
+        public static unsafe void MaskStore(ulong* address, Vector256<ulong> mask, Vector256<ulong> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_madd_epi16 (__m256i a, __m256i b)
+        ///   VPMADDWD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> MultiplyAddAdjacent(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_maddubs_epi16 (__m256i a, __m256i b)
+        ///   VPMADDUBSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> MultiplyAddAdjacent(Vector256<byte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_max_epi8 (__m256i a, __m256i b)
+        ///   VPMAXSB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Max(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_max_epu8 (__m256i a, __m256i b)
+        ///   VPMAXUB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Max(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_max_epi16 (__m256i a, __m256i b)
+        ///   VPMAXSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> Max(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_max_epu16 (__m256i a, __m256i b)
+        ///   VPMAXUW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Max(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_max_epi32 (__m256i a, __m256i b)
+        ///   VPMAXSD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Max(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_max_epu32 (__m256i a, __m256i b)
+        ///   VPMAXUD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Max(Vector256<uint> left, Vector256<uint> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_min_epi8 (__m256i a, __m256i b)
+        ///   VPMINSB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Min(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_min_epu8 (__m256i a, __m256i b)
+        ///   VPMINUB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Min(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_min_epi16 (__m256i a, __m256i b)
+        ///   VPMINSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> Min(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_min_epu16 (__m256i a, __m256i b)
+        ///   VPMINUW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Min(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_min_epi32 (__m256i a, __m256i b)
+        ///   VPMINSD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Min(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_min_epu32 (__m256i a, __m256i b)
+        ///   VPMINUD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Min(Vector256<uint> left, Vector256<uint> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm256_movemask_epi8 (__m256i a)
+        ///   VPMOVMSKB reg, ymm
+        /// </summary>
+        public static int MoveMask(Vector256<sbyte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm256_movemask_epi8 (__m256i a)
+        ///   VPMOVMSKB reg, ymm
+        /// </summary>
+        public static int MoveMask(Vector256<byte> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_mpsadbw_epu8 (__m256i a, __m256i b, const int imm8)
+        ///   VMPSADBW ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<ushort> MultipleSumAbsoluteDifferences(Vector256<byte> left, Vector256<byte> right, byte mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_mul_epi32 (__m256i a, __m256i b)
+        ///   VPMULDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> Multiply(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_mul_epu32 (__m256i a, __m256i b)
+        ///   VPMULUDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> Multiply(Vector256<uint> left, Vector256<uint> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_mulhi_epi16 (__m256i a, __m256i b)
+        ///   VPMULHW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> MultiplyHigh(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_mulhi_epu16 (__m256i a, __m256i b)
+        ///   VPMULHUW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> MultiplyHigh(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_mulhrs_epi16 (__m256i a, __m256i b)
+        ///   VPMULHRSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> MultiplyHighRoundScale(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_mullo_epi16 (__m256i a, __m256i b)
+        ///   VPMULLW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> MultiplyLow(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_mullo_epi32 (__m256i a, __m256i b)
+        ///   VPMULLD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> MultiplyLow(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Or(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Or(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> Or(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Or(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Or(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Or(Vector256<uint> left, Vector256<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> Or(Vector256<long> left, Vector256<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> Or(Vector256<ulong> left, Vector256<ulong> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_packs_epi16 (__m256i a, __m256i b)
+        ///   VPACKSSWB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> PackSignedSaturate(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_packs_epi32 (__m256i a, __m256i b)
+        ///   VPACKSSDW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> PackSignedSaturate(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_packus_epi16 (__m256i a, __m256i b)
+        ///   VPACKUSWB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> PackUnsignedSaturate(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_packus_epi32 (__m256i a, __m256i b)
+        ///   VPACKUSDW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> PackUnsignedSaturate(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<sbyte> Permute2x128(Vector256<sbyte> left, Vector256<sbyte> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<byte> Permute2x128(Vector256<byte> left, Vector256<byte> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<short> Permute2x128(Vector256<short> left, Vector256<short> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<ushort> Permute2x128(Vector256<ushort> left, Vector256<ushort> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<int> Permute2x128(Vector256<int> left, Vector256<int> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<uint> Permute2x128(Vector256<uint> left, Vector256<uint> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<long> Permute2x128(Vector256<long> left, Vector256<long> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<ulong> Permute2x128(Vector256<ulong> left, Vector256<ulong> right, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_permute4x64_epi64 (__m256i a, const int imm8)
+        ///   VPERMQ ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<long> Permute4x64(Vector256<long> value, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_permute4x64_epi64 (__m256i a, const int imm8)
+        ///   VPERMQ ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<ulong> Permute4x64(Vector256<ulong> value, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_permute4x64_pd (__m256d a, const int imm8)
+        ///   VPERMPD ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<double> Permute4x64(Vector256<double> value, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_permutevar8x32_epi32 (__m256i a, __m256i idx)
+        ///   VPERMD ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<int> PermuteVar8x32(Vector256<int> left, Vector256<int> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_permutevar8x32_epi32 (__m256i a, __m256i idx)
+        ///   VPERMD ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<uint> PermuteVar8x32(Vector256<uint> left, Vector256<uint> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_permutevar8x32_ps (__m256 a, __m256i idx)
+        ///   VPERMPS ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<float> PermuteVar8x32(Vector256<float> left, Vector256<float> mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_sll_epi16 (__m256i a, __m128i count)
+        ///   VPSLLW ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<short> ShiftLeftLogical(Vector256<short> value, Vector128<short> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sll_epi16 (__m256i a, __m128i count)
+        ///   VPSLLW ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ushort> ShiftLeftLogical(Vector256<ushort> value, Vector128<ushort> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sll_epi32 (__m256i a, __m128i count)
+        ///   VPSLLD ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<int> ShiftLeftLogical(Vector256<int> value, Vector128<int> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sll_epi32 (__m256i a, __m128i count)
+        ///   VPSLLD ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<uint> ShiftLeftLogical(Vector256<uint> value, Vector128<uint> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sll_epi64 (__m256i a, __m128i count)
+        ///   VPSLLQ ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<long> ShiftLeftLogical(Vector256<long> value, Vector128<long> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sll_epi64 (__m256i a, __m128i count)
+        ///   VPSLLQ ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ulong> ShiftLeftLogical(Vector256<ulong> value, Vector128<ulong> count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_slli_epi16 (__m256i a, int imm8)
+        ///   VPSLLW ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<short> ShiftLeftLogical(Vector256<short> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_slli_epi16 (__m256i a, int imm8)
+        ///   VPSLLW ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ushort> ShiftLeftLogical(Vector256<ushort> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_slli_epi32 (__m256i a, int imm8)
+        ///   VPSLLD ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<int> ShiftLeftLogical(Vector256<int> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_slli_epi32 (__m256i a, int imm8)
+        ///   VPSLLD ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<uint> ShiftLeftLogical(Vector256<uint> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_slli_epi64 (__m256i a, int imm8)
+        ///   VPSLLQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<long> ShiftLeftLogical(Vector256<long> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_slli_epi64 (__m256i a, int imm8)
+        ///   VPSLLQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ulong> ShiftLeftLogical(Vector256<ulong> value, byte count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<sbyte> ShiftLeftLogical128BitLane(Vector256<sbyte> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<byte> ShiftLeftLogical128BitLane(Vector256<byte> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<short> ShiftLeftLogical128BitLane(Vector256<short> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ushort> ShiftLeftLogical128BitLane(Vector256<ushort> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<int> ShiftLeftLogical128BitLane(Vector256<int> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<uint> ShiftLeftLogical128BitLane(Vector256<uint> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<long> ShiftLeftLogical128BitLane(Vector256<long> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ulong> ShiftLeftLogical128BitLane(Vector256<ulong> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_sllv_epi32 (__m256i a, __m256i count)
+        ///   VPSLLVD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> ShiftLeftLogicalVariable(Vector256<int> value, Vector256<uint> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sllv_epi32 (__m256i a, __m256i count)
+        ///   VPSLLVD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> ShiftLeftLogicalVariable(Vector256<uint> value, Vector256<uint> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sllv_epi64 (__m256i a, __m256i count)
+        ///   VPSLLVQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> ShiftLeftLogicalVariable(Vector256<long> value, Vector256<ulong> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sllv_epi64 (__m256i a, __m256i count)
+        ///   VPSLLVQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> ShiftLeftLogicalVariable(Vector256<ulong> value, Vector256<ulong> count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_sllv_epi32 (__m128i a, __m128i count)
+        ///   VPSLLVD xmm, ymm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ShiftLeftLogicalVariable(Vector128<int> value, Vector128<uint> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sllv_epi32 (__m128i a, __m128i count)
+        ///   VPSLLVD xmm, ymm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> ShiftLeftLogicalVariable(Vector128<uint> value, Vector128<uint> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sllv_epi64 (__m128i a, __m128i count)
+        ///   VPSLLVQ xmm, ymm, xmm/m128
+        /// </summary>
+        public static Vector128<long> ShiftLeftLogicalVariable(Vector128<long> value, Vector128<ulong> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sllv_epi64 (__m128i a, __m128i count)
+        ///   VPSLLVQ xmm, ymm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> ShiftLeftLogicalVariable(Vector128<ulong> value, Vector128<ulong> count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// _mm256_sra_epi16 (__m256i a, __m128i count)
+        ///   VPSRAW ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<short> ShiftRightArithmetic(Vector256<short> value, Vector128<short> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// _mm256_sra_epi32 (__m256i a, __m128i count)
+        ///   VPSRAD ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<int> ShiftRightArithmetic(Vector256<int> value, Vector128<int> count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_srai_epi16 (__m256i a, int imm8)
+        ///   VPSRAW ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<short> ShiftRightArithmetic(Vector256<short> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_srai_epi32 (__m256i a, int imm8)
+        ///   VPSRAD ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<int> ShiftRightArithmetic(Vector256<int> value, byte count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_srav_epi32 (__m256i a, __m256i count)
+        ///   VPSRAVD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> ShiftRightArithmeticVariable(Vector256<int> value, Vector256<uint> count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_srav_epi32 (__m128i a, __m128i count)
+        ///   VPSRAVD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ShiftRightArithmeticVariable(Vector128<int> value, Vector128<uint> count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_srl_epi16 (__m256i a, __m128i count)
+        ///   VPSRLW ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<short> ShiftRightLogical(Vector256<short> value, Vector128<short> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_srl_epi16 (__m256i a, __m128i count)
+        ///   VPSRLW ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ushort> ShiftRightLogical(Vector256<ushort> value, Vector128<ushort> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_srl_epi32 (__m256i a, __m128i count)
+        ///   VPSRLD ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<int> ShiftRightLogical(Vector256<int> value, Vector128<int> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_srl_epi32 (__m256i a, __m128i count)
+        ///   VPSRLD ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<uint> ShiftRightLogical(Vector256<uint> value, Vector128<uint> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_srl_epi64 (__m256i a, __m128i count)
+        ///   VPSRLQ ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<long> ShiftRightLogical(Vector256<long> value, Vector128<long> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_srl_epi64 (__m256i a, __m128i count)
+        ///   VPSRLQ ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ulong> ShiftRightLogical(Vector256<ulong> value, Vector128<ulong> count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_srli_epi16 (__m256i a, int imm8)
+        ///   VPSRLW ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<short> ShiftRightLogical(Vector256<short> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_srli_epi16 (__m256i a, int imm8)
+        ///   VPSRLW ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ushort> ShiftRightLogical(Vector256<ushort> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_srli_epi32 (__m256i a, int imm8)
+        ///   VPSRLD ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<int> ShiftRightLogical(Vector256<int> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_srli_epi32 (__m256i a, int imm8)
+        ///   VPSRLD ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<uint> ShiftRightLogical(Vector256<uint> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_srli_epi64 (__m256i a, int imm8)
+        ///   VPSRLQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<long> ShiftRightLogical(Vector256<long> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_srli_epi64 (__m256i a, int imm8)
+        ///   VPSRLQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ulong> ShiftRightLogical(Vector256<ulong> value, byte count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<sbyte> ShiftRightLogical128BitLane(Vector256<sbyte> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<byte> ShiftRightLogical128BitLane(Vector256<byte> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<short> ShiftRightLogical128BitLane(Vector256<short> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ushort> ShiftRightLogical128BitLane(Vector256<ushort> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<int> ShiftRightLogical128BitLane(Vector256<int> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<uint> ShiftRightLogical128BitLane(Vector256<uint> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<long> ShiftRightLogical128BitLane(Vector256<long> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ulong> ShiftRightLogical128BitLane(Vector256<ulong> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_srlv_epi32 (__m256i a, __m256i count)
+        ///   VPSRLVD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> ShiftRightLogicalVariable(Vector256<int> value, Vector256<uint> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_srlv_epi32 (__m256i a, __m256i count)
+        ///   VPSRLVD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> ShiftRightLogicalVariable(Vector256<uint> value, Vector256<uint> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_srlv_epi64 (__m256i a, __m256i count)
+        ///   VPSRLVQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> ShiftRightLogicalVariable(Vector256<long> value, Vector256<ulong> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_srlv_epi64 (__m256i a, __m256i count)
+        ///   VPSRLVQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> ShiftRightLogicalVariable(Vector256<ulong> value, Vector256<ulong> count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_srlv_epi32 (__m128i a, __m128i count)
+        ///   VPSRLVD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ShiftRightLogicalVariable(Vector128<int> value, Vector128<uint> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_srlv_epi32 (__m128i a, __m128i count)
+        ///   VPSRLVD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> ShiftRightLogicalVariable(Vector128<uint> value, Vector128<uint> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_srlv_epi64 (__m128i a, __m128i count)
+        ///   VPSRLVQ xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> ShiftRightLogicalVariable(Vector128<long> value, Vector128<ulong> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_srlv_epi64 (__m128i a, __m128i count)
+        ///   VPSRLVQ xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> ShiftRightLogicalVariable(Vector128<ulong> value, Vector128<ulong> count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_shuffle_epi8 (__m256i a, __m256i b)
+        ///   VPSHUFB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Shuffle(Vector256<sbyte> value, Vector256<sbyte> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_shuffle_epi8 (__m256i a, __m256i b)
+        ///   VPSHUFB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Shuffle(Vector256<byte> value, Vector256<byte> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_shuffle_epi32 (__m256i a, const int imm8)
+        ///   VPSHUFD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Shuffle(Vector256<int> value, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_shuffle_epi32 (__m256i a, const int imm8)
+        ///   VPSHUFD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Shuffle(Vector256<uint> value, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_shufflehi_epi16 (__m256i a, const int imm8)
+        ///   VPSHUFHW ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<short> ShuffleHigh(Vector256<short> value, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_shufflehi_epi16 (__m256i a, const int imm8)
+        ///   VPSHUFHW ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<ushort> ShuffleHigh(Vector256<ushort> value, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_shufflelo_epi16 (__m256i a, const int imm8)
+        ///   VPSHUFLW ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<short> ShuffleLow(Vector256<short> value, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_shufflelo_epi16 (__m256i a, const int imm8)
+        ///   VPSHUFLW ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<ushort> ShuffleLow(Vector256<ushort> value, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_sign_epi8 (__m256i a, __m256i b)
+        ///   VPSIGNB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Sign(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sign_epi16 (__m256i a, __m256i b)
+        ///   VPSIGNW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> Sign(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sign_epi32 (__m256i a, __m256i b)
+        ///   VPSIGND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Sign(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_sub_epi8 (__m256i a, __m256i b)
+        ///   VPSUBB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Subtract(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sub_epi8 (__m256i a, __m256i b)
+        ///   VPSUBB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Subtract(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sub_epi16 (__m256i a, __m256i b)
+        ///   VPSUBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> Subtract(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sub_epi16 (__m256i a, __m256i b)
+        ///   VPSUBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Subtract(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sub_epi32 (__m256i a, __m256i b)
+        ///   VPSUBD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Subtract(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sub_epi32 (__m256i a, __m256i b)
+        ///   VPSUBD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Subtract(Vector256<uint> left, Vector256<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sub_epi64 (__m256i a, __m256i b)
+        ///   VPSUBQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> Subtract(Vector256<long> left, Vector256<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_sub_epi64 (__m256i a, __m256i b)
+        ///   VPSUBQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> Subtract(Vector256<ulong> left, Vector256<ulong> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_subs_epi8 (__m256i a, __m256i b)
+        ///   VPSUBSB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> SubtractSaturate(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_subs_epi16 (__m256i a, __m256i b)
+        ///   VPSUBSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> SubtractSaturate(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_subs_epu8 (__m256i a, __m256i b)
+        ///   VPSUBUSB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> SubtractSaturate(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_subs_epu16 (__m256i a, __m256i b)
+        ///   VPSUBUSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> SubtractSaturate(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_sad_epu8 (__m256i a, __m256i b)
+        ///   VPSADBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> SumAbsoluteDifferences(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi8 (__m256i a, __m256i b)
+        ///   VPUNPCKHBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> UnpackHigh(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi8 (__m256i a, __m256i b)
+        ///   VPUNPCKHBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> UnpackHigh(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi16 (__m256i a, __m256i b)
+        ///   VPUNPCKHWD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> UnpackHigh(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi16 (__m256i a, __m256i b)
+        ///   VPUNPCKHWD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> UnpackHigh(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi32 (__m256i a, __m256i b)
+        ///   VPUNPCKHDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> UnpackHigh(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi32 (__m256i a, __m256i b)
+        ///   VPUNPCKHDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> UnpackHigh(Vector256<uint> left, Vector256<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi64 (__m256i a, __m256i b)
+        ///   VPUNPCKHQDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> UnpackHigh(Vector256<long> left, Vector256<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi64 (__m256i a, __m256i b)
+        ///   VPUNPCKHQDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> UnpackHigh(Vector256<ulong> left, Vector256<ulong> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi8 (__m256i a, __m256i b)
+        ///   VPUNPCKLBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> UnpackLow(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi8 (__m256i a, __m256i b)
+        ///   VPUNPCKLBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> UnpackLow(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi16 (__m256i a, __m256i b)
+        ///   VPUNPCKLWD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> UnpackLow(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi16 (__m256i a, __m256i b)
+        ///   VPUNPCKLWD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> UnpackLow(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi32 (__m256i a, __m256i b)
+        ///   VPUNPCKLDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> UnpackLow(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi32 (__m256i a, __m256i b)
+        ///   VPUNPCKLDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> UnpackLow(Vector256<uint> left, Vector256<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi64 (__m256i a, __m256i b)
+        ///   VPUNPCKLQDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> UnpackLow(Vector256<long> left, Vector256<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi64 (__m256i a, __m256i b)
+        ///   VPUNPCKLQDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> UnpackLow(Vector256<ulong> left, Vector256<ulong> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Xor(Vector256<sbyte> left, Vector256<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Xor(Vector256<byte> left, Vector256<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> Xor(Vector256<short> left, Vector256<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Xor(Vector256<ushort> left, Vector256<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Xor(Vector256<int> left, Vector256<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Xor(Vector256<uint> left, Vector256<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> Xor(Vector256<long> left, Vector256<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> Xor(Vector256<ulong> left, Vector256<ulong> right) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Avx2.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Avx2.cs
new file mode 100644
index 0000000000..0231eca2bf
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Avx2.cs
@@ -0,0 +1,1871 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel AVX2 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Avx2
+    {
+        public static bool IsSupported { get => IsSupported; }
+
+        /// <summary>
+        /// __m256i _mm256_abs_epi8 (__m256i a)
+        ///   VPABSB ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Abs(Vector256<sbyte> value) => Abs(value);
+        /// <summary>
+        /// __m256i _mm256_abs_epi16 (__m256i a)
+        ///   VPABSW ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Abs(Vector256<short> value) => Abs(value);
+        /// <summary>
+        /// __m256i _mm256_abs_epi32 (__m256i a)
+        ///   VPABSD ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Abs(Vector256<int> value) => Abs(value);
+
+        /// <summary>
+        /// __m256i _mm256_add_epi8 (__m256i a, __m256i b)
+        ///   VPADDB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Add(Vector256<sbyte> left, Vector256<sbyte> right) => Add(left, right);
+        /// <summary>
+        /// __m256i _mm256_add_epi8 (__m256i a, __m256i b)
+        ///   VPADDB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Add(Vector256<byte> left, Vector256<byte> right) => Add(left, right);
+        /// <summary>
+        /// __m256i _mm256_add_epi16 (__m256i a, __m256i b)
+        ///   VPADDW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> Add(Vector256<short> left, Vector256<short> right) => Add(left, right);
+        /// <summary>
+        /// __m256i _mm256_add_epi16 (__m256i a, __m256i b)
+        ///   VPADDW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Add(Vector256<ushort> left, Vector256<ushort> right) => Add(left, right);
+        /// <summary>
+        /// __m256i _mm256_add_epi32 (__m256i a, __m256i b)
+        ///   VPADDD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Add(Vector256<int> left, Vector256<int> right) => Add(left, right);
+        /// <summary>
+        /// __m256i _mm256_add_epi32 (__m256i a, __m256i b)
+        ///   VPADDD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Add(Vector256<uint> left, Vector256<uint> right) => Add(left, right);
+        /// <summary>
+        /// __m256i _mm256_add_epi64 (__m256i a, __m256i b)
+        ///   VPADDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> Add(Vector256<long> left, Vector256<long> right) => Add(left, right);
+        /// <summary>
+        /// __m256i _mm256_add_epi64 (__m256i a, __m256i b)
+        ///   VPADDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> Add(Vector256<ulong> left, Vector256<ulong> right) => Add(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_adds_epi8 (__m256i a, __m256i b)
+        ///   VPADDSB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> AddSaturate(Vector256<sbyte> left, Vector256<sbyte> right) => AddSaturate(left, right);
+        /// <summary>
+        /// __m256i _mm256_adds_epu8 (__m256i a, __m256i b)
+        ///   VPADDUSB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> AddSaturate(Vector256<byte> left, Vector256<byte> right) => AddSaturate(left, right);
+        /// <summary>
+        /// __m256i _mm256_adds_epi16 (__m256i a, __m256i b)
+        ///   VPADDSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> AddSaturate(Vector256<short> left, Vector256<short> right) => AddSaturate(left, right);
+        /// <summary>
+        /// __m256i _mm256_adds_epu16 (__m256i a, __m256i b)
+        ///   VPADDUSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> AddSaturate(Vector256<ushort> left, Vector256<ushort> right) => AddSaturate(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_alignr_epi8 (__m256i a, __m256i b, const int count)
+        ///   VPALIGNR ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<sbyte> AlignRight(Vector256<sbyte> left, Vector256<sbyte> right, byte mask) => AlignRight(left, right, mask);
+
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> And(Vector256<sbyte> left, Vector256<sbyte> right) => And(left, right);
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> And(Vector256<byte> left, Vector256<byte> right) => And(left, right);
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> And(Vector256<short> left, Vector256<short> right) => And(left, right);
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> And(Vector256<ushort> left, Vector256<ushort> right) => And(left, right);
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> And(Vector256<int> left, Vector256<int> right) => And(left, right);
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> And(Vector256<uint> left, Vector256<uint> right) => And(left, right);
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> And(Vector256<long> left, Vector256<long> right) => And(left, right);
+        /// <summary>
+        /// __m256i _mm256_and_si256 (__m256i a, __m256i b)
+        ///   VPAND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> And(Vector256<ulong> left, Vector256<ulong> right) => And(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> AndNot(Vector256<sbyte> left, Vector256<sbyte> right) => AndNot(left, right);
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> AndNot(Vector256<byte> left, Vector256<byte> right) => AndNot(left, right);
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> AndNot(Vector256<short> left, Vector256<short> right) => AndNot(left, right);
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> AndNot(Vector256<ushort> left, Vector256<ushort> right) => AndNot(left, right);
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> AndNot(Vector256<int> left, Vector256<int> right) => AndNot(left, right);
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> AndNot(Vector256<uint> left, Vector256<uint> right) => AndNot(left, right);
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> AndNot(Vector256<long> left, Vector256<long> right) => AndNot(left, right);
+        /// <summary>
+        /// __m256i _mm256_andnot_si256 (__m256i a, __m256i b)
+        ///   VPANDN ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> AndNot(Vector256<ulong> left, Vector256<ulong> right) => AndNot(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_avg_epu8 (__m256i a, __m256i b)
+        ///   VPAVGB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Average(Vector256<byte> left, Vector256<byte> right) => Average(left, right);
+        /// <summary>
+        /// __m256i _mm256_avg_epu16 (__m256i a, __m256i b)
+        ///   VPAVGW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Average(Vector256<ushort> left, Vector256<ushort> right) => Average(left, right);
+
+        /// <summary>
+        /// __m128i _mm_blend_epi32 (__m128i a, __m128i b, const int imm8)
+        ///   VPBLENDD xmm, xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<int> Blend(Vector128<int> left, Vector128<int> right, byte control) => Blend(left, right, control);
+        /// <summary>
+        /// __m128i _mm_blend_epi32 (__m128i a, __m128i b, const int imm8)
+        ///   VPBLENDD xmm, xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<uint> Blend(Vector128<uint> left, Vector128<uint> right, byte control) => Blend(left, right, control);
+        /// <summary>
+        /// __m256i _mm256_blend_epi16 (__m256i a, __m256i b, const int imm8)
+        ///   VPBLENDW ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<short> Blend(Vector256<short> left, Vector256<short> right, byte control) => Blend(left, right, control);
+        /// <summary>
+        /// __m256i _mm256_blend_epi16 (__m256i a, __m256i b, const int imm8)
+        ///   VPBLENDW ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<ushort> Blend(Vector256<ushort> left, Vector256<ushort> right, byte control) => Blend(left, right, control);
+        /// <summary>
+        /// __m256i _mm256_blend_epi32 (__m256i a, __m256i b, const int imm8)
+        ///   VPBLENDD ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<int> Blend(Vector256<int> left, Vector256<int> right, byte control) => Blend(left, right, control);
+        /// <summary>
+        /// __m256i _mm256_blend_epi32 (__m256i a, __m256i b, const int imm8)
+        ///   VPBLENDD ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<uint> Blend(Vector256<uint> left, Vector256<uint> right, byte control) => Blend(left, right, control);
+
+        /// <summary>
+        /// __m256i _mm256_blendv_epi8 (__m256i a, __m256i b, __m256i mask)
+        ///   PBLENDVB ymm, ymm, ymm/m256, ymm
+        /// </summary>
+        public static Vector256<sbyte> BlendVariable(Vector256<sbyte> left, Vector256<sbyte> right, Vector256<sbyte> mask) => BlendVariable(left, right, mask);
+        /// <summary>
+        /// __m256i _mm256_blendv_epi8 (__m256i a, __m256i b, __m256i mask)
+        ///   PBLENDVB ymm, ymm, ymm/m256, ymm
+        /// </summary>
+        public static Vector256<byte> BlendVariable(Vector256<byte> left, Vector256<byte> right, Vector256<byte> mask) => BlendVariable(left, right, mask);
+
+        /// <summary>
+        /// __m128i _mm_broadcastb_epi8 (__m128i a)
+        ///   VPBROADCASTB xmm, xmm
+        /// __m128i _mm_broadcastw_epi16 (__m128i a)
+        ///   VPBROADCASTW xmm, xmm
+        /// __m128i _mm_broadcastd_epi32 (__m128i a)
+        ///   VPBROADCASTD xmm, xmm
+        /// __m128i _mm_broadcastq_epi64 (__m128i a)
+        ///   VPBROADCASTQ xmm, xmm
+        /// __m128 _mm_broadcastss_ps (__m128 a)
+        ///   VBROADCASTSS xmm, xmm
+        /// __m128d _mm_broadcastsd_pd (__m128d a)
+        ///   VMOVDDUP xmm, xmm
+        /// </summary>
+        public static Vector128<T> BroadcastScalarToVector128<T>(Vector128<T> value) where T : struct
+        {
+            return BroadcastScalarToVector128<T>(value);
+        }
+
+        /// <summary>
+        /// __m256i _mm256_broadcastb_epi8 (__m128i a)
+        ///   VPBROADCASTB ymm, xmm
+        /// __m256i _mm256_broadcastw_epi16 (__m128i a)
+        ///   VPBROADCASTW ymm, xmm
+        /// __m256i _mm256_broadcastd_epi32 (__m128i a)
+        ///   VPBROADCASTD ymm, xmm
+        /// __m256i _mm256_broadcastq_epi64 (__m128i a)
+        ///   VPBROADCASTQ ymm, xmm
+        /// __m256 _mm256_broadcastss_ps (__m128 a)
+        ///   VBROADCASTSS ymm, xmm
+        /// __m256d _mm256_broadcastsd_pd (__m128d a)
+        ///   VBROADCASTSD ymm, xmm
+        /// </summary>
+        public static Vector256<T> BroadcastScalarToVector256<T>(Vector128<T> value) where T : struct
+        {
+            return BroadcastScalarToVector256<T>(value);
+        }
+
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m8
+        /// </summary>
+        public static unsafe Vector256<sbyte> BroadcastVector128ToVector256(sbyte* address) => BroadcastVector128ToVector256(address);
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m8
+        /// </summary>
+        public static unsafe Vector256<byte> BroadcastVector128ToVector256(byte* address) => BroadcastVector128ToVector256(address);
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m16
+        /// </summary>
+        public static unsafe Vector256<short> BroadcastVector128ToVector256(short* address) => BroadcastVector128ToVector256(address);
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m16
+        /// </summary>
+        public static unsafe Vector256<ushort> BroadcastVector128ToVector256(ushort* address) => BroadcastVector128ToVector256(address);
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m32
+        /// </summary>
+        public static unsafe Vector256<int> BroadcastVector128ToVector256(int* address) => BroadcastVector128ToVector256(address);
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m32
+        /// </summary>
+        public static unsafe Vector256<uint> BroadcastVector128ToVector256(uint* address) => BroadcastVector128ToVector256(address);
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m64
+        /// </summary>
+        public static unsafe Vector256<long> BroadcastVector128ToVector256(long* address) => BroadcastVector128ToVector256(address);
+        /// <summary>
+        /// __m256i _mm256_broadcastsi128_si256 (__m128i a)
+        ///   VBROADCASTI128 xmm, m64
+        /// </summary>
+        public static unsafe Vector256<ulong> BroadcastVector128ToVector256(ulong* address) => BroadcastVector128ToVector256(address);
+
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi8 (__m256i a, __m256i b)
+        ///   VPCMPEQB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> CompareEqual(Vector256<sbyte> left, Vector256<sbyte> right) => CompareEqual(left, right);
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi8 (__m256i a, __m256i b)
+        ///   VPCMPEQB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> CompareEqual(Vector256<byte> left, Vector256<byte> right) => CompareEqual(left, right);
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi16 (__m256i a, __m256i b)
+        ///   VPCMPEQW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> CompareEqual(Vector256<short> left, Vector256<short> right) => CompareEqual(left, right);
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi16 (__m256i a, __m256i b)
+        ///   VPCMPEQW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> CompareEqual(Vector256<ushort> left, Vector256<ushort> right) => CompareEqual(left, right);
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi32 (__m256i a, __m256i b)
+        ///   VPCMPEQD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> CompareEqual(Vector256<int> left, Vector256<int> right) => CompareEqual(left, right);
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi32 (__m256i a, __m256i b)
+        ///   VPCMPEQD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> CompareEqual(Vector256<uint> left, Vector256<uint> right) => CompareEqual(left, right);
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi64 (__m256i a, __m256i b)
+        ///   VPCMPEQQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> CompareEqual(Vector256<long> left, Vector256<long> right) => CompareEqual(left, right);
+        /// <summary>
+        /// __m256i _mm256_cmpeq_epi64 (__m256i a, __m256i b)
+        ///   VPCMPEQQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> CompareEqual(Vector256<ulong> left, Vector256<ulong> right) => CompareEqual(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_cmpgt_epi8 (__m256i a, __m256i b)
+        ///   VPCMPGTB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> CompareGreaterThan(Vector256<sbyte> left, Vector256<sbyte> right) => CompareGreaterThan(left, right);
+        /// <summary>
+        /// __m256i _mm256_cmpgt_epi16 (__m256i a, __m256i b)
+        ///   VPCMPGTW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> CompareGreaterThan(Vector256<short> left, Vector256<short> right) => CompareGreaterThan(left, right);
+        /// <summary>
+        /// __m256i _mm256_cmpgt_epi32 (__m256i a, __m256i b)
+        ///   VPCMPGTD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> CompareGreaterThan(Vector256<int> left, Vector256<int> right) => CompareGreaterThan(left, right);
+        /// <summary>
+        /// __m256i _mm256_cmpgt_epi64 (__m256i a, __m256i b)
+        ///   VPCMPGTQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> CompareGreaterThan(Vector256<long> left, Vector256<long> right) => CompareGreaterThan(left, right);
+
+        /// <summary>
+        /// double _mm256_cvtsd_f64 (__m256d a)
+        ///   HELPER: MOVSD
+        /// </summary>
+        public static double ConvertToDouble(Vector256<double> value) => ConvertToDouble(value);
+        /// <summary>
+        /// int _mm256_cvtsi256_si32 (__m256i a)
+        ///   MOVD reg/m32, xmm
+        /// </summary>
+        public static int ConvertToInt32(Vector256<int> value) => ConvertToInt32(value);
+        /// <summary>
+        /// int _mm256_cvtsi256_si32 (__m256i a)
+        ///   MOVD reg/m32, xmm
+        /// </summary>
+        public static uint ConvertToUInt32(Vector256<uint> value) => ConvertToUInt32(value);
+
+        /// <summary>
+        /// __m256i _mm256_cvtepi8_epi16 (__m128i a)
+        ///   VPMOVSXBW ymm, xmm/m128
+        /// </summary>
+        public static Vector256<short> ConvertToVector256Int16(Vector128<sbyte> value) => ConvertToVector256Int16(value);
+        /// <summary>
+        /// __m256i _mm256_cvtepu8_epi16 (__m128i a)
+        ///   VPMOVZXBW ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ushort> ConvertToVector256UInt16(Vector128<byte> value) => ConvertToVector256UInt16(value);
+        /// <summary>
+        /// __m256i _mm256_cvtepi8_epi32 (__m128i a)
+        ///   VPMOVSXBD ymm, xmm/m128
+        /// </summary>
+        public static Vector256<int> ConvertToVector256Int32(Vector128<sbyte> value) => ConvertToVector256Int32(value);
+        /// <summary>
+        /// __m256i _mm256_cvtepi16_epi32 (__m128i a)
+        ///   VPMOVSXWD ymm, xmm/m128
+        /// </summary>
+        public static Vector256<int> ConvertToVector256Int32(Vector128<short> value) => ConvertToVector256Int32(value);
+        /// <summary>
+        /// __m256i _mm256_cvtepu8_epi32 (__m128i a)
+        ///   VPMOVZXBD ymm, xmm/m128
+        /// </summary>
+        public static Vector256<uint> ConvertToVector256UInt32(Vector128<byte> value) => ConvertToVector256UInt32(value);
+        /// <summary>
+        /// __m256i _mm256_cvtepu16_epi32 (__m128i a)
+        ///   VPMOVZXWD ymm, xmm/m128
+        /// </summary>
+        public static Vector256<uint> ConvertToVector256UInt32(Vector128<ushort> value) => ConvertToVector256UInt32(value);
+        /// <summary>
+        /// __m256i _mm256_cvtepi8_epi64 (__m128i a)
+        ///   VPMOVSXBQ ymm, xmm/m128
+        /// </summary>
+        public static Vector256<long> ConvertToVector256Int64(Vector128<sbyte> value) => ConvertToVector256Int64(value);
+        /// <summary>
+        /// __m256i _mm256_cvtepi16_epi64 (__m128i a)
+        ///   VPMOVSXWQ ymm, xmm/m128
+        /// </summary>
+        public static Vector256<long> ConvertToVector256Int64(Vector128<short> value) => ConvertToVector256Int64(value);
+        /// <summary>
+        /// __m256i _mm256_cvtepi32_epi64 (__m128i a)
+        ///   VPMOVSXDQ ymm, xmm/m128
+        /// </summary>
+        public static Vector256<long> ConvertToVector256Int64(Vector128<int> value) => ConvertToVector256Int64(value);
+        /// <summary>
+        /// __m256i _mm256_cvtepu8_epi64 (__m128i a)
+        ///   VPMOVZXBQ ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ulong> ConvertToVector256UInt64(Vector128<byte> value) => ConvertToVector256UInt64(value);
+        /// <summary>
+        /// __m256i _mm256_cvtepu16_epi64 (__m128i a)
+        ///   VPMOVZXWQ ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ulong> ConvertToVector256UInt64(Vector128<ushort> value) => ConvertToVector256UInt64(value);
+        /// <summary>
+        /// __m256i _mm256_cvtepu32_epi64 (__m128i a)
+        ///   VPMOVZXDQ ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ulong> ConvertToVector256UInt64(Vector128<uint> value) => ConvertToVector256UInt64(value);
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<sbyte> ExtractVector128(Vector256<sbyte> value, byte index) => ExtractVector128(value, index);
+        // <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(sbyte* address, Vector256<sbyte> value, byte index) => ExtractVector128(address, value, index);
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<byte> ExtractVector128(Vector256<byte> value, byte index) => ExtractVector128(value, index);
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(byte* address, Vector256<byte> value, byte index) => ExtractVector128(address, value, index);
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<short> ExtractVector128(Vector256<short> value, byte index) => ExtractVector128(value, index);
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(short* address, Vector256<short> value, byte index) => ExtractVector128(address, value, index);
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<ushort> ExtractVector128(Vector256<ushort> value, byte index) => ExtractVector128(value, index);
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(ushort* address, Vector256<ushort> value, byte index) => ExtractVector128(address, value, index);
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<int> ExtractVector128(Vector256<int> value, byte index) => ExtractVector128(value, index);
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(int* address, Vector256<int> value, byte index) => ExtractVector128(address, value, index);
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<uint> ExtractVector128(Vector256<uint> value, byte index) => ExtractVector128(value, index);
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(uint* address, Vector256<uint> value, byte index) => ExtractVector128(address, value, index);
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<long> ExtractVector128(Vector256<long> value, byte index) => ExtractVector128(value, index);
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(long* address, Vector256<long> value, byte index) => ExtractVector128(address, value, index);
+
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 xmm, ymm, imm8
+        /// </summary>
+        public static Vector128<ulong> ExtractVector128(Vector256<ulong> value, byte index) => ExtractVector128(value, index);
+        /// <summary>
+        /// __m128i _mm256_extracti128_si256 (__m256i a, const int imm8)
+        ///   VEXTRACTI128 m128, ymm, imm8
+        /// </summary>
+        public static unsafe void ExtractVector128(ulong* address, Vector256<ulong> value, byte index) => ExtractVector128(address, value, index);
+
+        /// <summary>
+        /// __m128i _mm_i32gather_epi32 (int const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERDD xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<int> GatherVector128(int* baseAddress, Vector128<int> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m128i _mm_i32gather_epi32 (int const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERDD xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<uint> GatherVector128(uint* baseAddress, Vector128<int> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m128i _mm_i32gather_epi64 (__int64 const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERDQ xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<long> GatherVector128(long* baseAddress, Vector128<int> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m128i _mm_i32gather_epi64 (__int64 const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERDQ xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<ulong> GatherVector128(ulong* baseAddress, Vector128<int> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m128 _mm_i32gather_ps (float const* base_addr, __m128i vindex, const int scale)
+        ///   VGATHERDPS xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<float> GatherVector128(float* baseAddress, Vector128<int> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m128d _mm_i32gather_pd (double const* base_addr, __m128i vindex, const int scale)
+        ///   VGATHERDPD xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<double> GatherVector128(double* baseAddress, Vector128<int> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m128i _mm_i64gather_epi32 (int const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERQD xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<int> GatherVector128(int* baseAddress, Vector128<long> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m128i _mm_i64gather_epi32 (int const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERQD xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<uint> GatherVector128(uint* baseAddress, Vector128<long> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m128i _mm_i64gather_epi64 (__int64 const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERQQ xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<long> GatherVector128(long* baseAddress, Vector128<long> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m128i _mm_i64gather_epi64 (__int64 const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERQQ xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<ulong> GatherVector128(ulong* baseAddress, Vector128<long> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m128 _mm_i64gather_ps (float const* base_addr, __m128i vindex, const int scale)
+        ///   VGATHERQPS xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<float> GatherVector128(float* baseAddress, Vector128<long> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m128d _mm_i64gather_pd (double const* base_addr, __m128i vindex, const int scale)
+        ///   VGATHERQPD xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<double> GatherVector128(double* baseAddress, Vector128<long> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m256i _mm256_i32gather_epi32 (int const* base_addr, __m256i vindex, const int scale)
+        ///   VPGATHERDD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<int> GatherVector256(int* baseAddress, Vector256<int> index, byte scale) => GatherVector256(baseAddress, index, scale);
+        /// <summary>
+        /// __m256i _mm256_i32gather_epi32 (int const* base_addr, __m256i vindex, const int scale)
+        ///   VPGATHERDD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<uint> GatherVector256(uint* baseAddress, Vector256<int> index, byte scale) => GatherVector256(baseAddress, index, scale);
+        /// <summary>
+        /// __m256i _mm256_i32gather_epi64 (__int64 const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERDQ ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<long> GatherVector256(long* baseAddress, Vector128<int> index, byte scale) => GatherVector256(baseAddress, index, scale);
+        /// <summary>
+        /// __m256i _mm256_i32gather_epi64 (__int64 const* base_addr, __m128i vindex, const int scale)
+        ///   VPGATHERDQ ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<ulong> GatherVector256(ulong* baseAddress, Vector128<int> index, byte scale) => GatherVector256(baseAddress, index, scale);
+        /// <summary>
+        /// __m256 _mm256_i32gather_ps (float const* base_addr, __m256i vindex, const int scale)
+        ///   VGATHERDPS ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<float> GatherVector256(float* baseAddress, Vector256<int> index, byte scale) => GatherVector256(baseAddress, index, scale);
+        /// <summary>
+        /// __m256d _mm256_i32gather_pd (double const* base_addr, __m128i vindex, const int scale)
+        ///   VGATHERDPD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<double> GatherVector256(double* baseAddress, Vector128<int> index, byte scale) => GatherVector256(baseAddress, index, scale);
+        /// <summary>
+        /// __m128i _mm256_i64gather_epi32 (int const* base_addr, __m256i vindex, const int scale)
+        ///   VPGATHERQD ymm, vm64y, ymm
+        /// </summary>
+        public static unsafe Vector128<int> GatherVector128(int* baseAddress, Vector256<long> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m128i _mm256_i64gather_epi32 (int const* base_addr, __m256i vindex, const int scale)
+        ///   VPGATHERQD ymm, vm64y, ymm
+        /// </summary>
+        public static unsafe Vector128<uint> GatherVector128(uint* baseAddress, Vector256<long> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m256i _mm256_i64gather_epi64 (__int64 const* base_addr, __m256i vindex, const int scale)
+        ///   VPGATHERQQ ymm, vm64y, ymm
+        /// </summary>
+        public static unsafe Vector256<long> GatherVector256(long* baseAddress, Vector256<long> index, byte scale) => GatherVector256(baseAddress, index, scale);
+        /// <summary>
+        /// __m256i _mm256_i64gather_epi64 (__int64 const* base_addr, __m256i vindex, const int scale)
+        ///   VPGATHERQQ ymm, vm64y, ymm
+        /// </summary>
+        public static unsafe Vector256<ulong> GatherVector256(ulong* baseAddress, Vector256<long> index, byte scale) => GatherVector256(baseAddress, index, scale);
+        /// <summary>
+        /// __m128 _mm256_i64gather_ps (float const* base_addr, __m256i vindex, const int scale)
+        ///   VGATHERQPS ymm, vm64y, ymm
+        /// </summary>
+        public static unsafe Vector128<float> GatherVector128(float* baseAddress, Vector256<long> index, byte scale) => GatherVector128(baseAddress, index, scale);
+        /// <summary>
+        /// __m256d _mm256_i64gather_pd (double const* base_addr, __m256i vindex, const int scale)
+        ///   VGATHERQPD ymm, vm64y, ymm
+        /// </summary>
+        public static unsafe Vector256<double> GatherVector256(double* baseAddress, Vector256<long> index, byte scale) => GatherVector256(baseAddress, index, scale);
+
+        /// <summary>
+        /// __m128i _mm_mask_i32gather_epi32 (__m128i src, int const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERDD xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<int> GatherMaskVector128(Vector128<int> source, int* baseAddress, Vector128<int> index, Vector128<int> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m128i _mm_mask_i32gather_epi32 (__m128i src, int const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERDD xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<uint> GatherMaskVector128(Vector128<uint> source, uint* baseAddress, Vector128<int> index, Vector128<uint> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m128i _mm_mask_i32gather_epi64 (__m128i src, __int64 const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERDQ xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<long> GatherMaskVector128(Vector128<long> source, long* baseAddress, Vector128<int> index, Vector128<long> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m128i _mm_mask_i32gather_epi64 (__m128i src, __int64 const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERDQ xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<ulong> GatherMaskVector128(Vector128<ulong> source, ulong* baseAddress, Vector128<int> index, Vector128<ulong> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m128 _mm_mask_i32gather_ps (__m128 src, float const* base_addr, __m128i vindex, __m128 mask, const int scale)
+        ///   VGATHERDPS xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<float> GatherMaskVector128(Vector128<float> source, float* baseAddress, Vector128<int> index, Vector128<float> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m128d _mm_mask_i32gather_pd (__m128d src, double const* base_addr, __m128i vindex, __m128d mask, const int scale)
+        ///   VGATHERDPD xmm, vm32x, xmm
+        /// </summary>
+        public static unsafe Vector128<double> GatherMaskVector128(Vector128<double> source, double* baseAddress, Vector128<int> index, Vector128<double> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m128i _mm_mask_i64gather_epi32 (__m128i src, int const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERQD xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<int> GatherMaskVector128(Vector128<int> source, int* baseAddress, Vector128<long> index, Vector128<int> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m128i _mm_mask_i64gather_epi32 (__m128i src, int const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERQD xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<uint> GatherMaskVector128(Vector128<uint> source, uint* baseAddress, Vector128<long> index, Vector128<uint> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m128i _mm_mask_i64gather_epi64 (__m128i src, __int64 const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERQQ xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<long> GatherMaskVector128(Vector128<long> source, long* baseAddress, Vector128<long> index, Vector128<long> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m128i _mm_mask_i64gather_epi64 (__m128i src, __int64 const* base_addr, __m128i vindex, __m128i mask, const int scale)
+        ///   VPGATHERQQ xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<ulong> GatherMaskVector128(Vector128<ulong> source, ulong* baseAddress, Vector128<long> index, Vector128<ulong> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m128 _mm_mask_i64gather_ps (__m128 src, float const* base_addr, __m128i vindex, __m128 mask, const int scale)
+        ///   VPGATHERQPS xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<float> GatherMaskVector128(Vector128<float> source, float* baseAddress, Vector128<long> index, Vector128<float> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m128d _mm_mask_i64gather_pd (__m128d src, double const* base_addr, __m128i vindex, __m128d mask, const int scale)
+        ///   VPGATHERQPD xmm, vm64x, xmm
+        /// </summary>
+        public static unsafe Vector128<double> GatherMaskVector128(Vector128<double> source, double* baseAddress, Vector128<long> index, Vector128<double> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m256i _mm256_mask_i32gather_epi32 (__m256i src, int const* base_addr, __m256i vindex, __m256i mask, const int scale)
+        ///   VPGATHERDD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<int> GatherMaskVector256(Vector256<int> source, int* baseAddress, Vector256<int> index, Vector256<int> mask, byte scale) => GatherMaskVector256(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m256i _mm256_mask_i32gather_epi32 (__m256i src, int const* base_addr, __m256i vindex, __m256i mask, const int scale)
+        ///   VPGATHERDD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<uint> GatherMaskVector256(Vector256<uint> source, uint* baseAddress, Vector256<int> index, Vector256<uint> mask, byte scale) => GatherMaskVector256(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m256i _mm256_mask_i32gather_epi64 (__m256i src, __int64 const* base_addr, __m128i vindex, __m256i mask, const int scale)
+        ///   VPGATHERDQ ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<long> GatherMaskVector256(Vector256<long> source, long* baseAddress, Vector128<int> index, Vector256<long> mask, byte scale) => GatherMaskVector256(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m256i _mm256_mask_i32gather_epi64 (__m256i src, __int64 const* base_addr, __m128i vindex, __m256i mask, const int scale)
+        ///   VPGATHERDQ ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<ulong> GatherMaskVector256(Vector256<ulong> source, ulong* baseAddress, Vector128<int> index, Vector256<ulong> mask, byte scale) => GatherMaskVector256(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m256 _mm256_mask_i32gather_ps (__m256 src, float const* base_addr, __m256i vindex, __m256 mask, const int scale)
+        ///   VPGATHERDPS ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<float> GatherMaskVector256(Vector256<float> source, float* baseAddress, Vector256<int> index, Vector256<float> mask, byte scale) => GatherMaskVector256(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m256d _mm256_mask_i32gather_pd (__m256d src, double const* base_addr, __m128i vindex, __m256d mask, const int scale)
+        ///   VPGATHERDPD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<double> GatherMaskVector256(Vector256<double> source, double* baseAddress, Vector128<int> index, Vector256<double> mask, byte scale) => GatherMaskVector256(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m128i _mm256_mask_i64gather_epi32 (__m128i src, int const* base_addr, __m256i vindex, __m128i mask, const int scale)
+        ///   VPGATHERQD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector128<int> GatherMaskVector128(Vector128<int> source, int* baseAddress, Vector256<long> index, Vector128<int> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m128i _mm256_mask_i64gather_epi32 (__m128i src, int const* base_addr, __m256i vindex, __m128i mask, const int scale)
+        ///   VPGATHERQD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector128<uint> GatherMaskVector128(Vector128<uint> source, uint* baseAddress, Vector256<long> index, Vector128<uint> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m256i _mm256_mask_i64gather_epi64 (__m256i src, __int64 const* base_addr, __m256i vindex, __m256i mask, const int scale)
+        ///   VPGATHERQQ ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<long> GatherMaskVector256(Vector256<long> source, long* baseAddress, Vector256<long> index, Vector256<long> mask, byte scale) => GatherMaskVector256(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m256i _mm256_mask_i64gather_epi64 (__m256i src, __int64 const* base_addr, __m256i vindex, __m256i mask, const int scale)
+        ///   VPGATHERQQ ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<ulong> GatherMaskVector256(Vector256<ulong> source, ulong* baseAddress, Vector256<long> index, Vector256<ulong> mask, byte scale) => GatherMaskVector256(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m128 _mm256_mask_i64gather_ps (__m128 src, float const* base_addr, __m256i vindex, __m128 mask, const int scale)
+        ///   VPGATHERQPS ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector128<float> GatherMaskVector128(Vector128<float> source, float* baseAddress, Vector256<long> index, Vector128<float> mask, byte scale) => GatherMaskVector128(source, baseAddress, index, mask, scale);
+        /// <summary>
+        /// __m256d _mm256_mask_i64gather_pd (__m256d src, double const* base_addr, __m256i vindex, __m256d mask, const int scale)
+        ///   VPGATHERQPD ymm, vm32y, ymm
+        /// </summary>
+        public static unsafe Vector256<double> GatherMaskVector256(Vector256<double> source, double* baseAddress, Vector256<long> index, Vector256<double> mask, byte scale) => GatherMaskVector256(source, baseAddress, index, mask, scale);
+
+        /// <summary>
+        /// __m256i _mm256_hadd_epi16 (__m256i a, __m256i b)
+        ///   VPHADDW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> HorizontalAdd(Vector256<short> left, Vector256<short> right) => HorizontalAdd(left, right);
+        /// <summary>
+        /// __m256i _mm256_hadd_epi32 (__m256i a, __m256i b)
+        ///   VPHADDD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> HorizontalAdd(Vector256<int> left, Vector256<int> right) => HorizontalAdd(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_hadds_epi16 (__m256i a, __m256i b)
+        ///   VPHADDSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> HorizontalAddSaturate(Vector256<short> left, Vector256<short> right) => HorizontalAddSaturate(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_hsub_epi16 (__m256i a, __m256i b)
+        ///   VPHSUBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> HorizontalSubtract(Vector256<short> left, Vector256<short> right) => HorizontalSubtract(left, right);
+        /// <summary>
+        /// __m256i _mm256_hsub_epi32 (__m256i a, __m256i b)
+        ///   VPHSUBD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> HorizontalSubtract(Vector256<int> left, Vector256<int> right) => HorizontalSubtract(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_hsubs_epi16 (__m256i a, __m256i b)
+        ///   VPHSUBSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> HorizontalSubtractSaturate(Vector256<short> left, Vector256<short> right) => HorizontalSubtractSaturate(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<sbyte> InsertVector128(Vector256<sbyte> value, Vector128<sbyte> data, byte index) => InsertVector128(value, data, index);
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xm128, imm8
+        /// </summary>
+        public static unsafe Vector256<sbyte> InsertVector128(Vector256<sbyte> value, sbyte* address, byte index) => InsertVector128(value, address, index);
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<byte> InsertVector128(Vector256<byte> value, Vector128<byte> data, byte index) => InsertVector128(value, data, index);
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<byte> InsertVector128(Vector256<byte> value, byte* address, byte index) => InsertVector128(value, address, index);
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<short> InsertVector128(Vector256<short> value, Vector128<short> data, byte index) => InsertVector128(value, data, index);
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<short> InsertVector128(Vector256<short> value, short* address, byte index) => InsertVector128(value, address, index);
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<ushort> InsertVector128(Vector256<ushort> value, Vector128<ushort> data, byte index) => InsertVector128(value, data, index);
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<ushort> InsertVector128(Vector256<ushort> value, ushort* address, byte index) => InsertVector128(value, address, index);
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<int> InsertVector128(Vector256<int> value, Vector128<int> data, byte index) => InsertVector128(value, data, index);
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<int> InsertVector128(Vector256<int> value, int* address, byte index) => InsertVector128(value, address, index);
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<uint> InsertVector128(Vector256<uint> value, Vector128<uint> data, byte index) => InsertVector128(value, data, index);
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<uint> InsertVector128(Vector256<uint> value, uint* address, byte index) => InsertVector128(value, address, index);
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<long> InsertVector128(Vector256<long> value, Vector128<long> data, byte index) => InsertVector128(value, data, index);
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<long> InsertVector128(Vector256<long> value, long* address, byte index) => InsertVector128(value, address, index);
+
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, xmm, imm8
+        /// </summary>
+        public static Vector256<ulong> InsertVector128(Vector256<ulong> value, Vector128<ulong> data, byte index) => InsertVector128(value, data, index);
+        /// <summary>
+        /// __m256i _mm256_inserti128_si256 (__m256i a, __m128i b, const int imm8)
+        ///   VINSERTI128 ymm, ymm, m128, imm8
+        /// </summary>
+        public static unsafe Vector256<ulong> InsertVector128(Vector256<ulong> value, ulong* address, byte index) => InsertVector128(value, address, index);
+
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<sbyte> LoadAlignedVector256NonTemporal(sbyte* address) => LoadAlignedVector256NonTemporal(address);
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<byte> LoadAlignedVector256NonTemporal(byte* address) => LoadAlignedVector256NonTemporal(address);
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<short> LoadAlignedVector256NonTemporal(short* address) => LoadAlignedVector256NonTemporal(address);
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ushort> LoadAlignedVector256NonTemporal(ushort* address) => LoadAlignedVector256NonTemporal(address);
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<int> LoadAlignedVector256NonTemporal(int* address) => LoadAlignedVector256NonTemporal(address);
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<uint> LoadAlignedVector256NonTemporal(uint* address) => LoadAlignedVector256NonTemporal(address);
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<long> LoadAlignedVector256NonTemporal(long* address) => LoadAlignedVector256NonTemporal(address);
+        /// <summary>
+        /// __m256i _mm256_stream_load_si256 (__m256i const* mem_addr)
+        ///   VMOVNTDQA ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ulong> LoadAlignedVector256NonTemporal(ulong* address) => LoadAlignedVector256NonTemporal(address);
+
+        /// <summary>
+        /// __m128i _mm_maskload_epi32 (int const* mem_addr, __m128i mask)
+        ///   VPMASKMOVD xmm, xmm, m128
+        /// </summary>
+        public static unsafe Vector128<int> MaskLoad(int* address, Vector128<int> mask) => MaskLoad(address, mask);
+        /// <summary>
+        /// __m128i _mm_maskload_epi32 (int const* mem_addr, __m128i mask)
+        ///   VPMASKMOVD xmm, xmm, m128
+        /// </summary>
+        public static unsafe Vector128<uint> MaskLoad(uint* address, Vector128<uint> mask) => MaskLoad(address, mask);
+        /// <summary>
+        /// __m128i _mm_maskload_epi64 (__int64 const* mem_addr, __m128i mask)
+        ///   VPMASKMOVQ xmm, xmm, m128
+        /// </summary>
+        public static unsafe Vector128<long> MaskLoad(long* address, Vector128<long> mask) => MaskLoad(address, mask);
+        /// <summary>
+        /// __m128i _mm_maskload_epi64 (__int64 const* mem_addr, __m128i mask)
+        ///   VPMASKMOVQ xmm, xmm, m128
+        /// </summary>
+        public static unsafe Vector128<ulong> MaskLoad(ulong* address, Vector128<ulong> mask) => MaskLoad(address, mask);
+
+        /// <summary>
+        /// __m256i _mm256_maskload_epi32 (int const* mem_addr, __m256i mask)
+        ///   VPMASKMOVD ymm, ymm, m256
+        /// </summary>
+        public static unsafe Vector256<int> MaskLoad(int* address, Vector256<int> mask) => MaskLoad(address, mask);
+        /// <summary>
+        /// __m256i _mm256_maskload_epi32 (int const* mem_addr, __m256i mask)
+        ///   VPMASKMOVD ymm, ymm, m256
+        /// </summary>
+        public static unsafe Vector256<uint> MaskLoad(uint* address, Vector256<uint> mask) => MaskLoad(address, mask);
+        /// <summary>
+        /// __m256i _mm256_maskload_epi64 (__int64 const* mem_addr, __m256i mask)
+        ///   VPMASKMOVQ ymm, ymm, m256
+        /// </summary>
+        public static unsafe Vector256<long> MaskLoad(long* address, Vector256<long> mask) => MaskLoad(address, mask);
+        /// <summary>
+        /// __m256i _mm256_maskload_epi64 (__int64 const* mem_addr, __m256i mask)
+        ///   VPMASKMOVQ ymm, ymm, m256
+        /// </summary>
+        public static unsafe Vector256<ulong> MaskLoad(ulong* address, Vector256<ulong> mask) => MaskLoad(address, mask);
+
+        /// <summary>
+        /// void _mm_maskstore_epi32 (int* mem_addr, __m128i mask, __m128i a)
+        ///   VPMASKMOVD m128, xmm, xmm
+        /// </summary>
+        public static unsafe void MaskStore(int* address, Vector128<int> mask, Vector128<int> source) => MaskStore(address, mask, source);
+        /// <summary>
+        /// void _mm_maskstore_epi32 (int* mem_addr, __m128i mask, __m128i a)
+        ///   VPMASKMOVD m128, xmm, xmm
+        /// </summary>
+        public static unsafe void MaskStore(uint* address, Vector128<uint> mask, Vector128<uint> source) => MaskStore(address, mask, source);
+        /// <summary>
+        /// void _mm_maskstore_epi64 (__int64* mem_addr, __m128i mask, __m128i a)
+        ///   VPMASKMOVQ m128, xmm, xmm
+        /// </summary>
+        public static unsafe void MaskStore(long* address, Vector128<long> mask, Vector128<long> source) => MaskStore(address, mask, source);
+        /// <summary>
+        /// void _mm_maskstore_epi64 (__int64* mem_addr, __m128i mask, __m128i a)
+        ///   VPMASKMOVQ m128, xmm, xmm
+        /// </summary>
+        public static unsafe void MaskStore(ulong* address, Vector128<ulong> mask, Vector128<ulong> source) => MaskStore(address, mask, source);
+
+        /// <summary>
+        /// void _mm256_maskstore_epi32 (int* mem_addr, __m256i mask, __m256i a)
+        ///   VPMASKMOVD m256, ymm, ymm
+        /// </summary>
+        public static unsafe void MaskStore(int* address, Vector256<int> mask, Vector256<int> source) => MaskStore(address, mask, source);
+        /// <summary>
+        /// void _mm256_maskstore_epi32 (int* mem_addr, __m256i mask, __m256i a)
+        ///   VPMASKMOVD m256, ymm, ymm
+        /// </summary>
+        public static unsafe void MaskStore(uint* address, Vector256<uint> mask, Vector256<uint> source) => MaskStore(address, mask, source);
+        /// <summary>
+        /// void _mm256_maskstore_epi64 (__int64* mem_addr, __m256i mask, __m256i a)
+        ///   VPMASKMOVQ m256, ymm, ymm
+        /// </summary>
+        public static unsafe void MaskStore(long* address, Vector256<long> mask, Vector256<long> source) => MaskStore(address, mask, source);
+        /// <summary>
+        /// void _mm256_maskstore_epi64 (__int64* mem_addr, __m256i mask, __m256i a)
+        ///   VPMASKMOVQ m256, ymm, ymm
+        /// </summary>
+        public static unsafe void MaskStore(ulong* address, Vector256<ulong> mask, Vector256<ulong> source) => MaskStore(address, mask, source);
+
+        /// <summary>
+        /// __m256i _mm256_madd_epi16 (__m256i a, __m256i b)
+        ///   VPMADDWD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> MultiplyAddAdjacent(Vector256<short> left, Vector256<short> right) => MultiplyAddAdjacent(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_maddubs_epi16 (__m256i a, __m256i b)
+        ///   VPMADDUBSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> MultiplyAddAdjacent(Vector256<byte> left, Vector256<sbyte> right) => MultiplyAddAdjacent(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_max_epi8 (__m256i a, __m256i b)
+        ///   VPMAXSB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Max(Vector256<sbyte> left, Vector256<sbyte> right) => Max(left, right);
+        /// <summary>
+        /// __m256i _mm256_max_epu8 (__m256i a, __m256i b)
+        ///   VPMAXUB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Max(Vector256<byte> left, Vector256<byte> right) => Max(left, right);
+        /// <summary>
+        /// __m256i _mm256_max_epi16 (__m256i a, __m256i b)
+        ///   VPMAXSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> Max(Vector256<short> left, Vector256<short> right) => Max(left, right);
+        /// <summary>
+        /// __m256i _mm256_max_epu16 (__m256i a, __m256i b)
+        ///   VPMAXUW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Max(Vector256<ushort> left, Vector256<ushort> right) => Max(left, right);
+        /// <summary>
+        /// __m256i _mm256_max_epi32 (__m256i a, __m256i b)
+        ///   VPMAXSD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Max(Vector256<int> left, Vector256<int> right) => Max(left, right);
+        /// <summary>
+        /// __m256i _mm256_max_epu32 (__m256i a, __m256i b)
+        ///   VPMAXUD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Max(Vector256<uint> left, Vector256<uint> right) => Max(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_min_epi8 (__m256i a, __m256i b)
+        ///   VPMINSB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Min(Vector256<sbyte> left, Vector256<sbyte> right) => Min(left, right);
+        /// <summary>
+        /// __m256i _mm256_min_epu8 (__m256i a, __m256i b)
+        ///   VPMINUB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Min(Vector256<byte> left, Vector256<byte> right) => Min(left, right);
+        /// <summary>
+        /// __m256i _mm256_min_epi16 (__m256i a, __m256i b)
+        ///   VPMINSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> Min(Vector256<short> left, Vector256<short> right) => Min(left, right);
+        /// <summary>
+        /// __m256i _mm256_min_epu16 (__m256i a, __m256i b)
+        ///   VPMINUW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Min(Vector256<ushort> left, Vector256<ushort> right) => Min(left, right);
+        /// <summary>
+        /// __m256i _mm256_min_epi32 (__m256i a, __m256i b)
+        ///   VPMINSD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Min(Vector256<int> left, Vector256<int> right) => Min(left, right);
+        /// <summary>
+        /// __m256i _mm256_min_epu32 (__m256i a, __m256i b)
+        ///   VPMINUD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Min(Vector256<uint> left, Vector256<uint> right) => Min(left, right);
+
+        /// <summary>
+        /// int _mm256_movemask_epi8 (__m256i a)
+        ///   VPMOVMSKB reg, ymm
+        /// </summary>
+        public static int MoveMask(Vector256<sbyte> value) => MoveMask(value);
+        /// <summary>
+        /// int _mm256_movemask_epi8 (__m256i a)
+        ///   VPMOVMSKB reg, ymm
+        /// </summary>
+        public static int MoveMask(Vector256<byte> value) => MoveMask(value);
+
+        /// <summary>
+        /// __m256i _mm256_mpsadbw_epu8 (__m256i a, __m256i b, const int imm8)
+        ///   VMPSADBW ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<ushort> MultipleSumAbsoluteDifferences(Vector256<byte> left, Vector256<byte> right, byte mask) => MultipleSumAbsoluteDifferences(left, right, mask);
+
+        /// <summary>
+        /// __m256i _mm256_mul_epi32 (__m256i a, __m256i b)
+        ///   VPMULDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> Multiply(Vector256<int> left, Vector256<int> right) => Multiply(left, right);
+        /// <summary>
+        /// __m256i _mm256_mul_epu32 (__m256i a, __m256i b)
+        ///   VPMULUDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> Multiply(Vector256<uint> left, Vector256<uint> right) => Multiply(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_mulhi_epi16 (__m256i a, __m256i b)
+        ///   VPMULHW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> MultiplyHigh(Vector256<short> left, Vector256<short> right) => MultiplyHigh(left, right);
+        /// <summary>
+        /// __m256i _mm256_mulhi_epu16 (__m256i a, __m256i b)
+        ///   VPMULHUW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> MultiplyHigh(Vector256<ushort> left, Vector256<ushort> right) => MultiplyHigh(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_mulhrs_epi16 (__m256i a, __m256i b)
+        ///   VPMULHRSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> MultiplyHighRoundScale(Vector256<short> left, Vector256<short> right) => MultiplyHighRoundScale(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_mullo_epi16 (__m256i a, __m256i b)
+        ///   VPMULLW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> MultiplyLow(Vector256<short> left, Vector256<short> right) => MultiplyLow(left, right);
+        /// <summary>
+        /// __m256i _mm256_mullo_epi32 (__m256i a, __m256i b)
+        ///   VPMULLD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> MultiplyLow(Vector256<int> left, Vector256<int> right) => MultiplyLow(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Or(Vector256<sbyte> left, Vector256<sbyte> right) => Or(left, right);
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Or(Vector256<byte> left, Vector256<byte> right) => Or(left, right);
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> Or(Vector256<short> left, Vector256<short> right) => Or(left, right);
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Or(Vector256<ushort> left, Vector256<ushort> right) => Or(left, right);
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Or(Vector256<int> left, Vector256<int> right) => Or(left, right);
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Or(Vector256<uint> left, Vector256<uint> right) => Or(left, right);
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> Or(Vector256<long> left, Vector256<long> right) => Or(left, right);
+        /// <summary>
+        /// __m256i _mm256_or_si256 (__m256i a, __m256i b)
+        ///   VPOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> Or(Vector256<ulong> left, Vector256<ulong> right) => Or(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_packs_epi16 (__m256i a, __m256i b)
+        ///   VPACKSSWB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> PackSignedSaturate(Vector256<short> left, Vector256<short> right) => PackSignedSaturate(left, right);
+        /// <summary>
+        /// __m256i _mm256_packs_epi32 (__m256i a, __m256i b)
+        ///   VPACKSSDW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> PackSignedSaturate(Vector256<int> left, Vector256<int> right) => PackSignedSaturate(left, right);
+        /// <summary>
+        /// __m256i _mm256_packus_epi16 (__m256i a, __m256i b)
+        ///   VPACKUSWB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> PackUnsignedSaturate(Vector256<short> left, Vector256<short> right) => PackUnsignedSaturate(left, right);
+        /// <summary>
+        /// __m256i _mm256_packus_epi32 (__m256i a, __m256i b)
+        ///   VPACKUSDW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> PackUnsignedSaturate(Vector256<int> left, Vector256<int> right) => PackUnsignedSaturate(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<sbyte> Permute2x128(Vector256<sbyte> left, Vector256<sbyte> right, byte control) => Permute2x128(left, right, control);
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<byte> Permute2x128(Vector256<byte> left, Vector256<byte> right, byte control) => Permute2x128(left, right, control);
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<short> Permute2x128(Vector256<short> left, Vector256<short> right, byte control) => Permute2x128(left, right, control);
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<ushort> Permute2x128(Vector256<ushort> left, Vector256<ushort> right, byte control) => Permute2x128(left, right, control);
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<int> Permute2x128(Vector256<int> left, Vector256<int> right, byte control) => Permute2x128(left, right, control);
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<uint> Permute2x128(Vector256<uint> left, Vector256<uint> right, byte control) => Permute2x128(left, right, control);
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<long> Permute2x128(Vector256<long> left, Vector256<long> right, byte control) => Permute2x128(left, right, control);
+        /// <summary>
+        /// __m256i _mm256_permute2x128_si256 (__m256i a, __m256i b, const int imm8)
+        ///   VPERM2I128 ymm, ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<ulong> Permute2x128(Vector256<ulong> left, Vector256<ulong> right, byte control) => Permute2x128(left, right, control);
+
+        /// <summary>
+        /// __m256i _mm256_permute4x64_epi64 (__m256i a, const int imm8)
+        ///   VPERMQ ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<long> Permute4x64(Vector256<long> value, byte control) => Permute4x64(value, control);
+        /// <summary>
+        /// __m256i _mm256_permute4x64_epi64 (__m256i a, const int imm8)
+        ///   VPERMQ ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<ulong> Permute4x64(Vector256<ulong> value, byte control) => Permute4x64(value, control);
+        /// <summary>
+        /// __m256d _mm256_permute4x64_pd (__m256d a, const int imm8)
+        ///   VPERMPD ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<double> Permute4x64(Vector256<double> value, byte control) => Permute4x64(value, control);
+
+        /// <summary>
+        /// __m256i _mm256_permutevar8x32_epi32 (__m256i a, __m256i idx)
+        ///   VPERMD ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<int> PermuteVar8x32(Vector256<int> left, Vector256<int> mask) => PermuteVar8x32(left, mask);
+        /// <summary>
+        /// __m256i _mm256_permutevar8x32_epi32 (__m256i a, __m256i idx)
+        ///   VPERMD ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<uint> PermuteVar8x32(Vector256<uint> left, Vector256<uint> mask) => PermuteVar8x32(left, mask);
+        /// <summary>
+        /// __m256 _mm256_permutevar8x32_ps (__m256 a, __m256i idx)
+        ///   VPERMPS ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<float> PermuteVar8x32(Vector256<float> left, Vector256<float> mask) => PermuteVar8x32(left, mask);
+
+        /// <summary>
+        /// __m256i _mm256_sll_epi16 (__m256i a, __m128i count)
+        ///   VPSLLW ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<short> ShiftLeftLogical(Vector256<short> value, Vector128<short> count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_sll_epi16 (__m256i a, __m128i count)
+        ///   VPSLLW ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ushort> ShiftLeftLogical(Vector256<ushort> value, Vector128<ushort> count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_sll_epi32 (__m256i a, __m128i count)
+        ///   VPSLLD ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<int> ShiftLeftLogical(Vector256<int> value, Vector128<int> count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_sll_epi32 (__m256i a, __m128i count)
+        ///   VPSLLD ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<uint> ShiftLeftLogical(Vector256<uint> value, Vector128<uint> count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_sll_epi64 (__m256i a, __m128i count)
+        ///   VPSLLQ ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<long> ShiftLeftLogical(Vector256<long> value, Vector128<long> count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_sll_epi64 (__m256i a, __m128i count)
+        ///   VPSLLQ ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ulong> ShiftLeftLogical(Vector256<ulong> value, Vector128<ulong> count) => ShiftLeftLogical(value, count);
+
+        /// <summary>
+        /// __m256i _mm256_slli_epi16 (__m256i a, int imm8)
+        ///   VPSLLW ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<short> ShiftLeftLogical(Vector256<short> value, byte count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_slli_epi16 (__m256i a, int imm8)
+        ///   VPSLLW ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ushort> ShiftLeftLogical(Vector256<ushort> value, byte count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_slli_epi32 (__m256i a, int imm8)
+        ///   VPSLLD ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<int> ShiftLeftLogical(Vector256<int> value, byte count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_slli_epi32 (__m256i a, int imm8)
+        ///   VPSLLD ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<uint> ShiftLeftLogical(Vector256<uint> value, byte count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_slli_epi64 (__m256i a, int imm8)
+        ///   VPSLLQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<long> ShiftLeftLogical(Vector256<long> value, byte count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_slli_epi64 (__m256i a, int imm8)
+        ///   VPSLLQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ulong> ShiftLeftLogical(Vector256<ulong> value, byte count) => ShiftLeftLogical(value, count);
+
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<sbyte> ShiftLeftLogical128BitLane(Vector256<sbyte> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<byte> ShiftLeftLogical128BitLane(Vector256<byte> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<short> ShiftLeftLogical128BitLane(Vector256<short> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ushort> ShiftLeftLogical128BitLane(Vector256<ushort> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<int> ShiftLeftLogical128BitLane(Vector256<int> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<uint> ShiftLeftLogical128BitLane(Vector256<uint> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<long> ShiftLeftLogical128BitLane(Vector256<long> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m256i _mm256_bslli_epi128 (__m256i a, const int imm8)
+        ///   VPSLLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ulong> ShiftLeftLogical128BitLane(Vector256<ulong> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+
+        /// <summary>
+        /// __m256i _mm256_sllv_epi32 (__m256i a, __m256i count)
+        ///   VPSLLVD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> ShiftLeftLogicalVariable(Vector256<int> value, Vector256<uint> count) => ShiftLeftLogicalVariable(value, count);
+        /// <summary>
+        /// __m256i _mm256_sllv_epi32 (__m256i a, __m256i count)
+        ///   VPSLLVD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> ShiftLeftLogicalVariable(Vector256<uint> value, Vector256<uint> count) => ShiftLeftLogicalVariable(value, count);
+        /// <summary>
+        /// __m256i _mm256_sllv_epi64 (__m256i a, __m256i count)
+        ///   VPSLLVQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> ShiftLeftLogicalVariable(Vector256<long> value, Vector256<ulong> count) => ShiftLeftLogicalVariable(value, count);
+        /// <summary>
+        /// __m256i _mm256_sllv_epi64 (__m256i a, __m256i count)
+        ///   VPSLLVQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> ShiftLeftLogicalVariable(Vector256<ulong> value, Vector256<ulong> count) => ShiftLeftLogicalVariable(value, count);
+
+        /// <summary>
+        /// __m128i _mm_sllv_epi32 (__m128i a, __m128i count)
+        ///   VPSLLVD xmm, ymm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ShiftLeftLogicalVariable(Vector128<int> value, Vector128<uint> count) => ShiftLeftLogicalVariable(value, count);
+        /// <summary>
+        /// __m128i _mm_sllv_epi32 (__m128i a, __m128i count)
+        ///   VPSLLVD xmm, ymm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> ShiftLeftLogicalVariable(Vector128<uint> value, Vector128<uint> count) => ShiftLeftLogicalVariable(value, count);
+        /// <summary>
+        /// __m128i _mm_sllv_epi64 (__m128i a, __m128i count)
+        ///   VPSLLVQ xmm, ymm, xmm/m128
+        /// </summary>
+        public static Vector128<long> ShiftLeftLogicalVariable(Vector128<long> value, Vector128<ulong> count) => ShiftLeftLogicalVariable(value, count);
+        /// <summary>
+        /// __m128i _mm_sllv_epi64 (__m128i a, __m128i count)
+        ///   VPSLLVQ xmm, ymm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> ShiftLeftLogicalVariable(Vector128<ulong> value, Vector128<ulong> count) => ShiftLeftLogicalVariable(value, count);
+
+        /// <summary>
+        /// _mm256_sra_epi16 (__m256i a, __m128i count)
+        ///   VPSRAW ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<short> ShiftRightArithmetic(Vector256<short> value, Vector128<short> count) => ShiftRightArithmetic(value, count);
+        /// <summary>
+        /// _mm256_sra_epi32 (__m256i a, __m128i count)
+        ///   VPSRAD ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<int> ShiftRightArithmetic(Vector256<int> value, Vector128<int> count) => ShiftRightArithmetic(value, count);
+
+        /// <summary>
+        /// __m256i _mm256_srai_epi16 (__m256i a, int imm8)
+        ///   VPSRAW ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<short> ShiftRightArithmetic(Vector256<short> value, byte count) => ShiftRightArithmetic(value, count);
+        /// <summary>
+        /// __m256i _mm256_srai_epi32 (__m256i a, int imm8)
+        ///   VPSRAD ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<int> ShiftRightArithmetic(Vector256<int> value, byte count) => ShiftRightArithmetic(value, count);
+
+        /// <summary>
+        /// __m256i _mm256_srav_epi32 (__m256i a, __m256i count)
+        ///   VPSRAVD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> ShiftRightArithmeticVariable(Vector256<int> value, Vector256<uint> count) => ShiftRightArithmeticVariable(value, count);
+
+        /// <summary>
+        /// __m128i _mm_srav_epi32 (__m128i a, __m128i count)
+        ///   VPSRAVD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ShiftRightArithmeticVariable(Vector128<int> value, Vector128<uint> count) => ShiftRightArithmeticVariable(value, count);
+
+        /// <summary>
+        /// __m256i _mm256_srl_epi16 (__m256i a, __m128i count)
+        ///   VPSRLW ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<short> ShiftRightLogical(Vector256<short> value, Vector128<short> count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_srl_epi16 (__m256i a, __m128i count)
+        ///   VPSRLW ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ushort> ShiftRightLogical(Vector256<ushort> value, Vector128<ushort> count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_srl_epi32 (__m256i a, __m128i count)
+        ///   VPSRLD ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<int> ShiftRightLogical(Vector256<int> value, Vector128<int> count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_srl_epi32 (__m256i a, __m128i count)
+        ///   VPSRLD ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<uint> ShiftRightLogical(Vector256<uint> value, Vector128<uint> count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_srl_epi64 (__m256i a, __m128i count)
+        ///   VPSRLQ ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<long> ShiftRightLogical(Vector256<long> value, Vector128<long> count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_srl_epi64 (__m256i a, __m128i count)
+        ///   VPSRLQ ymm, ymm, xmm/m128
+        /// </summary>
+        public static Vector256<ulong> ShiftRightLogical(Vector256<ulong> value, Vector128<ulong> count) => ShiftRightLogical(value, count);
+
+        /// <summary>
+        /// __m256i _mm256_srli_epi16 (__m256i a, int imm8)
+        ///   VPSRLW ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<short> ShiftRightLogical(Vector256<short> value, byte count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_srli_epi16 (__m256i a, int imm8)
+        ///   VPSRLW ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ushort> ShiftRightLogical(Vector256<ushort> value, byte count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_srli_epi32 (__m256i a, int imm8)
+        ///   VPSRLD ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<int> ShiftRightLogical(Vector256<int> value, byte count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_srli_epi32 (__m256i a, int imm8)
+        ///   VPSRLD ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<uint> ShiftRightLogical(Vector256<uint> value, byte count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_srli_epi64 (__m256i a, int imm8)
+        ///   VPSRLQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<long> ShiftRightLogical(Vector256<long> value, byte count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m256i _mm256_srli_epi64 (__m256i a, int imm8)
+        ///   VPSRLQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ulong> ShiftRightLogical(Vector256<ulong> value, byte count) => ShiftRightLogical(value, count);
+
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<sbyte> ShiftRightLogical128BitLane(Vector256<sbyte> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<byte> ShiftRightLogical128BitLane(Vector256<byte> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<short> ShiftRightLogical128BitLane(Vector256<short> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ushort> ShiftRightLogical128BitLane(Vector256<ushort> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<int> ShiftRightLogical128BitLane(Vector256<int> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<uint> ShiftRightLogical128BitLane(Vector256<uint> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<long> ShiftRightLogical128BitLane(Vector256<long> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m256i _mm256_bsrli_epi128 (__m256i a, const int imm8)
+        ///   VPSRLDQ ymm, ymm, imm8
+        /// </summary>
+        public static Vector256<ulong> ShiftRightLogical128BitLane(Vector256<ulong> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+
+        /// <summary>
+        /// __m256i _mm256_srlv_epi32 (__m256i a, __m256i count)
+        ///   VPSRLVD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> ShiftRightLogicalVariable(Vector256<int> value, Vector256<uint> count) => ShiftRightLogicalVariable(value, count);
+        /// <summary>
+        /// __m256i _mm256_srlv_epi32 (__m256i a, __m256i count)
+        ///   VPSRLVD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> ShiftRightLogicalVariable(Vector256<uint> value, Vector256<uint> count) => ShiftRightLogicalVariable(value, count);
+        /// <summary>
+        /// __m256i _mm256_srlv_epi64 (__m256i a, __m256i count)
+        ///   VPSRLVQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> ShiftRightLogicalVariable(Vector256<long> value, Vector256<ulong> count) => ShiftRightLogicalVariable(value, count);
+        /// <summary>
+        /// __m256i _mm256_srlv_epi64 (__m256i a, __m256i count)
+        ///   VPSRLVQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> ShiftRightLogicalVariable(Vector256<ulong> value, Vector256<ulong> count) => ShiftRightLogicalVariable(value, count);
+
+        /// <summary>
+        /// __m128i _mm_srlv_epi32 (__m128i a, __m128i count)
+        ///   VPSRLVD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ShiftRightLogicalVariable(Vector128<int> value, Vector128<uint> count) => ShiftRightLogicalVariable(value, count);
+        /// <summary>
+        /// __m128i _mm_srlv_epi32 (__m128i a, __m128i count)
+        ///   VPSRLVD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> ShiftRightLogicalVariable(Vector128<uint> value, Vector128<uint> count) => ShiftRightLogicalVariable(value, count);
+        /// <summary>
+        /// __m128i _mm_srlv_epi64 (__m128i a, __m128i count)
+        ///   VPSRLVQ xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> ShiftRightLogicalVariable(Vector128<long> value, Vector128<ulong> count) => ShiftRightLogicalVariable(value, count);
+        /// <summary>
+        /// __m128i _mm_srlv_epi64 (__m128i a, __m128i count)
+        ///   VPSRLVQ xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> ShiftRightLogicalVariable(Vector128<ulong> value, Vector128<ulong> count) => ShiftRightLogicalVariable(value, count);
+
+        /// <summary>
+        /// __m256i _mm256_shuffle_epi8 (__m256i a, __m256i b)
+        ///   VPSHUFB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Shuffle(Vector256<sbyte> value, Vector256<sbyte> mask) => Shuffle(value, mask);
+        /// <summary>
+        /// __m256i _mm256_shuffle_epi8 (__m256i a, __m256i b)
+        ///   VPSHUFB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Shuffle(Vector256<byte> value, Vector256<byte> mask) => Shuffle(value, mask);
+        /// <summary>
+        /// __m256i _mm256_shuffle_epi32 (__m256i a, const int imm8)
+        ///   VPSHUFD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Shuffle(Vector256<int> value, byte control) => Shuffle(value, control);
+        /// <summary>
+        /// __m256i _mm256_shuffle_epi32 (__m256i a, const int imm8)
+        ///   VPSHUFD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Shuffle(Vector256<uint> value, byte control) => Shuffle(value, control);
+
+        /// <summary>
+        /// __m256i _mm256_shufflehi_epi16 (__m256i a, const int imm8)
+        ///   VPSHUFHW ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<short> ShuffleHigh(Vector256<short> value, byte control) => ShuffleHigh(value, control);
+        /// <summary>
+        /// __m256i _mm256_shufflehi_epi16 (__m256i a, const int imm8)
+        ///   VPSHUFHW ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<ushort> ShuffleHigh(Vector256<ushort> value, byte control) => ShuffleHigh(value, control);
+
+        /// <summary>
+        /// __m256i _mm256_shufflelo_epi16 (__m256i a, const int imm8)
+        ///   VPSHUFLW ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<short> ShuffleLow(Vector256<short> value, byte control) => ShuffleLow(value, control);
+        /// <summary>
+        /// __m256i _mm256_shufflelo_epi16 (__m256i a, const int imm8)
+        ///   VPSHUFLW ymm, ymm/m256, imm8
+        /// </summary>
+        public static Vector256<ushort> ShuffleLow(Vector256<ushort> value, byte control) => ShuffleLow(value, control);
+
+        /// <summary>
+        /// __m256i _mm256_sign_epi8 (__m256i a, __m256i b)
+        ///   VPSIGNB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Sign(Vector256<sbyte> left, Vector256<sbyte> right) => Sign(left, right);
+        /// <summary>
+        /// __m256i _mm256_sign_epi16 (__m256i a, __m256i b)
+        ///   VPSIGNW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> Sign(Vector256<short> left, Vector256<short> right) => Sign(left, right);
+        /// <summary>
+        /// __m256i _mm256_sign_epi32 (__m256i a, __m256i b)
+        ///   VPSIGND ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Sign(Vector256<int> left, Vector256<int> right) => Sign(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_sub_epi8 (__m256i a, __m256i b)
+        ///   VPSUBB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Subtract(Vector256<sbyte> left, Vector256<sbyte> right) => Subtract(left, right);
+        /// <summary>
+        /// __m256i _mm256_sub_epi8 (__m256i a, __m256i b)
+        ///   VPSUBB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Subtract(Vector256<byte> left, Vector256<byte> right) => Subtract(left, right);
+        /// <summary>
+        /// __m256i _mm256_sub_epi16 (__m256i a, __m256i b)
+        ///   VPSUBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> Subtract(Vector256<short> left, Vector256<short> right) => Subtract(left, right);
+        /// <summary>
+        /// __m256i _mm256_sub_epi16 (__m256i a, __m256i b)
+        ///   VPSUBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Subtract(Vector256<ushort> left, Vector256<ushort> right) => Subtract(left, right);
+        /// <summary>
+        /// __m256i _mm256_sub_epi32 (__m256i a, __m256i b)
+        ///   VPSUBD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Subtract(Vector256<int> left, Vector256<int> right) => Subtract(left, right);
+        /// <summary>
+        /// __m256i _mm256_sub_epi32 (__m256i a, __m256i b)
+        ///   VPSUBD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Subtract(Vector256<uint> left, Vector256<uint> right) => Subtract(left, right);
+        /// <summary>
+        /// __m256i _mm256_sub_epi64 (__m256i a, __m256i b)
+        ///   VPSUBQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> Subtract(Vector256<long> left, Vector256<long> right) => Subtract(left, right);
+        /// <summary>
+        /// __m256i _mm256_sub_epi64 (__m256i a, __m256i b)
+        ///   VPSUBQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> Subtract(Vector256<ulong> left, Vector256<ulong> right) => Subtract(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_subs_epi8 (__m256i a, __m256i b)
+        ///   VPSUBSB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> SubtractSaturate(Vector256<sbyte> left, Vector256<sbyte> right) => SubtractSaturate(left, right);
+        /// <summary>
+        /// __m256i _mm256_subs_epi16 (__m256i a, __m256i b)
+        ///   VPSUBSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> SubtractSaturate(Vector256<short> left, Vector256<short> right) => SubtractSaturate(left, right);
+        /// <summary>
+        /// __m256i _mm256_subs_epu8 (__m256i a, __m256i b)
+        ///   VPSUBUSB ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> SubtractSaturate(Vector256<byte> left, Vector256<byte> right) => SubtractSaturate(left, right);
+        /// <summary>
+        /// __m256i _mm256_subs_epu16 (__m256i a, __m256i b)
+        ///   VPSUBUSW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> SubtractSaturate(Vector256<ushort> left, Vector256<ushort> right) => SubtractSaturate(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_sad_epu8 (__m256i a, __m256i b)
+        ///   VPSADBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> SumAbsoluteDifferences(Vector256<byte> left, Vector256<byte> right) => SumAbsoluteDifferences(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi8 (__m256i a, __m256i b)
+        ///   VPUNPCKHBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> UnpackHigh(Vector256<sbyte> left, Vector256<sbyte> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi8 (__m256i a, __m256i b)
+        ///   VPUNPCKHBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> UnpackHigh(Vector256<byte> left, Vector256<byte> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi16 (__m256i a, __m256i b)
+        ///   VPUNPCKHWD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> UnpackHigh(Vector256<short> left, Vector256<short> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi16 (__m256i a, __m256i b)
+        ///   VPUNPCKHWD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> UnpackHigh(Vector256<ushort> left, Vector256<ushort> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi32 (__m256i a, __m256i b)
+        ///   VPUNPCKHDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> UnpackHigh(Vector256<int> left, Vector256<int> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi32 (__m256i a, __m256i b)
+        ///   VPUNPCKHDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> UnpackHigh(Vector256<uint> left, Vector256<uint> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi64 (__m256i a, __m256i b)
+        ///   VPUNPCKHQDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> UnpackHigh(Vector256<long> left, Vector256<long> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m256i _mm256_unpackhi_epi64 (__m256i a, __m256i b)
+        ///   VPUNPCKHQDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> UnpackHigh(Vector256<ulong> left, Vector256<ulong> right) => UnpackHigh(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi8 (__m256i a, __m256i b)
+        ///   VPUNPCKLBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> UnpackLow(Vector256<sbyte> left, Vector256<sbyte> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi8 (__m256i a, __m256i b)
+        ///   VPUNPCKLBW ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> UnpackLow(Vector256<byte> left, Vector256<byte> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi16 (__m256i a, __m256i b)
+        ///   VPUNPCKLWD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> UnpackLow(Vector256<short> left, Vector256<short> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi16 (__m256i a, __m256i b)
+        ///   VPUNPCKLWD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> UnpackLow(Vector256<ushort> left, Vector256<ushort> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi32 (__m256i a, __m256i b)
+        ///   VPUNPCKLDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> UnpackLow(Vector256<int> left, Vector256<int> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi32 (__m256i a, __m256i b)
+        ///   VPUNPCKLDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> UnpackLow(Vector256<uint> left, Vector256<uint> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi64 (__m256i a, __m256i b)
+        ///   VPUNPCKLQDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> UnpackLow(Vector256<long> left, Vector256<long> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m256i _mm256_unpacklo_epi64 (__m256i a, __m256i b)
+        ///   VPUNPCKLQDQ ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> UnpackLow(Vector256<ulong> left, Vector256<ulong> right) => UnpackLow(left, right);
+
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<sbyte> Xor(Vector256<sbyte> left, Vector256<sbyte> right) => Xor(left, right);
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<byte> Xor(Vector256<byte> left, Vector256<byte> right) => Xor(left, right);
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<short> Xor(Vector256<short> left, Vector256<short> right) => Xor(left, right);
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ushort> Xor(Vector256<ushort> left, Vector256<ushort> right) => Xor(left, right);
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<int> Xor(Vector256<int> left, Vector256<int> right) => Xor(left, right);
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<uint> Xor(Vector256<uint> left, Vector256<uint> right) => Xor(left, right);
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<long> Xor(Vector256<long> left, Vector256<long> right) => Xor(left, right);
+        /// <summary>
+        /// __m256i _mm256_xor_si256 (__m256i a, __m256i b)
+        ///   VPXOR ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<ulong> Xor(Vector256<ulong> left, Vector256<ulong> right) => Xor(left, right);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Bmi1.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Bmi1.PlatformNotSupported.cs
new file mode 100644
index 0000000000..f74cc7b84f
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Bmi1.PlatformNotSupported.cs
@@ -0,0 +1,94 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel BMI1 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Bmi1
+    {
+        public static bool IsSupported { get { return false; } }
+
+        /// <summary>
+        /// unsigned int _andn_u32 (unsigned int a, unsigned int b)
+        ///   ANDN r32a, r32b, reg/m32
+        /// </summary>
+        public static uint AndNot(uint left, uint right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned __int64 _andn_u64 (unsigned __int64 a, unsigned __int64 b)
+        ///   ANDN r64a, r64b, reg/m64
+        /// </summary>
+        public static ulong AndNot(ulong left, ulong right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// unsigned int _bextr_u32 (unsigned int a, unsigned int start, unsigned int len)
+        ///   BEXTR r32a, reg/m32, r32b
+        /// </summary>
+        public static uint BitFieldExtract(uint value, uint start, uint length) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned __int64 _bextr_u64 (unsigned __int64 a, unsigned int start, unsigned int len)
+        ///   BEXTR r64a, reg/m64, r64b
+        /// </summary>
+        public static ulong BitFieldExtract(ulong value, ulong start, ulong length) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned int _bextr2_u32 (unsigned int a, unsigned int control)
+        ///   BEXTR r32a, reg/m32, r32b
+        /// </summary>
+        public static uint BitFieldExtract(uint value, uint control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned __int64 _bextr2_u64 (unsigned __int64 a, unsigned __int64 control)
+        ///   BEXTR r64a, reg/m64, r64b
+        /// </summary>
+        public static ulong BitFieldExtract(ulong value, ulong control) { throw new PlatformNotSupportedException(); }
+        
+        /// <summary>
+        /// unsigned int _blsi_u32 (unsigned int a)
+        ///   BLSI reg, reg/m32
+        /// </summary>
+        public static uint ExtractLowestSetBit(uint value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned __int64 _blsi_u64 (unsigned __int64 a)
+        ///   BLSI reg, reg/m64
+        /// </summary>
+        public static ulong ExtractLowestSetBit(ulong value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// unsigned int _blsmsk_u32 (unsigned int a)
+        ///   BLSMSK reg, reg/m32
+        /// </summary>
+        public static uint GetMaskUptoLowestSetBit(uint value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned __int64 _blsmsk_u64 (unsigned __int64 a)
+        ///   BLSMSK reg, reg/m64
+        /// </summary>
+        public static ulong GetMaskUptoLowestSetBit(ulong value) { throw new PlatformNotSupportedException(); }
+        
+        /// <summary>
+        /// unsigned int _blsr_u32 (unsigned int a)
+        ///   BLSR reg, reg/m32
+        /// </summary>
+        public static uint ResetLowestSetBit(uint value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned __int64 _blsr_u64 (unsigned __int64 a)
+        ///   BLSR reg, reg/m64
+        /// </summary>
+        public static ulong ResetLowestSetBit(ulong value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_tzcnt_32 (unsigned int a)
+        ///   TZCNT reg, reg/m32
+        /// </summary>
+        public static uint TrailingZeroCount(uint value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int64 _mm_tzcnt_64 (unsigned __int64 a)
+        ///   TZCNT reg, reg/m64
+        /// </summary>
+        public static ulong TrailingZeroCount(ulong value) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Bmi1.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Bmi1.cs
new file mode 100644
index 0000000000..d8e41ea0a2
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Bmi1.cs
@@ -0,0 +1,94 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel BMI1 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Bmi1
+    {
+        public static bool IsSupported { get => IsSupported; }
+
+        /// <summary>
+        /// unsigned int _andn_u32 (unsigned int a, unsigned int b)
+        ///   ANDN r32a, r32b, reg/m32
+        /// </summary>
+        public static uint AndNot(uint left, uint right) => AndNot(left, right);
+        /// <summary>
+        /// unsigned __int64 _andn_u64 (unsigned __int64 a, unsigned __int64 b)
+        ///   ANDN r64a, r64b, reg/m64
+        /// </summary>
+        public static ulong AndNot(ulong left, ulong right) => AndNot(left, right);
+
+        /// <summary>
+        /// unsigned int _bextr_u32 (unsigned int a, unsigned int start, unsigned int len)
+        ///   BEXTR r32a, reg/m32, r32b
+        /// </summary>
+        public static uint BitFieldExtract(uint value, uint start, uint length) => BitFieldExtract(value, start, length);
+        /// <summary>
+        /// unsigned __int64 _bextr_u64 (unsigned __int64 a, unsigned int start, unsigned int len)
+        ///   BEXTR r64a, reg/m64, r64b
+        /// </summary>
+        public static ulong BitFieldExtract(ulong value, ulong start, ulong length) => BitFieldExtract(value, start, length);
+        /// <summary>
+        /// unsigned int _bextr2_u32 (unsigned int a, unsigned int control)
+        ///   BEXTR r32a, reg/m32, r32b
+        /// </summary>
+        public static uint BitFieldExtract(uint value, uint control) => BitFieldExtract(value, control);
+        /// <summary>
+        /// unsigned __int64 _bextr2_u64 (unsigned __int64 a, unsigned __int64 control)
+        ///   BEXTR r64a, reg/m64, r64b
+        /// </summary>
+        public static ulong BitFieldExtract(ulong value, ulong control) => BitFieldExtract(value, control);
+        
+        /// <summary>
+        /// unsigned int _blsi_u32 (unsigned int a)
+        ///   BLSI reg, reg/m32
+        /// </summary>
+        public static uint ExtractLowestSetBit(uint value) => ExtractLowestSetBit(value);
+        /// <summary>
+        /// unsigned __int64 _blsi_u64 (unsigned __int64 a)
+        ///   BLSI reg, reg/m64
+        /// </summary>
+        public static ulong ExtractLowestSetBit(ulong value) => ExtractLowestSetBit(value);
+
+        /// <summary>
+        /// unsigned int _blsmsk_u32 (unsigned int a)
+        ///   BLSMSK reg, reg/m32
+        /// </summary>
+        public static uint GetMaskUptoLowestSetBit(uint value) => GetMaskUptoLowestSetBit(value);
+        /// <summary>
+        /// unsigned __int64 _blsmsk_u64 (unsigned __int64 a)
+        ///   BLSMSK reg, reg/m64
+        /// </summary>
+        public static ulong GetMaskUptoLowestSetBit(ulong value) => GetMaskUptoLowestSetBit(value);
+        
+        /// <summary>
+        /// unsigned int _blsr_u32 (unsigned int a)
+        ///   BLSR reg, reg/m32
+        /// </summary>
+        public static uint ResetLowestSetBit(uint value) => ResetLowestSetBit(value);
+        /// <summary>
+        /// unsigned __int64 _blsr_u64 (unsigned __int64 a)
+        ///   BLSR reg, reg/m64
+        /// </summary>
+        public static ulong ResetLowestSetBit(ulong value) => ResetLowestSetBit(value);
+
+        /// <summary>
+        /// int _mm_tzcnt_32 (unsigned int a)
+        ///   TZCNT reg, reg/m32
+        /// </summary>
+        public static uint TrailingZeroCount(uint value) => TrailingZeroCount(value);
+        /// <summary>
+        /// __int64 _mm_tzcnt_64 (unsigned __int64 a)
+        ///   TZCNT reg, reg/m64
+        /// </summary>
+        public static ulong TrailingZeroCount(ulong value) => TrailingZeroCount(value);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Bmi2.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Bmi2.PlatformNotSupported.cs
new file mode 100644
index 0000000000..85082c7305
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Bmi2.PlatformNotSupported.cs
@@ -0,0 +1,62 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel BMI2 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Bmi2
+    {
+        public static bool IsSupported { get { return false; } }
+
+        /// <summary>
+        /// unsigned int _bzhi_u32 (unsigned int a, unsigned int index)
+        ///   BZHI r32a, reg/m32, r32b
+        /// </summary>
+        public static uint ZeroHighBits(uint value, uint index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned __int64 _bzhi_u64 (unsigned __int64 a, unsigned int index)
+        ///   BZHI r64a, reg/m32, r64b
+        /// </summary>
+        public static ulong ZeroHighBits(ulong value, ulong index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// unsigned int _mulx_u32 (unsigned int a, unsigned int b, unsigned int* hi)
+        ///   MULX r32a, r32b, reg/m32
+        /// </summary>
+        public static unsafe uint MultiplyNoFlags(uint left, uint right, uint* high) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned __int64 _mulx_u64 (unsigned __int64 a, unsigned __int64 b, unsigned __int64* hi)
+        ///   MULX r64a, r64b, reg/m64
+        /// </summary>
+        public static unsafe ulong MultiplyNoFlags(ulong left, ulong right, ulong* high) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// unsigned int _pdep_u32 (unsigned int a, unsigned int mask)
+        ///   PDEP r32a, r32b, reg/m32
+        /// </summary>
+        public static uint ParallelBitDeposit(uint value, uint mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned __int64 _pdep_u64 (unsigned __int64 a, unsigned __int64 mask)
+        ///   PDEP r64a, r64b, reg/m64
+        /// </summary>
+        public static ulong ParallelBitDeposit(ulong value, ulong mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// unsigned int _pext_u32 (unsigned int a, unsigned int mask)
+        ///   PEXT r32a, r32b, reg/m32
+        /// </summary>
+        public static uint ParallelBitExtract(uint value, uint mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned __int64 _pext_u64 (unsigned __int64 a, unsigned __int64 mask)
+        ///   PEXT r64a, r64b, reg/m64
+        /// </summary>
+        public static ulong ParallelBitExtract(ulong value, ulong mask) { throw new PlatformNotSupportedException(); }        
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Bmi2.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Bmi2.cs
new file mode 100644
index 0000000000..fd09704a2c
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Bmi2.cs
@@ -0,0 +1,62 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel BMI2 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Bmi2
+    {
+        public static bool IsSupported { get => IsSupported; }
+
+        /// <summary>
+        /// unsigned int _bzhi_u32 (unsigned int a, unsigned int index)
+        ///   BZHI r32a, reg/m32, r32b
+        /// </summary>
+        public static uint ZeroHighBits(uint value, uint index) => ZeroHighBits(value, index);
+        /// <summary>
+        /// unsigned __int64 _bzhi_u64 (unsigned __int64 a, unsigned int index)
+        ///   BZHI r64a, reg/m32, r64b
+        /// </summary>
+        public static ulong ZeroHighBits(ulong value, ulong index) => ZeroHighBits(value, index);
+
+        /// <summary>
+        /// unsigned int _mulx_u32 (unsigned int a, unsigned int b, unsigned int* hi)
+        ///   MULX r32a, r32b, reg/m32
+        /// </summary>
+        public static unsafe uint MultiplyNoFlags(uint left, uint right, uint* high) => MultiplyNoFlags(left, right, high);
+        /// <summary>
+        /// unsigned __int64 _mulx_u64 (unsigned __int64 a, unsigned __int64 b, unsigned __int64* hi)
+        ///   MULX r64a, r64b, reg/m64
+        /// </summary>
+        public static unsafe ulong MultiplyNoFlags(ulong left, ulong right, ulong* high) => MultiplyNoFlags(left, right, high);
+
+        /// <summary>
+        /// unsigned int _pdep_u32 (unsigned int a, unsigned int mask)
+        ///   PDEP r32a, r32b, reg/m32
+        /// </summary>
+        public static uint ParallelBitDeposit(uint value, uint mask) => ParallelBitDeposit(value, mask);
+        /// <summary>
+        /// unsigned __int64 _pdep_u64 (unsigned __int64 a, unsigned __int64 mask)
+        ///   PDEP r64a, r64b, reg/m64
+        /// </summary>
+        public static ulong ParallelBitDeposit(ulong value, ulong mask) => ParallelBitDeposit(value, mask);
+
+        /// <summary>
+        /// unsigned int _pext_u32 (unsigned int a, unsigned int mask)
+        ///   PEXT r32a, r32b, reg/m32
+        /// </summary>
+        public static uint ParallelBitExtract(uint value, uint mask) => ParallelBitExtract(value, mask);
+        /// <summary>
+        /// unsigned __int64 _pext_u64 (unsigned __int64 a, unsigned __int64 mask)
+        ///   PEXT r64a, r64b, reg/m64
+        /// </summary>
+        public static ulong ParallelBitExtract(ulong value, ulong mask) => ParallelBitExtract(value, mask);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Enums.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Enums.cs
new file mode 100644
index 0000000000..6d6a09a0b6
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Enums.cs
@@ -0,0 +1,189 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.Intrinsics.X86
+{
+    public enum FloatComparisonMode : byte
+    {
+        /// <summary>
+        /// _CMP_EQ_OQ
+        /// </summary>
+        EqualOrderedNonSignaling = 0,
+
+        /// <summary>
+        /// _CMP_LT_OS
+        /// </summary>
+        LessThanOrderedSignaling = 1,
+
+        /// <summary>
+        /// _CMP_LE_OS
+        /// </summary>
+        LessThanOrEqualOrderedSignaling = 2,
+
+        /// <summary>
+        /// _CMP_UNORD_Q
+        /// </summary>
+        UnorderedNonSignaling = 3,
+
+        /// <summary>
+        /// _CMP_NEQ_UQ
+        /// </summary>
+        NotEqualUnorderedNonSignaling = 4,
+
+        /// <summary>
+        /// _CMP_NLT_US
+        /// </summary>
+        NotLessThanUnorderedSignaling = 5,
+
+        /// <summary>
+        /// _CMP_NLE_US
+        /// </summary>
+        NotLessThanOrEqualUnorderedSignaling = 6,
+
+        /// <summary>
+        /// _CMP_ORD_Q
+        /// </summary>
+        OrderedNonSignaling = 7,
+
+        /// <summary>
+        /// _CMP_EQ_UQ
+        /// </summary>
+        EqualUnorderedNonSignaling = 8,
+
+        /// <summary>
+        /// _CMP_NGE_US
+        /// </summary>
+        NotGreaterThanOrEqualUnorderedSignaling = 9,
+
+        /// <summary>
+        /// _CMP_NGT_US
+        /// </summary>
+        NotGreaterThanUnorderedSignaling = 10,
+
+        /// <summary>
+        /// _CMP_FALSE_OQ
+        /// </summary>
+        FalseOrderedNonSignaling = 11,
+
+        /// <summary>
+        /// _CMP_NEQ_OQ
+        /// </summary>
+        NotEqualOrderedNonSignaling = 12,
+
+        /// <summary>
+        /// _CMP_GE_OS
+        /// </summary>
+        GreaterThanOrEqualOrderedSignaling = 13,
+
+        /// <summary>
+        /// _CMP_GT_OS
+        /// </summary>
+        GreaterThanOrderedSignaling = 14,
+
+        /// <summary>
+        /// _CMP_TRUE_UQ
+        /// </summary>
+        TrueUnorderedNonSignaling = 15,
+
+        /// <summary>
+        /// _CMP_EQ_OS
+        /// </summary>
+        EqualOrderedSignaling = 16,
+
+        /// <summary>
+        /// _CMP_LT_OQ
+        /// </summary>
+        LessThanOrderedNonSignaling = 17,
+        
+        /// <summary>
+        /// _CMP_LE_OQ
+        /// </summary>
+        LessThanOrEqualOrderedNonSignaling = 18,
+
+        /// <summary>
+        /// _CMP_UNORD_S
+        /// </summary>
+        UnorderedSignaling = 19,
+
+        /// <summary>
+        /// _CMP_NEQ_US
+        /// </summary>
+        NotEqualUnorderedSignaling = 20,
+
+        /// <summary>
+        /// _CMP_NLT_UQ
+        /// </summary>
+        NotLessThanUnorderedNonSignaling = 21,
+
+        /// <summary>
+        /// _CMP_NLE_UQ
+        /// </summary>
+        NotLessThanOrEqualUnorderedNonSignaling = 22,
+
+        /// <summary>
+        /// _CMP_ORD_S
+        /// </summary>
+        OrderedSignaling = 23,
+
+        /// <summary>
+        /// _CMP_EQ_US
+        /// </summary>
+        EqualUnorderedSignaling = 24,
+
+        /// <summary>
+        /// _CMP_NGE_UQ 
+        /// </summary>
+        NotGreaterThanOrEqualUnorderedNonSignaling = 25,
+
+        /// <summary>
+        /// _CMP_NGT_UQ 
+        /// </summary>
+        NotGreaterThanUnorderedNonSignaling = 26,
+
+        /// <summary>
+        /// _CMP_FALSE_OS 
+        /// </summary>
+        FalseOrderedSignaling = 27,
+
+        /// <summary>
+        /// _CMP_NEQ_OS
+        /// </summary>
+        NotEqualOrderedSignaling = 28,
+
+        /// <summary>
+        /// _CMP_GE_OQ
+        /// </summary>
+        GreaterThanOrEqualOrderedNonSignaling = 29,
+
+        /// <summary>
+        /// _CMP_GT_OQ
+        /// </summary>
+        GreaterThanOrderedNonSignaling = 30,
+
+        /// <summary>
+        /// _CMP_TRUE_US
+        /// </summary>
+        TrueUnorderedSignaling = 31,
+    }
+
+    public enum StringComparisonMode : byte {
+        EqualAny = 0x00,
+        Ranges = 0x04,
+        EqualEach = 0x08,
+        EqualOrdered = 0x0c,
+        NegativePolarity = 0x10,
+        MaskedNegativePolarity = 0x30,
+        LeastSignificant = 0x00,
+        MostSignificant = 0x40,
+    }
+
+
+    public enum ResultsFlag : byte {
+        CFlag = 0,
+        NotCFlagAndNotZFlag = 1,
+        OFlag = 2,
+        SFlag = 3,
+        ZFlag = 4,
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Fma.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Fma.PlatformNotSupported.cs
new file mode 100644
index 0000000000..dbeaf8fa84
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Fma.PlatformNotSupported.cs
@@ -0,0 +1,187 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel FMA hardware instructions via intrinsics
+    /// </summary>
+    public static class Fma
+    {
+        public static bool IsSupported { get { return false; } }
+
+        /// <summary>
+        /// __m128 _mm_fmadd_ps (__m128 a, __m128 b, __m128 c)
+        ///   VFMADDPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MultiplyAdd(Vector128<float> a, Vector128<float> b, Vector128<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_fmadd_pd (__m128d a, __m128d b, __m128d c)
+        ///   VFMADDPD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> MultiplyAdd(Vector128<double> a, Vector128<double> b, Vector128<double> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_fmadd_ps (__m256 a, __m256 b, __m256 c)
+        ///   VFMADDPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> MultiplyAdd(Vector256<float> a, Vector256<float> b, Vector256<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_fmadd_pd (__m256d a, __m256d b, __m256d c)
+        ///   VFMADDPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> MultiplyAdd(Vector256<double> a, Vector256<double> b, Vector256<double> c) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_fmadd_ss (__m128 a, __m128 b, __m128 c)
+        ///   VFMADDSS xmm, xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> MultiplyAddScalar(Vector128<float> a, Vector128<float> b, Vector128<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_fmadd_sd (__m128d a, __m128d b, __m128d c)
+        ///   VFMADDSS xmm, xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MultiplyAddScalar(Vector128<double> a, Vector128<double> b, Vector128<double> c) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_fmaddsub_ps (__m128 a, __m128 b, __m128 c)
+        ///   VFMADDSUBPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MultiplyAddSubtract(Vector128<float> a, Vector128<float> b, Vector128<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_fmaddsub_pd (__m128d a, __m128d b, __m128d c)
+        ///   VFMADDSUBPD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> MultiplyAddSubtract(Vector128<double> a, Vector128<double> b, Vector128<double> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_fmaddsub_ps (__m256 a, __m256 b, __m256 c)
+        ///   VFMADDSUBPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> MultiplyAddSubtract(Vector256<float> a, Vector256<float> b, Vector256<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_fmaddsub_pd (__m256d a, __m256d b, __m256d c)
+        ///   VFMADDSUBPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> MultiplyAddSubtract(Vector256<double> a, Vector256<double> b, Vector256<double> c) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_fmsub_ps (__m128 a, __m128 b, __m128 c)
+        ///   VFMSUBPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MultiplySubtract(Vector128<float> a, Vector128<float> b, Vector128<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_fmsub_pd (__m128d a, __m128d b, __m128d c)
+        ///   VFMSUBPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> MultiplySubtract(Vector128<double> a, Vector128<double> b, Vector128<double> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_fmsub_ps (__m256 a, __m256 b, __m256 c)
+        ///   VFMSUBPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> MultiplySubtract(Vector256<float> a, Vector256<float> b, Vector256<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_fmsub_pd (__m256d a, __m256d b, __m256d c)
+        ///   VFMSUBPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> MultiplySubtract(Vector256<double> a, Vector256<double> b, Vector256<double> c) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_fmsub_ss (__m128 a, __m128 b, __m128 c)
+        ///   VFMSUBSS xmm, xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> MultiplySubtractScalar(Vector128<float> a, Vector128<float> b, Vector128<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_fmsub_sd (__m128d a, __m128d b, __m128d c)
+        ///   VFMSUBSD xmm, xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MultiplySubtractScalar(Vector128<double> a, Vector128<double> b, Vector128<double> c) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_fmsubadd_ps (__m128 a, __m128 b, __m128 c)
+        ///   VFMSUBADDPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MultiplySubtractAdd(Vector128<float> a, Vector128<float> b, Vector128<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_fmsubadd_pd (__m128d a, __m128d b, __m128d c)
+        ///   VFMSUBADDPD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> MultiplySubtractAdd(Vector128<double> a, Vector128<double> b, Vector128<double> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_fmsubadd_ps (__m256 a, __m256 b, __m256 c)
+        ///   VFMSUBADDPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> MultiplySubtractAdd(Vector256<float> a, Vector256<float> b, Vector256<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_fmsubadd_pd (__m256d a, __m256d b, __m256d c)
+        ///   VFMSUBADDPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> MultiplySubtractAdd(Vector256<double> a, Vector256<double> b, Vector256<double> c) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_fnmadd_ps (__m128 a, __m128 b, __m128 c)
+        ///   VFNMADDPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MultiplyAddNegated(Vector128<float> a, Vector128<float> b, Vector128<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_fnmadd_pd (__m128d a, __m128d b, __m128d c)
+        ///   VFNMADDPD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> MultiplyAddNegated(Vector128<double> a, Vector128<double> b, Vector128<double> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_fnmadd_ps (__m256 a, __m256 b, __m256 c)
+        ///   VFNMADDPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> MultiplyAddNegated(Vector256<float> a, Vector256<float> b, Vector256<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_fnmadd_pd (__m256d a, __m256d b, __m256d c)
+        ///   VFNMADDPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> MultiplyAddNegated(Vector256<double> a, Vector256<double> b, Vector256<double> c) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_fnmadd_ss (__m128 a, __m128 b, __m128 c)
+        ///   VFNMADDSS xmm, xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> MultiplyAddNegatedScalar(Vector128<float> a, Vector128<float> b, Vector128<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_fnmadd_sd (__m128d a, __m128d b, __m128d c)
+        ///   VFNMADDSD xmm, xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MultiplyAddNegatedScalar(Vector128<double> a, Vector128<double> b, Vector128<double> c) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_fnmsub_ps (__m128 a, __m128 b, __m128 c)
+        ///   VFNMSUBPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MultiplySubtractNegated(Vector128<float> a, Vector128<float> b, Vector128<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_fnmsub_pd (__m128d a, __m128d b, __m128d c)
+        ///   VFNMSUBPD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> MultiplySubtractNegated(Vector128<double> a, Vector128<double> b, Vector128<double> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256 _mm256_fnmsub_ps (__m256 a, __m256 b, __m256 c)
+        ///   VFNMSUBPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> MultiplySubtractNegated(Vector256<float> a, Vector256<float> b, Vector256<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m256d _mm256_fnmsub_pd (__m256d a, __m256d b, __m256d c)
+        ///   VFNMSUBPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> MultiplySubtractNegated(Vector256<double> a, Vector256<double> b, Vector256<double> c) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_fnmsub_ss (__m128 a, __m128 b, __m128 c)
+        ///   VFNMSUBSS xmm, xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> MultiplySubtractNegatedScalar(Vector128<float> a, Vector128<float> b, Vector128<float> c) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_fnmsub_sd (__m128d a, __m128d b, __m128d c)
+        ///   VFNMSUBSD xmm, xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MultiplySubtractNegatedScalar(Vector128<double> a, Vector128<double> b, Vector128<double> c) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Fma.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Fma.cs
new file mode 100644
index 0000000000..a18a4f5773
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Fma.cs
@@ -0,0 +1,187 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel FMA hardware instructions via intrinsics
+    /// </summary>
+    public static class Fma
+    {
+        public static bool IsSupported { get => IsSupported; }
+
+        /// <summary>
+        /// __m128 _mm_fmadd_ps (__m128 a, __m128 b, __m128 c)
+        ///   VFMADDPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MultiplyAdd(Vector128<float> a, Vector128<float> b, Vector128<float> c) => MultiplyAdd(a, b, c);
+        /// <summary>
+        /// __m128d _mm_fmadd_pd (__m128d a, __m128d b, __m128d c)
+        ///   VFMADDPD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> MultiplyAdd(Vector128<double> a, Vector128<double> b, Vector128<double> c) => MultiplyAdd(a, b, c);
+        /// <summary>
+        /// __m256 _mm256_fmadd_ps (__m256 a, __m256 b, __m256 c)
+        ///   VFMADDPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> MultiplyAdd(Vector256<float> a, Vector256<float> b, Vector256<float> c) => MultiplyAdd(a, b, c);
+        /// <summary>
+        /// __m256d _mm256_fmadd_pd (__m256d a, __m256d b, __m256d c)
+        ///   VFMADDPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> MultiplyAdd(Vector256<double> a, Vector256<double> b, Vector256<double> c) => MultiplyAdd(a, b, c);
+
+        /// <summary>
+        /// __m128 _mm_fmadd_ss (__m128 a, __m128 b, __m128 c)
+        ///   VFMADDSS xmm, xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> MultiplyAddScalar(Vector128<float> a, Vector128<float> b, Vector128<float> c) => MultiplyAddScalar(a, b, c);
+        /// <summary>
+        /// __m128d _mm_fmadd_sd (__m128d a, __m128d b, __m128d c)
+        ///   VFMADDSS xmm, xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MultiplyAddScalar(Vector128<double> a, Vector128<double> b, Vector128<double> c) => MultiplyAddScalar(a, b, c);
+
+        /// <summary>
+        /// __m128 _mm_fmaddsub_ps (__m128 a, __m128 b, __m128 c)
+        ///   VFMADDSUBPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MultiplyAddSubtract(Vector128<float> a, Vector128<float> b, Vector128<float> c) => MultiplyAddSubtract(a, b, c);
+        /// <summary>
+        /// __m128d _mm_fmaddsub_pd (__m128d a, __m128d b, __m128d c)
+        ///   VFMADDSUBPD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> MultiplyAddSubtract(Vector128<double> a, Vector128<double> b, Vector128<double> c) => MultiplyAddSubtract(a, b, c);
+        /// <summary>
+        /// __m256 _mm256_fmaddsub_ps (__m256 a, __m256 b, __m256 c)
+        ///   VFMADDSUBPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> MultiplyAddSubtract(Vector256<float> a, Vector256<float> b, Vector256<float> c) => MultiplyAddSubtract(a, b, c);
+        /// <summary>
+        /// __m256d _mm256_fmaddsub_pd (__m256d a, __m256d b, __m256d c)
+        ///   VFMADDSUBPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> MultiplyAddSubtract(Vector256<double> a, Vector256<double> b, Vector256<double> c) => MultiplyAddSubtract(a, b, c);
+
+        /// <summary>
+        /// __m128 _mm_fmsub_ps (__m128 a, __m128 b, __m128 c)
+        ///   VFMSUBPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MultiplySubtract(Vector128<float> a, Vector128<float> b, Vector128<float> c) => MultiplySubtract(a, b, c);
+        /// <summary>
+        /// __m128d _mm_fmsub_pd (__m128d a, __m128d b, __m128d c)
+        ///   VFMSUBPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> MultiplySubtract(Vector128<double> a, Vector128<double> b, Vector128<double> c) => MultiplySubtract(a, b, c);
+        /// <summary>
+        /// __m256 _mm256_fmsub_ps (__m256 a, __m256 b, __m256 c)
+        ///   VFMSUBPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> MultiplySubtract(Vector256<float> a, Vector256<float> b, Vector256<float> c) => MultiplySubtract(a, b, c);
+        /// <summary>
+        /// __m256d _mm256_fmsub_pd (__m256d a, __m256d b, __m256d c)
+        ///   VFMSUBPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> MultiplySubtract(Vector256<double> a, Vector256<double> b, Vector256<double> c) => MultiplySubtract(a, b, c);
+
+        /// <summary>
+        /// __m128 _mm_fmsub_ss (__m128 a, __m128 b, __m128 c)
+        ///   VFMSUBSS xmm, xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> MultiplySubtractScalar(Vector128<float> a, Vector128<float> b, Vector128<float> c) => MultiplySubtractScalar(a, b, c);
+        /// <summary>
+        /// __m128d _mm_fmsub_sd (__m128d a, __m128d b, __m128d c)
+        ///   VFMSUBSD xmm, xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MultiplySubtractScalar(Vector128<double> a, Vector128<double> b, Vector128<double> c) => MultiplySubtractScalar(a, b, c);
+
+        /// <summary>
+        /// __m128 _mm_fmsubadd_ps (__m128 a, __m128 b, __m128 c)
+        ///   VFMSUBADDPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MultiplySubtractAdd(Vector128<float> a, Vector128<float> b, Vector128<float> c) => MultiplySubtractAdd(a, b, c);
+        /// <summary>
+        /// __m128d _mm_fmsubadd_pd (__m128d a, __m128d b, __m128d c)
+        ///   VFMSUBADDPD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> MultiplySubtractAdd(Vector128<double> a, Vector128<double> b, Vector128<double> c) => MultiplySubtractAdd(a, b, c);
+        /// <summary>
+        /// __m256 _mm256_fmsubadd_ps (__m256 a, __m256 b, __m256 c)
+        ///   VFMSUBADDPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> MultiplySubtractAdd(Vector256<float> a, Vector256<float> b, Vector256<float> c) => MultiplySubtractAdd(a, b, c);
+        /// <summary>
+        /// __m256d _mm256_fmsubadd_pd (__m256d a, __m256d b, __m256d c)
+        ///   VFMSUBADDPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> MultiplySubtractAdd(Vector256<double> a, Vector256<double> b, Vector256<double> c) => MultiplySubtractAdd(a, b, c);
+
+        /// <summary>
+        /// __m128 _mm_fnmadd_ps (__m128 a, __m128 b, __m128 c)
+        ///   VFNMADDPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MultiplyAddNegated(Vector128<float> a, Vector128<float> b, Vector128<float> c) => MultiplyAddNegated(a, b, c);
+        /// <summary>
+        /// __m128d _mm_fnmadd_pd (__m128d a, __m128d b, __m128d c)
+        ///   VFNMADDPD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> MultiplyAddNegated(Vector128<double> a, Vector128<double> b, Vector128<double> c) => MultiplyAddNegated(a, b, c);
+        /// <summary>
+        /// __m256 _mm256_fnmadd_ps (__m256 a, __m256 b, __m256 c)
+        ///   VFNMADDPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> MultiplyAddNegated(Vector256<float> a, Vector256<float> b, Vector256<float> c) => MultiplyAddNegated(a, b, c);
+        /// <summary>
+        /// __m256d _mm256_fnmadd_pd (__m256d a, __m256d b, __m256d c)
+        ///   VFNMADDPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> MultiplyAddNegated(Vector256<double> a, Vector256<double> b, Vector256<double> c) => MultiplyAddNegated(a, b, c);
+
+        /// <summary>
+        /// __m128 _mm_fnmadd_ss (__m128 a, __m128 b, __m128 c)
+        ///   VFNMADDSS xmm, xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> MultiplyAddNegatedScalar(Vector128<float> a, Vector128<float> b, Vector128<float> c) => MultiplyAddNegatedScalar(a, b, c);
+        /// <summary>
+        /// __m128d _mm_fnmadd_sd (__m128d a, __m128d b, __m128d c)
+        ///   VFNMADDSD xmm, xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MultiplyAddNegatedScalar(Vector128<double> a, Vector128<double> b, Vector128<double> c) => MultiplyAddNegatedScalar(a, b, c);
+
+        /// <summary>
+        /// __m128 _mm_fnmsub_ps (__m128 a, __m128 b, __m128 c)
+        ///   VFNMSUBPS xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MultiplySubtractNegated(Vector128<float> a, Vector128<float> b, Vector128<float> c) => MultiplySubtractNegated(a, b, c);
+        /// <summary>
+        /// __m128d _mm_fnmsub_pd (__m128d a, __m128d b, __m128d c)
+        ///   VFNMSUBPD xmm, xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> MultiplySubtractNegated(Vector128<double> a, Vector128<double> b, Vector128<double> c) => MultiplySubtractNegated(a, b, c);
+        /// <summary>
+        /// __m256 _mm256_fnmsub_ps (__m256 a, __m256 b, __m256 c)
+        ///   VFNMSUBPS ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<float> MultiplySubtractNegated(Vector256<float> a, Vector256<float> b, Vector256<float> c) => MultiplySubtractNegated(a, b, c);
+        /// <summary>
+        /// __m256d _mm256_fnmsub_pd (__m256d a, __m256d b, __m256d c)
+        ///   VFNMSUBPD ymm, ymm, ymm/m256
+        /// </summary>
+        public static Vector256<double> MultiplySubtractNegated(Vector256<double> a, Vector256<double> b, Vector256<double> c) => MultiplySubtractNegated(a, b, c);
+
+        /// <summary>
+        /// __m128 _mm_fnmsub_ss (__m128 a, __m128 b, __m128 c)
+        ///   VFNMSUBSS xmm, xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> MultiplySubtractNegatedScalar(Vector128<float> a, Vector128<float> b, Vector128<float> c) => MultiplySubtractNegatedScalar(a, b, c);
+        /// <summary>
+        /// __m128d _mm_fnmsub_sd (__m128d a, __m128d b, __m128d c)
+        ///   VFNMSUBSD xmm, xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MultiplySubtractNegatedScalar(Vector128<double> a, Vector128<double> b, Vector128<double> c) => MultiplySubtractNegatedScalar(a, b, c);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Lzcnt.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Lzcnt.PlatformNotSupported.cs
new file mode 100644
index 0000000000..155ec63ffa
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Lzcnt.PlatformNotSupported.cs
@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel LZCNT hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Lzcnt
+    {
+        public static bool IsSupported { get { return false; } }
+
+        /// <summary>
+        /// unsigned int _lzcnt_u32 (unsigned int a)
+        ///   LZCNT reg, reg/m32
+        /// </summary>
+        public static uint LeadingZeroCount(uint value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned __int64 _lzcnt_u64 (unsigned __int64 a)
+        ///   LZCNT reg, reg/m64
+        /// </summary>
+        public static ulong LeadingZeroCount(ulong value) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Lzcnt.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Lzcnt.cs
new file mode 100644
index 0000000000..67a31050e2
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Lzcnt.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel LZCNT hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Lzcnt
+    {
+        public static bool IsSupported { get => IsSupported; }
+
+        /// <summary>
+        /// unsigned int _lzcnt_u32 (unsigned int a)
+        ///   LZCNT reg, reg/m32
+        /// </summary>
+        public static uint LeadingZeroCount(uint value) => LeadingZeroCount(value);
+        /// <summary>
+        /// unsigned __int64 _lzcnt_u64 (unsigned __int64 a)
+        ///   LZCNT reg, reg/m64
+        /// </summary>
+        public static ulong LeadingZeroCount(ulong value) => LeadingZeroCount(value);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Pclmulqdq.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Pclmulqdq.PlatformNotSupported.cs
new file mode 100644
index 0000000000..32e8519d22
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Pclmulqdq.PlatformNotSupported.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel PCLMULQDQ hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Pclmulqdq
+    {
+        public static bool IsSupported { get { return false; } }
+
+        /// <summary>
+        /// __m128i _mm_clmulepi64_si128 (__m128i a, __m128i b, const int imm8)
+        ///   PCLMULQDQ xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<long> CarryLessMultiply(Vector128<long> left, Vector128<long> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_clmulepi64_si128 (__m128i a, __m128i b, const int imm8)
+        ///   PCLMULQDQ xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ulong> CarryLessMultiply(Vector128<ulong> left, Vector128<ulong> right, byte control) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Pclmulqdq.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Pclmulqdq.cs
new file mode 100644
index 0000000000..0e009da715
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Pclmulqdq.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel PCLMULQDQ hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Pclmulqdq
+    {
+        public static bool IsSupported { get => IsSupported; }
+
+        /// <summary>
+        /// __m128i _mm_clmulepi64_si128 (__m128i a, __m128i b, const int imm8)
+        ///   PCLMULQDQ xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<long> CarryLessMultiply(Vector128<long> left, Vector128<long> right, byte control) => CarryLessMultiply(left, right, control);
+        /// <summary>
+        /// __m128i _mm_clmulepi64_si128 (__m128i a, __m128i b, const int imm8)
+        ///   PCLMULQDQ xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ulong> CarryLessMultiply(Vector128<ulong> left, Vector128<ulong> right, byte control) => CarryLessMultiply(left, right, control);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Popcnt.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Popcnt.PlatformNotSupported.cs
new file mode 100644
index 0000000000..1e153f6956
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Popcnt.PlatformNotSupported.cs
@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel POPCNT hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Popcnt
+    {
+        public static bool IsSupported { get { return false; } }
+
+        /// <summary>
+        /// int _mm_popcnt_u32 (unsigned int a)
+        ///   POPCNT reg, reg/m32
+        /// </summary>
+        public static int PopCount(uint value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int64 _mm_popcnt_u64 (unsigned __int64 a)
+        ///   POPCNT reg64, reg/m64
+        /// </summary>
+        public static long PopCount(ulong value) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Popcnt.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Popcnt.cs
new file mode 100644
index 0000000000..79f24c9fd9
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Popcnt.cs
@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel POPCNT hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Popcnt
+    {
+        public static bool IsSupported { get => IsSupported; }
+
+        /// <summary>
+        /// int _mm_popcnt_u32 (unsigned int a)
+        ///   POPCNT reg, reg/m32
+        /// </summary>
+        public static int PopCount(uint value) => PopCount(value);
+        /// <summary>
+        /// __int64 _mm_popcnt_u64 (unsigned __int64 a)
+        ///   POPCNT reg, reg/m64
+        /// </summary>
+        public static long PopCount(ulong value) => PopCount(value);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse.PlatformNotSupported.cs
new file mode 100644
index 0000000000..b667178490
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse.PlatformNotSupported.cs
@@ -0,0 +1,604 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel SSE hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Sse
+    {
+        public static bool IsSupported { get { return false; } }
+
+        /// <summary>
+        /// __m128 _mm_add_ps (__m128 a,  __m128 b)
+        ///   ADDPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Add(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_add_ss (__m128 a,  __m128 b)
+        ///   ADDSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> AddScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_and_ps (__m128 a, __m128 b)
+        ///   ANDPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> And(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_andnot_ps (__m128 a, __m128 b)
+        ///   ANDNPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> AndNot(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpeq_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(0)
+        /// </summary>
+        public static Vector128<float> CompareEqual(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_comieq_ss (__m128 a, __m128 b)
+        ///   COMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareEqualOrderedScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_ucomieq_ss (__m128 a, __m128 b)
+        ///   UCOMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareEqualUnorderedScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpeq_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(0)
+        /// </summary>
+        public static Vector128<float> CompareEqualScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpgt_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(6)
+        /// </summary>
+        public static Vector128<float> CompareGreaterThan(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_comigt_ss (__m128 a, __m128 b)
+        ///   COMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareGreaterThanOrderedScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_ucomigt_ss (__m128 a, __m128 b)
+        ///   UCOMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareGreaterThanUnorderedScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpgt_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(6)
+        /// </summary>
+        public static Vector128<float> CompareGreaterThanScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpge_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(5)
+        /// </summary>
+        public static Vector128<float> CompareGreaterThanOrEqual(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_comige_ss (__m128 a, __m128 b)
+        ///   COMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareGreaterThanOrEqualOrderedScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_ucomige_ss (__m128 a, __m128 b)
+        ///   UCOMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareGreaterThanOrEqualUnorderedScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpge_ss (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m32, imm8(5)
+        /// </summary>
+        public static Vector128<float> CompareGreaterThanOrEqualScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmplt_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(1)
+        /// </summary>
+        public static Vector128<float> CompareLessThan(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_comilt_ss (__m128 a, __m128 b)
+        ///   COMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareLessThanOrderedScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_ucomilt_ss (__m128 a, __m128 b)
+        ///   UCOMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareLessThanUnorderedScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmplt_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(1)
+        /// </summary>
+        public static Vector128<float> CompareLessThanScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmple_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(2)
+        /// </summary>
+        public static Vector128<float> CompareLessThanOrEqual(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_comile_ss (__m128 a, __m128 b)
+        ///   COMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareLessThanOrEqualOrderedScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_ucomile_ss (__m128 a, __m128 b)
+        ///   UCOMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareLessThanOrEqualUnorderedScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmple_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(2)
+        /// </summary>
+        public static Vector128<float> CompareLessThanOrEqualScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpneq_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(4)
+        /// </summary>
+        public static Vector128<float> CompareNotEqual(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_comineq_ss (__m128 a, __m128 b)
+        ///   COMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareNotEqualOrderedScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_ucomineq_ss (__m128 a, __m128 b)
+        ///   UCOMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareNotEqualUnorderedScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpneq_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(4)
+        /// </summary>
+        public static Vector128<float> CompareNotEqualScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpngt_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(2)
+        /// </summary>
+        public static Vector128<float> CompareNotGreaterThan(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpngt_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(2)
+        /// </summary>
+        public static Vector128<float> CompareNotGreaterThanScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpnge_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(1)
+        /// </summary>
+        public static Vector128<float> CompareNotGreaterThanOrEqual(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpnge_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(1)
+        /// </summary>
+        public static Vector128<float> CompareNotGreaterThanOrEqualScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpnlt_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(5)
+        /// </summary>
+        public static Vector128<float> CompareNotLessThan(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpnlt_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(5)
+        /// </summary>
+        public static Vector128<float> CompareNotLessThanScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpnle_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(6)
+        /// </summary>
+        public static Vector128<float> CompareNotLessThanOrEqual(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpnle_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(6)
+        /// </summary>
+        public static Vector128<float> CompareNotLessThanOrEqualScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpord_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(7)
+        /// </summary>
+        public static Vector128<float> CompareOrdered(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpord_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(7)
+        /// </summary>
+        public static Vector128<float> CompareOrderedScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpunord_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(3)
+        /// </summary>
+        public static Vector128<float> CompareUnordered(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cmpunord_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(3)
+        /// </summary>
+        public static Vector128<float> CompareUnorderedScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cvtss_si32 (__m128 a)
+        ///   CVTSS2SI r32, xmm/m32
+        /// </summary>
+        public static int ConvertToInt32(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int64 _mm_cvtss_si64 (__m128 a)
+        ///   CVTSS2SI r64, xmm/m32
+        /// </summary>
+        public static long ConvertToInt64(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// float _mm_cvtss_f32 (__m128 a)
+        ///   HELPER: MOVSS
+        /// </summary>
+        public static float ConvertToSingle(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_cvtsi32_ss (__m128 a, int b)
+        ///   CVTSI2SS xmm, reg/m32
+        /// </summary>
+        public static Vector128<float> ConvertScalarToVector128Single(Vector128<float> upper, int value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_cvtsi64_ss (__m128 a, __int64 b)
+        ///   CVTSI2SS xmm, reg/m64
+        /// </summary>
+        public static Vector128<float> ConvertScalarToVector128Single(Vector128<float> upper, long value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cvttss_si32 (__m128 a)
+        ///   CVTTSS2SI r32, xmm/m32
+        /// </summary>
+        public static int ConvertToInt32WithTruncation(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int64 _mm_cvttss_si64 (__m128 a)
+        ///   CVTTSS2SI r64, xmm/m32
+        /// </summary>
+        public static long ConvertToInt64WithTruncation(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_div_ps (__m128 a,  __m128 b)
+        ///   DIVPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Divide(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_div_ss (__m128 a,  __m128 b)
+        ///   DIVSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> DivideScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_loadu_ps (float const* mem_address)
+        ///   MOVUPS xmm, m128
+        /// </summary>
+        public static unsafe Vector128<float> LoadVector128(float* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_load_ss (float const* mem_address)
+        ///   MOVSS xmm, m32
+        /// </summary>
+        public static unsafe Vector128<float> LoadScalarVector128(float* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_load_ps (float const* mem_address)
+        ///   MOVAPS xmm, m128
+        /// </summary>
+        public static unsafe Vector128<float> LoadAlignedVector128(float* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_loadh_pi (__m128 a, __m64 const* mem_addr)
+        ///   MOVHPS xmm, m64
+        /// </summary>
+        public static unsafe Vector128<float> LoadHigh(Vector128<float> lower, float* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_loadl_pi (__m128 a, __m64 const* mem_addr)
+        ///   MOVLPS xmm, m64
+        /// </summary>
+        public static unsafe Vector128<float> LoadLow(Vector128<float> upper, float* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_max_ps (__m128 a,  __m128 b)
+        ///   MAXPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Max(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_max_ss (__m128 a,  __m128 b)
+        ///   MAXSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> MaxScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_min_ps (__m128 a,  __m128 b)
+        ///   MINPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Min(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_min_ss (__m128 a,  __m128 b)
+        ///   MINSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> MinScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_move_ss (__m128 a, __m128 b)
+        ///   MOVSS xmm, xmm
+        /// </summary>
+        public static Vector128<float> MoveScalar(Vector128<float> upper, Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_movehl_ps (__m128 a,  __m128 b)
+        ///   MOVHLPS xmm, xmm
+        /// </summary>
+        public static Vector128<float> MoveHighToLow(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_movelh_ps (__m128 a,  __m128 b)
+        ///   MOVLHPS xmm, xmm
+        /// </summary>
+        public static Vector128<float> MoveLowToHigh(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_movemask_ps (__m128 a)
+        ///   MOVMSKPS reg, xmm
+        /// </summary>
+        public static int MoveMask(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_mul_ps (__m128 a, __m128 b)
+        ///   MULPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Multiply(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_mul_ss (__m128 a, __m128 b)
+        ///   MULPS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> MultiplyScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_prefetch(char* p, int i)
+        ///   PREFETCHT0 m8
+        /// </summary>
+        public static unsafe void Prefetch0(void* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_prefetch(char* p, int i)
+        ///   PREFETCHT1 m8
+        /// </summary>
+        public static unsafe void Prefetch1(void* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_prefetch(char* p, int i)
+        ///   PREFETCHT2 m8
+        /// </summary>
+        public static unsafe void Prefetch2(void* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_prefetch(char* p, int i)
+        ///   PREFETCHNTA m8
+        /// </summary>
+        public static unsafe void PrefetchNonTemporal(void* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_or_ps (__m128 a,  __m128 b)
+        ///   ORPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Or(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_rcp_ps (__m128 a)
+        ///   RCPPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Reciprocal(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_rcp_ss (__m128 a)
+        ///   RCPSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> ReciprocalScalar(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_rcp_ss (__m128 a, __m128 b)
+        ///   RCPSS xmm, xmm/m32
+        /// The above native signature does not exist. We provide this additional overload for consistency with the other scalar APIs.
+        /// </summary>
+        public static Vector128<float> ReciprocalScalar(Vector128<float> upper, Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_rsqrt_ps (__m128 a)
+        ///   RSQRTPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> ReciprocalSqrt(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_rsqrt_ss (__m128 a)
+        ///   RSQRTSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> ReciprocalSqrtScalar(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_rsqrt_ss (__m128 a, __m128 b)
+        ///   RSQRTSS xmm, xmm/m32
+        /// The above native signature does not exist. We provide this additional overload for consistency with the other scalar APIs.
+        /// </summary>
+        public static Vector128<float> ReciprocalSqrtScalar(Vector128<float> upper, Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_set_ps (float e3, float e2, float e1, float e0)
+        /// </summary>
+        public static Vector128<float> SetVector128(float e3, float e2, float e1, float e0) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_set_ss (float a)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<float> SetScalarVector128(float value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_set1_ps (float a)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<float> SetAllVector128(float value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_setzero_ps (void)
+        ///   HELPER - XORPS
+        /// </summary>
+        public static Vector128<float> SetZeroVector128() { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_castpd_ps (__m128d a)
+        ///   HELPER - No Codegen
+        /// __m128i _mm_castpd_si128 (__m128d a)
+        ///   HELPER - No Codegen
+        /// __m128d _mm_castps_pd (__m128 a)
+        ///   HELPER - No Codegen
+        /// __m128i _mm_castps_si128 (__m128 a)
+        ///   HELPER - No Codegen
+        /// __m128d _mm_castsi128_pd (__m128i a)
+        ///   HELPER - No Codegen
+        /// __m128 _mm_castsi128_ps (__m128i a)
+        ///   HELPER - No Codegen
+        /// </summary>
+        public static Vector128<U> StaticCast<T, U>(Vector128<T> value) where T : struct where U : struct { throw new PlatformNotSupportedException(); }
+
+
+        /// <summary>
+        /// __m128 _mm_shuffle_ps (__m128 a,  __m128 b, unsigned int control)
+        ///   SHUFPS xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<float> Shuffle(Vector128<float> left, Vector128<float> right, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_sqrt_ps (__m128 a)
+        ///   SQRTPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Sqrt(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_sqrt_ss (__m128 a)
+        ///   SQRTSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> SqrtScalar(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_sqrt_ss (__m128 a, __m128 b)
+        ///   SQRTSS xmm, xmm/m32
+        /// The above native signature does not exist. We provide this additional overload for consistency with the other scalar APIs.
+        /// </summary>
+        public static Vector128<float> SqrtScalar(Vector128<float> upper, Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_store_ps (float* mem_addr, __m128 a)
+        ///   MOVAPS m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(float* address, Vector128<float> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_stream_ps (float* mem_addr, __m128 a)
+        ///   MOVNTPS m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(float* address, Vector128<float> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_storeu_ps (float* mem_addr, __m128 a)
+        ///   MOVUPS m128, xmm
+        /// </summary>
+        public static unsafe void Store(float* address, Vector128<float> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_sfence(void)
+        ///   SFENCE
+        /// </summary>
+        public static void StoreFence() { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_store_ss (float* mem_addr, __m128 a)
+        ///   MOVSS m32, xmm
+        /// </summary>
+        public static unsafe void StoreScalar(float* address, Vector128<float> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_storeh_pi (__m64* mem_addr, __m128 a)
+        ///   MOVHPS m64, xmm
+        /// </summary>
+        public static unsafe void StoreHigh(float* address, Vector128<float> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_storel_pi (__m64* mem_addr, __m128 a)
+        ///   MOVLPS m64, xmm
+        /// </summary>
+        public static unsafe void StoreLow(float* address, Vector128<float> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_sub_ps (__m128d a, __m128d b)
+        ///   SUBPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Subtract(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_sub_ss (__m128 a, __m128 b)
+        ///   SUBSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> SubtractScalar(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_unpackhi_ps (__m128 a,  __m128 b)
+        ///   UNPCKHPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> UnpackHigh(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_unpacklo_ps (__m128 a,  __m128 b)
+        ///   UNPCKLPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> UnpackLow(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_xor_ps (__m128 a,  __m128 b)
+        ///   XORPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Xor(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse.cs
new file mode 100644
index 0000000000..ecece0bd0a
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse.cs
@@ -0,0 +1,629 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel SSE hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Sse
+    {
+        public static bool IsSupported { get => IsSupported; }
+
+        /// <summary>
+        /// __m128 _mm_add_ps (__m128 a,  __m128 b)
+        ///   ADDPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Add(Vector128<float> left, Vector128<float> right) => Add(left, right);
+
+        /// <summary>
+        /// __m128 _mm_add_ss (__m128 a,  __m128 b)
+        ///   ADDSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> AddScalar(Vector128<float> left, Vector128<float> right) => AddScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_and_ps (__m128 a, __m128 b)
+        ///   ANDPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> And(Vector128<float> left, Vector128<float> right) => And(left, right);
+
+        /// <summary>
+        /// __m128 _mm_andnot_ps (__m128 a, __m128 b)
+        ///   ANDNPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> AndNot(Vector128<float> left, Vector128<float> right) => AndNot(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpeq_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(0)
+        /// </summary>
+        public static Vector128<float> CompareEqual(Vector128<float> left, Vector128<float> right) => CompareEqual(left, right);
+
+        /// <summary>
+        /// int _mm_comieq_ss (__m128 a, __m128 b)
+        ///   COMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareEqualOrderedScalar(Vector128<float> left, Vector128<float> right) => CompareEqualOrderedScalar(left, right);
+
+        /// <summary>
+        /// int _mm_ucomieq_ss (__m128 a, __m128 b)
+        ///   UCOMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareEqualUnorderedScalar(Vector128<float> left, Vector128<float> right) => CompareEqualUnorderedScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpeq_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(0)
+        /// </summary>
+        public static Vector128<float> CompareEqualScalar(Vector128<float> left, Vector128<float> right) => CompareEqualScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpgt_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(6)
+        /// </summary>
+        public static Vector128<float> CompareGreaterThan(Vector128<float> left, Vector128<float> right) => CompareGreaterThan(left, right);
+
+        /// <summary>
+        /// int _mm_comigt_ss (__m128 a, __m128 b)
+        ///   COMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareGreaterThanOrderedScalar(Vector128<float> left, Vector128<float> right) => CompareGreaterThanOrderedScalar(left, right);
+
+        /// <summary>
+        /// int _mm_ucomigt_ss (__m128 a, __m128 b)
+        ///   UCOMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareGreaterThanUnorderedScalar(Vector128<float> left, Vector128<float> right) => CompareGreaterThanUnorderedScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpgt_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(6)
+        /// </summary>
+        public static Vector128<float> CompareGreaterThanScalar(Vector128<float> left, Vector128<float> right) => CompareGreaterThanScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpge_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(5)
+        /// </summary>
+        public static Vector128<float> CompareGreaterThanOrEqual(Vector128<float> left, Vector128<float> right) => CompareGreaterThanOrEqual(left, right);
+
+        /// <summary>
+        /// int _mm_comige_ss (__m128 a, __m128 b)
+        ///   COMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareGreaterThanOrEqualOrderedScalar(Vector128<float> left, Vector128<float> right) => CompareGreaterThanOrEqualOrderedScalar(left, right);
+
+        /// <summary>
+        /// int _mm_ucomige_ss (__m128 a, __m128 b)
+        ///   UCOMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareGreaterThanOrEqualUnorderedScalar(Vector128<float> left, Vector128<float> right) => CompareGreaterThanOrEqualUnorderedScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpge_ss (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m32, imm8(5)
+        /// </summary>
+        public static Vector128<float> CompareGreaterThanOrEqualScalar(Vector128<float> left, Vector128<float> right) => CompareGreaterThanOrEqualScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmplt_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(1)
+        /// </summary>
+        public static Vector128<float> CompareLessThan(Vector128<float> left, Vector128<float> right) => CompareLessThan(left, right);
+
+        /// <summary>
+        /// int _mm_comilt_ss (__m128 a, __m128 b)
+        ///   COMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareLessThanOrderedScalar(Vector128<float> left, Vector128<float> right) => CompareLessThanOrderedScalar(left, right);
+
+        /// <summary>
+        /// int _mm_ucomilt_ss (__m128 a, __m128 b)
+        ///   UCOMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareLessThanUnorderedScalar(Vector128<float> left, Vector128<float> right) => CompareLessThanUnorderedScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmplt_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(1)
+        /// </summary>
+        public static Vector128<float> CompareLessThanScalar(Vector128<float> left, Vector128<float> right) => CompareLessThanScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmple_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(2)
+        /// </summary>
+        public static Vector128<float> CompareLessThanOrEqual(Vector128<float> left, Vector128<float> right) => CompareLessThanOrEqual(left, right);
+
+        /// <summary>
+        /// int _mm_comile_ss (__m128 a, __m128 b)
+        ///   COMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareLessThanOrEqualOrderedScalar(Vector128<float> left, Vector128<float> right) => CompareLessThanOrEqualOrderedScalar(left, right);
+
+        /// <summary>
+        /// int _mm_ucomile_ss (__m128 a, __m128 b)
+        ///   UCOMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareLessThanOrEqualUnorderedScalar(Vector128<float> left, Vector128<float> right) => CompareLessThanOrEqualUnorderedScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmple_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(2)
+        /// </summary>
+        public static Vector128<float> CompareLessThanOrEqualScalar(Vector128<float> left, Vector128<float> right) => CompareLessThanOrEqualScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpneq_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(4)
+        /// </summary>
+        public static Vector128<float> CompareNotEqual(Vector128<float> left, Vector128<float> right) => CompareNotEqual(left, right);
+
+        /// <summary>
+        /// int _mm_comineq_ss (__m128 a, __m128 b)
+        ///   COMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareNotEqualOrderedScalar(Vector128<float> left, Vector128<float> right) => CompareNotEqualOrderedScalar(left, right);
+
+        /// <summary>
+        /// int _mm_ucomineq_ss (__m128 a, __m128 b)
+        ///   UCOMISS xmm, xmm/m32
+        /// </summary>
+        public static bool CompareNotEqualUnorderedScalar(Vector128<float> left, Vector128<float> right) => CompareNotEqualUnorderedScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpneq_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(4)
+        /// </summary>
+        public static Vector128<float> CompareNotEqualScalar(Vector128<float> left, Vector128<float> right) => CompareNotEqualScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpngt_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(2)
+        /// </summary>
+        public static Vector128<float> CompareNotGreaterThan(Vector128<float> left, Vector128<float> right) => CompareNotGreaterThan(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpngt_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(2)
+        /// </summary>
+        public static Vector128<float> CompareNotGreaterThanScalar(Vector128<float> left, Vector128<float> right) => CompareNotGreaterThanScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpnge_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(1)
+        /// </summary>
+        public static Vector128<float> CompareNotGreaterThanOrEqual(Vector128<float> left, Vector128<float> right) => CompareNotGreaterThanOrEqual(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpnge_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(1)
+        /// </summary>
+        public static Vector128<float> CompareNotGreaterThanOrEqualScalar(Vector128<float> left, Vector128<float> right) => CompareNotGreaterThanOrEqualScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpnlt_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(5)
+        /// </summary>
+        public static Vector128<float> CompareNotLessThan(Vector128<float> left, Vector128<float> right) => CompareNotLessThan(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpnlt_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(5)
+        /// </summary>
+        public static Vector128<float> CompareNotLessThanScalar(Vector128<float> left, Vector128<float> right) => CompareNotLessThanScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpnle_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(6)
+        /// </summary>
+        public static Vector128<float> CompareNotLessThanOrEqual(Vector128<float> left, Vector128<float> right) => CompareNotLessThanOrEqual(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpnle_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(6)
+        /// </summary>
+        public static Vector128<float> CompareNotLessThanOrEqualScalar(Vector128<float> left, Vector128<float> right) => CompareNotLessThanOrEqualScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpord_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(7)
+        /// </summary>
+        public static Vector128<float> CompareOrdered(Vector128<float> left, Vector128<float> right) => CompareOrdered(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpord_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(7)
+        /// </summary>
+        public static Vector128<float> CompareOrderedScalar(Vector128<float> left, Vector128<float> right) => CompareOrderedScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpunord_ps (__m128 a,  __m128 b)
+        ///   CMPPS xmm, xmm/m128, imm8(3)
+        /// </summary>
+        public static Vector128<float> CompareUnordered(Vector128<float> left, Vector128<float> right) => CompareUnordered(left, right);
+
+        /// <summary>
+        /// __m128 _mm_cmpunord_ss (__m128 a,  __m128 b)
+        ///   CMPSS xmm, xmm/m32, imm8(3)
+        /// </summary>
+        public static Vector128<float> CompareUnorderedScalar(Vector128<float> left, Vector128<float> right) => CompareUnorderedScalar(left, right);
+
+        /// <summary>
+        /// int _mm_cvtss_si32 (__m128 a)
+        ///   CVTSS2SI r32, xmm/m32
+        /// </summary>
+        public static int ConvertToInt32(Vector128<float> value) => ConvertToInt32(value);
+        /// <summary>
+        /// __int64 _mm_cvtss_si64 (__m128 a)
+        ///   CVTSS2SI r64, xmm/m32
+        /// </summary>
+        public static long ConvertToInt64(Vector128<float> value) => ConvertToInt64(value);
+
+        /// <summary>
+        /// float _mm_cvtss_f32 (__m128 a)
+        ///   HELPER: MOVSS
+        /// </summary>
+        public static float ConvertToSingle(Vector128<float> value) => ConvertToSingle(value);
+
+        /// <summary>
+        /// __m128 _mm_cvtsi32_ss (__m128 a, int b)
+        ///   CVTSI2SS xmm, reg/m32
+        /// </summary>
+        public static Vector128<float> ConvertScalarToVector128Single(Vector128<float> upper, int value) => ConvertScalarToVector128Single(upper, value);
+        /// <summary>
+        /// __m128 _mm_cvtsi64_ss (__m128 a, __int64 b)
+        ///   CVTSI2SS xmm, reg/m64
+        /// </summary>
+        public static Vector128<float> ConvertScalarToVector128Single(Vector128<float> upper, long value) => ConvertScalarToVector128Single(upper, value);
+
+        /// <summary>
+        /// int _mm_cvttss_si32 (__m128 a)
+        ///   CVTTSS2SI r32, xmm/m32
+        /// </summary>
+        public static int ConvertToInt32WithTruncation(Vector128<float> value) => ConvertToInt32WithTruncation(value);
+        /// <summary>
+        /// __int64 _mm_cvttss_si64 (__m128 a)
+        ///   CVTTSS2SI r64, xmm/m32
+        /// </summary>
+        public static long ConvertToInt64WithTruncation(Vector128<float> value) => ConvertToInt64WithTruncation(value);
+
+        /// <summary>
+        /// __m128 _mm_div_ps (__m128 a,  __m128 b)
+        ///   DIVPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Divide(Vector128<float> left, Vector128<float> right) => Divide(left, right);
+
+        /// <summary>
+        /// __m128 _mm_div_ss (__m128 a,  __m128 b)
+        ///   DIVSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> DivideScalar(Vector128<float> left, Vector128<float> right) => DivideScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_loadu_ps (float const* mem_address)
+        ///   MOVUPS xmm, m128
+        /// </summary>
+        public static unsafe Vector128<float> LoadVector128(float* address) => LoadVector128(address);
+
+        /// <summary>
+        /// __m128 _mm_load_ss (float const* mem_address)
+        ///   MOVSS xmm, m32
+        /// </summary>
+        public static unsafe Vector128<float> LoadScalarVector128(float* address) => LoadScalarVector128(address);
+
+        /// <summary>
+        /// __m128 _mm_load_ps (float const* mem_address)
+        ///   MOVAPS xmm, m128
+        /// </summary>
+        public static unsafe Vector128<float> LoadAlignedVector128(float* address) => LoadAlignedVector128(address);
+
+        /// <summary>
+        /// __m128 _mm_loadh_pi (__m128 a, __m64 const* mem_addr)
+        ///   MOVHPS xmm, m64
+        /// </summary>
+        public static unsafe Vector128<float> LoadHigh(Vector128<float> lower, float* address) => LoadHigh(lower, address);
+
+        /// <summary>
+        /// __m128 _mm_loadl_pi (__m128 a, __m64 const* mem_addr)
+        ///   MOVLPS xmm, m64
+        /// </summary>
+        public static unsafe Vector128<float> LoadLow(Vector128<float> upper, float* address) => LoadLow(upper, address);
+
+        /// <summary>
+        /// __m128 _mm_max_ps (__m128 a,  __m128 b)
+        ///   MAXPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Max(Vector128<float> left, Vector128<float> right) => Max(left, right);
+
+        /// <summary>
+        /// __m128 _mm_max_ss (__m128 a,  __m128 b)
+        ///   MAXSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> MaxScalar(Vector128<float> left, Vector128<float> right) => MaxScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_min_ps (__m128 a,  __m128 b)
+        ///   MINPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Min(Vector128<float> left, Vector128<float> right) => Min(left, right);
+
+        /// <summary>
+        /// __m128 _mm_min_ss (__m128 a,  __m128 b)
+        ///   MINSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> MinScalar(Vector128<float> left, Vector128<float> right) => MinScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_move_ss (__m128 a, __m128 b)
+        ///   MOVSS xmm, xmm
+        /// </summary>
+        public static Vector128<float> MoveScalar(Vector128<float> upper, Vector128<float> value) => MoveScalar(upper, value);
+
+        /// <summary>
+        /// __m128 _mm_movehl_ps (__m128 a,  __m128 b)
+        ///   MOVHLPS xmm, xmm
+        /// </summary>
+        public static Vector128<float> MoveHighToLow(Vector128<float> left, Vector128<float> right) => MoveHighToLow(left, right);
+
+        /// <summary>
+        /// __m128 _mm_movelh_ps (__m128 a,  __m128 b)
+        ///   MOVLHPS xmm, xmm
+        /// </summary>
+        public static Vector128<float> MoveLowToHigh(Vector128<float> left, Vector128<float> right) => MoveLowToHigh(left, right);
+
+        /// <summary>
+        /// int _mm_movemask_ps (__m128 a)
+        ///   MOVMSKPS reg, xmm
+        /// </summary>
+        public static int MoveMask(Vector128<float> value) => MoveMask(value);
+
+        /// <summary>
+        /// __m128 _mm_mul_ps (__m128 a, __m128 b)
+        ///   MULPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Multiply(Vector128<float> left, Vector128<float> right) => Multiply(left, right);
+
+        /// <summary>
+        /// __m128 _mm_mul_ss (__m128 a, __m128 b)
+        ///   MULPS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> MultiplyScalar(Vector128<float> left, Vector128<float> right) => MultiplyScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_or_ps (__m128 a,  __m128 b)
+        ///   ORPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Or(Vector128<float> left, Vector128<float> right) => Or(left, right);
+
+        /// <summary>
+        /// void _mm_prefetch(char* p, int i)
+        ///   PREFETCHT0 m8
+        /// </summary>
+        public static unsafe void Prefetch0(void* address) => Prefetch0(address);
+
+        /// <summary>
+        /// void _mm_prefetch(char* p, int i)
+        ///   PREFETCHT1 m8
+        /// </summary>
+        public static unsafe void Prefetch1(void* address) => Prefetch1(address);
+
+        /// <summary>
+        /// void _mm_prefetch(char* p, int i)
+        ///   PREFETCHT2 m8
+        /// </summary>
+        public static unsafe void Prefetch2(void* address) => Prefetch2(address);
+
+        /// <summary>
+        /// void _mm_prefetch(char* p, int i)
+        ///   PREFETCHNTA m8
+        /// </summary>
+        public static unsafe void PrefetchNonTemporal(void* address) => PrefetchNonTemporal(address);
+
+        /// <summary>
+        /// __m128 _mm_rcp_ps (__m128 a)
+        ///   RCPPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Reciprocal(Vector128<float> value) => Reciprocal(value);
+
+        /// <summary>
+        /// __m128 _mm_rcp_ss (__m128 a)
+        ///   RCPSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> ReciprocalScalar(Vector128<float> value) => ReciprocalScalar(value);
+
+        /// <summary>
+        /// __m128 _mm_rcp_ss (__m128 a, __m128 b)
+        ///   RCPSS xmm, xmm/m32
+        /// The above native signature does not exist. We provide this additional overload for consistency with the other scalar APIs.
+        /// </summary>
+        public static Vector128<float> ReciprocalScalar(Vector128<float> upper, Vector128<float> value) => ReciprocalScalar(upper, value);
+
+        /// <summary>
+        /// __m128 _mm_rsqrt_ps (__m128 a)
+        ///   RSQRTPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> ReciprocalSqrt(Vector128<float> value) => ReciprocalSqrt(value);
+
+        /// <summary>
+        /// __m128 _mm_rsqrt_ss (__m128 a)
+        ///   RSQRTSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> ReciprocalSqrtScalar(Vector128<float> value) => ReciprocalSqrtScalar(value);
+
+        /// <summary>
+        /// __m128 _mm_rsqrt_ss (__m128 a, __m128 b)
+        ///   RSQRTSS xmm, xmm/m32
+        /// The above native signature does not exist. We provide this additional overload for consistency with the other scalar APIs.
+        /// </summary>
+        public static Vector128<float> ReciprocalSqrtScalar(Vector128<float> upper, Vector128<float> value) => ReciprocalSqrtScalar(upper, value);
+
+        /// <summary>
+        /// __m128 _mm_set1_ps (float a)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<float> SetAllVector128(float value)
+        {
+            // Zero vector and load value et index 0
+            Vector128<float> vector = SetScalarVector128(value);
+            // Create { vl vl vl vl } and return result
+            return Shuffle(vector, vector, 0);
+        }
+
+        /// <summary>
+        /// __m128 _mm_set_ss (float a)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<float> SetScalarVector128(float value) => SetScalarVector128(value);
+
+        /// <summary>
+        /// __m128 _mm_set_ps (float e3, float e2, float e1, float e0)
+        /// </summary>
+        public static unsafe Vector128<float> SetVector128(float e3, float e2, float e1, float e0)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load e2 et index 0
+            Vector128<float> e2Vector = SetScalarVector128(e2);
+            Vector128<float> e1Vector = SetScalarVector128(e1);
+            Vector128<float> e0Vector = SetScalarVector128(e0);
+            // Create { -- -- e2 e0 }
+            e0Vector = UnpackLow(e0Vector, e2Vector);
+            e2Vector = SetScalarVector128(e3);
+            // Create { -- -- e3 e1 }
+            e1Vector = UnpackLow(e1Vector, e2Vector);
+            // Create { e3 e2 e1 e0 } and return result
+            return UnpackLow(e0Vector, e1Vector);
+        }
+
+        /// <summary>
+        /// __m128d _mm_setzero_ps (void)
+        ///   HELPER - XORPS
+        /// </summary>
+        public static Vector128<float> SetZeroVector128() => SetZeroVector128();
+
+        /// <summary>
+        /// __m128 _mm_castpd_ps (__m128d a)
+        ///   HELPER - No Codegen
+        /// __m128i _mm_castpd_si128 (__m128d a)
+        ///   HELPER - No Codegen
+        /// __m128d _mm_castps_pd (__m128 a)
+        ///   HELPER - No Codegen
+        /// __m128i _mm_castps_si128 (__m128 a)
+        ///   HELPER - No Codegen
+        /// __m128d _mm_castsi128_pd (__m128i a)
+        ///   HELPER - No Codegen
+        /// __m128 _mm_castsi128_ps (__m128i a)
+        ///   HELPER - No Codegen
+        /// </summary>
+        public static Vector128<U> StaticCast<T, U>(Vector128<T> value) where T : struct where U : struct
+        {
+            return StaticCast<T, U>(value);
+        }
+
+        /// <summary>
+        /// __m128 _mm_shuffle_ps (__m128 a,  __m128 b, unsigned int control)
+        ///   SHUFPS xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<float> Shuffle(Vector128<float> left, Vector128<float> right, byte control) => Shuffle(left, right, control);
+
+        /// <summary>
+        /// __m128 _mm_sqrt_ps (__m128 a)
+        ///   SQRTPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Sqrt(Vector128<float> value) => Sqrt(value);
+
+        /// <summary>
+        /// __m128 _mm_sqrt_ss (__m128 a)
+        ///   SQRTSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> SqrtScalar(Vector128<float> value) => SqrtScalar(value);
+
+        /// <summary>
+        /// __m128 _mm_sqrt_ss (__m128 a, __m128 b)
+        ///   SQRTSS xmm, xmm/m32
+        /// The above native signature does not exist. We provide this additional overload for consistency with the other scalar APIs.
+        /// </summary>
+        public static Vector128<float> SqrtScalar(Vector128<float> upper, Vector128<float> value) => SqrtScalar(upper, value);
+
+        /// <summary>
+        /// void _mm_store_ps (float* mem_addr, __m128 a)
+        ///   MOVAPS m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(float* address, Vector128<float> source) => StoreAligned(address, source);
+
+        /// <summary>
+        /// void _mm_stream_ps (float* mem_addr, __m128 a)
+        ///   MOVNTPS m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(float* address, Vector128<float> source) => StoreAlignedNonTemporal(address, source);
+
+        /// <summary>
+        /// void _mm_storeu_ps (float* mem_addr, __m128 a)
+        ///   MOVUPS m128, xmm
+        /// </summary>
+        public static unsafe void Store(float* address, Vector128<float> source) => Store(address, source);
+
+        /// <summary>
+        /// void _mm_sfence(void)
+        ///   SFENCE
+        /// </summary>
+        public static void StoreFence() => StoreFence();
+
+        /// <summary>
+        /// void _mm_store_ss (float* mem_addr, __m128 a)
+        ///   MOVSS m32, xmm
+        /// </summary>
+        public static unsafe void StoreScalar(float* address, Vector128<float> source) => StoreScalar(address, source);
+
+        /// <summary>
+        /// void _mm_storeh_pi (__m64* mem_addr, __m128 a)
+        ///   MOVHPS m64, xmm
+        /// </summary>
+        public static unsafe void StoreHigh(float* address, Vector128<float> source) => StoreHigh(address, source);
+
+        /// <summary>
+        /// void _mm_storel_pi (__m64* mem_addr, __m128 a)
+        ///   MOVLPS m64, xmm
+        /// </summary>
+        public static unsafe void StoreLow(float* address, Vector128<float> source) => StoreLow(address, source);
+
+        /// <summary>
+        /// __m128d _mm_sub_ps (__m128d a, __m128d b)
+        ///   SUBPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Subtract(Vector128<float> left, Vector128<float> right) => Subtract(left, right);
+
+        /// <summary>
+        /// __m128 _mm_sub_ss (__m128 a, __m128 b)
+        ///   SUBSS xmm, xmm/m32
+        /// </summary>
+        public static Vector128<float> SubtractScalar(Vector128<float> left, Vector128<float> right) => SubtractScalar(left, right);
+
+        /// <summary>
+        /// __m128 _mm_unpackhi_ps (__m128 a,  __m128 b)
+        ///   UNPCKHPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> UnpackHigh(Vector128<float> left, Vector128<float> right) => UnpackHigh(left, right);
+
+        /// <summary>
+        /// __m128 _mm_unpacklo_ps (__m128 a,  __m128 b)
+        ///   UNPCKLPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> UnpackLow(Vector128<float> left, Vector128<float> right) => UnpackLow(left, right);
+
+        /// <summary>
+        /// __m128 _mm_xor_ps (__m128 a,  __m128 b)
+        ///   XORPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> Xor(Vector128<float> left, Vector128<float> right) => Xor(left, right);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse2.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse2.PlatformNotSupported.cs
new file mode 100644
index 0000000000..8aaa454eeb
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse2.PlatformNotSupported.cs
@@ -0,0 +1,1766 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel SSE2 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Sse2
+    {
+        public static bool IsSupported { get { return false; } }
+        
+                /// <summary>
+        /// __m128i _mm_add_epi8 (__m128i a,  __m128i b)
+        ///   PADDB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Add(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_add_epi8 (__m128i a,  __m128i b)
+        ///   PADDB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Add(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_add_epi16 (__m128i a,  __m128i b)
+        ///   PADDW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> Add(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_add_epi16 (__m128i a,  __m128i b)
+        ///   PADDW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Add(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_add_epi32 (__m128i a,  __m128i b)
+        ///   PADDD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> Add(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_add_epi32 (__m128i a,  __m128i b)
+        ///   PADDD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> Add(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_add_epi64 (__m128i a,  __m128i b)
+        ///   PADDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> Add(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_add_epi64 (__m128i a,  __m128i b)
+        ///   PADDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> Add(Vector128<ulong> left, Vector128<ulong> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_add_pd (__m128d a,  __m128d b)
+        ///   ADDPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Add(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_add_sd (__m128d a,  __m128d b)
+        ///   ADDSD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> AddScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_adds_epi8 (__m128i a,  __m128i b)
+        ///   PADDSB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> AddSaturate(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_adds_epu8 (__m128i a,  __m128i b)
+        ///   PADDUSB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> AddSaturate(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_adds_epi16 (__m128i a,  __m128i b)
+        ///   PADDSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> AddSaturate(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_adds_epu16 (__m128i a,  __m128i b)
+        ///   PADDUSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> AddSaturate(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> And(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> And(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> And(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> And(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> And(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> And(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> And(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> And(Vector128<ulong> left, Vector128<ulong> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_and_pd (__m128d a, __m128d b)
+        ///   ANDPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> And(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> AndNot(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> AndNot(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> AndNot(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> AndNot(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> AndNot(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> AndNot(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> AndNot(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> AndNot(Vector128<ulong> left, Vector128<ulong> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_andnot_pd (__m128d a, __m128d b)
+        ///   ADDNPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> AndNot(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_avg_epu8 (__m128i a,  __m128i b)
+        ///   PAVGB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Average(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_avg_epu16 (__m128i a,  __m128i b)
+        ///   PAVGW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Average(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi8 (__m128i a,  __m128i b)
+        ///   PCMPEQB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> CompareEqual(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi8 (__m128i a,  __m128i b)
+        ///   PCMPEQB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> CompareEqual(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi16 (__m128i a,  __m128i b)
+        ///   PCMPEQW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> CompareEqual(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi16 (__m128i a,  __m128i b)
+        ///   PCMPEQW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> CompareEqual(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi32 (__m128i a,  __m128i b)
+        ///   PCMPEQD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> CompareEqual(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi32 (__m128i a,  __m128i b)
+        ///   PCMPEQD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> CompareEqual(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_cmpeq_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(0)
+        /// </summary>
+        public static Vector128<double> CompareEqual(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_comieq_sd (__m128d a, __m128d b)
+        ///   COMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareEqualOrderedScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_ucomieq_sd (__m128d a, __m128d b)
+        ///   UCOMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareEqualUnorderedScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpeq_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(0)
+        /// </summary>
+        public static Vector128<double> CompareEqualScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpgt_epi8 (__m128i a,  __m128i b)
+        ///   PCMPGTB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> CompareGreaterThan(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cmpgt_epi16 (__m128i a,  __m128i b)
+        ///   PCMPGTW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> CompareGreaterThan(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cmpgt_epi32 (__m128i a,  __m128i b)
+        ///   PCMPGTD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> CompareGreaterThan(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_cmpgt_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(6)
+        /// </summary>
+        public static Vector128<double> CompareGreaterThan(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_comigt_sd (__m128d a, __m128d b)
+        ///   COMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareGreaterThanOrderedScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_ucomigt_sd (__m128d a, __m128d b)
+        ///   UCOMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareGreaterThanUnorderedScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpgt_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(6)
+        /// </summary>
+        public static Vector128<double> CompareGreaterThanScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpge_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(5)
+        /// </summary>
+        public static Vector128<double> CompareGreaterThanOrEqual(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_comige_sd (__m128d a, __m128d b)
+        ///   COMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareGreaterThanOrEqualOrderedScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_ucomige_sd (__m128d a, __m128d b)
+        ///   UCOMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareGreaterThanOrEqualUnorderedScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpge_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(5)
+        /// </summary>
+        public static Vector128<double> CompareGreaterThanOrEqualScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmplt_epi8 (__m128i a,  __m128i b)
+        ///   PCMPGTB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> CompareLessThan(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cmplt_epi16 (__m128i a,  __m128i b)
+        ///   PCMPGTW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> CompareLessThan(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cmplt_epi32 (__m128i a,  __m128i b)
+        ///   PCMPGTD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> CompareLessThan(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_cmplt_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(1)
+        /// </summary>
+        public static Vector128<double> CompareLessThan(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_comilt_sd (__m128d a, __m128d b)
+        ///   COMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareLessThanOrderedScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_ucomilt_sd (__m128d a, __m128d b)
+        ///   UCOMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareLessThanUnorderedScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmplt_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(1)
+        /// </summary>
+        public static Vector128<double> CompareLessThanScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmple_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(2)
+        /// </summary>
+        public static Vector128<double> CompareLessThanOrEqual(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_comile_sd (__m128d a, __m128d b)
+        ///   COMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareLessThanOrEqualOrderedScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_ucomile_sd (__m128d a, __m128d b)
+        ///   UCOMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareLessThanOrEqualUnorderedScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmple_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(2)
+        /// </summary>
+        public static Vector128<double> CompareLessThanOrEqualScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpneq_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(4)
+        /// </summary>
+        public static Vector128<double> CompareNotEqual(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_comineq_sd (__m128d a, __m128d b)
+        ///   COMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareNotEqualOrderedScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_ucomineq_sd (__m128d a, __m128d b)
+        ///   UCOMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareNotEqualUnorderedScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpneq_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(4)
+        /// </summary>
+        public static Vector128<double> CompareNotEqualScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpngt_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(2)
+        /// </summary>
+        public static Vector128<double> CompareNotGreaterThan(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpngt_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(2)
+        /// </summary>
+        public static Vector128<double> CompareNotGreaterThanScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpnge_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(1)
+        /// </summary>
+        public static Vector128<double> CompareNotGreaterThanOrEqual(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpnge_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(1)
+        /// </summary>
+        public static Vector128<double> CompareNotGreaterThanOrEqualScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpnlt_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(5)
+        /// </summary>
+        public static Vector128<double> CompareNotLessThan(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpnlt_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(5)
+        /// </summary>
+        public static Vector128<double> CompareNotLessThanScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpnle_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(6)
+        /// </summary>
+        public static Vector128<double> CompareNotLessThanOrEqual(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpnle_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(6)
+        /// </summary>
+        public static Vector128<double> CompareNotLessThanOrEqualScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpord_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(7)
+        /// </summary>
+        public static Vector128<double> CompareOrdered(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpord_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(7)
+        /// </summary>
+        public static Vector128<double> CompareOrderedScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpunord_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(3)
+        /// </summary>
+        public static Vector128<double> CompareUnordered(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cmpunord_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(3)
+        /// </summary>
+        public static Vector128<double> CompareUnorderedScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cvtps_epi32 (__m128 a)
+        ///   CVTPS2DQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtpd_epi32 (__m128d a)
+        ///   CVTPD2DQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_cvtepi32_ps (__m128i a)
+        ///   CVTDQ2PS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> ConvertToVector128Single(Vector128<int> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_cvtpd_ps (__m128d a)
+        ///   CVTPD2PS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> ConvertToVector128Single(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_cvtepi32_pd (__m128i a)
+        ///   CVTDQ2PD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> ConvertToVector128Double(Vector128<int> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_cvtps_pd (__m128 a)
+        ///   CVTPS2PD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> ConvertToVector128Double(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// double _mm_cvtsd_f64(__m128d a)
+        ///   HELPER: MOVSD
+        /// </summary>
+        public static double ConvertToDouble(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm_cvtsd_si32 (__m128d a)
+        ///   CVTSD2SI r32, xmm/m64
+        /// </summary>
+        public static int ConvertToInt32(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm_cvtsi128_si32 (__m128i a)
+        ///   MOVD reg/m32, xmm
+        /// </summary>
+        public static int ConvertToInt32(Vector128<int> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int64 _mm_cvtsd_si64 (__m128d a)
+        ///   CVTSD2SI r64, xmm/m64
+        /// </summary>
+        public static long ConvertToInt64(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int64 _mm_cvtsi128_si64 (__m128i a)
+        ///   MOVQ reg/m64, xmm
+        /// </summary>
+        public static long ConvertToInt64(Vector128<long> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm_cvtsi128_si32 (__m128i a)
+        ///   MOVD reg/m32, xmm
+        /// </summary>
+        public static uint ConvertToUInt32(Vector128<uint> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int64 _mm_cvtsi128_si64 (__m128i a)
+        ///   MOVQ reg/m64, xmm
+        /// </summary>
+        public static ulong ConvertToUInt64(Vector128<ulong> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_cvtsi32_sd (__m128d a, int b)
+        ///   CVTSI2SD xmm, reg/m64
+        /// </summary>
+        public static Vector128<double> ConvertScalarToVector128Double(Vector128<double> upper, int value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_cvtsi64_sd (__m128d a, int b)
+        ///   CVTSI2SD xmm, reg/m64
+        /// </summary>
+        public static Vector128<double> ConvertScalarToVector128Double(Vector128<double> upper, long value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_cvtss_sd (__m128d a, __m128 b)
+        ///   CVTSS2SD xmm, xmm/m32
+        /// </summary>
+        public static Vector128<double> ConvertScalarToVector128Double(Vector128<double> upper, Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtsi32_si128 (int a)
+        ///   MOVD xmm, reg/m32
+        /// </summary>
+        public static Vector128<int> ConvertScalarToVector128Int32(int value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtsi64_si128 (__int64 a)
+        ///   MOVQ xmm, reg/m64
+        /// </summary>
+        public static Vector128<long> ConvertScalarToVector128Int64(long value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_cvtsd_ss (__m128 a, __m128d b)
+        ///   CVTSD2SS xmm, xmm/m64
+        /// </summary>
+        public static Vector128<float> ConvertScalarToVector128Single(Vector128<float> upper, Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtsi32_si128 (int a)
+        ///   MOVD xmm, reg/m32
+        /// </summary>
+        public static Vector128<uint> ConvertScalarToVector128UInt32(uint value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtsi64_si128 (__int64 a)
+        ///   MOVQ xmm, reg/m64
+        /// </summary>
+        public static Vector128<ulong> ConvertScalarToVector128UInt64(ulong value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cvttps_epi32 (__m128 a)
+        ///   CVTTPS2DQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32WithTruncation(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvttpd_epi32 (__m128d a)
+        ///   CVTTPD2DQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32WithTruncation(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cvttsd_si32 (__m128d a)
+        ///   CVTTSD2SI reg, xmm/m64
+        /// </summary>
+        public static int ConvertToInt32WithTruncation(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int64 _mm_cvttsd_si64 (__m128d a)
+        ///   CVTTSD2SI reg, xmm/m64
+        /// </summary>
+        public static long ConvertToInt64WithTruncation(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_div_pd (__m128d a,  __m128d b)
+        ///   DIVPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Divide(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_div_sd (__m128d a,  __m128d b)
+        ///   DIVSD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> DivideScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_extract_epi16 (__m128i a,  int immediate)
+        ///   PEXTRW reg, xmm, imm8
+        /// </summary>
+        public static short Extract(Vector128<short> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm_extract_epi16 (__m128i a,  int immediate)
+        ///   PEXTRW reg, xmm, imm8
+        /// </summary>
+        public static ushort Extract(Vector128<ushort> value, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_insert_epi16 (__m128i a,  int i, int immediate)
+        ///   PINSRW xmm, reg/m16, imm8
+        /// </summary>
+        public static Vector128<short> Insert(Vector128<short> value, short data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_insert_epi16 (__m128i a,  int i, int immediate)
+        ///   PINSRW xmm, reg/m16, imm8
+        /// </summary>
+        public static Vector128<ushort> Insert(Vector128<ushort> value, ushort data, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<sbyte> LoadVector128(sbyte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<byte> LoadVector128(byte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<short> LoadVector128(short* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<ushort> LoadVector128(ushort* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<int> LoadVector128(int* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<uint> LoadVector128(uint* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<long> LoadVector128(long* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<ulong> LoadVector128(ulong* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_loadu_pd (double const* mem_address)
+        ///   MOVUPD xmm, m128
+        /// </summary>
+        public static unsafe Vector128<double> LoadVector128(double* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_load_sd (double const* mem_address)
+        ///   MOVSD xmm, m64
+        /// </summary>
+        public static unsafe Vector128<double> LoadScalarVector128(double* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<sbyte> LoadAlignedVector128(sbyte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<byte> LoadAlignedVector128(byte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<short> LoadAlignedVector128(short* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<ushort> LoadAlignedVector128(ushort* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<int> LoadAlignedVector128(int* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<uint> LoadAlignedVector128(uint* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<long> LoadAlignedVector128(long* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<ulong> LoadAlignedVector128(ulong* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_load_pd (double const* mem_address)
+        ///   MOVAPD xmm, m128
+        /// </summary>
+        public static unsafe Vector128<double> LoadAlignedVector128(double* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_lfence(void)
+        ///   LFENCE
+        /// </summary>
+        public static void LoadFence() { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_loadh_pd (__m128d a, double const* mem_addr)
+        ///   MOVHPD xmm, m64
+        /// </summary>
+        public static unsafe Vector128<double> LoadHigh(Vector128<double> lower, double* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_loadl_pd (__m128d a, double const* mem_addr)
+        ///   MOVLPD xmm, m64
+        /// </summary>
+        public static unsafe Vector128<double> LoadLow(Vector128<double> upper, double* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_loadl_epi32 (__m128i const* mem_addr)
+        ///   MOVD xmm, reg/m64
+        /// The above native signature does not exist. We provide this additional overload for completeness.
+        /// </summary>
+        public static unsafe Vector128<int> LoadScalarVector128(int* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_loadl_epi32 (__m128i const* mem_addr)
+        ///   MOVD xmm, reg/m64
+        /// The above native signature does not exist. We provide this additional overload for completeness.
+        /// </summary>
+        public static unsafe Vector128<uint> LoadScalarVector128(uint* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_loadl_epi64 (__m128i const* mem_addr)
+        ///   MOVQ xmm, reg/m64
+        /// </summary>
+        public static unsafe Vector128<long> LoadScalarVector128(long* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_loadl_epi64 (__m128i const* mem_addr)
+        ///   MOVQ xmm, reg/m64
+        /// </summary>
+        public static unsafe Vector128<ulong> LoadScalarVector128(ulong* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_maskmoveu_si128 (__m128i a,  __m128i mask, char* mem_address)
+        ///   MASKMOVDQU xmm, xmm
+        /// </summary>
+        public static unsafe void MaskMove(Vector128<sbyte> source, Vector128<sbyte> mask, sbyte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_maskmoveu_si128 (__m128i a,  __m128i mask, char* mem_address)
+        ///   MASKMOVDQU xmm, xmm
+        /// </summary>
+        public static unsafe void MaskMove(Vector128<byte> source, Vector128<byte> mask, byte* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_max_epu8 (__m128i a,  __m128i b)
+        ///   PMAXUB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Max(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_max_epi16 (__m128i a,  __m128i b)
+        ///   PMAXSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> Max(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_max_pd (__m128d a,  __m128d b)
+        ///   MAXPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Max(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_max_sd (__m128d a,  __m128d b)
+        ///   MAXSD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MaxScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_mfence(void)
+        ///   MFENCE
+        /// </summary>
+        public static void MemoryFence() { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_min_epu8 (__m128i a,  __m128i b)
+        ///   PMINUB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Min(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_min_epi16 (__m128i a,  __m128i b)
+        ///   PMINSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> Min(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_min_pd (__m128d a,  __m128d b)
+        ///   MINPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Min(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_min_sd (__m128d a,  __m128d b)
+        ///   MINSD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MinScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_move_sd (__m128d a, __m128d b)
+        ///   MOVSD xmm, xmm
+        /// </summary>
+        public static Vector128<double> MoveScalar(Vector128<double> upper, Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_movemask_epi8 (__m128i a)
+        ///   PMOVMSKB reg, xmm
+        /// </summary>
+        public static int MoveMask(Vector128<sbyte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm_movemask_epi8 (__m128i a)
+        ///   PMOVMSKB reg, xmm
+        /// </summary>
+        public static int MoveMask(Vector128<byte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm_movemask_pd (__m128d a)
+        ///   MOVMSKPD reg, xmm
+        /// </summary>
+        public static int MoveMask(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_move_epi64 (__m128i a)
+        ///   MOVQ xmm, xmm
+        /// </summary>
+        public static Vector128<long> MoveScalar(Vector128<long> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_move_epi64 (__m128i a)
+        ///   MOVQ xmm, xmm
+        /// </summary>
+        public static Vector128<ulong> MoveScalar(Vector128<ulong> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_mul_epu32 (__m128i a,  __m128i b)
+        ///   PMULUDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> Multiply(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_mul_pd (__m128d a,  __m128d b)
+        ///   MULPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Multiply(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_mul_sd (__m128d a,  __m128d b)
+        ///   MULSD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MultiplyScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_mulhi_epi16 (__m128i a,  __m128i b)
+        ///   PMULHW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> MultiplyHigh(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_mulhi_epu16 (__m128i a,  __m128i b)
+        ///   PMULHUW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> MultiplyHigh(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_madd_epi16 (__m128i a,  __m128i b)
+        ///   PMADDWD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> MultiplyHorizontalAdd(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_mullo_epi16 (__m128i a,  __m128i b)
+        ///   PMULLW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> MultiplyLow(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Or(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Or(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> Or(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Or(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> Or(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> Or(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> Or(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> Or(Vector128<ulong> left, Vector128<ulong> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_or_pd (__m128d a,  __m128d b)
+        ///   ORPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Or(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_packs_epi16 (__m128i a,  __m128i b)
+        ///   PACKSSWB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> PackSignedSaturate(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_packs_epi32 (__m128i a,  __m128i b)
+        ///   PACKSSDW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> PackSignedSaturate(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_packus_epi16 (__m128i a,  __m128i b)
+        ///   PACKUSWB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> PackUnsignedSaturate(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// ___m128i _mm_set_epi8 (char e15, char e14, char e13, char e12, char e11, char e10, char e9, char e8, char e7, char e6, char e5, char e4, char e3, char e2, char e1, char e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<sbyte> SetVector128(sbyte e15, sbyte e14, sbyte e13, sbyte e12, sbyte e11, sbyte e10, sbyte e9, sbyte e8, sbyte e7, sbyte e6, sbyte e5, sbyte e4, sbyte e3, sbyte e2, sbyte e1, sbyte e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// ___m128i _mm_set_epi8 (char e15, char e14, char e13, char e12, char e11, char e10, char e9, char e8, char e7, char e6, char e5, char e4, char e3, char e2, char e1, char e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<byte> SetVector128(byte e15, byte e14, byte e13, byte e12, byte e11, byte e10, byte e9, byte e8, byte e7, byte e6, byte e5, byte e4, byte e3, byte e2, byte e1, byte e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_set_epi16 (short e7, short e6, short e5, short e4, short e3, short e2, short e1, short e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<short> SetVector128(short e7, short e6, short e5, short e4, short e3, short e2, short e1, short e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_set_epi16 (short e7, short e6, short e5, short e4, short e3, short e2, short e1, short e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<ushort> SetVector128(ushort e7, ushort e6, ushort e5, ushort e4, ushort e3, ushort e2, ushort e1, ushort e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_set_epi32 (int e3, int e2, int e1, int e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<int> SetVector128(int e3, int e2, int e1, int e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_set_epi32 (int e3, int e2, int e1, int e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<uint> SetVector128(uint e3, uint e2, uint e1, uint e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_set_epi64x (__int64 e1, __int64 e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<long> SetVector128(long e1, long e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_set_epi64x (__int64 e1, __int64 e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<ulong> SetVector128(ulong e1, ulong e0) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_set_pd (double e1, double e0)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<double> SetVector128(double e1, double e0) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_set_sd (double a)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<double> SetScalarVector128(double value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_set1_epi8 (char a)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<byte> SetAllVector128(byte value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_set1_epi8 (char a)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<sbyte> SetAllVector128(sbyte value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_set1_epi16 (short a)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<short> SetAllVector128(short value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_set1_epi16 (short a)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<ushort> SetAllVector128(ushort value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_set1_epi32 (int a)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<int> SetAllVector128(int value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_set1_epi32 (int a)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<uint> SetAllVector128(uint value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_set1_epi64x (long long a)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<long> SetAllVector128(long value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_set1_epi64x (long long a)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<ulong> SetAllVector128(ulong value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_set1_pd (double a)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<double> SetAllVector128(double value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_setzero_si128 ()
+        ///   HELPER: PXOR
+        /// __m128d _mm_setzero_pd (void)
+        ///   HELPER: XORPD
+        /// </summary>
+        public static Vector128<T> SetZeroVector128<T>() where T : struct { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_sad_epu8 (__m128i a,  __m128i b)
+        ///   PSADBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> SumAbsoluteDifferences(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_shuffle_epi32 (__m128i a,  int immediate)
+        ///   PSHUFD xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<int> Shuffle(Vector128<int> value, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_shuffle_epi32 (__m128i a,  int immediate)
+        ///   PSHUFD xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<uint> Shuffle(Vector128<uint> value, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_shuffle_pd (__m128d a,  __m128d b, int immediate)
+        ///   SHUFPD xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<double> Shuffle(Vector128<double> left, Vector128<double> right, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_shufflehi_epi16 (__m128i a,  int immediate)
+        ///   PSHUFHW xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<short> ShuffleHigh(Vector128<short> value, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_shufflehi_epi16 (__m128i a,  int control)
+        ///   PSHUFHW xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> ShuffleHigh(Vector128<ushort> value, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_shufflelo_epi16 (__m128i a,  int control)
+        ///   PSHUFLW xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<short> ShuffleLow(Vector128<short> value, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_shufflelo_epi16 (__m128i a,  int control)
+        ///   PSHUFLW xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> ShuffleLow(Vector128<ushort> value, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_sll_epi16 (__m128i a, __m128i count)
+        ///   PSLLW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> ShiftLeftLogical(Vector128<short> value, Vector128<short> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sll_epi16 (__m128i a,  __m128i count)
+        ///   PSLLW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> ShiftLeftLogical(Vector128<ushort> value, Vector128<ushort> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sll_epi32 (__m128i a, __m128i count)
+        ///   PSLLD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ShiftLeftLogical(Vector128<int> value, Vector128<int> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sll_epi32 (__m128i a, __m128i count)
+        ///   PSLLD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> ShiftLeftLogical(Vector128<uint> value, Vector128<uint> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sll_epi64 (__m128i a, __m128i count)
+        ///   PSLLQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> ShiftLeftLogical(Vector128<long> value, Vector128<long> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sll_epi64 (__m128i a, __m128i count)
+        ///   PSLLQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> ShiftLeftLogical(Vector128<ulong> value, Vector128<ulong> count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_slli_epi16 (__m128i a,  int immediate)
+        ///   PSLLW xmm, imm8
+        /// </summary>
+        public static Vector128<short> ShiftLeftLogical(Vector128<short> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_slli_epi16 (__m128i a,  int immediate)
+        ///   PSLLW xmm, imm8
+        /// </summary>
+        public static Vector128<ushort> ShiftLeftLogical(Vector128<ushort> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_slli_epi32 (__m128i a,  int immediate)
+        ///   PSLLD xmm, imm8
+        /// </summary>
+        public static Vector128<int> ShiftLeftLogical(Vector128<int> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_slli_epi32 (__m128i a,  int immediate)
+        ///   PSLLD xmm, imm8
+        /// </summary>
+        public static Vector128<uint> ShiftLeftLogical(Vector128<uint> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_slli_epi64 (__m128i a,  int immediate)
+        ///   PSLLQ xmm, imm8
+        /// </summary>
+        public static Vector128<long> ShiftLeftLogical(Vector128<long> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_slli_epi64 (__m128i a,  int immediate)
+        ///   PSLLQ xmm, imm8
+        /// </summary>
+        public static Vector128<ulong> ShiftLeftLogical(Vector128<ulong> value, byte count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<sbyte> ShiftLeftLogical128BitLane(Vector128<sbyte> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<byte> ShiftLeftLogical128BitLane(Vector128<byte> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<short> ShiftLeftLogical128BitLane(Vector128<short> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<ushort> ShiftLeftLogical128BitLane(Vector128<ushort> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<int> ShiftLeftLogical128BitLane(Vector128<int> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<uint> ShiftLeftLogical128BitLane(Vector128<uint> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<long> ShiftLeftLogical128BitLane(Vector128<long> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<ulong> ShiftLeftLogical128BitLane(Vector128<ulong> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_sra_epi16 (__m128i a, __m128i count)
+        ///   PSRAW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> ShiftRightArithmetic(Vector128<short> value, Vector128<short> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sra_epi32 (__m128i a, __m128i count)
+        ///   PSRAD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ShiftRightArithmetic(Vector128<int> value, Vector128<int> count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_srai_epi16 (__m128i a,  int immediate)
+        ///   PSRAW xmm, imm8
+        /// </summary>
+        public static Vector128<short> ShiftRightArithmetic(Vector128<short> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_srai_epi32 (__m128i a,  int immediate)
+        ///   PSRAD xmm, imm8
+        /// </summary>
+        public static Vector128<int> ShiftRightArithmetic(Vector128<int> value, byte count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_srl_epi16 (__m128i a, __m128i count)
+        ///   PSRLW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> ShiftRightLogical(Vector128<short> value, Vector128<short> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_srl_epi16 (__m128i a, __m128i count)
+        ///   PSRLW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> ShiftRightLogical(Vector128<ushort> value, Vector128<ushort> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_srl_epi32 (__m128i a, __m128i count)
+        ///   PSRLD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ShiftRightLogical(Vector128<int> value, Vector128<int> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_srl_epi32 (__m128i a, __m128i count)
+        ///   PSRLD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> ShiftRightLogical(Vector128<uint> value, Vector128<uint> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_srl_epi64 (__m128i a, __m128i count)
+        ///   PSRLQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> ShiftRightLogical(Vector128<long> value, Vector128<long> count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_srl_epi64 (__m128i a, __m128i count)
+        ///   PSRLQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> ShiftRightLogical(Vector128<ulong> value, Vector128<ulong> count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_srli_epi16 (__m128i a,  int immediate)
+        ///   PSRLW xmm, imm8
+        /// </summary>
+        public static Vector128<short> ShiftRightLogical(Vector128<short> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_srli_epi16 (__m128i a,  int immediate)
+        ///   PSRLW xmm, imm8
+        /// </summary>
+        public static Vector128<ushort> ShiftRightLogical(Vector128<ushort> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_srli_epi32 (__m128i a,  int immediate)
+        ///   PSRLD xmm, imm8
+        /// </summary>
+        public static Vector128<int> ShiftRightLogical(Vector128<int> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_srli_epi32 (__m128i a,  int immediate)
+        ///   PSRLD xmm, imm8
+        /// </summary>
+        public static Vector128<uint> ShiftRightLogical(Vector128<uint> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_srli_epi64 (__m128i a,  int immediate)
+        ///   PSRLQ xmm, imm8
+        /// </summary>
+        public static Vector128<long> ShiftRightLogical(Vector128<long> value, byte count) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_srli_epi64 (__m128i a,  int immediate)
+        ///   PSRLQ xmm, imm8
+        /// </summary>
+        public static Vector128<ulong> ShiftRightLogical(Vector128<ulong> value, byte count) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<sbyte> ShiftRightLogical128BitLane(Vector128<sbyte> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<byte> ShiftRightLogical128BitLane(Vector128<byte> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<short> ShiftRightLogical128BitLane(Vector128<short> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<ushort> ShiftRightLogical128BitLane(Vector128<ushort> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<int> ShiftRightLogical128BitLane(Vector128<int> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<uint> ShiftRightLogical128BitLane(Vector128<uint> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<long> ShiftRightLogical128BitLane(Vector128<long> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<ulong> ShiftRightLogical128BitLane(Vector128<ulong> value, byte numBytes) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_sqrt_pd (__m128d a)
+        ///   SQRTPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Sqrt(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_sqrt_sd (__m128d a)
+        ///   SQRTSD xmm, xmm/64
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> SqrtScalar(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_sqrt_sd (__m128d a, __m128d b)
+        ///   SQRTSD xmm, xmm/64
+        /// </summary>
+        public static Vector128<double> SqrtScalar(Vector128<double> upper, Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_store_sd (double* mem_addr, __m128d a)
+        ///   MOVSD m64, xmm
+        /// </summary>
+        public static unsafe void StoreScalar(double* address, Vector128<double> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(sbyte* address, Vector128<sbyte> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(byte* address, Vector128<byte> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(short* address, Vector128<short> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(ushort* address, Vector128<ushort> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(int* address, Vector128<int> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(uint* address, Vector128<uint> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(long* address, Vector128<long> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(ulong* address, Vector128<ulong> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_store_pd (double* mem_addr, __m128d a)
+        ///   MOVAPD m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(double* address, Vector128<double> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(sbyte* address, Vector128<sbyte> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(byte* address, Vector128<byte> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(short* address, Vector128<short> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(ushort* address, Vector128<ushort> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(int* address, Vector128<int> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(uint* address, Vector128<uint> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(long* address, Vector128<long> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(ulong* address, Vector128<ulong> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_stream_pd (double* mem_addr, __m128d a)
+        ///   MOVNTPD m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(double* address, Vector128<double> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(sbyte* address, Vector128<sbyte> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(byte* address, Vector128<byte> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(short* address, Vector128<short> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(ushort* address, Vector128<ushort> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(int* address, Vector128<int> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(uint* address, Vector128<uint> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(long* address, Vector128<long> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(ulong* address, Vector128<ulong> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_storeu_pd (double* mem_addr, __m128d a)
+        ///   MOVUPD m128, xmm
+        /// </summary>
+        public static unsafe void Store(double* address, Vector128<double> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_storeh_pd (double* mem_addr, __m128d a)
+        ///   MOVHPD m64, xmm
+        /// </summary>
+        public static unsafe void StoreHigh(double* address, Vector128<double> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_storel_epi64 (__m128i* mem_addr, __m128i a)
+        ///   MOVQ m64, xmm
+        /// </summary>
+        public static unsafe void StoreLow(long* address, Vector128<long> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_storel_epi64 (__m128i* mem_addr, __m128i a)
+        ///   MOVQ m64, xmm
+        /// </summary>
+        public static unsafe void StoreLow(ulong* address, Vector128<ulong> source) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_storel_pd (double* mem_addr, __m128d a)
+        ///   MOVLPD m64, xmm
+        /// </summary>
+        public static unsafe void StoreLow(double* address, Vector128<double> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_stream_si32(int *p, int a)
+        ///   MOVNTI m32, r32
+        /// </summary>
+        public static unsafe void StoreNonTemporal(int* address, int value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_stream_si32(int *p, int a)
+        ///   MOVNTI m32, r32
+        /// </summary>
+        public static unsafe void StoreNonTemporal(uint* address, uint value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// void _mm_stream_si64(__int64 *p, __int64 a)
+        ///   MOVNTI m64, r64
+        /// </summary>
+        public static unsafe void StoreNonTemporal(long* address, long value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// void _mm_stream_si64(__int64 *p, __int64 a)
+        ///   MOVNTI m64, r64
+        /// </summary>
+        public static unsafe void StoreNonTemporal(ulong* address, ulong value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_sub_epi8 (__m128i a,  __m128i b)
+        ///   PSUBB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Subtract(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sub_epi8 (__m128i a,  __m128i b)
+        ///   PSUBB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Subtract(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sub_epi16 (__m128i a,  __m128i b)
+        ///   PSUBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> Subtract(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sub_epi16 (__m128i a,  __m128i b)
+        ///   PSUBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Subtract(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sub_epi32 (__m128i a,  __m128i b)
+        ///   PSUBD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> Subtract(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sub_epi32 (__m128i a,  __m128i b)
+        ///   PSUBD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> Subtract(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sub_epi64 (__m128i a,  __m128i b)
+        ///   PSUBQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> Subtract(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sub_epi64 (__m128i a,  __m128i b)
+        ///   PSUBQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> Subtract(Vector128<ulong> left, Vector128<ulong> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_sub_pd (__m128d a, __m128d b)
+        ///   SUBPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Subtract(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_sub_sd (__m128d a, __m128d b)
+        ///   SUBSD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> SubtractScalar(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_subs_epi8 (__m128i a,  __m128i b)
+        ///   PSUBSB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> SubtractSaturate(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_subs_epi16 (__m128i a,  __m128i b)
+        ///   PSUBSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> SubtractSaturate(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_subs_epu8 (__m128i a,  __m128i b)
+        ///   PSUBUSB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> SubtractSaturate(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_subs_epu16 (__m128i a,  __m128i b)
+        ///   PSUBUSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> SubtractSaturate(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi8 (__m128i a,  __m128i b)
+        ///   PUNPCKHBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> UnpackHigh(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi8 (__m128i a,  __m128i b)
+        ///   PUNPCKHBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> UnpackHigh(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi16 (__m128i a,  __m128i b)
+        ///   PUNPCKHWD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> UnpackHigh(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi16 (__m128i a,  __m128i b)
+        ///   PUNPCKHWD xmm, xmm/m128
+        /// </summary
+        public static Vector128<ushort> UnpackHigh(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi32 (__m128i a,  __m128i b)
+        ///   PUNPCKHDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> UnpackHigh(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi32 (__m128i a,  __m128i b)
+        ///   PUNPCKHDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> UnpackHigh(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi64 (__m128i a,  __m128i b)
+        ///   PUNPCKHQDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> UnpackHigh(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi64 (__m128i a,  __m128i b)
+        ///   PUNPCKHQDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> UnpackHigh(Vector128<ulong> left, Vector128<ulong> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_unpackhi_pd (__m128d a,  __m128d b)
+        ///   UNPCKHPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> UnpackHigh(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi8 (__m128i a,  __m128i b)
+        ///   PUNPCKLBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> UnpackLow(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi8 (__m128i a,  __m128i b)
+        ///   PUNPCKLBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> UnpackLow(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi16 (__m128i a,  __m128i b)
+        ///   PUNPCKLWD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> UnpackLow(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi16 (__m128i a,  __m128i b)
+        ///   PUNPCKLWD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> UnpackLow(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi32 (__m128i a,  __m128i b)
+        ///   PUNPCKLDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> UnpackLow(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi32 (__m128i a,  __m128i b)
+        ///   PUNPCKLDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> UnpackLow(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi64 (__m128i a,  __m128i b)
+        ///   PUNPCKLQDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> UnpackLow(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi64 (__m128i a,  __m128i b)
+        ///   PUNPCKLQDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> UnpackLow(Vector128<ulong> left, Vector128<ulong> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_unpacklo_pd (__m128d a,  __m128d b)
+        ///   UNPCKLPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> UnpackLow(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Xor(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Xor(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> Xor(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Xor(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> Xor(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> Xor(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> Xor(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> Xor(Vector128<ulong> left, Vector128<ulong> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_xor_pd (__m128d a,  __m128d b)
+        ///   XORPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Xor(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse2.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse2.cs
new file mode 100644
index 0000000000..d0eb9ef4da
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse2.cs
@@ -0,0 +1,2005 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel SSE2 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Sse2
+    {
+        public static bool IsSupported { get => IsSupported; }
+
+        /// <summary>
+        /// __m128i _mm_add_epi8 (__m128i a,  __m128i b)
+        ///   PADDB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Add(Vector128<byte> left, Vector128<byte> right) => Add(left, right);
+        /// <summary>
+        /// __m128i _mm_add_epi8 (__m128i a,  __m128i b)
+        ///   PADDB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Add(Vector128<sbyte> left, Vector128<sbyte> right) => Add(left, right);
+        /// <summary>
+        /// __m128i _mm_add_epi16 (__m128i a,  __m128i b)
+        ///   PADDW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> Add(Vector128<short> left, Vector128<short> right) => Add(left, right);
+        /// <summary>
+        /// __m128i _mm_add_epi16 (__m128i a,  __m128i b)
+        ///   PADDW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Add(Vector128<ushort> left, Vector128<ushort> right) => Add(left, right);
+        /// <summary>
+        /// __m128i _mm_add_epi32 (__m128i a,  __m128i b)
+        ///   PADDD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> Add(Vector128<int> left, Vector128<int> right) => Add(left, right);
+        /// <summary>
+        /// __m128i _mm_add_epi32 (__m128i a,  __m128i b)
+        ///   PADDD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> Add(Vector128<uint> left, Vector128<uint> right) => Add(left, right);
+        /// <summary>
+        /// __m128i _mm_add_epi64 (__m128i a,  __m128i b)
+        ///   PADDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> Add(Vector128<long> left, Vector128<long> right) => Add(left, right);
+        /// <summary>
+        /// __m128i _mm_add_epi64 (__m128i a,  __m128i b)
+        ///   PADDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> Add(Vector128<ulong> left, Vector128<ulong> right) => Add(left, right);
+        /// <summary>
+        /// __m128d _mm_add_pd (__m128d a,  __m128d b)
+        ///   ADDPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Add(Vector128<double> left, Vector128<double> right) => Add(left, right);
+
+        /// <summary>
+        /// __m128d _mm_add_sd (__m128d a,  __m128d b)
+        ///   ADDSD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> AddScalar(Vector128<double> left, Vector128<double> right) => AddScalar(left, right);
+
+        /// <summary>
+        /// __m128i _mm_adds_epi8 (__m128i a,  __m128i b)
+        ///   PADDSB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> AddSaturate(Vector128<sbyte> left, Vector128<sbyte> right) => AddSaturate(left, right);
+        /// <summary>
+        /// __m128i _mm_adds_epu8 (__m128i a,  __m128i b)
+        ///   PADDUSB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> AddSaturate(Vector128<byte> left, Vector128<byte> right) => AddSaturate(left, right);
+        /// <summary>
+        /// __m128i _mm_adds_epi16 (__m128i a,  __m128i b)
+        ///   PADDSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> AddSaturate(Vector128<short> left, Vector128<short> right) => AddSaturate(left, right);
+        /// <summary>
+        /// __m128i _mm_adds_epu16 (__m128i a,  __m128i b)
+        ///   PADDUSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> AddSaturate(Vector128<ushort> left, Vector128<ushort> right) => AddSaturate(left, right);
+
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> And(Vector128<byte> left, Vector128<byte> right) => And(left, right);
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> And(Vector128<sbyte> left, Vector128<sbyte> right) => And(left, right);
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> And(Vector128<short> left, Vector128<short> right) => And(left, right);
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> And(Vector128<ushort> left, Vector128<ushort> right) => And(left, right);
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> And(Vector128<int> left, Vector128<int> right) => And(left, right);
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> And(Vector128<uint> left, Vector128<uint> right) => And(left, right);
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> And(Vector128<long> left, Vector128<long> right) => And(left, right);
+        /// <summary>
+        /// __m128i _mm_and_si128 (__m128i a,  __m128i b)
+        ///   PAND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> And(Vector128<ulong> left, Vector128<ulong> right) => And(left, right);
+        /// <summary>
+        /// __m128d _mm_and_pd (__m128d a, __m128d b)
+        ///   ANDPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> And(Vector128<double> left, Vector128<double> right) => And(left, right);
+
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> AndNot(Vector128<byte> left, Vector128<byte> right) => AndNot(left, right);
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> AndNot(Vector128<sbyte> left, Vector128<sbyte> right) => AndNot(left, right);
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> AndNot(Vector128<short> left, Vector128<short> right) => AndNot(left, right);
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> AndNot(Vector128<ushort> left, Vector128<ushort> right) => AndNot(left, right);
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> AndNot(Vector128<int> left, Vector128<int> right) => AndNot(left, right);
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> AndNot(Vector128<uint> left, Vector128<uint> right) => AndNot(left, right);
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> AndNot(Vector128<long> left, Vector128<long> right) => AndNot(left, right);
+        /// <summary>
+        /// __m128i _mm_andnot_si128 (__m128i a,  __m128i b)
+        ///   PANDN xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> AndNot(Vector128<ulong> left, Vector128<ulong> right) => AndNot(left, right);
+        /// <summary>
+        /// __m128d _mm_andnot_pd (__m128d a, __m128d b)
+        ///   ADDNPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> AndNot(Vector128<double> left, Vector128<double> right) => AndNot(left, right);
+
+        /// <summary>
+        /// __m128i _mm_avg_epu8 (__m128i a,  __m128i b)
+        ///   PAVGB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Average(Vector128<byte> left, Vector128<byte> right) => Average(left, right);
+        /// <summary>
+        /// __m128i _mm_avg_epu16 (__m128i a,  __m128i b)
+        ///   PAVGW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Average(Vector128<ushort> left, Vector128<ushort> right) => Average(left, right);
+
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi8 (__m128i a,  __m128i b)
+        ///   PCMPEQB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> CompareEqual(Vector128<sbyte> left, Vector128<sbyte> right) => CompareEqual(left, right);
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi8 (__m128i a,  __m128i b)
+        ///   PCMPEQB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> CompareEqual(Vector128<byte> left, Vector128<byte> right) => CompareEqual(left, right);
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi16 (__m128i a,  __m128i b)
+        ///   PCMPEQW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> CompareEqual(Vector128<short> left, Vector128<short> right) => CompareEqual(left, right);
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi16 (__m128i a,  __m128i b)
+        ///   PCMPEQW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> CompareEqual(Vector128<ushort> left, Vector128<ushort> right) => CompareEqual(left, right);
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi32 (__m128i a,  __m128i b)
+        ///   PCMPEQD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> CompareEqual(Vector128<int> left, Vector128<int> right) => CompareEqual(left, right);
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi32 (__m128i a,  __m128i b)
+        ///   PCMPEQD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> CompareEqual(Vector128<uint> left, Vector128<uint> right) => CompareEqual(left, right);
+        /// <summary>
+        /// __m128d _mm_cmpeq_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(0)
+        /// </summary>
+        public static Vector128<double> CompareEqual(Vector128<double> left, Vector128<double> right) => CompareEqual(left, right);
+
+        /// <summary>
+        /// int _mm_comieq_sd (__m128d a, __m128d b)
+        ///   COMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareEqualOrderedScalar(Vector128<double> left, Vector128<double> right) => CompareEqualOrderedScalar(left, right);
+
+        /// <summary>
+        /// int _mm_ucomieq_sd (__m128d a, __m128d b)
+        ///   UCOMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareEqualUnorderedScalar(Vector128<double> left, Vector128<double> right) => CompareEqualUnorderedScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpeq_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(0)
+        /// </summary>
+        public static Vector128<double> CompareEqualScalar(Vector128<double> left, Vector128<double> right) => CompareEqualScalar(left, right);
+
+        /// <summary>
+        /// __m128i _mm_cmpgt_epi8 (__m128i a,  __m128i b)
+        ///   PCMPGTB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> CompareGreaterThan(Vector128<sbyte> left, Vector128<sbyte> right) => CompareGreaterThan(left, right);
+        /// <summary>
+        /// __m128i _mm_cmpgt_epi16 (__m128i a,  __m128i b)
+        ///   PCMPGTW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> CompareGreaterThan(Vector128<short> left, Vector128<short> right) => CompareGreaterThan(left, right);
+        /// <summary>
+        /// __m128i _mm_cmpgt_epi32 (__m128i a,  __m128i b)
+        ///   PCMPGTD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> CompareGreaterThan(Vector128<int> left, Vector128<int> right) => CompareGreaterThan(left, right);
+        /// <summary>
+        /// __m128d _mm_cmpgt_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(6)
+        /// </summary>
+        public static Vector128<double> CompareGreaterThan(Vector128<double> left, Vector128<double> right) => CompareGreaterThan(left, right);
+
+        /// <summary>
+        /// int _mm_comigt_sd (__m128d a, __m128d b)
+        ///   COMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareGreaterThanOrderedScalar(Vector128<double> left, Vector128<double> right) => CompareGreaterThanOrderedScalar(left, right);
+
+        /// <summary>
+        /// int _mm_ucomigt_sd (__m128d a, __m128d b)
+        ///   UCOMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareGreaterThanUnorderedScalar(Vector128<double> left, Vector128<double> right) => CompareGreaterThanUnorderedScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpgt_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(6)
+        /// </summary>
+        public static Vector128<double> CompareGreaterThanScalar(Vector128<double> left, Vector128<double> right) => CompareGreaterThanScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpge_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(5)
+        /// </summary>
+        public static Vector128<double> CompareGreaterThanOrEqual(Vector128<double> left, Vector128<double> right) => CompareGreaterThanOrEqual(left, right);
+
+        /// <summary>
+        /// int _mm_comige_sd (__m128d a, __m128d b)
+        ///   COMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareGreaterThanOrEqualOrderedScalar(Vector128<double> left, Vector128<double> right) => CompareGreaterThanOrEqualOrderedScalar(left, right);
+
+        /// <summary>
+        /// int _mm_ucomige_sd (__m128d a, __m128d b)
+        ///   UCOMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareGreaterThanOrEqualUnorderedScalar(Vector128<double> left, Vector128<double> right) => CompareGreaterThanOrEqualUnorderedScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpge_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(5)
+        /// </summary>
+        public static Vector128<double> CompareGreaterThanOrEqualScalar(Vector128<double> left, Vector128<double> right) => CompareGreaterThanOrEqualScalar(left, right);
+
+        /// <summary>
+        /// __m128i _mm_cmplt_epi8 (__m128i a,  __m128i b)
+        ///   PCMPGTB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> CompareLessThan(Vector128<sbyte> left, Vector128<sbyte> right) => CompareLessThan(left, right);
+        /// <summary>
+        /// __m128i _mm_cmplt_epi16 (__m128i a,  __m128i b)
+        ///   PCMPGTW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> CompareLessThan(Vector128<short> left, Vector128<short> right) => CompareLessThan(left, right);
+        /// <summary>
+        /// __m128i _mm_cmplt_epi32 (__m128i a,  __m128i b)
+        ///   PCMPGTD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> CompareLessThan(Vector128<int> left, Vector128<int> right) => CompareLessThan(left, right);
+        /// <summary>
+        /// __m128d _mm_cmplt_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(1)
+        /// </summary>
+        public static Vector128<double> CompareLessThan(Vector128<double> left, Vector128<double> right) => CompareLessThan(left, right);
+
+        /// <summary>
+        /// int _mm_comilt_sd (__m128d a, __m128d b)
+        ///   COMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareLessThanOrderedScalar(Vector128<double> left, Vector128<double> right) => CompareLessThanOrderedScalar(left, right);
+
+        /// <summary>
+        /// int _mm_ucomilt_sd (__m128d a, __m128d b)
+        ///   UCOMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareLessThanUnorderedScalar(Vector128<double> left, Vector128<double> right) => CompareLessThanUnorderedScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmplt_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(1)
+        /// </summary>
+        public static Vector128<double> CompareLessThanScalar(Vector128<double> left, Vector128<double> right) => CompareLessThanScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmple_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(2)
+        /// </summary>
+        public static Vector128<double> CompareLessThanOrEqual(Vector128<double> left, Vector128<double> right) => CompareLessThanOrEqual(left, right);
+
+        /// <summary>
+        /// int _mm_comile_sd (__m128d a, __m128d b)
+        ///   COMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareLessThanOrEqualOrderedScalar(Vector128<double> left, Vector128<double> right) => CompareLessThanOrEqualOrderedScalar(left, right);
+
+        /// <summary>
+        /// int _mm_ucomile_sd (__m128d a, __m128d b)
+        ///   UCOMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareLessThanOrEqualUnorderedScalar(Vector128<double> left, Vector128<double> right) => CompareLessThanOrEqualUnorderedScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmple_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(2)
+        /// </summary>
+        public static Vector128<double> CompareLessThanOrEqualScalar(Vector128<double> left, Vector128<double> right) => CompareLessThanOrEqualScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpneq_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(4)
+        /// </summary>
+        public static Vector128<double> CompareNotEqual(Vector128<double> left, Vector128<double> right) => CompareNotEqual(left, right);
+
+        /// <summary>
+        /// int _mm_comineq_sd (__m128d a, __m128d b)
+        ///   COMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareNotEqualOrderedScalar(Vector128<double> left, Vector128<double> right) => CompareNotEqualOrderedScalar(left, right);
+
+        /// <summary>
+        /// int _mm_ucomineq_sd (__m128d a, __m128d b)
+        ///   UCOMISS xmm, xmm/m64
+        /// </summary>
+        public static bool CompareNotEqualUnorderedScalar(Vector128<double> left, Vector128<double> right) => CompareNotEqualUnorderedScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpneq_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(4)
+        /// </summary>
+        public static Vector128<double> CompareNotEqualScalar(Vector128<double> left, Vector128<double> right) => CompareNotEqualScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpngt_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(2)
+        /// </summary>
+        public static Vector128<double> CompareNotGreaterThan(Vector128<double> left, Vector128<double> right) => CompareNotGreaterThan(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpngt_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(2)
+        /// </summary>
+        public static Vector128<double> CompareNotGreaterThanScalar(Vector128<double> left, Vector128<double> right) => CompareNotGreaterThanScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpnge_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(1)
+        /// </summary>
+        public static Vector128<double> CompareNotGreaterThanOrEqual(Vector128<double> left, Vector128<double> right) => CompareNotGreaterThanOrEqual(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpnge_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(1)
+        /// </summary>
+        public static Vector128<double> CompareNotGreaterThanOrEqualScalar(Vector128<double> left, Vector128<double> right) => CompareNotGreaterThanOrEqualScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpnlt_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(5)
+        /// </summary>
+        public static Vector128<double> CompareNotLessThan(Vector128<double> left, Vector128<double> right) => CompareNotLessThan(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpnlt_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(5)
+        /// </summary>
+        public static Vector128<double> CompareNotLessThanScalar(Vector128<double> left, Vector128<double> right) => CompareNotLessThanScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpnle_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(6)
+        /// </summary>
+        public static Vector128<double> CompareNotLessThanOrEqual(Vector128<double> left, Vector128<double> right) => CompareNotLessThanOrEqual(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpnle_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(6)
+        /// </summary>
+        public static Vector128<double> CompareNotLessThanOrEqualScalar(Vector128<double> left, Vector128<double> right) => CompareNotLessThanOrEqualScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpord_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(7)
+        /// </summary>
+        public static Vector128<double> CompareOrdered(Vector128<double> left, Vector128<double> right) => CompareOrdered(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpord_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(7)
+        /// </summary>
+        public static Vector128<double> CompareOrderedScalar(Vector128<double> left, Vector128<double> right) => CompareOrderedScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpunord_pd (__m128d a,  __m128d b)
+        ///   CMPPD xmm, xmm/m128, imm8(3)
+        /// </summary>
+        public static Vector128<double> CompareUnordered(Vector128<double> left, Vector128<double> right) => CompareUnordered(left, right);
+
+        /// <summary>
+        /// __m128d _mm_cmpunord_sd (__m128d a,  __m128d b)
+        ///   CMPSD xmm, xmm/m64, imm8(3)
+        /// </summary>
+        public static Vector128<double> CompareUnorderedScalar(Vector128<double> left, Vector128<double> right) => CompareUnorderedScalar(left, right);
+
+        /// <summary>
+        /// __m128i _mm_cvtps_epi32 (__m128 a)
+        ///   CVTPS2DQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32(Vector128<float> value) => ConvertToVector128Int32(value);
+        /// <summary>
+        /// __m128i _mm_cvtpd_epi32 (__m128d a)
+        ///   CVTPD2DQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32(Vector128<double> value) => ConvertToVector128Int32(value);
+        /// <summary>
+        /// __m128 _mm_cvtepi32_ps (__m128i a)
+        ///   CVTDQ2PS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> ConvertToVector128Single(Vector128<int> value) => ConvertToVector128Single(value);
+        /// <summary>
+        /// __m128 _mm_cvtpd_ps (__m128d a)
+        ///   CVTPD2PS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> ConvertToVector128Single(Vector128<double> value) => ConvertToVector128Single(value);
+        /// <summary>
+        /// __m128d _mm_cvtepi32_pd (__m128i a)
+        ///   CVTDQ2PD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> ConvertToVector128Double(Vector128<int> value) => ConvertToVector128Double(value);
+        /// <summary>
+        /// __m128d _mm_cvtps_pd (__m128 a)
+        ///   CVTPS2PD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> ConvertToVector128Double(Vector128<float> value) => ConvertToVector128Double(value);
+
+        /// <summary>
+        /// double _mm_cvtsd_f64(__m128d a)
+        ///   HELPER: MOVSD
+        /// </summary>
+        public static double ConvertToDouble(Vector128<double> value) => ConvertToDouble(value);
+        /// <summary>
+        /// int _mm_cvtsd_si32 (__m128d a)
+        ///   CVTSD2SI r32, xmm/m64
+        /// </summary>
+        public static int ConvertToInt32(Vector128<double> value) => ConvertToInt32(value);
+        /// <summary>
+        /// int _mm_cvtsi128_si32 (__m128i a)
+        ///   MOVD reg/m32, xmm
+        /// </summary>
+        public static int ConvertToInt32(Vector128<int> value) => ConvertToInt32(value);
+        /// <summary>
+        /// __int64 _mm_cvtsd_si64 (__m128d a)
+        ///   CVTSD2SI r64, xmm/m64
+        /// </summary>
+        public static long ConvertToInt64(Vector128<double> value) => ConvertToInt64(value);
+        /// <summary>
+        /// __int64 _mm_cvtsi128_si64 (__m128i a)
+        ///   MOVQ reg/m64, xmm
+        /// </summary>
+        public static long ConvertToInt64(Vector128<long> value) => ConvertToInt64(value);
+        /// <summary>
+        /// int _mm_cvtsi128_si32 (__m128i a)
+        ///   MOVD reg/m32, xmm
+        /// </summary>
+        public static uint ConvertToUInt32(Vector128<uint> value) => ConvertToUInt32(value);
+        /// <summary>
+        /// __int64 _mm_cvtsi128_si64 (__m128i a)
+        ///   MOVQ reg/m64, xmm
+        /// </summary>
+        public static ulong ConvertToUInt64(Vector128<ulong> value) => ConvertToUInt64(value);
+
+        /// <summary>
+        /// __m128d _mm_cvtsi32_sd (__m128d a, int b)
+        ///   CVTSI2SD xmm, reg/m64
+        /// </summary>
+        public static Vector128<double> ConvertScalarToVector128Double(Vector128<double> upper, int value) => ConvertScalarToVector128Double(upper, value);
+        /// <summary>
+        /// __m128d _mm_cvtsi64_sd (__m128d a, int b)
+        ///   CVTSI2SD xmm, reg/m64
+        /// </summary>
+        public static Vector128<double> ConvertScalarToVector128Double(Vector128<double> upper, long value) => ConvertScalarToVector128Double(upper, value);
+        /// <summary>
+        /// __m128d _mm_cvtss_sd (__m128d a, __m128 b)
+        ///   CVTSS2SD xmm, xmm/m32
+        /// </summary>
+        public static Vector128<double> ConvertScalarToVector128Double(Vector128<double> upper, Vector128<float> value) => ConvertScalarToVector128Double(upper, value);
+        /// <summary>
+        /// __m128i _mm_cvtsi32_si128 (int a)
+        ///   MOVD xmm, reg/m32
+        /// </summary>
+        public static Vector128<int> ConvertScalarToVector128Int32(int value) => ConvertScalarToVector128Int32(value);
+        /// <summary>
+        /// __m128i _mm_cvtsi64_si128 (__int64 a)
+        ///   MOVQ xmm, reg/m64
+        /// </summary>
+        public static Vector128<long> ConvertScalarToVector128Int64(long value) => ConvertScalarToVector128Int64(value);
+        /// <summary>
+        /// __m128 _mm_cvtsd_ss (__m128 a, __m128d b)
+        ///   CVTSD2SS xmm, xmm/m64
+        /// </summary>
+        public static Vector128<float> ConvertScalarToVector128Single(Vector128<float> upper, Vector128<double> value) => ConvertScalarToVector128Single(upper, value);
+        /// <summary>
+        /// __m128i _mm_cvtsi32_si128 (int a)
+        ///   MOVD xmm, reg/m32
+        /// </summary>
+        public static Vector128<uint> ConvertScalarToVector128UInt32(uint value) => ConvertScalarToVector128UInt32(value);
+        /// <summary>
+        /// __m128i _mm_cvtsi64_si128 (__int64 a)
+        ///   MOVQ xmm, reg/m64
+        /// </summary>
+        public static Vector128<ulong> ConvertScalarToVector128UInt64(ulong value) => ConvertScalarToVector128UInt64(value);
+
+        /// <summary>
+        /// __m128i _mm_cvttps_epi32 (__m128 a)
+        ///   CVTTPS2DQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32WithTruncation(Vector128<float> value) => ConvertToVector128Int32WithTruncation(value);
+        /// <summary>
+        /// __m128i _mm_cvttpd_epi32 (__m128d a)
+        ///   CVTTPD2DQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32WithTruncation(Vector128<double> value) => ConvertToVector128Int32WithTruncation(value);
+
+        /// <summary>
+        /// int _mm_cvttsd_si32 (__m128d a)
+        ///   CVTTSD2SI reg, xmm/m64
+        /// </summary>
+        public static int ConvertToInt32WithTruncation(Vector128<double> value) => ConvertToInt32WithTruncation(value);
+        /// <summary>
+        /// __int64 _mm_cvttsd_si64 (__m128d a)
+        ///   CVTTSD2SI reg, xmm/m64
+        /// </summary>
+        public static long ConvertToInt64WithTruncation(Vector128<double> value) => ConvertToInt64WithTruncation(value);
+
+        /// <summary>
+        /// __m128d _mm_div_pd (__m128d a,  __m128d b)
+        ///   DIVPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Divide(Vector128<double> left, Vector128<double> right) => Divide(left, right);
+
+        /// <summary>
+        /// __m128d _mm_div_sd (__m128d a,  __m128d b)
+        ///   DIVSD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> DivideScalar(Vector128<double> left, Vector128<double> right) => DivideScalar(left, right);
+
+        /// <summary>
+        /// int _mm_extract_epi16 (__m128i a,  int immediate)
+        ///   PEXTRW reg, xmm, imm8
+        /// </summary>
+        public static short Extract(Vector128<short> value, byte index) => Extract(value, index);
+        /// <summary>
+        /// int _mm_extract_epi16 (__m128i a,  int immediate)
+        ///   PEXTRW reg, xmm, imm8
+        /// </summary>
+        public static ushort Extract(Vector128<ushort> value, byte index) => Extract(value, index);
+
+        /// <summary>
+        /// __m128i _mm_insert_epi16 (__m128i a,  int i, int immediate)
+        ///   PINSRW xmm, reg/m16, imm8
+        /// </summary>
+        public static Vector128<short> Insert(Vector128<short> value, short data, byte index) => Insert(value, data, index);
+        /// <summary>
+        /// __m128i _mm_insert_epi16 (__m128i a,  int i, int immediate)
+        ///   PINSRW xmm, reg/m16, imm8
+        /// </summary>
+        public static Vector128<ushort> Insert(Vector128<ushort> value, ushort data, byte index) => Insert(value, data, index);
+
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<sbyte> LoadVector128(sbyte* address) => LoadVector128(address);
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<byte> LoadVector128(byte* address) => LoadVector128(address);
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<short> LoadVector128(short* address) => LoadVector128(address);
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<ushort> LoadVector128(ushort* address) => LoadVector128(address);
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<int> LoadVector128(int* address) => LoadVector128(address);
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<uint> LoadVector128(uint* address) => LoadVector128(address);
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<long> LoadVector128(long* address) => LoadVector128(address);
+        /// <summary>
+        /// __m128i _mm_loadu_si128 (__m128i const* mem_address)
+        ///   MOVDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<ulong> LoadVector128(ulong* address) => LoadVector128(address);
+        /// <summary>
+        /// __m128d _mm_loadu_pd (double const* mem_address)
+        ///   MOVUPD xmm, m128
+        /// </summary>
+        public static unsafe Vector128<double> LoadVector128(double* address) => LoadVector128(address);
+
+        /// <summary>
+        /// __m128d _mm_load_sd (double const* mem_address)
+        ///   MOVSD xmm, m64
+        /// </summary>
+        public static unsafe Vector128<double> LoadScalarVector128(double* address) => LoadScalarVector128(address);
+
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<sbyte> LoadAlignedVector128(sbyte* address) => LoadAlignedVector128(address);
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<byte> LoadAlignedVector128(byte* address) => LoadAlignedVector128(address);
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<short> LoadAlignedVector128(short* address) => LoadAlignedVector128(address);
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<ushort> LoadAlignedVector128(ushort* address) => LoadAlignedVector128(address);
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<int> LoadAlignedVector128(int* address) => LoadAlignedVector128(address);
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<uint> LoadAlignedVector128(uint* address) => LoadAlignedVector128(address);
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<long> LoadAlignedVector128(long* address) => LoadAlignedVector128(address);
+        /// <summary>
+        /// __m128i _mm_load_si128 (__m128i const* mem_address)
+        ///   MOVDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<ulong> LoadAlignedVector128(ulong* address) => LoadAlignedVector128(address);
+        /// <summary>
+        /// __m128d _mm_load_pd (double const* mem_address)
+        ///   MOVAPD xmm, m128
+        /// </summary>
+        public static unsafe Vector128<double> LoadAlignedVector128(double* address) => LoadAlignedVector128(address);
+
+        /// <summary>
+        /// void _mm_lfence(void)
+        ///   LFENCE
+        /// </summary>
+        public static void LoadFence() => LoadFence();
+
+        /// <summary>
+        /// __m128d _mm_loadh_pd (__m128d a, double const* mem_addr)
+        ///   MOVHPD xmm, m64
+        /// </summary>
+        public static unsafe Vector128<double> LoadHigh(Vector128<double> lower, double* address) => LoadHigh(lower, address);
+
+        /// <summary>
+        /// __m128d _mm_loadl_pd (__m128d a, double const* mem_addr)
+        ///   MOVLPD xmm, m64
+        /// </summary>
+        public static unsafe Vector128<double> LoadLow(Vector128<double> upper, double* address) => LoadLow(upper, address);
+
+        /// <summary>
+        /// __m128i _mm_loadl_epi32 (__m128i const* mem_addr)
+        ///   MOVD xmm, reg/m32
+        /// The above native signature does not exist. We provide this additional overload for completeness.
+        /// </summary>
+        public static unsafe Vector128<int> LoadScalarVector128(int* address) => LoadScalarVector128(address);
+        /// <summary>
+        /// __m128i _mm_loadl_epi32 (__m128i const* mem_addr)
+        ///   MOVD xmm, reg/m32
+        /// The above native signature does not exist. We provide this additional overload for completeness.
+        /// </summary>
+        public static unsafe Vector128<uint> LoadScalarVector128(uint* address) => LoadScalarVector128(address);
+        /// <summary>
+        /// __m128i _mm_loadl_epi64 (__m128i const* mem_addr)
+        ///   MOVQ xmm, reg/m64
+        /// </summary>
+        public static unsafe Vector128<long> LoadScalarVector128(long* address) => LoadScalarVector128(address);
+        /// <summary>
+        /// __m128i _mm_loadl_epi64 (__m128i const* mem_addr)
+        ///   MOVQ xmm, reg/m64
+        /// </summary>
+        public static unsafe Vector128<ulong> LoadScalarVector128(ulong* address) => LoadScalarVector128(address);
+
+        /// <summary>
+        /// void _mm_maskmoveu_si128 (__m128i a,  __m128i mask, char* mem_address)
+        ///   MASKMOVDQU xmm, xmm
+        /// </summary>
+        public static unsafe void MaskMove(Vector128<sbyte> source, Vector128<sbyte> mask, sbyte* address) => MaskMove(source, mask, address);
+        /// <summary>
+        /// void _mm_maskmoveu_si128 (__m128i a,  __m128i mask, char* mem_address)
+        ///   MASKMOVDQU xmm, xmm
+        /// </summary>
+        public static unsafe void MaskMove(Vector128<byte> source, Vector128<byte> mask, byte* address) => MaskMove(source, mask, address);
+
+        /// <summary>
+        /// __m128i _mm_max_epu8 (__m128i a,  __m128i b)
+        ///   PMAXUB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Max(Vector128<byte> left, Vector128<byte> right) => Max(left, right);
+        /// <summary>
+        /// __m128i _mm_max_epi16 (__m128i a,  __m128i b)
+        ///   PMAXSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> Max(Vector128<short> left, Vector128<short> right) => Max(left, right);
+        /// <summary>
+        /// __m128d _mm_max_pd (__m128d a,  __m128d b)
+        ///   MAXPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Max(Vector128<double> left, Vector128<double> right) => Max(left, right);
+
+        /// <summary>
+        /// __m128d _mm_max_sd (__m128d a,  __m128d b)
+        ///   MAXSD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MaxScalar(Vector128<double> left, Vector128<double> right) => MaxScalar(left, right);
+
+        /// <summary>
+        /// void _mm_mfence(void)
+        ///   MFENCE
+        /// </summary>
+        public static void MemoryFence() => MemoryFence();
+
+        /// <summary>
+        /// __m128i _mm_min_epu8 (__m128i a,  __m128i b)
+        ///   PMINUB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Min(Vector128<byte> left, Vector128<byte> right) => Min(left, right);
+        /// <summary>
+        /// __m128i _mm_min_epi16 (__m128i a,  __m128i b)
+        ///   PMINSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> Min(Vector128<short> left, Vector128<short> right) => Min(left, right);
+        /// <summary>
+        /// __m128d _mm_min_pd (__m128d a,  __m128d b)
+        ///   MINPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Min(Vector128<double> left, Vector128<double> right) => Min(left, right);
+
+        /// <summary>
+        /// __m128d _mm_min_sd (__m128d a,  __m128d b)
+        ///   MINSD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MinScalar(Vector128<double> left, Vector128<double> right) => MinScalar(left, right);
+
+        /// <summary>
+        /// __m128d _mm_move_sd (__m128d a, __m128d b)
+        ///   MOVSD xmm, xmm
+        /// </summary>
+        public static Vector128<double> MoveScalar(Vector128<double> upper, Vector128<double> value) => MoveScalar(upper, value);
+
+        /// <summary>
+        /// int _mm_movemask_epi8 (__m128i a)
+        ///   PMOVMSKB reg, xmm
+        /// </summary>
+        public static int MoveMask(Vector128<sbyte> value) => MoveMask(value);
+        /// <summary>
+        /// int _mm_movemask_epi8 (__m128i a)
+        ///   PMOVMSKB reg, xmm
+        /// </summary>
+        public static int MoveMask(Vector128<byte> value) => MoveMask(value);
+        /// <summary>
+        /// int _mm_movemask_pd (__m128d a)
+        ///   MOVMSKPD reg, xmm
+        /// </summary>
+        public static int MoveMask(Vector128<double> value) => MoveMask(value);
+
+        /// <summary>
+        /// __m128i _mm_move_epi64 (__m128i a)
+        ///   MOVQ xmm, xmm
+        /// </summary>
+        public static Vector128<long> MoveScalar(Vector128<long> value) => MoveScalar(value);
+        /// <summary>
+        /// __m128i _mm_move_epi64 (__m128i a)
+        ///   MOVQ xmm, xmm
+        /// </summary>
+        public static Vector128<ulong> MoveScalar(Vector128<ulong> value) => MoveScalar(value);
+
+        /// <summary>
+        /// __m128i _mm_mul_epu32 (__m128i a,  __m128i b)
+        ///   PMULUDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> Multiply(Vector128<uint> left, Vector128<uint> right) => Multiply(left, right);
+        /// <summary>
+        /// __m128d _mm_mul_pd (__m128d a,  __m128d b)
+        ///   MULPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Multiply(Vector128<double> left, Vector128<double> right) => Multiply(left, right);
+
+        /// <summary>
+        /// __m128d _mm_mul_sd (__m128d a,  __m128d b)
+        ///   MULSD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MultiplyScalar(Vector128<double> left, Vector128<double> right) => MultiplyScalar(left, right);
+
+        /// <summary>
+        /// __m128i _mm_mulhi_epi16 (__m128i a,  __m128i b)
+        ///   PMULHW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> MultiplyHigh(Vector128<short> left, Vector128<short> right) => MultiplyHigh(left, right);
+        /// <summary>
+        /// __m128i _mm_mulhi_epu16 (__m128i a,  __m128i b)
+        ///   PMULHUW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> MultiplyHigh(Vector128<ushort> left, Vector128<ushort> right) => MultiplyHigh(left, right);
+
+        /// <summary>
+        /// __m128i _mm_madd_epi16 (__m128i a,  __m128i b)
+        ///   PMADDWD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> MultiplyHorizontalAdd(Vector128<short> left, Vector128<short> right) => MultiplyHorizontalAdd(left, right);
+
+        /// <summary>
+        /// __m128i _mm_mullo_epi16 (__m128i a,  __m128i b)
+        ///   PMULLW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> MultiplyLow(Vector128<short> left, Vector128<short> right) => MultiplyLow(left, right);
+
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Or(Vector128<byte> left, Vector128<byte> right) => Or(left, right);
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Or(Vector128<sbyte> left, Vector128<sbyte> right) => Or(left, right);
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> Or(Vector128<short> left, Vector128<short> right) => Or(left, right);
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Or(Vector128<ushort> left, Vector128<ushort> right) => Or(left, right);
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> Or(Vector128<int> left, Vector128<int> right) => Or(left, right);
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> Or(Vector128<uint> left, Vector128<uint> right) => Or(left, right);
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> Or(Vector128<long> left, Vector128<long> right) => Or(left, right);
+        /// <summary>
+        /// __m128i _mm_or_si128 (__m128i a,  __m128i b)
+        ///   POR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> Or(Vector128<ulong> left, Vector128<ulong> right) => Or(left, right);
+        /// <summary>
+        /// __m128d _mm_or_pd (__m128d a,  __m128d b)
+        ///   ORPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Or(Vector128<double> left, Vector128<double> right) => Or(left, right);
+
+        /// <summary>
+        /// __m128i _mm_packs_epi16 (__m128i a,  __m128i b)
+        ///   PACKSSWB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> PackSignedSaturate(Vector128<short> left, Vector128<short> right) => PackSignedSaturate(left, right);
+        /// <summary>
+        /// __m128i _mm_packs_epi32 (__m128i a,  __m128i b)
+        ///   PACKSSDW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> PackSignedSaturate(Vector128<int> left, Vector128<int> right) => PackSignedSaturate(left, right);
+
+        /// <summary>
+        /// __m128i _mm_packus_epi16 (__m128i a,  __m128i b)
+        ///   PACKUSWB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> PackUnsignedSaturate(Vector128<short> left, Vector128<short> right) => PackUnsignedSaturate(left, right);
+
+        /// <summary>
+        /// __m128i _mm_set1_epi8 (char a)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<byte> SetAllVector128(byte value)
+        {
+            // Zero vector and load value et index 0
+            Vector128<byte> vector1 = Sse.StaticCast<uint, byte>(ConvertScalarToVector128UInt32(value));
+            // Create { -- -- -- -- -- -- -- --  -- -- -- -- -- -- vl vl }
+            Vector128<ushort> tmpVector1 = Sse.StaticCast<byte, ushort>(UnpackLow(vector1, vector1));
+            // Create { -- -- -- -- -- -- -- --  -- -- -- -- vl vl vl vl }
+            Vector128<uint> tmpVector2 = Sse.StaticCast<ushort, uint>(UnpackLow(tmpVector1, tmpVector1));
+            // Create { vl vl vl vl vl vl vl vl vl vl vl vl vl vl vl vl } and return result
+            return Sse.StaticCast<uint, byte>(Shuffle(tmpVector2, 0));
+        }
+        /// <summary>
+        /// __m128i _mm_set1_epi8 (char a)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<sbyte> SetAllVector128(sbyte value)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load value et index 0
+            Vector128<sbyte> vector = Sse.StaticCast<int, sbyte>(ConvertScalarToVector128Int32(value));
+            // Create { -- -- -- -- -- -- -- --  -- -- -- -- -- -- vl vl }
+            Vector128<short> tmpVector1 = Sse.StaticCast<sbyte, short>(UnpackLow(vector, vector));
+            // Create { -- -- -- -- -- -- -- --  -- -- -- -- vl vl vl vl }
+            Vector128<int> tmpVector2 = Sse.StaticCast<short, int>(UnpackLow(tmpVector1, tmpVector1));
+            // Create { vl vl vl vl vl vl vl vl vl vl vl vl vl vl vl vl } and return result
+            return Sse.StaticCast<int, sbyte>(Shuffle(tmpVector2, 0));
+        }
+        /// <summary>
+        /// __m128i _mm_set1_epi16 (short a)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<short> SetAllVector128(short value)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load value et index 0
+            Vector128<short> vector = Sse.StaticCast<int, short>(ConvertScalarToVector128Int32(value));
+            // Create { -- -- -- -- -- -- vl vl }
+            Vector128<int> tmpVector = Sse.StaticCast<short, int>(UnpackLow(vector, vector));
+            // Create { vl vl vl vl vl vl vl vl } and return result
+            return Sse.StaticCast<int, short>(Shuffle(tmpVector, (byte)0));
+        }
+        /// <summary>
+        /// __m128i _mm_set1_epi16 (short a)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<ushort> SetAllVector128(ushort value)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load value et index 0
+            Vector128<ushort> vector = Sse.StaticCast<uint, ushort>(ConvertScalarToVector128UInt32(value));
+            // Create { -- -- -- -- -- -- vl vl }
+            Vector128<uint> tmpVector = Sse.StaticCast<ushort, uint>(UnpackLow(vector, vector));
+            // Create { vl vl vl vl vl vl vl vl } and return result
+            return Sse.StaticCast<uint, ushort>(Shuffle(tmpVector, (byte)0));
+        }
+        /// <summary>
+        /// __m128i _mm_set1_epi32 (int a)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<int> SetAllVector128(int value)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load value et index 0
+            Vector128<int> vector = ConvertScalarToVector128Int32(value);
+            // Create { vl vl vl vl } and return result
+            return Shuffle(vector, 0);
+        }
+        /// <summary>
+        /// __m128i _mm_set1_epi32 (int a)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<uint> SetAllVector128(uint value)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load value et index 0
+            Vector128<uint> vector = ConvertScalarToVector128UInt32(value);
+            // Create { vl vl vl vl } and return result
+            return Shuffle(vector, 0);
+        }
+        /// <summary>
+        /// __m128i _mm_set1_epi64x (long long a)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<long> SetAllVector128(long value)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load value et index 0
+            Vector128<long> vector = ConvertScalarToVector128Int64(value);
+            // Create { vl vl } and return result
+            return UnpackLow(vector, vector);
+        }
+        /// <summary>
+        /// __m128i _mm_set1_epi64x (long long a)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<ulong> SetAllVector128(ulong value)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load value et index 0
+            Vector128<ulong> vector = ConvertScalarToVector128UInt64(value);
+            // Create { vl vl } and return result
+            return UnpackLow(vector, vector);
+        }
+        /// <summary>
+        /// __m128d _mm_set1_pd (double a)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<double> SetAllVector128(double value)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load value et index 0
+            Vector128<double> vector = SetScalarVector128(value);
+            // Create { vl vl } and return result
+            return UnpackLow(vector, vector);
+        }
+
+        /// <summary>
+        /// __m128d _mm_set_sd (double a)
+        ///   HELPER
+        /// </summary>
+        public static Vector128<double> SetScalarVector128(double value) => SetScalarVector128(value);
+
+        /// <summary>
+        /// ___m128i _mm_set_epi8 (char e15, char e14, char e13, char e12, char e11, char e10, char e9, char e8, char e7, char e6, char e5, char e4, char e3, char e2, char e1, char e0)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe Vector128<sbyte> SetVector128(sbyte e15, sbyte e14, sbyte e13, sbyte e12, sbyte e11, sbyte e10, sbyte e9, sbyte e8, sbyte e7, sbyte e6, sbyte e5, sbyte e4, sbyte e3, sbyte e2, sbyte e1, sbyte e0)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            sbyte* buffer = stackalloc sbyte[16];
+            buffer[0] = e0;
+            buffer[1] = e1;
+            buffer[2] = e2;
+            buffer[3] = e3;
+            buffer[4] = e4;
+            buffer[5] = e5;
+            buffer[6] = e6;
+            buffer[7] = e7;
+            buffer[8] = e8;
+            buffer[9] = e9;
+            buffer[10] = e10;
+            buffer[11] = e11;
+            buffer[12] = e12;
+            buffer[13] = e13;
+            buffer[14] = e14;
+            buffer[15] = e15;
+
+            // Load 16-byte buffer into Vector
+            return LoadVector128(buffer);
+        }
+        /// <summary>
+        /// ___m128i _mm_set_epi8 (char e15, char e14, char e13, char e12, char e11, char e10, char e9, char e8, char e7, char e6, char e5, char e4, char e3, char e2, char e1, char e0)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe Vector128<byte> SetVector128(byte e15, byte e14, byte e13, byte e12, byte e11, byte e10, byte e9, byte e8, byte e7, byte e6, byte e5, byte e4, byte e3, byte e2, byte e1, byte e0)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            byte* buffer = stackalloc byte[16];
+            buffer[0] = e0;
+            buffer[1] = e1;
+            buffer[2] = e2;
+            buffer[3] = e3;
+            buffer[4] = e4;
+            buffer[5] = e5;
+            buffer[6] = e6;
+            buffer[7] = e7;
+            buffer[8] = e8;
+            buffer[9] = e9;
+            buffer[10] = e10;
+            buffer[11] = e11;
+            buffer[12] = e12;
+            buffer[13] = e13;
+            buffer[14] = e14;
+            buffer[15] = e15;
+
+            // Load 16-byte buffer into Vector
+            return LoadVector128(buffer);
+        }
+        /// <summary>
+        /// __m128i _mm_set_epi16 (short e7, short e6, short e5, short e4, short e3, short e2, short e1, short e0)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<short> SetVector128(short e7, short e6, short e5, short e4, short e3, short e2, short e1, short e0)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load e0 et index 0
+            Vector128<int> e0Vector = ConvertScalarToVector128Int32(e0);
+            Vector128<short> vector = Sse.StaticCast<int, short>(e0Vector);
+            // Insert e1 ... e7 at corresponding index
+            vector = Insert(vector, e1, (byte)1);
+            vector = Insert(vector, e2, (byte)2);
+            vector = Insert(vector, e3, (byte)3);
+            vector = Insert(vector, e4, (byte)4);
+            vector = Insert(vector, e5, (byte)5);
+            vector = Insert(vector, e6, (byte)6);
+            return Insert(vector, e7, (byte)7);
+        }
+        /// <summary>
+        /// __m128i _mm_set_epi16 (short e7, short e6, short e5, short e4, short e3, short e2, short e1, short e0)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<ushort> SetVector128(ushort e7, ushort e6, ushort e5, ushort e4, ushort e3, ushort e2, ushort e1, ushort e0)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load e0 et index 0
+            Vector128<uint> e0vector = ConvertScalarToVector128UInt32(e0);
+            Vector128<ushort> vector = Sse.StaticCast<uint, ushort>(e0vector);
+            // Insert e1 ... e7 at corresponding index
+            vector = Insert(vector, e1, (byte)1);
+            vector = Insert(vector, e2, (byte)2);
+            vector = Insert(vector, e3, (byte)3);
+            vector = Insert(vector, e4, (byte)4);
+            vector = Insert(vector, e5, (byte)5);
+            vector = Insert(vector, e6, (byte)6);
+            return Insert(vector, e7, (byte)7);
+        }
+        /// <summary>
+        /// __m128i _mm_set_epi32 (int e3, int e2, int e1, int e0)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<int> SetVector128(int e3, int e2, int e1, int e0)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load e2 et index 0
+            Vector128<int> e2Vector = ConvertScalarToVector128Int32(e2);
+            Vector128<int> e1Vector = ConvertScalarToVector128Int32(e1);
+            Vector128<int> e0Vector = ConvertScalarToVector128Int32(e0);
+            // Create { -- -- e2 e0 }
+            e0Vector = UnpackLow(e0Vector, e2Vector);
+            e2Vector = ConvertScalarToVector128Int32(e3);
+            // Create { -- -- e3 e1 }
+            e1Vector = UnpackLow(e1Vector, e2Vector);
+            // Create { e3 e2 e1 e0 } and return result
+            return UnpackLow(e0Vector, e1Vector);
+        }
+        /// <summary>
+        /// __m128i _mm_set_epi32 (int e3, int e2, int e1, int e0)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<uint> SetVector128(uint e3, uint e2, uint e1, uint e0)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load e2 et index 0
+            Vector128<uint> e2Vector = ConvertScalarToVector128UInt32(e2);
+            Vector128<uint> e1Vector = ConvertScalarToVector128UInt32(e1);
+            Vector128<uint> e0Vector = ConvertScalarToVector128UInt32(e0);
+            // Create { -- -- e2 e0 }
+            e0Vector = UnpackLow(e0Vector, e2Vector);
+            e2Vector = ConvertScalarToVector128UInt32(e3);
+            // Create { -- -- e3 e1 }
+            e1Vector = UnpackLow(e1Vector, e2Vector);
+            // Create { e3 e2 e1 e0 } and return result
+            return UnpackLow(e0Vector, e1Vector);
+        }
+        /// <summary>
+        /// __m128i _mm_set_epi64x (__int64 e1, __int64 e0)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<long> SetVector128(long e1, long e0)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load e1 et index 0
+            Vector128<long> e1Vector = ConvertScalarToVector128Int64(e1);
+            Vector128<long> e0vector = ConvertScalarToVector128Int64(e0);
+            // Create { e1 e0 } and return result
+            return UnpackLow(e0vector, e1Vector);
+        }
+        /// <summary>
+        /// __m128i _mm_set_epi64x (__int64 e1, __int64 e0)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<ulong> SetVector128(ulong e1, ulong e0)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load e1 et index 0
+            Vector128<ulong> e1vector = ConvertScalarToVector128UInt64(e1);
+            Vector128<ulong> e0Vector = ConvertScalarToVector128UInt64(e0);
+            // Create { e1 e0 } and return result
+            return UnpackLow(e0Vector, e1vector);
+        }
+        /// <summary>
+        /// __m128d _mm_set_pd (double e1, double e0)
+        ///   HELPER
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static unsafe Vector128<double> SetVector128(double e1, double e0)
+        {
+            // TODO-CQ Optimize algorithm choice based on benchmarks
+
+            // Zero vector and load e1 et index 0
+            Vector128<double> e1Vector = SetScalarVector128(e1);
+            Vector128<double> e0Vector = SetScalarVector128(e0);
+            // Create { e1 e0 } and return result
+            return UnpackLow(e0Vector, e1Vector);
+        }
+
+        /// <summary>
+        /// __m128i _mm_setzero_si128 ()
+        ///   HELPER: PXOR
+        /// __m128d _mm_setzero_pd (void)
+        ///   HELPER: XORPD
+        /// </summary>
+        public static Vector128<T> SetZeroVector128<T>() where T : struct
+        {
+            return SetZeroVector128<T>();
+        }
+
+        /// <summary>
+        /// __m128i _mm_sad_epu8 (__m128i a,  __m128i b)
+        ///   PSADBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> SumAbsoluteDifferences(Vector128<byte> left, Vector128<byte> right) => SumAbsoluteDifferences(left, right);
+
+        /// <summary>
+        /// __m128i _mm_shuffle_epi32 (__m128i a,  int immediate)
+        ///   PSHUFD xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<int> Shuffle(Vector128<int> value, byte control) => Shuffle(value, control);
+        /// <summary>
+        /// __m128i _mm_shuffle_epi32 (__m128i a,  int immediate)
+        ///   PSHUFD xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<uint> Shuffle(Vector128<uint> value, byte control) => Shuffle(value, control);
+        /// <summary>
+        /// __m128d _mm_shuffle_pd (__m128d a,  __m128d b, int immediate)
+        ///   SHUFPD xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<double> Shuffle(Vector128<double> left, Vector128<double> right, byte control) => Shuffle(left, right, control);
+
+        /// <summary>
+        /// __m128i _mm_shufflehi_epi16 (__m128i a,  int immediate)
+        ///   PSHUFHW xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<short> ShuffleHigh(Vector128<short> value, byte control) => ShuffleHigh(value, control);
+        /// <summary>
+        /// __m128i _mm_shufflehi_epi16 (__m128i a,  int control)
+        ///   PSHUFHW xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> ShuffleHigh(Vector128<ushort> value, byte control) => ShuffleHigh(value, control);
+
+        /// <summary>
+        /// __m128i _mm_shufflelo_epi16 (__m128i a,  int control)
+        ///   PSHUFLW xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<short> ShuffleLow(Vector128<short> value, byte control) => ShuffleLow(value, control);
+        /// <summary>
+        /// __m128i _mm_shufflelo_epi16 (__m128i a,  int control)
+        ///   PSHUFLW xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> ShuffleLow(Vector128<ushort> value, byte control) => ShuffleLow(value, control);
+
+        /// <summary>
+        /// __m128i _mm_sll_epi16 (__m128i a, __m128i count)
+        ///   PSLLW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> ShiftLeftLogical(Vector128<short> value, Vector128<short> count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_sll_epi16 (__m128i a,  __m128i count)
+        ///   PSLLW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> ShiftLeftLogical(Vector128<ushort> value, Vector128<ushort> count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_sll_epi32 (__m128i a, __m128i count)
+        ///   PSLLD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ShiftLeftLogical(Vector128<int> value, Vector128<int> count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_sll_epi32 (__m128i a, __m128i count)
+        ///   PSLLD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> ShiftLeftLogical(Vector128<uint> value, Vector128<uint> count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_sll_epi64 (__m128i a, __m128i count)
+        ///   PSLLQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> ShiftLeftLogical(Vector128<long> value, Vector128<long> count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_sll_epi64 (__m128i a, __m128i count)
+        ///   PSLLQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> ShiftLeftLogical(Vector128<ulong> value, Vector128<ulong> count) => ShiftLeftLogical(value, count);
+
+        /// <summary>
+        /// __m128i _mm_slli_epi16 (__m128i a,  int immediate)
+        ///   PSLLW xmm, imm8
+        /// </summary>
+        public static Vector128<short> ShiftLeftLogical(Vector128<short> value, byte count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_slli_epi16 (__m128i a,  int immediate)
+        ///   PSLLW xmm, imm8
+        /// </summary>
+        public static Vector128<ushort> ShiftLeftLogical(Vector128<ushort> value, byte count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_slli_epi32 (__m128i a,  int immediate)
+        ///   PSLLD xmm, imm8
+        /// </summary>
+        public static Vector128<int> ShiftLeftLogical(Vector128<int> value, byte count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_slli_epi32 (__m128i a,  int immediate)
+        ///   PSLLD xmm, imm8
+        /// </summary>
+        public static Vector128<uint> ShiftLeftLogical(Vector128<uint> value, byte count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_slli_epi64 (__m128i a,  int immediate)
+        ///   PSLLQ xmm, imm8
+        /// </summary>
+        public static Vector128<long> ShiftLeftLogical(Vector128<long> value, byte count) => ShiftLeftLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_slli_epi64 (__m128i a,  int immediate)
+        ///   PSLLQ xmm, imm8
+        /// </summary>
+        public static Vector128<ulong> ShiftLeftLogical(Vector128<ulong> value, byte count) => ShiftLeftLogical(value, count);
+
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<sbyte> ShiftLeftLogical128BitLane(Vector128<sbyte> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<byte> ShiftLeftLogical128BitLane(Vector128<byte> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<short> ShiftLeftLogical128BitLane(Vector128<short> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<ushort> ShiftLeftLogical128BitLane(Vector128<ushort> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<int> ShiftLeftLogical128BitLane(Vector128<int> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<uint> ShiftLeftLogical128BitLane(Vector128<uint> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<long> ShiftLeftLogical128BitLane(Vector128<long> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m128i _mm_bslli_si128 (__m128i a, int imm8)
+        ///   PSLLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<ulong> ShiftLeftLogical128BitLane(Vector128<ulong> value, byte numBytes) => ShiftLeftLogical128BitLane(value, numBytes);
+
+        /// <summary>
+        /// __m128i _mm_sra_epi16 (__m128i a, __m128i count)
+        ///   PSRAW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> ShiftRightArithmetic(Vector128<short> value, Vector128<short> count) => ShiftRightArithmetic(value, count);
+        /// <summary>
+        /// __m128i _mm_sra_epi32 (__m128i a, __m128i count)
+        ///   PSRAD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ShiftRightArithmetic(Vector128<int> value, Vector128<int> count) => ShiftRightArithmetic(value, count);
+
+        /// <summary>
+        /// __m128i _mm_srai_epi16 (__m128i a,  int immediate)
+        ///   PSRAW xmm, imm8
+        /// </summary>
+        public static Vector128<short> ShiftRightArithmetic(Vector128<short> value, byte count) => ShiftRightArithmetic(value, count);
+        /// <summary>
+        /// __m128i _mm_srai_epi32 (__m128i a,  int immediate)
+        ///   PSRAD xmm, imm8
+        /// </summary>
+        public static Vector128<int> ShiftRightArithmetic(Vector128<int> value, byte count) => ShiftRightArithmetic(value, count);
+
+        /// <summary>
+        /// __m128i _mm_srl_epi16 (__m128i a, __m128i count)
+        ///   PSRLW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> ShiftRightLogical(Vector128<short> value, Vector128<short> count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_srl_epi16 (__m128i a, __m128i count)
+        ///   PSRLW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> ShiftRightLogical(Vector128<ushort> value, Vector128<ushort> count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_srl_epi32 (__m128i a, __m128i count)
+        ///   PSRLD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> ShiftRightLogical(Vector128<int> value, Vector128<int> count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_srl_epi32 (__m128i a, __m128i count)
+        ///   PSRLD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> ShiftRightLogical(Vector128<uint> value, Vector128<uint> count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_srl_epi64 (__m128i a, __m128i count)
+        ///   PSRLQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> ShiftRightLogical(Vector128<long> value, Vector128<long> count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_srl_epi64 (__m128i a, __m128i count)
+        ///   PSRLQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> ShiftRightLogical(Vector128<ulong> value, Vector128<ulong> count) => ShiftRightLogical(value, count);
+
+        /// <summary>
+        /// __m128i _mm_srli_epi16 (__m128i a,  int immediate)
+        ///   PSRLW xmm, imm8
+        /// </summary>
+        public static Vector128<short> ShiftRightLogical(Vector128<short> value, byte count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_srli_epi16 (__m128i a,  int immediate)
+        ///   PSRLW xmm, imm8
+        /// </summary>
+        public static Vector128<ushort> ShiftRightLogical(Vector128<ushort> value, byte count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_srli_epi32 (__m128i a,  int immediate)
+        ///   PSRLD xmm, imm8
+        /// </summary>
+        public static Vector128<int> ShiftRightLogical(Vector128<int> value, byte count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_srli_epi32 (__m128i a,  int immediate)
+        ///   PSRLD xmm, imm8
+        /// </summary>
+        public static Vector128<uint> ShiftRightLogical(Vector128<uint> value, byte count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_srli_epi64 (__m128i a,  int immediate)
+        ///   PSRLQ xmm, imm8
+        /// </summary>
+        public static Vector128<long> ShiftRightLogical(Vector128<long> value, byte count) => ShiftRightLogical(value, count);
+        /// <summary>
+        /// __m128i _mm_srli_epi64 (__m128i a,  int immediate)
+        ///   PSRLQ xmm, imm8
+        /// </summary>
+        public static Vector128<ulong> ShiftRightLogical(Vector128<ulong> value, byte count) => ShiftRightLogical(value, count);
+
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<sbyte> ShiftRightLogical128BitLane(Vector128<sbyte> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<byte> ShiftRightLogical128BitLane(Vector128<byte> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<short> ShiftRightLogical128BitLane(Vector128<short> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<ushort> ShiftRightLogical128BitLane(Vector128<ushort> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<int> ShiftRightLogical128BitLane(Vector128<int> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<uint> ShiftRightLogical128BitLane(Vector128<uint> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<long> ShiftRightLogical128BitLane(Vector128<long> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+        /// <summary>
+        /// __m128i _mm_bsrli_si128 (__m128i a, int imm8)
+        ///   PSRLDQ xmm, imm8
+        /// </summary>
+        public static Vector128<ulong> ShiftRightLogical128BitLane(Vector128<ulong> value, byte numBytes) => ShiftRightLogical128BitLane(value, numBytes);
+
+        /// <summary>
+        /// __m128d _mm_sqrt_pd (__m128d a)
+        ///   SQRTPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Sqrt(Vector128<double> value) => Sqrt(value);
+
+        /// <summary>
+        /// __m128d _mm_sqrt_sd (__m128d a)
+        ///   SQRTSD xmm, xmm/64
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> SqrtScalar(Vector128<double> value) => SqrtScalar(value);
+
+        /// <summary>
+        /// __m128d _mm_sqrt_sd (__m128d a, __m128d b)
+        ///   SQRTSD xmm, xmm/64
+        /// </summary>
+        public static Vector128<double> SqrtScalar(Vector128<double> upper, Vector128<double> value) => SqrtScalar(upper, value);
+
+        /// <summary>
+        /// void _mm_store_sd (double* mem_addr, __m128d a)
+        ///   MOVSD m64, xmm
+        /// </summary>
+        public static unsafe void StoreScalar(double* address, Vector128<double> source) => StoreScalar(address, source);
+
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(sbyte* address, Vector128<sbyte> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(byte* address, Vector128<byte> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(short* address, Vector128<short> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(ushort* address, Vector128<ushort> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(int* address, Vector128<int> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(uint* address, Vector128<uint> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(long* address, Vector128<long> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm_store_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQA m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(ulong* address, Vector128<ulong> source) => StoreAligned(address, source);
+        /// <summary>
+        /// void _mm_store_pd (double* mem_addr, __m128d a)
+        ///   MOVAPD m128, xmm
+        /// </summary>
+        public static unsafe void StoreAligned(double* address, Vector128<double> source) => StoreAligned(address, source);
+
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(sbyte* address, Vector128<sbyte> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(byte* address, Vector128<byte> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(short* address, Vector128<short> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(ushort* address, Vector128<ushort> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(int* address, Vector128<int> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(uint* address, Vector128<uint> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(long* address, Vector128<long> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm_stream_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVNTDQ m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(ulong* address, Vector128<ulong> source) => StoreAlignedNonTemporal(address, source);
+        /// <summary>
+        /// void _mm_stream_pd (double* mem_addr, __m128d a)
+        ///   MOVNTPD m128, xmm
+        /// </summary>
+        public static unsafe void StoreAlignedNonTemporal(double* address, Vector128<double> source) => StoreAlignedNonTemporal(address, source);
+
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(sbyte* address, Vector128<sbyte> source) => Store(address, source);
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(byte* address, Vector128<byte> source) => Store(address, source);
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(short* address, Vector128<short> source) => Store(address, source);
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(ushort* address, Vector128<ushort> source) => Store(address, source);
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(int* address, Vector128<int> source) => Store(address, source);
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(uint* address, Vector128<uint> source) => Store(address, source);
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(long* address, Vector128<long> source) => Store(address, source);
+        /// <summary>
+        /// void _mm_storeu_si128 (__m128i* mem_addr, __m128i a)
+        ///   MOVDQU m128, xmm
+        /// </summary>
+        public static unsafe void Store(ulong* address, Vector128<ulong> source) => Store(address, source);
+        /// <summary>
+        /// void _mm_storeu_pd (double* mem_addr, __m128d a)
+        ///   MOVUPD m128, xmm
+        /// </summary>
+        public static unsafe void Store(double* address, Vector128<double> source) => Store(address, source);
+
+        /// <summary>
+        /// void _mm_storeh_pd (double* mem_addr, __m128d a)
+        ///   MOVHPD m64, xmm
+        /// </summary>
+        public static unsafe void StoreHigh(double* address, Vector128<double> source) => StoreHigh(address, source);
+
+        /// <summary>
+        /// void _mm_storel_epi64 (__m128i* mem_addr, __m128i a)
+        ///   MOVQ m64, xmm
+        /// </summary>
+        public static unsafe void StoreLow(long* address, Vector128<long> source) => StoreLow(address, source);
+        /// <summary>
+        /// void _mm_storel_epi64 (__m128i* mem_addr, __m128i a)
+        ///   MOVQ m64, xmm
+        /// </summary>
+        public static unsafe void StoreLow(ulong* address, Vector128<ulong> source) => StoreLow(address, source);
+        /// <summary>
+        /// void _mm_storel_pd (double* mem_addr, __m128d a)
+        ///   MOVLPD m64, xmm
+        /// </summary>
+        public static unsafe void StoreLow(double* address, Vector128<double> source) => StoreLow(address, source);
+
+        /// <summary>
+        /// void _mm_stream_si32(int *p, int a)
+        ///   MOVNTI m32, r32
+        /// </summary>
+        public static unsafe void StoreNonTemporal(int* address, int value) => StoreNonTemporal(address, value);
+        /// <summary>
+        /// void _mm_stream_si32(int *p, int a)
+        ///   MOVNTI m32, r32
+        /// </summary>
+        public static unsafe void StoreNonTemporal(uint* address, uint value) => StoreNonTemporal(address, value);
+
+        /// <summary>
+        /// void _mm_stream_si64(__int64 *p, __int64 a)
+        ///   MOVNTI m64, r64
+        /// </summary>
+        public static unsafe void StoreNonTemporal(long* address, long value) => StoreNonTemporal(address, value);
+        /// <summary>
+        /// void _mm_stream_si64(__int64 *p, __int64 a)
+        ///   MOVNTI m64, r64
+        /// </summary>
+        public static unsafe void StoreNonTemporal(ulong* address, ulong value) => StoreNonTemporal(address, value);
+
+        /// <summary>
+        /// __m128i _mm_sub_epi8 (__m128i a,  __m128i b)
+        ///   PSUBB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Subtract(Vector128<byte> left, Vector128<byte> right) => Subtract(left, right);
+        /// <summary>
+        /// __m128i _mm_sub_epi8 (__m128i a,  __m128i b)
+        ///   PSUBB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Subtract(Vector128<sbyte> left, Vector128<sbyte> right) => Subtract(left, right);
+        /// <summary>
+        /// __m128i _mm_sub_epi16 (__m128i a,  __m128i b)
+        ///   PSUBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> Subtract(Vector128<short> left, Vector128<short> right) => Subtract(left, right);
+        /// <summary>
+        /// __m128i _mm_sub_epi16 (__m128i a,  __m128i b)
+        ///   PSUBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Subtract(Vector128<ushort> left, Vector128<ushort> right) => Subtract(left, right);
+        /// <summary>
+        /// __m128i _mm_sub_epi32 (__m128i a,  __m128i b)
+        ///   PSUBD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> Subtract(Vector128<int> left, Vector128<int> right) => Subtract(left, right);
+        /// <summary>
+        /// __m128i _mm_sub_epi32 (__m128i a,  __m128i b)
+        ///   PSUBD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> Subtract(Vector128<uint> left, Vector128<uint> right) => Subtract(left, right);
+        /// <summary>
+        /// __m128i _mm_sub_epi64 (__m128i a,  __m128i b)
+        ///   PSUBQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> Subtract(Vector128<long> left, Vector128<long> right) => Subtract(left, right);
+        /// <summary>
+        /// __m128i _mm_sub_epi64 (__m128i a,  __m128i b)
+        ///   PSUBQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> Subtract(Vector128<ulong> left, Vector128<ulong> right) => Subtract(left, right);
+        /// <summary>
+        /// __m128d _mm_sub_pd (__m128d a, __m128d b)
+        ///   SUBPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Subtract(Vector128<double> left, Vector128<double> right) => Subtract(left, right);
+
+        /// <summary>
+        /// __m128d _mm_sub_sd (__m128d a, __m128d b)
+        ///   SUBSD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> SubtractScalar(Vector128<double> left, Vector128<double> right) => SubtractScalar(left, right);
+
+        /// <summary>
+        /// __m128i _mm_subs_epi8 (__m128i a,  __m128i b)
+        ///   PSUBSB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> SubtractSaturate(Vector128<sbyte> left, Vector128<sbyte> right) => SubtractSaturate(left, right);
+        /// <summary>
+        /// __m128i _mm_subs_epi16 (__m128i a,  __m128i b)
+        ///   PSUBSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> SubtractSaturate(Vector128<short> left, Vector128<short> right) => SubtractSaturate(left, right);
+        /// <summary>
+        /// __m128i _mm_subs_epu8 (__m128i a,  __m128i b)
+        ///   PSUBUSB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> SubtractSaturate(Vector128<byte> left, Vector128<byte> right) => SubtractSaturate(left, right);
+        /// <summary>
+        /// __m128i _mm_subs_epu16 (__m128i a,  __m128i b)
+        ///   PSUBUSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> SubtractSaturate(Vector128<ushort> left, Vector128<ushort> right) => SubtractSaturate(left, right);
+
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi8 (__m128i a,  __m128i b)
+        ///   PUNPCKHBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> UnpackHigh(Vector128<byte> left, Vector128<byte> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi8 (__m128i a,  __m128i b)
+        ///   PUNPCKHBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> UnpackHigh(Vector128<sbyte> left, Vector128<sbyte> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi16 (__m128i a,  __m128i b)
+        ///   PUNPCKHWD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> UnpackHigh(Vector128<short> left, Vector128<short> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi16 (__m128i a,  __m128i b)
+        ///   PUNPCKHWD xmm, xmm/m128
+        /// </summary
+        public static Vector128<ushort> UnpackHigh(Vector128<ushort> left, Vector128<ushort> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi32 (__m128i a,  __m128i b)
+        ///   PUNPCKHDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> UnpackHigh(Vector128<int> left, Vector128<int> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi32 (__m128i a,  __m128i b)
+        ///   PUNPCKHDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> UnpackHigh(Vector128<uint> left, Vector128<uint> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi64 (__m128i a,  __m128i b)
+        ///   PUNPCKHQDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> UnpackHigh(Vector128<long> left, Vector128<long> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m128i _mm_unpackhi_epi64 (__m128i a,  __m128i b)
+        ///   PUNPCKHQDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> UnpackHigh(Vector128<ulong> left, Vector128<ulong> right) => UnpackHigh(left, right);
+        /// <summary>
+        /// __m128d _mm_unpackhi_pd (__m128d a,  __m128d b)
+        ///   UNPCKHPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> UnpackHigh(Vector128<double> left, Vector128<double> right) => UnpackHigh(left, right);
+
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi8 (__m128i a,  __m128i b)
+        ///   PUNPCKLBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> UnpackLow(Vector128<byte> left, Vector128<byte> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi8 (__m128i a,  __m128i b)
+        ///   PUNPCKLBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> UnpackLow(Vector128<sbyte> left, Vector128<sbyte> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi16 (__m128i a,  __m128i b)
+        ///   PUNPCKLWD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> UnpackLow(Vector128<short> left, Vector128<short> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi16 (__m128i a,  __m128i b)
+        ///   PUNPCKLWD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> UnpackLow(Vector128<ushort> left, Vector128<ushort> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi32 (__m128i a,  __m128i b)
+        ///   PUNPCKLDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> UnpackLow(Vector128<int> left, Vector128<int> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi32 (__m128i a,  __m128i b)
+        ///   PUNPCKLDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> UnpackLow(Vector128<uint> left, Vector128<uint> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi64 (__m128i a,  __m128i b)
+        ///   PUNPCKLQDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> UnpackLow(Vector128<long> left, Vector128<long> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m128i _mm_unpacklo_epi64 (__m128i a,  __m128i b)
+        ///   PUNPCKLQDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> UnpackLow(Vector128<ulong> left, Vector128<ulong> right) => UnpackLow(left, right);
+        /// <summary>
+        /// __m128d _mm_unpacklo_pd (__m128d a,  __m128d b)
+        ///   UNPCKLPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> UnpackLow(Vector128<double> left, Vector128<double> right) => UnpackLow(left, right);
+
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Xor(Vector128<byte> left, Vector128<byte> right) => Xor(left, right);
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Xor(Vector128<sbyte> left, Vector128<sbyte> right) => Xor(left, right);
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> Xor(Vector128<short> left, Vector128<short> right) => Xor(left, right);
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Xor(Vector128<ushort> left, Vector128<ushort> right) => Xor(left, right);
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> Xor(Vector128<int> left, Vector128<int> right) => Xor(left, right);
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> Xor(Vector128<uint> left, Vector128<uint> right) => Xor(left, right);
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> Xor(Vector128<long> left, Vector128<long> right) => Xor(left, right);
+        /// <summary>
+        /// __m128i _mm_xor_si128 (__m128i a,  __m128i b)
+        ///   PXOR xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> Xor(Vector128<ulong> left, Vector128<ulong> right) => Xor(left, right);
+        /// <summary>
+        /// __m128d _mm_xor_pd (__m128d a,  __m128d b)
+        ///   XORPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> Xor(Vector128<double> left, Vector128<double> right) => Xor(left, right);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse3.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse3.PlatformNotSupported.cs
new file mode 100644
index 0000000000..f2d21bb51e
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse3.PlatformNotSupported.cs
@@ -0,0 +1,89 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel SSE3 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Sse3
+    {
+        public static bool IsSupported { get { return false; } }
+        
+        /// <summary>
+        /// __m128 _mm_addsub_ps (__m128 a, __m128 b)
+        ///   ADDSUBPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> AddSubtract(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_addsub_pd (__m128d a, __m128d b)
+        ///   ADDSUBPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> AddSubtract(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_hadd_ps (__m128 a, __m128 b)
+        ///   HADDPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> HorizontalAdd(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_hadd_pd (__m128d a, __m128d b)
+        ///   HADDPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> HorizontalAdd(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_hsub_ps (__m128 a, __m128 b)
+        ///   HSUBPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> HorizontalSubtract(Vector128<float> left, Vector128<float> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_hsub_pd (__m128d a, __m128d b)
+        ///   HSUBPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> HorizontalSubtract(Vector128<double> left, Vector128<double> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_loaddup_pd (double const* mem_addr)
+        /// MOVDDUP xmm, m64
+        /// </summary>
+        public static unsafe Vector128<double> LoadAndDuplicateToVector128(double* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_lddqu_si128 (__m128i const* mem_addr)
+        ///   LDDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<sbyte> LoadDquVector128(sbyte* address) { throw new PlatformNotSupportedException(); }
+        public static unsafe Vector128<byte> LoadDquVector128(byte* address) { throw new PlatformNotSupportedException(); }
+        public static unsafe Vector128<short> LoadDquVector128(short* address) { throw new PlatformNotSupportedException(); }
+        public static unsafe Vector128<ushort> LoadDquVector128(ushort* address) { throw new PlatformNotSupportedException(); }
+        public static unsafe Vector128<int> LoadDquVector128(int* address) { throw new PlatformNotSupportedException(); }
+        public static unsafe Vector128<uint> LoadDquVector128(uint* address) { throw new PlatformNotSupportedException(); }
+        public static unsafe Vector128<long> LoadDquVector128(long* address) { throw new PlatformNotSupportedException(); }
+        public static unsafe Vector128<ulong> LoadDquVector128(ulong* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_movedup_pd (__m128d a)
+        ///   MOVDDUP xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MoveAndDuplicate(Vector128<double> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_movehdup_ps (__m128 a)
+        ///   MOVSHDUP xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MoveHighAndDuplicate(Vector128<float> source) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_moveldup_ps (__m128 a)
+        ///   MOVSLDUP xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MoveLowAndDuplicate(Vector128<float> source) { throw new PlatformNotSupportedException(); }
+
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse3.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse3.cs
new file mode 100644
index 0000000000..b7dd1de014
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse3.cs
@@ -0,0 +1,88 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel SSE3 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Sse3
+    {
+        public static bool IsSupported { get => IsSupported; }
+        
+        /// <summary>
+        /// __m128 _mm_addsub_ps (__m128 a, __m128 b)
+        ///   ADDSUBPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> AddSubtract(Vector128<float> left, Vector128<float> right) => AddSubtract(left, right);
+        /// <summary>
+        /// __m128d _mm_addsub_pd (__m128d a, __m128d b)
+        ///   ADDSUBPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> AddSubtract(Vector128<double> left, Vector128<double> right) => AddSubtract(left, right);
+
+        /// <summary>
+        /// __m128 _mm_hadd_ps (__m128 a, __m128 b)
+        ///   HADDPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> HorizontalAdd(Vector128<float> left, Vector128<float> right) => HorizontalAdd(left, right);
+        /// <summary>
+        /// __m128d _mm_hadd_pd (__m128d a, __m128d b)
+        ///   HADDPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> HorizontalAdd(Vector128<double> left, Vector128<double> right) => HorizontalAdd(left, right);
+
+        /// <summary>
+        /// __m128 _mm_hsub_ps (__m128 a, __m128 b)
+        ///   HSUBPS xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> HorizontalSubtract(Vector128<float> left, Vector128<float> right) => HorizontalSubtract(left, right);
+        /// <summary>
+        /// __m128d _mm_hsub_pd (__m128d a, __m128d b)
+        ///   HSUBPD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<double> HorizontalSubtract(Vector128<double> left, Vector128<double> right) => HorizontalSubtract(left, right);
+
+        /// <summary>
+        /// __m128d _mm_loaddup_pd (double const* mem_addr)
+        /// MOVDDUP xmm, m64
+        /// </summary>
+        public static unsafe Vector128<double> LoadAndDuplicateToVector128(double* address) => LoadAndDuplicateToVector128(address);
+
+        /// <summary>
+        /// __m128i _mm_lddqu_si128 (__m128i const* mem_addr)
+        ///   LDDQU xmm, m128
+        /// </summary>
+        public static unsafe Vector128<sbyte> LoadDquVector128(sbyte* address) => LoadDquVector128(address);
+        public static unsafe Vector128<byte> LoadDquVector128(byte* address) => LoadDquVector128(address);
+        public static unsafe Vector128<short> LoadDquVector128(short* address) => LoadDquVector128(address);
+        public static unsafe Vector128<ushort> LoadDquVector128(ushort* address) => LoadDquVector128(address);
+        public static unsafe Vector128<int> LoadDquVector128(int* address) => LoadDquVector128(address);
+        public static unsafe Vector128<uint> LoadDquVector128(uint* address) => LoadDquVector128(address);
+        public static unsafe Vector128<long> LoadDquVector128(long* address) => LoadDquVector128(address);
+        public static unsafe Vector128<ulong> LoadDquVector128(ulong* address) => LoadDquVector128(address);
+
+        /// <summary>
+        /// __m128d _mm_movedup_pd (__m128d a)
+        ///   MOVDDUP xmm, xmm/m64
+        /// </summary>
+        public static Vector128<double> MoveAndDuplicate(Vector128<double> source) => MoveAndDuplicate(source);
+
+        /// <summary>
+        /// __m128 _mm_movehdup_ps (__m128 a)
+        ///   MOVSHDUP xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MoveHighAndDuplicate(Vector128<float> source) => MoveHighAndDuplicate(source);
+
+        /// <summary>
+        /// __m128 _mm_moveldup_ps (__m128 a)
+        ///   MOVSLDUP xmm, xmm/m128
+        /// </summary>
+        public static Vector128<float> MoveLowAndDuplicate(Vector128<float> source) => MoveLowAndDuplicate(source);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse41.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse41.PlatformNotSupported.cs
new file mode 100644
index 0000000000..063b8dc2cb
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse41.PlatformNotSupported.cs
@@ -0,0 +1,639 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel SSE4.1 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Sse41
+    {
+        public static bool IsSupported { get { return false; } }
+
+        /// <summary>
+        /// __m128i _mm_blend_epi16 (__m128i a, __m128i b, const int imm8)
+        ///   PBLENDW xmm, xmm/m128 imm8
+        /// </summary>
+        public static Vector128<short> Blend(Vector128<short> left, Vector128<short> right, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_blend_epi16 (__m128i a, __m128i b, const int imm8)
+        ///   PBLENDW xmm, xmm/m128 imm8
+        /// </summary>
+        public static Vector128<ushort> Blend(Vector128<ushort> left, Vector128<ushort> right, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_blend_ps (__m128 a, __m128 b, const int imm8)
+        ///   BLENDPS xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<float> Blend(Vector128<float> left, Vector128<float> right, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_blend_pd (__m128d a, __m128d b, const int imm8)
+        ///   BLENDPD xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<double> Blend(Vector128<double> left, Vector128<double> right, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_blendv_epi8 (__m128i a, __m128i b, __m128i mask)
+        ///   PBLENDVB xmm, xmm/m128, xmm
+        /// </summary>
+        public static Vector128<sbyte> BlendVariable(Vector128<sbyte> left, Vector128<sbyte> right, Vector128<sbyte> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_blendv_epi8 (__m128i a, __m128i b, __m128i mask)
+        ///   PBLENDVB xmm, xmm/m128, xmm
+        /// </summary>
+        public static Vector128<byte> BlendVariable(Vector128<byte> left, Vector128<byte> right, Vector128<byte> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_blendv_ps (__m128 a, __m128 b, __m128 mask)
+        ///   BLENDVPS xmm, xmm/m128, xmm0
+        /// </summary>
+        public static Vector128<float> BlendVariable(Vector128<float> left, Vector128<float> right, Vector128<float> mask) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_blendv_pd (__m128d a, __m128d b, __m128d mask)
+        ///   BLENDVPD xmm, xmm/m128, xmm0
+        /// </summary>
+        public static Vector128<double> BlendVariable(Vector128<double> left, Vector128<double> right, Vector128<double> mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_ceil_ps (__m128 a)
+        ///   ROUNDPS xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<float> Ceiling(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_ceil_pd (__m128d a)
+        ///   ROUNDPD xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<double> Ceiling(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_ceil_sd (__m128d a)
+        ///   ROUNDSD xmm, xmm/m128, imm8(10)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> CeilingScalar(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_ceil_ss (__m128 a)
+        ///   ROUNDSD xmm, xmm/m128, imm8(10)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<float> CeilingScalar(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_ceil_sd (__m128d a, __m128d b)
+        ///   ROUNDSD xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<double> CeilingScalar(Vector128<double> upper, Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_ceil_ss (__m128 a, __m128 b)
+        ///   ROUNDSS xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<float> CeilingScalar(Vector128<float> upper, Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi64 (__m128i a, __m128i b)
+        ///   PCMPEQQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> CompareEqual(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi64 (__m128i a, __m128i b)
+        ///   PCMPEQQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> CompareEqual(Vector128<ulong> left, Vector128<ulong> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cvtepi8_epi16 (__m128i a)
+        ///   PMOVSXBW xmm, xmm/m64
+        /// </summary>
+        public static Vector128<short> ConvertToVector128Int16(Vector128<sbyte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtepu8_epi16 (__m128i a)
+        ///   PMOVZXBW xmm, xmm/m64
+        /// </summary>
+        public static Vector128<short> ConvertToVector128Int16(Vector128<byte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtepi8_epi32 (__m128i a)
+        ///   PMOVSXBD xmm, xmm/m32
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32(Vector128<sbyte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtepu8_epi32 (__m128i a)
+        ///   PMOVZXBD xmm, xmm/m32
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32(Vector128<byte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtepi16_epi32 (__m128i a)
+        ///   PMOVSXWD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32(Vector128<short> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtepu16_epi32 (__m128i a)
+        ///   PMOVZXWD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32(Vector128<ushort> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtepi8_epi64 (__m128i a)
+        ///   PMOVSXBQ xmm, xmm/m16
+        /// </summary>
+        public static Vector128<long> ConvertToVector128Int64(Vector128<sbyte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtepu8_epi64 (__m128i a)
+        ///   PMOVZXBQ xmm, xmm/m16
+        /// </summary>
+        public static Vector128<long> ConvertToVector128Int64(Vector128<byte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtepi16_epi64 (__m128i a)
+        ///   PMOVSXWQ xmm, xmm/m32
+        /// </summary>
+        public static Vector128<long> ConvertToVector128Int64(Vector128<short> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtepu16_epi64 (__m128i a)
+        ///   PMOVZXWQ xmm, xmm/m32
+        /// </summary>
+        public static Vector128<long> ConvertToVector128Int64(Vector128<ushort> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtepi32_epi64 (__m128i a)
+        ///   PMOVSXDQ xmm, xmm/m64
+        /// </summary>
+        public static Vector128<long> ConvertToVector128Int64(Vector128<int> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_cvtepu32_epi64 (__m128i a)
+        ///   PMOVZXDQ xmm, xmm/m64
+        /// </summary>
+        public static Vector128<long> ConvertToVector128Int64(Vector128<uint> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_dp_ps (__m128 a, __m128 b, const int imm8)
+        ///   DPPS xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<float> DotProduct(Vector128<float> left, Vector128<float> right, byte control) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_dp_pd (__m128d a, __m128d b, const int imm8)
+        ///   DPPD xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<double> DotProduct(Vector128<double> left, Vector128<double> right, byte control) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_extract_epi8 (__m128i a, const int imm8)
+        ///   PEXTRB reg/m8, xmm, imm8
+        /// </summary>
+        public static sbyte Extract(Vector128<sbyte> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm_extract_epi8 (__m128i a, const int imm8)
+        ///   PEXTRB reg/m8, xmm, imm8
+        /// </summary>
+        public static byte Extract(Vector128<byte> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm_extract_epi32 (__m128i a, const int imm8)
+        ///   PEXTRD reg/m32, xmm, imm8
+        /// </summary>
+        public static int Extract(Vector128<int> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm_extract_epi32 (__m128i a, const int imm8)
+        ///   PEXTRD reg/m32, xmm, imm8
+        /// </summary>
+        public static uint Extract(Vector128<uint> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int64 _mm_extract_epi64 (__m128i a, const int imm8)
+        ///   PEXTRQ reg/m64, xmm, imm8
+        /// </summary>
+        public static long Extract(Vector128<long> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __int64 _mm_extract_epi64 (__m128i a, const int imm8)
+        ///   PEXTRQ reg/m64, xmm, imm8
+        /// </summary>
+        public static ulong Extract(Vector128<ulong> value, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// int _mm_extract_ps (__m128 a, const int imm8)
+        ///   EXTRACTPS xmm, xmm/m32, imm8
+        /// </summary>
+        public static float Extract(Vector128<float> value, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_floor_ps (__m128 a)
+        ///   ROUNDPS xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<float> Floor(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_floor_pd (__m128d a)
+        ///   ROUNDPD xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<double> Floor(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_floor_sd (__m128d a)
+        ///   ROUNDSD xmm, xmm/m128, imm8(9)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> FloorScalar(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_floor_ss (__m128 a)
+        ///   ROUNDSS xmm, xmm/m128, imm8(9)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<float> FloorScalar(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_floor_sd (__m128d a, __m128d b)
+        ///   ROUNDSD xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<double> FloorScalar(Vector128<double> upper, Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_floor_ss (__m128 a, __m128 b)
+        ///   ROUNDSS xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<float> FloorScalar(Vector128<float> upper, Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_insert_epi8 (__m128i a, int i, const int imm8)
+        ///   PINSRB xmm, reg/m8, imm8
+        /// </summary>
+        public static Vector128<sbyte> Insert(Vector128<sbyte> value, sbyte data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_insert_epi8 (__m128i a, int i, const int imm8)
+        ///   PINSRB xmm, reg/m8, imm8
+        /// </summary>
+        public static Vector128<byte> Insert(Vector128<byte> value, byte data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_insert_epi32 (__m128i a, int i, const int imm8)
+        ///   PINSRD xmm, reg/m32, imm8
+        /// </summary>
+        public static Vector128<int> Insert(Vector128<int> value, int data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_insert_epi32 (__m128i a, int i, const int imm8)
+        ///   PINSRD xmm, reg/m32, imm8
+        /// </summary>
+        public static Vector128<uint> Insert(Vector128<uint> value, uint data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_insert_epi64 (__m128i a, __int64 i, const int imm8)
+        ///   PINSRQ xmm, reg/m64, imm8
+        /// </summary>
+        public static Vector128<long> Insert(Vector128<long> value, long data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_insert_epi64 (__m128i a, __int64 i, const int imm8)
+        ///   PINSRQ xmm, reg/m64, imm8
+        /// </summary>
+        public static Vector128<ulong> Insert(Vector128<ulong> value, ulong data, byte index) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_insert_ps (__m128 a, __m128 b, const int imm8)
+        ///   INSERTPS xmm, xmm/m32, imm8
+        /// </summary>
+        public static Vector128<float> Insert(Vector128<float> value, float data, byte index) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_max_epi8 (__m128i a, __m128i b)
+        ///   PMAXSB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Max(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_max_epu16 (__m128i a, __m128i b)
+        ///   PMAXUW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Max(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_max_epi32 (__m128i a, __m128i b)
+        ///   PMAXSD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> Max(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_max_epu32 (__m128i a, __m128i b)
+        ///   PMAXUD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> Max(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_min_epi8 (__m128i a, __m128i b)
+        ///   PMINSB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Min(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_min_epu16 (__m128i a, __m128i b)
+        ///   PMINUW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Min(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_min_epi32 (__m128i a, __m128i b)
+        ///   PMINSD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> Min(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_min_epu32 (__m128i a, __m128i b)
+        ///   PMINUD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> Min(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_minpos_epu16 (__m128i a)
+        ///   PHMINPOSUW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> MinHorizontal(Vector128<ushort> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_mpsadbw_epu8 (__m128i a, __m128i b, const int imm8)
+        ///   MPSADBW xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> MultipleSumAbsoluteDifferences(Vector128<byte> left, Vector128<byte> right, byte mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_mul_epi32 (__m128i a, __m128i b)
+        ///   PMULDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> Multiply(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_mullo_epi32 (__m128i a, __m128i b)
+        ///   PMULLD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> MultiplyLow(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_packus_epi32 (__m128i a, __m128i b)
+        ///   PACKUSDW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> PackUnsignedSaturate(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_round_ps (__m128 a, int rounding)
+        ///   ROUNDPS xmm, xmm/m128, imm8(8)
+        /// _MM_FROUND_TO_NEAREST_INT |_MM_FROUND_NO_EXC
+        /// </summary>
+        public static Vector128<float> RoundToNearestInteger(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// _MM_FROUND_TO_NEG_INF |_MM_FROUND_NO_EXC; ROUNDPS xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<float> RoundToNegativeInfinity(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// _MM_FROUND_TO_POS_INF |_MM_FROUND_NO_EXC; ROUNDPS xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<float> RoundToPositiveInfinity(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// _MM_FROUND_TO_ZERO |_MM_FROUND_NO_EXC; ROUNDPS xmm, xmm/m128, imm8(11)
+        /// </summary>
+        public static Vector128<float> RoundToZero(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// _MM_FROUND_CUR_DIRECTION; ROUNDPS xmm, xmm/m128, imm8(4)
+        /// </summary>
+        public static Vector128<float> RoundCurrentDirection(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_round_pd (__m128d a, int rounding)
+        ///   ROUNDPD xmm, xmm/m128, imm8(8)
+        /// _MM_FROUND_TO_NEAREST_INT |_MM_FROUND_NO_EXC
+        /// </summary>
+        public static Vector128<double> RoundToNearestInteger(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// _MM_FROUND_TO_NEG_INF |_MM_FROUND_NO_EXC; ROUNDPD xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<double> RoundToNegativeInfinity(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// _MM_FROUND_TO_POS_INF |_MM_FROUND_NO_EXC; ROUNDPD xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<double> RoundToPositiveInfinity(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// _MM_FROUND_TO_ZERO |_MM_FROUND_NO_EXC; ROUNDPD xmm, xmm/m128, imm8(11)
+        /// </summary>
+        public static Vector128<double> RoundToZero(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// _MM_FROUND_CUR_DIRECTION; ROUNDPD xmm, xmm/m128, imm8(4)
+        /// </summary>
+        public static Vector128<double> RoundCurrentDirection(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, _MM_FROUND_CUR_DIRECTION)
+        ///   ROUNDSD xmm, xmm/m128, imm8(4)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> RoundCurrentDirectionScalar(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, _MM_FROUND_TO_NEAREST_INT |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(8)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> RoundToNearestIntegerScalar(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, _MM_FROUND_TO_NEG_INF |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(9)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> RoundToNegativeInfinityScalar(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, _MM_FROUND_TO_POS_INF |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(10)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> RoundToPositiveInfinityScalar(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, _MM_FROUND_TO_ZERO |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(11)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> RoundToZeroScalar(Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, __m128d b, _MM_FROUND_CUR_DIRECTION)
+        ///   ROUNDSD xmm, xmm/m128, imm8(4)
+        /// </summary>
+        public static Vector128<double> RoundCurrentDirectionScalar(Vector128<double> upper, Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, __m128d b, _MM_FROUND_TO_NEAREST_INT |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(8)
+        /// </summary>
+        public static Vector128<double> RoundToNearestIntegerScalar(Vector128<double> upper, Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, __m128d b, _MM_FROUND_TO_NEG_INF |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<double> RoundToNegativeInfinityScalar(Vector128<double> upper, Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, __m128d b, _MM_FROUND_TO_POS_INF |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<double> RoundToPositiveInfinityScalar(Vector128<double> upper, Vector128<double> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, __m128d b, _MM_FROUND_TO_ZERO |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(11)
+        /// </summary>
+        public static Vector128<double> RoundToZeroScalar(Vector128<double> upper, Vector128<double> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, _MM_FROUND_CUR_DIRECTION)
+        ///   ROUNDSS xmm, xmm/m128, imm8(4)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<float> RoundCurrentDirectionScalar(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, _MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(8)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<float> RoundToNearestIntegerScalar(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, _MM_FROUND_TO_NEG_INF | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(9)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<float> RoundToNegativeInfinityScalar(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, _MM_FROUND_TO_POS_INF | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(10)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<float> RoundToPositiveInfinityScalar(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, _MM_FROUND_TO_ZERO | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(11)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<float> RoundToZeroScalar(Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, __m128 b, _MM_FROUND_CUR_DIRECTION)
+        ///   ROUNDSS xmm, xmm/m128, imm8(4)
+        /// </summary>
+        public static Vector128<float> RoundCurrentDirectionScalar(Vector128<float> upper, Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, __m128 b, _MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(8)
+        /// </summary>
+        public static Vector128<float> RoundToNearestIntegerScalar(Vector128<float> upper, Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, __m128 b, _MM_FROUND_TO_NEG_INF | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<float> RoundToNegativeInfinityScalar(Vector128<float> upper, Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, __m128 b, _MM_FROUND_TO_POS_INF | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<float> RoundToPositiveInfinityScalar(Vector128<float> upper, Vector128<float> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, __m128 b, _MM_FROUND_TO_ZERO | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(11)
+        /// </summary>
+        public static Vector128<float> RoundToZeroScalar(Vector128<float> upper, Vector128<float> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<sbyte> LoadAlignedVector128NonTemporal(sbyte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<byte> LoadAlignedVector128NonTemporal(byte* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<short> LoadAlignedVector128NonTemporal(short* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<ushort> LoadAlignedVector128NonTemporal(ushort* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<int> LoadAlignedVector128NonTemporal(int* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<uint> LoadAlignedVector128NonTemporal(uint* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<long> LoadAlignedVector128NonTemporal(long* address) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<ulong> LoadAlignedVector128NonTemporal(ulong* address) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_test_all_ones (__m128i a)
+        ///   HELPER
+        /// </summary>
+        public static bool TestAllOnes(Vector128<sbyte> value) { throw new PlatformNotSupportedException(); }
+        public static bool TestAllOnes(Vector128<byte> value) { throw new PlatformNotSupportedException(); }
+        public static bool TestAllOnes(Vector128<short> value) { throw new PlatformNotSupportedException(); }
+        public static bool TestAllOnes(Vector128<ushort> value) { throw new PlatformNotSupportedException(); }
+        public static bool TestAllOnes(Vector128<int> value) { throw new PlatformNotSupportedException(); }
+        public static bool TestAllOnes(Vector128<uint> value) { throw new PlatformNotSupportedException(); }
+        public static bool TestAllOnes(Vector128<long> value) { throw new PlatformNotSupportedException(); }
+        public static bool TestAllOnes(Vector128<ulong> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_test_all_zeros (__m128i a, __m128i mask)
+        ///   PTEST xmm, xmm/m128
+        /// </summary>
+        public static bool TestAllZeros(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestAllZeros(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestAllZeros(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestAllZeros(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestAllZeros(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestAllZeros(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestAllZeros(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestAllZeros(Vector128<ulong> left, Vector128<ulong> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_testc_si128 (__m128i a, __m128i b)
+        ///   PTEST xmm, xmm/m128
+        /// </summary>
+        public static bool TestC(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestC(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestC(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestC(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestC(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestC(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestC(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestC(Vector128<ulong> left, Vector128<ulong> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_test_mix_ones_zeros (__m128i a, __m128i mask)
+        ///   PTEST xmm, xmm/m128
+        /// </summary>
+        public static bool TestMixOnesZeros(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestMixOnesZeros(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestMixOnesZeros(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestMixOnesZeros(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestMixOnesZeros(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestMixOnesZeros(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestMixOnesZeros(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestMixOnesZeros(Vector128<ulong> left, Vector128<ulong> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_testnzc_si128 (__m128i a, __m128i b)
+        ///   PTEST xmm, xmm/m128
+        /// </summary>
+        public static bool TestNotZAndNotC(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestNotZAndNotC(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestNotZAndNotC(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestNotZAndNotC(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestNotZAndNotC(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestNotZAndNotC(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestNotZAndNotC(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestNotZAndNotC(Vector128<ulong> left, Vector128<ulong> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_testz_si128 (__m128i a, __m128i b)
+        ///   PTEST xmm, xmm/m128
+        /// </summary>
+        public static bool TestZ(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestZ(Vector128<byte> left, Vector128<byte> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestZ(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestZ(Vector128<ushort> left, Vector128<ushort> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestZ(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestZ(Vector128<uint> left, Vector128<uint> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestZ(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+        public static bool TestZ(Vector128<ulong> left, Vector128<ulong> right) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse41.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse41.cs
new file mode 100644
index 0000000000..dd81168a24
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse41.cs
@@ -0,0 +1,639 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel SSE4.1 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Sse41
+    {
+        public static bool IsSupported { get => IsSupported; }
+        
+        /// <summary>
+        /// __m128i _mm_blend_epi16 (__m128i a, __m128i b, const int imm8)
+        ///   PBLENDW xmm, xmm/m128 imm8
+        /// </summary>
+        public static Vector128<short> Blend(Vector128<short> left, Vector128<short> right, byte control) => Blend(left, right, control);
+
+        /// <summary>
+        /// __m128i _mm_blend_epi16 (__m128i a, __m128i b, const int imm8)
+        ///   PBLENDW xmm, xmm/m128 imm8
+        /// </summary>
+        public static Vector128<ushort> Blend(Vector128<ushort> left, Vector128<ushort> right, byte control) => Blend(left, right, control);
+
+        /// <summary>
+        /// __m128 _mm_blend_ps (__m128 a, __m128 b, const int imm8)
+        ///   BLENDPS xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<float> Blend(Vector128<float> left, Vector128<float> right, byte control) => Blend(left, right, control);
+
+        /// <summary>
+        /// __m128d _mm_blend_pd (__m128d a, __m128d b, const int imm8)
+        ///   BLENDPD xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<double> Blend(Vector128<double> left, Vector128<double> right, byte control) => Blend(left, right, control);
+
+        /// <summary>
+        /// __m128i _mm_blendv_epi8 (__m128i a, __m128i b, __m128i mask)
+        ///   PBLENDVB xmm, xmm/m128, xmm
+        /// </summary>
+        public static Vector128<sbyte> BlendVariable(Vector128<sbyte> left, Vector128<sbyte> right, Vector128<sbyte> mask) => BlendVariable(left, right, mask);
+        /// <summary>
+        /// __m128i _mm_blendv_epi8 (__m128i a, __m128i b, __m128i mask)
+        ///   PBLENDVB xmm, xmm/m128, xmm
+        /// </summary>
+        public static Vector128<byte> BlendVariable(Vector128<byte> left, Vector128<byte> right, Vector128<byte> mask) => BlendVariable(left, right, mask);
+        /// <summary>
+        /// __m128 _mm_blendv_ps (__m128 a, __m128 b, __m128 mask)
+        ///   BLENDVPS xmm, xmm/m128, xmm0
+        /// </summary>
+        public static Vector128<float> BlendVariable(Vector128<float> left, Vector128<float> right, Vector128<float> mask) => BlendVariable(left, right, mask);
+        /// <summary>
+        /// __m128d _mm_blendv_pd (__m128d a, __m128d b, __m128d mask)
+        ///   BLENDVPD xmm, xmm/m128, xmm0
+        /// </summary>
+        public static Vector128<double> BlendVariable(Vector128<double> left, Vector128<double> right, Vector128<double> mask) => BlendVariable(left, right, mask);
+
+        /// <summary>
+        /// __m128 _mm_ceil_ps (__m128 a)
+        ///   ROUNDPS xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<float> Ceiling(Vector128<float> value) => Ceiling(value);
+        /// <summary>
+        /// __m128d _mm_ceil_pd (__m128d a)
+        ///   ROUNDPD xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<double> Ceiling(Vector128<double> value) => Ceiling(value);
+
+        /// <summary>
+        /// __m128d _mm_ceil_sd (__m128d a)
+        ///   ROUNDSD xmm, xmm/m128, imm8(10)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> CeilingScalar(Vector128<double> value) => CeilingScalar(value);
+        /// <summary>
+        /// __m128 _mm_ceil_ss (__m128 a)
+        ///   ROUNDSD xmm, xmm/m128, imm8(10)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<float> CeilingScalar(Vector128<float> value) => CeilingScalar(value);
+
+        /// <summary>
+        /// __m128d _mm_ceil_sd (__m128d a, __m128d b)
+        ///   ROUNDSD xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<double> CeilingScalar(Vector128<double> upper, Vector128<double> value) => CeilingScalar(upper, value);
+        /// <summary>
+        /// __m128 _mm_ceil_ss (__m128 a, __m128 b)
+        ///   ROUNDSS xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<float> CeilingScalar(Vector128<float> upper, Vector128<float> value) => CeilingScalar(upper, value);
+
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi64 (__m128i a, __m128i b)
+        ///   PCMPEQQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> CompareEqual(Vector128<long> left, Vector128<long> right) => CompareEqual(left, right);
+        /// <summary>
+        /// __m128i _mm_cmpeq_epi64 (__m128i a, __m128i b)
+        ///   PCMPEQQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ulong> CompareEqual(Vector128<ulong> left, Vector128<ulong> right) => CompareEqual(left, right);
+
+        /// <summary>
+        /// __m128i _mm_cvtepi8_epi16 (__m128i a)
+        ///   PMOVSXBW xmm, xmm/m64
+        /// </summary>
+        public static Vector128<short> ConvertToVector128Int16(Vector128<sbyte> value) => ConvertToVector128Int16(value);
+        /// <summary>
+        /// __m128i _mm_cvtepu8_epi16 (__m128i a)
+        ///   PMOVZXBW xmm, xmm/m64
+        /// </summary>
+        public static Vector128<short> ConvertToVector128Int16(Vector128<byte> value) => ConvertToVector128Int16(value);
+        /// <summary>
+        /// __m128i _mm_cvtepi8_epi32 (__m128i a)
+        ///   PMOVSXBD xmm, xmm/m32
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32(Vector128<sbyte> value) => ConvertToVector128Int32(value);
+        /// <summary>
+        /// __m128i _mm_cvtepu8_epi32 (__m128i a)
+        ///   PMOVZXBD xmm, xmm/m32
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32(Vector128<byte> value) => ConvertToVector128Int32(value);
+        /// <summary>
+        /// __m128i _mm_cvtepi16_epi32 (__m128i a)
+        ///   PMOVSXWD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32(Vector128<short> value) => ConvertToVector128Int32(value);
+        /// <summary>
+        /// __m128i _mm_cvtepu16_epi32 (__m128i a)
+        ///   PMOVZXWD xmm, xmm/m64
+        /// </summary>
+        public static Vector128<int> ConvertToVector128Int32(Vector128<ushort> value) => ConvertToVector128Int32(value);
+        /// <summary>
+        /// __m128i _mm_cvtepi8_epi64 (__m128i a)
+        ///   PMOVSXBQ xmm, xmm/m16
+        /// </summary>
+        public static Vector128<long> ConvertToVector128Int64(Vector128<sbyte> value) => ConvertToVector128Int64(value);
+        /// <summary>
+        /// __m128i _mm_cvtepu8_epi64 (__m128i a)
+        ///   PMOVZXBQ xmm, xmm/m16
+        /// </summary>
+        public static Vector128<long> ConvertToVector128Int64(Vector128<byte> value) => ConvertToVector128Int64(value);
+        /// <summary>
+        /// __m128i _mm_cvtepi16_epi64 (__m128i a)
+        ///   PMOVSXWQ xmm, xmm/m32
+        /// </summary>
+        public static Vector128<long> ConvertToVector128Int64(Vector128<short> value) => ConvertToVector128Int64(value);
+        /// <summary>
+        /// __m128i _mm_cvtepu16_epi64 (__m128i a)
+        ///   PMOVZXWQ xmm, xmm/m32
+        /// </summary>
+        public static Vector128<long> ConvertToVector128Int64(Vector128<ushort> value) => ConvertToVector128Int64(value);
+        /// <summary>
+        /// __m128i _mm_cvtepi32_epi64 (__m128i a)
+        ///   PMOVSXDQ xmm, xmm/m64
+        /// </summary>
+        public static Vector128<long> ConvertToVector128Int64(Vector128<int> value) => ConvertToVector128Int64(value);
+        /// <summary>
+        /// __m128i _mm_cvtepu32_epi64 (__m128i a)
+        ///   PMOVZXDQ xmm, xmm/m64
+        /// </summary>
+        public static Vector128<long> ConvertToVector128Int64(Vector128<uint> value) => ConvertToVector128Int64(value);
+
+        /// <summary>
+        /// __m128 _mm_dp_ps (__m128 a, __m128 b, const int imm8)
+        ///   DPPS xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<float> DotProduct(Vector128<float> left, Vector128<float> right, byte control) => DotProduct(left, right, control);
+        /// <summary>
+        /// __m128d _mm_dp_pd (__m128d a, __m128d b, const int imm8)
+        ///   DPPD xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<double> DotProduct(Vector128<double> left, Vector128<double> right, byte control) => DotProduct(left, right, control);
+
+        /// <summary>
+        /// int _mm_extract_epi8 (__m128i a, const int imm8)
+        ///   PEXTRB reg/m8, xmm, imm8
+        /// </summary>
+        public static sbyte Extract(Vector128<sbyte> value, byte index) => Extract(value, index);
+        /// <summary>
+        /// int _mm_extract_epi8 (__m128i a, const int imm8)
+        ///   PEXTRB reg/m8, xmm, imm8
+        /// </summary>
+        public static byte Extract(Vector128<byte> value, byte index) => Extract(value, index);
+        /// <summary>
+        /// int _mm_extract_epi32 (__m128i a, const int imm8)
+        ///   PEXTRD reg/m32, xmm, imm8
+        /// </summary>
+        public static int Extract(Vector128<int> value, byte index) => Extract(value, index);
+        /// <summary>
+        /// int _mm_extract_epi32 (__m128i a, const int imm8)
+        ///   PEXTRD reg/m32, xmm, imm8
+        /// </summary>
+        public static uint Extract(Vector128<uint> value, byte index) => Extract(value, index);
+        /// <summary>
+        /// __int64 _mm_extract_epi64 (__m128i a, const int imm8)
+        ///   PEXTRQ reg/m64, xmm, imm8
+        /// </summary>
+        public static long Extract(Vector128<long> value, byte index) => Extract(value, index);
+        /// <summary>
+        /// __int64 _mm_extract_epi64 (__m128i a, const int imm8)
+        ///   PEXTRQ reg/m64, xmm, imm8
+        /// </summary>
+        public static ulong Extract(Vector128<ulong> value, byte index) => Extract(value, index);
+        /// <summary>
+        /// int _mm_extract_ps (__m128 a, const int imm8)
+        ///   EXTRACTPS xmm, xmm/m32, imm8
+        /// </summary>
+        public static float Extract(Vector128<float> value, byte index) => Extract(value, index);
+
+        /// <summary>
+        /// __m128 _mm_floor_ps (__m128 a)
+        ///   ROUNDPS xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<float> Floor(Vector128<float> value) => Floor(value);
+        /// <summary>
+        /// __m128d _mm_floor_pd (__m128d a)
+        ///   ROUNDPD xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<double> Floor(Vector128<double> value) => Floor(value);
+
+        /// <summary>
+        /// __m128d _mm_floor_sd (__m128d a)
+        ///   ROUNDSD xmm, xmm/m128, imm8(9)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> FloorScalar(Vector128<double> value) => FloorScalar(value);
+        /// <summary>
+        /// __m128 _mm_floor_ss (__m128 a)
+        ///   ROUNDSS xmm, xmm/m128, imm8(9)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<float> FloorScalar(Vector128<float> value) => FloorScalar(value);
+
+        /// <summary>
+        /// __m128d _mm_floor_sd (__m128d a, __m128d b)
+        ///   ROUNDSD xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<double> FloorScalar(Vector128<double> upper, Vector128<double> value) => FloorScalar(upper, value);
+        /// <summary>
+        /// __m128 _mm_floor_ss (__m128 a, __m128 b)
+        ///   ROUNDSS xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<float> FloorScalar(Vector128<float> upper, Vector128<float> value) => FloorScalar(upper, value);
+
+        /// <summary>
+        /// __m128i _mm_insert_epi8 (__m128i a, int i, const int imm8)
+        ///   PINSRB xmm, reg/m8, imm8
+        /// </summary>
+        public static Vector128<sbyte> Insert(Vector128<sbyte> value, sbyte data, byte index) => Insert(value, data, index);
+        /// <summary>
+        /// __m128i _mm_insert_epi8 (__m128i a, int i, const int imm8)
+        ///   PINSRB xmm, reg/m8, imm8
+        /// </summary>
+        public static Vector128<byte> Insert(Vector128<byte> value, byte data, byte index) => Insert(value, data, index);
+        /// <summary>
+        /// __m128i _mm_insert_epi32 (__m128i a, int i, const int imm8)
+        ///   PINSRD xmm, reg/m32, imm8
+        /// </summary>
+        public static Vector128<int> Insert(Vector128<int> value, int data, byte index) => Insert(value, data, index);
+        /// <summary>
+        /// __m128i _mm_insert_epi32 (__m128i a, int i, const int imm8)
+        ///   PINSRD xmm, reg/m32, imm8
+        /// </summary>
+        public static Vector128<uint> Insert(Vector128<uint> value, uint data, byte index) => Insert(value, data, index);
+        /// <summary>
+        /// __m128i _mm_insert_epi64 (__m128i a, __int64 i, const int imm8)
+        ///   PINSRQ xmm, reg/m64, imm8
+        /// </summary>
+        public static Vector128<long> Insert(Vector128<long> value, long data, byte index) => Insert(value, data, index);
+        /// <summary>
+        /// __m128i _mm_insert_epi64 (__m128i a, __int64 i, const int imm8)
+        ///   PINSRQ xmm, reg/m64, imm8
+        /// </summary>
+        public static Vector128<ulong> Insert(Vector128<ulong> value, ulong data, byte index) => Insert(value, data, index);
+        /// <summary>
+        /// __m128 _mm_insert_ps (__m128 a, __m128 b, const int imm8)
+        ///   INSERTPS xmm, xmm/m32, imm8
+        /// </summary>
+        public static Vector128<float> Insert(Vector128<float> value, float data, byte index) => Insert(value, data, index);
+
+        /// <summary>
+        /// __m128i _mm_max_epi8 (__m128i a, __m128i b)
+        ///   PMAXSB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Max(Vector128<sbyte> left, Vector128<sbyte> right) => Max(left, right);
+        /// <summary>
+        /// __m128i _mm_max_epu16 (__m128i a, __m128i b)
+        ///   PMAXUW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Max(Vector128<ushort> left, Vector128<ushort> right) => Max(left, right);
+        /// <summary>
+        /// __m128i _mm_max_epi32 (__m128i a, __m128i b)
+        ///   PMAXSD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> Max(Vector128<int> left, Vector128<int> right) => Max(left, right);
+        /// <summary>
+        /// __m128i _mm_max_epu32 (__m128i a, __m128i b)
+        ///   PMAXUD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> Max(Vector128<uint> left, Vector128<uint> right) => Max(left, right);
+
+        /// <summary>
+        /// __m128i _mm_min_epi8 (__m128i a, __m128i b)
+        ///   PMINSB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Min(Vector128<sbyte> left, Vector128<sbyte> right) => Min(left, right);
+        /// <summary>
+        /// __m128i _mm_min_epu16 (__m128i a, __m128i b)
+        ///   PMINUW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Min(Vector128<ushort> left, Vector128<ushort> right) => Min(left, right);
+        /// <summary>
+        /// __m128i _mm_min_epi32 (__m128i a, __m128i b)
+        ///   PMINSD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> Min(Vector128<int> left, Vector128<int> right) => Min(left, right);
+        /// <summary>
+        /// __m128i _mm_min_epu32 (__m128i a, __m128i b)
+        ///   PMINUD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> Min(Vector128<uint> left, Vector128<uint> right) => Min(left, right);
+
+        /// <summary>
+        /// __m128i _mm_minpos_epu16 (__m128i a)
+        ///   PHMINPOSUW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> MinHorizontal(Vector128<ushort> value) => MinHorizontal(value);
+
+        /// <summary>
+        /// __m128i _mm_mpsadbw_epu8 (__m128i a, __m128i b, const int imm8)
+        ///   MPSADBW xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> MultipleSumAbsoluteDifferences(Vector128<byte> left, Vector128<byte> right, byte mask) => MultipleSumAbsoluteDifferences(left, right, mask);
+
+        /// <summary>
+        /// __m128i _mm_mul_epi32 (__m128i a, __m128i b)
+        ///   PMULDQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> Multiply(Vector128<int> left, Vector128<int> right) => Multiply(left, right);
+
+        /// <summary>
+        /// __m128i _mm_mullo_epi32 (__m128i a, __m128i b)
+        ///   PMULLD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> MultiplyLow(Vector128<int> left, Vector128<int> right) => MultiplyLow(left, right);
+
+        /// <summary>
+        /// __m128i _mm_packus_epi32 (__m128i a, __m128i b)
+        ///   PACKUSDW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> PackUnsignedSaturate(Vector128<int> left, Vector128<int> right) => PackUnsignedSaturate(left, right);
+
+        /// <summary>
+        /// __m128 _mm_round_ps (__m128 a, int rounding)
+        ///   ROUNDPS xmm, xmm/m128, imm8(8)
+        /// _MM_FROUND_TO_NEAREST_INT |_MM_FROUND_NO_EXC
+        /// </summary>
+        public static Vector128<float> RoundToNearestInteger(Vector128<float> value) => RoundToNearestInteger(value);
+        /// <summary>
+        /// _MM_FROUND_TO_NEG_INF |_MM_FROUND_NO_EXC; ROUNDPS xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<float> RoundToNegativeInfinity(Vector128<float> value) => RoundToNegativeInfinity(value);
+        /// <summary>
+        /// _MM_FROUND_TO_POS_INF |_MM_FROUND_NO_EXC; ROUNDPS xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<float> RoundToPositiveInfinity(Vector128<float> value) => RoundToPositiveInfinity(value);
+        /// <summary>
+        /// _MM_FROUND_TO_ZERO |_MM_FROUND_NO_EXC; ROUNDPS xmm, xmm/m128, imm8(11)
+        /// </summary>
+        public static Vector128<float> RoundToZero(Vector128<float> value) => RoundToZero(value);
+        /// <summary>
+        /// _MM_FROUND_CUR_DIRECTION; ROUNDPS xmm, xmm/m128, imm8(4)
+        /// </summary>
+        public static Vector128<float> RoundCurrentDirection(Vector128<float> value) => RoundCurrentDirection(value);
+
+        /// <summary>
+        /// __m128d _mm_round_pd (__m128d a, int rounding)
+        ///   ROUNDPD xmm, xmm/m128, imm8(8)
+        /// _MM_FROUND_TO_NEAREST_INT |_MM_FROUND_NO_EXC
+        /// </summary>
+        public static Vector128<double> RoundToNearestInteger(Vector128<double> value) => RoundToNearestInteger(value);
+        /// <summary>
+        /// _MM_FROUND_TO_NEG_INF |_MM_FROUND_NO_EXC; ROUNDPD xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<double> RoundToNegativeInfinity(Vector128<double> value) => RoundToNegativeInfinity(value);
+        /// <summary>
+        /// _MM_FROUND_TO_POS_INF |_MM_FROUND_NO_EXC; ROUNDPD xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<double> RoundToPositiveInfinity(Vector128<double> value) => RoundToPositiveInfinity(value);
+        /// <summary>
+        /// _MM_FROUND_TO_ZERO |_MM_FROUND_NO_EXC; ROUNDPD xmm, xmm/m128, imm8(11)
+        /// </summary>
+        public static Vector128<double> RoundToZero(Vector128<double> value) => RoundToZero(value);
+        /// <summary>
+        /// _MM_FROUND_CUR_DIRECTION; ROUNDPD xmm, xmm/m128, imm8(4)
+        /// </summary>
+        public static Vector128<double> RoundCurrentDirection(Vector128<double> value) => RoundCurrentDirection(value);
+
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, _MM_FROUND_CUR_DIRECTION)
+        ///   ROUNDSD xmm, xmm/m128, imm8(4)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> RoundCurrentDirectionScalar(Vector128<double> value) => RoundCurrentDirectionScalar(value);
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, _MM_FROUND_TO_NEAREST_INT |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(8)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> RoundToNearestIntegerScalar(Vector128<double> value) => RoundToNearestIntegerScalar(value);
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, _MM_FROUND_TO_NEG_INF |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(9)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> RoundToNegativeInfinityScalar(Vector128<double> value) => RoundToNegativeInfinityScalar(value);
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, _MM_FROUND_TO_POS_INF |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(10)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> RoundToPositiveInfinityScalar(Vector128<double> value) => RoundToPositiveInfinityScalar(value);
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, _MM_FROUND_TO_ZERO |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(11)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<double> RoundToZeroScalar(Vector128<double> value) => RoundToZeroScalar(value);
+
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, __m128d b, _MM_FROUND_CUR_DIRECTION)
+        ///   ROUNDSD xmm, xmm/m128, imm8(4)
+        /// </summary>
+        public static Vector128<double> RoundCurrentDirectionScalar(Vector128<double> upper, Vector128<double> value) => RoundCurrentDirectionScalar(upper, value);
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, __m128d b, _MM_FROUND_TO_NEAREST_INT |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(8)
+        /// </summary>
+        public static Vector128<double> RoundToNearestIntegerScalar(Vector128<double> upper, Vector128<double> value) => RoundToNearestIntegerScalar(upper, value);
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, __m128d b, _MM_FROUND_TO_NEG_INF |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<double> RoundToNegativeInfinityScalar(Vector128<double> upper, Vector128<double> value) => RoundToNegativeInfinityScalar(upper, value);
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, __m128d b, _MM_FROUND_TO_POS_INF |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<double> RoundToPositiveInfinityScalar(Vector128<double> upper, Vector128<double> value) => RoundToPositiveInfinityScalar(upper, value);
+        /// <summary>
+        /// __m128d _mm_round_sd (__m128d a, __m128d b, _MM_FROUND_TO_ZERO |_MM_FROUND_NO_EXC)
+        ///   ROUNDSD xmm, xmm/m128, imm8(11)
+        /// </summary>
+        public static Vector128<double> RoundToZeroScalar(Vector128<double> upper, Vector128<double> value) => RoundToZeroScalar(upper, value);
+
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, _MM_FROUND_CUR_DIRECTION)
+        ///   ROUNDSS xmm, xmm/m128, imm8(4)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<float> RoundCurrentDirectionScalar(Vector128<float> value) => RoundCurrentDirectionScalar(value);
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, _MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(8)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<float> RoundToNearestIntegerScalar(Vector128<float> value) => RoundToNearestIntegerScalar(value);
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, _MM_FROUND_TO_NEG_INF | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(9)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<float> RoundToNegativeInfinityScalar(Vector128<float> value) => RoundToNegativeInfinityScalar(value);
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, _MM_FROUND_TO_POS_INF | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(10)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<float> RoundToPositiveInfinityScalar(Vector128<float> value) => RoundToPositiveInfinityScalar(value);
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, _MM_FROUND_TO_ZERO | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(11)
+        /// The above native signature does not exist. We provide this additional overload for the recommended use case of this intrinsic.
+        /// </summary>
+        public static Vector128<float> RoundToZeroScalar(Vector128<float> value) => RoundToZeroScalar(value);
+
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, __m128 b, _MM_FROUND_CUR_DIRECTION)
+        ///   ROUNDSS xmm, xmm/m128, imm8(4)
+        /// </summary>
+        public static Vector128<float> RoundCurrentDirectionScalar(Vector128<float> upper, Vector128<float> value) => RoundCurrentDirectionScalar(upper, value);
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, __m128 b, _MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(8)
+        /// </summary>
+        public static Vector128<float> RoundToNearestIntegerScalar(Vector128<float> upper, Vector128<float> value) => RoundToNearestIntegerScalar(upper, value);
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, __m128 b, _MM_FROUND_TO_NEG_INF | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(9)
+        /// </summary>
+        public static Vector128<float> RoundToNegativeInfinityScalar(Vector128<float> upper, Vector128<float> value) => RoundToNegativeInfinityScalar(upper, value);
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, __m128 b, _MM_FROUND_TO_POS_INF | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(10)
+        /// </summary>
+        public static Vector128<float> RoundToPositiveInfinityScalar(Vector128<float> upper, Vector128<float> value) => RoundToPositiveInfinityScalar(upper, value);
+        /// <summary>
+        /// __m128 _mm_round_ss (__m128 a, __m128 b, _MM_FROUND_TO_ZERO | _MM_FROUND_NO_EXC)
+        ///   ROUNDSS xmm, xmm/m128, imm8(11)
+        /// </summary>
+        public static Vector128<float> RoundToZeroScalar(Vector128<float> upper, Vector128<float> value) => RoundToZeroScalar(upper, value);
+
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<sbyte> LoadAlignedVector128NonTemporal(sbyte* address) => LoadAlignedVector128NonTemporal(address);
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<byte> LoadAlignedVector128NonTemporal(byte* address) => LoadAlignedVector128NonTemporal(address);
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<short> LoadAlignedVector128NonTemporal(short* address) => LoadAlignedVector128NonTemporal(address);
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<ushort> LoadAlignedVector128NonTemporal(ushort* address) => LoadAlignedVector128NonTemporal(address);
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<int> LoadAlignedVector128NonTemporal(int* address) => LoadAlignedVector128NonTemporal(address);
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<uint> LoadAlignedVector128NonTemporal(uint* address) => LoadAlignedVector128NonTemporal(address);
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<long> LoadAlignedVector128NonTemporal(long* address) => LoadAlignedVector128NonTemporal(address);
+        /// <summary>
+        /// __m128i _mm_stream_load_si128 (const __m128i* mem_addr)
+        ///   MOVNTDQA xmm, m128
+        /// </summary>
+        public static unsafe Vector128<ulong> LoadAlignedVector128NonTemporal(ulong* address) => LoadAlignedVector128NonTemporal(address);
+
+        /// <summary>
+        /// int _mm_test_all_ones (__m128i a)
+        ///   HELPER
+        /// </summary>
+        public static bool TestAllOnes(Vector128<sbyte> value) => TestAllOnes(value);
+        public static bool TestAllOnes(Vector128<byte> value) => TestAllOnes(value);
+        public static bool TestAllOnes(Vector128<short> value) => TestAllOnes(value);
+        public static bool TestAllOnes(Vector128<ushort> value) => TestAllOnes(value);
+        public static bool TestAllOnes(Vector128<int> value) => TestAllOnes(value);
+        public static bool TestAllOnes(Vector128<uint> value) => TestAllOnes(value);
+        public static bool TestAllOnes(Vector128<long> value) => TestAllOnes(value);
+        public static bool TestAllOnes(Vector128<ulong> value) => TestAllOnes(value);
+
+        /// <summary>
+        /// int _mm_test_all_zeros (__m128i a, __m128i mask)
+        ///   PTEST xmm, xmm/m128
+        /// </summary>
+        public static bool TestAllZeros(Vector128<sbyte> left, Vector128<sbyte> right) => TestAllZeros(left, right);
+        public static bool TestAllZeros(Vector128<byte> left, Vector128<byte> right) => TestAllZeros(left, right);
+        public static bool TestAllZeros(Vector128<short> left, Vector128<short> right) => TestAllZeros(left, right);
+        public static bool TestAllZeros(Vector128<ushort> left, Vector128<ushort> right) => TestAllZeros(left, right);
+        public static bool TestAllZeros(Vector128<int> left, Vector128<int> right) => TestAllZeros(left, right);
+        public static bool TestAllZeros(Vector128<uint> left, Vector128<uint> right) => TestAllZeros(left, right);
+        public static bool TestAllZeros(Vector128<long> left, Vector128<long> right) => TestAllZeros(left, right);
+        public static bool TestAllZeros(Vector128<ulong> left, Vector128<ulong> right) => TestAllZeros(left, right);
+
+        /// <summary>
+        /// int _mm_testc_si128 (__m128i a, __m128i b)
+        ///   PTEST xmm, xmm/m128
+        /// </summary>
+        public static bool TestC(Vector128<sbyte> left, Vector128<sbyte> right) => TestC(left, right);
+        public static bool TestC(Vector128<byte> left, Vector128<byte> right) => TestC(left, right);
+        public static bool TestC(Vector128<short> left, Vector128<short> right) => TestC(left, right);
+        public static bool TestC(Vector128<ushort> left, Vector128<ushort> right) => TestC(left, right);
+        public static bool TestC(Vector128<int> left, Vector128<int> right) => TestC(left, right);
+        public static bool TestC(Vector128<uint> left, Vector128<uint> right) => TestC(left, right);
+        public static bool TestC(Vector128<long> left, Vector128<long> right) => TestC(left, right);
+        public static bool TestC(Vector128<ulong> left, Vector128<ulong> right) => TestC(left, right);
+
+        /// <summary>
+        /// int _mm_test_mix_ones_zeros (__m128i a, __m128i mask)
+        ///   PTEST xmm, xmm/m128
+        /// </summary>
+        public static bool TestMixOnesZeros(Vector128<sbyte> left, Vector128<sbyte> right) => TestMixOnesZeros(left, right);
+        public static bool TestMixOnesZeros(Vector128<byte> left, Vector128<byte> right) => TestMixOnesZeros(left, right);
+        public static bool TestMixOnesZeros(Vector128<short> left, Vector128<short> right) => TestMixOnesZeros(left, right);
+        public static bool TestMixOnesZeros(Vector128<ushort> left, Vector128<ushort> right) => TestMixOnesZeros(left, right);
+        public static bool TestMixOnesZeros(Vector128<int> left, Vector128<int> right) => TestMixOnesZeros(left, right);
+        public static bool TestMixOnesZeros(Vector128<uint> left, Vector128<uint> right) => TestMixOnesZeros(left, right);
+        public static bool TestMixOnesZeros(Vector128<long> left, Vector128<long> right) => TestMixOnesZeros(left, right);
+        public static bool TestMixOnesZeros(Vector128<ulong> left, Vector128<ulong> right) => TestMixOnesZeros(left, right);
+
+        /// <summary>
+        /// int _mm_testnzc_si128 (__m128i a, __m128i b)
+        ///   PTEST xmm, xmm/m128
+        /// </summary>
+        public static bool TestNotZAndNotC(Vector128<sbyte> left, Vector128<sbyte> right) => TestNotZAndNotC(left, right);
+        public static bool TestNotZAndNotC(Vector128<byte> left, Vector128<byte> right) => TestNotZAndNotC(left, right);
+        public static bool TestNotZAndNotC(Vector128<short> left, Vector128<short> right) => TestNotZAndNotC(left, right);
+        public static bool TestNotZAndNotC(Vector128<ushort> left, Vector128<ushort> right) => TestNotZAndNotC(left, right);
+        public static bool TestNotZAndNotC(Vector128<int> left, Vector128<int> right) => TestNotZAndNotC(left, right);
+        public static bool TestNotZAndNotC(Vector128<uint> left, Vector128<uint> right) => TestNotZAndNotC(left, right);
+        public static bool TestNotZAndNotC(Vector128<long> left, Vector128<long> right) => TestNotZAndNotC(left, right);
+        public static bool TestNotZAndNotC(Vector128<ulong> left, Vector128<ulong> right) => TestNotZAndNotC(left, right);
+
+        /// <summary>
+        /// int _mm_testz_si128 (__m128i a, __m128i b)
+        ///   PTEST xmm, xmm/m128
+        /// </summary>
+        public static bool TestZ(Vector128<sbyte> left, Vector128<sbyte> right) => TestZ(left, right);
+        public static bool TestZ(Vector128<byte> left, Vector128<byte> right) => TestZ(left, right);
+        public static bool TestZ(Vector128<short> left, Vector128<short> right) => TestZ(left, right);
+        public static bool TestZ(Vector128<ushort> left, Vector128<ushort> right) => TestZ(left, right);
+        public static bool TestZ(Vector128<int> left, Vector128<int> right) => TestZ(left, right);
+        public static bool TestZ(Vector128<uint> left, Vector128<uint> right) => TestZ(left, right);
+        public static bool TestZ(Vector128<long> left, Vector128<long> right) => TestZ(left, right);
+        public static bool TestZ(Vector128<ulong> left, Vector128<ulong> right) => TestZ(left, right);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse42.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse42.PlatformNotSupported.cs
new file mode 100644
index 0000000000..43f78dc3e6
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse42.PlatformNotSupported.cs
@@ -0,0 +1,302 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel SSE4.2 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Sse42
+    {
+        public static bool IsSupported { get { return false; } }
+
+        /// <summary>
+        /// int _mm_cmpistra (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrc (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistro (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrs (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrz (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareImplicitLength(Vector128<sbyte> left, Vector128<sbyte> right, ResultsFlag flag, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cmpistra (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrc (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistro (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrs (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrz (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareImplicitLength(Vector128<byte> left, Vector128<byte> right, ResultsFlag flag, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cmpistra (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrc (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistro (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrs (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrz (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareImplicitLength(Vector128<short> left, Vector128<short> right, ResultsFlag flag, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+
+        /// <summary>
+        /// int _mm_cmpistra (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrc (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistro (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrs (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrz (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareImplicitLength(Vector128<ushort> left, Vector128<ushort> right, ResultsFlag flag, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cmpestra (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrc (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestro (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrs (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrz (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareExplicitLength(Vector128<sbyte> left, byte leftLength, Vector128<sbyte> right, byte rightLength, ResultsFlag flag, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cmpestra (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrc (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestro (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrs (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrz (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareExplicitLength(Vector128<byte> left, byte leftLength, Vector128<byte> right, byte rightLength, ResultsFlag flag, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cmpestra (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrc (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestro (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrs (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrz (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareExplicitLength(Vector128<short> left, byte leftLength, Vector128<short> right, byte rightLength, ResultsFlag flag, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cmpestra (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrc (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestro (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrs (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrz (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareExplicitLength(Vector128<ushort> left, byte leftLength, Vector128<ushort> right, byte rightLength, ResultsFlag flag, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cmpistri (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareImplicitLengthIndex(Vector128<sbyte> left, Vector128<sbyte> right, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cmpistri (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareImplicitLengthIndex(Vector128<byte> left, Vector128<byte> right, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cmpistri (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareImplicitLengthIndex(Vector128<short> left, Vector128<short> right, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cmpistri (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareImplicitLengthIndex(Vector128<ushort> left, Vector128<ushort> right, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cmpestri (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareExplicitLengthIndex(Vector128<sbyte> left, byte leftLength, Vector128<sbyte> right, byte rightLength, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cmpestri (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareExplicitLengthIndex(Vector128<byte> left, byte leftLength, Vector128<byte> right, byte rightLength, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cmpestri (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareExplicitLengthIndex(Vector128<short> left, byte leftLength, Vector128<short> right, byte rightLength, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// int _mm_cmpestri (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareExplicitLengthIndex(Vector128<ushort> left, byte leftLength, Vector128<ushort> right, byte rightLength, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareImplicitLengthBitMask(Vector128<sbyte> left, Vector128<sbyte> right, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareImplicitLengthBitMask(Vector128<byte> left, Vector128<byte> right, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareImplicitLengthBitMask(Vector128<short> left, Vector128<short> right, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareImplicitLengthBitMask(Vector128<ushort> left, Vector128<ushort> right, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareImplicitLengthUnitMask(Vector128<sbyte> left, Vector128<sbyte> right, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareImplicitLengthUnitMask(Vector128<byte> left, Vector128<byte> right, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareImplicitLengthUnitMask(Vector128<short> left, Vector128<short> right, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareImplicitLengthUnitMask(Vector128<ushort> left, Vector128<ushort> right, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareExplicitLengthBitMask(Vector128<sbyte> left, byte leftLength, Vector128<sbyte> right, byte rightLength, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareExplicitLengthBitMask(Vector128<byte> left, byte leftLength, Vector128<byte> right, byte rightLength, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareExplicitLengthBitMask(Vector128<short> left, byte leftLength, Vector128<short> right, byte rightLength, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareExplicitLengthBitMask(Vector128<ushort> left, byte leftLength, Vector128<ushort> right, byte rightLength, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareExplicitLengthUnitMask(Vector128<sbyte> left, byte leftLength, Vector128<sbyte> right, byte rightLength, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareExplicitLengthUnitMask(Vector128<byte> left, byte leftLength, Vector128<byte> right, byte rightLength, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareExplicitLengthUnitMask(Vector128<short> left, byte leftLength, Vector128<short> right, byte rightLength, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareExplicitLengthUnitMask(Vector128<ushort> left, byte leftLength, Vector128<ushort> right, byte rightLength, StringComparisonMode mode) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_cmpgt_epi64 (__m128i a, __m128i b)
+        ///   PCMPGTQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> CompareGreaterThan(Vector128<long> left, Vector128<long> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// unsigned int _mm_crc32_u8 (unsigned int crc, unsigned char v)
+        ///   CRC32 reg, reg/m8
+        /// </summary>
+        public static uint Crc32(uint crc, byte data) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned int _mm_crc32_u16 (unsigned int crc, unsigned short v)
+        ///   CRC32 reg, reg/m16
+        /// </summary>
+        public static uint Crc32(uint crc, ushort data) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned int _mm_crc32_u32 (unsigned int crc, unsigned int v)
+        ///   CRC32 reg, reg/m32
+        /// </summary>
+        public static uint Crc32(uint crc, uint data) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// unsigned __int64 _mm_crc32_u64 (unsigned __int64 crc, unsigned __int64 v)
+        ///   CRC32 reg, reg/m64
+        /// </summary>
+        public static ulong Crc32(ulong crc, ulong data) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse42.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse42.cs
new file mode 100644
index 0000000000..205e72ed4f
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Sse42.cs
@@ -0,0 +1,302 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel SSE4.2 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Sse42
+    {
+        public static bool IsSupported { get => IsSupported; }
+
+        /// <summary>
+        /// int _mm_cmpistra (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrc (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistro (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrs (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrz (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareImplicitLength(Vector128<sbyte> left, Vector128<sbyte> right, ResultsFlag flag, StringComparisonMode mode) => CompareImplicitLength(left, right, flag, mode);
+
+        /// <summary>
+        /// int _mm_cmpistra (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrc (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistro (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrs (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrz (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareImplicitLength(Vector128<byte> left, Vector128<byte> right, ResultsFlag flag, StringComparisonMode mode) => CompareImplicitLength(left, right, flag, mode);
+
+        /// <summary>
+        /// int _mm_cmpistra (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrc (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistro (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrs (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrz (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareImplicitLength(Vector128<short> left, Vector128<short> right, ResultsFlag flag, StringComparisonMode mode) => CompareImplicitLength(left, right, flag, mode);
+
+
+        /// <summary>
+        /// int _mm_cmpistra (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrc (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistro (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrs (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpistrz (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareImplicitLength(Vector128<ushort> left, Vector128<ushort> right, ResultsFlag flag, StringComparisonMode mode) => CompareImplicitLength(left, right, flag, mode);
+
+        /// <summary>
+        /// int _mm_cmpestra (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrc (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestro (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrs (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrz (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareExplicitLength(Vector128<sbyte> left, byte leftLength, Vector128<sbyte> right, byte rightLength, ResultsFlag flag, StringComparisonMode mode) => CompareExplicitLength(left, leftLength, right, rightLength, flag, mode);
+
+        /// <summary>
+        /// int _mm_cmpestra (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrc (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestro (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrs (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrz (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareExplicitLength(Vector128<byte> left, byte leftLength, Vector128<byte> right, byte rightLength, ResultsFlag flag, StringComparisonMode mode) => CompareExplicitLength(left, leftLength, right, rightLength, flag, mode);
+
+        /// <summary>
+        /// int _mm_cmpestra (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrc (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestro (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrs (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrz (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareExplicitLength(Vector128<short> left, byte leftLength, Vector128<short> right, byte rightLength, ResultsFlag flag, StringComparisonMode mode) => CompareExplicitLength(left, leftLength, right, rightLength, flag, mode);
+
+        /// <summary>
+        /// int _mm_cmpestra (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrc (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestro (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrs (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// int _mm_cmpestrz (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static bool CompareExplicitLength(Vector128<ushort> left, byte leftLength, Vector128<ushort> right, byte rightLength, ResultsFlag flag, StringComparisonMode mode) => CompareExplicitLength(left, leftLength, right, rightLength, flag, mode);
+
+        /// <summary>
+        /// int _mm_cmpistri (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareImplicitLengthIndex(Vector128<sbyte> left, Vector128<sbyte> right, StringComparisonMode mode) => CompareImplicitLengthIndex(left, right, mode);
+
+        /// <summary>
+        /// int _mm_cmpistri (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareImplicitLengthIndex(Vector128<byte> left, Vector128<byte> right, StringComparisonMode mode) => CompareImplicitLengthIndex(left, right, mode);
+
+        /// <summary>
+        /// int _mm_cmpistri (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareImplicitLengthIndex(Vector128<short> left, Vector128<short> right, StringComparisonMode mode) => CompareImplicitLengthIndex(left, right, mode);
+
+        /// <summary>
+        /// int _mm_cmpistri (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareImplicitLengthIndex(Vector128<ushort> left, Vector128<ushort> right, StringComparisonMode mode) => CompareImplicitLengthIndex(left, right, mode);
+
+        /// <summary>
+        /// int _mm_cmpestri (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareExplicitLengthIndex(Vector128<sbyte> left, byte leftLength, Vector128<sbyte> right, byte rightLength, StringComparisonMode mode) => CompareExplicitLengthIndex(left, leftLength, right, rightLength, mode);
+
+        /// <summary>
+        /// int _mm_cmpestri (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareExplicitLengthIndex(Vector128<byte> left, byte leftLength, Vector128<byte> right, byte rightLength, StringComparisonMode mode) => CompareExplicitLengthIndex(left, leftLength, right, rightLength, mode);
+
+        /// <summary>
+        /// int _mm_cmpestri (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareExplicitLengthIndex(Vector128<short> left, byte leftLength, Vector128<short> right, byte rightLength, StringComparisonMode mode) => CompareExplicitLengthIndex(left, leftLength, right, rightLength, mode);
+
+        /// <summary>
+        /// int _mm_cmpestri (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRI xmm, xmm/m128, imm8
+        /// </summary>
+        public static int CompareExplicitLengthIndex(Vector128<ushort> left, byte leftLength, Vector128<ushort> right, byte rightLength, StringComparisonMode mode) => CompareExplicitLengthIndex(left, leftLength, right, rightLength, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareImplicitLengthBitMask(Vector128<sbyte> left, Vector128<sbyte> right, StringComparisonMode mode) => CompareImplicitLengthBitMask(left, right, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareImplicitLengthBitMask(Vector128<byte> left, Vector128<byte> right, StringComparisonMode mode) => CompareImplicitLengthBitMask(left, right, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareImplicitLengthBitMask(Vector128<short> left, Vector128<short> right, StringComparisonMode mode) => CompareImplicitLengthBitMask(left, right, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareImplicitLengthBitMask(Vector128<ushort> left, Vector128<ushort> right, StringComparisonMode mode) => CompareImplicitLengthBitMask(left, right, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareImplicitLengthUnitMask(Vector128<sbyte> left, Vector128<sbyte> right, StringComparisonMode mode) => CompareImplicitLengthUnitMask(left, right, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareImplicitLengthUnitMask(Vector128<byte> left, Vector128<byte> right, StringComparisonMode mode) => CompareImplicitLengthUnitMask(left, right, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareImplicitLengthUnitMask(Vector128<short> left, Vector128<short> right, StringComparisonMode mode) => CompareImplicitLengthUnitMask(left, right, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpistrm (__m128i a, __m128i b, const int imm8)
+        ///   PCMPISTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareImplicitLengthUnitMask(Vector128<ushort> left, Vector128<ushort> right, StringComparisonMode mode) => CompareImplicitLengthUnitMask(left, right, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareExplicitLengthBitMask(Vector128<sbyte> left, byte leftLength, Vector128<sbyte> right, byte rightLength, StringComparisonMode mode) => CompareExplicitLengthBitMask(left, leftLength, right, rightLength, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareExplicitLengthBitMask(Vector128<byte> left, byte leftLength, Vector128<byte> right, byte rightLength, StringComparisonMode mode) => CompareExplicitLengthBitMask(left, leftLength, right, rightLength, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareExplicitLengthBitMask(Vector128<short> left, byte leftLength, Vector128<short> right, byte rightLength, StringComparisonMode mode) => CompareExplicitLengthBitMask(left, leftLength, right, rightLength, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareExplicitLengthBitMask(Vector128<ushort> left, byte leftLength, Vector128<ushort> right, byte rightLength, StringComparisonMode mode) => CompareExplicitLengthBitMask(left, leftLength, right, rightLength, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareExplicitLengthUnitMask(Vector128<sbyte> left, byte leftLength, Vector128<sbyte> right, byte rightLength, StringComparisonMode mode) => CompareExplicitLengthUnitMask(left, leftLength, right, rightLength, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<byte> CompareExplicitLengthUnitMask(Vector128<byte> left, byte leftLength, Vector128<byte> right, byte rightLength, StringComparisonMode mode) => CompareExplicitLengthUnitMask(left, leftLength, right, rightLength, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareExplicitLengthUnitMask(Vector128<short> left, byte leftLength, Vector128<short> right, byte rightLength, StringComparisonMode mode) => CompareExplicitLengthUnitMask(left, leftLength, right, rightLength, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpestrm (__m128i a, int la, __m128i b, int lb, const int imm8)
+        ///   PCMPESTRM xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<ushort> CompareExplicitLengthUnitMask(Vector128<ushort> left, byte leftLength, Vector128<ushort> right, byte rightLength, StringComparisonMode mode) => CompareExplicitLengthUnitMask(left, leftLength, right, rightLength, mode);
+
+        /// <summary>
+        /// __m128i _mm_cmpgt_epi64 (__m128i a, __m128i b)
+        ///   PCMPGTQ xmm, xmm/m128
+        /// </summary>
+        public static Vector128<long> CompareGreaterThan(Vector128<long> left, Vector128<long> right) => CompareGreaterThan(left, right);
+
+        /// <summary>
+        /// unsigned int _mm_crc32_u8 (unsigned int crc, unsigned char v)
+        ///   CRC32 reg, reg/m8
+        /// </summary>
+        public static uint Crc32(uint crc, byte data) => Crc32(crc, data);
+        /// <summary>
+        /// unsigned int _mm_crc32_u16 (unsigned int crc, unsigned short v)
+        ///   CRC32 reg, reg/m16
+        /// </summary>
+        public static uint Crc32(uint crc, ushort data) => Crc32(crc, data);
+        /// <summary>
+        /// unsigned int _mm_crc32_u32 (unsigned int crc, unsigned int v)
+        ///   CRC32 reg, reg/m32
+        /// </summary>
+        public static uint Crc32(uint crc, uint data) => Crc32(crc, data);
+        /// <summary>
+        /// unsigned __int64 _mm_crc32_u64 (unsigned __int64 crc, unsigned __int64 v)
+        ///   CRC32 reg, reg/m64
+        /// </summary>
+        public static ulong Crc32(ulong crc, ulong data) => Crc32(crc, data);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Ssse3.PlatformNotSupported.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Ssse3.PlatformNotSupported.cs
new file mode 100644
index 0000000000..20e9bbb8b7
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Ssse3.PlatformNotSupported.cs
@@ -0,0 +1,108 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel SSSE3 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Ssse3
+    {
+        public static bool IsSupported { get { return false; } }
+        
+        /// <summary>
+        /// __m128i _mm_abs_epi8 (__m128i a)
+        ///   PABSB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Abs(Vector128<sbyte> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_abs_epi16 (__m128i a)
+        ///   PABSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Abs(Vector128<short> value) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_abs_epi32 (__m128i a)
+        ///   PABSD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> Abs(Vector128<int> value) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_alignr_epi8 (__m128i a, __m128i b, int count)
+        ///   PALIGNR xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<sbyte> AlignRight(Vector128<sbyte> left, Vector128<sbyte> right, byte mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_hadd_epi16 (__m128i a, __m128i b)
+        ///   PHADDW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> HorizontalAdd(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_hadd_epi32 (__m128i a, __m128i b)
+        ///   PHADDD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> HorizontalAdd(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_hadds_epi16 (__m128i a, __m128i b)
+        ///   PHADDSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> HorizontalAddSaturate(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_hsub_epi16 (__m128i a, __m128i b)
+        ///   PHSUBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> HorizontalSubtract(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_hsub_epi32 (__m128i a, __m128i b)
+        ///   PHSUBD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> HorizontalSubtract(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_hsubs_epi16 (__m128i a, __m128i b)
+        ///   PHSUBSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> HorizontalSubtractSaturate(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_maddubs_epi16 (__m128i a, __m128i b)
+        ///   PMADDUBSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> MultiplyAddAdjacent(Vector128<byte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_mulhrs_epi16 (__m128i a, __m128i b)
+        ///   PMULHRSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> MultiplyHighRoundScale(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_shuffle_epi8 (__m128i a, __m128i b)
+        ///   PSHUFB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Shuffle(Vector128<sbyte> value, Vector128<sbyte> mask) { throw new PlatformNotSupportedException(); }
+
+        /// <summary>
+        /// __m128i _mm_sign_epi8 (__m128i a, __m128i b)
+        ///   PSIGNB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Sign(Vector128<sbyte> left, Vector128<sbyte> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sign_epi16 (__m128i a, __m128i b)
+        ///   PSIGNW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> Sign(Vector128<short> left, Vector128<short> right) { throw new PlatformNotSupportedException(); }
+        /// <summary>
+        /// __m128i _mm_sign_epi32 (__m128i a, __m128i b)
+        ///   PSIGND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> Sign(Vector128<int> left, Vector128<int> right) { throw new PlatformNotSupportedException(); }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Ssse3.cs b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Ssse3.cs
new file mode 100644
index 0000000000..0403a0a4e2
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Intrinsics/X86/Ssse3.cs
@@ -0,0 +1,108 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.Intrinsics;
+
+namespace System.Runtime.Intrinsics.X86
+{
+    /// <summary>
+    /// This class provides access to Intel SSSE3 hardware instructions via intrinsics
+    /// </summary>
+    [CLSCompliant(false)]
+    public static class Ssse3
+    {
+        public static bool IsSupported { get => IsSupported; }
+        
+        /// <summary>
+        /// __m128i _mm_abs_epi8 (__m128i a)
+        ///   PABSB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<byte> Abs(Vector128<sbyte> value) => Abs(value);
+        /// <summary>
+        /// __m128i _mm_abs_epi16 (__m128i a)
+        ///   PABSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<ushort> Abs(Vector128<short> value) => Abs(value);
+        /// <summary>
+        /// __m128i _mm_abs_epi32 (__m128i a)
+        ///   PABSD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<uint> Abs(Vector128<int> value) => Abs(value);
+
+        /// <summary>
+        /// __m128i _mm_alignr_epi8 (__m128i a, __m128i b, int count)
+        ///   PALIGNR xmm, xmm/m128, imm8
+        /// </summary>
+        public static Vector128<sbyte> AlignRight(Vector128<sbyte> left, Vector128<sbyte> right, byte mask) => AlignRight(left, right, mask);
+
+        /// <summary>
+        /// __m128i _mm_hadd_epi16 (__m128i a, __m128i b)
+        ///   PHADDW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> HorizontalAdd(Vector128<short> left, Vector128<short> right) => HorizontalAdd(left, right);
+        /// <summary>
+        /// __m128i _mm_hadd_epi32 (__m128i a, __m128i b)
+        ///   PHADDD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> HorizontalAdd(Vector128<int> left, Vector128<int> right) => HorizontalAdd(left, right);
+
+        /// <summary>
+        /// __m128i _mm_hadds_epi16 (__m128i a, __m128i b)
+        ///   PHADDSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> HorizontalAddSaturate(Vector128<short> left, Vector128<short> right) => HorizontalAddSaturate(left, right);
+
+        /// <summary>
+        /// __m128i _mm_hsub_epi16 (__m128i a, __m128i b)
+        ///   PHSUBW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> HorizontalSubtract(Vector128<short> left, Vector128<short> right) => HorizontalSubtract(left, right);
+        /// <summary>
+        /// __m128i _mm_hsub_epi32 (__m128i a, __m128i b)
+        ///   PHSUBD xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> HorizontalSubtract(Vector128<int> left, Vector128<int> right) => HorizontalSubtract(left, right);
+
+        /// <summary>
+        /// __m128i _mm_hsubs_epi16 (__m128i a, __m128i b)
+        ///   PHSUBSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> HorizontalSubtractSaturate(Vector128<short> left, Vector128<short> right) => HorizontalSubtractSaturate(left, right);
+
+        /// <summary>
+        /// __m128i _mm_maddubs_epi16 (__m128i a, __m128i b)
+        ///   PMADDUBSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> MultiplyAddAdjacent(Vector128<byte> left, Vector128<sbyte> right) => MultiplyAddAdjacent(left, right);
+
+        /// <summary>
+        /// __m128i _mm_mulhrs_epi16 (__m128i a, __m128i b)
+        ///   PMULHRSW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> MultiplyHighRoundScale(Vector128<short> left, Vector128<short> right) => MultiplyHighRoundScale(left, right);
+
+        /// <summary>
+        /// __m128i _mm_shuffle_epi8 (__m128i a, __m128i b)
+        ///   PSHUFB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Shuffle(Vector128<sbyte> value, Vector128<sbyte> mask) => Shuffle(value, mask);
+
+        /// <summary>
+        /// __m128i _mm_sign_epi8 (__m128i a, __m128i b)
+        ///   PSIGNB xmm, xmm/m128
+        /// </summary>
+        public static Vector128<sbyte> Sign(Vector128<sbyte> left, Vector128<sbyte> right) => Sign(left, right);
+        /// <summary>
+        /// __m128i _mm_sign_epi16 (__m128i a, __m128i b)
+        ///   PSIGNW xmm, xmm/m128
+        /// </summary>
+        public static Vector128<short> Sign(Vector128<short> left, Vector128<short> right) => Sign(left, right);
+        /// <summary>
+        /// __m128i _mm_sign_epi32 (__m128i a, __m128i b)
+        ///   PSIGND xmm, xmm/m128
+        /// </summary>
+        public static Vector128<int> Sign(Vector128<int> left, Vector128<int> right) => Sign(left, right);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Loader/AssemblyLoadContext.cs b/src/System.Private.CoreLib/src/System/Runtime/Loader/AssemblyLoadContext.cs
new file mode 100644
index 0000000000..806c2f7f4b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Loader/AssemblyLoadContext.cs
@@ -0,0 +1,473 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System;
+using System.Reflection;
+using System.IO;
+using System.Runtime.Versioning;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Security;
+using System.Threading;
+
+
+namespace System.Runtime.Loader
+{
+    public abstract class AssemblyLoadContext
+    {
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern bool CanUseAppPathAssemblyLoadContextInCurrentDomain();
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern IntPtr InitializeAssemblyLoadContext(IntPtr ptrAssemblyLoadContext, bool fRepresentsTPALoadContext);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern IntPtr LoadFromStream(IntPtr ptrNativeAssemblyLoadContext, IntPtr ptrAssemblyArray, int iAssemblyArrayLen, IntPtr ptrSymbols, int iSymbolArrayLen, ObjectHandleOnStack retAssembly);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void InternalSetProfileRoot(string directoryPath);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void InternalStartProfile(string profile, IntPtr ptrNativeAssemblyLoadContext);
+
+        protected AssemblyLoadContext()
+        {
+            // Initialize the ALC representing non-TPA LoadContext
+            InitializeLoadContext(false);
+        }
+
+        internal AssemblyLoadContext(bool fRepresentsTPALoadContext)
+        {
+            // Initialize the ALC representing TPA LoadContext
+            InitializeLoadContext(fRepresentsTPALoadContext);
+        }
+
+        private void InitializeLoadContext(bool fRepresentsTPALoadContext)
+        {
+            // Initialize the VM side of AssemblyLoadContext if not already done.
+            GCHandle gchALC = GCHandle.Alloc(this);
+            IntPtr ptrALC = GCHandle.ToIntPtr(gchALC);
+            m_pNativeAssemblyLoadContext = InitializeAssemblyLoadContext(ptrALC, fRepresentsTPALoadContext);
+
+            // Initialize event handlers to be null by default
+            Resolving = null;
+            Unloading = null;
+
+            // Since unloading an AssemblyLoadContext is not yet implemented, this is a temporary solution to raise the
+            // Unloading event on process exit. Register for the current AppDomain's ProcessExit event, and the handler will in
+            // turn raise the Unloading event.
+            AppContext.Unloading += OnAppContextUnloading;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void LoadFromPath(IntPtr ptrNativeAssemblyLoadContext, string ilPath, string niPath, ObjectHandleOnStack retAssembly);
+
+        public static Assembly[] GetLoadedAssemblies()
+        {
+            return AppDomain.CurrentDomain.GetAssemblies(false);
+        }
+
+        // These are helpers that can be used by AssemblyLoadContext derivations.
+        // They are used to load assemblies in DefaultContext.
+        public Assembly LoadFromAssemblyPath(string assemblyPath)
+        {
+            if (assemblyPath == null)
+            {
+                throw new ArgumentNullException(nameof(assemblyPath));
+            }
+
+            if (PathInternal.IsPartiallyQualified(assemblyPath))
+            {
+                throw new ArgumentException(SR.Argument_AbsolutePathRequired, nameof(assemblyPath));
+            }
+
+            RuntimeAssembly loadedAssembly = null;
+            LoadFromPath(m_pNativeAssemblyLoadContext, assemblyPath, null, JitHelpers.GetObjectHandleOnStack(ref loadedAssembly));
+            return loadedAssembly;
+        }
+
+        public Assembly LoadFromNativeImagePath(string nativeImagePath, string assemblyPath)
+        {
+            if (nativeImagePath == null)
+            {
+                throw new ArgumentNullException(nameof(nativeImagePath));
+            }
+
+            if (PathInternal.IsPartiallyQualified(nativeImagePath))
+            {
+                throw new ArgumentException(SR.Argument_AbsolutePathRequired, nameof(nativeImagePath));
+            }
+
+            if (assemblyPath != null && PathInternal.IsPartiallyQualified(assemblyPath))
+            {
+                throw new ArgumentException(SR.Argument_AbsolutePathRequired, nameof(assemblyPath));
+            }
+
+            // Basic validation has succeeded - lets try to load the NI image.
+            // Ask LoadFile to load the specified assembly in the DefaultContext
+            RuntimeAssembly loadedAssembly = null;
+            LoadFromPath(m_pNativeAssemblyLoadContext, assemblyPath, nativeImagePath, JitHelpers.GetObjectHandleOnStack(ref loadedAssembly));
+            return loadedAssembly;
+        }
+
+        public Assembly LoadFromStream(Stream assembly)
+        {
+            return LoadFromStream(assembly, null);
+        }
+
+        public Assembly LoadFromStream(Stream assembly, Stream assemblySymbols)
+        {
+            if (assembly == null)
+            {
+                throw new ArgumentNullException(nameof(assembly));
+            }
+
+            if (assembly.Length <= 0)
+            {
+                throw new BadImageFormatException(SR.BadImageFormat_BadILFormat);
+            }
+
+            int iAssemblyStreamLength = (int)assembly.Length;
+            int iSymbolLength = 0;
+
+            // Allocate the byte[] to hold the assembly
+            byte[] arrAssembly = new byte[iAssemblyStreamLength];
+
+            // Copy the assembly to the byte array
+            assembly.Read(arrAssembly, 0, iAssemblyStreamLength);
+
+            // Get the symbol stream in byte[] if provided
+            byte[] arrSymbols = null;
+            if (assemblySymbols != null)
+            {
+                iSymbolLength = (int)assemblySymbols.Length;
+                arrSymbols = new byte[iSymbolLength];
+
+                assemblySymbols.Read(arrSymbols, 0, iSymbolLength);
+            }
+
+            RuntimeAssembly loadedAssembly = null;
+            unsafe
+            {
+                fixed (byte* ptrAssembly = arrAssembly, ptrSymbols = arrSymbols)
+                {
+                    LoadFromStream(m_pNativeAssemblyLoadContext, new IntPtr(ptrAssembly), iAssemblyStreamLength, new IntPtr(ptrSymbols), iSymbolLength, JitHelpers.GetObjectHandleOnStack(ref loadedAssembly));
+                }
+            }
+
+            return loadedAssembly;
+        }
+
+        // Custom AssemblyLoadContext implementations can override this
+        // method to perform custom processing and use one of the protected
+        // helpers above to load the assembly.
+        protected abstract Assembly Load(AssemblyName assemblyName);
+
+        // This method is invoked by the VM when using the host-provided assembly load context
+        // implementation.
+        private static Assembly Resolve(IntPtr gchManagedAssemblyLoadContext, AssemblyName assemblyName)
+        {
+            AssemblyLoadContext context = (AssemblyLoadContext)(GCHandle.FromIntPtr(gchManagedAssemblyLoadContext).Target);
+
+            return context.ResolveUsingLoad(assemblyName);
+        }
+
+        // This method is invoked by the VM to resolve an assembly reference using the Resolving event
+        // after trying assembly resolution via Load override and TPA load context without success.
+        private static Assembly ResolveUsingResolvingEvent(IntPtr gchManagedAssemblyLoadContext, AssemblyName assemblyName)
+        {
+            AssemblyLoadContext context = (AssemblyLoadContext)(GCHandle.FromIntPtr(gchManagedAssemblyLoadContext).Target);
+
+            // Invoke the AssemblyResolve event callbacks if wired up
+            return context.ResolveUsingEvent(assemblyName);
+        }
+
+        private Assembly GetFirstResolvedAssembly(AssemblyName assemblyName)
+        {
+            Assembly resolvedAssembly = null;
+
+            Func<AssemblyLoadContext, AssemblyName, Assembly> assemblyResolveHandler = Resolving;
+
+            if (assemblyResolveHandler != null)
+            {
+                // Loop through the event subscribers and return the first non-null Assembly instance
+                foreach (Func<AssemblyLoadContext, AssemblyName, Assembly> handler in assemblyResolveHandler.GetInvocationList())
+                {
+                    resolvedAssembly = handler(this, assemblyName);
+                    if (resolvedAssembly != null)
+                    {
+                        break;
+                    }
+                }
+            }
+
+            return resolvedAssembly;
+        }
+
+        private Assembly ValidateAssemblyNameWithSimpleName(Assembly assembly, string requestedSimpleName)
+        {
+            // Get the name of the loaded assembly
+            string loadedSimpleName = null;
+
+            // Derived type's Load implementation is expected to use one of the LoadFrom* methods to get the assembly
+            // which is a RuntimeAssembly instance. However, since Assembly type can be used build any other artifact (e.g. AssemblyBuilder),
+            // we need to check for RuntimeAssembly.
+            RuntimeAssembly rtLoadedAssembly = assembly as RuntimeAssembly;
+            if (rtLoadedAssembly != null)
+            {
+                loadedSimpleName = rtLoadedAssembly.GetSimpleName();
+            }
+
+            // The simple names should match at the very least
+            if (String.IsNullOrEmpty(loadedSimpleName) || (!requestedSimpleName.Equals(loadedSimpleName, StringComparison.InvariantCultureIgnoreCase)))
+                throw new InvalidOperationException(SR.Argument_CustomAssemblyLoadContextRequestedNameMismatch);
+
+            return assembly;
+        }
+
+        private Assembly ResolveUsingLoad(AssemblyName assemblyName)
+        {
+            string simpleName = assemblyName.Name;
+            Assembly assembly = Load(assemblyName);
+
+            if (assembly != null)
+            {
+                assembly = ValidateAssemblyNameWithSimpleName(assembly, simpleName);
+            }
+
+            return assembly;
+        }
+
+        private Assembly ResolveUsingEvent(AssemblyName assemblyName)
+        {
+            string simpleName = assemblyName.Name;
+
+            // Invoke the AssemblyResolve event callbacks if wired up
+            Assembly assembly = GetFirstResolvedAssembly(assemblyName);
+            if (assembly != null)
+            {
+                assembly = ValidateAssemblyNameWithSimpleName(assembly, simpleName);
+            }
+
+            // Since attempt to resolve the assembly via Resolving event is the last option,
+            // throw an exception if we do not find any assembly.
+            if (assembly == null)
+            {
+                throw new FileNotFoundException(SR.IO_FileLoad, simpleName);
+            }
+
+            return assembly;
+        }
+
+        public Assembly LoadFromAssemblyName(AssemblyName assemblyName)
+        {
+            // Attempt to load the assembly, using the same ordering as static load, in the current load context.
+            Assembly loadedAssembly = Assembly.Load(assemblyName, m_pNativeAssemblyLoadContext);
+
+            return loadedAssembly;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern IntPtr InternalLoadUnmanagedDllFromPath(string unmanagedDllPath);
+
+        // This method provides a way for overriders of LoadUnmanagedDll() to load an unmanaged DLL from a specific path in a
+        // platform-independent way. The DLL is loaded with default load flags.
+        protected IntPtr LoadUnmanagedDllFromPath(string unmanagedDllPath)
+        {
+            if (unmanagedDllPath == null)
+            {
+                throw new ArgumentNullException(nameof(unmanagedDllPath));
+            }
+            if (unmanagedDllPath.Length == 0)
+            {
+                throw new ArgumentException(SR.Argument_EmptyPath, nameof(unmanagedDllPath));
+            }
+            if (PathInternal.IsPartiallyQualified(unmanagedDllPath))
+            {
+                throw new ArgumentException(SR.Argument_AbsolutePathRequired, nameof(unmanagedDllPath));
+            }
+
+            return InternalLoadUnmanagedDllFromPath(unmanagedDllPath);
+        }
+
+        // Custom AssemblyLoadContext implementations can override this
+        // method to perform the load of unmanaged native dll
+        // This function needs to return the HMODULE of the dll it loads
+        protected virtual IntPtr LoadUnmanagedDll(String unmanagedDllName)
+        {
+            //defer to default coreclr policy of loading unmanaged dll
+            return IntPtr.Zero;
+        }
+
+        // This method is invoked by the VM when using the host-provided assembly load context
+        // implementation.
+        private static IntPtr ResolveUnmanagedDll(String unmanagedDllName, IntPtr gchManagedAssemblyLoadContext)
+        {
+            AssemblyLoadContext context = (AssemblyLoadContext)(GCHandle.FromIntPtr(gchManagedAssemblyLoadContext).Target);
+            return context.LoadUnmanagedDll(unmanagedDllName);
+        }
+
+        public static AssemblyLoadContext Default
+        {
+            get
+            {
+                if (s_DefaultAssemblyLoadContext == null)
+                {
+                    // Try to initialize the default assembly load context with apppath one if we are allowed to
+                    if (AssemblyLoadContext.CanUseAppPathAssemblyLoadContextInCurrentDomain())
+                    {
+                        // Synchronize access to initializing Default ALC
+                        lock (s_initLock)
+                        {
+                            if (s_DefaultAssemblyLoadContext == null)
+                            {
+                                s_DefaultAssemblyLoadContext = new AppPathAssemblyLoadContext();
+                            }
+                        }
+                    }
+                }
+
+                return s_DefaultAssemblyLoadContext;
+            }
+        }
+
+        // Helper to return AssemblyName corresponding to the path of an IL assembly
+        public static AssemblyName GetAssemblyName(string assemblyPath)
+        {
+            if (assemblyPath == null)
+            {
+                throw new ArgumentNullException(nameof(assemblyPath));
+            }
+
+            return AssemblyName.GetAssemblyName(assemblyPath);
+        }
+        
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern IntPtr GetLoadContextForAssembly(RuntimeAssembly assembly);
+
+        // Returns the load context in which the specified assembly has been loaded
+        public static AssemblyLoadContext GetLoadContext(Assembly assembly)
+        {
+            if (assembly == null)
+            {
+                throw new ArgumentNullException(nameof(assembly));
+            }
+
+            AssemblyLoadContext loadContextForAssembly = null;
+
+            RuntimeAssembly rtAsm = assembly as RuntimeAssembly;
+
+            // We only support looking up load context for runtime assemblies.
+            if (rtAsm != null)
+            {
+                IntPtr ptrAssemblyLoadContext = GetLoadContextForAssembly(rtAsm);
+                if (ptrAssemblyLoadContext == IntPtr.Zero)
+                {
+                    // If the load context is returned null, then the assembly was bound using the TPA binder
+                    // and we shall return reference to the active "Default" binder - which could be the TPA binder
+                    // or an overridden CLRPrivBinderAssemblyLoadContext instance.
+                    loadContextForAssembly = AssemblyLoadContext.Default;
+                }
+                else
+                {
+                    loadContextForAssembly = (AssemblyLoadContext)(GCHandle.FromIntPtr(ptrAssemblyLoadContext).Target);
+                }
+            }
+
+            return loadContextForAssembly;
+        }
+
+        // Set the root directory path for profile optimization.
+        public void SetProfileOptimizationRoot(string directoryPath)
+        {
+            InternalSetProfileRoot(directoryPath);
+        }
+
+        // Start profile optimization for the specified profile name.
+        public void StartProfileOptimization(string profile)
+        {
+            InternalStartProfile(profile, m_pNativeAssemblyLoadContext);
+        }
+
+        private void OnAppContextUnloading(object sender, EventArgs e)
+        {
+            var unloading = Unloading;
+            if (unloading != null)
+            {
+                unloading(this);
+            }
+        }
+
+        public event Func<AssemblyLoadContext, AssemblyName, Assembly> Resolving;
+        public event Action<AssemblyLoadContext> Unloading;
+
+        // Contains the reference to VM's representation of the AssemblyLoadContext
+        private IntPtr m_pNativeAssemblyLoadContext;
+
+        // Each AppDomain contains the reference to its AssemblyLoadContext instance, if one is
+        // specified by the host. By having the field as a static, we are
+        // making it an AppDomain-wide field.
+        private static volatile AssemblyLoadContext s_DefaultAssemblyLoadContext;
+
+        // Synchronization primitive for controlling initialization of Default load context
+        private static readonly object s_initLock = new Object();
+
+        // Occurs when an Assembly is loaded
+        public static event AssemblyLoadEventHandler AssemblyLoad
+        {
+            add { AppDomain.CurrentDomain.AssemblyLoad += value; }
+            remove { AppDomain.CurrentDomain.AssemblyLoad -= value; }
+        }
+
+        // Occurs when resolution of type fails
+        public static event ResolveEventHandler TypeResolve
+        {
+            add { AppDomain.CurrentDomain.TypeResolve += value; }
+            remove { AppDomain.CurrentDomain.TypeResolve -= value; }
+        }
+
+        // Occurs when resolution of resource fails
+        public static event ResolveEventHandler ResourceResolve
+        {
+            add { AppDomain.CurrentDomain.ResourceResolve += value; }
+            remove { AppDomain.CurrentDomain.ResourceResolve -= value; }
+        }
+
+        // Occurs when resolution of assembly fails
+        // This event is fired after resolve events of AssemblyLoadContext fails
+        public static event ResolveEventHandler AssemblyResolve
+        {
+            add { AppDomain.CurrentDomain.AssemblyResolve += value; }
+            remove { AppDomain.CurrentDomain.AssemblyResolve -= value; }
+        }
+    }
+
+    internal class AppPathAssemblyLoadContext : AssemblyLoadContext
+    {
+        internal AppPathAssemblyLoadContext() : base(true)
+        {
+        }
+
+        protected override Assembly Load(AssemblyName assemblyName)
+        {
+            // We were loading an assembly into TPA ALC that was not found on TPA list. As a result we are here.
+            // Returning null will result in the AssemblyResolve event subscribers to be invoked to help resolve the assembly.
+            return null;
+        }
+    }
+
+    internal class IndividualAssemblyLoadContext : AssemblyLoadContext
+    {
+        internal IndividualAssemblyLoadContext() : base(false)
+        {
+        }
+
+        protected override Assembly Load(AssemblyName assemblyName)
+        {
+            return null;
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Runtime/MemoryFailPoint.cs b/src/System.Private.CoreLib/src/System/Runtime/MemoryFailPoint.cs
new file mode 100644
index 0000000000..d05c346156
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/MemoryFailPoint.cs
@@ -0,0 +1,484 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Provides a way for an app to not start an operation unless
+** there's a reasonable chance there's enough memory 
+** available for the operation to succeed.
+**
+** 
+===========================================================*/
+
+using System;
+using System.IO;
+using Microsoft.Win32;
+using System.Runtime.InteropServices;
+using System.Threading;
+using System.Runtime.CompilerServices;
+using System.Runtime.ConstrainedExecution;
+using System.Runtime.Versioning;
+using System.Diagnostics;
+
+/* 
+   This class allows an application to fail before starting certain 
+   activities.  The idea is to fail early instead of failing in the middle
+   of some long-running operation to increase the survivability of the 
+   application and ensure you don't have to write tricky code to handle an 
+   OOM anywhere in your app's code (which implies state corruption, meaning you
+   should unload the appdomain, if you have a transacted environment to ensure
+   rollback of individual transactions).  This is an incomplete tool to attempt
+   hoisting all your OOM failures from anywhere in your worker methods to one 
+   particular point where it is easier to handle an OOM failure, and you can
+   optionally choose to not start a workitem if it will likely fail.  This does 
+   not help the performance of your code directly (other than helping to avoid 
+   AD unloads).  The point is to avoid starting work if it is likely to fail.  
+   The Enterprise Services team has used these memory gates effectively in the 
+   unmanaged world for a decade.
+
+   In Whidbey, we will simply check to see if there is enough memory available
+   in the OS's page file & attempt to ensure there might be enough space free
+   within the process's address space (checking for address space fragmentation
+   as well).  We will not commit or reserve any memory.  To avoid race conditions with
+   other threads using MemoryFailPoints, we'll also keep track of a 
+   process-wide amount of memory "reserved" via all currently-active 
+   MemoryFailPoints.  This has two problems:
+      1) This can account for memory twice.  If a thread creates a 
+         MemoryFailPoint for 100 MB then allocates 99 MB, we'll see 99 MB 
+         less free memory and 100 MB less reserved memory.  Yet, subtracting 
+         off the 100 MB is necessary because the thread may not have started
+         allocating memory yet.  Disposing of this class immediately after 
+         front-loaded allocations have completed is a great idea.
+      2) This is still vulnerable to race conditions with other threads that don't use 
+         MemoryFailPoints.
+   So this class is far from perfect.  But it may be good enough to 
+   meaningfully reduce the frequency of OutOfMemoryExceptions in managed apps.
+
+   In Orcas or later, we might allocate some memory from the OS and add it
+   to a allocation context for this thread.  Obviously, at that point we need
+   some way of conveying when we release this block of memory.  So, we 
+   implemented IDisposable on this type in Whidbey and expect all users to call
+   this from within a using block to provide lexical scope for their memory 
+   usage.  The call to Dispose (implicit with the using block) will give us an
+   opportunity to release this memory, perhaps.  We anticipate this will give 
+   us the possibility of a more effective design in a future version.
+
+   In Orcas, we may also need to differentiate between allocations that would
+   go into the normal managed heap vs. the large object heap, or we should 
+   consider checking for enough free space in both locations (with any 
+   appropriate adjustments to ensure the memory is contiguous).
+*/
+
+namespace System.Runtime
+{
+    public sealed class MemoryFailPoint : CriticalFinalizerObject, IDisposable
+    {
+        // Find the top section of user mode memory.  Avoid the last 64K.
+        // Windows reserves that block for the kernel, apparently, and doesn't
+        // let us ask about that memory.  But since we ask for memory in 1 MB
+        // chunks, we don't have to special case this.  Also, we need to
+        // deal with 32 bit machines in 3 GB mode.
+        // Using Win32's GetSystemInfo should handle all this for us.
+        private static readonly ulong TopOfMemory;
+
+        // Walking the address space is somewhat expensive, taking around half
+        // a millisecond.  Doing that per transaction limits us to a max of 
+        // ~2000 transactions/second.  Instead, let's do this address space 
+        // walk once every 10 seconds, or when we will likely fail.  This
+        // amortization scheme can reduce the cost of a memory gate by about
+        // a factor of 100.
+        private static long hiddenLastKnownFreeAddressSpace = 0;
+        private static long hiddenLastTimeCheckingAddressSpace = 0;
+        private const int CheckThreshold = 10 * 1000;  // 10 seconds
+
+        private static long LastKnownFreeAddressSpace
+        {
+            get { return Volatile.Read(ref hiddenLastKnownFreeAddressSpace); }
+            set { Volatile.Write(ref hiddenLastKnownFreeAddressSpace, value); }
+        }
+
+        private static long AddToLastKnownFreeAddressSpace(long addend)
+        {
+            return Interlocked.Add(ref hiddenLastKnownFreeAddressSpace, addend);
+        }
+
+        private static long LastTimeCheckingAddressSpace
+        {
+            get { return Volatile.Read(ref hiddenLastTimeCheckingAddressSpace); }
+            set { Volatile.Write(ref hiddenLastTimeCheckingAddressSpace, value); }
+        }
+
+        // When allocating memory segment by segment, we've hit some cases
+        // where there are only 22 MB of memory available on the machine,
+        // we need 1 16 MB segment, and the OS does not succeed in giving us
+        // that memory.  Reasons for this could include:
+        // 1) The GC does allocate memory when doing a collection.
+        // 2) Another process on the machine could grab that memory.
+        // 3) Some other part of the runtime might grab this memory.
+        // If we build in a little padding, we can help protect
+        // ourselves against some of these cases, and we want to err on the
+        // conservative side with this class.
+        private const int LowMemoryFudgeFactor = 16 << 20;
+
+        // Round requested size to a 16MB multiple to have a better granularity
+        // when checking for available memory.
+        private const int MemoryCheckGranularity = 16;
+
+        // Note: This may become dynamically tunable in the future.
+        // Also note that we can have different segment sizes for the normal vs. 
+        // large object heap.  We currently use the max of the two.
+        private static readonly ulong GCSegmentSize;
+
+        // For multi-threaded workers, we want to ensure that if two workers
+        // use a MemoryFailPoint at the same time, and they both succeed, that
+        // they don't trample over each other's memory.  Keep a process-wide
+        // count of "reserved" memory, and decrement this in Dispose and
+        // in the critical finalizer.  See 
+        // SharedStatics.MemoryFailPointReservedMemory
+
+        private ulong _reservedMemory;  // The size of this request (from user)
+        private bool _mustSubtractReservation; // Did we add data to SharedStatics?
+
+        static MemoryFailPoint()
+        {
+            GetMemorySettings(out GCSegmentSize, out TopOfMemory);
+        }
+
+        // We can remove this link demand in a future version - we will
+        // have scenarios for this in partial trust in the future, but
+        // we're doing this just to restrict this in case the code below
+        // is somehow incorrect.
+        public MemoryFailPoint(int sizeInMegabytes)
+        {
+            if (sizeInMegabytes <= 0)
+                throw new ArgumentOutOfRangeException(nameof(sizeInMegabytes), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+#if !FEATURE_PAL // Remove this when CheckForAvailableMemory is able to provide legitimate estimates
+            ulong size = ((ulong)sizeInMegabytes) << 20;
+            _reservedMemory = size;
+
+            // Check to see that we both have enough memory on the system
+            // and that we have enough room within the user section of the 
+            // process's address space.  Also, we need to use the GC segment
+            // size, not the amount of memory the user wants to allocate.
+            // Consider correcting this to reflect free memory within the GC
+            // heap, and to check both the normal & large object heaps.
+            ulong segmentSize = (ulong)(Math.Ceiling((double)size / GCSegmentSize) * GCSegmentSize);
+            if (segmentSize >= TopOfMemory)
+                throw new InsufficientMemoryException(SR.InsufficientMemory_MemFailPoint_TooBig);
+
+            ulong requestedSizeRounded = (ulong)(Math.Ceiling((double)sizeInMegabytes / MemoryCheckGranularity) * MemoryCheckGranularity);
+            //re-convert into bytes
+            requestedSizeRounded <<= 20;
+
+            ulong availPageFile = 0;  // available VM (physical + page file)
+            ulong totalAddressSpaceFree = 0;  // non-contiguous free address space
+
+            // Check for available memory, with 2 attempts at getting more 
+            // memory.  
+            // Stage 0: If we don't have enough, trigger a GC.  
+            // Stage 1: If we don't have enough, try growing the swap file.
+            // Stage 2: Update memory state, then fail or leave loop.
+            //
+            // (In the future, we could consider adding another stage after 
+            // Stage 0 to run finalizers.  However, before doing that make sure
+            // that we could abort this constructor when we call 
+            // GC.WaitForPendingFinalizers, noting that this method uses a CER
+            // so it can't be aborted, and we have a critical finalizer.  It
+            // would probably work, but do some thinking first.)
+            for (int stage = 0; stage < 3; stage++)
+            {
+                CheckForAvailableMemory(out availPageFile, out totalAddressSpaceFree);
+
+                // If we have enough room, then skip some stages.
+                // Note that multiple threads can still lead to a race condition for our free chunk
+                // of address space, which can't be easily solved.
+                ulong reserved = SharedStatics.MemoryFailPointReservedMemory;
+                ulong segPlusReserved = segmentSize + reserved;
+                bool overflow = segPlusReserved < segmentSize || segPlusReserved < reserved;
+                bool needPageFile = availPageFile < (requestedSizeRounded + reserved + LowMemoryFudgeFactor) || overflow;
+                bool needAddressSpace = totalAddressSpaceFree < segPlusReserved || overflow;
+
+                // Ensure our cached amount of free address space is not stale.
+                long now = Environment.TickCount;  // Handle wraparound.
+                if ((now > LastTimeCheckingAddressSpace + CheckThreshold || now < LastTimeCheckingAddressSpace) ||
+                    LastKnownFreeAddressSpace < (long)segmentSize)
+                {
+                    CheckForFreeAddressSpace(segmentSize, false);
+                }
+                bool needContiguousVASpace = (ulong)LastKnownFreeAddressSpace < segmentSize;
+
+#if false
+                Console.WriteLine($"MemoryFailPoint:" +
+                    $"Checking for {(segmentSize >> 20)} MB, " +
+                    $"for allocation size of {sizeInMegabytes} MB, " +
+                    $"stage {stage}. " +
+                    $"Need page file? {needPageFile} " +
+                    $"Need Address Space? {needAddressSpace} " +
+                    $"Need Contiguous address space? {needContiguousVASpace} " +
+                    $"Avail page file: {(availPageFile >> 20)} MB " +
+                    $"Total free VA space: {totalAddressSpaceFree >> 20} MB " +
+                    $"Contiguous free address space (found): {LastKnownFreeAddressSpace >> 20} MB " +
+                    $"Space reserved via process's MemoryFailPoints: {reserved} MB");
+#endif
+
+                if (!needPageFile && !needAddressSpace && !needContiguousVASpace)
+                    break;
+
+                switch (stage)
+                {
+                    case 0:
+                        // The GC will release empty segments to the OS.  This will
+                        // relieve us from having to guess whether there's
+                        // enough memory in either GC heap, and whether 
+                        // internal fragmentation will prevent those 
+                        // allocations from succeeding.
+                        GC.Collect();
+                        continue;
+
+                    case 1:
+                        // Do this step if and only if the page file is too small.
+                        if (!needPageFile)
+                            continue;
+
+                        // Attempt to grow the OS's page file.  Note that we ignore
+                        // any allocation routines from the host intentionally.
+                        RuntimeHelpers.PrepareConstrainedRegions();
+
+                        // This shouldn't overflow due to the if clauses above.
+                        UIntPtr numBytes = new UIntPtr(segmentSize);
+                        unsafe
+                        {
+                            void* pMemory = Win32Native.VirtualAlloc(null, numBytes, Win32Native.MEM_COMMIT, Win32Native.PAGE_READWRITE);
+                            if (pMemory != null)
+                            {
+                                bool r = Win32Native.VirtualFree(pMemory, UIntPtr.Zero, Win32Native.MEM_RELEASE);
+                                if (!r)
+                                    throw Win32Marshal.GetExceptionForLastWin32Error();
+                            }
+                        }
+
+                        continue;
+
+                    case 2:
+                        // The call to CheckForAvailableMemory above updated our 
+                        // state.
+                        if (needPageFile || needAddressSpace)
+                        {
+                            InsufficientMemoryException e = new InsufficientMemoryException(SR.InsufficientMemory_MemFailPoint);
+#if DEBUG
+                            e.Data["MemFailPointState"] = new MemoryFailPointState(sizeInMegabytes, segmentSize,
+                                 needPageFile, needAddressSpace, needContiguousVASpace,
+                                 availPageFile >> 20, totalAddressSpaceFree >> 20,
+                                 LastKnownFreeAddressSpace >> 20, reserved);
+#endif
+                            throw e;
+                        }
+
+                        if (needContiguousVASpace)
+                        {
+                            InsufficientMemoryException e = new InsufficientMemoryException(SR.InsufficientMemory_MemFailPoint_VAFrag);
+#if DEBUG
+                            e.Data["MemFailPointState"] = new MemoryFailPointState(sizeInMegabytes, segmentSize,
+                                 needPageFile, needAddressSpace, needContiguousVASpace,
+                                 availPageFile >> 20, totalAddressSpaceFree >> 20,
+                                 LastKnownFreeAddressSpace >> 20, reserved);
+#endif
+                            throw e;
+                        }
+
+                        break;
+
+                    default:
+                        Debug.Fail("Fell through switch statement!");
+                        break;
+                }
+            }
+
+            // Success - we have enough room the last time we checked.
+            // Now update our shared state in a somewhat atomic fashion
+            // and handle a simple race condition with other MemoryFailPoint instances.
+            AddToLastKnownFreeAddressSpace(-((long)size));
+            if (LastKnownFreeAddressSpace < 0)
+                CheckForFreeAddressSpace(segmentSize, true);
+
+            RuntimeHelpers.PrepareConstrainedRegions();
+
+            SharedStatics.AddMemoryFailPointReservation((long)size);
+            _mustSubtractReservation = true;
+#endif
+        }
+
+        private static void CheckForAvailableMemory(out ulong availPageFile, out ulong totalAddressSpaceFree)
+        {
+            bool r;
+            Win32Native.MEMORYSTATUSEX memory = new Win32Native.MEMORYSTATUSEX();
+            r = Win32Native.GlobalMemoryStatusEx(ref memory);
+            if (!r)
+                throw Win32Marshal.GetExceptionForLastWin32Error();
+            availPageFile = memory.availPageFile;
+            totalAddressSpaceFree = memory.availVirtual;
+            // Console.WriteLine($"Memory gate:  Mem load: {memory.memoryLoad}%  Available memory (physical + page file): {(memory.availPageFile >> 20)} MB  Total free address space: {memory.availVirtual >> 20} MB  GC Heap: {(GC.GetTotalMemory(true) >> 20)} MB");
+        }
+
+        // Based on the shouldThrow parameter, this will throw an exception, or 
+        // returns whether there is enough space.  In all cases, we update
+        // our last known free address space, hopefully avoiding needing to 
+        // probe again.
+        private static unsafe bool CheckForFreeAddressSpace(ulong size, bool shouldThrow)
+        {
+            // Start walking the address space at 0.  VirtualAlloc may wrap
+            // around the address space.  We don't need to find the exact
+            // pages that VirtualAlloc would return - we just need to
+            // know whether VirtualAlloc could succeed.
+            ulong freeSpaceAfterGCHeap = MemFreeAfterAddress(null, size);
+
+            // Console.WriteLine($"MemoryFailPoint: Checked for free VA space.  Found enough? {(freeSpaceAfterGCHeap >= size)}  Asked for: {size}  Found: {freeSpaceAfterGCHeap}");
+
+            // We may set these without taking a lock - I don't believe
+            // this will hurt, as long as we never increment this number in 
+            // the Dispose method.  If we do an extra bit of checking every
+            // once in a while, but we avoid taking a lock, we may win.
+            LastKnownFreeAddressSpace = (long)freeSpaceAfterGCHeap;
+            LastTimeCheckingAddressSpace = Environment.TickCount;
+
+            if (freeSpaceAfterGCHeap < size && shouldThrow)
+                throw new InsufficientMemoryException(SR.InsufficientMemory_MemFailPoint_VAFrag);
+            return freeSpaceAfterGCHeap >= size;
+        }
+
+        // Returns the amount of consecutive free memory available in a block
+        // of pages.  If we didn't have enough address space, we still return 
+        // a positive value < size, to help potentially avoid the overhead of 
+        // this check if we use a MemoryFailPoint with a smaller size next.
+        private static unsafe ulong MemFreeAfterAddress(void* address, ulong size)
+        {
+            if (size >= TopOfMemory)
+                return 0;
+
+            ulong largestFreeRegion = 0;
+            Win32Native.MEMORY_BASIC_INFORMATION memInfo = new Win32Native.MEMORY_BASIC_INFORMATION();
+            UIntPtr sizeOfMemInfo = (UIntPtr)Marshal.SizeOf(memInfo);
+
+            while (((ulong)address) + size < TopOfMemory)
+            {
+                UIntPtr r = Win32Native.VirtualQuery(address, ref memInfo, sizeOfMemInfo);
+                if (r == UIntPtr.Zero)
+                    throw Win32Marshal.GetExceptionForLastWin32Error();
+
+                ulong regionSize = memInfo.RegionSize.ToUInt64();
+                if (memInfo.State == Win32Native.MEM_FREE)
+                {
+                    if (regionSize >= size)
+                        return regionSize;
+                    else
+                        largestFreeRegion = Math.Max(largestFreeRegion, regionSize);
+                }
+                address = (void*)((ulong)address + regionSize);
+            }
+            return largestFreeRegion;
+        }
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern void GetMemorySettings(out ulong maxGCSegmentSize, out ulong topOfMemory);
+
+        ~MemoryFailPoint()
+        {
+            Dispose(false);
+        }
+
+        // Applications must call Dispose, which conceptually "releases" the
+        // memory that was "reserved" by the MemoryFailPoint.  This affects a
+        // global count of reserved memory in this version (helping to throttle
+        // future MemoryFailPoints) in this version.  We may in the 
+        // future create an allocation context and release it in the Dispose
+        // method.  While the finalizer will eventually free this block of 
+        // memory, apps will help their performance greatly by calling Dispose.
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        private void Dispose(bool disposing)
+        {
+            // This is just bookkeeping to ensure multiple threads can really
+            // get enough memory, and this does not actually reserve memory
+            // within the GC heap.
+            if (_mustSubtractReservation)
+            {
+                RuntimeHelpers.PrepareConstrainedRegions();
+
+                SharedStatics.AddMemoryFailPointReservation(-((long)_reservedMemory));
+                _mustSubtractReservation = false;
+            }
+
+            /*
+            // Prototype performance 
+            // Let's pretend that we returned at least some free memory to
+            // the GC heap.  We don't know this is true - the objects could
+            // have a longer lifetime, and the memory could be elsewhere in the 
+            // GC heap.  Additionally, we subtracted off the segment size, not
+            // this size.  That's ok - we don't mind if this slowly degrades
+            // and requires us to refresh the value a little bit sooner.
+            // But releasing the memory here should help us avoid probing for
+            // free address space excessively with large workItem sizes.
+            Interlocked.Add(ref LastKnownFreeAddressSpace, _reservedMemory);
+            */
+        }
+
+#if DEBUG
+        [Serializable]
+        internal sealed class MemoryFailPointState
+        {
+            private ulong _segmentSize;
+            private int _allocationSizeInMB;
+            private bool _needPageFile;
+            private bool _needAddressSpace;
+            private bool _needContiguousVASpace;
+            private ulong _availPageFile;
+            private ulong _totalFreeAddressSpace;
+            private long _lastKnownFreeAddressSpace;
+            private ulong _reservedMem;
+            private String _stackTrace;  // Where did we fail, for additional debugging.
+
+            internal MemoryFailPointState(int allocationSizeInMB, ulong segmentSize, bool needPageFile, bool needAddressSpace, bool needContiguousVASpace, ulong availPageFile, ulong totalFreeAddressSpace, long lastKnownFreeAddressSpace, ulong reservedMem)
+            {
+                _allocationSizeInMB = allocationSizeInMB;
+                _segmentSize = segmentSize;
+                _needPageFile = needPageFile;
+                _needAddressSpace = needAddressSpace;
+                _needContiguousVASpace = needContiguousVASpace;
+                _availPageFile = availPageFile;
+                _totalFreeAddressSpace = totalFreeAddressSpace;
+                _lastKnownFreeAddressSpace = lastKnownFreeAddressSpace;
+                _reservedMem = reservedMem;
+                try
+                {
+                    _stackTrace = Environment.StackTrace;
+                }
+                catch (System.Security.SecurityException)
+                {
+                    _stackTrace = "no permission";
+                }
+                catch (OutOfMemoryException)
+                {
+                    _stackTrace = "out of memory";
+                }
+            }
+
+            public override String ToString()
+            {
+                return String.Format(System.Globalization.CultureInfo.InvariantCulture, "MemoryFailPoint detected insufficient memory to guarantee an operation could complete.  Checked for {0} MB, for allocation size of {1} MB.  Need page file? {2}  Need Address Space? {3}  Need Contiguous address space? {4}  Avail page file: {5} MB  Total free VA space: {6} MB  Contiguous free address space (found): {7} MB  Space reserved by process's MemoryFailPoints: {8} MB",
+                    _segmentSize >> 20, _allocationSizeInMB, _needPageFile,
+                    _needAddressSpace, _needContiguousVASpace,
+                    _availPageFile >> 20, _totalFreeAddressSpace >> 20,
+                    _lastKnownFreeAddressSpace >> 20, _reservedMem);
+            }
+        }
+#endif
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/RuntimeImports.cs b/src/System.Private.CoreLib/src/System/Runtime/RuntimeImports.cs
new file mode 100644
index 0000000000..9ac9150725
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/RuntimeImports.cs
@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+#if BIT64
+using nuint = System.UInt64;
+#else
+using nuint = System.UInt32;
+#endif
+
+namespace System.Runtime
+{
+    public class RuntimeImports
+    {
+        // Non-inlinable wrapper around the QCall that avoids poluting the fast path
+        // with P/Invoke prolog/epilog.
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        internal static unsafe void RhZeroMemory(ref byte b, nuint byteLength)
+        {
+            fixed (byte* bytePointer = &b)
+            {
+                RhZeroMemory(bytePointer, byteLength);
+            }
+        }
+
+        internal static unsafe void RhZeroMemory(IntPtr p, UIntPtr byteLength)
+        {
+            RhZeroMemory((void*)p, (nuint)byteLength);
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern unsafe void RhZeroMemory(void* b, nuint byteLength);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal static extern unsafe void RhBulkMoveWithWriteBarrier(ref byte destination, ref byte source, nuint byteCount);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Serialization/FormatterConverter.cs b/src/System.Private.CoreLib/src/System/Runtime/Serialization/FormatterConverter.cs
new file mode 100644
index 0000000000..a6e03e7099
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Serialization/FormatterConverter.cs
@@ -0,0 +1,185 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: A base implementation of the IFormatterConverter
+**          interface that uses the Convert class and the 
+**          IConvertible interface.
+**
+**
+============================================================*/
+
+using System;
+using System.Globalization;
+
+namespace System.Runtime.Serialization
+{
+    internal class FormatterConverter : IFormatterConverter
+    {
+        public FormatterConverter()
+        {
+        }
+
+        public Object Convert(Object value, Type type)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ChangeType(value, type, CultureInfo.InvariantCulture);
+        }
+
+        public Object Convert(Object value, TypeCode typeCode)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ChangeType(value, typeCode, CultureInfo.InvariantCulture);
+        }
+
+        public bool ToBoolean(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToBoolean(value, CultureInfo.InvariantCulture);
+        }
+
+        public char ToChar(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToChar(value, CultureInfo.InvariantCulture);
+        }
+
+        [CLSCompliant(false)]
+        public sbyte ToSByte(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToSByte(value, CultureInfo.InvariantCulture);
+        }
+
+        public byte ToByte(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToByte(value, CultureInfo.InvariantCulture);
+        }
+
+        public short ToInt16(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToInt16(value, CultureInfo.InvariantCulture);
+        }
+
+        [CLSCompliant(false)]
+        public ushort ToUInt16(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToUInt16(value, CultureInfo.InvariantCulture);
+        }
+
+        public int ToInt32(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToInt32(value, CultureInfo.InvariantCulture);
+        }
+
+        [CLSCompliant(false)]
+        public uint ToUInt32(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToUInt32(value, CultureInfo.InvariantCulture);
+        }
+
+        public long ToInt64(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToInt64(value, CultureInfo.InvariantCulture);
+        }
+
+        [CLSCompliant(false)]
+        public ulong ToUInt64(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToUInt64(value, CultureInfo.InvariantCulture);
+        }
+
+        public float ToSingle(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToSingle(value, CultureInfo.InvariantCulture);
+        }
+
+        public double ToDouble(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToDouble(value, CultureInfo.InvariantCulture);
+        }
+
+        public Decimal ToDecimal(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToDecimal(value, CultureInfo.InvariantCulture);
+        }
+
+        public DateTime ToDateTime(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToDateTime(value, CultureInfo.InvariantCulture);
+        }
+
+        public String ToString(Object value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+            return System.Convert.ToString(value, CultureInfo.InvariantCulture);
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Serialization/FormatterServices.cs b/src/System.Private.CoreLib/src/System/Runtime/Serialization/FormatterServices.cs
new file mode 100644
index 0000000000..1377350b80
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Serialization/FormatterServices.cs
@@ -0,0 +1,64 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Provides some static methods to aid with the implementation
+**          of a Formatter for Serialization.
+**
+**
+============================================================*/
+
+using System;
+using System.Reflection;
+using System.Collections;
+using System.Collections.Generic;
+using System.Security;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+using System.Threading;
+using System.IO;
+using System.Text;
+using System.Globalization;
+using System.Diagnostics;
+
+namespace System.Runtime.Serialization
+{
+    // This class duplicates a class on CoreFX. We are keeping it here -- just this one method --
+    // as it was widely invoked by reflection to workaround it being missing in .NET Core 1.0
+    internal static class FormatterServices
+    {
+        // Gets a new instance of the object.  The entire object is initalized to 0 and no 
+        // constructors have been run. **THIS MEANS THAT THE OBJECT MAY NOT BE IN A STATE
+        // CONSISTENT WITH ITS INTERNAL REQUIREMENTS** This method should only be used for
+        // deserialization when the user intends to immediately populate all fields.  This method
+        // will not create an unitialized string because it is non-sensical to create an empty
+        // instance of an immutable type.
+        //
+        public static Object GetUninitializedObject(Type type)
+        {
+            if ((object)type == null)
+            {
+                throw new ArgumentNullException(nameof(type));
+            }
+
+            if (!(type is RuntimeType))
+            {
+                throw new SerializationException(SR.Format(SR.Serialization_InvalidType, type.ToString()));
+            }
+
+            return nativeGetUninitializedObject((RuntimeType)type);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern Object nativeGetUninitializedObject(RuntimeType type);
+    }
+}
+
+
+
+
+
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Serialization/SerializationInfo.cs b/src/System.Private.CoreLib/src/System/Runtime/Serialization/SerializationInfo.cs
new file mode 100644
index 0000000000..979d5fee2a
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Serialization/SerializationInfo.cs
@@ -0,0 +1,689 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: The structure for holding all of the data needed
+**          for object serialization and deserialization.
+**
+**
+===========================================================*/
+
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using System.Globalization;
+using System.Diagnostics;
+using System.Security;
+using System.Runtime.CompilerServices;
+
+namespace System.Runtime.Serialization
+{
+    public sealed class SerializationInfo
+    {
+        private const int defaultSize = 4;
+        private const string s_mscorlibAssemblySimpleName = System.CoreLib.Name;
+        private const string s_mscorlibFileName = s_mscorlibAssemblySimpleName + ".dll";
+
+        // Even though we have a dictionary, we're still keeping all the arrays around for back-compat. 
+        // Otherwise we may run into potentially breaking behaviors like GetEnumerator() not returning entries in the same order they were added.
+        internal String[] m_members;
+        internal Object[] m_data;
+        internal Type[] m_types;
+        private Dictionary<string, int> m_nameToIndex;
+        internal int m_currMember;
+        internal IFormatterConverter m_converter;
+        private String m_fullTypeName;
+        private String m_assemName;
+        private Type objectType;
+        private bool isFullTypeNameSetExplicit;
+        private bool isAssemblyNameSetExplicit;
+        private bool requireSameTokenInPartialTrust;
+
+        [CLSCompliant(false)]
+        public SerializationInfo(Type type, IFormatterConverter converter)
+            : this(type, converter, false)
+        {
+        }
+
+        [CLSCompliant(false)]
+        public SerializationInfo(Type type, IFormatterConverter converter, bool requireSameTokenInPartialTrust)
+        {
+            if ((object)type == null)
+            {
+                throw new ArgumentNullException(nameof(type));
+            }
+
+            if (converter == null)
+            {
+                throw new ArgumentNullException(nameof(converter));
+            }
+
+
+            objectType = type;
+            m_fullTypeName = type.FullName;
+            m_assemName = type.Module.Assembly.FullName;
+
+            m_members = new String[defaultSize];
+            m_data = new Object[defaultSize];
+            m_types = new Type[defaultSize];
+
+            m_nameToIndex = new Dictionary<string, int>();
+
+            m_converter = converter;
+
+            this.requireSameTokenInPartialTrust = requireSameTokenInPartialTrust;
+        }
+
+        public String FullTypeName
+        {
+            get
+            {
+                return m_fullTypeName;
+            }
+            set
+            {
+                if (null == value)
+                {
+                    throw new ArgumentNullException(nameof(value));
+                }
+
+                m_fullTypeName = value;
+                isFullTypeNameSetExplicit = true;
+            }
+        }
+
+        public String AssemblyName
+        {
+            get
+            {
+                return m_assemName;
+            }
+            set
+            {
+                if (null == value)
+                {
+                    throw new ArgumentNullException(nameof(value));
+                }
+                if (requireSameTokenInPartialTrust)
+                {
+                    DemandForUnsafeAssemblyNameAssignments(m_assemName, value);
+                }
+                m_assemName = value;
+                isAssemblyNameSetExplicit = true;
+            }
+        }
+
+        public void SetType(Type type)
+        {
+            if ((object)type == null)
+            {
+                throw new ArgumentNullException(nameof(type));
+            }
+
+            if (requireSameTokenInPartialTrust)
+            {
+                DemandForUnsafeAssemblyNameAssignments(this.ObjectType.Assembly.FullName, type.Assembly.FullName);
+            }
+
+            if (!Object.ReferenceEquals(objectType, type))
+            {
+                objectType = type;
+                m_fullTypeName = type.FullName;
+                m_assemName = type.Module.Assembly.FullName;
+                isFullTypeNameSetExplicit = false;
+                isAssemblyNameSetExplicit = false;
+            }
+        }
+
+        internal static void DemandForUnsafeAssemblyNameAssignments(string originalAssemblyName, string newAssemblyName)
+        {
+        }
+
+        public int MemberCount
+        {
+            get
+            {
+                return m_currMember;
+            }
+        }
+
+        public Type ObjectType
+        {
+            get
+            {
+                return objectType;
+            }
+        }
+
+        public bool IsFullTypeNameSetExplicit
+        {
+            get
+            {
+                return isFullTypeNameSetExplicit;
+            }
+        }
+
+        public bool IsAssemblyNameSetExplicit
+        {
+            get
+            {
+                return isAssemblyNameSetExplicit;
+            }
+        }
+
+        public SerializationInfoEnumerator GetEnumerator()
+        {
+            return new SerializationInfoEnumerator(m_members, m_data, m_types, m_currMember);
+        }
+
+        private void ExpandArrays()
+        {
+            int newSize;
+            Debug.Assert(m_members.Length == m_currMember, "[SerializationInfo.ExpandArrays]m_members.Length == m_currMember");
+
+            newSize = (m_currMember * 2);
+
+            //
+            // In the pathological case, we may wrap
+            //
+            if (newSize < m_currMember)
+            {
+                if (Int32.MaxValue > m_currMember)
+                {
+                    newSize = Int32.MaxValue;
+                }
+            }
+
+            //
+            // Allocate more space and copy the data
+            //
+            String[] newMembers = new String[newSize];
+            Object[] newData = new Object[newSize];
+            Type[] newTypes = new Type[newSize];
+
+            Array.Copy(m_members, newMembers, m_currMember);
+            Array.Copy(m_data, newData, m_currMember);
+            Array.Copy(m_types, newTypes, m_currMember);
+
+            //
+            // Assign the new arrys back to the member vars.
+            //
+            m_members = newMembers;
+            m_data = newData;
+            m_types = newTypes;
+        }
+
+        public void AddValue(String name, Object value, Type type)
+        {
+            if (null == name)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
+            if ((object)type == null)
+            {
+                throw new ArgumentNullException(nameof(type));
+            }
+
+            AddValueInternal(name, value, type);
+        }
+
+        public void AddValue(String name, Object value)
+        {
+            if (null == value)
+            {
+                AddValue(name, value, typeof(Object));
+            }
+            else
+            {
+                AddValue(name, value, value.GetType());
+            }
+        }
+
+        public void AddValue(String name, bool value)
+        {
+            AddValue(name, (Object)value, typeof(bool));
+        }
+
+        public void AddValue(String name, char value)
+        {
+            AddValue(name, (Object)value, typeof(char));
+        }
+
+
+        [CLSCompliant(false)]
+        public void AddValue(String name, sbyte value)
+        {
+            AddValue(name, (Object)value, typeof(sbyte));
+        }
+
+        public void AddValue(String name, byte value)
+        {
+            AddValue(name, (Object)value, typeof(byte));
+        }
+
+        public void AddValue(String name, short value)
+        {
+            AddValue(name, (Object)value, typeof(short));
+        }
+
+        [CLSCompliant(false)]
+        public void AddValue(String name, ushort value)
+        {
+            AddValue(name, (Object)value, typeof(ushort));
+        }
+
+        public void AddValue(String name, int value)
+        {
+            AddValue(name, (Object)value, typeof(int));
+        }
+
+        [CLSCompliant(false)]
+        public void AddValue(String name, uint value)
+        {
+            AddValue(name, (Object)value, typeof(uint));
+        }
+
+        public void AddValue(String name, long value)
+        {
+            AddValue(name, (Object)value, typeof(long));
+        }
+
+        [CLSCompliant(false)]
+        public void AddValue(String name, ulong value)
+        {
+            AddValue(name, (Object)value, typeof(ulong));
+        }
+
+        public void AddValue(String name, float value)
+        {
+            AddValue(name, (Object)value, typeof(float));
+        }
+
+        public void AddValue(String name, double value)
+        {
+            AddValue(name, (Object)value, typeof(double));
+        }
+
+        public void AddValue(String name, decimal value)
+        {
+            AddValue(name, (Object)value, typeof(decimal));
+        }
+
+        public void AddValue(String name, DateTime value)
+        {
+            AddValue(name, (Object)value, typeof(DateTime));
+        }
+
+        internal void AddValueInternal(String name, Object value, Type type)
+        {
+            if (m_nameToIndex.ContainsKey(name))
+            {
+                throw new SerializationException(SR.Serialization_SameNameTwice);
+            }
+            m_nameToIndex.Add(name, m_currMember);
+
+            //
+            // If we need to expand the arrays, do so.
+            //
+            if (m_currMember >= m_members.Length)
+            {
+                ExpandArrays();
+            }
+
+            //
+            // Add the data and then advance the counter.
+            //
+            m_members[m_currMember] = name;
+            m_data[m_currMember] = value;
+            m_types[m_currMember] = type;
+            m_currMember++;
+        }
+
+        /*=================================UpdateValue==================================
+        **Action: Finds the value if it exists in the current data.  If it does, we replace
+        **        the values, if not, we append it to the end.  This is useful to the 
+        **        ObjectManager when it's performing fixups.
+        **Returns: void
+        **Arguments: name  -- the name of the data to be updated.
+        **           value -- the new value.
+        **           type  -- the type of the data being added.
+        **Exceptions: None.  All error checking is done with asserts. Although public in coreclr,
+        **            it's not exposed in a contract and is only meant to be used by corefx.
+        ==============================================================================*/
+        // This should not be used by clients: exposing out this functionality would allow children
+        // to overwrite their parent's values. It is public in order to give corefx access to it for
+        // its ObjectManager implementation, but it should not be exposed out of a contract.
+        public void UpdateValue(String name, Object value, Type type)
+        {
+            Debug.Assert(null != name, "[SerializationInfo.UpdateValue]name!=null");
+            Debug.Assert(null != value, "[SerializationInfo.UpdateValue]value!=null");
+            Debug.Assert(null != (object)type, "[SerializationInfo.UpdateValue]type!=null");
+
+            int index = FindElement(name);
+            if (index < 0)
+            {
+                AddValueInternal(name, value, type);
+            }
+            else
+            {
+                m_data[index] = value;
+                m_types[index] = type;
+            }
+        }
+
+        private int FindElement(String name)
+        {
+            if (null == name)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+            int index;
+            if (m_nameToIndex.TryGetValue(name, out index))
+            {
+                return index;
+            }
+            return -1;
+        }
+
+        /*==================================GetElement==================================
+        **Action: Use FindElement to get the location of a particular member and then return
+        **        the value of the element at that location.  The type of the member is
+        **        returned in the foundType field.
+        **Returns: The value of the element at the position associated with name.
+        **Arguments: name -- the name of the element to find.
+        **           foundType -- the type of the element associated with the given name.
+        **Exceptions: None.  FindElement does null checking and throws for elements not 
+        **            found.
+        ==============================================================================*/
+        private Object GetElement(String name, out Type foundType)
+        {
+            int index = FindElement(name);
+            if (index == -1)
+            {
+                throw new SerializationException(SR.Format(SR.Serialization_NotFound, name));
+            }
+
+            Debug.Assert(index < m_data.Length, "[SerializationInfo.GetElement]index<m_data.Length");
+            Debug.Assert(index < m_types.Length, "[SerializationInfo.GetElement]index<m_types.Length");
+
+            foundType = m_types[index];
+            Debug.Assert((object)foundType != null, "[SerializationInfo.GetElement]foundType!=null");
+            return m_data[index];
+        }
+
+        private Object GetElementNoThrow(String name, out Type foundType)
+        {
+            int index = FindElement(name);
+            if (index == -1)
+            {
+                foundType = null;
+                return null;
+            }
+
+            Debug.Assert(index < m_data.Length, "[SerializationInfo.GetElement]index<m_data.Length");
+            Debug.Assert(index < m_types.Length, "[SerializationInfo.GetElement]index<m_types.Length");
+
+            foundType = m_types[index];
+            Debug.Assert((object)foundType != null, "[SerializationInfo.GetElement]foundType!=null");
+            return m_data[index];
+        }
+
+        //
+        // The user should call one of these getters to get the data back in the 
+        // form requested.  
+        //
+
+        public Object GetValue(String name, Type type)
+        {
+            if ((object)type == null)
+            {
+                throw new ArgumentNullException(nameof(type));
+            }
+
+            RuntimeType rt = type as RuntimeType;
+            if (rt == null)
+                throw new ArgumentException(SR.Argument_MustBeRuntimeType);
+
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+
+            if (Object.ReferenceEquals(foundType, type) || type.IsAssignableFrom(foundType) || value == null)
+            {
+                return value;
+            }
+
+            Debug.Assert(m_converter != null, "[SerializationInfo.GetValue]m_converter!=null");
+
+            return m_converter.Convert(value, type);
+        }
+
+        internal Object GetValueNoThrow(String name, Type type)
+        {
+            Type foundType;
+            Object value;
+
+            Debug.Assert((object)type != null, "[SerializationInfo.GetValue]type ==null");
+            Debug.Assert(type is RuntimeType, "[SerializationInfo.GetValue]type is not a runtime type");
+
+            value = GetElementNoThrow(name, out foundType);
+            if (value == null)
+                return null;
+
+            if (Object.ReferenceEquals(foundType, type) || type.IsAssignableFrom(foundType) || value == null)
+            {
+                return value;
+            }
+
+            Debug.Assert(m_converter != null, "[SerializationInfo.GetValue]m_converter!=null");
+
+            return m_converter.Convert(value, type);
+        }
+
+        public bool GetBoolean(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(bool)))
+            {
+                return (bool)value;
+            }
+            return m_converter.ToBoolean(value);
+        }
+
+        public char GetChar(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(char)))
+            {
+                return (char)value;
+            }
+            return m_converter.ToChar(value);
+        }
+
+        [CLSCompliant(false)]
+        public sbyte GetSByte(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(sbyte)))
+            {
+                return (sbyte)value;
+            }
+            return m_converter.ToSByte(value);
+        }
+
+        public byte GetByte(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(byte)))
+            {
+                return (byte)value;
+            }
+            return m_converter.ToByte(value);
+        }
+
+        public short GetInt16(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(short)))
+            {
+                return (short)value;
+            }
+            return m_converter.ToInt16(value);
+        }
+
+        [CLSCompliant(false)]
+        public ushort GetUInt16(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(ushort)))
+            {
+                return (ushort)value;
+            }
+            return m_converter.ToUInt16(value);
+        }
+
+        public int GetInt32(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(int)))
+            {
+                return (int)value;
+            }
+            return m_converter.ToInt32(value);
+        }
+
+        [CLSCompliant(false)]
+        public uint GetUInt32(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(uint)))
+            {
+                return (uint)value;
+            }
+            return m_converter.ToUInt32(value);
+        }
+
+        public long GetInt64(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(long)))
+            {
+                return (long)value;
+            }
+            return m_converter.ToInt64(value);
+        }
+
+        [CLSCompliant(false)]
+        public ulong GetUInt64(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(ulong)))
+            {
+                return (ulong)value;
+            }
+            return m_converter.ToUInt64(value);
+        }
+
+        public float GetSingle(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(float)))
+            {
+                return (float)value;
+            }
+            return m_converter.ToSingle(value);
+        }
+
+
+        public double GetDouble(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(double)))
+            {
+                return (double)value;
+            }
+            return m_converter.ToDouble(value);
+        }
+
+        public decimal GetDecimal(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(decimal)))
+            {
+                return (decimal)value;
+            }
+            return m_converter.ToDecimal(value);
+        }
+
+        public DateTime GetDateTime(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(DateTime)))
+            {
+                return (DateTime)value;
+            }
+            return m_converter.ToDateTime(value);
+        }
+
+        public String GetString(String name)
+        {
+            Type foundType;
+            Object value;
+
+            value = GetElement(name, out foundType);
+            if (Object.ReferenceEquals(foundType, typeof(String)) || value == null)
+            {
+                return (String)value;
+            }
+            return m_converter.ToString(value);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Runtime/Versioning/CompatibilitySwitch.cs b/src/System.Private.CoreLib/src/System/Runtime/Versioning/CompatibilitySwitch.cs
new file mode 100644
index 0000000000..3410f020be
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Runtime/Versioning/CompatibilitySwitch.cs
@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+using System;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+
+namespace System.Runtime.Versioning
+{
+    internal static class CompatibilitySwitch
+    {
+        /* This class contains 3 sets of api:
+                * 1. internal apis : These apis are supposed to be used by mscorlib.dll and other assemblies which use the <runtime> section in config 
+                *                          These apis query for the value of quirk not only in windows quirk DB but also in runtime section of config files,  
+                *                          registry and environment vars.
+                * 2. public apis : These apis are supposed to be used by FX assemblies which do not read the runtime section of config files and have
+                *                       have their own section in config files or do not use configs at all.
+                *
+                * 3. specialized apis: These apis are defined in order to retrieve a specific value defined in CLR Config. That value can have specific look-up rules
+                *                        for the order and location of the config sources used.
+                *                        
+                *     These apis are for internal use only for FX assemblies. It has not been decided if they can be used by OOB components due to EULA restrictions
+                */
+        internal static string GetValueInternal(string compatibilitySwitchName)
+        {
+            return GetValueInternalCall(compatibilitySwitchName, false);
+        }
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern string GetValueInternalCall(string compatibilitySwitchName, bool onlyDB);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/RuntimeArgumentHandle.cs b/src/System.Private.CoreLib/src/System/RuntimeArgumentHandle.cs
new file mode 100644
index 0000000000..2066ed71eb
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/RuntimeArgumentHandle.cs
@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System;
+
+namespace System
+{
+    //  This value type is used for constructing System.ArgIterator. 
+    // 
+    //  SECURITY : m_ptr cannot be set to anything other than null by untrusted
+    //  code.  
+    // 
+    //  This corresponds to EE VARARGS cookie.
+
+    // Cannot be serialized
+    public ref struct RuntimeArgumentHandle
+    {
+        private IntPtr m_ptr;
+
+        internal IntPtr Value { get { return m_ptr; } }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/RuntimeHandles.cs b/src/System.Private.CoreLib/src/System/RuntimeHandles.cs
new file mode 100644
index 0000000000..dc659e3dee
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/RuntimeHandles.cs
@@ -0,0 +1,1537 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+namespace System
+{
+    using System;
+    using System.Reflection;
+    using System.Reflection.Emit;
+    using System.Runtime;
+    using System.Runtime.ConstrainedExecution;
+    using System.Diagnostics;
+    using System.Runtime.Serialization;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.InteropServices;
+    using System.Threading;
+    using System.Runtime.Versioning;
+    using System.Text;
+    using System.Globalization;
+    using System.Security;
+    using Microsoft.Win32.SafeHandles;
+    using StackCrawlMark = System.Threading.StackCrawlMark;
+
+    public unsafe struct RuntimeTypeHandle : ISerializable
+    {
+        // Returns handle for interop with EE. The handle is guaranteed to be non-null.
+        internal RuntimeTypeHandle GetNativeHandle()
+        {
+            // Create local copy to avoid a race condition
+            RuntimeType type = m_type;
+            if (type == null)
+                throw new ArgumentNullException(null, SR.Arg_InvalidHandle);
+            return new RuntimeTypeHandle(type);
+        }
+
+        // Returns type for interop with EE. The type is guaranteed to be non-null.
+        internal RuntimeType GetTypeChecked()
+        {
+            // Create local copy to avoid a race condition
+            RuntimeType type = m_type;
+            if (type == null)
+                throw new ArgumentNullException(null, SR.Arg_InvalidHandle);
+            return type;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsInstanceOfType(RuntimeType type, Object o);
+
+        internal static unsafe Type GetTypeHelper(Type typeStart, Type[] genericArgs, IntPtr pModifiers, int cModifiers)
+        {
+            Type type = typeStart;
+
+            if (genericArgs != null)
+            {
+                type = type.MakeGenericType(genericArgs);
+            }
+
+            if (cModifiers > 0)
+            {
+                int* arModifiers = (int*)pModifiers.ToPointer();
+                for (int i = 0; i < cModifiers; i++)
+                {
+                    if ((CorElementType)Marshal.ReadInt32((IntPtr)arModifiers, i * sizeof(int)) == CorElementType.Ptr)
+                        type = type.MakePointerType();
+
+                    else if ((CorElementType)Marshal.ReadInt32((IntPtr)arModifiers, i * sizeof(int)) == CorElementType.ByRef)
+                        type = type.MakeByRefType();
+
+                    else if ((CorElementType)Marshal.ReadInt32((IntPtr)arModifiers, i * sizeof(int)) == CorElementType.SzArray)
+                        type = type.MakeArrayType();
+
+                    else
+                        type = type.MakeArrayType(Marshal.ReadInt32((IntPtr)arModifiers, ++i * sizeof(int)));
+                }
+            }
+
+            return type;
+        }
+
+        public static bool operator ==(RuntimeTypeHandle left, object right) { return left.Equals(right); }
+
+        public static bool operator ==(object left, RuntimeTypeHandle right) { return right.Equals(left); }
+
+        public static bool operator !=(RuntimeTypeHandle left, object right) { return !left.Equals(right); }
+
+        public static bool operator !=(object left, RuntimeTypeHandle right) { return !right.Equals(left); }
+
+
+        // This is the RuntimeType for the type
+        private RuntimeType m_type;
+
+        public override int GetHashCode()
+        {
+            return m_type != null ? m_type.GetHashCode() : 0;
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (!(obj is RuntimeTypeHandle))
+                return false;
+
+            RuntimeTypeHandle handle = (RuntimeTypeHandle)obj;
+            return handle.m_type == m_type;
+        }
+
+        public bool Equals(RuntimeTypeHandle handle)
+        {
+            return handle.m_type == m_type;
+        }
+
+        public IntPtr Value
+        {
+            get
+            {
+                return m_type != null ? m_type.m_handle : IntPtr.Zero;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr GetValueInternal(RuntimeTypeHandle handle);
+
+        internal RuntimeTypeHandle(RuntimeType type)
+        {
+            m_type = type;
+        }
+
+        internal static bool IsTypeDefinition(RuntimeType type)
+        {
+            CorElementType corElemType = GetCorElementType(type);
+            if (!((corElemType >= CorElementType.Void && corElemType < CorElementType.Ptr) ||
+                    corElemType == CorElementType.ValueType ||
+                    corElemType == CorElementType.Class ||
+                    corElemType == CorElementType.TypedByRef ||
+                    corElemType == CorElementType.I ||
+                    corElemType == CorElementType.U ||
+                    corElemType == CorElementType.Object))
+                return false;
+
+            if (HasInstantiation(type) && !IsGenericTypeDefinition(type))
+                return false;
+
+            return true;
+        }
+
+        internal static bool IsPrimitive(RuntimeType type)
+        {
+            CorElementType corElemType = GetCorElementType(type);
+            return (corElemType >= CorElementType.Boolean && corElemType <= CorElementType.R8) ||
+                    corElemType == CorElementType.I ||
+                    corElemType == CorElementType.U;
+        }
+
+        internal static bool IsByRef(RuntimeType type)
+        {
+            CorElementType corElemType = GetCorElementType(type);
+            return (corElemType == CorElementType.ByRef);
+        }
+
+        internal static bool IsPointer(RuntimeType type)
+        {
+            CorElementType corElemType = GetCorElementType(type);
+            return (corElemType == CorElementType.Ptr);
+        }
+
+        internal static bool IsArray(RuntimeType type)
+        {
+            CorElementType corElemType = GetCorElementType(type);
+            return (corElemType == CorElementType.Array || corElemType == CorElementType.SzArray);
+        }
+
+        internal static bool IsSZArray(RuntimeType type)
+        {
+            CorElementType corElemType = GetCorElementType(type);
+            return (corElemType == CorElementType.SzArray);
+        }
+
+        internal static bool HasElementType(RuntimeType type)
+        {
+            CorElementType corElemType = GetCorElementType(type);
+
+            return ((corElemType == CorElementType.Array || corElemType == CorElementType.SzArray) // IsArray
+                   || (corElemType == CorElementType.Ptr)                                          // IsPointer
+                   || (corElemType == CorElementType.ByRef));                                      // IsByRef
+        }
+
+        internal static IntPtr[] CopyRuntimeTypeHandles(RuntimeTypeHandle[] inHandles, out int length)
+        {
+            if (inHandles == null || inHandles.Length == 0)
+            {
+                length = 0;
+                return null;
+            }
+
+            IntPtr[] outHandles = new IntPtr[inHandles.Length];
+            for (int i = 0; i < inHandles.Length; i++)
+            {
+                outHandles[i] = inHandles[i].Value;
+            }
+            length = outHandles.Length;
+            return outHandles;
+        }
+
+        internal static IntPtr[] CopyRuntimeTypeHandles(Type[] inHandles, out int length)
+        {
+            if (inHandles == null || inHandles.Length == 0)
+            {
+                length = 0;
+                return null;
+            }
+
+            IntPtr[] outHandles = new IntPtr[inHandles.Length];
+            for (int i = 0; i < inHandles.Length; i++)
+            {
+                outHandles[i] = inHandles[i].GetTypeHandleInternal().Value;
+            }
+            length = outHandles.Length;
+            return outHandles;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Object CreateInstance(RuntimeType type, bool publicOnly, bool wrapExceptions, ref bool canBeCached, ref RuntimeMethodHandleInternal ctor);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Object CreateCaInstance(RuntimeType type, IRuntimeMethodInfo ctor);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Object Allocate(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Object CreateInstanceForAnotherGenericParameter(RuntimeType type, RuntimeType genericParameter);
+
+        internal RuntimeType GetRuntimeType()
+        {
+            return m_type;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern CorElementType GetCorElementType(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern RuntimeAssembly GetAssembly(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern RuntimeModule GetModule(RuntimeType type);
+
+        public ModuleHandle GetModuleHandle()
+        {
+            return new ModuleHandle(RuntimeTypeHandle.GetModule(m_type));
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern RuntimeType GetBaseType(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern TypeAttributes GetAttributes(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern RuntimeType GetElementType(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool CompareCanonicalHandles(RuntimeType left, RuntimeType right);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int GetArrayRank(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int GetToken(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern RuntimeMethodHandleInternal GetMethodAt(RuntimeType type, int slot);
+
+        // This is managed wrapper for MethodTable::IntroducedMethodIterator
+        internal struct IntroducedMethodEnumerator
+        {
+            private bool _firstCall;
+            private RuntimeMethodHandleInternal _handle;
+
+            internal IntroducedMethodEnumerator(RuntimeType type)
+            {
+                _handle = RuntimeTypeHandle.GetFirstIntroducedMethod(type);
+                _firstCall = true;
+            }
+
+            public bool MoveNext()
+            {
+                if (_firstCall)
+                {
+                    _firstCall = false;
+                }
+                else if (_handle.Value != IntPtr.Zero)
+                {
+                    RuntimeTypeHandle.GetNextIntroducedMethod(ref _handle);
+                }
+                return !(_handle.Value == IntPtr.Zero);
+            }
+
+            public RuntimeMethodHandleInternal Current
+            {
+                get
+                {
+                    return _handle;
+                }
+            }
+
+            // Glue to make this work nicely with C# foreach statement
+            public IntroducedMethodEnumerator GetEnumerator()
+            {
+                return this;
+            }
+        }
+
+        internal static IntroducedMethodEnumerator GetIntroducedMethods(RuntimeType type)
+        {
+            return new IntroducedMethodEnumerator(type);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern RuntimeMethodHandleInternal GetFirstIntroducedMethod(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void GetNextIntroducedMethod(ref RuntimeMethodHandleInternal method);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool GetFields(RuntimeType type, IntPtr* result, int* count);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Type[] GetInterfaces(RuntimeType type);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetConstraints(RuntimeTypeHandle handle, ObjectHandleOnStack types);
+
+        internal Type[] GetConstraints()
+        {
+            Type[] types = null;
+            GetConstraints(GetNativeHandle(), JitHelpers.GetObjectHandleOnStack(ref types));
+
+            return types;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern IntPtr GetGCHandle(RuntimeTypeHandle handle, GCHandleType type);
+
+        internal IntPtr GetGCHandle(GCHandleType type)
+        {
+            return GetGCHandle(GetNativeHandle(), type);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int GetNumVirtuals(RuntimeType type);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void VerifyInterfaceIsImplemented(RuntimeTypeHandle handle, RuntimeTypeHandle interfaceHandle);
+
+        internal void VerifyInterfaceIsImplemented(RuntimeTypeHandle interfaceHandle)
+        {
+            VerifyInterfaceIsImplemented(GetNativeHandle(), interfaceHandle.GetNativeHandle());
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern RuntimeMethodHandleInternal GetInterfaceMethodImplementation(RuntimeTypeHandle handle, RuntimeTypeHandle interfaceHandle, RuntimeMethodHandleInternal interfaceMethodHandle);
+
+        internal RuntimeMethodHandleInternal GetInterfaceMethodImplementation(RuntimeTypeHandle interfaceHandle, RuntimeMethodHandleInternal interfaceMethodHandle)
+        {
+            return GetInterfaceMethodImplementation(GetNativeHandle(), interfaceHandle.GetNativeHandle(), interfaceMethodHandle);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsComObject(RuntimeType type, bool isGenericCOM);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsInterface(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsByRefLike(RuntimeType type);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static extern bool _IsVisible(RuntimeTypeHandle typeHandle);
+
+        internal static bool IsVisible(RuntimeType type)
+        {
+            return _IsVisible(new RuntimeTypeHandle(type));
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsValueType(RuntimeType type);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void ConstructName(RuntimeTypeHandle handle, TypeNameFormatFlags formatFlags, StringHandleOnStack retString);
+
+        internal string ConstructName(TypeNameFormatFlags formatFlags)
+        {
+            string name = null;
+            ConstructName(GetNativeHandle(), formatFlags, JitHelpers.GetStringHandleOnStack(ref name));
+            return name;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void* _GetUtf8Name(RuntimeType type);
+
+        internal static MdUtf8String GetUtf8Name(RuntimeType type)
+        {
+            return new MdUtf8String(_GetUtf8Name(type));
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool CanCastTo(RuntimeType type, RuntimeType target);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern RuntimeType GetDeclaringType(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IRuntimeMethodInfo GetDeclaringMethod(RuntimeType type);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetDefaultConstructor(RuntimeTypeHandle handle, ObjectHandleOnStack method);
+
+        internal IRuntimeMethodInfo GetDefaultConstructor()
+        {
+            IRuntimeMethodInfo ctor = null;
+            GetDefaultConstructor(GetNativeHandle(), JitHelpers.GetObjectHandleOnStack(ref ctor));
+            return ctor;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetTypeByName(string name, bool throwOnError, bool ignoreCase, bool reflectionOnly, StackCrawlMarkHandle stackMark,
+            IntPtr pPrivHostBinder,
+            bool loadTypeFromPartialName, ObjectHandleOnStack type, ObjectHandleOnStack keepalive);
+
+        // Wrapper function to reduce the need for ifdefs.
+        internal static RuntimeType GetTypeByName(string name, bool throwOnError, bool ignoreCase, bool reflectionOnly, ref StackCrawlMark stackMark, bool loadTypeFromPartialName)
+        {
+            return GetTypeByName(name, throwOnError, ignoreCase, reflectionOnly, ref stackMark, IntPtr.Zero, loadTypeFromPartialName);
+        }
+
+        internal static RuntimeType GetTypeByName(string name, bool throwOnError, bool ignoreCase, bool reflectionOnly, ref StackCrawlMark stackMark,
+                                                  IntPtr pPrivHostBinder,
+                                                  bool loadTypeFromPartialName)
+        {
+            if (name == null || name.Length == 0)
+            {
+                if (throwOnError)
+                    throw new TypeLoadException(SR.Arg_TypeLoadNullStr);
+
+                return null;
+            }
+
+            RuntimeType type = null;
+
+            Object keepAlive = null;
+            GetTypeByName(name, throwOnError, ignoreCase, reflectionOnly,
+                JitHelpers.GetStackCrawlMarkHandle(ref stackMark),
+                pPrivHostBinder,
+                loadTypeFromPartialName, JitHelpers.GetObjectHandleOnStack(ref type), JitHelpers.GetObjectHandleOnStack(ref keepAlive));
+            GC.KeepAlive(keepAlive);
+
+            return type;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetTypeByNameUsingCARules(string name, RuntimeModule scope, ObjectHandleOnStack type);
+
+        internal static RuntimeType GetTypeByNameUsingCARules(string name, RuntimeModule scope)
+        {
+            if (name == null || name.Length == 0)
+                throw new ArgumentException(null, nameof(name));
+
+            RuntimeType type = null;
+            GetTypeByNameUsingCARules(name, scope.GetNativeHandle(), JitHelpers.GetObjectHandleOnStack(ref type));
+
+            return type;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void GetInstantiation(RuntimeTypeHandle type, ObjectHandleOnStack types, bool fAsRuntimeTypeArray);
+
+        internal RuntimeType[] GetInstantiationInternal()
+        {
+            RuntimeType[] types = null;
+            GetInstantiation(GetNativeHandle(), JitHelpers.GetObjectHandleOnStack(ref types), true);
+            return types;
+        }
+
+        internal Type[] GetInstantiationPublic()
+        {
+            Type[] types = null;
+            GetInstantiation(GetNativeHandle(), JitHelpers.GetObjectHandleOnStack(ref types), false);
+            return types;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void Instantiate(RuntimeTypeHandle handle, IntPtr* pInst, int numGenericArgs, ObjectHandleOnStack type);
+
+        internal RuntimeType Instantiate(Type[] inst)
+        {
+            // defensive copy to be sure array is not mutated from the outside during processing
+            int instCount;
+            IntPtr[] instHandles = CopyRuntimeTypeHandles(inst, out instCount);
+
+            fixed (IntPtr* pInst = instHandles)
+            {
+                RuntimeType type = null;
+                Instantiate(GetNativeHandle(), pInst, instCount, JitHelpers.GetObjectHandleOnStack(ref type));
+                GC.KeepAlive(inst);
+                return type;
+            }
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void MakeArray(RuntimeTypeHandle handle, int rank, ObjectHandleOnStack type);
+
+        internal RuntimeType MakeArray(int rank)
+        {
+            RuntimeType type = null;
+            MakeArray(GetNativeHandle(), rank, JitHelpers.GetObjectHandleOnStack(ref type));
+            return type;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void MakeSZArray(RuntimeTypeHandle handle, ObjectHandleOnStack type);
+
+        internal RuntimeType MakeSZArray()
+        {
+            RuntimeType type = null;
+            MakeSZArray(GetNativeHandle(), JitHelpers.GetObjectHandleOnStack(ref type));
+            return type;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void MakeByRef(RuntimeTypeHandle handle, ObjectHandleOnStack type);
+
+        internal RuntimeType MakeByRef()
+        {
+            RuntimeType type = null;
+            MakeByRef(GetNativeHandle(), JitHelpers.GetObjectHandleOnStack(ref type));
+            return type;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void MakePointer(RuntimeTypeHandle handle, ObjectHandleOnStack type);
+
+        internal RuntimeType MakePointer()
+        {
+            RuntimeType type = null;
+            MakePointer(GetNativeHandle(), JitHelpers.GetObjectHandleOnStack(ref type));
+            return type;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern bool IsCollectible(RuntimeTypeHandle handle);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool HasInstantiation(RuntimeType type);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetGenericTypeDefinition(RuntimeTypeHandle type, ObjectHandleOnStack retType);
+
+        internal static RuntimeType GetGenericTypeDefinition(RuntimeType type)
+        {
+            RuntimeType retType = type;
+
+            if (HasInstantiation(retType) && !IsGenericTypeDefinition(retType))
+                GetGenericTypeDefinition(retType.GetTypeHandleInternal(), JitHelpers.GetObjectHandleOnStack(ref retType));
+
+            return retType;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsGenericTypeDefinition(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsGenericVariable(RuntimeType type);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int GetGenericVariableIndex(RuntimeType type);
+
+        internal int GetGenericVariableIndex()
+        {
+            RuntimeType type = GetTypeChecked();
+
+            if (!IsGenericVariable(type))
+                throw new InvalidOperationException(SR.Arg_NotGenericParameter);
+
+            return GetGenericVariableIndex(type);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool ContainsGenericVariables(RuntimeType handle);
+
+        internal bool ContainsGenericVariables()
+        {
+            return ContainsGenericVariables(GetTypeChecked());
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool SatisfiesConstraints(RuntimeType paramType, IntPtr* pTypeContext, int typeContextLength, IntPtr* pMethodContext, int methodContextLength, RuntimeType toType);
+
+        internal static bool SatisfiesConstraints(RuntimeType paramType, RuntimeType[] typeContext, RuntimeType[] methodContext, RuntimeType toType)
+        {
+            int typeContextLength;
+            int methodContextLength;
+            IntPtr[] typeContextHandles = CopyRuntimeTypeHandles(typeContext, out typeContextLength);
+            IntPtr[] methodContextHandles = CopyRuntimeTypeHandles(methodContext, out methodContextLength);
+
+            fixed (IntPtr* pTypeContextHandles = typeContextHandles, pMethodContextHandles = methodContextHandles)
+            {
+                bool result = SatisfiesConstraints(paramType, pTypeContextHandles, typeContextLength, pMethodContextHandles, methodContextLength, toType);
+
+                GC.KeepAlive(typeContext);
+                GC.KeepAlive(methodContext);
+
+                return result;
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern IntPtr _GetMetadataImport(RuntimeType type);
+
+        internal static MetadataImport GetMetadataImport(RuntimeType type)
+        {
+            return new MetadataImport(_GetMetadataImport(type), type);
+        }
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            throw new PlatformNotSupportedException();
+        }
+    }
+
+    // This type is used to remove the expense of having a managed reference object that is dynamically 
+    // created when we can prove that we don't need that object. Use of this type requires code to ensure
+    // that the underlying native resource is not freed. 
+    // Cases in which this may be used:
+    //  1. When native code calls managed code passing one of these as a parameter
+    //  2. When managed code acquires one of these from an IRuntimeMethodInfo, and ensure that the IRuntimeMethodInfo is preserved
+    //     across the lifetime of the RuntimeMethodHandleInternal instance
+    //  3. When another object is used to keep the RuntimeMethodHandleInternal alive. See delegates, CreateInstance cache, Signature structure
+    // When in doubt, do not use. 
+    internal struct RuntimeMethodHandleInternal
+    {
+        internal static RuntimeMethodHandleInternal EmptyHandle
+        {
+            get
+            {
+                return new RuntimeMethodHandleInternal();
+            }
+        }
+
+        internal bool IsNullHandle()
+        {
+            return m_handle == IntPtr.Zero;
+        }
+
+        internal IntPtr Value
+        {
+            get
+            {
+                return m_handle;
+            }
+        }
+
+        internal RuntimeMethodHandleInternal(IntPtr value)
+        {
+            m_handle = value;
+        }
+
+        internal IntPtr m_handle;
+    }
+
+    internal class RuntimeMethodInfoStub : IRuntimeMethodInfo
+    {
+        public RuntimeMethodInfoStub(RuntimeMethodHandleInternal methodHandleValue, object keepalive)
+        {
+            m_keepalive = keepalive;
+            m_value = methodHandleValue;
+        }
+
+        public RuntimeMethodInfoStub(IntPtr methodHandleValue, object keepalive)
+        {
+            m_keepalive = keepalive;
+            m_value = new RuntimeMethodHandleInternal(methodHandleValue);
+        }
+
+        private object m_keepalive;
+
+        // These unused variables are used to ensure that this class has the same layout as RuntimeMethodInfo
+#pragma warning disable 169
+        private object m_a;
+        private object m_b;
+        private object m_c;
+        private object m_d;
+        private object m_e;
+        private object m_f;
+        private object m_g;
+#pragma warning restore 169
+
+        public RuntimeMethodHandleInternal m_value;
+
+        RuntimeMethodHandleInternal IRuntimeMethodInfo.Value
+        {
+            get
+            {
+                return m_value;
+            }
+        }
+    }
+
+    internal interface IRuntimeMethodInfo
+    {
+        RuntimeMethodHandleInternal Value
+        {
+            get;
+        }
+    }
+
+    public unsafe struct RuntimeMethodHandle : ISerializable
+    {
+        // Returns handle for interop with EE. The handle is guaranteed to be non-null.
+        internal static IRuntimeMethodInfo EnsureNonNullMethodInfo(IRuntimeMethodInfo method)
+        {
+            if (method == null)
+                throw new ArgumentNullException(null, SR.Arg_InvalidHandle);
+            return method;
+        }
+
+        private IRuntimeMethodInfo m_value;
+
+        internal RuntimeMethodHandle(IRuntimeMethodInfo method)
+        {
+            m_value = method;
+        }
+
+        internal IRuntimeMethodInfo GetMethodInfo()
+        {
+            return m_value;
+        }
+
+        // Used by EE
+        private static IntPtr GetValueInternal(RuntimeMethodHandle rmh)
+        {
+            return rmh.Value;
+        }
+
+        // ISerializable interface
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            throw new PlatformNotSupportedException();
+        }
+
+        public IntPtr Value
+        {
+            get
+            {
+                return m_value != null ? m_value.Value.Value : IntPtr.Zero;
+            }
+        }
+
+        public override int GetHashCode()
+        {
+            return ValueType.GetHashCodeOfPtr(Value);
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (!(obj is RuntimeMethodHandle))
+                return false;
+
+            RuntimeMethodHandle handle = (RuntimeMethodHandle)obj;
+
+            return handle.Value == Value;
+        }
+
+        public static bool operator ==(RuntimeMethodHandle left, RuntimeMethodHandle right)
+        {
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(RuntimeMethodHandle left, RuntimeMethodHandle right)
+        {
+            return !left.Equals(right);
+        }
+
+        public bool Equals(RuntimeMethodHandle handle)
+        {
+            return handle.Value == Value;
+        }
+
+        internal bool IsNullHandle()
+        {
+            return m_value == null;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern IntPtr GetFunctionPointer(RuntimeMethodHandleInternal handle);
+
+        public IntPtr GetFunctionPointer()
+        {
+            IntPtr ptr = GetFunctionPointer(EnsureNonNullMethodInfo(m_value).Value);
+            GC.KeepAlive(m_value);
+            return ptr;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern bool IsCAVisibleFromDecoratedType(
+            RuntimeTypeHandle attrTypeHandle,
+            IRuntimeMethodInfo attrCtor,
+            RuntimeTypeHandle sourceTypeHandle,
+            RuntimeModule sourceModule);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern IRuntimeMethodInfo _GetCurrentMethod(ref StackCrawlMark stackMark);
+        internal static IRuntimeMethodInfo GetCurrentMethod(ref StackCrawlMark stackMark)
+        {
+            return _GetCurrentMethod(ref stackMark);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern MethodAttributes GetAttributes(RuntimeMethodHandleInternal method);
+
+        internal static MethodAttributes GetAttributes(IRuntimeMethodInfo method)
+        {
+            MethodAttributes retVal = RuntimeMethodHandle.GetAttributes(method.Value);
+            GC.KeepAlive(method);
+            return retVal;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern MethodImplAttributes GetImplAttributes(IRuntimeMethodInfo method);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void ConstructInstantiation(IRuntimeMethodInfo method, TypeNameFormatFlags format, StringHandleOnStack retString);
+
+        internal static string ConstructInstantiation(IRuntimeMethodInfo method, TypeNameFormatFlags format)
+        {
+            string name = null;
+            ConstructInstantiation(EnsureNonNullMethodInfo(method), format, JitHelpers.GetStringHandleOnStack(ref name));
+            return name;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern RuntimeType GetDeclaringType(RuntimeMethodHandleInternal method);
+
+        internal static RuntimeType GetDeclaringType(IRuntimeMethodInfo method)
+        {
+            RuntimeType type = RuntimeMethodHandle.GetDeclaringType(method.Value);
+            GC.KeepAlive(method);
+            return type;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int GetSlot(RuntimeMethodHandleInternal method);
+
+        internal static int GetSlot(IRuntimeMethodInfo method)
+        {
+            Debug.Assert(method != null);
+
+            int slot = RuntimeMethodHandle.GetSlot(method.Value);
+            GC.KeepAlive(method);
+            return slot;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int GetMethodDef(IRuntimeMethodInfo method);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern string GetName(RuntimeMethodHandleInternal method);
+
+        internal static string GetName(IRuntimeMethodInfo method)
+        {
+            string name = RuntimeMethodHandle.GetName(method.Value);
+            GC.KeepAlive(method);
+            return name;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void* _GetUtf8Name(RuntimeMethodHandleInternal method);
+
+        internal static MdUtf8String GetUtf8Name(RuntimeMethodHandleInternal method)
+        {
+            return new MdUtf8String(_GetUtf8Name(method));
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool MatchesNameHash(RuntimeMethodHandleInternal method, uint hash);
+
+        [DebuggerStepThroughAttribute]
+        [Diagnostics.DebuggerHidden]
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern object InvokeMethod(object target, object[] arguments, Signature sig, bool constructor, bool wrapExceptions);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetMethodInstantiation(RuntimeMethodHandleInternal method, ObjectHandleOnStack types, bool fAsRuntimeTypeArray);
+
+        internal static RuntimeType[] GetMethodInstantiationInternal(IRuntimeMethodInfo method)
+        {
+            RuntimeType[] types = null;
+            GetMethodInstantiation(EnsureNonNullMethodInfo(method).Value, JitHelpers.GetObjectHandleOnStack(ref types), true);
+            GC.KeepAlive(method);
+            return types;
+        }
+
+        internal static RuntimeType[] GetMethodInstantiationInternal(RuntimeMethodHandleInternal method)
+        {
+            RuntimeType[] types = null;
+            GetMethodInstantiation(method, JitHelpers.GetObjectHandleOnStack(ref types), true);
+            return types;
+        }
+
+        internal static Type[] GetMethodInstantiationPublic(IRuntimeMethodInfo method)
+        {
+            RuntimeType[] types = null;
+            GetMethodInstantiation(EnsureNonNullMethodInfo(method).Value, JitHelpers.GetObjectHandleOnStack(ref types), false);
+            GC.KeepAlive(method);
+            return types;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool HasMethodInstantiation(RuntimeMethodHandleInternal method);
+
+        internal static bool HasMethodInstantiation(IRuntimeMethodInfo method)
+        {
+            bool fRet = RuntimeMethodHandle.HasMethodInstantiation(method.Value);
+            GC.KeepAlive(method);
+            return fRet;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern RuntimeMethodHandleInternal GetStubIfNeeded(RuntimeMethodHandleInternal method, RuntimeType declaringType, RuntimeType[] methodInstantiation);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern RuntimeMethodHandleInternal GetMethodFromCanonical(RuntimeMethodHandleInternal method, RuntimeType declaringType);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsGenericMethodDefinition(RuntimeMethodHandleInternal method);
+
+        internal static bool IsGenericMethodDefinition(IRuntimeMethodInfo method)
+        {
+            bool fRet = RuntimeMethodHandle.IsGenericMethodDefinition(method.Value);
+            GC.KeepAlive(method);
+            return fRet;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsTypicalMethodDefinition(IRuntimeMethodInfo method);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetTypicalMethodDefinition(IRuntimeMethodInfo method, ObjectHandleOnStack outMethod);
+
+        internal static IRuntimeMethodInfo GetTypicalMethodDefinition(IRuntimeMethodInfo method)
+        {
+            if (!IsTypicalMethodDefinition(method))
+                GetTypicalMethodDefinition(method, JitHelpers.GetObjectHandleOnStack(ref method));
+
+            return method;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int GetGenericParameterCount(RuntimeMethodHandleInternal method);
+
+        internal static int GetGenericParameterCount(IRuntimeMethodInfo method) => GetGenericParameterCount(method.Value);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void StripMethodInstantiation(IRuntimeMethodInfo method, ObjectHandleOnStack outMethod);
+
+        internal static IRuntimeMethodInfo StripMethodInstantiation(IRuntimeMethodInfo method)
+        {
+            IRuntimeMethodInfo strippedMethod = method;
+
+            StripMethodInstantiation(method, JitHelpers.GetObjectHandleOnStack(ref strippedMethod));
+
+            return strippedMethod;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsDynamicMethod(RuntimeMethodHandleInternal method);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void Destroy(RuntimeMethodHandleInternal method);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Resolver GetResolver(RuntimeMethodHandleInternal method);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal static extern MethodBody GetMethodBody(IRuntimeMethodInfo method, RuntimeType declaringType);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal static extern bool IsConstructor(RuntimeMethodHandleInternal method);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal static extern LoaderAllocator GetLoaderAllocator(RuntimeMethodHandleInternal method);
+    }
+
+    // This type is used to remove the expense of having a managed reference object that is dynamically 
+    // created when we can prove that we don't need that object. Use of this type requires code to ensure
+    // that the underlying native resource is not freed. 
+    // Cases in which this may be used:
+    //  1. When native code calls managed code passing one of these as a parameter
+    //  2. When managed code acquires one of these from an RtFieldInfo, and ensure that the RtFieldInfo is preserved
+    //     across the lifetime of the RuntimeFieldHandleInternal instance
+    //  3. When another object is used to keep the RuntimeFieldHandleInternal alive.
+    // When in doubt, do not use. 
+    internal struct RuntimeFieldHandleInternal
+    {
+        internal bool IsNullHandle()
+        {
+            return m_handle == IntPtr.Zero;
+        }
+
+        internal IntPtr Value
+        {
+            get
+            {
+                return m_handle;
+            }
+        }
+
+        internal RuntimeFieldHandleInternal(IntPtr value)
+        {
+            m_handle = value;
+        }
+
+        internal IntPtr m_handle;
+    }
+
+    internal interface IRuntimeFieldInfo
+    {
+        RuntimeFieldHandleInternal Value
+        {
+            get;
+        }
+    }
+
+    [StructLayout(LayoutKind.Sequential)]
+    internal class RuntimeFieldInfoStub : IRuntimeFieldInfo
+    {
+        // These unused variables are used to ensure that this class has the same layout as RuntimeFieldInfo
+#pragma warning disable 169
+        private object m_keepalive;
+        private object m_c;
+        private object m_d;
+        private int m_b;
+        private object m_e;
+        private RuntimeFieldHandleInternal m_fieldHandle;
+#pragma warning restore 169
+
+        RuntimeFieldHandleInternal IRuntimeFieldInfo.Value
+        {
+            get
+            {
+                return m_fieldHandle;
+            }
+        }
+    }
+
+    public unsafe struct RuntimeFieldHandle : ISerializable
+    {
+        // Returns handle for interop with EE. The handle is guaranteed to be non-null.
+        internal RuntimeFieldHandle GetNativeHandle()
+        {
+            // Create local copy to avoid a race condition
+            IRuntimeFieldInfo field = m_ptr;
+            if (field == null)
+                throw new ArgumentNullException(null, SR.Arg_InvalidHandle);
+            return new RuntimeFieldHandle(field);
+        }
+
+        private IRuntimeFieldInfo m_ptr;
+
+        internal RuntimeFieldHandle(IRuntimeFieldInfo fieldInfo)
+        {
+            m_ptr = fieldInfo;
+        }
+
+        internal IRuntimeFieldInfo GetRuntimeFieldInfo()
+        {
+            return m_ptr;
+        }
+
+        public IntPtr Value
+        {
+            get
+            {
+                return m_ptr != null ? m_ptr.Value.Value : IntPtr.Zero;
+            }
+        }
+
+        internal bool IsNullHandle()
+        {
+            return m_ptr == null;
+        }
+
+        public override int GetHashCode()
+        {
+            return ValueType.GetHashCodeOfPtr(Value);
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (!(obj is RuntimeFieldHandle))
+                return false;
+
+            RuntimeFieldHandle handle = (RuntimeFieldHandle)obj;
+
+            return handle.Value == Value;
+        }
+
+        public unsafe bool Equals(RuntimeFieldHandle handle)
+        {
+            return handle.Value == Value;
+        }
+
+        public static bool operator ==(RuntimeFieldHandle left, RuntimeFieldHandle right)
+        {
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(RuntimeFieldHandle left, RuntimeFieldHandle right)
+        {
+            return !left.Equals(right);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern String GetName(RtFieldInfo field);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe void* _GetUtf8Name(RuntimeFieldHandleInternal field);
+
+        internal static unsafe MdUtf8String GetUtf8Name(RuntimeFieldHandleInternal field) { return new MdUtf8String(_GetUtf8Name(field)); }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool MatchesNameHash(RuntimeFieldHandleInternal handle, uint hash);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern FieldAttributes GetAttributes(RuntimeFieldHandleInternal field);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern RuntimeType GetApproxDeclaringType(RuntimeFieldHandleInternal field);
+
+        internal static RuntimeType GetApproxDeclaringType(IRuntimeFieldInfo field)
+        {
+            RuntimeType type = GetApproxDeclaringType(field.Value);
+            GC.KeepAlive(field);
+            return type;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int GetToken(RtFieldInfo field);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Object GetValue(RtFieldInfo field, Object instance, RuntimeType fieldType, RuntimeType declaringType, ref bool domainInitialized);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Object GetValueDirect(RtFieldInfo field, RuntimeType fieldType, void* pTypedRef, RuntimeType contextType);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void SetValue(RtFieldInfo field, Object obj, Object value, RuntimeType fieldType, FieldAttributes fieldAttr, RuntimeType declaringType, ref bool domainInitialized);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void SetValueDirect(RtFieldInfo field, RuntimeType fieldType, void* pTypedRef, Object value, RuntimeType contextType);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern RuntimeFieldHandleInternal GetStaticFieldForGenericType(RuntimeFieldHandleInternal field, RuntimeType declaringType);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool AcquiresContextFromThis(RuntimeFieldHandleInternal field);
+
+        // ISerializable interface
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            throw new PlatformNotSupportedException();
+        }
+    }
+
+    public unsafe struct ModuleHandle
+    {
+        // Returns handle for interop with EE. The handle is guaranteed to be non-null.
+        #region Public Static Members
+        public static readonly ModuleHandle EmptyHandle = GetEmptyMH();
+        #endregion
+
+        unsafe private static ModuleHandle GetEmptyMH()
+        {
+            return new ModuleHandle();
+        }
+
+        #region Private Data Members
+        private RuntimeModule m_ptr;
+        #endregion
+
+        #region Constructor
+        internal ModuleHandle(RuntimeModule module)
+        {
+            m_ptr = module;
+        }
+        #endregion
+
+        #region Internal FCalls
+
+        internal RuntimeModule GetRuntimeModule()
+        {
+            return m_ptr;
+        }
+
+        public override int GetHashCode()
+        {
+            return m_ptr != null ? m_ptr.GetHashCode() : 0;
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (!(obj is ModuleHandle))
+                return false;
+
+            ModuleHandle handle = (ModuleHandle)obj;
+
+            return handle.m_ptr == m_ptr;
+        }
+
+        public unsafe bool Equals(ModuleHandle handle)
+        {
+            return handle.m_ptr == m_ptr;
+        }
+
+        public static bool operator ==(ModuleHandle left, ModuleHandle right)
+        {
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(ModuleHandle left, ModuleHandle right)
+        {
+            return !left.Equals(right);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IRuntimeMethodInfo GetDynamicMethod(DynamicMethod method, RuntimeModule module, string name, byte[] sig, Resolver resolver);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int GetToken(RuntimeModule module);
+
+        private static void ValidateModulePointer(RuntimeModule module)
+        {
+            // Make sure we have a valid Module to resolve against.
+            if (module == null)
+                throw new InvalidOperationException(SR.InvalidOperation_NullModuleHandle);
+        }
+
+        // SQL-CLR LKG9 Compiler dependency
+        public RuntimeTypeHandle GetRuntimeTypeHandleFromMetadataToken(int typeToken) { return ResolveTypeHandle(typeToken); }
+        public RuntimeTypeHandle ResolveTypeHandle(int typeToken)
+        {
+            return new RuntimeTypeHandle(ResolveTypeHandleInternal(GetRuntimeModule(), typeToken, null, null));
+        }
+        public RuntimeTypeHandle ResolveTypeHandle(int typeToken, RuntimeTypeHandle[] typeInstantiationContext, RuntimeTypeHandle[] methodInstantiationContext)
+        {
+            return new RuntimeTypeHandle(ModuleHandle.ResolveTypeHandleInternal(GetRuntimeModule(), typeToken, typeInstantiationContext, methodInstantiationContext));
+        }
+
+        internal static RuntimeType ResolveTypeHandleInternal(RuntimeModule module, int typeToken, RuntimeTypeHandle[] typeInstantiationContext, RuntimeTypeHandle[] methodInstantiationContext)
+        {
+            ValidateModulePointer(module);
+            if (!ModuleHandle.GetMetadataImport(module).IsValidToken(typeToken))
+                throw new ArgumentOutOfRangeException(nameof(typeToken),
+                    SR.Format(SR.Argument_InvalidToken, typeToken, new ModuleHandle(module)));
+
+            int typeInstCount, methodInstCount;
+            IntPtr[] typeInstantiationContextHandles = RuntimeTypeHandle.CopyRuntimeTypeHandles(typeInstantiationContext, out typeInstCount);
+            IntPtr[] methodInstantiationContextHandles = RuntimeTypeHandle.CopyRuntimeTypeHandles(methodInstantiationContext, out methodInstCount);
+
+            fixed (IntPtr* typeInstArgs = typeInstantiationContextHandles, methodInstArgs = methodInstantiationContextHandles)
+            {
+                RuntimeType type = null;
+                ResolveType(module, typeToken, typeInstArgs, typeInstCount, methodInstArgs, methodInstCount, JitHelpers.GetObjectHandleOnStack(ref type));
+                GC.KeepAlive(typeInstantiationContext);
+                GC.KeepAlive(methodInstantiationContext);
+                return type;
+            }
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void ResolveType(RuntimeModule module,
+                                                            int typeToken,
+                                                            IntPtr* typeInstArgs,
+                                                            int typeInstCount,
+                                                            IntPtr* methodInstArgs,
+                                                            int methodInstCount,
+                                                            ObjectHandleOnStack type);
+
+        // SQL-CLR LKG9 Compiler dependency
+        public RuntimeMethodHandle GetRuntimeMethodHandleFromMetadataToken(int methodToken) { return ResolveMethodHandle(methodToken); }
+        public RuntimeMethodHandle ResolveMethodHandle(int methodToken) { return ResolveMethodHandle(methodToken, null, null); }
+        internal static IRuntimeMethodInfo ResolveMethodHandleInternal(RuntimeModule module, int methodToken) { return ModuleHandle.ResolveMethodHandleInternal(module, methodToken, null, null); }
+        public RuntimeMethodHandle ResolveMethodHandle(int methodToken, RuntimeTypeHandle[] typeInstantiationContext, RuntimeTypeHandle[] methodInstantiationContext)
+        {
+            return new RuntimeMethodHandle(ResolveMethodHandleInternal(GetRuntimeModule(), methodToken, typeInstantiationContext, methodInstantiationContext));
+        }
+
+        internal static IRuntimeMethodInfo ResolveMethodHandleInternal(RuntimeModule module, int methodToken, RuntimeTypeHandle[] typeInstantiationContext, RuntimeTypeHandle[] methodInstantiationContext)
+        {
+            int typeInstCount, methodInstCount;
+
+            IntPtr[] typeInstantiationContextHandles = RuntimeTypeHandle.CopyRuntimeTypeHandles(typeInstantiationContext, out typeInstCount);
+            IntPtr[] methodInstantiationContextHandles = RuntimeTypeHandle.CopyRuntimeTypeHandles(methodInstantiationContext, out methodInstCount);
+
+            RuntimeMethodHandleInternal handle = ResolveMethodHandleInternalCore(module, methodToken, typeInstantiationContextHandles, typeInstCount, methodInstantiationContextHandles, methodInstCount);
+            IRuntimeMethodInfo retVal = new RuntimeMethodInfoStub(handle, RuntimeMethodHandle.GetLoaderAllocator(handle));
+            GC.KeepAlive(typeInstantiationContext);
+            GC.KeepAlive(methodInstantiationContext);
+            return retVal;
+        }
+
+        internal static RuntimeMethodHandleInternal ResolveMethodHandleInternalCore(RuntimeModule module, int methodToken, IntPtr[] typeInstantiationContext, int typeInstCount, IntPtr[] methodInstantiationContext, int methodInstCount)
+        {
+            ValidateModulePointer(module);
+            if (!ModuleHandle.GetMetadataImport(module.GetNativeHandle()).IsValidToken(methodToken))
+                throw new ArgumentOutOfRangeException(nameof(methodToken),
+                    SR.Format(SR.Argument_InvalidToken, methodToken, new ModuleHandle(module)));
+
+            fixed (IntPtr* typeInstArgs = typeInstantiationContext, methodInstArgs = methodInstantiationContext)
+            {
+                return ResolveMethod(module.GetNativeHandle(), methodToken, typeInstArgs, typeInstCount, methodInstArgs, methodInstCount);
+            }
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern RuntimeMethodHandleInternal ResolveMethod(RuntimeModule module,
+                                                        int methodToken,
+                                                        IntPtr* typeInstArgs,
+                                                        int typeInstCount,
+                                                        IntPtr* methodInstArgs,
+                                                        int methodInstCount);
+
+        // SQL-CLR LKG9 Compiler dependency
+        public RuntimeFieldHandle GetRuntimeFieldHandleFromMetadataToken(int fieldToken) { return ResolveFieldHandle(fieldToken); }
+        public RuntimeFieldHandle ResolveFieldHandle(int fieldToken) { return new RuntimeFieldHandle(ResolveFieldHandleInternal(GetRuntimeModule(), fieldToken, null, null)); }
+        public RuntimeFieldHandle ResolveFieldHandle(int fieldToken, RuntimeTypeHandle[] typeInstantiationContext, RuntimeTypeHandle[] methodInstantiationContext)
+        { return new RuntimeFieldHandle(ResolveFieldHandleInternal(GetRuntimeModule(), fieldToken, typeInstantiationContext, methodInstantiationContext)); }
+
+        internal static IRuntimeFieldInfo ResolveFieldHandleInternal(RuntimeModule module, int fieldToken, RuntimeTypeHandle[] typeInstantiationContext, RuntimeTypeHandle[] methodInstantiationContext)
+        {
+            ValidateModulePointer(module);
+            if (!ModuleHandle.GetMetadataImport(module.GetNativeHandle()).IsValidToken(fieldToken))
+                throw new ArgumentOutOfRangeException(nameof(fieldToken),
+                    SR.Format(SR.Argument_InvalidToken, fieldToken, new ModuleHandle(module)));
+
+            // defensive copy to be sure array is not mutated from the outside during processing
+            int typeInstCount, methodInstCount;
+            IntPtr[] typeInstantiationContextHandles = RuntimeTypeHandle.CopyRuntimeTypeHandles(typeInstantiationContext, out typeInstCount);
+            IntPtr[] methodInstantiationContextHandles = RuntimeTypeHandle.CopyRuntimeTypeHandles(methodInstantiationContext, out methodInstCount);
+
+            fixed (IntPtr* typeInstArgs = typeInstantiationContextHandles, methodInstArgs = methodInstantiationContextHandles)
+            {
+                IRuntimeFieldInfo field = null;
+                ResolveField(module.GetNativeHandle(), fieldToken, typeInstArgs, typeInstCount, methodInstArgs, methodInstCount, JitHelpers.GetObjectHandleOnStack(ref field));
+                GC.KeepAlive(typeInstantiationContext);
+                GC.KeepAlive(methodInstantiationContext);
+                return field;
+            }
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void ResolveField(RuntimeModule module,
+                                                      int fieldToken,
+                                                      IntPtr* typeInstArgs,
+                                                      int typeInstCount,
+                                                      IntPtr* methodInstArgs,
+                                                      int methodInstCount,
+                                                      ObjectHandleOnStack retField);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern bool _ContainsPropertyMatchingHash(RuntimeModule module, int propertyToken, uint hash);
+
+        internal static bool ContainsPropertyMatchingHash(RuntimeModule module, int propertyToken, uint hash)
+        {
+            return _ContainsPropertyMatchingHash(module.GetNativeHandle(), propertyToken, hash);
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern void GetModuleType(RuntimeModule handle, ObjectHandleOnStack type);
+
+        internal static RuntimeType GetModuleType(RuntimeModule module)
+        {
+            RuntimeType type = null;
+            GetModuleType(module.GetNativeHandle(), JitHelpers.GetObjectHandleOnStack(ref type));
+            return type;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetPEKind(RuntimeModule handle, out int peKind, out int machine);
+
+        // making this internal, used by Module.GetPEKind
+        internal static void GetPEKind(RuntimeModule module, out PortableExecutableKinds peKind, out ImageFileMachine machine)
+        {
+            int lKind, lMachine;
+            GetPEKind(module.GetNativeHandle(), out lKind, out lMachine);
+            peKind = (PortableExecutableKinds)lKind;
+            machine = (ImageFileMachine)lMachine;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int GetMDStreamVersion(RuntimeModule module);
+
+        public int MDStreamVersion
+        {
+            get { return GetMDStreamVersion(GetRuntimeModule().GetNativeHandle()); }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern IntPtr _GetMetadataImport(RuntimeModule module);
+
+        internal static MetadataImport GetMetadataImport(RuntimeModule module)
+        {
+            return new MetadataImport(_GetMetadataImport(module.GetNativeHandle()), module);
+        }
+        #endregion
+    }
+
+    internal unsafe class Signature
+    {
+        #region Definitions
+        internal enum MdSigCallingConvention : byte
+        {
+            Generics = 0x10,
+            HasThis = 0x20,
+            ExplicitThis = 0x40,
+            CallConvMask = 0x0F,
+            Default = 0x00,
+            C = 0x01,
+            StdCall = 0x02,
+            ThisCall = 0x03,
+            FastCall = 0x04,
+            Vararg = 0x05,
+            Field = 0x06,
+            LocalSig = 0x07,
+            Property = 0x08,
+            Unmgd = 0x09,
+            GenericInst = 0x0A,
+            Max = 0x0B,
+        }
+        #endregion
+
+        #region FCalls
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern void GetSignature(
+            void* pCorSig, int cCorSig,
+            RuntimeFieldHandleInternal fieldHandle, IRuntimeMethodInfo methodHandle, RuntimeType declaringType);
+
+        #endregion
+
+        #region Private Data Members
+        //
+        // Keep the layout in sync with SignatureNative in the VM
+        //
+        internal RuntimeType[] m_arguments;
+        internal RuntimeType m_declaringType;
+        internal RuntimeType m_returnTypeORfieldType;
+        internal object m_keepalive;
+        internal void* m_sig;
+        internal int m_managedCallingConventionAndArgIteratorFlags; // lowest byte is CallingConvention, upper 3 bytes are ArgIterator flags
+        internal int m_nSizeOfArgStack;
+        internal int m_csig;
+        internal RuntimeMethodHandleInternal m_pMethod;
+        #endregion
+
+        #region Constructors
+        public Signature(
+            IRuntimeMethodInfo method,
+            RuntimeType[] arguments,
+            RuntimeType returnType,
+            CallingConventions callingConvention)
+        {
+            m_pMethod = method.Value;
+            m_arguments = arguments;
+            m_returnTypeORfieldType = returnType;
+            m_managedCallingConventionAndArgIteratorFlags = (byte)callingConvention;
+
+            GetSignature(null, 0, new RuntimeFieldHandleInternal(), method, null);
+        }
+
+        public Signature(IRuntimeMethodInfo methodHandle, RuntimeType declaringType)
+        {
+            GetSignature(null, 0, new RuntimeFieldHandleInternal(), methodHandle, declaringType);
+        }
+
+        public Signature(IRuntimeFieldInfo fieldHandle, RuntimeType declaringType)
+        {
+            GetSignature(null, 0, fieldHandle.Value, null, declaringType);
+            GC.KeepAlive(fieldHandle);
+        }
+
+        public Signature(void* pCorSig, int cCorSig, RuntimeType declaringType)
+        {
+            GetSignature(pCorSig, cCorSig, new RuntimeFieldHandleInternal(), null, declaringType);
+        }
+        #endregion
+
+        #region Internal Members
+        internal CallingConventions CallingConvention { get { return (CallingConventions)(byte)m_managedCallingConventionAndArgIteratorFlags; } }
+        internal RuntimeType[] Arguments { get { return m_arguments; } }
+        internal RuntimeType ReturnType { get { return m_returnTypeORfieldType; } }
+        internal RuntimeType FieldType { get { return m_returnTypeORfieldType; } }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool CompareSig(Signature sig1, Signature sig2);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern Type[] GetCustomModifiers(int position, bool required);
+        #endregion
+    }
+
+
+    internal abstract class Resolver
+    {
+        internal struct CORINFO_EH_CLAUSE
+        {
+            internal int Flags;
+            internal int TryOffset;
+            internal int TryLength;
+            internal int HandlerOffset;
+            internal int HandlerLength;
+            internal int ClassTokenOrFilterOffset;
+        }
+
+        // ILHeader info
+        internal abstract RuntimeType GetJitContext(ref int securityControlFlags);
+        internal abstract byte[] GetCodeInfo(ref int stackSize, ref int initLocals, ref int EHCount);
+        internal abstract byte[] GetLocalsSignature();
+        internal abstract unsafe void GetEHInfo(int EHNumber, void* exception);
+        internal abstract unsafe byte[] GetRawEHInfo();
+        // token resolution
+        internal abstract String GetStringLiteral(int token);
+        internal abstract void ResolveToken(int token, out IntPtr typeHandle, out IntPtr methodHandle, out IntPtr fieldHandle);
+        internal abstract byte[] ResolveSignature(int token, int fromMethod);
+        // 
+        internal abstract MethodInfo GetDynamicMethod();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Security/DynamicSecurityMethodAttribute.cs b/src/System.Private.CoreLib/src/System/Security/DynamicSecurityMethodAttribute.cs
new file mode 100644
index 0000000000..83be902a2c
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Security/DynamicSecurityMethodAttribute.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.InteropServices;
+
+namespace System.Security
+{
+    // DynamicSecurityMethodAttribute:
+    //  All methods that use StackCrawlMark should be marked with this attribute. This attribute
+    //  disables inlining of the calling method to allow stackwalking to find the exact caller.
+    //
+    //  This attribute used to indicate that the target method requires space for a security object 
+    //  to be allocated on the callers stack. It is not used for this purpose anymore because of security 
+    //  stackwalks are not ever done in CoreCLR.
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor, AllowMultiple = true, Inherited = false)]
+    internal sealed class DynamicSecurityMethodAttribute : Attribute
+    {
+        public DynamicSecurityMethodAttribute() { }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/SharedStatics.cs b/src/System.Private.CoreLib/src/System/SharedStatics.cs
new file mode 100644
index 0000000000..8111b9b1d1
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/SharedStatics.cs
@@ -0,0 +1,55 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Container for statics that are shared across AppDomains.
+**
+**
+=============================================================================*/
+
+using System.Threading;
+using System.Security;
+using System.Runtime.CompilerServices;
+using System.Runtime.ConstrainedExecution;
+using System.Diagnostics;
+
+namespace System
+{
+    internal sealed class SharedStatics
+    {
+        // this is declared static but is actually forced to be the same object 
+        // for each AppDomain at AppDomain create time.
+        private static SharedStatics _sharedStatics;
+
+        // Note: Do not add any code in this ctor because it is not called 
+        // when we set up _sharedStatics via AppDomain::SetupSharedStatics
+        private SharedStatics()
+        {
+            Debug.Fail("SharedStatics..ctor() is never called.");
+        }
+
+        // This is the total amount of memory currently "reserved" via
+        // all MemoryFailPoints allocated within the process.
+        // Stored as a long because we need to use Interlocked.Add.
+        private long _memFailPointReservedMemory;
+
+        internal static long AddMemoryFailPointReservation(long size)
+        {
+            // Size can legitimately be negative - see Dispose.
+            return Interlocked.Add(ref _sharedStatics._memFailPointReservedMemory, (long)size);
+        }
+
+        internal static ulong MemoryFailPointReservedMemory
+        {
+            get
+            {
+                Debug.Assert(Volatile.Read(ref _sharedStatics._memFailPointReservedMemory) >= 0, "Process-wide MemoryFailPoint reserved memory was negative!");
+                return (ulong)Volatile.Read(ref _sharedStatics._memFailPointReservedMemory);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/String.CoreCLR.cs b/src/System.Private.CoreLib/src/System/String.CoreCLR.cs
new file mode 100644
index 0000000000..a9688fe8a8
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/String.CoreCLR.cs
@@ -0,0 +1,152 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading;
+
+namespace System
+{
+    public partial class String
+    {
+        //
+        // These fields map directly onto the fields in an EE StringObject.  See object.h for the layout.
+        //
+        [NonSerialized] private int _stringLength;
+
+        // For empty strings, this will be '\0' since
+        // strings are both null-terminated and length prefixed
+        [NonSerialized] private char _firstChar;
+
+        // The Empty constant holds the empty string value. It is initialized by the EE during startup.
+        // It is treated as intrinsic by the JIT as so the static constructor would never run.
+        // Leaving it uninitialized would confuse debuggers.
+        //
+        // We need to call the String constructor so that the compiler doesn't mark this as a literal.
+        // Marking this as a literal would mean that it doesn't show up as a field which we can access 
+        // from native.
+        public static readonly String Empty;
+
+        // Gets the character at a specified position.
+        //
+        [System.Runtime.CompilerServices.IndexerName("Chars")]
+        public extern char this[int index]
+        {
+            [MethodImpl(MethodImplOptions.InternalCall)]
+            get;
+        }
+
+        // Gets the length of this string
+        //
+        // This is a EE implemented function so that the JIT can recognise it specially
+        // and eliminate checks on character fetches in a loop like:
+        //        for(int i = 0; i < str.Length; i++) str[i]
+        // The actual code generated for this will be one instruction and will be inlined.
+        //
+        public extern int Length
+        {
+            [MethodImplAttribute(MethodImplOptions.InternalCall)]
+            get;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern String FastAllocateString(int length);
+
+        // Is this a string that can be compared quickly (that is it has only characters > 0x80 
+        // and not a - or '
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern bool IsFastSort();
+        // Is this a string that only contains characters < 0x80.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern bool IsAscii();
+
+#if FEATURE_COMINTEROP
+        // Set extra byte for odd-sized strings that came from interop as BSTR.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern void SetTrailByte(byte data);
+        // Try to retrieve the extra byte - returns false if not present.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern bool TryGetTrailByte(out byte data);
+#endif
+
+        public static String Intern(String str)
+        {
+            if (str == null)
+            {
+                throw new ArgumentNullException(nameof(str));
+            }
+
+            return Thread.GetDomain().GetOrInternString(str);
+        }
+
+        public static String IsInterned(String str)
+        {
+            if (str == null)
+            {
+                throw new ArgumentNullException(nameof(str));
+            }
+
+            return Thread.GetDomain().IsStringInterned(str);
+        }
+
+        // Copies the source String (byte buffer) to the destination IntPtr memory allocated with len bytes.
+        internal static unsafe void InternalCopy(String src, IntPtr dest, int len)
+        {
+            if (len == 0)
+                return;
+            fixed (char* charPtr = &src._firstChar)
+            {
+                byte* srcPtr = (byte*)charPtr;
+                byte* dstPtr = (byte*)dest;
+                Buffer.Memcpy(dstPtr, srcPtr, len);
+            }
+        }
+
+        internal unsafe int GetBytesFromEncoding(byte* pbNativeBuffer, int cbNativeBuffer, Encoding encoding)
+        {
+            // encoding == Encoding.UTF8
+            fixed (char* pwzChar = &_firstChar)
+            {
+                return encoding.GetBytes(pwzChar, Length, pbNativeBuffer, cbNativeBuffer);
+            }
+        }
+
+        internal unsafe int ConvertToAnsi(byte* pbNativeBuffer, int cbNativeBuffer, bool fBestFit, bool fThrowOnUnmappableChar)
+        {
+            Debug.Assert(cbNativeBuffer >= (Length + 1) * Marshal.SystemMaxDBCSCharSize, "Insufficient buffer length passed to ConvertToAnsi");
+
+            const uint CP_ACP = 0;
+            int nb;
+
+            const uint WC_NO_BEST_FIT_CHARS = 0x00000400;
+
+            uint flgs = (fBestFit ? 0 : WC_NO_BEST_FIT_CHARS);
+            uint DefaultCharUsed = 0;
+
+            fixed (char* pwzChar = &_firstChar)
+            {
+                nb = Win32Native.WideCharToMultiByte(
+                    CP_ACP,
+                    flgs,
+                    pwzChar,
+                    this.Length,
+                    pbNativeBuffer,
+                    cbNativeBuffer,
+                    IntPtr.Zero,
+                    (fThrowOnUnmappableChar ? new IntPtr(&DefaultCharUsed) : IntPtr.Zero));
+            }
+
+            if (0 != DefaultCharUsed)
+            {
+                throw new ArgumentException(SR.Interop_Marshal_Unmappable_Char);
+            }
+
+            pbNativeBuffer[nb] = 0;
+            return nb;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/StubHelpers.cs b/src/System.Private.CoreLib/src/System/StubHelpers.cs
new file mode 100644
index 0000000000..6322cf566b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/StubHelpers.cs
@@ -0,0 +1,1802 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+namespace System.StubHelpers
+{
+    using System.Text;
+    using Microsoft.Win32;
+    using System.Security;
+    using System.Collections.Generic;
+    using System.Runtime;
+    using System.Runtime.InteropServices;
+#if FEATURE_COMINTEROP
+    using System.Runtime.InteropServices.WindowsRuntime;
+#endif // FEATURE_COMINTEROP
+    using System.Runtime.CompilerServices;
+    using System.Runtime.ConstrainedExecution;
+    using System.Diagnostics;
+
+    internal static class AnsiCharMarshaler
+    {
+        // The length of the returned array is an approximation based on the length of the input string and the system
+        // character set. It is only guaranteed to be larger or equal to cbLength, don't depend on the exact value.
+        unsafe internal static byte[] DoAnsiConversion(string str, bool fBestFit, bool fThrowOnUnmappableChar, out int cbLength)
+        {
+            byte[] buffer = new byte[(str.Length + 1) * Marshal.SystemMaxDBCSCharSize];
+            Debug.Assert(buffer.Length != 0);
+            fixed (byte* bufferPtr = &buffer[0])
+            {
+                cbLength = str.ConvertToAnsi(bufferPtr, buffer.Length, fBestFit, fThrowOnUnmappableChar);
+            }
+            return buffer;
+        }
+
+        unsafe internal static byte ConvertToNative(char managedChar, bool fBestFit, bool fThrowOnUnmappableChar)
+        {
+            int cbAllocLength = (1 + 1) * Marshal.SystemMaxDBCSCharSize;
+            byte* bufferPtr = stackalloc byte[cbAllocLength];
+
+            int cbLength = managedChar.ToString().ConvertToAnsi(bufferPtr, cbAllocLength, fBestFit, fThrowOnUnmappableChar);
+
+            Debug.Assert(cbLength > 0, "Zero bytes returned from DoAnsiConversion in AnsiCharMarshaler.ConvertToNative");
+            return bufferPtr[0];
+        }
+
+        internal static char ConvertToManaged(byte nativeChar)
+        {
+            Span<byte> bytes = new Span<byte>(ref nativeChar, 1);
+            string str = Encoding.Default.GetString(bytes);
+            return str[0];
+        }
+    }  // class AnsiCharMarshaler
+
+    internal static class CSTRMarshaler
+    {
+        internal static unsafe IntPtr ConvertToNative(int flags, string strManaged, IntPtr pNativeBuffer)
+        {
+            if (null == strManaged)
+            {
+                return IntPtr.Zero;
+            }
+
+            StubHelpers.CheckStringLength(strManaged.Length);
+
+            int nb;
+            byte* pbNativeBuffer = (byte*)pNativeBuffer;
+
+            if (pbNativeBuffer != null || Marshal.SystemMaxDBCSCharSize == 1)
+            {
+                // If we are marshaling into a stack buffer or we can accurately estimate the size of the required heap
+                // space, we will use a "1-pass" mode where we convert the string directly into the unmanaged buffer.
+
+                // + 1 for the null character from the user
+                nb = (strManaged.Length + 1) * Marshal.SystemMaxDBCSCharSize;
+
+                // Use the pre-allocated buffer (allocated by localloc IL instruction) if not NULL, 
+                // otherwise fallback to AllocCoTaskMem
+                if (pbNativeBuffer == null)
+                {
+                    // + 1 for the null character we put in
+                    pbNativeBuffer = (byte*)Marshal.AllocCoTaskMem(nb + 1);
+                }
+
+                nb = strManaged.ConvertToAnsi(pbNativeBuffer, nb + 1, 0 != (flags & 0xFF), 0 != (flags >> 8));
+            }
+            else
+            {
+                // Otherwise we use a slower "2-pass" mode where we first marshal the string into an intermediate buffer
+                // (managed byte array) and then allocate exactly the right amount of unmanaged memory. This is to avoid
+                // wasting memory on systems with multibyte character sets where the buffer we end up with is often much
+                // smaller than the upper bound for the given managed string.
+
+                byte[] bytes = AnsiCharMarshaler.DoAnsiConversion(strManaged, 0 != (flags & 0xFF), 0 != (flags >> 8), out nb);
+
+                // + 1 for the null character from the user.  + 1 for the null character we put in.
+                pbNativeBuffer = (byte*)Marshal.AllocCoTaskMem(nb + 2);
+
+                Buffer.Memcpy(pbNativeBuffer, 0, bytes, 0, nb);
+            }
+
+            pbNativeBuffer[nb] = 0x00;
+            pbNativeBuffer[nb + 1] = 0x00;
+
+            return (IntPtr)pbNativeBuffer;
+        }
+
+        internal static unsafe string ConvertToManaged(IntPtr cstr)
+        {
+            if (IntPtr.Zero == cstr)
+                return null;
+            else
+                return new String((sbyte*)cstr);
+        }
+
+        internal static void ClearNative(IntPtr pNative)
+        {
+            Win32Native.CoTaskMemFree(pNative);
+        }
+    }  // class CSTRMarshaler
+
+    internal static class UTF8Marshaler
+    {
+        private const int MAX_UTF8_CHAR_SIZE = 3;
+        internal static unsafe IntPtr ConvertToNative(int flags, string strManaged, IntPtr pNativeBuffer)
+        {
+            if (null == strManaged)
+            {
+                return IntPtr.Zero;
+            }
+            StubHelpers.CheckStringLength(strManaged.Length);
+
+            int nb;
+            byte* pbNativeBuffer = (byte*)pNativeBuffer;
+
+            // If we are marshaling into a stack buffer allocated by the ILStub
+            // we will use a "1-pass" mode where we convert the string directly into the unmanaged buffer.   
+            // else we will allocate the precise native heap memory.
+            if (pbNativeBuffer != null)
+            {
+                // this is the number of bytes allocated by the ILStub.
+                nb = (strManaged.Length + 1) * MAX_UTF8_CHAR_SIZE;
+
+                // nb is the actual number of bytes written by Encoding.GetBytes.
+                // use nb to de-limit the string since we are allocating more than 
+                // required on stack
+                nb = strManaged.GetBytesFromEncoding(pbNativeBuffer, nb, Encoding.UTF8);
+            }
+            // required bytes > 260 , allocate required bytes on heap
+            else
+            {
+                nb = Encoding.UTF8.GetByteCount(strManaged);
+                // + 1 for the null character.
+                pbNativeBuffer = (byte*)Marshal.AllocCoTaskMem(nb + 1);
+                strManaged.GetBytesFromEncoding(pbNativeBuffer, nb, Encoding.UTF8);
+            }
+            pbNativeBuffer[nb] = 0x0;
+            return (IntPtr)pbNativeBuffer;
+        }
+
+        internal static unsafe string ConvertToManaged(IntPtr cstr)
+        {
+            if (IntPtr.Zero == cstr)
+                return null;
+            int nbBytes = StubHelpers.strlen((sbyte*)cstr);
+            return String.CreateStringFromEncoding((byte*)cstr, nbBytes, Encoding.UTF8);
+        }
+
+        internal static void ClearNative(IntPtr pNative)
+        {
+            if (pNative != IntPtr.Zero)
+            {
+                Win32Native.CoTaskMemFree(pNative);
+            }
+        }
+    }
+
+    internal static class UTF8BufferMarshaler
+    {
+        internal static unsafe IntPtr ConvertToNative(StringBuilder sb, IntPtr pNativeBuffer, int flags)
+        {
+            if (null == sb)
+            {
+                return IntPtr.Zero;
+            }
+
+            // Convert to string first  
+            string strManaged = sb.ToString();
+
+            // Get byte count 
+            int nb = Encoding.UTF8.GetByteCount(strManaged);
+
+            // EmitConvertSpaceCLRToNative allocates memory
+            byte* pbNativeBuffer = (byte*)pNativeBuffer;
+            nb = strManaged.GetBytesFromEncoding(pbNativeBuffer, nb, Encoding.UTF8);
+
+            pbNativeBuffer[nb] = 0x0;
+            return (IntPtr)pbNativeBuffer;
+        }
+
+        internal static unsafe void ConvertToManaged(StringBuilder sb, IntPtr pNative)
+        {
+            if (pNative == null)
+                return;
+
+            int nbBytes = StubHelpers.strlen((sbyte*)pNative);
+            int numChar = Encoding.UTF8.GetCharCount((byte*)pNative, nbBytes);
+
+            // +1 GetCharCount return 0 if the pNative points to a 
+            // an empty buffer.We still need to allocate an empty 
+            // buffer with a '\0' to distingiush it from null.
+            // Note that pinning on (char *pinned = new char[0])
+            // return null and  Encoding.UTF8.GetChars do not like 
+            // null argument.
+            char[] cCharBuffer = new char[numChar + 1];
+            cCharBuffer[numChar] = '\0';
+            fixed (char* pBuffer = &cCharBuffer[0])
+            {
+                numChar = Encoding.UTF8.GetChars((byte*)pNative, nbBytes, pBuffer, numChar);
+                // replace string builder internal buffer
+                sb.ReplaceBufferInternal(pBuffer, numChar);
+            }
+        }
+    }
+
+#if FEATURE_COMINTEROP
+
+    internal static class BSTRMarshaler
+    {
+        internal static unsafe IntPtr ConvertToNative(string strManaged, IntPtr pNativeBuffer)
+        {
+            if (null == strManaged)
+            {
+                return IntPtr.Zero;
+            }
+            else
+            {
+                StubHelpers.CheckStringLength(strManaged.Length);
+
+                byte trailByte;
+                bool hasTrailByte = strManaged.TryGetTrailByte(out trailByte);
+
+                uint lengthInBytes = (uint)strManaged.Length * 2;
+
+                if (hasTrailByte)
+                {
+                    // this is an odd-sized string with a trailing byte stored in its sync block
+                    lengthInBytes++;
+                }
+
+                byte* ptrToFirstChar;
+
+                if (pNativeBuffer != IntPtr.Zero)
+                {
+                    // If caller provided a buffer, construct the BSTR manually. The size
+                    // of the buffer must be at least (lengthInBytes + 6) bytes.
+#if DEBUG
+                    uint length = *((uint*)pNativeBuffer.ToPointer());
+                    Debug.Assert(length >= lengthInBytes + 6, "BSTR localloc'ed buffer is too small");
+#endif
+
+                    // set length
+                    *((uint*)pNativeBuffer.ToPointer()) = lengthInBytes;
+
+                    ptrToFirstChar = (byte*)pNativeBuffer.ToPointer() + 4;
+                }
+                else
+                {
+                    // If not provided, allocate the buffer using SysAllocStringByteLen so
+                    // that odd-sized strings will be handled as well.
+                    ptrToFirstChar = (byte*)Win32Native.SysAllocStringByteLen(null, lengthInBytes).ToPointer();
+
+                    if (ptrToFirstChar == null)
+                    {
+                        throw new OutOfMemoryException();
+                    }
+                }
+
+                // copy characters from the managed string
+                fixed (char* ch = strManaged)
+                {
+                    Buffer.Memcpy(
+                        ptrToFirstChar,
+                        (byte*)ch,
+                        (strManaged.Length + 1) * 2);
+                }
+
+                // copy the trail byte if present
+                if (hasTrailByte)
+                {
+                    ptrToFirstChar[lengthInBytes - 1] = trailByte;
+                }
+
+                // return ptr to first character
+                return (IntPtr)ptrToFirstChar;
+            }
+        }
+
+        internal static unsafe string ConvertToManaged(IntPtr bstr)
+        {
+            if (IntPtr.Zero == bstr)
+            {
+                return null;
+            }
+            else
+            {
+                uint length = Win32Native.SysStringByteLen(bstr);
+
+                // Intentionally checking the number of bytes not characters to match the behavior
+                // of ML marshalers. This prevents roundtripping of very large strings as the check
+                // in the managed->native direction is done on String length but considering that
+                // it's completely moot on 32-bit and not expected to be important on 64-bit either,
+                // the ability to catch random garbage in the BSTR's length field outweighs this
+                // restriction. If an ordinary null-terminated string is passed instead of a BSTR,
+                // chances are that the length field - possibly being unallocated memory - contains
+                // a heap fill pattern that will have the highest bit set, caught by the check.
+                StubHelpers.CheckStringLength(length);
+
+                string ret;
+                if (length == 1)
+                {
+                    // In the empty string case, we need to use FastAllocateString rather than the
+                    // String .ctor, since newing up a 0 sized string will always return String.Emtpy.
+                    // When we marshal that out as a bstr, it can wind up getting modified which
+                    // corrupts String.Empty.
+                    ret = String.FastAllocateString(0);
+                }
+                else
+                {
+                    ret = new String((char*)bstr, 0, (int)(length / 2));
+                }
+
+                if ((length & 1) == 1)
+                {
+                    // odd-sized strings need to have the trailing byte saved in their sync block
+                    ret.SetTrailByte(((byte*)bstr.ToPointer())[length - 1]);
+                }
+
+                return ret;
+            }
+        }
+
+        internal static void ClearNative(IntPtr pNative)
+        {
+            if (IntPtr.Zero != pNative)
+            {
+                Win32Native.SysFreeString(pNative);
+            }
+        }
+    }  // class BSTRMarshaler
+
+#endif // FEATURE_COMINTEROP
+
+
+    internal static class VBByValStrMarshaler
+    {
+        internal static unsafe IntPtr ConvertToNative(string strManaged, bool fBestFit, bool fThrowOnUnmappableChar, ref int cch)
+        {
+            if (null == strManaged)
+            {
+                return IntPtr.Zero;
+            }
+
+            byte* pNative;
+
+            cch = strManaged.Length;
+
+            StubHelpers.CheckStringLength(cch);
+
+            // length field at negative offset + (# of characters incl. the terminator) * max ANSI char size
+            int nbytes = sizeof(uint) + ((cch + 1) * Marshal.SystemMaxDBCSCharSize);
+
+            pNative = (byte*)Marshal.AllocCoTaskMem(nbytes);
+            int* pLength = (int*)pNative;
+
+            pNative = pNative + sizeof(uint);
+
+            if (0 == cch)
+            {
+                *pNative = 0;
+                *pLength = 0;
+            }
+            else
+            {
+                int nbytesused;
+                byte[] bytes = AnsiCharMarshaler.DoAnsiConversion(strManaged, fBestFit, fThrowOnUnmappableChar, out nbytesused);
+
+                Debug.Assert(nbytesused < nbytes, "Insufficient buffer allocated in VBByValStrMarshaler.ConvertToNative");
+                Buffer.Memcpy(pNative, 0, bytes, 0, nbytesused);
+
+                pNative[nbytesused] = 0;
+                *pLength = nbytesused;
+            }
+
+            return new IntPtr(pNative);
+        }
+
+        internal static unsafe string ConvertToManaged(IntPtr pNative, int cch)
+        {
+            if (IntPtr.Zero == pNative)
+            {
+                return null;
+            }
+
+            return new String((sbyte*)pNative, 0, cch);
+        }
+
+        internal static unsafe void ClearNative(IntPtr pNative)
+        {
+            if (IntPtr.Zero != pNative)
+            {
+                Win32Native.CoTaskMemFree((IntPtr)(((long)pNative) - sizeof(uint)));
+            }
+        }
+    }  // class VBByValStrMarshaler
+
+
+#if FEATURE_COMINTEROP
+
+    internal static class AnsiBSTRMarshaler
+    {
+        internal static unsafe IntPtr ConvertToNative(int flags, string strManaged)
+        {
+            if (null == strManaged)
+            {
+                return IntPtr.Zero;
+            }
+
+            int length = strManaged.Length;
+
+            StubHelpers.CheckStringLength(length);
+
+            byte[] bytes = null;
+            int nb = 0;
+
+            if (length > 0)
+            {
+                bytes = AnsiCharMarshaler.DoAnsiConversion(strManaged, 0 != (flags & 0xFF), 0 != (flags >> 8), out nb);
+            }
+
+            return Win32Native.SysAllocStringByteLen(bytes, (uint)nb);
+        }
+
+        internal static unsafe string ConvertToManaged(IntPtr bstr)
+        {
+            if (IntPtr.Zero == bstr)
+            {
+                return null;
+            }
+            else
+            {
+                // We intentionally ignore the length field of the BSTR for back compat reasons.
+                // Unfortunately VB.NET uses Ansi BSTR marshaling when a string is passed ByRef
+                // and we cannot afford to break this common scenario.
+                return new String((sbyte*)bstr);
+            }
+        }
+
+        internal static unsafe void ClearNative(IntPtr pNative)
+        {
+            if (IntPtr.Zero != pNative)
+            {
+                Win32Native.SysFreeString(pNative);
+            }
+        }
+    }  // class AnsiBSTRMarshaler
+
+#endif // FEATURE_COMINTEROP
+
+
+    internal static class WSTRBufferMarshaler
+    {
+        internal static IntPtr ConvertToNative(string strManaged)
+        {
+            Debug.Fail("NYI");
+            return IntPtr.Zero;
+        }
+
+        internal static unsafe string ConvertToManaged(IntPtr bstr)
+        {
+            Debug.Fail("NYI");
+            return null;
+        }
+
+        internal static void ClearNative(IntPtr pNative)
+        {
+            Debug.Fail("NYI");
+        }
+    }  // class WSTRBufferMarshaler
+
+
+#if FEATURE_COMINTEROP
+
+
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct DateTimeNative
+    {
+        public Int64 UniversalTime;
+    };
+
+    internal static class DateTimeOffsetMarshaler
+    {
+        // Numer of ticks counted between 0001-01-01, 00:00:00 and 1601-01-01, 00:00:00.
+        // You can get this through:  (new DateTimeOffset(1601, 1, 1, 0, 0, 1, TimeSpan.Zero)).Ticks;
+        private const Int64 ManagedUtcTicksAtNativeZero = 504911232000000000;
+
+        internal static void ConvertToNative(ref DateTimeOffset managedDTO, out DateTimeNative dateTime)
+        {
+            Int64 managedUtcTicks = managedDTO.UtcTicks;
+            dateTime.UniversalTime = managedUtcTicks - ManagedUtcTicksAtNativeZero;
+        }
+
+        internal static void ConvertToManaged(out DateTimeOffset managedLocalDTO, ref DateTimeNative nativeTicks)
+        {
+            Int64 managedUtcTicks = ManagedUtcTicksAtNativeZero + nativeTicks.UniversalTime;
+            DateTimeOffset managedUtcDTO = new DateTimeOffset(managedUtcTicks, TimeSpan.Zero);
+
+            // Some Utc times cannot be represented in local time in certain timezones. E.g. 0001-01-01 12:00:00 AM cannot 
+            // be represented in any timezones with a negative offset from Utc. We throw an ArgumentException in that case.
+            managedLocalDTO = managedUtcDTO.ToLocalTime(true);
+        }
+    }  // class DateTimeOffsetMarshaler
+
+#endif  // FEATURE_COMINTEROP
+
+
+#if FEATURE_COMINTEROP
+    internal static class HStringMarshaler
+    {
+        // Slow-path, which requires making a copy of the managed string into the resulting HSTRING
+        internal static unsafe IntPtr ConvertToNative(string managed)
+        {
+            if (!Environment.IsWinRTSupported)
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_WinRT);
+            if (managed == null)
+                throw new ArgumentNullException(); // We don't have enough information to get the argument name 
+
+            IntPtr hstring;
+            int hrCreate = System.Runtime.InteropServices.WindowsRuntime.UnsafeNativeMethods.WindowsCreateString(managed, managed.Length, &hstring);
+            Marshal.ThrowExceptionForHR(hrCreate, new IntPtr(-1));
+            return hstring;
+        }
+
+        // Fast-path, which creates a reference over a pinned managed string.  This may only be used if the
+        // pinned string and HSTRING_HEADER will outlive the HSTRING produced (for instance, as an in parameter).
+        //
+        // Note that the managed string input to this method MUST be pinned, and stay pinned for the lifetime of
+        // the returned HSTRING object.  If the string is not pinned, or becomes unpinned before the HSTRING's
+        // lifetime ends, the HSTRING instance will be corrupted.
+        internal static unsafe IntPtr ConvertToNativeReference(string managed,
+                                                               [Out] HSTRING_HEADER* hstringHeader)
+        {
+            if (!Environment.IsWinRTSupported)
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_WinRT);
+            if (managed == null)
+                throw new ArgumentNullException();  // We don't have enough information to get the argument name 
+
+            // The string must also be pinned by the caller to ConvertToNativeReference, which also owns
+            // the HSTRING_HEADER.
+            fixed (char* pManaged = managed)
+            {
+                IntPtr hstring;
+                int hrCreate = System.Runtime.InteropServices.WindowsRuntime.UnsafeNativeMethods.WindowsCreateStringReference(pManaged, managed.Length, hstringHeader, &hstring);
+                Marshal.ThrowExceptionForHR(hrCreate, new IntPtr(-1));
+                return hstring;
+            }
+        }
+
+        internal static string ConvertToManaged(IntPtr hstring)
+        {
+            if (!Environment.IsWinRTSupported)
+            {
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_WinRT);
+            }
+
+            return WindowsRuntimeMarshal.HStringToString(hstring);
+        }
+
+        internal static void ClearNative(IntPtr hstring)
+        {
+            Debug.Assert(Environment.IsWinRTSupported);
+
+            if (hstring != IntPtr.Zero)
+            {
+                System.Runtime.InteropServices.WindowsRuntime.UnsafeNativeMethods.WindowsDeleteString(hstring);
+            }
+        }
+    }  // class HStringMarshaler
+
+    internal static class ObjectMarshaler
+    {
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertToNative(object objSrc, IntPtr pDstVariant);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern object ConvertToManaged(IntPtr pSrcVariant);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ClearNative(IntPtr pVariant);
+    }  // class ObjectMarshaler
+
+#endif // FEATURE_COMINTEROP
+
+    internal static class ValueClassMarshaler
+    {
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertToNative(IntPtr dst, IntPtr src, IntPtr pMT, ref CleanupWorkList pCleanupWorkList);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertToManaged(IntPtr dst, IntPtr src, IntPtr pMT);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ClearNative(IntPtr dst, IntPtr pMT);
+    }  // class ValueClassMarshaler
+
+    internal static class DateMarshaler
+    {
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern double ConvertToNative(DateTime managedDate);
+
+        // The return type is really DateTime but we use long to avoid the pain associated with returning structures.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern long ConvertToManaged(double nativeDate);
+    }  // class DateMarshaler
+
+#if FEATURE_COMINTEROP
+    // [FriendAccessAllowed]
+    internal static class InterfaceMarshaler
+    {
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr ConvertToNative(object objSrc, IntPtr itfMT, IntPtr classMT, int flags);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern object ConvertToManaged(IntPtr pUnk, IntPtr itfMT, IntPtr classMT, int flags);
+
+        [DllImport(JitHelpers.QCall)]
+        internal static extern void ClearNative(IntPtr pUnk);
+
+        // [FriendAccessAllowed]
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern object ConvertToManagedWithoutUnboxing(IntPtr pNative);
+    }  // class InterfaceMarshaler
+#endif // FEATURE_COMINTEROP
+
+#if FEATURE_COMINTEROP
+    internal static class UriMarshaler
+    {
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern string GetRawUriFromNative(IntPtr pUri);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern unsafe IntPtr CreateNativeUriInstanceHelper(char* rawUri, int strLen);
+
+        internal static unsafe IntPtr CreateNativeUriInstance(string rawUri)
+        {
+            fixed (char* pManaged = rawUri)
+            {
+                return CreateNativeUriInstanceHelper(pManaged, rawUri.Length);
+            }
+        }
+    }  // class InterfaceMarshaler
+
+    // [FriendAccessAllowed]
+    internal static class EventArgsMarshaler
+    {
+        // [FriendAccessAllowed]
+        internal static IntPtr CreateNativeNCCEventArgsInstance(int action, object newItems, object oldItems, int newIndex, int oldIndex)
+        {
+            IntPtr newItemsIP = IntPtr.Zero;
+            IntPtr oldItemsIP = IntPtr.Zero;
+
+            RuntimeHelpers.PrepareConstrainedRegions();
+            try
+            {
+                if (newItems != null)
+                    newItemsIP = Marshal.GetComInterfaceForObject(newItems, typeof(IBindableVector));
+                if (oldItems != null)
+                    oldItemsIP = Marshal.GetComInterfaceForObject(oldItems, typeof(IBindableVector));
+
+                return CreateNativeNCCEventArgsInstanceHelper(action, newItemsIP, oldItemsIP, newIndex, oldIndex);
+            }
+            finally
+            {
+                if (oldItemsIP != IntPtr.Zero)
+                    Marshal.Release(oldItemsIP);
+                if (newItemsIP != IntPtr.Zero)
+                    Marshal.Release(newItemsIP);
+            }
+        }
+
+        // [FriendAccessAllowed]
+        [DllImport(JitHelpers.QCall)]
+        static internal extern IntPtr CreateNativePCEventArgsInstance([MarshalAs(UnmanagedType.HString)]string name);
+
+        [DllImport(JitHelpers.QCall)]
+        static internal extern IntPtr CreateNativeNCCEventArgsInstanceHelper(int action, IntPtr newItem, IntPtr oldItem, int newIndex, int oldIndex);
+    }
+#endif // FEATURE_COMINTEROP
+
+    internal static class MngdNativeArrayMarshaler
+    {
+        // Needs to match exactly with MngdNativeArrayMarshaler in ilmarshalers.h
+        internal struct MarshalerState
+        {
+            IntPtr m_pElementMT;
+            IntPtr m_Array;
+            int m_NativeDataValid;
+            int m_BestFitMap;
+            int m_ThrowOnUnmappableChar;
+            short m_vt;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void CreateMarshaler(IntPtr pMarshalState, IntPtr pMT, int dwFlags);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertSpaceToNative(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertContentsToNative(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertSpaceToManaged(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome,
+                                                          int cElements);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertContentsToManaged(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ClearNative(IntPtr pMarshalState, IntPtr pNativeHome, int cElements);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ClearNativeContents(IntPtr pMarshalState, IntPtr pNativeHome, int cElements);
+    }  // class MngdNativeArrayMarshaler
+
+#if FEATURE_COMINTEROP
+    internal static class MngdSafeArrayMarshaler
+    {
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void CreateMarshaler(IntPtr pMarshalState, IntPtr pMT, int iRank, int dwFlags);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertSpaceToNative(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertContentsToNative(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome, object pOriginalManaged);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertSpaceToManaged(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertContentsToManaged(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ClearNative(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome);
+    }  // class MngdSafeArrayMarshaler
+
+    internal static class MngdHiddenLengthArrayMarshaler
+    {
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void CreateMarshaler(IntPtr pMarshalState, IntPtr pMT, IntPtr cbElementSize, ushort vt);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertSpaceToNative(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertContentsToNative(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome);
+
+        internal static unsafe void ConvertContentsToNative_DateTime(ref DateTimeOffset[] managedArray, IntPtr pNativeHome)
+        {
+            if (managedArray != null)
+            {
+                DateTimeNative* nativeBuffer = *(DateTimeNative**)pNativeHome;
+                for (int i = 0; i < managedArray.Length; i++)
+                {
+                    DateTimeOffsetMarshaler.ConvertToNative(ref managedArray[i], out nativeBuffer[i]);
+                }
+            }
+        }
+
+        internal static unsafe void ConvertContentsToNative_Type(ref System.Type[] managedArray, IntPtr pNativeHome)
+        {
+            if (managedArray != null)
+            {
+                TypeNameNative* nativeBuffer = *(TypeNameNative**)pNativeHome;
+                for (int i = 0; i < managedArray.Length; i++)
+                {
+                    SystemTypeMarshaler.ConvertToNative(managedArray[i], &nativeBuffer[i]);
+                }
+            }
+        }
+
+        internal static unsafe void ConvertContentsToNative_Exception(ref Exception[] managedArray, IntPtr pNativeHome)
+        {
+            if (managedArray != null)
+            {
+                Int32* nativeBuffer = *(Int32**)pNativeHome;
+                for (int i = 0; i < managedArray.Length; i++)
+                {
+                    nativeBuffer[i] = HResultExceptionMarshaler.ConvertToNative(managedArray[i]);
+                }
+            }
+        }
+
+        internal static unsafe void ConvertContentsToNative_Nullable<T>(ref Nullable<T>[] managedArray, IntPtr pNativeHome)
+            where T : struct
+        {
+            if (managedArray != null)
+            {
+                IntPtr* nativeBuffer = *(IntPtr**)pNativeHome;
+                for (int i = 0; i < managedArray.Length; i++)
+                {
+                    nativeBuffer[i] = NullableMarshaler.ConvertToNative<T>(ref managedArray[i]);
+                }
+            }
+        }
+
+        internal static unsafe void ConvertContentsToNative_KeyValuePair<K, V>(ref KeyValuePair<K, V>[] managedArray, IntPtr pNativeHome)
+        {
+            if (managedArray != null)
+            {
+                IntPtr* nativeBuffer = *(IntPtr**)pNativeHome;
+                for (int i = 0; i < managedArray.Length; i++)
+                {
+                    nativeBuffer[i] = KeyValuePairMarshaler.ConvertToNative<K, V>(ref managedArray[i]);
+                }
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertSpaceToManaged(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome, int elementCount);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertContentsToManaged(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome);
+
+        internal static unsafe void ConvertContentsToManaged_DateTime(ref DateTimeOffset[] managedArray, IntPtr pNativeHome)
+        {
+            if (managedArray != null)
+            {
+                DateTimeNative* nativeBuffer = *(DateTimeNative**)pNativeHome;
+                for (int i = 0; i < managedArray.Length; i++)
+                {
+                    DateTimeOffsetMarshaler.ConvertToManaged(out managedArray[i], ref nativeBuffer[i]);
+                }
+            }
+        }
+
+        internal static unsafe void ConvertContentsToManaged_Type(ref System.Type[] managedArray, IntPtr pNativeHome)
+        {
+            if (managedArray != null)
+            {
+                TypeNameNative* nativeBuffer = *(TypeNameNative**)pNativeHome;
+                for (int i = 0; i < managedArray.Length; i++)
+                {
+                    SystemTypeMarshaler.ConvertToManaged(&nativeBuffer[i], ref managedArray[i]);
+                }
+            }
+        }
+
+        internal static unsafe void ConvertContentsToManaged_Exception(ref Exception[] managedArray, IntPtr pNativeHome)
+        {
+            if (managedArray != null)
+            {
+                Int32* nativeBuffer = *(Int32**)pNativeHome;
+                for (int i = 0; i < managedArray.Length; i++)
+                {
+                    managedArray[i] = HResultExceptionMarshaler.ConvertToManaged(nativeBuffer[i]);
+                }
+            }
+        }
+
+        internal static unsafe void ConvertContentsToManaged_Nullable<T>(ref Nullable<T>[] managedArray, IntPtr pNativeHome)
+            where T : struct
+        {
+            if (managedArray != null)
+            {
+                IntPtr* nativeBuffer = *(IntPtr**)pNativeHome;
+                for (int i = 0; i < managedArray.Length; i++)
+                {
+                    managedArray[i] = NullableMarshaler.ConvertToManaged<T>(nativeBuffer[i]);
+                }
+            }
+        }
+
+        internal static unsafe void ConvertContentsToManaged_KeyValuePair<K, V>(ref KeyValuePair<K, V>[] managedArray, IntPtr pNativeHome)
+        {
+            if (managedArray != null)
+            {
+                IntPtr* nativeBuffer = *(IntPtr**)pNativeHome;
+                for (int i = 0; i < managedArray.Length; i++)
+                {
+                    managedArray[i] = KeyValuePairMarshaler.ConvertToManaged<K, V>(nativeBuffer[i]);
+                }
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ClearNativeContents(IntPtr pMarshalState, IntPtr pNativeHome, int cElements);
+
+        internal static unsafe void ClearNativeContents_Type(IntPtr pNativeHome, int cElements)
+        {
+            Debug.Assert(Environment.IsWinRTSupported);
+
+            TypeNameNative* pNativeTypeArray = *(TypeNameNative**)pNativeHome;
+            if (pNativeTypeArray != null)
+            {
+                for (int i = 0; i < cElements; ++i)
+                {
+                    SystemTypeMarshaler.ClearNative(pNativeTypeArray);
+                    pNativeTypeArray++;
+                }
+            }
+        }
+    }  // class MngdHiddenLengthArrayMarshaler
+
+#endif // FEATURE_COMINTEROP
+
+    internal static class MngdRefCustomMarshaler
+    {
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void CreateMarshaler(IntPtr pMarshalState, IntPtr pCMHelper);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertContentsToNative(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ConvertContentsToManaged(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ClearNative(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ClearManaged(IntPtr pMarshalState, ref object pManagedHome, IntPtr pNativeHome);
+    }  // class MngdRefCustomMarshaler
+
+    internal struct AsAnyMarshaler
+    {
+        private const ushort VTHACK_ANSICHAR = 253;
+        private const ushort VTHACK_WINBOOL = 254;
+
+        private enum BackPropAction
+        {
+            None,
+            Array,
+            Layout,
+            StringBuilderAnsi,
+            StringBuilderUnicode
+        }
+
+        // Pointer to MngdNativeArrayMarshaler, ownership not assumed.
+        private IntPtr pvArrayMarshaler;
+
+        // Type of action to perform after the CLR-to-unmanaged call.
+        private BackPropAction backPropAction;
+
+        // The managed layout type for BackPropAction.Layout.
+        private Type layoutType;
+
+        // Cleanup list to be destroyed when clearing the native view (for layouts with SafeHandles).
+        private CleanupWorkList cleanupWorkList;
+
+        [Flags]
+        internal enum AsAnyFlags
+        {
+            In = 0x10000000,
+            Out = 0x20000000,
+            IsAnsi = 0x00FF0000,
+            IsThrowOn = 0x0000FF00,
+            IsBestFit = 0x000000FF
+        }
+
+        private static bool IsIn(int dwFlags) { return ((dwFlags & (int)AsAnyFlags.In) != 0); }
+        private static bool IsOut(int dwFlags) { return ((dwFlags & (int)AsAnyFlags.Out) != 0); }
+        private static bool IsAnsi(int dwFlags) { return ((dwFlags & (int)AsAnyFlags.IsAnsi) != 0); }
+        private static bool IsThrowOn(int dwFlags) { return ((dwFlags & (int)AsAnyFlags.IsThrowOn) != 0); }
+        private static bool IsBestFit(int dwFlags) { return ((dwFlags & (int)AsAnyFlags.IsBestFit) != 0); }
+
+        internal AsAnyMarshaler(IntPtr pvArrayMarshaler)
+        {
+            // we need this in case the value being marshaled turns out to be array
+            Debug.Assert(pvArrayMarshaler != IntPtr.Zero, "pvArrayMarshaler must not be null");
+
+            this.pvArrayMarshaler = pvArrayMarshaler;
+            backPropAction = BackPropAction.None;
+            layoutType = null;
+            cleanupWorkList = null;
+        }
+
+        #region ConvertToNative helpers
+
+        private unsafe IntPtr ConvertArrayToNative(object pManagedHome, int dwFlags)
+        {
+            Type elementType = pManagedHome.GetType().GetElementType();
+            VarEnum vt = VarEnum.VT_EMPTY;
+
+            switch (Type.GetTypeCode(elementType))
+            {
+                case TypeCode.SByte: vt = VarEnum.VT_I1; break;
+                case TypeCode.Byte: vt = VarEnum.VT_UI1; break;
+                case TypeCode.Int16: vt = VarEnum.VT_I2; break;
+                case TypeCode.UInt16: vt = VarEnum.VT_UI2; break;
+                case TypeCode.Int32: vt = VarEnum.VT_I4; break;
+                case TypeCode.UInt32: vt = VarEnum.VT_UI4; break;
+                case TypeCode.Int64: vt = VarEnum.VT_I8; break;
+                case TypeCode.UInt64: vt = VarEnum.VT_UI8; break;
+                case TypeCode.Single: vt = VarEnum.VT_R4; break;
+                case TypeCode.Double: vt = VarEnum.VT_R8; break;
+                case TypeCode.Char: vt = (IsAnsi(dwFlags) ? (VarEnum)VTHACK_ANSICHAR : VarEnum.VT_UI2); break;
+                case TypeCode.Boolean: vt = (VarEnum)VTHACK_WINBOOL; break;
+
+                case TypeCode.Object:
+                    {
+                        if (elementType == typeof(IntPtr))
+                        {
+                            vt = (IntPtr.Size == 4 ? VarEnum.VT_I4 : VarEnum.VT_I8);
+                        }
+                        else if (elementType == typeof(UIntPtr))
+                        {
+                            vt = (IntPtr.Size == 4 ? VarEnum.VT_UI4 : VarEnum.VT_UI8);
+                        }
+                        else goto default;
+                        break;
+                    }
+
+                default:
+                    throw new ArgumentException(SR.Arg_NDirectBadObject);
+            }
+
+            // marshal the object as C-style array (UnmanagedType.LPArray)
+            int dwArrayMarshalerFlags = (int)vt;
+            if (IsBestFit(dwFlags)) dwArrayMarshalerFlags |= (1 << 16);
+            if (IsThrowOn(dwFlags)) dwArrayMarshalerFlags |= (1 << 24);
+
+            MngdNativeArrayMarshaler.CreateMarshaler(
+                pvArrayMarshaler,
+                IntPtr.Zero,      // not needed as we marshal primitive VTs only
+                dwArrayMarshalerFlags);
+
+            IntPtr pNativeHome;
+            IntPtr pNativeHomeAddr = new IntPtr(&pNativeHome);
+
+            MngdNativeArrayMarshaler.ConvertSpaceToNative(
+                pvArrayMarshaler,
+                ref pManagedHome,
+                pNativeHomeAddr);
+
+            if (IsIn(dwFlags))
+            {
+                MngdNativeArrayMarshaler.ConvertContentsToNative(
+                    pvArrayMarshaler,
+                    ref pManagedHome,
+                    pNativeHomeAddr);
+            }
+            if (IsOut(dwFlags))
+            {
+                backPropAction = BackPropAction.Array;
+            }
+
+            return pNativeHome;
+        }
+
+        private static IntPtr ConvertStringToNative(string pManagedHome, int dwFlags)
+        {
+            IntPtr pNativeHome;
+
+            // IsIn, IsOut are ignored for strings - they're always in-only
+            if (IsAnsi(dwFlags))
+            {
+                // marshal the object as Ansi string (UnmanagedType.LPStr)
+                pNativeHome = CSTRMarshaler.ConvertToNative(
+                    dwFlags & 0xFFFF, // (throw on unmappable char << 8 | best fit)
+                    pManagedHome,     //
+                    IntPtr.Zero);     // unmanaged buffer will be allocated
+            }
+            else
+            {
+                // marshal the object as Unicode string (UnmanagedType.LPWStr)
+                StubHelpers.CheckStringLength(pManagedHome.Length);
+
+                int allocSize = (pManagedHome.Length + 1) * 2;
+                pNativeHome = Marshal.AllocCoTaskMem(allocSize);
+
+                String.InternalCopy(pManagedHome, pNativeHome, allocSize);
+            }
+
+            return pNativeHome;
+        }
+
+        private unsafe IntPtr ConvertStringBuilderToNative(StringBuilder pManagedHome, int dwFlags)
+        {
+            IntPtr pNativeHome;
+
+            // P/Invoke can be used to call Win32 apis that don't strictly follow CLR in/out semantics and thus may
+            // leave garbage in the buffer in circumstances that we can't detect. To prevent us from crashing when
+            // converting the contents back to managed, put a hidden NULL terminator past the end of the official buffer.
+
+            // Unmanaged layout:
+            // +====================================+
+            // | Extra hidden NULL                  |
+            // +====================================+ \
+            // |                                    | |
+            // | [Converted] NULL-terminated string | |- buffer that the target may change
+            // |                                    | |
+            // +====================================+ / <-- native home
+
+            // Note that StringBuilder.Capacity is the number of characters NOT including any terminators.
+
+            if (IsAnsi(dwFlags))
+            {
+                StubHelpers.CheckStringLength(pManagedHome.Capacity);
+
+                // marshal the object as Ansi string (UnmanagedType.LPStr)
+                int allocSize = (pManagedHome.Capacity * Marshal.SystemMaxDBCSCharSize) + 4;
+                pNativeHome = Marshal.AllocCoTaskMem(allocSize);
+
+                byte* ptr = (byte*)pNativeHome;
+                *(ptr + allocSize - 3) = 0;
+                *(ptr + allocSize - 2) = 0;
+                *(ptr + allocSize - 1) = 0;
+
+                if (IsIn(dwFlags))
+                {
+                    int length = pManagedHome.ToString().ConvertToAnsi(
+                        ptr, allocSize,
+                        IsBestFit(dwFlags),
+                        IsThrowOn(dwFlags));
+                    Debug.Assert(length < allocSize, "Expected a length less than the allocated size");
+                }
+                if (IsOut(dwFlags))
+                {
+                    backPropAction = BackPropAction.StringBuilderAnsi;
+                }
+            }
+            else
+            {
+                // marshal the object as Unicode string (UnmanagedType.LPWStr)
+                int allocSize = (pManagedHome.Capacity * 2) + 4;
+                pNativeHome = Marshal.AllocCoTaskMem(allocSize);
+
+                byte* ptr = (byte*)pNativeHome;
+                *(ptr + allocSize - 1) = 0;
+                *(ptr + allocSize - 2) = 0;
+
+                if (IsIn(dwFlags))
+                {
+                    int length = pManagedHome.Length * 2;
+                    pManagedHome.InternalCopy(pNativeHome, length);
+
+                    // null-terminate the native string
+                    *(ptr + length + 0) = 0;
+                    *(ptr + length + 1) = 0;
+                }
+                if (IsOut(dwFlags))
+                {
+                    backPropAction = BackPropAction.StringBuilderUnicode;
+                }
+            }
+
+            return pNativeHome;
+        }
+
+        private unsafe IntPtr ConvertLayoutToNative(object pManagedHome, int dwFlags)
+        {
+            // Note that the following call will not throw exception if the type
+            // of pManagedHome is not marshalable. That's intentional because we
+            // want to maintain the original behavior where this was indicated
+            // by TypeLoadException during the actual field marshaling.
+            int allocSize = Marshal.SizeOfHelper(pManagedHome.GetType(), false);
+            IntPtr pNativeHome = Marshal.AllocCoTaskMem(allocSize);
+
+            // marshal the object as class with layout (UnmanagedType.LPStruct)
+            if (IsIn(dwFlags))
+            {
+                StubHelpers.FmtClassUpdateNativeInternal(pManagedHome, (byte*)pNativeHome.ToPointer(), ref cleanupWorkList);
+            }
+            if (IsOut(dwFlags))
+            {
+                backPropAction = BackPropAction.Layout;
+            }
+            layoutType = pManagedHome.GetType();
+
+            return pNativeHome;
+        }
+
+        #endregion
+
+        internal IntPtr ConvertToNative(object pManagedHome, int dwFlags)
+        {
+            if (pManagedHome == null)
+                return IntPtr.Zero;
+
+            if (pManagedHome is ArrayWithOffset)
+                throw new ArgumentException(SR.Arg_MarshalAsAnyRestriction);
+
+            IntPtr pNativeHome;
+
+            if (pManagedHome.GetType().IsArray)
+            {
+                // array (LPArray)
+                pNativeHome = ConvertArrayToNative(pManagedHome, dwFlags);
+            }
+            else
+            {
+                string strValue;
+                StringBuilder sbValue;
+
+                if ((strValue = pManagedHome as string) != null)
+                {
+                    // string (LPStr or LPWStr)
+                    pNativeHome = ConvertStringToNative(strValue, dwFlags);
+                }
+                else if ((sbValue = pManagedHome as StringBuilder) != null)
+                {
+                    // StringBuilder (LPStr or LPWStr)
+                    pNativeHome = ConvertStringBuilderToNative(sbValue, dwFlags);
+                }
+                else if (pManagedHome.GetType().IsLayoutSequential || pManagedHome.GetType().IsExplicitLayout)
+                {
+                    // layout (LPStruct)
+                    pNativeHome = ConvertLayoutToNative(pManagedHome, dwFlags);
+                }
+                else
+                {
+                    // this type is not supported for AsAny marshaling
+                    throw new ArgumentException(SR.Arg_NDirectBadObject);
+                }
+            }
+
+            return pNativeHome;
+        }
+
+        internal unsafe void ConvertToManaged(object pManagedHome, IntPtr pNativeHome)
+        {
+            switch (backPropAction)
+            {
+                case BackPropAction.Array:
+                    {
+                        MngdNativeArrayMarshaler.ConvertContentsToManaged(
+                            pvArrayMarshaler,
+                            ref pManagedHome,
+                            new IntPtr(&pNativeHome));
+                        break;
+                    }
+
+                case BackPropAction.Layout:
+                    {
+                        StubHelpers.FmtClassUpdateCLRInternal(pManagedHome, (byte*)pNativeHome.ToPointer());
+                        break;
+                    }
+
+                case BackPropAction.StringBuilderAnsi:
+                    {
+                        sbyte* ptr = (sbyte*)pNativeHome.ToPointer();
+                        ((StringBuilder)pManagedHome).ReplaceBufferAnsiInternal(ptr, Win32Native.lstrlenA(pNativeHome));
+                        break;
+                    }
+
+                case BackPropAction.StringBuilderUnicode:
+                    {
+                        char* ptr = (char*)pNativeHome.ToPointer();
+                        ((StringBuilder)pManagedHome).ReplaceBufferInternal(ptr, Win32Native.lstrlenW(pNativeHome));
+                        break;
+                    }
+
+                    // nothing to do for BackPropAction.None
+            }
+        }
+
+        internal void ClearNative(IntPtr pNativeHome)
+        {
+            if (pNativeHome != IntPtr.Zero)
+            {
+                if (layoutType != null)
+                {
+                    // this must happen regardless of BackPropAction
+                    Marshal.DestroyStructure(pNativeHome, layoutType);
+                }
+                Win32Native.CoTaskMemFree(pNativeHome);
+            }
+            StubHelpers.DestroyCleanupList(ref cleanupWorkList);
+        }
+    }  // struct AsAnyMarshaler
+
+#if FEATURE_COMINTEROP
+    internal static class NullableMarshaler
+    {
+        internal static IntPtr ConvertToNative<T>(ref Nullable<T> pManaged) where T : struct
+        {
+            if (pManaged.HasValue)
+            {
+                object impl = IReferenceFactory.CreateIReference(pManaged);
+                return Marshal.GetComInterfaceForObject(impl, typeof(IReference<T>));
+            }
+            else
+            {
+                return IntPtr.Zero;
+            }
+        }
+
+        internal static void ConvertToManagedRetVoid<T>(IntPtr pNative, ref Nullable<T> retObj) where T : struct
+        {
+            retObj = ConvertToManaged<T>(pNative);
+        }
+
+
+        internal static Nullable<T> ConvertToManaged<T>(IntPtr pNative) where T : struct
+        {
+            if (pNative != IntPtr.Zero)
+            {
+                object wrapper = InterfaceMarshaler.ConvertToManagedWithoutUnboxing(pNative);
+                return (Nullable<T>)CLRIReferenceImpl<T>.UnboxHelper(wrapper);
+            }
+            else
+            {
+                return new Nullable<T>();
+            }
+        }
+    }  // class NullableMarshaler
+
+    // Corresponds to Windows.UI.Xaml.Interop.TypeName
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct TypeNameNative
+    {
+        internal IntPtr typeName;           // HSTRING
+        internal TypeKind typeKind;           // TypeKind enum
+    }
+
+    // Corresponds to Windows.UI.Xaml.TypeSource
+    internal enum TypeKind
+    {
+        Primitive,
+        Metadata,
+        Projection
+    };
+
+    internal static class WinRTTypeNameConverter
+    {
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern string ConvertToWinRTTypeName(System.Type managedType, out bool isPrimitive);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern System.Type GetTypeFromWinRTTypeName(string typeName, out bool isPrimitive);
+    }
+
+    internal static class SystemTypeMarshaler
+    {
+        internal static unsafe void ConvertToNative(System.Type managedType, TypeNameNative* pNativeType)
+        {
+            if (!Environment.IsWinRTSupported)
+            {
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_WinRT);
+            }
+
+            string typeName;
+            if (managedType != null)
+            {
+                if (managedType.GetType() != typeof(System.RuntimeType))
+                {   // The type should be exactly System.RuntimeType (and not its child System.ReflectionOnlyType, or other System.Type children)
+                    throw new ArgumentException(SR.Format(SR.Argument_WinRTSystemRuntimeType, managedType.GetType().ToString()));
+                }
+
+                bool isPrimitive;
+                string winrtTypeName = WinRTTypeNameConverter.ConvertToWinRTTypeName(managedType, out isPrimitive);
+                if (winrtTypeName != null)
+                {
+                    // Must be a WinRT type, either in a WinMD or a Primitive
+                    typeName = winrtTypeName;
+                    if (isPrimitive)
+                        pNativeType->typeKind = TypeKind.Primitive;
+                    else
+                        pNativeType->typeKind = TypeKind.Metadata;
+                }
+                else
+                {
+                    // Custom .NET type
+                    typeName = managedType.AssemblyQualifiedName;
+                    pNativeType->typeKind = TypeKind.Projection;
+                }
+            }
+            else
+            {   // Marshal null as empty string + Projection
+                typeName = "";
+                pNativeType->typeKind = TypeKind.Projection;
+            }
+
+            int hrCreate = System.Runtime.InteropServices.WindowsRuntime.UnsafeNativeMethods.WindowsCreateString(typeName, typeName.Length, &pNativeType->typeName);
+            Marshal.ThrowExceptionForHR(hrCreate, new IntPtr(-1));
+        }
+
+        internal static unsafe void ConvertToManaged(TypeNameNative* pNativeType, ref System.Type managedType)
+        {
+            if (!Environment.IsWinRTSupported)
+            {
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_WinRT);
+            }
+
+            string typeName = WindowsRuntimeMarshal.HStringToString(pNativeType->typeName);
+            if (String.IsNullOrEmpty(typeName))
+            {
+                managedType = null;
+                return;
+            }
+
+            if (pNativeType->typeKind == TypeKind.Projection)
+            {
+                managedType = Type.GetType(typeName, /* throwOnError = */ true);
+            }
+            else
+            {
+                bool isPrimitive;
+                managedType = WinRTTypeNameConverter.GetTypeFromWinRTTypeName(typeName, out isPrimitive);
+
+                // TypeSource must match
+                if (isPrimitive != (pNativeType->typeKind == TypeKind.Primitive))
+                    throw new ArgumentException(SR.Argument_Unexpected_TypeSource);
+            }
+        }
+
+        internal static unsafe void ClearNative(TypeNameNative* pNativeType)
+        {
+            Debug.Assert(Environment.IsWinRTSupported);
+
+            if (pNativeType->typeName != IntPtr.Zero)
+            {
+                System.Runtime.InteropServices.WindowsRuntime.UnsafeNativeMethods.WindowsDeleteString(pNativeType->typeName);
+            }
+        }
+    }  // class SystemTypeMarshaler
+
+    // For converting WinRT's Windows.Foundation.HResult into System.Exception and vice versa.
+    internal static class HResultExceptionMarshaler
+    {
+        internal static unsafe int ConvertToNative(Exception ex)
+        {
+            if (!Environment.IsWinRTSupported)
+            {
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_WinRT);
+            }
+
+            if (ex == null)
+                return 0;  // S_OK;
+
+            return ex._HResult;
+        }
+
+        internal static unsafe Exception ConvertToManaged(int hr)
+        {
+            if (!Environment.IsWinRTSupported)
+            {
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_WinRT);
+            }
+
+            Exception e = null;
+            if (hr < 0)
+            {
+                e = StubHelpers.InternalGetCOMHRExceptionObject(hr, IntPtr.Zero, null, /* fForWinRT */ true);
+            }
+
+            // S_OK should be marshaled as null.  WinRT API's should not return S_FALSE by convention.
+            // We've chosen to treat S_FALSE as success and return null.
+            Debug.Assert(e != null || hr == 0 || hr == 1, "Unexpected HRESULT - it is a success HRESULT (without the high bit set) other than S_OK & S_FALSE.");
+            return e;
+        }
+    }  // class HResultExceptionMarshaler
+
+    internal static class KeyValuePairMarshaler
+    {
+        internal static IntPtr ConvertToNative<K, V>([In] ref KeyValuePair<K, V> pair)
+        {
+            IKeyValuePair<K, V> impl = new CLRIKeyValuePairImpl<K, V>(ref pair);
+            return Marshal.GetComInterfaceForObject(impl, typeof(IKeyValuePair<K, V>));
+        }
+
+        internal static KeyValuePair<K, V> ConvertToManaged<K, V>(IntPtr pInsp)
+        {
+            object obj = InterfaceMarshaler.ConvertToManagedWithoutUnboxing(pInsp);
+
+            IKeyValuePair<K, V> pair = (IKeyValuePair<K, V>)obj;
+            return new KeyValuePair<K, V>(pair.Key, pair.Value);
+        }
+
+        // Called from COMInterfaceMarshaler
+        internal static object ConvertToManagedBox<K, V>(IntPtr pInsp)
+        {
+            return (object)ConvertToManaged<K, V>(pInsp);
+        }
+    }  // class KeyValuePairMarshaler
+
+#endif // FEATURE_COMINTEROP
+
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct NativeVariant
+    {
+        private ushort vt;
+        private ushort wReserved1;
+        private ushort wReserved2;
+        private ushort wReserved3;
+
+        // The union portion of the structure contains at least one 64-bit type that on some 32-bit platforms
+        // (notably  ARM) requires 64-bit alignment. So on 32-bit platforms we'll actually size the variant
+        // portion of the struct with an Int64 so the type loader notices this requirement (a no-op on x86,
+        // but on ARM it will allow us to correctly determine the layout of native argument lists containing
+        // VARIANTs). Note that the field names here don't matter: none of the code refers to these fields,
+        // the structure just exists to provide size information to the IL marshaler.
+#if BIT64
+        private IntPtr data1;
+        private IntPtr data2;
+#else
+        Int64  data1;
+#endif
+    }  // struct NativeVariant
+
+    // Aggregates SafeHandle and the "owned" bit which indicates whether the SafeHandle
+    // has been successfully AddRef'ed. This allows us to do realiable cleanup (Release)
+    // if and only if it is needed.
+    internal sealed class CleanupWorkListElement
+    {
+        public CleanupWorkListElement(SafeHandle handle)
+        {
+            m_handle = handle;
+        }
+
+        public SafeHandle m_handle;
+
+        // This field is passed by-ref to SafeHandle.DangerousAddRef.
+        // CleanupWorkList.Destroy ignores this element if m_owned is not set to true.
+        public bool m_owned;
+    }  // class CleanupWorkListElement
+
+    internal sealed class CleanupWorkList
+    {
+        private List<CleanupWorkListElement> m_list = new List<CleanupWorkListElement>();
+
+        public void Add(CleanupWorkListElement elem)
+        {
+            Debug.Assert(elem.m_owned == false, "m_owned is supposed to be false and set later by DangerousAddRef");
+            m_list.Add(elem);
+        }
+
+        public void Destroy()
+        {
+            for (int i = m_list.Count - 1; i >= 0; i--)
+            {
+                if (m_list[i].m_owned)
+                    StubHelpers.SafeHandleRelease(m_list[i].m_handle);
+            }
+        }
+    }  // class CleanupWorkList
+
+    internal static class StubHelpers
+    {
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsQCall(IntPtr pMD);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void InitDeclaringType(IntPtr pMD);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr GetNDirectTarget(IntPtr pMD);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr GetDelegateTarget(Delegate pThis, ref IntPtr pStubArg);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ClearLastError();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void SetLastError();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ThrowInteropParamException(int resID, int paramIdx);
+
+        internal static IntPtr AddToCleanupList(ref CleanupWorkList pCleanupWorkList, SafeHandle handle)
+        {
+            if (pCleanupWorkList == null)
+                pCleanupWorkList = new CleanupWorkList();
+
+            CleanupWorkListElement element = new CleanupWorkListElement(handle);
+            pCleanupWorkList.Add(element);
+
+            // element.m_owned will be true iff the AddRef succeeded
+            return SafeHandleAddRef(handle, ref element.m_owned);
+        }
+
+        internal static void DestroyCleanupList(ref CleanupWorkList pCleanupWorkList)
+        {
+            if (pCleanupWorkList != null)
+            {
+                pCleanupWorkList.Destroy();
+                pCleanupWorkList = null;
+            }
+        }
+
+        internal static Exception GetHRExceptionObject(int hr)
+        {
+            Exception ex = InternalGetHRExceptionObject(hr);
+            ex.InternalPreserveStackTrace();
+            return ex;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Exception InternalGetHRExceptionObject(int hr);
+
+#if FEATURE_COMINTEROP
+        internal static Exception GetCOMHRExceptionObject(int hr, IntPtr pCPCMD, object pThis)
+        {
+            Exception ex = InternalGetCOMHRExceptionObject(hr, pCPCMD, pThis, false);
+            ex.InternalPreserveStackTrace();
+            return ex;
+        }
+
+        internal static Exception GetCOMHRExceptionObject_WinRT(int hr, IntPtr pCPCMD, object pThis)
+        {
+            Exception ex = InternalGetCOMHRExceptionObject(hr, pCPCMD, pThis, true);
+            ex.InternalPreserveStackTrace();
+            return ex;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Exception InternalGetCOMHRExceptionObject(int hr, IntPtr pCPCMD, object pThis, bool fForWinRT);
+
+#endif // FEATURE_COMINTEROP
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr CreateCustomMarshalerHelper(IntPtr pMD, int paramToken, IntPtr hndManagedType);
+
+        //-------------------------------------------------------
+        // SafeHandle Helpers
+        //-------------------------------------------------------
+
+        // AddRefs the SH and returns the underlying unmanaged handle.
+        internal static IntPtr SafeHandleAddRef(SafeHandle pHandle, ref bool success)
+        {
+            if (pHandle == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.pHandle, ExceptionResource.ArgumentNull_SafeHandle);
+            }
+
+            pHandle.DangerousAddRef(ref success);
+            return pHandle.DangerousGetHandle();
+        }
+
+        // Releases the SH (to be called from finally block).
+        internal static void SafeHandleRelease(SafeHandle pHandle)
+        {
+            if (pHandle == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.pHandle, ExceptionResource.ArgumentNull_SafeHandle);
+            }
+
+            try
+            {
+                pHandle.DangerousRelease();
+            }
+#if MDA_SUPPORTED
+            catch (Exception ex)
+            {
+                Mda.ReportErrorSafeHandleRelease(ex);
+            }
+#else // MDA_SUPPORTED
+            catch (Exception)
+            { }
+#endif // MDA_SUPPORTED
+        }
+
+#if FEATURE_COMINTEROP
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr GetCOMIPFromRCW(object objSrc, IntPtr pCPCMD, out IntPtr ppTarget, out bool pfNeedsRelease);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr GetCOMIPFromRCW_WinRT(object objSrc, IntPtr pCPCMD, out IntPtr ppTarget);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr GetCOMIPFromRCW_WinRTSharedGeneric(object objSrc, IntPtr pCPCMD, out IntPtr ppTarget);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr GetCOMIPFromRCW_WinRTDelegate(object objSrc, IntPtr pCPCMD, out IntPtr ppTarget);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool ShouldCallWinRTInterface(object objSrc, IntPtr pCPCMD);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Delegate GetTargetForAmbiguousVariantCall(object objSrc, IntPtr pMT, out bool fUseString);
+
+        //-------------------------------------------------------
+        // Helper for the MDA RaceOnRCWCleanup
+        //-------------------------------------------------------
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void StubRegisterRCW(object pThis);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void StubUnregisterRCW(object pThis);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr GetDelegateInvokeMethod(Delegate pThis);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern object GetWinRTFactoryObject(IntPtr pCPCMD);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr GetWinRTFactoryReturnValue(object pThis, IntPtr pCtorEntry);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr GetOuterInspectable(object pThis, IntPtr pCtorMD);
+
+#if MDA_SUPPORTED
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern Exception TriggerExceptionSwallowedMDA(Exception ex, IntPtr pManagedTarget);
+#endif // MDA_SUPPORTED
+
+#endif // FEATURE_COMINTEROP
+
+#if MDA_SUPPORTED
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void CheckCollectedDelegateMDA(IntPtr pEntryThunk);
+#endif // MDA_SUPPORTED
+
+        //-------------------------------------------------------
+        // Profiler helpers
+        //-------------------------------------------------------
+#if PROFILING_SUPPORTED
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr ProfilerBeginTransitionCallback(IntPtr pSecretParam, IntPtr pThread, object pThis);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ProfilerEndTransitionCallback(IntPtr pMD, IntPtr pThread);
+#endif // PROFILING_SUPPORTED
+
+        //------------------------------------------------------
+        // misc
+        //------------------------------------------------------
+        internal static void CheckStringLength(int length)
+        {
+            CheckStringLength((uint)length);
+        }
+
+        internal static void CheckStringLength(uint length)
+        {
+            if (length > 0x7ffffff0)
+            {
+                throw new MarshalDirectiveException(SR.Marshaler_StringTooLong);
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern unsafe int strlen(sbyte* ptr);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void DecimalCanonicalizeInternal(ref Decimal dec);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern unsafe void FmtClassUpdateNativeInternal(object obj, byte* pNative, ref CleanupWorkList pCleanupWorkList);
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern unsafe void FmtClassUpdateCLRInternal(object obj, byte* pNative);
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern unsafe void LayoutDestroyNativeInternal(byte* pNative, IntPtr pMT);
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern object AllocateInternal(IntPtr typeHandle);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void MarshalToUnmanagedVaListInternal(IntPtr va_list, uint vaListSize, IntPtr pArgIterator);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void MarshalToManagedVaListInternal(IntPtr va_list, IntPtr pArgIterator);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern uint CalcVaListSize(IntPtr va_list);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ValidateObject(object obj, IntPtr pMD, object pThis);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void LogPinnedArgument(IntPtr localDesc, IntPtr nativeArg);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ValidateByref(IntPtr byref, IntPtr pMD, object pThis); // the byref is pinned so we can safely "cast" it to IntPtr
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr GetStubContext();
+
+#if BIT64
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr GetStubContextAddr();
+#endif // BIT64
+
+#if MDA_SUPPORTED
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void TriggerGCForMDA();        
+#endif // MDA_SUPPORTED
+
+#if FEATURE_ARRAYSTUB_AS_IL
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ArrayTypeCheck(object o, Object[] arr);
+#endif
+
+#if FEATURE_MULTICASTSTUB_AS_IL
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void MulticastDebuggerTraceHelper(object o, Int32 count);
+#endif
+    }  // class StubHelpers
+}
diff --git a/src/System.Private.CoreLib/src/System/Text/CodePageDataItem.Unix.cs b/src/System.Private.CoreLib/src/System/Text/CodePageDataItem.Unix.cs
new file mode 100644
index 0000000000..249457f0c1
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Text/CodePageDataItem.Unix.cs
@@ -0,0 +1,68 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Text
+{
+    internal class CodePageDataItem
+    {
+        private readonly int _codePage;
+        private readonly int _uiFamilyCodePage;
+        private readonly string _webName;
+        private readonly uint _flags;
+        private string _displayNameResourceKey;
+
+        internal CodePageDataItem(int codePage, int uiFamilyCodePage, string webName, uint flags)
+        {
+            _codePage = codePage;
+            _uiFamilyCodePage = uiFamilyCodePage;
+            _webName = webName;
+            _flags = flags;
+        }
+
+        public int CodePage
+        {
+            get { return _codePage; }
+        }
+
+        public int UIFamilyCodePage
+        {
+            get { return _uiFamilyCodePage; }
+        }
+
+        public String WebName
+        {
+            get { return _webName; }
+        }
+
+        public String HeaderName
+        {
+            get { return _webName; } // all the code pages used on unix only have a single name
+        }
+
+        public String BodyName
+        {
+            get { return _webName; } // all the code pages used on unix only have a single name
+        }
+
+        public uint Flags
+        {
+            get { return _flags; }
+        }
+
+        // PAL ends here
+
+        public string DisplayNameResourceKey
+        {
+            get
+            {
+                if (_displayNameResourceKey == null)
+                {
+                    _displayNameResourceKey = "Globalization_cp_" + CodePage;
+                }
+
+                return _displayNameResourceKey;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Text/CodePageDataItem.cs b/src/System.Private.CoreLib/src/System/Text/CodePageDataItem.cs
new file mode 100644
index 0000000000..6c7171a3e9
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Text/CodePageDataItem.cs
@@ -0,0 +1,123 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text;
+using System;
+using System.Security;
+
+namespace System.Text
+{
+    //
+    // Data item for EncodingTable.  Along with EncodingTable, they are used by 
+    // System.Text.Encoding.
+    // 
+    // This class stores a pointer to the internal data and the index into that data
+    // where our required information is found.  We load the code page, flags and uiFamilyCodePage
+    // immediately because they don't require creating an object.  Creating any of the string
+    // names is delayed until somebody actually asks for them and the names are then cached.
+
+    internal class CodePageDataItem
+    {
+        internal int m_dataIndex;
+        internal int m_uiFamilyCodePage;
+        internal String m_webName;
+        internal String m_headerName;
+        internal String m_bodyName;
+        internal uint m_flags;
+
+        internal unsafe CodePageDataItem(int dataIndex)
+        {
+            m_dataIndex = dataIndex;
+            m_uiFamilyCodePage = EncodingTable.codePageDataPtr[dataIndex].uiFamilyCodePage;
+            m_flags = EncodingTable.codePageDataPtr[dataIndex].flags;
+        }
+
+        internal static unsafe String CreateString(sbyte* pStrings, uint index)
+        {
+            if (pStrings[0] == '|') // |str1|str2|str3
+            {
+                int start = 1;
+
+                for (int i = 1; true; i++)
+                {
+                    sbyte ch = pStrings[i];
+
+                    if ((ch == '|') || (ch == 0))
+                    {
+                        if (index == 0)
+                        {
+                            return new String(pStrings, start, i - start);
+                        }
+
+                        index--;
+                        start = i + 1;
+
+                        if (ch == 0)
+                        {
+                            break;
+                        }
+                    }
+                }
+
+                throw new ArgumentException(null, nameof(pStrings));
+            }
+            else
+            {
+                return new String(pStrings);
+            }
+        }
+
+        public unsafe String WebName
+        {
+            get
+            {
+                if (m_webName == null)
+                {
+                    m_webName = CreateString(EncodingTable.codePageDataPtr[m_dataIndex].Names, 0);
+                }
+                return m_webName;
+            }
+        }
+
+        public virtual int UIFamilyCodePage
+        {
+            get
+            {
+                return m_uiFamilyCodePage;
+            }
+        }
+
+        public unsafe String HeaderName
+        {
+            get
+            {
+                if (m_headerName == null)
+                {
+                    m_headerName = CreateString(EncodingTable.codePageDataPtr[m_dataIndex].Names, 1);
+                }
+                return m_headerName;
+            }
+        }
+
+        public unsafe String BodyName
+        {
+            get
+            {
+                if (m_bodyName == null)
+                {
+                    m_bodyName = CreateString(EncodingTable.codePageDataPtr[m_dataIndex].Names, 2);
+                }
+                return m_bodyName;
+            }
+        }
+
+        public unsafe uint Flags
+        {
+            get
+            {
+                return (m_flags);
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Text/EncodingTable.Unix.cs b/src/System.Private.CoreLib/src/System/Text/EncodingTable.Unix.cs
new file mode 100644
index 0000000000..dda6d84a84
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Text/EncodingTable.Unix.cs
@@ -0,0 +1,178 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using System.Text;
+
+namespace System.Text
+{
+    internal static class EncodingTable
+    {
+        // Return a list of all EncodingInfo objects describing all of our encodings
+        internal static EncodingInfo[] GetEncodings()
+        {
+            EncodingInfo[] arrayEncodingInfo = new EncodingInfo[s_encodingDataTableItems.Length];
+
+            for (int i = 0; i < s_encodingDataTableItems.Length; i++)
+            {
+                CodePageDataItem dataItem = s_encodingDataTableItems[i];
+
+                arrayEncodingInfo[i] = new EncodingInfo(dataItem.CodePage, dataItem.WebName,
+                    SR.GetResourceString(dataItem.DisplayNameResourceKey));
+            }
+
+            return arrayEncodingInfo;
+        }
+
+        internal static int GetCodePageFromName(string name)
+        {
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
+            ushort codePage;
+            if (s_encodingDataTable.TryGetValue(name, out codePage))
+            {
+                return codePage;
+            }
+
+            // The encoding name is not valid.
+            throw new ArgumentException(
+                string.Format(
+                    CultureInfo.CurrentCulture,
+                    SR.Argument_EncodingNotSupported, name), nameof(name));
+        }
+
+        internal static CodePageDataItem GetCodePageDataItem(int codepage)
+        {
+            CodePageDataItem item;
+
+            switch (codepage)
+            {
+                case 1200:
+                    item = s_encodingDataTableItems[0];
+                    break;
+                case 1201:
+                    item = s_encodingDataTableItems[1];
+                    break;
+                case 12000:
+                    item = s_encodingDataTableItems[2];
+                    break;
+                case 12001:
+                    item = s_encodingDataTableItems[3];
+                    break;
+                case 20127:
+                    item = s_encodingDataTableItems[4];
+                    break;
+                case 28591:
+                    item = s_encodingDataTableItems[5];
+                    break;
+                case 65000:
+                    item = s_encodingDataTableItems[6];
+                    break;
+                case 65001:
+                    item = s_encodingDataTableItems[7];
+                    break;
+                default:
+                    item = null;
+                    break;
+            }
+
+            Debug.Assert(item == null || item.CodePage == codepage, "item.CodePage needs to equal the specified codepage");
+            return item;
+        }
+
+        // PAL ends here.
+
+#if DEBUG
+        static EncodingTable()
+        {
+            Debug.Assert(
+                s_encodingDataTable.Count == EncodingTableCapacity,
+                string.Format(CultureInfo.InvariantCulture,
+                    "EncodingTable s_encodingDataTable's initial capacity (EncodingTableCapacity) is incorrect.{0}Expected (s_encodingDataTable.Count): {1}, Actual (EncodingTableCapacity): {2}",
+                    Environment.NewLine,
+                    s_encodingDataTable.Count,
+                    EncodingTableCapacity));
+        }
+#endif
+
+        // NOTE: the following two lists were taken from ~\src\classlibnative\nls\encodingdata.cpp
+        // and should be kept in sync with those lists
+
+        private const int EncodingTableCapacity = 42;
+        private readonly static Dictionary<string, ushort> s_encodingDataTable =
+            new Dictionary<string, ushort>(EncodingTableCapacity, StringComparer.OrdinalIgnoreCase)
+        {
+            { "ANSI_X3.4-1968", 20127 },
+            { "ANSI_X3.4-1986", 20127 },
+            { "ascii", 20127 },
+            { "cp367", 20127 },
+            { "cp819", 28591 },
+            { "csASCII", 20127 },
+            { "csISOLatin1", 28591 },
+            { "csUnicode11UTF7", 65000 },
+            { "IBM367", 20127 },
+            { "ibm819", 28591 },
+            { "ISO-10646-UCS-2", 1200 },
+            { "iso-8859-1", 28591 },
+            { "iso-ir-100", 28591 },
+            { "iso-ir-6", 20127 },
+            { "ISO646-US", 20127 },
+            { "iso8859-1", 28591 },
+            { "ISO_646.irv:1991", 20127 },
+            { "iso_8859-1", 28591 },
+            { "iso_8859-1:1987", 28591 },
+            { "l1", 28591 },
+            { "latin1", 28591 },
+            { "ucs-2", 1200 },
+            { "unicode", 1200},
+            { "unicode-1-1-utf-7", 65000 },
+            { "unicode-1-1-utf-8", 65001 },
+            { "unicode-2-0-utf-7", 65000 },
+            { "unicode-2-0-utf-8", 65001 },
+            // People get confused about the FFFE here.  We can't change this because it'd break existing apps.
+            // This has been this way for a long time, including in Mlang.
+            // Big Endian, BOM seems backwards, think of the BOM in little endian order.
+            { "unicodeFFFE", 1201},
+            { "us", 20127 },
+            { "us-ascii", 20127 },
+            { "utf-16", 1200 },
+            { "UTF-16BE", 1201},
+            { "UTF-16LE", 1200},
+            { "utf-32", 12000 },
+            { "UTF-32BE", 12001 },
+            { "UTF-32LE", 12000 },
+            { "utf-7", 65000 },
+            { "utf-8", 65001 },
+            { "x-unicode-1-1-utf-7", 65000 },
+            { "x-unicode-1-1-utf-8", 65001 },
+            { "x-unicode-2-0-utf-7", 65000 },
+            { "x-unicode-2-0-utf-8", 65001 },
+        };
+
+        // redeclaring these constants here for readability below
+        private const uint MIMECONTF_MAILNEWS = Encoding.MIMECONTF_MAILNEWS;
+        private const uint MIMECONTF_BROWSER = Encoding.MIMECONTF_BROWSER;
+        private const uint MIMECONTF_SAVABLE_MAILNEWS = Encoding.MIMECONTF_SAVABLE_MAILNEWS;
+        private const uint MIMECONTF_SAVABLE_BROWSER = Encoding.MIMECONTF_SAVABLE_BROWSER;
+
+        // keep this array sorted by code page, so the order is consistent for GetEncodings()
+        // Remember to update GetCodePageDataItem() if this list is updated
+        private readonly static CodePageDataItem[] s_encodingDataTableItems = new[]
+        {
+            new CodePageDataItem(1200, 1200, "utf-16", MIMECONTF_SAVABLE_BROWSER), // "Unicode"
+            new CodePageDataItem(1201, 1200, "utf-16BE", 0), // Big Endian, old FFFE BOM seems backwards, think of the BOM in little endian order.
+            new CodePageDataItem(12000, 1200, "utf-32", 0), // "Unicode (UTF-32)"
+            new CodePageDataItem(12001, 1200, "utf-32BE", 0), // "Unicode (UTF-32 Big Endian)"
+            new CodePageDataItem(20127, 1252, "us-ascii", MIMECONTF_MAILNEWS | MIMECONTF_SAVABLE_MAILNEWS), // "US-ASCII"
+            new CodePageDataItem(28591, 1252, "iso-8859-1", MIMECONTF_MAILNEWS | MIMECONTF_BROWSER | MIMECONTF_SAVABLE_MAILNEWS | MIMECONTF_SAVABLE_BROWSER), // "Western European (ISO)"
+            new CodePageDataItem(65000, 1200, "utf-7", MIMECONTF_MAILNEWS | MIMECONTF_SAVABLE_MAILNEWS), // "Unicode (UTF-7)"
+            new CodePageDataItem(65001, 1200, "utf-8", MIMECONTF_MAILNEWS | MIMECONTF_BROWSER | MIMECONTF_SAVABLE_MAILNEWS | MIMECONTF_SAVABLE_BROWSER), // "Unicode (UTF-8)"
+        };
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Text/EncodingTable.cs b/src/System.Private.CoreLib/src/System/Text/EncodingTable.cs
new file mode 100644
index 0000000000..ab9fbc0ef5
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Text/EncodingTable.cs
@@ -0,0 +1,250 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Text;
+using System.Collections;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+using System.Security;
+using System.Threading;
+
+namespace System.Text
+{
+    //
+    // Data table for encoding classes.  Used by System.Text.Encoding.
+    // This class contains two hashtables to allow System.Text.Encoding
+    // to retrieve the data item either by codepage value or by webName.
+    //
+
+    // Only statics, does not need to be marked with the serializable attribute
+    internal static class EncodingTable
+    {
+        //This number is the size of the table in native.  The value is retrieved by
+        //calling the native GetNumEncodingItems().
+        private static int lastEncodingItem = GetNumEncodingItems() - 1;
+
+        //This number is the size of the code page table.  Its generated when we walk the table the first time.
+        private static volatile int lastCodePageItem;
+
+        //
+        // This points to a native data table which maps an encoding name to the correct code page.        
+        //
+        internal static unsafe InternalEncodingDataItem* encodingDataPtr = GetEncodingData();
+        //
+        // This points to a native data table which stores the properties for the code page, and
+        // the table is indexed by code page.
+        //
+        internal static unsafe InternalCodePageDataItem* codePageDataPtr = GetCodePageData();
+        //
+        // This caches the mapping of an encoding name to a code page.
+        //
+        private static Hashtable hashByName = Hashtable.Synchronized(new Hashtable(StringComparer.OrdinalIgnoreCase));
+        //
+        // THe caches the data item which is indexed by the code page value.
+        //
+        private static Hashtable hashByCodePage = Hashtable.Synchronized(new Hashtable());
+
+        // Find the data item by binary searching the table that we have in native.
+        // nativeCompareOrdinalWC is an internal-only function.
+        private static unsafe int internalGetCodePageFromName(String name)
+        {
+            int left = 0;
+            int right = lastEncodingItem;
+            int index;
+            int result;
+
+            //Binary search the array until we have only a couple of elements left and then
+            //just walk those elements.
+            while ((right - left) > 3)
+            {
+                index = ((right - left) / 2) + left;
+
+                result = nativeCompareOrdinalIgnoreCaseWC(name, encodingDataPtr[index].webName);
+
+                if (result == 0)
+                {
+                    //We found the item, return the associated codepage.
+                    return (encodingDataPtr[index].codePage);
+                }
+                else if (result < 0)
+                {
+                    //The name that we're looking for is less than our current index.
+                    right = index;
+                }
+                else
+                {
+                    //The name that we're looking for is greater than our current index
+                    left = index;
+                }
+            }
+
+            //Walk the remaining elements (it'll be 3 or fewer).
+            for (; left <= right; left++)
+            {
+                if (nativeCompareOrdinalIgnoreCaseWC(name, encodingDataPtr[left].webName) == 0)
+                {
+                    return (encodingDataPtr[left].codePage);
+                }
+            }
+            // The encoding name is not valid.
+            throw new ArgumentException(
+                String.Format(
+                    CultureInfo.CurrentCulture,
+                    SR.Argument_EncodingNotSupported, name), nameof(name));
+        }
+
+        // Return a list of all EncodingInfo objects describing all of our encodings
+        internal static unsafe EncodingInfo[] GetEncodings()
+        {
+            if (lastCodePageItem == 0)
+            {
+                int count;
+                for (count = 0; codePageDataPtr[count].codePage != 0; count++)
+                {
+                    // Count them
+                }
+                lastCodePageItem = count;
+            }
+
+            EncodingInfo[] arrayEncodingInfo = new EncodingInfo[lastCodePageItem];
+
+            int i;
+            for (i = 0; i < lastCodePageItem; i++)
+            {
+                arrayEncodingInfo[i] = new EncodingInfo(codePageDataPtr[i].codePage, CodePageDataItem.CreateString(codePageDataPtr[i].Names, 0),
+                    SR.GetResourceString("Globalization_cp_" + codePageDataPtr[i].codePage));
+            }
+
+            return arrayEncodingInfo;
+        }
+
+        /*=================================GetCodePageFromName==========================
+        **Action: Given a encoding name, return the correct code page number for this encoding.
+        **Returns: The code page for the encoding.
+        **Arguments:
+        **  name    the name of the encoding
+        **Exceptions:
+        **  ArgumentNullException if name is null.
+        **  internalGetCodePageFromName will throw ArgumentException if name is not a valid encoding name.
+        ============================================================================*/
+
+        internal static int GetCodePageFromName(String name)
+        {
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
+            Object codePageObj;
+
+            //
+            // The name is case-insensitive, but ToLower isn't free.  Check for
+            // the code page in the given capitalization first.
+            //
+            codePageObj = hashByName[name];
+
+            if (codePageObj != null)
+            {
+                return ((int)codePageObj);
+            }
+
+            //Okay, we didn't find it in the hash table, try looking it up in the 
+            //unmanaged data.
+            int codePage = internalGetCodePageFromName(name);
+
+            hashByName[name] = codePage;
+
+            return codePage;
+        }
+
+        internal static unsafe CodePageDataItem GetCodePageDataItem(int codepage)
+        {
+            CodePageDataItem dataItem;
+
+            // We synchronize around dictionary gets/sets. There's still a possibility that two threads
+            // will create a CodePageDataItem and the second will clobber the first in the dictionary. 
+            // However, that's acceptable because the contents are correct and we make no guarantees
+            // other than that. 
+
+            //Look up the item in the hashtable.
+            dataItem = (CodePageDataItem)hashByCodePage[codepage];
+
+            //If we found it, return it.
+            if (dataItem != null)
+            {
+                return dataItem;
+            }
+
+
+            //If we didn't find it, try looking it up now.
+            //If we find it, add it to the hashtable.
+            //This is a linear search, but we probably won't be doing it very often.
+            //
+            int i = 0;
+            int data;
+            while ((data = codePageDataPtr[i].codePage) != 0)
+            {
+                if (data == codepage)
+                {
+                    dataItem = new CodePageDataItem(i);
+                    hashByCodePage[codepage] = dataItem;
+                    return (dataItem);
+                }
+                i++;
+            }
+
+            //Nope, we didn't find it.
+            return null;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe InternalEncodingDataItem* GetEncodingData();
+
+        //
+        // Return the number of encoding data items.
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int GetNumEncodingItems();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe InternalCodePageDataItem* GetCodePageData();
+
+        //This will not work in case-insensitive mode for any character greater than 0x7F.  
+        //We'll throw an ArgumentException.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe int nativeCompareOrdinalIgnoreCaseWC(String strA, sbyte* strBBytes);
+    }
+
+    /*=================================InternalEncodingDataItem==========================
+    **Action: This is used to map a encoding name to a correct code page number. By doing this,
+    ** we can get the properties of this encoding via the InternalCodePageDataItem.
+    **
+    ** We use this structure to access native data exposed by the native side.
+    ============================================================================*/
+
+    [System.Runtime.InteropServices.StructLayout(LayoutKind.Sequential)]
+    internal unsafe struct InternalEncodingDataItem
+    {
+        internal sbyte* webName;
+        internal UInt16 codePage;
+    }
+
+    /*=================================InternalCodePageDataItem==========================
+    **Action: This is used to access the properties related to a code page.
+    ** We use this structure to access native data exposed by the native side.
+    ============================================================================*/
+
+    [System.Runtime.InteropServices.StructLayout(LayoutKind.Sequential)]
+    internal unsafe struct InternalCodePageDataItem
+    {
+        internal UInt16 codePage;
+        internal UInt16 uiFamilyCodePage;
+        internal uint flags;
+        internal sbyte* Names;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Text/StringBuilder.CoreCLR.cs b/src/System.Private.CoreLib/src/System/Text/StringBuilder.CoreCLR.cs
new file mode 100644
index 0000000000..c7e0cb3b74
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Text/StringBuilder.CoreCLR.cs
@@ -0,0 +1,123 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System.Text
+{
+    public partial class StringBuilder
+    {
+        private int GetReplaceBufferCapacity(int requiredCapacity)
+        {
+            // This function assumes that required capacity will be less 
+            // than the max capacity of the StringBuilder
+            Diagnostics.Debug.Assert(requiredCapacity <= m_MaxCapacity);
+
+            int newCapacity = Capacity;
+            // Round the current capacity to the nearest multiple of 2
+            // that is larger than the required capacity.
+            if (newCapacity < requiredCapacity)
+            {
+                newCapacity = (requiredCapacity + 1) & ~1;
+            }
+            return newCapacity;
+        }
+
+        internal unsafe void ReplaceBufferInternal(char* newBuffer, int newLength)
+        {
+            if (newLength > m_MaxCapacity)
+                throw new ArgumentOutOfRangeException("capacity", SR.ArgumentOutOfRange_Capacity);
+
+            // Leave space for a NUL character at the end, the previous implementation did this
+            m_ChunkChars = new char[GetReplaceBufferCapacity(newLength + 1)];
+            new Span<char>(newBuffer, newLength).CopyTo(m_ChunkChars);
+            m_ChunkLength = newLength;
+            m_ChunkPrevious = null;
+            m_ChunkOffset = 0;
+        }
+
+        internal unsafe void ReplaceBufferAnsiInternal(sbyte* newBuffer, int newLength)
+        {
+            if (newLength > m_MaxCapacity)
+                throw new ArgumentOutOfRangeException("capacity", SR.ArgumentOutOfRange_Capacity);
+
+            // Leave space for a NUL character at the end, the previous implementation did this
+            m_ChunkChars = new char[GetReplaceBufferCapacity(newLength + 1)];
+
+            int convertedChars;
+
+            fixed (char* pChunkChars = m_ChunkChars)
+            {
+                Diagnostics.Debug.Assert(newLength < m_ChunkChars.Length);
+
+                // The incoming string buffer is supposed to have been populated by the 
+                // P/Invoke-called native function but there's no way to know if that really
+                // happened, the native function might populate the buffer only in certain
+                // circumstances (e.g. only if the function succeeds).
+                //
+                // As such, the buffer might contain bogus characters that cannot be converted 
+                // to Unicode and in that case conversion should not result in exceptions that
+                // the managed caller does not expect. Instead, the caller is expected to know
+                // when the resulting string is not valid and not use it.
+                //
+                // Both MultiByteToWideChar and the UTF8Encoding instance used on Unix-like
+                // platforms default to replacing invalid characters with the Unicode replacement
+                // character U+FFFD.
+#if PLATFORM_UNIX
+                convertedChars = Encoding.UTF8.GetChars((byte*)newBuffer, newLength, pChunkChars, newLength);
+#else
+                convertedChars = Interop.Kernel32.MultiByteToWideChar(
+                    Interop.Kernel32.CP_ACP,
+                    Interop.Kernel32.MB_PRECOMPOSED,
+                    (byte*)newBuffer,
+                    newLength,
+                    pChunkChars,
+                    newLength);
+#endif
+            }
+
+            m_ChunkOffset = 0;
+            m_ChunkLength = convertedChars;
+            m_ChunkPrevious = null;
+        }
+
+        /// <summary>
+        /// Copies the contents of this builder to the specified buffer.
+        /// </summary>
+        /// <param name="dest">The destination buffer.</param>
+        /// <param name="len">The number of bytes in the destination buffer.</param>
+        internal unsafe void InternalCopy(IntPtr dest, int len)
+        {
+            if (len == 0)
+            {
+                return;
+            }
+
+            bool isLastChunk = true;
+            byte* dstPtr = (byte*)dest.ToPointer();
+            StringBuilder currentSrc = FindChunkForByte(len);
+
+            do
+            {
+                int chunkOffsetInBytes = currentSrc.m_ChunkOffset * sizeof(char);
+                int chunkLengthInBytes = currentSrc.m_ChunkLength * sizeof(char);
+                fixed (char* charPtr = &currentSrc.m_ChunkChars[0])
+                {
+                    byte* srcPtr = (byte*)charPtr;
+                    if (isLastChunk)
+                    {
+                        isLastChunk = false;
+                        Buffer.Memcpy(dstPtr + chunkOffsetInBytes, srcPtr, len - chunkOffsetInBytes);
+                    }
+                    else
+                    {
+                        Buffer.Memcpy(dstPtr + chunkOffsetInBytes, srcPtr, chunkLengthInBytes);
+                    }
+                }
+                currentSrc = currentSrc.m_ChunkPrevious;
+            }
+            while (currentSrc != null);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Text/StringBuilderCache.cs b/src/System.Private.CoreLib/src/System/Text/StringBuilderCache.cs
new file mode 100644
index 0000000000..a8a5e2c7f4
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Text/StringBuilderCache.cs
@@ -0,0 +1,84 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+** Purpose: provide a cached reusable instance of stringbuilder
+**          per thread  it's an optimisation that reduces the 
+**          number of instances constructed and collected.
+**
+**  Acquire - is used to get a string builder to use of a 
+**            particular size.  It can be called any number of 
+**            times, if a stringbuilder is in the cache then
+**            it will be returned and the cache emptied.
+**            subsequent calls will return a new stringbuilder.
+**
+**            A StringBuilder instance is cached in 
+**            Thread Local Storage and so there is one per thread
+**
+**  Release - Place the specified builder in the cache if it is 
+**            not too big.
+**            The stringbuilder should not be used after it has 
+**            been released.
+**            Unbalanced Releases are perfectly acceptable.  It
+**            will merely cause the runtime to create a new 
+**            stringbuilder next time Acquire is called.
+**
+**  GetStringAndRelease
+**          - ToString() the stringbuilder, Release it to the 
+**            cache and return the resulting string
+**
+===========================================================*/
+
+using System.Threading;
+
+namespace System.Text
+{
+    internal static class StringBuilderCache
+    {
+        // The value 360 was chosen in discussion with performance experts as a compromise between using
+        // as litle memory (per thread) as possible and still covering a large part of short-lived
+        // StringBuilder creations on the startup path of VS designers.
+        private const int MAX_BUILDER_SIZE = 360;
+
+        [ThreadStatic]
+        private static StringBuilder CachedInstance;
+
+        public static StringBuilder Acquire(int capacity = StringBuilder.DefaultCapacity)
+        {
+            if (capacity <= MAX_BUILDER_SIZE)
+            {
+                StringBuilder sb = StringBuilderCache.CachedInstance;
+                if (sb != null)
+                {
+                    // Avoid stringbuilder block fragmentation by getting a new StringBuilder
+                    // when the requested size is larger than the current capacity
+                    if (capacity <= sb.Capacity)
+                    {
+                        StringBuilderCache.CachedInstance = null;
+                        sb.Clear();
+                        return sb;
+                    }
+                }
+            }
+            return new StringBuilder(capacity);
+        }
+
+        public static void Release(StringBuilder sb)
+        {
+            if (sb.Capacity <= MAX_BUILDER_SIZE)
+            {
+                StringBuilderCache.CachedInstance = sb;
+            }
+        }
+
+        public static string GetStringAndRelease(StringBuilder sb)
+        {
+            string result = sb.ToString();
+            Release(sb);
+            return result;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/CancellationToken.cs b/src/System.Private.CoreLib/src/System/Threading/CancellationToken.cs
new file mode 100644
index 0000000000..886210c560
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/CancellationToken.cs
@@ -0,0 +1,317 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+
+namespace System.Threading
+{
+    /// <summary>
+    /// Propagates notification that operations should be canceled.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// A <see cref="CancellationToken"/> may be created directly in an unchangeable canceled or non-canceled state
+    /// using the CancellationToken's constructors. However, to have a CancellationToken that can change 
+    /// from a non-canceled to a canceled state, 
+    /// <see cref="System.Threading.CancellationTokenSource">CancellationTokenSource</see> must be used.
+    /// CancellationTokenSource exposes the associated CancellationToken that may be canceled by the source through its 
+    /// <see cref="System.Threading.CancellationTokenSource.Token">Token</see> property. 
+    /// </para>
+    /// <para>
+    /// Once canceled, a token may not transition to a non-canceled state, and a token whose 
+    /// <see cref="CanBeCanceled"/> is false will never change to one that can be canceled.
+    /// </para>
+    /// <para>
+    /// All members of this struct are thread-safe and may be used concurrently from multiple threads.
+    /// </para>
+    /// </remarks>
+    [DebuggerDisplay("IsCancellationRequested = {IsCancellationRequested}")]
+    public readonly struct CancellationToken
+    {
+        private readonly static Action<object> s_actionToActionObjShunt = obj => ((Action)obj)();
+
+        // The backing TokenSource.  
+        // if null, it implicitly represents the same thing as new CancellationToken(false).
+        // When required, it will be instantiated to reflect this.
+        private readonly CancellationTokenSource _source;
+        //!! warning. If more fields are added, the assumptions in CreateLinkedToken may no longer be valid
+
+        /// <summary>
+        /// Returns an empty CancellationToken value.
+        /// </summary>
+        /// <remarks>
+        /// The <see cref="CancellationToken"/> value returned by this property will be non-cancelable by default.
+        /// </remarks>
+        public static CancellationToken None => default(CancellationToken);
+
+        /// <summary>
+        /// Gets whether cancellation has been requested for this token.
+        /// </summary>
+        /// <value>Whether cancellation has been requested for this token.</value>
+        /// <remarks>
+        /// <para>
+        /// This property indicates whether cancellation has been requested for this token, 
+        /// either through the token initially being constructed in a canceled state, or through
+        /// calling <see cref="System.Threading.CancellationTokenSource.Cancel()">Cancel</see> 
+        /// on the token's associated <see cref="CancellationTokenSource"/>.
+        /// </para>
+        /// <para>
+        /// If this property is true, it only guarantees that cancellation has been requested.  
+        /// It does not guarantee that every registered handler
+        /// has finished executing, nor that cancellation requests have finished propagating
+        /// to all registered handlers.  Additional synchronization may be required,
+        /// particularly in situations where related objects are being canceled concurrently.
+        /// </para>
+        /// </remarks>
+        public bool IsCancellationRequested => _source != null && _source.IsCancellationRequested;
+
+        /// <summary>
+        /// Gets whether this token is capable of being in the canceled state.
+        /// </summary>
+        /// <remarks>
+        /// If CanBeCanceled returns false, it is guaranteed that the token will never transition
+        /// into a canceled state, meaning that <see cref="IsCancellationRequested"/> will never
+        /// return true.
+        /// </remarks>
+        public bool CanBeCanceled => _source != null;
+
+        /// <summary>
+        /// Gets a <see cref="T:System.Threading.WaitHandle"/> that is signaled when the token is canceled.</summary>
+        /// <remarks>
+        /// Accessing this property causes a <see cref="T:System.Threading.WaitHandle">WaitHandle</see>
+        /// to be instantiated.  It is preferable to only use this property when necessary, and to then
+        /// dispose the associated <see cref="CancellationTokenSource"/> instance at the earliest opportunity (disposing
+        /// the source will dispose of this allocated handle).  The handle should not be closed or disposed directly.
+        /// </remarks>
+        /// <exception cref="T:System.ObjectDisposedException">The associated <see
+        /// cref="T:System.Threading.CancellationTokenSource">CancellationTokenSource</see> has been disposed.</exception>
+        public WaitHandle WaitHandle => (_source ?? CancellationTokenSource.s_neverCanceledSource).WaitHandle;
+
+        // public CancellationToken()
+        // this constructor is implicit for structs
+        //   -> this should behaves exactly as for new CancellationToken(false)
+
+        /// <summary>
+        /// Internal constructor only a CancellationTokenSource should create a CancellationToken
+        /// </summary>
+        internal CancellationToken(CancellationTokenSource source) => _source = source;
+
+        /// <summary>
+        /// Initializes the <see cref="T:System.Threading.CancellationToken">CancellationToken</see>.
+        /// </summary>
+        /// <param name="canceled">
+        /// The canceled state for the token.
+        /// </param>
+        /// <remarks>
+        /// Tokens created with this constructor will remain in the canceled state specified
+        /// by the <paramref name="canceled"/> parameter.  If <paramref name="canceled"/> is false,
+        /// both <see cref="CanBeCanceled"/> and <see cref="IsCancellationRequested"/> will be false.
+        /// If <paramref name="canceled"/> is true,
+        /// both <see cref="CanBeCanceled"/> and <see cref="IsCancellationRequested"/> will be true. 
+        /// </remarks>
+        public CancellationToken(bool canceled) : this(canceled ? CancellationTokenSource.s_canceledSource : null)
+        {
+        }
+
+        /// <summary>
+        /// Registers a delegate that will be called when this <see cref="T:System.Threading.CancellationToken">CancellationToken</see> is canceled.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// If this token is already in the canceled state, the
+        /// delegate will be run immediately and synchronously. Any exception the delegate generates will be
+        /// propagated out of this method call.
+        /// </para>
+        /// <para>
+        /// The current <see cref="System.Threading.ExecutionContext">ExecutionContext</see>, if one exists, will be captured
+        /// along with the delegate and will be used when executing it.
+        /// </para>
+        /// </remarks>
+        /// <param name="callback">The delegate to be executed when the <see cref="T:System.Threading.CancellationToken">CancellationToken</see> is canceled.</param>
+        /// <returns>The <see cref="T:System.Threading.CancellationTokenRegistration"/> instance that can 
+        /// be used to unregister the callback.</returns>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="callback"/> is null.</exception>
+        public CancellationTokenRegistration Register(Action callback) =>
+            Register(
+                s_actionToActionObjShunt,
+                callback ?? throw new ArgumentNullException(nameof(callback)),
+                useSyncContext: false,
+                useExecutionContext: true);
+
+        /// <summary>
+        /// Registers a delegate that will be called when this 
+        /// <see cref="T:System.Threading.CancellationToken">CancellationToken</see> is canceled.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// If this token is already in the canceled state, the
+        /// delegate will be run immediately and synchronously. Any exception the delegate generates will be
+        /// propagated out of this method call.
+        /// </para>
+        /// <para>
+        /// The current <see cref="System.Threading.ExecutionContext">ExecutionContext</see>, if one exists, will be captured
+        /// along with the delegate and will be used when executing it.
+        /// </para>
+        /// </remarks>
+        /// <param name="callback">The delegate to be executed when the <see cref="T:System.Threading.CancellationToken">CancellationToken</see> is canceled.</param>
+        /// <param name="useSynchronizationContext">A Boolean value that indicates whether to capture
+        /// the current <see cref="T:System.Threading.SynchronizationContext">SynchronizationContext</see> and use it
+        /// when invoking the <paramref name="callback"/>.</param>
+        /// <returns>The <see cref="T:System.Threading.CancellationTokenRegistration"/> instance that can 
+        /// be used to unregister the callback.</returns>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="callback"/> is null.</exception>
+        public CancellationTokenRegistration Register(Action callback, bool useSynchronizationContext) =>
+            Register(
+                s_actionToActionObjShunt,
+                callback ?? throw new ArgumentNullException(nameof(callback)),
+                useSynchronizationContext,
+                useExecutionContext: true);
+
+        /// <summary>
+        /// Registers a delegate that will be called when this 
+        /// <see cref="T:System.Threading.CancellationToken">CancellationToken</see> is canceled.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// If this token is already in the canceled state, the
+        /// delegate will be run immediately and synchronously. Any exception the delegate generates will be
+        /// propagated out of this method call.
+        /// </para>
+        /// <para>
+        /// The current <see cref="System.Threading.ExecutionContext">ExecutionContext</see>, if one exists, will be captured
+        /// along with the delegate and will be used when executing it.
+        /// </para>
+        /// </remarks>
+        /// <param name="callback">The delegate to be executed when the <see cref="T:System.Threading.CancellationToken">CancellationToken</see> is canceled.</param>
+        /// <param name="state">The state to pass to the <paramref name="callback"/> when the delegate is invoked.  This may be null.</param>
+        /// <returns>The <see cref="T:System.Threading.CancellationTokenRegistration"/> instance that can 
+        /// be used to unregister the callback.</returns>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="callback"/> is null.</exception>
+        public CancellationTokenRegistration Register(Action<object> callback, object state) =>
+            Register(callback, state, useSyncContext: false, useExecutionContext: true);
+
+        /// <summary>
+        /// Registers a delegate that will be called when this 
+        /// <see cref="T:System.Threading.CancellationToken">CancellationToken</see> is canceled.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// If this token is already in the canceled state, the
+        /// delegate will be run immediately and synchronously. Any exception the delegate generates will be
+        /// propagated out of this method call.
+        /// </para>
+        /// <para>
+        /// The current <see cref="System.Threading.ExecutionContext">ExecutionContext</see>, if one exists, 
+        /// will be captured along with the delegate and will be used when executing it.
+        /// </para>
+        /// </remarks>
+        /// <param name="callback">The delegate to be executed when the <see cref="T:System.Threading.CancellationToken">CancellationToken</see> is canceled.</param>
+        /// <param name="state">The state to pass to the <paramref name="callback"/> when the delegate is invoked.  This may be null.</param>
+        /// <param name="useSynchronizationContext">A Boolean value that indicates whether to capture
+        /// the current <see cref="T:System.Threading.SynchronizationContext">SynchronizationContext</see> and use it
+        /// when invoking the <paramref name="callback"/>.</param>
+        /// <returns>The <see cref="T:System.Threading.CancellationTokenRegistration"/> instance that can 
+        /// be used to unregister the callback.</returns>
+        /// <exception cref="T:System.ArgumentNullException"><paramref name="callback"/> is null.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The associated <see
+        /// cref="T:System.Threading.CancellationTokenSource">CancellationTokenSource</see> has been disposed.</exception>
+        public CancellationTokenRegistration Register(Action<object> callback, object state, bool useSynchronizationContext) =>
+            Register(callback, state, useSynchronizationContext, useExecutionContext: true);
+
+        // helper for internal registration needs that don't require an EC capture (e.g. creating linked token sources, or registering unstarted TPL tasks)
+        // has a handy signature, and skips capturing execution context.
+        internal CancellationTokenRegistration InternalRegisterWithoutEC(Action<object> callback, object state) =>
+            Register(callback, state, useSyncContext: false, useExecutionContext: false);
+
+        // the real work..
+        private CancellationTokenRegistration Register(Action<object> callback, object state, bool useSyncContext, bool useExecutionContext)
+        {
+            if (callback == null)
+            {
+                throw new ArgumentNullException(nameof(callback));
+            }
+
+            CancellationTokenSource source = _source;
+            return source != null ?
+                source.InternalRegister(callback, state, useSyncContext ? SynchronizationContext.Current : null, useExecutionContext ? ExecutionContext.Capture() : null) :
+                default(CancellationTokenRegistration); // Nothing to do for tokens than can never reach the canceled state. Give back a dummy registration.
+        }
+
+        /// <summary>
+        /// Determines whether the current <see cref="T:System.Threading.CancellationToken">CancellationToken</see> instance is equal to the 
+        /// specified token.
+        /// </summary>
+        /// <param name="other">The other <see cref="T:System.Threading.CancellationToken">CancellationToken</see> to which to compare this
+        /// instance.</param>
+        /// <returns>True if the instances are equal; otherwise, false. Two tokens are equal if they are associated
+        /// with the same <see cref="T:System.Threading.CancellationTokenSource">CancellationTokenSource</see> or if they were both constructed 
+        /// from public CancellationToken constructors and their <see cref="IsCancellationRequested"/> values are equal.</returns>
+        public bool Equals(CancellationToken other) => _source == other._source;
+
+        /// <summary>
+        /// Determines whether the current <see cref="T:System.Threading.CancellationToken">CancellationToken</see> instance is equal to the 
+        /// specified <see cref="T:System.Object"/>.
+        /// </summary>
+        /// <param name="other">The other object to which to compare this instance.</param>
+        /// <returns>True if <paramref name="other"/> is a <see cref="T:System.Threading.CancellationToken">CancellationToken</see>
+        /// and if the two instances are equal; otherwise, false. Two tokens are equal if they are associated
+        /// with the same <see cref="T:System.Threading.CancellationTokenSource">CancellationTokenSource</see> or if they were both constructed 
+        /// from public CancellationToken constructors and their <see cref="IsCancellationRequested"/> values are equal.</returns>
+        /// <exception cref="T:System.ObjectDisposedException">An associated <see
+        /// cref="T:System.Threading.CancellationTokenSource">CancellationTokenSource</see> has been disposed.</exception>
+        public override bool Equals(object other) => other is CancellationToken && Equals((CancellationToken)other);
+
+        /// <summary>
+        /// Serves as a hash function for a <see cref="T:System.Threading.CancellationToken">CancellationToken</see>.
+        /// </summary>
+        /// <returns>A hash code for the current <see cref="T:System.Threading.CancellationToken">CancellationToken</see> instance.</returns>
+        public override int GetHashCode() => (_source ?? CancellationTokenSource.s_neverCanceledSource).GetHashCode();
+
+        /// <summary>
+        /// Determines whether two <see cref="T:System.Threading.CancellationToken">CancellationToken</see> instances are equal.
+        /// </summary>
+        /// <param name="left">The first instance.</param>
+        /// <param name="right">The second instance.</param>
+        /// <returns>True if the instances are equal; otherwise, false.</returns>
+        /// <exception cref="T:System.ObjectDisposedException">An associated <see
+        /// cref="T:System.Threading.CancellationTokenSource">CancellationTokenSource</see> has been disposed.</exception>
+        public static bool operator ==(CancellationToken left, CancellationToken right) => left.Equals(right);
+
+        /// <summary>
+        /// Determines whether two <see cref="T:System.Threading.CancellationToken">CancellationToken</see> instances are not equal.
+        /// </summary>
+        /// <param name="left">The first instance.</param>
+        /// <param name="right">The second instance.</param>
+        /// <returns>True if the instances are not equal; otherwise, false.</returns>
+        /// <exception cref="T:System.ObjectDisposedException">An associated <see
+        /// cref="T:System.Threading.CancellationTokenSource">CancellationTokenSource</see> has been disposed.</exception>
+        public static bool operator !=(CancellationToken left, CancellationToken right) => !left.Equals(right);
+
+        /// <summary>
+        /// Throws a <see cref="T:System.OperationCanceledException">OperationCanceledException</see> if
+        /// this token has had cancellation requested.
+        /// </summary>
+        /// <remarks>
+        /// This method provides functionality equivalent to:
+        /// <code>
+        /// if (token.IsCancellationRequested) 
+        ///    throw new OperationCanceledException(token);
+        /// </code>
+        /// </remarks>
+        /// <exception cref="System.OperationCanceledException">The token has had cancellation requested.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The associated <see
+        /// cref="T:System.Threading.CancellationTokenSource">CancellationTokenSource</see> has been disposed.</exception>
+        public void ThrowIfCancellationRequested()
+        {
+            if (IsCancellationRequested)
+            {
+                ThrowOperationCanceledException();
+            }
+        }
+
+        // Throws an OCE; separated out to enable better inlining of ThrowIfCancellationRequested
+        private void ThrowOperationCanceledException() =>
+            throw new OperationCanceledException(SR.OperationCanceled, this);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/CancellationTokenRegistration.cs b/src/System.Private.CoreLib/src/System/Threading/CancellationTokenRegistration.cs
new file mode 100644
index 0000000000..3c964a954c
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/CancellationTokenRegistration.cs
@@ -0,0 +1,126 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Threading
+{
+    /// <summary>
+    /// Represents a callback delegate that has been registered with a <see cref="T:System.Threading.CancellationToken">CancellationToken</see>.
+    /// </summary>
+    /// <remarks>
+    /// To unregister a callback, dispose the corresponding Registration instance.
+    /// </remarks>
+    public readonly struct CancellationTokenRegistration : IEquatable<CancellationTokenRegistration>, IDisposable
+    {
+        private readonly long _id;
+        private readonly CancellationTokenSource.CallbackNode _node;
+
+        internal CancellationTokenRegistration(long id, CancellationTokenSource.CallbackNode node)
+        {
+            _id = id;
+            _node = node;
+        }
+
+        /// <summary>
+        /// Disposes of the registration and unregisters the target callback from the associated 
+        /// <see cref="T:System.Threading.CancellationToken">CancellationToken</see>.
+        /// If the target callback is currently executing, this method will wait until it completes, except
+        /// in the degenerate cases where a callback method unregisters itself.
+        /// </summary>
+        public void Dispose()
+        {
+            CancellationTokenSource.CallbackNode node = _node;
+            if (node != null && !node.Partition.Unregister(_id, node))
+            {
+                WaitForCallbackIfNecessary();
+            }
+        }
+
+        /// <summary>
+        /// Gets the <see cref="CancellationToken"/> with which this registration is associated.  If the
+        /// registration isn't associated with a token (such as after the registration has been disposed),
+        /// this will return a default token.
+        /// </summary>
+        public CancellationToken Token => _node?.Partition.Source.Token ?? default(CancellationToken);
+
+        /// <summary>
+        /// Disposes of the registration and unregisters the target callback from the associated 
+        /// <see cref="T:System.Threading.CancellationToken">CancellationToken</see>.
+        /// </summary>
+        internal bool Unregister() // corefx currently has an InternalsVisibleTo dependency on this
+        {
+            CancellationTokenSource.CallbackNode node = _node;
+            return node != null && node.Partition.Unregister(_id, node);
+        }
+
+        private void WaitForCallbackIfNecessary()
+        {
+            // We're a valid registration but we were unable to unregister, which means the callback wasn't in the list,
+            // which means either it already executed or it's currently executing. We guarantee that we will not return
+            // if the callback is being executed (assuming we are not currently called by the callback itself)
+            // We achieve this by the following rules:
+            //    1. If we are called in the context of an executing callback, no need to wait (determined by tracking callback-executor threadID)
+            //       - if the currently executing callback is this CTR, then waiting would deadlock. (We choose to return rather than deadlock)
+            //       - if not, then this CTR cannot be the one executing, hence no need to wait
+            //    2. If unregistration failed, and we are on a different thread, then the callback may be running under control of cts.Cancel()
+            //       => poll until cts.ExecutingCallback is not the one we are trying to unregister.
+            CancellationTokenSource source = _node.Partition.Source;
+            if (source.IsCancellationRequested && // Running callbacks has commenced.
+                !source.IsCancellationCompleted && // Running callbacks hasn't finished.
+                source.ThreadIDExecutingCallbacks != Thread.CurrentThread.ManagedThreadId) // The executing thread ID is not this thread's ID.
+            {
+                // Callback execution is in progress, the executing thread is different to us and has taken the callback for execution
+                // so observe and wait until this target callback is no longer the executing callback.
+                source.WaitForCallbackToComplete(_id);
+            }
+        }
+
+        /// <summary>
+        /// Determines whether two <see
+        /// cref="T:System.Threading.CancellationTokenRegistration">CancellationTokenRegistration</see>
+        /// instances are equal.
+        /// </summary>
+        /// <param name="left">The first instance.</param>
+        /// <param name="right">The second instance.</param>
+        /// <returns>True if the instances are equal; otherwise, false.</returns>
+        public static bool operator ==(CancellationTokenRegistration left, CancellationTokenRegistration right) => left.Equals(right);
+
+        /// <summary>
+        /// Determines whether two <see cref="T:System.Threading.CancellationTokenRegistration">CancellationTokenRegistration</see> instances are not equal.
+        /// </summary>
+        /// <param name="left">The first instance.</param>
+        /// <param name="right">The second instance.</param>
+        /// <returns>True if the instances are not equal; otherwise, false.</returns>
+        public static bool operator !=(CancellationTokenRegistration left, CancellationTokenRegistration right) => !left.Equals(right);
+
+        /// <summary>
+        /// Determines whether the current <see cref="T:System.Threading.CancellationTokenRegistration">CancellationTokenRegistration</see> instance is equal to the 
+        /// specified <see cref="T:System.Object"/>.
+        /// </summary> 
+        /// <param name="obj">The other object to which to compare this instance.</param>
+        /// <returns>True, if both this and <paramref name="obj"/> are equal. False, otherwise.
+        /// Two <see cref="T:System.Threading.CancellationTokenRegistration">CancellationTokenRegistration</see> instances are equal if
+        /// they both refer to the output of a single call to the same Register method of a 
+        /// <see cref="T:System.Threading.CancellationToken">CancellationToken</see>. 
+        /// </returns>
+        public override bool Equals(object obj) => obj is CancellationTokenRegistration && Equals((CancellationTokenRegistration)obj);
+
+        /// <summary>
+        /// Determines whether the current <see cref="T:System.Threading.CancellationToken">CancellationToken</see> instance is equal to the 
+        /// specified <see cref="T:System.Object"/>.
+        /// </summary> 
+        /// <param name="other">The other <see cref="T:System.Threading.CancellationTokenRegistration">CancellationTokenRegistration</see> to which to compare this instance.</param>
+        /// <returns>True, if both this and <paramref name="other"/> are equal. False, otherwise.
+        /// Two <see cref="T:System.Threading.CancellationTokenRegistration">CancellationTokenRegistration</see> instances are equal if
+        /// they both refer to the output of a single call to the same Register method of a 
+        /// <see cref="T:System.Threading.CancellationToken">CancellationToken</see>. 
+        /// </returns>
+        public bool Equals(CancellationTokenRegistration other) => _node == other._node && _id == other._id;
+
+        /// <summary>
+        /// Serves as a hash function for a <see cref="T:System.Threading.CancellationTokenRegistration">CancellationTokenRegistration.</see>.
+        /// </summary>
+        /// <returns>A hash code for the current <see cref="T:System.Threading.CancellationTokenRegistration">CancellationTokenRegistration</see> instance.</returns>
+        public override int GetHashCode() => _node != null ? _node.GetHashCode() ^ _id.GetHashCode()  : _id.GetHashCode();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/CancellationTokenSource.cs b/src/System.Private.CoreLib/src/System/Threading/CancellationTokenSource.cs
new file mode 100644
index 0000000000..3b47cf57cf
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/CancellationTokenSource.cs
@@ -0,0 +1,943 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System.Threading
+{
+    /// <summary>Signals to a <see cref="CancellationToken"/> that it should be canceled.</summary>
+    /// <remarks>
+    /// <para>
+    /// <see cref="CancellationTokenSource"/> is used to instantiate a <see cref="CancellationToken"/> (via
+    /// the source's <see cref="Token">Token</see> property) that can be handed to operations that wish to be
+    /// notified of cancellation or that can be used to register asynchronous operations for cancellation. That
+    /// token may have cancellation requested by calling to the source's <see cref="Cancel()"/> method.
+    /// </para>
+    /// <para>
+    /// All members of this class, except <see cref="Dispose"/>, are thread-safe and may be used
+    /// concurrently from multiple threads.
+    /// </para>
+    /// </remarks>
+    public class CancellationTokenSource : IDisposable
+    {
+        /// <summary>A <see cref="CancellationTokenSource"/> that's already canceled.</summary>
+        internal static readonly CancellationTokenSource s_canceledSource = new CancellationTokenSource() { _state = NotifyingCompleteState };
+        /// <summary>A <see cref="CancellationTokenSource"/> that's never canceled.  This isn't enforced programmatically, only by usage.  Do not cancel!</summary>
+        internal static readonly CancellationTokenSource s_neverCanceledSource = new CancellationTokenSource();
+
+        /// <summary>Delegate used with <see cref="Timer"/> to trigger cancellation of a <see cref="CancellationTokenSource"/>.</summary>
+        private static readonly TimerCallback s_timerCallback = obj =>
+            ((CancellationTokenSource)obj).NotifyCancellation(throwOnFirstException: false); // skip ThrowIfDisposed() check in Cancel()
+
+        /// <summary>The number of callback partitions to use in a <see cref="CancellationTokenSource"/>. Must be a power of 2.</summary>
+        private static readonly int s_numPartitions = GetPartitionCount();
+        /// <summary><see cref="s_numPartitions"/> - 1, used to quickly mod into <see cref="_callbackPartitions"/>.</summary>
+        private static readonly int s_numPartitionsMask = s_numPartitions - 1;
+
+        /// <summary>The current state of the CancellationTokenSource.</summary>
+        private volatile int _state;
+        /// <summary>The ID of the thread currently executing the main body of CTS.Cancel()</summary>
+        /// <remarks>
+        /// This helps us to know if a call to ctr.Dispose() is running 'within' a cancellation callback.
+        /// This is updated as we move between the main thread calling cts.Cancel() and any syncContexts
+        /// that are used to actually run the callbacks.
+        /// </remarks>
+        private volatile int _threadIDExecutingCallbacks = -1;
+        /// <summary>Tracks the running callback to assist ctr.Dispose() to wait for the target callback to complete.</summary>
+        private long _executingCallbackId;
+        /// <summary>Partitions of callbacks.  Split into multiple partitions to help with scalability of registering/unregistering; each is protected by its own lock.</summary>
+        private volatile CallbackPartition[] _callbackPartitions;
+        /// <summary>Timer used by CancelAfter and Timer-related ctors.</summary>
+        private volatile Timer _timer;
+        /// <summary><see cref="System.Threading.WaitHandle"/> lazily initialized and returned from <see cref="WaitHandle"/>.</summary>
+        private volatile ManualResetEvent _kernelEvent;
+        /// <summary>Whether this <see cref="CancellationTokenSource"/> has been disposed.</summary>
+        private bool _disposed;
+
+        // legal values for _state
+        private const int NotCanceledState = 1;
+        private const int NotifyingState = 2;
+        private const int NotifyingCompleteState = 3;
+
+        /// <summary>Gets whether cancellation has been requested for this <see cref="CancellationTokenSource" />.</summary>
+        /// <value>Whether cancellation has been requested for this <see cref="CancellationTokenSource" />.</value>
+        /// <remarks>
+        /// <para>
+        /// This property indicates whether cancellation has been requested for this token source, such as
+        /// due to a call to its <see cref="Cancel()"/> method.
+        /// </para>
+        /// <para>
+        /// If this property returns true, it only guarantees that cancellation has been requested. It does not
+        /// guarantee that every handler registered with the corresponding token has finished executing, nor
+        /// that cancellation requests have finished propagating to all registered handlers. Additional
+        /// synchronization may be required, particularly in situations where related objects are being
+        /// canceled concurrently.
+        /// </para>
+        /// </remarks>
+        public bool IsCancellationRequested => _state >= NotifyingState;
+
+        /// <summary>A simple helper to determine whether cancellation has finished.</summary>
+        internal bool IsCancellationCompleted => _state == NotifyingCompleteState;
+
+        /// <summary>A simple helper to determine whether disposal has occurred.</summary>
+        internal bool IsDisposed => _disposed;
+
+        /// <summary>The ID of the thread that is running callbacks.</summary>
+        internal int ThreadIDExecutingCallbacks
+        {
+            get => _threadIDExecutingCallbacks;
+            set => _threadIDExecutingCallbacks = value;
+        }
+
+        /// <summary>Gets the <see cref="CancellationToken"/> associated with this <see cref="CancellationTokenSource"/>.</summary>
+        /// <value>The <see cref="CancellationToken"/> associated with this <see cref="CancellationTokenSource"/>.</value>
+        /// <exception cref="ObjectDisposedException">The token source has been disposed.</exception>
+        public CancellationToken Token
+        {
+            get
+            {
+                ThrowIfDisposed();
+                return new CancellationToken(this);
+            }
+        }
+
+        internal WaitHandle WaitHandle
+        {
+            get
+            {
+                ThrowIfDisposed();
+
+                // Return the handle if it was already allocated.
+                if (_kernelEvent != null)
+                {
+                    return _kernelEvent;
+                }
+
+                // Lazily-initialize the handle.
+                var mre = new ManualResetEvent(false);
+                if (Interlocked.CompareExchange(ref _kernelEvent, mre, null) != null)
+                {
+                    mre.Dispose();
+                }
+
+                // There is a race condition between checking IsCancellationRequested and setting the event.
+                // However, at this point, the kernel object definitely exists and the cases are:
+                //   1. if IsCancellationRequested = true, then we will call Set()
+                //   2. if IsCancellationRequested = false, then NotifyCancellation will see that the event exists, and will call Set().
+                if (IsCancellationRequested)
+                {
+                    _kernelEvent.Set();
+                }
+
+                return _kernelEvent;
+            }
+        }
+
+
+        /// <summary>Gets the ID of the currently executing callback.</summary>
+        internal long ExecutingCallback => Volatile.Read(ref _executingCallbackId);
+
+        /// <summary>Initializes the <see cref="CancellationTokenSource"/>.</summary>
+        public CancellationTokenSource() => _state = NotCanceledState;
+
+        /// <summary>
+        /// Constructs a <see cref="CancellationTokenSource"/> that will be canceled after a specified time span.
+        /// </summary>
+        /// <param name="delay">The time span to wait before canceling this <see cref="CancellationTokenSource"/></param>
+        /// <exception cref="ArgumentOutOfRangeException">
+        /// The exception that is thrown when <paramref name="delay"/> is less than -1 or greater than Int32.MaxValue.
+        /// </exception>
+        /// <remarks>
+        /// <para>
+        /// The countdown for the delay starts during the call to the constructor.  When the delay expires, 
+        /// the constructed <see cref="CancellationTokenSource"/> is canceled, if it has
+        /// not been canceled already.
+        /// </para>
+        /// <para>
+        /// Subsequent calls to CancelAfter will reset the delay for the constructed 
+        /// <see cref="CancellationTokenSource"/>, if it has not been
+        /// canceled already.
+        /// </para>
+        /// </remarks>
+        public CancellationTokenSource(TimeSpan delay)
+        {
+            long totalMilliseconds = (long)delay.TotalMilliseconds;
+            if (totalMilliseconds < -1 || totalMilliseconds > int.MaxValue)
+            {
+                throw new ArgumentOutOfRangeException(nameof(delay));
+            }
+
+            InitializeWithTimer((int)totalMilliseconds);
+        }
+
+        /// <summary>
+        /// Constructs a <see cref="CancellationTokenSource"/> that will be canceled after a specified time span.
+        /// </summary>
+        /// <param name="millisecondsDelay">The time span to wait before canceling this <see cref="CancellationTokenSource"/></param>
+        /// <exception cref="ArgumentOutOfRangeException">
+        /// The exception that is thrown when <paramref name="millisecondsDelay"/> is less than -1.
+        /// </exception>
+        /// <remarks>
+        /// <para>
+        /// The countdown for the millisecondsDelay starts during the call to the constructor.  When the millisecondsDelay expires, 
+        /// the constructed <see cref="CancellationTokenSource"/> is canceled (if it has
+        /// not been canceled already).
+        /// </para>
+        /// <para>
+        /// Subsequent calls to CancelAfter will reset the millisecondsDelay for the constructed 
+        /// <see cref="CancellationTokenSource"/>, if it has not been
+        /// canceled already.
+        /// </para>
+        /// </remarks>
+        public CancellationTokenSource(int millisecondsDelay)
+        {
+            if (millisecondsDelay < -1)
+            {
+                throw new ArgumentOutOfRangeException(nameof(millisecondsDelay));
+            }
+
+            InitializeWithTimer(millisecondsDelay);
+        }
+
+        /// <summary>Common initialization logic when constructing a CTS with a delay parameter</summary>
+        private void InitializeWithTimer(int millisecondsDelay)
+        {
+            _state = NotCanceledState;
+            _timer = new Timer(s_timerCallback, this, millisecondsDelay, -1);
+        }
+
+        /// <summary>Communicates a request for cancellation.</summary>
+        /// <remarks>
+        /// <para>
+        /// The associated <see cref="CancellationToken" /> will be notified of the cancellation
+        /// and will transition to a state where <see cref="CancellationToken.IsCancellationRequested"/> returns true. 
+        /// Any callbacks or cancelable operations registered with the <see cref="CancellationToken"/>  will be executed.
+        /// </para>
+        /// <para>
+        /// Cancelable operations and callbacks registered with the token should not throw exceptions.
+        /// However, this overload of Cancel will aggregate any exceptions thrown into a <see cref="AggregateException"/>,
+        /// such that one callback throwing an exception will not prevent other registered callbacks from being executed.
+        /// </para>
+        /// <para>
+        /// The <see cref="ExecutionContext"/> that was captured when each callback was registered
+        /// will be reestablished when the callback is invoked.
+        /// </para>
+        /// </remarks>
+        /// <exception cref="AggregateException">An aggregate exception containing all the exceptions thrown
+        /// by the registered callbacks on the associated <see cref="CancellationToken"/>.</exception>
+        /// <exception cref="ObjectDisposedException">This <see cref="CancellationTokenSource"/> has been disposed.</exception> 
+        public void Cancel() => Cancel(false);
+
+        /// <summary>Communicates a request for cancellation.</summary>
+        /// <remarks>
+        /// <para>
+        /// The associated <see cref="CancellationToken" /> will be notified of the cancellation and will transition to a state where 
+        /// <see cref="CancellationToken.IsCancellationRequested"/> returns true. Any callbacks or cancelable operationsregistered
+        /// with the <see cref="CancellationToken"/>  will be executed.
+        /// </para>
+        /// <para>
+        /// Cancelable operations and callbacks registered with the token should not throw exceptions. 
+        /// If <paramref name="throwOnFirstException"/> is true, an exception will immediately propagate out of the
+        /// call to Cancel, preventing the remaining callbacks and cancelable operations from being processed.
+        /// If <paramref name="throwOnFirstException"/> is false, this overload will aggregate any 
+        /// exceptions thrown into a <see cref="AggregateException"/>,
+        /// such that one callback throwing an exception will not prevent other registered callbacks from being executed.
+        /// </para>
+        /// <para>
+        /// The <see cref="ExecutionContext"/> that was captured when each callback was registered
+        /// will be reestablished when the callback is invoked.
+        /// </para>
+        /// </remarks>
+        /// <param name="throwOnFirstException">Specifies whether exceptions should immediately propagate.</param>
+        /// <exception cref="AggregateException">An aggregate exception containing all the exceptions thrown
+        /// by the registered callbacks on the associated <see cref="CancellationToken"/>.</exception>
+        /// <exception cref="ObjectDisposedException">This <see cref="CancellationTokenSource"/> has been disposed.</exception> 
+        public void Cancel(bool throwOnFirstException)
+        {
+            ThrowIfDisposed();
+            NotifyCancellation(throwOnFirstException);
+        }
+
+        /// <summary>Schedules a Cancel operation on this <see cref="CancellationTokenSource"/>.</summary>
+        /// <param name="delay">The time span to wait before canceling this <see cref="CancellationTokenSource"/>.
+        /// </param>
+        /// <exception cref="ObjectDisposedException">The exception thrown when this <see
+        /// cref="CancellationTokenSource"/> has been disposed.
+        /// </exception>
+        /// <exception cref="ArgumentOutOfRangeException">
+        /// The exception thrown when <paramref name="delay"/> is less than -1 or 
+        /// greater than Int32.MaxValue.
+        /// </exception>
+        /// <remarks>
+        /// <para>
+        /// The countdown for the delay starts during this call.  When the delay expires, 
+        /// this <see cref="CancellationTokenSource"/> is canceled, if it has
+        /// not been canceled already.
+        /// </para>
+        /// <para>
+        /// Subsequent calls to CancelAfter will reset the delay for this  
+        /// <see cref="CancellationTokenSource"/>, if it has not been canceled already.
+        /// </para>
+        /// </remarks>
+        public void CancelAfter(TimeSpan delay)
+        {
+            long totalMilliseconds = (long)delay.TotalMilliseconds;
+            if (totalMilliseconds < -1 || totalMilliseconds > int.MaxValue)
+            {
+                throw new ArgumentOutOfRangeException(nameof(delay));
+            }
+
+            CancelAfter((int)totalMilliseconds);
+        }
+
+        /// <summary>
+        /// Schedules a Cancel operation on this <see cref="CancellationTokenSource"/>.
+        /// </summary>
+        /// <param name="millisecondsDelay">The time span to wait before canceling this <see
+        /// cref="CancellationTokenSource"/>.
+        /// </param>
+        /// <exception cref="ObjectDisposedException">The exception thrown when this <see
+        /// cref="CancellationTokenSource"/> has been disposed.
+        /// </exception>
+        /// <exception cref="ArgumentOutOfRangeException">
+        /// The exception thrown when <paramref name="millisecondsDelay"/> is less than -1.
+        /// </exception>
+        /// <remarks>
+        /// <para>
+        /// The countdown for the millisecondsDelay starts during this call.  When the millisecondsDelay expires, 
+        /// this <see cref="CancellationTokenSource"/> is canceled, if it has
+        /// not been canceled already.
+        /// </para>
+        /// <para>
+        /// Subsequent calls to CancelAfter will reset the millisecondsDelay for this  
+        /// <see cref="CancellationTokenSource"/>, if it has not been
+        /// canceled already.
+        /// </para>
+        /// </remarks>
+        public void CancelAfter(int millisecondsDelay)
+        {
+            ThrowIfDisposed();
+
+            if (millisecondsDelay < -1)
+            {
+                throw new ArgumentOutOfRangeException(nameof(millisecondsDelay));
+            }
+
+            if (IsCancellationRequested)
+            {
+                return;
+            }
+
+            // There is a race condition here as a Cancel could occur between the check of
+            // IsCancellationRequested and the creation of the timer.  This is benign; in the 
+            // worst case, a timer will be created that has no effect when it expires.
+
+            // Also, if Dispose() is called right here (after ThrowIfDisposed(), before timer
+            // creation), it would result in a leaked Timer object (at least until the timer
+            // expired and Disposed itself).  But this would be considered bad behavior, as
+            // Dispose() is not thread-safe and should not be called concurrently with CancelAfter().
+
+            if (_timer == null)
+            {
+                // Lazily initialize the timer in a thread-safe fashion.
+                // Initially set to "never go off" because we don't want to take a
+                // chance on a timer "losing" the initialization and then
+                // cancelling the token before it (the timer) can be disposed.
+                Timer newTimer = new Timer(s_timerCallback, this, -1, -1);
+                if (Interlocked.CompareExchange(ref _timer, newTimer, null) != null)
+                {
+                    // We did not initialize the timer.  Dispose the new timer.
+                    newTimer.Dispose();
+                }
+            }
+
+            // It is possible that m_timer has already been disposed, so we must do
+            // the following in a try/catch block.
+            try
+            {
+                _timer.Change(millisecondsDelay, -1);
+            }
+            catch (ObjectDisposedException)
+            {
+                // Just eat the exception.  There is no other way to tell that
+                // the timer has been disposed, and even if there were, there
+                // would not be a good way to deal with the observe/dispose
+                // race condition.
+            }
+        }
+
+
+
+        /// <summary>Releases the resources used by this <see cref="CancellationTokenSource" />.</summary>
+        /// <remarks>This method is not thread-safe for any other concurrent calls.</remarks>
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// Releases the unmanaged resources used by the <see cref="CancellationTokenSource" /> class and optionally releases the managed resources.
+        /// </summary>
+        /// <param name="disposing">true to release both managed and unmanaged resources; false to release only unmanaged resources.</param>
+        protected virtual void Dispose(bool disposing)
+        {
+            if (disposing && !_disposed)
+            {
+                // We specifically tolerate that a callback can be unregistered
+                // after the CTS has been disposed and/or concurrently with cts.Dispose().
+                // This is safe without locks because Dispose doesn't interact with values
+                // in the callback partitions, only nulling out the ref to existing partitions.
+                // 
+                // We also tolerate that a callback can be registered after the CTS has been
+                // disposed.  This is safe because InternalRegister is tolerant
+                // of _callbackPartitions becoming null during its execution.  However,
+                // we run the acceptable risk of _callbackPartitions getting reinitialized
+                // to non-null if there is a race between Dispose and Register, in which case this
+                // instance may unnecessarily hold onto a registered callback.  But that's no worse
+                // than if Dispose wasn't safe to use concurrently, as Dispose would never be called,
+                // and thus no handlers would be dropped.
+                //
+                // And, we tolerate Dispose being used concurrently with Cancel.  This is necessary
+                // to properly support, e.g., LinkedCancellationTokenSource, where, due to common usage patterns,
+                // it's possible for this pairing to occur with valid usage (e.g. a component accepts
+                // an external CancellationToken and uses CreateLinkedTokenSource to combine it with an
+                // internal source of cancellation, then Disposes of that linked source, which could
+                // happen at the same time the external entity is requesting cancellation).
+
+                _timer?.Dispose(); // Timer.Dispose is thread-safe
+
+                _callbackPartitions = null; // free for GC; Cancel correctly handles a null field
+
+                // If a kernel event was created via WaitHandle, we'd like to Dispose of it.  However,
+                // we only want to do so if it's not being used by Cancel concurrently.  First, we
+                // interlocked exchange it to be null, and then we check whether cancellation is currently
+                // in progress.  NotifyCancellation will only try to set the event if it exists after it's
+                // transitioned to and while it's in the NotifyingState.
+                if (_kernelEvent != null)
+                {
+                    ManualResetEvent mre = Interlocked.Exchange(ref _kernelEvent, null);
+                    if (mre != null && _state != NotifyingState)
+                    {
+                        mre.Dispose();
+                    }
+                }
+
+                _disposed = true;
+            }
+        }
+
+        /// <summary>Throws an exception if the source has been disposed.</summary>
+        private void ThrowIfDisposed()
+        {
+            if (_disposed)
+            {
+                ThrowObjectDisposedException();
+            }
+        }
+
+        /// <summary>Throws an <see cref="ObjectDisposedException"/>.  Separated out from ThrowIfDisposed to help with inlining.</summary>
+        private static void ThrowObjectDisposedException() =>
+            throw new ObjectDisposedException(null, SR.CancellationTokenSource_Disposed);
+
+        /// <summary>
+        /// Registers a callback object. If cancellation has already occurred, the
+        /// callback will have been run by the time this method returns.
+        /// </summary>
+        internal CancellationTokenRegistration InternalRegister(
+            Action<object> callback, object stateForCallback, SynchronizationContext syncContext, ExecutionContext executionContext)
+        {
+            Debug.Assert(this != s_neverCanceledSource, "This source should never be exposed via a CancellationToken.");
+
+            // If not canceled, register the handler; if canceled already, run the callback synchronously.
+            // This also ensures that during ExecuteCallbackHandlers() there will be no mutation of the _callbackPartitions.
+            if (!IsCancellationRequested)
+            {
+                // In order to enable code to not leak too many handlers, we allow Dispose to be called concurrently
+                // with Register.  While this is not a recommended practice, consumers can and do use it this way.
+                // We don't make any guarantees about whether the CTS will hold onto the supplied callback if the CTS
+                // has already been disposed when the callback is registered, but we try not to while at the same time
+                // not paying any non-negligible overhead.  The simple compromise is to check whether we're disposed
+                // (not volatile), and if we see we are, to return an empty registration. If there's a race and _disposed
+                // is false even though it's been disposed, or if the disposal request comes in after this line, we simply
+                // run the minor risk of having _callbackPartitions reinitialized (after it was cleared to null during Dispose).
+                if (_disposed)
+                {
+                    return new CancellationTokenRegistration();
+                }
+
+                // Get the partitions...
+                CallbackPartition[] partitions = _callbackPartitions;
+                if (partitions == null)
+                {
+                    partitions = new CallbackPartition[s_numPartitions];
+                    partitions = Interlocked.CompareExchange(ref _callbackPartitions, partitions, null) ?? partitions;
+                }
+
+                // ...and determine which partition to use.
+                int partitionIndex = Environment.CurrentManagedThreadId & s_numPartitionsMask;
+                Debug.Assert(partitionIndex < partitions.Length, $"Expected {partitionIndex} to be less than {partitions.Length}");
+                CallbackPartition partition = partitions[partitionIndex];
+                if (partition == null)
+                {
+                    partition = new CallbackPartition(this);
+                    partition = Interlocked.CompareExchange(ref partitions[partitionIndex], partition, null) ?? partition;
+                }
+
+                // Store the callback information into the callback arrays.
+                long id;
+                CallbackNode node;
+                bool lockTaken = false;
+                partition.Lock.Enter(ref lockTaken);
+                try
+                {
+                    // Assign the next available unique ID.
+                    id = partition.NextAvailableId++;
+
+                    // Get a node, from the free list if possible or else a new one.
+                    node = partition.FreeNodeList;
+                    if (node != null)
+                    {
+                        partition.FreeNodeList = node.Next;
+                        Debug.Assert(node.Prev == null, "Nodes in the free list should all have a null Prev");
+                        // node.Next will be overwritten below so no need to set it here.
+                    }
+                    else
+                    {
+                        node = new CallbackNode(partition);
+                    }
+
+                    // Configure the node.
+                    node.Id = id;
+                    node.Callback = callback;
+                    node.CallbackState = stateForCallback;
+                    node.ExecutionContext = executionContext;
+                    node.SynchronizationContext = syncContext;
+
+                    // Add it to the callbacks list.
+                    node.Next = partition.Callbacks;
+                    if (node.Next != null)
+                    {
+                        node.Next.Prev = node;
+                    }
+                    partition.Callbacks = node;
+                }
+                finally
+                {
+                    partition.Lock.Exit(useMemoryBarrier: false); // no check on lockTaken needed without thread aborts
+                }
+
+                // If cancellation hasn't been requested, return the registration.
+                // if cancellation has been requested, try to undo the registration and run the callback
+                // ourselves, but if we can't unregister it (e.g. the thread running Cancel snagged
+                // our callback for execution), return the registration so that the caller can wait
+                // for callback completion in ctr.Dispose().
+                var ctr = new CancellationTokenRegistration(id, node);
+                if (!IsCancellationRequested || !partition.Unregister(id, node))
+                {
+                    return ctr;
+                }
+            }
+
+            // Cancellation already occurred.  Run the callback on this thread and return an empty registration.
+            callback(stateForCallback);
+            return default(CancellationTokenRegistration);
+        }
+
+        private void NotifyCancellation(bool throwOnFirstException)
+        {
+            // If we're the first to signal cancellation, do the main extra work.
+            if (!IsCancellationRequested && Interlocked.CompareExchange(ref _state, NotifyingState, NotCanceledState) == NotCanceledState)
+            {
+                // Dispose of the timer, if any.  Dispose may be running concurrently here, but Timer.Dispose is thread-safe.
+                _timer?.Dispose();
+
+                // Set the event if it's been lazily initialized and hasn't yet been disposed of.  Dispose may
+                // be running concurrently, in which case either it'll have set m_kernelEvent back to null and
+                // we won't see it here, or it'll see that we've transitioned to NOTIFYING and will skip disposing it,
+                // leaving cleanup to finalization.
+                _kernelEvent?.Set(); // update the MRE value.
+
+                // - late enlisters to the Canceled event will have their callbacks called immediately in the Register() methods.
+                // - Callbacks are not called inside a lock.
+                // - After transition, no more delegates will be added to the 
+                // - list of handlers, and hence it can be consumed and cleared at leisure by ExecuteCallbackHandlers.
+                ExecuteCallbackHandlers(throwOnFirstException);
+                Debug.Assert(IsCancellationCompleted, "Expected cancellation to have finished");
+            }
+        }
+
+        /// <summary>Invoke all registered callbacks.</summary>
+        /// <remarks>The handlers are invoked synchronously in LIFO order.</remarks>
+        private void ExecuteCallbackHandlers(bool throwOnFirstException)
+        {
+            Debug.Assert(IsCancellationRequested, "ExecuteCallbackHandlers should only be called after setting IsCancellationRequested->true");
+
+            // Record the threadID being used for running the callbacks.
+            ThreadIDExecutingCallbacks = Thread.CurrentThread.ManagedThreadId;
+
+            // If there are no callbacks to run, we can safely exit.  Any race conditions to lazy initialize it
+            // will see IsCancellationRequested and will then run the callback themselves.
+            CallbackPartition[] partitions = Interlocked.Exchange(ref _callbackPartitions, null);
+            if (partitions == null)
+            {
+                Interlocked.Exchange(ref _state, NotifyingCompleteState);
+                return;
+            }
+
+            List<Exception> exceptionList = null;
+            try
+            {
+                // For each partition, and each callback in that partition, execute the associated handler.
+                // We call the delegates in LIFO order on each partition so that callbacks fire 'deepest first'.
+                // This is intended to help with nesting scenarios so that child enlisters cancel before their parents.
+                foreach (CallbackPartition partition in partitions)
+                {
+                    if (partition == null)
+                    {
+                        // Uninitialized partition. Nothing to do.
+                        continue;
+                    }
+
+                    // Get the callbacks from the partition, substituting in null so that anyone
+                    // else coming along (e.g. CTR.Dispose) will find the callbacks gone.
+                    CallbackNode node;
+                    bool lockTaken = false;
+                    partition.Lock.Enter(ref lockTaken); // try/finally not needed without thread aborts
+                    {
+                        node = partition.Callbacks;
+                        partition.Callbacks = null;
+                    }
+                    partition.Lock.Exit(useMemoryBarrier: false);
+
+                    for (; node != null; node = node.Next)
+                    {
+                        // Publish the intended callback, to ensure ctr.Dispose can tell if a wait is necessary.
+                        Volatile.Write(ref _executingCallbackId, node.Id);
+
+                        // Invoke the callback on this thread if there's no sync context or on the
+                        // target sync context if there is one.
+                        try
+                        {
+                            if (node.SynchronizationContext != null)
+                            {
+                                // Transition to the target syncContext and continue there.
+                                node.SynchronizationContext.Send(s =>
+                                {
+                                    var n = (CallbackNode)s;
+                                    n.Partition.Source.ThreadIDExecutingCallbacks = Thread.CurrentThread.ManagedThreadId;
+                                    n.ExecuteCallback();
+                                }, node);
+                                ThreadIDExecutingCallbacks = Thread.CurrentThread.ManagedThreadId; // above may have altered ThreadIDExecutingCallbacks, so reset it
+                            }
+                            else
+                            {
+                                node.ExecuteCallback();
+                            }
+                        }
+                        catch (Exception ex) when (!throwOnFirstException)
+                        {
+                            // Store the exception and continue
+                            (exceptionList ?? (exceptionList = new List<Exception>())).Add(ex);
+                        }
+                    }
+                }
+            }
+            finally
+            {
+                _state = NotifyingCompleteState;
+                Volatile.Write(ref _executingCallbackId, 0);
+                Interlocked.MemoryBarrier(); // for safety, prevent reorderings crossing this point and seeing inconsistent state.
+            }
+
+            if (exceptionList != null)
+            {
+                Debug.Assert(exceptionList.Count > 0, $"Expected {exceptionList.Count} > 0");
+                throw new AggregateException(exceptionList);
+            }
+        }
+
+        /// <summary>Gets the number of callback partitions to use based on the number of cores.</summary>
+        /// <returns>A power of 2 representing the number of partitions to use.</returns>
+        private static int GetPartitionCount()
+        {
+            int procs = PlatformHelper.ProcessorCount;
+            int count =
+                procs > 8 ? 16 : // capped at 16 to limit memory usage on larger machines
+                procs > 4 ? 8 :
+                procs > 2 ? 4 :
+                procs > 1 ? 2 :
+                1;
+            Debug.Assert(count > 0 && (count & (count - 1)) == 0, $"Got {count}, but expected a power of 2");
+            return count;
+        }
+
+        /// <summary>
+        /// Creates a <see cref="CancellationTokenSource"/> that will be in the canceled state
+        /// when any of the source tokens are in the canceled state.
+        /// </summary>
+        /// <param name="token1">The first <see cref="CancellationToken">CancellationToken</see> to observe.</param>
+        /// <param name="token2">The second <see cref="CancellationToken">CancellationToken</see> to observe.</param>
+        /// <returns>A <see cref="CancellationTokenSource"/> that is linked 
+        /// to the source tokens.</returns>
+        public static CancellationTokenSource CreateLinkedTokenSource(CancellationToken token1, CancellationToken token2) =>
+            !token1.CanBeCanceled ? CreateLinkedTokenSource(token2) :
+            token2.CanBeCanceled ? new Linked2CancellationTokenSource(token1, token2) :
+            (CancellationTokenSource)new Linked1CancellationTokenSource(token1);
+
+        /// <summary>
+        /// Creates a <see cref="CancellationTokenSource"/> that will be in the canceled state
+        /// when any of the source tokens are in the canceled state.
+        /// </summary>
+        /// <param name="token">The first <see cref="CancellationToken">CancellationToken</see> to observe.</param>
+        /// <returns>A <see cref="CancellationTokenSource"/> that is linked to the source tokens.</returns>
+        internal static CancellationTokenSource CreateLinkedTokenSource(CancellationToken token) =>
+            token.CanBeCanceled ? new Linked1CancellationTokenSource(token) : new CancellationTokenSource();
+
+        /// <summary>
+        /// Creates a <see cref="CancellationTokenSource"/> that will be in the canceled state
+        /// when any of the source tokens are in the canceled state.
+        /// </summary>
+        /// <param name="tokens">The <see cref="CancellationToken">CancellationToken</see> instances to observe.</param>
+        /// <returns>A <see cref="CancellationTokenSource"/> that is linked to the source tokens.</returns>
+        /// <exception cref="System.ArgumentNullException"><paramref name="tokens"/> is null.</exception>
+        public static CancellationTokenSource CreateLinkedTokenSource(params CancellationToken[] tokens)
+        {
+            if (tokens == null)
+            {
+                throw new ArgumentNullException(nameof(tokens));
+            }
+
+            switch (tokens.Length)
+            {
+                case 0:
+                    throw new ArgumentException(SR.CancellationToken_CreateLinkedToken_TokensIsEmpty);
+                case 1:
+                    return CreateLinkedTokenSource(tokens[0]);
+                case 2:
+                    return CreateLinkedTokenSource(tokens[0], tokens[1]);
+                default:
+                    // a defensive copy is not required as the array has value-items that have only a single reference field,
+                    // hence each item cannot be null itself, and reads of the payloads cannot be torn.
+                    return new LinkedNCancellationTokenSource(tokens);
+            }
+        }
+
+
+
+        /// <summary>
+        /// Wait for a single callback to complete (or, more specifically, to not be running).
+        /// It is ok to call this method if the callback has already finished.
+        /// Calling this method before the target callback has been selected for execution would be an error.
+        /// </summary>
+        internal void WaitForCallbackToComplete(long id)
+        {
+            var sw = new SpinWait();
+            while (ExecutingCallback == id)
+            {
+                sw.SpinOnce();  // spin, as we assume callback execution is fast and that this situation is rare.
+            }
+        }
+
+        private sealed class Linked1CancellationTokenSource : CancellationTokenSource
+        {
+            private readonly CancellationTokenRegistration _reg1;
+
+            internal Linked1CancellationTokenSource(CancellationToken token1)
+            {
+                _reg1 = token1.InternalRegisterWithoutEC(LinkedNCancellationTokenSource.s_linkedTokenCancelDelegate, this);
+            }
+
+            protected override void Dispose(bool disposing)
+            {
+                if (!disposing || _disposed)
+                {
+                    return;
+                }
+
+                _reg1.Dispose();
+                base.Dispose(disposing);
+            }
+        }
+
+        private sealed class Linked2CancellationTokenSource : CancellationTokenSource
+        {
+            private readonly CancellationTokenRegistration _reg1;
+            private readonly CancellationTokenRegistration _reg2;
+
+            internal Linked2CancellationTokenSource(CancellationToken token1, CancellationToken token2)
+            {
+                _reg1 = token1.InternalRegisterWithoutEC(LinkedNCancellationTokenSource.s_linkedTokenCancelDelegate, this);
+                _reg2 = token2.InternalRegisterWithoutEC(LinkedNCancellationTokenSource.s_linkedTokenCancelDelegate, this);
+            }
+
+            protected override void Dispose(bool disposing)
+            {
+                if (!disposing || _disposed)
+                {
+                    return;
+                }
+
+                _reg1.Dispose();
+                _reg2.Dispose();
+                base.Dispose(disposing);
+            }
+        }
+
+        private sealed class LinkedNCancellationTokenSource : CancellationTokenSource
+        {
+            internal static readonly Action<object> s_linkedTokenCancelDelegate =
+                s => ((CancellationTokenSource)s).NotifyCancellation(throwOnFirstException: false); // skip ThrowIfDisposed() check in Cancel()
+            private CancellationTokenRegistration[] m_linkingRegistrations;
+
+            internal LinkedNCancellationTokenSource(params CancellationToken[] tokens)
+            {
+                m_linkingRegistrations = new CancellationTokenRegistration[tokens.Length];
+
+                for (int i = 0; i < tokens.Length; i++)
+                {
+                    if (tokens[i].CanBeCanceled)
+                    {
+                        m_linkingRegistrations[i] = tokens[i].InternalRegisterWithoutEC(s_linkedTokenCancelDelegate, this);
+                    }
+                    // Empty slots in the array will be default(CancellationTokenRegistration), which are nops to Dispose.
+                    // Based on usage patterns, such occurrences should also be rare, such that it's not worth resizing
+                    // the array and incurring the related costs.
+                }
+            }
+
+            protected override void Dispose(bool disposing)
+            {
+                if (!disposing || _disposed)
+                {
+                    return;
+                }
+
+                CancellationTokenRegistration[] linkingRegistrations = m_linkingRegistrations;
+                if (linkingRegistrations != null)
+                {
+                    m_linkingRegistrations = null; // release for GC once we're done enumerating
+                    for (int i = 0; i < linkingRegistrations.Length; i++)
+                    {
+                        linkingRegistrations[i].Dispose();
+                    }
+                }
+
+                base.Dispose(disposing);
+            }
+        }
+
+        internal sealed class CallbackPartition
+        {
+            /// <summary>The associated source that owns this partition.</summary>
+            public readonly CancellationTokenSource Source;
+            /// <summary>Lock that protects all state in the partition.</summary>
+            public SpinLock Lock = new SpinLock(enableThreadOwnerTracking: false); // mutable struct; do not make this readonly
+            /// <summary>
+            /// The array of callbacks registered in the partition.  Slots may be empty, meaning a default value of the struct.
+            /// <see cref="NextCallbacksSlot"/> - 1 defines the last filled slot.
+            /// </summary>
+            /// <remarks>
+            /// Initialized to an array with at least 1 slot because a partition is only ever created if we're about
+            /// to store something into it.  And initialized with at most 1 slot to help optimize the common case where
+            /// there's only ever a single registration in a CTS (that and many registrations are the most common cases).
+            /// </remarks>
+            public CallbackNode Callbacks;
+            public CallbackNode FreeNodeList;
+            /// <summary>
+            /// Every callback is assigned a unique, never-reused ID.  This defines the next available ID.
+            /// </summary>
+            public long NextAvailableId = 1; // avoid using 0, as that's the default long value and used to represent an empty slot
+
+            public CallbackPartition(CancellationTokenSource source)
+            {
+                Debug.Assert(source != null, "Expected non-null source");
+                Source = source;
+            }
+
+            internal bool Unregister(long id, CallbackNode node)
+            {
+                Debug.Assert(id != 0, "Expected non-zero id");
+                Debug.Assert(node != null, "Expected non-null node");
+
+                bool lockTaken = false;
+                Lock.Enter(ref lockTaken);
+                try
+                {
+                    if (Callbacks == null || node.Id != id)
+                    {
+                        // Cancellation was already requested or the callback was already disposed.
+                        // Even though we have the node itself, it's important to check Callbacks
+                        // in order to synchronize with callback execution.
+                        return false;
+                    }
+
+                    // Remove the registration from the list.
+                    if (node.Prev != null) node.Prev.Next = node.Next;
+                    if (node.Next != null) node.Next.Prev = node.Prev;
+                    if (Callbacks == node) Callbacks = node.Next;
+
+                    // Clear it out and put it on the free list
+                    node.Clear();
+                    node.Prev = null;
+                    node.Next = FreeNodeList;
+                    FreeNodeList = node;
+
+                    return true;
+                }
+                finally
+                {
+                    Lock.Exit(useMemoryBarrier: false); // no check on lockTaken needed without thread aborts
+                }
+            }
+        }
+
+        /// <summary>All of the state associated a registered callback, in a node that's part of a linked list of registered callbacks.</summary>
+        internal sealed class CallbackNode
+        {
+            public readonly CallbackPartition Partition;
+            public CallbackNode Prev;
+            public CallbackNode Next;
+
+            public long Id;
+            public Action<object> Callback;
+            public object CallbackState;
+            public ExecutionContext ExecutionContext;
+            public SynchronizationContext SynchronizationContext;
+            
+            public CallbackNode(CallbackPartition partition)
+            {
+                Debug.Assert(partition != null, "Expected non-null partition");
+                Partition = partition;
+            }
+
+            public void Clear()
+            {
+                Id = 0;
+                Callback = null;
+                CallbackState = null;
+                ExecutionContext = null;
+                SynchronizationContext = null;
+            }
+
+            public void ExecuteCallback()
+            {
+                ExecutionContext context = ExecutionContext;
+                if (context != null)
+                {
+                    ExecutionContext.RunInternal(context, s =>
+                    {
+                        CallbackNode n = (CallbackNode)s;
+                        n.Callback(n.CallbackState);
+                    }, this);
+                }
+                else
+                {
+                    Callback(CallbackState);
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolBoundHandle.Unix.cs b/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolBoundHandle.Unix.cs
new file mode 100644
index 0000000000..b7cdaa801c
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolBoundHandle.Unix.cs
@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System.Threading
+{
+    public sealed partial class ThreadPoolBoundHandle
+    {
+        private static ThreadPoolBoundHandle BindHandleCore(SafeHandle handle)
+        {
+            Debug.Assert(handle != null);
+            Debug.Assert(!handle.IsClosed);
+            Debug.Assert(!handle.IsInvalid);
+
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_OverlappedIO);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolBoundHandle.Windows.cs b/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolBoundHandle.Windows.cs
new file mode 100644
index 0000000000..a40661c1b6
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolBoundHandle.Windows.cs
@@ -0,0 +1,43 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System.Threading
+{
+    public sealed partial class ThreadPoolBoundHandle
+    {
+        private static ThreadPoolBoundHandle BindHandleCore(SafeHandle handle)
+        {
+            Debug.Assert(handle != null);
+            Debug.Assert(!handle.IsClosed);
+            Debug.Assert(!handle.IsInvalid);
+
+            try
+            {
+                // ThreadPool.BindHandle will always return true, otherwise, it throws. See the underlying FCall
+                // implementation in ThreadPoolNative::CorBindIoCompletionCallback to see the implementation.
+                bool succeeded = ThreadPool.BindHandle(handle);
+                Debug.Assert(succeeded);
+            }
+            catch (Exception ex)
+            {   // BindHandle throws ApplicationException on full CLR and Exception on CoreCLR.
+                // We do not let either of these leak and convert them to ArgumentException to 
+                // indicate that the specified handles are invalid.
+
+                if (ex.HResult == HResults.E_HANDLE)         // Bad handle
+                    throw new ArgumentException(SR.Argument_InvalidHandle, nameof(handle));
+
+                if (ex.HResult == HResults.E_INVALIDARG)     // Handle already bound or sync handle
+                    throw new ArgumentException(SR.Argument_AlreadyBoundOrSyncHandle, nameof(handle));
+
+                throw;
+            }
+
+            return new ThreadPoolBoundHandle(handle);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolBoundHandle.cs b/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolBoundHandle.cs
new file mode 100644
index 0000000000..ea03087dbb
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolBoundHandle.cs
@@ -0,0 +1,298 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System.Threading
+{
+    //
+    // Implementation of ThreadPoolBoundHandle that sits on top of the CLR's ThreadPool and Overlapped infrastructure
+    //
+
+    /// <summary>
+    ///     Represents an I/O handle that is bound to the system thread pool and enables low-level
+    ///     components to receive notifications for asynchronous I/O operations.
+    /// </summary>
+    public sealed partial class ThreadPoolBoundHandle : IDisposable
+    {
+        private readonly SafeHandle _handle;
+        private bool _isDisposed;
+
+        private ThreadPoolBoundHandle(SafeHandle handle)
+        {
+            _handle = handle;
+        }
+
+        /// <summary>
+        ///     Gets the bound operating system handle.
+        /// </summary>
+        /// <value>
+        ///     A <see cref="SafeHandle"/> object that holds the bound operating system handle.
+        /// </value>
+        public SafeHandle Handle
+        {
+            get { return _handle; }
+        }
+
+        /// <summary>
+        ///     Returns a <see cref="ThreadPoolBoundHandle"/> for the specific handle, 
+        ///     which is bound to the system thread pool.
+        /// </summary>
+        /// <param name="handle">
+        ///     A <see cref="SafeHandle"/> object that holds the operating system handle. The 
+        ///     handle must have been opened for overlapped I/O on the unmanaged side.
+        /// </param>
+        /// <returns>
+        ///     <see cref="ThreadPoolBoundHandle"/> for <paramref name="handle"/>, which 
+        ///     is bound to the system thread pool.
+        /// </returns>
+        /// <exception cref="ArgumentNullException">
+        ///     <paramref name="handle"/> is <see langword="null"/>.
+        /// </exception>
+        /// <exception cref="ArgumentException">
+        ///     <paramref name="handle"/> has been disposed.
+        ///     <para>
+        ///         -or-
+        ///     </para>
+        ///     <paramref name="handle"/> does not refer to a valid I/O handle.
+        ///     <para>
+        ///         -or-
+        ///     </para>
+        ///     <paramref name="handle"/> refers to a handle that has not been opened 
+        ///     for overlapped I/O.
+        ///     <para>
+        ///         -or-
+        ///     </para>
+        ///     <paramref name="handle"/> refers to a handle that has already been bound.
+        /// </exception>
+        /// <remarks>
+        ///     This method should be called once per handle.
+        ///     <para>
+        ///         -or-
+        ///     </para>
+        ///     <see cref="ThreadPoolBoundHandle"/> does not take ownership of <paramref name="handle"/>, 
+        ///     it remains the responsibility of the caller to call <see cref="SafeHandle.Dispose"/>.
+        /// </remarks>
+        public static ThreadPoolBoundHandle BindHandle(SafeHandle handle)
+        {
+            if (handle == null)
+                throw new ArgumentNullException(nameof(handle));
+
+            if (handle.IsClosed || handle.IsInvalid)
+                throw new ArgumentException(SR.Argument_InvalidHandle, nameof(handle));
+
+            return BindHandleCore(handle);
+        }
+
+        /// <summary>
+        ///     Returns an unmanaged pointer to a <see cref="NativeOverlapped"/> structure, specifying 
+        ///     a delegate that is invoked when the asynchronous I/O operation is complete, a user-provided 
+        ///     object providing context, and managed objects that serve as buffers.
+        /// </summary>
+        /// <param name="callback">
+        ///     An <see cref="IOCompletionCallback"/> delegate that represents the callback method 
+        ///     invoked when the asynchronous I/O operation completes.
+        /// </param>
+        /// <param name="state">
+        ///     A user-provided object that distinguishes this <see cref="NativeOverlapped"/> from other 
+        ///     <see cref="NativeOverlapped"/> instances. Can be <see langword="null"/>.
+        /// </param>
+        /// <param name="pinData">
+        ///     An object or array of objects representing the input or output buffer for the operation. Each 
+        ///     object represents a buffer, for example an array of bytes.  Can be <see langword="null"/>.
+        /// </param>
+        /// <returns>
+        ///     An unmanaged pointer to a <see cref="NativeOverlapped"/> structure.
+        /// </returns>
+        /// <remarks>
+        ///     <para>
+        ///         The unmanaged pointer returned by this method can be passed to the operating system in 
+        ///         overlapped I/O operations. The <see cref="NativeOverlapped"/> structure is fixed in 
+        ///         physical memory until <see cref="FreeNativeOverlapped(NativeOverlapped*)"/> is called.
+        ///     </para>
+        ///     <para>
+        ///         The buffer or buffers specified in <paramref name="pinData"/> must be the same as those passed 
+        ///         to the unmanaged operating system function that performs the asynchronous I/O.
+        ///     </para>
+        ///     <note>
+        ///         The buffers specified in <paramref name="pinData"/> are pinned for the duration of 
+        ///         the I/O operation.
+        ///     </note>
+        /// </remarks>
+        /// <exception cref="ArgumentNullException">
+        ///     <paramref name="callback"/> is <see langword="null"/>.
+        /// </exception>
+        /// <exception cref="ObjectDisposedException">
+        ///     This method was called after the <see cref="ThreadPoolBoundHandle"/> was disposed.
+        /// </exception>
+        [CLSCompliant(false)]
+        public unsafe NativeOverlapped* AllocateNativeOverlapped(IOCompletionCallback callback, object state, object pinData)
+        {
+            if (callback == null)
+                throw new ArgumentNullException(nameof(callback));
+
+            EnsureNotDisposed();
+
+            ThreadPoolBoundHandleOverlapped overlapped = new ThreadPoolBoundHandleOverlapped(callback, state, pinData, preAllocated: null);
+            overlapped._boundHandle = this;
+            return overlapped._nativeOverlapped;
+        }
+
+        /// <summary>
+        ///     Returns an unmanaged pointer to a <see cref="NativeOverlapped"/> structure, using the callback,
+        ///     state, and buffers associated with the specified <see cref="PreAllocatedOverlapped"/> object.
+        /// </summary>
+        /// <param name="preAllocated">
+        ///     A <see cref="PreAllocatedOverlapped"/> object from which to create the NativeOverlapped pointer.
+        /// </param>
+        /// <returns>
+        ///     An unmanaged pointer to a <see cref="NativeOverlapped"/> structure.
+        /// </returns>
+        /// <remarks>
+        ///     <para>
+        ///         The unmanaged pointer returned by this method can be passed to the operating system in 
+        ///         overlapped I/O operations. The <see cref="NativeOverlapped"/> structure is fixed in 
+        ///         physical memory until <see cref="FreeNativeOverlapped(NativeOverlapped*)"/> is called.
+        ///     </para>
+        /// </remarks>
+        /// <exception cref="ArgumentNullException">
+        ///     <paramref name="preAllocated"/> is <see langword="null"/>.
+        /// </exception>
+        /// <exception cref="ArgumentException">
+        ///     <paramref name="preAllocated"/> is currently in use for another I/O operation.  
+        /// </exception>
+        /// <exception cref="ObjectDisposedException">
+        ///     This method was called after the <see cref="ThreadPoolBoundHandle"/> was disposed, or 
+        ///     this method was called after <paramref name="preAllocated"/> was disposed.
+        /// </exception>
+        /// <seealso cref="PreAllocatedOverlapped"/>
+        [CLSCompliant(false)]
+        public unsafe NativeOverlapped* AllocateNativeOverlapped(PreAllocatedOverlapped preAllocated)
+        {
+            if (preAllocated == null)
+                throw new ArgumentNullException(nameof(preAllocated));
+
+            EnsureNotDisposed();
+
+            preAllocated.AddRef();
+            try
+            {
+                ThreadPoolBoundHandleOverlapped overlapped = preAllocated._overlapped;
+
+                if (overlapped._boundHandle != null)
+                    throw new ArgumentException(SR.Argument_PreAllocatedAlreadyAllocated, nameof(preAllocated));
+
+                overlapped._boundHandle = this;
+
+                return overlapped._nativeOverlapped;
+            }
+            catch
+            {
+                preAllocated.Release();
+                throw;
+            }
+        }
+
+        /// <summary>
+        ///     Frees the unmanaged memory associated with a <see cref="NativeOverlapped"/> structure 
+        ///     allocated by the <see cref="AllocateNativeOverlapped"/> method.
+        /// </summary>
+        /// <param name="overlapped">
+        ///     An unmanaged pointer to the <see cref="NativeOverlapped"/> structure to be freed.
+        /// </param>
+        /// <remarks>
+        ///     <note type="caution">
+        ///         You must call the <see cref="FreeNativeOverlapped(NativeOverlapped*)"/> method exactly once 
+        ///         on every <see cref="NativeOverlapped"/> unmanaged pointer allocated using the 
+        ///         <see cref="AllocateNativeOverlapped"/> method. 
+        ///         If you do not call the <see cref="FreeNativeOverlapped(NativeOverlapped*)"/> method, you will 
+        ///         leak memory. If you call the <see cref="FreeNativeOverlapped(NativeOverlapped*)"/> method more 
+        ///         than once on the same <see cref="NativeOverlapped"/> unmanaged pointer, memory will be corrupted.
+        ///     </note>
+        /// </remarks>
+        /// <exception cref="ArgumentNullException">
+        ///     <paramref name="overlapped"/> is <see langword="null"/>.
+        /// </exception>
+        /// <exception cref="ObjectDisposedException">
+        ///     This method was called after the <see cref="ThreadPoolBoundHandle"/> was disposed.
+        /// </exception>
+        [CLSCompliant(false)]
+        public unsafe void FreeNativeOverlapped(NativeOverlapped* overlapped)
+        {
+            if (overlapped == null)
+                throw new ArgumentNullException(nameof(overlapped));
+
+            // Note: we explicitly allow FreeNativeOverlapped calls after the ThreadPoolBoundHandle has been Disposed.
+
+            ThreadPoolBoundHandleOverlapped wrapper = GetOverlappedWrapper(overlapped, this);
+
+            if (wrapper._boundHandle != this)
+                throw new ArgumentException(SR.Argument_NativeOverlappedWrongBoundHandle, nameof(overlapped));
+
+            if (wrapper._preAllocated != null)
+                wrapper._preAllocated.Release();
+            else
+                Overlapped.Free(overlapped);
+        }
+
+        /// <summary>
+        ///     Returns the user-provided object specified when the <see cref="NativeOverlapped"/> instance was
+        ///     allocated using the <see cref="AllocateNativeOverlapped(IOCompletionCallback, object, byte[])"/>.
+        /// </summary>
+        /// <param name="overlapped">
+        ///     An unmanaged pointer to the <see cref="NativeOverlapped"/> structure from which to return the 
+        ///     associated user-provided object.
+        /// </param>
+        /// <returns>
+        ///     A user-provided object that distinguishes this <see cref="NativeOverlapped"/> 
+        ///     from other <see cref="NativeOverlapped"/> instances, otherwise, <see langword="null"/> if one was 
+        ///     not specified when the instance was allocated using <see cref="AllocateNativeOverlapped"/>.
+        /// </returns>
+        /// <exception cref="ArgumentNullException">
+        ///     <paramref name="overlapped"/> is <see langword="null"/>.
+        /// </exception>
+        [CLSCompliant(false)]
+        public static unsafe object GetNativeOverlappedState(NativeOverlapped* overlapped)
+        {
+            if (overlapped == null)
+                throw new ArgumentNullException(nameof(overlapped));
+
+            ThreadPoolBoundHandleOverlapped wrapper = GetOverlappedWrapper(overlapped, null);
+            Debug.Assert(wrapper._boundHandle != null);
+            return wrapper._userState;
+        }
+
+        private static unsafe ThreadPoolBoundHandleOverlapped GetOverlappedWrapper(NativeOverlapped* overlapped, ThreadPoolBoundHandle expectedBoundHandle)
+        {
+            ThreadPoolBoundHandleOverlapped wrapper;
+            try
+            {
+                wrapper = (ThreadPoolBoundHandleOverlapped)Overlapped.Unpack(overlapped);
+            }
+            catch (NullReferenceException ex)
+            {
+                throw new ArgumentException(SR.Argument_NativeOverlappedAlreadyFree, nameof(overlapped), ex);
+            }
+
+            return wrapper;
+        }
+
+        public void Dispose()
+        {
+            // .NET Native's version of ThreadPoolBoundHandle that wraps the Win32 ThreadPool holds onto
+            // native resources so it needs to be disposable. To match the contract, we are also disposable.
+            // We also implement a disposable state to mimic behavior between this implementation and 
+            // .NET Native's version (code written against us, will also work against .NET Native's version).
+            _isDisposed = true;
+        }
+
+
+        private void EnsureNotDisposed()
+        {
+            if (_isDisposed)
+                throw new ObjectDisposedException(GetType().ToString());
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolBoundHandleOverlapped.cs b/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolBoundHandleOverlapped.cs
new file mode 100644
index 0000000000..7ce8936bf7
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolBoundHandleOverlapped.cs
@@ -0,0 +1,52 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Threading
+{
+    /// <summary>
+    /// Overlapped subclass adding data needed by ThreadPoolBoundHandle.
+    /// </summary>
+    internal sealed class ThreadPoolBoundHandleOverlapped : Overlapped
+    {
+        private static readonly unsafe IOCompletionCallback s_completionCallback = CompletionCallback;
+
+        private readonly IOCompletionCallback _userCallback;
+        internal readonly object _userState;
+        internal PreAllocatedOverlapped _preAllocated;
+        internal unsafe NativeOverlapped* _nativeOverlapped;
+        internal ThreadPoolBoundHandle _boundHandle;
+        internal bool _completed;
+
+        public unsafe ThreadPoolBoundHandleOverlapped(IOCompletionCallback callback, object state, object pinData, PreAllocatedOverlapped preAllocated)
+        {
+            _userCallback = callback;
+            _userState = state;
+            _preAllocated = preAllocated;
+
+            _nativeOverlapped = Pack(s_completionCallback, pinData);
+            _nativeOverlapped->OffsetLow = 0;        // CLR reuses NativeOverlapped instances and does not reset these
+            _nativeOverlapped->OffsetHigh = 0;
+        }
+
+        private static unsafe void CompletionCallback(uint errorCode, uint numBytes, NativeOverlapped* nativeOverlapped)
+        {
+            ThreadPoolBoundHandleOverlapped overlapped = (ThreadPoolBoundHandleOverlapped)Overlapped.Unpack(nativeOverlapped);
+
+            //
+            // The Win32 thread pool implementation of ThreadPoolBoundHandle does not permit reuse of NativeOverlapped
+            // pointers without freeing them and allocating new a new one.  We need to ensure that code using the CLR
+            // ThreadPool implementation follows those rules.
+            //
+            if (overlapped._completed)
+                throw new InvalidOperationException(SR.InvalidOperation_NativeOverlappedReused);
+
+            overlapped._completed = true;
+
+            if (overlapped._boundHandle == null)
+                throw new InvalidOperationException(SR.Argument_NativeOverlappedAlreadyFree);
+
+            overlapped._userCallback(errorCode, numBytes, nativeOverlapped);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolPreAllocatedOverlapped.cs b/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolPreAllocatedOverlapped.cs
new file mode 100644
index 0000000000..a42e0c7983
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/ClrThreadPoolPreAllocatedOverlapped.cs
@@ -0,0 +1,105 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Threading
+{
+    /// <summary>
+    /// Represents pre-allocated state for native overlapped I/O operations.
+    /// </summary>
+    /// <seealso cref="ThreadPoolBoundHandle.AllocateNativeOverlapped(PreAllocatedOverlapped)"/>
+    public sealed class PreAllocatedOverlapped : IDisposable, IDeferredDisposable
+    {
+        internal readonly ThreadPoolBoundHandleOverlapped _overlapped;
+        private DeferredDisposableLifetime<PreAllocatedOverlapped> _lifetime;
+
+        /// <summary>
+        ///     Initializes a new instance of the <see cref="PreAllocatedOverlapped"/> class, specifying 
+        ///     a delegate that is invoked when each asynchronous I/O operation is complete, a user-provided 
+        ///     object providing context, and managed objects that serve as buffers.
+        /// </summary>
+        /// <param name="callback">
+        ///     An <see cref="IOCompletionCallback"/> delegate that represents the callback method 
+        ///     invoked when each asynchronous I/O operation completes.
+        /// </param>
+        /// <param name="state">
+        ///     A user-provided object that distinguishes <see cref="NativeOverlapped"/> instance produced from this
+        ///     object from other <see cref="NativeOverlapped"/> instances. Can be <see langword="null"/>.
+        /// </param>
+        /// <param name="pinData">
+        ///     An object or array of objects representing the input or output buffer for the operations. Each 
+        ///     object represents a buffer, for example an array of bytes.  Can be <see langword="null"/>.
+        /// </param>
+        /// <remarks>
+        ///     The new <see cref="PreAllocatedOverlapped"/> instance can be passed to 
+        ///     <see cref="ThreadPoolBoundHandle.AllocateNativeOverlapped(PreAllocatedOverlapped)"/>, to produce
+        ///     a <see cref="NativeOverlapped"/> instance that can be passed to the operating system in overlapped
+        ///     I/O operations.  A single <see cref="PreAllocatedOverlapped"/> instance can only be used for 
+        ///     a single native I/O operation at a time.  However, the state stored in the <see cref="PreAllocatedOverlapped"/>
+        ///     instance can be reused for subsequent native operations.
+        ///     <note>
+        ///         The buffers specified in <paramref name="pinData"/> are pinned until <see cref="Dispose"/> is called.
+        ///     </note>
+        /// </remarks>
+        /// <exception cref="ArgumentNullException">
+        ///     <paramref name="callback"/> is <see langword="null"/>.
+        /// </exception>
+        /// <exception cref="ObjectDisposedException">
+        ///     This method was called after the <see cref="ThreadPoolBoundHandle"/> was disposed.
+        /// </exception>
+        [CLSCompliant(false)]
+        public unsafe PreAllocatedOverlapped(IOCompletionCallback callback, object state, object pinData)
+        {
+            if (callback == null)
+                throw new ArgumentNullException(nameof(callback));
+
+            _overlapped = new ThreadPoolBoundHandleOverlapped(callback, state, pinData, this);
+        }
+
+        internal bool AddRef()
+        {
+            return _lifetime.AddRef(this);
+        }
+
+        internal void Release()
+        {
+            _lifetime.Release(this);
+        }
+
+        /// <summary>
+        /// Frees the resources associated with this <see cref="PreAllocatedOverlapped"/> instance. 
+        /// </summary>
+        public unsafe void Dispose()
+        {
+            _lifetime.Dispose(this);
+            GC.SuppressFinalize(this);
+        }
+
+        ~PreAllocatedOverlapped()
+        {
+            //
+            // During shutdown, don't automatically clean up, because this instance may still be
+            // reachable/usable by other code.
+            //
+            if (!Environment.HasShutdownStarted)
+                Dispose();
+        }
+
+        unsafe void IDeferredDisposable.OnFinalRelease(bool disposed)
+        {
+            if (_overlapped != null)
+            {
+                if (disposed)
+                {
+                    Overlapped.Free(_overlapped._nativeOverlapped);
+                }
+                else
+                {
+                    _overlapped._boundHandle = null;
+                    _overlapped._completed = false;
+                    *_overlapped._nativeOverlapped = default(NativeOverlapped);
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/EventWaitHandle.cs b/src/System.Private.CoreLib/src/System/Threading/EventWaitHandle.cs
new file mode 100644
index 0000000000..c2ffb8c5b1
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/EventWaitHandle.cs
@@ -0,0 +1,232 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+/*=============================================================================
+**
+**
+**
+** Purpose: Base class for representing Events
+**
+**
+=============================================================================*/
+
+
+namespace System.Security.AccessControl
+{
+    internal class EventWaitHandleSecurity
+    {
+    }
+    internal enum EventWaitHandleRights
+    {
+    }
+}
+
+namespace System.Threading
+{
+    using System;
+    using System.Threading;
+    using System.Runtime.CompilerServices;
+    using System.IO;
+    using Microsoft.Win32;
+    using Microsoft.Win32.SafeHandles;
+    using System.Runtime.InteropServices;
+    using System.Runtime.Versioning;
+    using System.Security.AccessControl;
+
+    [ComVisibleAttribute(true)]
+    public class EventWaitHandle : WaitHandle
+    {
+        private const uint AccessRights =
+            (uint)Win32Native.MAXIMUM_ALLOWED | Win32Native.SYNCHRONIZE | Win32Native.EVENT_MODIFY_STATE;
+
+        public EventWaitHandle(bool initialState, EventResetMode mode) : this(initialState, mode, null) { }
+
+        public EventWaitHandle(bool initialState, EventResetMode mode, string name)
+        {
+            if (name != null)
+            {
+#if PLATFORM_UNIX
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_NamedSynchronizationPrimitives);
+#else
+                if (Interop.Kernel32.MAX_PATH < name.Length)
+                {
+                    throw new ArgumentException(SR.Format(SR.Argument_WaitHandleNameTooLong, name, Interop.Kernel32.MAX_PATH), nameof(name));
+                }
+#endif
+            }
+
+            uint eventFlags = initialState ? Win32Native.CREATE_EVENT_INITIAL_SET : 0;
+            switch (mode)
+            {
+                case EventResetMode.ManualReset:
+                    eventFlags |= Win32Native.CREATE_EVENT_MANUAL_RESET;
+                    break;
+
+                case EventResetMode.AutoReset:
+                    break;
+
+                default:
+                    throw new ArgumentException(SR.Format(SR.Argument_InvalidFlag, name));
+            };
+
+            SafeWaitHandle _handle = Win32Native.CreateEventEx(null, name, eventFlags, AccessRights);
+
+            if (_handle.IsInvalid)
+            {
+                int errorCode = Marshal.GetLastWin32Error();
+
+                _handle.SetHandleAsInvalid();
+                if (null != name && 0 != name.Length && Interop.Errors.ERROR_INVALID_HANDLE == errorCode)
+                    throw new WaitHandleCannotBeOpenedException(SR.Format(SR.Threading_WaitHandleCannotBeOpenedException_InvalidHandle, name));
+
+                throw Win32Marshal.GetExceptionForWin32Error(errorCode, name);
+            }
+            SetHandleInternal(_handle);
+        }
+
+        public EventWaitHandle(bool initialState, EventResetMode mode, string name, out bool createdNew)
+            : this(initialState, mode, name, out createdNew, null)
+        {
+        }
+
+        internal unsafe EventWaitHandle(bool initialState, EventResetMode mode, string name, out bool createdNew, EventWaitHandleSecurity eventSecurity)
+        {
+            if (name != null)
+            {
+#if PLATFORM_UNIX
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_NamedSynchronizationPrimitives);
+#else
+                if (Interop.Kernel32.MAX_PATH < name.Length)
+                {
+                    throw new ArgumentException(SR.Format(SR.Argument_WaitHandleNameTooLong, name, Interop.Kernel32.MAX_PATH), nameof(name));
+                }
+#endif
+            }
+            Win32Native.SECURITY_ATTRIBUTES secAttrs = null;
+
+            uint eventFlags = initialState ? Win32Native.CREATE_EVENT_INITIAL_SET : 0;
+            switch (mode)
+            {
+                case EventResetMode.ManualReset:
+                    eventFlags |= Win32Native.CREATE_EVENT_MANUAL_RESET;
+                    break;
+
+                case EventResetMode.AutoReset:
+                    break;
+
+                default:
+                    throw new ArgumentException(SR.Format(SR.Argument_InvalidFlag, name));
+            };
+
+            SafeWaitHandle _handle = Win32Native.CreateEventEx(secAttrs, name, eventFlags, AccessRights);
+
+            int errorCode = Marshal.GetLastWin32Error();
+            if (_handle.IsInvalid)
+            {
+                _handle.SetHandleAsInvalid();
+                if (null != name && 0 != name.Length && Interop.Errors.ERROR_INVALID_HANDLE == errorCode)
+                    throw new WaitHandleCannotBeOpenedException(SR.Format(SR.Threading_WaitHandleCannotBeOpenedException_InvalidHandle, name));
+
+                throw Win32Marshal.GetExceptionForWin32Error(errorCode, name);
+            }
+            createdNew = errorCode != Interop.Errors.ERROR_ALREADY_EXISTS;
+            SetHandleInternal(_handle);
+        }
+
+        private EventWaitHandle(SafeWaitHandle handle)
+        {
+            SetHandleInternal(handle);
+        }
+
+        public static EventWaitHandle OpenExisting(string name)
+        {
+            return OpenExisting(name, (EventWaitHandleRights)0);
+        }
+
+        internal static EventWaitHandle OpenExisting(string name, EventWaitHandleRights rights)
+        {
+            EventWaitHandle result;
+            switch (OpenExistingWorker(name, rights, out result))
+            {
+                case OpenExistingResult.NameNotFound:
+                    throw new WaitHandleCannotBeOpenedException();
+
+                case OpenExistingResult.NameInvalid:
+                    throw new WaitHandleCannotBeOpenedException(SR.Format(SR.Threading_WaitHandleCannotBeOpenedException_InvalidHandle, name));
+
+                case OpenExistingResult.PathNotFound:
+                    throw Win32Marshal.GetExceptionForWin32Error(Interop.Errors.ERROR_PATH_NOT_FOUND, "");
+
+                default:
+                    return result;
+            }
+        }
+
+        public static bool TryOpenExisting(string name, out EventWaitHandle result)
+        {
+            return OpenExistingWorker(name, (EventWaitHandleRights)0, out result) == OpenExistingResult.Success;
+        }
+
+        private static OpenExistingResult OpenExistingWorker(string name, EventWaitHandleRights rights, out EventWaitHandle result)
+        {
+#if PLATFORM_UNIX
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_NamedSynchronizationPrimitives);
+#else
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
+            if (name.Length == 0)
+            {
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(name));
+            }
+
+            if (null != name && Interop.Kernel32.MAX_PATH < name.Length)
+            {
+                throw new ArgumentException(SR.Format(SR.Argument_WaitHandleNameTooLong, name, Interop.Kernel32.MAX_PATH), nameof(name));
+            }
+
+
+            result = null;
+
+            SafeWaitHandle myHandle = Win32Native.OpenEvent(AccessRights, false, name);
+
+            if (myHandle.IsInvalid)
+            {
+                int errorCode = Marshal.GetLastWin32Error();
+
+                if (Interop.Errors.ERROR_FILE_NOT_FOUND == errorCode || Interop.Errors.ERROR_INVALID_NAME == errorCode)
+                    return OpenExistingResult.NameNotFound;
+                if (Interop.Errors.ERROR_PATH_NOT_FOUND == errorCode)
+                    return OpenExistingResult.PathNotFound;
+                if (null != name && 0 != name.Length && Interop.Errors.ERROR_INVALID_HANDLE == errorCode)
+                    return OpenExistingResult.NameInvalid;
+                //this is for passed through Win32Native Errors
+                throw Win32Marshal.GetExceptionForWin32Error(errorCode, "");
+            }
+            result = new EventWaitHandle(myHandle);
+            return OpenExistingResult.Success;
+#endif
+        }
+        public bool Reset()
+        {
+            bool res = Win32Native.ResetEvent(safeWaitHandle);
+            if (!res)
+                throw Win32Marshal.GetExceptionForLastWin32Error();
+            return res;
+        }
+        public bool Set()
+        {
+            bool res = Win32Native.SetEvent(safeWaitHandle);
+
+            if (!res)
+                throw Win32Marshal.GetExceptionForLastWin32Error();
+
+            return res;
+        }
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Threading/Interlocked.cs b/src/System.Private.CoreLib/src/System/Threading/Interlocked.cs
new file mode 100644
index 0000000000..898b0b1823
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Interlocked.cs
@@ -0,0 +1,173 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+using Internal.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace System.Threading
+{
+    // After much discussion, we decided the Interlocked class doesn't need 
+    // any HPA's for synchronization or external threading.  They hurt C#'s 
+    // codegen for the yield keyword, and arguably they didn't protect much.  
+    // Instead, they penalized people (and compilers) for writing threadsafe 
+    // code.
+    public static class Interlocked
+    {
+        /******************************
+         * Increment
+         *   Implemented: int
+         *                        long
+         *****************************/
+
+        public static int Increment(ref int location)
+        {
+            return Add(ref location, 1);
+        }
+
+        public static long Increment(ref long location)
+        {
+            return Add(ref location, 1);
+        }
+
+        /******************************
+         * Decrement
+         *   Implemented: int
+         *                        long
+         *****************************/
+
+        public static int Decrement(ref int location)
+        {
+            return Add(ref location, -1);
+        }
+
+        public static long Decrement(ref long location)
+        {
+            return Add(ref location, -1);
+        }
+
+        /******************************
+         * Exchange
+         *   Implemented: int
+         *                        long
+         *                        float
+         *                        double
+         *                        Object
+         *                        IntPtr
+         *****************************/
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern int Exchange(ref int location1, int value);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern long Exchange(ref long location1, long value);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern float Exchange(ref float location1, float value);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern double Exchange(ref double location1, double value);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern Object Exchange(ref Object location1, Object value);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern IntPtr Exchange(ref IntPtr location1, IntPtr value);
+
+        // This whole method reduces to a single call to Exchange(ref object, object) but
+        // the JIT thinks that it will generate more native code than it actually does.
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static T Exchange<T>(ref T location1, T value) where T : class
+        {
+            return Unsafe.As<T>(Exchange(ref Unsafe.As<T, object>(ref location1), value));
+        }
+
+        /******************************
+         * CompareExchange
+         *    Implemented: int
+         *                         long
+         *                         float
+         *                         double
+         *                         Object
+         *                         IntPtr
+         *****************************/
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern int CompareExchange(ref int location1, int value, int comparand);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern long CompareExchange(ref long location1, long value, long comparand);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern float CompareExchange(ref float location1, float value, float comparand);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern double CompareExchange(ref double location1, double value, double comparand);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern Object CompareExchange(ref Object location1, Object value, Object comparand);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern IntPtr CompareExchange(ref IntPtr location1, IntPtr value, IntPtr comparand);
+
+        // Note that getILIntrinsicImplementationForInterlocked() in vm\jitinterface.cpp replaces
+        // the body of this method with the the following IL:
+        //     ldarg.0 
+        //     ldarg.1
+        //     ldarg.2
+        //     call System.Threading.Interlocked::CompareExchange(ref Object, Object, Object)
+        //     ret
+        // The workaround is no longer strictly necessary now that we have Unsafe.As but it does
+        // have the advantage of being less sensitive to JIT's inliner decisions.
+        public static T CompareExchange<T>(ref T location1, T value, T comparand) where T : class
+        {
+            return Unsafe.As<T>(CompareExchange(ref Unsafe.As<T, object>(ref location1), value, comparand));
+        }
+
+        // BCL-internal overload that returns success via a ref bool param, useful for reliable spin locks.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int CompareExchange(ref int location1, int value, int comparand, ref bool succeeded);
+
+        /******************************
+         * Add
+         *    Implemented: int
+         *                         long
+         *****************************/
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int ExchangeAdd(ref int location1, int value);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern long ExchangeAdd(ref long location1, long value);
+
+        public static int Add(ref int location1, int value)
+        {
+            return ExchangeAdd(ref location1, value) + value;
+        }
+
+        public static long Add(ref long location1, long value)
+        {
+            return ExchangeAdd(ref location1, value) + value;
+        }
+
+        /******************************
+         * Read
+         *****************************/
+        public static long Read(ref long location)
+        {
+            return Interlocked.CompareExchange(ref location, 0, 0);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void MemoryBarrier();
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void _MemoryBarrierProcessWide();
+
+        public static void MemoryBarrierProcessWide()
+        {
+            _MemoryBarrierProcessWide();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/ManualResetEventSlim.cs b/src/System.Private.CoreLib/src/System/Threading/ManualResetEventSlim.cs
new file mode 100644
index 0000000000..d0a8d34d04
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/ManualResetEventSlim.cs
@@ -0,0 +1,770 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+#pragma warning disable 0420
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+// SlimManualResetEvent.cs
+//
+//
+// An manual-reset event that mixes a little spinning with a true Win32 event.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Diagnostics;
+
+namespace System.Threading
+{
+    // ManualResetEventSlim wraps a manual-reset event internally with a little bit of
+    // spinning. When an event will be set imminently, it is often advantageous to avoid
+    // a 4k+ cycle context switch in favor of briefly spinning. Therefore we layer on to
+    // a brief amount of spinning that should, on the average, make using the slim event
+    // cheaper than using Win32 events directly. This can be reset manually, much like
+    // a Win32 manual-reset would be.
+    //
+    // Notes:
+    //     We lazily allocate the Win32 event internally. Therefore, the caller should
+    //     always call Dispose to clean it up, just in case. This API is a no-op of the
+    //     event wasn't allocated, but if it was, ensures that the event goes away
+    //     eagerly, instead of waiting for finalization.
+
+    /// <summary>
+    /// Provides a slimmed down version of <see cref="T:System.Threading.ManualResetEvent"/>.
+    /// </summary>
+    /// <remarks>
+    /// All public and protected members of <see cref="ManualResetEventSlim"/> are thread-safe and may be used
+    /// concurrently from multiple threads, with the exception of Dispose, which
+    /// must only be used when all other operations on the <see cref="ManualResetEventSlim"/> have
+    /// completed, and Reset, which should only be used when no other threads are
+    /// accessing the event.
+    /// </remarks>
+    [DebuggerDisplay("Set = {IsSet}")]
+    public class ManualResetEventSlim : IDisposable
+    {
+        // These are the default spin counts we use on single-proc and MP machines.
+        private const int DEFAULT_SPIN_SP = 1;
+
+        private volatile object m_lock;
+        // A lock used for waiting and pulsing. Lazily initialized via EnsureLockObjectCreated()
+
+        private volatile ManualResetEvent m_eventObj; // A true Win32 event used for waiting.
+
+        // -- State -- //
+        //For a packed word a uint would seem better, but Interlocked.* doesn't support them as uint isn't CLS-compliant.
+        private volatile int m_combinedState; //ie a UInt32. Used for the state items listed below. 
+
+        //1-bit for  signalled state
+        private const int SignalledState_BitMask = unchecked((int)0x80000000);//1000 0000 0000 0000 0000 0000 0000 0000
+        private const int SignalledState_ShiftCount = 31;
+
+        //1-bit for disposed state
+        private const int Dispose_BitMask = unchecked((int)0x40000000);//0100 0000 0000 0000 0000 0000 0000 0000
+
+        //11-bits for m_spinCount
+        private const int SpinCountState_BitMask = unchecked((int)0x3FF80000); //0011 1111 1111 1000 0000 0000 0000 0000
+        private const int SpinCountState_ShiftCount = 19;
+        private const int SpinCountState_MaxValue = (1 << 11) - 1; //2047
+
+        //19-bits for m_waiters.  This allows support of 512K threads waiting which should be ample
+        private const int NumWaitersState_BitMask = unchecked((int)0x0007FFFF); // 0000 0000 0000 0111 1111 1111 1111 1111
+        private const int NumWaitersState_ShiftCount = 0;
+        private const int NumWaitersState_MaxValue = (1 << 19) - 1; //512K-1
+        // ----------- //
+
+#if DEBUG
+        private static int s_nextId; // The next id that will be given out.
+        private int m_id = Interlocked.Increment(ref s_nextId); // A unique id for debugging purposes only.
+        private long m_lastSetTime;
+        private long m_lastResetTime;
+#endif
+
+        /// <summary>
+        /// Gets the underlying <see cref="T:System.Threading.WaitHandle"/> object for this <see
+        /// cref="ManualResetEventSlim"/>.
+        /// </summary>
+        /// <value>The underlying <see cref="T:System.Threading.WaitHandle"/> event object fore this <see
+        /// cref="ManualResetEventSlim"/>.</value>
+        /// <remarks>
+        /// Accessing this property forces initialization of an underlying event object if one hasn't
+        /// already been created.  To simply wait on this <see cref="ManualResetEventSlim"/>, 
+        /// the public Wait methods should be preferred.
+        /// </remarks>
+        public WaitHandle WaitHandle
+        {
+            get
+            {
+                ThrowIfDisposed();
+                if (m_eventObj == null)
+                {
+                    // Lazily initialize the event object if needed.
+                    LazyInitializeEvent();
+                }
+
+                return m_eventObj;
+            }
+        }
+
+        /// <summary>
+        /// Gets whether the event is set.
+        /// </summary>
+        /// <value>true if the event has is set; otherwise, false.</value>
+        public bool IsSet
+        {
+            get
+            {
+                return 0 != ExtractStatePortion(m_combinedState, SignalledState_BitMask);
+            }
+
+            private set
+            {
+                UpdateStateAtomically(((value) ? 1 : 0) << SignalledState_ShiftCount, SignalledState_BitMask);
+            }
+        }
+
+        /// <summary>
+        /// Gets the number of spin waits that will be occur before falling back to a true wait.
+        /// </summary>
+        public int SpinCount
+        {
+            get
+            {
+                return ExtractStatePortionAndShiftRight(m_combinedState, SpinCountState_BitMask, SpinCountState_ShiftCount);
+            }
+
+            private set
+            {
+                Debug.Assert(value >= 0, "SpinCount is a restricted-width integer. The value supplied is outside the legal range.");
+                Debug.Assert(value <= SpinCountState_MaxValue, "SpinCount is a restricted-width integer. The value supplied is outside the legal range.");
+                // Don't worry about thread safety because it's set one time from the constructor
+                m_combinedState = (m_combinedState & ~SpinCountState_BitMask) | (value << SpinCountState_ShiftCount);
+            }
+        }
+
+        /// <summary>
+        /// How many threads are waiting.
+        /// </summary>
+        private int Waiters
+        {
+            get
+            {
+                return ExtractStatePortionAndShiftRight(m_combinedState, NumWaitersState_BitMask, NumWaitersState_ShiftCount);
+            }
+
+            set
+            {
+                //setting to <0 would indicate an internal flaw, hence Assert is appropriate.
+                Debug.Assert(value >= 0, "NumWaiters should never be less than zero. This indicates an internal error.");
+
+                // it is possible for the max number of waiters to be exceeded via user-code, hence we use a real exception here.
+                if (value >= NumWaitersState_MaxValue)
+                    throw new InvalidOperationException(String.Format(SR.ManualResetEventSlim_ctor_TooManyWaiters, NumWaitersState_MaxValue));
+
+                UpdateStateAtomically(value << NumWaitersState_ShiftCount, NumWaitersState_BitMask);
+            }
+        }
+
+        //-----------------------------------------------------------------------------------
+        // Constructs a new event, optionally specifying the initial state and spin count.
+        // The defaults are that the event is unsignaled and some reasonable default spin.
+        //
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ManualResetEventSlim"/>
+        /// class with an initial state of nonsignaled.
+        /// </summary>
+        public ManualResetEventSlim()
+            : this(false)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ManualResetEventSlim"/>
+        /// class with a boolean value indicating whether to set the initial state to signaled.
+        /// </summary>
+        /// <param name="initialState">true to set the initial state signaled; false to set the initial state
+        /// to nonsignaled.</param>
+        public ManualResetEventSlim(bool initialState)
+        {
+            // Specify the defualt spin count, and use default spin if we're
+            // on a multi-processor machine. Otherwise, we won't.
+            Initialize(initialState, SpinWait.SpinCountforSpinBeforeWait);
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ManualResetEventSlim"/>
+        /// class with a Boolean value indicating whether to set the initial state to signaled and a specified
+        /// spin count.
+        /// </summary>
+        /// <param name="initialState">true to set the initial state to signaled; false to set the initial state
+        /// to nonsignaled.</param>
+        /// <param name="spinCount">The number of spin waits that will occur before falling back to a true
+        /// wait.</param>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="spinCount"/> is less than
+        /// 0 or greater than the maximum allowed value.</exception>
+        public ManualResetEventSlim(bool initialState, int spinCount)
+        {
+            if (spinCount < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(spinCount));
+            }
+
+            if (spinCount > SpinCountState_MaxValue)
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(spinCount),
+                    String.Format(SR.ManualResetEventSlim_ctor_SpinCountOutOfRange, SpinCountState_MaxValue));
+            }
+
+            // We will suppress default spin  because the user specified a count.
+            Initialize(initialState, spinCount);
+        }
+
+        /// <summary>
+        /// Initializes the internal state of the event.
+        /// </summary>
+        /// <param name="initialState">Whether the event is set initially or not.</param>
+        /// <param name="spinCount">The spin count that decides when the event will block.</param>
+        private void Initialize(bool initialState, int spinCount)
+        {
+            m_combinedState = initialState ? (1 << SignalledState_ShiftCount) : 0;
+            //the spinCount argument has been validated by the ctors.
+            //but we now sanity check our predefined constants.
+            Debug.Assert(DEFAULT_SPIN_SP >= 0, "Internal error - DEFAULT_SPIN_SP is outside the legal range.");
+            Debug.Assert(DEFAULT_SPIN_SP <= SpinCountState_MaxValue, "Internal error - DEFAULT_SPIN_SP is outside the legal range.");
+
+            SpinCount = PlatformHelper.IsSingleProcessor ? DEFAULT_SPIN_SP : spinCount;
+        }
+
+        /// <summary>
+        /// Helper to ensure the lock object is created before first use.
+        /// </summary>
+        private void EnsureLockObjectCreated()
+        {
+            if (m_lock != null)
+                return;
+
+            object newObj = new object();
+            Interlocked.CompareExchange(ref m_lock, newObj, null); // failure is benign. Someone else set the value.
+        }
+
+        /// <summary>
+        /// This method lazily initializes the event object. It uses CAS to guarantee that
+        /// many threads racing to call this at once don't result in more than one event
+        /// being stored and used. The event will be signaled or unsignaled depending on
+        /// the state of the thin-event itself, with synchronization taken into account.
+        /// </summary>
+        /// <returns>True if a new event was created and stored, false otherwise.</returns>
+        private bool LazyInitializeEvent()
+        {
+            bool preInitializeIsSet = IsSet;
+            ManualResetEvent newEventObj = new ManualResetEvent(preInitializeIsSet);
+
+            // We have to CAS this in case we are racing with another thread. We must
+            // guarantee only one event is actually stored in this field.
+            if (Interlocked.CompareExchange(ref m_eventObj, newEventObj, null) != null)
+            {
+                // Someone else set the value due to a race condition. Destroy the garbage event.
+                newEventObj.Close();
+
+                return false;
+            }
+            else
+            {
+                // Now that the event is published, verify that the state hasn't changed since
+                // we snapped the preInitializeState. Another thread could have done that
+                // between our initial observation above and here. The barrier incurred from
+                // the CAS above (in addition to m_state being volatile) prevents this read
+                // from moving earlier and being collapsed with our original one.
+                bool currentIsSet = IsSet;
+                if (currentIsSet != preInitializeIsSet)
+                {
+                    Debug.Assert(currentIsSet,
+                        "The only safe concurrent transition is from unset->set: detected set->unset.");
+
+                    // We saw it as unsignaled, but it has since become set.
+                    lock (newEventObj)
+                    {
+                        // If our event hasn't already been disposed of, we must set it.
+                        if (m_eventObj == newEventObj)
+                        {
+                            newEventObj.Set();
+                        }
+                    }
+                }
+
+                return true;
+            }
+        }
+
+        /// <summary>
+        /// Sets the state of the event to signaled, which allows one or more threads waiting on the event to
+        /// proceed.
+        /// </summary>
+        public void Set()
+        {
+            Set(false);
+        }
+
+        /// <summary>
+        /// Private helper to actually perform the Set.
+        /// </summary>
+        /// <param name="duringCancellation">Indicates whether we are calling Set() during cancellation.</param>
+        /// <exception cref="T:System.OperationCanceledException">The object has been canceled.</exception>
+        private void Set(bool duringCancellation)
+        {
+            // We need to ensure that IsSet=true does not get reordered past the read of m_eventObj
+            // This would be a legal movement according to the .NET memory model. 
+            // The code is safe as IsSet involves an Interlocked.CompareExchange which provides a full memory barrier.
+            IsSet = true;
+
+            // If there are waiting threads, we need to pulse them.
+            if (Waiters > 0)
+            {
+                Debug.Assert(m_lock != null); //if waiters>0, then m_lock has already been created.
+                lock (m_lock)
+                {
+                    Monitor.PulseAll(m_lock);
+                }
+            }
+
+            ManualResetEvent eventObj = m_eventObj;
+
+            //Design-decision: do not set the event if we are in cancellation -> better to deadlock than to wake up waiters incorrectly
+            //It would be preferable to wake up the event and have it throw OCE. This requires MRE to implement cancellation logic
+
+            if (eventObj != null && !duringCancellation)
+            {
+                // We must surround this call to Set in a lock.  The reason is fairly subtle.
+                // Sometimes a thread will issue a Wait and wake up after we have set m_state,
+                // but before we have gotten around to setting m_eventObj (just below). That's
+                // because Wait first checks m_state and will only access the event if absolutely
+                // necessary.  However, the coding pattern { event.Wait(); event.Dispose() } is
+                // quite common, and we must support it.  If the waiter woke up and disposed of
+                // the event object before the setter has finished, however, we would try to set a
+                // now-disposed Win32 event.  Crash!  To deal with this race condition, we use a lock to
+                // protect access to the event object when setting and disposing of it.  We also
+                // double-check that the event has not become null in the meantime when in the lock.
+
+                lock (eventObj)
+                {
+                    if (m_eventObj != null)
+                    {
+                        // If somebody is waiting, we must set the event.
+                        m_eventObj.Set();
+                    }
+                }
+            }
+
+#if DEBUG
+            m_lastSetTime = DateTime.UtcNow.Ticks;
+#endif
+        }
+
+        /// <summary>
+        /// Sets the state of the event to nonsignaled, which causes threads to block.
+        /// </summary>
+        /// <remarks>
+        /// Unlike most of the members of <see cref="ManualResetEventSlim"/>, <see cref="Reset()"/> is not
+        /// thread-safe and may not be used concurrently with other members of this instance.
+        /// </remarks>
+        public void Reset()
+        {
+            ThrowIfDisposed();
+            // If there's an event, reset it.
+            if (m_eventObj != null)
+            {
+                m_eventObj.Reset();
+            }
+
+            // There is a race condition here. If another thread Sets the event, we will get into a state
+            // where m_state will be unsignaled, yet the Win32 event object will have been signaled.
+            // This could cause waiting threads to wake up even though the event is in an
+            // unsignaled state. This is fine -- those that are calling Reset concurrently are
+            // responsible for doing "the right thing" -- e.g. rechecking the condition and
+            // resetting the event manually.
+
+            // And finally set our state back to unsignaled.
+            IsSet = false;
+
+#if DEBUG
+            m_lastResetTime = DateTime.UtcNow.Ticks;
+#endif
+        }
+
+        /// <summary>
+        /// Blocks the current thread until the current <see cref="ManualResetEventSlim"/> is set.
+        /// </summary>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The maximum number of waiters has been exceeded.
+        /// </exception>
+        /// <remarks>
+        /// The caller of this method blocks indefinitely until the current instance is set. The caller will
+        /// return immediately if the event is currently in a set state.
+        /// </remarks>
+        public void Wait()
+        {
+            Wait(Timeout.Infinite, new CancellationToken());
+        }
+
+        /// <summary>
+        /// Blocks the current thread until the current <see cref="ManualResetEventSlim"/> receives a signal,
+        /// while observing a <see cref="T:System.Threading.CancellationToken"/>.
+        /// </summary>
+        /// <param name="cancellationToken">The <see cref="T:System.Threading.CancellationToken"/> to
+        /// observe.</param>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The maximum number of waiters has been exceeded.
+        /// </exception>
+        /// <exception cref="T:System.OperationCanceledExcepton"><paramref name="cancellationToken"/> was
+        /// canceled.</exception>
+        /// <remarks>
+        /// The caller of this method blocks indefinitely until the current instance is set. The caller will
+        /// return immediately if the event is currently in a set state.
+        /// </remarks>
+        public void Wait(CancellationToken cancellationToken)
+        {
+            Wait(Timeout.Infinite, cancellationToken);
+        }
+
+        /// <summary>
+        /// Blocks the current thread until the current <see cref="ManualResetEventSlim"/> is set, using a
+        /// <see cref="T:System.TimeSpan"/> to measure the time interval.
+        /// </summary>
+        /// <param name="timeout">A <see cref="System.TimeSpan"/> that represents the number of milliseconds
+        /// to wait, or a <see cref="System.TimeSpan"/> that represents -1 milliseconds to wait indefinitely.
+        /// </param>
+        /// <returns>true if the <see cref="System.Threading.ManualResetEventSlim"/> was set; otherwise,
+        /// false.</returns>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="timeout"/> is a negative
+        /// number other than -1 milliseconds, which represents an infinite time-out -or- timeout is greater
+        /// than <see cref="System.Int32.MaxValue"/>.</exception>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The maximum number of waiters has been exceeded.
+        /// </exception>
+        public bool Wait(TimeSpan timeout)
+        {
+            long totalMilliseconds = (long)timeout.TotalMilliseconds;
+            if (totalMilliseconds < -1 || totalMilliseconds > int.MaxValue)
+            {
+                throw new ArgumentOutOfRangeException(nameof(timeout));
+            }
+
+            return Wait((int)totalMilliseconds, new CancellationToken());
+        }
+
+        /// <summary>
+        /// Blocks the current thread until the current <see cref="ManualResetEventSlim"/> is set, using a
+        /// <see cref="T:System.TimeSpan"/> to measure the time interval, while observing a <see
+        /// cref="T:System.Threading.CancellationToken"/>.
+        /// </summary>
+        /// <param name="timeout">A <see cref="System.TimeSpan"/> that represents the number of milliseconds
+        /// to wait, or a <see cref="System.TimeSpan"/> that represents -1 milliseconds to wait indefinitely.
+        /// </param>
+        /// <param name="cancellationToken">The <see cref="T:System.Threading.CancellationToken"/> to
+        /// observe.</param>
+        /// <returns>true if the <see cref="System.Threading.ManualResetEventSlim"/> was set; otherwise,
+        /// false.</returns>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="timeout"/> is a negative
+        /// number other than -1 milliseconds, which represents an infinite time-out -or- timeout is greater
+        /// than <see cref="System.Int32.MaxValue"/>.</exception>
+        /// <exception cref="T:System.Threading.OperationCanceledException"><paramref
+        /// name="cancellationToken"/> was canceled.</exception>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The maximum number of waiters has been exceeded.
+        /// </exception>
+        public bool Wait(TimeSpan timeout, CancellationToken cancellationToken)
+        {
+            long totalMilliseconds = (long)timeout.TotalMilliseconds;
+            if (totalMilliseconds < -1 || totalMilliseconds > int.MaxValue)
+            {
+                throw new ArgumentOutOfRangeException(nameof(timeout));
+            }
+
+            return Wait((int)totalMilliseconds, cancellationToken);
+        }
+
+        /// <summary>
+        /// Blocks the current thread until the current <see cref="ManualResetEventSlim"/> is set, using a
+        /// 32-bit signed integer to measure the time interval.
+        /// </summary>
+        /// <param name="millisecondsTimeout">The number of milliseconds to wait, or <see
+        /// cref="Timeout.Infinite"/>(-1) to wait indefinitely.</param>
+        /// <returns>true if the <see cref="System.Threading.ManualResetEventSlim"/> was set; otherwise,
+        /// false.</returns>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="millisecondsTimeout"/> is a
+        /// negative number other than -1, which represents an infinite time-out.</exception>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The maximum number of waiters has been exceeded.
+        /// </exception>
+        public bool Wait(int millisecondsTimeout)
+        {
+            return Wait(millisecondsTimeout, new CancellationToken());
+        }
+
+        /// <summary>
+        /// Blocks the current thread until the current <see cref="ManualResetEventSlim"/> is set, using a
+        /// 32-bit signed integer to measure the time interval, while observing a <see
+        /// cref="T:System.Threading.CancellationToken"/>.
+        /// </summary>
+        /// <param name="millisecondsTimeout">The number of milliseconds to wait, or <see
+        /// cref="Timeout.Infinite"/>(-1) to wait indefinitely.</param>
+        /// <param name="cancellationToken">The <see cref="T:System.Threading.CancellationToken"/> to
+        /// observe.</param>
+        /// <returns>true if the <see cref="System.Threading.ManualResetEventSlim"/> was set; otherwise,
+        /// false.</returns>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="millisecondsTimeout"/> is a
+        /// negative number other than -1, which represents an infinite time-out.</exception>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The maximum number of waiters has been exceeded.
+        /// </exception>
+        /// <exception cref="T:System.Threading.OperationCanceledException"><paramref
+        /// name="cancellationToken"/> was canceled.</exception>
+        public bool Wait(int millisecondsTimeout, CancellationToken cancellationToken)
+        {
+            ThrowIfDisposed();
+            cancellationToken.ThrowIfCancellationRequested(); // an early convenience check
+
+            if (millisecondsTimeout < -1)
+            {
+                throw new ArgumentOutOfRangeException(nameof(millisecondsTimeout));
+            }
+
+            if (!IsSet)
+            {
+                if (millisecondsTimeout == 0)
+                {
+                    // For 0-timeouts, we just return immediately.
+                    return false;
+                }
+
+
+                // We spin briefly before falling back to allocating and/or waiting on a true event.
+                uint startTime = 0;
+                bool bNeedTimeoutAdjustment = false;
+                int realMillisecondsTimeout = millisecondsTimeout; //this will be adjusted if necessary.
+
+                if (millisecondsTimeout != Timeout.Infinite)
+                {
+                    // We will account for time spent spinning, so that we can decrement it from our
+                    // timeout.  In most cases the time spent in this section will be negligible.  But
+                    // we can't discount the possibility of our thread being switched out for a lengthy
+                    // period of time.  The timeout adjustments only take effect when and if we actually
+                    // decide to block in the kernel below.
+
+                    startTime = TimeoutHelper.GetTime();
+                    bNeedTimeoutAdjustment = true;
+                }
+
+                // Spin
+                int spinCount = SpinCount;
+                var spinner = new SpinWait();
+                while (spinner.Count < spinCount)
+                {
+                    spinner.SpinOnce(SpinWait.Sleep1ThresholdForSpinBeforeWait);
+
+                    if (IsSet)
+                    {
+                        return true;
+                    }
+
+                    if (spinner.Count >= 100 && spinner.Count % 10 == 0) // check the cancellation token if the user passed a very large spin count
+                        cancellationToken.ThrowIfCancellationRequested();
+                }
+
+                // Now enter the lock and wait.
+                EnsureLockObjectCreated();
+
+                // We must register and unregister the token outside of the lock, to avoid deadlocks.
+                using (cancellationToken.InternalRegisterWithoutEC(s_cancellationTokenCallback, this))
+                {
+                    lock (m_lock)
+                    {
+                        // Loop to cope with spurious wakeups from other waits being canceled
+                        while (!IsSet)
+                        {
+                            // If our token was canceled, we must throw and exit.
+                            cancellationToken.ThrowIfCancellationRequested();
+
+                            //update timeout (delays in wait commencement are due to spinning and/or spurious wakeups from other waits being canceled)
+                            if (bNeedTimeoutAdjustment)
+                            {
+                                realMillisecondsTimeout = TimeoutHelper.UpdateTimeOut(startTime, millisecondsTimeout);
+                                if (realMillisecondsTimeout <= 0)
+                                    return false;
+                            }
+
+                            // There is a race condition that Set will fail to see that there are waiters as Set does not take the lock, 
+                            // so after updating waiters, we must check IsSet again.
+                            // Also, we must ensure there cannot be any reordering of the assignment to Waiters and the
+                            // read from IsSet.  This is guaranteed as Waiters{set;} involves an Interlocked.CompareExchange
+                            // operation which provides a full memory barrier.
+                            // If we see IsSet=false, then we are guaranteed that Set() will see that we are
+                            // waiting and will pulse the monitor correctly.
+
+                            Waiters = Waiters + 1;
+
+                            if (IsSet) //This check must occur after updating Waiters.
+                            {
+                                Waiters--; //revert the increment.
+                                return true;
+                            }
+
+                            // Now finally perform the wait.
+                            try
+                            {
+                                // ** the actual wait **
+                                if (!Monitor.Wait(m_lock, realMillisecondsTimeout))
+                                    return false; //return immediately if the timeout has expired.
+                            }
+                            finally
+                            {
+                                // Clean up: we're done waiting.
+                                Waiters = Waiters - 1;
+                            }
+
+                            // Now just loop back around, and the right thing will happen.  Either:
+                            //     1. We had a spurious wake-up due to some other wait being canceled via a different cancellationToken (rewait)
+                            // or  2. the wait was successful. (the loop will break)
+                        }
+                    }
+                }
+            } // automatically disposes (and unregisters) the callback
+
+            return true; //done. The wait was satisfied.
+        }
+
+        /// <summary>
+        /// Releases all resources used by the current instance of <see cref="ManualResetEventSlim"/>.
+        /// </summary>
+        /// <remarks>
+        /// Unlike most of the members of <see cref="ManualResetEventSlim"/>, <see cref="Dispose()"/> is not
+        /// thread-safe and may not be used concurrently with other members of this instance.
+        /// </remarks>
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// When overridden in a derived class, releases the unmanaged resources used by the 
+        /// <see cref="ManualResetEventSlim"/>, and optionally releases the managed resources.
+        /// </summary>
+        /// <param name="disposing">true to release both managed and unmanaged resources;
+        /// false to release only unmanaged resources.</param>
+        /// <remarks>
+        /// Unlike most of the members of <see cref="ManualResetEventSlim"/>, <see cref="Dispose(Boolean)"/> is not
+        /// thread-safe and may not be used concurrently with other members of this instance.
+        /// </remarks>
+        protected virtual void Dispose(bool disposing)
+        {
+            if ((m_combinedState & Dispose_BitMask) != 0)
+                return; // already disposed
+
+            m_combinedState |= Dispose_BitMask; //set the dispose bit
+            if (disposing)
+            {
+                // We will dispose of the event object.  We do this under a lock to protect
+                // against the race condition outlined in the Set method above.
+                ManualResetEvent eventObj = m_eventObj;
+                if (eventObj != null)
+                {
+                    lock (eventObj)
+                    {
+                        eventObj.Close();
+                        m_eventObj = null;
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Throw ObjectDisposedException if the MRES is disposed
+        /// </summary>
+        private void ThrowIfDisposed()
+        {
+            if ((m_combinedState & Dispose_BitMask) != 0)
+                throw new ObjectDisposedException(SR.ManualResetEventSlim_Disposed);
+        }
+
+        /// <summary>
+        /// Private helper method to wake up waiters when a cancellationToken gets canceled.
+        /// </summary>
+        private static Action<object> s_cancellationTokenCallback = new Action<object>(CancellationTokenCallback);
+        private static void CancellationTokenCallback(object obj)
+        {
+            ManualResetEventSlim mre = obj as ManualResetEventSlim;
+            Debug.Assert(mre != null, "Expected a ManualResetEventSlim");
+            Debug.Assert(mre.m_lock != null); //the lock should have been created before this callback is registered for use.
+            lock (mre.m_lock)
+            {
+                Monitor.PulseAll(mre.m_lock); // awaken all waiters
+            }
+        }
+
+        /// <summary>
+        /// Private helper method for updating parts of a bit-string state value.
+        /// Mainly called from the IsSet and Waiters properties setters
+        /// </summary>
+        /// <remarks>
+        /// Note: the parameter types must be int as CompareExchange cannot take a Uint
+        /// </remarks>
+        /// <param name="newBits">The new value</param>
+        /// <param name="updateBitsMask">The mask used to set the bits</param>
+        private void UpdateStateAtomically(int newBits, int updateBitsMask)
+        {
+            SpinWait sw = new SpinWait();
+
+            Debug.Assert((newBits | updateBitsMask) == updateBitsMask, "newBits do not fall within the updateBitsMask.");
+
+            do
+            {
+                int oldState = m_combinedState; // cache the old value for testing in CAS
+
+                // Procedure:(1) zero the updateBits.  eg oldState = [11111111] flag= [00111000] newState = [11000111]
+                //           then (2) map in the newBits. eg [11000111] newBits=00101000, newState=[11101111]
+                int newState = (oldState & ~updateBitsMask) | newBits;
+
+                if (Interlocked.CompareExchange(ref m_combinedState, newState, oldState) == oldState)
+                {
+                    return;
+                }
+
+                sw.SpinOnce();
+            } while (true);
+        }
+
+        /// <summary>
+        /// Private helper method - performs Mask and shift, particular helpful to extract a field from a packed word.
+        /// eg ExtractStatePortionAndShiftRight(0x12345678, 0xFF000000, 24) => 0x12, ie extracting the top 8-bits as a simple integer 
+        /// 
+        /// ?? is there a common place to put this rather than being private to MRES?
+        /// </summary>
+        /// <param name="state"></param>
+        /// <param name="mask"></param>
+        /// <param name="rightBitShiftCount"></param>
+        /// <returns></returns>
+        private static int ExtractStatePortionAndShiftRight(int state, int mask, int rightBitShiftCount)
+        {
+            //convert to uint before shifting so that right-shift does not replicate the sign-bit,
+            //then convert back to int.
+            return unchecked((int)(((uint)(state & mask)) >> rightBitShiftCount));
+        }
+
+        /// <summary>
+        /// Performs a Mask operation, but does not perform the shift.
+        /// This is acceptable for boolean values for which the shift is unnecessary
+        /// eg (val &amp; Mask) != 0 is an appropriate way to extract a boolean rather than using
+        /// ((val &amp; Mask) &gt;&gt; shiftAmount) == 1
+        /// 
+        /// ?? is there a common place to put this rather than being private to MRES?
+        /// </summary>
+        /// <param name="state"></param>
+        /// <param name="mask"></param>
+        private static int ExtractStatePortion(int state, int mask)
+        {
+            return state & mask;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Monitor.cs b/src/System.Private.CoreLib/src/System/Threading/Monitor.cs
new file mode 100644
index 0000000000..dee4118fe1
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Monitor.cs
@@ -0,0 +1,238 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+/*=============================================================================
+**
+**
+**
+** Purpose: Synchronizes access to a shared resource or region of code in a multi-threaded 
+**             program.
+**
+**
+=============================================================================*/
+
+
+
+using System;
+using System.Runtime;
+using System.Threading;
+using System.Runtime.CompilerServices;
+using System.Runtime.ConstrainedExecution;
+using System.Runtime.Versioning;
+using System.Diagnostics;
+
+namespace System.Threading
+{
+    public static class Monitor
+    {
+        /*=========================================================================
+        ** Obtain the monitor lock of obj. Will block if another thread holds the lock
+        ** Will not block if the current thread holds the lock,
+        ** however the caller must ensure that the same number of Exit
+        ** calls are made as there were Enter calls.
+        **
+        ** Exceptions: ArgumentNullException if object is null.
+        =========================================================================*/
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void Enter(Object obj);
+
+
+        // Use a ref bool instead of out to ensure that unverifiable code must
+        // initialize this value to something.  If we used out, the value 
+        // could be uninitialized if we threw an exception in our prolog.
+        // The JIT should inline this method to allow check of lockTaken argument to be optimized out
+        // in the typical case. Note that the method has to be transparent for inlining to be allowed by the VM.
+        public static void Enter(Object obj, ref bool lockTaken)
+        {
+            if (lockTaken)
+                ThrowLockTakenException();
+
+            ReliableEnter(obj, ref lockTaken);
+            Debug.Assert(lockTaken);
+        }
+
+        private static void ThrowLockTakenException()
+        {
+            throw new ArgumentException(SR.Argument_MustBeFalse, "lockTaken");
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void ReliableEnter(Object obj, ref bool lockTaken);
+
+
+
+        /*=========================================================================
+        ** Release the monitor lock. If one or more threads are waiting to acquire the
+        ** lock, and the current thread has executed as many Exits as
+        ** Enters, one of the threads will be unblocked and allowed to proceed.
+        **
+        ** Exceptions: ArgumentNullException if object is null.
+        **             SynchronizationLockException if the current thread does not
+        **             own the lock.
+        =========================================================================*/
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern void Exit(Object obj);
+
+        /*=========================================================================
+        ** Similar to Enter, but will never block. That is, if the current thread can
+        ** acquire the monitor lock without blocking, it will do so and TRUE will
+        ** be returned. Otherwise FALSE will be returned.
+        **
+        ** Exceptions: ArgumentNullException if object is null.
+        =========================================================================*/
+        public static bool TryEnter(Object obj)
+        {
+            bool lockTaken = false;
+            TryEnter(obj, 0, ref lockTaken);
+            return lockTaken;
+        }
+
+        // The JIT should inline this method to allow check of lockTaken argument to be optimized out
+        // in the typical case. Note that the method has to be transparent for inlining to be allowed by the VM.
+        public static void TryEnter(Object obj, ref bool lockTaken)
+        {
+            if (lockTaken)
+                ThrowLockTakenException();
+
+            ReliableEnterTimeout(obj, 0, ref lockTaken);
+        }
+
+        /*=========================================================================
+        ** Version of TryEnter that will block, but only up to a timeout period
+        ** expressed in milliseconds. If timeout == Timeout.Infinite the method
+        ** becomes equivalent to Enter.
+        **
+        ** Exceptions: ArgumentNullException if object is null.
+        **             ArgumentException if timeout < 0.
+        =========================================================================*/
+        // The JIT should inline this method to allow check of lockTaken argument to be optimized out
+        // in the typical case. Note that the method has to be transparent for inlining to be allowed by the VM.
+        public static bool TryEnter(Object obj, int millisecondsTimeout)
+        {
+            bool lockTaken = false;
+            TryEnter(obj, millisecondsTimeout, ref lockTaken);
+            return lockTaken;
+        }
+
+        private static int MillisecondsTimeoutFromTimeSpan(TimeSpan timeout)
+        {
+            long tm = (long)timeout.TotalMilliseconds;
+            if (tm < -1 || tm > (long)Int32.MaxValue)
+                throw new ArgumentOutOfRangeException(nameof(timeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            return (int)tm;
+        }
+
+        public static bool TryEnter(Object obj, TimeSpan timeout)
+        {
+            return TryEnter(obj, MillisecondsTimeoutFromTimeSpan(timeout));
+        }
+
+        // The JIT should inline this method to allow check of lockTaken argument to be optimized out
+        // in the typical case. Note that the method has to be transparent for inlining to be allowed by the VM.
+        public static void TryEnter(Object obj, int millisecondsTimeout, ref bool lockTaken)
+        {
+            if (lockTaken)
+                ThrowLockTakenException();
+
+            ReliableEnterTimeout(obj, millisecondsTimeout, ref lockTaken);
+        }
+
+        public static void TryEnter(Object obj, TimeSpan timeout, ref bool lockTaken)
+        {
+            if (lockTaken)
+                ThrowLockTakenException();
+
+            ReliableEnterTimeout(obj, MillisecondsTimeoutFromTimeSpan(timeout), ref lockTaken);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void ReliableEnterTimeout(Object obj, int timeout, ref bool lockTaken);
+
+        public static bool IsEntered(object obj)
+        {
+            if (obj == null)
+                throw new ArgumentNullException(nameof(obj));
+
+            return IsEnteredNative(obj);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool IsEnteredNative(Object obj);
+
+        /*========================================================================
+    ** Waits for notification from the object (via a Pulse/PulseAll). 
+    ** timeout indicates how long to wait before the method returns.
+    ** This method acquires the monitor waithandle for the object 
+    ** If this thread holds the monitor lock for the object, it releases it. 
+    ** On exit from the method, it obtains the monitor lock back. 
+    ** If exitContext is true then the synchronization domain for the context 
+    ** (if in a synchronized context) is exited before the wait and reacquired 
+    **
+        ** Exceptions: ArgumentNullException if object is null.
+    ========================================================================*/
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool ObjWait(bool exitContext, int millisecondsTimeout, Object obj);
+
+        public static bool Wait(Object obj, int millisecondsTimeout, bool exitContext)
+        {
+            if (obj == null)
+                throw (new ArgumentNullException(nameof(obj)));
+            return ObjWait(exitContext, millisecondsTimeout, obj);
+        }
+
+        public static bool Wait(Object obj, TimeSpan timeout, bool exitContext)
+        {
+            return Wait(obj, MillisecondsTimeoutFromTimeSpan(timeout), exitContext);
+        }
+
+        public static bool Wait(Object obj, int millisecondsTimeout)
+        {
+            return Wait(obj, millisecondsTimeout, false);
+        }
+
+        public static bool Wait(Object obj, TimeSpan timeout)
+        {
+            return Wait(obj, MillisecondsTimeoutFromTimeSpan(timeout), false);
+        }
+
+        public static bool Wait(Object obj)
+        {
+            return Wait(obj, Timeout.Infinite, false);
+        }
+
+        /*========================================================================
+        ** Sends a notification to a single waiting object. 
+        * Exceptions: SynchronizationLockException if this method is not called inside
+        * a synchronized block of code.
+        ========================================================================*/
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void ObjPulse(Object obj);
+
+        public static void Pulse(Object obj)
+        {
+            if (obj == null)
+            {
+                throw new ArgumentNullException(nameof(obj));
+            }
+
+            ObjPulse(obj);
+        }
+        /*========================================================================
+        ** Sends a notification to all waiting objects. 
+        ========================================================================*/
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void ObjPulseAll(Object obj);
+
+        public static void PulseAll(Object obj)
+        {
+            if (obj == null)
+            {
+                throw new ArgumentNullException(nameof(obj));
+            }
+
+            ObjPulseAll(obj);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Mutex.cs b/src/System.Private.CoreLib/src/System/Threading/Mutex.cs
new file mode 100644
index 0000000000..86981b5642
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Mutex.cs
@@ -0,0 +1,178 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System.IO;
+using Microsoft.Win32;
+using Microsoft.Win32.SafeHandles;
+using System.Runtime.InteropServices;
+using System.Diagnostics;
+
+namespace System.Threading
+{
+    /// <summary>
+    /// Synchronization primitive that can also be used for interprocess synchronization
+    /// </summary>
+    public sealed class Mutex : WaitHandle
+    {
+        private const uint AccessRights =
+            (uint)Win32Native.MAXIMUM_ALLOWED | Win32Native.SYNCHRONIZE | Win32Native.MUTEX_MODIFY_STATE;
+
+#if PLATFORM_UNIX
+        // Maximum file name length on tmpfs file system.
+        private const int WaitHandleNameMax = 255;
+#endif
+
+        public Mutex(bool initiallyOwned, string name, out bool createdNew)
+        {
+#if !PLATFORM_UNIX
+            VerifyNameForCreate(name);
+#endif
+            CreateMutexCore(initiallyOwned, name, out createdNew);
+        }
+
+        public Mutex(bool initiallyOwned, string name)
+        {
+#if !PLATFORM_UNIX
+            VerifyNameForCreate(name);
+#endif
+            CreateMutexCore(initiallyOwned, name, out _);
+        }
+
+        public Mutex(bool initiallyOwned)
+        {
+            CreateMutexCore(initiallyOwned, null, out _);
+        }
+
+        public Mutex()
+        {
+            CreateMutexCore(false, null, out _);
+        }
+
+        private Mutex(SafeWaitHandle handle)
+        {
+            SafeWaitHandle = handle;
+        }
+
+        public static Mutex OpenExisting(string name)
+        {
+            switch (OpenExistingWorker(name, out Mutex result))
+            {
+                case OpenExistingResult.NameNotFound:
+                    throw new WaitHandleCannotBeOpenedException();
+
+                case OpenExistingResult.NameInvalid:
+                    throw new WaitHandleCannotBeOpenedException(SR.Format(SR.Threading_WaitHandleCannotBeOpenedException_InvalidHandle, name));
+
+                case OpenExistingResult.PathNotFound:
+                    throw Win32Marshal.GetExceptionForWin32Error(Interop.Errors.ERROR_PATH_NOT_FOUND, name);
+
+                default:
+                    return result;
+            }
+        }
+
+        public static bool TryOpenExisting(string name, out Mutex result) =>
+            OpenExistingWorker(name, out result) == OpenExistingResult.Success;
+
+        // Note: To call ReleaseMutex, you must have an ACL granting you
+        // MUTEX_MODIFY_STATE rights (0x0001). The other interesting value
+        // in a Mutex's ACL is MUTEX_ALL_ACCESS (0x1F0001).
+        public void ReleaseMutex()
+        {
+            if (!Win32Native.ReleaseMutex(safeWaitHandle))
+            {
+                throw new ApplicationException(SR.Arg_SynchronizationLockException);
+            }
+        }
+
+#if !PLATFORM_UNIX
+        private static void VerifyNameForCreate(string name)
+        {
+            if (name != null && (Interop.Kernel32.MAX_PATH < name.Length))
+            {
+                throw new ArgumentException(SR.Format(SR.Argument_WaitHandleNameTooLong, name, Interop.Kernel32.MAX_PATH), nameof(name));
+            }
+        }
+#endif
+
+        private void CreateMutexCore(bool initiallyOwned, string name, out bool createdNew)
+        {
+#if !PLATFORM_UNIX
+            Debug.Assert(name == null || name.Length <= Interop.Kernel32.MAX_PATH);
+#endif
+
+            uint mutexFlags = initiallyOwned ? Win32Native.CREATE_MUTEX_INITIAL_OWNER : 0;
+
+            SafeWaitHandle mutexHandle = Win32Native.CreateMutexEx(null, name, mutexFlags, AccessRights);
+            int errorCode = Marshal.GetLastWin32Error();
+
+            if (mutexHandle.IsInvalid)
+            {
+                mutexHandle.SetHandleAsInvalid();
+#if PLATFORM_UNIX
+                if (errorCode == Interop.Errors.ERROR_FILENAME_EXCED_RANGE)
+                    // On Unix, length validation is done by CoreCLR's PAL after converting to utf-8
+                    throw new ArgumentException(SR.Format(SR.Argument_WaitHandleNameTooLong, name, WaitHandleNameMax), nameof(name));
+#endif
+                if (errorCode == Interop.Errors.ERROR_INVALID_HANDLE)
+                    throw new WaitHandleCannotBeOpenedException(SR.Format(SR.Threading_WaitHandleCannotBeOpenedException_InvalidHandle, name));
+                throw Win32Marshal.GetExceptionForWin32Error(errorCode, name);
+            }
+
+            createdNew = errorCode != Interop.Errors.ERROR_ALREADY_EXISTS;
+            SafeWaitHandle = mutexHandle;
+        }
+
+        private static OpenExistingResult OpenExistingWorker(string name, out Mutex result)
+        {
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
+            if (name.Length == 0)
+            {
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(name));
+            }
+
+#if !PLATFORM_UNIX
+            VerifyNameForCreate(name);
+#endif
+
+            result = null;
+            // To allow users to view & edit the ACL's, call OpenMutex
+            // with parameters to allow us to view & edit the ACL.  This will
+            // fail if we don't have permission to view or edit the ACL's.  
+            // If that happens, ask for less permissions.
+            SafeWaitHandle myHandle = Win32Native.OpenMutex(AccessRights, false, name);
+
+            if (myHandle.IsInvalid)
+            {
+                int errorCode = Marshal.GetLastWin32Error();
+
+#if PLATFORM_UNIX
+                if (name != null && errorCode == Interop.Errors.ERROR_FILENAME_EXCED_RANGE)
+                {
+                    // On Unix, length validation is done by CoreCLR's PAL after converting to utf-8
+                    throw new ArgumentException(SR.Format(SR.Argument_WaitHandleNameTooLong, name, WaitHandleNameMax), nameof(name));
+                }
+#endif
+                if (Interop.Errors.ERROR_FILE_NOT_FOUND == errorCode || Interop.Errors.ERROR_INVALID_NAME == errorCode)
+                    return OpenExistingResult.NameNotFound;
+                if (Interop.Errors.ERROR_PATH_NOT_FOUND == errorCode)
+                    return OpenExistingResult.PathNotFound;
+                if (null != name && Interop.Errors.ERROR_INVALID_HANDLE == errorCode)
+                    return OpenExistingResult.NameInvalid;
+
+                // this is for passed through Win32Native Errors
+                throw Win32Marshal.GetExceptionForWin32Error(errorCode, name);
+            }
+
+            result = new Mutex(myHandle);
+
+            return OpenExistingResult.Success;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Overlapped.cs b/src/System.Private.CoreLib/src/System/Threading/Overlapped.cs
new file mode 100644
index 0000000000..51df27f735
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Overlapped.cs
@@ -0,0 +1,372 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+/*
+ * This files defines the following types:
+ *  - NativeOverlapped
+ *  - _IOCompletionCallback
+ *  - OverlappedData
+ *  - Overlapped
+ *  - OverlappedDataCache
+ */
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Class for converting information to and from the native 
+**          overlapped structure used in asynchronous file i/o
+**
+**
+=============================================================================*/
+
+
+using System;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+using System.Security;
+using System.Runtime.ConstrainedExecution;
+using System.Diagnostics;
+using System.Collections.Concurrent;
+
+namespace System.Threading
+{
+    #region struct NativeOverlapped
+
+    // Valuetype that represents the (unmanaged) Win32 OVERLAPPED structure
+    // the layout of this structure must be identical to OVERLAPPED.
+    // The first five matches OVERLAPPED structure.
+    // The remaining are reserved at the end
+    [System.Runtime.InteropServices.StructLayout(LayoutKind.Sequential)]
+    public struct NativeOverlapped
+    {
+        public IntPtr InternalLow;
+        public IntPtr InternalHigh;
+        public int OffsetLow;
+        public int OffsetHigh;
+        public IntPtr EventHandle;
+    }
+
+    #endregion struct NativeOverlapped
+
+
+    #region class _IOCompletionCallback
+
+    internal unsafe class _IOCompletionCallback
+    {
+        private IOCompletionCallback _ioCompletionCallback;
+        private ExecutionContext _executionContext;
+        private uint _errorCode; // Error code
+        private uint _numBytes; // No. of bytes transferred 
+        private NativeOverlapped* _pOVERLAP;
+
+        internal _IOCompletionCallback(IOCompletionCallback ioCompletionCallback, ExecutionContext executionContext)
+        {
+            _ioCompletionCallback = ioCompletionCallback;
+            _executionContext = executionContext;
+        }
+        // Context callback: same sig for SendOrPostCallback and ContextCallback
+        internal static ContextCallback _ccb = new ContextCallback(IOCompletionCallback_Context);
+        internal static void IOCompletionCallback_Context(Object state)
+        {
+            _IOCompletionCallback helper = (_IOCompletionCallback)state;
+            Debug.Assert(helper != null, "_IOCompletionCallback cannot be null");
+            helper._ioCompletionCallback(helper._errorCode, helper._numBytes, helper._pOVERLAP);
+        }
+
+
+        // call back helper
+        internal static unsafe void PerformIOCompletionCallback(uint errorCode, // Error code
+                                                                            uint numBytes, // No. of bytes transferred 
+                                                                            NativeOverlapped* pOVERLAP // ptr to OVERLAP structure
+                                                                            )
+        {
+            Overlapped overlapped;
+            _IOCompletionCallback helper;
+
+            do
+            {
+                overlapped = OverlappedData.GetOverlappedFromNative(pOVERLAP).m_overlapped;
+                helper = overlapped.iocbHelper;
+
+                if (helper == null || helper._executionContext == null || helper._executionContext.IsDefault)
+                {
+                    // We got here because of UnsafePack (or) Pack with EC flow suppressed
+                    IOCompletionCallback callback = overlapped.UserCallback;
+                    callback(errorCode, numBytes, pOVERLAP);
+                }
+                else
+                {
+                    // We got here because of Pack
+                    helper._errorCode = errorCode;
+                    helper._numBytes = numBytes;
+                    helper._pOVERLAP = pOVERLAP;
+                    ExecutionContext.RunInternal(helper._executionContext, _ccb, helper);
+                }
+
+                //Quickly check the VM again, to see if a packet has arrived.
+                OverlappedData.CheckVMForIOPacket(out pOVERLAP, out errorCode, out numBytes);
+            } while (pOVERLAP != null);
+        }
+    }
+
+    #endregion class _IOCompletionCallback
+
+
+    #region class OverlappedData
+
+    sealed internal class OverlappedData
+    {
+        // ! If you make any change to the layout here, you need to make matching change 
+        // ! to OverlappedObject in vm\nativeoverlapped.h
+        internal IAsyncResult m_asyncResult;
+        internal IOCompletionCallback m_iocb;
+        internal _IOCompletionCallback m_iocbHelper;
+        internal Overlapped m_overlapped;
+        private Object m_userObject;
+        private IntPtr m_pinSelf;
+        private IntPtr m_userObjectInternal;
+        private int m_AppDomainId;
+#pragma warning disable 414  // Field is not used from managed.        
+#pragma warning disable 169
+        private byte m_isArray;
+        private byte m_toBeCleaned;
+#pragma warning restore 414        
+#pragma warning restore 169
+        internal NativeOverlapped m_nativeOverlapped;
+
+        // Adding an empty default ctor for annotation purposes
+        internal OverlappedData() { }
+
+        internal void ReInitialize()
+        {
+            m_asyncResult = null;
+            m_iocb = null;
+            m_iocbHelper = null;
+            m_overlapped = null;
+            m_userObject = null;
+            Debug.Assert(m_pinSelf == IntPtr.Zero, "OverlappedData has not been freed: m_pinSelf");
+            m_pinSelf = IntPtr.Zero;
+            m_userObjectInternal = IntPtr.Zero;
+            Debug.Assert(m_AppDomainId == 0 || m_AppDomainId == AppDomain.CurrentDomain.Id, "OverlappedData is not in the current domain");
+            m_AppDomainId = 0;
+            m_nativeOverlapped.EventHandle = IntPtr.Zero;
+            m_isArray = 0;
+            m_nativeOverlapped.InternalLow = IntPtr.Zero;
+            m_nativeOverlapped.InternalHigh = IntPtr.Zero;
+        }
+
+        internal unsafe NativeOverlapped* Pack(IOCompletionCallback iocb, Object userData)
+        {
+            if (m_pinSelf != IntPtr.Zero)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_Overlapped_Pack);
+            }
+
+            if (iocb != null)
+            {
+                ExecutionContext ec = ExecutionContext.Capture();
+                m_iocbHelper = ec != null ? new _IOCompletionCallback(iocb, ec) : null;
+                m_iocb = iocb;
+            }
+            else
+            {
+                m_iocbHelper = null;
+                m_iocb = null;
+            }
+            m_userObject = userData;
+            if (m_userObject != null)
+            {
+                if (m_userObject.GetType() == typeof(Object[]))
+                {
+                    m_isArray = 1;
+                }
+                else
+                {
+                    m_isArray = 0;
+                }
+            }
+            return AllocateNativeOverlapped();
+        }
+
+        internal unsafe NativeOverlapped* UnsafePack(IOCompletionCallback iocb, Object userData)
+        {
+            if (m_pinSelf != IntPtr.Zero)
+            {
+                throw new InvalidOperationException(SR.InvalidOperation_Overlapped_Pack);
+            }
+            m_userObject = userData;
+            if (m_userObject != null)
+            {
+                if (m_userObject.GetType() == typeof(Object[]))
+                {
+                    m_isArray = 1;
+                }
+                else
+                {
+                    m_isArray = 0;
+                }
+            }
+            m_iocb = iocb;
+            m_iocbHelper = null;
+            return AllocateNativeOverlapped();
+        }
+
+        internal IntPtr UserHandle
+        {
+            get { return m_nativeOverlapped.EventHandle; }
+            set { m_nativeOverlapped.EventHandle = value; }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern unsafe NativeOverlapped* AllocateNativeOverlapped();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern unsafe void FreeNativeOverlapped(NativeOverlapped* nativeOverlappedPtr);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern unsafe OverlappedData GetOverlappedFromNative(NativeOverlapped* nativeOverlappedPtr);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern unsafe void CheckVMForIOPacket(out NativeOverlapped* pOVERLAP, out uint errorCode, out uint numBytes);
+    }
+
+    #endregion class OverlappedData
+
+
+    #region class Overlapped
+
+    public class Overlapped
+    {
+        private OverlappedData m_overlappedData;
+        private static PinnableBufferCache s_overlappedDataCache = new PinnableBufferCache("System.Threading.OverlappedData", () => new OverlappedData());
+
+        public Overlapped()
+        {
+            m_overlappedData = (OverlappedData)s_overlappedDataCache.Allocate();
+            m_overlappedData.m_overlapped = this;
+        }
+
+        public Overlapped(int offsetLo, int offsetHi, IntPtr hEvent, IAsyncResult ar)
+        {
+            m_overlappedData = (OverlappedData)s_overlappedDataCache.Allocate();
+            m_overlappedData.m_overlapped = this;
+            m_overlappedData.m_nativeOverlapped.OffsetLow = offsetLo;
+            m_overlappedData.m_nativeOverlapped.OffsetHigh = offsetHi;
+            m_overlappedData.UserHandle = hEvent;
+            m_overlappedData.m_asyncResult = ar;
+        }
+
+        [Obsolete("This constructor is not 64-bit compatible.  Use the constructor that takes an IntPtr for the event handle.  http://go.microsoft.com/fwlink/?linkid=14202")]
+        public Overlapped(int offsetLo, int offsetHi, int hEvent, IAsyncResult ar) : this(offsetLo, offsetHi, new IntPtr(hEvent), ar)
+        {
+        }
+
+        public IAsyncResult AsyncResult
+        {
+            get { return m_overlappedData.m_asyncResult; }
+            set { m_overlappedData.m_asyncResult = value; }
+        }
+
+        public int OffsetLow
+        {
+            get { return m_overlappedData.m_nativeOverlapped.OffsetLow; }
+            set { m_overlappedData.m_nativeOverlapped.OffsetLow = value; }
+        }
+
+        public int OffsetHigh
+        {
+            get { return m_overlappedData.m_nativeOverlapped.OffsetHigh; }
+            set { m_overlappedData.m_nativeOverlapped.OffsetHigh = value; }
+        }
+
+        [Obsolete("This property is not 64-bit compatible.  Use EventHandleIntPtr instead.  http://go.microsoft.com/fwlink/?linkid=14202")]
+        public int EventHandle
+        {
+            get { return m_overlappedData.UserHandle.ToInt32(); }
+            set { m_overlappedData.UserHandle = new IntPtr(value); }
+        }
+
+        public IntPtr EventHandleIntPtr
+        {
+            get { return m_overlappedData.UserHandle; }
+            set { m_overlappedData.UserHandle = value; }
+        }
+
+        internal _IOCompletionCallback iocbHelper
+        {
+            get { return m_overlappedData.m_iocbHelper; }
+        }
+
+        internal IOCompletionCallback UserCallback
+        {
+            get { return m_overlappedData.m_iocb; }
+        }
+
+        /*====================================================================
+        *  Packs a managed overlapped class into native Overlapped struct.
+        *  Roots the iocb and stores it in the ReservedCOR field of native Overlapped 
+        *  Pins the native Overlapped struct and returns the pinned index. 
+        ====================================================================*/
+        [Obsolete("This method is not safe.  Use Pack (iocb, userData) instead.  http://go.microsoft.com/fwlink/?linkid=14202")]
+        [CLSCompliant(false)]
+        public unsafe NativeOverlapped* Pack(IOCompletionCallback iocb)
+        {
+            return Pack(iocb, null);
+        }
+
+        [CLSCompliant(false)]
+        public unsafe NativeOverlapped* Pack(IOCompletionCallback iocb, Object userData)
+        {
+            return m_overlappedData.Pack(iocb, userData);
+        }
+
+        [Obsolete("This method is not safe.  Use UnsafePack (iocb, userData) instead.  http://go.microsoft.com/fwlink/?linkid=14202")]
+        [CLSCompliant(false)]
+        public unsafe NativeOverlapped* UnsafePack(IOCompletionCallback iocb)
+        {
+            return UnsafePack(iocb, null);
+        }
+
+        [CLSCompliant(false)]
+        public unsafe NativeOverlapped* UnsafePack(IOCompletionCallback iocb, Object userData)
+        {
+            return m_overlappedData.UnsafePack(iocb, userData);
+        }
+
+        /*====================================================================
+        *  Unpacks an unmanaged native Overlapped struct. 
+        *  Unpins the native Overlapped struct
+        ====================================================================*/
+        [CLSCompliant(false)]
+        public static unsafe Overlapped Unpack(NativeOverlapped* nativeOverlappedPtr)
+        {
+            if (nativeOverlappedPtr == null)
+                throw new ArgumentNullException(nameof(nativeOverlappedPtr));
+
+            Overlapped overlapped = OverlappedData.GetOverlappedFromNative(nativeOverlappedPtr).m_overlapped;
+
+            return overlapped;
+        }
+
+        [CLSCompliant(false)]
+        public static unsafe void Free(NativeOverlapped* nativeOverlappedPtr)
+        {
+            if (nativeOverlappedPtr == null)
+                throw new ArgumentNullException(nameof(nativeOverlappedPtr));
+
+            Overlapped overlapped = OverlappedData.GetOverlappedFromNative(nativeOverlappedPtr).m_overlapped;
+            OverlappedData.FreeNativeOverlapped(nativeOverlappedPtr);
+            OverlappedData overlappedData = overlapped.m_overlappedData;
+            overlapped.m_overlappedData = null;
+            overlappedData.ReInitialize();
+            s_overlappedDataCache.Free(overlappedData);
+        }
+    }
+
+    #endregion class Overlapped
+}  // namespace
diff --git a/src/System.Private.CoreLib/src/System/Threading/Semaphore.cs b/src/System.Private.CoreLib/src/System/Threading/Semaphore.cs
new file mode 100644
index 0000000000..8380c56801
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Semaphore.cs
@@ -0,0 +1,191 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32;
+using Microsoft.Win32.SafeHandles;
+using System.Diagnostics;
+using System.IO;
+using System.Runtime.InteropServices;
+using System.Security;
+
+namespace System.Threading
+{
+    public sealed partial class Semaphore : WaitHandle
+    {
+        private const uint AccessRights =
+            (uint)Win32Native.MAXIMUM_ALLOWED | Win32Native.SYNCHRONIZE | Win32Native.SEMAPHORE_MODIFY_STATE;
+
+        public Semaphore(int initialCount, int maximumCount) : this(initialCount, maximumCount, null) { }
+
+        public Semaphore(int initialCount, int maximumCount, string name)
+        {
+            if (initialCount < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(initialCount), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (maximumCount < 1)
+            {
+                throw new ArgumentOutOfRangeException(nameof(maximumCount), SR.ArgumentOutOfRange_NeedPosNum);
+            }
+
+            if (initialCount > maximumCount)
+            {
+                throw new ArgumentException(SR.Argument_SemaphoreInitialMaximum);
+            }
+
+            SafeWaitHandle myHandle = CreateSemaphore(initialCount, maximumCount, name);
+
+            if (myHandle.IsInvalid)
+            {
+                int errorCode = Marshal.GetLastWin32Error();
+
+                if (null != name && 0 != name.Length && Interop.Errors.ERROR_INVALID_HANDLE == errorCode)
+                    throw new WaitHandleCannotBeOpenedException(
+                        SR.Format(SR.Threading_WaitHandleCannotBeOpenedException_InvalidHandle, name));
+
+                throw Win32Marshal.GetExceptionForLastWin32Error();
+            }
+            this.SafeWaitHandle = myHandle;
+        }
+
+        public Semaphore(int initialCount, int maximumCount, string name, out bool createdNew)
+        {
+            if (initialCount < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(initialCount), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (maximumCount < 1)
+            {
+                throw new ArgumentOutOfRangeException(nameof(maximumCount), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            if (initialCount > maximumCount)
+            {
+                throw new ArgumentException(SR.Argument_SemaphoreInitialMaximum);
+            }
+
+            SafeWaitHandle myHandle = CreateSemaphore(initialCount, maximumCount, name);
+
+            int errorCode = Marshal.GetLastWin32Error();
+            if (myHandle.IsInvalid)
+            {
+                if (null != name && 0 != name.Length && Interop.Errors.ERROR_INVALID_HANDLE == errorCode)
+                    throw new WaitHandleCannotBeOpenedException(
+                        SR.Format(SR.Threading_WaitHandleCannotBeOpenedException_InvalidHandle, name));
+                throw Win32Marshal.GetExceptionForLastWin32Error();
+            }
+            createdNew = errorCode != Interop.Errors.ERROR_ALREADY_EXISTS;
+            this.SafeWaitHandle = myHandle;
+        }
+
+        private Semaphore(SafeWaitHandle handle)
+        {
+            this.SafeWaitHandle = handle;
+        }
+
+        private static SafeWaitHandle CreateSemaphore(int initialCount, int maximumCount, string name)
+        {
+            if (name != null)
+            {
+#if PLATFORM_UNIX
+                throw new PlatformNotSupportedException(SR.PlatformNotSupported_NamedSynchronizationPrimitives);
+#else
+                if (name.Length > Interop.Kernel32.MAX_PATH)
+                    throw new ArgumentException(SR.Format(SR.Argument_WaitHandleNameTooLong, name, Interop.Kernel32.MAX_PATH), nameof(name));
+#endif
+            }
+
+            Debug.Assert(initialCount >= 0);
+            Debug.Assert(maximumCount >= 1);
+            Debug.Assert(initialCount <= maximumCount);
+
+            return Win32Native.CreateSemaphoreEx(null, initialCount, maximumCount, name, 0, AccessRights);
+        }
+
+        public static Semaphore OpenExisting(string name)
+        {
+            Semaphore result;
+            switch (OpenExistingWorker(name, out result))
+            {
+                case OpenExistingResult.NameNotFound:
+                    throw new WaitHandleCannotBeOpenedException();
+                case OpenExistingResult.NameInvalid:
+                    throw new WaitHandleCannotBeOpenedException(SR.Format(SR.Threading_WaitHandleCannotBeOpenedException_InvalidHandle, name));
+                case OpenExistingResult.PathNotFound:
+                    throw new IOException(Interop.Kernel32.GetMessage(Interop.Errors.ERROR_PATH_NOT_FOUND));
+                default:
+                    return result;
+            }
+        }
+
+        public static bool TryOpenExisting(string name, out Semaphore result)
+        {
+            return OpenExistingWorker(name, out result) == OpenExistingResult.Success;
+        }
+
+        private static OpenExistingResult OpenExistingWorker(string name, out Semaphore result)
+        {
+#if PLATFORM_UNIX
+            throw new PlatformNotSupportedException(SR.PlatformNotSupported_NamedSynchronizationPrimitives);
+#else
+            if (name == null)
+                throw new ArgumentNullException(nameof(name));
+            if (name.Length == 0)
+                throw new ArgumentException(SR.Argument_EmptyName, nameof(name));
+            if (name.Length > Interop.Kernel32.MAX_PATH)
+                throw new ArgumentException(SR.Format(SR.Argument_WaitHandleNameTooLong, name, Interop.Kernel32.MAX_PATH), nameof(name));
+
+            //Pass false to OpenSemaphore to prevent inheritedHandles
+            SafeWaitHandle myHandle = Win32Native.OpenSemaphore(AccessRights, false, name);
+
+            if (myHandle.IsInvalid)
+            {
+                result = null;
+
+                int errorCode = Marshal.GetLastWin32Error();
+
+                if (Interop.Errors.ERROR_FILE_NOT_FOUND == errorCode || Interop.Errors.ERROR_INVALID_NAME == errorCode)
+                    return OpenExistingResult.NameNotFound;
+                if (Interop.Errors.ERROR_PATH_NOT_FOUND == errorCode)
+                    return OpenExistingResult.PathNotFound;
+                if (null != name && 0 != name.Length && Interop.Errors.ERROR_INVALID_HANDLE == errorCode)
+                    return OpenExistingResult.NameInvalid;
+                //this is for passed through NativeMethods Errors
+                throw Win32Marshal.GetExceptionForLastWin32Error();
+            }
+
+            result = new Semaphore(myHandle);
+            return OpenExistingResult.Success;
+#endif   
+        }
+
+        public int Release()
+        {
+            return Release(1);
+        }
+
+        // increase the count on a semaphore, returns previous count
+        public int Release(int releaseCount)
+        {
+            if (releaseCount < 1)
+            {
+                throw new ArgumentOutOfRangeException(nameof(releaseCount), SR.ArgumentOutOfRange_NeedNonNegNum);
+            }
+
+            //If ReleaseSempahore returns false when the specified value would cause
+            //   the semaphore's count to exceed the maximum count set when Semaphore was created
+            //Non-Zero return 
+
+            int previousCount;
+            if (!Win32Native.ReleaseSemaphore(SafeWaitHandle, releaseCount, out previousCount))
+            {
+                throw new SemaphoreFullException();
+            }
+
+            return previousCount;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/SemaphoreSlim.cs b/src/System.Private.CoreLib/src/System/Threading/SemaphoreSlim.cs
new file mode 100644
index 0000000000..997dbb99ec
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/SemaphoreSlim.cs
@@ -0,0 +1,962 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// A lightweight semahore class that contains the basic semaphore functions plus some useful functions like interrupt
+// and wait handle exposing to allow waiting on multiple semaphores.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Security;
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
+
+// The class will be part of the current System.Threading namespace
+
+namespace System.Threading
+{
+    /// <summary>
+    /// Limits the number of threads that can access a resource or pool of resources concurrently.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// The <see cref="SemaphoreSlim"/> provides a lightweight semaphore class that doesn't
+    /// use Windows kernel semaphores.
+    /// </para>
+    /// <para>
+    /// All public and protected members of <see cref="SemaphoreSlim"/> are thread-safe and may be used
+    /// concurrently from multiple threads, with the exception of Dispose, which
+    /// must only be used when all other operations on the <see cref="SemaphoreSlim"/> have
+    /// completed.
+    /// </para>
+    /// </remarks>
+    [DebuggerDisplay("Current Count = {m_currentCount}")]
+    public class SemaphoreSlim : IDisposable
+    {
+        #region Private Fields
+
+        // The semaphore count, initialized in the constructor to the initial value, every release call incremetns it
+        // and every wait call decrements it as long as its value is positive otherwise the wait will block.
+        // Its value must be between the maximum semaphore value and zero
+        private volatile int m_currentCount;
+
+        // The maximum semaphore value, it is initialized to Int.MaxValue if the client didn't specify it. it is used 
+        // to check if the count excceeded the maxi value or not.
+        private readonly int m_maxCount;
+
+        // The number of synchronously waiting threads, it is set to zero in the constructor and increments before blocking the
+        // threading and decrements it back after that. It is used as flag for the release call to know if there are
+        // waiting threads in the monitor or not.
+        private int m_waitCount;
+
+        /// <summary>
+        /// This is used to help prevent waking more waiters than necessary. It's not perfect and sometimes more waiters than
+        /// necessary may still be woken, see <see cref="WaitUntilCountOrTimeout"/>.
+        /// </summary>
+        private int m_countOfWaitersPulsedToWake;
+
+        // Dummy object used to in lock statements to protect the semaphore count, wait handle and cancelation
+        private object m_lockObj;
+
+        // Act as the semaphore wait handle, it's lazily initialized if needed, the first WaitHandle call initialize it
+        // and wait an release sets and resets it respectively as long as it is not null
+        private volatile ManualResetEvent m_waitHandle;
+
+        // Head of list representing asynchronous waits on the semaphore.
+        private TaskNode m_asyncHead;
+
+        // Tail of list representing asynchronous waits on the semaphore.
+        private TaskNode m_asyncTail;
+
+        // A pre-completed task with Result==true
+        private readonly static Task<bool> s_trueTask =
+            new Task<bool>(false, true, (TaskCreationOptions)InternalTaskOptions.DoNotDispose, default(CancellationToken));
+        // A pre-completed task with Result==false
+        private readonly static Task<bool> s_falseTask =
+            new Task<bool>(false, false, (TaskCreationOptions)InternalTaskOptions.DoNotDispose, default(CancellationToken));
+
+        // No maximum constant
+        private const int NO_MAXIMUM = Int32.MaxValue;
+
+        // Task in a linked list of asynchronous waiters
+        private sealed class TaskNode : Task<bool>, IThreadPoolWorkItem
+        {
+            internal TaskNode Prev, Next;
+            internal TaskNode() : base() { }
+
+            void IThreadPoolWorkItem.ExecuteWorkItem()
+            {
+                bool setSuccessfully = TrySetResult(true);
+                Debug.Assert(setSuccessfully, "Should have been able to complete task");
+            }
+
+            void IThreadPoolWorkItem.MarkAborted(ThreadAbortException tae) { /* nop */ }
+        }
+        #endregion
+
+        #region Public properties
+
+        /// <summary>
+        /// Gets the current count of the <see cref="SemaphoreSlim"/>.
+        /// </summary>
+        /// <value>The current count of the <see cref="SemaphoreSlim"/>.</value>
+        public int CurrentCount
+        {
+            get { return m_currentCount; }
+        }
+
+        /// <summary>
+        /// Returns a <see cref="T:System.Threading.WaitHandle"/> that can be used to wait on the semaphore.
+        /// </summary>
+        /// <value>A <see cref="T:System.Threading.WaitHandle"/> that can be used to wait on the
+        /// semaphore.</value>
+        /// <remarks>
+        /// A successful wait on the <see cref="AvailableWaitHandle"/> does not imply a successful wait on
+        /// the <see cref="SemaphoreSlim"/> itself, nor does it decrement the semaphore's
+        /// count. <see cref="AvailableWaitHandle"/> exists to allow a thread to block waiting on multiple
+        /// semaphores, but such a wait should be followed by a true wait on the target semaphore.
+        /// </remarks>
+        /// <exception cref="T:System.ObjectDisposedException">The <see
+        /// cref="SemaphoreSlim"/> has been disposed.</exception>
+        public WaitHandle AvailableWaitHandle
+        {
+            get
+            {
+                CheckDispose();
+
+                // Return it directly if it is not null
+                if (m_waitHandle != null)
+                    return m_waitHandle;
+
+                //lock the count to avoid multiple threads initializing the handle if it is null
+                lock (m_lockObj)
+                {
+                    if (m_waitHandle == null)
+                    {
+                        // The initial state for the wait handle is true if the count is greater than zero
+                        // false otherwise
+                        m_waitHandle = new ManualResetEvent(m_currentCount != 0);
+                    }
+                }
+                return m_waitHandle;
+            }
+        }
+
+        #endregion
+
+        #region Constructors
+        /// <summary>
+        /// Initializes a new instance of the <see cref="SemaphoreSlim"/> class, specifying
+        /// the initial number of requests that can be granted concurrently.
+        /// </summary>
+        /// <param name="initialCount">The initial number of requests for the semaphore that can be granted
+        /// concurrently.</param>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="initialCount"/>
+        /// is less than 0.</exception>
+        public SemaphoreSlim(int initialCount)
+            : this(initialCount, NO_MAXIMUM)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="SemaphoreSlim"/> class, specifying
+        /// the initial and maximum number of requests that can be granted concurrently.
+        /// </summary>
+        /// <param name="initialCount">The initial number of requests for the semaphore that can be granted
+        /// concurrently.</param>
+        /// <param name="maxCount">The maximum number of requests for the semaphore that can be granted
+        /// concurrently.</param>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"> <paramref name="initialCount"/>
+        /// is less than 0. -or-
+        /// <paramref name="initialCount"/> is greater than <paramref name="maxCount"/>. -or-
+        /// <paramref name="maxCount"/> is less than 0.</exception>
+        public SemaphoreSlim(int initialCount, int maxCount)
+        {
+            if (initialCount < 0 || initialCount > maxCount)
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(initialCount), initialCount, SR.SemaphoreSlim_ctor_InitialCountWrong);
+            }
+
+            //validate input
+            if (maxCount <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(maxCount), maxCount, SR.SemaphoreSlim_ctor_MaxCountWrong);
+            }
+
+            m_maxCount = maxCount;
+            m_lockObj = new object();
+            m_currentCount = initialCount;
+        }
+
+        #endregion
+
+        #region  Methods
+        /// <summary>
+        /// Blocks the current thread until it can enter the <see cref="SemaphoreSlim"/>.
+        /// </summary>
+        /// <exception cref="T:System.ObjectDisposedException">The current instance has already been
+        /// disposed.</exception>
+        public void Wait()
+        {
+            // Call wait with infinite timeout
+            Wait(Timeout.Infinite, new CancellationToken());
+        }
+
+        /// <summary>
+        /// Blocks the current thread until it can enter the <see cref="SemaphoreSlim"/>, while observing a
+        /// <see cref="T:System.Threading.CancellationToken"/>.
+        /// </summary>
+        /// <param name="cancellationToken">The <see cref="T:System.Threading.CancellationToken"/> token to
+        /// observe.</param>
+        /// <exception cref="T:System.OperationCanceledException"><paramref name="cancellationToken"/> was
+        /// canceled.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The current instance has already been
+        /// disposed.</exception>
+        public void Wait(CancellationToken cancellationToken)
+        {
+            // Call wait with infinite timeout
+            Wait(Timeout.Infinite, cancellationToken);
+        }
+
+        /// <summary>
+        /// Blocks the current thread until it can enter the <see cref="SemaphoreSlim"/>, using a <see
+        /// cref="T:System.TimeSpan"/> to measure the time interval.
+        /// </summary>
+        /// <param name="timeout">A <see cref="System.TimeSpan"/> that represents the number of milliseconds
+        /// to wait, or a <see cref="System.TimeSpan"/> that represents -1 milliseconds to wait indefinitely.
+        /// </param>
+        /// <returns>true if the current thread successfully entered the <see cref="SemaphoreSlim"/>;
+        /// otherwise, false.</returns>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="timeout"/> is a negative
+        /// number other than -1 milliseconds, which represents an infinite time-out -or- timeout is greater
+        /// than <see cref="System.Int32.MaxValue"/>.</exception>
+        public bool Wait(TimeSpan timeout)
+        {
+            // Validate the timeout
+            Int64 totalMilliseconds = (Int64)timeout.TotalMilliseconds;
+            if (totalMilliseconds < -1 || totalMilliseconds > Int32.MaxValue)
+            {
+                throw new System.ArgumentOutOfRangeException(
+                    nameof(timeout), timeout, SR.SemaphoreSlim_Wait_TimeoutWrong);
+            }
+
+            // Call wait with the timeout milliseconds
+            return Wait((int)timeout.TotalMilliseconds, new CancellationToken());
+        }
+
+        /// <summary>
+        /// Blocks the current thread until it can enter the <see cref="SemaphoreSlim"/>, using a <see
+        /// cref="T:System.TimeSpan"/> to measure the time interval, while observing a <see
+        /// cref="T:System.Threading.CancellationToken"/>.
+        /// </summary>
+        /// <param name="timeout">A <see cref="System.TimeSpan"/> that represents the number of milliseconds
+        /// to wait, or a <see cref="System.TimeSpan"/> that represents -1 milliseconds to wait indefinitely.
+        /// </param>
+        /// <param name="cancellationToken">The <see cref="T:System.Threading.CancellationToken"/> to
+        /// observe.</param>
+        /// <returns>true if the current thread successfully entered the <see cref="SemaphoreSlim"/>;
+        /// otherwise, false.</returns>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="timeout"/> is a negative
+        /// number other than -1 milliseconds, which represents an infinite time-out -or- timeout is greater
+        /// than <see cref="System.Int32.MaxValue"/>.</exception>
+        /// <exception cref="System.OperationCanceledException"><paramref name="cancellationToken"/> was canceled.</exception>
+        public bool Wait(TimeSpan timeout, CancellationToken cancellationToken)
+        {
+            // Validate the timeout
+            Int64 totalMilliseconds = (Int64)timeout.TotalMilliseconds;
+            if (totalMilliseconds < -1 || totalMilliseconds > Int32.MaxValue)
+            {
+                throw new System.ArgumentOutOfRangeException(
+                    nameof(timeout), timeout, SR.SemaphoreSlim_Wait_TimeoutWrong);
+            }
+
+            // Call wait with the timeout milliseconds
+            return Wait((int)timeout.TotalMilliseconds, cancellationToken);
+        }
+
+        /// <summary>
+        /// Blocks the current thread until it can enter the <see cref="SemaphoreSlim"/>, using a 32-bit
+        /// signed integer to measure the time interval.
+        /// </summary>
+        /// <param name="millisecondsTimeout">The number of milliseconds to wait, or <see
+        /// cref="Timeout.Infinite"/>(-1) to wait indefinitely.</param>
+        /// <returns>true if the current thread successfully entered the <see cref="SemaphoreSlim"/>;
+        /// otherwise, false.</returns>
+        /// <exception cref="ArgumentOutOfRangeException"><paramref name="millisecondsTimeout"/> is a
+        /// negative number other than -1, which represents an infinite time-out.</exception>
+        public bool Wait(int millisecondsTimeout)
+        {
+            return Wait(millisecondsTimeout, new CancellationToken());
+        }
+
+
+        /// <summary>
+        /// Blocks the current thread until it can enter the <see cref="SemaphoreSlim"/>,
+        /// using a 32-bit signed integer to measure the time interval, 
+        /// while observing a <see cref="T:System.Threading.CancellationToken"/>.
+        /// </summary>
+        /// <param name="millisecondsTimeout">The number of milliseconds to wait, or <see cref="Timeout.Infinite"/>(-1) to
+        /// wait indefinitely.</param>
+        /// <param name="cancellationToken">The <see cref="T:System.Threading.CancellationToken"/> to observe.</param>
+        /// <returns>true if the current thread successfully entered the <see cref="SemaphoreSlim"/>; otherwise, false.</returns>
+        /// <exception cref="ArgumentOutOfRangeException"><paramref name="millisecondsTimeout"/> is a negative number other than -1,
+        /// which represents an infinite time-out.</exception>
+        /// <exception cref="System.OperationCanceledException"><paramref name="cancellationToken"/> was canceled.</exception>
+        public bool Wait(int millisecondsTimeout, CancellationToken cancellationToken)
+        {
+            CheckDispose();
+
+            // Validate input
+            if (millisecondsTimeout < -1)
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(millisecondsTimeout), millisecondsTimeout, SR.SemaphoreSlim_Wait_TimeoutWrong);
+            }
+
+            cancellationToken.ThrowIfCancellationRequested();
+
+            // Perf: Check the stack timeout parameter before checking the volatile count
+            if (millisecondsTimeout == 0 && m_currentCount == 0)
+            {
+                // Pessimistic fail fast, check volatile count outside lock (only when timeout is zero!)
+                return false;
+            }
+
+            uint startTime = 0;
+            if (millisecondsTimeout != Timeout.Infinite && millisecondsTimeout > 0)
+            {
+                startTime = TimeoutHelper.GetTime();
+            }
+
+            bool waitSuccessful = false;
+            Task<bool> asyncWaitTask = null;
+            bool lockTaken = false;
+
+            //Register for cancellation outside of the main lock.
+            //NOTE: Register/unregister inside the lock can deadlock as different lock acquisition orders could
+            //      occur for (1)this.m_lockObj and (2)cts.internalLock
+            CancellationTokenRegistration cancellationTokenRegistration = cancellationToken.InternalRegisterWithoutEC(s_cancellationTokenCanceledEventHandler, this);
+            try
+            {
+                // Perf: first spin wait for the count to be positive.
+                //       This additional amount of spinwaiting in addition
+                //       to Monitor.Enter()’s spinwaiting has shown measurable perf gains in test scenarios.
+                if (m_currentCount == 0)
+                {
+                    // Monitor.Enter followed by Monitor.Wait is much more expensive than waiting on an event as it involves another
+                    // spin, contention, etc. The usual number of spin iterations that would otherwise be used here is increased to
+                    // lessen that extra expense of doing a proper wait.
+                    int spinCount = SpinWait.SpinCountforSpinBeforeWait * 4;
+                    const int Sleep1Threshold = SpinWait.Sleep1ThresholdForSpinBeforeWait * 4;
+
+                    var spinner = new SpinWait();
+                    while (spinner.Count < spinCount)
+                    {
+                        spinner.SpinOnce(Sleep1Threshold);
+
+                        if (m_currentCount != 0)
+                        {
+                            break;
+                        }
+                    }
+                }
+
+                // entering the lock and incrementing waiters must not suffer a thread-abort, else we cannot
+                // clean up m_waitCount correctly, which may lead to deadlock due to non-woken waiters.
+                try { }
+                finally
+                {
+                    Monitor.Enter(m_lockObj, ref lockTaken);
+                    if (lockTaken)
+                    {
+                        m_waitCount++;
+                    }
+                }
+
+                // If there are any async waiters, for fairness we'll get in line behind
+                // then by translating our synchronous wait into an asynchronous one that we 
+                // then block on (once we've released the lock).
+                if (m_asyncHead != null)
+                {
+                    Debug.Assert(m_asyncTail != null, "tail should not be null if head isn't");
+                    asyncWaitTask = WaitAsync(millisecondsTimeout, cancellationToken);
+                }
+                // There are no async waiters, so we can proceed with normal synchronous waiting.
+                else
+                {
+                    // If the count > 0 we are good to move on.
+                    // If not, then wait if we were given allowed some wait duration
+
+                    OperationCanceledException oce = null;
+
+                    if (m_currentCount == 0)
+                    {
+                        if (millisecondsTimeout == 0)
+                        {
+                            return false;
+                        }
+
+                        // Prepare for the main wait...
+                        // wait until the count become greater than zero or the timeout is expired
+                        try
+                        {
+                            waitSuccessful = WaitUntilCountOrTimeout(millisecondsTimeout, startTime, cancellationToken);
+                        }
+                        catch (OperationCanceledException e) { oce = e; }
+                    }
+
+                    // Now try to acquire.  We prioritize acquisition over cancellation/timeout so that we don't
+                    // lose any counts when there are asynchronous waiters in the mix.  Asynchronous waiters
+                    // defer to synchronous waiters in priority, which means that if it's possible an asynchronous
+                    // waiter didn't get released because a synchronous waiter was present, we need to ensure
+                    // that synchronous waiter succeeds so that they have a chance to release.
+                    Debug.Assert(!waitSuccessful || m_currentCount > 0,
+                        "If the wait was successful, there should be count available.");
+                    if (m_currentCount > 0)
+                    {
+                        waitSuccessful = true;
+                        m_currentCount--;
+                    }
+                    else if (oce != null)
+                    {
+                        throw oce;
+                    }
+
+                    // Exposing wait handle which is lazily initialized if needed
+                    if (m_waitHandle != null && m_currentCount == 0)
+                    {
+                        m_waitHandle.Reset();
+                    }
+                }
+            }
+            finally
+            {
+                // Release the lock
+                if (lockTaken)
+                {
+                    m_waitCount--;
+                    Monitor.Exit(m_lockObj);
+                }
+
+                // Unregister the cancellation callback.
+                cancellationTokenRegistration.Dispose();
+            }
+
+            // If we had to fall back to asynchronous waiting, block on it
+            // here now that we've released the lock, and return its
+            // result when available.  Otherwise, this was a synchronous
+            // wait, and whether we successfully acquired the semaphore is
+            // stored in waitSuccessful.
+
+            return (asyncWaitTask != null) ? asyncWaitTask.GetAwaiter().GetResult() : waitSuccessful;
+        }
+
+        /// <summary>
+        /// Local helper function, waits on the monitor until the monitor receives signal or the
+        /// timeout is expired
+        /// </summary>
+        /// <param name="millisecondsTimeout">The maximum timeout</param>
+        /// <param name="startTime">The start ticks to calculate the elapsed time</param>
+        /// <param name="cancellationToken">The CancellationToken to observe.</param>
+        /// <returns>true if the monitor received a signal, false if the timeout expired</returns>
+        private bool WaitUntilCountOrTimeout(int millisecondsTimeout, uint startTime, CancellationToken cancellationToken)
+        {
+            int remainingWaitMilliseconds = Timeout.Infinite;
+
+            //Wait on the monitor as long as the count is zero
+            while (m_currentCount == 0)
+            {
+                // If cancelled, we throw. Trying to wait could lead to deadlock.
+                cancellationToken.ThrowIfCancellationRequested();
+
+                if (millisecondsTimeout != Timeout.Infinite)
+                {
+                    remainingWaitMilliseconds = TimeoutHelper.UpdateTimeOut(startTime, millisecondsTimeout);
+                    if (remainingWaitMilliseconds <= 0)
+                    {
+                        // The thread has expires its timeout
+                        return false;
+                    }
+                }
+
+                // ** the actual wait **
+                bool waitSuccessful = Monitor.Wait(m_lockObj, remainingWaitMilliseconds);
+
+                // This waiter has woken up and this needs to be reflected in the count of waiters pulsed to wake. Since we
+                // don't have thread-specific pulse state, there is not enough information to tell whether this thread woke up
+                // because it was pulsed. For instance, this thread may have timed out and may have been waiting to reacquire
+                // the lock before returning from Monitor.Wait, in which case we don't know whether this thread got pulsed. So
+                // in any woken case, decrement the count if possible. As such, timeouts could cause more waiters to wake than
+                // necessary.
+                if (m_countOfWaitersPulsedToWake != 0)
+                {
+                    --m_countOfWaitersPulsedToWake;
+                }
+
+                if (!waitSuccessful)
+                {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// Asynchronously waits to enter the <see cref="SemaphoreSlim"/>.
+        /// </summary>
+        /// <returns>A task that will complete when the semaphore has been entered.</returns>
+        public Task WaitAsync()
+        {
+            return WaitAsync(Timeout.Infinite, default(CancellationToken));
+        }
+
+        /// <summary>
+        /// Asynchronously waits to enter the <see cref="SemaphoreSlim"/>, while observing a
+        /// <see cref="T:System.Threading.CancellationToken"/>.
+        /// </summary>
+        /// <returns>A task that will complete when the semaphore has been entered.</returns>
+        /// <param name="cancellationToken">
+        /// The <see cref="T:System.Threading.CancellationToken"/> token to observe.
+        /// </param>
+        /// <exception cref="T:System.ObjectDisposedException">
+        /// The current instance has already been disposed.
+        /// </exception>
+        public Task WaitAsync(CancellationToken cancellationToken)
+        {
+            return WaitAsync(Timeout.Infinite, cancellationToken);
+        }
+
+        /// <summary>
+        /// Asynchronously waits to enter the <see cref="SemaphoreSlim"/>,
+        /// using a 32-bit signed integer to measure the time interval.
+        /// </summary>
+        /// <param name="millisecondsTimeout">
+        /// The number of milliseconds to wait, or <see cref="Timeout.Infinite"/>(-1) to wait indefinitely.
+        /// </param>
+        /// <returns>
+        /// A task that will complete with a result of true if the current thread successfully entered 
+        /// the <see cref="SemaphoreSlim"/>, otherwise with a result of false.
+        /// </returns>
+        /// <exception cref="T:System.ObjectDisposedException">The current instance has already been
+        /// disposed.</exception>
+        /// <exception cref="ArgumentOutOfRangeException"><paramref name="millisecondsTimeout"/> is a negative number other than -1,
+        /// which represents an infinite time-out.
+        /// </exception>
+        public Task<bool> WaitAsync(int millisecondsTimeout)
+        {
+            return WaitAsync(millisecondsTimeout, default(CancellationToken));
+        }
+
+        /// <summary>
+        /// Asynchronously waits to enter the <see cref="SemaphoreSlim"/>, using a <see
+        /// cref="T:System.TimeSpan"/> to measure the time interval, while observing a
+        /// <see cref="T:System.Threading.CancellationToken"/>.
+        /// </summary>
+        /// <param name="timeout">
+        /// A <see cref="System.TimeSpan"/> that represents the number of milliseconds
+        /// to wait, or a <see cref="System.TimeSpan"/> that represents -1 milliseconds to wait indefinitely.
+        /// </param>
+        /// <param name="cancellationToken">
+        /// The <see cref="T:System.Threading.CancellationToken"/> token to observe.
+        /// </param>
+        /// <returns>
+        /// A task that will complete with a result of true if the current thread successfully entered 
+        /// the <see cref="SemaphoreSlim"/>, otherwise with a result of false.
+        /// </returns>
+        /// <exception cref="T:System.ObjectDisposedException">
+        /// The current instance has already been disposed.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// <paramref name="timeout"/> is a negative number other than -1 milliseconds, which represents 
+        /// an infinite time-out -or- timeout is greater than <see cref="System.Int32.MaxValue"/>.
+        /// </exception>
+        public Task<bool> WaitAsync(TimeSpan timeout)
+        {
+            return WaitAsync(timeout, default(CancellationToken));
+        }
+
+        /// <summary>
+        /// Asynchronously waits to enter the <see cref="SemaphoreSlim"/>, using a <see
+        /// cref="T:System.TimeSpan"/> to measure the time interval.
+        /// </summary>
+        /// <param name="timeout">
+        /// A <see cref="System.TimeSpan"/> that represents the number of milliseconds
+        /// to wait, or a <see cref="System.TimeSpan"/> that represents -1 milliseconds to wait indefinitely.
+        /// </param>
+        /// <returns>
+        /// A task that will complete with a result of true if the current thread successfully entered 
+        /// the <see cref="SemaphoreSlim"/>, otherwise with a result of false.
+        /// </returns>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// <paramref name="timeout"/> is a negative number other than -1 milliseconds, which represents 
+        /// an infinite time-out -or- timeout is greater than <see cref="System.Int32.MaxValue"/>.
+        /// </exception>
+        public Task<bool> WaitAsync(TimeSpan timeout, CancellationToken cancellationToken)
+        {
+            // Validate the timeout
+            Int64 totalMilliseconds = (Int64)timeout.TotalMilliseconds;
+            if (totalMilliseconds < -1 || totalMilliseconds > Int32.MaxValue)
+            {
+                throw new System.ArgumentOutOfRangeException(
+                    nameof(timeout), timeout, SR.SemaphoreSlim_Wait_TimeoutWrong);
+            }
+
+            // Call wait with the timeout milliseconds
+            return WaitAsync((int)timeout.TotalMilliseconds, cancellationToken);
+        }
+
+        /// <summary>
+        /// Asynchronously waits to enter the <see cref="SemaphoreSlim"/>,
+        /// using a 32-bit signed integer to measure the time interval, 
+        /// while observing a <see cref="T:System.Threading.CancellationToken"/>.
+        /// </summary>
+        /// <param name="millisecondsTimeout">
+        /// The number of milliseconds to wait, or <see cref="Timeout.Infinite"/>(-1) to wait indefinitely.
+        /// </param>
+        /// <param name="cancellationToken">The <see cref="T:System.Threading.CancellationToken"/> to observe.</param>
+        /// <returns>
+        /// A task that will complete with a result of true if the current thread successfully entered 
+        /// the <see cref="SemaphoreSlim"/>, otherwise with a result of false.
+        /// </returns>
+        /// <exception cref="T:System.ObjectDisposedException">The current instance has already been
+        /// disposed.</exception>
+        /// <exception cref="ArgumentOutOfRangeException"><paramref name="millisecondsTimeout"/> is a negative number other than -1,
+        /// which represents an infinite time-out.
+        /// </exception>
+        public Task<bool> WaitAsync(int millisecondsTimeout, CancellationToken cancellationToken)
+        {
+            CheckDispose();
+
+            // Validate input
+            if (millisecondsTimeout < -1)
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(millisecondsTimeout), millisecondsTimeout, SR.SemaphoreSlim_Wait_TimeoutWrong);
+            }
+
+            // Bail early for cancellation
+            if (cancellationToken.IsCancellationRequested)
+                return Task.FromCanceled<bool>(cancellationToken);
+
+            lock (m_lockObj)
+            {
+                // If there are counts available, allow this waiter to succeed.
+                if (m_currentCount > 0)
+                {
+                    --m_currentCount;
+                    if (m_waitHandle != null && m_currentCount == 0) m_waitHandle.Reset();
+                    return s_trueTask;
+                }
+                else if (millisecondsTimeout == 0)
+                {
+                    // No counts, if timeout is zero fail fast
+                    return s_falseTask;
+                }
+                // If there aren't, create and return a task to the caller.
+                // The task will be completed either when they've successfully acquired
+                // the semaphore or when the timeout expired or cancellation was requested.
+                else
+                {
+                    Debug.Assert(m_currentCount == 0, "m_currentCount should never be negative");
+                    var asyncWaiter = CreateAndAddAsyncWaiter();
+                    return (millisecondsTimeout == Timeout.Infinite && !cancellationToken.CanBeCanceled) ?
+                        asyncWaiter :
+                        WaitUntilCountOrTimeoutAsync(asyncWaiter, millisecondsTimeout, cancellationToken);
+                }
+            }
+        }
+
+        /// <summary>Creates a new task and stores it into the async waiters list.</summary>
+        /// <returns>The created task.</returns>
+        private TaskNode CreateAndAddAsyncWaiter()
+        {
+            Debug.Assert(Monitor.IsEntered(m_lockObj), "Requires the lock be held");
+
+            // Create the task
+            var task = new TaskNode();
+
+            // Add it to the linked list
+            if (m_asyncHead == null)
+            {
+                Debug.Assert(m_asyncTail == null, "If head is null, so too should be tail");
+                m_asyncHead = task;
+                m_asyncTail = task;
+            }
+            else
+            {
+                Debug.Assert(m_asyncTail != null, "If head is not null, neither should be tail");
+                m_asyncTail.Next = task;
+                task.Prev = m_asyncTail;
+                m_asyncTail = task;
+            }
+
+            // Hand it back
+            return task;
+        }
+
+        /// <summary>Removes the waiter task from the linked list.</summary>
+        /// <param name="task">The task to remove.</param>
+        /// <returns>true if the waiter was in the list; otherwise, false.</returns>
+        private bool RemoveAsyncWaiter(TaskNode task)
+        {
+            Debug.Assert(task != null, "Expected non-null task");
+            Debug.Assert(Monitor.IsEntered(m_lockObj), "Requires the lock be held");
+
+            // Is the task in the list?  To be in the list, either it's the head or it has a predecessor that's in the list.
+            bool wasInList = m_asyncHead == task || task.Prev != null;
+
+            // Remove it from the linked list
+            if (task.Next != null) task.Next.Prev = task.Prev;
+            if (task.Prev != null) task.Prev.Next = task.Next;
+            if (m_asyncHead == task) m_asyncHead = task.Next;
+            if (m_asyncTail == task) m_asyncTail = task.Prev;
+            Debug.Assert((m_asyncHead == null) == (m_asyncTail == null), "Head is null iff tail is null");
+
+            // Make sure not to leak
+            task.Next = task.Prev = null;
+
+            // Return whether the task was in the list
+            return wasInList;
+        }
+
+        /// <summary>Performs the asynchronous wait.</summary>
+        /// <param name="millisecondsTimeout">The timeout.</param>
+        /// <param name="cancellationToken">The cancellation token.</param>
+        /// <returns>The task to return to the caller.</returns>
+        private async Task<bool> WaitUntilCountOrTimeoutAsync(TaskNode asyncWaiter, int millisecondsTimeout, CancellationToken cancellationToken)
+        {
+            Debug.Assert(asyncWaiter != null, "Waiter should have been constructed");
+            Debug.Assert(Monitor.IsEntered(m_lockObj), "Requires the lock be held");
+
+            // Wait until either the task is completed, timeout occurs, or cancellation is requested.
+            // We need to ensure that the Task.Delay task is appropriately cleaned up if the await
+            // completes due to the asyncWaiter completing, so we use our own token that we can explicitly
+            // cancel, and we chain the caller's supplied token into it.
+            using (var cts = cancellationToken.CanBeCanceled ?
+                CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, default(CancellationToken)) :
+                new CancellationTokenSource())
+            {
+                var waitCompleted = Task.WhenAny(asyncWaiter, Task.Delay(millisecondsTimeout, cts.Token));
+                if (asyncWaiter == await waitCompleted.ConfigureAwait(false))
+                {
+                    cts.Cancel(); // ensure that the Task.Delay task is cleaned up
+                    return true; // successfully acquired
+                }
+            }
+
+            // If we get here, the wait has timed out or been canceled.
+
+            // If the await completed synchronously, we still hold the lock.  If it didn't,
+            // we no longer hold the lock.  As such, acquire it.
+            lock (m_lockObj)
+            {
+                // Remove the task from the list.  If we're successful in doing so,
+                // we know that no one else has tried to complete this waiter yet,
+                // so we can safely cancel or timeout.
+                if (RemoveAsyncWaiter(asyncWaiter))
+                {
+                    cancellationToken.ThrowIfCancellationRequested(); // cancellation occurred
+                    return false; // timeout occurred
+                }
+            }
+
+            // The waiter had already been removed, which means it's already completed or is about to
+            // complete, so let it, and don't return until it does.
+            return await asyncWaiter.ConfigureAwait(false);
+        }
+
+        /// <summary>
+        /// Exits the <see cref="SemaphoreSlim"/> once.
+        /// </summary>
+        /// <returns>The previous count of the <see cref="SemaphoreSlim"/>.</returns>
+        /// <exception cref="T:System.ObjectDisposedException">The current instance has already been
+        /// disposed.</exception>
+        public int Release()
+        {
+            return Release(1);
+        }
+
+        /// <summary>
+        /// Exits the <see cref="SemaphoreSlim"/> a specified number of times.
+        /// </summary>
+        /// <param name="releaseCount">The number of times to exit the semaphore.</param>
+        /// <returns>The previous count of the <see cref="SemaphoreSlim"/>.</returns>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="releaseCount"/> is less
+        /// than 1.</exception>
+        /// <exception cref="T:System.Threading.SemaphoreFullException">The <see cref="SemaphoreSlim"/> has
+        /// already reached its maximum size.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The current instance has already been
+        /// disposed.</exception>
+        public int Release(int releaseCount)
+        {
+            CheckDispose();
+
+            // Validate input
+            if (releaseCount < 1)
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(releaseCount), releaseCount, SR.SemaphoreSlim_Release_CountWrong);
+            }
+            int returnCount;
+
+            lock (m_lockObj)
+            {
+                // Read the m_currentCount into a local variable to avoid unnecessary volatile accesses inside the lock.
+                int currentCount = m_currentCount;
+                returnCount = currentCount;
+
+                // If the release count would result exceeding the maximum count, throw SemaphoreFullException.
+                if (m_maxCount - currentCount < releaseCount)
+                {
+                    throw new SemaphoreFullException();
+                }
+
+                // Increment the count by the actual release count
+                currentCount += releaseCount;
+
+                // Signal to any synchronous waiters, taking into account how many waiters have previously been pulsed to wake
+                // but have not yet woken
+                int waitCount = m_waitCount;
+                Debug.Assert(m_countOfWaitersPulsedToWake <= waitCount);
+                int waitersToNotify = Math.Min(currentCount, waitCount) - m_countOfWaitersPulsedToWake;
+                if (waitersToNotify > 0)
+                {
+                    // Ideally, limiting to a maximum of releaseCount would not be necessary and could be an assert instead, but
+                    // since WaitUntilCountOrTimeout() does not have enough information to tell whether a woken thread was
+                    // pulsed, it's possible for m_countOfWaitersPulsedToWake to be less than the number of threads that have
+                    // actually been pulsed to wake.
+                    if (waitersToNotify > releaseCount)
+                    {
+                        waitersToNotify = releaseCount;
+                    }
+
+                    m_countOfWaitersPulsedToWake += waitersToNotify;
+                    for (int i = 0; i < waitersToNotify; i++)
+                    {
+                        Monitor.Pulse(m_lockObj);
+                    }
+                }
+
+                // Now signal to any asynchronous waiters, if there are any.  While we've already
+                // signaled the synchronous waiters, we still hold the lock, and thus
+                // they won't have had an opportunity to acquire this yet.  So, when releasing
+                // asynchronous waiters, we assume that all synchronous waiters will eventually
+                // acquire the semaphore.  That could be a faulty assumption if those synchronous
+                // waits are canceled, but the wait code path will handle that.
+                if (m_asyncHead != null)
+                {
+                    Debug.Assert(m_asyncTail != null, "tail should not be null if head isn't null");
+                    int maxAsyncToRelease = currentCount - waitCount;
+                    while (maxAsyncToRelease > 0 && m_asyncHead != null)
+                    {
+                        --currentCount;
+                        --maxAsyncToRelease;
+
+                        // Get the next async waiter to release and queue it to be completed
+                        var waiterTask = m_asyncHead;
+                        RemoveAsyncWaiter(waiterTask); // ensures waiterTask.Next/Prev are null
+                        QueueWaiterTask(waiterTask);
+                    }
+                }
+                m_currentCount = currentCount;
+
+                // Exposing wait handle if it is not null
+                if (m_waitHandle != null && returnCount == 0 && currentCount > 0)
+                {
+                    m_waitHandle.Set();
+                }
+            }
+
+            // And return the count
+            return returnCount;
+        }
+
+        /// <summary>
+        /// Queues a waiter task to the ThreadPool. We use this small helper method so that
+        /// the larger Release(count) method does not need to be SecuritySafeCritical.
+        /// </summary>
+        private static void QueueWaiterTask(TaskNode waiterTask)
+        {
+            ThreadPool.UnsafeQueueCustomWorkItem(waiterTask, forceGlobal: false);
+        }
+
+        /// <summary>
+        /// Releases all resources used by the current instance of <see
+        /// cref="SemaphoreSlim"/>.
+        /// </summary>
+        /// <remarks>
+        /// Unlike most of the members of <see cref="SemaphoreSlim"/>, <see cref="Dispose()"/> is not
+        /// thread-safe and may not be used concurrently with other members of this instance.
+        /// </remarks>
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// When overridden in a derived class, releases the unmanaged resources used by the 
+        /// <see cref="T:System.Threading.ManualResetEventSlim"/>, and optionally releases the managed resources.
+        /// </summary>
+        /// <param name="disposing">true to release both managed and unmanaged resources;
+        /// false to release only unmanaged resources.</param>
+        /// <remarks>
+        /// Unlike most of the members of <see cref="SemaphoreSlim"/>, <see cref="Dispose(Boolean)"/> is not
+        /// thread-safe and may not be used concurrently with other members of this instance.
+        /// </remarks>
+        protected virtual void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                if (m_waitHandle != null)
+                {
+                    m_waitHandle.Close();
+                    m_waitHandle = null;
+                }
+                m_lockObj = null;
+                m_asyncHead = null;
+                m_asyncTail = null;
+            }
+        }
+
+
+
+        /// <summary>
+        /// Private helper method to wake up waiters when a cancellationToken gets canceled.
+        /// </summary>
+        private static Action<object> s_cancellationTokenCanceledEventHandler = new Action<object>(CancellationTokenCanceledEventHandler);
+        private static void CancellationTokenCanceledEventHandler(object obj)
+        {
+            SemaphoreSlim semaphore = obj as SemaphoreSlim;
+            Debug.Assert(semaphore != null, "Expected a SemaphoreSlim");
+            lock (semaphore.m_lockObj)
+            {
+                Monitor.PulseAll(semaphore.m_lockObj); //wake up all waiters.
+            }
+        }
+
+        /// <summary>
+        /// Checks the dispose status by checking the lock object, if it is null means that object
+        /// has been disposed and throw ObjectDisposedException
+        /// </summary>
+        private void CheckDispose()
+        {
+            if (m_lockObj == null)
+            {
+                throw new ObjectDisposedException(null, SR.SemaphoreSlim_Disposed);
+            }
+        }
+
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/SpinLock.cs b/src/System.Private.CoreLib/src/System/Threading/SpinLock.cs
new file mode 100644
index 0000000000..7e58a6cf89
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/SpinLock.cs
@@ -0,0 +1,650 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+#pragma warning disable 0420
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+// A spin lock is a mutual exclusion lock primitive where a thread trying to acquire the lock waits in a loop ("spins")
+// repeatedly checking until the lock becomes available. As the thread remains active performing a non-useful task,
+// the use of such a lock is a kind of busy waiting and consumes CPU resources without performing real work. 
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+
+namespace System.Threading
+{
+    /// <summary>
+    /// Provides a mutual exclusion lock primitive where a thread trying to acquire the lock waits in a loop
+    /// repeatedly checking until the lock becomes available.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// Spin locks can be used for leaf-level locks where the object allocation implied by using a <see
+    /// cref="System.Threading.Monitor"/>, in size or due to garbage collection pressure, is overly
+    /// expensive. Avoiding blocking is another reason that a spin lock can be useful, however if you expect
+    /// any significant amount of blocking, you are probably best not using spin locks due to excessive
+    /// spinning. Spinning can be beneficial when locks are fine grained and large in number (for example, a
+    /// lock per node in a linked list) as well as when lock hold times are always extremely short. In
+    /// general, while holding a spin lock, one should avoid blocking, calling anything that itself may
+    /// block, holding more than one spin lock at once, making dynamically dispatched calls (interface and
+    /// virtuals), making statically dispatched calls into any code one doesn't own, or allocating memory.
+    /// </para>
+    /// <para>
+    /// <see cref="SpinLock"/> should only be used when it's been determined that doing so will improve an
+    /// application's performance. It's also important to note that <see cref="SpinLock"/> is a value type,
+    /// for performance reasons. As such, one must be very careful not to accidentally copy a SpinLock
+    /// instance, as the two instances (the original and the copy) would then be completely independent of
+    /// one another, which would likely lead to erroneous behavior of the application. If a SpinLock instance
+    /// must be passed around, it should be passed by reference rather than by value.
+    /// </para>
+    /// <para>
+    /// Do not store <see cref="SpinLock"/> instances in readonly fields.
+    /// </para>
+    /// <para>
+    /// All members of <see cref="SpinLock"/> are thread-safe and may be used from multiple threads
+    /// concurrently.
+    /// </para>
+    /// </remarks>
+    [DebuggerTypeProxy(typeof(SystemThreading_SpinLockDebugView))]
+    [DebuggerDisplay("IsHeld = {IsHeld}")]
+    public struct SpinLock
+    {
+        // The current ownership state is a single signed int. There are two modes:
+        //
+        //    1) Ownership tracking enabled: the high bit is 0, and the remaining bits
+        //       store the managed thread ID of the current owner.  When the 31 low bits
+        //       are 0, the lock is available.
+        //    2) Performance mode: when the high bit is 1, lock availability is indicated by the low bit.  
+        //       When the low bit is 1 -- the lock is held; 0 -- the lock is available.
+        //
+        // There are several masks and constants below for convenience.
+
+        private volatile int m_owner;
+
+        // After how many yields, call Sleep(1)
+        private const int SLEEP_ONE_FREQUENCY = 40;
+
+        // After how many yields, check the timeout
+        private const int TIMEOUT_CHECK_FREQUENCY = 10;
+
+        // Thr thread tracking disabled mask
+        private const int LOCK_ID_DISABLE_MASK = unchecked((int)0x80000000);        //1000 0000 0000 0000 0000 0000 0000 0000
+
+        //the lock is held by some thread, but we don't know which
+        private const int LOCK_ANONYMOUS_OWNED = 0x1;                               //0000 0000 0000 0000 0000 0000 0000 0001
+
+        // Waiters mask if the thread tracking is disabled
+        private const int WAITERS_MASK = ~(LOCK_ID_DISABLE_MASK | 1);               //0111 1111 1111 1111 1111 1111 1111 1110
+
+        // The Thread tacking is disabled and the lock bit is set, used in Enter fast path to make sure the id is disabled and lock is available
+        private const int ID_DISABLED_AND_ANONYMOUS_OWNED = unchecked((int)0x80000001); //1000 0000 0000 0000 0000 0000 0000 0001
+
+        // If the thread is unowned if:
+        // m_owner zero and the thread tracking is enabled
+        // m_owner & LOCK_ANONYMOUS_OWNED = zero and the thread tracking is disabled
+        private const int LOCK_UNOWNED = 0;
+
+        // The maximum number of waiters (only used if the thread tracking is disabled)
+        // The actual maximum waiters count is this number divided by two because each waiter increments the waiters count by 2
+        // The waiters count is calculated by m_owner & WAITERS_MASK 01111....110
+        private static int MAXIMUM_WAITERS = WAITERS_MASK;
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int CompareExchange(ref int location, int value, int comparand, ref bool success)
+        {
+            int result = Interlocked.CompareExchange(ref location, value, comparand);
+            success = (result == comparand);
+            return result;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.SpinLock"/>
+        /// structure with the option to track thread IDs to improve debugging.
+        /// </summary>
+        /// <remarks>
+        /// The default constructor for <see cref="SpinLock"/> tracks thread ownership.
+        /// </remarks>
+        /// <param name="enableThreadOwnerTracking">Whether to capture and use thread IDs for debugging
+        /// purposes.</param>
+        public SpinLock(bool enableThreadOwnerTracking)
+        {
+            m_owner = LOCK_UNOWNED;
+            if (!enableThreadOwnerTracking)
+            {
+                m_owner |= LOCK_ID_DISABLE_MASK;
+                Debug.Assert(!IsThreadOwnerTrackingEnabled, "property should be false by now");
+            }
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="T:System.Threading.SpinLock"/>
+        /// structure with the option to track thread IDs to improve debugging.
+        /// </summary>
+        /// <remarks>
+        /// The default constructor for <see cref="SpinLock"/> tracks thread ownership.
+        /// </remarks>
+        /// <summary>
+        /// Acquires the lock in a reliable manner, such that even if an exception occurs within the method
+        /// call, <paramref name="lockTaken"/> can be examined reliably to determine whether the lock was
+        /// acquired.
+        /// </summary>
+        /// <remarks>
+        /// <see cref="SpinLock"/> is a non-reentrant lock, meaning that if a thread holds the lock, it is
+        /// not allowed to enter the lock again. If thread ownership tracking is enabled (whether it's
+        /// enabled is available through <see cref="IsThreadOwnerTrackingEnabled"/>), an exception will be
+        /// thrown when a thread tries to re-enter a lock it already holds. However, if thread ownership
+        /// tracking is disabled, attempting to enter a lock already held will result in deadlock.
+        /// </remarks>
+        /// <param name="lockTaken">True if the lock is acquired; otherwise, false. <paramref
+        /// name="lockTaken"/> must be initialized to false prior to calling this method.</param>
+        /// <exception cref="T:System.Threading.LockRecursionException">
+        /// Thread ownership tracking is enabled, and the current thread has already acquired this lock.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="lockTaken"/> argument must be initialized to false prior to calling Enter.
+        /// </exception>
+        public void Enter(ref bool lockTaken)
+        {
+            //Try to keep the code and branching in this method as small as possible in order to inline the method
+            int observedOwner = m_owner;
+            if (lockTaken || //invalid parameter
+                (observedOwner & ID_DISABLED_AND_ANONYMOUS_OWNED) != LOCK_ID_DISABLE_MASK || //thread tracking is enabled or the lock is already acquired
+                CompareExchange(ref m_owner, observedOwner | LOCK_ANONYMOUS_OWNED, observedOwner, ref lockTaken) != observedOwner) //acquiring the lock failed
+                ContinueTryEnter(Timeout.Infinite, ref lockTaken); // Then try the slow path if any of the above conditions is met
+        }
+
+        /// <summary>
+        /// Attempts to acquire the lock in a reliable manner, such that even if an exception occurs within
+        /// the method call, <paramref name="lockTaken"/> can be examined reliably to determine whether the
+        /// lock was acquired.
+        /// </summary>
+        /// <remarks>
+        /// Unlike <see cref="Enter"/>, TryEnter will not block waiting for the lock to be available. If the
+        /// lock is not available when TryEnter is called, it will return immediately without any further
+        /// spinning.
+        /// </remarks>
+        /// <param name="lockTaken">True if the lock is acquired; otherwise, false. <paramref
+        /// name="lockTaken"/> must be initialized to false prior to calling this method.</param>
+        /// <exception cref="T:System.Threading.LockRecursionException">
+        /// Thread ownership tracking is enabled, and the current thread has already acquired this lock.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="lockTaken"/> argument must be initialized to false prior to calling TryEnter.
+        /// </exception>
+        public void TryEnter(ref bool lockTaken)
+        {
+            int observedOwner = m_owner;
+            if (((observedOwner & LOCK_ID_DISABLE_MASK) == 0) | lockTaken)
+            {
+                // Thread tracking enabled or invalid arg. Take slow path.
+                ContinueTryEnter(0, ref lockTaken);
+            }
+            else if ((observedOwner & LOCK_ANONYMOUS_OWNED) != 0)
+            {
+                // Lock already held by someone
+                lockTaken = false;
+            }
+            else
+            {
+                // Lock wasn't held; try to acquire it.
+                CompareExchange(ref m_owner, observedOwner | LOCK_ANONYMOUS_OWNED, observedOwner, ref lockTaken);
+            }
+        }
+
+        /// <summary>
+        /// Attempts to acquire the lock in a reliable manner, such that even if an exception occurs within
+        /// the method call, <paramref name="lockTaken"/> can be examined reliably to determine whether the
+        /// lock was acquired.
+        /// </summary>
+        /// <remarks>
+        /// Unlike <see cref="Enter"/>, TryEnter will not block indefinitely waiting for the lock to be
+        /// available. It will block until either the lock is available or until the <paramref
+        /// name="timeout"/>
+        /// has expired.
+        /// </remarks>
+        /// <param name="timeout">A <see cref="System.TimeSpan"/> that represents the number of milliseconds
+        /// to wait, or a <see cref="System.TimeSpan"/> that represents -1 milliseconds to wait indefinitely.
+        /// </param>
+        /// <param name="lockTaken">True if the lock is acquired; otherwise, false. <paramref
+        /// name="lockTaken"/> must be initialized to false prior to calling this method.</param>
+        /// <exception cref="T:System.Threading.LockRecursionException">
+        /// Thread ownership tracking is enabled, and the current thread has already acquired this lock.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="lockTaken"/> argument must be initialized to false prior to calling TryEnter.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="timeout"/> is a negative
+        /// number other than -1 milliseconds, which represents an infinite time-out -or- timeout is greater
+        /// than <see cref="System.Int32.MaxValue"/> milliseconds.
+        /// </exception>
+        public void TryEnter(TimeSpan timeout, ref bool lockTaken)
+        {
+            // Validate the timeout
+            Int64 totalMilliseconds = (Int64)timeout.TotalMilliseconds;
+            if (totalMilliseconds < -1 || totalMilliseconds > int.MaxValue)
+            {
+                throw new System.ArgumentOutOfRangeException(
+                    nameof(timeout), timeout, SR.SpinLock_TryEnter_ArgumentOutOfRange);
+            }
+
+            // Call reliable enter with the int-based timeout milliseconds
+            TryEnter((int)timeout.TotalMilliseconds, ref lockTaken);
+        }
+
+        /// <summary>
+        /// Attempts to acquire the lock in a reliable manner, such that even if an exception occurs within
+        /// the method call, <paramref name="lockTaken"/> can be examined reliably to determine whether the
+        /// lock was acquired.
+        /// </summary>
+        /// <remarks>
+        /// Unlike <see cref="Enter"/>, TryEnter will not block indefinitely waiting for the lock to be
+        /// available. It will block until either the lock is available or until the <paramref
+        /// name="millisecondsTimeout"/> has expired.
+        /// </remarks>
+        /// <param name="millisecondsTimeout">The number of milliseconds to wait, or <see
+        /// cref="System.Threading.Timeout.Infinite"/> (-1) to wait indefinitely.</param>
+        /// <param name="lockTaken">True if the lock is acquired; otherwise, false. <paramref
+        /// name="lockTaken"/> must be initialized to false prior to calling this method.</param>
+        /// <exception cref="T:System.Threading.LockRecursionException">
+        /// Thread ownership tracking is enabled, and the current thread has already acquired this lock.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="lockTaken"/> argument must be initialized to false prior to calling TryEnter.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="millisecondsTimeout"/> is
+        /// a negative number other than -1, which represents an infinite time-out.</exception>
+        public void TryEnter(int millisecondsTimeout, ref bool lockTaken)
+        {
+            int observedOwner = m_owner;
+            if (millisecondsTimeout < -1 || //invalid parameter
+                lockTaken || //invalid parameter
+                (observedOwner & ID_DISABLED_AND_ANONYMOUS_OWNED) != LOCK_ID_DISABLE_MASK ||  //thread tracking is enabled or the lock is already acquired
+                CompareExchange(ref m_owner, observedOwner | LOCK_ANONYMOUS_OWNED, observedOwner, ref lockTaken) != observedOwner) // acquiring the lock failed
+                ContinueTryEnter(millisecondsTimeout, ref lockTaken); // The call the slow pth
+        }
+
+        /// <summary>
+        /// Try acquire the lock with long path, this is usually called after the first path in Enter and
+        /// TryEnter failed The reason for short path is to make it inline in the run time which improves the
+        /// performance. This method assumed that the parameter are validated in Enter or TryEnter method.
+        /// </summary>
+        /// <param name="millisecondsTimeout">The timeout milliseconds</param>
+        /// <param name="lockTaken">The lockTaken param</param>
+        private void ContinueTryEnter(int millisecondsTimeout, ref bool lockTaken)
+        {
+            // The fast path doesn't throw any exception, so we have to validate the parameters here
+            if (lockTaken)
+            {
+                lockTaken = false;
+                throw new System.ArgumentException(SR.SpinLock_TryReliableEnter_ArgumentException);
+            }
+
+            if (millisecondsTimeout < -1)
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(millisecondsTimeout), millisecondsTimeout, SR.SpinLock_TryEnter_ArgumentOutOfRange);
+            }
+
+            uint startTime = 0;
+            if (millisecondsTimeout != Timeout.Infinite && millisecondsTimeout != 0)
+            {
+                startTime = TimeoutHelper.GetTime();
+            }
+
+            if (IsThreadOwnerTrackingEnabled)
+            {
+                // Slow path for enabled thread tracking mode
+                ContinueTryEnterWithThreadTracking(millisecondsTimeout, startTime, ref lockTaken);
+                return;
+            }
+
+            // then thread tracking is disabled
+            // In this case there are three ways to acquire the lock
+            // 1- the first way the thread either tries to get the lock if it's free or updates the waiters, if the turn >= the processors count then go to 3 else go to 2
+            // 2- In this step the waiter threads spins and tries to acquire the lock, the number of spin iterations and spin count is dependent on the thread turn
+            // the late the thread arrives the more it spins and less frequent it check the lock availability
+            // Also the spins count is increases each iteration
+            // If the spins iterations finished and failed to acquire the lock, go to step 3
+            // 3- This is the yielding step, there are two ways of yielding Thread.Yield and Sleep(1)
+            // If the timeout is expired in after step 1, we need to decrement the waiters count before returning
+
+            int observedOwner;
+            int turn = int.MaxValue;
+            //***Step 1, take the lock or update the waiters
+
+            // try to acquire the lock directly if possible or update the waiters count
+            observedOwner = m_owner;
+            if ((observedOwner & LOCK_ANONYMOUS_OWNED) == LOCK_UNOWNED)
+            {
+                if (CompareExchange(ref m_owner, observedOwner | 1, observedOwner, ref lockTaken) == observedOwner)
+                {
+                    // Acquired lock
+                    return;
+                }
+
+                if (millisecondsTimeout == 0)
+                {
+                    // Did not acquire lock in CompareExchange and timeout is 0 so fail fast
+                    return;
+                }
+            }
+            else if (millisecondsTimeout == 0)
+            {
+                // Did not acquire lock as owned and timeout is 0 so fail fast
+                return;
+            }
+            else //failed to acquire the lock, then try to update the waiters. If the waiters count reached the maximum, just break the loop to avoid overflow
+            {
+                if ((observedOwner & WAITERS_MASK) != MAXIMUM_WAITERS)
+                {
+                    // This can still overflow, but maybe there will never be that many waiters
+                    turn = (Interlocked.Add(ref m_owner, 2) & WAITERS_MASK) >> 1;
+                }
+            }
+
+            //lock acquired failed and waiters updated
+
+            //*** Step 2, Spinning and Yielding
+            var spinner = new SpinWait();
+            if (turn > PlatformHelper.ProcessorCount)
+            {
+                spinner.Count = SpinWait.YieldThreshold;
+            }
+            while (true)
+            {
+                spinner.SpinOnce(SLEEP_ONE_FREQUENCY);
+
+                observedOwner = m_owner;
+                if ((observedOwner & LOCK_ANONYMOUS_OWNED) == LOCK_UNOWNED)
+                {
+                    int newOwner = (observedOwner & WAITERS_MASK) == 0 ? // Gets the number of waiters, if zero
+                           observedOwner | 1 // don't decrement it. just set the lock bit, it is zero because a previous call of Exit(false) which corrupted the waiters
+                           : (observedOwner - 2) | 1; // otherwise decrement the waiters and set the lock bit
+                    Debug.Assert((newOwner & WAITERS_MASK) >= 0);
+
+                    if (CompareExchange(ref m_owner, newOwner, observedOwner, ref lockTaken) == observedOwner)
+                    {
+                        return;
+                    }
+                }
+
+                if (spinner.Count % TIMEOUT_CHECK_FREQUENCY == 0)
+                {
+                    //Check the timeout.
+                    if (millisecondsTimeout != Timeout.Infinite && TimeoutHelper.UpdateTimeOut(startTime, millisecondsTimeout) <= 0)
+                    {
+                        DecrementWaiters();
+                        return;
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// decrements the waiters, in case of the timeout is expired
+        /// </summary>
+        private void DecrementWaiters()
+        {
+            SpinWait spinner = new SpinWait();
+            while (true)
+            {
+                int observedOwner = m_owner;
+                if ((observedOwner & WAITERS_MASK) == 0) return; // don't decrement the waiters if it's corrupted by previous call of Exit(false)
+                if (Interlocked.CompareExchange(ref m_owner, observedOwner - 2, observedOwner) == observedOwner)
+                {
+                    Debug.Assert(!IsThreadOwnerTrackingEnabled); // Make sure the waiters never be negative which will cause the thread tracking bit to be flipped
+                    break;
+                }
+                spinner.SpinOnce();
+            }
+        }
+
+        /// <summary>
+        /// ContinueTryEnter for the thread tracking mode enabled
+        /// </summary>
+        private void ContinueTryEnterWithThreadTracking(int millisecondsTimeout, uint startTime, ref bool lockTaken)
+        {
+            Debug.Assert(IsThreadOwnerTrackingEnabled);
+
+            int lockUnowned = 0;
+            // We are using thread IDs to mark ownership. Snap the thread ID and check for recursion.
+            // We also must or the ID enablement bit, to ensure we propagate when we CAS it in.
+            int m_newOwner = Environment.CurrentManagedThreadId;
+            if (m_owner == m_newOwner)
+            {
+                // We don't allow lock recursion.
+                throw new LockRecursionException(SR.SpinLock_TryEnter_LockRecursionException);
+            }
+
+
+            SpinWait spinner = new SpinWait();
+
+            // Loop until the lock has been successfully acquired or, if specified, the timeout expires.
+            do
+            {
+                // We failed to get the lock, either from the fast route or the last iteration
+                // and the timeout hasn't expired; spin once and try again.
+                spinner.SpinOnce();
+
+                // Test before trying to CAS, to avoid acquiring the line exclusively unnecessarily.
+
+                if (m_owner == lockUnowned)
+                {
+                    if (CompareExchange(ref m_owner, m_newOwner, lockUnowned, ref lockTaken) == lockUnowned)
+                    {
+                        return;
+                    }
+                }
+                // Check the timeout.  We only RDTSC if the next spin will yield, to amortize the cost.
+                if (millisecondsTimeout == 0 ||
+                    (millisecondsTimeout != Timeout.Infinite && spinner.NextSpinWillYield &&
+                    TimeoutHelper.UpdateTimeOut(startTime, millisecondsTimeout) <= 0))
+                {
+                    return;
+                }
+            } while (true);
+        }
+
+        /// <summary>
+        /// Releases the lock.
+        /// </summary>
+        /// <remarks>
+        /// The default overload of <see cref="Exit()"/> provides the same behavior as if calling <see
+        /// cref="Exit(Boolean)"/> using true as the argument, but Exit() could be slightly faster than Exit(true).
+        /// </remarks>
+        /// <exception cref="SynchronizationLockException">
+        /// Thread ownership tracking is enabled, and the current thread is not the owner of this lock.
+        /// </exception>
+        public void Exit()
+        {
+            //This is the fast path for the thread tracking is disabled, otherwise go to the slow path
+            if ((m_owner & LOCK_ID_DISABLE_MASK) == 0)
+                ExitSlowPath(true);
+            else
+                Interlocked.Decrement(ref m_owner);
+        }
+
+        /// <summary>
+        /// Releases the lock.
+        /// </summary>
+        /// <param name="useMemoryBarrier">
+        /// A Boolean value that indicates whether a memory fence should be issued in order to immediately
+        /// publish the exit operation to other threads.
+        /// </param>
+        /// <remarks>
+        /// Calling <see cref="Exit(Boolean)"/> with the <paramref name="useMemoryBarrier"/> argument set to
+        /// true will improve the fairness of the lock at the expense of some performance. The default <see
+        /// cref="Enter"/>
+        /// overload behaves as if specifying true for <paramref name="useMemoryBarrier"/>.
+        /// </remarks>
+        /// <exception cref="SynchronizationLockException">
+        /// Thread ownership tracking is enabled, and the current thread is not the owner of this lock.
+        /// </exception>
+        public void Exit(bool useMemoryBarrier)
+        {
+            // This is the fast path for the thread tracking is disabled and not to use memory barrier, otherwise go to the slow path
+            // The reason not to add else statement if the usememorybarrier is that it will add more branching in the code and will prevent
+            // method inlining, so this is optimized for useMemoryBarrier=false and Exit() overload optimized for useMemoryBarrier=true.
+            int tmpOwner = m_owner;
+            if ((tmpOwner & LOCK_ID_DISABLE_MASK) != 0 & !useMemoryBarrier)
+            {
+                m_owner = tmpOwner & (~LOCK_ANONYMOUS_OWNED);
+            }
+            else
+                ExitSlowPath(useMemoryBarrier);
+        }
+
+        /// <summary>
+        /// The slow path for exit method if the fast path failed
+        /// </summary>
+        /// <param name="useMemoryBarrier">
+        /// A Boolean value that indicates whether a memory fence should be issued in order to immediately
+        /// publish the exit operation to other threads
+        /// </param>
+        private void ExitSlowPath(bool useMemoryBarrier)
+        {
+            bool threadTrackingEnabled = (m_owner & LOCK_ID_DISABLE_MASK) == 0;
+            if (threadTrackingEnabled && !IsHeldByCurrentThread)
+            {
+                throw new System.Threading.SynchronizationLockException(
+                    SR.SpinLock_Exit_SynchronizationLockException);
+            }
+
+            if (useMemoryBarrier)
+            {
+                if (threadTrackingEnabled)
+                    Interlocked.Exchange(ref m_owner, LOCK_UNOWNED);
+                else
+                    Interlocked.Decrement(ref m_owner);
+            }
+            else
+            {
+                if (threadTrackingEnabled)
+                    m_owner = LOCK_UNOWNED;
+                else
+                {
+                    int tmpOwner = m_owner;
+                    m_owner = tmpOwner & (~LOCK_ANONYMOUS_OWNED);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets whether the lock is currently held by any thread.
+        /// </summary>
+        public bool IsHeld
+        {
+            get
+            {
+                if (IsThreadOwnerTrackingEnabled)
+                    return m_owner != LOCK_UNOWNED;
+
+                return (m_owner & LOCK_ANONYMOUS_OWNED) != LOCK_UNOWNED;
+            }
+        }
+
+        /// <summary>
+        /// Gets whether the lock is currently held by any thread.
+        /// </summary>
+        /// <summary>
+        /// Gets whether the lock is held by the current thread.
+        /// </summary>
+        /// <remarks>
+        /// If the lock was initialized to track owner threads, this will return whether the lock is acquired
+        /// by the current thread. It is invalid to use this property when the lock was initialized to not
+        /// track thread ownership.
+        /// </remarks>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// Thread ownership tracking is disabled.
+        /// </exception>
+        public bool IsHeldByCurrentThread
+        {
+            get
+            {
+                if (!IsThreadOwnerTrackingEnabled)
+                {
+                    throw new InvalidOperationException(SR.SpinLock_IsHeldByCurrentThread);
+                }
+                return ((m_owner & (~LOCK_ID_DISABLE_MASK)) == Environment.CurrentManagedThreadId);
+            }
+        }
+
+        /// <summary>Gets whether thread ownership tracking is enabled for this instance.</summary>
+        public bool IsThreadOwnerTrackingEnabled
+        {
+            get { return (m_owner & LOCK_ID_DISABLE_MASK) == 0; }
+        }
+
+        #region Debugger proxy class
+        /// <summary>
+        /// Internal class used by debug type proxy attribute to display the owner thread ID 
+        /// </summary>
+        internal class SystemThreading_SpinLockDebugView
+        {
+            // SpinLock object
+            private SpinLock m_spinLock;
+
+            /// <summary>
+            /// SystemThreading_SpinLockDebugView constructor
+            /// </summary>
+            /// <param name="spinLock">The SpinLock to be proxied.</param>
+            public SystemThreading_SpinLockDebugView(SpinLock spinLock)
+            {
+                // Note that this makes a copy of the SpinLock (struct). It doesn't hold a reference to it.
+                m_spinLock = spinLock;
+            }
+
+            /// <summary>
+            /// Checks if the lock is held by the current thread or not
+            /// </summary>
+            public bool? IsHeldByCurrentThread
+            {
+                get
+                {
+                    try
+                    {
+                        return m_spinLock.IsHeldByCurrentThread;
+                    }
+                    catch (InvalidOperationException)
+                    {
+                        return null;
+                    }
+                }
+            }
+
+            /// <summary>
+            /// Gets the current owner thread, zero if it is released
+            /// </summary>
+            public int? OwnerThreadID
+            {
+                get
+                {
+                    if (m_spinLock.IsThreadOwnerTrackingEnabled)
+                    {
+                        return m_spinLock.m_owner;
+                    }
+                    else
+                    {
+                        return null;
+                    }
+                }
+            }
+
+
+            /// <summary>
+            ///  Gets whether the lock is currently held by any thread or not.
+            /// </summary>
+            public bool IsHeld
+            {
+                get { return m_spinLock.IsHeld; }
+            }
+        }
+        #endregion
+
+    }
+}
+#pragma warning restore 0420
diff --git a/src/System.Private.CoreLib/src/System/Threading/SynchronizationContext.cs b/src/System.Private.CoreLib/src/System/Threading/SynchronizationContext.cs
new file mode 100644
index 0000000000..f438e9a03d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/SynchronizationContext.cs
@@ -0,0 +1,233 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+/*============================================================
+**
+**
+**
+** Purpose: Capture synchronization semantics for asynchronous callbacks
+**
+** 
+===========================================================*/
+
+namespace System.Threading
+{
+    using Microsoft.Win32.SafeHandles;
+    using System.Runtime.InteropServices;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.ExceptionServices;
+    using System.Runtime;
+    using System.Runtime.Versioning;
+    using System.Runtime.ConstrainedExecution;
+    using System.Reflection;
+    using System.Security;
+    using System.Diagnostics;
+    using System.Diagnostics.CodeAnalysis;
+
+
+    [Flags]
+    internal enum SynchronizationContextProperties
+    {
+        None = 0,
+        RequireWaitNotification = 0x1
+    };
+
+#if FEATURE_COMINTEROP && FEATURE_APPX
+    //
+    // This is implemented in System.Runtime.WindowsRuntime, allowing us to ask that assembly for a WinRT-specific SyncCtx.
+    //
+    // [FriendAccessAllowed]
+    internal abstract class WinRTSynchronizationContextFactoryBase
+    {
+        public abstract SynchronizationContext Create(object coreDispatcher);
+    }
+#endif //FEATURE_COMINTEROP
+
+    public class SynchronizationContext
+    {
+        private SynchronizationContextProperties _props = SynchronizationContextProperties.None;
+
+        public SynchronizationContext()
+        {
+        }
+
+
+        // helper delegate to statically bind to Wait method
+        private delegate int WaitDelegate(IntPtr[] waitHandles, bool waitAll, int millisecondsTimeout);
+
+        private static Type s_cachedPreparedType1;
+        private static Type s_cachedPreparedType2;
+        private static Type s_cachedPreparedType3;
+        private static Type s_cachedPreparedType4;
+        private static Type s_cachedPreparedType5;
+
+        // protected so that only the derived sync context class can enable these flags
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "We never dereference s_cachedPreparedType*, so ordering is unimportant")]
+        protected void SetWaitNotificationRequired()
+        {
+            //
+            // Prepare the method so that it can be called in a reliable fashion when a wait is needed.
+            // This will obviously only make the Wait reliable if the Wait method is itself reliable. The only thing
+            // preparing the method here does is to ensure there is no failure point before the method execution begins.
+            //
+            // Preparing the method in this way is quite expensive, but only needs to be done once per type, per AppDomain.
+            // So we keep track of a few types we've already prepared in this AD.  It is uncommon to have more than
+            // a few SynchronizationContext implementations, so we only cache the first five we encounter; this lets
+            // our cache be much faster than a more general cache might be.  This is important, because this
+            // is a *very* hot code path for many WPF and WinForms apps.
+            //
+            Type type = this.GetType();
+            if (s_cachedPreparedType1 != type &&
+                s_cachedPreparedType2 != type &&
+                s_cachedPreparedType3 != type &&
+                s_cachedPreparedType4 != type &&
+                s_cachedPreparedType5 != type)
+            {
+                RuntimeHelpers.PrepareDelegate(new WaitDelegate(this.Wait));
+
+                if (s_cachedPreparedType1 == null) s_cachedPreparedType1 = type;
+                else if (s_cachedPreparedType2 == null) s_cachedPreparedType2 = type;
+                else if (s_cachedPreparedType3 == null) s_cachedPreparedType3 = type;
+                else if (s_cachedPreparedType4 == null) s_cachedPreparedType4 = type;
+                else if (s_cachedPreparedType5 == null) s_cachedPreparedType5 = type;
+            }
+
+            _props |= SynchronizationContextProperties.RequireWaitNotification;
+        }
+
+        public bool IsWaitNotificationRequired()
+        {
+            return ((_props & SynchronizationContextProperties.RequireWaitNotification) != 0);
+        }
+
+
+        public virtual void Send(SendOrPostCallback d, Object state)
+        {
+            d(state);
+        }
+
+        public virtual void Post(SendOrPostCallback d, Object state)
+        {
+            ThreadPool.QueueUserWorkItem(s => s.d(s.state), (d, state), preferLocal: false);
+        }
+
+
+        /// <summary>
+        ///     Optional override for subclasses, for responding to notification that operation is starting.
+        /// </summary>
+        public virtual void OperationStarted()
+        {
+        }
+
+        /// <summary>
+        ///     Optional override for subclasses, for responding to notification that operation has completed.
+        /// </summary>
+        public virtual void OperationCompleted()
+        {
+        }
+
+        // Method called when the CLR does a wait operation
+        [CLSCompliant(false)]
+        public virtual int Wait(IntPtr[] waitHandles, bool waitAll, int millisecondsTimeout)
+        {
+            return WaitHelper(waitHandles, waitAll, millisecondsTimeout);
+        }
+
+        // Method that can be called by Wait overrides
+        [CLSCompliant(false)]
+        protected static int WaitHelper(IntPtr[] waitHandles, bool waitAll, int millisecondsTimeout)
+        {
+            if (waitHandles == null)
+            {
+                throw new ArgumentNullException(nameof(waitHandles));
+            }
+
+            return WaitHelperNative(waitHandles, waitAll, millisecondsTimeout);
+        }
+
+        // Static helper to which the above method can delegate to in order to get the default
+        // COM behavior.
+        [CLSCompliant(false)]
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int WaitHelperNative(IntPtr[] waitHandles, bool waitAll, int millisecondsTimeout);
+
+        public static void SetSynchronizationContext(SynchronizationContext syncContext)
+        {
+            Thread.CurrentThread.SynchronizationContext = syncContext;
+        }
+
+        public static SynchronizationContext Current
+        {
+            get
+            {
+                SynchronizationContext context = Thread.CurrentThread.SynchronizationContext;
+
+#if FEATURE_APPX
+                if (context == null && AppDomain.IsAppXModel())
+                    context = GetWinRTContext();
+#endif
+
+                return context;
+            }
+        }
+
+#if FEATURE_APPX
+        private static SynchronizationContext GetWinRTContext()
+        {
+            Debug.Assert(Environment.IsWinRTSupported);
+            Debug.Assert(AppDomain.IsAppXModel());
+
+            //
+            // We call into the VM to get the dispatcher.  This is because:
+            //
+            //  a) We cannot call the WinRT APIs directly from mscorlib, because we don't have the fancy projections here.
+            //  b) We cannot call into System.Runtime.WindowsRuntime here, because we don't want to load that assembly
+            //     into processes that don't need it (for performance reasons).
+            //
+            // So, we check the VM to see if the current thread has a dispatcher; if it does, we pass that along to
+            // System.Runtime.WindowsRuntime to get a corresponding SynchronizationContext.
+            //
+            object dispatcher = GetWinRTDispatcherForCurrentThread();
+            if (dispatcher != null)
+                return GetWinRTSynchronizationContextFactory().Create(dispatcher);
+
+            return null;
+        }
+
+        private static WinRTSynchronizationContextFactoryBase s_winRTContextFactory;
+
+        private static WinRTSynchronizationContextFactoryBase GetWinRTSynchronizationContextFactory()
+        {
+            //
+            // Since we can't directly reference System.Runtime.WindowsRuntime from mscorlib, we have to get the factory via reflection.
+            // It would be better if we could just implement WinRTSynchronizationContextFactory in mscorlib, but we can't, because
+            // we can do very little with WinRT stuff in mscorlib.
+            //
+            WinRTSynchronizationContextFactoryBase factory = s_winRTContextFactory;
+            if (factory == null)
+            {
+                Type factoryType = Type.GetType("System.Threading.WinRTSynchronizationContextFactory, System.Runtime.WindowsRuntime", throwOnError: true);
+                s_winRTContextFactory = factory = (WinRTSynchronizationContextFactoryBase)Activator.CreateInstance(factoryType, true);
+            }
+            return factory;
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        [return: MarshalAs(UnmanagedType.Interface)]
+        private static extern object GetWinRTDispatcherForCurrentThread();
+#endif //FEATURE_APPX
+
+
+        // helper to Clone this SynchronizationContext, 
+        public virtual SynchronizationContext CreateCopy()
+        {
+            // the CLR dummy has an empty clone function - no member data
+            return new SynchronizationContext();
+        }
+
+        private static int InvokeWaitMethodHelper(SynchronizationContext syncContext, IntPtr[] waitHandles, bool waitAll, int millisecondsTimeout)
+        {
+            return syncContext.Wait(waitHandles, waitAll, millisecondsTimeout);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Tasks/AsyncCausalityTracer.cs b/src/System.Private.CoreLib/src/System/Threading/Tasks/AsyncCausalityTracer.cs
new file mode 100644
index 0000000000..0e4ed9bd64
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Tasks/AsyncCausalityTracer.cs
@@ -0,0 +1,289 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+//
+
+using System;
+using System.Security;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+#if FEATURE_COMINTEROP
+using System.Runtime.InteropServices.WindowsRuntime;
+
+using WFD = Windows.Foundation.Diagnostics;
+#endif
+
+
+namespace System.Threading.Tasks
+{
+    // [FriendAccessAllowed]
+    internal enum CausalityTraceLevel
+    {
+#if FEATURE_COMINTEROP
+        Required = WFD.CausalityTraceLevel.Required,
+        Important = WFD.CausalityTraceLevel.Important,
+        Verbose = WFD.CausalityTraceLevel.Verbose
+#else
+        Required,
+        Important,
+        Verbose
+#endif
+    }
+
+    // [FriendAccessAllowed]
+    internal enum AsyncCausalityStatus
+    {
+#if FEATURE_COMINTEROP
+        Canceled = WFD.AsyncCausalityStatus.Canceled,
+        Completed = WFD.AsyncCausalityStatus.Completed,
+        Error = WFD.AsyncCausalityStatus.Error,
+        Started = WFD.AsyncCausalityStatus.Started
+#else
+        Started,
+        Completed,
+        Canceled,
+        Error
+#endif
+    }
+
+    internal enum CausalityRelation
+    {
+#if FEATURE_COMINTEROP
+        AssignDelegate = WFD.CausalityRelation.AssignDelegate,
+        Join = WFD.CausalityRelation.Join,
+        Choice = WFD.CausalityRelation.Choice,
+        Cancel = WFD.CausalityRelation.Cancel,
+        Error = WFD.CausalityRelation.Error
+#else
+        AssignDelegate,
+        Join,
+        Choice,
+        Cancel,
+        Error
+#endif
+    }
+
+    internal enum CausalitySynchronousWork
+    {
+#if FEATURE_COMINTEROP
+        CompletionNotification = WFD.CausalitySynchronousWork.CompletionNotification,
+        ProgressNotification = WFD.CausalitySynchronousWork.ProgressNotification,
+        Execution = WFD.CausalitySynchronousWork.Execution
+#else
+        CompletionNotification,
+        ProgressNotification,
+        Execution
+#endif
+    }
+
+    // [FriendAccessAllowed]
+    internal static class AsyncCausalityTracer
+    {
+        internal static void EnableToETW(bool enabled)
+        {
+#if FEATURE_COMINTEROP
+            if (enabled)
+                f_LoggingOn |= Loggers.ETW;
+            else
+                f_LoggingOn &= ~Loggers.ETW;
+#endif
+        }
+
+        internal static bool LoggingOn
+        {
+            // [FriendAccessAllowed]
+            get
+            {
+#if FEATURE_COMINTEROP
+                return f_LoggingOn != 0;
+#else
+                return false;
+#endif
+            }
+        }
+
+#if FEATURE_COMINTEROP
+        //s_PlatformId = {4B0171A6-F3D0-41A0-9B33-02550652B995}
+        private static readonly Guid s_PlatformId = new Guid(0x4B0171A6, 0xF3D0, 0x41A0, 0x9B, 0x33, 0x02, 0x55, 0x06, 0x52, 0xB9, 0x95);
+
+        //Indicates this information comes from the BCL Library
+        private const WFD.CausalitySource s_CausalitySource = WFD.CausalitySource.Library;
+
+        //Lazy initialize the actual factory
+        private static WFD.IAsyncCausalityTracerStatics s_TracerFactory;
+
+        // The loggers that this Tracer knows about. 
+        [Flags]
+        private enum Loggers : byte
+        {
+            CausalityTracer = 1,
+            ETW = 2
+        }
+
+
+        //We receive the actual value for these as a callback
+        private static Loggers f_LoggingOn; //assumes false by default
+
+        // The precise static constructor will run first time somebody attempts to access this class
+        static AsyncCausalityTracer()
+        {
+            if (!Environment.IsWinRTSupported) return;
+
+            //COM Class Id
+            string ClassId = "Windows.Foundation.Diagnostics.AsyncCausalityTracer";
+
+            //COM Interface GUID  {50850B26-267E-451B-A890-AB6A370245EE}
+            Guid guid = new Guid(0x50850B26, 0x267E, 0x451B, 0xA8, 0x90, 0XAB, 0x6A, 0x37, 0x02, 0x45, 0xEE);
+
+            Object factory = null;
+
+            try
+            {
+                int hresult = Microsoft.Win32.UnsafeNativeMethods.RoGetActivationFactory(ClassId, ref guid, out factory);
+
+                if (hresult < 0 || factory == null) return; //This prevents having an exception thrown in case IAsyncCausalityTracerStatics isn't registered.
+
+                s_TracerFactory = (WFD.IAsyncCausalityTracerStatics)factory;
+
+                EventRegistrationToken token = s_TracerFactory.add_TracingStatusChanged(new EventHandler<WFD.TracingStatusChangedEventArgs>(TracingStatusChangedHandler));
+                Debug.Assert(token != default(EventRegistrationToken), "EventRegistrationToken is null");
+            }
+            catch (Exception ex)
+            {
+                // Although catching generic Exception is not recommended, this file is one exception
+                // since we don't want to propagate any kind of exception to the user since all we are
+                // doing here depends on internal state.
+                LogAndDisable(ex);
+            }
+        }
+
+        private static void TracingStatusChangedHandler(Object sender, WFD.TracingStatusChangedEventArgs args)
+        {
+            if (args.Enabled)
+                f_LoggingOn |= Loggers.CausalityTracer;
+            else
+                f_LoggingOn &= ~Loggers.CausalityTracer;
+        }
+#endif
+
+        //
+        // The TraceXXX methods should be called only if LoggingOn property returned true
+        //
+
+        // [FriendAccessAllowed]
+        [MethodImplAttribute(MethodImplOptions.NoInlining)] // Tracking is slow path. Disable inlining for it.
+        internal static void TraceOperationCreation(CausalityTraceLevel traceLevel, int taskId, string operationName, ulong relatedContext)
+        {
+#if FEATURE_COMINTEROP
+            try
+            {
+                if ((f_LoggingOn & Loggers.ETW) != 0)
+                    TplEtwProvider.Log.TraceOperationBegin(taskId, operationName, (long)relatedContext);
+                if ((f_LoggingOn & Loggers.CausalityTracer) != 0)
+                    s_TracerFactory.TraceOperationCreation((WFD.CausalityTraceLevel)traceLevel, s_CausalitySource, s_PlatformId, GetOperationId((uint)taskId), operationName, relatedContext);
+            }
+            catch (Exception ex)
+            {
+                //view function comment
+                LogAndDisable(ex);
+            }
+#endif
+        }
+
+        // [FriendAccessAllowed]
+        [MethodImplAttribute(MethodImplOptions.NoInlining)]
+        internal static void TraceOperationCompletion(CausalityTraceLevel traceLevel, int taskId, AsyncCausalityStatus status)
+        {
+#if FEATURE_COMINTEROP
+            try
+            {
+                if ((f_LoggingOn & Loggers.ETW) != 0)
+                    TplEtwProvider.Log.TraceOperationEnd(taskId, status);
+                if ((f_LoggingOn & Loggers.CausalityTracer) != 0)
+                    s_TracerFactory.TraceOperationCompletion((WFD.CausalityTraceLevel)traceLevel, s_CausalitySource, s_PlatformId, GetOperationId((uint)taskId), (WFD.AsyncCausalityStatus)status);
+            }
+            catch (Exception ex)
+            {
+                //view function comment
+                LogAndDisable(ex);
+            }
+#endif
+        }
+
+        [MethodImplAttribute(MethodImplOptions.NoInlining)]
+        internal static void TraceOperationRelation(CausalityTraceLevel traceLevel, int taskId, CausalityRelation relation)
+        {
+#if FEATURE_COMINTEROP
+            try
+            {
+                if ((f_LoggingOn & Loggers.ETW) != 0)
+                    TplEtwProvider.Log.TraceOperationRelation(taskId, relation);
+                if ((f_LoggingOn & Loggers.CausalityTracer) != 0)
+                    s_TracerFactory.TraceOperationRelation((WFD.CausalityTraceLevel)traceLevel, s_CausalitySource, s_PlatformId, GetOperationId((uint)taskId), (WFD.CausalityRelation)relation);
+            }
+            catch (Exception ex)
+            {
+                //view function comment
+                LogAndDisable(ex);
+            }
+#endif
+        }
+
+        [MethodImplAttribute(MethodImplOptions.NoInlining)]
+        internal static void TraceSynchronousWorkStart(CausalityTraceLevel traceLevel, int taskId, CausalitySynchronousWork work)
+        {
+#if FEATURE_COMINTEROP
+            try
+            {
+                if ((f_LoggingOn & Loggers.ETW) != 0)
+                    TplEtwProvider.Log.TraceSynchronousWorkBegin(taskId, work);
+                if ((f_LoggingOn & Loggers.CausalityTracer) != 0)
+                    s_TracerFactory.TraceSynchronousWorkStart((WFD.CausalityTraceLevel)traceLevel, s_CausalitySource, s_PlatformId, GetOperationId((uint)taskId), (WFD.CausalitySynchronousWork)work);
+            }
+            catch (Exception ex)
+            {
+                //view function comment
+                LogAndDisable(ex);
+            }
+#endif
+        }
+
+        [MethodImplAttribute(MethodImplOptions.NoInlining)]
+        internal static void TraceSynchronousWorkCompletion(CausalityTraceLevel traceLevel, CausalitySynchronousWork work)
+        {
+#if FEATURE_COMINTEROP
+            try
+            {
+                if ((f_LoggingOn & Loggers.ETW) != 0)
+                    TplEtwProvider.Log.TraceSynchronousWorkEnd(work);
+                if ((f_LoggingOn & Loggers.CausalityTracer) != 0)
+                    s_TracerFactory.TraceSynchronousWorkCompletion((WFD.CausalityTraceLevel)traceLevel, s_CausalitySource, (WFD.CausalitySynchronousWork)work);
+            }
+            catch (Exception ex)
+            {
+                //view function comment
+                LogAndDisable(ex);
+            }
+#endif
+        }
+
+#if FEATURE_COMINTEROP
+        //fix for 796185: leaking internal exceptions to customers,
+        //we should catch and log exceptions but never propagate them.
+        private static void LogAndDisable(Exception ex)
+        {
+            f_LoggingOn = 0;
+            Debugger.Log(0, "AsyncCausalityTracer", ex.ToString());
+        }
+#endif
+
+        private static ulong GetOperationId(uint taskId)
+        {
+            return (((ulong)AppDomain.CurrentDomain.Id) << 32) + taskId;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Tasks/FutureFactory.cs b/src/System.Private.CoreLib/src/System/Threading/Tasks/FutureFactory.cs
new file mode 100644
index 0000000000..4615d43826
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Tasks/FutureFactory.cs
@@ -0,0 +1,2158 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// As with TaskFactory, TaskFactory<TResult> encodes common factory patterns into helper methods.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System;
+using System.Security;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using System.Diagnostics;
+using System.Runtime.Versioning;
+
+namespace System.Threading.Tasks
+{
+    /// <summary>
+    /// Provides support for creating and scheduling
+    /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task{TResult}</see> objects.
+    /// </summary>
+    /// <typeparam name="TResult">The type of the results that are available though 
+    /// the <see cref="T:System.Threading.Tasks.Task{TResult}">Task{TResult}</see> objects that are associated with 
+    /// the methods in this class.</typeparam>
+    /// <remarks>
+    /// <para>
+    /// There are many common patterns for which tasks are relevant. The <see cref="TaskFactory{TResult}"/>
+    /// class encodes some of these patterns into methods that pick up default settings, which are
+    /// configurable through its constructors.
+    /// </para>
+    /// <para>
+    /// A default instance of <see cref="TaskFactory{TResult}"/> is available through the
+    /// <see cref="System.Threading.Tasks.Task{TResult}.Factory">Task{TResult}.Factory</see> property.
+    /// </para>
+    /// </remarks>
+    public class TaskFactory<TResult>
+    {
+        // Member variables, DefaultScheduler, other properties and ctors 
+        // copied right out of TaskFactory...  Lots of duplication here...
+        // Should we be thinking about a TaskFactoryBase class?
+
+        // member variables
+        private CancellationToken m_defaultCancellationToken;
+        private TaskScheduler m_defaultScheduler;
+        private TaskCreationOptions m_defaultCreationOptions;
+        private TaskContinuationOptions m_defaultContinuationOptions;
+
+        private TaskScheduler DefaultScheduler
+        {
+            get
+            {
+                if (m_defaultScheduler == null) return TaskScheduler.Current;
+                else return m_defaultScheduler;
+            }
+        }
+
+        // sister method to above property -- avoids a TLS lookup
+        private TaskScheduler GetDefaultScheduler(Task currTask)
+        {
+            if (m_defaultScheduler != null) return m_defaultScheduler;
+            else if ((currTask != null)
+                && ((currTask.CreationOptions & TaskCreationOptions.HideScheduler) == 0)
+                )
+                return currTask.ExecutingTaskScheduler;
+            else return TaskScheduler.Default;
+        }
+
+        /* Constructors */
+
+        /// <summary>
+        /// Initializes a <see cref="TaskFactory{TResult}"/> instance with the default configuration.
+        /// </summary>
+        /// <remarks>
+        /// This constructor creates a <see cref="TaskFactory{TResult}"/> instance with a default configuration. The
+        /// <see cref="TaskCreationOptions"/> property is initialized to
+        /// <see cref="System.Threading.Tasks.TaskCreationOptions.None">TaskCreationOptions.None</see>, the
+        /// <see cref="TaskContinuationOptions"/> property is initialized to <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.None">TaskContinuationOptions.None</see>,
+        /// and the <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> property is
+        /// initialized to the current scheduler (see <see
+        /// cref="System.Threading.Tasks.TaskScheduler.Current">TaskScheduler.Current</see>).
+        /// </remarks>
+        public TaskFactory()
+            : this(default(CancellationToken), TaskCreationOptions.None, TaskContinuationOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a <see cref="TaskFactory{TResult}"/> instance with the default configuration.
+        /// </summary>
+        /// <param name="cancellationToken">The default <see cref="CancellationToken"/> that will be assigned 
+        /// to tasks created by this <see cref="TaskFactory"/> unless another CancellationToken is explicitly specified 
+        /// while calling the factory methods.</param>
+        /// <remarks>
+        /// This constructor creates a <see cref="TaskFactory{TResult}"/> instance with a default configuration. The
+        /// <see cref="TaskCreationOptions"/> property is initialized to
+        /// <see cref="System.Threading.Tasks.TaskCreationOptions.None">TaskCreationOptions.None</see>, the
+        /// <see cref="TaskContinuationOptions"/> property is initialized to <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.None">TaskContinuationOptions.None</see>,
+        /// and the <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> property is
+        /// initialized to the current scheduler (see <see
+        /// cref="System.Threading.Tasks.TaskScheduler.Current">TaskScheduler.Current</see>).
+        /// </remarks>
+        public TaskFactory(CancellationToken cancellationToken)
+            : this(cancellationToken, TaskCreationOptions.None, TaskContinuationOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a <see cref="TaskFactory{TResult}"/> instance with the specified configuration.
+        /// </summary>
+        /// <param name="scheduler">
+        /// The <see cref="System.Threading.Tasks.TaskScheduler">
+        /// TaskScheduler</see> to use to schedule any tasks created with this TaskFactory{TResult}. A null value
+        /// indicates that the current TaskScheduler should be used.
+        /// </param>
+        /// <remarks>
+        /// With this constructor, the
+        /// <see cref="TaskCreationOptions"/> property is initialized to
+        /// <see cref="System.Threading.Tasks.TaskCreationOptions.None">TaskCreationOptions.None</see>, the
+        /// <see cref="TaskContinuationOptions"/> property is initialized to <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.None">TaskContinuationOptions.None</see>,
+        /// and the <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> property is
+        /// initialized to <paramref name="scheduler"/>, unless it's null, in which case the property is
+        /// initialized to the current scheduler (see <see
+        /// cref="System.Threading.Tasks.TaskScheduler.Current">TaskScheduler.Current</see>).
+        /// </remarks>
+        public TaskFactory(TaskScheduler scheduler) // null means to use TaskScheduler.Current
+            : this(default(CancellationToken), TaskCreationOptions.None, TaskContinuationOptions.None, scheduler)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a <see cref="TaskFactory{TResult}"/> instance with the specified configuration.
+        /// </summary>
+        /// <param name="creationOptions">
+        /// The default <see cref="System.Threading.Tasks.TaskCreationOptions">
+        /// TaskCreationOptions</see> to use when creating tasks with this TaskFactory{TResult}.
+        /// </param>
+        /// <param name="continuationOptions">
+        /// The default <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> to use when creating continuation tasks with this TaskFactory{TResult}.
+        /// </param>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument or the <paramref name="continuationOptions"/>
+        /// argument specifies an invalid value.
+        /// </exception>
+        /// <remarks>
+        /// With this constructor, the
+        /// <see cref="TaskCreationOptions"/> property is initialized to <paramref name="creationOptions"/>,
+        /// the
+        /// <see cref="TaskContinuationOptions"/> property is initialized to <paramref
+        /// name="continuationOptions"/>, and the <see
+        /// cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> property is initialized to the
+        /// current scheduler (see <see
+        /// cref="System.Threading.Tasks.TaskScheduler.Current">TaskScheduler.Current</see>).
+        /// </remarks>
+        public TaskFactory(TaskCreationOptions creationOptions, TaskContinuationOptions continuationOptions)
+            : this(default(CancellationToken), creationOptions, continuationOptions, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a <see cref="TaskFactory{TResult}"/> instance with the specified configuration.
+        /// </summary>
+        /// <param name="cancellationToken">The default <see cref="CancellationToken"/> that will be assigned 
+        /// to tasks created by this <see cref="TaskFactory"/> unless another CancellationToken is explicitly specified 
+        /// while calling the factory methods.</param>
+        /// <param name="creationOptions">
+        /// The default <see cref="System.Threading.Tasks.TaskCreationOptions">
+        /// TaskCreationOptions</see> to use when creating tasks with this TaskFactory{TResult}.
+        /// </param>
+        /// <param name="continuationOptions">
+        /// The default <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> to use when creating continuation tasks with this TaskFactory{TResult}.
+        /// </param>
+        /// <param name="scheduler">
+        /// The default <see cref="System.Threading.Tasks.TaskScheduler">
+        /// TaskScheduler</see> to use to schedule any Tasks created with this TaskFactory{TResult}. A null value
+        /// indicates that TaskScheduler.Current should be used.
+        /// </param>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument or the <paramref name="continuationOptions"/>
+        /// argumentspecifies an invalid value.
+        /// </exception>
+        /// <remarks>
+        /// With this constructor, the
+        /// <see cref="TaskCreationOptions"/> property is initialized to <paramref name="creationOptions"/>,
+        /// the
+        /// <see cref="TaskContinuationOptions"/> property is initialized to <paramref
+        /// name="continuationOptions"/>, and the <see
+        /// cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> property is initialized to
+        /// <paramref name="scheduler"/>, unless it's null, in which case the property is initialized to the
+        /// current scheduler (see <see
+        /// cref="System.Threading.Tasks.TaskScheduler.Current">TaskScheduler.Current</see>).
+        /// </remarks>
+        public TaskFactory(CancellationToken cancellationToken, TaskCreationOptions creationOptions, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            TaskFactory.CheckMultiTaskContinuationOptions(continuationOptions);
+            TaskFactory.CheckCreationOptions(creationOptions);
+
+            m_defaultCancellationToken = cancellationToken;
+            m_defaultScheduler = scheduler;
+            m_defaultCreationOptions = creationOptions;
+            m_defaultContinuationOptions = continuationOptions;
+        }
+
+        /* Properties */
+
+        /// <summary>
+        /// Gets the default <see cref="System.Threading.CancellationToken">CancellationToken</see> of this
+        /// TaskFactory.
+        /// </summary>
+        /// <remarks>
+        /// This property returns the default <see cref="CancellationToken"/> that will be assigned to all 
+        /// tasks created by this factory unless another CancellationToken value is explicitly specified 
+        /// during the call to the factory methods.
+        /// </remarks>
+        public CancellationToken CancellationToken { get { return m_defaultCancellationToken; } }
+
+        /// <summary>
+        /// Gets the <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> of this
+        /// TaskFactory{TResult}.
+        /// </summary>
+        /// <remarks>
+        /// This property returns the default scheduler for this factory.  It will be used to schedule all 
+        /// tasks unless another scheduler is explicitly specified during calls to this factory's methods.  
+        /// If null, <see cref="System.Threading.Tasks.TaskScheduler.Current">TaskScheduler.Current</see> 
+        /// will be used.
+        /// </remarks>
+        public TaskScheduler Scheduler { get { return m_defaultScheduler; } }
+
+        /// <summary>
+        /// Gets the <see cref="System.Threading.Tasks.TaskCreationOptions">TaskCreationOptions
+        /// </see> value of this TaskFactory{TResult}.
+        /// </summary>
+        /// <remarks>
+        /// This property returns the default creation options for this factory.  They will be used to create all 
+        /// tasks unless other options are explicitly specified during calls to this factory's methods.
+        /// </remarks>
+        public TaskCreationOptions CreationOptions { get { return m_defaultCreationOptions; } }
+
+        /// <summary>
+        /// Gets the <see cref="System.Threading.Tasks.TaskCreationOptions">TaskContinuationOptions
+        /// </see> value of this TaskFactory{TResult}.
+        /// </summary>
+        /// <remarks>
+        /// This property returns the default continuation options for this factory.  They will be used to create 
+        /// all continuation tasks unless other options are explicitly specified during calls to this factory's methods.
+        /// </remarks>
+        public TaskContinuationOptions ContinuationOptions { get { return m_defaultContinuationOptions; } }
+
+
+        /* StartNew */
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew(Func<TResult> function)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task<TResult>.StartNew(currTask, function, m_defaultCancellationToken,
+                m_defaultCreationOptions, InternalTaskOptions.None, GetDefaultScheduler(currTask));
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew(Func<TResult> function, CancellationToken cancellationToken)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task<TResult>.StartNew(currTask, function, cancellationToken,
+                m_defaultCreationOptions, InternalTaskOptions.None, GetDefaultScheduler(currTask));
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="creationOptions">A TaskCreationOptions value that controls the behavior of the
+        /// created
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew(Func<TResult> function, TaskCreationOptions creationOptions)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task<TResult>.StartNew(currTask, function, m_defaultCancellationToken,
+                creationOptions, InternalTaskOptions.None, GetDefaultScheduler(currTask));
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="creationOptions">A TaskCreationOptions value that controls the behavior of the
+        /// created
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <param name="scheduler">The <see
+        /// cref="T:System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created <see cref="T:System.Threading.Tasks.Task{TResult}">
+        /// Task{TResult}</see>.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="scheduler"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew(Func<TResult> function, CancellationToken cancellationToken, TaskCreationOptions creationOptions, TaskScheduler scheduler)
+        {
+            return Task<TResult>.StartNew(
+                Task.InternalCurrentIfAttached(creationOptions), function, cancellationToken,
+                creationOptions, InternalTaskOptions.None, scheduler);
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="function"/>
+        /// delegate.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew(Func<Object, TResult> function, Object state)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task<TResult>.StartNew(currTask, function, state, m_defaultCancellationToken,
+                m_defaultCreationOptions, InternalTaskOptions.None, GetDefaultScheduler(currTask));
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="function"/>
+        /// delegate.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew(Func<Object, TResult> function, Object state, CancellationToken cancellationToken)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task<TResult>.StartNew(currTask, function, state, cancellationToken,
+                m_defaultCreationOptions, InternalTaskOptions.None, GetDefaultScheduler(currTask));
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="function"/>
+        /// delegate.</param>
+        /// <param name="creationOptions">A TaskCreationOptions value that controls the behavior of the
+        /// created
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew(Func<Object, TResult> function, Object state, TaskCreationOptions creationOptions)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task<TResult>.StartNew(currTask, function, state, m_defaultCancellationToken,
+                creationOptions, InternalTaskOptions.None, GetDefaultScheduler(currTask));
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="function"/>
+        /// delegate.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <param name="creationOptions">A TaskCreationOptions value that controls the behavior of the
+        /// created
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="scheduler">The <see
+        /// cref="T:System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created <see cref="T:System.Threading.Tasks.Task{TResult}">
+        /// Task{TResult}</see>.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="scheduler"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew(Func<Object, TResult> function, Object state, CancellationToken cancellationToken, TaskCreationOptions creationOptions, TaskScheduler scheduler)
+        {
+            return Task<TResult>.StartNew(Task.InternalCurrentIfAttached(creationOptions), function, state, cancellationToken,
+                creationOptions, InternalTaskOptions.None, scheduler);
+        }
+
+        //
+        // APM Factory methods
+        //
+
+        // Common core logic for FromAsync calls.  This minimizes the chance of "drift" between overload implementations.
+        private static void FromAsyncCoreLogic(
+            IAsyncResult iar,
+            Func<IAsyncResult, TResult> endFunction,
+            Action<IAsyncResult> endAction,
+            Task<TResult> promise,
+            bool requiresSynchronization)
+        {
+            Debug.Assert((endFunction != null) != (endAction != null), "Expected exactly one of endFunction/endAction to be non-null");
+
+            Exception ex = null;
+            OperationCanceledException oce = null;
+            TResult result = default(TResult);
+
+            try
+            {
+                if (endFunction != null)
+                {
+                    result = endFunction(iar);
+                }
+                else
+                {
+                    endAction(iar);
+                }
+            }
+            catch (OperationCanceledException _oce) { oce = _oce; }
+            catch (Exception e) { ex = e; }
+            finally
+            {
+                if (oce != null)
+                {
+                    promise.TrySetCanceled(oce.CancellationToken, oce);
+                }
+                else if (ex != null)
+                {
+                    bool bWonSetException = promise.TrySetException(ex);
+                    if (bWonSetException && ex is ThreadAbortException)
+                    {
+                        promise.m_contingentProperties.m_exceptionsHolder.MarkAsHandled(false);
+                    }
+                }
+                else
+                {
+                    if (AsyncCausalityTracer.LoggingOn)
+                        AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, promise.Id, AsyncCausalityStatus.Completed);
+
+                    if (Task.s_asyncDebuggingEnabled)
+                    {
+                        Task.RemoveFromActiveTasks(promise.Id);
+                    }
+                    if (requiresSynchronization)
+                    {
+                        promise.TrySetResult(result);
+                    }
+                    else
+                    {
+                        promise.DangerousSetResult(result);
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that executes an end
+        /// method function when a specified <see cref="T:System.IAsyncResult">IAsyncResult</see> completes.
+        /// </summary>
+        /// <param name="asyncResult">The IAsyncResult whose completion should trigger the processing of the
+        /// <paramref name="endMethod"/>.</param>
+        /// <param name="endMethod">The function delegate that processes the completed <paramref
+        /// name="asyncResult"/>.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="asyncResult"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>A <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents the
+        /// asynchronous operation.</returns>
+        public Task<TResult> FromAsync(IAsyncResult asyncResult, Func<IAsyncResult, TResult> endMethod)
+        {
+            return FromAsyncImpl(asyncResult, endMethod, null, m_defaultCreationOptions, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that executes an end
+        /// method function when a specified <see cref="T:System.IAsyncResult">IAsyncResult</see> completes.
+        /// </summary>
+        /// <param name="asyncResult">The IAsyncResult whose completion should trigger the processing of the
+        /// <paramref name="endMethod"/>.</param>
+        /// <param name="endMethod">The function delegate that processes the completed <paramref
+        /// name="asyncResult"/>.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="asyncResult"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>A <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents the
+        /// asynchronous operation.</returns>
+        public Task<TResult> FromAsync(
+            IAsyncResult asyncResult,
+            Func<IAsyncResult, TResult> endMethod,
+            TaskCreationOptions creationOptions)
+        {
+            return FromAsyncImpl(asyncResult, endMethod, null, creationOptions, DefaultScheduler);
+        }
+
+
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that executes an end
+        /// method function when a specified <see cref="T:System.IAsyncResult">IAsyncResult</see> completes.
+        /// </summary>
+        /// <param name="asyncResult">The IAsyncResult whose completion should trigger the processing of the
+        /// <paramref name="endMethod"/>.</param>
+        /// <param name="endMethod">The function delegate that processes the completed <paramref
+        /// name="asyncResult"/>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the task that executes the end method.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="asyncResult"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>A <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents the
+        /// asynchronous operation.</returns>
+        public Task<TResult> FromAsync(
+            IAsyncResult asyncResult,
+            Func<IAsyncResult, TResult> endMethod,
+            TaskCreationOptions creationOptions,
+            TaskScheduler scheduler)
+        {
+            return FromAsyncImpl(asyncResult, endMethod, null, creationOptions, scheduler);
+        }
+
+        // We need this logic broken out into a static method so that the similar TaskFactory.FromAsync()
+        // method can access the logic w/o declaring a TaskFactory<TResult> instance.
+        internal static Task<TResult> FromAsyncImpl(
+            IAsyncResult asyncResult,
+            Func<IAsyncResult, TResult> endFunction,
+            Action<IAsyncResult> endAction,
+            TaskCreationOptions creationOptions,
+            TaskScheduler scheduler)
+        {
+            if (asyncResult == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.asyncResult);
+
+            if (endFunction == null && endAction == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.endMethod);
+
+            Debug.Assert((endFunction != null) != (endAction != null), "Both endFunction and endAction were non-null");
+
+            if (scheduler == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+
+            TaskFactory.CheckFromAsyncOptions(creationOptions, false);
+
+            Task<TResult> promise = new Task<TResult>((object)null, creationOptions);
+
+            if (AsyncCausalityTracer.LoggingOn)
+                AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, promise.Id, "TaskFactory.FromAsync", 0);
+
+            if (Task.s_asyncDebuggingEnabled)
+            {
+                Task.AddToActiveTasks(promise);
+            }
+
+            // Just specify this task as detached. No matter what happens, we want endMethod 
+            // to be called -- even if the parent is canceled.  So we don't want to flow 
+            // RespectParentCancellation.
+            Task t = new Task(new Action<object>(delegate
+            {
+                FromAsyncCoreLogic(asyncResult, endFunction, endAction, promise, requiresSynchronization: true);
+            }),
+                (object)null, null,
+                default(CancellationToken), TaskCreationOptions.None, InternalTaskOptions.None, null);
+
+            if (AsyncCausalityTracer.LoggingOn)
+                AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Verbose, t.Id, "TaskFactory.FromAsync Callback", 0);
+
+            if (Task.s_asyncDebuggingEnabled)
+            {
+                Task.AddToActiveTasks(t);
+            }
+
+            if (asyncResult.IsCompleted)
+            {
+                try { t.InternalRunSynchronously(scheduler, waitForCompletion: false); }
+                catch (Exception e) { promise.TrySetException(e); } // catch and log any scheduler exceptions
+            }
+            else
+            {
+                ThreadPool.RegisterWaitForSingleObject(
+                    asyncResult.AsyncWaitHandle,
+                    delegate
+                    {
+                        try { t.InternalRunSynchronously(scheduler, waitForCompletion: false); }
+                        catch (Exception e) { promise.TrySetException(e); } // catch and log any scheduler exceptions
+                    },
+                    null,
+                    Timeout.Infinite,
+                    true);
+            }
+
+            return promise;
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync(
+            Func<AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod, object state)
+        {
+            return FromAsyncImpl(beginMethod, endMethod, null, state, m_defaultCreationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync(
+            Func<AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod, object state, TaskCreationOptions creationOptions)
+        {
+            return FromAsyncImpl(beginMethod, endMethod, null, state, creationOptions);
+        }
+
+        // We need this logic broken out into a static method so that the similar TaskFactory.FromAsync()
+        // method can access the logic w/o declaring a TaskFactory<TResult> instance.
+        internal static Task<TResult> FromAsyncImpl(Func<AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endFunction, Action<IAsyncResult> endAction,
+            object state, TaskCreationOptions creationOptions)
+        {
+            if (beginMethod == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.beginMethod);
+
+            if (endFunction == null && endAction == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.endMethod);
+
+            Debug.Assert((endFunction != null) != (endAction != null), "Both endFunction and endAction were non-null");
+
+            TaskFactory.CheckFromAsyncOptions(creationOptions, true);
+
+            Task<TResult> promise = new Task<TResult>(state, creationOptions);
+
+            if (AsyncCausalityTracer.LoggingOn)
+                AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, promise.Id, "TaskFactory.FromAsync: " + beginMethod.Method.Name, 0);
+
+            if (Task.s_asyncDebuggingEnabled)
+            {
+                Task.AddToActiveTasks(promise);
+            }
+
+            try
+            {
+                //This is 4.5 behaviour
+                //if we don't require synchronization, a faster set result path is taken
+                var asyncResult = beginMethod(iar =>
+                {
+                    if (!iar.CompletedSynchronously)
+                        FromAsyncCoreLogic(iar, endFunction, endAction, promise, requiresSynchronization: true);
+                }, state);
+                if (asyncResult.CompletedSynchronously)
+                {
+                    Debug.Assert(asyncResult.IsCompleted, "If the operation completed synchronously, it must be completed.");
+                    FromAsyncCoreLogic(asyncResult, endFunction, endAction, promise, requiresSynchronization: false);
+                }
+            }
+            catch
+            {
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, promise.Id, AsyncCausalityStatus.Error);
+
+                if (Task.s_asyncDebuggingEnabled)
+                {
+                    Task.RemoveFromActiveTasks(promise.Id);
+                }
+
+                // Make sure we don't leave promise "dangling".
+                promise.TrySetResult(default(TResult));
+                throw;
+            }
+
+            return promise;
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/> delegate.</typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync<TArg1>(
+            Func<TArg1, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod,
+            TArg1 arg1, object state)
+        {
+            return FromAsyncImpl(beginMethod, endMethod, null, arg1, state, m_defaultCreationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/> delegate.</typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync<TArg1>(
+            Func<TArg1, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod,
+            TArg1 arg1, object state, TaskCreationOptions creationOptions)
+        {
+            return FromAsyncImpl(beginMethod, endMethod, null, arg1, state, creationOptions);
+        }
+
+        // We need this logic broken out into a static method so that the similar TaskFactory.FromAsync()
+        // method can access the logic w/o declaring a TaskFactory<TResult> instance.
+        internal static Task<TResult> FromAsyncImpl<TArg1>(Func<TArg1, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endFunction, Action<IAsyncResult> endAction,
+            TArg1 arg1, object state, TaskCreationOptions creationOptions)
+        {
+            if (beginMethod == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.beginMethod);
+
+            if (endFunction == null && endAction == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.endFunction);
+
+            Debug.Assert((endFunction != null) != (endAction != null), "Both endFunction and endAction were non-null");
+
+            TaskFactory.CheckFromAsyncOptions(creationOptions, true);
+
+            Task<TResult> promise = new Task<TResult>(state, creationOptions);
+
+            if (AsyncCausalityTracer.LoggingOn)
+                AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, promise.Id, "TaskFactory.FromAsync: " + beginMethod.Method.Name, 0);
+
+            if (Task.s_asyncDebuggingEnabled)
+            {
+                Task.AddToActiveTasks(promise);
+            }
+
+            try
+            {
+                //if we don't require synchronization, a faster set result path is taken
+                var asyncResult = beginMethod(arg1, iar =>
+                {
+                    if (!iar.CompletedSynchronously)
+                        FromAsyncCoreLogic(iar, endFunction, endAction, promise, requiresSynchronization: true);
+                }, state);
+                if (asyncResult.CompletedSynchronously)
+                {
+                    Debug.Assert(asyncResult.IsCompleted, "If the operation completed synchronously, it must be completed.");
+                    FromAsyncCoreLogic(asyncResult, endFunction, endAction, promise, requiresSynchronization: false);
+                }
+            }
+            catch
+            {
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, promise.Id, AsyncCausalityStatus.Error);
+
+                if (Task.s_asyncDebuggingEnabled)
+                {
+                    Task.RemoveFromActiveTasks(promise.Id);
+                }
+
+                // Make sure we don't leave promise "dangling".
+                promise.TrySetResult(default(TResult));
+                throw;
+            }
+
+            return promise;
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/> delegate.</typeparam>
+        /// <typeparam name="TArg2">The type of the second argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg2">The second argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync<TArg1, TArg2>(
+            Func<TArg1, TArg2, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod,
+            TArg1 arg1, TArg2 arg2, object state)
+        {
+            return FromAsyncImpl(beginMethod, endMethod, null, arg1, arg2, state, m_defaultCreationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/> delegate.</typeparam>
+        /// <typeparam name="TArg2">The type of the second argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg2">The second argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync<TArg1, TArg2>(
+            Func<TArg1, TArg2, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod,
+            TArg1 arg1, TArg2 arg2, object state, TaskCreationOptions creationOptions)
+        {
+            return FromAsyncImpl(beginMethod, endMethod, null, arg1, arg2, state, creationOptions);
+        }
+
+        // We need this logic broken out into a static method so that the similar TaskFactory.FromAsync()
+        // method can access the logic w/o declaring a TaskFactory<TResult> instance.
+        internal static Task<TResult> FromAsyncImpl<TArg1, TArg2>(Func<TArg1, TArg2, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endFunction, Action<IAsyncResult> endAction,
+            TArg1 arg1, TArg2 arg2, object state, TaskCreationOptions creationOptions)
+        {
+            if (beginMethod == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.beginMethod);
+
+            if (endFunction == null && endAction == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.endMethod);
+
+            Debug.Assert((endFunction != null) != (endAction != null), "Both endFunction and endAction were non-null");
+
+            TaskFactory.CheckFromAsyncOptions(creationOptions, true);
+
+            Task<TResult> promise = new Task<TResult>(state, creationOptions);
+
+            if (AsyncCausalityTracer.LoggingOn)
+                AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, promise.Id, "TaskFactory.FromAsync: " + beginMethod.Method.Name, 0);
+
+            if (Task.s_asyncDebuggingEnabled)
+            {
+                Task.AddToActiveTasks(promise);
+            }
+
+            try
+            {
+                //if we don't require synchronization, a faster set result path is taken
+                var asyncResult = beginMethod(arg1, arg2, iar =>
+                {
+                    if (!iar.CompletedSynchronously)
+                        FromAsyncCoreLogic(iar, endFunction, endAction, promise, requiresSynchronization: true);
+                }, state);
+                if (asyncResult.CompletedSynchronously)
+                {
+                    Debug.Assert(asyncResult.IsCompleted, "If the operation completed synchronously, it must be completed.");
+                    FromAsyncCoreLogic(asyncResult, endFunction, endAction, promise, requiresSynchronization: false);
+                }
+            }
+            catch
+            {
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, promise.Id, AsyncCausalityStatus.Error);
+
+                if (Task.s_asyncDebuggingEnabled)
+                {
+                    Task.RemoveFromActiveTasks(promise.Id);
+                }
+
+                // Make sure we don't leave promise "dangling".
+                promise.TrySetResult(default(TResult));
+                throw;
+            }
+
+            return promise;
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/> delegate.</typeparam>
+        /// <typeparam name="TArg2">The type of the second argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <typeparam name="TArg3">The type of the third argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg2">The second argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg3">The third argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync<TArg1, TArg2, TArg3>(
+            Func<TArg1, TArg2, TArg3, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod,
+            TArg1 arg1, TArg2 arg2, TArg3 arg3, object state)
+        {
+            return FromAsyncImpl(beginMethod, endMethod, null, arg1, arg2, arg3, state, m_defaultCreationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/> delegate.</typeparam>
+        /// <typeparam name="TArg2">The type of the second argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <typeparam name="TArg3">The type of the third argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg2">The second argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg3">The third argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync<TArg1, TArg2, TArg3>(
+            Func<TArg1, TArg2, TArg3, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod,
+            TArg1 arg1, TArg2 arg2, TArg3 arg3, object state, TaskCreationOptions creationOptions)
+        {
+            return FromAsyncImpl(beginMethod, endMethod, null, arg1, arg2, arg3, state, creationOptions);
+        }
+
+        // We need this logic broken out into a static method so that the similar TaskFactory.FromAsync()
+        // method can access the logic w/o declaring a TaskFactory<TResult> instance.
+        internal static Task<TResult> FromAsyncImpl<TArg1, TArg2, TArg3>(Func<TArg1, TArg2, TArg3, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endFunction, Action<IAsyncResult> endAction,
+            TArg1 arg1, TArg2 arg2, TArg3 arg3, object state, TaskCreationOptions creationOptions)
+        {
+            if (beginMethod == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.beginMethod);
+
+            if (endFunction == null && endAction == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.endMethod);
+
+            Debug.Assert((endFunction != null) != (endAction != null), "Both endFunction and endAction were non-null");
+
+            TaskFactory.CheckFromAsyncOptions(creationOptions, true);
+
+            Task<TResult> promise = new Task<TResult>(state, creationOptions);
+
+            if (AsyncCausalityTracer.LoggingOn)
+                AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, promise.Id, "TaskFactory.FromAsync: " + beginMethod.Method.Name, 0);
+
+            if (Task.s_asyncDebuggingEnabled)
+            {
+                Task.AddToActiveTasks(promise);
+            }
+
+            try
+            {
+                //if we don't require synchronization, a faster set result path is taken
+                var asyncResult = beginMethod(arg1, arg2, arg3, iar =>
+                {
+                    if (!iar.CompletedSynchronously)
+                        FromAsyncCoreLogic(iar, endFunction, endAction, promise, requiresSynchronization: true);
+                }, state);
+                if (asyncResult.CompletedSynchronously)
+                {
+                    Debug.Assert(asyncResult.IsCompleted, "If the operation completed synchronously, it must be completed.");
+                    FromAsyncCoreLogic(asyncResult, endFunction, endAction, promise, requiresSynchronization: false);
+                }
+            }
+            catch
+            {
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, promise.Id, AsyncCausalityStatus.Error);
+
+                if (Task.s_asyncDebuggingEnabled)
+                {
+                    Task.RemoveFromActiveTasks(promise.Id);
+                }
+
+                // Make sure we don't leave the promise "dangling".
+                promise.TrySetResult(default(TResult));
+                throw;
+            }
+
+            return promise;
+        }
+
+        /// <summary>
+        /// Special internal-only FromAsync support used by System.IO to wrap
+        /// APM implementations with minimal overhead, avoiding unnecessary closure
+        /// and delegate allocations.
+        /// </summary>
+        /// <typeparam name="TInstance">Specifies the type of the instance on which the APM implementation lives.</typeparam>
+        /// <typeparam name="TArg1">Specifies the type containing the arguments.</typeparam>
+        /// <param name="thisRef">The instance from which the begin and end methods are invoked.</param>
+        /// <param name="beginMethod">The begin method.</param>
+        /// <param name="endMethod">The end method.</param>
+        /// <param name="args">The arguments.</param>
+        /// <returns>A task representing the asynchronous operation.</returns>
+        internal static Task<TResult> FromAsyncTrim<TInstance, TArgs>(
+            TInstance thisRef, TArgs args,
+            Func<TInstance, TArgs, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<TInstance, IAsyncResult, TResult> endMethod)
+            where TInstance : class
+        {
+            // Validate arguments, but only with asserts, as this is an internal only implementation.
+            Debug.Assert(thisRef != null, "Expected a non-null thisRef");
+            Debug.Assert(beginMethod != null, "Expected a non-null beginMethod");
+            Debug.Assert(endMethod != null, "Expected a non-null endMethod");
+
+            // Create the promise and start the operation.
+            // No try/catch is necessary here as we want exceptions to bubble out, and because
+            // the task doesn't have AttachedToParent set on it, there's no need to complete it in
+            // case of an exception occurring... we can just let it go unresolved.
+            var promise = new FromAsyncTrimPromise<TInstance>(thisRef, endMethod);
+            var asyncResult = beginMethod(thisRef, args, FromAsyncTrimPromise<TInstance>.s_completeFromAsyncResult, promise);
+
+            // If the IAsyncResult completed asynchronously, completing the promise will be handled by the callback.
+            // If it completed synchronously, we'll handle that here.
+            if (asyncResult.CompletedSynchronously)
+            {
+                Debug.Assert(asyncResult.IsCompleted, "If the operation completed synchronously, it must be completed.");
+                promise.Complete(thisRef, endMethod, asyncResult, requiresSynchronization: false);
+            }
+
+            // Return the promise
+            return promise;
+        }
+
+        /// <summary>
+        /// A specialized task used by FromAsyncTrim.  Stores relevant information as instance
+        /// state so that we can avoid unnecessary closure/delegate allocations.
+        /// </summary>
+        /// <typeparam name="TInstance">Specifies the type of the instance on which the APM implementation lives.</typeparam>
+        private sealed class FromAsyncTrimPromise<TInstance> : Task<TResult> where TInstance : class
+        {
+            /// <summary>A cached delegate used as the callback for the BeginXx method.</summary>
+            internal readonly static AsyncCallback s_completeFromAsyncResult = CompleteFromAsyncResult;
+
+            /// <summary>A reference to the object on which the begin/end methods are invoked.</summary>
+            private TInstance m_thisRef;
+            /// <summary>The end method.</summary>
+            private Func<TInstance, IAsyncResult, TResult> m_endMethod;
+
+            /// <summary>Initializes the promise.</summary>
+            /// <param name="thisRef">A reference to the object on which the begin/end methods are invoked.</param>
+            /// <param name="endMethod">The end method.</param>
+            internal FromAsyncTrimPromise(TInstance thisRef, Func<TInstance, IAsyncResult, TResult> endMethod) : base()
+            {
+                Debug.Assert(thisRef != null, "Expected a non-null thisRef");
+                Debug.Assert(endMethod != null, "Expected a non-null endMethod");
+                m_thisRef = thisRef;
+                m_endMethod = endMethod;
+            }
+
+            /// <summary>
+            /// Completes the asynchronous operation using information in the IAsyncResult.  
+            /// IAsyncResult.AsyncState needs to be the FromAsyncTrimPromise to complete.
+            /// </summary>
+            /// <param name="asyncResult">The IAsyncResult for the async operation.</param>
+            internal static void CompleteFromAsyncResult(IAsyncResult asyncResult)
+            {
+                // Validate argument
+                if (asyncResult == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.asyncResult);
+
+                var promise = asyncResult.AsyncState as FromAsyncTrimPromise<TInstance>;
+                if (promise == null) ThrowHelper.ThrowArgumentException(ExceptionResource.InvalidOperation_WrongAsyncResultOrEndCalledMultiple, ExceptionArgument.asyncResult);
+
+                // Grab the relevant state and then null it out so that the task doesn't hold onto the state unnecessarily
+                var thisRef = promise.m_thisRef;
+                var endMethod = promise.m_endMethod;
+                promise.m_thisRef = default(TInstance);
+                promise.m_endMethod = null;
+                if (endMethod == null) ThrowHelper.ThrowArgumentException(ExceptionResource.InvalidOperation_WrongAsyncResultOrEndCalledMultiple, ExceptionArgument.asyncResult);
+
+                // Complete the promise.  If the IAsyncResult completed synchronously,
+                // we'll instead complete the promise at the call site.
+                if (!asyncResult.CompletedSynchronously)
+                {
+                    promise.Complete(thisRef, endMethod, asyncResult, requiresSynchronization: true);
+                }
+            }
+
+            /// <summary>Completes the promise.</summary>
+            /// <param name="requiresSynchronization">
+            /// true if synchronization is needed to completed the task;
+            /// false if the task may be completed without synchronization
+            /// because it hasn't been handed out.
+            /// </param>
+            /// <param name="thisRef">The target instance on which the end method should be called.</param>
+            /// <param name="endMethod">The end method to call to retrieve the result.</param>
+            /// <param name="asyncResult">The IAsyncResult for the async operation.</param>
+            /// <permission cref="requiresSynchronization">
+            /// Whether completing the task requires synchronization.  This should be true
+            /// unless absolutely sure that the task has not yet been handed out to any consumers.
+            /// </permission>
+            internal void Complete(
+                TInstance thisRef, Func<TInstance, IAsyncResult, TResult> endMethod, IAsyncResult asyncResult,
+                bool requiresSynchronization)
+            {
+                Debug.Assert(!IsCompleted, "The task should not have been completed yet.");
+
+                // Run the end method and complete the task
+                bool successfullySet = false;
+                try
+                {
+                    var result = endMethod(thisRef, asyncResult);
+                    if (requiresSynchronization)
+                    {
+                        successfullySet = TrySetResult(result);
+                    }
+                    else
+                    {
+                        // If requiresSynchronization is false, we can use the DangerousSetResult
+                        // method, which uses no synchronization to complete the task.  This is
+                        // only valid when the operation is completing synchronously such
+                        // that the task has not yet been handed out to any consumers.
+                        DangerousSetResult(result);
+                        successfullySet = true;
+                    }
+                }
+                catch (OperationCanceledException oce)
+                {
+                    successfullySet = TrySetCanceled(oce.CancellationToken, oce);
+                }
+                catch (Exception exc)
+                {
+                    successfullySet = TrySetException(exc);
+                }
+                Debug.Assert(successfullySet, "Expected the task to not yet be completed");
+            }
+        }
+
+        // Utility method to create a canceled future-style task.
+        // Used by ContinueWhenAll/Any to bail out early on a pre-canceled token.
+        private static Task<TResult> CreateCanceledTask(TaskContinuationOptions continuationOptions, CancellationToken ct)
+        {
+            TaskCreationOptions tco;
+            InternalTaskOptions dontcare;
+            Task.CreationOptionsFromContinuationOptions(continuationOptions, out tco, out dontcare);
+            return new Task<TResult>(true, default(TResult), tco, ct);
+        }
+
+        //
+        // ContinueWhenAll() methods
+        //
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> 
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in 
+        /// the <paramref name="tasks"/> array have completed.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the 
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array is empty.</exception>
+        public Task<TResult> ContinueWhenAll(Task[] tasks, Func<Task[], TResult> continuationFunction)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAllImpl(tasks, continuationFunction, null, m_defaultContinuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> 
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in 
+        /// the <paramref name="tasks"/> array have completed.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the 
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TResult> ContinueWhenAll(Task[] tasks, Func<Task[], TResult> continuationFunction, CancellationToken cancellationToken)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAllImpl(tasks, continuationFunction, null, m_defaultContinuationOptions, cancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in the <paramref
+        /// name="tasks"/> array have completed.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAll.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAll(Task[] tasks, Func<Task[], TResult> continuationFunction, TaskContinuationOptions continuationOptions)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAllImpl(tasks, continuationFunction, null, continuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in the <paramref
+        /// name="tasks"/> array have completed.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created continuation <see
+        /// cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAll.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAll(Task[] tasks, Func<Task[], TResult> continuationFunction,
+            CancellationToken cancellationToken, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAllImpl(tasks, continuationFunction, null, continuationOptions, cancellationToken, scheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in the
+        /// <paramref name="tasks"/> array have completed.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        public Task<TResult> ContinueWhenAll<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>[], TResult> continuationFunction)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAllImpl<TAntecedentResult>(tasks, continuationFunction, null, m_defaultContinuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in the
+        /// <paramref name="tasks"/> array have completed.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TResult> ContinueWhenAll<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>[], TResult> continuationFunction,
+            CancellationToken cancellationToken)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAllImpl<TAntecedentResult>(tasks, continuationFunction, null, m_defaultContinuationOptions, cancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in the
+        /// <paramref name="tasks"/> array have completed.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAll.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAll<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>[], TResult> continuationFunction,
+            TaskContinuationOptions continuationOptions)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAllImpl<TAntecedentResult>(tasks, continuationFunction, null, continuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in the
+        /// <paramref name="tasks"/> array have completed.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created continuation <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAll.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAll<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>[], TResult> continuationFunction,
+            CancellationToken cancellationToken, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAllImpl<TAntecedentResult>(tasks, continuationFunction, null, continuationOptions, cancellationToken, scheduler);
+        }
+
+
+        // Core implementation of ContinueWhenAll -- the generic version
+        // Note: if you make any changes to this method, please do the same to the non-generic version too. 
+        internal static Task<TResult> ContinueWhenAllImpl<TAntecedentResult>(Task<TAntecedentResult>[] tasks,
+            Func<Task<TAntecedentResult>[], TResult> continuationFunction, Action<Task<TAntecedentResult>[]> continuationAction,
+            TaskContinuationOptions continuationOptions, CancellationToken cancellationToken, TaskScheduler scheduler)
+        {
+            // check arguments
+            TaskFactory.CheckMultiTaskContinuationOptions(continuationOptions);
+            if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
+            //ArgumentNullException of continuationFunction or continuationAction is checked by the caller
+            Debug.Assert((continuationFunction != null) != (continuationAction != null), "Expected exactly one of endFunction/endAction to be non-null");
+            if (scheduler == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+
+            // Check tasks array and make defensive copy
+            Task<TAntecedentResult>[] tasksCopy = TaskFactory.CheckMultiContinuationTasksAndCopy<TAntecedentResult>(tasks);
+
+            // Bail early if cancellation has been requested.
+            if (cancellationToken.IsCancellationRequested
+                && ((continuationOptions & TaskContinuationOptions.LazyCancellation) == 0)
+                )
+            {
+                return CreateCanceledTask(continuationOptions, cancellationToken);
+            }
+
+            // Call common ContinueWhenAll() setup logic, extract starter task.
+            var starter = TaskFactory.CommonCWAllLogic(tasksCopy);
+
+            // returned continuation task, off of starter
+            if (continuationFunction != null)
+            {
+                return starter.ContinueWith<TResult>(
+                   // use a cached delegate
+                   GenericDelegateCache<TAntecedentResult, TResult>.CWAllFuncDelegate,
+                   continuationFunction, scheduler, cancellationToken, continuationOptions);
+            }
+            else
+            {
+                Debug.Assert(continuationAction != null);
+
+                return starter.ContinueWith<TResult>(
+                   // use a cached delegate
+                   GenericDelegateCache<TAntecedentResult, TResult>.CWAllActionDelegate,
+                   continuationAction, scheduler, cancellationToken, continuationOptions);
+            }
+        }
+
+        // Core implementation of ContinueWhenAll -- the non-generic version
+        // Note: if you make any changes to this method, please do the same to the generic version too. 
+        internal static Task<TResult> ContinueWhenAllImpl(Task[] tasks,
+            Func<Task[], TResult> continuationFunction, Action<Task[]> continuationAction,
+            TaskContinuationOptions continuationOptions, CancellationToken cancellationToken, TaskScheduler scheduler)
+        {
+            // check arguments
+            TaskFactory.CheckMultiTaskContinuationOptions(continuationOptions);
+            if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
+            //ArgumentNullException of continuationFunction or continuationAction is checked by the caller
+            Debug.Assert((continuationFunction != null) != (continuationAction != null), "Expected exactly one of endFunction/endAction to be non-null");
+            if (scheduler == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+
+            // Check tasks array and make defensive copy
+            Task[] tasksCopy = TaskFactory.CheckMultiContinuationTasksAndCopy(tasks);
+
+            // Bail early if cancellation has been requested.
+            if (cancellationToken.IsCancellationRequested
+                && ((continuationOptions & TaskContinuationOptions.LazyCancellation) == 0)
+                )
+            {
+                return CreateCanceledTask(continuationOptions, cancellationToken);
+            }
+
+            // Perform common ContinueWhenAll() setup logic, extract starter task
+            var starter = TaskFactory.CommonCWAllLogic(tasksCopy);
+
+            // returned continuation task, off of starter
+            if (continuationFunction != null)
+            {
+                return starter.ContinueWith(
+                    //the following delegate avoids closure capture as much as possible
+                    //completedTasks.Result == tasksCopy;
+                    //state == continuationFunction
+                    (completedTasks, state) =>
+                    {
+                        completedTasks.NotifyDebuggerOfWaitCompletionIfNecessary();
+                        return ((Func<Task[], TResult>)state)(completedTasks.Result);
+                    },
+                    continuationFunction, scheduler, cancellationToken, continuationOptions);
+            }
+            else
+            {
+                Debug.Assert(continuationAction != null);
+                return starter.ContinueWith<TResult>(
+                   //the following delegate avoids closure capture as much as possible
+                   //completedTasks.Result == tasksCopy;
+                   //state == continuationAction
+                   (completedTasks, state) =>
+                   {
+                       completedTasks.NotifyDebuggerOfWaitCompletionIfNecessary();
+                       ((Action<Task[]>)state)(completedTasks.Result); return default(TResult);
+                   },
+                   continuationAction, scheduler, cancellationToken, continuationOptions);
+            }
+        }
+
+        //
+        // ContinueWhenAny() methods
+        //
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the <paramref
+        /// name="tasks"/> array completes.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        public Task<TResult> ContinueWhenAny(Task[] tasks, Func<Task, TResult> continuationFunction)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAnyImpl(tasks, continuationFunction, null, m_defaultContinuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the <paramref
+        /// name="tasks"/> array completes.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TResult> ContinueWhenAny(Task[] tasks, Func<Task, TResult> continuationFunction, CancellationToken cancellationToken)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAnyImpl(tasks, continuationFunction, null, m_defaultContinuationOptions, cancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the <paramref
+        /// name="tasks"/> array completes.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAny.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAny(Task[] tasks, Func<Task, TResult> continuationFunction, TaskContinuationOptions continuationOptions)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAnyImpl(tasks, continuationFunction, null, continuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the <paramref
+        /// name="tasks"/> array completes.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created continuation <see
+        /// cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAny.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAny(Task[] tasks, Func<Task, TResult> continuationFunction,
+            CancellationToken cancellationToken, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAnyImpl(tasks, continuationFunction, null, continuationOptions, cancellationToken, scheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        public Task<TResult> ContinueWhenAny<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>, TResult> continuationFunction)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAnyImpl<TAntecedentResult>(tasks, continuationFunction, null, m_defaultContinuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TResult> ContinueWhenAny<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>, TResult> continuationFunction,
+            CancellationToken cancellationToken)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAnyImpl<TAntecedentResult>(tasks, continuationFunction, null, m_defaultContinuationOptions, cancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAny.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAny<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>, TResult> continuationFunction,
+            TaskContinuationOptions continuationOptions)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAnyImpl<TAntecedentResult>(tasks, continuationFunction, null, continuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created continuation <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAny.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAny<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>, TResult> continuationFunction,
+            CancellationToken cancellationToken, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            if (continuationFunction == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+
+            return ContinueWhenAnyImpl<TAntecedentResult>(tasks, continuationFunction, null, continuationOptions, cancellationToken, scheduler);
+        }
+
+        // Core implementation of ContinueWhenAny, non-generic version
+        // Note: if you make any changes to this method, be sure to do the same to the generic version 
+        internal static Task<TResult> ContinueWhenAnyImpl(Task[] tasks,
+            Func<Task, TResult> continuationFunction, Action<Task> continuationAction,
+            TaskContinuationOptions continuationOptions, CancellationToken cancellationToken, TaskScheduler scheduler)
+        {
+            // check arguments
+            TaskFactory.CheckMultiTaskContinuationOptions(continuationOptions);
+            if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
+            if (tasks.Length == 0) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_EmptyTaskList, ExceptionArgument.tasks);
+
+            //ArgumentNullException of continuationFunction or continuationAction is checked by the caller
+            Debug.Assert((continuationFunction != null) != (continuationAction != null), "Expected exactly one of endFunction/endAction to be non-null");
+            if (scheduler == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+
+            // Call common ContinueWhenAny() setup logic, extract starter
+            Task<Task> starter = TaskFactory.CommonCWAnyLogic(tasks);
+
+            // Bail early if cancellation has been requested.
+            if (cancellationToken.IsCancellationRequested
+                && ((continuationOptions & TaskContinuationOptions.LazyCancellation) == 0)
+                )
+            {
+                return CreateCanceledTask(continuationOptions, cancellationToken);
+            }
+
+            // returned continuation task, off of starter
+            if (continuationFunction != null)
+            {
+                return starter.ContinueWith(
+                     //the following delegate avoids closure capture as much as possible
+                     //completedTask.Result is the winning task; state == continuationAction
+                     (completedTask, state) => { return ((Func<Task, TResult>)state)(completedTask.Result); },
+                     continuationFunction, scheduler, cancellationToken, continuationOptions);
+            }
+            else
+            {
+                Debug.Assert(continuationAction != null);
+                return starter.ContinueWith<TResult>(
+                    //the following delegate avoids closure capture as much as possible
+                    //completedTask.Result is the winning task; state == continuationAction
+                    (completedTask, state) => { ((Action<Task>)state)(completedTask.Result); return default(TResult); },
+                    continuationAction, scheduler, cancellationToken, continuationOptions);
+            }
+        }
+
+
+        // Core implementation of ContinueWhenAny, generic version
+        // Note: if you make any changes to this method, be sure to do the same to the non-generic version 
+        internal static Task<TResult> ContinueWhenAnyImpl<TAntecedentResult>(Task<TAntecedentResult>[] tasks,
+            Func<Task<TAntecedentResult>, TResult> continuationFunction, Action<Task<TAntecedentResult>> continuationAction,
+            TaskContinuationOptions continuationOptions, CancellationToken cancellationToken, TaskScheduler scheduler)
+        {
+            // check arguments
+            TaskFactory.CheckMultiTaskContinuationOptions(continuationOptions);
+            if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
+            if (tasks.Length == 0) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_EmptyTaskList, ExceptionArgument.tasks);
+            //ArgumentNullException of continuationFunction or continuationAction is checked by the caller
+            Debug.Assert((continuationFunction != null) != (continuationAction != null), "Expected exactly one of endFunction/endAction to be non-null");
+            if (scheduler == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+
+            // Call common ContinueWhenAny setup logic, extract starter
+            var starter = TaskFactory.CommonCWAnyLogic(tasks);
+
+            // Bail early if cancellation has been requested.
+            if (cancellationToken.IsCancellationRequested
+                && ((continuationOptions & TaskContinuationOptions.LazyCancellation) == 0)
+                )
+            {
+                return CreateCanceledTask(continuationOptions, cancellationToken);
+            }
+
+            // returned continuation task, off of starter
+            if (continuationFunction != null)
+            {
+                return starter.ContinueWith<TResult>(
+                    // Use a cached delegate
+                    GenericDelegateCache<TAntecedentResult, TResult>.CWAnyFuncDelegate,
+                    continuationFunction, scheduler, cancellationToken, continuationOptions);
+            }
+            else
+            {
+                Debug.Assert(continuationAction != null);
+                return starter.ContinueWith<TResult>(
+                    // Use a cached delegate
+                    GenericDelegateCache<TAntecedentResult, TResult>.CWAnyActionDelegate,
+                    continuationAction, scheduler, cancellationToken, continuationOptions);
+            }
+        }
+    }
+
+    // For the ContinueWhenAnyImpl/ContinueWhenAllImpl methods that are generic on TAntecedentResult,
+    // the compiler won't cache the internal ContinueWith delegate because it is generic on both
+    // TAntecedentResult and TResult.  The GenericDelegateCache serves as a cache for those delegates.
+    internal static class GenericDelegateCache<TAntecedentResult, TResult>
+    {
+        // ContinueWith delegate for TaskFactory<TResult>.ContinueWhenAnyImpl<TAntecedentResult>(non-null continuationFunction)
+        internal static Func<Task<Task>, object, TResult> CWAnyFuncDelegate =
+            (Task<Task> wrappedWinner, object state) =>
+            {
+                var func = (Func<Task<TAntecedentResult>, TResult>)state;
+                var arg = (Task<TAntecedentResult>)wrappedWinner.Result;
+                return func(arg);
+            };
+
+        // ContinueWith delegate for TaskFactory<TResult>.ContinueWhenAnyImpl<TAntecedentResult>(non-null continuationAction)
+        internal static Func<Task<Task>, object, TResult> CWAnyActionDelegate =
+            (Task<Task> wrappedWinner, object state) =>
+            {
+                var action = (Action<Task<TAntecedentResult>>)state;
+                var arg = (Task<TAntecedentResult>)wrappedWinner.Result;
+                action(arg);
+                return default(TResult);
+            };
+
+        // ContinueWith delegate for TaskFactory<TResult>.ContinueWhenAllImpl<TAntecedentResult>(non-null continuationFunction)
+        internal static Func<Task<Task<TAntecedentResult>[]>, object, TResult> CWAllFuncDelegate =
+            (Task<Task<TAntecedentResult>[]> wrappedAntecedents, object state) =>
+            {
+                wrappedAntecedents.NotifyDebuggerOfWaitCompletionIfNecessary();
+                var func = (Func<Task<TAntecedentResult>[], TResult>)state;
+                return func(wrappedAntecedents.Result);
+            };
+
+        // ContinueWith delegate for TaskFactory<TResult>.ContinueWhenAllImpl<TAntecedentResult>(non-null continuationAction)
+        internal static Func<Task<Task<TAntecedentResult>[]>, object, TResult> CWAllActionDelegate =
+            (Task<Task<TAntecedentResult>[]> wrappedAntecedents, object state) =>
+            {
+                wrappedAntecedents.NotifyDebuggerOfWaitCompletionIfNecessary();
+                var action = (Action<Task<TAntecedentResult>[]>)state;
+                action(wrappedAntecedents.Result);
+                return default(TResult);
+            };
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Tasks/IAsyncCausalityTracerStatics.cs b/src/System.Private.CoreLib/src/System/Threading/Tasks/IAsyncCausalityTracerStatics.cs
new file mode 100644
index 0000000000..17dd1f8bde
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Tasks/IAsyncCausalityTracerStatics.cs
@@ -0,0 +1,101 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+//
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.InteropServices.WindowsRuntime;
+
+// Windows.Foundation.Diagnostics cannot be referenced from managed code because
+// they're hidden by the metadata adapter. We redeclare the interfaces manually
+// to be able to talk to native WinRT objects.
+
+namespace Windows.Foundation.Diagnostics
+{
+    [ComImport]
+    [Guid("50850B26-267E-451B-A890-AB6A370245EE")]
+    [WindowsRuntimeImport]
+    internal interface IAsyncCausalityTracerStatics
+    {
+        void TraceOperationCreation(CausalityTraceLevel traceLevel, CausalitySource source, Guid platformId, ulong operationId, string operationName, ulong relatedContext);
+        void TraceOperationCompletion(CausalityTraceLevel traceLevel, CausalitySource source, Guid platformId, ulong operationId, AsyncCausalityStatus status);
+        void TraceOperationRelation(CausalityTraceLevel traceLevel, CausalitySource source, Guid platformId, ulong operationId, CausalityRelation relation);
+        void TraceSynchronousWorkStart(CausalityTraceLevel traceLevel, CausalitySource source, Guid platformId, ulong operationId, CausalitySynchronousWork work);
+        void TraceSynchronousWorkCompletion(CausalityTraceLevel traceLevel, CausalitySource source, CausalitySynchronousWork work);
+        //These next 2 functions could've been represented as an event except that the EventRegistrationToken wasn't being propagated to WinRT
+        EventRegistrationToken add_TracingStatusChanged(System.EventHandler<TracingStatusChangedEventArgs> eventHandler);
+        void remove_TracingStatusChanged(EventRegistrationToken token);
+    }
+
+    [ComImport]
+    [Guid("410B7711-FF3B-477F-9C9A-D2EFDA302DC3")]
+    [WindowsRuntimeImport]
+    internal interface ITracingStatusChangedEventArgs
+    {
+        bool Enabled { get; }
+        CausalityTraceLevel TraceLevel { get; }
+    }
+
+    // We need this dummy class to satisfy a QI when the TracingStatusChangedHandler
+    // after being stored in a GIT cookie and then called by the WinRT API. This usually
+    // happens when calling a MAnaged WinMD which access this feature.
+    [ComImport]
+    [Guid("410B7711-FF3B-477F-9C9A-D2EFDA302DC3")]
+    [WindowsRuntimeImport]
+    internal sealed class TracingStatusChangedEventArgs : ITracingStatusChangedEventArgs
+    {
+        public extern bool Enabled
+        {
+            [MethodImpl(MethodImplOptions.InternalCall)]
+            get;
+        }
+
+        public extern CausalityTraceLevel TraceLevel
+        {
+            [MethodImpl(MethodImplOptions.InternalCall)]
+            get;
+        }
+    }
+
+    internal enum CausalityRelation
+    {
+        AssignDelegate,
+        Join,
+        Choice,
+        Cancel,
+        Error
+    }
+
+    internal enum CausalitySource
+    {
+        Application,
+        Library,
+        System
+    }
+
+    internal enum CausalitySynchronousWork
+    {
+        CompletionNotification,
+        ProgressNotification,
+        Execution
+    }
+
+    internal enum CausalityTraceLevel
+    {
+        Required,
+        Important,
+        Verbose
+    }
+
+    internal enum AsyncCausalityStatus
+    {
+        Canceled = 2,
+        Completed = 1,
+        Error = 3,
+        Started = 0
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Tasks/ProducerConsumerQueues.cs b/src/System.Private.CoreLib/src/System/Threading/Tasks/ProducerConsumerQueues.cs
new file mode 100644
index 0000000000..1994c490d3
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Tasks/ProducerConsumerQueues.cs
@@ -0,0 +1,368 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// Specialized producer/consumer queues.
+//
+//
+// ************<IMPORTANT NOTE>*************
+//
+//  src\ndp\clr\src\bcl\system\threading\tasks\producerConsumerQueue.cs
+//  src\ndp\fx\src\dataflow\system\threading\tasks\dataflow\internal\producerConsumerQueue.cs
+// Keep both of them consistent by changing the other file when you change this one, also avoid:
+//  1- To reference interneal types in mscorlib
+//  2- To reference any dataflow specific types
+// This should be fixed post Dev11 when this class becomes public.
+//
+// ************</IMPORTANT NOTE>*************
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Collections;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System.Threading.Tasks
+{
+    /// <summary>Represents a producer/consumer queue used internally by dataflow blocks.</summary>
+    /// <typeparam name="T">Specifies the type of data contained in the queue.</typeparam>
+    internal interface IProducerConsumerQueue<T> : IEnumerable<T>
+    {
+        /// <summary>Enqueues an item into the queue.</summary>
+        /// <param name="item">The item to enqueue.</param>
+        /// <remarks>This method is meant to be thread-safe subject to the particular nature of the implementation.</remarks>
+        void Enqueue(T item);
+
+        /// <summary>Attempts to dequeue an item from the queue.</summary>
+        /// <param name="result">The dequeued item.</param>
+        /// <returns>true if an item could be dequeued; otherwise, false.</returns>
+        /// <remarks>This method is meant to be thread-safe subject to the particular nature of the implementation.</remarks>
+        bool TryDequeue(out T result);
+
+        /// <summary>Gets whether the collection is currently empty.</summary>
+        /// <remarks>This method may or may not be thread-safe.</remarks>
+        bool IsEmpty { get; }
+
+        /// <summary>Gets the number of items in the collection.</summary>
+        /// <remarks>In many implementations, this method will not be thread-safe.</remarks>
+        int Count { get; }
+    }
+
+    /// <summary>
+    /// Provides a producer/consumer queue safe to be used by any number of producers and consumers concurrently.
+    /// </summary>
+    /// <typeparam name="T">Specifies the type of data contained in the queue.</typeparam>
+    [DebuggerDisplay("Count = {Count}")]
+    internal sealed class MultiProducerMultiConsumerQueue<T> : ConcurrentQueue<T>, IProducerConsumerQueue<T>
+    {
+        /// <summary>Enqueues an item into the queue.</summary>
+        /// <param name="item">The item to enqueue.</param>
+        void IProducerConsumerQueue<T>.Enqueue(T item) { base.Enqueue(item); }
+
+        /// <summary>Attempts to dequeue an item from the queue.</summary>
+        /// <param name="result">The dequeued item.</param>
+        /// <returns>true if an item could be dequeued; otherwise, false.</returns>
+        bool IProducerConsumerQueue<T>.TryDequeue(out T result) { return base.TryDequeue(out result); }
+
+        /// <summary>Gets whether the collection is currently empty.</summary>
+        bool IProducerConsumerQueue<T>.IsEmpty { get { return base.IsEmpty; } }
+
+        /// <summary>Gets the number of items in the collection.</summary>
+        int IProducerConsumerQueue<T>.Count { get { return base.Count; } }
+    }
+
+    /// <summary>
+    /// Provides a producer/consumer queue safe to be used by only one producer and one consumer concurrently.
+    /// </summary>
+    /// <typeparam name="T">Specifies the type of data contained in the queue.</typeparam>
+    [DebuggerDisplay("Count = {Count}")]
+    [DebuggerTypeProxy(typeof(SingleProducerSingleConsumerQueue<>.SingleProducerSingleConsumerQueue_DebugView))]
+    internal sealed class SingleProducerSingleConsumerQueue<T> : IProducerConsumerQueue<T>
+    {
+        // Design:
+        //
+        // SingleProducerSingleConsumerQueue (SPSCQueue) is a concurrent queue designed to be used 
+        // by one producer thread and one consumer thread. SPSCQueue does not work correctly when used by 
+        // multiple producer threads concurrently or multiple consumer threads concurrently.
+        // 
+        // SPSCQueue is based on segments that behave like circular buffers. Each circular buffer is represented 
+        // as an array with two indexes: m_first and m_last. m_first is the index of the array slot for the consumer 
+        // to read next, and m_last is the slot for the producer to write next. The circular buffer is empty when 
+        // (m_first == m_last), and full when ((m_last+1) % m_array.Length == m_first).
+        //
+        // Since m_first is only ever modified by the consumer thread and m_last by the producer, the two indices can 
+        // be updated without interlocked operations. As long as the queue size fits inside a single circular buffer, 
+        // enqueues and dequeues simply advance the corresponding indices around the circular buffer. If an enqueue finds 
+        // that there is no room in the existing buffer, however, a new circular buffer is allocated that is twice as big 
+        // as the old buffer. From then on, the producer will insert values into the new buffer. The consumer will first 
+        // empty out the old buffer and only then follow the producer into the new (larger) buffer.
+        //
+        // As described above, the enqueue operation on the fast path only modifies the m_first field of the current segment. 
+        // However, it also needs to read m_last in order to verify that there is room in the current segment. Similarly, the 
+        // dequeue operation on the fast path only needs to modify m_last, but also needs to read m_first to verify that the 
+        // queue is non-empty. This results in true cache line sharing between the producer and the consumer.
+        //
+        // The cache line sharing issue can be mitigating by having a possibly stale copy of m_first that is owned by the producer, 
+        // and a possibly stale copy of m_last that is owned by the consumer. So, the consumer state is described using 
+        // (m_first, m_lastCopy) and the producer state using (m_firstCopy, m_last). The consumer state is separated from 
+        // the producer state by padding, which allows fast-path enqueues and dequeues from hitting shared cache lines. 
+        // m_lastCopy is the consumer's copy of m_last. Whenever the consumer can tell that there is room in the buffer 
+        // simply by observing m_lastCopy, the consumer thread does not need to read m_last and thus encounter a cache miss. Only 
+        // when the buffer appears to be empty will the consumer refresh m_lastCopy from m_last. m_firstCopy is used by the producer 
+        // in the same way to avoid reading m_first on the hot path.
+
+        /// <summary>The initial size to use for segments (in number of elements).</summary>
+        private const int INIT_SEGMENT_SIZE = 32; // must be a power of 2
+        /// <summary>The maximum size to use for segments (in number of elements).</summary>
+        private const int MAX_SEGMENT_SIZE = 0x1000000; // this could be made as large as Int32.MaxValue / 2
+
+        /// <summary>The head of the linked list of segments.</summary>
+        private volatile Segment m_head;
+        /// <summary>The tail of the linked list of segments.</summary>
+        private volatile Segment m_tail;
+
+        /// <summary>Initializes the queue.</summary>
+        internal SingleProducerSingleConsumerQueue()
+        {
+            // Validate constants in ctor rather than in an explicit cctor that would cause perf degradation
+            Debug.Assert(INIT_SEGMENT_SIZE > 0, "Initial segment size must be > 0.");
+            Debug.Assert((INIT_SEGMENT_SIZE & (INIT_SEGMENT_SIZE - 1)) == 0, "Initial segment size must be a power of 2");
+            Debug.Assert(INIT_SEGMENT_SIZE <= MAX_SEGMENT_SIZE, "Initial segment size should be <= maximum.");
+            Debug.Assert(MAX_SEGMENT_SIZE < Int32.MaxValue / 2, "Max segment size * 2 must be < Int32.MaxValue, or else overflow could occur.");
+
+            // Initialize the queue
+            m_head = m_tail = new Segment(INIT_SEGMENT_SIZE);
+        }
+
+        /// <summary>Enqueues an item into the queue.</summary>
+        /// <param name="item">The item to enqueue.</param>
+        public void Enqueue(T item)
+        {
+            Segment segment = m_tail;
+            var array = segment.m_array;
+            int last = segment.m_state.m_last; // local copy to avoid multiple volatile reads
+
+            // Fast path: there's obviously room in the current segment
+            int tail2 = (last + 1) & (array.Length - 1);
+            if (tail2 != segment.m_state.m_firstCopy)
+            {
+                array[last] = item;
+                segment.m_state.m_last = tail2;
+            }
+            // Slow path: there may not be room in the current segment.
+            else EnqueueSlow(item, ref segment);
+        }
+
+        /// <summary>Enqueues an item into the queue.</summary>
+        /// <param name="item">The item to enqueue.</param>
+        /// <param name="segment">The segment in which to first attempt to store the item.</param>
+        private void EnqueueSlow(T item, ref Segment segment)
+        {
+            Debug.Assert(segment != null, "Expected a non-null segment.");
+
+            if (segment.m_state.m_firstCopy != segment.m_state.m_first)
+            {
+                segment.m_state.m_firstCopy = segment.m_state.m_first;
+                Enqueue(item); // will only recur once for this enqueue operation
+                return;
+            }
+
+            int newSegmentSize = m_tail.m_array.Length << 1; // double size
+            Debug.Assert(newSegmentSize > 0, "The max size should always be small enough that we don't overflow.");
+            if (newSegmentSize > MAX_SEGMENT_SIZE) newSegmentSize = MAX_SEGMENT_SIZE;
+
+            var newSegment = new Segment(newSegmentSize);
+            newSegment.m_array[0] = item;
+            newSegment.m_state.m_last = 1;
+            newSegment.m_state.m_lastCopy = 1;
+
+            try { }
+            finally
+            {
+                // Finally block to protect against corruption due to a thread abort 
+                // between setting m_next and setting m_tail.
+                Volatile.Write(ref m_tail.m_next, newSegment); // ensure segment not published until item is fully stored
+                m_tail = newSegment;
+            }
+        }
+
+        /// <summary>Attempts to dequeue an item from the queue.</summary>
+        /// <param name="result">The dequeued item.</param>
+        /// <returns>true if an item could be dequeued; otherwise, false.</returns>
+        public bool TryDequeue(out T result)
+        {
+            Segment segment = m_head;
+            var array = segment.m_array;
+            int first = segment.m_state.m_first; // local copy to avoid multiple volatile reads
+
+            // Fast path: there's obviously data available in the current segment
+            if (first != segment.m_state.m_lastCopy)
+            {
+                result = array[first];
+                array[first] = default(T); // Clear the slot to release the element
+                segment.m_state.m_first = (first + 1) & (array.Length - 1);
+                return true;
+            }
+            // Slow path: there may not be data available in the current segment
+            else return TryDequeueSlow(ref segment, ref array, out result);
+        }
+
+        /// <summary>Attempts to dequeue an item from the queue.</summary>
+        /// <param name="array">The array from which the item was dequeued.</param>
+        /// <param name="segment">The segment from which the item was dequeued.</param>
+        /// <param name="result">The dequeued item.</param>
+        /// <returns>true if an item could be dequeued; otherwise, false.</returns>
+        private bool TryDequeueSlow(ref Segment segment, ref T[] array, out T result)
+        {
+            Debug.Assert(segment != null, "Expected a non-null segment.");
+            Debug.Assert(array != null, "Expected a non-null item array.");
+
+            if (segment.m_state.m_last != segment.m_state.m_lastCopy)
+            {
+                segment.m_state.m_lastCopy = segment.m_state.m_last;
+                return TryDequeue(out result); // will only recur once for this dequeue operation
+            }
+
+            if (segment.m_next != null && segment.m_state.m_first == segment.m_state.m_last)
+            {
+                segment = segment.m_next;
+                array = segment.m_array;
+                m_head = segment;
+            }
+
+            var first = segment.m_state.m_first; // local copy to avoid extraneous volatile reads
+
+            if (first == segment.m_state.m_last)
+            {
+                result = default(T);
+                return false;
+            }
+
+            result = array[first];
+            array[first] = default(T); // Clear the slot to release the element
+            segment.m_state.m_first = (first + 1) & (segment.m_array.Length - 1);
+            segment.m_state.m_lastCopy = segment.m_state.m_last; // Refresh m_lastCopy to ensure that m_first has not passed m_lastCopy
+
+            return true;
+        }
+
+        /// <summary>Gets whether the collection is currently empty.</summary>
+        /// <remarks>WARNING: This should not be used concurrently without further vetting.</remarks>
+        public bool IsEmpty
+        {
+            // This implementation is optimized for calls from the consumer.
+            get
+            {
+                var head = m_head;
+                if (head.m_state.m_first != head.m_state.m_lastCopy) return false; // m_first is volatile, so the read of m_lastCopy cannot get reordered
+                if (head.m_state.m_first != head.m_state.m_last) return false;
+                return head.m_next == null;
+            }
+        }
+
+        /// <summary>Gets an enumerable for the collection.</summary>
+        /// <remarks>WARNING: This should only be used for debugging purposes.  It is not safe to be used concurrently.</remarks>
+        public IEnumerator<T> GetEnumerator()
+        {
+            for (Segment segment = m_head; segment != null; segment = segment.m_next)
+            {
+                for (int pt = segment.m_state.m_first;
+                    pt != segment.m_state.m_last;
+                    pt = (pt + 1) & (segment.m_array.Length - 1))
+                {
+                    yield return segment.m_array[pt];
+                }
+            }
+        }
+        /// <summary>Gets an enumerable for the collection.</summary>
+        /// <remarks>WARNING: This should only be used for debugging purposes.  It is not safe to be used concurrently.</remarks>
+        IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
+
+        /// <summary>Gets the number of items in the collection.</summary>
+        /// <remarks>WARNING: This should only be used for debugging purposes.  It is not meant to be used concurrently.</remarks>
+        public int Count
+        {
+            get
+            {
+                int count = 0;
+                for (Segment segment = m_head; segment != null; segment = segment.m_next)
+                {
+                    int arraySize = segment.m_array.Length;
+                    int first, last;
+                    while (true) // Count is not meant to be used concurrently, but this helps to avoid issues if it is
+                    {
+                        first = segment.m_state.m_first;
+                        last = segment.m_state.m_last;
+                        if (first == segment.m_state.m_first) break;
+                    }
+                    count += (last - first) & (arraySize - 1);
+                }
+                return count;
+            }
+        }
+
+        /// <summary>A segment in the queue containing one or more items.</summary>
+        [StructLayout(LayoutKind.Sequential)]
+        private sealed class Segment
+        {
+            /// <summary>The next segment in the linked list of segments.</summary>
+            internal Segment m_next;
+            /// <summary>The data stored in this segment.</summary>
+            internal readonly T[] m_array;
+            /// <summary>Details about the segment.</summary>
+            internal SegmentState m_state; // separated out to enable StructLayout attribute to take effect
+
+            /// <summary>Initializes the segment.</summary>
+            /// <param name="size">The size to use for this segment.</param>
+            internal Segment(int size)
+            {
+                Debug.Assert((size & (size - 1)) == 0, "Size must be a power of 2");
+                m_array = new T[size];
+            }
+        }
+
+        /// <summary>Stores information about a segment.</summary>
+        [StructLayout(LayoutKind.Sequential)] // enforce layout so that padding reduces false sharing
+        private struct SegmentState
+        {
+            /// <summary>Padding to reduce false sharing between the segment's array and m_first.</summary>
+            internal Internal.PaddingFor32 m_pad0;
+
+            /// <summary>The index of the current head in the segment.</summary>
+            internal volatile int m_first;
+            /// <summary>A copy of the current tail index.</summary>
+            internal int m_lastCopy; // not volatile as read and written by the producer, except for IsEmpty, and there m_lastCopy is only read after reading the volatile m_first
+
+            /// <summary>Padding to reduce false sharing between the first and last.</summary>
+            internal Internal.PaddingFor32 m_pad1;
+
+            /// <summary>A copy of the current head index.</summary>
+            internal int m_firstCopy; // not voliatle as only read and written by the consumer thread
+            /// <summary>The index of the current tail in the segment.</summary>
+            internal volatile int m_last;
+
+            /// <summary>Padding to reduce false sharing with the last and what's after the segment.</summary>
+            internal Internal.PaddingFor32 m_pad2;
+        }
+
+        /// <summary>Debugger type proxy for a SingleProducerSingleConsumerQueue of T.</summary>
+        private sealed class SingleProducerSingleConsumerQueue_DebugView
+        {
+            /// <summary>The queue being visualized.</summary>
+            private readonly SingleProducerSingleConsumerQueue<T> m_queue;
+
+            /// <summary>Initializes the debug view.</summary>
+            /// <param name="enumerable">The queue being debugged.</param>
+            public SingleProducerSingleConsumerQueue_DebugView(SingleProducerSingleConsumerQueue<T> queue)
+            {
+                Debug.Assert(queue != null, "Expected a non-null queue.");
+                m_queue = queue;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Tasks/TPLETWProvider.cs b/src/System.Private.CoreLib/src/System/Threading/Tasks/TPLETWProvider.cs
new file mode 100644
index 0000000000..14d5fe88c4
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Tasks/TPLETWProvider.cs
@@ -0,0 +1,596 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// EventSource for TPL.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Security;
+using System.Runtime.CompilerServices;
+
+using System.Diagnostics.Tracing;
+
+namespace System.Threading.Tasks
+{
+    /// <summary>Provides an event source for tracing TPL information.</summary>
+    [EventSource(
+        Name = "System.Threading.Tasks.TplEventSource",
+        Guid = "2e5dba47-a3d2-4d16-8ee0-6671ffdcd7b5",
+        LocalizationResources = "FxResources.System.Private.CoreLib.SR")]
+    internal sealed class TplEtwProvider : EventSource
+    {
+        /// Used to determine if tasks should generate Activity IDs for themselves
+        internal bool TasksSetActivityIds;        // This keyword is set
+        internal bool Debug;
+        private bool DebugActivityId;
+
+        /// <summary>
+        /// Get callbacks when the ETW sends us commands`
+        /// </summary>
+        protected override void OnEventCommand(EventCommandEventArgs command)
+        {
+            // To get the AsyncCausality events, we need to inform the AsyncCausalityTracer
+            if (command.Command == EventCommand.Enable)
+                AsyncCausalityTracer.EnableToETW(true);
+            else if (command.Command == EventCommand.Disable)
+                AsyncCausalityTracer.EnableToETW(false);
+
+            if (IsEnabled(EventLevel.Informational, Keywords.TasksFlowActivityIds))
+                ActivityTracker.Instance.Enable();
+            else
+                TasksSetActivityIds = IsEnabled(EventLevel.Informational, Keywords.TasksSetActivityIds);
+
+            Debug = IsEnabled(EventLevel.Informational, Keywords.Debug);
+            DebugActivityId = IsEnabled(EventLevel.Informational, Keywords.DebugActivityId);
+        }
+
+        /// <summary>
+        /// Defines the singleton instance for the TPL ETW provider.
+        /// The TPL Event provider GUID is {2e5dba47-a3d2-4d16-8ee0-6671ffdcd7b5}.
+        /// </summary>
+        public static readonly TplEtwProvider Log = new TplEtwProvider();
+
+        /// <summary>Prevent external instantiation.  All logging should go through the Log instance.</summary>
+        private TplEtwProvider() : base(new Guid(0x2e5dba47, 0xa3d2, 0x4d16, 0x8e, 0xe0, 0x66, 0x71, 0xff, 0xdc, 0xd7, 0xb5), "System.Threading.Tasks.TplEventSource") { }
+
+        /// <summary>Configured behavior of a task wait operation.</summary>
+        public enum TaskWaitBehavior : int
+        {
+            /// <summary>A synchronous wait.</summary>
+            Synchronous = 1,
+            /// <summary>An asynchronous await.</summary>
+            Asynchronous = 2
+        }
+
+        /// <summary>ETW tasks that have start/stop events.</summary>
+        public class Tasks // this name is important for EventSource
+        {
+            /// <summary>A parallel loop.</summary>
+            public const EventTask Loop = (EventTask)1;
+            /// <summary>A parallel invoke.</summary>
+            public const EventTask Invoke = (EventTask)2;
+            /// <summary>Executing a Task.</summary>
+            public const EventTask TaskExecute = (EventTask)3;
+            /// <summary>Waiting on a Task.</summary>
+            public const EventTask TaskWait = (EventTask)4;
+            /// <summary>A fork/join task within a loop or invoke.</summary>
+            public const EventTask ForkJoin = (EventTask)5;
+            /// <summary>A task is scheduled to execute.</summary>
+            public const EventTask TaskScheduled = (EventTask)6;
+            /// <summary>An await task continuation is scheduled to execute.</summary>
+            public const EventTask AwaitTaskContinuationScheduled = (EventTask)7;
+
+            /// <summary>AsyncCausalityFunctionality.</summary>
+            public const EventTask TraceOperation = (EventTask)8;
+            public const EventTask TraceSynchronousWork = (EventTask)9;
+        }
+
+        public class Keywords // thisname is important for EventSource
+        {
+            /// <summary>
+            /// Only the most basic information about the workings of the task library
+            /// This sets activity IDS and logs when tasks are schedules (or waits begin)
+            /// But are otherwise silent
+            /// </summary>
+            public const EventKeywords TaskTransfer = (EventKeywords)1;
+            /// <summary>
+            /// TaskTranser events plus events when tasks start and stop 
+            /// </summary>
+            public const EventKeywords Tasks = (EventKeywords)2;
+            /// <summary>
+            /// Events associted with the higher level parallel APIs
+            /// </summary>
+            public const EventKeywords Parallel = (EventKeywords)4;
+            /// <summary>
+            /// These are relatively verbose events that effectively just redirect
+            /// the windows AsyncCausalityTracer to ETW
+            /// </summary>
+            public const EventKeywords AsyncCausalityOperation = (EventKeywords)8;
+            public const EventKeywords AsyncCausalityRelation = (EventKeywords)0x10;
+            public const EventKeywords AsyncCausalitySynchronousWork = (EventKeywords)0x20;
+
+            /// <summary>
+            /// Emit the stops as well as the schedule/start events
+            /// </summary>
+            public const EventKeywords TaskStops = (EventKeywords)0x40;
+
+            /// <summary>
+            /// TasksFlowActivityIds indicate that activity ID flow from one task
+            /// to any task created by it. 
+            /// </summary>
+            public const EventKeywords TasksFlowActivityIds = (EventKeywords)0x80;
+
+            /// <summary>
+            /// Events related to the happenings of async methods.
+            /// </summary>
+            public const EventKeywords AsyncMethod = (EventKeywords)0x100;
+
+            /// <summary>
+            /// TasksSetActivityIds will cause the task operations to set Activity Ids 
+            /// This option is incompatible with TasksFlowActivityIds flow is ignored
+            /// if that keyword is set.   This option is likely to be removed in the future
+            /// </summary>
+            public const EventKeywords TasksSetActivityIds = (EventKeywords)0x10000;
+
+            /// <summary>
+            /// Relatively Verbose logging meant for debugging the Task library itself. Will probably be removed in the future
+            /// </summary>
+            public const EventKeywords Debug = (EventKeywords)0x20000;
+            /// <summary>
+            /// Relatively Verbose logging meant for debugging the Task library itself.  Will probably be removed in the future
+            /// </summary>
+            public const EventKeywords DebugActivityId = (EventKeywords)0x40000;
+        }
+
+        /// <summary>Enabled for all keywords.</summary>
+        private const EventKeywords ALL_KEYWORDS = (EventKeywords)(-1);
+
+        //-----------------------------------------------------------------------------------
+        //        
+        // TPL Event IDs (must be unique)
+        //
+
+        /// <summary>The beginning of a parallel loop.</summary>
+        private const int PARALLELLOOPBEGIN_ID = 1;
+        /// <summary>The ending of a parallel loop.</summary>
+        private const int PARALLELLOOPEND_ID = 2;
+        /// <summary>The beginning of a parallel invoke.</summary>
+        private const int PARALLELINVOKEBEGIN_ID = 3;
+        /// <summary>The ending of a parallel invoke.</summary>
+        private const int PARALLELINVOKEEND_ID = 4;
+        /// <summary>A task entering a fork/join construct.</summary>
+        private const int PARALLELFORK_ID = 5;
+        /// <summary>A task leaving a fork/join construct.</summary>
+        private const int PARALLELJOIN_ID = 6;
+
+        /// <summary>A task is scheduled to a task scheduler.</summary>
+        private const int TASKSCHEDULED_ID = 7;
+        /// <summary>A task is about to execute.</summary>
+        private const int TASKSTARTED_ID = 8;
+        /// <summary>A task has finished executing.</summary>
+        private const int TASKCOMPLETED_ID = 9;
+        /// <summary>A wait on a task is beginning.</summary>
+        private const int TASKWAITBEGIN_ID = 10;
+        /// <summary>A wait on a task is ending.</summary>
+        private const int TASKWAITEND_ID = 11;
+        /// <summary>A continuation of a task is scheduled.</summary>
+        private const int AWAITTASKCONTINUATIONSCHEDULED_ID = 12;
+        /// <summary>A continuation of a taskWaitEnd is complete </summary>
+        private const int TASKWAITCONTINUATIONCOMPLETE_ID = 13;
+        /// <summary>A continuation of a taskWaitEnd is complete </summary>
+        private const int TASKWAITCONTINUATIONSTARTED_ID = 19;
+
+        private const int TRACEOPERATIONSTART_ID = 14;
+        private const int TRACEOPERATIONSTOP_ID = 15;
+        private const int TRACEOPERATIONRELATION_ID = 16;
+        private const int TRACESYNCHRONOUSWORKSTART_ID = 17;
+        private const int TRACESYNCHRONOUSWORKSTOP_ID = 18;
+
+
+        //-----------------------------------------------------------------------------------
+        //        
+        // Task Events
+        //
+
+        // These are all verbose events, so we need to call IsEnabled(EventLevel.Verbose, ALL_KEYWORDS) 
+        // call. However since the IsEnabled(l,k) call is more expensive than IsEnabled(), we only want 
+        // to incur this cost when instrumentation is enabled. So the Task codepaths that call these
+        // event functions still do the check for IsEnabled()
+
+        #region TaskScheduled
+        /// <summary>
+        /// Fired when a task is queued to a TaskScheduler.
+        /// </summary>
+        /// <param name="OriginatingTaskSchedulerID">The scheduler ID.</param>
+        /// <param name="OriginatingTaskID">The task ID.</param>
+        /// <param name="TaskID">The task ID.</param>
+        /// <param name="CreatingTaskID">The task ID</param>
+        /// <param name="TaskCreationOptions">The options used to create the task.</param>
+        [Event(TASKSCHEDULED_ID, Task = Tasks.TaskScheduled, Version = 1, Opcode = EventOpcode.Send,
+         Level = EventLevel.Informational, Keywords = Keywords.TaskTransfer | Keywords.Tasks)]
+        public void TaskScheduled(
+            int OriginatingTaskSchedulerID, int OriginatingTaskID,  // PFX_COMMON_EVENT_HEADER
+            int TaskID, int CreatingTaskID, int TaskCreationOptions, int appDomain)
+        {
+            // IsEnabled() call is an inlined quick check that makes this very fast when provider is off 
+            if (IsEnabled() && IsEnabled(EventLevel.Informational, Keywords.TaskTransfer | Keywords.Tasks))
+            {
+                unsafe
+                {
+                    EventData* eventPayload = stackalloc EventData[6];
+                    eventPayload[0].Size = sizeof(int);
+                    eventPayload[0].DataPointer = ((IntPtr)(&OriginatingTaskSchedulerID));
+                    eventPayload[0].Reserved = 0;
+                    eventPayload[1].Size = sizeof(int);
+                    eventPayload[1].DataPointer = ((IntPtr)(&OriginatingTaskID));
+                    eventPayload[1].Reserved = 0;
+                    eventPayload[2].Size = sizeof(int);
+                    eventPayload[2].DataPointer = ((IntPtr)(&TaskID));
+                    eventPayload[2].Reserved = 0;
+                    eventPayload[3].Size = sizeof(int);
+                    eventPayload[3].DataPointer = ((IntPtr)(&CreatingTaskID));
+                    eventPayload[3].Reserved = 0;
+                    eventPayload[4].Size = sizeof(int);
+                    eventPayload[4].DataPointer = ((IntPtr)(&TaskCreationOptions));
+                    eventPayload[4].Reserved = 0;
+                    eventPayload[5].Size = sizeof(int);
+                    eventPayload[5].DataPointer = ((IntPtr)(&appDomain));
+                    eventPayload[5].Reserved = 0;
+                    if (TasksSetActivityIds)
+                    {
+                        Guid childActivityId = CreateGuidForTaskID(TaskID);
+                        WriteEventWithRelatedActivityIdCore(TASKSCHEDULED_ID, &childActivityId, 6, eventPayload);
+                    }
+                    else
+                        WriteEventCore(TASKSCHEDULED_ID, 6, eventPayload);
+                }
+            }
+        }
+        #endregion
+
+        #region TaskStarted
+        /// <summary>
+        /// Fired just before a task actually starts executing.
+        /// </summary>
+        /// <param name="OriginatingTaskSchedulerID">The scheduler ID.</param>
+        /// <param name="OriginatingTaskID">The task ID.</param>
+        /// <param name="TaskID">The task ID.</param>
+        [Event(TASKSTARTED_ID,
+         Level = EventLevel.Informational, Keywords = Keywords.Tasks)]
+        public void TaskStarted(
+            int OriginatingTaskSchedulerID, int OriginatingTaskID,  // PFX_COMMON_EVENT_HEADER
+            int TaskID)
+        {
+            if (IsEnabled(EventLevel.Informational, Keywords.Tasks))
+                WriteEvent(TASKSTARTED_ID, OriginatingTaskSchedulerID, OriginatingTaskID, TaskID);
+        }
+        #endregion
+
+        #region TaskCompleted
+        /// <summary>
+        /// Fired right after a task finished executing.
+        /// </summary>
+        /// <param name="OriginatingTaskSchedulerID">The scheduler ID.</param>
+        /// <param name="OriginatingTaskID">The task ID.</param>
+        /// <param name="TaskID">The task ID.</param>
+        /// <param name="IsExceptional">Whether the task completed due to an error.</param>
+        [Event(TASKCOMPLETED_ID, Version = 1,
+         Level = EventLevel.Informational, Keywords = Keywords.TaskStops)]
+        public void TaskCompleted(
+            int OriginatingTaskSchedulerID, int OriginatingTaskID,  // PFX_COMMON_EVENT_HEADER
+            int TaskID, bool IsExceptional)
+        {
+            if (IsEnabled(EventLevel.Informational, Keywords.Tasks))
+            {
+                unsafe
+                {
+                    EventData* eventPayload = stackalloc EventData[4];
+                    Int32 isExceptionalInt = IsExceptional ? 1 : 0;
+                    eventPayload[0].Size = sizeof(int);
+                    eventPayload[0].DataPointer = ((IntPtr)(&OriginatingTaskSchedulerID));
+                    eventPayload[0].Reserved = 0;
+                    eventPayload[1].Size = sizeof(int);
+                    eventPayload[1].DataPointer = ((IntPtr)(&OriginatingTaskID));
+                    eventPayload[1].Reserved = 0;
+                    eventPayload[2].Size = sizeof(int);
+                    eventPayload[2].DataPointer = ((IntPtr)(&TaskID));
+                    eventPayload[2].Reserved = 0;
+                    eventPayload[3].Size = sizeof(int);
+                    eventPayload[3].DataPointer = ((IntPtr)(&isExceptionalInt));
+                    eventPayload[3].Reserved = 0;
+                    WriteEventCore(TASKCOMPLETED_ID, 4, eventPayload);
+                }
+            }
+        }
+        #endregion
+
+        #region TaskWaitBegin
+        /// <summary>
+        /// Fired when starting to wait for a taks's completion explicitly or implicitly.
+        /// </summary>
+        /// <param name="OriginatingTaskSchedulerID">The scheduler ID.</param>
+        /// <param name="OriginatingTaskID">The task ID.</param>
+        /// <param name="TaskID">The task ID.</param>
+        /// <param name="Behavior">Configured behavior for the wait.</param>
+        /// <param name="ContinueWithTaskID">If known, if 'TaskID' has a 'continueWith' task, mention give its ID here.  
+        ///      0 means unknown.   This allows better visualization of the common sequential chaining case.</param>
+        /// </summary>
+        [Event(TASKWAITBEGIN_ID, Version = 3, Task = TplEtwProvider.Tasks.TaskWait, Opcode = EventOpcode.Send,
+         Level = EventLevel.Informational, Keywords = Keywords.TaskTransfer | Keywords.Tasks)]
+        public void TaskWaitBegin(
+            int OriginatingTaskSchedulerID, int OriginatingTaskID,  // PFX_COMMON_EVENT_HEADER
+            int TaskID, TaskWaitBehavior Behavior, int ContinueWithTaskID)
+        {
+            if (IsEnabled() && IsEnabled(EventLevel.Informational, Keywords.TaskTransfer | Keywords.Tasks))
+            {
+                unsafe
+                {
+                    EventData* eventPayload = stackalloc EventData[5];
+                    eventPayload[0].Size = sizeof(int);
+                    eventPayload[0].DataPointer = ((IntPtr)(&OriginatingTaskSchedulerID));
+                    eventPayload[0].Reserved = 0;
+                    eventPayload[1].Size = sizeof(int);
+                    eventPayload[1].DataPointer = ((IntPtr)(&OriginatingTaskID));
+                    eventPayload[1].Reserved = 0;
+                    eventPayload[2].Size = sizeof(int);
+                    eventPayload[2].DataPointer = ((IntPtr)(&TaskID));
+                    eventPayload[2].Reserved = 0;
+                    eventPayload[3].Size = sizeof(int);
+                    eventPayload[3].DataPointer = ((IntPtr)(&Behavior));
+                    eventPayload[3].Reserved = 0;
+                    eventPayload[4].Size = sizeof(int);
+                    eventPayload[4].DataPointer = ((IntPtr)(&ContinueWithTaskID));
+                    eventPayload[4].Reserved = 0;
+                    if (TasksSetActivityIds)
+                    {
+                        Guid childActivityId = CreateGuidForTaskID(TaskID);
+                        WriteEventWithRelatedActivityIdCore(TASKWAITBEGIN_ID, &childActivityId, 5, eventPayload);
+                    }
+                    else
+                    {
+                        WriteEventCore(TASKWAITBEGIN_ID, 5, eventPayload);
+                    }
+                }
+            }
+        }
+        #endregion
+
+        /// <summary>
+        /// Fired when the wait for a tasks completion returns.
+        /// </summary>
+        /// <param name="OriginatingTaskSchedulerID">The scheduler ID.</param>
+        /// <param name="OriginatingTaskID">The task ID.</param>
+        /// <param name="TaskID">The task ID.</param>
+        [Event(TASKWAITEND_ID,
+         Level = EventLevel.Verbose, Keywords = Keywords.Tasks)]
+        public void TaskWaitEnd(
+            int OriginatingTaskSchedulerID, int OriginatingTaskID,  // PFX_COMMON_EVENT_HEADER
+            int TaskID)
+        {
+            // Log an event if indicated.  
+            if (IsEnabled() && IsEnabled(EventLevel.Verbose, Keywords.Tasks))
+                WriteEvent(TASKWAITEND_ID, OriginatingTaskSchedulerID, OriginatingTaskID, TaskID);
+        }
+
+        /// <summary>
+        /// Fired when the work (method) associated with a TaskWaitEnd completes
+        /// </summary>
+        /// <param name="OriginatingTaskSchedulerID">The scheduler ID.</param>
+        /// <param name="OriginatingTaskID">The task ID.</param>
+        /// <param name="TaskID">The task ID.</param>
+        [Event(TASKWAITCONTINUATIONCOMPLETE_ID,
+         Level = EventLevel.Verbose, Keywords = Keywords.TaskStops)]
+        public void TaskWaitContinuationComplete(int TaskID)
+        {
+            // Log an event if indicated.  
+            if (IsEnabled() && IsEnabled(EventLevel.Verbose, Keywords.Tasks))
+                WriteEvent(TASKWAITCONTINUATIONCOMPLETE_ID, TaskID);
+        }
+
+        /// <summary>
+        /// Fired when the work (method) associated with a TaskWaitEnd completes
+        /// </summary>
+        /// <param name="OriginatingTaskSchedulerID">The scheduler ID.</param>
+        /// <param name="OriginatingTaskID">The task ID.</param>
+        /// <param name="TaskID">The task ID.</param>
+        [Event(TASKWAITCONTINUATIONSTARTED_ID,
+         Level = EventLevel.Verbose, Keywords = Keywords.TaskStops)]
+        public void TaskWaitContinuationStarted(int TaskID)
+        {
+            // Log an event if indicated.  
+            if (IsEnabled() && IsEnabled(EventLevel.Verbose, Keywords.Tasks))
+                WriteEvent(TASKWAITCONTINUATIONSTARTED_ID, TaskID);
+        }
+
+        /// <summary>
+        /// Fired when the an asynchronous continuation for a task is scheduled
+        /// </summary>
+        /// <param name="OriginatingTaskSchedulerID">The scheduler ID.</param>
+        /// <param name="OriginatingTaskID">The task ID.</param>
+        /// <param name="TaskID">The activityId for the continuation.</param>
+        [Event(AWAITTASKCONTINUATIONSCHEDULED_ID, Task = Tasks.AwaitTaskContinuationScheduled, Opcode = EventOpcode.Send,
+         Level = EventLevel.Informational, Keywords = Keywords.TaskTransfer | Keywords.Tasks)]
+        public void AwaitTaskContinuationScheduled(
+            int OriginatingTaskSchedulerID, int OriginatingTaskID,  // PFX_COMMON_EVENT_HEADER
+            int ContinuwWithTaskId)
+        {
+            if (IsEnabled() && IsEnabled(EventLevel.Informational, Keywords.TaskTransfer | Keywords.Tasks))
+            {
+                unsafe
+                {
+                    EventData* eventPayload = stackalloc EventData[3];
+                    eventPayload[0].Size = sizeof(int);
+                    eventPayload[0].DataPointer = ((IntPtr)(&OriginatingTaskSchedulerID));
+                    eventPayload[0].Reserved = 0;
+                    eventPayload[1].Size = sizeof(int);
+                    eventPayload[1].DataPointer = ((IntPtr)(&OriginatingTaskID));
+                    eventPayload[1].Reserved = 0;
+                    eventPayload[2].Size = sizeof(int);
+                    eventPayload[2].DataPointer = ((IntPtr)(&ContinuwWithTaskId));
+                    eventPayload[2].Reserved = 0;
+                    if (TasksSetActivityIds)
+                    {
+                        Guid continuationActivityId = CreateGuidForTaskID(ContinuwWithTaskId);
+                        WriteEventWithRelatedActivityIdCore(AWAITTASKCONTINUATIONSCHEDULED_ID, &continuationActivityId, 3, eventPayload);
+                    }
+                    else
+                        WriteEventCore(AWAITTASKCONTINUATIONSCHEDULED_ID, 3, eventPayload);
+                }
+            }
+        }
+
+        [Event(TRACEOPERATIONSTART_ID, Version = 1,
+         Level = EventLevel.Informational, Keywords = Keywords.AsyncCausalityOperation)]
+        public void TraceOperationBegin(int TaskID, string OperationName, long RelatedContext)
+        {
+            if (IsEnabled() && IsEnabled(EventLevel.Informational, Keywords.AsyncCausalityOperation))
+            {
+                unsafe
+                {
+                    fixed (char* operationNamePtr = OperationName)
+                    {
+                        EventData* eventPayload = stackalloc EventData[3];
+                        eventPayload[0].Size = sizeof(int);
+                        eventPayload[0].DataPointer = ((IntPtr)(&TaskID));
+                        eventPayload[0].Reserved = 0;
+
+                        eventPayload[1].Size = ((OperationName.Length + 1) * 2);
+                        eventPayload[1].DataPointer = ((IntPtr)operationNamePtr);
+                        eventPayload[1].Reserved = 0;
+
+                        eventPayload[2].Size = sizeof(long);
+                        eventPayload[2].DataPointer = ((IntPtr)(&RelatedContext));
+                        eventPayload[2].Reserved = 0;
+                        WriteEventCore(TRACEOPERATIONSTART_ID, 3, eventPayload);
+                    }
+                }
+            }
+        }
+
+        [Event(TRACEOPERATIONRELATION_ID, Version = 1,
+         Level = EventLevel.Informational, Keywords = Keywords.AsyncCausalityRelation)]
+        public void TraceOperationRelation(int TaskID, CausalityRelation Relation)
+        {
+            if (IsEnabled() && IsEnabled(EventLevel.Informational, Keywords.AsyncCausalityRelation))
+                WriteEvent(TRACEOPERATIONRELATION_ID, TaskID, (int)Relation);                // optmized overload for this exists
+        }
+
+        [Event(TRACEOPERATIONSTOP_ID, Version = 1,
+         Level = EventLevel.Informational, Keywords = Keywords.AsyncCausalityOperation)]
+        public void TraceOperationEnd(int TaskID, AsyncCausalityStatus Status)
+        {
+            if (IsEnabled() && IsEnabled(EventLevel.Informational, Keywords.AsyncCausalityOperation))
+                WriteEvent(TRACEOPERATIONSTOP_ID, TaskID, (int)Status);                     // optmized overload for this exists
+        }
+
+        [Event(TRACESYNCHRONOUSWORKSTART_ID, Version = 1,
+         Level = EventLevel.Informational, Keywords = Keywords.AsyncCausalitySynchronousWork)]
+        public void TraceSynchronousWorkBegin(int TaskID, CausalitySynchronousWork Work)
+        {
+            if (IsEnabled() && IsEnabled(EventLevel.Informational, Keywords.AsyncCausalitySynchronousWork))
+                WriteEvent(TRACESYNCHRONOUSWORKSTART_ID, TaskID, (int)Work);               // optmized overload for this exists
+        }
+
+        [Event(TRACESYNCHRONOUSWORKSTOP_ID, Version = 1,
+         Level = EventLevel.Informational, Keywords = Keywords.AsyncCausalitySynchronousWork)]
+        public void TraceSynchronousWorkEnd(CausalitySynchronousWork Work)
+        {
+            if (IsEnabled() && IsEnabled(EventLevel.Informational, Keywords.AsyncCausalitySynchronousWork))
+            {
+                unsafe
+                {
+                    EventData* eventPayload = stackalloc EventData[1];
+                    eventPayload[0].Size = sizeof(int);
+                    eventPayload[0].DataPointer = ((IntPtr)(&Work));
+                    eventPayload[0].Reserved = 0;
+
+                    WriteEventCore(TRACESYNCHRONOUSWORKSTOP_ID, 1, eventPayload);
+                }
+            }
+        }
+
+        [NonEvent]
+        public unsafe void RunningContinuation(int TaskID, object Object) { RunningContinuation(TaskID, (long)*((void**)JitHelpers.UnsafeCastToStackPointer(ref Object))); }
+        [Event(20, Keywords = Keywords.Debug)]
+        private void RunningContinuation(int TaskID, long Object)
+        {
+            if (Debug)
+                WriteEvent(20, TaskID, Object);
+        }
+
+        [NonEvent]
+        public unsafe void RunningContinuationList(int TaskID, int Index, object Object) { RunningContinuationList(TaskID, Index, (long)*((void**)JitHelpers.UnsafeCastToStackPointer(ref Object))); }
+
+        [Event(21, Keywords = Keywords.Debug)]
+        public void RunningContinuationList(int TaskID, int Index, long Object)
+        {
+            if (Debug)
+                WriteEvent(21, TaskID, Index, Object);
+        }
+
+        [Event(23, Keywords = Keywords.Debug)]
+        public void DebugFacilityMessage(string Facility, string Message) { WriteEvent(23, Facility, Message); }
+
+        [Event(24, Keywords = Keywords.Debug)]
+        public void DebugFacilityMessage1(string Facility, string Message, string Value1) { WriteEvent(24, Facility, Message, Value1); }
+
+        [Event(25, Keywords = Keywords.DebugActivityId)]
+        public void SetActivityId(Guid NewId)
+        {
+            if (DebugActivityId)
+                WriteEvent(25, NewId);
+        }
+
+        [Event(26, Keywords = Keywords.Debug)]
+        public void NewID(int TaskID)
+        {
+            if (Debug)
+                WriteEvent(26, TaskID);
+        }
+
+        [NonEvent]
+        public void IncompleteAsyncMethod(IAsyncStateMachineBox stateMachineBox)
+        {
+            System.Diagnostics.Debug.Assert(stateMachineBox != null);
+            if (IsEnabled(EventLevel.Warning, Keywords.AsyncMethod))
+            {
+                IAsyncStateMachine stateMachine = stateMachineBox.GetStateMachineObject();
+                if (stateMachine != null)
+                {
+                    string description = AsyncMethodBuilderCore.GetAsyncStateMachineDescription(stateMachine);
+                    IncompleteAsyncMethod(description);
+                }
+            }
+        }
+
+        [Event(27, Level = EventLevel.Warning, Keywords = Keywords.AsyncMethod)]
+        private void IncompleteAsyncMethod(string stateMachineDescription) =>
+            WriteEvent(27, stateMachineDescription);
+
+        /// <summary>
+        /// Activity IDs are GUIDS but task IDS are integers (and are not unique across appdomains
+        /// This routine creates a process wide unique GUID given a task ID
+        /// </summary>
+        internal static Guid CreateGuidForTaskID(int taskID)
+        {
+            // The thread pool generated a process wide unique GUID from a task GUID by
+            // using the taskGuid, the appdomain ID, and 8 bytes of 'randomization' chosen by
+            // using the last 8 bytes  as the provider GUID for this provider.  
+            // These were generated by CreateGuid, and are reasonably random (and thus unlikley to collide
+            uint pid = EventSource.s_currentPid;
+            int appDomainID = System.Threading.Thread.GetDomainID();
+            return new Guid(taskID,
+                            (short)appDomainID, (short)(appDomainID >> 16),
+                            (byte)pid, (byte)(pid >> 8), (byte)(pid >> 16), (byte)(pid >> 24),
+                            0xff, 0xdc, 0xd7, 0xb5);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs b/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs
new file mode 100644
index 0000000000..8a288edb83
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs
@@ -0,0 +1,6713 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// A schedulable unit of work.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using System.Diagnostics.Tracing;
+using System.Runtime.CompilerServices;
+using System.Runtime.ExceptionServices;
+using Internal.Runtime.Augments;
+
+// Disable the "reference to volatile field not treated as volatile" error.
+#pragma warning disable 0420
+
+namespace System.Threading.Tasks
+{
+    /// <summary>
+    /// Utility class for allocating structs as heap variables
+    /// </summary>
+    internal class Shared<T>
+    {
+        internal T Value;
+
+        internal Shared(T value)
+        {
+            this.Value = value;
+        }
+    }
+
+    /// <summary>
+    /// Represents the current stage in the lifecycle of a <see cref="Task"/>.
+    /// </summary>
+    public enum TaskStatus
+    {
+        /// <summary> 
+        /// The task has been initialized but has not yet been scheduled.
+        /// </summary>
+        Created,
+        /// <summary> 
+        /// The task is waiting to be activated and scheduled internally by the .NET Framework infrastructure.
+        /// </summary>
+        WaitingForActivation,
+        /// <summary>
+        /// The task has been scheduled for execution but has not yet begun executing.
+        /// </summary>
+        WaitingToRun,
+        /// <summary>
+        /// The task is running but has not yet completed.
+        /// </summary>
+        Running,
+        // /// <summary>
+        // /// The task is currently blocked in a wait state.
+        // /// </summary>
+        // Blocked,
+        /// <summary>
+        /// The task has finished executing and is implicitly waiting for
+        /// attached child tasks to complete.
+        /// </summary>
+        WaitingForChildrenToComplete,
+        /// <summary>
+        /// The task completed execution successfully.
+        /// </summary>
+        RanToCompletion,
+        /// <summary>
+        /// The task acknowledged cancellation by throwing an OperationCanceledException with its own CancellationToken
+        /// while the token was in signaled state, or the task's CancellationToken was already signaled before the
+        /// task started executing.
+        /// </summary>
+        Canceled,
+        /// <summary>
+        /// The task completed due to an unhandled exception.
+        /// </summary>
+        Faulted
+    }
+
+    /// <summary>
+    /// Represents an asynchronous operation.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// <see cref="Task"/> instances may be created in a variety of ways. The most common approach is by
+    /// using the Task type's <see cref="Factory"/> property to retrieve a <see
+    /// cref="System.Threading.Tasks.TaskFactory"/> instance that can be used to create tasks for several
+    /// purposes. For example, to create a <see cref="Task"/> that runs an action, the factory's StartNew
+    /// method may be used:
+    /// <code>
+    /// // C# 
+    /// var t = Task.Factory.StartNew(() => DoAction());
+    /// 
+    /// ' Visual Basic 
+    /// Dim t = Task.Factory.StartNew(Function() DoAction())
+    /// </code>
+    /// </para>
+    /// <para>
+    /// The <see cref="Task"/> class also provides constructors that initialize the Task but that do not
+    /// schedule it for execution. For performance reasons, TaskFactory's StartNew method should be the
+    /// preferred mechanism for creating and scheduling computational tasks, but for scenarios where creation
+    /// and scheduling must be separated, the constructors may be used, and the task's <see cref="Start()"/>
+    /// method may then be used to schedule the task for execution at a later time.
+    /// </para>
+    /// <para>
+    /// All members of <see cref="Task"/>, except for <see cref="Dispose()"/>, are thread-safe
+    /// and may be used from multiple threads concurrently.
+    /// </para>
+    /// <para>
+    /// For operations that return values, the <see cref="System.Threading.Tasks.Task{TResult}"/> class
+    /// should be used.
+    /// </para>
+    /// <para>
+    /// For developers implementing custom debuggers, several internal and private members of Task may be
+    /// useful (these may change from release to release). The Int32 m_taskId field serves as the backing
+    /// store for the <see cref="Id"/> property, however accessing this field directly from a debugger may be
+    /// more efficient than accessing the same value through the property's getter method (the
+    /// s_taskIdCounter Int32 counter is used to retrieve the next available ID for a Task). Similarly, the
+    /// Int32 m_stateFlags field stores information about the current lifecycle stage of the Task,
+    /// information also accessible through the <see cref="Status"/> property. The m_action System.Object
+    /// field stores a reference to the Task's delegate, and the m_stateObject System.Object field stores the
+    /// async state passed to the Task by the developer. Finally, for debuggers that parse stack frames, the
+    /// InternalWait method serves a potential marker for when a Task is entering a wait operation.
+    /// </para>
+    /// </remarks>
+    [DebuggerTypeProxy(typeof(SystemThreadingTasks_TaskDebugView))]
+    [DebuggerDisplay("Id = {Id}, Status = {Status}, Method = {DebuggerDisplayMethodDescription}")]
+    public class Task : IThreadPoolWorkItem, IAsyncResult, IDisposable
+    {
+        [ThreadStatic]
+        internal static Task t_currentTask;  // The currently executing task.
+        [ThreadStatic]
+        private static StackGuard t_stackGuard;  // The stack guard object for this thread
+
+        internal static int s_taskIdCounter; //static counter used to generate unique task IDs
+
+        private volatile int m_taskId; // this task's unique ID. initialized only if it is ever requested
+
+        internal Delegate m_action;    // The body of the task.  Might be Action<object>, Action<TState> or Action.  Or possibly a Func.
+        // If m_action is set to null it will indicate that we operate in the
+        // "externally triggered completion" mode, which is exclusively meant 
+        // for the signalling Task<TResult> (aka. promise). In this mode,
+        // we don't call InnerInvoke() in response to a Wait(), but simply wait on
+        // the completion event which will be set when the Future class calls Finish().
+        // But the event would now be signalled if Cancel() is called
+
+
+        internal object m_stateObject; // A state object that can be optionally supplied, passed to action.
+        internal TaskScheduler m_taskScheduler; // The task scheduler this task runs under. 
+
+        internal volatile int m_stateFlags;
+
+        private Task ParentForDebugger => m_contingentProperties?.m_parent; // Private property used by a debugger to access this Task's parent
+        private int StateFlagsForDebugger => m_stateFlags; // Private property used by a debugger to access this Task's state flags
+
+        // State constants for m_stateFlags;
+        // The bits of m_stateFlags are allocated as follows:
+        //   0x40000000 - TaskBase state flag
+        //   0x3FFF0000 - Task state flags
+        //   0x0000FF00 - internal TaskCreationOptions flags
+        //   0x000000FF - publicly exposed TaskCreationOptions flags
+        //
+        // See TaskCreationOptions for bit values associated with TaskCreationOptions
+        //
+        private const int OptionsMask = 0xFFFF; // signifies the Options portion of m_stateFlags bin: 0000 0000 0000 0000 1111 1111 1111 1111
+        internal const int TASK_STATE_STARTED = 0x10000;                                       //bin: 0000 0000 0000 0001 0000 0000 0000 0000
+        internal const int TASK_STATE_DELEGATE_INVOKED = 0x20000;                              //bin: 0000 0000 0000 0010 0000 0000 0000 0000
+        internal const int TASK_STATE_DISPOSED = 0x40000;                                      //bin: 0000 0000 0000 0100 0000 0000 0000 0000
+        internal const int TASK_STATE_EXCEPTIONOBSERVEDBYPARENT = 0x80000;                     //bin: 0000 0000 0000 1000 0000 0000 0000 0000
+        internal const int TASK_STATE_CANCELLATIONACKNOWLEDGED = 0x100000;                     //bin: 0000 0000 0001 0000 0000 0000 0000 0000
+        internal const int TASK_STATE_FAULTED = 0x200000;                                      //bin: 0000 0000 0010 0000 0000 0000 0000 0000
+        internal const int TASK_STATE_CANCELED = 0x400000;                                     //bin: 0000 0000 0100 0000 0000 0000 0000 0000
+        internal const int TASK_STATE_WAITING_ON_CHILDREN = 0x800000;                          //bin: 0000 0000 1000 0000 0000 0000 0000 0000
+        internal const int TASK_STATE_RAN_TO_COMPLETION = 0x1000000;                           //bin: 0000 0001 0000 0000 0000 0000 0000 0000
+        internal const int TASK_STATE_WAITINGFORACTIVATION = 0x2000000;                        //bin: 0000 0010 0000 0000 0000 0000 0000 0000
+        internal const int TASK_STATE_COMPLETION_RESERVED = 0x4000000;                         //bin: 0000 0100 0000 0000 0000 0000 0000 0000
+        internal const int TASK_STATE_THREAD_WAS_ABORTED = 0x8000000;                          //bin: 0000 1000 0000 0000 0000 0000 0000 0000
+        internal const int TASK_STATE_WAIT_COMPLETION_NOTIFICATION = 0x10000000;               //bin: 0001 0000 0000 0000 0000 0000 0000 0000
+        //This could be moved to InternalTaskOptions enum
+        internal const int TASK_STATE_EXECUTIONCONTEXT_IS_NULL = 0x20000000;                   //bin: 0010 0000 0000 0000 0000 0000 0000 0000
+        internal const int TASK_STATE_TASKSCHEDULED_WAS_FIRED = 0x40000000;                    //bin: 0100 0000 0000 0000 0000 0000 0000 0000
+
+        // A mask for all of the final states a task may be in
+        private const int TASK_STATE_COMPLETED_MASK = TASK_STATE_CANCELED | TASK_STATE_FAULTED | TASK_STATE_RAN_TO_COMPLETION;
+
+        // Values for ContingentProperties.m_internalCancellationRequested.
+        private const int CANCELLATION_REQUESTED = 0x1;
+
+        // Can be null, a single continuation, a list of continuations, or s_taskCompletionSentinel,
+        // in that order. The logic arround this object assumes it will never regress to a previous state.
+        private volatile object m_continuationObject = null;
+
+        // m_continuationObject is set to this when the task completes.
+        private static readonly object s_taskCompletionSentinel = new object();
+
+        // A private flag that would be set (only) by the debugger
+        // When true the Async Causality logging trace is enabled as well as a dictionary to relate operation ids with Tasks
+        // [FriendAccessAllowed]
+        internal static bool s_asyncDebuggingEnabled; //false by default
+
+        // This dictonary relates the task id, from an operation id located in the Async Causality log to the actual
+        // task. This is to be used by the debugger ONLY. Task in this dictionary represent current active tasks.
+        private static readonly Dictionary<int, Task> s_currentActiveTasks = new Dictionary<int, Task>();
+        private static readonly Object s_activeTasksLock = new Object();
+
+        // These methods are a way to access the dictionary both from this class and for other classes that also
+        // activate dummy tasks. Specifically the AsyncTaskMethodBuilder and AsyncTaskMethodBuilder<>
+        // [FriendAccessAllowed]
+        internal static bool AddToActiveTasks(Task task)
+        {
+            Debug.Assert(task != null, "Null Task objects can't be added to the ActiveTasks collection");
+            lock (s_activeTasksLock)
+            {
+                s_currentActiveTasks[task.Id] = task;
+            }
+            //always return true to keep signature as bool for backwards compatibility
+            return true;
+        }
+
+        // [FriendAccessAllowed]
+        internal static void RemoveFromActiveTasks(int taskId)
+        {
+            lock (s_activeTasksLock)
+            {
+                s_currentActiveTasks.Remove(taskId);
+            }
+        }
+
+        // We moved a number of Task properties into this class.  The idea is that in most cases, these properties never
+        // need to be accessed during the life cycle of a Task, so we don't want to instantiate them every time.  Once
+        // one of these properties needs to be written, we will instantiate a ContingentProperties object and set
+        // the appropriate property.
+        internal class ContingentProperties
+        {
+            // Additional context
+
+            internal ExecutionContext m_capturedContext; // The execution context to run the task within, if any. Only set from non-concurrent contexts.
+
+            // Completion fields (exceptions and event)
+
+            internal volatile ManualResetEventSlim m_completionEvent; // Lazily created if waiting is required.
+            internal volatile TaskExceptionHolder m_exceptionsHolder; // Tracks exceptions, if any have occurred
+
+            // Cancellation fields (token, registration, and internally requested)
+
+            internal CancellationToken m_cancellationToken; // Task's cancellation token, if it has one
+            internal Shared<CancellationTokenRegistration> m_cancellationRegistration; // Task's registration with the cancellation token
+            internal volatile int m_internalCancellationRequested; // Its own field because multiple threads legally try to set it.
+
+            // Parenting fields
+
+            // # of active children + 1 (for this task itself).
+            // Used for ensuring all children are done before this task can complete
+            // The extra count helps prevent the race condition for executing the final state transition
+            // (i.e. whether the last child or this task itself should call FinishStageTwo())
+            internal volatile int m_completionCountdown = 1;
+            // A list of child tasks that threw an exception (TCEs don't count),
+            // but haven't yet been waited on by the parent, lazily initialized.
+            internal volatile List<Task> m_exceptionalChildren;
+            // A task's parent, or null if parent-less. Only set during Task construction.
+            internal Task m_parent;
+
+            /// <summary>
+            /// Sets the internal completion event.
+            /// </summary>
+            internal void SetCompleted()
+            {
+                var mres = m_completionEvent;
+                if (mres != null) mres.Set();
+            }
+
+            /// <summary>
+            /// Checks if we registered a CT callback during construction, and unregisters it.
+            /// This should be called when we know the registration isn't useful anymore. Specifically from Finish() if the task has completed
+            /// successfully or with an exception.
+            /// </summary>
+            internal void UnregisterCancellationCallback()
+            {
+                if (m_cancellationRegistration != null)
+                {
+                    // Harden against ODEs thrown from disposing of the CTR.
+                    // Since the task has already been put into a final state by the time this
+                    // is called, all we can do here is suppress the exception.
+                    try { m_cancellationRegistration.Value.Dispose(); }
+                    catch (ObjectDisposedException) { }
+                    m_cancellationRegistration = null;
+                }
+            }
+        }
+
+
+        // This field will only be instantiated to some non-null value if any ContingentProperties need to be set.
+        // This will be a ContingentProperties instance or a type derived from it
+        internal ContingentProperties m_contingentProperties;
+
+        // Special internal constructor to create an already-completed task.
+        // if canceled==true, create a Canceled task, or else create a RanToCompletion task.
+        // Constructs the task as already completed
+        internal Task(bool canceled, TaskCreationOptions creationOptions, CancellationToken ct)
+        {
+            int optionFlags = (int)creationOptions;
+            if (canceled)
+            {
+                m_stateFlags = TASK_STATE_CANCELED | TASK_STATE_CANCELLATIONACKNOWLEDGED | optionFlags;
+                m_contingentProperties = new ContingentProperties() // can't have children, so just instantiate directly
+                {
+                    m_cancellationToken = ct,
+                    m_internalCancellationRequested = CANCELLATION_REQUESTED,
+                };
+            }
+            else
+                m_stateFlags = TASK_STATE_RAN_TO_COMPLETION | optionFlags;
+        }
+
+        /// <summary>Constructor for use with promise-style tasks that aren't configurable.</summary>
+        internal Task()
+        {
+            m_stateFlags = TASK_STATE_WAITINGFORACTIVATION | (int)InternalTaskOptions.PromiseTask;
+        }
+
+        // Special constructor for use with promise-style tasks.
+        // Added promiseStyle parameter as an aid to the compiler to distinguish between (state,TCO) and
+        // (action,TCO).  It should always be true.
+        internal Task(object state, TaskCreationOptions creationOptions, bool promiseStyle)
+        {
+            Debug.Assert(promiseStyle, "Promise CTOR: promiseStyle was false");
+
+            // Check the creationOptions. We allow the AttachedToParent option to be specified for promise tasks.
+            // Also allow RunContinuationsAsynchronously because this is the constructor called by TCS
+            if ((creationOptions & ~(TaskCreationOptions.AttachedToParent | TaskCreationOptions.RunContinuationsAsynchronously)) != 0)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.creationOptions);
+            }
+
+            // Only set a parent if AttachedToParent is specified.
+            if ((creationOptions & TaskCreationOptions.AttachedToParent) != 0)
+            {
+                Task parent = Task.InternalCurrent;
+                if (parent != null)
+                {
+                    EnsureContingentPropertiesInitializedUnsafe().m_parent = parent;
+                }
+            }
+
+            TaskConstructorCore(null, state, default(CancellationToken), creationOptions, InternalTaskOptions.PromiseTask, null);
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref="Task"/> with the specified action.
+        /// </summary>
+        /// <param name="action">The delegate that represents the code to execute in the Task.</param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="action"/> argument is null.</exception>
+        public Task(Action action)
+            : this(action, null, null, default(CancellationToken), TaskCreationOptions.None, InternalTaskOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref="Task"/> with the specified action and <see cref="System.Threading.CancellationToken">CancellationToken</see>.
+        /// </summary>
+        /// <param name="action">The delegate that represents the code to execute in the Task.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// that will be assigned to the new Task.</param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="action"/> argument is null.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task(Action action, CancellationToken cancellationToken)
+            : this(action, null, null, cancellationToken, TaskCreationOptions.None, InternalTaskOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref="Task"/> with the specified action and creation options.
+        /// </summary>
+        /// <param name="action">The delegate that represents the code to execute in the task.</param>
+        /// <param name="creationOptions">
+        /// The <see cref="System.Threading.Tasks.TaskCreationOptions">TaskCreationOptions</see> used to
+        /// customize the Task's behavior.
+        /// </param>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="action"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="creationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskCreationOptions"/>.
+        /// </exception>
+        public Task(Action action, TaskCreationOptions creationOptions)
+            : this(action, null, Task.InternalCurrentIfAttached(creationOptions), default(CancellationToken), creationOptions, InternalTaskOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref="Task"/> with the specified action and creation options.
+        /// </summary>
+        /// <param name="action">The delegate that represents the code to execute in the task.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <param name="creationOptions">
+        /// The <see cref="System.Threading.Tasks.TaskCreationOptions">TaskCreationOptions</see> used to
+        /// customize the Task's behavior.
+        /// </param>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="action"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="creationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskCreationOptions"/>.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task(Action action, CancellationToken cancellationToken, TaskCreationOptions creationOptions)
+            : this(action, null, Task.InternalCurrentIfAttached(creationOptions), cancellationToken, creationOptions, InternalTaskOptions.None, null)
+        {
+        }
+
+
+        /// <summary>
+        /// Initializes a new <see cref="Task"/> with the specified action and state.
+        /// </summary>
+        /// <param name="action">The delegate that represents the code to execute in the task.</param>
+        /// <param name="state">An object representing data to be used by the action.</param>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="action"/> argument is null.
+        /// </exception>
+        public Task(Action<object> action, object state)
+            : this(action, state, null, default(CancellationToken), TaskCreationOptions.None, InternalTaskOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref="Task"/> with the specified action, state, and options.
+        /// </summary>
+        /// <param name="action">The delegate that represents the code to execute in the task.</param>
+        /// <param name="state">An object representing data to be used by the action.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="action"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task(Action<object> action, object state, CancellationToken cancellationToken)
+            : this(action, state, null, cancellationToken, TaskCreationOptions.None, InternalTaskOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref="Task"/> with the specified action, state, and options.
+        /// </summary>
+        /// <param name="action">The delegate that represents the code to execute in the task.</param>
+        /// <param name="state">An object representing data to be used by the action.</param>
+        /// <param name="creationOptions">
+        /// The <see cref="System.Threading.Tasks.TaskCreationOptions">TaskCreationOptions</see> used to
+        /// customize the Task's behavior.
+        /// </param>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="action"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="creationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskCreationOptions"/>.
+        /// </exception>
+        public Task(Action<object> action, object state, TaskCreationOptions creationOptions)
+            : this(action, state, Task.InternalCurrentIfAttached(creationOptions), default(CancellationToken), creationOptions, InternalTaskOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref="Task"/> with the specified action, state, and options.
+        /// </summary>
+        /// <param name="action">The delegate that represents the code to execute in the task.</param>
+        /// <param name="state">An object representing data to be used by the action.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <param name="creationOptions">
+        /// The <see cref="System.Threading.Tasks.TaskCreationOptions">TaskCreationOptions</see> used to
+        /// customize the Task's behavior.
+        /// </param>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="action"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="creationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskCreationOptions"/>.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task(Action<object> action, object state, CancellationToken cancellationToken, TaskCreationOptions creationOptions)
+            : this(action, state, Task.InternalCurrentIfAttached(creationOptions), cancellationToken, creationOptions, InternalTaskOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// An internal constructor used by the factory methods on task and its descendent(s).
+        /// </summary>
+        /// <param name="action">An action to execute.</param>
+        /// <param name="state">Optional state to pass to the action.</param>
+        /// <param name="parent">Parent of Task.</param>
+        /// <param name="cancellationToken">A CancellationToken for the task.</param>
+        /// <param name="scheduler">A task scheduler under which the task will run.</param>
+        /// <param name="creationOptions">Options to control its execution.</param>
+        /// <param name="internalOptions">Internal options to control its execution</param>
+        internal Task(Delegate action, object state, Task parent, CancellationToken cancellationToken,
+            TaskCreationOptions creationOptions, InternalTaskOptions internalOptions, TaskScheduler scheduler)
+        {
+            if (action == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.action);
+            }
+
+            // Keep a link to the parent if attached
+            if (parent != null && (creationOptions & TaskCreationOptions.AttachedToParent) != 0)
+            {
+                EnsureContingentPropertiesInitializedUnsafe().m_parent = parent;
+            }
+
+            TaskConstructorCore(action, state, cancellationToken, creationOptions, internalOptions, scheduler);
+        }
+
+        /// <summary>
+        /// Common logic used by the following internal ctors:
+        ///     Task()
+        ///     Task(object action, object state, Task parent, TaskCreationOptions options, TaskScheduler taskScheduler)
+        /// </summary>
+        /// <param name="action">Action for task to execute.</param>
+        /// <param name="state">Object to which to pass to action (may be null)</param>
+        /// <param name="scheduler">Task scheduler on which to run thread (only used by continuation tasks).</param>
+        /// <param name="cancellationToken">A CancellationToken for the Task.</param>
+        /// <param name="creationOptions">Options to customize behavior of Task.</param>
+        /// <param name="internalOptions">Internal options to customize behavior of Task.</param>
+        internal void TaskConstructorCore(Delegate action, object state, CancellationToken cancellationToken,
+            TaskCreationOptions creationOptions, InternalTaskOptions internalOptions, TaskScheduler scheduler)
+        {
+            m_action = action;
+            m_stateObject = state;
+            m_taskScheduler = scheduler;
+
+            // Check for validity of options
+            if ((creationOptions &
+                    ~(TaskCreationOptions.AttachedToParent |
+                      TaskCreationOptions.LongRunning |
+                      TaskCreationOptions.DenyChildAttach |
+                      TaskCreationOptions.HideScheduler |
+                      TaskCreationOptions.PreferFairness |
+                      TaskCreationOptions.RunContinuationsAsynchronously)) != 0)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.creationOptions);
+            }
+
+#if DEBUG
+            // Check the validity of internalOptions
+            int illegalInternalOptions =
+                    (int)(internalOptions &
+                            ~(InternalTaskOptions.PromiseTask |
+                              InternalTaskOptions.ContinuationTask |
+                              InternalTaskOptions.LazyCancellation |
+                              InternalTaskOptions.QueuedByRuntime));
+            Debug.Assert(illegalInternalOptions == 0, "TaskConstructorCore: Illegal internal options");
+#endif
+
+            // Assign options to m_stateAndOptionsFlag.
+            Debug.Assert(m_stateFlags == 0, "TaskConstructorCore: non-zero m_stateFlags");
+            Debug.Assert((((int)creationOptions) | OptionsMask) == OptionsMask, "TaskConstructorCore: options take too many bits");
+            int tmpFlags = (int)creationOptions | (int)internalOptions; // one write to the volatile m_stateFlags instead of two when setting the above options
+            m_stateFlags = m_action == null || (internalOptions & InternalTaskOptions.ContinuationTask) != 0 ?
+                tmpFlags | TASK_STATE_WAITINGFORACTIVATION :
+                tmpFlags;
+
+            // Now is the time to add the new task to the children list 
+            // of the creating task if the options call for it.
+            // We can safely call the creator task's AddNewChild() method to register it, 
+            // because at this point we are already on its thread of execution.
+
+            ContingentProperties props = m_contingentProperties;
+            if (props != null)
+            {
+                Task parent = props.m_parent;
+                if (parent != null
+                    && ((creationOptions & TaskCreationOptions.AttachedToParent) != 0)
+                    && ((parent.CreationOptions & TaskCreationOptions.DenyChildAttach) == 0))
+                {
+                    parent.AddNewChild();
+                }
+            }
+
+            // if we have a non-null cancellationToken, allocate the contingent properties to save it
+            // we need to do this as the very last thing in the construction path, because the CT registration could modify m_stateFlags
+            if (cancellationToken.CanBeCanceled)
+            {
+                Debug.Assert((internalOptions & InternalTaskOptions.ContinuationTask) == 0, "TaskConstructorCore: Did not expect to see cancelable token for continuation task.");
+
+                AssignCancellationToken(cancellationToken, null, null);
+            }
+
+            Debug.Assert(m_contingentProperties == null || m_contingentProperties.m_capturedContext == null,
+                "Captured an ExecutionContext when one was already captured.");
+            CapturedContext = ExecutionContext.Capture();
+        }
+
+        /// <summary>
+        /// Handles everything needed for associating a CancellationToken with a task which is being constructed.
+        /// This method is meant to be called either from the TaskConstructorCore or from ContinueWithCore.
+        /// </summary>
+        private void AssignCancellationToken(CancellationToken cancellationToken, Task antecedent, TaskContinuation continuation)
+        {
+            // There is no need to worry about concurrency issues here because we are in the constructor path of the task --
+            // there should not be any race conditions to set m_contingentProperties at this point.
+            ContingentProperties props = EnsureContingentPropertiesInitializedUnsafe();
+            props.m_cancellationToken = cancellationToken;
+
+            try
+            {
+                // If an unstarted task has a valid CancellationToken that gets signalled while the task is still not queued
+                // we need to proactively cancel it, because it may never execute to transition itself. 
+                // The only way to accomplish this is to register a callback on the CT.
+                // We exclude Promise tasks from this, because TaskCompletionSource needs to fully control the inner tasks's lifetime (i.e. not allow external cancellations)                
+                if ((((InternalTaskOptions)Options &
+                    (InternalTaskOptions.QueuedByRuntime | InternalTaskOptions.PromiseTask | InternalTaskOptions.LazyCancellation)) == 0))
+                {
+                    if (cancellationToken.IsCancellationRequested)
+                    {
+                        // Fast path for an already-canceled cancellationToken
+                        this.InternalCancel(false);
+                    }
+                    else
+                    {
+                        // Regular path for an uncanceled cancellationToken
+                        CancellationTokenRegistration ctr;
+                        if (antecedent == null)
+                        {
+                            // if no antecedent was specified, use this task's reference as the cancellation state object
+                            ctr = cancellationToken.InternalRegisterWithoutEC(s_taskCancelCallback, this);
+                        }
+                        else
+                        {
+                            // If an antecedent was specified, pack this task, its antecedent and the TaskContinuation together as a tuple 
+                            // and use it as the cancellation state object. This will be unpacked in the cancellation callback so that 
+                            // antecedent.RemoveCancellation(continuation) can be invoked.
+                            ctr = cancellationToken.InternalRegisterWithoutEC(s_taskCancelCallback,
+                                                                              new Tuple<Task, Task, TaskContinuation>(this, antecedent, continuation));
+                        }
+
+                        props.m_cancellationRegistration = new Shared<CancellationTokenRegistration>(ctr);
+                    }
+                }
+            }
+            catch
+            {
+                // If we have an exception related to our CancellationToken, then we need to subtract ourselves
+                // from our parent before throwing it.
+                Task parent = m_contingentProperties?.m_parent;
+                if ((parent != null) &&
+                    ((Options & TaskCreationOptions.AttachedToParent) != 0)
+                     && ((parent.Options & TaskCreationOptions.DenyChildAttach) == 0))
+                {
+                    parent.DisregardChild();
+                }
+                throw;
+            }
+        }
+
+
+        // Static delegate to be used as a cancellation callback on unstarted tasks that have a valid cancellation token.
+        // This is necessary to transition them into canceled state if their cancellation token is signalled while they are still not queued
+        private readonly static Action<Object> s_taskCancelCallback = new Action<Object>(TaskCancelCallback);
+        private static void TaskCancelCallback(Object o)
+        {
+            var targetTask = o as Task;
+            if (targetTask == null)
+            {
+                var tuple = o as Tuple<Task, Task, TaskContinuation>;
+                if (tuple != null)
+                {
+                    targetTask = tuple.Item1;
+
+                    Task antecedentTask = tuple.Item2;
+                    TaskContinuation continuation = tuple.Item3;
+                    antecedentTask.RemoveContinuation(continuation);
+                }
+            }
+            Debug.Assert(targetTask != null,
+                "targetTask should have been non-null, with the supplied argument being a task or a tuple containing one");
+            targetTask.InternalCancel(false);
+        }
+
+        // Debugger support
+        private string DebuggerDisplayMethodDescription
+        {
+            get
+            {
+                Delegate d = m_action;
+                return d != null ? d.Method.ToString() : "{null}";
+            }
+        }
+
+        // Internal property to process TaskCreationOptions access and mutation.
+        internal TaskCreationOptions Options => OptionsMethod(m_stateFlags);
+
+        // Similar to Options property, but allows for the use of a cached flags value rather than
+        // a read of the volatile m_stateFlags field.
+        internal static TaskCreationOptions OptionsMethod(int flags)
+        {
+            Debug.Assert((OptionsMask & 1) == 1, "OptionsMask needs a shift in Options.get");
+            return (TaskCreationOptions)(flags & OptionsMask);
+        }
+
+        // Atomically OR-in newBits to m_stateFlags, while making sure that
+        // no illegalBits are set.  Returns true on success, false on failure.
+        internal bool AtomicStateUpdate(int newBits, int illegalBits)
+        {
+            int oldFlags = m_stateFlags;
+            return
+                (oldFlags & illegalBits) == 0 &&
+                (Interlocked.CompareExchange(ref m_stateFlags, oldFlags | newBits, oldFlags) == oldFlags ||
+                 AtomicStateUpdateSlow(newBits, illegalBits));
+        }
+
+        private bool AtomicStateUpdateSlow(int newBits, int illegalBits)
+        {
+            var sw = new SpinWait();
+            do
+            {
+                int oldFlags = m_stateFlags;
+                if ((oldFlags & illegalBits) != 0) return false;
+                if (Interlocked.CompareExchange(ref m_stateFlags, oldFlags | newBits, oldFlags) == oldFlags)
+                {
+                    return true;
+                }
+                sw.SpinOnce();
+            } while (true);
+        }
+
+        internal bool AtomicStateUpdate(int newBits, int illegalBits, ref int oldFlags)
+        {
+            SpinWait sw = new SpinWait();
+            do
+            {
+                oldFlags = m_stateFlags;
+                if ((oldFlags & illegalBits) != 0) return false;
+                if (Interlocked.CompareExchange(ref m_stateFlags, oldFlags | newBits, oldFlags) == oldFlags)
+                {
+                    return true;
+                }
+                sw.SpinOnce();
+            } while (true);
+        }
+
+        /// <summary>
+        /// Sets or clears the TASK_STATE_WAIT_COMPLETION_NOTIFICATION state bit.
+        /// The debugger sets this bit to aid it in "stepping out" of an async method body.
+        /// If enabled is true, this must only be called on a task that has not yet been completed.
+        /// If enabled is false, this may be called on completed tasks.
+        /// Either way, it should only be used for promise-style tasks.
+        /// </summary>
+        /// <param name="enabled">true to set the bit; false to unset the bit.</param>
+        internal void SetNotificationForWaitCompletion(bool enabled)
+        {
+            Debug.Assert((Options & (TaskCreationOptions)InternalTaskOptions.PromiseTask) != 0,
+                "Should only be used for promise-style tasks"); // hasn't been vetted on other kinds as there hasn't been a need
+
+            if (enabled)
+            {
+                // Atomically set the END_AWAIT_NOTIFICATION bit
+                bool success = AtomicStateUpdate(TASK_STATE_WAIT_COMPLETION_NOTIFICATION,
+                                  TASK_STATE_COMPLETED_MASK | TASK_STATE_COMPLETION_RESERVED);
+                Debug.Assert(success, "Tried to set enabled on completed Task");
+            }
+            else
+            {
+                // Atomically clear the END_AWAIT_NOTIFICATION bit
+                SpinWait sw = new SpinWait();
+                while (true)
+                {
+                    int oldFlags = m_stateFlags;
+                    int newFlags = oldFlags & (~TASK_STATE_WAIT_COMPLETION_NOTIFICATION);
+                    if (Interlocked.CompareExchange(ref m_stateFlags, newFlags, oldFlags) == oldFlags) break;
+                    sw.SpinOnce();
+                }
+            }
+        }
+
+        /// <summary>
+        /// Calls the debugger notification method if the right bit is set and if
+        /// the task itself allows for the notification to proceed.
+        /// </summary>
+        /// <returns>true if the debugger was notified; otherwise, false.</returns>
+        internal bool NotifyDebuggerOfWaitCompletionIfNecessary()
+        {
+            // Notify the debugger if of any of the tasks we've waited on requires notification
+            if (IsWaitNotificationEnabled && ShouldNotifyDebuggerOfWaitCompletion)
+            {
+                NotifyDebuggerOfWaitCompletion();
+                return true;
+            }
+            return false;
+        }
+
+        /// <summary>Returns true if any of the supplied tasks require wait notification.</summary>
+        /// <param name="tasks">The tasks to check.</param>
+        /// <returns>true if any of the tasks require notification; otherwise, false.</returns>
+        internal static bool AnyTaskRequiresNotifyDebuggerOfWaitCompletion(Task[] tasks)
+        {
+            Debug.Assert(tasks != null, "Expected non-null array of tasks");
+            foreach (var task in tasks)
+            {
+                if (task != null &&
+                    task.IsWaitNotificationEnabled &&
+                    task.ShouldNotifyDebuggerOfWaitCompletion) // potential recursion
+                {
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        /// <summary>Gets whether either the end await bit is set or (not xor) the task has not completed successfully.</summary>
+        /// <returns>(DebuggerBitSet || !RanToCompletion)</returns>
+        internal bool IsWaitNotificationEnabledOrNotRanToCompletion
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                return (m_stateFlags & (Task.TASK_STATE_WAIT_COMPLETION_NOTIFICATION | Task.TASK_STATE_RAN_TO_COMPLETION))
+                        != Task.TASK_STATE_RAN_TO_COMPLETION;
+            }
+        }
+
+        /// <summary>
+        /// Determines whether we should inform the debugger that we're ending a join with a task.  
+        /// This should only be called if the debugger notification bit is set, as it is has some cost,
+        /// namely it is a virtual call (however calling it if the bit is not set is not functionally 
+        /// harmful).  Derived implementations may choose to only conditionally call down to this base 
+        /// implementation.
+        /// </summary>
+        internal virtual bool ShouldNotifyDebuggerOfWaitCompletion // ideally would be familyAndAssembly, but that can't be done in C#
+        {
+            get
+            {
+                // It's theoretically possible but extremely rare that this assert could fire because the 
+                // bit was unset between the time that it was checked and this method was called.
+                // It's so remote a chance that it's worth having the assert to protect against misuse.
+                bool isWaitNotificationEnabled = IsWaitNotificationEnabled;
+                Debug.Assert(isWaitNotificationEnabled, "Should only be called if the wait completion bit is set.");
+                return isWaitNotificationEnabled;
+            }
+        }
+
+        /// <summary>Gets whether the task's debugger notification for wait completion bit is set.</summary>
+        /// <returns>true if the bit is set; false if it's not set.</returns>
+        internal bool IsWaitNotificationEnabled // internal only to enable unit tests; would otherwise be private
+        {
+            get { return (m_stateFlags & TASK_STATE_WAIT_COMPLETION_NOTIFICATION) != 0; }
+        }
+
+        /// <summary>Placeholder method used as a breakpoint target by the debugger.  Must not be inlined or optimized.</summary>
+        /// <remarks>All joins with a task should end up calling this if their debugger notification bit is set.</remarks>
+        [MethodImpl(MethodImplOptions.NoOptimization | MethodImplOptions.NoInlining)]
+        private void NotifyDebuggerOfWaitCompletion()
+        {
+            // It's theoretically possible but extremely rare that this assert could fire because the 
+            // bit was unset between the time that it was checked and this method was called.
+            // It's so remote a chance that it's worth having the assert to protect against misuse.
+            Debug.Assert(IsWaitNotificationEnabled, "Should only be called if the wait completion bit is set.");
+
+            // Now that we're notifying the debugger, clear the bit.  The debugger should do this anyway,
+            // but this adds a bit of protection in case it fails to, and given that the debugger is involved, 
+            // the overhead here for the interlocked is negligable.  We do still rely on the debugger
+            // to clear bits, as this doesn't recursively clear bits in the case of, for example, WhenAny.
+            SetNotificationForWaitCompletion(enabled: false);
+        }
+
+
+        // Atomically mark a Task as started while making sure that it is not canceled.
+        internal bool MarkStarted()
+        {
+            return AtomicStateUpdate(TASK_STATE_STARTED, TASK_STATE_CANCELED | TASK_STATE_STARTED);
+        }
+
+        internal bool FireTaskScheduledIfNeeded(TaskScheduler ts)
+        {
+            var etwLog = TplEtwProvider.Log;
+            if (etwLog.IsEnabled() && (m_stateFlags & Task.TASK_STATE_TASKSCHEDULED_WAS_FIRED) == 0)
+            {
+                m_stateFlags |= Task.TASK_STATE_TASKSCHEDULED_WAS_FIRED;
+
+                Task currentTask = Task.InternalCurrent;
+                Task parentTask = m_contingentProperties?.m_parent;
+                etwLog.TaskScheduled(ts.Id, currentTask == null ? 0 : currentTask.Id,
+                                     this.Id, parentTask == null ? 0 : parentTask.Id, (int)this.Options,
+                                     System.Threading.Thread.GetDomainID());
+                return true;
+            }
+            else
+                return false;
+        }
+
+        /// <summary>
+        /// Internal function that will be called by a new child task to add itself to 
+        /// the children list of the parent (this).
+        /// 
+        /// Since a child task can only be created from the thread executing the action delegate
+        /// of this task, reentrancy is neither required nor supported. This should not be called from
+        /// anywhere other than the task construction/initialization codepaths.
+        /// </summary>
+        internal void AddNewChild()
+        {
+            Debug.Assert(Task.InternalCurrent == this, "Task.AddNewChild(): Called from an external context");
+
+            var props = EnsureContingentPropertiesInitialized();
+
+            if (props.m_completionCountdown == 1)
+            {
+                // A count of 1 indicates so far there was only the parent, and this is the first child task
+                // Single kid => no fuss about who else is accessing the count. Let's save ourselves 100 cycles
+                props.m_completionCountdown++;
+            }
+            else
+            {
+                // otherwise do it safely
+                Interlocked.Increment(ref props.m_completionCountdown);
+            }
+        }
+
+        // This is called in the case where a new child is added, but then encounters a CancellationToken-related exception.
+        // We need to subtract that child from m_completionCountdown, or the parent will never complete.
+        internal void DisregardChild()
+        {
+            Debug.Assert(Task.InternalCurrent == this, "Task.DisregardChild(): Called from an external context");
+
+            var props = EnsureContingentPropertiesInitialized();
+            Debug.Assert(props.m_completionCountdown >= 2, "Task.DisregardChild(): Expected parent count to be >= 2");
+            Interlocked.Decrement(ref props.m_completionCountdown);
+        }
+
+        /// <summary>
+        /// Starts the <see cref="Task"/>, scheduling it for execution to the current <see
+        /// cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>.
+        /// </summary>
+        /// <remarks>
+        /// A task may only be started and run only once.  Any attempts to schedule a task a second time
+        /// will result in an exception.
+        /// </remarks>
+        /// <exception cref="InvalidOperationException">
+        /// The <see cref="Task"/> is not in a valid state to be started. It may have already been started,
+        /// executed, or canceled, or it may have been created in a manner that doesn't support direct
+        /// scheduling.
+        /// </exception>
+        public void Start()
+        {
+            Start(TaskScheduler.Current);
+        }
+
+        /// <summary>
+        /// Starts the <see cref="Task"/>, scheduling it for execution to the specified <see
+        /// cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>.
+        /// </summary>
+        /// <remarks>
+        /// A task may only be started and run only once. Any attempts to schedule a task a second time will
+        /// result in an exception.
+        /// </remarks>
+        /// <param name="scheduler">
+        /// The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> with which to associate
+        /// and execute this task.
+        /// </param>
+        /// <exception cref="ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        /// <exception cref="InvalidOperationException">
+        /// The <see cref="Task"/> is not in a valid state to be started. It may have already been started,
+        /// executed, or canceled, or it may have been created in a manner that doesn't support direct
+        /// scheduling.
+        /// </exception>
+        public void Start(TaskScheduler scheduler)
+        {
+            // Read the volatile m_stateFlags field once and cache it for subsequent operations
+            int flags = m_stateFlags;
+
+            // Need to check this before (m_action == null) because completed tasks will
+            // set m_action to null.  We would want to know if this is the reason that m_action == null.
+            if (IsCompletedMethod(flags))
+            {
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.Task_Start_TaskCompleted);
+            }
+
+            if (scheduler == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+            }
+
+            var options = OptionsMethod(flags);
+            if ((options & (TaskCreationOptions)InternalTaskOptions.PromiseTask) != 0)
+            {
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.Task_Start_Promise);
+            }
+            if ((options & (TaskCreationOptions)InternalTaskOptions.ContinuationTask) != 0)
+            {
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.Task_Start_ContinuationTask);
+            }
+
+            // Make sure that Task only gets started once.  Or else throw an exception.
+            if (Interlocked.CompareExchange(ref m_taskScheduler, scheduler, null) != null)
+            {
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.Task_Start_AlreadyStarted);
+            }
+
+            ScheduleAndStart(true);
+        }
+
+        /// <summary>
+        /// Runs the <see cref="Task"/> synchronously on the current <see
+        /// cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// A task may only be started and run only once. Any attempts to schedule a task a second time will
+        /// result in an exception.
+        /// </para>
+        /// <para>
+        /// Tasks executed with <see cref="RunSynchronously()"/> will be associated with the current <see
+        /// cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>.
+        /// </para>
+        /// <para>
+        /// If the target scheduler does not support running this Task on the current thread, the Task will
+        /// be scheduled for execution on the scheduler, and the current thread will block until the
+        /// Task has completed execution.
+        /// </para>
+        /// </remarks>
+        /// <exception cref="InvalidOperationException">
+        /// The <see cref="Task"/> is not in a valid state to be started. It may have already been started,
+        /// executed, or canceled, or it may have been created in a manner that doesn't support direct
+        /// scheduling.
+        /// </exception>
+        public void RunSynchronously()
+        {
+            InternalRunSynchronously(TaskScheduler.Current, waitForCompletion: true);
+        }
+
+        /// <summary>
+        /// Runs the <see cref="Task"/> synchronously on the <see
+        /// cref="System.Threading.Tasks.TaskScheduler">scheduler</see> provided.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// A task may only be started and run only once. Any attempts to schedule a task a second time will
+        /// result in an exception.
+        /// </para>
+        /// <para>
+        /// If the target scheduler does not support running this Task on the current thread, the Task will
+        /// be scheduled for execution on the scheduler, and the current thread will block until the
+        /// Task has completed execution.
+        /// </para>
+        /// </remarks>
+        /// <exception cref="InvalidOperationException">
+        /// The <see cref="Task"/> is not in a valid state to be started. It may have already been started,
+        /// executed, or canceled, or it may have been created in a manner that doesn't support direct
+        /// scheduling.
+        /// </exception>
+        /// <exception cref="ArgumentNullException">The <paramref name="scheduler"/> parameter
+        /// is null.</exception>
+        /// <param name="scheduler">The scheduler on which to attempt to run this task inline.</param>
+        public void RunSynchronously(TaskScheduler scheduler)
+        {
+            if (scheduler == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+            }
+
+            InternalRunSynchronously(scheduler, waitForCompletion: true);
+        }
+
+        //
+        // Internal version of RunSynchronously that allows not waiting for completion.
+        // 
+        internal void InternalRunSynchronously(TaskScheduler scheduler, bool waitForCompletion)
+        {
+            Debug.Assert(scheduler != null, "Task.InternalRunSynchronously(): null TaskScheduler");
+
+            // Read the volatile m_stateFlags field once and cache it for subsequent operations
+            int flags = m_stateFlags;
+
+            // Can't call this method on a continuation task
+            var options = OptionsMethod(flags);
+            if ((options & (TaskCreationOptions)InternalTaskOptions.ContinuationTask) != 0)
+            {
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.Task_RunSynchronously_Continuation);
+            }
+
+            // Can't call this method on a promise-style task
+            if ((options & (TaskCreationOptions)InternalTaskOptions.PromiseTask) != 0)
+            {
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.Task_RunSynchronously_Promise);
+            }
+
+            // Can't call this method on a task that has already completed
+            if (IsCompletedMethod(flags))
+            {
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.Task_RunSynchronously_TaskCompleted);
+            }
+
+            // Make sure that Task only gets started once.  Or else throw an exception.
+            if (Interlocked.CompareExchange(ref m_taskScheduler, scheduler, null) != null)
+            {
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.Task_RunSynchronously_AlreadyStarted);
+            }
+
+            // execute only if we successfully cancel when concurrent cancel attempts are made.
+            // otherwise throw an exception, because we've been canceled.
+            if (MarkStarted())
+            {
+                bool taskQueued = false;
+                try
+                {
+                    // We wrap TryRunInline() in a try/catch block and move an excepted task to Faulted here,
+                    // but not in Wait()/WaitAll()/FastWaitAll().  Here, we know for sure that the
+                    // task will not be subsequently scheduled (assuming that the scheduler adheres
+                    // to the guideline that an exception implies that no state change took place),
+                    // so it is safe to catch the exception and move the task to a final state.  The
+                    // same cannot be said for Wait()/WaitAll()/FastWaitAll().
+                    if (!scheduler.TryRunInline(this, false))
+                    {
+                        scheduler.InternalQueueTask(this);
+                        taskQueued = true; // only mark this after successfully queuing the task.
+                    }
+
+                    // A successful TryRunInline doesn't guarantee completion, as there may be unfinished children.
+                    // Also if we queued the task above, the task may not be done yet.
+                    if (waitForCompletion && !IsCompleted)
+                    {
+                        SpinThenBlockingWait(Timeout.Infinite, default(CancellationToken));
+                    }
+                }
+                catch (Exception e)
+                {
+                    // we 1) either received an unexpected exception originating from a custom scheduler, which needs to be wrapped in a TSE and thrown
+                    //    2) or a a ThreadAbortException, which we need to skip here, because it would already have been handled in Task.Execute
+                    if (!taskQueued && !(e is ThreadAbortException))
+                    {
+                        // We had a problem with TryRunInline() or QueueTask().  
+                        // Record the exception, marking ourselves as Completed/Faulted.
+                        TaskSchedulerException tse = new TaskSchedulerException(e);
+                        AddException(tse);
+                        Finish(false);
+
+                        // Mark ourselves as "handled" to avoid crashing the finalizer thread if the caller neglects to
+                        // call Wait() on this task.
+                        // m_contingentProperties.m_exceptionsHolder *should* already exist after AddException()
+                        Debug.Assert(
+                            (m_contingentProperties != null) &&
+                            (m_contingentProperties.m_exceptionsHolder != null) &&
+                            (m_contingentProperties.m_exceptionsHolder.ContainsFaultList),
+                            "Task.InternalRunSynchronously(): Expected m_contingentProperties.m_exceptionsHolder to exist " +
+                            "and to have faults recorded.");
+                        m_contingentProperties.m_exceptionsHolder.MarkAsHandled(false);
+
+                        // And re-throw.
+                        throw tse;
+                    }
+                    // We had a problem with waiting or this is a thread abort.  Just re-throw.
+                    else throw;
+                }
+            }
+            else
+            {
+                Debug.Assert((m_stateFlags & TASK_STATE_CANCELED) != 0, "Task.RunSynchronously: expected TASK_STATE_CANCELED to be set");
+                // Can't call this method on canceled task.
+                ThrowHelper.ThrowInvalidOperationException(ExceptionResource.Task_RunSynchronously_TaskCompleted);
+            }
+        }
+
+
+        ////
+        //// Helper methods for Factory StartNew methods.
+        ////
+
+
+        // Implicitly converts action to object and handles the meat of the StartNew() logic.
+        internal static Task InternalStartNew(
+            Task creatingTask, Delegate action, object state, CancellationToken cancellationToken, TaskScheduler scheduler,
+            TaskCreationOptions options, InternalTaskOptions internalOptions)
+        {
+            // Validate arguments.
+            if (scheduler == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+            }
+
+            // Create and schedule the task. This throws an InvalidOperationException if already shut down.
+            // Here we add the InternalTaskOptions.QueuedByRuntime to the internalOptions, so that TaskConstructorCore can skip the cancellation token registration
+            Task t = new Task(action, state, creatingTask, cancellationToken, options, internalOptions | InternalTaskOptions.QueuedByRuntime, scheduler);
+
+            t.ScheduleAndStart(false);
+            return t;
+        }
+
+        /// <summary>
+        /// Gets a unique ID for a <see cref="Task">Task</see> or task continuation instance.
+        /// </summary>
+        internal static int NewId()
+        {
+            int newId = 0;
+            // We need to repeat if Interlocked.Increment wraps around and returns 0.
+            // Otherwise next time this task's Id is queried it will get a new value
+            do
+            {
+                newId = Interlocked.Increment(ref s_taskIdCounter);
+            }
+            while (newId == 0);
+            TplEtwProvider.Log.NewID(newId);
+            return newId;
+        }
+
+
+        /////////////
+        // properties
+
+        /// <summary>
+        /// Gets a unique ID for this <see cref="Task">Task</see> instance.
+        /// </summary>
+        /// <remarks>
+        /// Task IDs are assigned on-demand and do not necessarily represent the order in the which Task
+        /// instances were created.
+        /// </remarks>
+        public int Id
+        {
+            get
+            {
+                if (m_taskId == 0)
+                {
+                    int newId = NewId();
+                    Interlocked.CompareExchange(ref m_taskId, newId, 0);
+                }
+
+                return m_taskId;
+            }
+        }
+
+        /// <summary>
+        /// Returns the unique ID of the currently executing <see cref="Task">Task</see>.
+        /// </summary>
+        public static int? CurrentId
+        {
+            get
+            {
+                Task currentTask = InternalCurrent;
+                if (currentTask != null)
+                    return currentTask.Id;
+                else
+                    return null;
+            }
+        }
+
+        /// <summary>
+        /// Gets the <see cref="Task">Task</see> instance currently executing, or
+        /// null if none exists.
+        /// </summary>
+        internal static Task InternalCurrent
+        {
+            get { return t_currentTask; }
+        }
+
+        /// <summary>
+        /// Gets the Task instance currently executing if the specified creation options
+        /// contain AttachedToParent.
+        /// </summary>
+        /// <param name="options">The options to check.</param>
+        /// <returns>The current task if there is one and if AttachToParent is in the options; otherwise, null.</returns>
+        internal static Task InternalCurrentIfAttached(TaskCreationOptions creationOptions)
+        {
+            return (creationOptions & TaskCreationOptions.AttachedToParent) != 0 ? InternalCurrent : null;
+        }
+
+        /// <summary>
+        /// Gets the StackGuard object assigned to the current thread.
+        /// </summary>
+        internal static StackGuard CurrentStackGuard
+        {
+            get
+            {
+                StackGuard sg = t_stackGuard;
+                if (sg == null)
+                {
+                    t_stackGuard = sg = new StackGuard();
+                }
+                return sg;
+            }
+        }
+
+
+        /// <summary>
+        /// Gets the <see cref="T:System.AggregateException">Exception</see> that caused the <see
+        /// cref="Task">Task</see> to end prematurely. If the <see
+        /// cref="Task">Task</see> completed successfully or has not yet thrown any
+        /// exceptions, this will return null.
+        /// </summary>
+        /// <remarks>
+        /// Tasks that throw unhandled exceptions store the resulting exception and propagate it wrapped in a
+        /// <see cref="System.AggregateException"/> in calls to <see cref="Wait()">Wait</see>
+        /// or in accesses to the <see cref="Exception"/> property.  Any exceptions not observed by the time
+        /// the Task instance is garbage collected will be propagated on the finalizer thread.
+        /// </remarks>
+        public AggregateException Exception
+        {
+            get
+            {
+                AggregateException e = null;
+
+                // If you're faulted, retrieve the exception(s)
+                if (IsFaulted) e = GetExceptions(false);
+
+                // Only return an exception in faulted state (skip manufactured exceptions)
+                // A "benevolent" race condition makes it possible to return null when IsFaulted is
+                // true (i.e., if IsFaulted is set just after the check to IsFaulted above).
+                Debug.Assert((e == null) || IsFaulted, "Task.Exception_get(): returning non-null value when not Faulted");
+
+                return e;
+            }
+        }
+
+        /// <summary>
+        /// Gets the <see cref="T:System.Threading.Tasks.TaskStatus">TaskStatus</see> of this Task. 
+        /// </summary>
+        public TaskStatus Status
+        {
+            get
+            {
+                TaskStatus rval;
+
+                // get a cached copy of the state flags.  This should help us
+                // to get a consistent view of the flags if they are changing during the
+                // execution of this method.
+                int sf = m_stateFlags;
+
+                if ((sf & TASK_STATE_FAULTED) != 0) rval = TaskStatus.Faulted;
+                else if ((sf & TASK_STATE_CANCELED) != 0) rval = TaskStatus.Canceled;
+                else if ((sf & TASK_STATE_RAN_TO_COMPLETION) != 0) rval = TaskStatus.RanToCompletion;
+                else if ((sf & TASK_STATE_WAITING_ON_CHILDREN) != 0) rval = TaskStatus.WaitingForChildrenToComplete;
+                else if ((sf & TASK_STATE_DELEGATE_INVOKED) != 0) rval = TaskStatus.Running;
+                else if ((sf & TASK_STATE_STARTED) != 0) rval = TaskStatus.WaitingToRun;
+                else if ((sf & TASK_STATE_WAITINGFORACTIVATION) != 0) rval = TaskStatus.WaitingForActivation;
+                else rval = TaskStatus.Created;
+
+                return rval;
+            }
+        }
+
+        /// <summary>
+        /// Gets whether this <see cref="Task">Task</see> instance has completed
+        /// execution due to being canceled.
+        /// </summary>
+        /// <remarks>
+        /// A <see cref="Task">Task</see> will complete in Canceled state either if its <see cref="CancellationToken">CancellationToken</see> 
+        /// was marked for cancellation before the task started executing, or if the task acknowledged the cancellation request on 
+        /// its already signaled CancellationToken by throwing an 
+        /// <see cref="System.OperationCanceledException">OperationCanceledException</see> that bears the same 
+        /// <see cref="System.Threading.CancellationToken">CancellationToken</see>.
+        /// </remarks>
+        public bool IsCanceled
+        {
+            get
+            {
+                // Return true if canceled bit is set and faulted bit is not set
+                return (m_stateFlags & (TASK_STATE_CANCELED | TASK_STATE_FAULTED)) == TASK_STATE_CANCELED;
+            }
+        }
+
+        /// <summary>
+        /// Returns true if this task has a cancellation token and it was signaled.
+        /// To be used internally in execute entry codepaths.
+        /// </summary>
+        internal bool IsCancellationRequested
+        {
+            get
+            {
+                // check both the internal cancellation request flag and the CancellationToken attached to this task
+                var props = Volatile.Read(ref m_contingentProperties);
+                return props != null &&
+                    (props.m_internalCancellationRequested == CANCELLATION_REQUESTED ||
+                     props.m_cancellationToken.IsCancellationRequested);
+            }
+        }
+
+        /// <summary>
+        /// Ensures that the contingent properties field has been initialized.
+        /// ASSUMES THAT m_stateFlags IS ALREADY SET!
+        /// </summary>
+        /// <returns>The initialized contingent properties object.</returns>
+        internal ContingentProperties EnsureContingentPropertiesInitialized()
+        {
+            return LazyInitializer.EnsureInitialized(ref m_contingentProperties, () => new ContingentProperties());
+        }
+
+        /// <summary>
+        /// Without synchronization, ensures that the contingent properties field has been initialized.
+        /// ASSUMES THAT m_stateFlags IS ALREADY SET!
+        /// </summary>
+        /// <returns>The initialized contingent properties object.</returns>
+        internal ContingentProperties EnsureContingentPropertiesInitializedUnsafe()
+        {
+            return m_contingentProperties ?? (m_contingentProperties = new ContingentProperties());
+        }
+
+        /// <summary>
+        /// This internal property provides access to the CancellationToken that was set on the task 
+        /// when it was constructed.
+        /// </summary>
+        internal CancellationToken CancellationToken
+        {
+            get
+            {
+                var props = Volatile.Read(ref m_contingentProperties);
+                return (props == null) ? default(CancellationToken) : props.m_cancellationToken;
+            }
+        }
+
+        /// <summary>
+        /// Gets whether this <see cref="Task"/> threw an OperationCanceledException while its CancellationToken was signaled.
+        /// </summary>
+        internal bool IsCancellationAcknowledged
+        {
+            get { return (m_stateFlags & TASK_STATE_CANCELLATIONACKNOWLEDGED) != 0; }
+        }
+
+
+        /// <summary>
+        /// Gets whether this <see cref="Task">Task</see> has completed.
+        /// </summary>
+        /// <remarks>
+        /// <see cref="IsCompleted"/> will return true when the Task is in one of the three
+        /// final states: <see cref="System.Threading.Tasks.TaskStatus.RanToCompletion">RanToCompletion</see>,
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>, or
+        /// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>.
+        /// </remarks>
+        public bool IsCompleted
+        {
+            get
+            {
+                int stateFlags = m_stateFlags; // enable inlining of IsCompletedMethod by "cast"ing away the volatility
+                return IsCompletedMethod(stateFlags);
+            }
+        }
+
+        // Similar to IsCompleted property, but allows for the use of a cached flags value
+        // rather than reading the volatile m_stateFlags field.
+        private static bool IsCompletedMethod(int flags)
+        {
+            return (flags & TASK_STATE_COMPLETED_MASK) != 0;
+        }
+
+        public bool IsCompletedSuccessfully
+        {
+            get { return (m_stateFlags & TASK_STATE_COMPLETED_MASK) == TASK_STATE_RAN_TO_COMPLETION; }
+        }
+
+        /// <summary>
+        /// Gets the <see cref="T:System.Threading.Tasks.TaskCreationOptions">TaskCreationOptions</see> used
+        /// to create this task.
+        /// </summary>
+        public TaskCreationOptions CreationOptions
+        {
+            get { return Options & (TaskCreationOptions)(~InternalTaskOptions.InternalOptionsMask); }
+        }
+
+        /// <summary>
+        /// Gets a <see cref="T:System.Threading.WaitHandle"/> that can be used to wait for the task to
+        /// complete.
+        /// </summary>
+        /// <remarks>
+        /// Using the wait functionality provided by <see cref="Wait()"/>
+        /// should be preferred over using <see cref="IAsyncResult.AsyncWaitHandle"/> for similar
+        /// functionality.
+        /// </remarks>
+        /// <exception cref="T:System.ObjectDisposedException">
+        /// The <see cref="Task"/> has been disposed.
+        /// </exception>
+        WaitHandle IAsyncResult.AsyncWaitHandle
+        {
+            // Although a slim event is used internally to avoid kernel resource allocation, this function
+            // forces allocation of a true WaitHandle when called.
+            get
+            {
+                bool isDisposed = (m_stateFlags & TASK_STATE_DISPOSED) != 0;
+                if (isDisposed)
+                {
+                    ThrowHelper.ThrowObjectDisposedException(ExceptionResource.Task_ThrowIfDisposed);
+                }
+                return CompletedEvent.WaitHandle;
+            }
+        }
+
+        /// <summary>
+        /// Gets the state object supplied when the <see cref="Task">Task</see> was created,
+        /// or null if none was supplied.
+        /// </summary>
+        public object AsyncState
+        {
+            get { return m_stateObject; }
+        }
+
+        /// <summary>
+        /// Gets an indication of whether the asynchronous operation completed synchronously.
+        /// </summary>
+        /// <value>true if the asynchronous operation completed synchronously; otherwise, false.</value>
+        bool IAsyncResult.CompletedSynchronously
+        {
+            get
+            {
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// Provides access to the TaskScheduler responsible for executing this Task.
+        /// </summary>
+        internal TaskScheduler ExecutingTaskScheduler
+        {
+            get { return m_taskScheduler; }
+        }
+
+        /// <summary>
+        /// Provides access to factory methods for creating <see cref="Task"/> and <see cref="Task{TResult}"/> instances.
+        /// </summary>
+        /// <remarks>
+        /// The factory returned from <see cref="Factory"/> is a default instance
+        /// of <see cref="System.Threading.Tasks.TaskFactory"/>, as would result from using
+        /// the default constructor on TaskFactory.
+        /// </remarks>
+        public static TaskFactory Factory { get; } = new TaskFactory();
+
+        /// <summary>Gets a task that's already been completed successfully.</summary>
+        public static Task CompletedTask { get; } = new Task(false, (TaskCreationOptions)InternalTaskOptions.DoNotDispose, default(CancellationToken));
+
+        /// <summary>
+        /// Provides an event that can be used to wait for completion.
+        /// Only called by IAsyncResult.AsyncWaitHandle, which means that we really do need to instantiate a completion event.
+        /// </summary>
+        internal ManualResetEventSlim CompletedEvent
+        {
+            get
+            {
+                var contingentProps = EnsureContingentPropertiesInitialized();
+                if (contingentProps.m_completionEvent == null)
+                {
+                    bool wasCompleted = IsCompleted;
+                    ManualResetEventSlim newMre = new ManualResetEventSlim(wasCompleted);
+                    if (Interlocked.CompareExchange(ref contingentProps.m_completionEvent, newMre, null) != null)
+                    {
+                        // Someone else already set the value, so we will just close the event right away.
+                        newMre.Dispose();
+                    }
+                    else if (!wasCompleted && IsCompleted)
+                    {
+                        // We published the event as unset, but the task has subsequently completed.
+                        // Set the event's state properly so that callers don't deadlock.
+                        newMre.Set();
+                    }
+                }
+
+                return contingentProps.m_completionEvent;
+            }
+        }
+
+
+        /// <summary>
+        /// The property formerly known as IsFaulted.
+        /// </summary>
+        internal bool ExceptionRecorded
+        {
+            get
+            {
+                var props = Volatile.Read(ref m_contingentProperties);
+                return (props != null) && (props.m_exceptionsHolder != null) && (props.m_exceptionsHolder.ContainsFaultList);
+            }
+        }
+
+        /// <summary>
+        /// Gets whether the <see cref="Task"/> completed due to an unhandled exception.
+        /// </summary>
+        /// <remarks>
+        /// If <see cref="IsFaulted"/> is true, the Task's <see cref="Status"/> will be equal to
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">TaskStatus.Faulted</see>, and its
+        /// <see cref="Exception"/> property will be non-null.
+        /// </remarks>
+        public bool IsFaulted
+        {
+            get
+            {
+                // Faulted is "king" -- if that bit is present (regardless of other bits), we are faulted.
+                return ((m_stateFlags & TASK_STATE_FAULTED) != 0);
+            }
+        }
+
+        /// <summary>
+        /// The captured execution context for the current task to run inside
+        /// If the TASK_STATE_EXECUTIONCONTEXT_IS_NULL flag is set, this means ExecutionContext.Capture returned null, otherwise
+        /// If the captured context is the default, nothing is saved, otherwise the m_contingentProperties inflates to save the context
+        /// </summary>
+        internal ExecutionContext CapturedContext
+        {
+            get
+            {
+                if ((m_stateFlags & TASK_STATE_EXECUTIONCONTEXT_IS_NULL) == TASK_STATE_EXECUTIONCONTEXT_IS_NULL)
+                {
+                    return null;
+                }
+                else
+                {
+                    return m_contingentProperties?.m_capturedContext ?? ExecutionContext.Default;
+                }
+            }
+            set
+            {
+                // There is no need to atomically set this bit because this set() method is only called during construction, and therefore there should be no contending accesses to m_stateFlags
+                if (value == null)
+                {
+                    m_stateFlags |= TASK_STATE_EXECUTIONCONTEXT_IS_NULL;
+                }
+                else if (value != ExecutionContext.Default) // not the default context, then inflate the contingent properties and set it
+                {
+                    EnsureContingentPropertiesInitializedUnsafe().m_capturedContext = value;
+                }
+                //else do nothing, this is the default context
+            }
+        }
+
+        /////////////
+        // methods
+
+
+        /// <summary>
+        /// Disposes the <see cref="Task"/>, releasing all of its unmanaged resources.  
+        /// </summary>
+        /// <remarks>
+        /// Unlike most of the members of <see cref="Task"/>, this method is not thread-safe.
+        /// Also, <see cref="Dispose()"/> may only be called on a <see cref="Task"/> that is in one of
+        /// the final states: <see cref="System.Threading.Tasks.TaskStatus.RanToCompletion">RanToCompletion</see>,
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>, or
+        /// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>.
+        /// </remarks>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The exception that is thrown if the <see cref="Task"/> is not in 
+        /// one of the final states: <see cref="System.Threading.Tasks.TaskStatus.RanToCompletion">RanToCompletion</see>,
+        /// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>, or
+        /// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>.
+        /// </exception>        
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// Disposes the <see cref="Task"/>, releasing all of its unmanaged resources.  
+        /// </summary>
+        /// <param name="disposing">
+        /// A Boolean value that indicates whether this method is being called due to a call to <see
+        /// cref="Dispose()"/>.
+        /// </param>
+        /// <remarks>
+        /// Unlike most of the members of <see cref="Task"/>, this method is not thread-safe.
+        /// </remarks>
+        protected virtual void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                // Dispose is a nop if this task was created with the DoNotDispose internal option.
+                // This is done before the completed check, because if we're not touching any 
+                // state on the task, it's ok for it to happen before completion.
+                if ((Options & (TaskCreationOptions)InternalTaskOptions.DoNotDispose) != 0)
+                {
+                    return;
+                }
+
+                // Task must be completed to dispose
+                if (!IsCompleted)
+                {
+                    ThrowHelper.ThrowInvalidOperationException(ExceptionResource.Task_Dispose_NotCompleted);
+                }
+
+                // Dispose of the underlying completion event if it exists
+                var cp = Volatile.Read(ref m_contingentProperties);
+                if (cp != null)
+                {
+                    // Make a copy to protect against racing Disposes.
+                    // If we wanted to make this a bit safer, we could use an interlocked here,
+                    // but we state that Dispose is not thread safe.
+                    var ev = cp.m_completionEvent;
+                    if (ev != null)
+                    {
+                        // Null out the completion event in contingent props; we'll use our copy from here on out
+                        cp.m_completionEvent = null;
+
+                        // In the unlikely event that our completion event is inflated but not yet signaled,
+                        // go ahead and signal the event.  If you dispose of an unsignaled MRES, then any waiters
+                        // will deadlock; an ensuing Set() will not wake them up.  In the event of an AppDomainUnload,
+                        // there is no guarantee that anyone else is going to signal the event, and it does no harm to 
+                        // call Set() twice on m_completionEvent.
+                        if (!ev.IsSet) ev.Set();
+
+                        // Finally, dispose of the event
+                        ev.Dispose();
+                    }
+                }
+            }
+
+            // We OR the flags to indicate the object has been disposed. The task
+            // has already completed at this point, and the only conceivable race condition would
+            // be with the unsetting of the TASK_STATE_WAIT_COMPLETION_NOTIFICATION flag, which
+            // is extremely unlikely and also benign.  (Worst case: we hit a breakpoint
+            // twice instead of once in the debugger.  Weird, but not lethal.)
+            m_stateFlags |= TASK_STATE_DISPOSED;
+        }
+
+        /////////////
+        // internal helpers
+
+
+        /// <summary>
+        /// Schedules the task for execution.
+        /// </summary>
+        /// <param name="needsProtection">If true, TASK_STATE_STARTED bit is turned on in
+        /// an atomic fashion, making sure that TASK_STATE_CANCELED does not get set
+        /// underneath us.  If false, TASK_STATE_STARTED bit is OR-ed right in.  This
+        /// allows us to streamline things a bit for StartNew(), where competing cancellations
+        /// are not a problem.</param>
+        internal void ScheduleAndStart(bool needsProtection)
+        {
+            Debug.Assert(m_taskScheduler != null, "expected a task scheduler to have been selected");
+            Debug.Assert((m_stateFlags & TASK_STATE_STARTED) == 0, "task has already started");
+
+            // Set the TASK_STATE_STARTED bit
+            if (needsProtection)
+            {
+                if (!MarkStarted())
+                {
+                    // A cancel has snuck in before we could get started.  Quietly exit.
+                    return;
+                }
+            }
+            else
+            {
+                m_stateFlags |= TASK_STATE_STARTED;
+            }
+
+            if (s_asyncDebuggingEnabled)
+            {
+                AddToActiveTasks(this);
+            }
+
+            if (AsyncCausalityTracer.LoggingOn && (Options & (TaskCreationOptions)InternalTaskOptions.ContinuationTask) == 0)
+            {
+                //For all other task than TaskContinuations we want to log. TaskContinuations log in their constructor
+                AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, this.Id, "Task: " + m_action.Method.Name, 0);
+            }
+
+
+            try
+            {
+                // Queue to the indicated scheduler.
+                m_taskScheduler.InternalQueueTask(this);
+            }
+            catch (ThreadAbortException tae)
+            {
+                AddException(tae);
+                FinishThreadAbortedTask(delegateRan: false);
+            }
+            catch (Exception e)
+            {
+                // The scheduler had a problem queueing this task.  Record the exception, leaving this task in
+                // a Faulted state.
+                TaskSchedulerException tse = new TaskSchedulerException(e);
+                AddException(tse);
+                Finish(false);
+
+                // Now we need to mark ourselves as "handled" to avoid crashing the finalizer thread if we are called from StartNew(),
+                // because the exception is either propagated outside directly, or added to an enclosing parent. However we won't do this for
+                // continuation tasks, because in that case we internally eat the exception and therefore we need to make sure the user does
+                // later observe it explicitly or see it on the finalizer.
+
+                if ((Options & (TaskCreationOptions)InternalTaskOptions.ContinuationTask) == 0)
+                {
+                    // m_contingentProperties.m_exceptionsHolder *should* already exist after AddException()
+                    Debug.Assert(
+                        (m_contingentProperties != null) &&
+                        (m_contingentProperties.m_exceptionsHolder != null) &&
+                        (m_contingentProperties.m_exceptionsHolder.ContainsFaultList),
+                            "Task.ScheduleAndStart(): Expected m_contingentProperties.m_exceptionsHolder to exist " +
+                            "and to have faults recorded.");
+
+                    m_contingentProperties.m_exceptionsHolder.MarkAsHandled(false);
+                }
+                // re-throw the exception wrapped as a TaskSchedulerException.
+                throw tse;
+            }
+        }
+
+        /// <summary>
+        /// Adds an exception to the list of exceptions this task has thrown.
+        /// </summary>
+        /// <param name="exceptionObject">An object representing either an Exception or a collection of Exceptions.</param>
+        internal void AddException(object exceptionObject)
+        {
+            Debug.Assert(exceptionObject != null, "Task.AddException: Expected a non-null exception object");
+            AddException(exceptionObject, representsCancellation: false);
+        }
+
+        /// <summary>
+        /// Adds an exception to the list of exceptions this task has thrown.
+        /// </summary>
+        /// <param name="exceptionObject">An object representing either an Exception or a collection of Exceptions.</param>
+        /// <param name="representsCancellation">Whether the exceptionObject is an OperationCanceledException representing cancellation.</param>
+        internal void AddException(object exceptionObject, bool representsCancellation)
+        {
+            Debug.Assert(exceptionObject != null, "Task.AddException: Expected a non-null exception object");
+
+#if DEBUG
+            var eoAsException = exceptionObject as Exception;
+            var eoAsEnumerableException = exceptionObject as IEnumerable<Exception>;
+            var eoAsEdi = exceptionObject as ExceptionDispatchInfo;
+            var eoAsEnumerableEdi = exceptionObject as IEnumerable<ExceptionDispatchInfo>;
+
+            Debug.Assert(
+                eoAsException != null || eoAsEnumerableException != null || eoAsEdi != null || eoAsEnumerableEdi != null,
+                "Task.AddException: Expected an Exception, ExceptionDispatchInfo, or an IEnumerable<> of one of those");
+
+            var eoAsOce = exceptionObject as OperationCanceledException;
+
+            Debug.Assert(
+                !representsCancellation ||
+                eoAsOce != null ||
+                (eoAsEdi != null && eoAsEdi.SourceException is OperationCanceledException),
+                "representsCancellation should be true only if an OCE was provided.");
+#endif
+
+            //
+            // WARNING: A great deal of care went into ensuring that
+            // AddException() and GetExceptions() are never called
+            // simultaneously.  See comment at start of GetExceptions().
+            //
+
+            // Lazily initialize the holder, ensuring only one thread wins.
+            var props = EnsureContingentPropertiesInitialized();
+            if (props.m_exceptionsHolder == null)
+            {
+                TaskExceptionHolder holder = new TaskExceptionHolder(this);
+                if (Interlocked.CompareExchange(ref props.m_exceptionsHolder, holder, null) != null)
+                {
+                    // If someone else already set the value, suppress finalization.
+                    holder.MarkAsHandled(false);
+                }
+            }
+
+            lock (props)
+            {
+                props.m_exceptionsHolder.Add(exceptionObject, representsCancellation);
+            }
+        }
+
+        /// <summary>
+        /// Returns a list of exceptions by aggregating the holder's contents. Or null if
+        /// no exceptions have been thrown.
+        /// </summary>
+        /// <param name="includeTaskCanceledExceptions">Whether to include a TCE if cancelled.</param>
+        /// <returns>An aggregate exception, or null if no exceptions have been caught.</returns>
+        private AggregateException GetExceptions(bool includeTaskCanceledExceptions)
+        {
+            //
+            // WARNING: The Task/Task<TResult>/TaskCompletionSource classes
+            // have all been carefully crafted to insure that GetExceptions()
+            // is never called while AddException() is being called.  There
+            // are locks taken on m_contingentProperties in several places:
+            //
+            // -- Task<TResult>.TrySetException(): The lock allows the
+            //    task to be set to Faulted state, and all exceptions to
+            //    be recorded, in one atomic action.  
+            //
+            // -- Task.Exception_get(): The lock ensures that Task<TResult>.TrySetException()
+            //    is allowed to complete its operation before Task.Exception_get()
+            //    can access GetExceptions().
+            //
+            // -- Task.ThrowIfExceptional(): The lock insures that Wait() will
+            //    not attempt to call GetExceptions() while Task<TResult>.TrySetException()
+            //    is in the process of calling AddException().
+            //
+            // For "regular" tasks, we effectively keep AddException() and GetException()
+            // from being called concurrently by the way that the state flows.  Until
+            // a Task is marked Faulted, Task.Exception_get() returns null.  And
+            // a Task is not marked Faulted until it and all of its children have
+            // completed, which means that all exceptions have been recorded.
+            //
+            // It might be a lot easier to follow all of this if we just required
+            // that all calls to GetExceptions() and AddExceptions() were made
+            // under a lock on m_contingentProperties.  But that would also
+            // increase our lock occupancy time and the frequency with which we
+            // would need to take the lock.
+            //
+            // If you add a call to GetExceptions() anywhere in the code,
+            // please continue to maintain the invariant that it can't be
+            // called when AddException() is being called.
+            //
+
+            // We'll lazily create a TCE if the task has been canceled.
+            Exception canceledException = null;
+            if (includeTaskCanceledExceptions && IsCanceled)
+            {
+                // Backcompat: 
+                // Ideally we'd just use the cached OCE from this.GetCancellationExceptionDispatchInfo()
+                // here.  However, that would result in a potentially breaking change from .NET 4, which
+                // has the code here that throws a new exception instead of the original, and the EDI
+                // may not contain a TCE, but an OCE or any OCE-derived type, which would mean we'd be
+                // propagating an exception of a different type.
+                canceledException = new TaskCanceledException(this);
+            }
+
+            if (ExceptionRecorded)
+            {
+                // There are exceptions; get the aggregate and optionally add the canceled
+                // exception to the aggregate (if applicable).
+                Debug.Assert(m_contingentProperties != null); // ExceptionRecorded ==> m_contingentProperties != null
+
+                // No need to lock around this, as other logic prevents the consumption of exceptions
+                // before they have been completely processed.
+                return m_contingentProperties.m_exceptionsHolder.CreateExceptionObject(false, canceledException);
+            }
+            else if (canceledException != null)
+            {
+                // No exceptions, but there was a cancelation. Aggregate and return it.
+                return new AggregateException(canceledException);
+            }
+
+            return null;
+        }
+
+        /// <summary>Gets the exception dispatch infos once the task has faulted.</summary>
+        internal ReadOnlyCollection<ExceptionDispatchInfo> GetExceptionDispatchInfos()
+        {
+            bool exceptionsAvailable = IsFaulted && ExceptionRecorded;
+            Debug.Assert(exceptionsAvailable, "Must only be used when the task has faulted with exceptions.");
+            return exceptionsAvailable ?
+                m_contingentProperties.m_exceptionsHolder.GetExceptionDispatchInfos() :
+                new ReadOnlyCollection<ExceptionDispatchInfo>(new ExceptionDispatchInfo[0]);
+        }
+
+        /// <summary>Gets the ExceptionDispatchInfo containing the OperationCanceledException for this task.</summary>
+        /// <returns>The ExceptionDispatchInfo.  May be null if no OCE was stored for the task.</returns>
+        internal ExceptionDispatchInfo GetCancellationExceptionDispatchInfo()
+        {
+            Debug.Assert(IsCanceled, "Must only be used when the task has canceled.");
+            return Volatile.Read(ref m_contingentProperties)?.m_exceptionsHolder?.GetCancellationExceptionDispatchInfo(); // may be null
+        }
+
+        /// <summary>
+        /// Throws an aggregate exception if the task contains exceptions. 
+        /// </summary>
+        internal void ThrowIfExceptional(bool includeTaskCanceledExceptions)
+        {
+            Debug.Assert(IsCompleted, "ThrowIfExceptional(): Expected IsCompleted == true");
+
+            Exception exception = GetExceptions(includeTaskCanceledExceptions);
+            if (exception != null)
+            {
+                UpdateExceptionObservedStatus();
+                throw exception;
+            }
+        }
+
+        /// <summary>
+        /// Checks whether this is an attached task, and whether we are being called by the parent task.
+        /// And sets the TASK_STATE_EXCEPTIONOBSERVEDBYPARENT status flag based on that.
+        /// 
+        /// This is meant to be used internally when throwing an exception, and when WaitAll is gathering 
+        /// exceptions for tasks it waited on. If this flag gets set, the implicit wait on children 
+        /// will skip exceptions to prevent duplication.
+        /// 
+        /// This should only be called when this task has completed with an exception
+        /// 
+        /// </summary>
+        internal void UpdateExceptionObservedStatus()
+        {
+            Task parent = m_contingentProperties?.m_parent;
+            if ((parent != null)
+                && ((Options & TaskCreationOptions.AttachedToParent) != 0)
+                && ((parent.CreationOptions & TaskCreationOptions.DenyChildAttach) == 0)
+                && Task.InternalCurrent == parent)
+            {
+                m_stateFlags |= TASK_STATE_EXCEPTIONOBSERVEDBYPARENT;
+            }
+        }
+
+        /// <summary>
+        /// Checks whether the TASK_STATE_EXCEPTIONOBSERVEDBYPARENT status flag is set,
+        /// This will only be used by the implicit wait to prevent double throws
+        /// 
+        /// </summary>
+        internal bool IsExceptionObservedByParent
+        {
+            get
+            {
+                return (m_stateFlags & TASK_STATE_EXCEPTIONOBSERVEDBYPARENT) != 0;
+            }
+        }
+
+        /// <summary>
+        /// Checks whether the body was ever invoked. Used by task scheduler code to verify custom schedulers actually ran the task.
+        /// </summary>
+        internal bool IsDelegateInvoked
+        {
+            get
+            {
+                return (m_stateFlags & TASK_STATE_DELEGATE_INVOKED) != 0;
+            }
+        }
+
+        /// <summary>
+        /// Signals completion of this particular task.
+        ///
+        /// The userDelegateExecute parameter indicates whether this Finish() call comes following the
+        /// full execution of the user delegate. 
+        /// 
+        /// If userDelegateExecute is false, it mean user delegate wasn't invoked at all (either due to
+        /// a cancellation request, or because this task is a promise style Task). In this case, the steps
+        /// involving child tasks (i.e. WaitForChildren) will be skipped.
+        /// 
+        /// </summary>
+        internal void Finish(bool userDelegateExecute)
+        {
+            if (m_contingentProperties == null)
+            {
+                FinishStageTwo();
+            }
+            else
+            {
+                FinishSlow(userDelegateExecute);
+            }
+        }
+
+        private void FinishSlow(bool userDelegateExecute)
+        {
+            Debug.Assert(userDelegateExecute || m_contingentProperties != null);
+
+            if (!userDelegateExecute)
+            {
+                // delegate didn't execute => no children. We can safely call the remaining finish stages
+                FinishStageTwo();
+            }
+            else
+            {
+                ContingentProperties props = m_contingentProperties;
+
+                // Count of 1 => either all children finished, or there were none. Safe to complete ourselves 
+                // without paying the price of an Interlocked.Decrement.
+                if ((props.m_completionCountdown == 1) ||
+                    Interlocked.Decrement(ref props.m_completionCountdown) == 0) // Reaching this sub clause means there may be remaining active children,
+                                                                                 // and we could be racing with one of them to call FinishStageTwo().
+                                                                                 // So whoever does the final Interlocked.Dec is responsible to finish.
+                {
+                    FinishStageTwo();
+                }
+                else
+                {
+                    // Apparently some children still remain. It will be up to the last one to process the completion of this task on their own thread.
+                    // We will now yield the thread back to ThreadPool. Mark our state appropriately before getting out.
+
+                    // We have to use an atomic update for this and make sure not to overwrite a final state, 
+                    // because at this very moment the last child's thread may be concurrently completing us.
+                    // Otherwise we risk overwriting the TASK_STATE_RAN_TO_COMPLETION, _CANCELED or _FAULTED bit which may have been set by that child task.
+                    // Note that the concurrent update by the last child happening in FinishStageTwo could still wipe out the TASK_STATE_WAITING_ON_CHILDREN flag, 
+                    // but it is not critical to maintain, therefore we dont' need to intruduce a full atomic update into FinishStageTwo
+
+                    AtomicStateUpdate(TASK_STATE_WAITING_ON_CHILDREN, TASK_STATE_FAULTED | TASK_STATE_CANCELED | TASK_STATE_RAN_TO_COMPLETION);
+                }
+
+                // Now is the time to prune exceptional children. We'll walk the list and removes the ones whose exceptions we might have observed after they threw.
+                // we use a local variable for exceptional children here because some other thread may be nulling out m_contingentProperties.m_exceptionalChildren 
+                List<Task> exceptionalChildren = props.m_exceptionalChildren;
+                if (exceptionalChildren != null)
+                {
+                    lock (exceptionalChildren)
+                    {
+                        exceptionalChildren.RemoveAll(s_IsExceptionObservedByParentPredicate); // RemoveAll has better performance than doing it ourselves
+                    }
+                }
+            }
+        }
+
+        // statically allocated delegate for the removeall expression in Finish()
+        private readonly static Predicate<Task> s_IsExceptionObservedByParentPredicate = new Predicate<Task>((t) => { return t.IsExceptionObservedByParent; });
+
+        /// <summary>
+        /// FinishStageTwo is to be executed as soon as we known there are no more children to complete. 
+        /// It can happen i) either on the thread that originally executed this task (if no children were spawned, or they all completed by the time this task's delegate quit)
+        ///              ii) or on the thread that executed the last child.
+        /// </summary>
+        private void FinishStageTwo()
+        {
+            // At this point, the task is done executing and waiting for its children,
+            // we can transition our task to a completion state.  
+
+            ContingentProperties cp = Volatile.Read(ref m_contingentProperties);
+            if (cp != null)
+            {
+                AddExceptionsFromChildren(cp);
+            }
+
+            int completionState;
+            if (ExceptionRecorded)
+            {
+                completionState = TASK_STATE_FAULTED;
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, this.Id, AsyncCausalityStatus.Error);
+
+                if (Task.s_asyncDebuggingEnabled)
+                {
+                    RemoveFromActiveTasks(this.Id);
+                }
+            }
+            else if (IsCancellationRequested && IsCancellationAcknowledged)
+            {
+                // We transition into the TASK_STATE_CANCELED final state if the task's CT was signalled for cancellation, 
+                // and the user delegate acknowledged the cancellation request by throwing an OCE, 
+                // and the task hasn't otherwise transitioned into faulted state. (TASK_STATE_FAULTED trumps TASK_STATE_CANCELED)
+                //
+                // If the task threw an OCE without cancellation being requestsed (while the CT not being in signaled state),
+                // then we regard it as a regular exception
+
+                completionState = TASK_STATE_CANCELED;
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, this.Id, AsyncCausalityStatus.Canceled);
+
+                if (Task.s_asyncDebuggingEnabled)
+                {
+                    RemoveFromActiveTasks(this.Id);
+                }
+            }
+            else
+            {
+                completionState = TASK_STATE_RAN_TO_COMPLETION;
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, this.Id, AsyncCausalityStatus.Completed);
+
+                if (Task.s_asyncDebuggingEnabled)
+                {
+                    RemoveFromActiveTasks(this.Id);
+                }
+            }
+
+            // Use Interlocked.Exchange() to effect a memory fence, preventing
+            // any SetCompleted() (or later) instructions from sneak back before it.
+            Interlocked.Exchange(ref m_stateFlags, m_stateFlags | completionState);
+
+            // Set the completion event if it's been lazy allocated.
+            // And if we made a cancellation registration, it's now unnecessary.
+            cp = Volatile.Read(ref m_contingentProperties); // need to re-read after updating state
+            if (cp != null)
+            {
+                cp.SetCompleted();
+                cp.UnregisterCancellationCallback();
+            }
+
+            // ready to run continuations and notify parent.
+            FinishStageThree();
+        }
+
+
+        /// <summary>
+        /// Final stage of the task completion code path. Notifies the parent (if any) that another of its children are done, and runs continuations.
+        /// This function is only separated out from FinishStageTwo because these two operations are also needed to be called from CancellationCleanupLogic()
+        /// </summary>
+        internal void FinishStageThree()
+        {
+            // Release the action so that holding this task object alive doesn't also
+            // hold alive the body of the task.  We do this before notifying a parent,
+            // so that if notifying the parent completes the parent and causes
+            // its synchronous continuations to run, the GC can collect the state
+            // in the interim.  And we do it before finishing continuations, because
+            // continuations hold onto the task, and therefore are keeping it alive.
+            m_action = null;
+
+            // Notify parent if this was an attached task
+            if (m_contingentProperties != null)
+            {
+                NotifyParentIfPotentiallyAttachedTask();
+            }
+
+            // Activate continuations (if any).
+            FinishContinuations();
+        }
+
+        internal void NotifyParentIfPotentiallyAttachedTask()
+        {
+            Task parent = m_contingentProperties?.m_parent;
+            if (parent != null
+                 && ((parent.CreationOptions & TaskCreationOptions.DenyChildAttach) == 0)
+                 && (((TaskCreationOptions)(m_stateFlags & OptionsMask)) & TaskCreationOptions.AttachedToParent) != 0)
+            {
+                parent.ProcessChildCompletion(this);
+            }
+        }
+
+        /// <summary>
+        /// This is called by children of this task when they are completed.
+        /// </summary>
+        internal void ProcessChildCompletion(Task childTask)
+        {
+            Debug.Assert(childTask != null);
+            Debug.Assert(childTask.IsCompleted, "ProcessChildCompletion was called for an uncompleted task");
+
+            Debug.Assert(childTask.m_contingentProperties?.m_parent == this, "ProcessChildCompletion should only be called for a child of this task");
+
+            var props = Volatile.Read(ref m_contingentProperties);
+
+            // if the child threw and we haven't observed it we need to save it for future reference
+            if (childTask.IsFaulted && !childTask.IsExceptionObservedByParent)
+            {
+                // Lazily initialize the child exception list
+                if (props.m_exceptionalChildren == null)
+                {
+                    Interlocked.CompareExchange(ref props.m_exceptionalChildren, new List<Task>(), null);
+                }
+
+                // In rare situations involving AppDomainUnload, it's possible (though unlikely) for FinishStageTwo() to be called
+                // multiple times for the same task.  In that case, AddExceptionsFromChildren() could be nulling m_exceptionalChildren
+                // out at the same time that we're processing it, resulting in a NullReferenceException here.  We'll protect
+                // ourselves by caching m_exceptionChildren in a local variable.
+                List<Task> tmp = props.m_exceptionalChildren;
+                if (tmp != null)
+                {
+                    lock (tmp)
+                    {
+                        tmp.Add(childTask);
+                    }
+                }
+            }
+
+            if (Interlocked.Decrement(ref props.m_completionCountdown) == 0)
+            {
+                // This call came from the final child to complete, and apparently we have previously given up this task's right to complete itself.
+                // So we need to invoke the final finish stage.
+
+                FinishStageTwo();
+            }
+        }
+
+        /// <summary>
+        /// This is to be called just before the task does its final state transition. 
+        /// It traverses the list of exceptional children, and appends their aggregate exceptions into this one's exception list
+        /// </summary>
+        internal void AddExceptionsFromChildren(ContingentProperties props)
+        {
+            Debug.Assert(props != null);
+
+            // In rare occurences during AppDomainUnload() processing, it is possible for this method to be called
+            // simultaneously on the same task from two different contexts.  This can result in m_exceptionalChildren
+            // being nulled out while it is being processed, which could lead to a NullReferenceException.  To
+            // protect ourselves, we'll cache m_exceptionalChildren in a local variable.
+            List<Task> exceptionalChildren = props.m_exceptionalChildren;
+
+            if (exceptionalChildren != null)
+            {
+                // This lock is necessary because even though AddExceptionsFromChildren is last to execute, it may still 
+                // be racing with the code segment at the bottom of Finish() that prunes the exceptional child array. 
+                lock (exceptionalChildren)
+                {
+                    foreach (Task task in exceptionalChildren)
+                    {
+                        // Ensure any exceptions thrown by children are added to the parent.
+                        // In doing this, we are implicitly marking children as being "handled".
+                        Debug.Assert(task.IsCompleted, "Expected all tasks in list to be completed");
+                        if (task.IsFaulted && !task.IsExceptionObservedByParent)
+                        {
+                            TaskExceptionHolder exceptionHolder = Volatile.Read(ref task.m_contingentProperties).m_exceptionsHolder;
+                            Debug.Assert(exceptionHolder != null);
+
+                            // No locking necessary since child task is finished adding exceptions
+                            // and concurrent CreateExceptionObject() calls do not constitute
+                            // a concurrency hazard.
+                            AddException(exceptionHolder.CreateExceptionObject(false, null));
+                        }
+                    }
+                }
+
+                // Reduce memory pressure by getting rid of the array
+                props.m_exceptionalChildren = null;
+            }
+        }
+
+        /// <summary>
+        /// Special purpose Finish() entry point to be used when the task delegate throws a ThreadAbortedException
+        /// This makes a note in the state flags so that we avoid any costly synchronous operations in the finish codepath
+        /// such as inlined continuations
+        /// </summary>
+        /// <param name="delegateRan">Whether the delegate was executed.</param>
+        internal void FinishThreadAbortedTask(bool delegateRan)
+        {
+            Debug.Assert(m_contingentProperties?.m_exceptionsHolder != null,
+                "FinishThreadAbortedTask() called on a task whose exception holder wasn't initialized");
+
+            m_contingentProperties.m_exceptionsHolder.MarkAsHandled(false);
+
+            // If this method has already been called for this task, or if this task has already completed, then
+            // return before actually calling Finish().
+            if (!AtomicStateUpdate(TASK_STATE_THREAD_WAS_ABORTED,
+                            TASK_STATE_THREAD_WAS_ABORTED | TASK_STATE_RAN_TO_COMPLETION | TASK_STATE_FAULTED | TASK_STATE_CANCELED))
+            {
+                return;
+            }
+
+            Finish(delegateRan);
+        }
+
+        /// <summary>
+        /// IThreadPoolWorkItem override, which is the entry function for this task when the TP scheduler decides to run it.
+        /// 
+        /// </summary>
+        void IThreadPoolWorkItem.ExecuteWorkItem()
+        {
+            ExecuteEntryUnsafe();
+        }
+
+        /// <summary>
+        /// The ThreadPool calls this if a ThreadAbortException is thrown while trying to execute this workitem.  This may occur
+        /// before Task would otherwise be able to observe it.  
+        /// </summary>
+        void IThreadPoolWorkItem.MarkAborted(ThreadAbortException tae)
+        {
+            // If the task has marked itself as Completed, then it either a) already observed this exception (so we shouldn't handle it here)
+            // or b) completed before the exception ocurred (in which case it shouldn't count against this Task).
+            if (!IsCompleted)
+            {
+                HandleException(tae);
+                FinishThreadAbortedTask(delegateRan: false);
+            }
+        }
+
+        /// <summary>
+        /// Outermost entry function to execute this task. Handles all aspects of executing a task on the caller thread.
+        /// </summary>
+        internal bool ExecuteEntry()
+        {
+            // Do atomic state transition from queued to invoked. If we observe a task that's already invoked,
+            // we will return false so that TaskScheduler.ExecuteTask can throw an exception back to the custom scheduler.
+            // However we don't want this exception to be throw if the task was already canceled, because it's a
+            // legitimate scenario for custom schedulers to dequeue a task and mark it as canceled (example: throttling scheduler)
+            int previousState = 0;
+            if (!AtomicStateUpdate(TASK_STATE_DELEGATE_INVOKED,
+                                    TASK_STATE_DELEGATE_INVOKED | TASK_STATE_COMPLETED_MASK,
+                                    ref previousState) && (previousState & TASK_STATE_CANCELED) == 0)
+            {
+                // This task has already been invoked.  Don't invoke it again.
+                return false;
+            }
+
+            if (!IsCancellationRequested & !IsCanceled)
+            {
+                ExecuteWithThreadLocal(ref t_currentTask);
+            }
+            else
+            {
+                ExecuteEntryCancellationRequestedOrCanceled();
+            }
+
+            return true;
+        }
+
+        internal void ExecuteEntryUnsafe() // used instead of ExecuteEntry() when we don't have to worry about double-execution prevent
+        {
+            // Remember that we started running the task delegate.
+            m_stateFlags |= TASK_STATE_DELEGATE_INVOKED;
+
+            if (!IsCancellationRequested & !IsCanceled)
+            {
+                ExecuteWithThreadLocal(ref t_currentTask);
+            }
+            else
+            {
+                ExecuteEntryCancellationRequestedOrCanceled();
+            }
+        }
+
+        internal void ExecuteEntryCancellationRequestedOrCanceled()
+        {
+            if (!IsCanceled)
+            {
+                int prevState = Interlocked.Exchange(ref m_stateFlags, m_stateFlags | TASK_STATE_CANCELED);
+                if ((prevState & TASK_STATE_CANCELED) == 0)
+                {
+                    CancellationCleanupLogic();
+                }
+            }
+        }
+
+        // A trick so we can refer to the TLS slot with a byref.
+        private void ExecuteWithThreadLocal(ref Task currentTaskSlot)
+        {
+            // Remember the current task so we can restore it after running, and then
+            Task previousTask = currentTaskSlot;
+
+            // ETW event for Task Started
+            var etwLog = TplEtwProvider.Log;
+            Guid savedActivityID = new Guid();
+            bool etwIsEnabled = etwLog.IsEnabled();
+            if (etwIsEnabled)
+            {
+                if (etwLog.TasksSetActivityIds)
+                    EventSource.SetCurrentThreadActivityId(TplEtwProvider.CreateGuidForTaskID(this.Id), out savedActivityID);
+                // previousTask holds the actual "current task" we want to report in the event
+                if (previousTask != null)
+                    etwLog.TaskStarted(previousTask.m_taskScheduler.Id, previousTask.Id, this.Id);
+                else
+                    etwLog.TaskStarted(TaskScheduler.Current.Id, 0, this.Id);
+            }
+
+            bool loggingOn = AsyncCausalityTracer.LoggingOn;
+            if (loggingOn)
+                AsyncCausalityTracer.TraceSynchronousWorkStart(CausalityTraceLevel.Required, this.Id, CausalitySynchronousWork.Execution);
+
+            try
+            {
+                // place the current task into TLS.
+                currentTaskSlot = this;
+
+                // Execute the task body
+                try
+                {
+                    ExecutionContext ec = CapturedContext;
+                    if (ec == null)
+                    {
+                        // No context, just run the task directly.
+                        InnerInvoke();
+                    }
+                    else
+                    {
+                        // Invoke it under the captured ExecutionContext
+                        ExecutionContext.RunInternal(ec, s_ecCallback, this);
+                    }
+                }
+                catch (Exception exn)
+                {
+                    // Record this exception in the task's exception list
+                    HandleException(exn);
+                    if (exn is ThreadAbortException)
+                    {
+                        // This is a ThreadAbortException and it will be rethrown from this catch clause, causing us to 
+                        // skip the regular Finish codepath. In order not to leave the task unfinished, we now call 
+                        // FinishThreadAbortedTask here.
+                        FinishThreadAbortedTask(delegateRan: true);
+                    }
+                }
+
+                if (loggingOn)
+                    AsyncCausalityTracer.TraceSynchronousWorkCompletion(CausalityTraceLevel.Required, CausalitySynchronousWork.Execution);
+
+                Finish(true);
+            }
+            finally
+            {
+                currentTaskSlot = previousTask;
+
+                // ETW event for Task Completed
+                if (etwIsEnabled)
+                {
+                    // previousTask holds the actual "current task" we want to report in the event
+                    if (previousTask != null)
+                        etwLog.TaskCompleted(previousTask.m_taskScheduler.Id, previousTask.Id, this.Id, IsFaulted);
+                    else
+                        etwLog.TaskCompleted(TaskScheduler.Current.Id, 0, this.Id, IsFaulted);
+
+                    if (etwLog.TasksSetActivityIds)
+                        EventSource.SetCurrentThreadActivityId(savedActivityID);
+                }
+            }
+        }
+
+        private static readonly ContextCallback s_ecCallback = obj => ((Task)obj).InnerInvoke();
+
+        /// <summary>
+        /// The actual code which invokes the body of the task. This can be overridden in derived types.
+        /// </summary>
+        internal virtual void InnerInvoke()
+        {
+            // Invoke the delegate
+            Debug.Assert(m_action != null, "Null action in InnerInvoke()");
+            var action = m_action as Action;
+            if (action != null)
+            {
+                action();
+                return;
+            }
+            var actionWithState = m_action as Action<object>;
+            if (actionWithState != null)
+            {
+                actionWithState(m_stateObject);
+                return;
+            }
+            Debug.Fail("Invalid m_action in Task");
+        }
+
+        /// <summary>
+        /// Performs whatever handling is necessary for an unhandled exception. Normally
+        /// this just entails adding the exception to the holder object. 
+        /// </summary>
+        /// <param name="unhandledException">The exception that went unhandled.</param>
+        private void HandleException(Exception unhandledException)
+        {
+            Debug.Assert(unhandledException != null);
+
+            OperationCanceledException exceptionAsOce = unhandledException as OperationCanceledException;
+            if (exceptionAsOce != null && IsCancellationRequested &&
+                m_contingentProperties.m_cancellationToken == exceptionAsOce.CancellationToken)
+            {
+                // All conditions are satisfied for us to go into canceled state in Finish().
+                // Mark the acknowledgement.  The exception is also stored to enable it to be
+                // the exception propagated from an await.
+
+                SetCancellationAcknowledged();
+                AddException(exceptionAsOce, representsCancellation: true);
+            }
+            else
+            {
+                // Other exceptions, including any OCE from the task that doesn't match the tasks' own CT, 
+                // or that gets thrown without the CT being set will be treated as an ordinary exception 
+                // and added to the aggregate.
+
+                AddException(unhandledException);
+            }
+        }
+
+        #region Await Support
+        /// <summary>Gets an awaiter used to await this <see cref="System.Threading.Tasks.Task"/>.</summary>
+        /// <returns>An awaiter instance.</returns>
+        /// <remarks>This method is intended for compiler user rather than use directly in code.</remarks>
+        public TaskAwaiter GetAwaiter()
+        {
+            return new TaskAwaiter(this);
+        }
+
+        /// <summary>Configures an awaiter used to await this <see cref="System.Threading.Tasks.Task"/>.</summary>
+        /// <param name="continueOnCapturedContext">
+        /// true to attempt to marshal the continuation back to the original context captured; otherwise, false.
+        /// </param>
+        /// <returns>An object used to await this task.</returns>
+        public ConfiguredTaskAwaitable ConfigureAwait(bool continueOnCapturedContext)
+        {
+            return new ConfiguredTaskAwaitable(this, continueOnCapturedContext);
+        }
+
+        /// <summary>
+        /// Sets a continuation onto the <see cref="System.Threading.Tasks.Task"/>.
+        /// The continuation is scheduled to run in the current synchronization context is one exists, 
+        /// otherwise in the current task scheduler.
+        /// </summary>
+        /// <param name="continuationAction">The action to invoke when the <see cref="System.Threading.Tasks.Task"/> has completed.</param>
+        /// <param name="continueOnCapturedContext">
+        /// true to attempt to marshal the continuation back to the original context captured; otherwise, false.
+        /// </param>
+        /// <param name="flowExecutionContext">Whether to flow ExecutionContext across the await.</param>
+        /// <exception cref="System.InvalidOperationException">The awaiter was not properly initialized.</exception>
+        internal void SetContinuationForAwait(
+            Action continuationAction, bool continueOnCapturedContext, bool flowExecutionContext)
+        {
+            Debug.Assert(continuationAction != null);
+
+            // Create the best AwaitTaskContinuation object given the request.
+            // If this remains null by the end of the function, we can use the 
+            // continuationAction directly without wrapping it.
+            TaskContinuation tc = null;
+
+            // If the user wants the continuation to run on the current "context" if there is one...
+            if (continueOnCapturedContext)
+            {
+                // First try getting the current synchronization context.
+                // If the current context is really just the base SynchronizationContext type, 
+                // which is intended to be equivalent to not having a current SynchronizationContext at all, 
+                // then ignore it.  This helps with performance by avoiding unnecessary posts and queueing
+                // of work items, but more so it ensures that if code happens to publish the default context 
+                // as current, it won't prevent usage of a current task scheduler if there is one.
+                var syncCtx = SynchronizationContext.Current;
+                if (syncCtx != null && syncCtx.GetType() != typeof(SynchronizationContext))
+                {
+                    tc = new SynchronizationContextAwaitTaskContinuation(syncCtx, continuationAction, flowExecutionContext);
+                }
+                else
+                {
+                    // If there was no SynchronizationContext, then try for the current scheduler.
+                    // We only care about it if it's not the default.
+                    var scheduler = TaskScheduler.InternalCurrent;
+                    if (scheduler != null && scheduler != TaskScheduler.Default)
+                    {
+                        tc = new TaskSchedulerAwaitTaskContinuation(scheduler, continuationAction, flowExecutionContext);
+                    }
+                }
+            }
+
+            if (tc == null && flowExecutionContext)
+            {
+                // We're targeting the default scheduler, so we can use the faster path
+                // that assumes the default, and thus we don't need to store it.  If we're flowing
+                // ExecutionContext, we need to capture it and wrap it in an AwaitTaskContinuation.
+                // Otherwise, we're targeting the default scheduler and we don't need to flow ExecutionContext, so
+                // we don't actually need a continuation object.  We can just store/queue the action itself.
+                tc = new AwaitTaskContinuation(continuationAction, flowExecutionContext: true);
+            }
+
+            // Now register the continuation, and if we couldn't register it because the task is already completing,
+            // process the continuation directly (in which case make sure we schedule the continuation
+            // rather than inlining it, the latter of which could result in a rare but possible stack overflow).
+            if (tc != null)
+            {
+                if (!AddTaskContinuation(tc, addBeforeOthers: false))
+                    tc.Run(this, bCanInlineContinuationTask: false);
+            }
+            else
+            {
+                Debug.Assert(!flowExecutionContext, "We already determined we're not required to flow context.");
+                if (!AddTaskContinuation(continuationAction, addBeforeOthers: false))
+                    AwaitTaskContinuation.UnsafeScheduleAction(continuationAction, this);
+            }
+        }
+
+        /// <summary>
+        /// Sets a continuation onto the <see cref="System.Threading.Tasks.Task"/>.
+        /// The continuation is scheduled to run in the current synchronization context is one exists, 
+        /// otherwise in the current task scheduler.
+        /// </summary>
+        /// <param name="stateMachineBox">The action to invoke when the <see cref="System.Threading.Tasks.Task"/> has completed.</param>
+        /// <param name="continueOnCapturedContext">
+        /// true to attempt to marshal the continuation back to the original context captured; otherwise, false.
+        /// </param>
+        /// <exception cref="System.InvalidOperationException">The awaiter was not properly initialized.</exception>
+        internal void UnsafeSetContinuationForAwait(IAsyncStateMachineBox stateMachineBox, bool continueOnCapturedContext)
+        {
+            Debug.Assert(stateMachineBox != null);
+
+            // If the caller wants to continue on the current context/scheduler and there is one,
+            // fall back to using the state machine's delegate.
+            if (continueOnCapturedContext)
+            {
+                SynchronizationContext syncCtx = SynchronizationContext.Current;
+                if (syncCtx != null && syncCtx.GetType() != typeof(SynchronizationContext))
+                {
+                    var tc = new SynchronizationContextAwaitTaskContinuation(syncCtx, stateMachineBox.MoveNextAction, flowExecutionContext: false);
+                    if (!AddTaskContinuation(tc, addBeforeOthers: false))
+                    {
+                        tc.Run(this, canInlineContinuationTask: false);
+                    }
+                    return;
+                }
+                else
+                {
+                    TaskScheduler scheduler = TaskScheduler.InternalCurrent;
+                    if (scheduler != null && scheduler != TaskScheduler.Default)
+                    {
+                        var tc = new TaskSchedulerAwaitTaskContinuation(scheduler, stateMachineBox.MoveNextAction, flowExecutionContext: false);
+                        if (!AddTaskContinuation(tc, addBeforeOthers: false))
+                        {
+                            tc.Run(this, canInlineContinuationTask: false);
+                        }
+                        return;
+                    }
+                }
+            }
+
+            // Otherwise, add the state machine box directly as the ITaskCompletionAction continuation.
+            // If we're unable to because the task has already completed, queue the delegate.
+            if (!AddTaskContinuation(stateMachineBox, addBeforeOthers: false))
+            {
+                AwaitTaskContinuation.UnsafeScheduleAction(stateMachineBox.MoveNextAction, this);
+            }
+        }
+
+        /// <summary>Creates an awaitable that asynchronously yields back to the current context when awaited.</summary>
+        /// <returns>
+        /// A context that, when awaited, will asynchronously transition back into the current context at the 
+        /// time of the await. If the current SynchronizationContext is non-null, that is treated as the current context.
+        /// Otherwise, TaskScheduler.Current is treated as the current context.
+        /// </returns>
+        public static YieldAwaitable Yield()
+        {
+            return new YieldAwaitable();
+        }
+        #endregion
+
+        /// <summary>
+        /// Waits for the <see cref="Task"/> to complete execution.
+        /// </summary>
+        /// <exception cref="T:System.AggregateException">
+        /// The <see cref="Task"/> was canceled -or- an exception was thrown during
+        /// the execution of the <see cref="Task"/>.
+        /// </exception>
+        public void Wait()
+        {
+#if DEBUG
+            bool waitResult =
+#endif
+            Wait(Timeout.Infinite, default(CancellationToken));
+
+#if DEBUG
+            Debug.Assert(waitResult, "expected wait to succeed");
+#endif
+        }
+
+        /// <summary>
+        /// Waits for the <see cref="Task"/> to complete execution.
+        /// </summary>
+        /// <param name="timeout">
+        /// A <see cref="System.TimeSpan"/> that represents the number of milliseconds to wait, or a <see
+        /// cref="System.TimeSpan"/> that represents -1 milliseconds to wait indefinitely.
+        /// </param>
+        /// <returns>
+        /// true if the <see cref="Task"/> completed execution within the allotted time; otherwise, false.
+        /// </returns>
+        /// <exception cref="T:System.AggregateException">
+        /// The <see cref="Task"/> was canceled -or- an exception was thrown during the execution of the <see
+        /// cref="Task"/>.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// <paramref name="timeout"/> is a negative number other than -1 milliseconds, which represents an
+        /// infinite time-out -or- timeout is greater than
+        /// <see cref="System.Int32.MaxValue"/>.
+        /// </exception>
+        public bool Wait(TimeSpan timeout)
+        {
+            long totalMilliseconds = (long)timeout.TotalMilliseconds;
+            if (totalMilliseconds < -1 || totalMilliseconds > Int32.MaxValue)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.timeout);
+            }
+
+            return Wait((int)totalMilliseconds, default(CancellationToken));
+        }
+
+
+        /// <summary>
+        /// Waits for the <see cref="Task"/> to complete execution.
+        /// </summary>
+        /// <param name="cancellationToken">
+        /// A <see cref="CancellationToken"/> to observe while waiting for the task to complete.
+        /// </param>
+        /// <exception cref="T:System.OperationCanceledException">
+        /// The <paramref name="cancellationToken"/> was canceled.
+        /// </exception>
+        /// <exception cref="T:System.AggregateException">
+        /// The <see cref="Task"/> was canceled -or- an exception was thrown during the execution of the <see
+        /// cref="Task"/>.
+        /// </exception>
+        public void Wait(CancellationToken cancellationToken)
+        {
+            Wait(Timeout.Infinite, cancellationToken);
+        }
+
+
+        /// <summary>
+        /// Waits for the <see cref="Task"/> to complete execution.
+        /// </summary>
+        /// <param name="millisecondsTimeout">
+        /// The number of milliseconds to wait, or <see cref="System.Threading.Timeout.Infinite"/> (-1) to
+        /// wait indefinitely.</param>
+        /// <returns>true if the <see cref="Task"/> completed execution within the allotted time; otherwise,
+        /// false.
+        /// </returns>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// <paramref name="millisecondsTimeout"/> is a negative number other than -1, which represents an
+        /// infinite time-out.
+        /// </exception>
+        /// <exception cref="T:System.AggregateException">
+        /// The <see cref="Task"/> was canceled -or- an exception was thrown during the execution of the <see
+        /// cref="Task"/>.
+        /// </exception>
+        public bool Wait(int millisecondsTimeout)
+        {
+            return Wait(millisecondsTimeout, default(CancellationToken));
+        }
+
+
+        /// <summary>
+        /// Waits for the <see cref="Task"/> to complete execution.
+        /// </summary>
+        /// <param name="millisecondsTimeout">
+        /// The number of milliseconds to wait, or <see cref="System.Threading.Timeout.Infinite"/> (-1) to
+        /// wait indefinitely.
+        /// </param>
+        /// <param name="cancellationToken">
+        /// A <see cref="CancellationToken"/> to observe while waiting for the task to complete.
+        /// </param>
+        /// <returns>
+        /// true if the <see cref="Task"/> completed execution within the allotted time; otherwise, false.
+        /// </returns>
+        /// <exception cref="T:System.AggregateException">
+        /// The <see cref="Task"/> was canceled -or- an exception was thrown during the execution of the <see
+        /// cref="Task"/>.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// <paramref name="millisecondsTimeout"/> is a negative number other than -1, which represents an
+        /// infinite time-out.
+        /// </exception>
+        /// <exception cref="T:System.OperationCanceledException">
+        /// The <paramref name="cancellationToken"/> was canceled.
+        /// </exception>
+        public bool Wait(int millisecondsTimeout, CancellationToken cancellationToken)
+        {
+            if (millisecondsTimeout < -1)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.millisecondsTimeout);
+            }
+
+            // Return immediately if we know that we've completed "clean" -- no exceptions, no cancellations
+            // and if no notification to the debugger is required
+            if (!IsWaitNotificationEnabledOrNotRanToCompletion) // (!DebuggerBitSet && RanToCompletion)
+                return true;
+
+            // Wait, and then return if we're still not done.
+            if (!InternalWait(millisecondsTimeout, cancellationToken))
+                return false;
+
+            if (IsWaitNotificationEnabledOrNotRanToCompletion) // avoid a few unnecessary volatile reads if we completed successfully
+            {
+                // Notify the debugger of the wait completion if it's requested such a notification
+                NotifyDebuggerOfWaitCompletionIfNecessary();
+
+                // If cancellation was requested and the task was canceled, throw an 
+                // OperationCanceledException.  This is prioritized ahead of the ThrowIfExceptional
+                // call to bring more determinism to cases where the same token is used to 
+                // cancel the Wait and to cancel the Task.  Otherwise, there's a race condition between
+                // whether the Wait or the Task observes the cancellation request first,
+                // and different exceptions result from the different cases.
+                if (IsCanceled) cancellationToken.ThrowIfCancellationRequested();
+
+                // If an exception occurred, or the task was cancelled, throw an exception.
+                ThrowIfExceptional(true);
+            }
+
+            Debug.Assert((m_stateFlags & TASK_STATE_FAULTED) == 0, "Task.Wait() completing when in Faulted state.");
+
+            return true;
+        }
+
+        // Convenience method that wraps any scheduler exception in a TaskSchedulerException
+        // and rethrows it.
+        private bool WrappedTryRunInline()
+        {
+            if (m_taskScheduler == null)
+                return false;
+
+            try
+            {
+                return m_taskScheduler.TryRunInline(this, true);
+            }
+            catch (Exception e)
+            {
+                // we 1) either received an unexpected exception originating from a custom scheduler, which needs to be wrapped in a TSE and thrown
+                //    2) or a a ThreadAbortException, which we need to skip here, because it would already have been handled in Task.Execute
+                if (!(e is ThreadAbortException))
+                {
+                    TaskSchedulerException tse = new TaskSchedulerException(e);
+                    throw tse;
+                }
+                else
+                {
+                    throw;
+                }
+            }
+        }
+
+        /// <summary>
+        /// The core wait function, which is only accessible internally. It's meant to be used in places in TPL code where 
+        /// the current context is known or cached.
+        /// </summary>
+        [MethodImpl(MethodImplOptions.NoOptimization)]  // this is needed for the parallel debugger
+        internal bool InternalWait(int millisecondsTimeout, CancellationToken cancellationToken) =>
+            InternalWaitCore(millisecondsTimeout, cancellationToken);
+
+        // Separated out to allow it to be optimized (caller is marked NoOptimization for VS parallel debugger
+        // to be able to see the method on the stack and inspect arguments).
+        private bool InternalWaitCore(int millisecondsTimeout, CancellationToken cancellationToken)
+        {
+            // If the task has already completed, there's nothing to wait for.
+            bool returnValue = IsCompleted;
+            if (returnValue)
+            {
+                return true;
+            }
+
+            // ETW event for Task Wait Begin
+            var etwLog = TplEtwProvider.Log;
+            bool etwIsEnabled = etwLog.IsEnabled();
+            if (etwIsEnabled)
+            {
+                Task currentTask = Task.InternalCurrent;
+                etwLog.TaskWaitBegin(
+                    (currentTask != null ? currentTask.m_taskScheduler.Id : TaskScheduler.Default.Id), (currentTask != null ? currentTask.Id : 0),
+                    this.Id, TplEtwProvider.TaskWaitBehavior.Synchronous, 0);
+            }
+
+            // Alert a listening debugger that we can't make forward progress unless it slips threads.
+            // We call NOCTD for two reasons:
+            //    1. If the task runs on another thread, then we'll be blocked here indefinitely.
+            //    2. If the task runs inline but takes some time to complete, it will suffer ThreadAbort with possible state corruption,
+            //       and it is best to prevent this unless the user explicitly asks to view the value with thread-slipping enabled.
+            Debugger.NotifyOfCrossThreadDependency();
+
+            // We will attempt inline execution only if an infinite wait was requested
+            // Inline execution doesn't make sense for finite timeouts and if a cancellation token was specified
+            // because we don't know how long the task delegate will take.
+            if (millisecondsTimeout == Timeout.Infinite && !cancellationToken.CanBeCanceled &&
+                WrappedTryRunInline() && IsCompleted) // TryRunInline doesn't guarantee completion, as there may be unfinished children.
+            {
+                returnValue = true;
+            }
+            else
+            {
+                returnValue = SpinThenBlockingWait(millisecondsTimeout, cancellationToken);
+            }
+
+            Debug.Assert(IsCompleted || millisecondsTimeout != Timeout.Infinite);
+
+            // ETW event for Task Wait End
+            if (etwIsEnabled)
+            {
+                Task currentTask = Task.InternalCurrent;
+                if (currentTask != null)
+                {
+                    etwLog.TaskWaitEnd(currentTask.m_taskScheduler.Id, currentTask.Id, this.Id);
+                }
+                else
+                {
+                    etwLog.TaskWaitEnd(TaskScheduler.Default.Id, 0, this.Id);
+                }
+                // logically the continuation is empty so we immediately fire
+                etwLog.TaskWaitContinuationComplete(this.Id);
+            }
+
+            return returnValue;
+        }
+
+        // An MRES that gets set when Invoke is called.  This replaces old logic that looked like this:
+        //      ManualResetEventSlim mres = new ManualResetEventSlim(false, 0);
+        //      Action<Task> completionAction = delegate {mres.Set();}
+        //      AddCompletionAction(completionAction);
+        // with this:
+        //      SetOnInvokeMres mres = new SetOnInvokeMres();
+        //      AddCompletionAction(mres, addBeforeOthers: true);
+        // which saves a couple of allocations.
+        //
+        // Used in SpinThenBlockingWait (below), but could be seen as a general purpose mechanism.
+        private sealed class SetOnInvokeMres : ManualResetEventSlim, ITaskCompletionAction
+        {
+            internal SetOnInvokeMres() : base(false, 0) { }
+            public void Invoke(Task completingTask) { Set(); }
+            public bool InvokeMayRunArbitraryCode { get { return false; } }
+        }
+
+        /// <summary>
+        /// Waits for the task to complete, for a timeout to occur, or for cancellation to be requested.
+        /// The method first spins and then falls back to blocking on a new event.
+        /// </summary>
+        /// <param name="millisecondsTimeout">The timeout.</param>
+        /// <param name="cancellationToken">The token.</param>
+        /// <returns>true if the task is completed; otherwise, false.</returns>
+        private bool SpinThenBlockingWait(int millisecondsTimeout, CancellationToken cancellationToken)
+        {
+            bool infiniteWait = millisecondsTimeout == Timeout.Infinite;
+            uint startTimeTicks = infiniteWait ? 0 : (uint)Environment.TickCount;
+            bool returnValue = SpinWait(millisecondsTimeout);
+            if (!returnValue)
+            {
+                var mres = new SetOnInvokeMres();
+                try
+                {
+                    AddCompletionAction(mres, addBeforeOthers: true);
+                    if (infiniteWait)
+                    {
+                        returnValue = mres.Wait(Timeout.Infinite, cancellationToken);
+                    }
+                    else
+                    {
+                        uint elapsedTimeTicks = ((uint)Environment.TickCount) - startTimeTicks;
+                        if (elapsedTimeTicks < millisecondsTimeout)
+                        {
+                            returnValue = mres.Wait((int)(millisecondsTimeout - elapsedTimeTicks), cancellationToken);
+                        }
+                    }
+                }
+                finally
+                {
+                    if (!IsCompleted) RemoveContinuation(mres);
+                    // Don't Dispose of the MRES, because the continuation off of this task may
+                    // still be running.  This is ok, however, as we never access the MRES' WaitHandle,
+                    // and thus no finalizable resources are actually allocated.
+                }
+            }
+            return returnValue;
+        }
+
+        /// <summary>
+        /// Spins briefly while checking IsCompleted
+        /// </summary>
+        /// <param name="millisecondsTimeout">The timeout.</param>
+        /// <returns>true if the task is completed; otherwise, false.</returns>
+        /// <exception cref="System.OperationCanceledException">The wait was canceled.</exception>
+        private bool SpinWait(int millisecondsTimeout)
+        {
+            if (IsCompleted) return true;
+
+            if (millisecondsTimeout == 0)
+            {
+                // For 0-timeouts, we just return immediately.
+                return false;
+            }
+
+            int spinCount = Threading.SpinWait.SpinCountforSpinBeforeWait;
+            var spinner = new SpinWait();
+            while (spinner.Count < spinCount)
+            {
+                spinner.SpinOnce(Threading.SpinWait.Sleep1ThresholdForSpinBeforeWait);
+
+                if (IsCompleted)
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        /// <summary>
+        /// Cancels the <see cref="Task"/>.
+        /// </summary>
+        /// <param name="bCancelNonExecutingOnly"> 
+        /// Indicates whether we should only cancel non-invoked tasks.
+        /// For the default scheduler this option will only be serviced through TryDequeue.
+        /// For custom schedulers we also attempt an atomic state transition.
+        /// </param>
+        /// <returns>true if the task was successfully canceled; otherwise, false.</returns>
+        internal bool InternalCancel(bool bCancelNonExecutingOnly)
+        {
+            Debug.Assert((Options & (TaskCreationOptions)InternalTaskOptions.PromiseTask) == 0, "Task.InternalCancel() did not expect promise-style task");
+
+            bool bPopSucceeded = false;
+            bool mustCleanup = false;
+
+            TaskSchedulerException tse = null;
+
+            // If started, and running in a task context, we can try to pop the chore.
+            if ((m_stateFlags & TASK_STATE_STARTED) != 0)
+            {
+                TaskScheduler ts = m_taskScheduler;
+
+                try
+                {
+                    bPopSucceeded = (ts != null) && ts.TryDequeue(this);
+                }
+                catch (Exception e)
+                {
+                    // TryDequeue threw. We don't know whether the task was properly dequeued or not. So we must let the rest of 
+                    // the cancellation logic run its course (record the request, attempt atomic state transition and do cleanup where appropriate)
+                    // Here we will only record a TaskSchedulerException, which will later be thrown at function exit.
+
+                    if (!(e is ThreadAbortException))
+                    {
+                        tse = new TaskSchedulerException(e);
+                    }
+                }
+
+                bool bRequiresAtomicStartTransition = ts != null && ts.RequiresAtomicStartTransition;
+
+                if (!bPopSucceeded && bCancelNonExecutingOnly && bRequiresAtomicStartTransition)
+                {
+                    // The caller requested cancellation of non-invoked tasks only, and TryDequeue was one way of doing it...
+                    // Since that seems to have failed, we should now try an atomic state transition (from non-invoked state to canceled)
+                    // An atomic transition here is only safe if we know we're on a custom task scheduler, which also forces a CAS on ExecuteEntry
+
+                    // Even though this task can't have any children, we should be ready for handling any continuations that 
+                    // may be attached to it (although currently 
+                    // So we need to remeber whether we actually did the flip, so we can do clean up (finish continuations etc)
+                    mustCleanup = AtomicStateUpdate(TASK_STATE_CANCELED, TASK_STATE_DELEGATE_INVOKED | TASK_STATE_CANCELED);
+
+                    // PS: This is slightly different from the regular cancellation codepath 
+                    // since we record the cancellation request *after* doing the state transition. 
+                    // However that shouldn't matter too much because the task was never invoked, thus can't have children
+                }
+            }
+
+            if (!bCancelNonExecutingOnly || bPopSucceeded || mustCleanup)
+            {
+                // Record the cancellation request.
+                RecordInternalCancellationRequest();
+
+                // Determine whether we need to clean up
+                // This will be the case 
+                //     1) if we were able to pop, and we are able to update task state to TASK_STATE_CANCELED
+                //     2) if the task seems to be yet unstarted, and we can transition to
+                //        TASK_STATE_CANCELED before anyone else can transition into _STARTED or _CANCELED or 
+                //        _RAN_TO_COMPLETION or _FAULTED
+                // Note that we do not check for TASK_STATE_COMPLETION_RESERVED.  That only applies to promise-style
+                // tasks, and a promise-style task should not enter into this codepath.
+                if (bPopSucceeded)
+                {
+                    // hitting this would mean something wrong with the AtomicStateUpdate above
+                    Debug.Assert(!mustCleanup, "Possibly an invalid state transition call was made in InternalCancel()");
+
+                    // Include TASK_STATE_DELEGATE_INVOKED in "illegal" bits to protect against the situation where
+                    // TS.TryDequeue() returns true but the task is still left on the queue.
+                    mustCleanup = AtomicStateUpdate(TASK_STATE_CANCELED, TASK_STATE_CANCELED | TASK_STATE_DELEGATE_INVOKED);
+                }
+                else if (!mustCleanup && (m_stateFlags & TASK_STATE_STARTED) == 0)
+                {
+                    mustCleanup = AtomicStateUpdate(TASK_STATE_CANCELED,
+                        TASK_STATE_CANCELED | TASK_STATE_STARTED | TASK_STATE_RAN_TO_COMPLETION |
+                        TASK_STATE_FAULTED | TASK_STATE_DELEGATE_INVOKED);
+                }
+
+                // do the cleanup (i.e. set completion event and finish continuations)
+                if (mustCleanup)
+                {
+                    CancellationCleanupLogic();
+                }
+            }
+
+            if (tse != null)
+                throw tse;
+            else
+                return (mustCleanup);
+        }
+
+        // Breaks out logic for recording a cancellation request
+        internal void RecordInternalCancellationRequest()
+        {
+            // Record the cancellation request.
+            EnsureContingentPropertiesInitialized().m_internalCancellationRequested = CANCELLATION_REQUESTED;
+        }
+
+        // Breaks out logic for recording a cancellation request
+        // This overload should only be used for promise tasks where no cancellation token
+        // was supplied when the task was created.
+        internal void RecordInternalCancellationRequest(CancellationToken tokenToRecord)
+        {
+            RecordInternalCancellationRequest();
+
+            Debug.Assert((Options & (TaskCreationOptions)InternalTaskOptions.PromiseTask) != 0, "Task.RecordInternalCancellationRequest(CancellationToken) only valid for promise-style task");
+            Debug.Assert(m_contingentProperties.m_cancellationToken == default(CancellationToken));
+
+            // Store the supplied cancellation token as this task's token.
+            // Waiting on this task will then result in an OperationCanceledException containing this token.
+            if (tokenToRecord != default(CancellationToken))
+            {
+                m_contingentProperties.m_cancellationToken = tokenToRecord;
+            }
+        }
+
+        // Breaks out logic for recording a cancellation request
+        // This overload should only be used for promise tasks where no cancellation token
+        // was supplied when the task was created.
+        internal void RecordInternalCancellationRequest(CancellationToken tokenToRecord, object cancellationException)
+        {
+            RecordInternalCancellationRequest(tokenToRecord);
+
+            // Store the supplied cancellation exception
+            if (cancellationException != null)
+            {
+#if DEBUG
+                var oce = cancellationException as OperationCanceledException;
+                if (oce == null)
+                {
+                    var edi = cancellationException as ExceptionDispatchInfo;
+                    Debug.Assert(edi != null, "Expected either an OCE or an EDI");
+                    oce = edi.SourceException as OperationCanceledException;
+                    Debug.Assert(oce != null, "Expected EDI to contain an OCE");
+                }
+                Debug.Assert(oce.CancellationToken == tokenToRecord,
+                                "Expected OCE's token to match the provided token.");
+#endif
+                AddException(cancellationException, representsCancellation: true);
+            }
+        }
+
+        // ASSUMES THAT A SUCCESSFUL CANCELLATION HAS JUST OCCURRED ON THIS TASK!!!
+        // And this method should be called at most once per task.
+        internal void CancellationCleanupLogic()
+        {
+            Debug.Assert((m_stateFlags & (TASK_STATE_CANCELED | TASK_STATE_COMPLETION_RESERVED)) != 0, "Task.CancellationCleanupLogic(): Task not canceled or reserved.");
+            // I'd like to do this, but there is a small window for a race condition.  If someone calls Wait() between InternalCancel() and
+            // here, that will set m_completionEvent, leading to a meaningless/harmless assertion.
+            //Debug.Assert((m_completionEvent == null) || !m_completionEvent.IsSet, "Task.CancellationCleanupLogic(): Completion event already set.");
+
+            // This may have been set already, but we need to make sure.
+            Interlocked.Exchange(ref m_stateFlags, m_stateFlags | TASK_STATE_CANCELED);
+
+            // Fire completion event if it has been lazily initialized
+            var cp = Volatile.Read(ref m_contingentProperties);
+            if (cp != null)
+            {
+                cp.SetCompleted();
+                cp.UnregisterCancellationCallback();
+            }
+
+            if (AsyncCausalityTracer.LoggingOn)
+                AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, this.Id, AsyncCausalityStatus.Canceled);
+
+            if (Task.s_asyncDebuggingEnabled)
+            {
+                RemoveFromActiveTasks(this.Id);
+            }
+
+            // Notify parents, fire continuations, other cleanup.
+            FinishStageThree();
+        }
+
+
+        /// <summary>
+        /// Sets the task's cancellation acknowledged flag.
+        /// </summary>    
+        private void SetCancellationAcknowledged()
+        {
+            Debug.Assert(this == Task.InternalCurrent, "SetCancellationAcknowledged() should only be called while this is still the current task");
+            Debug.Assert(IsCancellationRequested, "SetCancellationAcknowledged() should not be called if the task's CT wasn't signaled");
+
+            m_stateFlags |= TASK_STATE_CANCELLATIONACKNOWLEDGED;
+        }
+
+
+        //
+        // Continuation passing functionality (aka ContinueWith)
+        //
+
+
+
+
+        /// <summary>
+        /// Runs all of the continuations, as appropriate.
+        /// </summary>
+        internal void FinishContinuations()
+        {
+            // Atomically store the fact that this task is completing.  From this point on, the adding of continuations will
+            // result in the continuations being run/launched directly rather than being added to the continuation list.
+            // Then if we grabbed any continuations, run them.
+            object continuationObject = Interlocked.Exchange(ref m_continuationObject, s_taskCompletionSentinel);
+            if (continuationObject != null)
+            {
+                RunContinuations(continuationObject);
+            }
+        }
+
+        private void RunContinuations(object continuationObject) // separated out of FinishContinuations to enable it to be inlined
+        {
+            Debug.Assert(continuationObject != null);
+
+            TplEtwProvider etw = TplEtwProvider.Log;
+            bool tplEtwProviderLoggingEnabled = etw.IsEnabled();
+            if (tplEtwProviderLoggingEnabled)
+            {
+                etw.RunningContinuation(Id, continuationObject);
+            }
+
+            if (AsyncCausalityTracer.LoggingOn)
+                AsyncCausalityTracer.TraceSynchronousWorkStart(CausalityTraceLevel.Required, this.Id, CausalitySynchronousWork.CompletionNotification);
+
+            // Skip synchronous execution of continuations if this task's thread was aborted
+            bool canInlineContinuations = !(((m_stateFlags & TASK_STATE_THREAD_WAS_ABORTED) != 0) ||
+                                             (RuntimeThread.CurrentThread.ThreadState == ThreadState.AbortRequested) ||
+                                             ((m_stateFlags & (int)TaskCreationOptions.RunContinuationsAsynchronously) != 0));
+
+            switch (continuationObject)
+            {
+                // Handle the single IAsyncStateMachineBox case.  This could be handled as part of the ITaskCompletionAction
+                // but we want to ensure that inlining is properly handled in the face of schedulers, so its behavior
+                // needs to be customized ala raw Actions.  This is also the most important case, as it represents the
+                // most common form of continuation, so we check it first.
+                case IAsyncStateMachineBox stateMachineBox:
+                    AwaitTaskContinuation.RunOrScheduleAction(stateMachineBox, canInlineContinuations);
+                    LogFinishCompletionNotification();
+                    return;
+
+                // Handle the single Action case.
+                case Action action:
+                    AwaitTaskContinuation.RunOrScheduleAction(action, canInlineContinuations);
+                    LogFinishCompletionNotification();
+                    return;
+
+                // Handle the single TaskContinuation case.
+                case TaskContinuation tc:
+                    tc.Run(this, canInlineContinuations);
+                    LogFinishCompletionNotification();
+                    return;
+
+                // Handle the single ITaskCompletionAction case.
+                case ITaskCompletionAction completionAction:
+                    RunOrQueueCompletionAction(completionAction, canInlineContinuations);
+                    LogFinishCompletionNotification();
+                    return;
+            }
+
+            // Not a single; it must be a list.
+            List<object> continuations = (List<object>)continuationObject;
+
+            //
+            // Begin processing of continuation list
+            //
+
+            // Wait for any concurrent adds or removes to be retired
+            lock (continuations) { }
+            int continuationCount = continuations.Count;
+
+            // Fire the asynchronous continuations first ...
+            for (int i = 0; i < continuationCount; i++)
+            {
+                // Synchronous continuation tasks will have the ExecuteSynchronously option,
+                // and we're looking for asynchronous tasks...
+                if (continuations[i] is StandardTaskContinuation tc &&
+                    (tc.m_options & TaskContinuationOptions.ExecuteSynchronously) == 0)
+                {
+                    if (tplEtwProviderLoggingEnabled)
+                    {
+                        etw.RunningContinuationList(Id, i, tc);
+                    }
+                    continuations[i] = null; // so that we can skip this later
+                    tc.Run(this, canInlineContinuations);
+                }
+            }
+
+            // ... and then fire the synchronous continuations (if there are any).
+            // This includes ITaskCompletionAction, AwaitTaskContinuations, IAsyncStateMachineBox,
+            // and Action delegates, which are all by default implicitly synchronous.
+            for (int i = 0; i < continuationCount; i++)
+            {
+                object currentContinuation = continuations[i];
+                if (currentContinuation == null)
+                {
+                    continue;
+                }
+                continuations[i] = null; // to enable free'ing up memory earlier
+                if (tplEtwProviderLoggingEnabled)
+                {
+                    etw.RunningContinuationList(Id, i, currentContinuation);
+                }
+
+                switch (currentContinuation)
+                {
+                    case IAsyncStateMachineBox stateMachineBox:
+                        AwaitTaskContinuation.RunOrScheduleAction(stateMachineBox, canInlineContinuations);
+                        break;
+
+                    case Action action:
+                        AwaitTaskContinuation.RunOrScheduleAction(action, canInlineContinuations);
+                        break;
+
+                    case TaskContinuation tc:
+                        tc.Run(this, canInlineContinuations);
+                        break;
+
+                    default:
+                        Debug.Assert(currentContinuation is ITaskCompletionAction);
+                        RunOrQueueCompletionAction((ITaskCompletionAction)currentContinuation, canInlineContinuations);
+                        break;
+                }
+            }
+
+            LogFinishCompletionNotification();
+        }
+
+        private void RunOrQueueCompletionAction(ITaskCompletionAction completionAction, bool allowInlining)
+        {
+            if (allowInlining || !completionAction.InvokeMayRunArbitraryCode)
+            {
+                completionAction.Invoke(this);
+            }
+            else
+            {
+                ThreadPool.UnsafeQueueCustomWorkItem(new CompletionActionInvoker(completionAction, this), forceGlobal: false);
+            }
+        }
+
+        private void LogFinishCompletionNotification()
+        {
+            if (AsyncCausalityTracer.LoggingOn)
+                AsyncCausalityTracer.TraceSynchronousWorkCompletion(CausalityTraceLevel.Required, CausalitySynchronousWork.CompletionNotification);
+        }
+
+        #region Continuation methods
+
+        #region Action<Task> continuation
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        public Task ContinueWith(Action<Task> continuationAction)
+        {
+            return ContinueWith(continuationAction, TaskScheduler.Current, default(CancellationToken), TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="cancellationToken"> The <see cref="CancellationToken"/> that will be assigned to the new continuation task.</param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task ContinueWith(Action<Task> continuationAction, CancellationToken cancellationToken)
+        {
+            return ContinueWith(continuationAction, TaskScheduler.Current, cancellationToken, TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task"/> completes.  When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        public Task ContinueWith(Action<Task> continuationAction, TaskScheduler scheduler)
+        {
+            return ContinueWith(continuationAction, scheduler, default(CancellationToken), TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed. If the continuation criteria specified through the <paramref
+        /// name="continuationOptions"/> parameter are not met, the continuation task will be canceled
+        /// instead of scheduled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        public Task ContinueWith(Action<Task> continuationAction, TaskContinuationOptions continuationOptions)
+        {
+            return ContinueWith(continuationAction, TaskScheduler.Current, default(CancellationToken), continuationOptions);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new continuation task.</param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its
+        /// execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed. If the criteria specified through the <paramref name="continuationOptions"/> parameter
+        /// are not met, the continuation task will be canceled instead of scheduled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task ContinueWith(Action<Task> continuationAction, CancellationToken cancellationToken,
+                                 TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            return ContinueWith(continuationAction, scheduler, cancellationToken, continuationOptions);
+        }
+
+        // Same as the above overload, just with a stack mark parameter.
+        private Task ContinueWith(Action<Task> continuationAction, TaskScheduler scheduler,
+            CancellationToken cancellationToken, TaskContinuationOptions continuationOptions)
+        {
+            // Throw on continuation with null action
+            if (continuationAction == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationAction);
+            }
+
+            // Throw on continuation with null TaskScheduler
+            if (scheduler == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+            }
+
+            TaskCreationOptions creationOptions;
+            InternalTaskOptions internalOptions;
+            CreationOptionsFromContinuationOptions(continuationOptions, out creationOptions, out internalOptions);
+
+            Task continuationTask = new ContinuationTaskFromTask(
+                this, continuationAction, null,
+                creationOptions, internalOptions
+            );
+
+            // Register the continuation.  If synchronous execution is requested, this may
+            // actually invoke the continuation before returning.
+            ContinueWithCore(continuationTask, scheduler, cancellationToken, continuationOptions);
+
+            return continuationTask;
+        }
+        #endregion
+
+        #region Action<Task, Object> continuation
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task as and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation action.</param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        public Task ContinueWith(Action<Task, Object> continuationAction, Object state)
+        {
+            return ContinueWith(continuationAction, state, TaskScheduler.Current, default(CancellationToken), TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation action.</param>
+        /// <param name="cancellationToken"> The <see cref="CancellationToken"/> that will be assigned to the new continuation task.</param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task ContinueWith(Action<Task, Object> continuationAction, Object state, CancellationToken cancellationToken)
+        {
+            return ContinueWith(continuationAction, state, TaskScheduler.Current, cancellationToken, TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task"/> completes.  When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation action.</param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        public Task ContinueWith(Action<Task, Object> continuationAction, Object state, TaskScheduler scheduler)
+        {
+            return ContinueWith(continuationAction, state, scheduler, default(CancellationToken), TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation action.</param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed. If the continuation criteria specified through the <paramref
+        /// name="continuationOptions"/> parameter are not met, the continuation task will be canceled
+        /// instead of scheduled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        public Task ContinueWith(Action<Task, Object> continuationAction, Object state, TaskContinuationOptions continuationOptions)
+        {
+            return ContinueWith(continuationAction, state, TaskScheduler.Current, default(CancellationToken), continuationOptions);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation action.</param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new continuation task.</param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its
+        /// execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed. If the criteria specified through the <paramref name="continuationOptions"/> parameter
+        /// are not met, the continuation task will be canceled instead of scheduled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task ContinueWith(Action<Task, Object> continuationAction, Object state, CancellationToken cancellationToken,
+                                 TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            return ContinueWith(continuationAction, state, scheduler, cancellationToken, continuationOptions);
+        }
+
+        // Same as the above overload, just with a stack mark parameter.
+        private Task ContinueWith(Action<Task, Object> continuationAction, Object state, TaskScheduler scheduler,
+            CancellationToken cancellationToken, TaskContinuationOptions continuationOptions)
+        {
+            // Throw on continuation with null action
+            if (continuationAction == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationAction);
+            }
+
+            // Throw on continuation with null TaskScheduler
+            if (scheduler == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+            }
+
+            TaskCreationOptions creationOptions;
+            InternalTaskOptions internalOptions;
+            CreationOptionsFromContinuationOptions(continuationOptions, out creationOptions, out internalOptions);
+
+            Task continuationTask = new ContinuationTaskFromTask(
+                this, continuationAction, state,
+                creationOptions, internalOptions
+            );
+
+            // Register the continuation.  If synchronous execution is requested, this may
+            // actually invoke the continuation before returning.
+            ContinueWithCore(continuationTask, scheduler, cancellationToken, continuationOptions);
+
+            return continuationTask;
+        }
+
+        #endregion
+
+        #region Func<Task, TResult> continuation
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <typeparam name="TResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task{TResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TResult}"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        public Task<TResult> ContinueWith<TResult>(Func<Task, TResult> continuationFunction)
+        {
+            return ContinueWith<TResult>(continuationFunction, TaskScheduler.Current, default(CancellationToken),
+                TaskContinuationOptions.None);
+        }
+
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <typeparam name="TResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new continuation task.</param>
+        /// <returns>A new continuation <see cref="Task{TResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TResult}"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TResult> ContinueWith<TResult>(Func<Task, TResult> continuationFunction, CancellationToken cancellationToken)
+        {
+            return ContinueWith<TResult>(continuationFunction, TaskScheduler.Current, cancellationToken, TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <typeparam name="TResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task"/> completes.  When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task{TResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TResult}"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        public Task<TResult> ContinueWith<TResult>(Func<Task, TResult> continuationFunction, TaskScheduler scheduler)
+        {
+            return ContinueWith<TResult>(continuationFunction, scheduler, default(CancellationToken), TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <typeparam name="TResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task{TResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TResult}"/> will not be scheduled for execution until the current task has
+        /// completed. If the continuation criteria specified through the <paramref
+        /// name="continuationOptions"/> parameter are not met, the continuation task will be canceled
+        /// instead of scheduled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        public Task<TResult> ContinueWith<TResult>(Func<Task, TResult> continuationFunction, TaskContinuationOptions continuationOptions)
+        {
+            return ContinueWith<TResult>(continuationFunction, TaskScheduler.Current, default(CancellationToken), continuationOptions);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <typeparam name="TResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its
+        /// execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task{TResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TResult}"/> will not be scheduled for execution until the current task has
+        /// completed. If the criteria specified through the <paramref name="continuationOptions"/> parameter
+        /// are not met, the continuation task will be canceled instead of scheduled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TResult> ContinueWith<TResult>(Func<Task, TResult> continuationFunction, CancellationToken cancellationToken,
+                                                   TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            return ContinueWith<TResult>(continuationFunction, scheduler, cancellationToken, continuationOptions);
+        }
+
+        // Same as the above overload, just with a stack mark parameter.
+        private Task<TResult> ContinueWith<TResult>(Func<Task, TResult> continuationFunction, TaskScheduler scheduler,
+            CancellationToken cancellationToken, TaskContinuationOptions continuationOptions)
+        {
+            // Throw on continuation with null function
+            if (continuationFunction == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+            }
+
+            // Throw on continuation with null task scheduler
+            if (scheduler == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+            }
+
+            TaskCreationOptions creationOptions;
+            InternalTaskOptions internalOptions;
+            CreationOptionsFromContinuationOptions(continuationOptions, out creationOptions, out internalOptions);
+
+            Task<TResult> continuationTask = new ContinuationResultTaskFromTask<TResult>(
+                this, continuationFunction, null,
+                creationOptions, internalOptions
+            );
+
+            // Register the continuation.  If synchronous execution is requested, this may
+            // actually invoke the continuation before returning.
+            ContinueWithCore(continuationTask, scheduler, cancellationToken, continuationOptions);
+
+            return continuationTask;
+        }
+        #endregion
+
+        #region Func<Task, Object, TResult> continuation
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <typeparam name="TResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation function.</param>
+        /// <returns>A new continuation <see cref="Task{TResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TResult}"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        public Task<TResult> ContinueWith<TResult>(Func<Task, Object, TResult> continuationFunction, Object state)
+        {
+            return ContinueWith<TResult>(continuationFunction, state, TaskScheduler.Current, default(CancellationToken),
+                TaskContinuationOptions.None);
+        }
+
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <typeparam name="TResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation function.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new continuation task.</param>
+        /// <returns>A new continuation <see cref="Task{TResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TResult}"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TResult> ContinueWith<TResult>(Func<Task, Object, TResult> continuationFunction, Object state, CancellationToken cancellationToken)
+        {
+            return ContinueWith<TResult>(continuationFunction, state, TaskScheduler.Current, cancellationToken, TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <typeparam name="TResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task"/> completes.  When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation function.</param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task{TResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TResult}"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        public Task<TResult> ContinueWith<TResult>(Func<Task, Object, TResult> continuationFunction, Object state, TaskScheduler scheduler)
+        {
+            return ContinueWith<TResult>(continuationFunction, state, scheduler, default(CancellationToken), TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <typeparam name="TResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation function.</param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task{TResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TResult}"/> will not be scheduled for execution until the current task has
+        /// completed. If the continuation criteria specified through the <paramref
+        /// name="continuationOptions"/> parameter are not met, the continuation task will be canceled
+        /// instead of scheduled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        public Task<TResult> ContinueWith<TResult>(Func<Task, Object, TResult> continuationFunction, Object state, TaskContinuationOptions continuationOptions)
+        {
+            return ContinueWith<TResult>(continuationFunction, state, TaskScheduler.Current, default(CancellationToken), continuationOptions);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task"/> completes.
+        /// </summary>
+        /// <typeparam name="TResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation function.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its
+        /// execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task{TResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TResult}"/> will not be scheduled for execution until the current task has
+        /// completed. If the criteria specified through the <paramref name="continuationOptions"/> parameter
+        /// are not met, the continuation task will be canceled instead of scheduled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TResult> ContinueWith<TResult>(Func<Task, Object, TResult> continuationFunction, Object state, CancellationToken cancellationToken,
+                                                   TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            return ContinueWith<TResult>(continuationFunction, state, scheduler, cancellationToken, continuationOptions);
+        }
+
+        // Same as the above overload, just with a stack mark parameter.
+        private Task<TResult> ContinueWith<TResult>(Func<Task, Object, TResult> continuationFunction, Object state, TaskScheduler scheduler,
+            CancellationToken cancellationToken, TaskContinuationOptions continuationOptions)
+        {
+            // Throw on continuation with null function
+            if (continuationFunction == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+            }
+
+            // Throw on continuation with null task scheduler
+            if (scheduler == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+            }
+
+            TaskCreationOptions creationOptions;
+            InternalTaskOptions internalOptions;
+            CreationOptionsFromContinuationOptions(continuationOptions, out creationOptions, out internalOptions);
+
+            Task<TResult> continuationTask = new ContinuationResultTaskFromTask<TResult>(
+                this, continuationFunction, state,
+                creationOptions, internalOptions
+            );
+
+            // Register the continuation.  If synchronous execution is requested, this may
+            // actually invoke the continuation before returning.
+            ContinueWithCore(continuationTask, scheduler, cancellationToken, continuationOptions);
+
+            return continuationTask;
+        }
+        #endregion
+
+        /// <summary>
+        /// Converts TaskContinuationOptions to TaskCreationOptions, and also does
+        /// some validity checking along the way.
+        /// </summary>
+        /// <param name="continuationOptions">Incoming TaskContinuationOptions</param>
+        /// <param name="creationOptions">Outgoing TaskCreationOptions</param>
+        /// <param name="internalOptions">Outgoing InternalTaskOptions</param>
+        internal static void CreationOptionsFromContinuationOptions(
+            TaskContinuationOptions continuationOptions,
+            out TaskCreationOptions creationOptions,
+            out InternalTaskOptions internalOptions)
+        {
+            // This is used a couple of times below
+            const TaskContinuationOptions NotOnAnything =
+                TaskContinuationOptions.NotOnCanceled |
+                TaskContinuationOptions.NotOnFaulted |
+                TaskContinuationOptions.NotOnRanToCompletion;
+
+            const TaskContinuationOptions CreationOptionsMask =
+                TaskContinuationOptions.PreferFairness |
+                TaskContinuationOptions.LongRunning |
+                TaskContinuationOptions.DenyChildAttach |
+                TaskContinuationOptions.HideScheduler |
+                TaskContinuationOptions.AttachedToParent |
+                TaskContinuationOptions.RunContinuationsAsynchronously;
+
+            // Check that LongRunning and ExecuteSynchronously are not specified together
+            const TaskContinuationOptions IllegalMask = TaskContinuationOptions.ExecuteSynchronously | TaskContinuationOptions.LongRunning;
+            if ((continuationOptions & IllegalMask) == IllegalMask)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.continuationOptions, ExceptionResource.Task_ContinueWith_ESandLR);
+            }
+
+            // Check that no illegal options were specified
+            if ((continuationOptions &
+                ~(CreationOptionsMask | NotOnAnything |
+                    TaskContinuationOptions.LazyCancellation | TaskContinuationOptions.ExecuteSynchronously)) != 0)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.continuationOptions);
+            }
+
+            // Check that we didn't specify "not on anything"
+            if ((continuationOptions & NotOnAnything) == NotOnAnything)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.continuationOptions, ExceptionResource.Task_ContinueWith_NotOnAnything);
+            }
+
+            // This passes over all but LazyCancellation, which has no representation in TaskCreationOptions
+            creationOptions = (TaskCreationOptions)(continuationOptions & CreationOptionsMask);
+
+            // internalOptions has at least ContinuationTask and possibly LazyCancellation
+            internalOptions = (continuationOptions & TaskContinuationOptions.LazyCancellation) != 0 ?
+                InternalTaskOptions.ContinuationTask | InternalTaskOptions.LazyCancellation :
+                InternalTaskOptions.ContinuationTask;
+        }
+
+
+        /// <summary>
+        /// Registers the continuation and possibly runs it (if the task is already finished).
+        /// </summary>
+        /// <param name="continuationTask">The continuation task itself.</param>
+        /// <param name="scheduler">TaskScheduler with which to associate continuation task.</param>
+        /// <param name="options">Restrictions on when the continuation becomes active.</param>
+        internal void ContinueWithCore(Task continuationTask,
+                                       TaskScheduler scheduler,
+                                       CancellationToken cancellationToken,
+                                       TaskContinuationOptions options)
+        {
+            Debug.Assert(continuationTask != null, "Task.ContinueWithCore(): null continuationTask");
+            Debug.Assert(scheduler != null, "Task.ContinueWithCore(): null scheduler");
+            Debug.Assert(!continuationTask.IsCompleted, "Did not expect continuationTask to be completed");
+
+            // Create a TaskContinuation
+            TaskContinuation continuation = new StandardTaskContinuation(continuationTask, options, scheduler);
+
+            // If cancellationToken is cancellable, then assign it.  
+            if (cancellationToken.CanBeCanceled)
+            {
+                if (IsCompleted || cancellationToken.IsCancellationRequested)
+                {
+                    // If the antecedent has completed, then we will not be queuing up
+                    // the continuation in the antecedent's continuation list.  Likewise,
+                    // if the cancellationToken has been canceled, continuationTask will
+                    // be completed in the AssignCancellationToken call below, and there
+                    // is no need to queue the continuation to the antecedent's continuation
+                    // list.  In either of these two cases, we will pass "null" for the antecedent,
+                    // meaning "the cancellation callback should not attempt to remove the
+                    // continuation from its antecedent's continuation list".
+                    continuationTask.AssignCancellationToken(cancellationToken, null, null);
+                }
+                else
+                {
+                    // The antecedent is not yet complete, so there is a pretty good chance
+                    // that the continuation will be queued up in the antecedent.  Assign the
+                    // cancellation token with information about the antecedent, so that the
+                    // continuation can be dequeued upon the signalling of the token.
+                    //
+                    // It's possible that the antecedent completes before the call to AddTaskContinuation,
+                    // and that is a benign race condition.  It just means that the cancellation will result in
+                    // a futile search of the antecedent's continuation list.
+                    continuationTask.AssignCancellationToken(cancellationToken, this, continuation);
+                }
+            }
+
+            // In the case of a pre-canceled token, continuationTask will have been completed
+            // in a Canceled state by now.  If such is the case, there is no need to go through
+            // the motions of queuing up the continuation for eventual execution.
+            if (!continuationTask.IsCompleted)
+            {
+                // We need additional correlation produced here to ensure that at least the continuation 
+                // code will be correlatable to the currrent activity that initiated "this" task:
+                //  . when the antecendent ("this") is a promise we have very little control over where 
+                //    the code for the promise will run (e.g. it can be a task from a user provided 
+                //    TaskCompletionSource or from a classic Begin/End async operation); this user or 
+                //    system code will likely not have stamped an activity id on the thread, so there's
+                //    generally no easy correlation that can be provided between the current activity
+                //    and the promise. Also the continuation code may run practically on any thread. 
+                //    Since there may be no correlation between the current activity and the TCS's task
+                //    activity, we ensure we at least create a correlation from the current activity to
+                //    the continuation that runs when the promise completes.
+                if ((this.Options & (TaskCreationOptions)InternalTaskOptions.PromiseTask) != 0 &&
+                    !(this is ITaskCompletionAction))
+                {
+                    var etwLog = TplEtwProvider.Log;
+                    if (etwLog.IsEnabled())
+                    {
+                        etwLog.AwaitTaskContinuationScheduled(TaskScheduler.Current.Id, Task.CurrentId ?? 0, continuationTask.Id);
+                    }
+                }
+
+                // Attempt to enqueue the continuation
+                bool continuationQueued = AddTaskContinuation(continuation, addBeforeOthers: false);
+
+                // If the continuation was not queued (because the task completed), then run it now.
+                if (!continuationQueued) continuation.Run(this, bCanInlineContinuationTask: true);
+            }
+        }
+        #endregion
+
+        // Adds a lightweight completion action to a task.  This is similar to a continuation
+        // task except that it is stored as an action, and thus does not require the allocation/
+        // execution resources of a continuation task.
+        //
+        // Used internally by ContinueWhenAll() and ContinueWhenAny().
+        internal void AddCompletionAction(ITaskCompletionAction action)
+        {
+            AddCompletionAction(action, addBeforeOthers: false);
+        }
+
+        private void AddCompletionAction(ITaskCompletionAction action, bool addBeforeOthers)
+        {
+            if (!AddTaskContinuation(action, addBeforeOthers))
+                action.Invoke(this); // run the action directly if we failed to queue the continuation (i.e., the task completed)
+        }
+
+        // Support method for AddTaskContinuation that takes care of multi-continuation logic.
+        // Returns true if and only if the continuation was successfully queued.
+        // THIS METHOD ASSUMES THAT m_continuationObject IS NOT NULL.  That case was taken
+        // care of in the calling method, AddTaskContinuation().
+        private bool AddTaskContinuationComplex(object tc, bool addBeforeOthers)
+        {
+            Debug.Assert(tc != null, "Expected non-null tc object in AddTaskContinuationComplex");
+
+            object oldValue = m_continuationObject;
+
+            // Logic for the case where we were previously storing a single continuation
+            if ((oldValue != s_taskCompletionSentinel) && (!(oldValue is List<object>)))
+            {
+                // Construct a new TaskContinuation list
+                List<object> newList = new List<object>();
+
+                // Add in the old single value
+                newList.Add(oldValue);
+
+                // Now CAS in the new list
+                Interlocked.CompareExchange(ref m_continuationObject, newList, oldValue);
+
+                // We might be racing against another thread converting the single into
+                // a list, or we might be racing against task completion, so resample "list"
+                // below.
+            }
+
+            // m_continuationObject is guaranteed at this point to be either a List or
+            // s_taskCompletionSentinel.
+            List<object> list = m_continuationObject as List<object>;
+            Debug.Assert((list != null) || (m_continuationObject == s_taskCompletionSentinel),
+                "Expected m_continuationObject to be list or sentinel");
+
+            // If list is null, it can only mean that s_taskCompletionSentinel has been exchanged
+            // into m_continuationObject.  Thus, the task has completed and we should return false
+            // from this method, as we will not be queuing up the continuation.
+            if (list != null)
+            {
+                lock (list)
+                {
+                    // It is possible for the task to complete right after we snap the copy of
+                    // the list.  If so, then fall through and return false without queuing the
+                    // continuation.
+                    if (m_continuationObject != s_taskCompletionSentinel)
+                    {
+                        // Before growing the list we remove possible null entries that are the
+                        // result from RemoveContinuations()
+                        if (list.Count == list.Capacity)
+                        {
+                            list.RemoveAll(s_IsTaskContinuationNullPredicate);
+                        }
+
+                        if (addBeforeOthers)
+                            list.Insert(0, tc);
+                        else
+                            list.Add(tc);
+
+                        return true; // continuation successfully queued, so return true.
+                    }
+                }
+            }
+
+            // We didn't succeed in queuing the continuation, so return false.
+            return false;
+        }
+
+        // Record a continuation task or action.
+        // Return true if and only if we successfully queued a continuation.
+        private bool AddTaskContinuation(object tc, bool addBeforeOthers)
+        {
+            Debug.Assert(tc != null);
+
+            // Make sure that, if someone calls ContinueWith() right after waiting for the predecessor to complete,
+            // we don't queue up a continuation.
+            if (IsCompleted) return false;
+
+            // Try to just jam tc into m_continuationObject
+            if ((m_continuationObject != null) || (Interlocked.CompareExchange(ref m_continuationObject, tc, null) != null))
+            {
+                // If we get here, it means that we failed to CAS tc into m_continuationObject.
+                // Therefore, we must go the more complicated route.
+                return AddTaskContinuationComplex(tc, addBeforeOthers);
+            }
+            else return true;
+        }
+
+        // Removes a continuation task from m_continuations
+        internal void RemoveContinuation(object continuationObject) // could be TaskContinuation or Action<Task>
+        {
+            // We need to snap a local reference to m_continuations since reading a volatile object is more costly.
+            // Also to prevent the value to be changed as result of a race condition with another method.
+            object continuationsLocalRef = m_continuationObject;
+
+            // Task is completed. Nothing to do here.
+            if (continuationsLocalRef == s_taskCompletionSentinel) return;
+
+            List<object> continuationsLocalListRef = continuationsLocalRef as List<object>;
+
+            if (continuationsLocalListRef == null)
+            {
+                // This is not a list. If we have a single object (the one we want to remove) we try to replace it with an empty list.
+                // Note we cannot go back to a null state, since it will mess up the AddTaskContinuation logic.
+                if (Interlocked.CompareExchange(ref m_continuationObject, new List<object>(), continuationObject) != continuationObject)
+                {
+                    // If we fail it means that either AddContinuationComplex won the race condition and m_continuationObject is now a List
+                    // that contains the element we want to remove. Or FinishContinuations set the s_taskCompletionSentinel.
+                    // So we should try to get a list one more time
+                    continuationsLocalListRef = m_continuationObject as List<object>;
+                }
+                else
+                {
+                    // Exchange was successful so we can skip the last comparison
+                    return;
+                }
+            }
+
+            // if continuationsLocalRef == null it means s_taskCompletionSentinel has been set already and there is nothing else to do.
+            if (continuationsLocalListRef != null)
+            {
+                lock (continuationsLocalListRef)
+                {
+                    // There is a small chance that this task completed since we took a local snapshot into
+                    // continuationsLocalRef.  In that case, just return; we don't want to be manipulating the
+                    // continuation list as it is being processed.
+                    if (m_continuationObject == s_taskCompletionSentinel) return;
+
+                    // Find continuationObject in the continuation list
+                    int index = continuationsLocalListRef.IndexOf(continuationObject);
+
+                    if (index != -1)
+                    {
+                        // null out that TaskContinuation entry, which will be interpreted as "to be cleaned up"
+                        continuationsLocalListRef[index] = null;
+                    }
+                }
+            }
+        }
+
+        // statically allocated delegate for the RemoveAll expression in RemoveContinuations() and AddContinuationComplex()
+        private readonly static Predicate<object> s_IsTaskContinuationNullPredicate =
+            new Predicate<object>((tc) => { return (tc == null); });
+
+
+        //
+        // Wait methods
+        //
+
+        /// <summary>
+        /// Waits for all of the provided <see cref="Task"/> objects to complete execution.
+        /// </summary>
+        /// <param name="tasks">
+        /// An array of <see cref="Task"/> instances on which to wait.
+        /// </param>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument contains a null element.
+        /// </exception>
+        /// <exception cref="T:System.AggregateException">
+        /// At least one of the <see cref="Task"/> instances was canceled -or- an exception was thrown during
+        /// the execution of at least one of the <see cref="Task"/> instances.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.NoOptimization)]  // this is needed for the parallel debugger
+        public static void WaitAll(params Task[] tasks)
+        {
+#if DEBUG
+            bool waitResult =
+#endif
+            WaitAllCore(tasks, Timeout.Infinite, default(CancellationToken));
+
+#if DEBUG
+            Debug.Assert(waitResult, "expected wait to succeed");
+#endif
+        }
+
+        /// <summary>
+        /// Waits for all of the provided <see cref="Task"/> objects to complete execution.
+        /// </summary>
+        /// <returns>
+        /// true if all of the <see cref="Task"/> instances completed execution within the allotted time;
+        /// otherwise, false.
+        /// </returns>
+        /// <param name="tasks">
+        /// An array of <see cref="Task"/> instances on which to wait.
+        /// </param>
+        /// <param name="timeout">
+        /// A <see cref="System.TimeSpan"/> that represents the number of milliseconds to wait, or a <see
+        /// cref="System.TimeSpan"/> that represents -1 milliseconds to wait indefinitely.
+        /// </param>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> argument contains a null element.
+        /// </exception>
+        /// <exception cref="T:System.AggregateException">
+        /// At least one of the <see cref="Task"/> instances was canceled -or- an exception was thrown during
+        /// the execution of at least one of the <see cref="Task"/> instances.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// <paramref name="timeout"/> is a negative number other than -1 milliseconds, which represents an
+        /// infinite time-out -or- timeout is greater than
+        /// <see cref="System.Int32.MaxValue"/>.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.NoOptimization)]  // this is needed for the parallel debugger
+        public static bool WaitAll(Task[] tasks, TimeSpan timeout)
+        {
+            long totalMilliseconds = (long)timeout.TotalMilliseconds;
+            if (totalMilliseconds < -1 || totalMilliseconds > Int32.MaxValue)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.timeout);
+            }
+
+            return WaitAllCore(tasks, (int)totalMilliseconds, default(CancellationToken));
+        }
+
+        /// <summary>
+        /// Waits for all of the provided <see cref="Task"/> objects to complete execution.
+        /// </summary>
+        /// <returns>
+        /// true if all of the <see cref="Task"/> instances completed execution within the allotted time;
+        /// otherwise, false.
+        /// </returns>
+        /// <param name="millisecondsTimeout">
+        /// The number of milliseconds to wait, or <see cref="System.Threading.Timeout.Infinite"/> (-1) to
+        /// wait indefinitely.</param>
+        /// <param name="tasks">An array of <see cref="Task"/> instances on which to wait.
+        /// </param>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> argument contains a null element.
+        /// </exception>
+        /// <exception cref="T:System.AggregateException">
+        /// At least one of the <see cref="Task"/> instances was canceled -or- an exception was thrown during
+        /// the execution of at least one of the <see cref="Task"/> instances.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// <paramref name="millisecondsTimeout"/> is a negative number other than -1, which represents an
+        /// infinite time-out.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.NoOptimization)]  // this is needed for the parallel debugger
+        public static bool WaitAll(Task[] tasks, int millisecondsTimeout)
+        {
+            return WaitAllCore(tasks, millisecondsTimeout, default(CancellationToken));
+        }
+
+        /// <summary>
+        /// Waits for all of the provided <see cref="Task"/> objects to complete execution.
+        /// </summary>
+        /// <returns>
+        /// true if all of the <see cref="Task"/> instances completed execution within the allotted time;
+        /// otherwise, false.
+        /// </returns>
+        /// <param name="tasks">
+        /// An array of <see cref="Task"/> instances on which to wait.
+        /// </param>
+        /// <param name="cancellationToken">
+        /// A <see cref="CancellationToken"/> to observe while waiting for the tasks to complete.
+        /// </param>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> argument contains a null element.
+        /// </exception>
+        /// <exception cref="T:System.AggregateException">
+        /// At least one of the <see cref="Task"/> instances was canceled -or- an exception was thrown during
+        /// the execution of at least one of the <see cref="Task"/> instances.
+        /// </exception>
+        /// <exception cref="T:System.OperationCanceledException">
+        /// The <paramref name="cancellationToken"/> was canceled.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.NoOptimization)]  // this is needed for the parallel debugger
+        public static void WaitAll(Task[] tasks, CancellationToken cancellationToken)
+        {
+            WaitAllCore(tasks, Timeout.Infinite, cancellationToken);
+        }
+
+        /// <summary>
+        /// Waits for all of the provided <see cref="Task"/> objects to complete execution.
+        /// </summary>
+        /// <returns>
+        /// true if all of the <see cref="Task"/> instances completed execution within the allotted time;
+        /// otherwise, false.
+        /// </returns>
+        /// <param name="tasks">
+        /// An array of <see cref="Task"/> instances on which to wait.
+        /// </param>
+        /// <param name="millisecondsTimeout">
+        /// The number of milliseconds to wait, or <see cref="System.Threading.Timeout.Infinite"/> (-1) to
+        /// wait indefinitely.
+        /// </param>
+        /// <param name="cancellationToken">
+        /// A <see cref="CancellationToken"/> to observe while waiting for the tasks to complete.
+        /// </param>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> argument contains a null element.
+        /// </exception>
+        /// <exception cref="T:System.AggregateException">
+        /// At least one of the <see cref="Task"/> instances was canceled -or- an exception was thrown during
+        /// the execution of at least one of the <see cref="Task"/> instances.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// <paramref name="millisecondsTimeout"/> is a negative number other than -1, which represents an
+        /// infinite time-out.
+        /// </exception>
+        /// <exception cref="T:System.OperationCanceledException">
+        /// The <paramref name="cancellationToken"/> was canceled.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.NoOptimization)]  // this is needed for the parallel debugger
+        public static bool WaitAll(Task[] tasks, int millisecondsTimeout, CancellationToken cancellationToken) =>
+            WaitAllCore(tasks, millisecondsTimeout, cancellationToken);
+
+        // Separated out to allow it to be optimized (caller is marked NoOptimization for VS parallel debugger
+        // to be able to see the method on the stack and inspect arguments).
+        private static bool WaitAllCore(Task[] tasks, int millisecondsTimeout, CancellationToken cancellationToken)
+        {
+            if (tasks == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
+            }
+            if (millisecondsTimeout < -1)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.millisecondsTimeout);
+            }
+
+            cancellationToken.ThrowIfCancellationRequested(); // early check before we make any allocations
+
+            //
+            // In this WaitAll() implementation we have 2 alternate code paths for a task to be handled:
+            // CODEPATH1: skip an already completed task, CODEPATH2: actually wait on tasks
+            // We make sure that the exception behavior of Task.Wait() is replicated the same for tasks handled in either of these codepaths
+            //
+
+            List<Exception> exceptions = null;
+            List<Task> waitedOnTaskList = null;
+            List<Task> notificationTasks = null;
+
+            // If any of the waited-upon tasks end as Faulted or Canceled, set these to true.
+            bool exceptionSeen = false, cancellationSeen = false;
+
+            bool returnValue = true;
+
+            // Collects incomplete tasks in "waitedOnTaskList"
+            for (int i = tasks.Length - 1; i >= 0; i--)
+            {
+                Task task = tasks[i];
+
+                if (task == null)
+                {
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.Task_WaitMulti_NullTask, ExceptionArgument.tasks);
+                }
+
+                bool taskIsCompleted = task.IsCompleted;
+                if (!taskIsCompleted)
+                {
+                    // try inlining the task only if we have an infinite timeout and an empty cancellation token
+                    if (millisecondsTimeout != Timeout.Infinite || cancellationToken.CanBeCanceled)
+                    {
+                        // We either didn't attempt inline execution because we had a non-infinite timeout or we had a cancellable token.
+                        // In all cases we need to do a full wait on the task (=> add its event into the list.)
+                        AddToList(task, ref waitedOnTaskList, initSize: tasks.Length);
+                    }
+                    else
+                    {
+                        // We are eligible for inlining.  If it doesn't work, we'll do a full wait.
+                        taskIsCompleted = task.WrappedTryRunInline() && task.IsCompleted; // A successful TryRunInline doesn't guarantee completion
+                        if (!taskIsCompleted) AddToList(task, ref waitedOnTaskList, initSize: tasks.Length);
+                    }
+                }
+
+                if (taskIsCompleted)
+                {
+                    if (task.IsFaulted) exceptionSeen = true;
+                    else if (task.IsCanceled) cancellationSeen = true;
+                    if (task.IsWaitNotificationEnabled) AddToList(task, ref notificationTasks, initSize: 1);
+                }
+            }
+
+            if (waitedOnTaskList != null)
+            {
+                // Block waiting for the tasks to complete.
+                returnValue = WaitAllBlockingCore(waitedOnTaskList, millisecondsTimeout, cancellationToken);
+
+                // If the wait didn't time out, ensure exceptions are propagated, and if a debugger is
+                // attached and one of these tasks requires it, that we notify the debugger of a wait completion.
+                if (returnValue)
+                {
+                    // Add any exceptions for this task to the collection, and if it's wait
+                    // notification bit is set, store it to operate on at the end.
+                    foreach (var task in waitedOnTaskList)
+                    {
+                        if (task.IsFaulted) exceptionSeen = true;
+                        else if (task.IsCanceled) cancellationSeen = true;
+                        if (task.IsWaitNotificationEnabled) AddToList(task, ref notificationTasks, initSize: 1);
+                    }
+                }
+
+                // We need to prevent the tasks array from being GC'ed until we come out of the wait.
+                // This is necessary so that the Parallel Debugger can traverse it during the long wait and 
+                // deduce waiter/waitee relationships
+                GC.KeepAlive(tasks);
+            }
+
+            // Now that we're done and about to exit, if the wait completed and if we have 
+            // any tasks with a notification bit set, signal the debugger if any requires it.
+            if (returnValue && notificationTasks != null)
+            {
+                // Loop through each task tha that had its bit set, and notify the debugger
+                // about the first one that requires it.  The debugger will reset the bit
+                // for any tasks we don't notify of as soon as we break, so we only need to notify
+                // for one.
+                foreach (var task in notificationTasks)
+                {
+                    if (task.NotifyDebuggerOfWaitCompletionIfNecessary()) break;
+                }
+            }
+
+            // If one or more threw exceptions, aggregate and throw them.
+            if (returnValue && (exceptionSeen || cancellationSeen))
+            {
+                // If the WaitAll was canceled and tasks were canceled but not faulted, 
+                // prioritize throwing an OCE for canceling the WaitAll over throwing an 
+                // AggregateException for all of the canceled Tasks.  This helps
+                // to bring determinism to an otherwise non-determistic case of using
+                // the same token to cancel both the WaitAll and the Tasks.
+                if (!exceptionSeen) cancellationToken.ThrowIfCancellationRequested();
+
+                // Now gather up and throw all of the exceptions.
+                foreach (var task in tasks) AddExceptionsForCompletedTask(ref exceptions, task);
+                Debug.Assert(exceptions != null, "Should have seen at least one exception");
+                ThrowHelper.ThrowAggregateException(exceptions);
+            }
+
+            return returnValue;
+        }
+
+        /// <summary>Adds an element to the list, initializing the list if it's null.</summary>
+        /// <typeparam name="T">Specifies the type of data stored in the list.</typeparam>
+        /// <param name="item">The item to add.</param>
+        /// <param name="list">The list.</param>
+        /// <param name="initSize">The size to which to initialize the list if the list is null.</param>
+        private static void AddToList<T>(T item, ref List<T> list, int initSize)
+        {
+            if (list == null) list = new List<T>(initSize);
+            list.Add(item);
+        }
+
+        /// <summary>Performs a blocking WaitAll on the vetted list of tasks.</summary>
+        /// <param name="tasks">The tasks, which have already been checked and filtered for completion.</param>
+        /// <param name="millisecondsTimeout">The timeout.</param>
+        /// <param name="cancellationToken">The cancellation token.</param>
+        /// <returns>true if all of the tasks completed; otherwise, false.</returns>
+        private static bool WaitAllBlockingCore(List<Task> tasks, int millisecondsTimeout, CancellationToken cancellationToken)
+        {
+            Debug.Assert(tasks != null, "Expected a non-null list of tasks");
+            Debug.Assert(tasks.Count > 0, "Expected at least one task");
+
+            bool waitCompleted = false;
+            var mres = new SetOnCountdownMres(tasks.Count);
+            try
+            {
+                foreach (var task in tasks)
+                {
+                    task.AddCompletionAction(mres, addBeforeOthers: true);
+                }
+                waitCompleted = mres.Wait(millisecondsTimeout, cancellationToken);
+            }
+            finally
+            {
+                if (!waitCompleted)
+                {
+                    foreach (var task in tasks)
+                    {
+                        if (!task.IsCompleted) task.RemoveContinuation(mres);
+                    }
+                }
+                // It's ok that we don't dispose of the MRES here, as we never
+                // access the MRES' WaitHandle, and thus no finalizable resources
+                // are actually created.  We don't always just Dispose it because
+                // a continuation that's accessing the MRES could still be executing.
+            }
+            return waitCompleted;
+        }
+
+        // A ManualResetEventSlim that will get Set after Invoke is called count times.
+        // This allows us to replace this logic:
+        //      var mres = new ManualResetEventSlim(tasks.Count);
+        //      Action<Task> completionAction = delegate { if(Interlocked.Decrement(ref count) == 0) mres.Set(); };
+        //      foreach(var task in tasks) task.AddCompletionAction(completionAction);
+        // with this logic:
+        //      var mres = new SetOnCountdownMres(tasks.Count);
+        //      foreach(var task in tasks) task.AddCompletionAction(mres);
+        // which saves a couple of allocations.
+        //
+        // Used in WaitAllBlockingCore (above).
+        private sealed class SetOnCountdownMres : ManualResetEventSlim, ITaskCompletionAction
+        {
+            private int _count;
+
+            internal SetOnCountdownMres(int count)
+            {
+                Debug.Assert(count > 0, "Expected count > 0");
+                _count = count;
+            }
+
+            public void Invoke(Task completingTask)
+            {
+                if (Interlocked.Decrement(ref _count) == 0) Set();
+                Debug.Assert(_count >= 0, "Count should never go below 0");
+            }
+
+            public bool InvokeMayRunArbitraryCode { get { return false; } }
+        }
+
+        /// <summary>
+        /// This internal function is only meant to be called by WaitAll()
+        /// If the completed task is canceled or it has other exceptions, here we will add those
+        /// into the passed in exception list (which will be lazily initialized here).
+        /// </summary>
+        internal static void AddExceptionsForCompletedTask(ref List<Exception> exceptions, Task t)
+        {
+            AggregateException ex = t.GetExceptions(true);
+            if (ex != null)
+            {
+                // make sure the task's exception observed status is set appropriately
+                // it's possible that WaitAll was called by the parent of an attached child,
+                // this will make sure it won't throw again in the implicit wait
+                t.UpdateExceptionObservedStatus();
+
+                if (exceptions == null)
+                {
+                    exceptions = new List<Exception>(ex.InnerExceptions.Count);
+                }
+
+                exceptions.AddRange(ex.InnerExceptions);
+            }
+        }
+
+
+        /// <summary>
+        /// Waits for any of the provided <see cref="Task"/> objects to complete execution.
+        /// </summary>
+        /// <param name="tasks">
+        /// An array of <see cref="Task"/> instances on which to wait.
+        /// </param>
+        /// <returns>The index of the completed task in the <paramref name="tasks"/> array argument.</returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> argument contains a null element.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.NoOptimization)]  // this is needed for the parallel debugger
+        public static int WaitAny(params Task[] tasks)
+        {
+            int waitResult = WaitAnyCore(tasks, Timeout.Infinite, default(CancellationToken));
+            Debug.Assert(tasks.Length == 0 || waitResult != -1, "expected wait to succeed");
+            return waitResult;
+        }
+
+        /// <summary>
+        /// Waits for any of the provided <see cref="Task"/> objects to complete execution.
+        /// </summary>
+        /// <param name="tasks">
+        /// An array of <see cref="Task"/> instances on which to wait.
+        /// </param>
+        /// <param name="timeout">
+        /// A <see cref="System.TimeSpan"/> that represents the number of milliseconds to wait, or a <see
+        /// cref="System.TimeSpan"/> that represents -1 milliseconds to wait indefinitely.
+        /// </param>
+        /// <returns>
+        /// The index of the completed task in the <paramref name="tasks"/> array argument, or -1 if the
+        /// timeout occurred.
+        /// </returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> argument contains a null element.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// <paramref name="timeout"/> is a negative number other than -1 milliseconds, which represents an
+        /// infinite time-out -or- timeout is greater than
+        /// <see cref="System.Int32.MaxValue"/>.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.NoOptimization)]  // this is needed for the parallel debugger
+        public static int WaitAny(Task[] tasks, TimeSpan timeout)
+        {
+            long totalMilliseconds = (long)timeout.TotalMilliseconds;
+            if (totalMilliseconds < -1 || totalMilliseconds > Int32.MaxValue)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.timeout);
+            }
+
+            return WaitAnyCore(tasks, (int)totalMilliseconds, default(CancellationToken));
+        }
+
+        /// <summary>
+        /// Waits for any of the provided <see cref="Task"/> objects to complete execution.
+        /// </summary>
+        /// <param name="tasks">
+        /// An array of <see cref="Task"/> instances on which to wait.
+        /// </param>
+        /// <param name="cancellationToken">
+        /// A <see cref="CancellationToken"/> to observe while waiting for a task to complete.
+        /// </param>
+        /// <returns>
+        /// The index of the completed task in the <paramref name="tasks"/> array argument.
+        /// </returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> argument contains a null element.
+        /// </exception>
+        /// <exception cref="T:System.OperationCanceledException">
+        /// The <paramref name="cancellationToken"/> was canceled.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.NoOptimization)]  // this is needed for the parallel debugger
+        public static int WaitAny(Task[] tasks, CancellationToken cancellationToken)
+        {
+            return WaitAnyCore(tasks, Timeout.Infinite, cancellationToken);
+        }
+
+        /// <summary>
+        /// Waits for any of the provided <see cref="Task"/> objects to complete execution.
+        /// </summary>
+        /// <param name="tasks">
+        /// An array of <see cref="Task"/> instances on which to wait.
+        /// </param>
+        /// <param name="millisecondsTimeout">
+        /// The number of milliseconds to wait, or <see cref="System.Threading.Timeout.Infinite"/> (-1) to
+        /// wait indefinitely.
+        /// </param>
+        /// <returns>
+        /// The index of the completed task in the <paramref name="tasks"/> array argument, or -1 if the
+        /// timeout occurred.
+        /// </returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> argument contains a null element.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// <paramref name="millisecondsTimeout"/> is a negative number other than -1, which represents an
+        /// infinite time-out.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.NoOptimization)]  // this is needed for the parallel debugger
+        public static int WaitAny(Task[] tasks, int millisecondsTimeout)
+        {
+            return WaitAnyCore(tasks, millisecondsTimeout, default(CancellationToken));
+        }
+
+        /// <summary>
+        /// Waits for any of the provided <see cref="Task"/> objects to complete execution.
+        /// </summary>
+        /// <param name="tasks">
+        /// An array of <see cref="Task"/> instances on which to wait.
+        /// </param>
+        /// <param name="millisecondsTimeout">
+        /// The number of milliseconds to wait, or <see cref="System.Threading.Timeout.Infinite"/> (-1) to
+        /// wait indefinitely.
+        /// </param>
+        /// <param name="cancellationToken">
+        /// A <see cref="CancellationToken"/> to observe while waiting for a task to complete.
+        /// </param>
+        /// <returns>
+        /// The index of the completed task in the <paramref name="tasks"/> array argument, or -1 if the
+        /// timeout occurred.
+        /// </returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> argument contains a null element.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// <paramref name="millisecondsTimeout"/> is a negative number other than -1, which represents an
+        /// infinite time-out.
+        /// </exception>
+        /// <exception cref="T:System.OperationCanceledException">
+        /// The <paramref name="cancellationToken"/> was canceled.
+        /// </exception>
+        [MethodImpl(MethodImplOptions.NoOptimization)]  // this is needed for the parallel debugger
+        public static int WaitAny(Task[] tasks, int millisecondsTimeout, CancellationToken cancellationToken) =>
+            WaitAnyCore(tasks, millisecondsTimeout, cancellationToken);
+
+        // Separated out to allow it to be optimized (caller is marked NoOptimization for VS parallel debugger
+        // to be able to inspect arguments).
+        private static int WaitAnyCore(Task[] tasks, int millisecondsTimeout, CancellationToken cancellationToken)
+        {
+            if (tasks == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
+            }
+            if (millisecondsTimeout < -1)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.millisecondsTimeout);
+            }
+
+            cancellationToken.ThrowIfCancellationRequested(); // early check before we make any allocations
+
+            int signaledTaskIndex = -1;
+
+            // Make a pass through the loop to check for any tasks that may have
+            // already been completed, and to verify that no tasks are null.
+
+            for (int taskIndex = 0; taskIndex < tasks.Length; taskIndex++)
+            {
+                Task task = tasks[taskIndex];
+
+                if (task == null)
+                {
+                    ThrowHelper.ThrowArgumentException(ExceptionResource.Task_WaitMulti_NullTask, ExceptionArgument.tasks);
+                }
+
+                if (signaledTaskIndex == -1 && task.IsCompleted)
+                {
+                    // We found our first completed task.  Store it, but we can't just return here,
+                    // as we still need to validate the whole array for nulls.
+                    signaledTaskIndex = taskIndex;
+                }
+            }
+
+            if (signaledTaskIndex == -1 && tasks.Length != 0)
+            {
+                Task<Task> firstCompleted = TaskFactory.CommonCWAnyLogic(tasks);
+                bool waitCompleted = firstCompleted.Wait(millisecondsTimeout, cancellationToken);
+                if (waitCompleted)
+                {
+                    Debug.Assert(firstCompleted.Status == TaskStatus.RanToCompletion);
+                    signaledTaskIndex = Array.IndexOf(tasks, firstCompleted.Result);
+                    Debug.Assert(signaledTaskIndex >= 0);
+                }
+                else
+                {
+                    TaskFactory.CommonCWAnyLogicCleanup(firstCompleted);
+                }
+            }
+
+            // We need to prevent the tasks array from being GC'ed until we come out of the wait.
+            // This is necessary so that the Parallel Debugger can traverse it during the long wait 
+            // and deduce waiter/waitee relationships
+            GC.KeepAlive(tasks);
+
+            // Return the index
+            return signaledTaskIndex;
+        }
+
+        #region FromResult / FromException / FromCanceled
+
+        /// <summary>Creates a <see cref="Task{TResult}"/> that's completed successfully with the specified result.</summary>
+        /// <typeparam name="TResult">The type of the result returned by the task.</typeparam>
+        /// <param name="result">The result to store into the completed task.</param>
+        /// <returns>The successfully completed task.</returns>
+        public static Task<TResult> FromResult<TResult>(TResult result)
+        {
+            return new Task<TResult>(result);
+        }
+
+        /// <summary>Creates a <see cref="Task{TResult}"/> that's completed exceptionally with the specified exception.</summary>
+        /// <typeparam name="TResult">The type of the result returned by the task.</typeparam>
+        /// <param name="exception">The exception with which to complete the task.</param>
+        /// <returns>The faulted task.</returns>
+        public static Task FromException(Exception exception)
+        {
+            return FromException<VoidTaskResult>(exception);
+        }
+
+        /// <summary>Creates a <see cref="Task{TResult}"/> that's completed exceptionally with the specified exception.</summary>
+        /// <typeparam name="TResult">The type of the result returned by the task.</typeparam>
+        /// <param name="exception">The exception with which to complete the task.</param>
+        /// <returns>The faulted task.</returns>
+        public static Task<TResult> FromException<TResult>(Exception exception)
+        {
+            if (exception == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.exception);
+
+            var task = new Task<TResult>();
+            bool succeeded = task.TrySetException(exception);
+            Debug.Assert(succeeded, "This should always succeed on a new task.");
+            return task;
+        }
+
+        /// <summary>Creates a <see cref="Task"/> that's completed due to cancellation with the specified token.</summary>
+        /// <param name="cancellationToken">The token with which to complete the task.</param>
+        /// <returns>The canceled task.</returns>
+        public static Task FromCanceled(CancellationToken cancellationToken)
+        {
+            if (!cancellationToken.IsCancellationRequested)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.cancellationToken);
+            return new Task(true, TaskCreationOptions.None, cancellationToken);
+        }
+
+        /// <summary>Creates a <see cref="Task{TResult}"/> that's completed due to cancellation with the specified token.</summary>
+        /// <typeparam name="TResult">The type of the result returned by the task.</typeparam>
+        /// <param name="cancellationToken">The token with which to complete the task.</param>
+        /// <returns>The canceled task.</returns>
+        public static Task<TResult> FromCanceled<TResult>(CancellationToken cancellationToken)
+        {
+            if (!cancellationToken.IsCancellationRequested)
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.cancellationToken);
+            return new Task<TResult>(true, default(TResult), TaskCreationOptions.None, cancellationToken);
+        }
+
+        /// <summary>Creates a <see cref="Task{TResult}"/> that's completed due to cancellation with the specified exception.</summary>
+        /// <typeparam name="TResult">The type of the result returned by the task.</typeparam>
+        /// <param name="exception">The exception with which to complete the task.</param>
+        /// <returns>The canceled task.</returns>
+        internal static Task<TResult> FromCancellation<TResult>(OperationCanceledException exception)
+        {
+            if (exception == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.exception);
+
+            var task = new Task<TResult>();
+            bool succeeded = task.TrySetCanceled(exception.CancellationToken, exception);
+            Debug.Assert(succeeded, "This should always succeed on a new task.");
+            return task;
+        }
+
+        #endregion
+
+        #region Run methods
+
+
+        /// <summary>
+        /// Queues the specified work to run on the ThreadPool and returns a Task handle for that work.
+        /// </summary>
+        /// <param name="action">The work to execute asynchronously</param>
+        /// <returns>A Task that represents the work queued to execute in the ThreadPool.</returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="action"/> parameter was null.
+        /// </exception>
+        public static Task Run(Action action)
+        {
+            return Task.InternalStartNew(null, action, null, default(CancellationToken), TaskScheduler.Default,
+                TaskCreationOptions.DenyChildAttach, InternalTaskOptions.None);
+        }
+
+        /// <summary>
+        /// Queues the specified work to run on the ThreadPool and returns a Task handle for that work.
+        /// </summary>
+        /// <param name="action">The work to execute asynchronously</param>
+        /// <param name="cancellationToken">A cancellation token that should be used to cancel the work</param>
+        /// <returns>A Task that represents the work queued to execute in the ThreadPool.</returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="action"/> parameter was null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">
+        /// The <see cref="T:System.CancellationTokenSource"/> associated with <paramref name="cancellationToken"/> was disposed.
+        /// </exception>
+        public static Task Run(Action action, CancellationToken cancellationToken)
+        {
+            return Task.InternalStartNew(null, action, null, cancellationToken, TaskScheduler.Default,
+                TaskCreationOptions.DenyChildAttach, InternalTaskOptions.None);
+        }
+
+        /// <summary>
+        /// Queues the specified work to run on the ThreadPool and returns a Task(TResult) handle for that work.
+        /// </summary>
+        /// <param name="function">The work to execute asynchronously</param>
+        /// <returns>A Task(TResult) that represents the work queued to execute in the ThreadPool.</returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="function"/> parameter was null.
+        /// </exception>
+        public static Task<TResult> Run<TResult>(Func<TResult> function)
+        {
+            return Task<TResult>.StartNew(null, function, default(CancellationToken),
+                TaskCreationOptions.DenyChildAttach, InternalTaskOptions.None, TaskScheduler.Default);
+        }
+
+        /// <summary>
+        /// Queues the specified work to run on the ThreadPool and returns a Task(TResult) handle for that work.
+        /// </summary>
+        /// <param name="function">The work to execute asynchronously</param>
+        /// <param name="cancellationToken">A cancellation token that should be used to cancel the work</param>
+        /// <returns>A Task(TResult) that represents the work queued to execute in the ThreadPool.</returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="function"/> parameter was null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">
+        /// The <see cref="T:System.CancellationTokenSource"/> associated with <paramref name="cancellationToken"/> was disposed.
+        /// </exception>
+        public static Task<TResult> Run<TResult>(Func<TResult> function, CancellationToken cancellationToken)
+        {
+            return Task<TResult>.StartNew(null, function, cancellationToken,
+                TaskCreationOptions.DenyChildAttach, InternalTaskOptions.None, TaskScheduler.Default);
+        }
+
+        /// <summary>
+        /// Queues the specified work to run on the ThreadPool and returns a proxy for the
+        /// Task returned by <paramref name="function"/>.
+        /// </summary>
+        /// <param name="function">The work to execute asynchronously</param>
+        /// <returns>A Task that represents a proxy for the Task returned by <paramref name="function"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="function"/> parameter was null.
+        /// </exception>
+        public static Task Run(Func<Task> function)
+        {
+            return Run(function, default(CancellationToken));
+        }
+
+
+        /// <summary>
+        /// Queues the specified work to run on the ThreadPool and returns a proxy for the
+        /// Task returned by <paramref name="function"/>.
+        /// </summary>
+        /// <param name="function">The work to execute asynchronously</param>
+        /// <param name="cancellationToken">A cancellation token that should be used to cancel the work</param>
+        /// <returns>A Task that represents a proxy for the Task returned by <paramref name="function"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="function"/> parameter was null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">
+        /// The <see cref="T:System.CancellationTokenSource"/> associated with <paramref name="cancellationToken"/> was disposed.
+        /// </exception>
+        public static Task Run(Func<Task> function, CancellationToken cancellationToken)
+        {
+            // Check arguments
+            if (function == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.function);
+
+            // Short-circuit if we are given a pre-canceled token
+            if (cancellationToken.IsCancellationRequested)
+                return Task.FromCanceled(cancellationToken);
+
+            // Kick off initial Task, which will call the user-supplied function and yield a Task.
+            Task<Task> task1 = Task<Task>.Factory.StartNew(function, cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+
+            // Create a promise-style Task to be used as a proxy for the operation
+            // Set lookForOce == true so that unwrap logic can be on the lookout for OCEs thrown as faults from task1, to support in-delegate cancellation.
+            UnwrapPromise<VoidTaskResult> promise = new UnwrapPromise<VoidTaskResult>(task1, lookForOce: true);
+
+            return promise;
+        }
+
+        /// <summary>
+        /// Queues the specified work to run on the ThreadPool and returns a proxy for the
+        /// Task(TResult) returned by <paramref name="function"/>.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result returned by the proxy Task.</typeparam>
+        /// <param name="function">The work to execute asynchronously</param>
+        /// <returns>A Task(TResult) that represents a proxy for the Task(TResult) returned by <paramref name="function"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="function"/> parameter was null.
+        /// </exception>
+        public static Task<TResult> Run<TResult>(Func<Task<TResult>> function)
+        {
+            return Run(function, default(CancellationToken));
+        }
+
+        /// <summary>
+        /// Queues the specified work to run on the ThreadPool and returns a proxy for the
+        /// Task(TResult) returned by <paramref name="function"/>.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result returned by the proxy Task.</typeparam>
+        /// <param name="function">The work to execute asynchronously</param>
+        /// <param name="cancellationToken">A cancellation token that should be used to cancel the work</param>
+        /// <returns>A Task(TResult) that represents a proxy for the Task(TResult) returned by <paramref name="function"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="function"/> parameter was null.
+        /// </exception>
+        public static Task<TResult> Run<TResult>(Func<Task<TResult>> function, CancellationToken cancellationToken)
+        {
+            // Check arguments
+            if (function == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.function);
+
+            // Short-circuit if we are given a pre-canceled token
+            if (cancellationToken.IsCancellationRequested)
+                return Task.FromCanceled<TResult>(cancellationToken);
+
+            // Kick off initial Task, which will call the user-supplied function and yield a Task.
+            Task<Task<TResult>> task1 = Task<Task<TResult>>.Factory.StartNew(function, cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
+
+            // Create a promise-style Task to be used as a proxy for the operation
+            // Set lookForOce == true so that unwrap logic can be on the lookout for OCEs thrown as faults from task1, to support in-delegate cancellation.
+            UnwrapPromise<TResult> promise = new UnwrapPromise<TResult>(task1, lookForOce: true);
+
+            return promise;
+        }
+
+
+        #endregion
+
+        #region Delay methods
+
+        /// <summary>
+        /// Creates a Task that will complete after a time delay.
+        /// </summary>
+        /// <param name="delay">The time span to wait before completing the returned Task</param>
+        /// <returns>A Task that represents the time delay</returns>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="delay"/> is less than -1 or greater than Int32.MaxValue.
+        /// </exception>
+        /// <remarks>
+        /// After the specified time delay, the Task is completed in RanToCompletion state.
+        /// </remarks>
+        public static Task Delay(TimeSpan delay)
+        {
+            return Delay(delay, default(CancellationToken));
+        }
+
+        /// <summary>
+        /// Creates a Task that will complete after a time delay.
+        /// </summary>
+        /// <param name="delay">The time span to wait before completing the returned Task</param>
+        /// <param name="cancellationToken">The cancellation token that will be checked prior to completing the returned Task</param>
+        /// <returns>A Task that represents the time delay</returns>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="delay"/> is less than -1 or greater than Int32.MaxValue.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">
+        /// The provided <paramref name="cancellationToken"/> has already been disposed.
+        /// </exception>        
+        /// <remarks>
+        /// If the cancellation token is signaled before the specified time delay, then the Task is completed in
+        /// Canceled state.  Otherwise, the Task is completed in RanToCompletion state once the specified time
+        /// delay has expired.
+        /// </remarks>        
+        public static Task Delay(TimeSpan delay, CancellationToken cancellationToken)
+        {
+            long totalMilliseconds = (long)delay.TotalMilliseconds;
+            if (totalMilliseconds < -1 || totalMilliseconds > Int32.MaxValue)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.delay, ExceptionResource.Task_Delay_InvalidDelay);
+            }
+
+            return Delay((int)totalMilliseconds, cancellationToken);
+        }
+
+        /// <summary>
+        /// Creates a Task that will complete after a time delay.
+        /// </summary>
+        /// <param name="millisecondsDelay">The number of milliseconds to wait before completing the returned Task</param>
+        /// <returns>A Task that represents the time delay</returns>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="millisecondsDelay"/> is less than -1.
+        /// </exception>
+        /// <remarks>
+        /// After the specified time delay, the Task is completed in RanToCompletion state.
+        /// </remarks>
+        public static Task Delay(int millisecondsDelay)
+        {
+            return Delay(millisecondsDelay, default(CancellationToken));
+        }
+
+        /// <summary>
+        /// Creates a Task that will complete after a time delay.
+        /// </summary>
+        /// <param name="millisecondsDelay">The number of milliseconds to wait before completing the returned Task</param>
+        /// <param name="cancellationToken">The cancellation token that will be checked prior to completing the returned Task</param>
+        /// <returns>A Task that represents the time delay</returns>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="millisecondsDelay"/> is less than -1.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">
+        /// The provided <paramref name="cancellationToken"/> has already been disposed.
+        /// </exception>        
+        /// <remarks>
+        /// If the cancellation token is signaled before the specified time delay, then the Task is completed in
+        /// Canceled state.  Otherwise, the Task is completed in RanToCompletion state once the specified time
+        /// delay has expired.
+        /// </remarks>        
+        public static Task Delay(int millisecondsDelay, CancellationToken cancellationToken)
+        {
+            // Throw on non-sensical time
+            if (millisecondsDelay < -1)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.millisecondsDelay, ExceptionResource.Task_Delay_InvalidMillisecondsDelay);
+            }
+
+            // some short-cuts in case quick completion is in order
+            if (cancellationToken.IsCancellationRequested)
+            {
+                // return a Task created as already-Canceled
+                return Task.FromCanceled(cancellationToken);
+            }
+            else if (millisecondsDelay == 0)
+            {
+                // return a Task created as already-RanToCompletion
+                return Task.CompletedTask;
+            }
+
+            // Construct a promise-style Task to encapsulate our return value
+            var promise = new DelayPromise(cancellationToken);
+
+            // Register our cancellation token, if necessary.
+            if (cancellationToken.CanBeCanceled)
+            {
+                promise.Registration = cancellationToken.InternalRegisterWithoutEC(state => ((DelayPromise)state).Complete(), promise);
+            }
+
+            // ... and create our timer and make sure that it stays rooted.
+            if (millisecondsDelay != Timeout.Infinite) // no need to create the timer if it's an infinite timeout
+            {
+                promise.Timer = new TimerQueueTimer(state => ((DelayPromise)state).Complete(), promise, (uint)millisecondsDelay, Timeout.UnsignedInfinite);
+            }
+
+            // Return the timer proxy task
+            return promise;
+        }
+
+        /// <summary>Task that also stores the completion closure and logic for Task.Delay implementation.</summary>
+        private sealed class DelayPromise : Task<VoidTaskResult>
+        {
+            internal DelayPromise(CancellationToken token)
+                : base()
+            {
+                this.Token = token;
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, this.Id, "Task.Delay", 0);
+
+                if (Task.s_asyncDebuggingEnabled)
+                {
+                    AddToActiveTasks(this);
+                }
+            }
+
+            internal readonly CancellationToken Token;
+            internal CancellationTokenRegistration Registration;
+            internal TimerQueueTimer Timer;
+
+            internal void Complete()
+            {
+                // Transition the task to completed.
+                bool setSucceeded;
+
+                if (Token.IsCancellationRequested)
+                {
+                    setSucceeded = TrySetCanceled(Token);
+                }
+                else
+                {
+                    if (AsyncCausalityTracer.LoggingOn)
+                        AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, this.Id, AsyncCausalityStatus.Completed);
+
+                    if (Task.s_asyncDebuggingEnabled)
+                    {
+                        RemoveFromActiveTasks(this.Id);
+                    }
+                    setSucceeded = TrySetResult(default(VoidTaskResult));
+                }
+
+                // If we set the value, also clean up.
+                if (setSucceeded)
+                {
+                    Timer?.Close();
+                    Registration.Dispose();
+                }
+            }
+        }
+        #endregion
+
+        #region WhenAll
+        /// <summary>
+        /// Creates a task that will complete when all of the supplied tasks have completed.
+        /// </summary>
+        /// <param name="tasks">The tasks to wait on for completion.</param>
+        /// <returns>A task that represents the completion of all of the supplied tasks.</returns>
+        /// <remarks>
+        /// <para>
+        /// If any of the supplied tasks completes in a faulted state, the returned task will also complete in a Faulted state, 
+        /// where its exceptions will contain the aggregation of the set of unwrapped exceptions from each of the supplied tasks.  
+        /// </para>
+        /// <para>
+        /// If none of the supplied tasks faulted but at least one of them was canceled, the returned task will end in the Canceled state.
+        /// </para>
+        /// <para>
+        /// If none of the tasks faulted and none of the tasks were canceled, the resulting task will end in the RanToCompletion state.   
+        /// </para>
+        /// <para>
+        /// If the supplied array/enumerable contains no tasks, the returned task will immediately transition to a RanToCompletion 
+        /// state before it's returned to the caller.  
+        /// </para>
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument was null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> collection contained a null task.
+        /// </exception>
+        public static Task WhenAll(IEnumerable<Task> tasks)
+        {
+            // Take a more efficient path if tasks is actually an array
+            Task[] taskArray = tasks as Task[];
+            if (taskArray != null)
+            {
+                return WhenAll(taskArray);
+            }
+
+            // Skip a List allocation/copy if tasks is a collection
+            ICollection<Task> taskCollection = tasks as ICollection<Task>;
+            if (taskCollection != null)
+            {
+                int index = 0;
+                taskArray = new Task[taskCollection.Count];
+                foreach (var task in tasks)
+                {
+                    if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
+                    taskArray[index++] = task;
+                }
+                return InternalWhenAll(taskArray);
+            }
+
+            // Do some argument checking and convert tasks to a List (and later an array).
+            if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
+            List<Task> taskList = new List<Task>();
+            foreach (Task task in tasks)
+            {
+                if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
+                taskList.Add(task);
+            }
+
+            // Delegate the rest to InternalWhenAll()
+            return InternalWhenAll(taskList.ToArray());
+        }
+
+        /// <summary>
+        /// Creates a task that will complete when all of the supplied tasks have completed.
+        /// </summary>
+        /// <param name="tasks">The tasks to wait on for completion.</param>
+        /// <returns>A task that represents the completion of all of the supplied tasks.</returns>
+        /// <remarks>
+        /// <para>
+        /// If any of the supplied tasks completes in a faulted state, the returned task will also complete in a Faulted state, 
+        /// where its exceptions will contain the aggregation of the set of unwrapped exceptions from each of the supplied tasks.  
+        /// </para>
+        /// <para>
+        /// If none of the supplied tasks faulted but at least one of them was canceled, the returned task will end in the Canceled state.
+        /// </para>
+        /// <para>
+        /// If none of the tasks faulted and none of the tasks were canceled, the resulting task will end in the RanToCompletion state.   
+        /// </para>
+        /// <para>
+        /// If the supplied array/enumerable contains no tasks, the returned task will immediately transition to a RanToCompletion 
+        /// state before it's returned to the caller.  
+        /// </para>
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument was null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> array contained a null task.
+        /// </exception>
+        public static Task WhenAll(params Task[] tasks)
+        {
+            // Do some argument checking and make a defensive copy of the tasks array
+            if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
+
+            int taskCount = tasks.Length;
+            if (taskCount == 0) return InternalWhenAll(tasks); // Small optimization in the case of an empty array.
+
+            Task[] tasksCopy = new Task[taskCount];
+            for (int i = 0; i < taskCount; i++)
+            {
+                Task task = tasks[i];
+                if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
+                tasksCopy[i] = task;
+            }
+
+            // The rest can be delegated to InternalWhenAll()
+            return InternalWhenAll(tasksCopy);
+        }
+
+        // Some common logic to support WhenAll() methods
+        // tasks should be a defensive copy.
+        private static Task InternalWhenAll(Task[] tasks)
+        {
+            Debug.Assert(tasks != null, "Expected a non-null tasks array");
+            return (tasks.Length == 0) ? // take shortcut if there are no tasks upon which to wait
+                Task.CompletedTask :
+                new WhenAllPromise(tasks);
+        }
+
+        // A Task<VoidTaskResult> that gets completed when all of its constituent tasks complete.
+        // Completion logic will analyze the antecedents in order to choose completion status.
+        // This type allows us to replace this logic:
+        //      Task<VoidTaskResult> promise = new Task<VoidTaskResult>(...);
+        //      Action<Task> completionAction = delegate { <completion logic>};
+        //      TaskFactory.CommonCWAllLogic(tasksCopy).AddCompletionAction(completionAction);
+        //      return promise;
+        // which involves several allocations, with this logic:
+        //      return new WhenAllPromise(tasksCopy);
+        // which saves a couple of allocations and enables debugger notification specialization.
+        //
+        // Used in InternalWhenAll(Task[])
+        private sealed class WhenAllPromise : Task<VoidTaskResult>, ITaskCompletionAction
+        {
+            /// <summary>
+            /// Stores all of the constituent tasks.  Tasks clear themselves out of this
+            /// array as they complete, but only if they don't have their wait notification bit set.
+            /// </summary>
+            private readonly Task[] m_tasks;
+            /// <summary>The number of tasks remaining to complete.</summary>
+            private int m_count;
+
+            internal WhenAllPromise(Task[] tasks) :
+                base()
+            {
+                Debug.Assert(tasks != null, "Expected a non-null task array");
+                Debug.Assert(tasks.Length > 0, "Expected a non-zero length task array");
+
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, this.Id, "Task.WhenAll", 0);
+
+                if (s_asyncDebuggingEnabled)
+                {
+                    AddToActiveTasks(this);
+                }
+
+                m_tasks = tasks;
+                m_count = tasks.Length;
+
+                foreach (var task in tasks)
+                {
+                    if (task.IsCompleted) this.Invoke(task); // short-circuit the completion action, if possible
+                    else task.AddCompletionAction(this); // simple completion action
+                }
+            }
+
+            public void Invoke(Task completedTask)
+            {
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationRelation(CausalityTraceLevel.Important, this.Id, CausalityRelation.Join);
+
+                // Decrement the count, and only continue to complete the promise if we're the last one.
+                if (Interlocked.Decrement(ref m_count) == 0)
+                {
+                    // Set up some accounting variables
+                    List<ExceptionDispatchInfo> observedExceptions = null;
+                    Task canceledTask = null;
+
+                    // Loop through antecedents:
+                    //   If any one of them faults, the result will be faulted
+                    //   If none fault, but at least one is canceled, the result will be canceled
+                    //   If none fault or are canceled, then result will be RanToCompletion
+                    for (int i = 0; i < m_tasks.Length; i++)
+                    {
+                        var task = m_tasks[i];
+                        Debug.Assert(task != null, "Constituent task in WhenAll should never be null");
+
+                        if (task.IsFaulted)
+                        {
+                            if (observedExceptions == null) observedExceptions = new List<ExceptionDispatchInfo>();
+                            observedExceptions.AddRange(task.GetExceptionDispatchInfos());
+                        }
+                        else if (task.IsCanceled)
+                        {
+                            if (canceledTask == null) canceledTask = task; // use the first task that's canceled
+                        }
+
+                        // Regardless of completion state, if the task has its debug bit set, transfer it to the
+                        // WhenAll task.  We must do this before we complete the task.
+                        if (task.IsWaitNotificationEnabled) this.SetNotificationForWaitCompletion(enabled: true);
+                        else m_tasks[i] = null; // avoid holding onto tasks unnecessarily
+                    }
+
+                    if (observedExceptions != null)
+                    {
+                        Debug.Assert(observedExceptions.Count > 0, "Expected at least one exception");
+
+                        //We don't need to TraceOperationCompleted here because TrySetException will call Finish and we'll log it there
+
+                        TrySetException(observedExceptions);
+                    }
+                    else if (canceledTask != null)
+                    {
+                        TrySetCanceled(canceledTask.CancellationToken, canceledTask.GetCancellationExceptionDispatchInfo());
+                    }
+                    else
+                    {
+                        if (AsyncCausalityTracer.LoggingOn)
+                            AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, this.Id, AsyncCausalityStatus.Completed);
+
+                        if (Task.s_asyncDebuggingEnabled)
+                        {
+                            RemoveFromActiveTasks(this.Id);
+                        }
+                        TrySetResult(default(VoidTaskResult));
+                    }
+                }
+                Debug.Assert(m_count >= 0, "Count should never go below 0");
+            }
+
+            public bool InvokeMayRunArbitraryCode { get { return true; } }
+
+            /// <summary>
+            /// Returns whether we should notify the debugger of a wait completion.  This returns 
+            /// true iff at least one constituent task has its bit set.
+            /// </summary>
+            internal override bool ShouldNotifyDebuggerOfWaitCompletion
+            {
+                get
+                {
+                    return
+                        base.ShouldNotifyDebuggerOfWaitCompletion &&
+                        Task.AnyTaskRequiresNotifyDebuggerOfWaitCompletion(m_tasks);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Creates a task that will complete when all of the supplied tasks have completed.
+        /// </summary>
+        /// <param name="tasks">The tasks to wait on for completion.</param>
+        /// <returns>A task that represents the completion of all of the supplied tasks.</returns>
+        /// <remarks>
+        /// <para>
+        /// If any of the supplied tasks completes in a faulted state, the returned task will also complete in a Faulted state, 
+        /// where its exceptions will contain the aggregation of the set of unwrapped exceptions from each of the supplied tasks.  
+        /// </para>
+        /// <para>
+        /// If none of the supplied tasks faulted but at least one of them was canceled, the returned task will end in the Canceled state.
+        /// </para>
+        /// <para>
+        /// If none of the tasks faulted and none of the tasks were canceled, the resulting task will end in the RanToCompletion state.  
+        /// The Result of the returned task will be set to an array containing all of the results of the 
+        /// supplied tasks in the same order as they were provided (e.g. if the input tasks array contained t1, t2, t3, the output 
+        /// task's Result will return an TResult[] where arr[0] == t1.Result, arr[1] == t2.Result, and arr[2] == t3.Result). 
+        /// </para>
+        /// <para>
+        /// If the supplied array/enumerable contains no tasks, the returned task will immediately transition to a RanToCompletion 
+        /// state before it's returned to the caller.  The returned TResult[] will be an array of 0 elements.
+        /// </para>
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument was null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> collection contained a null task.
+        /// </exception>       
+        public static Task<TResult[]> WhenAll<TResult>(IEnumerable<Task<TResult>> tasks)
+        {
+            // Take a more efficient route if tasks is actually an array
+            Task<TResult>[] taskArray = tasks as Task<TResult>[];
+            if (taskArray != null)
+            {
+                return WhenAll<TResult>(taskArray);
+            }
+
+            // Skip a List allocation/copy if tasks is a collection
+            ICollection<Task<TResult>> taskCollection = tasks as ICollection<Task<TResult>>;
+            if (taskCollection != null)
+            {
+                int index = 0;
+                taskArray = new Task<TResult>[taskCollection.Count];
+                foreach (var task in tasks)
+                {
+                    if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
+                    taskArray[index++] = task;
+                }
+                return InternalWhenAll<TResult>(taskArray);
+            }
+
+            // Do some argument checking and convert tasks into a List (later an array)
+            if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
+            List<Task<TResult>> taskList = new List<Task<TResult>>();
+            foreach (Task<TResult> task in tasks)
+            {
+                if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
+                taskList.Add(task);
+            }
+
+            // Delegate the rest to InternalWhenAll<TResult>().
+            return InternalWhenAll<TResult>(taskList.ToArray());
+        }
+
+        /// <summary>
+        /// Creates a task that will complete when all of the supplied tasks have completed.
+        /// </summary>
+        /// <param name="tasks">The tasks to wait on for completion.</param>
+        /// <returns>A task that represents the completion of all of the supplied tasks.</returns>
+        /// <remarks>
+        /// <para>
+        /// If any of the supplied tasks completes in a faulted state, the returned task will also complete in a Faulted state, 
+        /// where its exceptions will contain the aggregation of the set of unwrapped exceptions from each of the supplied tasks.  
+        /// </para>
+        /// <para>
+        /// If none of the supplied tasks faulted but at least one of them was canceled, the returned task will end in the Canceled state.
+        /// </para>
+        /// <para>
+        /// If none of the tasks faulted and none of the tasks were canceled, the resulting task will end in the RanToCompletion state.  
+        /// The Result of the returned task will be set to an array containing all of the results of the 
+        /// supplied tasks in the same order as they were provided (e.g. if the input tasks array contained t1, t2, t3, the output 
+        /// task's Result will return an TResult[] where arr[0] == t1.Result, arr[1] == t2.Result, and arr[2] == t3.Result). 
+        /// </para>
+        /// <para>
+        /// If the supplied array/enumerable contains no tasks, the returned task will immediately transition to a RanToCompletion 
+        /// state before it's returned to the caller.  The returned TResult[] will be an array of 0 elements.
+        /// </para>
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument was null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> array contained a null task.
+        /// </exception>
+        public static Task<TResult[]> WhenAll<TResult>(params Task<TResult>[] tasks)
+        {
+            // Do some argument checking and make a defensive copy of the tasks array
+            if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
+
+            int taskCount = tasks.Length;
+            if (taskCount == 0) return InternalWhenAll<TResult>(tasks); // small optimization in the case of an empty task array
+
+            Task<TResult>[] tasksCopy = new Task<TResult>[taskCount];
+            for (int i = 0; i < taskCount; i++)
+            {
+                Task<TResult> task = tasks[i];
+                if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
+                tasksCopy[i] = task;
+            }
+
+            // Delegate the rest to InternalWhenAll<TResult>()
+            return InternalWhenAll<TResult>(tasksCopy);
+        }
+
+        // Some common logic to support WhenAll<TResult> methods
+        private static Task<TResult[]> InternalWhenAll<TResult>(Task<TResult>[] tasks)
+        {
+            Debug.Assert(tasks != null, "Expected a non-null tasks array");
+            return (tasks.Length == 0) ? // take shortcut if there are no tasks upon which to wait
+                new Task<TResult[]>(false, new TResult[0], TaskCreationOptions.None, default(CancellationToken)) :
+                new WhenAllPromise<TResult>(tasks);
+        }
+
+        // A Task<T> that gets completed when all of its constituent tasks complete.
+        // Completion logic will analyze the antecedents in order to choose completion status.
+        // See comments for non-generic version of WhenAllPromise class.
+        //
+        // Used in InternalWhenAll<TResult>(Task<TResult>[])
+        private sealed class WhenAllPromise<T> : Task<T[]>, ITaskCompletionAction
+        {
+            /// <summary>
+            /// Stores all of the constituent tasks.  Tasks clear themselves out of this
+            /// array as they complete, but only if they don't have their wait notification bit set.
+            /// </summary>
+            private readonly Task<T>[] m_tasks;
+            /// <summary>The number of tasks remaining to complete.</summary>
+            private int m_count;
+
+            internal WhenAllPromise(Task<T>[] tasks) :
+                base()
+            {
+                Debug.Assert(tasks != null, "Expected a non-null task array");
+                Debug.Assert(tasks.Length > 0, "Expected a non-zero length task array");
+
+                m_tasks = tasks;
+                m_count = tasks.Length;
+
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, this.Id, "Task.WhenAll", 0);
+
+                if (s_asyncDebuggingEnabled)
+                {
+                    AddToActiveTasks(this);
+                }
+
+                foreach (var task in tasks)
+                {
+                    if (task.IsCompleted) this.Invoke(task); // short-circuit the completion action, if possible
+                    else task.AddCompletionAction(this); // simple completion action
+                }
+            }
+
+            public void Invoke(Task ignored)
+            {
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationRelation(CausalityTraceLevel.Important, this.Id, CausalityRelation.Join);
+
+                // Decrement the count, and only continue to complete the promise if we're the last one.
+                if (Interlocked.Decrement(ref m_count) == 0)
+                {
+                    // Set up some accounting variables
+                    T[] results = new T[m_tasks.Length];
+                    List<ExceptionDispatchInfo> observedExceptions = null;
+                    Task canceledTask = null;
+
+                    // Loop through antecedents:
+                    //   If any one of them faults, the result will be faulted
+                    //   If none fault, but at least one is canceled, the result will be canceled
+                    //   If none fault or are canceled, then result will be RanToCompletion
+                    for (int i = 0; i < m_tasks.Length; i++)
+                    {
+                        Task<T> task = m_tasks[i];
+                        Debug.Assert(task != null, "Constituent task in WhenAll should never be null");
+
+                        if (task.IsFaulted)
+                        {
+                            if (observedExceptions == null) observedExceptions = new List<ExceptionDispatchInfo>();
+                            observedExceptions.AddRange(task.GetExceptionDispatchInfos());
+                        }
+                        else if (task.IsCanceled)
+                        {
+                            if (canceledTask == null) canceledTask = task; // use the first task that's canceled
+                        }
+                        else
+                        {
+                            Debug.Assert(task.Status == TaskStatus.RanToCompletion);
+                            results[i] = task.GetResultCore(waitCompletionNotification: false); // avoid Result, which would triggering debug notification
+                        }
+
+                        // Regardless of completion state, if the task has its debug bit set, transfer it to the
+                        // WhenAll task.  We must do this before we complete the task.
+                        if (task.IsWaitNotificationEnabled) this.SetNotificationForWaitCompletion(enabled: true);
+                        else m_tasks[i] = null; // avoid holding onto tasks unnecessarily
+                    }
+
+                    if (observedExceptions != null)
+                    {
+                        Debug.Assert(observedExceptions.Count > 0, "Expected at least one exception");
+
+                        //We don't need to TraceOperationCompleted here because TrySetException will call Finish and we'll log it there
+
+                        TrySetException(observedExceptions);
+                    }
+                    else if (canceledTask != null)
+                    {
+                        TrySetCanceled(canceledTask.CancellationToken, canceledTask.GetCancellationExceptionDispatchInfo());
+                    }
+                    else
+                    {
+                        if (AsyncCausalityTracer.LoggingOn)
+                            AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, this.Id, AsyncCausalityStatus.Completed);
+
+                        if (Task.s_asyncDebuggingEnabled)
+                        {
+                            RemoveFromActiveTasks(this.Id);
+                        }
+                        TrySetResult(results);
+                    }
+                }
+                Debug.Assert(m_count >= 0, "Count should never go below 0");
+            }
+
+            public bool InvokeMayRunArbitraryCode { get { return true; } }
+
+            /// <summary>
+            /// Returns whether we should notify the debugger of a wait completion.  This returns true
+            /// iff at least one constituent task has its bit set.
+            /// </summary>
+            internal override bool ShouldNotifyDebuggerOfWaitCompletion
+            {
+                get
+                {
+                    return
+                        base.ShouldNotifyDebuggerOfWaitCompletion &&
+                        Task.AnyTaskRequiresNotifyDebuggerOfWaitCompletion(m_tasks);
+                }
+            }
+        }
+        #endregion
+
+        #region WhenAny
+        /// <summary>
+        /// Creates a task that will complete when any of the supplied tasks have completed.
+        /// </summary>
+        /// <param name="tasks">The tasks to wait on for completion.</param>
+        /// <returns>A task that represents the completion of one of the supplied tasks.  The return Task's Result is the task that completed.</returns>
+        /// <remarks>
+        /// The returned task will complete when any of the supplied tasks has completed.  The returned task will always end in the RanToCompletion state 
+        /// with its Result set to the first task to complete.  This is true even if the first task to complete ended in the Canceled or Faulted state.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument was null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> array contained a null task, or was empty.
+        /// </exception>
+        public static Task<Task> WhenAny(params Task[] tasks)
+        {
+            if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
+            if (tasks.Length == 0)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_EmptyTaskList, ExceptionArgument.tasks);
+            }
+
+            // Make a defensive copy, as the user may manipulate the tasks array
+            // after we return but before the WhenAny asynchronously completes.
+            int taskCount = tasks.Length;
+            Task[] tasksCopy = new Task[taskCount];
+            for (int i = 0; i < taskCount; i++)
+            {
+                Task task = tasks[i];
+                if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
+                tasksCopy[i] = task;
+            }
+
+            // Previously implemented CommonCWAnyLogic() can handle the rest
+            return TaskFactory.CommonCWAnyLogic(tasksCopy);
+        }
+
+        /// <summary>
+        /// Creates a task that will complete when any of the supplied tasks have completed.
+        /// </summary>
+        /// <param name="tasks">The tasks to wait on for completion.</param>
+        /// <returns>A task that represents the completion of one of the supplied tasks.  The return Task's Result is the task that completed.</returns>
+        /// <remarks>
+        /// The returned task will complete when any of the supplied tasks has completed.  The returned task will always end in the RanToCompletion state 
+        /// with its Result set to the first task to complete.  This is true even if the first task to complete ended in the Canceled or Faulted state.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument was null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> collection contained a null task, or was empty.
+        /// </exception>
+        public static Task<Task> WhenAny(IEnumerable<Task> tasks)
+        {
+            if (tasks == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.tasks);
+
+            // Make a defensive copy, as the user may manipulate the tasks collection
+            // after we return but before the WhenAny asynchronously completes.
+            List<Task> taskList = new List<Task>();
+            foreach (Task task in tasks)
+            {
+                if (task == null) ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_NullTask, ExceptionArgument.tasks);
+                taskList.Add(task);
+            }
+
+            if (taskList.Count == 0)
+            {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Task_MultiTaskContinuation_EmptyTaskList, ExceptionArgument.tasks);
+            }
+
+            // Previously implemented CommonCWAnyLogic() can handle the rest
+            return TaskFactory.CommonCWAnyLogic(taskList);
+        }
+
+        /// <summary>
+        /// Creates a task that will complete when any of the supplied tasks have completed.
+        /// </summary>
+        /// <param name="tasks">The tasks to wait on for completion.</param>
+        /// <returns>A task that represents the completion of one of the supplied tasks.  The return Task's Result is the task that completed.</returns>
+        /// <remarks>
+        /// The returned task will complete when any of the supplied tasks has completed.  The returned task will always end in the RanToCompletion state 
+        /// with its Result set to the first task to complete.  This is true even if the first task to complete ended in the Canceled or Faulted state.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument was null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> array contained a null task, or was empty.
+        /// </exception>
+        public static Task<Task<TResult>> WhenAny<TResult>(params Task<TResult>[] tasks)
+        {
+            // We would just like to do this:
+            //    return (Task<Task<TResult>>) WhenAny( (Task[]) tasks);
+            // but classes are not covariant to enable casting Task<TResult> to Task<Task<TResult>>.
+
+            // Call WhenAny(Task[]) for basic functionality
+            Task<Task> intermediate = WhenAny((Task[])tasks);
+
+            // Return a continuation task with the correct result type
+            return intermediate.ContinueWith(Task<TResult>.TaskWhenAnyCast, default(CancellationToken),
+                TaskContinuationOptions.ExecuteSynchronously | TaskContinuationOptions.DenyChildAttach, TaskScheduler.Default);
+        }
+
+        /// <summary>
+        /// Creates a task that will complete when any of the supplied tasks have completed.
+        /// </summary>
+        /// <param name="tasks">The tasks to wait on for completion.</param>
+        /// <returns>A task that represents the completion of one of the supplied tasks.  The return Task's Result is the task that completed.</returns>
+        /// <remarks>
+        /// The returned task will complete when any of the supplied tasks has completed.  The returned task will always end in the RanToCompletion state 
+        /// with its Result set to the first task to complete.  This is true even if the first task to complete ended in the Canceled or Faulted state.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="tasks"/> argument was null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="tasks"/> collection contained a null task, or was empty.
+        /// </exception>
+        public static Task<Task<TResult>> WhenAny<TResult>(IEnumerable<Task<TResult>> tasks)
+        {
+            // We would just like to do this:
+            //    return (Task<Task<TResult>>) WhenAny( (IEnumerable<Task>) tasks);
+            // but classes are not covariant to enable casting Task<TResult> to Task<Task<TResult>>.
+
+            // Call WhenAny(IEnumerable<Task>) for basic functionality
+            Task<Task> intermediate = WhenAny((IEnumerable<Task>)tasks);
+
+            // Return a continuation task with the correct result type
+            return intermediate.ContinueWith(Task<TResult>.TaskWhenAnyCast, default(CancellationToken),
+                TaskContinuationOptions.ExecuteSynchronously | TaskContinuationOptions.DenyChildAttach, TaskScheduler.Default);
+        }
+        #endregion
+
+        internal static Task<TResult> CreateUnwrapPromise<TResult>(Task outerTask, bool lookForOce)
+        {
+            Debug.Assert(outerTask != null);
+
+            return new UnwrapPromise<TResult>(outerTask, lookForOce);
+        }
+
+        internal virtual Delegate[] GetDelegateContinuationsForDebugger()
+        {
+            //Avoid an infinite loop by making sure the continuation object is not a reference to istelf.
+            if (m_continuationObject != this)
+                return GetDelegatesFromContinuationObject(m_continuationObject);
+            else
+                return null;
+        }
+
+        internal static Delegate[] GetDelegatesFromContinuationObject(object continuationObject)
+        {
+            if (continuationObject != null)
+            {
+                Action singleAction = continuationObject as Action;
+                if (singleAction != null)
+                {
+                    return new Delegate[] { AsyncMethodBuilderCore.TryGetStateMachineForDebugger(singleAction) };
+                }
+
+                TaskContinuation taskContinuation = continuationObject as TaskContinuation;
+                if (taskContinuation != null)
+                {
+                    return taskContinuation.GetDelegateContinuationsForDebugger();
+                }
+
+                Task continuationTask = continuationObject as Task;
+                if (continuationTask != null)
+                {
+                    Debug.Assert(continuationTask.m_action == null);
+                    Delegate[] delegates = continuationTask.GetDelegateContinuationsForDebugger();
+                    if (delegates != null)
+                        return delegates;
+                }
+
+                //We need this ITaskCompletionAction after the Task because in the case of UnwrapPromise
+                //the VS debugger is more interested in the continuation than the internal invoke()
+                ITaskCompletionAction singleCompletionAction = continuationObject as ITaskCompletionAction;
+                if (singleCompletionAction != null)
+                {
+                    return new Delegate[] { new Action<Task>(singleCompletionAction.Invoke) };
+                }
+
+                List<object> continuationList = continuationObject as List<object>;
+                if (continuationList != null)
+                {
+                    List<Delegate> result = new List<Delegate>();
+                    foreach (object obj in continuationList)
+                    {
+                        var innerDelegates = GetDelegatesFromContinuationObject(obj);
+                        if (innerDelegates != null)
+                        {
+                            foreach (var del in innerDelegates)
+                            {
+                                if (del != null)
+                                    result.Add(del);
+                            }
+                        }
+                    }
+
+                    return result.ToArray();
+                }
+            }
+
+            return null;
+        }
+
+        //Do not remove: VS debugger calls this API directly using func-eval to populate data in the tasks window
+        private static Task GetActiveTaskFromId(int taskId)
+        {
+            Task task = null;
+            s_currentActiveTasks.TryGetValue(taskId, out task);
+            return task;
+        }
+    }
+
+    internal sealed class CompletionActionInvoker : IThreadPoolWorkItem
+    {
+        private readonly ITaskCompletionAction m_action;
+        private readonly Task m_completingTask;
+
+        internal CompletionActionInvoker(ITaskCompletionAction action, Task completingTask)
+        {
+            m_action = action;
+            m_completingTask = completingTask;
+        }
+
+        void IThreadPoolWorkItem.ExecuteWorkItem()
+        {
+            m_action.Invoke(m_completingTask);
+        }
+
+        void IThreadPoolWorkItem.MarkAborted(ThreadAbortException tae)
+        {
+            /* NOP */
+        }
+    }
+
+    // Proxy class for better debugging experience
+    internal class SystemThreadingTasks_TaskDebugView
+    {
+        private Task m_task;
+
+        public SystemThreadingTasks_TaskDebugView(Task task)
+        {
+            m_task = task;
+        }
+
+        public object AsyncState { get { return m_task.AsyncState; } }
+        public TaskCreationOptions CreationOptions { get { return m_task.CreationOptions; } }
+        public Exception Exception { get { return m_task.Exception; } }
+        public int Id { get { return m_task.Id; } }
+        public bool CancellationPending { get { return (m_task.Status == TaskStatus.WaitingToRun) && m_task.CancellationToken.IsCancellationRequested; } }
+        public TaskStatus Status { get { return m_task.Status; } }
+    }
+
+    /// <summary>
+    /// Specifies flags that control optional behavior for the creation and execution of tasks.
+    /// </summary>
+    // NOTE: These options are a subset of TaskContinuationsOptions, thus before adding a flag check it is
+    // not already in use.
+    [Flags]
+    public enum TaskCreationOptions
+    {
+        /// <summary>
+        /// Specifies that the default behavior should be used.
+        /// </summary>
+        None = 0x0,
+
+        /// <summary>
+        /// A hint to a <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> to schedule a
+        /// task in as fair a manner as possible, meaning that tasks scheduled sooner will be more likely to
+        /// be run sooner, and tasks scheduled later will be more likely to be run later.
+        /// </summary>
+        PreferFairness = 0x01,
+
+        /// <summary>
+        /// Specifies that a task will be a long-running, course-grained operation. It provides a hint to the
+        /// <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> that oversubscription may be
+        /// warranted. 
+        /// </summary>
+        LongRunning = 0x02,
+
+        /// <summary>
+        /// Specifies that a task is attached to a parent in the task hierarchy.
+        /// </summary>
+        AttachedToParent = 0x04,
+
+        /// <summary>
+        /// Specifies that an InvalidOperationException will be thrown if an attempt is made to attach a child task to the created task.
+        /// </summary>
+        DenyChildAttach = 0x08,
+
+        /// <summary>
+        /// Prevents the ambient scheduler from being seen as the current scheduler in the created task.  This means that operations
+        /// like StartNew or ContinueWith that are performed in the created task will see TaskScheduler.Default as the current scheduler.
+        /// </summary>
+        HideScheduler = 0x10,
+
+        // 0x20 is already being used in TaskContinuationOptions
+
+        /// <summary>
+        /// Forces continuations added to the current task to be executed asynchronously.
+        /// This option has precedence over TaskContinuationOptions.ExecuteSynchronously
+        /// </summary>
+        RunContinuationsAsynchronously = 0x40
+    }
+
+
+    /// <summary>
+    /// Task creation flags which are only used internally.
+    /// </summary>
+    [Flags]
+    internal enum InternalTaskOptions
+    {
+        /// <summary> Specifies "No internal task options" </summary>
+        None,
+
+        /// <summary>Used to filter out internal vs. public task creation options.</summary>
+        InternalOptionsMask = 0x0000FF00,
+
+        ContinuationTask = 0x0200,
+        PromiseTask = 0x0400,
+
+        /// <summary>
+        /// Store the presence of TaskContinuationOptions.LazyCancellation, since it does not directly
+        /// translate into any TaskCreationOptions.
+        /// </summary>
+        LazyCancellation = 0x1000,
+
+        /// <summary>Specifies that the task will be queued by the runtime before handing it over to the user. 
+        /// This flag will be used to skip the cancellationtoken registration step, which is only meant for unstarted tasks.</summary>
+        QueuedByRuntime = 0x2000,
+
+        /// <summary>
+        /// Denotes that Dispose should be a complete nop for a Task.  Used when constructing tasks that are meant to be cached/reused.
+        /// </summary>
+        DoNotDispose = 0x4000
+    }
+
+    /// <summary>
+    /// Specifies flags that control optional behavior for the creation and execution of continuation tasks.
+    /// </summary>
+    [Flags]
+    public enum TaskContinuationOptions
+    {
+        /// <summary>
+        /// Default = "Continue on any, no task options, run asynchronously"
+        /// Specifies that the default behavior should be used.  Continuations, by default, will
+        /// be scheduled when the antecedent task completes, regardless of the task's final <see
+        /// cref="System.Threading.Tasks.TaskStatus">TaskStatus</see>.
+        /// </summary>
+        None = 0,
+
+        // These are identical to their meanings and values in TaskCreationOptions
+
+        /// <summary>
+        /// A hint to a <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> to schedule a
+        /// task in as fair a manner as possible, meaning that tasks scheduled sooner will be more likely to
+        /// be run sooner, and tasks scheduled later will be more likely to be run later.
+        /// </summary>
+        PreferFairness = 0x01,
+
+        /// <summary>
+        /// Specifies that a task will be a long-running, course-grained operation.  It provides
+        /// a hint to the <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> that
+        /// oversubscription may be warranted.
+        /// </summary>
+        LongRunning = 0x02,
+        /// <summary>
+        /// Specifies that a task is attached to a parent in the task hierarchy.
+        /// </summary>
+        AttachedToParent = 0x04,
+
+        /// <summary>
+        /// Specifies that an InvalidOperationException will be thrown if an attempt is made to attach a child task to the created task.
+        /// </summary>
+        DenyChildAttach = 0x08,
+        /// <summary>
+        /// Prevents the ambient scheduler from being seen as the current scheduler in the created task.  This means that operations
+        /// like StartNew or ContinueWith that are performed in the created task will see TaskScheduler.Default as the current scheduler.
+        /// </summary>
+        HideScheduler = 0x10,
+
+        /// <summary>
+        /// In the case of continuation cancellation, prevents completion of the continuation until the antecedent has completed.
+        /// </summary>
+        LazyCancellation = 0x20,
+
+        RunContinuationsAsynchronously = 0x40,
+
+        // These are specific to continuations
+
+        /// <summary>
+        /// Specifies that the continuation task should not be scheduled if its antecedent ran to completion.
+        /// This option is not valid for multi-task continuations.
+        /// </summary>
+        NotOnRanToCompletion = 0x10000,
+        /// <summary>
+        /// Specifies that the continuation task should not be scheduled if its antecedent threw an unhandled
+        /// exception. This option is not valid for multi-task continuations.
+        /// </summary>
+        NotOnFaulted = 0x20000,
+        /// <summary>
+        /// Specifies that the continuation task should not be scheduled if its antecedent was canceled. This
+        /// option is not valid for multi-task continuations.
+        /// </summary>
+        NotOnCanceled = 0x40000,
+        /// <summary>
+        /// Specifies that the continuation task should be scheduled only if its antecedent ran to
+        /// completion. This option is not valid for multi-task continuations.
+        /// </summary>
+        OnlyOnRanToCompletion = NotOnFaulted | NotOnCanceled,
+        /// <summary>
+        /// Specifies that the continuation task should be scheduled only if its antecedent threw an
+        /// unhandled exception. This option is not valid for multi-task continuations.
+        /// </summary>
+        OnlyOnFaulted = NotOnRanToCompletion | NotOnCanceled,
+        /// <summary>
+        /// Specifies that the continuation task should be scheduled only if its antecedent was canceled.
+        /// This option is not valid for multi-task continuations.
+        /// </summary>
+        OnlyOnCanceled = NotOnRanToCompletion | NotOnFaulted,
+        /// <summary>
+        /// Specifies that the continuation task should be executed synchronously. With this option
+        /// specified, the continuation will be run on the same thread that causes the antecedent task to
+        /// transition into its final state. If the antecedent is already complete when the continuation is
+        /// created, the continuation will run on the thread creating the continuation.  Only very
+        /// short-running continuations should be executed synchronously.
+        /// </summary>
+        ExecuteSynchronously = 0x80000
+    }
+
+    /// <summary>
+    /// Internal helper class to keep track of stack depth and decide whether we should inline or not.
+    /// </summary>
+    internal class StackGuard
+    {
+        // current thread's depth of nested inline task executions
+        private int m_inliningDepth = 0;
+
+        // For relatively small inlining depths we don't want to get into the business of stack probing etc.
+        // This clearly leaves a window of opportunity for the user code to SO. However a piece of code
+        // that can SO in 20 inlines on a typical 1MB stack size probably needs to be revisited anyway.
+        private const int MAX_UNCHECKED_INLINING_DEPTH = 20;
+
+        /// <summary>
+        /// This method needs to be called before attempting inline execution on the current thread. 
+        /// If false is returned, it means we are too close to the end of the stack and should give up inlining.
+        /// Each call to TryBeginInliningScope() that returns true must be matched with a 
+        /// call to EndInliningScope() regardless of whether inlining actually took place.
+        /// </summary>
+        internal bool TryBeginInliningScope()
+        {
+            // If we're still under the 'safe' limit we'll just skip the stack probe to save p/invoke calls
+            if (m_inliningDepth < MAX_UNCHECKED_INLINING_DEPTH || CheckForSufficientStack())
+            {
+                m_inliningDepth++;
+                return true;
+            }
+            else
+                return false;
+        }
+
+        /// <summary>
+        /// This needs to be called once for each previous successful TryBeginInliningScope() call after
+        /// inlining related logic runs.
+        /// </summary>
+        internal void EndInliningScope()
+        {
+            m_inliningDepth--;
+            Debug.Assert(m_inliningDepth >= 0, "Inlining depth count should never go negative.");
+
+            // do the right thing just in case...
+            if (m_inliningDepth < 0) m_inliningDepth = 0;
+        }
+
+        private unsafe bool CheckForSufficientStack()
+        {
+            return RuntimeHelpers.TryEnsureSufficientExecutionStack();
+        }
+    }
+
+    // Special internal struct that we use to signify that we are not interested in
+    // a Task<VoidTaskResult>'s result.
+    internal struct VoidTaskResult { }
+
+    // Interface to which all completion actions must conform.
+    // This interface allows us to combine functionality and reduce allocations.
+    // For example, see Task.SetOnInvokeMres, and its use in Task.SpinThenBlockingWait().
+    // This code:
+    //      ManualResetEvent mres = new ManualResetEventSlim(false, 0);
+    //      Action<Task> completionAction = delegate { mres.Set() ; };
+    //      AddCompletionAction(completionAction);
+    // gets replaced with this:
+    //      SetOnInvokeMres mres = new SetOnInvokeMres();
+    //      AddCompletionAction(mres);
+    // For additional examples of where this is used, see internal classes Task.SignalOnInvokeCDE,
+    // Task.WhenAllPromise, Task.WhenAllPromise<T>, TaskFactory.CompleteOnCountdownPromise,
+    // TaskFactory.CompleteOnCountdownPromise<T>, and TaskFactory.CompleteOnInvokePromise.
+    internal interface ITaskCompletionAction
+    {
+        /// <summary>Invoked to run the completion action.</summary>
+        void Invoke(Task completingTask);
+
+        /// <summary>
+        /// Some completion actions are considered internal implementation details of tasks,
+        /// using the continuation mechanism only for performance reasons.  Such actions perform
+        /// known quantities and types of work, and can be invoked safely as a continuation even
+        /// if the system wants to prevent arbitrary continuations from running synchronously.
+        /// This should only return false for a limited set of implementations where a small amount
+        /// of work is guaranteed to be performed, e.g. setting a ManualResetEventSlim.
+        /// </summary>
+        bool InvokeMayRunArbitraryCode { get; }
+    }
+
+    // This class encapsulates all "unwrap" logic, and also implements ITaskCompletionAction,
+    // which minimizes the allocations needed for queuing it to its antecedent.  This
+    // logic is used by both the Unwrap extension methods and the unwrap-style Task.Run methods.
+    internal sealed class UnwrapPromise<TResult> : Task<TResult>, ITaskCompletionAction
+    {
+        // The possible states for our UnwrapPromise, used by Invoke() to determine which logic to execute
+        private const byte STATE_WAITING_ON_OUTER_TASK = 0; // Invoke() means "process completed outer task"
+        private const byte STATE_WAITING_ON_INNER_TASK = 1; // Invoke() means "process completed inner task"
+        private const byte STATE_DONE = 2;                  // Invoke() means "something went wrong and we are hosed!"
+
+        // Keep track of our state; initialized to STATE_WAITING_ON_OUTER_TASK in the constructor
+        private byte _state;
+
+        // "Should we check for OperationCanceledExceptions on the outer task and interpret them as proxy cancellation?"
+        // Unwrap() sets this to false, Run() sets it to true.
+        private readonly bool _lookForOce;
+
+        public UnwrapPromise(Task outerTask, bool lookForOce)
+            : base((object)null, outerTask.CreationOptions & TaskCreationOptions.AttachedToParent)
+        {
+            Debug.Assert(outerTask != null, "Expected non-null outerTask");
+            _lookForOce = lookForOce;
+            _state = STATE_WAITING_ON_OUTER_TASK;
+
+            if (AsyncCausalityTracer.LoggingOn)
+                AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, this.Id, "Task.Unwrap", 0);
+
+            if (Task.s_asyncDebuggingEnabled)
+            {
+                AddToActiveTasks(this);
+            }
+
+            // Link ourselves to the outer task.
+            // If the outer task has already completed, take the fast path
+            // of immediately transferring its results or processing the inner task.
+            if (outerTask.IsCompleted)
+            {
+                ProcessCompletedOuterTask(outerTask);
+            }
+            else // Otherwise, process its completion asynchronously.
+            {
+                outerTask.AddCompletionAction(this);
+            }
+        }
+
+        // For ITaskCompletionAction 
+        public void Invoke(Task completingTask)
+        {
+            // Check the current stack guard.  If we're ok to inline,
+            // process the task, and reset the guard when we're done.
+            var sg = Task.CurrentStackGuard;
+            if (sg.TryBeginInliningScope())
+            {
+                try { InvokeCore(completingTask); }
+                finally { sg.EndInliningScope(); }
+            }
+            // Otherwise, we're too deep on the stack, and
+            // we shouldn't run the continuation chain here, so queue a work
+            // item to call back here to Invoke asynchronously.
+            else InvokeCoreAsync(completingTask);
+        }
+
+        /// <summary>
+        /// Processes the completed task. InvokeCore could be called twice:
+        /// once for the outer task, once for the inner task.
+        /// </summary>
+        /// <param name="completingTask">The completing outer or inner task.</param>
+        private void InvokeCore(Task completingTask)
+        {
+            switch (_state)
+            {
+                case STATE_WAITING_ON_OUTER_TASK:
+                    ProcessCompletedOuterTask(completingTask);
+                    // We bump the state inside of ProcessCompletedOuterTask because it can also be called from the constructor.
+                    break;
+                case STATE_WAITING_ON_INNER_TASK:
+                    bool result = TrySetFromTask(completingTask, lookForOce: false);
+                    _state = STATE_DONE; // bump the state
+                    Debug.Assert(result, "Expected TrySetFromTask from inner task to succeed");
+                    break;
+                default:
+                    Debug.Fail("UnwrapPromise in illegal state");
+                    break;
+            }
+        }
+
+        // Calls InvokeCore asynchronously.
+        private void InvokeCoreAsync(Task completingTask)
+        {
+            // Queue a call to Invoke.  If we're so deep on the stack that we're at risk of overflowing,
+            // there's a high liklihood this thread is going to be doing lots more work before
+            // returning to the thread pool (at the very least unwinding through thousands of
+            // stack frames).  So we queue to the global queue.
+            ThreadPool.UnsafeQueueUserWorkItem(state =>
+            {
+                // InvokeCore(completingTask);
+                var tuple = (Tuple<UnwrapPromise<TResult>, Task>)state;
+                tuple.Item1.InvokeCore(tuple.Item2);
+            }, Tuple.Create<UnwrapPromise<TResult>, Task>(this, completingTask));
+        }
+
+        /// <summary>Processes the outer task once it's completed.</summary>
+        /// <param name="task">The now-completed outer task.</param>
+        private void ProcessCompletedOuterTask(Task task)
+        {
+            Debug.Assert(task != null && task.IsCompleted, "Expected non-null, completed outer task");
+            Debug.Assert(_state == STATE_WAITING_ON_OUTER_TASK, "We're in the wrong state!");
+
+            // Bump our state before proceeding any further
+            _state = STATE_WAITING_ON_INNER_TASK;
+
+            switch (task.Status)
+            {
+                // If the outer task did not complete successfully, then record the 
+                // cancellation/fault information to tcs.Task.
+                case TaskStatus.Canceled:
+                case TaskStatus.Faulted:
+                    bool result = TrySetFromTask(task, _lookForOce);
+                    Debug.Assert(result, "Expected TrySetFromTask from outer task to succeed");
+                    break;
+
+                // Otherwise, process the inner task it returned.
+                case TaskStatus.RanToCompletion:
+                    var taskOfTaskOfTResult = task as Task<Task<TResult>>; // it's either a Task<Task> or Task<Task<TResult>>
+                    ProcessInnerTask(taskOfTaskOfTResult != null ?
+                        taskOfTaskOfTResult.Result : ((Task<Task>)task).Result);
+                    break;
+            }
+        }
+
+        /// <summary>Transfer the completion status from "task" to ourself.</summary>
+        /// <param name="task">The source task whose results should be transfered to <paramref name="promise"/>.</param>
+        /// <param name="lookForOce">Whether or not to look for OperationCanceledExceptions in task's exceptions if it faults.</param>
+        /// <returns>true if the transfer was successful; otherwise, false.</returns>
+        private bool TrySetFromTask(Task task, bool lookForOce)
+        {
+            Debug.Assert(task != null && task.IsCompleted, "TrySetFromTask: Expected task to have completed.");
+
+            if (AsyncCausalityTracer.LoggingOn)
+                AsyncCausalityTracer.TraceOperationRelation(CausalityTraceLevel.Important, this.Id, CausalityRelation.Join);
+
+            bool result = false;
+            switch (task.Status)
+            {
+                case TaskStatus.Canceled:
+                    result = TrySetCanceled(task.CancellationToken, task.GetCancellationExceptionDispatchInfo());
+                    break;
+
+                case TaskStatus.Faulted:
+                    var edis = task.GetExceptionDispatchInfos();
+                    ExceptionDispatchInfo oceEdi;
+                    OperationCanceledException oce;
+                    if (lookForOce && edis.Count > 0 &&
+                        (oceEdi = edis[0]) != null &&
+                        (oce = oceEdi.SourceException as OperationCanceledException) != null)
+                    {
+                        result = TrySetCanceled(oce.CancellationToken, oceEdi);
+                    }
+                    else
+                    {
+                        result = TrySetException(edis);
+                    }
+                    break;
+
+                case TaskStatus.RanToCompletion:
+                    var taskTResult = task as Task<TResult>;
+
+                    if (AsyncCausalityTracer.LoggingOn)
+                        AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, this.Id, AsyncCausalityStatus.Completed);
+
+                    if (Task.s_asyncDebuggingEnabled)
+                    {
+                        RemoveFromActiveTasks(this.Id);
+                    }
+
+                    result = TrySetResult(taskTResult != null ? taskTResult.Result : default(TResult));
+                    break;
+            }
+            return result;
+        }
+
+        /// <summary>
+        /// Processes the inner task of a Task{Task} or Task{Task{TResult}}, 
+        /// transferring the appropriate results to ourself.
+        /// </summary>
+        /// <param name="task">The inner task returned by the task provided by the user.</param>
+        private void ProcessInnerTask(Task task)
+        {
+            // If the inner task is null, the proxy should be canceled.
+            if (task == null)
+            {
+                TrySetCanceled(default(CancellationToken));
+                _state = STATE_DONE; // ... and record that we are done
+            }
+
+            // Fast path for if the inner task is already completed
+            else if (task.IsCompleted)
+            {
+                TrySetFromTask(task, lookForOce: false);
+                _state = STATE_DONE; // ... and record that we are done
+            }
+
+            // The inner task exists but is not yet complete, so when it does complete,
+            // take some action to set our completion state.
+            else
+            {
+                task.AddCompletionAction(this);
+                // We'll record that we are done when Invoke() is called.
+            }
+        }
+
+        public bool InvokeMayRunArbitraryCode { get { return true; } }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs b/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs
new file mode 100644
index 0000000000..3f72500ce4
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs
@@ -0,0 +1,856 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// Implementation of task continuations, TaskContinuation, and its descendants.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Security;
+using System.Diagnostics;
+using System.Runtime.ExceptionServices;
+using System.Runtime.CompilerServices;
+using System.Threading;
+
+#if FEATURE_COMINTEROP
+using System.Runtime.InteropServices.WindowsRuntime;
+#endif // FEATURE_COMINTEROP
+
+namespace System.Threading.Tasks
+{
+    // Task type used to implement: Task ContinueWith(Action<Task,...>)
+    internal sealed class ContinuationTaskFromTask : Task
+    {
+        private Task m_antecedent;
+
+        public ContinuationTaskFromTask(
+            Task antecedent, Delegate action, object state, TaskCreationOptions creationOptions, InternalTaskOptions internalOptions) :
+            base(action, state, Task.InternalCurrentIfAttached(creationOptions), default(CancellationToken), creationOptions, internalOptions, null)
+        {
+            Debug.Assert(action is Action<Task> || action is Action<Task, object>,
+                "Invalid delegate type in ContinuationTaskFromTask");
+            m_antecedent = antecedent;
+        }
+
+        /// <summary>
+        /// Evaluates the value selector of the Task which is passed in as an object and stores the result.
+        /// </summary>        
+        internal override void InnerInvoke()
+        {
+            // Get and null out the antecedent.  This is crucial to avoid a memory
+            // leak with long chains of continuations.
+            var antecedent = m_antecedent;
+            Debug.Assert(antecedent != null,
+                "No antecedent was set for the ContinuationTaskFromTask.");
+            m_antecedent = null;
+
+            // Notify the debugger we're completing an asynchronous wait on a task
+            antecedent.NotifyDebuggerOfWaitCompletionIfNecessary();
+
+            // Invoke the delegate
+            Debug.Assert(m_action != null);
+            var action = m_action as Action<Task>;
+            if (action != null)
+            {
+                action(antecedent);
+                return;
+            }
+            var actionWithState = m_action as Action<Task, object>;
+            if (actionWithState != null)
+            {
+                actionWithState(antecedent, m_stateObject);
+                return;
+            }
+            Debug.Fail("Invalid m_action in ContinuationTaskFromTask");
+        }
+    }
+
+    // Task type used to implement: Task<TResult> ContinueWith(Func<Task,...>)
+    internal sealed class ContinuationResultTaskFromTask<TResult> : Task<TResult>
+    {
+        private Task m_antecedent;
+
+        public ContinuationResultTaskFromTask(
+            Task antecedent, Delegate function, object state, TaskCreationOptions creationOptions, InternalTaskOptions internalOptions) :
+            base(function, state, Task.InternalCurrentIfAttached(creationOptions), default(CancellationToken), creationOptions, internalOptions, null)
+        {
+            Debug.Assert(function is Func<Task, TResult> || function is Func<Task, object, TResult>,
+                "Invalid delegate type in ContinuationResultTaskFromTask");
+            m_antecedent = antecedent;
+        }
+
+        /// <summary>
+        /// Evaluates the value selector of the Task which is passed in as an object and stores the result.
+        /// </summary>        
+        internal override void InnerInvoke()
+        {
+            // Get and null out the antecedent.  This is crucial to avoid a memory
+            // leak with long chains of continuations.
+            var antecedent = m_antecedent;
+            Debug.Assert(antecedent != null,
+                "No antecedent was set for the ContinuationResultTaskFromTask.");
+            m_antecedent = null;
+
+            // Notify the debugger we're completing an asynchronous wait on a task
+            antecedent.NotifyDebuggerOfWaitCompletionIfNecessary();
+
+            // Invoke the delegate
+            Debug.Assert(m_action != null);
+            var func = m_action as Func<Task, TResult>;
+            if (func != null)
+            {
+                m_result = func(antecedent);
+                return;
+            }
+            var funcWithState = m_action as Func<Task, object, TResult>;
+            if (funcWithState != null)
+            {
+                m_result = funcWithState(antecedent, m_stateObject);
+                return;
+            }
+            Debug.Fail("Invalid m_action in ContinuationResultTaskFromTask");
+        }
+    }
+
+    // Task type used to implement: Task ContinueWith(Action<Task<TAntecedentResult>,...>)
+    internal sealed class ContinuationTaskFromResultTask<TAntecedentResult> : Task
+    {
+        private Task<TAntecedentResult> m_antecedent;
+
+        public ContinuationTaskFromResultTask(
+            Task<TAntecedentResult> antecedent, Delegate action, object state, TaskCreationOptions creationOptions, InternalTaskOptions internalOptions) :
+            base(action, state, Task.InternalCurrentIfAttached(creationOptions), default(CancellationToken), creationOptions, internalOptions, null)
+        {
+            Debug.Assert(action is Action<Task<TAntecedentResult>> || action is Action<Task<TAntecedentResult>, object>,
+                "Invalid delegate type in ContinuationTaskFromResultTask");
+            m_antecedent = antecedent;
+        }
+
+        /// <summary>
+        /// Evaluates the value selector of the Task which is passed in as an object and stores the result.
+        /// </summary>
+        internal override void InnerInvoke()
+        {
+            // Get and null out the antecedent.  This is crucial to avoid a memory
+            // leak with long chains of continuations.
+            var antecedent = m_antecedent;
+            Debug.Assert(antecedent != null,
+                "No antecedent was set for the ContinuationTaskFromResultTask.");
+            m_antecedent = null;
+
+            // Notify the debugger we're completing an asynchronous wait on a task
+            antecedent.NotifyDebuggerOfWaitCompletionIfNecessary();
+
+            // Invoke the delegate
+            Debug.Assert(m_action != null);
+            var action = m_action as Action<Task<TAntecedentResult>>;
+            if (action != null)
+            {
+                action(antecedent);
+                return;
+            }
+            var actionWithState = m_action as Action<Task<TAntecedentResult>, object>;
+            if (actionWithState != null)
+            {
+                actionWithState(antecedent, m_stateObject);
+                return;
+            }
+            Debug.Fail("Invalid m_action in ContinuationTaskFromResultTask");
+        }
+    }
+
+    // Task type used to implement: Task<TResult> ContinueWith(Func<Task<TAntecedentResult>,...>)
+    internal sealed class ContinuationResultTaskFromResultTask<TAntecedentResult, TResult> : Task<TResult>
+    {
+        private Task<TAntecedentResult> m_antecedent;
+
+        public ContinuationResultTaskFromResultTask(
+            Task<TAntecedentResult> antecedent, Delegate function, object state, TaskCreationOptions creationOptions, InternalTaskOptions internalOptions) :
+            base(function, state, Task.InternalCurrentIfAttached(creationOptions), default(CancellationToken), creationOptions, internalOptions, null)
+        {
+            Debug.Assert(function is Func<Task<TAntecedentResult>, TResult> || function is Func<Task<TAntecedentResult>, object, TResult>,
+                "Invalid delegate type in ContinuationResultTaskFromResultTask");
+            m_antecedent = antecedent;
+        }
+
+        /// <summary>
+        /// Evaluates the value selector of the Task which is passed in as an object and stores the result.
+        /// </summary>
+        internal override void InnerInvoke()
+        {
+            // Get and null out the antecedent.  This is crucial to avoid a memory
+            // leak with long chains of continuations.
+            var antecedent = m_antecedent;
+            Debug.Assert(antecedent != null,
+                "No antecedent was set for the ContinuationResultTaskFromResultTask.");
+            m_antecedent = null;
+
+            // Notify the debugger we're completing an asynchronous wait on a task
+            antecedent.NotifyDebuggerOfWaitCompletionIfNecessary();
+
+            // Invoke the delegate
+            Debug.Assert(m_action != null);
+            var func = m_action as Func<Task<TAntecedentResult>, TResult>;
+            if (func != null)
+            {
+                m_result = func(antecedent);
+                return;
+            }
+            var funcWithState = m_action as Func<Task<TAntecedentResult>, object, TResult>;
+            if (funcWithState != null)
+            {
+                m_result = funcWithState(antecedent, m_stateObject);
+                return;
+            }
+            Debug.Fail("Invalid m_action in ContinuationResultTaskFromResultTask");
+        }
+    }
+
+    // For performance reasons, we don't just have a single way of representing
+    // a continuation object.  Rather, we have a hierarchy of types:
+    // - TaskContinuation: abstract base that provides a virtual Run method
+    //     - StandardTaskContinuation: wraps a task,options,and scheduler, and overrides Run to process the task with that configuration
+    //     - AwaitTaskContinuation: base for continuations created through TaskAwaiter; targets default scheduler by default
+    //         - TaskSchedulerAwaitTaskContinuation: awaiting with a non-default TaskScheduler
+    //         - SynchronizationContextAwaitTaskContinuation: awaiting with a "current" sync ctx
+
+    /// <summary>Represents a continuation.</summary>
+    internal abstract class TaskContinuation
+    {
+        /// <summary>Inlines or schedules the continuation.</summary>
+        /// <param name="completedTask">The antecedent task that has completed.</param>
+        /// <param name="canInlineContinuationTask">true if inlining is permitted; otherwise, false.</param>
+        internal abstract void Run(Task completedTask, bool bCanInlineContinuationTask);
+
+        /// <summary>Tries to run the task on the current thread, if possible; otherwise, schedules it.</summary>
+        /// <param name="task">The task to run</param>
+        /// <param name="needsProtection">
+        /// true if we need to protect against multiple threads racing to start/cancel the task; otherwise, false.
+        /// </param>
+        protected static void InlineIfPossibleOrElseQueue(Task task, bool needsProtection)
+        {
+            Debug.Assert(task != null);
+            Debug.Assert(task.m_taskScheduler != null);
+
+            // Set the TASK_STATE_STARTED flag.  This only needs to be done
+            // if the task may be canceled or if someone else has a reference to it
+            // that may try to execute it.
+            if (needsProtection)
+            {
+                if (!task.MarkStarted())
+                    return; // task has been previously started or canceled.  Stop processing.
+            }
+            else
+            {
+                task.m_stateFlags |= Task.TASK_STATE_STARTED;
+            }
+
+            // Try to inline it but queue if we can't
+            try
+            {
+                if (!task.m_taskScheduler.TryRunInline(task, taskWasPreviouslyQueued: false))
+                {
+                    task.m_taskScheduler.InternalQueueTask(task);
+                }
+            }
+            catch (Exception e)
+            {
+                // Either TryRunInline() or QueueTask() threw an exception. Record the exception, marking the task as Faulted.
+                // However if it was a ThreadAbortException coming from TryRunInline we need to skip here, 
+                // because it would already have been handled in Task.Execute()
+                if (!(e is ThreadAbortException &&
+                      (task.m_stateFlags & Task.TASK_STATE_THREAD_WAS_ABORTED) != 0))    // this ensures TAEs from QueueTask will be wrapped in TSE
+                {
+                    TaskSchedulerException tse = new TaskSchedulerException(e);
+                    task.AddException(tse);
+                    task.Finish(false);
+                }
+
+                // Don't re-throw.
+            }
+        }
+
+        internal abstract Delegate[] GetDelegateContinuationsForDebugger();
+    }
+
+    /// <summary>Provides the standard implementation of a task continuation.</summary>
+    internal class StandardTaskContinuation : TaskContinuation
+    {
+        /// <summary>The unstarted continuation task.</summary>
+        internal readonly Task m_task;
+        /// <summary>The options to use with the continuation task.</summary>
+        internal readonly TaskContinuationOptions m_options;
+        /// <summary>The task scheduler with which to run the continuation task.</summary>
+        private readonly TaskScheduler m_taskScheduler;
+
+        /// <summary>Initializes a new continuation.</summary>
+        /// <param name="task">The task to be activated.</param>
+        /// <param name="options">The continuation options.</param>
+        /// <param name="scheduler">The scheduler to use for the continuation.</param>
+        internal StandardTaskContinuation(Task task, TaskContinuationOptions options, TaskScheduler scheduler)
+        {
+            Debug.Assert(task != null, "TaskContinuation ctor: task is null");
+            Debug.Assert(scheduler != null, "TaskContinuation ctor: scheduler is null");
+            m_task = task;
+            m_options = options;
+            m_taskScheduler = scheduler;
+            if (AsyncCausalityTracer.LoggingOn)
+                AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, m_task.Id, "Task.ContinueWith: " + task.m_action.Method.Name, 0);
+
+            if (Task.s_asyncDebuggingEnabled)
+            {
+                Task.AddToActiveTasks(m_task);
+            }
+        }
+
+        /// <summary>Invokes the continuation for the target completion task.</summary>
+        /// <param name="completedTask">The completed task.</param>
+        /// <param name="bCanInlineContinuationTask">Whether the continuation can be inlined.</param>
+        internal override void Run(Task completedTask, bool bCanInlineContinuationTask)
+        {
+            Debug.Assert(completedTask != null);
+            Debug.Assert(completedTask.IsCompleted, "ContinuationTask.Run(): completedTask not completed");
+
+            // Check if the completion status of the task works with the desired 
+            // activation criteria of the TaskContinuationOptions.
+            TaskContinuationOptions options = m_options;
+            bool isRightKind =
+                completedTask.IsCompletedSuccessfully ?
+                    (options & TaskContinuationOptions.NotOnRanToCompletion) == 0 :
+                    (completedTask.IsCanceled ?
+                        (options & TaskContinuationOptions.NotOnCanceled) == 0 :
+                        (options & TaskContinuationOptions.NotOnFaulted) == 0);
+
+            // If the completion status is allowed, run the continuation.
+            Task continuationTask = m_task;
+            if (isRightKind)
+            {
+                //If the task was cancel before running (e.g a ContinueWhenAll with a cancelled caancelation token)
+                //we will still flow it to ScheduleAndStart() were it will check the status before running
+                //We check here to avoid faulty logs that contain a join event to an operation that was already set as completed.
+                if (!continuationTask.IsCanceled && AsyncCausalityTracer.LoggingOn)
+                {
+                    // Log now that we are sure that this continuation is being ran
+                    AsyncCausalityTracer.TraceOperationRelation(CausalityTraceLevel.Important, continuationTask.Id, CausalityRelation.AssignDelegate);
+                }
+                continuationTask.m_taskScheduler = m_taskScheduler;
+
+                // Either run directly or just queue it up for execution, depending
+                // on whether synchronous or asynchronous execution is wanted.
+                if (bCanInlineContinuationTask && // inlining is allowed by the caller
+                    (options & TaskContinuationOptions.ExecuteSynchronously) != 0) // synchronous execution was requested by the continuation's creator
+                {
+                    InlineIfPossibleOrElseQueue(continuationTask, needsProtection: true);
+                }
+                else
+                {
+                    try { continuationTask.ScheduleAndStart(needsProtection: true); }
+                    catch (TaskSchedulerException)
+                    {
+                        // No further action is necessary -- ScheduleAndStart() already transitioned the 
+                        // task to faulted.  But we want to make sure that no exception is thrown from here.
+                    }
+                }
+            }
+            // Otherwise, the final state of this task does not match the desired
+            // continuation activation criteria; cancel it to denote this.
+            else continuationTask.InternalCancel(false);
+        }
+
+        internal override Delegate[] GetDelegateContinuationsForDebugger()
+        {
+            if (m_task.m_action == null)
+            {
+                return m_task.GetDelegateContinuationsForDebugger();
+            }
+
+            return new Delegate[] { m_task.m_action };
+        }
+    }
+
+    /// <summary>Task continuation for awaiting with a current synchronization context.</summary>
+    internal sealed class SynchronizationContextAwaitTaskContinuation : AwaitTaskContinuation
+    {
+        /// <summary>SendOrPostCallback delegate to invoke the action.</summary>
+        private readonly static SendOrPostCallback s_postCallback = state => ((Action)state)(); // can't use InvokeAction as it's SecurityCritical
+        /// <summary>Cached delegate for PostAction</summary>
+        private static ContextCallback s_postActionCallback;
+        /// <summary>The context with which to run the action.</summary>
+        private readonly SynchronizationContext m_syncContext;
+
+        /// <summary>Initializes the SynchronizationContextAwaitTaskContinuation.</summary>
+        /// <param name="context">The synchronization context with which to invoke the action.  Must not be null.</param>
+        /// <param name="action">The action to invoke. Must not be null.</param>
+        /// <param name="flowExecutionContext">Whether to capture and restore ExecutionContext.</param>
+        internal SynchronizationContextAwaitTaskContinuation(
+            SynchronizationContext context, Action action, bool flowExecutionContext) :
+            base(action, flowExecutionContext)
+        {
+            Debug.Assert(context != null);
+            m_syncContext = context;
+        }
+
+        /// <summary>Inlines or schedules the continuation.</summary>
+        /// <param name="ignored">The antecedent task, which is ignored.</param>
+        /// <param name="canInlineContinuationTask">true if inlining is permitted; otherwise, false.</param>
+        internal sealed override void Run(Task task, bool canInlineContinuationTask)
+        {
+            // If we're allowed to inline, run the action on this thread.
+            if (canInlineContinuationTask &&
+                m_syncContext == SynchronizationContext.Current)
+            {
+                RunCallback(GetInvokeActionCallback(), m_action, ref Task.t_currentTask);
+            }
+            // Otherwise, Post the action back to the SynchronizationContext.
+            else
+            {
+                TplEtwProvider etwLog = TplEtwProvider.Log;
+                if (etwLog.IsEnabled())
+                {
+                    m_continuationId = Task.NewId();
+                    etwLog.AwaitTaskContinuationScheduled((task.ExecutingTaskScheduler ?? TaskScheduler.Default).Id, task.Id, m_continuationId);
+                }
+                RunCallback(GetPostActionCallback(), this, ref Task.t_currentTask);
+            }
+            // Any exceptions will be handled by RunCallback.
+        }
+
+        /// <summary>Calls InvokeOrPostAction(false) on the supplied SynchronizationContextAwaitTaskContinuation.</summary>
+        /// <param name="state">The SynchronizationContextAwaitTaskContinuation.</param>
+        private static void PostAction(object state)
+        {
+            var c = (SynchronizationContextAwaitTaskContinuation)state;
+
+            TplEtwProvider etwLog = TplEtwProvider.Log;
+            if (etwLog.TasksSetActivityIds && c.m_continuationId != 0)
+            {
+                c.m_syncContext.Post(s_postCallback, GetActionLogDelegate(c.m_continuationId, c.m_action));
+            }
+            else
+            {
+                c.m_syncContext.Post(s_postCallback, c.m_action); // s_postCallback is manually cached, as the compiler won't in a SecurityCritical method
+            }
+        }
+
+        private static Action GetActionLogDelegate(int continuationId, Action action)
+        {
+            return () =>
+                {
+                    Guid savedActivityId;
+                    Guid activityId = TplEtwProvider.CreateGuidForTaskID(continuationId);
+                    System.Diagnostics.Tracing.EventSource.SetCurrentThreadActivityId(activityId, out savedActivityId);
+                    try { action(); }
+                    finally { System.Diagnostics.Tracing.EventSource.SetCurrentThreadActivityId(savedActivityId); }
+                };
+        }
+
+        /// <summary>Gets a cached delegate for the PostAction method.</summary>
+        /// <returns>
+        /// A delegate for PostAction, which expects a SynchronizationContextAwaitTaskContinuation 
+        /// to be passed as state.
+        /// </returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static ContextCallback GetPostActionCallback()
+        {
+            ContextCallback callback = s_postActionCallback;
+            if (callback == null) { s_postActionCallback = callback = PostAction; } // lazily initialize SecurityCritical delegate
+            return callback;
+        }
+    }
+
+    /// <summary>Task continuation for awaiting with a task scheduler.</summary>
+    internal sealed class TaskSchedulerAwaitTaskContinuation : AwaitTaskContinuation
+    {
+        /// <summary>The scheduler on which to run the action.</summary>
+        private readonly TaskScheduler m_scheduler;
+
+        /// <summary>Initializes the TaskSchedulerAwaitTaskContinuation.</summary>
+        /// <param name="scheduler">The task scheduler with which to invoke the action.  Must not be null.</param>
+        /// <param name="action">The action to invoke. Must not be null.</param>
+        /// <param name="flowExecutionContext">Whether to capture and restore ExecutionContext.</param>
+        internal TaskSchedulerAwaitTaskContinuation(
+            TaskScheduler scheduler, Action action, bool flowExecutionContext) :
+            base(action, flowExecutionContext)
+        {
+            Debug.Assert(scheduler != null);
+            m_scheduler = scheduler;
+        }
+
+        /// <summary>Inlines or schedules the continuation.</summary>
+        /// <param name="ignored">The antecedent task, which is ignored.</param>
+        /// <param name="canInlineContinuationTask">true if inlining is permitted; otherwise, false.</param>
+        internal sealed override void Run(Task ignored, bool canInlineContinuationTask)
+        {
+            // If we're targeting the default scheduler, we can use the faster path provided by the base class.
+            if (m_scheduler == TaskScheduler.Default)
+            {
+                base.Run(ignored, canInlineContinuationTask);
+            }
+            else
+            {
+                // We permit inlining if the caller allows us to, and 
+                // either we're on a thread pool thread (in which case we're fine running arbitrary code)
+                // or we're already on the target scheduler (in which case we'll just ask the scheduler
+                // whether it's ok to run here).  We include the IsThreadPoolThread check here, whereas
+                // we don't in AwaitTaskContinuation.Run, since here it expands what's allowed as opposed
+                // to in AwaitTaskContinuation.Run where it restricts what's allowed.
+                bool inlineIfPossible = canInlineContinuationTask &&
+                    (TaskScheduler.InternalCurrent == m_scheduler || Thread.CurrentThread.IsThreadPoolThread);
+
+                // Create the continuation task task. If we're allowed to inline, try to do so.  
+                // The target scheduler may still deny us from executing on this thread, in which case this'll be queued.
+                var task = CreateTask(state =>
+                {
+                    try { ((Action)state)(); }
+                    catch (Exception exc) { ThrowAsyncIfNecessary(exc); }
+                }, m_action, m_scheduler);
+
+                if (inlineIfPossible)
+                {
+                    InlineIfPossibleOrElseQueue(task, needsProtection: false);
+                }
+                else
+                {
+                    // We need to run asynchronously, so just schedule the task.
+                    try { task.ScheduleAndStart(needsProtection: false); }
+                    catch (TaskSchedulerException) { } // No further action is necessary, as ScheduleAndStart already transitioned task to faulted
+                }
+            }
+        }
+    }
+
+    /// <summary>Base task continuation class used for await continuations.</summary>
+    internal class AwaitTaskContinuation : TaskContinuation, IThreadPoolWorkItem
+    {
+        /// <summary>The ExecutionContext with which to run the continuation.</summary>
+        private readonly ExecutionContext m_capturedContext;
+        /// <summary>The action to invoke.</summary>
+        protected readonly Action m_action;
+
+        protected int m_continuationId;
+
+        /// <summary>Initializes the continuation.</summary>
+        /// <param name="action">The action to invoke. Must not be null.</param>
+        /// <param name="flowExecutionContext">Whether to capture and restore ExecutionContext.</param>
+        internal AwaitTaskContinuation(Action action, bool flowExecutionContext)
+        {
+            Debug.Assert(action != null);
+            m_action = action;
+            if (flowExecutionContext)
+            {
+                m_capturedContext = ExecutionContext.Capture();
+            }
+        }
+
+        /// <summary>Creates a task to run the action with the specified state on the specified scheduler.</summary>
+        /// <param name="action">The action to run. Must not be null.</param>
+        /// <param name="state">The state to pass to the action. Must not be null.</param>
+        /// <param name="scheduler">The scheduler to target.</param>
+        /// <returns>The created task.</returns>
+        protected Task CreateTask(Action<object> action, object state, TaskScheduler scheduler)
+        {
+            Debug.Assert(action != null);
+            Debug.Assert(scheduler != null);
+
+            return new Task(
+                action, state, null, default(CancellationToken),
+                TaskCreationOptions.None, InternalTaskOptions.QueuedByRuntime, scheduler)
+            {
+                CapturedContext = m_capturedContext
+            };
+        }
+
+        /// <summary>Inlines or schedules the continuation onto the default scheduler.</summary>
+        /// <param name="ignored">The antecedent task, which is ignored.</param>
+        /// <param name="canInlineContinuationTask">true if inlining is permitted; otherwise, false.</param>
+        internal override void Run(Task task, bool canInlineContinuationTask)
+        {
+            // For the base AwaitTaskContinuation, we allow inlining if our caller allows it
+            // and if we're in a "valid location" for it.  See the comments on 
+            // IsValidLocationForInlining for more about what's valid.  For performance
+            // reasons we would like to always inline, but we don't in some cases to avoid
+            // running arbitrary amounts of work in suspected "bad locations", like UI threads.
+            if (canInlineContinuationTask && IsValidLocationForInlining)
+            {
+                RunCallback(GetInvokeActionCallback(), m_action, ref Task.t_currentTask); // any exceptions from m_action will be handled by s_callbackRunAction
+            }
+            else
+            {
+                TplEtwProvider etwLog = TplEtwProvider.Log;
+                if (etwLog.IsEnabled())
+                {
+                    m_continuationId = Task.NewId();
+                    etwLog.AwaitTaskContinuationScheduled((task.ExecutingTaskScheduler ?? TaskScheduler.Default).Id, task.Id, m_continuationId);
+                }
+
+                // We couldn't inline, so now we need to schedule it
+                ThreadPool.UnsafeQueueCustomWorkItem(this, forceGlobal: false);
+            }
+        }
+
+        /// <summary>
+        /// Gets whether the current thread is an appropriate location to inline a continuation's execution.
+        /// </summary>
+        /// <remarks>
+        /// Returns whether SynchronizationContext is null and we're in the default scheduler.
+        /// If the await had a SynchronizationContext/TaskScheduler where it began and the 
+        /// default/ConfigureAwait(true) was used, then we won't be on this path.  If, however, 
+        /// ConfigureAwait(false) was used, or the SynchronizationContext and TaskScheduler were 
+        /// naturally null/Default, then we might end up here.  If we do, we need to make sure
+        /// that we don't execute continuations in a place that isn't set up to handle them, e.g.
+        /// running arbitrary amounts of code on the UI thread.  It would be "correct", but very
+        /// expensive, to always run the continuations asynchronously, incurring lots of context
+        /// switches and allocations and locks and the like.  As such, we employ the heuristic
+        /// that if the current thread has a non-null SynchronizationContext or a non-default
+        /// scheduler, then we better not run arbitrary continuations here.
+        /// </remarks>
+        internal static bool IsValidLocationForInlining
+        {
+            get
+            {
+                // If there's a SynchronizationContext, we'll be conservative and say 
+                // this is a bad location to inline.
+                var ctx = SynchronizationContext.Current;
+                if (ctx != null && ctx.GetType() != typeof(SynchronizationContext)) return false;
+
+                // Similarly, if there's a non-default TaskScheduler, we'll be conservative
+                // and say this is a bad location to inline.
+                var sched = TaskScheduler.InternalCurrent;
+                return sched == null || sched == TaskScheduler.Default;
+            }
+        }
+
+        /// <summary>IThreadPoolWorkItem override, which is the entry function for this when the ThreadPool scheduler decides to run it.</summary>
+        private void ExecuteWorkItemHelper()
+        {
+            var etwLog = TplEtwProvider.Log;
+            Guid savedActivityId = Guid.Empty;
+            if (etwLog.TasksSetActivityIds && m_continuationId != 0)
+            {
+                Guid activityId = TplEtwProvider.CreateGuidForTaskID(m_continuationId);
+                System.Diagnostics.Tracing.EventSource.SetCurrentThreadActivityId(activityId, out savedActivityId);
+            }
+            try
+            {
+                // We're not inside of a task, so t_currentTask doesn't need to be specially maintained.
+                // We're on a thread pool thread with no higher-level callers, so exceptions can just propagate.
+
+                // If there's no execution context, just invoke the delegate.
+                ExecutionContext context = m_capturedContext;
+                if (context == null)
+                {
+                    m_action();
+                }
+                // If there is an execution context, get the cached delegate and run the action under the context.
+                else
+                {
+                    ExecutionContext.RunInternal(context, GetInvokeActionCallback(), m_action);
+                }
+            }
+            finally
+            {
+                if (etwLog.TasksSetActivityIds && m_continuationId != 0)
+                {
+                    System.Diagnostics.Tracing.EventSource.SetCurrentThreadActivityId(savedActivityId);
+                }
+            }
+        }
+
+        void IThreadPoolWorkItem.ExecuteWorkItem()
+        {
+            // inline the fast path
+            if (m_capturedContext == null && !TplEtwProvider.Log.IsEnabled())
+            {
+                m_action();
+            }
+            else
+            {
+                ExecuteWorkItemHelper();
+            }
+        }
+
+        /// <summary>
+        /// The ThreadPool calls this if a ThreadAbortException is thrown while trying to execute this workitem.
+        /// </summary>
+        void IThreadPoolWorkItem.MarkAborted(ThreadAbortException tae) { /* nop */ }
+
+        /// <summary>Cached delegate that invokes an Action passed as an object parameter.</summary>
+        private static ContextCallback s_invokeActionCallback;
+
+        /// <summary>Runs an action provided as an object parameter.</summary>
+        /// <param name="state">The Action to invoke.</param>
+        private static void InvokeAction(object state) { ((Action)state)(); }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        protected static ContextCallback GetInvokeActionCallback()
+        {
+            ContextCallback callback = s_invokeActionCallback;
+            if (callback == null) { s_invokeActionCallback = callback = InvokeAction; } // lazily initialize SecurityCritical delegate
+            return callback;
+        }
+
+        /// <summary>Runs the callback synchronously with the provided state.</summary>
+        /// <param name="callback">The callback to run.</param>
+        /// <param name="state">The state to pass to the callback.</param>
+        /// <param name="currentTask">A reference to Task.t_currentTask.</param>
+        protected void RunCallback(ContextCallback callback, object state, ref Task currentTask)
+        {
+            Debug.Assert(callback != null);
+            Debug.Assert(currentTask == Task.t_currentTask);
+
+            // Pretend there's no current task, so that no task is seen as a parent
+            // and TaskScheduler.Current does not reflect false information
+            var prevCurrentTask = currentTask;
+            try
+            {
+                if (prevCurrentTask != null) currentTask = null;
+
+                ExecutionContext context = m_capturedContext;
+                if (context == null)
+                {
+                    // If there's no captured context, just run the callback directly.
+                    callback(state);
+                }
+                else
+                {
+                    // Otherwise, use the captured context to do so.
+                    ExecutionContext.RunInternal(context, callback, state);
+                }
+            }
+            catch (Exception exc) // we explicitly do not request handling of dangerous exceptions like AVs
+            {
+                ThrowAsyncIfNecessary(exc);
+            }
+            finally
+            {
+                // Restore the current task information
+                if (prevCurrentTask != null) currentTask = prevCurrentTask;
+            }
+        }
+
+        /// <summary>Invokes or schedules the action to be executed.</summary>
+        /// <param name="action">The action to invoke or queue.</param>
+        /// <param name="allowInlining">
+        /// true to allow inlining, or false to force the action to run asynchronously.
+        /// </param>
+        /// <remarks>
+        /// No ExecutionContext work is performed used.  This method is only used in the
+        /// case where a raw Action continuation delegate was stored into the Task, which
+        /// only happens in Task.SetContinuationForAwait if execution context flow was disabled
+        /// via using TaskAwaiter.UnsafeOnCompleted or a similar path.
+        /// </remarks>
+        internal static void RunOrScheduleAction(Action action, bool allowInlining)
+        {
+            ref Task currentTask = ref Task.t_currentTask;
+            Task prevCurrentTask = currentTask;
+
+            // If we're not allowed to run here, schedule the action
+            if (!allowInlining || !IsValidLocationForInlining)
+            {
+                UnsafeScheduleAction(action, prevCurrentTask);
+                return;
+            }
+
+            // Otherwise, run it, making sure that t_currentTask is null'd out appropriately during the execution
+            try
+            {
+                if (prevCurrentTask != null) currentTask = null;
+                action();
+            }
+            catch (Exception exception)
+            {
+                ThrowAsyncIfNecessary(exception);
+            }
+            finally
+            {
+                if (prevCurrentTask != null) currentTask = prevCurrentTask;
+            }
+        }
+
+        /// <summary>Invokes or schedules the action to be executed.</summary>
+        /// <param name="box">The <see cref="IAsyncStateMachineBox"/> that needs to be invoked or queued.</param>
+        /// <param name="allowInlining">
+        /// true to allow inlining, or false to force the box's action to run asynchronously.
+        /// </param>
+        internal static void RunOrScheduleAction(IAsyncStateMachineBox box, bool allowInlining)
+        {
+            // Same logic as in the RunOrScheduleAction(Action, ...) overload, except invoking
+            // box.Invoke instead of action().
+
+            ref Task currentTask = ref Task.t_currentTask;
+            Task prevCurrentTask = currentTask;
+
+            // If we're not allowed to run here, schedule the action
+            if (!allowInlining || !IsValidLocationForInlining)
+            {
+                UnsafeScheduleAction(box.MoveNextAction, prevCurrentTask);
+                return;
+            }
+
+            // Otherwise, run it, making sure that t_currentTask is null'd out appropriately during the execution
+            try
+            {
+                if (prevCurrentTask != null) currentTask = null;
+                box.MoveNext();
+            }
+            catch (Exception exception)
+            {
+                ThrowAsyncIfNecessary(exception);
+            }
+            finally
+            {
+                if (prevCurrentTask != null) currentTask = prevCurrentTask;
+            }
+        }
+
+        /// <summary>Schedules the action to be executed.  No ExecutionContext work is performed used.</summary>
+        /// <param name="action">The action to invoke or queue.</param>
+        internal static void UnsafeScheduleAction(Action action, Task task)
+        {
+            AwaitTaskContinuation atc = new AwaitTaskContinuation(action, flowExecutionContext: false);
+
+            var etwLog = TplEtwProvider.Log;
+            if (etwLog.IsEnabled() && task != null)
+            {
+                atc.m_continuationId = Task.NewId();
+                etwLog.AwaitTaskContinuationScheduled((task.ExecutingTaskScheduler ?? TaskScheduler.Default).Id, task.Id, atc.m_continuationId);
+            }
+
+            ThreadPool.UnsafeQueueCustomWorkItem(atc, forceGlobal: false);
+        }
+
+        /// <summary>Throws the exception asynchronously on the ThreadPool.</summary>
+        /// <param name="exc">The exception to throw.</param>
+        protected static void ThrowAsyncIfNecessary(Exception exc)
+        {
+            // Awaits should never experience an exception (other than an TAE or ADUE), 
+            // unless a malicious user is explicitly passing a throwing action into the TaskAwaiter. 
+            // We don't want to allow the exception to propagate on this stack, as it'll emerge in random places, 
+            // and we can't fail fast, as that would allow for elevation of privilege.
+            //
+            // If unhandled error reporting APIs are available use those, otherwise since this 
+            // would have executed on the thread pool otherwise, let it propagate there.
+
+            if (!(exc is ThreadAbortException || exc is AppDomainUnloadedException))
+            {
+#if FEATURE_COMINTEROP
+                if (!WindowsRuntimeMarshal.ReportUnhandledError(exc))
+#endif // FEATURE_COMINTEROP
+                {
+                    var edi = ExceptionDispatchInfo.Capture(exc);
+                    ThreadPool.QueueUserWorkItem(s => ((ExceptionDispatchInfo)s).Throw(), edi);
+                }
+            }
+        }
+
+        internal override Delegate[] GetDelegateContinuationsForDebugger()
+        {
+            Debug.Assert(m_action != null);
+            return new Delegate[] { AsyncMethodBuilderCore.TryGetStateMachineForDebugger(m_action) };
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskExceptionHolder.cs b/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskExceptionHolder.cs
new file mode 100644
index 0000000000..a96852a6f0
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskExceptionHolder.cs
@@ -0,0 +1,402 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// An abstraction for holding and aggregating exceptions.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+// Disable the "reference to volatile field not treated as volatile" error.
+#pragma warning disable 0420
+
+namespace System.Threading.Tasks
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Collections.ObjectModel;
+    using System.Diagnostics;
+    using System.Runtime.ExceptionServices;
+    using System.Security;
+
+    /// <summary>
+    /// An exception holder manages a list of exceptions for one particular task.
+    /// It offers the ability to aggregate, but more importantly, also offers intrinsic
+    /// support for propagating unhandled exceptions that are never observed. It does
+    /// this by aggregating and throwing if the holder is ever GC'd without the holder's
+    /// contents ever having been requested (e.g. by a Task.Wait, Task.get_Exception, etc).
+    /// This behavior is prominent in .NET 4 but is suppressed by default beyond that release.
+    /// </summary>
+    internal class TaskExceptionHolder
+    {
+        /// <summary>Whether we should propagate exceptions on the finalizer.</summary>
+        private readonly static bool s_failFastOnUnobservedException = ShouldFailFastOnUnobservedException();
+        /// <summary>Whether the AppDomain has started to unload.</summary>
+        private static volatile bool s_domainUnloadStarted;
+        /// <summary>An event handler used to notify of domain unload.</summary>
+        private static volatile EventHandler s_adUnloadEventHandler;
+
+        /// <summary>The task with which this holder is associated.</summary>
+        private readonly Task m_task;
+        /// <summary>
+        /// The lazily-initialized list of faulting exceptions.  Volatile
+        /// so that it may be read to determine whether any exceptions were stored.
+        /// </summary>
+        private volatile List<ExceptionDispatchInfo> m_faultExceptions;
+        /// <summary>An exception that triggered the task to cancel.</summary>
+        private ExceptionDispatchInfo m_cancellationException;
+        /// <summary>Whether the holder was "observed" and thus doesn't cause finalization behavior.</summary>
+        private volatile bool m_isHandled;
+
+        /// <summary>
+        /// Creates a new holder; it will be registered for finalization.
+        /// </summary>
+        /// <param name="task">The task this holder belongs to.</param>
+        internal TaskExceptionHolder(Task task)
+        {
+            Debug.Assert(task != null, "Expected a non-null task.");
+            m_task = task;
+            EnsureADUnloadCallbackRegistered();
+        }
+
+        private static bool ShouldFailFastOnUnobservedException()
+        {
+            return false;
+        }
+
+        private static void EnsureADUnloadCallbackRegistered()
+        {
+            if (s_adUnloadEventHandler == null &&
+                Interlocked.CompareExchange(ref s_adUnloadEventHandler,
+                                             AppDomainUnloadCallback,
+                                             null) == null)
+            {
+                AppDomain.CurrentDomain.DomainUnload += s_adUnloadEventHandler;
+            }
+        }
+
+        private static void AppDomainUnloadCallback(object sender, EventArgs e)
+        {
+            s_domainUnloadStarted = true;
+        }
+
+        /// <summary>
+        /// A finalizer that repropagates unhandled exceptions.
+        /// </summary>
+        ~TaskExceptionHolder()
+        {
+            // Raise unhandled exceptions only when we know that neither the process or nor the appdomain is being torn down.
+            // We need to do this filtering because all TaskExceptionHolders will be finalized during shutdown or unload
+            // regardles of reachability of the task (i.e. even if the user code was about to observe the task's exception),
+            // which can otherwise lead to spurious crashes during shutdown.
+            if (m_faultExceptions != null && !m_isHandled &&
+                !Environment.HasShutdownStarted && !AppDomain.CurrentDomain.IsFinalizingForUnload() && !s_domainUnloadStarted)
+            {
+                // We don't want to crash the finalizer thread if any ThreadAbortExceptions 
+                // occur in the list or in any nested AggregateExceptions.  
+                // (Don't rethrow ThreadAbortExceptions.)
+                foreach (ExceptionDispatchInfo edi in m_faultExceptions)
+                {
+                    var exp = edi.SourceException;
+                    AggregateException aggExp = exp as AggregateException;
+                    if (aggExp != null)
+                    {
+                        AggregateException flattenedAggExp = aggExp.Flatten();
+                        foreach (Exception innerExp in flattenedAggExp.InnerExceptions)
+                        {
+                            if (innerExp is ThreadAbortException)
+                                return;
+                        }
+                    }
+                    else if (exp is ThreadAbortException)
+                    {
+                        return;
+                    }
+                }
+
+                // We will only propagate if this is truly unhandled. The reason this could
+                // ever occur is somewhat subtle: if a Task's exceptions are observed in some
+                // other finalizer, and the Task was finalized before the holder, the holder
+                // will have been marked as handled before even getting here.
+
+                // Give users a chance to keep this exception from crashing the process
+
+                // First, publish the unobserved exception and allow users to observe it
+                AggregateException exceptionToThrow = new AggregateException(
+                    SR.TaskExceptionHolder_UnhandledException,
+                    m_faultExceptions);
+                UnobservedTaskExceptionEventArgs ueea = new UnobservedTaskExceptionEventArgs(exceptionToThrow);
+                TaskScheduler.PublishUnobservedTaskException(m_task, ueea);
+
+                // Now, if we are still unobserved and we're configured to crash on unobserved, throw the exception.
+                // We need to publish the event above even if we're not going to crash, hence
+                // why this check doesn't come at the beginning of the method.
+                if (s_failFastOnUnobservedException && !ueea.m_observed)
+                {
+                    throw exceptionToThrow;
+                }
+            }
+        }
+
+        /// <summary>Gets whether the exception holder is currently storing any exceptions for faults.</summary>
+        internal bool ContainsFaultList { get { return m_faultExceptions != null; } }
+
+        /// <summary>
+        /// Add an exception to the holder.  This will ensure the holder is
+        /// in the proper state (handled/unhandled) depending on the list's contents.
+        /// </summary>
+        /// <param name="representsCancellation">
+        /// Whether the exception represents a cancellation request (true) or a fault (false).
+        /// </param>
+        /// <param name="exceptionObject">
+        /// An exception object (either an Exception, an ExceptionDispatchInfo,
+        /// an IEnumerable{Exception}, or an IEnumerable{ExceptionDispatchInfo}) 
+        /// to add to the list.
+        /// </param>
+        /// <remarks>
+        /// Must be called under lock.
+        /// </remarks>
+        internal void Add(object exceptionObject, bool representsCancellation)
+        {
+            Debug.Assert(exceptionObject != null, "TaskExceptionHolder.Add(): Expected a non-null exceptionObject");
+            Debug.Assert(
+                exceptionObject is Exception || exceptionObject is IEnumerable<Exception> ||
+                exceptionObject is ExceptionDispatchInfo || exceptionObject is IEnumerable<ExceptionDispatchInfo>,
+                "TaskExceptionHolder.Add(): Expected Exception, IEnumerable<Exception>, ExceptionDispatchInfo, or IEnumerable<ExceptionDispatchInfo>");
+
+            if (representsCancellation) SetCancellationException(exceptionObject);
+            else AddFaultException(exceptionObject);
+        }
+
+        /// <summary>Sets the cancellation exception.</summary>
+        /// <param name="exceptionObject">The cancellation exception.</param>
+        /// <remarks>
+        /// Must be called under lock.
+        /// </remarks>
+        private void SetCancellationException(object exceptionObject)
+        {
+            Debug.Assert(exceptionObject != null, "Expected exceptionObject to be non-null.");
+
+            Debug.Assert(m_cancellationException == null,
+                "Expected SetCancellationException to be called only once.");
+            // Breaking this assumption will overwrite a previously OCE,
+            // and implies something may be wrong elsewhere, since there should only ever be one.
+
+            Debug.Assert(m_faultExceptions == null,
+                "Expected SetCancellationException to be called before any faults were added.");
+            // Breaking this assumption shouldn't hurt anything here, but it implies something may be wrong elsewhere.
+            // If this changes, make sure to only conditionally mark as handled below.
+
+            // Store the cancellation exception
+            var oce = exceptionObject as OperationCanceledException;
+            if (oce != null)
+            {
+                m_cancellationException = ExceptionDispatchInfo.Capture(oce);
+            }
+            else
+            {
+                var edi = exceptionObject as ExceptionDispatchInfo;
+                Debug.Assert(edi != null && edi.SourceException is OperationCanceledException,
+                    "Expected an OCE or an EDI that contained an OCE");
+                m_cancellationException = edi;
+            }
+
+            // This is just cancellation, and there are no faults, so mark the holder as handled.
+            MarkAsHandled(false);
+        }
+
+        /// <summary>Adds the exception to the fault list.</summary>
+        /// <param name="exceptionObject">The exception to store.</param>
+        /// <remarks>
+        /// Must be called under lock.
+        /// </remarks>
+        private void AddFaultException(object exceptionObject)
+        {
+            Debug.Assert(exceptionObject != null, "AddFaultException(): Expected a non-null exceptionObject");
+
+            // Initialize the exceptions list if necessary.  The list should be non-null iff it contains exceptions.
+            var exceptions = m_faultExceptions;
+            if (exceptions == null) m_faultExceptions = exceptions = new List<ExceptionDispatchInfo>(1);
+            else Debug.Assert(exceptions.Count > 0, "Expected existing exceptions list to have > 0 exceptions.");
+
+            // Handle Exception by capturing it into an ExceptionDispatchInfo and storing that
+            var exception = exceptionObject as Exception;
+            if (exception != null)
+            {
+                exceptions.Add(ExceptionDispatchInfo.Capture(exception));
+            }
+            else
+            {
+                // Handle ExceptionDispatchInfo by storing it into the list
+                var edi = exceptionObject as ExceptionDispatchInfo;
+                if (edi != null)
+                {
+                    exceptions.Add(edi);
+                }
+                else
+                {
+                    // Handle enumerables of exceptions by capturing each of the contained exceptions into an EDI and storing it
+                    var exColl = exceptionObject as IEnumerable<Exception>;
+                    if (exColl != null)
+                    {
+#if DEBUG
+                        int numExceptions = 0;
+#endif
+                        foreach (var exc in exColl)
+                        {
+#if DEBUG
+                            Debug.Assert(exc != null, "No exceptions should be null");
+                            numExceptions++;
+#endif
+                            exceptions.Add(ExceptionDispatchInfo.Capture(exc));
+                        }
+#if DEBUG
+                        Debug.Assert(numExceptions > 0, "Collection should contain at least one exception.");
+#endif
+                    }
+                    else
+                    {
+                        // Handle enumerables of EDIs by storing them directly
+                        var ediColl = exceptionObject as IEnumerable<ExceptionDispatchInfo>;
+                        if (ediColl != null)
+                        {
+                            exceptions.AddRange(ediColl);
+#if DEBUG
+                            Debug.Assert(exceptions.Count > 0, "There should be at least one dispatch info.");
+                            foreach (var tmp in exceptions)
+                            {
+                                Debug.Assert(tmp != null, "No dispatch infos should be null");
+                            }
+#endif
+                        }
+                        // Anything else is a programming error
+                        else
+                        {
+                            throw new ArgumentException(SR.TaskExceptionHolder_UnknownExceptionType, nameof(exceptionObject));
+                        }
+                    }
+                }
+            }
+
+
+            // If all of the exceptions are ThreadAbortExceptions and/or
+            // AppDomainUnloadExceptions, we do not want the finalization
+            // probe to propagate them, so we consider the holder to be
+            // handled.  If a subsequent exception comes in of a different
+            // kind, we will reactivate the holder.
+            for (int i = 0; i < exceptions.Count; i++)
+            {
+                var t = exceptions[i].SourceException.GetType();
+                if (t != typeof(ThreadAbortException) && t != typeof(AppDomainUnloadedException))
+                {
+                    MarkAsUnhandled();
+                    break;
+                }
+                else if (i == exceptions.Count - 1)
+                {
+                    MarkAsHandled(false);
+                }
+            }
+        }
+
+        /// <summary>
+        /// A private helper method that ensures the holder is considered
+        /// unhandled, i.e. it is registered for finalization.
+        /// </summary>
+        private void MarkAsUnhandled()
+        {
+            // If a thread partially observed this thread's exceptions, we
+            // should revert back to "not handled" so that subsequent exceptions
+            // must also be seen. Otherwise, some could go missing. We also need
+            // to reregister for finalization.
+            if (m_isHandled)
+            {
+                GC.ReRegisterForFinalize(this);
+                m_isHandled = false;
+            }
+        }
+
+        /// <summary>
+        /// A private helper method that ensures the holder is considered
+        /// handled, i.e. it is not registered for finalization.
+        /// </summary>
+        /// <param name="calledFromFinalizer">Whether this is called from the finalizer thread.</param> 
+        internal void MarkAsHandled(bool calledFromFinalizer)
+        {
+            if (!m_isHandled)
+            {
+                if (!calledFromFinalizer)
+                {
+                    GC.SuppressFinalize(this);
+                }
+
+                m_isHandled = true;
+            }
+        }
+
+        /// <summary>
+        /// Allocates a new aggregate exception and adds the contents of the list to
+        /// it. By calling this method, the holder assumes exceptions to have been
+        /// "observed", such that the finalization check will be subsequently skipped.
+        /// </summary>
+        /// <param name="calledFromFinalizer">Whether this is being called from a finalizer.</param>
+        /// <param name="includeThisException">An extra exception to be included (optionally).</param>
+        /// <returns>The aggregate exception to throw.</returns>
+        internal AggregateException CreateExceptionObject(bool calledFromFinalizer, Exception includeThisException)
+        {
+            var exceptions = m_faultExceptions;
+            Debug.Assert(exceptions != null, "Expected an initialized list.");
+            Debug.Assert(exceptions.Count > 0, "Expected at least one exception.");
+
+            // Mark as handled and aggregate the exceptions.
+            MarkAsHandled(calledFromFinalizer);
+
+            // If we're only including the previously captured exceptions, 
+            // return them immediately in an aggregate.
+            if (includeThisException == null)
+                return new AggregateException(exceptions);
+
+            // Otherwise, the caller wants a specific exception to be included, 
+            // so return an aggregate containing that exception and the rest.
+            Exception[] combinedExceptions = new Exception[exceptions.Count + 1];
+            for (int i = 0; i < combinedExceptions.Length - 1; i++)
+            {
+                combinedExceptions[i] = exceptions[i].SourceException;
+            }
+            combinedExceptions[combinedExceptions.Length - 1] = includeThisException;
+            return new AggregateException(combinedExceptions);
+        }
+
+        /// <summary>
+        /// Wraps the exception dispatch infos into a new read-only collection. By calling this method, 
+        /// the holder assumes exceptions to have been "observed", such that the finalization 
+        /// check will be subsequently skipped.
+        /// </summary>
+        internal ReadOnlyCollection<ExceptionDispatchInfo> GetExceptionDispatchInfos()
+        {
+            var exceptions = m_faultExceptions;
+            Debug.Assert(exceptions != null, "Expected an initialized list.");
+            Debug.Assert(exceptions.Count > 0, "Expected at least one exception.");
+            MarkAsHandled(false);
+            return new ReadOnlyCollection<ExceptionDispatchInfo>(exceptions);
+        }
+
+        /// <summary>
+        /// Gets the ExceptionDispatchInfo representing the singular exception 
+        /// that was the cause of the task's cancellation.
+        /// </summary>
+        /// <returns>
+        /// The ExceptionDispatchInfo for the cancellation exception.  May be null.
+        /// </returns>
+        internal ExceptionDispatchInfo GetCancellationExceptionDispatchInfo()
+        {
+            var edi = m_cancellationException;
+            Debug.Assert(edi == null || edi.SourceException is OperationCanceledException,
+                "Expected the EDI to be for an OperationCanceledException");
+            return edi;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskFactory.cs b/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskFactory.cs
new file mode 100644
index 0000000000..875d47b1e7
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskFactory.cs
@@ -0,0 +1,3056 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// There are a plethora of common patterns for which Tasks are created.  TaskFactory encodes 
+// these patterns into helper methods.  These helpers also pick up default configuration settings 
+// applicable to the entire factory and configurable through its constructors.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System;
+using System.Collections.Generic;
+using System.Security;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using System.Diagnostics;
+
+namespace System.Threading.Tasks
+{
+    /// <summary>
+    /// Provides support for creating and scheduling
+    /// <see cref="T:System.Threading.Tasks.Task">Tasks</see>.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// There are many common patterns for which tasks are relevant. The <see cref="TaskFactory"/>
+    /// class encodes some of these patterns into methods that pick up default settings, which are
+    /// configurable through its constructors.
+    /// </para>
+    /// <para>
+    /// A default instance of <see cref="TaskFactory"/> is available through the
+    /// <see cref="System.Threading.Tasks.Task.Factory">Task.Factory</see> property.
+    /// </para>
+    /// </remarks>
+    public class TaskFactory
+    {
+        // member variables
+        private readonly CancellationToken m_defaultCancellationToken;
+        private readonly TaskScheduler m_defaultScheduler;
+        private readonly TaskCreationOptions m_defaultCreationOptions;
+        private readonly TaskContinuationOptions m_defaultContinuationOptions;
+
+        private TaskScheduler DefaultScheduler => m_defaultScheduler ?? TaskScheduler.Current;
+
+        // sister method to above property -- avoids a TLS lookup
+        private TaskScheduler GetDefaultScheduler(Task currTask)
+        {
+            return
+                m_defaultScheduler ??
+                (currTask != null && (currTask.CreationOptions & TaskCreationOptions.HideScheduler) == 0 ? currTask.ExecutingTaskScheduler :
+                 TaskScheduler.Default);
+        }
+
+        /* Constructors */
+
+        // ctor parameters provide defaults for the factory, which can be overridden by options provided to
+        // specific calls on the factory
+
+
+        /// <summary>
+        /// Initializes a <see cref="TaskFactory"/> instance with the default configuration.
+        /// </summary>
+        /// <remarks>
+        /// This constructor creates a <see cref="TaskFactory"/> instance with a default configuration. The
+        /// <see cref="TaskCreationOptions"/> property is initialized to
+        /// <see cref="System.Threading.Tasks.TaskCreationOptions.None">TaskCreationOptions.None</see>, the
+        /// <see cref="TaskContinuationOptions"/> property is initialized to <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.None">TaskContinuationOptions.None</see>,
+        /// and the <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> property is
+        /// initialized to the current scheduler (see <see
+        /// cref="System.Threading.Tasks.TaskScheduler.Current">TaskScheduler.Current</see>).
+        /// </remarks>
+        public TaskFactory()
+            : this(default(CancellationToken), TaskCreationOptions.None, TaskContinuationOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a <see cref="TaskFactory"/> instance with the specified configuration.
+        /// </summary>
+        /// <param name="cancellationToken">The default <see cref="CancellationToken"/> that will be assigned 
+        /// to tasks created by this <see cref="TaskFactory"/> unless another CancellationToken is explicitly specified 
+        /// while calling the factory methods.</param>
+        /// <remarks>
+        /// This constructor creates a <see cref="TaskFactory"/> instance with a default configuration. The
+        /// <see cref="TaskCreationOptions"/> property is initialized to
+        /// <see cref="System.Threading.Tasks.TaskCreationOptions.None">TaskCreationOptions.None</see>, the
+        /// <see cref="TaskContinuationOptions"/> property is initialized to <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.None">TaskContinuationOptions.None</see>,
+        /// and the <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> property is
+        /// initialized to the current scheduler (see <see
+        /// cref="System.Threading.Tasks.TaskScheduler.Current">TaskScheduler.Current</see>).
+        /// </remarks>
+        public TaskFactory(CancellationToken cancellationToken)
+            : this(cancellationToken, TaskCreationOptions.None, TaskContinuationOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a <see cref="TaskFactory"/> instance with the specified configuration.
+        /// </summary>
+        /// <param name="scheduler">
+        /// The <see cref="System.Threading.Tasks.TaskScheduler">
+        /// TaskScheduler</see> to use to schedule any tasks created with this TaskFactory. A null value
+        /// indicates that the current TaskScheduler should be used.
+        /// </param>
+        /// <remarks>
+        /// With this constructor, the
+        /// <see cref="TaskCreationOptions"/> property is initialized to
+        /// <see cref="System.Threading.Tasks.TaskCreationOptions.None">TaskCreationOptions.None</see>, the
+        /// <see cref="TaskContinuationOptions"/> property is initialized to <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.None">TaskContinuationOptions.None</see>,
+        /// and the <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> property is
+        /// initialized to <paramref name="scheduler"/>, unless it's null, in which case the property is
+        /// initialized to the current scheduler (see <see
+        /// cref="System.Threading.Tasks.TaskScheduler.Current">TaskScheduler.Current</see>).
+        /// </remarks>
+        public TaskFactory(TaskScheduler scheduler) // null means to use TaskScheduler.Current
+            : this(default(CancellationToken), TaskCreationOptions.None, TaskContinuationOptions.None, scheduler)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a <see cref="TaskFactory"/> instance with the specified configuration.
+        /// </summary>
+        /// <param name="creationOptions">
+        /// The default <see cref="System.Threading.Tasks.TaskCreationOptions">
+        /// TaskCreationOptions</see> to use when creating tasks with this TaskFactory.
+        /// </param>
+        /// <param name="continuationOptions">
+        /// The default <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> to use when creating continuation tasks with this TaskFactory.
+        /// </param>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument or the <paramref name="continuationOptions"/>
+        /// argument specifies an invalid value.
+        /// </exception>
+        /// <remarks>
+        /// With this constructor, the
+        /// <see cref="TaskCreationOptions"/> property is initialized to <paramref name="creationOptions"/>,
+        /// the
+        /// <see cref="TaskContinuationOptions"/> property is initialized to <paramref
+        /// name="continuationOptions"/>, and the <see
+        /// cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> property is initialized to the
+        /// current scheduler (see <see
+        /// cref="System.Threading.Tasks.TaskScheduler.Current">TaskScheduler.Current</see>).
+        /// </remarks>
+        public TaskFactory(TaskCreationOptions creationOptions, TaskContinuationOptions continuationOptions)
+            : this(default(CancellationToken), creationOptions, continuationOptions, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a <see cref="TaskFactory"/> instance with the specified configuration.
+        /// </summary>
+        /// <param name="cancellationToken">The default <see cref="CancellationToken"/> that will be assigned 
+        /// to tasks created by this <see cref="TaskFactory"/> unless another CancellationToken is explicitly specified 
+        /// while calling the factory methods.</param>
+        /// <param name="creationOptions">
+        /// The default <see cref="System.Threading.Tasks.TaskCreationOptions">
+        /// TaskCreationOptions</see> to use when creating tasks with this TaskFactory.
+        /// </param>
+        /// <param name="continuationOptions">
+        /// The default <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> to use when creating continuation tasks with this TaskFactory.
+        /// </param>
+        /// <param name="scheduler">
+        /// The default <see cref="System.Threading.Tasks.TaskScheduler">
+        /// TaskScheduler</see> to use to schedule any Tasks created with this TaskFactory. A null value
+        /// indicates that TaskScheduler.Current should be used.
+        /// </param>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument or the <paramref name="continuationOptions"/>
+        /// argumentspecifies an invalid value.
+        /// </exception>
+        /// <remarks>
+        /// With this constructor, the
+        /// <see cref="TaskCreationOptions"/> property is initialized to <paramref name="creationOptions"/>,
+        /// the
+        /// <see cref="TaskContinuationOptions"/> property is initialized to <paramref
+        /// name="continuationOptions"/>, and the <see
+        /// cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> property is initialized to
+        /// <paramref name="scheduler"/>, unless it's null, in which case the property is initialized to the
+        /// current scheduler (see <see
+        /// cref="System.Threading.Tasks.TaskScheduler.Current">TaskScheduler.Current</see>).
+        /// </remarks>
+        public TaskFactory(CancellationToken cancellationToken, TaskCreationOptions creationOptions, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            CheckMultiTaskContinuationOptions(continuationOptions);
+            CheckCreationOptions(creationOptions);
+
+            m_defaultCancellationToken = cancellationToken;
+            m_defaultScheduler = scheduler;
+            m_defaultCreationOptions = creationOptions;
+            m_defaultContinuationOptions = continuationOptions;
+        }
+
+        internal static void CheckCreationOptions(TaskCreationOptions creationOptions)
+        {
+            // Check for validity of options
+            if ((creationOptions &
+                    ~(TaskCreationOptions.AttachedToParent |
+                      TaskCreationOptions.DenyChildAttach |
+                      TaskCreationOptions.HideScheduler |
+                      TaskCreationOptions.LongRunning |
+                      TaskCreationOptions.PreferFairness |
+                      TaskCreationOptions.RunContinuationsAsynchronously)) != 0)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.creationOptions);
+            }
+        }
+
+        /* Properties */
+
+        /// <summary>
+        /// Gets the default <see cref="System.Threading.CancellationToken">CancellationToken</see> of this
+        /// TaskFactory.
+        /// </summary>
+        /// <remarks>
+        /// This property returns the default <see cref="CancellationToken"/> that will be assigned to all 
+        /// tasks created by this factory unless another CancellationToken value is explicitly specified 
+        /// during the call to the factory methods.
+        /// </remarks>
+        public CancellationToken CancellationToken { get { return m_defaultCancellationToken; } }
+
+        /// <summary>
+        /// Gets the <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> of this
+        /// TaskFactory.
+        /// </summary>
+        /// <remarks>
+        /// This property returns the default scheduler for this factory.  It will be used to schedule all 
+        /// tasks unless another scheduler is explicitly specified during calls to this factory's methods.  
+        /// If null, <see cref="System.Threading.Tasks.TaskScheduler.Current">TaskScheduler.Current</see> 
+        /// will be used.
+        /// </remarks>
+        public TaskScheduler Scheduler { get { return m_defaultScheduler; } }
+
+        /// <summary>
+        /// Gets the <see cref="System.Threading.Tasks.TaskCreationOptions">TaskCreationOptions
+        /// </see> value of this TaskFactory.
+        /// </summary>
+        /// <remarks>
+        /// This property returns the default creation options for this factory.  They will be used to create all 
+        /// tasks unless other options are explicitly specified during calls to this factory's methods.
+        /// </remarks>
+        public TaskCreationOptions CreationOptions { get { return m_defaultCreationOptions; } }
+
+        /// <summary>
+        /// Gets the <see cref="System.Threading.Tasks.TaskCreationOptions">TaskContinuationOptions
+        /// </see> value of this TaskFactory.
+        /// </summary>
+        /// <remarks>
+        /// This property returns the default continuation options for this factory.  They will be used to create 
+        /// all continuation tasks unless other options are explicitly specified during calls to this factory's methods.
+        /// </remarks>
+        public TaskContinuationOptions ContinuationOptions { get { return m_defaultContinuationOptions; } }
+
+        //
+        // StartNew methods
+        //
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task">Task</see>.
+        /// </summary>
+        /// <param name="action">The action delegate to execute asynchronously.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref name="action"/> 
+        /// argument is null.</exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a Task using one of its constructors 
+        /// and then calling 
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.  However,
+        /// unless creation and scheduling must be separated, StartNew is the recommended
+        /// approach for both simplicity and performance.
+        /// </remarks>
+        public Task StartNew(Action action)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task.InternalStartNew(currTask, action, null, m_defaultCancellationToken, GetDefaultScheduler(currTask),
+                m_defaultCreationOptions, InternalTaskOptions.None);
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task">Task</see>.
+        /// </summary>
+        /// <param name="action">The action delegate to execute asynchronously.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref name="action"/> 
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a Task using one of its constructors 
+        /// and then calling 
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.  However,
+        /// unless creation and scheduling must be separated, StartNew is the recommended
+        /// approach for both simplicity and performance.
+        /// </remarks>
+        public Task StartNew(Action action, CancellationToken cancellationToken)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task.InternalStartNew(currTask, action, null, cancellationToken, GetDefaultScheduler(currTask),
+                m_defaultCreationOptions, InternalTaskOptions.None);
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task">Task</see>.
+        /// </summary>
+        /// <param name="action">The action delegate to execute asynchronously.</param>
+        /// <param name="creationOptions">A TaskCreationOptions value that controls the behavior of the
+        /// created
+        /// <see cref="T:System.Threading.Tasks.Task">Task.</see></param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="action"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a Task using one of its constructors and
+        /// then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task StartNew(Action action, TaskCreationOptions creationOptions)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task.InternalStartNew(currTask, action, null, m_defaultCancellationToken, GetDefaultScheduler(currTask), creationOptions,
+                InternalTaskOptions.None);
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task">Task</see>.
+        /// </summary>
+        /// <param name="action">The action delegate to execute asynchronously.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new <see cref="Task"/></param>
+        /// <param name="creationOptions">A TaskCreationOptions value that controls the behavior of the
+        /// created
+        /// <see cref="T:System.Threading.Tasks.Task">Task.</see></param>
+        /// <param name="scheduler">The <see
+        /// cref="T:System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created <see
+        /// cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="action"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="scheduler"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a Task using one of its constructors and
+        /// then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task StartNew(Action action, CancellationToken cancellationToken, TaskCreationOptions creationOptions, TaskScheduler scheduler)
+        {
+            return Task.InternalStartNew(
+                Task.InternalCurrentIfAttached(creationOptions), action, null, cancellationToken, scheduler, creationOptions,
+                InternalTaskOptions.None);
+        }
+
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task">Task</see>.
+        /// </summary>
+        /// <param name="action">The action delegate to execute asynchronously.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="action"/>
+        /// delegate.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="action"/>
+        /// argument is null.</exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a Task using one of its constructors and
+        /// then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task StartNew(Action<Object> action, Object state)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task.InternalStartNew(currTask, action, state, m_defaultCancellationToken, GetDefaultScheduler(currTask),
+                m_defaultCreationOptions, InternalTaskOptions.None);
+        }
+
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task">Task</see>.
+        /// </summary>
+        /// <param name="action">The action delegate to execute asynchronously.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="action"/>
+        /// delegate.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new <see cref="Task"/></param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="action"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a Task using one of its constructors and
+        /// then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task StartNew(Action<Object> action, Object state, CancellationToken cancellationToken)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task.InternalStartNew(currTask, action, state, cancellationToken, GetDefaultScheduler(currTask),
+                m_defaultCreationOptions, InternalTaskOptions.None);
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task">Task</see>.
+        /// </summary>
+        /// <param name="action">The action delegate to execute asynchronously.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="action"/>
+        /// delegate.</param>
+        /// <param name="creationOptions">A TaskCreationOptions value that controls the behavior of the
+        /// created
+        /// <see cref="T:System.Threading.Tasks.Task">Task.</see></param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="action"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a Task using one of its constructors and
+        /// then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task StartNew(Action<Object> action, Object state, TaskCreationOptions creationOptions)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task.InternalStartNew(currTask, action, state, m_defaultCancellationToken, GetDefaultScheduler(currTask),
+                creationOptions, InternalTaskOptions.None);
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task">Task</see>.
+        /// </summary>
+        /// <param name="action">The action delegate to execute asynchronously.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="action"/>
+        /// delegate.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <param name="creationOptions">A TaskCreationOptions value that controls the behavior of the
+        /// created
+        /// <see cref="T:System.Threading.Tasks.Task">Task.</see></param>
+        /// <param name="scheduler">The <see
+        /// cref="T:System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created <see
+        /// cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="action"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="scheduler"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a Task using one of its constructors and
+        /// then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task StartNew(Action<Object> action, Object state, CancellationToken cancellationToken,
+                            TaskCreationOptions creationOptions, TaskScheduler scheduler)
+        {
+            return Task.InternalStartNew(
+                Task.InternalCurrentIfAttached(creationOptions), action, state, cancellationToken, scheduler,
+                creationOptions, InternalTaskOptions.None);
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew<TResult>(Func<TResult> function)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task<TResult>.StartNew(currTask, function, m_defaultCancellationToken,
+                m_defaultCreationOptions, InternalTaskOptions.None, GetDefaultScheduler(currTask));
+        }
+
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new <see cref="Task"/></param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew<TResult>(Func<TResult> function, CancellationToken cancellationToken)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task<TResult>.StartNew(currTask, function, cancellationToken,
+                m_defaultCreationOptions, InternalTaskOptions.None, GetDefaultScheduler(currTask));
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="creationOptions">A TaskCreationOptions value that controls the behavior of the
+        /// created
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew<TResult>(Func<TResult> function, TaskCreationOptions creationOptions)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task<TResult>.StartNew(currTask, function, m_defaultCancellationToken,
+                creationOptions, InternalTaskOptions.None, GetDefaultScheduler(currTask));
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <param name="creationOptions">A TaskCreationOptions value that controls the behavior of the
+        /// created
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="scheduler">The <see
+        /// cref="T:System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created <see cref="T:System.Threading.Tasks.Task{TResult}">
+        /// Task{TResult}</see>.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="scheduler"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew<TResult>(Func<TResult> function, CancellationToken cancellationToken, TaskCreationOptions creationOptions, TaskScheduler scheduler)
+        {
+            return Task<TResult>.StartNew(
+                Task.InternalCurrentIfAttached(creationOptions), function, cancellationToken,
+                creationOptions, InternalTaskOptions.None, scheduler);
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="function"/>
+        /// delegate.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew<TResult>(Func<Object, TResult> function, Object state)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task<TResult>.StartNew(currTask, function, state, m_defaultCancellationToken,
+                m_defaultCreationOptions, InternalTaskOptions.None, GetDefaultScheduler(currTask));
+        }
+
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="function"/>
+        /// delegate.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new <see cref="Task"/></param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew<TResult>(Func<Object, TResult> function, Object state, CancellationToken cancellationToken)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task<TResult>.StartNew(currTask, function, state, cancellationToken,
+                m_defaultCreationOptions, InternalTaskOptions.None, GetDefaultScheduler(currTask));
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="function"/>
+        /// delegate.</param>
+        /// <param name="creationOptions">A TaskCreationOptions value that controls the behavior of the
+        /// created
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew<TResult>(Func<Object, TResult> function, Object state, TaskCreationOptions creationOptions)
+        {
+            Task currTask = Task.InternalCurrent;
+            return Task<TResult>.StartNew(currTask, function, state, m_defaultCancellationToken,
+                creationOptions, InternalTaskOptions.None, GetDefaultScheduler(currTask));
+        }
+
+        /// <summary>
+        /// Creates and starts a <see cref="T:System.Threading.Tasks.Task{TResult}"/>.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="function">A function delegate that returns the future result to be available through
+        /// the <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="function"/>
+        /// delegate.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <param name="creationOptions">A TaskCreationOptions value that controls the behavior of the
+        /// created
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <param name="scheduler">The <see
+        /// cref="T:System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created <see cref="T:System.Threading.Tasks.Task{TResult}">
+        /// Task{TResult}</see>.</param>
+        /// <returns>The started <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="function"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the <paramref
+        /// name="scheduler"/>
+        /// argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// Calling StartNew is functionally equivalent to creating a <see cref="Task{TResult}"/> using one
+        /// of its constructors and then calling
+        /// <see cref="System.Threading.Tasks.Task.Start()">Start</see> to schedule it for execution.
+        /// However, unless creation and scheduling must be separated, StartNew is the recommended approach
+        /// for both simplicity and performance.
+        /// </remarks>
+        public Task<TResult> StartNew<TResult>(Func<Object, TResult> function, Object state, CancellationToken cancellationToken,
+            TaskCreationOptions creationOptions, TaskScheduler scheduler)
+        {
+            return Task<TResult>.StartNew(
+                Task.InternalCurrentIfAttached(creationOptions), function, state, cancellationToken,
+                creationOptions, InternalTaskOptions.None, scheduler);
+        }
+
+        //
+        // FromAsync methods
+        //
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task">Task</see> that executes an end method action
+        /// when a specified <see cref="T:System.IAsyncResult">IAsyncResult</see> completes.
+        /// </summary>
+        /// <param name="asyncResult">The IAsyncResult whose completion should trigger the processing of the
+        /// <paramref name="endMethod"/>.</param>
+        /// <param name="endMethod">The action delegate that processes the completed <paramref
+        /// name="asyncResult"/>.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="asyncResult"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>A <see cref="T:System.Threading.Tasks.Task">Task</see> that represents the asynchronous
+        /// operation.</returns>
+        public Task FromAsync(
+            IAsyncResult asyncResult,
+            Action<IAsyncResult> endMethod)
+        {
+            return FromAsync(asyncResult, endMethod, m_defaultCreationOptions, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task">Task</see> that executes an end method action
+        /// when a specified <see cref="T:System.IAsyncResult">IAsyncResult</see> completes.
+        /// </summary>
+        /// <param name="asyncResult">The IAsyncResult whose completion should trigger the processing of the
+        /// <paramref name="endMethod"/>.</param>
+        /// <param name="endMethod">The action delegate that processes the completed <paramref
+        /// name="asyncResult"/>.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="asyncResult"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>A <see cref="T:System.Threading.Tasks.Task">Task</see> that represents the asynchronous
+        /// operation.</returns>
+        public Task FromAsync(
+            IAsyncResult asyncResult,
+            Action<IAsyncResult> endMethod,
+            TaskCreationOptions creationOptions)
+        {
+            return FromAsync(asyncResult, endMethod, creationOptions, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task">Task</see> that executes an end method action
+        /// when a specified <see cref="T:System.IAsyncResult">IAsyncResult</see> completes.
+        /// </summary>
+        /// <param name="asyncResult">The IAsyncResult whose completion should trigger the processing of the
+        /// <paramref name="endMethod"/>.</param>
+        /// <param name="endMethod">The action delegate that processes the completed <paramref
+        /// name="asyncResult"/>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the task that executes the end method.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="asyncResult"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>A <see cref="T:System.Threading.Tasks.Task">Task</see> that represents the asynchronous
+        /// operation.</returns>
+        public Task FromAsync(
+            IAsyncResult asyncResult,
+            Action<IAsyncResult> endMethod,
+            TaskCreationOptions creationOptions,
+            TaskScheduler scheduler)
+        {
+            return TaskFactory<VoidTaskResult>.FromAsyncImpl(asyncResult, null, endMethod, creationOptions, scheduler);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task">Task</see> that represents a pair of begin
+        /// and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task">Task</see> that represents the
+        /// asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task FromAsync(
+            Func<AsyncCallback, object, IAsyncResult> beginMethod,
+            Action<IAsyncResult> endMethod,
+            object state)
+        {
+            return FromAsync(beginMethod, endMethod, state, m_defaultCreationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task">Task</see> that represents a pair of begin
+        /// and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task">Task</see> that represents the
+        /// asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task FromAsync(
+            Func<AsyncCallback, object, IAsyncResult> beginMethod,
+            Action<IAsyncResult> endMethod, object state, TaskCreationOptions creationOptions)
+        {
+            return TaskFactory<VoidTaskResult>.FromAsyncImpl(beginMethod, null, endMethod, state, creationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task">Task</see> that represents a pair of begin
+        /// and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task">Task</see> that represents the
+        /// asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task FromAsync<TArg1>(
+            Func<TArg1, AsyncCallback, object, IAsyncResult> beginMethod,
+            Action<IAsyncResult> endMethod,
+            TArg1 arg1,
+            object state)
+        {
+            return FromAsync(beginMethod, endMethod, arg1, state, m_defaultCreationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task">Task</see> that represents a pair of begin
+        /// and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task">Task</see> that represents the
+        /// asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task FromAsync<TArg1>(
+            Func<TArg1, AsyncCallback, object, IAsyncResult> beginMethod,
+            Action<IAsyncResult> endMethod,
+            TArg1 arg1, object state, TaskCreationOptions creationOptions)
+        {
+            return TaskFactory<VoidTaskResult>.FromAsyncImpl(beginMethod, null, endMethod, arg1, state, creationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task">Task</see> that represents a pair of begin
+        /// and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <typeparam name="TArg2">The type of the second argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg2">The second argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task">Task</see> that represents the
+        /// asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task FromAsync<TArg1, TArg2>(
+            Func<TArg1, TArg2, AsyncCallback, object, IAsyncResult> beginMethod,
+            Action<IAsyncResult> endMethod,
+            TArg1 arg1, TArg2 arg2, object state)
+        {
+            return FromAsync(beginMethod, endMethod, arg1, arg2, state, m_defaultCreationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task">Task</see> that represents a pair of begin
+        /// and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <typeparam name="TArg2">The type of the second argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg2">The second argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task">Task</see> that represents the
+        /// asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task FromAsync<TArg1, TArg2>(
+            Func<TArg1, TArg2, AsyncCallback, object, IAsyncResult> beginMethod,
+            Action<IAsyncResult> endMethod,
+            TArg1 arg1, TArg2 arg2, object state, TaskCreationOptions creationOptions)
+        {
+            return TaskFactory<VoidTaskResult>.FromAsyncImpl(beginMethod, null, endMethod, arg1, arg2, state, creationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task">Task</see> that represents a pair of begin
+        /// and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <typeparam name="TArg2">The type of the second argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <typeparam name="TArg3">The type of the third argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg2">The second argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg3">The third argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task">Task</see> that represents the
+        /// asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task FromAsync<TArg1, TArg2, TArg3>(
+            Func<TArg1, TArg2, TArg3, AsyncCallback, object, IAsyncResult> beginMethod,
+            Action<IAsyncResult> endMethod,
+            TArg1 arg1, TArg2 arg2, TArg3 arg3, object state)
+        {
+            return FromAsync(beginMethod, endMethod, arg1, arg2, arg3, state, m_defaultCreationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task">Task</see> that represents a pair of begin
+        /// and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <typeparam name="TArg2">The type of the second argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <typeparam name="TArg3">The type of the third argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg2">The second argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg3">The third argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task">Task</see> that represents the
+        /// asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task FromAsync<TArg1, TArg2, TArg3>(
+            Func<TArg1, TArg2, TArg3, AsyncCallback, object, IAsyncResult> beginMethod,
+            Action<IAsyncResult> endMethod,
+            TArg1 arg1, TArg2 arg2, TArg3 arg3, object state, TaskCreationOptions creationOptions)
+        {
+            return TaskFactory<VoidTaskResult>.FromAsyncImpl<TArg1, TArg2, TArg3>(beginMethod, null, endMethod, arg1, arg2, arg3, state, creationOptions);
+        }
+
+        //
+        // Additional FromAsync() overloads used for inferencing convenience
+        //
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that executes an end
+        /// method function when a specified <see cref="T:System.IAsyncResult">IAsyncResult</see> completes.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="asyncResult">The IAsyncResult whose completion should trigger the processing of the
+        /// <paramref name="endMethod"/>.</param>
+        /// <param name="endMethod">The function delegate that processes the completed <paramref
+        /// name="asyncResult"/>.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="asyncResult"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>A <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents the
+        /// asynchronous operation.</returns>
+        public Task<TResult> FromAsync<TResult>(
+            IAsyncResult asyncResult, Func<IAsyncResult, TResult> endMethod)
+        {
+            return TaskFactory<TResult>.FromAsyncImpl(asyncResult, endMethod, null, m_defaultCreationOptions, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that executes an end
+        /// method function when a specified <see cref="T:System.IAsyncResult">IAsyncResult</see> completes.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="asyncResult">The IAsyncResult whose completion should trigger the processing of the
+        /// <paramref name="endMethod"/>.</param>
+        /// <param name="endMethod">The function delegate that processes the completed <paramref
+        /// name="asyncResult"/>.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="asyncResult"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>A <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents the
+        /// asynchronous operation.</returns>
+        public Task<TResult> FromAsync<TResult>(
+            IAsyncResult asyncResult, Func<IAsyncResult, TResult> endMethod, TaskCreationOptions creationOptions)
+        {
+            return TaskFactory<TResult>.FromAsyncImpl(asyncResult, endMethod, null, creationOptions, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that executes an end
+        /// method function when a specified <see cref="T:System.IAsyncResult">IAsyncResult</see> completes.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="asyncResult">The IAsyncResult whose completion should trigger the processing of the
+        /// <paramref name="endMethod"/>.</param>
+        /// <param name="endMethod">The function delegate that processes the completed <paramref
+        /// name="asyncResult"/>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the task that executes the end method.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="asyncResult"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>A <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents the
+        /// asynchronous operation.</returns>
+        public Task<TResult> FromAsync<TResult>(
+            IAsyncResult asyncResult, Func<IAsyncResult, TResult> endMethod, TaskCreationOptions creationOptions, TaskScheduler scheduler)
+        {
+            return TaskFactory<TResult>.FromAsyncImpl(asyncResult, endMethod, null, creationOptions, scheduler);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync<TResult>(
+            Func<AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod, object state)
+        {
+            return TaskFactory<TResult>.FromAsyncImpl(beginMethod, endMethod, null, state, m_defaultCreationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync<TResult>(
+            Func<AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod, object state, TaskCreationOptions creationOptions)
+        {
+            return TaskFactory<TResult>.FromAsyncImpl(beginMethod, endMethod, null, state, creationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/> delegate.</typeparam>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync<TArg1, TResult>(
+            Func<TArg1, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod, TArg1 arg1, object state)
+        {
+            return TaskFactory<TResult>.FromAsyncImpl(beginMethod, endMethod, null, arg1, state, m_defaultCreationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/> delegate.</typeparam>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync<TArg1, TResult>(Func<TArg1, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod, TArg1 arg1, object state, TaskCreationOptions creationOptions)
+        {
+            return TaskFactory<TResult>.FromAsyncImpl(beginMethod, endMethod, null, arg1, state, creationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/> delegate.</typeparam>
+        /// <typeparam name="TArg2">The type of the second argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg2">The second argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync<TArg1, TArg2, TResult>(Func<TArg1, TArg2, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod, TArg1 arg1, TArg2 arg2, object state)
+        {
+            return TaskFactory<TResult>.FromAsyncImpl(beginMethod, endMethod, null, arg1, arg2, state, m_defaultCreationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/> delegate.</typeparam>
+        /// <typeparam name="TArg2">The type of the second argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg2">The second argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync<TArg1, TArg2, TResult>(
+            Func<TArg1, TArg2, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod, TArg1 arg1, TArg2 arg2, object state, TaskCreationOptions creationOptions)
+        {
+            return TaskFactory<TResult>.FromAsyncImpl(beginMethod, endMethod, null, arg1, arg2, state, creationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/> delegate.</typeparam>
+        /// <typeparam name="TArg2">The type of the second argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <typeparam name="TArg3">The type of the third argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg2">The second argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg3">The third argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync<TArg1, TArg2, TArg3, TResult>(
+            Func<TArg1, TArg2, TArg3, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod, TArg1 arg1, TArg2 arg2, TArg3 arg3, object state)
+        {
+            return TaskFactory<TResult>.FromAsyncImpl(beginMethod, endMethod, null, arg1, arg2, arg3, state, m_defaultCreationOptions);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that represents a pair of
+        /// begin and end methods that conform to the Asynchronous Programming Model pattern.
+        /// </summary>
+        /// <typeparam name="TArg1">The type of the first argument passed to the <paramref
+        /// name="beginMethod"/> delegate.</typeparam>
+        /// <typeparam name="TArg2">The type of the second argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <typeparam name="TArg3">The type of the third argument passed to <paramref name="beginMethod"/>
+        /// delegate.</typeparam>
+        /// <typeparam name="TResult">The type of the result available through the
+        /// <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.
+        /// </typeparam>
+        /// <param name="beginMethod">The delegate that begins the asynchronous operation.</param>
+        /// <param name="endMethod">The delegate that ends the asynchronous operation.</param>
+        /// <param name="arg1">The first argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg2">The second argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="arg3">The third argument passed to the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <param name="creationOptions">The TaskCreationOptions value that controls the behavior of the
+        /// created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="state">An object containing data to be used by the <paramref name="beginMethod"/>
+        /// delegate.</param>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="beginMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="endMethod"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="creationOptions"/> argument specifies an invalid TaskCreationOptions
+        /// value.</exception>
+        /// <returns>The created <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see> that
+        /// represents the asynchronous operation.</returns>
+        /// <remarks>
+        /// This method throws any exceptions thrown by the <paramref name="beginMethod"/>.
+        /// </remarks>
+        public Task<TResult> FromAsync<TArg1, TArg2, TArg3, TResult>(
+            Func<TArg1, TArg2, TArg3, AsyncCallback, object, IAsyncResult> beginMethod,
+            Func<IAsyncResult, TResult> endMethod, TArg1 arg1, TArg2 arg2, TArg3 arg3, object state, TaskCreationOptions creationOptions)
+        {
+            return TaskFactory<TResult>.FromAsyncImpl(beginMethod, endMethod, null, arg1, arg2, arg3, state, creationOptions);
+        }
+
+        /// <summary>
+        /// Check validity of options passed to FromAsync method
+        /// </summary>
+        /// <param name="creationOptions">The options to be validated.</param>
+        /// <param name="hasBeginMethod">determines type of FromAsync method that called this method</param>
+        internal static void CheckFromAsyncOptions(TaskCreationOptions creationOptions, bool hasBeginMethod)
+        {
+            if (hasBeginMethod)
+            {
+                // Options detected here cause exceptions in FromAsync methods that take beginMethod as a parameter
+                if ((creationOptions & TaskCreationOptions.LongRunning) != 0)
+                    throw new ArgumentOutOfRangeException(nameof(creationOptions), SR.Task_FromAsync_LongRunning);
+                if ((creationOptions & TaskCreationOptions.PreferFairness) != 0)
+                    throw new ArgumentOutOfRangeException(nameof(creationOptions), SR.Task_FromAsync_PreferFairness);
+            }
+
+            // Check for general validity of options
+            if ((creationOptions &
+                    ~(TaskCreationOptions.AttachedToParent |
+                      TaskCreationOptions.DenyChildAttach |
+                      TaskCreationOptions.HideScheduler |
+                      TaskCreationOptions.PreferFairness |
+                      TaskCreationOptions.LongRunning)) != 0)
+            {
+                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.creationOptions);
+            }
+        }
+
+
+        //
+        // ContinueWhenAll methods
+        //
+
+        // A Task<Task[]> that, given an initial collection of N tasks, will complete when
+        // it has been invoked N times.  This allows us to replace this logic:
+        //      Task<Task[]> promise = new Task<Task[]>(...);
+        //      int _count = tasksCopy.Length;
+        //      Action<Task> completionAction = delegate {if(Interlocked.Decrement(ref _count) == 0) promise.TrySetResult(tasksCopy);
+        //      for(int i=0; i<_count; i++)
+        //          tasksCopy[i].AddCompletionAction(completionAction);
+        // with this logic:
+        //      CompletionOnCountdownPromise promise = new CompletionOnCountdownPromise(tasksCopy);
+        //      for(int i=0; i<tasksCopy.Length; i++) tasksCopy[i].AddCompletionAction(promise);
+        // which saves a few allocations.
+        //
+        // Used in TaskFactory.CommonCWAllLogic(Task[]), below.
+        private sealed class CompleteOnCountdownPromise : Task<Task[]>, ITaskCompletionAction
+        {
+            private readonly Task[] _tasks;
+            private int _count;
+
+            internal CompleteOnCountdownPromise(Task[] tasksCopy) : base()
+            {
+                Debug.Assert((tasksCopy != null) && (tasksCopy.Length > 0), "Expected non-null task array with at least one element in it");
+                _tasks = tasksCopy;
+                _count = tasksCopy.Length;
+
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, this.Id, "TaskFactory.ContinueWhenAll", 0);
+
+                if (Task.s_asyncDebuggingEnabled)
+                {
+                    AddToActiveTasks(this);
+                }
+            }
+
+            public void Invoke(Task completingTask)
+            {
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationRelation(CausalityTraceLevel.Important, this.Id, CausalityRelation.Join);
+
+                if (completingTask.IsWaitNotificationEnabled) this.SetNotificationForWaitCompletion(enabled: true);
+                if (Interlocked.Decrement(ref _count) == 0)
+                {
+                    if (AsyncCausalityTracer.LoggingOn)
+                        AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, this.Id, AsyncCausalityStatus.Completed);
+
+                    if (Task.s_asyncDebuggingEnabled)
+                    {
+                        RemoveFromActiveTasks(this.Id);
+                    }
+
+                    TrySetResult(_tasks);
+                }
+                Debug.Assert(_count >= 0, "Count should never go below 0");
+            }
+
+            public bool InvokeMayRunArbitraryCode { get { return true; } }
+
+            /// <summary>
+            /// Returns whether we should notify the debugger of a wait completion.  This returns 
+            /// true iff at least one constituent task has its bit set.
+            /// </summary>
+            internal override bool ShouldNotifyDebuggerOfWaitCompletion
+            {
+                get
+                {
+                    return
+                        base.ShouldNotifyDebuggerOfWaitCompletion &&
+                        Task.AnyTaskRequiresNotifyDebuggerOfWaitCompletion(_tasks);
+                }
+            }
+        }
+
+        // Performs some logic common to all ContinueWhenAll() overloads
+        internal static Task<Task[]> CommonCWAllLogic(Task[] tasksCopy)
+        {
+            Debug.Assert(tasksCopy != null);
+
+            // Create a promise task to be returned to the user
+            CompleteOnCountdownPromise promise = new CompleteOnCountdownPromise(tasksCopy);
+
+            for (int i = 0; i < tasksCopy.Length; i++)
+            {
+                if (tasksCopy[i].IsCompleted) promise.Invoke(tasksCopy[i]); // Short-circuit the completion action, if possible
+                else tasksCopy[i].AddCompletionAction(promise); // simple completion action
+            }
+
+            return promise;
+        }
+
+
+        // A Task<Task<T>[]> that, given an initial collection of N tasks, will complete when
+        // it has been invoked N times.  See comments for non-generic CompleteOnCountdownPromise class.
+        //
+        // Used in TaskFactory.CommonCWAllLogic<TResult>(Task<TResult>[]), below.
+        private sealed class CompleteOnCountdownPromise<T> : Task<Task<T>[]>, ITaskCompletionAction
+        {
+            private readonly Task<T>[] _tasks;
+            private int _count;
+
+            internal CompleteOnCountdownPromise(Task<T>[] tasksCopy) : base()
+            {
+                Debug.Assert((tasksCopy != null) && (tasksCopy.Length > 0), "Expected non-null task array with at least one element in it");
+                _tasks = tasksCopy;
+                _count = tasksCopy.Length;
+
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, this.Id, "TaskFactory.ContinueWhenAll<>", 0);
+
+                if (Task.s_asyncDebuggingEnabled)
+                {
+                    AddToActiveTasks(this);
+                }
+            }
+
+            public void Invoke(Task completingTask)
+            {
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationRelation(CausalityTraceLevel.Important, this.Id, CausalityRelation.Join);
+
+                if (completingTask.IsWaitNotificationEnabled) this.SetNotificationForWaitCompletion(enabled: true);
+                if (Interlocked.Decrement(ref _count) == 0)
+                {
+                    if (AsyncCausalityTracer.LoggingOn)
+                        AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, this.Id, AsyncCausalityStatus.Completed);
+
+                    if (Task.s_asyncDebuggingEnabled)
+                    {
+                        RemoveFromActiveTasks(this.Id);
+                    }
+
+                    TrySetResult(_tasks);
+                }
+                Debug.Assert(_count >= 0, "Count should never go below 0");
+            }
+
+            public bool InvokeMayRunArbitraryCode { get { return true; } }
+
+            /// <summary>
+            /// Returns whether we should notify the debugger of a wait completion.  This returns 
+            /// true iff at least one constituent task has its bit set.
+            /// </summary>
+            internal override bool ShouldNotifyDebuggerOfWaitCompletion
+            {
+                get
+                {
+                    return
+                        base.ShouldNotifyDebuggerOfWaitCompletion &&
+                        Task.AnyTaskRequiresNotifyDebuggerOfWaitCompletion(_tasks);
+                }
+            }
+        }
+
+
+        internal static Task<Task<T>[]> CommonCWAllLogic<T>(Task<T>[] tasksCopy)
+        {
+            Debug.Assert(tasksCopy != null);
+
+            // Create a promise task to be returned to the user
+            CompleteOnCountdownPromise<T> promise = new CompleteOnCountdownPromise<T>(tasksCopy);
+
+            for (int i = 0; i < tasksCopy.Length; i++)
+            {
+                if (tasksCopy[i].IsCompleted) promise.Invoke(tasksCopy[i]); // Short-circuit the completion action, if possible
+                else tasksCopy[i].AddCompletionAction(promise); // simple completion action
+            }
+
+            return promise;
+        }
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see> 
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationAction">The action delegate to execute when all tasks in 
+        /// the <paramref name="tasks"/> array have completed.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the 
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array is empty.</exception>
+        public Task ContinueWhenAll(Task[] tasks, Action<Task[]> continuationAction)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAllImpl(tasks, null, continuationAction, m_defaultContinuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see> 
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationAction">The action delegate to execute when all tasks in 
+        /// the <paramref name="tasks"/> array have completed.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the 
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task ContinueWhenAll(Task[] tasks, Action<Task[]> continuationAction, CancellationToken cancellationToken)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAllImpl(tasks, null, continuationAction, m_defaultContinuationOptions, cancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationAction">The action delegate to execute when all tasks in the <paramref
+        /// name="tasks"/> array have completed.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAll.
+        /// </remarks>
+        public Task ContinueWhenAll(Task[] tasks, Action<Task[]> continuationAction, TaskContinuationOptions continuationOptions)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAllImpl(tasks, null, continuationAction, continuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationAction">The action delegate to execute when all tasks in the <paramref
+        /// name="tasks"/> array have completed.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created continuation <see
+        /// cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAll.
+        /// </remarks>
+        public Task ContinueWhenAll(Task[] tasks, Action<Task[]> continuationAction, CancellationToken cancellationToken,
+            TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAllImpl(tasks, null, continuationAction, continuationOptions, cancellationToken, scheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see> 
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationAction">The action delegate to execute when all tasks in 
+        /// the <paramref name="tasks"/> array have completed.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the 
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array is empty.</exception>
+        public Task ContinueWhenAll<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Action<Task<TAntecedentResult>[]> continuationAction)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAllImpl<TAntecedentResult>(tasks, null, continuationAction, m_defaultContinuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see> 
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationAction">The action delegate to execute when all tasks in 
+        /// the <paramref name="tasks"/> array have completed.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the 
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the 
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task ContinueWhenAll<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Action<Task<TAntecedentResult>[]> continuationAction,
+            CancellationToken cancellationToken)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAllImpl<TAntecedentResult>(tasks, null, continuationAction, m_defaultContinuationOptions, cancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationAction">The action delegate to execute when all tasks in the <paramref
+        /// name="tasks"/> array have completed.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAll.
+        /// </remarks>
+        public Task ContinueWhenAll<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Action<Task<TAntecedentResult>[]> continuationAction,
+            TaskContinuationOptions continuationOptions)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAllImpl<TAntecedentResult>(tasks, null, continuationAction, continuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationAction">The action delegate to execute when all tasks in the <paramref
+        /// name="tasks"/> array have completed.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created continuation <see
+        /// cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAll.
+        /// </remarks>
+        public Task ContinueWhenAll<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Action<Task<TAntecedentResult>[]> continuationAction,
+            CancellationToken cancellationToken, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAllImpl<TAntecedentResult>(tasks, null, continuationAction, continuationOptions, cancellationToken, scheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in the
+        /// <paramref name="tasks"/> array have completed.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        public Task<TResult> ContinueWhenAll<TResult>(Task[] tasks, Func<Task[], TResult> continuationFunction)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAllImpl(tasks, continuationFunction, null, m_defaultContinuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in the
+        /// <paramref name="tasks"/> array have completed.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TResult> ContinueWhenAll<TResult>(Task[] tasks, Func<Task[], TResult> continuationFunction, CancellationToken cancellationToken)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAllImpl(tasks, continuationFunction, null, m_defaultContinuationOptions, cancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in the
+        /// <paramref name="tasks"/> array have completed.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAll.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAll<TResult>(Task[] tasks, Func<Task[], TResult> continuationFunction, TaskContinuationOptions continuationOptions)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAllImpl(tasks, continuationFunction, null, continuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in the
+        /// <paramref name="tasks"/> array have completed.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created continuation <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAll.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAll<TResult>(Task[] tasks, Func<Task[], TResult> continuationFunction, CancellationToken cancellationToken,
+            TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAllImpl(tasks, continuationFunction, null, continuationOptions, cancellationToken, scheduler);
+        }
+
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in the
+        /// <paramref name="tasks"/> array have completed.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        public Task<TResult> ContinueWhenAll<TAntecedentResult, TResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>[], TResult> continuationFunction)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAllImpl<TAntecedentResult>(tasks, continuationFunction, null, m_defaultContinuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in the
+        /// <paramref name="tasks"/> array have completed.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TResult> ContinueWhenAll<TAntecedentResult, TResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>[], TResult> continuationFunction,
+            CancellationToken cancellationToken)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAllImpl<TAntecedentResult>(tasks, continuationFunction, null, m_defaultContinuationOptions, cancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in the
+        /// <paramref name="tasks"/> array have completed.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAll.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAll<TAntecedentResult, TResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>[], TResult> continuationFunction,
+            TaskContinuationOptions continuationOptions)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAllImpl<TAntecedentResult>(tasks, continuationFunction, null, continuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of a set of provided Tasks.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue.</param>
+        /// <param name="continuationFunction">The function delegate to execute when all tasks in the
+        /// <paramref name="tasks"/> array have completed.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created continuation <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAll.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAll<TAntecedentResult, TResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>[], TResult> continuationFunction,
+            CancellationToken cancellationToken, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAllImpl<TAntecedentResult>(tasks, continuationFunction, null, continuationOptions, cancellationToken, scheduler);
+        }
+
+        //
+        // ContinueWhenAny methods
+        //
+
+        // A Task<Task> that will be completed the first time that Invoke is called.
+        // It allows us to replace this logic:
+        //      Task<Task> promise = new Task<Task>(...);
+        //      Action<Task> completionAction = delegate(Task completingTask) { promise.TrySetResult(completingTask); }
+        //      for(int i=0; i<tasksCopy.Length; i++) tasksCopy[i].AddCompletionAction(completionAction);
+        // with this logic:
+        //      CompletionOnInvokePromise promise = new CompletionOnInvokePromise(tasksCopy);
+        //      for(int i=0; i<tasksCopy.Length; i++) tasksCopy[i].AddCompletionAction(promise);
+        // which saves a couple of allocations.
+        //
+        // Used in TaskFactory.CommonCWAnyLogic(), below.
+        internal sealed class CompleteOnInvokePromise : Task<Task>, ITaskCompletionAction
+        {
+            private IList<Task> _tasks; // must track this for cleanup
+            private int m_firstTaskAlreadyCompleted;
+
+            public CompleteOnInvokePromise(IList<Task> tasks) : base()
+            {
+                Debug.Assert(tasks != null, "Expected non-null collection of tasks");
+                _tasks = tasks;
+
+                if (AsyncCausalityTracer.LoggingOn)
+                    AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, this.Id, "TaskFactory.ContinueWhenAny", 0);
+
+                if (Task.s_asyncDebuggingEnabled)
+                {
+                    AddToActiveTasks(this);
+                }
+            }
+
+            public void Invoke(Task completingTask)
+            {
+                if (m_firstTaskAlreadyCompleted == 0 &&
+                    Interlocked.Exchange(ref m_firstTaskAlreadyCompleted, 1) == 0)
+                {
+                    if (AsyncCausalityTracer.LoggingOn)
+                    {
+                        AsyncCausalityTracer.TraceOperationRelation(CausalityTraceLevel.Important, this.Id, CausalityRelation.Choice);
+                        AsyncCausalityTracer.TraceOperationCompletion(CausalityTraceLevel.Required, this.Id, AsyncCausalityStatus.Completed);
+                    }
+
+                    if (Task.s_asyncDebuggingEnabled)
+                    {
+                        RemoveFromActiveTasks(this.Id);
+                    }
+
+                    bool success = TrySetResult(completingTask);
+                    Debug.Assert(success, "Only one task should have gotten to this point, and thus this must be successful.");
+
+                    // We need to remove continuations that may be left straggling on other tasks.
+                    // Otherwise, repeated calls to WhenAny using the same task could leak actions.
+                    // This may also help to avoided unnecessary invocations of this whenComplete delegate.
+                    // Note that we may be attempting to remove a continuation from a task that hasn't had it
+                    // added yet; while there's overhead there, the operation won't hurt anything.
+                    var tasks = _tasks;
+                    int numTasks = tasks.Count;
+                    for (int i = 0; i < numTasks; i++)
+                    {
+                        var task = tasks[i];
+                        if (task != null && // if an element was erroneously nulled out concurrently, just skip it; worst case is we don't remove a continuation
+                            !task.IsCompleted) task.RemoveContinuation(this);
+                    }
+                    _tasks = null;
+                }
+            }
+
+            public bool InvokeMayRunArbitraryCode { get { return true; } }
+        }
+        // Common ContinueWhenAny logic
+        // If the tasks list is not an array, it must be an internal defensive copy so that 
+        // we don't need to be concerned about concurrent modifications to the list.  If the task list
+        // is an array, it should be a defensive copy if this functionality is being used
+        // asynchronously (e.g. WhenAny) rather than synchronously (e.g. WaitAny).
+        internal static Task<Task> CommonCWAnyLogic(IList<Task> tasks)
+        {
+            Debug.Assert(tasks != null);
+
+            // Create a promise task to be returned to the user.
+            // (If this logic ever changes, also update CommonCWAnyLogicCleanup.)
+            var promise = new CompleteOnInvokePromise(tasks);
+
+            // At the completion of any of the tasks, complete the promise.
+
+            bool checkArgsOnly = false;
+            int numTasks = tasks.Count;
+            for (int i = 0; i < numTasks; i++)
+            {
+                var task = tasks[i];
+                if (task == null) throw new ArgumentException(SR.Task_MultiTaskContinuation_NullTask, nameof(tasks));
+
+                if (checkArgsOnly) continue;
+
+                // If the promise has already completed, don't bother with checking any more tasks.
+                if (promise.IsCompleted)
+                {
+                    checkArgsOnly = true;
+                }
+                // If a task has already completed, complete the promise.
+                else if (task.IsCompleted)
+                {
+                    promise.Invoke(task);
+                    checkArgsOnly = true;
+                }
+                // Otherwise, add the completion action and keep going.
+                else
+                {
+                    task.AddCompletionAction(promise);
+                    if (promise.IsCompleted)
+                    {
+                        // One of the previous tasks that already had its continuation registered may have
+                        // raced to complete with our adding the continuation to this task.  The completion
+                        // routine would have gone through and removed the continuation from all of the tasks
+                        // with which it was already registered, but if the race causes this continuation to
+                        // be added after that, it'll never be removed.  As such, after adding the continuation,
+                        // we check to see whether the promise has already completed, and if it has, we try to
+                        // manually remove the continuation from this task.  If it was already removed, it'll be
+                        // a nop, and if we race to remove it, the synchronization in RemoveContinuation will
+                        // keep things consistent.
+                        task.RemoveContinuation(promise);
+                    }
+                }
+            }
+
+            return promise;
+        }
+
+        /// <summary>
+        /// Cleans up the operations performed by CommonCWAnyLogic in a case where
+        /// the created continuation task is being discarded.
+        /// </summary>
+        /// <param name="continuation">The task returned from CommonCWAnyLogic.</param>
+        internal static void CommonCWAnyLogicCleanup(Task<Task> continuation)
+        {
+            // Force cleanup of the promise (e.g. removing continuations from each
+            // constituent task), by completing the promise with any value.
+            ((CompleteOnInvokePromise)continuation).Invoke(null);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationAction">The action delegate to execute when one task in the <paramref
+        /// name="tasks"/> array completes.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        public Task ContinueWhenAny(Task[] tasks, Action<Task> continuationAction)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAnyImpl(tasks, null, continuationAction, m_defaultContinuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationAction">The action delegate to execute when one task in the <paramref
+        /// name="tasks"/> array completes.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task ContinueWhenAny(Task[] tasks, Action<Task> continuationAction, CancellationToken cancellationToken)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAnyImpl(tasks, null, continuationAction, m_defaultContinuationOptions, cancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationAction">The action delegate to execute when one task in the <paramref
+        /// name="tasks"/> array completes.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAny.
+        /// </remarks>
+        public Task ContinueWhenAny(Task[] tasks, Action<Task> continuationAction, TaskContinuationOptions continuationOptions)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAnyImpl(tasks, null, continuationAction, continuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationAction">The action delegate to execute when one task in the <paramref
+        /// name="tasks"/> array completes.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created continuation <see
+        /// cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAny.
+        /// </remarks>
+        public Task ContinueWhenAny(Task[] tasks, Action<Task> continuationAction, CancellationToken cancellationToken,
+            TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAnyImpl(tasks, null, continuationAction, continuationOptions, cancellationToken, scheduler);
+        }
+
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        public Task<TResult> ContinueWhenAny<TResult>(Task[] tasks, Func<Task, TResult> continuationFunction)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAnyImpl(tasks, continuationFunction, null, m_defaultContinuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TResult> ContinueWhenAny<TResult>(Task[] tasks, Func<Task, TResult> continuationFunction, CancellationToken cancellationToken)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAnyImpl(tasks, continuationFunction, null, m_defaultContinuationOptions, cancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAny.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAny<TResult>(Task[] tasks, Func<Task, TResult> continuationFunction, TaskContinuationOptions continuationOptions)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAnyImpl(tasks, continuationFunction, null, continuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created continuation <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAny.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAny<TResult>(Task[] tasks, Func<Task, TResult> continuationFunction, CancellationToken cancellationToken,
+            TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAnyImpl(tasks, continuationFunction, null, continuationOptions, cancellationToken, scheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        public Task<TResult> ContinueWhenAny<TAntecedentResult, TResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>, TResult> continuationFunction)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+            return TaskFactory<TResult>.ContinueWhenAnyImpl<TAntecedentResult>(tasks, continuationFunction, null, m_defaultContinuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TResult> ContinueWhenAny<TAntecedentResult, TResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>, TResult> continuationFunction,
+            CancellationToken cancellationToken)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAnyImpl<TAntecedentResult>(tasks, continuationFunction, null, m_defaultContinuationOptions, cancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAny.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAny<TAntecedentResult, TResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>, TResult> continuationFunction,
+            TaskContinuationOptions continuationOptions)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAnyImpl<TAntecedentResult>(tasks, continuationFunction, null, continuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the result that is returned by the <paramref
+        /// name="continuationFunction"/>
+        /// delegate and associated with the created <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</typeparam>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationFunction">The function delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task{TResult}">Task</see>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created continuation <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task{TResult}"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationFunction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAny.
+        /// </remarks>
+        public Task<TResult> ContinueWhenAny<TAntecedentResult, TResult>(Task<TAntecedentResult>[] tasks, Func<Task<TAntecedentResult>, TResult> continuationFunction,
+            CancellationToken cancellationToken, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            if (continuationFunction == null) throw new ArgumentNullException(nameof(continuationFunction));
+
+            return TaskFactory<TResult>.ContinueWhenAnyImpl<TAntecedentResult>(tasks, continuationFunction, null, continuationOptions, cancellationToken, scheduler);
+        }
+
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationAction">The action delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        public Task ContinueWhenAny<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Action<Task<TAntecedentResult>> continuationAction)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAnyImpl<TAntecedentResult>(tasks, null, continuationAction, m_defaultContinuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationAction">The action delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task ContinueWhenAny<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Action<Task<TAntecedentResult>> continuationAction,
+            CancellationToken cancellationToken)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAnyImpl<TAntecedentResult>(tasks, null, continuationAction, m_defaultContinuationOptions, cancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationAction">The action delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAny.
+        /// </remarks>
+        public Task ContinueWhenAny<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Action<Task<TAntecedentResult>> continuationAction,
+            TaskContinuationOptions continuationOptions)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAnyImpl<TAntecedentResult>(tasks, null, continuationAction, continuationOptions, m_defaultCancellationToken, DefaultScheduler);
+        }
+
+        /// <summary>
+        /// Creates a continuation <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// that will be started upon the completion of any Task in the provided set.
+        /// </summary>
+        /// <typeparam name="TAntecedentResult">The type of the result of the antecedent <paramref name="tasks"/>.</typeparam>
+        /// <param name="tasks">The array of tasks from which to continue when one task completes.</param>
+        /// <param name="continuationAction">The action delegate to execute when one task in the
+        /// <paramref name="tasks"/> array completes.</param>
+        /// <param name="cancellationToken">The <see cref="System.Threading.CancellationToken">CancellationToken</see> 
+        /// that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">The <see cref="System.Threading.Tasks.TaskContinuationOptions">
+        /// TaskContinuationOptions</see> value that controls the behavior of
+        /// the created continuation <see cref="T:System.Threading.Tasks.Task">Task</see>.</param>
+        /// <param name="scheduler">The <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// that is used to schedule the created continuation <see
+        /// cref="T:System.Threading.Tasks.Task{TResult}"/>.</param>
+        /// <returns>The new continuation <see cref="T:System.Threading.Tasks.Task"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="continuationAction"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentNullException">The exception that is thrown when the
+        /// <paramref name="scheduler"/> argument is null.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array contains a null value.</exception>
+        /// <exception cref="T:System.ArgumentException">The exception that is thrown when the
+        /// <paramref name="tasks"/> array is empty.</exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">The exception that is thrown when the
+        /// <paramref name="continuationOptions"/> argument specifies an invalid TaskContinuationOptions
+        /// value.</exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        /// <remarks>
+        /// The NotOn* and OnlyOn* <see cref="System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>, 
+        /// which constrain for which <see cref="System.Threading.Tasks.TaskStatus">TaskStatus</see> states a continuation 
+        /// will be executed, are illegal with ContinueWhenAny.
+        /// </remarks>
+        public Task ContinueWhenAny<TAntecedentResult>(Task<TAntecedentResult>[] tasks, Action<Task<TAntecedentResult>> continuationAction,
+            CancellationToken cancellationToken, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            if (continuationAction == null) throw new ArgumentNullException(nameof(continuationAction));
+
+            return TaskFactory<VoidTaskResult>.ContinueWhenAnyImpl<TAntecedentResult>(tasks, null, continuationAction, continuationOptions, cancellationToken, scheduler);
+        }
+
+        // Check task array and return a defensive copy.
+        // Used with ContinueWhenAll()/ContinueWhenAny().
+        internal static Task[] CheckMultiContinuationTasksAndCopy(Task[] tasks)
+        {
+            if (tasks == null)
+                throw new ArgumentNullException(nameof(tasks));
+            if (tasks.Length == 0)
+                throw new ArgumentException(SR.Task_MultiTaskContinuation_EmptyTaskList, nameof(tasks));
+
+            Task[] tasksCopy = new Task[tasks.Length];
+            for (int i = 0; i < tasks.Length; i++)
+            {
+                tasksCopy[i] = tasks[i];
+
+                if (tasksCopy[i] == null)
+                    throw new ArgumentException(SR.Task_MultiTaskContinuation_NullTask, nameof(tasks));
+            }
+
+            return tasksCopy;
+        }
+
+        internal static Task<TResult>[] CheckMultiContinuationTasksAndCopy<TResult>(Task<TResult>[] tasks)
+        {
+            if (tasks == null)
+                throw new ArgumentNullException(nameof(tasks));
+            if (tasks.Length == 0)
+                throw new ArgumentException(SR.Task_MultiTaskContinuation_EmptyTaskList, nameof(tasks));
+
+            Task<TResult>[] tasksCopy = new Task<TResult>[tasks.Length];
+            for (int i = 0; i < tasks.Length; i++)
+            {
+                tasksCopy[i] = tasks[i];
+
+                if (tasksCopy[i] == null)
+                    throw new ArgumentException(SR.Task_MultiTaskContinuation_NullTask, nameof(tasks));
+            }
+
+            return tasksCopy;
+        }
+
+        // Throw an exception if "options" argument specifies illegal options
+        internal static void CheckMultiTaskContinuationOptions(TaskContinuationOptions continuationOptions)
+        {
+            // Construct a mask to check for illegal options
+            const TaskContinuationOptions NotOnAny = TaskContinuationOptions.NotOnCanceled |
+                                               TaskContinuationOptions.NotOnFaulted |
+                                               TaskContinuationOptions.NotOnRanToCompletion;
+
+            // Check that LongRunning and ExecuteSynchronously are not specified together
+            const TaskContinuationOptions illegalMask = TaskContinuationOptions.ExecuteSynchronously | TaskContinuationOptions.LongRunning;
+            if ((continuationOptions & illegalMask) == illegalMask)
+            {
+                throw new ArgumentOutOfRangeException(nameof(continuationOptions), SR.Task_ContinueWith_ESandLR);
+            }
+
+            // Check that no nonsensical options are specified.
+            if ((continuationOptions & ~(
+                TaskContinuationOptions.LongRunning |
+                TaskContinuationOptions.PreferFairness |
+                TaskContinuationOptions.AttachedToParent |
+                TaskContinuationOptions.DenyChildAttach |
+                TaskContinuationOptions.HideScheduler |
+                TaskContinuationOptions.LazyCancellation |
+                NotOnAny |
+                TaskContinuationOptions.ExecuteSynchronously)) != 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(continuationOptions));
+            }
+
+            // Check that no "fire" options are specified.
+            if ((continuationOptions & NotOnAny) != 0)
+                throw new ArgumentOutOfRangeException(nameof(continuationOptions), SR.Task_MultiTaskContinuation_FireOptions);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskScheduler.cs b/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskScheduler.cs
new file mode 100644
index 0000000000..e1fda2530d
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Tasks/TaskScheduler.cs
@@ -0,0 +1,735 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// This file contains the primary interface and management of tasks and queues.  
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+// Disable the "reference to volatile field not treated as volatile" error.
+#pragma warning disable 0420
+
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Threading;
+using System.Security;
+using System.Collections.Concurrent;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+
+namespace System.Threading.Tasks
+{
+    /// <summary>
+    /// Represents an abstract scheduler for tasks.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> acts as the extension point for all 
+    /// pluggable scheduling logic.  This includes mechanisms such as how to schedule a task for execution, and
+    /// how scheduled tasks should be exposed to debuggers.
+    /// </para>
+    /// <para>
+    /// All members of the abstract <see cref="TaskScheduler"/> type are thread-safe
+    /// and may be used from multiple threads concurrently.
+    /// </para>
+    /// </remarks>
+    [DebuggerDisplay("Id={Id}")]
+    [DebuggerTypeProxy(typeof(SystemThreadingTasks_TaskSchedulerDebugView))]
+    public abstract class TaskScheduler
+    {
+        ////////////////////////////////////////////////////////////
+        //
+        // User Provided Methods and Properties
+        //
+
+        /// <summary>
+        /// Queues a <see cref="T:System.Threading.Tasks.Task">Task</see> to the scheduler.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// A class derived from <see cref="T:System.Threading.Tasks.TaskScheduler">TaskScheduler</see>  
+        /// implements this method to accept tasks being scheduled on the scheduler.
+        /// A typical implementation would store the task in an internal data structure, which would
+        /// be serviced by threads that would execute those tasks at some time in the future.
+        /// </para>
+        /// <para>
+        /// This method is only meant to be called by the .NET Framework and
+        /// should not be called directly by the derived class. This is necessary 
+        /// for maintaining the consistency of the system.
+        /// </para>
+        /// </remarks>
+        /// <param name="task">The <see cref="T:System.Threading.Tasks.Task">Task</see> to be queued.</param>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="task"/> argument is null.</exception>
+        protected internal abstract void QueueTask(Task task);
+
+        /// <summary>
+        /// Determines whether the provided <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// can be executed synchronously in this call, and if it can, executes it.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// A class derived from <see cref="TaskScheduler">TaskScheduler</see> implements this function to
+        /// support inline execution of a task on a thread that initiates a wait on that task object. Inline
+        /// execution is optional, and the request may be rejected by returning false. However, better
+        /// scalability typically results the more tasks that can be inlined, and in fact a scheduler that
+        /// inlines too little may be prone to deadlocks. A proper implementation should ensure that a
+        /// request executing under the policies guaranteed by the scheduler can successfully inline. For
+        /// example, if a scheduler uses a dedicated thread to execute tasks, any inlining requests from that
+        /// thread should succeed.
+        /// </para>
+        /// <para>
+        /// If a scheduler decides to perform the inline execution, it should do so by calling to the base
+        /// TaskScheduler's
+        /// <see cref="TryExecuteTask">TryExecuteTask</see> method with the provided task object, propagating
+        /// the return value. It may also be appropriate for the scheduler to remove an inlined task from its
+        /// internal data structures if it decides to honor the inlining request. Note, however, that under
+        /// some circumstances a scheduler may be asked to inline a task that was not previously provided to
+        /// it with the <see cref="QueueTask"/> method.
+        /// </para>
+        /// <para>
+        /// The derived scheduler is responsible for making sure that the calling thread is suitable for
+        /// executing the given task as far as its own scheduling and execution policies are concerned.
+        /// </para>
+        /// </remarks>
+        /// <param name="task">The <see cref="T:System.Threading.Tasks.Task">Task</see> to be
+        /// executed.</param>
+        /// <param name="taskWasPreviouslyQueued">A Boolean denoting whether or not task has previously been
+        /// queued. If this parameter is True, then the task may have been previously queued (scheduled); if
+        /// False, then the task is known not to have been queued, and this call is being made in order to
+        /// execute the task inline without queueing it.</param>
+        /// <returns>A Boolean value indicating whether the task was executed inline.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="task"/> argument is
+        /// null.</exception>
+        /// <exception cref="T:System.InvalidOperationException">The <paramref name="task"/> was already
+        /// executed.</exception>
+        protected abstract bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued);
+
+        /// <summary>
+        /// Generates an enumerable of <see cref="T:System.Threading.Tasks.Task">Task</see> instances
+        /// currently queued to the scheduler waiting to be executed.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// A class derived from <see cref="TaskScheduler"/> implements this method in order to support
+        /// integration with debuggers. This method will only be invoked by the .NET Framework when the
+        /// debugger requests access to the data. The enumerable returned will be traversed by debugging
+        /// utilities to access the tasks currently queued to this scheduler, enabling the debugger to
+        /// provide a representation of this information in the user interface.
+        /// </para>
+        /// <para>
+        /// It is important to note that, when this method is called, all other threads in the process will
+        /// be frozen. Therefore, it's important to avoid synchronization with other threads that may lead to
+        /// blocking. If synchronization is necessary, the method should prefer to throw a <see
+        /// cref="System.NotSupportedException"/>
+        /// than to block, which could cause a debugger to experience delays. Additionally, this method and
+        /// the enumerable returned must not modify any globally visible state.
+        /// </para>
+        /// <para>
+        /// The returned enumerable should never be null. If there are currently no queued tasks, an empty
+        /// enumerable should be returned instead.
+        /// </para>
+        /// <para>
+        /// For developers implementing a custom debugger, this method shouldn't be called directly, but
+        /// rather this functionality should be accessed through the internal wrapper method
+        /// GetScheduledTasksForDebugger:
+        /// <c>internal Task[] GetScheduledTasksForDebugger()</c>. This method returns an array of tasks,
+        /// rather than an enumerable. In order to retrieve a list of active schedulers, a debugger may use
+        /// another internal method: <c>internal static TaskScheduler[] GetTaskSchedulersForDebugger()</c>.
+        /// This static method returns an array of all active TaskScheduler instances.
+        /// GetScheduledTasksForDebugger then may be used on each of these scheduler instances to retrieve
+        /// the list of scheduled tasks for each.
+        /// </para>
+        /// </remarks>
+        /// <returns>An enumerable that allows traversal of tasks currently queued to this scheduler.
+        /// </returns>
+        /// <exception cref="T:System.NotSupportedException">
+        /// This scheduler is unable to generate a list of queued tasks at this time.
+        /// </exception>
+        protected abstract IEnumerable<Task> GetScheduledTasks();
+
+        /// <summary>
+        /// Indicates the maximum concurrency level this 
+        /// <see cref="TaskScheduler"/>  is able to support.
+        /// </summary>
+        public virtual Int32 MaximumConcurrencyLevel
+        {
+            get
+            {
+                return Int32.MaxValue;
+            }
+        }
+
+        ////////////////////////////////////////////////////////////
+        //
+        // Internal overridable methods
+        //
+
+
+        /// <summary>
+        /// Attempts to execute the target task synchronously.
+        /// </summary>
+        /// <param name="task">The task to run.</param>
+        /// <param name="taskWasPreviouslyQueued">True if the task may have been previously queued,
+        /// false if the task was absolutely not previously queued.</param>
+        /// <returns>True if it ran, false otherwise.</returns>
+        internal bool TryRunInline(Task task, bool taskWasPreviouslyQueued)
+        {
+            // Do not inline unstarted tasks (i.e., task.ExecutingTaskScheduler == null).
+            // Do not inline TaskCompletionSource-style (a.k.a. "promise") tasks.
+            // No need to attempt inlining if the task body was already run (i.e. either TASK_STATE_DELEGATE_INVOKED or TASK_STATE_CANCELED bits set)
+            TaskScheduler ets = task.ExecutingTaskScheduler;
+
+            // Delegate cross-scheduler inlining requests to target scheduler
+            if (ets != this && ets != null) return ets.TryRunInline(task, taskWasPreviouslyQueued);
+
+            StackGuard currentStackGuard;
+            if ((ets == null) ||
+                (task.m_action == null) ||
+                task.IsDelegateInvoked ||
+                task.IsCanceled ||
+                (currentStackGuard = Task.CurrentStackGuard).TryBeginInliningScope() == false)
+            {
+                return false;
+            }
+
+            // Task class will still call into TaskScheduler.TryRunInline rather than TryExecuteTaskInline() so that 
+            // 1) we can adjust the return code from TryExecuteTaskInline in case a buggy custom scheduler lies to us
+            // 2) we maintain a mechanism for the TLS lookup optimization that we used to have for the ConcRT scheduler (will potentially introduce the same for TP)
+            bool bInlined = false;
+            try
+            {
+                if (TplEtwProvider.Log.IsEnabled())
+                {
+                    task.FireTaskScheduledIfNeeded(this);
+                }
+                bInlined = TryExecuteTaskInline(task, taskWasPreviouslyQueued);
+            }
+            finally
+            {
+                currentStackGuard.EndInliningScope();
+            }
+
+            // If the custom scheduler returned true, we should either have the TASK_STATE_DELEGATE_INVOKED or TASK_STATE_CANCELED bit set
+            // Otherwise the scheduler is buggy
+            if (bInlined && !(task.IsDelegateInvoked || task.IsCanceled))
+            {
+                throw new InvalidOperationException(SR.TaskScheduler_InconsistentStateAfterTryExecuteTaskInline);
+            }
+
+            return bInlined;
+        }
+
+        /// <summary>
+        /// Attempts to dequeue a <see cref="T:System.Threading.Tasks.Task">Task</see> that was previously queued to
+        /// this scheduler.
+        /// </summary>
+        /// <param name="task">The <see cref="T:System.Threading.Tasks.Task">Task</see> to be dequeued.</param>
+        /// <returns>A Boolean denoting whether the <paramref name="task"/> argument was successfully dequeued.</returns>
+        /// <exception cref="T:System.ArgumentNullException">The <paramref name="task"/> argument is null.</exception>
+        protected internal virtual bool TryDequeue(Task task)
+        {
+            return false;
+        }
+
+        /// <summary>
+        /// Notifies the scheduler that a work item has made progress.
+        /// </summary>
+        internal virtual void NotifyWorkItemProgress()
+        {
+        }
+
+        /// <summary>
+        /// Indicates whether this is a custom scheduler, in which case the safe code paths will be taken upon task entry
+        /// using a CAS to transition from queued state to executing.
+        /// </summary>
+        internal virtual bool RequiresAtomicStartTransition
+        {
+            get { return true; }
+        }
+
+        /// <summary>
+        /// Calls QueueTask() after performing any needed firing of events
+        /// </summary>
+        internal void InternalQueueTask(Task task)
+        {
+            Debug.Assert(task != null);
+
+            if (TplEtwProvider.Log.IsEnabled())
+            {
+                task.FireTaskScheduledIfNeeded(this);
+            }
+
+            this.QueueTask(task);
+        }
+
+
+        ////////////////////////////////////////////////////////////
+        //
+        // Member variables
+        //
+
+        // The global container that keeps track of TaskScheduler instances for debugging purposes.
+        private static ConditionalWeakTable<TaskScheduler, object> s_activeTaskSchedulers;
+
+        // An AppDomain-wide default manager.
+        private static readonly TaskScheduler s_defaultTaskScheduler = new ThreadPoolTaskScheduler();
+
+        //static counter used to generate unique TaskScheduler IDs
+        internal static int s_taskSchedulerIdCounter;
+
+        // this TaskScheduler's unique ID
+        private volatile int m_taskSchedulerId;
+
+
+
+        ////////////////////////////////////////////////////////////
+        //
+        // Constructors and public properties
+        //
+
+        /// <summary>
+        /// Initializes the <see cref="System.Threading.Tasks.TaskScheduler"/>.
+        /// </summary>
+        protected TaskScheduler()
+        {
+            // Register the scheduler in the active scheduler list.  This is only relevant when debugging, 
+            // so we only pay the cost if the debugger is attached when the scheduler is created.  This
+            // means that the internal TaskScheduler.GetTaskSchedulersForDebugger() will only include
+            // schedulers created while the debugger is attached.
+            if (Debugger.IsAttached)
+            {
+                AddToActiveTaskSchedulers();
+            }
+        }
+
+        /// <summary>Adds this scheduler ot the active schedulers tracking collection for debugging purposes.</summary>
+        private void AddToActiveTaskSchedulers()
+        {
+            ConditionalWeakTable<TaskScheduler, object> activeTaskSchedulers = s_activeTaskSchedulers;
+            if (activeTaskSchedulers == null)
+            {
+                Interlocked.CompareExchange(ref s_activeTaskSchedulers, new ConditionalWeakTable<TaskScheduler, object>(), null);
+                activeTaskSchedulers = s_activeTaskSchedulers;
+            }
+            activeTaskSchedulers.Add(this, null);
+        }
+
+        /// <summary>
+        /// Gets the default <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> instance.
+        /// </summary>
+        public static TaskScheduler Default
+        {
+            get
+            {
+                return s_defaultTaskScheduler;
+            }
+        }
+
+        /// <summary>
+        /// Gets the <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// associated with the currently executing task.
+        /// </summary>
+        /// <remarks>
+        /// When not called from within a task, <see cref="Current"/> will return the <see cref="Default"/> scheduler.
+        /// </remarks>
+        public static TaskScheduler Current
+        {
+            get
+            {
+                TaskScheduler current = InternalCurrent;
+                return current ?? TaskScheduler.Default;
+            }
+        }
+
+        /// <summary>
+        /// Gets the <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see>
+        /// associated with the currently executing task.
+        /// </summary>
+        /// <remarks>
+        /// When not called from within a task, <see cref="InternalCurrent"/> will return null.
+        /// </remarks>
+        internal static TaskScheduler InternalCurrent
+        {
+            get
+            {
+                Task currentTask = Task.InternalCurrent;
+                return ((currentTask != null)
+                    && ((currentTask.CreationOptions & TaskCreationOptions.HideScheduler) == 0)
+                    ) ? currentTask.ExecutingTaskScheduler : null;
+            }
+        }
+
+        /// <summary>
+        /// Creates a <see cref="TaskScheduler"/>
+        /// associated with the current <see cref="T:System.Threading.SynchronizationContext"/>.
+        /// </summary>
+        /// <remarks>
+        /// All <see cref="System.Threading.Tasks.Task">Task</see> instances queued to 
+        /// the returned scheduler will be executed through a call to the
+        /// <see cref="System.Threading.SynchronizationContext.Post">Post</see> method
+        /// on that context.
+        /// </remarks>
+        /// <returns>
+        /// A <see cref="TaskScheduler"/> associated with 
+        /// the current <see cref="T:System.Threading.SynchronizationContext">SynchronizationContext</see>, as
+        /// determined by <see cref="System.Threading.SynchronizationContext.Current">SynchronizationContext.Current</see>.
+        /// </returns>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The current SynchronizationContext may not be used as a TaskScheduler.
+        /// </exception>
+        public static TaskScheduler FromCurrentSynchronizationContext()
+        {
+            return new SynchronizationContextTaskScheduler();
+        }
+
+        /// <summary>
+        /// Gets the unique ID for this <see cref="TaskScheduler"/>.
+        /// </summary>
+        public Int32 Id
+        {
+            get
+            {
+                if (m_taskSchedulerId == 0)
+                {
+                    int newId = 0;
+
+                    // We need to repeat if Interlocked.Increment wraps around and returns 0.
+                    // Otherwise next time this scheduler's Id is queried it will get a new value
+                    do
+                    {
+                        newId = Interlocked.Increment(ref s_taskSchedulerIdCounter);
+                    } while (newId == 0);
+
+                    Interlocked.CompareExchange(ref m_taskSchedulerId, newId, 0);
+                }
+
+                return m_taskSchedulerId;
+            }
+        }
+
+        /// <summary>
+        /// Attempts to execute the provided <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// on this scheduler.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// Scheduler implementations are provided with <see cref="T:System.Threading.Tasks.Task">Task</see>
+        /// instances to be executed through either the <see cref="QueueTask"/> method or the
+        /// <see cref="TryExecuteTaskInline"/> method. When the scheduler deems it appropriate to run the
+        /// provided task, <see cref="TryExecuteTask"/> should be used to do so. TryExecuteTask handles all
+        /// aspects of executing a task, including action invocation, exception handling, state management,
+        /// and lifecycle control.
+        /// </para>
+        /// <para>
+        /// <see cref="TryExecuteTask"/> must only be used for tasks provided to this scheduler by the .NET
+        /// Framework infrastructure. It should not be used to execute arbitrary tasks obtained through
+        /// custom mechanisms.
+        /// </para>
+        /// </remarks>
+        /// <param name="task">
+        /// A <see cref="T:System.Threading.Tasks.Task">Task</see> object to be executed.</param>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The <paramref name="task"/> is not associated with this scheduler.
+        /// </exception>
+        /// <returns>A Boolean that is true if <paramref name="task"/> was successfully executed, false if it
+        /// was not. A common reason for execution failure is that the task had previously been executed or
+        /// is in the process of being executed by another thread.</returns>
+        protected bool TryExecuteTask(Task task)
+        {
+            if (task.ExecutingTaskScheduler != this)
+            {
+                throw new InvalidOperationException(SR.TaskScheduler_ExecuteTask_WrongTaskScheduler);
+            }
+
+            return task.ExecuteEntry();
+        }
+
+        ////////////////////////////////////////////////////////////
+        //
+        // Events
+        //
+
+        private static EventHandler<UnobservedTaskExceptionEventArgs> _unobservedTaskException;
+        private static readonly object _unobservedTaskExceptionLockObject = new object();
+
+        /// <summary>
+        /// Occurs when a faulted <see cref="System.Threading.Tasks.Task"/>'s unobserved exception is about to trigger exception escalation
+        /// policy, which, by default, would terminate the process.
+        /// </summary>
+        /// <remarks>
+        /// This AppDomain-wide event provides a mechanism to prevent exception
+        /// escalation policy (which, by default, terminates the process) from triggering. 
+        /// Each handler is passed a <see cref="T:System.Threading.Tasks.UnobservedTaskExceptionEventArgs"/>
+        /// instance, which may be used to examine the exception and to mark it as observed.
+        /// </remarks>
+        public static event EventHandler<UnobservedTaskExceptionEventArgs> UnobservedTaskException
+        {
+            add
+            {
+                if (value != null)
+                {
+                    RuntimeHelpers.PrepareContractedDelegate(value);
+                    lock (_unobservedTaskExceptionLockObject) _unobservedTaskException += value;
+                }
+            }
+
+            remove
+            {
+                lock (_unobservedTaskExceptionLockObject) _unobservedTaskException -= value;
+            }
+        }
+
+
+
+
+
+
+        ////////////////////////////////////////////////////////////
+        //
+        // Internal methods
+        //
+
+        // This is called by the TaskExceptionHolder finalizer.
+        internal static void PublishUnobservedTaskException(object sender, UnobservedTaskExceptionEventArgs ueea)
+        {
+            // Lock this logic to prevent just-unregistered handlers from being called.
+            lock (_unobservedTaskExceptionLockObject)
+            {
+                // Since we are under lock, it is technically no longer necessary
+                // to make a copy.  It is done here for convenience.
+                EventHandler<UnobservedTaskExceptionEventArgs> handler = _unobservedTaskException;
+                if (handler != null)
+                {
+                    handler(sender, ueea);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Provides an array of all queued <see cref="System.Threading.Tasks.Task">Task</see> instances
+        /// for the debugger.
+        /// </summary>
+        /// <remarks>
+        /// The returned array is populated through a call to <see cref="GetScheduledTasks"/>.
+        /// Note that this function is only meant to be invoked by a debugger remotely. 
+        /// It should not be called by any other codepaths.
+        /// </remarks>
+        /// <returns>An array of <see cref="System.Threading.Tasks.Task">Task</see> instances.</returns> 
+        /// <exception cref="T:System.NotSupportedException">
+        /// This scheduler is unable to generate a list of queued tasks at this time.
+        /// </exception>
+        internal Task[] GetScheduledTasksForDebugger()
+        {
+            // this can throw InvalidOperationException indicating that they are unable to provide the info
+            // at the moment. We should let the debugger receive that exception so that it can indicate it in the UI
+            IEnumerable<Task> activeTasksSource = GetScheduledTasks();
+
+            if (activeTasksSource == null)
+                return null;
+
+            // If it can be cast to an array, use it directly
+            Task[] activeTasksArray = activeTasksSource as Task[];
+            if (activeTasksArray == null)
+            {
+                activeTasksArray = (new List<Task>(activeTasksSource)).ToArray();
+            }
+
+            // touch all Task.Id fields so that the debugger doesn't need to do a lot of cross-proc calls to generate them
+            foreach (Task t in activeTasksArray)
+            {
+                int tmp = t.Id;
+            }
+
+            return activeTasksArray;
+        }
+
+        /// <summary>
+        /// Provides an array of all active <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> 
+        /// instances for the debugger.
+        /// </summary>
+        /// <remarks>
+        /// This function is only meant to be invoked by a debugger remotely. 
+        /// It should not be called by any other codepaths.
+        /// </remarks>
+        /// <returns>An array of <see cref="System.Threading.Tasks.TaskScheduler">TaskScheduler</see> instances.</returns> 
+        internal static TaskScheduler[] GetTaskSchedulersForDebugger()
+        {
+            if (s_activeTaskSchedulers == null)
+            {
+                // No schedulers were tracked.  Just give back the default.
+                return new TaskScheduler[] { s_defaultTaskScheduler };
+            }
+
+            List<TaskScheduler> schedulers = new List<TaskScheduler>();
+            foreach (var item in s_activeTaskSchedulers)
+            {
+                schedulers.Add(item.Key);
+            }
+
+            if (!schedulers.Contains(s_defaultTaskScheduler))
+            {
+                // Make sure the default is included, in case the debugger attached
+                // after it was created.
+                schedulers.Add(s_defaultTaskScheduler);
+            }
+
+            var arr = schedulers.ToArray();
+            foreach (var scheduler in arr)
+            {
+                Debug.Assert(scheduler != null, "Table returned an incorrect Count or CopyTo failed");
+                int tmp = scheduler.Id; // force Ids for debugger
+            }
+            return arr;
+        }
+
+        /// <summary>
+        /// Nested class that provides debugger view for TaskScheduler
+        /// </summary>
+        internal sealed class SystemThreadingTasks_TaskSchedulerDebugView
+        {
+            private readonly TaskScheduler m_taskScheduler;
+            public SystemThreadingTasks_TaskSchedulerDebugView(TaskScheduler scheduler)
+            {
+                m_taskScheduler = scheduler;
+            }
+
+            // returns the scheduler�s Id
+            public Int32 Id
+            {
+                get { return m_taskScheduler.Id; }
+            }
+
+            // returns the scheduler�s GetScheduledTasks
+            public IEnumerable<Task> ScheduledTasks
+            {
+                get { return m_taskScheduler.GetScheduledTasks(); }
+            }
+        }
+    }
+
+
+
+
+    /// <summary>
+    /// A TaskScheduler implementation that executes all tasks queued to it through a call to 
+    /// <see cref="System.Threading.SynchronizationContext.Post"/> on the <see cref="T:System.Threading.SynchronizationContext"/> 
+    /// that its associated with. The default constructor for this class binds to the current <see cref="T:System.Threading.SynchronizationContext"/> 
+    /// </summary>
+    internal sealed class SynchronizationContextTaskScheduler : TaskScheduler
+    {
+        private SynchronizationContext m_synchronizationContext;
+
+        /// <summary>
+        /// Constructs a SynchronizationContextTaskScheduler associated with <see cref="T:System.Threading.SynchronizationContext.Current"/> 
+        /// </summary>
+        /// <exception cref="T:System.InvalidOperationException">This constructor expects <see cref="T:System.Threading.SynchronizationContext.Current"/> to be set.</exception>
+        internal SynchronizationContextTaskScheduler()
+        {
+            SynchronizationContext synContext = SynchronizationContext.Current;
+
+            // make sure we have a synccontext to work with
+            if (synContext == null)
+            {
+                throw new InvalidOperationException(SR.TaskScheduler_FromCurrentSynchronizationContext_NoCurrent);
+            }
+
+            m_synchronizationContext = synContext;
+        }
+
+        /// <summary>
+        /// Implementation of <see cref="T:System.Threading.Tasks.TaskScheduler.QueueTask"/> for this scheduler class.
+        /// 
+        /// Simply posts the tasks to be executed on the associated <see cref="T:System.Threading.SynchronizationContext"/>.
+        /// </summary>
+        /// <param name="task"></param>
+        protected internal override void QueueTask(Task task)
+        {
+            m_synchronizationContext.Post(s_postCallback, (object)task);
+        }
+
+        /// <summary>
+        /// Implementation of <see cref="T:System.Threading.Tasks.TaskScheduler.TryExecuteTaskInline"/>  for this scheduler class.
+        /// 
+        /// The task will be executed inline only if the call happens within 
+        /// the associated <see cref="T:System.Threading.SynchronizationContext"/>.
+        /// </summary>
+        /// <param name="task"></param>
+        /// <param name="taskWasPreviouslyQueued"></param>
+        protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
+        {
+            if (SynchronizationContext.Current == m_synchronizationContext)
+            {
+                return TryExecuteTask(task);
+            }
+            else
+                return false;
+        }
+
+        // not implemented
+        protected override IEnumerable<Task> GetScheduledTasks()
+        {
+            return null;
+        }
+
+        /// <summary>
+        /// Implements the <see cref="T:System.Threading.Tasks.TaskScheduler.MaximumConcurrencyLevel"/> property for
+        /// this scheduler class.
+        /// 
+        /// By default it returns 1, because a <see cref="T:System.Threading.SynchronizationContext"/> based
+        /// scheduler only supports execution on a single thread.
+        /// </summary>
+        public override Int32 MaximumConcurrencyLevel
+        {
+            get
+            {
+                return 1;
+            }
+        }
+
+        // preallocated SendOrPostCallback delegate
+        private static readonly SendOrPostCallback s_postCallback = s => ((Task)s).ExecuteEntry(); // with double-execute check because SC could be buggy
+    }
+
+    /// <summary>
+    /// Provides data for the event that is raised when a faulted <see cref="System.Threading.Tasks.Task"/>'s
+    /// exception goes unobserved.
+    /// </summary>
+    /// <remarks>
+    /// The Exception property is used to examine the exception without marking it
+    /// as observed, whereas the <see cref="SetObserved"/> method is used to mark the exception
+    /// as observed.  Marking the exception as observed prevents it from triggering exception escalation policy
+    /// which, by default, terminates the process.
+    /// </remarks>
+    public class UnobservedTaskExceptionEventArgs : EventArgs
+    {
+        private AggregateException m_exception;
+        internal bool m_observed = false;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="UnobservedTaskExceptionEventArgs"/> class
+        /// with the unobserved exception.
+        /// </summary>
+        /// <param name="exception">The Exception that has gone unobserved.</param>
+        public UnobservedTaskExceptionEventArgs(AggregateException exception) { m_exception = exception; }
+
+        /// <summary>
+        /// Marks the <see cref="Exception"/> as "observed," thus preventing it
+        /// from triggering exception escalation policy which, by default, terminates the process.
+        /// </summary>
+        public void SetObserved() { m_observed = true; }
+
+        /// <summary>
+        /// Gets whether this exception has been marked as "observed."
+        /// </summary>
+        public bool Observed { get { return m_observed; } }
+
+        /// <summary>
+        /// The Exception that went unobserved.
+        /// </summary>
+        public AggregateException Exception { get { return m_exception; } }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Tasks/ThreadPoolTaskScheduler.cs b/src/System.Private.CoreLib/src/System/Threading/Tasks/ThreadPoolTaskScheduler.cs
new file mode 100644
index 0000000000..87d6d7b523
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Tasks/ThreadPoolTaskScheduler.cs
@@ -0,0 +1,125 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+// TaskScheduler.cs
+//
+//
+// This file contains the primary interface and management of tasks and queues.  
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System;
+using System.Security;
+using System.Diagnostics;
+using System.Collections.Generic;
+using System.Text;
+
+namespace System.Threading.Tasks
+{
+    /// <summary>
+    /// An implementation of TaskScheduler that uses the ThreadPool scheduler
+    /// </summary>
+    internal sealed class ThreadPoolTaskScheduler : TaskScheduler
+    {
+        /// <summary>
+        /// Constructs a new ThreadPool task scheduler object
+        /// </summary>
+        internal ThreadPoolTaskScheduler()
+        {
+            int id = base.Id; // force ID creation of the default scheduler
+        }
+
+        // static delegate for threads allocated to handle LongRunning tasks.
+        private static readonly ParameterizedThreadStart s_longRunningThreadWork = s => ((Task)s).ExecuteEntryUnsafe();
+
+        /// <summary>
+        /// Schedules a task to the ThreadPool.
+        /// </summary>
+        /// <param name="task">The task to schedule.</param>
+        protected internal override void QueueTask(Task task)
+        {
+            if ((task.Options & TaskCreationOptions.LongRunning) != 0)
+            {
+                // Run LongRunning tasks on their own dedicated thread.
+                Thread thread = new Thread(s_longRunningThreadWork);
+                thread.IsBackground = true; // Keep this thread from blocking process shutdown
+                thread.Start(task);
+            }
+            else
+            {
+                // Normal handling for non-LongRunning tasks.
+                bool forceToGlobalQueue = ((task.Options & TaskCreationOptions.PreferFairness) != 0);
+                ThreadPool.UnsafeQueueCustomWorkItem(task, forceToGlobalQueue);
+            }
+        }
+
+        /// <summary>
+        /// This internal function will do this:
+        ///   (1) If the task had previously been queued, attempt to pop it and return false if that fails.
+        ///   (2) Return whether the task is executed
+        /// 
+        /// IMPORTANT NOTE: TryExecuteTaskInline will NOT throw task exceptions itself. Any wait code path using this function needs
+        /// to account for exceptions that need to be propagated, and throw themselves accordingly.
+        /// </summary>
+        protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
+        {
+            // If the task was previously scheduled, and we can't pop it, then return false.
+            if (taskWasPreviouslyQueued && !ThreadPool.TryPopCustomWorkItem(task))
+                return false;
+
+            try
+            {
+                task.ExecuteEntryUnsafe(); // handles switching Task.Current etc.
+            }
+            finally
+            {
+                //   Only call NWIP() if task was previously queued
+                if (taskWasPreviouslyQueued) NotifyWorkItemProgress();
+            }
+
+            return true;
+        }
+
+        protected internal override bool TryDequeue(Task task)
+        {
+            // just delegate to TP
+            return ThreadPool.TryPopCustomWorkItem(task);
+        }
+
+        protected override IEnumerable<Task> GetScheduledTasks()
+        {
+            return FilterTasksFromWorkItems(ThreadPool.GetQueuedWorkItems());
+        }
+
+        private IEnumerable<Task> FilterTasksFromWorkItems(IEnumerable<IThreadPoolWorkItem> tpwItems)
+        {
+            foreach (IThreadPoolWorkItem tpwi in tpwItems)
+            {
+                if (tpwi is Task)
+                {
+                    yield return (Task)tpwi;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Notifies the scheduler that work is progressing (no-op).
+        /// </summary>
+        internal override void NotifyWorkItemProgress()
+        {
+            ThreadPool.NotifyWorkItemProgress();
+        }
+
+        /// <summary>
+        /// This is the only scheduler that returns false for this property, indicating that the task entry codepath is unsafe (CAS free)
+        /// since we know that the underlying scheduler already takes care of atomic transitions from queued to non-queued.
+        /// </summary>
+        internal override bool RequiresAtomicStartTransition
+        {
+            get { return false; }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Tasks/future.cs b/src/System.Private.CoreLib/src/System/Threading/Tasks/future.cs
new file mode 100644
index 0000000000..f9199d35cc
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Tasks/future.cs
@@ -0,0 +1,1555 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// A task that produces a value.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System;
+using System.Collections.Generic;
+using System.Runtime;
+using System.Runtime.CompilerServices;
+using System.Runtime.ExceptionServices;
+using System.Security;
+using System.Threading;
+using System.Diagnostics;
+
+// Disable the "reference to volatile field not treated as volatile" error.
+#pragma warning disable 0420
+
+namespace System.Threading.Tasks
+{
+    /// <summary>
+    /// Represents an asynchronous operation that produces a result at some time in the future.
+    /// </summary>
+    /// <typeparam name="TResult">
+    /// The type of the result produced by this <see cref="Task{TResult}"/>.
+    /// </typeparam>
+    /// <remarks>
+    /// <para>
+    /// <see cref="Task{TResult}"/> instances may be created in a variety of ways. The most common approach is by
+    /// using the task's <see cref="Factory"/> property to retrieve a <see
+    /// cref="System.Threading.Tasks.TaskFactory{TResult}"/> instance that can be used to create tasks for several
+    /// purposes. For example, to create a <see cref="Task{TResult}"/> that runs a function, the factory's StartNew
+    /// method may be used:
+    /// <code>
+    /// // C# 
+    /// var t = Task&lt;int&gt;.Factory.StartNew(() => GenerateResult());
+    /// - or -
+    /// var t = Task.Factory.StartNew(() => GenerateResult());
+    /// 
+    /// ' Visual Basic 
+    /// Dim t = Task&lt;int&gt;.Factory.StartNew(Function() GenerateResult())
+    /// - or -
+    /// Dim t = Task.Factory.StartNew(Function() GenerateResult())
+    /// </code>
+    /// </para>
+    /// <para>
+    /// The <see cref="Task{TResult}"/> class also provides constructors that initialize the task but that do not
+    /// schedule it for execution. For performance reasons, the StartNew method should be the
+    /// preferred mechanism for creating and scheduling computational tasks, but for scenarios where creation
+    /// and scheduling must be separated, the constructors may be used, and the task's 
+    /// <see cref="System.Threading.Tasks.Task.Start()">Start</see>
+    /// method may then be used to schedule the task for execution at a later time.
+    /// </para>
+    /// <para>
+    /// All members of <see cref="Task{TResult}"/>, except for 
+    /// <see cref="System.Threading.Tasks.Task.Dispose()">Dispose</see>, are thread-safe
+    /// and may be used from multiple threads concurrently.
+    /// </para>
+    /// </remarks>
+    [DebuggerTypeProxy(typeof(SystemThreadingTasks_FutureDebugView<>))]
+    [DebuggerDisplay("Id = {Id}, Status = {Status}, Method = {DebuggerDisplayMethodDescription}, Result = {DebuggerDisplayResultDescription}")]
+    public class Task<TResult> : Task
+#if SUPPORT_IOBSERVABLE        
+        ,  IObservable<TResult>
+#endif
+    {
+        internal TResult m_result; // The value itself, if set.
+
+        private static readonly TaskFactory<TResult> s_Factory = new TaskFactory<TResult>();
+
+        // Delegate used by:
+        //     public static Task<Task<TResult>> WhenAny<TResult>(IEnumerable<Task<TResult>> tasks);
+        //     public static Task<Task<TResult>> WhenAny<TResult>(params Task<TResult>[] tasks);
+        // Used to "cast" from Task<Task> to Task<Task<TResult>>.
+        internal static readonly Func<Task<Task>, Task<TResult>> TaskWhenAnyCast = completed => (Task<TResult>)completed.Result;
+
+        // Construct a promise-style task without any options. 
+        internal Task() :
+            base()
+        {
+        }
+
+        // Construct a promise-style task with state and options.  
+        internal Task(object state, TaskCreationOptions options) :
+            base(state, options, promiseStyle: true)
+        {
+        }
+
+
+        // Construct a pre-completed Task<TResult>
+        internal Task(TResult result) :
+            base(false, TaskCreationOptions.None, default(CancellationToken))
+        {
+            m_result = result;
+        }
+
+        internal Task(bool canceled, TResult result, TaskCreationOptions creationOptions, CancellationToken ct)
+            : base(canceled, creationOptions, ct)
+        {
+            if (!canceled)
+            {
+                m_result = result;
+            }
+        }
+
+        // Uncomment if/when we want Task.FromException
+        //// Construct a pre-faulted Task<TResult>
+        //internal Task(Exception exception)
+        //    : base(exception)
+        //{
+        //}
+
+        /// <summary>
+        /// Initializes a new <see cref="Task{TResult}"/> with the specified function.
+        /// </summary>
+        /// <param name="function">
+        /// The delegate that represents the code to execute in the task. When the function has completed,
+        /// the task's <see cref="Result"/> property will be set to return the result value of the function.
+        /// </param>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="function"/> argument is null.
+        /// </exception>
+        public Task(Func<TResult> function)
+            : this(function, null, default(CancellationToken),
+                TaskCreationOptions.None, InternalTaskOptions.None, null)
+        {
+        }
+
+
+        /// <summary>
+        /// Initializes a new <see cref="Task{TResult}"/> with the specified function.
+        /// </summary>
+        /// <param name="function">
+        /// The delegate that represents the code to execute in the task. When the function has completed,
+        /// the task's <see cref="Result"/> property will be set to return the result value of the function.
+        /// </param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> to be assigned to this task.</param>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="function"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task(Func<TResult> function, CancellationToken cancellationToken)
+            : this(function, null, cancellationToken,
+                TaskCreationOptions.None, InternalTaskOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref="Task{TResult}"/> with the specified function and creation options.
+        /// </summary>
+        /// <param name="function">
+        /// The delegate that represents the code to execute in the task. When the function has completed,
+        /// the task's <see cref="Result"/> property will be set to return the result value of the function.
+        /// </param>
+        /// <param name="creationOptions">
+        /// The <see cref="System.Threading.Tasks.TaskCreationOptions">TaskCreationOptions</see> used to
+        /// customize the task's behavior.
+        /// </param>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="function"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="creationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskCreationOptions"/>.
+        /// </exception>
+        public Task(Func<TResult> function, TaskCreationOptions creationOptions)
+            : this(function, Task.InternalCurrentIfAttached(creationOptions), default(CancellationToken), creationOptions, InternalTaskOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref="Task{TResult}"/> with the specified function and creation options.
+        /// </summary>
+        /// <param name="function">
+        /// The delegate that represents the code to execute in the task. When the function has completed,
+        /// the task's <see cref="Result"/> property will be set to return the result value of the function.
+        /// </param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <param name="creationOptions">
+        /// The <see cref="System.Threading.Tasks.TaskCreationOptions">TaskCreationOptions</see> used to
+        /// customize the task's behavior.
+        /// </param>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="function"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="creationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskCreationOptions"/>.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task(Func<TResult> function, CancellationToken cancellationToken, TaskCreationOptions creationOptions)
+            : this(function, Task.InternalCurrentIfAttached(creationOptions), cancellationToken, creationOptions, InternalTaskOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref="Task{TResult}"/> with the specified function and state.
+        /// </summary>
+        /// <param name="function">
+        /// The delegate that represents the code to execute in the task. When the function has completed,
+        /// the task's <see cref="Result"/> property will be set to return the result value of the function.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the action.</param>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="function"/> argument is null.
+        /// </exception>
+        public Task(Func<object, TResult> function, object state)
+            : this(function, state, null, default(CancellationToken),
+                TaskCreationOptions.None, InternalTaskOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref="Task{TResult}"/> with the specified action, state, and options.
+        /// </summary>
+        /// <param name="function">
+        /// The delegate that represents the code to execute in the task. When the function has completed,
+        /// the task's <see cref="Result"/> property will be set to return the result value of the function.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the function.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> to be assigned to the new task.</param>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="function"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task(Func<object, TResult> function, object state, CancellationToken cancellationToken)
+            : this(function, state, null, cancellationToken,
+                    TaskCreationOptions.None, InternalTaskOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new <see cref="Task{TResult}"/> with the specified action, state, and options.
+        /// </summary>
+        /// <param name="function">
+        /// The delegate that represents the code to execute in the task. When the function has completed,
+        /// the task's <see cref="Result"/> property will be set to return the result value of the function.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the function.</param>
+        /// <param name="creationOptions">
+        /// The <see cref="System.Threading.Tasks.TaskCreationOptions">TaskCreationOptions</see> used to
+        /// customize the task's behavior.
+        /// </param>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="function"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="creationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskCreationOptions"/>.
+        /// </exception>
+        public Task(Func<object, TResult> function, object state, TaskCreationOptions creationOptions)
+            : this(function, state, Task.InternalCurrentIfAttached(creationOptions), default(CancellationToken),
+                    creationOptions, InternalTaskOptions.None, null)
+        {
+        }
+
+
+        /// <summary>
+        /// Initializes a new <see cref="Task{TResult}"/> with the specified action, state, and options.
+        /// </summary>
+        /// <param name="function">
+        /// The delegate that represents the code to execute in the task. When the function has completed,
+        /// the task's <see cref="Result"/> property will be set to return the result value of the function.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the function.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> to be assigned to the new task.</param>
+        /// <param name="creationOptions">
+        /// The <see cref="System.Threading.Tasks.TaskCreationOptions">TaskCreationOptions</see> used to
+        /// customize the task's behavior.
+        /// </param>
+        /// <exception cref="T:System.ArgumentException">
+        /// The <paramref name="function"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="creationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskCreationOptions"/>.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task(Func<object, TResult> function, object state, CancellationToken cancellationToken, TaskCreationOptions creationOptions)
+            : this(function, state, Task.InternalCurrentIfAttached(creationOptions), cancellationToken,
+                    creationOptions, InternalTaskOptions.None, null)
+        {
+        }
+
+        /// <summary>
+        /// Creates a new future object.
+        /// </summary>
+        /// <param name="parent">The parent task for this future.</param>
+        /// <param name="valueSelector">A function that yields the future value.</param>
+        /// <param name="scheduler">The task scheduler which will be used to execute the future.</param>
+        /// <param name="cancellationToken">The CancellationToken for the task.</param>
+        /// <param name="creationOptions">Options to control the future's behavior.</param>
+        /// <param name="internalOptions">Internal options to control the future's behavior.</param>
+        internal Task(Func<TResult> valueSelector, Task parent, CancellationToken cancellationToken,
+            TaskCreationOptions creationOptions, InternalTaskOptions internalOptions, TaskScheduler scheduler) :
+            base(valueSelector, null, parent, cancellationToken, creationOptions, internalOptions, scheduler)
+        {
+        }
+
+        /// <summary>
+        /// Creates a new future object.
+        /// </summary>
+        /// <param name="parent">The parent task for this future.</param>
+        /// <param name="state">An object containing data to be used by the action; may be null.</param>
+        /// <param name="valueSelector">A function that yields the future value.</param>
+        /// <param name="cancellationToken">The CancellationToken for the task.</param>
+        /// <param name="scheduler">The task scheduler which will be used to execute the future.</param>
+        /// <param name="creationOptions">Options to control the future's behavior.</param>
+        /// <param name="internalOptions">Internal options to control the future's behavior.</param>
+        internal Task(Delegate valueSelector, object state, Task parent, CancellationToken cancellationToken,
+            TaskCreationOptions creationOptions, InternalTaskOptions internalOptions, TaskScheduler scheduler) :
+            base(valueSelector, state, parent, cancellationToken, creationOptions, internalOptions, scheduler)
+        {
+        }
+
+
+        // Internal method used by TaskFactory<TResult>.StartNew() methods
+        internal static Task<TResult> StartNew(Task parent, Func<TResult> function, CancellationToken cancellationToken,
+            TaskCreationOptions creationOptions, InternalTaskOptions internalOptions, TaskScheduler scheduler)
+        {
+            if (function == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.function);
+            }
+            if (scheduler == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+            }
+
+            // Create and schedule the future.
+            Task<TResult> f = new Task<TResult>(function, parent, cancellationToken, creationOptions, internalOptions | InternalTaskOptions.QueuedByRuntime, scheduler);
+
+            f.ScheduleAndStart(false);
+            return f;
+        }
+
+        // Internal method used by TaskFactory<TResult>.StartNew() methods
+        internal static Task<TResult> StartNew(Task parent, Func<object, TResult> function, object state, CancellationToken cancellationToken,
+            TaskCreationOptions creationOptions, InternalTaskOptions internalOptions, TaskScheduler scheduler)
+        {
+            if (function == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.function);
+            }
+            if (scheduler == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+            }
+
+            // Create and schedule the future.
+            Task<TResult> f = new Task<TResult>(function, state, parent, cancellationToken, creationOptions, internalOptions | InternalTaskOptions.QueuedByRuntime, scheduler);
+
+            f.ScheduleAndStart(false);
+            return f;
+        }
+
+        // Debugger support
+        private string DebuggerDisplayResultDescription
+        {
+            get
+            {
+                return IsCompletedSuccessfully ? "" + m_result : SR.TaskT_DebuggerNoResult;
+            }
+        }
+
+        // Debugger support
+        private string DebuggerDisplayMethodDescription
+        {
+            get
+            {
+                Delegate d = m_action;
+                return d != null ? d.Method.ToString() : "{null}";
+            }
+        }
+
+
+        // internal helper function breaks out logic used by TaskCompletionSource
+        internal bool TrySetResult(TResult result)
+        {
+            Debug.Assert(m_action == null, "Task<T>.TrySetResult(): non-null m_action");
+
+            // "Reserve" the completion for this task, while making sure that: (1) No prior reservation
+            // has been made, (2) The result has not already been set, (3) An exception has not previously 
+            // been recorded, and (4) Cancellation has not been requested.
+            //
+            // If the reservation is successful, then set the result and finish completion processing.
+            if (AtomicStateUpdate(TASK_STATE_COMPLETION_RESERVED,
+                    TASK_STATE_COMPLETION_RESERVED | TASK_STATE_RAN_TO_COMPLETION | TASK_STATE_FAULTED | TASK_STATE_CANCELED))
+            {
+                m_result = result;
+
+                // Signal completion, for waiting tasks
+
+                // This logic used to be:
+                //     Finish(false);
+                // However, that goes through a windy code path, involves many non-inlineable functions
+                // and which can be summarized more concisely with the following snippet from
+                // FinishStageTwo, omitting everything that doesn't pertain to TrySetResult.
+                Interlocked.Exchange(ref m_stateFlags, m_stateFlags | TASK_STATE_RAN_TO_COMPLETION);
+                ContingentProperties props = m_contingentProperties;
+                if (props != null)
+                {
+                    NotifyParentIfPotentiallyAttachedTask();
+                    props.SetCompleted();
+                }
+                FinishContinuations();
+                return true;
+            }
+
+            return false;
+        }
+
+        // Transitions the promise task into a successfully completed state with the specified result.
+        // This is dangerous, as no synchronization is used, and thus must only be used
+        // before this task is handed out to any consumers, before any continuations are hooked up,
+        // before its wait handle is accessed, etc.  It's use is limited to places like in FromAsync
+        // where the operation completes synchronously, and thus we know we can forcefully complete
+        // the task, avoiding expensive completion paths, before the task is actually given to anyone.
+        internal void DangerousSetResult(TResult result)
+        {
+            Debug.Assert(!IsCompleted, "The promise must not yet be completed.");
+
+            // If we have a parent, we need to notify it of the completion.  Take the slow path to handle that.
+            if (m_contingentProperties?.m_parent != null)
+            {
+                bool success = TrySetResult(result);
+
+                // Nobody else has had a chance to complete this Task yet, so we should succeed.
+                Debug.Assert(success);
+            }
+            else
+            {
+                m_result = result;
+                m_stateFlags |= TASK_STATE_RAN_TO_COMPLETION;
+            }
+        }
+
+        /// <summary>
+        /// Gets the result value of this <see cref="Task{TResult}"/>.
+        /// </summary>
+        /// <remarks>
+        /// The get accessor for this property ensures that the asynchronous operation is complete before
+        /// returning. Once the result of the computation is available, it is stored and will be returned
+        /// immediately on later calls to <see cref="Result"/>.
+        /// </remarks>
+        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
+        public TResult Result
+        {
+            get { return IsWaitNotificationEnabledOrNotRanToCompletion ? GetResultCore(waitCompletionNotification: true) : m_result; }
+        }
+
+        /// <summary>
+        /// Gets the result value of this <see cref="Task{TResult}"/> once the task has completed successfully.
+        /// </summary>
+        /// <remarks>
+        /// This version of Result should only be used if the task completed successfully and if there's
+        /// no debugger wait notification enabled for this task.
+        /// </remarks>
+        internal TResult ResultOnSuccess
+        {
+            get
+            {
+                Debug.Assert(!IsWaitNotificationEnabledOrNotRanToCompletion,
+                    "Should only be used when the task completed successfully and there's no wait notification enabled");
+                return m_result;
+            }
+        }
+
+        // Implements Result.  Result delegates to this method if the result isn't already available.
+        internal TResult GetResultCore(bool waitCompletionNotification)
+        {
+            // If the result has not been calculated yet, wait for it.
+            if (!IsCompleted) InternalWait(Timeout.Infinite, default(CancellationToken)); // won't throw if task faulted or canceled; that's handled below
+
+            // Notify the debugger of the wait completion if it's requested such a notification
+            if (waitCompletionNotification) NotifyDebuggerOfWaitCompletionIfNecessary();
+
+            // Throw an exception if appropriate.
+            if (!IsCompletedSuccessfully) ThrowIfExceptional(includeTaskCanceledExceptions: true);
+
+            // We shouldn't be here if the result has not been set.
+            Debug.Assert(IsCompletedSuccessfully, "Task<T>.Result getter: Expected result to have been set.");
+
+            return m_result;
+        }
+
+        // Allow multiple exceptions to be assigned to a promise-style task.
+        // This is useful when a TaskCompletionSource<T> stands in as a proxy
+        // for a "real" task (as we do in Unwrap(), ContinueWhenAny() and ContinueWhenAll())
+        // and the "real" task ends up with multiple exceptions, which is possible when
+        // a task has children.
+        //
+        // Called from TaskCompletionSource<T>.SetException(IEnumerable<Exception>).
+        internal bool TrySetException(object exceptionObject)
+        {
+            Debug.Assert(m_action == null, "Task<T>.TrySetException(): non-null m_action");
+
+            // TCS.{Try}SetException() should have checked for this
+            Debug.Assert(exceptionObject != null, "Expected non-null exceptionObject argument");
+
+            // Only accept these types.
+            Debug.Assert(
+                (exceptionObject is Exception) || (exceptionObject is IEnumerable<Exception>) ||
+                (exceptionObject is ExceptionDispatchInfo) || (exceptionObject is IEnumerable<ExceptionDispatchInfo>),
+                "Expected exceptionObject to be either Exception, ExceptionDispatchInfo, or IEnumerable<> of one of those");
+
+            bool returnValue = false;
+
+            // "Reserve" the completion for this task, while making sure that: (1) No prior reservation
+            // has been made, (2) The result has not already been set, (3) An exception has not previously 
+            // been recorded, and (4) Cancellation has not been requested.
+            //
+            // If the reservation is successful, then add the exception(s) and finish completion processing.
+            //
+            // The lazy initialization may not be strictly necessary, but I'd like to keep it here
+            // anyway.  Some downstream logic may depend upon an inflated m_contingentProperties.
+            EnsureContingentPropertiesInitialized();
+            if (AtomicStateUpdate(TASK_STATE_COMPLETION_RESERVED,
+                TASK_STATE_COMPLETION_RESERVED | TASK_STATE_RAN_TO_COMPLETION | TASK_STATE_FAULTED | TASK_STATE_CANCELED))
+            {
+                AddException(exceptionObject); // handles singleton exception or exception collection
+                Finish(false);
+                returnValue = true;
+            }
+
+            return returnValue;
+        }
+
+        // internal helper function breaks out logic used by TaskCompletionSource and AsyncMethodBuilder
+        // If the tokenToRecord is not None, it will be stored onto the task.
+        // This method is only valid for promise tasks.
+        internal bool TrySetCanceled(CancellationToken tokenToRecord)
+        {
+            return TrySetCanceled(tokenToRecord, null);
+        }
+
+        // internal helper function breaks out logic used by TaskCompletionSource and AsyncMethodBuilder
+        // If the tokenToRecord is not None, it will be stored onto the task.
+        // If the OperationCanceledException is not null, it will be stored into the task's exception holder.
+        // This method is only valid for promise tasks.
+        internal bool TrySetCanceled(CancellationToken tokenToRecord, object cancellationException)
+        {
+            Debug.Assert(m_action == null, "Task<T>.TrySetCanceled(): non-null m_action");
+#if DEBUG
+            var ceAsEdi = cancellationException as ExceptionDispatchInfo;
+            Debug.Assert(
+                cancellationException == null ||
+                cancellationException is OperationCanceledException ||
+                (ceAsEdi != null && ceAsEdi.SourceException is OperationCanceledException),
+                "Expected null or an OperationCanceledException");
+#endif
+
+            bool returnValue = false;
+
+            // "Reserve" the completion for this task, while making sure that: (1) No prior reservation
+            // has been made, (2) The result has not already been set, (3) An exception has not previously 
+            // been recorded, and (4) Cancellation has not been requested.
+            //
+            // If the reservation is successful, then record the cancellation and finish completion processing.
+            //
+            // Note: I had to access static Task variables through Task<object>
+            // instead of Task, because I have a property named Task and that
+            // was confusing the compiler.  
+            if (AtomicStateUpdate(Task<object>.TASK_STATE_COMPLETION_RESERVED,
+                Task<object>.TASK_STATE_COMPLETION_RESERVED | Task<object>.TASK_STATE_CANCELED |
+                Task<object>.TASK_STATE_FAULTED | Task<object>.TASK_STATE_RAN_TO_COMPLETION))
+            {
+                RecordInternalCancellationRequest(tokenToRecord, cancellationException);
+                CancellationCleanupLogic(); // perform cancellation cleanup actions
+                returnValue = true;
+            }
+
+            return returnValue;
+        }
+
+        /// <summary>
+        /// Provides access to factory methods for creating <see cref="Task{TResult}"/> instances.
+        /// </summary>
+        /// <remarks>
+        /// The factory returned from <see cref="Factory"/> is a default instance
+        /// of <see cref="System.Threading.Tasks.TaskFactory{TResult}"/>, as would result from using
+        /// the default constructor on the factory type.
+        /// </remarks>
+        public new static TaskFactory<TResult> Factory { get { return s_Factory; } }
+
+        /// <summary>
+        /// Evaluates the value selector of the Task which is passed in as an object and stores the result.
+        /// </summary>        
+        internal override void InnerInvoke()
+        {
+            // Invoke the delegate
+            Debug.Assert(m_action != null);
+            var func = m_action as Func<TResult>;
+            if (func != null)
+            {
+                m_result = func();
+                return;
+            }
+            var funcWithState = m_action as Func<object, TResult>;
+            if (funcWithState != null)
+            {
+                m_result = funcWithState(m_stateObject);
+                return;
+            }
+            Debug.Fail("Invalid m_action in Task<TResult>");
+        }
+
+        #region Await Support
+
+        /// <summary>Gets an awaiter used to await this <see cref="System.Threading.Tasks.Task{TResult}"/>.</summary>
+        /// <returns>An awaiter instance.</returns>
+        /// <remarks>This method is intended for compiler user rather than use directly in code.</remarks>
+        public new TaskAwaiter<TResult> GetAwaiter()
+        {
+            return new TaskAwaiter<TResult>(this);
+        }
+
+        /// <summary>Configures an awaiter used to await this <see cref="System.Threading.Tasks.Task{TResult}"/>.</summary>
+        /// <param name="continueOnCapturedContext">
+        /// true to attempt to marshal the continuation back to the original context captured; otherwise, false.
+        /// </param>
+        /// <returns>An object used to await this task.</returns>
+        public new ConfiguredTaskAwaitable<TResult> ConfigureAwait(bool continueOnCapturedContext)
+        {
+            return new ConfiguredTaskAwaitable<TResult>(this, continueOnCapturedContext);
+        }
+
+        #endregion
+
+        #region Continuation methods
+
+        #region Action<Task<TResult>> continuations
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        public Task ContinueWith(Action<Task<TResult>> continuationAction)
+        {
+            return ContinueWith(continuationAction, TaskScheduler.Current, default(CancellationToken), TaskContinuationOptions.None);
+        }
+
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new continuation task.</param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task ContinueWith(Action<Task<TResult>> continuationAction, CancellationToken cancellationToken)
+        {
+            return ContinueWith(continuationAction, TaskScheduler.Current, cancellationToken, TaskContinuationOptions.None);
+        }
+
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        public Task ContinueWith(Action<Task<TResult>> continuationAction, TaskScheduler scheduler)
+        {
+            return ContinueWith(continuationAction, scheduler, default(CancellationToken), TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed. If the continuation criteria specified through the <paramref
+        /// name="continuationOptions"/> parameter are not met, the continuation task will be canceled
+        /// instead of scheduled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        public Task ContinueWith(Action<Task<TResult>> continuationAction, TaskContinuationOptions continuationOptions)
+        {
+            return ContinueWith(continuationAction, TaskScheduler.Current, default(CancellationToken), continuationOptions);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its
+        /// execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed. If the criteria specified through the <paramref name="continuationOptions"/> parameter
+        /// are not met, the continuation task will be canceled instead of scheduled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task ContinueWith(Action<Task<TResult>> continuationAction, CancellationToken cancellationToken,
+                                 TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            return ContinueWith(continuationAction, scheduler, cancellationToken, continuationOptions);
+        }
+
+        // Same as the above overload, only with a stack mark.
+        internal Task ContinueWith(Action<Task<TResult>> continuationAction, TaskScheduler scheduler, CancellationToken cancellationToken,
+                                   TaskContinuationOptions continuationOptions)
+        {
+            if (continuationAction == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationAction);
+            }
+
+            if (scheduler == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+            }
+
+            TaskCreationOptions creationOptions;
+            InternalTaskOptions internalOptions;
+            CreationOptionsFromContinuationOptions(
+                continuationOptions,
+                out creationOptions,
+                out internalOptions);
+
+            Task continuationTask = new ContinuationTaskFromResultTask<TResult>(
+                this, continuationAction, null,
+                creationOptions, internalOptions
+            );
+
+            // Register the continuation.  If synchronous execution is requested, this may
+            // actually invoke the continuation before returning.
+            ContinueWithCore(continuationTask, scheduler, cancellationToken, continuationOptions);
+
+            return continuationTask;
+        }
+        #endregion
+
+        #region Action<Task<TResult>, Object> continuations
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation action.</param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        public Task ContinueWith(Action<Task<TResult>, Object> continuationAction, Object state)
+        {
+            return ContinueWith(continuationAction, state, TaskScheduler.Current, default(CancellationToken), TaskContinuationOptions.None);
+        }
+
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation action.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new continuation task.</param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task ContinueWith(Action<Task<TResult>, Object> continuationAction, Object state, CancellationToken cancellationToken)
+        {
+            return ContinueWith(continuationAction, state, TaskScheduler.Current, cancellationToken, TaskContinuationOptions.None);
+        }
+
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation action.</param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        public Task ContinueWith(Action<Task<TResult>, Object> continuationAction, Object state, TaskScheduler scheduler)
+        {
+            return ContinueWith(continuationAction, state, scheduler, default(CancellationToken), TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation action.</param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed. If the continuation criteria specified through the <paramref
+        /// name="continuationOptions"/> parameter are not met, the continuation task will be canceled
+        /// instead of scheduled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        public Task ContinueWith(Action<Task<TResult>, Object> continuationAction, Object state, TaskContinuationOptions continuationOptions)
+        {
+            return ContinueWith(continuationAction, state, TaskScheduler.Current, default(CancellationToken), continuationOptions);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <param name="continuationAction">
+        /// An action to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation action.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new continuation task.</param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its
+        /// execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task"/> will not be scheduled for execution until the current task has
+        /// completed. If the criteria specified through the <paramref name="continuationOptions"/> parameter
+        /// are not met, the continuation task will be canceled instead of scheduled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationAction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task ContinueWith(Action<Task<TResult>, Object> continuationAction, Object state, CancellationToken cancellationToken,
+                                 TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            return ContinueWith(continuationAction, state, scheduler, cancellationToken, continuationOptions);
+        }
+
+        // Same as the above overload, only with a stack mark.
+        internal Task ContinueWith(Action<Task<TResult>, Object> continuationAction, Object state, TaskScheduler scheduler, CancellationToken cancellationToken,
+                                   TaskContinuationOptions continuationOptions)
+        {
+            if (continuationAction == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationAction);
+            }
+
+            if (scheduler == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+            }
+
+            TaskCreationOptions creationOptions;
+            InternalTaskOptions internalOptions;
+            CreationOptionsFromContinuationOptions(
+                continuationOptions,
+                out creationOptions,
+                out internalOptions);
+
+            Task continuationTask = new ContinuationTaskFromResultTask<TResult>(
+                this, continuationAction, state,
+                creationOptions, internalOptions
+            );
+
+            // Register the continuation.  If synchronous execution is requested, this may
+            // actually invoke the continuation before returning.
+            ContinueWithCore(continuationTask, scheduler, cancellationToken, continuationOptions);
+
+            return continuationTask;
+        }
+
+        #endregion
+
+        #region Func<Task<TResult>,TNewResult> continuations
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <typeparam name="TNewResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task{TNewResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TNewResult}"/> will not be scheduled for execution until the current
+        /// task has completed, whether it completes due to running to completion successfully, faulting due
+        /// to an unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        public Task<TNewResult> ContinueWith<TNewResult>(Func<Task<TResult>, TNewResult> continuationFunction)
+        {
+            return ContinueWith<TNewResult>(continuationFunction, TaskScheduler.Current, default(CancellationToken), TaskContinuationOptions.None);
+        }
+
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <typeparam name="TNewResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <returns>A new continuation <see cref="Task{TNewResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TNewResult}"/> will not be scheduled for execution until the current
+        /// task has completed, whether it completes due to running to completion successfully, faulting due
+        /// to an unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TNewResult> ContinueWith<TNewResult>(Func<Task<TResult>, TNewResult> continuationFunction, CancellationToken cancellationToken)
+        {
+            return ContinueWith<TNewResult>(continuationFunction, TaskScheduler.Current, cancellationToken, TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <typeparam name="TNewResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task{TResult}"/> completes.  When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task{TNewResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TNewResult}"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        public Task<TNewResult> ContinueWith<TNewResult>(Func<Task<TResult>, TNewResult> continuationFunction, TaskScheduler scheduler)
+        {
+            return ContinueWith<TNewResult>(continuationFunction, scheduler, default(CancellationToken), TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <typeparam name="TNewResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task as an argument.
+        /// </param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task{TNewResult}"/>.</returns>
+        /// <remarks>
+        /// <para>
+        /// The returned <see cref="Task{TNewResult}"/> will not be scheduled for execution until the current
+        /// task has completed, whether it completes due to running to completion successfully, faulting due
+        /// to an unhandled exception, or exiting out early due to being canceled.
+        /// </para>
+        /// <para>
+        /// The <paramref name="continuationFunction"/>, when executed, should return a <see
+        /// cref="Task{TNewResult}"/>. This task's completion state will be transferred to the task returned
+        /// from the ContinueWith call.
+        /// </para>
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        public Task<TNewResult> ContinueWith<TNewResult>(Func<Task<TResult>, TNewResult> continuationFunction, TaskContinuationOptions continuationOptions)
+        {
+            return ContinueWith<TNewResult>(continuationFunction, TaskScheduler.Current, default(CancellationToken), continuationOptions);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <typeparam name="TNewResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be passed as
+        /// an argument this completed task.
+        /// </param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its
+        /// execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task{TNewResult}"/>.</returns>
+        /// <remarks>
+        /// <para>
+        /// The returned <see cref="Task{TNewResult}"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </para>
+        /// <para>
+        /// The <paramref name="continuationFunction"/>, when executed, should return a <see cref="Task{TNewResult}"/>.
+        /// This task's completion state will be transferred to the task returned from the
+        /// ContinueWith call.
+        /// </para>
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TNewResult> ContinueWith<TNewResult>(Func<Task<TResult>, TNewResult> continuationFunction, CancellationToken cancellationToken,
+            TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            return ContinueWith<TNewResult>(continuationFunction, scheduler, cancellationToken, continuationOptions);
+        }
+
+        // Same as the above overload, just with a stack mark.
+        internal Task<TNewResult> ContinueWith<TNewResult>(Func<Task<TResult>, TNewResult> continuationFunction, TaskScheduler scheduler,
+            CancellationToken cancellationToken, TaskContinuationOptions continuationOptions)
+        {
+            if (continuationFunction == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+            }
+
+            if (scheduler == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+            }
+
+            TaskCreationOptions creationOptions;
+            InternalTaskOptions internalOptions;
+            CreationOptionsFromContinuationOptions(
+                continuationOptions,
+                out creationOptions,
+                out internalOptions);
+
+            Task<TNewResult> continuationFuture = new ContinuationResultTaskFromResultTask<TResult, TNewResult>(
+                this, continuationFunction, null,
+                creationOptions, internalOptions
+            );
+
+            // Register the continuation.  If synchronous execution is requested, this may
+            // actually invoke the continuation before returning.
+            ContinueWithCore(continuationFuture, scheduler, cancellationToken, continuationOptions);
+
+            return continuationFuture;
+        }
+        #endregion
+
+        #region Func<Task<TResult>, Object,TNewResult> continuations
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <typeparam name="TNewResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation function.</param>
+        /// <returns>A new continuation <see cref="Task{TNewResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TNewResult}"/> will not be scheduled for execution until the current
+        /// task has completed, whether it completes due to running to completion successfully, faulting due
+        /// to an unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        public Task<TNewResult> ContinueWith<TNewResult>(Func<Task<TResult>, Object, TNewResult> continuationFunction, Object state)
+        {
+            return ContinueWith<TNewResult>(continuationFunction, state, TaskScheduler.Current, default(CancellationToken), TaskContinuationOptions.None);
+        }
+
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <typeparam name="TNewResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation function.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <returns>A new continuation <see cref="Task{TNewResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TNewResult}"/> will not be scheduled for execution until the current
+        /// task has completed, whether it completes due to running to completion successfully, faulting due
+        /// to an unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TNewResult> ContinueWith<TNewResult>(Func<Task<TResult>, Object, TNewResult> continuationFunction, Object state,
+            CancellationToken cancellationToken)
+        {
+            return ContinueWith<TNewResult>(continuationFunction, state, TaskScheduler.Current, cancellationToken, TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <typeparam name="TNewResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task{TResult}"/> completes.  When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation function.</param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task{TNewResult}"/>.</returns>
+        /// <remarks>
+        /// The returned <see cref="Task{TNewResult}"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        public Task<TNewResult> ContinueWith<TNewResult>(Func<Task<TResult>, Object, TNewResult> continuationFunction, Object state,
+            TaskScheduler scheduler)
+        {
+            return ContinueWith<TNewResult>(continuationFunction, state, scheduler, default(CancellationToken), TaskContinuationOptions.None);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <typeparam name="TNewResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation function.</param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task{TNewResult}"/>.</returns>
+        /// <remarks>
+        /// <para>
+        /// The returned <see cref="Task{TNewResult}"/> will not be scheduled for execution until the current
+        /// task has completed, whether it completes due to running to completion successfully, faulting due
+        /// to an unhandled exception, or exiting out early due to being canceled.
+        /// </para>
+        /// <para>
+        /// The <paramref name="continuationFunction"/>, when executed, should return a <see
+        /// cref="Task{TNewResult}"/>. This task's completion state will be transferred to the task returned
+        /// from the ContinueWith call.
+        /// </para>
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        public Task<TNewResult> ContinueWith<TNewResult>(Func<Task<TResult>, Object, TNewResult> continuationFunction, Object state,
+            TaskContinuationOptions continuationOptions)
+        {
+            return ContinueWith<TNewResult>(continuationFunction, state, TaskScheduler.Current, default(CancellationToken), continuationOptions);
+        }
+
+        /// <summary>
+        /// Creates a continuation that executes when the target <see cref="Task{TResult}"/> completes.
+        /// </summary>
+        /// <typeparam name="TNewResult">
+        /// The type of the result produced by the continuation.
+        /// </typeparam>
+        /// <param name="continuationFunction">
+        /// A function to run when the <see cref="Task{TResult}"/> completes. When run, the delegate will be
+        /// passed the completed task and the caller-supplied state object as arguments.
+        /// </param>
+        /// <param name="state">An object representing data to be used by the continuation function.</param>
+        /// <param name="cancellationToken">The <see cref="CancellationToken"/> that will be assigned to the new task.</param>
+        /// <param name="continuationOptions">
+        /// Options for when the continuation is scheduled and how it behaves. This includes criteria, such
+        /// as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.OnlyOnCanceled">OnlyOnCanceled</see>, as
+        /// well as execution options, such as <see
+        /// cref="System.Threading.Tasks.TaskContinuationOptions.ExecuteSynchronously">ExecuteSynchronously</see>.
+        /// </param>
+        /// <param name="scheduler">
+        /// The <see cref="TaskScheduler"/> to associate with the continuation task and to use for its
+        /// execution.
+        /// </param>
+        /// <returns>A new continuation <see cref="Task{TNewResult}"/>.</returns>
+        /// <remarks>
+        /// <para>
+        /// The returned <see cref="Task{TNewResult}"/> will not be scheduled for execution until the current task has
+        /// completed, whether it completes due to running to completion successfully, faulting due to an
+        /// unhandled exception, or exiting out early due to being canceled.
+        /// </para>
+        /// <para>
+        /// The <paramref name="continuationFunction"/>, when executed, should return a <see cref="Task{TNewResult}"/>.
+        /// This task's completion state will be transferred to the task returned from the
+        /// ContinueWith call.
+        /// </para>
+        /// </remarks>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="continuationFunction"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentOutOfRangeException">
+        /// The <paramref name="continuationOptions"/> argument specifies an invalid value for <see
+        /// cref="T:System.Threading.Tasks.TaskContinuationOptions">TaskContinuationOptions</see>.
+        /// </exception>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="scheduler"/> argument is null.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">The provided <see cref="System.Threading.CancellationToken">CancellationToken</see>
+        /// has already been disposed.
+        /// </exception>
+        public Task<TNewResult> ContinueWith<TNewResult>(Func<Task<TResult>, Object, TNewResult> continuationFunction, Object state,
+            CancellationToken cancellationToken, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
+        {
+            return ContinueWith<TNewResult>(continuationFunction, state, scheduler, cancellationToken, continuationOptions);
+        }
+
+        // Same as the above overload, just with a stack mark.
+        internal Task<TNewResult> ContinueWith<TNewResult>(Func<Task<TResult>, Object, TNewResult> continuationFunction, Object state,
+            TaskScheduler scheduler, CancellationToken cancellationToken, TaskContinuationOptions continuationOptions)
+        {
+            if (continuationFunction == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.continuationFunction);
+            }
+
+            if (scheduler == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.scheduler);
+            }
+
+            TaskCreationOptions creationOptions;
+            InternalTaskOptions internalOptions;
+            CreationOptionsFromContinuationOptions(
+                continuationOptions,
+                out creationOptions,
+                out internalOptions);
+
+            Task<TNewResult> continuationFuture = new ContinuationResultTaskFromResultTask<TResult, TNewResult>(
+                this, continuationFunction, state,
+                creationOptions, internalOptions
+            );
+
+            // Register the continuation.  If synchronous execution is requested, this may
+            // actually invoke the continuation before returning.
+            ContinueWithCore(continuationFuture, scheduler, cancellationToken, continuationOptions);
+
+            return continuationFuture;
+        }
+
+        #endregion
+
+        #endregion
+
+        /// <summary>
+        /// Subscribes an <see cref="IObserver{TResult}"/> to receive notification of the final state of this <see cref="Task{TResult}"/>.
+        /// </summary>
+        /// <param name="observer">
+        /// The <see cref="IObserver{TResult}"/> to call on task completion. If this Task throws an exception, 
+        /// observer.OnError is called with this Task's AggregateException. If this Task RanToCompletion, 
+        /// observer.OnNext is called with this Task's result, followed by a call to observer.OnCompleted.
+        /// If this Task is Canceled,  observer.OnError is called with a TaskCanceledException
+        /// containing this Task's CancellationToken
+        /// </param>
+        /// <returns>An IDisposable object <see cref="Task"/>.</returns>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// The <paramref name="observer"/> argument is null.
+        /// </exception>
+#if SUPPORT_IOBSERVABLE
+        IDisposable IObservable<TResult>.Subscribe(IObserver<TResult> observer)
+        {
+            if (observer == null)
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.observer);
+
+            
+            var continuationTask = 
+                this.ContinueWith(delegate(Task<TResult> observedTask, object taskObserverObject)
+                {
+                    IObserver<TResult> taskObserver = (IObserver<TResult>)taskObserverObject;
+                    if (observedTask.IsFaulted)
+                        taskObserver.OnError(observedTask.Exception);
+                    else if (observedTask.IsCanceled)
+                        taskObserver.OnError(new TaskCanceledException(observedTask));
+                    else
+                    {
+                        taskObserver.OnNext(observedTask.Result);
+                        taskObserver.OnCompleted();
+                    }
+
+                }, observer, TaskScheduler.Default);
+    
+            return new DisposableSubscription(this, continuationTask);
+        }
+#endif
+    }
+
+#if SUPPORT_IOBSERVABLE
+    // Class that calls RemoveContinuation if Dispose() is called before task completion
+    internal class DisposableSubscription : IDisposable
+    {
+        private Task _notifyObserverContinuationTask;
+        private Task _observedTask;
+        
+        internal DisposableSubscription(Task observedTask, Task notifyObserverContinuationTask)
+        {
+            _observedTask = observedTask;
+            _notifyObserverContinuationTask = notifyObserverContinuationTask;
+        }
+        void IDisposable.Dispose()
+        {
+            Task localObservedTask = _observedTask;
+            Task localNotifyingContinuationTask = _notifyObserverContinuationTask;
+            if (localObservedTask != null && localNotifyingContinuationTask != null && !localObservedTask.IsCompleted)
+            {
+                localObservedTask.RemoveContinuation(localNotifyingContinuationTask);
+            }
+            _observedTask = null;
+            _notifyObserverContinuationTask = null;
+        }
+    }
+#endif
+
+    // Proxy class for better debugging experience
+    internal class SystemThreadingTasks_FutureDebugView<TResult>
+    {
+        private Task<TResult> m_task;
+
+        public SystemThreadingTasks_FutureDebugView(Task<TResult> task)
+        {
+            m_task = task;
+        }
+
+        public TResult Result { get { return m_task.Status == TaskStatus.RanToCompletion ? m_task.Result : default(TResult); } }
+        public object AsyncState { get { return m_task.AsyncState; } }
+        public TaskCreationOptions CreationOptions { get { return m_task.CreationOptions; } }
+        public Exception Exception { get { return m_task.Exception; } }
+        public int Id { get { return m_task.Id; } }
+        public bool CancellationPending { get { return (m_task.Status == TaskStatus.WaitingToRun) && m_task.CancellationToken.IsCancellationRequested; } }
+        public TaskStatus Status { get { return m_task.Status; } }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Thread.cs b/src/System.Private.CoreLib/src/System/Threading/Thread.cs
new file mode 100644
index 0000000000..51bfd27cd3
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Thread.cs
@@ -0,0 +1,540 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+/*=============================================================================
+**
+**
+**
+** Purpose: Class for creating and managing a thread.
+**
+**
+=============================================================================*/
+
+using Internal.Runtime.Augments;
+
+namespace System.Threading
+{
+    using System.Threading;
+    using System.Runtime;
+    using System.Runtime.InteropServices;
+    using System;
+    using System.Globalization;
+    using System.Collections.Generic;
+    using System.Runtime.Serialization;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.ConstrainedExecution;
+    using System.Security;
+    using System.Runtime.Versioning;
+    using System.Diagnostics;
+
+    internal delegate Object InternalCrossContextDelegate(Object[] args);
+
+    internal class ThreadHelper
+    {
+        private Delegate _start;
+        private Object _startArg = null;
+        private ExecutionContext _executionContext = null;
+        internal ThreadHelper(Delegate start)
+        {
+            _start = start;
+        }
+
+        internal void SetExecutionContextHelper(ExecutionContext ec)
+        {
+            _executionContext = ec;
+        }
+
+        internal static ContextCallback _ccb = new ContextCallback(ThreadStart_Context);
+
+        private static void ThreadStart_Context(Object state)
+        {
+            ThreadHelper t = (ThreadHelper)state;
+            if (t._start is ThreadStart)
+            {
+                ((ThreadStart)t._start)();
+            }
+            else
+            {
+                ((ParameterizedThreadStart)t._start)(t._startArg);
+            }
+        }
+
+        // call back helper
+        internal void ThreadStart(object obj)
+        {
+            _startArg = obj;
+            ExecutionContext context = _executionContext;
+            if (context != null)
+            {
+                ExecutionContext.RunInternal(context, _ccb, (Object)this);
+            }
+            else
+            {
+                ((ParameterizedThreadStart)_start)(obj);
+            }
+        }
+
+        // call back helper
+        internal void ThreadStart()
+        {
+            ExecutionContext context = _executionContext;
+            if (context != null)
+            {
+                ExecutionContext.RunInternal(context, _ccb, (Object)this);
+            }
+            else
+            {
+                ((ThreadStart)_start)();
+            }
+        }
+    }
+
+    internal struct ThreadHandle
+    {
+        private IntPtr m_ptr;
+
+        internal ThreadHandle(IntPtr pThread)
+        {
+            m_ptr = pThread;
+        }
+    }
+
+    internal sealed class Thread : RuntimeThread
+    {
+        /*=========================================================================
+        ** Data accessed from managed code that needs to be defined in
+        ** ThreadBaseObject to maintain alignment between the two classes.
+        ** DON'T CHANGE THESE UNLESS YOU MODIFY ThreadBaseObject in vm\object.h
+        =========================================================================*/
+        private ExecutionContext m_ExecutionContext;    // this call context follows the logical thread
+        private SynchronizationContext m_SynchronizationContext;    // On CoreCLR, this is maintained separately from ExecutionContext
+
+        private String m_Name;
+        private Delegate m_Delegate;             // Delegate
+
+        private Object m_ThreadStartArg;
+
+        /*=========================================================================
+        ** The base implementation of Thread is all native.  The following fields
+        ** should never be used in the C# code.  They are here to define the proper
+        ** space so the thread object may be allocated.  DON'T CHANGE THESE UNLESS
+        ** YOU MODIFY ThreadBaseObject in vm\object.h
+        =========================================================================*/
+#pragma warning disable 169
+#pragma warning disable 414  // These fields are not used from managed.
+        // IntPtrs need to be together, and before ints, because IntPtrs are 64-bit
+        //  fields on 64-bit platforms, where they will be sorted together.
+
+        private IntPtr DONT_USE_InternalThread;        // Pointer
+        private int m_Priority;                     // INT32
+
+        // The following field is required for interop with the VS Debugger
+        // Prior to making any changes to this field, please reach out to the VS Debugger 
+        // team to make sure that your changes are not going to prevent the debugger
+        // from working.
+        private int _managedThreadId;              // INT32
+
+#pragma warning restore 414
+#pragma warning restore 169
+
+
+        // Do not move! Order of above fields needs to be preserved for alignment
+        // with native code
+        // See code:#threadCultureInfo
+        [ThreadStatic]
+        internal static CultureInfo m_CurrentCulture;
+        [ThreadStatic]
+        internal static CultureInfo m_CurrentUICulture;
+
+        // Adding an empty default ctor for annotation purposes
+        internal Thread() { }
+
+        /*=========================================================================
+        ** Creates a new Thread object which will begin execution at
+        ** start.ThreadStart on a new thread when the Start method is called.
+        **
+        ** Exceptions: ArgumentNullException if start == null.
+        =========================================================================*/
+        public Thread(ThreadStart start)
+        {
+            if (start == null)
+            {
+                throw new ArgumentNullException(nameof(start));
+            }
+            SetStartHelper((Delegate)start, 0);  //0 will setup Thread with default stackSize
+        }
+
+        internal Thread(ThreadStart start, int maxStackSize)
+        {
+            if (start == null)
+            {
+                throw new ArgumentNullException(nameof(start));
+            }
+            if (0 > maxStackSize)
+                throw new ArgumentOutOfRangeException(nameof(maxStackSize), SR.ArgumentOutOfRange_NeedNonNegNum);
+            SetStartHelper((Delegate)start, maxStackSize);
+        }
+        public Thread(ParameterizedThreadStart start)
+        {
+            if (start == null)
+            {
+                throw new ArgumentNullException(nameof(start));
+            }
+            SetStartHelper((Delegate)start, 0);
+        }
+
+        internal Thread(ParameterizedThreadStart start, int maxStackSize)
+        {
+            if (start == null)
+            {
+                throw new ArgumentNullException(nameof(start));
+            }
+            if (0 > maxStackSize)
+                throw new ArgumentOutOfRangeException(nameof(maxStackSize), SR.ArgumentOutOfRange_NeedNonNegNum);
+            SetStartHelper((Delegate)start, maxStackSize);
+        }
+
+        public override int GetHashCode()
+        {
+            return _managedThreadId;
+        }
+
+        public extern new int ManagedThreadId
+        {
+            [MethodImplAttribute(MethodImplOptions.InternalCall)]
+            get;
+        }
+
+        // Returns handle for interop with EE. The handle is guaranteed to be non-null.
+        internal unsafe ThreadHandle GetNativeHandle()
+        {
+            IntPtr thread = DONT_USE_InternalThread;
+
+            // This should never happen under normal circumstances. m_assembly is always assigned before it is handed out to the user.
+            // There are ways how to create an uninitialized objects through remoting, etc. Avoid AVing in the EE by throwing a nice
+            // exception here.
+            if (thread == IntPtr.Zero)
+                throw new ArgumentException(null, SR.Argument_InvalidHandle);
+
+            return new ThreadHandle(thread);
+        }
+
+
+        /*=========================================================================
+        ** Spawns off a new thread which will begin executing at the ThreadStart
+        ** method on the IThreadable interface passed in the constructor. Once the
+        ** thread is dead, it cannot be restarted with another call to Start.
+        **
+        ** Exceptions: ThreadStateException if the thread has already been started.
+        =========================================================================*/
+        public new void Start(object parameter)
+        {
+            //In the case of a null delegate (second call to start on same thread)
+            //    StartInternal method will take care of the error reporting
+            if (m_Delegate is ThreadStart)
+            {
+                //We expect the thread to be setup with a ParameterizedThreadStart
+                //    if this constructor is called.
+                //If we got here then that wasn't the case
+                throw new InvalidOperationException(SR.InvalidOperation_ThreadWrongThreadStart);
+            }
+            m_ThreadStartArg = parameter;
+            Start();
+        }
+
+        public new void Start()
+        {
+#if FEATURE_COMINTEROP_APARTMENT_SUPPORT
+            // Eagerly initialize the COM Apartment state of the thread if we're allowed to.
+            StartupSetApartmentStateInternal();
+#endif // FEATURE_COMINTEROP_APARTMENT_SUPPORT
+
+            // Attach current thread's security principal object to the new
+            // thread. Be careful not to bind the current thread to a principal
+            // if it's not already bound.
+            if (m_Delegate != null)
+            {
+                // If we reach here with a null delegate, something is broken. But we'll let the StartInternal method take care of
+                // reporting an error. Just make sure we don't try to dereference a null delegate.
+                ThreadHelper t = (ThreadHelper)(m_Delegate.Target);
+                ExecutionContext ec = ExecutionContext.Capture();
+                t.SetExecutionContextHelper(ec);
+            }
+
+            StartInternal();
+        }
+
+        internal ExecutionContext ExecutionContext
+        {
+            get { return m_ExecutionContext; }
+            set { m_ExecutionContext = value; }
+        }
+
+        internal SynchronizationContext SynchronizationContext
+        {
+            get { return m_SynchronizationContext; }
+            set { m_SynchronizationContext = value; }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern void StartInternal();
+
+
+        // Helper method to get a logical thread ID for StringBuilder (for
+        // correctness) and for FileStream's async code path (for perf, to
+        // avoid creating a Thread instance).
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern IntPtr InternalGetCurrentThread();
+
+        /*=========================================================================
+        ** Suspends the current thread for timeout milliseconds. If timeout == 0,
+        ** forces the thread to give up the remainder of its timeslice.  If timeout
+        ** == Timeout.Infinite, no timeout will occur.
+        **
+        ** Exceptions: ArgumentException if timeout < 0.
+        **             ThreadInterruptedException if the thread is interrupted while sleeping.
+        =========================================================================*/
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void SleepInternal(int millisecondsTimeout);
+
+        public static new void Sleep(int millisecondsTimeout)
+        {
+            SleepInternal(millisecondsTimeout);
+        }
+
+        public static void Sleep(TimeSpan timeout)
+        {
+            long tm = (long)timeout.TotalMilliseconds;
+            if (tm < -1 || tm > (long)Int32.MaxValue)
+                throw new ArgumentOutOfRangeException(nameof(timeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            Sleep((int)tm);
+        }
+
+
+        /* wait for a length of time proportional to 'iterations'.  Each iteration is should
+           only take a few machine instructions.  Calling this API is preferable to coding
+           a explicit busy loop because the hardware can be informed that it is busy waiting. */
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void SpinWaitInternal(int iterations);
+
+        public static new void SpinWait(int iterations)
+        {
+            SpinWaitInternal(iterations);
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern bool YieldInternal();
+
+        internal static new bool Yield()
+        {
+            return YieldInternal();
+        }
+
+        public static new Thread CurrentThread
+        {
+            get
+            {
+                return GetCurrentThreadNative();
+            }
+        }
+        [MethodImplAttribute(MethodImplOptions.InternalCall), ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
+        private static extern Thread GetCurrentThreadNative();
+
+        private void SetStartHelper(Delegate start, int maxStackSize)
+        {
+            Debug.Assert(maxStackSize >= 0);
+
+            ThreadHelper threadStartCallBack = new ThreadHelper(start);
+            if (start is ThreadStart)
+            {
+                SetStart(new ThreadStart(threadStartCallBack.ThreadStart), maxStackSize);
+            }
+            else
+            {
+                SetStart(new ParameterizedThreadStart(threadStartCallBack.ThreadStart), maxStackSize);
+            }
+        }
+
+        /*=========================================================================
+        ** PRIVATE Sets the IThreadable interface for the thread. Assumes that
+        ** start != null.
+        =========================================================================*/
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern void SetStart(Delegate start, int maxStackSize);
+
+        /*=========================================================================
+        ** Clean up the thread when it goes away.
+        =========================================================================*/
+        ~Thread()
+        {
+            // Delegate to the unmanaged portion.
+            InternalFinalize();
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern void InternalFinalize();
+
+#if FEATURE_COMINTEROP_APARTMENT_SUPPORT
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern void StartupSetApartmentStateInternal();
+#endif // FEATURE_COMINTEROP_APARTMENT_SUPPORT
+
+        // #threadCultureInfo
+        //
+        // Background:
+        // In the desktop runtime, we allow a thread's cultures to travel with the thread
+        // across AppDomain boundaries. Furthermore we update the native thread with the
+        // culture of the managed thread. Because of security concerns and potential SxS
+        // effects, in Silverlight we are making the changes listed below. 
+        // 
+        // Silverlight Changes:
+        // - thread instance member cultures (CurrentCulture and CurrentUICulture) 
+        //   confined within AppDomains
+        // - changes to these properties don't affect the underlying native thread
+        // 
+        // Implementation notes:
+        // In Silverlight, culture members thread static (per Thread, per AppDomain). 
+        //
+        // Quirks:
+        // An interesting side-effect of isolating cultures within an AppDomain is that we
+        // now need to special case resource lookup for mscorlib, which transitions to the 
+        // default domain to lookup resources. See Environment.cs for more details.
+        // 
+
+        // As the culture can be customized object then we cannot hold any 
+        // reference to it before we check if it is safe because the app domain 
+        // owning this customized culture may get unloaded while executing this 
+        // code. To achieve that we have to do the check using nativeGetSafeCulture 
+        // as the thread cannot get interrupted during the FCALL. 
+        // If the culture is safe (not customized or created in current app domain) 
+        // then the FCALL will return a reference to that culture otherwise the 
+        // FCALL will return failure. In case of failure we'll return the default culture.
+        // If the app domain owning a customized culture that is set to the thread and this
+        // app domain get unloaded there is a code to clean up the culture from the thread
+        // using the code in AppDomain::ReleaseDomainStores.
+
+        public CultureInfo CurrentUICulture
+        {
+            get
+            {
+                return CultureInfo.CurrentUICulture;
+            }
+
+            set
+            {
+                // If you add more pre-conditions to this method, check to see if you also need to 
+                // add them to CultureInfo.DefaultThreadCurrentUICulture.set.
+
+                if (m_CurrentUICulture == null && m_CurrentCulture == null)
+                    nativeInitCultureAccessors();
+
+                CultureInfo.CurrentUICulture = value;
+            }
+        }
+
+        // This returns the exposed context for a given context ID.
+
+        // As the culture can be customized object then we cannot hold any 
+        // reference to it before we check if it is safe because the app domain 
+        // owning this customized culture may get unloaded while executing this 
+        // code. To achieve that we have to do the check using nativeGetSafeCulture 
+        // as the thread cannot get interrupted during the FCALL. 
+        // If the culture is safe (not customized or created in current app domain) 
+        // then the FCALL will return a reference to that culture otherwise the 
+        // FCALL will return failure. In case of failure we'll return the default culture.
+        // If the app domain owning a customized culture that is set to the thread and this
+        // app domain get unloaded there is a code to clean up the culture from the thread
+        // using the code in AppDomain::ReleaseDomainStores.
+
+        public CultureInfo CurrentCulture
+        {
+            get
+            {
+                return CultureInfo.CurrentCulture;
+            }
+
+            set
+            {
+                // If you add more pre-conditions to this method, check to see if you also need to 
+                // add them to CultureInfo.DefaultThreadCurrentCulture.set.
+
+                if (m_CurrentCulture == null && m_CurrentUICulture == null)
+                    nativeInitCultureAccessors();
+                
+                CultureInfo.CurrentCulture = value;
+            }
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void nativeInitCultureAccessors();
+
+        /*======================================================================
+        ** Returns the current domain in which current thread is running.
+        ======================================================================*/
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern AppDomain GetDomainInternal();
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern AppDomain GetFastDomainInternal();
+
+        internal static AppDomain GetDomain()
+        {
+
+            AppDomain ad;
+            ad = GetFastDomainInternal();
+            if (ad == null)
+                ad = GetDomainInternal();
+
+            return ad;
+        }
+
+
+        /*
+         *  This returns a unique id to identify an appdomain.
+         */
+        internal static int GetDomainID()
+        {
+            return GetDomain().GetId();
+        }
+
+
+        // Retrieves the name of the thread.
+        //
+        public new String Name
+        {
+            get
+            {
+                return m_Name;
+            }
+            set
+            {
+                lock (this)
+                {
+                    if (m_Name != null)
+                        throw new InvalidOperationException(SR.InvalidOperation_WriteOnce);
+                    m_Name = value;
+
+                    InformThreadNameChange(GetNativeHandle(), value, (value != null) ? value.Length : 0);
+                }
+            }
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void InformThreadNameChange(ThreadHandle t, String name, int len);
+
+    } // End of class Thread
+
+    // declaring a local var of this enum type and passing it by ref into a function that needs to do a
+    // stack crawl will both prevent inlining of the callee and pass an ESP point to stack crawl to
+    // Declaring these in EH clauses is illegal; they must declared in the main method body
+    internal enum StackCrawlMark
+    {
+        LookForMe = 0,
+        LookForMyCaller = 1,
+        LookForMyCallersCaller = 2,
+        LookForThread = 3
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/ThreadInterruptedException.cs b/src/System.Private.CoreLib/src/System/Threading/ThreadInterruptedException.cs
new file mode 100644
index 0000000000..80e25e6e04
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/ThreadInterruptedException.cs
@@ -0,0 +1,48 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+/*=============================================================================
+**
+**
+**
+** Purpose: An exception class to indicate that the thread was interrupted
+**          from a waiting state.
+**
+**
+=============================================================================*/
+
+using System.Threading;
+using System;
+using System.Runtime.Serialization;
+
+namespace System.Threading
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class ThreadInterruptedException : SystemException
+    {
+        public ThreadInterruptedException()
+            : base(GetMessageFromNativeResources(ExceptionMessageKind.ThreadInterrupted))
+        {
+            HResult = HResults.COR_E_THREADINTERRUPTED;
+        }
+
+        public ThreadInterruptedException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_THREADINTERRUPTED;
+        }
+
+        public ThreadInterruptedException(String message, Exception innerException)
+            : base(message, innerException)
+        {
+            HResult = HResults.COR_E_THREADINTERRUPTED;
+        }
+
+        protected ThreadInterruptedException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/ThreadLocal.cs b/src/System.Private.CoreLib/src/System/Threading/ThreadLocal.cs
new file mode 100644
index 0000000000..6c823d5573
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/ThreadLocal.cs
@@ -0,0 +1,811 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+#pragma warning disable 0420
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+//
+//
+// A class that provides a simple, lightweight implementation of thread-local lazy-initialization, where a value is initialized once per accessing 
+// thread; this provides an alternative to using a ThreadStatic static variable and having 
+// to check the variable prior to every access to see if it's been initialized.
+//
+// 
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Collections.Generic;
+using System.Diagnostics;
+
+namespace System.Threading
+{
+    /// <summary>
+    /// Provides thread-local storage of data.
+    /// </summary>
+    /// <typeparam name="T">Specifies the type of data stored per-thread.</typeparam>
+    /// <remarks>
+    /// <para>
+    /// With the exception of <see cref="Dispose()"/>, all public and protected members of 
+    /// <see cref="ThreadLocal{T}"/> are thread-safe and may be used
+    /// concurrently from multiple threads.
+    /// </para>
+    /// </remarks>
+    [DebuggerTypeProxy(typeof(SystemThreading_ThreadLocalDebugView<>))]
+    [DebuggerDisplay("IsValueCreated={IsValueCreated}, Value={ValueForDebugDisplay}, Count={ValuesCountForDebugDisplay}")]
+    public class ThreadLocal<T> : IDisposable
+    {
+        // a delegate that returns the created value, if null the created value will be default(T)
+        private Func<T> m_valueFactory;
+
+        //
+        // ts_slotArray is a table of thread-local values for all ThreadLocal<T> instances
+        //
+        // So, when a thread reads ts_slotArray, it gets back an array of *all* ThreadLocal<T> values for this thread and this T.
+        // The slot relevant to this particular ThreadLocal<T> instance is determined by the m_idComplement instance field stored in
+        // the ThreadLocal<T> instance.
+        //
+        [ThreadStatic]
+        private static LinkedSlotVolatile[] ts_slotArray;
+
+        [ThreadStatic]
+        private static FinalizationHelper ts_finalizationHelper;
+
+        // Slot ID of this ThreadLocal<> instance. We store a bitwise complement of the ID (that is ~ID), which allows us to distinguish
+        // between the case when ID is 0 and an incompletely initialized object, either due to a thread abort in the constructor, or
+        // possibly due to a memory model issue in user code.
+        private int m_idComplement;
+
+        // This field is set to true when the constructor completes. That is helpful for recognizing whether a constructor
+        // threw an exception - either due to invalid argument or due to a thread abort. Finally, the field is set to false
+        // when the instance is disposed.
+        private volatile bool m_initialized;
+
+        // IdManager assigns and reuses slot IDs. Additionally, the object is also used as a global lock.
+        private static IdManager s_idManager = new IdManager();
+
+        // A linked list of all values associated with this ThreadLocal<T> instance.
+        // We create a dummy head node. That allows us to remove any (non-dummy)  node without having to locate the m_linkedSlot field. 
+        private LinkedSlot m_linkedSlot = new LinkedSlot(null);
+
+        // Whether the Values property is supported
+        private bool m_trackAllValues;
+
+        /// <summary>
+        /// Initializes the <see cref="System.Threading.ThreadLocal{T}"/> instance.
+        /// </summary>
+        public ThreadLocal()
+        {
+            Initialize(null, false);
+        }
+
+        /// <summary>
+        /// Initializes the <see cref="System.Threading.ThreadLocal{T}"/> instance.
+        /// </summary>
+        /// <param name="trackAllValues">Whether to track all values set on the instance and expose them through the Values property.</param>
+        public ThreadLocal(bool trackAllValues)
+        {
+            Initialize(null, trackAllValues);
+        }
+
+
+        /// <summary>
+        /// Initializes the <see cref="System.Threading.ThreadLocal{T}"/> instance with the
+        /// specified <paramref name="valueFactory"/> function.
+        /// </summary>
+        /// <param name="valueFactory">
+        /// The <see cref="T:System.Func{T}"/> invoked to produce a lazily-initialized value when 
+        /// an attempt is made to retrieve <see cref="Value"/> without it having been previously initialized.
+        /// </param>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// <paramref name="valueFactory"/> is a null reference (Nothing in Visual Basic).
+        /// </exception>
+        public ThreadLocal(Func<T> valueFactory)
+        {
+            if (valueFactory == null)
+                throw new ArgumentNullException(nameof(valueFactory));
+
+            Initialize(valueFactory, false);
+        }
+
+        /// <summary>
+        /// Initializes the <see cref="System.Threading.ThreadLocal{T}"/> instance with the
+        /// specified <paramref name="valueFactory"/> function.
+        /// </summary>
+        /// <param name="valueFactory">
+        /// The <see cref="T:System.Func{T}"/> invoked to produce a lazily-initialized value when 
+        /// an attempt is made to retrieve <see cref="Value"/> without it having been previously initialized.
+        /// </param>
+        /// <param name="trackAllValues">Whether to track all values set on the instance and expose them via the Values property.</param>
+        /// <exception cref="T:System.ArgumentNullException">
+        /// <paramref name="valueFactory"/> is a null reference (Nothing in Visual Basic).
+        /// </exception>
+        public ThreadLocal(Func<T> valueFactory, bool trackAllValues)
+        {
+            if (valueFactory == null)
+                throw new ArgumentNullException(nameof(valueFactory));
+
+            Initialize(valueFactory, trackAllValues);
+        }
+
+        private void Initialize(Func<T> valueFactory, bool trackAllValues)
+        {
+            m_valueFactory = valueFactory;
+            m_trackAllValues = trackAllValues;
+
+            // Assign the ID and mark the instance as initialized. To avoid leaking IDs, we assign the ID and set m_initialized
+            // in a finally block, to avoid a thread abort in between the two statements.
+            try { }
+            finally
+            {
+                m_idComplement = ~s_idManager.GetId();
+
+                // As the last step, mark the instance as fully initialized. (Otherwise, if m_initialized=false, we know that an exception
+                // occurred in the constructor.)
+                m_initialized = true;
+            }
+        }
+
+        /// <summary>
+        /// Releases the resources used by this <see cref="T:System.Threading.ThreadLocal{T}" /> instance.
+        /// </summary>
+        ~ThreadLocal()
+        {
+            // finalizer to return the type combination index to the pool
+            Dispose(false);
+        }
+
+        #region IDisposable Members
+
+        /// <summary>
+        /// Releases the resources used by this <see cref="T:System.Threading.ThreadLocal{T}" /> instance.
+        /// </summary>
+        /// <remarks>
+        /// Unlike most of the members of <see cref="T:System.Threading.ThreadLocal{T}"/>, this method is not thread-safe.
+        /// </remarks>
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// Releases the resources used by this <see cref="T:System.Threading.ThreadLocal{T}" /> instance.
+        /// </summary>
+        /// <param name="disposing">
+        /// A Boolean value that indicates whether this method is being called due to a call to <see cref="Dispose()"/>.
+        /// </param>
+        /// <remarks>
+        /// Unlike most of the members of <see cref="T:System.Threading.ThreadLocal{T}"/>, this method is not thread-safe.
+        /// </remarks>
+        protected virtual void Dispose(bool disposing)
+        {
+            int id;
+
+            lock (s_idManager)
+            {
+                id = ~m_idComplement;
+                m_idComplement = 0;
+
+                if (id < 0 || !m_initialized)
+                {
+                    Debug.Assert(id >= 0 || !m_initialized, "expected id >= 0 if initialized");
+
+                    // Handle double Dispose calls or disposal of an instance whose constructor threw an exception.
+                    return;
+                }
+                m_initialized = false;
+
+                for (LinkedSlot linkedSlot = m_linkedSlot.Next; linkedSlot != null; linkedSlot = linkedSlot.Next)
+                {
+                    LinkedSlotVolatile[] slotArray = linkedSlot.SlotArray;
+
+                    if (slotArray == null)
+                    {
+                        // The thread that owns this slotArray has already finished.
+                        continue;
+                    }
+
+                    // Remove the reference from the LinkedSlot to the slot table.
+                    linkedSlot.SlotArray = null;
+
+                    // And clear the references from the slot table to the linked slot and the value so that
+                    // both can get garbage collected.
+                    slotArray[id].Value.Value = default(T);
+                    slotArray[id].Value = null;
+                }
+            }
+            m_linkedSlot = null;
+            s_idManager.ReturnId(id);
+        }
+
+        #endregion
+
+        /// <summary>Creates and returns a string representation of this instance for the current thread.</summary>
+        /// <returns>The result of calling <see cref="System.Object.ToString"/> on the <see cref="Value"/>.</returns>
+        /// <exception cref="T:System.NullReferenceException">
+        /// The <see cref="Value"/> for the current thread is a null reference (Nothing in Visual Basic).
+        /// </exception>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The initialization function referenced <see cref="Value"/> in an improper manner.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">
+        /// The <see cref="ThreadLocal{T}"/> instance has been disposed.
+        /// </exception>
+        /// <remarks>
+        /// Calling this method forces initialization for the current thread, as is the
+        /// case with accessing <see cref="Value"/> directly.
+        /// </remarks>
+        public override string ToString()
+        {
+            return Value.ToString();
+        }
+
+        /// <summary>
+        /// Gets or sets the value of this instance for the current thread.
+        /// </summary>
+        /// <exception cref="T:System.InvalidOperationException">
+        /// The initialization function referenced <see cref="Value"/> in an improper manner.
+        /// </exception>
+        /// <exception cref="T:System.ObjectDisposedException">
+        /// The <see cref="ThreadLocal{T}"/> instance has been disposed.
+        /// </exception>
+        /// <remarks>
+        /// If this instance was not previously initialized for the current thread,
+        /// accessing <see cref="Value"/> will attempt to initialize it. If an initialization function was 
+        /// supplied during the construction, that initialization will happen by invoking the function 
+        /// to retrieve the initial value for <see cref="Value"/>.  Otherwise, the default value of 
+        /// <typeparamref name="T"/> will be used.
+        /// </remarks>
+        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
+        public T Value
+        {
+            get
+            {
+                LinkedSlotVolatile[] slotArray = ts_slotArray;
+                LinkedSlot slot;
+                int id = ~m_idComplement;
+
+                //
+                // Attempt to get the value using the fast path
+                //
+                if (slotArray != null   // Has the slot array been initialized?
+                    && id >= 0   // Is the ID non-negative (i.e., instance is not disposed)?
+                    && id < slotArray.Length   // Is the table large enough?
+                    && (slot = slotArray[id].Value) != null   // Has a LinkedSlot object has been allocated for this ID?
+                    && m_initialized // Has the instance *still* not been disposed (important for a race condition with Dispose)?
+                )
+                {
+                    // We verified that the instance has not been disposed *after* we got a reference to the slot.
+                    // This guarantees that we have a reference to the right slot.
+                    // 
+                    // Volatile read of the LinkedSlotVolatile.Value property ensures that the m_initialized read
+                    // will not be reordered before the read of slotArray[id].
+                    return slot.Value;
+                }
+
+                return GetValueSlow();
+            }
+            set
+            {
+                LinkedSlotVolatile[] slotArray = ts_slotArray;
+                LinkedSlot slot;
+                int id = ~m_idComplement;
+
+                //
+                // Attempt to set the value using the fast path
+                //
+                if (slotArray != null   // Has the slot array been initialized?
+                    && id >= 0   // Is the ID non-negative (i.e., instance is not disposed)?
+                    && id < slotArray.Length   // Is the table large enough?
+                    && (slot = slotArray[id].Value) != null   // Has a LinkedSlot object has been allocated for this ID?
+                    && m_initialized // Has the instance *still* not been disposed (important for a race condition with Dispose)?
+                    )
+                {
+                    // We verified that the instance has not been disposed *after* we got a reference to the slot.
+                    // This guarantees that we have a reference to the right slot.
+                    // 
+                    // Volatile read of the LinkedSlotVolatile.Value property ensures that the m_initialized read
+                    // will not be reordered before the read of slotArray[id].
+                    slot.Value = value;
+                }
+                else
+                {
+                    SetValueSlow(value, slotArray);
+                }
+            }
+        }
+
+        private T GetValueSlow()
+        {
+            // If the object has been disposed, the id will be -1.
+            int id = ~m_idComplement;
+            if (id < 0)
+            {
+                throw new ObjectDisposedException(SR.ThreadLocal_Disposed);
+            }
+
+            Debugger.NotifyOfCrossThreadDependency();
+
+            // Determine the initial value
+            T value;
+            if (m_valueFactory == null)
+            {
+                value = default(T);
+            }
+            else
+            {
+                value = m_valueFactory();
+
+                if (IsValueCreated)
+                {
+                    throw new InvalidOperationException(SR.ThreadLocal_Value_RecursiveCallsToValue);
+                }
+            }
+
+            // Since the value has been previously uninitialized, we also need to set it (according to the ThreadLocal semantics).
+            Value = value;
+            return value;
+        }
+
+        private void SetValueSlow(T value, LinkedSlotVolatile[] slotArray)
+        {
+            int id = ~m_idComplement;
+
+            // If the object has been disposed, id will be -1.
+            if (id < 0)
+            {
+                throw new ObjectDisposedException(SR.ThreadLocal_Disposed);
+            }
+
+            // If a slot array has not been created on this thread yet, create it.
+            if (slotArray == null)
+            {
+                slotArray = new LinkedSlotVolatile[GetNewTableSize(id + 1)];
+                ts_finalizationHelper = new FinalizationHelper(slotArray, m_trackAllValues);
+                ts_slotArray = slotArray;
+            }
+
+            // If the slot array is not big enough to hold this ID, increase the table size.
+            if (id >= slotArray.Length)
+            {
+                GrowTable(ref slotArray, id + 1);
+                ts_finalizationHelper.SlotArray = slotArray;
+                ts_slotArray = slotArray;
+            }
+
+            // If we are using the slot in this table for the first time, create a new LinkedSlot and add it into
+            // the linked list for this ThreadLocal instance.
+            if (slotArray[id].Value == null)
+            {
+                CreateLinkedSlot(slotArray, id, value);
+            }
+            else
+            {
+                // Volatile read of the LinkedSlotVolatile.Value property ensures that the m_initialized read
+                // that follows will not be reordered before the read of slotArray[id].
+                LinkedSlot slot = slotArray[id].Value;
+
+                // It is important to verify that the ThreadLocal instance has not been disposed. The check must come
+                // after capturing slotArray[id], but before assigning the value into the slot. This ensures that
+                // if this ThreadLocal instance was disposed on another thread and another ThreadLocal instance was
+                // created, we definitely won't assign the value into the wrong instance.
+
+                if (!m_initialized)
+                {
+                    throw new ObjectDisposedException(SR.ThreadLocal_Disposed);
+                }
+
+                slot.Value = value;
+            }
+        }
+
+        /// <summary>
+        /// Creates a LinkedSlot and inserts it into the linked list for this ThreadLocal instance.
+        /// </summary>
+        private void CreateLinkedSlot(LinkedSlotVolatile[] slotArray, int id, T value)
+        {
+            // Create a LinkedSlot
+            var linkedSlot = new LinkedSlot(slotArray);
+
+            // Insert the LinkedSlot into the linked list maintained by this ThreadLocal<> instance and into the slot array
+            lock (s_idManager)
+            {
+                // Check that the instance has not been disposed. It is important to check this under a lock, since
+                // Dispose also executes under a lock.
+                if (!m_initialized)
+                {
+                    throw new ObjectDisposedException(SR.ThreadLocal_Disposed);
+                }
+
+                LinkedSlot firstRealNode = m_linkedSlot.Next;
+
+                //
+                // Insert linkedSlot between nodes m_linkedSlot and firstRealNode. 
+                // (m_linkedSlot is the dummy head node that should always be in the front.)
+                //
+                linkedSlot.Next = firstRealNode;
+                linkedSlot.Previous = m_linkedSlot;
+                linkedSlot.Value = value;
+
+                if (firstRealNode != null)
+                {
+                    firstRealNode.Previous = linkedSlot;
+                }
+                m_linkedSlot.Next = linkedSlot;
+
+                // Assigning the slot under a lock prevents a race condition with Dispose (dispose also acquires the lock).
+                // Otherwise, it would be possible that the ThreadLocal instance is disposed, another one gets created
+                // with the same ID, and the write would go to the wrong instance.
+                slotArray[id].Value = linkedSlot;
+            }
+        }
+
+        /// <summary>
+        /// Gets a list for all of the values currently stored by all of the threads that have accessed this instance.
+        /// </summary>
+        /// <exception cref="T:System.ObjectDisposedException">
+        /// The <see cref="ThreadLocal{T}"/> instance has been disposed.
+        /// </exception>
+        public IList<T> Values
+        {
+            get
+            {
+                if (!m_trackAllValues)
+                {
+                    throw new InvalidOperationException(SR.ThreadLocal_ValuesNotAvailable);
+                }
+
+                var list = GetValuesAsList(); // returns null if disposed
+                if (list == null) throw new ObjectDisposedException(SR.ThreadLocal_Disposed);
+                return list;
+            }
+        }
+
+        /// <summary>Gets all of the threads' values in a list.</summary>
+        private List<T> GetValuesAsList()
+        {
+            List<T> valueList = new List<T>();
+            int id = ~m_idComplement;
+            if (id == -1)
+            {
+                return null;
+            }
+
+            // Walk over the linked list of slots and gather the values associated with this ThreadLocal instance.
+            for (LinkedSlot linkedSlot = m_linkedSlot.Next; linkedSlot != null; linkedSlot = linkedSlot.Next)
+            {
+                // We can safely read linkedSlot.Value. Even if this ThreadLocal has been disposed in the meantime, the LinkedSlot
+                // objects will never be assigned to another ThreadLocal instance.
+                valueList.Add(linkedSlot.Value);
+            }
+
+            return valueList;
+        }
+
+        /// <summary>Gets the number of threads that have data in this instance.</summary>
+        private int ValuesCountForDebugDisplay
+        {
+            get
+            {
+                int count = 0;
+                for (LinkedSlot linkedSlot = m_linkedSlot.Next; linkedSlot != null; linkedSlot = linkedSlot.Next)
+                {
+                    count++;
+                }
+                return count;
+            }
+        }
+
+        /// <summary>
+        /// Gets whether <see cref="Value"/> is initialized on the current thread.
+        /// </summary>
+        /// <exception cref="T:System.ObjectDisposedException">
+        /// The <see cref="ThreadLocal{T}"/> instance has been disposed.
+        /// </exception>
+        public bool IsValueCreated
+        {
+            get
+            {
+                int id = ~m_idComplement;
+                if (id < 0)
+                {
+                    throw new ObjectDisposedException(SR.ThreadLocal_Disposed);
+                }
+
+                LinkedSlotVolatile[] slotArray = ts_slotArray;
+                return slotArray != null && id < slotArray.Length && slotArray[id].Value != null;
+            }
+        }
+
+
+        /// <summary>Gets the value of the ThreadLocal&lt;T&gt; for debugging display purposes. It takes care of getting
+        /// the value for the current thread in the ThreadLocal mode.</summary>
+        internal T ValueForDebugDisplay
+        {
+            get
+            {
+                LinkedSlotVolatile[] slotArray = ts_slotArray;
+                int id = ~m_idComplement;
+
+                LinkedSlot slot;
+                if (slotArray == null || id >= slotArray.Length || (slot = slotArray[id].Value) == null || !m_initialized)
+                    return default(T);
+                return slot.Value;
+            }
+        }
+
+        /// <summary>Gets the values of all threads that accessed the ThreadLocal&lt;T&gt;.</summary>
+        internal List<T> ValuesForDebugDisplay // same as Values property, but doesn't throw if disposed
+        {
+            get { return GetValuesAsList(); }
+        }
+
+        /// <summary>
+        /// Resizes a table to a certain length (or larger).
+        /// </summary>
+        private void GrowTable(ref LinkedSlotVolatile[] table, int minLength)
+        {
+            Debug.Assert(table.Length < minLength);
+
+            // Determine the size of the new table and allocate it.
+            int newLen = GetNewTableSize(minLength);
+            LinkedSlotVolatile[] newTable = new LinkedSlotVolatile[newLen];
+
+            //
+            // The lock is necessary to avoid a race with ThreadLocal.Dispose. GrowTable has to point all 
+            // LinkedSlot instances referenced in the old table to reference the new table. Without locking, 
+            // Dispose could use a stale SlotArray reference and clear out a slot in the old array only, while 
+            // the value continues to be referenced from the new (larger) array.
+            //
+            lock (s_idManager)
+            {
+                for (int i = 0; i < table.Length; i++)
+                {
+                    LinkedSlot linkedSlot = table[i].Value;
+                    if (linkedSlot != null && linkedSlot.SlotArray != null)
+                    {
+                        linkedSlot.SlotArray = newTable;
+                        newTable[i] = table[i];
+                    }
+                }
+            }
+
+            table = newTable;
+        }
+
+        /// <summary>
+        /// Chooses the next larger table size
+        /// </summary>
+        private static int GetNewTableSize(int minSize)
+        {
+            if ((uint)minSize > Array.MaxArrayLength)
+            {
+                // Intentionally return a value that will result in an OutOfMemoryException
+                return int.MaxValue;
+            }
+            Debug.Assert(minSize > 0);
+
+            //
+            // Round up the size to the next power of 2
+            //
+            // The algorithm takes three steps: 
+            //   input -> subtract one -> propagate 1-bits to the right -> add one
+            //
+            // Let's take a look at the 3 steps in both interesting cases: where the input 
+            // is (Example 1) and isn't (Example 2) a power of 2.
+            //
+            //   Example 1: 100000 -> 011111 -> 011111 -> 100000
+            //   Example 2: 011010 -> 011001 -> 011111 -> 100000
+            // 
+            int newSize = minSize;
+
+            // Step 1: Decrement
+            newSize--;
+
+            // Step 2: Propagate 1-bits to the right.
+            newSize |= newSize >> 1;
+            newSize |= newSize >> 2;
+            newSize |= newSize >> 4;
+            newSize |= newSize >> 8;
+            newSize |= newSize >> 16;
+
+            // Step 3: Increment
+            newSize++;
+
+            // Don't set newSize to more than Array.MaxArrayLength
+            if ((uint)newSize > Array.MaxArrayLength)
+            {
+                newSize = Array.MaxArrayLength;
+            }
+
+            return newSize;
+        }
+
+        /// <summary>
+        /// A wrapper struct used as LinkedSlotVolatile[] - an array of LinkedSlot instances, but with volatile semantics
+        /// on array accesses.
+        /// </summary>
+        private struct LinkedSlotVolatile
+        {
+            internal volatile LinkedSlot Value;
+        }
+
+        /// <summary>
+        /// A node in the doubly-linked list stored in the ThreadLocal instance.
+        /// 
+        /// The value is stored in one of two places:
+        /// 
+        ///     1. If SlotArray is not null, the value is in SlotArray.Table[id]
+        ///     2. If SlotArray is null, the value is in FinalValue.
+        /// </summary>
+        private sealed class LinkedSlot
+        {
+            internal LinkedSlot(LinkedSlotVolatile[] slotArray)
+            {
+                SlotArray = slotArray;
+            }
+
+            // The next LinkedSlot for this ThreadLocal<> instance
+            internal volatile LinkedSlot Next;
+
+            // The previous LinkedSlot for this ThreadLocal<> instance
+            internal volatile LinkedSlot Previous;
+
+            // The SlotArray that stores this LinkedSlot at SlotArray.Table[id].
+            internal volatile LinkedSlotVolatile[] SlotArray;
+
+            // The value for this slot.
+            internal T Value;
+        }
+
+        /// <summary>
+        /// A manager class that assigns IDs to ThreadLocal instances
+        /// </summary>
+        private class IdManager
+        {
+            // The next ID to try
+            private int m_nextIdToTry = 0;
+
+            // Stores whether each ID is free or not. Additionally, the object is also used as a lock for the IdManager.
+            private List<bool> m_freeIds = new List<bool>();
+
+            internal int GetId()
+            {
+                lock (m_freeIds)
+                {
+                    int availableId = m_nextIdToTry;
+                    while (availableId < m_freeIds.Count)
+                    {
+                        if (m_freeIds[availableId]) { break; }
+                        availableId++;
+                    }
+
+                    if (availableId == m_freeIds.Count)
+                    {
+                        m_freeIds.Add(false);
+                    }
+                    else
+                    {
+                        m_freeIds[availableId] = false;
+                    }
+
+                    m_nextIdToTry = availableId + 1;
+
+                    return availableId;
+                }
+            }
+
+            // Return an ID to the pool
+            internal void ReturnId(int id)
+            {
+                lock (m_freeIds)
+                {
+                    m_freeIds[id] = true;
+                    if (id < m_nextIdToTry) m_nextIdToTry = id;
+                }
+            }
+        }
+
+        /// <summary>
+        /// A class that facilitates ThreadLocal cleanup after a thread exits.
+        /// 
+        /// After a thread with an associated thread-local table has exited, the FinalizationHelper 
+        /// is responsible for removing back-references to the table. Since an instance of FinalizationHelper 
+        /// is only referenced from a single thread-local slot, the FinalizationHelper will be GC'd once
+        /// the thread has exited.
+        /// 
+        /// The FinalizationHelper then locates all LinkedSlot instances with back-references to the table
+        /// (all those LinkedSlot instances can be found by following references from the table slots) and
+        /// releases the table so that it can get GC'd.
+        /// </summary>
+        private class FinalizationHelper
+        {
+            internal LinkedSlotVolatile[] SlotArray;
+            private bool m_trackAllValues;
+
+            internal FinalizationHelper(LinkedSlotVolatile[] slotArray, bool trackAllValues)
+            {
+                SlotArray = slotArray;
+                m_trackAllValues = trackAllValues;
+            }
+
+            ~FinalizationHelper()
+            {
+                LinkedSlotVolatile[] slotArray = SlotArray;
+                Debug.Assert(slotArray != null);
+
+                for (int i = 0; i < slotArray.Length; i++)
+                {
+                    LinkedSlot linkedSlot = slotArray[i].Value;
+                    if (linkedSlot == null)
+                    {
+                        // This slot in the table is empty
+                        continue;
+                    }
+
+                    if (m_trackAllValues)
+                    {
+                        // Set the SlotArray field to null to release the slot array.
+                        linkedSlot.SlotArray = null;
+                    }
+                    else
+                    {
+                        // Remove the LinkedSlot from the linked list. Once the FinalizationHelper is done, all back-references to
+                        // the table will be have been removed, and so the table can get GC'd.
+                        lock (s_idManager)
+                        {
+                            if (linkedSlot.Next != null)
+                            {
+                                linkedSlot.Next.Previous = linkedSlot.Previous;
+                            }
+
+                            // Since the list uses a dummy head node, the Previous reference should never be null.
+                            Debug.Assert(linkedSlot.Previous != null);
+                            linkedSlot.Previous.Next = linkedSlot.Next;
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    /// <summary>A debugger view of the ThreadLocal&lt;T&gt; to surface additional debugging properties and 
+    /// to ensure that the ThreadLocal&lt;T&gt; does not become initialized if it was not already.</summary>
+    internal sealed class SystemThreading_ThreadLocalDebugView<T>
+    {
+        //The ThreadLocal object being viewed.
+        private readonly ThreadLocal<T> m_tlocal;
+
+        /// <summary>Constructs a new debugger view object for the provided ThreadLocal object.</summary>
+        /// <param name="tlocal">A ThreadLocal object to browse in the debugger.</param>
+        public SystemThreading_ThreadLocalDebugView(ThreadLocal<T> tlocal)
+        {
+            m_tlocal = tlocal;
+        }
+
+        /// <summary>Returns whether the ThreadLocal object is initialized or not.</summary>
+        public bool IsValueCreated
+        {
+            get { return m_tlocal.IsValueCreated; }
+        }
+
+        /// <summary>Returns the value of the ThreadLocal object.</summary>
+        public T Value
+        {
+            get
+            {
+                return m_tlocal.ValueForDebugDisplay;
+            }
+        }
+
+        /// <summary>Return all values for all threads that have accessed this instance.</summary>
+        public List<T> Values
+        {
+            get
+            {
+                return m_tlocal.ValuesForDebugDisplay;
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/ThreadPool.cs b/src/System.Private.CoreLib/src/System/Threading/ThreadPool.cs
new file mode 100644
index 0000000000..ad70726cbe
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/ThreadPool.cs
@@ -0,0 +1,1547 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: Class for creating and managing a threadpool
+**
+**
+=============================================================================*/
+
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Diagnostics.Tracing;
+using System.Runtime.CompilerServices;
+using System.Runtime.ConstrainedExecution;
+using System.Runtime.InteropServices;
+using System.Security;
+using Microsoft.Win32;
+
+namespace System.Threading
+{
+    internal static class ThreadPoolGlobals
+    {
+        //Per-appDomain quantum (in ms) for which the thread keeps processing
+        //requests in the current domain.
+        public const uint TP_QUANTUM = 30U;
+
+        public static readonly int processorCount = Environment.ProcessorCount;
+
+        public static volatile bool vmTpInitialized;
+        public static bool enableWorkerTracking;
+
+        public static readonly ThreadPoolWorkQueue workQueue = new ThreadPoolWorkQueue();
+    }
+
+    [StructLayout(LayoutKind.Sequential)] // enforce layout so that padding reduces false sharing
+    internal sealed class ThreadPoolWorkQueue
+    {
+        internal static class WorkStealingQueueList
+        {
+            private static volatile WorkStealingQueue[] _queues = new WorkStealingQueue[0];
+
+            public static WorkStealingQueue[] Queues => _queues;
+
+            public static void Add(WorkStealingQueue queue)
+            {
+                Debug.Assert(queue != null);
+                while (true)
+                {
+                    WorkStealingQueue[] oldQueues = _queues;
+                    Debug.Assert(Array.IndexOf(oldQueues, queue) == -1);
+
+                    var newQueues = new WorkStealingQueue[oldQueues.Length + 1];
+                    Array.Copy(oldQueues, 0, newQueues, 0, oldQueues.Length);
+                    newQueues[newQueues.Length - 1] = queue;
+                    if (Interlocked.CompareExchange(ref _queues, newQueues, oldQueues) == oldQueues)
+                    {
+                        break;
+                    }
+                }
+            }
+
+            public static void Remove(WorkStealingQueue queue)
+            {
+                Debug.Assert(queue != null);
+                while (true)
+                {
+                    WorkStealingQueue[] oldQueues = _queues;
+                    if (oldQueues.Length == 0)
+                    {
+                        return;
+                    }
+
+                    int pos = Array.IndexOf(oldQueues, queue);
+                    if (pos == -1)
+                    {
+                        Debug.Fail("Should have found the queue");
+                        return;
+                    }
+
+                    var newQueues = new WorkStealingQueue[oldQueues.Length - 1];
+                    if (pos == 0)
+                    {
+                        Array.Copy(oldQueues, 1, newQueues, 0, newQueues.Length);
+                    }
+                    else if (pos == oldQueues.Length - 1)
+                    {
+                        Array.Copy(oldQueues, 0, newQueues, 0, newQueues.Length);
+                    }
+                    else
+                    {
+                        Array.Copy(oldQueues, 0, newQueues, 0, pos);
+                        Array.Copy(oldQueues, pos + 1, newQueues, pos, newQueues.Length - pos);
+                    }
+
+                    if (Interlocked.CompareExchange(ref _queues, newQueues, oldQueues) == oldQueues)
+                    {
+                        break;
+                    }
+                }
+            }
+        }
+
+        internal sealed class WorkStealingQueue
+        {
+            private const int INITIAL_SIZE = 32;
+            internal volatile IThreadPoolWorkItem[] m_array = new IThreadPoolWorkItem[INITIAL_SIZE];
+            private volatile int m_mask = INITIAL_SIZE - 1;
+
+#if DEBUG
+            // in debug builds, start at the end so we exercise the index reset logic.
+            private const int START_INDEX = int.MaxValue;
+#else
+            private const int START_INDEX = 0;
+#endif
+
+            private volatile int m_headIndex = START_INDEX;
+            private volatile int m_tailIndex = START_INDEX;
+
+            private SpinLock m_foreignLock = new SpinLock(enableThreadOwnerTracking: false);
+
+            public void LocalPush(IThreadPoolWorkItem obj)
+            {
+                int tail = m_tailIndex;
+
+                // We're going to increment the tail; if we'll overflow, then we need to reset our counts
+                if (tail == int.MaxValue)
+                {
+                    bool lockTaken = false;
+                    try
+                    {
+                        m_foreignLock.Enter(ref lockTaken);
+
+                        if (m_tailIndex == int.MaxValue)
+                        {
+                            //
+                            // Rather than resetting to zero, we'll just mask off the bits we don't care about.
+                            // This way we don't need to rearrange the items already in the queue; they'll be found
+                            // correctly exactly where they are.  One subtlety here is that we need to make sure that
+                            // if head is currently < tail, it remains that way.  This happens to just fall out from
+                            // the bit-masking, because we only do this if tail == int.MaxValue, meaning that all
+                            // bits are set, so all of the bits we're keeping will also be set.  Thus it's impossible
+                            // for the head to end up > than the tail, since you can't set any more bits than all of 
+                            // them.
+                            //
+                            m_headIndex = m_headIndex & m_mask;
+                            m_tailIndex = tail = m_tailIndex & m_mask;
+                            Debug.Assert(m_headIndex <= m_tailIndex);
+                        }
+                    }
+                    finally
+                    {
+                        if (lockTaken)
+                            m_foreignLock.Exit(useMemoryBarrier: true);
+                    }
+                }
+
+                // When there are at least 2 elements' worth of space, we can take the fast path.
+                if (tail < m_headIndex + m_mask)
+                {
+                    Volatile.Write(ref m_array[tail & m_mask], obj);
+                    m_tailIndex = tail + 1;
+                }
+                else
+                {
+                    // We need to contend with foreign pops, so we lock.
+                    bool lockTaken = false;
+                    try
+                    {
+                        m_foreignLock.Enter(ref lockTaken);
+
+                        int head = m_headIndex;
+                        int count = m_tailIndex - m_headIndex;
+
+                        // If there is still space (one left), just add the element.
+                        if (count >= m_mask)
+                        {
+                            // We're full; expand the queue by doubling its size.
+                            var newArray = new IThreadPoolWorkItem[m_array.Length << 1];
+                            for (int i = 0; i < m_array.Length; i++)
+                                newArray[i] = m_array[(i + head) & m_mask];
+
+                            // Reset the field values, incl. the mask.
+                            m_array = newArray;
+                            m_headIndex = 0;
+                            m_tailIndex = tail = count;
+                            m_mask = (m_mask << 1) | 1;
+                        }
+
+                        Volatile.Write(ref m_array[tail & m_mask], obj);
+                        m_tailIndex = tail + 1;
+                    }
+                    finally
+                    {
+                        if (lockTaken)
+                            m_foreignLock.Exit(useMemoryBarrier: false);
+                    }
+                }
+            }
+
+            [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "Reviewed for thread safety")]
+            public bool LocalFindAndPop(IThreadPoolWorkItem obj)
+            {
+                // Fast path: check the tail. If equal, we can skip the lock.
+                if (m_array[(m_tailIndex - 1) & m_mask] == obj)
+                {
+                    IThreadPoolWorkItem unused = LocalPop();
+                    Debug.Assert(unused == null || unused == obj);
+                    return unused != null;
+                }
+
+                // Else, do an O(N) search for the work item. The theory of work stealing and our
+                // inlining logic is that most waits will happen on recently queued work.  And
+                // since recently queued work will be close to the tail end (which is where we
+                // begin our search), we will likely find it quickly.  In the worst case, we
+                // will traverse the whole local queue; this is typically not going to be a
+                // problem (although degenerate cases are clearly an issue) because local work
+                // queues tend to be somewhat shallow in length, and because if we fail to find
+                // the work item, we are about to block anyway (which is very expensive).
+                for (int i = m_tailIndex - 2; i >= m_headIndex; i--)
+                {
+                    if (m_array[i & m_mask] == obj)
+                    {
+                        // If we found the element, block out steals to avoid interference.
+                        bool lockTaken = false;
+                        try
+                        {
+                            m_foreignLock.Enter(ref lockTaken);
+
+                            // If we encountered a race condition, bail.
+                            if (m_array[i & m_mask] == null)
+                                return false;
+
+                            // Otherwise, null out the element.
+                            Volatile.Write(ref m_array[i & m_mask], null);
+
+                            // And then check to see if we can fix up the indexes (if we're at
+                            // the edge).  If we can't, we just leave nulls in the array and they'll
+                            // get filtered out eventually (but may lead to superfluous resizing).
+                            if (i == m_tailIndex)
+                                m_tailIndex -= 1;
+                            else if (i == m_headIndex)
+                                m_headIndex += 1;
+
+                            return true;
+                        }
+                        finally
+                        {
+                            if (lockTaken)
+                                m_foreignLock.Exit(useMemoryBarrier: false);
+                        }
+                    }
+                }
+
+                return false;
+            }
+
+            public IThreadPoolWorkItem LocalPop() => m_headIndex < m_tailIndex ? LocalPopCore() : null;
+
+            [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "Reviewed for thread safety")]
+            private IThreadPoolWorkItem LocalPopCore()
+            {
+                while (true)
+                {
+                    int tail = m_tailIndex;
+                    if (m_headIndex >= tail)
+                    {
+                        return null;
+                    }
+
+                    // Decrement the tail using a fence to ensure subsequent read doesn't come before.
+                    tail -= 1;
+                    Interlocked.Exchange(ref m_tailIndex, tail);
+
+                    // If there is no interaction with a take, we can head down the fast path.
+                    if (m_headIndex <= tail)
+                    {
+                        int idx = tail & m_mask;
+                        IThreadPoolWorkItem obj = Volatile.Read(ref m_array[idx]);
+
+                        // Check for nulls in the array.
+                        if (obj == null) continue;
+
+                        m_array[idx] = null;
+                        return obj;
+                    }
+                    else
+                    {
+                        // Interaction with takes: 0 or 1 elements left.
+                        bool lockTaken = false;
+                        try
+                        {
+                            m_foreignLock.Enter(ref lockTaken);
+
+                            if (m_headIndex <= tail)
+                            {
+                                // Element still available. Take it.
+                                int idx = tail & m_mask;
+                                IThreadPoolWorkItem obj = Volatile.Read(ref m_array[idx]);
+
+                                // Check for nulls in the array.
+                                if (obj == null) continue;
+
+                                m_array[idx] = null;
+                                return obj;
+                            }
+                            else
+                            {
+                                // If we encountered a race condition and element was stolen, restore the tail.
+                                m_tailIndex = tail + 1;
+                                return null;
+                            }
+                        }
+                        finally
+                        {
+                            if (lockTaken)
+                                m_foreignLock.Exit(useMemoryBarrier: false);
+                        }
+                    }
+                }
+            }
+
+            public bool CanSteal => m_headIndex < m_tailIndex;
+
+            public IThreadPoolWorkItem TrySteal(ref bool missedSteal)
+            {
+                while (true)
+                {
+                    if (CanSteal)
+                    {
+                        bool taken = false;
+                        try
+                        {
+                            m_foreignLock.TryEnter(ref taken);
+                            if (taken)
+                            {
+                                // Increment head, and ensure read of tail doesn't move before it (fence).
+                                int head = m_headIndex;
+                                Interlocked.Exchange(ref m_headIndex, head + 1);
+
+                                if (head < m_tailIndex)
+                                {
+                                    int idx = head & m_mask;
+                                    IThreadPoolWorkItem obj = Volatile.Read(ref m_array[idx]);
+
+                                    // Check for nulls in the array.
+                                    if (obj == null) continue;
+
+                                    m_array[idx] = null;
+                                    return obj;
+                                }
+                                else
+                                {
+                                    // Failed, restore head.
+                                    m_headIndex = head;
+                                }
+                            }
+                        }
+                        finally
+                        {
+                            if (taken)
+                                m_foreignLock.Exit(useMemoryBarrier: false);
+                        }
+
+                        missedSteal = true;
+                    }
+
+                    return null;
+                }
+            }
+        }
+
+        internal bool loggingEnabled;
+        internal readonly ConcurrentQueue<IThreadPoolWorkItem> workItems = new ConcurrentQueue<IThreadPoolWorkItem>();
+
+        private Internal.PaddingFor32 pad1;
+
+        private volatile int numOutstandingThreadRequests = 0;
+
+        private Internal.PaddingFor32 pad2;
+
+        public ThreadPoolWorkQueue()
+        {
+            loggingEnabled = FrameworkEventSource.Log.IsEnabled(EventLevel.Verbose, FrameworkEventSource.Keywords.ThreadPool | FrameworkEventSource.Keywords.ThreadTransfer);
+        }
+
+        public ThreadPoolWorkQueueThreadLocals EnsureCurrentThreadHasQueue() =>
+            ThreadPoolWorkQueueThreadLocals.threadLocals ??
+            (ThreadPoolWorkQueueThreadLocals.threadLocals = new ThreadPoolWorkQueueThreadLocals(this));
+
+        internal void EnsureThreadRequested()
+        {
+            //
+            // If we have not yet requested #procs threads from the VM, then request a new thread
+            // as needed
+            //
+            // Note that there is a separate count in the VM which will also be incremented in this case, 
+            // which is handled by RequestWorkerThread.
+            //
+            int count = numOutstandingThreadRequests;
+            while (count < ThreadPoolGlobals.processorCount)
+            {
+                int prev = Interlocked.CompareExchange(ref numOutstandingThreadRequests, count + 1, count);
+                if (prev == count)
+                {
+                    ThreadPool.RequestWorkerThread();
+                    break;
+                }
+                count = prev;
+            }
+        }
+
+        internal void MarkThreadRequestSatisfied()
+        {
+            //
+            // The VM has called us, so one of our outstanding thread requests has been satisfied.
+            // Decrement the count so that future calls to EnsureThreadRequested will succeed.
+            // Note that there is a separate count in the VM which has already been decremented by the VM
+            // by the time we reach this point.
+            //
+            int count = numOutstandingThreadRequests;
+            while (count > 0)
+            {
+                int prev = Interlocked.CompareExchange(ref numOutstandingThreadRequests, count - 1, count);
+                if (prev == count)
+                {
+                    break;
+                }
+                count = prev;
+            }
+        }
+
+        public void Enqueue(IThreadPoolWorkItem callback, bool forceGlobal)
+        {
+            if (loggingEnabled)
+                System.Diagnostics.Tracing.FrameworkEventSource.Log.ThreadPoolEnqueueWorkObject(callback);
+
+            ThreadPoolWorkQueueThreadLocals tl = null;
+            if (!forceGlobal)
+                tl = ThreadPoolWorkQueueThreadLocals.threadLocals;
+
+            if (null != tl)
+            {
+                tl.workStealingQueue.LocalPush(callback);
+            }
+            else
+            {
+                workItems.Enqueue(callback);
+            }
+
+            EnsureThreadRequested();
+        }
+
+        internal bool LocalFindAndPop(IThreadPoolWorkItem callback)
+        {
+            ThreadPoolWorkQueueThreadLocals tl = ThreadPoolWorkQueueThreadLocals.threadLocals;
+            return tl != null && tl.workStealingQueue.LocalFindAndPop(callback);
+        }
+
+        public IThreadPoolWorkItem Dequeue(ThreadPoolWorkQueueThreadLocals tl, ref bool missedSteal)
+        {
+            WorkStealingQueue localWsq = tl.workStealingQueue;
+            IThreadPoolWorkItem callback;
+
+            if ((callback = localWsq.LocalPop()) == null && // first try the local queue
+                !workItems.TryDequeue(out callback)) // then try the global queue
+            {
+                // finally try to steal from another thread's local queue
+                WorkStealingQueue[] queues = WorkStealingQueueList.Queues;
+                int c = queues.Length;
+                Debug.Assert(c > 0, "There must at least be a queue for this thread.");
+                int maxIndex = c - 1;
+                int i = tl.random.Next(c);
+                while (c > 0)
+                {
+                    i = (i < maxIndex) ? i + 1 : 0;
+                    WorkStealingQueue otherQueue = queues[i];
+                    if (otherQueue != localWsq && otherQueue.CanSteal)
+                    {
+                        callback = otherQueue.TrySteal(ref missedSteal);
+                        if (callback != null)
+                        {
+                            break;
+                        }
+                    }
+                    c--;
+                }
+            }
+
+            return callback;
+        }
+
+        internal static bool Dispatch()
+        {
+            var workQueue = ThreadPoolGlobals.workQueue;
+            //
+            // The clock is ticking!  We have ThreadPoolGlobals.TP_QUANTUM milliseconds to get some work done, and then
+            // we need to return to the VM.
+            //
+            int quantumStartTime = Environment.TickCount;
+
+            //
+            // Update our records to indicate that an outstanding request for a thread has now been fulfilled.
+            // From this point on, we are responsible for requesting another thread if we stop working for any
+            // reason, and we believe there might still be work in the queue.
+            //
+            // Note that if this thread is aborted before we get a chance to request another one, the VM will
+            // record a thread request on our behalf.  So we don't need to worry about getting aborted right here.
+            //
+            workQueue.MarkThreadRequestSatisfied();
+
+            // Has the desire for logging changed since the last time we entered?
+            workQueue.loggingEnabled = FrameworkEventSource.Log.IsEnabled(EventLevel.Verbose, FrameworkEventSource.Keywords.ThreadPool | FrameworkEventSource.Keywords.ThreadTransfer);
+
+            //
+            // Assume that we're going to need another thread if this one returns to the VM.  We'll set this to 
+            // false later, but only if we're absolutely certain that the queue is empty.
+            //
+            bool needAnotherThread = true;
+            IThreadPoolWorkItem workItem = null;
+            try
+            {
+                //
+                // Set up our thread-local data
+                //
+                ThreadPoolWorkQueueThreadLocals tl = workQueue.EnsureCurrentThreadHasQueue();
+
+                //
+                // Loop until our quantum expires.
+                //
+                while ((Environment.TickCount - quantumStartTime) < ThreadPoolGlobals.TP_QUANTUM)
+                {
+                    bool missedSteal = false;
+                    workItem = workQueue.Dequeue(tl, ref missedSteal);
+
+                    if (workItem == null)
+                    {
+                        //
+                        // No work.  We're going to return to the VM once we leave this protected region.
+                        // If we missed a steal, though, there may be more work in the queue.
+                        // Instead of looping around and trying again, we'll just request another thread.  This way
+                        // we won't starve other AppDomains while we spin trying to get locks, and hopefully the thread
+                        // that owns the contended work-stealing queue will pick up its own workitems in the meantime, 
+                        // which will be more efficient than this thread doing it anyway.
+                        //
+                        needAnotherThread = missedSteal;
+
+                        // Tell the VM we're returning normally, not because Hill Climbing asked us to return.
+                        return true;
+                    }
+
+                    if (workQueue.loggingEnabled)
+                        System.Diagnostics.Tracing.FrameworkEventSource.Log.ThreadPoolDequeueWorkObject(workItem);
+
+                    //
+                    // If we found work, there may be more work.  Ask for another thread so that the other work can be processed
+                    // in parallel.  Note that this will only ask for a max of #procs threads, so it's safe to call it for every dequeue.
+                    //
+                    workQueue.EnsureThreadRequested();
+
+                    //
+                    // Execute the workitem outside of any finally blocks, so that it can be aborted if needed.
+                    //
+                    if (ThreadPoolGlobals.enableWorkerTracking)
+                    {
+                        bool reportedStatus = false;
+                        try
+                        {
+                            ThreadPool.ReportThreadStatus(isWorking: true);
+                            reportedStatus = true;
+                            workItem.ExecuteWorkItem();
+                        }
+                        finally
+                        {
+                            if (reportedStatus)
+                                ThreadPool.ReportThreadStatus(isWorking: false);
+                        }
+                    }
+                    else
+                    {
+                        workItem.ExecuteWorkItem();
+                    }
+                    workItem = null;
+
+                    // 
+                    // Notify the VM that we executed this workitem.  This is also our opportunity to ask whether Hill Climbing wants
+                    // us to return the thread to the pool or not.
+                    //
+                    if (!ThreadPool.NotifyWorkItemComplete())
+                        return false;
+                }
+
+                // If we get here, it's because our quantum expired.  Tell the VM we're returning normally.
+                return true;
+            }
+            catch (ThreadAbortException tae)
+            {
+                //
+                // This is here to catch the case where this thread is aborted between the time we exit the finally block in the dispatch
+                // loop, and the time we execute the work item.  QueueUserWorkItemCallback uses this to update its accounting of whether
+                // it was executed or not (in debug builds only).  Task uses this to communicate the ThreadAbortException to anyone
+                // who waits for the task to complete.
+                //
+                workItem?.MarkAborted(tae);
+
+                //
+                // In this case, the VM is going to request another thread on our behalf.  No need to do it twice.
+                //
+                needAnotherThread = false;
+                // throw;  //no need to explicitly rethrow a ThreadAbortException, and doing so causes allocations on amd64.
+            }
+            finally
+            {
+                //
+                // If we are exiting for any reason other than that the queue is definitely empty, ask for another
+                // thread to pick up where we left off.
+                //
+                if (needAnotherThread)
+                    workQueue.EnsureThreadRequested();
+            }
+
+            // we can never reach this point, but the C# compiler doesn't know that, because it doesn't know the ThreadAbortException will be reraised above.
+            Debug.Fail("Should never reach this point");
+            return true;
+        }
+    }
+
+    // Simple random number generator. We don't need great randomness, we just need a little and for it to be fast.
+    internal struct FastRandom // xorshift prng
+    {
+        private uint _w, _x, _y, _z;
+
+        public FastRandom(int seed)
+        {
+            _x = (uint)seed;
+            _w = 88675123;
+            _y = 362436069;
+            _z = 521288629;
+        }
+
+        public int Next(int maxValue)
+        {
+            Debug.Assert(maxValue > 0);
+
+            uint t = _x ^ (_x << 11);
+            _x = _y; _y = _z; _z = _w;
+            _w = _w ^ (_w >> 19) ^ (t ^ (t >> 8));
+
+            return (int)(_w % (uint)maxValue);
+        }
+    }
+
+    // Holds a WorkStealingQueue, and removes it from the list when this object is no longer referenced.
+    internal sealed class ThreadPoolWorkQueueThreadLocals
+    {
+        [ThreadStatic]
+        public static ThreadPoolWorkQueueThreadLocals threadLocals;
+
+        public readonly ThreadPoolWorkQueue workQueue;
+        public readonly ThreadPoolWorkQueue.WorkStealingQueue workStealingQueue;
+        public FastRandom random = new FastRandom(Thread.CurrentThread.ManagedThreadId); // mutable struct, do not copy or make readonly
+
+        public ThreadPoolWorkQueueThreadLocals(ThreadPoolWorkQueue tpq)
+        {
+            workQueue = tpq;
+            workStealingQueue = new ThreadPoolWorkQueue.WorkStealingQueue();
+            ThreadPoolWorkQueue.WorkStealingQueueList.Add(workStealingQueue);
+        }
+
+        private void CleanUp()
+        {
+            if (null != workStealingQueue)
+            {
+                if (null != workQueue)
+                {
+                    IThreadPoolWorkItem cb;
+                    while ((cb = workStealingQueue.LocalPop()) != null)
+                    {
+                        Debug.Assert(null != cb);
+                        workQueue.Enqueue(cb, forceGlobal: true);
+                    }
+                }
+
+                ThreadPoolWorkQueue.WorkStealingQueueList.Remove(workStealingQueue);
+            }
+        }
+
+        ~ThreadPoolWorkQueueThreadLocals()
+        {
+            // Since the purpose of calling CleanUp is to transfer any pending workitems into the global
+            // queue so that they will be executed by another thread, there's no point in doing this cleanup
+            // if we're in the process of shutting down or unloading the AD.  In those cases, the work won't
+            // execute anyway.  And there are subtle race conditions involved there that would lead us to do the wrong
+            // thing anyway.  So we'll only clean up if this is a "normal" finalization.
+            if (!(Environment.HasShutdownStarted || AppDomain.CurrentDomain.IsFinalizingForUnload()))
+                CleanUp();
+        }
+    }
+
+    internal sealed class RegisteredWaitHandleSafe : CriticalFinalizerObject
+    {
+        private static IntPtr InvalidHandle => Win32Native.INVALID_HANDLE_VALUE;
+        private IntPtr registeredWaitHandle = InvalidHandle;
+        private WaitHandle m_internalWaitObject;
+        private bool bReleaseNeeded = false;
+        private volatile int m_lock = 0;
+
+        internal IntPtr GetHandle() => registeredWaitHandle;
+
+        internal void SetHandle(IntPtr handle)
+        {
+            registeredWaitHandle = handle;
+        }
+
+        internal void SetWaitObject(WaitHandle waitObject)
+        {
+            // needed for DangerousAddRef
+            RuntimeHelpers.PrepareConstrainedRegions();
+
+            m_internalWaitObject = waitObject;
+            if (waitObject != null)
+            {
+                m_internalWaitObject.SafeWaitHandle.DangerousAddRef(ref bReleaseNeeded);
+            }
+        }
+
+        internal bool Unregister(
+             WaitHandle waitObject          // object to be notified when all callbacks to delegates have completed
+             )
+        {
+            bool result = false;
+            // needed for DangerousRelease
+            RuntimeHelpers.PrepareConstrainedRegions();
+
+            // lock(this) cannot be used reliably in Cer since thin lock could be
+            // promoted to syncblock and that is not a guaranteed operation
+            bool bLockTaken = false;
+            do
+            {
+                if (Interlocked.CompareExchange(ref m_lock, 1, 0) == 0)
+                {
+                    bLockTaken = true;
+                    try
+                    {
+                        if (ValidHandle())
+                        {
+                            result = UnregisterWaitNative(GetHandle(), waitObject == null ? null : waitObject.SafeWaitHandle);
+                            if (result == true)
+                            {
+                                if (bReleaseNeeded)
+                                {
+                                    m_internalWaitObject.SafeWaitHandle.DangerousRelease();
+                                    bReleaseNeeded = false;
+                                }
+                                // if result not true don't release/suppress here so finalizer can make another attempt
+                                SetHandle(InvalidHandle);
+                                m_internalWaitObject = null;
+                                GC.SuppressFinalize(this);
+                            }
+                        }
+                    }
+                    finally
+                    {
+                        m_lock = 0;
+                    }
+                }
+                Thread.SpinWait(1);     // yield to processor
+            }
+            while (!bLockTaken);
+
+            return result;
+        }
+
+        private bool ValidHandle() =>
+            registeredWaitHandle != InvalidHandle && registeredWaitHandle != IntPtr.Zero;
+
+        ~RegisteredWaitHandleSafe()
+        {
+            // if the app has already unregistered the wait, there is nothing to cleanup
+            // we can detect this by checking the handle. Normally, there is no race condition here
+            // so no need to protect reading of handle. However, if this object gets 
+            // resurrected and then someone does an unregister, it would introduce a race condition
+            //
+            // PrepareConstrainedRegions call not needed since finalizer already in Cer
+            //
+            // lock(this) cannot be used reliably even in Cer since thin lock could be
+            // promoted to syncblock and that is not a guaranteed operation
+            //
+            // Note that we will not "spin" to get this lock.  We make only a single attempt;
+            // if we can't get the lock, it means some other thread is in the middle of a call
+            // to Unregister, which will do the work of the finalizer anyway.
+            //
+            // Further, it's actually critical that we *not* wait for the lock here, because
+            // the other thread that's in the middle of Unregister may be suspended for shutdown.
+            // Then, during the live-object finalization phase of shutdown, this thread would
+            // end up spinning forever, as the other thread would never release the lock.
+            // This will result in a "leak" of sorts (since the handle will not be cleaned up)
+            // but the process is exiting anyway.
+            //
+            // During AD-unload, we don�t finalize live objects until all threads have been 
+            // aborted out of the AD.  Since these locked regions are CERs, we won�t abort them 
+            // while the lock is held.  So there should be no leak on AD-unload.
+            //
+            if (Interlocked.CompareExchange(ref m_lock, 1, 0) == 0)
+            {
+                try
+                {
+                    if (ValidHandle())
+                    {
+                        WaitHandleCleanupNative(registeredWaitHandle);
+                        if (bReleaseNeeded)
+                        {
+                            m_internalWaitObject.SafeWaitHandle.DangerousRelease();
+                            bReleaseNeeded = false;
+                        }
+                        SetHandle(InvalidHandle);
+                        m_internalWaitObject = null;
+                    }
+                }
+                finally
+                {
+                    m_lock = 0;
+                }
+            }
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void WaitHandleCleanupNative(IntPtr handle);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool UnregisterWaitNative(IntPtr handle, SafeHandle waitObject);
+    }
+
+    public sealed class RegisteredWaitHandle : MarshalByRefObject
+    {
+        private readonly RegisteredWaitHandleSafe internalRegisteredWait;
+
+        internal RegisteredWaitHandle()
+        {
+            internalRegisteredWait = new RegisteredWaitHandleSafe();
+        }
+
+        internal void SetHandle(IntPtr handle)
+        {
+            internalRegisteredWait.SetHandle(handle);
+        }
+
+        internal void SetWaitObject(WaitHandle waitObject)
+        {
+            internalRegisteredWait.SetWaitObject(waitObject);
+        }
+
+        // This is the only public method on this class
+        public bool Unregister(
+             WaitHandle waitObject          // object to be notified when all callbacks to delegates have completed
+             )
+        {
+            return internalRegisteredWait.Unregister(waitObject);
+        }
+    }
+
+    public delegate void WaitCallback(Object state);
+
+    public delegate void WaitOrTimerCallback(Object state, bool timedOut);  // signaled or timed out
+
+    //
+    // This type is necessary because VS 2010's debugger looks for a method named _ThreadPoolWaitCallbacck.PerformWaitCallback
+    // on the stack to determine if a thread is a ThreadPool thread or not.  We have a better way to do this for .NET 4.5, but
+    // still need to maintain compatibility with VS 2010.  When compat with VS 2010 is no longer an issue, this type may be
+    // removed.
+    //
+    internal static class _ThreadPoolWaitCallback
+    {
+        internal static bool PerformWaitCallback() => ThreadPoolWorkQueue.Dispatch();
+    }
+
+    //
+    // Interface to something that can be queued to the TP.  This is implemented by 
+    // QueueUserWorkItemCallback, Task, and potentially other internal types.
+    // For example, SemaphoreSlim represents callbacks using its own type that
+    // implements IThreadPoolWorkItem.
+    //
+    // If we decide to expose some of the workstealing
+    // stuff, this is NOT the thing we want to expose to the public.
+    //
+    internal interface IThreadPoolWorkItem
+    {
+        void ExecuteWorkItem();
+        void MarkAborted(ThreadAbortException tae);
+    }
+
+    internal abstract class QueueUserWorkItemCallbackBase : IThreadPoolWorkItem
+    {
+#if DEBUG
+        private volatile int executed;
+
+        ~QueueUserWorkItemCallbackBase()
+        {
+            Debug.Assert(
+                executed != 0 || Environment.HasShutdownStarted || AppDomain.CurrentDomain.IsFinalizingForUnload(),
+                "A QueueUserWorkItemCallback was never called!");
+        }
+
+        protected void MarkExecuted(bool aborted)
+        {
+            GC.SuppressFinalize(this);
+            Debug.Assert(
+                0 == Interlocked.Exchange(ref executed, 1) || aborted,
+                "A QueueUserWorkItemCallback was called twice!");
+        }
+#endif
+
+        void IThreadPoolWorkItem.MarkAborted(ThreadAbortException tae)
+        {
+#if DEBUG
+            // This workitem didn't execute because we got a ThreadAbortException prior to the call to ExecuteWorkItem.
+            // This counts as being executed for our purposes.
+            MarkExecuted(aborted: true);
+#endif
+        }
+
+        public virtual void ExecuteWorkItem()
+        {
+#if DEBUG
+            MarkExecuted(aborted: false);
+#endif
+        }
+    }
+
+    internal sealed class QueueUserWorkItemCallback : QueueUserWorkItemCallbackBase
+    {
+        private WaitCallback _callback;
+        private readonly object _state;
+        private readonly ExecutionContext _context;
+
+        internal static readonly ContextCallback s_executionContextShim = state =>
+        {
+            var obj = (QueueUserWorkItemCallback)state;
+            WaitCallback c = obj._callback;
+            Debug.Assert(c != null);
+            obj._callback = null;
+            c(obj._state);
+        };
+
+        internal QueueUserWorkItemCallback(WaitCallback callback, object state, ExecutionContext context)
+        {
+            _callback = callback;
+            _state = state;
+            _context = context;
+        }
+
+        public override void ExecuteWorkItem()
+        {
+            base.ExecuteWorkItem();
+            ExecutionContext context = _context;
+            if (context == null)
+            {
+                WaitCallback c = _callback;
+                _callback = null;
+                c(_state);
+            }
+            else
+            {
+                ExecutionContext.RunInternal(context, s_executionContextShim, this);
+            }
+        }
+    }
+
+    internal sealed class QueueUserWorkItemCallback<TState> : QueueUserWorkItemCallbackBase
+    {
+        private Action<TState> _callback;
+        private readonly TState _state;
+        private readonly ExecutionContext _context;
+
+        internal static readonly ContextCallback s_executionContextShim = state =>
+        {
+            var obj = (QueueUserWorkItemCallback<TState>)state;
+            Action<TState> c = obj._callback;
+            Debug.Assert(c != null);
+            obj._callback = null;
+            c(obj._state);
+        };
+
+        internal QueueUserWorkItemCallback(Action<TState> callback, TState state, ExecutionContext context)
+        {
+            _callback = callback;
+            _state = state;
+            _context = context;
+        }
+
+        public override void ExecuteWorkItem()
+        {
+            base.ExecuteWorkItem();
+            ExecutionContext context = _context;
+            if (context == null)
+            {
+                Action<TState> c = _callback;
+                _callback = null;
+                c(_state);
+            }
+            else
+            {
+                ExecutionContext.RunInternal(context, s_executionContextShim, this);
+            }
+        }
+    }
+
+    internal sealed class QueueUserWorkItemCallbackDefaultContext : QueueUserWorkItemCallbackBase
+    {
+        private WaitCallback _callback;
+        private readonly object _state;
+
+        internal static readonly ContextCallback s_executionContextShim = state =>
+        {
+            var obj = (QueueUserWorkItemCallbackDefaultContext)state;
+            WaitCallback c = obj._callback;
+            Debug.Assert(c != null);
+            obj._callback = null;
+            c(obj._state);
+        };
+
+        internal QueueUserWorkItemCallbackDefaultContext(WaitCallback callback, object state)
+        {
+            _callback = callback;
+            _state = state;
+        }
+
+        public override void ExecuteWorkItem()
+        {
+            base.ExecuteWorkItem();
+            ExecutionContext.RunInternal(executionContext: null, s_executionContextShim, this); // null executionContext on RunInternal is Default context
+        }
+    }
+
+    internal sealed class QueueUserWorkItemCallbackDefaultContext<TState> : QueueUserWorkItemCallbackBase
+    {
+        private Action<TState> _callback;
+        private readonly TState _state;
+
+        internal static readonly ContextCallback s_executionContextShim = state =>
+        {
+            var obj = (QueueUserWorkItemCallbackDefaultContext<TState>)state;
+            Action<TState> c = obj._callback;
+            Debug.Assert(c != null);
+            obj._callback = null;
+            c(obj._state);
+        };
+
+        internal QueueUserWorkItemCallbackDefaultContext(Action<TState> callback, TState state)
+        {
+            _callback = callback;
+            _state = state;
+        }
+
+        public override void ExecuteWorkItem()
+        {
+            base.ExecuteWorkItem();
+            ExecutionContext.RunInternal(executionContext: null, s_executionContextShim, this); // null executionContext on RunInternal is Default context
+        }
+    }
+
+    internal class _ThreadPoolWaitOrTimerCallback
+    {
+        private WaitOrTimerCallback _waitOrTimerCallback;
+        private ExecutionContext _executionContext;
+        private Object _state;
+        private static readonly ContextCallback _ccbt = new ContextCallback(WaitOrTimerCallback_Context_t);
+        private static readonly ContextCallback _ccbf = new ContextCallback(WaitOrTimerCallback_Context_f);
+
+        internal _ThreadPoolWaitOrTimerCallback(WaitOrTimerCallback waitOrTimerCallback, Object state, bool compressStack)
+        {
+            _waitOrTimerCallback = waitOrTimerCallback;
+            _state = state;
+
+            if (compressStack)
+            {
+                // capture the exection context
+                _executionContext = ExecutionContext.Capture();
+            }
+        }
+
+        private static void WaitOrTimerCallback_Context_t(Object state) =>
+            WaitOrTimerCallback_Context(state, timedOut: true);
+
+        private static void WaitOrTimerCallback_Context_f(Object state) =>
+            WaitOrTimerCallback_Context(state, timedOut: false);
+
+        private static void WaitOrTimerCallback_Context(Object state, bool timedOut)
+        {
+            _ThreadPoolWaitOrTimerCallback helper = (_ThreadPoolWaitOrTimerCallback)state;
+            helper._waitOrTimerCallback(helper._state, timedOut);
+        }
+
+        // call back helper
+        internal static void PerformWaitOrTimerCallback(Object state, bool timedOut)
+        {
+            _ThreadPoolWaitOrTimerCallback helper = (_ThreadPoolWaitOrTimerCallback)state;
+            Debug.Assert(helper != null, "Null state passed to PerformWaitOrTimerCallback!");
+            // call directly if it is an unsafe call OR EC flow is suppressed
+            ExecutionContext context = helper._executionContext;
+            if (context == null)
+            {
+                WaitOrTimerCallback callback = helper._waitOrTimerCallback;
+                callback(helper._state, timedOut);
+            }
+            else
+            {
+                ExecutionContext.Run(context, timedOut ? _ccbt : _ccbf, helper);
+            }
+        }
+    }
+
+    [CLSCompliant(false)]
+    public unsafe delegate void IOCompletionCallback(uint errorCode, // Error code
+                                       uint numBytes, // No. of bytes transferred 
+                                       NativeOverlapped* pOVERLAP // ptr to OVERLAP structure
+                                       );
+
+    public static class ThreadPool
+    {
+        public static bool SetMaxThreads(int workerThreads, int completionPortThreads)
+        {
+            return SetMaxThreadsNative(workerThreads, completionPortThreads);
+        }
+
+        public static void GetMaxThreads(out int workerThreads, out int completionPortThreads)
+        {
+            GetMaxThreadsNative(out workerThreads, out completionPortThreads);
+        }
+
+        public static bool SetMinThreads(int workerThreads, int completionPortThreads)
+        {
+            return SetMinThreadsNative(workerThreads, completionPortThreads);
+        }
+
+        public static void GetMinThreads(out int workerThreads, out int completionPortThreads)
+        {
+            GetMinThreadsNative(out workerThreads, out completionPortThreads);
+        }
+
+        public static void GetAvailableThreads(out int workerThreads, out int completionPortThreads)
+        {
+            GetAvailableThreadsNative(out workerThreads, out completionPortThreads);
+        }
+
+        [CLSCompliant(false)]
+        public static RegisteredWaitHandle RegisterWaitForSingleObject(  // throws RegisterWaitException
+             WaitHandle waitObject,
+             WaitOrTimerCallback callBack,
+             Object state,
+             uint millisecondsTimeOutInterval,
+             bool executeOnlyOnce    // NOTE: we do not allow other options that allow the callback to be queued as an APC
+             )
+        {
+            return RegisterWaitForSingleObject(waitObject, callBack, state, millisecondsTimeOutInterval, executeOnlyOnce, true);
+        }
+
+        [CLSCompliant(false)]
+        public static RegisteredWaitHandle UnsafeRegisterWaitForSingleObject(  // throws RegisterWaitException
+             WaitHandle waitObject,
+             WaitOrTimerCallback callBack,
+             Object state,
+             uint millisecondsTimeOutInterval,
+             bool executeOnlyOnce    // NOTE: we do not allow other options that allow the callback to be queued as an APC
+             )
+        {
+            return RegisterWaitForSingleObject(waitObject, callBack, state, millisecondsTimeOutInterval, executeOnlyOnce, false);
+        }
+
+
+        private static RegisteredWaitHandle RegisterWaitForSingleObject(  // throws RegisterWaitException
+             WaitHandle waitObject,
+             WaitOrTimerCallback callBack,
+             Object state,
+             uint millisecondsTimeOutInterval,
+             bool executeOnlyOnce,   // NOTE: we do not allow other options that allow the callback to be queued as an APC
+             bool compressStack
+             )
+        {
+            RegisteredWaitHandle registeredWaitHandle = new RegisteredWaitHandle();
+
+            if (callBack != null)
+            {
+                _ThreadPoolWaitOrTimerCallback callBackHelper = new _ThreadPoolWaitOrTimerCallback(callBack, state, compressStack);
+                state = (Object)callBackHelper;
+                // call SetWaitObject before native call so that waitObject won't be closed before threadpoolmgr registration
+                // this could occur if callback were to fire before SetWaitObject does its addref
+                registeredWaitHandle.SetWaitObject(waitObject);
+                IntPtr nativeRegisteredWaitHandle = RegisterWaitForSingleObjectNative(waitObject,
+                                                                               state,
+                                                                               millisecondsTimeOutInterval,
+                                                                               executeOnlyOnce,
+                                                                               registeredWaitHandle);
+                registeredWaitHandle.SetHandle(nativeRegisteredWaitHandle);
+            }
+            else
+            {
+                throw new ArgumentNullException(nameof(WaitOrTimerCallback));
+            }
+            return registeredWaitHandle;
+        }
+
+
+        public static RegisteredWaitHandle RegisterWaitForSingleObject(  // throws RegisterWaitException
+             WaitHandle waitObject,
+             WaitOrTimerCallback callBack,
+             Object state,
+             int millisecondsTimeOutInterval,
+             bool executeOnlyOnce    // NOTE: we do not allow other options that allow the callback to be queued as an APC
+             )
+        {
+            if (millisecondsTimeOutInterval < -1)
+                throw new ArgumentOutOfRangeException(nameof(millisecondsTimeOutInterval), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            return RegisterWaitForSingleObject(waitObject, callBack, state, (UInt32)millisecondsTimeOutInterval, executeOnlyOnce, true);
+        }
+
+        public static RegisteredWaitHandle UnsafeRegisterWaitForSingleObject(  // throws RegisterWaitException
+             WaitHandle waitObject,
+             WaitOrTimerCallback callBack,
+             Object state,
+             int millisecondsTimeOutInterval,
+             bool executeOnlyOnce    // NOTE: we do not allow other options that allow the callback to be queued as an APC
+             )
+        {
+            if (millisecondsTimeOutInterval < -1)
+                throw new ArgumentOutOfRangeException(nameof(millisecondsTimeOutInterval), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            return RegisterWaitForSingleObject(waitObject, callBack, state, (UInt32)millisecondsTimeOutInterval, executeOnlyOnce, false);
+        }
+
+        public static RegisteredWaitHandle RegisterWaitForSingleObject(  // throws RegisterWaitException
+            WaitHandle waitObject,
+            WaitOrTimerCallback callBack,
+            Object state,
+            long millisecondsTimeOutInterval,
+            bool executeOnlyOnce    // NOTE: we do not allow other options that allow the callback to be queued as an APC
+        )
+        {
+            if (millisecondsTimeOutInterval < -1)
+                throw new ArgumentOutOfRangeException(nameof(millisecondsTimeOutInterval), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            return RegisterWaitForSingleObject(waitObject, callBack, state, (UInt32)millisecondsTimeOutInterval, executeOnlyOnce, true);
+        }
+
+        public static RegisteredWaitHandle UnsafeRegisterWaitForSingleObject(  // throws RegisterWaitException
+            WaitHandle waitObject,
+            WaitOrTimerCallback callBack,
+            Object state,
+            long millisecondsTimeOutInterval,
+            bool executeOnlyOnce    // NOTE: we do not allow other options that allow the callback to be queued as an APC
+        )
+        {
+            if (millisecondsTimeOutInterval < -1)
+                throw new ArgumentOutOfRangeException(nameof(millisecondsTimeOutInterval), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            return RegisterWaitForSingleObject(waitObject, callBack, state, (UInt32)millisecondsTimeOutInterval, executeOnlyOnce, false);
+        }
+
+        public static RegisteredWaitHandle RegisterWaitForSingleObject(
+                          WaitHandle waitObject,
+                          WaitOrTimerCallback callBack,
+                          Object state,
+                          TimeSpan timeout,
+                          bool executeOnlyOnce
+                          )
+        {
+            long tm = (long)timeout.TotalMilliseconds;
+            if (tm < -1)
+                throw new ArgumentOutOfRangeException(nameof(timeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            if (tm > (long)Int32.MaxValue)
+                throw new ArgumentOutOfRangeException(nameof(timeout), SR.ArgumentOutOfRange_LessEqualToIntegerMaxVal);
+            return RegisterWaitForSingleObject(waitObject, callBack, state, (UInt32)tm, executeOnlyOnce, true);
+        }
+
+        public static RegisteredWaitHandle UnsafeRegisterWaitForSingleObject(
+                          WaitHandle waitObject,
+                          WaitOrTimerCallback callBack,
+                          Object state,
+                          TimeSpan timeout,
+                          bool executeOnlyOnce
+                          )
+        {
+            long tm = (long)timeout.TotalMilliseconds;
+            if (tm < -1)
+                throw new ArgumentOutOfRangeException(nameof(timeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            if (tm > (long)Int32.MaxValue)
+                throw new ArgumentOutOfRangeException(nameof(timeout), SR.ArgumentOutOfRange_LessEqualToIntegerMaxVal);
+            return RegisterWaitForSingleObject(waitObject, callBack, state, (UInt32)tm, executeOnlyOnce, false);
+        }
+
+        public static bool QueueUserWorkItem(WaitCallback callBack) =>
+            QueueUserWorkItem(callBack, null);
+
+        public static bool QueueUserWorkItem(WaitCallback callBack, object state)
+        {
+            if (callBack == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.callBack);
+            }
+
+            EnsureVMInitialized();
+
+            ExecutionContext context = ExecutionContext.Capture();
+
+            IThreadPoolWorkItem tpcallBack = (context != null && context.IsDefault) ?
+                new QueueUserWorkItemCallbackDefaultContext(callBack, state) :
+                (IThreadPoolWorkItem)new QueueUserWorkItemCallback(callBack, state, context);
+
+            ThreadPoolGlobals.workQueue.Enqueue(tpcallBack, forceGlobal: true);
+
+            return true;
+        }
+
+        public static bool QueueUserWorkItem<TState>(Action<TState> callBack, TState state, bool preferLocal)
+        {
+            if (callBack == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.callBack);
+            }
+
+            EnsureVMInitialized();
+
+            ExecutionContext context = ExecutionContext.Capture();
+
+            IThreadPoolWorkItem tpcallBack = (context != null && context.IsDefault) ?
+                new QueueUserWorkItemCallbackDefaultContext<TState>(callBack, state) :
+                (IThreadPoolWorkItem)new QueueUserWorkItemCallback<TState>(callBack, state, context);
+
+            ThreadPoolGlobals.workQueue.Enqueue(tpcallBack, forceGlobal: !preferLocal);
+
+            return true;
+        }
+
+        public static bool UnsafeQueueUserWorkItem(WaitCallback callBack, Object state)
+        {
+            if (callBack == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.callBack);
+            }
+
+            EnsureVMInitialized();
+
+            IThreadPoolWorkItem tpcallBack = new QueueUserWorkItemCallback(callBack, state, null);
+
+            ThreadPoolGlobals.workQueue.Enqueue(tpcallBack, forceGlobal: true);
+
+            return true;
+        }
+
+        internal static void UnsafeQueueCustomWorkItem(IThreadPoolWorkItem workItem, bool forceGlobal)
+        {
+            Debug.Assert(null != workItem);
+            EnsureVMInitialized();
+            ThreadPoolGlobals.workQueue.Enqueue(workItem, forceGlobal);
+        }
+
+        // This method tries to take the target callback out of the current thread's queue.
+        internal static bool TryPopCustomWorkItem(IThreadPoolWorkItem workItem)
+        {
+            Debug.Assert(null != workItem);
+            return
+                ThreadPoolGlobals.vmTpInitialized && // if not initialized, so there's no way this workitem was ever queued.
+                ThreadPoolGlobals.workQueue.LocalFindAndPop(workItem);
+        }
+
+        // Get all workitems.  Called by TaskScheduler in its debugger hooks.
+        internal static IEnumerable<IThreadPoolWorkItem> GetQueuedWorkItems()
+        {
+            // Enumerate global queue
+            foreach (IThreadPoolWorkItem workItem in ThreadPoolGlobals.workQueue.workItems)
+            {
+                yield return workItem;
+            }
+
+            // Enumerate each local queue
+            foreach (ThreadPoolWorkQueue.WorkStealingQueue wsq in ThreadPoolWorkQueue.WorkStealingQueueList.Queues)
+            {
+                if (wsq != null && wsq.m_array != null)
+                {
+                    IThreadPoolWorkItem[] items = wsq.m_array;
+                    for (int i = 0; i < items.Length; i++)
+                    {
+                        IThreadPoolWorkItem item = items[i];
+                        if (item != null)
+                        {
+                            yield return item;
+                        }
+                    }
+                }
+            }
+        }
+
+        internal static IEnumerable<IThreadPoolWorkItem> GetLocallyQueuedWorkItems()
+        {
+            ThreadPoolWorkQueue.WorkStealingQueue wsq = ThreadPoolWorkQueueThreadLocals.threadLocals.workStealingQueue;
+            if (wsq != null && wsq.m_array != null)
+            {
+                IThreadPoolWorkItem[] items = wsq.m_array;
+                for (int i = 0; i < items.Length; i++)
+                {
+                    IThreadPoolWorkItem item = items[i];
+                    if (item != null)
+                        yield return item;
+                }
+            }
+        }
+
+        internal static IEnumerable<IThreadPoolWorkItem> GetGloballyQueuedWorkItems() => ThreadPoolGlobals.workQueue.workItems;
+
+        private static object[] ToObjectArray(IEnumerable<IThreadPoolWorkItem> workitems)
+        {
+            int i = 0;
+            foreach (IThreadPoolWorkItem item in workitems)
+            {
+                i++;
+            }
+
+            object[] result = new object[i];
+            i = 0;
+            foreach (IThreadPoolWorkItem item in workitems)
+            {
+                if (i < result.Length) //just in case someone calls us while the queues are in motion
+                    result[i] = item;
+                i++;
+            }
+
+            return result;
+        }
+
+        // This is the method the debugger will actually call, if it ends up calling
+        // into ThreadPool directly.  Tests can use this to simulate a debugger, as well.
+        internal static object[] GetQueuedWorkItemsForDebugger() =>
+            ToObjectArray(GetQueuedWorkItems());
+
+        internal static object[] GetGloballyQueuedWorkItemsForDebugger() =>
+            ToObjectArray(GetGloballyQueuedWorkItems());
+
+        internal static object[] GetLocallyQueuedWorkItemsForDebugger() =>
+            ToObjectArray(GetLocallyQueuedWorkItems());
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        internal static extern bool RequestWorkerThread();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern unsafe bool PostQueuedCompletionStatus(NativeOverlapped* overlapped);
+
+        [CLSCompliant(false)]
+        public static unsafe bool UnsafeQueueNativeOverlapped(NativeOverlapped* overlapped) =>
+            PostQueuedCompletionStatus(overlapped);
+
+        // The thread pool maintains a per-appdomain managed work queue.
+        // New thread pool entries are added in the managed queue.
+        // The VM is responsible for the actual growing/shrinking of 
+        // threads. 
+        private static void EnsureVMInitialized()
+        {
+            if (!ThreadPoolGlobals.vmTpInitialized)
+            {
+                EnsureVMInitializedCore(); // separate out to help with inlining
+            }
+        }
+
+        private static void EnsureVMInitializedCore()
+        {
+            ThreadPool.InitializeVMTp(ref ThreadPoolGlobals.enableWorkerTracking);
+            ThreadPoolGlobals.vmTpInitialized = true;
+        }
+
+        // Native methods: 
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool SetMinThreadsNative(int workerThreads, int completionPortThreads);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool SetMaxThreadsNative(int workerThreads, int completionPortThreads);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void GetMinThreadsNative(out int workerThreads, out int completionPortThreads);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void GetMaxThreadsNative(out int workerThreads, out int completionPortThreads);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern void GetAvailableThreadsNative(out int workerThreads, out int completionPortThreads);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool NotifyWorkItemComplete();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ReportThreadStatus(bool isWorking);
+
+        internal static void NotifyWorkItemProgress()
+        {
+            if (!ThreadPoolGlobals.vmTpInitialized)
+                ThreadPool.InitializeVMTp(ref ThreadPoolGlobals.enableWorkerTracking);
+            NotifyWorkItemProgressNative();
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void NotifyWorkItemProgressNative();
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void InitializeVMTp(ref bool enableWorkerTracking);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern IntPtr RegisterWaitForSingleObjectNative(
+             WaitHandle waitHandle,
+             Object state,
+             uint timeOutInterval,
+             bool executeOnlyOnce,
+             RegisteredWaitHandle registeredWaitHandle
+             );
+
+
+        [Obsolete("ThreadPool.BindHandle(IntPtr) has been deprecated.  Please use ThreadPool.BindHandle(SafeHandle) instead.", false)]
+        public static bool BindHandle(IntPtr osHandle)
+        {
+            return BindIOCompletionCallbackNative(osHandle);
+        }
+
+        public static bool BindHandle(SafeHandle osHandle)
+        {
+            if (osHandle == null)
+                throw new ArgumentNullException(nameof(osHandle));
+
+            bool ret = false;
+            bool mustReleaseSafeHandle = false;
+            RuntimeHelpers.PrepareConstrainedRegions();
+            try
+            {
+                osHandle.DangerousAddRef(ref mustReleaseSafeHandle);
+                ret = BindIOCompletionCallbackNative(osHandle.DangerousGetHandle());
+            }
+            finally
+            {
+                if (mustReleaseSafeHandle)
+                    osHandle.DangerousRelease();
+            }
+            return ret;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool BindIOCompletionCallbackNative(IntPtr fileHandle);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Timer.cs b/src/System.Private.CoreLib/src/System/Threading/Timer.cs
new file mode 100644
index 0000000000..a58c2883bf
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Timer.cs
@@ -0,0 +1,804 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Security;
+using Microsoft.Win32;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.ConstrainedExecution;
+using System.Runtime.Versioning;
+using System.Diagnostics;
+using System.Diagnostics.Tracing;
+using Microsoft.Win32.SafeHandles;
+
+using Internal.Runtime.Augments;
+
+namespace System.Threading
+{
+    public delegate void TimerCallback(Object state);
+
+    //
+    // TimerQueue maintains a list of active timers in this AppDomain.  We use a single native timer, supplied by the VM,
+    // to schedule all managed timers in the AppDomain.
+    //
+    // Perf assumptions:  We assume that timers are created and destroyed frequently, but rarely actually fire.
+    // There are roughly two types of timer:
+    //
+    //  - timeouts for operations.  These are created and destroyed very frequently, but almost never fire, because
+    //    the whole point is that the timer only fires if something has gone wrong.
+    //
+    //  - scheduled background tasks.  These typically do fire, but they usually have quite long durations.
+    //    So the impact of spending a few extra cycles to fire these is negligible.
+    //
+    // Because of this, we want to choose a data structure with very fast insert and delete times, but we can live
+    // with linear traversal times when firing timers.
+    //
+    // The data structure we've chosen is an unordered doubly-linked list of active timers.  This gives O(1) insertion
+    // and removal, and O(N) traversal when finding expired timers.
+    //
+    // Note that all instance methods of this class require that the caller hold a lock on the TimerQueue instance.
+    //
+    internal class TimerQueue
+    {
+        #region Shared TimerQueue instances
+
+        public static TimerQueue[] Instances { get; } = CreateTimerQueues();
+
+        private TimerQueue(int id)
+        {
+            m_id = id;
+        }
+
+        private static TimerQueue[] CreateTimerQueues()
+        {
+            var queues = new TimerQueue[Environment.ProcessorCount];
+            for (int i = 0; i < queues.Length; i++)
+            {
+                queues[i] = new TimerQueue(i);
+            }
+            return queues;
+        }
+
+        #endregion
+
+        #region interface to native per-AppDomain timer
+
+        //
+        // We need to keep our notion of time synchronized with the calls to SleepEx that drive
+        // the underlying native timer.  In Win8, SleepEx does not count the time the machine spends
+        // sleeping/hibernating.  Environment.TickCount (GetTickCount) *does* count that time,
+        // so we will get out of sync with SleepEx if we use that method.
+        //
+        // So, on Win8, we use QueryUnbiasedInterruptTime instead; this does not count time spent
+        // in sleep/hibernate mode.
+        //
+        private static int TickCount
+        {
+            get
+            {
+#if !FEATURE_PAL
+                if (Environment.IsWindows8OrAbove)
+                {
+                    ulong time100ns;
+
+                    bool result = Win32Native.QueryUnbiasedInterruptTime(out time100ns);
+                    if (!result)
+                        throw Marshal.GetExceptionForHR(Marshal.GetLastWin32Error());
+
+                    // convert to 100ns to milliseconds, and truncate to 32 bits.
+                    return (int)(uint)(time100ns / 10000);
+                }
+                else
+#endif
+                {
+                    return Environment.TickCount;
+                }
+            }
+        }
+
+        //
+        // We use a SafeHandle to ensure that the native timer is destroyed when the AppDomain is unloaded.
+        //
+        private class AppDomainTimerSafeHandle : SafeHandleZeroOrMinusOneIsInvalid
+        {
+            public AppDomainTimerSafeHandle()
+                : base(true)
+            {
+            }
+
+            protected override bool ReleaseHandle()
+            {
+                return DeleteAppDomainTimer(handle);
+            }
+        }
+
+        private readonly int m_id; // TimerQueues[m_id] == this
+        private AppDomainTimerSafeHandle m_appDomainTimer;
+
+        private bool m_isAppDomainTimerScheduled;
+        private int m_currentAppDomainTimerStartTicks;
+        private uint m_currentAppDomainTimerDuration;
+
+        private bool EnsureAppDomainTimerFiresBy(uint requestedDuration)
+        {
+            //
+            // The VM's timer implementation does not work well for very long-duration timers.
+            // See kb 950807.
+            // So we'll limit our native timer duration to a "small" value.
+            // This may cause us to attempt to fire timers early, but that's ok - 
+            // we'll just see that none of our timers has actually reached its due time,
+            // and schedule the native timer again.
+            //
+            const uint maxPossibleDuration = 0x0fffffff;
+            uint actualDuration = Math.Min(requestedDuration, maxPossibleDuration);
+
+            if (m_isAppDomainTimerScheduled)
+            {
+                uint elapsed = (uint)(TickCount - m_currentAppDomainTimerStartTicks);
+                if (elapsed >= m_currentAppDomainTimerDuration)
+                    return true; //the timer's about to fire
+
+                uint remainingDuration = m_currentAppDomainTimerDuration - elapsed;
+                if (actualDuration >= remainingDuration)
+                    return true; //the timer will fire earlier than this request
+            }
+
+            // If Pause is underway then do not schedule the timers
+            // A later update during resume will re-schedule
+            if (m_pauseTicks != 0)
+            {
+                Debug.Assert(!m_isAppDomainTimerScheduled);
+                Debug.Assert(m_appDomainTimer == null);
+                return true;
+            }
+
+            if (m_appDomainTimer == null || m_appDomainTimer.IsInvalid)
+            {
+                Debug.Assert(!m_isAppDomainTimerScheduled);
+                Debug.Assert(m_id >= 0 && m_id < Instances.Length && this == Instances[m_id]);
+
+                m_appDomainTimer = CreateAppDomainTimer(actualDuration, m_id);
+                if (!m_appDomainTimer.IsInvalid)
+                {
+                    m_isAppDomainTimerScheduled = true;
+                    m_currentAppDomainTimerStartTicks = TickCount;
+                    m_currentAppDomainTimerDuration = actualDuration;
+                    return true;
+                }
+                else
+                {
+                    return false;
+                }
+            }
+            else
+            {
+                if (ChangeAppDomainTimer(m_appDomainTimer, actualDuration))
+                {
+                    m_isAppDomainTimerScheduled = true;
+                    m_currentAppDomainTimerStartTicks = TickCount;
+                    m_currentAppDomainTimerDuration = actualDuration;
+                    return true;
+                }
+                else
+                {
+                    return false;
+                }
+            }
+        }
+
+        //
+        // The VM calls this when a native timer fires.
+        //
+        internal static void AppDomainTimerCallback(int id)
+        {
+            Debug.Assert(id >= 0 && id < Instances.Length && Instances[id].m_id == id);
+            Instances[id].FireNextTimers();
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern AppDomainTimerSafeHandle CreateAppDomainTimer(uint dueTime, int id);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern bool ChangeAppDomainTimer(AppDomainTimerSafeHandle handle, uint dueTime);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern bool DeleteAppDomainTimer(IntPtr handle);
+
+        #endregion
+
+        #region Firing timers
+
+        //
+        // The list of timers
+        //
+        private TimerQueueTimer m_timers;
+
+
+        private volatile int m_pauseTicks = 0; // Time when Pause was called
+
+
+        //
+        // Fire any timers that have expired, and update the native timer to schedule the rest of them.
+        // We're in a thread pool work item here, and if there are multiple timers to be fired, we want
+        // to queue all but the first one.  The first may can then be invoked synchronously or queued,
+        // a task left up to our caller, which might be firing timers from multiple queues.
+        //
+        private void FireNextTimers()
+        {
+            //
+            // we fire the first timer on this thread; any other timers that might have fired are queued
+            // to the ThreadPool.
+            //
+            TimerQueueTimer timerToFireOnThisThread = null;
+
+            lock (this)
+            {
+                // prevent ThreadAbort while updating state
+                try { }
+                finally
+                {
+                    //
+                    // since we got here, that means our previous timer has fired.
+                    //
+                    m_isAppDomainTimerScheduled = false;
+                    bool haveTimerToSchedule = false;
+                    uint nextAppDomainTimerDuration = uint.MaxValue;
+
+                    int nowTicks = TickCount;
+
+                    //
+                    // Sweep through all timers.  The ones that have reached their due time
+                    // will fire.  We will calculate the next native timer due time from the
+                    // other timers.
+                    //
+                    TimerQueueTimer timer = m_timers;
+                    while (timer != null)
+                    {
+                        Debug.Assert(timer.m_dueTime != Timeout.UnsignedInfinite);
+
+                        uint elapsed = (uint)(nowTicks - timer.m_startTicks);
+                        if (elapsed >= timer.m_dueTime)
+                        {
+                            //
+                            // Remember the next timer in case we delete this one
+                            //
+                            TimerQueueTimer nextTimer = timer.m_next;
+
+                            if (timer.m_period != Timeout.UnsignedInfinite)
+                            {
+                                timer.m_startTicks = nowTicks;
+                                uint elapsedForNextDueTime = elapsed - timer.m_dueTime;
+                                if (elapsedForNextDueTime < timer.m_period)
+                                {
+                                    // Discount the extra amount of time that has elapsed since the previous firing time to
+                                    // prevent timer ticks from drifting
+                                    timer.m_dueTime = timer.m_period - elapsedForNextDueTime;
+                                }
+                                else
+                                {
+                                    // Enough time has elapsed to fire the timer yet again. The timer is not able to keep up
+                                    // with the short period, have it fire 1 ms from now to avoid spinning without a delay.
+                                    timer.m_dueTime = 1;
+                                }
+
+                                //
+                                // This is a repeating timer; schedule it to run again.
+                                //
+                                if (timer.m_dueTime < nextAppDomainTimerDuration)
+                                {
+                                    haveTimerToSchedule = true;
+                                    nextAppDomainTimerDuration = timer.m_dueTime;
+                                }
+                            }
+                            else
+                            {
+                                //
+                                // Not repeating; remove it from the queue
+                                //
+                                DeleteTimer(timer);
+                            }
+
+                            //
+                            // If this is the first timer, we'll fire it on this thread.  Otherwise, queue it
+                            // to the ThreadPool.
+                            //
+                            if (timerToFireOnThisThread == null)
+                                timerToFireOnThisThread = timer;
+                            else
+                                QueueTimerCompletion(timer);
+
+                            timer = nextTimer;
+                        }
+                        else
+                        {
+                            //
+                            // This timer hasn't fired yet.  Just update the next time the native timer fires.
+                            //
+                            uint remaining = timer.m_dueTime - elapsed;
+                            if (remaining < nextAppDomainTimerDuration)
+                            {
+                                haveTimerToSchedule = true;
+                                nextAppDomainTimerDuration = remaining;
+                            }
+                            timer = timer.m_next;
+                        }
+                    }
+
+                    if (haveTimerToSchedule)
+                        EnsureAppDomainTimerFiresBy(nextAppDomainTimerDuration);
+                }
+            }
+
+            //
+            // Fire the user timer outside of the lock!
+            //
+            if (timerToFireOnThisThread != null)
+                timerToFireOnThisThread.Fire();
+        }
+
+        private static void QueueTimerCompletion(TimerQueueTimer timer)
+        {
+            // Can use "unsafe" variant because we take care of capturing and restoring the ExecutionContext.
+            ThreadPool.UnsafeQueueCustomWorkItem(timer, forceGlobal: true);
+        }
+
+        #endregion
+
+        #region Queue implementation
+
+        public bool UpdateTimer(TimerQueueTimer timer, uint dueTime, uint period)
+        {
+            if (timer.m_dueTime == Timeout.UnsignedInfinite)
+            {
+                // the timer is not in the list; add it (as the head of the list).
+                timer.m_next = m_timers;
+                timer.m_prev = null;
+                if (timer.m_next != null)
+                    timer.m_next.m_prev = timer;
+                m_timers = timer;
+            }
+            timer.m_dueTime = dueTime;
+            timer.m_period = (period == 0) ? Timeout.UnsignedInfinite : period;
+            timer.m_startTicks = TickCount;
+            return EnsureAppDomainTimerFiresBy(dueTime);
+        }
+
+        public void DeleteTimer(TimerQueueTimer timer)
+        {
+            if (timer.m_dueTime != Timeout.UnsignedInfinite)
+            {
+                if (timer.m_next != null)
+                    timer.m_next.m_prev = timer.m_prev;
+                if (timer.m_prev != null)
+                    timer.m_prev.m_next = timer.m_next;
+                if (m_timers == timer)
+                    m_timers = timer.m_next;
+
+                timer.m_dueTime = Timeout.UnsignedInfinite;
+                timer.m_period = Timeout.UnsignedInfinite;
+                timer.m_startTicks = 0;
+                timer.m_prev = null;
+                timer.m_next = null;
+            }
+        }
+
+        #endregion
+    }
+
+    //
+    // A timer in our TimerQueue.
+    //
+    internal sealed class TimerQueueTimer : IThreadPoolWorkItem
+    {
+        //
+        // The associated timer queue.
+        //
+        private readonly TimerQueue m_associatedTimerQueue;
+
+        //
+        // All fields of this class are protected by a lock on TimerQueue.Instance.
+        //
+        // The first four fields are maintained by TimerQueue itself.
+        //
+        internal TimerQueueTimer m_next;
+        internal TimerQueueTimer m_prev;
+
+        //
+        // The time, according to TimerQueue.TickCount, when this timer's current interval started.
+        //
+        internal int m_startTicks;
+
+        //
+        // Timeout.UnsignedInfinite if we are not going to fire.  Otherwise, the offset from m_startTime when we will fire.
+        //
+        internal uint m_dueTime;
+
+        //
+        // Timeout.UnsignedInfinite if we are a single-shot timer.  Otherwise, the repeat interval.
+        //
+        internal uint m_period;
+
+        //
+        // Info about the user's callback
+        //
+        private readonly TimerCallback m_timerCallback;
+        private readonly Object m_state;
+        private readonly ExecutionContext m_executionContext;
+
+
+        //
+        // When Timer.Dispose(WaitHandle) is used, we need to signal the wait handle only
+        // after all pending callbacks are complete.  We set m_canceled to prevent any callbacks that
+        // are already queued from running.  We track the number of callbacks currently executing in 
+        // m_callbacksRunning.  We set m_notifyWhenNoCallbacksRunning only when m_callbacksRunning
+        // reaches zero.
+        //
+        private int m_callbacksRunning;
+        private volatile bool m_canceled;
+        private volatile WaitHandle m_notifyWhenNoCallbacksRunning;
+
+
+        internal TimerQueueTimer(TimerCallback timerCallback, object state, uint dueTime, uint period)
+        {
+            m_timerCallback = timerCallback;
+            m_state = state;
+            m_dueTime = Timeout.UnsignedInfinite;
+            m_period = Timeout.UnsignedInfinite;
+            m_executionContext = ExecutionContext.Capture();
+            m_associatedTimerQueue = TimerQueue.Instances[RuntimeThread.GetCurrentProcessorId() % TimerQueue.Instances.Length];
+
+            //
+            // After the following statement, the timer may fire.  No more manipulation of timer state outside of
+            // the lock is permitted beyond this point!
+            //
+            if (dueTime != Timeout.UnsignedInfinite)
+                Change(dueTime, period);
+        }
+
+        internal bool Change(uint dueTime, uint period)
+        {
+            bool success;
+
+            lock (m_associatedTimerQueue)
+            {
+                if (m_canceled)
+                    throw new ObjectDisposedException(null, SR.ObjectDisposed_Generic);
+
+                // prevent ThreadAbort while updating state
+                try { }
+                finally
+                {
+                    m_period = period;
+
+                    if (dueTime == Timeout.UnsignedInfinite)
+                    {
+                        m_associatedTimerQueue.DeleteTimer(this);
+                        success = true;
+                    }
+                    else
+                    {
+                        if (FrameworkEventSource.IsInitialized && FrameworkEventSource.Log.IsEnabled(EventLevel.Informational, FrameworkEventSource.Keywords.ThreadTransfer))
+                            FrameworkEventSource.Log.ThreadTransferSendObj(this, 1, string.Empty, true);
+
+                        success = m_associatedTimerQueue.UpdateTimer(this, dueTime, period);
+                    }
+                }
+            }
+
+            return success;
+        }
+
+
+        public void Close()
+        {
+            lock (m_associatedTimerQueue)
+            {
+                // prevent ThreadAbort while updating state
+                try { }
+                finally
+                {
+                    if (!m_canceled)
+                    {
+                        m_canceled = true;
+                        m_associatedTimerQueue.DeleteTimer(this);
+                    }
+                }
+            }
+        }
+
+
+        public bool Close(WaitHandle toSignal)
+        {
+            bool success;
+            bool shouldSignal = false;
+
+            lock (m_associatedTimerQueue)
+            {
+                // prevent ThreadAbort while updating state
+                try { }
+                finally
+                {
+                    if (m_canceled)
+                    {
+                        success = false;
+                    }
+                    else
+                    {
+                        m_canceled = true;
+                        m_notifyWhenNoCallbacksRunning = toSignal;
+                        m_associatedTimerQueue.DeleteTimer(this);
+
+                        if (m_callbacksRunning == 0)
+                            shouldSignal = true;
+
+                        success = true;
+                    }
+                }
+            }
+
+            if (shouldSignal)
+                SignalNoCallbacksRunning();
+
+            return success;
+        }
+
+
+        internal void Fire()
+        {
+            bool canceled = false;
+
+            lock (m_associatedTimerQueue)
+            {
+                // prevent ThreadAbort while updating state
+                try { }
+                finally
+                {
+                    canceled = m_canceled;
+                    if (!canceled)
+                        m_callbacksRunning++;
+                }
+            }
+
+            if (canceled)
+                return;
+
+            CallCallback();
+
+            bool shouldSignal = false;
+            lock (m_associatedTimerQueue)
+            {
+                // prevent ThreadAbort while updating state
+                try { }
+                finally
+                {
+                    m_callbacksRunning--;
+                    if (m_canceled && m_callbacksRunning == 0 && m_notifyWhenNoCallbacksRunning != null)
+                        shouldSignal = true;
+                }
+            }
+
+            if (shouldSignal)
+                SignalNoCallbacksRunning();
+        }
+
+        void IThreadPoolWorkItem.ExecuteWorkItem() => Fire();
+
+        void IThreadPoolWorkItem.MarkAborted(ThreadAbortException tae) { }
+
+        internal void SignalNoCallbacksRunning()
+        {
+            Win32Native.SetEvent(m_notifyWhenNoCallbacksRunning.SafeWaitHandle);
+        }
+
+        internal void CallCallback()
+        {
+            if (FrameworkEventSource.IsInitialized && FrameworkEventSource.Log.IsEnabled(EventLevel.Informational, FrameworkEventSource.Keywords.ThreadTransfer))
+                FrameworkEventSource.Log.ThreadTransferReceiveObj(this, 1, string.Empty);
+
+            // call directly if EC flow is suppressed
+            ExecutionContext context = m_executionContext;
+            if (context == null)
+            {
+                m_timerCallback(m_state);
+            }
+            else
+            {
+                ExecutionContext.RunInternal(context, s_callCallbackInContext, this);
+            }
+        }
+
+        private static readonly ContextCallback s_callCallbackInContext = state =>
+        {
+            TimerQueueTimer t = (TimerQueueTimer)state;
+            t.m_timerCallback(t.m_state);
+        };
+    }
+
+    //
+    // TimerHolder serves as an intermediary between Timer and TimerQueueTimer, releasing the TimerQueueTimer 
+    // if the Timer is collected.
+    // This is necessary because Timer itself cannot use its finalizer for this purpose.  If it did,
+    // then users could control timer lifetimes using GC.SuppressFinalize/ReRegisterForFinalize.
+    // You might ask, wouldn't that be a good thing?  Maybe (though it would be even better to offer this
+    // via first-class APIs), but Timer has never offered this, and adding it now would be a breaking
+    // change, because any code that happened to be suppressing finalization of Timer objects would now
+    // unwittingly be changing the lifetime of those timers.
+    //
+    internal sealed class TimerHolder
+    {
+        internal TimerQueueTimer m_timer;
+
+        public TimerHolder(TimerQueueTimer timer)
+        {
+            m_timer = timer;
+        }
+
+        ~TimerHolder()
+        {
+            //
+            // If shutdown has started, another thread may be suspended while holding the timer lock.
+            // So we can't safely close the timer.  
+            //
+            // Similarly, we should not close the timer during AD-unload's live-object finalization phase.
+            // A rude abort may have prevented us from releasing the lock.
+            //
+            // Note that in either case, the Timer still won't fire, because ThreadPool threads won't be
+            // allowed to run in this AppDomain.
+            //
+            if (Environment.HasShutdownStarted || AppDomain.CurrentDomain.IsFinalizingForUnload())
+                return;
+
+            m_timer.Close();
+        }
+
+        public void Close()
+        {
+            m_timer.Close();
+            GC.SuppressFinalize(this);
+        }
+
+        public bool Close(WaitHandle notifyObject)
+        {
+            bool result = m_timer.Close(notifyObject);
+            GC.SuppressFinalize(this);
+            return result;
+        }
+    }
+
+
+    public sealed class Timer : MarshalByRefObject, IDisposable
+    {
+        private const UInt32 MAX_SUPPORTED_TIMEOUT = (uint)0xfffffffe;
+
+        private TimerHolder m_timer;
+
+        public Timer(TimerCallback callback,
+                     Object state,
+                     int dueTime,
+                     int period)
+        {
+            if (dueTime < -1)
+                throw new ArgumentOutOfRangeException(nameof(dueTime), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            if (period < -1)
+                throw new ArgumentOutOfRangeException(nameof(period), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+
+            TimerSetup(callback, state, (UInt32)dueTime, (UInt32)period);
+        }
+
+        public Timer(TimerCallback callback,
+                     Object state,
+                     TimeSpan dueTime,
+                     TimeSpan period)
+        {
+            long dueTm = (long)dueTime.TotalMilliseconds;
+            if (dueTm < -1)
+                throw new ArgumentOutOfRangeException(nameof(dueTm), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            if (dueTm > MAX_SUPPORTED_TIMEOUT)
+                throw new ArgumentOutOfRangeException(nameof(dueTm), SR.ArgumentOutOfRange_TimeoutTooLarge);
+
+            long periodTm = (long)period.TotalMilliseconds;
+            if (periodTm < -1)
+                throw new ArgumentOutOfRangeException(nameof(periodTm), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            if (periodTm > MAX_SUPPORTED_TIMEOUT)
+                throw new ArgumentOutOfRangeException(nameof(periodTm), SR.ArgumentOutOfRange_PeriodTooLarge);
+
+            TimerSetup(callback, state, (UInt32)dueTm, (UInt32)periodTm);
+        }
+
+        [CLSCompliant(false)]
+        public Timer(TimerCallback callback,
+                     Object state,
+                     UInt32 dueTime,
+                     UInt32 period)
+        {
+            TimerSetup(callback, state, dueTime, period);
+        }
+
+        public Timer(TimerCallback callback,
+                     Object state,
+                     long dueTime,
+                     long period)
+        {
+            if (dueTime < -1)
+                throw new ArgumentOutOfRangeException(nameof(dueTime), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            if (period < -1)
+                throw new ArgumentOutOfRangeException(nameof(period), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            if (dueTime > MAX_SUPPORTED_TIMEOUT)
+                throw new ArgumentOutOfRangeException(nameof(dueTime), SR.ArgumentOutOfRange_TimeoutTooLarge);
+            if (period > MAX_SUPPORTED_TIMEOUT)
+                throw new ArgumentOutOfRangeException(nameof(period), SR.ArgumentOutOfRange_PeriodTooLarge);
+            TimerSetup(callback, state, (UInt32)dueTime, (UInt32)period);
+        }
+
+        public Timer(TimerCallback callback)
+        {
+            int dueTime = -1;    // we want timer to be registered, but not activated.  Requires caller to call
+            int period = -1;    // Change after a timer instance is created.  This is to avoid the potential
+                                // for a timer to be fired before the returned value is assigned to the variable,
+                                // potentially causing the callback to reference a bogus value (if passing the timer to the callback). 
+
+            TimerSetup(callback, this, (UInt32)dueTime, (UInt32)period);
+        }
+
+        private void TimerSetup(TimerCallback callback,
+                                Object state,
+                                UInt32 dueTime,
+                                UInt32 period)
+        {
+            if (callback == null)
+                throw new ArgumentNullException(nameof(TimerCallback));
+
+            m_timer = new TimerHolder(new TimerQueueTimer(callback, state, dueTime, period));
+        }
+
+        public bool Change(int dueTime, int period)
+        {
+            if (dueTime < -1)
+                throw new ArgumentOutOfRangeException(nameof(dueTime), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            if (period < -1)
+                throw new ArgumentOutOfRangeException(nameof(period), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+
+            return m_timer.m_timer.Change((UInt32)dueTime, (UInt32)period);
+        }
+
+        public bool Change(TimeSpan dueTime, TimeSpan period)
+        {
+            return Change((long)dueTime.TotalMilliseconds, (long)period.TotalMilliseconds);
+        }
+
+        [CLSCompliant(false)]
+        public bool Change(UInt32 dueTime, UInt32 period)
+        {
+            return m_timer.m_timer.Change(dueTime, period);
+        }
+
+        public bool Change(long dueTime, long period)
+        {
+            if (dueTime < -1)
+                throw new ArgumentOutOfRangeException(nameof(dueTime), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            if (period < -1)
+                throw new ArgumentOutOfRangeException(nameof(period), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            if (dueTime > MAX_SUPPORTED_TIMEOUT)
+                throw new ArgumentOutOfRangeException(nameof(dueTime), SR.ArgumentOutOfRange_TimeoutTooLarge);
+            if (period > MAX_SUPPORTED_TIMEOUT)
+                throw new ArgumentOutOfRangeException(nameof(period), SR.ArgumentOutOfRange_PeriodTooLarge);
+
+            return m_timer.m_timer.Change((UInt32)dueTime, (UInt32)period);
+        }
+
+        public bool Dispose(WaitHandle notifyObject)
+        {
+            if (notifyObject == null)
+                throw new ArgumentNullException(nameof(notifyObject));
+
+            return m_timer.Close(notifyObject);
+        }
+
+        public void Dispose()
+        {
+            m_timer.Close();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/Volatile.cs b/src/System.Private.CoreLib/src/System/Threading/Volatile.cs
new file mode 100644
index 0000000000..6aac8d63cd
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/Volatile.cs
@@ -0,0 +1,404 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+
+using System;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+using System.Runtime.ConstrainedExecution;
+using System.Runtime.CompilerServices;
+using System.Runtime;
+using System.Security;
+
+namespace System.Threading
+{
+    //
+    // Methods for accessing memory with volatile semantics.  These are preferred over Thread.VolatileRead
+    // and Thread.VolatileWrite, as these are implemented more efficiently.
+    //
+    // (We cannot change the implementations of Thread.VolatileRead/VolatileWrite without breaking code
+    // that relies on their overly-strong ordering guarantees.)
+    //
+    // The actual implementations of these methods are typically supplied by the VM at JIT-time, because C# does
+    // not allow us to express a volatile read/write from/to a byref arg.
+    // See getILIntrinsicImplementationForVolatile() in jitinterface.cpp.
+    //
+    public static class Volatile
+    {
+        [System.Runtime.Versioning.NonVersionable]
+        public static bool Read(ref bool location)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            var value = location;
+            Interlocked.MemoryBarrier();
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        [System.Runtime.Versioning.NonVersionable]
+        public static sbyte Read(ref sbyte location)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            var value = location;
+            Interlocked.MemoryBarrier();
+            return value;
+        }
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static byte Read(ref byte location)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            var value = location;
+            Interlocked.MemoryBarrier();
+            return value;
+        }
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static short Read(ref short location)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            var value = location;
+            Interlocked.MemoryBarrier();
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        [System.Runtime.Versioning.NonVersionable]
+        public static ushort Read(ref ushort location)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            var value = location;
+            Interlocked.MemoryBarrier();
+            return value;
+        }
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static int Read(ref int location)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            var value = location;
+            Interlocked.MemoryBarrier();
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        [System.Runtime.Versioning.NonVersionable]
+        public static uint Read(ref uint location)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            var value = location;
+            Interlocked.MemoryBarrier();
+            return value;
+        }
+
+#if BIT64
+        [System.Runtime.Versioning.NonVersionable]
+        public static long Read(ref long location)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            var value = location;
+            Interlocked.MemoryBarrier();
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        [System.Runtime.Versioning.NonVersionable]
+        public static ulong Read(ref ulong location)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            var value = location;
+            Interlocked.MemoryBarrier();
+            return value;
+        }
+#else
+        public static long Read(ref long location)
+        {
+            //
+            // On 32-bit machines, we use this implementation, since an ordinary volatile read
+            // would not be atomic.
+            //
+            // On 64-bit machines, the VM will replace this with a more efficient implementation.
+            //
+            return Interlocked.CompareExchange(ref location, 0, 0);
+        }
+
+        [CLSCompliant(false)]
+        public static ulong Read(ref ulong location)
+        {
+            unsafe
+            {
+                //
+                // There is no overload of Interlocked.Exchange that accepts a ulong.  So we have
+                // to do some pointer tricks to pass our arguments to the overload that takes a long.
+                //
+                fixed (ulong* pLocation = &location)
+                {
+                    return (ulong)Interlocked.CompareExchange(ref *(long*)pLocation, 0, 0);
+                }
+            }
+        }
+#endif
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static IntPtr Read(ref IntPtr location)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            var value = location;
+            Interlocked.MemoryBarrier();
+            return value;
+        }
+
+        [CLSCompliant(false)]
+        [System.Runtime.Versioning.NonVersionable]
+        public static UIntPtr Read(ref UIntPtr location)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            var value = location;
+            Interlocked.MemoryBarrier();
+            return value;
+        }
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static float Read(ref float location)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            var value = location;
+            Interlocked.MemoryBarrier();
+            return value;
+        }
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static double Read(ref double location)
+        {
+            //
+            // On 32-bit machines, we use this implementation, since an ordinary volatile read
+            // would not be atomic.
+            //
+            // On 64-bit machines, the VM will replace this with a more efficient implementation.
+            //
+            return Interlocked.CompareExchange(ref location, 0, 0);
+        }
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static T Read<T>(ref T location) where T : class
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            var value = location;
+            Interlocked.MemoryBarrier();
+            return value;
+        }
+
+
+
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static void Write(ref bool location, bool value)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            Interlocked.MemoryBarrier();
+            location = value;
+        }
+
+        [CLSCompliant(false)]
+        [System.Runtime.Versioning.NonVersionable]
+        public static void Write(ref sbyte location, sbyte value)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            Interlocked.MemoryBarrier();
+            location = value;
+        }
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static void Write(ref byte location, byte value)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            Interlocked.MemoryBarrier();
+            location = value;
+        }
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static void Write(ref short location, short value)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            Interlocked.MemoryBarrier();
+            location = value;
+        }
+
+        [CLSCompliant(false)]
+        [System.Runtime.Versioning.NonVersionable]
+        public static void Write(ref ushort location, ushort value)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            Interlocked.MemoryBarrier();
+            location = value;
+        }
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static void Write(ref int location, int value)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            Interlocked.MemoryBarrier();
+            location = value;
+        }
+
+        [CLSCompliant(false)]
+        [System.Runtime.Versioning.NonVersionable]
+        public static void Write(ref uint location, uint value)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            Interlocked.MemoryBarrier();
+            location = value;
+        }
+
+#if BIT64
+        [System.Runtime.Versioning.NonVersionable]
+        public static void Write(ref long location, long value)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            Interlocked.MemoryBarrier();
+            location = value;
+        }
+
+        [CLSCompliant(false)]
+        [System.Runtime.Versioning.NonVersionable]
+        public static void Write(ref ulong location, ulong value)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            Interlocked.MemoryBarrier();
+            location = value;
+        }
+#else
+        public static void Write(ref long location, long value)
+        {
+            //
+            // On 32-bit machines, we use this implementation, since an ordinary volatile write 
+            // would not be atomic.
+            //
+            // On 64-bit machines, the VM will replace this with a more efficient implementation.
+            //
+            Interlocked.Exchange(ref location, value);
+        }
+
+        [CLSCompliant(false)]
+        public static void Write(ref ulong location, ulong value)
+        {
+            //
+            // On 32-bit machines, we use this implementation, since an ordinary volatile write 
+            // would not be atomic.
+            //
+            // On 64-bit machines, the VM will replace this with a more efficient implementation.
+            //
+            unsafe
+            {
+                //
+                // There is no overload of Interlocked.Exchange that accepts a ulong.  So we have
+                // to do some pointer tricks to pass our arguments to the overload that takes a long.
+                //
+                fixed (ulong* pLocation = &location)
+                {
+                    Interlocked.Exchange(ref *(long*)pLocation, (long)value);
+                }
+            }
+        }
+#endif
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static void Write(ref IntPtr location, IntPtr value)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            Interlocked.MemoryBarrier();
+            location = value;
+        }
+
+        [CLSCompliant(false)]
+        [System.Runtime.Versioning.NonVersionable]
+        public static void Write(ref UIntPtr location, UIntPtr value)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            Interlocked.MemoryBarrier();
+            location = value;
+        }
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static void Write(ref float location, float value)
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            Interlocked.MemoryBarrier();
+            location = value;
+        }
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static void Write(ref double location, double value)
+        {
+            //
+            // On 32-bit machines, we use this implementation, since an ordinary volatile write 
+            // would not be atomic.
+            //
+            // On 64-bit machines, the VM will replace this with a more efficient implementation.
+            //
+            Interlocked.Exchange(ref location, value);
+        }
+
+        [System.Runtime.Versioning.NonVersionable]
+        public static void Write<T>(ref T location, T value) where T : class
+        {
+            // 
+            // The VM will replace this with a more efficient implementation.
+            //
+            Interlocked.MemoryBarrier();
+            location = value;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Threading/WaitHandle.cs b/src/System.Private.CoreLib/src/System/Threading/WaitHandle.cs
new file mode 100644
index 0000000000..2de388dc49
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Threading/WaitHandle.cs
@@ -0,0 +1,523 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+//
+/*=============================================================================
+**
+**
+**
+** Purpose: Class to represent all synchronization objects in the runtime (that allow multiple wait)
+**
+**
+=============================================================================*/
+
+namespace System.Threading
+{
+    using System.Threading;
+    using System;
+    using System.Runtime.CompilerServices;
+    using System.Runtime.InteropServices;
+    using Microsoft.Win32.SafeHandles;
+    using System.Runtime.Versioning;
+    using System.Runtime.ConstrainedExecution;
+    using System.Diagnostics.CodeAnalysis;
+    using Win32Native = Microsoft.Win32.Win32Native;
+
+    public abstract class WaitHandle : MarshalByRefObject, IDisposable
+    {
+        public const int WaitTimeout = 0x102;
+
+        private const int MAX_WAITHANDLES = 64;
+
+#pragma warning disable 414  // Field is not used from managed.
+        private IntPtr waitHandle;  // !!! DO NOT MOVE THIS FIELD. (See defn of WAITHANDLEREF in object.h - has hard-coded access to this field.)
+#pragma warning restore 414
+
+        internal volatile SafeWaitHandle safeWaitHandle;
+
+        internal bool hasThreadAffinity;
+
+        private static IntPtr GetInvalidHandle()
+        {
+            return Win32Native.INVALID_HANDLE_VALUE;
+        }
+        protected static readonly IntPtr InvalidHandle = GetInvalidHandle();
+        private const int WAIT_OBJECT_0 = 0;
+        private const int WAIT_ABANDONED = 0x80;
+        private const int WAIT_FAILED = 0x7FFFFFFF;
+        private const int ERROR_TOO_MANY_POSTS = 0x12A;
+
+        internal enum OpenExistingResult
+        {
+            Success,
+            NameNotFound,
+            PathNotFound,
+            NameInvalid
+        }
+
+        protected WaitHandle()
+        {
+            Init();
+        }
+
+        private void Init()
+        {
+            safeWaitHandle = null;
+            waitHandle = InvalidHandle;
+            hasThreadAffinity = false;
+        }
+
+
+        [Obsolete("Use the SafeWaitHandle property instead.")]
+        public virtual IntPtr Handle
+        {
+            get { return safeWaitHandle == null ? InvalidHandle : safeWaitHandle.DangerousGetHandle(); }
+            set
+            {
+                if (value == InvalidHandle)
+                {
+                    // This line leaks a handle.  However, it's currently
+                    // not perfectly clear what the right behavior is here 
+                    // anyways.  This preserves Everett behavior.  We should 
+                    // ideally do these things:
+                    // *) Expose a settable SafeHandle property on WaitHandle.
+                    // *) Expose a settable OwnsHandle property on SafeHandle.
+                    if (safeWaitHandle != null)
+                    {
+                        safeWaitHandle.SetHandleAsInvalid();
+                        safeWaitHandle = null;
+                    }
+                }
+                else
+                {
+                    safeWaitHandle = new SafeWaitHandle(value, true);
+                }
+                waitHandle = value;
+            }
+        }
+
+        public SafeWaitHandle SafeWaitHandle
+        {
+            get
+            {
+                if (safeWaitHandle == null)
+                {
+                    safeWaitHandle = new SafeWaitHandle(InvalidHandle, false);
+                }
+                return safeWaitHandle;
+            }
+
+            set
+            {
+                // Set safeWaitHandle and waitHandle in a CER so we won't take
+                // a thread abort between the statements and leave the wait
+                // handle in an invalid state. Note this routine is not thread
+                // safe however.
+                RuntimeHelpers.PrepareConstrainedRegions();
+                try { }
+                finally
+                {
+                    if (value == null)
+                    {
+                        safeWaitHandle = null;
+                        waitHandle = InvalidHandle;
+                    }
+                    else
+                    {
+                        safeWaitHandle = value;
+                        waitHandle = safeWaitHandle.DangerousGetHandle();
+                    }
+                }
+            }
+        }
+
+        // Assembly-private version that doesn't do a security check.  Reduces the
+        // number of link-time security checks when reading & writing to a file,
+        // and helps avoid a link time check while initializing security (If you
+        // call a Serialization method that requires security before security
+        // has started up, the link time check will start up security, run 
+        // serialization code for some security attribute stuff, call into 
+        // FileStream, which will then call Sethandle, which requires a link time
+        // security check.).  While security has fixed that problem, we still
+        // don't need to do a linktime check here.
+        internal void SetHandleInternal(SafeWaitHandle handle)
+        {
+            safeWaitHandle = handle;
+            waitHandle = handle.DangerousGetHandle();
+        }
+
+        public virtual bool WaitOne(int millisecondsTimeout, bool exitContext)
+        {
+            if (millisecondsTimeout < -1)
+            {
+                throw new ArgumentOutOfRangeException(nameof(millisecondsTimeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            }
+            return WaitOne((long)millisecondsTimeout, exitContext);
+        }
+
+        public virtual bool WaitOne(TimeSpan timeout, bool exitContext)
+        {
+            long tm = (long)timeout.TotalMilliseconds;
+            if (-1 > tm || (long)Int32.MaxValue < tm)
+            {
+                throw new ArgumentOutOfRangeException(nameof(timeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            }
+            return WaitOne(tm, exitContext);
+        }
+
+        public virtual bool WaitOne()
+        {
+            //Infinite Timeout
+            return WaitOne(-1, false);
+        }
+
+        public virtual bool WaitOne(int millisecondsTimeout)
+        {
+            return WaitOne(millisecondsTimeout, false);
+        }
+
+        public virtual bool WaitOne(TimeSpan timeout)
+        {
+            return WaitOne(timeout, false);
+        }
+
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "Reviewed for thread-safety.")]
+        private bool WaitOne(long timeout, bool exitContext)
+        {
+            return InternalWaitOne(safeWaitHandle, timeout, hasThreadAffinity, exitContext);
+        }
+
+        internal static bool InternalWaitOne(SafeHandle waitableSafeHandle, long millisecondsTimeout, bool hasThreadAffinity, bool exitContext)
+        {
+            if (waitableSafeHandle == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_Generic);
+            }
+            int ret = WaitOneNative(waitableSafeHandle, (uint)millisecondsTimeout, hasThreadAffinity, exitContext);
+
+            if (ret == WAIT_ABANDONED)
+            {
+                ThrowAbandonedMutexException();
+            }
+            return (ret != WaitTimeout);
+        }
+
+        internal bool WaitOneWithoutFAS()
+        {
+            // version of waitone without fast application switch (FAS) support
+            // This is required to support the Wait which FAS needs (otherwise recursive dependency comes in)
+            if (safeWaitHandle == null)
+            {
+                throw new ObjectDisposedException(null, SR.ObjectDisposed_Generic);
+            }
+
+            long timeout = -1;
+            int ret = WaitOneNative(safeWaitHandle, (uint)timeout, hasThreadAffinity, false);
+            if (ret == WAIT_ABANDONED)
+            {
+                ThrowAbandonedMutexException();
+            }
+            return (ret != WaitTimeout);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int WaitOneNative(SafeHandle waitableSafeHandle, uint millisecondsTimeout, bool hasThreadAffinity, bool exitContext);
+
+        /*========================================================================
+        ** Waits for signal from all the objects. 
+        ** timeout indicates how long to wait before the method returns.
+        ** This method will return either when all the object have been pulsed
+        ** or timeout milliseconds have elapsed.
+        ** If exitContext is true then the synchronization domain for the context 
+        ** (if in a synchronized context) is exited before the wait and reacquired 
+        ========================================================================*/
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int WaitMultiple(WaitHandle[] waitHandles, int millisecondsTimeout, bool exitContext, bool WaitAll);
+
+        public static bool WaitAll(WaitHandle[] waitHandles, int millisecondsTimeout, bool exitContext)
+        {
+            if (waitHandles == null)
+            {
+                throw new ArgumentNullException(nameof(waitHandles), SR.ArgumentNull_Waithandles);
+            }
+            if (waitHandles.Length == 0)
+            {
+                //
+                // Some history: in CLR 1.0 and 1.1, we threw ArgumentException in this case, which was correct.
+                // Somehow, in 2.0, this became ArgumentNullException.  This was not fixed until Silverlight 2,
+                // which went back to ArgumentException.
+                //
+                // Now we're in a bit of a bind.  Backward-compatibility requires us to keep throwing ArgumentException
+                // in CoreCLR, and ArgumentNullException in the desktop CLR.  This is ugly, but so is breaking
+                // user code.
+                //
+                throw new ArgumentException(SR.Argument_EmptyWaithandleArray);
+            }
+            if (waitHandles.Length > MAX_WAITHANDLES)
+            {
+                throw new NotSupportedException(SR.NotSupported_MaxWaitHandles);
+            }
+            if (-1 > millisecondsTimeout)
+            {
+                throw new ArgumentOutOfRangeException(nameof(millisecondsTimeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            }
+            WaitHandle[] internalWaitHandles = new WaitHandle[waitHandles.Length];
+            for (int i = 0; i < waitHandles.Length; i++)
+            {
+                WaitHandle waitHandle = waitHandles[i];
+
+                if (waitHandle == null)
+                    throw new ArgumentNullException("waitHandles[" + i + "]", SR.ArgumentNull_ArrayElement);
+
+                internalWaitHandles[i] = waitHandle;
+            }
+#if DEBUG
+            // make sure we do not use waitHandles any more.
+            waitHandles = null;
+#endif
+
+            int ret = WaitMultiple(internalWaitHandles, millisecondsTimeout, exitContext, true /* waitall*/ );
+
+            if ((WAIT_ABANDONED <= ret) && (WAIT_ABANDONED + internalWaitHandles.Length > ret))
+            {
+                //In the case of WaitAll the OS will only provide the
+                //    information that mutex was abandoned.
+                //    It won't tell us which one.  So we can't set the Index or provide access to the Mutex
+                ThrowAbandonedMutexException();
+            }
+
+            GC.KeepAlive(internalWaitHandles);
+            return (ret != WaitTimeout);
+        }
+
+        public static bool WaitAll(
+                                    WaitHandle[] waitHandles,
+                                    TimeSpan timeout,
+                                    bool exitContext)
+        {
+            long tm = (long)timeout.TotalMilliseconds;
+            if (-1 > tm || (long)Int32.MaxValue < tm)
+            {
+                throw new ArgumentOutOfRangeException(nameof(timeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            }
+            return WaitAll(waitHandles, (int)tm, exitContext);
+        }
+
+
+        /*========================================================================
+        ** Shorthand for WaitAll with timeout = Timeout.Infinite and exitContext = true
+        ========================================================================*/
+        public static bool WaitAll(WaitHandle[] waitHandles)
+        {
+            return WaitAll(waitHandles, Timeout.Infinite, true);
+        }
+
+        public static bool WaitAll(WaitHandle[] waitHandles, int millisecondsTimeout)
+        {
+            return WaitAll(waitHandles, millisecondsTimeout, true);
+        }
+
+        public static bool WaitAll(WaitHandle[] waitHandles, TimeSpan timeout)
+        {
+            return WaitAll(waitHandles, timeout, true);
+        }
+
+
+        /*========================================================================
+        ** Waits for notification from any of the objects. 
+        ** timeout indicates how long to wait before the method returns.
+        ** This method will return either when either one of the object have been 
+        ** signaled or timeout milliseconds have elapsed.
+        ** If exitContext is true then the synchronization domain for the context 
+        ** (if in a synchronized context) is exited before the wait and reacquired 
+        ========================================================================*/
+
+        public static int WaitAny(WaitHandle[] waitHandles, int millisecondsTimeout, bool exitContext)
+        {
+            if (waitHandles == null)
+            {
+                throw new ArgumentNullException(nameof(waitHandles), SR.ArgumentNull_Waithandles);
+            }
+            if (waitHandles.Length == 0)
+            {
+                throw new ArgumentException(SR.Argument_EmptyWaithandleArray);
+            }
+            if (MAX_WAITHANDLES < waitHandles.Length)
+            {
+                throw new NotSupportedException(SR.NotSupported_MaxWaitHandles);
+            }
+            if (-1 > millisecondsTimeout)
+            {
+                throw new ArgumentOutOfRangeException(nameof(millisecondsTimeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            }
+            WaitHandle[] internalWaitHandles = new WaitHandle[waitHandles.Length];
+            for (int i = 0; i < waitHandles.Length; i++)
+            {
+                WaitHandle waitHandle = waitHandles[i];
+
+                if (waitHandle == null)
+                    throw new ArgumentNullException("waitHandles[" + i + "]", SR.ArgumentNull_ArrayElement);
+
+                internalWaitHandles[i] = waitHandle;
+            }
+#if DEBUG
+            // make sure we do not use waitHandles any more.
+            waitHandles = null;
+#endif
+            int ret = WaitMultiple(internalWaitHandles, millisecondsTimeout, exitContext, false /* waitany*/ );
+
+            if ((WAIT_ABANDONED <= ret) && (WAIT_ABANDONED + internalWaitHandles.Length > ret))
+            {
+                int mutexIndex = ret - WAIT_ABANDONED;
+                if (0 <= mutexIndex && mutexIndex < internalWaitHandles.Length)
+                {
+                    ThrowAbandonedMutexException(mutexIndex, internalWaitHandles[mutexIndex]);
+                }
+                else
+                {
+                    ThrowAbandonedMutexException();
+                }
+            }
+
+            GC.KeepAlive(internalWaitHandles);
+            return ret;
+        }
+
+        public static int WaitAny(
+                                    WaitHandle[] waitHandles,
+                                    TimeSpan timeout,
+                                    bool exitContext)
+        {
+            long tm = (long)timeout.TotalMilliseconds;
+            if (-1 > tm || (long)Int32.MaxValue < tm)
+            {
+                throw new ArgumentOutOfRangeException(nameof(timeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            }
+            return WaitAny(waitHandles, (int)tm, exitContext);
+        }
+        public static int WaitAny(WaitHandle[] waitHandles, TimeSpan timeout)
+        {
+            return WaitAny(waitHandles, timeout, true);
+        }
+
+
+        /*========================================================================
+        ** Shorthand for WaitAny with timeout = Timeout.Infinite and exitContext = true
+        ========================================================================*/
+        public static int WaitAny(WaitHandle[] waitHandles)
+        {
+            return WaitAny(waitHandles, Timeout.Infinite, true);
+        }
+
+        public static int WaitAny(WaitHandle[] waitHandles, int millisecondsTimeout)
+        {
+            return WaitAny(waitHandles, millisecondsTimeout, true);
+        }
+
+        /*=================================================
+        ==
+        ==  SignalAndWait
+        ==
+        ==================================================*/
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern int SignalAndWaitOne(SafeWaitHandle waitHandleToSignal, SafeWaitHandle waitHandleToWaitOn, int millisecondsTimeout,
+                                            bool hasThreadAffinity, bool exitContext);
+
+        public static bool SignalAndWait(
+                                        WaitHandle toSignal,
+                                        WaitHandle toWaitOn)
+        {
+            return SignalAndWait(toSignal, toWaitOn, -1, false);
+        }
+
+        public static bool SignalAndWait(
+                                        WaitHandle toSignal,
+                                        WaitHandle toWaitOn,
+                                        TimeSpan timeout,
+                                        bool exitContext)
+        {
+            long tm = (long)timeout.TotalMilliseconds;
+            if (-1 > tm || (long)Int32.MaxValue < tm)
+            {
+                throw new ArgumentOutOfRangeException(nameof(timeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            }
+            return SignalAndWait(toSignal, toWaitOn, (int)tm, exitContext);
+        }
+
+        [SuppressMessage("Microsoft.Concurrency", "CA8001", Justification = "Reviewed for thread-safety.")]
+        public static bool SignalAndWait(
+                                        WaitHandle toSignal,
+                                        WaitHandle toWaitOn,
+                                        int millisecondsTimeout,
+                                        bool exitContext)
+        {
+            if (null == toSignal)
+            {
+                throw new ArgumentNullException(nameof(toSignal));
+            }
+            if (null == toWaitOn)
+            {
+                throw new ArgumentNullException(nameof(toWaitOn));
+            }
+            if (-1 > millisecondsTimeout)
+            {
+                throw new ArgumentOutOfRangeException(nameof(millisecondsTimeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
+            }
+
+            //NOTE: This API is not supporting Pause/Resume as it's not exposed in CoreCLR (not in WP or SL)
+            int ret = SignalAndWaitOne(toSignal.safeWaitHandle, toWaitOn.safeWaitHandle, millisecondsTimeout,
+                                toWaitOn.hasThreadAffinity, exitContext);
+
+            if (WAIT_ABANDONED == ret)
+            {
+                ThrowAbandonedMutexException();
+            }
+
+            if (ERROR_TOO_MANY_POSTS == ret)
+            {
+                throw new InvalidOperationException(SR.Threading_WaitHandleTooManyPosts);
+            }
+
+            //Object was signaled
+            if (WAIT_OBJECT_0 == ret)
+            {
+                return true;
+            }
+
+            //Timeout
+            return false;
+        }
+
+        private static void ThrowAbandonedMutexException()
+        {
+            throw new AbandonedMutexException();
+        }
+
+        private static void ThrowAbandonedMutexException(int location, WaitHandle handle)
+        {
+            throw new AbandonedMutexException(location, handle);
+        }
+
+        public virtual void Close()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        protected virtual void Dispose(bool explicitDisposing)
+        {
+            if (safeWaitHandle != null)
+            {
+                safeWaitHandle.Close();
+            }
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/ThrowHelper.cs b/src/System.Private.CoreLib/src/System/ThrowHelper.cs
new file mode 100644
index 0000000000..b1a2fec7ef
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/ThrowHelper.cs
@@ -0,0 +1,597 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+// This file defines an internal class used to throw exceptions in BCL code.
+// The main purpose is to reduce code size.
+//
+// The old way to throw an exception generates quite a lot IL code and assembly code.
+// Following is an example:
+//     C# source
+//          throw new ArgumentNullException(nameof(key), SR.ArgumentNull_Key);
+//     IL code:
+//          IL_0003:  ldstr      "key"
+//          IL_0008:  ldstr      "ArgumentNull_Key"
+//          IL_000d:  call       string System.Environment::GetResourceString(string)
+//          IL_0012:  newobj     instance void System.ArgumentNullException::.ctor(string,string)
+//          IL_0017:  throw
+//    which is 21bytes in IL.
+//
+// So we want to get rid of the ldstr and call to Environment.GetResource in IL.
+// In order to do that, I created two enums: ExceptionResource, ExceptionArgument to represent the
+// argument name and resource name in a small integer. The source code will be changed to
+//    ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key, ExceptionResource.ArgumentNull_Key);
+//
+// The IL code will be 7 bytes.
+//    IL_0008:  ldc.i4.4
+//    IL_0009:  ldc.i4.4
+//    IL_000a:  call       void System.ThrowHelper::ThrowArgumentNullException(valuetype System.ExceptionArgument)
+//    IL_000f:  ldarg.0
+//
+// This will also reduce the Jitted code size a lot.
+//
+// It is very important we do this for generic classes because we can easily generate the same code
+// multiple times for different instantiation.
+//
+
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Runtime.Serialization;
+using System.Diagnostics;
+
+namespace System
+{
+    [StackTraceHidden]
+    internal static class ThrowHelper
+    {
+        internal static void ThrowArrayTypeMismatchException()
+        {
+            throw new ArrayTypeMismatchException();
+        }
+
+        internal static void ThrowInvalidTypeWithPointersNotSupported(Type targetType)
+        {
+            throw new ArgumentException(SR.Format(SR.Argument_InvalidTypeWithPointersNotSupported, targetType));
+        }
+
+        internal static void ThrowIndexOutOfRangeException()
+        {
+            throw new IndexOutOfRangeException();
+        }
+
+        internal static void ThrowArgumentOutOfRangeException()
+        {
+            throw new ArgumentOutOfRangeException();
+        }
+
+        internal static void ThrowArgumentException_DestinationTooShort()
+        {
+            throw new ArgumentException(SR.Argument_DestinationTooShort);
+        }
+
+        internal static void ThrowArgumentException_OverlapAlignmentMismatch()
+        {
+            throw new ArgumentException(SR.Argument_OverlapAlignmentMismatch);
+        }
+
+        internal static void ThrowArgumentOutOfRange_IndexException()
+        {
+            throw GetArgumentOutOfRangeException(ExceptionArgument.index,
+                                                    ExceptionResource.ArgumentOutOfRange_Index);
+        }
+
+        internal static void ThrowIndexArgumentOutOfRange_NeedNonNegNumException()
+        {
+            throw GetArgumentOutOfRangeException(ExceptionArgument.index,
+                                                    ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+        }
+
+        internal static void ThrowLengthArgumentOutOfRange_ArgumentOutOfRange_NeedNonNegNum()
+        {
+            throw GetArgumentOutOfRangeException(ExceptionArgument.length,
+                                                    ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+        }
+
+        internal static void ThrowStartIndexArgumentOutOfRange_ArgumentOutOfRange_Index()
+        {
+            throw GetArgumentOutOfRangeException(ExceptionArgument.startIndex,
+                                                    ExceptionResource.ArgumentOutOfRange_Index);
+        }
+
+        internal static void ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count()
+        {
+            throw GetArgumentOutOfRangeException(ExceptionArgument.count,
+                                                    ExceptionResource.ArgumentOutOfRange_Count);
+        }
+
+        internal static void ThrowWrongKeyTypeArgumentException<T>(T key, Type targetType)
+        {
+            // Generic key to move the boxing to the right hand side of throw
+            throw GetWrongKeyTypeArgumentException((object)key, targetType);
+        }
+
+        internal static void ThrowWrongValueTypeArgumentException<T>(T value, Type targetType)
+        {
+            // Generic key to move the boxing to the right hand side of throw
+            throw GetWrongValueTypeArgumentException((object)value, targetType);
+        }
+
+        private static ArgumentException GetAddingDuplicateWithKeyArgumentException(object key)
+        {
+            return new ArgumentException(SR.Format(SR.Argument_AddingDuplicateWithKey, key));
+        }
+
+        internal static void ThrowAddingDuplicateWithKeyArgumentException<T>(T key)
+        {
+            // Generic key to move the boxing to the right hand side of throw
+            throw GetAddingDuplicateWithKeyArgumentException((object)key);
+        }
+
+        internal static void ThrowKeyNotFoundException<T>(T key)
+        {
+            // Generic key to move the boxing to the right hand side of throw
+            throw GetKeyNotFoundException((object)key);
+        }
+
+        internal static void ThrowArgumentException(ExceptionResource resource)
+        {
+            throw GetArgumentException(resource);
+        }
+
+        internal static void ThrowArgumentException(ExceptionResource resource, ExceptionArgument argument)
+        {
+            throw GetArgumentException(resource, argument);
+        }
+
+        private static ArgumentNullException GetArgumentNullException(ExceptionArgument argument)
+        {
+            return new ArgumentNullException(GetArgumentName(argument));
+        }
+
+        internal static void ThrowArgumentNullException(ExceptionArgument argument)
+        {
+            throw GetArgumentNullException(argument);
+        }
+
+        internal static void ThrowArgumentNullException(ExceptionResource resource)
+        {
+            throw new ArgumentNullException(GetResourceString(resource));
+        }
+
+        internal static void ThrowArgumentNullException(ExceptionArgument argument, ExceptionResource resource)
+        {
+            throw new ArgumentNullException(GetArgumentName(argument), GetResourceString(resource));
+        }
+
+        internal static void ThrowArgumentOutOfRangeException(ExceptionArgument argument)
+        {
+            throw new ArgumentOutOfRangeException(GetArgumentName(argument));
+        }
+
+        internal static void ThrowArgumentOutOfRangeException(ExceptionArgument argument, ExceptionResource resource)
+        {
+            throw GetArgumentOutOfRangeException(argument, resource);
+        }
+
+        internal static void ThrowArgumentOutOfRangeException(ExceptionArgument argument, int paramNumber, ExceptionResource resource)
+        {
+            throw GetArgumentOutOfRangeException(argument, paramNumber, resource);
+        }
+
+        internal static void ThrowInvalidOperationException(ExceptionResource resource)
+        {
+            throw GetInvalidOperationException(resource);
+        }
+
+        internal static void ThrowInvalidOperationException_OutstandingReferences()
+        {
+            ThrowInvalidOperationException(ExceptionResource.Memory_OutstandingReferences);
+        }
+
+        internal static void ThrowInvalidOperationException(ExceptionResource resource, Exception e)
+        {
+            throw new InvalidOperationException(GetResourceString(resource), e);
+        }
+
+        internal static void ThrowSerializationException(ExceptionResource resource)
+        {
+            throw new SerializationException(GetResourceString(resource));
+        }
+
+        internal static void ThrowSecurityException(ExceptionResource resource)
+        {
+            throw new System.Security.SecurityException(GetResourceString(resource));
+        }
+
+        internal static void ThrowRankException(ExceptionResource resource)
+        {
+            throw new RankException(GetResourceString(resource));
+        }
+
+        internal static void ThrowNotSupportedException(ExceptionResource resource)
+        {
+            throw new NotSupportedException(GetResourceString(resource));
+        }
+
+        internal static void ThrowUnauthorizedAccessException(ExceptionResource resource)
+        {
+            throw new UnauthorizedAccessException(GetResourceString(resource));
+        }
+
+        internal static void ThrowObjectDisposedException(string objectName, ExceptionResource resource)
+        {
+            throw new ObjectDisposedException(objectName, GetResourceString(resource));
+        }
+
+        internal static void ThrowObjectDisposedException(ExceptionResource resource)
+        {
+            throw new ObjectDisposedException(null, GetResourceString(resource));
+        }
+
+        internal static void ThrowNotSupportedException()
+        {
+            throw new NotSupportedException();
+        }
+
+        internal static void ThrowAggregateException(List<Exception> exceptions)
+        {
+            throw new AggregateException(exceptions);
+        }
+
+        internal static void ThrowOutOfMemoryException()
+        {
+            throw new OutOfMemoryException();
+        }
+
+        internal static void ThrowArgumentException_Argument_InvalidArrayType()
+        {
+            throw GetArgumentException(ExceptionResource.Argument_InvalidArrayType);
+        }
+
+        internal static void ThrowInvalidOperationException_InvalidOperation_EnumNotStarted()
+        {
+            throw GetInvalidOperationException(ExceptionResource.InvalidOperation_EnumNotStarted);
+        }
+
+        internal static void ThrowInvalidOperationException_InvalidOperation_EnumEnded()
+        {
+            throw GetInvalidOperationException(ExceptionResource.InvalidOperation_EnumEnded);
+        }
+
+        internal static void ThrowInvalidOperationException_EnumCurrent(int index)
+        {
+            throw GetInvalidOperationException_EnumCurrent(index);
+        }
+
+        internal static void ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion()
+        {
+            throw GetInvalidOperationException(ExceptionResource.InvalidOperation_EnumFailedVersion);
+        }
+
+        internal static void ThrowInvalidOperationException_InvalidOperation_EnumOpCantHappen()
+        {
+            throw GetInvalidOperationException(ExceptionResource.InvalidOperation_EnumOpCantHappen);
+        }
+
+        internal static void ThrowInvalidOperationException_InvalidOperation_NoValue()
+        {
+            throw GetInvalidOperationException(ExceptionResource.InvalidOperation_NoValue);
+        }
+
+        internal static void ThrowInvalidOperationException_ConcurrentOperationsNotSupported()
+        {
+            throw GetInvalidOperationException(ExceptionResource.InvalidOperation_ConcurrentOperationsNotSupported);
+        }
+
+        internal static void ThrowArraySegmentCtorValidationFailedExceptions(Array array, int offset, int count)
+        {
+            throw GetArraySegmentCtorValidationFailedException(array, offset, count);
+        }
+
+        private static Exception GetArraySegmentCtorValidationFailedException(Array array, int offset, int count)
+        {
+            if (array == null)
+                return GetArgumentNullException(ExceptionArgument.array);
+            if (offset < 0)
+                return GetArgumentOutOfRangeException(ExceptionArgument.offset, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+            if (count < 0)
+                return GetArgumentOutOfRangeException(ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
+
+            Debug.Assert(array.Length - offset < count);
+            return GetArgumentException(ExceptionResource.Argument_InvalidOffLen);
+        }
+
+        private static ArgumentException GetArgumentException(ExceptionResource resource)
+        {
+            return new ArgumentException(GetResourceString(resource));
+        }
+
+        internal static InvalidOperationException GetInvalidOperationException(ExceptionResource resource)
+        {
+            return new InvalidOperationException(GetResourceString(resource));
+        }
+
+        private static ArgumentException GetWrongKeyTypeArgumentException(object key, Type targetType)
+        {
+            return new ArgumentException(SR.Format(SR.Arg_WrongType, key, targetType), nameof(key));
+        }
+
+        private static ArgumentException GetWrongValueTypeArgumentException(object value, Type targetType)
+        {
+            return new ArgumentException(SR.Format(SR.Arg_WrongType, value, targetType), nameof(value));
+        }
+
+        private static KeyNotFoundException GetKeyNotFoundException(object key)
+        {
+            return new KeyNotFoundException(SR.Format(SR.Arg_KeyNotFoundWithKey, key.ToString()));
+        }
+
+        internal static ArgumentOutOfRangeException GetArgumentOutOfRangeException(ExceptionArgument argument, ExceptionResource resource)
+        {
+            return new ArgumentOutOfRangeException(GetArgumentName(argument), GetResourceString(resource));
+        }
+
+        private static ArgumentException GetArgumentException(ExceptionResource resource, ExceptionArgument argument)
+        {
+            return new ArgumentException(GetResourceString(resource), GetArgumentName(argument));
+        }
+
+        private static ArgumentOutOfRangeException GetArgumentOutOfRangeException(ExceptionArgument argument, int paramNumber, ExceptionResource resource)
+        {
+            return new ArgumentOutOfRangeException(GetArgumentName(argument) + "[" + paramNumber.ToString() + "]", GetResourceString(resource));
+        }
+
+        private static InvalidOperationException GetInvalidOperationException_EnumCurrent(int index)
+        {
+            return GetInvalidOperationException(
+                index < 0 ?
+                ExceptionResource.InvalidOperation_EnumNotStarted :
+                ExceptionResource.InvalidOperation_EnumEnded);
+        }
+
+        // Allow nulls for reference types and Nullable<U>, but not for value types.
+        // Aggressively inline so the jit evaluates the if in place and either drops the call altogether
+        // Or just leaves null test and call to the Non-returning ThrowHelper.ThrowArgumentNullException
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static void IfNullAndNullsAreIllegalThenThrow<T>(object value, ExceptionArgument argName)
+        {
+            // Note that default(T) is not equal to null for value types except when T is Nullable<U>.
+            if (!(default(T) == null) && value == null)
+                ThrowHelper.ThrowArgumentNullException(argName);
+        }
+
+        // This function will convert an ExceptionArgument enum value to the argument name string.
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static string GetArgumentName(ExceptionArgument argument)
+        {
+            Debug.Assert(Enum.IsDefined(typeof(ExceptionArgument), argument),
+                "The enum value is not defined, please check the ExceptionArgument Enum.");
+
+            return argument.ToString();
+        }
+
+        // This function will convert an ExceptionResource enum value to the resource string.
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static string GetResourceString(ExceptionResource resource)
+        {
+            Debug.Assert(Enum.IsDefined(typeof(ExceptionResource), resource),
+                "The enum value is not defined, please check the ExceptionResource Enum.");
+
+            return SR.GetResourceString(resource.ToString());
+        }
+
+        internal static void ThrowNotSupportedExceptionIfNonNumericType<T>()
+        {
+            if (typeof(T) != typeof(Byte) && typeof(T) != typeof(SByte) &&
+                typeof(T) != typeof(Int16) && typeof(T) != typeof(UInt16) &&
+                typeof(T) != typeof(Int32) && typeof(T) != typeof(UInt32) &&
+                typeof(T) != typeof(Int64) && typeof(T) != typeof(UInt64) &&
+                typeof(T) != typeof(Single) && typeof(T) != typeof(Double))
+            {
+                throw new NotSupportedException(SR.Arg_TypeNotSupported);
+            }
+        }
+    }
+
+    //
+    // The convention for this enum is using the argument name as the enum name
+    //
+    internal enum ExceptionArgument
+    {
+        obj,
+        dictionary,
+        array,
+        info,
+        key,
+        collection,
+        list,
+        match,
+        converter,
+        capacity,
+        index,
+        startIndex,
+        value,
+        count,
+        arrayIndex,
+        name,
+        item,
+        options,
+        view,
+        sourceBytesToCopy,
+        action,
+        comparison,
+        offset,
+        newSize,
+        elementType,
+        length,
+        length1,
+        length2,
+        length3,
+        lengths,
+        len,
+        lowerBounds,
+        sourceArray,
+        destinationArray,
+        sourceIndex,
+        destinationIndex,
+        indices,
+        index1,
+        index2,
+        index3,
+        other,
+        comparer,
+        endIndex,
+        keys,
+        creationOptions,
+        timeout,
+        tasks,
+        scheduler,
+        continuationFunction,
+        millisecondsTimeout,
+        millisecondsDelay,
+        function,
+        exceptions,
+        exception,
+        cancellationToken,
+        delay,
+        asyncResult,
+        endMethod,
+        endFunction,
+        beginMethod,
+        continuationOptions,
+        continuationAction,
+        concurrencyLevel,
+        text,
+        callBack,
+        type,
+        stateMachine,
+        pHandle,
+        values,
+        task,
+        s,
+        keyValuePair,
+        input,
+        pointer,
+        start,
+        format,
+        culture,
+        comparable,
+        source,
+        state,
+        comparisonType,
+        manager
+    }
+
+    //
+    // The convention for this enum is using the resource name as the enum name
+    //
+    internal enum ExceptionResource
+    {
+        Argument_ImplementIComparable,
+        Argument_InvalidType,
+        Argument_InvalidArgumentForComparison,
+        Argument_InvalidRegistryKeyPermissionCheck,
+        ArgumentOutOfRange_NeedNonNegNum,
+
+        Arg_ArrayPlusOffTooSmall,
+        Arg_NonZeroLowerBound,
+        Arg_RankMultiDimNotSupported,
+        Arg_RegKeyDelHive,
+        Arg_RegKeyStrLenBug,
+        Arg_RegSetStrArrNull,
+        Arg_RegSetMismatchedKind,
+        Arg_RegSubKeyAbsent,
+        Arg_RegSubKeyValueAbsent,
+
+        Argument_AddingDuplicate,
+        Serialization_InvalidOnDeser,
+        Serialization_MissingKeys,
+        Serialization_NullKey,
+        Argument_InvalidArrayType,
+        NotSupported_KeyCollectionSet,
+        NotSupported_ValueCollectionSet,
+        ArgumentOutOfRange_SmallCapacity,
+        ArgumentOutOfRange_Index,
+        Argument_InvalidOffLen,
+        Argument_ItemNotExist,
+        ArgumentOutOfRange_Count,
+        ArgumentOutOfRange_InvalidThreshold,
+        ArgumentOutOfRange_ListInsert,
+        NotSupported_ReadOnlyCollection,
+        InvalidOperation_CannotRemoveFromStackOrQueue,
+        InvalidOperation_EmptyQueue,
+        InvalidOperation_EnumOpCantHappen,
+        InvalidOperation_EnumFailedVersion,
+        InvalidOperation_EmptyStack,
+        ArgumentOutOfRange_BiggerThanCollection,
+        InvalidOperation_EnumNotStarted,
+        InvalidOperation_EnumEnded,
+        NotSupported_SortedListNestedWrite,
+        InvalidOperation_NoValue,
+        InvalidOperation_RegRemoveSubKey,
+        Security_RegistryPermission,
+        UnauthorizedAccess_RegistryNoWrite,
+        ObjectDisposed_RegKeyClosed,
+        NotSupported_InComparableType,
+        Argument_InvalidRegistryOptionsCheck,
+        Argument_InvalidRegistryViewCheck,
+        InvalidOperation_NullArray,
+        Arg_MustBeType,
+        Arg_NeedAtLeast1Rank,
+        ArgumentOutOfRange_HugeArrayNotSupported,
+        Arg_RanksAndBounds,
+        Arg_RankIndices,
+        Arg_Need1DArray,
+        Arg_Need2DArray,
+        Arg_Need3DArray,
+        NotSupported_FixedSizeCollection,
+        ArgumentException_OtherNotArrayOfCorrectLength,
+        Rank_MultiDimNotSupported,
+        InvalidOperation_IComparerFailed,
+        ArgumentOutOfRange_EndIndexStartIndex,
+        Arg_LowerBoundsMustMatch,
+        Arg_BogusIComparer,
+        Task_WaitMulti_NullTask,
+        Task_ThrowIfDisposed,
+        Task_Start_TaskCompleted,
+        Task_Start_Promise,
+        Task_Start_ContinuationTask,
+        Task_Start_AlreadyStarted,
+        Task_RunSynchronously_TaskCompleted,
+        Task_RunSynchronously_Continuation,
+        Task_RunSynchronously_Promise,
+        Task_RunSynchronously_AlreadyStarted,
+        Task_MultiTaskContinuation_NullTask,
+        Task_MultiTaskContinuation_EmptyTaskList,
+        Task_Dispose_NotCompleted,
+        Task_Delay_InvalidMillisecondsDelay,
+        Task_Delay_InvalidDelay,
+        Task_ctor_LRandSR,
+        Task_ContinueWith_NotOnAnything,
+        Task_ContinueWith_ESandLR,
+        TaskT_TransitionToFinal_AlreadyCompleted,
+        TaskCompletionSourceT_TrySetException_NullException,
+        TaskCompletionSourceT_TrySetException_NoExceptions,
+        MemoryDisposed,
+        Memory_OutstandingReferences,
+        InvalidOperation_WrongAsyncResultOrEndCalledMultiple,
+        ConcurrentDictionary_ConcurrencyLevelMustBePositive,
+        ConcurrentDictionary_CapacityMustNotBeNegative,
+        ConcurrentDictionary_TypeOfValueIncorrect,
+        ConcurrentDictionary_TypeOfKeyIncorrect,
+        ConcurrentDictionary_KeyAlreadyExisted,
+        ConcurrentDictionary_ItemKeyIsNull,
+        ConcurrentDictionary_IndexIsNegative,
+        ConcurrentDictionary_ArrayNotLargeEnough,
+        ConcurrentDictionary_ArrayIncorrectType,
+        ConcurrentCollection_SyncRoot_NotSupported,
+        ArgumentOutOfRange_Enum,
+        InvalidOperation_HandleIsNotInitialized,
+        AsyncMethodBuilder_InstanceNotInitialized,
+        ArgumentNull_SafeHandle,
+        NotSupported_StringComparison,
+        InvalidOperation_ConcurrentOperationsNotSupported,
+    }
+}
+
diff --git a/src/System.Private.CoreLib/src/System/Type.CoreCLR.cs b/src/System.Private.CoreLib/src/System/Type.CoreCLR.cs
new file mode 100644
index 0000000000..571f53e473
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Type.CoreCLR.cs
@@ -0,0 +1,165 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using StackCrawlMark = System.Threading.StackCrawlMark;
+
+namespace System
+{
+    public abstract partial class Type : MemberInfo, IReflect
+    {
+        public bool IsInterface
+        {
+            get
+            {
+                RuntimeType rt = this as RuntimeType;
+                if (rt != null)
+                    return RuntimeTypeHandle.IsInterface(rt);
+                return ((GetAttributeFlagsImpl() & TypeAttributes.ClassSemanticsMask) == TypeAttributes.Interface);
+            }
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public static Type GetType(String typeName, bool throwOnError, bool ignoreCase)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return RuntimeType.GetType(typeName, throwOnError, ignoreCase, false, ref stackMark);
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public static Type GetType(String typeName, bool throwOnError)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return RuntimeType.GetType(typeName, throwOnError, false, false, ref stackMark);
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public static Type GetType(String typeName)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return RuntimeType.GetType(typeName, false, false, false, ref stackMark);
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public static Type GetType(
+            string typeName,
+            Func<AssemblyName, Assembly> assemblyResolver,
+            Func<Assembly, string, bool, Type> typeResolver)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return TypeNameParser.GetType(typeName, assemblyResolver, typeResolver, false, false, ref stackMark);
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public static Type GetType(
+            string typeName,
+            Func<AssemblyName, Assembly> assemblyResolver,
+            Func<Assembly, string, bool, Type> typeResolver,
+            bool throwOnError)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return TypeNameParser.GetType(typeName, assemblyResolver, typeResolver, throwOnError, false, ref stackMark);
+        }
+
+        [System.Security.DynamicSecurityMethod] // Methods containing StackCrawlMark local var has to be marked DynamicSecurityMethod
+        public static Type GetType(
+            string typeName,
+            Func<AssemblyName, Assembly> assemblyResolver,
+            Func<Assembly, string, bool, Type> typeResolver,
+            bool throwOnError,
+            bool ignoreCase)
+        {
+            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
+            return TypeNameParser.GetType(typeName, assemblyResolver, typeResolver, throwOnError, ignoreCase, ref stackMark);
+        }
+
+        ////////////////////////////////////////////////////////////////////////////////
+        // This will return a class based upon the progID.  This is provided for 
+        // COM classic support.  Program ID's are not used in COM+ because they 
+        // have been superceded by namespace.  (This routine is called this instead 
+        // of getClass() because of the name conflict with the first method above.)
+        //
+        //   param progID:     the progID of the class to retrieve
+        //   returns:          the class object associated to the progID
+        ////
+        public static Type GetTypeFromProgID(String progID, String server, bool throwOnError)
+        {
+            return RuntimeType.GetTypeFromProgIDImpl(progID, server, throwOnError);
+        }
+
+        ////////////////////////////////////////////////////////////////////////////////
+        // This will return a class based upon the CLSID.  This is provided for 
+        // COM classic support.  
+        //
+        //   param CLSID:      the CLSID of the class to retrieve
+        //   returns:          the class object associated to the CLSID
+        ////
+        public static Type GetTypeFromCLSID(Guid clsid, String server, bool throwOnError)
+        {
+            return RuntimeType.GetTypeFromCLSIDImpl(clsid, server, throwOnError);
+        }
+
+        internal virtual RuntimeTypeHandle GetTypeHandleInternal()
+        {
+            return TypeHandle;
+        }
+
+        // Given a class handle, this will return the class for that handle.
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        internal static extern RuntimeType GetTypeFromHandleUnsafe(IntPtr handle);
+
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        public static extern Type GetTypeFromHandle(RuntimeTypeHandle handle);
+
+
+
+
+#if FEATURE_COMINTEROP
+        internal bool IsWindowsRuntimeObject
+        {
+            get { return IsWindowsRuntimeObjectImpl(); }
+        }
+
+        internal bool IsExportedToWindowsRuntime
+        {
+            get { return IsExportedToWindowsRuntimeImpl(); }
+        }
+
+
+        // Protected routine to determine if this class represents a Windows Runtime object
+        virtual internal bool IsWindowsRuntimeObjectImpl()
+        {
+            throw new NotImplementedException();
+        }
+
+        // Determines if this type is exported to WinRT (i.e. is an activatable class in a managed .winmd)
+        virtual internal bool IsExportedToWindowsRuntimeImpl()
+        {
+            throw new NotImplementedException();
+        }
+#endif // FEATURE_COMINTEROP
+
+        // This is only ever called on RuntimeType objects.
+        internal string FormatTypeName()
+        {
+            return FormatTypeName(false);
+        }
+
+        internal virtual string FormatTypeName(bool serialization)
+        {
+            throw new NotImplementedException();
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern bool operator ==(Type left, Type right);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public static extern bool operator !=(Type left, Type right);
+
+        // Exists to faciliate code sharing between CoreCLR and CoreRT.
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal bool IsRuntimeImplemented() => this is RuntimeType;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/TypeLoadException.cs b/src/System.Private.CoreLib/src/System/TypeLoadException.cs
new file mode 100644
index 0000000000..4f31747994
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/TypeLoadException.cs
@@ -0,0 +1,135 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*=============================================================================
+**
+**
+**
+** Purpose: The exception class for type loading failures.
+**
+**
+=============================================================================*/
+
+using System;
+using System.Globalization;
+using System.Runtime.Serialization;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+using System.Security;
+using System.Diagnostics.Contracts;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    public class TypeLoadException : SystemException, ISerializable
+    {
+        public TypeLoadException()
+            : base(SR.Arg_TypeLoadException)
+        {
+            HResult = HResults.COR_E_TYPELOAD;
+        }
+
+        public TypeLoadException(String message)
+            : base(message)
+        {
+            HResult = HResults.COR_E_TYPELOAD;
+        }
+
+        public TypeLoadException(String message, Exception inner)
+            : base(message, inner)
+        {
+            HResult = HResults.COR_E_TYPELOAD;
+        }
+
+        public override String Message
+        {
+            get
+            {
+                SetMessageField();
+                return _message;
+            }
+        }
+
+        private void SetMessageField()
+        {
+            if (_message == null)
+            {
+                if ((ClassName == null) &&
+                    (ResourceId == 0))
+                    _message = SR.Arg_TypeLoadException;
+
+                else
+                {
+                    if (AssemblyName == null)
+                        AssemblyName = SR.IO_UnknownFileName;
+                    if (ClassName == null)
+                        ClassName = SR.IO_UnknownFileName;
+
+                    String format = null;
+                    GetTypeLoadExceptionMessage(ResourceId, JitHelpers.GetStringHandleOnStack(ref format));
+                    _message = String.Format(CultureInfo.CurrentCulture, format, ClassName, AssemblyName, MessageArg);
+                }
+            }
+        }
+
+        public String TypeName
+        {
+            get
+            {
+                if (ClassName == null)
+                    return String.Empty;
+
+                return ClassName;
+            }
+        }
+
+        // This is called from inside the EE. 
+        private TypeLoadException(String className,
+                                  String assemblyName,
+                                  String messageArg,
+                                  int resourceId)
+        : base(null)
+        {
+            HResult = HResults.COR_E_TYPELOAD;
+            ClassName = className;
+            AssemblyName = assemblyName;
+            MessageArg = messageArg;
+            ResourceId = resourceId;
+
+            // Set the _message field eagerly; debuggers look at this field to 
+            // display error info. They don't call the Message property.
+            SetMessageField();
+        }
+
+        protected TypeLoadException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+            ClassName = info.GetString("TypeLoadClassName");
+            AssemblyName = info.GetString("TypeLoadAssemblyName");
+            MessageArg = info.GetString("TypeLoadMessageArg");
+            ResourceId = info.GetInt32("TypeLoadResourceID");
+        }
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void GetTypeLoadExceptionMessage(int resourceId, StringHandleOnStack retString);
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("TypeLoadClassName", ClassName, typeof(string));
+            info.AddValue("TypeLoadAssemblyName", AssemblyName, typeof(string));
+            info.AddValue("TypeLoadMessageArg", MessageArg, typeof(string));
+            info.AddValue("TypeLoadResourceID", ResourceId);
+        }
+
+        // If ClassName != null, GetMessage will construct on the fly using it
+        // and ResourceId (mscorrc.dll). This allows customization of the
+        // class name format depending on the language environment.
+        private String ClassName;
+        private String AssemblyName;
+        private String MessageArg;
+        internal int ResourceId;
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/TypeNameParser.cs b/src/System.Private.CoreLib/src/System/TypeNameParser.cs
new file mode 100644
index 0000000000..2fe7cec813
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/TypeNameParser.cs
@@ -0,0 +1,340 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics;
+using System.IO;
+using System.Reflection;
+using System.Security;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading;
+using System.Runtime.Versioning;
+using Microsoft.Win32.SafeHandles;
+
+namespace System
+{
+    internal class SafeTypeNameParserHandle : SafeHandleZeroOrMinusOneIsInvalid
+    {
+        #region QCalls
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void _ReleaseTypeNameParser(IntPtr pTypeNameParser);
+        #endregion
+
+        public SafeTypeNameParserHandle()
+            : base(true)
+        {
+        }
+
+        protected override bool ReleaseHandle()
+        {
+            _ReleaseTypeNameParser(handle);
+            handle = IntPtr.Zero;
+            return true;
+        }
+    }
+
+    internal sealed class TypeNameParser : IDisposable
+    {
+        #region QCalls
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void _CreateTypeNameParser(string typeName, ObjectHandleOnStack retHandle, bool throwOnError);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void _GetNames(SafeTypeNameParserHandle pTypeNameParser, ObjectHandleOnStack retArray);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void _GetTypeArguments(SafeTypeNameParserHandle pTypeNameParser, ObjectHandleOnStack retArray);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void _GetModifiers(SafeTypeNameParserHandle pTypeNameParser, ObjectHandleOnStack retArray);
+
+        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
+        private static extern void _GetAssemblyName(SafeTypeNameParserHandle pTypeNameParser, StringHandleOnStack retString);
+        #endregion
+
+        #region Static Members
+        internal static Type GetType(
+            string typeName,
+            Func<AssemblyName, Assembly> assemblyResolver,
+            Func<Assembly, string, bool, Type> typeResolver,
+            bool throwOnError,
+            bool ignoreCase,
+            ref StackCrawlMark stackMark)
+        {
+            if (typeName == null)
+                throw new ArgumentNullException(nameof(typeName));
+            if (typeName.Length > 0 && typeName[0] == '\0')
+                throw new ArgumentException(SR.Format_StringZeroLength);
+
+            Type ret = null;
+
+            SafeTypeNameParserHandle handle = CreateTypeNameParser(typeName, throwOnError);
+
+            if (handle != null)
+            {
+                // If we get here the typeName must have been successfully parsed.
+                // Let's construct the Type object.
+                using (TypeNameParser parser = new TypeNameParser(handle))
+                {
+                    ret = parser.ConstructType(assemblyResolver, typeResolver, throwOnError, ignoreCase, ref stackMark);
+                }
+            }
+
+            return ret;
+        }
+        #endregion
+
+        #region Private Data Members
+        private SafeTypeNameParserHandle m_NativeParser;
+        private static readonly char[] SPECIAL_CHARS = { ',', '[', ']', '&', '*', '+', '\\' }; /* see typeparse.h */
+        #endregion
+
+        #region Constructor and Disposer
+        private TypeNameParser(SafeTypeNameParserHandle handle)
+        {
+            m_NativeParser = handle;
+        }
+
+        public void Dispose()
+        {
+            m_NativeParser.Dispose();
+        }
+        #endregion
+
+        #region private Members
+        private unsafe Type ConstructType(
+            Func<AssemblyName, Assembly> assemblyResolver,
+            Func<Assembly, string, bool, Type> typeResolver,
+            bool throwOnError,
+            bool ignoreCase,
+            ref StackCrawlMark stackMark)
+        {
+            // assembly name
+            Assembly assembly = null;
+            string asmName = GetAssemblyName();
+
+            // GetAssemblyName never returns null
+            Debug.Assert(asmName != null);
+
+            if (asmName.Length > 0)
+            {
+                assembly = ResolveAssembly(asmName, assemblyResolver, throwOnError, ref stackMark);
+
+                if (assembly == null)
+                {
+                    // Cannot resolve the assembly. If throwOnError is true we should have already thrown.
+                    return null;
+                }
+            }
+
+            string[] names = GetNames();
+            if (names == null)
+            {
+                // This can only happen if the type name is an empty string or if the first char is '\0'
+                if (throwOnError)
+                    throw new TypeLoadException(SR.Arg_TypeLoadNullStr);
+
+                return null;
+            }
+
+            Type baseType = ResolveType(assembly, names, typeResolver, throwOnError, ignoreCase, ref stackMark);
+
+            if (baseType == null)
+            {
+                // Cannot resolve the type. If throwOnError is true we should have already thrown.
+                Debug.Assert(throwOnError == false);
+                return null;
+            }
+
+            SafeTypeNameParserHandle[] typeArguments = GetTypeArguments();
+
+            Type[] types = null;
+            if (typeArguments != null)
+            {
+                types = new Type[typeArguments.Length];
+                for (int i = 0; i < typeArguments.Length; i++)
+                {
+                    Debug.Assert(typeArguments[i] != null);
+
+                    using (TypeNameParser argParser = new TypeNameParser(typeArguments[i]))
+                    {
+                        types[i] = argParser.ConstructType(assemblyResolver, typeResolver, throwOnError, ignoreCase, ref stackMark);
+                    }
+
+                    if (types[i] == null)
+                    {
+                        // If throwOnError is true argParser.ConstructType should have already thrown.
+                        Debug.Assert(throwOnError == false);
+                        return null;
+                    }
+                }
+            }
+
+            int[] modifiers = GetModifiers();
+
+            fixed (int* ptr = modifiers)
+            {
+                IntPtr intPtr = new IntPtr(ptr);
+                return RuntimeTypeHandle.GetTypeHelper(baseType, types, intPtr, modifiers == null ? 0 : modifiers.Length);
+            }
+        }
+
+        private static Assembly ResolveAssembly(string asmName, Func<AssemblyName, Assembly> assemblyResolver, bool throwOnError, ref StackCrawlMark stackMark)
+        {
+            Debug.Assert(asmName != null && asmName.Length > 0);
+
+            Assembly assembly = null;
+
+            if (assemblyResolver == null)
+            {
+                if (throwOnError)
+                {
+                    assembly = RuntimeAssembly.InternalLoad(asmName, ref stackMark);
+                }
+                else
+                {
+                    // When throwOnError is false we should only catch FileNotFoundException.
+                    // Other exceptions like BadImangeFormatException should still fly.
+                    try
+                    {
+                        assembly = RuntimeAssembly.InternalLoad(asmName, ref stackMark);
+                    }
+                    catch (FileNotFoundException)
+                    {
+                        return null;
+                    }
+                }
+            }
+            else
+            {
+                assembly = assemblyResolver(new AssemblyName(asmName));
+                if (assembly == null && throwOnError)
+                {
+                    throw new FileNotFoundException(SR.Format(SR.FileNotFound_ResolveAssembly, asmName));
+                }
+            }
+
+            return assembly;
+        }
+
+        private static Type ResolveType(Assembly assembly, string[] names, Func<Assembly, string, bool, Type> typeResolver, bool throwOnError, bool ignoreCase, ref StackCrawlMark stackMark)
+        {
+            Debug.Assert(names != null && names.Length > 0);
+
+            Type type = null;
+
+            // both the customer provided and the default type resolvers accept escaped type names
+            string OuterMostTypeName = EscapeTypeName(names[0]);
+
+            // Resolve the top level type.
+            if (typeResolver != null)
+            {
+                type = typeResolver(assembly, OuterMostTypeName, ignoreCase);
+
+                if (type == null && throwOnError)
+                {
+                    string errorString = assembly == null ?
+                        SR.Format(SR.TypeLoad_ResolveType, OuterMostTypeName):
+                        SR.Format(SR.TypeLoad_ResolveTypeFromAssembly, OuterMostTypeName, assembly.FullName);
+
+                    throw new TypeLoadException(errorString);
+                }
+            }
+            else
+            {
+                if (assembly == null)
+                {
+                    type = RuntimeType.GetType(OuterMostTypeName, throwOnError, ignoreCase, false, ref stackMark);
+                }
+                else
+                {
+                    type = assembly.GetType(OuterMostTypeName, throwOnError, ignoreCase);
+                }
+            }
+
+            // Resolve nested types.
+            if (type != null)
+            {
+                BindingFlags bindingFlags = BindingFlags.NonPublic | BindingFlags.Public;
+                if (ignoreCase)
+                    bindingFlags |= BindingFlags.IgnoreCase;
+
+                for (int i = 1; i < names.Length; i++)
+                {
+                    type = type.GetNestedType(names[i], bindingFlags);
+
+                    if (type == null)
+                    {
+                        if (throwOnError)
+                            throw new TypeLoadException(SR.Format(SR.TypeLoad_ResolveNestedType, names[i], names[i - 1]));
+                        else
+                            break;
+                    }
+                }
+            }
+
+            return type;
+        }
+
+        private static string EscapeTypeName(string name)
+        {
+            if (name.IndexOfAny(SPECIAL_CHARS) < 0)
+                return name;
+
+            StringBuilder sb = StringBuilderCache.Acquire();
+            foreach (char c in name)
+            {
+                if (Array.IndexOf<char>(SPECIAL_CHARS, c) >= 0)
+                    sb.Append('\\');
+
+                sb.Append(c);
+            }
+
+            return StringBuilderCache.GetStringAndRelease(sb);
+        }
+
+        private static SafeTypeNameParserHandle CreateTypeNameParser(string typeName, bool throwOnError)
+        {
+            SafeTypeNameParserHandle retHandle = null;
+            _CreateTypeNameParser(typeName, JitHelpers.GetObjectHandleOnStack(ref retHandle), throwOnError);
+
+            return retHandle;
+        }
+
+        private string[] GetNames()
+        {
+            string[] names = null;
+            _GetNames(m_NativeParser, JitHelpers.GetObjectHandleOnStack(ref names));
+
+            return names;
+        }
+
+        private SafeTypeNameParserHandle[] GetTypeArguments()
+        {
+            SafeTypeNameParserHandle[] arguments = null;
+            _GetTypeArguments(m_NativeParser, JitHelpers.GetObjectHandleOnStack(ref arguments));
+
+            return arguments;
+        }
+
+        private int[] GetModifiers()
+        {
+            int[] modifiers = null;
+            _GetModifiers(m_NativeParser, JitHelpers.GetObjectHandleOnStack(ref modifiers));
+
+            return modifiers;
+        }
+
+        private string GetAssemblyName()
+        {
+            string assemblyName = null;
+            _GetAssemblyName(m_NativeParser, JitHelpers.GetStringHandleOnStack(ref assemblyName));
+
+            return assemblyName;
+        }
+        #endregion
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/TypedReference.cs b/src/System.Private.CoreLib/src/System/TypedReference.cs
new file mode 100644
index 0000000000..748f2db461
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/TypedReference.cs
@@ -0,0 +1,124 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    // TypedReference is basically only ever seen on the call stack, and in param arrays.
+    //  These are blob that must be dealt with by the compiler.
+
+    using System;
+    using System.Reflection;
+    using System.Runtime.CompilerServices;
+    using CultureInfo = System.Globalization.CultureInfo;
+    using FieldInfo = System.Reflection.FieldInfo;
+    using System.Runtime.Versioning;
+
+    [CLSCompliant(false)]
+    [System.Runtime.Versioning.NonVersionable] // This only applies to field layout
+    public ref struct TypedReference
+    {
+        private IntPtr Value;
+        private IntPtr Type;
+
+        [CLSCompliant(false)]
+        public static TypedReference MakeTypedReference(Object target, FieldInfo[] flds)
+        {
+            if (target == null)
+                throw new ArgumentNullException(nameof(target));
+            if (flds == null)
+                throw new ArgumentNullException(nameof(flds));
+            if (flds.Length == 0)
+                throw new ArgumentException(SR.Arg_ArrayZeroError, nameof(flds));
+
+            IntPtr[] fields = new IntPtr[flds.Length];
+            // For proper handling of Nullable<T> don't change GetType() to something like 'IsAssignableFrom'
+            // Currently we can't make a TypedReference to fields of Nullable<T>, which is fine.  
+            RuntimeType targetType = (RuntimeType)target.GetType();
+            for (int i = 0; i < flds.Length; i++)
+            {
+                RuntimeFieldInfo field = flds[i] as RuntimeFieldInfo;
+                if (field == null)
+                    throw new ArgumentException(SR.Argument_MustBeRuntimeFieldInfo);
+
+                if (field.IsInitOnly || field.IsStatic)
+                    throw new ArgumentException(SR.Format(SR.Argument_TypedReferenceInvalidField, field.Name));
+
+                if (targetType != field.GetDeclaringTypeInternal() && !targetType.IsSubclassOf(field.GetDeclaringTypeInternal()))
+                    throw new MissingMemberException(SR.MissingMemberTypeRef);
+
+                RuntimeType fieldType = (RuntimeType)field.FieldType;
+                if (fieldType.IsPrimitive)
+                    throw new ArgumentException(SR.Format(SR.Arg_TypeRefPrimitve, field.Name));
+
+                if (i < (flds.Length - 1) && !fieldType.IsValueType)
+                    throw new MissingMemberException(SR.MissingMemberNestErr);
+
+                fields[i] = field.FieldHandle.Value;
+                targetType = fieldType;
+            }
+
+            TypedReference result = new TypedReference();
+
+            // reference to TypedReference is banned, so have to pass result as pointer
+            unsafe
+            {
+                InternalMakeTypedReference(&result, target, fields, targetType);
+            }
+            return result;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        // reference to TypedReference is banned, so have to pass result as pointer
+        private static extern unsafe void InternalMakeTypedReference(void* result, Object target, IntPtr[] flds, RuntimeType lastFieldType);
+
+        public override int GetHashCode()
+        {
+            if (Type == IntPtr.Zero)
+                return 0;
+            else
+                return __reftype(this).GetHashCode();
+        }
+
+        public override bool Equals(Object o)
+        {
+            throw new NotSupportedException(SR.NotSupported_NYI);
+        }
+
+        public static unsafe Object ToObject(TypedReference value)
+        {
+            return InternalToObject(&value);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern unsafe Object InternalToObject(void* value);
+
+        internal bool IsNull
+        {
+            get
+            {
+                return Value == IntPtr.Zero && Type == IntPtr.Zero;
+            }
+        }
+
+        public static Type GetTargetType(TypedReference value)
+        {
+            return __reftype(value);
+        }
+
+        public static RuntimeTypeHandle TargetTypeToken(TypedReference value)
+        {
+            return __reftype(value).TypeHandle;
+        }
+
+        //  This may cause the type to be changed.
+        [CLSCompliant(false)]
+        public static unsafe void SetTypedReference(TypedReference target, Object value)
+        {
+            InternalSetTypedReference(&target, value);
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern unsafe void InternalSetTypedReference(void* target, Object value);
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/ValueType.cs b/src/System.Private.CoreLib/src/System/ValueType.cs
new file mode 100644
index 0000000000..cd8d0e05aa
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/ValueType.cs
@@ -0,0 +1,96 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: Base class for all value classes.
+**
+**
+===========================================================*/
+
+using System;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")] 
+    public abstract class ValueType
+    {
+        public override bool Equals(Object obj)
+        {
+            if (null == obj)
+            {
+                return false;
+            }
+            RuntimeType thisType = (RuntimeType)this.GetType();
+            RuntimeType thatType = (RuntimeType)obj.GetType();
+
+            if (thatType != thisType)
+            {
+                return false;
+            }
+
+            Object thisObj = (Object)this;
+            Object thisResult, thatResult;
+
+            // if there are no GC references in this object we can avoid reflection 
+            // and do a fast memcmp
+            if (CanCompareBits(this))
+                return FastEqualsCheck(thisObj, obj);
+
+            FieldInfo[] thisFields = thisType.GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
+
+            for (int i = 0; i < thisFields.Length; i++)
+            {
+                thisResult = ((RtFieldInfo)thisFields[i]).UnsafeGetValue(thisObj);
+                thatResult = ((RtFieldInfo)thisFields[i]).UnsafeGetValue(obj);
+
+                if (thisResult == null)
+                {
+                    if (thatResult != null)
+                        return false;
+                }
+                else
+                if (!thisResult.Equals(thatResult))
+                {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool CanCompareBits(Object obj);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private static extern bool FastEqualsCheck(Object a, Object b);
+
+        /*=================================GetHashCode==================================
+        **Action: Our algorithm for returning the hashcode is a little bit complex.  We look
+        **        for the first non-static field and get it's hashcode.  If the type has no
+        **        non-static fields, we return the hashcode of the type.  We can't take the
+        **        hashcode of a static member because if that member is of the same type as
+        **        the original type, we'll end up in an infinite loop.
+        **Returns: The hashcode for the type.
+        **Arguments: None.
+        **Exceptions: None.
+        ==============================================================================*/
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        public extern override int GetHashCode();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern int GetHashCodeOfPtr(IntPtr ptr);
+
+        public override String ToString()
+        {
+            return this.GetType().ToString();
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/Variant.cs b/src/System.Private.CoreLib/src/System/Variant.cs
new file mode 100644
index 0000000000..7717fc485f
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/Variant.cs
@@ -0,0 +1,676 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** Purpose: The CLR implementation of Variant.
+**
+**
+===========================================================*/
+
+using System;
+using System.Reflection;
+using System.Threading;
+using System.Runtime.InteropServices;
+using System.Globalization;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+using System.Diagnostics;
+
+namespace System
+{
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct Variant
+    {
+        //Do Not change the order of these fields.
+        //They are mapped to the native VariantData * data structure.
+        private Object m_objref;
+        private int m_data1;
+        private int m_data2;
+        private int m_flags;
+
+        // The following bits have been taken up as follows
+        // bits 0-15    - Type code
+        // bit  16      - Array
+        // bits 19-23   - Enums
+        // bits 24-31   - Optional VT code (for roundtrip VT preservation)
+
+
+        //What are the consequences of making this an enum?
+        ///////////////////////////////////////////////////////////////////////
+        // If you update this, update the corresponding stuff in OAVariantLib.cs,
+        // COMOAVariant.cpp (2 tables, forwards and reverse), and perhaps OleVariant.h
+        ///////////////////////////////////////////////////////////////////////
+        internal const int CV_EMPTY = 0x0;
+        internal const int CV_VOID = 0x1;
+        internal const int CV_BOOLEAN = 0x2;
+        internal const int CV_CHAR = 0x3;
+        internal const int CV_I1 = 0x4;
+        internal const int CV_U1 = 0x5;
+        internal const int CV_I2 = 0x6;
+        internal const int CV_U2 = 0x7;
+        internal const int CV_I4 = 0x8;
+        internal const int CV_U4 = 0x9;
+        internal const int CV_I8 = 0xa;
+        internal const int CV_U8 = 0xb;
+        internal const int CV_R4 = 0xc;
+        internal const int CV_R8 = 0xd;
+        internal const int CV_STRING = 0xe;
+        internal const int CV_PTR = 0xf;
+        internal const int CV_DATETIME = 0x10;
+        internal const int CV_TIMESPAN = 0x11;
+        internal const int CV_OBJECT = 0x12;
+        internal const int CV_DECIMAL = 0x13;
+        internal const int CV_ENUM = 0x15;
+        internal const int CV_MISSING = 0x16;
+        internal const int CV_NULL = 0x17;
+        internal const int CV_LAST = 0x18;
+
+        internal const int TypeCodeBitMask = 0xffff;
+        internal const int VTBitMask = unchecked((int)0xff000000);
+        internal const int VTBitShift = 24;
+        internal const int ArrayBitMask = 0x10000;
+
+        // Enum enum and Mask
+        internal const int EnumI1 = 0x100000;
+        internal const int EnumU1 = 0x200000;
+        internal const int EnumI2 = 0x300000;
+        internal const int EnumU2 = 0x400000;
+        internal const int EnumI4 = 0x500000;
+        internal const int EnumU4 = 0x600000;
+        internal const int EnumI8 = 0x700000;
+        internal const int EnumU8 = 0x800000;
+        internal const int EnumMask = 0xF00000;
+
+        internal static readonly Type[] ClassTypes = {
+            typeof(System.Empty),
+            typeof(void),
+            typeof(Boolean),
+            typeof(Char),
+            typeof(SByte),
+            typeof(Byte),
+            typeof(Int16),
+            typeof(UInt16),
+            typeof(Int32),
+            typeof(UInt32),
+            typeof(Int64),
+            typeof(UInt64),
+            typeof(Single),
+            typeof(Double),
+            typeof(String),
+            typeof(void),           // ptr for the moment
+            typeof(DateTime),
+            typeof(TimeSpan),
+            typeof(Object),
+            typeof(Decimal),
+            typeof(Object),     // Treat enum as Object
+            typeof(System.Reflection.Missing),
+            typeof(System.DBNull),
+        };
+
+        internal static readonly Variant Empty = new Variant();
+        internal static readonly Variant Missing = new Variant(Variant.CV_MISSING, Type.Missing, 0, 0);
+        internal static readonly Variant DBNull = new Variant(Variant.CV_NULL, System.DBNull.Value, 0, 0);
+
+        //
+        // Native Methods
+        //
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern double GetR8FromVar();
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern float GetR4FromVar();
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern void SetFieldsR4(float val);
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern void SetFieldsR8(double val);
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal extern void SetFieldsObject(Object val);
+
+        // Use this function instead of an ECALL - saves about 150 clock cycles
+        // by avoiding the ecall transition and because the JIT inlines this.
+        // Ends up only taking about 1/8 the time of the ECALL version.
+        internal long GetI8FromVar()
+        {
+            return ((long)m_data2 << 32 | ((long)m_data1 & 0xFFFFFFFFL));
+        }
+
+        //
+        // Constructors
+        //
+
+        internal Variant(int flags, Object or, int data1, int data2)
+        {
+            m_flags = flags;
+            m_objref = or;
+            m_data1 = data1;
+            m_data2 = data2;
+        }
+
+        public Variant(bool val)
+        {
+            m_objref = null;
+            m_flags = CV_BOOLEAN;
+            m_data1 = (val) ? Boolean.True : Boolean.False;
+            m_data2 = 0;
+        }
+
+        public Variant(sbyte val)
+        {
+            m_objref = null;
+            m_flags = CV_I1;
+            m_data1 = (int)val;
+            m_data2 = (int)(((long)val) >> 32);
+        }
+
+
+        public Variant(byte val)
+        {
+            m_objref = null;
+            m_flags = CV_U1;
+            m_data1 = (int)val;
+            m_data2 = 0;
+        }
+
+        public Variant(short val)
+        {
+            m_objref = null;
+            m_flags = CV_I2;
+            m_data1 = (int)val;
+            m_data2 = (int)(((long)val) >> 32);
+        }
+
+        public Variant(ushort val)
+        {
+            m_objref = null;
+            m_flags = CV_U2;
+            m_data1 = (int)val;
+            m_data2 = 0;
+        }
+
+        public Variant(char val)
+        {
+            m_objref = null;
+            m_flags = CV_CHAR;
+            m_data1 = (int)val;
+            m_data2 = 0;
+        }
+
+        public Variant(int val)
+        {
+            m_objref = null;
+            m_flags = CV_I4;
+            m_data1 = val;
+            m_data2 = val >> 31;
+        }
+
+        public Variant(uint val)
+        {
+            m_objref = null;
+            m_flags = CV_U4;
+            m_data1 = (int)val;
+            m_data2 = 0;
+        }
+
+        public Variant(long val)
+        {
+            m_objref = null;
+            m_flags = CV_I8;
+            m_data1 = (int)val;
+            m_data2 = (int)(val >> 32);
+        }
+
+        public Variant(ulong val)
+        {
+            m_objref = null;
+            m_flags = CV_U8;
+            m_data1 = (int)val;
+            m_data2 = (int)(val >> 32);
+        }
+
+        public Variant(float val)
+        {
+            m_objref = null;
+            m_flags = CV_R4;
+            m_data1 = 0;
+            m_data2 = 0;
+            SetFieldsR4(val);
+        }
+
+        public Variant(double val)
+        {
+            m_objref = null;
+            m_flags = CV_R8;
+            m_data1 = 0;
+            m_data2 = 0;
+            SetFieldsR8(val);
+        }
+
+        public Variant(DateTime val)
+        {
+            m_objref = null;
+            m_flags = CV_DATETIME;
+            ulong ticks = (ulong)val.Ticks;
+            m_data1 = (int)ticks;
+            m_data2 = (int)(ticks >> 32);
+        }
+
+        public Variant(Decimal val)
+        {
+            m_objref = (Object)val;
+            m_flags = CV_DECIMAL;
+            m_data1 = 0;
+            m_data2 = 0;
+        }
+
+        public Variant(Object obj)
+        {
+            m_data1 = 0;
+            m_data2 = 0;
+
+            VarEnum vt = VarEnum.VT_EMPTY;
+
+            if (obj is DateTime)
+            {
+                m_objref = null;
+                m_flags = CV_DATETIME;
+                ulong ticks = (ulong)((DateTime)obj).Ticks;
+                m_data1 = (int)ticks;
+                m_data2 = (int)(ticks >> 32);
+                return;
+            }
+
+            if (obj is String)
+            {
+                m_flags = CV_STRING;
+                m_objref = obj;
+                return;
+            }
+
+            if (obj == null)
+            {
+                this = Empty;
+                return;
+            }
+            if (obj == System.DBNull.Value)
+            {
+                this = DBNull;
+                return;
+            }
+            if (obj == Type.Missing)
+            {
+                this = Missing;
+                return;
+            }
+
+            if (obj is Array)
+            {
+                m_flags = CV_OBJECT | ArrayBitMask;
+                m_objref = obj;
+                return;
+            }
+
+            // Compiler appeasement
+            m_flags = CV_EMPTY;
+            m_objref = null;
+
+            // Check to see if the object passed in is a wrapper object.
+            if (obj is UnknownWrapper)
+            {
+                vt = VarEnum.VT_UNKNOWN;
+                obj = ((UnknownWrapper)obj).WrappedObject;
+            }
+            else if (obj is DispatchWrapper)
+            {
+                vt = VarEnum.VT_DISPATCH;
+                obj = ((DispatchWrapper)obj).WrappedObject;
+            }
+            else if (obj is ErrorWrapper)
+            {
+                vt = VarEnum.VT_ERROR;
+                obj = (Object)(((ErrorWrapper)obj).ErrorCode);
+                Debug.Assert(obj != null, "obj != null");
+            }
+            else if (obj is CurrencyWrapper)
+            {
+                vt = VarEnum.VT_CY;
+                obj = (Object)(((CurrencyWrapper)obj).WrappedObject);
+                Debug.Assert(obj != null, "obj != null");
+            }
+            else if (obj is BStrWrapper)
+            {
+                vt = VarEnum.VT_BSTR;
+                obj = (Object)(((BStrWrapper)obj).WrappedObject);
+            }
+
+            if (obj != null)
+            {
+                SetFieldsObject(obj);
+            }
+
+            // If the object passed in is one of the wrappers then set the VARIANT type.
+            if (vt != VarEnum.VT_EMPTY)
+                m_flags |= ((int)vt << VTBitShift);
+        }
+
+        //This is a family-only accessor for the CVType.
+        //This is never to be exposed externally.
+        internal int CVType
+        {
+            get
+            {
+                return (m_flags & TypeCodeBitMask);
+            }
+        }
+
+        public Object ToObject()
+        {
+            switch (CVType)
+            {
+                case CV_EMPTY:
+                    return null;
+                case CV_BOOLEAN:
+                    return (Object)(m_data1 != 0);
+                case CV_I1:
+                    return (Object)((sbyte)m_data1);
+                case CV_U1:
+                    return (Object)((byte)m_data1);
+                case CV_CHAR:
+                    return (Object)((char)m_data1);
+                case CV_I2:
+                    return (Object)((short)m_data1);
+                case CV_U2:
+                    return (Object)((ushort)m_data1);
+                case CV_I4:
+                    return (Object)(m_data1);
+                case CV_U4:
+                    return (Object)((uint)m_data1);
+                case CV_I8:
+                    return (Object)(GetI8FromVar());
+                case CV_U8:
+                    return (Object)((ulong)GetI8FromVar());
+                case CV_R4:
+                    return (Object)(GetR4FromVar());
+                case CV_R8:
+                    return (Object)(GetR8FromVar());
+                case CV_DATETIME:
+                    return new DateTime(GetI8FromVar());
+                case CV_TIMESPAN:
+                    return new TimeSpan(GetI8FromVar());
+                case CV_ENUM:
+                    return BoxEnum();
+                case CV_MISSING:
+                    return Type.Missing;
+                case CV_NULL:
+                    return System.DBNull.Value;
+                case CV_DECIMAL:
+                case CV_STRING:
+                case CV_OBJECT:
+                default:
+                    return m_objref;
+            }
+        }
+
+        // This routine will return an boxed enum.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern Object BoxEnum();
+
+
+        // Helper code for marshaling managed objects to VARIANT's (we use
+        // managed variants as an intermediate type.
+        internal static void MarshalHelperConvertObjectToVariant(Object o, ref Variant v)
+        {
+            IConvertible ic = o as IConvertible;
+
+            if (o == null)
+            {
+                v = Empty;
+            }
+            else if (ic == null)
+            {
+                // This path should eventually go away. But until
+                // the work is done to have all of our wrapper types implement
+                // IConvertible, this is a cheapo way to get the work done.
+                v = new Variant(o);
+            }
+            else
+            {
+                IFormatProvider provider = CultureInfo.InvariantCulture;
+                switch (ic.GetTypeCode())
+                {
+                    case TypeCode.Empty:
+                        v = Empty;
+                        break;
+
+                    case TypeCode.Object:
+                        v = new Variant((Object)o);
+                        break;
+
+                    case TypeCode.DBNull:
+                        v = DBNull;
+                        break;
+
+                    case TypeCode.Boolean:
+                        v = new Variant(ic.ToBoolean(provider));
+                        break;
+
+                    case TypeCode.Char:
+                        v = new Variant(ic.ToChar(provider));
+                        break;
+
+                    case TypeCode.SByte:
+                        v = new Variant(ic.ToSByte(provider));
+                        break;
+
+                    case TypeCode.Byte:
+                        v = new Variant(ic.ToByte(provider));
+                        break;
+
+                    case TypeCode.Int16:
+                        v = new Variant(ic.ToInt16(provider));
+                        break;
+
+                    case TypeCode.UInt16:
+                        v = new Variant(ic.ToUInt16(provider));
+                        break;
+
+                    case TypeCode.Int32:
+                        v = new Variant(ic.ToInt32(provider));
+                        break;
+
+                    case TypeCode.UInt32:
+                        v = new Variant(ic.ToUInt32(provider));
+                        break;
+
+                    case TypeCode.Int64:
+                        v = new Variant(ic.ToInt64(provider));
+                        break;
+
+                    case TypeCode.UInt64:
+                        v = new Variant(ic.ToUInt64(provider));
+                        break;
+
+                    case TypeCode.Single:
+                        v = new Variant(ic.ToSingle(provider));
+                        break;
+
+                    case TypeCode.Double:
+                        v = new Variant(ic.ToDouble(provider));
+                        break;
+
+                    case TypeCode.Decimal:
+                        v = new Variant(ic.ToDecimal(provider));
+                        break;
+
+                    case TypeCode.DateTime:
+                        v = new Variant(ic.ToDateTime(provider));
+                        break;
+
+                    case TypeCode.String:
+                        v = new Variant(ic.ToString(provider));
+                        break;
+
+                    default:
+                        throw new NotSupportedException(SR.Format(SR.NotSupported_UnknownTypeCode, ic.GetTypeCode()));
+                }
+            }
+        }
+
+        // Helper code for marshaling VARIANTS to managed objects (we use
+        // managed variants as an intermediate type.
+        internal static Object MarshalHelperConvertVariantToObject(ref Variant v)
+        {
+            return v.ToObject();
+        }
+
+        // Helper code: on the back propagation path where a VT_BYREF VARIANT*
+        // is marshaled to a "ref Object", we use this helper to force the
+        // updated object back to the original type.
+        internal static void MarshalHelperCastVariant(Object pValue, int vt, ref Variant v)
+        {
+            IConvertible iv = pValue as IConvertible;
+            if (iv == null)
+            {
+                switch (vt)
+                {
+                    case 9: /*VT_DISPATCH*/
+                        v = new Variant(new DispatchWrapper(pValue));
+                        break;
+
+                    case 12: /*VT_VARIANT*/
+                        v = new Variant(pValue);
+                        break;
+
+                    case 13: /*VT_UNKNOWN*/
+                        v = new Variant(new UnknownWrapper(pValue));
+                        break;
+
+                    case 36: /*VT_RECORD*/
+                        v = new Variant(pValue);
+                        break;
+
+                    case 8: /*VT_BSTR*/
+                        if (pValue == null)
+                        {
+                            v = new Variant(null);
+                            v.m_flags = CV_STRING;
+                        }
+                        else
+                        {
+                            throw new InvalidCastException(SR.InvalidCast_CannotCoerceByRefVariant);
+                        }
+                        break;
+
+                    default:
+                        throw new InvalidCastException(SR.InvalidCast_CannotCoerceByRefVariant);
+                }
+            }
+            else
+            {
+                IFormatProvider provider = CultureInfo.InvariantCulture;
+                switch (vt)
+                {
+                    case 0: /*VT_EMPTY*/
+                        v = Empty;
+                        break;
+
+                    case 1: /*VT_NULL*/
+                        v = DBNull;
+                        break;
+
+                    case 2: /*VT_I2*/
+                        v = new Variant(iv.ToInt16(provider));
+                        break;
+
+                    case 3: /*VT_I4*/
+                        v = new Variant(iv.ToInt32(provider));
+                        break;
+
+                    case 4: /*VT_R4*/
+                        v = new Variant(iv.ToSingle(provider));
+                        break;
+
+                    case 5: /*VT_R8*/
+                        v = new Variant(iv.ToDouble(provider));
+                        break;
+
+                    case 6: /*VT_CY*/
+                        v = new Variant(new CurrencyWrapper(iv.ToDecimal(provider)));
+                        break;
+
+                    case 7: /*VT_DATE*/
+                        v = new Variant(iv.ToDateTime(provider));
+                        break;
+
+                    case 8: /*VT_BSTR*/
+                        v = new Variant(iv.ToString(provider));
+                        break;
+
+                    case 9: /*VT_DISPATCH*/
+                        v = new Variant(new DispatchWrapper((Object)iv));
+                        break;
+
+                    case 10: /*VT_ERROR*/
+                        v = new Variant(new ErrorWrapper(iv.ToInt32(provider)));
+                        break;
+
+                    case 11: /*VT_BOOL*/
+                        v = new Variant(iv.ToBoolean(provider));
+                        break;
+
+                    case 12: /*VT_VARIANT*/
+                        v = new Variant((Object)iv);
+                        break;
+
+                    case 13: /*VT_UNKNOWN*/
+                        v = new Variant(new UnknownWrapper((Object)iv));
+                        break;
+
+                    case 14: /*VT_DECIMAL*/
+                        v = new Variant(iv.ToDecimal(provider));
+                        break;
+
+                    // case 15: /*unused*/
+                    //  NOT SUPPORTED
+
+                    case 16: /*VT_I1*/
+                        v = new Variant(iv.ToSByte(provider));
+                        break;
+
+                    case 17: /*VT_UI1*/
+                        v = new Variant(iv.ToByte(provider));
+                        break;
+
+                    case 18: /*VT_UI2*/
+                        v = new Variant(iv.ToUInt16(provider));
+                        break;
+
+                    case 19: /*VT_UI4*/
+                        v = new Variant(iv.ToUInt32(provider));
+                        break;
+
+                    case 20: /*VT_I8*/
+                        v = new Variant(iv.ToInt64(provider));
+                        break;
+
+                    case 21: /*VT_UI8*/
+                        v = new Variant(iv.ToUInt64(provider));
+                        break;
+
+                    case 22: /*VT_INT*/
+                        v = new Variant(iv.ToInt32(provider));
+                        break;
+
+                    case 23: /*VT_UINT*/
+                        v = new Variant(iv.ToUInt32(provider));
+                        break;
+
+                    default:
+                        throw new InvalidCastException(SR.InvalidCast_CannotCoerceByRefVariant);
+                }
+            }
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/WeakReference.cs b/src/System.Private.CoreLib/src/System/WeakReference.cs
new file mode 100644
index 0000000000..b99e3683a6
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/WeakReference.cs
@@ -0,0 +1,119 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+** Purpose: A wrapper for establishing a WeakReference to an Object.
+**
+===========================================================*/
+
+using System;
+using System.Runtime.Serialization;
+using System.Security;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+using System.Diagnostics;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")] 
+    public class WeakReference : ISerializable
+    {
+        // If you fix bugs here, please fix them in WeakReference<T> at the same time.
+
+        // This field is not a regular GC handle. It can have a special values that are used to prevent a race condition between setting the target and finalization.
+        internal IntPtr m_handle;
+
+        // Migrating InheritanceDemands requires this default ctor, so we can mark it SafeCritical
+        protected WeakReference()
+        {
+            Debug.Fail("WeakReference's protected default ctor should never be used!");
+            throw new NotImplementedException();
+        }
+
+        // Creates a new WeakReference that keeps track of target.
+        // Assumes a Short Weak Reference (ie TrackResurrection is false.)
+        //
+        public WeakReference(Object target)
+            : this(target, false)
+        {
+        }
+
+        //Creates a new WeakReference that keeps track of target.
+        //
+        public WeakReference(Object target, bool trackResurrection)
+        {
+            Create(target, trackResurrection);
+        }
+
+        protected WeakReference(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+
+            Object target = info.GetValue("TrackedObject", typeof(Object)); // Do not rename (binary serialization)
+            bool trackResurrection = info.GetBoolean("TrackResurrection"); // Do not rename (binary serialization)
+
+            Create(target, trackResurrection);
+        }
+
+        //Determines whether or not this instance of WeakReference still refers to an object
+        //that has not been collected.
+        //
+        public extern virtual bool IsAlive
+        {
+            [MethodImplAttribute(MethodImplOptions.InternalCall)]
+            get;
+        }
+
+        //Returns a boolean indicating whether or not we're tracking objects until they're collected (true)
+        //or just until they're finalized (false).
+        //
+        public virtual bool TrackResurrection
+        {
+            // We need to call IsTrackResurrection non-virtually in GetObjectData, and so the virtual property cannot be FCall directly
+            get { return IsTrackResurrection(); }
+        }
+
+        //Gets the Object stored in the handle if it's accessible.
+        // Or sets it.
+        //
+        public extern virtual Object Target
+        {
+            [MethodImplAttribute(MethodImplOptions.InternalCall)]
+            get;
+            [MethodImplAttribute(MethodImplOptions.InternalCall)]
+            set;
+        }
+
+        // Free all system resources associated with this reference.
+        //
+        // Note: The WeakReference finalizer is not actually run, but
+        // treated specially in gc.cpp's ScanForFinalization
+        // This is needed for subclasses deriving from WeakReference, however.
+        // Additionally, there may be some cases during shutdown when we run this finalizer.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        extern ~WeakReference();
+
+        public virtual void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+            info.AddValue("TrackedObject", Target, typeof(Object)); // Do not rename (binary serialization)
+            info.AddValue("TrackResurrection", IsTrackResurrection()); // Do not rename (binary serialization)
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern void Create(Object target, bool trackResurrection);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern bool IsTrackResurrection();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/WeakReferenceOfT.cs b/src/System.Private.CoreLib/src/System/WeakReferenceOfT.cs
new file mode 100644
index 0000000000..15f6daf07a
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/WeakReferenceOfT.cs
@@ -0,0 +1,116 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+** Purpose: A wrapper for establishing a WeakReference to a generic type.
+**
+===========================================================*/
+
+using System;
+using System.Runtime.Serialization;
+using System.Security;
+using System.Runtime;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+    [Serializable]
+    [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")] 
+    // This class is sealed to mitigate security issues caused by Object::MemberwiseClone.
+    public sealed class WeakReference<T> : ISerializable
+        where T : class
+    {
+        // If you fix bugs here, please fix them in WeakReference at the same time.
+
+        // This field is not a regular GC handle. It can have a special values that are used to prevent a race condition between setting the target and finalization.
+        internal IntPtr m_handle;
+
+        // Creates a new WeakReference that keeps track of target.
+        // Assumes a Short Weak Reference (ie TrackResurrection is false.)
+        //
+        public WeakReference(T target)
+            : this(target, false)
+        {
+        }
+
+        //Creates a new WeakReference that keeps track of target.
+        //
+        public WeakReference(T target, bool trackResurrection)
+        {
+            Create(target, trackResurrection);
+        }
+
+        internal WeakReference(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+
+            T target = (T)info.GetValue("TrackedObject", typeof(T)); // Do not rename (binary serialization)
+            bool trackResurrection = info.GetBoolean("TrackResurrection"); // Do not rename (binary serialization)
+
+            Create(target, trackResurrection);
+        }
+
+        //
+        // We are exposing TryGetTarget instead of a simple getter to avoid a common problem where people write incorrect code like:
+        //
+        //      WeakReference ref = ...;
+        //      if (ref.Target != null)
+        //          DoSomething(ref.Target)
+        //
+        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
+        public bool TryGetTarget(out T target)
+        {
+            // Call the worker method that has more performant but less user friendly signature.
+            T o = this.Target;
+            target = o;
+            return o != null;
+        }
+
+        public void SetTarget(T target)
+        {
+            this.Target = target;
+        }
+
+        // This is property for better debugging experience (VS debugger shows values of properties when you hover over the variables)
+        private extern T Target
+        {
+            [MethodImplAttribute(MethodImplOptions.InternalCall)]
+            get;
+            [MethodImplAttribute(MethodImplOptions.InternalCall)]
+            set;
+        }
+
+        // Free all system resources associated with this reference.
+        //
+        // Note: The WeakReference<T> finalizer is not usually run, but
+        // treated specially in gc.cpp's ScanForFinalization
+        // This is needed for subclasses deriving from WeakReference<T>, however.
+        // Additionally, there may be some cases during shutdown when we run this finalizer.
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        extern ~WeakReference();
+
+        public void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            if (info == null)
+            {
+                throw new ArgumentNullException(nameof(info));
+            }
+
+            info.AddValue("TrackedObject", this.Target, typeof(T)); // Do not rename (binary serialization)
+            info.AddValue("TrackResurrection", IsTrackResurrection()); // Do not rename (binary serialization)
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern void Create(T target, bool trackResurrection);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        private extern bool IsTrackResurrection();
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/__ComObject.cs b/src/System.Private.CoreLib/src/System/__ComObject.cs
new file mode 100644
index 0000000000..412b763ab1
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/__ComObject.cs
@@ -0,0 +1,190 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+/*============================================================
+**
+**
+**
+** __ComObject is the root class for all COM wrappers.  This class
+** defines only the basics. This class is used for wrapping COM objects
+** accessed from COM+
+**
+** 
+===========================================================*/
+
+using System;
+using System.Collections;
+using System.Threading;
+using System.Runtime.InteropServices;
+using System.Runtime.InteropServices.WindowsRuntime;
+using System.Runtime.CompilerServices;
+using System.Reflection;
+
+namespace System
+{
+    internal class __ComObject : MarshalByRefObject
+    {
+        private Hashtable m_ObjectToDataMap;
+
+        /*============================================================
+        ** default constructor
+        ** can't instantiate this directly
+        =============================================================*/
+        protected __ComObject()
+        {
+        }
+
+        //====================================================================
+        // Overrides ToString() to make sure we call to IStringable if the 
+        // COM object implements it in the case of weakly typed RCWs
+        //====================================================================
+        public override string ToString()
+        {
+            //
+            // Only do the IStringable cast when running under AppX for better compat
+            // Otherwise we could do a IStringable cast in classic apps which could introduce
+            // a thread transition which would lead to deadlock
+            //
+            if (AppDomain.IsAppXModel())
+            {
+                // Check whether the type implements IStringable.
+                IStringable stringableType = this as IStringable;
+                if (stringableType != null)
+                {
+                    return stringableType.ToString();
+                }
+            }
+
+            return base.ToString();
+        }
+
+        //====================================================================
+        // This method retrieves the data associated with the specified
+        // key if any such data exists for the current __ComObject.
+        //====================================================================
+        internal Object GetData(Object key)
+        {
+            Object data = null;
+
+            // Synchronize access to the map.
+            lock (this)
+            {
+                // If the map hasn't been allocated, then there can be no data for the specified key.
+                if (m_ObjectToDataMap != null)
+                {
+                    // Look up the data in the map.
+                    data = m_ObjectToDataMap[key];
+                }
+            }
+
+            return data;
+        }
+
+        //====================================================================
+        // This method sets the data for the specified key on the current 
+        // __ComObject.
+        //====================================================================
+        internal bool SetData(Object key, Object data)
+        {
+            bool bAdded = false;
+
+            // Synchronize access to the map.
+            lock (this)
+            {
+                // If the map hasn't been allocated yet, allocate it.
+                if (m_ObjectToDataMap == null)
+                    m_ObjectToDataMap = new Hashtable();
+
+                // If there isn't already data in the map then add it.
+                if (m_ObjectToDataMap[key] == null)
+                {
+                    m_ObjectToDataMap[key] = data;
+                    bAdded = true;
+                }
+            }
+
+            return bAdded;
+        }
+
+        //====================================================================
+        // This method is called from within the EE and releases all the 
+        // cached data for the __ComObject.
+        //====================================================================
+        internal void ReleaseAllData()
+        {
+            // Synchronize access to the map.
+            lock (this)
+            {
+                // If the map hasn't been allocated, then there is nothing to do.
+                if (m_ObjectToDataMap != null)
+                {
+                    foreach (Object o in m_ObjectToDataMap.Values)
+                    {
+                        // Note: the value could be an object[]
+                        // We are fine for now as object[] doesn't implement IDisposable nor derive from __ComObject
+
+                        // If the object implements IDisposable, then call Dispose on it.
+                        IDisposable DisposableObj = o as IDisposable;
+                        if (DisposableObj != null)
+                            DisposableObj.Dispose();
+
+                        // If the object is a derived from __ComObject, then call Marshal.ReleaseComObject on it.
+                        __ComObject ComObj = o as __ComObject;
+                        if (ComObj != null)
+                            Marshal.ReleaseComObject(ComObj);
+                    }
+
+                    // Set the map to null to indicate it has been cleaned up.
+                    m_ObjectToDataMap = null;
+                }
+            }
+        }
+
+        //====================================================================
+        // This method is called from within the EE and is used to handle
+        // calls on methods of event interfaces.
+        //====================================================================
+        internal Object GetEventProvider(RuntimeType t)
+        {
+            // Check to see if we already have a cached event provider for this type.
+            Object EvProvider = GetData(t);
+
+            // If we don't then we need to create one.
+            if (EvProvider == null)
+                EvProvider = CreateEventProvider(t);
+
+            return EvProvider;
+        }
+
+        internal int ReleaseSelf()
+        {
+            return Marshal.InternalReleaseComObject(this);
+        }
+
+        internal void FinalReleaseSelf()
+        {
+            Marshal.InternalFinalReleaseComObject(this);
+        }
+
+        private Object CreateEventProvider(RuntimeType t)
+        {
+            // Create the event provider for the specified type.
+            Object EvProvider = Activator.CreateInstance(t, Activator.ConstructorDefault | BindingFlags.NonPublic, null, new Object[] { this }, null);
+
+            // Attempt to cache the wrapper on the object.
+            if (!SetData(t, EvProvider))
+            {
+                // Dispose the event provider if it implements IDisposable.
+                IDisposable DisposableEvProv = EvProvider as IDisposable;
+                if (DisposableEvProv != null)
+                    DisposableEvProv.Dispose();
+
+                // Another thead already cached the wrapper so use that one instead.
+                EvProvider = GetData(t);
+            }
+
+            return EvProvider;
+        }
+    }
+}
diff --git a/src/System.Private.CoreLib/src/System/mda.cs b/src/System.Private.CoreLib/src/System/mda.cs
new file mode 100644
index 0000000000..f750e99a8b
--- /dev/null
+++ b/src/System.Private.CoreLib/src/System/mda.cs
@@ -0,0 +1,77 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+
+namespace System
+{
+#if MDA_SUPPORTED
+    internal static class Mda
+    {
+        internal static class StreamWriterBufferedDataLost
+        {
+            // State: 0 (not queried); 1 (enabled); 2 (disabled)
+            private static volatile int _enabledState;
+            private static volatile int _captureAllocatedCallStackState;
+
+            internal static bool Enabled {
+                get {
+                    if (_enabledState == 0) {
+                        if (Mda.IsStreamWriterBufferedDataLostEnabled())
+                            _enabledState = 1;
+                        else
+                            _enabledState = 2;
+                    }
+
+                    return (_enabledState == 1);
+                }
+            }
+
+            internal static bool CaptureAllocatedCallStack {
+                get {
+                    if (_captureAllocatedCallStackState == 0) {
+                        if (Mda.IsStreamWriterBufferedDataLostCaptureAllocatedCallStack())
+                            _captureAllocatedCallStackState = 1;
+                        else
+                            _captureAllocatedCallStackState = 2;
+                    }
+
+                    return (_captureAllocatedCallStackState == 1);
+                }
+            }
+
+            internal static void ReportError(String text) {
+                Mda.ReportStreamWriterBufferedDataLost(text);
+            }
+
+        }
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ReportStreamWriterBufferedDataLost(String text);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsStreamWriterBufferedDataLostEnabled();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsStreamWriterBufferedDataLostCaptureAllocatedCallStack();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void MemberInfoCacheCreation();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void DateTimeInvalidLocalFormat();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern bool IsInvalidGCHandleCookieProbeEnabled();
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void FireInvalidGCHandleCookieProbe(IntPtr cookie);
+
+        [MethodImplAttribute(MethodImplOptions.InternalCall)]
+        internal static extern void ReportErrorSafeHandleRelease(Exception ex);
+    }
+#endif
+}
diff --git a/src/System.Private.CoreLib/src/mscorlib.Friends.cs b/src/System.Private.CoreLib/src/mscorlib.Friends.cs
new file mode 100644
index 0000000000..eadba9c97c
--- /dev/null
+++ b/src/System.Private.CoreLib/src/mscorlib.Friends.cs
@@ -0,0 +1,9 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+// Depends on things like WindowsRuntimeImportAttribute
+[assembly: InternalsVisibleTo("System.Runtime.WindowsRuntime, PublicKey=00000000000000000400000000000000", AllInternalsVisible = false)]
+[assembly: InternalsVisibleTo("System.Runtime.WindowsRuntime.UI.Xaml, PublicKey=00000000000000000400000000000000", AllInternalsVisible = false)]